The quantum mechanical two-Coulomb-centre problem in the Dirac equation framework in 2+1 dimensions

With the help of perturbation theory the asymptotic expansions (at small and large internuclear distances R) of the eigenvalues (potential curves) E(R) of the two-Coulomb-centre problem in 2+1 dimensions are obtained. We compare the results obtained with the data from similar approximation for two-Coulomb-centre problem in 3+1 dimensions.     

Characterization of minerals in natural and manufactured sand in Cauvery River belt,Tamilnadu, India

The present study investigates the characterization of minerals in the River Sand (R – Sand) and the Manufactured sand (M-Sand) through FTIR spectroscopic studies. The R – Sand is collected from seven different locations in Cauvery River and M – Sand is collected from eight different manufactures around the Cauvery River belt in Salem, Erode, Tirupur and Namakkal districts of Tamilnadu, India. To extend the effectiveness of the analysis, the samples were subjected to grain size separation to classify the bulk samples into different grain sizes. All the samples were analyzed using FTIR spectrometer. The number of minerals identified with the help of FTIR spectra in overall (bulk) samples of R – Sand is 14 and of M – Sand is 13. The number has been increased while going for grain size separation, i.e., from 14 to 31 for R – Sand and from 13 to 20 for M – Sand. Among all minerals, quartz plays a major role. The relative distribution and the crystallinity nature of quartz have been discussed based on the extinction co-efficient and the crystallinity index values computed. There is no major variation found in M – Sand while going for grain size separation.     

T1rho Dispersion profile of rat tissues in vitro at very low locking fields

The purpose of this study was to show the T(1rho) dispersion profile in various rat tissues (liver, brain, spleen, kidney, heart and skeletal muscle) at low (0.1 T) B(0) field at very low locking field B1, starting from 10 microT. The T(1rho) dispersion profile showed a quite similar pattern in all tissues. The highest R(1rho) relaxation rates were seen in the liver and muscle followed by the heart, whereas the values for spleen, kidney and brain were rather similar. The greatest difference between R2 relaxation rate and R(1rho) relaxation rate at B1=10 microT was seen in the liver and muscle. The steepest slope for a dispersion curve was seen in the muscle. The value of T(1rho) approximately approached the value of T2 when the locking field B1 approached 0. Except for the liver, the calculated apparent relaxation rate R2' was slightly larger than the calculated one. The potential value of T(1rho) imaging is to combine high R1 contrast of low-field imaging with the high signal-to-noise ratio (SNR) of high static field imaging. T(1rho) relaxation and dispersion data presented in the current study help to optimize the rotating-frame MR imaging.     

Scattering of a diatomic molecule by a stationary surface

The CCGM [N. Cabrera, V. Celli, F.O. Goodman and R. Manson, Surface Sci. 19 (1970) 67] theory of elastic scattering (diffraction) of atoms by surfaces is generalized to the case of scattering of diatomic molecules. No extensive applications of the theory are made, but an example considered by R.M. Logan [Mol. Phys. 17 (1969) 147] of the scattering of a low-energy beam of h₂ by a cold surface is re-examined in the context of the new theory. It is concluded that, because of the uncertainties in the form of the molecule-surface interaction potential and in the values of the interaction parameters, no quantitative reliance can be placed on calculations of molecule-surface scattering probabilities at the present time. Future comparisons with experimental data should help to reduce these uncertainties.     

Thermal Bias on the Pumped Spin-Current in a Single Quantum Dot

Temperature effect on the spin pump in a single quantum dot (QD) connected to Normal (NM) and/or Ferromagnetic (FM) leads is investigated with the help of master equation method. Results show that the magnitude and the direction of the temperature difference between the source (L) and drain (R) leads have great impact on the spin current processes. In practical devices, the thermal bias is quite general and then our results may be useful in quantum information processing and spintronics.     

Graphical method for determining the electrical parameters of epitaxial layers of n-type gallium arsenide and phosphide

The electrical parameters of epitaxial layers of n-type GaAs and GaP were determined by graphical analysis of the temperature dependence of the Hall coefficient with the help of the neutrality condition. The method is developed for application to both shallow and deep impurity levels.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 21–26, October, 1976.It is a genuine pleasure for the author to thank D. N. Nasledov and O. V. Emel'yanenko for interest and attention they have accorded this work, and R. K. Rad for supplying the gallium phosphide samples.     

Thermal Bias on the Pumped Spin-Current in a Single Quantum Dot

Temperature effect on the spin pump in a single quantum dot(QD) connected to Normal(NM) and/or Ferromagnetic(FM) leads is investigated with the help of master equation method. Results show that the magnitude and the direction of the temperature difference between the source(L) and drain(R) leads have great impact on the spin current processes. In practical devices, the thermal bias is quite general and then our results may be useful in quantum information processing and spintronics.     

