X-ray bright sources in the Chandra Small Magellanic Cloud Wing Survey – detection of two new pulsars     

K. E. McGowan  M. J. Coe  M. Schurch  V. A. McBride  J. L. Galache  W. R. T. Edge  R. H. D. Corbet  S. Laycock  A. Udalski  D. A. H. Buckley 《Monthly notices of the Royal Astronomical Society》2007,376(2):759-770

We investigate the X-ray and optical properties of a sample of X-ray bright sources from the Small Magellanic Cloud (SMC) Wing Survey. We have detected two new pulsars with pulse periods of 65.8 s (CXOU J010712.6−723533) and 700 s (CXOU J010206.6−714115), and present observations of two previously known pulsars RX J0057.3−7325 (SXP101) and SAX J0103.2−7209 (SXP348). Our analysis has led to three new optical identifications for the detected pulsars. We find long-term optical periods for two of the pulsars, CXOU J010206.6−714115 and SXP101, of 267 and 21.9 d, respectively. Spectral analysis of a subset of the sample shows that the pulsars have harder spectra than the other sources detected. By employing a quantile-based colour–colour analysis we are able to separate the detected pulsars from the rest of the sample. Using archival catalogues we have been able to identify counterparts for the majority of the sources in our sample. Combining this with our results from the temporal analysis of the Chandra data and archival optical data, the X-ray spectral analysis, and by determining the X-ray to optical flux ratios we present preliminary classifications for the sources. In addition to the four detected pulsars, our sample includes two candidate foreground stars, 12 probable active galactic nuclei, and five unclassified sources.  相似文献   

Electronic environments in carrollite, CuCo₂S₄, determined by soft X-ray photoelectron and absorption spectroscopy     

Alan N. Buckley  William M. Skinner  Allan Pring 《Geochimica et cosmochimica acta》2009,73(15):4452-4467

Fracture surfaces of a natural carrollite specimen have been characterised by synchrotron and conventional X-ray photoelectron spectroscopy and near-edge X-ray absorption spectroscopy. For the synchrotron X-ray measurements, the mineral surfaces were prepared under clean ultra high vacuum and were unoxidised. The characterisation was undertaken primarily to establish unequivocally the oxidation state of the Cu in the mineral, but also to obtain information on the electronic environments of the Co and S, and on the surface species. Experimental and simulated Cu L_2,3-edge absorption spectra confirmed an oxidation state of Cu^I, while Co 2p photoelectron and Co L_2,3 absorption spectra were largely consistent with the Co^III established previously by nuclear magnetic resonance spectroscopy. S 2p photoelectron spectra provided no evidence for S to be present in the bulk in more than one state, and were consistent with an oxidation state slightly less negative than S^-II. Therefore it was concluded that carrollite can be best represented by Cu^ICo^III₂(S₄)^-VII. The Cu^I oxidation state is in agreement with that expected for Cu tetrahedrally coordinated by S, but is in disagreement with the Cu^II deduced previously from some magnetic, magnetic resonance and Cu L-edge X-ray absorption spectroscopic measurements. A significant concentration of S species with core electron binding energies both lower and higher than the bulk value were formed at fracture surfaces, and these entities were assigned to monomeric and oligomeric surface S species. The density of Cu d states calculated for carrollite differed from that previously reported but was consistent with the observed Cu L₃ X-ray absorption spectrum. The initial oxidation of carrollite in air under ambient conditions was confirmed to be congruent, unlike the incongruent reaction undergone by a number of non-thiospinel sulfide minerals.  相似文献   

Palaeoleptus burmanicus n. gen., n. sp., an Early Cretaceous shore bug (Hemiptera: Palaeoleptidae n. fam.) in Burmese amber     

George Poinar Jr.  Ron Buckley 《Cretaceous Research》2009,30(4):1000-1004

Palaeoleptus burmanicus gen. et sp. nov. (Hemiptera: Leptopodomorpha: Palaeoleptidae fam. nov.) is described from Early Cretaceous Burmese amber. The fossil is characterized by nearly completely coreaceous wings with only a small membranous area at the distal tip, and a unique wing venation consisting of eight closed cells, including four obliquely orientated toward the embolar wing margin and two large vertically-positioned cells extending nearly to the apical wing margin. Additional characters are large, compound eyes, three pairs of cephalic trichobothria, four antennal segments all similar in texture, spines on the profemur, ocelli positioned on a tubercle and a rostrum extending to the mesocoxae, with the second segment bearing four pairs of spines. The female fossil contains an asymmetrical subgenital plate orientated toward the left side of the body, indicating a side-by-side mating behavior as occurs in extant Leptopodomorpha.  相似文献   

