Vakuummikro‐ und Vakuumnanoelektronik mit Feldemission

Vacuum microelectronics and nanoelectronics with field emission — features of breakdown voltage in vacuum gaps lower than 10 μm Further miniaturization in vacuum electronics will be possible only with field‐emitter cathodes. However in microscale vacuum gaps in the range 10 μm field emission is a dominant process in gas breakdown process, leading to signif icant deviations from the traditional Paschen's Law. At first a significant reduction of breakdown voltage is observed. The high surface‐to‐volume ratio in microscale dimensions 3 μm and in interactions with gas desorption, outgassing and gas ionization during electron field‐emission give a ignition and stabilization of micro plasmas (glow discharges) or/and micro arcs, which exist largely independent of surrounding vacuum, atmospheric or over pressure. In this range the Paschen's Law is invalid. This is an interesting approach which opens up new dimensions for basic research, field emission‐driven micro plasmas and for novel fieldemitter applications in vacuum electronics and plasma technology.     

Open peer review: promoting transparency in open science

Scientometrics - Open peer review (OPR), where review reports and reviewers’ identities are published alongside the articles, represents one of the last aspects of the open science movement...     

A Grain Orientation-Independent Single-Step Saw Damage Gettering/Wet texturing Process for Efficient Silicon Solar Cells

Improving electrical and optical properties is important in manufacturing high-efficiency solar cells. Previous studies focused on individual gettering and texturing methods to improve solar cell material quality and reduce reflection loss, respectively. This study presents a novel method called saw damage gettering with texturing that effectively combines both methods for multicrystalline silicon (mc-Si) wafers manufactured using the diamond wire sawing (DWS) method. Although mc-Si is not the Si material currently used in photovoltaic products, the applicability of this method using the mc-Si wafers as it contains all grain orientations is demonstrated. It utilizes saw damage sites on the wafer surfaces for gettering metal impurities during annealing. Additionally, it can crystallize amorphous silicon on wafer surfaces generated during the sawing process to allow conventional acid-based wet texturing. This texturing method and annealing for 10 min allow for the removal of metal impurities and effectively forms a textured DWS Si wafer. The results show that the open-circuit voltage (ΔV_oc = +29 mV), short-circuit current density (ΔJ_sc = +2.5 mA cm⁻²), and efficiency (Δη = +2.1%) improved in the p-type passivated emitter and rear cells (p-PERC) manufactured using this novel method, as compared to those in the reference solar cells.     

Intercomparison of infrared cavity leak-out spectroscopy and gas chromatography-flame ionization for trace analysis of ethane

Comparison of two different methods for the measurement of ethane at the parts-per-billion (ppb) level is reported. We used cavity leak-out spectroscopy (CALOS) in the 3 microm wavelength region and gas chromatography-flame ionization detection (GC-FID) for the analysis of various gas samples containing ethane fractions in synthetic air. Intraday and interday reproducibilities were studied. Intercomparing the results of two series involving seven samples with ethane mixing ratios ranging from 0.5 to 100 ppb, we found a reasonable agreement between both methods. The scatter plot of GC-FID data versus CALOS data yields a linear regression slope of 1.07 +/- 0.03. Furthermore, some of the ethane mixtures were checked over the course of 1 year, which proved the long-term stability of the ethane mixing ratio. We conclude that CALOS shows equivalent ethane analysis precision compared to GC-FID, with the significant advantage of a much higher time resolution (<1 s) since there is no requirement for sample preconcentration. This opens new analytical possibilities, e.g., for real-time monitoring of ethane traces in exhaled human breath.     

