405 research outputs found
A new method for the spectroscopic identification of stellar non-radial pulsation modes. II. Mode identification of the Delta Scuti star FG Virginis
We present a mode identification based on new high-resolution time-series
spectra of the non-radially pulsating Delta Scuti star FG~Vir (HD 106384, V =
6.57, A5V). From 2002 February to June a global Delta Scuti Network (DSN)
campaign, utilizing high-resolution spectroscopy and simultaneous photometry
has been conducted for FG~Vir in order to provide a theoretical pulsation
model. In this campaign we have acquired 969 Echelle spectra covering 147 hours
at six observatories. The mode identification was carried out by analyzing line
profile variations by means of the Fourier parameter fit method, where the
observational Fourier parameters across the line are fitted with theoretical
values. This method is especially well suited for determining the azimuthal
order m of non-radial pulsation modes and thus complementary with the method of
Daszynska-Daszkiewicz (2002) which does best at identifying the degree l. 15
frequencies between 9.2 and 33.5 c/d were detected spectroscopically. We
determined the azimuthal order m of 12 modes and constrained their harmonic
degree l. Only modes of low degree (l <= 4) were detected, most of them having
axisymmetric character mainly due to the relatively low projected rotational
velocity of FG Vir. The detected non-axisymmetric modes have azimuthal orders
between -2 and 1. We derived an inclination of 19 degrees, which implies an
equatorial rotational rate of 66 km/s.Comment: 14 pages, 26 figure
Lorentz violating electrodynamics
After summarizing the most interesting results in the calculation of
synchrotron radiation in the Myers-Pospelov effective model for Lorentz
invariance violating (LIV) electrodynamics, we present a general unified way of
describing the radiation regime of LIV electrodynamics which include the
following three different models : Gambini-Pullin, Ellis et al. and
Myers-Pospelov. Such unification reduces to the standard approach of radiation
in a dispersive and absortive (in general) medium with a given index of
refraction. The formulation is presented up to second order in the LIV
parameter and it is explicitly applied to the synchrotron radiation case.Comment: 11 pages, extended version of the talk given by L.F. Urrutia in the
VI Mexican School: Approaches to Quantum Gravity, Playa del Carmen, Mexico,
Nov. 2004. Minor chages in the text and added reference
Radiation in Lorentz violating electrodynamics
Synchrotron radiation is analyzed in the classical effective Lorentz
invariance violating model of Myers-Pospelov. Within the full far-field
approximation we compute the electric and magnetic fields, the angular
distribution of the power spectrum and the total emitted power in the m-th
harmonic, as well as the polarization. We find the appearance of rather
unexpected and large amplifying factors, which go together with the otherwise
negligible naive expansion parameter. This opens up the possibility of further
exploring Lorentz invariance violations by synchrotron radiation measurements
in astrophysical sources where these amplifying factors are important.Comment: Presented at the Second Mexican Meeting on Theoretical and
Experimental Physics, El Colegio Nacional, Mexico City, 6-10 September 200
Perturbative Hamiltonian constraints for higher order theories
We present a method for constructing a consistent low energy canonical
formalism for higher order time-derivative theories, extending the Dirac method
to include perturbative Hamiltonian constraints. We apply it to two
paradigmatic examples: the Pais-Uhlenbeck oscillator and the Bernard-Duncan
scalar field. We also compare the results, both at the classical and quantum
level, with the ones corresponding to a direct perturbative construction
applied to the exact higher order theory. This comparison highligths the
soundness of the present formalism.Comment: 26 pages, 4 figures; review section shortened and appendices change
Stochastic approach to inflation II: classicality, coarse-graining and noises
In this work we generalize a previously developed semiclassical approach to
inflation, devoted to the analysis of the effective dynamics of coarse-grained
fields, which are essential to the stochastic approach to inflation. We
consider general non-trivial momentum distributions when defining these fields.
