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Timelines of the "free-particle" and "fixed-particle" models of stone-formation: theoretical and experimental investigations
Get PDFTwo major theories on renal stone formation will be reviewed, the “free-particle” and “fixed-particle” mechanisms. These theories combine data on intrinsic factors (inborn metabolic errors), extrinsic factors (diet), renal cell responses and the physico-chemistry and biochemistry of urine into mechanisms of stone formation. This paper describes the specific role of time in both mechanisms. The timeline of crystal- and stone formation was deducted from literature data and was measured for two stones using radioisotope decay analysis. The stones of similar size and composition showed, respectively, a timeline of a few years and a development that took decades. In combination with data on stone architecture and patient characteristics these timelines are explained using the free-particle and fixed-particle mechanisms. Consideration of the timeline of stone formation has clinical implications. We conclude that the fixed-particle mechanism can be a slow process where decades pass between the first formation of a precipitate in the renal interstitium and the clinical presentation of the stone. Added to the fact that the mechanism of this initial precipitation is still ill defined, the conditions that started fixed-particle stone formation in an individual patient can be obscure. Blood and urine analysis in such patients does not necessarily reveal the individual’s risk for recurrence as lifestyle may have changed over time. This is in fact what defines the so-called idiopathic stoneformers. For these patients, prevention of outgrowth of previously formed precipitates, papillary plaques, may be more relevant than prevention of new plaque formation. In contrast, a patient who has formed a stone in a relatively short time through the free-particle mechanism is more likely to show abnormal values in blood and urine that explain the starting event of stone formation. In these patients, measurement of such values provides useful information to guide preventive measures. © 2016, The Author(s)
Radiocarbon age constraints for a Pleistocene–Holocene transition rock art style: The Northern Running Figures of the East Alligator River region, western Arnhem Land, Australia
No full textIn this article we present nine radiocarbon age determinations producing a minimum age and a minimum age range for a regionally distinct rock art style known as the Northern Running Figures from Red Lily Lagoon, western Arnhem Land Australia. These radiocarbon determinations provide age constraints for both Pleistocene and early Holocene rock art in western Arnhem Land. The radiocarbon age determinations are produced from extracting calcium oxalate contained within mineral crusts associated with the rock art. Significantly this study employs a novel separation technique, designed to effectively isolate the oxalate compounds from the mineral crust sample using chemical pre-treatment, and demonstrates significant time offsets between radiocarbon age determinations for the calcium oxalates and other carbon inclusions contained within mineral crusts.© 2016, Elsevier Ltd
Holocene record of long- and short-term environmental changes in a coastal wetland, New Zealand.
No full textLong- and short-term environmental changes in Moawhitu Wetland, D’Urville Island, New Zealand, were reconstructed using a multi-proxy approach. A local Māori oral tradition describes a giant wave destroying a
community in the 15th century, however, except for a study in 1962, little geological work had been carried out to investigate this event or to establish a record of paleoenvironmental changes in the area. Three sedimentary sequences sampled across the wetland over a distance of 2 km were analysed for grain size, organic content,
geochemistry (ICP-AES, ICP-MS and ITRAX), diatom assemblages and mineralogy, while the chronology was obtained
using 14C and 210Pb dating, corroborated with pollen biostratigraphy.
Results of this study indicate that the sand dune barrier at Moawhitu formed ca 7400–7200 years BP at the time when sea levels stabilised following the last deglaciation. This led to the establishment of a freshwater lake in the southern area, which gradually infilled to form a wetland with subsequent peat accumulation. In the central part of
Moawhitu, lake and peatland sequences alternated. By ca 1200 years BP, with the exception of the existing lagoon at
the northern end of the study area, conditions favourable to peatland formation were found throughout Moawhitu
and continued into the 20th century when they were disrupted by drainage activities.
Evidence for a tsunami 3300–3000 years BP was found in the northern part of Moawhitu wetland (based on
sedimentological, geochemical and microfossil data). Geochemical signatures and marine diatom assemblages
provide a record of tsunami inundation in the middle part of the wetland, beyond the extent of any sand deposit. No
geochemical evidence could be found at the site further inland in the southern part of the wetland. Evidence for a
contemporaneous tsunami deposit has also been reported ~100 km N, on Kapiti Island, on the west coast of the
North Island of New Zealand, and the event has been attributed to a local fault rupture. So far, no sedimentological,
geochemical or micropaleontological evidence for a giant wave in the 15th century has been found in the
sedimentary sequence of Moawhitu wetland. However, pebble layers extending across large areas of the dunes have
been recorded and these have also been associated with Maori occupation, thus inferring that the sand dune may
indeed have acted as an effect barrier to any 15th century tsunami. This study indicates that more than one tsunami has affected Moawhitu, and further work is planned to document environmental changes in the area. Copyright Geological Society of Australia Inc
Pacific Subduction zone palaeotsunamis – joining up the dots?
