199 research outputs found
Relativistic chiral representation of the scattering amplitude I: The Goldberger-Treiman relation
In this work we study the scattering process within the Baryon Chiral
Perturbation Theory framework in the covariant scheme of Extended-On-Mass-Shell
(EOMS).
We compare the description obtained in this scheme with the previously
obtained using the Infrared Regularization scheme and show that EOMS
accomplishes the best convergence, being able to extract from partial wave
analyses reliable values of important quantities as the Goldberger-Treiman
deviation. In regard to the latter, we solve the long-standing problem
concerning to the extraction of the Goldberger-Treiman deviation with covariant
ChPT that jeopardized the applicability of ChPT to the system.
We also show the potential of the unitarization techniques applied to the
perturbative calculation in the EOMS scheme, that allow us to increase the
range of validity of our description up to MeV in .Comment: PROCEEDINGS to the 33rd International School of Nuclear Physics "From
Quarks and Gluons to Hadrons and Nuclei"- 7 Pag,, 1 Table, 4 Figures.
Erice-Sicily: 16 - 24 September 201
Mathematical modeling and numerical simulation of heat dissipation In LED bulbs
[EN] We present a detailed study of heating and cooling processes in LED luminaires with passive heat sinks. Our analysis is supported by numerical simulations as well as experimental measurements, carried on commercial systems used for outdoor lighting.
We have focused our analysis on the common case of a single LED source in thermal contact with an aluminum passive heat sink, obtaining an excellent agreement with experimental measurements and the numerical simulations performed. Our results can be easily expanded, without loss of generality, to similar systems.D. A. acknowledges SENESCYT for financial support (Convocatoria Abierta 2015 para cursar estudios de doctorado). HM thanks funding from projects K133131H64102 and K044131H64502 Xunta de Galicia.P.F.C. and J.M.I. acknoweldges funding from grant MEC, grant RTI2018-102256-B-100 (Spain)Alarcon, D.; Balvis, E.; Bendaña, R.; Conejero, JA.; Fernández De Córdoba, P.; Higón Calvet, JL.; Isidro, J.... (2020). Mathematical modeling and numerical simulation of heat dissipation In LED bulbs. Thermal Science. 24(3A):1877-1884. https://doi.org/10.2298/TSCI190521076AS18771884243
On the van der Waals Gas, Contact Geometry and the Toda Chain
[EN] A Toda¿chain symmetry is shown to underlie the van derWaals gas and its close cousin, the ideal gas. Links to contact geometry are explored.This research was supported by Grant No. ENE2015-71333-R (Spain) and Convocatoria Abierta 2015 para Cursar Estudios de Doctorado, SENESCYT (Ecuador).Alarcon-Correa, D.; Fernández De Córdoba, P.; Isidro, J.; Orea, C. (2018). On the van der Waals Gas, Contact Geometry and the Toda Chain. Entropy. 20(8):554-558. https://doi.org/10.3390/e20080554S55455820
Probing exotic phenomena at the interface of nuclear and particle physics with the electric dipole moments of diamagnetic atoms: A unique window to hadronic and semi-leptonic CP violation
The current status of electric dipole moments of diamagnetic atoms which
involves the synergy between atomic experiments and three different theoretical
areas -- particle, nuclear and atomic is reviewed. Various models of particle
physics that predict CP violation, which is necessary for the existence of such
electric dipole moments, are presented. These include the standard model of
particle physics and various extensions of it. Effective hadron level combined
charge conjugation (C) and parity (P) symmetry violating interactions are
derived taking into consideration different ways in which a nucleon interacts
with other nucleons as well as with electrons. Nuclear structure calculations
of the CP-odd nuclear Schiff moment are discussed using the shell model and
other theoretical approaches. Results of the calculations of atomic electric
dipole moments due to the interaction of the nuclear Schiff moment with the
electrons and the P and time-reversal (T) symmetry violating
tensor-pseudotensor electron-nucleus are elucidated using different
relativistic many-body theories. The principles of the measurement of the
electric dipole moments of diamagnetic atoms are outlined. Upper limits for the
nuclear Schiff moment and tensor-pseudotensor coupling constant are obtained
combining the results of atomic experiments and relativistic many-body
theories. The coefficients for the different sources of CP violation have been
