Cation/H+ antiporters mediate potassium and sodium fluxes in Pichia sorbitophila. Cloning of the PsNHA1 and PsNHA2 genes and expression in Saccharomyces cerevisiae

Pichia sorbitophila grows rapidly in the presence of very high NaCl concentrations. Under these conditions, even when the K(+) concentration is low, P. sorbitophila cells can maintain low Na(+) and high K(+) contents. This remarkable capacity of P. sorbitophila fails when the external pH is not acidic. This indicates that Na(+) efflux is mediated by an electroneutral Na(+)/H(+) antiporter. We have cloned and sequenced two genes designated as PsNHA1 and PsNHA2, which probably encode two antiporters of this type. The genes present high similarity with the corresponding genes from other yeasts. The heterologous expression of PsNHA1 or PsNHA2 in a Saccharomyces cerevisiae mutant lacking the Na(+) efflux systems and sensitive to high concentrations of Na(+) and K(+) rescued the tolerance and the ability to extrude both cations. The Accession Nos of the sequenced DNA fragments are: PsNHA1, AJ496431; PsNHA2, AJ496432. (TC 2.A.36) Copyright 2002 John Wiley & Sons, Ltd.     

Geoceramic Matrices for Immobilization of Nonpartitioned Radioactive Wastes

Immobilization of radioactive wastes (RW) containing large amounts of process alkalis in ceramic matrices based on acid and basic rocks is studied. Immobilizing characteristics of samples with an RW content of 15% are obtained. The best geoceramic matrices are characterized by the forward leaching rates with double-distilled water of 1 × 10^{- 4} and 1 × 10^{- 5} g cm^{- 2} day^{- 1} for Sr and Cs, respectively, and the steady-state leaching rate of about 2 × 10^{- 6} g cm^{- 2} day^{- 1}. Possible fixation mechanisms of the radionuclides in the matrices studied are discussed. Comparative analysis of properties of the geoceramic matrices and borosilicate and some other existing matrices for RW immobilization makes it possible to recommend some kinds of the geoceramics as matrices for immobilization of nonfractionated intermediate- and high-level radioactive wastes.     

Photobleaching of a solid photochromic medium by a Gaussian laser beam

Equations that describe the photobleaching of photochromic layers illuminated by Gaussian laser beams are given. The photochromic samples are made of thionine, triethanolamine, and polyvinyl alcohol and follow simple kinetics law. Spatial absorbance and time-dependent power transmittance are well described by the developed equations. The model is used to calculate the Gaussian dimension of helium-neon laser beams from kinetics data.     

Effect of terbium gallium garnet crystal orientation on the isolation ratio of a Faraday isolator at high average power

We present a comprehensive and systematic investigation of the fundamental physical limitations of Faraday isolation performance at high average powers that are due to thermally induced birefringence. First, the operation of various Faraday isolator designs by use of arbitrary orientation of cubic magneto-optic crystals is studied theoretically. It is shown that, for different Faraday isolator designs, different crystal orientations can optimize the isolation ratio. Second, thermo-optic and photoelastic constants for terbium gallium garnet crystals grown by different manufacturers were measured. Measurements of self-induced depolarization are made for various orientations of crystallographic axes. The measurements are in good agreement with our theoretical predictions. Based on our results, it is possible to select a crystal orientation that optimizes isolation performance at high average powers, resulting in a 5-dB enhancement over nonoptimized orientations.     

New dendrimer-peptide host-guest complexes: towards dendrimers as peptide carriers

