2,079 research outputs found
Ultra-shallow-marine anoxia in an Early Triassic shallow-marine clastic ramp (Spitsbergen) and the suppression of benthic radiation
Lower Triassic marine strata in Spitsbergen accumulated on a mid-to-high latitude ramp in which high-energy foreshore and shoreface facies passed offshore into sheet sandstones of probable hyperpycnite origin. More distal facies include siltstones, shales and dolomitic limestones. Carbon isotope chemostratigraphy comparison allows improved age dating of the Boreal sections and shows a significant hiatus in the upper Spathian. Two major deepening events, in earliest Griesbachian and late Smithian time, are separated by shallowing-upwards trends that culminated in the Dienerian and Spathian substages. The redox record, revealed by changes in bioturbation, palaeoecology, pyrite framboid content and trace metal concentrations, shows anoxic phases alternating with intervals of better ventilation. Only Dienerian–early Smithian time witnessed persistent oxygenation that was sufficient to support a diverse benthic community. The most intensely anoxic, usually euxinic, conditions are best developed in offshore settings, but at times euxinia also developed in upper offshore settings where it is even recorded in hyperpycnite and storm-origin sandstone beds: an extraordinary facet of Spitsbergen's record. The euxinic phases do not track relative water depth changes. For example, the continuous shallowing upwards from the Griesbachian to lower Dienerian was witness to several euxinic phases separated by intervals of more oxic, bioturbated sediments. It is likely that the euxinia was controlled by climatic oscillations rather than intra-basinal factors. It remains to be seen if all the anoxic phases found in Spitsbergen are seen elsewhere, although the wide spread of anoxic facies in the Smithian/Spathian boundary interval is clearly a global event
Pharmacist-led management of chronic pain in primary care:results from a randomised controlled exploratory trial
To compare the effectiveness of pharmacist medication review, with or without pharmacist prescribing, with standard care, for patients with chronic pain
An abrupt extinction in the Middle Permian (Capitanian) of the Boreal Realm (Spitsbergen) and its link to anoxia and acidification
The controversial Capitanian (Middle Permian, 262 Ma) extinction event is only known from equatorial latitudes, and consequently its global extent is poorly resolved. We demonstrate that there were two, severe extinctions amongst brachiopods in northern Boreal latitudes (Spitsbergen) in the Middle to Late Permian, separated by a recovery phase. New age dating of the Spitsbergen strata (belonging to the Kapp Starostin Formation), using strontium isotopes and d13C trends and comparison with better-dated sections in Greenland, suggests that the first crisis occurred in the Capitanian. This age assignment indicates that this Middle Permian extinction is manifested at higher latitudes. Redox proxies (pyrite framboids and trace metals) show that the Boreal crisis coincided with an intensification of oxygen depletion, implicating anoxia in the extinction scenario. The widespread and near-total loss of carbonates across the Boreal Realm also suggests a role for acidification in the crisis. The recovery interval saw the appearance of new brachiopod and bivalve taxa alongside survivors, and an increased mollusk dominance, resulting in an assemblage reminiscent of younger Mesozoic assemblages. The subsequent end-Permian mass extinction terminated this Late Permian radiation
HST Images Flash Ionization of Old Ejecta by the 2011 Eruption of Recurrent Nova T Pyxidis
T Pyxidis is the only recurrent nova surrounded by knots of material ejected
in previous outbursts. Following the eruption that began on 2011 April 14.29,
we obtained seven epochs (from 4 to 383 days after eruption) of Hubble Space
Telescope narrowband Ha images of T Pyx . The flash of radiation from the nova
event had no effect on the ejecta until at least 55 days after the eruption
began. Photoionization of hydrogen located north and south of the central star
was seen 132 days after the beginning of the eruption. That hydrogen recombined
in the following 51 days, allowing us to determine a hydrogen atom density of
at least 7e5 cm^-3 - at least an order of magnitude denser than the previously
detected, unresolved [NII] knots surrounding T Pyx. Material to the northwest
and southeast was photoionized between 132 and 183 days after the eruption
began. 99 days later that hydrogen had recombined. Both then (282 days after
outburst) and 101 days later, we detected almost no trace of hydrogen emission
around T Pyx. There is a large reservoir of previously unseen, cold diffuse
hydrogen overlapping the previously detected, [NII] - emitting knots of T Pyx
ejecta. The mass of this newly detected hydrogen is probably an order of
magnitude larger than that of the [NII] knots. We also determine that there is
no significant reservoir of undetected ejecta from the outer boundaries of the
previously detected ejecta out to about twice that distance, near the plane of
the sky. The lack of distant ejecta is consistent with the Schaefer et al
(2010) scenario for T Pyx, in which the star underwent its first eruption
within five years of 1866 after many millennia of quiescence, followed by the
six observed recurrent nova eruptions since 1890. This lack of distant ejecta
is not consistent with scenarios in which T Pyx has been erupting continuously
