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The search for life in the Universe is a fundamental problem of astrobiology and modern science. The current progress in the detection of terrestrial-type exoplanets has opened a new avenue in the characterization of exoplanetary atmospheres and in the search for biosignatures of life with the upcoming ground-based and space missions. To specify the conditions favourable for the origin, development and sustainment of life as we know it in other worlds, we need to understand the nature of global (astrospheric), and local (atmospheric and surface) environments of exoplanets in the habitable zones (HZs) around G-K-M dwarf stars including our young Sun. Global environment is formed by propagated disturbances from the planet-hosting stars in the form of stellar flares, coronal mass ejections, energetic particles and winds collectively known as astrospheric space weather. Its characterization will help in understanding how an exoplanetary ecosystem interacts with its host star, as well as in the specification of the physical, chemical and biochemical conditions that can create favourable and/or detrimental conditions for planetary climate and habitability along with evolution of planetary internal dynamics over geological timescales. A key linkage of (astro)physical, chemical and geological processes can only be understood in the framework of interdisciplinary studies with the incorporation of progress in heliophysics, astrophysics, planetary and Earth sciences. The assessment of the impacts of host stars on the climate and habitability of terrestrial (exo)planets will significantly expand the current definition of the HZ to the biogenic zone and provide new observational strategies for searching for signatures of life. The major goal of this paper is to describe and discuss the current status and recent progress in this interdisciplinary field in light of presentations and discussions during the NASA Nexus for Exoplanetary System Science funded workshop ‘Exoplanetary Space Weather, Climate and Habitability’ and to provide a new roadmap for the future development of the emerging field of exoplanetary science and astrobiology.
Blood samples from normal and Plasmodium berghei infected mice are being analyzed for trace elements by charged particle induced x-rays. Approximately 0.25 ml of the sample (whole blood, washed red cells, or plasma) is dry ashed. The ashes are mounted on a 0.003 inch Kapton foil. The analysis is performed by bombardment of the samples by a beam of 2.0 MeV protons and detection of the characteristic x-rays by a 175-eV-resolution lithium-drifted silicon detector. The data are analyzed by an on-line PDP-9 computer-based data acquisition system. Results indicate an increase in the K, Ca, Cu, and Zn per unit volume of the red cells of the malaria infected mice relative to the amounts measured for uninfected blood, and a decrease in the K, Ca, and Fe and an increase in the Cu per unit volume in the plasma of the infected mice.
In the last decade observations have been able to probe the evolution of the galaxy luminosity function, in particular showing a variation of its faint-end with redshift. We employ the data of the Cluster-EAGLE project, a set of cosmological, hydrodynamical zoom-in simulations of 30 galaxy clusters, to study the evolution of the galaxy luminostity functions in clusters with redshift. We compile a catalogue of simulated galaxies’ luminosities in the SDSS bands using the E-MILES spectra database, and taking into account dust attenuation. Stacked luminosity functions present little evolution with redshift of the faint-end slope from z=3.5 to z=0, regardless of the cluster mass.
Observational evidence in space and astrophysical plasmas with a long collisional mean free path suggests that more massive charged particles may be preferentially heated. One possible mechanism for this is the turbulent cascade of energy from injection to dissipation scales, where the energy is converted to heat. Here we consider a simple system consisting of a magnetized plasma slab of electrons and a single ion species with a cross-field density gradient. We show that such a system is subject to an electron drift wave instability, known as the universal instability, which is stabilized only when the electron and ion thermal speeds are equal. For unequal thermal speeds, we find from quasilinear analysis and nonlinear simulations that the instability gives rise to turbulent energy exchange between ions and electrons that acts to equalize the thermal speeds. Consequently, this turbulent heating tends to equalize the component temperatures of pair plasmas and to heat ions to much higher temperatures than electrons for conventional mass-ratio plasmas.
The confinement of heat in the core of a magnetic fusion reactor is optimised using a multidimensional optimisation algorithm. For the first time in such a study, the loss of heat due to turbulence is modelled at every stage using first-principles nonlinear simulations which accurately capture the turbulent cascade and large-scale zonal flows. The simulations utilise a novel approach, with gyrofluid treatment of the small-scale drift waves and gyrokinetic treatment of the large-scale zonal flows. A simple near-circular equilibrium with standard parameters is chosen as the initial condition. The figure of merit, fusion power per unit volume, is calculated, and then two control parameters, the elongation and triangularity of the outer flux surface, are varied, with the algorithm seeking to optimise the chosen figure of merit. A twofold increase in the plasma power per unit volume is achieved by moving to higher elongation and strongly negative triangularity.
