438 research outputs found
Remarks on probability theory and TMJ diagnosis
On the basis of the classic concepts of events and probability theory, this article analyzes some recently introduced diagnostic probability concepts as they pertain to temporomandibular joint (TMJ) diseases and disorders.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/74644/1/j.1365-2842.1992.tb01486.x.pd
Global effects of local sound-speed perturbations in the Sun: A theoretical study
We study the effect of localized sound-speed perturbations on global mode
frequencies by applying techniques of global helioseismology on numerical
simulations of the solar acoustic wave field. Extending the method of
realization noise subtraction (e.g. Hanasoge et al. 2007) to global modes and
exploiting the luxury of full spherical coverage, we are able to achieve very
highly resolved frequency differences that are used to study sensitivities and
the signatures of the thermal asphericities. We find that (1) global modes are
almost twice as sensitive to sound-speed perturbations at the bottom of the
convection zone as in comparison to anomalies well in the radiative interior
(), (2) the -degeneracy is lifted ever so slightly,
as seen in the coefficients, and (3) modes that propagate in the vicinity
of the perturbations show small amplitude shifts ().Comment: Submitted to Solar Physic
Prospects for asteroseismology
The observational basis for asteroseismology is being dramatically
strengthened, through more than two years of data from the CoRoT satellite, the
flood of data coming from the Kepler mission and, in the slightly longer term,
from dedicated ground-based facilities. Our ability to utilize these data
depends on further development of techniques for basic data analysis, as well
as on an improved understanding of the relation between the observed
frequencies and the underlying properties of the stars. Also, stellar modelling
must be further developed, to match the increasing diagnostic potential of the
data. Here we discuss some aspects of data interpretation and modelling,
focussing on the important case of stars with solar-like oscillations.Comment: Proc. HELAS Workshop on 'Synergies between solar and stellar
modelling', eds M. Marconi, D. Cardini & M. P. Di Mauro, Astrophys. Space
Sci., in the press Revision: correcting abscissa labels on Figs 1 and
Measurement of quasi-elastic 12C(p,2p) scattering at high momentum transfer
We measured the high-momentum quasi-elastic 12C(p,2p) reaction (at center of
mass angle near 90 degrees) for 6 and 7.5 GeV/c incident protons. The
three-momentum components of both final state protons were measured and the
missing energy and momentum of the target proton in the nucleus were
determined.
The validity of the quasi-elastic picture was verified up to Fermi momenta of
about 450 MeV/c, where it might be questionable. Transverse and longitudinal
Fermi momentum distributions of the target proton were measured and compared to
independent particle models which do not reproduce the large momentum tails. We
also observed that the transverse Fermi distribution gets wider as the
longitudinal component increases in the beam direction, in contrast to a simple
Fermi gas model.Comment: 4 pages including 3 figure
Ab initio study of the beta$-tin->Imma->sh phase transitions in silicon and germanium
We have investigated the structural sequence of the high-pressure phases of
silicon and germanium. We have focussed on the cd->beta-tin->Imma->sh phase
transitions. We have used the plane-wave pseudopotential approach to the
density-functional theory implemented within the Vienna ab-initio simulation
package (VASP). We have determined the equilibrium properties of each structure
and the values of the critical parameters including a hysteresis effect at the
phase transitions. The order of the phase transitions has been obtained
alternatively from the pressure dependence of the enthalpy and of the internal
structure parameters. The commonly used tangent construction is shown to be
very unreliable. Our calculations identify a first-order phase transition from
the cd to the beta-tin and from the Imma to the sh phase, and they indicate the
possibility of a second-order phase-transition from the beta-tin to the Imma
phase. Finally, we have derived the enthalpy barriers between the phases.Comment: 12 pages, 16 figure
Stochastic excitation of acoustic modes in stars
For more than ten years, solar-like oscillations have been detected and
frequencies measured for a growing number of stars with various characteristics
(e.g. different evolutionary stages, effective temperatures, gravities, metal
abundances ...).
Excitation of such oscillations is attributed to turbulent convection and
takes place in the uppermost part of the convective envelope. Since the
pioneering work of Goldreich & Keely (1977), more sophisticated theoretical
models of stochastic excitation were developed, which differ from each other
both by the way turbulent convection is modeled and by the assumed sources of
excitation. We review here these different models and their underlying
approximations and assumptions.
We emphasize how the computed mode excitation rates crucially depend on the
way turbulent convection is described but also on the stratification and the
metal abundance of the upper layers of the star. In turn we will show how the
seismic measurements collected so far allow us to infer properties of turbulent
convection in stars.Comment: Notes associated with a lecture given during the fall school
organized by the CNRS and held in St-Flour (France) 20-24 October 2008 ; 39
pages ; 11 figure
Nurture, nature and some very dubious social skills: An interpretative phenomenological analysis of talent identification practices in elite English youth soccer
This paper reports qualitative findings regarding the concepts and practices utilised in talent identification (TI) among professional coaches working in English youth soccer. Using interpretative phenomenological analysis, detailed interviews with seven such coaches are explored, with a view to elucidating the links between understanding, practice, experience and professional context. Findings reveal three superordinate themes, relating to (1) a primarily ‘nurtured’ and trainable understanding of the broad concept of talent itself, (2) an ostensibly contradictory model of semi-static player psychology, and (3) a highly selective mechanism for separating evidence for ‘mental strength’ and ‘social skills’. It is contended that these findings underscore a case for more thorough interrogation of the real worlds inhabited by coaches, such that ideas about ‘good practice’ in TI might be more effectively reconciled with grounded knowledge of the practical everyday necessities of being a coach
Moral courage in the workplace: moving to and from the desire and decision to act
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72135/1/j.1467-8608.2007.00484.x.pd
Organic matter chemistry controls greenhouse gas emissions from permafrost peatlands
Large tracts of arctic and subarctic peatlands are underlain by permafrost. These peatlands store large quantities of carbon (C), and are currently under severe threat from climate change. The aim of this study was to determine the size and organic chemistry of the easily degradable C pool in permafrost peatlands and link the functional organic chemistry to temperature and moisture controls of greenhouse gas emissions. First, we used a combination of field measurements and laboratory experiments to assess the influence of increased temperature and flooding on CO₂ and CH₄ emissions from sixteen permafrost peatlands in subarctic Sweden and Canada. Second, we determined the variation in organic matter chemistry and the associated microbial community composition of the peat active layer, with depth using quantitative ¹³C solid-state NMR and molecular biomarkers respectively. We demonstrate that the peat organic chemistry strongly controls CO₂ release from peat and that ca. 35 and 26% of the peat organic matter, at the Swedish and Canadian peatlands sites, respectively, is easily degradable by heterotrophic microorganisms. In contrast to CO₂, CH₄ emissions were decoupled from peat functional organic chemistry. We show a strong relationship between the microbial community structure and the peat organic chemistry suggesting that substrate type and abundance is an important driver of microbial composition in sub-arctic peatlands. Despite considerable variation in peat chemistry and microbial community composition with depth the temperature sensitivity was comparable throughout the active layer. Our study shows that functional organic chemistry controls both soil respiration rates and the composition of the microbial community. Furthermore, if these peatlands collapse and flood on thawing, they are unlikely to become large emitters of CH₄ without additional input of labile substrates
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