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Sensors, Volume 9, Issue 7 (July 2009) – 45 articles , Pages 5040-5877

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1585 KiB  
Article
LoWMob: Intra-PAN Mobility Support Schemes for 6LoWPAN
by Gargi Bag, Muhammad Taqi Raza, Ki-Hyung Kim and Seung-Wha Yoo
Sensors 2009, 9(7), 5844-5877; https://doi.org/10.3390/s90705844 - 23 Jul 2009
Cited by 65 | Viewed by 14023
Abstract
Mobility in 6LoWPAN (IPv6 over Low Power Personal Area Networks) is being utilized in realizing many applications where sensor nodes, while moving, sense and transmit the gathered data to a monitoring server. By employing IEEE802.15.4 as a baseline for the link layer technology, [...] Read more.
Mobility in 6LoWPAN (IPv6 over Low Power Personal Area Networks) is being utilized in realizing many applications where sensor nodes, while moving, sense and transmit the gathered data to a monitoring server. By employing IEEE802.15.4 as a baseline for the link layer technology, 6LoWPAN implies low data rate and low power consumption with periodic sleep and wakeups for sensor nodes, without requiring them to incorporate complex hardware. Also enabling sensor nodes with IPv6 ensures that the sensor data can be accessed anytime and anywhere from the world. Several existing mobility-related schemes like HMIPv6, MIPv6, HAWAII, and Cellular IP require active participation of mobile nodes in the mobility signaling, thus leading to the mobility-related changes in the protocol stack of mobile nodes. In this paper, we present LoWMob, which is a network-based mobility scheme for mobile 6LoWPAN nodes in which the mobility of 6LoWPAN nodes is handled at the network-side. LoWMob ensures multi-hop communication between gateways and mobile nodes with the help of the static nodes within a 6LoWPAN. In order to reduce the signaling overhead of static nodes for supporting mobile nodes, LoWMob proposes a mobility support packet format at the adaptation layer of 6LoWPAN. Also we present a distributed version of LoWMob, named as DLoWMob (or Distributed LoWMob), which employs Mobility Support Points (MSPs) to distribute the traffic concentration at the gateways and to optimize the multi-hop routing path between source and destination nodes in a 6LoWPAN. Moreover, we have also discussed the security considerations for our proposed mobility schemes. The performance of our proposed schemes is evaluated in terms of mobility signaling costs, end-to-end delay, and packet success ratio. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
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<p>Possible mobility scenarios.</p> Full article ">
<p>The MN as joining the PAN.</p> Full article ">
<p>Next node activation process using AoA method.</p> Full article ">
<p>MN’s handoff support scenario.</p> Full article ">
<p>The algorithm for the handoff support.</p> Full article ">
<p>Location update (LU) message format.</p> Full article ">
<p>A typical 6lowpan message format of a data packet.</p> Full article ">
<p>Message format of a data packet sent from the MN to the CN via the tunnel from MN’s associated SN to the GW.</p> Full article ">
<p>Message format of a data packet sent from the CN the MN via the tunnel from GW to SN.</p> Full article ">
596 KiB  
Article
Fundamentals of in Situ Digital Camera Methodology for Water Quality Monitoring of Coast and Ocean
by Lonneke Goddijn-Murphy, Damien Dailloux, Martin White and Dave Bowers
Sensors 2009, 9(7), 5825-5843; https://doi.org/10.3390/s90705825 - 22 Jul 2009
Cited by 32 | Viewed by 14260
Abstract
Conventional digital cameras, the Nikon Coolpix885® and the SeaLife ECOshot®, were used as in situ optical instruments for water quality monitoring. Measured response spectra showed that these digital cameras are basically three-band radiometers. The response values in the red, green [...] Read more.
Conventional digital cameras, the Nikon Coolpix885® and the SeaLife ECOshot®, were used as in situ optical instruments for water quality monitoring. Measured response spectra showed that these digital cameras are basically three-band radiometers. The response values in the red, green and blue bands, quantified by RGB values of digital images of the water surface, were comparable to measurements of irradiance levels at red, green and cyan/blue wavelengths of water leaving light. Different systems were deployed to capture upwelling light from below the surface, while eliminating direct surface reflection. Relationships between RGB ratios of water surface images, and water quality parameters were found to be consistent with previous measurements using more traditional narrow-band radiometers. This current paper focuses on the method that was used to acquire digital images, derive RGB values and relate measurements to water quality parameters. Field measurements were obtained in Galway Bay, Ireland, and in the Southern Rockall Trough in the North Atlantic, where both yellow substance and chlorophyll concentrations were successfully assessed using the digital camera method. Full article
(This article belongs to the Special Issue Image Sensors 2009)
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Graphical abstract

Graphical abstract
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<p>Diagram illustrating camera deployment methods: (a) CP885 with a tube breaking the water surface attached to its lens (b) CP885 in an underwater housing, mounted in a frame kept afloat by four buoys (two shown in diagram) (c) ECOshot underwater camera imaging subsurface up welling light (d) ECOshot underwater camera imaging subsurface down welling light.</p> Full article ">
<p>Map of Ireland and the North Atlantic, the rectangle contains the survey area in Galway Bay. The contours at 200 and 1,000 m depth indicate the Porcupine Bank, and the x symbols station locations in the Southern Rockall Trough.</p> Full article ">
<p>Response spectra of (a) CP885, and (b) ECOshot digital cameras. Response was defined as <span class="html-italic">RGB</span> values in bits, normalized to their total. Camera settings were auto exposure mode using Exp. +/− = 0 eV, and white balance ‘Direct Sunlight’.</p> Full article ">
<p>Response spectra of (a) CP885, and (b) ECOshot digital cameras. Response was defined as <span class="html-italic">RGB</span> values in bits, normalized to unity. Camera settings as per <a href="#f3-sensors-09-05825" class="html-fig">Figure 3</a>.</p> Full article ">
<p>Scatter plot of OCS irradiance values in digital counts (DC), divided by total counts, against CP885’s <span class="html-italic">RGB</span>(<span class="html-italic">I<sub>tot</sub></span> = 400) values, obtained <span class="html-italic">in situ</span> in Galway Bay. The red marks indicate OCS red and CP885 red channel, the green marks OCS green and CP885 green channel, the cyan marks OCS cyan and CP885 blue channel, and the blue marks OCS blue and CP885 blue channel. The line shows a one-to-one relation.</p> Full article ">
<p>Scatter plot of slope <span class="html-italic">n<sub>ys</sub></span> for surveys I, II and VII (<a href="#t3-sensors-09-05825" class="html-table">Table 3a</a>), against average plume depth during these surveys. The continuous line and the equation show the result of a reduced major axis regression between plume depth and <span class="html-italic">n<sub>ys</sub></span>.</p> Full article ">
<p>Scatter plot of chlorophyll <span class="html-italic">a</span> concentration derived from SeaWiFS monthly mean values [<a href="#b37-sensors-09-05825" class="html-bibr">37</a>], against <span class="html-italic">B</span>/<span class="html-italic">G</span> obtained using the <span class="html-italic">in situ</span> CP885 digital camera (<a href="#f1-sensors-09-05825" class="html-fig">Figure 1b</a>) during the survey in the Southern Rockall Trough. The continuous line and the equation show the result of a reduced major axis regression between ln(<span class="html-italic">B</span>/<span class="html-italic">G</span>) and ln(Chl <span class="html-italic">a</span>).</p> Full article ">
<p>Map of upper northern half of inner Galway Bay, Ireland, (<a href="#f2-sensors-09-05825" class="html-fig">Figure 2</a>) indicating the locations of the sample stations (x symbols) where both the CP885 and the ECOshot digital cameras were applied.</p> Full article ">
<p>Scatter plot of <span class="html-italic">RGB</span> (<span class="html-italic">I<sub>tot</sub></span> = 400) values obtained with an ECOshot against obtained with a CP885, scaled to unity, derived from images of Galway Bay surface water (<span class="html-italic">r</span> = red, <span class="html-italic">g</span> = green and <span class="html-italic">b</span> = blue). The line indicates a one-to-one relation.</p> Full article ">
128 KiB  
Article
Evanescent Wave Fiber Optic Biosensor for Salmonella Detection in Food
by Angela M. Valadez, Carlos A. Lana, Shu-I Tu, Mark T. Morgan and Arun K. Bhunia
Sensors 2009, 9(7), 5810-5824; https://doi.org/10.3390/s90705810 - 21 Jul 2009
Cited by 76 | Viewed by 14199
Abstract
Salmonella enterica is a major food-borne pathogen of world-wide concern. Sensitive and rapid detection methods to assess product safety before retail distribution are highly desirable. Since Salmonella is most commonly associated with poultry products, an evanescent wave fiber-optic assay was developed to detect [...] Read more.
Salmonella enterica is a major food-borne pathogen of world-wide concern. Sensitive and rapid detection methods to assess product safety before retail distribution are highly desirable. Since Salmonella is most commonly associated with poultry products, an evanescent wave fiber-optic assay was developed to detect Salmonella in shell egg and chicken breast and data were compared with a time-resolved fluorescence (TRF) assay. Anti-Salmonella polyclonal antibody was immobilized onto the surface of an optical fiber using biotin-avidin interactions to capture Salmonella. Alexa Fluor 647-conjugated antibody (MAb 2F-11) was used as the reporter. Detection occurred when an evanescent wave from a laser (635 nm) excited the Alexa Fluor and the fluorescence was measured by a laser-spectrofluorometer at 710 nm. The biosensor was specific for Salmonella and the limit of detection was established to be 103 cfu/mL in pure culture and 104 cfu/mL with egg and chicken breast samples when spiked with 102 cfu/mL after 2–6 h of enrichment. The results indicate that the performance of the fiber-optic sensor is comparable to TRF, and can be completed in less than 8 h, providing an alternative to the current detection methods. Full article
(This article belongs to the Section Biosensors)
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<p>Sensitivity of the immunosensor using serial dilutions of <span class="html-italic">S</span>. Enteritidis cells suspended in phosphate buffered saline (PBS). Controls are devoid of bacteria.</p> Full article ">
<p>Fiber-optic signal recognition of <span class="html-italic">Salmonella</span> Enteritidis in a mixed bacterial culture. In mixture I, <span class="html-italic">S.</span> Enteritidis was used at 1 × 10<sup>5</sup> cfu/mL while <span class="html-italic">Enterococcus faecalis</span> and <span class="html-italic">Pseudomonas aeruginosa</span> at 1 × 10<sup>6</sup> cfu/mL each. In mixture II, <span class="html-italic">S.</span> Enteritidis was used at 1 × 10<sup>5</sup> cfu/mL while <span class="html-italic">Proteus vulgaris</span> and <span class="html-italic">Carnobacterium gallinarum</span> at 1 × 10<sup>6</sup> cfu/mL each.</p> Full article ">
<p>Sensitivity of immunomagnetic bead time-resolved immunofluorescence (IMB-TRF) for detection of <span class="html-italic">Salmonella</span> Enteritidis phage types (PT).</p> Full article ">
<p>Selectivity tests of immunomagnetic bead time-resolved immunofluorescence (IMB-TRF). Values are from an average of two wells each tested with two different concentrations of cells.</p> Full article ">
<p>Detection of <span class="html-italic">S.</span> Enteritidis grown in egg (A) and chicken breast (B) at 2 h intervals by using the fiber-optic biosensor. Bars represent the signals (left Y axis) from the biosensor. Line (growth curve) represents concentrations (right Y axis) of <span class="html-italic">S</span>. Enteritidis grown in egg suspended in TSB (A) and chicken breast (25 g in 225 mL TSB) (B). A total of 5-eggs were used for this experiment, one egg was used for each time point.</p> Full article ">
<p>Detection of <span class="html-italic">Salmonella</span> Enteritidis spiked in egg and chicken by IMB-TRF. A total of 24 eggs were used for this experiment, four eggs for each time point.</p> Full article ">
718 KiB  
Review
Waveguide-Based Biosensors for Pathogen Detection
by Harshini Mukundan, Aaron S. Anderson, W. Kevin Grace, Karen M. Grace, Nile Hartman, Jennifer S. Martinez and Basil I. Swanson
Sensors 2009, 9(7), 5783-5809; https://doi.org/10.3390/s90705783 - 21 Jul 2009
Cited by 164 | Viewed by 22053
Abstract
Optical phenomena such as fluorescence, phosphorescence, polarization, interference and non-linearity have been extensively used for biosensing applications. Optical waveguides (both planar and fiber-optic) are comprised of a material with high permittivity/high refractive index surrounded on all sides by materials with lower refractive indices, [...] Read more.
