169 research outputs found
The heavy quark potential in QCD with 2 flavors of dynamical quarks
We compute the heavy quark potential on configurations generated by the
HEMCGC collaboration with dynamical staggered fermions at and
with dynamical Wilson fermions at . The computations are done on
lattices, corresponding to physical sizes of about 1.6 and 2.3
fm, respectively. Up to the distances probed no sign of string breaking is
detectable. We also compute the recently proposed scale defined by .Comment: 8 pages with 3 figures. uuencoded postscript file. FSU-SCRI-94-0
An Eloquent Proof for a Common Challenge
Sorting cells means manipulating them. This induces biological responses of the cells, resulting in functionalities not representing the previous state of the cells, but indicating effects of sorting procedures. Namely in cases that negative selection is not possible, isolated cells are distinct to their previous characteristics. This is true for bead-based sorting or flow cytometric cell separation and heavily skews functional markers of target cells. Of course, this is a limitation for any following investigation of these cells
Topological susceptibility and Instanton size distribution from over-improved cooling
We measure the topological susceptibility by cooling with an over-improved
action. In contrast with usual cooling, large instantons survive over-improved
cooling {\em indefinitely}. By varying the parameter of the over-improved
cooling action, we measure the instanton size distribution.Comment: 4 uuencoded PostScript pages, contribution to LAT95 (fig.2 simplified
to conserve space; available upon request
Towards the glueball spectrum of full QCD
We present first results on masses of the scalar and tensor glueballs as well
as of the torelon from simulations of QCD with two light flavours of Wilson
fermions. The gauge configurations of extent 16^3*32 at beta = 5.6 and kappa =
0.156, 0.157 and 0.1575 have been generated as part of the SESAM collaboration
programme. The present lattice resolutions correspond to 1/a = 2.0-2.3 GeV and
ratios m(pi)/m(rho) = 0.83, 0.76 and 0.71, respectively. Studies on larger
lattice volumes and closer to the chiral limit are in progress.Comment: 4 pages, LaTeX, espcrc2 and epsf styles required, 4 epsf figures,
poster presented by G. Bali at Lattice '9
Flow cytometric evaluation of STAT phosphorylation in T cell population
Intracellular protein phosphorylation is a critical step in cellular activation stimulated by the binding of various ligands to cell surface receptors. This process is initiated by activation of specific protein-tyrosine kinases associated with intracellular domains of the respective ligand receptor. JAK-STATs pathway is one of the main pathways in the cell activation process and given their important role in various PIDs, STATs proteins have been extensively studied in immune function in health and disease.
Therefore, our work has focused on investigating and evaluating STATs activation and establishing flow cytometric methods to assess their phosphorylation to be a surrogate marker as a fast and sensitive diagnostic tool to current methods such as WB.
At the first, we studied STAT1 and STAT3 activation and established a flow cytometric procedure to analyze variations of INF-α- and IL-6-induced STAT1 and STAT3 phosphorylation in T cells from whole blood, respectively (publication ΙΙ). To examine whether our results were specific, the samples were also analyzed by WB in parallel. After that, we validated the normal values of pSTAT1 and pSTAT3 based on 21 healthy adult controls according to an appropriate validation process.
We showed that, in contrast to the conventional methods like WB, our assay offers a diagnostic benefit by avoiding labor and time consumption, with the advantage of achieving an earlier diagnosis, which potentially leads to improve treatment decisions; hence, patient’s outcome (publication ΙΙ).
Furthermore, we verified FCM-based pSTAT1 and pSTAT3 profiling established here in patients group suffering from CMC and HIES. Our results demonstrated that pSTAT1 and pSTAT3 assay is an effective tool to identify and characterize well-known PIDs such as CMC and HIES, respectively (publication ΙΙ).
Next, we introduced a fast and straightforward flow cytometric assay for the assessment of T cell proliferation, based on the staining of phosphorylated STAT5A (publication ΙΙΙ). We showed that pSTAT5A represents an appropriate approach to predict the behavior of T cells upon activation by CD3/CD28 and PHA. FCM-based pSTAT5A profiling is an intracellular flow cytometric method, enabling the early and reliable detection of T cell proliferation without long time incubation (within 24 h instead to 5 days). Importantly, measurement of pSTAT5A represents a new principle to assess T cell proliferation. It reveals important information on T cell biology by using series of kinetics and different kinds of T cell stimulation. For instance: [1] after stimulation via CD3/CD28 and negative pSTAT5A and T cell proliferation, the immune defect could be occurred in the whole signaling cascade (TCR-IL-2 transcription-JAK3-STAT5), [2] After stimulation via external IL-2 and negative pSTAT5A, the immune defect could be localized in the signaling cascade (IL-2R – JAK3 – STAT5), [3] After stimulation via external IL-2 and positive pSTAT5A, the immune defect could be localized in the signaling cascade (TCR - IL-2 transcription) (publication ΙΙΙ).
We showed a strong correlation between the STAT5A phosphorylation and the percentage of dividing cells (publication ΙΙΙ). Later on, we used the measurement established here to investigate whether the phosphorylation of STAT5A is an appropriate candidate for predicting CMV specific T cell proliferation.
