1,052 research outputs found
Volatile organic compounds in seawater
Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Woods Hole Oceanographic Institution January 1979Vapor phase stripping and solid adsorbent trapping were applied to seawater and related samples to concentrate volatile organic compounds. The concentrates were subsequently analyzed by glass capillary gas chromatography and combined gas chromatography-mass spectrometry. The
compound identities and the spatial and temporal distributions of their concentrations were used to determine some sources, transformations, and transport mechanisms of organic matter in the sea.
Volatile organic compounds were determined in seawater samples from the Sargasso Sea, the western Equatorial Atlantic, and the upwelling region off Peru. Pentadecane was present in all three areas in surface samples at 10-40ng/kg and decreased to 1-2 ng/kg in the deep water.
A source related to the transformation of the algal fatty acid, hexadecaugic acid, by zooplankton is proposed since anthropogenic and direct phytoplankton sources are unlikely. C2-alkylated benzenes were found in the upwelled water off Peru at about 4 ng/kg in the surface (5 and 20m), 3 ng/kg below the thermocline (100m), and 2 ng/kg or less in deeper water.
A surface or atmospheric source is required to produce this distribution.
C6-C10 aldehydes were also found in seawater from off Peru. The direct correlation of their concentrations with chlorophyll a and with oxygen indicated that they are derived from chemical oxidation of algal metabolites, for example, unsaturated fatty acids. Total volatiles in the oligotrophic Sargasso Sea were about 10-30 ng/kg while the biologically productive
upwelling region off Peru contained up to 100 ng/kg.
The temporal variations of volatile organic compound concentrations
were investigated in coastal seawater from Vineyard Sound, Massachusetts.
Pentadecane and heptadecane showed large summertime concentration increases
which were ascribed to benthic algal sources. Laboratory incubations of
benthic algal samples supported this conclusion. The saturated hydrocarbons,
from C13-C17, and alkylated benzenes and naphthalenes were all
abundant after an oil spill several miles from the sampling site. C2- and C3-
benzenes were the most persistently abundant volatile compounds and their
concentrations were observed to be 2-10 times higher than average immediately
after summer weekends, peak periods of tourist and recreational
activities on Cape Cod. Naphthalene and its homologues were more abundant
in the winter than in the summer. C6-C10 aldehydes were observed year-round,
but showed a concentration maximum at the time of the late-winter
phytoplankton bloom. C12-C15 aldehydes were also found in abundance at
that time. Oxidation of algal matter by zooplankton or photochemically-produced
oxidizing agents may produce the aldehydes, since laboratory
cultures of phytoplankton did not produce these oxygenated volatiles. An
alkene, structurally similar to the known benthic algal gamone, fucoserraten, was also found in Vineyard Sound seawater and in the upwelling
region off Peru. Its appearance in Vineyard Sound samples coincided with
the period of expected algal reproductive activity in February and March.
Dimethyl polysulfides were found in coastal seawater. They may be
produced within the water from precursors such as methyl mercaptan or other
known polysulfide metabolites. Total volatile concentrations in Vineyard
Sound seawater varied between 2OO and 500 ng/kg for the period from
January to June. Maximum concentrations occurred during the late-winter
phytoplankton bloom and again in the spring from anthropogenic inputs of
hydrocarbons.
The highest concentrations of C2- and C3-benzenes found in Vineyard Sound
seawater coincided with motorboat use in the immediate vicinity of the
sampling station. The average year-round isomer distribution most closely
resembled distributions from gasoline and auto exhaust dissolved in seawater,
consistent with an inboard or inboard/outboard motorboat source.