The Greening of Baltimore's Asphalt Schoolyards          下载免费PDF全文

Geoffrey L. Buckley  Christopher G. Boone  J. Morgan Grove 《Geographical review》2017,107(3):516-535

Asphalt was becoming an integral part of the urban American landscape by the end of the nineteenth century. Not only was it emerging as the preferred alternative for street paving, its promoters were endorsing it for other purposes as well. Although Baltimore was not in the vanguard when it came to adopting asphalt for road surfaces, it soon followed the trend. Like other cities, it too found other applications for this versatile petroleum product, including the paving of playgrounds and schoolyards. Despite low maintenance costs, widespread use of asphalt as a recreational surface started to meet resistance in Baltimore during the 1960s. Fifty years later, stringent storm‐water runoff requirements are causing city officials to rethink how they deploy asphalt in an urban setting. In an effort to meet these new requirements, while at the same time improve recreational opportunities for school children, an alliance of government agencies, nonprofit organizations, and private developers has developed a strategy to remove asphalt from schoolyards—one that may serve as a model for other cities facing financial and sustainability challenges similar to those of Baltimore.  相似文献   

Simultaneous optical polarimetry and X-ray observations of the magnetic CV CP Tuc (AX J2315−592)     

Gavin Ramsay  S. B. Potter  David A. H. Buckley  Peter J. Wheatley 《Monthly notices of the Royal Astronomical Society》1999,306(4):809-814

CP Tuc (AX J2315–592) shows a dip in X-rays which lasts for approximately half the binary orbit and is deeper in soft X-rays compared with hard X-rays. It has been proposed that this dip is due to the accretion stream obscuring the accretion region from view. If CP Tuc were a polar, as has been suggested, then the length of such a dip would make it unique amongst polars since in those polars in which a dip is seen in hard X-rays the dip lasts for only 0.1 of the orbit. We present optical polarimetry and RXTE observations of CP Tuc which show circular polarization levels of ∼10 per cent and find evidence for only one photometric period. These data confirm CP Tuc as a polar. Our modelling of the polarization data implies that the X-ray dip is due to the bulk of the primary accretion region being self-eclipsed by the white dwarf. The energy dependence of the dip is due to a combination of this self-eclipse and also the presence of an X-ray temperature gradient over the primary accretion region.  相似文献   

Orbital period of the dwarf nova HL Canis Majoris     

M. D. Still  †  D. Steeghs  V. S. Dhillon  D. A. H. Buckley 《Monthly notices of the Royal Astronomical Society》1999,310(1):39-42

We present a small sample of time-resolved optical spectroscopy of the dwarf nova HL CMa during an outburst state. By combining radial velocity measurements with published data we show that the previously quoted value is not the only candidate for the orbital period of this system. We reduce the significance of daily aliasing but cannot distinguish between two periods at 0.2146±0.0004 and 0.2212±0.0005 d. We show that the low-excitation emission lines are composites from an accretion disc and the companion star, and that high-excitation emission originates in the disc or outflowing material associated with the accreting white dwarf.  相似文献   

A free air gravity anomaly contour map of the Irish continental margin     

Buckley  J. S.  Bailey  R. J. 《Marine Geophysical Researches》1975,2(3):185-194

Compilation of currently-available gravity data permits the construction of a free-air anomaly contour map of the continental margin west of Ireland (51–54 N). Major elements in the structure of the margin, previously delineated on the basis of seismic reflection and magnetic surveys, are clearly seen on the FAA contour map, notably the Porcupine Seabight Trough, and Porcupine Ridge. However, contrary to earlier ideas, the gravity data imply that the Seabight Trough extends northwards onto the Slyne Ridge; and the Slyne Trough, formerly regarded as northeasterly prolongation of the Seabight Trough, appears to be a discrete, fault-bounded, feature separated from the latter by a basement ridge. East-west gravity profiles are modelled in terms of thinned crust with the Moho at a minimum depth of 15 km beneath the axis of the Seabight Trough. The models tend to support hypotheses invoking formation of the Seabight Trough by simple westward translation of Porcupine Ridge with respect to the Irish Mainland.  相似文献   

