73 research outputs found
Noble gases in deepwater oils of the U.S. Gulf of Mexico
Author Posting. © American Geophysical Union, 2018. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 19(11), (2018): 4218-4235. doi: 10.1029/2018GC007654Hydrocarbon migration and emplacement processes remain underconstrained despite the vast potential economic value associated with oil and gas. Noble gases provide information about hydrocarbon generation, fluid migration pathways, reservoir conditions, and the relative volumes of oil versus water in the subsurface. Produced gas HeâNeâArâKrâXe data from two distinct oil fields in the Gulf of Mexico (Genesis and HooverâDiana) are used to calibrate a model that takes into account both waterâoil solubility exchange and subsequent gas cap formation. Reconstructed noble gas signatures in oils reflect simple (twoâphase) oilâwater exchange imparted during migration from the source rock to the trap, which are subsequently modified by gas cap formation at current reservoir conditions. Calculated, oil to water volume ratios ( urn:x-wiley:15252027:media:ggge21714:ggge21714-math-0001) in Tertiaryâsourced oils from the HooverâDiana system are 2â3 times greater on average than those in the Jurassic sourced oils from the Genesis reservoirs. Higher urn:x-wiley:15252027:media:ggge21714:ggge21714-math-0002 in HooverâDiana versus Genesis can be interpreted in two ways: either (1) the Hoover reservoir interval has 2â3 times more oil than any of the individual Genesis reservoirs, which is consistent with independent estimates of oil in place for the respective reservoirs, or (2) Genesis oils have experienced longer migration pathways than HooverâDiana oils and thus have interacted with more water. The ability to determine a robust urn:x-wiley:15252027:media:ggge21714:ggge21714-math-0003, despite gas cap formation and possible gas cap loss, is extremely powerful. For example, when volumetric hydrocarbon ratios are combined with independent estimates of hydrocarbon migration distance and/or formation fluid volumes, this technique has the potential to differentiate between large and small oil accumulations.We thank ExxonMobil for funding and providing the samples. In addition, we thank James Scott and two anonymous reviewers for their comprehensive and constructive reviews, as well as Janne BlichertâToft for editorial handling.2019-04-1
The Magellan/IMACS Catalog of Optical Supernova Remnant Candidates in M83
We present a new optical imaging survey of supernova remnants in M83, using
data obtained with the Magellan I 6.5m telescope and IMACS instrument under
conditions of excellent seeing. Using the criterion of strong [S II] emission
relative to Halpha, we confirm all but three of the 71 SNR candidates listed in
our previous survey, and expand the SNR candidate list to 225 objects, more
than tripling the earlier sample. Comparing the optical survey with a new deep
X-ray survey of M83 with Chandra, we find 61 of these SNR candidates to have
X-ray counterparts. We also identify an additional list of 46 [O III] -selected
nebulae for follow-up as potential ejecta-dominated remnants, seven of which
have associated X-ray emission that makes them strong candidates. Some of the
other [O III]-bright objects could also be normal ISM-dominated supernova
remnants with shocks fast enough to doubly ionize oxygen, but with Halpha and
[S II] emission faint enough to have been missed. A few of these objects may
also be H II regions with abnormally high [O III] emission compared with the
majority of M83 H II regions, compact nebulae excited by young Wolf-Rayet
stars, or even background AGN. The supernova remnant Halpha luminosity function
in M83 is shifted a factor of ~ 4.5x higher than for M33 supernova remnants,
indicative of a higher mean ISM density in M83. We describe the search
technique used to identify the supernova remnant candidates and provide basic
information and finder charts for the objects.Comment: 40 pages, 15 figures, accepted for ApJ
Patient Preferences for Diagnostic Testing in the Emergency Department: A CrossĂą sectional Study
BackgroundDiagnostic testing is common during emergency department (ED) visits. Little is understood about patient preferences for such testing. We hypothesized that a patientâs willingness to undergo diagnostic testing is influenced by the potential benefit, risk, and personal cost.MethodsWe conducted a cross sectional survey among ED patients for diagnostic testing in two hypothetical scenarios: chest pain (CP) and mild traumatic brain injury (mTBI). Each scenario defined specific risks, benefits, and costs of testing. The odds of a participant desiring diagnostic testing were calculated using a series of nested multivariable logistic regression models.ResultsParticipants opted for diagnostic testing 68.2% of the time, including 69.7% of CP and 66.7% of all mTBI scenarios. In the CP scenario, 81% of participants desired free testing versus 59% when it was associated with a 100 copayment (differenceĂÂ = 17%, 95% CIĂÂ = 11% to 24%). Benefit and risk had mixed effects across the scenarios. In fully adjusted models, the association between cost and desire for testing persisted in the CP (odds ratio [OR]ĂÂ = 0.33, 95% CIĂÂ = 0.23 to 0.47) and adult mTBI (ORĂÂ = 0.47, 95% CIĂÂ = 0.33 to 0.67) scenarios.ConclusionsIn this EDĂą based study, patient preferences for diagnostic testing differed significantly across levels of risk, benefit, and cost of diagnostic testing. Cost was the strongest and most consistent factor associated with decreased desire for testing.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/144652/1/acem13404.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/144652/2/acem13404_am.pd
