X-ray observations of PSR B0355+54 and its pulsar wind nebula     

Katherine E. McGowan  W. Thomas Vestrand  Jamie A. Kennea  Silvia Zane  Mark Cropper  France A. Córdova 《Astrophysics and Space Science》2007,308(1-4):309-316

We present X-ray data of the middle-aged radio pulsar PSR B0355+54. The XMM-Newton and Chandra observations show not only emission from the pulsar itself, but also compact diffuse emission extending ∼50″ in the opposite direction to the pulsar’s proper motion. Our analysis also indicates the presence of fainter diffuse emission extending ∼5′ from the point source. The morphology of the diffuse component is similar to the ram-pressure confined pulsar wind nebulae detected for other sources. We find that the compact diffuse component is well-fitted with a power-law, with an index that is consistent with the values found for other pulsar wind nebulae. The core emission from the pulsar can be characterized with a thermal plus power-law fit, with the thermal emission most likely originating in a hot polar cap.  相似文献   

Simulating the effects of quasar structure on parameters from geodetic VLBI   总被引：1，自引：1，他引：0  

Stanislav S. Shabala  Jamie N. McCallum  Lucia Plank  Johannes Böhm 《Journal of Geodesy》2015,89(9):873-886

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Glacial and deglacial climatic patterns in Australia and surrounding regions from 35 000 to 10 000 years ago reconstructed from terrestrial and near-shore proxy data     

Martin Williams  Ellyn Cook  Sander van der Kaars  Tim Barrows  Jamie Shulmeister  Peter Kershaw 《Quaternary Science Reviews》2009,28(23-24):2398-2419

This study forms part of a wider investigation of late Quaternary environments in the Southern Hemisphere. We here review the terrestrial and near-shore proxy data from Australia, Indonesia, Papua New Guinea (PNG), New Zealand and surrounding oceans during 35–10 ka, an interval spanning the lead-up to the Last Glacial Maximum (LGM), the LGM proper (21 ± 2 ka), and the ensuing deglaciation. Sites selected for detailed discussion have a continuous or near continuous sedimentary record for this time interval, a stratigraphically consistent chronology, and one or more sources of proxy climatic data. Tropical Australia, Indonesia and PNG had LGM mean annual temperatures 3–7 °C below present values and summer precipitation reduced by at least 30%, consistent with a weaker summer monsoon and a northward displacement of the Intertropical Convergence Zone. The summer monsoon was re-established in northwest Australia by 14 ka. Precipitation in northeast Australia was reduced to less than 50% of present values until warmer and wetter conditions resumed at 17–16 ka, followed by a second warmer, wetter phase at 15–14 ka. LGM temperatures were up to 8 °C lower than today in mainland southeast Australia and up to 4 °C cooler in Tasmania. Winter rainfall was much reduced throughout much of southern Australia although periodic extreme flood events are evident in the fluvial record. Glacial advances in southeast Australia are dated to 32 ± 2.5, 19.1 ± 1.6 and 16.8 ± 1.4 ka, with periglacial activity concentrated towards 23–16 ka. Deglaciation was rapid in the Snowy Mountains, which were ice-free by 15.8 ka. Minimum effective precipitation in southern Australia was from 14 to 12 ka. In New Zealand the glacial advances date to ～28, 21.5 and 19 ka, with the onset of major cooling at ～28 ka, or well before the LGM. There is no convincing evidence for a Younger Dryas cooling event in or around New Zealand, but there are signs of the Antarctic Cold Reversal in and around New Zealand and off southern Australia. There remain unresolved discrepancies between the climates inferred from pollen and those inferred from the beetle and chironomid fauna at a number of New Zealand sites. One explanation may be that pollen provides a generalised regional climatic signal in contrast to the finer local resolution offered by beetles and chironomids. Sea surface temperatures (SSTs) were up to 5 °C cooler during the LGM with rapid warming after 20 ka to attain present values by 15 ka. The increase in summer monsoonal precipitation at or before 15 ka reflects higher insolation, warmer SSTs and steeper thermal gradients between land and sea. The postglacial increase in winter rainfall in southern Australia is probably related to the southward displacement of the westerlies as SSTs around Antarctica became warmer and the winter pack ice and Antarctic Convergence Zone retreated to the south.  相似文献   

