Hydromechanical analysis in geotechnical engineering using the material point method

The explicit version of the Material Point Method [1] has been extended in order to model coupled hydromechanical saturated problems. MPM discretizes the continuum, which is considered as a saturated soilfluid mixture, by dividing it into particles or material points. The discrete movement equations are not solved at the material points. Instead a support mesh, built to cover the domain of the problem, is used. In this paper it is assumed that particles carry all the variables needed to represent the state of the continuum including the pore pressure as a variable associated with each particle. The particle pore pressure increment is calculated explicitly using the equation of fluid mass balance, from the particle volumetric deformation and the fluid velocity relative to the soil skeleton, at the particle location. The shape functions used for the mesh elements are usually the same bilinear functions of the Finite Element Method and therefore the background mesh elements suffer the same drawbacks. These drawbacks include: volumetric locking for quasiincompressible materials when four particles per cell are used, which is equivalent to four integration points in the finite element method, pressure instability for quasiincompressible and low permeability materials and the generation of zero energy modes when one particle per cell is used, which corresponds to reduced integration in the finite element method. The MPM original version has also the disadvantage of generating "noise" in the solution [2] when a particle pass from one cell to another. A simple procedure that can be used to reduce instabilities is to consider constant stress at each cell equal to the stress average of the particles which are in the cell at the instant k. In this case the internal forces are obtained in the same way as in the finite element method when one point of integration is used, using the gradient of the shape functions calculated in the cell center. In this work, to avoid volumetric locking and simultaneously achieve a stable behavior, internal forces and pressure increments at the nodes are calculated using the gradients calculated at the cell center. The procedure is completely explicit and has proved to be stable for the low permeability values used to model the foundation of Aznalcollar dam. The simulation of Aznalcollar dam progressive failure is presented as an example [3]

Enhanced weak superconductivity in trigonal γ\gamma-PtBi2_2

Electrical transport experiments show superconductivity in a high-quality single crystal of trigonal $\gamma$-PtBi$_2$. The critical temperature shows a large dependence on the electrical current and in the limit of very low currents, a $T_c$ = 1.1 K is observed, while a zero temperature critical field $B_c$(0) $\approx$ 1.5 Tesla is estimated. These are the highest superconducting parameters reported (at ambient pressure) in a stoichiometric $\gamma$-PtBi$_2$ bulk sample so far. Under a magnetic field a strict zero resistance state is no longer observed even though an incipient superconducting transition is seen. Such a behavior is most probably associated with very low critical currents and is reminiscent of filamentary superconductivity. The superconducting state is elusive to magnetization measurements discarding a bulk phase down to $T =$ 0.3 K.Comment: 5 pages, 5 figure

Serially transplantable mammary epithelial cells express the Thy-1 antigen

Abstract Background Recent studies in murine mammary tissue have identified functionally distinct cell populations that may be isolated by surface phenotype or lineage tracing. Previous groups have shown that CD24medCD49fhigh cells enriched for long-lived mammary epithelial cells can be serially transplanted. Methods Flow cytometry-based enrichment of distinct phenotypic populations was assessed for their gene expression profiles and functional proliferative attributes in vitro and in vivo. Results Here, we show Thy-1 is differentially expressed in the CD24medCD49fhigh population, which allowed us to discern two functionally different populations. The Thy-1+CD24medCD49fhigh phenotype contained the majority of the serially transplantable epithelial cells. The Thy-1−CD24medCD49fhigh phenotype contains a rare progenitor population that is able to form primary mammary outgrowths with significantly decreased serial in vivo transplantation potential. Conclusions Therefore, Thy-1 expression in the immature cell compartment is a useful tool to study the functional heterogeneity that drives mammary gland development and has implications for disease etiology.https://deepblue.lib.umich.edu/bitstream/2027.42/145730/1/13058_2018_Article_1006.pd

Modelling the Effect of Maize Silage and Winter Oat Forage Crop on Cow-Calf Systems in Argentina

Cow-calf systems in the flooding Pampa - Argentina, are facing increasing competition with cropping systems for resources and land. In this context, to be more competitive livestock systems require system intensification, which demands an improvement on the feedbase. Forage crops and feeding silage have been used widely on dairy and beef cattle finishing systems. The purpose of the study was to assess with a model the level of intensification that can be achieved in cow calf systems and its economic effects by incorporating maize silage and winter grazing oat crops

