http://www.physmathcentral.com/pmcphysb/ The latest research articles published by PMC Physics B 2009-12-18T00:00:00Z This is an RSS newsfeed from BioMed Central It is intended to be used with an RSS reader. For more information about RSS newsfeeds from BioMed Central, visit http://www.biomedcentral.com/info/about/rss/ Absolute angle-differential cross-section data are presented for excitation of the 3p54s manifold in argon by electron impact. The investigation focuses on the near-threshold region, where previous studies have revealed persistent disparities between measurements and theoretical predictions. For the present experiment, the time-of-flight (TOF) technique is employed. This method allows for scattered electrons to be measured over a broad range of energies with a constant transmission, thereby eliminating a potential major source of error in relating relative intensities of elastic and inelastic transitions inherent to other experimental techniques. The present experimental data are compared to theoretical results obtained in relativistic distorted-wave and various R-matrix (close-coupling) approaches, as well as to other recently published experimental data.PACS Codes: 34.80.Dp http://www.physmathcentral.com/1754-0429/2/3 Subhendu Mondal Julian Lower Stephen Buckman Robert McEachran Gustavo Garcia Oleg Zatsarinny Klaus Bartschat PMC Physics B 2009, 2:3 2009-12-18T00:00:00Z doi:10.1186/1754-0429-2-3 PMC Physics B 1754-0429 2 3 2009-12-18T00:00:00Z XML A comparative study of two earlier three-state and fifteen-state [Chaudhuri et al., Pramana- J. Phys., 43, 175 (1994); ibid., Phys. Rev. A, 52, 1137 (1995)] close-coupled treatments of He2+-He single and double charge transfer collisions is made in this paper with a larger, 27-state close-coupled calculation. The calculations have been done using the diabatic molecular basis set used in the earlier work extended by adding excited orbitals leading to higher excitation channels up to 3s and 3p. For such molecular basis functions that go to the correct separated-atom limits used in this work, the present results show that without the inclusion of the electron translation factors (ETFs) the quantitative cross-section calculations up to velocity ~1.1 a.u. (~30 keV/amu) are in good agreement with both experiment and other calculations. This suggests that if ETFs are properly incorporated into the charge transfer collision studies at low energies this diabatic molecular basis can be used for benchmark calculations. With the aid of the Wannier's picture of the ground state correlations, a combined detailed analysis and comparison has been carried out to find a connection with the dynamic two-electron correlation picture in charge transfer collision processes which involve sequential/simultaneous two-electron exchange. If ETFs are included, the model approach of the present work may open up opportunities to investigate dynamic two-electron correlation effect in charge transfer ion-atom collision processes with benchmark accuracy.PACS codes: 34.70.+e, 34.20.-b http://www.physmathcentral.com/1754-0429/2/2 Chanchal Chaudhuri PMC Physics B 2009, 2:2 2009-06-09T00:00:00Z doi:10.1186/1754-0429-2-2 PMC Physics B 1754-0429 2 2 2009-06-09T00:00:00Z XML Recent measurements of the cross sections for electronic state excitations in H2O have made it possible to calculate rates applicable to these excitation processes. We thus present here calculations of electron energy transfer rates for electronic and vibrational state excitations in H2O, as well as rates for excitation of some of these states by atmospheric thermal and auroral secondary electrons. The calculation of these latter rates is an important first step towards our aim of including water into a statistical equilibrium model of the atmosphere under auroral conditions.PACS Codes: 34.50.Gb 34.50.Ez http://www.physmathcentral.com/1754-0429/2/1 Penny Thorn Laurence Campbell Michael Brunger PMC Physics B 2009, 2:1 2009-01-02T00:00:00Z doi:10.1186/1754-0429-2-1 PMC Physics B 1754-0429 2 1 2009-01-02T00:00:00Z XML The compound Cr1.4Fe0.6O3 has been synthesized through mechanical alloying of Cr2O3 and α-Fe2O3 powders and subsequent thermal annealing. The XRD spectrum, SEM picture and microanalysis of EDAX spectrum have been used to understand the structural evolution during alloy formation. The alloyed samples have been matched to rhombohedral structure with R3C space group. The observation of a modulated magnetic order confirmed the systematic diffusion of Fe atoms into the Cr sites of lattice structure. A field induced magnetic behaviour has been noted in the field dependence of magnetization data of the annealed samples. This feature is significantly different from that of the mechanical alloyed samples. The experimental results also provided the indications of considering the present material as a potential candidate for opto-electronic applications.PACS Codes: 75.30.