No full textIn 2011 we pointed out that the study of palaeotsunamis in the Pacific was in its infancy. This is still the case, but it is hardly surprising given that there are 1,000 kms of circum-Pacific coastline that are largely unstudied and even several countries where palaeotsunami research is yet to be carried out. Within the Pacific Basin there are some 20,000 Pacific Islands, all of which have the potential to add to our understanding of the magnitude, frequency and source of past tsunamis. This is a huge jigsaw puzzle and in reality we have only got a few of the pieces, but even so a combination of Pacific Island and circum-Pacific country data is starting to provide clues about past events.
We discuss some of our findings from the SW Pacific region with respect to palaeotsunamis generated by subduction zone events and look at not only the geological evidence, but also a wider multi-proxy toolkit that includes both archaeology and anthropology. In other words, we may argue about the dating or geological validity of a specific event on a specific island, but the bigger story being told of widespread, contemporaneous societal change provides an additional line of evidence that we ignore at our peril. This is all well and good, but what about the rest of the Pacific? Where to from here?
It has long been recognised that the Hawaiian Islands are exposed to tsunamis from almost every large subduction zone in the Pacific - Alaska (1946), Kamchatka (1952), Chile (1960) and Japan (2011) to name but a few. Furthermore, it has also been shown that the geological evidence for such events can be found in the islands. Recently, some researchers have suggested that the well-known Makauwahi Cave deposit on Kauai is the “missing link” of evidence for a giant Aleutian subduction zone event in the 16th/17th century. In the absence of more physical evidence this may be drawing something of a long bow, BUT the key take home message here is that different events from different sources affect different coasts of different Hawaiian Islands differently. Historical events alone indicate that the islands can act like a giant tsunami “rose diagram“, so why are we not looking harder at these islands and others within the Pacific to vastly improve our understanding of palaeotsunamis in the Pacific? For example, what about the now famous 1700 AD Cascadia and 869 AD Jogan events? © Copyright 2014 The Geological Society of America (GSA)
Cosmogenic 10Be ages from the Meirs and Garwood Valleys, Denton Hills, West Antarctica, suggest an absence in LGM Ice Sheet expansion
No full textIt has been hypothesised that during interglacials, thinning of the Ross Ice Shelf allowed a more open water environment with increased local precipitation. This resulted in outlet glaciers, which drain the Transantarctic Mountains and fed by the East Antarctic Ice Sheet, advancing during moist warmer periods, apparently out of phase with colder arid dry periods. Significantly the ice core record during these warm periods also shows increased accumulation continent wide The geomorphology of the Denton Hills in the Royal Society Range, West Antarctica, is a result of Miocene fluvial incision reworked by subsequent glacial advances throughout the Quaternary. The Garwood and Miers glacial valleys drain ice across the Denton Hills into the Shelf, and should thus show maximum extent during interstadials. To understand the chronology of late Quaternary glaciations, 15 granitic boulders from terminal moraines were sampled for 10Be and 26Al cosmogenic dating. Obtaining reliable exposure ages of erratics within moraines that represent timing of deposition (i.e. glacial advances) is problematic in polar regions, where glacial activity is principally controlled by ice sheet dynamics. Recycling of previously exposed debris, uncertainty in provenance of glacially transported boulders and a lack of a post-depositional hydrologic process to remove previously exposed material from a valley system, leads to ambiguities in multiple exposure ages from a single coeval glacial landform. More importantly, cold-based ice advance can leave a landform unmodified resulting in young erratics deposited on bedrock that shows weathering and/or inconsistent age-altitude relationships. Primarily, inheritance becomes a difficulty in qualifying exposure ages from polar regions. Preliminary results from the Garwood and Miers Valleys indicate that glaciers in the Denton Hills had begun to retreat from their last maximum positions no later than 23-37 ka, and thus the local last glacial maximum occurred prior to the Antarctic LGM (18-22 ka). No evidence based on cosmogenic ages for post-LGM or Holocene advances were found. These results support an extensive exposure age data set from the nearby Darwin-Hatherton Glacier system that indicates an absence of EAIS expansion across the Transantarctic Mnts during the global LGM period
Constraining hydrochemical pathways in a small internally draining basin (Lake George Basin, NSW) using isotopes of the water molecule
