共查询到20条相似文献,搜索用时 15 毫秒
1.
An efficient synthesis of alkyl 5-(dialkoxy- phosphoryl)-1,3-dimethyl-2, 6-dioxo-hexahydropyrimidine-4-carboxylates is described.
This involves the reaction of N,N′-dimethylurea and dialkyl acetylendicarboxylates in the presence of trialkyl phosphites. Under similar conditions, triphenyl
phosphite led to alkyl 5-(diphenoxyphosphoryl)-1,3-dimethyl-2,6-dioxo-hexahydro-4-pyrimidinecarboxylates. 相似文献
2.
V. Ya. Kirpichenkov N. V. Kirpichenkova O. I. Lozin A. A. Postnikov 《Bulletin of the Russian Academy of Sciences: Physics》2016,80(11):1326-1328
Formulas are obtained for the current–voltage characteristics and conductance of a quasi-one-dimensional N–I–N junction (where N is an ordinary metal and I is an insulator) with quantum resonance percolation trajectories (QRPTs) in a disordered I-layer at temperatures T > 0 K and the energy of local single-impurity electron level being equal to the Fermi energy ε0 = εF. Under these conditions, the impact QRPTs have on the current through the junctions weakens as the temperature grows, and the conductance drops; this is in contrast to the rise in conductance of an empty junction (with no impurities in the I-layer). 相似文献
3.
The process γ*γ → σ is investigated in the framework of the SU(2)×SU(2) chiral NJL model. The form factor of the process is derived for arbitrary virtuality of γ* in the Euclidean kinematic domain. The asymptotic behavior of this form factor resembles the asymptotic behavior of the γ*γ → π form factor. 相似文献
4.
One of the most remarkable features of black hole is the connection between properties of the classical solutions and thermodynamics.
We include the electric and magnetic charges and this lead us to resolve Einstein equations. We obtain thermodynamic properties,
such as temperature, entropy density and speed of sound with analytical solution. In that case we characterize equation of
state in to V(φ) language. 相似文献
5.
Xiang Liu Zheng-Tao Wei Xue-Qian Li 《The European Physical Journal C - Particles and Fields》2009,59(3):683-689
To test the validity of perturbative QCD (pQCD) and investigate its range of application, one should look for a suitable process.
B→J/ψ
D is a promising candidate. The linear momentum of the products is relatively small, so that there may exist a region where
exchanged gluons are soft and the perturbative treatment may fail, so that the non-perturbative effect would be significant.
We attribute such non-perturbative QCD effects to the long-distance final-state interaction (FSI) which is estimated in this
work. We find that the contribution from the FSI to the branching ratio is indeed sizable and may span the rather wide range
of 10−6∼10−5 and cover a region where the pQCD prediction is of the same order. A more accurate measurement of its branching ratio may
provide important information about the application region of pQCD and help to clarify the picture of inelastic rescattering
(i.e. FSI), which is generally believed to play an important role in B decays. 相似文献
6.
We establish some general theorems for the existence and nonexistence of ground state solutions of steady-state N coupled nonlinear Schrödinger equations. The sign of coupling constants β ij ’s is crucial for the existence of ground state solutions. When all β ij ’s are positive and the matrix Σ is positively definite, there exists a ground state solution which is radially symmetric. However, if all β ij ’s are negative, or one of β ij ’s is negative and the matrix Σ is positively definite, there is no ground state solution. Furthermore, we find a bound state solution which is non-radially symmetric when N=3. 相似文献
7.
The rare decay \(B\rightarrow {K^{*}}\ell ^+\ell ^-\) is a very significant mode to search for physics beyond the Standard Model (SM). The mode provides a very rich spectrum of observables obtained from the angular distribution of its decay products. The recent LHCb measured values of these observables are used to conclude an evidence of right-handed currents at the kinematic endpoint of this decay mode. As the conclusion is drawn at the maximum dilepton invariant mass square (\(q^2\)) kinematic endpoint, it relies only on heavy quark symmetries where it is valid without significant corrections. 相似文献
8.
Bastian Kubis Sebastian P. Schneider 《The European Physical Journal C - Particles and Fields》2009,62(3):511-523
Strong final-state interactions create a pronounced cusp in η′→η
π
0
π
0 decays. We adapt and generalize the non-relativistic effective field theory framework developed for the extraction of π
π scattering lengths from K→3π decays to this case. The cusp effect is predicted to have an effect of more than 8% on the decay spectrum below the π
+
π
− threshold. 相似文献
9.
