507 research outputs found

    The 158 micron (CII) mapping of galaxies: Probing the atomic medium

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    Using the MPE/UCB Far-infrared Imaging Fabry-Perot Interferometer (FIFI) on the Kuiper Airborne Observatory (KAO), we have made large scale maps of (CII) in the spiral galaxies NGC 6946, NGC 891, M83 and the peculiar elliptical Cen A, thus allowing for the first time, detailed studies of the spatial distribution of the FIR line emission in external galaxies. We find that the (CII) emission comes from a mixture of components of interstellar gas. The brightest emission is associated with the nuclear regions, a second component traces the spiral arms as seen in the nearly face on spiral galaxies NGC 6946 and M83 and the largest star forming/H2 regions contained within them, and another extended component of low brightness can be detected in all of the galaxies far from the nucleus, beyond the extent of CO emission

    SPIFI: a Direct-Detection Imaging Spectrometer for Submillimeter Wavelengths

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    The South Pole Imaging Fabry-Perot Interferometer (SPIFI) is the first instrument of its kind -a direct-detection imaging spectrometer for astronomy in the submillimeter band. SPIFI ’s focal plane is a square array of 25 silicon bolometers cooled to 60 mK; the spectrometer consists of two cryogenic scanning Fabry-Perot interferometers in series with a 60-mK bandpass filter. The instrument operates in the short submillimeter windows (350 and 450 μm) available from the ground, with spectral resolving power selectable between 500 and 10,000. At present, SPIFI’s sensitivity is within a factor of 1.5-3 of the photon background limit, comparable with the best heterodyne spectrometers. The instrument ’s large bandwidth and mapping capability provide substantial advantages for specific astrophysical projects, including deep extragalactic observations. We present the motivation for and design of SPIFI and its operational characteristics on the telescope

    A k-shell decomposition method for weighted networks

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    We present a generalized method for calculating the k-shell structure of weighted networks. The method takes into account both the weight and the degree of a network, in such a way that in the absence of weights we resume the shell structure obtained by the classic k-shell decomposition. In the presence of weights, we show that the method is able to partition the network in a more refined way, without the need of any arbitrary threshold on the weight values. Furthermore, by simulating spreading processes using the susceptible-infectious-recovered model in four different weighted real-world networks, we show that the weighted k-shell decomposition method ranks the nodes more accurately, by placing nodes with higher spreading potential into shells closer to the core. In addition, we demonstrate our new method on a real economic network and show that the core calculated using the weighted k-shell method is more meaningful from an economic perspective when compared with the unweighted one.Comment: 17 pages, 6 figure

    Mental health service use among South Africans for mood, anxiety and substance use disorders

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    Background. Europe and North America have low rates of mental health service use despite high rates of mental disorder. Little is known about mental health service use among South Africans. Design. A nationally representative survey of 4 351 adults. Twelve-month DSM-IV (Diagnostic and Statistical Manual, 4th edition) diagnoses, severity, and service utilisation were determined using the World Health Organization Composite International Diagnostic Interview (CIDI). Twelve-month treatment was categorised by sector and province. South Africans in households and hostel quarters were interviewed between 2002 and 2004 in all nine provinces. Outcome measures. 4 317 respondents 18 years and older were analysed. Bivariate logistic regression models predicted (i) 12-month treatment use of service sectors by gender, and (ii) 12-month treatment use by race by gender. Results. Of respondents with a mental disorder, 25.2% had sought treatment within the previous 12 months; 5.7% had used any formal mental health service. Mental health service use was highest for adults with mood and anxiety disorders, and among those with a mental disorder it varied by province, from 11.4% (Western Cape) to 2.2% (Mpumalanga). More women received treatment, and this was largely attributable to higher rates of treatment in women with mood disorders. Age, income, education and marital status were not significantly associated with mental health service use. Race was associated with the treatment sector accessed in those with a mental disorder. Conclusions. There is a substantial burden of untreated mental disorders in the South African population, across all provinces and even in those with substantial impairment. Greater allocation of resources to mental health services and more community awareness initiatives are needed to address the unmet need

