11,651 research outputs found


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    Land Economics/Use,

    Surviving Slavery. Mortality at Mesopotamia, a Jamaican sugar estate, 1762 - 1832

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    We use survival analysis to study the mortality experience of 1111 slaves living on the British West Indian sugar plantation of Mesopotamia for seven decades prior to the Emancipation Act of 1833. Using three different concepts of analysis time and employing non-parametric and semi-parametric models, our results suggest that female slaves first observed under Joseph Foster Barham II's period of ownership (1789-1832) faced an increased hazard of death compared with those first observed during his predecessor's tenure. We find no such relationship for males. We cite as a possible explanation the employment regime operated by Foster Barham II, which allocated increasing numbers of females to gang labour in the cane fields. A G-estimation model used to compensate for the 'healthy worker survivor effect' estimates that continuous exposure to such work reduced survival times by between 20 and 40 per cent. Our findings are compared with previous studies of Mesopotamia and related to the wider literature investigating the roles of fertility and mortality in undermining the sustainability of Caribbean slave populations.

    Pan-STARRS1 Discovery of Two Ultraluminous Supernovae at z ≈ 0.9

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    We present the discovery of two ultraluminous supernovae (SNe) at z ≈ 0.9 with the Pan-STARRS1 Medium Deep Survey. These SNe, PS1-10ky and PS1-10awh, are among the most luminous SNe ever discovered, comparable to the unusual transients SN 2005ap and SCP 06F6. Like SN 2005ap and SCP 06F6, they show characteristic high luminosities (M_(bol) ≈ –22.5 mag), blue spectra with a few broad absorption lines, and no evidence for H or He. We have constructed a full multi-color light curve sensitive to the peak of the spectral energy distribution in the rest-frame ultraviolet, and we have obtained time series spectroscopy for these SNe. Given the similarities between the SNe, we combine their light curves to estimate a total radiated energy over the course of explosion of (0.9-1.4) × 10^(51) erg. We find photospheric velocities of 12,000-19,000 km s^(–1) with no evidence for deceleration measured across ~3 rest-frame weeks around light curve peak, consistent with the expansion of an optically thick massive shell of material. We show that, consistent with findings for other ultraluminous SNe in this class, radioactive decay is not sufficient to power PS1-10ky, and we discuss two plausible origins for these events: the initial spin-down of a newborn magnetar in a core-collapse SN, or SN shock breakout from the dense circumstellar wind surrounding a Wolf-Rayet star

    Emergence of Long-range Correlations and Rigidity at the Dynamic Glass Transition

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    At the microscopic level, equilibrium liquid's translational symmetry is spontaneously broken at the so-called dynamic glass transition predicted by the mean-field replica approach. We show that this fact implies the emergence of Goldstone modes and long-range density correlations. We derive and evaluate a new statistical mechanical expression for the glass shear modulus.Comment: 4 page

    Supernova 2009kf: An Ultraviolet Bright Type IIP Supernova Discovered with Pan-STARRS 1 and GALEX

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    We present photometric and spectroscopic observations of a luminous Type IIP Supernova (SN) 2009kf discovered by the Pan-STARRS 1 (PS1) survey and also detected by the Galaxy Evolution Explorer. The SN shows a plateau in its optical and bolometric light curves, lasting approximately 70 days in the rest frame, with an absolute magnitude of M_V = -18.4 mag. The P-Cygni profiles of hydrogen indicate expansion velocities of 9000 km s^(-1) at 61 days after discovery which is extremely high for a Type IIP SN. SN 2009kf is also remarkably bright in the near-ultraviolet (NUV) and shows a slow evolution 10-20 days after optical discovery. The NUV and optical luminosity at these epochs can be modeled with a blackbody with a hot effective temperature (T ~ 16,000 K) and a large radius (R ~ 1 × 10^(15) cm). The bright bolometric and NUV luminosity, the light curve peak and plateau duration, the high velocities, and temperatures suggest that 2009kf is a Type IIP SN powered by a larger than normal explosion energy. Recently discovered high-z SNe (0.7 < z < 2.3) have been assumed to be IIn SNe, with the bright UV luminosities due to the interaction of SN ejecta with a dense circumstellar medium. UV-bright SNe similar to SN 2009kf could also account for these high-z events, and its absolute magnitude M_(NUV) = -21.5 ± 0.5 mag suggests such SNe could be discovered out to z ~ 2.5 in the PS1 survey

