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31.
Korneeva NL 《Chemistry & biology》2007,14(1):5-7
Pateamine A inhibits translation by preventing proper translational initiation complex formation. In the December issue of Chemistry & Biology, Bordeleau et al. demonstrated that the effects of Patemine A on translation are mediated through the interaction between the RNA helicase eIF4A and mRNA . 相似文献
32.
Yakov S. Vygodskii Olga A. Mel'nik Elena I. Lozinskaya Alexander S. Shaplov Inna A. Malyshkina Nadejda D. Gavrilova Konstantin A. Lyssenko Mikhail Yu. Antipin Denis G. Golovanov Alexander A. Korlyukov Nikolai Ignat'ev Urs Welz‐Biermann 《先进技术聚合物》2007,18(1):50-63
Various 1,3‐dialkylimidazolium and tetraalkylphosphonium ionic liquids (ILs), including novel ones, have been studied as reaction media for free radical polymerization of methyl methacrylate (MMA), acrylonitrile (AN) and 1‐vinyl‐3‐ethylimidazolium salts (ViEtIm+)Y?. The influence of IL's nature upon the polymer formulation was investigated. The use of different ionic liquids allows not only to obtain the polymers with high molecular weight (PMMA, up to 5,770,000 g/mol; PAN, up to 735,000 g/mol and poly[(ViEtIm+)Y?], up to 1,130,000 g/mol) in high yields, but also to control the polymerization rate and molecular mass. The physicochemical characteristics, including mechanical properties, thermal stability and heat‐resistance of the obtained polymers were studied in order to compare with those of polymers prepared in a traditional media. It was found that elongation, tensile modulus and strength of PAN, which was synthesized in ionic liquid, are reliatively higher. The influence of IL's nature upon their ionic conductivity and the formation of conductive polymers from molten‐salt‐type vinyl monomers was investigated. Molecular design of the polymers simultaneously with the influence of IL's nature in order to achieve higher ionic conductivity is discussed. Flexible, transparent polymer films, obtained in different ways, show relatively high ionic conductivity (of about 10?5 S cm?1 at 20°C). Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
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35.
José Luis Toca-Herrera Nadejda Krasteva Hans-Joachim Müller Rumen Krastev 《Advances in colloid and interface science》2014
The interaction between lipid bilayers in water has been intensively studied over the last decades. Osmotic stress was applied to evaluate the forces between two approaching lipid bilayers in aqueous solution. The force–distance relation between lipid mono- or bilayers deposited on mica sheets using a surface force apparatus (SFA) was also measured. Lipid stabilised foam films offer another possibility to study the interactions between lipid monolayers. These films can be prepared comparatively easy with very good reproducibility. Foam films consist usually of two adsorbed surfactant monolayers separated by a layer of the aqueous solution from which the film is created. Their thickness can be conveniently measured using microinterferometric techniques. Studies with foam films deliver valuable information on the interactions between lipid membranes and especially their stability and permeability. Presenting inverse black lipid membrane (BLM) foam films supply information about the properties of the lipid self-organisation in bilayers. The present paper summarises results on microscopic lipid stabilised foam films by measuring their thickness and contact angle. Most of the presented results concern foam films prepared from dispersions of the zwitterionic lipid 1,2-dimyristoyl-sn-glycero-3-phosphorylcholine (DMPC) and some of its mixtures with the anionic lipid — 1,2-dimyristoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (DMPG). 相似文献
36.
The low-temperature flexibility of polyethylene (PE)–chlorinated polyethylene (CPE) blends and their composites with a small amount of graphene oxide filler was studied. Quantitative height variation in the AFM images, rheological as well as fracture analyses were employed to gain insights into the generation of flexibility in the matrix phase. The semi-crystalline CPE (CPE25) polymer did not induce viscoelastic behavior at temperatures lower than the glass transition temperature of PE, whereas the amorphous CPE (CPE35) had completely different behavior. The samples with CPE35 could not be sufficiently hardened even at ?180 °C and remained too soft for cryosectioning. Therefore, compression, which results in a 30–60 % reduction in length along the cutting direction with no change in the dimension perpendicular to it, was very prominent for both thin section and block face of the sample. The composites had even higher degree of compression due to additional effect of weak filler matrix interactions and as a consequence, the topographical variations led to filler pull out during sectioning. It was also confirmed using the rheological analysis that composites (and blends with 10 % CPE35 content) had phase immiscibility as CPE phase was suspected to concentrate near the graphene oxide phase leading to generation of chlorine-rich phases. The addition of graphene oxide did not lead to reduced flexibility and the composites also retained the modulus similar to pure polymer. The mechanical fracture of the samples also confirmed the flexibility of the CPE containing blends and composites as these samples were still flexible at ?195 °C. 相似文献
37.
