881 research outputs found
Rehabilitation following first-time patellar dislocation: a randomised controlled trial of purported vastus medialis obliquus muscle versus general quadriceps strengthening exercises.
Purpose: Define whether distal vastus medialis (VM) muscle strengthening improves functional outcomes compared to general quadriceps muscles strengthening following first-time patellar dislocation (FTPD). Methods: Fifty patients post-FTPD were randomised to either a general quadriceps exercise or rehabilitation programme (n=25) or to a specific-VM exercise and rehabilitation regime (n=25). Primary outcome was the Lysholm Knee Score, secondary outcomes included the Tegner Level of Activity Scale, the Norwich Patellar Instability (NPI) Score, and isometric knee extensions strength at various knee flexion ranges of motion. Outcomes were assessed at baseline, six weeks, six months and 12 months. Results: There were statistically significant differences in functional outcome and activity levels through the Lysholm Knee Score and Tegner Level of Activity Scale at 12 months in the general quadriceps exercise group compared to the VM group (p=0.05; 95% CI: -14.0 to 0.0/p=0.04; 95% CI: -3.0 to 0.0). This did not reach a clinically important difference. There was no statistically significant difference between the groups for the NPI Score and isometric strength at any follow-up interval. The trial experienced substantial participant attrition (52% at 12 months). Conclusions: Whilst there was a statistical difference in Lysholm Knee Score and Tegner Level of Activity Score between general quadriceps and VM exercise groups at 12 months, this may not have necessarily been clinically important. This trial highlights that the recruitment and retention of participants from this population is a challenge and should be considered during the design of future trials in this populatio
Bose-Einstein Condensation in a Harmonic Potential
We examine several features of Bose-Einstein condensation (BEC) in an
external harmonic potential well. In the thermodynamic limit, there is a phase
transition to a spatial Bose-Einstein condensed state for dimension D greater
than or equal to 2. The thermodynamic limit requires maintaining constant
average density by weakening the potential while increasing the particle number
N to infinity, while of course in real experiments the potential is fixed and N
stays finite. For such finite ideal harmonic systems we show that a BEC still
occurs, although without a true phase transition, below a certain
``pseudo-critical'' temperature, even for D=1. We study the momentum-space
condensate fraction and find that it vanishes as 1/N^(1/2) in any number of
dimensions in the thermodynamic limit. In D less than or equal to 2 the lack of
a momentum condensation is in accord with the Hohenberg theorem, but must be
reconciled with the existence of a spatial BEC in D=2. For finite systems we
derive the N-dependence of the spatial and momentum condensate fractions and
the transition temperatures, features that may be experimentally testable. We
show that the N-dependence of the 2D ideal-gas transition temperature for a
finite system cannot persist in the interacting case because it violates a
theorem due to Chester, Penrose, and Onsager.Comment: 34 pages, LaTeX, 6 Postscript figures, Submitted to Jour. Low Temp.
Phy
The Inhibition of Mixing in Chaotic Quantum Dynamics
We study the quantum chaotic dynamics of an initially well-localized wave
packet in a cosine potential perturbed by an external time-dependent force. For
our choice of initial condition and with small but finite, we find that
the wave packet behaves classically (meaning that the quantum behavior is
indistinguishable from that of the analogous classical system) as long as the
motion is confined to the interior of the remnant separatrix of the cosine
potential. Once the classical motion becomes unbounded, however, we find that
quantum interference effects dominate. This interference leads to a long-lived
accumulation of quantum amplitude on top of the cosine barrier. This pinning of
the amplitude on the barrier is a dynamic mechanism for the quantum inhibition
of classical mixing.Comment: 20 pages, RevTeX format with 6 Postscript figures appended in
uuencoded tar.Z forma
Shape and structure of N=Z 64Ge; Electromagnetic transition rates from the application of the Recoil Distance Method to knock-out reaction
Transition rate measurements are reported for the first and the second 2+
states in N=Z 64Ge. The experimental results are in excellent agreement with
large-scale Shell Model calculations applying the recently developed GXPF1A
interactions. Theoretical analysis suggests that 64Ge is a collective
gamma-soft anharmonic vibrator. The measurement was done using the Recoil
Distance Method (RDM) and a unique combination of state-of-the-art instruments
at the National Superconducting Cyclotron Laboratory (NSCL). States of interest
were populated via an intermediate-energy single-neutron knock-out reaction.
