83 research outputs found

    Demonstration of an ecdysteroid receptor in a cultured cell line of Drosophila melanogaster.

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    The restructuring of schooling in England: the responses of well-positioned Headteachers

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    Research to date about the English government’s policy to make schools independent of local authorities (LAs) has looked at the ‘macro’ level of national policy and at the ‘micro’ level of the institution. The study of which this article is a part, explores changes at the ‘meso’ level – the locality. The article analyses interviews in three LAs with 15 headteachers whose schools were well positioned locally. We sought to understand how and why they responded to the changing policy environment. We applied Bourdieu’s concepts of forms of capital to model the relationships between schools and to ground explanations of their responses as positioning themselves in the local field. The article develops this general approach by identifying the varieties of capital available and actually possessed. The most important was categorization as a result of the inspection process. Many of the headteachers felt impelled to lead their schools into various associations with other schools. Some individuals were becoming notably more powerful in their competition arenas. The power of these elite schools to further accumulate advantage and the withdrawal of the LA role as an arbiter of conflict between schools in the interests of the whole community are discussed

    The positions of primary and secondary schools in the English school field: a case of durable inequality

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    In interviews as part of a research study of structural reform in England, some tension between primary head teachers and their secondary peers was evident. This was symptomatic of a long-standing difference in status between the two phases. At a time when relations between stakeholders in local systems are subject to change, we seek to understand anew why that might be the case and how the tension we found was evidence of a current difference of power within interactions between representatives of the phases. We analyse differences of size, resources, workforce, pedagogy and history, and how they have resulted in different, and differently valued, practices and professional identities. We explore how attributes of the two phases have been counterposed and how, in complex interaction with wider discourses of politics, gender and age, this process has invested the differences with meanings and values that tend to relegate attributes associated with primary school. By focusing on the activation of cumulative inequality in interactions, we contribute a complementary perspective to studies of perceived relative status and highlight the implications for understanding school positioning in local arenas as the role of local authorities is reduced

    Genome-wide examination of the transcriptional response to ecdysteroids 20-hydroxyecdysone and ponasterone A in Drosophila melanogaster

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    <p>Abstract</p> <p>Background</p> <p>The 20-hydroxyecdysone (20E) hierarchy of gene activation serves as an attractive model system for studying the mode of steroid hormone regulated gene expression and development. Many structural analogs of 20E exist in nature and among them the plant-derived ponasterone A (PoA) is the most potent. PoA has a higher affinity for the 20E nuclear receptor, composed of the ecysone receptor (EcR) and Ultraspiracle proteins, than 20E and a comparison of the genes regulated by these hormones has not been performed. Furthermore, in <it>Drosophila </it>different cell types elicit different morphological responses to 20E yet the cell type specificity of the 20E transcriptional response has not been examined on a genome-wide scale. We aim to characterize the transcriptional response to 20E and PoA in <it>Drosophila </it>Kc cells and to 20E in salivary glands and provide a robust comparison of genes involved in each response.</p> <p>Results</p> <p>Our genome-wide microarray analysis of Kc167 cells treated with 20E or PoA revealed that far more genes are regulated by PoA than by 20E (256 vs 148 respectively) and that there is very little overlap between the transcriptional responses to each hormone. Interestingly, genes induced by 20E relative to PoA are enriched in functions related to development. We also find that many genes regulated by 20E in Kc167 cells are not regulated by 20E in salivary glands of wandering 3<sup>rd </sup>instar larvae and we show that 20E-induced levels of <it>EcR </it>isoforms <it>EcR-RA, ER-RC</it>, and <it>EcR-RD/E </it>differ between Kc cells and salivary glands suggesting a possible cause for the observed differences in 20E-regulated gene transcription between the two cell types.</p> <p>Conclusions</p> <p>We report significant differences in the transcriptional responses of 20E and PoA, two steroid hormones that differ by only a single hydroxyl group. We also provide evidence that suggests that PoA induced death of non-adapted insects may be related to PoA regulating different set of genes when compared to 20E. In addition, we reveal large differences between Kc cells and salivary glands with regard to their genome-wide transcriptional response to 20E and show that the level of induction of certain EcR isoforms differ between Kc cells and salivary glands. We hypothesize that the differences in the transcriptional response may in part be due to differences in the EcR isoforms present in different cell types.</p

    Education-work relations: Theoretical reference points for a research domain

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    Reversible Thermoassociation of Water-Soluble Polymers

