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Search Results: 1 - 10 of 75 matches for " Menke "
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Short Report: A Sponge Phantom Provides a Homogeneous k-Space Pattern at MRI  [PDF]
Jan Menke
Open Journal of Radiology (OJRad) , 2014, DOI: 10.4236/ojrad.2014.42026
Abstract: Background: The spectral coverage of magnetic resonance (MR) sequences can be well assessed in k-space. However, many objects do not provide high signal intensities in the peripheral k-space. Purpose: To experimentally find a phantom that provides a homogeneous spectral pattern also at the high spatial frequencies of the k-space periphery. Material and Methods: Different phantoms were imaged on a 1.5 Tesla magnet, and the resulting MR images were viewed in k-space after fast Fourier transform. Results: Firstly, phantoms with a homogeneous physical structure were studied with a T2-weighted MR sequence, but they provided an inhomogeneous k-space pattern with dominant central low-frequency components. Secondly, phantoms with an inhomogeneous physical structure were studied. In this group, a water-soaked sponge showed a relatively homogeneous k-space pattern also at high spatial frequencies, owing to the fine porous structure. This sponge phantom can also be soaked with Gadolinium chelates for T1-weighted MR imaging. Conclusion: A simple sponge phantom provides a homogeneous k-space pattern, owing to its fine porous structure. This could be utilized in MR sequence development and for viewing the spectral coverage of MR sequences in k-space.


Coherence Modified for Sensitivity to Relative Phase of Real Band-Limited Time Series  [PDF]
William Menke
Applied Mathematics (AM) , 2014, DOI: 10.4236/am.2014.517261
Abstract: As is well known, coherence does not distinguish the relative phase of a pair of real, sinusoidal time series; the coherence between them is always unity. This behavior can limit the applicability of coherence analysis in the special case where the time series are band-limited (nearly-monoch- romatic) and where sensitivity to phase differences is advantageous. We propose a simple mod-ification to the usual formula for coherence in which the cross-spectrum is replaced by its real part. The resulting quantity behaves similarly to coherence, except that it is sensitive to relative phase when the signals being compared are strongly band-limited. Furthermore, it has a useful interpretation in terms of the zero-lag cross-correlation of real band-passed versions of the time series.
Construction of Equivalent Functions in Anisotropic Radon Tomography  [PDF]
William Menke
Applied Mathematics (AM) , 2019, DOI: 10.4236/am.2019.101001
Abstract:

We consider a real-valued function on a plane of the form

m(x,y,θ)=A(x,y)+Bc(x,y)cos(2θ)+Bs(x,y)sin(2θ)+Cc(x,y)cos(4θ)Cs(x,y)sin(4θ)

that models anisotropic acoustic slowness (reciprocal velocity) perturbations. This “slowness function” depends on Cartesian coordinates and polar angle θ. The five anisotropic “component functions” A (x,y), Bc(x,y), Bs(x,y), Cc(x,y) and Cs(x,y) are assumed to be real-valued Schwartz functions. The “travel time” function d(u, θ) models the travel time perturbations on an indefinitely long straight-line observation path, where the line is parameterized by perpendicular distance u from the origin and polar angle θ; it is the Radon transform of m ( x, y, θ). We show that: 1) an A can always be found with the same d(u, θ) as an arbitrary (Bc,Bs) and/or an arbitrary (Cc

