Supernova remnants, planetary nebulae and the distance to NGC 4214

We present narrow band, continuum subtracted Hα, [S ii], Hβ, [O iii] and [O ii] data taken with the Wide Field Camera 3 on the Hubble Space Telescope in the nearby dwarf starburst galaxy NGC 4214. From these images, we identify seventeen new planetary nebula candidates, and seven supernova remnant candidates. We use the observed emission line luminosity function of the planetary nebulae to establish a new velocity-independent distance to NGC 4214. We conclude that the PNLF technique gives a reddening independent distance to NGC 4214 of 3.19±0.36 Mpc, and that our current best-estimate of the distance to this galaxy ids 2.98±0.13 Mpc.     

Ra-partitioning between phlogopite and silicate melt and 226Ra/Ba–230Th/Ba isochrons

In this study we experimentally determine phlogopite/melt partition coefficients of Ra and other trace elements in a lamproitic system. This work was achieved using an analytical technique (LA-ICP-MS) with low detection limits (~ 0.01 fg) permitting the measurement of the very low Ra concentrations feasible in experiments (~ 1 ppb). D_Ra^{phlogopite/melt} was determined to 2.28 ± 0.44 and 2.84 ± 0.47 in two experiments, the ratio D_Ra/D_Ba is around 1.6. The compatibility of Ra in phlogopite results from an ionic radius being close to the apex of the lattice strain parabola for earth alkalis in the large XII-coordinated interlayer site of phlogopite. A re-evaluation of D_Ra and D_Ra/D_Ba for magmatic minerals containing appreciable Ra, yields D_Ra^mineral/melt ranging from ~ 2.6 for phlogopite down to 2–3 ? 10^? 5 for pyroxenes, and D_Ra/D_Ba^mineral/melt from ~ 4 for leucite to 2 ? 10^? 2 for orthopyroxene. The influence of melt composition on D_Ra/D_Ba is less than 10%. All investigated minerals have different D_Ra/D_Ba, strongly fractionating Ra from Ba. Thus, for magmatic systems, (²²⁶Ra)/Ba in the various minerals is not constant, these minerals do not form a straight line in the (²²⁶Ra)/Ba–(²³⁰Th)/Ba system at the time of crystallization and thus, there is no (²²⁶Ra)/Ba–(²³⁰Th)/Ba isochron at t₀. ²²⁶Ra–²³⁰Th–Ba mineral dating is thus applicable only to model ages calculated from mineral–glass pairs with known D_Ra.     

Insight to Ecosystem Based Approach (EBA) at Landscape Level Using a Geospatial Medium

Ecosystem based approach (EBA) for resource management is a concerted, environmentally tuned and an integrated framework that holistically addresses the ecological character of the natural resource, its societal benefit spectrum and its environmental functions. In this paper, the EBA concept is closely linked with the emerging concept of multiple use systems (MUS) while taking account of environmental, economic, and social factors that govern the ecosystems services and benefits. We elucidate a multi-scalar approach and multiple case studies to understand EBA particularly in context of a wetlandscape. At the global scale, Ramsar sites of international importance are geospatially analyzed with reference to their agro-ecology and biodiversity. At regional scale, the agrarian use of inland wetlands in India was re-evaluated taking account of database from a recent inland wetland inventory. At the local scale, drawing on the landscape characterization and the ecological economics for fresh water Lake Kolleru in India and the Muthurajawela Marsh-Negombo Lagoon coastal marsh in Sri Lanka, we illustrate some of the practical challenges in balancing wetland conservation, development needs and the overall well-being of local people. We also discuss how variability in the scale, geophysical characteristics of the site and the data availability confines the ability to simplify a single complete approach to address issues in complex ecosystem such as wetlands. All levels of the study are supported by a variety of earth observation data and the geographical information system (GIS) tools. The site level analysis also draws on socio-economic assessment tools.     

