1,609 research outputs found

    Penalized likelihood estimation of a trivariate additive probit model

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    This article proposes a penalized likelihood method to estimate a trivariate probit model, which accounts for several types of covariate effects (such as linear, nonlinear, random, and spatial effects), as well as error correlations. The proposed approach also addresses the difficulty in estimating accurately the correlation coefficients, which characterize the dependence of binary responses conditional on covariates. The parameters of the model are estimated within a penalized likelihood framework based on a carefully structured trust region algorithm with integrated automatic multiple smoothing parameter selection. The relevant numerical computation can be easily carried out using the SemiParTRIV() function in a freely available R package. The proposed method is illustrated through a case study whose aim is to model jointly adverse birth binary outcomes in North Carolina

    Neutrino-driven Turbulent Convection and Standing Accretion Shock Instability in Three-Dimensional Core-Collapse Supernovae

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    We conduct a series of numerical experiments into the nature of three-dimensional (3D) hydrodynamics in the postbounce stalled-shock phase of core-collapse supernovae using 3D general-relativistic hydrodynamic simulations of a 2727-MM_\odot progenitor star with a neutrino leakage/heating scheme. We vary the strength of neutrino heating and find three cases of 3D dynamics: (1) neutrino-driven convection, (2) initially neutrino-driven convection and subsequent development of the standing accretion shock instability (SASI), (3) SASI dominated evolution. This confirms previous 3D results of Hanke et al. 2013, ApJ 770, 66 and Couch & Connor 2014, ApJ 785, 123. We carry out simulations with resolutions differing by up to a factor of \sim4 and demonstrate that low resolution is artificially favorable for explosion in the 3D convection-dominated case, since it decreases the efficiency of energy transport to small scales. Low resolution results in higher radial convective fluxes of energy and enthalpy, more fully buoyant mass, and stronger neutrino heating. In the SASI-dominated case, lower resolution damps SASI oscillations. In the convection-dominated case, a quasi-stationary angular kinetic energy spectrum E()E(\ell) develops in the heating layer. Like other 3D studies, we find E()1E(\ell) \propto \ell^{-1} in the "inertial range," while theory and local simulations argue for E()5/3E(\ell) \propto \ell^{-5/3}. We argue that current 3D simulations do not resolve the inertial range of turbulence and are affected by numerical viscosity up to the energy containing scale, creating a "bottleneck" that prevents an efficient turbulent cascade.Comment: 24 pages, 15 figures. Accepted for publication in The Astrophysical Journal. Added one figure and made minor modifications to text according to suggestions from the refere

    Consequences of asteroid fragmentation during impact hazard mitigation

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    The consequences of the fragmentation of an Earth-threatening asteroid due to an attempted deflection are examined in this paper. The minimum required energy for a successful impulsive deflection of a threatening object is computed and compared to the energy required to break up a small size asteroid. The results show that the fragmentation of an asteroid that underwent an impulsive deflection, such as a kinetic impact or a nuclear explosion, is a very plausible event.Astatistical model is used to approximate the number and size of the fragments as well as the distribution of velocities at the instant after the deflection attempt takes place. This distribution of velocities is a function of the energy provided by the deflection attempt, whereas the number and size of the asteroidal fragments is a function of the size of the largest fragment. The model also takes into account the gravity forces that could lead to a reaggregation of the asteroid after fragmentation. The probability distribution of the pieces after the deflection is then propagated forward in time until the encounter with Earth. A probability damage factor (i.e., expected damage caused by a given size fragment multiplied by its impact probability) is then computed and analyzed for different plausible scenarios, characterized by different levels of deflection energies and lead times

    Toward a conceptual framework of emotional relationship marketing: an examination of two UK political parties

