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Dust, volcanic ash, and the evolution of the South Pacific Gyre through the Cenozoic
Get PDFWe examine the 0–100 Ma paleoceanographic record retained in pelagic clay from the South Pacific Gyre (SPG) by analyzing 47 major, trace, and rare earth elements in bulk sediment in 206 samples from seven sites drilled during Integrated Ocean Drilling Program Expedition 329. We use multivariate statistical analyses (Q-mode factor analysis and multiple linear regression) of the geochemical data to construct a model of bulk pelagic clay composition and mass accumulation rates (MAR) of six end-members, (post-Archean average Australian shale, rhyolite, basalt, Fe-Mn-oxyhydroxides, apatite, and excess Si). Integrating the results with Co-based age models at Sites U1365, U1366, U1369, and U1370, we link changes in MAR of these components to global oceanographic, terrestrial, and climatic transformations through the Cenozoic. Our results track the spatial extent (thousands of kilometers) of dust deposition in the SPG during the aridification of Australia. Dispersed ash is a significant component of the pelagic clay, often comprising >50% by mass, and records episodes of Southern Hemisphere volcanism. Because both are transported by wind, the correlation of dust and ash MAR depends on the site's latitude and suggests meridional shifts in the position of atmospheric circulation cells. The hydrothermal MARs provide evidence for rapid deposition from the Osbourn Trough spreading ridge before it went extinct. Excess Si MARs show that the abrupt increase in siliceous productivity observed at Site U1371 also extended at least as far north as Sites U1369 and U1370, suggesting large-scale reorganizations of oceanic Si distributions ~10–8 Ma in the southern SPGThis is the publisher’s final pdf. The article is copyrighted by the American Geophysical UnionSociety and published by John Wiley & Sons, Inc. It can be found at: http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/%28ISSN%291944-9186
Glacial Atlantic overturning increased by wind stress in climate models
Get PDFPrevious Paleoclimate Model Intercomparison Project (PMIP) simulations of the Last Glacial Maximum (LGM) Atlantic Meridional Overturning Circulation (AMOC) showed dissimilar results on transports and structure. Here we analyze the most recent PMIP3 models, which show a consistent increase (on average by 41 ± 26%) and deepening (663 ± 550 m) of the AMOC with respect to preindustrial simulations, in contrast to some reconstructions from proxy data. Simulations run with the University of Victoria (UVic) ocean circulation model suggest that this is caused by changes in the Northern Hemisphere wind stress, brought about by the presence of ice sheets over North America in the LGM. When forced with LGM wind stress anomalies from PMIP3 models, the UVic model responds with an increase of the northward salt transport in the North Atlantic, which strengthens North Atlantic Deep Water formation and the AMOC. These results improve our understanding of the LGM AMOC's driving forces and suggest that some ocean mechanisms may not be correctly represented in PMIP3 models or some proxy data may need reinterpretation.This is the publisher’s final pdf. The article is copyrighted by American Geophysical Union and published by John Wiley & Sons, Inc. It can be found at: http://agupubs.onlinelibrary.wiley.com/agu/journal/10.1002/%28ISSN%291944-8007
ShengIdentificationOfElaiophylinSkeletalVariantsFromIndonesianStreptomyces.pdf
No full textFour new elaiophylin macrolides (1–4), together with five known elaiophylins (5–9), have been isolated from cultures of the Indonesian soil bacterium Streptomyces sp. ICBB 9297. The new compounds have macrocyclic skeletons distinct from those of the known dimeric elaiophylins in that one or both of the polyketide chains contain(s) an additional pendant methyl group. Further investigations revealed that 1 and 2 were derived from 3 and 4, respectively, during isolation processes. Compounds 1–3 showed comparable antibacterial activity to elaiophylin against Staphylococcus aureus. However, interestingly, only compounds 1 and 3, which contain a pendant methyl group at C-2, showed activity against Mycobacterium smegmatis, whereas compound 2, which has two pendant methyl groups at C-2 and C-2′, and the known elaiophylin analogues (5–7), which lack pendant methyl groups at C-2 and/or C-2′, showed no activity. The production of 3 and 4 in strain ICBB 9297 indicates that one of the acyltransferase (AT) domains in the elaiophylin polyketide synthases (PKSs) can recruit both malonyl-CoA and methylmalonyl-CoA as substrates. Bioinformatic analysis of the AT domains of the elaiophylin PKSs revealed that the ela_AT7 domain contains atypical active site amino acid residues, distinct from those conserved in malonyl-CoA- or methylmalonyl-CoA-specific ATs
Highly Regioselective Nitrile Oxide Dipolar Cycloadditions with ortho-Nitrophenyl Alkynes
Get PDFThe dipolar cylcoadditions of ortho-nitrophenyl alkynes with aryl nitrile oxides has been demonstrated. A range of substituents are tolerated on the alkyne. These reactions proceed with excellent levels of regioselectivity. Subsequent functionalization of the isoxazole scaffold has been demonstrated.This is the author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the Royal Society of Chemistry and can be found at: http://pubs.rsc.org/en/journals/journalissues/ob. Supplementary information is included in the publisher's online version of the article
