CHILDREN'S PERCEPTION OF A DOWNTOWN SHOPPING CENTER

This paper offers an exploratory investigation of the effects of a child's age on three behavioral constructs (awareness space, activity space, and attitude) concerning a downtown shopping center in Bristol, England. The data are elicited from three samples of Bristol school children defined according to age and are analyzed using statistical inferential procedures. The results disclose that awareness space and activity space consistently increase with age. In addition, attitudinal responses to specific features of the shopping center exhibit a gradual change over a long-term period.     

Preliminary evaluation of the occurrence of herbicides and PAHs in the Wet Tropics region of the Great Barrier Reef, Australia, using passive samplers

The proximity of the Great Barrier Reef (GBR) Marine Park to areas of intensive agriculture and increasing urbanisation places the park under potential threat of contamination by land-based pollutants. Passive samplers were deployed at inshore reef and river mouth sites in the Wet Tropics region of the GBR during a dry and a wet season to measure levels of land-based organic pollutants in this environment. Two types of passive sampling devices were deployed: (i) a polar sampler, which can be used to monitor polar herbicides and (ii) semipermeable membrane devices (SPMDs) which sequester more hydrophobic compounds (e.g. PAHs, chlorpyrifos). Herbicides (diuron, simazine, atrazine, hexazinone and/or flumeturon) were detected at low concentrations (ng L⁻¹) at all sites sampled and in both seasons. Chlorpyrifos was not detected while PAHs were present in SPMDs at levels below limits of detection. The results show that the GBR environment does contain low levels of organic pollutants and that passive sampling provides a sensitive monitoring tool for measuring waterborne organic pollutants.     

Evaluation of an ensemble of Arctic regional climate models: spatiotemporal fields during the SHEBA year

Simulations of eight different regional climate models (RCMs) have been performed for the period September 1997–September 1998, which coincides with the Surface Heat Budget of the Arctic Ocean (SHEBA) project period. Each of the models employed approximately the same domain covering the western Arctic, the same horizontal resolution of 50 km, and the same boundary forcing. The models differ in their vertical resolution as well as in the treatments of dynamics and physical parameterizations. Both the common features and differences of the simulated spatiotemporal patterns of geopotential, temperature, cloud cover, and long-/shortwave downward radiation between the individual model simulations are investigated. With this work, we quantify the scatter among the models and therefore the magnitude of disagreement and unreliability of current Arctic RCM simulations. Even with the relatively constrained experimental design we notice a considerable scatter among the different RCMs. We found the largest across-model scatter in the 2 m temperature over land, in the surface radiation fluxes, and in the cloud cover which implies a reduced confidence level for these variables. An erratum to this article can be found at     

Sinton crater, Mars: Evidence for impact into a plateau icefield and melting to produce valley networks at the Hesperian-Amazonian boundary

The majority of martian valley networks are found on Noachian-aged terrain and are attributed to be the result of a ‘warm and wet’ climate that prevailed early in Mars' history. Younger valleys have been identified, though these are largely interpreted to be the result of localized conditions associated with the melting of ice from endogenic heat sources. Sinton crater, a 60 km diameter impact basin in the Deuteronilus Mensae region of the dichotomy boundary, is characterized by small anastomosing valley networks that are located radial to the crater rim. Large scale deposits, interpreted to be the remains of debris covered glaciers, have been identified in the area surrounding Sinton, and our observations have revealed the occurrence of an ice rich fill deposit within the crater itself. We have conducted a detailed investigated into the Sinton valley networks with all the available remote data sets and have dated their formation to the Amazonian/Hesperian boundary. The spatial and temporal association between Sinton crater and the valley networks suggest that the impact was responsible for their formation. We find that the energy provided by an asteroid impact into surficial deposits of snow/ice is sufficient to generate the required volumes of melt water needed for the valley formation. We therefore interpret these valleys to represent a distinct class of martian valley networks. This example demonstrates the potential for impacts to cause the onset of fluvial erosion on Mars. Our results also suggest that periods of glacial activity occurred throughout the Amazonian and into the Hesperian in association with variations in spin orbital parameters.     

