837 research outputs found

    Time relations and structural-stratigraphic patterns in ophiolite accretion, west central Klamath Mountains, California

    Get PDF
    New geochronological data and published structural and stratigraphic data show that two distinctly different ophiolitic assemblages formed in general proximity to one another at nearly the same time and were subsequently imbricated along a regional thrust zone. The Josephine ophiolite constitutes a complete oceanic crust and upper mantle sequence which lies within the western Jurassic belt of the Klamath province. Within the study area the Josephine ophiolite was formed by seafloor spreading at about 157 m.y. before present. It was immediately covered by a thin pelagic and hemipelagic sequence which grades into a thick flysch sequence, both of which comprise the Galice Formation. The Galice flysch was derived from volcanic arc and uplifted continental margin orogenic assemblages. A major nonvolcanic source for the Galice flysch appears to have been the western Paleozoic and Triassic belt of the Klamath province exposed to the east. Proximal volcanic arc activity migrated to the site of the Josephine-Galice section by 151 m.y. and is represented by numerous dikes and sills which intrude the ophiolite and Galice Formation. The Preston Peak ophiolite is a polygenetic assemblage consisting of (1) a pre-mid-Jurassic tectonitic peridotite-amphibolite substrate which represents disrupted and unroofed basement of the western Paleozoic and Triassic belt and (2) an upper mafic complex which was intruded through and constructed above the tectonite substrate at about 160 m.y. The mafic complex consists primarily of diabase hypabyssal rocks that are overlain by diabase-clast breccia and hemipelagic deposits. A major arc-plutonic complex was emplaced into the Preston Peak ophiolite in at least two pulses at 153 and 149 m.y. Major phases of this complex consist of wehrlite, gabbro, pyroxene diorite, and hornblende diorite. The Josephine ophiolite is interpreted as the remnants of interarc basin crust. The Preston Peak ophiolite is interpreted as either a primitive remnant arc complex or a rift edge facies for the Josephine interarc basin. The Galice Formation represents a submarine fan complex that was built on juvenile crust of the Josephine basin floor. During the time interval of 153 to 149 m.y. the locus or arc magmatism migrated to an area which included the interarc basin floor and the remnant arc or basin edge. The basin shortly thereafter closed by convergent tectonics during the Nevadan orogeny resulting in the imbrication of the Josephine and Preston Peak ophiolites and their superimposed arc assemblages. The transition from seafloor spreading generation of Josephine ophiolite to its tectonic accretion by convergence and basin closure occurred within 5 to 10 m.y. The process of rifting and ophiolite formation in series with convergence and ophiolite accretion is considered an important mechanism for generating and displacing allocthonous terranes in the Klamath Mountains-Sierra Nevada region, and perhaps throughout the western cordillera

    Northeast Indian stalagmite records Pacific decadal climate change: Implications for moisture transport and drought in India

    Get PDF
    This is the final version. It is currently under embargo. It was first published by Wiley at http://onlinelibrary.wiley.com/doi/10.1002/2015GL063826/full.Two types of El Niño events are distinguished by sea surface temperature (SST) anomalies centered in the central or eastern equatorial Pacific. The Central Pacific El Niño events (CP-El Niño) are more highly correlated with weakening of the central Indian Summer Monsoon and linked to decadal Pacific climate variability. We present a 50 year, subannually resolved speleothem δ18O record from northeast India that exhibits a significant correlation with northern Pacific decadal variability and central equatorial Pacific SSTs. Accordingly, we suggest that δ18O time series in similar northeast Indian speleothems are effective tools for investigating preinstrumental changes in Pacific climate, including changes in El Niño dynamics. In contrast to central India, rainfall amounts in northeast India are relatively unaffected by El Niño. However, back trajectory analysis indicates that during CP-El Niño events moisture transport distance to northeast India is reduced, suggesting that variations in moisture transport primarily control δ18O in the region.This work was supported through the BanglaPIRE project (NSF OISE-0968354), an award from the Vanderbilt International Office to JLO and SFMB, and awards from the Cave Research Foundation and the Geological Society of America to CGM. SFMB received financial support from the Schweizer National Fond (SNF), Sinergia grant CRSI22 132646/1

    Galaxy And Mass Assembly (GAMA)

