1,829 research outputs found
Supersymmetry solution for finitely extensible dumbbell model
Exact relaxation times and eigenfunctions for a simple mechanical model of
polymer dynamics are obtained using supersymmetry methods of quantum mechanics.
The model includes the finite extensibility of the molecule and does not make
use of the self-consistently averaging approximation. The finite extensibility
reduces the relaxation times when compared to a linear force. The linear
viscoelastic behaviour is obtained in the form of the ``generalized Maxwell
model''. Using these results, a numerical integration scheme is proposed in the
presence of a given flow kinematics.Comment: 5 pages, 2 figure
Generalized Supersymmetric Perturbation Theory
Using the basic ingredient of supersymmetry, we develop a simple alternative
approach to perturbation theory in one-dimensional non-relativistic quantum
mechanics. The formulae for the energy shifts and wave functions do not involve
tedious calculations which appear in the available perturbation theories. The
model applicable in the same form to both the ground state and excited bound
states, unlike the recently introduced supersymmetric perturbation technique
which, together with other approaches based on logarithmic perturbation theory,
are involved within the more general framework of the present formalism.Comment: 13 pages article in LaTEX (uses standard article.sty). No Figures.
Sent to Ann. Physics (2004
Are N=1 and N=2 supersymmetric quantum mechanics equivalent?
After recalling different formulations of the definition of supersymmetric
quantum mechanics given in the literature, we discuss the relationships between
them in order to provide an answer to the question raised in the title.Comment: 15 page
FBA-SimVis: interactive visualization of constraint-based metabolic models
Summary: FBA-SimVis is a VANTED plug-in for the constraint-based analysis of metabolic models with special focus on the visual exploration of metabolic flux data resulting from model analysis. The program provides a user-friendly environment for model reconstruction, constraint-based model analysis, and interactive visualization of the simulation results. With the ability to quantitatively analyse metabolic fluxes in an interactive and visual manner, FBA-SimVis supports a comprehensive understanding of constraint-based metabolic flux models in both overview and detail
MetaCrop 2.0: managing and exploring information about crop plant metabolism
MetaCrop is a manually curated repository of high-quality data about plant metabolism, providing different levels of detail from overview maps of primary metabolism to kinetic data of enzymes. It contains information about seven major crop plants with high agronomical importance and two model plants. MetaCrop is intended to support research aimed at the improvement of crops for both nutrition and industrial use. It can be accessed via web, web services and an add-on to the Vanted software. Here, we present several novel developments of the MetaCrop system and the extended database content. MetaCrop is now available in version 2.0 at http://metacrop.ipk-gatersleben.de
Feasibility of an in situ measurement device for bubble size and distribution
The feasibility of in situ measurement device for bubble size and distribution was explored. A novel in situ probe measurement system, the EnviroCamâą, was developed. Where possible, this probe incorporated strengths, and minimized weaknesses of historical and currently available real-time measurement methods for bubbles. The system was based on a digital, high-speed, high resolution, modular camera system, attached to a stainless steel shroud, compatible with standard Ingold ports on fermenters. Still frames and/or video were produced, capturing bubbles passing through the notch of the shroud. An LED light source was integral with the shroud. Bubbles were analyzed using customized commercially available image analysis software and standard statistical methods. Using this system, bubble sizes were measured as a function of various operating parameters (e.g., agitation rate, aeration rate) and as a function of media properties (e.g., viscosity, antifoam, cottonseed flour, and microbial/animal cell broths) to demonstrate system performance and its limitations. For selected conditions, mean bubble size changes qualitatively compared favorably with published relationships. Current instrument measurement capabilities were limited primarily to clear solutions that did not contain large numbers of overlapping bubbles
Quantum metastability in a class of moving potentials
In this paper we consider quantum metastability in a class of moving
potentials introduced by Berry and Klein. Potential in this class has its
height and width scaled in a specific way so that it can be transformed into a
stationary one. In deriving the non-decay probability of the system, we argue
that the appropriate technique to use is the less known method of scattering
states. This method is illustrated through two examples, namely, a moving
delta-potential and a moving barrier potential. For expanding potentials, one
finds that a small but finite non-decay probability persists at large times.
Generalization to scaling potentials of arbitrary shape is briefly indicated.Comment: 10 pages, 1 figure
Double Neutron Star Systems and Natal Neutron Star Kicks
We study the four double neutron star systems found in the Galactic disk in
terms of the orbital characteristics of their immediate progenitors and the
natal kicks imparted to neutron stars. Analysis of the effect of the second
supernova explosion on the orbital dynamics, combined with recent results from
simulations of rapid accretion onto neutron stars lead us to conclude that the
observed systems could not have been formed had the explosion been symmetric.
Their formation becomes possible if kicks are imparted to the radio-pulsar
companions at birth. We identify the constraints imposed on the immediate
progenitors of the observed double neutron stars and calculate the ranges
within which their binary characteristics (orbital separations and masses of
the exploding stars) are restricted. We also study the dependence of these
limits on the magnitude of the kick velocity and the time elapsed since the
second explosion. For each of the double neutron stars, we derive a minimum
kick magnitude required for their formation, and for the two systems in close
orbits we find it to exceed 200km/s. Lower limits are also set to the
center-of-mass velocities of double neutron stars, and we find them to be
consistent with the current proper motion observations.Comment: 25 pages, 6 figs (9 parts), 4 tables, AASTeX, Accepted in Ap
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