It is well-known that CMV specific T cells expand with CMV reactivation and are probably prerequisite for control and protection. We demonstrated that CMV specific pSTAT5A detection represents a fast and straightforward diagnostic tool to assess CMV specific T cell proliferation without requisite several days’ culture (publication ΙV).
Furthermore, we showed a positive correlation between the percentage of pSTAT5A+ T cells vs. (1) CMV-IgG concentrations vs. (2) the percentage of expanded T cells and vs. (3) the percentage of initial CMV specific T cells (publication ΙV).
Finally, we evaluated the diagnostic value of pSTAT5 assay and determined the percentage of pSTAT5A+ T cells cut-off value at which pSTAT5 assay has the greatest diagnostic potency. Our data showed that a cut-off value of 9.1 % could be used to assess CMV specific T cell proliferation with a specificity and sensitivity of 100% and 73%, respectively.
We verified measurement established here by CMV specific T cells stimulation in three selected patients diagnosed with CARMIL2-mutation and suffering from chronic CMV
infection. Our results showed that the complete and the partial deficiency of CMV and CD3/CD28 stimulated pSTAT5A correlated with the complete and the partial deficiency of CMV and CD3/CD28 stimulated T cell proliferation, respectively (publication ΙV).
In conclusion, disorders in JAKs-STATs signal pathways in T cells may result in insufficient response to stimulants. Therefore, FCM-based pSTATs profiling is an effective tool for clinical laboratory diagnostics [1] to understand the susceptibility to recurrent opportunistic infections [2] to rapidly identify T cell proliferation [3] to investigate tumor-specific responses of CD8 T effector and memory cells (56) and finally [4] to identify and distinguish well-known PIDs like CARMIL-2 mutations, CMC, AD-HIES or AR-HIES
Masses of singlet and non-singlet 0++ particles
We compute the mass of the singlet 0++ state using both (psi_bar psi) and
Wilson loop operators from a N_f=2 lattice QCD calculation.Comment: Lattice2002(spectrum
Effects of spatial size, lattice doubling and source operator on the hadron spectrum with dynamical staggered quarks
We have extended our previous study of the lattice QCD spectrum with 2
flavors of staggered dynamical quarks at and and 0.01
to larger lattices, with better statistics and with additional sources for the
propagators. The additional sources allowed us to estimate the mass
and to measure the masses of all mesons whose operators are local in time.
These mesons show good evidence for flavor symmetry restoration, except for the
masses of the Goldstone and non-Goldstone pions. PCAC is observed in that
, and is estimated. Use of undoubled lattices
removes problems with the pion propagator found in our earlier work. Previously
we found a large change in the nucleon mass at a quark mass of when
we increased the spatial size from 12 to 16. No such effect is observed at the
larger quark mass, . Two kinds of wall source were used, and we
have found difficulties in getting consistent results for the nucleon mass
between the two sources.Comment: 30 pages PostScript fil
A comprehensive lattice study of SU(3) glueballs
We present a study of the glueball spectrum for all values
at lattice spacings down to GeV () using lattices
of size up to . We extend previous studies and show that the continuum
limit has effectively been reached. The number of clearly identified
states has been substantially increased. There are no clear signals for
spin-exotic glueballs below 3 GeV. A comparison with current experimental
glueball candidates is made.Comment: 10 pages including 2 PS figures, Liverpool Preprint: LTH 303,
Wuppertal Preprint: WUB 93-1
QCD thermodynamics with two flavors of Wilson quarks at N_t=6
We report on a study of hadron thermodynamics with two flavors of Wilson
quarks on 12^3x6 lattices. We have studied the crossover between the high and
low temperature regimes for three values of the hopping parameter, kappa=0.16,
0.17, and 0.18. At each of these values of kappa we have carried out spectrum
calculations on 12^3x24 lattices for two values of the gauge coupling in the
vicinity of the crossover in order to set an energy scale for our
thermodynamics calculations and to determine the critical value of the gauge
coupling for which the pion and quark masses vanish. For kappa=0.17 and 0.18 we
find coexistence between the high and low temperature regimes over 1,000
simulation time units indicating either that the equilibration time is
extremely long or that there is a possibility of a first order phase
transition. The pion mass is large at the crossover values of the gauge
coupling, but the crossover curve has moved closer to the critical curve along
which the pion and quark masses vanish, than it was on lattices with four time
slices. In addition, values of the dimensionless quantity T_c/m_rho are in
closer agreement with those for staggered quarks than was the case at N_t=4. (A
POSTSCRIPT VERSION OF THIS PAPER IS AVAILABLE BY ANONYMOUS FTP FROM
sarek.physics.ucsb.edu (128.111.8.250) IN THE FILE pub/wilson_thermo.ps)Comment: 24 page
Hadron Spectrum in QCD with Valence Wilson Fermions and Dynamical Staggered Fermions at $6/g^2=5.6
We present an analysis of hadronic spectroscopy for Wilson valence quarks
with dynamical staggered fermions at lattice coupling at
sea quark mass and 0.025, and of Wilson valence quarks in quenched
approximation at and 5.95, both on lattices. We
make comparisons with our previous results with dynamical staggered fermions at
the same parameter values but on lattices doubled in the temporal
direction.Comment: 32 page
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