ABSTRACT
The transition between the standard snake instability of bright solitons of the hyperbolic nonlinear Schrödinger equation and the recently theoretically predicted oscillatory snake instability is experimentally demonstrated. The existence of this transition is proven on the basis of spatiotemporal spectral features of bright soliton laser beams propagating in normally dispersive Kerr-type nonlinear planar waveguides.
ABSTRACT
Using a standing light wave potential, a stable quasi-one-dimensional attractive dilute-gas Bose-Einstein condensate can be realized. In a mean-field approximation, this phenomenon is modeled by the cubic nonlinear Schrödinger equation with attractive nonlinearity and an elliptic function potential of which a standing light wave is a special case. New families of stationary solutions are presented. Some of these solutions have neither an analog in the linear Schrödinger equation nor in the integrable nonlinear Schrödinger equation. Their stability is examined using analytic and numerical methods. Trivial-phase solutions are experimentally stable provided they have nodes and their density is localized in the troughs of the potential. Stable time-periodic solutions are also examined.
ABSTRACT
The cubic nonlinear Schrödinger equation with repulsive nonlinearity and an elliptic function potential models a quasi-one-dimensional repulsive dilute gas Bose-Einstein condensate trapped in a standing light wave. New families of stationary solutions are presented. Some of these solutions have neither an analog in the linear Schrödinger equation nor in the integrable nonlinear Schrödinger equation. Their stability is examined using analytical and numerical methods. All trivial-phase stable solutions are deformations of the ground state of the linear Schrödinger equation. Our results show that a large number of condensed atoms is sufficient to form a stable, periodic condensate. Physically, this implies stability of states near the Thomas-Fermi limit.
ABSTRACT
We present a new family of stationary solutions to the cubic nonlinear Schrödinger equation with an elliptic function potential. In the limit of a sinusoidal potential our solutions model a quasi-one-dimensional dilute gas Bose-Einstein condensate trapped in a standing light wave. Provided that the ratio of the height of the variations of the condensate to its dc offset is small enough, both trivial phase and nontrivial phase solutions are shown to be stable. Recent developments allow for experimental investigation of these predictions.
ABSTRACT
A 48-year-old woman was referred from Zaire with suspected rabies encephalitis. Survival was 34 days after the onset of symptoms and the diagnosis of rabies was ultimately proven after brain autopsy. Serial neurophysiological investigations, including EEG and multimodality evoked potentials and radiological examinations (cerebral magnetic resonance imaging and computed tomodensitometry) were performed. Whereas the clinical findings and EEG were compatible with brain death at the end of the course, this diagnosis could be definitely ruled out by multimodality evoked potentials, magnetic resonance imaging and autopsy. The validity of multimodality evoked potentials is discussed in this particular setting.
Subject(s)
Brain Death/physiopathology , Encephalitis/physiopathology , Rabies/physiopathology , Brain/pathology , Brain/physiopathology , Brain Death/pathology , Diagnosis, Differential , Electroencephalography , Encephalitis/pathology , Evoked Potentials/physiology , Female , Humans , Magnetic Resonance Imaging , Middle Aged , Rabies/pathologyABSTRACT
Hydrocephalus developed in a 16-year-old boy with a severe Guillain-Barré syndrome and was demonstrated by computerized tomography (CT) and magnetic resonance imaging. No papilledema was observed. The spontaneous resolution of hydrocephalus was achieved in a 6-month period. Ventricular changes were followed by CT scan.
