Waveguide properties of single subwavelength holes demonstrated with radially and azimuthally polarized light

We investigate the transmission of focused beams through single subwavelength holes in a silver film. We use radially and azimuthally polarized light, respectively, to excite higher order waveguide modes as well as to match the radial symmetry of the aperture geometry. Remarkably, the transmission properties can be described by a classical waveguide model even for thicknesses of the silver film as thin as a quarter of a wavelength

German Survey on Volunteering - Deutscher Freiwilligensurvey (FWS) 2014: survey instrument - English version

The instrument for the telephone survey of the German Survey on Volunteering 2014 was developed by the German Centre of Gerontology. This documentation contains the English version of the questions, the answer categories, the programming instructions and the filter paths (see Table I for the columns structure of the instrument). Questions are documented according to the labels of the variables in the Scientific Use Files (DOI: 10.5156/FWS.2014.M.001). The survey was conducted in six languages: German, Russian, Turkish, Polish, Arabic and English. This document reproduces the English instrument. Question and answers were translated for use in the telephone survey by infas Institute for Applied Social Sciences. Filters, interviewer instructions and all other information were translated at the DZA for documentation purposes. Interviews were conducted by bilingual interviewer

Decoding Cytoskeleton-Anchored and Non-Anchored Receptors from Single-Cell Adhesion Force Data

AbstractComplementary to parameters established for cell-adhesion force curve analysis, we evaluated the slope before a force step together with the distance from the surface at which the step occurs and visualized the result in a two-dimensional density plot. This new tool allows detachment steps of long membrane tethers to be distinguished from shorter jumplike force steps, which are typical for cytoskeleton-anchored bonds. A prostate cancer cell line (PC3) immobilized on an atomic-force-microscopy sensor interacted with three different substrates: collagen-I (Col-I), bovine serum albumin, and a monolayer of bone marrow-derived stem cells (SCP1). To address PC3 cells’ predominant Col-I binding molecules, an antibody-blocking β1-integrin was used. Untreated PC3 cells on Col-I or SCP1 cells, which express Col-I, predominantly showed jumps in their force curves, while PC3 cells on bovine-serum-albumin- and antibody-treated PC3 cells showed long membrane tethers. The probability density plots thus revealed that β1-integrin-specific interactions are predominately anchored to the cytoskeleton, while the nonspecific interactions are mainly membrane-anchored. Experiments with latrunculin-A-treated PC3 cells corroborated these observations. The plots thus reveal details of the anchoring of bonds to the cell and provide a better understanding of receptor-ligand interactions

Interaction-induced delocalization of two particles in a random potential: Scaling properties

The localization length $\xi_2$ for coherent propagation of two interacting particles in a random potential is studied using a novel and efficient numerical method. We find that the enhancement of $\xi_2$ over the one-particle localization length $\xi_1$ satisfies the scaling relation $\xi_2/\xi_1=f(u/\Delta_\xi)$, where $u$ is the interaction strength and $\Delta_{\xi}$ the level spacing of a wire of length $\xi_1$. The scaling function $f$ is linear over the investigated parameter range. This implies that $\xi_2$ increases faster with $u$ than previously predicted. We also study a novel mapping of the problem to a banded-random-matrix model.Comment: 5 pages and two figures in a uuencoded, compressed tar file; uses revtex and psfig.sty (included); substantial revision of a previous version of the paper including newly discovered scaling behavio

Advancing multimer analysis of von Willebrand factor by single-molecule AFM imaging

The formation of hemostatic plugs at sites of vascular injury crucially involves the multimeric glycoprotein von Willebrand factor (VWF). VWF multimers are linear chains of N-terminally linked dimers. The latter are formed from monomers via formation of the C-terminal disulfide bonds Cys2771-Cys2773', Cys2773-Cys2771', and Cys2811-Cys2811'. Mutations in VWF that impair multimerization can lead to subtype 2A of the bleeding disorder von Willebrand Disease (VWD). Commonly, the multimer size distribution of VWF is assessed by electrophoretic multimer analysis. Here, we present atomic force microscopy (AFM) imaging as a method to determine the size distribution of VWF variants by direct visualization at the single-molecule level. We first validated our approach by investigating recombinant wildtype VWF and a previously studied mutant (p. Cys1099Tyr) that impairs N-terminal multimerization. We obtained excellent quantitative agreement with results from earlier studies and with electrophoretic multimer analysis. We then imaged specific mutants that are known to exhibit disturbed C-terminal dimerization. For the mutants p. Cys2771Arg and p. Cys2773Arg, we found the majority of monomers (87 +/- 5% and 73 +/- 4%, respectively) not to be C-terminally dimerized. While these results confirm that Cys2771 and Cys2773 are crucial for dimerization, they additionally provide quantitative information on the mutants' different abilities to form alternative C-terminal disulfides for residual dimerization. We further mutated Cys2811 to Ala and found that only 23 +/- 3% of monomers are not C-terminally dimerized, indicating that Cys2811 is structurally less important for dimerization. Furthermore, for mutants p. Cys2771Arg, p. Cys2773Arg, and p. Cys2811Ala we found 'even-numbered' non-native multimers, i.e. multimers with monomers attached on both termini;a multimer species that cannot be distinguished from native multimers by conventional multimer analysis. Summarizing, we demonstrate that AFM imaging can provide unique insights into VWF processing defects at the single-molecule level that cannot be gained from established methods of multimer analysis

