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111.
Raluca Nicoleta Darie Mihai Brebu Cornelia Vasile Marek Kozlowski 《Polymer Degradation and Stability》2003,80(3):551-566
Binary isotactic polypropylene (IPP)/polyamide 6 (PA6) and ternary IPP/PA6/ethylene–propylene diene terpolymer (EPDM) blends in various ratios were obtained in a Haake Rheocord mixer. Processing behaviour was changed in the presence of IPP functionalized with bismaleimide (BMI), maleic anhydride (MA) and acrylic acid (AA) as reactive compatibilizing agents. The thermal and thermo-oxidative behaviour of blends was studied by differential scanning calorimetry and thermogravimetry. The functionalized IPPs modify the crystallinity degree and the decomposition behaviour of both IPP and PA6 as a result of chemical reactions of functional groups with those of the PA6. The changes depend on the IPP/PA6 or IPP/PA6/EPDM ratio, the chemical nature and amount of the functionalized IPP. On the basis of the processing and thermal data one can conclude that the compatibilizing agent effect increases in the following order: IPP-AA 相似文献
112.
The sequential reaction of the amino(trimethylsilyl)carbene complex [(CO)5W=C(NH2)C≡CSiMe3] ( 1 ) with nBuLi and [I‐Fe(CO)2Cp] affords the C(carbene)‐N bridged heterobinuclear complex [(CO)5W=C{NHFe(CO)2Cp}C≡CSiMe3] ( 2 ). Desilylation of 1 is achieved by treatment with KF in THF/MeOH. From the reaction of the resulting complex [(CO)5W=C(NH2)C≡CH] ( 3 ) with nBuLi and [I‐Fe(CO)2Cp] two binuclear WFe compounds in a ratio of approximately 1:1 are obtained: the C(carbene)‐C≡C bridged complex 4 and the C(carbene)‐N bridged complex 5 . Repetition of the deprotonation/metallation sequence yields the trinuclear WFe2 complex 6 . One Fe(CO)2Cp fragment in 6 is bonded to the amino group and the other one to the terminal carbon atom of the ethynyl substituent. The analogous reaction of 3 with nBuLi and [Br‐Ni(PMe2Ph)2Mes] gives a ca. 1:1 mixture of two heterobinuclear complexes ( 7 and 8 ). Complex 7 is bridged by the C(carbene)‐C≡C and complex 8 by the C(carbene)‐N fragment. Subsequent reaction of 7 with BuLi and [Br‐Ni(PMe2Ph)2Mes] finally affords the trinuclear WNi2 complex 9 related to 6 . The solid‐state structure of 2 is established by an X‐ray diffraction analysis. The spectroscopic data of the bi‐ and trinuclear complexes indicate electronic communication between the metal centers through the bridging group. 相似文献
113.
Ede Kapuy Cornelia Kozmutza Raymond Daudel Michael E. Stephens 《Theoretical chemistry accounts》1978,50(1):31-38
The effects of Gaussian basis set contraction and addition of polarization functions on H2O localized orbitals have been studied at the experimental geometry. It is shown that the electric moments and moment features of localized orbitals are not influenced very much by basis set quality variations, as going from medium size to enlarged basis sets. The difference between bond pair and lone pair charge densities was found to be larger on approaching the Hartree-Fock limit. A minimal basis set, however, does not suitably characterize the localized charge distributions. 相似文献
114.
Bohne C Faulhaber K Giese B Häfner A Hofmann A Ihmels H Köhler AK Perä S Schneider F Sheepwash MA 《Journal of the American Chemical Society》2005,127(1):76-85
Mechanistic investigations of the photoinduced DNA damage by acridizinium salts (4a-azonia-anthracene derivatives) are presented. Irradiation of 9-bromoacridizinium in the presence of defined double- and single-stranded DNA oligomers under aerobic conditions leads to both frank strand breaks and alkali-labile sites as determined by polyacrylamide gel electrophoresis (PAGE). The extent of the DNA damage increases significantly in D(2)O and occurs selectively at guanosine residues. These observations reveal the formation of singlet oxygen ((1)O(2)) as reactive species, which oxidizes the DNA bases, above all the guanine bases. Further evidence for (1)O(2) formation was obtained from laser-flash spectroscopic investigations, which show intersystem crossing (S(1) to T(1)) of the excited states of the parent acridizinium and of the 9-bromo- and 9-amino-substituted derivatives. The resulting triplet state is efficiently quenched by oxygen (k(q) > 10(9) s(-)(1)M(-)(1)) to yield (1)O(2). Under anaerobic conditions, no significant alkali-labile lesions are observed, but frank strand breaks are induced; however, to lesser extent than under aerobic conditions. The DNA damage is suppressed in the presence of a radical scavenger, namely t-BuOH, and hydroxyl radicals are shown to be the reactive intermediates by trapping experiments with terephthalic acid. Moreover, the intercalated acridizinium molecules are not involved in the DNA damage reactions. The intercalated acridizinium salt leads to a primary PET reaction with the DNA bases; however, a fast BET transfer is proposed that regains the dye and the DNA, so that the excited intercalated dye does not contribute significantly to the overall DNA damage. 相似文献
115.
