2,888 research outputs found
Light scattering spectra of supercooled molecular liquids
The light scattering spectra of molecular liquids are derived within a
generalized hydrodynamics. The wave vector and scattering angle dependences are
given in the most general case and the change of the spectral features from
liquid to solidlike is discussed without phenomenological model assumptions for
(general) dielectric systems without long-ranged order. Exact microscopic
expressions are derived for the frequency-dependent transport kernels,
generalized thermodynamic derivatives and the background spectra.Comment: 12 page
Effective swimming strategies in low Reynolds number flows
The optimal strategy for a microscopic swimmer to migrate across a linear
shear flow is discussed. The two cases, in which the swimmer is located at
large distance, and in the proximity of a solid wall, are taken into account.
It is shown that migration can be achieved by means of a combination of sailing
through the flow and swimming, where the swimming strokes are induced by the
external flow without need of internal energy sources or external drives. The
structural dynamics required for the swimmer to move in the desired direction
is discussed and two simple models, based respectively on the presence of an
elastic structure, and on an orientation dependent friction, to control the
deformations induced by the external flow, are analyzed. In all cases, the
deformation sequence is a generalization of the tank-treading motion regimes
observed in vesicles in shear flows. Analytic expressions for the migration
velocity as a function of the deformation pattern and amplitude are provided.
The effects of thermal fluctuations on propulsion have been discussed and the
possibility that noise be exploited to overcome the limitations imposed on the
microswimmer by the scallop theorem have been discussed.Comment: 14 pages, 5 figure
NEXUS/Physics: An interdisciplinary repurposing of physics for biologists
In response to increasing calls for the reform of the undergraduate science
curriculum for life science majors and pre-medical students (Bio2010,
Scientific Foundations for Future Physicians, Vision & Change), an
interdisciplinary team has created NEXUS/Physics: a repurposing of an
introductory physics curriculum for the life sciences. The curriculum interacts
strongly and supportively with introductory biology and chemistry courses taken
by life sciences students, with the goal of helping students build general,
multi-discipline scientific competencies. In order to do this, our two-semester
NEXUS/Physics course sequence is positioned as a second year course so students
will have had some exposure to basic concepts in biology and chemistry.
NEXUS/Physics stresses interdisciplinary examples and the content differs
markedly from traditional introductory physics to facilitate this. It extends
the discussion of energy to include interatomic potentials and chemical
reactions, the discussion of thermodynamics to include enthalpy and Gibbs free
energy, and includes a serious discussion of random vs. coherent motion
including diffusion. The development of instructional materials is coordinated
with careful education research. Both the new content and the results of the
research are described in a series of papers for which this paper serves as an
overview and context.Comment: 12 page
The significance of work allocation in the professional apprenticeship of solicitors
It is a peculiarity of the solicitorsâ profession that it has historically relied on methods of pre-qualification âtrainingâ by way of apprenticeship and that an entirely respectable non-graduate route into the profession remains. In a political context, however, where the profession is called upon positively to demonstrate its standards of performance, the professional regulator seeks to attach a competence framework to the existing model; shifting the focus from how the trainee learns to what the trainee learns. This paper will explore the period of traineeship from the perspective of the trainees themselves, drawing on two small qualitative studies, focussing on the fundamental context factor of the allocation and structuring of their work. In the first study the context for this evaluation is the set of outcomes being tested by the professional regulator and in the second, the perceptions of qualified individuals looking back at their apprenticeship, The paper concludes that there remains work for the profession to do not only in fostering supportive and expansive apprenticeships, but in attending, however, supportive the surrounding environment, to the work being carried out by trainees and its relationship with the work carried out by newly qualified solicitors
Report on perceived policy needs and decision contexts
Adaptation to climate change is a new challenge for existing institutions and decision-making processes. In order to assess what form this challenge takes for decision-makers, we conducted interviews and a policy review to determine the perceived policy needs in Austria, Finland, France, Italy, Poland, Romania, Spain and the United Kingdom. In each country, interviews are conducted at the national level and the sub-national (state) level if the national level is not sufficiently active in adaptation planning yet. We focus on general adaptation policy as well as specific sectors for each country, in line with the distribution of MEDIATION case studies. Different countries are at different stages of developing adaptation policy, but the underlying needs are similar across them. We group the needs into nine categories: inter-agency coordination, multi-level governance, mainstreaming, awareness-raising, coping with uncertainty, research needs, tools and information access, financial and human resources, and political commitment. We also look at suggestions for the EU's role in coordinating adaptation policy
Reorientational relaxation of a linear probe molecule in a simple glassy liquid
Within the mode-coupling theory (MCT) for the evolution of structural
relaxation in glass-forming liquids, correlation functions and susceptibility
spectra are calculated characterizing the rotational dynamics of a top-down
symmetric dumbbell molecule, consisting of two fused hard spheres immersed in a
hard-sphere system. It is found that for sufficiently large dumbbell
elongations, the dynamics of the probe molecule follows the same universal
glass-transition scenario as known from the MCT results of simple liquids. The
-relaxation process of the angular-index-j=1 response is stronger,
slower and less stretched than the one for j=2, in qualitative agreement with
results found by dielectric-loss and depolarized-light-scattering spectroscopy
for some supercooled liquids. For sufficiently small elongations, the
reorientational relaxation occurs via large-angle flips, and the standard
scenario for the glass-transition dynamics is modified for odd-j responses due
to precursor phenomena of a nearby type-A MCT transition. In this case, a major
part of the relaxation outside the transient regime is described qualitatively
by the -relaxation scaling laws, while the -relaxation scaling
law is strongly disturbed.Comment: 40 pages. 10 figures as GIF-files, to be published in Phys. Rev.
Dynamics at a smeared phase transition
We investigate the effects of rare regions on the dynamics of Ising magnets
with planar defects, i.e., disorder perfectly correlated in two dimensions. In
these systems, the magnetic phase transition is smeared because static
long-range order can develop on isolated rare regions. We first study an
infinite-range model by numerically solving local dynamic mean-field equations.
Then we use extremal statistics and scaling arguments to discuss the dynamics
beyond mean-field theory. In the tail region of the smeared transition the
dynamics is even slower than in a conventional Griffiths phase: the spin
autocorrelation function decays like a stretched exponential at intermediate
times before approaching the exponentially small equilibrium value following a
power law at late times.Comment: 10 pages, 8eps figures included, final version as publishe
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