880 research outputs found
Effects of testosterone treatment on bone mineral density in hypogonadal men receiving intrathecal opioids
Background
Opioid induced depression of sex hormones is a common finding in chronic pain patients receiving long-term opioids by oral, parenteral and even intrathecal routes of administration. The hypothalamic suppression by opioids leads to a hypogonadal state with low testosterone levels in males and subsequent low bone mineral density (BMD).
Methods
We have studied the effects of intrathecally administered opioids on BMD in a group of male chronic pain patients. In addition, we have studied the effects of supplementary testosterone on bone metabolism to see if the adverse effects of intrathecal opioids can be reversed.
Results
Eleven of the 27 patients were on supplementary testosterone having previously been diagnosed as hypogonadal with low serum testosterone. Duration of testosterone supplementation was greater than 2 years in all 11 patients. Both serum total and free testosterone levels were higher in patients on supplementary testosterone than in patients who did not receive this treatment. Of the 16 patients not on testosterone supplement, 14 (87%) had low serum testosterone levels (<10 nmol/L) and 11 (69%) had low or osteoporotic T scores. Within this group, low free testosterone was associated with low BMD scores, and this persisted after correcting for age. Eight of the patients on testosterone supplement had normal BMDT scores and three (27%) had low or osteoporotic T scores. T and age-corrected BMDZ scores were significantly greater in the 11 patients on testosterone supplements than BMD scores in the other 16 patients.
Conclusion
Testosterone supplementation was found to largely correct the effects of intrathecal opioids on testosterone levels and BMD
Layer dynamics of a freely standing smectic-A film
We study the hydrodynamics of a freely-standing smectic-A film in the
isothermal, incompressible limit theoretically by analyzing the linearized
hydrodynamic equations of motion with proper boundary conditions. The dynamic
properties for the system can be obtained from the response functions for the
free surfaces. Permeation is included and its importance near the free surfaces
is discussed. The hydrodynamic mode structure for the dynamics of the system is
compared with that of bulk systems. We show that to describe the dynamic
correlation functions for the system, in general, it is necessary to consider
the smectic layer displacement and the velocity normal to the layers,
, together. Finally, our analysis also provides a basis for the
theoretical study of the off-equilibrium dynamics of freely-standing smectic-A
films.Comment: 22 pages, 4 figure
Plasma Wave Properties of the Schwarzschild Magnetosphere in a Veselago Medium
We re-formulate the 3+1 GRMHD equations for the Schwarzschild black hole in a
Veselago medium. Linear perturbation in rotating (non-magnetized and
magnetized) plasma is introduced and their Fourier analysis is considered. We
discuss wave properties with the help of wave vector, refractive index and
change in refractive index in the form of graphs. It is concluded that some
waves move away from the event horizon in this unusual medium. We conclude that
for the rotating non-magnetized plasma, our results confirm the presence of
Veselago medium while the rotating magnetized plasma does not provide any
evidence for this medium.Comment: 20 pages, 15 figures, accepted for publication in Astrophys. Space
Sc
Exchange-correlation vector potentials and vorticity-dependent exchange-correlation energy densities in two-dimensional systems
We present a new approach how to calculate the scalar exchange-correlation
potentials and the vector exchange-correlation potentials from current-carrying
ground states of two-dimensional quantum dots. From these exchange-correlation
potentials we derive exchange-correlation energy densities and examine their
vorticity (or current) dependence. Compared with parameterizations of
current-induced effects in literature we find an increased significance of
corrections due to paramagnetic current densities.Comment: 5 figures, submitted to PR
Wave Propagation in Gravitational Systems: Late Time Behavior
It is well-known that the dominant late time behavior of waves propagating on
a Schwarzschild spacetime is a power-law tail; tails for other spacetimes have
also been studied. This paper presents a systematic treatment of the tail
phenomenon for a broad class of models via a Green's function formalism and
establishes the following. (i) The tail is governed by a cut of the frequency
Green's function along the ~Im~ axis,
generalizing the Schwarzschild result. (ii) The dependence of the cut
is determined by the asymptotic but not the local structure of space. In
particular it is independent of the presence of a horizon, and has the same
form for the case of a star as well. (iii) Depending on the spatial
asymptotics, the late time decay is not necessarily a power law in time. The
