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Stishovite is a key mineral for understanding the deep Earth water cycle because of its potential as a main carrier for water into the transition zone and lower mantle. During subduction-related metamorphism of basaltic oceanic crust, stishovite stabilizes at 8-9 GPa and comprises 10-25 vol% of the bulk mineralogy, with some experimental studies indicating that stishovite can accommodate 3.5 wt% H.sub.2O or more in the transition zone and upper lower mantle. This large water solubility has been explained by a hydrogarnet substitution mechanism (1Si.sup.4+ â 4H.sup.+) and/or the incorporation of interstitial molecular water. To investigate water speciation and hydrogen isotope behavior, we synthesized partially deuterated hydrous stishovite at 9 GPa and 450 °C in a multi-anvil press (MA). The hydrous stishovite contains on average 1.69 ± 0.05 wt% water, which is consistent with earlier MA studies but is significantly lower than the 3.5 wt% reported from in situ diamond anvil cell (DAC) studies made at higher pressures and temperatures. .sup.1H MAS NMR spinning sideband characteristics suggest a high abundance of interstitial molecular water in hydrous stishovite, while the presence of a hydrogarnet defect cannot be ruled out. Unit-cell volumes and deuterium enrichment in the quenched hydrous stishovite indicate that ~ 45% of the water is lost from the stishovite upon quenching and decompression of the experiment, consistent with a higher solubility. This implies that the pristine water contents of a P-T-fO.sub.2 equilibrated hydrous stishovite cannot be quenched to 1 atm and room temperature from classical MA experiments. We further present a capillary-based recovery method for fluid from experimental capsules, allowing direct determination of the D/H ratio of the experimental fluid and indirect determination of the hydrous stishovite. Using Rayleigh modeling to account for the quench-related water loss, we find that, at 450 °C and 9 GPa, deuterium is 3.5-4.5 times enriched in hydrous stishovite relative to coexisting aqueous fluid. This is opposite of what is commonly observed for mineral-fluid pairs above 300 °C, rendering hydrous stishovite a potential sink for deuterium and decreasing the D/H ratio of coexisting aqueous fluids. Partial decomposition (30-60%) of hydrous stishovite during mantle upwelling and production of primary basaltic melts could be accompanied by high-temperature D/H fractionation, decreasing the hydrogen isotope composition of such melts towards 'mantle-like' [delta]D values between -75 and -220â°., Author(s): Nico Kueter [sup.1] [sup.2], Kara Brugman [sup.2] [sup.3], Francesca Miozzi [sup.2], George D. Cody [sup.2], Jing Yang [sup.2], Timothy A. Strobel [sup.2], Michael J. Walter [sup.2] Author Affiliations: (1) [...]

Author(s): Remco C. Hin (corresponding author) [1]; Christopher D. Coath [1]; Philip J. Carter [2]; Francis Nimmo [3]; Yi-Jen Lai [1]; Philip A. E. Pogge von Strandmann [1, 4]; Matthias [...]

Interactions between crustal and mantle reservoirs dominate the surface inventory of volatile elements over geological time, moderating atmospheric composition and maintaining a lifesupporting planet (1). While volcanoes expel volatile components into surface reservoirs, subduction of oceanic crust is responsible for replenishment of mantle reservoirs (2,3). Many natural, 'superdeep' diamonds originating in the deep upper mantle and transition zone host mineral inclusions, indicating an affinity to subducted oceanic crust (4-7). Here we show that the majority of slab geotherms will intersect a deep depression along the melting curve of carbonated oceanic crust at depths of approximately 300 to 700 kilometres, creating a barrier to direct carbonate recycling into the deep mantle. Low-degree partial melts are alkaline carbonatites that are highly reactive with reduced ambient mantle, producing diamond. Many inclusions in superdeep diamonds are best explained by carbonate melt-peridotite reaction. A deep carbon barrier may dominate the recycling of carbon in the mantle and contribute to chemical and isotopic heterogeneity of the mantle reservoir., Altered oceanic crust incorporates appreciable carbon, which is added by magmatic and hydrothermal processes (8), and by addition of C[O.sub.2] during interaction of basalt with sea water (9). Together, these [...]

