1,238 research outputs found
Data-constrained assessment of ocean circulation changes since the middle Miocene in an Earth system model
Since the middle Miocene (15âMa, million years ago), the Earth's climate has undergone a long-term cooling trend, characterised by a reduction in ocean temperatures of up to 7â8ââC. The causes of this cooling are primarily thought to be due to tectonic plate movements driving changes in large-scale ocean circulation patterns, and hence heat redistribution, in conjunction with a drop in atmospheric greenhouse gas forcing (and attendant ice-sheet growth and feedback). In this study, we assess the potential to constrain the evolving patterns of global ocean circulation and cooling over the last 15âMa by assimilating a variety of marine sediment proxy data in an Earth system model. We do this by first compiling surface and benthic ocean temperature and benthic carbon-13 (δ13C) data in a series of seven time slices spaced at approximately 2.5âMyr intervals. We then pair this with a corresponding series of tectonic and climate boundary condition reconstructions in the cGENIE (âmuffinâ release) Earth system model, including alternative possibilities for an open vs. closed Central American Seaway (CAS) from 10âMa onwards. In the cGENIE model, we explore uncertainty in greenhouse gas forcing and the magnitude of North Pacific to North Atlantic salinity flux adjustment required in the model to create an Atlantic Meridional Overturning Circulation (AMOC) of a specific strength, via a series of 12 (one for each tectonic reconstruction) 2D parameter ensembles. Each ensemble member is then tested against the observed global temperature and benthic δ13C patterns. We identify that a relatively high CO2 equivalent forcing of 1120âppm is required at 15âMa in cGENIE to reproduce proxy temperature estimates in the model, noting that this CO2 forcing is dependent on the cGENIE model's climate sensitivity and that it incorporates the effects of all greenhouse gases. We find that reproducing the observed long-term cooling trend requires a progressively declining greenhouse gas forcing in the model. In parallel to this, the strength of the AMOC increases with time despite a reduction in the salinity of the surface North Atlantic over the cooling period, attributable to falling intensity of the hydrological cycle and to lowering polar temperatures, both caused by CO2-driven global cooling. We also find that a closed CAS from 10âMa to present shows better agreement between benthic δ13C patterns and our particular series of model configurations and data. A final outcome of our analysis is a pronounced ca. 1.5ââ° decline occurring in atmospheric (and ca. 1ââ° ocean surface) δ13C that could be used to inform future δ13C-based proxy reconstructions.</p
Postmortem tissue distribution of morphine and its metabolites in a series of heroin related deaths
The abuse of heroin (diamorphine) and heroin deaths are growing around the world. The interpretation of the toxicological results from suspected heroin deaths is notoriously difficult especially in cases where there may be limited samples. In order to help forensic practitioners with heroin interpretation we determined the concentration of morphine (M), morphineâ3âglucuronide (M3G) and morphineâ6âglucuronide (M6G) in blood (femoral and cardiac), brain (thalamus), liver (deep right lobe), bone marrow (sternum), skeletal muscle (psoas) and vitreous humor in 44 heroin related deaths. The presence of 6âmonoacetylmorphine (6âMAM) in any of the postmortem samples was used as confirmation of heroin use. Quantitation was carried out using a validated LCâMS/MS method with solid phase extraction. We also determined the presence of papaverine, noscapine and codeine in the samples, substances often found in illicit heroin and that may help determine illicit heroin use. The results of this study show that vitreous is the best sample to detect 6âMAM (100% of cases), and thus heroin use. The results of the M, M3G and M6G quantitation in this study allow a degree of interpretation when samples are limited. However in some cases it may not be possible to determine heroin/morphine use as in 4 cases in muscle (3 cases in bone marrow) no morphine, morphineâ3âglucuronide or morphineâ6âglucuronide was detected, even though they were detected in other case samples. As always postmortem cases of suspected morphine/heroin intoxication should be interpreted with care and with as much case knowledge as possible
From stars to patients: Lessons from space science and astrophysics for health care informatics
Big Data are revolutionizing nearly every aspect of the modern society. One area where this can have a profound positive societal impact is the field of Health Care Informatics (HCI), which faces many challenges. The key idea behind this study is: can we use some of the experience and technical and methodological solutions from the fields that have successfully adapted to the Big Data era, namely astronomy and space science, to help accelerate the progress of HCI? We illustrate this with examples from the Virtual Observatory framework, and the NCI EDRN project. An effective sharing and reuse of tools, methods, and experiences from different fields can save a lot of effort, time, and expense. HCI can thus benefit from the proven solutions to big data challenges from other domains
