Classical Coulomb three-body problem in collinear eZe configuration

Classical dynamics of two-electron atom and ions H$^{-}$, He, Li$^{+}$, Be$^{2+}$,... in collinear eZe configuration is investigated. It is revealed that the mass ratio $\xi$ between necleus and electron plays an important role for dynamical behaviour of these systems. With the aid of analytical tool and numeircal computation, it is shown that thanks to large mass ratio $\xi$, classical dynamics of these systems is fully chaotic, probably hyperbolic. Experimental manifestation of this finding is also proposed.Comment: Largely rewritten. 21 pages. All figures are available in http://ace.phys.h.kyoto-u.ac.jp/~sano/3-body/index.htm

Multiwavelength study of the high-latitude cloud L1642: chain of star formation

L1642 is one of the two high galactic latitude (|b| > 30deg) clouds confirmed to have active star formation. We examine the properties of this cloud, especially the large-scale structure, dust properties, and compact sources in different stages of star formation. We present high-resolution far-infrared and submm observations with the Herschel and AKARI satellites and mm observations with the AzTEC/ASTE telescope, which we combined with archive data from near- and mid-infrared (2MASS, WISE) to mm observations (Planck). The Herschel observations, combined with other data, show a sequence of objects from a cold clump to young stellar objects at different evolutionary stages. Source B-3 (2MASS J04351455-1414468) appears to be a YSO forming inside the L1642 cloud, instead of a foreground brown dwarf, as previously classified. Herschel data reveal striation in the diffuse dust emission around L1642. The western region shows striation towards NE and has a steeper column density gradient on its southern side. The densest central region has a bow-shock like structure showing compression from the west and a filamentary tail extending towards east. The differences suggest that these may be spatially distinct structures, aligned only in projection. We derive values of the dust emission cross-section per H nucleon for different regions of the cloud. Modified black-body fits to the spectral energy distribution of Herschel and Planck data give emissivity spectral index beta values 1.8-2.0 for the different regions. The compact sources have lower beta values and show an anticorrelation between T and beta. Markov chain Monte Carlo calculations demonstrate the strong anticorrelation between beta and T errors and the importance of mm Planck data in constraining the estimates. L1642 reveals a more complex structure and sequence of star formation than previously known.Comment: 22 pages, 18 figures, accepted to Astronomy & Astrophysics; abstract shortened and figures reduced for astrop

Photonic mode dispersion of a two-dimensional distributed feedback polymer laser

G. A. Turnbull, P. Andrew, William L. Barnes, and I. D. W. Samuel, Physical Review B, Vol. 67, article 165107 (2003). "Copyright © 2003 by the American Physical Society."We present an analysis of the photonic mode dispersion of a two-dimensional (2D) distributed feedback polymer laser based on the conjugated polymer poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene]. We use a combination of a simple model, together with experimental measurements of the photonic mode dispersion in transmission and emission, to explain the operating characteristics of the laser. The laser was found to oscillate at 636 nm on one edge of a photonic stop band in the photonic dispersion. A 2D coupling of modes traveling perpendicular to the orthogonal gratings was found to lead to a low divergence laser emission normal to the waveguide. At pump energies well above the oscillation threshold for this mode, a divergent, cross-shaped far-field emission was observed, resulting from a distributed feedback occurring over a wide range of wave vectors in one band of the photonic dispersion

Relationship between photonic band structure and emission characteristics of a polymer distributed feedback laser

G. A. Turnbull, P. Andrew, M. J. Jory, William L. Barnes, and I. D. W. Samuel, Physical Review B, Vol. 64, article 125122 (2001). "Copyright © 2001 by the American Physical Society."We present an experimental study of the emission characteristics and photonic band structure of a distributed feedback polymer laser, based on the material poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene vinylene]. We use measurements of the photonic band dispersion to explain how the substrate microstructure modifies both spontaneous and stimulated emission. The lasing structure exhibits a one-dimensional photonic band gap around 610 nm, with lasing occurring at one of the two associated band edges. The band edge (frequency) selection mechanism is found to be a difference in the level of output coupling of the modes associated with the two band edges. This is a feature of the second-order distributed feedback mechanism we have employed and is clearly evident in the measured photonic band structur

A First Look at White Dwarf - M Dwarf Pairs in the Sloan Digital Sky Survey (SDSS)

We have identified 109 White Dwarf (WD) - M dwarf pairs in the Sloan Digital Sky Survey (SDSS) with g < 20th magnitude. For each system we determined the temperature of the WD primary and the spectral type of the M dwarf secondary. Using H-alpha emission as a proxy for the chromospheric activity level of the M dwarf, we investigated correlations between the activity level and properties of the system. Compared with field M dwarfs (Hawley et al. 1996), we see a slightly higher active fraction of early-type stars, with activity levels similar to the field. We have conducted followup observations at the ARC 3.5m telescope to obtain radial velocity information and to search for short period binaries, which may be on the verge of interacting. We report on one system with a 4.1 hour period, and several additional systems with significant velocity variations.Comment: 23 pages with 10 figures. Accepted by AJ, to appear in May 2003 issu

Challenging the responsibility of ‘responsible volunteer tourism’

© 2017 Informa UK Limited, trading as Taylor & Francis Group This section of the journal encourages discussion between several authors on a policy-related topic. The same question may, therefore, be addressed from different theoretical, cultural or spatial perspectives. Dialogues may be applied or highly abstract. This Dialogue starts with this contribution and is followed by four comments by Sharpley https://doi.org/10.1080/19407963.2017.1362798; Reid https://doi.org/10.1080/19407963.2017.1362799; Coghlan https://doi.org/10.1080/19407963.2017.1362800 and, finally, Burrai and Hannam’s reflections prompted by the observations of fellow contributors https://doi.org/10.1080/19407963.2017.1362810

On the nature of the EXor accretion events: an unfrequent manifestation of a common phenomenology ?