Schwarzschild case with a power-law tail is exceptional among the class of the
potentials having a logarithmic spatial dependence. (iv) Both the amplitude and
the time dependence of the tail for a broad class of models are obtained
analytically. (v) The analytical results are in perfect agreement with
numerical calculations
Wigner Crystalization in the Lowest Landau Level for
By means of exact diagonalization we study the low-energy states of seven
electrons in the lowest Landau level which are confined by a cylindric external
potential modelling the rest of a macroscopic system and thus controlling the
filling factor . Wigner crystal is found to be the ground state for
filling factors between and provided electrons
interact via the bare Coulomb potential. Even at the solid state has
lower energy than the Laughlin's one, although the two energies are rather
close. We also discuss the role of pseudopotential parameters in the lowest
Landau level and demonstrate that the earlier reported gapless state, appearing
when the short-range part of the interaction is suppressed, has nothing in
common with the Wigner crystalization in pure Coulomb case.Comment: 9 pages, LaTex, 8 figure
Magnetic field dependence of the exciton energy in a quantum disk
The groundstate energy and binding energy of an exciton, confined in a^M
quantum disk, are calculated as a function of an external magnetic field. The
confinement potential is a hard wall of finite height. The diamagnetic shift is
investigated for magnetic fields up to 40. Our results are applied to
self-assembled quantum dots and very good
agreement with experiments is obtained. Furthermore, we investigated the
influence of the dot size on the diamagnetic shift by changing the disk radius.
The exciton excited states are found as a function of the magnetic field. The
relative angular momentum is not a quantum number and changes with the magnetic
field strength.Comment: 10 pages, 17 figure
Isothermal Plasma Wave Properties of the Schwarzschild de-Sitter Black Hole in a Veselago Medium
In this paper, we study wave properties of isothermal plasma for the
Schwarzschild de-Sitter black hole in a Veselago medium. We use ADM 3+1
formalism to formulate general relativistic magnetohydrodynamical (GRMHD)
equations for the Schwarzschild de-Sitter spacetime in Rindler coordinates.
Further, Fourier analysis of the linearly perturbed GRMHD equations for the
rotating (non-magnetized and magnetized) background is taken whose determinant
leads to a dispersion relation. We investigate wave properties by using
graphical representation of the wave vector, the refractive index, change in
refractive index, phase and group velocities. Also, the modes of wave
dispersion are explored. The results indicate the existence of the Veselago
medium.Comment: 24 pages, 12 figures, accepted for publication in Astrophys. Space
Sci. arXiv admin note: text overlap with arXiv:1101.0884 and arxiv:1007.285
CMOS Active Pixel Sensors as energy-range detectors for proton Computed Tomography
Since the first proof of concept in the early 70s, a number of technologies has been proposed to perform proton CT (pCT), as a means of mapping tissue stopping power for accurate treatment planning in proton therapy. Previous prototypes of energy-range detectors for pCT have been mainly based on the use of scintillator-based calorimeters, to measure proton residual energy after passing through the patient. However, such an approach is limited by the need for only a single proton passing through the energy-range detector in a read-out cycle. A novel approach to this problem could be the use of pixelated detectors, where the independent read-out of each pixel allows to measure simultaneously the residual energy of a number of protons in the same read-out cycle, facilitating a faster and more efficient pCT scan.
This paper investigates the suitability of CMOS Active Pixel Sensors (APSs) to track indi- vidual protons as they go through a number of CMOS layers, forming an energy-range telescope. Measurements performed at the iThemba Laboratories will be presented and analysed in terms of correlation, to confirm capability of proton tracking for CMOS APSs
Frictional drag between non-equilibrium charged gases
The frictional drag force between separated but coupled two-dimensional
electron gases of different temperatures is studied using the non-equilibrium
Green function method based on the separation of center-of-mass and relative
dynamics of electrons. As the mechanisms of producing the frictional force we
include the direct Coulomb interaction, the interaction mediated via virtual
and real TA and LA phonons, optic phonons, plasmons, and TA and LA
phonon-electron collective modes. We found that, when the distance between the
two electron gases is large, and at intermediate temperature where plasmons and
collective modes play the most important role in the frictional drag, the
possibility of having a temperature difference between two subsystems modifies
greatly the transresistivity.Comment: 8figure
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