Compact charge and capacitance modeling of undoped ultra-thin body (UTB) SOI MOSFETs

We present an analytic, explicit and continuous charge model for a long-channel UTB (ultra-thin body) SOI (silicon-on-insulator) MOSFET, from which analytical expressions of the total capacitances are obtained. Our model is valid from below to well above threshold, without suffering from discontinuities between the regimes. It is based on a unified charge control model derived from Poisson’s equation. The drain-current, charge and capacitances expressions result in continuous explicit functions of the applied bias.The calculated capacitance characteristics are validated by 2D numerical simulations showing a very good agreement for different silicon film thicknesses.     

Enhanced UV- and visible-light driven photocatalytic performances and recycling properties of graphene oxide/ZnO hybrid layers

Light induced catalytic processes have attracted significant attention during the last years for wastewater treatment due to their efficiency in decomposition of organic contaminants. In this study we report the synthesis of graphene oxide (GO)/ZnO hybrid layers with high photocatalytic efficiency using laser radiation. The results show that the hybrid layers exhibit much improved photodecomposition efficiency as compared to pure GO or ZnO both under UV and visible-light irradiation. The enhanced photocatalytic efficiency of the hybrid as compared to the reference pure ZnO and GO layers was attributed to the contribution of GO to the separation and transport of the photogenerated charge carriers. Additionally, under visible light irradiation the organic molecules can act as first sensitizers in the degradation process. The recyclability of the layers was also investigated through repetitive photodegradation cycles under UV- or visible-light irradiation. After consecutive degradation runs, the hybrid photocatalyst layers were still stable and retained high degradation efficiency, ensuring reusability. The photocatalytic activity of the layers was correlated with the gradual change of their chemical structure during consecutive degradation cycles. Owing to the high photodegradation efficiency, reusability, and ease of recovery the synthesised hybrid layers consisting of easily available materials are suitable for environmental purification applications.     

Biosynthesis of silver nanoparticles in collagen gel improves their medical use in periodontitis treatment

Silver nanoparticles (AgNP) suspensions were biosynthesized by silver ions reduction in the presence of collagen, a nontoxic, organic polymer, intending to improve their medical use in periodontitis treatment. Spectrophotometric measurements showed a time- and concentration-dependent increase of AgNP formation in each suspension variant. Transmission electron microscopy revealed spherical morphology of AgNP in collagen and their mean diameter size was around 30?nm. The particle size distribution and zeta potential values of AgNP in collagen were determined by dynamic light scattering measurements. The surface charge of AgNP in collagen was positive, while commercial AgNP stabilized in citrate had negative surface charge. In vitro cytotoxicity testing of AgNP in collagen showed that they were biocompatible with human gingival fibroblasts in a wider range of concentrations than commercial nanoparticles. The antibacterial activity of AgNP in collagen against two pathogenic strains present in the periodontal pocket was dose-dependent and higher than that of AgNP in citrate. All these results demonstrated that AgNP prepared in collagen gel had improved properties, like small diameter, positive surface charge, high biocompatibility in human gingival fibroblasts, efficiency against bacterial growth and, thus, better therapeutic potential in periodontal disease treatment.     

Grain Boundaries in Cu(In,Ga)Se2: A Review of Composition–Electronic Property Relationships by Atom Probe Tomography and Correlative Microscopy

Cu(In,Ga)Se₂ thin-film solar cells have attracted significant research interest in recent decades due to their high efficiency in converting solar energy into electricity for enabling a sustainable future. Although the Cu(In,Ga)Se₂ absorber can be grown as a single crystal, its polycrystalline form is dominating the market not only due to its lower costs, but also due to its unexpectedly higher cell efficiency. However, this absorber contains a high fraction of grain boundaries. These are structural defects where deep-trap states can be localized leading to an increase in recombination activity. This controversy is mirrored in the existing literature studies where two main contradictory believes exist: 1) to be crucial grain boundaries in Cu(In,Ga)Se₂ absorber are anomalous, being benign in terms of cell performance, and 2) grain boundaries are regions characterized by an increased recombination activity leading to deteriorated cell performance. Therefore, the present review tackles this issue from a novel perspective unraveling correlations between chemical composition of grain boundaries and their corresponding electronic properties. It is shown that features such as Cu depletion/In enrichment, segregation of 1-2at.% of alkali dopants, and passivation by a wide-bandgap or type inversion at grain boundaries are crucial ingredients for low open-circuit voltage loss and, hence, for superior cell performance.     

