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421.
Malcolm P. Cutchin 《Geoforum》2008,39(4):1555-1569
John Dewey was the most significant and influential thinker associated with the American philosophy commonly known as pragmatism. Drawing on Dewey’s writings as well as the work of Deweyan scholars, I endeavor to explain Dewey’s unique contribution to philosophical discourse and how his overlooked scholarship can inform geographical inquiry. After an introduction, I provide a background understanding of Dewey and his context as well as the use of his philosophy in geography and sociology. I then turn to an exposition of Dewey’s metaphysics which are the heart of his philosophy. My discussion breaks his metaphysics into four parts: nature and continuity, contingency and change, situated sociality, and transaction. The subsequent section argues for Dewey’s distinction and value by arguing a particular implication of Dewey’s work for geography—a reconceptualization of place—and more general propositions about what a Dewey-informed geography would, at minimum, entail. A brief conclusion summarizes the Deweyan vision in the context of geographical inquiry. 相似文献
422.
A response to a recent paper by Barnes, arguing that the origins of geography’s quantitative revolution were not as monofocused as he suggests. 相似文献
423.
Artur?P.?DeditiusEmail author Martin?Reich Adam?C.?Simon Alexandra?Suvorova Jaayke?Knipping Malcolm?P.?Roberts Sergey?Rubanov Aaron?Dodd Martin?Saunders 《Contributions to Mineralogy and Petrology》2018,173(6):46
Magnetite from hydrothermal ore deposits can contain up to tens of thousands of parts per million (ppm) of elements such as Ti, Si, V, Al, Ca, Mg, Na, which tend to either structurally incorporate into growth and sector zones or form mineral micro- to nano-sized particles. Here, we report micro- to nano-structural and chemical data of hydrothermal magnetite from the Los Colorados iron oxide–apatite deposit in Chile, where magnetite displays both types of trace element incorporation. Three generations of magnetites (X–Z) were identified with concentrations of minor and trace elements that vary significantly: SiO2, from below detection limit (bdl) to 3.1 wt%; Al2O3, 0.3–2.3 wt%; CaO, bdl–0.9 wt%; MgO, 0.02–2.5 wt%; TiO2, 0.1–0.4 wt%; MnO, 0.04–0.2 wt%; Na2O, bdl–0.4 wt%; and K2O, bdl–0.4 wt%. An exception is V2O3, which is remarkably constant, ranging from 0.3 to 0.4 wt%. Six types of crystalline nanoparticles (NPs) were identified by means of transmission electron microscopy in the trace element-rich zones, which are each a few micrometres wide: (1) diopside, (2) clinoenstatite; (3) amphibole, (4) mica, (5) ulvöspinel, and (6) Ti-rich magnetite. In addition, Al-rich nanodomains, which contain 2–3 wt% of Al, occur within a single crystal of magnetite. The accumulation of NPs in the trace element-rich zones suggest that they form owing to supersaturation from a hydrothermal fluid, followed by entrapment during continuous growth of the magnetite surface. It is also concluded that mineral NPs promote exsolution of new phases from the mineral host, otherwise preserved as structurally bound trace elements. The presence of abundant mineral NPs in magnetite points to a complex incorporation of trace elements during growth, and provides a cautionary note on the interpretation of micron-scale chemical data of magnetite. 相似文献
424.
Sandra McLaren Malcolm W. Wallace Stephen J. Gallagher John A. Miranda Guy R. Holdgate Laura J. Gow Ian Snowball Per Sandgren 《Quaternary Science Reviews》2011,30(9-10):1086-1111
The Murray Basin is a low-lying but extensive intracratonic depocentre in southeastern Australia, preserving an extraordinary record of Late Neogene sedimentation. New stratigraphic and sedimentologic data allow the long-term evolution of the basin to be re-evaluated and suggest a significant role for: (1) tectonism in controlling basin evolution, and (2) progressive and step-wise climatic change beginning in the early Pleistocene. Tectonic change is associated with regional uplift, occurring at approximately the same rate from the early Pliocene until the present day, and possibly associated with changing mantle circulation patterns or plate boundary processes. This uplift led to the defeat and re-routing of the Murray River, Australia’s major continental drainage system. Key to our interpretation is recognition of timing relationships between four prominent palaeogeographic features – the Loxton-Parilla Sands strandplain, the Gambier coastal plain, palaeo megalake Bungunnia and the Kanawinka Escarpment. Geomorphic and stratigraphic evidence suggest that during the Early Pliocene the ancestral Murray River was located in western Victoria, flowing south along the Douglas Depression. Relatively small amounts of regional uplift (<200 m) defeated this drainage system, dramatically changing the palaeogeography of southeastern Australia and forming Plio-Pleistocene megalake Bungunnia. At its maximum extent Lake Bungunnia covered more than 50,000 km2, making it one of the largest known palaeo- or modern-lakes in an intracontinental setting. Magnetostratigraphic constraints suggest lake formation c. 2.4 Ma. The formation of Lake Bungunnia influenced the Pliocene coastal dynamics, depriving the coastline of a sediment source and changing the coastal system from a prograding strandline system to an erosional one. Erosion during this period formed the Kanawinka Escarpment, a palaeo sea-cliff and one of the most prominent and laterally extensive geomorphic features in southeastern Australia. Marine sediments c. 800 ka to c. 1.16 Ma represent the time of re-establishment of depositional coastal dynamics and of a permanent outlet for the Murray River. This age range is consistent with our best estimate of the age of the youngest Lake Bungunnia sediments and points towards an early Pleistocene age for the demise of the lake system. The youngest Lake Bungunnia sediment, present on a number of distinct terraces, suggests that progressive, step-wise climatic change played a role in the demise of the lake. However, in order for the ancestral Murray River system to have been able to breach the pre-existing tectonic dam, it is likely that tectonic change and/or temporarily enhanced discharge was also significant. This scenario indicates that the modern Murray River has only been in existence for at most 700 ka. 相似文献
425.