Exponential Size Distribution of von Willebrand Factor

AbstractVon Willebrand Factor (VWF) is a multimeric protein crucial for hemostasis. Under shear flow, it acts as a mechanosensor responding with a size-dependent globule-stretch transition to increasing shear rates. Here, we quantify for the first time, to our knowledge, the size distribution of recombinant VWF and VWF-eGFP using a multilateral approach that involves quantitative gel analysis, fluorescence correlation spectroscopy, and total internal reflection fluorescence microscopy. We find an exponentially decaying size distribution of multimers for recombinant VWF as well as for VWF derived from blood samples in accordance with the notion of a step-growth polymerization process during VWF biosynthesis. The distribution is solely described by the extent of polymerization, which was found to be reduced in the case of the pathologically relevant mutant VWF-IIC. The VWF-specific protease ADAMTS13 systematically shifts the VWF size distribution toward smaller sizes. This dynamic evolution is monitored using fluorescence correlation spectroscopy and compared to a computer simulation of a random cleavage process relating ADAMTS13 concentration to the degree of VWF breakdown. Quantitative assessment of VWF size distribution in terms of an exponential might prove to be useful both as a valuable biophysical characterization and as a possible disease indicator for clinical applications

Der Deutsche Freiwilligensurvey 2009, 2004 und 1999: Kurzbeschreibung der Scientific Use Files, Versionen 3.2; SUF FWS 2009, 3.2, SUF FWS 2004, 3.2 und SUF FWS 1999, 3.2

Der Deutsche Freiwilligensurvey (FWS) ist eine repräsentative Befragung zum freiwilligen Engagement in Deutschland, die sich an Personen ab 14 Jahren richtet. Freiwillige Tätigkeiten und die Bereitschaft zum Engagement werden in telefonischen Interviews erhoben und können nach Bevölkerungsgruppen und Landes-teilen dargestellt werden. Außerdem können die Engagierten und Personen, die sich nicht bzw. nicht mehr engagieren, beschrieben werden. Der Freiwilligensurvey ist damit die wesentliche Grundlage der Sozialberichterstattung zum freiwilligen Engagement und wird aus Mitteln des Bundesministeriums für Familie, Senio-ren, Frauen und Jugend (BMFSFJ) gefördert. Die Daten des Freiwilligensurveys wurden in den Jahren 1999, 2004, 2009 und 20141 erhoben. In jeder Welle wurde eine unabhängige Stichprobe gezogen, so dass es sich um vier Querschnittsdatensätze handelt. Bisher wurden die Erhebungen von TNS Infratest Sozialforschung (1999 Infratest Burke) geleitet und durchgeführt. Seit Ende 2011 liegt die wissenschaftliche Leitung beim Deutschen Zentrum für Altersfragen (DZA). Die Datenerhebung der vierten Welle wurde von infas Institut für angewandte Sozialwissenschaft im Jahr 2014 durchgeführt. Die Datensätze der Wellen 1999, 2004 und 2009, wurden vom DZA als Scientic Use Files (SUF) aufbereitet und stehen im Forschungsdatenzentrum (FDZ-DZA) zur Verfügung. Der SUF FWS 2009, SUF FWS 2004 sowie der SUF FWS 1999 werden im FDZ-DZA2 als Version 3.2 herausgegeben, um Verwechslungen mit Vorgängerversionen zu vermeiden. Die vorliegende Kurzbeschreibung gibt eine Übersicht über diese drei Datensätze

The effect of the pro-inflammatory cytokine tumor necrosis factor-alpha on human joint capsule myofibroblasts

Introduction: Previous studies have shown that the number of myoblastically differentiated fibroblasts known as myofibroblasts (MFs) is significantly increased in stiff joint capsules, indicating their crucial role in the pathogenesis of post-traumatic joint stiffness. Although the mode of MFs' function has been well defined for different diseases associated with tissue fibrosis, the underlying mechanisms of their regulation in the pathogenesis of post-traumatic joint capsule contracture are largely unknown. Methods: In this study, we examined the impact of the pro-inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha) on cellular functions of human joint capsule MFs. MFs were challenged with different concentrations of TNF-alpha with or without both its specifically inactivating antibody infliximab (IFX) and cyclooxygenase-2 (COX2) inhibitor diclofenac. Cell proliferation, gene expression of both alpha-smooth muscle actin (alpha-SMA) and collagen type I, the synthesis of prostaglandin derivates E(2), F(1A), and F(2A), as well as the ability to contract the extracellular matrix were assayed in monolayers and in a three-dimensional collagen gel contraction model. The a-SMA and COX2 protein expressions were evaluated by immunofluorescence staining and Western blot analysis. Results: The results indicate that TNF-alpha promotes cell viability and proliferation of MFs, but significantly inhibits the contraction of the extracellular matrix in a dose-dependent manner. This effect was associated with downregulation of a-SMA and collagen type I by TNF-alpha application. Furthermore, we found a significant time-dependent upregulation of prostaglandin E(2) synthesis upon TNF-alpha treatment. The effect of TNF-alpha on COX2-positive MFs could be specifically prevented by IFX and partially reduced by the COX2 inhibitor diclofenac. Conclusions: Our results provide evidence that TNF-alpha specifically modulates the function of MFs through regulation of prostaglandin E(2) synthesis and therefore may play a crucial role in the pathogenesis of joint capsule contractures

Deutscher Freiwilligensurvey 2014: Erhebungsinstrument

Das hier dokumentierte Instrument der telefonischen Erhebung des Deutschen Freiwilligensurveys 2014 wurde durch das Deutsche Zentrum für Altersfragen entwickelt. In dieser Dokumentation werden die Fragen, die Antwortkategorien, die Programmieranweisungen und die Filterführung lesefreundlich dargestellt (siehe Übersicht I zum Aufbau des Instruments). Die Fragen sind entsprechend der Variablenlabel im Scientific Use File (DOI: 10.5156/FWS.2014.M.001) dokumentiert