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Search Results: 1 - 10 of 455097 matches for " M. W. Hecht "
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More about orbitally excited hadrons from lattice QCD
T. A. DeGrand,M. W. Hecht
Physics , 1992, DOI: 10.1103/PhysRevD.46.3937
Abstract: This is a second paper describing the calculation of spectroscopy for orbitally excited states from lattice simulations of Quantum Chromodynamics. New features include higher statistics for P-wave systems and first results for the spectroscopy of D-wave mesons and baryons, for relatively heavy quark masses. We parameterize the Coulomb gauge wave functions for P-wave and D-wave systems and compare them to those of their corresponding S-wave states.
Comparison of Lattice Coulomb Gauge Wave Functions in Quenched Approximation and with Dynamical Fermions
M. Hecht
Physics , 1992, DOI: 10.1103/PhysRevD.47.285
Abstract: We present a comparison of Coulomb gauge wave functions from $6/{g^2}=6.0$ quenched simulations with two simulations which include the effects of dynamical fermions: simulations with two flavors of dynamical staggered quarks and valence Wilson quarks at $6/{g^2}=5.6$ and simulations with two flavors of dynamical Wilson quarks and Wilson valence quarks, at $6/{g^2}=5.3$. The spectroscopy of these systems is essentially identical. Parameterizations of the wave functions are presented which can be used as interpolating fields for spectroscopy calculations. The sizes of particles are calculated using these parameterized wave functions. The resulting sizes are small, approximately half the sizes of the physical states. The charge radius of the neutron, which provides an indication of the asymmetries between the wave functions of up and down quarks, is calculated. Although the size of the nucleon in these simulations is small, the ratio of the charge radius of the neutron to that of the proton is consistent with the physical value. We find no significant differences between the quenched and dynamical simulations.
Nucleon mass and pion loops
M. B. Hecht,M. Oettel,C. D. Roberts,S. M. Schmidt,P. C. Tandy,A. W. Thomas
Physics , 2002, DOI: 10.1103/PhysRevC.65.055204
Abstract: Poincare' covariant Faddeev equations for the nucleon and Delta are solved to illustrate that an internally consistent description in terms of confined-quark and nonpointlike confined-diquark-correlations can be obtained. pi N-loop induced self-energy corrections to the nucleon's mass are analysed and shown to be independent of whether a pseudoscalar or pseudovector coupling is used. Phenomenological constraints suggest that this self-energy correction reduces the nucleon's mass by up to several hundred MeV. That effect does not qualitatively alter the picture, suggested by the Faddeev equation, that baryons are quark-diquark composites. However, neglecting the pi-loops leads to a quantitative overestimate of the nucleon's axial-vector diquark component.
Comparison of three cell block techniques for detection of low frequency abnormal cells
Hecht SA, McCormack M
Pathology and Laboratory Medicine International , 2013, DOI: http://dx.doi.org/10.2147/PLMI.S37555
Abstract: mparison of three cell block techniques for detection of low frequency abnormal cells Original Research (725) Total Article Views Authors: Hecht SA, McCormack M Published Date January 2013 Volume 2013:5 Pages 1 - 7 DOI: http://dx.doi.org/10.2147/PLMI.S37555 Received: 31 August 2012 Accepted: 01 November 2012 Published: 04 January 2013 Steven A Hecht, Matthew McCormack Hologic Inc, Marlborough, MA, USA Background: The Cellient Automated Cell Block System rapidly creates paraffin-embedded cell blocks by using vacuum filtration to deposit a layer of cells on a filter and infiltrate those cells with reagents and paraffin. This study used a “tracer” cell model to mimic low frequency abnormal cells and compare detection and representative sampling with simple sedimentation, Richard-Allan HistoGel , and Cellient cell block techniques. Methods: Tracer cells were a cultured cell line (CaSki) fixed in methanol, prestained in solution with hematoxylin, and quantified using a hemacytometer. Tracer cells were diluted in a 10-fold dilution series ranging from 100 to 0.1 tracer/mL in a background of pooled clinical serous effusion specimens. Ten replicates of each dilution were processed using each cell block method, and the resulting blocks were cut to produce two slides from each block. The slides were deparaffinized, counterstained with eosin, cover-slipped, and screened for the presence of tracer cells. Blocks were considered to be representative of the specimen if tracer cells were detected on either of the slides. If no tracer cells were observed on either slide, the block was recut to generate a third slide. If tracer cells were seen on the third slide, the block was considered representative of the specimen. Results: Tracer cells were identified on the initial slides for 20 of 40 (50.0%) simple sedimentation, 21 of 40 (52.5%) of HistoGel, and 25 of 40 (62.5%) of Cellient cell blocks. Representative sampling of the 1 tracer/mL specimen was 10.0% for simple sedimentation and 30.0% for HistoGel and Cellient. Only Cellient showed representative sampling of the 0.1 tracer/mL specimen. Conclusion: The Cellient System blocks demonstrated representative sampling at the lowest tracer cell concentration compared with simple sedimentation and HistoGel.
