An experimental pressure compensated wet suit

Personal thermal insulation by means of neoprene from wet suits provides adequate temporary control of body heat loss only at the shallow end of the air diving depth range, but it constitutes by far the most popular approach to diver thermal support. Howewer, compression of the trapped gas phase in neoprene foam seriously reduces its insulation performance on exposure to high ambient pressure. With conventional wet suits equipped with heating, the necessary level of power required at depths greater than about 30 m is too high, and also unsafe without the back up that increased insulation would provide. One approach to the goal of depth-insensitive insulation is to use a wet suit with a continuous internal gas space pressurized nominally to ambient pressure, so that its thickness remains substantially constant at all depths. The composite material properties required are: outer skins that are tough, flexible and free of pin holes; an open foam internal structure capable of resisting, without significant dimensional change, the relatively small pressure changes that occur over the height of a man; and a high bond strength.Samples of a composite material that meets these requirements have been developed, and a prototype suit has been successfully fabricated by conventional techniques.     

Determination of the sources and circulation paths of thermal fluids: the Abano region,northern Italy

Water samples from natural springs and artesian wells in the Abano region of northern Italy are characterized by anomalous temperatures and compositions. Concentrations of major components and oxygen isotopes in samples of these fluids have been interpreted in the context of the regional geologic environment, circulation of groundwaters, and reactions between rocks and circulating groundwaters. These considerations define sourceregions and pathlines of the groundwaters.Circulation of fluids in the Abano region is interpreted to be the result of meteoric water infiltration into outcrops of Permian and Mesozoic aquifers in the pre-Alps, which lie north of the Abano region. These aquifers have southerly dips and, therefore, extend under the Abano region at depths between 0.5 and 2.5 km. This aquifer geometry is conducive to forced convection both of aqueous ions derived from the evaporate, limestone and dolomite bearing formations, and of thermal energy along flow paths which extend from the outcrops in the sourceregions to depths of 2 km below the Abano region and upward along high angle faults to thermal springs. Local variation in compositions of water samples is consistent with the mixing of local meteoric waters and formation fluids that were ultimately derived from Alpine sources.     

A record of phosphorus dynamics in oligotrophic lake sediment

Historical phosphorus (P) dynamics were studied using sediment cores from three oligotrophic, acidic lakes in Maine, USA. Long-term oligotrophy of these lakes is consistent with high sediment aluminum (as Al(OH)₃) concentrations, as Al inhibits internal P loading, even under reducing conditions. The role of microbially-mediated reactions in controlling redox conditions was evaluated by estimating microbial biomass and relative abundance of specific functional groups. Sediments were fractionated using a sequential chemical extraction technique and all lakes met criteria for P retention based on threshold sediment concentrations of Al, Fe, and P fractions as determined by (Kopáček et al. (2005) Limnol Oceanogr 52: 1147–1155). Sediment NaOH-extractable molybdate-reactive P (rP) and non-reactive P (nrP) represent P associated with non-reducible phases, and organic matter-related P, respectively. Total P (TP) does not decrease with sediment depth, as is typical of eutrophic lake sediments; however, nrP/TP decreases and rP/TP increases for all three lakes, indicating nrP mineralization without any significant upward diffusion and release into the hypolimnion; i.e. diagenesis of P is conservative within the sediment. Two diagenetic models were developed based on nrP and rP concentrations as a function of sediment age. The first model assumes a first-order decay of nrP, the rate coefficient being a function of time, and represents irreversible nrP mineralization, where the produced PO₄ is permanently sequestered by the sediment. The second model assumes a first-order reversible transformation between nrP and rP, representing biotic mineralization of organic P followed by incorporation of inorganic P into microbial biomass. Both models reflect preservation of TP with no loss to overlying water. The rate coefficients give us insight into qualities of the sediment that have affected mineralization and sequestration of phosphorus throughout the ²¹⁰Pb-dateable history of each lake. Similar models could be constructed for other lakes to help reconstruct their trophic histories. Paleolimnological reconstruction of the sediment P record in oligotrophic lakes shows mineralization of nrP to rP, but unlike the case in eutrophic lake sediments, sediment TP is preserved in these sediments.     

