1,201 research outputs found

    On the Anatomy of Prosthecocotyle torulosa (Linstow) and Prosthecocotyle heteroclita (Dies.)

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    In the Report on the Entozoa collected by H.M.S. "Challenger” Dr O. von Linstow described two new tapeworms, which he named Tetrabothrium torulosum and T. auriculatum. The resemblance of the head of T. auriculatum with that of Prosthecocotyle Forsteri described by Monticelli seemed to me to indicate that the Tetrabothrium described by Linstow probably belonged to the genus Prosthecocotyle. Through the kindness of Sir John Murray, I received from the British Museum the original specimens for inspection, for which I wish to express here my warmest thanks. The following lines give the results of my examination; but before entering upon the description, let me say something on the systematic position of these two animals. As I have already remarked, Prof. Monticelli has rightly erected a new genus named Prosthecocotyle for the tapeworm TƓnia Forsteri, Krefft. To this genus belongs, besides P. Forsteri, other parasites of birds which have been placed in the genera TƓnia, Tetrabothrium, Amphoterocotyle, BothridiotƓnia, Bothriocephalus. According to my researches the following species belong to the genus Prosthecocotyle:— 1. P. Forsteri (Krefft), (syn. TƓnia Forsteri, Krefft), from Delphinus Forsteri (Gray) and Delphinus delphinus, L. 2. P. Monticellii, Fuhrmann (syn. TƓnia erostris, ex parte, BothridiotƓnia erostris, var. minor, Lönnberg), from Fulmarus glacialis, L. 3. P. umbrella, Fuhrmann, from Diomedea sp. (?). 4. P. torulosa (Linstow), (syn. Tetrabothrium torulosum, Linstow), from Diomedea brachyura, Tem

    Detailed analysis of Balmer lines in cool dwarf stars

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    An analysis of H alpha and H beta spectra in a sample of 30 cool dwarf and subgiant stars is presented using MARCS model atmospheres based on the most recent calculations of the line opacities. A detailed quantitative comparison of the solar flux spectra with model spectra shows that Balmer line profile shapes, and therefore the temperature structure in the line formation region, are best represented under the mixing length theory by any combination of a low mixing-length parameter alpha and a low convective structure parameter y. A slightly lower effective temperature is obtained for the sun than the accepted value, which we attribute to errors in models and line opacities. The programme stars span temperatures from 4800 to 7100 K and include a small number of population II stars. Effective temperatures have been derived using a quantitative fitting method with a detailed error analysis. Our temperatures find good agreement with those from the Infrared Flux Method (IRFM) near solar metallicity but show differences at low metallicity where the two available IRFM determinations themselves are in disagreement. Comparison with recent temperature determinations using Balmer lines by Fuhrmann (1998, 2000), who employed a different description of the wing absorption due to self-broadening, does not show the large differences predicted by Barklem et al. (2000). In fact, perhaps fortuitously, reasonable agreement is found near solar metallicity, while we find significantly cooler temperatures for low metallicity stars of around solar temperature.Comment: 17 pages, 9 figures, to appear in A&

    Long-Term Multiwavelength Studies of High-Redshift Blazar 0836+710

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    Aims. The observation of gamma -ray flares from blazar 0836+710 in 2011, following a period of quiescence, offered an opportunity to study correlated activity at different wavelengths for a high-redshift (z=2.218) active galactic nucleus. Methods. Optical and radio monitoring, plus Fermi-LAT gamma-ray monitoring provided 2008-2012 coverage, while Swift offered auxiliary optical, ultraviolet, and X-ray information. Other contemporaneous observations were used to construct a broad-band spectral energy distribution. Results. There is evidence of correlation but not a measurable lag between the optical and gamma-ray flaring emission. On the contrary, there is no clear correlation between radio and gamma-ray activity, indicating radio emission regions that are unrelated to the parts of the jet that produce the gamma-rays. The gamma-ray energy spectrum is unusual in showing a change of shape from a power law to a curved spectrum when going from the quiescent state to the active state.Comment: 11 pages, 10 figures, Accepted for publication in A&

    Flaring Activity from 0836+710 (4C +71.07): What Can We Learn With Limited Multiwavelength Coverage?

