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41.
D. V. Koreshkov N. L. Levshin P. A. Forsh S. G. Yudin 《Moscow University Physics Bulletin》2007,62(2):90-92
Frequency dependences are obtained of the conductivity in Langmuir films of modified vanadyl phthalocyanine in vacuum and under the conditions of adsorption of donor and acceptor molecules. It is found that, upon the adsorption of NO2 and CH4O molecules, the film conductivity at f < 10 kHz increases by several orders of magnitude. It is shown that, in vacuum and upon adsorption of acceptor molecules, the dominant charge transfer mechanism is the hopping of holes via localized states. In the case of adsorption of donor molecules, the ionic conductivity mechanism appears to prevail. 相似文献
42.
Barskaya E. S. Beloglazkina E. K. Mazhuga A. G. Yudin I. V. Zyk N. V. 《Russian Chemical Bulletin》2015,64(8):1975-1977
Russian Chemical Bulletin - Reflux of imidazole-2-carboxaldehyde, 1-methylimidazole-2-carboxaldehyde, imidazole4-carboxaldehyde, or 5-bromopyridine-2-carboxaldehyde with 2-aminothiophenol in... 相似文献
43.
Andrei K. Yudin 《Chemical science》2015,6(1):30-49
A noticeable increase in molecular complexity of drug targets has created an unmet need in the therapeutic agents that are larger than traditional small molecules. Macrocycles, which are cyclic compounds comprising 12 atoms or more, are now recognized as molecules that “are up to the task” to interrogate extended protein interfaces. However, because macrocycles (particularly the ones based on peptides) are equipped with large polar surface areas, achieving cellular permeability and bioavailability is anything but straightforward. While one might consider this to be the Achilles'' heel of this class of compounds, the synthetic community continues to develop creative approaches toward the synthesis of macrocycles and their site-selective modification. This perspective provides an overview of both mechanistic and structural issues that bear on macrocycles as a unique class of molecules. The reader is offered a historical foray into some of the classic studies that have resulted in the current renaissance of macrocycles. In addition, an attempt is made to overview the more recent developments that give hope that macrocycles might indeed turn into a useful therapeutic modality. 相似文献
44.
Parameterization of electrostatic interactions for molecular dynamics simulations of heterocyclic polymers
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Victor M. Nazarychev Sergey V. Larin Alexander V. Yakimansky Natalia V. Lukasheva Andrey A. Gurtovenko Iosif V. Gofman Vladimir E. Yudin Valentin M. Svetlichnyi Jose M. Kenny Sergey V. Lyulin 《Journal of Polymer Science.Polymer Physics》2015,53(13):912-923
The paper focuses on the problem of electrostatic interactions in molecular dynamics simulations of thermal properties of heterocyclic polymers. The study focuses on three thermoplastic polyimides synthesized on the basis of 1,3‐bis‐(3′,4‐dicarboxyphenoxy)benzene (dianhydride R) and three diamines: 4,4′‐bis‐(4″‐aminophenoxy) diphenylsulfone (diamine BAPS), 4,4′‐bis‐(4″‐aminophenoxy) biphenyl (diamine BAPB), and 4,4′‐bis‐(4''‐aminophenoxy) diphenyloxide (diamine BAPO). In the molecular dynamics simulations these polyimides were described by the Gromos53a5 force field. To parameterize the electrostatic interactions four methods of calculating the partial atomic charges were chosen: B3LYP/6–31G*(Mulliken), AM1(Mulliken), HF/6–31G*(Mulliken), and HF/6–31G*(ChelpG). As our parameterization is targeted to reproduce thermal properties of the thermoplastic polyimides, the choice of proper partial charges was finalized on a basis of the closest match between computational and experimental data for the thermal expansion coefficients of the polyimides below glass transition temperatures. Our finding clearly show that the best agreement with experimental data is achieved with the Mulliken partial atomic charges calculated by the Hartree‐Fock method with 6–31G* basis set. Furthermore, in addition to the thermal expansion coefficients this set of partial atomic charges predicts an experimentally observed relationship between glass transition temperatures of the three polyimides under study: . A mechanism behind the change in thermal properties upon the change in the chemical structure in considered polyimides may be related to an additional spatial ordering of sulfone groups due to dipole‐dipole interactions. Overall, the modified force‐field is proved to be suitable for accurate prediction of thermal properties of thermoplastic polyimides and can serve as a basis for building up atomistic theoretical models for describing other heterocyclic polymers in bulk. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015 , 53, 912–923 相似文献
45.