    Get PDF
    The GAMA survey aims to deliver 250,000 optical spectra (3--7Ang resolution) over 250 sq. degrees to spectroscopic limits of r_{AB} <19.8 and K_{AB}<17.0 mag. Complementary imaging will be provided by GALEX, VST, UKIRT, VISTA, HERSCHEL and ASKAP to comparable flux levels leading to a definitive multi-wavelength galaxy database. The data will be used to study all aspects of cosmic structures on 1kpc to 1Mpc scales spanning all environments and out to a redshift limit of z ~ 0.4. Key science drivers include the measurement of: the halo mass function via group velocity dispersions; the stellar, HI, and baryonic mass functions; galaxy component mass-size relations; the recent merger and star-formation rates by mass, types and environment. Detailed modeling of the spectra, broad SEDs, and spatial distributions should provide individual star formation histories, ages, bulge-disc decompositions and stellar bulge, stellar disc, dust disc, neutral HI gas and total dynamical masses for a significant subset of the sample (~100k) spanning both the giant and dwarf galaxy populations. The survey commenced March 2008 with 50k spectra obtained in 21 clear nights using the Anglo Australian Observatory's new multi-fibre-fed bench-mounted dual-beam spectroscopic system (AAOmega).Comment: Invited talk at IAU 254 (The Galaxy Disk in Cosmological Context, Copenhagen), 6 pages, 5 figures, high quality PDF version available at http://www.eso.org/~jliske/gama

    A Comparison of Rectal Diazepam Gel and Placebo for Acute Repetitive Seizures

    Get PDF
    ABSTRACT Background Acute repetitive seizures are readily recognizable episodes involving increased seizure frequency. Urgent treatment is often required. Rectal diazepam gel is a promising therapy. Methods We conducted a randomized, doubleblind, parallel-group, placebo-controlled study of home-based treatment for acute repetitive seizures. Patients were randomly assigned to receive either rectal diazepam gel, at doses ranging from 0.2 to 0.5 mg per kilogram of body weight on the basis of age, or placebo. Children received one dose at the onset of acute repetitive seizures and a second dose four hours later. Adults received three doses — one dose at onset, and two more doses 4 and 12 hours after onset. Treatment was administered by a care giver, such as a parent, who had received special training. The number of seizures after the first dose was counted for 12 hours in children and for 24 hours in adults. Results Of 125 study patients (64 assigned to diazepam and 61 to placebo) with a history of acute repetitive seizures, 91 (47 children and 44 adults) were treated for an exacerbation of seizures during the study period. Diazepam treatment was superior to placebo with regard to the outcome variables related to efficacy: reduced seizure frequency (P\u3c0.001) and improved global assessment of treatment outcome by the care giver (frequency and severity of seizures and drug toxicity) (P\u3c0.001). Post hoc analysis showed diazepam to be superior to placebo in reducing seizure frequency in both children (P\u3c0.001) and adults (P=0.02), but only in children was it superior with regard to improvement in global outcome (P\u3c0.001). The time to the first recurrence of seizures after initial treatment was longer for the patients receiving diazepam (P\u3c0.001). Thirty-five patients reported at least one adverse effect of treatment; somnolence was the most frequent. Respiratory depression was not reported. Conclusions Rectal diazepam gel, administered at home by trained care givers, is an effective and welltolerated treatment for acute repetitive seizures. (N Engl J Med 1998;338:1869-75.

    A multi-wavelength survey of AGN in the XMM-LSS field: I. Quasar selection via the KX technique

    Get PDF
    AIMS: We present a sample of candidate quasars selected using the KX-technique. The data cover 0.68 deg^2 of the X-ray Multi-Mirror (XMM) Large-Scale Structure (LSS) survey area where overlapping multi-wavelength imaging data permits an investigation of the physical nature of selected sources. METHODS: The KX method identifies quasars on the basis of their optical (R and z') to near-infrared (Ks) photometry and point-like morphology. We combine these data with optical (u*,g'r',i',z') and mid-infrared (3.6-24 micron) wavebands to reconstruct the spectral energy distributions (SEDs) of candidate quasars. RESULTS: Of 93 sources selected as candidate quasars by the KX method, 25 are classified as quasars by the subsequent SED analysis. Spectroscopic observations are available for 12/25 of these sources and confirm the quasar hypothesis in each case. Even more, 90% of the SED-classified quasars show X-ray emission, a property not shared by any of the false candidates in the KX-selected sample. Applying a photometric redshift analysis to the sources without spectroscopy indicates that the 25 sources classified as quasars occupy the interval 0.7 < z < 2.5. The remaining 68/93 sources are classified as stars and unresolved galaxies.Comment: 13 pages, 9 figures, A&A 494, p. 579-589. Replaced with published version. Fig. 9 in first astro-ph submission has been update

    A criterion audit of women's awareness of blood transfusion in pregnancy

    Get PDF
    BACKGROUND: In the Confidential Enquiry into Maternal Deaths (CEMD) Report, the very high risk of mortality in women who refuse blood transfusions is highlighted. The objectives were to establish current knowledge about, and views of transfusion in our pregnant population and to establish the level of compliance with the set audit standard. METHOD: Questionnaire survey of 228 women, including both high and low risk pregnancies, attending ante-natal clinic between 2–9 May 2000 at the North Staffordshire Maternity Hospital, Stoke on Trent. RESULTS: The response rate was 100%. Only 43% were aware of the possible need for blood transfusion in pregnancy. If a blood transfusion was required, 92% stated that they would accept a blood transfusion in pregnancy. Four percent stated that they would not accept a transfusion because of religious reasons and risk of infection and the remaining four percent did not declare a reason. CONCLUSIONS: This short survey identified that 57% of women were not aware of the possible need for blood transfusion during pregnancy. There is a need for more information to be shared on this subject with all antenatal women. Women who would refuse a transfusion need to be identified at booking and be referred for counselling and a management plan made for pregnancy, labour and delivery

