Mucus glycoprotein secretion by tracheal explants: effects of pollutants.

Tracheal slices incubated with radioactive precursors in tissue culture medium secrete labeled mucus glycoproteins into the culture medium. We have used an in vivtro approach, a combined method utilizing exposure to pneumotoxins in vivo coupled with quantitation of mucus secretion rates in vitro, to study the effects of inhaled pollutants on mucus biosynthesis by rat airways. In addition, we have purified the mucus glycoproteins secreted by rat tracheal explants in order to determine putative structural changes that might by the basis for the observed augmented secretion rates after exposure of rats to H2SO4 aerosols in combination with high ambient levels of ozone. After digestion with papain, mucus glycoproteins secreted by tracheal explants may be separated into five fractions by ion-exchange chromatography, with recovery in high yield, on columns of DEAE-cellulose. Each of these five fractions, one neutral and four acidic, migrates as a single unique spot upon cellulose acetate electrophoresis at pH values of 8.6 and 1.2. The neutral fraction, which is labeled with [3H] glucosamine, does not contain radioactivity when Na2 35SO4 is used as the precursor. Acidic fractions I-IV are all labeled with either 3H-glucosamine or Na2 35SO4 as precursor. Acidic fraction II contains sialic acid as the terminal sugar on its oligosaccharide side chains, based upon its chromatographic behavior on columns of wheat-germ agglutinin-Agarose. Treatment of this fraction with neuraminidase shifts its elution position in the gradient to a lower salt concentration, coincident with acidic fraction I. After removal of terminal sialic acid residues with either neuraminidase or low pH treatment, the resultant terminal sugar on the oligosaccharide side chains is fucose. These results are identical with those observed with mucus glycoproteins secreted by cultured human tracheal explants and purified by these same techniques

Enhanced ionization in small rare gas clusters

A detailed theoretical investigation of rare gas atom clusters under intense short laser pulses reveals that the mechanism of energy absorption is akin to {\it enhanced ionization} first discovered for diatomic molecules. The phenomenon is robust under changes of the atomic element (neon, argon, krypton, xenon), the number of atoms in the cluster (16 to 30 atoms have been studied) and the fluency of the laser pulse. In contrast to molecules it does not dissappear for circular polarization. We develop an analytical model relating the pulse length for maximum ionization to characteristic parameters of the cluster

Suppressed spin dephasing for 2D and bulk electrons in GaAs wires due to engineered cancellation of spin-orbit interaction terms

We report a study of suppressed spin dephasing for quasi-one-dimensional electron ensembles in wires etched into a GaAs/AlGaAs heterojunction system. Time-resolved Kerr-rotation measurements show a suppression that is most pronounced for wires along the [110] crystal direction. This is the fingerprint of a suppression that is enhanced due to a strong anisotropy in spin-orbit fields that can occur when the Rashba and Dresselhaus contributions are engineered to cancel each other. A surprising observation is that this mechanisms for suppressing spin dephasing is not only effective for electrons in the heterojunction quantum well, but also for electrons in a deeper bulk layer.Comment: 5 pages, 3 figure

Double butterfly spectrum for two interacting particles in the Harper model

We study the effect of interparticle interaction $U$ on the spectrum of the Harper model and show that it leads to a pure-point component arising from the multifractal spectrum of non interacting problem. Our numerical studies allow to understand the global structure of the spectrum. Analytical approach developed permits to understand the origin of localized states in the limit of strong interaction $U$ and fine spectral structure for small $U$.Comment: revtex, 4 pages, 5 figure

Revision of the gunard fish subgenus Otohime (Triglidae: Pterygotrigla)

The subgenus Otohime of the triglid genus Pterygotrigla is revised and includes descriptions of six new species (P. amaokai, P. draiggoch, P. elicryste, P. hafizi, P. soela, and P. urashimai) and diagnoses of five previously described species (P. arabica, P. hemisticta, P. multipunctata, P. spirai, and P.tagala). All are poorly represented in museum collections and are distributed in tropical waters of the Indian and western Pacific oceans. The subgenus Otohime is unique within Pterygotrigla in having a very long opercular spine and cleithral spines reduced or absent . The species characters used for identification are the number of joined pectoral-fin rays and second dorsal-rays, colouration of the pectoral fin and first dorsal fin, breast squamation, and number of gill rakers and a few other meristic and morphometric features. Otohime species are very similar in morphometry and meristics and the extent of intraspecific variation is indeterminable from the small collections available. A brief discussion of the genus Pterygotrigla is provided together with its current species composition that is thought to include the unresolved triglid Prionotus alepis. A range extension is given for Pterygotrigla macrorhynchus

X-ray Phase-Contrast Imaging and Metrology through Unified Modulated Pattern Analysis

We present a method for x-ray phase-contrast imaging and metrology applications based on the sample-induced modulation and subsequent computational demodulation of a random or periodic reference interference pattern. The proposed unified modulated pattern analysis (UMPA) technique is a versatile approach and allows tuning of signal sensitivity, spatial resolution, and scan time. We characterize the method and demonstrate its potential for high-sensitivity, quantitative phase imaging, and metrology to overcome the limitations of existing methods

