1,083 research outputs found

    Deep infrared observations of the puzzling central X-ray source in RCW103

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    1E 161348-5055 (1E 1613) is a point-like, soft X-ray source originally identified as a radio-quiet, isolated neutron star, shining at the center of the 2000 yr old supernova remnant RCW103. 1E 1613 features a puzzling 6.67 hour periodicity as well as a dramatic variability over a time scale of few years. Such a temporal behavior, coupled to the young age and to the lack of an obvious optical counterpart, makes 1E 1613 a unique source among all compact objects associated to SNRs. It could either be the first low-mass X-ray binary system discovered inside a SNR, or a peculiar isolated magnetar with an extremely slow spin period. Analysis of archival IR observations, performed in 2001 with the VLT/ISAAC instrument, and in 2002 with the NICMOS camera onboard HST unveils a very crowded field. A few sources are positionally consistent with the refined X-ray error region that we derived from the analysis of 13 Chandra observations. To shed light on the nature of 1E 1613, we have performed deep IR observations of the field with the NACO instrument at the ESO/VLT, searching for variability. We find no compelling reasons to associate any of the candidates to 1E 1613. On one side, within the frame of the binary system model for the X-ray source, it is very unlikely that one of the candidates be a low-mass companion star to 1E 1613. On the other side, if the X-ray source is an isolated magnetar surrounded by a fallback disc, we cannot exclude that the IR counterpart be hidden among the candidates. If none of the potential counterparts is linked to the X-ray source, 1E 1613 would remain undetected in the IR down to Ks>22.1. Such an upper limit is consistent only with an extremely low-mass star (an M6-M8 dwarf) at the position of 1E 1613, and makes rather problematic the interpretation of 1E 1613 as an accreting binary system.Comment: 26 pages, 5 figures. Accepted for publication in Ap

    Hypothalamic Α 2 -Noradrenergic Receptor System Relation to Dietary, Genetic, and Hormonally Induced Obesity

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/73970/1/j.1749-6632.1989.tb53313.x.pd

    The 69 ms Radio Pulsar Near the Supernova Remnant RCW 103

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    We report the detection of the radio pulsar counterpart to the 69 ms X-ray pulsar discovered near the supernova remnant RCW 103 (G332.4-0.4). Our detection confirms that the pulsations arise from a rotation-powered neutron star, which we name PSR J1617-5055. The observed barycentric period derivative confirms that the pulsar has a characteristic age of only 8 kyr, the sixth smallest of all known pulsars. The unusual apparent youth of the pulsar and its proximity to a young remnant requires that an association be considered. Although the respective ages and distances are consistent within substantial uncertainties, the large inferred pulsar transverse velocity is difficult to explain given the observed pulsar velocity distribution, the absence of evidence for a pulsar wind nebula, and the symmetry of the remnant. Rather, we argue that the objects are likely superposed on the sky; this is reasonable given the complex area. Without an association, the question of where is the supernova remnant left behind following the birth of PSR J1617-5055 remains open. We also discuss a possible association between PSR J1617-5055 and the gamma-ray source 2CG 333+01. Though an association is energetically plausible, it is unlikely given that EGRET did not detect 2CG 333+01.Comment: 18 pages, 2 encapsulated Postscript figures, uses AAS LaTeX style files. Accepted for publication in The Astrophysical Journal Letter

    Whole Earth Telescope observations of the hot helium atmosphere pulsating white dwarf EC 20058-5234

