The Inhomogeneous Hall's Ray

We show that the inhomogenous approximation spectrum, associated to an irrational number \alpha\ always has a Hall's Ray; that is, there is an \epsilon>0 such that [0,\epsilon) is a subset of the spectrum. In the case when \alpha\ has unbounded partial quotients we show that the spectrum is just a ray.Comment: Fixed typos in bibliograph

Groundbased near-IR observations of the surface of Venus

We present images of the nightside of Venus taken in the near-infrared windows at 1.0, 1.1, 1.18, 1.28, 1.31, and 2.3 microns with the new infrared camera/spectrometer IRIS on the Anglo-Australian Telescope. These data were taken in spectral-mapping mode. This technique involves scanning the telescope perpendicular to the slit, while collecting spectra at successive slit positions across the planet. We produce data cubes with one spectral and two spatial dimensions. Images can be extracted over any wavelength regions. Each image has square pixels of 0.8 inch resolution. We reduced the scattered light from the sunlit crescent in images extracted from each window by subtracting images taken on either side of the window, where the Venus atmosphere is opaque. Unlike the short wavelength windows, which reveal thermal contrasts that originate primarily from the surface and deep atmosphere, the emission in the 2.3 microns window is produced at much higher altitudes (30-40 km). Emission contrasts seen near 2.3 microns are associated with horizontal variations in the cloud optical depths, and have rotation periods of about six days. We detect large contrasts in infrared emission (20-40 percent) across the disc of Venus in the 1.0-, 1.1-, 1.18-, 1.28-, and 1.31-micron images. Contrasts at these wavelengths may be due to a combination of variations in the optical depths of the overlying sulfuric acid clouds and differences in surface emission. Comparison with the 2.3-micron images show that the patterns seen in the 1.28- and 1.31-micron windows are consistent with cloud optical depth variations alone and require no contribution from the surface. However, images at 1.0, 1.1, and 1.8 microns from July 1991 show a dark feature having a contrast that increases with decreasing wavelength. This behavior is contrary to that expected of cloud absorption. Images taken on three successive days in October show another dark feature that is stationary with respect to the surface. These regions of lower emission correspond closely to the high-altitude surface regions of Beta Regio and Aphrodite Terra. The images can potentially reveal the near-infrared emissiveity of the surface of Venus, thereby complementing Magellan radar reflectivity and ground based radio emissivity measurements. The contrast ratio between highlands and plains is much smaller than would be expected for blackbody radiation from the surface along. Unlike at radio wavelengths, where the atmosphere is essentially transparent, at near-infrared wavelengths the atmosphere emits, absorbs, and scatters radiation, and can modify the observed topographically induced contrasts. The additional radiation from the atmosphere reduces the contrast, and further modification would be expected if terrain at different altitudes has different emissivities. A fit to our data therefore requires, and may constrain, a model of the lowest scale height of the atmosphere

Transverse instability of the antiproton beam in the Recycler Ring

The brightness of the antiproton beam in Fermilab's 8 GeV Recycler ring is limited by a transverse instability. This instability has occurred during the extraction process to the Tevatron for large stacks of antiprotons even with dampers in operation. This paper describes observed features of the instability, introduces the threshold phase density to characterize the beam stability, and finds the results to be in agreement with a resistive wall instability model. Effective exclusion of the longitudinal tails from Landau damping by decreasing the depth of the RF potential well is observed to lower the threshold density by up to a factor of two.Comment: 3 pp. Particle Accelerator, 24th Conference (PAC'11) 2011. 28 Mar - 1 Apr 2011. New York, US

First year student expectations: Results from a university-wide student survey

Although much has been written on the first-year experience of students at higher education institutions, less attention has been directed to the expectations of students when they enter an institution for the first time. This paper provides additional insights into the expectations of students at an Australian university and highlights areas in which students’ expectations may not necessarily align with the realities of common university practices. By providing opportunities for students to articulate their expectations, staff are able to use the responses for a constructive dialogue and work towards a more positive alignment between perceived expectations and levels of student satisfaction with their experience.Geoffrey Crisp, Edward Palmer, Deborah Turnbull, Ted Nettelbeck, Lynn Ward, Amanda LeCouteur, Aspa Sarris, Peter Strelan, and Luke Schneide

Unmet depression information needs in the community

Background Despite the well acknowledged importance of consumer health information, little is known about the public’s depression information needs. This study aimed to develop a formal measure of unmet need for depression information in the community, to investigate the level of this unmet need and to identify its predictors. Methods Data were collected as part of a survey of 12,319 Australian adults aged 18–65 years. This survey incorporated 21 questions targeting depression information need, together with measures of demographic status, self-reported current depression and personal stigma. The information needs data were subjected to principal components analysis followed by linear regression analyses to determine the demographic and other predictors of each of the resulting components. Results Between 50 and 75% of participants endorsed the need for more information on each of the 21 information need topics. The PCA yielded a 20-item Depression Information Needs Scale (DINS) of high reliability and factor validity comprising four subscales: General (facts about depression), Specific Treatments, Research and Policies, and Lived Experience. Controlling for other factors, those with self-reported current depression and those without tertiary education had greater information needs across all four factors. Limitations The survey response rate was low and further research is required to establish the adequacy of the psychometric properties of the DINS. Conclusions Given the high unmet need for depression information there is a need to develop and implement evidence-based strategies for ensuring the accessibility and uptake of depression information relevant to the needs of members of the community.This study was funded by a National Health and Medical Research Council (NHMRC) Project Grant 471435. K.G. is supported by NHMRC Fellowship no. 525413. The funding body played no further role in any aspect of this study

Near-infrared oxygen airglow from the Venus nightside

Groundbased imaging and spectroscopic observations of Venus reveal intense near-infrared oxygen airglow emission from the upper atmosphere and provide new constraints on the oxygen photochemistry and dynamics near the mesopause (approximately 100 km). Atomic oxygen is produced by the Photolysis of CO2 on the dayside of Venus. These atoms are transported by the general circulation, and eventually recombine to form molecular oxygen. Because this recombination reaction is exothermic, many of these molecules are created in an excited state known as O2(delta-1). The airglow is produced as these molecules emit a photon and return to their ground state. New imaging and spectroscopic observations acquired during the summer and fall of 1991 show unexpected spatial and temporal variations in the O2(delta-1) airglow. The implications of these observations for the composition and general circulation of the upper venusian atmosphere are not yet understood but they provide important new constraints on comprehensive dynamical and chemical models of the upper mesosphere and lower thermosphere of Venus