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Search Results: 1 - 10 of 297408 matches for " J Blitz "
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The infant-feeding practices of mothers enrolled in the prevention of mother-to-child transmission of HIV programme at a primary health care clinic in the Mpumalanga province, South Africa
IS Ukpe, J Blitz, J Hugo, M Theledi
South African Family Practice , 2009,
Abstract: Purpose: To determine whether mothers attending a primary health care (PHC) clinic in the Mpumalanga province, South Africa for post-delivery prevention of mother-to-child transmission (PMTCT) of the Human Immunodeficiency Virus (HIV) follow-up care were adhering to the recommendation of exclusive infant-feeding practices, and to identify possible areas for improvement of the PMTCT of HIV services at the clinic. Setting: A municipal PHC clinic in White River, a semi-urban town in Mpumalanga, South Africa. Design: A cross-sectional descriptive study using a structured infant-feeding questionnaire. Subjects: All mothers attending the clinic for post-delivery PMTCT of HIV follow-up care during a four-month period from 1 November 2007 to 29 February 2008. Results: A total of 33 mothers with infants attended the clinic during the period. All 33 mothers took part in the questionnaire study. Thirty questionnaires were subsequently found suitable for analysis. The mothers were predominantly rural, with low levels of education and no formal employment. Their ages ranged from 22 to 42 years, with a mean of 30.7 years. Fifteen (50%) of the 30 mothers practised exclusive replacement feeding (ERF), 8 (27%) practised exclusive breast-feeding (EBF), and 7 (23%) practised mixed feeding. Conclusion: More than three-quarters of the mothers practised the recommended exclusive infant-feeding methods for PMTCT of HIV, with ERF as the most popular choice. However, the infant-feeding practices could not be generalised as the attendance of mothers for post-delivery follow-up care at the clinic was very poor during the study period. This poor attendance was attributed to frequent non-availability of free formula milk for the programme. Better quality counselling is needed to further increase the adherence to exclusive infant-feeding practices, and to improve the uptake of post-delivery follow-up care.
High Velocity Clouds: the Missing Link
Leo Blitz,David N. Spergel,Peter J. Teuben,Dap Hartman
Physics , 1999,
Abstract: Hierarchical structure formation models predict the existence of large numbers of low velocity dispersion dark halos. Galaxy surveys find far fewer galaxies than predicted by analytical estimates and numerical simulations. In this paper, we suggest that these dark halos are not missing, but have been merely misplaced in the galactic astronomy section of the journals: they are the High Velocity Clouds (HVCs). We review the predictions of our model for the Local Group origin of the HVCs and its implications for the formation and the evolution of our Galaxy. We describe recent observations that confirm many of earlier predictions and discuss future tests of the model.
The Milky Way's dark matter halo appears to be lopsided
Kanak Saha,Evan S. Levine,Chanda J. Jog,Leo Blitz
Physics , 2009, DOI: 10.1088/0004-637X/697/2/2015
Abstract: The atomic hydrogen gas (HI) disk in the outer region (beyond ~10 kpc from the centre) of Milky Way can provide valuable information about the structure of the dark matter halo. The recent 3-D thickness map of the outer HI disk from the all sky 21-cm line LAB survey, gives us a unique opportunity to investigate the structure of the dark matter halo of Milky Way in great detail. A striking feature of this new survey is the North-South asymmetry in the thickness map of the atomic hydrogen gas. Assuming vertical hydrostatic equilibrium under the total potential of the Galaxy, we derive the model thickness map of the HI gas. We show that simple axisymmetric halo models, such as softened isothermal halo (producing a flat rotation curve with V_c ~ 220 km/s) or any halo with density falling faster than the isothermal one, are not able to explain the observed radial variation of the gas thickness. We also show that such axisymmetric halos along with different HI velocity dispersion in the two halves, cannot explain the observed asymmetry in the thickness map. Amongst the non-axisymmetric models, it is shown that a purely lopsided (m=1, first harmonic) dark matter halo with reasonable HI velocity dispersion fails to explain the North-South asymmetry satisfactorily. However, we show that by superposing a second harmonic (m=2) out of phase onto a purely lopsided halo e.g. our best fit and more acceptable model A (with parameters \epsilon_{h}^{1}=0.2, \epsilon_{h}^{2}=0.18 and \sigma_{HI}=8.5 km/s) can provide an excellent fit to the observation and reproduce the North-South asymmetry naturally. The emerging picture of the asymmetric dark matter halo is supported by the \Lambda CDM halos formed in the cosmological N-body simulation.
