286 research outputs found

    Transformation and patterning of supermicelles using dynamic holographic assembly

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    Although the solution self-assembly of block copolymers has enabled the fabrication of a broad range of complex, functional nanostructures, their precise manipulation and patterning remain a key challenge. Here we demonstrate that spherical and linear supermicelles, supramolecular structures held together by non-covalent solvophobic and coordination interactions and formed by the hierarchical self-assembly of block copolymer micelle and block comicelle precursors, can be manipulated, transformed and patterned with mediation by dynamic holographic assembly (optical tweezers). This allows the creation of new and stable soft-matter superstructures far from equilibrium. For example, individual spherical supermicelles can be optically held in close proximity and photocrosslinked through controlled coronal chemistry to generate linear oligomeric arrays. The use of optical tweezers also enables the directed deposition and immobilization of supermicelles on surfaces, allowing the precise creation of arrays of soft-matter nano-objects with potentially diverse functionality and a range of applications

    Microfibres and macroscopic films from the coordination-driven hierarchical self-assembly of cylindrical micelles

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    Anisotropic nanoparticles prepared from block copolymers are of growing importance as building blocks for the creation of synthetic hierarchical materials. However, the assembly of these structural units is generally limited to the use of amphiphilic interactions. Here we report a simple, reversible coordination-driven hierarchical self-assembly strategy for the preparation of micron-scale fibres and macroscopic films based on monodisperse cylindrical block copolymer micelles. Coordination of Pd(0) metal centres to phosphine ligands immobilized within the soluble coronas of block copolymer micelles is found to induce intermicelle crosslinking, affording stable linear fibres comprised of micelle subunits in a staggered arrangement. The mean length of the fibres can be varied by altering the micelle concentration, reaction stoichiometry or aspect ratio of the micelle building blocks. Furthermore, the fibres aggregate on drying to form robust, self-supporting macroscopic micelle-based thin films with useful mechanical properties that are analogous to crosslinked polymer networks, but on a longer length scale

    Perfectionism and achievement goals in young Finnish ice-hockey players aspiring to make the Under-16 national team

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    Research on perfectionism suggests that is it useful to differentiate between perfectionistic strivings and perfectionistic concerns. Regarding the 2 x 2 achievement goal framework, the usefulness of this differentiation was recently demonstrated in a study with university student athletes (Stoeber, Stoll, Pescheck, & Otto, 2008, Study 2), in which it was found that perfectionistic strivings were associated with mastery-approach and performance-approach goals and perfectionistic concerns with mastery-avoidance, performance-approach, and performance-avoidance goals. Because the study was largely exploratory and only used non-elite athletes, the aim of the present research was to replicate and extend these findings by investigating a sample of 138 young, elite ice-hockey players, while adding further measures of perfectionism and using structural equation modelling (SEM) to confirm the relationships between perfectionistic strivings, perfectionistic concerns,and the 2 x 2 achievement goals. The SEM results showed that, in elite athletes also, perfectionistic strivings are associated with mastery-approach and performance-approach goals, whereas perfectionistic concerns are associated with masteryavoidance, performance-approach, and performance-avoidance goals. Our findings corroborate the importance of differentiating between perfectionistic strivings and perfectionistic concerns when studying perfectionism in sports, because only perfectionistic concerns (and not perfectionistic strivings) are associated with maladaptive patterns of achievement goals

    Manipulation and Deposition of Complex, Functional Block Copolymer Nanostructures using Optical Tweezers

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    Block copolymer self-assembly has enabled the creation of a range of solution-phase nanostructures with applications from optoelectronics and biomedicine to catalysis. However, to incorporate such materials into devices a method that facilitates their precise manipulation and deposition is desirable. Herein we describe how optical tweezers can be used to trap, manipulate, and pattern individual cylindrical micelles and larger hybrid micellar materials. Through the combination of TIRF imaging and optical trapping we can precisely control the three-dimensional motion of individual cylindrical block copolymer micelles in solution, enabling the creation of customizable arrays. We also demonstrate that dynamic holographic assembly enables the creation of ordered customizable arrays of complex hybrid block copolymer structures. By creating a program which automatically identifies, traps, and then deposits multiple assemblies simultaneously we have been able to dramatically speed up this normally slow process, enabling the fabrication of arrays of hybrid structures containing hundreds of assemblies in minutes rather than hours

    The holistic phase model of early adult crisis

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    The objective of the current study was to explore the structural, temporal and experiential manifestations of crisis episodes in early adulthood, using a holistic-systemic theoretical framework. Based on an analysis of 50 interviews with individuals about a crisis episode between the ages of 25 and 35, a holistic model was developed. The model comprises four phases: (1) Locked-in, (2) Separation/Time-out, (3) Exploration and (4) Rebuilding, which in turn have characteristic features at four levels—person-in-environment, identity, motivation and affect-cognition. A crisis starts out with a commitment at work or home that has been made but is no longer desired, and this is followed by an emotionally volatile period of change as that commitment is terminated. The positive trajectory of crisis involves movement through an exploratory period towards active rebuilding of a new commitment, but ‘fast-forward’ and ‘relapse’ loops can interrupt Phases 3 and 4 and make a positive resolution of the episode less likely. The model shows conceptual links with life stage theories of emerging adulthood and early adulthood, and it extends current understandings of the transitional developmental challenges that young adults encounter

