Inter-element fractionation of highly siderophile elements in the Tonga Arc due to flux melting of a depleted source

Highly siderophile element concentrations (HSEs: Os, Ir, Ru, Pt, Pd, and Re) have been determined for a suite of fresh, submarine mafic lavas from the northern Tonga Arc front and the nascent backarc Fonualei Spreading Centre (FSC). Prior melt depletion of the Tongan mantle wedge combined with a high degree of fluid fluxed melting is thought to have produced boninitic magmas at several arc and FSC locations. As such, this arc system provides an opportunity to assess the fluid mobility of HSEs and to investigate the effects of fluid-induced melting and prior melt depletion on HSE behaviour during both mantle melting and magma evolution. Tongan lavas display extreme enrichment of Pt (2.5–32 ng/g) and Pd over Os (0.002–0.6 ng/g), Ir, and Ru, significantly greater than basalts from mid-ocean ridges. Magma evolution increases the degree of fractionation, resulting in the highest recorded Pt/Ru ratios (>300) in arc front samples with MgO <8 wt.%. This increasing fractionation is due to the mild incompatibility of Pt and Pd, and concurrent compatibility of Ru, during sulphide undersaturated magma evolution. However, the fractionation of Pt and Pd from Os, Ir, and Ru is observed in the highest MgO samples, indicating source inheritance. Prior melt depletion of the mantle and elevated oxygen fugacity both increase the likelihood of complete consumption of sulphide in the source during melting, which typically leads to melts with high concentrations of all the HSE. Indeed, modelling indicates that 25% aggregate partial melting of a depleted MORB-mantle source, proposed for the Tonga Arc, will lead to complete base-metal sulphide consumption unless there is considerable addition of S by the slab flux (at least 200 μg/g). Although source enrichment of Pt, Pd, and Re by slab fluids may take place, the fractionation of Pt and Pd from Os, Ir, and Ru can largely be explained by relatively low-temperature, yet high-degree, melting of fluid-fluxed melt-depleted mantle. The high Pt and Pd contents can be produced by the exhaustion of sulphide in the source, while the presence of Ru–Os–(Ir) alloys or sulphides (e.g. laurite) associated with Cr-spinel can explain Os, Ir, and Ru retention in the source residue. Such phases have been documented in fluid-fluxed sub-arc mantle from ophiolites. Osmium isotopes co-vary negatively with Os abundance and thus appear to be dominated by shallow level contamination. The most Os-rich samples, however, have 187Os/188Os ratios (0.126–0.132) which are typical of DMM and MORB, suggesting an indistinguishable flux of radiogenic Os from the slab. The significant fractionation of Pt and Re from Os in arc settings will lead, over time, to elevated 186Os and 187Os which may be relevant to the observed enrichments of these isotopes in some mantle regions. In addition, the differing behaviour of Ru and Ir, and the implication of a mantle source containing Ru-rich microphases, may have consequences for the estimation of the HSE composition of primitive upper mantle

Waters of Hot Springs National Park, Arkansas: their nature and origin

The 47 hot springs of Hot Springs National Park, Arkansas, issue from the plunging crestline of a large overturned anticline, along the southern margin of the Ouachita anticlinorium, in the Zigzag Mountains. The combined flow of the hot springs ranges from 750,000 to 950,000 gallons per day (3.29 x 10/sup -2/ to 4.16 x 10/sup -2/ cubic meters per second). The radioactivity and chemical composition of the hot-water springs are similar to that of the cold-water springs and wells in the area. The tritium and carbon-14 analyses of the water indicate that the water is a mixture of a very small amount of water less than 20 years old and a preponderance of water about 4400 years old. The presence of radium and radon in the hot-springs waters has been established by analyses. Mathematical models were employed to test various conceptual models of the hot-springs flow system. The geochemical data, flow measurements, and geologic structure of the region support the concept that virtually all the hot-springs water is of local, meteoric origin. Recharge to the hot-springs artesian-flow system is by infiltration of rainfall in the outcrop areas of the Bigfork Chert and the Arkansas Novaculite. The water moves slowly to depth where it is heated by contact with rocks of high temperature. Highly permeable zones, related to jointing or faulting, collect the heated water in the aquifer and provide avenues for the water to travel rapidly to the surface

