1,625 research outputs found
Ultraviolet jets and bright points in the solar chromosphere : II : statistical correlations
We use HRTS{VI rocket observations of the solar chromosphere to search
for relationships between high-Dopplershift \jets" observed in the CI lines near
= 156 nm and internetwork \bright points" observed in the = 160 nm continuum,
in sequel to the analysis by Cook et al. (1996) which failed to find a direct
connection between these phenomena. We now use the same data to establish
statistical correlations between CI Dopplershift and 160 nm brightness modulation
in internetwork areas. These mean relations emerge only after extensive spatial
averaging and have small amplitude, but are definitely significant. They show that
both CI Dopplershift and 160 nm brightness participate in oscillatory behavior with
three-minute periodicity and mesoscale (8 Mm wavelength) as well as small-scale
(1.4 Mm wavelength) spatial patterning. We find spatial and temporal phase relations
between Dopplershift and brightness that confirm that jets and bright points should
not be interpreted as isolated entities. Rather, they are chromospheric manifestations,
with much pattern interference, of the oscillatory acoustic shock dynamics in the
internetwork which also cause Ca II K2V grains. Additional small-scale modulation is
present which we attribute to waves with f-mode character
Ultraviolet jets and bright points in the solar chromosphere: I : search for one-to-one relationships
Ultraviolet spectrograms and spectroheliograms of the solar chromosphere are
used to test the suggestion (Dere et al. 1986, Rutten & Uitenbroek 1991a) that
bright points observed at h = 1600 Å, chromospheric jets observed in CI lines
near h = 1560 Å, and Ca II K2V bright points are associated with each other and
that they are all manifestations of the same wave interaction in the non-magnetic
chromosphere. We search for spatio-temporal connections between 1600 Å bright
points and CI blue jets using data from the HRTS VI rocket mission, comparing
1600 Å spectroheliograms and a co-spatial CI Dopplershift map on a pixel-by-pixel
basis. We find no direct evidence for spatial co-location of bright points and jets, not
for instantaneous correspondence and also not when allowing for phase delays as long
as three minutes. Also, the average brightness evolution and its rms uctuation are
not obviously different between sites of large CI blueshift and the remaining surface
Pilgrims and MERS-CoV: What's the risk?
10.1186/s12982-015-0025-8Emerging Themes in Epidemiology12
Conformal-thin-sandwich initial data for a single boosted or spinning black hole puncture
Sequences of initial-data sets representing binary black holes in
quasi-circular orbits have been used to calculate what may be interpreted as
the innermost stable circular orbit. These sequences have been computed with
two approaches. One method is based on the traditional
conformal-transverse-traceless decomposition and locates quasi-circular orbits
from the turning points in an effective potential. The second method uses a
conformal-thin-sandwich decomposition and determines quasi-circular orbits by
requiring the existence of an approximate helical Killing vector. Although the
parameters defining the innermost stable circular orbit obtained from these two
methods differ significantly, both approaches yield approximately the same
initial data, as the separation of the binary system increases. To help
understanding this agreement between data sets, we consider the case of initial
data representing a single boosted or spinning black hole puncture of the
Bowen-York type and show that the conformal-transverse-traceless and
conformal-thin-sandwich methods yield identical data, both satisfying the
conditions for the existence of an approximate Killing vector.Comment: 13 pages, 2 figure
Change Mining in Adaptive Process Management Systems
The wide-spread adoption of process-aware information systems has resulted in a bulk of computerized information about real-world processes. This data can be utilized for process performance analysis as well as for process improvement. In this context process mining offers promising perspectives. So far, existing mining techniques have been applied to operational processes, i.e., knowledge is extracted from execution logs (process discovery), or execution logs are compared with some a-priori process model (conformance checking). However, execution logs only constitute one kind of data gathered during process enactment. In particular, adaptive processes provide additional information about process changes (e.g., ad-hoc changes of single process instances) which can be used to enable organizational learning. In this paper we present an approach for mining change logs in adaptive process management systems. The change process discovered through process mining provides an aggregated overview of all changes that happened so far. This, in turn, can serve as basis for all kinds of process improvement actions, e.g., it may trigger process redesign or better control mechanisms
Photon Statistics; Nonlinear Spectroscopy of Single Quantum Systems
A unified description of multitime correlation functions, nonlinear response
functions, and quantum measurements is developed using a common generating
function which allows a direct comparison of their information content. A
general formal expression for photon counting statistics from single quantum
objects is derived in terms of Liouville space correlation functions of the
material system by making a single assumption that spontaneous emission is
described by a master equation
Pillared MOFs: structure and ring opening polymerization of cyclic esters
