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Search Results: 1 - 10 of 1842 matches for " Arnd Gross "
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KMWin – A Convenient Tool for Graphical Presentation of Results from Kaplan-Meier Survival Time Analysis
Arnd Gross, Marita Ziepert, Markus Scholz
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0038960
Abstract: Background Analysis of clinical studies often necessitates multiple graphical representations of the results. Many professional software packages are available for this purpose. Most packages are either only commercially available or hard to use especially if one aims to generate or customize a huge number of similar graphical outputs. We developed a new, freely available software tool called KMWin (Kaplan-Meier for Windows) facilitating Kaplan-Meier survival time analysis. KMWin is based on the statistical software environment R and provides an easy to use graphical interface. Survival time data can be supplied as SPSS (sav), SAS export (xpt) or text file (dat), which is also a common export format of other applications such as Excel. Figures can directly be exported in any graphical file format supported by R. Results On the basis of a working example, we demonstrate how to use KMWin and present its main functions. We show how to control the interface, customize the graphical output, and analyse survival time data. A number of comparisons are performed between KMWin and SPSS regarding graphical output, statistical output, data management and development. Although the general functionality of SPSS is larger, KMWin comprises a number of features useful for survival time analysis in clinical trials and other applications. These are for example number of cases and number of cases under risk within the figure or provision of a queue system for repetitive analyses of updated data sets. Moreover, major adjustments of graphical settings can be performed easily on a single window. Conclusions We conclude that our tool is well suited and convenient for repetitive analyses of survival time data. It can be used by non-statisticians and provides often used functions as well as functions which are not supplied by standard software packages. The software is routinely applied in several clinical study groups.
Decisive Parameters for Backwater Effects Caused by Floating Debris Jams  [PDF]
Arnd Hartlieb
Open Journal of Fluid Dynamics (OJFD) , 2017, DOI: 10.4236/ojfd.2017.74032
Abstract:
The dimensional analysis of the backwater effect caused by debris jams results in the Froude number of the approach flow in the initial situation prior to debris jam formation and the debris density as decisive parameters. For the more precise detection of the influence of both parameters the results of different hydraulic model test series at the Laboratory of Hydraulic and Water Resources Engineering of the Technical University of Munich concerning debris jams at spillways as well as at racks for the retention of wooden debris were uniformly evaluated. On the one hand a significant increase of the backwater effect with a rising Froude number of the approach flow could be shown. This is in good correlation to recent test results for debris jams at retention racks at the Laboratory of Hydraulics, Hydrology and Glaciology of the Swiss Federal Institute of Technology Zurich. On the other hand a significant increase of the backwater effect could also be shown for a rising debris density. However, the test results also show that significantly different backwater effects can occur in different test runs with identical test conditions. These differences are a result of the randomness of debris jam development, and therefore, a more exact quantification of the dependence of the backwater effect on the Froude number of the approach flow and on the debris density is not considered useful for the present results.
Model Independent $Z'$ Constraints at Future $e^+e^-$ Colliders}
Arnd Leike
Physics , 1993, DOI: 10.1007/BF01560242
Abstract: Model independent constraints on the mass of extra neutral gauge bosons and their couplings to charged leptons are given for LEP~II and a 500\,GeV $e^+e^-$ collider. Analytical exclusion limits are derived in the Born approximation. The $Z'$ limits obtained with radiative corrections are always worse than those calculated at the Born level. Polarized beams are only useful for degrees of polarization essentially larger than 50\%. Known discovery limits on extra $Z$ bosons predicted by popular $Z'$ models are reproduced as special cases. The $Z'$ constraints are compared to those predicted by four fermion contact interactions.
Spin-Spin Correlations of Top Quark Pairs at Hadron Colliders
Arnd Brandenburg
Physics , 1996, DOI: 10.1016/S0370-2693(96)01347-0
Abstract: Top quark pairs are produced with strongly correlated spins in the partonic reactions $q\bar{q}\to t\bar{t}$ and $gg\to t\bar{t}$. A complete description of these effects in terms of the spin density matrix of the $t\bar{t}$ system in leading order QCD is given. We further discuss the prospects to observe the spin-spin correlations at $p\bar{p}$ and $pp$ colliders by measuring suitable angular correlations among the $t$ and $\bar{t}$ decay products.
Spin Physics with Top Quarks at Hadron Colliders
Arnd Brandenburg
Physics , 1996,
Abstract: We discuss the prospects to observe effects of transverse polarization and spin-spin correlations of top quark pairs produced at hadron colliders.
Production of top quark pairs in association with a hard gluon to order $α_s^2$
Arnd Brandenburg
Physics , 1999, DOI: 10.1007/s100529900187
Abstract: The production of top quark pairs accompanied by a hard gluon in $e^+e^-$ annihilation is studied including next-to-leading order corrections in the strong coupling. At leading order, the fraction r of $t\bar{t}g$ events with respect to all $t\bar{t}$ events is computed analytically as a function of the minimal gluon energy. Next-to-leading order results for r are given for center-of-mass energies of 0.5 and 1 TeV. We further calculate the differential distribution of r with respect to several variables, including the top quark energy and the $t\bar{t}$ invariant mass. We then investigate how our results depend on the choice of the renormalization scheme for the top quark mass by comparing results expressed in terms of either the pole mass or the $\msbar$ mass. Finally we estimate the sensitivity of the fraction r on the value of the running top quark mass at a scale of 1 TeV.
SEMIANALYTIC DISTRIBUTIONS IN FOUR FERMION NEUTRAL CURRENT PROCESSES
Arnd Leike
Physics , 1995,
Abstract: Analytical formulae for triple differential distributions ${\rm d}^3\sigma/({\rm d}\cos\theta{\rm d}s_1{\rm d}s_2)$ in the neutral current process $e^+e^-\rightarrow f_1\bar f_1 f_2\bar f_2$ are given. They allow to obtain angular distributions, rapidity distributions and transversal momentum distributions of one fermion pair by only two numerical integrations. Cuts can be applied to the integration variables.
Scaling of Z' limits at the Linear Collider
Arnd Leike
Physics , 1997,
Abstract: Z' exclusion limits and errors of Z' model measurements are compared for different reactions at future linear colliders. The influence of the c.m. energy, integrated luminosity, beam polarization and systematic errors is discussed. The sensitivity to a Z' depends only on the product Ls and not on the integrated luminosity and the c.m. energy separately.
Scaling of Z' exclusion limits and Z' measurements with energy, luminosity and systematic errors
Arnd Leike
Physics , 1997,
Abstract: The influence of the c.m. energy, integrated luminosity and systematic errors on Z' exclusion limits and on errors of Z' model measurements is discussed. Simple scaling laws are given for e+e-, pp (p (bar)p) and e+-p colliders and compared with results of exact analyses.
New Charm(onium) Results from CDF
Arnd Meyer
Physics , 2003,
Abstract: After many upgrades to the CDF detector and to the accelerator complex, Run II began in April 2001. The new detector has improved capabilities for charm physics, and first results from the analysis of early Tevatron Run II data are reported here.
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