3,561 research outputs found
Scaling properties of step bunches induced by sublimation and related mechanisms: A unified perspective
This work provides a ground for a quantitative interpretation of experiments
on step bunching during sublimation of crystals with a pronounced
Ehrlich-Schwoebel (ES) barrier in the regime of weak desorption. A strong step
bunching instability takes place when the kinetic length is larger than the
average distance between the steps on the vicinal surface. In the opposite
limit the instability is weak and step bunching can occur only when the
magnitude of step-step repulsion is small. The central result are power law
relations of the between the width, the height, and the minimum interstep
distance of a bunch. These relations are obtained from a continuum evolution
equation for the surface profile, which is derived from the discrete step
dynamical equations for. The analysis of the continuum equation reveals the
existence of two types of stationary bunch profiles with different scaling
properties. Through a mathematical equivalence on the level of the discrete
step equations as well as on the continuum level, our results carry over to the
problems of step bunching induced by growth with a strong inverse ES effect,
and by electromigration in the attachment/detachment limited regime. Thus our
work provides support for the existence of universality classes of step
bunching instabilities [A. Pimpinelli et al., Phys. Rev. Lett. 88, 206103
(2002)], but some aspects of the universality scenario need to be revised.Comment: 21 pages, 8 figure
Equilibrium of anchored interfaces with quenched disordered growth
The roughening behavior of a one-dimensional interface fluctuating under
quenched disorder growth is examined while keeping an anchored boundary. The
latter introduces detailed balance conditions which allows for a thorough
analysis of equilibrium aspects at both macroscopic and microscopic scales. It
is found that the interface roughens linearly with the substrate size only in
the vicinity of special disorder realizations. Otherwise, it remains stiff and
tilted.Comment: 6 pages, 3 postscript figure
Drift causes anomalous exponents in growth processes
The effect of a drift term in the presence of fixed boundaries is studied for
the one-dimensional Edwards-Wilkinson equation, to reveal a general mechanism
that causes a change of exponents for a very broad class of growth processes.
This mechanism represents a relevant perturbation and therefore is important
for the interpretation of experimental and numerical results. In effect, the
mechanism leads to the roughness exponent assuming the same value as the growth
exponent. In the case of the Edwards-Wilkinson equation this implies exponents
deviating from those expected by dimensional analysis.Comment: 4 pages, 1 figure, REVTeX; accepted for publication in PRL; added
note and reference
Dynamics of a disordered, driven zero range process in one dimension
We study a driven zero range process which models a closed system of
attractive particles that hop with site-dependent rates and whose steady state
shows a condensation transition with increasing density. We characterise the
dynamical properties of the mass fluctuations in the steady state in one
dimension both analytically and numerically and show that the transport
properties are anomalous in certain regions of the density-disorder plane. We
also determine the form of the scaling function which describes the growth of
the condensate as a function of time, starting from a uniform density
distribution.Comment: Revtex4, 5 pages including 2 figures; Revised version; To appear in
Phys. Rev. Let
Internalizing European Court of Human Rights Interpretations: Russia\u27s Courts of General Jurisdiction and New Directions in Civil Defamation Law
The manuscript examines the steps that Russia\u27s courts of general jurisdiction have taken since 2002 to fashion major changes in Russia\u27s civil defamation law. The critical element in this process has been the courts\u27 internalization of the practice of the European Court of Human Rights in interpreting the freedom of expression provisions in Article 10 of the European Convention on Human Rights, to which Russia acceded in 1998. The internalization movement in the Russian courts began in 2002 in isolated lower court decisions, and culminated in a generally-applicable Decree of the Russian Federation Supreme Court in 2005. The manuscript examines a number of those lower court decisions, as well as the 2005 Decree, to identify the substantive changes in defamation law and the process by which the European Court\u27s practice has been used to fashion them. The manuscript also assesses the prospects for the courts’ further extension of the European Court\u27s positions to remaining unresolved questions in civil defamation law. In this inquiry, I seek to identify the methodology for implementation of the Supreme Court\u27s 2005 directive that the lower courts take into account the European Court\u27s practice in deciding defamation disputes
