Membrane-Mediated Alterations of Intracellular Na+ and K+ in Lytic-Virus-Infected and Retrovirus-Transformed Cells

Infection of chick-embryo fibroblasts and other ceils by certain animal viruses results in alterations in the intracellular concentrations of Na + and K +. Dramatic alterations in monovalent-cation concentrations of lytic-virus-infected ceils may favor the synthesis of viral proteins over cellular proteins. More subtle alterations in retrovirus-transformed cells may result in the expression of many morphological and biochemical changes associated with the transformed phenotype.Public Health Service Grant CA 26169, CA 27003National Cancer Institute CA 06593Integrative Biolog

Linking expansion behaviour of extruded potato starch/rapeseed press cake blends to rheological and technofunctional properties

In order to valorise food by-products into healthy and sustainable products, extrusion technology can be used. Thereby, a high expansion rate is often a targeted product property. Rapeseed press cake (RPC) is a protein- and fibre-rich side product of oil pressing. Although there is detailed knowledge about the expansion mechanism of starch, only a few studies describe the influence of press cake addition on the expansion and the physical quality of the extruded products. This study assessed the effect of RPC inclusion on the physical and technofunctional properties of starch-containing directly expanded products. The effect of starch type (native and waxy), RPC level (10, 40, 70 g/100 g), extrusion moisture content (24, 29 g/100 g) and barrel temperature (20–140 °C) on expansion, hardness, water absorption, and solubility of the extrudates and extruder response was evaluated. At temperatures above 120 °C, 70 g/100 g of RPC increased the sectional and volumetric expansion of extrudates, irrespective of starch type. Since expansion correlates with the rheological properties of the melt, RPC and RPC/starch blends were investigated pre- and postextrusion in a closed cavity rheometer at extrusion-like conditions. It was shown that with increasing RPC level the complex viscosity |ƞ*| of extruded starch/RPC blends increased, which could be linked to expansion behaviour

Alternative approach to computing transport coefficients: application to conductivity and Hall coefficient of hydrogenated amorphous silicon

We introduce a theoretical framework for computing transport coefficients for complex materials. As a first example, we resolve long-standing inconsistencies between experiment and theory pertaining to the conductivity and Hall mobility for amorphous silicon and show that the Hall sign anomaly is a consequence of localized states. Next, we compute the AC conductivity of amorphous polyanaline. The formalism is applicable to complex materials involving defects and band-tail states originating from static topological disorder and extended states. The method may be readily integrated with current \textit{ab initio} methods.Comment: 4 pages, 2 figures, submitted to Phys. Rev. Let

Atomistic modeling of amorphous silicon carbide: An approximate first-principles study in constrained solution space

Localized basis ab initio molecular dynamics simulation within the density functional framework has been used to generate realistic configurations of amorphous silicon carbide (a-SiC). Our approach consists of constructing a set of smart initial configurations that conform essential geometrical and structural aspects of the materials obtained from experimental data, which is subsequently driven via first-principles force-field to obtain the best solution in a reduced solution space. A combination of a priori information (primarily structural and topological) along with the ab-initio optimization of the total energy makes it possible to model large system size (1000 atoms) without compromising the quantum mechanical accuracy of the force-field to describe the complex bonding chemistry of Si and C. The structural, electronic and the vibrational properties of the models have been studied and compared to existing theoretical models and available data from experiments. We demonstrate that the approach is capable of producing large, realistic configurations of a-SiC from first-principles simulation that display excellent structural and electronic properties of a-SiC. Our study reveals the presence of predominant short-range order in the material originating from heteronuclear Si-C bonds with coordination defect concentration as small as 5% and the chemical disorder parameter of about 8%.Comment: 16 pages, 7 figure

Metabolic Changes Precede the Development of Pulmonary Hypertension in the Monocrotaline Exposed Rat Lung.

There is increasing interest in the potential for metabolic profiling to evaluate the progression of pulmonary hypertension (PH). However, a detailed analysis of the metabolic changes in lungs at the early stage of PH, characterized by increased pulmonary artery pressure but prior to the development of right ventricle hypertrophy and failure, is lacking in a preclinical animal model of PH. Thus, we undertook a study using rats 14 days after exposure to monocrotaline (MCT), to determine whether we could identify early stage metabolic changes prior to the manifestation of developed PH. We observed changes in multiple pathways associated with the development of PH, including activated glycolysis, increased markers of proliferation, disruptions in carnitine homeostasis, increased inflammatory and fibrosis biomarkers, and a reduction in glutathione biosynthesis. Further, our global metabolic profile data compare favorably with prior work carried out in humans with PH. We conclude that despite the MCT-model not recapitulating all the structural changes associated with humans with advanced PH, including endothelial cell proliferation and the formation of plexiform lesions, it is very similar at a metabolic level. Thus, we suggest that despite its limitations it can still serve as a useful preclinical model for the study of PH

