Volatile Contents of Izu-Bonin Forearc Volcanic Glasses

Eleven glasses recovered from Holes 786A and 786B were fresh enough for volatile analysis by infrared spectroscopy. The compositions of these glasses range from boninitic to rhyolitic. The glasses from the boninites contain 1.4 to 1.7 wt% H_2O, while the rhyolitic glasses contain 2 to 6 wt% H_2O, and all glasses have less than 30 to 40 ppm CO_2. The highest H_2O contents are probably the result of seawater alteration. The unaltered dacitic to rhyolitic glasses were probably quenched at low pressures corresponding to depths of 0-700 m below the seafloor, also corresponding to the depths of collection of these samples, although the water depths may have been different between the Eocene and the present. The lower boninitic H_2O contents in vesicular glasses suggest shallow quenching on the seafloor

Simulation and Analysis Chain for Acoustic Ultra-high Energy Neutrino Detectors in Water

Acousticneutrinodetectionisapromisingapproachforlarge-scaleultra-highenergyneutrinodetectorsinwater.In this article, a Monte Carlo simulation chain for acoustic neutrino detection devices in water will be presented. The simulation chain covers the generation of the acoustic pulse produced by a neutrino interaction and its propagation to the sensors within the detector. Currently, ambient and transient noise models for the Mediterranean Sea and simulations of the data acquisition hardware, equivalent to the one used in ANTARES/AMADEUS, are implemented. A pre-selection scheme for neutrino-like signals based on matched filtering is employed, as it is used for on-line filtering. To simulate the whole processing chain for experimental data, signal classification and acoustic source reconstruction algorithms are integrated in an analysis chain. An overview of design and capabilities of the simulation and analysis chain will be presented and preliminary studies will be discussed.Comment: 6 pages, 5 figures, ARENA 2012. arXiv admin note: substantial text overlap with arXiv:1304.057

Boninite and Harzburgite from Leg 125 (Bonin-Mariana Forearc): A Case Study of Magma Genesis during the Initial Stages of Subduction

Holes drilled into the volcanic and ultrabasic basement of the Izu-Ogasawara and Mariana forearc terranes during Leg 125 provide data on some of the earliest lithosphere created after the start of Eocene subduction in the Western Pacific. The volcanic basement contains three boninite series and one tholeiite series. (1) Eocene low-Ca boninite and low-Ca bronzite andesite pillow lavas and dikes dominate the lowermost part of the deep crustal section through the outer-arc high at Site 786. (2) Eocene intermediate-Ca boninite and its fractionation products (bronzite andesite, andesite, dacite, and rhyolite) make up the main part of the boninitic edifice at Site 786. (3) Early Oligocene intermediate-Ca to high-Ca boninite sills or dikes intrude the edifice and perhaps feed an uppermost breccia unit at Site 786. (4) Eocene or Early Oligocene tholeiitic andesite, dacite, and rhyolite form the uppermost part of the outer-arc high at Site 782. All four groups can be explained by remelting above a subduction zone of oceanic mantle lithosphere that has been depleted by its previous episode of partial melting at an ocean ridge. We estimate that the average boninite source had lost 10-15 wt% of melt at the ridge before undergoing further melting (5-10%) shortly after subduction started. The composition of the harzburgite (<2% clinopyroxene, Fo content of about 92%) indicates that it underwent a total of about 25% melting with respect to a fertile MORB mantle. The low concentration of Nb in the boninite indicates that the oceanic lithosphere prior to subduction was not enriched by any asthenospheric (OIB) component. The subduction component is characterized by (1) high Zr and Hf contents relative to Sm, Ti, Y, and middle-heavy REE, (2) light REE-enrichment, (3) low contents of Nb and Ta relative to Th, Rb, or La, (4) high contents of Na and Al, and (5) Pb isotopes on the Northern Hemisphere Reference Line. This component is unlike any subduction component from active arc volcanoes in the Izu-Mariana region or elsewhere. Modeling suggests that these characteristics fit a trondhjemitic melt from slab fusion in amphibolite facies. The resulting metasomatized mantle may have contained about 0.15 wt% water. The overall melting regime is constrained by experimental data to shallow depths and high temperatures (1250°C and 1.5 kb for an average boninite) of boninite segregation. We thus envisage that boninites were generated by decompression melting of a diapir of metasomatized residual MORB mantle leaving the harzburgites as the uppermost, most depleted residue from this second stage of melting. Thermal constraints require that both subducted lithosphere and overlying oceanic lithosphere of the mantle wedge be very young at the time of boninite genesis. This conclusion is consistent with models in which an active transform fault offsetting two ridge axes is placed under compression or transpression following the Eocene plate reorganization in the Pacific. Comparison between Leg 125 boninites and boninites and related rocks elsewhere in the Western Pacific highlights large regional differences in petrogenesis in terms of mantle mineralogy, degree of partial melting, composition of subduction components, and the nature of pre-subduction lithosphere. It is likely that, on a regional scale, the initiation of subduction involved subducted crust and lithospheric mantle wedge of a range of ages and compositions, as might be expected in this type of tectonic setting

Phase equilibria constraints on Archean crustal genesis from crystallization experiments on trondhjemite with water at 10-17 kbar

The formation of continental crust during the Archean and early Proterozoic occurred through a different mechanisms than the currently active processes of calc-alkaline volcanism in orogenic regions. In view that most crustal growth models imply that by the end of the Archean a continental mass equivalent to 75% or more of the current crust had evolved, it seems highly relevant to study early crustal genesis

