Radio-frequency design of a new C-band variable power splitter

A novel variable C-band radio-frequency(RF)power splitter was designed at Shanghai Institute of Applied Physics, Chinese Academy of Sciences. Using three RF impedance combiners, an H-bend, and an RF polarizer, this new power splitter is much more compact than a traditionally designed splitter, which comprises three3-dB hybrids. The parameters were optimized to achieve good matching and minimize reflection. Here, the RF design of the new C-band variable power splitter is presented.     

轴流风机叶尖泄漏流动的大涡模拟（英文）

本文采用大涡模拟(LES)的方法研究了在基于外壳直径的雷诺数为9.36×105条件下5叶片的轴流式风扇的流动特性,并且着重分析了叶尖泄漏的流动现象。本文使用了基于有限体积法和分层笛卡尔网格的可压流求解器进行数值计算,并应用了体积守恒的切割网格方法处理风扇几何结构的浸入式边界。同时开发了用于笛卡尔网格的旋转周期性边界条件,这样只需分析由2.5亿网格构造的包含一片叶片的72°区域。该研究首先对网格质量进行了分析,之后讨论了瞬态和时均流场的特性,并与使用RANS的5叶片模拟结果进行了对比。RANS和LES模拟结果的主要不同之处体现在叶尖泄漏涡尾流中的湍流动能。本文进而研究了叶尖间隙对叶尖泄漏涡的影响。研究表明,间隙的大小会影响叶尖泄漏涡的大小形状。此外,间隙中更多的分离现象和反向旋转涡会导致较低的湍流动能。     

First liquid single crystal elastomer containing lactic acid derivative as chiral co-monomer: Synthesis and properties

For the first time new type of liquid single crystal elastomers forming the chiral smectic A^* (SmA^*) phase has been prepared using chiral lactic acid derivative as a co-monomer. The synthesis and the basic characterization of the ferroelectric liquid crystalline co-monomer based on differential scanning calorimetry and small/wide-angle X-ray scattering are reported and discussed. The monomer possesses the paraelectric SmA^* and the ferroelectric SmC^* phases over a broad temperature range. The preparation of new smectic liquid crystalline elastomers together with characterization of their mesomorphic and structural properties is also reported. New elastomers possess the orthogonal paraelectric SmA^* phase over 50 K broad temperature range.     

1H‐decoupling and Isotopic Labeling for the Measurement of the Longitudinal Relaxation Time of Hyperpolarized 13C‐Methylenes in Choline Analogs

The T₁ of a hyperpolarized site in solution is a key parameter that determines the time‐window in which its NMR signals are observable. For ¹³C sites adjacent to protons, ¹H‐decoupling has been shown to increase the hyperpolarized signal resolution and SNR. Additionally, polarization transfer to protons has shown utility in increasing the sensitivity of detection. However, ¹H‐decoupling could lead to a change in the decay rate of a hyperpolarized ¹³C site. Here we tested this possible effect in a case where the protons are directly bound to an sp³ hyperpolarized ¹³C site (using [1,2‐¹³C₂]choline) and ¹H‐decoupling was applied continuously throughout the hyperpolarized decay measurement. We found that ¹H‐decoupling did not lead to any significant changes in the ¹³C polarization decay time but did result in the expected collapse of J‐coupling and produced sharper signals. This result suggested that ¹H‐decoupling did not affect the decay rate of hyperpolarized sp^{3 13}C sites. The deuterium‐substitution approach (using [1,1,2,2‐D₄,1‐¹³C]choline) showed a dramatic prolongation of T₁. Upper bounds on the T₁ of all investigated sites were calculated.     

Aroma von Wei?weinblüten: Korrelation sensorischer Daten mit Headspace-Inhaltsstoffen

Zusammenfassung Mittels Headspace-Analyse in Kombination mit gaschromatographisch-spektroskopischen Methoden (GC-FID und GC-FTIR-MS), sowie der GC-Schnüffel-Technik gelang es, Blüten verschiedener Weinsorten (sieben verschiedene Weißweinspecies) anhand der Duftstoff-Zusammensetzung bezüglich duftbestimmender Sesquiterpene und duftabrundender Monoterpene im Headspace zu korrelieren.-Alle untersuchten Weinblüten besitzen einen reseda-artigen, schönen, blumigen, staubigen, trockenen, angenehmen, interessanten, grünen, frischen, intensiven und süßen Duft wobei sich die einzelnen Blüten, je nach Weinsorte, lediglich in der Intensität der Einzeldüfte, nicht aber in der Gesamtduftrichtung unterscheiden. Die erstellten Geruchsprofile und die entsprechenden multivariaten Korrelationen dieser Profile zeigten eine weitgehende Übereinstimmung mit jenen Ergebnissen, die aus den Headspace-Inhaltsstoffkorrelationen der einzelnen Blütensorten erhalten werden konnten. -Die Möglichkeiten weiterer Zusammenhänge mit entsprechenden ampelographischen Aspekten der untersuchten Weinsorten werden diskutiert.