Hard QCD Results with Jets at the LHC
Menke Sven
EPJ Web of Conferences , 2012, DOI: 10.1051/epjconf/20122802012
Abstract: Hard QCD results in proton-proton collisions at √s = 7 TeV with jets from data recorded up to the end of 2010 by the CMS and ATLAS experiments at the LHC are reported. Inclusive jet and di-jet cross section measurements as well as observables sensitive to multi-jet activity are shown and compared to simulations based on leading log parton showers as well as NLO QCD predictions. Novel approaches to identify highly boosted massive final states by exploiting the jet substructure are tested on the dominant QCD background.
alpha_s at low Q^2 from e+e- and tau data
Sven Menke
Physics , 2001,
Abstract: It has been shown in recent analyses by ALEPH [1] and OPAL [2] that precision QCD tests are possible with hadronic tau decays by comparing spectral moments of the hadronic decay ratio of the tau with QCD calculations. In principle e+e- data can be used in a similar manner by evaluating spectral moments of R. The current e+e- data is compared with the OPAL tau data and a prediction is made on the achievable accuracy of QCD tests with the projected precision of PEP-N [3].
Thermoelectric properties of doped small molecule organic semiconductor films
Torben Menke
Physics , 2013,
Abstract: Doped films of organic small molecules are investigated with respect to their thermoelectric properties. A variety of hosts and dopants, for both n and p-doping, are compared. C$_{60}$ n-doped by Cr$_2$(hpp)$_4$ or o-MeO-DMBI-I are found to be the most promising material systems with a maximum of ZT$_\text{M}$ = 0.069 at T$_\text{M}$ = 40{\deg}C, assuming a doping-independent thermal conductivity due to phonon-based heat transport. This value is 16% of the current record reported for optimized devices employing the doped polymer PEDOT:PSS.
Proton and Neutron Irradiation Tests of Readout Electronics of the ATLAS Hadronic Endcap Calorimeter
Sven Menke
Physics , 2012,
Abstract: The readout electronics of the ATLAS Hadronic Endcap Calorimeter will have to withstand the about ten times larger radiation environment of the future high-luminosity LHC (HL-LHC) compared to their design values. The GaAs ASIC which comprises the heart of the readout electronics has been exposed to neutron and proton radiation with fluences up to ten times the total expected fluences for ten years of running of the HL-LHC. Neutron tests were performed at the NPI in Rez, Czech Republic, where a 36 MeV proton beam is directed on a thick heavy water target to produce neutrons. The proton irradiation was done with 200 MeV protons at the PROSCAN area of the Proton Irradiation Facility at the PSI in Villigen, Switzerland. In-situ measurements of S-parameters in both tests allow the evaluation of frequency dependent performance parameters - like gain and input impedance - as a function of the fluence. The linearity of the ASIC response has been measured directly in the neutron tests with a triangular input pulse of varying amplitude. The performance measurements and expected performance degradations under HL-LHC conditions are presented.
Determination of the Jet Energy Scale
Sven Menke
Physics , 2007, DOI: 10.1016/j.nuclphysbps.2007.11.109
Abstract: The uncertainty in jet energy scale is one of the dominating systematic errors for many measurements at hadron colliders - most notably for the measurement of the top-quark-mass, inclusive jet cross section measurements and last but not least for events with large missing transverse energy as expected in searches beyond the standard model. This talk will review the approaches taken at Tevatron towards controlling the jet energy scale and discuss prospects for the LHC experiments.
Measurements of the top quark mass using the ATLAS and CMS detectors at the LHC
Sven Menke
Physics , 2015,
Abstract: The latest measurements of the top quark mass obtained by the ATLAS and CMS experiments at the LHC for centre-of-mass energies of 7 and 8 TeV are presented. The mass of the top quark is measured using several methods and channels, including the reconstructed invariant mass distribution of the top quark and shapes of top quark decay distributions. Measurements based on the inclusive tt-bar cross section and novel observables based on the differential cross section in the tt-bar + 1 jet channel are also discussed. The results of the various channels are combined and compared to the world average.
On The Augmentation Categories of Positive Braid Closures
Michael Menke
Mathematics , 2015,
Abstract: In this paper we show that 0-resolution of a crossing in the Legendrian closure of a positive braid induces a cohomologically faithful $A_\infty$ functor on augmentation categories. In particular, we compute the bilinearized Legendrian contact cohomology of these knots for augmentations induced by 0-resolution.
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