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排序方式: 共有487条查询结果,搜索用时 0 毫秒
481.
Z. Homonnay P. Á. Szilágyi A. Vértes E. Kuzmann V. K. Sharma G. Molnár A. Bousseksou J.-M. Grenèche A. Brausam R. Meier R. van Eldik 《Hyperfine Interactions》2008,182(1-3):77-86
The speciation of iron in aqueous solutions containing Fe3?+ and selected chelates such as EDTA, EDDA, CDTA and HEDTA has been studied using transmission 57Fe Mössbauer spectrometry in frozen solutions. The protonation of various complexes as well as binuclear complex formation could be detected as a function of pH. Autoreduction of Fe3?+? to Fe2?+? was observed in several cases. Reaction with hydrogen peroxide proved to be rather different for the four ligands, while the dihapto complex [XFe(η 2-O2)]3??? had surprisingly identical Mössbauer parameters for X = EDTA, CDTA or HEDTA. Paramagnetic spin relaxation observed in the Mössbauer spectra was found to be strongly influenced by the identity of the chelating ligand, despite the basically spin-spin origin of the phenomenon. 相似文献
482.
Zsolt E. Horváth Antal A. Koós Krisztián Kertész György Molnár Gábor Vértesy Márton C. Bein Tamás Frigyes Zoltán Mészáros József Gyulai László P. Biró 《Applied Physics A: Materials Science & Processing》2008,93(2):495-504
The electrical resistance of 24 different carbon nanotube (CNT) thin film samples in blowing ambient air and 10 different
analyte vapor environments was measured. The effects of the CNT growth method, different chemical treatments, ball milling,
sample preparation conditions and Ar+-ion irradiation are compared. Significant differences in the response signal curves as a function of time in the case of
the studied sensor/vapor combinations show the important role of the defect structure and attached functional groups in the
chemical sensing properties of CNTs. 相似文献
483.
In this paper, we explore a new approach in which understanding is interpreted as a set representation. We prove that understanding/representation, finding the appropriate coordination of data, is equivalent to finding the minimum of the representational entropy. For the control of the search for the correct representation, we propose a loss function as a combination of the representational entropy, type one and type two errors. Computational complexity estimates are presented for the process of understanding and using the representation found. 相似文献
484.
485.
Two families of ester-type banana monomers are presented, 1,3-phenylene bis{4-[4′-(10-undecenyloxy)benzoyloxy]benzoate}s and 1,3-phenylene bis{[4′-(10-undecenyloxy)]-1,1′-biphenyl-4-carboxylate}s, in which the nature of the substituents on the central phenyl ring and the side arms was varied. The mesophase behavior of the monomers, including B2 and B7 phases, was correlated with their chemical structure and was compared with that of analogous azomethine-type banana mesogens. It is also shown that the banana monomers can be incorporated into new architectures of liquid crystal polymers. 相似文献
486.
Péter Angyal András M. Kotschy Ádám Dudás Dr. Szilárd Varga Dr. Tibor Soós 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2023,135(2):e202214096
A widely applicable, practical, and scalable synthetic method for efficient ene-type double oxidation of alkenes is reported via a two-step alkenyl thianthrenium umpolung/Kornblum-Ganem oxidation strategy. This chemo- and stereoselective procedure allows easy access to various α,β-unsaturated carbonyls that may be otherwise difficult or cumbersome to synthesize by conventional methods. For α-olefins, this metal-free transformation can be tuned according to synthetic needs to produce either the elusive (Z)-unsaturated aldehydes or their (E) counterparts. Moreover, this strategy has enabled streamlined synthesis of distinct butadienyl pheromones and kairomones. 相似文献
487.
Péter Angyal Kristóf Hegedüs Bence Balázs Mészáros Dr. János Daru Ádám Dudás Anna Rita Galambos Nariman Essmat Dr. Mahmoud Al-Khrasani Dr. Szilárd Varga Dr. Tibor Soós 《Angewandte Chemie (International ed. in English)》2023,62(35):e202303700
Mitragynine pseudoindoxyl, a kratom metabolite, has attracted increasing attention due to its favorable side effect profile as compared to conventional opioids. Herein, we describe the first enantioselective and scalable total synthesis of this natural product and its epimeric congener, speciogynine pseudoindoxyl. The characteristic spiro-5-5-6-tricyclic system of these alkaloids was formed through a protecting-group-free cascade relay process in which oxidized tryptamine and secologanin analogues were used. Furthermore, we discovered that mitragynine pseudoindoxyl acts not as a single molecular entity but as a dynamic ensemble of stereoisomers in protic environments; thus, it exhibits structural plasticity in biological systems. Accordingly, these synthetic, structural, and biological studies provide a basis for the planned design of mitragynine pseudoindoxyl analogues, which can guide the development of next-generation analgesics. 相似文献