Silicon surface passivation by Al2O3: Recombination parameters and inversion layer solar cells

The interface between p- and n-type FZ-Si and an amorphous aluminum oxide (Al2O3) surface passivation layer deposited by plasma-assisted atomic layer deposition (ALD) was investigated by frequency-dependent conductance measurements. The hole capture cross section in the lower half of the bandgap, σp = (4±3)×10 -16 cm2, was found to be independent of energy. The electron capture cross section σn in the upper half of the bandgap decreases from σn = (7±4)×10-15 cm2 at midgap over two orders of magnitude towards the conduction band edge. Numerical simulations of the effective surface recombination velocity based on these recombination parameters show a good agreement with experimental surface recombination velocities for a wide range of excess carrier and surface charge densities. Carrier transport in the inversion layer formed at the n-Si/Al2O3 interface was investigated yielding a sheet resistance of 15 kΩ/, which was reduced to 6 kΩ/ for a surface charge density of -2×1013 cm-2 obtained by corona charging. The applicability of Al2O3 inversion layers as emitters in n-type inversion layer solar cells was demonstrated by short circuit current densities of up to 25 mA/cm2, which show a pronounced dependence on surface charge density.BMU/032505

A Survey on FPGA-Based Heterogeneous Clusters Architectures

In recent years, the most powerful supercomputers have already reached megawatt power consumption levels, an important issue that challenges sustainability and shows the impossibility of maintaining this trend. To this date, the prevalent approach to supercomputing is dominated by CPUs and GPUs. Given their fixed architectures with generic instruction sets, they have been favored with lots of tools and mature workflows which led to mass adoption and further growth. However, reconfigurable hardware such as FPGAs has repeatedly proven that it offers substantial advantages over this supercomputing approach concerning performance and power consumption. In this survey, we review the most relevant works that advanced the field of heterogeneous supercomputing using FPGAs focusing on their architectural characteristics. Each work was divided into three main parts: network, hardware, and software tools. All implementations face challenges that involve all three parts. These dependencies result in compromises that designers must take into account. The advantages and limitations of each approach are discussed and compared in detail. The classification and study of the architectures illustrate the trade-offs of the solutions and help identify open problems and research lines

Systematic screening of polyphosphate (poly P) levels in yeast mutant cells reveals strong interdependence with primary metabolism

BACKGROUND: Inorganic polyphosphate (poly P) occurs universally in all organisms from bacteria to man. It functions, for example, as a phosphate and energy store, and is involved in the activation and regulation of proteins. Despite its ubiquitous occurrence and important functions, it is unclear how poly P is synthesized or how poly P metabolism is regulated in higher eukaryotes. This work describes a systematic analysis of poly P levels in yeast knockout strains mutated in almost every non-essential gene. RESULTS: After three consecutive screens, 255 genes (almost 4% of the yeast genome) were found to be involved in the maintenance of normal poly P content. Many of these genes encoded proteins functioning in the cytoplasm, the vacuole or in transport and transcription. Besides reduced poly P content, many strains also exhibited reduced total phosphate content, showed altered ATP and glycogen levels and were disturbed in the secretion of acid phosphatase. CONCLUSION: Cellular energy and phosphate homeostasis is suggested to result from the equilibrium between poly P, ATP and free phosphate within the cell. Poly P serves as a buffer for both ATP and free phosphate levels and is, therefore, the least essential and consequently most variable component in this network. However, strains with reduced poly P levels are not only affected in their ATP and phosphate content, but also in other components that depend on ATP or free phosphate content, such as glycogen or secreted phosphatase activity

Threshold resummation for high-transverse-momentum Higgs production at the LHC

We study the resummation of large logarithmic QCD corrections for the process pp ->H+ X when the Higgs boson H is produced at high transverse momentum. The corrections arise near the threshold for partonic reaction and originate from soft gluon emission. We perform the all-order resummation at next-to-leading logarithmic accuracy and match the resummed result with the next-to-leading order perturbative predictions. The effect of resummation on the Higgs transverse momentum distribution at the LHC is discussed.Comment: 19 pages, 3 figure

