Epitaxially grown crystalline silicon thin-film solar cells reaching 16.5% efficiency with basic cell process

We report about the current performance of crystalline silicon thin-film (cSiTF) solar cells that are a very attractive alternative to conventional wafer-based silicon solar cells if sufficiently high cell efficiencies are achieved at acceptable cost of production. Applying a standard cell process (diffused POCl₃ emitter, front contacts by photolithography, no surface texture) to thin-films deposited with a lab-type reactor, specifically designed for high-throughput photovoltaic applications, on highly-doped Cz substrates we routinely obtain efficiencies above 16%. On 1 Ω cm FZ material substrates we reach efficiencies up to 18.0%, which is among the highest thin-film efficiencies ever reported. Additionally, a comparison to microelectronic-grade epitaxially grown cSiTF material underlines the excellent electrical quality of the epitaxial layers deposited.     

Guideline on the assessment of timber structures: Summary

The domain “assessment of existing timber structures” has experienced increased interest and gained application in practice over the past years. The objective of the guideline which is summarized in this short communication is to provide the reader with a collection of applicable assessment methods which have been evaluated by a group of experts against keywords like applicability, expenditure of time/cost, validity of results and possible constraints. Since each method only allows the assessment of certain types of material properties, damages or degradation processes, it becomes necessary to combine different methods in order to derive a full picture of the residual performance of the structure. Against this background, common approaches towards the assessment of timber structures are given.The results received from an assessment should be incorporated into analytical models. Different approaches towards the modelling and updating of existing structures are presented, including deterministic, semi-probabilistic as well as probabilistic verification methods.The guideline concludes with a discussion on the present state of the art for the assessment of timber structures. Potential objectives towards an optimization of the methods with respect to a simplified application are defined and necessary developments that finally enable more consistent estimations of the reliability of existing timber structures are highlighted.     

Electronic structure and chemical bond in stoichiometric hydrides of the group Vb metals

The electronic structure of stoichiometric hydrides of the group Vb metals (V, Nb, Ta) has been investigated by means of the self-consistent full potential scalar-relativistic augmented plane wave method (FP-APW).

The theoretical study of the heat of solution of the ordered monohydrides VH, NbH, and TaH leads to good agreement with experimental values and allows the prediction of the preferred coordination of the hydrogen atoms in these phases, i.e. the octahedral coordination for the VH-system and the tetrahedral coordination for NbH and TaH. Analysis of the charge distribution according to the irreducible representations of the point groups yields a simple orbital picture of the bonding mechanism in the stoichiometric hydride phase. The use of an angular-dependent rather than a spherical-symmetric potential results in a distinct increase in the calculated covalent contribution to the chemical bond.     

Evidence of two oxidative reaction steps initiating anaerobic degradation of resorcinol (1,3-dihydroxybenzene) by the denitrifying bacterium Azoarcus anaerobius

The denitrifying bacterium Azoarcus anaerobius LuFRes1 grows anaerobically with resorcinol (1,3-dihydroxybenzene) as the sole source of carbon and energy. The anaerobic degradation of this compound was investigated in cell extracts. Resorcinol reductase, the key enzyme for resorcinol catabolism in fermenting bacteria, was not present in this organism. Instead, resorcinol was hydroxylated to hydroxyhydroquinone (HHQ; 1,2,4-trihydroxybenzene) with nitrate or K3Fe(CN)6 as the electron acceptor. HHQ was further oxidized with nitrate to 2-hydroxy-1,4-benzoquinone as identified by high-pressure liquid chromatography, UV/visible light spectroscopy, and mass spectroscopy. Average specific activities were 60 mU mg of protein-1 for resorcinol hydroxylation and 150 mU mg of protein-1 for HHQ dehydrogenation. Both activities were found nearly exclusively in the membrane fraction and were only barely detectable in extracts of cells grown with benzoate, indicating that both reactions were specific for resorcinol degradation. These findings suggest a new strategy of anaerobic degradation of aromatic compounds involving oxidative steps for destabilization of the aromatic ring, different from the reductive dearomatization mechanisms described so far.     

