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1.
Valentina I. Simagina Pavel A. Storozhenko Olga V. Netskina Oksana V. Komova Galina V. Odegova Yury V. Larichev Arcady V. Ishchenko Anna M. Ozerova 《Catalysis Today》2008,138(3-4):253
Catalytic hydrolysis of NaBH4 and NH3BH3 has been studied. It was shown that the nature of the support and the active component of the catalyst affect the H2 generation rate. Despite similar sizes of rhodium particles formed on the surface of different supports (γ-Al2O3, TiO2, carbon), their reactivity is different. Rh/TiO2 with low rhodium concentration (1 wt.%) is the most active catalyst both in the hydrolysis of NaBH4 and NH3BH3. The obtained results show that the rhodium chloride interaction with titania determines the reactivity of rhodium particles formed under action of NaBH4 medium. TEM, DRS UV–vis and XPS were used to characterize the catalysts. 相似文献
2.
Tkachenko Yurii G. Britun Yurchenko Djema Z. Ochkas Larisa F. Bovkun Galina A. 《Powder Metallurgy and Metal Ceramics》2004,43(1-2):99-104
The influence which the composition of powder mixtures, the treatment conditions which the mixtures are subjected to, and the conditions under which the hot-pressed composite materials B4C – (5-10 mass%) calcium-silicon are fabricated exert on the structure, nature of failure, and mechanical properties of these materials is investigated. Optimum properties are possessed by material containing 10 mass% of addition. It is shown that the structure, morphology, and dispersivity, as well as the nature of the distribution of the components that are added to the composite material (secondary phase) vary as the temperature of hot pressing changes. Maximal mechanical characteristics of the composite material (σbend = 560 MPa, K 1c = 4.7 MPa·m1/2, HV = 37 GPa) are attained at hot-pressing temperatures in the range 2000-2100°C. 相似文献
3.
Many new speciality polymers have been developed in the last few years. In this paper polymeric stabilizers (antioxidants, flame retardants and ultraviolet stabilizers) will be discussed. Polymeric antioxidants of the hindered-phenol type, copolymers of 2,6-ditertiarybutyl-4-vinyl(or isopropenyl)phenol with styrene, methyl methacrylate, or more importantly butadiene or isoprene have been prepared; hydrogenation of the latter copolymers gave copolymers of the two polymerizable phenolic antioxidants with ethylene or ethylene/propylene. The polymeric antioxidants have been blended with diene polymers and selected polyolefins and have improved the long-term oxidative stability of these polymers. Polymeric flame retardants have been prepared by copolymerizing styrene and/or acrylonitrile with acrylates and methacrylates of aliphatic bromine-containing alcohols or bromine-containing phenols. Polymers with polymer-bound flame retardants have a higher limiting oxygen index compared with the original polymer. A new class of polymerizable ultraviolet stabilizers has also been developed; these stabilizers are styryl, α-methylstyryl, acryloyl and methacryloyl derivatives of 2(2-hydroxyphenyl)2H-benzotriazoles. These monomers have been copolymerized with styrene, acrylates and methacrylates. 2(2-Hydroxyphenyl)2H-benzotriazoles substituted in the 4 position of the benzotriazole ring with hydroxyl, acetoxy or carboxyl groups suitable for incorporation into polyesters, polycarbonates, polyamides and epoxy resins have also been synthesized. All 2(2-hydroxyphenyl)2H-benzotriazole ultraviolet absorbers and the polymers into which they are incorporated have high light absorbency with γmax between 330 and 350 nm and extinction coefficients in some cases as high as 4.5 × 104 1 mol?1 cm?1. 相似文献
4.
5.
Olga Shilova Elena Shramova Galina Proshkina Sergey Deyev 《International journal of molecular sciences》2021,22(9)
Cancer cells frequently overexpress specific surface receptors providing tumor growth and survival which can be used for precise therapy. Targeting cancer cell receptors with protein toxins is an attractive approach widely used in contemporary experimental oncology and preclinical studies. Methods of targeted delivery of toxins to cancer cells, different drug carriers based on nanosized materials (liposomes, nanoparticles, polymers), the most promising designed light-activated toxins, as well as mechanisms of the cytotoxic action of the main natural toxins used in modern experimental oncology, are discussed in this review. The prospects of the combined therapy of tumors based on multimodal nanostructures are also discussed. 相似文献
6.
