Climate Change and Violent Conflict in Europe over the Last Millennium

We investigate the relationship between a thousand-year history of violent conflict in Europe and various reconstructions of temperature and precipitation. We find that conflict was more intense during colder periods. This relationship is weakening over time, and is not robust to the details of the climate reconstruction or to the sample period. We thus confirm Zhang et al. (2006, Climatic Change, 76, 459-477) that, at least in temperate climates, global warming would, if anything, lead to reduced violent conflict.history, violent conflict, Europe, climate change

Difference frequency generation by quasi-phase matching in periodically intermixed semiconductor superlattice waveguides

Wavelength conversion by difference frequency generation is demonstrated in domain-disordered quasi-phase-matched waveguides. The waveguide structure consisted of a GaAs/AlGaAs superlattice core that was periodically intermixed by ion implantation. For quasi-phase-matching periods of 3.0–3.8 μm, degeneracy pump wavelengths were found by second-harmonic generation experiments for fundamental wavelengths between 1520 and 1620 nm in both type-I and type-II configurations. In the difference frequency generation experiments, output powers up to 8.7 nW were generated for the type-I phase matching interaction and 1.9 nW for the type-II interaction. The conversion bandwidth was measured to be over 100 nm covering the C, L, and U optical communications bands, which agrees with predictions

Intensive monitoring of the strongly variable BL Lac S5 0716+714

The BL Lac object S5 0716+714 was monitored during a multifrequency campaign in 1996. Preliminary analysis of the optical, ROSAT and RXTE data are presented. Strong variability on short time scales was observed. The data suggest an interpretation within a multi-component model.Comment: To appear in The Active X-ray Sky: Results from BeppoSAX and Rossi-XTE, Rome, Italy, 21-24 October, 1997. Eds.: L. Scarsi, Bradt, P. Giommi and F. Fiore. PS-file avialable at http://www.lsw.uni-heidelberg.de/projects/extragalactic/bl_lac.htm

What the Integral Does: Physics Students\u27 Efforts at Making Sense of Integration

Students use a variety of resources to make sense of integration, and interpreting the definite integral as a sum of infinitesimal products (rooted in the concept of a Riemann sum) is particularly useful in many physical contexts. This study of beginning and upper-level undergraduate physics students examines some obstacles students encounter when trying to make sense of integration, as well as some discomforts and skepticism some students maintain even after constructing useful conceptions of the integral. In particular, many students attempt to explain what integration does by trying to interpret the algebraic manipulations and computations involved in finding antiderivatives. This tendency, perhaps arising from their past experience of making sense of algebraic expressions and equations, suggests a reluctance to use their understanding of what a Riemann sum does to interpret what an integral does.

Acute hypoxia reduces plasma myostatin independent of hypoxic dose

Background: Muscle atrophy is seen ~ 25 % of patients with cardiopulmonary disorders, such as chronic obstructive pulmonary disorder and chronic heart failure. Multiple hypotheses exist for this loss, including inactivity, inflammation, malnutrition and hypoxia. Healthy individuals exposed to chronic hypobaric hypoxia also show wasting, suggesting hypoxia alone is sufficient to induce atrophy. Myostatin regulates muscle mass and may underlie hypoxic-induced atrophy. Our previous work suggests a decrease in plasma myostatin and increase in muscle myostatin following 10 hours of exposure to 12 % O2. Aims: To establish the effect of hypoxic dose on plasma myostatin concentration. Concentration of plasma myostatin following two doses of normobaric hypoxia (10.7 % and 12.3 % O2) in a randomised, single-blinded crossover design (n = 8 lowlanders, n = 1 Sherpa), with plasma collected pre (0 hours), post (2 hours) and 2 hours following (4 hours) exposure. Results: An effect of time was noted, plasma myostatin decreased at 4 hours but not 2 hours relative to 0 hours (p = 0.01; 0 hours = 3.26 [0.408] ng.mL-1, 2 hours = 3.33, [0.426] ng.mL-1, 4 hours = 2.92, [0.342] ng.mL-1). No difference in plasma myostatin response was seen between hypoxic conditions (10.7 % vs. 12.3 % O2). Myostatin reduction in the Sherpa case study was similar to the lowlander cohort. Conclusions: Decreased myostatin peptide expression suggests hypoxia in isolation is sufficient to challenge muscle homeostasis, independent of confounding factors seen in chronic cardiopulmonary disorders, in a manner consistent with our previous work. Decreased myostatin peptide may represent flux towards peripheral muscle, or a reduction to protect muscle mass. Chronic adaption to hypoxia does not appear to protect against this response, however larger cohorts are needed to confirm this. Future work will examine tissue changes in parallel with systemic effects

Anomalous enrichment of molybdenum and associated metals in Lower Jurassic (Lias Group) black shales of central England, as revealed by systematic geochemical surveys

