9,441 research outputs found
Spiral diffusion of rotating self-propellers with stochastic perturbation
Translationally diffusive behavior arising from the combination of
orientational diffusion and powered motion at microscopic scales is a known
phenomenon, but the peculiarities of the evolution of expected position
conditioned on initial position and orientation have been neglected. A theory
is given of the spiral motion of the mean trajectory depending upon propulsion
speed, angular velocity, orientational diffusion and rate of random chirality
reversal. We demonstrate the experimental accessibility of this effect using
both tadpole-like and Janus sphere dimer rotating motors. Sensitivity of the
mean trajectory to the kinematic parameters suggest that it may be a useful way
to determine those parameters
Electromagnetic corrections for the analysis of low energy pi-p scattering data
We calculate the electromagnetic corrections to the isospin invariant mixing
angle and to the two eigenphases for the s and p-waves for low energy pi-p
elastic and charge exchange scattering. These corrections have to be applied to
the nuclear quantities obtained from phase shift analyses of the experimental
data in order to obtain the hadronic phases. We compare our results with
earlier calculations and estimate the uncertainties in the corrections.Comment: 19 pages, 5 figures. Uses elsart.cls Accepted for publication in
Nuclear Physics
The effect of payday lending restrictions on liquor sales
We exploit a change in lending laws to estimate the causal effect of restricting access to payday loans on liquor sales. Leveraging lender- and liquor store-level data, we find that the changes reduce sales, with the largest decreases at stores located nearest to lenders. By focusing on states with state-run liquor monopolies, we account for supply side variables that are typically unobserved. Our results are the first to quantify how credit constraints affect spending on liquor, and suggest mechanisms underlying some loan usage. These results illustrate that the benefits of lending restrictions extend beyond personal finance and may be large
Struggling and juggling: a comparison of assessment loads in research and teaching-intensive universities
In spite of the rising tide of metrics in UK higher education, there has been scant attention paid to assessment loads, when evidence demonstrates that heavy demands lead to surface learning. Our study seeks to redress the situation by defining assessment loads and comparing them across research-and teaching intensive universities. We clarify the concept of ‘assessment load’ in response to findings about high volumes of summative assessment on modular degrees. We define assessment load across whole undergraduate degrees, according to four measures: the volume of summative assessment; volume of formative assessment; proportion of examinations to coursework; number of different varieties of assessment. All four factors contribute to the weight of an assessment load, and influence students’ approaches to learning. Our research compares programme assessment data from 73 programmes in 14 UK universities, across two institutional categories. Research-intensives have higher summative assessment loads and a greater proportion of examinations; teaching-intensives have higher varieties of assessment. Formative assessment does not differ significantly across both university groups. These findings pose particular challenges for students in different parts of the sector. Our study questions the wisdom that ‘more’ is always better, proposing that lighter assessment loads may make room for ‘slow’ and deep learning
Matrix bandwidth and profile reduction
This program, REDUCE, reduces the bandwidth and profile of sparse symmetric matrices, using row and corresponding column permutations. It is a realization of the algorithm described by the authors elsewhere. It was extensively tested and compared with several other programs and was found to be considerably faster than the others, superior for bandwidth reduction and as satisfactory as any other for profile reduction
Elastic Scattering of Pions From the Three-nucleon System
We examine the scattering of charged pions from the trinucleon system at a
pion energy of 180 MeV. The motivation for this study is the structure seen in
the experimental angular distribution of back-angle scattering for pi+ 3He and
pi- 3H but for neither pi- 3He nor pi+ 3H. We consider the addition of a double
spin flip term to an optical model treatment and find that, though the
contribution of this term is non-negligible at large angles for pi+ 3He and pi-
3H, it does not reproduce the structure seen in the experiment.Comment: 15 pages + 5 figure
Starvation Resistance is Associated with Developmentally Specified Changes in Sleep, Feeding and Metabolic Rate
Food shortage represents a primary challenge to survival, and animals have adapted diverse developmental, physiological and behavioral strategies to survive when food becomes unavailable. Starvation resistance is strongly influenced by ecological and evolutionary history, yet the genetic basis for the evolution of starvation resistance remains poorly understood. The fruit fly Drosophila melanogaster provides a powerful model for leveraging experimental evolution to investigate traits associated with starvation resistance. While control populations only live a few days without food, selection for starvation resistance results in populations that can survive weeks. We have previously shown that selection for starvation resistance results in increased sleep and reduced feeding in adult flies. Here, we investigate the ontogeny of starvation resistance-associated behavioral and metabolic phenotypes in these experimentally selected flies. We found that selection for starvation resistance resulted in delayed development and a reduction in metabolic rate in larvae that persisted into adulthood, suggesting that these traits may allow for the accumulation of energy stores and an increase in body size within these selected populations. In addition, we found that larval sleep was largely unaffected by starvation selection and that feeding increased during the late larval stages, suggesting that experimental evolution for starvation resistance produces developmentally specified changes in behavioral regulation. Together, these findings reveal a critical role for development in the evolution of starvation resistance and indicate that selection can selectively influence behavior during defined developmental time points
On the work distribution for the adiabatic compression of a dilute classical gas
We consider the adiabatic and quasi-static compression of a dilute classical
gas, confined in a piston and initially equilibrated with a heat bath. We find
that the work performed during this process is described statistically by a
gamma distribution. We use this result to show that the model satisfies the
non-equilibrium work and fluctuation theorems, but not the
flucutation-dissipation relation. We discuss the rare but dominant realizations
that contribute most to the exponential average of the work, and relate our
results to potentially universal work distributions.Comment: 4 page
Charge Symmetry Violation Effects in Pion Scattering off the Deuteron
We discuss the theoretical and experimental situations for charge symmetry
violation (CSV) effects in the elastic scattering of pi+ and pi- on deuterium
(D) and 3He/3H. Accurate comparison of data for both types of targets provides
evidence for the presence of CSV effects. While there are indications of a CSV
effect in deuterium, it is much more pronounced in the case of 3He/3H. We
provide a description of the CSV effect on the deuteron in terms of single- and
double- scattering amplitudes. The Delta-mass splitting is taken into account.
Theoretical predictions are compared with existing experimental data for pi-d
scattering; a future article will speak to the pi-three nucleon case.Comment: 16 pages of RevTeX, 7 postscript figure
On the Geometry of Surface Stress
We present a fully general derivation of the Laplace--Young formula and
discuss the interplay between the intrinsic surface geometry and the extrinsic
one ensuing from the immersion of the surface in the ordinary euclidean
three-dimensional space. We prove that the (reversible) work done in a general
surface deformation can be expressed in terms of the surface stress tensor and
the variation of the intrinsic surface metric
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