    Spherical Slepian functions and the polar gap in geodesy

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    The estimation of potential fields such as the gravitational or magnetic potential at the surface of a spherical planet from noisy observations taken at an altitude over an incomplete portion of the globe is a classic example of an ill-posed inverse problem. Here we show that the geodetic estimation problem has deep-seated connections to Slepian's spatiospectral localization problem on the sphere, which amounts to finding bandlimited spherical functions whose energy is optimally concentrated in some closed portion of the unit sphere. This allows us to formulate an alternative solution to the traditional damped least-squares spherical harmonic approach in geodesy, whereby the source field is now expanded in a truncated Slepian function basis set. We discuss the relative performance of both methods with regard to standard statistical measures as bias, variance and mean-square error, and pay special attention to the algorithmic efficiency of computing the Slepian functions on the region complementary to the axisymmetric polar gap characteristic of satellite surveys. The ease, speed, and accuracy of this new method makes the use of spherical Slepian functions in earth and planetary geodesy practical.Comment: 14 figures, submitted to the Geophysical Journal Internationa

    2014 Epilepsy Benchmarks Area III: Improve Treatment Options for Controlling Seizures and Epilepsy-Related Conditions Without Side Effects

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    The Epilepsy Benchmark goals in Area III focus on making progress in understanding and controlling seizures and related conditions as well as on developing biomarkers and new therapies that will reduce seizures and improve outcomes for individuals with epilepsy. Area III emphasizes a need to better understand the ways in which seizures start, propagate, and terminate and whether those network processes are common or unique in different forms of epilepsy. The application of that knowledge to improved seizure prediction and detection will also play a role in improving patient outcomes. Animal models of treatment-resistant epilepsy that are aligned with etiologies and clinical features of human epilepsies are especially encouraged as necessary tools to understand mechanisms and test potential therapies. Antiseizure therapies that target (either alone or in combination) novel or multiple seizure mechanisms are prioritized in this section of the Benchmarks. Area III goals also highlight validation of biomarkers of treatment response and safety risk, effective self-management, and patient-centered outcome measures as important areas of emphasis for the next five to ten years

    Warm Molecular Gas Traced with CO J=7->6 in the Galaxy's Central 2 Parsecs: Dynamical Heating of the Circumnuclear Disk

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    We present an 11 arcsec resolution map of the central two parsecs of the Galaxy in the CO J =7->6 rotational transition. The CO emission shows rotation about Sgr A*, but also evidence for non-circular turbulent motion and a clumpy morphology. We combine our dataset with available CO measurements to model the physical conditions in the disk. We find that the molecular gas in the region is both warm and dense, with T~200-300 K, n_H2~50,000-70,000 cm^-3. The mass of warm molecular gas we measure in the central two parsecs is at least 2000 M_solar, about 20 times the UV-excited atomic gas mass, ruling out an UV heating scenario for the molecular material. We compare the available spectral tracers with theoretical models and conclude that molecular gas is heated with magneto-hydrodynamic shocks with v~10-20 kms and B~0.3-0.5 mG. Using the conditions derived with the CO analysis, we include the other important coolants--neutral oxygen and molecular hydrogen--to estimate the total cooling budget of the molecular material. We derive a mass to luminosity ratio of 2-3 M_solar/ L_solar, which is consistent with the total power dissipated via turbulent decay in 0.1 pc cells with v_rms~15 kms. These size and velocity scales are comparable to the observed clumping scale and the velocity dispersion. At this rate, the material near Sgr A* its dissipating its orbital energy on an orbital timescale, and cannot last for more than a few orbits. Our conclusions support a scenario in which the features near Sgr A* such as the CND and northern arm are generated by infalling clouds with low specific angular momentum.Comment: 31 pages, including 5 figures, accepted for publication in Ap
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