136 research outputs found
Stationary solutions of the one-dimensional nonlinear Schroedinger equation: I. Case of repulsive nonlinearity
All stationary solutions to the one-dimensional nonlinear Schroedinger
equation under box and periodic boundary conditions are presented in analytic
form. We consider the case of repulsive nonlinearity; in a companion paper we
treat the attractive case. Our solutions take the form of stationary trains of
dark or grey density-notch solitons. Real stationary states are in one-to-one
correspondence with those of the linear Schr\"odinger equation. Complex
stationary states are uniquely nonlinear, nodeless, and symmetry-breaking. Our
solutions apply to many physical contexts, including the Bose-Einstein
condensate and optical pulses in fibers.Comment: 11 pages, 7 figures -- revised versio
Serum- and bone-mineral status of ostriches with tibiotarsal rotation
Tibiotarsal rotation in ostrich chicks is a serious problem that accounts for considerable financial loss to ostrich farmers. Serum- and bone-mineral analyses of 20 ostrich chicks with tibiotarsal rotation were compared with serum- and bone-mineral analyses of eight normal ostrich chicks of comparable age, sex and body mass, and raised under identical conditions. The serum-zinc values were significantly higher and the bone-calcium and phosphorus values significantly lower in the affected group than in the group of normal ostrich chicks. The results indicated poor mineralization of bone with subsequent reactive osteoid formation.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201
Quantum carpet interferometry for trapped atomic Bose-Einstein condensates
We propose an ``interferometric'' scheme for Bose-Einstein condensates using
near-field diffraction. The scheme is based on the phenomenon of intermode
traces or quantum carpets; we show how it may be used in the detection of weak
forces.Comment: 4 figures. Submitted to Phys. Rev.
Sperm-storage tubules in the vagina of the ostrich (Struthio camelus)
Sperm-storage tubules have been described in a number of species of birds. The presence of these
tubules in the Rhea has been mentioned, but no description of these structures in ratites is available.
The purpose of this study was to determine the presence and morphology of sperm-storage tubules in
the vagina of the ostrich. The study was performed with the use of conventional light- and electron-microscopic
techniques. Sperm-storage tubules were located in a 200-mm-wide band of the vagina adjacent
to the utero-vaginal junction. The tubules were mostly branched and slightly coiled and lined by
columnar epithelial cells. The cells contained a basal nucleus and displayed extensive apical junctional
complexes. TEM revealed sperm in all the tubules examined.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201
Evidence for cryptosporidial infection as a cause of prolapse of the phallus and cloaca in ostrich chicks (Struthio camelus)
Cloacas of male ostrich chicks that had suffered prolapse of the phallus and cloaca were compared
with cloacas of normal ostrich chicks of both sexes from the same area. Heavy infection of the cloacal
and bursal tissue with Cryptosporidium sp. was present in all the cases of prolapse, while no cryptosporidia
were observed in the normal chicks. Histopathological lesions as described in cryptosporidial
infection in other species were present in the infected cloacas. These included loss of the microvillous
border and epithelial hyperplasia, and degeneration, which was indicated ultrastructurally by vacuolation
of the apical cytoplasm, swelling of organelles, and nuclear changes. It is suggested that these lesions,
in combination with the anatomy of the male ostrich cloaca, may be responsible for prolapse of the
phallus and cloaca.The articles have been scanned in colour with a HP Scanjet 5590; 600dpi.
Adobe Acrobat XI Pro was used to OCR the text and also for the merging and conversion to the final presentation PDF-format.mn201
Bacterial enteritis in ostrich (Struthio Camelus) chicks in the Western Cape Province, South Africa
Ostrich (Struthio camelus) chicks less
than 3 mo age are observed to experience a high
mortality rate that is often associated with enteritis.
