The NAIAD experiment for WIMP searches at Boulby mine and recent results     

B. Ahmed  G. J. Alner  H. Araujo  J. C. Barton  A. Bewick  M. J. Carson  D. Davidge  J. V. Dawson  T. Gamble  S. P. Hart  R. Hollingworth  A. S. Howard  W. G. Jones  M. K. Joshi  V. A. Kudryavtsev  T. B. Lawson  V. Lebedenko  M. J. Lehner  J. D. Lewin  P. K. Lightfoot  I. Liubarsky  R. Lüscher  J. E. McMillan  B. Morgan  G. Nicklin  S. M. Paling  R. M. Preece  J. J. Quenby  J. W. Roberts  M. Robinson  N. J. T. Smith  P. F. Smith  N. J. C. Spooner  T. J. Sumner  D. R. Tovey 《Astroparticle Physics》2003,19(6):691-702

The NAIAD experiment (NaI Advanced Detector) for weakly interacting massive particle (WIMP) dark matter searches at Boulby mine (UK) is described. The detector consists of an array of encapsulated and unencapsulated NaI(Tl) crystals with high light yield. Six crystals are collecting data at present. Data accumulated by four of them (10.6 kg × year exposure) have been used to set upper limits on the WIMP–nucleon spin-independent and WIMP–proton spin-dependent cross-sections. Pulse shape analysis has been applied to discriminate between nuclear recoils, as may be caused by WIMP interactions, and electron recoils due to gamma background. Various calibrations of crystals are presented.  相似文献   

River sediments,great floods and centennial‐scale Holocene climate change     

Mark G. Macklin  John Lewin 《第四纪科学杂志》2003,18(2):101-105

A new analysis of all 346 published ¹⁴C dated Holocene alluvial units in Britain offers a unique insight into the regional impacts of global change and shows how surprisingly sensitive British rivers have been to relatively modest but repeated changes in climate. Fourteen major but probably brief periods of flooding are identified bracketed within the periods 400–1070, 1940–3940, 7520–8100 and at ca. 10 420 cal. yr BP. There is a strong correspondence between climatic deteriorations inferred from mire wet shifts and major periods of flooding, especially at ca. 8000 cal. yr BP and since ca. 4000 cal. yr BP. The unusually long and complete British record also demonstrates that alterations in land cover have resulted in a step change in river basin sensitivity to variations in climate. This has very important implications for assessing and mitigating the impact of increasing severe flooding. In small and medium‐sized river basins land use is likely to play a key role in either moderating or amplifying the climatic signal. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

Chandra and RXTE spectroscopy of the Galactic microquasar XTE J1550−564 in outburst     

J. M. Miller  H. L. Marshall  R. Wijnands †  T. Di Matteo  D. W. Fox  J. Kommers  D. Pooley  T. Belloni  J. Casares  P. A. Charles  A. C. Fabian  M. van der Klis  W. H. G. Lewin 《Monthly notices of the Royal Astronomical Society》2003,338(1):7-13

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MS 1603.6+2600: an accretion disc corona source?     

P. G. Jonker  M. van der Klis  C. Kouveliotou  M. Méndez  W. H. G. Lewin  T. Belloni 《Monthly notices of the Royal Astronomical Society》2003,346(2):684-688

We have observed the eclipsing low-mass X-ray binary MS 1603.6+2600 with Chandra for 7 ks. The X-ray spectrum is well fit with a single absorbed power law with an index of ∼2. We find a clear sinusoidal modulation in the X-ray light curve with a period of  1.7 ± 0.2 h  , consistent with the period of 1.85 h found before. However, no (partial) eclipses were found. We argue that if the X-ray flare observed in earlier X-ray observations was a type I X-ray burst, then the source can only be an accretion disc corona source at a distance of ∼11–24 kpc (implying a height above the Galactic disc of ∼8–17 kpc). It has also been proposed in the literature that MS 1603.76+2600 is a dipper at ∼75 kpc. We argue that, in this dipper scenario, the observed optical properties of MS 1603.6+2600 are difficult to reconcile with the optical properties one would expect on the basis of comparisons with other high-inclination, low-mass X-ray binaries, unless the X-ray flare was not a type I X-ray burst. In that case, the source can be a nearby soft X-ray transient accreting at a quiescent rate, as was proposed by Hakala et al., or a high-inclination source at ∼15–20 kpc.  相似文献   

Sources and sinks for atmospheric H₂: A current analysis with projections for the influence of anthropogenic activity     

Joyce E. Penner  Michael B. McElroy  Steven C. Wofsy 《Planetary and Space Science》1977,25(6):521-540

Oxidation of CH₄ provides the major source for atmospheric H₂ which is removed mainly by reaction with OH. Biological activity at the Earth's surface appears to represent at most a minor sink for H₂. Anthropogenic activity is a significant source for both H₂ and CO in the present atmosphere and may be expected to exert a growing influence in the future. Models are presented which suggest a rise in the mixing ratio of H₂ from its present value of 5.6 × 10^?7 to about 1.8 × 10^?6 by the year 2100. The mixing ratio of CO should grow from 9.7 × 10^?8 to 2.3 × 10^?7 over the same time period and there should be a rise in CH₄ by about a factor of 1.5 associated with anthropogenically induced reductions in tropospheric OH.  相似文献   