Negative regulation of Raf-1 by phosphorylation of serine 621

The elevation of cyclic AMP (cAMP) levels in the cell downregulates the activity of the Raf-1 kinase. It has been suggested that this effect is due to the activation of cAMP-dependent protein kinase (PKA), which can directly phosphorylate Raf-1 in vitro. In this study, we confirmed this hypothesis by coexpressing Raf-1 with the constitutively active catalytic subunit of PKA, which could fully reproduce the inhibition previously achieved by cAMP. PKA-phosphorylated Raf-1 exhibits a reduced affinity for GTP-loaded Ras as well as impaired catalytic activity. As the binding to GTP-loaded Ras induces Raf-1 activation in the cell, we examined which mechanism is required for PKA-mediated Raf-1 inhibition in vivo. A Raf-1 point mutant (RafR89L), which is unable to bind Ras, as well as the isolated Raf-1 kinase domain were still fully susceptible to inhibition by PKA, demonstrating that the phosphorylation of the Raf-1 kinase suffices for inhibition. By the use of mass spectroscopy and point mutants, PKA phosphorylation site was mapped to a single site in the Raf-1 kinase domain, serine 621. Replacement of serine 621 by alanine or cysteine or destruction of the PKA consensus motif by changing arginine 618 resulted in the loss of catalytic activity. Notably, a mutation of serine 619 to alanine did not significantly affect kinase activity or regulation by activators or PKA. Changing serine 621 to aspartic acid yielded a Raf-1 protein which, when expressed to high levels in Sf-9 insect cells, retained a very low inducible kinase activity that was resistant to PKA downregulation. The purified Raf-1 kinase domain displayed slow autophosphorylation of serine 621, which correlated with a decrease in catalytic function. The Raf-1 kinase domain activated by tyrosine phosphorylation could be downregulated by PKA. Specific removal of the phosphate residue at serine 621 reactivated the catalytic activity. These results are most consistent with a dual role of serine 621. On the one hand, serine 621 appears essential for catalytic activity; on the other hand, it serves as a phosphorylation site which confers negative regulation.     

Preventive maintenance scheduling by variable dimension evolutionary algorithms

Black box optimization strategies have been proven to be useful tools for solving complex maintenance optimization problems. There has been a considerable amount of research on the right choice of optimization strategies for finding optimal preventive maintenance schedules. Much less attention is turned to the representation of the schedule to the algorithm. Either the search space is represented as a binary string leading to highly complex combinatorial problem or maintenance operations are defined by regular intervals which may restrict the search space to suboptimal solutions. An adequate representation however is vitally important for result quality.     

引领电容触控应用热潮 浅谈QMatrix技术

触控技术在家电,消费性电子产品及移动电子产品中,已逐渐取代电子机械式开关.它们之所以普及的动力,是因为设计人员认为触控技术能让他们创造风格独特及功能良好的设计,在产品差异化的同时,也能为终端使用者创造更高的价值.     

Reduction of investment costs by improvement of thermodynamic efficiency in cryogenic systems

Carefully directed investments to reduce the thermodynamic losses in critical subsystems often leads to a reduction of the overall investment costs. This is demonstrated by recent developments in the technology of low temperature refrigeration. By replacing the Joule-Thomson valve by a work extracting expander and other modifications of the cycle, operating costs are reduced by 40% and investment costs by 20%.     

Segmented gene conversion as a mechanism of correction of 18S rRNA pseudogene located outside of rDNA cluster in D. melanogaster

INTRODUCTION: Acute scrotum in the pediatric age is mainly related to surgical causes. Spermatic cord torsion and inguinoscrotal hernia must be ruled out first, because of the possible ischemic damage to gonadal tissue and therefore surgery is sometimes performed directly, thus representing also a diagnostic tool. Spermatic cord torsion is found in two age ranges, namely: the neonatal period, where it usually represents the evolution of an intrauterine process, and the peripubertal period, which is more frequent. An unquestionable and prompt diagnosis is particularly needed because of the extreme sensitivity of gonadal tissue to ischemia. In this particular field, color and power Doppler US, depicting gonadal flow, have greatly increased diagnostic imaging capabilities, which were previously limited to B-mode US. MATERIAL AND METHODS: We examined 19 peripubertal patients with the diagnosis of spermatic cord torsion made on the basis of B-mode US and then confirmed with color Doppler. RESULTS: We found two signs which can be considered highly suggestive of spermatic cord torsion: the spiral twist of spermatic vessels and the peculiar extent of reactive hydrocele, caused by the bell clapper anomaly of the vaginal sac. CONCLUSIONS: The above US patterns are very helpful to diagnose spermatic cord torsion.