7.
A new method of preparation of carboxyl cation exchangers directly from methacrylic acid and divinylbenzene is described. A suspension technique with a concentrated aqueous calcium chloride solution as the water phase was used. n-Octane and toluene were inert diluents of the monomers. The copolymers obtained have high ion-exchange capacity (9.6–10.6 mequ./g) and porous structure. 相似文献
8.
In drug delivery systems that use silicone elastomers as a diffusion matrix for the active drug, it is common to crosslink the material by the hydrosilylation reaction. In this platinum‐catalyzed reaction, vinyl groups on a polymer add to the methyl siloxane hydride (MHS) groups on a low molecular mass crosslinker. With an excess of crosslinker, a fast curing is achieved and a fully crosslinked material is formed. Unreacted MHS groups were shown to remain in the elastomer after curing because of the excess crosslinker. In this work, a simple procedure was developed to eliminate the unreacted MHS groups from the final product. We found that storage of the product at +40°C and 75% relative humidity for a few weeks will effectively destroy the residual MHS groups in the elastomer. The effects of varying levels of humidity, oxygen, and temperature on this postcuring procedure were studied. The amount of MHS groups was measured with NMR and IR spectroscopy. We also found that the hardness of the material increased by approximately 25% as a consequence of this postcuring treatment. This increase is probably due to a secondary crosslinking reaction between MHS and silanol groups. Heat treatment at higher temperatures led to an even further increase in the hardness and compression modulus. Because no MHS groups remained in the elastomer when this heat treatment was started, it is apparent that another secondary crosslinking reaction is occurring, probably silanol condensation. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2254–2264, 2002 相似文献
9.
Yurii G. Tkachenko Viktor F. Britun Emmanuil V. Prilutskii Dzhemma Z. Yurchenko Galina A. Bovkun 《Powder Metallurgy and Metal Ceramics》2005,44(3-4):196-201
We have investigated how the composition, grain morphology, and method of preparing the starting mixture affect the processes that form the structure and phase composition of B4C - SiC composites during hot pressing. We found that, depending on the composition of the initial powder mixtures, which is responsible for different mechanisms of consolidation of ceramic materials during hot pressing, the grain size of the main B4C phase and its defect content as well as the nature of the SiC phase distribution within the material differ significantly. When B4C - SiC composites with a low SiC content are made from initial B4C - B4Si - B - C powder mixtures those composites have a high cracking resistance because of their fine grain structure.__________Translated from Poroshkovaya Metallurgiya, Nos. 3–4(442), pp. 112–119, March–April, 2005. 相似文献
10.
In order to identify and describe a pattern in bus and coach incident related injuries and fatalities, and to suggest possible future measures for improvement of bus and coach safety, a literature analysis was performed. The results formed a multi-faceted pattern, which briefly can be described as follows; women travelled more frequently by bus as compared to men. Injuries sustained predominantly affected women 60 years of age and older. Of all traffic fatalities in Europe, bus and coach fatalities represented 0.3-0.5%. In the OECD countries, the risk of being killed or seriously injured was found to be seven to nine times lower for bus and coach occupants as compared to those of car occupants. Despite the fact that fatalities were more frequent on rural roads, a vast majority of all bus and coach casualties occurred on urban roads and in dry weather conditions. Boarding and alighting caused about one-third of all injury cases. Collisions were a major injury-contributing factor. Buses and coaches most frequently collided with cars, but unprotected road users were hit in about one-third of all cases of a collision, the point of impact on the bus or the coach being typically frontal or side. Rollovers occurred in almost all cases of severe coach crashes. In this type of crash projection, total ejection, partial ejection, intrusion and smoke inhalation were the main injury mechanisms and among those, ejection being the most dangerous. A 2-point belt may prevent passenger ejection, but in frontal crashes when the upper abdominal parts and the head hit the seatback in front, it could, however, contribute to head and thoracic injuries. Hence, a 3-point belt provides the best restraint in rollovers and frontal crashes. 相似文献