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Search Results: 1 - 10 of 32094 matches for " Thomas Hofmann "
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Probabilistic Latent Semantic Analysis
Thomas Hofmann
Computer Science , 2013,
Abstract: Probabilistic Latent Semantic Analysis is a novel statistical technique for the analysis of two-mode and co-occurrence data, which has applications in information retrieval and filtering, natural language processing, machine learning from text, and in related areas. Compared to standard Latent Semantic Analysis which stems from linear algebra and performs a Singular Value Decomposition of co-occurrence tables, the proposed method is based on a mixture decomposition derived from a latent class model. This results in a more principled approach which has a solid foundation in statistics. In order to avoid overfitting, we propose a widely applicable generalization of maximum likelihood model fitting by tempered EM. Our approach yields substantial and consistent improvements over Latent Semantic Analysis in a number of experiments.
Health policies in central and South Eastern Europe: challenges and chances
Thomas D. Hofmann
Italian Journal of Public Health , 2009, DOI: 10.2427/5806
Abstract: Background: Fundamental political changes in Central and South Eastern Europe in the aftermath of the fall of the iron curtain enter a new phase after accession of some countries to the EU. Methods: The article reviews and analyses current regional and international developments and factors, which are influential for health policies in the region. Special attention is given to collaboration – both of technical and of political nature – within the region and with international organizations and donors. The response to international health policy frameworks and the impact of international health strategies is being analysed. Results: The results point towards common political and structural features in the countries of the region. Regional networks seem to be a very promising structure for health policy development. Despite the political will, health care reforms still don’t show the expected results. The partnership with the EU is the most influential one. Conclusions: Regional networks need to be transformed into regionally owned structures. It seems to be rucial to tackle informal parallel systems and to increase responsibility for health professionals. The need for eforms and the prospect of neighbouring and joining the EU create a unique momentum to develop own health policies without international interferenc
Aged Garlic Extract and One of the Constituent, (+)-(2S,3R)-Dehydrodiconiferyl Alcohol, Inhibits Alkaline Phosphatase Activity Induced by Inflammation Factors in Human Vascular Smooth Muscle Cells  [PDF]
Takahiro Yamakawa, Toshiaki Matsutomo, Thomas Hofmann, Yukihiro Kodera
Food and Nutrition Sciences (FNS) , 2014, DOI: 10.4236/fns.2014.52023

Previous clinical study showed that aged garlic extract (AGE) has a preventive effect of vascular calcification in patients with coronary artery diseases. It has been reported that vascular smooth muscle cells (VSMC) and inflammatory cells including macrophages and lymphocytes migrate to sub-intimal region where atherosclerotic plaques are formed, and VSMC can differentiate into osteoblast-like cells, which are represented by the induction of alkaline phosphatase (ALP). We found that primary human coronary artery smooth muscle cells (HCASMC) showed the increased ALP activity, when cultured in the medium containing ascorbic acid, β-glycerophosphate, dexamethasone (IM), and supplemented with conditioned medium from macrophages (MCM). Then we tested the effect of AGE subdivided fractions and several compounds found in AGE, and then found that ((+)-(2S,3R)-Dehydrodiconiferyl alcohol, a dilignol compound existed in hydrophobic fraction of AGE, inhibited ALP activity in HCASMC.

Schulische und nicht-schulische Pr diktoren für die Studienplatzzusage an der Universit t Witten / Herdecke - Ergebnisse einer QUEST-Analyse [Academic and non-academic predictors for acceptance to medical studies at Witten/Herdecke University - findings of a QUEST-analysis]
Hofmann, Marzellus,Rieger, Monika A.,Ostermann, Thomas
GMS Zeitschrift für Medizinische Ausbildung , 2007,
Abstract: [english] Aims: Changes within the German Higher Education Framework act increasingly attract notice to the fact that the debate on different methods of selecting students lies in the responsibility of german medical schools. For more than 20 years the University of Witten/Herdecke has adhered to its own concept and procedure relating to its choice of students. Since 2005 this application procedure consists of a written and an oral application phase (assessment center). Within this study a retrospective classification of all applicants in the year 2005 was conducted, with the objective of finding academic and non-academic predictors for acceptance at Witten/Herdecke. Methods: All 172 applicants of the assessment center received a questionnaire asking for: age, gender, high school graduation mark, type of school, main school subjects, intended career, attendance at open house, parent graduation and profession. All duly completed questionnaires were classified according to the QUEST model from the viewpoint of acceptance versus refusal to medical studies at Witten/Herdecke. Outcomes: The QUEST model classifies the items of the questionnaire in sequence of declining power and in coherence to the targeted variable (acceptance). Affiliated with an increased probability of acceptance were: high school mark = 1.3, Steiner and Montessori schools, absence at open house, intended career as researcher and natural/social sciences and languages as main school subjects. Predictor sensitivity was 0.53, specificity reached 0.92. The positive predictive value accounted for 0.77, whereas the negative predictive value was 0.83. Conclusions: The high school graduation mark shows to be of high significance for the admission process at the University of Witten/Herdecke. Furthermore factors such as type of school, intended career and main school subjects play a major role. The high negative predictive value points out that the QUEST analysis is not suitable for replacing the existing admission process, but might be used for pre-selecting candidates. Further studies have to show whether the found effects are specific to the investigated group (applicants 2005) or whether they can be seen as representative for other cohorts of applicants at Witten/Herdecke. [german] Zielsetzung: Die Auseinandersetzung mit unterschiedlichen Verfahren der Studierendenauswahl rückt durch die Novellierung des Hochschulrahmengesetzes zunehmend in den Verantwortungsbereich deutscher Fakult ten. Als private Universit t führt die Universit t Witten/Herdecke (UWH) seit 20 Jahren universit tseigene Auswah
Di-μ-chlorido-bis{[μ-1,8-bis(diisopropylphosphanyl)-9,10-dihydro-9,10-ethanoanthracene-κ2P:P′]-μ-chlorido-μ-methylidene-dipalladium(II)} tetrahydrofuran pentasolvate
Thomas Schnetz,Frank Rominger,Peter Hofmann
Acta Crystallographica Section E , 2010, DOI: 10.1107/s1600536810010263
Abstract: The title compound, [Pd4(CH2)2Cl4(C28H40P2)2]·5C4H8O, possesses a tetranuclear palladium core with four bridging chlorido ligands and two bridging methylene units, as well as two bridging anthracene-based bis-phosphine ligands. This tetranuclear complex can be considered as being composed of two μ-chlorido-bridged LPd2 units. The structural motif of these LPd2 units shows two doubly bridged palladium centers between the P atoms of the bis-phosphine ligand. One of these bridges is a μ-Cl atom, the other a μ-methylene group. The coordination environment around each palladium center is essentially square planar. We ascribe the oxidation state +II to the palladium centers and do not assume Pd—Pd bonds [shortest distances 2.8110 (5) and 2.8109 (6) ]. Co-crystallized with the palladium complex we found five non-coordinating tetrahydrofuran solvent molecules, one of which is disordered over two positions in a 0.429 (9):0.571 (8) ratio.