FORTIS: Pathfinder to the Lyman Continuum
Shull et al. (1999) have asserted that the contribution of stars, relative to
quasars, to the metagalactic background radiation that ionizes most of the
baryons in the universe remains almost completely unknown at all epochs. The
potential to directly quantify this contribution at low redshift has recently
become possible with the identification by GALEX of large numbers of sparsely
distributed faint ultraviolet galaxies. Neither STIS nor FUSE nor GALEX have
the ability to efficiently survey these sparse fields and directly measure the
Lyman continuum radiation that may leak into the low redshift (z < 0.4)
intergalactic medium. We present here a design for a new type of far
ultraviolet spectrograph, one that is more sensitive, covers wider fields, and
can provide spectra and images of a large number of objects simultaneously,
called the Far-ultraviolet Off Rowland-circle Telescope for Imaging and
Spectroscopy (FORTIS). We intend to use a sounding rocket flight to validate
the new instrument with a simple long-slit observation of the starburst
populations in the galaxy M83. If however, the long-slit were replaced with
microshutter array, this design could isolate the chains of blue galaxies found
by GALEX over an ~30' diameter field-of-view and directly address the Lyman
continuum problem in a long duration orbital mission. Thus, our development of
the sounding rocket instrument is a pathfinder to a new wide field
spectroscopic technology for enabling the potential discovery of the long
hypothesized but elusive Lyman continuum radiation that is thought to leak from
low redshift galaxies and contribute to the ionization of the universe.Comment: 10 pages to appear in Proceeedings of SPIE Vol. 5488, UV to Gamma Ray
Space Telescope System
Discovery of Two Distant Type Ia Supernovae in the Hubble Deep Field North with the Advanced Camera for Surveys
We present observations of the first two supernovae discovered with the
recently installed Advanced Camera for Surveys (ACS) on the Hubble Space
Telescope. The supernovae were found in Wide Field Camera images of the Hubble
Deep Field North taken with the F775W, F850LP, and G800L optical elements as
part of the ACS guaranteed time observation program. Spectra extracted from the
ACS G800L grism exposures confirm that the objects are Type Ia supernovae (SNe
Ia) at redshifts z=0.47 and z=0.95. Follow-up HST observations have been
conducted with ACS in F775W and F850LP and with NICMOS in the near-infrared
F110W bandpass, yielding a total of 9 flux measurements in the 3 bandpasses
over a period of 50 days in the observed frame. We discuss many of the
important issues in doing accurate photometry with the ACS. We analyze the
multi-band light curves using two different fitting methods to calibrate the
supernovae luminosities and place them on the SNe Ia Hubble diagram. The
resulting distances are consistent with the redshift-distance relation of the
accelerating universe model, although evolving intergalactic grey dust remains
as a less likely possibility. The relative ease with which these SNe Ia were
found, confirmed, and monitored demonstrates the potential ACS holds for
revolutionizing the field of high-redshift SNe Ia, and therefore of testing the
accelerating universe cosmology and constraining the "epoch of deceleration".Comment: 11 pages, 8 embedded figures. Accepted for publication in Ap
Unraveling the sequence of serpentinization reactions : petrography, mineral chemistry, and petrophysics of serpentinites from MAR 15°N (ODP Leg 209, Site 1274)
Author Posting. © American Geophysical Union, 2006. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geophysical Research Letters 33 (2006): L13306, doi:10.1029/2006GL025681.The results of detailed textural, mineral chemical, and petrophysical studies shed new light on the poorly constrained fluid-rock reaction pathways during retrograde serpentinization at mid-ocean ridges. Uniformly depleted harzburgites and dunites from the Mid-Atlantic Ridge at 15°N show variable extents of static serpentinization. They reveal a simple sequence of reactions: serpentinization of olivine and development of a typical mesh texture with serpentine-brucite mesh rims, followed by replacement of olivine mesh centers by serpentine and brucite. The serpentine mesh rims on relic olivine are devoid of magnetite. Conversely, domains in the rock that are completely serpentinized show abundant magnetite. We propose that low-fluid-flux serpentinization of olivine to serpentine and ferroan brucite is followed by later stages of serpentinization under more open-system conditions and formation of magnetite by the breakdown of ferroan brucite. Modeling of this sequence of reactions can account for covariations in magnetic susceptibility and grain density of the rocks.Funding for this research was
provided by USSSP and NSF-OCE grant 9986135. WB acknowledges
support through a fellowship by the Deep Ocean Exploration Institute
Emergency department documentation templates: variability in template selection and association with physical examination and test ordering in dizziness presentations
Abstract
Background
Clinical documentation systems, such as templates, have been associated with process utilization. The T-System emergency department (ED) templates are widely used but lacking are analyses of the templates association with processes. This system is also unique because of the many different template options available, and thus the selection of the template may also be important. We aimed to describe the selection of templates in ED dizziness presentations and to investigate the association between items on templates and process utilization.