Accurate measurement of one-bond H-X heteronuclear dipolar couplings in MAS solid-state NMR

The accurate experimental determination of dipolar-coupling constants for one-bond heteronuclear dipolar couplings in solids is a key for the quantification of the amplitudes of motional processes. Averaging of the dipolar coupling reports on motions on time scales up to the inverse of the coupling constant, in our case tens of microseconds. Combining dipolar-coupling derived order parameters that characterize the amplitudes of the motion with relaxation data leads to a more precise characterization of the dynamical parameters and helps to disentangle the amplitudes and the time scales of the motional processes, which impact relaxation rates in a highly correlated way. Here. we describe and characterize an improved experimental protocol--based on REDOR--to measure these couplings in perdeuterated proteins with a reduced sensitivity to experimental missettings. Because such effects are presently the dominant source of systematic errors in experimental dipolar-coupling measurements, these compensated experiments should help to significantly improve the precision of such data. A detailed comparison with other commonly used pulse sequences (T-MREV, phase-inverted CP, R18(2)(5), and R18(1)(7)) is provided.     

Drinfeld-Sokolov reduction on a simple lie algebra from the bihamiltonian point of view

We show that the Drinfeld-Sokolov reduction can be framed in the general theory of bihamiltonian manifolds, with the help of a specialized version of a reduction theorem for Poisson manifolds by Marsden and Ratiu.This work has been supported by the Italian MURST and by the GNFM of the Italian C.N.R.     

Nb-甲基四氢海曼和合成中间体的1H NMR及立体化学

本文提供了N_b-甲基四氢海曼和合成中间体,共十个化合物的¹H NMR谱。各谱线的归属依据它们的2D NMR的同核二维相关谱,COSY指定。根据NOE效应,指定了化合物的构型。借助分子模型,讨论了可能的构象。     

Meson cloud of the nucleon in polarized semi-inclusive deep-inelastic scattering

We investigate the possibility of identifying an explicit pionic component of the nucleon through measurements of polarized ⁺⁺ baryon fragments produced in deep-inelastic leptoproduction off polarized protons, which may help to identify the physical mechanism responsible for the breaking of the Gottfried sum rule. The pion-exchange model predicts highly correlated polarizations of the ⁺⁺ and target proton, in marked contrast with the competing diquark fragmentation process. Measurement of asymmetries in polarized production may also reveal the presence of a kaon cloud in the nucleon.Communicated by: W. Weise     

All-optical 2R-regeneration and continuous wave to pulsed signal wavelength conversion based on fiber nonlinearity

In this paper, we propose a novel all-optical 2R (re-amplification and re-shaping) regenerator based on inducing nonlinear chirp over a continuous wave probe. The regenerator also performs continuous wave to pulsed wavelength conversion. The chirp is induced in a highly nonlinear fiber by the data modulated pulsed signal that is to be regenerated. Offset filtering is employed at the output of the highly nonlinear fiber to extract the frequencies generated as a result of chirping. The regenerator performance has been evaluated with the help of bit-error-rate plots and eye diagrams at different values of optical signal to noise ratios. Apart from re-shaping and re-amplification, inclusion of the regenerator results in better resilience to amplified spontaneous emission noise.     

Rotational self correlation functions of N2O dissolved in liquid SF6

Careful study of the I.R. and Raman spectra of N₂O dissolved in inert solvents has shown that, for solutions in SF₆, purely rotational correlation functions can be unambiguously deduced. The comparison with theoretical models usually proposed to describe the rotational motions proved to be inadequate in that case. The reasons of this failure are analysed with the help of a molecular dynamics simulation of a system of 2 Lennard-Jones centres molecules, where the rotational correlation functions are found to be identical to the experimental ones.     

Optimization and Benefit Analysis of Grain Trade in Belt and Road Countries

Grain trade in Belt and Road (B&R) countries shows a mismatch between the volume and direction of grain flows and actual demand. With economic and industrial development, the water crisis has intensified, which poses a great challenge to the security of world grain supply and demand. There are few studies on the reconstruction of grain trade relations from the perspective of grain economic value. In this paper, a linear optimization model considering opportunity cost is proposed to fill the gap, and it is compared and analyzed with the optimization model considering only transportation cost. The grain supply and demand structures in both optimization results show characteristics of geographical proximity and long-tail distribution. Furthermore, the economic and water resource benefits resulting from the two optimal configurations are compared and analyzed. It is found that the economic benefits generated by grain trade in B&R countries with the consideration of opportunity cost not only cover transportation costs but also generate an economic value of about 130 trillion US dollars. Therefore, considering opportunity cost in grain trade is of great significance for strengthening cooperation and promoting the economic development of countries under the B&R framework. In terms of resource benefits, the grain trade with consideration of opportunity cost saves nearly 28 billion cubic meters of water, or about 5% of the total virtual water flow. However, about 72 billion cubic meters of water is lost for the grain trade with consideration of transportation cost. This study will help to formulate and adjust policies related to the “Belt and Road Initiative” (B&R Initiative), so as to maximize the economic benefits while optimizing the structure of grain trade and alleviating water scarcity pressures.     

