11,000 research outputs found
Entropic forces generated by grafted semiflexible polymers
The entropic force exerted by the Brownian fluctuations of a grafted
semiflexible polymer upon a rigid smooth wall are calculated both analytically
and by Monte Carlo simulations. Such forces are thought to play an important
role for several cellular phenomena, in particular, the physics of
actin-polymerization-driven cell motility and movement of bacteria like
Listeria. In the stiff limit, where the persistence length of the polymer is
larger than its contour length, we find that the entropic force shows scaling
behavior. We identify the characteristic length scales and the explicit form of
the scaling functions. In certain asymptotic regimes we give simple analytical
expressions which describe the full results to a very high numerical accuracy.
Depending on the constraints imposed on the transverse fluctuations of the
filament there are characteristic differences in the functional form of the
entropic forces; in a two-dimensional geometry the entropic force exhibits a
marked peak.Comment: 21 pages, 18 figures, minor misprints correcte
Evaluation of electrode shape and nondestructive evaluation method for welded solar cell interconnects
Resistance welds of solar cell interconnect tabs were evaluated. Both copper-silver and silver-silver welds were made with various heat inputs and weld durations. Parallel gap and annular gap weld electrode designs were used. The welds were analyzed by light microscope, electron microprobe and scanning laser acoustic microscope. These analyses showed the size and shape of the weld, the relationship between the acoustic micrographs, the visible electrode footprint, and the effect of electrode misalignment. The effect of weld heat input on weld microstructure was also shown
Pair distribution function and structure factor of spherical particles
The availability of neutron spallation-source instruments that provide total
scattering powder diffraction has led to an increased application of real-space
structure analysis using the pair distribution function. Currently, the
analytical treatment of finite size effects within pair distribution refinement
procedures is limited. To that end, an envelope function is derived which
transforms the pair distribution function of an infinite solid into that of a
spherical particle with the same crystal structure. Distributions of particle
sizes are then considered, and the associated envelope function is used to
predict the particle size distribution of an experimental sample of gold
nanoparticles from its pair distribution function alone. Finally, complementing
the wealth of existing diffraction analysis, the peak broadening for the
structure factor of spherical particles, expressed as a convolution derived
from the envelope functions, is calculated exactly for all particle size
distributions considered, and peak maxima, offsets, and asymmetries are
discussed.Comment: 7 pages, 6 figure
Analysing and controlling the tax evasion dynamics via majority-vote model
Within the context of agent-based Monte-Carlo simulations, we study the
well-known majority-vote model (MVM) with noise applied to tax evasion on
simple square lattices, Voronoi-Delaunay random lattices, Barabasi-Albert
networks, and Erd\"os-R\'enyi random graphs. In the order to analyse and to
control the fluctuations for tax evasion in the economics model proposed by
Zaklan, MVM is applied in the neighborhod of the noise critical . The
Zaklan model had been studied recently using the equilibrium Ising model. Here
we show that the Zaklan model is robust and can be reproduced also through the
nonequilibrium MVM on various topologies.Comment: 18 pages, 7 figures, LAWNP'09, 200
Trichinellosis in Switzerland
Human trichinellosis is a food-borne zoonosis exhibiting significant health and economical problems predominantly in countries with high pork consumption. During the past ten years the number of human outbreaks around the world has increased in certain areas. In Europe, more than 20,000 human cases have been detected between the year 1991 and 2000. Conversely, Trichinella infection has not been reported for many decades among Swiss domestic pigs
Force-Velocity Relations of a Two-State Crossbridge Model for Molecular Motors
We discuss the force-velocity relations obtained in a two-state crossbridge
model for molecular motors. They can be calculated analytically in two limiting
cases: for a large number and for one pair of motors. The effect of the
strain-dependent detachment rate on the motor characteristics is studied. It
can lead to linear, myosin-like, kinesin-like and anomalous curves. In
particular, we specify the conditions under which oscillatory behavior may be
found.Comment: 5 pages, 4 figures, REVTeX; thoroughly revised version; also
available at http://www.physik.tu-muenchen.de/~frey
Duties to Organizational Clients
Loyalty to an organizational client means fidelity to the substantive legal structure that constitutes it. Although this principle is not controversial in the abstract, it is commonly ignored in professional discourse and doctrine. This article explains the basic notion of organizational loyalty and identifies some mistaken tendencies in discourse and doctrine, especially the Managerialist Fallacy that leads lawyers to conflate the client organization with its senior managers. The article then applies the basic notion to some hard cases, concluding with a critical appraisal of the rationale for confidentiality with organizational clients
Extended polarized semiclassical model for quantum-dot cavity QED and its application to single-photon sources
We present a simple extension of the semi-classical model for a two-level
system in a cavity, in order to incorporate multiple polarized transitions,
such as those appearing in neutral and charged quantum dots (QDs), and two
nondegenerate linearly polarized cavity modes. We verify the model by exact
quantum master equation calculations, and experimentally using a neutral QD in
a polarization non-degenerate micro-cavity, in both cases we observe excellent
agreement. Finally, the usefulness of this approach is demonstrated by
optimizing a single-photon source based on polarization postselection, where we
find an increase in the brightness for optimal polarization conditions as
predicted by the model.Comment: 8 pages, for simple code see https://doi.org/10.5281/zenodo.347666
Evolutionary game theory in growing populations
Existing theoretical models of evolution focus on the relative fitness
advantages of different mutants in a population while the dynamic behavior of
the population size is mostly left unconsidered. We here present a generic
stochastic model which combines the growth dynamics of the population and its
internal evolution. Our model thereby accounts for the fact that both
evolutionary and growth dynamics are based on individual reproduction events
and hence are highly coupled and stochastic in nature. We exemplify our
approach by studying the dilemma of cooperation in growing populations and show
that genuinely stochastic events can ease the dilemma by leading to a transient
but robust increase in cooperationComment: 4 pages, 2 figures and 2 pages supplementary informatio
Die blande Struma
Eine mechanische Teil-Indikation kann auch schon bei blander Struma des Stadium I bestehen. Die Indikation auf Wunsch des Patienten ist berechtigt, wenn die Schilddrüsenhormonbehandlung erfolglos oder wenig aussichtsreich ist. Die prophylaktischdiagnostische Operationsindikation wird nach Abwägung von statistischem und individuellem Malignom- und Operationsrisiko gestellt. Letztere Indikation überwiegt heute bei weitem. — Die Kropf-Prophylaxe mit jodiertem Speisesalz könnte die mittlere Strumafrequenz in der Bundesrepublick von 15 auf 3 % reduzieren.Surgical treatment can be justified already for nontoxic goiter stage I (WHO) because of tracheal stenosis. Surgery for cosmetic reasons may be adequate, if treatment with thyroid hormones is neither successful nor promising. Diagnostic (histologic) or prophylactic reasons are today the most frequent causes for surgery, in order to detect or avoid thyroid malignancies. — Iodine prophylaxis is advocated in the Federal Republic of Germany, where iodine deficiency and endemic goiter (15 %) are still prevalent
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