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71.
72.
Vadim A. Babkin Gheorghe Cata-Danil Viacheslav M. Golovatyuk Aleksandr G. Molokanov Mihaela M. Paraipan Gennady N. Timoshenko 《Central European Journal of Physics》2010,8(4):683-688
A ridge carbon beam filter for Spreading Out the Bragg Peak (SOBP) up to 20 mm in the targeted area has been designed and experimentally tested. The instrument was constructed of Plexiglas with a density of 1.165 g/cm3 and has a “teeth” structure with a period of 2.5 mm. The design is based on a simple analytical model and detailed GEANT4 Monte Carlo simulations. In-beam test measurements were performed with a 500-MeV/u 12C beam at the Nuclotron facility of the Joint Institute for Nuclear Research (JINR) in Dubna. The filter can be used as a static device positioned in front of patients undergoing carbon therapy. 相似文献
73.
It was demonstrated that the outcome of the reaction of hexafluoropropene, sulfur and vinyl ether strongly depends on the catalyst and reaction conditions. The reaction of HFP and Sx leading to the formation of 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietane (1) when it is catalyzed by CsF, proceeds under milder conditions and is easier to control compared to KF catalyzed process. The order of addition of reagents plays a crucial role on the outcome of the reaction. For example, the addition of vinyl ether to pregenerated solution of 1 in DMF solvent results in slow reaction, leading to the corresponding 2,2-bis(trifluoromethyl)-4-R-thietanes in 8-91% yield, and it is catalyzed by either by KF or CsF. The addition of second mole of sulfur to the solution of 2,2-bis(trifluoromethyl)-4-R-thietanes in the presence MF catalyst leads to insertion of sulfur into thietane ring with the formation of the corresponding cyclic disulfides—3,3-bis(trifluoromethyl)-5-R-1,2-dithietanes. On the other hand, the addition of second mole of sulfur to the solution of 1 in DMF in the presence of CsF catalyst, followed by addition of vinyl ether results in exothermic reaction, and it produces the corresponding 2,2-bis(trifluoromethyl)-4-alkoxy-1,3-dithiolanes in good yield.It was also demonstrated that 2,2-bis(trifluoromethyl)-4-R-thietanes can undergo disproportionation under action of fluoride anion, producing a mixture of the corresponding 1,2-dithiolane and CF2C(CF3)CH2CFHOR. The nucleophilic attack of fluoride anion in this case proceeds selectively on the carbon of the thietane ring, bearing alkoxy group.The structure of 2,2-bis(trifluoromethyl)-4-R-thietanes forming as the result of 2 + 2 cycloaddition reaction between hexafluorothioacetone generated “in situ” from dimer 1 and vinyl ether was firmly supported by single crystal X-ray diffraction data, obtained for thietane bearing t-BuO-group. 相似文献
74.
Z. A. Khushbaktova M. A. Agzamova V. N. Syrov N. V. Radchenko N. M. Mirsalikhova F. T. Umarova 《Chemistry of Natural Compounds》1994,30(4):469-473
An evaluation has been mde of the cardiotonic activities of cycloartane methylsteroids isolated from plants of the genusAstragalus and their synthetic analogs. It has been established that the compounds investigated exhibit a positive inotropic effect
expressed to different degrees. The mechanism of the realization of the positive inotropic action of cycloartane glycosides
differs from that of cardiosteroid drugs.
Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89
14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 510–514, July–August, 1994. 相似文献
75.
G. G. Sheina E. D. Radchenko S. A. Egupov Yu. P. Blagoy V. M. Orlov 《International journal of quantum chemistry》1979,16(2):387-394
The regularities of the donor-acceptor interaction of nucleic acid bases and some of their derivatives with the strong acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ) in thin amorphous films at 77 K were studied using UV and visible spectroscopy. Purine and pyrimidine bases are shown to form charge transfer TCNQ complexes whose band energies hνct = Ip ? EA ? (H* ? H0) are linearly dependent of the donor ionization potential Ip. Calculated differences between the interaction energies of uncharged molecules and ion radicals, ΔE ≈ 3.0 eV, are in good agreement with experimental variations of the complex dissociation energies in the ground and excited states, (H* ? H0) = 2.73 eV. Annealing of the films of complexes containing cytosine, 1-methylcytosine, uracil, and caffeine leads to ordering of their structure and the formation of ion radical salts. 相似文献
76.
