7,445 research outputs found
Numerical Model Water Quality for Hidalgo County, Texas; Main Drainage System
Increasing urbanization, water intake, and human water interaction of drainage canals of the Hidalgo County watershed seals the drainage basin and expands floodplains along the canal-side. Incremental use of drainage systems affects the amounts of nutrients that can cause an exposure to residues of agriculture chemicals, water related parasitic diseases, and fecal diseases. Proper water quality management is crucial for pollutant transport detection, estimation of non-point source discharge, and prediction of pollutant discharge at water endpoints. This research seeks to improve the understanding stormwater quality and quantity that is influenced by the frequency of human-water contacts and associated with treatment disposal of drainage water. This study developed one-dimensional water quality transport numerical analysis model, where a stable hydraulic analysis is moderated by fixed weirs as internal boundary conditions to reflect low flow conditions and are then used to construct a water quality analysis model. It estimates changes in temperature, nutrient transport, and flow effects of North Hidalgo County drainage canals. Model simulation results were compared to monthly measurements, an energy budget, nutrient concentration, and flow regime for each stream reach. Project results characterize energy exchange processes at the stream surface and their effect on nutrient biology and transportation. Understanding the physical processes of the canal systems will provide managers with improved information to sustainably manage these ecological complex systems
The Role of Stars in the Energetics of LINERs
Imaging studies have shown that about 25% of LINER galaxies display a compact
nuclear UV source. I compare the HST ultraviolet spectra now available for
seven such ``UV-bright'' LINERs. The spectra of NGC 404, NGC 4569, and NGC 5055
show clear absorption-line signatures of massive stars, indicating a stellar
origin for the UV continuum. Similar features are probably present in NGC 6500.
The same stellar signatures may be present but undetectable in NGC 4594, due to
the low signal-to-noise ratio of the spectrum, and in M81 and NGC 4579, due to
superposed strong, broad emission lines. The compact central UV continuum
source that is observed in these galaxies is a nuclear star cluster rather than
a low-luminosity active galactic nucleus (AGN), at least in some cases. At
least four of the LINERs suffer from an ionizing photon deficit, in the sense
that the ionizing photon flux inferred from the observed far-UV continuum is
insufficient to drive the optical H I recombination lines. Examination of the
nuclear X-ray flux of each galaxy shows a high X-ray/UV ratio in the four
``UV-photon starved'' LINERs. In these four objects, a separate component,
emitting predominantly in the extreme-UV, is the likely ionizing agent, and is
perhaps unrelated to the observed nuclear UV emission. Future observations can
determine whether the UV continuum in LINERs is always dominated by a starburst
or, alternatively, that there are two types of UV-bright LINERs:
starburst-dominated and AGN-dominated. Interestingly, recent results show that
starbursts dominate the nuclear energetics in many Seyfert 2s as well.Comment: LaTex, 10 pages, invited review to appear in Proc. of the 32nd COSPAR
Meeting, The AGN-Galaxy Connection, ed. H. R. Schmitt, A. L. Kinney, and L.
C. H
An X-ray view of 82 LINERs with Chandra and XMM-Newton data
We present the results of an homogeneous X-ray analysis for 82 nearby LINERs
selected from the catalogue of Carrillo et al. (1999). All sources have
available Chandra (68 sources) and/or XMM-Newton (55 sources) observations.
This is the largest sample of LINERs with X-ray spectral data (60 out of the 82
objects) and significantly improves our previous analysis based on Chandra data
for 51 LINERs (Gonzalez-Martin et al. 2006). It increases both the sample size
and adds XMM-Newton data. New models permit the inclusion of double absorbers
in the spectral fits. Nuclear X-ray morphology is inferred from the compactness
of detected nuclear sources in the hard band (4.5-8.0 keV). Sixty per cent of
the sample shows a compact nuclear source and are classified as AGN candidates.
