10,214 research outputs found

    Symbiotic stars in the Local Group of Galaxies

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    Preliminary results of the ongoing search for symbiotic binary stars in the Local Group of Galaxies are presented and discussed.Comment: Proceedings of Physics of Evolved Stars 2015: A Conference Dedicated to the Memory of Olivier Chesneau, Nice, 8-12 June 201

    The luminosity function of Palomar 5 and its tidal tails

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    We present the main sequence luminosity function of the tidally disrupted globular cluster Palomar 5 and its tidal tails. For this work we analyzed imaging data obtained with the Wide Field Camera at the INT (La Palma) and data from the Wide Field Imager at the MPG/ESO 2.2 m telescope at La Silla down to a limiting magnitude of approximately 24.5 mag in B. Our results indicate that preferentially fainter stars were removed from the cluster so that the LF of the cluster's main body exhibits a significant degree of flattening compared to other GCs. This is attributed to its advanced dynamical evolution. The LF of the tails is, in turn, enhanced with faint, low-mass stars, which we interpret as a consequence of mass segregation in the cluster.Comment: 4 pages, 3 figures, to be published in the proceedings of the conference "Satellites and tidal streams" held at La Palma, Canary Islands, May 26 - 30, 200

    Formation of Black Holes from Collapsed Cosmic String Loops

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    The fraction of cosmic string loops which collapse to form black holes is estimated using a set of realistic loops generated by loop fragmentation. The smallest radius sphere into which each cosmic string loop may fit is obtained by monitoring the loop through one period of oscillation. For a loop with invariant length LL which contracts to within a sphere of radius RR, the minimum mass-per-unit length ÎŒmin\mu_{\rm min} necessary for the cosmic string loop to form a black hole according to the hoop conjecture is ÎŒmin=R/(2GL)\mu_{\rm min} = R /(2 G L). Analyzing 25,57625,576 loops, we obtain the empirical estimate fBH=104.9±0.2(GÎŒ)4.1±0.1f_{\rm BH} = 10^{4.9\pm 0.2} (G\mu)^{4.1 \pm 0.1} for the fraction of cosmic string loops which collapse to form black holes as a function of the mass-per-unit length ÎŒ\mu in the range 10−3â‰ČGÎŒâ‰Č3×10−210^{-3} \lesssim G\mu \lesssim 3 \times 10^{-2}. We use this power law to extrapolate to GΌ∌10−6G\mu \sim 10^{-6}, obtaining the fraction fBHf_{\rm BH} of physically interesting cosmic string loops which collapse to form black holes within one oscillation period of formation. Comparing this fraction with the observational bounds on a population of evaporating black holes, we obtain the limit GΌ≀3.1(±0.7)×10−6G\mu \le 3.1 (\pm 0.7) \times 10^{-6} on the cosmic string mass-per-unit-length. This limit is consistent with all other observational bounds.Comment: uuencoded, compressed postscript; 20 pages including 7 figure

    Substance Abuse via Legally Prescribed Drugs: The Case of Vicodin in the United States

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    Vicodin is the most commonly prescribed pain reliever in the United States. Research indicates that there are two million people who are currently abusing Vicodin, and the majority of those who abuse Vicodin were initially exposed to it via prescription. Our goal is to determine the most effective strategies for reducing the overall population of Vicodin abusers. More specifically, we focus on whether prevention methods aimed at educating doctors and patients on the potential for drug abuse or treatment methods implemented after a person abuses Vicodin will have a greater overall impact. We consider one linear and two non-linear compartmental models in which medical users of Vicodin can transition into the abuser compartment or leave the population by no longer taking the drug. Once Vicodin abusers, people can transition into a treatment compartment, with the possibility of leaving the population through successful completion of treatment or of relapsing and re-entering the abusive compartment. The linear model assumes no social interaction, while both non-linear models consider interaction. One considers interaction with abusers affecting the relapse rate, while the other assumes both this and an additional interaction between the number of abusers and the number of new prescriptions. Sensitivity analyses are conducted varying the rates of success of these intervention methods measured by the parameters to determine which strategy has the greatest impact on controlling the population of Vicodin abusers. From these models and analyses, we determine that manipulating parameters tied to prevention measures has a greater impact on reducing the population of abusers than manipulating parameters associated with treatment. We also note that increasing the rate at which abusers seek treatment affects the population of abusers more than the success rate of treatment itself