Wind Modulation of Dissolved Oxygen in Chesapeake Bay 总被引:1,自引:0,他引:1
Malcolm E. Scully 《Estuaries and Coasts》2010,33(5):1164-1175
A numerical circulation model with a simplified dissolved oxygen module is used to examine the importance of wind-driven ventilation
of hypoxic waters in Chesapeake Bay. The model demonstrates that the interaction between wind-driven lateral circulation and
enhanced vertical mixing over shoal regions is the dominant mechanism for providing oxygen to hypoxic sub-pycnocline waters.
The effectiveness of this mechanism is strongly influenced by the direction of the wind forcing. Winds from the south are
most effective at supplying oxygen to hypoxic regions, and winds from the west are shown to be least effective. Simple numerical
simulations demonstrate that the volume of hypoxia in the bay is nearly 2.5 times bigger when the mean wind is from the southwest
as compared to the southeast. These results provide support for a recent analysis that suggests much of the long-term variability
of hypoxia in Chesapeake Bay can be explained by variations in the summertime wind direction. 相似文献
426.
Tsuyoshi Iizuka Malcolm T. McCulloch Tsuyoshi Komiya Takazo Shibuya Kenji Ohta Haruka Ozawa Emiko Sugimura Kenneth D. Collerson 《Contributions to Mineralogy and Petrology》2010,160(6):803-823
Mt. Narryer and Jack Hills meta-sedimentary rocks in the Narryer Gneiss Complex of the Yilgarn Craton, Western Australia are
of particular importance because they yield Hadean detrital zircons. To better understand the tectonothermal history and provenance
of these ancient sediments, we have integrated backscattered scanning electron images, in situ U–Pb isotopic and geochemical
data for monazites from the meta-sediments. The data indicate multiple periods of metamorphic monazite growth in the Mt. Narryer
meta-sediments during tectonothermal events, including metamorphism at ~3.3–3.2 and 2.7–2.6 Ga. These results set a new minimum
age of 3.2 Ga for deposition of the Mt. Narryer sediments, previously constrained between 3.28 and ~2.7 Ga. Despite the significant
metamorphic monazite growth, a relatively high proportion of detrital monazite survives in a Fe- and Mn-rich sample. This
is likely because the high Fe and Mn bulk composition resulted in the efficient shielding of early formed monazite by garnet.
In the Jack Hills meta-sediments, metamorphic monazite growth was minor, suggesting the absence of high-grade metamorphism
in the sequence. The detrital monazites provide evidence for the derivation of Mt. Narryer sediments from ca. 3.6 and 3.3 Ga
granites, likely corresponding to Meeberrie and Dugel granitic gneisses in the Narryer Gneiss Complex. No monazites older
than 3.65 Ga have been identified, implying either that the source rocks of >3.65 Ga detrital zircons in the sediments contained
little monazite, or that >3.65 Ga detrital minerals had experienced significant metamorphic events or prolonged sedimentary
recycling, resulting in the complete dissolution or recrystallization of monazite. 相似文献
427.