Optical measurement of torque exerted on an elongated object by a non-circular laser beam
We have developed a scheme to measure the optical torque, exerted by a laser
beam on a phase object, by measuring the orbital angular momentum of the
transmitted beam. The experiment is a macroscopic simulation of a situation in
optical tweezers, as orbital angular momentum has been widely used to apply
torque to microscopic objects. A hologram designed to generate LG02 modes and a
CCD camera are used to detect the orbital component of the beam. Experimental
results agree with theoretical numerical calculations, and the strength of the
orbital component suggest its usefulness in optical tweezers for
micromanipulation.Comment: 6 pages, 7 figures, v2: minor typographical correction
Incorporation of tetrahedral ferric iron in hydrous ringwoodite
Hydrous Fo_{91} ringwoodite crystals were synthesized at 20 GPa and high-temperature conditions using a multi-anvil press. Recovered crystals were analyzed using electron microprobe analysis, Raman spectroscopy, infrared spectroscopy, synchrotron MĂśssbauer spectroscopy, single-crystal X-ray diffraction, and single-crystal Laue neutron diffraction, to carefully characterize the chemistry and crystallography of the samples. Analysis of the combined data sets provides evidence for the presence of tetrahedrally coordinated ferric iron and multiple hydrogen incorporation mechanisms within these blue-colored iron-bearing ringwoodite crystals. Tetrahedral ferric iron is coupled with cation disorder of silicon onto the octahedrally coordinated site. Cation disorder in mantle ringwoodite minerals may be promoted in the presence of water, which could have implications for current models of seismic velocities within the transition zone. Additionally, the presence of tetrahedrally coordinated ferric iron may cause the blue color of many ringwoodite and other high-pressure crystals
The Atacama Cosmology Telescope: Cross-Correlation of Cosmic Microwave Background Lensing and Quasars
We measure the cross-correlation of Atacama cosmology telescope cosmic microwave background (CMB) lensing convergence maps with quasar maps made from the Sloan Digital Sky Survey DR8 SDSS-XDQSO photometric catalog. The CMB lensing quasar cross-power spectrum is detected for the first time at a significance of 3.8Ď, which directly confirms that the quasar distribution traces the mass distribution at high redshifts z\u3e1. Our detection passes a number of null tests and systematic checks. Using this cross-power spectrum, we measure the amplitude of the linear quasar bias assuming a template for its redshift dependence, and find the amplitude to be consistent with an earlier measurement from clustering; at redshift zâ1.4, the peak of the distribution of quasars in our maps, our measurement corresponds to a bias of b=2.5Âą0.6. With the signal-to-noise ratio on CMB lensing measurements likely to improve by an order of magnitude over the next few years, our results demonstrate the potential of CMB lensing cross-correlations to probe astrophysics at high redshifts
Trace formulae for non-equilibrium Casimir interactions, heat radiation and heat transfer for arbitrary objects
We present a detailed derivation of heat radiation, heat transfer and
(Casimir) interactions for N arbitrary objects in the framework of
fluctuational electrodynamics in thermal non-equilibrium. The results can be
expressed as basis-independent trace formulae in terms of the scattering
operators of the individual objects. We prove that heat radiation of a single
object is positive, and that heat transfer (for two arbitrary passive objects)
is from the hotter to a colder body. The heat transferred is also symmetric,
exactly reversed if the two temperatures are exchanged. Introducing partial
wave-expansions, we transform the results for radiation, transfer and forces
into traces of matrices that can be evaluated in any basis, analogous to the
equilibrium Casimir force. The method is illustrated by (re)deriving the heat
radiation of a plate, a sphere and a cylinder. We analyze the radiation of a
sphere for different materials, emphasizing that a simplification often
employed for metallic nano-spheres is typically invalid. We derive asymptotic
formulae for heat transfer and non-equilibrium interactions for the cases of a
sphere in front a plate and for two spheres, extending previous results. As an
example, we show that a hot nano-sphere can levitate above a plate with the
repulsive non-equilibrium force overcoming gravity -- an effect that is not due
to radiation pressure.Comment: 29 pages, 6 figures (v2: Sentence added in Sec. 1
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