Synthesis of 2-amino-6-(2-formyl-5-hydroxymethyl-1-pyrrolyl-)hexanoic acid

Summary The title compound has been synthesized by a novel route fromN -trifluoroacetyl lysine methyl ester and 2,9-dimethyldeca-2,8-diene-4,7-dione. Transformation of the pyrrole substituents and easy cleavage of protecting groups yields the compound in samples of high purity.

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Synthese der 2-Amino-6-(2-formyl-5-hydroxymethyl-l-pyrrolyl)-hexansäure

Zusammenfassung Die Titelverbindung wird auf einem neuen Weg ausN -Trifluoracetyllysinmethylester und 2,9-Dimethyldeca-2,8-dien-4,7-dion synthetisiert. Nach Umwandlung der Pyrrolsubstituenten und Abspaltung der Schutzgruppen unter milden Bedingungen erhält man die Titelverbindung in hoher Reinheit.

     

Mapping the Density of States Distribution of Organic Semiconductors by Employing Energy Resolved–Electrochemical Impedance Spectroscopy

Although the density of states (DOS) distribution of charge transporting states in an organic semiconductor is vital for device operation, its experimental assessment is not at all straightforward. In this work, the technique of energy resolved–electrochemical impedance spectroscopy (ER-EIS) is employed to determine the DOS distributions of valence (highest occupied molecular orbital (HOMO)) as well as electron (lowest unoccupied molecular orbital (LUMO)) states in several organic semiconductors in the form of neat and blended films. In all cases, the core of the inferred DOS distributions are Gaussians that sometimes carry low energy tails. A comparison of the HOMO and LUMO DOS of P3HT inferred from ER-EIS and photoemission (PE) or inverse PE (IPE) spectroscopy indicates that the PE/IPE spectra are by a factor of 2–3 broader than the ER-EIS spectra, implying that they overestimate the width of the distributions. A comparison of neat films of MeLPPP and SF-PDI₂ or PC(61)BM with corresponding blends reveals an increased width of the DOS in the blends. The results demonstrate that this technique does not only allow mapping the DOS distributions over five orders of magnitude and over a wide energy window of 7 eV, but can also delineate changes that occur upon blending.     

Correlation of calibration equations for test fixtures

This paper begins from the thru-short-open (TSO) and thru-line-match (TLM) methods to investigate the correlation of the calibration equations of these two methods. The relations among the measurements with the corresponding standards are obtained. It is found that the line standard with zero length can be used instead of ideal open and short, in the case that two test fixtures are symmetrical. For asymmetrical fixtures, the measurements with the standards line, open and short are related at certain frequencies, and the matched load can be replaced by the line standards. The relations established are used to test short and match standards and analyze the frequency limits of the TSO method. Good agreement between theory and experiment is obtained. It is found that the TSO method becomes very poor when the insertion phase of the thru standard is near nπ/4, and this method has a lower frequency limit. The TLM method is found unsuitable for calibrating asymmetrical fixtures     

采用遗传算法由电流环的近场测试识别辐射源

针对电大尺寸的电流环,通过遗传算法找到最佳等效基本辐射器.采用EMSCAN电磁干扰扫描系统进行电流环的近磁场测试,从而作出远场预测,并与仿真结果和半电波暗室的测试数据相比较.     

Surface-tension measurements of the eutectic alloy (Ag-Sn 96.2 at.%) with Cu additions

The maximum bubble-pressure method has been used to measure the surface tension and density of liquid alloys (Ag-Sn)_eut + Cu (X_Cu = 0.005, 0.020, 0.0375, and 0.065 (mole fraction)). The surface tension and density measurements were curried out in the temperature ranges of 262–942°C and 264–937°C, respectively. The linear dependencies of surface tensions and densities on temperature were observed, and they were described by straight-line equations. It has been found that the additions of Cu to the Ag-Sn eutectic alloy increase the surface tension. Experimental data of the surface tension were compared with those from modeling based on Butler’s method, using the optimized-thermodynamic parameters from the literature, and a slight tendency contrary to the experimental results was observed.     

Trans fatty acids in margarines and shortenings marketed in Austria

Margarines and shortenings available in Austria were repeatedly sampled in 1991/1992 and the content oftrans fatty acids (TFA) determined by using capillary GLC. Wide variations of the TFA contents with respect to intra- and inter-brand differences were observed. Diet margarines contained up to 1% TFA, while TFA concentrations in tub or stick margarines were much higher (15.7±5.8% and 21.3±5.3%, respectively). A sub-set of samples was also purchased in 1995 and a general reduction of the TFA content was noticed. Taking into account different market shares of certain margarine types, a weighted average of 15.7% TFA and 6.5% TFA was calculated for the 1991/1992 and the 1995 samples. Based on availability data the amount of TFA supplied with margarines was estimated to be 3.7 g per person per day, while a more accurate method of measuring dietary intakes, i.e. diet history and food frequency data, approximates the amount of TFA supplied with margarines to be 1.5 g per person per day for the 1991/1992 samples and 0.6 g for the 1995 samples.     

