Preferential adsorption of high density lipoprotein (HDL) in blood plasma/polymer interaction

A few studies on the adsorption of plasma proteins to polymeric surfaces show that major plasma proteins: albumin (Alb), fibrinogen (Fb) and immunoglobulin (IgG) are adsorbed in much smaller quantities from plasma than from protein solutions (1,2). Present results show that this difference in adsorption is due to the preferential adsorption of high density lipoprotein from plasma onto the material surfaces studied (PVC and PS)

Platelet deposition studies on copolyether urethanes modified with poly(ethylene oxide)

Pellethane ® 2363 80A films and tubings were chemically modified and the effect of these modifications on platelet deposition was studied. Grafting of high molecular weight poly(ethylene oxide) and graft polymerization of methoxy poly(ethylene glycol) 400 methacrylate resulted in surfaces with a good water wettability. The increased hydrophilicity of these modified surfaces could be demonstrated by contact angle measurements. The platelet deposition was investigated with tubings in a capillary flow system, using different types of perfusates. Platelet deposition from a buffer-containing perfusate on surfaces modified with either high molecular weight poly(ethylene oxide) or methoxy poly(ethylene glycol) 400 methacrylate was almost absent and less than on Pellethane 2363 80A. Using a citrated plasmacontaining perfusate the amount of deposited platelets on Pellethane 2363 80A modified with high molecular weight poly(ethylene oxide) was low and about the same as on unmodified surfaces. However, a marked reduced platelet deposition compared to unmodified Pellethane 2363 80A was found when the platelets were activated by Ca2+ ionophore. The improved blood compatibility of the modified Pellethane 2363 80A tubings obviously indicates the favourable effect of the presence of grafted PEO on the surface

Temperature Dependence of Interlayer Magnetoresistance in Anisotropic Layered Metals

Studies of interlayer transport in layered metals have generally made use of zero temperature conductivity expressions to analyze angle-dependent magnetoresistance oscillations (AMRO). However, recent high temperature AMRO experiments have been performed in a regime where the inclusion of finite temperature effects may be required for a quantitative description of the resistivity. We calculate the interlayer conductivity in a layered metal with anisotropic Fermi surface properties allowing for finite temperature effects. We find that resistance maxima are modified by thermal effects much more strongly than resistance minima. We also use our expressions to calculate the interlayer resistivity appropriate to recent AMRO experiments in an overdoped cuprate which led to the conclusion that there is an anisotropic, linear in temperature contribution to the scattering rate and find that this conclusion is robust.Comment: 8 pages, 4 figure

The Chandra LETGS high resolution X-ray spectrum of the isolated neutron star RX J1856.5-3754

We present the Chandra LETGS X-ray spectrum of the nearby (~60 pc) neutron star RX J1856.5-3754. Detailed spectral analysis of the combined X-ray and optical data rules out the nonmagnetic neutron star atmosphere models with hydrogen, helium, iron and solar compositions. We also conclude that strongly magnetized atmosphere models are unable to represent the data. The data can be explained with a two-component blackbody model. The harder component with temperature of kT_bb~63 eV and a radius R_bb~2.2 km of the emitting region well fits the X-ray data and can be interpreted as radiation from a hot region on the star's surface.Comment: 4 pages, 3 color figures; acceped by A&A Letters; http://www.xray.mpe.mpg.de/~burwitz/burwitz_refereed.htm

Analytical calculation of the Green's function and Drude weight for a correlated fermion-boson system

In classical Drude theory the conductivity is determined by the mass of the propagating particles and the mean free path between two scattering events. For a quantum particle this simple picture of diffusive transport loses relevance if strong correlations dominate the particle motion. We study a situation where the propagation of a fermionic particle is possible only through creation and annihilation of local bosonic excitations. This correlated quantum transport process is outside the Drude picture, since one cannot distinguish between free propagation and intermittent scattering. The characterization of transport is possible using the Drude weight obtained from the f-sum rule, although its interpretation in terms of free mass and mean free path breaks down. For the situation studied we calculate the Green's function and Drude weight using a Green's functions expansion technique, and discuss their physical meaning.Comment: final version, minor correction

Gate-tunable band structure of the LaAlO3_3-SrTiO3_3 interface

The 2-dimensional electron system at the interface between LaAlO$_{3}$ and SrTiO$_{3}$ has several unique properties that can be tuned by an externally applied gate voltage. In this work, we show that this gate-tunability extends to the effective band structure of the system. We combine a magnetotransport study on top-gated Hall bars with self-consistent Schr\"odinger-Poisson calculations and observe a Lifshitz transition at a density of $2.9\times10^{13}$ cm$^{-2}$. Above the transition, the carrier density of one of the conducting bands decreases with increasing gate voltage. This surprising decrease is accurately reproduced in the calculations if electronic correlations are included. These results provide a clear, intuitive picture of the physics governing the electronic structure at complex oxide interfaces.Comment: 14 pages, 4 figure

Dishevelled genes mediate a conserved mammalian PCP pathway to regulate convergent extension during neurulation

The planar cell polarity (PCP) pathway is conserved throughout evolution, but it mediates distinct developmental processes. In Drosophila, members of the PCP pathway localize in a polarized fashion to specify the cellular polarity within the plane of the epithelium, perpendicular to the apicobasal axis of the cell. In Xenopus and zebrafish, several homologs of the components of the fly PCP pathway control convergent extension. We have shown previously that mammalian PCP homologs regulate both cell polarity and polarized extension in the cochlea in the mouse. Here we show, using mice with null mutations in two mammalian Dishevelled homologs, Dvl1 and Dvl2, that during neurulation a homologous mammalian PCP pathway regulates concomitant lengthening and narrowing of the neural plate, a morphogenetic process defined as convergent extension. Dvl2 genetically interacts with Loop-tail, a point mutation in the mammalian PCP gene Vangl2, during neurulation. By generating Dvl2 BAC (bacterial artificial chromosome) transgenes and introducing different domain deletions and a point mutation identical to the dsh1 allele in fly, we further demonstrated a high degree of conservation between Dvl function in mammalian convergent extension and the PCP pathway in fly. In the neuroepithelium of neurulating embryos, Dvl2 shows DEP domain-dependent membrane localization, a pre-requisite for its involvement in convergent extension. Intriguing, the Loop-tail mutation that disrupts both convergent extension in the neuroepithelium and PCP in the cochlea does not disrupt Dvl2 membrane distribution in the neuroepithelium, in contrast to its drastic effect on Dvl2 localization in the cochlea. These results are discussed in light of recent models on PCP and convergent extension