Local Goup HVCs: Status of the Evidence
Leo Blitz
Physics , 2001,
Abstract: The evidence for locating the High Velocity Clouds in the Local Group is summarized and evaluated. Recent measurements of the H$\alpha$ surface brightness and metallicity of a number of HVCs appear to be fatal to the Galactic fountain as a significant contributor to the HVC phenomenon, but not to the existence of the fountain itself. Observations of extragalactic analogues to HVCs remain the {\it sine qua non} for deciding whether the Local Group hypothesis is viable, but the constraints based on existing surveys appear to be rather weak. MgII quasar absorption lines restrict how many HVC analogues exist at intermediate redshift, depending on where these lines originate. It is concluded that the evidence remains ambiguous, none of the main hypotheses is fully consistent with all of the data, and the Local Group hypothesis remains a viable explanation for the HVC phenomenon.
Medical student participation in community-based experiential learning: reflections from first exposure to making the diagnosis
D Cameron, L Wolvaardt, M Van Rooyen, J Hugo, J Blitz, A-M Bergh
South African Family Practice , 2011,
Abstract: Background: Fifth-year medical students from the University of Pretoria participated in a four-week rotation in the primary care clinics of a large metropolitan centre. An academic service-learning (ASL) approach was introduced into this rotation to improve the integration of theoretical learning and clinical practice through relevant community service and structured reflection. Methods: Students wrote semi-structured reflective journals as a means to gaining greater insight into their learning experiences. These reflections were analysed qualitatively with a view to improving the community-based curriculum. Results: Four major themes were identified: expectations and the reality of primary care; service and learning; becoming a doctor; and making a difference. Conclusion: While students gained a deeper insight into their development as clinicians, using an ASL approach also assisted the faculty in making an informed educational diagnosis of the curriculum.
Sural Intraneural Ganglion Cysts Are Joint-related
Robert J. Spinner,Kimberly K. Amrami,Mohanad Ahmed Ibrahim Elshiekh,Neal M. Blitz
Archives of Plastic Surgery , 2012, DOI: http://dx.doi.org/10.5999/aps.2012.39.1.77b
Abstract:
High Velocity Clouds: Building Blocks of the Local Group
Leo Blitz,David N. Spergel,Peter J. Teuben,Dap Hartmann,W. Butler Burton
Physics , 1998, DOI: 10.1086/306963
Abstract: We suggest that the high--velocity clouds (HVCs) are large clouds, with typical diameters of 25 kpc and containing 5e7 solar masses of neutral gas and 3e8 solar masses of dark matter, falling onto the Local Group; altogether the HVCs contain 10$^{11}$ solar masses of neutral gas. Our reexamination of the Local-Group hypothesis for the HVCs connects their properties to the hierarchical structure formation scenario and to the gas seen in absorbtion towards quasars. We begin by showing that at least one HVC complex (besides the Magellanic Stream) must be extragalactic at a distance > 40 kpc from the Galactic center, with a diameter > 20 kpc and a mass > 1e8 solar masses. We interpret the more distant HVCs as dark matter ``mini--halos'' moving along filaments towards the Local Group. Most poor galaxy groups should contain HI structures to large distances bound to the group. The HVCs are local analogues of the Lyman--limit clouds We argue that there is a Galactic fountain in the Milky Way, but that the fountain does not explain the origin of the HVCs. Our analysis of the HI data leads to the detection of a vertical infall of low-velocity gas towards the plane. This implies that the chemical evolution of the Galactic disk is governed by episodic infall of metal-poor HVC gas that only slowly mixes with the rest of the interstellar medium. The Local--Group infall hypothesis makes a number of testable predictions. The HVCs should have sub-solar metallicities. Their H$\alpha $ emission should be less than that seen from the Magellanic Stream. The clouds should not be seen in absorption to nearby stars. The clouds should be detectable in both emission and absorption around other groups.