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    We present the analysis of a total of 177h of high-quality optical time-series photometry of the helium atmosphere pulsating white dwarf (DBV) EC 20058-5234. The bulk of the observations (135h) were obtained during a WET campaign (XCOV15) in July 1997 that featured coordinated observing from 4 southern observatory sites over an 8-day period. The remaining data (42h) were obtained in June 2004 at Mt John Observatory in NZ over a one-week observing period. This work significantly extends the discovery observations of this low-amplitude (few percent) pulsator by increasing the number of detected frequencies from 8 to 18, and employs a simulation procedure to confirm the reality of these frequencies to a high level of significance (1 in 1000). The nature of the observed pulsation spectrum precludes identification of unique pulsation mode properties using any clearly discernable trends. However, we have used a global modelling procedure employing genetic algorithm techniques to identify the n, l values of 8 pulsation modes, and thereby obtain asteroseismic measurements of several model parameters, including the stellar mass (0.55 M_sun) and T_eff (~28200 K). These values are consistent with those derived from published spectral fitting: T_eff ~ 28400 K and log g ~ 7.86. We also present persuasive evidence from apparent rotational mode splitting for two of the modes that indicates this compact object is a relatively rapid rotator with a period of 2h. In direct analogy with the corresponding properties of the hydrogen (DAV) atmosphere pulsators, the stable low-amplitude pulsation behaviour of EC 20058 is entirely consistent with its inferred effective temperature, which indicates it is close to the blue edge of the DBV instability strip. (abridged)Comment: 19 pages, 8 figures, 5 tables, MNRAS accepte

    Normal modes and discovery of high-order cross-frequencies in the DBV white dwarf GD 358

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    We present a detailed mode identification performed on the 1994 Whole Earth Telescope (WET) run on GD 358. The results are compared with that obtained for the same star from the 1990 WET data. The two temporal spectra show very few qualitative differences, although amplitude changes are seen in most modes, including the disappearance of the mode identified as k=14 in the 1990 data. The excellent coverage and signal-to-noise ratio obtained during the 1994 run lead to the secure identification of combination frequencies up to fourth order, i.e. peaks that are sums or differences of up to four parent frequencies, including a virtually complete set of second-order frequencies, as expected from harmonic distortion. We show how the third-order frequencies are expected to affect the triplet structure of the normal modes by back-interacting with them. Finally, a search for â„“=2 modes was unsuccessful, not verifying the suspicion that such modes had been uncovered in the 1990 data set