as a recurrent nova for many centuries or millennia.Comment: 27 pages, 10 figures, submitted to the Astrophysical Journa
Enhancing deprescribing : a qualitative understanding of the complexities of pharmacist-led deprescribing in care homes
Funding statement This research is funded by the National Institute for Health Research (NIHR) Policy Research Programme (project reference NIHR202053). The views expressed are those of the authors and not necessarily those of the NIHR or the Department of Health and Social Care. Acknowledgements Thank you to the pharmacists, GP practice and care home staff who took part in the interviews. We would also like to acknowledge the Norfolk and Waveney Clinical Commissioning Group as the study sponsor and our patient and public involvement colleagues Janet Gray and Christine Hanford who were supported by Jacqueline Romero, manager of PPIRes.Peer reviewedPublisher PD
The Hot and Cold Spots in the WMAP Data are Not Hot and Cold Enough
This paper presents a frequentist analysis of the hot and cold spots of the
cosmic microwave background data collected by the Wilkinson Microwave
Anisotropy Probe (WMAP). We compare the WMAP temperature statistics of extrema
(number of extrema, mean excursion, variance, skewness and kurtosis of the
excursion) to Monte-Carlo simulations. We find that, on average, the local
maxima (high temperatures in the anisotropy) are too cold and the local minima
are too warm. In order to quantify this claim we describe a two-sided
statistical hypothesis test which we advocate for other investigations of the
Gaussianity hypothesis. Using this test we reject the isotropic Gaussian
hypothesis at more than 99% confidence in a well-defined way. Our claims are
based only on regions that are outside the most conservative WMAP foreground
mask. We perform our test separately on maxima and minima, and on the north and
south ecliptic and Galactic hemispheres and reject Gaussianity at above 95%
confidence for almost all tests of the mean excursions. The same test also
shows the variance of the maxima and minima to be low in the ecliptic north
(99% confidence), but consistent in the south; this effect is not as pronounced
in the Galactic north and south hemispheres.Comment: 5 pages, 1 figure, text updated to match published version,
conclusions unchange
The Red Nova-like Variable in M31 - A Blue Candidate in Quiescence
M31-RV was an extraordinarily luminous (~10^6 Lsun) eruptive variable,
displaying very cool temperatures (roughly 1000 Kelvins) as it faded. The
photometric behavior of M31-RV (and several other very red novae, i.e. luminous
eruptive red variables) has led to several models of this apparently new class
of astrophysical object. One of the most detailed models is that of
"mergebursts": hypothetical mergers of close binary stars. These are predicted
to rival or exceed the brightest classical novae in luminosity, but to be much
cooler and redder than classical novae, and to become slowly hotter and bluer
as they age. This prediction suggests two stringent and definitive tests of the
mergeburst hypothesis. First, there should always be a cool red remnant, and
NOT a hot blue remnant at the site of such an outburst. Second, the inflated
envelope of a mergeburst event should be slowly contracting, hence it must
display a slowly rising effective temperature. We have located a luminous,
UV-bright object within 0.4 arcsec (1.5 sigma of the astrometric position) of
M31-RV in archival WFPC2 images taken 10 years after the outburst: it resembles
an old nova. Twenty years after the outburst, the object remains much too hot
to be a mergeburst. Its behavior remains consistent with that of theoretical
nova models which erupt on a low mass white dwarf. Future Hubble UV and visible
images could determine if the M31-RV analogs (in M85 and in M99) are also
behaving like old novae.Comment: Accepted for publication in ApJ, comments welcom
Tellurium in Late Permian-Early Triassic Sediments as a Proxy for Siberian Flood Basalt Volcanism
We measured the concentrations of trace elements in Late Permian to Early Triassic sediments from Spitsbergen. High mercury concentrations in sediments from the level of the Permo-Triassic Mass Extinction (PTME) at this location were previously attributed to the emplacement of the Siberian Traps Large Igneous Province and used to link the timing of volcanism with the record of environmental change and extinction in these sediments. We investigated the use of the moderately to highly volatile, siderophile elements Ni, Zn, Cd, Sb, Te, Re, and Tl as proxies for the intensity of Siberian volcanism. These trace elements, like Hg, have high concentrations in volcanic gas compared to crustal rocks. Tellurium is highly enriched at the PTME, and Te/Th ratios increase by a factor of ∼20 across the PTME, similar to the variation in Hg/total organic carbon (TOC) in the same samples. Te/Th and Hg/TOC values imply that Siberian volcanism initiated at the onset of the PTME, coincident with the start of the δ13Corganic excursion and abrupt warming. Based on Te and Hg, most Siberian volcanism occurred between the two phases of the PTME boundary (a period of less than 100 ky), but also continued into the Early Triassic. The duration of Siberian volcanism inferred from Te/Th and Hg/TOC is shorter than that indicated by recent high-precision U-Pb ages of Siberian intrusive and extrusive rocks. Te concentrations and Te/Th ratios in sediments represent a useful new proxy for volcanism, which can be used to link the marine sedimentary record with large volcanic events on land
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