Tidal Imprints Of A Dark Sub-Halo On The Outskirts Of The Milky Way
Sukanya Chakrabarti,Leo Blitz
Physics , 2009,
Abstract: We present a new analysis of the observed perturbations of the HI disk of the Milky Way to infer the existence of a dark sub-halo that tidally interacted with the Milky Way disk. We examine tidal interactions between perturbing dark sub-halos and the gas disk of the Milky Way using high resolution Smoothed Particle Hydrodynamics (SPH) simulations. We compare our results to the observed HI map of the Milky Way to find that the Fourier amplitudes of the planar disturbances are best-fit by a perturbing dark sub-halo with a mass that is one-hundredth of the Milky Way with a pericentric distance of 5 kpc. This best-fit to the Fourier modes occurs about a dynamical time after pericentric approach, when the perturber is 90 kpc from the galactic center. Our analysis here represents a new method to indirectly characterize dark sub-halos from the tidal gravitational imprints they leave on the gaseous disks of galaxies. We also elucidate a fundamental property of parabolic orbits. We show that under certain conditions, one can break the degeneracy between the mass of the perturber and the pericentric distance in the evaluation of the tidal force -- to directly determine the mass of the dark perturber that produced the observed disturbances.
Fringe Field Effects on Bending Magnets, Derived for TRANSPORT/TURTLE
Sam Blitz,Riley Molloy
Physics , 2013,
Abstract: A realistic magnetic dipole has complex effects on a charged particle near the entrance and exit of the magnet, even with a constant and uniform magnetic field deep within the interior of the magnet. To satisfy Maxwell's equations, the field lines near either end of a realistic magnet are significantly more complicated, yielding non-trivial forces. The effects of this fringe field are calculated to first order, applying both the paraxial and thin lens approximations. We find that, in addition to zeroth order effects, the position of a particle directly impacts the forces in the horizontal and vertical directions.
Non-circular Gas Kinematics and Star Formation in the Ringed Galaxy NGC 4736
Tony Wong,Leo Blitz
Physics , 1999, DOI: 10.1086/309368
Abstract: We analyze the gas kinematics and star formation properties of the nearby RSab galaxy NGC 4736 using interferometric and single-dish CO(1-0) data and previously published Halpha and HI data. The CO morphology is dominated by a central molecular bar and tightly wound spiral arms associated with a bright ring of star formation. Strong HI emission is also found in the ring, but HI is absent from the central regions. Comparison of the HI and Halpha distributions suggests that HI in the ring is primarily dissociated H$_2$. Modeling of the CO kinematics reveals gas motion in elliptical orbits around the central bar, and we argue that the ring represents both the OLR of the bar and the ILR of a larger oval distortion. The HI kinematics show evidence for axisymmetric inflow towards the ring and are inconsistent with streaming in aligned elliptical orbits, but the highly supersonic (~40 km/s) inflow velocities required, corresponding to mass inflow rates of ~2 Msol/yr, suggest that more sophisticated models (e.g., gas orbiting in precessed elliptical orbits) should be considered. The radial CO and Halpha profiles are poorly correlated in the vicinity of the nuclear bar, but show a better correlation (in rough agreement with the Schmidt law) at the ring. Even along the ring, however, the azimuthal correspondence between CO and Halpha is poor, suggesting that massive stars form more efficiently at some (perhaps resonant) locations than at others. These results indicate that the star formation rate per unit gas mass exhibits strong spatial variations and is not solely a function of the available gas supply. The localization of star formation to the ring is broadly consistent with gravitational instability theory, although the instability parameter $Q \sim 3$ on average in the ring, only falling below 1 in localized regions.
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