Adamantyl urea and adamantyl thiourea modified poly(propylene imine) dendrimers act as hosts for N-terminal tert-butoxycarbonyl (Boc)-protected peptides and form chloroform-soluble complexes. Investigations with NMR spectroscopy show that the peptide is bound to the dendrimer by ionic interactions between the dendrimer outer shell tertiary amines and the C-terminal carboxylic acid of the peptide, and also through host-urea to peptide-amide hydrogen bonding. The hydrogen-bonding nature of the peptide-dendrimer interactions was further confirmed by using Fourier transform IR spectroscopy, for which the NH- and CO-stretch signals of the peptide amide moieties shift towards lower wavenumbers upon complexation with the dendrimer. Spatial analysis of the complexes with NOESY spectroscopy generally shows close proximity of the N-terminal Boc group of the peptide to the peripheral adamantyl groups on the dendrimer host. The influence of side-chain motif on interactions with the host is analyzed by using seven different N-Boc-protected tripeptides as guests for the dendrimer. Downfield shifts of up to 1.3 ppm were observed for the guest amide NH-proton signals. These shifts decreased with increasing 'bulkiness' of the amino acid side chains. Despite this, the dendrimer was capable of making multiple peptide-dendrimer complexes when presented with a library of seven peptides. The different peptides were all present in the host, which did not show specific preferences, and could be released under mild acidic conditions. These results show the general nature of the peptide-dendrimer interactions in the formation of either single- or multiple-peptide-dendrimer complexes.     

Reachability Sets of a Class of Multistep Control Processes: Their Design

An upper estimate and an iterative restriction algorithm for the reachability set for determining the optimal control for a class of multistep control processes are designed.     

An Auto-Adaptive Multidomain Spectral Technique for Linear Stability Analysis: Application to Viscous Compressible Flows

An auto-adaptive multidomain pseudo-spectral technique is considered in order to solve the linear stability problem of viscous compressible flows. Both the locations of the interfaces and the parameters of the mappings in each subdomain are adapted by minimizing the H ² -norm of the calculated solution. Such method provides automatically—this is the key point—the best polynomial interpolation of the basic state the stability of which is studied. It turns out that the whole procedure is needed to obtain reliable results. The method is first validated against results available in the literature (both viscous incompressible and inviscid compressible Rayleigh–Taylor configurations). The efficiency of the numerical method is illustrated with results on the linear stability of the compressible viscous diffusive Rayleigh–Taylor flow where no analytical or numerical results are available. New results showing the influence of stratification, viscosity, diffusity between species and thermal diffusivity are presented.     

Development of an electromagnetic tool for the accurate synthesis of manifold multiplexers: The dynamic inverter

This article presents an electromagnetic tool for the synthesis of manifold multiplexers — the dynamic inverter. By associating this model with the classical circuit model of the filter, the broadband behaviour of each filter can be analysed rapidly and then optimised accurately for an efficient synthesis of the manifold multiplexer. © 2005 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2005.     

Oxidative-gravimetric porosimetry of macroporous silicon

A simple nondestructive method to find the internal surface area, porosity, pore diameter, and pore density in macroporous silicon with through channels is suggested and tested. The porosity p is determined from the mass loss upon anodizing, and the surface area per unit volume, S _v , from the mass of SiO₂ formed on the pore surface upon thermal oxidation. The relations are given for calculation of the average pore diameter d and pore density N from the obtained S _v and p. Dependences of the specific surface area and porosity on the resistivity of initial n-Si in the range ρ = 3–25 Θ cm have been studied for samples with ordered and self-organized “lattices” of macropores. The obtained values are within the limits p = 27–50%, S _v = 2800–6000 cm²/cm³, d = 1.9–6.5 μm, and N = 1.4?10 × 10⁶ cm^?2, in agreement with the data fumished by microscopy.     

Effects of infant formula feeding on the distribution of copper in the body of 8-day-old rats

The oxidase activity of ceruloplasmin (Cp, EC 1.16.3.1), the content of immunoreactive Cp and copper ion concentration were measured in the serum of eight day-old rats receiving either breast feeding (control group) or commercial nutritive mixture which has been recommended for the newborn children beginning from zero age (experimental group). It was shown that the artificial feeding caused almost 3-fold increase of Cp oxidase activity and copper content in the serum when compared to age-matched controls. No changes in the copper content per Cp molecule were observed. Dot-hybridization of the total liver polyribosomal RNA with Cp [32P]cDNA showed that the increased Cp level in the blood of the rats of experimental group correlated well with the level of expression of Cp gene. The copper content in the liver of experimental rats was two times lower that in control animals while no differences was found in the brain copper content between two groups of rats. The role of the regulation of Cp gene expression in the lactating mammary gland and of milk Cp in the copper homeostasis in the newborn body is discussed.