Atmospheric and runoff delivery of C2- and C3-benzenes to Vineyard Sound
seawater during the period from spring through fall was concluded to be
of lesser importance. The atmosphere may serve as a buffer for seawater
concentrations of the aromatic compounds, supporting low concentrations in
the winter and limiting high concentrations in the summer.Financial support came from ONR Contract N-000-14-74~C0262 NR 083-004, NSF Grant OCE 22781, Sea Grant 04-7-158-44104 and 04-8-MOI-149, and the W.H.O.I. Education Office
The politics of opinion assignment: a conditional logit model with varying choice set
"This note replicates and extends Chapter 2 of Forrest Maltzman, James F. Spriggs and Paul J. Wahlbeck's (henceforth: MSW) "Crafting Law on the Supreme Court" (2000). Using a conditional logit model, the authors test the effects of both choice-specific and chooser-specific variables on majority opinion assignment on the United States Supreme Court during Chief Justice Burger's tenure. The authors find that the effect of ideology, as well as other variables, is conditioned on both case facts as well as justices' attributes. In this note, we take issue with the authors' specification of the model, specifically their failure to include choicespecific, i.e. the justices, constants. Below we argue for the statistical necessity of the inclusion of these controls and reassess the original theoretical model with the appropriate statistical specification. We first show that the failure to include these constants will yield biased estimates. We then test if the authors' substantive findings are robust to the correct specification of their original model. While we successfully replicate the original model (yielding biased estimates), we generally find that MSW's core findings, although confirmed, are diminished when correctly estimated." (author's abstract
Advances in targeted Alpha therapy for prostate cancer
BACKGROUND: Amongst therapeutic radiopharmaceuticals, targeted alpha therapy (TαT) can deliver potent and local radiation selectively to cancer cells as well as the tumor microenvironment and thereby control cancer while minimizing toxicity. DESIGN: In this review, we discuss the history, progress, and future potential of TαT in the treatment of prostate cancer, including dosimetry-individualized treatment planning, combinations with small-molecule therapies, and conjugation to molecules directed against antigens expressed by prostate cancer cells, such as prostate-specific membrane antigen (PSMA) or components of the tumor microenvironment. RESULTS: A clinical proof of concept that TαT is efficacious in treating bone-metastatic castration-resistant prostate cancer has been demonstrated by radium-223 via improved overall survival and long-term safety/tolerability in the phase III ALSYMPCA trial. Dosimetry calculation and pharmacokinetic measurements of TαT provide the potential for optimization and individualized treatment planning for a precision medicine-based cancer management paradigm. The ability to combine TαTs with other agents, including chemotherapy, androgen receptor (AR)-targeting agents, DNA repair inhibitors, and immuno-oncology agents, is under investigation. Currently, TαTs that specifically target prostate cancer cells expressing PSMA represents a promising therapeutic approach. Both PSMA-targeted actinium-225 and thorium-227 conjugates are under investigation. CONCLUSIONS: The described clinical benefit, safety and tolerability of radium-223 and the recent progress in TαT trial development suggest that TαT occupies an important new role in prostate cancer treatment. Ongoing studies with newer dosimetry methods, PSMA targeting, and novel approaches to combination therapies should expand the utility of TαT in prostate cancer treatment
Mobilization of colloids in groundwater due to infiltration of water at a coal ash disposal site
We investigated groundwaters in the vicinity of a coal ash site near an electric generating
station in the western U.S.A. The purpose of the study was to ascertain why fine particles or
colloids appear in some subsurface water samples there. If such fine particles are merely introduced
during bailing or pumping operations which suspend otherwise immobile soil colloids, we should
exclude these particulate materials from the water samples before analysis intended to quantify
what is moving through the aquifer. However, if the colloids were truly suspended and moving with
the groundwater flow in situ, then we should include their contribution to our assessment of the
mobile loads.
Application of very careful sampling techniques (slow pumping rates, no atmospheric exposure)
did not cause the large quantities of colloids observed previously to disappear from well water in
which they occurred. Additionally, the same sampling procedures did not cause similar abun-
dances of colloids to appear in waters collected from neighboring wells installed and' developed in
the same manner and in the same geologic strata. Thus we believe sampling artifacts do not explain
the colloids' presence in the groundwater samples.
On the other hand, the groundwater chemistry and the nature of the suspended colloids (size,
composition) strongly suggest these fine particles were suspended and therefore moving with the
groundwater flow. At wells exhibiting large amounts of suspended colloids (- 10-100mg L-), the
water was enriched in CO2 and depleted in 02 relative to nearby locations. The colloids were
typically between 0.1 and 2 gm in size and were primarily silicates. These results suggest to us that,
where infiltrating water is percolating through a site that has been mixed with coal ash, the
secondary carbonate minerals in the soils are being dissolved; removal of this cementing carbonate
phase may consequently release soil silicate colloids to be carried in the flowing water.