Knowledge of fluvial sediment supply to the coastal sediment budget is important for the assessment of the impacts on coastal stability. Such knowledge is valuable for designing coastal engineering schemes and the development of shoreline management planning policies. It also facilitates understanding of the connection between rivers in the hinterland and adjoining coastal systems. Ghana's coast has many fluvial sediment sources and this paper provides the first quantitative assessments of their contributions to the coastal sediment budget. The methods use largely existing data and attempt to cover all of Ghana's significant coastal rivers. Initially work was hindered by insufficient direct measured data. However, the problem was overcome by the application of a regression approach, which provides an estimated sediment yield for non-gauged rivers based on data from gauged rivers with similar characteristics. The regression approach was effective because a regional coherence in behaviour was determined between those rivers, where direct measured data were available. The results of the assessment revealed that Ghana's coast is dissected by many south-draining rivers, stream and lagoons. These rivers, streams and lagoons supply significant amounts of sediment to coastal lowlands and therefore contribute importantly to beaches. Anthropogenic impoundment of fluvial sediment, especially the Akosombo dam on the Volta River, has reduced the total fluvial sediment input to the coast from about 71 × 106 m3/a before 1964 (pre-Akosombo dam) to about 7 × 106 m3/a at present (post-Akosombo dam). This sharp reduction threatened the stability of the east coast and prompted an expensive ($83 million) defence scheme to be implemented to protect 8.4 km-long coastline at Keta. Sections of Ghana's coast are closely connected to the hinterland through the fluvial sediment input from local rivers. Therefore, development in the hinterland that alters the fluvial sediment input from those local rivers could have significant effects on the coast. There is the need, therefore, to ensure that catchment management plans and coastal management plans are integrated or interconnected. 相似文献
428.
Malcolm Luxton 《新西兰海洋与淡水研究杂志》2013,47(3):497-504
Tangaroellus porosus, gen. nov., sp. nov., is described from three coastal localities in New Zealand. Its affinities with the family Rhodacaridae are discussed. 相似文献
429.
Malcolm E. Forster 《新西兰海洋与淡水研究杂志》2013,47(1):85-90
Patterns of ventilation, oxygen consumption (VO2), blood gas tensions (PaO2 and PaCO2) and pH were determined in shortfin eels (Anguilla australis schmidtii (Phillips)). At rest, shortfin eels (average weight 646.5 ± 64.5 g) had a VO2 of 20.4 ± 1.2 ml. kg‐1.h‐1 (n = 13) at 17.5 ± 0.2°c, with smaller fish having the highest metabolic rates. The frequency of ventilation was inversely proportional to body weight in both A. australis schmidtii and A. dieffenbachii. In air‐saturated water 10 eels exhibited periodic apnoea (mean duration 3.59 min); periods of ventilation were more variable in duration (mean 4.92 min). After 2.62 min of apnoea, the PaO2 of dorsal aortic blood had fallen from 9.12 to 1.91 kPa. Thus, although the blood has a high affinity for oxygen and the haemoglobins are 30% oxygen‐saturated at this low PaO2, the eel allows its blood to be significantly depleted in oxygen during apnoeic pauses at rest. When ventilating its gills at rest, PaO2 does not approach the PO2 of the inspired water. It is suggested that these features of respiration in eels result in a saving of metabolic costs involved in ventilation. The results are discussed in terms of the eel's ability to withstand hypoxic conditions. 相似文献
430.
Elizabeth G. Malcolm Amanda C. Ford Tara A. Redding Matthew C. Richardson Brianna M. Strain Scott W. Tetzner 《Journal of Atmospheric Chemistry》2009,63(3):221-234
Sea salt aerosol may be an important sink for reactive gaseous mercury (RGM) in the marine boundary layer, reducing ambient
RGM concentrations and transferring the mercury (Hg) to the oceans and coastal ecosystems. The goal of this study was to determine
the affinity of gaseous mercury for sea salt aerosol (SSA) by conducting adsorption experiments with sea salt-coated sampling
denuders. In the first set of experiments, ambient outdoor air was passed through denuders coated with either KCl, as in the
widely accepted method to sample RGM, or with NaCl, a primary component of sea salt aerosols. On the one sampling day in which
RGM was above the MDL, the NaCl coated denuders removed Hg from the ambient air, equivalent to 87% of the RGM in the air (as
determined by KCl denuders). For the second set of experiments HgCl2 generated in the laboratory was passed through denuders coated with KCl and either NaCl or sea salt. The NaCl denuders collected
an average of 99 ± 16% of the mercury that the KCl denuders collected. Newly coated sea salt denuders collected 88 ± 17% of
the amount of mercury that the KCl denuders collected, but interestingly the sea salt denuders capacity decreased with repeated
use. These experiments demonstrate that HgCl2, a major component of RGM has a strong affinity for NaCl and sea salt and is therefore likely to be scavenged by SSA. This
study adds to the growing evidence that RGM is scavenged by sea salt aerosols and therefore more quickly deposited to the
ocean and coastal environment. 相似文献