Volume contents     

David L. Jauncey  Helen M. Johnston  Hayley E. Bignall  J.E.J. Lovell  Lucyna Kedziora-Chudczer 《Astrophysics and Space Science》2001,277(4):637-641

Volume Contents

Volume contents  相似文献   

HR 7275: A new variable star     

R. E. Fried  Joel A. Eaton  D. S. Hall  G. W. Henry  L. P. Lovell  K. Krisciunas  C. R. Chambliss  P. K. Detterline  H. J. Landis  H. Louth  D. R. Skillman 《Astrophysics and Space Science》1982,83(1-2):181-188

Differential photometry of the KI IV-III RS CVn-type binary HR 7275 in 1978, 1979, and 1980 at nine different observatories shows it definitely to be variable, thus confirming the suspicion of Herbst. The photometric period determined two ways was 27 _. ^d 91 or 27 _. ^d 65, thus about 3% shorter than the spectroscopically determined orbital period of 28 _. ^d 59. The total variation observed during the three years was 0 _. ^m 22 in theV. The light curve was always asymmetrical, with a stillstand on the rising branch in 1978 but on the falling branch in 1980.Kitt Peak National Observatory, operated by the Association of Universities for Research in Astronomy, under contract with the National Science Foundation.Of the AAVSO.  相似文献   

Five years of photometry of λ andromedae     

R. W. Boyd  J. A. Eaton  D. S. Hall  G. W. Henry  R. M. Genet  L. P. Lovell  J. L. Hopkins  J. D. Sabia  K. Krisciunas  C. R. Chambliss  P. K. Detterline  H. J. Landis  H. Louth  T. R. Renner  D. R. Skillman  R. E. Montle 《Astrophysics and Space Science》1983,90(1):197-206

We present photoelectric photometry of this bright long-period RS CVn binary and use it, along with earlier photometry, to derive the photometric period and discuss the changing light curve shape. The best ephemeris for times of minimum light is 2443829.2+53.^d95E. Because times of minimum and maximum extending back to those of Calder in 1933–37 can be phased together properly, the principal dark region must have maintained its identify for almost 50 yr. Over the last five years the brightness range has been 3 ^m .70<V<4 ^m .05. During 1980–81 shallow secondary minima developed at phases where maxima occurred in previous years. λ And remains the only wellestablished case of non synchronous rotation among the known RS CVn binaries.  相似文献   

The real country and the legal country: Spanish Ideals and mayan realities in colonial Guatemala     

W. G. Lovell Prof. Dr. 《GeoJournal》1992,26(2):181-185

Conquest by imperial Spain forced the Maya of Guatemala to contend with a dizzying array of European values and culturally-impregnated modes of geographic thought. Fundamentally different notions of where and how to live were thrust upon Maya communities by the policy of resettlement known as congregación. Imperial legislation evokes a utopian existence nowhere attained in the realm of actual practice. Archival documents, many of them penned by disenchanted clergy and concerned Crown officials, portray a lived experience quite unlike that enshrined in decrees and ordinances, edicts and commands. For the colonial Maya, as for natives throughout the Americas, the geography of everyday life bore little resemblance to the idealized arrangements of people in place promoted by imperial rhetoric.  相似文献   

Soil air carbon dioxide and oxygen measurements as a guide to concealed mineralization in semi-arid and arid regions     

J.S. Lovell  M. Hale  J.S. Webb 《Journal of Geochemical Exploration》1983,19(1-3)

The differences between the CO₂ and O₂ concentrations in soil air and atmospheric air have been measured where sulfide mineralization occurs beneath transported exotic overburden in semi-arid and arid areas of the USA, South West Africa (Namibia) and Saudi Arabia. These mineralizations are reflected near surface by anomalous levels of CO₂ and O₂ in soil air, whereas in most cases heavy-metal anomalies are absent. The normal background variability of CO₂ and O₂ in soil air falls with increasing aridity, and anomaly definition improves with increasing aridity. Thus soil air CO₂ and O₂ data are potentially useful in exploring for concealed mineralization, especially in regions with an arid climate or conspicuous dry season.  相似文献   

