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Magnetic fields in our Galaxy: How much do we know?  [PDF]
J. L. Han
Physics , 2000, DOI: 10.1023/A:1013102711400
Abstract: The large scale magnetic fields of our Galaxy have been mostly revealed by rotation measures ($RM$s) of pulsars and extragalactic radio sources. In the disk of our Galaxy, the average field strength over a few kpc scale is about 1.8 $\mu$G, while the total field, including the random fields on smaller scales, has a strength of about 5 $\mu$G. The local regular field, if it is part of the large scale field of a bisymmetric form, has a pitch angle of about $-8\degr$. There are at least three, and perhaps five, field reversals from the Norma arm to the outer skirt of our Galaxy.
Pediatric foreign body aspiration: How much does our community know?  [cached]
Singh Aprajita,Ghosh Dhruv,Samuel Clarence,Bhatti William
Journal of Indian Association of Pediatric Surgeons , 2010,
Abstract: Aims: Foreign body aspiration (FBA) is one of the main causes of accidental death in childhood. This study was designed to evaluate the level of awareness of FBA and its resultant dangers in the community. Materials and Methods: Sixty-three primary caregivers were interviewed about their awareness of FBA, its attendant dangers, preventive measures taken, and how will they take care of a child in the event of a FBA according to an agreed protocol. Results: Awareness levels about FBA were abysmally low in the population that was studied. Twenty-five percentage of the study population had not heard about this condition, and 46% could not recognize a FBA if it happened. Also, 76% of the study group did not know about the attendant dangers of this condition. Conclusions: There is a dire need to spread awareness about both prevention and treatment of this morbid condition. Health care professionals need to increase their efforts to spread more knowledge in the community about FBA.
Magnetic fields in the disk and halo of M51  [PDF]
E. M. Berkhuijsen,C. Horellou,M. Krause,N. Neininger,A. D. Poezd,A. Shukurov,D. D. Sokoloff
Physics , 1996,
Abstract: We discuss the regular magnetic field in the galaxy M51 on the basis of a new interpretation of polarization angles observed at the wavelengths 2.8, 6.2, 18.0 and 20.5 cm. We found a magneto-ionic halo in M51 with a radial extent of about 10 kpc. The regular magnetic fields in the disk and the halo have different structures. The regular magnetic field in the halo is axisymmetric and horizontal. Its field lines are spirals pointing inwards and generally opposite to those in the disk. The azimuthal structure of the magnetic field in the disk is neither axisymme- tric nor bisymmetric but can be represented by a superposition of these two basic harmonics with about equal weights. Magnetic lines of the regular field in the disk are spirals generally directed outwards. They are well aligned with the optical spiral arms as traced by the dust lanes. The regular magnetic field strength averaged in 3 kpc wide rings is about 5-10 muG in the disk and 3muG in the radial range 3--6 kpc in the halo. These values are in good agreement with independent estimates from the synchrotron emission. The general features of the magnetic patterns revealed in the disk and the halo seem to be in agreement with predictions of dynamo theory. Our results are also based on an analysis of the magneto-ionic medium in M51. For a range of radii in the galactic disk, we estimated the scale heights of synchrotron and thermal disks, electron densities and filling factors as well as the amount of depolarization.
What are Machos? Limits on Stellar Objects as the Dark Matter of our Halo  [PDF]
Katherine Freese,Brian Fields,David Graff
Physics , 1999,
Abstract: The nature of the Massive Compact Halo objects seen in microlensing experiments and interpreted as dark matter in the Halo of our Galaxy remains a mystery. Arguments are presented that these events are probably not ordinary stellar or substellar objects, i.e., they are probably not faint stars, brown dwarfs, white dwarfs, or neutron stars. On theoretical grounds one is then pushed to either exotic explanations or a "no-Macho" Halo (in which the Machos reside elsewhere than in the Halo). Indeed a nonbaryonic component in the Halo seems to be required.