Samples taken from the Dome C ice core, Antarctica, and the GRIP ice core, Greenland, are examined using the scanning electron microscope to determine their microstructure. In both cores, samples are taken from two differing climatic periods: the Holocene and the last glacial period. Many of the usual features observed in similar samples under the light microscope are observed, including: bubbles, grain boundaries and clathrate hydrates. Features not resolvable using the light microscope are also found. Dust particles are found in situ. Eighty-five per cent of those observed contained silicon, which was generally associated with aluminium and magnesium. An estimation is made of the relative proportions of dust particles located at grain boundaries and in the bulk of the ice grain. At Dome C a higher proportion than expected from a random distribution of particles was found located at grain boundaries, although in Greenland this was not found to be the case for most samples. Direct evidence is also presented indicating the role of dust particles and microscopical inclusions in impeding or ``pinning’’ grain-boundary migration. Soluble impurities are also detected at some triple junctions and grain boundaries.
Replicate ice cores have been drilled about 10 m apart for the top 790 m of the ice sheet at Dome C, Antarctica. This provides an opportunity to examine inter-core variation of the signal for identical events, based on dielectric profile (DEP) comparisons. Comparison of the signal from the same core (a section 48 m long), measured 1 year apart, showed good reproducibility, with peak heights varying by around 10% between the two measurements. For the two replicate cores, identical peaks were matched and showed variability between cores of typically a factor 1.5. This can be explained based on the likelihood of significant time periods of missing accumulation in any single core at sites with such low snow accumulation rate. To synchronize core depths by matching peaks, it is essential to use the pattern of peaks, rather than just widely spaced individual strong peaks. To derive a quantitative volcanic index from these low-accumulation rate sites, it will be necessary to combine or average the results from several closely spaced parallel cores.
Understanding the microstructure of ice underpins the interpretation of ice-core measurements and many ice-sheet properties. A detailed study of polar snow and ice using scanning electron microscope (SEM) and X-ray analysis revealed the micro-structural distribution of soluble impurities. Sublimation under vacuum (etching) concentrated impurity from both the bulk and grain boundaries on to the specimen surfaces in detectable quantities. Sublimation in the cold room before examination (pre-etching) collected previously unobservable quantities of impurity at triple junctions. A heterogeneous distribution of impurities was observed. Chloride was frequently found to originate from the lattice, but not usually at triple junctions. Other impurities, particularly sodium chloride, were detected at grain boundaries and bubble surfaces. Sulphate was often found at triple junctions in specimens containing a high bulk concentration of the acid, frequently in conjunction with cations. This suggests the possibility that veins were only filled with significant amounts of impurity when the surrounding grain boundaries were saturated. The model of impurity arrangement inferred from the results reconciles differences between previous SEM studies; additionally it is consistent with and explains recent electrical conduction observations. The disconnected arrangement of impurity-filled grain boundaries and veins limits opportunities for significant post-depositional solute movement.
We report progress on a spectroscopic and photometric programme devoted to the study of the dynamics of O-F5 stars within 15° of the North and South Galactic Poles. The aims of the programme are to test dynamical and chemical evolution models of the Galaxy by establishing velocity dispersions as a function of z-distance for stars of different population groups. We are also able to investigate the interstellar reddening at the poles and the kinematic properties of apparently normal early-type stars found more than 1 kpc from the galactic plane.
Ice observations and sediment samples were collected in the Beaufort Gyre in 1988. Fine sediment occurred in very small patches of turbid ice, as thin spotty surface layers, in mud pellets or in old snowdrifts. The latter were widespread south of 74°N, containing an estimated 22 tonnes of silt and clay km−2. Average particle concentration in sea ice (40mg l−1) was much higher than in sea water (0.8 mg l−1) or in new snow, but the sediment load was significantly smaller and of finer texture compared to that observed in a shelfal source area after a major entrainment event. About 30% of the sediment consisted of small pellets. Mud in pellets has similar texture, clay minerals and organic/inorganic carbon content as dispersed mud. Particle sizes <16μm dominate, sand is less than 1%, compared to as much as 8% in four samples obtained in 1971 and 1972. Organic carbon content is about 2%, illite dominates clay minerals (~50%), and diatoms suggest a shelf sediment source. From the prevalence of wind-reworked surficial deposits, the spotty occurrence of only small patches of turbid ice in old clean ice, and the virtual lack of sand-size material, we assume the sediment had drifted at least 2 years since entrainment and was distant from its source. Assuming one-third of the load is released each year, the estimated deposition rate would equal the measured Holocene rate (~2cm 1000year−1). Therefore, modern sea-ice rafting represents a substantial fraction of the total Arctic Ocean sediment budget.
