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981.
A. Ali BiswasY.M. Jana 《Journal of magnetism and magnetic materials》2011,323(24):3202-3209
The temperature dependence of the experimental results of dc (macroscopic) magnetic susceptibility and nuclear hyperfine properties of frustrated magnetic Gd-based pyrochlore compounds, Gd2Ti2O7, Gd2Sn2O7, Gd2Hf2O7 and Gd2Zr2O7, are analyzed within the frame work of appropriate crystal-field theory and a mean field approximation by introducing effective anisotropic molecular field tensors, and formulating an exact relation between single-ion susceptibility tensors and site susceptibility tensors. Components of the calculated susceptibility along and perpendicular to the local 〈1 1 1〉 axis of the tetrahedral sublattice of pyrochlore structure show that these pyrochlores are easy-planar anisotropic magnetic systems. The crystal-field parameters and anisotropic exchange coupling have been determined and their systematic variations over the Gd-based pyrochlores studied here are discussed. 相似文献
982.
Differential scanning calorimetry measurements were used to study enthalpic structural relaxation of Ge2Sb2Se5 glass. The Tool-Narayanaswamy-Moynihan (TNM) model was applied to describe the relaxation behavior. The curve-fitting results showed a significant dependence on experimental conditions, true values of the TNM parameters needed to be confirmed by the alternative non-fitting methods – apparent activation energy was confirmed by evaluations from classic and intrinsic cycles, the non-linearity parameter was determined on the basis of peak-shift method. Discussion on the origin of the trend in curve-fitting results was conducted in terms of influence of either the nonlinear Cp-T dependence or anomalous relaxation behavior of the material itself. For the latter case a suggestion regarding the proceeding molecular mechanisms was made. 相似文献
983.
In recent decades, food waste management has become a key priority of industrial and food companies, state authorities and consumers as well. The paper describes the biotechnological processing of mechanically deboned chicken meat (MDCM) by-product, rich in collagen, into gelatins. A factorial design at two levels was used to study three selected process conditions (enzyme conditioning time, gelatin extraction temperature and gelatin extraction time). The efficiency of the technological process of valorization of MDCM by-product into gelatins was evaluated by % conversion of the by-product into gelatins and some qualitative parameters of gelatins (gel strength, viscosity and ash content). Under optimal processing conditions (48–72 h of enzyme conditioning time, 73–78 °C gelatin extraction temperature and 100–150 min gelatin extraction time), MDCM by-product can be processed with 30–32% efficiency into gelatins with a gel strength of 140 Bloom, a viscosity of 2.5 mPa.s and an ash content of 5.0% (which can be reduced by deionization using ion-exchange resins). MDCM is a promising food by-product for valorization into gelatins, which have potential applications in food-, pharmaceutical- and cosmetic fields. The presented technology contributes not only to food sustainability but also to the model of a circular economy. 相似文献
984.
Houhua Li Rajesh Gontla Jana Flegel Christian Merten Slava Ziegler Andrey P. Antonchick Herbert Waldmann 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(1):313-317
Herein, we report the first enantioselective annulation of α‐arylidene pyrazolones through a formal C(sp3)?H activation under mild conditions enabled by highly variable RhIII‐Cpx catalysts. The method has a wide substrate scope and proceeds with good to excellent yields and enantioselectivities. Its synthetic utility was demonstrated by the late‐stage functionalization of drugs and natural products as well as the preparation of enantioenriched [3]dendralenes. Preliminary biological investigations also identified the spiropyrazolones as a novel class of Hedgehog pathway inhibitors. 相似文献
985.
Didier Villemin Nawel Cheikh Liang Liao Nathalie Bar Jean-François Lohier Jana Sopkova Noureddine Choukchou-Braham Bachir Mostefa-Kara 《Tetrahedron》2012,68(24):4906-4918
Simple and efficient routes to the natural alkaloid Cerpegin and new analogues are described herein. In a first approach, we extend the scope of a one pot three steps reaction, which permits the synthesis of new analogues of Cerpegin, substituted in different ways. In a second line of approach, we present an unprecedented synthesis of Cerpegin and analogues where methylfuranones are condensed with dimethylformamide diethylacetal (DMFDEA) to yield enaminolactone esters, which react easily with various primary amines affording Cerpegin and new analogues. We applied this second approach to the synthesis of new bis-Cerpegins and N-amino-Cerpegins. Most of the syntheses are performed under environmental friendly conditions. 相似文献
986.
Nicole Kroll Ina Speckmann Marc Schoknecht Jana Gülzow Marek Diekmann Johannes Pfrommer Anika Stritt Maria Schlangen Andreas Grohmann Gerald Hrner 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(38):13606-13612
Formation of the O?O bond is considered the critical step in oxidative water cleavage to produce dioxygen. High‐valent metal complexes with terminal oxo (oxido) ligands are commonly regarded as instrumental for oxygen evolution, but direct experimental evidence is lacking. Herein, we describe the formation of the O?O bond in solution, from non‐heme, N5‐coordinate oxoiron(IV) species. Oxygen evolution from oxoiron(IV) is instantaneous once meta‐chloroperbenzoic acid is administered in excess. Oxygen‐isotope labeling reveals two sources of dioxygen, pointing to mechanistic branching between HAT (hydrogen atom transfer)‐initiated free‐radical pathways of the peroxides, which are typical of catalase‐like reactivity, and iron‐borne O?O coupling, which is unprecedented for non‐heme/peroxide systems. Interpretation in terms of [FeIV(O)] and [FeV(O)] being the resting and active principles of the O?O coupling, respectively, concurs with fundamental mechanistic ideas of (electro‐) chemical O?O coupling in water oxidation catalysis (WOC), indicating that central mechanistic motifs of WOC can be mimicked in a catalase/peroxidase setting. 相似文献
987.
988.
In the paper we consider optimal control of a class of strongly monotone variational inequalities, whose solution map is directionally
differentiable in the control variable. This property is used to derive sharp pointwise necessary optimality conditions provided
we do not impose any control or state constraints. In presence of such constraints we make use of the generalized differential
calculus and derive, under a mild constraint qualification, optimality conditions in a “fuzzy” form. For strings, these conditions
may serve as an intermediate step toward pointwise conditions of limiting (Mordukhovich) type and in the case of membranes
they lead to a variant of Clarke stationarity conditions. 相似文献
989.
Honcová Pavla Sádovská Galina Binder Lukas Koštál Petr Honc Daniel 《Journal of Thermal Analysis and Calorimetry》2020,140(1):275-282
Journal of Thermal Analysis and Calorimetry - The influence of composition and neodymium doping on the crystallization kinetic of calcium aluminosilicate glasses, melted under vacuum atmosphere,... 相似文献
990.
A critical analysis has been made on contribution to green house molecules on global warming and surface air temperature rise.
The nature of yearly variations of concentrations of green house molecules and global and surface temperature has been presented.
Climate change, environmental and economic effects are briefly mentioned. Various diseases caused by global warming are also
discussed. 相似文献