685 research outputs found
The Future of Radiology Consultation
A more collaborative approach to consultation is one that every radiologist concerned about the future of radiology should be eager to embody
The Space Density Evolution of Wet and Dry Mergers in the Canada-France-Hawaii Telescope Legacy Survey
We analyze 1298 merging galaxies with redshifts up to z = 0.7 from the Canada-France-Hawaii Telescope Legacy Survey, taken from the catalog presented in Bridge et al. (2010). By analyzing the internal colors of these systems, we show that so-called wet and dry mergers evolve in different senses, and quantify the space densities of these systems. The local space density of wet mergers is essentially identical to the local space density of dry mergers. The evolution in the total merger rate is modest out to z ∼ 0.7, although the wet and dry populations have different evolutionary trends. At higher redshifts dry mergers make a smaller contribution to the total merging galaxy population, but this is offset by a roughly equivalent increase in the contribution from wet mergers. By comparing the mass density function of early-type galaxies to the corresponding mass density function for merging systems, we show that not all the major mergers with the highest masses (M_(stellar) > 10^(11)M☉) will end up with the most massive early-type galaxies, unless the merging timescale is dramatically longer than that usually assumed. On the other hand, the usually-assumed merging timescale of ∼ 0.5–1 Gyr is quite consistent with the data if we suppose that only less massive early-type galaxies form via mergers. Since low-intermediate mass ellipticals are 10–100 times more common than their most massive counterparts, the hierarchical explanation for the origin of early-type galaxies may be correct for the vast majority of early-types, even if incorrect for the most massive ones
A Close-pair Analysis of Damp Mergers at Intermediate Redshifts
We have studied the kinematics of ~2800 candidate close-pair galaxies at 0.1 < z < 1.2 identified from the Canada-France-Hawaii Telescope Legacy Survey fields. Spectra of these systems were obtained using spectrometers on the 6.5 m Magellan and 5 m Hale telescopes. These data allow us to constrain the rate of dry mergers at intermediate redshifts and to test the "hot halo" model for quenching of star formation. Using virial radii estimated from the correlation between dynamical and stellar masses published by Leauthaud et al., we find that around 1/5 of our candidate pairs are likely to share a common dark matter halo (our metric for close physical association). These pairs are divided into red-red, blue-red, and blue-blue systems using the rest-frame colors classification method introduced in Chou et al.. Galaxies classified as red in our sample have very low star formation rates, but they need not be totally quiescent, and hence we refer to them as "damp," rather than "dry," systems. After correcting for known selection effects, the fraction of blue-blue pairs is significantly greater than that of red-red and blue-red pairs. Red-red pairs are almost entirely absent from our sample, suggesting that damp mergers are rare at z ~ 0.5. Our data support models with a short merging timescale (<0.5 Gyr) in which star formation is enhanced in the early phase of mergers, but quenched in the late phase. Hot halo models may explain this behavior, but only if virial shocks that heat gas are inefficient until major mergers are nearly complete
The Space Density Evolution of Wet and Dry Mergers in the Canada-France-Hawaii Telescope Legacy Survey
We analyze 1298 merging galaxies with redshifts up to z=0.7 from the
Canada-France-Hawaii Telescope Legacy Survey, taken from the catalog presented
in Bridge et al. (2010). By analyzing the internal colors of these systems, we
show that so-called wet and dry mergers evolve in different senses, and
quantify the space densities of these systems. The local space density of wet
mergers is essentially dentical to the local space density of dry mergers. The
evolution in the total merger rate is modest out to z ~ 0.7, although the wet
and dry populations have different evolutionary trends. At higher redshifts dry
mergers make a smaller contribution to the total merging galaxy population, but
this is offset by a roughly equivalent increase in the contribution from wet
mergers. By comparing the mass density function of early-type galaxies to the
corresponding mass density function for merging systems, we show that not all
the major mergers with the highest masses (M_stellar > 10^11 M_solar) will end
up with the most massive early-type galaxies, unless the merging timescale is
dramatically longer than that usually assumed. On the other hand, the
usually-assumed merging timescale of ~ 0.5-1 Gyr is quite consistent with the
data if we suppose that only less massive early-type galaxies form via mergers.
