1,906 research outputs found
Finite-Temperature Quasicontinuum: Molecular Dynamics without All the Atoms
Using a combination of statistical mechanics and finite-element interpolation, we develop a coarse-grained (CG) alternative to molecular dynamics (MD) for crystalline solids at constant temperature. The new approach is significantly more efficient than MD and generalizes earlier work on the quasicontinuum method. The method is validated by recovering equilibrium properties of single crystal Ni as a function of temperature. CG dynamical simulations of nanoindentation reveal a strong dependence on temperature of the critical stress to nucleate dislocations under the indenter
Methodiek arbeidsmarktprognoses en -indicatoren 2003-2008
De weergave van de methodiek in dit werkdocument heeft betrekking op het samenstellen van de arbeidsmarktinformatie over 34 bedrijfssectoren, 127 beroepsgroepen en 104 opleidingstypen die is gebruikt in het rapport De arbeidsmarkt naar opleiding en beroep tot 2008. Dit rapport is in november 2003 uitgebracht in het kader van het Project Onderwijs-Arbeidsmarkt (POA) van het ROA. Het rapport biedt een overzicht van de huidige en toekomstige ontwikkelingen op de Nederlandse arbeidsmarkt in de periode 2003-2008. Het gepresenteerde overzicht heeft als doel inzicht te verschaffen in de actuele situatie en de prognoses van beroepen en opleidingen op de arbeidsmarkt. De prognoses worden elke twee jaar herhaald voor een nieuwe periode van vijf jaar. De beschrijvingen en analyses in het rapport spitsen zich toe op de grote lijnen van de huidige en toekomstige arbeidsmarktontwikkelingen.education, training and the labour market;
Human rights and ethical reasoning : capabilities, conventions and spheres of public action
This interdisciplinary article argues that human rights must be understood in terms of opportunities for social participation and that social and economic rights are integral to any discussion of the subject. We offer both a social constructionist and a normative framework for a sociology of human rights which reaches beyond liberal individualism, combining insights from the work of Amartya Sen and from French convention theory. Following Sen, we argue that human rights are founded on the promotion of human capabilities as ethical demands shaped by public reasoning. Using French convention theory, we show how the terms of such deliberation are shaped by different constructions of collectively held values and the compromises reached between them. We conclude by demonstrating how our approach offers a new perspective on spheres of public action and the role these should play in promoting social cohesion, individual capabilities and human rights
Rotational Velocities of Individual Components in Very Low Mass Binaries
We present rotational velocities for individual components of 11 very low mass (VLM) binaries with spectral types between M7 and L7.5. These results are based on observations taken with the near-infrared spectrograph, NIRSPEC, and the Keck II laser guide star adaptive optics system. We find that the observed sources tend to be rapid rotators (v sin i > 10 km s^(â1)), consistent with previous seeing-limited measurements of VLM objects. The two sources with the largest v sin i, LP 349â25B and HD 130948C, are rotating at ~30% of their break-up speed, and are among the most rapidly rotating VLM objects known. Furthermore, five binary systems, all with orbital semimajor axes âŸ3.5 AU, have component v sin i values that differ by greater than 3Ï. To bring the binary components with discrepant rotational velocities into agreement would require the rotational axes to be inclined with respect to each other, and that at least one component is inclined with respect to the orbital plane. Alternatively, each component could be rotating at a different rate, even though they have similar spectral types. Both differing rotational velocities and inclinations have implications for binary star formation and evolution. We also investigate possible dynamical evolution in the triple system HD 130948AâBC. The close binary brown dwarfs B and C have significantly different v sin i values. We demonstrate that components B and C could have been torqued into misalignment by the primary star, A, via orbital precession. Such a scenario can also be applied to another triple system in our sample, GJ 569AâBab. Interactions such as these may play an important role in the dynamical evolution of VLM binaries. Finally, we note that two of the binaries with large differences in component v sin i, LP 349â25AB and 2MASS 0746+20AB, are also known radio sources
Deep search for companions to probable young brown dwarfs
We have obtained high contrast images of four nearby, faint, and very low
mass objects 2MASSJ04351455-1414468, SDSSJ044337.61+000205.1,
2MASSJ06085283-2753583 and 2MASSJ06524851-5741376 (here after 2MASS0435-14,
SDSS0443+00, 2MASS0608-27 and 2MASS0652-57), identified in the field as
probable isolated young brown dwarfs. Our goal was to search for binary
companions down to the planetary mass regime. We used the NAOS-CONICA adaptive
optics instrument (NACO) and its unique capability to sense the wavefront in
the near-infrared to acquire sharp images of the four systems in Ks, with a
field of view of 28"*28". Additional J and L' imaging and follow-up
observations at a second epoch were obtained for 2MASS0652-57. With a typical
contrast DKs= 4.0-7.0 mag, our observations are sensitive down to the planetary
mass regime considering a minimum age of 10 to 120 Myr for these systems. No
additional point sources are detected in the environment of 2MASS0435-14,
SDSS0443+00 and 2MASS0608-27 between 0.1-12" (i.e about 2 to 250 AU at 20 pc).