Body Size and Growth Rate Influence Emigration Timing of Oncorhynchus mykiss
Get PDFJuvenile Oncorhynchus mykiss migrate extensively in freshwater during fall. We used individual tagging to study the spatial origin, influences, and outcomes of fall migration on fish that emigrated from summer rearing tributaries during fall (early-emigrants) and those that did not (late-emigrants) in the South Fork John Day River, Oregon. Fall migration amplified body size differences between early and late-emigrants. There were more early-emigrants from a lower gradient stream than from a higher gradient stream. Early-emigration was positively related to individual summer growth rate and fall body size. Oncorhynchus mykiss dispersed downstream into higher order streams during fall. Early-emigrants shifted to an alternative location and experienced significantly greater winter growth compared to late-emigrants that remained in tributaries. Early-emigrants initiated smolt migration sooner the following spring than late-emigrants. Early and late-emigration from the South Fork John Day was associated with asynchronous emigrant-to-adult survival rates.This is an author's peer-reviewed final manuscript, as accepted by the publisher. The article is copyrighted by the American Fisheries Society and published by Taylor & Francis. It can be found at: http://www.tandfonline.com/toc/utaf20/current#.UtczUhC2zB8
An Abrupt Transition in the Mechanical Response of the Upper Crust to Transpression along the Queen Charlotte Fault
Get PDFThe Queen Charlotte Fault (QCF) is a major strike-slip fault that forms the boundary between the Pacific and North American plates from 51° to 58° N. Near 53.2° N, the angle of oblique convergence predicted by the Mid-Ocean Ridge VELocity (MORVEL) interplate pole of rotation decreases from >15° in the south to <15° in the north. South of 53.2° N, the convergent component of plate motion results in the formation of a 40 km wide terrace on the Pacific plate west of QCF and earthquakes with thrust mechanisms (including the 2012 Haida Gwaii earthquake sequence) are observed. North of 53.2° N, in the primary rupture zone of the M 8.1 strike-slip earthquake of 1949, the linear terrace disappears, and topography of the continental slope west of the QCF is characterized by a complex pattern of ridges and basins that trend obliquely to the primary trace of the QCF. Deformation within the Pacific plate appears to occur primarily through strike-slip faulting with a minor thrust component on secondary synthetic faults. The orientations of these secondary faults, as determined from seismic reflection and bathymetric data, are consistent with the reactivation of faults originally formed as ridge-parallel normal faults and as thrust faults formed parallel to the QCF south of the bend at 53.2° N and subsequently translated to the north. We suggest that an oblique convergence angle of 15° represents a critical threshold separating distinct crustal responses to transpression. This result is consistent with theoretical and analog strain models of transpressive plate boundaries. The sharpness of this transition along the QCF, in contrast to purely continental transform boundaries, may be facilitated by the relatively simple structure of oceanic crust and the presence of pre-existing, optimally oriented faults in the young Pacific plate
Birds of Thornton Creek, Lincoln County, in 1991
Get PDFThis is a continuation of Faxon and Bayer (1991), which summarized Faxon's 1973-1990 observations. In 1991, Faxon made observations during 168 days and recorded 111 species. Monthly frequencies of occurrence are given for each species
Semimonthly bird records through 1992 for Lincoln County, Oregon; Part II: Records sorted by species
Get PDFThis paper supersedes and significantly revises my compilation of 1992. The focus remains on live birds seen on or from land, but special codes are now given for records of species only reported beached or at sea.
Additionally, confirmation codes are now listed for records of some rare species and rare unseasonal records.
Shortcomings to these records are discussed at length.
404 species have been reported for Lincoln County, but when erroneous or hypothetical records are excluded, the total is 349 species, five of which are humanly-introduced species that are not self-sustaining. Many species are rare or uncommon as only 236 species are not Review Species.
Our best records began in 1973, when I started compiling them, and our best yearly totals were during 1982-1992, when 242-253 species/year were recorded.
16 species appear to have arrived within the past 100 years and are now regularly reported, but, because of the paucity of records prior to 1973, it can be difficult to determine which other species have increased or decreased
Waterbird records for West and East Ponds, South Beach Peninsula, Lincoln County
Get PDFIn 1984-1986, Bayer made 171 and 67 waterbird censuses at West Pond and East Pond, respectively. From 1974 through June 1992, Bayer and others also made an additional 138 and 110 observations at West Pond and East Pond, respectively. A total of 48 waterbird taxa were reported at West Pond, and 23 waterbird taxa were discovered at East Pond. At both Ponds, Great Blue Herons and Belted Kingfishers were common, but no waterbirds were observed nesting. The records for each census or observation are given, as well as each taxon's monthly maximal abundance