33 research outputs found
Charmonium at finite temperature in quenched lattice QCD
We study charmonium correlators in pseudoscalar and vector channels at finite
temperature using lattice QCD simulation in the quenched approximation.
Anisotropic lattices are used in order to have sufficient numbers of degrees of
freedom in the Euclidean temporal direction. We focus on the low energy
structure of the spectral function, corresponding to the ground state in the
hadron phase, by applying the smearing technique to enhance the contribution to
the correlator from this region. We employ two analysis procedures: the maximum
entropy method (MEM) for the extraction of the spectral function without
assuming a specific form, to estimate the shape of the spectral function, and
the standard fit analysis using typical forms in accordance with the
result of MEM, for a more quantitative evaluation. To verify the applicability
of the procedures, we first analyze the smeared correlators as well as the
point correlators at zero temperature. We find that by shortening the
-interval used for the analysis (a situation inevitable at ) the
reliability of MEM for point correlators is lost, while it subsists for smeared
correlators. Then the smeared correlators at and
are analyzed. At , the spectral function exhibits a strong
peak, well approximated by a delta function corresponding to the ground state
with almost the same mass as at T=0. At , we find that the
strong peak structure still persists at almost the same place as below ,
but with a finite width of a few hundred MeV. This result indicates that the
correlators possess a nontrivial structure even in the deconfined phase.Comment: 19 pages, 26 figure
Numerical study of staggered quark action on quenched anisotropic lattices
The staggered quark action on anisotropic lattices is studied. We carry out
numerical simulations in the quenched approximation at three values of lattice
spacing ( GeV) with the anisotropy , where and are the spatial and
temporal lattice spacings, respectively. The bare anisotropy in the
quark action is numerically tuned through the ratio of meson masses in the fine
and coarse directions, and through the dispersion relation of a meson, so that
the renormalized fermionic anisotropy coincides with that of the gauge field.
The discrepancy between these two calibration schemes provides an estimate of
the finite lattice artifact, which is found to be sizable in the range of
cutoff explored in this work. We also compute the meson masses using
correlators with the wall source at the tuned anisotropy parameter. The flavor
symmetry breaking effect smoothly decreases as increases. The effect of
uncertainty in on the meson masses are examined. We also discuss a
perspective on dynamical simulations.Comment: 19 pages, 15 eps figure
Charmonium near the deconfining transition on the lattice
We study the charmonium properties at finite temperature using quenched
lattice QCD simulations. Although a simple potential model analysis indicates
no bound state at , our analyses of the spatial correlation between
quark and anti-quark and the spectral function indicate that a bound-state-like
structure may survive even above .Comment: 4 pages, 3 figures, Talk presented at the PANIC02 conference, Sept.
30 - Oct. 4, 2002, Osaka, Japa
Specific Egg Yolk Immunoglobulin as a New Preventive Approach for Shiga-Toxin-Mediated Diseases
Shiga toxins (Stxs) are involved in the development of severe systemic complications associated with enterohemorrhagic Escherichia coli (EHEC) infection. Various neutralizing agents against Stxs are under investigation for management of EHEC infection. In this study, we immunized chickens with formalin-inactivated Stx-1 or Stx-2, and obtained immunoglobulin Y (IgY) from the egg yolk. Anti-Stx-1 IgY and anti-Stx-2 IgY recognized the corresponding Stx A subunit and polymeric but not monomeric B subunit. Anti-Stx-1 IgY and anti-Stx-2 IgY suppressed the cytotoxicity of Stx-1 and Stx-2 to HeLa 229 cells, without cross-suppressive activity. The suppressive activity of these IgY was abrogated by pre-incubation with the corresponding recombinant B subunit, which suggests that the antibodies directed to the polymeric B subunits were predominantly involved in the suppression. In vivo, the intraperitoneal or intravenous administration of these IgY rescued mice from death caused by intraperitoneal injection of the corresponding toxin at a lethal dose. Moreover, oral administration of anti-Stx-2 IgY reduced the mortality of mice infected intestinally with EHEC O157:H7. Our results therefore suggest that anti-Stx IgY antibodies may be considered as preventive agents for Stx-mediated diseases in EHEC infection
Phosphatidylethanolamine Domains and Localization of Phospholipid Synthases in Bacillus subtilis Membranes
Application of the cardiolipin (CL)-specific fluorescent dye 10-N-nonyl-acridine orange has recently revealed CL-rich domains in the septal regions and at the poles of the Bacillus subtilis membrane (F. Kawai, M. Shoda, R. Harashima, Y. Sadaie, H. Hara, and K. Matsumoto, J. Bacteriol. 186:1475-1483, 2004). This finding prompted us to examine the localization of another phospholipid, phosphatidylethanolamine (PE), with the cyclic peptide probe, Ro09-0198 (Ro), that binds specifically to PE. Treatment with biotinylated Ro followed by tetramethyl rhodamine-conjugated streptavidin revealed that PE is localized in the septal membranes of vegetative cells and in the membranes of the polar septum and the engulfment membranes of sporulating cells. When the mutant cells of the strains SDB01 (psd1::neo) and SDB02 (pssA10::spc), which both lack PE, were examined under the same conditions, no fluorescence was observed. The localization of the fluorescence thus evidently reflected the localization of PE-rich domains in the septal membranes. Similar PE-rich domains were observed in the septal regions of the cells of many Bacillus species. In Escherichia coli cells, however, no PE-rich domains were found. Green fluorescent protein fusions to the enzymes that catalyze the committed steps in PE synthesis, phosphatidylserine synthase, and in CL synthesis, CL synthase and phosphatidylglycerophosphate synthase, were localized mainly in the septal membranes in B. subtilis cells. The majority of the lipid synthases were also localized in the septal membranes; this includes 1-acyl-glycerol-3-phosphate acyltransferase, CDP-diacylglycerol synthase, phosphatidylserine decarboxylase, diacylglycerol kinase, glucolipid synthase, and lysylphosphatidylglycerol synthase. These results suggest that phospholipids are produced mostly in the septal membranes and that CL and PE are kept from diffusing out to lateral ones