Laser Scanning for the Environmental Sciences     

Simon J.  Buckley 《The Photogrammetric Record》2010,25(129):84-85

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Collagen fingerprinting for the species identification of archaeological amphibian remains     

Michael Buckley  Marc Cheylan 《Boreas: An International Journal of Quaternary Research》2020,49(4):709-717

Amphibians are well known as being one of the main groups of animals today most threatened by environmental changes but they are also some of the least well understood of all terrestrial vertebrates. This gap in knowledge is much greater as we look further back into the relatively recent past, despite representing an invaluable resources in archaeological and palaeontological assemblages that are more indicative of palaeoclimate conditions than most other vertebrate taxa. This in part stems from their remains being typically much less studied, partly due to the less common forms of expertise required for identifications based on skeletal morphology – the most frequently observed tissue that remains in ancient assemblages. Here we apply a method of biomolecular species identification by collagen peptide mass fingerprinting to the British Late Pleistocene assemblage of Pin Hole Cave (Creswell Crags, UK) as well as a range of relevant extant taxa for comparison. Our results demonstrate the ability to separate at the species level with all modern taxa investigated, allowing for the identification of these archaeological remains to the amphibian taxa known to exist in Late Pleistocene Britain. Analyses of the Pin Hole assemblage found a dominance of the two species previously known from the site (common frogs and toads: Rana temporaria and Bufo bufo, respectively) and also a small number of the rarer natterjack toad (Epidalea calamita) not previously identified in the Creswell Crags region but known from other sites in the UK; additionally, one specimen appeared to yield the fingerprint of the moor frog (R. arvalis), now extinct in the UK. As such, collagen fingerprinting is here shown to widen the known palaeobiodiversity of taxa, and highlights the further potential to enhance our understanding of climate change in the past.  相似文献   

A global context for megadroughts in monsoon Asia during the past millennium   总被引：1，自引：0，他引：1  

Ashish Sinha  Lowell Stott  Max Berkelhammer  Hai Cheng  R. Lawrence Edwards  Brendan Buckley  Mark Aldenderfer  Manfred Mudelsee 《Quaternary Science Reviews》2011,30(1-2):47-62

Proxy reconstructions of precipitation from central India, north-central China, and southern Vietnam reveal a series of monsoon droughts during the mid 14th–15th centuries that each lasted for several years to decades. These monsoon megadroughts have no analog during the instrumental period. They occurred in the context of widespread thermal and hydrologic climate anomalies marking the onset of the Little Ice Age (LIA) and appear to have played a major role in shaping significant regional societal changes at that time. New tree ring-width based reconstructions of monsoon variability suggest episodic and widespread reoccurrences of monsoon megadroughts continued throughout the LIA. Although the El-Niño Southern Oscillation (ENSO) plays an important role in monsoon variability, there is no conclusive evidence to suggest that these megadroughts were associated with anomalous sea surface temperature anomalies that were solely the result of ENSO-like variability in the tropical Pacific. Instead, the causative mechanisms of these megadroughts may reside in protracted changes in the synoptic-scale monsoon climatology of the Indian Ocean. Today, the intra-seasonal monsoon variability is dominated by ‘active’ and the ‘break’ spells – two distinct oscillatory modes of monsoon that have radically different synoptic scale circulation and precipitation patterns. We suggest that protracted locking of the monsoon into the “break-dominated” mode – a mode that favors reduced precipitation over the Indian sub-continent and SE Asia and enhanced precipitation over the equatorial Indian Ocean, may have caused these exceptional droughts. Impetus for periodic locking of the monsoon into this mode may have been provided by cooler temperatures at the extratropical latitudes in the Northern Hemisphere which forced the mean position of the Inter-Tropical Convergence Zone (ITCZ) further southward in the Indian Ocean.  相似文献