Theoretical Study of Optically Pumped NH3 Far-Infrared Laser in Vibrational Ground State

In this paper, the density matrix equation of three-level system for far-infrared (FIR) Raman transition in vibrational ground state was solved. By means of iteration method and numerical calculation, the spectral characteristics of NH₃ molecules FIR laser with TEA CO₂-10R(14) laser pumping was studied theoretically. The theoretical result would help us to understand the physical mechanism of optically pumped molecular gases FIR laser with ground-state reversal transition.     

Stimulated emission by relativistic electrons in magnetic undulators

A quantum mechanical solution to the problem of stimulated emission in axial and flat magnetic undulators, including electron spin properties, is presented.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 12, pp. 45–49, December, 1985.In conclusion, the author considers it his pleasant duty to thank Professors I. M. Ternov and V. R. Khalilov for their help.     

Incoherent scattering cross-sections for elements with 23 ≤ Z ≤ 51 at 59.5 keV photon energy

With the help of a Ge(Li) detector, the incoherent scattering differential cross-sections by 59.54 keV γ-rays from the 10 elements in the atomic region 23 ≤ Z ≤ 51 were measured through angles from 30° to 140°. The background correction and detection efficiency are also included in this study. The present results constitute the first measurements for this combination of energy and angle. The present experimental results have been compared with those estimated on the basis of the nonrelativistic Hartree-Fock wave functions. The present results were in good agreement with those of [J.H. Hubbell, W.J. Veigele, E.A. Briggs, R.T. Brown, D.T. Cromer, R.J. Howerton, J. Phys. Chem. Ref. Data 4 (1975) 471].     

DFT and Monte Carlo study of the W(001) surface reconstruction

The driving force for the W(001) surface reconstruction and electronic structures of pristine and H-covered W(001) surfaces are studied by means of relativistic DFT calculations. The spin-orbit coupling leads to the splitting of the bands. Adsorbed physical monolayer of hydrogen due to forming adsorption bonds stabilizes the (1 × 1) structure of the H/W(001) surface. The performed calculations have not revealed any substantial nesting of Fermi surface, so do not support the Peierls-like charge-density-wave mechanism of the surface reconstruction. The total energy of the (√2 × √2)R45° W(001) surface structure is found to be lower, by 0.14 eV per atom, than for the (1 × 1 W(001). The dependence of the relative intensity of the characteristic LEED reflection on temperature, obtained with the help of Monte Carlo simulations using the interaction energies estimated from DFT calculations, is in good agreement with available experimental data, thus supporting the concept of the order-disorder type of the transition between the low-temperature ((√2 × √2)R45° and room-temperature (1 × 1) surface structures of W(001).     

Time-dependent transport coefficients: an effective macroscopic description of small scale dynamics?

Situations where particles taken from a thermal reservoir are immersed at some initial time in a fluid are considered. The diffusion model is the Ornstein–Uhlenbeck process. It is proven that particle transport in physical space can be described exactly at all times with the help of a time dependent diffusion coefficient; the result is, in particular, valid outside of the hydrodynamic regime. The use of time-dependent transport coefficients in other contexts in also discussed. To cite this article: F. Debbasch, J.-P. Rivet, C. R. Physique 9 (2008).     

胭脂红荧光光谱机理研究

胭脂红是食品添加剂中最常用的一种食用色素之一,国家标准对其在食品中添加的剂量有明确的规定,研究其荧光光谱特性具有一定的实际意义。文章分别从理论与实验上对220～400 nm不同激发波长下胭脂红标准溶液的荧光光谱进行了分析,结果表明,胭脂红可以产生较强的荧光,分别在420,530,635,687 nm波长处产生了4个荧光峰,各荧光峰的最佳激发波长也不尽相同,文章给出了相应的荧光光谱图。经研究认为胭脂红荧光是由—OH中的n电子的n→π*跃迁和奈环中的π电子的π→π*跃迁这两类跃迁而产生的,其中420 nm处的荧光峰是由n→π*跃迁产生的, 而530, 635和687 nm这3个波长处的荧光峰是由π→π*跃迁而产生的, 同时其4个波长处的荧光相对强度随激发波长的变化相对改变不同,文章分别从微观机理上给出了一定的解释。研究胭脂红的荧光光谱及其特性可为其他偶氮类色素的荧光光谱研究提供参考,同时能为食品安全检测提供新的方法与途径。