593 research outputs found
Quantitative dating of pleistocene deposits of the Kyrenia range, Northern Cyprus : implications for timing, rates of uplift and driving mechanisms
R.N.P. acknowledges the NERC CASE scholarship at the University of Edinburgh. Additional field and laboratory work was aided by the DARIUS Programme to A.H.F.R. and T.C.K. We are grateful for the additional financial support provided by the John Dixon Memorial Fund.The Kyrenia Range underwent tectonically driven uplift during the Pliocene to Pleistocene in response to the interaction of various tectonic processes. To understand the tectonic processes driving the uplift and how this is related to uplift of other areas of the Eastern Mediterranean, uranium-series disequilibrium and optically stimulated luminescence dating were applied to marine and non-marine terrace deposits exposed on the northern flank of the range. Palaeomagnetism and strontium isotope dating were used in conjunction to date the final stages of the marine environment adjacent to the Kyrenia Range prior to major surface uplift. Uplift rates range from >1.2 mm aâ1, inferred during the Early Pleistocene, to <0.2 mm aâ1during the Late Pleistocene. The new data show that the Kyrenia Range was uplifted contemporaneously with the Troodos Massif in southern Cyprus. The uplift of the Kyrenia Range appears to have been significantly faster than that affecting other comparable regions in the easternmost Mediterranean during the Pleistocene (e.g. Lebanon coast; southern Anatolian plateau). The driving mechanism for the uplift of both the Kyrenia Range and the Troodos Massif is inferred to be the collision of the Eratosthenes Seamount with the Cyprus trench to the south of Cyprus.Publisher PDFPeer reviewe
Planning the Future of U.S. Particle Physics (Snowmass 2013): Chapter 4: Cosmic Frontier
These reports present the results of the 2013 Community Summer Study of the
APS Division of Particles and Fields ("Snowmass 2013") on the future program of
particle physics in the U.S. Chapter 4, on the Cosmic Frontier, discusses the
program of research relevant to cosmology and the early universe. This area
includes the study of dark matter and the search for its particle nature, the
study of dark energy and inflation, and cosmic probes of fundamental
symmetries.Comment: 61 page
Lagrangian analysis of alignment dynamics for isentropic compressible magnetohydrodynamics
After a review of the isentropic compressible magnetohydrodynamics (ICMHD)
equations, a quaternionic framework for studying the alignment dynamics of a
general fluid flow is explained and applied to the ICMHD equations.Comment: 12 pages, 2 figures, submitted to a Focus Issue of New Journal of
Physics on "Magnetohydrodynamics and the Dynamo Problem" J-F Pinton, A
Pouquet, E Dormy and S Cowley, editor
Snowmass CF1 Summary: WIMP Dark Matter Direct Detection
As part of the Snowmass process, the Cosmic Frontier WIMP Direct Detection
subgroup (CF1) has drawn on input from the Cosmic Frontier and the broader
Particle Physics community to produce this document. The charge to CF1 was (a)
to summarize the current status and projected sensitivity of WIMP direct
detection experiments worldwide, (b) motivate WIMP dark matter searches over a
broad parameter space by examining a spectrum of WIMP models, (c) establish a
community consensus on the type of experimental program required to explore
that parameter space, and (d) identify the common infrastructure required to
practically meet those goals.Comment: Snowmass CF1 Final Summary Report: 47 pages and 28 figures with a 5
page appendix on instrumentation R&
A New Era in the Quest for Dark Matter
There is a growing sense of `crisis' in the dark matter community, due to the
absence of evidence for the most popular candidates such as weakly interacting
massive particles, axions, and sterile neutrinos, despite the enormous effort
that has gone into searching for these particles. Here, we discuss what we have
learned about the nature of dark matter from past experiments, and the
implications for planned dark matter searches in the next decade. We argue that
diversifying the experimental effort, incorporating astronomical surveys and
gravitational wave observations, is our best hope to make progress on the dark
matter problem.Comment: Published in Nature, online on 04 Oct 2018. 13 pages, 1 figur
Effects of Intracoronary Alteplase on Microvascular Function in Acute Myocardial Infarction
BackgroundâImpaired microcirculatory reperfusion worsens prognosis following acute STâsegmentâelevation myocardial infarction. In the TâTIME (A Trial of LowâDose Adjunctive Alteplase During Primary PCI) trial, microvascular obstruction on cardiovascular magnetic resonance imaging did not differ with adjunctive, lowâdose, intracoronary alteplase (10 or 20 mg) versus placebo during primary percutaneous coronary intervention. We evaluated the effects of intracoronary alteplase, during primary percutaneous coronary intervention, on the index of microcirculatory resistance, coronary flow reserve, and resistive reserve ratio.
