Cold-seep carbonates of the Laptev Sea continental slope: Constraints from fluid sources and environment of formation

This study presents results of the petrographic, mineralogical, stable isotopes of oxygen and carbon, and trace element investigation of authigenic carbonates collected at newly discovered active cold seeps on the Laptev Sea continental slope at ∼300 m water depth. These carbonates are mainly represented by Mg-calcite with MgCO3 content from 9.1 mol% to 14.0 mol%. The low δ13C values of carbonates ranging from −50.6 ‰ to −32.4 ‰ (V-PDB) indicate that they were formed from anaerobic oxidation of biogenic methane and minor participation of other carbon sources. The difference between measured (from 4.7 ‰ to 5.5 ‰) and calculated (4.0 ‰) δ18Ocarb values might be inherited from fluids enriched in 18O due to dissociation of gas hydrates, which could be the source of methane. The carbonates exhibit weak enrichment in Co, moderate and strong enrichments in As, Mo, and Sb, and strong enrichment in U. Interestingly, As, Sb, and Co correlate with the pyrite content. This indicates that authigenic iron sulfides promote the immobilization of these redox-sensitive elements in seep sediments. The (Mo/U)EF values and anomalies of concentration of Mo and U probably indicate variations in the redox conditions during carbonate formation due to episodically seepage activity changes. Ascending methane-bearing fluids were the main contributor to the enrichment of cold-seep carbonates in As, Mo, Sb, and U at the Laptev Sea continental slope. However additional input from the particulate shuttle process can not be ruled out

Conceptual Design of the Cryostat for a Highly Radiation Transparent 2 T Superconducting Detector Solenoid for FCC-ee⁺

The Future Circular Collider electron-positron version (FCC-ee$^{+}$) may be the next step towards a next generation of particle colliders. It may include an Experiment for probing ee$^{+}$ collisions using the IDEA (International Detector for Electron-positron Accelerator), or a similar detector, requiring a solenoid enclosing the inner tracking detector. An innovative 2 T superconducting solenoid with 4 m bore and 6 m long has been accepted as baseline. Positioning the solenoid in between tracker and calorimeter requires an ultra-thin and highly radiation transparent cold mass. Likewise, a thin and radiation transparent cryostat is needed. The set value for the solenoid's maximum radiation length is 1 × X0. The cryostat is designed as a sandwich of thin Aluminum alloy inner and outer shells, eventually locally reinforced, for achieving vacuum tightness, and layers of innovative insulation material providing lowest thermal conductivity and sufficient mechanical resistance. Cryogel Z, a composite blanket of silica aerogel and reinforcing fibers, has a density of 160 kg/m$^{3}$ and would allow a 250 mm cryostat thickness. As an alternative, glass spheres (e.g., K1 type, manufactured by 3M, with a 65μm diameter and a 125 kg/m$^{3}$ density), or similar material, can be dispersed between the vacuum vessel thin-walls providing structural support. Besides the cryostat conceptual design, we outline the setup developed at CERN to represent the real-case cryostat and to measure the heat load transferred through the above-mentioned materials and we present the test results for Cryogel Z

Organic matter composition and greenhouse gas production of thawing subsea permafrost in the Laptev Sea

Subsea permafrost represents a large carbon pool that might be or become a significant greenhouse gas source. Scarcity of observational data causes large uncertainties. We here use five 21-56 m long subsea permafrost cores from the Laptev Sea to constrain organic carbon (OC) storage and sources, degradation state and potential greenhouse gas production upon thaw. Grain sizes, optically-stimulated luminescence and biomarkers suggest deposition of aeolian silt and fluvial sand over 160 000 years, with dominant fluvial/alluvial deposition of forest- and tundra-derived organic matter. We estimate an annual thaw rate of 1.3 ± 0.6 kg OC m−2 in subsea permafrost in the area, nine-fold exceeding organic carbon thaw rates for terrestrial permafrost. During 20-month incubations, CH4 and CO2 production averaged 1.7 nmol and 2.4 µmol g−1 OC d−1, providing a baseline to assess the contribution of subsea permafrost to the high CH4 fluxes and strong ocean acidification observed in the region

Health effects associated with measured levels of contaminants in the Arctic

Published version. Source at http://dx.doi.org/10.3402/ijch.v75.33805 The Human Health Assessment Group has over the past decade recommended that effect studies be conducted in the circumpolar area. Such studies examine the association between contaminant exposure in the Arctic populations and health effects. Because foetuses and young children are the most vulnerable, effect studies are often prospective child cohort studies. The emphasis in this article is on a description of the effects associated with contaminant exposure in the Arctic. The main topics addressed are neurobehavioural, immunological, reproductive, cardiovascular, endocrine and carcinogenic effect. For each topic, the association between exposure and effects is described, and some results are reported for similar studies outside the Arctic