RDM studies of knock-out and fragmentation reaction products hold the promise
of reaching far from stability and providing lifetime information for excited
states in a wide range of nuclei
Phase separation in supersolids
We study quantum phase transitions in the ground state of the two dimensional
hard-core boson Hubbard Hamiltonian. Recent work on this and related models has
suggested ``supersolid'' phases with simultaneous diagonal and off-diagonal
long range order. We show numerically that, contrary to the generally held
belief, the most commonly discussed ``checkerboard'' supersolid is
thermodynamically unstable. Furthermore, this supersolid cannot be stabilized
by next near neighbour interaction. We obtain the correct phase diagram using
the Maxwell construction. We demonstrate the ``striped'' supersolid is
thermodynamically stable and is separated from the superfluid phase by a
continuous phase transition.Comment: 4 pages, 4 eps figures, include
Recommended from our members
DARTAB: a program to combine airborne radionuclide environmental exposure data with dosimetric and health effects data to generate tabulations of predicted health impacts
The DARTAB computer code combines radionuclide environmental exposure data with dosimetric and health effects data to generate tabulations of the predicted impact of radioactive airborne effluents. DARTAB is independent of the environmental transport code used to generate the environmental exposure data and the codes used to produce the dosimetric and health effects data. Therefore human dose and risk calculations need not be added to every environmental transport code. Options are included in DARTAB to permit the user to request tabulations by various topics (e.g., cancer site, exposure pathway, etc.) to facilitate characterization of the human health impacts of the effluents. The DARTAB code was written at ORNL for the US Environmental Protection Agency, Office of Radiation Programs
Optimizing thermal transport in the Falicov-Kimball model: binary-alloy picture
We analyze the thermal transport properties of the Falicov-Kimball model
concentrating on locating regions of parameter space where the thermoelectric
figure-of-merit ZT is large. We focus on high temperature for power generation
applications and low temperature for cooling applications. We constrain the
static particles (ions) to have a fixed concentration, and vary the conduction
electron concentration as in the binary-alloy picture of the Falicov-Kimball
model. We find a large region of parameter space with ZT>1 at high temperature
and we find a small region of parameter space with ZT>1 at low temperature for
correlated systems, but we believe inclusion of the lattice thermal
conductivity will greatly reduce the low-temperature figure-of-merit.Comment: 13 pages, 14 figures, typeset with ReVTe
Examination of a blood-brain barrier targeting β-galactosidase-monoclonal antibody fusion protein in a murine model of GM1-gangliosidosis
GM1-gangliosidosis is a lysosomal disease resulting from a deficiency in the hydrolase β-galactosidase (β-gal) and subsequent accumulation of gangliosides, primarily in neuronal tissue, leading to progressive neurological deterioration and eventually early death. Lysosomal diseases with neurological involvement have limited non-invasive therapies due to the inability of lysosomal enzymes to cross the blood-brain barrier (BBB). A novel fusion enzyme, labeled mTfR-GLB1, was designed to act as a ferry across the BBB by fusing β-gal to the mouse monoclonal antibody against the mouse transferrin receptor and tested in a murine model of GM1-gangliosidosis (β-ga
Collective excitations of a two-dimensional interacting Bose gas in anti-trap and linear external potentials
We present a method of finding approximate analytical solutions for the
spectra and eigenvectors of collective modes in a two-dimensional system of
interacting bosons subjected to a linear external potential or the potential of
a special form , where is the chemical
potential. The eigenvalue problem is solved analytically for an artificial
model allowing the unbounded density of the particles. The spectra of
collective modes are calculated numerically for the stripe, the rare density
valley and the edge geometry and compared with the analytical results. It is
shown that the energies of the modes localized at the rare density region and
at the edge are well approximated by the analytical expressions. We discuss
Bose-Einstein condensation (BEC) in the systems under investigations at and find that in case of a finite number of the particles the regime of BEC
can be realized, whereas the condensate disappears in the thermodynamic limit.Comment: 10 pages, 2 figures include
Condensation Energy and Spectral Functions in High Temperature Superconductors
If high temperature cuprate superconductivity is due to electronic
correlations, then the energy difference between the normal and superconducting
states can be expressed in terms of the occupied part of the single particle
spectral function. The latter can, in principle, be determined from angle
resolved photoemission (ARPES) data. As a consequence, the energy gain driving
the development of the superconducting state is intimately related to the
dramatic changes in the photoemission lineshape when going below Tc. These
points are illustrated in the context of the "mode" model used to fit ARPES
data in the normal and superconducting states, where the question of kinetic
energy versus potential energy driven superconductivity is explored in detail.
We use our findings to comment on the relation of ARPES data to the
condensation energy, and to various other experimental data. In particular, our
results suggest that the nature of the superconducting transition is strongly
related to how anomalous (non Fermi liquid like) the normal state spectral
function is, and as such, is dependent upon the doping level.Comment: 10 pages, revtex, 4 encapsulated postscript figure
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