501 research outputs found
Homology of free quantum groups
We compute the Hochschild homology of the free orthogonal quantum group
. We show that it satisfies Poincar\'e duality and should be considered
to be a 3-dimensional object. We then use recent results of R. Vergnioux to
derive results about the -homology of and estimates on the
free entropy dimension of its set of generators. In particular, we show that
the Betti-numbers of all vanish and that the free entropy
dimension is less than 1.Comment: 8 page
Free energies, vacancy concentrations and density distribution anisotropies in hard--sphere crystals: A combined density functional and simulation study
We perform a comparative study of the free energies and the density
distributions in hard sphere crystals using Monte Carlo simulations and density
functional theory (employing Fundamental Measure functionals). Using a recently
introduced technique (Schilling and Schmid, J. Chem. Phys 131, 231102 (2009))
we obtain crystal free energies to a high precision. The free energies from
Fundamental Measure theory are in good agreement with the simulation results
and demonstrate the applicability of these functionals to the treatment of
other problems involving crystallization. The agreement between FMT and
simulations on the level of the free energies is also reflected in the density
distributions around single lattice sites. Overall, the peak widths and
anisotropy signs for different lattice directions agree, however, it is found
that Fundamental Measure theory gives slightly narrower peaks with more
anisotropy than seen in the simulations. Among the three types of Fundamental
Measure functionals studied, only the White Bear II functional (Hansen-Goos and
Roth, J. Phys.: Condens. Matter 18, 8413 (2006)) exhibits sensible results for
the equilibrium vacancy concentration and a physical behavior of the chemical
potential in crystals constrained by a fixed vacancy concentration.Comment: 17 pages, submitted to Phys. Rev.
Tension and stiffness of the hard sphere crystal-fluid interface
A combination of fundamental measure density functional theory and Monte
Carlo computer simulation is used to determine the orientation-resolved
interfacial tension and stiffness for the equilibrium hard-sphere crystal-fluid
interface. Microscopic density functional theory is in quantitative agreement
with simulations and predicts a tension of 0.66 kT/\sigma^2 with a small
anisotropy of about 0.025 kT and stiffnesses with e.g. 0.53 kT/\sigma^2 for the
(001) orientation and 1.03 kT/\sigma^2 for the (111) orientation. Here kT is
denoting the thermal energy and \sigma the hard sphere diameter. We compare our
results with existing experimental findings
Validation and comparison of two methods to Assess Human Energy Expenditure during Free-Living Activities
Background:
The measurement of activity energy expenditure (AEE) via accelerometry is the most commonly used objective method for assessing human daily physical activity and has gained increasing importance in the medical, sports and psychological science research in recent years.
Objective: The purpose of this study was to determine which of the following procedures is more accurate to determine the energy cost during the most common everyday life activities; a single regression or an activity based approach. For this we used a device that utilizes single regression models (GT3X, ActiGraph Manufacturing Technology Inc., FL., USA) and a device using activity-dependent calculation models (move II, movisens GmbH, Karlsruhe, Germany).
Material and Methods:
Nineteen adults (11 male, 8 female; 30.469.0 years) wore the activity monitors attached to the waist and a portable indirect calorimeter (IC) as reference measure for AEE while performing several typical daily activities. The accuracy of the two devices for estimating AEE was assessed as the mean differences between their output and the reference and evaluated using Bland-Altman analysis.
Results:
The GT3X overestimated the AEE of walking (GT3X minus reference, 1.26 kcal/min), walking fast (1.72 kcal/min), walking up2/downhill (1.45 kcal/min) and walking upstairs (1.92 kcal/min) and underestimated the AEE of jogging (2 1.30 kcal/min) and walking upstairs (22.46 kcal/min). The errors for move II were smaller than those for GT3X for all activities. The move II overestimated AEE of walking (move II minus reference, 0.21 kcal/min), walking up2/downhill (0.06 kcal/min) and stair walking (upstairs: 0.13 kcal/min; downstairs: 0.29 kcal/min) and underestimated AEE of walking fast (20.11 kcal/min) and jogging (20.93 kcal/min).
Conclusions:
Our data suggest that the activity monitor using activity-dependent calculation models is more appropriate for predicting AEE in daily life than the activity monitor using a single regression model
Leader Cells Define Directionality of Trunk, but Not Cranial, Neural Crest Cell Migration.
Collective cell migration is fundamental for life and a hallmark of cancer. Neural crest (NC) cells migrate collectively, but the mechanisms governing this process remain controversial. Previous analyses in Xenopus indicate that cranial NC (CNC) cells are a homogeneous population relying on cell-cell interactions for directional migration, while chick embryo analyses suggest a heterogeneous population with leader cells instructing directionality. Our data in chick and zebrafish embryos show that CNC cells do not require leader cells for migration and all cells present similar migratory capacities. In contrast, laser ablation of trunk NC (TNC) cells shows that leader cells direct movement and cell-cell contacts are required for migration. Moreover, leader and follower identities are acquired before the initiation of migration and remain fixed thereafter. Thus, two distinct mechanisms establish the directionality of CNC cells and TNC cells. This implies the existence of multiple molecular mechanisms for collective cell migration.D11I1096 Fondo de Fomento al Desarrollo CientÃfico y TecnológicoThis is the final version of the article. It first appeared from Cell Press via httsp://doi.org/10.1016/j.celrep.2016.04.06
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