4,317 research outputs found
Free energy and extension of a semiflexible polymer in cylindrical confining geometries
We consider a long, semiflexible polymer, with persistence length and
contour length , fluctuating in a narrow cylindrical channel of diameter
. In the regime the free energy of confinement and
the length of the channel occupied by the polymer are given by
Odijk's relations and
, where and
are dimensionless amplitudes. Using a simulation algorithm inspired by PERM
(Pruned Enriched Rosenbluth Method), which yields results for very long
polymers, we determine and and the analogous
amplitudes for a channel with a rectangular cross section. For a semiflexible
polymer confined to the surface of a cylinder, the corresponding amplitudes are
derived with an exact analytic approach. The results are relevant for
interpreting experiments on biopolymers in microchannels or microfluidic
devices.Comment: 15 pages without figures, 5 figure
Two types of definites: Evidence for presupposition cost
This paper investigates the notion of definiteness from a psycholinguistic perspective and addresses Löbner’s (1987) distinction between semantic and pragmatic definites. To this end inherently definite noun phrases, proper names, and indexicals are investigated as instances of (relatively) rigid designators (i.e. semantic definites) and contrasted with definite noun phrases and third person pronouns that are contingent on context to unambiguously determine their reference (i.e. pragmatic definites). Electrophysiological data provide support for this distinction and further substantiate the claim that proper names differ from definite descriptions. These findings suggest that certain expressions carry a feature of inherent definiteness, which facilitates their discourse integration (i.e. semantic definites), while others rely on the establishment of a relation with prior information, which results in processing cost
Partial survival and inelastic collapse for a randomly accelerated particle
We present an exact derivation of the survival probability of a randomly
accelerated particle subject to partial absorption at the origin. We determine
the persistence exponent and the amplitude associated to the decay of the
survival probability at large times. For the problem of inelastic reflection at
the origin, with coefficient of restitution , we give a new derivation of
the condition for inelastic collapse, , and determine
the persistence exponent exactly.Comment: 6 page
A nonperturbative Real-Space Renormalization Group scheme
Based on the original idea of the density matrix renormalization group
(DMRG), i.e. to include the missing boundary conditions between adjacent blocks
of the blocked quantum system, we present a rigorous and nonperturbative
mathematical formulation for the real-space renormalization group (RG) idea
invented by L.P. Kadanoff and further developed by K.G. Wilson. This is
achieved by using additional Hilbert spaces called auxiliary spaces in the
construction of each single isolated block, which is then named a superblock
according to the original nomenclature. On this superblock we define two maps
called embedding and truncation for successively integrating out the small
scale structure. Our method overcomes the known difficulties of the numerical
DMRG, i.e. limitation to zero temperature and one space dimension.Comment: 13 pages, 5 figures, late
Cable compliance
The object of the investigation was to solve mechanical problems using cable-in-bending and cable-in-torsion. These problems included robotic contacts, targets, and controls using cable compliance. Studies continued in the use of cable compliance for the handicapped and the elderly. These included work stations, walkers, prosthetic knee joints, elbow joints, and wrist joints. More than half of these objects were met, and models were made and studies completed on most of the others. It was concluded that the many different and versatile solutions obtained only opened the door to many future challenges
Biomass partitioning and gas exchange parameters in different Musa cultivars as influenced by natural shade
Poster presented at Tropentag 2011 Development on the Margin. Bonn (Germany), 3-7 Oct 2011
A Note on Wetting Transition for Gradient Fields
We prove existence of a wetting transition for two types of gradient fields:
1) Continuous SOS models in any dimension and 2) Massless Gaussian model in two
dimensions. Combined with a recent result showing the absence of such a
transition for Gaussian models above two dimensions by Bolthausen et al, this
shows in particular that absolute-value and quadratic interactions can give
rise to completely different behaviors.Comment: 6 pages, latex2
Photosynthesis of three dessert banana cultivars along an altitudinal gradient
Poster presented at Tropentag 2011 - Development on the Margin. Bonn (Germany), 3-7 Oct 2011
Absolute Luminosity from Machine Parameters
The expected rates for proton proton collisions in the LHC are rather high. Monitoring can be based on several detector components and different physics channels can be used together and should allow for a good accuracy in the relative luminosity determination. The accuracy in the absolute luminosity determination may soon be limited by the uncertainty in the knowledge of the proton proton cross section at the LHC energy. Here we discuss the possibility to determine the absolute luminosity in the LHC from machine parameters, which does not require the knowledge of particle cross sections
Simulation of a semiflexible polymer in a narrow cylindrical pore
The probability that a randomly accelerated particle in two dimensions has
not yet left a simply connected domain after a time decays as
for long times. The same quantity also determines the
confinement free energy per unit length of a
semiflexible polymer in a narrow cylindrical pore with cross section . From simulations of a randomly accelerated particle we estimate the
universal amplitude of for both circular and rectangular cross
sections.Comment: 10 pages, 2 eps figure
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