    Swimming in a Sea of Shame: Incorporating Emotions into Explanations of Institutional Reproduction and Change

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    We theorize the role in institutional processes of what we call the shame nexus, a set of shame-related constructs: felt shame, systemic shame, sense of shame, and episodic shaming. As a discrete emotion, felt shame signals to a person that a social bond is at risk and catalyzes a fundamental motivation to preserve valued bonds. We conceptualize systemic shame as a form of disciplinary power, animated by persons’ sense of shame, a mechanism of ongoing intersubjective surveillance and self-regulation. We theorize how the duo of the sense of shame and systemic shame drives the self-regulation that underpins persons’ conformity to institutional prescriptions and institutional reproduction. We conceptualize episodic shaming as a form of juridical power used by institutional guardians to elicit renewed conformity and reassert institutional prescriptions. We also explain how episodic shaming may have unintended effects, including institutional disruption and recreation, when it triggers sensemaking among targets and observers that can lead to the reassessment of the appropriateness of institutional prescriptions or the value of social bonds. We link the shame nexus to three broad categories of institutional work

    XMeis3 Is Necessary for Mesodermal Hox Gene Expression and Function

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    Hox transcription factors provide positional information during patterning of the anteroposterior axis. Hox transcription factors can co-operatively bind with PBC-class co-factors, enhancing specificity and affinity for their appropriate binding sites. The nuclear localisation of these co-factors is regulated by the Meis-class of homeodomain proteins. During development of the zebrafish hindbrain, Meis3 has previously been shown to synergise with Hoxb1 in the autoregulation of Hoxb1. In Xenopus XMeis3 posteriorises the embryo upon ectopic expression. Recently, an early temporally collinear expression sequence of Hox genes was detected in Xenopus gastrula mesoderm (see intro. P3). There is evidence that this sequence sets up the embryo's later axial Hox expression pattern by time-space translation. We investigated whether XMeis3 is involved in regulation of this early mesodermal Hox gene expression. Here, we present evidence that XMeis3 is necessary for expression of Hoxd1, Hoxb4 and Hoxc6 in mesoderm during gastrulation. In addition, we show that XMeis3 function is necessary for the progression of gastrulation. Finally, we present evidence for synergy between XMeis3 and Hoxd1 in Hoxd1 autoregulation in mesoderm during gastrulation

    Comparative genomics of drug resistance in <i>Trypanosoma brucei rhodesiense</i>

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    Trypanosoma brucei rhodesiense is one of the causative agents of human sleeping sickness, a fatal disease that is transmitted by tsetse flies and restricted to Sub-Saharan Africa. Here we investigate two independent lines of T. b. rhodesiense that have been selected with the drugs melarsoprol and pentamidine over the course of 2 years, until they exhibited stable cross-resistance to an unprecedented degree. We apply comparative genomics and transcriptomics to identify the underlying mutations. Only few mutations have become fixed during selection. Three genes were affected by mutations in both lines: the aminopurine transporter AT1, the aquaporin AQP2, and the RNA-binding protein UBP1. The melarsoprol-selected line carried a large deletion including the adenosine transporter gene AT1, whereas the pentamidine-selected line carried a heterozygous point mutation in AT1, G430R, which rendered the transporter non-functional. Both resistant lines had lost AQP2, and both lines carried the same point mutation, R131L, in the RNA-binding motif of UBP1. The finding that concomitant deletion of the known resistance genes AT1 and AQP2 in T. b. brucei failed to phenocopy the high levels of resistance of the T. b. rhodesiense mutants indicated a possible role of UBP1 in melarsoprol-pentamidine cross-resistance. However, homozygous in situ expression of UBP1-Leu(131) in T. b. brucei did not affect the sensitivity to melarsoprol or pentamidine

    250 labels used to stigmatise people with mental illness

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    <p>Abstract</p> <p>Background</p> <p>The stigma against people with mental illness is a major barrier to help-seeking in young people for mental health problems. The objective of this study was to investigate the extent of stigma in relation to treatment avoidance in 14 year-old school students in England in relation to how they refer to people with mental illness.</p> <p>Methods</p> <p>This is a qualitative, cross-sectional study. The data were gathered as part of the baseline assessment for an intervention study intended to reduce stigma among 14 year old school students. The participating schools were two grammar (selective) schools and three comprehensive (non-selective) schools. At the start of the lesson, the students were asked 'What sorts of words or phrases might you use to describe someone who experiences mental health problems?' Words and terms used to refer to mental illness were enumerated. Using the grounded theory approach, words and terms were grouped in terms of their denotative and connotative meanings. Labels were then derived to capture the key themes attached by the students to the concepts of mental illness. The frequencies of occurrence for each word were also tabulated.</p> <p>Results</p> <p>400 of the 472 participating students (85%) provided 250 words and terms to describe a person with mental illness. Five themes were identified from the data. The first theme called 'popular derogatory terms' (116 items) accounted for nearly half of the words examined. The second theme occurred less often and was described as 'negative emotional state' (61 items). The third theme demonstrated the confusion of young people between physical disabilities, learning difficulties and mental health problems (38 items). The use of psychiatric diagnoses (15 items) and terms related to violence (9 items) were unexpectedly uncommon.</p> <p>Conclusion</p> <p>Our findings suggest the hypothesis that help-seeking by mentally ill young people may be improved by interventions that address both their lack of factual information about mental illness, and those which reduce their strong negative emotional reactions towards people with mental illness.</p
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