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91.
Physics of Atomic Nuclei - The role of weakly bound neutral clusters, such as dineutrons and tetraneutrons, in matter of high density and high temperature is discussed. Under such conditions, which... 相似文献
92.
93.
Dr. Sungjoon Huh Dr. George J. Saunders Prof. Andrei K. Yudin 《Angewandte Chemie (International ed. in English)》2023,62(5):e202214729
Site-selective transformations of densely functionalized scaffolds have been a topic of intense interest in chemical synthesis. Herein we have repurposed the rarely used Cornforth rearrangement as a tool to effect a single-atom ring contraction in cyclic peptide backbones. Investigations into the kinetics of the rearrangement were carried out to understand the impact of electronic factors, ring size, and linker type on the reaction efficiency. Conformational analysis was undertaken and showed how subtle differences in the peptide backbone result in substrate-dependent reaction profiles. This methodology can now be used to perform conformation-activity studies. The chemistry also offers an opportunity to install building blocks that are not compatible with traditional C-to-N iterative synthesis of macrocycle precursors. 相似文献
94.
Tsang DS Yang S Alphonse FA Yudin AK 《Chemistry (Weinheim an der Bergstrasse, Germany)》2008,14(3):886-894
In the presence of rhodium(I) hydride catalysts, tertiary N-allylamines are known to isomerise into E enamines. In contrast, we have recently found that N-allylaziridines isomerise to form Z enamines. On the basis of literature data, the most likely mechanism of isomerisation would involve a rhodium hydride addition/beta-hydride elimination sequence. We show that the observed selectivity cannot be adequately explained by this pathway and is more consistent with initial CH-activation followed by rearrangement to form a five-membered cyclometallated rhodium intermediate. This intermediate subsequently undergoes reductive elimination to form a C--H bond. The resulting geometrically stable Z enamines are useful building blocks for stereoselective synthesis. 相似文献
95.
V. L. Ivanov R. R. Akhmetshin A. N. Amirkhanov A. V. Anisenkov V. M. Aulchenko V. S. Banzarov N. S. Bashtovoy D. E. Berkaev A. V. Bragin S. I. Eidelman D. A. Epifanov L. B. Epshteyn A. L. Erofeev G. V. Fedotovich S. E. Gayazov A. A. Grebenuk D. N. Grigoriev E. M. Gromov F. V. Ignatov S. V. Karpov V. F. Kazanin B. I. Khazin I. A. Koop O. A. Kovalenko A. N. Kozyrev E. A. Kozyrev P. P. Krokovny A. E. Kuzmenko A. S. Kuzmin I. B. Logashenko P. A. Lukin K. Yu. Mikhailov V. S. Okhapkin Yu. N. Pestov E. A. Perevedentsev A. S. Popov G. P. Razuvaev Yu. A. Rogovsky A. L. Romanov A. A. Ruban N. M. Ryskulov A. E. Ryzhenenkov V. E. Shebalin D. N. Shemyakin B. A. Shwartz D. B. Shwartz A. L. Sibidanov Yu. M. Shatunov P. Yu. Shatunov E. P. Solodov V. M. Titov A. A. Talyshev A. I. Vorobiov Yu. V. Yudin 《Physics of Atomic Nuclei》2016,79(2):251-259
We report preliminary results on the cross section of the process e+e? → φ(1020)η measured at 30 center-of-mass energy points in the range from 1.59 up to 2.0 GeV. Data analysis is based on the integrated luminosity of 22 pb?1 collected with the CMD-3 detector in 2011–2012. The obtained cross section agrees with the BaBar measurement and has better statistical accuracy. 相似文献
96.
97.
O. Yu. Golubeva V. E. Yudin A. L. Didenko V. M. Svetlichnyi V. V. Gusarov 《Russian Journal of Applied Chemistry》2007,80(1):106-109
Nanocomposites based on a thermoplastic polyimide, poly{1,3-bis(3′,4-dicarboxyphenoxy)benzene[4,4′-bis(4″-N-phenoxy)diphenyl sulfone]imide}, and synthetic magnesium silicate nanoparticles with montmorillonite structure were prepared from melts. Efficient modification of the surface of the initial nanoparticles with (aminoethylaminomethyl)phenethyltrimethoxysilane was performed. 相似文献
98.
Synthetic organic chemists have long depended on protecting group manipulations when faced with the challenges of chemoselectivity and functional group incompatibility. Overcoming this dependence will improve the overall efficiency of chemical synthesis. By taking advantage of orthogonally reactive functional groups, amphoteric molecules can afford access not only to more efficient and strategic syntheses but also to the development of novel chemical transformations. 相似文献
99.
A ferroelectric phase transition is observed in Langmuir-Blodgett films prepared from substituted copper phthalocyanine molecules.
The linear and nonlinear dielectric properties of the films and the switching of their spontaneous polarization are investigated
in the temperature range of the phase transition. The observed features can be explained by the Landau-Ginzburg model of a
first-order phase transition.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 9, 625–631 (10 November 1999) 相似文献
100.
O. N. Prudnikov A. V. Taichenachev V. I. Yudin E. M. Rasel 《Bulletin of the Russian Academy of Sciences: Physics》2017,81(12):1420-1428
The possible deep laser cooling of 24Mg atoms in a deep optical lattice in the presence of an additional pumping field resonant to the narrow 3s3s1S0 → 3s3p3P1 (λ = 457 nm) optical transition is studied. Two quantum models of the laser cooling of atoms in the optical trap are compared. One is based on the direct numerical solution to the kinetic quantum equation for an atomic density matrix; it considers both optical pumping and quantum recoil effects during interaction between the atoms and field photons. The second, simplified model is based on decomposing the states of the atoms over the levels of vibration in the optical trap and analyzing the evolution of these states. The comparison allows derivation of optical field parameters (pumping field intensity and detuning) that ensure cooling of the atoms to minimal energies. The conditions for fast laser cooling in an optical trap are found. 相似文献