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排序方式: 共有491条查询结果,搜索用时 18 毫秒
341.
Anna Rakowska Maria Socjusz-Podosek Lidia Lityńska Ryszard Ciach 《Mikrochimica acta》2002,139(1-4):145-149
Microstructure and phase composition studies of QE-22 magnesium based alloy with 2–3% Ag, 1.8–2.5% Nd and min. 0.4% Zr, before
and after full heat treatment have been carried out using various electron microscopy techniques like EDX mapping, line scans
and TEM with SAED. An extrapolation technique enabled to eliminate the influence of Mg-matrix on the quantitative analysis
results and allowed to estimate the composition of the second phase which was mostly (Mg, Ag)12Nd type in the as cast alloy and (Mg, Ag)12Nd and Mg12Nd2Ag equilibrium precipitates after the precipitation process. 相似文献
342.
Lidia Prajer-Janczewska Hubert Bartosz-Bechowski 《Journal of inclusion phenomena and macrocyclic chemistry》1984,2(1-2):153-159
The new clathrates based on di- and triethylene glycol ether of phenol sulphonic acid-4 and 1-naphtolsulphonic acid-4 are presented. The four series of p-substituted phenol esters were obtained /Fig. 1/. Generally, only the derivatives of triethylene glycol ether of naphtolsulphonic acid give complexes with benzene or toluene /Tab. I/, but not with smaller molecules of acetonitrile or nitromethane. 相似文献
343.
The thermal degradation of thermosetting materials prepared by cationic copolymerization of mixtures of different proportions of diglycidylether of bisphenol A (DGEBA) with 6,6-dimethyl (4,8-dioxaspiro[2.5]octane-5,7-dione) (MCP) initiated by ytterbium or lanthanum triflate or using a conventional initiator, BF3·MEA was investigated. To study the thermal degradation, several techniques were used such as thermogravimetry (TGA), infrared spectroscopy (FTIR) and calorimetry (DSC) and the volatiles evolved during degradation were identified by mass spectrometry. The materials prepared possess the characteristics of thermally degradable thermosets, due to the presence of ester groups in the polymer chain, which are broken at the beginning of degradation. The degradability increased when lanthanide triflates were used in the curing, especially the ytterbium salt and when the proportion of MCP in the material increased. 相似文献
344.
Lidia Andreu Guillo Bénédicte Beylot Paul Vigny Annick Spassky 《Photochemistry and photobiology》1996,64(2):349-355
The present report provides evidence that thymine dimerization can be UVA photosensitized at a tetranucleotide, 5′-TATT-3′, by a 7-methyl-pyrido(3, 4-c)psoralen monoadduct in DNA. The efficiency of the photoprocess depends on the tetranucleotide flanking sequences. These results demonstrate that one DNA lesion can originate the contiguous formation of a second type of lesion and emphasize the sequence-specific response to interaction of drugs with DNA. Results are related to the sensitivity of DNA to 1, 10-phenanthroline-cuprous ion complex nucleolytic activity and discussed in terms of the major role of local deformability of DNA in interaction with ligands. 相似文献
345.
Lidia Litynska Joanna Wojewoda Paweł Zieba Marek Faryna Wolfgang Gust Eric J. Mittemeijer 《Mikrochimica acta》2004,145(1-4):107-110
Diffusion soldering was applied in order to fabricate durable Cu/Cu joints with pure In as a filler. Such joints are especially important in electronics as the starting point to form Si–Si interconnections. Soldering at 290°C results in the joint consisting of Cu11In9, (Cu2In) and (Cu7In3) intermetallic phases as shown by an energy dispersive X-ray microanalysis on a scanning and transmission electron microscopes and electron diffraction technique. Electron diffraction patterns also showed the formation of a low-temperature hexagonal phase with a large orthorhombic cell. Soldering at 430°C leads to the presence of a single (Cu7In3) phase in the joint. The sequence of the processes involved in the formation of Cu/Cu joint with In as an interlayer is presented. 相似文献
346.