    Monte Carlo simulations of liquid crystals near rough walls

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    The effect of surface roughness on the structure of liquid crystalline fluids near solid substrates is studied by Monte Carlo simulations. The liquid crystal is modeled as a fluid of soft ellipsoidal molecules and the substrate is modeled as a hard wall that excludes the centers of mass of the fluid molecules. Surface roughness is introduced by embedding a number of molecules with random positions and orientations within the wall. It is found that the density and order near the wall are reduced as the wall becomes rougher, i.e., the number of embedded molecules is increased). Anchoring coefficients are determined from fluctuations in the reciprocal space order tensor. It is found that the anchoring strength decreases with increasing surface roughness

    Resting state correlates of subdimensions of anxious affect

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    Resting state fMRI may help identify markers of risk for affective disorder. Given the comorbidity of anxiety and depressive disorders and the heterogeneity of these disorders as defined by DSM, an important challenge is to identify alterations in resting state brain connectivity uniquely associated with distinct profiles of negative affect. The current study aimed to address this by identifying differences in brain connectivity specifically linked to cognitive and physiological profiles of anxiety, controlling for depressed affect. We adopted a two-stage multivariate approach. Hierarchical clustering was used to independently identify dimensions of negative affective style and resting state brain networks. Combining the clustering results, we examined individual differences in resting state connectivity uniquely associated with subdimensions of anxious affect, controlling for depressed affect. Physiological and cognitive subdimensions of anxious affect were identified. Physiological anxiety was associated with widespread alterations in insula connectivity, including decreased connectivity between insula subregions and between the insula and other medial frontal and subcortical networks. This is consistent with the insula facilitating communication between medial frontal and subcortical regions to enable control of physiological affective states. Meanwhile, increased connectivity within a frontoparietal-posterior cingulate cortex-precunous network was specifically associated with cognitive anxiety, potentially reflecting increased spontaneous negative cognition (e.g., worry). These findings suggest that physiological and cognitive anxiety comprise subdimensions of anxiety-related affect and reveal associated alterations in brain connectivity

    Governance, Civil Conflict, And Refugee Protection In Sub-Saharan Africa: A Primer

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    This paper provides an introduction to the concepts of governance and state weakness, fragility or failure.&nbsp; Selected indices of performance are presented with an emphasis on Sub-Saharan Africa. As noted by the 2005 UK Commission for Africa &ldquo;The most extreme breakdown of governance is war.&rdquo; The paper discusses the concepts and definitions of civil conflict and civil war, and the prevalence of civil war in Sub &ndash;Saharan Africa.&nbsp; Among the costs of civil war are the people who are displaced due to their fear for life amidst the conflict.&nbsp; If displaced persons exit the country they become refugees. The paper provides an introduction to the evolution of international humanitarian law since World War II to protect non-combatants, including refugees

    Covid-19, racism and the ‘state of exception’? A theological ethical engagement with identity and human rights in an age of ‘Corona’ and beyond

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    The COVID-19 pandemic highlighted the role that religion and politics play at the intersection with individual and social rights. Religiously informed political actors capitalised on fears and prejudices to further science denialism, normalise nationalist ideologies, and curtail human rights. In the United States of America, Brazil, and South Africa, it took the form of problematic political theologies. In many instances, a state of exception, as understood in the work of Giorgio Agamben, was enacted. Such actions often have biopolitical significance revolving around making political choices informed by religious beliefs that impact on individual bodies and social freedoms. This extends from individual bodies tosocieties. This research employs a qualitative literature approach to investigate the intersection of political and theological beliefs during the pandemic. It highlights the impact of populist political theologies on the erosion of democracy and human rights in countries that have highly religious populations. It is argued that these strategies reach beyond the COVID-19 pandemic

    Improved electromechanical master-slave manipulator

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    Electric master-slave manipulator uses force multiplication and allows the operator to remotely control the slave arm. Both the master and slave arms execute seven distinct motions by a specially designed force-reflecting servo having a one to one correspondence between the motion at the master and slave