246 research outputs found
Nonlinear Self-Trapping of Matter Waves in Periodic Potentials
We report the first experimental observation of nonlinear self-trapping of
Bose-condensed 87Rb atoms in a one dimensional waveguide with a superimposed
deep periodic potential . The trapping effect is confirmed directly by imaging
the atomic spatial distribution. Increasing the nonlinearity we move the system
from the diffusive regime, characterized by an expansion of the condensate, to
the nonlinearity dominated self-trapping regime, where the initial expansion
stops and the width remains finite. The data are in quantitative agreement with
the solutions of the corresponding discrete nonlinear equation. Our results
reveal that the effect of nonlinear self-trapping is of local nature, and is
closely related to the macroscopic self-trapping phenomenon already predicted
for double-well systems.Comment: 5 pages, 4 figure
Immunohistological studies on neoplasms of female and male Onchocerca volvulus: filarial origin and absence of Wolbachia from tumor cells
Up to 5% of untreated female Onchocerca volvulus filariae develop potentially fatal pleomorphic neoplasms, whose incidence is increased following ivermectin treatment. We studied the occurrence of 8 filarial proteins and of Wolbachia endobacteria in the tumor cells. Onchocercomas from patients, untreated and treated with antibiotics and anthelminthics, were examined by immunohistology. Neoplasms were diagnosed in 112 of 3587 female and in 2 of 1570 male O. volvulus. The following proteins and other compounds of O. volvulus were expressed in the cells of the neoplasms: glutathione S-transferase 1, lysosomal aspartic protease, cAMP-dependent protein kinase, alpha-enolase, aspartate aminotransferase, ankyrin E1, tropomyosin, heat shock protein 60, transforming growth factor-beta, and prostaglandin E2. These findings prove the filarial origin of the neoplasms and confirm the pleomorphism of the tumor cells. Signs indicating malignancy of the neoplasms are described. Wolbachia were observed in the hypodermis, oocytes, and embryos of tumor-harbouring filariae using antibodies against Wolbachia surface protein, Wolbachia HtrA-type serine protease, and Wolbachia aspartate aminotransferase. In contrast, Wolbachia were not found in the cells of the neoplasms. Further, neoplasm-containing worms were not observed after more than 10 months after the start of sufficient treatment with doxycycline or doxycycline plus ivermectin
Towards many colors in FISH on 3D-preserved interphase nuclei
The article reviews the existing methods of multicolor FISH on nuclear targets, first of all, interphase chromosomes. FISH proper and image acquisition are considered as two related components of a single process. We discuss (1) M-FISH (combinatorial labeling + deconvolution + widefield microscopy); (2) multicolor labeling + SIM (structured illumination microscopy); (3) the standard approach to multicolor FISH + CLSM (confocal laser scanning microscopy; one fluorochrome - one color channel); (4) combinatorial labeling + CLSM; (5) non-combinatorial labeling + CLSM + linear unmixing. Two related issues, deconvolution of images acquired with CLSM and correction of data for chromatic Z-shift, are also discussed. All methods are illustrated with practical examples. Finally, several rules of thumb helping to choose an optimal labeling + microscopy combination for the planned experiment are suggested. Copyright (c) 2006 S. Karger AG, Basel
Realization of a single Josephson junction for Bose-Einstein condensates
We report on the realization of a double-well potential for Rubidium-87
Bose-Einstein condensates. The experimental setup allows the investigation of
two different dynamical phenomena known for this system - Josephson
oscillations and self-trapping. We give a detailed discussion of the
experimental setup and the methods used for calibrating the relevant
parameters. We compare our experimental findings with the predictions of an
extended two-mode model and find quantitative agreement
Bright gap solitons of atoms with repulsive interaction
We report on the first experimental observation of bright matter-wave
solitons for 87Rb atoms with repulsive atom-atom interaction. This counter
intuitive situation arises inside a weak periodic potential, where anomalous
dispersion can be realized at the Brillouin zone boundary. If the coherent
atomic wavepacket is prepared at the corresponding band edge a bright soliton
is formed inside the gap. The strength of our system is the precise control of
preparation and real time manipulation, allowing the systematic investigation
of gap solitons.Comment: 4 pages, 4 figure
Collective Excitations of Bose-Einstein Condensates in a Double-Well Potential
We investigate collective excitations of Bose-Einstein condensates at
absolute zero in a double-well trap. We solve the Bogoliubov equations with a
double-well trap, and show that the crossover from the dipole mode to the
Josephson plasma mode occurs in the lowest energy excitation. It is found that
the anomalous tunneling property of low energy excitations is crucial to the
crossover.Comment: 14 pages, 6 figure
Quantum Dynamics of Atom-molecule BECs in a Double-Well Potential
We investigate the dynamics of two-component Bose-Josephson junction composed
of atom-molecule BECs. Within the semiclassical approximation, the multi-degree
of freedom of this system permits chaotic dynamics, which does not occur in
single-component Bose-Josephson junctions. By investigating the level
statistics of the energy spectra using the exact diagonalization method, we
evaluate whether the dynamics of the system is periodic or non-periodic within
the semiclassical approximation. Additionally, we compare the semiclassical and
full-quantum dynamics.Comment: to appear in JLTP - QFS 200
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