TARGETED PHOTOCHEMICAL MODIFICATION OF HIV-DERIVED OLIGORIBONUCLEOTIDES BY ANTISENSE OLIGODEOXYNUCLEOTIDES LINKED TO PORPHYRINS 总被引:1,自引:0,他引:1
Lidia Mastruzzo Anne Woisard David D. F. Ma Enrico Rizzarelli Alain Favre Trung Le Doan † 《Photochemistry and photobiology》1994,60(4):316-322
Abstract Antisense oligodeoxynucleotides directed against a 24-mer RNA derived from the long terminal repeat (LTR) region of HIV were linked to proto- and methylpyrroporphyrin and their zinc derivatives. The oligonucleotide-porphyrin conjugates were tested for their ability to induce photodamage on the target RNA. Upon hybridization followed by irradiation at 405 nm, the photochemical reaction led to photocross-linking of the antisense derivative to the RNA substrate. The protoporphyrin exhibited a much higher cross-linking yield than the methylpyrroporphyrin while the Zn-porphyrin derivatives were found to be less efficient than their corresponding nonmetallated congeners. The specificity of the photocross-linking reaction between the porphyrin-oligomer and its target RNA was demonstrated by the following evidence: (1) hybrid formation was required for photocross-linking to occur, (2) the sites of cross-linking on the target RNA were identified at G residues located in close proximity to the porphyrin photoactive center in the hybrid and (3) addition of bulk calf liver RNA did not affect the photocross-linking efficiency. 相似文献
347.
Amelichev SA Konstantinova LS Lyssenko KA Rakitin OA Rees CW 《Organic & biomolecular chemistry》2005,3(19):3496-3501
Treatment of nucleophilic heterocycles like pyrroles and thiophenes, and their tetrahydro derivatives, with S2Cl2 and DABCO in chloroform at room temperature provides a simple one-pot synthesis of fused mono and bispentathiepins. N-Methylpyrrole and its 2-chloro and 2,5-dichloro derivatives and N-methylpyrrolidine all give the same dichloropentathiepin 1a. N-Ethyl, isopropyl and tert-butylpyrrolidine behave similarly; the isopropylpyrrolidine also gives the bispentathiepin 6which undergoes an intriguing rearrangement to the symmetrical monopentathiepin 1c. N-Methyl and ethyl indole give either 2,3-dichloro derivatives 8 or the pentathiepinoindoles 9, depending upon the reaction conditions. Thiophene and tetrahydrothiophene give the pentathiepin 10. X-Ray crystal structures are provided for the pentathiepins 1a and 1d, and possible reaction pathways are suggested for the extensive cascade reactions reported. 相似文献
348.
The suitability of the half-cell Pt/I2, KI in glacial acetic acid as reference electrode for potentiometric titrations of weak bases in the same medium was investigated. This electrode is easily prepared. It has been found very convenient in use and performing at least as well as the best electrodes used for the same purpose. Some phenomenological aspects of the behaviour of the above half-cell, of interest for the use as the reference electrode in the laboratory practice have been observed, that show important differences respect aqueous medium and other organic solvents. 相似文献
349.
Lidia?Okrasa Tadeusz?PakulaEmail author Yoshihisa?Inoue Krzysztof?Matyjaszewski 《Colloid and polymer science》2004,282(8):844-853
The morphology and thermomechanical properties of well-defined polyethylene-graft-poly(n-butyl acrylate) (PE-g-PBA) copolymers prepared via atom transfer radical polymerization were investigated. Differential scanning calorimetry (DSC), small angle X-ray scattering (SAXS), wide angle X-ray scattering (WAXS), dynamic mechanical measurement and large deformation tensile tests were performed on the graft copolymers and the results were compared with the behavior of the polyethylene macroinitiator. The existence of both crystalline polyethylene segments and amorphous poly(n-butyl acrylate) segments in the copolymers leads to microphase separation and unique thermomechanical behavior. Strong microphase separation was observed by DSC and X-ray diffraction studies. Correlation of morphology and thermomechanical properties was also studied using dynamic mechanical measurement and large deformation tensile tests.Dedicated to Prof. E. W. Fischer on the occasion of his 75th birthday 相似文献
350.
Sergio Daolio David Aj Gilberto Rossetto Carla Aschieri Lidia Armelao 《Journal of mass spectrometry : JMS》1992,27(11):1171-1175
Within a comprehensive programme including synthesis via metal organic chemical vapour deposition (MOCVD) and characterization of inorganic compounds and materials of possible interest in technologies based on thin films, results concerning the deposition of metal oxides by means of volatile organometal precursors are reported. In particular, thallium oxide films obtained by the MOCVD technique and commercial powders of Tl2O3 and Tl2O adsorbed on several metal substrates (stainless steel, Si, Cu, Mo, Pt) were studied by secondary ion mass Spectrometry (SIMS) under ion beam bombardment at different ion energies. The positive- and negative-ion mass spectra exhibit typical isotopic patterns of several ionic species produced by interesting interfacial reactions, and the analysis of their relative abundances provides a measure of oxide reactivity towards different substrates. SIMS measurements of metal substrates were also performed. The ability and limits of SIMS in the reactivity study of thallium oxide powders and films and, in addition, in the identification of reaction products evidencing impurity species that, in turn, can be ascribed to the substrates or to the precursors used for the oxide synthesis is pointed out. 相似文献