Cornelia Kozmutza 《Theoretical chemistry accounts》1981,60(1):53-63
Anab initio integral program is described. It utilizes the local symmetries to avoid the redundant computation of integrals over spatially equivalent subsets of the basis. The integrals are grouped in a particular way to facilitate their transfer. The program is very suitable for the treatment of related systems with model geometries. The computing times of different programs are compared and the efficiency of the presented one is demonstrated. 相似文献
116.
Cornelia Boberski Rainer Hamminger Marcell Peuckert Fritz Aldinger Reinhard Dillinger Jürgen Heinrich Jürgen Huber 《Angewandte Chemie (International ed. in English)》1989,28(11):1560-1569
The past decade has seen greatly increased interest in ceramic materials with special combinations of properties. Their hardness, high resistance to abrasive and erosive wear, and their good corrosion resistance when used under extreme mechanical and thermal conditions have made ceramics increasingly attractive for applications in mechanical and apparatus engineering. Silicon nitride (Si3N4) in particular, is suitable for the development of a high-performance, high-temperature material for vehicle engine construction. Although the properties of Si3N4 materials have been consistently improved in the last few years, they are still not adequate to allow these materials to be used in series production parts, for example as valves in automotive engines. One of the main reasons for this is the wide scatter and low reproducibility of the property parameters, which means that component reliability does not yet meet market requirements. Hence, one aim of Si3N4 materials development is to reduce the structural flaws resulting from physical and chemical inhomogeneity. This objective can only be achieved through a fundamental understanding of all the processing steps, from powder production to the final processing of the components. 相似文献
117.
118.
Thermoxidative Decomposition of Some Polysulfones under Dynamic Conditions of Heating 总被引:1,自引:0,他引:1
Vasile Cornelia Costea Elena Pascu Mihaela C. Warshawsky A. 《Journal of Thermal Analysis and Calorimetry》1998,52(2):569-579
Kinetic aspects of the first step of thermoxidative decomposition, under dynamic conditions of heating, of some polysulfones
have been studied.
The dependence of the kinetic parameters on the heating rate and conversion degree has been established. The compensation
effect and conversion function have also been discussed.
Polysulfone decomposes by the breaking of the main chain, a process involving very high activation energy.
Chemically modified polysulfones show the first step of thermoxidative decomposition at relatively low temperatures. This
step corresponds to the elimination of functional side - groups for the bromomethylated polysulfone while in the case of the
carboxylated polysolfone, the loss of the carboxyl group is probably accompanied by a crosslinking reaction.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
119.
Zusammenfassung In der vorliegenden Arbeit wird eine colorimetrische Methode zur Bestimmung von Brucin, Strychnin, Chinin und Cinchonin beschrieben, die darauf beruht, daß mit Kaliumhexathiocyanatochromat(III), [Cr(SCN)6]K3, komplexe Verbindungen entstehen, die in Wasser unlöslich, in Aceton hingegen mit violetter Färbung leicht löslich sind. Die acetonischen Lösungen können mit einem Pulfrich-Spektrophotometer mit Gelbfilter colorimetriert werden. Das Maximum der Absorption liegt bei 574 nm. Die Extinktion zeigt keine Veränderungen mit der Zeit. Für die Extinktionskonstanten sind folgende Werte ermittelt worden: Chinin 220, Brucin 191, Cinchonin 189 und Strychnin 135. 相似文献
120.
Stela DrÎgan Cornelia Luca I. Petrariu M. Dima 《Journal of polymer science. Part A, Polymer chemistry》1980,18(2):455-465
The reaction of chloromethylated polystyrene with tris(2-hydroxyethyl)amine in N,N-dimethylformamide is described for the conditions to prepare soluble reaction products. The groups of the quaternary ammonium salt, which appear in the first stage of the reaction, transpose to the amino-ether groups. The reaction was followed by elementary analysis, IR and 1H-NMR spectra, and viscosimetric measurements for nondialyzed and dialyzed samples. The presence of the tertiary amine groups on obtained polymers was also shown by titration. The polymers from the reaction of chloromethylated polystyrene with tris(2-hydroxyethyl)amine reacted easily with benzyl chloride. 相似文献