A new type of metalloprotein: The Mo storage protein from azotobacter vinelandii contains a polynuclear molybdenum-oxide cluster

Azotobacter vinelandii is a diazotrophic bacterium characterized by the outstanding capability of storing Mo in a special storage protein, which guarantees Mo-dependent nitrogen fixation even under growth conditions of extreme Mo starvation. The Mo storage protein is constitutively synthesized with respect to the nitrogen source and is regulated by molybdenum at an extremely low concentration level (0-50 nM). This protein was isolated as an alpha4beta4 octamer with a total molecular mass of about 240 kg mol(-1) and its shape was determined by small-angle X-ray scattering. The genes of the alpha and beta subunits were unequivocally identified; the amino acid sequences thereby determined reveal that the Mo storage protein is not related to any other known molybdoprotein. Each protein molecule can store at least 90 Mo atoms. Extended X-ray absorption fine-structure spectroscopy identified a metal-oxygen cluster bound to the Mo storage protein. The binding of Mo (biosynthesis and incorporation of the cluster) is dependent on adenosine triphosphate (ATP); Mo release is ATP-independent but pH-regulated, occurring only above pH 7.1. This Mo storage protein is the only known noniron metal storage system in the biosphere containing a metal-oxygen cluster.     

The KeY tool

KeY is a tool that provides facilities for formal specification and verification of programs within a commercial platform for UML based software development. Using the KeY tool, formal methods and object-oriented development techniques are applied in an integrated manner. Formal specification is performed using the Object Constraint Language (OCL), which is part of the UML standard. KeY provides support for the authoring and formal analysis of OCL constraints. The target language of KeY based development is Java Card DL, a proper subset of Java for smart card applications and embedded systems. KeY uses a dynamic logic for Java Card DL to express proof obligations, and provides a state-of-the-art theorem prover for interactive and automated verification. Apart from its integration into UML based software development, a characteristic feature of KeY is that formal specification and verification can be introduced incrementally.     

Zum Einfluß von Nahrungsfett auf die Plasmaspiegel von Lecithin,Lysolecithin und Sphingomyelin beim Menschen

Effect of Dietary Fat on Plasma Level of Lecithin, Lysolecithin and Sphingomyelin in Man Reduction of fat content of the diet leads to a decrease in total phosphatide level in plasma, mainly due to alteration in the lecithin fraction. The level of lecithin in experimental persons fed a formula diet containing 25% of the total energy as fat was distinctly lower than in those fed 33% of the total energy as fat. The P/S quotient at a fat level of 33% of total energy had still an influence on the lecithin level in blood. At a fat level of 25% of total energy, modification of the fat components did not alter the serum lecithin level to a statistically significant extent. The plasma level of lysolecithin decreased with reduction in the proportion of dietary fat, however, it did not vary with different types of fat. The level of sphingomyelin was almost the same for the two formula diets and it did not vary either by reduction in the proportion of fat or by modification of the fat components.     

Intractable unifiability problems and backtracking

Restrictions of the problem of finding all maximal unifiable or minimal nonunifiable subsets to those of certain sizes are shown to be NP-hard, and consequently inappropriate in general for reducing thrashing by intelligent backtracking in resolution theorem provers and logic program executions. We also show that existing backtrack methods based on the computation of all maximal unifiable subsets of assignments as a means to avoid thrashing are intractable because the solution length of these subsets can increase exponentially with the input length, and we give a corresponding result for minimal nonunifiability. The results apply not only to standard unification, but to a characterized collection of unification algorithms which includes unification without the occurs check. This now justifies the necessity for approximate or heuristic approaches to reduce thrashing in resolution theorem provers and the execution of logic programs.A version of this paper appears in Proceedings of the Third International Logic Programming Conference, London, Lecture Notes in Computer Science, Springer 225, 107–121 (1986).     

Zur Ernährungsphysiologie der Schlachttierfette

Nutritional Properties of Animal Fats Dietary fat plays two roles, as a carrier of energy, and, in the form of essential fatty acids, as an indispensable component of food. Animal fats can meet both requirements. Since fats are greatly accepted by the people due to their taste, the fat consumption by the entire population has been very high. High fat consumption are believed to have resulted in increased level of cholesterol and premature occurrence of coronary diseases. Increase in the incidence of deaths by coronary diseases has drawn attention to the nutritional properties of dietary fats, which affect the level of cholesterol. It has been established that saturated fatty acids in foods raise the level of serum cholesterol, whereas polyunsaturated fatty acids lower it. However, with diets of relatively low fat content the ratio of saturated to polyunsaturated fatty acids is not so significant with regard to level of serum cholesterol as with high-fat diets.