30,817 research outputs found
NRQCD results on the MILC extra coarse ensemble
We present preliminary results using NRQCD to describe heavy quarks on the
MILC 2+1 flavour dynamical extra coarse ensemble. We calculate the spectra of
low lying states in bottomonium to complement earlier results on the finer MILC
ensembles. We then exploit the coarseness of the lattices to calculate charm
propagators using NRQCD. These are used to examine the charmonium spectrum and
to calclate the mass of the using NRQCD. Finally we look breifly at the
and systems using the imporoved staggered formalism to describe the
light valence quarks.Comment: 6 pages, Talk presented at Lattice 2005 (Heavy Quarks), Dublin, 25-30
July 200
Fracture mechanics approach to design analysis of notches, steps and internal cut-outs in planar components
A new approach to the assessment and optimization of geometric stress-concentrating features is proposed on the basis of the correspondence between sharp crack or corner stressfield intensity factors and conventional elastic stress concentration factors (SCFs) for radiused transitions. This approach complements the application of finite element analysis (FEA) and the use of standard SCF data from the literature. The method makes it possible to develop closed-form solutions for SCFs in cases where corresponding solutions for the sharp crack geometries exist. This is helpful in the context of design optimization. The analytical basis of the correspondence is shown, together with the limits on applicability where stress-free boundaries near the stress concentrating feature are present or adjacent features interact. Examples are given which compare parametric results derived from FEA with closed-form solutions based on the proposed method. New information is given on the stress state at a 90° corner or width step, where the magnitude of the stress field intensity is related to that of the corresponding crack geometry. This correspondence enables the user to extend further the application of crack-tip stress-field intensity information to square-cornered steps, external U-grooves, and internal cut-outs
Rebuttal to "Comment by V.M. Krasnov on 'Counterintuitive consequence of heating in strongly-driven intrinsic junctions of Bi2Sr2CaCu2O8+d Mesas' "
In our article [1], we found that with increasing dissipation there is a
clear, systematic shift and sharpening of the conductance peak along with the
disappearance of the higher-bias dip/hump features (DHF), for a stack of
intrinsic Josephson junctions (IJJs) of intercalated Bi2Sr2CaCu2O8+{\delta}
(Bi2212). Our work agrees with Zhu et al [2] on unintercalated, pristine
Bi2212, as both studies show the same systematic changes with dissipation. The
broader peaks found with reduced dissipation [1,2] are consistent with broad
peaks in the density-of-states (DOS) found among scanning tunneling
spectroscopy [3] (STS), mechanical contact tunneling [4] (MCT) and inferred
from angle (momentum) resolved photoemission spectroscopy [5] (ARPES); results
that could not be ignored. Thus, sharp peaks are extrinsic and cannot
correspond to the superconducting DOS. We suggested that the commonality of the
sharp peaks in our conductance data, which is demonstrably shown to be
heating-dominated, and the peaks of previous intrinsic tunneling spectroscopy
(ITS) data implies that these ITS reports might need reinterpretation.Comment: Rebuttal to Comment of Krasnov arXiv:1007.451
Life long learning in rural areas: a report to the Countryside Agency
Lifelong Learning is a broad umbrella term which includes many different kinds of provision and different forms of learning. At its heart is formal learning, often classroom based, or involving paper and electronic media, undertaken within educational institutions such as colleges and universities. It may or may not lead to an award and it includes learning undertaken for vocational reasons as well as for general interest. It encompasses what are sometimes also known as adult education, continuing education, continuing professional development (cpd), vocational training and the acquisition of basic skills. It may also include work-based learning, and may overlap with post compulsory (post 16) education, i.e. with further education and higher education, but normally applies to all ‘adult learning’ i.e. by people over the age of 19, in particular those who are returning to study after completing their initial education.
From the perspective of the individual learner, however, non-formal learning (organised, systematic study carried on outside the framework of the formal system) is also important. This forms a continuum with informal learning that occurs frequently in the process of daily living, sometimes coincidentally for example through information media or through interpretive provision (such as at museums or heritage sites ).
This report focuses on those aspects of adult learning which are directly affected by government policies, and thus of prime concern for rural proofing
Statistics of opinion domains of the majority-vote model on a square lattice
The existence of juxtaposed regions of distinct cultures in spite of the fact
that people's beliefs have a tendency to become more similar to each other's as
the individuals interact repeatedly is a puzzling phenomenon in the social
sciences. Here we study an extreme version of the frequency-dependent bias
model of social influence in which an individual adopts the opinion shared by
the majority of the members of its extended neighborhood, which includes the
individual itself. This is a variant of the majority-vote model in which the
individual retains its opinion in case there is a tie among the neighbors'
opinions. We assume that the individuals are fixed in the sites of a square
lattice of linear size and that they interact with their nearest neighbors
only.
