final configurations of simulations of the systems
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Reparametrization of vdW parameters between Water and CO2 force fields were performed using solvation free energy. New parameters of Force Fields were used in the determination of the solubility of the CO2 in water.
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This paper describes experimental results of thermal diffusivity measurements performed on different concentrations of aqueous Tartrazine solutions. The measurements are performed using the frequency-resolved thermal lensing technique and... more
This paper describes experimental results of thermal diffusivity measurements performed on different concentrations of aqueous Tartrazine solutions. The measurements are performed using the frequency-resolved thermal lensing technique and the results are compared with the thermal diffusivity value of pure water used as a solvent or host liquid. The results show that at low concentrations, the thermal properties of the solution are roughly equal to those of the water. However, when the concentration is increased, the thermal properties of the solutions diverge from that of the host liquid.
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In this work, we report a joint experimental-theoretical investigation on interaction of vacuum-ultraviolet radiation with trimethylphosphate (TMP) molecule (C3H9O4P) in gas phase. This species together with tetrahydrofuran (THF) are... more
In this work, we report a joint experimental-theoretical investigation on interaction of vacuum-ultraviolet radiation with trimethylphosphate (TMP) molecule (C3H9O4P) in gas phase. This species together with tetrahydrofuran (THF) are model compounds of deoxyribose nucleic acids (DNA)/ribose nucleic acids (RNA) backbone. Absolute photoabsorption cross sections (σa) and ionization yields (η) are measured using the double-ion-chamber technique in the 11.0–21.45 eV energy range. Photoionization (σi) and neutral-decay (σn) cross sections in absolute scale are also derived. Moreover, theoretical photoabsorption cross sections are calculated using the time-dependent density functional theory from the excitation threshold up to 16 eV. Good agreement between the present calculated and experimental photoabsorption cross sections in the 11.0–14.5 eV range is encouraging. Also, the present measured data of σa and σi for TMP are about 1.3 and 1.5 times of those of THF, respectively. Thus, the experimental evidences that the majority of strand breaks being located at sugar rings in the irradiated DNA/RNA backbone moiety may be induced by a possible migration of the hole, initially created at phosphate group, to the linked sugar groups. Finally, absolute partial photoionization cross sections are derived from the experimental time-of-flight mass spectra.
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Two ices, O2 and a mixture of O2 and N2, are bombarded by 252Cf fission fragments (FF) (approximately 65 MeV at target surface); the emitted positive and negative secondary ions are analyzed by time-of-flight mass spectrometry (TOF-SIMS).... more
Two ices, O2 and a mixture of O2 and N2, are bombarded by 252Cf fission fragments (FF) (approximately 65 MeV at target surface); the emitted positive and negative secondary ions are analyzed by time-of-flight mass spectrometry (TOF-SIMS). These studies shall enlighten sputtering from planetary and interstellar ices. Three temperature regions in the 28-42-K range are analyzed: (1) before N2 sublimation, in which hybrid chemical species are formed, (2) before O2 sublimation, in which the TOF mass spectrum is dominated by low-mass (O2)p cluster ions and (3) after O2 sublimation, in which (N2)p or (O2)p cluster ions are practically inexistent. In the first region, four hybrid ion series are observed: NOn-1+, N2On-2(+/-), and N4On-4(-). In the second region, two positive and negative ion series are identified: (O2)pO(+/-) and (O2)pO2(+/-). Their yield distributions are fitted by the sum of two decreasing exponentials, whose decay constants are the same for all series. It is observed that the cluster ion desorption from solid oxygen is very similar to that of other frozen gases, but its yield distribution oscillates with a three- or six-atom periodicity, suggesting O3 or 3O2 units in the cluster structure, respectively.
