Metastable states and physical characteristics of a subsystem of interstitial impurities

The behavior of mobile interstitial impurities in a crystal matrix has been simulated numerically. The contribution of the impurity subsystem to the heat capacity, and the effect of clusterization on the temperature dependence of the impurity diffusion coefficient have been studied. Fiz. Tverd. Tela (St. Petersburg) 40, 475–480 (March 1998)     

Approximation du temps local des surfaces gaussiennes

Summary LetX be a centered stationary Gaussian stochastic process with ad-dimensional parameter (d2),F its spectral measure, (x denotes the Euclidean norm ofx). We consider regularizations of the trajectories ofX by means of convolutions of the formX (t)=( *X)(t) where stands for an approximation of unity (as tends to zero) satisfying certain regularity conditions.The aim of this paper is to recover the local time ofX at a given levelu, as a limit of appropriate normalizations of the geometric measure of theu-level set of the regular approximating processesX . A part of the difficulties comes from the fact that the geometric behavior of the covariance of the Gaussian processX can be a complex one as approaches O.The results are onL ²-convergence and include bounds for the speed of convergence.L ^presults may be obtained in similar ways, but almost sure convergence or simultaneous convergence for the various values ofu do not seem to follow from our methods. In Sect. 3 we have included examples showing a diversity of geometric behaviors, especially in what concerns the dependence on the thickness of the set in which the covariance of the original processX is irregular.Some technical results of analytic nature are included as appendices in Sect. 4.     

Elimination of Acetate Production to Improve Ethanol Yield During Continuous Synthesis Gas Fermentation by Engineered Biocatalyst Clostridium sp. MTEtOH550

Acetogen strain Clostridum sp. MT653 produced acetate 273?mM (p?<?0.005) and ethanol 250?mM (p?<?0.005) from synthesis gas blend mixture of 64?% CO and 36?%?H₂. Clostridum sp. MT653 was metabolically engineered to the biocatalyst strain Clostridium sp. MTEtOH550. The biocatalyst increased ethanol yield to 590?mM with no acetate production during single-stage continuous syngas fermentation due to expression of synthetic adh cloned in a multi-copy number expression vector. The acetate production was eliminated by inactivation of the pta gene in Clostridium sp. MTEtOH550. Gene introduction and gene elimination were achieved only using Syngas Biofuels Energy, Inc. electroporation generator. The electrotransformation efficiencies were 8.0?±?0.2?×?10⁶ per microgram of transforming DNA of the expression vector at cell viability ~15?%. The frequency of suicidal vector integration to inactivate pta was ~10^?5 per the number of recipient cells. This is the first report on elimination of acetate production and overexpression of synthetic adh gene to engineer acetogen biocatalyst for selective biofuel ethanol production during continuous syngas fermentation.     

Anisotropy induced by impurities of “random local field” type in <Emphasis Type="Italic">O</Emphasis>(<Emphasis Type="Italic">n</Emphasis>) models and suppression of the Imry–Ma inhomogeneous state

It is shown that in a system with anisotropic distribution of the impurity-induced random local field directions in the n-dimensional space of a vector order parameter with the O(n) symmetry, the impurityinduced effective anisotropy arises for the space dimensionality 2 < d < 4. If the anisotropy constant exceeds the threshold value, then an inhomogeneous state predicted by Imry and Ma becomes energetically unfavorable, and the system goes back to a state with the long-range order.     

Quasi-One-Dimensional Ising Models with Defects of the “Random Local Field” Type: the Imry–Ma Phase in Spaces with a Dimension Higher than the Lower Critical Dimensionality

Physics of the Solid State - The “temperature–defect concentration” phase diagram of quasi-one-dimensional Ising models with defects of the “random local field” type...     

Two-dimensional O(n) Models with Defects of “Random Local Anisotropy” Type

Physics of the Solid State - The phase diagram of two-dimensional systems with continuous symmetry of the vector order parameter containing defects of the “random local anisotropy” type...     

Simulation of 1/f noise spectra in YBa2Cu3O7 epitaxial films

A Monte Carlo simulation of the 1/f noise spectra in the normal phase of YBa₂Cu₃O₇ epitaxial films is reported. It is conjectured that the main contribution to the noise is from oxygen transitions to vacant sites in the CuO plane. It is shown that the annealing regime and the mismatch strains between the film and the substrate are the main factors governing the domain and defect structure of the film and, hence, the 1/f noise spectrum. Fiz. Tverd. Tela (St. Petersburg) 41, 957–964 (June 1999)     

Cre-lox66/lox71-Based Elimination of Phosphotransacetylase or Acetaldehyde Dehydrogenase Shifted Carbon Flux in Acetogen Rendering Selective Overproduction of Ethanol or Acetate

Acetogen strain Clostridium sp. MT1121 produced 300?mM acetate (p?<?0.005) and 321?mM ethanol (p?<?0.005) from synthesis gas (syngas) blend 60?% CO and 40?%?H₂. Clostridium sp. MT1121 was metabolically engineered to eliminate production of either acetate or acetaldehyde during syngas fermentation. We used Cre-lox66/lox71-based gene removal system to eliminate either phosphotransacetylase (pta), or acetaldehyde dehydrogenase (aldh). The resulted biocatalyst with eliminated pta increased ethanol yield to 610?mM (p?<?0.005). Inactivation of pta rendered only 502?mM of ethanol (p?<?0.005). The acetogen biocatalyst with eliminated aldh produced 450?mM acetate (p?<?0.005). The role of cell energy pool preservation for re-directed carbon flux is discussed. This is the first report on time- and cost-efficient gene elimination in acetogens using lox66/lox71 gene elimination system.     

Width of steps on a rough surface

Computer simulation of a rough surface indicates that a relation exists between the experimentally determined degree of roughness of interlayer boundaries and the correlation length, on the one hand, and the characteristic width of atomic steps on the layer interfaces in multilayered structures, on the other hand.     

Cubic anisotropy created by defects of “random local anisotropy” type,and phase diagram of the O(n) Model

Physics of the Solid State - The expression for the cubic-type-anisotropy constant created by defects of “random local anisotropy” type is derived. It is shown that the Imry–Ma...