Optical phenomena such as fluorescence, phosphorescence, polarization, interference and non-linearity have been extensively used for biosensing applications. Optical waveguides (both planar and fiber-optic) are comprised of a material with high permittivity/high refractive index surrounded on all sides by materials with lower refractive indices, such as a substrate and the media to be sensed. This arrangement allows coupled light to propagate through the high refractive index waveguide by total internal reflection and generates an electromagnetic wave—the evanescent field—whose amplitude decreases exponentially as the distance from the surface increases. Excitation of fluorophores within the evanescent wave allows for sensitive detection while minimizing background fluorescence from complex, “dirty” biological samples. In this review, we will describe the basic principles, advantages and disadvantages of planar optical waveguide-based biodetection technologies. This discussion will include already commercialized technologies (e.g., Corning’s EPIC® Ô, SRU Biosystems’ BIND™, Zeptosense®, etc.) and new technologies that are under research and development. We will also review differing assay approaches for the detection of various biomolecules, as well as the thin-film coatings that are often required for waveguide functionalization and effective detection. Finally, we will discuss reverse-symmetry waveguides, resonant waveguide grating sensors and metal-clad leaky waveguides as alternative signal transducers in optical biosensing. Full article
(This article belongs to the Special Issue Pathogen Sensors)
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<p>Waveguide cross-section illustrating zig-zag ray model for optical propagation.</p> Full article ">
<p>Grating coupler for efficient input/output.</p> Full article ">
<p>Physical Configuration for efficient input/output coupling.</p> Full article ">
<p>Electric field distribution for a low-contrast waveguide system.</p> Full article ">
<p>Electric field distribution of a high-contrast waveguide-system.</p> Full article ">
<p>Relative Detection sensitivity for a high contrast waveguide materials system.</p> Full article ">
<p>Chemistry of the Silane-based self-assembled monolayers used for waveguide functionalization (left) and a schematic representation of a waveguide-based sandwich immunoassay for biomarker detection used at LANL.</p> Full article ">
<p>Interferometer Response with exposure to water solutions containing <span class="html-italic">E. coli</span> O1:H57 at 3 × 10<sup>3</sup> cells/mL.</p> Full article ">
<p>Multichannel interferometer response with exposure to water solution containing <span class="html-italic">E. coli</span> O1: H57 at ∼ 10<sup>7</sup> cells/mL.</p> Full article ">
752 KiB  
Article
Potential of ILRIS3D Intensity Data for Planar Surfaces Segmentation
by Chi-Kuei Wang and Yao-Yu Lu
Sensors 2009, 9(7), 5770-5782; https://doi.org/10.3390/s90705770 - 20 Jul 2009
Cited by 6 | Viewed by 11454
Abstract
Intensity value based point cloud segmentation has received less attention because the intensity value of the terrestrial laser scanner is usually altered by receiving optics/hardware or the internal propriety software, which is unavailable to the end user. We offer a solution by assuming [...] Read more.
Intensity value based point cloud segmentation has received less attention because the intensity value of the terrestrial laser scanner is usually altered by receiving optics/hardware or the internal propriety software, which is unavailable to the end user. We offer a solution by assuming the terrestrial laser scanners are stable and the behavior of the intensity value can be characterized. Then, it is possible to use the intensity value for segmentation by observing its behavior, i.e., intensity value variation, pattern and presence of location of intensity values, etc. In this study, experiment results for characterizing the intensity data of planar surfaces collected by ILRIS3D, a terrestrial laser scanner, are reported. Two intensity formats, grey and raw, are employed by ILRIS3D. It is found from the experiment results that the grey intensity has less variation; hence it is preferable for point cloud segmentation. A warm-up time of approximate 1.5 hours is suggested for more stable intensity data. A segmentation method based on the visual cues of the intensity images sequence, which contains consecutive intensity images, is proposed in order to segment the 3D laser points of ILRIS3D. This method is unique to ILRIS3D data and does not require radiometric calibration. Full article
(This article belongs to the Special Issue LiDAR for 3D City Modeling)
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Graphical abstract

Graphical abstract
Full article ">
Full article ">
Full article ">
Full article ">
<p>(a) The homogeneous white wall, with the red rectangle denoting the scan area. (b) The flat concrete fence of yellow (surface I) and brown (surface II), (b) A scene including surfaces I – IV. Surface III is a small-grain decorated fence (dark grey); surface IV is a smooth concrete wall (light grey).</p> Full article ">
<p>Time series of five complete scans of the battery experiment. (a) mean of grey intensity, (b) mean of raw intensity, (c) standard deviation of grey intensity, and (d) standard deviation of raw intensity.</p> Full article ">
<p>Grey intensity images of 206 to 217 and 255 excerpted from the grey intensity image sequence of a homogeneous white wall [red rectangle in <a href="#f1-sensors-09-05770" class="html-fig">Figure 1(a)</a>] in Supplementary Material 1, which contains the complete grey intensity of 199–255.</p> Full article ">
<p>A concrete fence painted with two colors [cf. <a href="#f1-sensors-09-05770" class="html-fig">Figure 1(b)</a>]: (a)–(e) Grey intensity image of 210, 214, 217, 221, and 224, excerpted from the intensity image sequence in Supplementary Material 2, which contains the grey intensity from 187 to 255. The red rectangle denotes the linear discontinuity feature between the concentric circular patterns of surface I and II. See the text in Section 3.3 for the explanation of the red arrows. (f) Segmentation result using the visual cues of two distinct concentric circular patterns and a linear feature [denoted by the red rectangle in (a)] in the intensity image sequence in Supplementary Material 2. Red and yellow denote surfaces I and II, respectively, while blue represents the un-segmented 3D laser points.</p> Full article ">
<p>Results of four different surfaces [<a href="#f1-sensors-09-05770" class="html-fig">Figure 1(c)</a>]: (a) grey intensity image of 70 showing surfaces III and II, (b) grey intensity image of 77 showing surface IV, (c) grey intensity image of 92 showing surface III, (d) Segmentation results using the visual cues of the concentric circular patterns and linear features dividing each concentric circular pattern [red rectangles in (a)–(c); see the text in Section 3.3 for explanation] shown in the intensity image sequence in Supplementary Material 3. Cyan, yellow, red, and green denote surfaces I, II, III, and IV, respectively, while blue represents un-segmented 3D laser points. (e) The nadir view of the subset of point cloud excerpted from the black rectangle in (d). The red arrow indicates the boundary between surface I and III in (d).</p> Full article ">
519 KiB  
Review
Surface Generated Acoustic Wave Biosensors for the Detection of Pathogens: A Review
by María-Isabel Rocha-Gaso, Carmen March-Iborra, Ángel Montoya-Baides and Antonio Arnau-Vives
Sensors 2009, 9(7), 5740-5769; https://doi.org/10.3390/s90705740 - 20 Jul 2009
Cited by 212 | Viewed by 25518
Abstract
This review presents a deep insight into the Surface Generated Acoustic Wave (SGAW) technology for biosensing applications, based on more than 40 years of technological and scientific developments. In the last 20 years, SGAWs have been attracting the attention of the biochemical scientific [...] Read more.
This review presents a deep insight into the Surface Generated Acoustic Wave (SGAW) technology for biosensing applications, based on more than 40 years of technological and scientific developments. In the last 20 years, SGAWs have been attracting the attention of the biochemical scientific community, due to the fact that some of these devices - Shear Horizontal Surface Acoustic Wave (SH-SAW), Surface Transverse Wave (STW), Love Wave (LW), Flexural Plate Wave (FPW), Shear Horizontal Acoustic Plate Mode (SH-APM) and Layered Guided Acoustic Plate Mode (LG-APM) - have demonstrated a high sensitivity in the detection of biorelevant molecules in liquid media. In addition, complementary efforts to improve the sensing films have been done during these years. All these developments have been made with the aim of achieving, in a future, a highly sensitive, low cost, small size, multi-channel, portable, reliable and commercially established SGAW biosensor. A setup with these features could significantly contribute to future developments in the health, food and environmental industries. The second purpose of this work is to describe the state-of-the-art of SGAW biosensors for the detection of pathogens, being this topic an issue of extremely importance for the human health. Finally, the review discuses the commercial availability, trends and future challenges of the SGAW biosensors for such applications. Full article
(This article belongs to the Special Issue Pathogen Sensors)
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<p>a) Structure of a SGAW sensor. b) IDT configuration for SGAW.</p> Full article ">
<p>Interdigital Transducer (IDT) with period <span class="html-italic">p</span>, electrode width equal to space between electrodes and aperture A.</p> Full article ">
<p>Frequency response of an IDT (positive frequencies).</p> Full article ">
<p>a) Two IDTs SGAW configuration. b) Two-port SGAW delay line oscillator. The SGAW device provides a feedback path for the amplifier. For a stable oscillation the signal must return to its starting point having equal amplitude and being shifted in phase by an integral multiple of 2π radians [<a href="#b31-sensors-09-05740" class="html-bibr">31</a>].</p> Full article ">
<p>Scheme of a two-port SGAW resonator.</p> Full article ">
<p>Scheme of a one-port SGAW resonator.</p> Full article ">
<p>Dual-channel delay line configuration [<a href="#b46-sensors-09-05740" class="html-bibr">46</a>].</p> Full article ">
<p>(a) Oscillator circuit provides a single-frequency signal. (b)Vector voltmeter provides phase and amplitude. (c) Network analyzers are connected to one and two-port devices. M: matching network [<a href="#b29-sensors-09-05740" class="html-bibr">29</a>].</p> Full article ">
<p>Feedback system for an oscillator.</p> Full article ">
838 KiB  
Article
Adaptive Momentum-Based Motion Detection Approach and Its Application on Handoff in Wireless Networks
by Tein-Yaw Chung, Yung-Mu Chen and Chih-Hung Hsu
Sensors 2009, 9(7), 5715-5739; https://doi.org/10.3390/s90705715 - 17 Jul 2009
Cited by 9 | Viewed by 11292
Abstract
Positioning and tracking technologies can detect the location and the movement of mobile nodes (MNs), such as cellular phone, vehicular and mobile sensor, to predict potential handoffs. However, most motion detection mechanisms require additional hardware (e.g., GPS and directed antenna), costs (e.g., power [...] Read more.
Positioning and tracking technologies can detect the location and the movement of mobile nodes (MNs), such as cellular phone, vehicular and mobile sensor, to predict potential handoffs. However, most motion detection mechanisms require additional hardware (e.g., GPS and directed antenna), costs (e.g., power consumption and monetary cost) and supply systems (e.g., network fingerprint server). This paper proposes a Momentum of Received Signal Strength (MRSS) based motion detection method and its application on handoff. MRSS uses the exponentially weighted moving average filter with multiple moving average window size to analyze the received radio signal. With MRSS, an MN can predict its motion state and make a handoff trigger at the right time without any assistance from positioning systems. Moreover, a novel motion state dependent MRSS scheme called Dynamic MRSS (DMRSS) algorithm is proposed to adjust the motion detection sensitivity. In our simulation, the MRSSand DMRSS-based handoff algorithms can reduce the number of unnecessary handoffs up to 44% and save battery power up to 75%. Full article
(This article belongs to the Special Issue Motion Detectors)
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<p>The MRSS calculation.</p> Full article ">
<p>The detected user motion state of the MRSS method.</p> Full article ">
<p>The flow chart of DMRSS-based handoff algorithm.</p> Full article ">
<p>The mobility model and topology in simulations.</p> Full article ">
<p>The performance evalution of <span class="html-italic">α</span> and <span class="html-italic">k</span>.</p> Full article ">
<p>The effect of shadow deviation when <span class="html-italic">α</span> = 0.16, <span class="html-italic">k</span> = 32 in the WLAN environment.</p> Full article ">
<p>The effect of velocity in the WLAN environment.</p> Full article ">
<p>The effect of approaching movement in the WLAN environment.</p> Full article ">
<p>The effect of approaching movement in the Mobile WiMAX environment.</p> Full article ">
567 KiB  
Article
Antioxidant Activity and Total Phenolic and Flavonoid Contents of Hieracium pilosella L. Extracts
by Ljiljana Stanojević, Mihajlo Stanković, Vesna Nikolić, Ljubiša Nikolić, Dušica Ristić, Jasna Čanadanovic-Brunet and Vesna Tumbas
Sensors 2009, 9(7), 5702-5714; https://doi.org/10.3390/s90705702 - 16 Jul 2009
Cited by 133 | Viewed by 19113
Abstract
The antioxidant activity ofwater, ethanol and methanol Hieracium pilosella L.extracts is reported. The antioxidative activity was tested by spectrophotometrically measuring their ability to scavenge a stable DPPH· free radical and a reactive hydroxyl radical trapped by DMPO during the Fenton reaction, using [...] Read more.
