509 research outputs found
Afterglow polarizations in a stratified medium with effect of the equal arrival time surface
The environment of gamma-ray burst (GRB) has an important influence on the
evolution of jet dynamics and of its afterglow. Here we investigate the
afterglow polarizations in a stratified medium with the equal arrival time
surface (EATS) effect. Polarizations of multi-band afterglows are predicted.
The effects of the parameters of the stratified medium on the afterglow
polarizations are also investigated. We found the influences of the EATS effect
on the afterglow polarizations become important for off-axis detections and PD
bumps move to later times with the EATS effect. Even the magnetic field
configurations, jet structure and observational angles are fixed, polarization
properties of the jet emission could still evolve. Here, we assume a
large-scale ordered magnetic field in the reverse-shock region and a
two-dimensional random field in the forward-shock region. Then PD evolution is
mainly determined by the evolution of parameter (the flux ratio
between the reverse-shock region and forward-shock region) at early stage and
by the evolution of the bulk Lorentz factor at late stage. Through the
influences on the or , the observational energy band,
observational angles, and the parameters of the stratified medium will finally
affect the afterglow polarizations.Comment: 16 pages, 8 figures, accepted by Ap
Treatment of nonunions of humeral fractures with interlocking intramedullary nailing
ObjectiveTo introduce the experience of treating nonunions of humeral fractures with interlocking intramedullarynailing.MethodsTwelve patients with humeral nonunions were treated with interlocking intramedullary nailing. The time interval between trauma and surgery was 10.5 months on average. Open reduction with anterograde approach was performed. Axial compression was specially applied to the fracture site with humeral nail holder after insertion of distal locked screws. Iliac bone grafting was added.ResultsThe average follow-up period was 21 months (ranging 9-51 months). All patients achieved osseous union 5.8 months after treatment on average. Eleven patients had good functions of the shoulder joints and the upper extremities. No patient experienced any permanent neurological deficit. Refracture of the original ununited region occurred in one patient after removal of the internal fixator one year later, but union was achieved after closed re-intramedullarynailing fixation.ConclusionHumeral interlocking intramedullarynailing is an effective alternative treatment for humeral nonunion
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