10,444 research outputs found
Treatment of failed articular cartilage reconstructive procedures of the knee: A systematic review
Background: Symptomatic articular cartilage lesions of the knee are common and are being treated surgically with increasing frequency. While many studies have reported outcomes following a variety of cartilage restoration procedures, few have investigated outcomes of revision surgery after a failed attempt at cartilage repair or reconstruction. Purpose: To investigate outcomes of revision cartilage restoration procedures for symptomatic articular cartilage lesions of the knee following a previously failed cartilage reconstructive procedure. Study Design: Systematic review; Level of evidence, 4. Methods: A literature search was performed by use of the PubMed, EMBASE, and MEDLINE/Ovid databases for relevant articles published between 1975 and 2017 that evaluated patients undergoing revision cartilage restoration procedure(s) and reported outcomes using validated outcome measures. For studies meeting inclusion criteria, relevant information was extracted. Results: Ten studies met the inclusion criteria. Lesions most commonly occurred in the medial femoral condyle (MFC) (52.8%), with marrow stimulation techniques (MST) the index procedure most frequently performed (70.7%). Three studies demonstrated inferior outcomes of autologous chondrocyte implantation (ACI) following a previous failed cartilage procedure compared with primary ACI. One study comparing osteochondral allograft (OCA) transplant following failed microfracture (MFX) with primary OCA transplant demonstrated similar clinical outcomes and graft survival at midterm follow-up. No studies reported outcomes following osteochondral autograft transfer (OAT) or newer techniques. Conclusion: This systematic review of the literature reporting outcomes following revision articular cartilage restoration procedures (most commonly involving the MFC) demonstrated a high proportion of patients who underwent prior MST. Evidence is sufficient to suggest that caution should be taken in performing ACI in the setting of prior MST, likely secondary to subchondral bone compromise. OCA appears to be a good revision treatment option even if the subchondral bone has been violated from prior surgery or fracture. </jats:sec
Towards the theory of coherent hard dijet production on hadrons and nuclei
We carry out a detailed calculation of the cross section of pion diffraction
dissociation into two jets with large transverse momenta, originating from a
hard gluon exchange between the pion constituents. Both the quark and the gluon
contribution are considered and in the latter case we present calculations both
in covariant and in axial gauges. We find that the standard collinear
factorization does not hold in this reaction. The structure of non-factorizable
contributions is discussed and the results are compared with the experimental
data. Our conclusion is that the existing theoretical uncertainties do not
allow, for the time being, for a quantitative extraction of the pion
distribution amplitude.Comment: 45 pages, latex, 17 figures, final version to appear in Nuclear
Physics
The use of the Winograd matrix multiplication algorithm in digital multispectral processing
The Winograd procedure for matrix multiplication provides a method whereby general matrix products may be computed more efficiently than the normal method. The algorithm and the time savings that can be effected are described. A FORTRAN program is provided which performs a general matrix multiply according to this algorithm. A variation of this procedure that may be used to calculate Gaussian probability density functions is also described. It is shown how a time savings can be effected in this calculation. The extension of this method to other similar calculations should yield similar savings
Diquark Condensates and Compact Star Cooling
The effect of color superconductivity on the cooling of quark stars and
neutron stars with large quark cores is investigated. Various known and new
quark-neutrino processes are studied. As a result, stars being in the color
flavor locked (CFL) color superconducting phase cool down extremely fast. Quark
stars with no crust cool down too rapidly in disagreement with X-ray data. The
cooling of stars being in the N_f =2 color superconducting (2SC) phase with a
crust is compatible with existing X-ray data. Also the cooling history of stars
with hypothetic pion condensate nuclei and a crust does not contradict the
data.Comment: 10 pages, 5 figures, accepted for publication in Ap
Effective Gap Equation for the Inhomogeneous LOFF Superconductive Phase
We present an approximate gap equation for different crystalline structures
of the LOFF phase of high density QCD at T=0. This equation is derived by using
an effective condensate term obtained by averaging the inhomogeneous condensate
