24,594 research outputs found
Scattering Theory for Quantum Hall Anyons in a Saddle Point Potential
We study the theory of scattering of two anyons in the presence of a
quadratic saddle-point potential and a perpendicular magnetic field. The
scattering problem decouples in the centre-of-mass and the relative
coordinates. The scattering theory for the relative coordinate encodes the
effects of anyon statistics in the two-particle scattering. This is fully
characterized by two energy-dependent scattering phase shifts. We develop a
method to solve this scattering problem numerically, using a generalized lowest
Landau level approximation.Comment: 5 pages. Published version, with clarified presentatio
Tackling resistance: Emerging antimalarials and new parasite targets in the era of elimination [version 1; referees: 2 approved]
Malaria remains a significant contributor to global human mortality, and roughly half the worldâs population is at risk for infection with Plasmodium spp. parasites. Aggressive control measures have reduced the global prevalence of malaria significantly over the past decade. However, resistance to available antimalarials continues to spread, including resistance to the widely used artemisinin-based combination therapies. Novel antimalarial compounds and therapeutic targets are greatly needed. This review will briefly discuss several promising current antimalarial development projects, including artefenomel, ferroquine, cipargamin, SJ733, KAF156, MMV048, and tafenoquine. In addition, we describe recent large-scale genetic and resistance screens that have been instrumental in target discovery. Finally, we highlight new antimalarial targets, which include essential transporters and proteases. These emerging antimalarial compounds and therapeutic targets have the potential to overcome multi-drug resistance in ongoing efforts toward malaria elimination
A Luminous Companion to SGR 1806-20
We have obtained infrared spectra of the star suggested to be the counterpart
of the soft gamma-ray repeater (SGR) 1806-20. We found strong emission lines
similar to those seen in the spectra of the rare Luminous Blue Variables and
B[e] stars. A He I absorption line is also seen, from which we infer a spectral
type O9--B2. This classification, in combination with the minimum distance of
\simgt6 kpc inferred from its extinction, makes the star one of the most
luminous in the Galaxy. We infer that it is a companion to SGR 1806-20, and
suggest that the presence of a companion is somehow related to the SGR
phenomenon.Comment: 5 pages, AASTEX text+table and 2 PostScript figures (needs LaTeX
style files aaspptwo.sty, epsf.sty and rotate.sty). In case of problems,
contact [email protected]. Postscript file of complete article available
on request. (Replaced because first version had one wrong reference in it
Managing and Improving Upon Bandwidth Challenges in Computer Network
Managing the bandwidth of a computer network is always faced with great challenges. This research was
necessitated by the urgent need to manage the University network currently experiencing congestion in both the
local LAďż˝ and on the internet backhaul with a view to improving network performance and reduce the huge
recurrent on the WAďż˝ link. However, there exists various ways that have been deployed towards solving these
problems. In this paper we examined existing bandwidth management, effect of limited bandwidth on the
network performance and profound solutions of techniques that enhanced or improved the bandwidth efficiency.
Also, included in this research work are the studies of the effect of limited bandwidth on work load, type of
protocol used and the effect of network congestion on the quality of service of a Wide Area �etwork (WA�). By
comparison, from the modeling of the effect of work load and limited bandwidth on the throughput of a wide
area network based on experimental simulation and real time simulation scenarios, some observations were
made and recommendation of solutions were given from the analyzed results
The bloodstream differentiation - division of Trypanosoma brucei studied using mitochondrial markers
In the bloodstream of its mammalian host, the African trypanosome Trypanosoma brucei undergoes a life cycle stage differentiation from a long, slender form to a short, stumpy form. This involves three known major events: exit from a proliferative cell cycle, morphological change and mitochondrial biogenesis. Previously, models have been proposed accounting for these events (Matthews & Gull 1994a). Refinement of, and discrimination between, these models has been hindered by a lack of stage-regulated antigens useful as markers at the single-cell level. We have now evaluated a variety of cytological markers and applied them to investigate the coordination of phenotypic differentiation and cell cycle arrest. Our studies have focused on the differential expression of the mitochondrial enzyme dihydrolipoamide dehydrogenase relative to the differentiation-division of bloodstream trypanosomes. The results implicate a temporal order of events: commitment, division, phenotypic differentiation
Recent Experiments with Bose-Condensed Gases at JILA
We consider a binary mixture of two overlapping Bose-Einstein condensates in
two different hyperfine states of \Rb87 with nearly identical magnetic moments.
Such a system has been simply realized through application of radiofrequency
and microwave radiation which drives a two-photon transition between the two
states. The nearly identical magnetic moments afford a high degree of spatial
overlap, permitting a variety of new experiments. We discuss some of the
conditions under which the magnetic moments are identical, with particular
emphasis placed on the requirements for a time-averaged orbiting potential
(TOP) magnetic trap.Comment: 9 pages, 5 figures; corrected post-publication editio
Orbits and origins of the young stars in the central parsec of the galaxy
We present new proper motions from the 10 m Keck telescopes for a puzzling population of massive, young stars located within a parsec of the supermassive black hole at the Galactic Center. Our proper motion measurements have uncertainties of only 0.07 mas yr^(â1) (3 km s^(â1) ), which is âł7 times better than previous proper motion measurements for these stars, and enables us to measure accelerations as low as 0.2 mas yr^(â2) (7 km s^(â1) yr^(â1) ). These measurements, along with stellar line-of-sight velocities from the literature, constrain the true orbit of each individual star and allow us to directly test the hypothesis that the massive stars reside in two stellar disks as has been previously proposed. Analysis of the stellar orbits reveals only one disk of young stars using a method that is capable of detecting disks containing at least 7 stars. The detected disk contains 50% (38 of 73) of the young stars, is inclined by ~115° from the plane of the sky, and is oriented at a position angle of âź100° East of North. The on-disk and off-disk populations have similar K-band luminosity functions and radial distributions that decrease at larger radii as â r^(â2). The disk has an out-of-the-disk velocity dispersion of 28Âą6 km s^(â1) , which corresponds to a half-opening angle of 7°¹2° , and several candidate disk members have eccentricities greater than 0.2. Our findings suggest that the young stars may have formed in situ but in a more complex geometry than a simple thin circular disk
Testing for periodicities in near-IR light curves of Sgr A
We present the results of near-infrared (2 Îźm) monitoring of Sgr A*-IR with 1 minute time sampling using laser guide star adaptive optics (LGS AO) system at the Keck II
telescope. Sgr A*-IR was observed continuously for up to three hours on each of seven nights, between 2006 May and 2007 August. Sgr A*-IR is detected at all times and is continuously variable. These observations allow us to investigate Nyquist sampled periods ranging from
about 2 minutes to an hour. Of particular interest are periods of ~20 min, which corresponds to a quasi-periodic (QPO) signal claimed based upon previous near-infrared observations and interpreted as the orbit of a âhot spotâ at or near the last stable orbit of a spinning black hole.
We investigate these claims by comparing periodograms of the light curves with models for red noise and find no significant deviations that would indicate QPO activity at any time scale probed in the study. We find that the variability of Sgr A* is consistent with a model based on
correlated noise with a power spectrum having a frequency dependence of ~ f^(2.5), consistent with that observed in AGNs. Furthermore, the periodograms show power down to the minimum sampling time of 2 min, well below the period of the last stable orbit of a maximally spinning black hole, indicating that the Sgr A*-IR light curves observed in this study is unlikely to be from the Keplerian motion of a single âhot spotâ of orbiting plasma
- âŚ