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171.
172.
Kristen Coppin Mark Halpern Douglas Scott Colin Borys James Dunlop Loretta Dunne Rob Ivison Jeff Wagg Itziar Aretxaga Elia Battistelli rew Benson rew Blain Scott Chapman Dave Clements Simon Dye Duncan Farrah David Hughes Tim Jenness Eelco van Kampen Cedric Lacey Angela Mortier Alexandra Pope Robert Priddey Stephen Serjeant Ian Smail Jason Stevens Mattia Vaccari 《Monthly notices of the Royal Astronomical Society》2008,384(4):1597-1610
A follow-up survey using the Submillimetre High-Angular Resolution Camera (SHARC-II) at 350 μm has been carried out to map the regions around several 850-μm-selected sources from the Submillimetre HAlf Degree Extragalactic Survey (SHADES). These observations probe the infrared (IR) luminosities and hence star formation rates in the largest existing, most robust sample of submillimetre galaxies (SMGs). We measure 350-μm flux densities for 24 850-μm sources, seven of which are detected at ≥2.5σ within a 10 arcsec search radius of the 850-μm positions. When results from the literature are included the total number of 350-μm flux density constraints of SHADES SMGs is 31, with 15 detections. We fit a modified blackbody to the far-IR (FIR) photometry of each SMG, and confirm that typical SMGs are dust-rich ( M dust ≃ 9 × 108 M⊙ ) , luminous ( L FIR ≃ 2 × 1012 L⊙ ) star-forming galaxies with intrinsic dust temperatures of ≃35 K and star formation rates of ≃400 M⊙ yr−1 . We have measured the temperature distribution of SMGs and find that the underlying distribution is slightly broader than implied by the error bars, and that most SMGs are at 28 K with a few hotter. We also place new constraints on the 350-μm source counts, N 350 (>25 mJy) ∼ 200–500 deg−2 . 相似文献
173.
Non-similarity solutions of the equations governing the motion of a perfect gas behind a cylindrical shock wave of variable strength have been obtained. These solutions are applicable to both the weak and the strong shocks. The nature of flow and field variables are illustrated through graphs. The total energy of the wave is taken to be constant. 相似文献
174.
The TiO2–K2O–P2O5 ternary diagram is proposed as a method of discriminating between oceanic and non-oceanic (continental) basalts. This diagram is effective for non-alkaline “primitive” basalts: fractionated rocks cannot be adequately discriminated. Suitable analyses are those which have total alkalies ≤ 20% in an (Fe2O3 + FeO)–MgO–(Na2O + K2O) diagram. The proposed dividing line separates 93% of 222 ocean-floor and ocean-ridge basalts into the oceanic field and > 80% of continental basalt analyses into the non-oceanic field. Two exceptions are the Tertiary basalts of Greenland and the Deccan Traps which have oceanic affinities. “Continental” suites displaying an oceanic affinity in the TiO2–K2O–P2O5 diagram may be a result of abortive attempts to generate new sea floor. Preliminary results for dike swarms and Archean basalts suggest preponderant oceanic affinities. Alteration and metamorphism of oceanic basalts generally occasion enrichment of K2O relative to TiO2 and P2O5. 相似文献
175.
First identification and characterization of Borrobol‐type tephra in the Greenland ice cores: new deposits and improved age estimates 下载免费PDF全文
Eliza Cook Siwan M. Davies Esther R. Guðmundsdóttir Nicholas J. G. Pearce 《第四纪科学杂志》2018,33(2):212-224
Contiguous sampling of ice spanning key intervals of the deglaciation from the Greenland ice cores of NGRIP, GRIP and NEEM has revealed three new silicic cryptotephra deposits that are geochemically similar to the well‐known Borrobol Tephra (BT). The BT is complex and confounded by the younger closely timed and compositionally similar Penifiler Tephra (PT). Two of the deposits found in the ice are in Greenland Interstadial 1e (GI‐1e) and an older deposit is found in Greenland Stadial 2.1 (GS‐2.1). Until now, the BT was confined to GI‐1‐equivalent lacustrine sequences in the British Isles, Sweden and Germany, and our discovery in Greenland ice extends its distribution and geochemical composition. However, the two cryptotephras that fall within GI‐1e ice cannot be separated on the basis of geochemistry and are dated to 14358 ± 177 a b2k and 14252 ± 173 a b2k, just 106 ± 3 years apart. The older deposit is consistent with BT age estimates derived from Scottish sites, while the younger deposit overlaps with both BT and PT age estimates. We suggest that either the BT in Northern European terrestrial sequences represents an amalgamation of tephra from both of the GI‐1e events identified in the ice‐cores or that it relates to just one of the ice‐core events. A firm correlation cannot be established at present due to their strong geochemical similarities. The older tephra horizon, found within all three ice‐cores and dated to 17326 ± 319 a b2k, can be correlated to a known layer within marine sediment cores from the North Iceland Shelf (ca. 17179‐16754 cal a BP). Despite showing similarities to the BT, this deposit can be distinguished on the basis of lower CaO and TiO2 and is a valuable new tie‐point that could eventually be used in high‐resolution marine records to compare the climate signals from the ocean and atmosphere. 相似文献
176.