    On the continuous Cesàro operator in certain function spaces

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    “The final publication is available at Springer via http://dx.doi.org/10.1007/s11117-014-0321-5"Various properties of the (continuous) Cesàro operator C, acting on Banach and Fréchet spaces of continuous functions and L p-spaces, are investigated. For instance, the spectrum and point spectrum of C are completely determined and a study of certain dynamics of C is undertaken (eg. hyper- and supercyclicity, chaotic behaviour). In addition, the mean (and uniform mean) ergodic nature of C acting in the various spaces is identified.The research of the first two authors was partially supported by the projects MTM2010-15200 and GVA Prometeo II/2013/013 (Spain). The second author gratefully acknowledges the support of the Alexander von Humboldt Foundation.Albanese, AA.; Bonet Solves, JA.; Ricker, WJ. (2015). On the continuous Cesàro operator in certain function spaces. Positivity. 19:659-679. https://doi.org/10.1007/s11117-014-0321-5S65967919Albanese, A.A.: Primary products of Banach spaces. Arch. Math. 66, 397–405 (1996)Albanese, A.A.: On subspaces of the spaces LlocpL^p_{\rm loc} L loc p and of their strong duals. Math. Nachr. 197, 5–18 (1999)Albanese, A.A., Moscatelli, V.B.: Complemented subspaces of sums and products of copies of L1[0,1]L^1 [0,1] L 1 [ 0 , 1 ] . Rev. Mat. Univ. Complut. Madr. 9, 275–287 (1996)Albanese, A.A., Bonet, J., Ricker, W.J.: Mean ergodic operators in Fréchet spaces. Ann. Acad. Sci. Fenn. Math. 34, 401–436 (2009)Albanese, A.A., Bonet, J., Ricker, W.J.: On mean ergodic operators. In: Curbera, G.P. (eds.) Vector Measures, Integration and Related Topics. Operator Theory: Advances and Applications, vol. 201, pp. 1–20. Birkhäuser, Basel (2010)Albanese, A.A., Bonet, J., Ricker, W.J.: C0C_0 C 0 -semigroups and mean ergodic operators in a class of Fréchet spaces. J. Math. Anal. Appl. 365, 142–157 (2010)Albanese, A.A., Bonet, J., Ricker, W.J.: Convergence of arithmetic means of operators in Fréchet spaces. J. Math. Anal. Appl. 401, 160–173 (2013)Bayart, F., Matheron, E.: Dynamics of linear operators. Cambridge Tracts in Mathematics, vol. 179. Cambridge University Press, Cambridge (2009)Bellenot, S.F., Dubinsky, E.: Fréchet spaces with nuclear Köthe quotients. Trans. Am. Math. Soc. 273, 579–594 (1982)Bonet, J., Frerick, L., Peris, A., Wengenroth, J.: Transitive and hypercyclic operators on locally convex spaces. Bull. Lond. Math. Soc. 37, 254–264 (2005)Boyd, D.W.: The spectrum of the Cesàro operator. Acta Sci. Math. (Szeged) 29, 31–34 (1968)Brown, A., Halmos, P.R., Shields, A.L.: Cesàro operators. Acta Sci. Math. (Szeged) 26, 125–137 (1965)Dierolf, S., Zarnadze, D.N.: A note on strictly regular Fréchet spaces. Arch. Math. 42, 549–556 (1984)Dunford, N., Schwartz, J.T.: Linear Operators I: General Theory (2nd Printing). Wiley-Interscience, New York (1964)Galaz Fontes, F., Solís, F.J.: Iterating the Cesàro operators. Proc. Am. Math. Soc. 136, 2147–2153 (2008)Galaz Fontes, F., Ruiz-Aguilar, R.W.: Grados de ciclicidad de los operadores de Cesàro–Hardy. Misc. Mat. 57, 103–117 (2013)González, M., León-Saavedra, F.: Cyclic behaviour of the Cesàro operator on L2(0,+∞)L_2(0,+\infty ) L 2 ( 0 , + ∞ ) . Proc. Am. Math. Soc. 137, 2049–2055 (2009)Grosse-Erdmann, K.G., Peris Manguillot, A.: Linear chaos. In: Universitext. Springer, London (2011)Hardy, G.H., Littlewood, J.E., Pólya, G.: Inequalities. In: Reprint of the 1952 Edition. Cambridge Mathematical Library. Cambridge University Press, Cambridge (1988)Krengel, U.: Ergodic theorems. In: De Gruyter Studies in Mathematics, vol. 6. Walter de Gruyter Co., Berlin (1985)Leibowitz, G.M.: Spectra of finite range Cesàro operators. Acta Sci. Math. (Szeged) 35, 27–28 (1973)Leibowitz, G.M.: The Cesàro operators and their generalizations: examples in infinite-dimensional linear analysis. Am. Math. Mon. 80, 654–661 (1973)León-Saavedra, F., Piqueras-Lerena, A., Seoane-Sepúlveda, J.B.: Orbits of Cesàro type operators. Math. Nachr. 282, 764–773 (2009)Lin, M.: On the uniform ergodic theorem. Proc. Am. Math. Soc. 43, 337–340 (1974)Meise, R., Vogt, D.: Introduction to functional analysis. In: Oxford Graduate Texts in Mathematics, vol. 2. The Clarendon Press; Oxford University Press, New York (1997)Metafune, G., Moscatelli, V.B.: Quojections and prequojections. In: Terzioğlu, T. (ed.) Advances in the Theory of Fréchet spaces. NATO ASI Series, vol. 287, pp. 235–254. Kluwer Academic Publishers, Dordrecht (1989)Moscatelli, V.B.: Fréchet spaces without norms and without bases. Bull. Lond. Math. Soc. 12, 63–66 (1980)Piszczek, K.: Quasi-reflexive Fréchet spaces and mean ergodicity. J. Math. Anal. Appl. 361, 224–233 (2010)Piszczek, K.: Barrelled spaces and mean ergodicity. Rev R. Acad. Cienc. Exactas Fis. Nat. Ser. A Math. RACSAM 104, 5–11 (2010)Yosida, K.: Functional Analysis, 6th edn. Springer, Berlin (1980