The antioxidant activity ofwater, ethanol and methanol Hieracium pilosella L.extracts is reported. The antioxidative activity was tested by spectrophotometrically measuring their ability to scavenge a stable DPPH· free radical and a reactive hydroxyl radical trapped by DMPO during the Fenton reaction, using the ESR spectroscopy. Total phenolic content and total flavonoid content were evaluated according to the Folin-Ciocalteu procedure, and a colorimetric method, respectively. A HPLC method was used for identification of some phenolic compounds (chlorogenic acid, apigenin-7-O-glucoside and umbelliferone). The antioxidant activity of the investigated extracts slightly differs depending on the solvent used. The concentration of 0.30 mg/mL of water, ethanol and methanol extract is less effective in scavenging hydroxyl radicals (56.35, 58.73 and 54.35%, respectively) in comparison with the DPPH· radical scavenging activity (around 95% for all extracts). The high contents of total phenolic compounds (239.59–244.16 mg GAE/g of dry extract) and total flavonoids (79.13–82.18 mg RE/g of dry extract) indicated that these compounds contribute to the antioxidative activity. Full article
(This article belongs to the Section Biosensors)
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<p>ESR spectra of DMPO-OH spin adducts: with no addition of extracts (blank) (a); the same as blank but with 0.3 mg/mL DMF solution of aqueous (b), ethanolic (c) and methanolic extract (d).</p> Full article ">
<p>Antioxidant activity of different concentrations of aqueous, ethanolic and methanolic extracts of <span class="html-italic">Hieracium pilosella</span> L. on hydroxyl radical.</p> Full article ">
<p>The antioxidant activity of different concentrations of aqueous (a), ethanolic (b) and methanolic (c) extract of <span class="html-italic">Hieracium pilosella</span> L. on DPPH radicals; (–□–) without incubation; (–○–) 20 min of incubation.</p> Full article ">
2652 KiB  
Article
Object-Based Integration of Photogrammetric and LiDAR Data for Automated Generation of Complex Polyhedral Building Models
by Changjae Kim and Ayman Habib
Sensors 2009, 9(7), 5679-5701; https://doi.org/10.3390/s90705679 - 15 Jul 2009
Cited by 43 | Viewed by 8712
Abstract
This research is concerned with a methodology for automated generation of polyhedral building models for complex structures, whose rooftops are bounded by straight lines. The process starts by utilizing LiDAR data for building hypothesis generation and derivation of individual planar patches constituting building [...] Read more.
This research is concerned with a methodology for automated generation of polyhedral building models for complex structures, whose rooftops are bounded by straight lines. The process starts by utilizing LiDAR data for building hypothesis generation and derivation of individual planar patches constituting building rooftops. Initial boundaries of these patches are then refined through the integration of LiDAR and photogrammetric data and hierarchical processing of the planar patches. Building models for complex structures are finally produced using the refined boundaries. The performance of the developed methodology is evaluated through qualitative and quantitative analysis of the generated building models from real data. Full article
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<p>A flow diagram of the proposed DBM generation procedure.</p> Full article ">
<p>A dataset with complex and connected structures: (a) aerial photo; (b) LiDAR data; (c) classified terrain and off-terrain points; (d) generated building hypotheses; (e) building primitives; and (f) initial boundaries of the building primitives.</p> Full article ">
<p>(a) Initial boundaries of the primitives and (b) the precise boundary segment through the intersection of two neighbouring primitives and the remaining initial boundary points.</p> Full article ">
<p>Concept of warped imagery.</p> Full article ">
<p>(a) Initial boundary of the building primitive and a buffer surrounding the boundary; straight line segments detected in the (b) left and (c) right warped images; (d) matched 3D lines; (e) filtered matched 3D lines; (f) established reference lines; (g) grouped matched 3D lines; (h) established precise boundary segments; (i) closed-polygon generated from the established precise boundary segments; and (j) generated DBM wire frame.</p> Full article ">
<p>Matching straight line segments in warped images using (a) angle and normal distance constraints and (b) the presence of overlap and 3D matched lines.</p> Full article ">
<p>(a) A matched 3D line that follows the trend of the initial boundary of the building primitive and (b) one that does not.</p> Full article ">
<p>(a) Configuration of the regions around the matched 3D line segments in one group and regions on either side of the line segments (b) L1, (c) L2, and (d) L3.</p> Full article ">
<p>Different types of occlusions: caused by (a) a higher building primitive sharing a vertical wall with the one in question; (b) a higher and non-adjacent building primitive; and (c) trees closely located to the primitive in question.</p> Full article ">
274 KiB  
Article
A Survey of Geosensor Networks: Advances in Dynamic Environmental Monitoring
by Silvia Nittel
Sensors 2009, 9(7), 5664-5678; https://doi.org/10.3390/s90705664 - 15 Jul 2009
Cited by 91 | Viewed by 14154
Abstract
In the recent decade, several technology trends have influenced the field of geosciences in significant ways. The first trend is the more readily available technology of ubiquitous wireless communication networks and progress in the development of low-power, short-range radio-based communication networks, the miniaturization [...] Read more.
In the recent decade, several technology trends have influenced the field of geosciences in significant ways. The first trend is the more readily available technology of ubiquitous wireless communication networks and progress in the development of low-power, short-range radio-based communication networks, the miniaturization of computing and storage platforms as well as the development of novel microsensors and sensor materials. All three trends have changed the type of dynamic environmental phenomena that can be detected, monitored and reacted to. Another important aspect is the real-time data delivery of novel platforms today. In this paper, I will survey the field of geosensor networks, and mainly focus on the technology of small-scale geosensor networks, example applications and their feasibility and lessons learnt as well as the current research questions posed by using this technology today. Furthermore, my objective is to investigate how this technology can be embedded in the current landscape of intelligent sensor platforms in the geosciences and identify its place and purpose. Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)
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<p>Computing platform overview.</p> Full article ">
<p>Tracking continuous phenomena over space and time using geosensor networks.</p> Full article ">
637 KiB  
Article
Real-Time Ozone Detection Based on a Microfabricated Quartz Crystal Tuning Fork Sensor
by Rui Wang, Francis Tsow, Xuezhi Zhang, Jhih-Hong Peng, Erica S. Forzani, Yongsheng Chen, John C. Crittenden, Hugo Destaillats and Nongjian Tao
Sensors 2009, 9(7), 5655-5663; https://doi.org/10.3390/s90705655 - 15 Jul 2009
Cited by 22 | Viewed by 10927
Abstract
A chemical sensor for ozone based on an array of microfabricated tuning forks is described. The tuning forks are highly sensitive and stable, with low power consumption and cost. The selective detection is based on the specific reaction of the polymer with ozone. [...] Read more.
A chemical sensor for ozone based on an array of microfabricated tuning forks is described. The tuning forks are highly sensitive and stable, with low power consumption and cost. The selective detection is based on the specific reaction of the polymer with ozone. With a mass detection limit of ~2 pg/mm2 and response time of 1 second, the sensor coated with a polymer sensing material can detect ppb-level ozone in air. The sensor is integrated into a miniaturized wearable device containing a detection circuit, filtration, battery and wireless communication chip, which is ideal for personal and microenvironmental chemical exposure monitoring. Full article
(This article belongs to the Special Issue Gas Sensors 2009)
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<p>A) Schematic of a QTF sensor array; B) Record of the noise level of the circuit built for the QTF array; C) QTF array with Teflon housing; D) Individual QTF.</p> Full article ">
<p>Response of a 4.5 μg polybutadiene coated tuning fork towards alternate low ozone concentration and ozone-free air exposures (alternate time segments are separated in the plot using blue lines). Low ozone concentrations were generated with the UV source, and ozone-free air samples were generated with air samples passing through an ozone scrubber. The exposure was managed through a switching valve, and the actual concentration of ozone was monitored on-line at the outlet of the QTF cell. The slope of the frequency response increased when the sensor was exposed to ozone, and a positive slope (−Δf/Δt) change is indicative of increasing ozone concentrations levels. The response was wirelessly assessed from the device by using a Bluetooth®-enabled laptop.</p> Full article ">
<p>Calibration plots of the response of different tuning fork sensors vs ozone concentration. The inserted figure is the tuning fork response obtained at low ozone concentration range. The response of the sensors (corrected slope) is the frequency slope obtained at a given ozone concentration corrected by subtraction of the frequency slope obtained in presence of ozone-free exposure. The corrected frequency slope is proportional to ozone concentration. A least square linear fitting of the response gives a correlation factor of 3.0 × 10<sup>−6</sup> ± 1.7 × 10<sup>−7</sup> Hz<sup>2</sup>/ppbV with 5.6% error, indicating the sensitivity of the response is well-maintained across different ozone QTF sensors, and concentration ranges.</p> Full article ">
<p>Comparison of ozone level readings obtained from QTF sensors using a calibration plot and function as shown in <a href="#f3-sensors-09-05655" class="html-fig">Figure 3</a>, and readings from a commercial ozone monitor of indoor air samples and artificially ozone spiked samples. The agreement between both methods is 86 %, indicating the ozone QTF sensors have relatively good accuracy. The regression line is again fitted with least square method.</p> Full article ">
<p>Ozone measurements performed with a single QTF ozone sensor with ozone exposure events equivalent to increasing and decreasing ozone levels observed along a day.</p> Full article ">
<p>FTIR spectra of a polybutadiene film before and after exposure to 100 ppbV ozone during 2 hours.</p> Full article ">
167 KiB  
Article
High Temperature Long Period Grating Thermo-Mechanically Written
by Jose Miguel Lazaro, Antonio Quintela and Jose Miguel Lopez-Higuera
Sensors 2009, 9(7), 5649-5654; https://doi.org/10.3390/s90705649 - 15 Jul 2009
Cited by 4 | Viewed by 10447
Abstract
An optical fiber transducer able to work in high temperature environments is experimentally demonstrated in the laboratory. It is based on a permanent long period grating (LPG) written using a new technique based on a thermo-mechanical approach. Device precision was experimentally checked by [...] Read more.
An optical fiber transducer able to work in high temperature environments is experimentally demonstrated in the laboratory. It is based on a permanent long period grating (LPG) written using a new technique based on a thermo-mechanical approach. Device precision was experimentally checked by means of repetitive thermal cycles between 25 and 950 ºC. In addition device stability was assured by maintaining the temperature in steady state at 800 ºC during 23 hours. Full article
(This article belongs to the Section Chemical Sensors)
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<p>Coupling wavelength as a function of period for different cladding modes in a LPG on a standard telecommunication fiber. (It has been obtained from the simulation of the core and cladding effective indexes).</p> Full article ">
<p>Illustration of the experimental set-up used to write thermo-mechanically LPGs.</p> Full article ">
<p>Temporal LPG spectral response induced by mechanical pressure (red) and permanent LPG spectral response with the thermo-mechanical technique (blue).</p> Full article ">
<p>Evolution of the peak wavelength as a function of the temperature. Increasing (pink) and decreasing (blue) the temperature.</p> Full article ">
444 KiB  
Article
MEMS Biomimetic Acoustic Pressure Gradient Sensitive Structure for Sound Source Localization
by Peng An, Weizheng Yuan and Sen Ren
Sensors 2009, 9(7), 5637-5648; https://doi.org/10.3390/s90705637 - 15 Jul 2009
Cited by 11 | Viewed by 10290
Abstract
The parasitoid fly Ormia ochracea shows an astonishing localization ability with its tiny hearing organ. A novel MEMS biomimetic acoustic pressure gradient sensitive structure was designed and fabricated by mimicking the mechanically coupled tympana of the fly. Firstly, the analytic representation formulas of [...] Read more.
The parasitoid fly Ormia ochracea shows an astonishing localization ability with its tiny hearing organ. A novel MEMS biomimetic acoustic pressure gradient sensitive structure was designed and fabricated by mimicking the mechanically coupled tympana of the fly. Firstly, the analytic representation formulas of the resultant force and resultant moment of the incoming plane wave acting on the structure were derived. After that, structure modal analysis was performed and the results show that the structure has out-of-phase and in-phase vibration modes, and the corresponding eigenfrequency is decided by the stiffness of vertical torsional beam and horizontal beam respectively. Acoustic-structural coupled analysis was performed and the results show that phase difference and amplitude difference between the responses of the two square diaphragms of the sensitive structure are effectively enlarged through mechanical coupling beam. The phase difference and amplitude difference increase with increasing incident angle and can be used to distinguish the direction of sound arrival. At last, the fabrication process and results of the device is also presented. Full article
(This article belongs to the Special Issue Selected Papers from the 1st International Conference of the Chinese Society of Micro/Nano Technology)
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<p>Schematic diagram of acoustic array with two elements.</p> Full article ">
<p>Hearing organ of parasitoid fly <span class="html-italic">ormia ochracea</span> and its mechanical model.</p> Full article ">
<p>Schematic diagram of the sensitive structure.</p> Full article ">
<p>Resultant force (a) and resultant moment (b) versus incident angle.</p> Full article ">
<p>First (a) and second (b) mode shapes of the sensitive structure.</p> Full article ">
<p>Length of vertical beam versus first and second eigenfrequency.</p> Full article ">
<p>Phase difference (a) and amplitude of center point (b) versus the thickness of vertical beam.</p> Full article ">
<p>Phase difference (a) and amplitude difference (b) versus wave frequency and incident angle.</p> Full article ">
<p>Schematic diagram of the fabrication process.</p> Full article ">
1144 KiB  
Review
DNA Sensors with Diamond as a Promising Alternative Transducer Material
by Veronique Vermeeren, Sylvia Wenmackers, Patrick Wagner and Luc Michiels
Sensors 2009, 9(7), 5600-5636; https://doi.org/10.3390/s90705600 - 14 Jul 2009
Cited by 47 | Viewed by 13466
Abstract
Bio-electronics is a scientific field coupling the achievements in biology with electronics to obtain higher sensitivity, specificity and speed. Biosensors have played a pivotal role, and many have become established in the clinical and scientific world. They need to be sensitive, specific, fast [...] Read more.