    Preparation for cancer care: perceptions of newly qualified health care professionals

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    The present paper is derived from a larger survey which examined the perceptions of recently qualified health care professionals’ experience on evidence-based practice, team working and cancer care. This study reports solely on the findings relating to cancer care. The perceptions of recently qualified professionals in relation to their initial educational input on issues such as confidence, anxiety, communication skills and practice in cancer care as well as adequacy of support, professional supervision and use of reflection were gathered using a cross-sectional postal survey design. A total of 50 graduates from each professional category in nursing, occupational therapy, physiotherapy, and social work were sampled yielding a total sample of 200. Eighty-five questionnaires were returned yielding a response rate of 43%. Twenty-eight (33%) respondents stated that they were currently involved in working with people with cancer. These were as follows: 5 nurses, 8 physiotherapists, 9 occupational therapists and 6 social workers. Despite the low response rate, the findings suggest that health care professionals’ educational input and experiences of working with people with cancer were overall positive; for example, in the respondents’ confidence, communication skills, decrease in anxiety and application of knowledge gained in classroom to professional practice. Moreover, most respondents learnt about caring for cancer patients through practice rather than classroom teaching. A high percentage (i.e. 64%;18) across all groups felt supported when caring for people with cancer and reported receiving professional supervision as well as being able to actively reflect on their practice. The implications for education and practice were discussed particularly as there have been few studies conducted in relation to the specific needs and collaborative learning of these health care professional groups

    Cosmological milestones and energy conditions

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    Until recently, the physically relevant singularities occurring in FRW cosmologies had traditionally been thought to be limited to the "big bang", and possibly a "big crunch". However, over the last few years, the zoo of cosmological singularities considered in the literature has become considerably more extensive, with "big rips" and "sudden singularities" added to the mix, as well as renewed interest in non-singular cosmological events such as "bounces" and "turnarounds". In this talk, we present an extensive catalogue of such cosmological milestones, both at the kinematical and dynamical level. First, using generalized power series, purely kinematical definitions of these cosmological events are provided in terms of the behaviour of the scale factor a(t). The notion of a "scale-factor singularity" is defined, and its relation to curvature singularities (polynomial and differential) is explored. Second, dynamical information is extracted by using the Friedmann equations (without assuming even the existence of any equation of state) to place constraints on whether or not the classical energy conditions are satisfied at the cosmological milestones. Since the classification is extremely general, and modulo certain technical assumptions complete, the corresponding results are to a high degree model-independent.Comment: 8 pages, 1 table, conference proceedings for NEB XII conference in Nafplio, Greec

    Metabolic responses of osteochondral allografts to re-warming after MOPS(TM) preservation versus standard of care storage

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    Osteoarthritis (OA) affects ~90% of people older than 65, and associated costs top $100 billion annually in the U.S. One treatment available for large cartilage defects seen in osteoarthritis is osteochondral allograft (OCA) transplantation. Currently, tissue banks store OCAs at 4 degree C and implantation is recommended within 28 days after procurement due to significant loss in chondrocyte viability after this time. Because mandatory disease screening protocols typically take 14 days to complete, the window for surgical implantation is narrow, which severely limits clinical use. The MOPS(TM) protocol can maintain OCAs for 56 days. In this study, OCAs stored using MOPS(TM) and SOC protocol were assessed for cell viability and metabolic biomarker production

    The medical elective: A unique educational opportunity

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