Li, B and Be Contents of Harzburgites from the Dramala Complex (Pindos Ophiolite, Greece): Evidence for a MOR-type Mantle in a Supra-subduction Zone Environment

The Pindos ophiolite represents oceanic lithosphere obducted during the Jurassic. The Dramala mantle section mainly consists of highly depleted spinel harzburgite and minor plagioclase-bearing harzburgite. Textural observations and major element compositions of minerals indicate that the harzburgites experienced impregnation by a mafic, depleted melt and subsequent high-temperature (high-T) hydration and cooling (>750°C) forming pargasite and edenitic hornblende. During further cooling (from ≥ 350-400°C to < 100°C), talc + tremolite ± serpentine ± olivine, serpentine + magnetite, and finally plagioclase alteration phases formed. To test the hypothesis of a supra-subduction zone origin for the Dramala mantle, we measured Li, B and Be contents of minerals by secondary ion mass spectrometry. Whole-rock contents were measured using inductively coupled plasma-mass spectrometry and prompt gamma neutron activation analysis. We observe low Li and B contents of primary minerals (olivine, orthopyroxene, clinopyroxene) consistent with values for unmetasomatized mantle minerals; only Li contents of clinopyroxene (up to 3·7 μg/g) are slightly elevated. The bulk Li contents (0·5-1·1 μg/g) are in the upper range of values for unmetasomatized mantle, whereas B contents (<0·04-1·1 μg/g) are variable and slightly elevated compared with the unmetasomatized mantle as a result of serpentinization. Beryllium abundances in all minerals are very low (<0·005 μg/g), except for pargasite, where a maximum Be content of 0·012 μg/g was measured. The selective addition of Li to clinopyroxene can be related to the interaction with a depleted melt, and/or to partitioning of Li into clinopyroxene upon cooling. During high-T hydration and cooling, the fluid calculated to be in equilibrium with the pargasite or edenitic hornblende (based on Li, Be and B) could have been reaction-modified seawater. Low-T hydration may have led to a very minor increase in bulk B content of most samples and to the formation of serpentine with highly variable B contents (0·1-28 μg/g). Low-T hydration decreased the Li content of orthopyroxene, and Li was probably leached from some samples. The lack of correlation between degree of serpentinization and bulk B contents as well as the presence of high- and low-B serpentine can be explained by low fluid-rock ratios, decreasing T during serpentinization and lack of equilibrium as a result of fast obduction-exhumation. The low light-element contents of primary minerals and whole-rock samples clearly argue against a supra-subduction zone (SSZ) origin of the Dramala mantle section, and against the previous hypothesis of hydrous melting of the Pindos mantle above a subduction zone. We therefore conclude that the Dramala harzburgites represent a mid-ocean ridge (MOR)-type mantle, and not an SSZ-type mantle, juxtaposed with MOR-type and SSZ-type oceanic crust, either in a back-arc or in an intra-oceanic subduction zone settin

Mammalian models of extended healthy lifespan

Over the last two centuries, there has been a significant increase in average lifespan expectancy in the developed world. One unambiguous clinical implication of getting older is the risk of experiencing age-related diseases including various cancers, dementia, type-2 diabetes, cataracts and osteoporosis. Historically, the ageing process and its consequences were thought to be intractable. However, over the last two decades or so, a wealth of empirical data has been generated which demonstrates that longevity in model organisms can be extended through the manipulation of individual genes. In particular, many pathological conditions associated with the ageing process in model organisms, and importantly conserved from nematodes to humans, are attenuated in long-lived genetic mutants. For example, several long-lived genetic mouse models show attenuation in age-related cognitive decline, adiposity, cancer and glucose intolerance. Therefore, these long-lived mice enjoy a longer period without suffering the various sequelae of ageing. The greatest challenge in the biology of ageing is to now identify the mechanisms underlying increased healthy lifespan in these model organisms. Given that the elderly are making up an increasingly greater proportion of society, this focused approach in model organisms should help identify tractable interventions that can ultimately be translated to humans

Assessing Ability to Forecast Geomorphic System Responses to Climate and Land-Use Changes

As the global community faces the effects of ongoing and future climate and land-use changes (C&LUC), geoscientists are called to action to assess the risks associated with such changes, assist with forecasts of future Earth states, quantify hazards to life, and suggest reasonable adaptation strategies. Earth surface scientists have developed conceptual and mathematical models for how geomorphic systems, including those associated with natural hazards that put trillions of dollars in infrastructure and tens of millions of lives at risk, will respond to and give feedback on C&LUC

Fractional Hamiltonian Monodromy from a Gauss-Manin Monodromy

Fractional Hamiltonian Monodromy is a generalization of the notion of Hamiltonian Monodromy, recently introduced by N. N. Nekhoroshev, D. A. Sadovskii and B. I. Zhilinskii for energy-momentum maps whose image has a particular type of non-isolated singularities. In this paper, we analyze the notion of Fractional Hamiltonian Monodromy in terms of the Gauss-Manin Monodromy of a Riemann surface constructed from the energy-momentum map and associated to a loop in complex space which bypasses the line of singularities. We also prove some propositions on Fractional Hamiltonian Monodromy for 1:-n and m:-n resonant systems.Comment: 39 pages, 24 figures. submitted to J. Math. Phy

Energy analysis of organic crop systems. Impact of intensification level.