This study was undertaken to investigate the infectious
bacteria implicated in ostrich chick enteritis. Postmortems
were performed on 122 ostrich chicks aged
from 1 d to 3 mo and intestinal samples were subjected
to bacterial culture. Bacterial isolates were typed
by PCR and serotyping. Escherichia coli (E. coli;
49%) was the most frequently isolated from the samples
followed by Clostridium perfringens (C. perfringens;
20%), Enterococcus spp. (16%), and Salmonella
spp. (7%). Of the E. coli, 39% were categorized
as enteropathogenic E. coli, 4% enterotoxigenic E.
coli, and no enterohaemorrhagic E. coli were found.The majority (93%) of C. perfringens was Type A
and only 7% was Type E. C. perfringens Types B
through D were not present. The netB gene that
encodes NetB toxin was identified from 16% of the
C. perfringens isolated. All the C. perfringens Type
E harbored the netB gene and just 10% of the C.
perfringens Type A had this gene. Three Salmonella
serotypes were identified: Salmonella Muenchen (S.
Muenchen; 80%), S. Hayindongo (13%), and S. Othmarschen
(7%). The indication is that the cause of
enteritis in ostrich chicks is bacterial-involving: enteropathogenic
E. coli and enterotoxigenic E. coli; C.
perfringens Types A and E (with the possible influence
of netB gene); and S. Muenchen, S. Hayindongo, and
S. Othmarschen.South African Ostrich Business Chamber and the Technology and Human Resources
Program.http://ps.oxfordjournals.org2016-06-30hb201
Direct observation by resonant tunneling of the B^+ level in a delta-doped silicon barrier
We observe a resonance in the conductance of silicon tunneling devices with a
delta-doped barrier. The position of the resonance indicates that it arises
from tunneling through the B^+ state of the boron atoms of the delta-layer.
Since the emitter Fermi level in our devices is a field-independent reference
energy, we are able to directly observe the diamagnetic shift of the B^+ level.
This is contrary to the situation in magneto-optical spectroscopy, where the
shift is absorbed in the measured ionization energy.Comment: submitted to PR
Nonlinear atom optics and bright gap soliton generation in finite optical lattices
We theoretically investigate the transmission dynamics of coherent matter
wave pulses across finite optical lattices in both the linear and the nonlinear
regimes. The shape and the intensity of the transmitted pulse are found to
strongly depend on the parameters of the incident pulse, in particular its
velocity and density: a clear physical picture for the main features observed
in the numerical simulations is given in terms of the atomic band dispersion in
the periodic potential of the optical lattice. Signatures of nonlinear effects
due the atom-atom interaction are discussed in detail, such as atom optical
limiting and atom optical bistability. For positive scattering lengths, matter
waves propagating close to the top of the valence band are shown to be subject
to modulational instability. A new scheme for the experimental generation of
narrow bright gap solitons from a wide Bose-Einstein condensate is proposed:
the modulational instability is seeded in a controlled way starting from the
strongly modulated density profile of a standing matter wave and the solitonic
nature of the generated pulses is checked from their shape and their
collisional properties
Simple method for excitation of a Bose-Einstein condensate
An appropriate, time-dependent modification of the trapping potential may be
sufficient to create effectively collective excitations in a cold atom
Bose-Einstein condensate. The proposed method is complementary to earlier
suggestions and should allow the creation of both dark solitons and vortices.Comment: 8 pages, 7 figures, version accepted for publication in Phys. Rev.
Stability of dark solitons in a Bose-Einstein condensate trapped in an optical lattice
We investigate the stability of dark solitons (DSs) in an effectively
one-dimensional Bose-Einstein condensate in the presence of the magnetic
parabolic trap and an optical lattice (OL). The analysis is based on both the
full Gross-Pitaevskii equation and its tight-binding approximation counterpart
(discrete nonlinear Schr{\"o}dinger equation). We find that DSs are subject to
weak instabilities with an onset of instability mainly governed by the period
and amplitude of the OL. The instability, if present, sets in at large times
and it is characterized by quasi-periodic oscillations of the DS about the
minimum of the parabolic trap.Comment: Typo fixed in Eq. (1): cos^2 -> sin^
- …