OPUS 4 | Search

Visual working memory contents bias ambiguous structure from motion perception (2013)

Lisa Scocchia Matteo Valsecchi Karl R. Gegenfurtner Jochen Triesch

The way we perceive the visual world depends crucially on the state of the observer. In the present study we show that what we are holding in working memory (WM) can bias the way we perceive ambiguous structure from motion stimuli. Holding in memory the percept of an unambiguously rotating sphere influenced the perceived direction of motion of an ambiguously rotating sphere presented shortly thereafter. In particular, we found a systematic difference between congruent dominance periods where the perceived direction of the ambiguous stimulus corresponded to the direction of the unambiguous one and incongruent dominance periods. Congruent dominance periods were more frequent when participants memorized the speed of the unambiguous sphere for delayed discrimination than when they performed an immediate judgment on a change in its speed. The analysis of dominance time-course showed that a sustained tendency to perceive the same direction of motion as the prior stimulus emerged only in the WM condition, whereas in the attention condition perceptual dominance dropped to chance levels at the end of the trial. The results are explained in terms of a direct involvement of early visual areas in the active representation of visual motion in WM.

Stimulation of TRPV1 by Green Laser Light (2012)

Quanbao Gu Lina Wang Fang Huang Wolfgang Schwarz

Low-level laser irradiation of visible light had been introduced as a medical treatment already more than 40 years ago, but its medical application still remains controversial. Laser stimulation of acupuncture points has also been introduced, and mast-cells degranulation has been suggested. Activation of TRPV ion channels may be involved in the degranulation. Here, we investigated whether TRPV1 could serve as candidate for laser-induced mast cell activation. Activation of TRPV1 by capsaicin resulted in degranulation. To investigate the effect of laser irradiation on TRPV1, we used the Xenopus oocyte as expression and model system. We show that TRPV1 can functionally be expressed in the oocyte by (a) activation by capsaicin (K 1/2 = 1.1 μM), (b) activation by temperatures exceeding 42°C, (c) activation by reduced pH (from 7.4 to 6.2), and (d) inhibition by ruthenium red. Red (637 nm) as well as blue (406 nm) light neither affected membrane currents in oocytes nor did it modulate capsaicin-induced current. In contrast, green laser light (532 nm) produced power-dependent activation of TRPV1. In conclusion, we could show that green light is effective at the cellular level to activate TRPV1. To which extend green light is of medical relevance needs further investigation.

Inhibition of Activity of GABA Transporter GAT1 by δ-Opioid Receptor (2012)

Lu Pu Nanjie Xu Peng Xia Quanbao Gu Shuanglai Ren Thomas Fucke Gang Pei Wolfgang Schwarz

Analgesia is a well-documented effect of acupuncture. A critical role in pain sensation plays the nervous system, including the GABAergic system and opioid receptor (OR) activation. Here we investigated regulation of GABA transporter GAT1 by δOR in rats and in Xenopus oocytes. Synaptosomes of brain from rats chronically exposed to opiates exhibited reduced GABA uptake, indicating that GABA transport might be regulated by opioid receptors. For further investigation we have expressed GAT1 of mouse brain together with mouse δOR and μOR in Xenopus oocytes. The function of GAT1 was analyzed in terms of Na(+)-dependent [(3)H]GABA uptake as well as GAT1-mediated currents. Coexpression of δOR led to reduced number of fully functional GAT1 transporters, reduced substrate translocation, and GAT1-mediated current. Activation of δOR further reduced the rate of GABA uptake as well as GAT1-mediated current. Coexpression of μOR, as well as μOR activation, affected neither the number of transporters, nor rate of GABA uptake, nor GAT1-mediated current. Inhibition of GAT1-mediated current by activation of δOR was confirmed in whole-cell patch-clamp experiments on rat brain slices of periaqueductal gray. We conclude that inhibition of GAT1 function will strengthen the inhibitory action of the GABAergic system and hence may contribute to acupuncture-induced analgesia.