Portable infrared laser spectroscopy for on-site mycotoxin analysis

Mycotoxins are toxic secondary metabolites of fungi that spoil food, and severely impact human health (e.g., causing cancer). Therefore, the rapid determination of mycotoxin contamination including deoxynivalenol and aflatoxin B(1) in food and feed samples is of prime interest for commodity importers and processors. While chromatography-based techniques are well established in laboratory environments, only very few (i.e., mostly immunochemical) techniques exist enabling direct on-site analysis for traders and manufacturers. In this study, we present MYCOSPEC - an innovative approach for spectroscopic mycotoxin contamination analysis at EU regulatory limits for the first time utilizing mid-infrared tunable quantum cascade laser (QCL) spectroscopy. This analysis technique facilitates on-site mycotoxin analysis by combining QCL technology with GaAs/AlGaAs thin-film waveguides. Multivariate data mining strategies (i.e., principal component analysis) enabled the classification of deoxynivalenol-contaminated maize and wheat samples, and of aflatoxin B(1) affected peanuts at EU regulatory limits of 1250 μg kg(−1) and 8 μg kg(−1), respectively

Magnetic granularity in pulsed laser deposited YBCO films on technical templates at 5 K

The manifestation of granularity in the superconducting properties of pulsed laser deposited YBCO films on commercially available metallic templates was investigated by scanning Hall probe microscopy at 5 K and was related to local orientation mapping of the YBCO layer. The YBCO films on stainless steel templates with a textured buffer layer of yttrium stabilized ZrO2 grown by alternating beam assisted deposition have a mean grain size of less than with a sharp texture. This results in a homogeneous trapped field profile and spatial distribution of the current density. On the other hand, YBCO films on biaxially textured NiW substrates show magnetic granularity that persists down to a temperature of 5 K and up to an applied magnetic field of 4 T. The origin of the granular field profile is directly correlated to the microstructural properties of the YBCO layer adopted from the granular NiW substrate which leads to a spatially inhomogeneous current density. Grain-to-grain in-plane tilts lead to grain boundaries that obstruct the current while out-of-plane tilts mainly affect the grain properties, resulting in areas with low . Hence, not all grain boundaries cause detrimental effects on since the orientation of individual NiW grains also contributes to observed inhomogeneity and granularity

Clean Ultrahigh Vacuum System with Single-Structure Diffusion Pumps

A practical example of the use of single-structure diffusion pumping groups in an experiment requiring hydrocarbon-free, ultrahigh vacuum is presented. With the use of proper vacuum procedures and careful foreline design and operation, but with no exotic hardware or liquid nitrogen, we have demonstrated that such a pump could provide vacuum that was clean, i.e., which had no residual pump-oil contamination to a partial pressure below 10 -8 mbar. Their use is thus compatible, at least in peripheral vacuum chambers, with standard UHV-surface science processes. We discuss our vacuum system in detail, and present a review of the literature on the production of clean vacua with diffusion pumps. © 1994, American Vacuum Society. All rights reserved

Abnormal activity in the precuneus during time perception in Parkinson’s disease: An fMRI study

Background Parkinson's disease (PD) patients are deficient in time estimation. This deficit improves after dopamine (DA) treatment and it has been associated with decreased internal timekeeper speed, disruption of executive function and memory retrieval dysfunction. Methodology/Findings The aim of the present study was to explore the neurophysiologic correlates of this deficit. We performed functional magnetic resonance imaging on twelve PD patients while they were performing a time reproduction task (TRT). The TRT consisted of an encoding phase (during which visual stimuli of durations from 5s to 16.6s, varied at 8 levels were presented) and a reproduction phase (during which interval durations were reproduced by a button pressing). Patients were scanned twice, once while on their DA medication (ON condition) and once after medication withdrawal (OFF condition). Differences in Blood-Oxygenation-Level-Dependent (BOLD) signal in ON and OFF conditions were evaluated. The time course of activation in the brain areas with different BOLD signal was plotted. There were no significant differences in the behavioral results, but a trend toward overestimation of intervals ≤11.9s and underestimation of intervals ≥14.1s in the OFF condition (p<0.088). During the reproduction phase, higher activation in the precuneus was found in the ON condition (p<0.05 corrected). Time course was plotted separately for long (≥14.1s) and short (≤11.9s) intervals. Results showed that there was a significant difference only in long intervals, when activity gradually decreased in the OFF, but remained stable in the ON condition. This difference in precuneus activation was not found during random button presses in a control task. Conclusions/Significance Our results show that differences in precuneus activation during retrieval of a remembered duration may underlie some aspects of time perception deficit in PD patients. We suggest that DA medication may allow compensatory activation in the precuneus, which results in a more accurate retrieval of remembered interval duration

Volatile Contents of Izu-Bonin Forearc Volcanic Glasses

Eleven glasses recovered from Holes 786A and 786B were fresh enough for volatile analysis by infrared spectroscopy. The compositions of these glasses range from boninitic to rhyolitic. The glasses from the boninites contain 1.4 to 1.7 wt% H_2O, while the rhyolitic glasses contain 2 to 6 wt% H_2O, and all glasses have less than 30 to 40 ppm CO_2. The highest H_2O contents are probably the result of seawater alteration. The unaltered dacitic to rhyolitic glasses were probably quenched at low pressures corresponding to depths of 0-700 m below the seafloor, also corresponding to the depths of collection of these samples, although the water depths may have been different between the Eocene and the present. The lower boninitic H_2O contents in vesicular glasses suggest shallow quenching on the seafloor