18,170 research outputs found
The role of rotation on Petersen Diagrams. The period ratios
The present work explores the theoretical effects of rotation in calculating
the period ratios of double-mode radial pulsating stars with special emphasis
on high-amplitude delta Scuti stars (HADS). Diagrams showing these period
ratios vs. periods of the fundamental radial mode have been employed as a good
tracer of non-solar metallicities and are known as Petersen diagrams (PD).In
this paper we consider the effect of moderate rotation on both evolutionary
models and oscillation frequencies and we show that such effects cannot be
completely neglected as it has been done until now. In particular it is found
that even for low-to-moderate rotational velocities (15-50 km/s), differences
in period ratios of some hundredths can be found. The main consequence is
therefore the confusion scenario generated when trying to fit the metallicity
of a given star using this diagram without a previous knowledge of its
rotational velocity.Comment: A&A in pres
Stripe formation in horizontally oscillating granular suspensions
We present the results of an experimental study of pattern formation in
horizontally oscillating granular suspensions. Starting from a homogeneous
state, the suspension turns into a striped pattern within a specific range of
frequencies and amplitudes of oscillation. We observe an initial development of
layered structures perpendicular to the vibration direction and a gradual
coarsening of the stripes. However, both processes gradually slow down and
eventually saturate. The probability distribution of the stripe width
approaches a nonmonotonic steady-state form which can be approximated by a
Poisson distribution. We observe similar structures in MD simulations of soft
spherical particles coupled to the motion of the surrounding fluid.Comment: 7 pages, 8 figures, to appear in Europhys. Lett. (2014
An atlas of ECMWF analyses (1980-1987). Part 1: First moment quantities
This document is an atlas of the European Center for Medium Range Weather Forecasts (ECMWF) initialized analyses for 1980 to 1987. Various first moment quantities are presented for monthly, seasonal, and annual averages on a global cylindrical projection, as well as, cross section maps of zonal averages. Global maps of winds, temperature, stream function, and velocity potential are presented at 850 and 200 mb. In addition, global maps of the 300 mb height field (total and eddy), the 500 mb vertical velocity, the 850 mb moisture field, and sea level pressure are presented. The average seasonal cycle and anomalies during the 8 year period are presented for selected quantities
Violence and Gender: Marked Victims
Objectives: This paper aims to raise questions about the institutional assistance to violence within the health field, particularly on the topic sexual violence
Geomorphology subprogram: Geomorphological map of Occidental region of Bolivia, utilizing ERTS imagery
The author has identified the following significant results. Due to the receipt of ERTS-1 imagery, Bolivia will have for the first time a geomorphological map at a scale of 1:100,000. Now the researcher and the student will be able to compare the distribution of the existing shapes of the country, which have been modelled by diverse processes, factors, and agents. This geomorphological information will be very useful in its application to mining, especially alluvial beds, engineering work, and other geological studies. This map is divided into ten geomorphological units which coincide with the geostructural units of the western region of the country
Characterization of some aflatoxin-deficient mutants of Aspergillus parasiticus
Aflatoxins are polyketide secondary metabolites produced by isolates of Aspergillus flavus and A. parasiticus. Since 1960, when a wide toxic outbreak was associated with moldy feed contaminated with aflatoxins, many efforts have been concentrated on this topic because of both the carcinogenic properties of these mycotoxins, and the worldwide occurrence of aflatoxin-producing fungi in cereal, cereal products and other agricultural commodities
Magnetic Structure of Hydrogen Induced Defects on Graphene
Using density functional theory (DFT), Hartree-Fock, exact diagonalization,
and numerical renormalization group methods we study the electronic structure
of diluted hydrogen atoms chemisorbed on graphene. A comparison between DFT and
Hartree-Fock calculations allows us to identify the main characteristics of the
magnetic structure of the defect. We use this information to formulate an
Anderson-Hubbard model that captures the main physical ingredients of the
system, while still allowing a rigorous treatment of the electronic
correlations. We find that the large hydrogen-carbon hybridization puts the
structure of the defect half-way between the one corresponding to an adatom
weakly coupled to pristine graphene and a carbon vacancy. The impurity's
magnetic moment leaks into the graphene layer where the electronic correlations
on the C atoms play an important role in stabilizing the magnetic solution.
Finally, we discuss the implications for the Kondo effect.Comment: 10 pages, 10 fig
Weak Measurements in Non-Hermitian Systems
"Weak measurements" -- involving a weak unitary interaction between a quantum
system and a meter followed by a projective measurement -- are investigated
when the system has a non-Hermitian Hamiltonian. We show in particular how the
standard definition of the "weak value" of an observable must be modified.
These studies are undertaken in the context of bound state scattering theory, a
non-Hermitian formalism for which the Hilbert spaces involved are unambiguously
defined and the metric operators can be explicitly computed. Numerical examples
are given for a model system
Mercury: Risks and Handling as Hazardous Waste
The handling of some chemical substances, as is the case of Mercury used in the determination of the contraction characteristics of soils, becomes dangerous waste at the end of the test process, which requires an adequate management having as a reference the established measures in the legislation and complying with the legal and applicable requirements in this matter. In the present work the characteristics of the mercury, the measures for its use, transportation, and/or storage, as well as the risks to the occupationally exposed workers, are related in the Laboratories of the Applied Research Company. The objective of this research is to raise the culture in the procedures for the handling of chemical substances and hazardous waste, in the use and care of the means of individual protection, as well as compliance with everything established in the procedures for the realization of activities related to the use of mercury to form an environmental awareness focused on achieving an excellent quality of life in the workplace and contribute to the protection of the environment
Simultaneous computation of dynamical and equilibrium information using a weighted ensemble of trajectories
Equilibrium formally can be represented as an ensemble of uncoupled systems
undergoing unbiased dynamics in which detailed balance is maintained. Many
non-equilibrium processes can be described by suitable subsets of the
equilibrium ensemble. Here, we employ the "weighted ensemble" (WE) simulation
protocol [Huber and Kim, Biophys. J., 1996] to generate equilibrium trajectory
ensembles and extract non-equilibrium subsets for computing kinetic quantities.
States do not need to be chosen in advance. The procedure formally allows
estimation of kinetic rates between arbitrary states chosen after the
simulation, along with their equilibrium populations. We also describe a
related history-dependent matrix procedure for estimating equilibrium and
non-equilibrium observables when phase space has been divided into arbitrary
non-Markovian regions, whether in WE or ordinary simulation. In this
proof-of-principle study, these methods are successfully applied and validated
on two molecular systems: explicitly solvated methane association and the
implicitly solvated Ala4 peptide. We comment on challenges remaining in WE
calculations
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