9 research outputs found
Towards a New Standard Model for Black Hole Accretion
We briefly review recent developments in black hole accretion disk theory,
emphasizing the vital role played by magnetohydrodynamic (MHD) stresses in
transporting angular momentum. The apparent universality of accretion-related
outflow phenomena is a strong indicator that large-scale MHD torques facilitate
vertical transport of angular momentum. This leads to an enhanced overall rate
of angular momentum transport and allows accretion of matter to proceed at an
interesting rate. Furthermore, we argue that when vertical transport is
important, the radial structure of the accretion disk is modified at small
radii and this affects the disk emission spectrum. We present a simple model
demonstrating how energetic, magnetically-driven outflows modify the emergent
disk emission spectrum with respect to that predicted by standard accretion
disk theory. A comparison of the predicted spectra against observations of
quasar spectral energy distributions suggests that mass accretion rates
inferred using the standard disk model may severely underestimate their true
values.Comment: To appear in the Fifth Stromlo Symposium Proceedings special issue of
ApS
Automated Coronal Hole Detection using Local Intensity Thresholding Techniques
We identify coronal holes using a histogram-based intensity thresholding
technique and compare their properties to fast solar wind streams at three
different points in the heliosphere. The thresholding technique was tested on
EUV and X-ray images obtained using instruments onboard STEREO, SOHO and
Hinode. The full-disk images were transformed into Lambert equal-area
projection maps and partitioned into a series of overlapping sub-images from
which local histograms were extracted. The histograms were used to determine
the threshold for the low intensity regions, which were then classified as
coronal holes or filaments using magnetograms from the SOHO/MDI. For all three
instruments, the local thresholding algorithm was found to successfully
determine coronal hole boundaries in a consistent manner. Coronal hole
properties extracted using the segmentation algorithm were then compared with
in situ measurements of the solar wind at 1 AU from ACE and STEREO. Our results
indicate that flux tubes rooted in coronal holes expand super-radially within 1
AU and that larger (smaller) coronal holes result in longer (shorter) duration
high-speed solar wind streams
253 STUDY Z - EPIDEMIOLOGY OF NEUROPATHIC PAIN IN PATIENTS WITH HERPES ZOSTER AND POST HERPETIC NEURALGIA IN SÃO PAULO, BRAZIL
The relationship of PSA, PSAD and clinicopathological stage in patients with prostate cancer
Deployment of inflatable space structures - A review of recent developments
This paper reviews recent advances and future challenges in analytical and experimental methods for understanding and verifying the deployment of inflatable structures in space. Concepts for free and controlled deployments are discussed and examples are cited. Prior experiences with ground and flight experiments are examined and the promise of predictive analytical models is reviewed. In the early stage of inflatable developments, analytical simulations of deployment were noticeably lagging because of the high degree of problem complexity. However, recent experiences with a number of engineering and phenomenological models show that these models are particularly useful in explaining the physics of deployment. The paper concludes with likely future directions on the best use of deployment tests and analytical simulations to enhance the low mass and volume advantages of inflatables with greater deployment reliability, and at the same time, minimize the use of massive complex control devices