6,288 research outputs found
Dark Radiation in LARGE Volume Models
We consider reheating driven by volume modulus decays in the LARGE Volume
Scenario. Such reheating always generates non-zero dark radiation through the
decays to the axion partner, while the only competitive visible sector decays
are Higgs pairs via the Giudice-Masiero term. In the framework of sequestered
models where the cosmological moduli problem is absent, the simplest model with
a shift-symmetric Higgs sector generates 1.56 < N_{eff} - N_{eff,SM} < 1.74.
For more general cases, the known experimental bounds on N_{eff} strongly
constrain the parameters and matter content of the models.Comment: 6 pages; v2. refs update
A Note on the Magnitude of the Flux Superpotential
The magnitude of the flux superpotential plays a crucial role in
determining the scales of IIB string compactifications after moduli
stabilisation. It has been argued that values of much less than one
are preferred, and even required for physical and consistency reasons. This
note revisits these arguments. We establish that the coupling (g) of heavy
Kaluza-Klein modes to light states scales as (hence is
suppressed by two third powers of the inverse volume of compactification) and
argue that consistency of the superspace derivative expansion requires , where is the auxiliary field of the light
fields and the ultraviolet cutoff. This gives only a mild constraint on the
flux superpotential, (where V is the volume of the
compactification), which can be easily satisfied for order one values of
. This regime is also statistically favoured and makes the
Bousso-Polchinski mechanism for the vacuum energy hierarchically more
efficient.Comment: 14 page
Phylodynamic analysis of porcine circovirus type 2 reveals global waves of emerging genotypes and the circulation of recombinant forms
Since the first description of Porcine circovirus type 2 (PCV2), four genotypes (PCV2a, PCV2b, PCV2c and PCV2d) have been recognized and three of them have been shown to exhibit worldwide distribution. Here, the population dynamics of PCV2 has been reconstructed over time and the factors that have shaped its evolution determined. The results obtained confirm that PCV2 originated approximately at the beginning of the 20th century. The most recent common ancestor of genotypes PCV2a, PCV2b, PCV2c and PCV2d circulated in the 1950s, 1980s, 1960s and 1950s, respectively, and the population sizes of the individual genotypes remained low until the mid 90s, coinciding with the identification of PCV2 as a major pathogen of the pig industry.
The population dynamics of PCV2 have been characterized by the appearance of periodic waves of distinct genotypes that, after an initial rise, spread following major swine commercial routes and were then superseded by subsequent emerging genotypes. Various recombinant forms displayed comparable population dynamics and spreading routes to those of major genotypes, suggesting that recombinant strains are able to compete with parental ones. The capsid gene is subjected to immune selection and evasion of the host immune response seems to be a major force for the emergence and spread of new genotypes. In contrast, the evolution of other genes appears to be constrained by the particular genomic organization of PCV2. In summary, obtained results suggest that changes in farming strategies, international trade, host population immunity, recombination and the constraints imposed by genome organization have all played a major role in the evolutionary dynamics of PCV2
Phylodynamic analysis of porcine circovirus type 2: Methodological approach and datasets
Since its first description, PCV2 has emerged as one of the most economically relevant diseases for the swine industry. Despite the introduction of vaccines effective in controlling clinical syndromes, PCV2 spread was not prevented and some potential evidences of vaccine immuno escape have recently been reported (“Complete genome sequence of a novel porcine circovirus type 2b variant present in cases of vaccine failures in the United States” (Xiao and Halbur, 2012) [1], “Genetic and antigenic characterization of a newly emerging porcine circovirus type 2b mutant first isolated in cases of vaccine failure in Korea” (Seo et al., 2014) [2]). In this article, we used a collection of PCV2 full genomes, provided in the present manuscript, and several phylogentic, phylodynamic and bioinformatic methods to investigate different aspects of PCV2 epidemiology, history and evolution (more thoroughly described in “PHYLODYNAMIC ANALYSIS of PORCINE CIRCOVIRUS TYPE 2 REVEALS GLOBAL WAVES of EMERGING GENOTYPES and the CIRCULATION of RECOMBINANT FORMS”[3]). The methodological approaches used to consistently detect recombiantion events and estimate population dymanics and spreading patterns of rapidly evolving ssDNA viruses are herein reported. Programs used are described and original scripts have been provided. Ensembled databases used are also made available. These consist of a broad collection of complete genome sequences (i.e. 843 sequences; 63 complete genomes of PCV2a, 310 of PCV2b, 4 of PCV2c, 217 of PCV2d, 64 of CRF01, 140 of CRF02 and 45 of CRF03.), divided in differnt ORF (i.e. ORF1, ORF2 and intergenic regions), of PCV2 genotypes and major Circulating Recombinat Forms (CRF) properly annotated with respective collection data and country. Globally, all of these data can be used as a starting point for further studies and for classification purpose
Momentum distribution, vibrational dynamics and the potential of mean force in ice
By analyzing the momentum distribution obtained from path integral and phonon
calculations we find that the protons in hexagonal ice experience an
anisotropic quasi-harmonic effective potential with three distinct principal
frequencies that reflect molecular orientation. Due to the importance of