Viacheslav A. Petrov 《Journal of fluorine chemistry》2004,125(4):531-536
It was demonstrated that the reaction of 2,2-bis(trifluoromethyl)oxirane (1) with variety of alcohols could be successfully carried out under phase transfer catalysis conditions using sodium or potassium hydroxide as a base. For example, reaction of CH3OH, C2H5OCH2CH2OH, HOCH2CH2OH with one or two moles of 1 in the presence of the catalyst [(C4H9)4N+HSO4−] gives the corresponding tertiary alcohols R[OCH2C(CF3)2OH]n (n=1 or 2) in 43-53% yield, along with some O[CH2C(CF3)2OH]2. Benzyl alcohol and phenol under similar conditions are less active, producing in the reaction with 1 the corresponding adducts ArOCH2C(CF3)2OH in 31-35% yield. Fluorinated alcohols, such as CF3CH2OH, ClCF2CH2OH, HCF2CF2CH2OH have much higher reactivity towards 1 giving ring opening products in 82-97% yield. Even in the reaction of hindered hexafluoro-iso-propanol the corresponding adduct was isolated in 43% yield. Surprisingly, the reaction of iso-propanol and epoxide 1, results in the formation of O[CH2C(CF3)2OH]2 as a major product, isolated in 56% yield. Possible mechanism for the formation of the last product was proposed. 相似文献
77.
V. I. Radchenko 《Journal of Experimental and Theoretical Physics》2000,91(4):682-690
A closed variant of the Born approximation for calculating differential scattering cross sections in ion-atom collisions is developed. An expression in terms of the matrix elements J ij with respect to the single-electron states of the atom is found for the matrix element describing the target atom in the formula for the differential cross section. The matrix elements J ij are averaged over the relative orientation of the momentum transferred in the collision and the symmetry axis of the electronic orbitals of the target atom, using the single-electron Rutaan-Hartree-Fock wave functions. The algebraic representation of the matrix elements J ij makes it possible to perform calculations for atoms with any value of Z. The model developed is used to calculate the cross sections σΣ and characteristic scattering angles θc for the process of electron loss by H? ions with energy E = 0.1–100 MeV in targets consisting of atoms with Z = 2–54. It is shown that σΣ ∝ E ?1 and θc ∝ E ?1/2 for all Z, and for fixed E the behavior of σΣ(Z) and θc(Z) is determined by the order of filling of the electronic shells of the target atoms (the ionization potential). The computational results are analyzed and compared with the experimental data and the results of other calculations. 相似文献
78.
The results of experimental measurement of spatial-angular distributions of hydrogen particles (H−, H0, H+) obtained in scattering of a collimated ribbon beam of H− ions and H0(1s) atoms in He, Ar, Kr, Xe, H2, O2, and CO2 gas targets for certain values of energy in the range from 0.6 to 15 MeV are reported. The experimental setup and the measurement
procedure with an angular resolution of 5×10−6 rad are described. The angular characteristics of measured distributions, i.e., full width at half maximum and standard deviation,
were determined. It is shown that the shape of distribution for a beam of hydrogen atoms produced by neutralization of H− ions in a gas target varies with the type and thickness of the target, and the angular spread is smallest for the H2 target. The variations in the shape of distribution are due to the contribution of scattering processes without changing
the charge of particles. 相似文献
79.
S. P. Kulik G. A. Maslennikov S. P. Merkulova A. N. Penin L. K. Radchenko V. N. Krasheninnikov 《Journal of Experimental and Theoretical Physics》2004,98(1):31-38
Experiments on two-photon interference are discussed in the case when there is absorption of all the modes participating in the process of spontaneous parametric down-conversion (SPDC) of light. The objects of investigation are 10-to 80-Å-thick ultrathin gold films deposited on fused-silica substrates. Conditions are determined under which the effect of absorption of the signal and pump waves on the interference pattern is small. It is shown that, under these conditions, the visibility of the interference pattern and the shape of the frequency-angular spectrum at the signal frequency are determined by the optical parameters of the medium at the idler frequency, which belongs to the near-infrared region. 相似文献
80.
Lyakhova E. G. Fedorov S. N. Shubina L. K. Radchenko O. S. Kalinovsky A. I. Dvitrenok P. S. Stonik V. A. 《Russian Chemical Bulletin》2003,52(4):1022-1026
The structures of products obtained by reductive debromination and CF3COOH- and KOH-induced transformations of natural chamigrane-type sesquiterpenoid (6S,10R)-10-bromo-3,11,11-trimethyl-7-methylidenespiro[5,5]undec-2-en-4-one (dactylone) isolated from the sea hare Aplysia dactylomela were analyzed. The absolute configurations of the reaction products were established by CD spectra taking into account the configuration of the starting dactylone. 相似文献