282 research outputs found
Spectroscopy, Equation Of State And Monopole Percolation In Lattice QED With Two Flavors
Non-compact lattice QED with two flavors of light dynamical quarks is
simulated on lattices, and the chiral condensate, monopole density and
susceptibility and the meson masses are measured. Data from relatively high
statistics runs at relatively small bare fermion masses of 0.005, 0.01, 0.02
and 0.03 (lattice units) are presented. Three independent methods of data
analysis indicate that the critical point occurs at and that
the monopole condensation and chiral symmetry breaking transitions are
coincident. The monopole condensation data satisfies finite size scaling
hypotheses with critical indices compatible with four dimensional percolation.
The best chiral equation of state fit produces critical exponents
(, ) which deviate significantly from mean
field expectations. Data for the ratio of the sigma to pion masses produces an
estimate of the critical index in good agreement with chiral
condensate measurements. In the strong coupling phase the ratio of the meson
masses are ,
and , while on the weak coupling side of the
transition , ,
indicating the restoration of chiral symmetry.\footnote{\,^{}}{August 1992}Comment: 21 pages, 24 figures (not included
The Block Spin Renormalization Group Approach and Two-Dimensional Quantum Gravity
A block spin renormalization group approach is proposed for the dynamical
triangulation formulation of two-dimensional quantum gravity. The idea is to
update link flips on the block lattice in response to link flips on the
original lattice. Just as the connectivity of the original lattice is meant to
be a lattice representation of the metric, the block links are determined in
such a way that the connectivity of the block lattice represents a block
metric. As an illustration, this approach is applied to the Ising model coupled
to two-dimensional quantum gravity. The correct critical coupling is
reproduced, but the critical exponent is obscured by unusually large finite
size effects.Comment: 10 page
The Phase Diagram of Crystalline Surfaces
We report the status of a high-statistics Monte Carlo simulation of
non-self-avoiding crystalline surfaces with extrinsic curvature on lattices of
size up to nodes. We impose free boundary conditions. The free energy
is a gaussian spring tethering potential together with a normal-normal bending
energy. Particular emphasis is given to the behavior of the model in the cold
phase where we measure the decay of the normal-normal correlation function.Comment: 9 pages latex (epsf), 4 EPS figures, uuencoded and compressed.
Contribution to Lattice '9
QCD Thermodynamics at and 12
We present results from studies of high temperature QCD with two flavors of
Kogut-Susskind quarks on lattices at a quark mass of
and on lattices at quark masses and
0.016. The value of the crossover temperature is consistent with that obtained
on coarser lattices and/or at larger quark masses. Results are presented for
the chiral order parameter and for the baryon number susceptibility.Comment: 3-pages, uuencoded compressed postscript file, contribution to
Lattice'94 conferenc
Increased Ipsilateral M1 Activation after Incomplete Spinal Cord Injury Facilitates Motor Performance
Incomplete spinal cord injury (SCI) may result in muscle weakness and difficulties with force gradation. Although these impairments arise from the injury and subsequent changes at spinal levels, changes have also been demonstrated in the brain. Blood-oxygen-level dependent (BOLD) imaging was used to investigate these changes in brain activation in the context of unimanual contractions with the first dorsal interosseous muscle. BOLD- and force data were obtained in 19 individuals with SCI (AISA Impairment Scale [AIS] C/D, level C4-C8) and 24 able-bodied controls during maximal voluntary contractions (MVCs). To assess force modulation, participants performed 12 submaximal contractions with each hand (at 10, 30, 50, and 70% MVC) by matching their force level to a visual target. MVCs were weaker in the SCI group (both hands p < 0.001), but BOLD activation did not differ between SCI and control groups. For the submaximal contractions, force (as %MVC) was similar across groups. However, SCI participants showed increased activity of the ipsilateral motor cortex and contralateral cerebellum across all contractions, with no differential effect of force level. Activity of ipsilateral M1 was best explained by force of the target hand (vs. the non-target hand). In conclusion, the data suggest that after incomplete cervical SCI, individuals remain capable of producing maximal supraspinal drive and are able to modulate this drive adequately. Activity of the ipsilateral motor network appears to be task related, although it remains uncertain how this activity contributes to task performance and whether this effect could potentially be harnessed to improve motor functioning
