12,021 research outputs found
Information-theoretic determination of ponderomotive forces
From the equilibrium condition applied to an isolated
thermodynamic system of electrically charged particles and the fundamental
equation of thermodynamics () subject
to a new procedure, it is obtained the Lorentz's force together with
non-inertial terms of mechanical nature. Other well known ponderomotive forces,
like the Stern-Gerlach's force and a force term related to the Einstein-de
Haas's effect are also obtained. In addition, a new force term appears,
possibly related to a change in weight when a system of charged particles is
accelerated.Comment: 10 page
Generalized entropy arising from a distribution of q-indices
It is by now well known that the Boltzmann-Gibbs (BG) entropy
can be usefully generalized into the
entropy (). Microscopic dynamics determines, given classes of initial
conditions, the occupation of the accessible phase space (or of a
symmetry-determined nonzero-measure part of it), which in turn appears to
determine the entropic form to be used. This occupation might be a uniform one
(the usual {\it equal probability hypothesis} of BG statistical mechanics),
which corresponds to ; it might be a free-scale occupancy, which appears
to correspond to . Since occupancies of phase space more complex than
these are surely possible in both natural and artificial systems, the task of
further generalizing the entropy appears as a desirable one, and has in fact
been already undertaken in the literature. To illustrate the approach, we
introduce here a quite general entropy based on a distribution of -indices
thus generalizing . We establish some general mathematical properties for
the new entropic functional and explore some examples. We also exhibit a
procedure for finding, given any entropic functional, the -indices
distribution that produces it. Finally, on the road to establishing a quite
general statistical mechanics, we briefly address possible generalized
constraints under which the present entropy could be extremized, in order to
produce canonical-ensemble-like stationary-state distributions for Hamiltonian
systems.Comment: 14 pages including 3 figure
Editorial : environmental governance of urban and regional development – scales and sectors, conflict and cooperation
Recent years have continued to see a concern for the detrimental environmental impacts of human economic activities particularly in the form of enhanced global warming, sea level rise, land degradation and deforestation. Although it can be argued that economic development and growth remain the priority for governments at a variety of spatial scales or levels, these same governments also express a desire through a growing number of policy initiatives to make such development more sustainable and environmentally-friendly. A growing interest amongst policy makers has been in identifying the ways in which environmental protection measures can be made complementary to economic development aims. Rather than seeing the environment and the economy in opposition, there has been a focus on the growth potential from developing a green or low-carbon economy (OECD, 2011). At the urban and regional scale governments have increasingly begun to try and position themselves as destinations for new forms of green economy investments as a source of a new round of capital accumulation (GIBBS and O’NEILL, 2014). In total then, questions around the environment, climate change and sustainability look set to grow in importance for decision makers in cities and regions
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
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
Monte Carlo Eikonal Scattering
Monte Carlo evaluation is used to calculate heavy-ion elastic scattering
including the center-of-mass correction and the Coulomb interaction.Angular
distributions are presented for a number of nuclear pairs over a wide energy
range using nucleon-nucleon scattering parameters taken from phase-shift
analyses and densities from independent sources. A technique for the efficient
expansion of the Glauber amplitude in partial waves is developed
Nonlinear Fano resonance and bistable wave transmission
We consider a discrete model that describes a linear chain of particles
coupled to a single-site defect with instantaneous Kerr nonlinearity. We show
that this model can be regarded as a nonlinear generalization of the familiar
Fano-Anderson model, and it can generate the amplitude depended bistable
resonant transmission or reflection. We identify these effects as the nonlinear
Fano resonance, and study its properties for continuous waves and pulses.Comment: 9 pages, 14 figure, submitted to Phys. Rev.
Can prior exposure to stress enhance resilience to ocean warming in two oyster species?
Securing economically and ecologically significant molluscs, as our oceans warm due to climate change, is a global priority. South eastern Australia receives warm water in a strengthening East Australia Current and so resident species are vulnerable to elevated temperature and marine heat waves. This study tested whether prior exposure to elevated temperature can enhance resilience of oysters to ocean warming. Two Australian species, the flat oyster, Ostrea angasi, and the Sydney rock oyster, Saccostrea glomerata, were obtained as adults and "heat shocked" by exposure to a dose of warm water in the laboratory. Oysters were then transferred to elevated seawater temperature conditions where the thermal outfall from power generation was used as a proxy to investigate the impacts of ocean warming. Shell growth, condition index, lipid content and survival of flat oysters and condition of Sydney rock oysters were all significantly reduced by elevated seawater temperature in the field. Flat oysters grew faster than Sydney rock oysters at ambient temperature, but their growth and survival was more sensitive to elevated temperature. "Stress inoculation" by heat shock did little to ameliorate the negative effects of increased temperature, although the survival of heat-shocked flat oysters was greater than non-heat shocked oysters. Further investigations are required to determine if early exposure to heat stress can enhance resilience of oysters to ocean warming
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
Layer- and bulk roton excitations of 4He in porous media
We examine the energetics of bulk and layer-roton excitations of 4He in
various porous medial such as aerogel, Geltech, or Vycor, in order to find out
what conclusions can be drawn from experiments on the energetics about the
physisorption mechanism. The energy of the layer-roton minimum depends
sensitively on the substrate strength, thus providing a mechanism for a direct
measurement of this quantity. On the other hand, bulk-like roton excitations
are largely independent of the interaction between the medium and the helium
atoms, but the dependence of their energy on the degree of filling reflects the
internal structure of the matrix and can reveal features of 4He at negative
pressures. While bulk-like rotons are very similar to their true bulk
counterparts, the layer modes are not in close relation to two-dimensional
rotons and should be regarded as a third, completely independent kind of
excitation
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