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Search Results: 1 - 10 of 26436 matches for " Alexander St?hr "
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Mich interessierten kostengünstige Alternativen zu Citavi“: über den Fortbildungsworkshop Literaturverwaltung im Fokus“ im Rahmen der AGMB-Tagung 2012 [“I was interested in competitive alternatives to Citavi”: About the workshop “Reference Management at the focal point”, held at the AGMB-Conference 2012]
Sthr, Matti
GMS Medizin-Bibliothek-Information , 2012, DOI: 10.3205/mbi000261
Abstract: [english] A two hour taking workshop on reference management, covering several software types, library services and more were part of the program at the AGMB-Conference 2012 in Aachen. This article is dealing less with the offered workshop contents itself. Moreover the attendees’ perspective is described. With an email-based survey the following main question wanted to be answered: Was the workshop fruitful for the participants? [german] Zum Programm der AGMB-Tagung 2012 in Aachen geh rte u.a. der zweistündige Fortbildungsworkshop Literaturverwaltung im Fokus – Softwaretypen, bibliothekarische Services und mehr“. Im Beitrag werden weniger die referierten Workshopinhalte beschrieben, als vielmehr die Perspektive der Teilnehmerinnen und Teilnehmer anhand einer eMail-basierten Umfrage vorgestellt. Die Kernfrage lautet hierbei: War der Workshop für sie gewinnbringend?
Literaturpropaganda als Bibliothekskultur. Ideologie und Wirklichkeit im ffentlichen Bibliothekswesen der frühen DDR
Matti Sthr
Libreas : Library Ideas , 2006,
Abstract:
Population Inversion in Monolayer and Bilayer Graphene
Isabella Gierz,Matteo Mitrano,Jesse C. Petersen,Cephise Cacho,I. C. Edmond Turcu,Emma Springate,Alexander Sthr,Axel K?hler,Ulrich Starke,Andrea Cavalleri
Physics , 2014, DOI: 10.1088/0953-8984/27/16/164204
Abstract: The recent demonstration of saturable absorption and negative optical conductivity in the Terahertz range in graphene has opened up new opportunities for optoelectronic applications based on this and other low dimensional materials. Recently, population inversion across the Dirac point has been observed directly by time- and angle-resolved photoemission spectroscopy (tr-ARPES), revealing a relaxation time of only ~ 130 femtoseconds. This severely limits the applicability of single layer graphene to, for example, Terahertz light amplification. Here we use tr-ARPES to demonstrate long-lived population inversion in bilayer graphene. The effect is attributed to the small band gap found in this compound. We propose a microscopic model for these observations and speculate that an enhancement of both the pump photon energy and the pump fluence may further increase this lifetime.
Snapshots of non-equilibrium Dirac carrier distributions in graphene
Isabella Gierz,Jesse C. Petersen,Matteo Mitrano,Cephise Cacho,Edmond Turcu,Emma Springate,Alexander Sthr,Axel K?hler,Ulrich Starke,Andrea Cavalleri
Physics , 2013, DOI: 10.1038/nmat3757
Abstract: The optical properties of graphene are made unique by the linear band structure and the vanishing density of states at the Dirac point. It has been proposed that even in the absence of a semiconducting bandgap, a relaxation bottleneck at the Dirac point may allow for population inversion and lasing at arbitrarily long wavelengths. Furthermore, efficient carrier multiplication by impact ionization has been discussed in the context of light harvesting applications. However, all these effects are difficult to test quantitatively by measuring the transient optical properties alone, as these only indirectly reflect the energy and momentum dependent carrier distributions. Here, we use time- and angle-resolved photoemission spectroscopy with femtosecond extreme ultra-violet (EUV) pulses at 31.5 eV photon energy to directly probe the non-equilibrium response of Dirac electrons near the K-point of the Brillouin zone. In lightly hole-doped epitaxial graphene samples, we explore excitation in the mid- and near-infrared, both below and above the minimum photon energy for direct interband transitions. While excitation in the mid-infrared results only in heating of the equilibrium carrier distribution, interband excitations give rise to population inversion, suggesting that terahertz lasing may be possible. However, in neither excitation regime do we find indication for carrier multiplication, questioning the applicability of graphene for light harvesting. Time-resolved photoemission spectroscopy in the EUV emerges as the technique of choice to assess the suitability of new materials for optoelectronics, providing quantitatively accurate measurements of non-equilibrium carriers at all energies and wavevectors.