Systematic multi-media geochemical surveying by the British Geological Survey's Geochemical Baseline Survey of the Environment (G-BASE) project has revealed significant anomalous patterns of enrichment for a suite of elements – copper (Cu) and uranium (U) – with exceptionally high levels of molybdenum (Mo), in soils and stream sediments in central England. Enrichment of these elements is most often associated with organic-rich, sulphidic ‘black shale’ lithofacies, typical of oxygen-deficient, euxinic depositional environments. The main anomaly lies between Evesham and Rugby where the bedrock comprises the Blue Lias and Charmouth Mudstone formations. Concentrations of Mo are particularly high, reaching soil values of 50 mg/kg, where the regional background is <2 mg/kg. Analysis of black shale partings sampled from rhythmic limestone–shale couplets reveal Mo levels up to 320 mg/kg. Complementary X-ray diffraction analyses suggest that the anomalous Mo levels are hosted by sulphidic (pyrite) rather than organic phases. High Mo levels may have significant impacts on local agriculture, as well as revealing hitherto unsuspected periods of hypoxic and anoxic bottom water sedimentation within localised basins in central England during the Early Jurassic. Rhythmic alternations of thin beds of Mo-rich, sulphidic black shale (euxinic) with bioclastic and micritic limestone (oxic) represent primary depositional cycles rather than a diagenetic origin. The bed-scale cyclicity is attributed to previously described orbitally-induced precession cycles that influenced climate. These resulted in periods of basin anoxia and black shale sedimentation during periods of enhanced terrestrial fresh-water run-off (possibly below a low-salinity pycnocline), alternating with periods of oxygenation of the sea-water and bottom sediments during overturn of the water column

Complex shock structure in the western hot-spot of Pictor A

We have carried out simulations of supersonic light jets in order to model the features observed in optical and radio images of the western hot-spot in the radio galaxy Pictor A. We have considered jets with density ratios η =10[superscript −2] − 10[superscript −4], and Mach numbers ranging between 5 and 50. From each simulation, we have generated raytraced maps of radio surface brightness at a variety of jet inclinations, in order to study the appearance of time-dependent luminous structures in the vicinity of the western hotspot. We compare these rendered images with observed features of Pictor A. A remarkable feature of Pictor A observations is a bar-shaped “filament” inclined almost at right angles to the inferred jet direction and extending 24" (10.8h[superscript −1] kpc) along its longest axis. The constraints of reproducing the appearance of this structure in simulations indicate that the jet of Pictor A lies nearly in the plane of the sky. The results of the simulation are also consistent with other features found in the radio image of Pictor A. This filament arises from the surging behaviour of the jet near the hot-spot; the surging is provoked by alternate compression and decompression of the jet by the turbulent backflow in the cocoon. We also examine the arguments for the jet in Pictor A being at a more acute angle to the line of sight and find that our preferred orientation is just consistent with the limits on the brightness ratio of the X-ray jet and counter-jet. We determine from our simulations, the structure function of hot-spot brightness and also the cumulative distribution of the ratio of intrinsic hot-spot brightnesses. The latter may be used to quantify the use of hot-spot ratios for the estimation of relativistic effects

An improved approach to characterize potash-bearing evaporite deposits, evidenced in North Yorkshire, United Kingdom

Traditionally, potash mineral deposits have been characterized using downhole geophysical logging in tandem with geochemical analysis of core samples to establish the critical potassium (% K2O) content. These techniques have been employed in a recent exploration study of the Permian evaporite succession of North Yorkshire, United Kingdom, but the characterization of these complex deposits has been led by mineralogical analysis, using quantitative X-ray diffraction (QXRD). The novel QXRD approach provides data on K content with the level of confidence needed for reliable reporting of resources and also identifies and quantifies more precisely the nature of the K-bearing minerals. Errors have also been identified when employing traditional geochemical approaches for this deposit, which would have resulted in underestimated potash grades. QXRD analysis has consistently identified polyhalite (K2Ca2Mg(SO4)4·2(H2O) in the Fordon (Evaporite) Formation and sylvite (KCl) in the Boulby Potash and Sneaton Potash members as the principal K-bearing host minerals in North Yorkshire. However, other K hosts, including kalistrontite (K2Sr(SO4)2) a first recorded occurrence in the UK, and a range of boron-bearing minerals have also been detected. Application of the QXRD-led characterization program across the evaporitic basin has helped to produce a descriptive, empirical model for the deposits, including the polyhalite-bearing Shelf and Basin seams and two, newly discovered sylvite-bearing bittern salt horizons, the Pasture Beck and Gough seams. The characterization program has enabled a polyhalite mineral inventory in excess of 2.5 billion metric tons (Bt) to be identified, suggesting that this region possesses the world’s largest known resource of polyhalite. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed