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Search Results: 1 - 10 of 257814 matches for " Andreas Brühl "
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Karsten Rodenacker,Andreas Brühl,Martina Hausner,Martin Kühn
Image Analysis and Stereology , 2000, DOI: 10.5566/ias.v19.p151-156
Abstract: Populations of bacteria in sludge flocs and biofilm marked by fluorescence marked with fluorescent probes are digitised with a confocal laser scanning microscope. These data are used to analyse the microbial community structure, to obtain information on the localisation of specific bacterial groups and to examine gene expression. This information is urgently required for an in-depth understanding of the function and, more generally, the microbial ecology of biofilms. Methods derived from quantitative image analysis are applied to digitised data from confocal laser scanning microscopes to obtain quantitative descriptions of volumetric, topological (and topographical) properties of different compartments of the components under research. In addition to free-moving flocs, also biofilms attached to a substratum in an experimental environment are analysed. Growth form as well as interaction of components are quantitatively described. Classical measurements of volume and intensity (shape, distribution) and distance dependent interaction measurements using methods from mathematical morphology are performed. Mainly image (volume) processing methods are outlined. Segmented volumes are globally and individually (in terms of 3Dconnected components) measured and used for distance mapping transform as well as for estimation of geodesic distances from the substrate. All transformations are applied on the 3D data set. Resulting distance distributions are quantified and related to information on the identity and activity of the probe-identified bacteria.
Quantitative description of the azimuthal dependence of the exchange bias effect
Florin Radu,Andreas Westphalen,Katharina Theis-Brhl,Hartmut Zabel
Physics , 2005, DOI: 10.1088/0953-8984/18/3/L01
Abstract: While the principal features of the exchange bias between a ferromagnet and an antiferromagnet are believed to be understood, a quantitative description is still lacking. We show that interface spin disorder is the main reason for the discrepancy of model calculations versus experimental results. Taking into account spin disorder at the interface between the ferromagnet and the antiferromagnet by modifying the well known Meiklejohn and Bean model, an almost perfect agreement can be reached. As an example this is demonstrated for the CoFe/IrMn exchange biased bilayer by analyzing the azimuthal dependence of magnetic hysteresis loops from MOKE measurements. Both, exchange bias and coercive fields for the complete 360$^\circ$ angular range are reproduced by our model.
Magnetic Field-Induced Lattice Effects in a Quasi-2D Organic Conductor Close to the Mott Metal-Insulator Transition
Mariano de Souza,Andreas Brühl,Christian Strack,Dieter Schweitzer,Michael Lang
Physics , 2012, DOI: 10.1103/PhysRevB.86.085130
Abstract: We present ultra-high-resolution dilatometric studies in magnetic fields on a quasi-two-dimensional organic conductor $\kappa$-(D8-BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br, which is located close to the Mott metal-insulator (MI) transition. The obtained thermal expansion coefficient, $\alpha(T)$, reveals two remarkable features: (i) the Mott MI transition temperature $T_{MI}$ = (13.6 $\pm$ 0.6)\,K is insensitive to fields up to 10\,T, the highest applied field; (ii) for fields along the interlayer \emph{b}-axis, a magnetic-field-induced (FI) phase transition at $T_{FI}$ = (9.5 $\pm$ 0.5)\,K is observed above a threshold field $H_c \sim$ 1 T, indicative of a spin reorientation with strong magneto-elastic coupling.
