8,552 research outputs found
Study of heat sensitive radioisotopes for temperature measurement application Final report
Heat sensitive radioisotopes for temperature measurements in rocket nose cone
Ion collection by oblique surfaces of an object in a transversely-flowing strongly-magnetized plasma
The equations governing a collisionless obliquely-flowing plasma around an
ion-absorbing object in a strong magnetic field are shown to have an exact
analytic solution even for arbitrary (two-dimensional) object-shape, when
temperature is uniform, and diffusive transport can be ignored. The solution
has an extremely simple geometric embodiment. It shows that the ion collection
flux density to a convex body's surface depends only upon the orientation of
the surface, and provides the theoretical justification and calibration of
oblique `Mach-probes'. The exponential form of this exact solution helps
explain the approximate fit of this function to previous numerical solutions.Comment: Four pages, 2 figures. Submitted to Phys. Rev. Letter
Gapless finite- theory of collective modes of a trapped gas
We present predictions for the frequencies of collective modes of trapped
Bose-condensed Rb atoms at finite temperature. Our treatment includes a
self-consistent treatment of the mean-field from finite- excitations and the
anomolous average. This is the first gapless calculation of this type for a
trapped Bose-Einstein condensed gas. The corrections quantitatively account for
the downward shift in the excitation frequencies observed in recent
experiments as the critical temperature is approached.Comment: 4 pages Latex and 2 postscript figure
Observation of magnetocoriolis waves in a liquid metal Taylor-Couette experiment
The first observation of fast and slow magnetocoriolis (MC) waves in a
laboratory experiment is reported. Rotating nonaxisymmetric modes arising from
a magnetized turbulent Taylor-Couette flow of liquid metal are identified as
the fast and slow MC waves by the dependence of the rotation frequency on the
applied field strength. The observed slow MC wave is damped but the observation
provides a means for predicting the onset of the Magnetorotational Instability
Electron Temperature of Ultracold Plasmas
We study the evolution of ultracold plasmas by measuring the electron
temperature. Shortly after plasma formation, competition between heating and
cooling mechanisms drives the electron temperature to a value within a narrow
range regardless of the initial energy imparted to the electrons. In agreement
with theory predictions, plasmas exhibit values of the Coulomb coupling
parameter less than 1.Comment: 4 pages, plus four figure
Geometric scaling in the spectrum of an electron captured by a stationary finite dipole
We examine the energy spectrum of a charged particle in the presence of a
{\it non-rotating} finite electric dipole. For {\emph{any}} value of the dipole
moment above a certain critical value p_{\mathrm{c}}$ an infinite series of
bound states arises of which the energy eigenvalues obey an Efimov-like
geometric scaling law with an accumulation point at zero energy. These
properties are largely destroyed in a realistic situation when rotations are
included. Nevertheless, our analysis of the idealised case is of interest
because it may possibly be realised using quantum dots as artificial atoms.Comment: 5 figures; references added, outlook section reduce
Bivariate -distribution for transition matrix elements in Breit-Wigner to Gaussian domains of interacting particle systems
Interacting many-particle systems with a mean-field one body part plus a
chaos generating random two-body interaction having strength , exhibit
Poisson to GOE and Breit-Wigner (BW) to Gaussian transitions in level
fluctuations and strength functions with transition points marked by
and , respectively; . For these systems theory for matrix elements of one-body transition
operators is available, as valid in the Gaussian domain, with , in terms of orbitals occupation numbers, level densities and an
integral involving a bivariate Gaussian in the initial and final energies. Here
we show that, using bivariate -distribution, the theory extends below from
the Gaussian regime to the BW regime up to . This is well
tested in numerical calculations for six spinless fermions in twelve single
particle states.Comment: 7 pages, 2 figure
The prevalence of cam hip morphology in a general population sample
Objective
Cam hip morphology is associated with femoroacetabular impingement (FAI) syndrome and causes hip osteoarthritis (OA). We aimed to assess the prevalence of cam hip morphology in a sample representative of the general population, using a measure with a predefined diagnostic accuracy.
Design
Patients aged 16–65, who were admitted to a major trauma centre and received a computed tomography (CT) pelvis were retrospectively screened for eligibility. Subjects with proximal femoral, acetabular or pelvic fractures and those who were deceased were excluded. Eligible subjects were divided into 10 groups based on gender and age. 20 subjects from each group were included. Subjects' index of multiple deprivation (IMD) and ethnicity were recorded. CT imaging was assessed and alpha angles (a measure of cam morphology) measured in the anterosuperior aspect of the femoral head neck junction. An alpha angle greater than 60° was considered to represent cam morphology. This measure and technique has a predefined sensitivity of 80% and specificity of 73% to detect cam morphology associated with FAI syndrome. The prevalence of cam morphology was reported as a proportion of subjects affected with 95% confidence intervals.
Results
200 subjects were included. The sample was broadly representative of the UK general population in terms of IMD. 155 subjects (86%) identified as white. Cam morphology was present in 47% (95% CI 42,51) of subjects.
Conclusions
In this sample, broadly representative of the UK general population 47% of subjects had cam hip morphology; a hip shape associated with FAI syndrome and OA
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