GRB 060607A: a gamma-ray burst with bright asynchronous early X-ray and optical emissions     

Houri Ziaeepour  Stephen T. Holland  Patricia T. Boyd  Kim Page  Samantha Oates  Craig B. Markwardt  Peter Mészáros  Neil Gehrels  Francis E. Marshall  Jay Cummings  Mike Goad 《Monthly notices of the Royal Astronomical Society》2008,385(1):453-467

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The Swift Ultra-Violet/Optical Telescope: a view of today and tomorrow     

P. W. A. Roming  C. Gronwall  D. E. Vanden Berk  M. J. Page  P. T. Boyd 《Astrophysics and Space Science》2009,320(1-3):203-206

Currently there are four operating near-UV imaging space telescopes, one of which is the Swift Ultra-Violet/Optical Telescope (UVOT). Although the UVOT was primarily built for observations of γ-ray bursts, it has become a powerful instrument for studying other types of UV and optical astronomical phenomena. Here we discuss the properties of the UVOT, summarize some of the science undertaken with the UVOT, and present other possible science goals for the UVOT that have not yet been pursued. We also discuss some lessons learned that apply to future UV telescopes.  相似文献   

Dating martian climate change     

David P. Page  Matthew R. Balme  Monica M. Grady 《Icarus》2009,203(2):376-389

Geological evidence indicates that low-latitude polygonally-patterned grounds on Mars, generally thought to be the product of flood volcanism, are periglacial in nature and record a complex signal of changing climate. By studying the martian surface stratigraphically (in terms of the geometrical relations between surface landforms and the substrate) rather than genetically (by form analogy with Earth), we have identified dynamic surfaces across one-fifth of martian longitude. New stratigraphical observations in the Elysium-Amazonis plains have revealed a progressive surface polygonisation that is destructive of impact craters across the region. This activity is comparable to the climatically-driven degradation of periglacial landscapes on Earth, but because it affects impact craters—the martian chronometer—it can be dated. Here, we show that it is possible to directly date this activity based on the fraction of impact craters affected by polygon formation. Nearly 100% of craters (of all diameters) are superposed by polygonal sculpture: considering the few-100 Ma age of the substrate, this suggests that the process of polygon formation was active within the last few million years. Surface polygonisation in this region, often considered to be one of the signs of young, ‘plains-forming’ volcanism on Mars, is instead shown to postdate the majority of impact craters seen. We therefore conclude that it is post-depositional in origin and an artefact of thermal cycling of near-surface ground ice. Stratigraphically-controlled crater counts present the first way of dating climate change on a planet other than Earth: a record that may tell us something about climate change on our own planet. Parallel climate change on these two worlds—an ice age Mars coincident with Earth’s glacial Quaternary period—might suggest a coupled system linking both. We have previously been unable to generalise about the causes of long-term climate change based on a single terrestrial example—with the beginnings of a chronology for climate change on our nearest planetary neighbour, we can.  相似文献   

Biotite and muscovite <Superscript>40</Superscript>Ar–<Superscript>39</Superscript>Ar geochronological constraints on the post-Svecofennian tectonothermal evolution,Forsmark site,central Sweden     

Pia Söderlund  Tobias Hermansson  Laurence M. Page  Michael B. Stephens 《International Journal of Earth Sciences》2009,98(8):1835-1851

In order to characterize the post-Svecofennian tectonothermal evolution of the Fennoscandian Shield, ⁴⁰Ar–³⁹Ar biotite and some ⁴⁰Ar–³⁹Ar muscovite geochronological data are reported from a total of 30 surface outcrop and 1,000 m long borehole samples at Forsmark, central Sweden. The 13 surface samples were collected across 3 branches of a major WNW to NW trending system of deformation zones, whereas the boreholes were drilled within a tectonic lens, in between two of these zones. The ⁴⁰Ar–³⁹Ar biotite ages indicate that the present erosion surface, in central Sweden, cooled below c. 300°C at 1.73–1.66 Ga, and that the rocks could have accommodated strain in a brittle manner between 1.8 and 1.7 Ga. The variation in surface ages is suggested to be due to fault along the large WNW to NW trending deformation zones, following the establishment of a sub-Cambrian peneplain. The minor variation of ages within a single crustal block may be due to disturbance along ENE to NNE trending fracture zones. Possible cooling paths, derived from ⁴⁰Ar–³⁹Ar hornblende, muscovite and biotite ages, were calculated for the time interval from 1.80 to 1.67 Ga, when the area cooled from c. 500 to 300°C. Cooling rates of 1.9–4°C/m.y. have been attained. Between 1.68 and 1.64 Ga, uplift rates of c. 22 m/m.y. were calculated from borehole ⁴⁰Ar–³⁹Ar biotite data. Tectonothermal histories, inferred from the combined cooling and uplift rates, are related to simple cooling after the Svecofennian orogeny, to crustal movement in response to far-field effects of c. 1.7 Ga orogenic activities further to the west or to a combination of these possibilities.  相似文献   

Late Quaternary evolution of Lake Urana,New South Wales,Australia     

Kenneth Page  Anthony Dare-Edwards  Gerald Nanson  David Price 《第四纪科学杂志》1994,9(1):47-57

