460 research outputs found
Further restrictions on the topology of stationary black holes in five dimensions
We place further restriction on the possible topology of stationary
asymptotically flat vacuum black holes in 5 spacetime dimensions. We prove that
the horizon manifold can be either a connected sum of Lens spaces and "handles"
, or the quotient of by certain finite groups of
isometries (with no "handles"). The resulting horizon topologies include Prism
manifolds and quotients of the Poincare homology sphere. We also show that the
topology of the domain of outer communication is a cartesian product of the
time direction with a finite connected sum of 's
and 's, minus the black hole itself. We do not assume the existence of
any Killing vector beside the asymptotically timelike one required by
definition for stationarity.Comment: LaTex, 22 pages, 9 figure
Topological Lensing in Spherical Spaces
This article gives the construction and complete classification of all
three-dimensional spherical manifolds, and orders them by decreasing volume, in
the context of multiconnected universe models with positive spatial curvature.
It discusses which spherical topologies are likely to be detectable by
crystallographic methods using three-dimensional catalogs of cosmic objects.
The expected form of the pair separation histogram is predicted (including the
location and height of the spikes) and is compared to computer simulations,
showing that this method is stable with respect to observational uncertainties
and is well suited for detecting spherical topologies.Comment: 32 pages, 26 figure
Cancer survival for Aboriginal and Torres Strait Islander Australians: a national study of survival rates and excess mortality
BackgroundNational cancer survival statistics are available for the total Australian population but not Indigenous Australians, although their cancer mortality rates are known to be higher than those of other Australians. We aimed to validate analysis methods and report cancer survival rates for Indigenous Australians as the basis for regular national reporting.MethodsWe used national cancer registrations data to calculate all-cancer and site-specific relative survival for Indigenous Australians (compared with non-Indigenous Australians) diagnosed in 2001-2005. Because of limited availability of Indigenous life tables, we validated and used cause-specific survival (rather than relative survival) for proportional hazards regression to analyze time trends and regional variation in all-cancer survival between 1991 and 2005.ResultsSurvival was lower for Indigenous than non-Indigenous Australians for all cancers combined and for many cancer sites. The excess mortality of Indigenous people with cancer was restricted to the first three years after diagnosis, and greatest in the first year. Survival was lower for rural and remote than urban residents; this disparity was much greater for Indigenous people. Survival improved between 1991 and 2005 for non-Indigenous people (mortality decreased by 28%), but to a much lesser extent for Indigenous people (11%) and only for those in remote areas; cancer survival did not improve for urban Indigenous residents.ConclusionsCancer survival is lower for Indigenous than other Australians, for all cancers combined and many individual cancer sites, although more accurate recording of Indigenous status by cancer registers is required before the extent of this disadvantage can be known with certainty. Cancer care for Indigenous Australians needs to be considerably improved; cancer diagnosis, treatment, and support services need to be redesigned specifically to be accessible and acceptable to Indigenous people
A Tonnetz Model for pentachords
This article deals with the construction of surfaces that are suitable for
representing pentachords or 5-pitch segments that are in the same class.
It is a generalization of the well known \"Ottingen-Riemann torus for triads of
neo-Riemannian theories. Two pentachords are near if they differ by a
particular set of contextual inversions and the whole contextual group of
inversions produces a Tiling (Tessellation) by pentagons on the surfaces. A
description of the surfaces as coverings of a particular Tiling is given in the
twelve-tone enharmonic scale case.Comment: 27 pages, 12 figure
Effect of synthesis conditions on formation pathways of metal organic framework (MOF-5) Crystals
Metal Organic Frameworks (MOFs) represent a class of nanoporous crystalline materials with far reaching potential in gas storage, catalysis, and medical devices. We investigated the effects of synthesis process parameters on production of MOF-5 from terephthalic acid and zinc nitrate in diethylformamide. Under favorable synthesis conditions, we systematically mapped a solid formation diagram in terms of time and temperature for both stirred and unstirred conditions. The synthesis of MOF-5 has been previously reported as a straightforward reaction progressing from precursor compounds in solution directly to the final MOF-5 solid phase product. However, we show that the solid phase formation process is far more complex, invariably transferring through metastable intermediate crystalline phases before the final MOF-5 phase is reached, providing new insights into the formation pathways of MOFs. We also identify process parameters suitable for scale-up and continuous manufacturing of high purity MOF-5
Detecting Topology in a Nearly Flat Spherical Universe
When the density parameter is close to unity, the universe has a large
curvature radius independently of its being hyperbolic, flat, or spherical.
Whatever the curvature, the universe may have either a simply connected or a
multiply connected topology. In the flat case, the topology scale is arbitrary,
and there is no a priori reason for this scale to be of the same order as the
size of the observable universe. In the hyperbolic case any nontrivial topology
would almost surely be on a length scale too large to detect. In the spherical
case, by contrast, the topology could easily occur on a detectable scale. The
present paper shows how, in the spherical case, the assumption of a nearly flat
universe simplifies the algorithms for detecting a multiply connected topology,
but also reduces the amount of topology that can be seen. This is of primary
importance for the upcoming cosmic microwave background data analysis.
This article shows that for spherical spaces one may restrict the search to
diametrically opposite pairs of circles in the circles-in-the-sky method and
still detect the cyclic factor in the standard factorization of the holonomy
group. This vastly decreases the algorithm's run time. If the search is widened
to include pairs of candidate circles whose centers are almost opposite and
whose relative twist varies slightly, then the cyclic factor along with a
cyclic subgroup of the general factor may also be detected. Unfortunately the
full holonomy group is, in general, unobservable in a nearly flat spherical
universe, and so a full 6-parameter search is unnecessary. Crystallographic
methods could also potentially detect the cyclic factor and a cyclic subgroup
of the general factor, but nothing else.Comment: 16 pages, 7 figure
- …