No full textLake George, located in the Southern Tablelands of New South Wales, is a shallow, intermittent lake with highly variable salinity and water levels. The lake is the focus of drainage for a small internally draining basin containing six sub-catchments. It is currently believed that the lake’s water level is primarily affected by the short- and long-term variations in precipitation, runoff and evaporation. Contributions from the regional groundwater are thought to be low because of the thick (~40 m) clay unit that underlies the modern extent of the lake. As a result, the lake’s hydrograph, which is one of the oldest in the world, has recorded droughts and wet periods of southeastern Australia over the last 200 years. In this project, water chemistry and physical hydrometeorological data are being collected to determine hydrochemical pathways and recharge rates. This will provide much needed information regarding the sustainability of the Bungendore town water supply as well as identify potential risks to water quality in the basin. This project also forms one part of a much larger project to investigate the landscape and human evolution of the Lake George Basin. Four precipitation samplers have been installed at three sites around the catchment – one to the north of the lake at Winderadeen homestead, one to the south of the lake at Bungendore’s post office, and two at a rocky outcrop (‘Rocky Point’) on the eastern shore of Lake George. Three precipitation samplers (one located at each site) are used to collect monthly composite precipitation samples for deuterium and oxygen-18 analysis, and elemental concentrations. The additional sampler located at Rocky Point is used to collect precipitation for tritium analysis. In months when precipitation is too low to collect sufficient sample volume (~1 L), monthly samples are combined. These data are being combined with deuterium, oxygen-18, tritium and elemental compositions, as well as hydrometeorological measurements, of surface water, groundwater and atmospheric moisture from around the basin to help constrain recharge areas and rates, primary hydrochemical pathways and controls on water quality. Deuterium and oxygen-18 compositions indicate that groundwater is primarily recharged by winter rainfall. Despite variable precipitation compositions throughout the year, creek water maintains a winter rainfall/groundwater isotopic year-round, which may indicate that the creeks of the basin are fed by aquifers and through-flow rather than fresh precipitation. This is also supported by low tritium activity. A local evaporation line has also been determined for Lake George during the period July 2013 (after high rainfall) to November (when the lake dried out due high evaporation rates
The effect of gamma-irradiation conditions on the immunogenicity of whole-inactivated Influenza A virus vaccine
No full textGamma-irradiation, particularly an irradiation dose of 50 kGy, has been utilised widely to sterilise highly pathogenic agents such as Ebola, Marburg Virus, and Avian Influenza H5N1. We have reported previously that intranasal vaccination with a gamma-irradiated Influenza A virus vaccine (γ-Flu) results in cross-protective immunity. Considering the possible inclusion of highly pathogenic Influenza strains in future clinical development of γ-Flu, an irradiation dose of 50 kGy may be used to enhance vaccine safety beyond the internationally accepted Sterility Assurance Level (SAL). Thus, we investigated the effect of irradiation conditions, including high irradiation doses, on the immunogenicity of γ-Flu. Our data confirm that irradiation at low temperatures (using dry-ice) is associated with reduced damage to viral structure compared with irradiation at room temperature. In addition, a single intranasal vaccination with γ-Flu irradiated on dry-ice with either 25 or 50 kGy induced seroconversion and provided complete protection against lethal Influenza A challenge. Considering that low temperature is expected to reduce the protein damage associated with exposure to high irradiation doses, we titrated the vaccine dose to verify the efficacy of 50 kGy γ-Flu. Our data demonstrate that exposure to 50 kGy on dry-ice is associated with limited effect on vaccine immunogenicity, apparent only when using very low vaccine doses. Overall, our data highlight the immunogenicity of influenza virus irradiated at 50 kGy for induction of high titre antibody and cytotoxic T-cell responses. This suggests these conditions are suitable for development of γ-Flu vaccines based on highly pathogenic Influenza A viruses. © 2017 Elsevier Ltd
Reconsidering precolumbian human colonization in the Galapagos Islands, Republic of Ecuador
No full textFifty years ago, Heyerdahl and Skjølsvold (1956, 1990) collected material from five archaeological sites in the Galápagos Islands. They retained earthenwares of possible precolumbian origin and discarded ceramic, metal, and glass artifacts postdating the arrival of the Spanish in A.D. 1535. Consequently, they argued that each site was formed as the results of a series of discard events from unrelated short-term occupations extending from the precolumbian to the historical era, and that the earthenwares represented occasional visits by fishermen from precolumbian Peru and Ecuador. In 2005, we re-excavated the sites and collected all the excavated materials. Our results show that each class of material, irrespective of age or origin, was distributed spatially and stratigraphically in the same pattern, contradicting the former assumption of multiple, unrelated occupations. We reject the palimpsest model in favor of the null hypothesis of single-phase site occupation. Analysis of putatively precolumbian pottery using optically-stimulated