9,914 research outputs found
Ideal Linear Chain Polymers with Fixed Angular Momentum
The statistical mechanics of a linear non-interacting polymer chain with a
large number of monomers is considered with fixed angular momentum. The radius
of gyration for a linear polymer is derived exactly by functional integration.
This result is then compared to simulations done with a large number of
non-interacting rigid links at fixed angular momentum. The simulation agrees
with the theory up to finite size corrections. The simulations are also used to
investigate the anisotropic nature of a spinning polymer. We find universal
scaling of the polymer size along the direction of the angular momentum, as a
function of rescaled angular momentum.Comment: 7 pages, 3 figure
Management and Service-aware Networking Architectures (MANA) for Future Internet Position Paper: System Functions, Capabilities and Requirements
Future Internet (FI) research and development threads have recently been gaining momentum all over the world and as such the international race to create a new generation Internet is in full swing: GENI, Asia Future Internet, Future Internet Forum Korea, European Union Future Internet Assembly (FIA). This is a position paper identifying the research orientation with a time horizon of 10 years, together with the key challenges for the capabilities in the Management and Service-aware Networking Architectures (MANA) part of the Future Internet (FI) allowing for parallel and federated Internet(s)
The Numerical Solution of Two-Dimensional Volterra Integral Equations by Collocation and Iterated Collocation
While the numerical solution of one-dimensional Volterra integral equations of the second kind with regular kernels is now well understood there exist no systematic studies of the approximate solution of their two-dimensional counterparts. In the present paper we analyse the numerical solution of such equations by methods based on collocation and iterated collocation techniques in certain polynomial spline spaces. The analysis focuses on the global convergence and local superconvergence properties of the approximating spline function
End-stage renal failure due to analgesic nephropathy, its changing pattern and cardiovascular mortality
The changing pattern of prevalence and age distribution of analgesic nephropathy as a cause of end-stage renal failure (ESRF) in patients on RRT was analysed using the EDTA-ERA Registry's files. Comparing 1990 to 1981, the percentage of patients with analgesic nephropathy decreased in many European countries and the Registry's average came down from 3 to 2%. The highest prevalence was noted for Switzerland, which showed a decrease from 28 in 1981 to 12% in 1990. During the same interval the age distribution shifted to the right with an increase in median age from 57 to 63 at start of RRT for analgesic nephropathy. In Switzerland the age-specific acceptance rate to RRT for patients with analgesic nephropathy decreased to less than 1/3 in the age cohorts below 55 but increased in those aged 65 or older. This increase in the elderly cohorts appeared to be related to the growing acceptance rate to RRT of elderly patients in general rather than to an increasing incidence of ESRF due to analgesic nephropathy. Mortality in general and death rates due to cardiovascular causes were found not to differ in RRT patients with analgesic nephropathy from that of other standard primary renal diseases (excluding diabetic nephropathy and systemic diseases). Some 20 years after withdrawal of phenacetin from the analgesic market, analgesic nephropathy all but disappeared as a cause of ESRF in Sweden and Denmark, and the same may be expected to occur in countries like Switzerland, Belgium, and others in the not too far distant futur
Tensor Product and Permutation Branes on the Torus
We consider B-type D-branes in the Gepner model consisting of two minimal
models at k=2. This Gepner model is mirror to a torus theory. We establish the
dictionary identifying the B-type D-branes of the Gepner model with A-type
Neumann and Dirichlet branes on the torus.Comment: 26 page
Description of non-specific DNA-protein interaction and facilitated diffusion with a dynamical model
We propose a dynamical model for non-specific DNA-protein interaction, which
is based on the 'bead-spring' model previously developed by other groups, and
investigate its properties using Brownian Dynamics simulations. We show that
the model successfully reproduces some of the observed properties of real
systems and predictions of kinetic models. For example, sampling of the DNA
sequence by the protein proceeds via a succession of 3d motion in the solvent,
1d sliding along the sequence, short hops between neighboring sites, and
intersegmental transfers. Moreover, facilitated diffusion takes place in a
certain range of values of the protein effective charge, that is, the
combination of 1d sliding and 3d motion leads to faster DNA sampling than pure
3d motion. At last, the number of base pairs visited during a sliding event is
comparable to the values deduced from single-molecule experiments. We also
point out and discuss some discrepancies between the predictions of this model
and some recent experimental results as well as some hypotheses and predictions
of kinetic models
D-brane superpotentials and RG flows on the quintic
The behaviour of D2-branes on the quintic under complex structure
deformations is analysed by combining Landau-Ginzburg techniques with methods
from conformal field theory. It is shown that the boundary renormalisation
group flow induced by the bulk deformations is realised as a gradient flow of
the effective space time superpotential which is calculated explicitly to all
orders in the boundary coupling constant.Comment: 24 pages, 1 figure, v2:Typo in (3.14) correcte
Moduli Webs and Superpotentials for Five-Branes
We investigate the one-parameter Calabi-Yau models and identify families of
D5-branes which are associated to lines embedded in these manifolds. The moduli
spaces are given by sets of Riemann curves, which form a web whose intersection
points are described by permutation branes. We arrive at a geometric
interpretation for bulk-boundary correlators as holomorphic differentials on
the moduli space and use this to compute effective open-closed superpotentials
to all orders in the open string couplings. The fixed points of D5-brane moduli
under bulk deformations are determined.Comment: 41 pages, 1 figur
Defect Perturbations in Landau-Ginzburg Models
Perturbations of B-type defects in Landau-Ginzburg models are considered. In
particular, the effect of perturbations of defects on their fusion is analyzed
in the framework of matrix factorizations. As an application, it is discussed
how fusion with perturbed defects induces perturbations on boundary conditions.
It is shown that in some classes of models all boundary perturbations can be
obtained in this way. Moreover, a universal class of perturbed defects is
constructed, whose fusion under certain conditions obey braid relations. The
functors obtained by fusing these defects with boundary conditions are twist
functors as introduced in the work of Seidel and Thomas.Comment: 46 page
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