Static And Dynamic Properties Of Fibonacci Multilayers

We theoretically investigate static and dynamic properties of quasiperiodic magnetic multilayers. We considered identical ferromagnetic layers separated by non-magnetic spacers with two different thicknesses chosen based on the Fibonacci sequence. Using parameters for Fe/Cr, the minimum energy was determined and the equilibrium magnetization directions found were used to calculate magnetoresistance curves. Regarding dynamic behavior, ferromagnetic resonance (FMR) curves were calculated using an approximation known from the literature. Our numerical results illustrate the effects of quasiperiodicity on the static and dynamic properties of these structures. © 2013 American Institute of Physics.11317Grünberg, P., Schreiber, R., Pang, Y., Brodsky, M.B., Sowers, H., (1986) Phys. Rev. Lett., 57, p. 2442. , 10.1103/PhysRevLett.57.2442Baibich, M.N., Broto, J.M., Fert, A., Nguyen Van Dau, F., Petroff, F., Etienne, P., Creuzet, G., Chazelas, J., (1988) Phys. Rev. Lett., 61, p. 2472. , 10.1103/PhysRevLett.61.2472Binasch, G., Grünberg, P., Saurenbach, F., Zinn, W., (1989) Phys. Rev. B, 39, p. 4828. , 10.1103/PhysRevB.39.4828Prinz, G.A., (1998) Science, 282, p. 1660. , 10.1126/science.282.5394.1660Kools, J.C.S., (1996) IEEE Trans. Magn., 32, p. 3165. , 10.1109/20.508381Stiles, M.D., Zangwill, A., (2002) Phys. Rev. B, 66, p. 014407. , 10.1103/PhysRevB.66.014407Lakys, Y., Zhao, W.S., Devolder, T., Zhang, Y., Klein, J.O., Ravelosona, D., Chappert, C., (2012) IEEE Trans. Magn., 48, p. 2403. , 10.1109/TMAG.2012.2194790Chaves, R.C., Cardoso, S., Ferreira, R., Freitas, P.P., (2011) J. Appl. Phys, 109, pp. 07E506. , 10.1063/1.3537926Vedyayev, A., Dieny, B., Ryzhanova, N., Genin, J.B., Cowache, C., (1994) Europhys. Lett., 25, p. 465. , 10.1209/0295-5075/25/6/012Albuquerque, E.L., Cottam, M.G., (2004) Polaritons in Periodic and Quasiperiodic Structures, , (Elsevier, Amsterdam)Bezerra, C.G., Albuquerque, E.L., (1997) Physica A, 245, p. 379. , 10.1016/S0378-4371(97)00309-9Bezerra, C.G., De Araujo, J.M., Chesman, C., Albuquerque, E.L., (1999) Phys. Rev. B, 60, p. 9264. , 10.1103/PhysRevB.60.9264Bezerra, C.G., De Araujo, J.M., Chesman, C., Albuquerque, E.L., (2001) J. Appl. Phys., 89, p. 2286. , 10.1063/1.1340600Bezerra, C.G., Cottam, M.G., (2002) J. Magn. Magn. Mater., 240, p. 529. , 10.1016/S0304-8853(01)00838-1Bezerra, C.G., Cottam, M.G., (2002) Phys. Rev. B, 65, p. 054412. , 10.1103/PhysRevB.65.054412Mauriz, P.W., Albuquerque, E.L., Bezerra, C.G., (2002) J. Phys.: Condens. Matter, 14, p. 1785. , 10.1088/0953-8984/14/8/308Fullerton, E.E., Conover, M.J., Mattson, J.E., Sowers, C.H., Bader, S.D., (1993) Phys. Rev. B, 48, p. 15755. , 10.1103/PhysRevB.48.15755Machado, L.D., Bezerra, C.G., Correa, M.A., Chesman, C., Pearson, J.E., Hoffmann, A., (2012) Phys. Rev. B, 85, p. 224416. , 10.1103/PhysRevB.85.22441

Natural Orbitals and BEC in traps, a diffusion Monte Carlo analysis

We investigate the properties of hard core Bosons in harmonic traps over a wide range of densities. Bose-Einstein condensation is formulated using the one-body Density Matrix (OBDM) which is equally valid at low and high densities. The OBDM is calculated using diffusion Monte Carlo methods and it is diagonalized to obtain the "natural" single particle orbitals and their occupation, including the condensate fraction. At low Boson density, $na^3 < 10^{-5}$, where $n = N/V$ and $a$ is the hard core diameter, the condensate is localized at the center of the trap. As $na^3$ increases, the condensate moves to the edges of the trap. At high density it is localized at the edges of the trap. At $na^3 \leq 10^{-4}$ the Gross-Pitaevskii theory of the condensate describes the whole system within 1%. At $na^3 \approx 10^{-3}$ corrections are 3% to the GP energy but 30% to the Bogoliubov prediction of the condensate depletion. At $na^3 \gtrsim 10^{-2}$, mean field theory fails. At $na^3 \gtrsim 0.1$, the Bosons behave more like a liquid $^4$He droplet than a trapped Boson gas.Comment: 13 pages, 14 figures, submitted Phys. Rev.

Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought

The timing of human colonization of East Polynesia, a vast area lying between Hawai‘i, Rapa Nui, and New Zealand, is much debated and the underlying causes of this great migration have been enigmatic. Our study generates evidence for human dispersal into eastern Polynesia from islands to the west from around AD 900 and contemporaneous paleoclimate data from the likely source region. Lake cores from Atiu, Southern Cook Islands (SCIs) register evidence of pig and/or human occupation on a virgin landscape at this time, followed by changes in lake carbon around AD 1000 and significant anthropogenic disturbance from c. AD 1100. The broader paleoclimate context of these early voyages of exploration are derived from the Atiu lake core and complemented by additional lake cores from Samoa (directly west) and Vanuatu (southwest) and published hydroclimate proxies from the Society Islands (northeast) and Kiribati (north). Algal lipid and leaf wax biomarkers allow for comparisons of changing hydroclimate conditions across the region before, during, and after human arrival in the SCIs. The evidence indicates a prolonged drought in the likely western source region for these colonists, lasting c. 200 to 400 y, contemporaneous with the phasing of human dispersal into the Pacific. We propose that drying climate, coupled with documented social pressures and societal developments, instigated initial eastward exploration, resulting in SCI landfall(s) and return voyaging, with colonization a century or two later. This incremental settlement process likely involved the accumulation of critical maritime knowledge over several generations

Active Galactic Nuclei at the Crossroads of Astrophysics

Over the last five decades, AGN studies have produced a number of spectacular examples of synergies and multifaceted approaches in astrophysics. The field of AGN research now spans the entire spectral range and covers more than twelve orders of magnitude in the spatial and temporal domains. The next generation of astrophysical facilities will open up new possibilities for AGN studies, especially in the areas of high-resolution and high-fidelity imaging and spectroscopy of nuclear regions in the X-ray, optical, and radio bands. These studies will address in detail a number of critical issues in AGN research such as processes in the immediate vicinity of supermassive black holes, physical conditions of broad-line and narrow-line regions, formation and evolution of accretion disks and relativistic outflows, and the connection between nuclear activity and galaxy evolution.Comment: 16 pages, 5 figures; review contribution; "Exploring the Cosmic Frontier: Astrophysical Instruments for the 21st Century", ESO Astrophysical Symposia Serie

超伝導技術を応用した近未来船

Background: Low back pain (LBP) is one of the most disabling and costly disorders affecting modern society, and approximately 90% of patients are labelled as having non-specific LBP (NSLBP). Several interventions for patients with NSLBP have been assessed in clinical trials, but heterogeneous reporting of outcomes in these trials has hindered comparison of results and performance of meta-analyses. Moreover, there is a risk of selective outcome reporting bias. To address these issues, the development of a core outcome set (COS) that should be measured in all clinical trials for a specific health condition has been recommended. A standardized set of outcomes for LBP was proposed in 1998, however, with evolution in COS development methodology, new instruments, interventions, and understanding of measurement properties, it is appropriate to update that proposal. This protocol describes the methods used in the initial step in developing a COS for NSLBP, namely, establishing a core domain set that should be measured in all clinical trials. Methods/Design: An International Steering Committee including researchers, clinicians, and patient representatives from four continents was formed to guide the development of this COS. The approach of initiatives like Core Outcome Measures in Effectiveness Trials (COMET) and Outcome Measures in Rheumatology (OMERACT) was followed. Participants were invited to participate in a Delphi study aimed at generating a consensus-based core domain set for NSLBP. A list of potential core domains was drafted and presented to the Delphi participants who were asked to judge which domains were core. Participant suggestions about overlap, aggregation, or addition of potential core domains were addressed during the study. The patients' responses were isolated to assess whether there was substantial disagreement with the rest of the Delphi panel. A priori thresholds for consensus were established before each Delphi round. All participants' responses were analysed from a quantitative and qualitative perspective to ascertain that no substantial discrepancies between the two approaches emerged. Discussion: We present the initial step in developing a COS for NSLBP. The next step will be to determine which measurement instruments adequately cover the domains