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排序方式: 共有483条查询结果,搜索用时 31 毫秒
1.
Dominik Vítek Prof. Aleš Růžička Lise Vermeersch Dr. Libor Dostál Dr. Jan Turek Prof. Roman Jambor 《Chemistry (Weinheim an der Bergstrasse, Germany)》2022,28(70):e202202639
Reactivity studies of the GeII→B complex L(Cl)Ge⋅BH3 ( 1 ; L=2-Et2NCH2-4,6-tBu2-C6H2) were performed to determine the effect on the GeII→B donation. N-coordinated compounds L(OtBu)Ge⋅BH3 ( 2 ) and [LGe⋅BH3]2 ( 3 ) were prepared. The possible tuning of the GeII→B interaction was proved experimentally, yielding compounds 1-PPh2-8-(LGe)-C10H6 ( 4 ) and L(Cl)Ge⋅GaCl3 ( 5 ) without a GeII→B interaction. In 5 , an unprecedented GeII→Ga coordination was revealed. The experimental results were complemented by a theoretical study focusing on the bonding in 1 − 5 . The different strength of the GeII→E (E=B, Ga) donation was evaluated by using energy decomposition analysis. The basicity of different L(X)Ge groups through proton affinity is also assessed. 相似文献
2.
The paper is devoted to the research of large deviation probabilities in the approximation by compound Poisson law. 相似文献
3.
The method of hydride generation atomic fluorescence spectrometry (HG-AFS) was optimised for determination of selenium in food supplements. Due to the high and varied content of Cu, Mg and Zn in the samples, the standard addition method was found to be the most appropriate. The reliability of the method was checked by the independent method of radiochemical neutron activation analysis, and good agreement was found between the two methods. HG-AFS is simple and rapid for Se determination in food supplements based on minerals. Agreement between the selenium values found and declared was worse than 10% in 9 out of 13 supplements. Furthermore, 2 of the 14 supplements did not comply with the recommendations stated in the 27th edition of the U.S. Pharmacopoeia, which states that minerals and vitamins in food supplements should be in the range of 90 and 200% of the declared value. 相似文献
4.
The H2, N2/H2, CO2/H2, N2O/H2, CO/H2 and CH4 chemical ionization mass spectra of thirteen C8 to C11 alkylbenzenes are reported. Characteristic hydride and alkide ion abstraction reactions are observed with all reagent gases. The major fragmentation reactions of [MH]+ are olefin elimination to form a protonated arene and arene elimination to form an alkyl ion. From the effect of structure and protonation exothermicity it is concluded that rearrangement of primary alkyl groups to the more stable secondary or tertiary structure occurs prior to alkyl ion formation. A detailed fragmentation mechanism for protonated arenes is proposed. The ‘effective’ proton affinity of the methane-derived reagent system is estimated to be ~556 kJ mol?1. 相似文献
5.
R. M. Parr A. Fajgelj R. Dekner H. Vera Ruiz F. P. Carvalho P. P. Povinec 《Analytical and bioanalytical chemistry》1998,360(3-4):287-290
For many years the International Atomic Energy Agency (IAEA) has been promoting analytical quality assurance and quality control in its Member States with emphasis on measurands that are amenable to analysis by nuclear and related techniques, i.e. radionuclides, trace elements, and stable isotopes. This paper reviews briefly the rationale for some of these activities, particularly in relation to the needs of participants in developing countries arising out of co-ordinated research programmes, technical co-operation projects and global and regional networks. Emphasis is given to biological and environmental reference materials with a matrix of natural origin. Also described are some activities arising out of the requirements of ISO-25 and other relevant international quality standards. 相似文献
6.
Aleš Podgornik 《Journal of separation science》2022,45(12):1984-1996
Modern convection-based supports differ substantially in pore size, porosity, and microstructure topology. Due to such variability, it is challenging to evaluate the contribution of a particular microstructure topology on flow resistance. We demonstrated that the flow resistance parameter ( ) introduced decades ago can be used as a criterion to evaluate the effect of microstructure topology on a pressure drop when the pore size is used as a characteristic support dimension. Furthermore, the value of simple cubic packing was calculated over the entire range of open porosity and compared to the values determined for pressure drop models derived for particular convection-based supports and experimental values of various convection-based supports from the literature. It was shown that different convection-based supports become clustered into distinct groups when plotted according to their and open porosity values, allowing their discrimination. 相似文献
7.
Vladimír Kočí Tomáš Ocelka Martin Mlejnek Roman Grabic 《Central European Journal of Chemistry》2004,2(1):91-112
The efficiency of treatment processes forboth municipal and industrial wastewater (treatment plant-Ostrava, Czech Republic)
focused on persistent organic pollutants (POPs) was assessed. Semipermeable membrane devices (SPMDs) as a sampling system
were applied. Exposed SPMDs were analyzed both for chemical contaminants of POPs and toxicity response. The chemical analyses
of PAHs were made by HPLC-FLD, PCDD/Fs and PCBs were analysed by GC/MS/MS on GCQ or PolarisQ (Thermoquest). Ecotoxicity data
on chlorococcal alga Desmodesmus subspicatus (Scenedesmus subspicatus) and luminescent bacteria Vibrio fischeri are presented here. All toxicity data as effective volume Vtox are expressed. The results show good treatment ability of
the treatment plant and proved used system as an appropriate tool for efficiency assessment of treatment and/or decontamination
processes. 相似文献
8.
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10.
Vít Kremláček Erik Kertész Prof. Zoltán Benkő Milan Erben Robert Jirásko Prof. Aleš Růžička Prof. Roman Jambor Prof. Libor Dostál 《Chemistry (Weinheim an der Bergstrasse, Germany)》2021,27(52):13096-13097
Invited for the cover of this issue are Zoltán Benkő, Libor Dostál and co-workers at the University of Pardubice and the Budapest University of Technology and Economics. The image depicts signs for the two different pathways representing the two differing reaction types which were clearly observed for 2,1-benzazaphosphole. Read the full text of the article at 10.1002/chem.202101686 . 相似文献