933 research outputs found
The Goldberger-Treiman Discrepancy
The Golberger- Treiman discrepancy is related to the asymptotic behaviour of
the pionic form factor of the nucleon obtained from baryonic QCD sum rules. The
result is .015<=Delta_{GT}<=.022Comment: References updated and minor correction
Estimating Seroprevalence of Herpes Simplex Virus Type 1 among Different Middle East and North African Male Populations Residing in Qatar
HSV-1 epidemiology in the Middle East and North Africa (MENA) remains poorly understood. Our study aimed to measure HSV-1 antibody prevalence (seroprevalence) and its age-distribution among select MENA populations residing in Qatar. Sera were collected from male blood donors attending Hamad Medical Corporation 2013-2015. A total of 2,077 sera were tested for anti-HSV-1 antibodies using HerpeSelect® 1 ELISA IgG kits (Focus Diagnostics, USA). Robust Poisson regression was conducted to estimate adjusted infection prevalence ratios. Country-specific HSV-1 seroprevalence was estimated for 10 national populations: 97.5% among Egyptians, 92.6% among Yemenis, 90.7% among Sudanese, 88.5% among Syrians, 86.5% among Jordanians, 82.3% among Qataris, 81.4% among Iranians, 81.4% among Lebanese, 80.5% among Palestinians, and 77.0% among Pakistanis. Age-specific HSV-1 seroprevalence was estimated for Egypt, the Fertile Crescent (Iraq, Jordan, Lebanon, Palestine, and Syria), and Qatar. Seroprevalence increased with age among Fertile Crescent and Qatari nationals. Seroprevalence increased from 70.0% among those aged ≤24 years up to 98.0% among those aged ≥55 years among Fertile Crescent nationals. Seroprevalence was consistently above 90% for all ages among Egyptians. HSV-1 seroprevalence is high in MENA, though with some variation across countries. The seroprevalence appears to have declined among current young age cohorts compared to its levels a few decades ago
Up and down quark masses from Finite Energy QCD sum rules to five loops
The up and down quark masses are determined from an optimized QCD Finite
Energy Sum Rule (FESR) involving the correlator of axial-vector divergences, to
five loop order in Perturbative QCD (PQCD), and including leading
non-perturbative QCD and higher order quark mass corrections. This FESR is
designed to reduce considerably the systematic uncertainties arising from the
(unmeasured) hadronic resonance sector, which in this framework contributes
less than 3-4% to the quark mass. This is achieved by introducing an
integration kernel in the form of a second degree polynomial, restricted to
vanish at the peak of the two lowest lying resonances. The driving hadronic
contribution is then the pion pole, with parameters well known from experiment.
The determination is done in the framework of Contour Improved Perturbation
Theory (CIPT), which exhibits a very good convergence, leading to a remarkably
stable result in the unusually wide window , where
is the radius of the integration contour in the complex energy (squared)
plane. The results are: MeV, MeV, and Mev (at a scale Q=2 GeV).Comment: Additional references to lattice QCD results have been adde
Experimental Study of a Beta Stirling Thermal Machine Type Functioning in Receiver and Engine Modes
In this paper we studied a beta type Stirling machine. At first, we present the adopted theoretical quasi-stationary
model. Then, we pass to the physical and geometrical presentation of this machine. The Latter was experimented
according to two configurations: motor configuration and receiver configuration. For the first configuration, in order
to improve the performances of the machine, we proceeded to the insulation of the machine hot room to reduce losses
by radiation. For the second configuration, the machine is experimented as a heat pump and refrigerator.
Comparisons between the theoretical and experimental results are also presented. We finally validated the results
obtained by the model with experiments
Strange quark condensate from QCD sum rules to five loops
It is argued that it is valid to use QCD sum rules to determine the scalar
and pseudoscalar two-point functions at zero momentum, which in turn determine
the ratio of the strange to non-strange quark condensates with (). This is done in the framework
of a new set of QCD Finite Energy Sum Rules (FESR) that involve as integration
kernel a second degree polynomial, tuned to reduce considerably the systematic
uncertainties in the hadronic spectral functions. As a result, the parameters
limiting the precision of this determination are , and to a
major extent the strange quark mass. From the positivity of there
follows an upper bound on the latter: , for Comment: Minor changes to Sections 2 and
On the Spin content of the Nucleon
A QCD sum rule calculation of Balistky and Ji on the spin content of the
nucleon is done with a different approach to the evaluation of the bilocal
contributions and to the extraction of the nucleon pole residues. The result
obtained is much more numerically stable which puts their conclusion that about
half of the nucleon spin is carried by gluons on firmer ground.Comment: 7 pages, two (eps) figure, minor corrections and one figure adde
Endoglin potentiates nitric oxide synthesis to enhance definitive hematopoiesis.
