Monitoring sediment transfer processes on the desert margin

LANDSAT Thematic Mapper and Multispectral Scanner data have been used to construct change detection images for three playas in south-central Tunisia. Change detection images have been used to analyze changes in surface reflectance and absorption between wet and dry season (intra-annual change) and between different years (inter-annual change). Change detection imagery has been used to examine geomorphological changes on the playas. Changes in geomorphological phenomena are interpreted from changes in soil and foliar moisture levels, differences in reflectances between different salt and sediments and the spatial expression of geomorphological features. Intra-annual change phenomena that can be detected from multidate imagery are changes in surface moisture, texture and chemical composition, vegetation cover and the extent of aeolian activity. Inter-annual change phenomena are divisible into those restricted to marginal playa facies (sedimentation from sheetwash and alluvial fans, erosion from surface runoff and cliff retreat) and these are found in central playa facies which are related to the internal redistribution of water, salt and sediment

The Plasmodium falciparum, Nima-related kinase Pfnek-4: a marker for asexual parasites committed to sexual differentiation

<b>Background</b> Malaria parasites undergo, in the vertebrate host, a developmental switch from asexual replication to sexual differentiation leading to the formation of gametocytes, the only form able to survive in the mosquito vector. Regulation of the onset of the sexual phase remains largely unknown and represents an important gap in the understanding of the parasite's complex biology. <b>Methods:</b> The expression and function of the Nima-related kinase Pfnek-4 during the early sexual development of the human malaria parasite Plasmodium falciparum were investigated, using three types of transgenic Plasmodium falciparum 3D7 lines: (i) episomally expressing a Pfnek-4-GFP fusion protein under the control of its cognate pfnek-4 promoter; (ii) episomally expressing negative or positive selectable markers, yeast cytosine deaminase-uridyl phosphoribosyl transferase, or human dihydrofolate reductase, under the control of the pfnek-4 promoter; and (iii) lacking a functional pfnek-4 gene. Parasite transfectants were analysed by fluorescence microscopy and flow cytometry. In vitro growth rate and gametocyte formation were determined by Giemsa-stained blood smears. <b>Results:</b> The Pfnek-4-GFP protein was found to be expressed in stage II to V gametocytes and, unexpectedly, in a subset of asexual-stage parasites undergoing schizogony. Culture conditions stimulating gametocyte formation resulted in significant increase of this schizont subpopulation. Moreover, sorted asexual parasites expressing the Pfnek-4-GFP protein displayed elevated gametocyte formation when returned to in vitro culture in presence of fresh red blood cells, when compared to GFP- parasites from the same initial population. Negative selection of asexual parasites expressing pfnek-4 showed a marginal reduction in growth rate, whereas positive selection caused a marked reduction in parasitaemia, but was not sufficient to completely abolish proliferation. Pfnek-4- clones are not affected in their asexual growth and produced normal numbers of stage V gametocytes. <b>Conclusions:</b> The results indicate that Pfnek-4 is not strictly gametocyte-specific, and is expressed in a small subset of asexual parasites displaying high rate conversion to sexual development. Pfnek-4 is not required for erythrocytic schizogony and gametocytogenesis. This is the first study to report the use of a molecular marker for the sorting of sexually-committed schizont stage P. falciparum parasites, which opens the way to molecular characterization of this pre-differentiated subpopulation

Care-experienced youth and positive development: An exploratory study into the value and use of leisure-time activities

Numerous youth development outcomes are thought to ensue from participation in ‘positive’ activities (including leisure activities), yet little is known about how care-experienced youth access and benefit from such activities. Underpinned by a positive youth development perspective and informed by the socio-ecological model, this study aimed to: (1) identify how care-experienced youth spent their leisure-time and what shaped their participation; and (2) explore how care-experienced youth think leisure-time activities contributed to their positive development

Locating the place and meaning of physical activity in the lives of young people from low-income, lone-parent families

