2,930 research outputs found
Waxy Corn a New Crop
When Japan took the Netherland East Indies, we not only lost our main supply of rubber and tin, but also our tapioca starch
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
Combinatorial Games with a Pass: A dynamical systems approach
By treating combinatorial games as dynamical systems, we are able to address
a longstanding open question in combinatorial game theory, namely, how the
introduction of a "pass" move into a game affects its behavior. We consider two
well known combinatorial games, 3-pile Nim and 3-row Chomp. In the case of Nim,
we observe that the introduction of the pass dramatically alters the game's
underlying structure, rendering it considerably more complex, while for Chomp,
the pass move is found to have relatively minimal impact. We show how these
results can be understood by recasting these games as dynamical systems
describable by dynamical recursion relations. From these recursion relations we
are able to identify underlying structural connections between these "games
with passes" and a recently introduced class of "generic (perturbed) games."
This connection, together with a (non-rigorous) numerical stability analysis,
allows one to understand and predict the effect of a pass on a game.Comment: 39 pages, 13 figures, published versio
Interfacing GHz-bandwidth heralded single photons with a room-temperature Raman quantum memory
Photonics is a promising platform for quantum technologies. However, photon
sources and two-photon gates currently only operate probabilistically.
Large-scale photonic processing will therefore be impossible without a
multiplexing strategy to actively select successful events. High
time-bandwidth-product quantum memories - devices that store and retrieve
single photons on-demand - provide an efficient remedy via active
synchronisation. Here we interface a GHz-bandwidth heralded single-photon
source and a room-temperature Raman memory with a time-bandwidth product
exceeding 1000. We store heralded single photons and observe a clear influence
of the input photon statistics on the retrieved light, which agrees with our
theoretical model. The preservation of the stored field's statistics is limited
by four-wave-mixing noise, which we identify as the key remaining challenge in
the development of practical memories for scalable photonic information
processing
Ultrahigh and persistent optical depths of caesium in Kagom\'e-type hollow-core photonic crystal fibres
Alkali-filled hollow-core fibres are a promising medium for investigating
light-matter interactions, especially at the single-photon level, due to the
tight confinement of light and high optical depths achievable by light-induced
atomic desorption. However, until now these large optical depths could only be
generated for seconds at most once per day, severely limiting the practicality
of the technology. Here we report the generation of highest observed transient
( for up to a minute) and highest observed persistent ( for
hours) optical depths of alkali vapours in a light-guiding geometry to date,
using a caesium-filled Kagom\'e-type hollow-core photonic crystal fibre. Our
results pave the way to light-matter interaction experiments in confined
geometries requiring long operation times and large atomic number densities,
such as generation of single-photon-level nonlinearities and development of
single photon quantum memories.Comment: Author Accepted versio
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
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Deamidation of the human eye lens protein γS-crystallin accelerates oxidative aging
Cataract, a clouding of the eye lens from protein precipitation, affects millions of people every year. The lens proteins, the crystallins, show extensive post-translational modifications (PTMs) in cataractous lenses. The most common PTMs, deamidation and oxidation, promote crystallin aggregation; however, it is not clear precisely how these PTMs contribute to crystallin insolubilization. Here, we report six crystal structures of the lens protein γS-crystallin (γS): one of the wild-type and five of deamidated γS variants, from three to nine deamidation sites, after sample aging. The deamidation mutations do not change the overall fold of γS; however, increasing deamidation leads to accelerated disulfide-bond formation. Addition of deamidated sites progressively destabilized protein structure, and the deamidated variants display an increased propensity for aggregation. These results suggest that the deamidated variants are useful as models for accelerated aging; the structural changes observed provide support for redox activity of γS-crystallin in the lens
Molecular analysis of endocrine disruption in hornyhead turbot at wastewater outfalls in southern california using a second generation multi-species microarray.
Sentinel fish hornyhead turbot (Pleuronichthysverticalis) captured near wastewater outfalls are used for monitoring exposure to industrial and agricultural chemicals of ~ 20 million people living in coastal Southern California. Although analyses of hormones in blood and organ morphology and histology are useful for assessing contaminant exposure, there is a need for quantitative and sensitive molecular measurements, since contaminants of emerging concern are known to produce subtle effects. We developed a second generation multi-species microarray with expanded content and sensitivity to investigate endocrine disruption in turbot captured near wastewater outfalls in San Diego, Orange County and Los Angeles California. Analysis of expression of genes involved in hormone [e.g., estrogen, androgen, thyroid] responses and xenobiotic metabolism in turbot livers was correlated with a series of phenotypic end points. Molecular analyses of turbot livers uncovered altered expression of vitellogenin and zona pellucida protein, indicating exposure to one or more estrogenic chemicals, as well as, alterations in cytochrome P450 (CYP) 1A, CYP3A and glutathione S-transferase-α indicating induction of the detoxification response. Molecular responses indicative of exposure to endocrine disruptors were observed in field-caught hornyhead turbot captured in Southern California demonstrating the utility of molecular methods for monitoring environmental chemicals in wastewater outfalls. Moreover, this approach can be adapted to monitor other sites for contaminants of emerging concern in other fish species for which there are few available gene sequences
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