Logics of collaboration     

Jamie Peck 《GeoJournal》2015,80(2):193-196

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Virtual geology special issue: developing training,teaching and research skillsets for geoscientists          下载免费PDF全文

Jamie K. Pringle 《Geology Today》2015,31(6):213-215

Current physical science students and researchers are becoming ever more diverse in their learning needs and styles, in their ways of learning and indeed their scientific backgrounds in the subjects that they study. Current schools, colleges and Higher Education students are increasingly ‘digital natives’, connected 24/7 through mobile devices, generally goal‐orientated and responding well to digitally‐based activities and tasks. Whilst the structured nature of classrooms, traditional lectures and laboratory practicals obviously still dominate geoscience teaching, and core outdoor field trips and independent mapping/research are of paramount importance, more innovative complementary learning, teaching and research technologies are being developed by a wide variety of computer software developers, practitioners and educationalists.  相似文献   

Circuits of capital and industrial restructuring: adjustment in the australian clothing industry     

Jamie A. Peck∗ 《The Australian geographer》1990,21(1):33-52

Patterns and processes of industrial restructuring in the Australian clothing industry are examined, utilising a ‘circuits of capital’ approach in which the interrelationships between labour markets, labour processes and product markets are emphasised. Changes in product markets (where import competition is intensifying under the trade liberalisation policies of the Hawke government and where an increasingly concentrated retail sector has accrued enormous bargaining power in its dealings with clothing manufacturers) and changes in labour markets (where competition for the industry's traditional inner urban labour supply has intensified considerably) are argued to have provided the driving force behind the process of clothing industry adjustment. This process of adjustment has been characterised by: (i) increased use of outworking, which enables clothing manufacturers to reduce production costs and provides a means for new sources of home‐based labour within the urban labour market to be tapped; and (ii) the evolution of a spatial division of labour, as some of the labour‐intensive components of the industry have been relocated to non‐urban sites where a stable and plentiful labour supply is available. In contrast to experiences in Europe and the United States, there is little evidence in Australia at the present time of significant technical change nor of specialisation in the high quality/high fashion niche of the garment market.  相似文献   

Seismic response of a bridge–soil–foundation system under the combined effect of vertical and horizontal ground motions     

Zhenghua Wang  Leonardo Dueñas‐Osorio  Jamie E. Padgett 《地震工程与结构动力学》2013,42(4):545-564

Different levels of model sophistication have recently emerged to support seismic risk assessment of bridges, but mostly at the expense of neglecting the influence of vertical ground motions (VGMs). In this paper, the influence of VGMs on bridge seismic response is presented and the results are compared with the case of horizontal‐only excitations. An advanced finite element model that accounts for VGMs is first developed. Then, to investigate the effect of soil–structure interaction (SSI) including liquefaction potential, the same bridge with soil‐foundation and fixed boundary conditions is also analyzed. Results show that the inclusion of the VGMs has a significant influence on the seismic response, especially for the axial force in columns, normal force of bearings, and the vertical deck bending moments. However, VGMs do not have as much influence on the seismic demand of the pile cap displacements or pile maximum axial forces. Also, the significant fluctuation of the column axial force can reduce its shear and flexural capacity, and a heightened reversal of flexural effects may induce damage in the deck. In addition, relative to the fixed base case, SSI effects tend to reduce response quantities for certain ground motions while increasing demands for others. This phenomenon is explained as a function of the frequency content of the ground motions, the shift in natural vertical periods, and the VGM spectral accelerations at higher modes. Moreover, the mechanisms of liquefaction are isolated relative to SSI effects in nonliquefiable soils, revealing the influence of liquefaction on bridge response under VGMs. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Teaching Orientalism in Introductory Human Geography   总被引：1，自引：1，他引：0  

