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Lydia Kiroff 《Urban geography》2017,38(10):1573-1602
Auckland is New Zealand’s largest city with the largest concentration of creative sector employment and businesses in the country. This paper examines the spatial distribution of firms in the design creative subsector across the Auckland Region and in inner Auckland and ascertains the key determinants of firm location. The macrolevel findings indicate that the architectural and specialized design firms have similar spatial distribution patterns across the Auckland Region, while the advertising subsector demonstrates an extreme tendency toward spatial concentration only in inner Auckland. All three subsectors have a strong propensity to clustering within inner Auckland; however, one CBD (Central Business District) fringe area, Parnell outperforms the rest. The microlevel findings reveal hybridized creative clusters of uneven density. Parnell’s unique brand and place-specific characteristics were the key determinants of firm location which led to the spontaneous collocation of firms. These location decisions had the unintended consequence of creating agglomeration economies. 相似文献
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Arsenic speciation in Mono Lake, California: Response to seasonal stratification and anoxia 总被引：1，自引：0，他引：1
James T. Hollibaugh Steve Carini Robert Jellison Gary LeCleir Lydia Vasquez 《Geochimica et cosmochimica acta》2005,69(8):1925-1937
Mono Lake is a closed-basin, alkaline, hypersaline lake located at the western edge of the Great Basin in eastern California. We studied the distribution of arsenic (As) species in the water column of Mono Lake between February and November, 2002. This period captured the seasonal progression from winter mixing, through summer thermal stratification, to autumn overturn. Arsenic speciation was determined by ion chromatography-inductively coupled-plasma-mass spectrometry of samples preserved in the field by flash-freezing in liquid nitrogen. We found that arsenic speciation was dominated (>90%) by arsenate when oxygen was detectable. Once levels fell below 6 μmol/L O2, arsenic speciation shifted to dominance by reduced species. Arsenate and arsenite co-occurred in a transition zone immediately below the base of the oxycline and low but significant concentrations of arsenate were occasionally detected in sulfidic hypolimnion samples. Thio-arsenic species were the dominant form of As found in sulfidic waters. Maxima of thio-arsenic species with stoichiometries consistent with mono-, di- and trithio-arsenic occurred in succession as sulfide concentration increased. A compound with a stoichiometry consistent with trithio-arsenic was the dominant As species (∼50% of total As) in high sulfide (2 mmol/L) bottom water. Lower concentrations of total As in bottom water relative to surface water suggest precipitation of As/S mineral phases in response to sulfide accumulation during prolonged anoxia. 相似文献
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Srgio Luiz Martins Pereira Lydia Maria Lobato Juliano Efigênio Ferreira Eduardo Csar Jardim 《Ore Geology Reviews》2007,32(3-4):571
The orogenic banded iron formation (BIF)-hosted Au mineralization at São Bento is a structurally-controlled, hydrothermal deposit hosted by Archean rocks of the Rio das Velhas greenstone belt, Quadrilátero Ferrífero region, Brazil. The deposit has reserves of 14.3 t Au and historical (underground) production of 44.6 t Au between 1987 and 2001. The oxide-facies São Bento BIF is mineralized at its lower portion, where in contact with carbonaceous, pelitic schists, particularly in the proximity of sulfide-bearing quartz veins. Shear-related Au deposition is associated with the pervasive, hydrothermal sulfidation (mainly arsenopyrite) of the Fe-rich bands of the São Bento BIF. Auriferous, sulfide- and quartz-rich zones represent proximal alteration zones. They are enveloped by ankerite-dominated haloes, which reflect progressive substitution of siderite and magnetite within the BIF by ankerite and pyrrhotite, respectively. The São Bento BIF was intensely and extensively deformed, first into open, upright folds that evolved into tight, asymmetric, isoclinal folds. The inverse limb of these folds attenuated and gave way to sheath folds and the establishment of ductile thrusts. Mineralized horizons at São Bento result from early structural modifications imposed by major transcurrent and thrusts faults, comprising the Conceição, Barão