4,616 research outputs found

    Surgery on SL~×En\widetilde{\Bbb{SL}}\times\Bbb{E}^n-manifolds

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    We show that although closed SL~×En\widetilde{\Bbb{SL}}\times\Bbb{E}^n-manifolds do not admit metrics of nonpositive sectional curvature, the arguments of Farrell and Jones can be extended to show that such manifolds are topologically rigid, if n2n\geq2.Comment: 7 pages, AMS-LaTeX file, To appear in the Canadian Mathematical Bulletin

    Alexander quandle lower bounds for link genera

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    We denote by Q_F the family of the Alexander quandle structures supported by finite fields. For every k-component oriented link L, every partition P of L into h:=|P| sublinks, and every labelling z of such a partition by the natural numbers z_1,...,z_n, the number of X-colorings of any diagram of (L,z) is a well-defined invariant of (L,P), of the form q^(a_X(L,P,z)+1) for some natural number a_X(L,P,z). Letting X and z vary in Q_F and among the labellings of P, we define a derived invariant A_Q(L,P)=sup a_X(L,P,z). If P_M is such that |P_M|=k, we show that A_Q(L,P_M) is a lower bound for t(L), where t(L) is the tunnel number of L. If P is a "boundary partition" of L and g(L,P) denotes the infimum among the sums of the genera of a system of disjoint Seifert surfaces for the L_j's, then we show that A_Q(L,P) is at most 2g(L,P)+2k-|P|-1. We set A_Q(L):=A_Q(L,P_m), where |P_m|=1. By elaborating on a suitable version of a result by Inoue, we show that when L=K is a knot then A_Q(K) is bounded above by A(K), where A(K) is the breadth of the Alexander polynomial of K. However, for every g we exhibit examples of genus-g knots having the same Alexander polynomial but different quandle invariants A_Q. Moreover, in such examples A_Q provides sharp lower bounds for the genera of the knots. On the other hand, A_Q(L) can give better lower bounds on the genus than A(L), when L has at least two components. We show that in order to compute A_Q(L) it is enough to consider only colorings with respect to the constant labelling z=1. In the case when L=K is a knot, if either A_Q(K)=A(K) or A_Q(K) provides a sharp lower bound for the knot genus, or if A_Q(K)=1, then A_Q(K) can be realized by means of the proper subfamily of quandles X=(F_p,*), where p varies among the odd prime numbers.Comment: 36 pages; 16 figure

    Social enterprise as a potential niche innovation breakout for low carbon transition

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    While there is growing consensus that human behaviours need to change to a more sustainable paradigm, community driven approaches, such as social enterprise, have yet to be explored as serious instruments of sustainability transition. Social enterprises sit within the third sector of the economy, typically where market or governmental failures exist in the provision of social welfare, and have increasingly become a key driver of social progress. The autonomous nature of the social-economic model applied by such organisations can represent a viable means to reduce state social welfare dependence, and is a proven model for social change. The capability of social enterprises to create both social and economic value is considered a ‘win-win’. Yet there are clear potentials for social enterprise models to be more extensively applied to address contemporary ecological challenges of neo-liberal market economies, moving towards ‘win-win-win’ outcomes across social, economic and ecological domains. This paper investigates the value of social enterprises as drivers of low-carbon transition at the community level, with an emphasis on the energy sector. Evidence from seven organisations in the UK is presented and a socio- technical transitions conceptual framework is applied to analyse these social enterprise operations as a form of social innovation. © 2018 The Author(s

    Assessing changes in the internal worlds of early- and late-adopted children using the Story Stem Assessment Profile (SSAP)

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    A growing body of literature has consistently shown how adopted children often have previous history of trauma and neglect, and in turn develop negative representations of the self and others. This study assesses the internal representations of three groups of children, as measured by the Story Stem Assessment Profile (SSAP). These were: (1) a maltreated, late-adopted (MLA) sample (n = 63); (2) a non-maltreated, early-adopted (EA) sample (n = 48); and (3) a non-maltreated community sample (COMM) (n = 80). In addition, it examined whether MLA and EA adopted children’s attachment and internal representations changed over time. Results showed that children in the MLA sample significantly displayed more disorganised, avoidant and negative representations and fewer representations characteristic of ‘secure’ attachment when compared with EA and, especially, COMM children. Longitudinal follow-up of both MLA and EA samples demonstrated significant changes over a two-year period in SSAP representation; secure representations increased while the avoidant and disorganised ones diminished. These findings are discussed and the limitations and implications of the study presented

    A facility for high resolution spectroscopy: Laboratory and ground based observations in support of upper atmospheric research

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    This research task consists of operating a facility for making spectroscopic observations in support of upper atmospheric research. The facility responds to the needs and interests of the visiting investigators. Therefore, the research objectives are not predetermined except in broad outline. The emphasis is on studies that take advantage of the particular strengths of the Fourier Transform Spectrometer on Kitt Peak: high spectral resolution combined with wide spectral range and low noise

