The extreme, red afterglow of GRB 060923A: distance or dust?

Gamma-ray bursts (GRBs) are powerful probes of the early Universe, but locating and identifying very distant GRBs remain challenging. We report here the discovery of the K -band afterglow of Swift GRB 060923A, imaged within the first hour post-burst, and the faintest so far found. It was not detected in any bluer bands to deep limits, making it a candidate very high- z burst  ( z ≳ 11)  . However, our later-time optical imaging and spectroscopy reveal a faint galaxy coincident with the GRB position which, if it is the host, implies a more moderate redshift (most likely   z ≲ 2.8  ) and therefore that dust is the likely cause of the very red-afterglow colour. This being the case, it is one of the few instances so far found of a GRB afterglow with high-dust extinction.     

Overview of groundwater sources and water-supply systems,and associated microbial pollution,in Finland,Norway and Iceland

The characteristics of groundwater systems and groundwater contamination in Finland, Norway and Iceland are presented, as they relate to outbreaks of disease. Disparities among the Nordic countries in the approach to providing safe drinking water from groundwater are discussed, and recommendations are given for the future. Groundwater recharge is typically high in autumn or winter months or after snowmelt in the coldest regions. Most inland aquifers are unconfined and therefore vulnerable to pollution, but they are often without much anthropogenic influence and the water quality is good. In coastal zones, previously emplaced marine sediments may confine and protect aquifers to some extent. However, the water quality in these aquifers is highly variable, as the coastal regions are also most influenced by agriculture, sea-water intrusion and urban settlements resulting in challenging conditions for water abstraction and supply. Groundwater is typically extracted from Quaternary deposits for small and medium municipalities, from bedrock for single households, and from surface water for the largest cities, except for Iceland, which relies almost entirely on groundwater for public supply. Managed aquifer recharge, with or without prior water treatment, is widely used in Finland to extend present groundwater resources. Especially at small utilities, groundwater is often supplied without treatment. Despite generally good water quality, microbial contamination has occurred, principally by norovirus and Campylobacter, with larger outbreaks resulting from sewage contamination, cross-connections into drinking water supplies, heavy rainfall events, and ingress of polluted surface water to groundwater.     

Investigations of clay colloid aggregates by scanning transmission X-ray microspectroscopy of suspensions

The environmental behaviour of colloidal clay in aquatic systems is linked to the properties of their aggregates. Earlier investigations of clay colloids were performed with electron microscope techniques which caused de-hydration of the particles. Information on the structure of colloid aggregates is needed for understanding their sedimentation behaviour, as well as colloid contaminant transport properties in natural systems. Scanning transmission X-ray microspectroscopy successfully produced images of montmorillonite colloid aggregates in a pseudo-equilibrium state in 1 mM NaCl suspensions equilibrated for more than a year. These clay aggregates were revealed at photon energies below the O absorption edges of clay and water. They were spherical or ellipsoidal with diameters of the order of 100–800 nm. The aggregates are porous and gel like with lower densities than the clay mineral. These investigations are important for modelling the occurrence of clay aggregates in aqueous environments.     

The Late Cenozoic uplift – climate change paradox

The geologic evidence for worldwide uplift of mountain ranges in the Neogene is ambiguous. Estimates of paleoelevation vary, according to whether they are based on the characteristics of fossil floras, on the masses and grain sizes of eroded sediments, or on calculations of increased thickness of the lithosphere as a result of faulting. Detrital erosion rates can be increased both by increased relief in the drainage basin and by a change to more seasonal rainfall patterns. The geologic record provides no clear answer to the question whether uplift caused the climatic deterioration of the Neogene or whether the changing climate affected the erosion system in such a way as to create an illusion of uplift. We suggest that the spread of C₄ plants in the Late Miocene may have altered both the erosion and climate systems. These changes are responsible for the apparent contradictions between data supporting uplift and those supporting high elevations in the past.     

