893 research outputs found

    Descriptive epidemiology of mass mortality due to Ostreid herpesvirus-1 (OsHV-1) in commercially farmed Pacific oysters (Crassostrea gigas) in the Hawkesbury River estuary, Australia

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    postprintMortality of farmed triploid Pacific oysters (Crassostrea gigas) associated with Ostreid herpesvirus-1 (OsHV-1) was first recorded in Australia in the Georges River/Botany Bay estuary (New South Wales) in late 2010. Two years later, the first sign of possible inter-estuarine spread was observed when commercial triploid Pacific oysters in the Hawkesbury River estuary, located 50 km north of Botany Bay, were affected by mass mortality. The aim of this study was to describe the epidemiological features of the Hawkesbury outbreak via a formal investigation which was conducted in real time and comprised: an assessment of stock levels, past oyster acquisitions and a trace forward investigation to identify stock at greatest risk due to transfers of oysters; passive surveillance of the spread of mortalities in the estuary; active surveillance using PCR to identify the distribution of OsHV-1 infection on farms in the estuary and mortality estimates to identify age and size classes affected; identification of the time of first infection using data from sentinel oysters; and assessment of environmental risk factors. Mortalities were recorded in all age classes but were greater in spat and juveniles than in adults. The incubation period for mass mortality was < 4 days, however subclinical OsHV-1 infection was detected three months prior to the first signs of mortality in the index case (first location affected), which suggests that low viral loads of OsHV-1 are insufficient to induce the disease. While inefficient oyster-to-oyster transmission occurred at two locations, a synchronous infection arising from a common environmental source was required to explain the mass mortalities at the index case (Mullet Creek). Estuarine hydrodynamics then assisted rapid dispersal of viral particles throughout the estuary. Seawater temperatures were consistently above 24°C during the month preceding mass mortalities with variations (± 3°C) being observed over a few days during this period; however this did not necessarily lead to mortality events when the virus was present. There was no evidence of prior movement of potentially infected oysters or farming equipment into the Hawkesbury River estuary to explain the outbreak. Key words: Disease outbreak investigation; Pacific oysters; Ostreid herpesvirus-1; disease transmission; incubation period; water temperature; epidemiologyFunded by the Fisheries Research Development and Corporation (FRDC), The University of Sydney and the Sydney Metropolitan Catchment Management Authorit

    Low-energy magnetic response of the noncentrosymmetric heavy-fermion superconductor CePt3Si studied via inelastic neutron scattering

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    The low-energy magnetic excitations of the noncentrosymmetric heavy-fermion superconductor CePt3Si have been measured with inelastic neutron scattering on a single crystal. Kondo-type spin fluctuations with an anisotropic wave vector dependence are observed in the paramagnetic state. These fluctuations do not survive in the antiferromagnetically ordered state below TN=2.2 K but are replaced by damped spin waves, whose dispersion is much stronger along the c-axis than in other directions. No change is observed in the excitation spectrum or the magnetic order as the system enters the superconducting state below Tc=0.7 K.Comment: Revised version: 8 pages, 7 figure

    Predicting new venture survival and growth: does the fog lift?

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    This paper investigates whether new venture performance becomes easier to predict as the venture ages: does the fog lift? To address this question we primarily draw upon a theoretical framework, initially formulated in a managerial context by Levinthal (Adm Sci Q 36(3):397–420, 1991) that sees new venture sales as a random walk but survival being determined by the stock of available resources (proxied by size). We derive theoretical predictions that are tested with a 10-year cohort of 6579 UK new ventures in the UK. We observe that our ability to predict firm growth deteriorates in the years after entry—in terms of the selection environment, the ‘fog’ seems to thicken. However, our survival predictions improve with time—implying that the ‘fog’ does lift

    Metered Cryosprayℱ: a novel uniform, controlled, and consistent in vivo application of liquid nitrogen cryogenic spray

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    Typically, wood-based composite materials have been developed through empirical studies. In these products, the constituent wood elements have broad spectrums regarding species, size, and anatomical orientation relative to their own dimensions. To define special strength and stiffness properties during a long-term study, two types of corrugated wood composite panels were developed for possible structural utilization. The constitutional elements of the newly developed products included Appalachian hardwood veneer residues (side clippings) and/or rejected low quality, sliced veneer sheets. The proposed primary usage of these veneer-based panels is in applications where the edgewise loading may cause buckling (e.g., web elements of I-joists, shear-wall and composite beam core materials). This paper describes the development of flat and corrugated panels, including furnish preparations and laboratory-scale manufacturing processes as well as the determination of key mechanical properties. According to the results in parallel to grain direction bending, tension and compression strengths exceeded other structural panels’ similar characteristics, while the rigidities were comparable. Based on the research findings, sliced veneer clipping waste can be transformed into structural panels or used as reinforcement elements in beams and sandwich-type products

    Re-evaluation of the diagnosis of porphyria cutanea tarda in Admiral Sir Francis Beaufort

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    OBJECTIVES: Two biographies of Admiral Francis Beaufort (1774-1857) have stated that, aged 20-25 years, he suffered from porphyria cutanea tarda (PCT) that was 'cured' following severe blood loss during a naval skirmish. We have examined the evidence concerning the nature of his skin disease.  DESIGN: Primary records, most notably Beaufort's correspondence with his family, his journals and his father's diaries were sought out and analysed.  SETTING: This case report is discussed in the context of 18th-century naval medicine and concepts and treatment of skin disease.  RESULTS: The description of his lesions, their age of onset, their progression and response to treatment, particularly topical tar and associated features are quite inconsistent with a diagnosis of PCT. His mother, Mary Waller Beaufort (1739-1821), consulted Dr Robert Darwin in 1803 about a painful skin disease affecting her legs. Detailed description of the lesions and a contemporary diagnosis are not available but possible diagnoses include chronic psoriasis and stasis eczema.  CONCLUSIONS: A more tenable diagnosis is that Francis Beaufort had chronic plaque psoriasis remitted by bed rest and convalescence in the sunny Mediterranean climate with cessation of alcohol consumption and improved nutrition as well as topical and oral medications

