1,154 research outputs found
Histologic Evaluation of the Efficacy of rhBMP-2 Compared With Autograft Bone in Sheep Spinal Anterior Interbody Fusion
Study Design. The sheep anterior lumbar spinal fusion model was used to study the efficacy of recombinant human bone morphogenetic protein-2 (rhBMP-2)–collagen composite in comparison with autograft to enhance spinal interbody fusion. Comparisons were drawn from temporal radiographic and end-point biomechanical and histologic data.
Objective. To analyze histologically the ability of rhBMP-2 to achieve complete arthrodesis between vertebral bodies.
Summary of Background Data. Studies using rhBMP for enhancement of anterior interbody fusion have used numerous endpoints. However, systematic histologic evaluation of the fusion has not been conducted.
Methods. Twelve sheep underwent single-level anterior lumbar interbody fusion performed with a cylindrical fenestrated titanium interbody fusion device (INTER FIX, Medtronic Sofamor Danek, Inc., Memphis, TN). The device was filled either with rhBMP-2–collagen (n = 6) or autogenous iliac crest bone graft (n = 6). Radiologic evaluation was carried out at 2-month intervals, and all sheep were killed 6 months after surgery. Nondestructive biomechanical testing for stiffness to flexion, extension, and lateral bending moments, un-decalcified histology, and qualitative and quantitative histologic evaluation were performed.
Results. Radiographs revealed a bony bridge anterior to the cage in five of six rhBMP-2-treated animals, whereas it was present only in one of five in the autogenous bone graft group. Segments treated with rhBMP-2 were 20% stiffer in flexion than autograft-treated segments at 6 months. Six of six in the rhBMP-2 group and two of six in the autograft group showed complete fusion. There was a significantly higher rate of bony continuity observed at the fenestrations of the rhBMP-2 group. Three times more number of cage fenestrations in the rhBMP-2 group demonstrated “all-bone” when compared with the autograft group (P \u3c 0.001). Further, the scar tissue in and around the autograft-treated cages was 16-fold more (P \u3c 0.01) than that seen for rhBMP-2-treated cages.
Conclusions. The study demonstrates that rhBMP-2 can lead to earlier radiologic fusion and a more consistent increased stiffness of the segments when compared with autograft in sheep anterior lumbar interbody fusion. Furthermore, a three times higher histologic fusion rate is attainable with significantly reduced fibrous tissue around the implant when rhBMP-2 is used
Tests of the Standard Model Using Muon Polarization Asymmetries in Kaon Decays
We have examined the physics and the experimental feasibility of studying
various kaon decay processes in which the polarization of a muon in the final
state is measured. Valuable information on CP violation, the quark mixing (CKM)
matrix, and new physics can be obtained from such measurements. We have
considered muon polarization in K_L to mu+ mu- and K to pi mu+ mu- decays.
Although the effects are small, or difficult to measure because of the small
branching ratios involved, these studies could provide clean measurements of
the CKM parameters. The experimental difficulty appears comparable to the
observation of K to pi nu barnu. New sources of physics, involving non-standard
CP violation, could produce effects observable in these measurements. Limits
from new results on the neutron and electron electric dipole moment, and
epsilon-prime over epsilon in neutral kaon decays, do not eliminate certain
models that could contribute to the signal. A detailed examination of muon
polarization out of the decay plane in KMU3 and radiative KMU2 decays also
appears to be of interest. With current kaon beams and detector techniques, it
is possible to measure the T-violating polarization for KMU3 with uncertainties
approaching 0.0001. This level of sensitivity would provide an interesting
probe of new physics.Comment: 24 pages, 3 figures, To be published in the International Journal of
Modern Physics
Large Non-perturbative Effects of Small \Delta m^2_{21}/\Delta m^2_{31} and \sin \theta_{13} on Neutrino Oscillation and CP Violation in Matter
In the framework of three generations, we consider the CP violation in
neutrino oscillation with matter effects. At first, we show that the
non-perturbative effects of two small parameters, \Delta m_{21}^2/\Delta
m_{31}^2 and \sin \theta_{13}, become more than 50% in certain ranges of energy
and baseline length. This means that the non-perturbative effects should be
considered in detailed analysis in the long baseline experiments. Next, we