A study was conducted to evaluate the efficacy and safety of tiotropium bromide step-up therapy in the treatment of adults with uncontrolled asthma. Results indicated that such a form of treatment when used with inhaled glucocorticoid was very effective.

Byline: Galina P. Bulanova (1), Michael J. Walter (1), Chris B. Smith (1), Simon C. Kohn (1), Lora S. Armstrong (1), Jon Blundy (1), Luiz Gobbo (2) Keywords: Brazil; Collier 4 kimberlite; Sublithospheric diamonds; Inclusions; Carbon isotopes; Subduction; Carbonatite melt Abstract: We report on a suite of diamonds from the Cretaceous Collier 4 kimberlite pipe, Juina, Brazil, that are predominantly nitrogen-free type II crystals showing complex internal growth structures. Syngenetic mineral inclusions comprise calcium- and titanium-rich phases with perovskite stoichiometry, Ca-rich majoritic-garnet, clinopyroxene, olivine, TAPP phase, minerals with stoichiometries of CAS and K-hollandite phases, SiO.sub.2, FeO, native iron, low-Ni sulfides, and Ca--Mg-carbonate. We divide the diamonds into three groups on the basis of the carbon isotope compositions ([delt[a].sup.13]C) of diamond core zones. Group 1 diamonds have heavy, mantle-like [delt[a].sup.13]C (-5 to -10[per thousand]) with mineral inclusions indicating a transition zone origin from mafic protoliths. Group 2 diamonds have intermediate [delt[a].sup.13]C (-12 to -15[per thousand]), with inclusion compositions indicating crystallization from near-primary and differentiated carbonated melts derived from oceanic crust in the deep upper mantle or transition zone. A 206.sup.Pb/ [.sup.238]U age of 101 +- 7 Ma on a CaTiSi-perovskite inclusion (Group 2) is close to the kimberlite emplacement time (93.1 +- 1.5 Ma). Group 3 diamonds have extremely light [delt[a].sup.13]C (-25[per thousand]), and host inclusions have compositions akin to high-pressure--temperature phases expected to be stable in pelagic sediments subducted to transition zone depths. Collectively, the Collier 4 diamonds and their inclusions indicate multi-stage, polybaric growth histories in dynamically changing chemical environments. The young inclusion age, the ubiquitous chemical and isotopic characteristics indicative of subducted materials, and the regional tectonic history, suggest a model in which generation of sublithospheric diamonds and their inclusions, and the proto-kimberlite magmas, are related genetically, temporally and geographically to the interaction of subducted lithosphere and a Cretaceous plume. Author Affiliation: (1) Department of Earth Sciences, University of Bristol, Queen's Rd, Bristol, BS8 1RJ, UK (2) Rio Tinto Desenvolvimentos Minerais Ltda, Brasilia, Brazil Article History: Registration Date: 11/01/2010 Received Date: 04/06/2009 Accepted Date: 11/01/2010 Online Date: 07/02/2010 Article note: Communicated by M. W. Schmidt.

Author(s): Bernard J. Wood (corresponding author) [1]; Michael J. Walter [2]; Jonathan Wade [2] From observations of newly formed stars it appears that the Sun's planetary system formed from a [...]

Host defense against viruses probably depends on targeted death of infected host cells and then clearance of cellular corpses by macrophages. For this process to be effective, the macrophage must presumably avoid its own virus-induced death. Here we identify one such mechanism. We show that mice lacking the chemokine Ccl5 are immune compromised to the point of delayed viral clearance, excessive airway inflammation and respiratory death after mouse parainfluenza or human influenza virus infection. Virus-inducible levels of Ccl5 are required to prevent apoptosis of virus-infected mouse macrophages in vivo and mouse and human macrophages ex vivo. The protective effect of Ccl5 requires activation of the Ccr5 chemokine receptor and consequent bilateral activation of G[sub.[alpha]i]-PI3K-AKT and G[sub.[alpha]i]-MEK-ERK signaling pathways. The antiapoptotic action of chemokine signaling may therefore allow scavengers to finally stop the host cell-to-cell infectious process., Author(s): Jeffrey W Tyner [1]; Osamu Uchida [1]; Naohiro Kajiwara [1]; Edy Y Kim [1]; Anand C Patel [2]; Mary P O'Sullivan [1]; Michael J Walter [1]; Reto A Schwendener [...]