Zero-metallicity very low mass stars as halo dark matter  [PDF]
E. J. Kerins
Physics , 1996,
Abstract: Hubble Space Telescope (HST) limits on the amount of halo dark matter (DM) in the form of very low-mass (VLM) stars close to the hydrogen-burning limit have been interpreted as excluding such stars as viable candidates. However, these limits assume that the stars are smoothly distributed and have at least the metallicity of Population II stars, whilst some baryonic DM formation theories predict that they may instead be clumped into globular-cluster configurations and have close to zero metallicity. I re-analyse the HST data employing the zero-metallicity VLM star models of Saumon et al. (1994), which predict V-I colours below the cuts of previous analyses for stars below 0.2 Mo. From the models I derive new limits on the allowed halo fraction comprising VLM stars for both the unclustered and clustered cases. In the unclustered regime I find a 95% confidence upper limit on the allowed halo fraction of 1.4% inferred from 20 HST fields, comparable to limits derived by previous studies for non-zero metallicity populations. In the cluster scenario I show that clusters of mass M and radius R can satisfy both HST and the recent MACHO gravitational microlensing results, which indicate a lens halo fraction of 40% for a standard halo model, provided R < 1.2 (M/10^4 Mo)^0.74 pc. However, existing dynamical limits restrict the allowed range to a tiny region characterised by M \sim 4x10^4 Mo and R \sim 3 pc. Furthermore, consistency between MACHO and HST demands a present-day clustering efficiency of 92% or better. Intriguingly however, the cluster mass implied by these limits is theoretically well motivated and the VLM star scenario may also help to provide an explanation for the faint red `halo' light recently reported around another galaxy.
How Much Do We Know About Cardiopulmonary Resuscitation?
Nazire Belgin Ak?ll?,Ba?ar Cander,Ramazan K?ylü,Zerrin Defne Dündar
Journal of Academic Emergency Medicine , 2012,
Abstract: study, we aimed to investigate how much the physicians knew about resuscitation and the current guidelines were applied during the resuscitation. Materials and Methods: A total of 134 physicians working in the training and research hospitals, the university hospitals and 112 emergency medical services. A survey including questions about the participants’ resuscitation knowledge, age, specialty, the university graduated from and the number of cardiopulmonary resuscitations (CPR)carried out in a month was performed. The level of knowledge of the physicians working in the training and research hospitals, the university hospitals and 112 emergency medical services were compared. Results: We determined that, while 24.6% (n=33) of the participants applied the ILCOR protocols correctly, 38.8% (n=52) of them applied the protocols incorrectly or incompletely and 24.6% (n=33) of them did not know the protocols. The evaluation was performed according to the physician’s work place and the best results were obtained from the university hospital physicians, but the success rate was achieved in only around 50%. This rate was even lower in the training and research hospital and 112 emergency medical services groups. Conclusion: By reviewing the cardiopulmonary resuscitation training system in Turkey, implementation of resuscitation protocols with more current information should be provided. We believe that it is necessary to establish the in-service training programs, including the emergency medical system, as a part of training for using current information in daily practice.
Observations and Modeling of the Disk-Halo Interaction in our Galaxy  [PDF]
Magdalen Normandeau,Shantanu Basu
Physics , 1998,
Abstract: Galaxies are surrounded by large halos of hot gas which must be replenished as the gas cools. This led Norman & Ikeuchi (1989) to propose the chimney model of the interstellar medium, which predicts that there should be on the order of a thousand such conduits connecting the disk and the halo of a galaxy. Where then are these structures and other possible disk-halo connections in our galaxy? What do they look like, how can we detect them, and what do they tell us about the interstellar medium and about the Galaxy? We present a review of the observational evidence for Galactic disk-halo connections, beginning with large scale searches and then concentrating on the characteristics of selected candidates. We summarize how modeling these structures can provide information on the structure of the interstellar medium in which they evolved, focusing on the W4 superbubble and the Anchor as illustrations.