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Ion cluster desorption yields due to the impact of 252Cf fission fragments on condensed ammonia are determined. Identification and abundance of the ion desorbed species were provided by a time-of-flight mass spectrometer. Ammonia ice thin... more
Ion cluster desorption yields due to the impact of 252Cf fission fragments on condensed ammonia are determined. Identification and abundance of the ion desorbed species were provided by a time-of-flight mass spectrometer. Ammonia ice thin layers deposited on Au film were heated from 25K to complete sublimation. The typical pressure during heating process was 10−8mbar. Measurements in the 25–150K temperature
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Frozen CO was bombarded by ∼65MeV fission fragments and the emitted secondary ions were analyzed by time-of-flight mass spectrometry. Target was kept at UHV conditions and its temperature was varied from 25K up to complete sublimation of... more
Frozen CO was bombarded by ∼65MeV fission fragments and the emitted secondary ions were analyzed by time-of-flight mass spectrometry. Target was kept at UHV conditions and its temperature was varied from 25K up to complete sublimation of the ice film. The observed positive cluster ion series are well represented by the chemical expression (CO)mCn+, where m and n≥0, and the
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Phenylalanine (Phe) is an amino acid that has been identified in carbonaceous meteorites; its formation mechanism in space is unknown, and its radioresistance has been the subject of investigation. This work aims at studying, in the... more
Phenylalanine (Phe) is an amino acid that has been identified in carbonaceous meteorites; its formation mechanism in space is unknown, and its radioresistance has been the subject of investigation. This work aims at studying, in the laboratory, the Phe radiolysis by cosmic analogues. The Phe destruction rate, at 300 K, is measured for H, He, and N ion beam irradiation in the 0.5 to 2 kinetic MeV range. Fourier transform infrared (FTIR) spectroscopy was employed to monitor the molecular degradation as a function of fluence. The Phe apparent destruction cross-section, σapd, which includes radiolysis and sputtering processes, is determined to be proportional to the electronic stopping power, Se. The measured parameter D0 = 14.3 ± 2.2 eV/molec in the relationship, and σdap = Se/D0 is interpreted as the mean absorbed dose necessary to dissociate or eject a Phe molecule. The Phe half-life in the interstellar medium is predicted to be about 10 million years, H+ ions the main destructive cosmic ray constituent.
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CONH3 and CONH3–H2O ices at 25–130 K were bombarded by 252Cf fission fragments (∼65 MeV at the target surface) and the emitted secondary ions were analyzed by time‐of‐flight mass spectrometry (TOF‐SIMS). It is observed that the mass... more
CONH3 and CONH3–H2O ices at 25–130 K were bombarded by 252Cf fission fragments (∼65 MeV at the target surface) and the emitted secondary ions were analyzed by time‐of‐flight mass spectrometry (TOF‐SIMS). It is observed that the mass spectra obtained from both ices have similar patterns. The production of hybrid ions (formed from CO and NH3 molecules) emitted from CONH3 ice has already been reported by R. Martinez et al., Int. J. Mass. Spectrom. 262 (2006) 195; here, the secondary ion emission and the modifications of the CONH3 ice structure during the temperature increase of the ice are addressed. These studies are expected to throw light on the sputtering from planetary and interstellar ices and the possible formation of new organic molecules in CONH3–H2O ice by megaelectronvolt ion bombardment. The presence of water in the CONH3 ice mixture generates molecular ion series such as (NH3)p−q(H2O)qCO+ and replaces the cluster series (NH3)nNH4+ emission by the hybrid series (NH3)I−i(H2O)i=1, 2…IH+. The distribution of NH3 and H2O molecules within the cluster groups indicates that ammonia and water mix homogenously in the icy condensate at T = 25 K. The desorption yield distribution of the cluster series (NH3)nNH4+ is described by the sum of two exponential functions: one, slow‐decreasing, attributed to the fragmentation of the solid target into clusters; and another, fast‐decreasing, due to a local sublimation followed by recombination of ammonia molecules. The analysis of the time‐temperature dependence of these two yield components gives information on the formation process of molecular ions, the transient composition of the ice target and structural changes of the ice. Data suggest that the amorphous and porous structure of the NH3 ice, formed by the condensation of the CONH3 gas at T = 25 K, survives CO sublimation until the occurrence of a phase transition around 80 K, which produces a more fragile ice structure. Copyright © 2007 John Wiley & Sons, Ltd.
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... where R is the gas constant and T is the temperature in kelvin. The measurements were performed several times in order to check the reproducibility of the results. ... Soc. Am. B 6 2326 [16] Samson JAR and Stolte WC 2002 J. Electron... more
... where R is the gas constant and T is the temperature in kelvin. The measurements were performed several times in order to check the reproducibility of the results. ... Soc. Am. B 6 2326 [16] Samson JAR and Stolte WC 2002 J. Electron Spectrosc. Relat. Phenom. ...
