40,594 research outputs found
Dark matter and dark gauge fields
Following the unexpected theoretical discovery of a mass dimension one
fermionic quantum field of spin one half, we now present first results on two
_local_ versions. The Dirac and Majorana fields of the standard model of
particle physics are supplemented by their natural counterparts in the dark
matter sector. The possibility that a mass dimension transmuting symmetry may
underlie a new standard model of particle physics is briefly suggested.Comment: This manuscript combines a plenary talk (by DVA) and an invited talk
(by DS) at "Dark 2007 - Sixth International Heidelberg Conference on Dark
Matter in Astro and Particle Physics (Sydney, Australia, 24th-28th September
2007)." 11 pages. v2: minor typos correcte
Comparison of predictive scores of symptomatic intracerebral haemorrhage after stroke thrombolysis in a single centre
Peer reviewedPublisher PD
Enrichment Procedures for Soft Clusters: A Statistical Test and its Applications
Clusters, typically mined by modeling locality of attribute spaces, are often evaluated for their ability to demonstrate āenrichmentā of categorical features. A cluster enrichment procedure evaluates the membership of a cluster for significant representation in pre-defined categories of interest. While classical enrichment procedures assume a hard clustering deļ¬nition, in this paper we introduce a new statistical test that computes enrichments for soft clusters. We demonstrate an application of this test in reļ¬ning and evaluating soft clusters for classification of remotely sensed images
An Investigation, Using Standard Experimental Techniques, to Determine FLCs at Elevated Temperature for Aluminium Alloys
An experimental procedure has been developed for the determination of FLCs at elevated temperatures. The GOM ARGUS system was employed for measuring surface strain based on pre-applied grids (pattern), and limit strains were determined according to the ISO 12004-2:2008 standard. Forming limit curves (FLCs) have been determined for AA5754 under warm forming conditions in an isothermal environment. The tests were carried out at various temperatures up to 300oC and forming speeds ranging from 5 ā 300 mm s-1 . Results reveal the significant effect of both temperature and forming speed on FLCs of AA5754. Formability increases with increasing temperature above 200oC. Formability also increases with decreasing speed. The presented FLC results show that the best formability exists at low forming speed and the high temperature end of the warm forming range
An SMP Soft Classification Algorithm for Remote Sensing
This work introduces a symmetric multiprocessing (SMP) version of the continuous iterative
guided spectral class rejection (CIGSCR) algorithm, a semiautomated classiļ¬cation algorithm for remote
sensing (multispectral) images. The algorithm uses soft data clusters to produce a soft classiļ¬cation
containing inherently more information than a comparable hard classiļ¬cation at an increased computational
cost. Previous work suggests that similar algorithms achieve good parallel scalability, motivating the parallel
algorithm development work here. Experimental results of applying parallel CIGSCR to an image with
approximately 10^8 pixels and six bands demonstrate superlinear speedup. A soft two class classiļ¬cation is
generated in just over four minutes using 32 processors
High Redshift Standard Candles: Predicted Cosmological Constraints
We investigate whether future measurements of high redshift standard candles
(HzSCs) will be a powerful probe of dark energy, when compared to other types
of planned dark energy measurements. Active galactic nuclei and gamma ray
bursts have both been proposed as potential HzSC candidates. Due to their high
luminosity, they can be used to probe unexplored regions in the expansion
history of the universe. Information from these regions can help constrain the
properties of dark energy, and in particular, whether it varies over time.
We consider both linear and piecewise parameterizations of the dark energy
equation of state, , and assess the optimal redshift distribution a
high-redshift standard-candle survey could take to constrain these models.
The more general the form of the dark energy equation of state being
tested, the more useful high-redshift standard candles become. For a linear
parameterization of , HzSCs give only small improvements over planned
supernova and baryon acoustic oscillation measurements; a wide redshift range
with many low redshift points is optimal to constrain this linear model.
However to constrain a general, and thus potentially more informative, form of
, having many HzSCs can significantly improve limits on the nature of
dark energy.Comment: Accepted MNRAS, 27 Pages, 15 figures, matches published versio
Gamma-Ray Bursts observed by XMM-Newton
Analysis of observations with XMM-Newton have made a significant contribution
to the study of Gamma-ray Burst (GRB) X-ray afterglows. The effective area,
bandpass and resolution of the EPIC instrument permit the study of a wide
variety of spectral features. In particular, strong, time-dependent, soft X-ray
emission lines have been discovered in some bursts. The emission mechanism and
energy source for these lines pose major problems for the current generation of
GRB models. Other GRBs have intrinsic absorption, possibly related to the
environment around the progenitor, or possible iron emission lines similar to
those seen in GRBs observed with BeppoSAX. Further XMM-Newton observations of
GRBs discovered by the Swift satellite should help unlock the origin of the GRB
phenomenon over the next few years.Comment: To appear in proceedings of the "XMM-Newton EPIC Consortium meeting,
Palermo, 2003 October 14-16", published in Memorie della Societa Astronomica
Italian
Comparison of herbage yield, nutritive value and ensilability traits of three ryegrass species evaluated for the Irish Recommended List
peer-reviewedThis study examined 169 of the newest varieties of three ryegrass species, perennial (Lolium perenne L.), Italian (Lolium multiflorum Lam.) and hybrid (Lolium boucheanum Kunth), from Recommended List trials in Ireland. The traits examined were yield, dry matter concentration, three nutritive value traits (in vitro dry matter digestibility, water-soluble carbohydrate on a dry matter basis and crude protein concentration) and two ensilability traits (buffering capacity and water soluble carbohydrate concentration on an aqueous phase basis). Varietal monocultures of each species underwent a six cut combined simulated grazing and silage management in each of two years following sowing. Perennial ryegrass yielded less than both other species in one-year-old swards, but less than only Italian ryegrass in two-year-old swards, but generally had the higher in vitro dry matter digestibility and crude protein values. Italian ryegrass displayed the most favourable ensilability characteristics of the three species with perennial ryegrass less favourable and hybrid ryegrass intermediate. Overall, despite the high yields and favourable nutritive value and ensilability traits recorded, the general differences between the three ryegrass species studied were in line with industry expectations. These findings justify assessing the nutritive value and ensilability of ryegrass species, in addition to yield, to allow farmers select species that match farming enterprise requirements.We acknowledge the Department of Agriculture, Food and the Marine for funding provided through the Research Stimulus Fund (07 526
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