2,687 research outputs found
Antecedent flow conditions and nitrate concentrations in the Mississippi River basin
The relationship between antecedent flow conditions and nitrate
concentrations was explored at eight sites in the 2.9 million square kilometers
(km<sup>2</sup>) Mississippi River basin, USA. Antecedent flow conditions were
quantified as the ratio between the mean daily flow of the previous year and
the mean daily flow from the period of record (Qratio), and the Qratio was
statistically related to nitrate anomalies (the unexplained variability in
nitrate concentration after filtering out season, long-term trend, and
contemporaneous flow effects) at each site. Nitrate anomaly and Qratio were
negatively related at three of the four major tributary sites and upstream
in the Mississippi River, indicating that when mean daily streamflow during
the previous year was lower than average, nitrate concentrations were higher
than expected. The strength of these relationships increased when data were
subdivided by contemporaneous flow conditions. Five of the eight sites had
significant negative relationships (<i>p</i> ≤ 0.05) at high or moderately
high contemporaneous flows, suggesting nitrate that accumulates in these
basins during a drought is flushed during subsequent high flows. At half of
the sites, when mean daily flow during the previous year was 50 percent
lower than average, nitrate concentration can be from 9 to 27 percent
higher than nitrate concentrations that follow a year with average mean
daily flow. Conversely, nitrate concentration can be from 8 to 21 percent
lower than expected when flow during the previous year was 50 percent higher
than average. Previously documented for small, relatively homogenous basins,
our results suggest that relationships between antecedent flows and nitrate
concentrations are also observable at a regional scale. Relationships were
not observed (using all contemporaneous flow data together) for basins
larger than 1 million km<sup>2</sup>, suggesting that above this limit the overall
size and diversity within these basins may necessitate the use of more
complicated statistical approaches or that there may be no discernible
basin-wide relationship with antecedent flow. The relationships between
nitrate concentration and Qratio identified in this study serve as the basis
for future studies that can better define specific hydrologic processes
occurring during and after a drought (or high flow period) which influence
nitrate concentration, such as the duration or magnitude of low flows, and
the timing of low and high flows
Universal Behaviour of the Superfluid Fraction and Tc of He-3 in 99.5% Open Aerogel
We have investigated the superfluid transition of He-3 in a 99.5% porosity
silica aerogel. This very dilute sample shows behaviour intermediary between
bulk He-3 and He-3 confined to the denser aerogels previously studied. We
present data on both the superfluid transition temperature and the superfluid
density and compare our results with previous measurements. Finally, we show
that the suppression of the superfluid transition temperature and suppression
of the superfluid density of He-3 in aerogel follow a universal relation for a
range of aerogel samples.Comment: 4 pages, 5 figures; 1 new figure, minor change
Thermodynamic Potential for Superfluid 3He in Aerogel
We present a free energy functional for superfluid 3He in the presence of
homogeneously distributed impurity disorder which extends the Ginzburg-Landau
free energy functional to all temperatures. We use the new free energy
functional to calculate the thermodynamic potential, entropy, heat capacity and
density of states for the B-phase of superfluid 3He in homogeneous, isotropic
aerogel.Comment: 10 pages, 4 figure
zfishbook: connecting you to a world of zebrafish revertible mutants
zfishbook is an internet-based openly accessible database of revertible protein trap gene-breaking transposon (GBT) insertional mutants in the zebrafish, Danio rerio. In these lines, a monomeric red fluorescent protein (mRFP) is encoded by an artificial 3′ exon, resulting in a translational fusion to endogenous loci. The natural transparency of the zebrafish embryo and larvae greatly facilitates the expression annotation of tagged loci using new capillary-based SCORE imaging methods. Molecular annotation of each line is facilitated by cloning methods such as 5′-Rapid Amplification of cDNA Ends (RACE) and inverse polymerase chain reaction (PCR). zfishbook (http://zfishbook.org) represents a central hub for molecular, expression and mutational information about GBT lines from the International Zebrafish Protein Trap Consortium (IZPTC) that includes researchers from around the globe. zfishbook is open to community-wide contributions including expression and functional annotation. zfishbook also represents a central location for information on how to obtain these lines from diverse members of the IZPTC and integration within other zebrafish community databases including Zebrafish Information Network (ZFIN), Ensembl and National Center for Biotechnology Information