Comparison of three cell block techniques for detection of low frequency abnormal cells
Hecht SA,McCormack M
Pathology and Laboratory Medicine International , 2013,
Abstract: Steven A Hecht, Matthew McCormackHologic Inc, Marlborough, MA, USABackground: The Cellient Automated Cell Block System rapidly creates paraffin-embedded cell blocks by using vacuum filtration to deposit a layer of cells on a filter and infiltrate those cells with reagents and paraffin. This study used a “tracer” cell model to mimic low frequency abnormal cells and compare detection and representative sampling with simple sedimentation, Richard-Allan HistoGel , and Cellient cell block techniques.Methods: Tracer cells were a cultured cell line (CaSki) fixed in methanol, prestained in solution with hematoxylin, and quantified using a hemacytometer. Tracer cells were diluted in a 10-fold dilution series ranging from 100 to 0.1 tracer/mL in a background of pooled clinical serous effusion specimens. Ten replicates of each dilution were processed using each cell block method, and the resulting blocks were cut to produce two slides from each block. The slides were deparaffinized, counterstained with eosin, cover-slipped, and screened for the presence of tracer cells. Blocks were considered to be representative of the specimen if tracer cells were detected on either of the slides. If no tracer cells were observed on either slide, the block was recut to generate a third slide. If tracer cells were seen on the third slide, the block was considered representative of the specimen.Results: Tracer cells were identified on the initial slides for 20 of 40 (50.0%) simple sedimentation, 21 of 40 (52.5%) of HistoGel, and 25 of 40 (62.5%) of Cellient cell blocks. Representative sampling of the 1 tracer/mL specimen was 10.0% for simple sedimentation and 30.0% for HistoGel and Cellient. Only Cellient showed representative sampling of the 0.1 tracer/mL specimen.Conclusion: The Cellient System blocks demonstrated representative sampling at the lowest tracer cell concentration compared with simple sedimentation and HistoGel.Keywords: Cellient , HistoGel , simple sedimentation, CaSki, microtomy
Wave functions and their use in spectroscopy and phenomenology
T. DeGrand,M. Hecht
Physics , 1992, DOI: 10.1016/0920-5632(93)90239-3
Abstract: We describe the calculation of Coulomb gauge wave functions for light quark systems, and their use as interpolating fields for excited state spectroscopy.
Functional Neuroanatomy of Time-To-Passage Perception  [PDF]
Yansong Geng, Elif M. Sikoglu, Heiko Hecht, Lucia M. Vaina
Journal of Behavioral and Brain Science (JBBS) , 2018, DOI: 10.4236/jbbs.2018.811039
Abstract: The time until an approaching object passes the observer is referred to as time-to-passage (TTP). Accurate judgment of TTP is critical for visually guided navigation, such as when walking, riding a bicycle, or driving a car. Previous research has shown that observers are able to make TTP judgments in the absence of information about local retinal object expansion. In this paper we combine psychophysics and functional MRI (fMRI) to investigate the neural substrate of TTP processing. In a previous psychophysical study, we demonstrated that when local retinal expansion cues are not available, observers take advantage of multiple sources of information to judge TTP, such as optic flow and object retinal velocities, and integrate these cues through a flexible and economic strategy. To induce strategy changes, we introduced trials with motion but without coherent optic flow (0% coherence of the background), and trials with coherent, but noisy, optic flow (75% coherence of the background). In a functional magnetic resonance imaging (fMRI) study we found that coherent optic flow cues resulted in better behavioral performance as well as higher and broader cortical activations across the visual motion processing pathway. Blood oxygen-level-dependent (BOLD) signal changes showed significant involvement of optic flow processing in the precentral sulcus (PreCS), postcentral sulcus (PostCS) and middle temporal gyrus (MTG) across all conditions. Not only highly activated during motion processing, bilateral hMT areas also showed a complex pattern in TTP judgment processing, which reflected a flexible TTP response strategy.
Cytomegalovirus-Specific T Cells Persist at Very High Levels during Long-Term Antiretroviral Treatment of HIV Disease
David M. Naeger,Jeffrey N. Martin,Elizabeth Sinclair,Peter W. Hunt,David R. Bangsberg,Frederick Hecht,Priscilla Hsue,Joseph M. McCune,Steven G. Deeks
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0008886
Abstract: In healthy, HIV seronegative, CMV seropositive adults, a large proportion of T cells are CMV-specific. High-level CMV-specific T cell responses are associated with accelerated immunologic aging (“immunosenesence”) in the elderly population. The impact of untreated and treated HIV infection on the frequency of these cells remains undefined.
Development of position-sensitive time-of-flight spectrometer for fission fragment research
C. W. Arnold,F. Tovesson,K. Meierbachtol,T. Bredeweg,M. Jandel,H. J. Jorgenson,A. Laptev,G. Rusev,D. W. Shields,M. White,R. E. Blakeley,D. M. Mader,A. A. Hecht
Physics , 2014, DOI: 10.1016/j.nima.2014.07.001
Abstract: A position-sensitive, high-resolution time-of-flight detector for fission fragments has been developed. The SPectrometer for Ion DEterminiation in fission Research (SPIDER) is a $2E-2v$ spectrometer designed to measure the mass of light fission fragments to a single mass unit. The time pick-off detector pairs to be used in SPIDER have been tested with $\alpha$-particles from $^{229}$Th and its decay chain and $\alpha$-particles and spontaneous fission fragments from $^{252}$Cf. Each detector module is comprised of a thin electron conversion foil, electrostatic mirror, microchannel plates, and delay-line anodes. Particle trajectories on the order of 700 mm are determined accurately to within 0.7 mm. Flight times on the order of 70 ns were measured with 200 ps resolution FWHM. Computed particle velocities are accurate to within 0.06 mm/ns corresponding to precision of 0.5%. An ionization chamber capable of 400 keV energy resolution coupled with the velocity measurements described here will pave the way for modestly efficient measurements of light fission fragments with unit mass resolution.
Ovine mitochondrial DNA: mapping and sequencing data in comparison with bovine mtDNA
Hiendleder S,Hecht W,Wassmuth R
Genetics Selection Evolution , 1991, DOI: 10.1186/1297-9686-23-s1-s148
Abstract:
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