Ion stopping in dense plasma target for high energy density physics (2010)

Claude Deutsch Gilles Maynard Marin Chabot Daniel Gardes Serge Della-Negra René Bimbot Marie-France Rivet Claude Fleurier Christophe Couillaud Dieter H. H. Hoffmann H Wahl Karin Weyrich Olga N. Rosmej Naeem Ahmad Tahir Joachim Jacoby Masao Ogawa Yoshiyuki Oguri Jun Hasegawa Boris Y. Sharkov Alexey A. Golubev Alexander Fertman Vladimir E. Fortov Victor Mintsev

The basic physics of nonrelativistic and electromagnetic ion stopping in hot and ionized plasma targets is thoroughly updated. Corresponding projectile-target interactions involve enhanced projectile ionization and coupling with target free electrons leading to significantly larger energy losses in hot targets when contrasted to their cold homologues. Standard stoppping formalism is framed around the most economical extrapolation of high velocity stopping in cold matter. Further elaborations pay attention to target electron coupling and nonlinearities due to enhanced projectile charge state, as well. Scaling rules are then used to optimize the enhanced stopping of MeV/amu ions in plasmas with electron linear densities nel ~ 10 18 -10 20 cm -2 . The synchronous firing of dense and strongly ionized plasmas with the time structure of bunched and energetic multicharged ion beam then allow to probe, for the first time, the long searched enhanced plasma stopping and projectile charge at target exit. Laser ablated plasmas (SPQR1) and dense linear plasma columns (SPQR2) show up as targets of choice in providing accurate and on line measurements of plasma parameters. Corresponding stopping results are of a central significance in asserting the validity of intense ion beam scenarios for driving thermonuclear pellets. Other applications of note feature thorium induced fission, novel ion sources and specific material processing through low energy ion beams. Last but not least, the given ion beam-plasma target interaction physics is likely to pave a way to the production and diagnostics of warm dense matter (WDM).

Meteorologische Untersuchungen in Osnabrück 1875 - 1983 : mit 9 Tabellen (1986)

Johannes Niemann Günter Schmidt

Im Jahre 1871 wurde durch den Naturwissenschaftlichen Verein Osnabrück (gegründet 1870) eine meteorologische Station eingerichtet. Sie hatte ihren Standort am Sommerhaus des damaligen Obergerichtsrats JOHANN-VOLLRATH KETTLER,Osnabrück, Ziegelstraße 7. KETTLER hat 1872 im 1. Jahresbericht des . Naturwissenschaftlichen Vereins über die "Entstehung, Einrichtung und die ersten Ergebnisse" berichtet. Dieser Bericht ist hier wiedergegeben, legt er uns dar, daß alle Messungen exakt und gewissenhaft durchgeführt wurden.

Radiation-induced nanostructures: Formation processes and applications (2012)

Michael Huth

Spontaneous dissociation of Co2(CO)8 and autocatalytic growth of Co on SiO2: A combined experimental and theoretical investigation (2012)

Kaliappan Muthukumar Harald O. Jeschke Roser Valentí Evgeniya Begun Johannes Schwenk Fabrizio Porrati Michael Huth

We present experimental results and theoretical simulations of the adsorption behavior of the metal–organic precursor Co2(CO)8 on SiO2 surfaces after application of two different pretreatment steps, namely by air plasma cleaning or a focused electron beam pre-irradiation. We observe a spontaneous dissociation of the precursor molecules as well as autodeposition of cobalt on the pretreated SiO2 surfaces. We also find that the differences in metal content and relative stability of these deposits depend on the pretreatment conditions of the substrate. Transport measurements of these deposits are also presented. We are led to assume that the degree of passivation of the SiO2 surface by hydroxyl groups is an important controlling factor in the dissociation process. Our calculations of various slab settings, using dispersion-corrected density functional theory, support this assumption. We observe physisorption of the precursor molecule on a fully hydroxylated SiO2 surface (untreated surface) and chemisorption on a partially hydroxylated SiO2 surface (pretreated surface) with a spontaneous dissociation of the precursor molecule. In view of these calculations, we discuss the origin of this dissociation and the subsequent autocatalysis.

Nanolesions induced by heavy ions in human tissues: experimental and theoretical studies (2012)

Marcus Bleicher Lucas Burigo Marco Durante Maren Herrlitz Michael Krämer Igor Mishustin Iris Müller Francesco Natale Igor Pshenichnov Stefan Schramm Gisela Taucher-Scholz Cathrin Wälzlein

The biological effects of energetic heavy ions are attracting increasing interest for their applications in cancer therapy and protection against space radiation. The cascade of events leading to cell death or late effects starts from stochastic energy deposition on the nanometer scale and the corresponding lesions in biological molecules, primarily DNA. We have developed experimental techniques to visualize DNA nanolesions induced by heavy ions. Nanolesions appear in cells as “streaks” which can be visualized by using different DNA repair markers. We have studied the kinetics of repair of these “streaks” also with respect to the chromatin conformation. Initial steps in the modeling of the energy deposition patterns at the micrometer and nanometer scale were made with MCHIT and TRAX models, respectively.

