Reactivity of Nellore steers in two feedlot housing systems and its relationship with plasmatic cortisol

To evaluate reactivity to assess the temperament of Nellore steers in two feedlot housing systems (group pen or individual pen) and its relationship with plasmatic cortisol, 36 experimental units were observed five times at 28-day intervals of weight management during a 112-day feedlot confinement. A reactivity score scale ranging from 1 to 5 was applied when an animal was in the chute system. To the calmest animal, a reactivity score of 1 was ascribed and to the most agitated, 5. Blood samples were collected for cortisol analysis. No differences were found in reactivity and feedlot system. There was a relationship noted between reactivity and feedlot time in both housing systems (P < 0.01). There was a relation between reactivity and cortisol levels for group animals (P = 0.0616) and for individual ones (P < 0.01). Cortisol levels varied among housing systems (P < 0.01). Feedlot time influenced the cortisol levels (P < 0.09 individual; P < 0.01 group) and when variable time was included, these levels changed, decreasing in the group pen and increasing in individual pens. The continuous handling reduces reactivity and plasmatic cortisol, and group pen system seems to be less stressfully than individual pens. (C) 2010 Elsevier B.V. All rights reserved.

Two-Phase Mapping for Projecting Massive Data Sets

Most multidimensional projection techniques rely on distance (dissimilarity) information between data instances to embed high-dimensional data into a visual space. When data are endowed with Cartesian coordinates, an extra computational effort is necessary to compute the needed distances, making multidimensional projection prohibitive in applications dealing with interactivity and massive data. The novel multidimensional projection technique proposed in this work, called Part-Linear Multidimensional Projection (PLMP), has been tailored to handle multivariate data represented in Cartesian high-dimensional spaces, requiring only distance information between pairs of representative samples. This characteristic renders PLMP faster than previous methods when processing large data sets while still being competitive in terms of precision. Moreover, knowing the range of variation for data instances in the high-dimensional space, we can make PLMP a truly streaming data projection technique, a trait absent in previous methods.

A Robust, Fully Adaptive Hybrid Level-Set/Front-Tracking Method for Two-Phase Flows with an Accurate Surface Tension Computation

We present a variable time step, fully adaptive in space, hybrid method for the accurate simulation of incompressible two-phase flows in the presence of surface tension in two dimensions. The method is based on the hybrid level set/front-tracking approach proposed in [H. D. Ceniceros and A. M. Roma, J. Comput. Phys., 205, 391400, 2005]. Geometric, interfacial quantities are computed from front-tracking via the immersed-boundary setting while the signed distance (level set) function, which is evaluated fast and to machine precision, is used as a fluid indicator. The surface tension force is obtained by employing the mixed Eulerian/Lagrangian representation introduced in [S. Shin, S. I. Abdel-Khalik, V. Daru and D. Juric, J. Comput. Phys., 203, 493-516, 2005] whose success for greatly reducing parasitic currents has been demonstrated. The use of our accurate fluid indicator together with effective Lagrangian marker control enhance this parasitic current reduction by several orders of magnitude. To resolve accurately and efficiently sharp gradients and salient flow features we employ dynamic, adaptive mesh refinements. This spatial adaption is used in concert with a dynamic control of the distribution of the Lagrangian nodes along the fluid interface and a variable time step, linearly implicit time integration scheme. We present numerical examples designed to test the capabilities and performance of the proposed approach as well as three applications: the long-time evolution of a fluid interface undergoing Rayleigh-Taylor instability, an example of bubble ascending dynamics, and a drop impacting on a free interface whose dynamics we compare with both existing numerical and experimental data.

Discontinuous Galerkin approximation of two-phase flows in heterogeneous porous media with discontinuous capillary pressures

We design and investigate a sequential discontinuous Galerkin method to approximate two-phase immiscible incompressible flows in heterogeneous porous media with discontinuous capillary pressures. The nonlinear interface conditions are enforced weakly through an adequate design of the penalties on interelement jumps of the pressure and the saturation. An accurate reconstruction of the total velocity is considered in the Raviart-Thomas(-Nedelec) finite element spaces, together with diffusivity-dependent weighted averages to cope with degeneracies in the saturation equation and with media heterogeneities. The proposed method is assessed on one-dimensional test cases exhibiting rough solutions, degeneracies, and capillary barriers. Stable and accurate solutions are obtained without limiters. (C) 2010 Elsevier B.V. All rights reserved.

