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Phased Array Feed (PAF) technology is the next major advancement in radio astronomy in terms of combining high sensitivity and large field of view. The Focal L-band Array for the Green Bank Telescope (FLAG) is one of the most sensitive PAFs developed so far. It consists of 19 dual-polarization elements mounted on a prime focus dewar resulting in seven beams on the sky. Its unprecedented system temperature of ~17 K will lead to a 3 fold increase in pulsar survey speeds as compared to contemporary single pixel feeds. Early science observations were conducted in a recently concluded commissioning phase of the FLAG where we clearly demonstrated its science capabilities. We observed a selection of normal and millisecond pulsars and detected giant pulses from PSR B1937+21.
We have investigated Kelvin-Helmholtz (K-H) instabilities for a homogeneous compressible plasma containing a uniform magnetic field and a linear velocity shear. A derivation of the relevant K-H dispersion equation and details regarding method of solution are given elsewhere (submitted to Mon. Not. R. Astr. Soc.). We present here an outline of our results.
We present maps in the visible emission lines of [S II] and the infrared emission lines of H2, at 2.12μm, for several bipolar outflow complexes which exhibit jet structures. A comparison of the morphology of this infrared emission and that seen in visible emission lines shows both the visible and the H2 emission exhibit clumpy structure on similar scales. It appears that the brightest H2 emission occurs at the working surfaces of the jets. Virtually no H2 emission is associated with the jets themselves.
Velocity profiles are presented for several objects and possible emission mechanisms are discussed.
The present observational problem of understanding the nature and origin of comets is analogous to that we would face in attempting to understand a planet and its atmosphere if we possessed only data on its ionosphere and exosphere. Virtually everything we can observe remotely is a part of the rapidly escaping gas and dust atmosphere of the comet.
Spectra of infrared sources associated with molecular clouds have shown absorption features at wavelengths of 6.0 and 6.8 μm. We suggest that the 6.0 μm feature can be identified with the stretching vibration of C=0 and the 6.8 μm feature with the bending vibrations of CH2 and CH3. The amount of carbon in the form of hydrocarbon molecules may be comparable to the amount in CO. This abundance of hydrocarbons is probably too large to be consistent with radio observations if the molecules are gaseous, but large abundances of hydrocarbons on the surfaces of grains may explain the infrared features, yet be unobservable in the radio.
Pre-storage drying-transfer operations and early stage storage expose cladding to higher temperatures and much higher pressure-induced tensile hoop stresses relative to normal operation in-reactor and pool storage under these conditions. Radial hydrides precipitate during cooling and could provide an additional embrittlement mechanism as the cladding temperature decreases below the ductile-to-brittle transition temperature. To simulate this behavior, unirradiated Zircaloy-4 samples were hydrided by a gas charging method to levels that encompass the range of hydrogen concentrations observed in current used fuel. Mechanical testing was carried out by the ring compression test (RCT) method at various temperatures to evaluate the sample’s ductility for both as-hydrided and post-hydride reorientation treated specimens. As-hydrided samples with higher hydrogen concentration (>800 ppm) resulted in lower strain before fracture and reduced maximum load. Increasing RCT temperatures resulted in increased ductility of the as-hydrided cladding. A systematic radial hydride treatment was conducted at various pressures and temperatures for the hydrided samples with H content around 200 ppm. Following the radial hydride treatment, RCTs on the hydride reoriented samples were conducted and exhibited lower ductility compared to as-hydrided samples.
The neurocognitive deficits and other correlates of problem gambling are also observable in individuals with lower cognitive abilities, suggesting that a low IQ may be a determinant of problem gambling. There has been very little research into this possibility. This study aimed to investigate the characteristics associated with problem gambling in a large population-based study in England, with a particular focus on IQ.
The Adult Psychiatric Morbidity Survey (APMS) 2007 comprised detailed interviews with 7403 individuals living in private households in England. Problem gambling was ascertained using a questionnaire based on DSM-IV criteria. Verbal IQ was estimated using the National Adult Reading Test (NART). Confounders included socio-economic and demographic factors, common mental disorders, impulsivity, smoking, and hazardous drug and alcohol use.