The spectral analysis indicates that best fits involve a composite model:
absorbed primary continuum and (2) soft spectrum below 2 keV described by an
absorbed scatterer and/or a thermal component. The resulting median spectra
parameters and their standard deviations are: G=2.11, =0.54 keV,
=21.32 and =21.93. We complement our X-ray results with our
analysis of HST optical images and literature data on emission lines, radio
compactness and stellar population. Adding all these multiwavelength data, we
conclude that evidence do exist supporting the AGN nature of their nuclear
engine for 80% of the sample (66 out of 82 objects).Comment: Accepted for publications in Astronomy and Astrophysics, 49 pages, 12
figures. Catalogs only at:
http://www.star.le.ac.uk/~gmo4/O.Gonzalez-Martin-LINERs_xray.pd
A Search for Ultraviolet Emission from LINERs
We have obtained Hubble Space Telescope WFPC2 2200 A and optical V-band
images of 20 low-luminosity active galactic nuclei, most of which are
spectroscopically classified as LINERs, in order to search for a possible
photoionizing continuum. Six (30%) of the galaxies are detected in the UV. Two
of the detected galaxies (NGC 3642 and NGC 4203) have compact, unresolved
nuclear UV sources, while the remaining four UV sources (in NGC 4569, NGC 5005,
NGC 6500, and NGC 7743) are spatially extended. Combining our sample with that
of Maoz et al. (1995), we find that the probability of detection of a nuclear
UV source is greatest for galaxies having low internal reddening and low
inclination, and we conclude that dust obscuration is the dominant factor
determining whether or not a UV source is detected. Large emission-line
equivalent widths and the presence of broad-line emission also increase the
likelihood of detection of nuclear UV emission. Our results suggest that the
majority of LINERs harbor obscured nuclear UV sources, which may be either
accretion-powered active nuclei or young star clusters. Under the assumption
that the compact UV sources in NGC 3642 and NGC 4203 have nonstellar power-law
spectra extending into the extreme ultraviolet, the extrapolated ionizing
fluxes are sufficiently strong to photoionize the narrow-line regions of these
objects. The V-band images of many galaxies in our sample reveal remarkably
strong dust lanes which may be responsible for obscuring some UV sources.Comment: 25 pages, 4 figures, 3 tables, LaTeX, AASTeX v4.0 style file,
accepted for publication in The Astrophysical Journal, additional figures
available at http://astro.berkeley.edu/~barth/papers/u
Curved-space classical solutions of a massive supermatrix model
We investigate here a supermatrix model with a mass term and a cubic
interaction. It is based on the super Lie algebra osp(1|32,R), which could play
a role in the construction of the eleven-dimensional M-theory. This model
contains a massive version of the IIB matrix model, where some fields have a
tachyonic mass term. Therefore, the trivial vacuum of this theory is unstable.