This study reveals a wide variability in the major parameters of the energy analysis applied to 44 four-year-long organic crop sequences. The intensification level of the systems in terms of the use or nonuse of organic fertilisation on cereals and of irrigation on summer crops (mainly pulses) is largely responsible for this variability. Average energy consumption ranges from 5 000 to 12 270 MJ/ha/year depending on the intensification level. Energy production varies from 35 500 to 43 950 MJ/ha/year. Since energy consumption and production both vary in the same direction with the degree of intensification, the energy gain is stable at an average value of 29300 MJ/ha/year. Energy efficiency decreases from 7.1 MJ/MJ for unfertilised and unirrigated crop sequences, to 3.5 MJ/MJ for fertilised and irrigated sequences, where soy and faba bean are among the major crops

Transport of Cosmic Rays in Chaotic Magnetic Fields

The transport of charged particles in disorganised magnetic fields is an important issue which concerns the propagation of cosmic rays of all energies in a variety of astrophysical environments, such as the interplanetary, interstellar and even extra-galactic media, as well as the efficiency of Fermi acceleration processes. We have performed detailed numerical experiments using Monte-Carlo simulations of particle propagation in stochastic magnetic fields in order to measure the parallel and transverse spatial diffusion coefficients and the pitch angle scattering time as a function of rigidity and strength of the turbulent magnetic component. We confirm the extrapolation to high turbulence levels of the scaling predicted by the quasi-linear approximation for the scattering frequency and parallel diffusion coefficient at low rigidity. We show that the widely used Bohm diffusion coefficient does not provide a satisfactory approximation to diffusion even in the extreme case where the mean field vanishes. We find that diffusion also takes place for particles with Larmor radii larger than the coherence length of the turbulence. We argue that transverse diffusion is much more effective than predicted by the quasi-linear approximation, and appears compatible with chaotic magnetic diffusion of the field lines. We provide numerical estimates of the Kolmogorov length and magnetic line diffusion coefficient as a function of the level of turbulence. Finally we comment on applications of our results to astrophysical turbulence and the acceleration of high energy cosmic rays in supernovae remnants, in super-bubbles, and in jets and hot spots of powerful radio-galaxies.Comment: To be published in Physical Review D, 20 pages 9 figure

Pair Plasma Dominance in the Parsec-Scale Relativistic Jet of 3C345

We investigate whether a pc-scale jet of 3C345 is dominated by a normal plasma or an electron-positron plasma. We present a general condition that a jet component becomes optically thick for synchrotron self-absorption, by extending the method originally developed by Reynolds et al. The general condition gives a lower limit of the electron number density, with the aid of the surface brightness condition, which enables us to compute the magnetic field density. Comparing the lower limit with another independent constraint for the electron density that is deduced from the kinetic luminosity, we can distinguish the matter content. We apply the procedure to the five components of 3C345 (C2, C3, C4, C5, and C7) of which angular diameters and radio fluxes at the peak frequencies were obtainable from literature. Evaluating the representative values of Doppler beaming factors by their equipartition values, we find that all the five components are likely dominated by an electron-positron plasma. The conclusion does not depend on the lower cutoff energy of the power-law distribution of radiating particles.Comment: 17 page

Simulating the Multi-Epoch Direct Detection Technique to Isolate the Thermal Emission of the Non-Transiting Hot Jupiter HD187123B

We report the 6.5$\sigma$ detection of water from the hot Jupiter HD187123b with a Keplerian orbital velocity $K_p$ of 53 $\pm$ 13 km/s. This high confidence detection is made using a multi-epoch, high resolution, cross correlation technique, and corresponds to a planetary mass of 1.4$^{+0.5}_{-0.3}$ $M_J$ and an orbital inclination of 21 $\pm$ 5$^{\circ}$. The technique works by treating the planet/star system as a spectroscopic binary and obtaining high signal-to-noise, high resolution observations at multiple points across the planet's orbit to constrain the system's binary dynamical motion. All together, seven epochs of Keck/NIRSPEC $L$-band observations were obtained, with five before the instrument upgrade and two after. Using high resolution SCARLET planetary and PHOENIX stellar spectral models, along with a line-by-line telluric absorption model, we were able to drastically increase the confidence of the detection by running simulations that could reproduce, and thus remove, the non-random structured noise in the final likelihood space well. The ability to predict multi-epoch results will be extremely useful for furthering the technique. Here, we use these simulations to compare three different approaches to combining the cross correlations of high resolution spectra and find that the Zucker 2003 log(L) approach is least affected by unwanted planet/star correlation for our HD187123 data set. Furthermore, we find that the same total S/N spread across an orbit in many, lower S/N epochs rather than fewer, higher S/N epochs could provide a more efficient detection. This work provides a necessary validation of multi-epoch simulations which can be used to guide future observations and will be key to studying the atmospheres of further separated, non-transiting exoplanets.Comment: Accepted to AJ, 14 pages, 10 figure

Coronary steal syndrome after coronary artery bypass for anomalous aortic origin of a coronary artery.

Anomalous aortic origin of a coronary artery found in a symptomatic 9-year-old boy was initially treated with coronary artery bypass grafting using a left internal mammary artery anastomoses to the left anterior descending coronary artery, but resulted in coronary ischemia, likely from a steal phenomenon. Subsequent transection of the proximal left internal mammary artery with anastomosis to the ascending aorta, and coronary ostial enlargement, resulted in a durable treatment. We recommend caution in choosing coronary artery bypass grafting using a left internal mammary artery pedicle graft for the treatment of anomalous aortic origin of a coronary artery

Setting the stage: social-environmental and motivational predictors of optimal training engagement

In this paper, we will firstly explore the central tenets of SDT. Research that has examined the social-environmental and motivation-related correlates of optimal training, performance and health-related engagement through the theoretical lens of SDT will be reviewed. Drawing from SDT-driven work undertaken in educational, sport and dance settings, we will draw conclusions and suggest future directions from a research and applied perspective