anisotropy, anharmonic features of the environment cannot be extracted from
existing experimental distributions that involve the spherical average. The
full directional distribution is required, and we give a theoretical prediction
for this quantity that could be verified in future experiments. Within the
quasi-harmonic context, anharmonicity in the ground state dynamics of the
proton is substantial and has quantal origin, a finding that impacts the
interpretation of several spectroscopies
A 3.55 keV Photon Line and its Morphology from a 3.55 keV ALP Line
Galaxy clusters can efficiently convert axion-like particles (ALPs) to
photons. We propose that the recently claimed detection of a 3.55--3.57 keV
line in the stacked spectra of a large number of galaxy clusters and the
Andromeda galaxy may originate from the decay of either a scalar or fermionic
keV dark matter species into an axion-like particle (ALP) of mass , which subsequently converts to a photon in
the cluster magnetic field. In contrast to models in which the photon line
arises directly from dark matter decay or annihilation, this can explain the
anomalous line strength in the Perseus cluster. As axion-photon conversion
scales as and cool core clusters have high central magnetic fields, this
model can also explains the observed peaking of the line emission in the cool
cores of the Perseus, Ophiuchus and Centaurus clusters, as opposed to the much
larger dark matter halos. We describe distinctive predictions of this scenario
for future observations.Comment: 6 page
Displaced path integral formulation for the momentum distribution of quantum particles
The proton momentum distribution, accessible by deep inelastic neutron
scattering, is a very sensitive probe of the potential of mean force
experienced by the protons in hydrogen-bonded systems. In this work we
introduce a novel estimator for the end to end distribution of the Feynman
paths, i.e. the Fourier transform of the momentum distribution. In this
formulation, free particle and environmental contributions factorize. Moreover,
the environmental contribution has a natural analogy to a free energy surface
in statistical mechanics, facilitating the interpretation of experiments. The
new formulation is not only conceptually but also computationally advantageous.
We illustrate the method with applications to an empirical water model,
ab-initio ice, and one dimensional model systems
Recreational Sound Risk For A University Student: Case Study
Concern about noise exposure in recreational settings is growing and unsafe levels of sound are frequently being experienced in a variety of non-occupational settings such as pubs, nightclubs, concerts, parties, and fitness classes. Damage to the auditory system may occur with regular participation in these loud activities. A case study was conducted to estimate sound exposure levels and risk associated with common activities. Findings demonstrated that pubs presented a hazardous sound environment, so information about health-oriented behavior is essential to effectively improve hearing conservation awareness for university students. Public awareness and personal hearing protection should be strongly considered to prevent hearing loss. Audiologists should encourage a healthy-hearing lifestyle and discourage exposure to loud sports without use of protection. Children and young adults should be properly educated about entertainment-related excessive sound exposure and encouraged to periodically monitor their hearing. Protection should be used in both ears during exposure to loud sound and prevention of hearing loss should be prioritized, especially in the young adult population, to avoid irreversible damage to the auditory system. Entertainment authorities should be encouraged to educate spectators about the excessive sound levels that are likely to be experienced at their events and should also make hearing protection easily accessible
Estimation of elastic and viscous properties of the left ventricle based on annulus plane harmonic behavior
Assessment of left ventricular (LV) function
with an emphasis on contractility has been a challenge
in cardiac mechanics during the recent decades. The LV
function is usually described by the LV pressurevolume
(P-V) diagram. The standard P-V diagrams are
easy to interpret but difficult to obtain and require
invasive instrumentation for measuring the
corresponding volume and pressure data. In the present
study, we introduce a technique that can estimate the
viscoelastic properties of the LV based on harmonic
behavior of the ventricular chamber and it can be
applied non-invasively as well. The estimation technique
is based on modeling the actual long axis displacement
of the mitral annulus plane toward the cardiac base as a
linear damped oscillator with time-varying coefficients.
The time-varying parameters of the model were
estimated by a standard Recursive Linear Least
Squares (RLLS) technique. LV stiffness at end-systole
and end diastole was in the range of 61.86-136.00
dyne/g.cm and 1.25-21.02 dyne/g.cm, respectively. The
only input used in this model was the long axis
displacement of the annulus plane, which can also be
obtained non-invasively using tissue Doppler or MR
imaging
Method of remotely characterizing thermal properties of a sample
A sample in a wind tunnel is radiated from a thermal energy source outside of the wind tunnel. A thermal imager system, also located outside of the wind tunnel, reads surface radiations from the sample as a function of time. The produced thermal images are characteristic of the heat transferred from the sample to the flow across the sample. In turn, the measured rates of heat loss of the sample are characteristic of the flow and the sample
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