On the validity of the Boltzmann equation to describe low density granular systems

The departure of a granular gas in the instable region of parameters from the initial homogeneous cooling state is studied. Results from Molecular Dynamics and from Direct Monte Carlo simulation of the Boltzmann equation are compared. It is shown that the Boltzmann equation accurately predicts the low density limit of the system. The relevant role played by the parallelization of the velocities as time proceeds and the dependence of this effect on the density is analyzed in detail

Willingness to change car use to commute to the UPTC main campus, Colombia: A hybrid discrete choice modeling approach

This paper studies the willingness to change car use when commuting to a university campus. We estimated a hybrid discrete choice (HDC) model to test the hypothesis that, in addition to traditional tangible attributes, the willingness to change car use to more sustainable transportation modes also depends on the pro-environmental attitude and the perceived convenience of each transportation alternative. We found that teachers have better pro-environmental attitudes than students and administrative staff, but senior individuals and people who own an above-average priced car have negative effects on this attitude. We concluded that in addition to car ownership, the price of a car is also a decisive factor in the willingness to change car use. On-campus parking fees were identified as a key variable for reducing car use when commuting to campus and for financing more sustainable transportation modes. This paper contributes to the literature on sustainable mobility on university campuses and is the first based on an HDC modeling approach that integrates tangible attributes and latent variables into this context. © 2019 Luis Márquez, Luis F. Macea, & Jose J. Soto

Modificaciones de curva velocidad-tiempo de la cadera en el estilo braza a distintas velocidades de nado

El propósito del presente estudio fue observar cual era el comportamiento de la curva de velocidad de la cadera durante el nado estilo braza a diferentes velocidades de nado. Dos nadadoras de distinto nivel fueron seleccionadas para participar en el presente estudio en el que realizaron cuatro repeticiones de 25 m a velocidad diferente. Dos cámaras de vídeo PAL, una subacuática y otra exterior, fijas y perpendiculares a la dirección de desplazamiento del nadador, se emplearon para analizar un ciclo completo de nado de cada una de las repeticiones de nado. Se calcularon velocidades promedio de nado, velocidades máximas intra-ciclo, velocidades mínimas intra-ciclo, frecuencias, longitudes y duración de ciclo. Se encontró que al incrementar la velocidad promedio de nado, los valores máximos intra-ciclo aumentaban, no observándose modificación alguna en el valor mínimo. Además se observó un aumento de la frecuencia de ciclo y una disminución de la longitud de ciclo a medida que la velocidad se incrementaba, debido a la reducción del tiempo de deslizamiento tras la patada

Hydrodynamic theory for granular gases

A granular gas subjected to a permanent injection of energy is described by means of hydrodynamic equations derived from a moment expansion method. The method uses as reference function not a Maxwellian distribution $f_{\sf M}$ but a distribution $f_0 = \Phi f_{\sf M}$, such that $\Phi$ adds a fourth cumulant $\kappa$ to the velocity distribution. The formalism is applied to a stationary conductive case showing that the theory fits extraordinarily well the results coming from our molecular dynamic simulations once we determine $\kappa$ as a function of the inelasticity of the particle-particle collisions. The shape of $\kappa$ is independent of the size $N$ of the system.Comment: 10 pages, 9 figures, more about our research in http://www.cec.uchile.cl/cinetica

In Silico Analysis of Putative Paralytic Shellfish Poisoning Toxins Export Proteins in Cyanobacteria

Lopez-Cortes, XA (Lopez-Cortes, Xaviera A.) Univ Talca, Nanobiotechnol Div, Fraunhofer Chile Res Fdn, Ctr Syst Biotechnol, Talca, Chile.Paralytic shellfish poisoning toxins (PSTs) are a family of more than 30 natural alkaloids synthesized by dinoflagellates and cyanobacteria whose toxicity in animals is mediated by voltage-gated Na+ channel blocking. The export of PST analogues may be through SxtF and SxtM, two putative MATE (multidrug and toxic compound extrusion) family transporters encoded in PSTs biosynthetic gene cluster (sxt). sxtM is present in every sxt cluster analyzed; however, sxtF is only present in the Cylindrospermopsis-Raphidiopsis clade. These transporters are energetically coupled with an electrochemical gradient of proton (H+) or sodium (Na+) ions across membranes. Because the functional role of PSTs remains unknown and methods for genetic manipulation in PST-producing organisms have not yet been developed, protein structure analyses will allow us to understand their function. By analyzing the sxt cluster of eight PST-producing cyanobacteria, we found no correlation between the presence of sxtF or sxtM and a specific PSTs profile. Phylogenetic analyses of SxtF/M showed a high conservation of SxtF in the Cylindrospermopsis-Raphidiopsis clade, suggesting conserved substrate affinity. Two domains involved in Na+ and drug recognition from NorM proteins (MATE family) of Vibrio parahaemolyticus and V. cholerae are present in SxtF/M. The Na+ recognition domain was conserved in both SxtF/M, indicating that Na+ can maintain the role as a cation anti-transporter. Consensus motifs for toxin binding differed between SxtF and SxtM implying differential substrate binding. Through protein modeling and docking analysis, we found that there is no marked affinity between the recognition domain and a specific PST analogue. This agrees with our previous results of PST export in R. brookii D9, where we observed that the response to Na+ incubation was similar to different analogues. These results reassert the hypothesis regarding the involvement of Na+ in toxin export, as well as the motifs L(398)XGLQD(403) (SxtM) and L(390)VGLRD(395) (SxtF) in toxin recognition