Temporal fluctuations in weather disasters: 1950–1989     

Stanley A. Changnon  Joyce M. Changnon 《Climatic change》1992,22(3):191-208

A unique historical data set describing the 142 storms producing losses in excess of $100 million in the United States during the 1950–89 period were analyzed to describe their temporal characteristics. These weather disasters (WDs) caused $66.2 billion in losses, 76% of the nation's insured losses in this period. Disasters were most prevalent in the south, southeast, northeast, and central U.S., with few in and west of the Rockies. The incidence of WDs was high in the 1950s, low in the 1960s-early 1970s, and peaked in the 1980s. Losses due to WDs peaked in the 1950s, again in the late 1960s, and with a lesser peak after 1985. The areal extent of storm losses peaked after 1975 and was least in the 1960s. The temporal variations of the three storm measures (incidence, losses, and extent) had poor agreement, and agreed only when they peaked in the 1950s. Regionally-derived time distributions of WDs showed marked north-south differences with a U-shaped 40-year distribution in the northern half of the nation, whereas southern regions had a relatively flat trend until achieving a peak in the 1980s. The temporal distributions of hurricane-caused disasters differed regionally, with the distributions in the southern, southeastern, and northeastern U.S. each quite different. Temporal distributions of thunderstorm and winter storm-produced disasters were regionally more uniform. The national 5-year WD frequencies correlated moderately well with annual mean temperatures which explained 40% of the variability found in WDs during 1950–89. Weather disasters peaked in the relatively warm-dry 1950s and again in the warm-wet 1980s, and were least in the cool-wet 1960s and 1970s. The distribution of WDs during 1950–89 appears positively related to the temporal fluctuations in cyclonic activity.  相似文献   

Understanding Climatic Impacts, Vulnerabilities, and Adaptation in the United States: Building a Capacity for Assessment     

Edward A. Parson  Robert W. Corell  Eric J. Barron  Virginia Burkett  Anthony Janetos  Linda Joyce  Thomas R. Karl  Michael C. MacCracken  Jerry Melillo  M. Granger Morgan  David S. Schimel  Thomas Wilbanks 《Climatic change》2003,57(1-2):9-42

Based on the experience of the U.S. National Assessment, we propose a program of research and analysis to advance capability for assessment of climate impacts, vulnerabilities, and adaptation options. We identify specific priorities for scientific research on the responses of ecological and socioeconomic systems to climate and other stresses; for improvement in the climatic inputs to impact assessments; and for further development of assessment methods to improve their practical utility to decision-makers. Finally, we propose a new institutional model for assessment, based principally on regional efforts that integrate observations, research, data, applications, and assessment on climate and linked environmental-change issues. The proposed program will require effective collaboration between scientists, resource managers, and other stakeholders, all of whose expertise is needed to define and prioritize key regional issues, characterize relevant uncertainties, and assess potential responses. While both scientifically and organizationally challenging, such an integrated program holds the best promise of advancing our capacity to manage resources and the economy adaptively under a changing climate.  相似文献   

Primary aragonite and high‐Mg calcite in the late Cambrian (Furongian). Potential evidence from marine carbonates in Oman          下载免费PDF全文

Joyce E. Neilson  Alexander T. Brasier  Colin P. North 《地学学报》2016,28(5):306-315

Transient aragonite seas occurred in the early Cambrian but several models suggest the late Cambrian was a time of calcite seas. Here, evidence is presented from the Andam Group, Huqf High, Oman (Gondwana) that suggests a transient Furongian (late Cambrian) aragonite sea, characterized by the precipitation of aragonite and high‐Mg calcite ooids and aragonite isopachous, fibrous, cements. Stable carbon isotope data suggest that precipitation occurred just before and during the SPICE (Steptoean Positive Carbonate Isotope Excursion). Aragonite and high‐Mg calcite precipitation can be accounted for if mMg:Ca ratios were around 1.2 given the very high atmospheric CO₂ at that time and if precipitation occurred in warm waters associated with the SPICE. This, together with reported occurrences of early Furongian aragonite ooids from various locations in North America (Laurentia), suggests that aragonite and high‐Mg calcite precipitation from seawater may have been more than just a local phenomenon.  相似文献   

A topical evaluation and discussion of data movement technologies for data-intensive scientific applications   总被引：1，自引：1，他引：0  

Chris A. Mattmann  Luca Cinquini  Paul Zimdars  Michael Joyce  Shakeh Khudikyan 《Earth Science Informatics》2016,9(2):247-262

Transferring large volumes of information from one location to potentially many others that are geographically distributed and across varying networks is still prevalent in modern scientific data systems. This is despite the movement to push computation to the data and to reduce data movement needed to compute answers to challenging scientific problems, to disseminate information to the scientific community, and to acquire data for curation and enrichment. Because of this, it is imperative that decisions made regarding data movement systems and architectures be backed by both analytical rigor, and also by empirical evidence and measurement. The purpose of this study is to expand on the work performed by our research team over the last decade and to take a fresh look at the evaluation of multiple topical data transfer technologies in use cases derived from data-intensive scientific systems and applications in the areas of Earth science. We report on the evaluation of a set of data movement technologies against a set of empirically derived comparison dimensions. Based on this evaluation, we make recommendations towards the selection of appropriate data movement technologies in scientific applications and scenarios.  相似文献   

Determination of Elemental Concentrations in Nine CMEA Rock and Ore Standards,in NBS 98 Plastic Clay and in Fired Clay Gent (FCG) by Instrumental Neutron Activation Analysis*     

Joyce K. FROST 《Geostandards and Geoanalytical Research》1991,15(1):43-50

Data for as many as 31 elements were determined by instrumental thermal neutron activation analysis for nine European Council for Mutual Economic Assistance (CMEA) rock and ore standards. The National Bureau of Standards plastic clay 98 and the University of Gent fired clay FCG were also analyzed. Synthetic, multielement standards were used and USGS rock standards provided reference samples. Correction factors for uranium fission products on cerium and molybdenum, and also for less commonly encountered spectral interferences, such as those due to the 213 ppm tantalum in granitoid 2B, were evaluated.  相似文献