Study of exclusive one-pion and one-eta production using hadron and dielectron channels in pp reactions at kinetic beam energies of 1.25 GeV and 2.2 GeV with HADES (2012)

Geydar Agakishiev Alvarez-Pol Balanda Bassini Michael Böhmer Bokemeyer Boyard Cabanelas Chernenko Christ Destefanis Dohrmann Dybczak Eberl Laura Fabbietti Oleg Fateev Finocchiaro Jürgen Friese Ingo Fröhlich Tetyana Galatyuk Juan A. Garzón Roman Gernhäuser Camilla Gilardi Marina Golubeva Diego González-Dıaz Fedor Guber Gumberidze Hennino Holzmann Holzmann Ierusalimov Iori Alexander Ivashkin Martin Jurkovic Kämpfer Kanaki Tatiana Karavicheva Ilse Koenig Wolfgang Koenig Burkhard W. Kolb Kotte Kozuch Krizek Wolfgang Kühn Andrej Kugler Alexei Kurepin S Lang Kirill Lapidus T. Liu Ludwig Maier Jochen Markert Volker Metag Beata Michalska Emilie Morinière Jehad Mousa Mathias Münch Christian Münch Naumann Jacek Tomasz Otwinowski Yvonne C. Pachmayer Vladimir Pechenov Olga Pechenova Tiago Pérez Cavalcanti Jerzy Pietraszko Vladimir Pospısil Witold Przygoda Béatrice Ramstein Andrey Reshetin M. Roy-Stephan Anar Rustamov Alexander Sadovsky Benjamin Sailer Piotr Salabura M. Sánchez Alexander Schmah Erwin Schwab Yuri Sobolev Stefano Spataro Björn Spruck Herbert Ströbele Joachim Stroth Christian Sturm Attilio Tarantola Khaled Teilab Pavel Tlusty Alberica Toia Michael Traxler Radoslaw Trebacz Haralabos Tsertos Vladimir Wagner Marcin Wisniowski Tomasz Wojcik Jörn Wüstenfeld Sergey Yurevich Yuri Zanevsky Peter Zumbruch

We present measurements of exclusive ensuremathπ+,0 and η production in pp reactions at 1.25GeV and 2.2GeV beam kinetic energy in hadron and dielectron channels. In the case of π+ and π0 , high-statistics invariant-mass and angular distributions are obtained within the HADES acceptance as well as acceptance-corrected distributions, which are compared to a resonance model. The sensitivity of the data to the yield and production angular distribution of Δ (1232) and higher-lying baryon resonances is shown, and an improved parameterization is proposed. The extracted cross-sections are of special interest in the case of pp → pp η , since controversial data exist at 2.0GeV; we find \ensuremathσ=0.142±0.022 mb. Using the dielectron channels, the π0 and η Dalitz decay signals are reconstructed with yields fully consistent with the hadronic channels. The electron invariant masses and acceptance-corrected helicity angle distributions are found in good agreement with model predictions.

Dissipative hydrodynamics for multi-component systems (2012)

Andrej El Ioannis Bouras Christian Wesp Zhe Xu Carsten Greiner

Second-order dissipative hydrodynamic equations for each component of a multi-component system are derived using the entropy principle. Comparison of the solutions with kinetic transport results demonstrates validity of the obtained equations. We demonstrate how the shear viscosity of the total system can be calculated in terms of the involved cross-sections and partial densities. The presence of the inter-species interactions leads to a characteristic time dependence of the shear viscosity of the mixture, which also means that the shear viscosity of a mixture cannot be calculated using the Green-Kubo formalism the way it has been done recently. This finding is of interest for understanding of the shear viscosity of a quark-gluon plasma extracted from comparisons of hydrodynamic simulations with experimental results from RHIC and LHC.

Refine

Author

Year of publication

Document Type

Language

Has Fulltext

Keywords

Institute

433 search hits