over distances of the order of the crystal lattice size. The approximation is
expected to work better far off any second order phase transition. As a
function of the difference of the chemical potentials of the up and down
quarks, , we get that the octahedron is energetically favored from
to , where is the gap for
the homogeneous phase, while in the range the face
centered cube prevails. At a first order phase
transition to the normal phase occurs.Comment: 11 pages, 5 figure
Self-dual Yang-Mills fields in pseudoeuclidean spaces
The self-duality Yang-Mills equations in pseudoeuclidean spaces of dimensions
are investigated. New classes of solutions of the equations are
found. Extended solutions to the D=10, N=1 supergravity and super Yang-Mills
equations are constructed from these solutions.Comment: 9 pages, LaTeX, no figure
Local CP-violation and electric charge separation by magnetic fields from lattice QCD
We study local CP-violation on the lattice by measuring the local correlation
between the topological charge density and the electric dipole moment of
quarks, induced by a constant external magnetic field. This correlator is found
to increase linearly with the external field, with the coefficient of
proportionality depending only weakly on temperature. Results are obtained on
lattices with various spacings, and are extrapolated to the continuum limit
after the renormalization of the observables is carried out. This
renormalization utilizes the gradient flow for the quark and gluon fields. Our
findings suggest that the strength of local CP-violation in QCD with physical
quark masses is about an order of magnitude smaller than a model prediction
based on nearly massless quarks in domains of constant gluon backgrounds with
topological charge. We also show numerical evidence that the observed local
CP-violation correlates with spatially extended electric dipole structures in
the QCD vacuum.Comment: 19 pages, 7 figures. Additional lattice results about the induced
electric dipole structure, extended model description, specified terminology.
Version published in JHE
The Ginzburg-Landau Free Energy Functional of Color Superconductivity at Weak Coupling
We derive the Ginzburg-Landau free energy functional of color
superconductivity in terms of the thermal diagrams of QCD in its perturbative
region. The zero mode of the quadratic term coefficient yields the same
transition temperature, including the pre-exponential factor, as the one
obtained previously from the Fredholm determinant of the two quark scattering
amplitude. All coefficients of the free energy can be made identical to those
of a BCS model by setting the Fermi velocity of the latter equal to the speed
of light. We also calculate the induced symmetric color condensate near
and find that it scales as the cubic power of the dominant antisymmetric color
component. We show that in the presence of an inhomogeneity and a nonzero gauge
potential, while the color-flavor locked condensate dominates in the bulk, the
unlocked condensate, the octet, emerges as a result of a simultaneous
color-flavor rotation in the core region of a vortex filament or at the
junction of super and normal phases.Comment: 32 pages, Plain Tex, 3 figure
On highest-energy state in the su(1|1) sector of N=4 super Yang-Mills theory
We consider the highest-energy state in the su(1|1) sector of N=4 super
Yang-Mills theory containing operators of the form tr(Z^{L-M} \psi^M) where Z
is a complex scalar and \psi is a component of gaugino. We show that this state
corresponds to the operator tr(\psi^L) and can be viewed as an analogue of the
antiferromagnetic state in the su(2) sector. We find perturbative expansions of
the energy of this state in both weak and strong 't Hooft coupling regimes
using asymptotic gauge theory Bethe ansatz equations. We also discuss a
possible analog of this state in the conjectured string Bethe ansatz equations.Comment: 23 pages, Late
Alternativity and reciprocity in the Cayley-Dickson algebra
We calculate the eigenvalue \rho of the multiplication mapping R on the
Cayley-Dickson algebra A_n. If the element in A_n is composed of a pair of
alternative elements in A_{n-1}, half the eigenvectors of R in A_n are still
eigenvectors in the subspace which is isomorphic to A_{n-1}.
The invariant under the reciprocal transformation A_n \times A_{n} \ni (x,y)
-> (-y,x) plays a fundamental role in simplifying the functional form of \rho.
If some physical field can be identified with the eigenspace of R, with an
injective map from the field to a scalar quantity (such as a mass) m, then
there is a one-to-one map \pi: m \mapsto \rho. As an example, the electro-weak
gauge field can be regarded as the eigenspace of R, where \pi implies that the
W-boson mass is less than the Z-boson mass, as in the standard model.Comment: To be published in J. Phys. A: Mathematical and Genera
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