Lake Urana is a well-preserved relict lake in the semi-arid Riverine Plain of southeastern Australia. A compound lunette at its eastern shoreline consists of a quartz-sand-dominated unit (Bimbadeen Formation), thermoluminescence (TL) dated at 30 ka to 12 ka, and a clay and sand facies unit (Coonong Formation), dated at 55 ka to 35 ka. The intervening period indicates a phase of periodically exposed lake floor and soil formation. The older wet phase conforms well with similar environments recorded from the same period at Lake Mungo. However, the return to high water levels from 30 ka to 12 ka departs sharply from the generally accepted palaeoclimatic model from Australia, which demands severe glacial maximum desiccation and widespread construction of clay lunettes. Although hydrological budgets calculated for Lake Urana and nearby Lake Cullivel require high glacial maximum water levels they do not support higher precipitation.  相似文献   

Dispersion and toxicity to non-target aquatic organisms of pesticides used to treat sea lice on salmon in net pen enclosures     

Ernst W  Jackman P  Doe K  Page F  Julien G  Mackay K  Sutherland T 《Marine pollution bulletin》2001,42(6):433-444

Pesticides are used extensively in the finfish aquaculture industry to control sea lice infestations on farmed salmon. The most prevalent method of use is to enclose a net pen with an impervious tarpaulin and mix a pesticide solution within that enclosure. After treatment for short periods (1 h) the pesticide solution is released to the environment. Concerns have been raised that there is a potential risk to non-target aquatic organisms from those releases. The fate of dispersing pesticide solutions was measured after six simulated treatments in the Lower Bay of Fundy, New Brunswick. Three simulated treatments were done with azamethiphos and three with cypermethrin. Rhodamine dye was added to all pesticide solutions in order to facilitate tracking of the dispersing plume through real-time measurements of dye concentrations by a flow-through fluorometer coupled with a differential global positioning system (DGPS). Water samples were obtained from within the plumes at various times after release and analysed for pesticide content and toxicity to a benthic amphipod Eohaustorius estuaris. Dye concentrations were detectable for time periods after release which varied from 2 to 5.5 h. Distances travelled by the dye patches ranged from 900 to 3000 m and the dye concentrations at the final sampling period were generally 1/200-1/3000 the pre-release concentrations and cypermethrin concentrations were generally 1/1000-1/2000 the pre-release concentrations. Cypermethrin concentrations in water samples were closely correlated with dye concentrations, indicating that dye analyses were an accurate surrogate for cypermethrin concentrations. Most samples taken after the releases of azamethiphos were not toxic to test organisms in 48 h exposures and none were beyond 20 min post-release. By contrast, almost all samples taken after the release of cypermethrin, even up to 5-h post-release, were toxic. Data indicate the potential to cause toxic effects over areas of hectares from a single release of cypermethrin.  相似文献   

Anomalous geochemical patterns from northern Sumatra: their assessment in terms of mineral exploration and regional geology     

B.G.N. Page  R.D. Young   《Journal of Geochemical Exploration》1981,15(1-3)

A regional stream sediment survey has been conducted in Sumatra north of 4°N. The survey area is approximately 38,000 km² of mountainous terrain mostly covered by dense tropical rainforest. The overall sample density achieved by the survey was one per ten km². However, the difficult terrain and thick vegetation blanket have meant that a uniform sample density was not obtained. The uneven sample density has presented problems with interpretation of the geochemical patterns and identification of anomalous areas for mineral exploration purposes.Two methods have been designed for identifying mineral exploration targets from the geochemical results found by the survey. The first method uses computerised probability calculations and the second a simple empirical formula. Both methods appear to give similar results.Northern Sumatra has very distinct geochemical patterns. Copper shows a linear zone of high values along the axial Barisan Mountain Range, which are derived from two main sources: the Sumatran ophiolites and copper-rich calc-alkaline intrusives. High chromium values also occur not only over the ophiolites, but also over placers derived from them. High lead values are grouped to the east of the linear copper zone and they border the oil and gas basins of the eastern coastal strip. High tin values occur west of the copper rich intrusives, but east of the present-day subduction zone off the west coast of Sumatra. The overall pattern fails to conform to the classic zonation of mineral deposits across a simple subduction system, perhaps because large transcurrent faults have sliced northern Sumatra into blocks and so brought blocks of different provenance into contact. This explanation is confirmed by the lithium distribution, which reveals two wholly distinct provinces astride the Sumatran Fault System.  相似文献   

Ab initio elasticity of FeS2 pyrite from 0 to 135 GPa     

Y. Le Page  J. R. Rodgers 《Physics and Chemistry of Minerals》2005,32(8-9):564-567

Polynomial expressions for the elastic tensor coefficients, the bulk, the shear and Young’s moduli, the speed of sound for longitudinal and transverse waves, the equation of state and the x coordinate of the sulfur atom in pyrite are reported based on ab initio calculations in the range of 0–135 GPa. Comparison with published experimental data indicates good agreement for the equation of state and for values at 0 GPa as well as reasonable agreement for first derivatives. All modeling and interpretation was performed with Materials Toolkit v.2.0 and all ab initio computations with VASP.  相似文献   

Optimal Ground-Water Remediation Methods Applied to a Superfund Site: From Formulation to Implementation     

David P. Ahlfeld  Roger H. Page  George F. Pinder 《Ground water》1995,33(1):58-70

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Tourist organizations: Pearce, D.G. Harlow: Longman, 1992. 219pp. £14.99 paperback.     

Stephen J. Page 《Applied geography (Sevenoaks, England)》1993,13(4)

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