Science with ASKAP     

S. Johnston  R. Taylor  M. Bailes  N. Bartel  C. Baugh  M. Bietenholz  C. Blake  R. Braun  J. Brown  S. Chatterjee  J. Darling  A. Deller  R. Dodson  P. Edwards  R. Ekers  S. Ellingsen  I. Feain  B. Gaensler  M. Haverkorn  G. Hobbs  A. Hopkins  C. Jackson  C. James  G. Joncas  V. Kaspi  V. Kilborn  B. Koribalski  R. Kothes  T. Landecker  A. Lenc  J. Lovell  J.-P. Macquart  R. Manchester  D. Matthews  N. McClure-Griffiths  R. Norris  U.-L. Pen  C. Phillips  C. Power  R. Protheroe  E. Sadler  B. Schmidt  I. Stairs  L. Staveley-Smith  J. Stil  S. Tingay  A. Tzioumis  M. Walker  J. Wall  M. Wolleben 《Experimental Astronomy》2008,22(3):151-273

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THE STATUS OF RECREATION STUDIES IN BRlTAIN     

Geoffrey Wall 《The Professional geographer》1973,25(1):47-52

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Recent variations in the general circulation as related to glacier retreat in northern Scandinavia     

Dr. C. C. Wallén 《Pure and Applied Geophysics》1950,18(1):175-178

Summary A review is given of the investigations on variations in the general circulation in middle latitudes made byWillett andPetterssen. According toWillett a «high-index» type of circulation pattern with a strong zonal flow has probably caused the recent climatic improvement in the northern latitudes while the «low-index» type with meridional flow would create a cooling off in the same areas. According toPetterssen an other type of «low-index» pattern with a weak zonal flow and strong meridional exchange of air has been the essential cause of the warming up of the northern latitudes in Europe. This implies that the definition of the «low-index» type is not clear and gives rise to misunderstanding. Making use of our experience on glacier retreat in northern Scandinavia it is concluded that thePetterssen type of circulation more probably than the «high-index» type has caused the warming-up in the North Atlantic area from which the retreat of the glaciers has followed.  相似文献   

3D seismic imaging of a Tertiary Dyke Swarm in the Southern North Sea,UK     

Mostyn Wall  Joe Cartwright  Richard Davies  Andrew McGrandle 《Basin Research》2010,22(2):181-194

We use three‐dimensional (3D) seismic reflection and magnetic data to interpret and describe the 3D geometry of igneous dykes in the southern North Sea. The dykes were emplaced into Paleozoic and Mesozoic sediments and have a common upper termination in Early Tertiary sediments. We interpret the dykes to be part of the British Tertiary volcanic province and estimate the age of the dykes to be 58 Ma. The dykes are characterized by a narrow 0.5–2 km wide vertical disturbance of seismic reflections that have linear plan view geometry. Negative magnetic anomalies directly align with the vertical seismic disturbance zones and indicate the presence of igneous material. Linear coalesced collapse craters are found above the dykes. The collapse craters have been defined and visualized in 3D. Collapse craters have formed above the dyke due to the release of volatiles at the dyke tip and resulting volume loss. Larger craters have potentially formed due to explosive phreatomagmatic interaction between magma and pore water. The collapse craters are a new Earth analogue to Martian pit chain craters.  相似文献   

Testate amoeba analysis of lake sediments: impact of filter size and total count on estimates of density,species richness and assemblage structure     

A. A. J. Wall  D. Gilbert  M. Magny  E. A. D. Mitchell 《Journal of Paleolimnology》2010,43(4):689-704

Testate amoebae are informative about palaeoecological conditions, but the methods generally used for their analyses in lake sediments differ from those used for their analyses in peats, making comparisons difficult. This study examines how filter mesh size and total number of individuals counted affect species richness, Shannon diversity, equitability, density and assemblage structure. We analysed the complete testate amoeba contents of six sediment samples from Lake Lautrey, France. The abundance of testate amoebae was high (1,403–10,870 shells cm⁻³), and species smaller than 63 μm in both length and width represented up to 89% of total abundance and 43% of species richness. A simulation showed that using 47- or 63-μm mesh-size filters reduced inter-sample differences and changed the patterns of abundance, species richness and assemblage structure, causing loss of information and leading to potential erroneous palaeoecological interpretation. Rarefaction analyses suggest that although 170 shells are sufficient to assess the general structure of assemblages, such small sample sizes can underestimate species richness by overlooking taxa with relative abundances <4%. Total counts of 400 shells yield better estimates of assemblage structure and recover at least 50% of total species richness, although species with absolute frequencies below 2% may still be missed. Higher counts are required to obtain reliable estimates of species richness and assemblage structure in samples that have high testate amoeba densities but are dominated by a few small taxa. Further studies should determine the bioindicator value and functional roles of small and/or rare species in lakes and thus to what extent overlooking them affects palaeoecological interpretations.  相似文献   

Evolution of chemical composition of pyrochlore group minerals from phoscorites and carbonatites of the Khibina alkaline massif     

A. N. Zaitsev  C. T. Williams  F. Wall  A. A. Zolotarev 《Geology of Ore Deposits》2012,54(7):503-515

Phoscorites and carbonatites of the Khibina alkaline massif, Russia contain three minerals of the pyrochlore group. They are, in order of crystallization: uranpyrochlore and pyrochlore in the phoscorites, and pyrochlore and bariopyrochlore in late calcite carbonatites. Early calcite carbonatites also contain uranpyrochlore and pyrochlore, but they are xenocrysts derived from the phoscorites. Alteration of the pyrochlore group minerals led to increasing U, Ti and water contents and decreasing Na, Ca, Nb and F contents. Crystallization of zoned uranpyrochlore to pyrochlore crystals in the phoscorites is explained by the experiments of Ryabchikov and Hamilton (1993, 1994) on the interaction of carbonate-phosphate melts with mantle peridotites.  相似文献   

