Diatom assemblages from Adirondack lakes (New York,USA) and the development of inference models for retrospective environmental assessment

Detrended canonical coreespondence analysis (DCCA) was used to examine the relationships between diatom species distributions and environmental variables from 62 drainage lakes in the Adirondack region, New York (USA). The contribution of lakewater pH, Al_m (monomeric Al), NH₄, maximum depth, Mg, and DOC (dissolved organic carbon) were statistically significant in explaining the patterns of variation in the diatom species composition. Twenty-three and sixteen diatom taxa were identified as potential indicator species for pH and Al_m, respectively (i.e. a taxon with a strong statistical relationship to the environmental variable of interest, a well defined optimum, and a narrow tolerance to the variable of interest). Using weighted-averaging regression and calibration, predictive models were developed to infer lakewater pH (r ²=0.91), Al_m (r ²=0.83), DOC (dissolved organic carbon) (r ²=0.64), and ANC (acid neutralizing capacity; r ²=0.90). These variables are of key importance in understanding watershed acidification processes. These predictive models have been used in the PIRLA-II (Paleoecological Investigation of Recent Lake Acidification-II) project to answer policy-related questions concerning acidification, recovery, and fisheries loss.     

Extreme variations in strontium initial ratios in ore-related fluids

Magmato-hydrothermal cassiterite-topaz ore at the Carboniferous East Kemptville (EK) greisenhosted tin deposit (Nova Scotia, Canada) is cross-cut by veins containing apatite, triplite, vivianite and fluorite. Initial ⁸⁷Sr/⁸⁶Sr ratios of these minerals have an extreme range (0.7135 to 0.8284). The initial ratios of the host rocks, EK quartz-topaz rock and Davis Lake biotite monzogranite (0.729±0.001, 0.727±0.004), are also high. The adjacent Meguma Group metasedimentary rocks are more typical of crustal material (0.712–0.719 at 330 Ma). Rb and Sr contents of EK fluorite (max.: 13.0, 1420 ppm) and apatite (max.: 88.1, 6660 ppm) are unusually high and variable. Unexpectedly, high Sr contents correlate positively with the high initial ⁸⁷Sr/⁸⁶Sr ratios. Fluorite and phosphate minerals from the first set of post-greisen veins at East Kemptville reflect the unusual chemistry of a high ⁸⁷Sr/⁸⁶Sr fluid present in the deposit after ore formation. The most extreme composition of this fluid was characterized by ⁸⁷Sr/⁸⁶Sr>0.8284, high Rb/Sr, high P, Rb, Cu, Zn and Fe contents, but low abundances of Ca, Pb and Sn with respect to the Davis Lake monzogranite. Such a fluid could have been derived from the greisen fluid and modified by reaction with the overlying Meguma metawacke. A second alternative, which cannot be well constrained at present, is that an extremely radiogenic fluid entered the deposit after ore formation and mixed with the postore fluid. In either case, the modified fluid subsequently mixed with meteoric water and precipitated the minerals with much lower ⁸⁷Sr/⁸⁶Sr ratios and Rb and Sr contents.     

Katrina and Migration: Evacuation and Return by African Americans and Vietnamese Americans in an Eastern New Orleans Suburb

Hurricane Katrina constitutes the most costly natural as well as technology-induced disaster, in terms of both human suffering and financial loss in the history of the United States. Even years later, it continues to profoundly impact the livelihoods and the mental and physical health of those who have experienced evacuation and return and those who have begun lives anew elsewhere. Our study focuses on these geographical processes associated with the Katrina disaster experiences of African Americans and Vietnamese Americans comprising an overwhelming majority (93.4 percent) of residents in a racially mixed pre-Katrina eastern New Orleans neighborhood. We examine the spatial morphology of routes, volumes, and frequencies of evacuees; their return rates and experiences; and rationales and motivations to return or stay. The conceptual framework is based on the disaster migration, place attachment, and social network literature. Both quantitative and qualitative evidence indicates that the evacuation and return experiences of each minority group substantially differed, especially among African American women, and this was strongly influenced by existing social networks.     

Multi‐criteria evaluation and least‐cost path analysis for optimal haulage routing of dump trucks in large scale open‐pit mines

A new raster‐based GIS model that combines multi‐criteria evaluation and least‐cost path analysis was developed to determine the optimal haulage routes of dump trucks in large scale open‐pit mines. The model logic can consider multiple criteria simultaneously (i.e. speed, water body, ore body, curve, visibility, haul road maintenance) and can rate the adverse factor scores of truck movement using fuzzy membership functions. After establishing the weights of five factors by pairwise comparisons, the average adverse score grid can be generated by the weighted linear combination of factor and constraint scores. New software, called Dump Traveler, was implemented to improve the availability of the developed model. An application to the Roto South pit in the Pasir open‐pit coal mine, Indonesia, showed that the software can provide rational solutions to determine the optimal routes on truck haulage operations. Moreover, the layout of available haul roads can be evaluated to consider the trade‐off between road maintenance costs and the potential for traffic jams. Variations of weights for factors were found to be sensitive to the optimal haulage routes determined by least‐cost path analysis. The software provides both optimal routes on truck haulage operations and approximately estimated travel times along the routes, therefore it can support other truck dispatching software that mainly considers scheduling problems.     

H 0 from an orientation-unbiased sample of Sunyaev–Zel'dovich and X-ray clusters

We have observed the Sunyaev–Zel'dovich (SZ) effect in a sample of five moderate-redshift clusters with the Ryle Telescope, and used them in conjunction with X-ray imaging and spectral data from ROSAT and ASCA to measure the Hubble constant. This sample was chosen with a strict X-ray flux limit using both the Bright Cluster Sample and the Northern ROSAT All-Sky Survey (RASS) cluster catalogues to be well above the surface brightness limit of the RASS, and hence to be unbiased with respect to the orientation of the cluster. This controls a major potential systematic effect in the SZ/X-ray method of measuring H ₀. Taking the weighted geometric mean of the results and including the main sources of error, namely the noise in the SZ measurement, the uncertainty in the X-ray temperatures and the unknown ellipticity and substructure of the clusters, we find   H ₀= 59⁺¹⁰₋₉ (random)⁺⁸₋₇(systematic) km s⁻¹ Mpc⁻¹  assuming a standard cold dark matter model with  Ω_M= 1.0, Ω_Λ= 0.0  or   H ₀= 66⁺¹¹₋₁₀ ⁺⁹₋₈ km  s⁻¹ Mpc⁻¹  if  Ω_M= 0.3, Ω_Λ= 0.7  .     

Upper limits on the hot Jupiter fraction in the field of NGC 7789

We describe a method of estimating the abundance of short-period extra-solar planets based on the results of a photometric survey for planetary transits. We apply the method to a 21-night survey with the 2.5-m Isaac Newton Telescope of ∼32 000 stars in a ∼0.5 × 0.5 deg² field including the open cluster NGC 7789. From the colour–magnitude diagram, we estimate the mass and radius of each star by comparison with the cluster main sequence. We search for injected synthetic transits throughout the light curve of each star in order to determine their recovery rate, and thus calculate the expected number of transit detections and false alarms in the survey. We take proper account of the photometric accuracy, time sampling of the observations and criteria (signal-to-noise ratio and number of transits) adopted for transit detection. Assuming that none of the transit candidates found in the survey will be confirmed as real planets, we place conservative upper limits on the abundance of planets as a function of planet radius, orbital period and spectral type.