Photochemie von Acylaziden. VIII [1]. Reagieren Acylnitrene wie 1,3-Dipole??

Photochemistry of Acylazides. VIII. Do Acylnitrenes React like 1,3-Dipoles? The formation of three- ore five-membered heterocyclic rings by the reaction of acylnitrenes with olefins depends on the electron density at the double bond. The generally expected formation of aziridines by a cheletropic reaction was observed by photolysis of aroylazides 1 in the presence of 2,5-dihydrofuran 2 . But with enolethers 3 and 4 oxazolines were directly formed. This [3 + 2] cycloaddition is regiospecific. The cycloaddition is modestly stereoselective by steric hindrance within the cyclic enolether 3b . Very small de-values were found with chiral substituents in the acylazide 13 . The azide decomposition was also achieved by photoinduced electron transfer. The same cycloaddition products as obtained by direct photolysis of the azides were obtained via radical anions of the acylazide. Using Michler's ketone as electron donor in the triplet state the formation of isocyanate which diminishes the yield of cycloadducts can be avoided.     

SMART-Reactors: Tailoring Gas Holdup Distribution by Additively Manufactured Lattice Structures

In chemical process engineering, fast gas-liquid reactions often suffer from an inefficient distribution of gas and therefore mixing and mass transfer performance. This study deals with the possibility of influencing the local gas holdup and bubble size distribution in a gas-liquid process using additively manufactured lattice structures (AMLS). The used measuring technique to study bubble size, velocity, and the local gas holdup is a photo-optical needle probe. By using AMLS, a significant radial homogenization of the local gas holdup and the mean bubble size is achieved. Furthermore, it can be demonstrated that the bubble size can be tailored by the geometry of the inserted structure. It is illustrated that the mean bubble velocities are lowered within the lattice resulting in a higher residence time of the dispersed phase with an impact on the mass transfer performance within the AMLS.     

Effect of a nonionic surfactant on biodegradation of slowly desorbing PAHs in contaminated soils

The influence of the nonionic surfactant Brij 35 on biodegradation of slowly desorbing polycyclic aromatic hydrocarbons (PAHs) was determined in contaminated soils. We employed a soil originated from a creosote-polluted site, and a manufactured gas plant soil that had been treated by bioremediation. The two soils differed in their total content in five indicator 3-, 4-, and 5-ring PAHs (2923 mg kg(-1) and 183 mg kg(-1) in the creosote-polluted and bioremediated soils, respectively) but had a similar content (140 mg kg(-1) vs 156 mg kg(-1)) of slowly desorbing PAHs. The PAHs present in the bioremediated soil were highly recalcitrant. The surfactant at a concentration above its critical micelle concentration enhanced the biodegradation of slowly desorbing PAHs in suspensions of both soils, but it was especially efficient with bioremediated soil, causing a 62% loss of the total PAH content. An inhibition of biodegradation was observed with the high-molecular-weight PAHs pyrene and benzo[a]pyrene in the untreated soil, possibly due to competition effects with other solubilized PAHs present at relatively high concentrations. We suggest that nonionic surfactants may improve bioremediation performance with soils that have previously undergone extensive bioremediation to enrich for a slowly desorbing profile.     

采用水基前驱溶液喷墨印刷制备光催化活性TiO2薄膜

摘译 近年来,作为一种高能量带隙半导体,二氧化钛(TiO2)由于在紫外光照射下具有良好的光催化活性,已引起科研人员的广泛关注.由于TiO2无色透明,具有广泛的应用前景,如薄的TiO2涂层可用于创建自清洁、防雾、超亲水表面.同时,也能用于太阳能电池等光电子行业. 化学溶液沉积法因具有相对简单的大面积生产工艺,且较低的制膜成本和高可用性,成为TiO2薄膜制备常用的方法之一.针对另一种TiO2制备方法,即溶胶凝胶法,大量研究文献主要关注乙醇的水解控制.然而,工业需求鼓励开发水基前驱设计.其难度在于钛醇盐与水的高反应性.在有机介质中,加入少量的水往往导致水解.因此,需要采用络合剂作为稳定剂,阻止纯水中的水解反应和避免由此产生的产物沉淀.     

