Hydrogen ion passivation of multicrystalline silicon solar cells

It has been recognized that hydrogen can be chosen to passivate the defects present in polycrystalline materials. Technically, the best approach is to use hydrogen ion implantation at low energy (0.5 to 5 keV) by means of a Kaufman or similar type ion source in order to reduce the processing time. For our multiple beam ion source, we have determined the effective concentration profile of the introduced hydrogen, the modification of the optical properties of the implanted wafers and the conditions under which two multicrystalline materials (POLYX and SILSO) will give the greatest improvement in solar cell performance

On the Ca2 + binding and conformational change in EF-hand domains: Experimental evidence of Ca2 +-saturated intermediates of N-domain of calmodulin

Double mutation of Q41L and K75I in the N-domain of calmodulin (N-Cam) stabilizes the closed form of N-Cam such that binding of Ca2 + in solution no longer triggers a conformational change to the open form, and its Ca2 + binding affinity decreases dramatically. To further investigate the solvation effects on the structure, Ca2 + binding affinity and conformational dynamics of this N-Cam double mutant in the Ca2 + saturated state, we solved its X-ray structure. Surprisingly, the structure revealed an open conformation of the domain which contradicts its closed conformation in solution. Here we provide evidence that crystallization conditions were responsible for this Ca2 +-saturated domain open conformation in the crystal. Importantly, we demonstrate that the presence of the crystallization co-precipitant and alcohols were able to induce a progressive opening of the closed form of this domain, in Ca2 + saturated state, in solution. However, in the Ca2 + depleted state, addition of alcohols was unable to induce any opening of this domain in solution. In addition, in the Ca2 + saturated state, the molecular dynamics simulations show that while N-Cam can populate the open and closed conformation, the N-Cam double mutant exclusively populates the closed conformation. Our results provide experimental evidence of intermediate conformations of Ca2 +-saturated N-Cam in solution. We propose that conformational change of Ca2 + sensor EF-hand domains depends on solvation energetics, Ca2 + binding to promote the full open form, Ca2 + depleted state conformational dynamics, and the chemical properties of the molecules nearby key residues such as those at positions 41 and 75 in N-Cam

Effect of starting materials on the structure of pure and Gd-doped BaTiO3 elaborated by the sol gel process

Undoped and Gd-doped BaTiO3 samples, with the chemical formula BaGdxTi1-xO3-x/2□x/2, x = 0.00; 0.01; 0.02; 0.03; 0.04 and 0.05, were synthesized using the sol gel process. During the procedure of preparation of these samples acetic acid and distilled water were used as solvents. All the powders corresponding to the two series of undoped and doped samples were calcined in air at different temperatures and their crystalline phase was checked using results from XRD and Raman analyses. Acetic acid was shown to provoke the formation of the stable pseudo cubic structure for the two series of samples at relatively low temperature of crystallization, while with the use of distilled water only (without acetic acid) the tetragonal phase prevailed. In this study, the effect of acetic acid is discussed and the latter seems to play a more or less important role in the formation of the structure of BT material

Two-dimensional NMR lineshape analysis

NMR titration experiments are a rich source of structural, mechanistic, thermodynamic and kinetic information on biomolecular interactions, which can be extracted through the quantitative analysis of resonance lineshapes. However, applications of such analyses are frequently limited by peak overlap inherent to complex biomolecular systems. Moreover, systematic errors may arise due to the analysis of two-dimensional data using theoretical frameworks developed for one-dimensional experiments. Here we introduce a more accurate and convenient method for the analysis of such data, based on the direct quantum mechanical simulation and fitting of entire two-dimensional experiments, which we implement in a new software tool, TITAN (TITration ANalysis). We expect the approach, which we demonstrate for a variety of protein-protein and protein-ligand interactions, to be particularly useful in providing information on multi-step or multi-component interactions

EFFECT OF SALINITY ON THE PHYSIOLOGICAL BEHAVIOR OF THE OLIVE TREE (VARIETY SIGOISE

Salinity is a major problem directly affecting the ecological balance and the development of agriculture in the Mediterranean basin, particularly North Africa. This phenomenon is considered as the most important abiotic factor limiting crops growth and productivity, degrading and polluting soils in arid and semi-arid. In order to study the influence of salinity, on the physiological parameters and to assess the potential of adaptation of the olive tree in a saline environment, three parcels containing the Sigoise variety and subject to different degrees of salinity were selected: Parcel 1 (non-saline); Parcel 2 (saline); Parcel 3 (very saline). Under a saline constraint, the results showed two contrasting tendencies, an intense increase in the content of proline, sodium (Na+) and chlorophyll (b), while water content, potassium and chlorophyll (a) decreased strongly with increasing salinity

