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Search Results: 1 - 10 of 336796 matches for " András Kaiser "
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Symmetry Breaking in the Static Coordinate System of de Sitter Spacetime
András Kaiser,Alan Chodos
Physics , 1995, DOI: 10.1103/PhysRevD.53.787
Abstract: We study symmetry breaking in the static coordinate-system of de Sitter space. This is done with the help of the functional-Schr\"odinger approach used in previous calculations by Ratra [1]. We consider a massless, minimally coupled scalar field as the parameter of a continuous symmetry (the angular component of an O(2) symmetry). Then we study the correlation function of the massless scalar field, to derive the correlation function of the original field, which finally shows the restoration of the continuous symmetry.
Corrosion Behaviour of Aluminium Engine Block in 3.5% NaCl Solution  [PDF]
M. S. Kaiser, Swagata Dutta
Journal of Materials Science and Chemical Engineering (MSCE) , 2014, DOI: 10.4236/msce.2014.210008
Abstract:

In the present work, the corrosion behavior of aluminium alloy engine block in 3.5% NaCl solution was studied. The work was carried out using conventional gravimetric measurements and complemented by scanning electron microscopy (SEM) and X-ray analyzer (EDX) investigations. The results obtained indicate that the main process the alloy undergoes, under the medium of exposure studied, is related to localized corrosion that takes place as a consequence of the process of alkalinization around the cathodic precipitates existing in the alloy. The alloy suffers a process of corrosion localized to the area surrounding the precipitates of the Al (Si, Mg) and Al-Mg, which resulted in hemispherical pits. This identification was confirmed by SEM and EDX analysis. No evidence was found of the formation of crystallographic pitting for exposure times up to 54 days. Gravimetric analysis confirmed that with varying exposure periods the weight loss of the alloy increases and the corrosion rate decreases with time.

Only Slight Impact of Predicted Replicative Capacity for Therapy Response Prediction
Hendrik Weisser,André Altmann,Saleta Sierra,Francesca Incardona,Daniel Struck,Anders S?nnerborg,Rolf Kaiser,Maurizio Zazzi,Monika Tschochner,Hauke Walter,Thomas Lengauer
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0009044
Abstract: Replication capacity (RC) of specific HIV isolates is occasionally blamed for unexpected treatment responses. However, the role of viral RC in response to antiretroviral therapy is not yet fully understood.
Single-particle potential in a chiral approach to nuclear matter including short range NN-terms
S. Fritsch,N. Kaiser
Physics , 2002, DOI: 10.1140/epja/i2002-10149-x
Abstract: We extend a recent chiral approach to nuclear matter of Lutz et al. [Phys. Lett. B474 (2000) 7] by calculating the underlying (complex-valued) single-particle potential U(p,k_f) + i W(p,k_f). The potential for a nucleon at the bottom of the Fermi-sea, U(0,k_{f0})= - 20.0 MeV, comes out as much too weakly attractive in this approach. Even more seriously, the total single-particle energy does not rise monotonically with the nucleon momentum p, implying a negative effective nucleon mass at the Fermi-surface. Also, the imaginary single-particle potential, W(0,k_{f0}) = 51.1 MeV, is too large. More realistic single-particle properties together with a good nuclear matter equation of state can be obtained if the short range contributions of non-pionic origin are treated in mean-field approximation (i.e. if they are not further iterated with 1pi-exchange). We also consider the equation of state of pure neutron matter $bar E_n(k_n)$ and the asymmetry energy A(k_f) in that approach. The downward bending of these quantities above nuclear matter saturation density seems to be a generic feature of perturbative chiral pion-nucleon dynamics.
