2,054 research outputs found
The synoptic problem: on Matthew's and Luke's use of Mark
In New Testament studies, the synoptic problem is concerned with the relationships between the gospels of Matthew, Mark and Luke. Assuming Markan priority, we investigate the relationship between the words in Mark that are retained unchanged by Matthew and those that are retained unchanged by Luke. This is done by mapping the sequence of words in Mark into binary time series that represent the retention or non-retention of the individual words, and then carrying out a variety of logistic regression analyses
Two-Dimensional Helioseismic Power, Phase, and Coherence Spectra of {\it Solar Dynamics Observatory} Photospheric and Chromospheric Observables
While the {\it Helioseismic and Magnetic Imager} (HMI) onboard the {\it Solar
Dynamics Observatory} (SDO) provides Doppler velocity [], continuum
intensity [], and line-depth [] observations, each of which is
sensitive to the five-minute acoustic spectrum, the {\it Atmospheric Imaging
Array} (AIA) also observes at wavelengths -- specifically the 1600 and 1700
Angstrom bands -- that are partly formed in the upper photosphere and have good
sensitivity to acoustic modes. In this article we consider the characteristics
of the spatio--temporal Fourier spectra in AIA and HMI observables for a
15-degree region around NOAA Active Region 11072. We map the
spatio--temporal-power distribution for the different observables and the HMI
Line Core [], or Continuum minus Line Depth, and the phase and coherence
functions for selected observable pairs, as a function of position and
frequency. Five-minute oscillation power in all observables is suppressed in
the sunspot and also in plage areas. Above the acoustic cut-off frequency, the
behaviour is more complicated: power in HMI is still suppressed in the
presence of surface magnetic fields, while power in HMI and the AIA bands
is suppressed in areas of surface field but enhanced in an extended area around
the active region, and power in HMI is enhanced in a narrow zone around
strong-field concentrations and suppressed in a wider surrounding area. The
relative phase of the observables, and their cross-coherence functions, are
also altered around the active region. These effects may help us to understand
the interaction of waves and magnetic fields in the different layers of the
photosphere, and will need to be taken into account in multi-wavelength local
helioseismic analysis of active regions.Comment: 18 pages, 15 figures, to be published in Solar Physic
Versatile regularisation toolkit for iterative image reconstruction with proximal splitting algorithms
Ill-posed image recovery requires regularisation to ensure stability. The presented open-source regularisation toolkit consists of state-of-the-art variational algorithms which can be embedded in a plug-and-play fashion
into the general framework of proximal splitting methods. The packaged regularisers aim to satisfy various prior expectations of the investigated objects, e.g., their structural characteristics, smooth or non-smooth surface morphology.
The flexibility of the toolkit helps with the design of more advanced model-based iterative reconstruction methods
for different imaging modalities while operating with simpler building blocks. The toolkit is written for CPU and
GPU architectures and wrapped for Python/MATLAB. We demonstrate the functionality of the toolkit in application
to Positron Emission Tomography (PET) and X-ray synchrotron computed tomography (CT)
Multiresolution spatiotemporal mechanical model of the heart as a prior to constrain the solution for 4D models of the heart.
In several nuclear cardiac imaging applications (SPECT and PET), images are formed by reconstructing tomographic data using an iterative reconstruction algorithm with corrections for physical factors involved in the imaging detection process and with corrections for cardiac and respiratory motion. The physical factors are modeled as coefficients in the matrix of a system of linear equations and include attenuation, scatter, and spatially varying geometric response. The solution to the tomographic problem involves solving the inverse of this system matrix. This requires the design of an iterative reconstruction algorithm with a statistical model that best fits the data acquisition. The most appropriate model is based on a Poisson distribution. Using Bayes Theorem, an iterative reconstruction algorithm is designed to determine the maximum a posteriori estimate of the reconstructed image with constraints that maximizes the Bayesian likelihood function for the Poisson statistical model. The a priori distribution is formulated as the joint entropy (JE) to measure the similarity between the gated cardiac PET image and the cardiac MRI cine image modeled as a FE mechanical model. The developed algorithm shows the potential of using a FE mechanical model of the heart derived from a cardiac MRI cine scan to constrain solutions of gated cardiac PET images
Liberty in Law? Intellectual Property Rights and Global Alliance Networks
Do formal legal institutions complement or substitute social network mechanisms of knowledge protection? We explore how the composition and structure of firms’ international alliance networks changes in response to the passage of intellectual property rights (IPR) laws in their home countries. We find that, when IPR laws are strengthened, firms form more international alliances, particularly if they operate in IP intensive industries, and do so with partners from a greater diversity of countries. The significance of status (centrality) as a predictor of international alliance formation decreased after the passage of IPR laws, in line with a substitution effect that ‘democratized’ access to the global network by increasing the participation of firms that were peripheral before the legal changes. In contrast, the closure of firms’ alliance networks increased with stronger IPR laws, in line with a complementarity effect that increased the use of social control. The increase in closure was strongest in the networks of the low status entrants into the global network. Using a difference-in-difference empirical design, we found that these changes coincided exactly with the timing of the passage of the laws across thirteen countries between 1988 and 2005. This study addresses issues of great theoretical and practical importance to the literatures on institutions, networks, and IPR
Time--Distance Helioseismology Data Analysis Pipeline for Helioseismic and Magnetic Imager onboard Solar Dynamics Observatory (SDO/HMI) and Its Initial Results
The Helioseismic and Magnetic Imager onboard the Solar Dynamics Observatory
(SDO/HMI) provides continuous full-disk observations of solar oscillations. We
develop a data-analysis pipeline based on the time-distance helioseismology
method to measure acoustic travel times using HMI Doppler-shift observations,
and infer solar interior properties by inverting these measurements. The
pipeline is used for routine production of near-real-time full-disk maps of
subsurface wave-speed perturbations and horizontal flow velocities for depths
ranging from 0 to 20 Mm, every eight hours. In addition, Carrington synoptic
maps for the subsurface properties are made from these full-disk maps. The
pipeline can also be used for selected target areas and time periods. We
explain details of the pipeline organization and procedures, including
processing of the HMI Doppler observations, measurements of the travel times,
inversions, and constructions of the full-disk and synoptic maps. Some initial
results from the pipeline, including full-disk flow maps, sunspot subsurface
flow fields, and the interior rotation and meridional flow speeds, are
presented.Comment: Accepted by Solar Physics topical issue 'Solar Dynamics Observatory
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