Bio-electronics is a scientific field coupling the achievements in biology with electronics to obtain higher sensitivity, specificity and speed. Biosensors have played a pivotal role, and many have become established in the clinical and scientific world. They need to be sensitive, specific, fast and cheap. Electrochemical biosensors are most frequently cited in literature, often in the context of DNA sensing and mutation analysis. However, many popular electrochemical transduction materials, such as silicon, are susceptible to hydrolysis, leading to loss of bioreceptor molecules from the surface. Hence, increased attention has been shifted towards diamond, which surpasses silicon on many levels. Full article
(This article belongs to the Special Issue DNA Sensors and Biosensors)
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<p>Schematic diagram of the lattice structure of diamond, showing the tetrahedral orientation of each C atom.</p> Full article ">
<p>SEM image of a 600 μm thick freestanding homo-epitaxial SCD film grown at a 10% CH<sub>4</sub>/H<sub>2</sub> ratio removed from the substrate by laser cutting <span class="html-italic">(IMEC, Belgium, Wide Band Gap Materials)</span>.</p> Full article ">
<p>SEM images of a MCD film on Si. In a topographical view, the μm-sized grains on the surface are clearly visible (left panel). The cross-section shows the columnar growth nature of these grains (right panel) <span class="html-italic">(University of Bristol, UK, CVD Diamond Film Group)</span>.</p> Full article ">
<p>SEM images of a NCD film on Si. In a topographical view, the nm-sized grains on the surface are clearly visible (left panel). The cross-section shows the thinner diamond layer on top of the Si (right panel) <span class="html-italic">(Institute for Materials Research, Belgium).</span></p> Full article ">
<p>SEM images of a UNCD film on Si. In a topographical view, the even smaller grains on the surface are clearly visible (left panel). The cross-section is shown in the right panel <span class="html-italic">(Institute for Materials Research, Belgium).</span></p> Full article ">
<p>Cyclic voltammograms comparing various electrode materials. The graphs are shifted vertically for comparison. Two B-doped PCD films, B:PCD(NRL) containing 5 × 10<sup>19</sup> B·cm<sup>−3</sup> and B:PCD(USU) containing 5 × 10<sup>20</sup> B·cm<sup>−3</sup> [<a href="#b20-sensors-09-05600" class="html-bibr">20</a>], are compared with a B-doped SCD film, B:(H)SCD, containing 3 × 10<sup>20</sup> B·cm<sup>−3</sup>, and with an undoped SCD film, (H)SCD. Voltammograms of alternative electrodes such as Au, Pt and glassy carbon are also added for comparison [<a href="#b8-sensors-09-05600" class="html-bibr">8</a>].</p> Full article ">
<p>Energies of the valence and conduction band edges of several conventional semiconductors, including H-terminated and as-grown diamond relative to the vacuum level, E<sub>VAC</sub>. The lower dashed line represents the chemical potential, μ, for electrons in an acidic electrolyte under the conditions of a standard hydrogen electrode [<a href="#b21-sensors-09-05600" class="html-bibr">21</a>].</p> Full article ">
<p>Schematic diagram of the diamond/electrolyte interface. Under non-equilibrated conditions (left panel), electrons from the valence band of the diamond tunnel into empty electronic states of the electrolyte. This continues until the E<sub>F</sub> in the diamond and μ of the electrolyte align and reach thermodynamic equilibrium (right panel) [<a href="#b8-sensors-09-05600" class="html-bibr">8</a>].</p> Full article ">
<p>E<sub>F</sub> and μ alignment at the diamond/electrolyte interface at pH 0 and pH 14 [<a href="#b8-sensors-09-05600" class="html-bibr">8</a>].</p> Full article ">
233 KiB  
Article
Quantitative Analysis of Nucleic Acid Hybridization on Magnetic Particles and Quantum Dot-Based Probes
by Sun Hee Lim, Felix Bestvater, Philippe Buchy, Sek Mardy and Alexey Dan Chin Yu
Sensors 2009, 9(7), 5590-5599; https://doi.org/10.3390/s90705590 - 14 Jul 2009
Cited by 19 | Viewed by 13682
Abstract
In the present study we describe sandwich design hybridization probes consisting of magnetic particles (MP) and quantum dots (QD) with target DNA, and their application in the detection of avian influenza virus (H5N1) sequences. Hybridization of 25-, 40-, and 100-mer target DNA with [...] Read more.
In the present study we describe sandwich design hybridization probes consisting of magnetic particles (MP) and quantum dots (QD) with target DNA, and their application in the detection of avian influenza virus (H5N1) sequences. Hybridization of 25-, 40-, and 100-mer target DNA with both probes was analyzed and quantified by flow cytometry and fluorescence microscopy on the scale of single particles. The following steps were used in the assay: (i) target selection by MP probes and (ii) target detection by QD probes. Hybridization efficiency between MP conjugated probes and target DNA hybrids was controlled by a fluorescent dye specific for nucleic acids. Fluorescence was detected by flow cytometry to distinguish differences in oligo sequences as short as 25-mer capturing in target DNA and by gel-electrophoresis in the case of QD probes. This report shows that effective manipulation and control of micro- and nanoparticles in hybridization assays is possible. Full article
(This article belongs to the Section Biosensors)
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<p>Schematic procedure of the MP and QD-based hybridization assays.</p> Full article ">
<p>Oligo binding on the surface of MPs and hybridization of the MP probes and target strand. A. Different quantities of oligos with varying lengths of spacers from 0 to 54 chains were conjugated to MPs. After conjugation, they were stained with OliGreen and analyzed by flow cytometry. B. Hybridization of 100-mer target DNA and MP probes. In analogy to A, PicoGreen fluorescence was measured by flow cytometry and plotted as a function of target strand amount.</p> Full article ">
<p>Mobility shift assay of QD probes and DNA hybridization. M: 100 bp ladder, 1: biotinylated 25-mer oligo, 2: QD<sub>605</sub> streptavidin, 3: QD<sub>605</sub> streptavidin/oligo, 4: 100-mer target strand, 5: QD<sub>605</sub> streptavidin/oligo/100-mer target, 6: Non-complementary 100-mer, 7: QD<sub>605</sub> streptavidin/oligo/non-complementary 100-mer.</p> Full article ">
<p>A. Fluorescence images of MPs after hybridization with target DNA of varying length (25-, 40-, 100-mer) and QD probes. B. The hybridization complexes were characterized and quantified by fluorescence microscopy (upper panel) and flow cytometry (bottom panel). Fluorescence intensity is plotted as a function of concentration of the target DNA.</p> Full article ">
191 KiB  
Article
Variation of Cholinesterase-Based Biosensor Sensitivity to Inhibition by Organophosphate Due To Ionizing Radiation
by Miroslav Pohanka and Miroslav Koch
Sensors 2009, 9(7), 5580-5589; https://doi.org/10.3390/s90705580 - 14 Jul 2009
Cited by 1 | Viewed by 9414
Abstract
A cholinesterase based biosensor was constructed in order to assess the effects of ionizing radiation on exposed AChE. Although the primary objective of the experiment was to investigate the effect of ionizing radiation on the activity of the biosensor, no changes in cholinesterase [...] Read more.
A cholinesterase based biosensor was constructed in order to assess the effects of ionizing radiation on exposed AChE. Although the primary objective of the experiment was to investigate the effect of ionizing radiation on the activity of the biosensor, no changes in cholinesterase activity were observed. Current provided by oxidation of thiocholine previously created from acetylthiocholine by enzyme catalyzed reaction was in a range 395–455 nA. No significant influence of radiation on AChE activity was found, despite the current variation. However, a surprising phenomenon was observed when a model organophosphate paraoxon was assayed. Irradiated biosensors seem to be more susceptible to the inhibitory effects of paraoxon. Control biosensors provided a 94 ± 5 nA current after exposure to 1 ppm paraoxon. The biosensors irradiated by a 5 kGy radiation dose and exposed to paraoxon provided a current of 49 ± 6 nA. Irradiation by doses ranging from 5 mGy to 100 kGy were investigated and the mentioned effect was confirmed at doses above 50 Gy. After the first promising experiments, biosensors irradiated by 5 kGy were used for calibration on paraoxon and compared with the control biosensors. Limits of detection 2.5 and 3.8 ppb were achieved for irradiated and non-irradiated biosensors respectively. The overall impact of this effect is discussed. Full article
(This article belongs to the Special Issue Tissue, Cell and Molecular Bioelectrochemistry - New Trends and Approaches)
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<p>The figure depicts variation of AChE activity (as current) in biosensors due to ionizing radiation. The blue columns indicate current provided by biosensors without any inhibition. The red columns represent current provided by biosensors after exposition to paraoxon 1 ppm. Error bars indicate standard deviation (n = 5). Asterisks indicate significant difference against control at probability level P = 0.05 (ANOVA with Scheffe test).</p> Full article ">
<p>The figure depicts calibration curve provided by biosensors with AChE exposed to paraoxon–ethyl solution. The red curve was achieved by performance of biosensors previously stimulated to dose of ionizing radiation 5 kGy. The black curve represents assay of paraoxon by biosensors without any exposition to radiation. Points at brackets were achieved by assay of blank (no paraoxon). Error bars indicate standard deviation (n = 5).</p> Full article ">
<p>Principle of electrochemical evaluation AChE activity.</p> Full article ">
656 KiB  
Article
An Improved Cloud Classification Algorithm for China’s FY-2C Multi-Channel Images Using Artificial Neural Network
by Yu Liu, Jun Xia, Chun-Xiang Shi and Yang Hong
Sensors 2009, 9(7), 5558-5579; https://doi.org/10.3390/s90705558 - 14 Jul 2009
Cited by 67 | Viewed by 14725
Abstract
The crowning objective of this research was to identify a better cloud classification method to upgrade the current window-based clustering algorithm used operationally for China’s first operational geostationary meteorological satellite FengYun-2C (FY-2C) data. First, the capabilities of six widely-used Artificial Neural Network (ANN) [...] Read more.