Transcranial direct current stimulation (tDCS) over the left prefrontal cortex does not affect time-trial self-paced cycling performance: Evidence from oscillatory brain activity and power output

To test the hypothesis that transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) influences performance in a 20-min time-trial self-paced exercise and electroencephalographic (EEG) oscillatory brain activity in a group of trained male cyclists. There were no differences (F = 0.31, p > 0.05) in power output between the stimulation conditions: anodal (235W[95%CI 222–249 W]; cathodal (235W[95%CI 222–248 W] and sham (234W[95%CI 220–248 W]. Neither heart rate, sRPE nor EEG activity were affected by tDCS (all Ps > 0.05). tDCS over the left DLFC did not affect self-paced exercise performance in trained cyclists. Moreover, tDCS did not elicit any change on oscillatory brain activity either at baseline or during exercise. Our data suggest that the effects of tDCS on endurance performance should be taken with caution.This project was supported by grants from from the Spanish Ministerio de Economía, Industria y Competitividad-PSI2016-75956-P to D. S. and M.Z., a predoctoral grant from the Spanish Ministerio de Economía, Industria y Competitividad (BES-2014-069050) to L.F.C., and a Spanish “Ministerio de Educación, Cultura y Deporte” predoctoral grant (FPU14/06229) to D.H. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript

Evaluation HPDC Lubricant Spraying for Improved Cooling and Die Protection

This study tries to find out a better cooling and temperature homogenization as well as better die protection on high-pressure die-casting (HPDC) spray lubrication. Test procedures have been set up to study the Leidenfrost point (LFP), contact angle (CA), film thickness and protection from die soldering of lubricants typically applied into the die surfaces during HPDC process. Five different lubricants have been studied as well as the influence in different controllable process parameters (type of die material, oxidation of the surface, temperature, roughness, droplet diameter, water hardness and lubricant concentration). The increase of the LFP, avoiding film boiling regime, and a reduced CA, improve the cooling and film ability of die surface during spraying. The best chemistry exhibits high LFP, shows an increased thickness of the formed film and is more effective preventing the sticking of the aluminum part to the die surface. Thermogravimetric analysis shows better thermal properties for lubricants with anti-sticking performance. The study performed and the test protocols set up result in a better insight of the involved phenomena and allow selecting the most favorable operating window for HPDC lubrication

Electronic Properties of Ultra-Thin Aluminum Nanowires

We have carried out first principles electronic structure and total energy calculations for a series of ultrathin aluminum nanowires, based on structures obtained by relaxing the model wires of Gulseren et al. The number of conducting channels is followed as the wires radius is increased. The results suggest that pentagonal wires should be detectable, as the only ones who can yield a channel number between 8 and 10.Comment: 9 pages + 3 figures, to appear on Surface Scienc

Is juvenile anchovy a feeding resource for the demersal community in the Bay of Biscay? On the availability of pelagic prey to demersal predators

The role that juvenile anchovy (Engraulis encrasicolus) play as a food resource for the demersal community in the southern Bay of Biscay is assessed using 21 years of anchovy abundance data and demersal predator diets. During the study period, a total of 26 fish and elasmobranch species preyed on anchovy either frequently or occasionally. Predators with a crustacean-based diet targeted the smaller anchovy individuals. The size range of anchovy juveniles (centred at 7.5–8.9 cm) was comparable to that of the largest nektonic–benthic crustaceans, but generally smaller than other demersal and pelagic fish prey. Hake (Merluccius merluccius) and megrim (Lepidorhombus whiffiagonis) were the predators that consumed the highest number of anchovy, one of the main prey items driving the variability of their diets. Anchovy consumption conformed only partially to the abundance of anchovy in the southern Bay of Biscay, suggesting that factors other than abundance might condition its availability to demersal predators. Prey size could be one of them, as the size of the anchovy preyed on proved to be significantly smaller than the individuals collected with bottom trawls. However, other factors, such as the vertical position of the shoals of anchovy juveniles, could also constrain anchovy availability to demersal predators