1,336 research outputs found
On a Generalized Fifth-Order Integrable Evolution Equation and its Hierarchy
A general form of the fifth-order nonlinear evolution equation is considered.
Helmholtz solution of the inverse variational problem is used to derive
conditions under which this equation admits an analytic representation. A
Lennard type recursion operator is then employed to construct a hierarchy of
Lagrangian equations. It is explicitly demonstrated that the constructed system
of equations has a Lax representation and two compatible Hamiltonian
structures. The homogeneous balance method is used to derive analytic soliton
solutions of the third- and fifth-order equations.Comment: 16 pages, 1 figur
Bright solitons in asymmetrically trapped Bose-Einstein condensate
We study the dynamics of bright solitons in a Bose-Einstein condensate (BEC)
confined in a highly asymmetric trap. While working within the f ramework of a
variational approach we carry out the stability analysis o f BEC solitons
against collapse. When the number of atoms in the soliton exceeds a critical
number , it undergoes the so called primary col lapse. We find an
analytical expression for in terms of appropriat e experimental
quantities that are used to produce and confine the conde nsate. We further
demonstrate that, in the geometry of the problem consi dered, the width of the
soliton varies inversely as the number of consti tuent atoms.Comment: 5 pages, 1 figure
Experimental Realization of Quantum-Resonance Ratchets
Quantum-resonance ratchets associated with the periodically kicked particle
are experimentally realized for the first time. This is achieved by using a
Bose-Einstein condensate exposed to a pulsed standing light wave and prepared
in an initial state differing from the usual plane wave. Both the standing-wave
potential and the initial state have a point symmetry around some center and
the ratchet arises from the non-coincidence of the two centers. The dependence
of the directed quantum transport on the quasimomentum is studied. A detailed
theoretical analysis is used to explain the experimental results.Comment: Accepted for publication in Physical Review Letters (November 2007
Electronic Signatures in E-Healthcare: The Need for a Federal Standard
Healthcare, like many industries, is fast embracing the benefits of modern information technology ( IT ). The wide range of available publications on the use of IT in healthcare indicates that IT provides the promise of faster and more comprehensive information about all aspects of the healthcare delivery process, to all classes of its consumers - patients, doctors, nurses, insurance adjudicators, health inspectors, epidemiologists, and biostatisticians. But the drive towards electronic information in health care is not rooted merely in efficiency; more recently, significant emphasis has been placed on patient safety issues raised by the Institute of Medicine\u27s ( IOM ) year 2001 quality report on the subject. It is believed that the deficiencies indicated in that report can be substantially overcome by the use of IT in health care. However, to make this transition successful and complete, all aspects of health care delivery, information management, and business transactions, have to be logically migrated into the electronic world. This includes the function and use of the signature. The use of signatures in business contexts has traditionally provided two functions of legal significance: 1) evidence that can attribute documents to a particular party, and 2) indication of assent and intent that the documents have legal effect. In the recent decades, state and federal statutes have substantiated these functional attributes to digital or electronic signatures. Many of these statutes derive from model codes, such as the Uniform Electronic Transactions Act ( UETA ), that attempt to standardize use and technology surrounding electronic signatures. Subsequent sections will attempt to identify gaps in the standards which prevent true transaction portability. Lack of portability defeats one of the fundamental goals of health care IT solutions - improved efficiency. The discussion will end with a proposal for a uniform federal statutory scheme for standardized electronic signatures for health care
Sub-Fourier characteristics of a -kicked rotor resonance
We experimentally investigate the sub-Fourier behavior of a -kicked
rotor resonance by performing a measurement of the fidelity or overlap of a
Bose-Einstein condensate (BEC) exposed to a periodically pulsed standing wave.
The temporal width of the fidelity resonance peak centered at the Talbot time
and zero initial momentum exhibits an inverse cube pulse number ()
dependent scaling compared to a dependence for the mean energy width
at the same resonance. A theoretical analysis shows that for an accelerating
potential the width of the resonance in acceleration space depends on
, a property which we also verify experimentally. Such a sub-Fourier
effect could be useful for high precision gravity measurements.Comment: 4 pages, 5 figure
Implications of surface noise for the motional coherence of trapped ions
Electric noise from metallic surfaces is a major obstacle towards quantum
applications with trapped ions due to motional heating of the ions. Here, we
discuss how the same noise source can also lead to pure dephasing of motional
quantum states. The mechanism is particularly relevant at small ion-surface
distances, thus imposing a new constraint on trap miniaturization. By means of
a free induction decay experiment, we measure the dephasing time of the motion
of a single ion trapped 50~m above a Cu-Al surface. From the dephasing
times we extract the integrated noise below the secular frequency of the ion.
We find that none of the most commonly discussed surface noise models for ion
traps describes both, the observed heating as well as the measured dephasing,
satisfactorily. Thus, our measurements provide a benchmark for future models
for the electric noise emitted by metallic surfaces.Comment: (5 pages, 4 figures
Studies on Structural Defects on 60Co Irradiated Multi Walled Carbon Nanotubes.
AbstractAn attempt is made to study the effects of gamma irradiation on multi walled carbon nanotubes (MWCNTs) with a specific focus on surface modification, structural changes and identification of irradiation generated defects on their surface. The as-received MWCNTs were chemically treated in order to attach required functional group on the surface and to remove traces of metallic impurities. The MWCNTs were then gamma irradiated at 25, 50, 75 and 100 kGy doses. Micro Raman analysis was performed on irradiated MWCNTs to estimate the irradiation induced defects on their surface, which revealed that the number of defects increased with dose. XRD analysis was also performed to observe the same and it was revealed that the MWCNTs were subjected to micro-straining. The selective area electron diffraction pattern revealed that traces of amorphous carbon were formed after irradiation. Various defects such as bending, variation of internal and external diameter, wall damages formed on the MWCNTs was verified using TEM. It is concluded that subjecting MWCNTs to irradiation sources has produced structural changes and defects on their surface which can influence the properties of nanocomposites
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