Magneto-elastic couplings in the distorted diamond-chain compound azurite
Pham Thanh Cong,Bernd Wolf,Rudra Sekhar Manna,Ulrich Tutsch,Mariano de Souza,Andreas Brühl,Michael Lang
Physics , 2014, DOI: 10.1103/PhysRevB.89.174427
Abstract: We present results of ultrasonic measurements on a single crystal of the distorted diamond-chain compound azurite Cu$_3$(CO$_3$)$_2$(OH)$_2$. Pronounced elastic anomalies are observed in the temperature dependence of the longitudinal elastic mode $c_{22}$ which can be assigned to the relevant magnetic interactions in the system and their couplings to the lattice degrees of freedom. From a quantitative analysis of the magnetic contribution to $c_{22}$ the magneto-elastic coupling $G$ = $\partial J_2$/$\partial \epsilon_b$ can be determined, where $J_2$ is the intra-dimer coupling constant and $\epsilon_b$ the strain along the intra-chain $b$ axis. We find an exceptionally large coupling constant of $|G| \sim ($3650 $\pm$ 150) K highlighting an extraordinarily strong sensitivity of $J_2$ against changes of the $b$-axis lattice parameter. These results are complemented by measurements of the hydrostatic pressure dependence of $J_2$ by means of thermal expansion and magnetic susceptibility measurements performed both at ambient and finite hydrostatic pressure. We propose that a structural peculiarity of this compound, in which Cu$_2$O$_6$ dimer units are incorporated in an unusually stretched manner, is responsible for the anomalously large magneto-elastic coupling.
Isomorphisms of unitary forms of Kac-Moody groups over finite fields
Ralf K?hl,Andreas Mars
Mathematics , 2008,
Abstract: We use methods developed by Caprace and M\"uhlherr to solve the isomorphism problem of unitary forms of infinite split Kac-Moody groups over finite fields of square order.
Persistent expression of BMP-4 in embryonic chick adrenal cortical cells and its role in chromaffin cell development
Katrin Huber, Aylin Franke, Barbara Brühl, Shlomi Krispin, Uwe Ernsberger, Andreas Schober, Oliver Halbach, Hermann Rohrer, Chaya Kalcheim, Klaus Unsicker
Neural Development , 2008, DOI: 10.1186/1749-8104-3-28
Abstract: We report here that BMP-4 is also expressed by adrenal cortical cells throughout chick embryonic development, suggesting a putative role in chromaffin cell development. Moreover, bone morphogenetic protein receptor IA is expressed by both cortical and chromaffin cells. Inhibiting BMP-4 with noggin prevents the increase in the number of tyrosine hydroxylase positive cells in adrenal explants without affecting cell proliferation. Hence, adrenal BMP-4 is likely to induce tyrosine hydroxylase in sympathoadrenal progenitors. To investigate whether persistent BMP-4 exposure is able to induce chromaffin traits in sympathetic ganglia, we locally grafted BMP-4 overexpressing cells next to sympathetic ganglia. Embryonic day 8 chick sympathetic ganglia, in addition to principal neurons, contain about 25% chromaffin-like cells. Ectopic BMP-4 did not increase this proportion, yet numbers and sizes of 'chromaffin' granules were significantly increased.BMP-4 may serve to promote specific chromaffin traits, but is not sufficient to convert sympathetic neurons into a chromaffin phenotype.The neural crest (NC) plays a paradigmatic role for studying the diversification of multipotential progenitor cells into distinct cell types. Sympathetic neurons and the endocrine chromaffin cells of the adrenal medulla and extra-adrenal locations are derived from the NC [1]. Both cell types share many characteristics – for example, the synthesizing machinery for noradrenaline (see [2] for a review) – but are very distinct in other aspects. It is widely believed that chromaffin cells and sympathetic neurons develop from the NC via a common sympathaodrenal (SA) progenitor, which has the capacity to give rise to both sympathetic neurons and chromaffin cells. SA progenitors develop in the trunk region near the dorsal aorta [3-6]. In this location they acquire catecholaminergic neuronal features, and then are supposed to re-migrate to the sites of the secondary sympathetic ganglia and the adrenal gland.