Use of neural networks for the prediction of frictional drag and transmission of axial load in horizontal wellbores

The use of mud motors and other tools to accomplish forward motion of the bit in extended reach and horizontal wells allows avoiding large amounts of torque caused by rotation of the whole drill string. The forward motion of the drill string, however, is resisted by excessive amount of friction. In the presence of large compressive axial loads, the drill pipe or coiled tubing tends to buckle into a helix in horizontal boreholes. This causes additional frictional drag resisting the transmission of axial load (resulting from surface slack‐off force) to the bit. As the magnitude of the frictional drag increases, a buckled pipe may become ‘locked‐up’ making it almost impossible to drill further. In case of packers, the frictional drag may inhibit the transmission of set‐up load to the packer. A prior knowledge of the magnitude of frictional drag for a given axial load and radial clearance can help avoid lock‐up conditions and costly failure of the tubular. In this study a neural network model, for the prediction of frictional drag and axial load transmission in horizontal wellbores, is presented. Several neural network architectures were designed and tested to obtain the most accurate prediction. After cross‐validation of the Back Propagation Neural Network (BPNN) algorithm, a two‐hidden layer model was chosen for simultaneous prediction of frictional drag and axial load transmission. A comparison of results obtained from BPNN and General Regression Neural Network (GRNN) algorithms is also presented. Copyright © 2002 John Wiley & Sons, Ltd.     

Reduced survivorship of Himasthla (Trematoda, Digenea)-infected cockles (Cerastoderma edule) exposed to oxygen depletion

Bivalve populations from inshore waters often accommodate a diverse trematode fauna that may have a variety of effects on host specimens. In particular, larval trematodes that grow or reproduce within their host are known to be severe pathogens, whereas trematodes utilising bivalves only for encystment are thought to be relatively benign. Yet this may depend on the environmental conditions, and it can be expected that such trematodes in concert with other stress agents can be detrimental to host organisms. To examine the impact of such larval trematodes on hosts subjected to stress, we studied the digenetic trematode Himasthla elongata and one of its second intermediate hosts, the bivalve Cerastoderma edule. Experimentally infected cockles and non-infected cockles were exposed to oxygen depletion, whereupon we measured their burrowing ability and survivorship. After 30 h of hypoxia, the survival of infected cockles was significantly reduced compared to non-infected cockles, whereas no effect of parasites on cockles under normoxic conditions was found. In addition, parasites tended to reduce the burrowing ability of cockles exposed to hypoxia but the effect was not clear. The effect of parasites and possible ecological consequences are discussed and it is suggested that the combined effects of parasites and oxygen deficiency may explain some hitherto unexplained cases of mass mortalities in bivalve populations.     

Relation of selected mineral deposits to the mass/age distribution of Phanerozoic sediments

The global mass/age distribution of Phanerozoic sediment shows maxima in the Middle Paleozoic, at the Paleozoic-Mesozoic boundary, and in the Late Mesozoic. All of these total sediment mass maxima are also maxima of masses of volcanogenic sediment and non-marine sediment, and represent times of maximum sediment flux on the surface of the earth. The Middle Paleozoic and Late Mesozoic maxima correspond to the great marine inundations of the continents, and the Late Paleozoic-Early Mesozoic maximum to the time of transfer of a large number of terranes across the Tethys from Gondwanaland to Eurasia. All three maxima of sedimentary mass correspond to times of rapid sea-floor spreading and orogeny.Organic carbon in dispersed form is enriched in sediments forming hydrocarbons during the sediment flux maxima of the Middle Paleozoic and Late Mesozoic (Jurassic-Cretaceous), but is preserved as coal during sediment flux minima of the Carboniferous and Early Cenozoic. Sedimentary iron deposits and phosphorite deposition are most widespread when the global sedimentary flux is minimal. Potassium salts were deposited at times of sediment flux

