377 research outputs found
Preliminary Multivariate Comparison of Coral Assemblages on Carbonate Banks in the Western Gulf of Mexico
Hermatypic corals flourished on reefs in the Gulf of Mexico (GOM) in the late Pleistocene and early Holocene. Today, many of these relict reefs are mesophotic banks that have unique coral assemblages and provide critical habitat; however, the South Texas Banks (STB) lack quantitative surveys. Therefore, we used a remotely operated vehicle to conduct quantitative surveys of 5 banks: Baker, Aransas, Dream, Blackfish Ridge, and Harte. Coral communities, based on estimated coral densities (colonies/m2), significantly differed among banks for terraces, slopes, and overall (combined terrace and slope) communities for most banks examined. Within banks, terrace and slope communities significantly differed for all banks except Harte. Sea whips were the most abundant group on slopes and terraces of most banks and frequently contributed \u3e50% to community similarities and dissimilarities, whereas sea fans and Antipathes frequently contributed \u3e20%. Total coral abundance was twice as high and sea fans were 7 times more abundant on terraces than slopes. Among—bank differences in coral communities were highly correlated to geographic and geomorphic features, especially to bank area, rugosity, longitude, and number of site components. The drivers of these differences, their effects on ecosystem diversity and function, and the connectivity pathways within and among STB and other GOM banks require further investigation. Nevertheless, the observed diversity in community structure within and among banks should be considered in the development of monitoring, conservation, and management plans of these critical habitats
Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment
Socially Disorganized Rural Communities
The article talks about the social disorganization of rural communities in the U.S. It is stated that family farming has been on the decline for decades, with the numbers of farmers dropping by 16 million since 1950 and farms decreasing by over 4 million during the past century. It is inferred that a part of a community\u27s history and way of life are being forfeited when local business are closing. According to the author, the theory of social disorganization emphasizes social integration and stability as necessary conditions for community. It offers some of the disadvantages of disorganized communities, such as the lack of collective efficacy
Elliptic Curves over Real Quadratic Fields are Modular
We prove that all elliptic curves defined over real quadratic fields are
modular.Comment: 38 pages. Magma scripts available as ancillary files with this arXiv
versio
Lowering the radioactivity of the photomultiplier tubes for the XENON1T dark matter experiment
The low-background, VUV-sensitive 3-inch diameter photomultiplier tube R11410
has been developed by Hamamatsu for dark matter direct detection experiments
using liquid xenon as the target material. We present the results from the
joint effort between the XENON collaboration and the Hamamatsu company to
produce a highly radio-pure photosensor (version R11410-21) for the XENON1T
dark matter experiment. After introducing the photosensor and its components,
we show the methods and results of the radioactive contamination measurements
of the individual materials employed in the photomultiplier production. We then
discuss the adopted strategies to reduce the radioactivity of the various PMT
versions. Finally, we detail the results from screening 216 tubes with
ultra-low background germanium detectors, as well as their implications for the
expected electronic and nuclear recoil background of the XENON1T experiment.Comment: 10 pages, 5 figure
A Review of NEST Models, and Their Application to Improvement of Particle Identification in Liquid Xenon Experiments
Liquid xenon is a leader in rare-event physics searches. Accurate modeling of
charge and light production is key for simulating signals and backgrounds in
this medium. The signal- and background-production models in the Noble Element
Simulation Technique (NEST) are presented. NEST is a simulation toolkit based
on experimental data, fit using simple, empirical formulae for the average
charge and light yields and their variations. NEST also simulates the final
scintillation pulses and exhibits the correct energy resolution as a function
of the particle type, the energy, and the electric fields. After vetting of
NEST against raw data, with several specific examples pulled from XENON,
ZEPLIN, LUX/LZ, and PandaX, we interpolate and extrapolate its models to draw
new conclusions on the properties of future detectors (e.g., XLZD's), in terms
of the best possible discrimination of electron(ic) recoil backgrounds from a
potential nuclear recoil signal, especially WIMP dark matter. We discover that
the oft-quoted value of 99.5% discrimination is overly conservative,
demonstrating that another order of magnitude improvement (99.95%
discrimination) can be achieved with a high photon detection efficiency (g1 ~
15-20%) at reasonably achievable drift fields of 200-350 V/cm.Comment: 24 Pages, 6 Tables, 15 Figures, and 15 Equation
Crime as risk taking
Engagement in criminal activity may be viewed as risk-taking behaviour as it has both benefits and drawbacks that are probabilistic. In two studies, we examined how individuals' risk perceptions can inform our understanding of their intentions to engage in criminal activity. Study 1 measured youths' perceptions of the value and probability of the benefits and drawbacks of engaging in three common crimes (i.e. shoplifting, forgery, and buying illegal drugs), and examined how well these perceptions predicted youths' forecasted engagement in these crimes, controlling for their past engagement. We found that intentions to engage in criminal activity were best predicted by the perceived value of the benefits that may be obtained, irrespective of their probabilities or the drawbacks that may also be incurred. Study 2 specified the benefit and drawback that youth thought about and examined another crime (i.e. drinking and driving). The findings of Study 1 were replicated under these conditions. The present research supports a limited rationality perspective on criminal intentions, and can have implications for crime prevention/intervention strategies
Search for Event Rate Modulation in XENON100 Electronic Recoil Data
We have searched for periodic variations of the electronic recoil event rate
in the (2-6) keV energy range recorded between February 2011 and March 2012
with the XENON100 detector, adding up to 224.6 live days in total. Following a
detailed study to establish the stability of the detector and its background
contributions during this run, we performed an un-binned profile likelihood
analysis to identify any periodicity up to 500 days. We find a global
significance of less than 1 sigma for all periods suggesting no statistically
significant modulation in the data. While the local significance for an annual
modulation is 2.8 sigma, the analysis of a multiple-scatter control sample and
the phase of the modulation disfavor a dark matter interpretation. The
DAMA/LIBRA annual modulation interpreted as a dark matter signature with
axial-vector coupling of WIMPs to electrons is excluded at 4.8 sigma.Comment: 6 pages, 4 figure
An Overview of Marine Biodiversity in United States Waters
Marine biodiversity of the United States (U.S.) is extensively documented, but data assembled by the United States National Committee for the Census of Marine Life demonstrate that even the most complete taxonomic inventories are based on records scattered in space and time. The best-known taxa are those of commercial importance. Body size is directly correlated with knowledge of a species, and knowledge also diminishes with distance from shore and depth. Measures of biodiversity other than species diversity, such as ecosystem and genetic diversity, are poorly documented. Threats to marine biodiversity in the U.S. are the same as those for most of the world: overexploitation of living resources; reduced water quality; coastal development; shipping; invasive species; rising temperature and concentrations of carbon dioxide in the surface ocean, and other changes that may be consequences of global change, including shifting currents; increased number and size of hypoxic or anoxic areas; and increased number and duration of harmful algal blooms. More information must be obtained through field and laboratory research and monitoring that involve innovative sampling techniques (such as genetics and acoustics), but data that already exist must be made accessible. And all data must have a temporal component so trends can be identified. As data are compiled, techniques must be developed to make certain that scales are compatible, to combine and reconcile data collected for various purposes with disparate gear, and to automate taxonomic changes. Information on biotic and abiotic elements of the environment must be interactively linked. Impediments to assembling existing data and collecting new data on marine biodiversity include logistical problems as well as shortages in finances and taxonomic expertise
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