1,298 research outputs found
Evolving Conceptions of Sovereignty as Applied to Membership in International Organizations
In the current international climate, both nations and individuals increasingly question both the validity and necessity of international organizations. This paper seeks to answer some of those questions, and to determine why countries choose to surrender significant portions of the national power that they are afforded under traditional perceptions of “Westphalian sovereignty”. This question is answered through an analysis of historical political thought on the concept of Sovereignty, then is applied to two case studies: the United Nations and the European Union, in which the benefits and downsides of surrendering sovereignty are discussed. Ultimately, this thesis concludes that the concept of Westphalian sovereignty is weakening in the modern world, as the international system gradually adopts new ideas about what national power allows, and reapplies old concepts that had long fallen out of use. Additionally, many of the problems faced by humanity in the present day are too large and complicated to be solved by singular nations, and require concerted international action. Together, these evolving conceptions of sovereignty and increasingly complex global problems have greatly contributed to the growth and empowerment of international organizations
Electron-Capture and Low-Mass Iron-Core-Collapse Supernovae: New Neutrino-Radiation-Hydrodynamics Simulations
We present new 1D (spherical) and 2D (axisymmetric) simulations of
electron-capture (EC) and low-mass iron-core-collapse supernovae (SN). We
consider six progenitor models: the ECSN progenitor from Nomoto (1984, 1987);
two ECSN-like low-mass low-metallicity iron core progenitors from Heger
(private communication); and the 9-, 10-, and 11- (zero-age main
sequence) progenitors from Sukhbold et al. (2016). We confirm that the ECSN and
ESCN-like progenitors explode easily even in 1D with explosion energies of up
to a 0.15 Bethes (), and are a viable
mechanism for the production of very low-mass neutron stars. However, the 9-,
10-, and 11- progenitors do not explode in 1D and are not even
necessarily easier to explode than higher-mass progenitor stars in 2D. We study
the effect of perturbations and of changes to the microphysics and we find that
relatively small changes can result in qualitatively different outcomes, even
in 1D, for models sufficiently close to the explosion threshold. Finally, we
revisit the impact of convection below the protoneutron star (PNS) surface. We
analyze, 1D and 2D evolutions of PNSs subject to the same boundary conditions.
We find that the impact of PNS convection has been underestimated in previous
studies and could result in an increase of the neutrino luminosity by up to
factors of two.Comment: 18 pages, 17 figures, 3 tables. Major revisions following a fix in
the code input physics. Accepted on Ap
Neutrino-driven Turbulent Convection and Standing Accretion Shock Instability in Three-Dimensional Core-Collapse Supernovae
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 - 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 4 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 develops in the heating layer. Like other 3D studies, we
find in the "inertial range," while theory and
local simulations argue for . 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
Three approaches for the classification of protoneutron star oscillation modes
The future detection of gravitational waves (GWs) from a galactic
core-collapse supernova will provide information on the physics inside
protoneutron stars (PNS). In this work, we apply three different classification
methods for the PNS non-radial oscillation modes: Cowling classification,
Generalized Cowling Nomenclature (GCN), and a Classification Based on Modal
Properties (CBMP). Using PNS models from D simulations of core-collapse
supernovae, we find that in the early stages of the PNS evolution, typically
before seconds after the bounce, the Cowling classification is
inconsistent, but the GCN and the CBMP provide complementary information that
helps to understand the evolution of the modes. In the GCN, we note several
avoided crossings as the mode frequencies evolve at early times, while the CBMP
tracks the modes across the avoided crossings. We verify that the strongest
emission of GWs by the PNS corresponds to the -mode in the GCN, indicating
that the mode trapping region alternates between the core and the envelope at
each avoided crossing. At later times, approximately seconds after the
bounce, the three classification methods present a similar description of the
mode spectrum. We use our results to test universal relations for the PNS modes
according to their classification and find that the behaviour of the universal
relations for - and -modes is remarkably simple in the CBMP.Comment: 11 pages, 8 figures. Matches the version accepted on MNRA
Left ventricular diastolic function in normotensive adolescents with different genetic risk of hypertension.
Abnormalities of the diastolic function of the left ventricle are the first sign of cardiac involvement in arterial hypertension. We have studied the diastolic function in a group of normotensive adolescents with confirmed family history of hypertension. M-mode echocardiography was performed in 86 normotensive males aged 14-19 years: 41 sons of at least one hypertensive parent (SHT) and 45 sons of normotensive parents (SNT). Cross-sectional area of the left ventricle and left ventricular (LV) mass index were significantly greater in the SHT than in the SNT group (10.05 +/- 1.84 vs. 8.9 +/- 1.56 cm/m2, p less than 0.01 and 129.3 +/- 296.3 vs. 109.23 +/- 25.7 g/m2, p less than 0.002, respectively). No significant difference between the two groups was observed in the indices of left ventricular diastolic function, except for mitral valve opening rate (463.51 +/- 90.45 in SHT vs. 416.71 +/- 78.84 mm/s in SNT; p less than 0.02). From the analysis of the subgroup of adolescents having left ventricular mass greater than the upper normal value, we observed that they showed mean time of rapid filling significantly longer than SNT: this could represent an early marker of the pathological character of such hypertrophy. Our results suggest that the higher LV mass observed in the SHT is not associated with chamber and myocardial stiffness abnormalities
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