Within a mean-field framework, we derive the equations of motion for the
density of individuals adopting a particular opinion in the single-site and
pair approximations. Although the single-site approximation predicts a single
opinion domain that takes over the entire lattice, the pair approximation
yields a qualitatively correct picture with the coexistence of different
opinion domains and a strong dependence on the initial conditions. Extensive
Monte Carlo simulations indicate the existence of a rich distribution of
opinion domains or clusters, the number of which grows with whereas the
size of the largest cluster grows with . The analysis of the sizes of
the opinion domains shows that they obey a power-law distribution for not too
large sizes but that they are exponentially distributed in the limit of very
large clusters. In addition, similarly to other well-known social influence
model -- Axelrod's model -- we found that these opinion domains are unstable to
the effect of a thermal-like noise
Tunneling study of cavity grade Nb: possible magnetic scattering at the surface
Tunneling spectroscopy was performed on Nb pieces prepared by the same
processes used to etch and clean superconducting radio frequency (SRF)
cavities. Air exposed, electropolished Nb exhibited a surface superconducting
gap delta=1.55 meV, characteristic of clean, bulk Nb. However the tunneling
density of states (DOS) was broadened significantly. The Nb pieces treated with
the same mild baking used to improve the Q-slope in SRF cavities, reveal a
sharper DOS. Good fits to the DOS were obtained using Shiba theory, suggesting
that magnetic scattering of quasiparticles is the origin of the gapless surface
superconductivity and a heretofore unrecognized contributor to the Q-slope
problem of Nb SRF cavities.Comment: 3 pages, 3 figure
Rotation and Macroturbulence in Metal-poor Field Red Giant and Red Horizontal Branch Stars
We report the results for rotational velocities, Vrot sin i, and
macroturbulence dispersion, zeta(RT), for 12 metal-poor field red giant branch
stars and 7 metal-poor field red horizontal branch stars. The results are based
on Fourier transform analyses of absorption line profiles from high-resolution
(R ~ 120,000), high-S/N (~ 215 per pixel) spectra obtained with the Gecko
spectrograph at CFHT. We find that the zeta(RT) values for the metal-poor RGB
stars are very similar to those for metal-rich disk giants studied earlier by
Gray and his collaborators. Six of the RGB stars have small rotational values,
less than 2.0 km/sec, while five show significant rotation, over 3 km/sec. The
fraction of rapidly rotating RHB stars is somewhat lower than found among BHB
stars. We devise two empirical methods to translate the line-broadening results
obtained by Carney et al. (2003, 2008) into Vrot sin i for all the RGB and RHB
stars they studied. Binning the RGB stars by luminosity, we find that most
metal-poor field RGB stars show no detectable sign, on average, of rotation.
However, the most luminous stars, with M(V) <= -1.5, do show net rotation, with
mean values of 2 to 4 km/sec, depending on the algorithm employed, and these
stars also show signs of radial velocity jitter and mass loss.Comment: accepted for publication in the Astronomical Journa
Atmospheric velocity fields in tepid main sequence stars
The line profiles of the stars with v sin i below a few km/s can reveal
direct signatures of local velocity fields (e.g. convection) in stellar
atmospheres. This effect is well established in cool main sequence stars, and
has been detected and studied in three A stars. This paper reports observations
of main sequence B, A and F stars with two goals: (1) to identify additional
stars having sufficiently low values of v sin i to search for spectral line
profile signatures of local velocity fields, and (2) to explore how the
signatures of the local velocity fields in the atmosphere depend on stellar
parameters such as effective temperature T_eff and peculiarity type.
For stars having T_eff below about 10000 K, we always detect local
atmospheric velocity fields indirectly through a non-zero microturbulence
parameter, but not for hotter stars. Among the A and F stars in our sample
having the sharpest lines, direct tracers of atmospheric velocity fields are
found in six new stars. The velocity field signatures identified include
asymmetric excess line wing absorption, deeper in the blue line wing than in
the red; line profiles of strong lines that are poorly fit by computed
profiles; and strong lines that are broader than they should be for the v sin i
values deduced from weak lines. These effects are found in both normal and Am
stars, but seem stronger in Am stars.
These data still have not been satisfactorily explained by models of
atmospheric convection, including numerical simulations.Comment: Acepted for publication by Astronomy and Astrophysic
Corrections to Decay in the 2HDM
QCD corrections to the inclusive decay are
investigated within the two - Higgs doublet extension of the standard model
(2HDM). The analysis is performed in the so - called off-resonance region; the
dependence of the obtained results on the choice of the renormalization scale
is examined in details. It is shown that corrections can suppress
the decay width up to times (depending on the
choice of the dilepton invariant mass and the low - energy scale ). As
a result, in the experimentally allowed range of the parameters space, the
relations between the branching ratio and the new physics
parameters are strongly affected. It is found also that though the
renormalization scale dependence of the branching is
significantly reduced, higher order effects in the perturbation theory can
still be nonnegligible.Comment: 16 pages, latex, including 6 figures and 3 table
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