204,791 research outputs found
Theorising power and listening : the route to a culture of voice
No full textListening in early childhood education is more than the act of hearing; it is a processing of hearing, understanding and acting upon what is heard. While seemingly simple when written as this series of tasks, in reality it is a reciprocal process, involving a complex power-laden relationship between adults and children, or even between children. The relationship is framed by the social context within which the dialogue and communication (in a broad and not always verbal sense) occurs. This is not surprising when coming from the perspective that childhood is a social construction and lived experiences are unique (James et al., 1998). From this perspective, listening becomes a cultural process as part of everyday early childhood practice, which encompasses a relational and social pedagogy
Predicting the response of small-scale near-wall turbulence to large-scale outer motions
No full textThe paper deals with the question of how to determine – or “predict” - the near-wall-turbulence statistics from a Reynolds-number-independent, “universal”, small-scale signal, and the Reynolds-number-dependent large-scale outer motions in the log layer. An empirical model is proposed, which is intended to take into account the effect of “splatting”, not previously considered, thus offering an improved representation of the near-wall-turbulence field
Practitioner-enquiry : a reflexive method for playful pedagogy
No full textIn this chapter we are going to explore the productive learning associations we see between a practitioner enquiry approach to professional learning and playful pedagogy in the early years. In doing so we hope to show a complementary and facilitatory relationship that is evident in learning, tools and techniques used for research and dispositions that result for children and practitioners as researchers or participants in research projects. We will make clear the underlying assumptions of practitioner enquiry and what the implications of engaging in enquiry are in regards to an orientation towards play. Using real-life examples from early years settings to exemplify the discussion and ground this approach in practice, we will give guidance about the use of enquiry-based tools which have often been used to support professional learning. In particular, we will focus on the ways in which early childhood practices can support an approach to research that facilitates meaning and interpretation of data in playful spaces for learning. The basic premise behind this perspective is that practitioners in early childhood settings are already skilled researchers, unearthing and interpreting the intricacies in children’s play. This chapter suggests that it is important to harness those skills in order to explore children’s perspectives through play
Turbulent fluctuations above the buffer layer of wall-bounded flows
No full textThe behaviour of the velocity and pressure fluctuations in the logarithmic and outer layers of turbulent flows is analysed using spectral information and probability density functions from channel simulations at Reτ _2000. Comparisons are made with experimental data at higher Reynolds numbers. It is found, in agreement with previous investigations, that the intensity profiles of the streamwise and spanwise velocity components have logarithmic ranges that are traced to the widening spectral range of scales as the wall is approached. The same is true for the pressure, both theoretically and observationally, but not for the normal velocity or for the tangential stress cospectrum, although even those two quantities have structures with lengths of the order of several hundred times the wall distance. Because the logarithmic range grows longer as the Reynolds number increases, variables which are ‘attached’ in this sense scale in the buffer layer in mixed units. These results give strong support to the attached-eddy scenario proposed by Townsend (1976), but they are not linked to any particular eddy model. The scaling of the outer modes is also examined. The intensity of the streamwise velocity at fixed y/h increases with the Reynolds number. This is traced to the large-scale modes, and to an increased intensity of the ejections but not of the sweeps. Several differences are found between the outer structures of different flows. The outer modes of the spanwise and wall-normal velocities in boundary layers are stronger than in internal flows, and their streamwise velocities penetrate closer to the wall. As a consequence, their logarithmic layers are thinner, and some of their logarithmic slopes are different. The channel statistics are available electronically at http://torroja.dmt.upm.es/ftp/channels/
Can cell wall peroxidase activity explain the leaf growth response of Lolium temulentum L. during drought?
No full textIn two experiments, the effect has been investigated of a mild and a more prolonged drought on the spatial distribution of growth, epidermal cell lengths and cell wall peroxidase activities in the leaf elongation zone of the grass species Lolium temulentum L. In both experiments drought reduced the size of the elongation zone and local rates of elongation within it. Abrupt increases in cell wall-associated peroxidase activity occurred at or close to the position where elongation ceased in the leaf elongation zones of well-watered and mildly drought-stressed plants. More prolonged drought caused a 200–300% increase in the cell wallassociated peroxidase activity in the elongation zone only. The significant increase in the elongation zone cell wall peroxidase activity and its spatial variation provides evidence of a potentially causal role for cell wall-associated peroxidase in restricting cell expansion during drought
PODCAST#9 "Meet the team supporting teacher learning" : Dr Anna Beck, Prof Aileen Kennedy, Prof Kate Wall
No full textMeet the team supporting teacher learning. Dr. Anna Beck, Professor Aileen Kennedy and Professor Kate Wall discuss their Postgraduate Certificate in Supporting Teacher Learning and what makes for good teacher professional learning. They also recommend their go-to reading on the topic
Cell wall involvement in desiccation tolerance in the resurrection plant Craterostigma wilmsii
