Simulating Cosmic Microwave Background maps in multi-connected spaces

This article describes the computation of cosmic microwave background anisotropies in a universe with multi-connected spatial sections and focuses on the implementation of the topology in standard CMB computer codes. The key ingredient is the computation of the eigenmodes of the Laplacian with boundary conditions compatible with multi-connected space topology. The correlators of the coefficients of the decomposition of the temperature fluctuation in spherical harmonics are computed and examples are given for spatially flat spaces and one family of spherical spaces, namely the lens spaces. Under the hypothesis of Gaussian initial conditions, these correlators encode all the topological information of the CMB and suffice to simulate CMB maps.Comment: 33 pages, 55 figures, submitted to PRD. Higher resolution figures available on deman

Computationally Efficient Implementation of Convolution-based Locally Adaptive Binarization Techniques

One of the most important steps of document image processing is binarization. The computational requirements of locally adaptive binarization techniques make them unsuitable for devices with limited computing facilities. In this paper, we have presented a computationally efficient implementation of convolution based locally adaptive binarization techniques keeping the performance comparable to the original implementation. The computational complexity has been reduced from O(W2N2) to O(WN2) where WxW is the window size and NxN is the image size. Experiments over benchmark datasets show that the computation time has been reduced by 5 to 15 times depending on the window size while memory consumption remains the same with respect to the state-of-the-art algorithmic implementation

Active Galaxies in the UV

In this article we present different aspects of AGN studies demonstrating the importance of the UV spectral range. Most important diagnostic lines for studying the general physical conditions as well as the metalicities in the central broad line region in AGN are emitted in the UV. The UV/FUV continuum in AGN excites not only the emission lines in the immediate surrounding but it is responsible for the ionization of the intergalactic medium in the early stages of the universe. Variability studies of the emission line profiles of AGN in the UV give us information on the structure and kinematics of the immediate surrounding of the central supermassive black hole as well as on its mass itself.Comment: 29 pages, 13 figures, Ap&SS in pres

Critical discussion of Daniel C. Dennett, The Intentional Stance.

Daniel Dennett spends a good bit of time defending the possibility of a compromise position on the reality of beliefs and desires. It will be claimed that a puzzle remains in the interpretation of Dennett's position. In earlier works one finds a theme, which we can call 'near-fatalism', which has not been integrated with the kind of middle ground he describes. But the near-fatalism theme is dropped in later work. Is it because it is felt to be incompatible with that middle ground compromise? It is not obviously so

Accessory mineral microstructure and chronology reveals no evidence for late heavy bombardment on the asteroid 4-Vesta

A long-standing paradigm in planetary science is that the inner Solar System experienced a period of intense and sustained bombardment between 4.2 and 3.9 Ga. Evidence of this period, termed the Late Heavy Bombardment is provided by the 40Ar/39Ar isotope systematics of returned Apollo samples, lunar meteorites, and asteroidal meteorites. However, it has been largely unsupported by more recent and robust isotopic age data, such as isotopic age data obtained using the U-Pb system. Here we conduct careful microstructural characterisation of baddeleyite, zircon, and apatite in six different eucrites prior to conducting SIMS and LA-ICP-MS measurement of U, Th, and Pb isotopic ratios and radiometric dating. Baddeleyite, displaying complex internal twinning linked to reversion from a high symmetry polymorph in two samples, records the formation of the parent body (4554 ± 3 Ma 2σ; n = 8), while structurally simple zircon records a tight spread of ages representing metamorphism between 4574 ± 14 Ma and 4487 ± 31 Ma (n = 6). Apatite, a more readily reset shock chronometer, records crystallisation ages of ∼4509 Ma (n = 6), with structurally deformed grains (attributed to impact events) yielding U-Pb ages of 4228 Ma (n = 12). In concert, there is no evidence within the measured U-Pb systematics or microstructural record of the eucrites examined in this study to support a period of late heavy bombardment between 4.2 and 3.9 Ga

Far-from-equilibrium quantum many-body dynamics

The theory of real-time quantum many-body dynamics as put forward in Ref. [arXiv:0710.4627] is evaluated in detail. The formulation is based on a generating functional of correlation functions where the Keldysh contour is closed at a given time. Extending the Keldysh contour from this time to a later time leads to a dynamic flow of the generating functional. This flow describes the dynamics of the system and has an explicit causal structure. In the present work it is evaluated within a vertex expansion of the effective action leading to time evolution equations for Green functions. These equations are applicable for strongly interacting systems as well as for studying the late-time behaviour of nonequilibrium time evolution. For the specific case of a bosonic N-component phi^4 theory with contact interactions an s-channel truncation is identified to yield equations identical to those derived from the 2PI effective action in next-to-leading order of a 1/N expansion. The presented approach allows to directly obtain non-perturbative dynamic equations beyond the widely used 2PI approximations.Comment: 20 pp., 6 figs; submitted version with added references and typos corrected

The shocking state of apatite and merrillite in shergottite Northwest Africa 5298 and extreme nanoscale chlorine isotope variability revealed by atom probe tomography