Preparation of light-atom tips for Scanning Probe Microscopy by explosive delamination
Thomas Hofmann,Joachim Welker,Franz J. Giessibl
Physics , 2010, DOI: 10.1116/1.3294706
Abstract: To obtain maximal resolution in STM and AFM, the size of the protruding tip orbital has to be minimized. Beryllium as tip material is a promising candidate for enhanced resolution because a beryllium atom has just four electrons, leading to a small covalent radius of only 96 pm. Besides that, beryllium is conductive and has a high elastic modulus, which is a necessity for a stable tip apex. However beryllium tips that are prepared ex situ, are covered with a robust oxide layer, which cannot be removed by just heating the tip. Here we present a successful preparation method that combines the heating of the tip by field emission and a mild collision with a clean metal plate. That method yields a clean, oxide-free tip surface as proven by a work function of as deduced from a current-distance curve. Additionally, a STM image of the Si-(111)-(7x7) is presented to prove the single-atom termination of the beryllium tip.
Chemical and Crystallographic Characterization of the Tip Apex in Scanning Probe Microscopy
Thomas Hofmann,Florian Pielmeier,Franz J. Giessibl
Physics , 2013, DOI: 10.1103/PhysRevLett.112.066101
Abstract: The apex atom of a W scanning probe tip reveals a non-spherical charge distribution as probed by a CO molecule bonded to a Cu(111) surface [Welker et al. Science, 336, 444 (2012)]. Three high-symmetry images were observed and related to three low-index crystallographic directions of the W bcc crystal. Open questions remained, however, including the verification that the tip was indeed W-terminated, and whether this method can be easily applied to distinguish other atomic species. In this work, we investigate bulk Cu and Fe tips. In both cases we can associate our data with the fcc (Cu) and bcc (Fe) crystal structures. A model is presented, based on the partial filling of d orbitals, to relate the AFM images to the angular orientation of the tip structure.
Space-Time Galerkin Projection of Electro-Magnetic Fields
Zifu Wang,Thomas Henneron,Heath Hofmann
Physics , 2015,
Abstract: Spatial Galerkin projection transfers fields between different meshes. In the area of finite element analysis of electromagnetic fields, it provides great convenience for remeshing, multi-physics, domain decomposition methods, etc. In this paper, a space-time Galerkin projection is developed in order to transfer fields between different spatial and temporal discretization bases.
Newtonian N-body simulations are compatible with cosmological perturbation theory
Thomas Haugg,Stefan Hofmann,Michael Kopp
Physics , 2012,
Abstract: Contrary to recent claims in the literature, Newtonian N-body simulations of collisionless Dark Matter in a LambdaCDM background are compatible with general relativity and are not invalidated by general relativistic effects at the linear level. This verdict is based on four facts. (1) The system of linearized Einstein equations and conservation laws is well-posed in the gauge invariant formulation and physically meaningful. (2) Comparing general relativity with its Newtonian approximation at a given order in perturbation theory is only meaningful at the level of observables. (3) The dynamics of observables describing a dust fluid in general relativity and its Newtonian approximation agree at the linear level. Any disagreement for observables on the lightcone are well-known, of which the most dominant is gravitational lensing. (4) Large fluctuations in the Hubble parameter contribute significantly only to gravitational lensing effects. Therefore, these fluctuations are not in conflict with Newtonian N-body simulations beyond what has already been carefully taken into account using ray tracing technology.
Exponential Families for Conditional Random Fields
Yasemin Altun,Alex Smola,Thomas Hofmann
Computer Science , 2012,
Abstract: In this paper we de ne conditional random elds in reproducing kernel Hilbert spaces and show connections to Gaussian Process classi cation. More speci cally, we prove decomposition results for undirected graphical models and we give constructions for kernels. Finally we present e cient means of solving the optimization problem using reduced rank decompositions and we show how stationarity can be exploited e ciently in the optimization process.
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