Avian influenza and influenza pandemics
Lazzari Stefano,Sthr Klaus
Bulletin of the World Health Organization , 2004,
Abstract:
Creation of X-Ray Transparency of Matter by Stimulated Elastic Forward Scattering
Joachim Sthr,Andreas Scherz
Physics , 2015, DOI: 10.1103/PhysRevLett.115.107402
Abstract: X-ray absorption by matter has long been described by the famous Beer-Lambert law. Here we show how this fundamental law needs to be modified for high-intensity coherent x-ray pulses, now available at x-ray free electron lasers, due to the onset of stimulated elastic forward scattering. We present an analytical expression for the modified polarization-dependent Beer-Lambert law for the case of resonant core-to-valence electronic transitions and incident transform limited x-ray pulses. Upon transmission through a solid, the absorption and dichroic contrasts are found to vanish with increasing x-ray intensity, with the stimulation threshold lowered by orders of magnitude through a super-radiative coherent effect. Our results have broad implications for the study of matter with x-ray lasers.
Antinociceptive efficacy of lacosamide in the monosodium iodoacetate rat model for osteoarthritis pain
Bettina Beyreuther, No?lle Callizot, Thomas Sthr
Arthritis Research & Therapy , 2007, DOI: 10.1186/ar2121
Abstract: Osteoarthritis is the most common form of joint disease and a leading cause of chronic pain and disability [1]. Its prevalence after age 65 is about 60% in men and 70% in women [2]. Osteoarthritis is primarily noted in hands, knees, hips, and spine and involves degeneration of articular cartilage as well as changes to the subchondral bone, variable degrees of mild synovitis and thickening of the joint capsule. Characteristic osteoarthritis features are seen in X-ray examination of joints. However, the pathophysiology behind the structural changes associated with this disease is complex and the link to pain is poorly understood [3].Pain is the predominant clinical feature, yet therapy is ineffective for many patients. Drugs that modify disease progression represent the ultimate goal of treatment but are not clinically available. Treatment is currently based on symptomatic relief of pain and inflammation associated with osteoarthritis to increase joint function. Non-steroidal anti-inflammatory drugs (NSAIDs) and acetaminophen are the most widely used drugs but cyclooxygenase 2 inhibitors, steroids, and opiates are prescribed as well [4].Several arthritis animal models have been established [5]. One of the best characterized rat models for analyzing properties of drugs on the pathology of osteoarthritis is the injection of the metabolic inhibitor monosodium iodoacetate (MIA) into the joint, which inhibits the activity of glyceraldehyde-3-phosphate dehydrogenase in chondrocytes, resulting in disruption of glycolysis and eventually in cell death [6,7]. The progressive loss of chondrocytes results in histological and morphological changes of the articular cartilage, closely resembling those seen in osteoarthritis patients. However, analysis of pain behavior has only recently been established in the iodoacetate model [8-11]. In a previous study the anticonvulsant gabapentin was able to reduce secondary mechanical allodynia but not hyperalgesia in the iodoacetate rat model
Power, knowledge, and conflict in the shaping of commons governance. The case of EU Baltic fisheries
Tom R. Burns,Christian Sthr
International Journal of the Commons , 2011,
Abstract: This article aims at contributing to governance conceptualization and its application to case study analyses. Two of the challenges which the theoretical and empirical work in the article addresses concern the facilitation of comparability of diverse governance cases and a specification of several key mechanisms of governance formation and reform. A proposed model of the architecture of governance systems – their major components and inter-linkages – contributes, as argued and illustrated here, to greater comparability among cases and with the possibility of improved accumulation of knowledge about governance systems. These tools are applied to empirical cases of governance structure and their functioning and reformation. Baltic fisheries, a complex, multi-level case of commons governance, is considered in some detail in order to illustrate and elaborate the key factors of power, knowledge, and conflict in the functioning and transformation of governance systems. In addition to the Baltic fisheries case, we consider briefly for comparative purposes chemicals and gender relations as additional areas of EU governance. The paper is divided into four sections. Section I introduces the basic conceptualization and tools of analysis. Section II presents the case of Baltic fisheries. Section III elaborates the key concepts and tools presented in Section I, in particular considering additional cases of the functioning of governance systems. Section IV is a brief conclusion.
Upper bounds for the dimension of moduli spaces of curves with symmetric Weierstrass semigroups
André Contiero,Karl-Otto Sthr
Mathematics , 2012, DOI: 10.1112/jlms/jdt034
Abstract: We present an explicit method to produce upper bounds for the dimension of the moduli spaces of complete integral Gorenstein curves with prescribed symmetric Weierstrass semigroups.
Investigations of the Compressive Behaviour of Veneer in Thickness Direction
Beate Buchelt,Alexander Pfriem,André Wagenführ
Drvna Industrija , 2012,
Abstract: Compression tests were conducted with veneers in the thickness direction. Thereby differences between the stress-strain curves of veneers and other known stress-strain curves were observed. Based on microscopic studies during the compression, it was possible to describe the deformation behaviour of the veneer, and deviations from known, typical stress-strain curves were substantiated and explained. It was found that a considerable part of the strain occurs by straightening the veneer at a relatively low stress level due to the waved form of veneer sheets and specimens. A distinctive stress plateau has not been established.
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