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Institution

Vienna University of Technology

EducationVienna, Austria
About: Vienna University of Technology is a education organization based out in Vienna, Austria. It is known for research contribution in the topics: Laser & Cloud computing. The organization has 16723 authors who have published 49341 publications receiving 1302168 citations.


Papers
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Journal ArticleDOI
TL;DR: In this paper, a high-level possible approach for fusing the individual satellite data sets is presented, where the best possible approach is to merge Level 2 soil moisture data derived from different satellite data records.
Abstract: Soil moisture was recently included in the list of Essential Climate Variables (ECVs) that are deemed essential for IPCC (Intergovernmental Panel on Climate Change) and UNFCCC (United Nations Framework Convention on Climate Change) needs and considered feasible for global observation. ECVs data records should be as long, complete and consistent as possible, and in the case of soil moisture this means that the data record shall be based on multiple data sources, including but not limited to active (scatterometer) and passive (radiometer) microwave observations acquired preferably in the low-frequency microwave range. Among the list of sensors that can be used for this task are the C-band scatterometers on board of the ERS and METOP satellites and the multi-frequency radiometers SMMR, SSM/I, TMI, AMSR-E, and Windsat. Together, these sensors already cover a time period of more than 30 years and the question is how can observations acquired by these sensors be merged to create one consistent data record? This paper discusses on a high-level possible approaches for fusing the individual satellite data. It is argued that the best possible approach for the fusion of the different satellite data sets is to merge Level 2 soil moisture data derived from the individual satellite data records. This approach has already been demonstrated within the WACMOS project (http://wacmos.itc.nl/) funded by European Space Agency (ESA) and will be further improved within the Climate Change Initiative (CCI) programme of ESA (http://www.esa-cci.org/).

308 citations

Journal ArticleDOI
25 May 2006-Nature
TL;DR: Measurements of electron energy-loss magnetic chiral dichroism with XMCD spectra obtained from the same specimen are compared to show that chiral atomic transitions in a specimen are accessible with inelastic electron scattering under particular scattering conditions, which could have important consequences for the study of magnetism on the nanometre and subnanometre scales.
Abstract: The electron microscope, already a powerful research instrument, could become even more powerful following the discovery that magnetic circular dichroism can be detected with a conventional transmission electron microscope. Materials display magnetic circular dichroism if the absorption of left and right circularly polarized light differs in the presence of an applied magnetic field. Application of this effect using synchrotron X-ray photons is a powerful tool for the investigation of magnetic phenomena. The new technique — EMCD or energy loss magnetic chiral dichroism — exploits the similarities between X-ray absorption and inelastic electron scattering to give a TEM capabilities normally associated with expensive synchrotrons. EMCD could be useful in many fields including spintronics and nanomagnetism. Comparison of measurements of electron energy-loss magnetic chiral dichroism with X-ray magnetic circular dichroism spectra obtained from the same specimen, together with theoretical calculations, show that chiral atomic transitions in a specimen are accessible with inelastic electron scattering under particular scattering conditions. A material is said to exhibit dichroism if its photon absorption spectrum depends on the polarization of the incident radiation. In the case of X-ray magnetic circular dichroism (XMCD), the absorption cross-section of a ferromagnet or a paramagnet in a magnetic field changes when the helicity of a circularly polarized photon is reversed relative to the magnetization direction. Although similarities between X-ray absorption and electron energy-loss spectroscopy in a transmission electron microscope (TEM) have long been recognized, it has been assumed that extending such equivalence to circular dichroism would require the electron beam in the TEM to be spin-polarized. Recently, it was argued on theoretical grounds that this assumption is probably wrong1. Here we report the direct experimental detection of magnetic circular dichroism in a TEM. We compare our measurements of electron energy-loss magnetic chiral dichroism (EMCD) with XMCD spectra obtained from the same specimen that, together with theoretical calculations, show that chiral atomic transitions in a specimen are accessible with inelastic electron scattering under particular scattering conditions. This finding could have important consequences for the study of magnetism on the nanometre and subnanometre scales, as EMCD offers the potential for such spatial resolution down to the nanometre scale while providing depth information—in contrast to X-ray methods, which are mainly surface-sensitive.