    Electron-spin-resonance in the doped spin-Peierls compound Cu(1-x)Ni(x)GeO3

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    ESR-study of the Ni-doped spin-Peierls compound CuGeO3 has been performed in the frequency range 9-75 GHz. At low temperatures the g-factor is smaller than the value expected for Cu- and Ni-ions. This anomaly is explained by the formation of magnetic clusters around the Ni-ions within a nonmagnetic spin-Peierls matrix. The transition into the AFM-state detected earlier by neutron scattering for doped samples was studied by means of ESR. For x=0.032 a gap in the magnetic resonance spectrum is found below the Neel temperature and the spectrum is well described by the theory of antiferromagnetic resonance based on the molecular field approximation. For x=0.017 the spectrum below the Neel point remained gapless. The gapless spectrum of the antiferromagnetic state in weekly doped samples is attributed to the small value of the Neel order parameter and to the magnetically disordered spin-Peierls background.Comment: 16 pages, LATEX, 12 figures, submitted to Journal of Physics : Condensed Matte

    Antifungal coatings by caspofungin immobilization onto biomaterials surfaces via a plasma polymer interlayer

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    Published Online: 14 October 2015Not only bacteria but also fungal pathogens, particularly Candida species, can lead to biofilm infections on biomedical devices. By covalent grafting of the antifungal drug caspofungin, which targets the fungal cell wall, onto solid biomaterials, a surface layer can be created that might be able to provide long-term protection against fungal biofilm formation. Plasma polymerization of propionaldehyde (propanal) was used to deposit a thin (∌20 nm) interfacial bonding layer bearing aldehyde surface groups that can react with amine groups of caspofungin to form covalent interfacial bonds for immobilization. Surface analyses by x-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry confirmed the intended grafting and uniformity of the coatings, and durability upon extended washing. Testing for fungal cell attachment and ensuing biofilm formation showed that caspofungin retained activity when covalently bound onto surfaces, disrupting colonizing Candida cells. Mammalian cytotoxicity studies using human primary fibroblasts indicated that the caspofungin-grafted surfaces were selective in eliminating fungal cells while allowing attachment and spreading of mammalian cells. These in vitro data suggest promise for use as antifungal coatings, for example, on catheters, and the use of a plasma polymer interlayer enables facile transfer of the coating method onto a wide variety of biomaterials and biomedical devices.Stefani S. Griesser, Marek Jasieniak, Bryan R. Coad, and Hans J. Griesse

    Beryllium melting and erosion on the upper dump plates in JET during three ITER-like wall campaigns

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    Data on erosion and melting of beryllium upper limiter tiles, so-called dump plates (DP), are presented for all three campaigns in the JET tokamak with the ITER-like wall. High-resolution images of the upper wall of JET show clear signs of flash melting on the ridge of the roofshaped tiles. The melt layers move in the poloidal direction from the inboard to the outboard tile, ending on the last DP tile with an upward going waterfall-like melt structure. Melting was caused mainly by unmitigated plasma disruptions. During three ILW campaigns, around 15% of all 12376 plasma pulses were catalogued as disruptions. Thermocouple data from the upper dump plates tiles showed a reduction in energy delivered by disruptions with fewer extreme events in the third campaign, ILW-3, in comparison to ILW-1 and ILW-2. The total Be erosion assessed via precision weighing of tiles retrieved from JET during shutdowns indicated the increasing mass loss across campaigns of up to 0.6 g from a single tile. The mass of splashed melted Be on the upper walls was also estimated using the high-resolution images of wall components taken after each campaign. The results agree with the total material loss estimated by tile weighing (similar to 130 g). Morphological and structural analysis performed on Be melt layers revealed a multilayer structure of re-solidified material composed mainly of Be and BeO with some heavy metal impurities Ni, Fe, W. IBA analysis performed across the affected tile ridge in both poloidal and toroidal direction revealed a low D concentration, in the range 1-4 x 10(17) D atoms cm(-2)

    One step ATRP initiator immobilization on surfaces leading to gradient-grafted polymer brushes

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    Published: April 30, 2014A method is described that allows potentially any surface to be functionalized covalently with atom transfer radical polymerization (ATRP) initiators derived from ethyl-2-bromoisobutyrl bromide in a single step. In addition, the initiator surface density was variable and tunable such that the thickness of polymer chain grafted from the surface varied greatly on the surfaces providing examples, across the surface of a substrate, of increased chain stretching due to the entropic nature of crowded polymer chains leading toward polymer brushes. An initiator gradient of increasing surface density was deposited by plasma copolymerization of an ATRP initiator (ethyl 2-bromoisobutyrate) and a non-ATRP reactive diluent molecule (ethanol). The deposited plasma polymer retained its chemical ability to surface-initiate polymerization reactions as exemplified by N,N'-dimethyl acrylamide and poly(ethylene glycol) methyl ether methacrylate polymerizations, illustrating linear and bottle-brush-like chains, respectively. A large variation in graft thickness was observed from the low to high chain-density side suggesting that chains were forced to stretch away from the surface interface--a consequence of entropic effects resulting from increased surface crowding. The tert-butyl bromide group of ethyl 2-bromoisobutyrate is a commonly used initiator in ATRP, so a method for covalent linkage to any substrate in a single step desirably simplifies the multistep surface activation procedures currently used.Bryan R. Coad, Katie E. Styan, and Laurence Meaghe
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