Extraction of Spin-Dependent Parton Densities and Their Uncertainties

We discuss techniques and results for the extraction of the nucleon's spin-dependent parton distributions and their uncertainties from data for polarized deep-inelastic lepton-nucleon and proton-proton scattering by means of a global QCD analysis. Computational methods are described that significantly increase the speed of the required calculations to a level that allows to perform the full analysis consistently at next-to-leading order accuracy. We examine how the various data sets help to constrain different aspects of the quark, anti-quark, and gluon helicity distributions. Uncertainty estimates are performed using both the Lagrange multiplier and the Hessian approaches. We use the extracted parton distribution functions and their estimated uncertainties to predict spin asymmetries for high-transverse momentum pion and jet production in polarized proton-proton collisions at 500 GeV center-of-mass system energy at BNL-RHIC, as well as for W boson production.Comment: 25 pages, 15 eps figures, v2: minor changes, final version to appear in Phys. Rev.

In Vitro Antibacterial Activity of Microbial Natural Products against Bacterial Pathogens of Veterinary and Zoonotic Relevance

Antimicrobial resistance (AMR) is considered one of the greatest threats to both human and animal health. Efforts to address AMR include implementing antimicrobial stewardship programs and introducing alternative treatment options. Nevertheless, effective treatment of infectious diseases caused by bacteria will still require the identification and development of new antimicrobial agents. Eight different natural products were tested for antimicrobial activity against seven pathogenic bacterial species (Brachyspira sp., Chlamydia sp., Clostridioides sp., Mannheimia sp., Mycobacterium sp., Mycoplasma sp., Pasteurella sp.). In a first pre-screening, most compounds (five out of eight) inhibited bacterial growth only at high concentrations, but three natural products (celastramycin A [CA], closthioamide [CT], maduranic acid [MA]) displayed activity at concentrations 16 µg/mL against Mannheimia for CA, CT, and MA, respectively. CA, CT, and MA exhibited higher MIC50 and MIC90 values against Pasteurella isolates with a known AMR phenotype against commonly used therapeutic antimicrobial agents than against isolates with unknown AMR profiles. This study demonstrates the importance of whole-cell antibacterial screening of natural products to identify promising scaffolds with broad- or narrow-spectrum antimicrobial activity against important Gram-negative veterinary pathogens with zoonotic potentia

Joint Resummation for Higgs Production

We study the application of the joint resummation formalism to Higgs production via gluon-gluon fusion at the LHC, defining inverse transforms by analytic continuation. We work at next-to-leading logarithmic accuracy. We find that at low Q_T the resummed Higgs Q_T distributions are comparable in the joint and pure-Q_T formalisms, with relatively small influence from threshold enhancement in this range. We find a modest (about ten percent) decrease in the inclusive cross section, relative to pure threshold resummation.Comment: 22 pages, LaTeX, 5 figures as eps file

Substrate induced nanoscale resistance variation in epitaxial graphene

Graphene, the first true two-dimensional material, still reveals the most remarkable transport properties among the growing class of two-dimensional materials. Although many studies have investigated fundamental scattering processes, the surprisingly large variation in the experimentally determined resistances is still an open issue. Here, we quantitatively investigate local transport properties of graphene prepared by polymer assisted sublimation growth using scanning tunneling potentiometry. These samples exhibit a spatially homogeneous current density, which allows to analyze variations in the local electrochemical potential with high precision. We utilize this possibility by examining the local sheet resistance finding a significant variation of up to 270% at low temperatures. We identify a correlation of the sheet resistance with the stacking sequence of the 6H silicon carbide substrate and with the distance between the graphene and the substrate. Our results experimentally quantify the impact of the graphene-substrate interaction on the local transport properties of graphene

Reflections upon separability and distillability

We present an abstract formulation of the so-called Innsbruck-Hannover programme that investigates quantum correlations and entanglement in terms of convex sets. We present a unified description of optimal decompositions of quantum states and the optimization of witness operators that detect whether a given state belongs to a given convex set. We illustrate the abstract formulation with several examples, and discuss relations between optimal entanglement witnesses and n-copy non-distillable states with non-positive partial transpose.Comment: 12 pages, 7 figures, proceedings of the ESF QIT Conference Gdansk, July 2001, submitted to special issue of J. Mod. Op