Temperature dependence of photoluminescence in amorphous Si1-xCx:H films

We have investigated the temperature dependence of photoluminescence in hydrogenated amorphous silicon-carbon alloys a-Si_1-xC_x:H prepared by glow discharge in the low-power regime. The radiative recombination process, due to photocarriers trapped on band-edge states, is in competition with the thermal escape of the photocarriers into the mobility bands. The model gives a quantitative fit with experiment, without any adjustable parameter, provided the width of the band-edge distribution of states is taken as the width of the conduction band only (measured by “photo-induced infra-red spectroscopy”) and not as the Urbach energy, as it is usually assumed.     

Pion mass dependence of the nucleon mass in the chiral quark soliton model

The dependence of the nucleon mass on the mass of the pion is studied in the framework of the chiral quark-soliton model. A remarkable agreement is observed with lattice data from recent full dynamical simulations. The possibility and limitations to use the results from the chiral quark soliton model as a guideline for the chiral extrapolation of lattice data are discussed.     

Defect configurations in Ge-S chalcogenide glasses studied by Raman scattering and positron annihilation technique

Defect configurations of Ge-S binary glasses have been studied systemically by Raman scattering technique and positron annihilation lifetime spectra (PALS). The correlations between the positron lifetime data, structural features, and chemical compositions of Ge-S binary glasses have been established, and also the identification of open volume originated from coordination defects has been carried out. The cognizance of defect configuration will be very helpful to further understand the unique photosensitivity of chalcogenide glasses.     

Expression and distribution of N-acetyl and N-glycolylneuraminic acids in secreted and cell-associated glycoconjugates by two human osteosarcoma cell lines

N-acetylneuraminic acid (Neu5Ac) and N-glycolylneuraminic acid (Neu5Gc) are the dominant sialic acids (Sia) in mammals usually found in the non-reducing terminal of oligosaccharide side chains in glycoproteins and glycolipids. Their expression and distribution pattern have been correlated both with the malignant phenotype and tumor grade of human cancers. The aim of the present study was to determine by reversed-phase HPLC method the amounts of Neu5Ac and Neu5Gc as well as their distribution among the culture media and cell surface of MG-63 and Saos-2 human osteosarcoma cell lines of high and low metastatic potential. It was determined that MG-63 cells produce up to 5-fold more total sialic acid as compared with the Saos 2 cells. Neu5Ac accounts for ca 60% of the total sialic acids secreted by MG-63 cells, whereas Neu5Gc is the predominant sialic acid present on the MG-63 cell membrane. Saos 2 cells secrete considerable amounts of Neu5Ac to culture media. The obtained data indicate that the human osteosarcoma cells express both forms of Sia-containing glycoconjugates; the differences in the amounts of each of the two major Sia types and their distribution may be related to their differences in morphology and/or metastatic potentials.     

Perturbative chiral violations for domain-wall QCD with improved gauge actions

We investigate, in the framework of perturbation theory at finite Ns$N_s$, the effectiveness of improved gauge actions in suppressing the chiral violations of domain-wall fermions. Our calculations show substantial reductions of the residual mass when it is compared at the same value of the gauge coupling, the largest suppression being obtained when the DBW2 action is used. Similar effects can also be observed for a power-divergent mixing coefficient which is chirally suppressed. No significant reduction instead can be seen in the case of the difference between the vector and axial-vector renormalization constants when improved gauge actions are used in place of the plaquette action. We also find that one-loop perturbation theory is not an adequate tool to carry out comparisons at the same energy scale (of about 2 GeV), and in fact in this case even an enhancement of the chiral violations is frequently obtained.     

High temperature Mars atmosphere. Part I: transport cross sections

In the perspective of higher approximations of the Chapman-Enskog theory for transport property calculations, existing transport cross sections databases for interactions involving Earth atmosphere species have been updated and extended to Mars atmosphere components, proposing a phenomenological approach for the derivation of the relevant elastic collision integrals in neutral-neutral and neutral-ion interactions. Inelastic collision integrals terms, due to resonant charge exchange channels, have been considered and the asymptotic approach extended to the estimation of charge transfer cross section of multiple resonant processes. Electronic supplementary material  Supplementary Online Material     

Understanding nucleon structure using lattice simulations

This review focuses on the discussion of three key results of nucleon structure calculations on the lattice. These three results are the quark contribution to the nucleon spin, J_q, the nucleon-Δ transition form factors, and the nucleon axial coupling, g_A. The importance for phenomenology and experiment is discussed and the requirements for future simulations are pointed out.     

Comments on quasiparticle models of quark–gluon plasma

Here we comment on the thermodynamic inconsistency problem and the reformulation of statistical mechanics of widely studied quasiparticle models of quark–gluon plasma. Their starting relation, the expression for pressure itself is a wrong choice and lead to thermodynamic inconsistency and the requirements of the reformulation of statistical mechanics. We propose a new approach to the problem using the standard statistical mechanics and is thermodynamically consistent. We also show that the other quasiparticle models may be obtained from our general formalism as a special case under certain restrictive condition. Further, as an example, we have applied our model to explain the nonideal behaviour of gluon plasma and obtained a remarkable good fit to the lattice results by adjusting just a single parameter.     

GeSbTe deposition for the PRAM application

GeSbTe (GST) chalcogenide thin films for the phase-change random access memory (PRAM) were deposited by an atomic layer deposition (ALD) process. New precursors for GST thin films made with an ALD process were synthesized. Among the synthesized precursors, Ge(N(CH₃)₂)₄, Sb(N(CH₃)₂)₄, and Te(i-Pr)₂ (i-Pr = iso-propyl) were selected. Using the above precursors, GST thin films were deposited using an H₂ plasma-assisted ALD process. Film resistivity abruptly changed after an N₂ annealing process above a temperature of 350 °C. Cross-sectional scanning electron microscope (SEM) photographs of the GST films on the patterned substrate with aspect ratio of 7 shows that the step coverage is about 90%.