2,381 research outputs found
Correlation of Static Stress Changes and Earthquake Occurrence in
A systematic analysis is made of static Coulomb stress changes and
earthquake occurrence in the area of the North Aegean Sea, Greece, in order to assess the
prospect of using static stress changes to construct a regional earthquake likelihood
model. The earthquake data set comprises all events of magnitude M â„ 5.2 which have
occurred since 1964. This is compared to the evolving stress field due to constant tectonic
loading and perturbations due to coseismic slip associated with major earthquakes (M â„
6.4) over the same period. The stress was resolved for sixteen fault orientation classes,
covering the observed focal mechanisms of all earthquakes in the region. Analysis using
error diagrams shows that earthquake occurrence is better correlated with the constant
tectonic loading component of the stress field than with the total stress field changes since
1964, and that little, if any, information on earthquake occurrence is lost if only the
maximum of the tectonic loading over the fault orientation classes is considered.
Moreover, the information on earthquake occurrence is actually increased by taking the
maximum of the evolving stress field since 1964, and of its coseismicâslip component,
over the fault orientation classes. The maximum, over fault orientation classes, of linear
combinations of the tectonic loading and the evolving stress field is insignificantly better
correlated with earthquake occurrence than the maximum of the tectonic loading by itself.
A composite stressâchange variable is constructed from ordering of the maximum
tectonic loading component and the maximum coseismicâslip component, in order to
optimize the correlation with earthquake occurrence. The results indicate that it would be
difficult to construct a timeâvarying earthquake likelihood model from the evolving stress
field that is more informative than a timeâinvariant model based on the constant tectonic
loading
Asymptotic Normalization Coefficients for 13C+p->14N
The proton exchange reaction has been measured
at an incident energy of 162 MeV. Angular distributions were obtained for
proton transfer to the ground and low lying excited states in . Elastic
scattering of on also was measured out to the rainbow angle
region in order to find reliable optical model potentials. Asymptotic
normalization coefficients for the system have been
found for the ground state and the excited states at 2.313, 3.948, 5.106 and
5.834 MeV in . These asymptotic normalization coefficients will be used
in a determination of the S-factor for at solar
energies from a measurement of the proton transfer reaction
.Comment: 5 pages, 6 figure
High energy pion-deuteron elastic scattering
High energy pion-deuteron elastic scatterin
Expanding the parameters of academia
This paper draws on qualitative data gathered from two studies funded by the UK Leadership Foundation for Higher Education to examine the expansion of academic identities in higher education. It builds on Whitchurchâs earlier work, which focused primarily on professional staff, to suggest that the emergence of broadly based projects such as widening participation, learning support and community partnership is also impacting on academic identities. Thus, academic as well as professional staff are increasingly likely to work in multi-professional teams across a variety of constituencies, as well as with external partners, and the binary distinction between âacademicâ and ânon-academicâ roles and activities is no longer clear-cut. Moreover, there is evidence from the studies of an intentionality about deviations from mainstream academic career routes among respondents who could have gone either way. Consideration is therefore given to factors that influence individuals to work in more project-oriented areas, as well as to variables that affect ways in which these roles and identities develop. Finally, three models of academically oriented project activity are identified, and the implications of an expansion of academic identities are reviewed
Tests of Transfer Reaction Determinations of Astrophysical S-Factors
The reaction has been used to determine
asymptotic normalization coefficients for transitions to the ground and first
excited states of . The coefficients provide the normalization for
the tails of the overlap functions for and allow us
to calculate the S-factors for at astrophysical
energies. The calculated S-factors are compared to measurements and found to be
in very good agreement. This provides the first test of this indirect method to
determine astrophysical direct capture rates using transfer reactions. In
addition, our results yield S(0) for capture to the ground and first excited
states in , without the uncertainty associated with extrapolation from
higher energies.Comment: 6 pages, 2 figure
Weighing Super-Massive Black Holes with Narrow Fe K Line
It has been suggested that the narrow cores of the Fe K emission
lines in Active Galactic Nuclei (AGNs) are likely produced in the torus, the
inner radius of which can be measured by observing the lag time between the
and band flux variations. In this paper we compare the virial products of
the infrared time lags and the narrow Fe K widths for 10 type 1 AGNs
