Radio-wave propagation in the non-Gaussian interstellar medium

Radio waves propagating from distant pulsars in the interstellar medium (ISM), are refracted by electron density inhomogeneities, so that the intensity of observed pulses fluctuates with time. The theory relating the observed pulse time-shapes to the electron-density correlation function has developed for 30 years, however, two puzzles have remained. First, observational scaling of pulse broadening with the pulsar distance is anomalously strong; it is consistent with the standard model only when non-uniform statistics of electron fluctuations along the line of sight are assumed. Second, the observed pulse shapes are consistent with the standard model only when the scattering material is concentrated in a narrow slab between the pulsar and the Earth. We propose that both paradoxes are resolved at once if one assumes stationary and uniform, but non-Gaussian statistics of the electron-density distribution. Such statistics must be of Levy type, and the propagating ray should exhibit a Levy flight. We propose that a natural realization of such statistics may be provided by the interstellar medium with random electron-density discontinuities. We develop a theory of wave propagation in such a non-Gaussian random medium, and demonstrate its good agreement with observations. The qualitative introduction of the approach and the resolution of the anomalous-scaling paradox was presented earlier in [PRL 91, 131101 (2003); ApJ 584, 791 (2003)].Comment: 27 pages, changes to match published versio

Disclosure in lesbian, gay and bisexual cancer care: towards a salutogenic healthcare environment

open access articleBackground: The literature on sexual orientation disclosure is arguably one of the most developed in the field of lesbian, gay and bisexual (LGB) people in healthcare in English speaking countries however, relatively little research has been conducted into disclosure in cancer care. Studies have been mainly undertaken in primary care where distinct circumstances pertain and where the benefits of disclosure include obtaining appropriate health information, treatment advice and avoiding misdiagnosis. Methods: We conducted an in-depth qualitative study primarily recruiting patients through oncology care in hospital settings and through LGB community cancer support groups. Data were gathered through semi-structured interviews with 30 LGB patients with different cancer types. Results: Data were analysed using thematic analysis and interpreted and interrogated through salutogenesis theory which offers a useful lens through which to consider the health promoting effects of sexual orientation disclosure in cancer care. We present three themes as part of the analysis: Authenticity as a driver for disclosure in cancer care, Partners as a (potential) salutogenic resource and Creating safe, healing environments conducive to disclosure. The findings are reported and discussed in relation to three inter-related concepts from current salutogenesis theorising including a sense of coherence, generalised resistance resources and healing environments which can facilitate sexual orientation disclosure. Conclusion: Our findings enable a more nuanced approach to understanding disclosure in this context. This study contributes to the literature through its articulation of the salutogenic potential of disclosure (if responded to appropriately) for LGB patients as individuals, in relationship to their partners or carers and the role of creating a visible healing-oriented optimal environment to promote quality of life and recovery

Freight Rates and Productivity Gains in British Tramp Shipping 1869-1950

The standard source for pre-WWII global freight rate trends is the Isserlis British tramp shipping index. We think it is flawed, and that its sources offer vastly more information than the Isserlis aggregate contains. The new data confirm the precipitous decline in nominal freight rates before the World War I, but it also extends the series to the 1940s. Furthermore, our new series is linked to the post-World War II era (documented by David Hummels), so that we can be more precise about what has happened over the very long run. We also create route-specific deflators by using the prices of commodities transported. Previous scholars have deflated their nominal freight rate indices by a price index that includes tradables not carried on all routes and non-tradables not carried on any route. Our deflated indices offer a more effective measure of the contribution of declining freight rates to commodity-price convergence across trading regions. Using the pricedual method and new indices for factor prices, we then calculate total factor productivity growth pre-war and interwar for five global routes. Finally, we identify the sources of the total factor productivity growth.

Anomalous Radio-Wave Scattering from Interstellar Plasma Structures

This paper considers scattering screens that have arbitrary spatial variations of scattering strength transverse to the line of sight, including screens that are spatially well confined, such as disks and filaments. We calculate the scattered image of a point source and the observed pulse shape of a scattered impulse. The consequences of screen confinement include: (1) Source image shapes that are determined by the physical extent of the screen rather than by the shapes of much-smaller diffracting microirregularities. These include image elongations and orientations that are frequency dependent. (2) Variation with frequency of angular broadening that is much weaker than the trademark \nu^{-2} scaling law (for a cold, unmagnetized plasma), including frequency-independent cases; and (3) Similar departure of the pulse broadening time from the usually expected \nu^{-4} scaling law. We briefly discuss applications that include scattering of pulses from the Crab pulsar by filaments in the Crab Nebula; image asymmetries from Galactic scattering of the sources Cyg X-3, Sgr A*, and NGC 6334B; and scattering of background active galactic nuclei by intervening galaxies. We also address the consequences for inferences about the shape of the wavenumber spectrum of electron density irregularities, which depend on scaling laws for the image size and the pulse broadening. Future low-frequency (< 100 MHz) array observations will also be strongly affected by the Galactic structure of scattering material. Our formalism is derived in the context of radio scattering by plasma density fluctuations. It is also applicable to optical, UV and X-ray scattering by grains in the interstellar medium.Comment: 21 pages, LaTeX2e with AASTeX-4.0, 6 PostScript figures, accepted by ApJ, revised version has minor changes to respond to referee comments and suggestion

