525 research outputs found
14- by 22-Foot Subsonic Tunnel Laser Velocimeter Upgrade
A long-focal length laser velocimeter constructed in the early 1980's was upgraded using current technology to improve usability, reliability and future serviceability. The original, free-space optics were replaced with a state-of-the-art fiber-optic subsystem which allowed most of the optics, including the laser, to be remote from the harsh tunnel environment. General purpose high-speed digitizers were incorporated in a standard modular data acquisition system, along with custom signal processing software executed on a desktop computer, served as the replacement for the signal processors. The resulting system increased optical sensitivity with real-time signal/data processing that produced measurement precisions exceeding those of the original system. Monte Carlo simulations, along with laboratory and wind tunnel investigations were used to determine system characteristics and measurement precision
Supersonic Flow Field Investigation Using a Fiber-optic based Doppler Global Velocimeter
A three-component fiber-optic based Doppler Global Velocimeter was constructed, evaluated and used to measure shock structures about a low-sonic boom model in a Mach 2 flow. The system was designed to have maximum flexibility in its ability to measure flows with restricted optical access and in various facilities. System layout is described along with techniques developed for production supersonic testing. System evaluation in the Unitary Plan Wind Tunnel showed a common acceptance angle of f4 among the three views with velocity measurement resolutions comparable with free-space systems. Flow field measurements of shock structures above a flat plate with an attached ellipsoid-cylinder store and a low-sonic boom model are presented to demonstrate the capabilities of the system during production testing
Work-related psychological health among clergywomen in Australia
Drawing on the classic model of balanced affect, the Francis Burnout Inventory conceptualises good work-related psychological health among clergy in terms of negative affect being balanced by positive affect. This paper sets out to explore the relationship between work-related psychological health and psychological type (as assessed by the Francis Psychological-Type Scales) among a sample of 212 Australian clergywomen who completed the National Church Life Survey Form L in 2006. The data supported the internal consistency reliability of the Francis Burnout Inventory and Francis Psychological-Type Scales and found that work-related psychological health was positively related to extraversion and sensing
Replication-induced DNA secondary structures drive fork uncoupling and breakage
Sequences that form DNA secondary structures, such as G-quadruplexes (G4s) and intercalated-Motifs (iMs), are abundant in the human genome and play various physiological roles. However, they can also interfere with replication and threaten genome stability. Multiple lines of evidence suggest G4s inhibit replication, but the underlying mechanism remains unclear. Moreover, evidence of how iMs affect the replisome is lacking. Here, we reconstitute replication of physiologically derived structure-forming sequences to find that a single G4 or iM arrest DNA replication. Direct single-molecule structure detection within solid-state nanopores reveals structures form as a consequence of replication. Combined genetic and biophysical characterisation establishes that structure stability and probability of structure formation are key determinants of replisome arrest. Mechanistically, replication arrest is caused by impaired synthesis, resulting in helicase-polymerase uncoupling. Significantly, iMs also induce breakage of nascent DNA. Finally, stalled forks are only rescued by a specialised helicase, Pif1, but not Rrm3, Sgs1, Chl1 or Hrq1. Altogether, we provide a mechanism for quadruplex structure formation and resolution during replication and highlight G4s and iMs as endogenous sources of replication stress
MGC2214+3550: A New Binary Quasar
We report the discovery of a binary quasar, MGC2214+3550 A,B, whose
components have similar optical spectra at a redshift z=0.88. The quasars are
separated on the sky by 3.0", and have a magnitude difference of Delta(m_I)=0.5
mag. The VLA radio map at 3.6 cm shows a single 47mJy radio source with a
core-jet morphology that is coincident with the brighter optical quasar A.
Gravitational lensing is ruled out by the lack of radio emission from quasar B,
and the lack of any visible galaxies to act as the lens. We conclude that MGC
2214+3550 A and B are physically associated. With a projected separation of
12.7h^{-1} kpc (Omega_0=1), MGC 2214+3550 A,B is one of the smallest z>0.5
binary quasars.Comment: 13 pages, 3 .ps figs, submitted to ApJ
The Cosmology Large Angular Scale Surveyor
The Cosmology Large Angular Scale Surveyor (CLASS) is a four telescope array
designed to characterize relic primordial gravitational waves from inflation
and the optical depth to reionization through a measurement of the polarized
cosmic microwave background (CMB) on the largest angular scales. The
frequencies of the four CLASS telescopes, one at 38 GHz, two at 93 GHz, and one
dichroic system at 145/217 GHz, are chosen to avoid spectral regions of high
atmospheric emission and span the minimum of the polarized Galactic
foregrounds: synchrotron emission at lower frequencies and dust emission at
higher frequencies. Low-noise transition edge sensor detectors and a rapid
front-end polarization modulator provide a unique combination of high
sensitivity, stability, and control of systematics. The CLASS site, at 5200 m
in the Chilean Atacama desert, allows for daily mapping of up to 70\% of the
sky and enables the characterization of CMB polarization at the largest angular
scales. Using this combination of a broad frequency range, large sky coverage,
control over systematics, and high sensitivity, CLASS will observe the
reionization and recombination peaks of the CMB E- and B-mode power spectra.
CLASS will make a cosmic variance limited measurement of the optical depth to
reionization and will measure or place upper limits on the tensor-to-scalar
ratio, , down to a level of 0.01 (95\% C.L.)
Ring-Like Structure in the Radio Lobe of MG0248+0641
We present radio and optical observations of MG0248+0641, which contains a
kiloparsec-scale ring-like structure in one of its radio lobes. The radio
observations show a typical core-double morphology: a central core between two
lobes, each of which has a hotspot. The western radio lobe appears as a nearly
continuous ring, with linear polarization electric field vectors which are
oriented in a radial direction from the ring center. We consider several
different interpretations for the nature of this ring, including gravitational
lensing of a normal jet by a foreground galaxy. Even though simple lensing
models can describe the ring morphology reasonably well, the high linear
polarization seen around the ring cannot be easily explained. The chance
interposition of a galactic supernova remnant, nova, planetary nebula, or H II
region, has been ruled out. The highly polarized ring of MG0248+0641 is much
like the prominent ring seen in 3C219, and the multiple ones in 3C310 and
Hercules A, suggesting that similar physical processes are producing shell
structures in these radio galaxies. The ring in MG0248+0641 may be caused by
the formation of ``bubbles'', as a result of instabilities in the energy flow
down the western radio jet. It may also be possible that the required
instabilities are triggered by the infall of gas, via tidal interaction of the
central source with a nearby galaxy. This scenario may be indicated by our
marginal detection of an optical source close to the western hotspot.Comment: 21 pages. Submitted to AJ Aug 15, 1997; Accepted Sep 30, 1997. Minor
changes in conten
Radio Astronomy
Contains table of contents for Section 4 and reports on eight research projects.National Science Foundation Grant AST 88-19848National Aeronautics and Space Administration Goddard Space Flight Center Grant NAGW-2310SM Systems and Research, IncNational Aeronautics and Space Administration Goddard Space Flight Center Grant NAG 5-537National Aeronautics and Space Administration Goddard Space Flight Center Grant NAG 5-10Leaders for Manufacturing ProgramNational Aeronautics and Space Administration Goddard Space Flight Center Grant NAS 5-3079
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