Lavinia Petronela Curecheriu Marco Deluca Zina Violeta Mocanu Mihai Valentin Pop Valentin Nica Nadejda Horchidan 《Phase Transitions》2013,86(7):703-714
BaCe x Ti1? x O3 (x?=?0.06, 0.10, and 0.20) solid solutions were prepared via conventional the solid-state reaction and sintered at 1500°C for 4?h, resulting in dense single phase ceramics with homogeneous microstructures. The electric field dependence of permittivity of the BaCe x Ti1? x O3 ceramics was investigated in detail, together with the ferroelectric–paraelectric phase transition features. A transformation from normal to relaxor ferroelectrics was observed by increasing the Ce concentration. For low-Ce content, a substitution of Ce on both A and B site positions was proposed from the dielectric study and confirmed by Raman analysis. 相似文献
38.
Polina A. Ryabochkina Svetlana A. Antoshkina Evgeniya V. Bolshakova Michael A. Ivanov Vladimir V. Kochurihin Alexander V. Malov Sergey N. Ushakov Nadejda V. Shchuchkina Konstantin N. Nishchev 《Journal of luminescence》2012,132(8):1900-1905
In this work, spectroscopic characteristics (oscillator strengths, intensity parameters) of intermanifold f–f transitions of Tm3 +, Ho3+and Dy3+ions in garnet crystals are investigated. It has been found that the intensity change of the hypersensitive intermanifold f–f transitions of rare-earth ions in garnet crystals is determined by the characteristics of their local environment. 相似文献
39.
Alexander I. Drachev Laura A. Rishina Nadejda M. Galashina 《European Polymer Journal》2005,41(7):1688-1698
The effect of a direct current discharge on the films of polypropylene and copolymers of propylene and hexene-1 synthesized with an isospecific catalytic system, rac-Me2SiInd2ZrCl2-polymethylaluminoxane, was investigated. The treatment of isotactic polypropylene films by the discharge did not affect the ratio of crystalline phases in the polymer to a measurable extent. However, for the plasma treated films of copolymers of propylene and hexene-1 (the hexene-1 content of 1-2 mol%), a structural transformation of γ-modification into α-modification has been noticed. The observed phase transition has no apparent relation to any changes in microstructure of the copolymer chain because melting temperature values and the stereoregularity parameters of the samples remained practically unchanged. An experimental investigation of the specific influence exerted by individual components of a direct current discharge on the crystalline structure of copolymers has been undertaken. The exposure to a quantum component of the discharge did not induce any changes in the phase composition of the irradiated samples. The heating of the samples led to a negligible change of their phase composition. It has been determined that the surface of polypropylene and propylene/hexene-1 copolymer films facing the cathode in the course of the direct current discharge treatment had an accumulated negative charge Q > 10 nC/cm2 which persisted for a long time afterwards. It has been suggested that the electrical field of a negative discharge may be the main cause of the γ-into α-phase transition in propylene/hexene-1 copolymers under the plasma effect. To verify this assumption, a propylene/hexene-1 copolymer film was charged under electron beam with energy of 4 keV. The electron beam treatment of the film resulted to the negative charge value of 11 nC/cm2. The electron beam irradiation has induced the phase transition which was quite similar to the transition observed as the result of plasma treatment. So, it may be concluded that the phase transition from crystal γ-modification to α-modification under the effect of direct current discharge which has been investigated for copolymers of propylene and hexene-1 is induced by electric field of the negative charge accumulated at the surface layers of the films of the copolymers. 相似文献
40.
A method is described for the determination of Hf, Sc and Y simultaneously with the REE in geological materials. An earlier
method for REE separation from major elements was studied with the aim to apply it also to the determination of Hf, Sc and
Y. Sample decomposition was carried out by melting with LiBO2. The method involves separation and concentration stages, using the cation-exchange resin DOWEX AG 50W-X8. Matrix elements
were eluted with 2 mol/l HCl, whereas 6 mol/l HNO3 with oxalic acid and 8 mol/l HNO3 were used to elute the elements to be determined. Some of the matrix elements could not be completely removed. This effect
as well as the recovery rates of the determined elements were investigated. The measurements were performed by ICP-AES. Spectral
interferences were also tested.
Received: 8 November 1995/Revised: 12 March 1996/Accepted: 14 March 1996 相似文献