The crowning objective of this research was to identify a better cloud classification method to upgrade the current window-based clustering algorithm used operationally for China’s first operational geostationary meteorological satellite FengYun-2C (FY-2C) data. First, the capabilities of six widely-used Artificial Neural Network (ANN) methods are analyzed, together with the comparison of two other methods: Principal Component Analysis (PCA) and a Support Vector Machine (SVM), using 2864 cloud samples manually collected by meteorologists in June, July, and August in 2007 from three FY-2C channel (IR1, 10.3-11.3 μm; IR2, 11.5-12.5 μm and WV 6.3-7.6 μm) imagery. The result shows that: (1) ANN approaches, in general, outperformed the PCA and the SVM given sufficient training samples and (2) among the six ANN networks, higher cloud classification accuracy was obtained with the Self-Organizing Map (SOM) and Probabilistic Neural Network (PNN). Second, to compare the ANN methods to the present FY-2C operational algorithm, this study implemented SOM, one of the best ANN network identified from this study, as an automated cloud classification system for the FY-2C multi-channel data. It shows that SOM method has improved the results greatly not only in pixel-level accuracy but also in cloud patch-level classification by more accurately identifying cloud types such as cumulonimbus, cirrus and clouds in high latitude. Findings of this study suggest that the ANN-based classifiers, in particular the SOM, can be potentially used as an improved Automated Cloud Classification Algorithm to upgrade the current window-based clustering method for the FY-2C operational products. Full article
(This article belongs to the Special Issue Neural Networks and Sensors)
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<p>The frequency distribution of features of FY-2C cloud samples.</p> Full article ">
<p>Configuration for the cloud classification: on the lefts are the input satellite images; at the middle are features extracted by GLCM and configuration of classifier; and on the rights are the output cloud classification results. Note white circles on the left are input neurons, and in the right are output ones. Black circles are neurons in hidden layer. Lines around circles show the data flow.</p> Full article ">
<p>Schematic diagram of eight cloud classifiers: in general the left layer is input layer; the right layer is output layer; and the middle ones are hidden layers. Note that the white circles in the left are input neurons, and in the right are output ones. Black circles are neurons in hidden layer. Lines around circles and arrows between layers show the data flow between neuron and layers respectively. Curves in circles show the transfer function. The linear sum, sigmoid function and Gaussian function are three often used functions. (A) Back Propagation (BP): Its connections can jump over one or more layers. (B) Modular Neural Networks (MNN): It uses several parallel MLPs, and then recombines the results. (C) Jordan-Elman network: It extends the multilayer perceptron with context units, which are processing elements (PEs) that remember past activity. (D) Probabilistic Neural Network (PNN): It uses Gaussian transfer functions and all the weights can be calculated analytically. (E) Self-Organizing Map (SOM): It transforms the input of arbitrary dimension into a one or two dimensional discrete map subject to a topological constraint. (F) Co-Active Neuro-Fuzzy Inference System (CANFIS): It integrates adaptable fuzzy inputs with a modular neural network to rapidly and accurately approximate complex functions. (G) Support Vector Machine (SVM): It uses the kernel Adatron to change inputs to a high-dimensional feature space, and then optimally separates data into their respective classes by isolating those inputs which fall close to the data boundaries. (H) Principal Component Analysis (PCA): It is an unsupervised linear procedure that finds a set of uncorrelated features, principal components, from the input.</p> Full article ">
<p>The accuracy rate of the eight cloud classifiers for the test data.</p> Full article ">
<p>Location of cases: 6X (6A, 6B,6C) is the location of case A, B, C in high latitude (<a href="#f6-sensors-09-05558" class="html-fig">Figure 6</a>); 7X (7A, 7B,7C) is the location of case A, B, C of Cumulonimbus (<a href="#f7-sensors-09-05558" class="html-fig">Figure 7</a>); and 8X (8A, 8B, 8C) is the location of case A, B, C of cirrus (<a href="#f8-sensors-09-05558" class="html-fig">Figure 8</a>).</p> Full article ">
<p>(A) The first line (A1, A2, A3) are high latitude cases at 07: 00 UTC (daytime); (B) The second line (B1, B2, B3) are high latitude cases at 15: 00 UTC (night); (C) the third line (C1, C2, C3) are high latitude cases at 23: 00 UTC (twilight); The first column (A1, B1, C1) are false RGB composite of Tbb of IR1, IR2 and WV; The second column (A2, B2, C2) are cloud classification results of ANN; The third column (A3, B3, C3) are results of FY-2C operational products.</p> Full article ">
<p>(A) The first line (A1, A2, A3) are cumulonimbus cases at 07: 00 UTC (daytime); (B) The second line (B1, B2, B3) are cumulonimbus(Cb) cases at 15: 00 UTC (night); (C) the third line (C1, C2, C3) are cumulonimbus(Cb) cases at 23: 00 UTC (twilight); The first column (A1, B1, C1) are pseudo-color composite map of Tbb of IR1, IR2 and WV; The second column (A2, B2, C2) are cloud classification results of ANN; The third column (A3, B3, C3) are results of FY-2C operational products.</p> Full article ">
<p>(A) The first line (A1, A2, A3) are cirrus at 07: 00 UTC(daytime); (B) The second line (B1, B2, B3) are cirrus cases at 15: 00 UTC (night); (C) the third line (C1, C2, C3) are cirrus cases at 23: 00 UTC (twilight); The first column (A1, B1, C1) are pseudo-color composite map of Tbb of IR1, IR2 and WV; The second column (A2, B2, C2) are cloud classification results of ANN; The third column (A3, B3, C3) are results of the FY-2C operational product.</p> Full article ">
490 KiB  
Review
Recent Development of Nano-Materials Used in DNA Biosensors
by Kai Xu, Junran Huang, Zunzhong Ye, Yibin Ying and Yanbin Li
Sensors 2009, 9(7), 5534-5557; https://doi.org/10.3390/s90705534 - 14 Jul 2009
Cited by 132 | Viewed by 17276
Abstract
As knowledge of the structure and function of nucleic acid molecules has increased, sequence-specific DNA detection has gained increased importance. DNA biosensors based on nucleic acid hybridization have been actively developed because of their specificity, speed, portability, and low cost. Recently, there has [...] Read more.
As knowledge of the structure and function of nucleic acid molecules has increased, sequence-specific DNA detection has gained increased importance. DNA biosensors based on nucleic acid hybridization have been actively developed because of their specificity, speed, portability, and low cost. Recently, there has been considerable interest in using nano-materials for DNA biosensors. Because of their high surface-to-volume ratios and excellent biological compatibilities, nano-materials could be used to increase the amount of DNA immobilization; moreover, DNA bound to nano-materials can maintain its biological activity. Alternatively, signal amplification by labeling a targeted analyte with nano-materials has also been reported for DNA biosensors in many papers. This review summarizes the applications of various nano-materials for DNA biosensors during past five years. We found that nano-materials of small sizes were advantageous as substrates for DNA attachment or as labels for signal amplification; and use of two or more types of nano-materials in the biosensors could improve their overall quality and to overcome the deficiencies of the individual nano-components. Most current DNA biosensors require the use of polymerase chain reaction (PCR) in their protocols. However, further development of nano-materials with smaller size and/or with improved biological and chemical properties would substantially enhance the accuracy, selectivity and sensitivity of DNA biosensors. Thus, DNA biosensors without PCR amplification may become a reality in the foreseeable future. Full article
(This article belongs to the Section Biosensors)
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<p>Schematic representation of nanoparticles as substrates for DNA attachment.</p> Full article ">
<p>Schematic representation of CNTs as substrates for DNA attachment.</p> Full article ">
<p>Schematic representation of nanoparticles as signal amplifiers for hybridization.</p> Full article ">
<p>Schematic representation of nanotubes as signal amplifiers for hybridization.</p> Full article ">
1021 KiB  
Article
An Algorithm for Cold Patch Detection in the Sea off Northeast Taiwan Using Multi-Sensor Data
by Yu-Hsin Cheng, Chung-Ru Ho, Zhe-Wen Zheng, Yung-Hsiang Lee and Nan-Jung Kuo
Sensors 2009, 9(7), 5521-5533; https://doi.org/10.3390/s90705521 - 13 Jul 2009
Cited by 18 | Viewed by 10209
Abstract
Multi-sensor data from different satellites are used to identify an upwelling area in the sea off northeast Taiwan. Sea surface temperature (SST) data derived from infrared and microwave, as well as sea surface height anomaly (SSHA) data derived from satellite altimeters are used [...] Read more.
Multi-sensor data from different satellites are used to identify an upwelling area in the sea off northeast Taiwan. Sea surface temperature (SST) data derived from infrared and microwave, as well as sea surface height anomaly (SSHA) data derived from satellite altimeters are used for this study. An integration filtering algorithm based on SST data is developed for detecting the cold patch induced by the upwelling. The center of the cold patch is identified by the maximum negative deviation relative to the spatial mean of a SST image within the study area and its climatological mean of each pixel. The boundary of the cold patch is found by the largest SST gradient. The along track SSHA data derived from satellite altimeters are then used to verify the detected cold patch. Applying the detecting algorithm, spatial and temporal characteristics and variations of the cold patch are revealed. The cold patch has an average area of 1.92 ´ 104 km2. Its occurrence frequencies are high from June to October and reach a peak in July. The mean SST of the cold patch is 23.8 °C. In addition to the annual and the intraseasonal fluctuation with main peak centered at 60 days, the cold patch also has a variation period of about 4.7 years in the interannual timescale. This implies that the Kuroshio variations and long-term and large scale processes playing roles in modifying the cold patch occurrence frequency. Full article
(This article belongs to the Special Issue Sensor Algorithms)
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<p>MODIS SST image taken on the 2nd August 2007. The white arrow indicates the cold patch off northeast Taiwan.</p> Full article ">
<p>The bathymetry northeast off Taiwan. The inside of blue rectangle is the study area with bathymetry in color.</p> Full article ">
<p>SST image of July 29, 2006. The lower SST i.e., the cold patch off northeast Taiwan is detected within the area of 27.7 °C contour (white). The black dotted line is the ground track of T/P and Jason-1.</p> Full article ">
<p>Comparison of Jason-1 sea surface height anomaly on July 28, 2006 (dashed line) and NGSST data on the July 29, 2006 (solid line) along the same transect.</p> Full article ">
<p>Time series of SSHA of T/P and Jason-1 along track 240 across the upwelling area. The vertical axis is the region of T/P track from northwest to southeast as shown in <a href="#f3-sensors-09-05521" class="html-fig">Figure 3</a>. The study area is within the two dashed lines.</p> Full article ">
<p>The wavelet power spectrum. The horizontal axis is the wavelet location in time and the vertical axis denotes the wavelet period in years. White patches denote power less than 0.0020 (m)<sup>2</sup>.</p> Full article ">
<p>Distribution of the centroid of cold patch. Red stars denote the distribution of cold patch in summer (June to October) and green stars show the distribution of cold patch in winter and transaction periods (November to May). Red and green dots are the mean positions of distribution in summer and winter, respectively. The bathymetry is shown with contours in color.</p> Full article ">
648 KiB  
Review
Electroanalytical Sensors and Devices for Multiplexed Detection of Foodborne Pathogen Microorganisms
by María Pedrero, Susana Campuzano and José M. Pingarrón
Sensors 2009, 9(7), 5503-5520; https://doi.org/10.3390/s90705503 - 13 Jul 2009
Cited by 59 | Viewed by 14696
Abstract
The detection and identification of pathogen microorganisms still rely on conventional culturing techniques, which are not suitable for on-site monitoring. Therefore, a great research challenge in this field is focused on the need to develop rapid, reliable, specific, and sensitive methods to detect [...] Read more.
The detection and identification of pathogen microorganisms still rely on conventional culturing techniques, which are not suitable for on-site monitoring. Therefore, a great research challenge in this field is focused on the need to develop rapid, reliable, specific, and sensitive methods to detect these bacteria at low cost. Moreover, the growing interest in biochip development for large scale screening analysis implies improved miniaturization, reduction of analysis time and cost, and multi-analyte detection, which has nowadays become a crucial challenge. This paper reviews multiplexed foodborne pathogen microorganisms detection methods based on electrochemical sensors incorporating microarrays and other platforms. These devices usually involve antibody-antigen and DNA hybridization specific interactions, although other approaches such as the monitoring of oxygen consumption are also considered. Full article
(This article belongs to the Special Issue Pathogen Sensors)
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<p>Schematic illustration of impedance multiplexed detection of rat IgG, HBsAg and HBeAg (Yu <span class="html-italic">et al</span>. [<a href="#b16-sensors-09-05503" class="html-bibr">16</a>]).</p> Full article ">
<p>(A) Electrical biochip microarray design and detailed zoom view. (B) Fully automated eBioChip Array analyzer “eMicroLISA” with fluidic, rotor valve, reagent reservoirs, and one hand plug and play ChipStick. Reproduced from Elshoz <span class="html-italic">et al</span>. [<a href="#b13-sensors-09-05503" class="html-bibr">13</a>].</p> Full article ">
<p>DOX-PCA concept [<a href="#b32-sensors-09-05503" class="html-bibr">32</a>]. (A–C) represent DOX responses for high, medium and low cell concentrations, respectively.</p> Full article ">
510 KiB  
Article
Sharing Sensor Data with SensorSA and Cascading Sensor Observation Service
by Denis Havlik, Thomas Bleier and Gerald Schimak
Sensors 2009, 9(7), 5493-5502; https://doi.org/10.3390/s90705493 - 10 Jul 2009
Cited by 13 | Viewed by 10738
Abstract
The SANY IP consortium (http://www.sany-ip.eu) has recently developed several interesting service prototypes that extend the usability of the Open Geospatial Consortium “Sensor Web Enablement” (OGC SWE) architecture. One such service prototype, developed by the Austrian Research Centers, is the “cascading SOS” (SOS-X). SOS-X [...] Read more.
The SANY IP consortium (http://www.sany-ip.eu) has recently developed several interesting service prototypes that extend the usability of the Open Geospatial Consortium “Sensor Web Enablement” (OGC SWE) architecture. One such service prototype, developed by the Austrian Research Centers, is the “cascading SOS” (SOS-X). SOS-X is a client to the underlying OGC Sensor Observation service(s) (SOS). It provides alternative access routes to users (or services) interested in accessing data. In addition to a simple cascading, SOS-X can re-format, re-organize, and merge data from several sources into a single SOS offering. Thanks to the built-in “Formula 3” prototype, a kind of time series library, SOS-X will be enabled to derive new data sets on the fly executing arbitrary algebraic operations on one or more data input streams. This article will discuss the SOS-X development status (focusing at end of 2008), further development agenda in year 2009, and possibilities for using the SOS-X outside of the SANY IP. Full article
(This article belongs to the Special Issue Workshop Sensing A Changing World)
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<p>Cascading SOS.</p> Full article ">
<p>From left to right: (a) UC1 “data publishing”; (b) UC2 “custom view to data”.</p> Full article ">
<p>From left to right: (a) UC3 “Protocol Transducer”; (b) UC4 “SOS Proxy”; (c) UC5 “Load Balancing”.</p> Full article ">
<p>From left to right: (a) UC6 “Value Added SOS”; (b) UC2 “Sensor Data Store”.</p> Full article ">
1288 KiB  
Article
Remote Sensor for Spatial Measurements by Using Optical Scanning
by Oleg Sergiyenko, Wilmar Hernandez, Vira Tyrsa, Luis Felipe Devia Cruz, Oleg Starostenko and Mario Peña-Cabrera
Sensors 2009, 9(7), 5477-5492; https://doi.org/10.3390/s90705477 - 10 Jul 2009
Cited by 32 | Viewed by 11172
Abstract
In this paper, we propose a low-cost contact-free measurement system for both 3-D data acquisition and fast surface parameter registration by digitized points. Despite the fact that during the last decade several approaches for both contact-free measurement techniques aimed at carrying out object [...] Read more.
