2,369 research outputs found
Effective interactions in the colloidal suspensions from HNC theory
The HNC Ornstein-Zernike integral equations are used to determine the
properties of simple models of colloidal solutions where the colloids and ions
are immersed in a solvent considered as a dielectric continuum and have a size
ratio equal to 80 and a charge ratio varying between 1 and 4000. At an infinite
dilution of colloids, the effective interactions between colloids and ions are
determined for ionic concentrations ranging from 0.001 to 0.1 mol/l and
compared to those derived from the Poisson-Boltzmann theory. At finite
concentrations, we discuss on the basis of the HNC results the possibility of
an unambiguous definition of the effective interactions between the colloidal
molecules.Comment: 26 pages, 15 figure
The answer is blowing in the wind: Simulating the interaction of jets with dynamic cluster atmospheres
We present numerical simulations investigating the interaction of AGN jets
with galaxy clusters, for the first time taking into account the dynamic nature
of the cluster gas and detailed cluster physics. The simulations successfully
reproduce the observed morphologies of radio sources in clusters. We find that
cluster inhomogeneities and large scale flows have significant impact on the
morphology of the radio source and cannot be ignored a-priori when
investigating radio source dynamics. Morphological comparison suggests that the
gas in the centres of clusters like Virgo and Abell 4059 shows significant
shear and/or rotation. We find that shear and rotation in the intra-cluster
medium move large amounts of cold material back into the path of the jet,
ensuring that subsequent jet outbursts encounter a sufficient column density of
gas to couple with the inner cluster gas, thus alleviating the problem of
evacuated channels discussed in the recent literature. The same effects
redistribute the excess energy Delta_E deposited by the jets, making the
distribution of Delta_E at late times consistent with being isotropic.Comment: 5 Pages, 5 figures, submitted to MNRAS Letter
Simulations of decomposition kinetics of Fe-Cr solid solutions during thermal aging
The decomposition of Fe-Cr solid solutions during thermal aging is modeled by
Atomistic Kinetic Monte Carlo (AKMC) simulations, using a rigid lattice
approximation with composition dependant pair interactions that can reproduce
the change of sign of the mixing energy with the alloy composition. The
interactions are fitted on ab initio mixing energies and on the experimental
phase diagram, as well as on the migration barriers in iron and chromium rich
phases. Simulated kinetics is compared with 3D atom probe and neutron
scattering experiments.Comment: 6 pages, 5 figures, PTM 201
High-Speed imaging of the plasma response to resonant magnetic perturbations in HBT-EP
A Phantom v7.3 fast digital camera was used to study visible light fluctuations in the High Beta Tokamak–Extended Pulse (HBT–EP). This video data is the first to be used to analyze and understand the behavior of long wavelength kink perturbations in a wall-stabilized tokamak. The light was mostly comprised of Dα 656 nm light. Profiles of the plasma light at the midplane were hollow with a radial scale length of approximately 4 cm at the plasma edge. The fast camera was also used to measure the plasma's response to applied helical magnetic perturbations. The programmed toroidal phase angle of the resonant magnetic perturbation (RMP) was directly inferred from the resulting images of the plasma response. The plasma response and the intensity of the RMP were compared under different conditions. The resulting amplitude correlations are consistent with previous measurements of the static response using an array of magnetic sensors
Generalized Heisenberg algebras and k-generalized Fibonacci numbers
It is shown how some of the recent results of de Souza et al. [1] can be
generalized to describe Hamiltonians whose eigenvalues are given as
k-generalized Fibonacci numbers. Here k is an arbitrary integer and the cases
considered by de Souza et al. corespond to k=2.Comment: 8 page
Physical Activity among Mexicans and Mexican Americans in an Ecologic Systems Framework
Purpose: To operationalize the Ecologic Model of Physical Activity (EMPA) in an environmental and cultural context born in Mexico, but broadly adopted by Mexican Americans in the USA. Methods: Participant observation occurred over an immersive, ten month period in Jalisco, Baja California South, and the Distrito Federal, Mexico. Numerous meetings with researchers, school personnel, state health departments, and residents helped define environmental factors, cultural values, and the political context of Mexico. The EMPA was adapted to include examples from physical activity resources, health care settings and behavioral interventions. Results: Mexico is a middle income country leapfrogging from traditional physical activities born from work and culturally specific recreation to technological advancements and acceptance of westernized recreational activities leading to lower rates of physical activity. Micro-level environments such as parks and plazas are unique settings in which PA occurs. Meso-and Exo-level environmental factors are the dynamic social and physical linkages such as culturally driven communication and transportation styles between micro-level environments. These linkages connect events from one micro-level environment to events in another either via direct or indirect pathways. Macro-level environmental factors like the health care system and political changes impact large numbers of the population across many micro-level environments. Forces of change such as technological innovation impact all levels in unpredictable ways. These environmental factors directly and indirectly impact on PA. Conclusions: Mexico is a dynamic country undergoing technological advancements leading to acceptance of westernized recreational activities and lower rates of physical activity (PA). It is important to uniquely consider the environmental and cultural context when operationalizing the EMPA to aid PA promotion efforts in Mexico and among Mexicans and Mexican Americans
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