Effect of pasture vs. concentrate diet on CLA isomer distribution in different tissue lipids of beef cattle

This study examined the effects of feeding pasture vs. concentrate on the distribution of CLA isomers in the lipids of longissimus and semitendinosus muscle, liver and heart muscle, and subcutaneous fat in beef bulls. Sixty-four German Holstein and German Simmental bulls were randomly allocated to either an indoor concentrate system or periods of pasture feeding followed by a finishing period on a concentrate containing linseed to enhance their beef content of n−3 PUFA and CLA. The concentrations of CLA isomers in the different tissues were determined by GC and silver ion HPLC. The diet affected the distribution of individual CLA isomers in the lipids of the different tissues. The concentration (mg/100 g fresh tissue) of the most prominent isomer, cis-9,trans-11 18∶2, was increased up to 1.5 times in liver and heart tissue of bulls fed on pasture as compared with concentrate. However, no diet effect was observed for cis-9,trans-11 18∶2 in the lipids of longissimus muscle and subcutaneous fat. In all tissues, the second-most abundant CLA isomer in concentratefed bulls was trans-7,cis-9 18∶2. In contrast, trans-11,cis-13 18∶2 was the second-most abundant CLA isomer in all investigated tissue lipids of pasture-fed bulls. The concentration of the trans-11,cis-13 18∶2 isomer was up to 15 times higher in tissues of pasture-fed bulls as compared with concentrate-fed animals. Furthermone, diet affected the concentrations of the CLA trans,trans 18∶2 isomers. Pasture feeding significantly increased the concentrations of some trans,trans 18∶2 isomers as compared with concentrate, predominantly trans-12,trans-14 18∶2 and trans-11,trans-13 18∶2. Overall, pasture feeding resulted in significantly increased concentrations of the sum of CLA isomers in the lipids of longissimus, muscle, subcutaneous fat, heart and liver muscle of German Holstein and German Simmental bulls, but not in semitendinosus muscle.     

The acceptance of Tablet-PCs in classroom instruction: The teachers’ perspectives

Limited research has been conducted on the integration of Tablet-PCs in classroom instruction. This paper reports a qualitative study which investigates the acceptance of Tablet-PCs, seen as technological innovation, amongst teachers. The research approach intends to complement research on the acceptance of technology through a more detailed qualitative examination. Semi-structured interviews were conducted with 18 teachers during a pilot project introducing Tablet-PCs to classroom instruction at three different schools. The findings indicate diversity in the attitude of teachers towards the technology, but also with regards to the performance expectancy and the facilitating conditions.     

Identification of quasi-optimal regions in the design space using surrogate modeling

The use of Surrogate Based Optimization (SBO) is widely spread in engineering design to find optimal performance characteristics of expensive simulations (forward analysis: from input to optimal output). However, often the practitioner knows a priori the desired performance and is interested in finding the associated input parameters (reverse analysis: from desired output to input). A popular method to solve such reverse (inverse) problems is to minimize the error between the simulated performance and the desired goal. However, there might be multiple quasi-optimal solutions to the problem. In this paper, the authors propose a novel method to efficiently solve inverse problems and to sample Quasi-Optimal Regions (QORs) in the input (design) space more densely. The development of this technique, based on the probability of improvement criterion and kriging models, is driven by a real-life problem from bio-mechanics, i.e., determining the elasticity of the (rabbit) tympanic membrane, a membrane that converts acoustic sound wave into vibrations of the middle ear ossicular bones.     

Estimation of odour intensity of indoor air pollutants from building materials with a multi-gas sensor system

This study shows an approach to estimate odour intensity in an indoor environment with a multi-gas sensor system. The sensor system uses 38 non-specific gas sensors, each of which responds to a wide range of different volatile compounds. Due to the complexity of indoor air pollution, the study focuses on emissions of building products as one of the major contributors to indoor air quality. The system has been calibrated and tested, combining measurements from gas sensor systems and assessments of odour intensity by a human panel. To find a relation between the sensor signal and the odour intensity, a data processing model has been developed comprising a classification and a class-specific regression method. The model is able to map the odour intensity to the sensor signal pattern in order to predict the odour intensity caused by the investigated building products. Investigations with varying relative humidity have shown a significant influence by the humidity level, which will be considered for future measurements.