More than two-thirds of the population reported engaging in some form of gambling in the previous year, but problem gambling was rare [prevalence 0.7%, 95% confidence interval (CI) 0.5–1.0]. The odds of problem gambling doubled with each standard deviation drop in estimated verbal IQ [adjusted odds ratio (OR) 2.1, 95% CI 1.3–3.4, p = 0.003], after adjusting for other characteristics associated with problem gambling including age, sex, socio-economic factors, drug and alcohol dependence, smoking, impulsivity and common mental disorders. There was no strong relationship observed between IQ and non-problem gambling.
People with lower IQs may be at a higher risk of problem gambling. Further work is required to replicate and study the mechanisms behind these findings, and may aid the understanding of problem gambling and inform preventative measures and interventions.
EMU is a wide-field radio continuum survey planned for the new Australian Square Kilometre Array Pathfinder (ASKAP) telescope. The primary goal of EMU is to make a deep (rms ∼ 10 μJy/beam) radio continuum survey of the entire Southern sky at 1.3 GHz, extending as far North as +30° declination, with a resolution of 10 arcsec. EMU is expected to detect and catalogue about 70 million galaxies, including typical star-forming galaxies up to z ∼ 1, powerful starbursts to even greater redshifts, and active galactic nuclei to the edge of the visible Universe. It will undoubtedly discover new classes of object. This paper defines the science goals and parameters of the survey, and describes the development of techniques necessary to maximise the science return from EMU.
Long-term physical conditions (LTCs) consume the largest share of healthcare budgets. Although common mental disorders (CMDs) and LTCs often co-occur, the potential impact of improved mental health treatment on severe disability and hospital admissions for physical health problems remains unknown.
A cross-sectional study of 7403 adults aged 16–95 years living in private households in England was performed. LTCs were ascertained by prompted self-report. CMDs were ascertained by structured clinical interview. Disability was assessed using questions about problems with activities of daily living. Population impact and potential preventive gain were estimated using population-attributable fraction (PAF), and conservative estimates were obtained using ‘treated non-cases’ as the reference group.
Of the respondents, 20.7% reported at least one LTC. The prevalence of CMDs increased with the number of LTCs, but over two-thirds (71.2%) of CMD cases in people with LTCs were untreated. Statistically significant PAFs were found for CMDs and recent hospital admission [13.5%, 95% confidence intervals (CI) 6.6–20.0] and severe disability (31.3%, 95% CI 27.1–35.2) after adjusting for LTCs and other confounders. Only the latter remained significant when using the most conservative estimate of PAF (21.8%, 95% CI 14.0–28.9), and this was reduced only slightly when considering only participants with LTCs (18.5%, 95% CI 7.9–27.9).
Better treatments for CMDs in people with LTCs could achieve almost the same population health gain in terms of reducing severe disability as those targeted at the entire population. Interventions to reduce the prevalence of CMDs among people with LTCs should be part of routine medical care.
The Far-Infrared Radio Correlation (FRC) is the tightest and most universal correlation known among global parameters of galaxies. Here we present the results of our investigation of the 70 μm FRC of starforming galaxies in the Extended Chandra Deep Field South (ECDFS) out to z > 2. In order to quantify the evolution of the FRC we used both survival analysis and stacking techniques, which gave similar results. We also calculated the FRC using total infrared luminosity and rest-frame radio luminosity, qTIR, and find that qTIR is constant (within 0.22) over the redshift range 0 - 2. We see no evidence for evolution in the FRC at 70 μm, which is surprising given the many factors that are expected to change this ratio at high redshifts.
Poly(ethylene terephthalate), or PET, has been widely used in experiments due to its excellent properties and availability in sheets as thin as 1.5 µm. Its resistance to chemical attack makes PET a good choice as an inert substrate, but makes liquid phase deposition of thin films from solution challenging. Further, attempts to deposit films from the vapor phase have shown limited success. High quality PET films are desirable, as PET is transparent, hydrophobic, amenable to micropatterning, and is well characterized. As such, PET films are suited for use in microdevices. We report on liquid phase deposition of PET films, and on characterization of the films using optical methods.