Instantons and <A2><A^2> Condensate

We argue that the $$condensate found in the Landau gauge on lattices, when an Operator Product Expansion of Green functions is performed, might be explained by instantons. We use cooling to estimate the instanton contribution and extrapolate back the result to the thermalised configuration. The resulting$$ is similar to $$.Comment: 6 pages, 1 fig., 1 tab., RevTeX to be use

Transferable force fields for adsorption of small gases in zeolites

We provide transferable force fields for oxygen, nitrogen, and carbon monoxide that are able to reproduce experimental adsorption in both pure silica and alumino-substituted zeolites at cryogenic and high temperatures. The force field parameters can be combined with those previously reported for carbon dioxide, methane, and argon, opening the possibility for studying mixtures of interest containing the six components. Using these force field parameters we obtained some adsorption isotherms at cryogenic temperatures that at first sight were in discrepancies with experimental values for certain molecules and structures. We attribute these discrepancies to the sensitiveness of the equipment and to kinetic impedimenta that can lead to erratic results. Additional problems can be found during simulations when extra-framework cations are present in the system as their lack of mobility at low temperatures could lead to kinetic effects that hinder experimental adsorption.This work was supported by the European Research Council through an ERC Staring Grant (ERC-StG-279520-RASPA). A. Martin-Calvo thanks the Spanish “Ministerio de Educación Cultura y Deporte” for her predoctoral fellowship. The authors want to thank the “Instituto de Tecnología Química” (ITQ-CSIC) from Valencia, for providing the pure silica zeolites (RSIL and ITQ-29).Peer reviewe

Statistics of the purse seine spanish fleet in the Indian Ocean (1984- 2009)

This document presents summary statistics of the purse seiner Spanish fleet fishing in the Indian Ocean from 1990 to 2009. Data include catch and effort statistics as well as some fishery index by species and fishing mode. Information about the sampling scheme and the coverage of sampling, together with maps and diagrams representing the fishing patter n of this fleet by time and area strata is also included

NMR Experiments on a Three-Dimensional Vibrofluidized Granular Medium

A three-dimensional granular system fluidized by vertical container vibrations was studied using pulsed field gradient (PFG) NMR coupled with one-dimensional magnetic resonance imaging (MRI). The system consisted of mustard seeds vibrated vertically at 50 Hz, and the number of layers N_ell <= 4 was sufficiently low to achieve a nearly time-independent granular fluid. Using NMR, the vertical profiles of density and granular temperature were directly measured, along with the distributions of vertical and horizontal grain velocities. The velocity distributions showed modest deviations from Maxwell-Boltzmann statistics, except for the vertical velocity distribution near the sample bottom which was highly skewed and non-Gaussian. Data taken for three values of N_ell and two dimensionless accelerations Gamma=15,18 were fit to a hydrodynamic theory, which successfully models the density and temperature profiles including a temperature inversion near the free upper surface.Comment: 14 pages, 15 figure

Primary vs. secondary curved fold axes: Deciphering the origin of the Aït Attab syncline (Moroccan High Atlas) using paleomagnetic data

The Aït Attab syncline, located in the Central High Atlas, displays a curved geometry in plan view, and is considered as one of the most spectacular fold shapes in the Central High Atlasic belt. We conducted a paleomagnetic study in Jurassic-Cretaceous red beds to investigate the origin of this geometry. The Natural Remanent Magnetization (NRM) is dominated by a secondary magnetization carried by haematite with unvarying normal polarity that has been dated at about 100 Ma. The regional fold test performed in both limbs of the syncline is positive and the paleomagnetic vectors (after tectonic correction) are parallel throughout the curvature, indicating a negative oroclinal bending test. These results are inconsistent with previous works that consider the bent geometry of this syncline to result from subsequent distortion of originally NE–SW trending structures by rotation about a vertical axis. We interpret the NRM data to demonstrate that the changing trend of the Aït Attab syncline is a primary feature, resulting from the influence of pre-existing, NE–SW and E-W-striking extensional faults that developed during a strike-slip regime. Paleomagnetic results also reveal that the tilting observed in the sampled red beds is post Albian, probably linked to the Cenozoic inversion of the High Atlasic belt