Structured fixed-bed adsorber based on zeolite/sintered metal fibre for low concentration VOC removal
A novel adsorber with a structured fixed-bed made of sintered metal fibres (SMF) plates has been developed for purification of low-content VOCs gas-streams. The surface of the metal fibres was coated by a thin, homogeneous MFI-type (ZSM-5, Silicalite-1) zeolite film. The zeolite/SMF composite has been shown as an efficient adsorbent, in which VOCs in low content streams are first concentrated and desorbed in a second step with higher concentrations suitable for oxidation. The advantages of this structured zeolite/SMF composite are a low resistance to internal mass transfer, a relatively low pressure drop and compactness compared to conventional powders or extrudates. Propane was used as a model VOC compound. The isotherms and dynamics of adsorption (breakthrough points) were measured to characterize the properties of the adsorbent. A mathematical model was developed to simulate the experimental data
Gas holdup and longitudinal dispersion in different types of multiphase reactors and their possible application for microbial processes
Gas holdup and liq. phase longitudinal dispersion were detd. in concurrent 1- and 6-stage, 2-phase bubble columns, and in countercurrent 1-stage, 2- and 3-phase bubble columns, using the longitudinal dispersion and backflow cell models to describe the intensity of longitudinal mixing. The axial dispersion model in conjuction with Monod growth kinetics were used to examine the influence of fluid mixing on the performance of a microbial process. [on SciFinder (R)
An Effective Model for Crumpling in Two Dimensions?
We investigate the crumpling transition for a dynamically triangulated random
surface embedded in two dimensions using an effective model in which the
disordering effect of the variables on the correlations of the normals is
replaced by a long-range ``antiferromagnetic'' term. We compare the results
from a Monte Carlo simulation with those obtained for the standard action which
retains the 's and discuss the nature of the phase transition.Comment: 5 page
Bubble columns staged with structured fibrous catalytic layers: Residence time distribution and mass transfer
A new reactor concept for catalyzed three-phase reactions based on the use of woven fibrous materials for bubble columns is suggested. In comparison to conventional multistage bubble columns, the trays are made from woven fibrous catalytic layers. The hydrodynamic parameters such as the residence time distribution (RTD) and the volumetric gas-liquid mass transfer coefficient k(L)a are investigated in an air/water system for different layer structures and different superficial gas (u(g0) < 60 cm/s) and liquid (u(10) < 6 cm/s) velocities. The major reactor design parameters, such as the thread diameter D, the distance between the woven threads w, and the distance between the fibrous layers b, are discussed
Four-YearFollow-upof [F-18]Fluorodeoxyglucose Positron Emission Tomography-Based Parkinson's Disease-Related Pattern Expression in 20 Patients With Isolated Rapid Eye Movement Sleep Behavior Disorder Shows Prodromal Progression
Background: Isolated rapid eye movement sleep behavior disorder is known to be prodromal for alpha-synucleinopathies, such as Parkinson's disease (PD) and dementia with Lewy bodies. The [18F]fluorodeoxyglucose-positron emission tomography (PET)–based PD-related brain pattern can be used to monitor disease progression. Objective: We longitudinally investigated PD-related brain pattern expression changes in 20 subjects with isolated rapid eye movement sleep behavior disorder to investigate whether this may be a suitable technique to study prodromal PD progression in these patients and to identify potential phenoconverters. Methods: Subjects underwent two [18F]fluorodeoxyglucose-PET brain scans ~3.7 years apart, along with baseline and repeated motor, cognitive, and olfactory testing within roughly the same time frame. Results: At baseline, 8 of 20 (40%) subjects significantly expressed the PD-related brain pattern (with z scores above the receiver operating characteristic–determined threshold). At follow-up, six additional subjects exhibited significant PD-related brain pattern expression (70% in total). PD-related brain pattern expression increased in all subjects (P = 0.00008). Four subjects (20%), all with significant baseline PD-related brain pattern expression, phenoconverted to clinical PD. Conclusions: Suprathreshold PD-related brain pattern expression and greater score rate of change may signify greater shorter-term risk for phenoconversion. Our results support the use of serial PD-related brain pattern expression measurements as a prodromal PD progression biomarker in patients with isolated rapid eye movement sleep behavior disorder
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