890 research outputs found
A magnetic model for the incommensurate I phase of spin-Peierls systems
A magnetic model is proposed for describing the incommensurate I phase of
spin-Peierls systems. Based on the harmonicity of the lattice distortion, its
main ingredient is that the distortion of the lattice adjusts to the average
magnetization such that the system is always gapful. The presence of dynamical
incommensurabilities in the fluctuation spectra is also predicted. Recent
experimental results for CuGeO_3 obtained by NMR, ESR and light scattering
absorption are well understood within this model.Comment: 8 pages, 3 figures, Latex with EPL style files all include
Cystoid Macular Edema after Complicated Cataract Surgery Resolved by an Intravitreal Dexamethasone 0.7-mg Implant
Purpose: To report the effective treatment of cystoid macular edema (CME) following complicated cataract surgery (resulting in Irvine-Gass syndrome) with a dexamethasone 0.7-mg (Ozurdex®) intravitreal implant. Methods: An interventional case report with optical coherence tomography (OCT) scans. Results: An 83-year-old Caucasian woman was suffering from CME following complicated cataract surgery on her left eye. She had undergone 3 intravitreal injections of dexamethasone 0.4 mg in the 3 months following the surgery without any improvement of visual function. Seven months after the cataract surgery, she received a single intravitreal injection of dexamethasone 0.7 mg (Ozurdex). Four weeks following the injection, her best-corrected visual acuity improved from 0.3 to 0.8. CME resolved with a reduction of central retinal thickness from 393 µm pre-Ozurdex injection to 212 µm post-Ozurdex injection, as measured by OCT scan. Conclusion: Dexamethasone 0.7 mg (Ozurdex) has proven to be an effective treatment option in retinal vein occlusion and non-infectious uveitis. It can also be considered as off-label treatment in Irvine-Gass syndrome
Circular Orbits in Einstein-Gauss-Bonnet Gravity
The stability under radial and vertical perturbations of circular orbits
associated to particles orbiting a spherically symmetric center of attraction
is study in the context of the n-dimensional: Newtonian theory of gravitation,
Einstein's general relativity, and Einstein-Gauss-Bonnet theory of gravitation.
The presence of a cosmological constant is also considered. We find that this
constant as well as the Gauss-Bonnet coupling constant are crucial to have
stability for .Comment: 11 pages, 4 figs, RevTex, Phys. Rev. D, in pres
Finite Temperature DMRG Investigation of the Spin-Peierls Transition in CuGeO
We present a numerical study of thermodynamical properties of dimerized
frustrated Heisenberg chains down to extremely low temperatures with
applications to CuGeO. A variant of the finite temperature density matrix
renormalization group (DMRG) allows the study of the dimerized phase previously
unaccessible to ab initio calculations. We investigate static dimerized systems
as well as the instability of the quantum chain towards lattice dimerization.
The crossover from a quadratic response in the free energy to the distortion
field at finite temperature to nonanalytic behavior at zero temperature is
studied quantitatively. Various physical quantities are derived and compared
with experimental data for CuGeO such as magnetic dimerization, critical
temperature, susceptibility and entropy.Comment: LaTeX, 5 pages, 5 eps figures include
Thermal photon production in heavy ion collisions
Using a three-dimensional hydrodynamic simulation of the collision and an
equation of state containing a first order phase transition to the quark-gluon
plasma, we study thermal photon production for collisions at
AGeV and for collisions at AGeV. We obtain
surprisingly high rates of thermal photons even at the lower energy, suggesting
that, contrary to what was expected so far, photon production may be an
interesting topic for experimental search also at the Alternating Gradient
Synchrotron. When applied to the reaction at AGeV, our model can
reproduce preliminary data obtained by the WA80 Collaboration without having to
postulate the existence of an extremely long-lived mixed phase as was recently
proposed.Comment: 9 pages, figures are uudecoded compressed and tare
Soliton Lattices in the Incommensurate Spin-Peierls Phase: Local Distortions and Magnetizations
It is shown that nonadiabatic fluctuations of the soliton lattice in the
spin-Peierls system CuGeO_3 lead to an important reduction of the NMR line
widths. These fluctuations are the zero-point motion of the massless phasonic
excitations. Furthermore, we show that the discrepancy of X-ray and NMR soliton
widths can be understood as the difference between a distortive and a magnetic
width. Their ratio is controlled by the frustration of the spin system. By this
work, theoretical and experimental results can be reconciled in two important
points.Comment: 9 pages, 5 figures included, Revtex submitted to Physical Review
Bilateral Simultaneous Retinal Detachment in Pseudophakia
Cataract surgery is the most frequent surgical intervention, with approximately 700,000 operations per year in Germany alone. One of the most serious complications is retinal detachment, with a reported incidence rate of pseudophakic retinal detachment of 0.75-1.65%. We report the case of a patient who suffered from a simultaneous bilateral pseudophakic retinal detachment. Interestingly, the bilateral detachments in the left and the right eye started with only some hours' delay. He had no acute trigger for the retinal detachment and no risk factors besides the cataract surgery performed on both eyes some weeks earlier. Simultaneous bilateral retinal detachments will be more common, due to increasing numbers of cataract surgeries and the demographic development. We conclude that funduscopy should be regularly performed in mydriasis to avoid sight-threatening simultaneous bilateral retinal detachments
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