4,478 research outputs found
Dynamic Modeling and Simulation of a Real World Billiard
Gravitational billiards provide an experimentally accessible arena for
testing formulations of nonlinear dynamics. We present a mathematical model
that captures the essential dynamics required for describing the motion of a
realistic billiard for arbitrary boundaries. Simulations of the model are
applied to parabolic, wedge and hyperbolic billiards that are driven
sinusoidally. Direct comparisons are made between the model's predictions and
previously published experimental data. It is shown that the data can be
successfully modeled with a simple set of parameters without an assumption of
exotic energy dependence.Comment: 10 pages, 3 figure
General-Relativistic Curvature of Pulsar Vortex Structure
The motion of a neutron superfluid condensate in a pulsar is studied. Several
theorems of general-relativistic hydrodynamics are proved for a superfluid. The
average density distribution of vortex lines in pulsars and their
general-relativistic curvature are derived.Comment: 18 pages, 1 figure
Requirement for hsp70 in the mitochondrial matrix for translocation and folding of precursor proteins
Temporal and dimensional effects in evolutionary graph theory
The spread in time of a mutation through a population is studied analytically
and computationally in fully-connected networks and on spatial lattices. The
time, t_*, for a favourable mutation to dominate scales with population size N
as N^{(D+1)/D} in D-dimensional hypercubic lattices and as N ln N in
fully-connected graphs. It is shown that the surface of the interface between
mutants and non-mutants is crucial in predicting the dynamics of the system.
Network topology has a significant effect on the equilibrium fitness of a
simple population model incorporating multiple mutations and sexual
reproduction. Includes supplementary information.Comment: 6 pages, 4 figures Replaced after final round of peer revie
On a Conjecture of Rapoport and Zink
In their book Rapoport and Zink constructed rigid analytic period spaces
for Fontaine's filtered isocrystals, and period morphisms from PEL
moduli spaces of -divisible groups to some of these period spaces. They
conjectured the existence of an \'etale bijective morphism of
rigid analytic spaces and of a universal local system of -vector spaces on
. For Hodge-Tate weights and we construct in this article an
intrinsic Berkovich open subspace of and the universal local
system on . We conjecture that the rigid-analytic space associated with
is the maximal possible , and that is connected. We give
evidence for these conjectures and we show that for those period spaces
possessing PEL period morphisms, equals the image of the period morphism.
Then our local system is the rational Tate module of the universal
-divisible group and enjoys additional functoriality properties. We show
that only in exceptional cases equals all of and when the
Shimura group is we determine all these cases.Comment: v2: 48 pages; many new results added, v3: final version that will
appear in Inventiones Mathematica
EHL traction analysis of perfluoropolyether fluids based on bulk modulus
Using three kinds of commercial perfluoropolyether (PFPE) fluids, the authors carried out high pressure density test at the pressure up to 1.2 GPa. Tangent bulk modulus and secant bulk modulus of the PFPE fluids were calculated by using the test results. Relationships of these moduli with pressure and temperature were examined. High pressure viscosity of each PFPE fluid was measured and the pressure viscosity coefficients of the PFPE fluids were obtained. In addition, the maximum traction coefficient and the limiting shear stress of each fluid were evaluated from the traction test employing a ball-on-disk testing machine. As a result, it was found that the maximum traction coefficient and the limiting shear stress are closely related to the tangent bulk modulus and the secant bulk modulus, respectively. The significant relationship of the maximum traction coefficient with the molecular packing parameter represented by the product of the pressure viscosity coefficient and the mean Hertzian pressure was also confirmed
Structural Plasticity and Noncovalent Substrate Binding in the GroEL Apical Domain. A study using electrospray ionization mass spectrometry and fluorescence binding studies
Advances in understanding how GroEL binds to non-native proteins are reported. Conformational flexibility in the GroEL apical domain, which could account for the variety of substrates that GroEL binds, is illustrated by comparison of several independent crystallographic structures of apical domain constructs that show conformational plasticity in helices H and I. Additionally, ESI-MS indicates that apical domain constructs have co-populated conformations at neutral pH. To assess the ability of different apical domain conformers to bind co-chaperone and substrate, model peptides corresponding to the mobile loop of GroES and to helix D from rhodanese were studied. Analysis of apical domain-peptide complexes by ESI-MS indicates that only the folded or partially folded apical domain conformations form complexes that survive gas phase conditions. Fluorescence binding studies show that the apical domain can fully bind both peptides independently. No competition for binding was observed, suggesting the peptides have distinct apical domain-binding sites. Blocking the GroES-apical domain-binding site in GroEL rendered the chaperonin inactive in binding GroES and in assisting the folding of denatured rhodanese, but still capable of binding non-native proteins, supporting the conclusion that GroES and substrate proteins have, at least partially, distinct binding sites even in the intact GroEL tetradecamer
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