714 research outputs found
N_c and m_pi dependence of rho and sigma mesons from unitarized Chiral Perturbation Theory
We review our work on the rho and sigma resonances derived from the Inverse
Amplitude Method. In particular, we study the leading 1/N_c behavior of the
resonances masses and widths and their evolution with changing m_pi. The 1/N_c
expansion gives a clear definition of quark-antiquark states, which is neatly
satisfied by the rho but not by the sigma, showing that its dominant component
is not quark-antiquark. The m_pi dependence of the resonance properties is
relevant to connect with lattice studies. We show that our predictions compare
well with some lattice results and we find that the rho-pi-pi coupling constant
is m_pi independent, in contrast with the sigma-pi-pi coupling, that shows a
strong m_pi dependence.Comment: To appear in the Proceedings of the Chiral10 Workshop, June 21-24
2010. Valencia, Spai
Chiral extrapolation of light resonances from one and two-loop unitarized Chiral Perturbation Theory versus lattice results
We study the pion mass dependence of the rho(770) and f_0(600) masses and
widths from one and two-loop unitarized Chiral Perturbation Theory. We show the
consistency of one-loop calculations with lattice results for the M_rho, f_pi
and the isospin 2 scattering length a_20.Then, we develop and apply the
modified Inverse Amplitude Method formalism for two-loop ChPT. In contrast to
the f_0(600), the rho(770) is rather sensitive to the two-loop ChPT parameters
--our main source of systematic uncertainty. We thus provide two-loop
unitarized fits constrained by lattice information on M_rho, f_pi, by the qqbar
leading 1/N_c behavior of the rho and by existing estimates of low energy
constants. These fits yield relatively stable predictions up to m_pi\simeq
300-350 MeV for the rho coupling and width as well as for all the f_0(600)
parameters. We confirm, to two-loops, the weak m_pi dependence of the rho
coupling and the KSRF relation, and the existence of two virtual f_0(600) poles
for sufficiently high m_pi. At two loops one of these poles becomes a bound
state when m_pi is somewhat larger than 300 MeV.Comment: 15 pages, to appear in Phys. Rev.
Properties of light resonances from unitarized Chiral perturbation theory: Nc behavior and quark mass dependence
We review the unitarization of Chiral Perturbation Theory with dispersion
relations and how it describes meson-meson scattering data, generating light
resonances whose mass, width and nature can be related to QCD parameters like
quark masses and the number of colors.Comment: Invited review talk for the New Frontiers in QCD 2010, Yukawa
International Program for Quark-Hadron Sciences (YIPQS), January 18 (Mon) -
March 19 (Fri), 2010 Yukawa Institute for Theoretical Physics, Kyoto, Japan.
To appear in Progress of Theoretical Physic
High prevalence of scrapie in a dairy goat herd: tissue distribution of disease-associated PrP and effect of PRNP genotype and age
Following a severe outbreak of clinical scrapie in 2006–2007, a
large dairy goat herd was culled
and 200 animals were selected for post-mortem examinations in order to
ascertain the prevalence of infection,
the effect of age, breed and PRNP genotype on the susceptibility to scrapie,
the tissue distribution of diseaseassociated
PrP (PrP), and the comparative efficiency of different diagnostic methods.
As determined by immunohistochemical (IHC) examinations with Bar224 PrP antibody, the
prevalence of preclinical infection
was very high (72/200; 36.0%), with most infected animals being positive
for PrP in lymphoreticular system
(LRS) tissues (68/72; 94.4%) compared to those that were positive in
brain samples (38/72; 52.8%). The
retropharyngeal lymph node and the palatine tonsil showed the highest
frequency of PrP accumulation (87.3%
and 84.5%, respectively), while the recto-anal mucosa-associated lymphoid
tissue (RAMALT) was positive in
only 30 (41.7%) of the infected goats. However, the efficiency of rectal
and palatine tonsil biopsies taken
shortly before necropsy was similar. The probability of brain and RAMALT
being positive directly
correlated with the spread of PrP within the LRS. The prevalence of
infection was influenced by PRNP
genetics at codon 142 and by the age of the goats: methionine carriers older
than 60 months showed a much
lower prevalence of infection (12/78; 15.4%) than those younger than 60 months (20/42; 47.6%); these last
showed prevalence values similar to isoleucine homozygotes of any age
(40/80; 50.0%). Two of seven goats
with definite signs of scrapie were negative for PrP in brain but positive
in LRS tissues, and one goat showed
biochemical and IHC features of PrP different from all other infected
goats. The results of this study have
implications for surveillance and control policies for scrapie in goats
Dynamical study of the light scalar mesons below 1 GeV in a flux-tube model
The light scalar mesons below 1 GeV as tetraquark states are studied in the
framework of the flux-tube model, the multi-body confinement instead of the
additive two-body confinement is used. From the calculated results, we find
that the light scalar mesons, , could be well accommodated in
the diquark-antidiquark tetraquark picture in the flux-tube model and they
could be color confinement resonances. The mass of the first radial excited
state of is 1019 MeV, which is close to the mass of
. Whereas can not be fitted in this interpretation.Comment: 11 pages, 1 figur
Mobile Personal Healthcare System for Non-Invasive, Pervasive and Continuous Blood Pressure Monitoring: A Feasibility Study
Background: Smartphone-based blood pressure (BP) monitor using photoplethysmogram (PPG) technology has emerged as a promising approach to empower users with self-monitoring for effective diagnosis and control ofhypertension (HT).
Objective: This study aimed to develop a mobile personal healthcare system for non-invasive, pervasive, and continuous estimation of BP level and variability to be user-friendly to elderly.
Methods: The proposed approach was integrated by a self-designed cuffless, calibration-free, wireless and wearable PPG-only sensor, and a native purposely-designed smartphone application using multilayer perceptron machine learning techniques from raw signals. We performed a pilot study with three elder adults (mean age 61.3 ± 1.5 years; 66% women) to test usability and accuracy of the smartphone-based BP monitor.
Results: The employed artificial neural network (ANN) model performed with high accuracy in terms of predicting the reference BP values of our validation sample (n=150). On average, our approach predicted BP measures with accuracy \u3e90% and correlations \u3e0.90 (P \u3c .0001). Bland-Altman plots showed that most of the errors for BP prediction were less than 10 mmHg.
Conclusions: With further development and validation, the proposed system could provide a cost-effective strategy to improve the quality and coverage of healthcare, particularly in rural zones, areas lacking physicians, and solitary elderly populations
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