luminescence dating indicates that it is mostly of historical age. Radiocarbon dating confirms that the archaeological sites are younger than the sixteenth century. Research on sedimentary cores shows probable anthropogenic impacts as restricted to the last 500 years. We conclude that there was no human occupation in the Galápagos Islands until the historical era. Spanish Hace cincuenta años Heyerdahl y Skjølsvold (1956, 1990) recuperaron material arqueológico en cinco sitios de las Islas Galápagos. Estos investigadores se enfocaron en los fragmentos de cerámica de supuesto origen precolombino y descartaron los artefactos posteriores a la llegada de los europeos, en 1535 d.C. Asimismo, sostuvieron que estos sitios eran “palimpsestos”, resultado de la acumulación de materiales culturales durante distintas etapas de ocupación, desde el período prehistórico hasta tiempos modernos. Según ellos, los tiestos de barro sin esmalte vidrioso representaban visitas ocasionales de pescadores desde las costas del Perú y Ecuador. A partir del año 2005 hemos llevado a cabo nuevas investigaciones enfocadas en la reexcavación de los mismos cinco sitios, pero nuestro análisis incluyó a todo el material en conjunto y concluimos que todos los objetos, sin importar su edad y lugar de origen, se distribuyeron según los mismos patrones estratigráficos y espaciales. De esta forma, rechazamos el modelo del palimpsesto y proponemos que hubo una sola fase de ocupación en estos sitios. Gracias a estudios como los análisis por OSL y radiocarbono, hemos determinado que la cerámica de supuesto origen precolombino fue fabricada en el período histórico y que los sitios arqueológicos no fueron ocupados antes del siglo dieciséis. La investigación paleo-ecológica se basó en el análisis de muestras sedimentarias de las Islas y ha demostrado que los probables impactos antropogénicos ocurrieron sólo en los últimos 500 años. Por todas estas razones, concluimos que no hubo ocupación humana en las Galápagos antes de la época histórica. : © Society for American Archaeology 201
Geochemical signatures and source material of marine incursion deposits.
No full textThe geochemical signature of the Tohoku-oki tsunami deposit and underlying soil was assessed two months, five months and seven months after the 11 March 2011 tsunami inundated the Sendai Plain. The extent of the recognisable sand deposit was traced up to 2.9 km inland while a mud deposit was found up to 4.65 km inland, representing 60% and nearly 95% of the maximum tsunami inundation, respectively. The limit of tsunami inundation was identified 4.85 km from the shore using geochemical marine markers (S and Cl) two months after the tsunami, in the absence of any sedimentological evidence. Concentrations of other geochemical markers (K, Ca, Sr) indicative of the marine incursion and associated minerals were found to decrease landward. δ13C and δ15N and C/N ratios suggested a mixture of terrestrial and marine organic sources in the sediment, while δ34S of sulphate reflected the marine source of water soluble salts. The chemical composition of the 869 AD Jogan tsunami sand deposit was characterised by high Sr and Rb concentrations and was comparable to that of the Tohoku-oki tsunami deposit, suggesting that the sources of sediment may be similar. Marked decreases in S and Cl with time indicated that rainfall resulted in the leaching of salts from the sandy sediments. However, both S and Cl markers as well as Sr were still well preserved in the muddy sediments and underlying soil beyond the limit of the recognisable sand deposit seven months after the tsunami. This suggests that geochemical indicators may well be useful in identifying the extent of historical and palaeotsunamis by determining the marine origin of fine grained sediments beyond the limit of recognisable sand deposition, in particular when marine microfossils are sparse or lacking as is the case on the Sendai Plain. This would allow researchers to redraw palaeotsunami inundation maps and re-assess the magnitude of events such as the Jogan tsunami and other palaeotsunamis, not only on the Sendai Plain but also elsewhere around the world. This has important implications for tsunami risk assessment, hazard mitigation and preparedness.© 2012 Elsevier B.V
Numerical FE modelling of occupant injury in soil-vehicle blast interaction.
No full textIn ensuring occupant safety, analysis of blasts in soils has become increasingly important in evaluating the influence of the soil properties on the structural integrity of nearby structures. The proliferation of IED’s (improvised explosive devices) and land mines in areas where soil properties are unknown poses a significant threat to the occupants of armoured vehicle. It is therefore important to increase the accuracy of the numerical analysis by incorporating more sophisticated material models whilst maintaining mathematical tractability. The current study aims to incorporate a multi-physics blast FE simulation In LS-DYNA to investigate the interaction of soil blast with an idealised V-Hull vehicle. Using the Hybrid III Anthropomorphic Test Devices model the authors evaluated he dynamic response index (DRIz) and the head injury criterion (HIC), along with the acceleration and forces of the vehicle’s underbody, to assess the suitability of numerical modelling as a tool to optimise hull shape and reduce occupant injury.(© The Author