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    After a long period of quiescence in \gamma-rays, blazar 0836+710 (4C +71.07) flared in the Spring of 2011. We found only limited multiwavelength coverage of the source. An indication of correlated optical / \gamma-ray variability is not surprising for a Flat Spectrum Radio Quasar (FSRQ) like this one. Radio observations at high frequencies, however, had seen a flare in 2010, well offset from possible \gamma-ray activity. The 2011 \gamma-ray activity comes during a period of rising radio emission, a pattern that has been seen since the EGRET era.Comment: 5 pages,2 figures, proceedings of 'Fermi & Jansky:Our Evolving Understanding of AGN

    Detailed Analysis of Nearby Bulgelike Dwarf Stars III. Alpha and Heavy-element abundances

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    The present sample of nearby bulgelike dwarf stars has kinematics and metallicities characteristic of a probable inner disk or bulge origin. Ages derived by using isochrones give 10-11 Gyr for these stars and metallicities are in the range -0.80< [Fe/H]< +0.40. We calculate stellar parameters from spectroscopic data, and chemical abundances of Mg, Si, Ca, Ti, La, Ba, Y, Zr and Eu are derived by using spectrum synthesis. We found that [alpha-elements/Fe] show different patterns depending on the element. Si, Ca and Ti-to-iron ratios decline smoothly for increasing metallicities, and follow essentially the disk pattern. O and Mg, products of massive supernovae, and also the r-process element Eu, are overabundant relative to disk stars, showing a steeper decline for metallicities [Fe/H] > -0.3 dex. [s-elements/Fe] roughly track the solar values with no apparent trend with metallicity for [Fe/H] < 0, showing subsolar values for the metal rich stars. Both kinematical and chemical properties of the bulgelike stars indicate a distinct identity of this population when compared to disk stars.Comment: 21 pages, 9 figures, to appear in Ap

    An Augmented Reality system for the treatment of phobia to small animals viewed via an optical see-through HMD. Comparison with a similar system viewed via a video see-through