Contourites: Their recognition in modern and ancient sediments   总被引：1，自引：0，他引：1  

D.A.V. Stow  J.P.B. Lovell 《Earth》1979,14(3):251-291

We suggest that publication of evidence that the continental rise of the western North Atlantic has been shaped by bottom currents flowing parallel to bathymetric contours (Heezen, Hollister and Ruddiman, 1966) marked the beginning of a revolution in sedimentology comparable to the turbidite revolution launched by Kuenen and Migliorini in their classical 1950 paper.Intensification of slow, thermohaline circulation on the western margins of the ocean basins leads to high-velocity, deep, boundary currents, capable of eroding, transporting and depositing fine-grained sediment. Long-period, direct current measurements suggest a complex, periodic flow for these currents, while bottom photographs indicate their influence on the sediment surface. Sediment ridges in the North Atlantic can be closely related to the deep-water circulation pattern. Other morphological features (ripples, furrows, waves), echogram characteristics, and the presence of well-developed nepheloid layers cannot be uniquely attributed to the action of bottom currents.Critical review of marine-based investigations reveals a lack of generally accepted criteria for the recognition of contourites on the basis of sediment character. We discuss the problems in establishing such criteria and recognize that: (a) a continuum may exist between dilute turbidity flows, bottom currents and hemipelagic settling; (b) interbedded turbidites, contourites and hemipelagites are common, especially in a rise environment; and (c) composition and other criteria may be only locally applicable. However, we can identify two main contourite groups, muddy contourites and sandy contourites, and have proposed new criteria for their recognition. Muddy contourites are generally bioturbated, have poorly defined bedding, and contain biogenic sand often concentrated into irregular layers. They may be texturally and compositionally distinct from interbedded turbidites, and have relatively high CaCO₃ and organic carbon contents. Sandy contourites occur as thin, bioturbated, irregular lag-deposits, or as reworked tops of sandy turbidites. In the latter case they may be clean, well sorted, parallel- or cross-laminated, but show no offshore trends or vertical structural sequence. Grain orientation shows the bottom current direction, often superimposed upon the original turbidite fabric.Reveiw of land-based work shows that there is growing recognition of the need for a new concept to complement turbidity-current theory, but that there have been relatively few claims of firm contourite identification. Recognition of ancient contourites has been based either on the application of previous sedimentological criteria, or on an interpretation of the broader environmental framework. It is suggested that it is lack of suitable criteria for the identification of contourites rather than a true scarcity of these rocks that has led to such a restricted literature.Mindful of problems created by diagenesis, tectonic activity and the limited preservation potential of many diagnostic features of marine contourites, we do suggest criteria, and a procedure, for the recognition of contourites in land-based work. Sandy contourites of the reworked-turbidite variety may be the most easily recognised; the presence of bimodal palaeocurrent directions at about 90° is an important indicator of this type.The geological significance of contourites in palaeo-oceanographical, palaeogeographical and tectonic reconstructions is emphasised, especially in relation to work on passive (Atlantic-type) continental margins. We also refer to the possible economic significance of contourites as exploration for hydrocarbons moves into deeper waters.  相似文献   

Looking back and moving forward: Health geography in Aotearoa and beyond          下载免费PDF全文

Christina R. Ergler  Sarah Lovell  Alison Watkins  Christine Milligan  Lee Thompson  Daniel J. Exeter  Robin Kearns 《New Zealand geographer》2017,73(3):205-217

Health geography in Aotearoa New Zealand (NZ) has had a major impact on international sub‐disciplinary debates. It is timely to celebrate our domestic health geography achievements and alert ourselves to the challenges ahead. This reflection article provides a brief overview of Aotearoa NZ's maturing health geography community and includes the reflections of a panel discussion held during the bi‐annual NZ Geographical Society conference in 2016. We argue that the eclectism of health geography in NZ and beyond is both the sub‐discipline's major strength and challenge.  相似文献   

A GIS-based approach to site vegetated buffer strips for erosion control within an agricultural catchment in southern England     

Cat Hudson  Harold Lovell  Alastair W. Pearson  Martin Schaefer  Philip J. Soar 《水文研究》2024,38(5):e15165

