7,421 research outputs found
Matter Representations and Gauge Symmetry Breaking via Compactified Space
We study dynamical gauge symmetry breaking via compactified space in the
framework of SU(N) gauge theory in M^{d-1}\times S^1 (d=4,5,6) space-time. In
particular, we study in detail the gauge symmetry breaking in SU(2) and SU(3)
gauge theories when the models contain both fundamental and adjoint matter. As
a result, we find that any pattern of gauge symmetry breaking can be realized
by selecting an appropriate set of numbers (Nf,Nad) in these cases. This is
achieved without tuning boundary conditions of the matter fields. As a
by-product, in some cases we obtain an effective potential which has no
curvature at the minimum, thus leading to massless Higgs scalars, irrespective
of the size of the compactified space.Comment: PTPTeX, 15 pages, 8 Postscript figures;typos corrected, references
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Nuclear Activity and the Dynamics of Elliptical Galaxies
This paper looks for any correlation between the internal dynamics of
elliptical galaxies and the relatively mild nuclear activity found in many such
systems. We show that there is such a relation in the sense that the active
ellipticals tend to be significantly less rotationally supported than their
inactive cousins. The correlation can partly be related to the galaxies'
luminosities: the brightest galaxies tend to be more active and less
rotationally supported. However, even at lower luminosities the active and
inactive galaxies seem to have systematically different dynamics. This
variation suggests that there are significant large-scale structural
differences between active and inactive elliptical galaxies, and hence that the
existence of both types of system cannot just be the result of random sporadic
nuclear activity.Comment: 5 pages, 3 figures. Accepted for publication in MNRA
Nearly Massless Electrons in the Silicon Interface with a Metal Film
We demonstrate the realization of nearly massless electrons in the most
widely used device material, silicon, at the interface with a metal film. Using
angle-resolved photoemission, we found that the surface band of a monolayer
lead film drives a hole band of the Si inversion layer formed at the interface
with the film to have nearly linear dispersion with an effective mass about 20
times lighter than bulk Si and comparable to graphene. The reduction of mass
can be accounted for by repulsive interaction between neighboring bands of the
metal film and Si substrate. Our result suggests a promising way to take
advantage of massless carriers in silicon-based thin-film devices, which can
also be applied for various other semiconductor devices.Comment: 4 pages, 4 figures, accepted for publication in Physical Review
Letter
Monitoring of waterways for evidence of faecal contamination from biosolids using DNA techniques.
Increased nutrient levels in inland waterways have led to algal blooms and eutrophication in many agricultural regions. To ensure fertiliser inputs are managed more effectively, the source of contamination needs to be tracked and identified. Point sources could include inorganic fertilisers, livestock excreta, or more recently biosolids. The presence of faecal indicator microorganisms has been widely used to identify the presence of faeces, however, these methods cannot distinguish between human and animals samples. This study investigated PCR amplification as a molecular method to distinguish biosolids from livestock faeces of biosolids, cattle, sheep, poultry and kangaroo. This was achieved using published priming sequences and restriction site profiling of amplified DNA across the 16S rRNA gene of anaerobic gastrointestinal bacteria Bacteroides spp and Bifidobacteria spp. Preliminary investigation showed that of the three Bacteroides spp primer pairs investigated, two were useful for cow faecal material; though at lower annealing temperatures were also applicable to biosolids and sheep faecal material. The third primer pair was specific only for biosolids. All three primer pairs were unable to PCR-amplify Bacteroides spp sequences in faecal material of kangaroo. Of the three Bifidobacteria spp primer pairs, one was useful for sheep faecal material; though at lower annealing temperature was also applicable to biosolids and cow and kangaroo faecal material. The Bifidobacterium angulatum specific primer pair enabled the PCR detection of anaerobes only in biosolids and faecal material of kangaroo. The third, a Bifidobacterium catenulatum specific primer pair was suitable for faecal material of cow and at lower annealing temperatures was also applicable to the sample from sheep. Varying degrees of success were observed in faecal material from other animals. Generally, biosolids tested positive for Bacteroides and Bfidobacteria with all primers except for those specific for B. angulatum. For some primer sets, PCR amplification alone could not differentiate biosolids from other faecal samples. The serial dilution of water contaminated by a range of livestock excreta and biosolids is being examined further to enable the sensitivity of this method to be applied in the field