Methods
Dizziness visits were captured from a population-based study of EDs that use documentation templates. Two relevant process outcomes were assessed: head computerized tomography (CT) scan and nystagmus examination. Multivariable logistic regression was used to estimate the probability of each outcome for patients who did or did not receive a relevant-item template. Propensity scores were also used to adjust for selection effects.
Results
The final cohort was 1,485 visits. Thirty-one different templates were used. Use of a template with a head CT item was associated with an increase in the adjusted probability of head CT utilization from 12.2% (95% CI, 8.9%-16.6%) to 29.3% (95% CI, 26.0%-32.9%). The adjusted probability of documentation of a nystagmus assessment increased from 12.0% (95%CI, 8.8%-16.2%) when a nystagmus-item template was not used to 95.0% (95% CI, 92.8%-96.6%) when a nystagmus-item template was used. The associations remained significant after propensity score adjustments.
Conclusions
Providers use many different templates in dizziness presentations. Important differences exist in the various templates and the template that is used likely impacts process utilization, even though selection may be arbitrary. The optimal design and selection of templates may offer a feasible and effective opportunity to improve care delivery.http://deepblue.lib.umich.edu/bitstream/2027.42/112490/1/12913_2010_Article_1586.pd
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The adaptive designs CONSORT extension (ACE) statement: a checklist with explanation and elaboration guideline for reporting randomised trials that use an adaptive design
Abstract: Adaptive designs (ADs) allow pre-planned changes to an ongoing trial without compromising the validity of conclusions and it is essential to distinguish pre-planned from unplanned changes that may also occur. The reporting of ADs in randomised trials is inconsistent and needs improving. Incompletely reported AD randomised trials are difficult to reproduce and are hard to interpret and synthesise. This consequently hampers their ability to inform practice as well as future research and contributes to research waste. Better transparency and adequate reporting will enable the potential benefits of ADs to be realised. This extension to the Consolidated Standards Of Reporting Trials (CONSORT) 2010 statement was developed to enhance the reporting of randomised AD clinical trials. We developed an Adaptive designs CONSORT Extension (ACE) guideline through a two-stage Delphi process with input from multidisciplinary key stakeholders in clinical trials research in the public and private sectors from 21 countries, followed by a consensus meeting. Members of the CONSORT Group were involved during the development process. The paper presents the ACE checklists for AD randomised trial reports and abstracts, as well as an explanation with examples to aid the application of the guideline. The ACE checklist comprises seven new items, nine modified items, six unchanged items for which additional explanatory text clarifies further considerations for ADs, and 20 unchanged items not requiring further explanatory text. The ACE abstract checklist has one new item, one modified item, one unchanged item with additional explanatory text for ADs, and 15 unchanged items not requiring further explanatory text. The intention is to enhance transparency and improve reporting of AD randomised trials to improve the interpretability of their results and reproducibility of their methods, results and inference. We also hope indirectly to facilitate the much-needed knowledge transfer of innovative trial designs to maximise their potential benefits. In order to encourage its wide dissemination this article is freely accessible on the BMJ and Trials journal websites.âTo maximise the benefit to society, you need to not just do research but do it wellâ Douglas G Altma
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