Caspase-10 Is the Key Initiator Caspase Involved in Tributyltin-Mediated Apoptosis in Human Immune Cells
Tributyltin (TBT) is one of the most toxic compounds produced by man and distributed in the environment. A multitude of toxic activities have been described, for example, immunotoxic, neurotoxic, and endocrine disruptive effects. Moreover, it has been shown for many cell types that they undergo apoptosis after treatment with TBT and the cell death of immune cells could be the molecular background of its immunotoxic effect. As low as 200 nM up to 1 μM of TBT induces all signs of apoptosis in Jurkat T cells within 1 to 24 hrs of treatment. When compared to Fas-ligand control stimulation, the same sequence of events occurs: membrane blebbing, phosphatidylserine externalisation, the activation of the “death-inducing signalling complex,” and the following sequence of cleavage processes. In genetically modified caspase-8-deficient Jurkat cells, the apoptotic effects are only slightly reduced, whereas, in FADD-negative Jurkat cells, the TBT effect is significantly diminished. We could show that caspase-10 is recruited by the TRAIL-R2 receptor and apoptosis is totally prevented when caspase-10 is specifically inhibited in all three cell lines
Adaptation dynamics of the quasispecies model
We study the adaptation dynamics of an initially maladapted population
evolving via the elementary processes of mutation and selection. The evolution
occurs on rugged fitness landscapes which are defined on the multi-dimensional
genotypic space and have many local peaks separated by low fitness valleys. We
mainly focus on the Eigen's model that describes the deterministic dynamics of
an infinite number of self-replicating molecules. In the stationary state, for
small mutation rates such a population forms a {\it quasispecies} which
consists of the fittest genotype and its closely related mutants. The
quasispecies dynamics on rugged fitness landscape follow a punctuated (or
step-like) pattern in which a population jumps from a low fitness peak to a
higher one, stays there for a considerable time before shifting the peak again
and eventually reaches the global maximum of the fitness landscape. We
calculate exactly several properties of this dynamical process within a
simplified version of the quasispecies model.Comment: Proceedings of Statphys conference at IIT Guwahati, to be published
in Praman
Coarsening of Sand Ripples in Mass Transfer Models with Extinction
Coarsening of sand ripples is studied in a one-dimensional stochastic model,
where neighboring ripples exchange mass with algebraic rates, , and ripples of zero mass are removed from the system. For ripples vanish through rare fluctuations and the average ripples mass grows
as \avem(t) \sim -\gamma^{-1} \ln (t). Temporal correlations decay as
or depending on the symmetry of the mass transfer, and
asymptotically the system is characterized by a product measure. The stationary
ripple mass distribution is obtained exactly. For ripple evolution
is linearly unstable, and the noise in the dynamics is irrelevant. For the problem is solved on the mean field level, but the mean-field theory
does not adequately describe the full behavior of the coarsening. In
particular, it fails to account for the numerically observed universality with
respect to the initial ripple size distribution. The results are not restricted
to sand ripple evolution since the model can be mapped to zero range processes,
urn models, exclusion processes, and cluster-cluster aggregation.Comment: 10 pages, 8 figures, RevTeX4, submitted to Phys. Rev.
POSTURE CONTROL AFTER LONGITUDINAL ROTATIONS IN DIFFERENT DIRECTIONS
Fast rotations induce load on the human organism. Hanging vertical, young figure skaters perform rotations around the longitudinal axis. After the rotations we investigated the posture control. The differences between the direction of rotations will be explored. There were no differences between the rotations to preferred and not preferred direction of the rotations, but there were individual exceptions. Angular velocity about 500 deg/sec were reached. The results of the posture control show an effect of the rotations. But there is also no effect on the direction. The postural sway after rotation to preferred direction were not different to the postural sway after rotations to the opposite direction. Further investigations will use the results of this pilot study
Stimulation of Phospholipase A2 by Toxic Main Group Heavy Metals: Partly Dependent on G-proteins?
Organometals induce platelet aggregation and inorganic metal ions such as Cd2+ or Pb2+ sensitise
human blood platelets to aggregating agents and this action is associated with the liberation of arachidonic
acid and eicosanoid formation. The same mechanism is observed using human leukaemia cells (HL-60)
when treated with MeHgCl or Et3PbCl. The fatty acid liberation within human platelets and HL-60 cells
could only be inhibited with phospholipase A2 inhibitors of different specificity
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