916 research outputs found

    Jurassic Redbeds of the Connecticut Valley: (1) Brownstones of the Portland Formation; and (2) Playa-Playa Lake-Oligomictic Lake Model for Parts of the East Berlin, Shuttle Meadow, and Portland Formations

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    Guidebook for field trips in Connecticut and south central Massachusetts: New England Intercollegiate Geological Conference 74th annual meeting, University of Connecticut, Storrs Connecticut , October 2 and 3, 1982: Trip M-

    Biological Markers in Lower Jurassic Synrift Lacustrine Black Shales, Hartford Basin, Connecticut, U.S.A.

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    The East Berlin Formation (Lower Jurassic, Hartford basin, Connecticut, U.S.A.) is distinctive for its six cyclic units of lacustrine black shale and gray mudstone. separated by playa and fluvial redbeds. The black shales arc each about a meter thick and were deposited in subtropical, thermally stratified, oligomictic lakes, the youngest of which (lakes 3 through 6) were large enough to flood most of the basin and attained depths of several tens of meters. The saturate fractions of solvent extracts of organic-rich black shales from each of the six lakes, collected at fresh roadcuts near East Berlin, arc dominated by extended homologous series of n-alkanes, alkylcyclohexanes, and branched chain alkanes. A striking feature of the black shales is the presence of a series of extended tricyclic terpanes from C20 to at least C41. Hopanes arc either not detectable or present only in subordinate quantities relative to the tricyclic terpanes. The samples arc depleted in hopanes in part because of the elevated maturity level (mid to late oil window). Tricyclic terpane concentrations may also have been enhanced by fractionation effects related to oil expulsion out of the black shales. In addition, the original organic matter may have been exceptionally rich in tricyclic terpane precursors, i.e. fossil lipids of prokaryotes present in anoxic, moderately saline, alkaline lakes

    Organic Geochemistry of a Lower Jurassic Synrift Lacustrine Sequence, Hartford Basin, Connecticut, U.S.A.

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    Synrift terrestrial strata of the Lower Jurassic East Berlin Formation (Hartford basin, Connecticut, U.S.A.) record cyclical expansion and contraction of major lakes, six of which were deep enough to develop anoxic bottom waters. We have studied one representative lacustrine sequence in detail, sampling a new roadcut near the village of East Berlin. The section examined is 4 m thick, with a gray siltstone at the base, deposited in shallow water, overlain by an organic-rich black shale (deep water), succeeded in turn by another gray siltstone, deposited as the lake waters gradually receded. The upper gray siltstone is chemically distinct from the lower siltstone, as it contains small amounts of corrensite, analcime and gypsum, reflecting the increasing salinity and alkalinity of the contracting lake. The samples in the center of the black shale unit contain laminae of thermally-altered, yellowish orange-fluorescing, mottled telalginite. The fluorescence properties indicate a peak oil generation maturity level, confirmed by a vitrinite reflectance of 1.13% and a Methylphenanthrene Index of 1.08. The other samples have less organic matter, becoming increasingly lean towards the top and bottom of the sequence. Samples in the middle of the black shale unit are distinguished by the presence of an homologous series of tricyclic terpanes extending from C20 to at least C41 , and by the near absence of hopanes and steranes. Moving upsection into the gray siltstone, the samples contain markedly less extractable organic material (EOM) and the concentration of tricyclic terpanes relative to hopanes steadily decreases. In the uppermost sample, hopanes are the predominant terpanes. Moving downsection from the black shale into the lower gray siltstone, EOM and the ratio of tricyclic terpanes also decrease, except in the lowermost samples, which contain terpane distributions like those of the middle part of the black shale. This likely is migrated material, because bitumen fills microfractures and extensive megafractures. The lack of hopanes and steranes in the black shales cannot simply be a maturation effect, as these biomarkers appear in the adjacent beds. Instead, the unusual terpane distributions may indicate a changing depositional environment, documenting the geochemical evolution of the lake. Or, more likely, they may result from fractionation during expulsion of petroleum from these mature source rocks

    Coronary Spasm: Ethnic and Sex Differences

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    Coronary spasm (CS), which may occur at the epicardial (focal or diffuse spasm) and/or microvascular (microvascular spasm) level, is a well-established cause of myocardial ischaemia, in particular in patients with anginal chest pain despite unobstructed coronary arteries. The diagnosis of CS can be confirmed during coronary angiography by an additional provocation test with vasoactive substances such as acetylcholine. Due to partially inconsistent data from large clinical studies, especially between Asian and white CS patients, ethnic differences concerning the prevalence and angiographic patterns of CS seem to exist. Furthermore, several studies in patients with coronary vasomotor disorders pointed towards differences among male and female CS patients. This article gives an overview of ethnic- and sex-related differences in patients with CS

    Predictive response-relevant clustering of expression data provides insights into disease processes