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    The purpose of this paper is to review the notion of branding and evaluate its applicability to political parties. As ideological politics is in decline, branding may provide a consistent narrative where voters feel a sense of warmth and belonging. The paper aims to build an understanding of the complexity of building a political brand where a combination of image, logo, leadership, and values can all contribute to a compelling brand narrative. It investigates how competing positive and negative messages attempt to build and distort the brand identity. A critical review of bran ding, relationship marketing, and political science literature articulates the conceptual development of branding and its applicability to political parties. The success or failure of negative campaigning is due to the authenticity of a political party’s brand values — creating a coherent brand story — if there is no distance between the brand values articulated by the political party and the values their community perceives then this creates an "authentic" brand. However, if there is a gap this paper illustrates how negative campaigning can be used to build a "doppelganger brand," which undermines the credibility of the authentic political brand. The paper argues that political parties need to understand how brand stories are developed but also how they can be used to protect against negative advertising. This has implications for political marketing strategists and political parties. This paper draws together branding theory and relationship marketing and incorporates them into a framework that makes a contribution to the political marketing literature

    Critical Phenomena in Neutron Stars I: Linearly Unstable Nonrotating Models

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    We consider the evolution in full general relativity of a family of linearly unstable isolated spherical neutron stars under the effects of very small, perturbations as induced by the truncation error. Using a simple ideal-fluid equation of state we find that this system exhibits a type-I critical behaviour, thus confirming the conclusions reached by Liebling et al. [1] for rotating magnetized stars. Exploiting the relative simplicity of our system, we are able carry out a more in-depth study providing solid evidences of the criticality of this phenomenon and also to give a simple interpretation of the putative critical solution as a spherical solution with the unstable mode being the fundamental F-mode. Hence for any choice of the polytropic constant, the critical solution will distinguish the set of subcritical models migrating to the stable branch of the models of equilibrium from the set of subcritical models collapsing to a black hole. Finally, we study how the dynamics changes when the numerically perturbation is replaced by a finite-size, resolution independent velocity perturbation and show that in such cases a nearly-critical solution can be changed into either a sub or supercritical. The work reported here also lays the basis for the analysis carried in a companion paper, where the critical behaviour in the the head-on collision of two neutron stars is instead considered [2].Comment: 15 pages, 9 figure

    The time of the Roma in times of crisis: Where has European neoliberal capitalism failed?

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    This paper argues that the economic and financial crisis that has ensnared Europe from the late 2000s has been instrumental in reshaping employment and social relations in a detrimental way for the majority of the European people. It argues that the crisis has exacerbated the socio-economic position of most Roma people, immigrants as well as of other vulnerable groups. This development is approached here as an outcome of the widening structural inequalities that underpin the crisis within an increasingly neoliberalised Europe. Through recent policy developments and public discourses from a number of European countries I show how rising inequalities nurture racialised social tensions. My account draws on classic and contemporary theoretical propositions that have been propounded about the nature of capitalism, its contemporary re-articulation as well as its ramification for the future of Europe

    Clinical and pathologic characteristics of BRCA-positive and BRCA-negative male breast cancer patients: results from a collaborative multicenter study in Italy

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    Recently, the number of studies on male breast cancer (MBC) has been increasing. However, as MBC is a rare disease there are difficulties to undertake studies to identify specific MBC subgroups. At present, it is still largely unknown whether BRCA-related breast cancer (BC) in men may display specific characteristics as it is for BRCA-related BC in women. To investigate the clinical-pathologic features of MBC in association with BRCA mutations we established a collaborative Italian Multicenter Study on MBC with the aim to recruit a large series of MBCs. A total of 382 MBCs, including 50 BRCA carriers, were collected from ten Italian Investigation Centres covering the whole country. In MBC patients, BRCA2 mutations were associated with family history of breast/ovarian cancer (p < 0.0001), personal history of other cancers (p = 0.044) and contralateral BC (p = 0.001). BRCA2-associated MBCs presented with high tumor grade (p = 0.001), PR- (p = 0.026) and HER2+ (p = 0.001) status. In a multivariate logistic model BRCA2 mutations showed positive association with personal history of other cancers (OR 11.42, 95 % CI 1.79-73.08) and high tumor grade (OR 4.93, 95 % CI 1.02-23.88) and inverse association with PR+ status (OR 0.19, 95 % CI 0.04-0.92). Based on immunohistochemical (IHC) profile, four molecular subtypes of MBC were identified. Luminal A was the most common subtype (67.7 %), luminal B was observed in 26.5 % of the cases and HER2 positive and triple negative were represented by 2.1 % and 3.7 % of tumors, respectively. Intriguingly, we found that both luminal B and HER2 positive subtypes were associated with high tumor grade (p = 0.003 and 0.006, respectively) and with BRCA2 mutations (p = 0.016 and 0.001, respectively). In conclusion, our findings indicate that BRCA2-related MBCs represent a subgroup of tumors with a peculiar phenotype characterized by aggressive behavior. The identification of a BRCA2-associated phenotype might define a subset of MBC patients eligible for personalized clinical management