Magnetic fabric analysis in a mesoscopic fold     

M. A. Mamtani  M. Chadima  H. de Wall  R. O. Greiling 《International Journal of Earth Sciences》2012,101(3):611-611

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Monazite CHIME/EPMA dating of Erinpura granitoid deformation: Implications for Neoproterozoic tectono-thermal evolution of NW India     

Jana Just  Bernhard Schulz  Helga de Wall  Fred Jourdan  Manoj K. Pandit 《Gondwana Research》2011,19(2):402-412

The in-situ “chemical” Th–U–Pb dating of monazite with the electron microprobe is used to unravel the Neoproterozoic tectono-thermal history of the “Erinpura Granite” terrane in the foreland of the Delhi Fold Belt (DFB) in the NW Indian craton. These granitoids are variably deformed and show effects of shearing activity. Monazites from the Erinpura granitoids recorded two main events; (1) protolith crystallization at 863 ± 23 Ma and (2) recrystallization and formation of new Th-poor monazite at 775 ± 26 Ma during shear overprint. Some components of the Erinpura granitoids, such as the Siyawa Granite and granites exposed near Sirohi town, show evidence of migmatization. This migmatization event is documented by anatexis and associated monazite crystallization at 779 ± 16 Ma. The age data indicate an overlap in timing between anatectic event and ductile shear deformation. The end of the tectono-thermal event in the Sirohi area is constrained by a 736 ± 6 Ma Ar–Ar muscovite age data from the ductile shear zone.  相似文献   

The Growth of Estuarine Resources (Zostera marina, Mercenaria mercenaria, Crassostrea virginica, Argopecten irradians, Cyprinodon variegatus) in Response to Nutrient Loading and Enhanced Suspension Feeding by Adult Shellfish     

Charles C. Wall  Bradley J. Peterson  Christopher J. Gobler 《Estuaries and Coasts》2011,34(6):1262-1277

While many coastal ecosystems previously supported high densities of seagrass and abundant bivalves, the impacts of overfishing, eutrophication, harmful algal blooms, and habitat loss have collectively contributed to the decline of these important resources. Despite improvements in wastewater treatment in some watersheds and subsequent reduced nutrient loading to neighboring estuaries, seagrass and bivalve populations in these locations have generally not recovered. We performed three mesocosm experiments to simultaneously examine the contrasting effects of nutrient loading and historic suspension-feeding bivalve densities on the growth of eelgrass (Zostera marina), juvenile bivalves (northern quahogs, Mercenaria mercenaria; eastern oysters, Crassostrea virginica; and bay scallops, Argopecten irradians), and juvenile planktivorous fish (sheepshead minnow, Cyprinodon variegatus). High nutrient loading rates led to significantly higher phytoplankton (chlorophyll a) levels in all experiments, significantly increased growth of juvenile bivalves relative to controls with lower nutrient loading rates in two experiments, and significantly reduced the growth of eelgrass in one experiment. The filtration provided by adult suspension feeders (M. mercenaria and C. virginica) significantly decreased phytoplankton levels in all experiments, significantly increased light penetration and the growth of eelgrass in one experiment, and significantly decreased the growth of juvenile bivalves and fish in two experiments, all relative to controls with no filtration from adult suspension feeders. These results demonstrate that an appropriate level of nutrient loading can have a positive effect on some estuarine resources and that bivalve filtration can mediate the effects of nutrient loading to the benefit or detriment of different estuarine resources. Future ecosystem-based approaches will need to simultaneously account for anthropogenic nutrient loading and bivalve restoration to successfully manage estuarine resources.  相似文献   

居民地方感对区域旅游发展支持度影响——以九寨沟旅游核心社区为例   总被引：19，自引：3，他引：16  

许振晓  张捷  Geoffrey Wall  曹靖  张宏磊 《地理学报》2009,64(6):736-744

基于"地方感"、"期望理论"两个基本理论,从旅游核心社区居民地方感、旅游发展期望、旅游发展获益感知、旅游发展成本感知以及旅游发展支持度五个结构变量Ⅲ发,通过引入旅游发展期望值作为中介变量,构建居民地方感对旅游发展支持度内部影响机制的理论模型.以世界遗产地几寨沟为实证研究对象,通过验证性因子分析和三阶段结构方程模型的定量分析,校验理论模型中各结构因子、结构因子与其所含维度之间影响路径及其系数,定量测度了居民的旅游发展期望在居民地方感与旅游发展正反影响感知关联中的中介效用和影响机制,及对旅游发展支持度的潜在影响模式.研究结果表明:①居民地方感对居民旅游发展正反影响感知的作用存在差异,地方感对获益感知的作用远大于成本感知.②居民从旅游发展中感知获益有助于他们对当地旅游发展持更积极态度.而成本感知则会产生消极影响.③居民旅游发展期望中介效用的存在性和有效性,居民地方感通过发展期望,强化了对旅游发展影响感知及旅游支持度作用.④发展期望在居民旅游发展正反影响感知两结构模型中的中介效用存在强弱,在感知获益子结构模型的中介作用强于感知成本子模型.  相似文献