Since low-intermediate mass ellipticals are 10 --100 times more common than
their most massive counterparts, the hierarchical explanation for the origin of
early-type galaxies may be correct for the vast majority of early-types, even
if incorrect for the most massive ones.Comment: 10 pages, 8 figures. Accepted by A
Pancreatectomy for metastatic real cell carcinoma : twenty years of experience at a tertiary centre
Renal Cell Carcinoma (RCC) accounts for approximately 90% of primary renal malignancies, of which the clear cell subtype is most common. While metastatic disease is common at the time of diagnosis and generally confers a poor prognosis, metastatic RCC may demonstrate relatively indolent behaviour and present many years after resection of the primary tumour, including to the pancreas. The available literature suggested that surgical resection was appropriate for select patients, including those with a solitary pancreatic metastasis, minimal comorbidities and uncomplicated progress from initial treatment of their primary renal malignancy. A retrospective case series of patients presenting with RCC metastases to the pancreas, managed via surgical resection at a tertiary teaching hospital was reviewed. Analysis of patient demographics, investigations, management and outcomes were performed, with a focus on post-operative morbidity and overall survival. Between 2000 and 2020, 7 patients underwent pancreatic resection of RCC metastases at our tertiary teaching hospital with curative intent. Median age at time of resection was 66 years. No post-operative mortality or major morbidity was experienced by the 7 patients, although 4 patients developed some degree of pancreatic insufficiency. Four patients experienced recurrent metastatic RCC, with median time to recurrence of 3.5 years. This was the largest local study to describe an Australian experience of the surgical management of RCC pancreatic metastases. These patients are frequently afforded prolonged survival following pancreatic resection, but often develop other distant sites of disease and second renal tumours
Metrology Camera System of Prime Focus Spectrograph for Subaru Telescope
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber
spectrograph designed for the prime focus of the 8.2m Subaru telescope. PFS
will cover a 1.3 degree diameter field with 2394 fibers to complement the
imaging capabilities of Hyper SuprimeCam. To retain high throughput, the final
positioning accuracy between the fibers and observing targets of PFS is
required to be less than 10um. The metrology camera system (MCS) serves as the
optical encoder of the fiber motors for the configuring of fibers. MCS provides
the fiber positions within a 5um error over the 45 cm focal plane. The
information from MCS will be fed into the fiber positioner control system for
the closed loop control. MCS will be located at the Cassegrain focus of Subaru
telescope in order to to cover the whole focal plane with one 50M pixel Canon
CMOS camera. It is a 380mm Schmidt type telescope which generates a uniform
spot size with a 10 micron FWHM across the field for reasonable sampling of
PSF. Carbon fiber tubes are used to provide a stable structure over the
operating conditions without focus adjustments. The CMOS sensor can be read in
0.8s to reduce the overhead for the fiber configuration. The positions of all
fibers can be obtained within 0.5s after the readout of the frame. This enables
the overall fiber configuration to be less than 2 minutes. MCS will be
installed inside a standard Subaru Cassgrain Box. All components that generate
heat are located inside a glycol cooled cabinet to reduce the possible image
motion due to heat. The optics and camera for MCS have been delivered and
tested. The mechanical parts and supporting structure are ready as of spring
2016. The integration of MCS will start in the summer of 2016.Comment: 11 pages, 15 figures. SPIE proceeding. arXiv admin note: text overlap
with arXiv:1408.287
A Reconfigurable Motor for Experimental Emulation of Stator Winding Inter-Turn and Broken Bar Faults in Polyphase Induction Machines (Journal article)
The benefits and drawbacks of a 5-hp reconfigurable induction motor, which was designed for experimental emulation of stator winding interturn and broken rotor bar faults, are presented in this paper. It was perceived that this motor had the potential of quick and easy reconfiguration to produce the desired stator and rotor faults in a variety of different fault combinations. Hence, this motor was anticipated to make a useful test bed for evaluation of the efficacy of existing and new motor fault diagnostics techniques and not the study of insulation failure mechanisms. Accordingly, it was anticipated that this reconfigurable motor would eliminate the need to permanently destroy machine components such as stator windings or rotor bars when acquiring data from a faulty machine for fault diagnostic purposes. Experimental results under healthy and various faulty conditions are presented in this paper, including issues associated with rotor bar-end ring contact resistances that showed the drawbacks of this motor in so far as emulation of rotor bar breakages. However, emulation of stator-turn fault scenarios was successfully accomplished
Metrology Camera System of Prime Focus Spectrograph for Subaru Telescope
The Prime Focus Spectrograph (PFS) is a new optical/near-infrared multi-fiber
spectrograph designed for the prime focus of the 8.2m Subaru telescope. The
metrology camera system of PFS serves as the optical encoder of the COBRA fiber
motors for the configuring of fibers. The 380mm diameter aperture metrology
camera will locate at the Cassegrain focus of Subaru telescope to cover the
whole focal plane with one 50M pixel Canon CMOS sensor. The metrology camera is
designed to provide the fiber position information within 5{\mu}m error over
the 45cm focal plane. The positions of all fibers can be obtained within 1s
after the exposure is finished. This enables the overall fiber configuration to
be less than 2 minutes.Comment: 10 pages, 12 figures, SPIE Astronomical Telescopes and
Instrumentation 201
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