Nanoscaffold effects on the performance of air-cathodes for microbial fuel cells : Sustainable Fe/N-carbon electrocatalysts for the oxygen reduction reaction under neutral pH conditions

Nanostructured electrocatalysts for microbial fuel cell air-cathodes were obtained via use of conductive carbon blacks for the synthesis of high performing 3D conductive networks. We used two commercially available nanocarbons, Black Pearls 2000 and multiwalled carbon nanotubes, as conductive scaffolds for the synthesis of nanocomposite electrodes by combining: a hydrothermally carbonized resin, a sacrificial polymeric template, a nitrogenated organic precursor and iron centers. The resulting materials are micro-mesoporous, possess high specific surface area and display N-sites (N/C of 3–5 at%) and Fe-centers (Fe/C < 1.5 at.%) at the carbon surface as evidenced from characterization methods. Voltammetry studies of oxygen reduction reaction activity were carried out at neutral pH, which is relevant to microbial fuel cell applications, and activity trends are discussed in light of catalyst morphology and composition. Tests of the electrocatalyst using microbial fuel cell devices indicate that optimization of the nanocarbon scaffold for the Pt-free carbon-based electrocatalysts results in maximum power densities that are 25% better than those of Pt/C cathodes, at a fraction of the materials costs. Therefore, the proposed Fe/N-carbon catalysts are promising and sustainable high-performance cathodic materials for microbial fuel cells

From Profile to Surface Monitoring: SPC for Cylindrical Surfaces Via Gaussian Processes

Quality of machined products is often related to the shapes of surfaces that are constrained by geometric tolerances. In this case, statistical quality monitoring should be used to quickly detect unwanted deviations from the nominal pattern. The majority of the literature has focused on statistical profile monitoring, while there is little research on surface monitoring. This paper faces the challenging task of moving from profile to surface monitoring. To this aim, different parametric approaches and control-charting procedures are presented and compared with reference to a real case study dealing with cylindrical surfaces obtained by lathe turning. In particular, a novel method presented in this paper consists of modeling the manufactured surface via Gaussian processes models and monitoring the deviations of the actual surface from the target pattern estimated in phase I. Regardless of the specific case study in this paper, the proposed approach is general and can be extended to deal with different kinds of surfaces or profiles

Thermodynamic study of interactions between ZnO and ZnO binding peptides using isothermal titration calorimetry

Whilst material specific peptide binding sequences have been identified using a combination of combinato-rial methods and computational modelling tools, a deep molecular level understanding of the fundamental principles through which these interactions occur and in some instances modify the morphology of inorganic materials is far from being fully realized. Understanding the thermodynamic changes that occur during peptide-inorganic interactions and correlating these to structural modifications of the inorganic materials could be the key to achieving and mastering con-trol over material formation processes. This study is a detailed investigation applying isothermal titration calorimetry (ITC) to directly probe thermodynamic changes that occur during interaction of ZnO binding peptides (ZnO-BPs) and ZnO. The ZnO-BPs used are reported sequences G-12 (GLHVMHKVAPPR), GT-16 (GLHVMHKVAPPR-GGGC) and alanine mutants of G-12 (G-12A6, G-12A11 and G-12A12) whose interaction with ZnO during solution synthesis studies have been extensively investigated. The interactions of the ZnO-BPs with ZnO yielded biphasic isotherms comprising both an endo-thermic and an exothermic event. Qualitative differences were observed in the isothermal profiles of the different pep-tides and ZnO particles studied. Measured ΔG values were between -6 and -8.5 kcal/mol and high adsorption affinity val-ues indicated the occurrence of favourable ZnO-BP-ZnO interactions. ITC has great potential in its use to understand peptide-inorganic interactions and with continued development, the knowledge gained may be instrumental for simplifi-cation of selection processes of organic molecules for the advancement of material synthesis and design