4,086 research outputs found

    High Resolution Millimeter-Wave Mapping of Linearly Polarized Dust Emission: Magnetic Field Structure in Orion

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    We present 1.3 and 3.3 mm polarization maps of Orion-KL obtained with the BIMA array at approximately 4 arcsec resolution. Thermal emission from magnetically aligned dust grains produces the polarization. Along the Orion ``ridge'' the polarization position angle varies smoothly from about 10 degrees to 40 degrees, in agreement with previous lower resolution maps. In a small region south of the Orion ``hot core,'' however, the position angle changes by 90 degrees. This abrupt change in polarization direction is not necessarily the signpost of a twisted magnetic field. Rather, in this localized region processes other than the usual Davis-Greenstein mechanism might align the dust grains with their long axes parallel with the field, orthogonal to their normal orientation.Comment: AAS preprint:14 pages, 2 figures (3mm.eps and 1mm.eps); requires aaspp4.sty To be published in Astrophysical Journal Letter

    The Neon Abundance of Galactic Wolf-Rayet Stars

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    The fast, dense winds which characterize Wolf-Rayet (WR) stars obscure their underlying cores, and complicate the verification of evolving core and nucleosynthesis models. Core evolution can be probed by measuring abundances of wind-borne nuclear processed elements, partially overcoming this limitation. Using ground-based mid-infrared spectroscopy and the 12.81um [NeII] emission line measured in four Galactic WR stars, we estimate neon abundances and compare to long-standing predictions from evolved-core models. For the WC star WR121, this abundance is found to be >~11x the cosmic value, in good agreement with predictions. For the three less-evolved WN stars, little neon enhancement above cosmic values is measured, as expected. We discuss the impact of clumping in WR winds on this measurement, and the promise of using metal abundance ratios to eliminate sensitivity to wind density and ionization structure.Comment: Accepted for publication in ApJ; 9 pages, 2 color figures, 4 table

    Silicate absorption in heavily obscured galaxy nuclei

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    Spectroscopy at 8-13 microns with T-ReCS on Gemini-S is presented for 3 galaxies with substantial silicate absorption features, NGC 3094, NGC 7172 and NGC 5506. In the galaxies with the deepest absorption bands, the silicate profile towards the nuclei is well represented by the emissivity function derived from the circumstellar emission from the red supergiant, mu Cephei which is also representative of the mid-infrared absorption in the diffuse interstellar medium in the Galaxy. There is spectral structure near 11.2 microns in NGC 3094 which may be due to a component of crystalline silicates. In NGC 5506, the depth of the silicate absorption increases from north to south across the nucleus, suggestive of a dusty structure on scales of 10s of parsecs. We discuss the profile of the silicate absorption band towards galaxy nuclei and the relationship between the 9.7 micron silicate and 3.4 micron hydrocarbon absorption bands.Comment: 7 pages, accepted for publication in MNRA

    No evidence for killer sperm or other selective interactions between human spermatozoa in ejaculates of different males in vitro

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    This study examines one of the possible mechanisms of sperm competition, i.e. the kamikaze sperm hypothesis. This hypothesis states that sperm from different males interact to incapacitate each other in a variety of ways. We used ejaculates from human donors to compare mixes of semen in vitro from the same or different males. We measured the following parameters: (i) the degree of sperm aggregation, velocity and proportion of morphologically normal sperm after 1 and 3 h incubation in undiluted semen samples, (ii) the proportion of viable sperm plus the same parameters as in (i) in 'swim-up' sperm suspensions after 1 and 3 h incubation, (iii) the degree of self and non-self sperm aggregation using fluorescent dyes to distinguish the sperm of different males, and (iv) the extent of sperm capacitation and acrosome-reacted sperm in mixtures of sperm from the same and different males. We observed very few significant changes in sperm aggregation or performance in mixtures of sperm from different males compared with mixtures from the same male and none that were consistent with previously reported findings. The incapacitation of rival sperm therefore seems an unlikely mechanism of sperm competition in humans

    PROBE: preparedness and response - online bioterrorism education: foundation knowledge training

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    Terrorism and the resulting geo-political state of affairs have created a need for health professionals to be well prepared for bioterror. In our socio-political climate we need a rational approach to managing public perceptions and need to be able to lead an appropriate response to suspected bioterror events. This website was created as a resource for public health professionals interested in learning how to be more effective at preparing for and responding to a terrorist attack using bioweapons. Who is involved: The Anton Breinl Centre for Public Health and Tropical Medicine (ABC) at James Cook University, has particular expertise in disaster/emergency management, biological agents that constitute the greatest threat, and the sociology of terror. The ABC was the first institution in Australia to develop a bioterrorism course. What is PROBE? The PROBE (Preparedness & Response - Online Bioterrorism Education) project designs and develops multimedia-based, interactive decision support simulation modules for training and support of health professionals in the management of bioterrorism events in an Australian context. PROBE modules provide knowledge and experience that to enhance ability to make timely and appropriate decisions to management of bioterrorism events. In the foundation chapters, students develop an awareness of the increased focus and attention on bioterrorism research and preparedness and explore the implications for the public health sector

    Orexigenic Gene Expression in Late Gestation Ovine Foetal Hypothalamus is Sensitive to Maternal Undernutrition and Realimentation

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    Acknowledgements Research was funded by the Scottish Government's Rural and Environment Science and Analytical Services Division (RESAS), including the Strategic Partnership for Animal Science Excellence (SPASE). The authors have no conflicts of interest to declare.Peer reviewedPostprin

    A special simplex in the state space for entangled qudits

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    Focus is on two parties with Hilbert spaces of dimension d, i.e. "qudits". In the state space of these two possibly entangled qudits an analogue to the well known tetrahedron with the four qubit Bell states at the vertices is presented. The simplex analogue to this magic tetrahedron includes mixed states. Each of these states appears to each of the two parties as the maximally mixed state. Some studies on these states are performed, and special elements of this set are identified. A large number of them is included in the chosen simplex which fits exactly into conditions needed for teleportation and other applications. Its rich symmetry - related to that of a classical phase space - helps to study entanglement, to construct witnesses and perform partial transpositions. This simplex has been explored in details for d=3. In this paper the mathematical background and extensions to arbitrary dimensions are analysed.Comment: 24 pages, in connection with the Workshop 'Theory and Technology in Quantum Information, Communication, Computation and Cryptography' June 2006, Trieste; summary and outlook added, minor changes in notatio
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