Berry phases and pairing symmetry in Holstein-Hubbard polaron systems

We study the tunneling dynamics of dopant-induced hole polarons which are self-localized by electron-phonon coupling in a two-dimensional antiferro- magnet. Our treatment is based on a path integral formulation of the adia- batic approximation, combined with many-body tight-binding, instanton, con- strained lattice dynamics, and many-body exact diagonalization techniques. Our results are mainly based on the Holstein-$tJ$ and, for comparison, on the Holstein-Hubbard model. We also study effects of 2nd neighbor hopping and long-range electron-electron Coulomb repulsion. The polaron tunneling dynamics is mapped onto an effective low-energy Hamiltonian which takes the form of a fermion tight-binding model with occupancy dependent, predominant- ly 2nd and 3rd neighbor tunneling matrix elements, excluded double occupan- cy, and an effective intersite charge interactions. Antiferromagnetic spin correlations in the original many-electron Hamiltonian are reflected by an attractive contribution to the 1st neighbor charge interaction and by Berry phase factors which determine the signs of effective polaron tunneling ma- trix elements. In the two-polaron case, these phase factors lead to polaron pair wave functions of either $d_{x^2-y^2}$-wave symmetry or p-wave symme- try with zero and nonzero total pair momentum, respectively. Implications for the doping dependent isotope effect, pseudo-gap and Tc of a superconduc- ting polaron pair condensate are discussed/compared to observed in cuprates.Comment: 23 pages, revtex, 13 ps figure

Spatiotemporal evolution of polaronic states in finite quantum systems

We study the quantum dynamics of small polaron formation and polaron transport through finite quantum structures in the framework of the one-dimensional Holstein model with site-dependent potentials and interactions. Combining Lanczos diagonalization with Chebyshev moment expansion of the time evolution operator, we determine how different initial states, representing stationary ground states or injected wave packets, after an electron-phonon interaction quench, develop in real space and time. Thereby, the full quantum nature and dynamics of electrons and phonons is preserved. We find that the decay out of the initial state sensitively depends on the energy and momentum of the incoming particle, the electron-phonon coupling strength, and the phonon frequency, whereupon bound polaron-phonon excited states may emerge in the strong-coupling regime. The tunneling of a Holstein polaron through a quantum wall/dot is generally accompanied by strong phonon number fluctuations due to phonon emission and re-absorption processes.Comment: 13 pages, 15 figures, final versio

p-Type semiconducting properties in lithium-doped MgO single crystals

The phenomenally large enhancement in conductivity observed when Li-doped MgO crystals are oxidized at elevated temperatures was investigated by dc and ac electrical measurements in the temperature interval 250-673 K. The concentration of ([Li]^{0}) centers (Li^{+} ions each with a trapped hole) resulting from oxidation was monitored by optical absorption measurements. Both dc and ac experiments provide consistent values for the bulk resistance. The electricalconductivity of oxidized MgO:Li crystals increases linearly with the concentration of ([Li]^{0}) centers. The conductivity is thermally activated with an activation energy of (0.70 +/- 0.01) eV, which is independent of the ([Li]^{0}) content. The \textit{standard semiconducting} mechanism satisfactorily explains these results. Free holes are the main contribution to band conduction as they are trapped at or released from the ([Li]^{0})-acceptor centers. In as-grown MgO:Li crystals, electrical current increases dramatically with time due to the formation of ([Li]^{0}) centers. The activation energy values between 1.3 and 0.7 eV are likely a combination of the activation energy for the creation of ([Li]^{0}) centers and the activation energy of ionization of these centers. Destruction of ([Li]^{0}) centers can be induced in oxidized crystals by application of an electric field due to Joule heating up to temperatures at which ([Li]^{0}) centers are not stable.Comment: LaTeX, 20 pages, 9 Encapsulated Postscript Format Figures, use the version 4.0 of REVTEX 4 macro packag

Small and large polarons in nickelates, manganites, and cuprates

By comparing the optical conductivities of La_{1.67}Sr_{0.33}NiO_{4} (LSNO), Sr_{1.5}La_{0.5}MnO_4 (SLMO), Nd_2CuO_{4-y} (NCO), and Nd_{1.96}Ce_{0.04}CuO_{4} (NCCO), we have identified a peculiar behavior of polarons in this cuprate family. While in LSNO and SLMO small polarons localize into ordered structures below a transition temperature, in those cuprates the polarons appear to be large, and at low T their binding energy decreases. This reflects into an increase of the polaron radius, which may trigger coherent transport.Comment: File latex, 15 p. incl. 4 Figs. epsf, to appear on the Journal of Superconductivity - Proc. "Stripes 1996" - Roma Dec 199