Ishan Ashutosh  Jamie Winders 《The Professional geographer》2013,65(4):547-560

This article explores efforts to bring postcolonial theory into the undergraduate human geography classroom. Through a case study of teaching Edward Said's Orientalism in introductory human geography, we discuss the relevance of postcolonial theory to critical pedagogy in geography. We lay out how instructors can teach Orientalism in introductory courses, what happens when they do so, and where efforts to use postcolonial theory to help students analyze the “colonial present” can be improved. We suggest that postcolonial theory is particularly well suited pedagogically to show students the mechanisms and uneven power relations producing and sustaining past and present geographies of difference.  相似文献   

Reference hydrologic networks II. Using reference hydrologic networks to assess climate-driven changes in streamflow     

Donald H. Burn  Jamie Hannaford  Glenn A. Hodgkins  Paul H. Whitfield  Robin Thorne  Terry Marsh 《水文科学杂志》2013,58(8):1580-1593

Abstract

Reference hydrologic networks (RHNs) can play an important role in monitoring for changes in the hydrological regime related to climate variation and change. Currently, the literature concerning hydrological response to climate variations is complex and confounded by the combinations of many methods of analysis, wide variations in hydrology, and the inclusion of data series that include changes in land use, storage regulation and water use in addition to those of climate. Three case studies that illustrate a variety of approaches to the analysis of data from RHNs are presented and used, together with a summary of studies from the literature, to develop approaches for the investigation of changes in the hydrological regime at a continental or global scale, particularly for international comparison. We present recommendations for an analysis framework and the next steps to advance such an initiative. There is a particular focus on the desirability of establishing standardized procedures and methodologies for both the creation of new national RHNs and the systematic analysis of data derived from a collection of RHNs.

Editor Z.W. Kundzewicz; Associate editor K. Hamed

Citation Burn, D. H., et al., 2012 Whitfield, P.H. 2012. Reference hydrologic networks, I. The status of national reference hydrologic networks for detecting trends and future directions. Hydrological Sciences Journal, 57(8) this issue[Taylor & Francis Online] , [Google Scholar]. Reference hydrologic networks II. Using reference hydrologic networks to assess climate-driven changes in streamflow. Hydrological Sciences Journal, 57 (8), 1580–1593.  相似文献   

A propensity for n‐ω‐amino acids in thermally altered Antarctic meteorites     

Aaron S. BURTON  Jamie E. ELSILA  Michael P. CALLAHAN  Mildred G. MARTIN  Daniel P. GLAVIN  Natasha M. JOHNSON  Jason P. DWORKIN 《Meteoritics & planetary science》2012,47(3):374-386

Abstract– Asteroids and their fragments have impacted the Earth for the last 4.5 Gyr. Carbonaceous meteorites are known to contain a wealth of indigenous organic molecules, including amino acids, which suggests that these meteorites could have been an important source of prebiotic organic material during the origins of life on Earth and possibly elsewhere. We report the detection of extraterrestrial amino acids in thermally altered type 3 CV and CO carbonaceous chondrites and ureilites recovered from Antarctica. The amino acid concentrations of the thirteen Antarctic meteorites ranged from 300 to 3200 parts‐per‐billion (ppb), generally much less abundant than in amino acid‐rich CI, CM, and CR carbonaceous chondrites that experienced much lower temperature aqueous alteration on their parent bodies. In contrast to low‐temperature aqueously altered meteorites that show complete structural diversity in amino acids formed predominantly by Strecker–cyanohydrin synthesis, the thermally altered meteorites studied here are dominated by small, straight‐chain, amine terminal (n‐ω‐amino) amino acids that are not consistent with Strecker formation. The carbon isotopic ratios of two extraterrestrial n‐ω‐amino acids measured in one of the CV chondrites (δ¹³C approximately ?25‰) are consistent with ¹³C‐depletions observed previously in hydrocarbons produced by Fischer‐Tropsch type reactions. The predominance of n‐ω‐amino acid isomers in thermally altered meteorites hints at cosmochemical mechanisms for the preferential formation and preservation of a small subset of the possible amino acids.  相似文献