2,640 research outputs found
Management system requirements for wireless systems beyond 3G
This paper presents a comprehensive description of various management system requirements for systems beyond 3G, which have been identified as a result of the Software Based Systems activities within the Mobile VCE Core 2 program. Specific requirements for systems beyond 3G are discussed and potential technologies to address them proposed. The analysis has been carried out from network, service and security viewpoints
Fringe spacing and phase of interfering matter waves
We experimentally investigate the outcoupling of atoms from Bose-Einstein
condensates using two radio-frequency (rf) fields in the presence of gravity.
We show that the fringe separation in the resulting interference pattern
derives entirely from the energy difference between the two rf fields and not
the gravitational potential difference. We subsequently demonstrate how the
phase and polarisation of the rf radiation directly control the phase of the
matter wave interference and provide a semi-classical interpretation of the
results.Comment: 4 pages, 3 figure
The ELAIS Deep X-ray Survey
We present initial follow-up results of the ELAIS Deep X-ray Survey which is
being undertaken with the Chandra and XMM-Newton Observatories. 235 X-ray
sources are detected in our two 75 ks ACIS-I observations in the well-studied
ELAIS N1 and N2 areas. 90% of the X-ray sources are identified optically to
R=26 with a median magnitude of R=24. We show that objects which are unresolved
optically (i.e. quasars) follow a correlation between their optical and X-ray
fluxes, whereas galaxies do not. We also find that the quasars with fainter
optical counterparts have harder X-ray spectra, consistent with absorption at
both wavebands. Initial spectroscopic follow-up has revealed a large fraction
of high-luminosity Type 2 quasars. The prospects for studying the evolution of
the host galaxies of X-ray selected Type 2 AGN are considered.Comment: 9 pages, 5 figures, To appear in Proceedings of XXI Moriond
Conference: "Galaxy Clusters and the High Redshift Universe Observed in
X-rays", edited by D. Neumann, F.Durret, & J. Tran Thanh Va
The ELAIS deep X-ray survey - I. Chandra source catalogue and first results
We present an analysis of two deep (75 ks) Chandra observations of the European Large Area Infrared Space Observatory (ISO) Survey (ELAIS) fields N1 and N2 as the first results from the ELAIS deep X-ray survey. This survey is being conducted in well-studied regions with extensive multiwavelength coverage. Here we present the Chandra source catalogues along with an analysis of source counts, hardness ratios and optical classifications. A total of 233 X-ray point sources are detected in addition to two soft extended sources, which are found to be associated with galaxy clusters. An overdensity of sources is found in N1 with 30 per cent more sources than N2, which we attribute to large-scale structure. A similar variance is seen between other deep Chandra surveys. The source count statistics reveal an increasing fraction of hard sources at fainter fluxes. The number of galaxy-like counterparts also increases dramatically towards fainter fluxes, consistent with the emergence of a large population of obscured sources
How many species of fossil arachnids are there?
The species-level diversity of fossil Chelicerata is summarized for each order. 1952 valid species of fossil\ud
chelicerates are currently recognized, of which 1593 are arachnids. In order of abundance they are: Araneae (979 fossil\ud
species), Actinotrichida (283), Eurypterida (241), Scorpiones (111), Xiphosura (96), Trigonotarbida (71), Pseudoscorpiones\ud
(38), Phalangiotarbida (30), Opiliones (25), Ricinulei (15), and Anactinotrichida (11). Other groups are represented by ten\ud
fossil species or fewer. Based on published descriptions, spiders thus appear to dominate the fossil arachnid species\ud
assemblage, making up a greater proportion of paleodiversity than their Recent diversity would predict. Scorpions are also\ud
overrepresented, particularly in the Paleozoic, compared to their modern diversity. By contrast, groups like mites,\ud
harvestmen, pseudoscorpions and solifuges are noticeably under-represented as fossils when compared to modern patterns\ud
of diversity
Wetting of gradient fields: pathwise estimates
We consider the wetting transition in the framework of an effective interface
model of gradient type, in dimension 2 and higher. We prove pathwise estimates
showing that the interface is localized in the whole thermodynamically-defined
partial wetting regime considered in earlier works. Moreover, we study how the
interface delocalizes as the wetting transition is approached. Our main tool is
reflection positivity in the form of the chessboard estimate.Comment: Some typos removed after proofreading. Version to be published in
PTR
Number counts and clustering properties of bright Distant Red Galaxies in the UKIDSS Ultra Deep Survey Early Data Release
We describe the number counts and spatial distribution of 239 Distant Red
Galaxies (DRGs), selected from the Early Data Release of the UKIDSS Ultra Deep
Survey. The DRGs are identified by their very red infrared colours with
(J-K)AB>1.3, selected over 0.62 sq degree to a 90% completeness limit of
KAB~20.7. This is the first time a large sample of bright DRGs has been studied
within a contiguous area, and we provide the first measurements of their number
counts and clustering. The population shows strong angular clustering,
intermediate between those of K-selected field galaxies and
optical/infrared-selected Extremely Red Galaxies. Adopting the redshift
distributions determined from other recent studies, we infer a high correlation
length of r0~11 h-1 Mpc. Such strong clustering could imply that our galaxies
are hosted by very massive dark matter halos, consistent with the progenitors
of present-day L>L* elliptical galaxies.Comment: 5 pages, 4 figures, revised version accepted to MNRAS.
Higher-resolution figures available from the authors on reques
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