869 research outputs found
Lymphoma and hypercalcemia in a pediatric orthotopic liver transplant patient
We present a case report of a pediatric orthotopic liver transplant recipient who developed lymphoma with hypercalcemia on cyclosporine and prednisone immunosuppression. This is the first reported posttransplant lymphoproliferative disorder complicated by hypercalcemia, with a finding of an elevated 1,25 dihydroxyl vitamin D state, suggesting that it has a role in the pathophysiology of this B cell lymphoma hypercalcemia. The clinical course and management of this disorder with a 31-month follow-up are described. © 1989 by Williams & Wilkins
Renormalisation of quark propagators from twisted-mass lattice QCD at =2
We present results concerning the non-perturbative evaluation of the
renormalisation constant for the quark field, , from lattice simulations
with twisted mass quarks and three values of the lattice spacing. We use the
RI'-MOM scheme. has very large lattice spacing artefacts; it is
considered here as a test bed to elaborate accurate methods which will be used
for other renormalisation constants. We recall and develop the non-perturbative
correction methods and propose tools to test the quality of the correction.
These tests are also applied to the perturbative correction method. We check
that the lattice spacing artefacts scale indeed as . We then study the
running of with particular attention to the non-perturbative effects,
presumably dominated by the dimension-two gluon condensate \VEV{A^2} in
Landau gauge. We show indeed that this effect is present, and not small. We
check its scaling in physical units confirming that it is a continuum effect.
It gives a contribution at 2 GeV. Different variants are used in
order to test the reliability of our result and estimate the systematic
uncertainties. Finally combining all our results and using the known Wilson
coefficient of \VEV{A^2} we find g^2(\mu^2) \VEV{A^2}_{\mu^2\; CM} =
2.01(11)(^{+0.61}_{- 0.73}) \;\mathrm {GeV}^2 at , in
fair agreement within uncertainties with the value indepently extracted from
the strong coupling constant.Comment: 38 pages, 8 tables, 8 figure
Ghost-gluon coupling, power corrections and from twisted-mass lattice QCD at Nf=2
We present results concerning the non-perturbative evaluation of the
ghost-gluon running QCD coupling constant from twisted-mass lattice
calculations. A novel method for calibrating the lattice spacing, independent
of the string tension and hadron spectrum is presented with results in
agreement with previous estimates. The value of is
computed from the running of the QCD coupling only after extrapolating to zero
dynamical quark mass and after removing a non-perturbative OPE contribution
that is assumed to be dominated by the dimension-two \VEV{A^2} gluon
condensate. The effect due to the dynamical quark mass in the determination of
\Lams is discussed.Comment: 33 pages, 6 fig
f_B and f_Bs with maximally twisted Wilson fermions
We present a lattice QCD calculation of the heavy-light decay constants f_B
and f_Bs performed with Nf=2 maximally twisted Wilson fermions, at four values
of the lattice spacing. The decay constants have been also computed in the
static limit and the results are used to interpolate the observables between
the charm and the infinite-mass sectors, thus obtaining the value of the decay
constants at the physical b quark mass. Our preliminary results are f_B=191(14)
MeV, f_Bs=243(14) MeV, f_Bs/f_B=1.27(5). They are in good agreement with those
obtained with a novel approach, recently proposed by our Collaboration (ETMC),
based on the use of suitable ratios having an exactly known static limit.Comment: Proceedings of the 27th International Symposium on Lattice Field
Theory (Lattice 2009), Beijing, China, 2009 July 26-31. 8 pages, 3 figure
Nonuniversal scaling behavior of Barkhausen noise
We simulate Barkhausen avalanches on fractal clusters in a two-dimensional
diluted Ising ferromagnet with an effective Gaussian random field. We vary the
concentration of defect sites and find a scaling region for moderate
disorder, where the distribution of avalanche sizes has the form . The exponents for size
and for length distribution, and the fractal dimension of
avalanches satisfy the scaling relation .
