69 research outputs found
Radial Velocities of Six OB Stars
We present new results from a radial velocity study of six bright OB stars
with little or no prior measurements. One of these, HD 45314, may be a
long-period binary, but the velocity variations of this Be star may be related
to changes in its circumstellar disk. Significant velocity variations were also
found for HD 60848 (possibly related to nonradial pulsations) and HD 61827
(related to wind variations). The other three targets, HD 46150, HD 54879, and
HD 206183, are constant velocity objects, but we note that HD 54879 has
H emission that may originate from a binary companion. We illustrate
the average red spectrum of each target.Comment: Accepted for publication in PASP July 2007 issu
The Long Period, Massive Binaries HD 37366 and HD 54662: Potential Targets for Long Baseline Optical Interferometry
We present the results from an optical spectroscopic analysis of the massive
stars HD 37366 and HD 54662. We find that HD 37366 is a double-lined
spectroscopic binary with a period of 31.8187 +/- 0.0004 days, and HD 54662 is
also a double lined binary with a much longer period of 557.8 +/- 0.3 days. The
primary of HD 37366 is classified as O9.5 V, and it contributes approximately
two-thirds of the optical flux. The less luminous secondary is a broad-lined,
early B-type main-sequence star. Tomographic reconstruction of the individual
spectra of HD 37366 reveals absorption lines present in each component,
enabling us to constrain the nature of the secondary and physical
characteristics of both stars. Tomographic reconstruction was not possible for
HD 54662; however, we do present mean spectra from our observations that show
that the secondary component is approximately half as bright as the primary.
The observed spectral energy distributions (SEDs) were fit with model SEDs and
galactic reddening curves to determine the angular sizes of the stars. By
assuming radii appropriate for their classifications, we determine distance
ranges of 1.4 - 1.9 and 1.2 - 1.5 kpc for HD 37366 and HD 54662, respectively.Comment: 27 pages, 8 figures, Accepted for publication in Ap
Optically Thick Radio Cores of Narrow-Waist Bipolar Nebulae
We report our search for optically thick radio cores in sixteen narrow-waist
bipolar nebulae. Optically thick cores are a characteristic signature of
collimated ionized winds. Eleven northern nebulae were observed with the Very
Large Array (VLA) at 1.3 cm and 0.7 cm, and five southern nebulae were observed
with the Australia Telescope Compact Array (ATCA) at 6 cm and 3.6 cm. Two
northern objects, 19W32 and M 1-91, and three southern objects, He 2-25, He
2-84 and Mz 3, were found to exhibit a compact radio core with a rising
spectrum consistent with an ionized jet. Such jets have been seen in M 2-9 and
may be responsible for shaping bipolar structure in planetary nebulae.Comment: 29 pages, accepted for publication in Ap
Catalog of Galactic Beta Cephei Stars
We present an extensive and up-to-date catalog of Galactic Beta Cephei stars.
This catalog is intended to give a comprehensive overview of observational
characteristics of all known Beta Cephei stars. 93 stars could be confirmed to
be Beta Cephei stars. For some stars we re-analyzed published data or conducted
our own analyses. 61 stars were rejected from the final Beta Cephei list, and
77 stars are suspected to be Beta Cephei stars. A list of critically selected
pulsation frequencies for confirmed Beta Cephei stars is also presented. We
analyze the Beta Cephei stars as a group, such as the distributions of their
spectral types, projected rotational velocities, radial velocities, pulsation
periods, and Galactic coordinates. We confirm that the majority of these stars
are multiperiodic pulsators. We show that, besides two exceptions, the Beta
Cephei stars with high pulsation amplitudes are slow rotators. We construct a
theoretical HR diagram that suggests that almost all 93 Beta Cephei stars are
MS objects. We discuss the observational boundaries of Beta Cephei pulsation
and their physical parameters. We corroborate that the excited pulsation modes
are near to the radial fundamental mode in frequency and we show that the mass
distribution of the stars peaks at 12 solar masses. We point out that the
theoretical instability strip of the Beta Cephei stars is filled neither at the
cool nor at the hot end and attempt to explain this observation
Extrinsic Magnetotransport Phenomena in Ferromagnetic Oxides
This review is focused on extrinsic magnetotransport effects in ferromagnetic
oxides. It consists of two parts; the second part is devoted to an overview of
experimental data and theoretical models for extrinsic magnetotransport
phenomena. Here a critical discussion of domain-wall scattering is given.