The feasibility of fabricating Nb-Nb silicide microstructure by Physical Vapor Deposition with sufficient control of impurities has been investigated. It is demonstrated that electron beam evaporation can satisfy the requirement of impurity control under appropriate vacuum condition. In elemental layered structure of Nb and Si, NbSi2 is the first phase formed upon annealing. It was found that, at 600°C, the growth rate of NbSi2 phase at the interface of Nb and Si is 35Å/min. The Nb5Si3 phase nucleates at a higher temperature (around 900°C) at the interface of Nb and NbSi2. In the case of co-deposited film with overall composition around Nb5 Si3, NbSi2 formation is by-passed. Thus, multilayers of Nb/NbSi2 or Nb/Nb5Si3 can be formed from layered elemental deposition and subsequent heat treatment under controlled conditions by adjusting the starting thicknesses of the films. Alternate elemental and co-deposition and subsequent or in-situ heat treatment can directly form the layered Nb/desired silicide composite. Multilayers of Nb/NbSi2 and Nb/Nb5Si3 with layer thicknesses below 500Å have been formed from layered elemental deposition.
Amorphous carbon films grown with fluorohydrocarbons can be grown to have dielectric constant values around 2.0. The behavior of these films when subjected to thermal excursion is studied. We have investigated material deposited in an ECR plasma, and find that the F:H ratio of the gas mixture is a good guide to material properties. Films deposited at 5°C were placed in a vacuum chamber at 400°C as long as 60 minutes. The film thickness, dielectric constant, and infrared absorption spectrum change with the F:H ratio of the incoming gas and thermal cycling. It was found that the dielectric constant and loss tangent decrease upon heating and that there is an apparent increase in C=C groups. As expected, as the F:H ratio increases, the dielectric constant and thermal stability decrease. Good thermal stability is shown for F:H ratios of 1.5, which result in films with a dielectric constant of ∼2.4 after heating.
Carbon nanotubes represent an attractive material option for many applications, including electromechanical actuators. Though single wall carbon nanotubes exhibit advantageous actuator properties, such as large force generation and low operating voltage, functional devices based on carbon nanotube actuation have not yet been reported. Here we describe the fabrication and performance evaluation of a 1×2 electromechanical optical fiber switch based on a carbon nanotube actuator. The side-to-side movement of the input fiber of the device between two output fibers is a result of the actuation of an assembly of carbon nanotubes that have been attached to the fiber. The intensities of optical signals exiting the two outputs are monitored, and switching times down to 30 ms are demonstrated. Initial results indicate that mechanical optical switches using carbon nanotube actuators may be preferable to switches using alternative technologies due to the inexpensive assembly, low operating power, potentially high switching speeds, and potentially low insertion loss of the carbon nanotube based devices.
A refined thernodynamic analysis of the reaction between molen Al and SiC is presented. The calculations indicate much higher Si concentrations for saturation with respect to AkC 3 formation than previously reported. Preliminary microstructural studies confirm the formation of interfacial A14C3 for pure Al thin films on SiC reacted at 9000C. The implications of the calculations and experimental observations for the production of ohmic contacts to p-type SiC are discussed.
Nickel silicides were formed on Si (100) substrates and CVD grown Si0.9Ge0.1/Si layers by low thermal budget annealing of evaporated Ni films to evaluate their utility for ultra shallow junctions. The phase formation and microstructure of silicides formed using conventional furnace and rapid thermal annealing were studied by x-ray diffraction, Rutherford backscattering (RBS), x-ray photoelectron spectroscopy (XPS) and atomic force microscopy. RBS simulations and XPS study revealed the formation of a ternary nickel germanosilicide phase for the SiGe alloy. The incorporation of Ge resulted in a higher temperature window for the stability of low-resistive monosilicide phase. Electrical properties of the grown silicides were characterized by four-probe resistivity and contact resistance measurements.
We present a molecular dynamics simulation study of the liquid-solid transition in a two dimensional system consisting of particles of two different sizes interacting via a truncated Lennard-Jones potential. We work with equal number of particles of each kind and the dispersity Δ in the sizes of the particles is varied by changing the ratio of the particle sizes only. For the monodisperse case (Δ = 0) and for small values of Δ, we find a first order liquid-solid transition on increasing the volume fraction p of the particles. As we increase Δ, the first-order transition coexistence region weakens gradually and completely disappears at high dispersities around Δ = 0.10. At these values of dispersity the high density phase lacks long range translational order but possesses orientational order with a large but finite correlation length. The consequences of this effect of dispersity on the glass transition and on the melting transition in general are discussed.