Accurate velocity reconstruction for Discontinuous Galerkin approximations of two-phase porous media flows

We consider Discontinuous Galerkin approximations of two-phase, immiscible porous media flows in the global pressure/fractional flow formulation with capillary pressure. A sequential approach is used with a backward Euler step for the saturation equation, equal-order interpolation for the pressure and the saturation, and without any limiters. An accurate total velocity field is recovered from the global pressure equation to be used in the saturation equation. Numerical experiments show the advantages of the proposed reconstruction. To cite this article: A. Ern et al., C R. Acad. Sci. Paris, Ser. 1347 (2009). (C) 2009 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

Surface Activity of the Triflate Ion at the Air/Water Interface and Properties of N,N,N-Trimethyl-N-Dodecylammonium Triflate Aqueous Solutions

The surface activity of salts added to water is Air orders of magnitude lower than that of surfactants. Sodium trifluoromethanesulfonate (NaTf) produced a change in surface tension. with concentration, Delta gamma/Delta c, of -13.2 mN.L/m.mol. This value is ca. 4-fold larger than those of simple salts and that of methanesulfonate. This unexpected surface effect suggested that positively charged micelles containing Tf could exhibit interesting properties. Dodecyltrimethylammonium triflate (DTATf) had a higher Kraft temperature (37 degrees C) and a lower cmc (5 x 10(-3)M) and degree of dissociation (0.11) than the chloride and bromide salts of DTA. Above the Kraft temperature, at a characteristic temperature t(1), the addition of NaTf above 0.05 M. to a DTATf solution induced phase separation. By increasing the temperature of the two-phase system to above t(1), a homogeneous, transparent solution was obtained at a characteristic temperature t(2). These results, together with well-known triflate properties, led us to suggest that the Tf ion pairs With DTA and that the -CF(3) group may be dehydrated in the interfacial region, resulting in new and interesting self-aggregated structures.

Micelles forming biaxial lyotropic nematic phases

The paper by Yu and Saupe on the first biaxial nematic phase created excitement for a number of reasons. Some theories of biaxial phases already existed, but experimental observation was still lacking. The phase was discovered in a lyotropic system with three components, which in theory is difficult. Lyotropic liquid crystals are composed of supramolecular assemblies of amphiphilic molecules, which may change shape and size as a function of concentration and temperature. The experimental phase diagram of the lyotropic biaxial phase was rather complex, with the biaxial region inserted between nematic cylindrical and nematic discotic phases via second-order transitions. In addition, re-entrant behaviour was evident. Saupe investigated further systems experimentally, observing that the biaxial phase might be absent in cases where a direct transition between the cylindrical and discotic phases occurred. He provided a range of theoretical and experimental contributions on the properties of these lyotropics, but was very cautious regarding the detailed amphiphilic assemblies involved. The present paper reviews this area, focusing on proposals for the structure of the micellar assemblies. Emphasis is placed on recent papers which indicate a transformation of the two uniaxial shapes, in mixing conditions, both from the theoretical and the experimental point of view, and to questions still requiring further study.

Confinement-induced phase transition in a DNA-lipid hydrated complex

We study the effect of the soft confinement by fluid lipid bilayers on the spatial organisation of DNA molecules in a DNA-zwitterionic lipid hydrated lamellar complex. The confinement is increased by dehydrating the complex in a controlled way, which leads to a decrease of the water channel thickness separating the periodically stacked bilayers. Using grazing-incidence small-angle X-ray scattering on an oriented thin film, we probe in situ as dehydration proceeds the structure of the DNA-lipid complex. A structural phase transition is evidenced, where an apparently disordered phase of DNA rods embedded within the one-dimensionally ordered lipid lamellar phase observed at high hydration is replaced by a 2D hexagonal structure of DNA molecules intercalated between the lipid bilayers. Copyright (C) EPLA, 2010