In this paper, we propose a low-cost contact-free measurement system for both 3-D data acquisition and fast surface parameter registration by digitized points. Despite the fact that during the last decade several approaches for both contact-free measurement techniques aimed at carrying out object surface recognition and 3-D object recognition have been proposed, they often still require complex and expensive equipment. Therefore, alternative low cost solutions are in great demand. Here, two low-cost solutions to the above-mentioned problem are presented. These are two examples of practical applications of the novel passive optical scanning system presented in this paper. Full article
(This article belongs to the Section Remote Sensors)
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<p>POS system.</p> Full article ">
<p>Electric signals generated by POS system on spot and synchronous point detection.</p> Full article ">
<p>Horizontal POS placement for bridge monitoring.</p> Full article ">
<p>Placement of two vertical POSs for arch dam monitoring.</p> Full article ">
<p>POS and LPS placement for automatic navigation task. a) General view of the system with interaction of the parts in functioning. b) Triangulation angles distance and signals from sensors and reference <span class="html-italic">f</span> (“clock” pulses).</p> Full article ">
<p>Experiments using laser spot: a) on obstacle variable position. b) in order to determine coordinates (<span class="html-italic">x,y</span>).</p> Full article ">
<p>Experiments using laser spot: a) on obstacle variable position. b) in order to determine coordinates (<span class="html-italic">x,y</span>).</p> Full article ">
<p>90° angle measurement using a light bulb as the energy source.</p> Full article ">
<p>Signal energy attenuation and distribution in projected spot: a) striking distance 2.5 m. b) striking distance 5.0 m.</p> Full article ">
<p>POS output signal amplitude variation according to rpm on mirror motor.</p> Full article ">
<p>POS output signal amplitude variation according to rpm on mirror motor.</p> Full article ">
536 KiB  
Article
A MEMS-Based Flow Rate and Flow Direction Sensing Platform with Integrated Temperature Compensation Scheme
by Rong-Hua Ma, Dung-An Wang, Tzu-Han Hsueh and Chia-Yen Lee
Sensors 2009, 9(7), 5460-5476; https://doi.org/10.3390/s90705460 - 9 Jul 2009
Cited by 39 | Viewed by 15064
Abstract
This study develops a MEMS-based low-cost sensing platform for sensing gas flow rate and flow direction comprising four silicon nitride cantilever beams arranged in a cross-form configuration, a circular hot-wire flow meter suspended on a silicon nitride membrane, and an integrated resistive temperature [...] Read more.
This study develops a MEMS-based low-cost sensing platform for sensing gas flow rate and flow direction comprising four silicon nitride cantilever beams arranged in a cross-form configuration, a circular hot-wire flow meter suspended on a silicon nitride membrane, and an integrated resistive temperature detector (RTD). In the proposed device, the flow rate is inversely derived from the change in the resistance signal of the flow meter when exposed to the sensed air stream. To compensate for the effects of the ambient temperature on the accuracy of the flow rate measurements, the output signal from the flow meter is compensated using the resistance signal generated by the RTD. As air travels over the surface of the cross-form cantilever structure, the upstream cantilevers are deflected in the downward direction, while the downstream cantilevers are deflected in the upward direction. The deflection of the cantilever beams causes a corresponding change in the resistive signals of the piezoresistors patterned on their upper surfaces. The amount by which each beam deflects depends on both the flow rate and the orientation of the beam relative to the direction of the gas flow. Thus, following an appropriate compensation by the temperature-corrected flow rate, the gas flow direction can be determined through a suitable manipulation of the output signals of the four piezoresistors. The experimental results have confirmed that the resulting variation in the output signals of the integrated sensors can be used to determine not only the ambient temperature and the velocity of the air flow, but also its direction relative to the sensor with an accuracy of ± 7.5o error. Full article
(This article belongs to the Special Issue Sensor Configuration and Smart Sensors)
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<p>(a) Schematic illustration of micro-cantilever type flow sensor; (b) experimental (black lines) and theoretical (colored lines) results for flow rate sensitivity of sensors with different cantilever tip widths [<a href="#b20-sensors-09-05460" class="html-bibr">20</a>].</p> Full article ">
<p>Schematic illustration showing deflection of microcantilevers as air flows over their surfaces. (a) Gas flow direction sensor comprising four microcantilevers arranged in cross-form configuration; (b) deflection of microcantilevers as air flows over the sensor surface.</p> Full article ">
<p>Schematic illustration of circular thermal flow meter.</p> Full article ">
<p>Schematic overview of fabrication process used to accomplish flow direction sensor with integrated flow meter and RTD.</p> Full article ">
<p>SEM image of flow direction sensor comprising four microcantilevers in a cross-form configuration.</p> Full article ">
<p>Photograph of circular thermal flow meter and RTD used for temperature compensation purposes (upper: flow meter, lower: RTD).</p> Full article ">
<p>(a) Position of initial air flow direction relative to sensor; (b) correlation between resistance signal variations and air flow direction for air flow velocities in the range of 15∼30 ms<sup>−1</sup>.</p> Full article ">
<p>Variations of micro-heater temperature with magnitude of supplied electrical voltage for flow meters on diaphragm and bulk structure, respectively.</p> Full article ">
<p>Variations of measured resistance change with flow rate for flow meters on diaphragm and bulk structure, respectively, at 100 °C where the initial resistance is 580.6 Ω.</p> Full article ">
159 KiB  
Review
Sensing Mercury for Biomedical and Environmental Monitoring
by Paul D. Selid, Hanying Xu, E. Michael Collins, Marla Striped Face-Collins and Julia Xiaojun Zhao
Sensors 2009, 9(7), 5446-5459; https://doi.org/10.3390/s90705446 - 9 Jul 2009
Cited by 168 | Viewed by 19985
Abstract
Mercury is a very toxic element that is widely spread in the atmosphere, lithosphere, and surface water. Concentrated mercury poses serious problems to human health, as bioaccumulation of mercury within the brain and kidneys ultimately leads to neurological diseases. To control mercury pollution [...] Read more.
Mercury is a very toxic element that is widely spread in the atmosphere, lithosphere, and surface water. Concentrated mercury poses serious problems to human health, as bioaccumulation of mercury within the brain and kidneys ultimately leads to neurological diseases. To control mercury pollution and reduce mercury damage to human health, sensitive determination of mercury is important. This article summarizes some current sensors for the determination of both abiotic and biotic mercury. A wide array of sensors for monitoring mercury is described, including biosensors and chemical sensors, while piezoelectric and microcantilever sensors are also described. Additionally, newly developed nanomaterials offer great potential for fabricating novel mercury sensors. Some of the functional fluorescent nanosensors for the determination of mercury are covered. Afterwards, the in vivo determination of mercury and the characterization of different forms of mercury are discussed. Finally, the future direction for mercury detection is outlined, suggesting that nanomaterials may provide revolutionary tools in biomedical and environmental monitoring of mercury. Full article
(This article belongs to the Special Issue Fluorescent Chemosensors)
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<p>A EP2-19G2-cofactor biosensor for mercury. Reprinted with permission from [<a href="#b29-sensors-09-05446" class="html-bibr">29</a>]. Copyright American Chemical Society (2005).</p> Full article ">
<p>Schematic diagram of a flow system in a mercury chemical sensor. A and B, valves; C, thermostatted water bath; D, cooling coil; E, fluorescence flow cell. Reprinted with permission from [<a href="#b32-sensors-09-05446" class="html-bibr">32</a>]. Copyright Elsevier (1999).</p> Full article ">
<p>Ionic mercury reacts with thiamine to generate a “turn-on” fluorescence signal when thiochrome is formed.</p> Full article ">
<p>Schematic diagram of a microcantilever sensor system. Reprinted with permission from [<a href="#b42-sensors-09-05446" class="html-bibr">42</a>]. Copyright American Chemical Society (2002).</p> Full article ">
<p>Rhodamine B-AuNP mercury sensor modified by thiol ligands and PDCA. Reprinted with permission from [<a href="#b8-sensors-09-05446" class="html-bibr">8</a>]. Copyright American Chemical Society (2006).</p> Full article ">
1634 KiB  
Article
Translocation Biosensors – Cellular System Integrators to Dissect CRM1-Dependent Nuclear Export by Chemicogenomics
by Verena Fetz, Shirley K. Knauer, Carolin Bier, Jens Peter Von Kries and Roland H. Stauber
Sensors 2009, 9(7), 5423-5445; https://doi.org/10.3390/s90705423 - 9 Jul 2009
Cited by 30 | Viewed by 13821
Abstract
Fluorescent protein biosensors are powerful cellular systems biology tools for dissecting the complexity of cellular processes with high spatial and temporal resolution. As regulated nucleo-cytoplasmic transport is crucial for the modulation of numerous (patho)physiological cellular responses, a detailed understanding of its molecular mechanism [...] Read more.
