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排序方式: 共有171条查询结果,搜索用时 15 毫秒
31.
Gbor Horvth Istvn Hermecz gnes Horvth Marianna Pongor-Cskvri Levente Pusztay rpd Istvn Kiss Lszl Czak Osman Hassan Abdirizak 《Journal of heterocyclic chemistry》1985,22(2):481-489
The characteristic features of ir and uv spectra of 43 4H-pyrido[1,2-a]pyrimidin-4-one derivatives with electron donor or acceptor groups in position 3, and positions 6, 7, 8, or 9, respectively, have been systematically studied. On the basis of the spectra some conclusions have been drawn for the molecular structure. The negative solvent effect of the lowest-energy π → π* transition is investigated by the PPP method. 相似文献
32.
The freeze-out of particles from a layer of finite thickness is discussed in a phenomenological kinetic model. The proposed model, based on the Modified Boltzman Transport Equation, is Lorentz invariant and can be applied equally well for the freeze-out layers with space-like and time-like normal vectors. It leads to non-equilibrated post freeze-out distributions. The dependence of the resulting distribution on the thickness of the layer is presented and discussed for a space-like freeze-out scenario. 相似文献
33.
Reinhard Grabowski Werner Schweizer Joseph Molnar Lothar Unger 《Optics and Lasers in Engineering》1989,10(3-4):205-226
For small scale ranging, a light beam, modulated with a wavelength typical for radio waves, is a suitable means of scanning. The ranging beam can be focussed to illuminate only a small spot. The diffuse reflection on the spot ensures that an echo appears. By applying phase comparison techniques to the ranging and echo beam the optical path length and thus the height of the illuminated surface element can be determined. By systematically deflecting the beam and thereby scanning the scene, a discrete height map is obtained. The realisation of such a small scale ‘optical radar’ is described, the main elements of which are a semiconductor diode laser for emission, an avalanche photo diode for detection, and a two-dimensional beam deflection mechanics for scanning. The typical performance is taking a picture of a volume of about 0·5 m × 0·5 m × 0·5 m within 1s, consisting of about 64 000 pixels. 相似文献
34.
Markus Allmendinger Robert Eberhardt Ferenc Molnar 《Journal of organometallic chemistry》2004,689(5):971-979
In situ ATR-IR spectroscopy is applied as a powerful tool to study the factors that control the reaction of epoxides with carbon monoxide in the presence of [Lewis acid]+[Co(CO)4]− salts. Based on these investigations, a consistent mechanistic scheme is presented, comprising the main lactone and polyester products and minor components, e.g., acetone and crotonic acid derivatives. β-Alkoxy-acyl-cobalttetracarbonyl species are shown to be key intermediates from which two reaction routes start in dependence of the applied Lewis acid (LA). Labile LA-alkoxy combinations favor a backbiting process of the oxygen function on the Co-acyl bond, primarily producing lactone products. More stable LA-alkoxy entities are unreactive toward PO conversion and afford a polymerization reaction after the addition of a nucleophile. In that case, the Lewis acid remains bonded to the chain end. 相似文献
35.
Sharon M. Molnar Glen E. Jensen Lisa M. Vogler Sumner W. Jones Leroy Laverman Jon S. Bridgewater Mark M. Richter Karen J. Brewer 《Journal of photochemistry and photobiology. A, Chemistry》1994,80(1-3):315-322
We have prepared a series of mixed-metal trimetallic complexes of the form {[(bpy)2Ru(BL)]2MCl2}n+(bpy 2,2′-bipyridine; BL 2,3-bis(2-pyridyl)pyrazine (dpp), 2,3-bis(2-pyridyl)quinoxaline (dpq) or 2,3-bis(2-pyridyl)-benzoquinozaline (dpb); M Ir(III), Rh(III) or Os(II). This new class of trimetallic complexes can be prepared with a good yield, often as high as 95%, using our building block strategy. The central rhodium and iridium fragments of these trimetallic, namely [M(BL)2Cl2]+, have been shown in our laboratory to be capable of delivering multiple electrons, “stored” on the bridging ligand π* orbitals, to a substrate as they functioned as electrocatalysts for the reduction of carbon dioxide to formate. The two terminal ruthenium metals are good light absorbers designed to give rise to photochemical activity. These bichromophoric systems should be capable of absorbing two photons of light, each giving rise to a desired photochemical reaction, namely excited-state electron transfer. Thus these systems form the basis of a molecular device for photoinitiated electron collection. The properties of these supramolecular complexes have been tuned by variation in the central metal and bridging ligand. Comparison of this array of nine complexes is described herein. 相似文献
36.
37.
Kragulj Isakovski Marijana Molnar Jazić Jelena Maletić Snežana Tubić Aleksandra Agbaba Jasmina Tričković Jelena Dalmacija Božo 《Accreditation and quality assurance》2018,23(4):243-250
Accreditation and Quality Assurance - This study investigates measurement procedure validation for the determination of hexachlorobenzene, pentachlorobenzene and trifluralin as priority hazardous... 相似文献
38.
Cacić M Molnar M Sarkanj B Has-Schön E Rajković V 《Molecules (Basel, Switzerland)》2010,15(10):6795-6809
A series of Schiff's bases (E)-N-2-aryliden-2-(4-methyl-2-oxo-2H-chromen-7-yloxy)acetohydrazides 2a-l and N-(2-(substituted phenyl)-4-oxo-thiazolidin-3-yl)-2-(4-methyl-2-oxo-2H-chromen-7-yloxy)acetamides 3a-l were synthesized and evaluated for their antioxidant activity by the phosphomolybdenum method. Most of the Schiff's bases and thiazolidine-4-ones bearing two hydroxyl groups on the phenyl ring showed excellent antioxidant activity in comparison with ascorbic acid. Preliminary investigation on cytotoxic and antifungal activity was done on some representative samples. 相似文献
39.
Moyle PM Olive C Ho MF Burgess M Karpati L Good MF Toth I 《The Journal of organic chemistry》2006,71(18):6846-6850
The aim of this study was to investigate methods for the synthesis of highly pure, well-characterized analogues of the lipid core peptide (LCP) system. Difficulties synthesizing and purifying conventional LCP systems have led to the requirement for a technique to produce highly pure, LCP-based vaccines for potential use in human clinical trials. The current study describes methods for the attachment of lipophilic adjuvants onto multi-epitopic peptide vaccines. Described is the synthesis, using native chemical ligation, of a highly pure, tri-epitopic, group A streptococcal (GAS) lipopeptide vaccine candidate. Intranasal immunization of the described tri-epitopic GAS lipopeptide with the mucosal adjuvant cholera toxin B subunit induced high serum IgG antibody titers specific for each of the incorporated peptide epitopes. 相似文献
40.
Gréta Gergely Ferenc Wéber István Lukács Levente Illés Attila L. Tóth Zsolt E. Horváth Judit Mihály Csaba Balázsi 《Central European Journal of Chemistry》2010,8(2):375-381
Hydroxyapatite (HAp) was successfully produced from recycled eggshell, seashell and phosphoric acid. The phases obtained depended
on the ratio of calcined eggshell/ seashell to phosphoric acid, the calcination temperature and the mechanochemical activation
method (ball milling or attrition milling). The HAp structures were characterized by X-ray diffraction, scanning electron
microsopy and infrared spectroscopy. Attrition milling was more effective than ball milling, yielding nanosize, homogenous
and pure Hap.
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