96,777 research outputs found
GIS Characterization of Beaver Watershed
Beaver Reservoir watershed is located in Northwest Arkansas including portions of Madison, Washington, Benton, Carroll, Franklin and Crawford counties. This watershed is important to the Northwest Arkansas region because it supplies most of the drinking water for the major towns and cities, and several rural water systems. The watershed consists of 308,971 ha with elevations ranging from approximately 341 m to 731 m above mean sea level. It includes the Springfield Plateau and the Boston Mountains provinces within the Ozark Plateau physiographic region. There are approximately 581 km of streams, 532 km of shore line, and 3712 km of roads in the watershed most of which are city streets and rural roads. The soils in the watershed vary extensively and are quite complex due to the differences in parent material, topography and time. Most parent material of the soils in the Springfield Plateau is limestone, whereas in the Boston Mountains the dominant parent material is sandstone and shale. The differences in soils have led to the differences in landuse and land cover. The near surface geology in the watershed is also divided by physiographic provinces. Most of the Springfield Plateau surface geology is limestone, whereas the Boston Mountains are primarily sandstone and shale. Spatial details of the streams, roads, soils and geology attributes in the watershed are presented in this report. The GIS database and characterization of the watershed offers an excellent beginning to future research and modeling of various water quality parameters in this and other watersheds
Another Look at Confidence Intervals: Proposal for a More Relevant and Transparent Approach
The behaviors of various confidence/credible interval constructions are
explored, particularly in the region of low statistics where methods diverge
most. We highlight a number of challenges, such as the treatment of nuisance
parameters, and common misconceptions associated with such constructions. An
informal survey of the literature suggests that confidence intervals are not
always defined in relevant ways and are too often misinterpreted and/or
misapplied. This can lead to seemingly paradoxical behaviours and flawed
comparisons regarding the relevance of experimental results. We therefore
conclude that there is a need for a more pragmatic strategy which recognizes
that, while it is critical to objectively convey the information content of the
data, there is also a strong desire to derive bounds on models and a natural
instinct to interpret things this way. Accordingly, we attempt to put aside
philosophical biases in favor of a practical view to propose a more transparent
and self-consistent approach that better addresses these issues.Comment: 23 pages, 11 figure
A compact steep spectrum radio source in NGC1977
A compact steep spectrum radio source (J0535-0452) is located in the sky
coincident with a bright optical rim in the HII region NGC1977. J0535-0452 is
observed to be mas in angular size at 8.44 GHz. The spectrum for the
radio source is steep and straight with a spectral index of -1.3 between 330
and 8440 MHz. No 2 \mu m IR counter part for the source is detected. These
characteristics indicate that the source may be either a rare high redshift
radio galaxy or a millisecond pulsar (MSP). Here we investigate whether the
steep spectrum source is a millisecond pulsar.The optical rim is believed to be
the interface between the HII region and the adjacent molecular cloud. If the
compact source is a millisecond pulsar, it would have eluded detection in
previous pulsar surveys because of the extreme scattering due to the HII
region--molecular cloud interface. The limits obtained on the angular
broadening along with the distance to the scattering screen are used to
estimate the pulse broadening. The pulse broadening is shown to be less than a
few msec at frequencies \gtsim 5 GHz. We therefore searched for pulsed
emission from J0535-0452 at 14.8 and 4.8 GHz with the Green Bank Telescope
(GBT). No pulsed emission is detected to 55 and 30 \mu Jy level at 4.8 and 14.8
GHz. Based on the parameter space explored by our pulsar search algorithm, we
conclude that, if J0535-0452 is a pulsar, then it could only be a binary MSP of
orbital period \ltsim 5 hrs.Comment: Accepted for publication in A&A (3pages, 1 fig
Investigation of the Statistical and Spatial Distributions of Mercury Contaminated Fish, Surface Waters and Soils in Arkansas
Mercury (Hg) contamination of fish is a widespread problem throughout much of the United States and the world (Louisiana WWW page, 1997). Levels ofHg in fish suffic1ent to exceed the FDA action level of 1 mg kg-1 have been found in many water bodies, including some in Arkansas and Louisiana. As a result of the serious public health ramifications for developing fetuses and for people that subsist on native fish, fish consumption advisories due to Hg contamination have been issued in 29 states. Contamination of surface water bodies by Hg results from deforestation, forest fires, fossil fuels, mining, natural emissions and commercial emissions (Armstrong, 1994). In addition, Hg has a high affinity for organic matter in soil and sediments, and therefore, long-term storage of Hg is an environmental problem. An excellent review of the integration and synthesis of recent work on Hg pollution is given in several papers edited by Watras and Huckabee (1994). The general consensus of the reports in this document seems to be that increases in Hg levels can be attributed to one or more of several mechanisms including atmospheric deposition, acidification of soils and lakes by sulfur deposition followed by an increased sulfate reduction, and transport from other source areas