Such processes may enhance contaminant transport in groundwater by augmenting the
pollutant load moving in the groundwater, and increasing the permeability of the porous medium
to pollutant infiltration with waste water and/or rainwater
Stimmensplitting und Koalitionswahl
Hat sich die UnabhĂ€ngigkeitsstrategie der FDP bei der letzten Bundestagswahl ausgezahlt? WĂ€re die FDP erfolgreicher gewesen, wenn sie im Vorfeld klar signalisiert hĂ€tte, dass man eine Koalition mit der Union anstrebt? Wie war das bei den GrĂŒnen, die ja im Gegensatz zur FDP keine Zweifel aufkommen lieĂen? NatĂŒrlich können wir nicht wie in einer Simulation oder einem Experiment einfach den Wahlkampf wiederholen und noch einmal wĂ€hlen lassen. Um eine befriedigende Antwort auf diese Frage zu finden, vergleichen wir den Kontext der Bundestagswahl 2002 mit den zurĂŒckliegenden Bundestagswahlen. Aus dem LĂ€ngsschnittvergleich versuchen wir RĂŒckschlĂŒsse auf den substanziellen Einfluss von strategischem Stimmensplitting im Sinne einer Koalitionswahl auf das Wahlergebnis gerade der kleinen Parteien zu ziehen. Um unsere Forschungsfrage zu beantworten und substanzielle SchlĂŒsse ziehen zu können, muss zuerst klar sein, in welcher Form und warum Stimmensplitting relevant sein kann, welche Rolle dabei Koalitionsabsprachen vor einer jeden Wahl spielen und, schlieĂlich, welche alternativen ErklĂ€rungsmöglichkeiten die Literatur zum Thema Stimmensplitting und strategischem WĂ€hlen anzubieten hat. Nur wenn wir auch die Wirkung alternativer und zum Teil konkurrierender Hypothesen zulassen, können wir unserer SchluĂfolgerungen sicher sein
Sodium butyrate and tributyrin induce in vivo growth inhibition and apoptosis in human prostate cancer
Transfer learning for galaxy morphology from one survey to another
© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.Deep Learning (DL) algorithms for morphological classification of galaxies have proven very successful, mimicking (or even improving) visual classifications. However, these algorithms rely on large training samples of labelled galaxies (typically thousands of them). A key question for using DL classifications in future Big Data surveys is how much of the knowledge acquired from an existing survey can be exported to a new dataset, i.e. if the features learned by the machines are meaningful for different data. We test the performance of DL models, trained with Sloan Digital Sky Survey (SDSS) data, on Dark Energy survey (DES) using images for a sample of 5000 galaxies with a similar redshift distribution to SDSS. Applying the models directly to DES data provides a reasonable global accuracy ( 90%), but small completeness and purity values. A fast domain adaptation step, consisting in a further training with a small DES sample of galaxies (500-300), is enough for obtaining an accuracy > 95% and a significant improvement in the completeness and purity values. This demonstrates that, once trained with a particular dataset, machines can quickly adapt to new instrument characteristics (e.g., PSF, seeing, depth), reducing by almost one order of magnitude the necessary training sample for morphological classification. Redshift evolution effects or significant depth differences are not taken into account in this study.Peer reviewedFinal Accepted Versio
Astrometric calibration and performance of the Dark Energy Camera
We characterize the ability of the Dark Energy Camera (DECam) to perform
relative astrometry across its 500~Mpix, 3 deg^2 science field of view, and
across 4 years of operation. This is done using internal comparisons of ~4x10^7
measurements of high-S/N stellar images obtained in repeat visits to fields of
moderate stellar density, with the telescope dithered to move the sources
around the array. An empirical astrometric model includes terms for: optical
distortions; stray electric fields in the CCD detectors; chromatic terms in the
instrumental and atmospheric optics; shifts in CCD relative positions of up to
~10 um when the DECam temperature cycles; and low-order distortions to each
exposure from changes in atmospheric refraction and telescope alignment. Errors
in this astrometric model are dominated by stochastic variations with typical
amplitudes of 10-30 mas (in a 30 s exposure) and 5-10 arcmin coherence length,
plausibly attributed to Kolmogorov-spectrum atmospheric turbulence. The size of
these atmospheric distortions is not closely related to the seeing. Given an
astrometric reference catalog at density ~0.7 arcmin^{-2}, e.g. from Gaia, the
typical atmospheric distortions can be interpolated to 7 mas RMS accuracy (for
30 s exposures) with 1 arcmin coherence length for residual errors. Remaining
detectable error contributors are 2-4 mas RMS from unmodelled stray electric
fields in the devices, and another 2-4 mas RMS from focal plane shifts between
camera thermal cycles. Thus the astrometric solution for a single DECam
exposure is accurate to 3-6 mas (0.02 pixels, or 300 nm) on the focal plane,
plus the stochastic atmospheric distortion.Comment: Submitted to PAS
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