285 research outputs found
Modern Families or Modernized Family Traditionalism ? Master Status and the Gender Order in Switzerland
Optimally Dense Packings for Fully Asymptotic Coxeter Tilings by Horoballs of Different Types
The goal of this paper to determine the optimal horoball packing arrangements
and their densities for all four fully asymptotic Coxeter tilings (Coxeter
honeycombs) in hyperbolic 3-space . Centers of horoballs are
required to lie at vertices of the regular polyhedral cells constituting the
tiling. We allow horoballs of different types at the various vertices. Our
results are derived through a generalization of the projective methodology for
hyperbolic spaces. The main result states that the known B\"or\"oczky--Florian
density upper bound for "congruent horoball" packings of remains
valid for the class of fully asymptotic Coxeter tilings, even if packing
conditions are relaxed by allowing for horoballs of different types under
prescribed symmetry groups. The consequences of this remarkable result are
discussed for various Coxeter tilings.Comment: 26 pages, 10 figure
On commensurable hyperbolic Coxeter groups
For Coxeter groups acting non-cocompactly but with finite covolume on real hyperbolic space Hn, new methods are presented to distinguish them up to (wide) commensurability. We exploit these ideas and determine the commensurability classes of all hyperbolic Coxeter groups whose fundamental polyhedra are pyramids over a product of two simplices of positive dimensions
Tentative de comparaison de l'équité des systÚmes éducatifs français et américain
Two-sided combinatorial volume bounds for non-obtuse hyperbolic polyhedra
We give a method for computing upper and lower bounds for the volume of a
non-obtuse hyperbolic polyhedron in terms of the combinatorics of the
1-skeleton. We introduce an algorithm that detects the geometric decomposition
of good 3-orbifolds with planar singular locus and underlying manifold the
3-sphere. The volume bounds follow from techniques related to the proof of
Thurston's Orbifold Theorem, Schl\"afli's formula, and previous results of the
author giving volume bounds for right-angled hyperbolic polyhedra.Comment: 36 pages, 19 figure
Global ocean heat content in the Last Interglacial
The Last Interglacial (129-116 ka) represents one of the warmest climate intervals of the last 800,000 years and the most recent time when sea level was meters higher than today. However, the timing and magnitude of peak warmth varies between reconstructions, and the relative importance of individual sources contributing to elevated sea level (mass gain versus seawater expansion) during the Last Interglacial remains uncertain. Here we present the first mean ocean temperature record for this interval from noble gas measurements in ice cores and constrain the thermal expansion contribution to sea level. Mean ocean temperature reaches its maximum value of 1.1±0.3°C warmer-than-modern at the end of the penultimate deglaciation at 129 ka, resulting in 0.7±0.3m of elevated sea level, relative to present. However, this maximum in ocean heat content is a transient feature; mean ocean temperature decreases in the first several thousand years of the interglacial and achieves a stable, comparable-to-modern value by ~127 ka. The synchroneity of the peak in mean ocean temperature with proxy records of abrupt transitions in oceanic and atmospheric circulation suggests that the mean ocean temperature maximum is related to the accumulation of heat in the ocean interior during the preceding period of reduced overturning circulation
Global ocean heat content in the Last Interglacial
The Last Interglacial (129â116âthousand years ago (ka)) represents one of the warmest climate intervals of the past 800,000 years and the most recent time when sea level was metres higher than today. However, the timing and magnitude of the peak warmth varies between reconstructions, and the relative importance of individual sources that contribute to the elevated sea level (mass gain versus seawater expansion) during the Last Interglacial remains uncertain. Here we present the first mean ocean temperature record for this interval from noble gas measurements in ice cores and constrain the thermal expansion contribution to sea level. Mean ocean temperature reached its maximum value of 1.1â±â0.3â°C warmer-than-modern values at the end of the penultimate deglaciation at 129âka, which resulted in 0.7â±â0.3âm of thermosteric sea-level rise relative to present level. However, this maximum in ocean heat content was a transient feature; mean ocean temperature decreased in the first several thousand years of the interglacial and achieved a stable, comparable-to-modern value by ~127âka. The synchroneity of the peak in mean ocean temperature with proxy records of abrupt transitions in the oceanic and atmospheric circulation suggests that the mean ocean temperature maximum is related to the accumulation of heat in the ocean interior during the preceding period of reduced overturning circulation
Volume formula for a -symmetric spherical tetrahedron through its edge lengths
The present paper considers volume formulae, as well as trigonometric
identities, that hold for a tetrahedron in 3-dimensional spherical space of
constant sectional curvature +1. The tetrahedron possesses a certain symmetry:
namely rotation through angle in the middle points of a certain pair of
its skew edges.Comment: 27 pages, 2 figures; enhanced and improved exposition, typos
corrected; Arkiv foer Matematik, 201
Evidence for self-similar bedload transport on Andean alluvial fans, Iglesia basin, south Central Argentina
Selfâsimilar downstream grainâsize fining trends in fluvial deposits are being increasingly used to simplify equilibrium sediment transport dynamics in numerical models. Their ability to collapse timeâaveraged behavior of a depositional system into a simple mass balance framework makes them ideal for exploring the sensitivity of sediment routing systems to their climatic and tectonic boundary conditions. This is important if we want to better understand the sensitivity of landscapes to environmental change over timescales >102 years. However, the extent to which selfâsimilarity is detectable in the deposits of natural rivers is not fully constrained. In transportâlimited rivers, stored sediment can be remobilized or ârecycledâ and this behavior has been highlighted as a mechanism by which externally forced grainâsize fining trends are distorted. Here we evaluate evidence of selfâsimilarity in surface gravelâsize distributions on three geomorphically diverse alluvial fans in the Iglesia basin, south Central Argentine Andes. We find that size distributions are selfâsimilar, deviating from that condition only when significant variability occurs in the coarse tails of the distributions. Our analysis indicates a strong correlation between the degree of sediment recycling and the proportion of coarse clasts present on the bed surface. However, by fitting a relative mobility transfer function, we demonstrate that sizeâselectivity alone can explain the bulk size distributions observed. This strengthens the application of selfâsimilar grain size fining models to solving problems of mass balance in a range of geomorphic settings, with an aim for reconstructing environmental boundary conditions from stratigraphy
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