Nanocrystal inks without ligands: stable colloids of bare germanium nanocrystals

Colloidal semiconductor nanocrystals typically have ligands attached to their surfaces that afford solubility in common solvents but hinder charge transport in nanocrystal films. Here, an alternative route is explored in which bare germanium nanocrystals are solubilized by select solvents to form stable colloids without the use of ligands. A survey of candidate solvents shows that germanium nanocrystals are completely solubilized by benzonitrile, likely because of electrostatic stabilization. Films cast from these dispersions are uniform, dense, and smooth, making them suitable for device applications without postdeposition treatment.     

An intercomparison study of the determination of sulfite in tropical shrimps by the West European Fish Technologists’ Association (WEFTA)

Eight WEFTA laboratories participated in two series of intercomparison exercises on sulfite determination in tropical shrimps. Samples of tropical shrimps were spiked with sodium metabisulfite (Na₂S₂O₅) and hydroxymethylsulfonate (HMS) at a level of 25–90?mg SO₂/kg. Most of the laboratories determined the sulfite content with (modified) methods of Monier-Williams or De Vries et al. The overall mean recovery of sulfite was rather low (47–60%), which may be attributed to an irreversible reaction of sulfite with the tropical shrimps. The repeatability of the methods within the participating laboratories was good. However, reproducibility among the laboratries was poor. It has been shown that the sulfite content in tropical shrimps spiked with Na₂S₂O₅ decreased during storage at ?20°C and at +4°C. Hydroxymethyl- sulfonate was stable during storage.     

Primary odorants of chicken broth

Summary Aroma extract dilution analysis (AEDA) of the volatiles obtained by the simultaneous distillation/extraction of a chicken broth resulted in 16 primary odour compounds with FD factor values between 64 and 2048. Fourteen of these compounds were identified as: 2-methyl-3-furanthiol, 2-furfurylthiol, methional, 2,4,5-trimethylthiazole, nonanal, 2(E)-nonenal, 2-formyl-5-methylthiophene,p-cresol, 2(E),4(E)-nonadienal, 2(E),4(E)-decadienal, 2-undecenal,-ionone, -decalactone and -dodecalactone. The primary odorants of chicken broth were compared with those resulting from the AEDA of broths from cow and ox meat. The major differences were that 2(E),4(E)-decadienal (fatty) and -dodecalactone (tallowy, fruity) prevailed in the chicken broth, whereas the sulphur compounds, bis(2-methyl-3-furyl)disulphide (meat-like-aroma) and methional (aroma like cooked potatoes), predominated in broths prepared from cow and ox meats. The odour thresholds (in air) of important meat aroma compounds are reported.

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Primäre Geruchsstoffe bei Hühnerbrühe Eine vergleichende Untersuchung mit Brühen aus Kuh- und Ochsenfleisch

Zusammenfassung Durch Aromaextraktverdünnungsanalyse (AEVA) der flüchtigen Verbindungen, isoliert durch simultane Destillation/Extraktion aus Hühnerbrühe, wurden 16 primäre Aromastoffe mit FD-Faktoren im Bereich 64 bis 2048 wahrgenommen. Von diesen Verbindungen wurden 14 identifiziert: 2-Methyl-3-furanthiol, 2-Furfurylthiol, Methional, 2,4,5-Trimethylthiazol, Nonanal, 2(E)-Nonenal, 2-Formyl-5-methylthiophen,p-Kresol, 2(E),4(E)-Nonadienal, 2(E),4(E)-Decadienal, 2-Undecenal,-Ionon, -Decalacton, -Dodecalacton. Die primären Geruchsstoffe der Hühnerbrühe wurden mit denen verglichen, die aus einer AEVA von Kuh- und Ochsenfleischbrühe stammten. Hauptunterschiede waren: 2(E),4(E)-Decadienal (fettig) und -Dodecalacton (talgig, fruchtig) überwogen in Hühnerbrühe, während die Schwefelverbindungen Bis(2-methyl-3-furyl)disulfid (fleischartig) und Methional (gekochte Kartoffeln) in den Brühen aus Rindfleisch dominierten. Die Geruchsschwellen (in Luft) wichtiger Fleischaromastoffe wurden bestimmt.

     

A comparison between thin film solar cells made from co‐evaporated CuIn1‐xGaxSe2 using a one‐stage process versus a three‐stage process

Until this day, the most efficient Cu(In,Ga)Se₂ thin film solar cells have been prepared using a rather complex growth process often referred to as three‐stage or multistage. This family of processes is mainly characterized by a first step deposited with only In, Ga and Se flux to form a first layer. Cu is added in a second step until the film becomes slightly Cu‐rich, where‐after the film is converted to its final Cu‐poor composition by a third stage, again with no or very little addition of Cu. In this paper, a comparison between solar cells prepared with the three‐stage process and a one‐stage/in‐line process with the same composition, thickness, and solar cell stack is made. The one‐stage process is easier to be used in an industrial scale and do not have Cu‐rich transitions. The samples were analyzed using glow discharge optical emission spectroscopy, scanning electron microscopy, X‐ray diffraction, current–voltage‐temperature, capacitance‐voltage, external quantum efficiency, transmission/reflection, and photoluminescence. It was concluded that in spite of differences in the texturing, morphology and Ga gradient, the electrical performance of the two types of samples is quite similar as demonstrated by the similar J–V behavior, quantum spectral response, and the estimated recombination losses. Copyright © 2014 John Wiley & Sons, Ltd.     

A new 2D model for the electrical potential in a cell stripe in thin‐film solar modules including local defects

The performance of solar modules is strongly influenced by the presence of local defects (shunts) in the module. Modeling cell stripes with local defects requires at least a 2D model. Most works on such 2D models are based on the numerical solution of the involved differential equations. These numerical models are quite computationally intensive and hence tedious for applications that require many evaluations of the model, for example, fitting experiments, computing accurate current/voltage characteristics, and finding a maximum power point. In this work, we present a fast 2D model for a cell stripe based on the superposition of several analytical expressions. This model uses a linearization of the solar cell current/voltage characteristics and takes the sheet resistance of one electrode into account (i.e., the other electrode is assumed to be a perfect conductor). With our model, the potential distribution in a cell stripe in the presence of local shunts can be computed in a matter of seconds. The model has been made freely available. Copyright © 2013 John Wiley & Sons, Ltd.     

Scleral topography analysed by optical coherence tomography

Purpose

A detailed evaluation of the corneo-scleral-profile (CSP) is of particular relevance in soft and scleral lenses fitting. The aim of this study was to use optical coherence tomography (OCT) to analyse the profile of the limbal sclera and to evaluate the relationship between central corneal radii, corneal eccentricity and scleral radii.

木材隔热材料刨削加工的研究

房屋结构隔热的经济意义越来越受重视。因为将来的能源价格将越来越贵。在产生能量的同时也造成二氧化碳含量的增高。考虑到这两方面的原因，一个节能的方法是使用木材的隔热材料。一个由BMBF资助的项目——包括了研究传统刨削加工产生可作为隔热材料的木屑的优化。考虑到它作为隔热材料的性能。另外还有切屑与加工表面质量的关系等。