The effect of the Jessica grounding on Galápagos reef fish communities adjacent to the wreck site

The grounding of the oil tanker Jessica off San Cristóbal Island, Galápagos, resulted in generally elevated rather than depressed densities of fishes adjacent to the wreck site 15 weeks post spill. Species richness of fishes declined along transects out from the wreck; however, patterns were inconsistent for different depth strata, with the most clearly defined decline evident for the intermediate 5-7 m depth stratum. Fish species attracted to the immediate wreck site, most notably the surgeonfish Prionurus laticlavius, the damselfish Microspathodon dorsalis and the angelfish Holacanthus passer, were considered to be responding either to the heterogeneity provided by the wreck structure or elevated densities of macroalgae. The fish community at the wreck site lay outside the range of variation for other sites investigated in the region; however, contrary to predictions of grounding impacts, the fish assemblage immediately adjacent to the wreckage showed greater faunal similarity to reference sites than did fish assemblage at 60-90 m distance from the grounding.     

LOCAL GOVERNMENT,ENTERPRISES AND INDIVIDUALS:ECONOMIC TRANSFORMATION IN THE PEARL RIVER DELTA—A Case Study in Beijiao Township,Shunde City

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A distinct variant of high-titanium mare basalt from the Van Serg core,Apollo 17 landing site

Abstract— A fragment of basalt picked from the drive tube collected at Van Serg crater at the Apollo 17 landing site has a bulk chemistry more primitive than that of other high-titanium mare basalt groups collected at the site. The sample has a fine-grained olivine phyric, subophitic texture that is distinct from that of other high-titanium basalt samples. The grain size and texture suggest that the sample has a composition close to that of a magma. The crystallization sequence, with appearance of oxide minerals later than in other groups, and other petrographic features such as more-calcic plagioclase and early pigeonite rather than augite, are consistent with this sample representing a distinct variant of Apollo 17 high-titanium basalts. It is not related through closed-system igneous processes to any of the other mare basalt groups identified among Apollo 17 samples. Its characters emphasize the complexity of contemporaneous magma processes on the Moon and the heterogeneity of that part of the mantle that was melted.     

THE LAHRAULI UREILITE

A meteorite which fell at Lahrauli, district Basti, U.P. (India) in 1955 has been examined for mineralogical, chemical and cosmogenic characteristics. It contains pigeonite Wo_7.7Fs₁₈ (with Cr₂O₃ = 1.2% and Al₂O₃ = 0.4%), olivine Fo₇₉ (with CaO = 0.3% and Cr₂O₃ = 0.7%) and diamond. The basic similarities of this meteorite to Goalpara, Dyalpur, Havero and Novo Urei indicate that it is a ureilite. Cosmic ray tracks have been measured in the olivine and pyroxene grains. Track density of 2.3 × 10⁶ per cm² in olivines and VVH/VH ratio of 10^?3 is similar to that observed in other meteorites.     

Identification of isotopically primitive interplanetary dust particles: A NanoSIMS isotopic imaging study

We have carried out a comprehensive survey of the isotopic compositions (H, B, C, N, O, and S) of a suite of interplanetary dust particles (IDPs), including both cluster and individual particles. Isotopic imaging with the NanoSIMS shows the presence of numerous discrete hotspots that are strongly enriched in ¹⁵N, up to ∼1300‰. A number of the IDPs also contain larger regions with more modest enrichments in ¹⁵N, leading to average bulk N isotopic compositions that are ¹⁵N-enriched in these IDPs. Although C isotopic compositions are normal in most of the IDPs, two ¹⁵N-rich hotspots have correlated ¹³C anomalies. CN⁻/C⁻ ratios suggest that most of the ¹⁵N-rich hotspots are associated with relatively N-poor carbonaceous matter, although specific carriers have not been determined. H isotopic distributions are similar to those of N: D anomalies are present both as distinct D-rich hotspots and as larger regions with more modest enrichments. Nevertheless, H and N isotopic anomalies are not directly correlated, consistent with results from previous studies. Oxygen isotopic imaging shows the presence of abundant presolar silicate grains in some of the IDPs. The O isotopic compositions of the grains are similar to those of presolar oxide and silicate grains from primitive meteorites. Most of the silicate grains in the IDPs have isotopic ratios consistent with meteoritic Group 1 oxide grains, indicating origins in oxygen-rich red giant and asymptotic giant branch stars, but several presolar silicates exhibit the ¹⁷O and ¹⁸O enrichments of Group 4 oxide grains, whose origin is less well understood. Based on their N isotopic compositions, the IDPs studied here can be divided into two groups. One group is characterized as being “isotopically primitive” and consists of those IDPs that have anomalous bulk N isotopic compositions. These particles typically also contain numerous ¹⁵N-rich hotspots, occasional C isotopic anomalies, and abundant presolar silicate grains. In contrast, the other “isotopically normal” IDPs have normal bulk N isotopic compositions and, although some contain ¹⁵N-rich hotspots, none exhibit C isotopic anomalies and none contain presolar silicate or oxide grains. Thus, isotopically interesting IDPs can be identified and selected on the basis of their bulk N isotopic compositions for further study. However, this distinction does not appear to extend to H isotopic compositions. Although both H and N anomalies are frequently attributed to the survival of molecular cloud material in IDPs and, thus, should be more common in IDPs with anomalous bulk N compositions, D anomalies are as common in normal IDPs as they are in those characterized as isotopically primitive, based on their N isotopes.     

Reducing the bias of multitaper spectrum estimates

The power spectral density of geophysical signals provides information about the processes that generated them. We present a new approach to determine power spectra based on Thomson's multitaper analysis method. Our method reduces the bias due to the curvature of the spectrum close to the frequency of interest. Even while maintaining the same resolution bandwidth, bias is reduced in areas where the power spectrum is significantly quadratic. No additional sidelobe leakage is introduced. In addition, our methodology reliably estimates the derivatives (slope and curvature) of the spectrum. The extra information gleaned from the signal is useful for parameter estimation or to compare different signals.