WASP-1b and WASP-2b: two new transiting exoplanets detected with SuperWASP and SOPHIE

We have detected low-amplitude radial-velocity variations in two stars, USNO-B1.0 1219–0005465 (GSC  02265–00107 = WASP–1  ) and USNO-B1.0 0964–0543604 (GSC  00522–01199 = WASP–2  ). Both stars were identified as being likely host stars of transiting exoplanets in the 2004 SuperWASP wide-field transit survey. Using the newly commissioned radial-velocity spectrograph SOPHIE at the Observatoire de Haute-Provence, we found that both objects exhibit reflex orbital radial-velocity variations with amplitudes characteristic of planetary-mass companions and in-phase with the photometric orbits. Line-bisector studies rule out faint blended binaries as the cause of either the radial-velocity variations or the transits. We perform preliminary spectral analyses of the host stars, which together with their radial-velocity variations and fits to the transit light curves yield estimates of the planetary masses and radii. WASP-1b and WASP-2b have orbital periods of 2.52 and 2.15 d, respectively. Given mass estimates for their F7V and K1V primaries, we derive planet masses 0.80–0.98 and 0.81–0.95 times that of Jupiter, respectively. WASP-1b appears to have an inflated radius of at least 1.33 R _Jup, whereas WASP-2b has a radius in the range 0.65–1.26 R _Jup.     

Stratigraphy of total metals in PIRLA sediment cores

Sediment cores from 30 low-alkalinity lakes in northern New England (NE), New York (NY), the northern Great Lakes States (NGLS) of Minnesota, Michigan, and Wisconsin, and Florida (FL) have been dated by ²¹⁰Pb and analyzed for water and organic content, eight major elements (Al, Ti, Fe, Mn, Ca, Mg, Na, K) plus four trace metals (Pb, Zn, Cu, and V). Variations in the percentages of major elements through time are dominated by long-term independent variations in the abundance of SiO₂, FeO, and to a lesser extent Ca and Al. Additional variations are caused by varying proportions of inorganic matter. Major variations in chemistry are generally unrelated to documented distrubances in the watersheds; most disturbances are minor fires or selective logging.Accelerated accumulation of Pb from atmospheric sources into sediment first occurs in sediment dated between 1800 and 1850 in NY and NE, slightly later in the NGLS region, and about 1900 in FL. Modern accumulation rates in all areas are comparable (ca. 1 to 4 g cm^–2 yr^–1). Accumulation rates of Pb in some lakes have declined significantly from 1975 to 1985. Atmospheric deposition of anthropogenic Zn and Cu is also indicated by generally increasing accumulation rates in sediment cores, but the record is not as clear nor are chemical profiles in all lakes parallel to the trends in atmospheric emissions inferred on the basis of fossil fuel consumption, smelting, and other industrial activities. Inter-lake variations in profiles of Cu and Zn are large. Vanadium accumulation rates increase by the 1940s in NY and NE, but not until the 1950s in the NGLS region. This timing correlates with regional trends in the combustion of fuel oil, a major source of atmospheric V.Acidification of some of the lakes is suggested by decreases in the concentration and accumulation rates of Mn, Ca, and Zn in recent sediment, relative to other elements of catchment origin. The decreases generally occur slightly before the onset of acidification as indicated by diatoms. Increased sediment accumulation rates for Fe may indicate the acidification of watershed soils. The use of the accumulation rate of TiO₂ as an indicator of rates of erosion and for normalization of trace metal accumulation rates is in question for lakes where the flux of TiO₂ from the atmosphere varies and is a significant fraction of the total flux of TiO₂ to the sediment.This is the thirteenth of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D. F. Charles and D. R. Whitehead are guest editors for this series.     

Erosion-driven uplift of the modern Central Alps

We present a compilation of data of modern tectono-geomorphic processes in the Central European Alps which suggest that observed rock uplift is a response to climate-driven denudation. This interpretation is predominantly based on the recent quantification of basin-averaged Late Holocene denudation rates that are so similar to the pattern and rates of rock uplift rates as determined by geodetic leveling. Furthermore, a GPS data-based synthesis of Adriatic microplate kinematics suggests that the Central Alps are currently not in a state of active convergence. Finally, we illustrate that the Central Alps have acted as a closed system for Holocene redistribution of sediment in which the peri-Alpine lakes have operated as a sink for the erosional products of the inner Central Alps.While various hypotheses have been put forward to explain Central Alpine rock uplift (e.g. lithospheric forcing by convergence, mantle processes, or ice melting) we show with an elastic model of lithospheric deformation, that the correlation between erosion and rock uplift rates reflects a positive feedback between denudation and the associated isostatic response to unloading. Thus, erosion does not passively respond to advection of crustal material as might be the case in actively converging orogens. Rather, we suggest that the geomorphic response of the Alpine topography to glacial and fluvial erosion and the resulting disequilibrium for modern channelized and associated hillslope processes explains much of the pattern of modern denudation and hence rock uplift. Therefore, in a non-convergent orogen such as the Central European Alps, the observed vertical rock uplift is primarily a consequence of passive unloading due to erosion.     