During embryonic development, hematopoietic cells develop by a process of endothelial-to hematopoietic transition of a specialized population of endothelial cells. These hemogenic endothelium (HE) cells in turn develop from a primitive population of FLK1(+) mesodermal cells. Endoglin (ENG) is an accessory TGF-β receptor that is enriched on the surface of endothelial and hematopoietic stem cells and is also required for the normal development of hemogenic precursors. However, the functional role of ENG during the transition of FLK1(+) mesoderm to hematopoietic cells is ill defined. To address this we used a murine embryonic stem cell model that has been shown to mirror the temporal emergence of these cells in the embryo. We noted that FLK1(+) mesodermal cells expressing ENG generated fewer blast colony-forming cells but had increased hemogenic potential when compared with ENG non-expressing cells. TIE2(+)/CD117(+) HE cells expressing ENG also showed increased hemogenic potential compared with non-expressing cells. To evaluate whether high ENG expression accelerates hematopoiesis, we generated an inducible ENG expressing ES cell line and forced expression in FLK1(+) mesodermal or TIE2(+)/CD117(+) HE cells. High ENG expression at both stages accelerated the emergence of CD45(+) definitive hematopoietic cells. High ENG expression was associated with increased pSMAD2/eNOS expression and NO synthesis in hemogenic precursors. Inhibition of eNOS blunted the ENG induced increase in definitive hematopoiesis. Taken together, these data show that ENG potentiates the emergence of definitive hematopoietic cells by modulating TGF-β/pSMAD2 signalling and increasing eNOS/NO synthesis.The authors thank Dr Zúñiga-Pflücker (University of Toronto) for the ENG-/- and +/- murine ES cells. This work was supported by grants from the National Health and Medical Research Council of Australia, Australian Research Council and the Dr Tom Bee Stem Cell Research Fund to JEP, Cancer Research UK to VK and GL and the BBSRC, Leukaemia and Lymphoma Research, The Leukaemia and Lymphoma Society, Cancer Research UK, and core support grants by the Wellcome Trust to the Cambridge Institute for Medical Research and Wellcome Trust - MRC Cambridge Stem Cell Institute to BG.This is the final version of the article. It first appeared from the Company of Biologists via http://dx.doi.org/10.1242/bio.01149
Revealing the KH2PO4 soft-mode coupling mechanism with infrared spectroscopy under pressure
We measured the far-infrared reflectivity of a KH2PO4 single crystal up to
pressures of 2 GPa in the ferroelectric and paraelectric phases. We find that
the nu4 vibrational mode of the PO4 tetrahedron is strongly affected by the
applied pressure. At ambient pressure this phonon is destabilized by the
presence of the H ions and hence shows a highly damped character, beyond the
phonon propagation threshold. Applying a pressure close to 0.6 GPa makes this
phonon clearly underdamped. Its behavior closely follows the soft-mode behavior
observed in Raman spectroscopy. Our results solve a long standing open problem,
demonstrating that the nu4 mode is the excitation mediating the coupling of the
hydrogen network to the lattice modes that create the ferroelectic polarization
in KH2PO4.Comment: 5 pages, 4 figure
Targeting the CBM complex causes Treg cells to prime tumours for immune checkpoint therapy.
Solid tumours are infiltrated by effector T cells with the potential to control or reject them, as well as by regulatory T (Treg) cells that restrict the function of effector T cells and thereby promote tumour growth1. The anti-tumour activity of effector T cells can be therapeutically unleashed, and is now being exploited for the treatment of some forms of human cancer. However, weak tumour-associated inflammatory responses and the immune-suppressive function of Treg cells remain major hurdles to broader effectiveness of tumour immunotherapy2. Here we show that, after disruption of the CARMA1-BCL10-MALT1 (CBM) signalosome complex, most tumour-infiltrating Treg cells produce IFNγ, resulting in stunted tumour growth. Notably, genetic deletion of both or even just one allele of CARMA1 (also known as Card11) in only a fraction of Treg cells-which avoided systemic autoimmunity-was sufficient to produce this anti-tumour effect, showing that it is not the mere loss of suppressive function but the gain of effector activity by Treg cells that initiates tumour control. The production of IFNγ by Treg cells was accompanied by activation of macrophages and upregulation of class I molecules of the major histocompatibility complex on tumour cells. However, tumour cells also upregulated the expression of PD-L1, which indicates activation of adaptive immune resistance3. Consequently, blockade of PD-1 together with CARMA1 deletion caused rejection of tumours that otherwise do not respond to anti-PD-1 monotherapy. This effect was reproduced by pharmacological inhibition of the CBM protein MALT1. Our results demonstrate that partial disruption of the CBM complex and induction of IFNγ secretion in the preferentially self-reactive Treg cell pool does not cause systemic autoimmunity but is sufficient to prime the tumour environment for successful immune checkpoint therapy
Two photon decay of the pseudoscalars, the chiral symmetry breaking corrections
The extrapolation of the decay amplitudes of the pseudoscalar mesons into two
photons from the soft meson limit where it is obtained from the axial-anomaly
to the mass shell involves the contribution of the 0^ - continuum. These chiral
symmetry breaking corrections turn out to be large. The effects of these
corrections on the calculated pi ^0 decay rate, on the values of the
singlet-octet mixing angle and on the ratios f_8 / f_pi and f_0 / f_pi are
discussed. The implications for the transition form factors gamma gamma* -->
pseudoscalars are also evaluated and confronted with the available experimental
data.Comment: Computational errors straightened and study of the implications on
the form factors of the transitions gamma gamma* --> pseudoscalars adde
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