3,932 research outputs found
Mini-charged tau neutrinos?
Theoretically, the electric charge of the tau neutrino may be non-zero. The
experimental bound on the electric charge of the tau neutrino is many orders of
magnitude weaker than that for any other known neutrino. If the tau neutrino
does have a small electric charge, and its mass is greater than 1 MeV, then it
can annihilate sufficiently in the early Universe by electromagnetic
interactions to avoid conflict with the standard cosmology model. A novel
feature of this scenario is that there can be effectively less than three
neutrino species present during nucleosynthesis.Comment: 8 pages in LaTeX, 1 uuencoded figure file appended, PURD-TH-93-1
Unbroken versus broken mirror world: a tale of two vacua
If the Lagrangian of nature respects parity invariance then there are two
distinct possibilities: either parity is unbroken by the vacuum or it is
spontaneously broken. We examine the two simplest phenomenologically consistent
gauge models which have unbroken and spontaneously broken parity symmetries,
respectively. These two models have a Lagrangian of the same form, but a
different parameter range is chosen in the Higgs potential. They both predict
the existence of dark matter and can explain the MACHO events. However, the
models predict quite different neutrino physics. Although both have light
mirror (effectively sterile) neutrinos, the ordinary-mirror neutrino mixing
angles are unobservably tiny in the broken parity case. The minimal broken
parity model therefore cannot simultaneously explain the solar, atmospheric and
LSND data. By contrast, the unbroken parity version can explain all of the
neutrino anomalies. Furthermore, we argue that the unbroken case provides the
most natural explanation of the neutrino physics anomalies (irrespective of
whether evidence from the LSND experiment is included) because of its
characteristic maximal mixing prediction.Comment: About 15 pages, Late
Analysis of Gray Fox (Urocyon cinereoargenteus) Fur Harvests in Arkansas
An investigation was conducted on gray fox (Urocyon cinereoargenteus) fur harvest in Arkansas. Data were gathered from a mail survey of Arkansas trappers and from Arkansas Game and Fish Commission fur harvest records from 1939 to 1983. Analyses of these data demonstrated: 1) gray fox were abundant statewide with lower levels in the Delta region; 2) there was a need for fox trappers to keep better records on their trapping efforts, success and composition of catch, including sex and age data; 3) market price: harvest correlation was high (r = 0.956, p \u3c .001); 4) over the past 10 years, the Ozark Mountain region provided the greatest contribution to annual fox harvests, the Ouachita Mountain and Gulf Coastal Plain regions were similar to each other, but lower than the Ozarks, and the Delta region contributed the least, but with a generally stable harvest
JPL initiative on historically black colleges and universities
Executive order number 12320 of September 15, 1981, established a program designed to significantly increase the participation of historically black colleges and universities (HBCU's) in Federal programs. Because of its geographical remoteness and position as a contractor operated center, JPL had not participated in grant and training programs with the HBCU's. In recognition of JPL's responsibility to the national commitment on behalf of the historically black colleges and universities, an initiative with effective, achievable guidelines and early progress for a better and more productive interaction between JPL and the HBCU's is described. Numerous areas of interaction with the historically black colleges and universities have been identified and are being inplemented. They have two broad objectives: research interactions and faculty/student interactions. Plans and progress to date for each specific area are summarized
Building Artificial Reefs from Recycled Construction Materials: A Feasibility Study
Naturally occurring reefs are some of the worldâs most biologically diverse ecosystems formed by jagged rocks tucked slightly below sea level. In recent years global warming began to pose a major threat to many reef habitats. Most relevant is the increase in surface seawater temperatures that cause coral to bleach, taking away major food sources for larger marine species. Researchers have combated this by deploying artificial reefs in substitution for naturally formed limestone rock formations in order to promote the expansion of coastal habitats. This project specifically aims to utilize construction waste towards the production of artificial reefs, effectively upcycling waste from one of the worldâs largest waste-generating industries and providing proper habitat for marine organisms. Construction is one of the worldâs major contributors to waste and carbon production, so this project aims to find creative solutions to utilize material that would otherwise end up in landfills and contribute to global warning. Furthermore, the elements of an effective habitat must also be outlined in order to ensure that the end product serves its intended purpose. Material properties and previous designs will need to be referenced in order to ensure that the reef is both non-toxic and effective at providing shelter and nurturing coral growth. A suitable location will also need to be established in order to ensure that the reef is serving its intended purpose. A conceptual design will be developed as a result of the findings. Materials used in the fabrication of this design will include recycled cement, reused concrete base rock, and miscellaneous piping
Decreased Neuron Density and Increased Glia Density in the Ventromedial Prefrontal Cortex (Brodmann Area 25) in Williams Syndrome.
Williams Syndrome (WS) is a neurodevelopmental disorder caused by a deletion of 25â»28 genes on chromosome 7 and characterized by a specific behavioral phenotype, which includes hypersociability and anxiety. Here, we examined the density of neurons and glia in fourteen human brains in Brodmann area 25 (BA 25), in the ventromedial prefrontal cortex (vmPFC), using a postmortem sample of five adult and two infant WS brains and seven age-, sex- and hemisphere-matched typically developing control (TD) brains. We found decreased neuron density, which reached statistical significance in the supragranular layers, and increased glia density and glia to neuron ratio, which reached statistical significance in both supra- and infragranular layers. Combined with our previous findings in the amygdala, caudate nucleus and frontal pole (BA 10), these results in the vmPFC suggest that abnormalities in frontostriatal and frontoamygdala circuitry may contribute to the anxiety and atypical social behavior observed in WS
Dynamics of a nanowire superlattice in an ac electric field
With a one-band envelope function theory, we investigate the dynamics of a
finite nanowire superlattice driven by an ac electric field by solving
numerically the time-dependent Schroedinger equation. We find that for an ac
electric field resonant with two energy levels located in two different
minibands, the coherent dynamics in nanowire superlattices is much more complex
as compared to the standard two-level description. Depending on the energy
levels involved in the transitions, the coherent oscillations exhibit different
patterns. A signature of barrier-well inversion phenomenon in nanowire
superlattices is also obtained.Comment: 14 pages, 4 figure
- âŠ