Radio sky mapping from satellites at very low frequencies

Wave Distribution Function (WDF) analysis is a procedure for making sky maps of the sources of natural electromagnetic waves in space plasmas, given local measurements of some or all of the three magnetic and three electric field components. The work that still needs to be done on this subject includes solving basic methodological problems, translating the solution into efficient algorithms, and embodying the algorithms in computer software. One important scientific use of WDF analysis is to identify the mode of origin of plasmaspheric hiss. Some of the data from the Japanese satellite Akebono (EXOS D) are likely to be suitable for this purpose

Data synthesis and display programs for wave distribution function analysis

At the National Space Science Data Center (NSSDC) software was written to synthesize and display artificial data for use in developing the methodology of wave distribution analysis. The software comprises two separate interactive programs, one for data synthesis and the other for data display

Particle simulation of plasmas on the massively parallel processor

Particle simulations, in which collective phenomena in plasmas are studied by following the self consistent motions of many discrete particles, involve several highly repetitive sets of calculations that are readily adaptable to SIMD parallel processing. A fully electromagnetic, relativistic plasma simulation for the massively parallel processor is described. The particle motions are followed in 2 1/2 dimensions on a 128 x 128 grid, with periodic boundary conditions. The two dimensional simulation space is mapped directly onto the processor network; a Fast Fourier Transform is used to solve the field equations. Particle data are stored according to an Eulerian scheme, i.e., the information associated with each particle is moved from one local memory to another as the particle moves across the spatial grid. The method is applied to the study of the nonlinear development of the whistler instability in a magnetospheric plasma model, with an anisotropic electron temperature. The wave distribution function is included as a new diagnostic to allow simulation results to be compared with satellite observations

Afshar's Experiment does not show a Violation of Complementarity

A recent experiment performed by S. Afshar [first reported by M. Chown, New Scientist {\bf 183}, 30 (2004)] is analyzed. It was claimed that this experiment could be interpreted as a demonstration of a violation of the principle of complementarity in quantum mechanics. Instead, it is shown here that it can be understood in terms of classical wave optics and the standard interpretation of quantum mechanics. Its performance is quantified and it is concluded that the experiment is suboptimal in the sense that it does not fully exhaust the limits imposed by quantum mechanics.Comment: 6 pages, 6 figure

Consequence of superfluidity on the expansion of a rotating Bose-Einstein condensate

We study the time evolution of a rotating condensate, that expands after being suddenly released from the confining trap, by solving the hydrodynamic equations of irrotational superfluids. For slow initial rotation speeds, $\Omega_{0}$, we find that the condensate's angular velocity increases rapidly to a maximum value and this is accompanied by a minimum in the deformation of the condensate in the rotating plane. During the expansion the sample makes a global rotation of approximately $\pi/2$, where the exact value depends on $\Omega_{0}$. This minimum deformation can serve as an easily detectable signature of superfluidity in a Bose--Einstein condensate.Comment: 4 pages, 3 figures, submitted to PR

The Uncertainty Relation in "Which-Way" Experiments: How to Observe Directly the Momentum Transfer using Weak Values

A which-way measurement destroys the twin-slit interference pattern. Bohr argued that distinguishing between two slits a distance s apart gives the particle a random momentum transfer \wp of order h/s. This was accepted for more than 60 years, until Scully, Englert and Walther (SEW) proposed a which-way scheme that, they claimed, entailed no momentum transfer. Storey, Tan, Collett and Walls (STCW) in turn proved a theorem that, they claimed, showed that Bohr was right. This work reviews and extends a recent proposal [Wiseman, Phys. Lett. A 311, 285 (2003)] to resolve the issue using a weak-valued probability distribution for momentum transfer, P_wv(\wp). We show that P_wv(\wp) must be wider than h/6s. However, its moments can still be zero because P_wv(\wp) is not necessarily positive definite. Nevertheless, it is measurable in a way understandable to a classical physicist. We introduce a new measure of spread for P_wv(\wp): half of the unit-confidence interval, and conjecture that it is never less than h/4s. For an idealized example with infinitely narrow slits, the moments of P_wv(\wp) and of the momentum distributions are undefined unless a process of apodization is used. We show that by considering successively smoother initial wave functions, successively more moments of both P_wv(\wp) and the momentum distributions become defined. For this example the moments of P_wv(\wp) are zero, and these are equal to the changes in the moments of the momentum distribution. We prove that this relation holds for schemes in which the moments of P_wv(\wp) are non-zero, but only for the first two moments. We also compare these moments to those of two other momentum-transfer distributions and \hat{p}_f-\hat{p}_i. We find agreement between all of these, but again only for the first two moments.Comment: 14 pages, 6 figures, submitted to J. Opt.