Chiral approach to nuclear matter: Role of explicit short-range NN-terms
S. Fritsch,N. Kaiser
Physics , 2003, DOI: 10.1140/epja/i2003-10179-x
Abstract: We extend a recent chiral approach to nuclear matter by including the most general (momentum-independent) NN-contact interaction. Iterating this two-parameter contact-vertex with itself and with one-pion exchange the emerging energy per particle exhausts all terms possible up-to-and-including fourth order in the small momentum expansion. The equation of state of pure neutron matter, $\bar E_n(k_n)$, can be reproduced very well up to quite high neutron densities of $\rho_n=0.5\fmd$ by adjusting the strength of a repulsive $nn$-contact interaction. Binding and saturation of isospin-symmetric nuclear matter is a generic feature of our perturbative calculation. Fixing the maximum binding energy per particle to $-\bar E(k_{f0})= 15.3 $MeV we find that any possible equilibrium density $\rho_0$ lies below $\rho_0^{\rm max}=0.191\fmd$. The additional constraint from the neutron matter equation of state leads however to a somewhat too low saturation density of $\rho_0 =0.134 \fmd$. We also investigate the effects of the NN-contact interaction on the complex single-particle potential $U(p,k_f)+i W(p,k_f)$. We find that the effective nucleon mass at the Fermi-surface is bounded from below by $M^*(k_{f0}) \geq 1.4 M$. This property keeps the critical temperature of the liquid-gas phase transition at somewhat too high values $T_c \geq 21 $MeV. The downward bending of the asymmetry energy $A(k_f)$ above nuclear matter saturation density is a generic feature of the approximation to fourth order. Altogether, there is within this complete fourth-order calculation no "magic" set of adjustable short-range parameters with which one could reproduce simultaneously and accurately all semi-empirical properties of nuclear matter.
Detection of a Supervoid Aligned with the Cold Spot of the Cosmic Microwave Background
István Szapudi,András Kovács,Benjamin R. Granett,Zsolt Frei,Joseph Silk,Will Burgett,Shaun Cole,Peter W. Draper,Daniel J. Farrow,Nicholas Kaiser,Eugene A. Magnier,Nigel Metcalfe,Jeffrey S. Morgan,Paul Price,John Tonry,Richard Wainscoat
Physics , 2014, DOI: 10.1093/mnras/stv488
Abstract: We use the WISE-2MASS infrared galaxy catalog matched with Pan-STARRS1 (PS1) galaxies to search for a supervoid in the direction of the Cosmic Microwave Background Cold Spot. Our imaging catalog has median redshift $z\simeq 0.14$, and we obtain photometric redshifts from PS1 optical colours to create a tomographic map of the galaxy distribution. The radial profile centred on the Cold Spot shows a large low density region, extending over 10's of degrees. Motivated by previous Cosmic Microwave Background results, we test for underdensities within two angular radii, $5^\circ$, and $15^\circ$. The counts in photometric redshift bins show significantly low densities at high detection significance, $\gtrsim 5 \sigma$ and $\gtrsim 6 \sigma$, respectively, for the two fiducial radii. The line-of-sight position of the deepest region of the void is $z\simeq 0.15-0.25$. Our data, combined with an earlier measurement by Granett et al. 2010, are consistent with a large $R_{\rm void}=(220 \pm 50) h^{-1}Mpc $ supervoid with $\delta_{m} \simeq -0.14 \pm 0.04$ centered at $z=0.22\pm0.03$. Such a supervoid, constituting at least a $\simeq 3.3\sigma$ fluctuation in a Gaussian distribution of the $\Lambda CDM$ model, is a plausible cause for the Cold Spot.
Supervoid Origin of the Cold Spot in the Cosmic Microwave Background
András Kovács,István Szapudi,Benjamin R. Granett,Zsolt Frei,Joseph Silk,Will Burgett,Shaun Cole,Peter W. Draper,Daniel J. Farrow,Nicholas Kaiser,Eugene A. Magnier,Nigel Metcalfe,Jeffrey S. Morgan,Paul Price,John Tonry,Richard Wainscoat
Physics , 2014,
Abstract: We use a WISE-2MASS-Pan-STARRS1 galaxy catalog to search for a supervoid in the direction of the Cosmic Microwave Background Cold Spot. We obtain photometric redshifts using our multicolor data set to create a tomographic map of the galaxy distribution. The radial density profile centred on the Cold Spot shows a large low density region, extending over 10's of degrees. Motivated by previous Cosmic Microwave Background results, we test for underdensities within two angular radii, $5^\circ$, and $15^\circ$. Our data, combined with an earlier measurement by Granett et al 2010, are consistent with a large $R_{\rm void}=(192 \pm 15)h^{-1} Mpc $ $(2\sigma)$ supervoid with $\delta \simeq -0.13 \pm 0.03$ centered at $z=0.22\pm0.01$. Such a supervoid, constituting a $\sim3.5 \sigma$ fluctuation in the $\Lambda CDM$ model, is a plausible cause for the Cold Spot.
