2,565 research outputs found

    Efficient solution of three-body quantum collision problems: Application to the Temkin-Poet model

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    The solution for the three-body quantum oscillation problems were developed using a variable-spacing finite-difference algorithm. This method was applied to the Temkin-Poet electron-hydrogen model collision problem. The calculation were performed for electrons colliding with hydrogen atoms in the Temkin-Poet model for the impact energies ranging from 17.6 to 150 eV

    Mobihealth: mobile health services based on body area networks

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    In this chapter we describe the concept of MobiHealth and the approach developed during the MobiHealth project (MobiHealth, 2002). The concept was to bring together the technologies of Body Area Networks (BANs), wireless broadband communications and wearable medical devices to provide mobile healthcare services for patients and health professionals. These technologies enable remote patient care services such as management of chronic conditions and detection of health emergencies. Because the patient is free to move anywhere whilst wearing the MobiHealth BAN, patient mobility is maximised. The vision is that patients can enjoy enhanced freedom and quality of life through avoidance or reduction of hospital stays. For the health services it means that pressure on overstretched hospital services can be alleviated

    Microbial use of low molecular weight DOM in filtered and unfiltered freshwater:Role of ultra-small microorganisms and implications for water quality monitoring

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    Dissolved organic matter (DOM) plays a central role in regulating productivity and nutrient cycling in freshwaters. It is therefore vital that we can representatively sample and preserve DOM in freshwaters for subsequent analysis. Here we investigated the effect of filtration, temperature (5 and 25 °C) and acidification (HCl) on the persistence of low molecular weight (MW) dissolved organic carbon (DOC), nitrogen (DON) and orthophosphate in oligotrophic and eutrophic freshwater environments. Our results showed the rapid loss of isotopically-labelled glucose and amino acids from both filtered (0.22 and 0.45 Όm) and unfiltered waters. We ascribe this substrate depletion in filtered samples to the activity of ultra-small (< 0.45 Όm) microorganisms (bacteria and archaea) present in the water. As expected, the rate of C, N and P loss was much greater at higher temperatures and was repressed by the addition of HCl. Based on our results and an evaluation of the protocols used in recently published studies, we conclude that current techniques used to sample water for low MW DOM characterisation are frequently inadequate and lack proper validation. In contrast to the high degree of analytical precision and rigorous statistical analysis of most studies, we argue that insufficient consideration is still given to the presence of ultra-small microorganisms and potential changes that can occur in the low MW fraction of DOM prior to analysis

    Integrated side-scan, sub-bottom profiler and seismic signatures of methane seepage from Omakere Ridge on New Zealand’s Hikurangi margin

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    Omakere Ridge is one of a series of prominent northeast-southwest orientated anticlinal ridges associated with major thrust faults on New Zealand’s Hikurangi margin. The Hikurangi margin is an extensive gas hydrate province and recent marine surveys have confirmed that the mid-slope Omakere Ridge is a zone of methane-rich seabed seepage. Acoustic flares initially observed in the area by fishermen, were imaged in the water column at Omakere Ridge during a 2006 RV Tangaroa survey (TAN06-07). Anomalous methane concentrations (up to 165 nM) were detected by a methane sensor (METS) attached to a conductivity-temperature-depth-optical backscatter device (CTD) on TAN06-07 and a 2007 RV Sonne survey (SO-191). Six seep sites have been identified at the southern end of Omakere Ridge, where it bifurcates into two parallel ridgelines. All sites are located towards the crests of the two ridgelines in approximately 1150 m water depth. The seabed seeps were identified acoustically with an EdgeTech Deep-Tow side-scan operating at 75 kHz, and are shown as high backscatter intensity areas on processed side-scan data, which are interpreted to be methane derived authigenic carbonate hardgrounds. Acoustic shadows behind hardgrounds in the side-scan far range suggest the seabed features have moderate relief. Sub-bottom profiles acquired with an EdgeTech Deep-Tow chirper system, operating at 2-10 kHz, identified numerous signatures of shallow gas in the near subsurface. These signatures include zones of acoustic turbidity and gas blanking, interpreted to mark shallow gas fronts. The evidence for shallow gas in the subsurface from the sub-bottom profiler displays a marked spatial correlation with seabed expressions of seepage. The seepage sites also correspond to potential gas indicators in multi-channel seismic data, such as interpreted amplitude anomalies. Enigmatic subsurface features in the subbottom profiler data, such as potential amplitude anomalies and gas blanking, which are below the depression that bifurcates the ridge and are not associated with surface expressions of seepage, may represent lithological and topographic features or may be a component of the gas migration pathway which feeds the seeps on the ridge crest. Underwater video and still camera images show seabed seepage sites of high backscatter intensity represent widespread authigenic carbonate concretions and chemoherms associated with biological assemblages including siboglinid tube worms, vesicomyid clams, bathymodiolin mussels, and bacterial mats. A high backscatter intensity site of similar acoustic character to, and directly adjacent to, seep sites on the southern part of the ridge does not contain seep fauna and is interpreted to be a cold-water reef. While this feature may represent a relict seep, this finding highlights the fact that present day seepage cannot be identified with acoustic techniques alone

    DNA-decorated carbon nanotube-based FETs as ultrasensitive chemical sensors: Discrimination of homologues, structural isomers, and optical isomers

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    We have explored the abilities of all-electronic DNA-carbon nanotube (DNA-NT) vapor sensors to discriminate very similar classes ofmolecules.We screened hundreds ofDNA-NT devices against a panel of compounds chosen because of their similarities. We demonstrated that DNA-NT vapor sensors readily discriminate between series of chemical homologues that differ by single methyl groups. DNA-NT devices also discriminate among structural isomers and optical isomers, a trait common in biological olfactory systems, but only recently demonstrated for electronic FET based chemical sensors

    Determining patterns in the composition of dissolved organic matter in fresh waters according to land use and management

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    In fresh waters, the origins of dissolved organic matter (DOM) have been found to exert a fundamental control on its reactivity, and ultimately, its ecosystem functional role. A detailed understanding of landscape scale factors that control the export of DOM to aquatic ecosystems is, therefore, pivotal if the effects of DOM flux to fresh waters are to be fully understood. In this study we present data from a national sampling campaign across the United Kingdom in which we explore the variability in DOM composition in three broad landscape types defined by similar precipitation, geology, land use and management, hydrology, and nutrient enrichment status. We characterised samples from fifty-one sites, grouping them into one of three major underlying classifications: circumneutral streams underlain by clay and mudstone (referred to as ‘clay’), alkaline streams underlain by Cretaceous Chalk or by Carboniferous or Jurassic Limestone (‘limestone’), and acidic streams in peatland catchments underlain by a range of low permeability lithologies (‘peat’). DOM composition was assessed through organic matter stoichiometry (organic carbon: organic nitrogen; organic carbon: organic phosphorus; C/N(P)DOM) and metrics derived from ultra-violet (UV)/visible spectroscopic analysis of DOM such as specific UV absorption (a254 nm; SUVA254). We found similar SUVA254, C/NDOM and DOM/a254 relationships within classifications, demonstrating that despite a large degree of heterogeneity within environments, catchments with shared environmental character and anthropogenic disturbance export DOM with a similar composition and character. Improving our understanding of DOM characterisation is important to help predict shifts in stream ecosystem function, and ecological responses to enrichment or mitigation efforts and how these may result in species composition shifts and biodiversity loss in freshwater ecosystems
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