propose a method to include these effects in approximate formulas for
oscillation probabilities. Assuming the two natural conditions,
\theta_{23}=45^\circ and the fact that the matter density is symmetric, a set
of approximate formulas, which involve the non-perturbative effects, has been
derived in all channels.Comment: 25 pages, 4 figures, version to appear in JHE
Radiative Mechanism to Light Fermion Masses in the MSSM
In a previous work we have showed that the Symmetry,
imply that the light fermions, the electron and the quarks, and , get
their masses only at one loop level. Here, we considere the more general
hypothesis for flavour mixing in the sfermion sector in the MSSM. Then, we
present our results to the masses of these light fermions and as a final result
we can explain why the quark is heavier than the quarks. This
mechanism is in agrement with the experimental constraint on the sfermion's
masses values.Comment: 22 pages, 8 figures, TeX mistakes corrected, accepted for publication
in JHE
From parameter space constraints to the precision determination of the leptonic Dirac CP phase
We discuss the precision determination of the leptonic Dirac CP phase
in neutrino oscillation experiments, where we apply the concept
of ``CP coverage''. We demonstrate that this approach carries more information
than a conventional CP violation measurement, since it also describes the
exclusion of parameter regions. This will be very useful for next-generation
long baseline experiments where for sizable first
constraints on can be obtained. As the most sophisticated
experimental setup, we analyze neutrino factories, where we illustrate the
major difficulties in their analysis. In addition, we compare their potential
to the one of superbeam upgrades and next-generation experiments, which also
includes a discussion of synergy effects. We find a strong dependence on the
yet unknown true values of and , as well as
a strong, non-Gaussian dependence on the confidence level. A systematic
understanding of the complicated parameter dependence will be given. In
addition, it is shown that comparisons of experiments and synergy discussions
do in general not allow for an unbiased judgment if they are only performed at
selected points in parameter space. Therefore, we present our results in
dependence of the yet unknown true values of and
. Finally we show that for precision measurements
there exist simple strategies including superbeams, reactor experiments,
superbeam upgrades, and neutrino factories, where the crucial discriminator is
.Comment: 32 pages, 9 figure
Neutrino oscillation physics at an upgraded CNGS with large next generation liquid Argon TPC detectors
The determination of the missing element (magnitude and phase) of
the PMNS neutrino mixing matrix is possible via the detection of \numu\to\nue
oscillations at a baseline and energy given by the atmospheric
observations, corresponding to a mass squared difference . While the current optimization of the CNGS
beam provides limited sensitivity to this reaction, we discuss in this document
the physics potential of an intensity upgraded and energy re-optimized CNGS
neutrino beam coupled to an off-axis detector. We show that improvements in
sensitivity to compared to that of T2K and NoVA are possible with
a next generation large liquid Argon TPC detector located at an off-axis
position (position rather distant from LNGS, possibly at shallow depth). We
also address the possibility to discover CP-violation and disentangle the mass
hierarchy via matter effects. The considered intensity enhancement of the CERN
SPS has strong synergies with the upgrade/replacement of the elements of its
injector chain (Linac, PSB, PS) and the refurbishing of its own elements,
envisioned for an optimal and/or upgraded LHC luminosity programme.Comment: 37 pages, 20 figure
Physics at a Fermilab Proton Driver
This report documents the physics case for building a 2 MW, 8 GeV
superconducting linac proton driver at Fermilab.Comment: 52 pages, 15 figure
Secondary Beam Monitors for the NuMI Facility at FNAL
The Neutrinos at the Main Injector (NuMI) facility is a conventional neutrino
beam which produces muon neutrinos by focusing a beam of mesons into a long
evacuated decay volume. We have built four arrays of ionization chambers to
monitor the position and intensity of the hadron and muon beams associated with
neutrino production at locations downstream of the decay volume. This article
describes the chambers' construction, calibration, and commissioning in the
beam.Comment: Accepted for publication in Nucl. Instr. Meth.
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