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排序方式: 共有1019条查询结果,搜索用时 31 毫秒
11.
O. Böse E. Kemnitz A. Lippitz W. E. S. Unger 《Analytical and bioanalytical chemistry》1997,358(1-2):175-179
A number of partially catalytically active aluminium compounds characterised by powder XRD have been investigated by XPS and
XAES using a new method for static charge referencing [1, 2]. In detail, α-Al2O3, γ-Al2O3, boehmite γ-AlO(OH), bayerite α-Al(OH)3, hydrargillite γ-Al(OH)3, α-AlF3, β-AlF3, and AlF2.3(OH)0.7· H2O and a hexa-fluoropropylene oxide (HFPO) modified γ-Al2O3 are examined. Well defined and chemically inert 20 nm gold particles are deposited as a nearly statistical distribution on
the sample surface avoiding large coagulation effects. This procedure allows a determination of gold referenced XPS and XAES
data sets. Binding energies (BE) of Al 2p, Al 2s, O 1s and F 1s photoelectron peaks as well as kinetic energies (KE) of Al
KLL and F KLL Auger electron emission peaks are presented in relation to the Au 4f7/2 BE reference. XPS and XAES data found in literature are, in most cases, C 1s referenced and scatter in a broad range. BE
differences Δ between the C 1s charge reference BE and Au 4f7/2 charge reference BE obtained with our samples are monitored by using the Al 2p orbital. These BE differences Δ clearly suggest
that the chemical state of carbon observed in this study is not as uniform as required for reliable static charge referencing.
Received: 24 June 1996 / Revised: 12 December 1996 / Accepted: 14 December 1996 相似文献
12.
Bühl M Grigoleit S Kabrede H Mauschick FT 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,12(2):477-488
59Co chemical shifts were computed at the GIAO-B3LYP level for [Co(CN)6]3-, [Co(H2O)6]3+, [Co(NH3)6]3+, and [Co(CO)4]- in water. The aqueous solutions were modeled by Car-Parrinello molecular dynamics (CPMD) simulations, or by propagation on a hybrid quantum-mechanical/molecular-mechanical Born-Oppenheimer surface (QM/MM-BOMD). Mean absolute deviations from experiment obtained with these methods are on the order of 400 and 600 ppm, respectively, over a total delta(59Co) range of about 18,000 ppm. The effect of the solvent on delta(59Co) is mostly indirect, resulting primarily from substantial metal-ligand bond contractions on going from the gas phase to the bulk. The simulated solvent effects on geometries and delta(59Co) values are well reproduced by using a polarizable continuum model (PCM), based on optimization and perturbational evaluation of quantum-mechanical zero-point corrections. 相似文献
13.
[RhH(CO)(PPh3)2] (1) reacts with Et3N·3HF to give the fluoro compound [RhF(CO)(PPh3)2] (2). In a comparable reaction [RhF(PEt3)3] (5) has been obtained from [RhH(PEt3)3] (3) or [RhH(PEt3)4] (4) with substoichiometric amounts of Et3N·3HF in THF. If the latter reaction is carried out in benzene, the complexes 5, cis-mer-[Rh(H)2F(PEt3)3] (6) and cis-fac-[Rh(H)2F(PEt3)3] (7) are obtained. Treatment of 5 with HCl in ether effects the generation of [RhCl(PEt3)3] (8) and the bifluoride compound [Rh(FHF)(PEt3)3] (9), which can be converted into 5 in the presence of Et3N and Cs2CO3. Treatment of 5 with HSiR2Ph (R=Ph, Me) leads to the formation of 3 and the rhodium(III) silyl complexes fac-[Rh(H)2(SiR2Ph)(PEt3)3] (10: R=Ph, 11: R=Me). 相似文献
14.
Novel representatives of the important group of biologically active dibenzosuberone derivatives were prepared: 3,7-dibromo-5-(dimethylaminoethyl- oxyimino)-10,11-dihydro-5H-dibenzo[a,d]cyclohepta-1,4-diene (1), 3,7-dibromo-5-(3- dimethylaminopropylidene)-10,11-dihydro-5H-dibenzo[a,d]cycloheptene (2) and 1,7- dibromo-5-(3-dimethylaminopropylidene)-10,11-dihydro-5H-dibenzo-[a,d]-cycloheptene (3). These compounds are potential tricyclic antidepressants (TCAs), which are still the most frequently prescribed antidepressants in many countries. 相似文献
15.
Boris Pejin Kristina Tešanović Dragica Jakovljević Sonja Kaišarević Filip Šibul Milena Rašeta 《Natural product research》2019,33(5):750-754
The polysaccharide (PSH) extracts from the edible mushroom species Coprinus comatus and Coprinellus truncorum were screened in liquid for their acetylcholinesterase inhibitory (AChE) activity. Both extracts were found to display inhibition of the aforementioned enzyme reaching similar IC50 values of 0.62 ± 0.07 and 0.61 ± 0.03 mg/mL, respectively. According to the means of FTIR spectroscopy, these PSH extracts mostly contained β-glucans. However, the presence of some proteins and polyphenolics as minor ingredients were also detected. Compared with existing literature data for anti-AChE activity of the sugar samples, the findings within this study may be treated as a profound bioactivity. Consequently, this study puts some light on the possible use of the screened macrofungi in the palliative treatment of Alzheimer’s disease. 相似文献
16.
On the Harary index for the characterization of chemical graphs 总被引:1,自引:0,他引:1
17.
The construction of the Z-counting polynomial for edge-weighted graphs is discussed.Dedicated to Professor Haruo Hosoya (Tokyo) on the occasion of his 55th birthday for enriching chemical graph theory with the elegant concept of the Z-counting polynomial. 相似文献
18.
Microphysiometry was used to evaluate the effects of terpene trilactone and flavonoid constituents of Ginkgo biloba on human platelet‐activating‐factor receptor (PAFR). Inhibition of the platelet‐activating factor response by terpene trilactones was confirmed using this functional assay. Ginkgolide B (GB) and 10‐O‐benzyl‐GB showed the strongest inhibition (81 and 93%, resp.) of the PAFR response, while the flavonoids rutin, quercetin, and kaempferol showed negligible response inhibition. G. biloba extract mixtures were also tested, and results indicate possible synergistic effects among various components. 相似文献
19.
K. Unger 《Trends in analytical chemistry : TRAC》1983,2(12):271-274
High performance size exclusion chromatography (HPSEC), employing microparticulate, hydrophilic, surface-modified silicas or hydrophilic, cross-linked, organic polymers and buffered eluents, is an effective means of separating native and denatured proteins of molecular weights in the 10 000–500 000 range. HPSEC can be further used for molecular weight identification, and the fractionation and isolation of proteins. 相似文献
20.