Fluorescent protein biosensors are powerful cellular systems biology tools for dissecting the complexity of cellular processes with high spatial and temporal resolution. As regulated nucleo-cytoplasmic transport is crucial for the modulation of numerous (patho)physiological cellular responses, a detailed understanding of its molecular mechanism would open up novel options for a rational manipulation of the cell. In contrast to genetic approaches, we here established and employed high-content cellular translocation biosensors applicable for dissecting nuclear export by chemicogenomics. A431 cell lines, stably expressing a translocation biosensor composed of glutathione S-transferase, GFP and a rational combination of nuclear import and export signals, were engineered by antibiotic selection and flow cytometry sorting. Using an optimized nuclear translocation algorithm, the translocation response could be robustly quantified on the Cellomics Arrayscan® VTI platform. Subsequent to assay optimization, the assay was developed into a higher density 384-well format high-content assay and employed for the screening of the 17K ChemBioNet compound collection. This library was selected on the basis of a genetic algorithm used to identify maximum common chemical substructures in a database of annotated bioactive molecules and hence, is well-placed in the chemical space covered by bioactive compounds. Automated multiparameter data analysis combined with visual inspection allowed us to identify and to rationally discriminate true export inhibitors from false positives, which included fluorescent compounds or cytotoxic substances that dramatically affected the cellular morphology. A total of 120 potential hit compounds were selected for Cellomics Arrayscan® VTI based rescreening. The export inhibitory activity of 20 compounds effective at concentrations < 25 μM were confirmed by fluorescence microscopy in several cell lines. Interestingly, kinetic analysis allowed the identification of inhibitors capable to interfere with the export receptor CRM1-mediated nuclear export not only in an irreversible, but also in a reversible fashion. In sum, exploitation of biosensor based screening allows the identification of chemicogenomic tools applicable for dissecting nucleo-cytoplasmic transport in living cells. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Germany)
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<p>(a) Schematic illustration of the regulation of nucleo-cytoplasmic transport. As an example for nuclear export, the CRM1-dependent pathway is depicted. (b) Heat-repeat map of CRM1, which is predicted to contain 19 repeats separated by a loop within repeat 8. (c) Kinetic classification of NES sequences established by microinjection experiments of recombinant GST-NES-GFP substrates into the nucleus. Amino acids essential for function are highlighted in grey, putative consensus sequence for leucine-rich NES is shown below.(a) NLS-bearing cargoes are imported via binding to importins. In the nucleus, the importin-cargo complex dissociates upon Ran<sub>GTP</sub> binding. CAS exports the respective importin back into the cytoplasm. RanGAP hydrolyses Ran<sub>GTP</sub> to Ran<sub>GDP</sub> resulting in release of the importin from CAS. Leucine-rich NES-bearing cargoes bind to CRM1 in the presence of Ran<sub>GTP</sub>, and the complex translocates into the cytoplasm, where the cargo is released following hydrolysis of Ran<sub>GTP</sub> to Ran<sub>GDP</sub>. Ran<sub>GDP</sub> is reimported by NTF2 and reconverted into Ran<sub>GTP</sub> by RanGEF. Leptomycin B (LMB) inactivates CRM1 by covalent binding to Cys<sub>528</sub>, thereby irreversibly inhibiting NES-mediated nuclear export. For the selective export of cargoes, NES-specific cofactors (X) have been suggested. RanGEF - Ran guanine nucleotide exchange factor, RanGAP - Ran GTPase activating protein 1, NTF2 - Nuclear Transport Factor 2, CAS - cellular apoptosis susceptibility, X – putative NES-specific cofactor. (b) Heat repeat 10 contains the cysteine residue 528, which is covalently modified by LMB. The C-terminal region (CTR) comprises heat repeats 14 to 19, colored from yellow to black. The CTRs of two proteolytic fragments of CRM1 (residues 707–1027, PDB 1W9C) are displayed as a dimeric solid ribbon representation of the backbone superposition (heat repeats of one fragment colored as above).</p> Full article ">
<p>(a) Schematic representation of the modular RevNES-biosensor. (b) In living HeLa cells transiently expressing the RevNES-biosensor, the protein localized predominantly to the cytoplasm, whereas treatment with LMB resulted in its nuclear accumulation. Scale bar, 10 μm. (c) Schematic illustration of the masks used to mark the nucleus and the cytoplasm in order to define the cytoplasmic to nuclear translocation of the autofluorescent biosensor (details see text).</p> Full article ">
<p>Generation and characterization of RevNES-biosensor expressing cell lines. (a/b) A431 were transduced with pINCO_Rev-sensor containing retroviruses and subjected to two rounds of FACS sorting. A distinct cell population based on cell size (gate R1, left panels) and GFP fluorescence intensity (gate R2, right panel), was isolated. For the second round of FACS, only cells robustly expressing the RevNES biosensor were selected (b, R2 right panel). (c) Fluorescent microscopic images of the A431<sub>bio</sub> cell population isolated after two rounds of FACS. All cells showed a high expression of the RevNES-biosensor, which localized predominantly in the cytoplasm with some accumulation at the nuclear membrane (left panel). Treatment with LMB (10 nM; 2h) resulted in almost complete accumulation of the biosensor in living cells. Scale bar, 10 μm.</p> Full article ">
<p>(a) Optimized object selection parameters (min/max settings) for channel 1 and 2 (highlighted in blue and green, respectively). (b) LMB treatment (10 nM) of A431<sub>bio</sub> cells resulted in a rapid nuclear accumulation of the biosensor already after 30 min, which remained stable also after 5 h without obvious cytotoxic effect on cell morphology. Scale bar, 10 μm. (c) Translocation assay analysis of A431<sub>bio</sub> cells using the Cellomics Arrayscan<sup>®</sup> VTI platform. The Hoechst and GFP signals were recorded in channel 1 and 2 (highlighted in blue and green), respectively, following LMB treatment (10 nM, 5 h). In the upper panel, the original raw images are shown. The lower panel shows the overlay with the respective masks. In channel 1, cells selected for further analysis are outlined in blue, cells rejected due to their size or shape are outlined in orange. In channel 2, the CIRC mask and RING region are outlined in green or red, respectively. Scale bar, 50 μm. (d) Average signal difference (CIRC-RING) of LMB treated cells (10 nM, 5 h) versus DMSO assay controls in one representative 384-well plate. 1 × 10<sup>4</sup> cells/well were seeded, and the values were derived from analyzing ∼500 cells/well (see <a href="#t1-sensors-09-05423" class="html-table">Table 1</a> for details) revealing a translocation index of &gt; 5-fold. (e) Differences in assay performance depending on cell density. The indicated numbers of A431<sub>bio</sub> cells were seeded into 384-well plates. Sixteen h later, cells were treated with LMB (10 nM) or DMSO as a control for 5 h, and the translocation index quantitated using the Cellomics Arrayscan<sup>®</sup> VTI imager. CIRC-RING differences were plotted for DMSO control (grey) and LMB treated (red) cells (left scale). The ratio of these values (white columns) performed best for 1 × 10<sup>4</sup> seeded cells/well. Columns, mean; bars, SD.</p> Full article ">
<p>Intersection of the biological and chemical space. Translocation index-based analysis for cytotoxicity and fluorescence interference. (a) CIRC-RING values representative for negative and positive control substances (DMSO, LMB), export antagonists, substances showing no effect on export, cytotoxic and autofluorescent compounds obtained from the analysis of a representative 384-well plate. (b) Scatter plot of the nuclear intensity/well versus the cytoplasmic intensity/well in the “green” target channel 2 (GFP) subsequent to compound exposure to mark the intersection of the chemical and biological space. Values from a representative 384-well plate are shown. The DMSO controls (dark grey) are grouped together with the non-hit compounds (light grey), and are well separated from the LMB controls (red) and a potential hit population (black dotted circle). Potential hit compounds partially overlap with cytotoxic substances (violet), identified by visual inspection. Autofluorescent compounds (orange) usually display high fluorescence intensities and are well separated. (c) Representative images from compound wells that exhibited either a dose-dependent autofluorescence (upper panel) or a dose-dependent cytotoxicity (lower panel). Raw images and mask overlays are shown for both channels. In the Hoechst channel, objects selected for further analysis are outlined in blue, objects rejected are outlined in orange. In the “GFP channel”, the green outline represents the nuclear region mask, and the red outline the cytoplasmic ring region. Scale bar, 50 μm. The chemical structure of the respective compounds are shown on the right.</p> Full article ">
<p>Intersection of the biological and chemical space. Translocation index-based analysis for cytotoxicity and fluorescence interference. (a) CIRC-RING values representative for negative and positive control substances (DMSO, LMB), export antagonists, substances showing no effect on export, cytotoxic and autofluorescent compounds obtained from the analysis of a representative 384-well plate. (b) Scatter plot of the nuclear intensity/well versus the cytoplasmic intensity/well in the “green” target channel 2 (GFP) subsequent to compound exposure to mark the intersection of the chemical and biological space. Values from a representative 384-well plate are shown. The DMSO controls (dark grey) are grouped together with the non-hit compounds (light grey), and are well separated from the LMB controls (red) and a potential hit population (black dotted circle). Potential hit compounds partially overlap with cytotoxic substances (violet), identified by visual inspection. Autofluorescent compounds (orange) usually display high fluorescence intensities and are well separated. (c) Representative images from compound wells that exhibited either a dose-dependent autofluorescence (upper panel) or a dose-dependent cytotoxicity (lower panel). Raw images and mask overlays are shown for both channels. In the Hoechst channel, objects selected for further analysis are outlined in blue, objects rejected are outlined in orange. In the “GFP channel”, the green outline represents the nuclear region mask, and the red outline the cytoplasmic ring region. Scale bar, 50 μm. The chemical structure of the respective compounds are shown on the right.</p> Full article ">
<p>(a) Secondary ArrayScan<sup>®</sup>-based validation of potential export antagonists. 1 × 10<sup>4</sup> A431<sub>bio</sub> cells/well were seeded into 384-well plates. 16 h later, cells were treated with LMB (10nM), DMSO or the indicated compounds (C1-C11; 25 μM) for 5 h, and translocation was quantitated using the Cellomics ArrayScan<sup>®</sup> VTI imager. The CIRC-RING differences are indicative of efficient export inhibition. Columns, mean; bars, SD. (b) In lab verification of hit compound performance in living HeLa cells transiently expressing the RevNES biosensor. Indicated compounds were applied at a concentration of 25 μM for 5 h, resulting in efficient nuclear accumulation of the biosensor. Scale bar, 10 μm. (c) Compound specific kinetics of inhibition. HeLa cells transiently expressing the RevNES biosensor were treated with LMB (10nM) or the indicated compounds (25 μM). The localization of the biosensor is shown at the indicated time points when the compounds displayed their maximum inhibitory activity (top panel), as well as 24 h post treatment. The inhibitory activity of C3 and C11 was reversed after 24 h. Scale bar, 10 μm. (d) Kinetic activity profile of export inhibitors. Selection of different time points (indicated by the arrows) for snapshot analysis (highlighted in grey) may significantly influence the number and type of compounds identified in primary screens. A continuous kinetic monitoring of the biosensor translocation may ensure the identification of the maximum number of bioactive substances and the optimal extraction of informations concerning their bioactivity. Time point used for analysis of the primary RevNES-biosensor screen is marked by the asterisks. An optimal kinetic window is highlighted in blue.</p> Full article ">
<p>(a) Secondary ArrayScan<sup>®</sup>-based validation of potential export antagonists. 1 × 10<sup>4</sup> A431<sub>bio</sub> cells/well were seeded into 384-well plates. 16 h later, cells were treated with LMB (10nM), DMSO or the indicated compounds (C1-C11; 25 μM) for 5 h, and translocation was quantitated using the Cellomics ArrayScan<sup>®</sup> VTI imager. The CIRC-RING differences are indicative of efficient export inhibition. Columns, mean; bars, SD. (b) In lab verification of hit compound performance in living HeLa cells transiently expressing the RevNES biosensor. Indicated compounds were applied at a concentration of 25 μM for 5 h, resulting in efficient nuclear accumulation of the biosensor. Scale bar, 10 μm. (c) Compound specific kinetics of inhibition. HeLa cells transiently expressing the RevNES biosensor were treated with LMB (10nM) or the indicated compounds (25 μM). The localization of the biosensor is shown at the indicated time points when the compounds displayed their maximum inhibitory activity (top panel), as well as 24 h post treatment. The inhibitory activity of C3 and C11 was reversed after 24 h. Scale bar, 10 μm. (d) Kinetic activity profile of export inhibitors. Selection of different time points (indicated by the arrows) for snapshot analysis (highlighted in grey) may significantly influence the number and type of compounds identified in primary screens. A continuous kinetic monitoring of the biosensor translocation may ensure the identification of the maximum number of bioactive substances and the optimal extraction of informations concerning their bioactivity. Time point used for analysis of the primary RevNES-biosensor screen is marked by the asterisks. An optimal kinetic window is highlighted in blue.</p> Full article ">
<p>Model summarizing potential modes of action of the identified export inhibitors. Compounds may bind to CRM1 and, in an allosterical or competitive manner, affect its NES-binding domain, thereby preventing the assembly of a functional export complex. Alternatively, the compounds may directly interact with the specific NES itself or target putative cofactors required for the assembly of protein specific export complexes. Compounds displaying such a bioactivity profile would be of therapeutic interest.</p> Full article ">
1436 KiB  
Article
Adjacency Matrix-Based Transmit Power Allocation Strategies in Wireless Sensor Networks
by Luca Consolini, Paolo Medagliani and Gianluigi Ferrari
Sensors 2009, 9(7), 5390-5422; https://doi.org/10.3390/s90705390 - 9 Jul 2009
Cited by 7 | Viewed by 12178
Abstract
In this paper, we present an innovative transmit power control scheme, based on optimization theory, for wireless sensor networks (WSNs) which use carrier sense multiple access (CSMA) with collision avoidance (CA) as medium access control (MAC) protocol. In particular, we focus on schemes [...] Read more.
In this paper, we present an innovative transmit power control scheme, based on optimization theory, for wireless sensor networks (WSNs) which use carrier sense multiple access (CSMA) with collision avoidance (CA) as medium access control (MAC) protocol. In particular, we focus on schemes where several remote nodes send data directly to a common access point (AP). Under the assumption of finite overall network transmit power and low traffic load, we derive the optimal transmit power allocation strategy that minimizes the packet error rate (PER) at the AP. This approach is based on modeling the CSMA/CA MAC protocol through a finite state machine and takes into account the network adjacency matrix, depending on the transmit power distribution and determining the network connectivity. It will be then shown that the transmit power allocation problem reduces to a convex constrained minimization problem. Our results show that, under the assumption of low traffic load, the power allocation strategy, which guarantees minimal delay, requires the maximization of network connectivity, which can be equivalently interpreted as the maximization of the number of non-zero entries of the adjacency matrix. The obtained theoretical results are confirmed by simulations for unslotted Zigbee WSNs. Full article
(This article belongs to the Special Issue Wireless Sensor Technologies and Applications)
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<p>Pairwise connections in a scenario with <span class="html-italic">N</span> = 10 nodes (this scenario will correspond to that in <a href="#f4-sensors-09-05390" class="html-fig">Figure 4a</a>). Two values for the total network transmit power are considered: (a) <span class="html-italic">P</span><sub>tot</sub> = 5 · 10<span class="html-italic"><sup>−</sup></span><sup>5</sup> W and (b) <span class="html-italic">P</span><sub>tot</sub> = 2.5 · 10<span class="html-italic"><sup>−</sup></span><sup>5</sup> W. In both cases, the proposed optimized power allocation strategy is used.</p> Full article ">
<p>Graphical notation for communication links: (a) A and B communicate with each other (bidirectional communication); (b) only A can transmit to B (monodirectional communication).</p> Full article ">
<p>Considered network topologies with <span class="html-italic">N</span> = 20 nodes.</p> Full article ">
<p>Considered network topologies with <span class="html-italic">N</span> = 10 nodes.</p> Full article ">
<p>Network topologies with <span class="html-italic">N</span> = 10 nodes randomly deployed over a 10 m<sup>2</sup> square surface, used for (a) PER comparison and (b) evaluation of the network lifetime. (c) Network topology with <span class="html-italic">N</span> = 10 nodes randomly deployed over a 50 m<sup>2</sup> square surface, used for the evaluation of the network lifetime.</p> Full article ">
<p>PER as a function of the total offered traffic load. The simulation results are obtained considering (i) default backoff exponent, i.e., <span class="html-italic">BE</span><sub>min</sub> = 3 and <span class="html-italic">BE</span><sub>max</sub> = 5, and (ii) modified backoff exponent, i.e., <span class="html-italic">BE</span><sub>min</sub> = <span class="html-italic">BE</span><sub>max</sub> = 7. Different values of per-node transmit powers are considered. The allocated transmit power is the same at each node.</p> Full article ">
<p>(a) Network transmission rate and (b) delay, as functions of the total offered traffic load (<span class="html-italic">Ng</span>), in the presence of (i) default backoff exponent, i.e., <span class="html-italic">BE</span><sub>min</sub> = 3 and <span class="html-italic">BE</span><sub>max</sub> = 5, and (ii) modified backoff exponent, i.e., <span class="html-italic">BE</span><sub>min</sub> = <span class="html-italic">BE</span><sub>max</sub> = 7. Different values of transmit powers are considered. The allocated transmit power is the same at each node.</p> Full article ">
<p>PER as a function of the sparsity index of the adjacency matrix. In the simulations, for scenarios with <span class="html-italic">N</span> = 20 nodes, the packet generation rate is set to <span class="html-italic">g</span> = 0.1 pck/s, whereas for scenarios with <span class="html-italic">N</span> = 10 nodes, the packet generation rate is set to <span class="html-italic">g</span> = 0.2 pck/s.</p> Full article ">
<p>PER as a function of the sparsity index of the adjacency matrix. In the simulations, for scenarios with <span class="html-italic">N</span> = 20 nodes, the packet generation rate is set to <span class="html-italic">g</span> = 1 pck/s, whereas for scenarios with <span class="html-italic">N</span> = 10 nodes, the packet generation rate is set to <span class="html-italic">g</span> = 2 pck/s.</p> Full article ">
362 KiB  
Article
Biophysical Micromixer
by Chin-Tsan Wang, Yuh-Chung Hu and Tzu-Yang Hu
Sensors 2009, 9(7), 5379-5389; https://doi.org/10.3390/s90705379 - 8 Jul 2009
Cited by 20 | Viewed by 10125
Abstract
In this study a biophysical passive micromixer with channel anamorphosis in a space of 370 mm, which is shorter than traditional passive micromixers, could be created by mimicing features of vascular flow networks and executed with Reynolds numbers ranging from 1 to 90. [...] Read more.