Relating an archive of in situ vertical chlorophyll-a profiles to concurrent remotely sensed surface data

Includes bibliographical references (leaves 56-67).Knowledge of the vertical distribution of phytoplankton in the upper ocean is essential for accurate estimates of primary production. Satellite remote sensing has given scientists an unprecedented view of near-surface chlorophyll distribution and other surface conditions, including sea surface temperature and wind data, from regional to global scales but little information on the dynamics below the surface. As a result estimates of global production tend to use regional profile averages but these methods oversimplify the smaller scale dynamics, particularly in coastal regions where productivity is highly variable on time scales of weeks. A pilot study by computer science honours students in 2006 showed the viability of using a Dynamic Bayesian Network (DBN) in predicting a representative profile per pixel of a satellite map based on a database of time series satellite surface data. In this study, 5813 in situ profiles were obtained from the highly dynamic upwelling region around the southwestern coastline of southern Africa. The samples were collected between 1988 and 2006 between the coast and the continental slope. The region was divided into three sub-regions according to biophysical processes: the west Coast; the west Agulhas Bank; and the east Agulhas Bank. Of the 5813 profiles, 5557 were included in the sub-regions. Two consecutive processes were then applied to the profile database. First, the profiles were clustered using a k-means clustering program which produced 16 representative clusters

Seeking Civilian Control: Rule of Law, Democracy, and Civil-Military Relations in Zimbabwe

Rule of law and democratic reform projects often concern lofty questions of constitutional law. But in many countries desperate for reform, deeply entrenched social and political problems present preconditions to any discussion of constitutional reforms aimed at democracy and the rule of law. Zimbabwe is one such nation, which like many others faces the problem of military intervention into domestic politics. This Note examines structural and historical aspects of Zimbabwe\u27s military problem and utilizes the theory of objective civilian control to demonstrate the plausibility of meaningful reforms. In so doing, this Note provides a demonstrative model for reforming civilmilitary relations in rule of law and democratic reform projects the world over

Master of Laws

thesisWildlife, one of the United States' most treasured natural resources, faces a dire future. Changing climate conditions will upend the natural world wild creatures inhabit. Dramatic shifts in precipitation, spreading disease, cascading ecological events, and catastrophic events such as wildfires and floods will present wildlife with challenges of a degree and frequency not seen in U.S. history. These shifts in climate will in turn bring to bear great pressure on the heralded U.S. approach to wildlife management. Ill equipped to respond to the jurisdictional fragmentation and scientific uncertainty that will predominate wildlife management in a changing climate, U.S. wildlife managers must seek out new tools to cope with the difficulties that lie ahead. Collaborative governance and adaptive management-management techniques designed to cope with fragmentation and uncertainty-have obvious appeal. While both have failed to date to deliver their theoretical appeal in practice, these failures can be readily attributed to inadequate implementation efforts. Remedying those deficiencies can greatly increase the likelihood of successful implementation. The federal land management agencies, which oversee the vast majority of wildlife habitat in the United States, are well suited to advance collaborative and adaptive experiments in wildlife habitat management. Acting as hubs to deploy collaboration and adaptation more broadly in the context of wildlife management, the Forest Service, Bureau of Land Management, Fish and Wildlife Service, and National Park Service should incorporate implementation baselines to ensure the appropriate and sufficient deployment of collaborative and adaptive processes. Such efforts will not eliminate the grave risks wild animals face, but will help wildlife managers to have at least a chance of ushering the United States' other inhabitants through the storm

What can GLAST say about the origin of cosmic rays in other galaxies ?

Gamma rays in the band from 20 MeV to 300 GeV, used in combination with data from radio and X-ray bands, provide a powerful tool for studying the origin of cosmic rays in our sister galaxies Andromeda and the Magellanic Clouds. Gamma-ray Large Area Space Telescope (GLAST) will spatially resolve these galaxies and measure the spectrum and intensity of diffuse gamma radiation from the collisions of cosmic rays with gas and dust in them. Observations of Andromeda will give an external perspective on a spiral galaxy like the Milky Way. Observations of the Magellanic Clouds will permit a study of cosmic rays in dwarf irregular galaxies, where the confinement is certainly different and the massive star formation rate is much greater.Comment: 4 pages including 6 figures; to appear in Proc. ACE-2000 Symp. "The Acceleration and Transport of Energetic Particles Observed in the Heliosphere" (Jan. 5-8, 2000, Indian Wells, CA), AIP Conf. Proc. More details can be found at the LHEA GLAST page at http://lhea-glast.gsfc.nasa.gov/pub/science/index.htm