177.
In this study we perform a statistical study on, 8319 X-Ray solar flares observed with the Hard X-Ray Burst Spectrometer (HXRBS) on the Solar Maximum Mission satellite (SMM). The events are examined in terms of the durations, maximum intensities, and intensity profiles. It is concluded that there is no evidence for a correlation between flare intensity, flare duration, and flare asymmetry. However, we do find evidence for a rapid fall-of in the number of short-duration events. 相似文献
178.
Douglas G. Pearce 《GeoJournal》1989,19(3):257-262
This paper reviews the interfaces between international and domestic tourism and explores a number of associated issues. Within the origin the interface is between domestic tourism and the outbound component of international tourism. Questions arise relating to the different propensities for domestic and outbound travel and reasons accounting for this variation at a national scale — size, national tourist resources and levels of economic development — and at an individual level where motivations and the ability to travel play a major role. Within destinations interfaces exist between domestic tourism and inbound international tourism. Questions there relate to the size and distribution of these two types of tourist traffic, their respective impacts and the interaction between the two groups. Issues raised include those of the substitution of domestic and outbound travel and the formulation of policies whose varied aims are likely to be met by different spatial strategies. Future research needs to examine differences and interactions between domestic and international tourism more fully and explicitly so that more effective policies might be derived. 相似文献
179.
Shells of the common cockle Cerastoderma edule have been analysed using Laser Ablation Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) for a suite of elements (Pb, Cu, As, Zn and U). The samples of C. edule were obtained from four sites in the British Isles, two facing the Atlantic and two adjacent to the Irish Sea. The LA-ICP-MS technique, permits high resolution examination of the relationship between the concentrations of elements in the hard parts and that in the environment. This study shows that this bivalve can be used as a biomonitor of pollution. All four areas under investigation are affected by anthropogenic pollution, in particular Zn and Cu, and are characterized by short-term extreme pollution events. Furthermore, high levels of U are recorded from the cockles sampled from the sites adjacent to the Irish Sea, probably related to a combination of both natural and industrial effluents discharged into the area. 相似文献
180.
The deepest part of the Canary Basin, the Madeira Abyssal Plain, receives allochthonous sediments derived from a large drainage basin which, if its subaerial continuation is included, covers an area of 3.36 times 106 km2. An international research effort over the last 10 years has recovered over 160 sediment cores from the plain, and the development of a high-resolution stratigraphy has enabled individual turbidites to be correlated layer by layer. Sedimentation on the Madeira Abyssal Plain during the late Quaternary is dominated by thick turbidite muds separated by thin pelagic intervals. The core density has allowed the mapping of each sedimentary unit throughout the abyssal plain, thus building up a layer by layer picture of sediment accumulation. Over the last 300 kyr, 600 km3 of turbidites compared to 60 km3 of pelagic sediments have been deposited on the plain. Sedimentary structures developed in the coarse basal facies of the larger turbidites are more complex than simple models predict due to surging flows, fluctuating flow velocities and reflection from adjacent high ground. Over the last 300 kyr, there has been a switching of entry points for turbidity currents entering the abyssal plain. From 300 ka to 200 ka, organic-rich turbidites were emplaced predominantly from the south but around 200 ka this source switched off and subsequent organic- and volcanic-rich turbidites, which included units deposited by giant, possibly hyperconcentrated flows, were emplaced from northern or eastern sources. Although restricted to the late Quaternary, the data presented provides a detailed case study of the evolution of an oceanic basin fill. 相似文献