Comparison of Classifier Fusion Methods for Predicting Response to Anti HIV-1 Therapy
André Altmann, Michal Rosen-Zvi, Mattia Prosperi, Ehud Aharoni, Hani Neuvirth, Eugen Schülter, Joachim Büch, Daniel Struck, Yardena Peres, Francesca Incardona, Anders S?nnerborg, Rolf Kaiser, Maurizio Zazzi, Thomas Lengauer
PLOS ONE , 2008, DOI: 10.1371/journal.pone.0003470
Abstract: Background Analysis of the viral genome for drug resistance mutations is state-of-the-art for guiding treatment selection for human immunodeficiency virus type 1 (HIV-1)-infected patients. These mutations alter the structure of viral target proteins and reduce or in the worst case completely inhibit the effect of antiretroviral compounds while maintaining the ability for effective replication. Modern anti-HIV-1 regimens comprise multiple drugs in order to prevent or at least delay the development of resistance mutations. However, commonly used HIV-1 genotype interpretation systems provide only classifications for single drugs. The EuResist initiative has collected data from about 18,500 patients to train three classifiers for predicting response to combination antiretroviral therapy, given the viral genotype and further information. In this work we compare different classifier fusion methods for combining the individual classifiers. Principal Findings The individual classifiers yielded similar performance, and all the combination approaches considered performed equally well. The gain in performance due to combining methods did not reach statistical significance compared to the single best individual classifier on the complete training set. However, on smaller training set sizes (200 to 1,600 instances compared to 2,700) the combination significantly outperformed the individual classifiers (p<0.01; paired one-sided Wilcoxon test). Together with a consistent reduction of the standard deviation compared to the individual prediction engines this shows a more robust behavior of the combined system. Moreover, using the combined system we were able to identify a class of therapy courses that led to a consistent underestimation (about 0.05 AUC) of the system performance. Discovery of these therapy courses is a further hint for the robustness of the combined system. Conclusion The combined EuResist prediction engine is freely available at http://engine.euresist.org.
Antiretroviral Therapy Optimisation without Genotype Resistance Testing: A Perspective on Treatment History Based Models
Mattia C. F. Prosperi,Michal Rosen-Zvi,André Altmann,Maurizio Zazzi,Simona Di Giambenedetto,Rolf Kaiser,Eugen Schülter,Daniel Struck,Peter Sloot,David A. van de Vijver,Anne-Mieke Vandamme,Anders S?nnerborg
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013753
Abstract: Although genotypic resistance testing (GRT) is recommended to guide combination antiretroviral therapy (cART), funding and/or facilities to perform GRT may not be available in low to middle income countries. Since treatment history (TH) impacts response to subsequent therapy, we investigated a set of statistical learning models to optimise cART in the absence of GRT information.
Doppler tecidual como índice prognóstico em longo prazo na disfun??o sistólica do ventrículo esquerdo
Saraiva, Roberto Magalh?es;Rocha, Rita de Cássia Castelli da;Martins, Adriana Ferraz;Duarte, Dario Marins;Peixoto, Renata da Silva;Castro, Simone Henriques de;Gallicchio, Carla Tavares;Araújo, Andréa Lúcia de;Kaiser, Sérgio Emanuel;
Arquivos Brasileiros de Cardiologia , 2008, DOI: 10.1590/S0066-782X2008001400004
Abstract: background: tissue doppler parameters correlate with left ventricular (lv) filling pressure and can be useful as prognostic indexes for patients with heart failure. objective: determine whether tissue doppler parameters can predict events during long term follow-up of outpatients with lv systolic dysfunction. methods: retrospective study with 73 patients (aged 60.9±12.1 years) who underwent doppler echocardiogram between march 2001 and may 2004. the primary endpoint studied was death or hospitalization due to heart failure worsening. results: the mean follow-up period was 1,367±665 days. after logistic stepwise multivariate analysis, including echocardiographic parameters, the ratio of maximal early diastolic filling wave velocity to maximal early diastolic myocardial velocity (e/e` ratio; p=0.0007), and lv ejection fraction (ef; p=0.01) remained significant predictors of the primary outcome. the optimal cutoffs for primary endpoint prediction for e/e' ratio (auc 0.77; p=0.0001) and ef (auc 0.68, p=0.006) were respectively 12.7 and 30%. accordingly, patients with e/e' ratio > 12.7 (hazard ratio=3.8, p =0.001) or ef <30% (hazard ratio=2.3, p=0.03) had a poorer outcome by survival curve analysis. it is noteworthy that 47% of the patients with ef above the optimal cutoff point, but with high e/e' ratio, presented events during follow-up. conclusion: e/e' ratio is an important independent long-term prognostic index of death or hospitalization due to worsening heart failure in outpatients with lv systolic dysfunction. therefore, we recommend the measurement of this variable in the routine evaluation of such patients.
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