排序方式: 共有39条查询结果,搜索用时 15 毫秒
21.
Michael Quentin Dirk Blondin Janina Klasen Rotem Shlomo Lanzman Falk-Roland Miese Christian Arsov Peter Albers Gerald Antoch Hans-Jörg Wittsack 《Magnetic resonance imaging》2012
Purpose
To evaluate which mathematical model (monoexponential, biexponential, statistical, kurtosis) fits best to the diffusion-weighted signal in prostate magnetic resonance imaging (MRI).Materials and Methods
24 prostate 3-T MRI examinations of young volunteers (YV, n= 8), patients with biopsy proven prostate cancer (PC, n= 8) and an aged matched control group (AC, n= 8) were included. Diffusion-weighted imaging was performed using 11 b-values ranging from 0 to 800 s/mm2.Results
Monoexponential apparent diffusion coefficient (ADC) values were significantly (P<.001) lower in the peripheral (PZ) zone (1.18±0.16 mm2/s) and the central (CZ) zone (0.73±0.13 mm2/s) of YV compared to AC (PZ 1.92±0.17 mm2/s; CZ 1.35±0.21 mm2/s). In PC ADCmono values (0.61±0.06 mm2/s) were significantly (P<.001) lower than in the peripheral of central zone of AC. Using the statistical analysis (Akaike information criteria) in YV most pixels were best described by the biexponential model (82%), the statistical model, respectively kurtosis (93%) each compared to the monoexponential model. In PC the majority of pixels was best described by the monoexponential model (57%) compared to the biexponential model.Conclusion
Although a more complex model might provide a better fitting when multiple b-values are used, the monoexponential analyses for ADC calculation in prostate MRI is sufficient to discriminate prostate cancer from normal tissue using b-values ranging from 0 to 800 s/mm2. 相似文献22.
H. Abramowicz J. G. H. de Groot J. Knobloch J. May P. Palazzi A. Para F. Ranjard A. Savoy-Navarro D. Schlatter J. Steinberger H. Taureg W. von Rüden H. Wahl J. Wotschack P. Buchholz F. Eisele H. P. Klasen K. Kleinknecht H. Lierl D. Pollmann B. Pszola B. Renk H. J. Willutzki F. Dydak T. Flottmann C. Geweniger J. Królikowski K. Tittel P. Bloch B. Devaux C. Guyot J. P. Merlo B. Peyaud J. Rander J. Rothberg R. Turlay J. T. He T. Z. Ruan W. M. Wu 《Zeitschrift fur Physik C Particles and Fields》1983,17(4):283-307
Inclusive charged-current interactions of high-energy neutrinos and antineutrinos have been studied with high statistics in a counter experiment at the CERN Super Proton Synchrotron. The energy dependence of the total cross-sections, the longitudinal structure function, and the nucleon structure functionsF 2,xF 3, and \(\bar q^{\bar v} \) are determined from these data. The analysis of theQ 2-dependence of the structure functions is used to test quantum chromodynamics, to determine the scale parameter Λ and the gluon distribution in the nucleon. 相似文献
23.
Dr. Matthias Bremer Prof. Dr. Peer Kirsch Dr. Melanie Klasen‐Memmer Dr. Kazuaki Tarumi 《Angewandte Chemie (International ed. in English)》2013,52(34):8880-8896
New liquid crystals with very low viscosity, good mesophase behavior, and high reliability are necessary to achieve the breakthrough from flat computer monitors to large displays for television. Fluorine plays a decisive role not only because of the polarity it induces in organic molecules but also because of its low polarizability and weak propensity for ion solvation. In addition, subtle stereoelectronic effects in fluorine‐containing liquid crystals influence material properties and allow these to be tuned to some extent to achieve the desired outcome. Some fairly sophisticated chemistry is required that is normally ruled out in the specialty chemicals industry because of cost. The television display market is now entering a phase of saturation. The broad availability of the internet has led to an ever increasing tendency for mobile products. Tablet PCs and smartphones require touch‐panel functionality and low power consumption. New LCD modes with high‐performance liquid crystals and additional components, such as polymerizable materials, can be used in such products. 相似文献
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Michael Klasen Karol Kovařík Paolo Nason Carole Weydert 《The European Physical Journal C - Particles and Fields》2012,72(9):1-21
The associated production of charged Higgs bosons and top quarks at hadron colliders is an important discovery channel to establish the existence of a non-minimal Higgs sector. Here, we present details of a next-to-leading order (NLO) calculation of this process using the Catani–Seymour dipole formalism and describe its implementation in POWHEG, which allows to match NLO calculations to parton showers. Numerical predictions are presented using the PYTHIA parton shower and are compared to those obtained previously at fixed order, to a leading order calculation matched to the PYTHIA parton shower, and to a different NLO calculation matched to the HERWIG parton shower with MC@NLO. We also present numerical predictions and theoretical uncertainties for various Two Higgs Doublet Models at the Tevatron and LHC. 相似文献
27.