Silver versus white sheet as a back reflector for microcrystalline silicon solar cells deposited on LPCVD‐ZnO electrodes of various textures

We compare the performance of two back reflector designs on the optoelectrical properties of microcrystalline silicon solar cells. The first one consists of a 5‐µm‐thick low‐pressure chemical vapor deposition (LPCVD)‐ZnO electrode combined with a white sheet; the second one incorporates an Ag reflector deposited on a thin LPCVD‐ZnO layer (with thickness below 200 nm). For this latter design, the optical loss in the nano‐rough Ag reflector can be strongly reduced by smoothing the surface of the thin underlying ZnO layer, by means of an Ar‐plasma treatment. Because of its superior lateral conductivity, the thin‐ZnO/Ag back reflector design provides a higher fill factor than the dielectric back reflector design. When decreasing the roughness of the front electrode with respect to our standard front LPCVD‐ZnO layer, the electrical cell performance is improved; in addition, the implementation of the thin‐ZnO/Ag back reflector leads to a significant relative gain in light trapping. Applying this newly optimized combination of front and back electrodes, the conversion efficiency is improved from 8.9% up to 9.4%, for cells with an active‐layer thickness of only 1.1 µm. We thereby highlight the necessity to optimize simultaneously the front and back electrodes. Copyright © 2014 John Wiley & Sons, Ltd.     

Bildung von Pyrrolinonreduktonen beim Erhitzen von Hexosen mit Aminosauren

Zusammenfassung Beim Erhitzen von Glucose mit primären Aminen oder Aminosäuren in wäßriger Lösung werden u.a. Pyrrolinonreduktone der Struktur(10) gebildet. Das Reaktionsverhalten dieser bisher nicht bekannten Aminoreduktone wird untersucht und der Nachweis in Glucose-Glycin-Umsetzungsgemischen and in Malz durchgeführt. Die beim Erhitzen von Hexosen mit sekunddren Aminen beobachtete Bildung der sog. Aminohexosereduktone(5a) wird in Gegenwart von primären Aminen fast völlig zugunsten der Pyrrolinone unterdrückt.

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Formation of pyrrolinone reductones by heating hexoses with amino acids

Summary When an aqueous solution of glucose and primary amines or amino acids is heated pyrrolinone reductones of structure(10) are formed. Reactions of these till now unknown amino reductones are studied. Detection in heated glucose glycine mixtures and in malt is performed. Formation of the so-called amino hexose reductones (5a), observed when secondary amines are heated with hexoses, is almost completely suppressed in the presence of primary amines in favour of pyrrolinones.

     

Quantized UWB Transmitted Reference Systems

Digital implementation of ultra-wideband receivers requires analog-to-digital conversion (ADC) at an extremely high speed, thereby limiting the available bit resolution. Herein, the effect of low bit resolution quantization on the performance of UWB transmitted reference receivers is investigated. It is verified that the gain of the automatic-gain-control (AGC) has a significant effect on the achievable performance. Because of the considerable performance loss of conventional transmitted reference receivers in the presence of a low resolution ADC a new family of receiver structures optimized and tailored to quantized observations is presented. In particular, the generalized- likelihood ratio test (GLRT) based on the quantized samples is derived and shown to provide modest performance gains relative to the infinite resolution GLRT rule employed on the quantized received signal suggesting that conventional receiver structures can also be employed in the presence of a low resolution ADC. Results reveal that four bits of resolution in combination with an optimal choice for the AGC gain are sufficient to closely approach the performance of an infinite resolution receiver.     

Physical Mechanisms behind the Field‐Cycling Behavior of HfO2‐Based Ferroelectric Capacitors

Novel hafnium oxide (HfO₂)‐based ferroelectrics reveal full scalability and complementary metal oxide semiconductor integratability compared to perovskite‐based ferroelectrics that are currently used in nonvolatile ferroelectric random access memories (FeRAMs). Within the lifetime of the device, two main regimes of wake‐up and fatigue can be identified. Up to now, the mechanisms behind these two device stages have not been revealed. Thus, the main scope of this study is an identification of the root cause for the increase of the remnant polarization during the wake‐up phase and subsequent polarization degradation with further cycling. Combining the comprehensive ferroelectric switching current experiments, Preisach density analysis, and transmission electron microscopy (TEM) study with compact and Technology Computer Aided Design (TCAD) modeling, it has been found out that during the wake‐up of the device no new defects are generated but the existing defects redistribute within the device. Furthermore, vacancy diffusion has been identified as the main cause for the phase transformation and consequent increase of the remnant polarization. Utilizing trap density spectroscopy for examining defect evolution with cycling of the device together with modeling of the degradation results in an understanding of the main mechanisms behind the evolution of the ferroelectric response.