12,052 research outputs found
Corrections to the Gell-Mann-Oakes-Renner relation and chiral couplings and
Next to leading order corrections to the
Gell-Mann-Oakes-Renner relation (GMOR) are obtained using weighted QCD Finite
Energy Sum Rules (FESR) involving the pseudoscalar current correlator. Two
types of integration kernels in the FESR are used to suppress the contribution
of the kaon radial excitations to the hadronic spectral function, one with
local and the other with global constraints. The result for the pseudoscalar
current correlator at zero momentum is , leading to the chiral corrections to GMOR: . The resulting uncertainties are mostly due to variations in the upper
limit of integration in the FESR, within the stability regions, and to a much
lesser extent due to the uncertainties in the strong coupling and the strange
quark mass. Higher order quark mass corrections, vacuum condensates, and the
hadronic resonance sector play a negligible role in this determination. These
results confirm an independent determination from chiral perturbation theory
giving also very large corrections, i.e. roughly an order of magnitude larger
than the corresponding corrections in chiral . Combining
these results with our previous determination of the corrections to GMOR in
chiral , , we are able to determine two low
energy constants of chiral perturbation theory, i.e. , and , both at the
scale of the -meson mass.Comment: Revised version with minor correction
Numerical simulation of a binary communication channel: Comparison between a replica calculation and an exact solution
The mutual information of a single-layer perceptron with Gaussian inputs
and deterministic binary outputs is studied by numerical simulations. The
relevant parameters of the problem are the ratio between the number of output
and input units, , and those describing the two-point
correlations between inputs. The main motivation of this work refers to the
comparison between the replica computation of the mutual information and an
analytical solution valid up to . The most relevant results
are: (1) the simulation supports the validity of the analytical prediction, and
(2) it also verifies a previously proposed conjecture that the replica solution
interpolates well between large and small values of .Comment: 6 pages, 8 figures, LaTeX fil
Circadian Entrainment Triggers Maturation of Human In Vitro Islets
Stem-cell-derived tissues could transform disease research and therapy, yet most methods generate functionally immature products. We investigate how human pluripotent stem cells (hPSCs) differentiate into pancreatic islets in vitro by profiling DNA methylation, chromatin accessibility, and histone modification changes. We find that enhancer potential is reset upon lineage commitment and show how pervasive epigenetic priming steers endocrine cell fates. Modeling islet differentiation and maturation regulatory circuits reveals genes critical for generating endocrine cells and identifies circadian control as limiting for in vitro islet function. Entrainment to circadian feeding/fasting cycles triggers islet metabolic maturation by inducing cyclic synthesis of energy metabolism and insulin secretion effectors, including antiphasic insulin and glucagon pulses. Following entrainment, hPSC-derived islets gain persistent chromatin changes and rhythmic insulin responses with a raised glucose threshold, a hallmark of functional maturity, and function within days of transplantation. Thus, hPSC-derived tissues are amenable to functional improvement by circadian modulation
Magnesium and hypertension in old age
Hypertension is a complex condition in which various actors and mechanisms combine, resulting in cardiovascular and cerebrovascular complications that today represent the most fre-quent causes of mortality, morbidity, disability, and health expenses worldwide. In the last decades, there has been an exceptional amount of experimental, epidemiological, and clinical studies confirm-ing a close relationship between magnesium deficit and high blood pressure. Multiple mechanisms may help to explain the bulk of evidence supporting a protective effect of magnesium against hypertension and its complications. Hypertension increases sharply with advancing age, hence older persons are those most affected by its negative consequences. They are also more frequently at risk of magnesium deficiency by multiple mechanisms, which may, at least in part, explain the higher frequency of hypertension and its long-term complications. The evidence for a favorable effect of magnesium on hypertension risk emphasizes the importance of broadly encouraging the intake of foods such as vegetables, nuts, whole cereals and legumes, optimal dietary sources of magnesium, avoiding processed food, which are very poor in magnesium and other fundamental nutrients, in order to prevent hypertension. In some cases, when diet is not enough to maintain an adequate magnesium status, magnesium supplementation may be of benefit and has been shown to be well tolerated