The solvothermal reaction of Zn(NO3)2·6H2O with 5-aminoisophthalic acid and 4,4′-bipyridyl (4,4′-bipy) led to the self-assembly of the known 3-D hybrid H-bonded/covalent structure {[Zn(5-AIP)(4,4′-bipy)0.5]·DMF}n (1·DMF), but with DMF here (rather than H2O as previously): an analogous reaction using the related 4,4′-azopyridine (4,4′-azopy) in place of 4,4′-bipyridyl afforded the structurally related framework {[Zn(5-AIP)(4,4′-azopy)0.5]·0.75DMF}n (2·0.75DMF). Similar solvothermal reactions of Co(NO3)·6H2O, Mn(NO3)·4H2O and Cd(NO3)·4H2O with 5-aminoisophthalate and the potential linkers 4,4′-bipy, 2-di(4-pyridyl)ethylene (DPE), and 4,4′-azopy afforded the porous 3-D structures {[Co2(NO3)2(5-AIP)(4,4′-bipy)2]·2EtOH}n (3·2EtOH), {[Co(5-AIP)(DPE)]·2DMF}n (4·2DMF), {[Co(5-AIP)(4,4′-azopy)]·2DMA}n (5·2DMA), {[Mn(5-AIP)(4,4′-bipy)]·2DMA}n (6·2DMA), {[Mn(5-AIP)(DPE)]·6DMF}n (7·6DMF), {[Mn(5-AIP)(4,4′-azopy)]·2.5DMF}n (8·2.5DMF), the previously reported {[Cd(5-AIP)(4,4′-bipy)]·3DMF}n (9·3DMF), {[Cd(5-AIP)(DPE)]·DMF}n (10), and {Cd(5-AIP)(4,4′-azopy)(DMF)}n (11), with structures 4-10 bearing the same network topologies with metal atoms and 5-AIP ligands in sheets, bipy ligands acting as pillars, and solvent molecules of crystallisation located around the bipy ligands. The activated MOFs were employed as catalysts for the ring opening polymerization (ROP) of ϵ-caprolactone and δ-valerolactone. ROPs were conducted as melts, and under N2 only 1 with δ-VL (∼93% conversion) was active. In the case of ϵ-CL under air, all the systems were active with 1, 2, and 11 affording >90% conversion. Molecular weights (Mn) were in the range 3760-17 940 Da and the products formed were identified as both cyclic and linear PCL. For δ-VL, the catalysts performed somewhat better, with all systems (except 8) affording ∼90% conversion or more under air. Molecular weights (Mn) were in the range 2180-7940 and as for PCL, the products formed were identified as both cyclic and linear PCL
A skeleton approximate solution of the Einstein field equations for multiple black-hole systems
An approximate analytical and non-linear solution of the Einstein field
equations is derived for a system of multiple non-rotating black holes. The
associated space-time has the same asymptotic structure as the Brill-Lindquist
initial data solution for multiple black holes. The system admits an
Arnowitt-Deser-Misner (ADM) Hamiltonian that can particularly evolve the
Brill-Lindquist solution over finite time intervals. The gravitational field of
this model may properly be referred to as a skeleton approximate solution of
the Einstein field equations. The approximation is based on a conformally flat
truncation, which excludes gravitational radiation, as well as a removal of
some additional gravitational field energy. After these two simplifications,
only source terms proportional to Dirac delta distributions remain in the
constraint equations. The skeleton Hamiltonian is exact in the test-body limit,
it leads to the Einsteinian dynamics up to the first post-Newtonian
approximation, and in the time-symmetric limit it gives the energy of the
Brill-Lindquist solution exactly. The skeleton model for binary systems may be
regarded as a kind of analytical counterpart to the numerical treatment of
orbiting Misner-Lindquist binary black holes proposed by Gourgoulhon,
Grandclement, and Bonazzola, even if they actually treat the corotating case.
Along circular orbits, the two-black-hole skeleton solution is quasi-stationary
and it fulfills the important property of equality of Komar and ADM masses.
Explicit calculations for the determination of the last stable circular orbit
of the binary system are performed up to the tenth post-Newtonian order within
the skeleton model.Comment: 15 pages, 1 figure, submitted to Phys. Rev. D, 3 references added,
minor correction
Consistent histories, the quantum Zeno effect, and time of arrival
We present a decomposition of the general quantum mechanical evolution
operator, that corresponds to the path decomposition expansion, and interpret
its constituents in terms of the quantum Zeno effect (QZE). This decomposition
is applied to a finite dimensional example and to the case of a free particle
in the real line, where the possibility of boundary conditions more general
than those hitherto considered in the literature is shown. We reinterpret the
assignment of consistent probabilities to different regions of spacetime in
terms of the QZE. The comparison of the approach of consistent histories to the
problem of time of arrival with the solution provided by the probability
distribution of Kijowski shows the strength of the latter point of view
The Lazarus project: A pragmatic approach to binary black hole evolutions
We present a detailed description of techniques developed to combine 3D
numerical simulations and, subsequently, a single black hole close-limit
approximation. This method has made it possible to compute the first complete
waveforms covering the post-orbital dynamics of a binary black hole system with
the numerical simulation covering the essential non-linear interaction before
the close limit becomes applicable for the late time dynamics. To determine
when close-limit perturbation theory is applicable we apply a combination of
invariant a priori estimates and a posteriori consistency checks of the
robustness of our results against exchange of linear and non-linear treatments
near the interface. Once the numerically modeled binary system reaches a regime
that can be treated as perturbations of the Kerr spacetime, we must
approximately relate the numerical coordinates to the perturbative background
coordinates. We also perform a rotation of a numerically defined tetrad to
asymptotically reproduce the tetrad required in the perturbative treatment. We
can then produce numerical Cauchy data for the close-limit evolution in the
form of the Weyl scalar and its time derivative
with both objects being first order coordinate and tetrad invariant. The
Teukolsky equation in Boyer-Lindquist coordinates is adopted to further
continue the evolution. To illustrate the application of these techniques we
evolve a single Kerr hole and compute the spurious radiation as a measure of
the error of the whole procedure. We also briefly discuss the extension of the
project to make use of improved full numerical evolutions and outline the
approach to a full understanding of astrophysical black hole binary systems
which we can now pursue.Comment: New typos found in the version appeared in PRD. (Mostly found and
collected by Bernard Kelly
- …