869 research outputs found
Spectroscopy using the Anisotropic Clover Action
The calculation of the light-hadron spectrum in the quenched approximation to
QCD using an anisotropic clover fermion action is presented. The tuning of the
parameters of the action is discussed, using the pion and rho dispersion
relation. The adoption of an anisotropic lattice provides clear advantages in
the determination of the baryonic resonances, and in particular that of the
so-called Roper resonance, the lightest radial excitation of the nucleon.Comment: Lattice2002(spectrum), 3 pages, 3 figures, to appear in Proceedings
of Lattice 200
L^2-Betti numbers of one-relator groups
We determine the L^2-Betti numbers of all one-relator groups and all
surface-plus-one-relation groups (surface-plus-one-relation groups were
introduced by Hempel who called them one-relator surface groups). In particular
we show that for all such groups G, the L^2-Betti numbers b_n^{(2)}(G) are 0
for all n>1. We also obtain some information about the L^2-cohomology of
left-orderable groups, and deduce the non-L^2 result that, in any
left-orderable group of homological dimension one, all two-generator subgroups
are free.Comment: 18 pages, version 3, minor changes. To appear in Math. An
Changes in Plasma Fibronectin Isoform Levels Predict Distinct Clinical Outcomes in Critically Ill Patients
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Baryon Operators and Baryon Spectroscopy
The issues involved in a determination of the baryon resonance spectrum in
lattice QCD are discussed. The variational method is introduced and the need to
construct a sufficient basis of interpolating operators is emphasised. The
construction of baryon operators using group-theory techniques is outlined. We
find that the use both of quark-field smearing and link-field smearing in the
operators is essential firstly to reduce the coupling of operators to
high-frequency modes and secondly to reduce the gauge-field fluctuations in
correlators. We conclude with a status report of our current investigation of
baryon spectroscopy.Comment: Invited talk at Workshop on Computational Hadron Physics, Cyprus,
Sept. 14-17, 200
Implant augmentation: Adding bone cement to improve the treatment of osteoporotic distal femur fractures:A biomechanical study using human cadaver bones
The increasing problems in the field of osteoporotic fracture fixation results in specialized implants as well as new operation methods, for example, implant augmentation with bone cement. The aim of this study was to determine the biomechanical impact of augmentation in the treatment of osteoporotic distal femur fractures. Seven pairs of osteoporotic fresh frozen distal femora were randomly assigned to either an augmented or nonaugmented group. In both groups, an Orthopaedic Trauma Association 33 A3 fractures was fixed using the locking compression plate distal femur and cannulated and perforated screws. In the augmented group, additionally, 1 mL of polymethylmethacrylate cement was injected through the screw. Prior to mechanical testing, bone mineral density (BMD) and local bone strength were determined. Mechanical testing was performed by cyclic axial loading (100 N to 750 N + 0.05N/cycle) using a servo-hydraulic testing machine. As a result, the BMD as well as the axial stiffness did not significantly differ between the groups. The number of cycles to failure was significantly higher in the augmented group with the BMD as a significant covariate. In conclusion, cement augmentation can significantly improve implant anchorage in plating of osteoporotic distal femur fractures
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