de Cocais and São Bento shear zones. Dextral movement on the SW–NE-directed Conceição shear zone may have generated splays at a compressional side-stepping zone, such as the São Bento shear zone, which is the structural locus for the São Bento gold mineralization. Relaxation of the Conceição shear zone under more brittle conditions resulted in the development of dilatational zones where gold–sulfide–quartz veins formed. These structures are considered to have been generated in the Archean. Geochronological data are scarce, with Pb–Pb analyses of refractory arsenopyrite and pyrite from bedded and remobilized ore plotting on a single-stage growth curve at 2.65 Ga. A later compressional, ductile deformation of unknown age overprinted, rotated and flattened the original, N60E-directed structure of the whole rock succession, with development of planar and linear fabrics that appear similar to Proterozoic-aged structures. Fluid inclusion studies indicate low salinity, aqueous fluids, with or without CO2 and/or CH4, with extremely variable CO2/CH4 ratios, of probable metamorphic origin. Fluid evolution shows a paragenetic decrease in the carbonic phase from 10–15% to 5%, and increase in the H2O/(CO2 + CH4) and CO2/CH4 ratios, suggesting important interaction with carbonaceous sediment. Trapping conditions indicate a temperature of 300 °C at 3.2 kbar. 相似文献
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Understanding the temporal and spatial variability of water sources within a basin is vital to our ability to interpret hydrologic controls on biogeochemical processes and to manage water resources. Water stable isotopes can be used as a tool to determine geographic and seasonal sources of water at the basin scale. Previous studies in the Coastal Range of Oregon reported that the variation in the isotopic signatures of surface water did not conform to the commonly observed “elevation effect,” which exhibits a trend of increasing isotopic depletion with rising elevation. The primary purpose of this research is to investigate the mechanisms governing seasonal and spatial variations in the isotopic signature of surface waters within the Marys River Basin, located in the leeward side of the Oregon Coastal Range. Surface water and precipitation samples were collected every 2–3 weeks for isotopic analysis for 1 year. Our results confirmed the lack of elevational variation of surface water isotopes within this leeward basin. Although we find elevational variation in precipitation in the eastern portion of the watershed, this elevation effect is counteracted by rainout with distance from the Pacific coast. In addition, we found significant variation in surface water isotope values between catchments underlain predominantly by basalt or sandstone. The degree of separation was strongest during the summer when low flows reflect deeper groundwater sources. This indicates that baseflow within streams drained by each lithology is being supplied from two distinctly separate water sources. In addition, the flow of the Marys River is dominated by water originating from the sandstone water source, particularly during the low‐flow summer months. We interpreted that the difference in water source results from sandstone catchments having highly fractured geology or locally tipping to the east facilitating cross‐basin water exchange from the windward to the leeward side of the Coast Range. Our results challenge topographic derived watershed boundaries in permeable sedimentary rocks; highlighting the overwhelming importance of underlying geology. 相似文献
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Overview of eutrophication indicators to assess environmental status within the European Marine Strategy Framework Directive 总被引：1，自引：0，他引：1
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Terrestrial biological atmospheric carbon dioxide removal (BCDR) through bioenergy with carbon capture and storage (BECS), afforestation/reforestation, and forest and soil management is a family of proposed climate change mitigation strategies. Very high sequestration potentials for these strategies have been reported, but there has been no systematic analysis of the potential ecological limits to and environmental impacts of implementation at the scale relevant to climate change mitigation. In this analysis, we identified site-specific aspects of land, water, nutrients, and habitat that will affect local project-scale carbon sequestration and ecological impacts. Using this framework, we estimated global-scale land and resource requirements for BCDR, implemented at a rate of 1 Pg C y?1. We estimate that removing 1 Pg C y?1 via tropical afforestation would require at least 7?