1,979 research outputs found
Protein-mediated DNA Loop Formation and Breakdown in a Fluctuating Environment
Living cells provide a fluctuating, out-of-equilibrium environment in which
genes must coordinate cellular function. DNA looping, which is a common means
of regulating transcription, is very much a stochastic process; the loops arise
from the thermal motion of the DNA and other fluctuations of the cellular
environment. We present single-molecule measurements of DNA loop formation and
breakdown when an artificial fluctuating force, applied to mimic a fluctuating
cellular environment, is imposed on the DNA. We show that loop formation is
greatly enhanced in the presence of noise of only a fraction of , yet
find that hypothetical regulatory schemes that employ mechanical tension in the
DNA--as a sensitive switch to control transcription--can be surprisingly robust
due to a fortuitous cancellation of noise effects
Urban-rural comparison of adult day care centres in British Columbia
In 1979, Adult Day Care became a part of the B.C. Ministry of Health\u27s Continuing Care Program. By 1989, there were 49 centres in operation in the province and it was felt timely to undertake a comprehensive review of the Adult Day Care component of the Continuing Care Program. As part of that review and as an aid for future planning, the Simon Fraser University Gerontology Research Centre was commissioned to conduct a study that would provide information concerning: 1. activities and services provided by the 49 centres; 2. characteristics of the clients currently being served; 3. reasons clients are referred to Adult Day Care; 4. reasons some referred clients do not attend; and 5. the referral process and the interface between the Long Term Care Program and Adult Day Care
Adult day care centres in British Columbia : their operating characteristics, activities and services, clients, and interface with the long term care program. Final report.
Previews the literature concerning the objectives, models of service delivery, operating characteristics, activities, services and clients of Adult Day Care (ADC) Centres. Presents findings from a 3-phase study conducted in British Columbia. In phase 1, a 100% sample of B.C. ADCs provided information on their operating characteristics, activities and services. In phase 2, the characteristics of 479 new admissions to 22 ADCs were determined. Phase 3 focused on reasons for referring clients to ADC, why some referred clients do not attend and on the interface between ADCs and the province\u27s Continuing Care Program
Feshbach resonances and collapsing Bose-Einstein condensates
We investigate the quantum state of burst atoms seen in the recent Rb-85
experiments at JILA. We show that the presence of a resonance scattering state
can lead to a pairing instability generating an outflow of atoms with energy
comparable to that observed. A resonance effective field theory is used to
study this dynamical process in an inhomogeneous system with spherical
symmetry
Virtual light-by-light scattering and the g factor of a bound electron
The contribution of the light-by-light diagram to the g factor of electron
and muon bound in Coulomb field is obtained. For electron in a ground state,
our results are in good agreement with the results of other authors obtained
numerically for large Z. For relatively small Z our results have essentially
higher accuracy as compared to the previous ones. For muonic atoms, the
contribution is obtained for the first time with the high accuracy in whole
region of Z.Comment: 10 pages, 3 figures, RevTe
Superfluidity and binary-correlations within clusters of fermions
We propose a method for simulating the behaviour of small clusters of
particles that explicitly accounts for all mean-field and binary-correlation
effects. Our approach leads to a set of variational equations that can be used
to study both the dynamics and thermodynamics of these clusters. As an
illustration of this method, we explore the BCS-BEC crossover in the simple
model of four fermions, interacting with finite-range potentials, in a harmonic
potential. We find, in the crossover regime, that the particles prefer to
occupy two distinct pair states as opposed to the one assumed by BCS theory
Strained tetragonal states and Bain paths in metals
Paths of tetragonal states between two phases of a material, such as bcc and
fcc, are called Bain paths. Two simple Bain paths can be defined in terms of
special imposed stresses, one of which applies directly to strained epitaxial
films. Each path goes far into the range of nonlinear elasticity and reaches a
range of structural parameters in which the structure is inherently unstable.
In this paper we identify and analyze the general properties of these paths by
density functional theory. Special examples include vanadium, cobalt and
copper, and the epitaxial path is used to identify an epitaxial film as related
uniquely to a bulk phase.Comment: RevTeX, 4 pages, 4 figures, submitted to Phys. Rev. Let
Finite nuclear size and Lamb shift of p-wave atomic states
We consider corrections to the Lamb shift of p-wave atomic states due to the
finite nuclear size (FNS). In other words, these are radiative corrections to
the atomic isotop shift related to FNS. It is shown that the structure of the
corrections is qualitatively different from that for s-wave states. The
perturbation theory expansion for the relative correction for a -state
starts from -term, while for -states it starts
from term. Here is the fine structure constant and is
the nuclear charge. In the present work we calculate the -terms for
-states, the result for -state reads
. Even more interesting are
-states. In this case the ``correction'' is by several orders of
magnitude larger than the ``leading'' FNS shift.Comment: 4 pages, 2 figure
Bose-Einstein Condensation from a Rotating Thermal Cloud: Vortex Nucleation and Lattice Formation
We develop a stochastic Gross-Pitaveskii theory suitable for the study of
Bose-Einstein condensation in a {\em rotating} dilute Bose gas. The theory is
used to model the dynamical and equilibrium properties of a rapidly rotating
Bose gas quenched through the critical point for condensation, as in the
experiment of Haljan et al. [Phys. Rev. Lett., 87, 21043 (2001)]. In contrast
to stirring a vortex-free condensate, where topological constraints require
that vortices enter from the edge of the condensate, we find that phase defects
in the initial non-condensed cloud are trapped en masse in the emerging
condensate. Bose-stimulated condensate growth proceeds into a disordered vortex
configuration. At sufficiently low temperature the vortices then order into a
regular Abrikosov lattice in thermal equilibrium with the rotating cloud. We
calculate the effect of thermal fluctuations on vortex ordering in the final
gas at different temperatures, and find that the BEC transition is accompanied
by lattice melting associated with diminishing long range correlations between
vortices across the system.Comment: 15 pages, 12 figure
Dynamical formation and interaction of bright solitary waves and solitons in the collapse of Bose-Einstein condensates with attractive interactions
We model the dynamics of formation of multiple, long-lived, bright solitary
waves in the collapse of Bose-Einstein condensates with attractive interactions
as studied in the experiment of Cornish et al. [Phys. Rev. Lett. 96 (2006)
170401]. Using both mean-field and quantum field simulation techniques, we find
that while a number of separated wave packets form as observed in the
experiment, they do not have a repulsive \pi phase difference that has been
previously inferred. We observe that the inclusion of quantum fluctuations
causes soliton dynamics to be predominantly repulsive in one dimensional
simulations independent of their initial relative phase. However, indicative
three-dimensional simulations do not support this conclusion and in fact show
that quantum noise has a negative impact on bright solitary wave lifetimes.
Finally, we show that condensate oscillations, after the collapse, may serve to
deduce three-body recombination rates, and that the remnant atom number may
still exceed the critical number for collapse for as long as three seconds
independent of the relative phases of the bright solitary waves.Comment: 14 pages, 5 figure
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