162 research outputs found

    Adsorption of colloidal particles in the presence of external field

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    We present a new class of sequential adsorption models in which the adsorbing particles reach the surface following an inclined direction (shadow models). Capillary electrophoresis, adsorption in the presence of a shear or on an inclined substrate are physical manifestations of these models. Numerical simulations are carried out to show how the new adsorption mechanisms are responsible for the formation of more ordered adsorbed layers and have important implications in the kinetics, in particular modifying the jamming limit.Comment: LaTex file, 3 figures available upon request, to appear in Phys.Rev.Let

    Non-Relativistic Spacetimes with Cosmological Constant

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    Recent data on supernovae favor high values of the cosmological constant. Spacetimes with a cosmological constant have non-relativistic kinematics quite different from Galilean kinematics. De Sitter spacetimes, vacuum solutions of Einstein's equations with a cosmological constant, reduce in the non-relativistic limit to Newton-Hooke spacetimes, which are non-metric homogeneous spacetimes with non-vanishing curvature. The whole non-relativistic kinematics would then be modified, with possible consequences to cosmology, and in particular to the missing-mass problem.Comment: 15 pages, RevTeX, no figures, major changes in the presentation which includes a new title and a whole new emphasis, version to appear in Clas. Quant. Gra

    Remembering, Reflecting, Returning: A Return to Professional Practice Journey Through Poetry, Music and Images:A Return to Professional Practice Journey Through Poetry, Music and Images

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    <p>Our composition brings together poetry, music, images and personal narratives based around the experiences of an occupational therapist, Karen, who following a family career break, returned to her profession. Our work demonstrates collaborative research practices and illuminates our experiences and journeying as practitioner-artists/researchers/teachers.</p> <p>This autoethnographic inquiry employs bricolage, drawing on theory and hybridized methods, inspired by the notion of ‘returning to practice’. The conversations of Karen and Katherine (mentee and mentor) as qualitative data, analyzed, interpreted and made accessible through poetry and images – along with Peter’s musical and autobiographical compositions – explore possibilities to re-examine and share alternative avenues of scholarship and theoretical understanding, not least in redefining what contribution to knowledge that artistic processes and ‘artwork’ makes methodologically, pedagogically, aesthetically, and therapeutically. Our intention is to engage the reader-viewer-listener to (re)think, take notice, disrupt, re-examine and extend personal meanings about return to practice journeys, enabling each of us to benefit and be (re)inspired.</p> <p>We recast aspects of ‘knowing and experience’ metaphorically, to consider and express our sense of being and becoming in the world. Importantly, we seek to explore how arts informed ways of knowing and learning about the self and other can serve to enhance our students/researchers/practitioners learning experiences.</p

    How Sensory Experiences Affect Adolescents with an Autistic Spectrum Condition within the Classroom

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    Sensory processing difficulties are consistently reported amongst individuals with an autistic spectrum condition (ASC); these have a significant impact on daily functioning. Evidence in this area comes from observer reports and first-hand accounts; both have limitations. The current study used the Adolescent/Adult Sensory Profile (AASP; Brown and Dunn in The Adolescent/Adult Sensory Profile: self questionnaire. Pearson, 2002a), and a qualitative questionnaire to investigate sensory issues in school children with ASC. The AASP found that the participants’ mean scores were outside normal parameters. Participants reported difficulties in at least one sensory domain, with hearing affecting them the most. Content analysis revealed sensory sensitivity to affect the participant’s learning and that sensory experiences were largely negative. Results suggest that schools need to create sensory profiles for each individual with ASC

    Decomposers and root feeders interactively affect plant defence in Sinapis alba

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    Aboveground herbivory is well known to change plant growth and defence. In contrast, effects of soil organisms, acting alone or in concert, on allocation patterns are less well understood. We investigated separate and combined effects of the endogeic earthworm species Aporrectodea caliginosa and the root feeding nematode species Pratylenchus penetrans and Meloidogyne incognita on plant responses including growth and defence metabolite concentrations in leaves of white mustard, Sinapis alba. Soil biota had a strong impact on plant traits, with the intensity varying due to species combinations. Nematode infestation reduced shoot biomass and nitrogen concentration but only in the absence of earthworms. Earthworms likely counteracted the negative effects of nematodes. Infestation with the migratory lesion-nematode P. penetrans combined with earthworms led to increased root length. Earthworm biomass increased in the presence of this species, indicating that these nematodes increased the food resources of earthworms—presumably dead and decaying roots. Nitrogen-based defence compounds, i.e. glucosinolates, did not correlate with nitrogen levels. In the presence of earthworms, concentrations of aromatic glucosinolates in leaves were significantly increased. In contrast, infection with P. penetrans strongly decreased concentrations of glucosinolates (up to 81%). Infestation with the sedentary nematode M. incognita induced aromatic glucosinolates by more than 50% but only when earthworms were also present. Myrosinase activities, glucosinolate-hydrolysing enzymes, were unaffected by nematodes but reduced in the presence of earthworms. Our results document that root-feeding nematodes elicit systemic plant responses in defence metabolites, with the responses varying drastically with nematode species of different functional groups. Furthermore, systemic plant responses are also altered by decomposer animals, such as earthworms, challenging the assumption that induction of plant responses including defence traits is restricted to herbivores. Soil animals even interact and modulate the individual effects on plant growth and plant defence, thereby likely also influencing shoot herbivore attack
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