308 citations

Journal ArticleDOI
TL;DR: The major laccase isoenzyme LAP2 secreted by the white-rot basidiomycete Trametes pubescens in response to high copper concentrations was purified to apparent electrophoretic homogeneity using anion-exchange chromatography and gel filtration.
Abstract: The major laccase isoenzyme LAP2 secreted by the white-rot basidiomycete Trametes pubescens in response to high copper concentrations was purified to apparent electrophoretic homogeneity using anion-exchange chromatography and gel filtration. The monomeric protein has a molecular mass of 65 kDa, of which 18% is glycosylation, and a pI value of 2·6. The pH optima of the laccase depend on the substrates oxidized and show bell-shaped pH activity profiles with an optimum of 3–4·5 for phenolic substrates such as 2,6-dimethoxyphenol or syringaldazine, while the non-phenolic substrates ABTS [2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)] and ferrocyanide show a monotonic pH profile with a rate increasing with decreasing pH. The catalytic efficiencies k cat/K m determined for some of its substrates were 48×106, 47×106, 20×106 and 7×106 M−1 s−1 for ABTS, syringaldazine, ferrocyanide and oxygen, respectively. Furthermore, the gene lap2 encoding the purified laccase was cloned and its nucleotide sequence determined. The gene consists of 1997 bp, with the coding sequence interrupted by eight introns and flanked by an upstream region in which putative CAAT, TATA, MRE and CreA consensus sequences were identified. Based on Northern analysis containing total RNA from both induced and uninduced cultures, expression of lap2 is highly induced by copper, which is also corroborated by an increase in laccase activity in response to copper. A stimulating effect of various other heavy metal ions on laccase synthesis was also observed. In addition to induction, a second regulatory mechanism seems to be repression of lap2 transcription by glucose.

308 citations

Journal ArticleDOI
TL;DR: A survey of the fundamental physical quantities for the electron-solid interaction is presented and sources for these quantities in the literature as well as semi-empirical formulae are given as discussed by the authors.
Abstract: The influence of electron transport on the signal generation process in electron beam techniques is reviewed. A survey of the fundamental physical quantities for the electron–solid interaction is presented and sources for these quantities in the literature as well as semi-empirical formulae are given. The theoretical approaches used to describe multiple scattering in solids are outlined. These include the partial intensity approach and the continuous slowing down approximation to describe multiple energy losses and the transport approximation to tackle multiple deflections. A detailed description of the Monte Carlo technique is presented because this constitutes an effective means to study transport processes. The different theoretical approaches are illustrated in a survey of applications. These include: quantitative description of the surface sensitivity in Auger and photoelectron spectroscopy; line shape analysis of electron spectra; extracting information on the compositional depth profile from the combined energy/angular distribution in an electron spectrum; quasi-elastic electron reflection; inelastic electron backscattering; depth distribution of production of x-rays caused by electron bombardment; and the surface sensitivity in total electron yield electron spectroscopy. These applications demonstrate that the outlined approaches have a broad field of application, not only for electrons with energies ranging from thermal to the relativistic energy range, but also for other microbeam analysis techniques. Copyright © 2001 John Wiley & Sons, Ltd.

308 citations

Journal ArticleDOI
TL;DR: In this article, the structural, cohesive, and electronic properties of various polymorphic forms of carbon and boron nitride have been analyzed using a variational approach to the solution of the Kohn-Sham equations.
Abstract: We present ab initio calculations of the structural, cohesive, and electronic properties of various polymorphic forms of carbon and boron nitride. Our calculations are based on ultrasoft pseudopotentials and a variational approach to the solution of the Kohn-Sham equations. Optimization of the atomic geometries is performed using total energy calculations and by minimizing the energy via a quasi-Newton quench using the Hellmann-Feynman forces. Special attention is devoted to the convergence of the results with respect to the plane-wave basis. The entire set of structural energy differences calculated in our work is in good agreement with the most accurate results obtained using a variety of different techniques---our results represent a consistent set of data based all on the same potential. We show that the use of ultrasoft potentials allows one to achieve accurate results with low cutoff energies (and hence small basis sets).

308 citations


Authors

Showing all 16934 results

NameH-indexPapersCitations
Krzysztof Matyjaszewski1691431128585
Wolfgang Wagner1562342123391
Marco Zanetti1451439104610
Sridhara Dasu1401675103185
Duncan Carlsmith1381660103642
Ulrich Heintz136168899829
Matthew Herndon133173297466
Frank Würthwein133158494613
Alain Hervé132127987763
Manfred Jeitler132127889645
David Taylor131246993220
Roberto Covarelli131151689981
Patricia McBride129123081787
David Smith1292184100917
Lindsey Gray129117081317
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
2023171
2022379
20212,527
20202,811
20192,846
20182,650