For fixed disorder the exponents vary with driving rate in agreement with
experiments on amorphous Si-Fe alloys.Comment: 5 pages, Latex, 4 PostScript figures include
Self-organized criticality in the hysteresis of the Sherrington - Kirkpatrick model
We study hysteretic phenomena in random ferromagnets. We argue that the angle
dependent magnetostatic (dipolar) terms introduce frustration and long range
interactions in these systems. This makes it plausible that the Sherrington -
Kirkpatrick model may be able to capture some of the relevant physics of these
systems. We use scaling arguments, replica calculations and large scale
numerical simulations to characterize the hysteresis of the zero temperature SK
model. By constructing the distribution functions of the avalanche sizes,
magnetization jumps and local fields, we conclude that the system exhibits
self-organized criticality everywhere on the hysteresis loop.Comment: 4 pages, 4 eps figure
Casimir Effect in the Presence of Minimal Lengths
It is expected that the implementation of minimal length in quantum models
leads to a consequent lowering of Planck's scale. In this paper, using the
quantum model with minimal length of Kempf et al \cite{kempf0}, we examine the
effect of the minimal length on the Casimir force between parallel plates.Comment: 10 pages, 2 figure
Sexual Dimorphism and Estrogen Regulation of KCNE3 Expression Modulates the Functional Properties of KCNQ1 K+ Channels
The KCNQ1 potassium channel associates with various KCNE ancillary subunits that drastically affect channel gating and pharmacology. Co-assembly with KCNE3 produces a current with nearly instantaneous activation, some time-dependent activation at very positive potentials, a linear current voltage relationship and a 10-fold higher sensitivity to chromanol 293B. KCNQ1:KCNE3 channels are expressed in colonic crypts and mediate basolateral K+ recycling required for Cl- secretion. We have previously reported the female-specific anti-secretory effects of estrogen via KCNQ1:KCNE3 channel inhibition in colonic crypts. This study was designed to determine whether gender and estrogen regulate the expression and function of KCNQ1 and KCNE3 in rat distal colon. Colonic crypts were isolated from Sprague-Dawley rats and used for whole-cell patch-clamp and to extract total RNA and protein. Sheets of epithelium were used for short-circuit current recordings. KCNE1 and KCNE3 mRNA and protein abundance was significantly higher in male than female crypts. No expression of KCNE2 was found and no difference was observed in KCNQ1 expression between male and female (at estrous) colonic crypts. Male crypts showed a 2.2-fold higher level of association of KCNQ1 and KCNE3 compared to female cells. In female colonic crypts, KCNQ1 and KCNE3 protein expression fluctuated throughout the estrous cycle and 17-estradiol (E2 10 nM) produced a rapid (\u3c15\u3emin) dissociation of KCNQ1 and KCNE3 in female crypts only. Whole-cell K+ currents showed a linear current-voltage relationship in male crypts, while K+ currents in colonic crypts isolated from females displayed voltage-dependent outward rectification. Currents in isolated male crypts and epithelial sheets were 10-fold more sensitive to specific KCNQ1 inhibitors, such as chromanol 293B and HMR-1556, than in female. The effect of E2 on K+ currents mediated by KCNQ1 with or without different -subunits was assayed from current-voltage relations elicited in CHO cells transfected with KCNQ1 and KCNE3 or KCNE1 cDNA. E2 (100 nM) reduced the currents mediated by the KCNQ1:KCNE3 potassium channel and had no effect on currents via KCNQ1:KCNE1 or KCNQ1 alone. Currents mediated by the complex formed by KCNQ1 and the mutant KCNE3-S82A β-subunit showed rapid run-down and insensitivity to E2. Together, these data suggest that estrogen regulates the expression of the KCNE1 and KCNE3 and with it the gating and pharmacological properties of the K+ conductance required for Cl- secretion. The decreased association of the KCNQ1:KCNE3 channel complex promoted by estrogen exposure underlies the molecular mechanism for the sexual dimorphism and estrous cycle dependence of the anti-secretory actions of estrogen in the intestine
The thermal QCD transition with two flavours of twisted mass fermions
We investigate the thermal QCD transition with two flavors of maximally
twisted mass fermions for a set of pion masses, 300 MeV \textless
\textless 500 MeV, and lattice spacings \textless 0.09 fm. We determine the
pseudo-critical temperatures and discuss their extrapolation to the chiral
limit using scaling forms for different universality classes, as well as the
scaling form for the magnetic equation of state. For all pion masses considered
we find resonable consistency with O(4) scaling plus leading corrections.
However, a true distinction between the O(4) scenario and a first order
scenario in the chiral limit requires lighter pions than are currently in use
in simulations of Wilson fermions.Comment: 11 pages, 11 figure
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