-m, 75.20.En, 81.40.Rs http://www.physmathcentral.com/1754-0429/1/20 R n Bhowmik Nrisimha Murty Sekhar Srinadhu PMC Physics B 2008, 1:20 2008-12-29T00:00:00Z doi:10.1186/1754-0429-1-20 PMC Physics B 1754-0429 1 20 2008-12-29T00:00:00Z XML The symmetry of the superconductivity in Bechgaard salts is still unknown, though the triplet pairing has been established by Hc2 and NMR for (TMTSF)2PF6. The large upper critical field at T = 0K (Hc2 ~ 5 Tesla) both for H→||a→ MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaiqbdIeaizaalaGaeiiFaWNaeiiFaWNafmyyaeMbaSaaaaa@307F@ and H→||b→′ MathType@MTEF@5@5@+=feaagaart1ev2aaatCvAUfKttLearuWrP9MDH5MBPbIqV92AaeXatLxBI9gBaebbnrfifHhDYfgasaacH8bkY=wiFfYlOipiY=Hhbbf9v8qqaqFr0xc9vqpe0di9q8qqpG0dHiVcFbIOFHK8Feei0lXdar=Jb9qqFfeaYRXxe9vr0=vr0=LqpWqaaeaabiGaciaacaqabeaabeqacmaaaOqaaiqbdIeaizaalaGaeiiFaWNaeiiFaWNafmOyaiMbaSGbauaaaaa@308C@ also indicates strongly the triplet pairing.Here we start with a low energy effective Hamiltonian and study the temperature dependence of the corresponding Hc2(T)'s.The present analysis suggests that one chiral f-wave superconductor should be the most likely candidate near the upper critical field.PACS Codes: 74.70.Kn ; 74.20.Rp; 74.25.Op. http://www.physmathcentral.com/1754-0429/1/19 Ana Folgueras Kazumi Maki PMC Physics B 2008, 1:19 2008-12-09T00:00:00Z doi:10.1186/1754-0429-1-19 PMC Physics B 1754-0429 1 19 2008-12-09T00:00:00Z XML The Schlegel-Frisch ab initio molecular dynamics (ADMP) (DFT:B3LYP), T = 310 K, is used to study complexation between adenosinetriphosphate (ATP), ATP subsystem, and magnesium cofactor [Mg(H2O)6]2+, Mg subsystem, in a water pool, modeled with 78 water molecules, in singlet (S) and triplet (T) states. The computations prove that the way of ATP cleavage is governed by the electron spin of Mg. In the S state Mg prefers chelation of γ-β-phosphate oxygens (O1-O2), whereas in the T state it chelates β-α-phosphate oxygens (O2-O3) or produces a single-bonded intermediate. Unlike the chelates, which initiate ionic reaction paths, the single-bonded intermediate starts off a free-radical path of ATP cleavage, yielding a highly reactive adenosinemonophosphate ion-radical, •AMP-, earlier observed in the CIDNP (Chemically Induced Dynamic Nuclear Polarization) experiment (A.A. Tulub, 2006). The free-radical path is highly sensitive to Mg nuclear spin, which through a hyperfine interaction favors the production of unpaired electron spins. The unique role of Mg in ATP cleavage comes through its ability to serve as a unique redox center, initially accepting an electron from ATP and then giving it back to products. Redox activity of Mg differs for T and S states and affects the number of coordinated water molecules. The findings give a new insight into the NTP (N = nucleoside) energetics and assembly of NTP-operating molecules, including proteins.PACS codes: 87.15.-v http://www.physmathcentral.com/1754-0429/1/18 Alexander Tulub PMC Physics B 2008, 1:18 2008-12-04T00:00:00Z doi:10.1186/1754-0429-1-18 PMC Physics B 1754-0429 1 18 2008-12-04T00:00:00Z XML Effect of biased noise fluctuations on the degree of squeezing as well as the intensity of a radiation generated by a one-photon coherent beat laser is presented. It turns out that the radiation exhibits squeezing inside and outside the cavity under certain conditions. The degree of squeezing is enhanced by the biased noise input significantly in both regions. Despite the presence of the biased environment modes outside the cavity, the degree of squeezing outside the cavity can be greater than or equal to or even less than the cavity radiation depending on the initial preparation of the atomic superposition and amplitude of the external driving radiation. But the intensity of the