    Ethical implications of the perception and portrayal of dementia

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    yesThe way we perceive and portray dementia has implications for how we act towards people with dementia and how we address the issue of dementia within society. As a multi-disciplinary working group, established within the framework of the European Dementia Ethics Network of Alzheimer Europe, we aimed to describe the different ways that people with dementia are perceived and portrayed within society and to consider the moral implications of this. In the current paper, we address perceptions of dementia as reflected in explanatory models of its cause and nature, descriptions of characteristics of people with dementia, the use of language, media portrayals and the views of people living with dementia. Academics and professionals could use this exploration to reflect on their behaviour and their use of language regarding people with dementiaThe taskforce’s work arises from the 2013 Work Plan of Alzheimer Europe, which received funding from the European Union in the framework of the Health Programme

    The breadth of primary care: a systematic literature review of its core dimensions

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    Background: Even though there is general agreement that primary care is the linchpin of effective health care delivery, to date no efforts have been made to systematically review the scientific evidence supporting this supposition. The aim of this study was to examine the breadth of primary care by identifying its core dimensions and to assess the evidence for their interrelations and their relevance to outcomes at (primary) health system level. Methods: A systematic review of the primary care literature was carried out, restricted to English language journals reporting original research or systematic reviews. Studies published between 2003 and July 2008 were searched in MEDLINE, Embase, Cochrane Library, CINAHL, King's Fund Database, IDEAS Database, and EconLit. Results: Eighty-five studies were identified. This review was able to provide insight in the complexity of primary care as a multidimensional system, by identifying ten core dimensions that constitute a primary care system. The structure of a primary care system consists of three dimensions: 1. governance; 2. economic conditions; and 3. workforce development. The primary care process is determined by four dimensions: 4. access; 5. continuity of care; 6. coordination of care; and 7. comprehensiveness of care. The outcome of a primary care system includes three dimensions: 8. quality of care; 9. efficiency care; and 10. equity in health. There is a considerable evidence base showing that primary care contributes through its dimensions to overall health system performance and health. Conclusions: A primary care system can be defined and approached as a multidimensional system contributing to overall health system performance and health

    Managing authenticity and performance in Gulag tourism, Kazakhstan

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    To date, there has been limited research concerning the methodology and approach to Gulag heritage and how it has been memorialised and commodified for tourism purposes. The recent cultural commodification of the Soviet past and the development of participatory visitor experiences at Gulag museums in Kazakhstan necessitate to advance understandings of the roles authenticity and performance play in the management of Gulag museum practices in the country. Using a qualitative case study research approach based on a combination of semi-structured interviews with stakeholders involved in the development of Gulag tourism including senior management of museums, museum guides, policy-makers, tourism operators, local NGOs and experts in Soviet Gulag heritage, direct observations and qualitative document analysis of two Gulag museums and sites in Kazakhstan, the commodification and management of Soviet Gulag heritage is explored. Results reveal that beyond objects on display and images regarded as interpretive illustrations that allow visitors to connect with the past and verify history, dioramas and staged performances re-enacting various elements of the Gulag life are used as immersive and emotional tools to accentuate the ‘dark’ atmosphere of the epoch and induce a more impactful and participatory visitor experience. The findings contribute to literature on authenticity and performance in Gulag tourism by examining the delicate question of the extent to which stakeholders involved in the management of the Gulag tragedy can offer meaningful visitor experiences that are historically accurate and protect the dignity of the victims while adapting to the dynamic roles of museums as heritage and education sites
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