Transition metal amides and imides as precursors to metal nitride and carbonitride thin films via chemical vapor deposition
Transition metal nitrides are known for their hardness and semiconducting properties. These properties have lead to their use as barrier layers, which prevent the diffusion of copper into silicon in gate electrodes. Chemical vapour deposition (CVD) and atomic layer deposition (ALD) of transition metal nitrides and carbonitrides at low temperatures (200-600 °C), using imido and amido complexes as precursors, has been reported. We have been investigating the synthesis of a range of tungsten imido and amido complexes, and zirconium cyclopentadienyl and amido compounds via transamination and metathesis reactions. We have investigated the potential of the compounds synthesised as single-source precursors to their respective metal nitrides via CVD, involving studies at low pressure (LPCVD) and using an aerosol-assisted (AACVD) technique
A Survey for Planetary Nebulae in M31 Globular Clusters
We report the results of an [O III] 5007 spectroscopic survey for planetary
nebulae (PNe) located within the star clusters of M31. By examining R ~ 5000
spectra taken with the WIYN+Hydra spectrograph, we identify 3 PN candidates in
a sample of 274 likely globular clusters, 2 candidates in objects which may be
globular clusters, and 5 candidates in a set of 85 younger systems. The
possible PNe are all faint, between ~2.5 and ~6.8 mag down the PN luminosity
function, and, partly as a consequence of our selection criteria, have high
excitation, with [O III] 5007 to H-beta ratios ranging from 2 to ~12. We
discuss the individual candidates, their likelihood of cluster membership, and
the possibility that they were formed via binary interactions within the
clusters. Our data are consistent with the suggestion that PN formation within
globular clusters correlates with binary encounter frequency, though, due to
the small numbers and large uncertainties in the candidate list, this study
does not provide sufficient evidence to confirm the hypothesis.Comment: Accepted for publication in the Astrophysical Journal. 54 pages,
including 9 figures and 4 table
NASA Provides the Capability to Deliver Near Real-Time JPSS Data to Users in Order to Monitor Time-Sensitive Applications Such as Wildfires, Floods, Volcanic Eruptions, Tropical Cyclones and Extreme Weather Events
NASA's Land, Atmosphere Near real-time Capability for EOS (Earth Observing System) (LANCE https://earthdata.nasa.gov/lance) serves near real time (NRT) data to monitor time sensitive applications such as monitoring wildfires, floods, volcanic eruptions, tropical cyclones and extreme weather events. It currently serves data and imagery from the Visible Infrared Imager Radiometer Suite (VIIRS) and Ozone Mapping and Profiler Suite (OMPS) S NPP (Suomi National Polar-orbiting Partnership) instruments and is in the process of integrating continuity data products from VIIRS and OMPS onboard the Joint Polar Satellite System (JPSS), via the JPSS data Hub, to continue to meet the needs of agencies, scientists and members of the general public. NASA's Earth Science Division (ESD) sponsored the EOSDIS development of LANCE in 2009 to provide a central point of access to high quality NRT data products and imagery for applications users. LANCE makes data available to the public within 3 hours of satellite observation and imagery within 4-5 hours of satellite observation. Full resolution browse imagery from LANCE are provided through the Global Imagery Browse Services (GIBS) which also fuels NASA's Worldview tool so that users can interactively browse near real time data. This data supports time critical applications and allows users to view current natural hazards and events and animate the imagery over time
Cold Dark Matter with MOND Scaling
We provide a holographic dual description of Milgrom's scaling associated
with galactic rotation curves. Our argument is based on the recent entropic
reinterpretation of Newton's laws of motion. We propose a duality between cold
dark matter and modified Newtonian dynamics (MOND). We introduce the concept of
MONDian dark matter, and discuss some of its phenomenological implications. At
cluster as well as cosmological scales, the MONDian dark matter would behave as
cold dark matter, but at the galactic scale, the MONDian dark matter would act
as MOND.Comment: 5 pages, v3: version to appear in PLB with the title changed and more
discussion
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