A log analysis study of 10 years of ebook consumption in academic library collections
Even though libraries have been offering eBooks for more than a decade, very little is known about eBook access and consumption in academic library collections. This paper addresses this gap with a log analysis study of eBook access at the library of the University of Waikato. This in-depth analysis covers a period spanning 10 years of eBook use at this university. We draw conclusions about the use of eBooks at this institution and compare the results with other published studies of eBook usage at tertiary institutes
New Chiral Phases of Superfluid 3He Stabilized by Anisotropic Silica Aerogel
A rich variety of Fermi systems condense by forming bound pairs, including
high temperature [1] and heavy fermion [2] superconductors, Sr2RuO4 [3], cold
atomic gases [4], and superfluid 3He [5]. Some of these form exotic quantum
states having non-zero orbital angular momentum. We have discovered, in the
case of 3He, that anisotropic disorder, engineered from highly porous silica
aerogel, stabilizes a chiral superfluid state that otherwise would not exist.
Additionally, we find that the chiral axis of this state can be uniquely
oriented with the application of a magnetic field perpendicular to the aerogel
anisotropy axis. At suffciently low temperature we observe a sharp transition
from a uniformly oriented chiral state to a disordered structure consistent
with locally ordered domains, contrary to expectations for a superfluid glass
phase [6].Comment: 6 pages, 4 figure, and Supplementary Informatio
Mercury: Mid-infrared (7.3 - 13.5 microns) spectroscopic observations showing features characteristic of plagioclase
Mid-infrared spectroscopic observations of the surface of Mercury are reported for the wavelength range 7.3 to 13.5 microns. The observed spectral radiance emanated from equatorial and low latitude regions between 110-130 deg Mercurian longitude. The area is primarily an intercrater plain. The spectra show distinct and recognizable features, the principal Christiansen emission peak being the most prominent. The Christiansen feature strongly suggests the presence of plagioclase (Ca,Na)(Al,Si)AlSi2O8, (in particular labradorite: Ab(50) - Ab(30)). In addition we have studied the effects of thermal gradients to gain insight into the effects of thermal conditions on the spectral radiance of rock samples. This simulates the thermophysical effects as the rotating surface of Mercury is alternately heated and cooled. The spectral features of the samples are retained; however, the relative and absolute amplitudes vary as illustrated by laboratory reflectance and emittance spectra from quartzite
Biochemical markers associated with two Mv chromosomes from Aegilops ventricosa in wheat-Aegilops addition lines
The distribution of three biochemical markers, U-1, CM-4 and Aphv-a, -b, among wheat-Aegilops addition lines carrying Mv chromosomes from Aegilops ventricosa (genomes DvMv) has been investigated. Addition lines which had been previously grouped together on the basis of common non-biochemical characters carried marker U-1, a protein component from the 2M urea extract. The added chromosome, in the appropriate genetic background, seems to confer a high level of resistance to the eyespot disease, caused by the fungus Cercosporella herpotrichoides. The other two markers were concomitantly associated with another similarly formed group of addition lines. Both CM-4, a protein component from the chloroform:methanol extract, and Aphv-a, -b, alkaline phosphate isozymes, have been previously shown to be associated with homoeologous chromosome group 4, which suggests that the added chromosome in the second group of addition lines is 4Mv
Mid-IR Spectroscopy of the Jovian Stratosphere perturbed by comet P/Shoemaker-Levy 9 Impact
The objective was to obtain spectra from 5 to 14 micron before, during, and after the impacts. We were awarded 2 flights of the KAO which was based in Melbourne, Australia for the events. Impacts R and W were covered, and the observations were completely successful. A paper reporting the observation of water vapor is in press, and other work is in progress as limited funding permits. The text of this report is adapted from that of the Icarus paper
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