1,337 research outputs found
An anatomical study in a Chinese population of the position of the rib head for placing anterior vertebral body screws
The instrumentation of anterior vertebral body screws has become an important
approach for the treatment of unstable fractures or curvature of the spine,
but little attention has been paid to the starting point of placing the screws
and the variability of the rib head position. We analysed the variability of rib
head position in a Chinese population in terms of the spinal canal and vertebral
body using computed tomography (CT). Images from transverse CT scans of
the T4–T12 vertebral bodies of 30 normal individuals were 3-D reconstructed
and analysed for measurement of parameters which included: 1) distance between
the left (or right) anterior border of the rib head and the posterior (or
anterior) margin of the vertebral body [L(R)ARHP(A)VB]; 2) left (or right) transverse
dimension [L(R)TD]; 3) left (or right) posterior (or anterior) safe angle
[L(R)P(A)SA]; and 4) distance between the inferior border of the left (or right) rib
head and the superior (or inferior) end-plate in the sagittal plane [I L(R)RHS(I)EP].
The ARHPVB, PSA, and IRHIEP gradually decrease, but ARHAVB, TD, ASA, and
IRHSEP gradually increase, from T4 to T12, indicating that the position of the
rib head changes from a more anterior position to a more posterior position
and from a more superior position to a more inferior position, as the number of
the vertebra increases. Our study has provided a comprehensive reference guide
for accurate and safe instrumentation of vertebral body screws in treating related
spine diseases. (Folia Morphol 2010; 69, 4: 232-240
Acoustic phonon transport through a double-bend quantum waveguide
In this work, using the scattering matrix method, we have investigated the
transmission coefficients and the thermal conductivity in a double-bend
waveguide structure. The transmission coefficients show strong resonances due
to the scattering in the midsection of a double-bend structure; the positions
and the widths of the resonance peaks are determined by the dimensions of the
midsection of the structure. And the scattering in the double-bend structure
makes the thermal conductivity decreases with the increasing of the temperature
first, then increases after reaches a minimum. Furthermore, the investigations
of the multiple double-bend structures indicate that the first additional
double-bend structure suppresses the transmission coefficient and the frequency
gap formed; and the additional double-bend structures determine the numbers of
the resonance peaks at the frequency just above the gap region. These results
could be useful for the design of phonon devices.Comment: 13 pages, 6 figures, elsart.cls is use
BES3 time of flight monitoring system
A Time of Flight monitoring system has been developed for BES3.
The light source is a 442-443 nm laser diode, which is stable and provides a
pulse width as narrow as 50 ps and a peak power as large as 2.6 W. Two
optical-fiber bundles with a total of 512 optical fibers, including spares, are
used to distribute the light pulses to the Time of Flight counters. The design,
operation, and performance of the system are described.Comment: 8 pages 16 figures, submitted to NI
Experimental Study and Finite Element Analysis of Critical Stresses of Reinforced Thermoplastic Pipes under Various Loads
In this paper, reinforced thermoplastic pipes (RTP) were studied under various loads. A total of five groups of specimens were designed to study the mechanical properties of RTPs under internal pressure, bending, a combination of internal pressure and bending moment, external pressure, and tension. This study obtained the bursting pressure of RTPs under internal pressure, the minimum bending radius under the bending moment, and the failure pressure under external pressure. At the same time, the mechanical properties of RTPs under various loads were analyzed using the finite element analysis. Analytical results agree well with the experimental ones. The finite element model established in this paper can be used for further research on the mechanical properties of RTPs
Revisiting the B {\to} {\pi} {\rho}, {\pi} {\omega} Decays in the Perturbative QCD Approach Beyond the Leading Order
We calculate the branching ratios and CP asymmetries of the ,
decays in the perturbative QCD factorization approach up to the
next-to-leading-order contributions. We find that the next-to-leading-order
contributions can interfere with the leading-order part constructively or
destructively for different decay modes. Our numerical results have a much
better agreement with current available data than previous leading-order
calculations, e.g., the next-to-leading-order corrections enhance the
branching ratios by a factor 2.5, which is helpful
to narrow the gaps between theoretic predictions and experimental data. We also
update the direct CP-violation parameters, the mixing-induced CP-violation
parameters of these modes, which show a better agreement with experimental data
than many of the other approaches.Comment: 23 pages, 4 figures, 4 table
Larmor precession and tunneling time of a relativistic neutral spinning particle through an arbitrary potential barrier
The Larmor precession of a relativistic neutral spin-1/2 particle in a
uniform constant magnetic field confined to the region of a one-dimensional
arbitrary potential barrier is investigated. The spin precession serves as a
clock to measure the time spent by a quantum particle traversing a potential
barrier. With the help of general spin coherent state it is explicitly shown
that the precession time is equal to the dwell time.Comment: 10 pages, 1 figure. To be published in Phys. Rev. A (01 February
2002
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