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The Glen Rose and Walnut formations of southcentral and northcentral Texas comprise shallow-water carbonates deposited during the late Aptian to middle Albian on a carbonate platform. The formations are famous for their rich fossil faunas. Although bryozoans are absent in late Aptian sediments, they are frequently found encrusting bivalve shells from the early to middle Albian parts of these formations. Here, we describe the cyclostome bryozoan fauna, which includes six species; Stomatopora sp., Oncousoecia khirar n. sp., Reptomultisparsa mclemoreae n. sp., Hyporosopora keera n. sp., Mesonopora bernardwalteri n. sp., and ?Unicavea sp. Most cyclostomes are found encrusting rudist shells from Unit 2 of the Lower Member of the Glen Rose Formation and units 3 and 6 of the Upper Member of the Glen Rose Formation.
Gymnolaemate bryozoans are common encrusters on bivalve shells from the early to middle Albian parts of the Glen Rose and Walnut formations of southcentral and northcentral Texas. Here, we report for the first time the presence of seven gymnolaemate bryozoans, all of which represent new species. They include the bioimmured ctenostome Simplicidium jontoddi n. sp., and the cheilostomes Rhammatopora glenrosa n. sp., Iyarispora ikaanakiteeh n. gen. n. sp., Iyarispora chiass n. gen. n. sp., Charixa bispinata n. sp., Charixa sexspinata n. sp., and Charixa emanuelae n. sp. The Glen Rose bryozoans slightly antedate the commencement of an explosive bryozoan radiation and the first appearance of neocheilostomes in the late Albian. Although the diversity of cheilostomes in the Glen Rose and Walnut formations is similar to that of cyclostomes, cheilostomes are more abundant and produced larger colonies. These formations therefore yield the oldest known bryozoan assemblage dominated in terms of biomass by cheilostomes. The genus concept of Charixa is discussed and amended.
Salmonella is a leading cause of bacterial foodborne illness. We report the collaborative investigative efforts of US and Canadian public health officials during the 2013–2014 international outbreak of multiple Salmonella serotype infections linked to sprouted chia seed powder. The investigation included open-ended interviews of ill persons, traceback, product testing, facility inspections, and trace forward. Ninety-four persons infected with outbreak strains from 16 states and four provinces were identified; 21% were hospitalized and none died. Fifty-four (96%) of 56 persons who consumed chia seed powder, reported 13 different brands that traced back to a single Canadian firm, distributed by four US and eight Canadian companies. Laboratory testing yielded outbreak strains from leftover and intact product. Contaminated product was recalled. Although chia seed powder is a novel outbreak vehicle, sprouted seeds are recognized as an important cause of foodborne illness; firms should follow available guidance to reduce the risk of bacterial contamination during sprouting.
Accurate reconstruction of the biomass, structure, and productivity of ancient forests from their fossilized remnants remains an interesting challenge in paleoecology. In well-preserved Tertiary fossil Metasequoia forests of Canada's Arctic, in situ stumps and fragments of stems, treetops, and branches contain substantial information about tree dimensions that can be used to determine tree height, stand biomass, and other characteristics such as canopy depth and structure, and the history of stand development. To validate a method for reconstructing the biomass of the Eocene floodplain Metasequoia forests of Axel Heiberg Island, we measured stump diameters and spacing, and stem, branch, and treetop characteristics in living Metasequoia glyptostroboides and Chamaecyparis thyoides stands in ways that simulate the limited measurements that can be made in well-preserved fossil forests in Canada and probably elsewhere. We used those limited measurements to estimate tree height and volume, branch and foliar dry weights, and tree biomass. The estimates derived from the limited data set are usually within 15% of the estimates derived from the methods currently used in forest ecology for determining those metrics in modern forests. Under appropriate conditions, the biomass of ancient forests can be estimated with reasonable confidence.
The aim of this study was to estimate the amount of childhood hepatitis B virus transmission in children born in the UK, a very low-prevalence country, that is preventable only by universal hepatitis B immunization of infants. Oral fluid specimens were collected from schoolchildren aged 7–11 years in four inner city multi-ethnic areas and tested for the presence of antibody to hepatitis B core antigen (anti-HBc). Those found positive or indeterminate were followed up with testing on serum to confirm their hepatitis B status. The overall prevalence of anti-HBc in children was low [0·26%, 95% confidence interval (CI) 0·14–0·44]. The estimated average annual incidence of hepatitis B was estimated to be 29·26/100 000 children (95% CI 16·00–49·08). The total incidence that is preventable only by a universal infant immunization programme in the UK was estimated to be between 5·00 and 12·49/100 000. The study demonstrates that the extent of horizontal childhood hepatitis B virus transmission is low in children born in the UK and suggests that schools in the UK are an uncommon setting for the transmission of the virus. Targeted hepatitis B testing and immunization of migrants from intermediate- and high-prevalence countries is likely to be a more effective measure to reduce childhood transmission than a universal infant immunization programme.