2MASS0652-57 is resolved as a \sim230 mas binary. Follow-up observations reject
a background contaminate, resolve the orbital motion of the pair, and confirm
with high confidence that the system is physically bound. The J, Ks and L'
photometry suggest a q\sim0.7-0.8 mass ratio binary with a probable semi-major
axis of 5-6 AU. Among the four systems, 2MASS0652-57 is probably the less
constrained in terms of age determination. Further analysis would be necessary
to confirm its youth. It would then be interesting to determine its orbital and
physical properties to derive the system's dynamical mass and to test
evolutionary model predictions.Comment: Research note, 5 pages, 2 tables and 3 figures, accepted to A&
ADAPTIVE OPTICS IMAGING OF VHS 1256-1257: A LOW MASS COMPANION TO A BROWN DWARF BINARY SYSTEM
Recently, Gauza et al. (2015) reported the discovery of a companion to the
late M-dwarf, VHS J125601.92-125723.9 (VHS 1256-1257). The companion's absolute
photometry suggests its mass and atmosphere are similar to the HR 8799 planets.
However, as a wide companion to a late-type star, it is more accessible to
spectroscopic characterization. We discovered that the primary of this system
is an equal-magnitude binary. For an age Myr the A and B components
each have a mass of , and the b component
has a mass of , making VHS 1256-1257 only the third brown
dwarf triple system. There exists some tension between the spectrophotometric
distance of pc and the parallax distance of pc. At
12.7 pc VHS1256-1257 A and B would be the faintest known M7.5 objects, and are
even faint outliers among M8 types. If the larger spectrophotmetric distance is
more accurate than the parallax, then the mass of each component increases. In
particular, the mass of the b component increases well above the deuterium
burning limit to and the mass of each binary
component increases to . At 17.1 pc, the UVW
kinematics of the system are consistent with membership in the AB~Dor moving
group. The architecture of the system resembles a hierarchical stellar multiple
suggesting it formed via an extension of the star-formation process to low
masses. Continued astrometric monitoring will resolve this distance uncertainty
and will provide dynamical masses for a new benchmark system.Comment: Accepted to ApJ
Risk-based inspection as a cost-effective strategy to reduce human exposure to cysticerci of Taenia saginata in low-prevalence settings
Taenia saginata cysticercus is the larval stage of the zoonotic parasite Taenia saginata, with a life-cycle involving both cattle and humans. The public health impact is considered low. The current surveillance system, based on post-mortem inspection of carcasses has low sensitivity and leads to considerable economic burden. Therefore, in the interests of public health and food production efficiency, this study aims to explore the potential of risk-based and cost-effective meat inspection activities for the detection and control of T. saginata cysticercus in low prevalence settings
The use of wholeâbody cryotherapy: timeâ and doseâresponse investigation on circulating blood catecholamines and heart rate variability
Purpose A predominance of parasympathetic drive is observed following cold exposure. Such modulation of the autonomic nervous system (ANS) is associated with faster post-exercise recovery. Within this context, whole-body cryotherapy (WBC) has been spreading in sport medicine, though the optimal temperature and frequency are unclear. The aim of this study was to examine the effects of different cryotherapy conditions on the sympathovagal balance. Methods Forty healthy males were randomly assigned into five different groups (â 110 °C, â 60 °C, â 10 °C, control temperature [â 24 °C]) and undertook 5 WBC sessions over 5 consecutive days. Cardiac autonomic activity was assessed through heart rate variability (HRV) using power density of high frequency (HF), root-mean square difference of successive RâR intervals (RMSSD) and sympathovagal balance (LF/HF). Systemic sympathetic activity was assessed via circulating blood catecholamines. Results Mean weekly RMSSD (pre: 48 ± 22 ms, post: 68 ± 29 ms) and HF (pre: 607 ± 692 ms2, post: 1271 ± 1180 ms2) increased (p < 0.05) from pre to post WBC, only in the â 110 °C condition. A rise in plasma norepinephrine was found after the first â 110 °C WBC session only (pre: 173 ± 98, post: 352 ± 231 ng Lâ1, p < 0.01); whereas, it was not significant after the 5th session (pre: 161 ± 120, post: 293 ± 245 ng Lâ1, p = 0.15). Conclusion These results suggest that one â 110 °C WBC exposure is required to stimulate the ANS. After five daily exposures, a lower autonomic response was recorded compared to day one, therefore suggesting the development of physiological habituation to WBC
- âŠ