The use of smooth cutoffs in momentum space avoids highly singular quantum
noise correlations and allows us to consider the whole quantum noise sector
when analyzing the conditions for the validity of an effective classical
dynamical description of the coarse-grained field. We show that the weighting
of modes has physical consequences, and thus cannot be considered as a mere
mathematical artifact. In particular we discuss the exponential inflationary
scenario and show that colored noises appear with cutoff dependent amplitudes.Comment: 18 pages, revtex, no figure
Towards a sustainable and equitable blue economy
The global rush to develop the \u2018blue economy\u2019 risks harming both the marine environment and human wellbeing. Bold policies and actions are urgently needed. We identify five priorities to chart a course towards an environmentally sustainable and socially equitable blue economy
Gene expression profiling in hepatic tissue of newly weaned pigs fed pharmacological zinc and phytase supplemented diets
<p>Abstract</p> <p>Background</p> <p>Zinc (Zn) is an essential trace element. However, Zn bioavailability from commonly consumed plants may be reduced due to phytic acid. Zn supplementation has been used to treat diarrheal disease in children, and in the U.S. swine industry at pharmacological levels to promote growth and fecal consistency, but underlying mechanisms explaining these beneficial effects remain unknown. Moreover, adding supplemental phytase improves Zn bioavailability. Thus, we hypothesized that benefits of pharmacological Zn supplementation result from changes in gene expression that could be further affected by supplemental phytase. The goal of this study was to investigate the effects of feeding newly weaned pigs dietary Zn (150, 1,000, or 2,000 mg Zn/kg) as Zn oxide with or without phytase [500 phytase units (FTU)/kg] for 14 d on hepatic gene expression. Liver RNA from pigs fed 150, 1,000, or 2,000 mg Zn/kg, or 1,000 mg Zn/kg with phytase (n = 4 per treatment) was reverse transcribed and examined using the differential display reverse transcription polymerase chain reaction technique. Liver RNA from pigs fed 150 or 2,000 mg Zn/kg (n = 4 per treatment) was also evaluated using a 70-mer oligonucleotide microarray.</p> <p>Results</p> <p>Expressed sequence tags for 61 putatively differentially expressed transcripts were cloned and sequenced. In addition, interrogation of a 13,297 element oligonucleotide microarray revealed 650 annotated transcripts (FDR ≤ 0.05) affected by pharmacological Zn supplementation. Seven transcripts exhibiting differential expression in pigs fed pharmacological Zn with sequence similarities to genes encoding <it>GLO1</it>, <it>PRDX4</it>, <it>ACY1</it>, <it>ORM1</it>, <it>CPB2</it>, <it>GSTM4</it>, and <it>HSP70.2 </it>were selected for confirmation. Relative hepatic <it>GLO1 </it>(<it>P </it>< 0.0007), <it>PRDX4 </it>(<it>P </it>< 0.009) and <it>ACY1 </it>(<it>P </it>< 0.01) mRNA abundances were confirmed to be greater in pigs fed 1,000 (n = 8) and 2,000 (n = 8) mg Zn/kg than in pigs fed 150 (n = 7) mg Zn/kg. Relative hepatic <it>HSP70.2 </it>(P < 0.002) mRNA abundance was confirmed to be lower in pigs fed 2,000 mg Zn/kg than in pigs fed 150 or 1,000 mg Zn/kg.</p> <p>Conclusion</p> <p>Results suggest that feeding pharmacological Zn (1,000 or 2,000 mg Zn/kg) affects genes involved in reducing oxidative stress and in amino acid metabolism, which are essential for cell detoxification and proper cell function.</p
VEP oscillation solutions to the solar neutrino problem
We study the solar neutrino problem within the framework of a parametrized
post-Newtonian formulation for the gravitational interaction of the neutrinos,
which incorporates a violation to the equivalence principle (VEP). Using the
current data on the rates and the energy spectrum we find two possible
oscillation solutions, both for a large mixing angle. One of them involves the
MSW effect in matter and the other corresponds to vacuum oscillations. An
interesting characteristic of this mechanism is that it predicts a semi-annual
variation of the neutrino flux. Our analysis provides new constraints for some
VEP parameters.Comment: revtex, 18 pages, 11 figure
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