Effect of freeze–thaw cycles on the void topologies and mechanical properties of asphalt

Frost and thawing damage asphalt in cold climates. Water that enters the pores of asphalt at low temperatures may accelerate its degradation. Water can expand into pores, altering the void content and shape, thus affecting the asphalt's internal structure and fracture properties. We can develop more durable asphalt types if we understand how void topology changes with freeze–thaw cycles. The purpose of this study is to establish a correlation between the mechanical properties of asphalts and the topological properties of voids. To determine their internal structure, various asphalt types representing dense asphalt and asphalt with voids were made and X-rayed before and after each freeze–thaw cycle. We also obtained the mechanical properties of asphalt and correlated them with the void properties. It was found that dense asphalt has the lowest degradation rate in wet conditions characterised by non-connected gaps, which was approximately constant with freeze–thaw cycles; however, dense asphalt was least durable under dry conditions compared with asphalts with more voids. Due to its high water retention rate, asphalt with a 10% void content degraded at an accelerated rate during the initial cycles. As a result of bigger voids, asphalt with a higher pore content plateaued in later cycles due to reduced water retention. This study demonstrates that the internal void topology affects the mechanical properties of asphalt during freeze–thaw cycles. These results can be used to understand changes in asphalt mechanical losses resulting from freeze-thaw cycles and to validate numerical models to perform parametric studies of the asphalt's freeze–thaw degradation

Anomalous Hall conductivity control in Mn3_3NiN antiperovskite by epitaxial strain along the kagome plane

Antiferromagnetic manganese-based nitride antiperovskites, such as Mn$_3$NiN, hold a triangular frustrated magnetic ordering over their kagome lattice formed by the Mn atoms along the (111)-plane. As such, frustration imposes a non-trivial interplay between the symmetric and asymmetric magnetic interactions, which can only reach equilibrium in a noncollinear magnetic configuration. Consequently, the associated electronic interactions and their possible tuning by external constraints, such as applied epitaxial strain, play a crucial role in defining the microscopic and macroscopic properties of such topological condensed matter systems. Thus, in the present work, we explored and explained the effect of the epitaxial strain imposed within the (111)-plane, in which the magnetic and crystallographic symmetry operations are kept fixed, and only the magnitude of the ionic and electronic interactions are tuned. We found a linear shifting in the energy of the band structure and a linear increase/decrease of the available states near the Fermi level with the applied strain. Concretely, the compression strain reduces the Mn-Mn distances in the (111) kagome plane but linearly increases the separation between the stacked kagome lattices and the available states near the Fermi level. Despite the linear controlling of the available states across the Fermi energy, the anomalous Hall conductivity shows a non-linear behavior where the $\sigma_{111}$ conductivity nearly vanishes for tensile strain. On the other hand, $\sigma_{111}$ fetches a maximum increase of 26\% about the unstrained structure for a compression value close to $-$1.5\%.This behavior found an explanation in the non-divergent Berry curvature within the kagome plane, which is increased for constraining but significantly reduced for expansion strain values..

The Double Dust Envelopes of R Coronae Borealis Stars

The study of extended, cold dust envelopes surrounding R Coronae Borealis (RCB) stars began with their discovery by the Infrared Astronomical Satellite. RCB stars are carbon-rich supergiants characterized by their extreme hydrogen deficiency and their irregular and spectacular declines in brightness (up to 9 mag). We have analyzed new and archival Spitzer Space Telescope and Herschel Space Observatory data of the envelopes of seven RCB stars to examine the morphology and investigate the origin of these dusty shells. Herschel, in particular, has revealed the first-ever bow shock associated with an RCB star with its observations of SU Tauri. These data have allowed the assembly of the most comprehensive spectral energy distributions (SEDs) of these stars with multiwavelength data from the ultraviolet to the submillimeter. Radiative transfer modeling of the SEDs implies that the RCB stars in this sample are surrounded by an inner warm (up to 1200 K) and an outer cold (up to 200 K) envelope. The outer shells are suggested to contain up to 10-3 M o of dust and have existed for up to 105 years depending on the expansion rate of the dust. This age limit indicates that these structures have most likely been formed during the RCB phase

High-pressure x-ray diffraction and ab initio study of Ni2Mo3N, Pd2Mo3N, Pt2Mo3N, Co3Mo3N, and Fe3Mo3N: Two families of ultra-incompressible bimetallic interstitial nitrides

We have studied by means of high-pressure x-ray diffraction the structural stability of Ni2Mo3N, Co3Mo3N, and Fe3Mo3N. We also report ab initio computing modeling of the high-pressure properties of these compounds, Pd2Mo3N, and Pt2Mo3N. We have found that the nitrides remain stable in the ambient-pressure cubic structure at least up to 50 GPa and determined their equation of state. All of them have a bulk modulus larger than 300 GPa. Single-crystal elastic constants have been calculated in order to quantify the stiffness of the investigated nitrides. We found that they should have a Vickers hardness similar to that of cubic spinel nitrides like gamma-Si3N4Comment: 25 pages, 6 figures, 3 table

