103 research outputs found
A New Atom Trap: The Annular Shell Atom Trap (ASAT)
In the course of exploring some aspects of atom guiding in a hollow, optical
fiber, a small negative potential energy well was found just in front of the
repulsive or guiding barrier. This results from the optical dipole and the van
der Waals potentials. The ground state for atoms bound in this negative
potential well was determined by numerically solving the Schrodinger eq. and it
was found that this negative well could serve as an atom trap. This trap is
referred to as the Annular Shell Atom Trap or ASAT because of the geometry of
the trapped atoms which are located in the locus of points defining a very thin
annular shell just in front of the guiding barrier. A unique feature of the
ASAT is the compression of the atoms from the entire volume to the volume of
the annular shell resulting in a very high density of atoms in this trap. This
trap may have applications to very low temperatures using evaporative cooling
and possibly the formation of BEC. Finally, a scheme is discussed for taking
advantage of the de Broglie wavelength to store atoms in a bottle trap based on
the inability of long de Broglie wavelengths to escape through a selective de
Broglie wavelength filter in the atom bottle trap.Comment: 13 pages total, 5 figure
Interacting Bosons at Finite Temperature: How Bogolubov Visited a Black Hole and Came Home Again
The structure of the thermal equilibrium state of a weakly interacting Bose
gas is of current interest. We calculate the density matrix of that state in
two ways. The most effective method, in terms of yielding a simple, explicit
answer, is to construct a generating function within the traditional framework
of quantum statistical mechanics. The alternative method, arguably more
interesting, is to construct the thermal state as a vector state in an
artificial system with twice as many degrees of freedom. It is well known that
this construction has an actual physical realization in the quantum
thermodynamics of black holes, where the added degrees of freedom correspond to
the second sheet of the Kruskal manifold and the thermal vector state is a
state of the Unruh or the Hartle-Hawking type. What is unusual about the
present work is that the Bogolubov transformation used to construct the thermal
state combines in a rather symmetrical way with Bogolubov's original
transformation of the same form, used to implement the interaction of the
nonideal gas in linear approximation. In addition to providing a density
matrix, the method makes it possible to calculate efficiently certain
expectation values directly in terms of the thermal vector state of the doubled
system.Comment: 25 pages, LaTeX. To appear in a special issue of Foundations of
Physics in honor of Jacob Bekenstei
FAST CARS: Engineering a Laser Spectroscopic Technique for Rapid Identification of Bacterial Spores
Airborne contaminants, e.g., bacterial spores, are usually analyzed by time
consuming microscopic, chemical and biological assays. Current research into
real time laser spectroscopic detectors of such contaminants is based on e.g.
resonant Raman spectroscopy. The present approach derives from recent
experiments in which atoms and molecules are prepared by one (or more) coherent
laser(s) and probed by another set of lasers. The connection with previous
studies based on "Coherent Anti-Stokes Raman Spectroscopy" (CARS) is to be
noted. However generating and utilizing maximally coherent oscillation in
macromolecules having an enormous number of degrees of freedom is much more
challenging. This extension of the CARS technique is called FAST CARS
(Femtosecond Adaptive Spectroscopic Techniques for Coherent Anti-Stokes Raman
Spectroscopy), and the present paper proposes and analyses ways in which it
could be used to rapidly identify pre-selected molecules in real time.Comment: 43 pages, 21 figures; replacement with references added. Submitted to
the Proceedings of National Academy of Science
Expression and Purification of Z Protein from JunĂn Virus
Arenaviridae comprises 23 recognized virus species with a bipartite ssRNA genome and an ambisense coding strategy. The virions are enveloped and include nonequimolar amounts of each genomic RNA species, designated L and S, coding for four ORFs (N, GPC, L, and Z). The arenavirus JunĂn (JUNV) is the etiological agent of Argentine Hemorrhagic Fever, an acute disease with high mortality rate. It has been proposed that Z is the functional counterpart of the matrix proteins found in other negative-stranded enveloped RNA viruses. Here we report the optimized expression of a synthetic gene of Z protein, using three expression systems (two bacterial and a baculoviral one). One of these recombinant proteins was used to generate antibodies. A bioinformatic analysis was made where Z was subdivided into three domains. The data presented contributes methodologies for Z recombinant production and provides the basis for the development of new experiments to test its function
Post-Merger Performance of Bank Holding Companies, 1987-1998
This paper examines the results of material mergers between bank holding companies (BHCs). Merged BHCs experience post-merger profitability below the industry average. The market reaction to the merger announcements is significantly negative. The most important causes of the poor post-merger performance are credit quality and the inadequate generation of fee income. Asset mix and capitalization also play a major part. The controllability of these items demonstrates the management challenge associated with a material merger. Copyright 2005 by the Eastern Finance Association.
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