Modeling of a solar receiver–reactor for sulfur‐based thermochemical cycles for hydrogen generation

Sulfur‐based thermochemical cycles for hydrogen generation from water have one reaction step in common, which is the decomposition of sulfuric acid, which is one of the most energy‐consuming steps. The present work deals with the development of a dynamic mathematical model of a solar reactor for this key step. One of the core parts of the model is a partial model of the reaction kinetics of the decomposition of sulfur trioxide, which is based on experiments investigating the kinetics of the used catalyst platinum coated on a ceramic solar absorber. Other partial models describe, e.g. the absorption of solar radiation, heat conduction in the absorber, convection between gas and the absorber walls and energy losses due to heat radiation. A comprehensive validation of the reactor model is performed using measured data, which is gained in experiments with a prototype reactor. The operating behavior of the real reactor is compared with the results of the numerical simulation with the model. The validation is, in particular, performed by reproducing the influences of individual parameters on the chemical conversion and the reactor efficiency. The relative deviations between the experimental data and the simulation results are mostly within the range of measurement accuracy. In particular, the good agreement of calculated values of the derived parameters, SO₃ conversion and reactor efficiency with those determined from the experiments qualifies the model for optimization purposes. Copyright © 2010 John Wiley & Sons, Ltd.     

Silent mutations in secondary Shine-Dalgarno sequences in the cDNA of human serum amyloid A4 promotes expression of recombinant protein in Escherichia coli

The serum amyloid A (SAA) superfamily comprises a number ofdifferentially expressed genes with a high degree of homologyin mammalian species. SAA4, an apolipoprotein constitutivelyexpressed only in humans and mice, is associated almost entirelywith lipoproteins of the high-density range. The presence ofSAA4 mRNA and protein in macrophage-derived foam cells of coronaryand carotid arteries suggested a specific role of human SAA4during inflammation including atherosclerosis. Here we underlinethe importance of ribosome binding site (rbs)-like sequences(also known as Shine–Dalgarno sequences) in the SAA4 cDNAfor expression of recombinant SAA4 protein in Escherichia coli.In contrast to rbs sequences coded by the expression vectors,rbs-like sequences in the cDNA of target protein(s) are knownto interfere with protein translation via binding to the small16S ribosome subunit, yielding low or even no expression. Herewe show that PCR mutations of two rbs-like sequences in thehuman SAA4 cDNA promote expression of considerable amounts ofrecombinant SAA4 in E.coli.     

Relation between size and density of nonmetallic inclusions and the J-integral at crack initiation

Two quantitative relations for the calculation of the fracture toughness of ductile materials available in the literature in mathematically closed form — the relation of Stroppe relating the critical value J_c of the J-integral to microstructural data as well as data of tensile tests and the relation of Hahn and Rosenfield relating fracture toughness and data of tensile tests — are applied to three conditions of different toughness of the 12% Cr-steel X 20 CrMoV 12 1.The microstructural parameters necessary for the calculation of the J-integral at crack initiation such as type, size, density and arrangement of nonmetallic inclusions as well as precipitates were determined for the three material conditions, X 20 CrMoV 12 1 optimized (low sulphur content), X 20 CrMoV 12 1 conventional (higher sulphur content) and the aged similar weld metal. The tensile tests and J—R-tests were performed at 150°C, where the energy absorbed corresponds to the upper shelf.Comparing the J_i-values calculated according to the equation of Stroppe with the J_i-values experimentally determined it is shown that the calculated values fall into the scatterband of the experimentally determined ones, showing a good agreement of calculated with the measured values for the three material conditions. In the case of the optimized X 20 CrMoV 12 1 the value of J_i, calculated according to the relation of Hahn and Rosenfield, corresponds to the measured one. However in the case of the conventional X 20 CrMoV 12 1 and the similar weld metal no more correspondence is found.     

Synthesis of 9-oxononanoyl cholesterol by ozonization

A new route for the preparation of 9-oxononanoyl cholesterol (5) and its stable dimethylacetal (4) is described. The core aldehyde 5 is one of the major products formed during lipid peroxidation. The synthesis starts with the ozonization of oleic acid in methanol and further reduction with dimethyl sulfide to yield 9,9-dimethoxy nonanoic acid (2a). The condensation of 2a with cholesterol is achieved with N,N'-dicyclohexylcarbodiimide in dichloromethane to give 4. Further hydrolysis of 4 with the help of an acidic ion exchange resin yields 9-oxononanoyl cholesterol.     

New SMMW laser transitions optically pumped by a tunable CO2waveguide laser

Optical pumping of a submillimeter wave (SMMW) laser with a relatively compact RF-excited CW CO2laser is described. The increased frequency tunability of the waveguide pump laser has resulted in new low threshold SMMW emissions in C2H2F2, CDF3, and CD2F2by pumping into absorption lines which are beyond the tuning range of a conventional CO2laser. Frequency offsets and some assignments obtained with the aid of a tunable diode laser heterodyne spectrometer are reported.     

Dielectric properties of beryllia ceramics in the near-millimeter wavelength range

We report the refractive indices and absorption coefficients for four beryllia (BeO) ceramic samples. These dielectric properties have been measured over the range from 4 to 18 cm^?1 by use of a Michelson interferometer. The index n, follows the linear relationship n=0.6517 cm³/g×ρ+0.7130 with density, ρ, over the range 2.8<ρ<3.0 g/cm³.     

Halo effect in examiner scoring of intelligence test responses.

Two experiments evaluating the halo effect on graduate student Es' scoring of test responses from some Verbal scale subtests of the Wechsler Intelligence Scale for Children and Wechsler Adult Intelligence Scale are reported. In each experiment, ambiguous responses on one or more subtests, Vocabulary but not the Comprehension subtest in the first experiment and the Vocabulary and Comprehension but not the Similarities subtest in the second experiment, were given significantly more credit when produced by examinees with superior or above-average intelligence than by examinees with average or below-average intelligence. Responses were presented on paper and via tape recordings. The results suggest that the IQ may not be as objectively determined as has been commonly assumed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of cues and examiner influence on two Wechsler subtests.

Studied the effects of cues on the WISC and the Wechsler-Bellevue Scale in 2 experiments. In Exp. I 170 adolescent Ss received the Block Design subtest, and results showed that 1 cue/item did not significantly affect performance on the initial or repeated administration. In Exp. II 146 adolescent Ss received the Block Design and Picture Arrangement subtests, and results showed that a series of cues/item significantly raised scores on both the initial and repeated administrations of both subtests. Test-form order significantly affected scores, while subtest order and Es did not. (PsycINFO Database Record (c) 2010 APA, all rights reserved)