The elemental and chlorine isotope compositions of calcium-phosphate minerals are key recorders of the volatile inventory of Mars, as well as the planet’s endogenous magmatic and hydrothermal history. Most martian meteorites have clear evidence for exogenous impact-generated deformation and metamorphism, yet the effects of these shock metamorphic processes on chlorine isotopic records contained within calcium phosphates have not been evaluated. Here we test the effects of a single shock metamorphic cycle on chlorine isotope systematics in apatite from the highly shocked, enriched shergottite Northwest Africa (NWA) 5298. Detailed nanostructural (EBSD, Raman and TEM) data reveals a wide range of distributed shock features. These are principally the result of intensive plastic deformation, recrystallization and/or impact melting. These shock features are directly linked with chemical heterogeneities, including crosscutting microscale chlorine-enriched features that are associated with shock melt and iron-rich veins. NanoSIMS chlorine isotope measurements of NWA 5298 apatite reveal a range of δ37Cl values (-3 to 1 ‰; 2σ uncertainties 37Cl values can be readily linked with different nanostructural states of targeted apatite. High spatial resolution atom probe tomography (APT) data reveal that chlorine-enriched and defect-rich nanoscale boundaries have highly negative δ37Cl values (mean of -15 ± 8 ‰). Our results show that shock metamorphism can have significant effects on chemical and chlorine isotopic records in calcium phosphates, principally as a result of chlorine mobilization during shock melting and recrystallization. Despite this, low-strain apatite domains have been identified by EBSD, and yield a mean δ37Cl value of -0.3 ± 0.6 ‰ that is taken as the best estimate of the primary chlorine isotopic composition of NWA 5298. The combined nanostructural, microscale-chemical and nanoscale APT isotopic approach gives the ability to better isolate and identify endogenous volatile-element records of magmatic and near-surface processes as well as exogenous, shock-related effects

Lunar samples record an impact 4.2 billion years ago that may have formed the Serenitatis Basin

Impact cratering on the Moon and the derived size-frequency distribution functions of lunar impact craters are used to determine the ages of unsampled planetary surfaces across the Solar System. Radiometric dating of lunar samples provides an absolute age baseline, however, crater-chronology functions for the Moon remain poorly constrained for ages beyond 3.9 billion years. Here we present U–Pb geochronology of phosphate minerals within shocked lunar norites of a boulder from the Apollo 17 Station 8. These minerals record an older impact event around 4.2 billion years ago, and a younger disturbance at around 0.5 billion years ago. Based on nanoscale observations using atom probe tomography, lunar cratering records, and impact simulations, we ascribe the older event to the formation of the large Serenitatis Basin and the younger possibly to that of the Dawes crater. This suggests the Serenitatis Basin formed unrelated to or in the early stages of a protracted Late Heavy Bombardment

Atomic X-ray Spectroscopy of Accreting Black Holes

Current astrophysical research suggests that the most persistently luminous objects in the Universe are powered by the flow of matter through accretion disks onto black holes. Accretion disk systems are observed to emit copious radiation across the electromagnetic spectrum, each energy band providing access to rather distinct regimes of physical conditions and geometric scale. X-ray emission probes the innermost regions of the accretion disk, where relativistic effects prevail. While this has been known for decades, it also has been acknowledged that inferring physical conditions in the relativistic regime from the behavior of the X-ray continuum is problematic and not satisfactorily constraining. With the discovery in the 1990s of iron X-ray lines bearing signatures of relativistic distortion came the hope that such emission would more firmly constrain models of disk accretion near black holes, as well as provide observational criteria by which to test general relativity in the strong field limit. Here we provide an introduction to this phenomenon. While the presentation is intended to be primarily tutorial in nature, we aim also to acquaint the reader with trends in current research. To achieve these ends, we present the basic applications of general relativity that pertain to X-ray spectroscopic observations of black hole accretion disk systems, focusing on the Schwarzschild and Kerr solutions to the Einstein field equations. To this we add treatments of the fundamental concepts associated with the theoretical and modeling aspects of accretion disks, as well as relevant topics from observational and theoretical X-ray spectroscopy.Comment: 63 pages, 21 figures, Einstein Centennial Review Article, Canadian Journal of Physics, in pres

A comprehensive approach to managing a neglected, neglected tropical disease; The Myanmar Snakebite Project (MSP)

Snakebite is predominantly an occupational disease affecting poor rural farmers in tropical regions and was recently added to the World Health Organisation list of Neglected Tropical Diseases (NTD). We document an overview of methodologies developed and deployed in the Myanmar Snakebite Project, a foreign aid project largely funded by the Australian Government, with the core aim to “improve outcomes for snakebite patients”. A multidisciplinary team of experts was assembled that worked in a collaborative manner with colleagues in Myanmar, first to identify problems related to managing snakebite and then develop interventions aimed to improve selected problem areas. A broad approach was adopted, covering antivenom production, antivenom distribution and health system management of snakebite. Problems identified in antivenom production included poor snake husbandry resulting in poor survival of captive specimens, lack of geographical diversity; poor horse husbandry, resulting in high mortality, inadequate stock acquisition protocols and data collection, and inappropriate immunisation and bleeding techniques; and inadequate production capacity for freeze dried antivenoms and quality control systems. These problems were addressed in various ways, resulting in some substantial improvements. Antivenom distribution is being reorganised to achieve better availability and utilisation of stock. Health system management of snakebite was assessed across all levels within the area selected for the study, in Mandalay region. A comprehensive community survey indicated that hospital statistics substantially underestimated the snakebite burden, and that access to care by local villagers was delayed by transport and cost issues compounded by lack of antivenom at the most peripheral level of the health service. A health system survey confirmed under-resourcing at the local village level. Prospective case data collection initiated at tertiary hospitals indicated the extent of the snakebite burden on health resources. Interventions initiated or planned include training of health staff, development of a core of senior trainers who can “train the trainers” nationwide in a sustainable way, development and deployment of management guidelines and algorithms for snakebite and a distribution of solar powered fridges to remote health facilities to allow storage of antivenom and prompt treatment of snakebite cases before transfer to major hospitals, thereby reducing the “bite to needle” time.Julian White, Mohammad Afzal Mahmood, Sam Alfred, Khin Thida Thwin, Khin Maung Kyaw, Aung Zaw, David Warrell, Robert Cumming, John Moody Debbie Eagles, Keiran Ragas h, Nathan Dunstan, David Bacon, Plinio Hurtado, Chen Au Pe