Size-Controlled Water-Soluble Ag Nanoparticles
Ag nanoparticles of two different sizes (1 and 4 nm) were prepared within an apoferritin cavity by using an Ag+-loaded apoferritin as a nanoconfined environment for their construction. The initial amount of Ag' ions injected in the apoferritin cavity dictates the size of the final Ag particles. The protein shell prevents bulk aggregation of the metal particles, which renders them water soluble and extremely stable
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Information and Communication Technologies (ICT): Components, Dimensions, and its Correlates
Information and Communication Technologies (ICT) has been identified as one of the crucial factors that affect teaching effectiveness and student learning worldwide. UNESCO, many international organizations, and many governments emphasized the importance of ICT and try to incorporate ICT into education systems. This study examined self-assessed computer competency in thirteen ICT areas from two samples, e.g., the United States and Mexico. Reliability tests were conducted, and rank analysis was done among them. By using factor analysis, these thirteen areas were grouped into three categories: “basic ICT skills”; “advanced ICT skills;” and “multimedia skills and attitudes towards ICT”. Subjects showed the highest scores in basic ICT skills, which include knowledge of computer systems, use of the operating system, search internet and communication and networking. The multimedia skills and attitudes towards ICT demonstrated the second highest scores. Advanced ICT skills that include image processing, use of database, technological platforms, and web 2.0 tools was found to have the lowest competency scores among subjects. Multivariate analysis was also conducted and found that age and gender are two significant factors to predict ICT competency, and age was found to have a non-linear relationship on advanced ICT skills
Two photon decay of neutral scalars below 1.5 GeV in a chiral model for bar{q}q and bar{q}bar{q}qq states
We study the two photon decay of neutral scalars below 1.5 GeV in the context
of a recently proposed chiral model for bar{q}q and bar{q}bar{q}qq states. We
find good agreement with experimental results for the a_{0}(980)->gamma gamma.
Our calculations for f_{0}(980)->gamma gamma shows that further work is
necessary in order to understand the structure of this meson. The model
predicts Gamma(a_{0}(1450)->gamma gamma)=0.16+/-0.10KeV, Gamma(sigma->gamma
gamma)=0.47+/-0.66 KeV, Gamma(f(1370)->gamma gamma)=0.07+/-0.15 KeV,
Gamma(f(1500)->gamma gamma)=0.74+/-0.78 KeV.Comment: 6 pages, 1 figur
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
Magnesium in infectious diseases in older people
Reduced magnesium (Mg) intake is a frequent cause of deficiency with age together with reduced absorption, renal wasting, and polypharmacotherapy. Chronic Mg deficiency may result in increased oxidative stress and low-grade inflammation, which may be linked to several age-related diseases, including higher predisposition to infectious diseases. Mg might play a role in the immune response being a cofactor for immunoglobulin synthesis and other processes strictly associated with the function of T and B cells. Mg is necessary for the biosynthesis, transport, and activation of vitamin D, another key factor in the pathogenesis of infectious diseases. The regulation of cytosolic free Mg in immune cells involves Mg transport systems, such as the melastatin-like transient receptor potential 7 channel, the solute carrier family, and the magnesium transporter 1 (MAGT1). The functional importance of Mg transport in immunity was unknown until the description of the primary immunodeficiency XMEN (X-linked immunodeficiency with Mg defect, Epstein–Barr virus infection, and neoplasia) due to a genetic deficiency of MAGT1 characterized by chronic Epstein–Barr virus infection. This and other research reporting associations of Mg deficit with viral and bacterial infections indicate a possible role of Mg deficit in the recent coronavirus disease 2019 (COVID-19) and its complications. In this review, we will discuss the importance of Mg for the immune system and for infectious diseases, including the recent pandemic of COVID-19
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