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Janette Tourney Bryne T. Ngwenya J.W. Fred Mosselmans Laurence Tetley Gregory L. Cowie 《Chemical Geology》2008,247(1-2):1-15
This study investigated proton adsorption to an extracellular polymeric substance (EPS) producing bacterial strain, Bacillus licheniformis S-86, in order to characterise and quantify the contribution made by EPS to cell surface reactivity. Potentiometric titrations were conducted using both untreated cells and cells from which the EPS layer had been extracted. Surface-complexation modelling indicated the presence of four different functional groups in both untreated and EPS-free cells. These sites are assigned to phosphodiester, (pKa 3.3–3.4), carboxylic (pKa 5.3–5.4), phosphoryl/ (pKa 7.4–7.5) and hydroxyl/amine (pKa 9.9–10.1) type groups. The pKa values for the four groups were very similar for untreated and EPS-free cells, indicating no qualitative difference in composition, but site concentrations in the untreated cells were statistically found to be significantly higher than those in the EPS-free cells for the pKa 3.3–3.4 and pKa 9.9–10.1 sites. Infrared analysis provided supporting evidence that site 2 is carboxylic in nature but did not reveal any difference in IR absorption between the native and EPS-free cells. Dissolved organic carbon (DOC) analysis conducted during this study indicated that DOC release by cells is significant, and that the EPS layer is the major contributor. 相似文献
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Janette Deacon 《Quaternary Research》1978,10(1):84-111
The dating of the Stone Age sequence in southern Africa has been considerably revised over the last decade, and one of the anomalies which has resulted is that the Middle Stone Age, now dated to beyond 30,000 B.P., does not immediately precede the Later Stone Age sensu stricto. The excavation and analysis of occupation horizons dating between the most recent Middle Stone Age assemblages and the Holocene is therefore of particular interest. Nelson Bay Cave, situated on the southern coast of South Africa, contains deposits which partly fill the “gap” between the Middle and Later Stone Ages, and the occupation horizons dating between about 18,000 and 5000 years ago are described in this paper. Changes in the habitat in the vicinity of the site caused by sea-level and vegetation changes coincident with the amelioration of temperatures at the end of the Pleistocene are clearly marked in the faunal remains at the site. Largely correlated with the faunal changes (which includes the introduction of marine resources to the cave at about 12,000 B.P.) are changes in the stone artifact assemblages. Three industries are recognized in the sequence: the Robberg, characterized by microbladelets produced from bladelet cores and a few small scrapers and backed tools; the Albany, characterized by large scrapers and an absence of backed tools; and the Wilton, characterized by a variety of Formal Tools including relatively large numbers of small scrapers and backed tools. These changes in artifact-manufacturing traditions are interpreted as signaling adjustments to changing environmental conditions. An explanation for these adjustments is not sought in a simple cause-and-effect relationship between the environment and the cultural response; artifact changes are seen instead as the result of a twofold process, with the environment acting as an external stimulus to change, and the direction of the artifact change governed by the selection of a range of possibilities offered by the technology of the Later Stone Age sensu lato that was widespread in subequatorial Africa during the last 20,000 years. 相似文献
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Hyperspectral mapping of alteration assemblages within a hydrothermal vug at the Haughton impact structure,Canada 
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下载免费PDF全文 Rebecca N. Greenberger John F. Mustard Gordon R. Osinski Livio L. Tornabene Alexandra J. Pontefract Cassandra L. Marion Roberta L. Flemming Janette H. Wilson Edward A. Cloutis 《Meteoritics & planetary science》2016,51(12):2274-2292
Meteorite impacts on Earth and Mars can generate hydrothermal systems that alter the primary mineralogies of rocks and provide suitable environments for microbial colonization. We investigate a calcite–marcasite‐bearing vug at the ~23 km diameter Haughton impact structure, Devon Island, Nunavut, Canada, using imaging spectroscopy of the outcrop in the field (0.65–1.1 μm) and samples in the laboratory (0.4–2.5 μm), point spectroscopy (0.35–2.5 μm), major element chemistry, and X‐ray diffraction analyses. The mineral assemblages mapped at the outcrop include marcasite; marcasite with minor gypsum and jarosite; fibroferrite and copiapite with minor gypsum and melanterite; gypsum, Fe3+ oxides, and jarosite; and calcite, gypsum, clay, microcline, and quartz. Hyperspectral mapping of alteration phases shows spatial patterns that illuminate changes in alteration conditions and formation of specific mineral phases. Marcasite formed from the postimpact hydrothermal system under reducing conditions, while subsequent weathering oxidized the marcasite at low temperatures and water/rock ratios. The acidic fluids resulting from the oxidation collected on flat‐lying portions of the outcrop, precipitating fibroferrite + copiapite. That assemblage then likely dissolved, and the changing chemistry and pH resulting from interaction with the calcite‐rich host rock formed gypsum‐bearing red coatings. These results have implications for understanding water–rock interactions and habitabilities at this site and on Mars. 相似文献
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Ingo Heinrich Kathrin Weidner Gerhard Helle Heinz Vos Janette Lindesay John C. G. Banks 《Climate Dynamics》2009,33(1):63-73