The Working Group on the Natural Planetary Satellites has been created to promote the development of high-quality ephemerides. The Working Group encourages theoretical studies, coordinated observations, and makes all data available to the users through the NSDC web site (http://www.imcce.fr/nsdc).
The U. S. Department of Energy (DOE) is developing a nuclear waste management system that will accept high-level radioactive waste, transport it, store it, and ultimately emplace it in a deep geologic repository. The key activity now is determining whether Yucca Mountain, Nevada is suitable as a site for the repository. If so, the crucial technological advance will be the demonstration that disposal of nuclear waste will be safe for thousands of years after closure. This paper assesses the impact of regulatory developments, legal developments, and scientific developments on such a demonstration.
Practical methods for directly patterning hydrogenated amorphous silicon (a-Si:H) films have been developed. Direct patterning involves selectively oxidizing the hydrogen passivated aSi:H surface, with the oxide then serving as an etch mask for subsequent hydrogen plasma removal of the unoxidized regions. Photo induced oxidation has been extensively studied using both far field projected patterns and near field scanning optical microscopy (NSOM) for direct write patterning. Examination of the threshold dose for pattern generation for excitation wavelengths from 248 to 633nm provides indirect evidence for involvement of electron-hole recombination in optically induced oxidation. Optical exposure of a-Si:H in vacuum demonstrated that oxygen must be present in the ambient atmosphere during exposure for successful pattern generation. This suggests that oxidation of the surface may not involve removal of hydrogen, but rather breaking of Si-Si backbonds and insertion of oxygen. An additional mechanism for oxide generation was observed whereby pattern generation resulted from simple proximity of an NSOM probe within ∼30nm from the sample surface. The probe dither amplitude was found to greatly affect the line width and height of patterns generated without light. Line widths of approximately 100nm, comparable to the probe diameter, were obtained.
Pulsed laser deposition of Si on dihydride-terminated (l×1) Si (001) at low temperatures yields epitaxial layers, unlike molecular beam epitaxy. Si films were grown by ultrahigh vacuum pulsed laser deposition on the dihydride surface at substrate temperatures from 40 °C to 350 ° C. Epitaxial thickness and interface roughness were measured by high-resolution cross-sectional transmission electron microscopy and found to be comparable to known data for Si films grown by molecular beam epitaxy on monohydride-terminated (2×l) Si (001). Si films were grown at 200 °C by pulsed laser deposition on the dihydride surface at argon background pressures between 10− torr and 10−1 torr. Ion probe time of flight data was collected over the same pressure range. Comparison of the results suggests that loss of epitaxy is correlated with low incident energy. This, in conjunction with information on surface reconstruction obtained from reflection high-energy electron diffraction, suggests that the mechanism enabling epitaxy on the dihydride surface is Si subplantation, a mechanism only possible in growth with an energetic beam.
The formation of isolated silicon nanowires and silicon nanowire networks using aluminum thin film is investigated. The formation mechanism of the network mainly depends on the diffusion of silicon in the aluminum thin film. The silicon stops at the film grain boundaries. The continuous accumulations of silicon at these boundaries give raise to a continuous network of silicon nanowires. Characterization of the nanowires has been done using scanning electron microscopy and energy dispersive x-ray spectroscopy. These results are unique in the fact that the nanowires found are grown in a horizontal fashion instead of the more common vertical direction. Most of the nanowires have a diameter of about 60 nm and a length of over 10 μm.
The Tarantula Survey is an ESO Large Programme which has obtained multi-epoch spectroscopy of over 1,000 massive stars in the 30 Doradus region of the Large Magellanic Cloud. The assembled consortium will exploit these data to address a range of fundamental questions in both stellar and cluster evolution.
697 taxa of planktonic graptolites are recorded, and their stratigraphical ranges are given, through 60 biozones and subzones in the Ordovician and Silurian strata of England, Wales and Scotland, in the first such stratigraphical compilation for Great Britain since the synthesis of Elles & Wood (1901–1918).