Impurities

The aim of this paper is to research the impact of physical parameters which characterize the MOSFET transistors structure on the threshold voltage values and its influence on critical voltage values which characterize digital circuits that contain the MOSFET transistors. The results obtained emphasize the impact of each single physical parameter on the total value of the threshold voltage. By adjusting the values of MOSFET physical parameters the accepted threshold voltage can be achieved. Since the threshold voltage will have influence on critical voltage values which characterise MOS inverters and delay times during transfer logic states between stages, it must be taken into consideration during design phase of logic gates that contain the MOSFET transistors.

The synthesis of two principal impurities of irbesartan prepd. via its N-trityl deriv. is described. The impurities were isolated and unambiguously identified by NMR. IR, UV, and mass spectra of these compds. are also given. [on SciFinder(R)]

Polymeric-insulated power cables are often subjected to multiple sources of degradation. Generally, the main cause for electrical breakdown in this type of cable insulation is usually due to the microscopic impurities and defects located in the bulk, or even at the interfaces of the material. When the dielectric is subjected to a high electrical stress, imperfections such as protrusions, contaminants and microvoids, will all act as points where the electric field is enhanced; increasing the likelihood that degradation processes will be initiated. The intensification of electric field within the insulating material can cause localized discharge to occur continuously, and thus tree-like channels can be developed in the long-run. This paper attempts to investigate whether the existence of water tree region can be detected within polymeric-insulated cables, and the proposed method for the detection mechanism is the time domain reflectometry (TDR). When water trees are present within an insulation system, the characteristic impedance of the material also changes so this can cause reflection of signal propagating along the cable. It was found that there is a difference in TDR signals between un-degraded cable and water tree degraded cable. It is hoped that the difference in these time domain signals can actually assist in determining the location where the presence of water trees can be considered as significant. © 2012 IEEE.

http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6416367

Two impurities found in both stressed and aged solid-state formulations of olanzapine have been identified as (Z)-1,3-dihydro-4-(4-methyl-1-piperazinyl)-2-(2-oxopropylidene)-2H-1,5-benzodiazepin-2-one (1) and (Z)-1-[1,2-dihydro-4-(4-methyl-1-piperazinyl)-2-thioxo-3H-1,5-benzodiazepin-3-ylidene]propan-2-one (2). The structures indicate that the two impurities are degradation products resulting from oxidation of the thiophene ring of olanzapine. The impurities were isolated by preparative HPLC from a thermally stressed formulation, and characterized by UV, IR, MS, and NMR. A synthetic preparation of compounds 1 and 2 by reaction of olanzapine with the singlet oxygen mimic 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) is presented. The structure of 2 was also determined by single-crystal X-ray diffraction analysis. A degradation pathway for the formation of 1 and 2 is proposed. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:883–892, 2008

The purpose of this study was to assess the water quality parameters of Ala River found in Akure, Ondo State, Southwest Nigeria. The river is considered as one of the most important irrigation and drinking water resources in Akure, Nigeria. Three locations were chosen spatially along the watercourse to reflect a consideration of all possible human activities that are capable of affecting the quality of the river water. The water samples were collected monthly for three consecutive months (February to April 2015) at the three sampling sites. The water samples collected were analysed for physicochemical parameters which include pH, total dissolved solids, dissolved oxygen, biochemical oxygen demand, total hardness, phosphate, temperature, calcium, magnesium, chlorine, nitrate, iron and zinc using standard methods and their environmental effects on the river were investigated. There were variations in the quality of the sampled water when compared with the World Health Organization standards for domestic and commercial water for the selected parameters. The traces of some hazardous physical and chemical impurities in the river were above the acceptable limits, and thereby pose a health risk to several rural communities who rely heavily on the river primarily as their source of domestic water. Therefore, the law should be enforced to discourage unnecessary waste dumping and discharging of another form of pollutants into surface water in Nigeria.

We report on an ab initio study of the structural, electronic and optical properties of boron and phosphorous doped silicon nanocrystals. The scaling with the Si-nanocrystal size is investigated for both the neutral formation energies (FE) and the impurity activation energies. Both these energies scale with the nanocrystal inverse radius. The optical properties reveal the existence of new absorption peaks in the low energy region related to the presence of the impurity. The effects of B and P co-doping show that the formation ...