Australian climate-proxy reconstructions based on tree rings from tropical and subtropical forests have not been achieved so far due to the rarity of species producing anatomically distinct annual growth rings. Our study identifies the Australian Red Cedar (Toona ciliata) as one of the most promising tree species for tree-ring research in Australasia because this species exhibits distinct annual tree rings, a prerequisite for high quality tropical dendroclimatology. Based on these preliminary studies, we were able, for the first time in subtropical and tropical Australia, to develop a statistically robust, precisely dated and annually resolved chronology back to AD1854. We show that the variability in ring widths of T. ciliata is mainly dependent on annual precipitation. The developed proxy data series contains both high- and low-frequency climate signals which can be associated with the El Niño Southern Oscillation (ENSO) and the Interdecadal Pacific Oscillation (IPO). A comparison of different data sets (Brisbane precipitation, tree rings, coral luminescence record from the Great Barrier Reef, ENSO and IPO) revealed non-stationary correlation patterns throughout the twentieth century but little instability between the new tree-ring chronology and Brisbane precipitation. 相似文献
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Summary Breast cancer is a disease whose incidence is increasing in both developed and developing countries, but whose complex aetiology is not dearly understood. Recent research suggests that the environment may be an important factor, hence an investigation into spatial patterning of incidence could inform such research. We use data on incidence in north-west Lancashire and apply some techniques for exploratory spatial analysis, at a variety of spatial scales. Issues relating to the use of incidence data and the interpretation of results are discussed. 相似文献
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Bryne T. Ngwenya J. Fred W. Mosselmans Kirk D. Atkinson Janette Tourney Valerie Olive 《Geochimica et cosmochimica acta》2009,73(11):3134-6719
This study was designed to combine surface complexation modelling of macroscopic adsorption data with X-ray Absorption Spectroscopic (XAS) measurements to identify lanthanide sorption sites on the bacterial surface. The adsorption of selected representatives for light (La and Nd), middle (Sm and Gd) and heavy (Er and Yb) lanthanides was measured as a function of pH, and biomass samples exposed to 4 mg/L lanthanide at pH 3.5 and 6 were analysed using XAS. Surface complexation modelling was consistent with the light lanthanides adsorbing to phosphate sites, whereas the adsorption of middle and heavy lanthanides could be modelled equally well by carboxyl and phosphate sites. The existence of such mixed mode coordination was confirmed by Extended X-ray Absorption Fine Structure (EXAFS) analysis, which was also consistent with adsorption to phosphate sites at low pH, with secondary involvement of carboxyl sites at high adsorption density (high pH). Thus, the two approaches yield broadly consistent information with regard to surface site identity and lanthanide coordination environment. Furthermore, spectroscopic analysis suggests that coordination to phosphate sites is monodentate at the metal/biomass ratios used. Based on the best-fitting pKa site, we infer that the phosphate sites are located on N-acetylglucosamine phosphate, the most likely polymer on gram-negative cells with potential phosphate sites that deprotonate around neutral pH. 相似文献
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Serena Coetzee Martijn Odijk Bastiaan van Loenen Janette Storm Jantien Stoter 《International Journal of Digital Earth》2020,13(3):355-373
ABSTRACTNational spatial data infrastructures are key to achieving the Digital Earth vision. In many cases, national datasets are integrated from local datasets created and maintained by municipalities. Examples are address, building and topographic information. Integration of local datasets may result in a dataset satisfying the needs of users of national datasets, but is it productive for those who create and maintain the data? This article presents a stakeholder analysis of the Basisregistratie Adressen en Gebouwen (BAG), a collection of base information about addresses and buildings in the Netherlands. The information is captured and maintained by municipalities and integrated into a national base register by Kadaster, the Cadastre, Land Registry and Mapping Agency of the Netherlands. The stakeholder analysis identifies organisations involved in the BAG governance framework, describes their interests, rights, ownerships and responsibilities in the BAG, and maps the relationships between them. Analysis results indicate that Kadaster and the municipalities have the highest relative importance in the governance framework of the BAG. The study reveals challenges of setting up a governance framework that maintains the delicate balance between the interests of all stakeholders. The results provide guidance for SDI role players setting up governance frameworks for national or global datasets. 相似文献
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ABSTRACTWhat is successful migration? At a macro-socio-political level migration by individuals may appear to be successful when it has met the objectives of governments, industries and domestic profit makers. However, delving beneath the surface can reveal contradictions and other measures of success at the individual, or micro-level. Within a broader critical historical ethnography, we interviewed 26 post-World War 2 (WW2) British migrants living in South Australia. All interviewees could be viewed as successful at the macro-level, having remained in Australia for many years and having established multi-generational Australian families. Their migration was a ‘success’ when measured against the priorities that were actively promoted by Australian governments in the post-WW2 period. At a micro-level, the migrants involved in this study reported mixed outcomes. While migration did result in self-identified aims of migration including employment, opportunities and adventure, some migrants reported high levels of distress and longing, linked to loss and dislocation from people and places in geographically distant locales. For some, these feelings extended into the present, raising questions over the ‘success’ of their migration experiences at a personal level. We argue that pro-active migration recruitment—such as that undertaken by Australian governments in the post-WW2 period—has the potential to pressure some persons into migration, creating ongoing and unresolvable tensions. Experiences of such disruptions merit further exploration to develop deeper critical understandings of migration success. 相似文献
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Rafael B. de Andrade Jennifer K. Balch Amoreena L. Parsons Dolors Armenteras Rosa Maria Roman-Cuesta Janette Bulkan 《Carbon balance and management》2017,12(1):6