The production of dijets with a leading neutron in ep interactions at HERA is calculated in leading order and next-to-leading
order of perturbative QCD using a pion-exchange model. Differential cross sections for deep-inelastic scattering and photoproduction
are presented as a function of several kinematic variables. By comparing the theoretical predictions for DIS dijets to recent
H1 data, the pion flux factor together with the parton distribution functions of the pion is determined. The dijet cross sections
in photoproduction show factorization breaking if compared to the H1 photoproduction data. The suppression factor is S=0.48
(0.64) for resolved (global) suppression.
PACS 12.38.Bx; 13.60.-r 相似文献
28.
We present a complete analysis of threshold resummation effects on direct light and heavy gaugino pair production at the Tevatron and the LHC. Based on a new perturbative calculation at next-to-leading order of SUSY-QCD, which includes also squark mixing effects, we resum soft gluon radiation in the threshold region at leading and next-to-leading logarithmic accuracy, retaining at the same time the full SUSY-QCD corrections in the finite coefficient function. This allows us to correctly match the resummed to the perturbative cross section. Universal subleading logarithms are resummed in full matrix form. We find that threshold resummation slightly increases and considerably stabilizes the invariant mass spectra and total cross sections with respect to the next-to-leading order calculation. For future reference, we present total cross sections and their theoretical errors in tabular form for several commonly used SUSY benchmark points, gaugino pairs, and hadron collider energies. 相似文献
29.
Michael Klasen Florian Lyonnet Farinaldo S. Queiroz 《The European Physical Journal C - Particles and Fields》2017,77(5):348
Baryon and lepton numbers being accidental global symmetries of the Standard Model (SM), it is natural to promote them to local symmetries. However, to preserve anomaly-freedom, only combinations of B–L are viable. In this spirit, we investigate possible dark matter realizations in the context of the \(U(1)_\mathrm{B{-}L}\) model: (i) Dirac fermion with unbroken B–L; (ii) Dirac fermion with broken B–L; (iii) scalar dark matter; (iv) two-component dark matter. We compute the relic abundance, direct and indirect detection observables and confront them with recent results from Planck, LUX-2016, and Fermi-LAT and prospects from XENON1T. In addition to the well-known LEP bound \(M_{Z^{\prime }}/g_\mathrm{BL} \gtrsim 7\) TeV, we include often ignored LHC bounds using 13 TeV dilepton (dimuon + dielectron) data at next-to-leading order plus next-to-leading logarithmic accuracy. We show that, for gauge couplings smaller than 0.4, the LHC gives rise to the strongest collider limit. In particular, we find \(M_{Z^{\prime }}/g_\mathrm{BL} > 8.7\) TeV for \(g_\mathrm{BL}=0.3\). We conclude that the NLO+NLL corrections improve the dilepton bounds on the \(Z^{\prime }\) mass and that both dark matter candidates are only viable in the \(Z^{\prime }\) resonance region, with the parameter space for scalar dark matter being fully probed by XENON1T. Lastly, we show that one can successfully have a minimal two-component dark matter model. 相似文献
30.
Janina Klasen Rotem Shlomo Lanzman Hans-Jörg Wittsack Gerald Kircheis Julia Schek Michael Quentin Gerald Antoch Dieter Häussinger Dirk Blondin 《Magnetic resonance imaging》2013