1,559 research outputs found
Equilibrium vortex formation in ultrarapidly rotating two-component Bose-Einstein condensates
Equilibrium vortex formation in rotating binary Bose gases with a rotating
frequency higher than the harmonic trapping frequency is investigated
theoretically. We consider the system being evaporatively cooled to form
condensates and a combined numerical scheme is applied to ensure the binary
system being in an authentic equilibrium state. To keep the system stable
against the large centrifugal force of ultrafast rotation, a quartic trapping
potential is added to the existing harmonic part. Using the Thomas-Fermi
approximation, a critical rotating frequency \Omega_c is derived, which
characterizes the structure with or without a central density hole. Vortex
structures are studied in detail with rotation frequency both above and below
?\Omega_c and with respect to the miscible, symmetrically separated, and
asymmetrically separated phases in their nonrotating ground-state counterparts.Comment: 7 pages, 7 figure
Transcritical flow of a stratified fluid over topography: analysis of the forced Gardner equation
Transcritical flow of a stratified fluid past a broad localised topographic
obstacle is studied analytically in the framework of the forced extended
Korteweg--de Vries (eKdV), or Gardner, equation. We consider both possible
signs for the cubic nonlinear term in the Gardner equation corresponding to
different fluid density stratification profiles. We identify the range of the
input parameters: the oncoming flow speed (the Froude number) and the
topographic amplitude, for which the obstacle supports a stationary localised
hydraulic transition from the subcritical flow upstream to the supercritical
flow downstream. Such a localised transcritical flow is resolved back into the
equilibrium flow state away from the obstacle with the aid of unsteady coherent
nonlinear wave structures propagating upstream and downstream. Along with the
regular, cnoidal undular bores occurring in the analogous problem for the
single-layer flow modeled by the forced KdV equation, the transcritical
internal wave flows support a diverse family of upstream and downstream wave
structures, including solibores, rarefaction waves, reversed and trigonometric
undular bores, which we describe using the recent development of the nonlinear
modulation theory for the (unforced) Gardner equation. The predictions of the
developed analytic construction are confirmed by direct numerical simulations
of the forced Gardner equation for a broad range of input parameters.Comment: 34 pages, 24 figure
Single ICCII Sinusoidal Oscillators Employing Grounded Capacitors
Two inverting second-generation current conveyors (ICCII) based sinusoidal oscillators are presented. The first sinusoidal oscillator is composed of one ICCII, two grounded capacitors and two resistors. The oscillation condition and oscillation frequency can be orthogonally controllable. The second sinusoidal oscillator is composed of one ICCII, two grounded capacitors and three resistors. The oscillation condition and oscillation frequency can be independently controllable through different resistors
Bending-wave Instability of a Vortex Ring in a Trapped Bose-Einstein Condensate
Based on a velocity formula derived by matched asymptotic expansion, we
investigate the dynamics of a circular vortex ring in an axisymmetric
Bose-Einstein condensate in the Thomas-Fermi limit. The trajectory for an
axisymmetrically placed and oriented vortex ring is entirely determined,
revealing that the vortex ring generally precesses in condensate. The linear
instability due to bending waves is investigated both numerically and
analytically. General stability boundaries for various perturbed wavenumbers
are computed. In particular, the excitation spectrum and the absolutely stable
region for the static ring are analytically determined.Comment: 4 pages, 4 figure
Stationary wave patterns generated by an impurity moving with supersonic velocity through a Bose-Einstein condensate
Formation of stationary 3D wave patterns generated by a small point-like
impurity moving through a Bose-Einstein condensate with supersonic velocity is
studied. Asymptotic formulae for a stationary far-field density distribution
are obtained. Comparison with three-dimensional numerical simulations
demonstrates that these formulae are accurate enough already at distances from
the obstacle equal to a few wavelengths.Comment: 7 pages, 3 figure
Performance Evaluation of a Database of Repetitive Elements in Complete Genomes
[[abstract]]The analysis of repetitive elements reveals repetitive elements in our genome may have been very important in the evolutionary genomics. In this work, we propose approaches to improve the performance of the repetitive elements in a database, namely Repetitive Sequence Database (RSDB). There are hundreds of millions of repetitive elements in RSDB. Performance evaluation and tuning are critical for us to manage such a large database. Not only does this study have a lot of performance improvements on centralized RSDB, but also this study provides a comparison of performance between centralized RSDB and distributed RSDB. From the experimental results, we find the improvements proposed speed up our RSDB very much
Mining putative Regulatory Elements in promoter Regions of Saccharomyces cerevisiae
[[abstract]]The availability of genome-wide gene expression data provides a unique set of genes from which
we can decipher the mechanisms underlying the common transcriptional response. Transcription factors, which
can bind to specific DNA sites, cooperatively regulate the transcription of genes. This study attempts to mine
putative binding sites to investigate how combinations of the sites predicted from known sites and overrepresented
repetitive elements are distributed in the promoter regions of groups of functionally related genes.
The over-represented repetitive elements appearing in the associations are possible transcription factor binding
sites. The deduced association rules would facilitate to predict putative regulatory elements and to identify genes
which are potentially co-regulated by the putative regulatory elements. Our proposed approach is applied to
Saccharomyces cerevisiae and the promoter regions of yeast ORFs
Computing motif correlations in proteins
[[abstract]]Protein motifs, which are specific regions and conserved regions, are found by comparing multiple protein sequences. These conserved regions in general play an important role in protein functions and protein folds, for example, for their binding properties or enzymatic activities. The aim here is to find the existence correlations of protein motifs. The knowledge of protein motif/domain sharing should be important in shedding new light on the biologic functions of proteins and offering a basis in analyzing the evolution in the human genome or other genomes. The protein sequences used here are obtained from the PIR-NREF database and the protein motifs are retrieved from the PROSITE database. We apply data mining approach to discover the occurrence correlations of motif in protein sequences. The correlation of motifs mined can be used in evolution analyses and protein structure prediction. We discuss the latter, i.e., protein structure prediction in this study. The correlations mined are stored and maintained in a database system. The database is now available at http://bioinfo.csie.ncu.edu.tw/ProMotif/. Copyright 2003 Wiley Periodicals, Inc. J Comput Chem 24: 2032-2043, 200
Identifying the combination of genetic factors that determine susceptibility to cervical cancer
[[abstract]]Cervical cancer is common among women all over the world. Although infection with high-risk types of human papillomavirus (HPV) has been identified as the primary cause of cervical cancer, only some of those infected go on to develop cervical cancer. Obviously, the progression from HPV infection to cancer involves other environmental and host factors. Recent populationbased twin and family studies have demonstrated the importance of the hereditary component of cervical cancer, associated with genetic susceptibility. Consequently, single-nucleotide polymorphism
(SNP) markers and microsatellites should be considered genetic factors for determining what combinations of genetic factors are involved in precancerous changes to cervical cancer. This study employs a Bayesian network and four different decision tree algorithms, and compares the performance of these learning algorithms. The results of this study raise the possibility of investigations that could identify combinations of genetic factors, such as SNPs and microsatellites, that influence the risk associated with common complex multifactorial diseases, such as cervical cancer. The web site associated with this study is http://140.115.155.8/FactorAnalysis/
- …