Background: In the United Kingdom (UK), it is predicted that economic cuts and a subsequent increase in child poverty will affect those already on the lowest incomes and, in particular, those living in lone-parent families. As a result, the informal pedagogic encounters within the family that contribute to the development of physical activity-related values, beliefs and dispositions from a very early age will be affected. Therefore, it is vital that we gain an understanding of the place and meaning of physical activity in the lives of young people, as well as the informal pedagogic practices and the socio-cultural forces that influence individual agency. Purpose: Based on Bourdieu's key concepts, this paper explores the interplay of structural conditions and personal agency with regard to physical activity in the lives of young people from low-income, lone-parent families. Methods: This study reports on the voices of 24 participants (aged 11–14) from low-income, lone-parent families in the West Midlands, UK. These participants were engaged in paired, semi-structured interviews to explore issues of personal agency by listening to how they reported on their present lives, past experiences and future possibilities with regard to physical activity. All corresponding interview data were analysed using analytical induction. Findings: This paper suggests that young people exhibited diminished desires to engage in activity due to structural constraints of time, parents' work commitments and a lack of transport that resulted in engagement in sedentary alternatives. Informal pedagogic practices within these families were restricted due to the associated structural conditions of living in a lone-parent family. As such, young people's choice to not seek out physical activities when at home reflected a ‘taste for necessity’ resulting from a lack of cultural and economic capital, placing restrictions on physical activity opportunities that stemmed from their family doxa. Conclusions: To succeed in fostering dispositions and opportunities to participate in physical activity, we must engage with young people from low-income, lone-parent families from an early age. Certainly though, further consideration of the informal pedagogic practices within, and the demands on, lone-parent families is required when designing any intervention or policy that seeks to enhance their current circumstances and provide opportunities for engagement in a variety of contexts

Chemical pavement modifications to reduce ice adhesion

The formation of ice and snow on road pavement surfaces is a recurring problem, creating hazardous driving conditions, restricting public mobility as well as having adverse economic effects. It would be desirable to develop new and improved ways of modifying the pavement surface, to prevent or at least delay the build-up of ice and to weaken the pavement–ice bond, and making the ice which forms easier to remove. This development could lead to economic, environmental and safety benefits for winter service providers and road users. This paper describes how environmental scanning electron microscopy was used to examine the mechanism by which de-icing chemicals, added as a filler replacement to bituminous materials, can be transferred to the pavement surface. The paper assesses the potential for chemical modifications to reduce the adhesion between ice and the pavement surface by means of work of adhesion calculations, based on surface energy parameters and a new physical ice bond test. The paper also examines the influence that the chemical modifications have on the durability of the pavement surface course

Sport and physical activity in the lives of looked-after children: a ‘hidden group’ in research, policy and practice

Looked-after children are arguably one of the most disadvantaged groups in society and constitute a ‘hidden group’ in relation to sport and physical activity research, policy and practice. Research on looked-after children has explored the views of caregivers, practitioners and policy-makers who have often been asked to speak for children on their behalf. Through the use of the mosaic approach and innovative participatory methods, including peer interviewing, the purpose of this paper was to provide an insight into a new area of research in the field of sport and physical activity. As such, it reports on initial findings from a wider project with looked-after children that explores their sport and physical activity experiences. Specifically, it asks the following: (1) What are the sport and physical activity experiences of looked-after children? (2) What meanings and values do looked-after children ascribe to their engagement in sport and physical activity? Findings from the voices of four male looked-after children highlight that these young people used sport as a means to an end; to spend time with friends and develop stocks of social capital. However, due to changes in placement, they also experienced disrupted patterns of engagement coupled with additional institutional constraints that shaped access to sporting activities

‘I actually used to like PE, but not now’: Understanding care-experienced young people’s (dis)engagement with physical education

Young people’s experiences of, and (dis)engagement with, physical education has received considerable attention in recent years. Yet one ‘group’, care-experienced young people, remain ‘hidden’ within the prevailing literature. In light of their apparent invisibility within research, this novel, exploratory study seeks to gain some understanding of the factors associated with (dis)engagement from/with physical education among this youth population. In contrast to the few studies that explore the broader physical culture experiences of care-experienced youth that prioritise the voices of adults, this paper combines data from two studies to give voice to the experiences of four care-experienced young men in England, alongside those of key adults, namely residential staff, foster carers and physical education teachers. Data were derived from participatory research methods with the young people and semi-structured interviews with the adults who work with/for them. Drawing upon Bourdieu, principally his notions of field, habitus and capital, the findings suggest that these care-experienced young people are at a pedagogic disadvantage, since they are not as well positioned to access opportunities for learning and participation or develop, maintain and extend those skills and dispositions that are recognised as valued capital in physical education. Moreover, the changing room, as a sub-field of the broader physical education space, where bodies are particularly on display, may present obstacles for care-experienced young people’s engagement due to their prior experiences of physical and/or sexual abuse. This study therefore calls for further research exploring care-experienced young people’s experiences of physical education, teachers’ understandings of care-experienced youth, and how their pedagogic practice might shape (dis)engagement with physical education