33,566 research outputs found
Effect of Bio-Oss® Collagen and Collagen Matrix on Bone Formation
Objective: to compare the amount of new bone produced by Bio-Oss ® Collagen to that produced by collagen matrix in vivo. Method: eighteen bone defects, 5mm by 10mm were created in the parietal bone of 9 New Zealand White rabbits. 6 defects were grafted with Bio-Oss ® Collagen. 6 defects were grafted with collagen matrix alone (positive control) and 6 were left empty (negative control). Animals were killed on day 14 and the defects were dissected and prepared for histological assessment. Quantitative analysis of new bone formation was made on 100 sections (50 sections for each group) using image analysis. Results: A total of 339% more new bone was present in defects grafted with Bio-Oss ® Collagen than those grafted with collagen matrix (positive control). No bone was formed in the negative control group. Conclusion: Bio-Oss ® Collagen has the effect of stimulating new bone formation locally compared with collagen matrix in vivo. Bio-Oss ® Collagen may be utilized as a bone graft material. © Wong and Rabie; Licensee Bentham Open.published_or_final_versio
Human engineering design criteria study Final report
Human engineering design criteria for use in designing earth launch vehicle systems and equipmen
Trajectory generation for road vehicle obstacle avoidance using convex optimization
This paper presents a method for trajectory generation using convex optimization to find a feasible, obstacle-free path for a road vehicle. Consideration of vehicle rotation is shown to be necessary if the trajectory is to avoid obstacles specified in a fixed Earth axis system. The paper establishes that, despite the presence of significant non-linearities, it is possible to articulate the obstacle avoidance problem in a tractable convex form using multiple optimization passes. Finally, it is shown by simulation that an optimal trajectory that accounts for the vehicle’s changing velocity throughout the manoeuvre is superior to a previous analytical method that assumes constant speed
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Construction and testing of an 11.4 GHz dielectric structure based travelling wave accelerator
One major challenge in constructing a dielectric loaded traveling wave accelerator powered by an external rf power source is the difficulty in achieving efficient coupling. In this paper, we report that we have achieved high efficiency broadband coupling by using a combination of a tapered dielectric section and a carefully adjusted coupling slot. We are currently constructing an 11.4 GHz accelerator structure loaded with a permitivity=20 dielectric. Bench testing has demonstrated a coupling efficiency in excess of 95% with bandwidth of 600 MHz. The final setup will be tested at high power at SLAC using an X-band klystron rf source
Non-existence of Skyrmion-Skyrmion and Skyrmion-anti-Skyrmion static equilibria
We consider classical static Skyrmion-anti-Skyrmion and Skyrmion-Skyrmion
configurations, symmetric with respect to a reflection plane, or symmetric up
to a -parity transformation respectively. We show that the stress tensor
component completely normal to the reflection plane, and hence its integral
over the plane, is negative definite or positive definite respectively.
Classical Skyrmions always repel classical Skyrmions and classical Skyrmions
always attract classical anti-Skyrmions and thus no static equilibrium, whether
stable or unstable, is possible in either case. No other symmetry assumption is
made and so our results also apply to multi-Skyrmion configurations. Our
results are consistent with existing analyses of Skyrmion forces at large
separation, and with numerical results on Skymion-anti-Skyrmion configurations
in the literature which admit a different reflection symmetry. They also hold
for the massive Skyrme model. We also point out that reflection symmetric
self-gravitating Skyrmions or black holes with Skyrmion hair cannot rest in
symmetric equilibrium with self-gravitating anti-Skyrmions.Comment: v2 Typos corrected, refs added. v3 Journal versio
Angularly localized Skyrmions
Quantized Skyrmions with baryon numbers and 4 are considered and
angularly localized wavefunctions for them are found. By combining a few low
angular momentum states, one can construct a quantum state whose spatial
density is close to that of the classical Skyrmion, and has the same
symmetries. For the B=1 case we find the best localized wavefunction among
linear combinations of and angular momentum states. For B=2, we
find that the ground state has toroidal symmetry and a somewhat reduced
localization compared to the classical solution. For B=4, where the classical
Skyrmion has cubic symmetry, we construct cubically symmetric quantum states by
combining the ground state with the lowest rotationally excited
state. We use the rational map approximation to compare the classical and
quantum baryon densities in the B=2 and B=4 cases.Comment: 22 page
On the dominance of J(P)=0(+) ground states in even-even nuclei from random two-body interactions
Recent calculations using random two-body interactions showed a preponderance
of J(P)=0(+) ground states, despite the fact that there is no strong pairing
character in the force. We carry out an analysis of a system of identical
particles occupying orbits with j=1/2, 3/2 and 5/2 and discuss some general
features of the spectra derived from random two-body interactions. We show that
for random two-body interactions that are not time-reversal invariant the
dominance of 0(+) states in this case is more pronounced, indicating that
time-reversal invariance cannot be the origin of the 0(+) dominance.Comment: 8 pages, 3 tables and 3 figures. Phys. Rev. C, in pres
Achieving sub-diffraction imaging through bound surface states in negative-refracting photonic crystals at the near-infrared
We report the observation of imaging beyond the diffraction limit due to
bound surface states in negative refraction photonic crystals. We achieve an
effective negative index figure-of-merit [-Re(n)/Im(n)] of at least 380, ~125x
improvement over recent efforts in the near-infrared, with a 0.4 THz bandwidth.
Supported by numerical and theoretical analyses, the observed near-field
resolution is 0.47 lambda, clearly smaller than the diffraction limit of 0.61
lambda. Importantly, we show this sub-diffraction imaging is due to the
resonant excitation of surface slab modes, allowing refocusing of
non-propagating evanescent waves
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