Radiative source-function predictions for finite and semi-infinite non-conservative atmospheres

The probabilistic method of Sobolev and Case's method of normal mode expansion are combined to predict source-function distributions for radiative transfer in non-conservative, planeparallel atmospheres. The solutions obtained for semi-infinite atmospheres are exact and can be expressed in terms of functions and parameters associated with the non-conservative Milne problem. The predictions for finite atmospheres are approximate and are constructed from the semi-infinite solutions. Tabular values of the requisite functions and parameters are provided to facilitate rapid numerical evaluation of the solutions. Although the finite solutions corresponds to the zeroth-order (optically thick) approximation by Case's method, an assessment of the accuracy indicates that the results are useful for optical thicknesses as small as one or even less. The close connection between the results obtained and the method of point-direction gain of Van de Hulst is discussed.     

Stochastic diffusion in inverse square fields: General formulation for interplanetary gas

The Fokker-Planck equation for small stochastic changes to particles in Kepler orbits has to be formulated in terms of the integrals of motion. We generalize the modelling of proton and electron collisional perturbations to gas particles on trajectories through the solar system in order to include both spatial and velocity diffusion. The general solution is obtained in terms of a 4-dimensional normal distribution. Treatment of the singularity in the Fokker-Planck operator reduces the dimensionality by one. In addition to extending earlier results for anisotropic collisional heating in the thermal approximation, the present formulation gives the changes in density due to the mean repulsive force and to perturbations of trajectories (spatial diffusion). The net diffusion is almost everywhere towards the sun and the density increase is significant in the downstream hydrogen wake, particularly where destructive depletion is strong and gravitational focussing weak.     

Second round of evaluations of proposed earthquake precursors

This review summarizes the result of the second round of nominations for the IASPEI Preliminary List of Significant Precursors. Currently this List contains five cases of precursors: (1) foreshocks, (2) preshocks, (3) seismic quiescence before major aftershocks, (4) radon decrease in ground water, and (5) ground water level increase. A list of four cases that could not be accepted nor rejected by the panels reviewing them contains three on crustal deformations and one on seismic quiescence. In the second round 10 nominations were evaluated, nine new ones and one which had been considered previously. Two were accepted for the List, two were placed in the category of undecided cases. To date, a total of 40 nominations have been evaluated by IASPEI. For 37 of these the nominations, the mail reviews, the panel opinions, and, where supplied, the author's reply were published. This evaluation process remains active throughout the International Decade for Natural Hazards Reduction. Additional nominations are invited.The IASPEI Sub-commission on Earthquake Prediction does not guarantee that precursors accepted for the List can be used for earthquake prediction, nor does rejection of a nomination mean that the particular method could never become useful for prediction. However, the List, as well as the interchanges between authors and reviewers, allow us to gauge the state-of-the-art in earthquake prediction research. It is clear that we do not have an earthquake prediction capability, because the manner in which to use the few precursors on the List for predictions is not known. It also appears that many of the results thought to be conclusive by the authors, may not command the respect of the seismological research community at large. A more quantitative approach to data analysis, the use of rigorous statistical techniques, and high quality, long-term data sets are needed to make progress in earthquake prediction research.     

Anomalously high b-values in the South Flank of Kilauea volcano, Hawaii: evidence for the distribution of magma below Kilauea's East rift zone