Dynamical ionization ignition of clusters in intense and short laser pulses

The electron dynamics of rare gas clusters in laser fields is investigated quantum mechanically by means of time-dependent density functional theory. The mechanism of early inner and outer ionization is revealed. The formation of an electron wave packet inside the cluster shortly after the first removal of a small amount of electron density is observed. By collisions with the cluster boundary the wave packet oscillation is driven into resonance with the laser field, hence leading to higher absorption of laser energy. Inner ionization is increased because the electric field of the bouncing electron wave packet adds up constructively to the laser field. The fastest electrons in the wave packet escape from the cluster as a whole so that outer ionization is increased as well.Comment: 8 pages, revtex4, PDF-file with high resolution figures is available from http://mitarbeiter.mbi-berlin.de/bauer/publist.html, publication no. 24. Accepted for publication in Phys. Rev.

Statistics of resonances and of delay times in quasiperiodic Schr"odinger equations

We study the statistical distributions of the resonance widths ${\cal P} (\Gamma)$, and of delay times ${\cal P} (\tau)$ in one dimensional quasi-periodic tight-binding systems with one open channel. Both quantities are found to decay algebraically as $\Gamma^{-\alpha}$, and $\tau^{-\gamma}$ on small and large scales respectively. The exponents $\alpha$, and $\gamma$ are related to the fractal dimension $D_0^E$ of the spectrum of the closed system as $\alpha=1+D_0^E$ and $\gamma=2-D_0^E$. Our results are verified for the Harper model at the metal-insulator transition and for Fibonacci lattices.Comment: 4 pages, 3 figures, submitted to Phys. Rev. Let

Ferroelectric and Incipient Ferroelectric Properties of a Novel Sr_(9-x)PbxCe2Ti2O36 (x=0-9) Ceramic System

Sr_(9-x)PbxCe2Ti12O36 system is derived from the perovskite SrTiO3 and its chemical formula can be written as (Sr_(1-y)Pby)0.75Ce0.167TiO3. We investigated dielectric response of Sr_(9-x)PbxCe2Ti12O36 ceramics (x = 0-9) between 100 Hz and 100 THz at temperatures from 10 to 700 K using low- and high-frequency dielectric, microwave (MW), THz and infrared spectroscopy. We revealed that Sr9Ce2Ti12O36 is an incipient ferroelectric with the R-3c trigonal structure whose relative permittivity e' increases from 167 at 300 K and saturates near 240 below 30 K. The subsequent substitution of Sr by Pb enhances e' to several thousands and induces a ferroelectric phase transition to monoclinic Cc phase for x>=3. Its critical temperature Tc linearly depends on the Pb concentration and reaches 550 K for x=9. The phase transition is of displacive type. The soft mode frequency follows the Barrett formula in samples with x=3. The MW dispersion is lacking and quality factor Q is high in samples with low Pb concentration, although the permittivity is very high in some cases. However, due to the lattice softening, the temperature coefficient of the permittivity is rather high. The best MW quality factor was observed for x=1: Q*f=5800 GHz and e'=250. Concluding, the dielectric properties of Sr_(9- x)PbxCe2Ti12O36 are similar to those of Ba_(1-x)SrxTiO3 so that this system can be presumably used as an alternative for MW devices or capacitors.Comment: subm. to Chem. Mate

Cell shape analysis of random tessellations based on Minkowski tensors

To which degree are shape indices of individual cells of a tessellation characteristic for the stochastic process that generates them? Within the context of stochastic geometry and the physics of disordered materials, this corresponds to the question of relationships between different stochastic models. In the context of image analysis of synthetic and biological materials, this question is central to the problem of inferring information about formation processes from spatial measurements of resulting random structures. We address this question by a theory-based simulation study of shape indices derived from Minkowski tensors for a variety of tessellation models. We focus on the relationship between two indices: an isoperimetric ratio of the empirical averages of cell volume and area and the cell elongation quantified by eigenvalue ratios of interfacial Minkowski tensors. Simulation data for these quantities, as well as for distributions thereof and for correlations of cell shape and volume, are presented for Voronoi mosaics of the Poisson point process, determinantal and permanental point processes, and Gibbs hard-core and random sequential absorption processes as well as for Laguerre tessellations of polydisperse spheres and STIT- and Poisson hyperplane tessellations. These data are complemented by mechanically stable crystalline sphere and disordered ellipsoid packings and area-minimising foam models. We find that shape indices of individual cells are not sufficient to unambiguously identify the generating process even amongst this limited set of processes. However, we identify significant differences of the shape indices between many of these tessellation models. Given a realization of a tessellation, these shape indices can narrow the choice of possible generating processes, providing a powerful tool which can be further strengthened by density-resolved volume-shape correlations.Comment: Chapter of the forthcoming book "Tensor Valuations and their Applications in Stochastic Geometry and Imaging" in Lecture Notes in Mathematics edited by Markus Kiderlen and Eva B. Vedel Jense