Investigation of acidic dissolution of mixed clays between pH 1.0 and −3.0 using Si and Al X-ray absorption near edge structure

Although widely investigated in relation to acid mine drainage systems at pH > 1.0, we know little about the impact of sulfuric acid (H₂SO₄) on the geochemistry and mineralogy of clays at pH < 1.0 (including negative pH values). Thus, laboratory batch experiments were conducted on three mixed clay samples with different mass ratios of phyllosilicates (smectite, illite, and kaolinite) to investigate the impact of H₂SO₄ from pH 1.0 to −3.0 for exposure periods of 14, 90, 180, and 365 days. Si and Al K- and L_2,3-edge X-ray absorption near edge structure (XANES) spectroscopy were employed on these samples to determine the chemical and structural changes that occur during acidic dissolution of phyllosilicates that cannot be distinguished using X-ray diffraction analyses. A series of silicate, phyllosilicate, and Al-bearing standard compounds were also studied to provide an explanation for the observed changes in the clay samples. The Si XANES results indicated the preferential dissolution of the phyllosilicates (pH ? 1.0, t ? 14 d), the persistence of quartz even at pH ? −3.0 and t ? 365 d, and the formation of an amorphous silica-like phase that was confined to the surface layer of the altered clay samples at pH ? 0.0 and t ? 90 d). Al XANES results demonstrated dissolution of Al-octahedral layers (pH ? 1.0, t ? 14 d), the persistence of four-fold relative to six-fold coordinated Al, and the precipitation of an Al-SO₄-rich phase (pH ? −1.0, t ? 90 d). An existing conceptual model of phyllosilicate dissolution under extremely acidic conditions was modified to include the results of this study.     

Globalising initiatives for gender equality and poverty reduction: Exploring ‘failure’ with reference to education and work among urban youth in The Gambia and Ghana

This paper focuses on what observers have perceived to be a failure of development leading to a ‘crisis of youth’ as increasing numbers of young people find it more difficult to gain education, access to health, a job and meet standard of living aspirations. For some, a possible escape is offered by migration to Europe, the United States or Australia, often illegally. For those remaining behind, however, international development agencies offer a ‘globalisation of solutions’ to employment, gender inequality and poverty through the millennium development goals and the programmes to attain them. In this paper we do not take the failures of development at face value but look at local contexts to present a more complex picture of the relation between education, work and social life. Based on fieldwork conducted in urban areas of The Gambia and Ghana, we argue that rather than education as a catch-all solution we need to give more attention to the costs incurred by and for young people in pursuing education and training, to the operation of and actual opportunities in labour markets, and to patterns of gender socialisation which give women limited scope to exercise agency. This paper explores key gender dimensions of work and education among low-income urban youth noting that despite on-going efforts to increase young women’s enrolment in schools and access to employment, gender inequalities have been far from eradicated. Our field interviews reveal how social expectations that women should perform the bulk of reproductive labour in their youth as well as in adulthood and constraints placed on young women’s personal freedom in respect of their social relationships reduce time dedicated to education and establish fewer contacts relevant to securing paid employment. The result is for men to end up with more educational qualifications, more skills, and higher-paying jobs, even if unemployment among young people in general remains a major problem.     