    Gender in the neoliberalised global academy: the affective economy of women and leadership in South Asia

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    As higher education (HE) institutions globally become increasingly performative, competitive and corporatised in response to neoliberal rationalities, the exigencies of HE leadership are being realigned to accommodate its value system. This article draws on recent British Council-funded research, including 30 semi-structured interviews, to explore women’s engagement with leadership in HE in South Asia. A potent affective economy was discovered. Leadership was associated with affects such as competitiveness, aggression, impropriety, stress and anxiety, in ways that were intensified by highly patriarchal and corporatised HE cultures. Indeed, its difficulties and toxicities meant that leadership was rejected or resisted as an object of desire by many women. We illuminate how different forms of competition contribute to the affective economy of HE leadership. The research also raises wider questions about the possibilities of disrupting dominant neoliberal constructions of HE if those who question such values are excluded (or self-exclude) from leadership positions

    Education: Expectation and the Unexpected

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    In this paper I consider the concept of expectation in Higher Education. To focus the discussion I begin by sketching out some examples of how this notion pervades a number of practices in the university, and how in particular, expectation drives the way that the university tutorial operates between tutors and students. In relating this to the tendency towards what has been identified as the marketization and consumerism of higher education, I draw on the distinction that Paul Standish identifies between and ‘economy of exchange’ and an ‘economy of excess’, and suggest how expectation and responsibility figure in these economies. In moving to think beyond narrow conceptions of expectation and responsibility, and beyond the literature on policy and management in higher education, I turn to the work of the Jewish philosophers, Martin Buber and Emmanuel Levinas to show how they have both given attention to richer ideas of relationship, responsibility and the other. I initially outline Buber’s central work on the distinction between I-It and I-Thou modes of relationship, and how the latter is characterised by a dialogic intersubjectivity. I contrast this with the work of Emmanuel Levinas and draw out the distinction between the mutuality at the heart of Buber’s work, and the relationship of asymmetry that mark’s Levinas’ conception of our responsibility to the other, which is ethics. Having drawn the distinction, I then show how there are lines of connection in their respective philosophical projects, specifically how speech or dialogue is central to the relationship with the other in both thinkers. I find in both Buber and Levinas that speech cannot be thought of solely as communication. This has significant implications for education: speech is not simply the communication of (curricular) content between tutor and student. Given this, teaching can be thought of as a space for encounter with the other through language. This has further implications for thinking about the place of the tutorial in a university education. At this point I return to the scene of the university tutorial and suggest that, rather than seeing it as a place only for the meeting of expectations (which would suggest a closed economy of exchange), it might be envisioned as a space for encounter with the unexpected. In considering the nature of the encounter in relation to an example from the film adaptation of Alan Bennett’s The History Boys, I argue that the tutorial opens up the possibility for a mutual encounter with otherness. This positions the tutorial as a space of educational otherness, - a Foucauldian heterotopia which rejects the expectation-bound economy of exchange, and which offers instead the possibility of an education marked instead by an economy of excess. <br/
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