Improving neurocognitive outcomes following treatment for brain metastases have become increasingly important. We propose that a brief telephone-based neurocognitive assessment may improve follow-up cognitive assessments in this palliative population. Aim: To prospectively assess the feasibility and reliability of a telephone based brief neurocognitive assessment compared to the same tests delivered face-to-face. Methods: Brain metastases patients to be treated with whole brain radiotherapy (WBRT) were assessed using a brief validated neurocognitive battery at baseline, at 1 month and 3 months following WBRT (in person and over the phone). The primary outcome was feasibility and inter-procedural (in person versus telephone) reliability. The secondary objective was to evaluate the change in neurocognitive function before and after WBRT. Results: Out of 39 patients enrolled, 82% of patients completed the baseline in-person and telephone neurocognitive assessments. However, at 1 month, only 41% of enrolled patients completed the in-person and telephone cognitive assessments and at 3 months, only 10% of patients completed them. Results pertaining to reliability and change in neurocognitive function will be updated. Conclusion: The pre-defined definition of feasibility (at least 80% completion for face to face and telephone neurocognitive assessments) was met at baseline. However, a large proportion of participants did not complete either telephone or in person neurocognitive follow-up at 1 month and at 3 months post-WBRT. Attrition remained a challenge for neurocognitive testing in this population even when a telephone-based brief assessment was used.
The aim of this study was to compare patterns of cognitive decline in older Latinos and non-Latinos. At annual intervals for a mean of 5.7 years, older Latino (n=104) and non-Latino (n=104) persons of equivalent age, education, and race completed a battery of 17 cognitive tests from which previously established composite measures of episodic memory, semantic memory, working memory, perceptual speed, and visuospatial ability were derived. In analyses adjusted for age, sex, and education, performance declined over time in each cognitive domain, but there were no ethnic group differences in initial level of function or annual rate of decline. There was evidence of retest learning following the baseline evaluation, but neither the magnitude nor duration of the effect was related to Latino ethnicity, and eliminating the first two evaluations, during which much of retest learning occurred, did not affect ethnic group comparisons. Compared to the non-Latino group, the Latino group had more diabetes (38.5% vs. 25.0; χ2=4.4; p=.037), fewer histories of smoking (24.0% vs. 39.4%, χ2=5.7; p=.017), and lower childhood household socioeconomic level (−0.410 vs. −0.045, t[185.0]=3.1; p=.002), but controlling for these factors did not affect results. Trajectories of cognitive aging in different abilities are similar in Latino and non-Latino individuals of equivalent age, education, and race. (JINS, 2016, 22, 58–65)
The sandbar shark, Carcharhinus plumbeus, is a common coastal shark in the regions of the world where it occurs. Here, the first documented record of the sandbar shark is reported from north-western Indian waters, off the coast of Gujarat. Two specimens, one male and one female, were recorded and landed by a trawl vessel in Porbandar on 23 October 2014, measuring 610 and 760 mm in total length, respectively. This occurrence represents the first confirmed record of C. plumbeus in both western and eastern Indian waters.
The Murchison Widefield Array is a Square Kilometre Array Precursor. The telescope is located at the Murchison Radio–astronomy Observatory in Western Australia. The MWA consists of 4 096 dipoles arranged into 128 dual polarisation aperture arrays forming a connected element interferometer that cross-correlates signals from all 256 inputs. A hybrid approach to the correlation task is employed, with some processing stages being performed by bespoke hardware, based on Field Programmable Gate Arrays, and others by Graphics Processing Units housed in general purpose rack mounted servers. The correlation capability required is approximately 8 tera floating point operations per second. The MWA has commenced operations and the correlator is generating 8.3 TB day−1 of correlation products, that are subsequently transferred 700 km from the MRO to Perth (WA) in real-time for storage and offline processing. In this paper, we outline the correlator design, signal path, and processing elements and present the data format for the internal and external interfaces.