Zircon Hf Isotopic Evidence for Mixing of Crustal and Silicic Mantle-derived Magmas in a Zoned Granite Pluton, Eastern Australia

Zircon Hf isotopic data from a zoned pluton of the Moonbi supersuite,New England batholith, eastern Australia, are consistent withmagma mixing between two silicic melts, each derived from isotopicallydistinct sources. Although zircons from three zones within theWalcha Road pluton give a U–Pb crystallization age of249 ± 3 Ma, zircon populations from each zone have arange in _Hf. Zircons from the mafic hornblende–biotitemonzogranite pluton margin and intermediate zones have _Hf +5to +11, whereas those from the more felsic centre of the plutonhave _Hf +7 to +16, representing a total variation of 11 _Hfunits. The Lu–Hf depleted mantle model ages range from650 to 250 Ma, with the younger zircons present only in thefelsic pluton centre. The variation in _Hf indicates the involvementof silicic melts from at least two sources, one a crustal componentwith a Neoproterozoic model age and the other a primitive mantle-derivedcomponent with model ages similar to the U–Pb crystallizationage of the pluton. The zircons reflect the isotopic compositionsof the different proportions of crustal-derived silicic melt,relative to mantle-derived silicic melt, between melt generationand final pluton construction. The Walcha Road pluton is consideredto have formed by incremental assembly of progressively morefelsic melt batches resulting from mixing, replenishment andcrystal–melt separation, with final pluton constructioninvolving mechanical concentration as zones of crystal mush.The zoned pluton and, more broadly, the Moonbi supersuite provideexamples of magma mixing by which the more silicic units havemore juvenile isotopic compositions as a result of increasingproportions of residual melt from basalt fractionation, relativeto crustal partial melt. KEY WORDS: Australia; granite magma mixing; zircon; zoned pluton; Hf isotopes     

The effect of target properties on crater morphology: Comparison of central peak craters on the Moon and Ganymede

Abstract— We examine the morphology of central peak craters on the Moon and Ganymede in order to investigate differences in the near‐surface properties of these bodies. We have extracted topographic profiles across craters on Ganymede using Galileo images, and use these data to compile scaling trends. Comparisons between lunar and Ganymede craters show that crater depth, wall slope and amount of central uplift are all affected by material properties. We observe no major differences between similar‐sized craters in the dark and bright terrain of Ganymede, suggesting that dark terrain does not contain enough silicate material to significantly increase the strength of the surface ice. Below crater diameters of ?12 km, central peak craters on Ganymede and simple craters on the Moon have similar rim heights, indicating comparable amounts of rim collapse. This suggests that the formation of central peaks at smaller crater diameters on Ganymede than the Moon is dominated by enhanced central floor uplift rather than rim collapse. Crater wall slope trends are similar on the Moon and Ganymede, indicating that there is a similar trend in material weakening with increasing crater size, and possibly that the mechanism of weakening during impact is analogous in icy and rocky targets. We have run a suite of numerical models to simulate the formation of central peak craters on Ganymede and the Moon. Our modeling shows that the same styles of strength model can be applied to ice and rock, and that the strength model parameters do not differ significantly between materials.     

Interannual variability in glacier contribution to runoff from a high‐elevation Andean catchment: understanding the role of debris cover in glacier hydrology

We present a field‐data rich modelling analysis to reconstruct the climatic forcing, glacier response, and runoff generation from a high‐elevation catchment in central Chile over the period 2000–2015 to provide insights into the differing contributions of debris‐covered and debris‐free glaciers under current and future changing climatic conditions. Model simulations with the physically based glacio‐hydrological model TOPKAPI‐ETH reveal a period of neutral or slightly positive mass balance between 2000 and 2010, followed by a transition to increasingly large annual mass losses, associated with a recent mega drought. Mass losses commence earlier, and are more severe, for a heavily debris‐covered glacier, most likely due to its strong dependence on snow avalanche accumulation, which has declined in recent years. Catchment runoff shows a marked decreasing trend over the study period, but with high interannual variability directly linked to winter snow accumulation, and high contribution from ice melt in dry periods and drought conditions. The study demonstrates the importance of incorporating local‐scale processes such as snow avalanche accumulation and spatially variable debris thickness, in understanding the responses of different glacier types to climate change. We highlight the increased dependency of runoff from high Andean catchments on the diminishing resource of glacier ice during dry years.