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CO–NH3 ice at 25K is bombarded by 65MeV fission fragments and the emitted secondary ions are analyzed by time-of-flight mass spectrometry. The yields of the specific ion species (those formed only from CO or from NH3 molecules) and of the... more
CO–NH3 ice at 25K is bombarded by 65MeV fission fragments and the emitted secondary ions are analyzed by time-of-flight mass spectrometry. The yields of the specific ion species (those formed only from CO or from NH3 molecules) and of the hybrid ion species (formed from both CO and NH3 molecules) are determined as a function of the ice temperature. The
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AbstractProperties of the non-Born–Oppenheimer two-matrix are examined for four-particle systems of the Coulomb–Hooke and Moshinsky types. We obtain for both these models explicit closed-form analytic expressions for the electron and... more
AbstractProperties of the non-Born–Oppenheimer two-matrix are examined for four-particle systems of the Coulomb–Hooke and Moshinsky types. We obtain for both these models explicit closed-form analytic expressions for the electron and nuclear 2-RDM. An explicit expression is also obtained for the electron–nuclear 2-RDM in the Moshinsky case, which shows coupling between the electron and nuclear coordinates.
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Based on orbital angular momentum (OAM) properties of Laguerre Gaussian beams LG(p,ℓ), a robust optical encoding model for efficient data transmission applications is designed. This paper presents an optical encoding model based on... more
Based on orbital angular momentum (OAM) properties of Laguerre Gaussian beams LG(p,ℓ), a robust optical encoding model for efficient data transmission applications is designed. This paper presents an optical encoding model based on intensity profile generated by a coherent superposition of two OAM-carrying Laguerre-Gaussian modes and Machine-learning detection method. In the encoding process, the intensity profile for data encoding is generated based on selection of p and ℓ indices, while the decoding process is performed using support vector machine (SVM) algorithm. Two different decoding models based on SVM algorithm are tested to verify the robustness of optical encoding model, finding a BER =10−9 for 10.2dB of signal-to-noise ratio in one of the SVM models.
Einstein, Podolsky and Rosen's paper presented in 1935 is briefly discusses in this work, from which a series of scientific discussions were generated subsequently at that time. A simple language is used to describe the original... more
Einstein, Podolsky and Rosen's paper presented in 1935 is briefly discusses in this work, from which a series of scientific discussions were generated subsequently at that time. A simple language is used to describe the original paper. En este trabajo se analiza brevemente el artículo presentado por Einstein, Podolsky y Rosen en 1935, a partir del cual se generó una serie de discusiones científicas, posteriormente en esa época. Se utiliza un lenguaje común para describir el artículo original
Conduction models of ion through voltage-gated ion channels, at symmetrical concentration in cellular membrane, have been developed. These channels are highly selective to K or Na ions due to a potential difference. First, it is... more
Conduction models of ion through voltage-gated ion channels, at symmetrical concentration in cellular membrane, have been developed. These channels are highly selective to K or Na ions due to a potential difference. First, it is considered the theory of metallic conduction, where, it is assumed a random distribution of obstacles, which oppose to free motion of ions inside the channel. This spacing distribution among obstacles turned out to be very narrow and its mean value is very small, that implies an almost continuous collision of ion with the channel obstacles. In addition, a model based on the crystal periodic structure is proposed. These models would describe the experimental values of conduction, but the parameters associated to each model would take values that are not easy to verify experimentally, and they are related to the channel structure.  Se desarrolla dos modelos de conducción de iones a través de una membrana celular en condiciones simétricas de concentración considerando canales iónicos activados por voltaje. Estos canales son altamente selectivos a iones K o Na en presencia de una diferencia de potencial. Primero se plantea un modelo de conducción similar al de la conducción de electrones libres en metales donde se modela una distribución aleatoria de obstáculos que impiden el movimiento libre del ion dentro del canal. Esta distribución de espaciamiento entre obstáculos resultó ser muy angosta y su valor medio muy pequeño, implicando un casi continuo choque del ion con los obstáculos presentes en el canal. Adicionalmente, se propone un modelo considerando al canal como una estructura periódica. Para que estos modelos describan los valores experimentales de conducción, los parámetros asociados a cada modelo tienen valores que no son fáciles de comprobar experimentalmente los cuales tienen relación con la estructura del canal.&nbsp
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Research Interests: Matemática and Einstein
Reparametrization of vdW parameters between Water and CO2 force fields were performed using solvation free energy. New parameters of Force Fields were used in the determination of the solubility of the CO2 in water.