Geophysical Finite-Element Simulation Tool (GeoFEST): Algorithms and Validation for Quasistatic Regional Faulted Crust Problems

GeoFEST (Geophysical Finite Element Simulation Tool) is a two- and three-dimensional finite element software package for the modeling of solid stress and strain in geophysical and other continuum domain applications. It is one of the featured high-performance applications of the NASA QuakeSim project. The program is targeted to be compiled and run on UNIX systems, and is running on diverse systems including sequential and message-passing parallel systems. Solution to the elliptical partial differential equations is obtained by finite element basis sampling, resulting in a sparse linear system primarily solved by conjugate gradient iteration to a tolerance level; on sequential systems a Crout factorization for the direct inversion of the linear system is also supported. The physics models supported include isotropic linear elasticity and both Newtonian and power-law viscoelasticity, via implicit quasi-static time stepping. In addition to triangular, quadrilateral, tetrahedral and hexahedral continuum elements, GeoFEST supports split-node faulting, body forces, and surface tractions. This software and related mesh refinement strategies have been validated on a variety of test cases with rigorous comparison to analytical solutions. These include a box-shaped domain with imposed motion on one surface, a pair of strike slip faults in stepover arrangement, and two community-agreed benchmark cases: a strike slip fault in an enclosing box, and a quarter-domain circular fault problem. Scientific applications of the code include the modeling of static and transient co- and post-seismic earth deformation, Earth response to glacial, atmospheric and hydrological loading, and other scenarios involving the bulk deformation of geologic media.     

Mesozoic magnetic lineations in the Mozambique Basin

East-west-trending Mesozoic magnetic anomalies M2 through M22 have been identified in the northern Mozambique Basin. These anomalies are best matched by sea floor created at 50°S trending N120°E and spreading at a rate of around 1.5 cm/yr. The northward increase in age inferred from the identifications of these anomalies are compatible with observed decrease in the “reliable” heat flow values from 1.4 to 1.1 μcal/cm² s to the north in the basin. The anomalies terminate in the southern part of the Mozambique Channel against a magnetic quiet zone to the north. Both the Mozambique Basin anomalies and those recently observed off Antarctica are strong evidence in favour of a Gondwanaland reconstruction that places Dronning Maud Land against southern Mozambique, and a late Jurassic or older separation between Africa and Antarctica.     

The Bear Brook Watershed in Maine: Multi-decadal whole-watershed experimental acidification

The Bear Brook Watershed in Maine (BBWM) is a long-term research site established to study the response of forest ecosystem function to environmental disturbances of chronic acidic deposition and ecosystem nitrogen enrichment. Starting in 1989, the West Bear (treated) watershed received bimonthly applications of ammonium sulfate [(NH₄)₂SO₄] fertilizer from above the canopy, whereas East Bear (reference) received ambient deposition. The treatments were stopped in 2016, marking the beginning of the recovery phase. Research at the site has focused on soils, streams, and vegetation. Here, we describe data collected over three decades at the BBWM—input and stream output nutrient fluxes, quantitative soil pits and soil chemistry, and soil temperature and moisture.     

Effects of terrain smoothing on topographic shielding correction factors for cosmogenic nuclide‐derived estimates of basin‐averaged denudation rates

Estimation of spatially averaged denudation rates from cosmogenic nuclide concentrations in sediments depends on the surface production rates, the scaling methods of cosmic ray intensities, and the correction algorithms for skyline, snow and vegetation shielding used to calculate terrestrial cosmogenic nuclide production. While the calculation of surface nuclide production and application of latitude, altitude and palaeointensity scaling algorithms are subjects of active research, the importance of additional correction for shielding by topographic obstructions, snow and vegetation is the subject of ongoing debate. The derivation of an additional correction factor for skyline shielding for large areas is still problematic. One important issue that has yet to be addressed is the effect of the accuracy and resolution of terrain representation by a digital elevation model (DEM) on topographic shielding correction factors. Topographic metrics scale with the resolution of the elevation data, and terrain smoothing has a potentially large effect on the correction of terrestrial cosmogenic nuclide production rates for skyline shielding. For rough, high‐relief landscapes, the effect of terrain smoothing can easily exceed analytical errors, and should be taken into account. Here we demonstrate the effect of terrain smoothing on topographic shielding correction factors for various topographic settings, and introduce an empirical model for the estimation of topographic shielding factors based on landscape metrics. Copyright © 2008 John Wiley and Sons, Ltd.