We present the results of a comparison between classical and newly identified EXor based on literature data and aimed at recognizing possible differences or similarities of both categories. Optical and near-IR two-color diagrams, modalities of fluctuations, and derived values of the mass accretion rates are indicative of strong similarities between the two samples. We demonstrate how the difference between the outburst and the quiescence spectral energy distribution of all the EXor can be well fitted with a single blackbody, as if an additional thermal component appears during the outbursting phase. Temperatures of this additional component span between 1000 and 4500 K, while the radii of the emitting regions (assumed to be a uniform disk) span between 0.01 and 0.1 AU, sizes typical of the inner portions of the circumstellar disk. Spots persisting up to 50% of the outburst duration, not exceeding the 10% of the stellar surface, and with temperatures compatible with the EXor mass accretion rates, are able to account for both the appearance of the additional thermal component and the dust sublimation in the inner structures of the disk. We also compare the EXor events with the most significant color and magnitude fluctuations of active T Tauri stars finding that (i} burst accretion phenomena should also be important for this latter class; (ii} EXor events could be more frequent then those accidentally discovered. Remarkable is the case of the source V2493 Cyg, a T Tauri star recently identified as a strong outbursting object: new optical and near-IR photometric and spectroscopic data are presented trying to clarify its EXor or FUor nature.Comment: Accepted for publication in Ap

'Making a Difference': Volunteer Tourism and Development,

Abstract: In recent decades there has been a boom in international volunteer tourism, mainly in the form of the growth of gap-year companies offering placements, linked to conservation and community well-being goals. This paper makes two points: firstly, it argues that the growth of volunteer tourism is in part a product of the politics of the current period – the decline of grand narratives and the growth of ‘life political’ alternative forms of agency. Hence volunteer tourism, motivated by the impulse to ‘make a difference’, tells us something about the way in which development issues are being conceived of by idealistic young people who comprise the majority of volunteer tourists. Secondly, the paper takes issue with the view that today’s volunteer tourists are part of a tradition of colonialism and neo-colonialism that projects western conceptions of modernization onto the Third World societies to the detriment of the latter. Rather, it is argued that the politics behind volunteer tourism is better characterized as a rejection of modernization as development in favour of a post-development influenced approach. Keywords: volunteer tourism; life politics; gap-year; ethical consumption; tourism and development

Planck 2015 results. XXVII. The Second Planck Catalogue of Sunyaev-Zeldovich Sources

We present the all-sky Planck catalogue of Sunyaev-Zeldovich (SZ) sources detected from the 29 month full-mission data. The catalogue (PSZ2) is the largest SZ-selected sample of galaxy clusters yet produced and the deepest all-sky catalogue of galaxy clusters. It contains 1653 detections, of which 1203 are confirmed clusters with identified counterparts in external data-sets, and is the first SZ-selected cluster survey containing > $10^3$ confirmed clusters. We present a detailed analysis of the survey selection function in terms of its completeness and statistical reliability, placing a lower limit of 83% on the purity. Using simulations, we find that the Y5R500 estimates are robust to pressure-profile variation and beam systematics, but accurate conversion to Y500 requires. the use of prior information on the cluster extent. We describe the multi-wavelength search for counterparts in ancillary data, which makes use of radio, microwave, infra-red, optical and X-ray data-sets, and which places emphasis on the robustness of the counterpart match. We discuss the physical properties of the new sample and identify a population of low-redshift X-ray under- luminous clusters revealed by SZ selection. These objects appear in optical and SZ surveys with consistent properties for their mass, but are almost absent from ROSAT X-ray selected samples

The Seventh Data Release of the Sloan Digital Sky Survey

This paper describes the Seventh Data Release of the Sloan Digital Sky Survey (SDSS), marking the completion of the original goals of the SDSS and the end of the phase known as SDSS-II. It includes 11663 deg^2 of imaging data, with most of the roughly 2000 deg^2 increment over the previous data release lying in regions of low Galactic latitude. The catalog contains five-band photometry for 357 million distinct objects. The survey also includes repeat photometry over 250 deg^2 along the Celestial Equator in the Southern Galactic Cap. A coaddition of these data goes roughly two magnitudes fainter than the main survey. The spectroscopy is now complete over a contiguous area of 7500 deg^2 in the Northern Galactic Cap, closing the gap that was present in previous data releases. There are over 1.6 million spectra in total, including 930,000 galaxies, 120,000 quasars, and 460,000 stars. The data release includes improved stellar photometry at low Galactic latitude. The astrometry has all been recalibrated with the second version of the USNO CCD Astrograph Catalog (UCAC-2), reducing the rms statistical errors at the bright end to 45 milli-arcseconds per coordinate. A systematic error in bright galaxy photometr is less severe than previously reported for the majority of galaxies. Finally, we describe a series of improvements to the spectroscopic reductions, including better flat-fielding and improved wavelength calibration at the blue end, better processing of objects with extremely strong narrow emission lines, and an improved determination of stellar metallicities. (Abridged)Comment: 20 pages, 10 embedded figures. Accepted to ApJS after minor correction