Author(s): Takashi Yoshino (corresponding author); Michael J. Walter; Tomoo Katsura The tungsten isotope composition of meteorites indicates that core formation in planetesimals occurred within a few million years of Solar [...]

Holtzman, Michael J., Jeffrey D. Morton, Laurie P. Shornick, Jeffrey W. Tyner, Mary P. O'Sullivan, Aurita Antao, Mindy Lo, Mario Castro, and Michael J. Walter. Immunity, Inflammation, and Remodeling in [...]

The 'excess' of siderophile elements in Earth's mantle is a long-standing problem in understanding the evolution of Earth. Determination of the partitioning behavior of tungsten and molybdenum between liquid metal and silicate melt at high pressure and temperature shows that partition coefficients ([D.sub.metal/silicate]) vary by two orders of magnitude depending on whether metal segregated from a basaltic or peridotitic melt. This compositional dependence is likely a response to changes in the degree of polymerization of the silicate melt caused by compositional variations of the network-modifying cations [Mg.sup.2+] and [Fe.sup.2+]. Silicate melt compositional effects on partition coefficients for siderophile elements are potentially more important than the effects of high pressure and temperature., If core formation in the Earth was a simple equilibrium process whereby metal segregated from silicate, then the abundance of siderophile (metal-seeking) elements retained in the silicate mantle of the [...]

Higher strength, better corrosion resistance, and improved biocompatibility compared with other BioDur alloys have been demonstrated by BioDur 108, an essentially nickel-free stainless steel alloy designed for medical implants. As […]

Magmas that have erupted at Earth's surface reveal a potential new mantle source. This source, which is rich in nickel and has a primordial helium isotopic content, may have originated at great depth in the mantle. See Letter p.393 Nickel-rich peridotites in the deep mantle Claude Herzberg and co-authors examine lavas from Baffin Island, West Greenland, the Ontong Java Plateau, Isla Gorgona, and Fernandina in the Galapagos Islands. The basalts at these locations, thought to have derived from deep mantle (mantle plume) sources, are shown to have formed from peridotite with a nickel content about 20% higher than those that form modern oceanic crust at mid-ocean ridges. The authors propose that such nickel-rich mantle plumes may be sampling a less-degassed nickel-rich source formed by core-mantle interaction., Author(s): Michael J. Walter [sup.1] Author Affiliations: (1) Michael J. Walter is in the Department of Earth Sciences, University of Bristol, Bristol BS8 1RJ, UK., Melting of source rocks in [...]

Melting of source rocks in the mantle generates magmas that erupt at Earth's surface. Identifying chemically unique mantle source rocks is a big deal because they can reveal much about [...]

Author(s): Michael J. Walter (corresponding author) A popular model for the formation of the Earth's core has iron-rich liquid metal segregating gravitationally from a molten silicate mantle (a so-called magma [...]

New experimental data for partitioning of Co and Ni in Earth's upper mantle between metal and Mg-perovsite, the most abundant mineral in the lower mantle, suggest that metal-silicate equilibration would lead to an enrichment of these elements in the lower mantle in relation to the upper mantle. This finding may prompt some changes to the core-formation model that indicates a magma ocean. This research indicates the need for continued investigation of metal-silicate partitioning under lower-mantle conditions.

Author(s): Michael J. Walter [1] The oxidation of iron is a process with which we are all familiar. The surface of Mars, the rust on our cars, the blood in [...]