Electrical conduction in γ-irradiated and unirradiated pure and Mn-doped MgAl2O4 spinel

The electrical conductivity of pure and Mn-doped MgAl₂O₄ spinel has been studied in nitrogen atmosphere as a function of temperature. The conduction process is explained by the motion of cation vacancies in each of -irradiated and unirradiated samples. The effect of -irradiation on the conductivity and activation energy has been discussed.     

Measurement of the ground state 2n pickup probability for 28Si+68Zn and its role in sub-barrier fusion enhancement

The ground state and excited state transfer yields for the 2-neutron pickup channel in the ²⁸Si+⁶⁸Zn system have been measured explicitly. The recoil mass separator at the nuclear Science Centre, New Delhi was used for the measurement. A NaI(T1) detector was used for detecting the deexcitation γ’s from the transfer products. The kinematic coincidence technique was employed for the transfer measurement. Simplified coupled channels calculations show that out of all transfer channels the major contribution to the sub-barrier enhancement comes from the ground state 2 neutron pickup channel with a ground state Q-value of+1.83 MeV.     

Effects of reactor type and mass transfer on the morphology of CuS and ZnS crystals

For the precipitation of CuS and ZnS, the effects of the reactor/precipitator type, mass transfer and process conditions on crystal morphology were studied. Either H₂S gas or a S^2– solution were applied. Three different types of reactors have been tested, namely a laminar jet, a bubble column and an MSMPR reactor. The choice of reactor type as well as mass transfer and metal concentration all have a considerable influence on the morphology of the produced crystals. A well mixed bubble column with H₂S containing gas as feed yields the coarsest crystals. Use is then made of the surface active properties of CuS‐particles, which induce agglomeration at the gas‐liquid interface, where as the low metal concentrations inside the reactor also contribute to the formation of coarser particles (especially for ZnS). (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Heavy Heparin: A Stable Isotope‐Enriched,Chemoenzymatically‐Synthesized,Poly‐Component Drug

Heparin is a highly sulfated, complex polysaccharide and widely used anticoagulant pharmaceutical. In this work, we chemoenzymatically synthesized perdeuteroheparin from biosynthetically enriched heparosan precursor obtained from microbial culture in deuterated medium. Chemical de‐N‐acetylation, chemical N‐sulfation, enzymatic epimerization, and enzymatic sulfation with recombinant heparin biosynthetic enzymes afforded perdeuteroheparin comparable to pharmaceutical heparin. A series of applications for heavy heparin and its heavy biosynthetic intermediates are demonstrated, including generation of stable isotope labeled disaccharide standards, development of a non‐radioactive NMR assay for glucuronosyl‐C5‐epimerase, and background‐free quantification of in vivo half‐life following administration to rabbits. We anticipate that this approach can be extended to produce other isotope‐enriched glycosaminoglycans.     

前后排列旋转圆柱体对流热交换的格子Boltzmann方法解

用格子Boltzmann方法,数值研究流过前后排列两旋转圆柱体的二维层流．用二阶精度的速度场和温度场,数值化涉及运动的曲线边界．在Reynolds数为100,Prandtl数为0.71时,研究旋转速度比的变化和不同间距的影响．在4种不同间距(3, 1.5, 0.7, 0.2)下,研究旋转速度比的不同范围．结果表明,当间距取大数值时,第1个圆柱体的升力和阻力系数,与单个圆柱体相类似;对所有间距(除间距3以外),第2个圆柱体的升力系数,随着角速度的增加而减小,而阻力系数反而增加．圆柱体表面平均周期Nusselt数的结果表明,当两圆柱体间距小且角速度又低时,热传导是主要的传热机理,而当间距大且角速度又高时,对流是主要的传热机理．     

Chemistry of C-heteroarylnitrilimines. Synthesis and cycloaddition reactions of N-phenyl-C-(2-thienyl)nitrilimine

The nitrilimine 7 , generated in situ from N-phenyl-C-(2-thienyl)formohydrazidoyl chloride 5 in chloroform in the presence of triethylamine, reacts with acrylonitrile, acrylamide and arylidene acetophenones to give exclusively the 5-substituted 2-pyrazoline derivatives 9, 10 and 16 , respectively. On the other hand, the cycloaddition of 7 to coumarin, benzalmalononitrile and the enolate anions of active methylene compounds yield the pyrazole derivatives 12, 14 and 23 , respectively. The structures of the cycloadducts prepared were attributed on the basis of spectroscopic and chemical evidence. The regioselectivity in the studied reactions is discussed in terms of the frontier orbital theory.     

Dispersive solid phase extraction combined with dispersive liquid–liquid extraction for the determination of BTEX in soil samples: ant colony optimization–artificial neural network

In this study, dispersive solid phase extraction combined with dispersive liquid–liquid extraction has been developed for the extraction of benzene, toluene, ethylbenzene, and xylenes isomers (BTEX) in soil samples prior to gas chromatography–mass spectrometry. The BTEX were extracted from soil sample into acetonitrile by dispersive solid phase extraction method, and the extract was then used as dispersive solvent in dispersive liquid–liquid extraction procedure. Ant colony optimization–artificial neural network (ACO–ANN) has been employed to develop the model for simulation and optimization of this method. The volume of dispersive solvent, volume of extraction solvent, extraction time, and ultrasonic time were the input variables, while the multiple response function (R_m) of analytes was the output. The optimum operating condition was then determined by ant colony optimization method. At the optimum conditions, the limit of detections of 0.12–0.75 ng g⁻¹ was obtained for the BTEX. The developed procedure was then applied to the extraction and determination of BTEX in the soil samples and one certified soil. Copyright © 2015 John Wiley & Sons, Ltd.