    A 3D measurement of the offset in paleoseismological studies

    Get PDF
    The slip rate of a seismogenic fault is a crucial parameter for establishing the contribution of the fault to the seismic hazard. It is calculated from measurements of the offset of linear landforms, such channels, produced by the fault combined with their age. The three-dimensional measurement of offset in buried paleochannels is subject to uncertainties that need to be quantitatively assessed and propagated into the slip rate. Here, we present a set of adapted scripts to calculate the net, lateral and vertical tectonic offset components caused by faults, together with their associated uncertainties. This technique is applied here to a buried channel identified in the stratigraphic record during a paleoseismological study at the El Saltador site (Alhama de Murcia fault, Iberian Peninsula). After defining and measuring the coordinates of the key points of a buried channel in the walls of eight trenches excavated parallel to the fault, we (a) adjusted a 3D straight line to these points and then extrapolated the tendency of this line onto a simplified fault plane; (b) repeated these two steps for the segment of the channel in the other side of the fault; and (c) measured the distance between the two resulting intersection points with the fault plane. In doing so, we avoided the near fault modification of the channel trace and obtained a three-dimensional measurement of offset and its uncertainty. This methodology is a substantial modification of previous procedures that require excavating progressively towards the fault, leading to possible underestimation of offset due to diffuse deformation near the fault. Combining the offset with numerical dating of the buried channel via U-series on soil carbonate, we calculated a maximum estimate of the net slip rate and its vertical and lateral components for the Alhama de Murcia fault. (C) 2016 Elsevier Ltd. All rights reserved

    Climate response to the 8.2 ka event in coastal California

    Get PDF
    A fast-growing stalagmite from the central California coast provides a high-resolution record of climatic changes synchronous with global perturbations resulting from the catastrophic drainage of proglacial Lake Agassiz at ca. 8.2 ka. High frequency, large amplitude variations in carbon isotopes during the 8.2 ka event, coupled with pulsed increases in phosphorus concentrations, indicate more frequent or intense winter storms on the California coast. Decreased magnesium-calcium ratios point toward a sustained increase in effective moisture during the event, however the magnitude of change in Mg/Ca suggests this event was not as pronounced on the western North American coast as anomalies seen in the high northern latitudes and monsoon-influenced areas. Nevertheless, shifts in the White Moon Cave record that are synchronous within age uncertainties with cooling of Greenland, and changes in global monsoon systems, suggest rapid changes in atmospheric circulation occurred in response to freshwater input and associated cooling in the North Atlantic region. Our record is consistent with intensification of the Pacific winter storm track in response to North Atlantic freshwater forcing, a mechanism suggested by simulations of the last deglaciation, and indicates this intensification led to increases in precipitation and infiltration along the California coast during the Holocene

    Galaxy and Mass Assembly (GAMA): survey diagnostics and core data release

    Get PDF
    The Galaxy and Mass Assembly (GAMA) survey has been operating since 2008 February on the 3.9-m Anglo-Australian Telescope using the AAOmega fibre-fed spectrograph facility to acquire spectra with a resolution of R≈ 1300 for 120 862 Sloan Digital Sky Survey selected galaxies. The target catalogue constitutes three contiguous equatorial regions centred at 9h (G09), 12h (G12) and 14.5h (G15) each of 12 × 4 deg2 to limiting fluxes of rpet < 19.4, rpet < 19.8 and rpet < 19.4 mag, respectively (and additional limits at other wavelengths). Spectra and reliable redshifts have been acquired for over 98 per cent of the galaxies within these limits. Here we present the survey footprint, progression, data reduction, redshifting, re-redshifting, an assessment of data quality after 3 yr, additional image analysis products (including ugrizYJHK photometry, Sérsic profiles and photometric redshifts), observing mask and construction of our core survey catalogue (GamaCore). From this we create three science-ready catalogues: GamaCoreDR1 for public release, which includes data acquired during year 1 of operations within specified magnitude limits (2008 February to April); GamaCoreMainSurvey containing all data above our survey limits for use by the GAMA Team and collaborators; and GamaCoreAtlasSV containing year 1, 2 and 3 data matched to Herschel-ATLAS science demonstration data. These catalogues along with the associated spectra, stamps and profiles can be accessed via the GAMA website: http://www.gama-survey.or
    corecore