38,642 research outputs found
A three dimensional model of the Venusian thermosphere with superrotation
An improved three dimensional spectral model of the thermosphere of Venus is described. The model solves the Navier-Stokes equations and includes nonlinear effects for an arbitrary number of atmospheric species. A two dimensional axisymmetric model of the superrotation of the thermosphere is also presented. This model addresses the Pioneer-Venus mission finding, which suggested the thermospheric rotation rate to be much higher than that of the planet as seen from the asymmetric distribution of hydrogen and helium. Both models include the effects of an anisotropic eddy diffusion that is consistent with atmospheric mixing length theory
Zero range model of traffic flow
A multi--cluster model of traffic flow is studied, in which the motion of
cars is described by a stochastic master equation. Assuming that the escape
rate from a cluster depends only on the cluster size, the dynamics of the model
is directly mapped to the mathematically well-studied zero-range process.
Knowledge of the asymptotic behaviour of the transition rates for large
clusters allows us to apply an established criterion for phase separation in
one-dimensional driven systems. The distribution over cluster sizes in our
zero-range model is given by a one--step master equation in one dimension. It
provides an approximate mean--field dynamics, which, however, leads to the
exact stationary state. Based on this equation, we have calculated the critical
density at which phase separation takes place. We have shown that within a
certain range of densities above the critical value a metastable homogeneous
state exists before coarsening sets in. Within this approach we have estimated
the critical cluster size and the mean nucleation time for a condensate in a
large system. The metastablity in the zero-range process is reflected in a
metastable branch of the fundamental flux--density diagram of traffic flow. Our
work thus provides a possible analytical description of traffic jam formation
as well as important insight into condensation in the zero-range process.Comment: 10 pages, 13 figures, small changes are made according to finally
accepted version for publication in Phys. Rev.
Properties of the mechanosensitive channel MscS pore revealed by tryptophan scanning mutagenesis
Funding This work was supported by a Wellcome Trust Programme grant [092552/A/10/Z awarded to I.R.B., S.M., J. H. Naismith (University of St Andrews, St Andrews, U.K.), and S. J. Conway (University of Oxford, Oxford, U.K.)] (T.R. and M.D.E.), by a BBSRC grant (A.R.) [BB/H017917/1 awarded to I.R.B., J. H. Naismith, and O. Schiemann (University of St Andrews)], by a Leverhulme Emeritus Fellowship (EM-2012-060\2), and by a CEMI grant to I.R.B. from the California Institute of Technology. The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013 FP7/2007-2011) under Grant PITN-GA-2011-289384 (FP7-PEOPLE-2011-ITN NICHE) (H.G.) (awarded to S.M.).Peer reviewedPublisher PD
Understanding the Psychology of Gang Violence: Implications for Designing Effective Violence Reduction Interventions
An exploratory study to add to the understanding of the psychological processes contributing to violence carried out by gang members
Ethical assessment of new technologies: a meta-methodology
Purpose – The purpose of this paper is to set out a structured meta-methodology, named DIODE, for the ethical assessment of new and emerging technologies. DIODE has been designed by a mixture of academics, governmental people and commercial practitioners. It is designed to help diverse organisations and individuals conduct ethical assessments of new and emerging technologies.
Design/methodology/approach - framework discussion paper was developed for consultation to ensure that DIODE addresses fundamental ethical concerns, has appropriate and manageable scope and is comprehensive in its ethical compass. The resulting DIODE meta-methodology uses flowcharts and templates, encompassing the use of diverse tools and techniques.
Findings - There are two different angles for the ethical assessment of new technologies; a strategic/abstract angle and a project/application specific angle. DIODE includes two channels to accommodate this distinction. Early stage testing yielded positive feedback and mostly favourable comment. Additional guidance materials are being developed in response to the feedback.
Practical implications - Without training and guidance, it is difficult for technologists to take ethical concerns into account during the development and deployment of new technologies. DIODE can provide that training and guidance through a practical meta-methodology which should help ICT professionals, policy makers and academics.
Originality/valueThere is very little structured methodology material available on the ethical assessment of new technologies. The depth and sophistication contained in DIODE is therefore believed to be unique. DIODE provides practical help while remaining rooted in the philosophical and theoretical concepts of ethics
Boundary Effects in Chiral Polymer Hexatics
Boundary effects in liquid-crystalline phases can be large due to long-ranged
orientational correlations. We show that the chiral hexatic phase can be locked
into an apparent three-dimensional N+6 phase via such effects. Simple numerical
estimates suggest that the recently discovered "polymer hexatic" may actually
be this locked phase.Comment: 4 pages, RevTex, 3 included eps figure
Radar observations of ash eruptions
Radar systems located at Portland, Oreg., Seattle, Wash., and near Spokane, Wash., have been used extensively for observations of ash clouds from explosive volcanic eruptions at Mount St. Helens during 1980. Eruption clouds are composed of silicate particles and are therefore detectable by radar. Radar observations can be made at night and in overcast weather when conventional observations of eruptions are difficult.-from Author
Phase Modulated Thermal Conductance of Josephson Weak Links
We present a theory for quasiparticle heat transport through superconducting
weak links. The thermal conductance depends on the phase difference () of
the superconducting leads. Branch conversion processes, low-energy Andreev
bound states near the contact and the suppression of the local density of
states near the gap edge are related to phase-sensitive transport processes.
Theoretical results for the influence of junction transparency, temperature and
disorder, on the phase modulation of the conductance are reported. For
high-transmission weak links, , the formation of an Andreev bound state
at leads to suppression of the
density of states for the continuum excitations that transport heat, and thus,
to a reduction in the conductance for . For low-transmission
() barriers resonant scattering at energies
leads to an increase in the thermal conductance
as drops below (for phase differences near ).Comment: 4 pages, 3 figures Expanded discussion of boundary conditions for
Ricatti amplitude
- …