estimated at the elementary particle level for all the diamagnetic atoms of
current experimental interest and their implications for physics beyond the
standard model is discussed. Possible improvements of the current results of
the measurements as well as quantum chromodynamics, nuclear and atomic
calculations are suggested.Comment: 46 pages, 19 tables and 16 figures. A review article accepted for
EPJ
Constraints on Supersymmetry from LHC data on SUSY searches and Higgs bosons combined with cosmology and direct dark matter searches
The ATLAS and CMS experiments did not find evidence for Supersymmetry using
close to 5/fb of published LHC data at a center-of-mass energy of 7 TeV. We
combine these LHC data with data on B_s -> mu mu (LHCb experiment), the relic
density (WMAP and other cosmological data) and upper limits on the dark matter
scattering cross sections on nuclei (XENON100 data). The excluded regions in
the constrained Minimal Supersymmetric SM (CMSSM) lead to gluinos excluded
below 1270 GeV and dark matter candidates below 220 GeV for values of the
scalar masses (m_0) below 1500 GeV. For large m_0 values the limits of the
gluinos and the dark matter candidate are reduced to 970 GeV and 130 GeV,
respectively. If a Higgs mass of 125 GeV is imposed in the fit, the preferred
SUSY region is above this excluded region, but the size of the preferred region
is strongly dependent on the assumed theoretical error.Comment: 12 pages, 5 figures, Refs. updated, Published version in Eur. Phys.
J. C with updated references and minor corrections. arXiv admin note:
substantial text overlap with arXiv:1202.336
Burden and risk factors for Pseudomonas aeruginosa community-acquired pneumonia:a Multinational Point Prevalence Study of Hospitalised Patients
Pseudornonas aeruginosa is a challenging bacterium to treat due to its intrinsic resistance to the antibiotics used most frequently in patients with community-acquired pneumonia (CAP). Data about the global burden and risk factors associated with P. aeruginosa-CAP are limited. We assessed the multinational burden and specific risk factors associated with P. aeruginosa-CAP.
We enrolled 3193 patients in 54 countries with confirmed diagnosis of CAP who underwent microbiological testing at admission. Prevalence was calculated according to the identification of P. aeruginosa. Logistic regression analysis was used to identify risk factors for antibiotic-susceptible and antibiotic-resistant P. aeruginosa-CAP.
The prevalence of P. aeruginosa and antibiotic-resistant P. aeruginosa-CAP was 4.2% and 2.0%, respectively. The rate of P. aeruginosa CAP in patients with prior infection/colonisation due to P. aeruginosa and at least one of the three independently associated chronic lung diseases (i.e. tracheostomy, bronchiectasis and/or very severe chronic obstructive pulmonary disease) was 67%. In contrast, the rate of P. aeruginosa-CAP was 2% in patients without prior P. aeruginosa infection/colonisation and none of the selected chronic lung diseases. The multinational prevalence of P. aeruginosa-CAP is low.
The risk factors identified in this study may guide healthcare professionals in deciding empirical antibiotic coverage for CAP patients
Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET
The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutron emission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of a measured time-of-flight spectrum from TOFOR
Autoantibodies against type I IFNs in patients with life-threatening COVID-19
Interindividual clinical variability in the course of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection is vast. We report that at least 101 of 987 patients with life-threatening coronavirus disease 2019 (COVID-19) pneumonia had neutralizing immunoglobulin G (IgG) autoantibodies (auto-Abs) against interferon-w (IFN-w) (13 patients), against the 13 types of IFN-a (36), or against both (52) at the onset of critical disease; a few also had auto-Abs against the other three type I IFNs. The auto-Abs neutralize the ability of the corresponding type I IFNs to block SARS-CoV-2 infection in vitro. These auto-Abs were not found in 663 individuals with asymptomatic or mild SARS-CoV-2 infection and were present in only 4 of 1227 healthy individuals. Patients with auto-Abs were aged 25 to 87 years and 95 of the 101 were men. A B cell autoimmune phenocopy of inborn errors of type I IFN immunity accounts for life-threatening COVID-19 pneumonia in at least 2.6% of women and 12.5% of men
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