Magnetic fields in our Milky Way Galaxy and nearby galaxies  [PDF]
JinLin Han
Physics , 2012, DOI: 10.1017/S1743921313002561
Abstract: Magnetic fields in our Galaxy and nearby galaxies have been revealed by starlight polarization, polarized emission from dust grains and clouds at millimeter and submillimeter wavelength, the Zeeman effect of spectral lines or maser lines from clouds or clumps, diffuse radio synchrotron emission from relativistic electrons in interstellar magnetic fields, and the Faraday rotation of background radio sources as well as pulsars for our Milky Way. It is easy to get a global structure for magnetic fields in nearby galaxies, while we have observed many details of magnetic fields in our Milky Way, especially by using pulsar rotation measure data. In general, magnetic fields in spiral galaxies probably have a large-scale structure. The fields follow the spiral arms with or without the field direction reversals. In the halo of spiral galaxies magnetic fields exist and probably also have a large-scale structure as toroidal and poloidal fields, but seem to be slightly weaker than those in the disk. In the central region of some galaxies, poloidal fields have been detected as vertical components. Magnetic field directions in galaxies seem to have been preserved during cloud formation and star formation, from large-scale diffuse interstellar medium to molecular clouds and then to the cloud cores in star formation regions or clumps for the maser spots. Magnetic fields in galaxies are passive to dynamics.
The Magellanic Stream to Halo Interface: Processes that shape our nearest gaseous Halo Stream  [PDF]
Lou Nigra,Snezana Stanimirovic,J. S. Gallagher III,Felix J. Lockman,David L. Nidever,Steven R. Majewski
Physics , 2009,
Abstract: Understanding the hydrodynamical processes and conditions at the interface between the Magellanic Stream (MS) and the Galactic halo is critical to understanding the MS and by extension, gaseous tails in other interacting galaxies. These processes operate on relatively small scales and not only help shape this clumpy stream, but also affect the neutral gas dynamics and transfer of mass from the stream to the halo, thus affecting metal enrichment and gas replenishment of the Galaxy. We describe an observational program to place constraints on these processes through high-resolution measurements of HI emission, HI absorption and Halpha emission with unprecedented sensitivity. Methods will include structural analysis, searching for cold gas cores in clumps and analyzing gas kinematics as it transitions to the halo. The latter method includes sophisticated spatial integration techniques to deeply probe the neutral gas, which we apply to a new HI map obtained from the Green Bank Telescope with the highest sensitivity HI observations of the MS to date. We demonstrate that the integration techniques enhance sensitivity even further, thus allowing detection of apparent MS gas components with density approaching that of the Galactic halo.
Dissipation of Magnetic Fields in the Galactic Halo  [PDF]
F. Zimmer,H. Lesch,G. T. Birk
Physics , 1996,
Abstract: This paper shows that magnetic reconnection could be an important heating process in cosmic gases. In any volume where magnetized plasmas collide, the dissipation of magnetic energy via reconnection seems to be unavoidable. Since most cosmic plasmas are highly conductive, the magnetic field lines are transported with the gas and no dissipation occurs for the most part of the volume. This ideal frozen-in property of the magnetic field is broken in small volumes if field gradients with different field polarity appear, in which localized dissipative effects, e.g. anomalous resistivity, become important. On the base of X-ray measurements exhibiting a clear connection of infalling high-velocity clouds (HVC) with ROSAT "hotspots" we perform resistive magnetohydrodynamic simulations to investigate the capabilities of magnetic dissipation as a major heating process in the interaction zone of the cloud with the halo. The main result is that in the physical environment of a galactic halo heating by externally driven magnetic reconnection cannot be suppressed by thermal conduction and/or radiative cooling. Thus, the gas reaches the maximum temperature given by the magnetic field pressure in the interaction zone of the HVC with the galactic halo.
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