The pattern of b-value of the frequency–magnitude relation, or mean magnitude, varies little in the Kaoiki-Hilea area of Hawaii, and the b-values are normal, with b=0.8 in the top 10 km and somewhat lower values below that depth. We interpret the Kaoiki-Hilea area as relatively stable, normal Hawaiian crust. In contrast, the b-values beneath Kilauea's South Flank are anomalously high (b=1.3–1.7) at depths between 4 and 8 km, with the highest values near the East Rift zone, but extending 5–8 km away from the rift. Also, the anomalously high b-values vary along strike, parallel to the rift zone. The highest b-values are observed near Hiiaka and Pauahi craters at the bend in the rift, the next highest are near Makaopuhi and also near Puu Kaliu. The mildest anomalies occur adjacent to the central section of the rift. The locations of the three major and two minor b-value anomalies correspond to places where shallow magma reservoirs have been proposed based on analyses of seismicity, geodetic data and differentiated lava chemistry. The existence of the magma reservoirs is also supported by magnetic anomalies, which may be areas of dike concentration, and self-potential anomalies, which are areas of thermal upwelling above a hot source. The simplest explanation of these anomalously high b-values is that they are due to the presence of active magma bodies beneath the East Rift zone at depths down to 8 km. In other volcanoes, anomalously high b-values correlate with volumes adjacent to active magma chambers. This supports a model of a magma body beneath the East Rift zone, which may widen and thin along strike, and which may reach 8 km depth and extend from Kilauea's summit to a distance of at least 40 km down rift. The anomalously high b-values at the center of the South Flank, several kilometers away from the rift, may be explained by unusually high pore pressure throughout the South Flank, or by anomalously strong heterogeneity due to extensive cracking, or by both phenomena. The major b-value anomalies are located SSE of their parent reservoirs, in the direction of motion of the flank, suggesting that magma reservoirs leave an imprint in the mobile flank. We hypothesize that the extensive cracking may have been acquired when the anomalous parts of the South Flank, now several kilometers distant from the rift zone, were generated at the rift zone near persistent reservoirs. Since their generation, these volumes may have moved seaward, away from the rift, but earthquakes occurring in them still use the preexisting complex crack distribution. Along the decollement plane at 10 km depth, the b-values are exceptionally low (b=0.5), suggesting faulting in a more homogeneous medium.     

Precise two chronometer dating of Pleistocene travertine: The Th/U and Raex/Ra(0) approach

In order to determine the geochemical evolution of a freshwater limestone cave system located in central Switzerland (Hell Grottoes at Baar/Zug,) young postglacial tufaceous limestone and travertine precipitates were investigated using the ²³⁰Th/²³⁴U ingrowth system. Additional analyses of further radionuclides within the ²³⁸U decay chain, i.e. ²²⁶Ra and ²¹⁰Pb, showed that the Th/U chronometer started with insignificant inherited ²³⁰Th over the entire formation period of the travertine setting (i.e. ²³⁰Th(0)=0). A contribution from detrital impurities with ²³⁰Th/²³⁴U in secular equilibrium could be precisely subtracted by applying isochron dating of cogenetic phases and recently formed travertine. The resulting precise ²³⁰Th/²³⁴U formation ages were found to be consistent with the geological stratigraphy and were furthermore used to demonstrate the applicability of the next geologically important chronometer in the ²³⁸U-decay series, based on decay of excess ²²⁶Ra normalized to the initial, i.e.²²⁶Ra_ex/²²⁶Ra(0). This system is suitable for dating phases younger than 7000 yr when the correction of a detritus component increasingly limits the precision of the ²³⁰Th/²³⁴U chronometer. Analytical solutions of the coupled ²³⁴U/²³⁰Th/²²⁶Ra radionuclide system predicted that the ²²⁶Ra_ex/²²⁶Ra(0) chronometer is independent of the actual ²³⁰Th activity build up from decay of ²³⁴U, if the systems starts with zero inherited ²³⁰Th(0). The data set confirmed this hypothesis and showed furthermore that the initially incorporated ²²⁶Ra excess must have remained almost uniform in all limestone over a period of at least 7000 yr, i.e. 4–5 half-lives of ²²⁶Ra. This is concluded because (i) the ²²⁶Ra_ex/²²⁶Ra(0) ages agreed well with those derived from ²³⁰Th/²³⁴U, (ii) all data plot within uncertainty on the ²²⁶Ra_ex/²²⁶Ra(0) decay curve and (iii) the atomic Ba/Ca ratio was found to be constant in the travertine material independent of the sample ages. Provided that such boundary conditions hold, ²²⁶Ra_ex/²²⁶Ra(0) should be applicable to materials which are suitable for ²³⁰Th/²³⁴U dating in sedimentology and oceanography, i.e. travertine, corals, phosphorites, etc., and should strongly support ²³⁰Th/²³⁴U for samples that have been formed a few thousand years ago.