Results on surfacial and interfacial magnetism in oxides are presented.
Spin-polarized tunnelling in ferromagnetic junctions is reviewed and
grain-boundary magnetoresistance is interpreted within a model of
spin-polarized tunnelling through natural oxide barriers. The situation in
ferromagnetic oxides is compared with data and models for conventional
ferromagnets. The first part of the review summarizes basic material
properties, especially data on the spin-polarization and evidence for
half-metallicity. Furthermore, intrinsic conduction mechanisms are discussed.
An outlook on the further development of oxide spin-electronics concludes this
review.Comment: 133 pages, 47 figures, submitted to Rep. Prog. Phy
TEM observation of dislocation loops correlated with individual swirl defects in asâgrown silicon
all - simply - immediately: service in medical libraries: Annual Meeting 2010 of "Arbeitsgemeinschaft fĂŒr Medizinisches Bibliothekswesen" (AGMB e.V.) 27th to 29th September in Mainz
The annual meeting 2010 of "Arbeitsgemeinschaft fĂŒr Medizinisches Bibliothekswesen" (AGMB e.V.) took place 27th-29th September at Mainz university.During the main event for Advanced training of medical librarianship in Germany, Austria and Switzerland the following topics were presented and discussed: Increasing digitalization of scientific communication and the consequences, innovative services in hybrid libraries (virtual textbook collections and E-Books On-Demand), education (Master degree programm "Informations- und Wissensmanagement" in Hannover), concept and building of the medical library at DĂŒsseldorf university (O.A.S.E.), quality management according to ISO 9001, subito (new services based on § 5 2a+b UrhG), future of the programm "Nationallizenzen" and "Allianz-Initiative der deutschen Wissenschaftsorganisationen", information l itera cy (particularly blended-learning), public relation and new strategies for communication and services, future concepts for medical libraries, library services in a UK research institute, reference management, Web 2.0 and other emerging technologies, BibNet.org, Cochrane library, MedPilot, PubMed.All relevant publishers and providers for medical libraries presented new products and services in an accompanying exhibition.Vom 27.-29.9.2010 fand an der UniversitĂ€t Mainz die Jahrestagung der Arbeitsgemeinschaft fĂŒr Medizinisches Bibliothekswesen (AGMB e.V.) statt.Auf der zentralen Fortbildungsveranstaltung fĂŒr das medizinische Bibliothekswesen in Deutschland, Ăsterreich und der Schweiz konnten sich die Teilnehmer unter anderem ĂŒber folgende Themen informieren: Zunehmende Digitalisierung der wissenschaftlichen Kommunikation und deren Auswirkungen, innovative Services in Hybridbibliotheken (Virtuelle Lehrbuchsammlung und E-Books On-Demand), Ausbildung (Weiterbildungs-Masterstudiengang Informations- und Wissensmanagement in Hannover), Neubau der Fachbibliothek Medizin O.A.S.E. an der UniversitĂ€t DĂŒsseldorf, QualitĂ€tsmanagement nach ISO 9001, subito (neue Dienste auf der Basis von § 52a+b UrhG), Zukunft der Nationallizenzen und Allianz-Initiative der deutschen Wissenschaftsorganisationen, Informationskompetenz am Beispiel von Blended-Learning, Public Relation sowie neue Kommunikations- und Servicestrategien, Zukunftskonzepte fĂŒr Medizinbibliotheken, Dienstleistungen der Bibliothek an einem Forschungsinstitut in GroĂbritannien, Literaturverwaltung, Web 2.0 und andere Emerging Technologies, BibNet.org, Cochrane Library, MedPilot, PubMed.In einer begleitenden Firmenausstellung prĂ€sentierten alle fĂŒr medizinische Bibliotheken wichtigen Verlage und Dienstleister neue Produkte und Services
MAGNETIC AND TRANSPORT PROPERTIES OF a-UxGd1-x FILMS
a - UxGd1-x films show Arrott plots and AC susceptibility characteristic of random-exchange dominated systems. Both the resistivity and the magnetoresistance show the possible coexistence of magnetic scattering and weak-localization effects below a temperature T1. The anisotropic magnetoresistance is zero as expected for a Gd containing system (S-state)
- âŠ