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A psychological process by which parents incorporate humor into their relationships with their children, aged birth to six.
Nasa desalting kit development, phase ii first progress report
NASA desalting kit development - container and processor desig
Are gravitational waves from giant magnetar flares observable?
Are giant flares in magnetars viable sources of gravitational radiation? Few
theoretical studies have been concerned with this problem, with the small
number using either highly idealized models or assuming a magnetic field orders
of magnitude beyond what is supported by observations. We perform nonlinear
general-relativistic magnetohydrodynamics simulations of large-scale
hydromagnetic instabilities in magnetar models. We utilise these models to find
gravitational wave emissions over a wide range of energies, from 10^40 to 10^47
erg. This allows us to derive a systematic relationship between the surface
field strength and the gravitational wave strain, which we find to be highly
nonlinear. In particular, for typical magnetar fields of a few times 10^15 G,
we conclude that a direct observation of f-modes excited by global magnetic
field reconfigurations is unlikely with present or near-future gravitational
wave observatories, though we also discuss the possibility that modes in a
low-frequency band up to 100 Hz could be sufficiently excited to be relevant
for observation.Comment: 4 pages, 3 figures. Further information can be found at
http://www.physik.uni-tuebingen.de/institute/astronomie-astrophysik/institut/theoretische-astrophysik/forschung.htm
The runaway instability in general relativistic accretion disks
When an accretion disk falls prey to the runaway instability, a large portion
of its mass is devoured by the black hole within a few dynamical times. Despite
decades of effort, it is still unclear under what conditions such an
instability can occur. The technically most advanced relativistic simulations
to date were unable to find a clear sign for the onset of the instability. In
this work, we present three-dimensional relativistic hydrodynamics simulations
of accretion disks around black holes in dynamical space-time. We focus on the
configurations that are expected to be particularly prone to the development of
this instability. We demonstrate, for the first time, that the fully
self-consistent general relativistic evolution does indeed produce a runaway
instability.Comment: 5 pages, 3 figures, minor corrections to match published version in
MNRAS, +link to animatio
Correlated Binary Regression Using Orthogonalized Residuals
This paper focuses on marginal regression models for correlated binary responses when estimation of the association structure is of primary interest. A new estimating function approach based on orthogonalized residuals is proposed. This procedure allows a new representation and addresses some of the difficulties of the conditional-residual formulation of alternating logistic regressions of Carey, Zeger & Diggle (1993). The new method is illustrated with an analysis of data on impaired pulmonary function
Cauchy-perturbative matching revisited: tests in spherical symmetry
During the last few years progress has been made on several fronts making it
possible to revisit Cauchy-perturbative matching (CPM) in numerical relativity
in a more robust and accurate way. This paper is the first in a series where we
plan to analyze CPM in the light of these new results.
Here we start by testing high-order summation-by-parts operators, penalty
boundaries and contraint-preserving boundary conditions applied to CPM in a
setting that is simple enough to study all the ingredients in great detail:
Einstein's equations in spherical symmetry, describing a black hole coupled to
a massless scalar field. We show that with the techniques described above, the
errors introduced by Cauchy-perturbative matching are very small, and that very
long term and accurate CPM evolutions can be achieved. Our tests include the
accretion and ring-down phase of a Schwarzschild black hole with CPM, where we
find that the discrete evolution introduces, with a low spatial resolution of
\Delta r = M/10, an error of 0.3% after an evolution time of 1,000,000 M. For a
black hole of solar mass, this corresponds to approximately 5 s, and is
therefore at the lower end of timescales discussed e.g. in the collapsar model
of gamma-ray burst engines.
(abridged)Comment: 14 pages, 20 figure
Bending Properties of Wood Flakes of Three Southern Species
This research focuses on experimental investigations of the bending properties of wood flakes of three southern species. Modulus of elasticity (MOE), modulus of rupture (MOR), and strength at proportional limit (SPL) of flakes were measured based on Methods of Testing Small Clear Specimens of Timber (ASTM D143-94; ASTM 1994a) using a miniature material tester. Effect of species, cutting direction, and temperature were evaluated. Bending properties were found to vary between and within the three species. Southern yellow pine had the lowest bending stiffness and strength followed by sweetgum, while yellow-poplar had the highest bending properties. Radially cut specimens (force applied on the tangential axis) were found to have lower MOE, MOR, and SPL than tangentially cut specimens (force applied on the radial axis). Drying temperature was also found to have a significant effect on bending stiffness and strength. A decreasing trend in bending properties was observed when drying temperature was increased
Time-division SQUID multiplexers with reduced sensitivity to external magnetic fields
Time-division SQUID multiplexers are used in many applications that require
exquisite control of systematic error. One potential source of systematic error
is the pickup of external magnetic fields in the multiplexer. We present
measurements of the field sensitivity figure of merit, effective area, for both
the first stage and second stage SQUID amplifiers in three NIST SQUID
multiplexer designs. These designs include a new variety with improved
gradiometry that significantly reduces the effective area of both the first and
second stage SQUID amplifiers.Comment: 4 pages, 7 figures. Submitted for publication in the IEEE
Transactions on Applied Superconductivity, August 201
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