Generalized model for dynamic percolation

We study the dynamics of a carrier, which performs a biased motion under the influence of an external field E, in an environment which is modeled by dynamic percolation and created by hard-core particles. The particles move randomly on a simple cubic lattice, constrained by hard-core exclusion, and they spontaneously annihilate and re-appear at some prescribed rates. Using decoupling of the third-order correlation functions into the product of the pairwise carrier-particle correlations we determine the density profiles of the "environment" particles, as seen from the stationary moving carrier, and calculate its terminal velocity, V_c, as the function of the applied field and other system parameters. We find that for sufficiently small driving forces the force exerted on the carrier by the "environment" particles shows a viscous-like behavior. An analog Stokes formula for such dynamic percolative environments and the corresponding friction coefficient are derived. We show that the density profile of the environment particles is strongly inhomogeneous: In front of the stationary moving carrier the density is higher than the average density, $\rho_s$, and approaches the average value as an exponential function of the distance from the carrier. Past the carrier the local density is lower than $\rho_s$ and the relaxation towards $\rho_s$ may proceed differently depending on whether the particles number is or is not explicitly conserved.Comment: Latex, 32 pages, 4 ps-figures, submitted to PR

Weekday and weekend patterns of physical activity and sedentary time among Liverpool and Madrid youth

Levels of physical inactivity and sedentary behaviour among English and Spanish youth are high and vary within different regions of each country. Little though is known about these during specific periods of the day. The purpose of this study was to describe physical activity (PA) and sedentary time during segments of the day and week, and compare these critical contexts between youth in the Liverpool and Madrid areas of England and Spain, respectively. PA was objectively assessed in 235 Liverpool- and 241 Madrid youth (aged 10-14 years) who wore accelerometers for seven consecutive days. Minutes of sedentary time, moderate PA, vigorous PA and moderate-to-vigorous physical activity (MVPA) were calculated for weekdays, weekend days, school time, non-school time and after-school. Between-country differences were analysed using analysis of covariance (ANCOVA). Madrid youth spent significantly more time in sedentary activities than their Liverpool counterparts. Madrid youth engaged in more minutes of moderate intensity physical activity (MPA) than Liverpool youth during weekdays, school time and non-school time (P < 0.01). Liverpool children recorded more time in vigorous physical activity (VPA) than Madrid peers during week days and weekend days (P < 0.01) and during school time and after-school periods (P < 0.01). The MVPA was significantly higher among Madrid youth during non-school time (P < 0.01). Around 25% of all youth achieved recommended levels of MVPA. Low levels of MVPA and systematic differences in sedentary time, MPA and VPA exist between Liverpool and Madrid youth. Interventions targeted at the least-active children during weekends, after-school and non-school periods within the cultural contexts common to each city are required. © 2013 © 2013 European College of Sport Science

Evaluation of Analgesic Tolerance Induced by Metamizole in the Writhing Test Model

La tolerancia analgésica se define como la necesidad de dosis crecientes para lograr el efecto deseado. En este artículo presentamos datos experimentales de la búsqueda de tolerancia analgésica inducida por metamizol en un modelo de dolor inducido por ácido acético al 0,9% conocido como prueba de constricción abdominal o prueba de Writhing. El objetivo de este estudio fue identificar el desarrollo de tolerancia analgésica al metamizol en el modelo de prueba de Writhing. Experimental: se utilizaron grupos de ratones Balb/C 6±2. Se les administró metamizol en diferentes protocolos, posteriormente se les realizó un estímulo doloroso con ácido acético al 0,9% vía intraperitoneal, se evaluó durante 30 minutos y se contó tiempo de latencia, número de estiramientos abdominales para calificar la respuesta al dolor, posteriormente se les administró naloxona para buscar signos de abstinencia. Nuestros resultados demostraron que existe una tendencia a desarrollar tolerancia analgésica al metamizol después de su administración repetida.Analgesic tolerance is defined as the need for increasing doses to achieve the intended effect. In this paper we present experimental data from the search for analgesic tolerance induced by metamizole in a pain model induced by 0.9% acetic acid known as abdominal constriction test or Writhing test. The aim of this study was to identify the development of analgesic tolerance to metamizole in the Writhing test model. Experimental: groups of Balb/C mice 6±2 were used. They were administered metamizole in different protocols, and subsequently underwent a pain stimulus with 0.9% acetic acid via intraperitoneal, evaluated for 30 minutes and counting time of latency, number of abdominal stretches in order to rate pain response, subsequently naloxone was administered to look for signs of withdrawal. Our results demonstrated that there is a tendency to develop analgesic tolerance to metamizole after its repeated administration

A multilayer service data acquisition and operation system for oceanographic ships and instrumentation networks

A new Data Acquisition and Operation System for Oceanographic ships and Instrumentation Networks has been developed by the Marine Technology Unit of the Spanish Research Vessels for their networked remote acquisition platforms. The new system built over LABVIR project background follows a Service Oriented Architecture to allow expandable access to acquired data in real time and to archived data. Several Data layers are implemented to allow data access from the more common tools and formats used in marine sciences.Peer Reviewe

The Dynamical Behaviour of Test Particles in a Quasi-Spherical Spacetime and the Physical Meaning of Superenergy

We calculate the instantaneous proper radial acceleration of test particles (as measured by a locally defined Lorentzian observer) in a Weyl spacetime, close to the horizon. As expected from the Israel theorem, there appear some bifurcations with respect to the spherically symmetric case (Schwarzschild), which are explained in terms of the behaviour of the superenergy, bringing out the physical relevance of this quantity in the study of general relativistic systems.Comment: 14 pages, Latex. 4 figures. New references added. Typos corrected. To appear in Int. J. Theor. Phy