The [CII] 158 um Line Deficit in Ultraluminous Infrared Galaxies Revisited

We present a study of the [CII] 157.74 um fine-structure line in a sample of 15 ultraluminous infrared (IR) galaxies (L_IR>10^12 Lsun; ULIRGs) using the Long Wavelength Spectrometer (LWS) on the Infrared Space Observatory (ISO). We confirm the observed order of magnitude deficit (compared to normal and starburst galaxies) in the strength of the [CII] line relative to the far-IR dust continuum emission found in our initial report (Luhman et al. 1998), but here with a sample that is twice as large. This result suggests that the deficit is a general phenomenon affecting 4/5 ULIRGs. We present an analysis using observations of generally acknowledged photodissociation region (PDR) tracers ([CII], [OI] 63 and 145 um, and FIR continuum emission), which suggests that a high UV flux G_o incident on a moderate density n PDR could explain the deficit. However, comparisons with other ULIRG observations, including CO (1-0), [CI] (1-0), and 6.2 um polycyclic aromatic hydrocarbon (PAH) emission, suggest that high G_o/n PDRs alone cannot produce a self-consistent solution that is compatible with all of the observations. We propose that non-PDR contributions to the FIR continuum can explain the apparent [CII] deficiency. Here, unusually high G_o and/or n physical conditions in ULIRGs as compared to those in normal and starburst galaxies are not required to explain the [CII] deficit. Dust-bounded photoionization regions, which generate much of the FIR emission but do not contribute significant [CII] emission, offer one possible physical origin for this additional non-PDR component. Such environments may also contribute to the observed suppression of FIR fine-structure emission from ionized gas and PAHs, as well as the warmer FIR colors found in ULIRGs. The implications for observations at higher redshifts are also revisited.Comment: to be published in The Astrophysical Journal, 58 page

The Science Case for PILOT I: Summary and Overview

Original article can be found at: http://www.publish.csiro.au/?nid=139&aid=108 DOI: 10.1071/AS08048 [Open access article]PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed 2.5-m optical/infrared telescope to be located at Dome C on the Antarctic plateau. Conditions at Dome C are known to be exceptional for astronomy. The seeing (above ∼30 m height), coherence time, and isoplanatic angle are all twice as good as at typical mid-latitude sites, while the water-vapour column, and the atmosphere and telescope thermal emission are all an order of magnitude better. These conditions enable a unique scientific capability for PILOT, which is addressed in this series of papers. The current paper presents an overview of the optical and instrumentation suite for PILOT and its expected performance, a summary of the key science goals and observational approach for the facility, a discussion of the synergies between the science goals for PILOT and other telescopes, and a discussion of the future of Antarctic astronomy. Paper II and Paper III present details of the science projects divided, respectively, between the distant Universe (i.e. studies of first light, and the assembly and evolution of structure) and the nearby Universe (i.e. studies of Local Group galaxies, the Milky Way, and the Solar System).Peer reviewe

Expert consensus guidelines for the genetic diagnosis of Alport syndrome

Recent expert guidelines recommend genetic testing for the diagnosis of Alport syndrome. Here, we describe current best practice and likely future developments. In individuals with suspected Alport syndrome, all three COL4A5, COL4A3 and COL4A4 genes should be examined for pathogenic variants, probably by high throughput-targeted next generation sequencing (NGS) technologies, with a customised panel for simultaneous testing of the three Alport genes. These techniques identify up to 95% of pathogenic COL4A variants. Where causative pathogenic variants cannot be demonstrated, the DNA should be examined for deletions or insertions by re-examining the NGS sequencing data or with multiplex ligation-dependent probe amplification (MLPA). These techniques identify a further 5% of variants, and the remaining few changes include deep intronic splicing variants or cases of somatic mosaicism. Where no pathogenic variants are found, the basis for the clinical diagnosis should be reviewed. Genes in which mutations produce similar clinical features to Alport syndrome (resulting in focal and segmental glomerulosclerosis, complement pathway disorders, MYH9-related disorders, etc.) should be examined. NGS approaches have identified novel combinations of pathogenic variants in Alport syndrome. Two variants, with one in COL4A3 and another in COL4A4, produce a more severe phenotype than an uncomplicated heterozygous change. NGS may also identify further coincidental pathogenic variants in genes for podocyte-expressed proteins that also modify the phenotype. Our understanding of the genetics of Alport syndrome is evolving rapidly, and both genetic and non-genetic factors are likely to contribute to the observed phenotypic variability

Bright Planetary Nebulae and their Progenitors in Galaxies Without Star Formation

We present chemical abundances for planetary nebulae in M32, NGC 185, and NGC 205 based upon spectroscopy obtained at the Canada-France-Hawaii Telescope using the Multi-Object Spectrograph. From these and similar data compiled from the literature for other Local Group galaxies, we consider the origin and evolution of the stellar progenitors of bright planetary nebulae in galaxies where star formation ceased long ago. The ratio of neon to oxygen abundances in bright planetary nebulae is either identical to that measured in the interstellar medium of star-forming dwarf galaxies or at most changed by a few percent, indicating that neither abundance is significantly altered as a result of the evolution of their stellar progenitors. Several planetary nebulae appear to have dredged up oxygen, but these are the exception, not the rule. The progenitors of bright planetary nebulae typically enhance their original helium abundances by less than 50%. In contrast, nitrogen enhancements can reach factors of 100. However, nitrogen often shows little or no enhancement, suggesting that nitrogen enrichment is a random process. The helium, oxygen, and neon abundances argue that the typical bright planetary nebulae in all of the galaxies considered here are the progeny of stars with initial masses of approximately 1.5 Msun or less, based upon the nucleosynthesis predictions of current theoretical models. These models, however, are unable to explain the nitrogen enrichment or its scatter. Similar conclusions hold for the bright planetary nebulae in galaxies with ongoing star formation. Thus, though composition varies significantly, there is unity in the sense that the progenitors of typical bright planetary nebulae appear to have undergone similar physical processes. (Abridged)Comment: accepted for publication in the Astrophysical Journa