×?106 ha y?1 of land, 0.09 Tg y?1 of nitrogen, and 0.2 Tg y?1 of phosphorous, and would increase evapotranspiration from those lands by almost 50 %. Switchgrass BECS would require at least 2?×?108 ha of land (20 times U.S. area currently under bioethanol production) and 20 Tg y?1 of nitrogen (20 % of global fertilizer nitrogen production), consuming 4?×?1012?m3 y?1 of water. While BCDR promises some direct (climate) and ancillary (restoration, habitat protection) benefits, Pg C-scale implementation may be constrained by ecological factors, and may compromise the ultimate goals of climate change mitigation. 相似文献
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Atmospheric models of He-peculiar stars: synthetic He I line profiles and absolute visual magnitudes
Rodolfo Vallverdú Lydia Cidale René Rohrmann Adela Ringuelet 《Astrophysics and Space Science》2014,352(1):95-102
We analyze the influence of magnetic pressure effects on the atmospheric structure of B peculiar type stars, as well as, on the emergent He?I line profiles and absolute visual magnitudes. We consider a photosphere in local thermodynamic and hydrostatic equilibrium. The hydrostatic equilibrium equation is modified to include the Lorentz force. Atomic occupational numbers are computed in LTE considering non-ideal effects in the gas equation of state. We depict the influence of a magnetic field on local He?I line profiles and discuss the effects of the helium abundance in magnetic B-type stars. The Lorentz force might explain local variations up to 7 % in the equivalent width of helium lines, while local enhancements of He chemical abundances would produce larger changes. To analyze the line variations in real stars we computed the net contribution of a bipolar magnetic field over the stellar disk. The resulting disk-averaged magnetic field predicts variations with the rotation phase up to 2–3 % in the line EWs for a dipolar magnetic field of 1000 G. 相似文献
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Lydia A. Olaka Eric O. Odada Martin H. Trauth Daniel O. Olago 《Journal of Paleolimnology》2010,44(2):629-644
Sequences of paleo-shorelines and the deposits of rift lakes are used to reconstruct past climate changes in East Africa.
These recorders of hydrological changes in the Rift Valley indicate extreme lake-level variations on the order of tens to
hundreds of meters during the last 20,000 years. Lake-balance and climate modeling results, on the other hand, suggest relatively
moderate changes in the precipitation-evaporation balance during that time interval. What could cause such a disparity? We
investigated the physical characteristics and hydrology of lake basins to resolve this difference. Nine closed-basin lakes,
Ziway-Shalla, Awassa, Turkana, Suguta, Baringo-Bogoria, Nakuru-Elmenteita, Naivasha, Magadi-Natron, Manyara, and open-basin
Lake Victoria in the eastern branch of the East African Rift System (EARS) were used for this study. We created a classification
scheme of lake response to climate based on empirical measures of topography (hypsometric integral) and climate (aridity index).
With reference to early Holocene lake levels, we found that lakes in the crest of the Ethiopian and Kenyan domes were most
sensitive to recording regional climatic shifts. Their hypsometric values fall between 0.23–0.29, in a graben-shaped basin,
and their aridity index is above unity (humid). Of the ten lakes, three lakes in the EARS are sensitive lakes: Naivasha (HI
= 0.23, AI = 1.20) in the Kenya Rift, Awassa (HI = 0.23, AI = 1.03) and Ziway-Shalla (HI = 0.23, AI = 1.33) in the Main Ethiopian
Rift (Main Ethiopian Rift). Two lakes have the graben shape, but lower aridity indices, and thus Lakes Suguta (HI = 0.29,
AI = 0.43) and Nakuru-Elmenteita (HI = 0.30, AI = 0.85) are most sensitive to local climate changes. Though relatively shallow
and slightly alkaline today, they fluctuated by four to ten times the modern water depth during the last 20,000 years. Five
of the study lakes are pan-shaped and experienced lower magnitudes of lake level change during the same time period. Understanding
the sensitivity of these lakes is critical in establishing the timing or synchronicity of regional-scale events or trends
and predicting future hydrological variations in the wake of global climate changes. 相似文献