Connected to the Organization: A Survey of Communication Technologies in the Modern Organizational Landscape
In today’s organizations, traditional and cutting-edge technologies compete for increased usage. This exploratory project provides a snapshot of the communication technology (CT) landscape by examining the use of 25 different CTs and their relations to a variety of common demographic variables. Results suggest that, although newer CTs are in use today, more traditional and established CTs such as e-mail, Internet, telephones, and voicemail still dominate the landscape
The COBE Normalization for Standard CDM
The COBE detection of CMB anisotropies provides the best way of fixing the
amplitude of fluctuations on the largest scales. This normalization is usually
given for an n=1 spectrum, including only the anisotropy caused by the Sachs-
Wolfe effect. This is certainly not a good approximation for a model containing
any reasonable amount of baryonic matter. In fact, even tilted S-W spectra are
not a good fit to models like CDM. Here we normalize standard CDM (sCDM) to the
2-year COBE data, and quote the best amplitude in terms of the conventionally
used measures of power. We also give normalizations for some specific variants
of this standard model, and we indicate how the normalization depends on the
assumed values of n, Omega_B and H_0. For sCDM we find =19.9\pm1.5uK,
corresponding to sigma_8=1.34\pm0.10, with the normalization at large scales
being B=(8.16\pm1.04)\times10^5 (Mpc/h)^4, and other numbers given in the
Table. The measured rms temperature fluctuation smoothed on 10deg is a little
low relative to this normalization. This is mainly due to the low quadrupole in
the data: when the quadrupole is removed, the measured value of sigma(10) is
quite consistent with the best-fitting . The use of should be preferred
over sigma(10), when its value can be determined for a particular theory, since
it makes full use of the data.Comment: 4 pages compressed uuencoded postscript. We have corrected an error
in our analysi
Dark biological superoxide production as a significant flux and sink of marine dissolved oxygen
© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Sutherland, K. M., Wankel, S. D., & Hansel, C. M. Dark biological superoxide production as a significant flux and sink of marine dissolved oxygen. Proceedings of the National Academy of Sciences of the United States of America, 117(7), (2020): 3433-3439, doi:10.1073/pnas.1912313117.The balance between sources and sinks of molecular oxygen in the oceans has greatly impacted the composition of Earth’s atmosphere since the evolution of oxygenic photosynthesis, thereby exerting key influence on Earth’s climate and the redox state of (sub)surface Earth. The canonical source and sink terms of the marine oxygen budget include photosynthesis, respiration, photorespiration, the Mehler reaction, and other smaller terms. However, recent advances in understanding cryptic oxygen cycling, namely the ubiquitous one-electron reduction of O2 to superoxide by microorganisms outside the cell, remains unexplored as a potential player in global oxygen dynamics. Here we show that dark extracellular superoxide production by marine microbes represents a previously unconsidered global oxygen flux and sink comparable in magnitude to other key terms. We estimate that extracellular superoxide production represents a gross oxygen sink comprising about a third of marine gross oxygen production, and a net oxygen sink amounting to 15 to 50% of that. We further demonstrate that this total marine dark extracellular superoxide flux is consistent with concentrations of superoxide in marine environments. These findings underscore prolific marine sources of reactive oxygen species and a complex and dynamic oxygen cycle in which oxygen consumption and corresponding carbon oxidation are not necessarily confined to cell membranes or exclusively related to respiration. This revised model of the marine oxygen cycle will ultimately allow for greater reconciliation among estimates of primary production and respiration and a greater mechanistic understanding of redox cycling in the ocean.This work was supported by NASA Earth and Space Science Fellowship NNX15AR62H to K.M.S., NASA Exobiology grant NNX15AM04G to S.D.W. and C.M.H., and NSF Division of Ocean Sciences grant 1355720 to C.M.H. This research was further supported in part by Hanse-Wissenschaftskolleg Institute of Advanced Study fellowships to C.M.H. and S.D.W. We thank Danielle Hicks for assistance with figures and Community Earth Systems Model (CESM) Large Ensemble Project for the availability and use of its data product. The CESM project is primarily supported by the NSF
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