10,084 research outputs found
Radiographic Evaluation of Osteoporosis Through Detection of Jaw Bone Changes: a Simplified Early Osteoporosis Detection Effort
Osteoporosis has become a worldwide problem and has been known as a silence disease. Nowadays, there are a lot of diagnostic tools for detecting osteoporosis. Eighty eight postmenopausal were included and underwent digital panoramic, digital periapical, and conventional radiography. Ultrasound bone densitometry of os calcis used as gold standard. Correlation between stiffness index (SI) with a digital dental, digital panoramic and conventional dental radiography are 0.170 (p = 0.11), -0382 (p = 0.001) and 0.246 (p = 0.021) respectively. Significant relationship was found between the SI only with digital panoramic and conventional dental. The highest correlation was found between SI values with mandibular Inferior Cortex on digital panoramic (-0.382, Pearson Correlation Tests). Correlation between digital panoramic radiographs and the SI values was the highest of the three radiographic modalities in this study. This indicates that evaluation of cortical bone is more accurate than cancellous bone. Bone quality evaluation in patients at high risk for osteoporosis using panoramic and dental conventional radiograph by dentist, contributes in preventing further occurrence of osteoporosis which in turn could reduce mortality and morbidity of osteoporosis in Indonesia
Ultrasonic detection of flaws in fusion butt welds
Reliable and accurate Delta technique, a nondestructive ultrasonics method, uses redirection of energy to detect randomly oriented imperfections in fusion butt welds. Data on flaws can be read from either an oscilloscope or a printout
Evolution of the bilayer nu = 1 quantum Hall state under charge imbalance
We use high-mobility bilayer hole systems with negligible tunneling to
examine how the bilayer nu = 1 quantum Hall state evolves as charge is
transferred from one layer to the other at constant total density. We map
bilayer nu = 1 state stability versus imbalance for five total densities
spanning the range from strongly interlayer coherent to incoherent. We observe
competition between single-layer correlations and interlayer coherence. Most
significantly, we find that bilayer systems that are incoherent at balance can
develop spontaneous interlayer coherence with imbalance, in agreement with
recent theoretical predictions.Comment: 4 pages, 4 figure
Broken symmetry, excitons, gapless modes and topological excitations in Trilayer Quantum Hall systems
We study the interlayer coherent incompressible phase in Trilayer Quantum
Hall systems (TLQH) at total filling factor from three
approaches:
Mutual Composite Fermion (MCF), Composite Boson (CB) and wavefunction
approach.
Just like in Bilayer Quantum Hall system, CB approach is superior than
MCF approach in studying TLQH with broken symmetry. The Hall and Hall drag
resistivities are found to be quantized at . Two neutral gapless
modes with linear dispersion relations are identified and the ratio of the two
velocities is close to .
The novel excitation spectra are classified into two classes: Charge neutral
bosonic
2-body bound states and Charge fermionic 3-body bound states.
In general, there are two 2-body Kosterlize-Thouless (KT) transition
temperatures and one 3-body KT transition. The Charge 3-body
fermionic bound states may be the main dissipation source of transport
measurements.
The broken symmetry in terms of algebra is studied. The structure
of excitons and their flowing patterns are given. The coupling between the two
Goldstone modes may lead to the broadening in the zero-bias peak in the
interlayer correlated tunnelings of the TLQH. Several interesting features
unique to TLQH are outlined.
Limitations of the CB approach are also pointed out.Comment: 10 pages, 3 figures, Final version to be published in Phys. Rev.
Spin Susceptibility and Gap Structure of the Fractional-Statistics Gas
This paper establishes and tests procedures which can determine the electron
energy gap of the high-temperature superconductors using the model
with spinon and holon quasiparticles obeying fractional statistics. A simpler
problem with similar physics, the spin susceptibility spectrum of the spin 1/2
fractional-statistics gas, is studied. Interactions with the density
oscillations of the system substantially decrease the spin gap to a value of
, much less than the mean-field value of
. The lower few Landau levels remain visible, though broadened
and shifted, in the spin susceptibility. As a check of the methods, the
single-particle Green's function of the non-interacting Bose gas viewed in the
fermionic representation, as computed by the same approximation scheme, agrees
well with the exact results. The same mechanism would reduce the gap of the
model without eliminating it.Comment: 35 pages, written in REVTeX, 16 figures available upon request from
[email protected]
Surfactant-induced migration of a spherical drop in Stokes flow
In Stokes flows, symmetry considerations dictate that a neutrally-buoyant
spherical particle will not migrate laterally with respect to the local flow
direction. We show that a loss of symmetry due to flow-induced surfactant
redistribution leads to cross-stream drift of a spherical drop in Poiseuille
flow. We derive analytical expressions for the migration velocity in the limit
of small non-uniformities in the surfactant distribution, corresponding to
weak-flow conditions or a high-viscosity drop. The analysis predicts that the
direction of migration is always towards the flow centerline.Comment: Significant extension with additional text, figures, equations, et
Simulations of a Scintillator Compton Gamma Imager for Safety and Security
We are designing an all-scintillator Compton gamma imager for use in security
investigations and remediation actions involving radioactive threat material.
To satisfy requirements for a rugged and portable instrument, we have chosen
solid scintillator for the active volumes of both the scatter and absorber
detectors. Using the BEAMnrc/EGSnrc Monte Carlo simulation package, we have
constructed models using four different materials for the scatter detector:
LaBr_3, NaI, CaF_2 and PVT. We have compared the detector performances using
angular resolution, efficiency, and image resolution. We find that while PVT
provides worse performance than that of the detectors based entirely on
inorganic scintillators, all of the materials investigated for the scatter
detector have the potential to provide performance adequate for our purposes.Comment: Revised text and figures, Presented at SORMA West 2008, Published in
IEEE Transactions on Nuclear Scienc
Onset of Interlayer Phase Coherence in a Bilayer Two-Dimensional Electron System: Effect of Layer Density Imbalance
Tunneling and Coulomb drag are sensitive probes of spontaneous interlayer
phase coherence in bilayer two-dimensional electron systems at total Landau
level filling factor . We find that the phase boundary between the
interlayer phase coherent state and the weakly-coupled compressible phase moves
to larger layer separations as the electron density distribution in the bilayer
is imbalanced. The critical layer separation increases quadratically with layer
density difference.Comment: 4 pages, 3 figure
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