    Social enterprise as an engine for sustainability transition

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    Embedded socio-ecological problems urgently require novel approaches with a long-term orientation, including reflexive and adaptive policy design and conceptualisations which move far beyond business as usual approaches and which meaningfully address underlying complexes of technologies and institutions. The transitions literature has stimulated debate to increasingly recognise the multi-dimensional shifts required for delivery of sustainable modes of production and consumption. However, transition studies have to date focused heavily on technological and on historical analyses. Within this emerging body of investigation, there is a need for research which more exclusively and explicitly addresses organisational and community level responses to sustainability in a strategic and forward looking manner. While there is growing consensus that human behaviours need to change to a more sustainable paradigm, community driven approaches, such as social enterprise, have yet to be explored as serious instruments of sustainability transition. Social enterprises sit within the third sector of the economy, typically where market or governmental failures exist in the provision of social welfare, and have increasingly become a key driver of social progress. The autonomous nature of the social-economic model applied by such organisations can represent a viable means to reduce state social welfare dependence, and as a proven model for social change. The capability of social enterprises to create both social and economic value is considered a ‘win-win’. However, there are clear potentials for social enterprise models to be more extensively applied to address contemporary ecological challenges of neo-liberal market economies, moving towards ‘win-win-win’ outcomes across social, economic and ecological domains; particularly as these organisations are not motivated by a relentless profit imperative. This paper investigates the value of utilising social enterprises as a driver of sustainability at the community level, with an emphasis on application in the energy sector. Evidence from four social enterprises in the UK is presented and a socio-technical transitions conceptual framework is applied to analyse these social enterprise operations as a form of social innovation. The paper critically evaluates the characteristics of social enterprises which suggest potential for wider socio-technical systemic transformation and appraises the potential for such organisational models to act as ‘engines of socio-technical transformation’. Barriers to the widespread diffusion of social enterprise models are identified, as well as operational and strategic challenges in actively delivering on the ‘win-win-win’ potential of these organisations for sustainability

    Tunable control of the hydrophilicity and wettability of conjugated polymers by a postpolymerization modification approach.

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    A facile method to prepare hydrophilic polymers by a postpolymerization nucleophillic aromatic substitution reaction of fluoride on an emissive conjugated polymer (CP) backbone is reported. Quantitative functionalization by a series of monofunctionalized ethylene glycol oligomers, from dimer to hexamer, as well as with high molecular weight polyethylene glycol is demonstrated. The length of the ethylene glycol sidechains is shown to have a direct impact on the surface wettability of the polymer, as well as its solubility in polar solvents. However, the energetics and band gap of the CPs remain essentially constant. This method therefore allows an easy way to modulate the wettability and solubility of CP materials for a diverse series of applications

    Routine placental histopathology findings from women testing positive for SARS-CoV-2 during pregnancy: Retrospective cohort comparative study

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    OBJECTIVE: To assess the impact of maternal Coronavirus disease 2019 (COVID-19) infection on placental histopathological findings in an unselected population and evaluate the potential effect on the fetus, including the possibility of vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). DESIGN: Retrospective cohort comparative study of placental histopathological findings in patients with COVID-19, compared with controls. SETTING: During the COVID-19 pandemic, placentas were studied from women at University College Hospital London who reported and/or tested positive for COVID-19. POPULATION: Of 10 508 deliveries, 369 (3.5%) women had COVID-19 during pregnancy, with placental histopathology available for 244 women. METHODS: Retrospective review of maternal and neonatal characteristics, where placental analysis had been performed. This was compared with available, previously published, histopathological findings from placentas of unselected women. MAIN OUTCOME MEASURES: Frequency of placental histopathological findings and relevant clinical outcomes. RESULTS: Histological abnormalities were reported in 117 of 244 (47.95%) cases, with the most common diagnosis being ascending maternal genital tract infection. There was no statistically significant difference in the frequency of most abnormalities compared with controls. There were four cases of COVID-19 placentitis (1.52%, 95% CI 0.04%-3.00%) and one possible congenital infection, with placental findings of acute maternal genital tract infection. The rate of fetal vascular malperfusion (FVM), at 4.5%, was higher compared with controls (p = 0.00044). CONCLUSIONS: In most cases, placentas from pregnant women infected with SARS-CoV-2 virus do not show a significantly increased frequency of pathology. Evidence for transplacental transmission of SARS-CoV-2 is lacking from this cohort. There is a need for further study into the association between FVM, infection and diabetes

    "Driven to distraction?" Children's experiences of car travel

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    This is an Author's Accepted Manuscript of an article published in volume, 4, issue 1, pages 59-76 in Mobilities 2009. Copyright @ 2009 Taylor & Francis, available online at: http://www.tandfonline.com/doi/abs/10.1080/17450100802657962.Cars have become increasingly significant features in the lives of many children and adults in the UK and elsewhere. Whilst there is a growing body of research considering how adults experience automobility, that is the increasingly central role of cars within societies, there has been little equivalent research exploring children's perspectives. Drawing upon a variety of methods including personal diaries, photographs, in‐depth interviews and surveys amongst schools within Buckinghamshire and North London, the paper contributes to filling this gap in existing research through exploring how cars are not only journey spaces for children, but are also sites for play, relaxation, homework, companionship, technology and the consumption of commodities. Using a Foucauldian analysis of power, insights into wider familial processes relating to mobility are provided by exploring how cars are sites of conflicting power relations between parents and children. The paper also explores how children's everyday experiences of cars were framed by wider sets of power relations, including car corporations which design and manufacture these spaces, and the role of capital which commodifies everyday activities in cars. In doing so, the paper challenges existing research on automobility for only focusing upon adults' experiences of cars and begins to theorise a more inclusive account of automobility which incorporates children and young people
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