Multi-step approach to microscopic models for frustrated quantum magnets - the case of the natural mineral azurite
Harald Jeschke,Ingo Opahle,Hem Kandpal,Roser Valentí,Hena Das,Tanusri Saha-Dasgupta,Oleg Janson,Helge Rosner,Andreas Brühl,Bernd Wolf,Michael Lang,Johannes Richter,Shijie Hu,Xiaoqun Wang,Robert Peters,Thomas Pruschke,Andreas Honecker
Physics , 2010, DOI: 10.1103/PhysRevLett.106.217201
Abstract: The natural mineral azurite Cu$_3$(CO$_3$)$_2$(OH)$_2$ is a frustrated magnet displaying unusual and controversially discussed magnetic behavior. Motivated by the lack of a unified description for this system, we perform a theoretical study based on density functional theory as well as state-of-the-art numerical many-body calculations. We propose an effective generalized spin-1/2 diamond chain model which provides a consistent description of experiments: low-temperature magnetization, inelastic neutron scattering, nuclear magnetic resonance measurements, magnetic susceptibility as well as new specific heat measurements. With this study we demonstrate that the balanced combination of first principles with powerful many-body methods successfully describes the behavior of this frustrated material.
Antisepsis and genital hygiene in scrotal surgery: liability claims in the event of treatment errors
Brühl, Peter
GMS Krankenhaushygiene Interdisziplin?r , 2007,
Abstract: Systematic observance of infection control principles in surgery, whether conducted on an inpatient or outpatient basis, is an indispensable precondition for quality management. In Germany, the introduction of the Protection against Infection Act (IfSG) on 1 January 2001 represented a milestone for regulation of the framework conditions in outpatient surgery. Once again, infection control issues were the main focus of attention. Section 36(1) IfSG stipulates that infection control policies specify in-house procedures for infection prophylaxis in agreement with quality assurance measures. On 1 January 2004 this was further reinforced, inter alia, by means of a new tripartite contract based on Section 115b of Book 5 of the German Code of Social Law (SGB V). Since experience shows that incidents are more likely to result in liability claims the smaller the operation and the more unexpected the complications from a lay person’s perspective, surgery carried out on patients who spend the night before and after the operation outside the hospital or clinic is becoming a particularly liability-prone area. In the event of a postoperative infection, often involving a protracted hospital stay and in some cases considerable permanent damage, the patient often cites an infection control error. This paper highlights by way of example some liability aspects whose observance as a matter of principle can reduce the liability risk for the physician.
On topological twin buildings and topological split Kac-Moody groups
Tobias Hartnick,Ralf K?hl,Andreas Mars
Mathematics , 2012,
Abstract: We prove that a two-spherical split Kac-Moody group over a local field naturally provides a topological twin building in the sense of Kramer. This existence result and the local-to-global principle for twin building topologies combined with the theory of Moufang foundations as introduced and studied by M\"uhlherr, Ronan, and Tits allows one to immediately obtain a classification of two-spherical split Moufang topological twin buildings whose underlying Coxeter diagram contains no loop and no isolated vertices.
Fractalkine Is Expressed in Early and Advanced Atherosclerotic Lesions and Supports Monocyte Recruitment via CX3CR1
Moritz Stolla, Jaroslav Pelisek, Marie-Luise von Brühl, Andreas Sch?fer, Verena Barocke, Peter Heider, Michael Lorenz, Anca Tirniceriu, Alexander Steinhart, Johann Bauersachs, Paul F. Bray, Steffen Massberg, Christian Schulz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0043572
Abstract: Fractalkine (CX3CL1, FKN) is expressed in the inflamed vascular wall and absence of FKN reduces atherogenesis. Whether FKN is expressed throughout all stages of atherosclerotic disease and whether it directly contributes to monocyte recruitment to atherosclerotic lesions is not known. We collected human atherosclerotic plaque material and blood samples from patients with carotid artery disease undergoing endarterectomy. Plaques were analyzed by immunohistochemistry and qPCR. We found that FKN is expressed at all stages of atherosclerotic lesion formation, and that the number of FKN-expressing cells positively correlates with the number of CX3CR1-positive cells in human carotid artery plaques. In the circulation, soluble FKN levels are significantly elevated in the presence of high-grade (sub-occlusive) stenosis. To determine the role of the FKN-CX3CR1 axis for monocyte adhesion in vivo we then performed intravital videofluorescence microscopy of the carotid artery in ApoE?/? mice. Notably, FKN-CX3CR1 interactions are critical for recruitment of circulating monocytes to the injured atherosclerotic vascular wall. Thus, this chemokine dyad could represent an attractive target for anti-atherosclerotic strategies.
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