In this study a biophysical passive micromixer with channel anamorphosis in a space of 370 mm, which is shorter than traditional passive micromixers, could be created by mimicing features of vascular flow networks and executed with Reynolds numbers ranging from 1 to 90. Split and recombination (SAR) was the main mixing method for enhancing the convection effect and promoting the mixing performance in the biophysical channel. The 2D numerical results reveal that good mixing efficiency of the mixer was possible, with εmixing = 0.876 at Reynolds number ration Rer = 0.85. Generally speaking, increasing the Reynolds number will enhance the mixing. In addition, the sidewall effect will influence the mixing performance and an optimal mixing performance with εmixing = 0.803 will occur at an aspect ratio of AR = 2. These findings will be useful for enhancing mixing performance for passive micromixers. Full article
(This article belongs to the Section Chemical Sensors)
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<p>Prototype of biophysical micromixer (unit: μm), the arrows indicate the inlet and outlet flow direction.</p> Full article ">
<p>Reynolds number ratios versus the mixing efficiency and pressure drop.</p> Full article ">
<p>Reynolds number effect versus the mixing and pressure drop at Rer = 1.</p> Full article ">
<p>Reynolds number effect related to the mixing and pressure drop at Rer = 1.</p> Full article ">
659 KiB  
Review
Label-Free Electrical Detection Using Carbon Nanotube-Based Biosensors
by Kenzo Maehashi and Kazuhiko Matsumoto
Sensors 2009, 9(7), 5368-5378; https://doi.org/10.3390/s90705368 - 8 Jul 2009
Cited by 91 | Viewed by 16798
Abstract
Label-free detections of biomolecules have attracted great attention in a lot of life science fields such as genomics, clinical diagnosis and practical pharmacy. In this article, we reviewed amperometric and potentiometric biosensors based on carbon nanotubes (CNTs). In amperometric detections, CNT-modified electrodes were [...] Read more.
Label-free detections of biomolecules have attracted great attention in a lot of life science fields such as genomics, clinical diagnosis and practical pharmacy. In this article, we reviewed amperometric and potentiometric biosensors based on carbon nanotubes (CNTs). In amperometric detections, CNT-modified electrodes were used as working electrodes to significantly enhance electroactive surface area. In contrast, the potentiometric biosensors were based on aptamer-modified CNT field-effect transistors (CNTFETs). Since aptamers are artificial oligonucleotides and thus are smaller than the Debye length, proteins can be detected with high sensitivity. In this review, we discussed on the technology, characteristics and developments for commercialization in label-free CNT-based biosensors. Full article
(This article belongs to the Special Issue State-of-the-Art Sensors Technology in Japan)
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Graphical abstract

Graphical abstract
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<p>Schematic illustration of the CNT-arrayed electrodes. Inset: a scanning electron microscope (SEM) image of a CNT electrode.</p> Full article ">
<p>(a) Schematic illustration of experimental setup for the label-free amperometric biosensor. (b) Electrochemical signals obtained from CNT electrodes recorded using DPV. The dotted and solid lines correspond to the electrochemical signals from PSA-mAb and after introduction of 1 ng/mL PSA, respectivity. PSA-mAb was covalently immobilized on the CNTs using linkers.</p> Full article ">
<p>(a) Optical image and (b) schematic illustration of a microfluidic chip based on CNT electrodes. Inset: a SEM image of a CNT electrode and an optical image of a pneumatic micropump.</p> Full article ">
<p>(a) Schematic illustration of detection mechanism for biomolecule using CNTFET. (b) Optical image of arrayed CNTFETs.</p> Full article ">
<p>(a) Schematic structure of experimental setup for aptamer-modified CNTFET. (b) Time dependence of drain current in CNTFET after introduction of target IgE at various concentrations into IgE aptamer-modified CNTFET.</p> Full article ">
<p>(a) IgE concentration / amount of net drain current as a function of IgE concentration. (b) Coverage of IgE as a function of IgE concentration.</p> Full article ">
331 KiB  
Article
Multivalent Anchoring and Oriented Display of Single-Domain Antibodies on Cellulose
by Greg Hussack, Yan Luo, Linda Veldhuis, J. Christopher Hall, Jamshid Tanha and Roger MacKenzie
Sensors 2009, 9(7), 5351-5367; https://doi.org/10.3390/s90705351 - 7 Jul 2009
Cited by 40 | Viewed by 13374
Abstract
Antibody engineering has allowed for the rapid generation of binding agents against virtually any antigen of interest, predominantly for therapeutic applications. Considerably less attention has been given to the development of diagnostic reagents and biosensors using engineered antibodies. Recently, we produced a novel [...] Read more.
Antibody engineering has allowed for the rapid generation of binding agents against virtually any antigen of interest, predominantly for therapeutic applications. Considerably less attention has been given to the development of diagnostic reagents and biosensors using engineered antibodies. Recently, we produced a novel pentavalent bispecific antibody (i.e., decabody) by pentamerizing two single-domain antibodies (sdAbs) through the verotoxin B subunit (VTB) and found both fusion partners to be functional. Using a similar approach, we have engineered a bispecific pentameric fusion protein consisting of five sdAbs and five cellulose-binding modules (CBMs) linked via VTB. To find an optimal design format, we constructed six bispecific pentamers consisting of three different CBMs, fused to the Staphylococcus aureus-specific human sdAb HVHP428, in both orientations. One bispecific pentamer, containing an N-terminal CBM9 and C-terminal HVHP428, was soluble, non-aggregating, and did not degrade upon storage at 4 ºC for over six months. This molecule was dually functional as it bound to cellulose-based filters as well as S. aureus cells. When impregnated in cellulose filters, the bispecific pentamer recognized S. aureus cells in a flow-through detection assay. The ability of pentamerized CBMs to bind cellulose may form the basis of an immobilization platform for multivalent display of high-avidity binding reagents on cellulosic filters for sensing of pathogens, biomarkers and environmental pollutants. Full article
(This article belongs to the Special Issue Pathogen Sensors)
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<p>Overview of fusion protein construction and characterization.</p> Full article ">
<p>Assembly of bispecific pentamers. (A) Schematic representation of a bispecific pentamer displaying five human sdAbs fused to five CBMs through the verotoxin subunit (VTB). (B-D) Schematic representation of the coding sequences assembled and expressed in pVT1 (B, C) or pPICZαA (D).</p> Full article ">
<p>Analysis of purified monospecific and bispecific pentamers. (A) SDS-PAGE (reducing conditions, ∼3 μg protein per lane) demonstrating the stability of purified proteins which had been stored at 4 °C for six months. The reducing conditions separated the pentamerized molecules into five single polypeptide chains. The expected masses of monospecific HVHP428-VTB and bispecific CBM9-VTB-HVHP428 in an SDS-PAGE gel are 24.4 kDa and 45.7 kDa, respectively. (B) Size exclusion chromatography using a Superdex 200™ column revealed both HVHP428-VTB and CBM9-VTB-HVHP428 were non-aggregating since a single, homogeneous peak was observed for each within the expected mass range. The bispecific CBM9-VTB-HVHP428 pentamer eluted later than expected. Protein standards are indicated with arrows. 1: thyroglobulin (M<sub>r</sub> 669,000); 2: ferritin (M<sub>r</sub> 440,000); 3: BSA (M<sub>r</sub> 67,000); 4: beta-lactoglobulin (M<sub>r</sub> 35,000); 5: ribonuclease A (M<sub>r</sub> 13,700).</p> Full article ">
<p>Functional characterization of CBM9-VTB-HVHP428. (A) Agglutination of <span class="html-italic">S. aureus</span> (wells without small white dots in the middle) was seen for CBM9-VTB-HVHP428 with an end limit of 150 nM compared to an end limit of 18.7 nM for the positive control, HVHP428-VTB. No agglutination was seen for the negative control, HVLP335-VTB [<a href="#b26-sensors-09-05351" class="html-bibr">26</a>]. (B) Binding of CBM9-VTB-HVHP428 to cellulose. Serial dilutions of purified CBM9-VTB-HVHP428 and HVHP428-VTB were applied to Whatman No. 5 filter paper using a vacuum manifold. Binding was detected by incubating the paper with alkaline phosphatase-labeled protein A.</p> Full article ">
<p>Detection of <span class="html-italic">S. aureus</span> with immobilized CBM9-VTB-HVHP428. (A) Schematic representation of the CBM9-VTB-HVHP428-based biosensor. (i) Loading of bispecific pentamer onto the filter, (ii) <span class="html-italic">S. aureus</span> cells passed over the filter, (iii) HRP labeled anti-protein A IgG passed over the filter, (iv) the filter moved to 96 well plates, substrate applied, and the absorbance read at 450 nm, (v) aerial view of filter after substrate. (B) Photograph of experimental filter discs after removal of HRP substrate from a 96 well plate. (C) Plot of absorbance A (A<sub>450</sub> of CBM9-VTB-HVHP428 impregnated discs) - A<sub>o</sub> (A<sub>450</sub> of control discs with HVHP428-VTB) <span class="html-italic">versus</span> the number of <span class="html-italic">S. aureus</span> colony forming units (cfu) applied to each disc. Limit of detection = 10<sup>5</sup> cfu/mL (p = 0.05). Error bars represent standard error of the mean (SEM) based on A<sub>450</sub> values from two independent experiments with three replicates in each.</p> Full article ">
128 KiB  
Article
Metaheuristic Based Scheduling Meta-Tasks in Distributed Heterogeneous Computing Systems
by Hesam Izakian, Ajith Abraham and Václav Snášel
Sensors 2009, 9(7), 5339-5350; https://doi.org/10.3390/s90705339 - 7 Jul 2009
Cited by 31 | Viewed by 11467
Abstract
Scheduling is a key problem in distributed heterogeneous computing systems in order to benefit from the large computing capacity of such systems and is an NP-complete problem. In this paper, we present a metaheuristic technique, namely the Particle Swarm Optimization (PSO) algorithm, for [...] Read more.
Scheduling is a key problem in distributed heterogeneous computing systems in order to benefit from the large computing capacity of such systems and is an NP-complete problem. In this paper, we present a metaheuristic technique, namely the Particle Swarm Optimization (PSO) algorithm, for this problem. PSO is a population-based search algorithm based on the simulation of the social behavior of bird flocking and fish schooling. Particles fly in problem search space to find optimal or near-optimal solutions. The scheduler aims at minimizing makespan, which is the time when finishes the latest task. Experimental studies show that the proposed method is more efficient and surpasses those of reported PSO and GA approaches for this problem. Full article
(This article belongs to the Section Chemical Sensors)
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<p>Pseudo-code of particle swarm optimization approach.</p> Full article ">
<p>Velocity updating method.</p> Full article ">
<p>Pseudo-code of the proposed method.</p> Full article ">
<p>Standard deviation in scenario (a).</p> Full article ">
<p>Standard deviation in scenario (b).</p> Full article ">
<p>Comparison of convergence time between different methods.</p> Full article ">
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