V. V. Matrenichev M. A. Shishov P. V. Popryadukhin I. Yu. Sapurina E. M. Ivan’kova I. P. Dobrovol’skaya V. E. Yudin 《Russian Journal of Applied Chemistry》2017,90(10):1680-1685
Conducting materials based on polypyrrole-modified nanofibers of polylactides of different molecular masses and copolymers of ε-caprolactam (–NH–(CH2)5–CO–) and hexamethylenediamine adipate (–H(CH2)6NHCO(CH2)4CO–) were prepared. As shown by scanning electron microscopy, oxidative polymerization of pyrrole on the polymer nanofiber matrix depends on the nanofib er hydrophilicity. The heterophase synthesis of polypyrrole on the surface of hydrophilic nanofibers of the aliphatic copolyamide allowed uniform coating of the material surface with polypyrrole nanoparticles. The surface resistivity of the composite material was about 0.4 kΩ sq–1. 相似文献
46.
Rostov State University Scientific-Research Institute of Mechanics and Applied Mathematics, Rostovon-Don. Translated from Prikladnaya Mekhanika, Vol. 25, No. 12, pp. 63–68, December, 1989. 相似文献
47.
A. M. Valenkov I. V. Gofman K. S. Nosov V. M. Shapovalov V. E. Yudin 《Russian Journal of Applied Chemistry》2011,84(5):735-750
Most widely occurring classes of carbon nanoparticles used to create polymeric composite systems are considered. The possibility
is demonstrated of using “polymer-carbon nanoparticles” composites for raising the level of mechanical properties of polymeric
materials, creating friction units with improved tribological characteristics, developing new electrochemical, microelectronic,
and optical devices, and modifying barrier properties of polymeric membranes. Methods for treatment of nanoparticles to provide
their compatibility with polymeric matrices and preclude their aggregation are discussed. 相似文献
48.
V. V. Yudin E. S. Startzev I. G. Permyakova 《Theoretical and Mathematical Physics》2011,167(1):517-537
We construct the group bundle for the inverse Fibonacci semigroups in the axiomatic approach framework. The proper Fibonacci
semigroup is the corresponding group bundle for the Penrose semigroups, which can be interpreted as the generating grammar
of the morphogenetic synthesis of the pentasymmetric Penrose parquet in the numbers of tiling by golden rhombuses. This morphogenetic
synthesis of the Penrose parquet satisfies the scaling principle. Parquet plates are not absolutely rigid, and the relations
between their metric characteristics are governed by the golden section and other magic numbers. The characteristic form factors
of three-level dual alphabets are the corresponding invariants. We realize the morphogenetic synthesis in the examples of
square-octagonal and bihexagonal lattices. We consider cumulative properties of magic series and the evolutionary aspects
of semigroup orbits in the entropy representation. 相似文献
49.
A. G. Babenko Yu. V. Kryakin V. A. Yudin 《Proceedings of the Steklov Institute of Mathematics》2011,273(1):37-48
In 1935, Ya.L. Geronimus found the best integral approximation on the period [?π,π) of the function sin(n + 1)t ? 2q sin nt, q ∈ ?, by the subspace of trigonometric polynomials of degree at most n ? 1. This result is an integral analog of the known theorem by E.I. Zolotarev (1868). At present, there are several methods of proving this fact. We propose one more variant of the proof. In the case |q| ≥ 1, we apply the (2π/n)-periodization and the fact that the function | sin nt| is orthogonal to the harmonic cos t on the period. In the case |q| < 1, we use the duality relations for Chebyshev’s theorem (1859) on a rational function least deviating from zero on a closed interval with respect to the uniform metric. 相似文献
50.
V. E. Yudin J. U. Otaigbe S. I. Nazarenko W. D. Kim E. N. Korytkova 《Mechanics of Composite Materials》2011,47(3):335-342
Polyimide (PI) films based on poly(pyromellitic dianhydride-co-4,4′-oxydianiline) (PI-PM) were filled with different nanoparticles,
such as organically modified montmorillonite (MMT), vapor-grown carbon nanofibers (VGCF), and silicate nanotubes (SNT) of
different concentration.. Rheological measurements and structural investigations showed a relatively good dispersion of the
nanoparticles in the PI matrix to an extent that depended on the type and morphology of the nanoparticles used. The mechanical
(tensile modulus, strength, and deformation at break) and the barrier (oxygen permeability) properties of PI-PM nanocomposite
films were investigated. The polyimide nanocomposites filled with SNT and tubular VGCF nanoparticles showed an increased tensile
modulus with increasing volume concentration of the nanoparticles without a catastrophic decrease in the elongation at break.
In addition, the MMT particles, chemically modified with 4,4'-bis-(4′′-aminophenoxy)diphenylsulfone, significantly improved
the barrier properties of the PI-PM films, which exceeded those of the nanocomposites filled with VGCF or SNT. The relative
poor oxygen barrier and mechanical properties of the PI-PM/VGCF nanocomposite films are ascribed to the relative weak adhesion
between the VGCF and the polyimide matrix, which was confirmed by scanning electron microscopy of the fracture surface of
these films. 相似文献