No full textBibliography: leaves 92-129.Resurrection plants have the unique capacity to revive from an air-dried state. In order to cope with desiccation, resurrection plants have to overcome a number of stresses, mechanical stress being one. This occurs when the cytoplasm shrinks creating tension between the plasma membrane and the cell wall. In leaves of the Craterostigma species, an extensive shrinkage occurs during drying as well as a considerable wall folding. It is thought that this folding is a well controlled process rather than a simple collapse and that the ability of the wall to fold is important for the viability of the tissues upon drying. The aim of this study was to characterize the cell wall architecture and composition in hydrated and dry leaves of C. wilmsii using microscopical and biochemical techniques. Calcium and hormone contents were also determined during drying. The development of anhydrous fixation for microscopy confirmed the important folding of the wall previously observed with chemical fixation. Using immunocytochemical techniques and a variety of well characterized antibodies, the nature and composition of wall polymers was investigated. There was nothing unusual in the wall composition of C. wilmsii leaves as compared with other dicotyledonous plants. The results show a significant increase of the hemicellulosic polysaccharide xyloglucan and of the unesterified pectins during drying with levels declining again during rehydration. In contrast no increase was observed in others polysaccharides such as ß (1-4) galactans and methylesterified pectins. Biochemical analysis allowed further characterization of cell wall composition of C. wilmsii. The data demonstrate marked changes in the pectic and hemicellulosic wall fraction from dry plants compared to hydrated ones. The most conspicuous change was a decrease in glucose content in the hemicellulose fraction of the dry plant. Together these findings show that dehydration causes important alteration of polysaccharides content in the cell wall of C. wilmsii. Such modifications might be involved in the modulation of the mechanical properties of the wall during dehydration. Furthermore calcium ions content was shown to increase in the cell wall of dry plants, this could also have a role in stabilizing the wall architecture. All these alterations might be under the control of auxin, an hormone whose content was shown to increase during dehydration
Off the wall: characterisation and exploitation of a cell wall-deficient life style in filamentous actinomycetes
No full textAlmost all bacteria are enveloped by a cell wall that provides cellular protection. In this thesis I show that some filamentous actinomycetes have a surprising natural ability to adopt a cell wall-deficient life style. The formation of these newly identified S-cells is a transient morphological adaptation in response to hyperosmotic stress conditions. In contrast, prolonged exposure to cell wall-targeting antibiotics or osmotic stress leads to the formation of so-called L-form cells, which are mutants that can proliferate indefinitely without their cell wall. The exciting properties of L-forms were used to discover a new cell-wall biosynthetic enzyme and to study enzyme secretion in the absence of a cell wall
An investigation of secondary flow in a turbine blade with end wall profiling
No full textSecondary flows have been long recognised as a significant form of loss mechanism in turbomachinery. They have a major influence over the performance of the blade rows since they cause unsteadiness in the mainstream flow. This consequently affects not only the mechanical integrity of the blades but also causes extra loss. This research is aimed to reduce secondary flows using a novel method; end wall profiling. Profile 2 end wall was designed by Rolls Royce pic. with improved design features compared to its predecessor, Profile 1 end wall. Profile 2 end wall was manufactured and tested using the test facility available at the University of Durham. The flow was measured at two different axial positions, together with end wall static measurements and flow visualisation. The inlet flow conditions were also checked for consistency. These results were analysed and compared to Profile 1 and Planar end wall profile results, which have been studied previously by Hartland [1999]. Profile 2 end wall achieved better secondary flow reduction compared to the Planar end wall. However Profile 1 end wall still proved to be better compared to both Profile 2 and the Planar end wall. This project has provided a thorough understanding of the various flow mechanisms in turbines and the available techniques in eliminating secondary flows. The application of end wall profiling has still shown potential in being a reliable method. It is also important that the flow physics is understood in detail to determine the shape of the end wall profile that will be effective
Identification and characterisation of the Arabidopsis thaliana cell wall proteome: unravelling novel cell wall proteins and new potential functions of the plant extracellular matrix
No full textThe application of the proteomic approach has facilitated efforts directed toward the mapping of the entire Arabidopsis cell wall proteome. Proteins were sequentially extracted from purified cell walls using 0.2 M CaC1(_2) followed by a urea buffer. The extracts were resolved via large format two dimensional polyacrylamide gel electrophoresis (2-D PAGE) and were visualised via Coomassie brilliant blue staining. The aim was to identify and characterise as many cell wall proteins as possible, with the hope of identifying novel cell wall proteins. Out of 325 spots visualised on the 2-D polyacrylamide gel, 144 gave a positive protein identification representing 104 different proteins. The identified proteins were divided into 3 categories. The first category included proteins that have been previously identified as plant cell wall proteins. The second category was designated to include novel cell wall proteins (hypothetical proteins) and the third category was made up of proteins, which had recognised functions, but had never hitherto been known to be secreted to the extracellular matrix. Among the identified novel cell wall proteins there were several that shared high homology with protein kinases. These proteins possessed all the characteristics of secreted polypeptides, such as the cleavable N-terminal signal peptide, and were found to lack both the transmembrane domain and the endoplasmic reticulum retention tetrapeptides (HDEL and KDEL). These observations suggested that, as in animal cells, plant cells had extracellular protein kinase activity (phosphorylation). This was supported by the recent discovery that plant cells secrete ATP to the extracellular matrix (Thomas et al., 2000). Verification of the occurrence of extracellular protein kinase activity was further strengthened by the identification of phosphorylated bona fide cell wall proteins and stress responses caused by the depletion extracellular ATP
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