Invertebrate food supply and breeding success of Mallards Anas platyrhynchos at flooded gravel quarries in southern Britain

Reproductive parameters of Mallard Anas platyrhynchos were investigated in relation to vegetative development, physical characteristics and invertebrate food abundance of a complex of flooded gravel quarries in southern Britain. Breeding pair density over the study area was particularly high with 2.2 pairs km(-1) of shoreline. Across all lakes breeding success was limited to an average of 0.9 ducklings fledged pair(-1), yet an associated study showed that very little of the mortality could be attributed to predation. The results of stepwise multiple regressions indicated that the availability of emerging insects was important in determining the breeding density and breeding success of Mallards rather than habitat structure. We suggest that the overall great availability of suitable nest-sites combined with the variable but unmeasured stocking densities of fish may explain the lack of the latter correlations.

Ballet-Granite

Live Performance, Szuper Gallery + Curtain Razors Dur: 50 mins NTSC HD 2011 Direction/Conception - Susanne Clausen, Pavlo Kerestey, Michele Sereda Performance Installation - Susanne Clausen, Pavlo Kerestey Performers - Jason Cawood, Susanne Clausen, Blair Fornwald, Morgan Garneau, John Hampton, Pavlo Kerestey, Michele Sereda Cave Video - Susanne Clausen and Pavlo Kerestey Sound scape - Szuper Gallery Voice - Michele Sereda Ballet Band - Billy Hughes, Trent Mailander and Otis Young Music - Dance of the Spirits - Danilo Villalta Technical Direction - Kenneth Young Stage Management - Paul Crepeau Sound Support - Jeff Morton Structural Design Consultant - James Phillips and Caragana Production Design Inc Set Assistants - Rebbeca Donison and Shelby Lowe Headress - Alla Sidorenko Costume consultation - Dean Renwick Documentation, Still - Carey Shaw, Szuper Gallery Documentation, Moving - Gabriel Yahyahkeekoot Administration + PR - Carey Shaw and the Mackenzie Art Gallery Poster Design - Rio Saxon Design Produced by Curtain Razors and Szuper Gallery in collaboration with the Mackenzie Art Gallery with the support of the Canada Council for the Arts, the Saskatchewan Arts Board and the City of Regina Arts Advisory Committee.

Edaphic influences on plant community adaptation in the Chiquibul forest of Belize

Edaphic variables figure significantly in plant community adaptations in tropical ecosystems but are often difficult to resolve because of the confounding influence of climate. Within the Chiquibul forest of Belize, large areas of Ultisols and Inceptisols occur juxtaposed within a larger zone of similar climate, permitting unambiguous assessment of edaphic contributions to forest composition. Wet chemical analyses, X-ray diffraction and X-ray fluorescence spectroscopy were employed to derive chemical (pH, exchangeable cations, CEC, total and organic C, total trace elements) and physical (texture, mineralogy) properties of four granite-derived Ustults from the Mountain Pine Ridge plateau and four limestone-derived Ustepts from the San Pastor region. The soils of these two regions support two distinct forests, each possessing a species composition reflecting the many contrasting physicochemical properties of the underlying soil. Within the Mountain Pine Ridge forest, species abundance and diversity is constrained by nutrient deficiencies and water-holding limitations imposed by the coarse textured, highly weathered Ultisols. As a consequence, the forest is highly adapted to seasonal drought, frequent fires and the significant input of atmospherically derived nutrients. The nutrient-rich Inceptisols of the San Pastor region, conversely, support an abundant and diverse evergreen forest, dominated by Sabal mauritiiformis, Cryosophila stauracantha and Manilkara spp. Moreover, the deep, fine textured soils in the depressions of the karstic San Pastor landscape collect and retain during the wet season much available water, thereby serving as refugia during particularly long periods of severe drought. To the extent that the soils of the Chiquibul region promote and maintain forest diversity, they also confer redundancy and resilience to these same forests and, to the broader ecosystem, of which they are a central part. (C) 2005 Elsevier B.V. All rights reserved.

Characterization of mineral surfaces using FIB and TEM: a case study of naturally weathered alkali feldspars

Using a focused ion beam (FIB) instrument, electron-transparent samples (termed foils) have been cut from the naturally weathered surfaces of perthitic alkali feldspars recovered from soils overlying the Shap granite, northwest England. Characterization of these foils by transmission electron microscopy (TEM) has enabled determination of the crystallinity and chemical composition of near-surface regions of the feldspar and an assessment of the influence of intragranular microtextures on the microtopography of grain surfaces and development of etch pits. Damage accompanying implantation of the 30 kV Ga+ ions used for imaging and deposition of protective platinum prior to ion milling creates amorphous layers beneath outer grain surfaces, but can be overcome by coating grains with > 85 nm of gold before FIB work. The sidewalls of the foil and feldspar surrounding original voids are also partially amorphized during later stages of ion milling. No evidence was found for the presence of amorphous or crystalline weathering products or amorphous "leached layers" immediately beneath outer grain surfaces. The absence of a leached layer indicates that chemical weathering of feldspar in the Shap soils is stoichiometric, or if non-stoichiometric, either the layer is too thin to resolve by the TEM techniques used (i.e., <=similar to 2.5 nm) or an insufficient proportion of ions have been leached from near-surface regions so that feldspar crystallinity is maintained. No evidence was found for any difference in the mechanisms of weathering where a microbial filament rests on the feldspar surface. Sub-micrometer-sized steps on the grain surface have formed where subgrains and exsolution lamellae have influenced the propagation of fractures during physical weathering, whereas finer scale corrugations form due to compositional or strain-related differences in dissolution rates of albite platelets and enclosing tweed orthoclase. With progressive weathering, etch pits that initiated at the grain surface extend into grain interiors as etch tubes by exploiting preexisting networks of nanopores that formed during the igneous history of the grain. The combination of FIB and TEM techniques is an especially powerful way of exploring mechanisms of weathering within the "internal zone" beneath outer grain surfaces, but results must be interpreted with caution owing to the ease with which artifacts can be created by the high-energy ion and electron beams used in the preparation and characterization of the foils.