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Aroma of white vine blossoms: correlation of sensoric data with headspace constituents

Using headspace-analysis in combination with gaschromatographic-spectroscopic methods (GC-FID and GC-FTIR-MS) as well as with the GC-sniffing-technique it was possible to correlate blossoms of 7 different vine-varieties by means of the composition of odor compounds in their headspace considering only odor-dominant sesquiterpenes and odor-assistant monoterpenes. -All investigated vineblossoms possess a mignonette-like, pleasant, floral, dusty, dry, interesting, green, fresh, intense and sweet odour and with regard to the vine-species they only differ in the intensity of single odournotes, but not in the direction of the total odour. The odour-profiles and the corresponding multivariate data analysis of these profiles showed a significant agreement with those results, which were obtained by correlations of headspace constituents. -The possibility of further connectivities with the corresponding ampelographic aspects of the investigated vine-species is also discussed.

     

Aroma von Rotweinblüten: Korrelation sensorischer Daten mit Headspace-Inhaltsstoffen

By headspace-analysis in combination with gas Chromatographic-spectroscopic systems (GC-FID and GC-FTIR-MS) as well as by GC-sniffing-technique it was possible to correlate different vine-varieties by means of the composition of their corresponding vine blossoms fragrance compounds. Red vine blossoms possess a similar odor to white vine blossoms [1, 2] with a beautiful floral and fruity-fresh note as well as a mignonette-like, acriddusty and green side-note. The blossoms differ, depending on the vine-variety, only in the intensity of single odor impressions, but not in the direction of the total odor. The analysis of headspace [3, 4] constituents of different samples of blossoms using of GC-FID, GC-FTIR-MS and the combination with the GC-sniffing-technique allows the identification of odor dominating sesquiterpenes and odor assistant monoterpenes. Various correlations (odor profiles, qualitative and quantitative statistics and multivariate data analyses) give additional information for the characterization of investigated red vine species. A clear separation of the red vine species from the white vine species in respect of the multivariate data analysis [5, 6] of the investigations of headspace constituents of single blossoms is also possible.     

Cuticular hydrocarbons of Tetramorium ants from central Europe: analysis of GC-MS data with self-organizing maps (SOM) and implications for systematics

Cuticular hydrocarbons were extracted from workers of 63 different nests of five species of Tetramorium ants (Hymenoptera: Formicidae) from Austria, Hungary, and Spain. The GC-MS data were classified (data mining) by self-organizing maps (SOM). SOM neurons derived from primary neuron separation were subjected to hierarchical SOM (HSOM) and were grouped to neuron areas on the basis of vicinity in the hexagonal output grid. While primary neuron separation and HSOM resulted in classifications on a level more sensitive than species differences, neuron areas resulted in chemical phenotypes apparently of the order of species. These chemical phenotypes have implications for systematics: while the chemical phenotypes for T. ferox and T. moravicum correspond to morphological determination, in T. caespitum and T. impurum a total of six chemical phenotypes is found. Three hypotheses are discussed to explain this disparity between morphological and chemical classifications, including in particular the possibility of hybridization and the existence of cryptic species. Overall, the GC-MS profiles classified by SOM prove to be a practical alternative to morphological determination (T. ferox, T. moravicum) and indicate the need to revisit systematics (T. caespitum, T. impurum).     

Zum Aroma von Speisepilzen

Zusammenfassung Kopfraum-Proben, Wasserdampfdestillate und Dichlormethanextrakte der beliebtesten Speisepilze Champignon (Agaricus campestris undAgaricus bisporus), Parasol (Riesenschirmpilz,Lepiota procera), Hallimasch (Armillaria mellea), Steinpilz (Herrenpilz,Boletus edulis) und Pfifferling (Eierschwamm,Cantharellus cibarius) wurden mittels GC/FID, GC/FTIR/MS und GC-Sniffing-Technik untersucht. Ziel dieser Untersuchungen war es, die für den typischen Duft der einzelnen Pilzarten verantwortlichen Inhaltsstoffe zu identifizieren. Um Daten aus GC/FTIR/MS-Messungen mit olfactorischen Daten direkt vergleichen zu können, wurde die GC-Sniffing-Technik verwendet. Die Ergebnisse, besonders solche von Kopfraumproben, zeigten, daß 1-Octen-3-o1, ein bekannter Pilzduftstoff, von grundlegender Bedeutung für die Kopfnote der untersuchten Pilze ist. Mehr als 70 Einzelkomponenten tragen qualitativ und quantitativ zum Gesamtgeruchseindruck der einzelnen Arten bei, wobei besonders C₈-Derivate in signifikanter Weise den Duft der meisten Kopfraumproben beeinflussen. Carbonylverbindungen und Ester (C₄-C₁₄) dagegen spielen eine wesentliche Rolle (z. B. Anisaldehyd in Champignonproben) vor allem in den Wasserdampfdestillations- und Extraktproben.