with the black hole masses from other techniques. We find the narrow Fe
K line width is in average 2.6 times broader than
expected assuming an isotropic velocity distribution of the torus at the
distance measured by the infrared lags. We propose the thick disk model of the
torus could explain the observed larger line width. Another possibility is the
contamination by emission from the broad line region or the outer accretion
disk. Alternatively, the narrow iron line might originate from the inner most
part of the obscuring torus within the sublimation radius, while the infrared
emission from outer cooler part. We note the correlation between the black hole
masses based on this new technique and those based on other known techniques is
statistically insignificant. We argue that this could be attributed to the
small sample size and the very large uncertainties in the measurements of iron
K line widths. The next generation of X-ray observatories could help verify the
origin of the narrow iron K line and the reliability of this new
technique.Comment: 12 pages, 2 figures, 2 tables, Science China G, in pres
Optical model potentials involving loosely bound p-shell nuclei around 10 MeV/A
We present the results of a search for optical model potentials for use in
the description of elastic scattering and transfer reactions involving stable
and radioactive p-shell nuclei. This was done in connection with our program to
use transfer reactions to obtain data for nuclear astrophysics, in particular
for the determination of the astrophysical S_17 factor for 7Be(p,\gamma)8B
using two (7Be,8B) proton transfer reactions. Elastic scattering was measured
using 7Li, 10B, 13C and 14N projectiles on 9Be and 13C targets at or about
E/A=10 MeV/nucleon. Woods-Saxon type optical model potentials were extracted
and are compared with potentials obtained from a microscopic double folding
model. We use these results to find optical model potentials for unstable
nuclei with emphasis on the reliability of the description they provide for
peripheral proton transfer reactions. We discuss the uncertainty introduced by
the procedure in the prediction of the DWBA cross sections for the (7Be,8B)
reactions used in extracting the astrophysical factor S_17(0).Comment: 16 pages, LaTEX file, 9 figures (PostScript files
Residence Time Statistics for Normal and Fractional Diffusion in a Force Field
We investigate statistics of occupation times for an over-damped Brownian
particle in an external force field. A backward Fokker-Planck equation
introduced by
Majumdar and Comtet describing the distribution of occupation times is
solved. The solution gives a general relation between occupation time
statistics and probability currents which are found from solutions of the
corresponding problem of first passage time. This general relationship between
occupation times and first passage times, is valid for normal Markovian
diffusion and for non-Markovian sub-diffusion, the latter modeled using the
fractional Fokker-Planck equation. For binding potential fields we find in the
long time limit ergodic behavior for normal diffusion, while for the fractional
framework weak ergodicity breaking is found, in agreement with previous results
of Bel and Barkai on the continuous time random walk on a lattice. For
non-binding potential rich physical behaviors are obtained, and classification
of occupation time statistics is made possible according to whether or not the
underlying random walk is recurrent and the averaged first return time to the
origin is finite. Our work establishes a link between fractional calculus and
ergodicity breaking.Comment: 12 page
Conformational changes of calmodulin upon Ca2+ binding studied with a microfluidic mixer
A microfluidic mixer is applied to study the kinetics of calmodulin conformational changes upon Ca2+ binding. The device facilitates rapid, uniform mixing by decoupling hydrodynamic focusing from diffusive mixing and accesses time scales of tens of microseconds. The mixer is used in conjunction with multiphoton microscopy to examine the fast Ca2+-induced transitions of acrylodan-labeled calmodulin. We find that the kinetic rates of the conformational changes in two homologous globular domains differ by more than an order of magnitude. The characteristic time constants are â490 ÎŒs for the transitions in the C-terminal domain and â20 ms for those in the N-terminal domain of the protein. We discuss possible mechanisms for the two distinct events and the biological role of the stable intermediate, half-saturated calmodulin
A new algorithm for anisotropic solutions
We establish a new algorithm that generates a new solution to the Einstein
field equations, with an anisotropic matter distribution, from a seed isotropic
solution. The new solution is expressed in terms of integrals of an isotropic
gravitational potential; and the integration can be completed exactly for
particular isotropic seed metrics. A good feature of our approach is that the
anisotropic solutions necessarily have an isotropic limit. We find two examples
of anisotropic solutions which generalise the isothermal sphere and the
Schwarzschild interior sphere. Both examples are expressed in closed form
involving elementary functions only.Comment: 16 pages, to appear in Pramana - J. Phy
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