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    This article describes and illustrates a novel method of microarray data analysis that couples model-based clustering and binary classification to form clusters of ;response-relevant' genes; that is, genes that are informative when discriminating between the different values of the response. Predictions are subsequently made using an appropriate statistical summary of each gene cluster, which we call the ;meta-covariate' representation of the cluster, in a probit regression model. We first illustrate this method by analysing a leukaemia expression dataset, before focusing closely on the meta-covariate analysis of a renal gene expression dataset in a rat model of salt-sensitive hypertension. We explore the biological insights provided by our analysis of these data. In particular, we identify a highly influential cluster of 13 genes-including three transcription factors (Arntl, Bhlhe41 and Npas2)-that is implicated as being protective against hypertension in response to increased dietary sodium. Functional and canonical pathway analysis of this cluster using Ingenuity Pathway Analysis implicated transcriptional activation and circadian rhythm signalling, respectively. Although we illustrate our method using only expression data, the method is applicable to any high-dimensional datasets

    The Peculiar SN 2005hk: Do Some Type Ia Supernovae Explode as Deflagrations?

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    We present extensive u'g'r'i'BVRIYJHKs photometry and optical spectroscopy of SN 2005hk. These data reveal that SN 2005hk was nearly identical in its observed properties to SN 2002cx, which has been called ``the most peculiar known type Ia supernova.'' Both supernovae exhibited high ionization SN 1991T-like pre-maximum spectra, yet low peak luminosities like SN 1991bg. The spectra reveal that SN 2005hk, like SN 2002cx, exhibited expansion velocities that were roughly half those of typical type Ia supernovae. The R and I light curves of both supernovae were also peculiar in not displaying the secondary maximum observed for normal type Ia supernovae. Our YJH photometry of SN 2005hk reveals the same peculiarity in the near-infrared. By combining our optical and near-infrared photometry of SN 2005hk with published ultraviolet light curves obtained with the Swift satellite, we are able to construct a bolometric light curve from ~10 days before to ~60 days after B maximum. The shape and unusually low peak luminosity of this light curve, plus the low expansion velocities and absence of a secondary maximum at red and near-infrared wavelengths, are all in reasonable agreement with model calculations of a 3D deflagration which produces ~0.25 M_sun of 56Ni.Comment: Accepted by PASP, to appear in April 2007 issue, 63 pages, 16 figures, 11 table

    Bacterial Adaptation to Venom in Snakes and Arachnida

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    Animal venoms are considered sterile sources of antimicrobial compounds with strong membrane-disrupting activity against multidrug-resistant bacteria. However, venomous bite wound infections are common in developing nations. Investigating the envenomation organ and venom microbiota of five snake and two spider species, we observed venom community structures that depend on the host venomous animal species and evidenced recovery of viable microorganisms from black-necked spitting cobra (Naja nigricollis) and Indian ornamental tarantula (Poecilotheria regalis) venoms. Among the bacterial isolates recovered from , we identified two venom-resistant, novel sequence types of Enterococcus faecalis whose genomes feature 16 virulence genes, indicating infectious potential, and 45 additional genes, nearly half of which improve bacterial membrane integrity. Our findings challenge the dogma of venom sterility and indicate an increased primary infection risk in the clinical management of venomous animal bite wounds. Notwithstanding their 3 to 5% mortality, the 2.7 million envenomation-related injuries occurring annually-predominantly across Africa, Asia, and Latin America-are also major causes of morbidity. Venom toxin-damaged tissue will develop infections in some 75% of envenomation victims, with E. faecalis being a common culprit of disease; however, such infections are generally considered to be independent of envenomation. Here, we provide evidence on venom microbiota across snakes and arachnida and report on the convergent evolution mechanisms that can facilitate adaptation to black-necked cobra venom in two independent E. faecalis strains, easily misidentified by biochemical diagnostics. Therefore, since inoculation with viable and virulence gene-harboring bacteria can occur during envenomation, acute infection risk management following envenomation is warranted, particularly for immunocompromised and malnourished victims in resource-limited settings. These results shed light on how bacteria evolve for survival in one of the most extreme environments on Earth and how venomous bites must be also treated for infections

    Preliminary Comparison of Two-Way Satellite Time and Frequency Transfer and GPS Common-View Time Transfer During the INTELSAT Field Trial

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    For a decade and a half Global Positioning System (GPS) common-view time transfer has greatly served the needs of primary timing laboratories for regular intercomparisons of remote atomic clocks. However, GPS as a one-way technique has natural limits and may not meet all challenges of the comparison of the coming new generation of atomic clocks. Two-way satellite time and frequency transfer (TWSTFT) is a promising technique which may successfully complement GPS. For two years, regular TWSTFT's have been performed between eight laboratories situated in both Europe and North America, using INTELSAT satellites. This has enabled an extensive direct comparison to be made between these two high performance time transfer methods. The performance of the TWSTFT and GPS common view methods are compared over a number of time-transfer links. These links use a variety of time-transfer hardware and atomic clocks and have baselines of substantially different lengths. The relative merits of the two time-transfer systems are discussed
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