---

Zusammenfassung Die globale Verteilung der Sedimentmassen nach ihrem Alter zeigt Massenmaxima im Mittel-Paläozoikum, an der Grenze Paläozoikum-Mesozoikum und im Spät-Mesozoikum, sowie Massenminima dazwischen. Die Maxima der gesamten Sedimentmasse sind auch Maxima der vulkanogenen und terrestrischen Sedimente; sie fallen in Zeiten maximaler Erosion, Umlagerung und Sedimentation. Die mittel-paläozoischen und spät-mesozoischen Maxima sind zeitlich mit den größten Überflutungen der Kontinenten verbunden. An der Wende vom Paläozoikum zum Mesozoikum, an der es keinen Hochstand des Meeresspiegels gab, überwucherten viele kleinere Kontinentschollen die Tethys von Gondwana nach Asien. Vermutlich waren alle drei Maxima auch Zeiten maximalen Sea-floor Spreadings und der Orogenese.Organischer Kohlenstoff wurde während der Sedimentations-Maxima im mittleren Paläozoikum und späteren Mesozoikum (Jura-Kreide) in marinen Sedimenten angereichert aber während der Sedimentationsminima im Spät-Paläozoikum und im frühen Känozoikum als Kohle abgelagert. Eisenoolite und Phosphorite finden ihre weiteste Verbreitung zu Zeiten der Sedimentationsminima. Kalisalze wurden zu den Zeiten der Sedimentationsmaxima ausgeschieden.

---

Résumé Au cours du Phanérozoïque, la répartition a l'échelle globale de la masse des sédiments déposés en fonction de leur âge présente des maxima au Paléozoïque moyen, à la limite Paléozoïque-Mésozoïque et au Mésozoïque supérieur; elle présente des minima aux autres périodes. Tous ces maxima de la masse totale des sédiments sont aussi des maxima des sédiments volcanoclastiques et des sédiments continentaux; ils représentent les périodes oú les transports sédimentaires étaient les plus importants à la surface du globe. Les maxima du Paléozoïque supérieur correspondent aux grandes invasions marines des continents, tandis que le maximum paléozoïque-mésozoïque correspond au transfert à travers la Téthys d'un grand nombre de «terranes» du Gondwana vers l'Eurasie. Les trois maxima correspondent également à des périodes d'expansion océanique rapide et d'orogenèse active.Le carbone organique s'est déposé sous forme dispersée dans les sédiments marins (roches-mères des hydrocarburse) lors des maxima du Paléozoïque moyen et du Mésozoïque supérieur, tandis qu'il a été conservé sous forme de charbon lors des minima du Carbonifère et du Cénozoïque inférieur. Les dépôts de minerais de fer sédimentaires oolitiques et de phosphate présentent leur plus grande extension au cours des périodes de sédimentation globale minimale. Les sels potassiques se sont déposés pendant les périodes de sédimentation maximale.

---

, / , . ; , . . , .. , , . , . / , . . .

     

Ni(II) sorption on natural chlorite

Sorption of Ni(II) onto chlorite surfaces was studied as a function of pH (5–10), ionic strength (0.01–0.5 M) and Ni concentration (10⁻⁸–10⁻⁶ M) in an Ar atmosphere using batch sorption with radioactive ⁶³Ni as tracer. Such studies are important since Ni(II) is one of the major activation products in spent nuclear fuel and sorption data on minerals such as chlorite are lacking. The sorption of Ni(II) onto chlorite was dependent on pH but not ionic strength, which indicates that the process primarily comprises sorption by surface complexation. The maximum sorption was at pH ∼ 8 (K_d = ∼10⁻³ cm³/g). Desorption studies over a period of 1–2 weeks involving replacement of the aqueous solution indicated a low degree of desorption. The acid–base properties of the chlorite mineral were determined by titration and described using a non-electrostatic surface complexation model in FITEQL. A 2-pK NEM model and three surface complexes, Chl_OHNi²⁺, Chl_OHNi(OH)⁺ and Chl_OHNi(OH)₂, gave the best fit to the sorption results using FITEQL. The high K_d values and low degree of desorption observed indicate that under expected groundwater conditions, a large fraction of Ni(II) that is potentially leachable from spent nuclear fuel may be prevented from migrating by sorption onto chlorite surfaces.