The composition and crystallinity of the near-surface regions of weathered alkali feldspars

Our ability to identify thin non-stoichiometric and amorphous layers beneath mineral surfaces has been tested by undertaking X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) work on alkali feldspars from pH 1 dissolution experiments. The outcomes of this work were used to help interpret XPS and TEM results from alkali feldspars weathered for <10,000 years in soils overlying the Shap Granite (north-west England). The chemistry of effluent solutions indicates that silica-rich layers a few nanometers in thickness formed during the pH I experiments. These layers can be successfully identified by XPS and have lower Al/Si, Na/Si, K/Si and Ca/Si values than the outermost similar to 9 nm of unweathered controls. Development of Al-Si non-stoichiometry is coupled with loss of crystal structure to produce amorphous layers that are identifiable by TEM where >similar to 2.5 nm thick, whereas the crystallinity of albite is retained despite leaching of Na to depths of tens to hundreds on nanometers. Integration of XPS data over the outermost 6-9 nm of naturally weathered Shap feldspars shows that they have stoichiometric Al/Si and K/Si ratios, which is consistent with findings of previous TEM work on the same material that they lack amorphous layers. There is some XPS evidence for loss of K from the outermost couple of nanometers of Shap orthoclase, and the possibility of leaching of Na from albite to greater depths cannot be excluded using the XPS or TEM results. This study demonstrates that the leached layer model, as formulated from laboratory experiments, is inapplicable to the weathering of alkali feldspars within acidic soils, which is an essentially stoichiometric reaction. (C) 2008 Elsevier Ltd. All rights reserved.

New age estimates for the Palaeolithic assemblages and Pleistocene succession of Casablanca, Morocco

Marine and aeolian Quaternary sediments from Casablanca, Morocco were dated using the optically stimulated luminescence (OSL) signal of quartz grains. These sediments form part of an extensive succession spanning the Pleistocene, and contain a rich faunal and archaeological record, including an Acheulian lithic assemblage from before the Brunhes–Matayama boundary, and a Homo erectus jaw from younger cave deposits. Sediment samples from the sites of Reddad Ben Ali, Oulad J’mel, Sidi Abderhamane and Thomas Quarries have been dated, in order to assess the upper limits of OSL. The revision of previously measured mammalian tooth enamel electron spin resonance (ESR) dates from the Grotte des Rhinocéros, Oulad Hamida Quarry 1, incorporating updated environmental dose rate measurements and attenuation calculations, also provide chronological constraint for the archaeological material preserved at Thomas Quarries. Several OSL age estimates extend back to around 500,000 years, with a single sample providing an OSL age close to 1 Ma in magnetically reversed sediments. These luminescence dates are some of the oldest determined, and their reliability is assessed using both internal criteria based on stratigraphic consistency, and external lithostratigraphic, morphostratigraphic and independent chronological constraints. For most samples, good internal agreement is observed using single aliquot regenerative-dose OSL measurements, while multiple aliquot additive-dose measurements generally have poorer resolution and consistency. Novel slow-component and component-resolved OSL approaches applied to four samples provide significantly enhanced dating precision, and an examination of the degree of signal zeroing at deposition. A comparison of the OSL age estimates with the updated ESR dates and one U-series date demonstrate that this method has great potential for providing reliable age estimates for sediments of this antiquity. We consider the cause of some slight age inversion observed at Thomas Quarries, and provide recommendations for further luminescence dating within this succession.

Travail des enfants et droit à l’éducation au Burkina Faso: L’exemple de la carrière de Pissy

Cet article décrit et analyse le travail des enfants dans une carrière de granit d’un quartier de la ville de Ouagadougou, interroge le rapport entre l’école et le travail du point de vue des acteurs du site pour apprécier l’argument de la scolarisation comme solution alternative au travail des enfants. Les données proviennent d’une enquête réalisée dans le cadre de notre recherche doctorale au Burkina Faso, de février à avril 2009, dont la carrière de Pissy a été un des terrains d’enquête1. Les enquêtés sont constitués de parents et de leurs enfants âgés de moins de 16 ans ayant des trajectoires différentes : non scolarisés,scolarisés, déscolarisés et à la fois écoliers et travailleurs. Les personnes ont été choisies aléatoirement selon leur accord et disponibilité, en variant leur emplacement. L’approche choisie privilégie le point de vue des différents acteurs du site,l’analyse de leurs discours et l’observation de leurs pratiques de travail. La prise en compte du point de vue des enfants s’appuie sur la perspective théorique développée par James & Prout (1997), où les enfants sont des acteurs compétents dans la sphère du travail et de la vie sociale. L’article présente d’abord le processus d’institutionnalisation de l’école et la situation du travail des enfants au Burkina Faso, puis décrit les logiques autour du travail des enfants dans la carrière en montrant que celui-ci n’est pas seulement lié à la nécessité économique. Enfin, il confronte les alternatives au travaildes enfants invoquées par les enfants et leurs parents aux solutions d’éducation proposées par l’état et la société civile. This article is about a particular case of children in working situation: children crushing the granite in the quarry of Pissy. Their working conditions are considered as dangerous by national and international legal texts. This article aims to grasp the experience of children who work in this frame in order to test the hypothesis according to which schooling would be an effective tool of struggle against child labour. The fieldwork reveals that child labour in the quarry is not only guided by economic aspects. The wish of the parents (and of some children and teenagers) to find another job for working children reopen the debate on “the right to work” for children.