Methods and ResultsâA prespecified physiology substudy of the TâTIME trial. From 2016 to 2017, patients with STâsegmentâelevation myocardial infarction â€6 hours from symptom onset were randomized in a doubleâblind study to receive alteplase 20 mg, alteplase 10 mg, or placebo infused into the culprit artery postreperfusion, but prestenting. Index of microcirculatory resistance, coronary flow reserve, and resistive reserve ratio were measured after percutaneous coronary intervention. Cardiovascular magnetic resonance was performed at 2 to 7 days and 3 months. Analyses in relation to ischemic time (<2, 2â4, and â„4 hours) were prespecified. One hundred fortyâfour patients (mean age, 59±11 years; 80% male) were prospectively enrolled, representing 33% of the overall population (n=440). Overall, index of microcirculatory resistance (median, 29.5; interquartile range, 17.0â55.0), coronary flow reserve(1.4 [1.1â2.0]), and resistive reserve ratio (1.7 [1.3â2.3]) at the end of percutaneous coronary intervention did not differ between treatment groups. Interactions were observed between ischemic time and alteplase for coronary flow reserve (P=0.013), resistive reserve ratio (P=0.026), and microvascular obstruction (P=0.022), but not index of microcirculatory resistance.
ConclusionsâIn STâsegmentâelevation myocardial infarction with ischemic time â€6 hours, there was overall no difference in microvascular function with alteplase versus placebo
An atlas of seabed biodiversity for Aotearoa New Zealand
\ua9 2023 Copernicus GmbH. All rights reserved. The waters of Aotearoa New Zealand span over 4.2ÄâŹ\uafmillionÄâŹ\uafkm2 of the South Pacific Ocean and harbour a rich diversity of seafloor-Associated taxa. Due to the immensity and remoteness of the area, there are significant gaps in the availability of data that can be used to quantify and map the distribution of seafloor and demersal biodiversity, limiting effective management. In this study, we describe the development and accessibility of an online atlas of seabed biodiversity that aims to fill these gaps. Species distribution models were developed for 579 taxa across four taxonomic groups: demersal fish, reef fish, subtidal invertebrates and macroalgae. Spatial layers for taxa distribution based on habitat suitability were statistically validated and then, as a further check, evaluated by taxonomic experts to provide measures of confidence to guide the future use of these layers. Spatially explicit uncertainty (SD) layers were also developed for each taxon distribution. We generated layer-specific metadata, including statistical and expert evaluation scores, which were uploaded alongside the accompanying spatial layers to the open access database Zenodo. This database provides the most comprehensive source of information on the distribution of seafloor taxa for Aotearoa New Zealand and is thus a valuable resource for managers, researchers and the public that will guide the management and conservation of seafloor communities. The atlas of seabed biodiversity for Aotearoa New Zealand is freely accessible via the open-Access database Zenodo under 10.5281/zenodo.7083642 (Stephenson et al., 2022)
Wide-Angle Seismic Imaging of Two Modes of Crustal Accretion in Mature Atlantic Ocean Crust
We present a highâresolution 2âD Pâwave velocity model from a 225âkmâlong active seismic profile, collected over ~60â75 Ma central Atlantic crust. The profile crosses five ridge segments separated by a transform and three nontransform offsets. All ridge discontinuities share similar primary characteristics, independent of the offset. We identify two types of crustal segment. The first displays a classic twoâlayer velocity structure with a high gradient Layer 2 (~0.9 s) above a lower gradient Layer 3 (0.2 s). Here, PmP coincides with the 7.5 km s contour, and velocity increases to >7.8 km s within 1 km below. We interpret these segments as magmatically robust, with PmP representing a petrological boundary between crust and mantle. The second has a reduced contrast in velocity gradient between the upper and lower crust and PmP shallower than the 7.5 km s contour. We interpret these segments as tectonically dominated, with PmP representing a serpentinized (alteration) front. While velocityâdepth profiles fit within previous envelopes for slowâspreading crust, our results suggest that such generalizations give a misleading impression of uniformity. We estimate that the two crustal styles are present in equal proportions on the floor of the Atlantic. Within two tectonically dominated segments, we make the first wideâangle seismic identifications of buried oceanic core complexes in mature (>20 Ma) Atlantic Ocean crust. They have a ~20âkmâwide âdomalâ morphology with shallow basement and increased upper crustal velocities. We interpret their midcrustal seismic velocity inversions as alteration and rockâtype assemblage contrasts across crustalâscale detachment faults
First narrow-band search for continuous gravitational waves from known pulsars in advanced detector data
Spinning neutron stars asymmetric with respect to their rotation axis are potential sources of
continuous gravitational waves for ground-based interferometric detectors. In the case of known pulsars a
fully coherent search, based on matched filtering, which uses the position and rotational parameters
obtained from electromagnetic observations, can be carried out. Matched filtering maximizes the signalto-
noise (SNR) ratio, but a large sensitivity loss is expected in case of even a very small mismatch
between the assumed and the true signal parameters. For this reason, narrow-band analysis methods have
been developed, allowing a fully coherent search for gravitational waves from known pulsars over a
fraction of a hertz and several spin-down values. In this paper we describe a narrow-band search of
11 pulsars using data from Advanced LIGOâs first observing run. Although we have found several initial
outliers, further studies show no significant evidence for the presence of a gravitational wave signal.
Finally, we have placed upper limits on the signal strain amplitude lower than the spin-down limit for 5 of
the 11 targets over the bands searched; in the case of J1813-1749 the spin-down limit has been beaten for
the first time. For an additional 3 targets, the median upper limit across the search bands is below the
spin-down limit. This is the most sensitive narrow-band search for continuous gravitational waves carried
out so far
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