Correlations between differential absorbance and the formation of individual DBPs

This study examined correlations between the differential absorbance at 272nm (deltaA272) and the formation of disinfection by-products (DBPs) in chlorinated water from the Tolt River, a water source for Seattle, WA. The DBPs investigated included chloroform (CHCl3), dichlorobromomethane (CHCl2Br), mono-, di- and trichloroacetic acids (MCAA, DCAA, and TCAA, respectively), chloral hydrate (CH), dichloroacetonitrile (DCAN) and 1,1,1-trichloropropanone (TCP). Whereas the kinetics of DBP formation are complex and are non-linear, the same DBP data represented as a function of deltaA272 are quite simple. Absorbance decreases when the water is chlorinated, i.e., deltaA272 is always negative. The DBP vs. -deltaA272 correlations can almost always be quantified by linear equations, at least above some threshold value of -deltaA272, with R2 values > 0.95. The only DBP that did not follow this trend was CH, for which an exponential relationship better described the data. TCP and DCAN were unstable at pH 7 and 8, but at pH 6 linear correlations between their concentrations and -deltaA272 were as strong as those for the more stable DBPs. The threshold -deltaA272 value is approximately the same for many of the DBPs studied, supporting the hypothesis that individual DBPs are released following the formation of a common intermediate, or at least a small group of similar intermediates. The DBP vs. -deltaA272 correlations may have practical value since they provide an alternative approach for monitoring the formation of individual DBP species on-line, but the generality of the relationships needs to be further examined.     

Chronic Activation of AMPK Induces Mitochondrial Biogenesis through Differential Phosphorylation and Abundance of Mitochondrial Proteins in Dictyostelium discoideum

Mitochondrial biogenesis is a highly controlled process that depends on diverse signalling pathways responding to cellular and environmental signals. AMP-activated protein kinase (AMPK) is a critical metabolic enzyme that acts at a central control point in cellular energy homeostasis. Numerous studies have revealed the crucial roles of AMPK in the regulation of mitochondrial biogenesis; however, molecular mechanisms underlying this process are still largely unknown. Previously, we have shown that, in cellular slime mould Dictyostelium discoideum, the overexpression of the catalytic α subunit of AMPK led to enhanced mitochondrial biogenesis, which was accompanied by reduced cell growth and aberrant development. Here, we applied mass spectrometry-based proteomics of Dictyostelium mitochondria to determine the impact of chronically active AMPKα on the phosphorylation state and abundance of mitochondrial proteins and to identify potential protein targets leading to the biogenesis of mitochondria. Our results demonstrate that enhanced mitochondrial biogenesis is associated with variations in the phosphorylation levels and abundance of proteins related to energy metabolism, protein synthesis, transport, inner membrane biogenesis, and cellular signalling. The observed changes are accompanied by elevated mitochondrial respiratory activity in the AMPK overexpression strain. Our work is the first study reporting on the global phosphoproteome profiling of D. discoideum mitochondria and its changes as a response to constitutively active AMPK. We also propose an interplay between the AMPK and mTORC1 signalling pathways in controlling the cellular growth and biogenesis of mitochondria in Dictyostelium as a model organism.     

Synthesis of new polyesters containing phosphorus heterocycles and halogen

Two series of polyesters containing phenoxaphosphine rings and several halogens were synthesized by low-temperature solution polycondensation in the presence of triethylamine. One series, containing halogens only in the bisphenol moiety, was obtained from 2,8-dichloroformyl-10-phenylphenoxaphosphine-10-oxide and chlorinated bisphenol. In the second series, halogens belonged both to bisphenol and diacid dichlorides. For the last series, 2,8-dichloroformyl-10-(4-bromophenyl)phenoxaphosphine-10-oxide was prepared as a new monomer. All resulting polyesters were characterized by elemental analysis, reduced viscosity, IR and ¹H NMR spectroscopy, and thermogravimetric analysis. These polymers began to lose weight at about 400°C in air being seen as self-extinguishing ones.     

Accurate prediction of the volume inversion impact on undoped Double Gate MOSFET capacitances

This paper demonstrates the capability of our previously published undoped Double‐Gate (DG) MOSFET explicit and analytical compact model to also forecast the effect of the volume inversion (VI) on the intrinsic capacitances. For that purpose, we present simulation results for these capacitances. We show now that the model presents an accurate dependence on the silicon layer thickness, consistent with two‐dimensional numerical simulations, for both thin and thick silicon films. As opposed to our previous work, here we test the capacitance model for three different film thicknesses and also show that the transition from VI regime to dual gate behaviour is well simulated. We demonstrate in this paper that even if the current drive and transconductance are enhanced in VI regime, our results show that intrinsic capacitances are higher as well, which may limit the high‐speed (delay time) behaviour of DG MOSFETs under VI regime. The good agreement between the numerical simulations and our model shows the high potential of our complete DG MOSFET model. Copyright © 2010 John Wiley & Sons, Ltd.     

Some considerations regarding finishing by abrasive flap wheels

The diminishing of the surface roughness of a metallic part can be performed by using various finishing methods, polishing by means of abrasive flap wheels being one of them. There are several factors that influence the roughness of surfaces finished by means of abrasive flap wheels. When polishing external cylindrical surfaces by means of abrasive flap wheels, the surface roughness can be changed more easily if the following elements are modified: the peripheral speed of the workpiece and of the abrasive flap wheel, the speed of the longitudinal feed, and the grit size of the abrasive material. Experimental research has allowed for the establishment of power-type functions which highlight the influence exerted by the above-mentioned factors on the size of the surface roughness parameters R _a , RS, RSm, Rku. Analyses of the experimental results have shown that, in the case of the R _a roughness parameter, from among the range of interactions of orders 2 and 3, only the interaction between the rotation speed of the abrasive flap wheel and the speed of the longitudinal feed seems to be significant.