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    This article presents an optical see-through (OST) Augmented Reality system for the treatment of phobia to small animals. The technical characteristics of the OST system are described, and a comparative study of the sense of presence and anxiety in a nonphobic population (24 participants) using the OST and an equivalent video see-though (VST) system is presented. The results indicate that if all participants are analyzed, the VST system induces greater sense of presence than the OST system. If the participants who had more fear are analyzed, the two systems induce a similar sense of presence. For the anxiety level, the two systems provoke similar and significant anxiety during the experiment. © Taylor & Francis Group, LLC.Juan, M.; Calatrava, J. (2011). An Augmented Reality system for the treatment of phobia to small animals viewed via an optical see-through HMD. Comparison with a similar system viewed via a video see-through. International Journal of Human-Computer Interaction. 27(5):436-449. doi:10.1080/10447318.2011.552059S436449275Azuma, R. and Bishop, G. Improving static and dynamic registration in an optical see-through HMD. Proceedings of 21st Annual Conference on Computer Graphics and Interactive techniques (SIGGRAPH'94). pp.197–204.Bimber, O., & Raskar, R. (2005). Spatial Augmented Reality. doi:10.1201/b10624Botella, C., Quero, S., Banos, R. M., Garcia-Palacios, A., Breton-Lopez, J., Alcaniz, M., & Fabregat, S. (2008). Telepsychology and Self-Help: The Treatment of Phobias Using the Internet. CyberPsychology & Behavior, 11(6), 659-664. doi:10.1089/cpb.2008.0012Botella, C. M., Juan, M. C., Baños, R. M., Alcañiz, M., GuillĂ©n, V., & Rey, B. (2005). Mixing Realities? An Application of Augmented Reality for the Treatment of Cockroach Phobia. CyberPsychology & Behavior, 8(2), 162-171. doi:10.1089/cpb.2005.8.162Carlin, A. S., Hoffman, H. G., & Weghorst, S. (1997). Virtual reality and tactile augmentation in the treatment of spider phobia: a case report. Behaviour Research and Therapy, 35(2), 153-158. doi:10.1016/s0005-7967(96)00085-xGarcia-Palacios, A., Hoffman, H., Carlin, A., Furness, T. ., & Botella, C. (2002). Virtual reality in the treatment of spider phobia: a controlled study. Behaviour Research and Therapy, 40(9), 983-993. doi:10.1016/s0005-7967(01)00068-7Genc, Y., Tuceryan, M., & Navab, N. (s. f.). Practical solutions for calibration of optical see-through devices. Proceedings. International Symposium on Mixed and Augmented Reality. doi:10.1109/ismar.2002.1115086Hoffman, H. G., Garcia-Palacios, A., Carlin, A., Furness III, T. A., & Botella-Arbona, C. (2003). Interfaces That Heal: Coupling Real and Virtual Objects to Treat Spider Phobia. International Journal of Human-Computer Interaction, 16(2), 283-300. doi:10.1207/s15327590ijhc1602_08Juan, M. C., Alcaniz, M., Monserrat, C., Botella, C., Banos, R. M., & Guerrero, B. (2005). Using Augmented Reality to Treat Phobias. IEEE Computer Graphics and Applications, 25(6), 31-37. doi:10.1109/mcg.2005.143Juan, M. C., Baños, R., Botella, C., PĂ©rez, D., AlcanĂ­iz, M., & Monserrat, C. (2006). An Augmented Reality System for the Treatment of Acrophobia: The Sense of Presence Using Immersive Photography. Presence: Teleoperators and Virtual Environments, 15(4), 393-402. doi:10.1162/pres.15.4.393Kato, H., & Billinghurst, M. (s. f.). Marker tracking and HMD calibration for a video-based augmented reality conferencing system. Proceedings 2nd IEEE and ACM International Workshop on Augmented Reality (IWAR’99). doi:10.1109/iwar.1999.803809Nash, E. B., Edwards, G. W., Thompson, J. A., & Barfield, W. (2000). A Review of Presence and Performance in Virtual Environments. International Journal of Human-Computer Interaction, 12(1), 1-41. doi:10.1207/s15327590ijhc1201_1Owen, C. B., Ji Zhou, Tang, A., & Fan Xiao. (s. f.). Display-Relative Calibration for Optical See-Through Head-Mounted Displays. Third IEEE and ACM International Symposium on Mixed and Augmented Reality. doi:10.1109/ismar.2004.28Özbek, C., Giesler, B. and Dillmann, R. Jedi training: Playful evaluation of head-mounted augmented reality display systems. SPIE Conference Medical Imaging. Vol. 5291, pp.454–463.Renaud, P., Bouchard, S., & Proulx, R. (2002). Behavioral avoidance dynamics in the presence of a virtual spider. IEEE Transactions on Information Technology in Biomedicine, 6(3), 235-243. doi:10.1109/titb.2002.802381Schwald, B. and Laval, B. An Augmented Reality system for training and assistance to maintenance in the industrial context. International Conference in Central Europe on Computer Graphics, Visualization and Computer Vision. pp.425–432.Slater, M., Usoh, M., & Steed, A. (1994). Depth of Presence in Virtual Environments. Presence: Teleoperators and Virtual Environments, 3(2), 130-144. doi:10.1162/pres.1994.3.2.130Szymanski, J., & O’Donohue, W. (1995). Fear of Spiders Questionnaire. Journal of Behavior Therapy and Experimental Psychiatry, 26(1), 31-34. doi:10.1016/0005-7916(94)00072-