Agricultural soil erosion is largely attributed to arable intensification and increased mechanization. Runoff from arable land and intensively managed grassland transports sediment and contaminants across the landscape and into watercourses, causing crop loss, land degradation, and water quality issues. One low-cost and low-maintenance nature-based mitigation approach is the implementation of vegetated buffer strips (VBS): grassland sited along field margins to trap sediment and contaminants, reducing transportation and diffuse pollution rates. GIS modelling using remotely sensed landscape indices and land parcel data can provide an efficient means of identifying priority areas for intervention at sub-catchment or farm system scales. We develop and test a scalable runoff risk model in the lower Rother catchment, West Sussex. The model uses the Normalized Difference Vegetation Index (NDVI) applied to satellite images as an erodibility proxy and identifies locations along pathways that are conceivably at greatest risk of sediment accumulation and transfer, guided by field observations. We assess current and historical field boundaries near high-risk locations, evaluating the potential capacity of their margins to contribute to runoff risk reduction using an innovative ranking system. Recommendations are made for VBS implementation and the value of historical field boundary and margin restoration is discussed. Our method offers a rapid approach with minimal data requirements to identify high-risk sediment runoff locations and priority sites for intervention. The tool has the potential to guide decision-makers responsible for targeting and implementing soil erosion and runoff control measures such as VBS, while also maximizing agri-environmental and cultural benefits.  相似文献   

The glacial landsystem of a tropical glacier: Charquini Sur,Bolivian Andes          下载免费PDF全文

Jakub Małecki  Harold Lovell  Wojciech Ewertowski  Łukasz Górski  Tomasz Kurczaba  Beata Latos  Michał Miara  Dorota Piniarska  Jacek Płocieniczak  Tomasz Sowada  Marcin Spiralski  Anna Warczachowska  Antoine Rabatel 《地球表面变化过程与地形》2018,43(12):2584-2602

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Sub-annual moraine formation at an active temperate Icelandic glacier     

Benjamin M.P. Chandler  Samuel J.P. Chandler  David J.A. Evans  Marek W. Ewertowski  Harold Lovell  David H. Roberts  Martin Schaefer  Aleksandra M. Tomczyk 《地球表面变化过程与地形》2020,45(7):1622-1643

This paper presents detailed geomorphological and sedimentological investigations of small recessional moraines at Fjallsjökull, an active temperate outlet of Öræfajökull, southeast Iceland. The moraines are characterized by striking sawtooth or hairpin planforms, which are locally superimposed, giving rise to a complex spatial pattern. We recognize two distinct populations of moraines, namely a group of relatively prominent moraine ridges (mean height ~1.2 m) and a group of comparatively low-relief moraines (mean height ~0.4 m). These two groups often occur in sets/systems, comprising one pronounced outer ridge and several inset smaller moraines. Using a representative subsample of the moraines, we establish that they form by either (i) submarginal deformation and squeezing of subglacial till or (ii) pushing of extruded tills. Locally, proglacial (glaciofluvial) sediments are also incorporated within the moraines during pushing. For the first time, to our knowledge, we demonstrate categorically that these moraines formed sub-annually using repeat uncrewed aerial vehicle (UAV) imagery. We present a conceptual model for sub-annual moraine formation at Fjallsjökull that proposes the sawtooth moraine sequence comprises (i) sets of small squeeze moraines formed during melt-driven squeeze events and (ii) larger push moraines formed during winter re-advances. We suggest the development of this process-form regime is linked to a combination of elevated temperatures, high surface meltwater fluxes to the bed and emerging basal topography (a depositional overdeepening). These factors result in highly saturated subglacial sediments and high porewater pressures, which induces submarginal deformation and ice-marginal squeezing during the melt season. Strong glacier recession during the summer, driven by elevated temperatures, allows several squeeze moraines to be emplaced. This process-form regime may be characteristic of active temperate glaciers receding into overdeepenings during phases of elevated temperatures, especially where their englacial drainage systems allow efficient transfer of surface meltwater to the glacier bed near the snout margin. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献