However, this model possesses several classical solutions where these fields
build noncommutative curved spaces and these solutions are shown to be
energetically more favorable than the trivial vacuum. In particular, we
describe in details two cases, the SO(3) \times SO(3) \times SO(3) (three fuzzy
2-spheres) and the SO(9) (fuzzy 8-sphere) classical backgrounds.Comment: 16 pages, no figure, v2: shortened and clarified version, v3: some
minor typos correcte
Two Physically Distinct Populations of Low-Ionization Nuclear Emission-Line Regions
The nature of Low-ionization Nuclear Emission-line Regions (LINERs) has been
an open question for a long time. We study the properties of LINERs from
several different aspects. The LINERs are found to consist of two different
categories that can be clearly separated in the traditional BPT diagrams,
especially in the [OI]/Ha vs. [OIII]/Hb diagram. LINERs with high [O]/Ha ratios
(population I) differ from ones with low ratios (population II) in several
properties. Broad emission lines are only identified in the spectra of
population I LINERs. While only the population II LINERs show luminous infrared
emission and occurrence of core-collapse supernovae in the host. Combining
these results with the known distribution of stellar populations not only
suggests that the two populations have different line excitation mechanisms,
but also implies that they are at different evolutionary stages.Comment: 12 pages, 2 figures, accepted by ApJ Lette
HPV Knowledge, Attitudes, and Vaccination Among Hispanic/Latino College Students in the USA
This study evaluated Human Papillomavirus-related knowledge and attitudes, vaccination practices, and explored associated factors among Hispanic/Latino college students in the United States of America. Using a self-administered survey, a descriptive, cross-sectional quantitative study was conducted in 2018 at colleges and universities in the United States of America. Our results indicate that Hispanic/Latino college students had a low level of HPV-related knowledge, a moderately positive attitude, and a moderate rate of HPV vaccination. Students who were in a health-related major, married/divorced, and had health insurance had greater knowledge and more positive attitudes towards HPV and its vaccines. This study is important due to the disproportionate high rate of HPV associated cervical cancers among Hispanic/Latinos when compared to other races and ethnicities. Our findings will inform the development of innovative intervention to promote HPV vaccination uptake across educational institutions
Physicochemical stability of lycopene-loaded emulsions stabilized by plant or dairy proteins
Lycopene is a lipophilic bioactive compound that has many health benefits but can be challenging to deliver in vivo. To mediate this, delivery strategies should be developed, and protein-stabilized oil-in-water (O/W) emulsions have been suggested to improve the physicochemical stability, bioaccessibility and bioavailability of lycopene. In this research different proteins were compared to determine their impact on the physical stability (droplet size, charge, interfacial rheology) and lycopene retention in canola O/W emulsions. Two were of dairy (whey protein isolate, sodium caseinate) and two of plant (soy and pea protein isolate) origin; plant proteins being of interest due to their wider availability, reduced cost, and lower impact on the environment compared to dairy proteins.
Particle size distribution for sodium caseinate and pea protein-stabilized emulsions remained unchanged after 14 days of refrigerated storage, while whey and soy protein isolate-stabilized emulsions became unstable. The droplet charge was largely negative (~ -45 â -60 mV) for all emulsions and the lycopene concentration in plant protein-stabilized emulsions at 14 days of storage was similar to that in sodium caseinate-stabilized emulsions, but significantly higher than that in whey proteinstabilized emulsions. While sodium caseinate formed relatively viscous films at the oil-water interface, the other proteins showed more viscoelastic behaviour. In spite of this difference, both the caseinate and pea protein stabilized emulsions were promising delivery vehicles. This also indicates that plant-derived proteins can be feasible alternatives to dairy emulsifiers
The Broad-Line and Narrow-Line Regions of the LINER NGC 4579
We report the discovery of an extremely broad H-alpha emission line in the
LINER nucleus of NGC 4579. From ground-based observations, the galaxy was
previously known to contain a Type 1 nucleus with a broad H-alpha line of FWHM
= 2300 km/s and FWZI ~ 5000 km/s. New spectra obtained with the Hubble Space
Telescope and a 0.2 arcsec-wide slit reveal an H-alpha component with FWZI ~
18,000 km/s. The line is not obviously double-peaked, but it does possess
shoulders on the red and blue sides which resemble the H-alpha profiles of
double-peaked emitters such as NGC 4203 and NGC 4450. This similarity suggests
that the very broad H-alpha profile in NGC 4579 may represent emission from an
accretion disk. Three such objects have been found recently in two HST programs
which have targeted a total of 30 galaxies, demonstrating that double-peaked or
extremely broad-line emission in LINERs must be much more common than would be
inferred from ground-based surveys. The ratio of the narrow [S II] 6716, 6731
lines shows a pronounced gradient indicating a steep rise in density toward the
nucleus. The direct detection of a density gradient within the inner arcsecond
of the narrow-line region confirms expectations from previous observations of
linewidth-critical density correlations in several LINERs.Comment: 8 pages, includes 3 figures. To appear in The Astrophysical Journa
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