    Exploring the Local Milky Way: M Dwarfs as Tracers of Galactic Populations

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    We have assembled a spectroscopic sample of low-mass dwarfs observed as part of the Sloan Digital Sky Survey along one Galactic sightline, designed to investigate the observable properties of the thin and thick disks. This sample of ~7400 K and M stars also has measured ugriz photometry, proper motions, and radial velocities. We have computed UVW space motion distributions, and investigate their structure with respect to vertical distance from the Galactic Plane. We place constraints on the velocity dispersions of the thin and thick disks, using two-component Gaussian fits. We also compare these kinematic distributions to a leading Galactic model. Finally, we investigate other possible observable differences between the thin and thick disks, such as color, active fraction and metallicity.Comment: 11 pages, 12 figures, Accepted by A

    The N2K Consortium. II. A Transiting Hot Saturn Around HD 149026 With a Large Dense Core

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    Doppler measurements from Subaru and Keck have revealed radial velocity variations in the V=8.15, G0IV star HD 149026 consistent with a Saturn-Mass planet in a 2.8766 day orbit. Photometric observations at Fairborn Observatory have detected three complete transit events with depths of 0.003 mag at the predicted times of conjunction. HD 149026 is now the second brightest star with a transiting extrasolar planet. The mass of the star, based on interpolation of stellar evolutionary models, is 1.3 +/- 0.1 solar masses; together with the Doppler amplitude, K=43.3 m s^-1, we derive a planet mass Msin(i)=0.36 Mjup, and orbital radius of 0.042 AU. HD 149026 is chromospherically inactive and metal-rich with spectroscopically derived [Fe/H]=+0.36, Teff=6147 K, log g=4.26 and vsin(i)=6.0 km s^-1. Based on Teff and the stellar luminosity of 2.72 Lsun, we derive a stellar radius of 1.45 Rsun. Modeling of the three photometric transits provides an orbital inclination of 85.3 +/- 1.0 degrees and (including the uncertainty in the stellar radius) a planet radius of 0.725 +/- 0.05 Rjup. Models for this planet mass and radius suggest the presence of a ~67 Mearth core composed of elements heavier than hydrogen and helium. This substantial planet core would be difficult to construct by gravitational instability.Comment: 25 pages, 5 figures, accepted by the Astrophysical Journa

    Multi-frequency VLBA study of the blazar S5 0716+714 during the active state in 2004: I. Inner jet kinematics

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    We observed the blazar \object{0716+714} with the VLBA during its active state in 2003-2004. In this paper we discuss multi-frequency analysis of the inner jet (first 1 mas) kinematics. The unprecedentedly dense time sampling allows us to trace jet components without misidentification and to calculate the component speeds with good accuracy. In the smooth superluminal jet we were able to identify and track three components over time moving outwards with relatively high apparent superluminal speeds (8.5-19.4 cc), which contradicts the hypothesis of a stationary oscillating jet in this source. Component ejections occur at a relatively high rate (once in two months), and they are accompanied by mm-continuum outbursts. Superluminal jet components move along wiggling trajectories, which is an indication of actual helical motion. Fast proper motion and rapid decay of the components suggest that this source should be observed with the VLBI at a rate of at least once in one or two months in order to trace superluminal jet components without confusion.Comment: 4 pages, 3 figures, Astronomy & Astrophysics Letter, language corrections adde

    Highly charged ion X-rays from Electron-Cyclotron Resonance Ion Sources

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    Radiation from the highly-charged ions contained in the plasma of Electron-Cyclotron Resonance Ion Sources constitutes a very bright source of X-rays. Because the ions have a relatively low kinetic energy (≈1\approx 1 eV) transitions can be very narrow, containing only small Doppler broadening. We describe preliminary accurate measurements of two and three-electron ions with Z=16--18. We show how these measurement can test sensitively many-body relativistic calculations or can be used as X-ray standards for precise measurements of X-ray transitions in exotic atoms
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