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    International audienceIn various industrial fields, water soluble polymers are commonly used as thickening agents to control the reology of aqueous fluids. Nevertheless, their properties are weakened as the temperature increases. In order to overcome this problem, the concept of thermoassociativewater soluble polymers was developed. Such new amphilic systems can be obtained by grafting on an hydrophilic backbone, side chains which become non water soluble above a Lower Critical Solution Temperature (LCST). Semidilute solutions of these copolymers present reversible thickening properties as the temperature increases and reaches a critical value, close to the side chains LCST. This behaviour can be related to the agregation of the grafts above their LCST, into hydrophobic microdomains , inducing the formation of a three dimensional network. At higher temperature, the viscosity of the solution sheared at a constant rate reaches a maximum value. This can be interpreted in terms of the reorganisation of the physical network under shear, from a structure with mainly intermolecular associationsto a system with an increasing number of intramolecular associations . Owing to the diversity of water soluble polymers exhibiting a phase separation on heating (LCST), different thermoassociativecopolymers were realized [1] and [2], using either polyelectrolyte or neutral hydrophilic backbone. In the aim of applications of such systems in the oilfield industry, copolymers containing 2-acrylamido 2-methyl propane sulfonic acid (AMPS) were developed, using polyethylene oxide (PEO) as LCST grafts. A general description of their rheological behaviour will be given here. Their properties can be controlled either by varying the solution characteristic (polymer concentration, salinity, etc. ) or by modifying the chemical structure of the copolymer (grafting ratio, molecular weight of the backbone, etc. ). This rheological study showed the potentiality of the thermoassociativesystem, particularly towards the oilfield industry [3]. It is now possible to have thin cement slurries at ambient temperature and still viscous slurries at bottom hole temperature, as desired. The reversibility of the phenomenon joint to the shear thinning properties of the polymer solution are adding a plus for cement slurries and drilling fluids designs. The thermoassociative phenomenon was also studied by Small Angle Neutrons Scattering (SANS) using copolymers composed by a deuterated polyacrylate backbone and protonated polyethylene oxide grafts. The scattering properties of our system were studied by varying the temperature, the salinity and the polymer concentration of the solution. A good agreement between the microscopic characteristics of the solutions and their rheological properties was found

    Reversible Thermoassociation of Water-Soluble Polymers

    No full text
    In various industrial fields, water soluble polymers are commonly used as thickening agents to control the reology of aqueous fluids. Nevertheless, their properties are weakened as the temperature increases. In order to overcome this problem, the concept of thermoassociativewater soluble polymers was developed. Such new amphilic systems can be obtained by grafting on an hydrophilic backbone, side chains which become non water soluble above a Lower Critical Solution Temperature (LCST). Semidilute solutions of these copolymers present reversible thickening properties as the temperature increases and reaches a critical value, close to the side chains LCST. This behaviour can be related to the agregation of the grafts above their LCST, into hydrophobic microdomains , inducing the formation of a three dimensional network. At higher temperature, the viscosity of the solution sheared at a constant rate reaches a maximum value. This can be interpreted in terms of the reorganisation of the physical network under shear, from a structure with mainly intermolecular associationsto a system with an increasing number of intramolecular associations . Owing to the diversity of water soluble polymers exhibiting a phase separation on heating (LCST), different thermoassociativecopolymers were realized [1] and [2], using either polyelectrolyte or neutral hydrophilic backbone. In the aim of applications of such systems in the oilfield industry, copolymers containing 2-acrylamido 2-methyl propane sulfonic acid (AMPS) were developed, using polyethylene oxide (PEO) as LCST grafts. A general description of their rheological behaviour will be given here. Their properties can be controlled either by varying the solution characteristic (polymer concentration, salinity, etc. ) or by modifying the chemical structure of the copolymer (grafting ratio, molecular weight of the backbone, etc. ). This rheological study showed the potentiality of the thermoassociativesystem, particularly towards the oilfield industry [3]. It is now possible to have thin cement slurries at ambient temperature and still viscous slurries at bottom hole temperature, as desired. The reversibility of the phenomenon joint to the shear thinning properties of the polymer solution are adding a plus for cement slurries and drilling fluids designs. The thermoassociative phenomenon was also studied by Small Angle Neutrons Scattering (SANS) using copolymers composed by a deuterated polyacrylate backbone and protonated polyethylene oxide grafts. The scattering properties of our system were studied by varying the temperature, the salinity and the polymer concentration of the solution. A good agreement between the microscopic characteristics of the solutions and their rheological properties was found
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