Absorption and fluorescence emission properties of an N-salicylideneamine fluorescent dye molecule N, N-bis(2-hydroxy-5-methylbenzylidene)-1,2-ethanediamine (1) have been studied in three typical solvents—2-methylbutane, ethanol, dimethyl sulphoxide (DMSO), and its DNA complex in methanol/H2O mixed solvent. The normal absorption band of 1 is observed in both aprotic and protic solvents and has been assigned to the l a transition in the enol form of 1. The long-wavelength absorption band of 1, which is caused by the formation of a cis-keto species in the ground state, is absent in aprotic solvents, but is observable in protic ones. Normal fluorescence emission from the excited enol state of 1 is obtained only when the normal absorption band is excited, while the excited-state intramolecular proton transfer (ESIPT) emissions from both cis- and trans-keto species are recorded in all cases, being acceptable for the variation of the relative emission intensities. A preliminary spectroscopic study of the 1–DNA complex indicates an intercalation-binding mode, the convincing supporting evidence being the enhanced ESIPT fluorescence intensity of 1 when complexed with DNA. Finally, a universal energy-state diagram is given to interpret the experimental results. 相似文献
10.
F. Toppan 《Physics of Atomic Nuclei》2010,73(3):541-545
We discuss the minimal representations of the 1D N-Extended Supersymmetry algebra (the Z
2-graded symmetry algebra of the Supersymmetric Quantum Mechanics) linearly realized on a finite number of fields depending
on a real parameter t, the time. Their knowledge allows to construct onedimensional sigma-models with extended off-shell supersymmetries without
using superfields. 相似文献
11.
We have studied the important astrophysical S-factor for 36 known p-nuclei with (p, γ) reactions at low energy in the mass region A\(\approx \) 74–196. This is done by folding the density-dependent M3Y (DDM3Y) interaction with spherical relativistic mean field (RMF) densities. The densities are obtained from different parameter sets such as G1, G2, NL1, NL2, NL3*, NL-SH, DD-ME1, DD-ME2 and DD-PC1. The independence of the S-factor on different densities is discussed and compared with experimental data and with NON-SMOKER calculations whenever available. 相似文献
12.
13.
R. Wolsky I. A. Gnilozub S. D. Kurgalin Yu. M. Tchuvil’sky 《Physics of Atomic Nuclei》2010,73(8):1405-1415
States that exhibit the properties of an α-cluster or an α-binucleon condensate are studied in 1p-shell nuclei. The generalized Hamiltonian of the Elliott SU(3) model is used to classify these states and to calculate their spectra. The results of the calculations are found to be
in good agreement with experimental data. States not observed so far in the cluster spectra of the 12C, 16O, 10Be, and 12Be nuclei are predicted. 相似文献
14.
15.
K. Saaidi S. W. Rabiei A. Aghamohammadi 《International Journal of Theoretical Physics》2011,50(8):2514-2519
We study spherically symmetric static empty space solutions in R+ε/R model of f(R) gravity. We show that the Schwarzschild metric is an exact solution of the resulted field equations and consequently there
are general solutions which are perturbed Schwarzschild metric and viable for solar system. Our results for large scale contains
a logarithmic term with a coefficient producing a repulsive gravity force which is in agreement with the positive acceleration
of the universe. 相似文献
16.
D. O. Kotov 《Physics of Atomic Nuclei》2011,74(5):794-798
Light hadrons provide a convenient tool for studying the properties of hot and dense media formed in central collisions of
relativistic heavy nuclei. The results obtained in the PHENIX experiment at the relativistic heavy-ion collider (RHIC, Brookhaven
National Laboratory, USA) by measuring nuclearmodification factors for light hadrons in various colliding systems (pp, dAu, CuCu, and AuAu) at the c.m. energies of √s
NN
= 62.4 and 200 GeV are presented. 相似文献
17.
A. Sissakian O. Shevchenko A. Nagaytsev O. Ivanov 《The European Physical Journal C - Particles and Fields》2009,59(3):659-673
We estimate the single-spin asymmetries (SSA) which provide the access to transversity as well as to Boer–Mulders and Sivers
PDFs via investigation of the single-polarized Drell–Yan (DY) processes with pp, pD and DD collisions available to RHIC, NICA, COMPASS, and J-PARC. The feasibility of these SSA is studied with the new generator of
polarized DY events. The estimations performed demonstrate that there exist kinematical regions where SSA are presumably measurable.
Most useful for PDFs extraction are the limiting kinematical ranges, where one can neglect the sea PDFs contributions which
occur at large values of the Bjorken variable x. It is of interest that, contrary to the Sivers PDF, the transversity PDF is presumably accessible only in a particular kinematical
region. Contrary to the option with the symmetric collider mode (RHIC, NICA), this is of importance for the COMPASS experiment
and the future J-PARC facility, where the fixed-target mode is available. 相似文献
18.
We study the effect of Z′-mediated flavor-changing neutral current on the B → ππ decays. The branching ratios of these decays can be enhanced remarkably in the nonuniversal Z′ model. Our estimated branching ratios B(B 0 → π 0 π 0) are enhanced significantly from their standard model (SM) value. For g′/g = 1, the branching ratios B(B 0 → π 0 π 0) are very close to the recently observed experimental values and for higher values of g′/g branching ratios are more. Our calculated branching ratios B(B 0 → π + π ?) and B(B + → π + π 0) are also enhanced from the SM value as well as the recently observed experimental values. These enhancements of branching ratios from their SM value give the possibility of new physics. 相似文献
19.