radiation is found to be lesser outside the cavity regardless of these parameters.PACS Codes: 42.50.Dv, 42.50.Ar, 42.50.Gy, 32.80.Bx http://www.physmathcentral.com/1754-0429/1/17 Sintayehu Tesfa PMC Physics B 2008, 1:17 2008-12-01T00:00:00Z doi:10.1186/1754-0429-1-17 PMC Physics B 1754-0429 1 17 2008-12-01T00:00:00Z XML Evolution of structure of spherical SiO2 nanoparticles upon cooling from the melt has been investigated via molecular-dynamics (MD) simulations under non-periodic boundary conditions (NPBC). We use the pair interatomic potentials which have weak Coulomb interaction and Morse type short-range interaction. The change in structure of SiO2 nanoparticles upon cooling process has been studied through the partial radial distribution functions (PRDFs), coordination number and bond-angle distributions at different temperatures. The core and surface structures of nanoparticles have been studied in details. Our results show significant temperature dependence of structure of nanoparticles. Moreover, temperature dependence of concentration of structural defects in nanoparticles upon cooling from the melt toward glassy state has been found and discussed.PACS Codes: 61.43.Bn; 78.55.Qr; 78.67.Bf http://www.physmathcentral.com/content/1/1/16 Huynh Nguyen Hoang Vo Zung Hoang PMC Physics B 2008, 1:16 2008-10-30T00:00:00Z doi:10.1186/1754-0429-1-16 PMC Physics B 1754-0429 1 16 2008-10-30T00:00:00Z XML Formation of complex polyaniline (PANI) films with diamagnetic TCNQ and paramagnetic metal ion impurities cast under applied magnetic field was studied. It has been found that the applied magnetic field affects interaction of PANI chains with the impurities and induces formation of magnetically ordered regions in the complex film doped by paramagnetic metal ions in contrast to the reference film of the same composition but prepared under ambient conditions. The magnetically ordered regions have been observed directly by scanning magnetic force microscopy. It was found a correlation in distribution of the magnetically ordered regions and peculiarities of the surface relief of a film. Electronic absorption spectra and conductivity measurements showed that an applied stationary magnetic field can suppress the interaction of PANI chains and paramagnetic metal ions and lowers conductivity of the resulting complex film up to one order of magnitude as compared with the reference film. An alternating magnetic field was found to improve interaction of PANI and diamagnetic TCNQ molecules. The mechanisms of the magnetic field influence on the complex film formation are discussed.PACS: 75.70.-i; 72.80. Le; 78.40. Me http://www.physmathcentral.com/1754-0429/1/15 Oleg Dimitriev Petro Lytvyn Alla Dimitriyeva Ostap Getsko PMC Physics B 2008, 1:15 2008-10-21T00:00:00Z doi:10.1186/1754-0429-1-15 PMC Physics B 1754-0429 1 15 2008-10-21T00:00:00Z XML We investigate the effect of a microwave field on a confined two dimensional electron gas which contains an insulating region comparable to the Fermi wavelength. The insulating region causes the electron wave function to vanish in that region. We describe the insulating region as a static vortex. The vortex carries a flux which is determined by vanishing of the charge density of the electronic fluid due to the insulating region. The sign of the vorticity for a hole is opposite to the vorticity for adding additional electrons. The vorticity gives rise to non-commuting kinetic momenta. The two dimensional electron gas is described as fluid with a density which obeys the Fermi-Dirac statistics. The presence of the confinement potential gives rise to vanishing kinetic momenta in the vicinity of the classical turning points. As a result, the Cartesian coordinate do not commute and gives rise to a Hall current which in the presence of a modified Fermi-Surface caused by the microwave field results in a rectified voltage. Using a Bosonized formulation of the two dimensional gas in the presence of insulating regions allows us to compute the rectified current. The proposed theory may explain the experimental results recently reported by J. Zhang et al.PACS numbers: 71.10.PM http://www.physmathcentral.com/1754-0429/1/14 D. Schmeltzer Hsuanyeh Chang PMC Physics B 2008, 1:14 2008-10-21T00:00:00Z doi:10.1186/1754-0429-1-14 PMC Physics B 1754-0429 1 14 2008-10-21T00:00:00Z XML