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The aroma of edible mushrooms. Headspace analysis using GC/FID and GC/FTIR/MS

Headspace samples, steam distillates and dichloromethane extracts of the most well liked edible mushrooms (Agaricus campestris, Agaricus bisporus, Lepiota procera, Armillaria mellea, Boletus edulis and Cantharellus cibarius) were investigated by means of GC/FID, GC/FTIR/MS and a GC-sniffing technique. The aim of these analyses was the identification of constituents responsible for the typical mushroom odour of each species. To relate GC/Fouriertransform Infrarot-Detektor/MS (GC/FTIR/MS) data with olfactoric ones, the GC-sniffing technique was used. The results, especially of the headspace samples, showed that 1-octen-3-ol, a well-known mushroom aroma compound, is of basic importance for the top note of the investigated mushrooms. More than seventy constituents that additionally have an effect (qualitatively and quantitatively) on the odour impression of these species were identified. Among them especially C₈-derivatives contribute in a significant way to the headspace odour of most of the samples. Carbonyls and esters (C₄-C₁₄) on the other hand play an important role (e.g. anisaldehyde inAgaricus samples) more in the steam distillate and extract samples.

     

Overcoming adverse effects of hailnets on fruit quality and microclimate in an apple orchard

BACKGROUND: With the increase of hailstorms as a possible result of global warming, fruit crops are increasingly grown under hailnets. This results in lesser fruit quality in terms of colouration, fruit mass, firmness, starch and taste, i.e. sugar and acid, and vitamin content under hailnet due to altered microclimate and light deprivation. Reflective mulches (Extenday and Daybright) were spread in autumn 2006 to improve fruit quality and light utilisation under hailnet at Klein‐Altendorf Research Station near Bonn, Germany. A monophosphate (Seniphos) was applied twice for the same purpose; untreated apple cv. ‘Elstar’ trees served as control. RESULTS: Under the translucent, ‘white’ hailnet, humidity was increased by ca. 6%, air temperature reduced by ca. 1.6 °C, soil temperature increased by ca. 0.5 °C and light reduced by 11–15% resulting in lesser fruit quality of 2.5% less sugar and less taste. The two reflective mulches increased light reflection at 45° and 90° angles by 2.5‐ to 6.3‐fold. No differences in fruit ripening and firmness were observed, but fruit from trees under hailnet with reflective mulch contained up to 2.4% (from 13.3 to 15.7%) more sugar than those of the control (uncovered grass alleys). A less negative normalised differential vegetation index (NDVI) of ? 0.3 on the red compared with ? 0.5 on the green fruit side indicated more chlorophyll in the outer, sun‐exposed, red side of the apples relative to the shaded side. Monophosphate‐treated fruits maintained the peel chlorophyll with a greener ground colour of 92–97° hue and a NDVI of ? 0.3 as in the grassed control. Fruit in the lower canopy with reflective mulch were darker red (a value 30; 22° hue) relative to the grassed control with a = 25 and 43° hue (light red), expressed in a 4‐fold increase in normalised anthocyanin index (NAI), but showed enhanced chlorophyll breakdown (NDVI from ? 0.2 to ? 0.5); similarly, the monophosphate increased the NAI by up to 2.5‐fold. CONCLUSIONS: The effect of both reflective mulch cloths was most pronounced on apple fruit in the lower canopy under hailnet, which developed large vitamin C contents and a dark red top colour relative to the grassed control with enhanced chlorophyll breakdown. Both reflective mulch cloths increased the percentage of class I fruit with > 25% colouration by 12% (from 82 to 94%) without and under hailnet by 23% (from 69 to 89%) relative to the grassed control resulting in financial net gains of up to 1300 € ha^?1 Copyright © 2007 Society of Chemical Industry     

7Li MRI of Li batteries reveals location of microstructural lithium

There is an ever-increasing need for advanced batteries for portable electronics, to power electric vehicles and to facilitate the distribution and storage of energy derived from renewable energy sources. The increasing demands on batteries and other electrochemical devices have spurred research into the development of new electrode materials that could lead to better performance and lower cost (increased capacity, stability and cycle life, and safety). These developments have, in turn, given rise to a vigorous search for the development of robust and reliable diagnostic tools to monitor and analyse battery performance, where possible, in situ. Yet, a proven, convenient and non-invasive technology, with an ability to image in three dimensions the chemical changes that occur inside a full battery as it cycles, has yet to emerge. Here we demonstrate techniques based on magnetic resonance imaging, which enable a completely non-invasive visualization and characterization of the changes that occur on battery electrodes and in the electrolyte. The current application focuses on lithium-metal batteries and the observation of electrode microstructure build-up as a result of charging. The methods developed here will be highly valuable in the quest for enhanced battery performance and in the evaluation of other electrochemical devices.