Shock-wave and spalling phenomena in ultrafine-grained and coarse-grained (α + β) alloy Ti-Al-V treated by a nanosecond relativistic high-current electron beam

The results of experimental and theoretical research of shock-wave and spalling phenomena in ultrafine-grained and coarse-grained (α + β) alloy Ti–6.2% Al–4.0% V (wt %) treated by a nanosecond relativistic high-current electron beam are presented. Data on the dynamics of mass velocity, temperature and shock waves as well as on the interaction of the unloading wave with the rarefaction wave reflected from the back surface have been obtained for an axisymmetric position of the target. It is shown that the strain rate increase from 10−3 to 105 s−1 in the both grain structures does not change the fracture mechanism and the phase composition in the zone of spalling. The obtained theoretical dependence of the spalling layer thickness to the target thickness corresponds to experimental data

Investigation of structural-scale levels of spall fracture induced by a nanosecond relativistic high-current electron beam in ultrafine-grained Ti–Al–V–Mo alloy

The results of an experimental and theoretical study of shock-wave processes and spall fracture in an ultrafine-grained and coarse-grained (α + β) Ti–Al–V–Mo alloy under the action of a nanosecond relativistic high-current electron beam are reported. Mathematical modeling is performed to show that when an electron beam with a power density of 1.65 × 1010 W/cm2 impacts this alloy, a shock wave with a compression amplitude of 13 GPa appears and its reflection gives rise to a tensile wave. Its amplitude increases with decreasing target thickness. The calculated increase in the thickness of the spalled layer at the rear surface of the target corresponds to the experimental data. It is established experimentally that plastic deformation precedes the spall fracture sequentially at three structural-scale levels. At the beginning pores are formed and merge, then microcracks are formed at different angles to the back surface of the target between the pores, and then a macrocrack is formed. As a result, the macrocrack surface is not smooth but exhibits pits of ductile fracture

Overview of ongoing cohort and dietary studies in the Arctic

Published version. Source at http://dx.doi.org/10.3402/ijch.v75.33803 This article gives an overview of the ongoing cohort and dietary studies underlying the assessment of population health in the Arctic. The emphasis here is on a description of the material, methods and results or preliminary results for each study. Detailed exposure information is available in an article in this journal, whereas another paper describes the effects associated with contaminant exposure in the Arctic. The cohort descriptions have been arranged geographically, beginning in Norway and moving east to Finland, Sweden, Russia and the other Arctic countries and ultimately to the Faroe Islands. No cohort studies have been reported for Alaska or Iceland

Measuring the free fall of antihydrogen

After the first production of cold antihydrogen by the ATHENA and ATRAP experiments ten years ago, new second-generation experiments are aimed at measuring the fundamental properties of this anti-atom. The goal of AEGIS (Antimatter Experiment: Gravity, Interferometry, Spectroscopy) is to test the weak equivalence principle by studying the gravitational interaction between matter and antimatter with a pulsed, cold antihydrogen beam. The experiment is currently being assembled at CERN's Antiproton Decelerator. In AEGIS, antihydrogen will be produced by charge exchange of cold antiprotons with positronium excited to a high Rydberg state (n > 20). An antihydrogen beam will be produced by controlled acceleration in an electric-field gradient (Stark acceleration). The deflection of the horizontal beam due to its free fall in the gravitational field of the earth will be measured with a moire deflectometer. Initially, the gravitational acceleration will be determined to a precision of 1%, requiring the detection of about 105 antihydrogen atoms. In this paper, after a general description, the present status of the experiment will be reviewed

A Call for Urgent Monitoring of Food and Water Security Based on Relevant Indicators for the Arctic

This perspective paper argues for an urgent need to monitor a set of 12 concrete, measurable indicators of food and water security in the Arctic over time. Such a quantitative indicator approach may be viewed as representing a reductionist rather than a holistic perspective, but is nevertheless necessary for actually knowing what reality aspects to monitor in order to accurately understand, quantify, and be able to project critical changes to food and water security of both indigenous and non-indigenous people in the Arctic. More relevant indicators may be developed in the future, taking us further toward reconciliation between reductionist and holistic approaches to change assessment and understanding. However, the potential of such further development to improved holistic change assessment is not an argument not to urgently start to monitor and quantify the changes in food and water security indicators that are immediately available and adequate for the Arctic context

Towards a muon collider

A muon collider would enable the big jump ahead in energy reach that is needed for a fruitful exploration of fundamental interactions. The challenges of producing muon collisions at high luminosity and 10 TeV centre of mass energy are being investigated by the recently-formed International Muon Collider Collaboration. This Review summarises the status and the recent advances on muon colliders design, physics and detector studies. The aim is to provide a global perspective of the field and to outline directions for future work