296 research outputs found

    Far Ultraviolet Spectroscopy of Seven Nova-Like Variables

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    We present the results of a multi-component synthetic spectral analysis of the archival far ultraviolet spectra of several key nova-like variables including members of the SW Sex, RW Tri, UX UMa and VY Scl subclasses: KR Aur, RW Tri, V825 Her, V795 Her, BP Lyn, V425 Cas and HL Aqr. Accretion rates as well as the possible flux contribution of the accreting white dwarf are included in our analysis. Except for RW Tri which has a reliable trigonometric parallax, we computed the distances to the nova-like systems using the method of Knigge (2006). Our analysis of seven archival IUE spectra of RW Tri at its parallax distance of 341 pc consistently indicates a low mass (0.4Msun) white dwarf and an average accretion rate, 6.3 E-9Msun/yr. For KR Aur, we estimate that the white dwarf has Teff=29,000K, log g = 8.4 and contributes 18% of the FUV flux while an accretion disk with accretion rate of 3 E-10Msun/yr at an inclination of 41 degrees, contributes the remainder. We find that an accretion disk dominates the far UV spectrum of V425 Cas but a white dwarf contributes non-negligibly with approximately 18% of the FUV flux. For the two high state nova-likes, HL Aqr and V825 Her, their accretion disks totally dominate with 1 E-9Msun/yr and 3 E-9Msun/yr, respectively. For BP Lyn we find an accretion rate of 1 E-8Msun/yr while for V795 Her, we find an accretion rate of 1 E-10Msun/yr. We discuss the implications of our results for the evolutionary status of nova-like variables.Comment: ApJ, accepte

    Harnessing Museum Resources for the Census of Marine Life: The FISHNET Project

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    Research Article CRITICAL EVIDENCE: A Test of the Critical-Period Hypothesis for Second-Language Acquisition

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    Abstract-me crirical-period hypothesisfor second-language acquisition was rested on doto from the 1990 U.S. Census using responses from 2.3 million immigrants with Spanish or Chinese language backgrounds. The analyses rested a key prediction of the hypothesis, namely, that the line regressing second-language attainment on age of immigration would be markedly different on either side ofrhe criticalage point. Predictions tested were that there would be a difference in slope, a difference in the mean while controlling for slope, or both. The results showed large linear effectsfor level ofeducation and for age of immigration, but a negligible amount of additional variance was accounted for when the parameters for diffeerence in slope and difference in means were estimated. Thus, the pattern of decline in second-language acquisitionfailed to produce the discontinuity that is an essential hallmark o f a critical period. The idea that there is a biologically based critical period for secondlanguage acquisition that prevents older learners from achieving nativeLike competence has appeal lo both theorists and social policymakers (Bailey, Brner, Symons, & Lichtman, 2001). The critical-period hypothesis was originally proposed in the neurolinguistic litemture by Penfield and Robem (1959) and vigorously followed up by Lenneberg (1967). who speculated that maturational aspects of the brain that limited recovery from brain traumas and disorders would extend to second-language acquisition. Subsequent research using behavioral evidence appeared to confirm this hypothesis (Johnson, 1992; Johnson & NewpoIf 1989; The claim that there is an age-related decline in the success with which individuals master a second language is not controversial. The diminished average achievement of older learners is supported by personal anecdote and documented by empirical evidence (Flege, YeniKomshian, & Liu, 1999; Stevens, 1999). What is controversial, though, is whether this pattern meets the conditions for concluding that a critical period constrains learning in a way predicted by the theory. A critical period minimally entails two characteristics: (a) a high level of preparedness for learning within a specified developmental period to ensure the domain is mastered by the species and @) a lack of preparedness outside this period (Bornstein, 1989; Colombo, 1982). The consequence of these conditions is that the relation between learning and age is different inside and outside the critical period. hponents of a critical-period explanation have attempted to place the description of second-language learning within these pammeters. Johnso

    Complementary and Alternative Medicine Use in Musculoskeletal Disorders: Does Medical Skepticism Matter?

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    Medical skepticism is the reservation about the ability of conventional medical care to significantly improve health. Individuals with musculoskeletal disorders seeing specialists usually experience higher levels of disability; therefore it is expected they might be more skeptical of current treatment and thus more likely to try Complementary and Alternative Medicine (CAM). The goal of this study was to define these relationships. These data were drawn from a cross-sectional survey from two cohorts: those seeing specialists (n=1,344) and non-specialists (n=724). Site-level fixed effects logistic regression models were used to test associations between medical skepticism and 10 CAM use categories. Some form of CAM was used by 88% of the sample. Increased skepticism was associated with one CAM category for the non-specialist group and six categories for the specialist group. Increased medical skepticism is associated with CAM use, but medical skepticism is more often associated with CAM use for those seeing specialists

    A Response to Mooi, Williams and Gill

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    This is the publisher's version, which the author has permission to share. The original version may be found at the following link: http://www.mapress.com/zootaxa/list/2011/2946.htm

    Will the Real Phylogeneticists Please Stand Up?

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    This is the publisher's version, also availalble electronically from http://www.mapress.com/zootaxa/list/2011/2946.html.In a recently published commentary, Mooi & Gill asserted that there is a crisis brewing in systematic ichthyology caused by a failure of investigators to apply the basic tenets of outgroup comparison to recover clades based solely on shared apomorphic characters. The result, they claim, is that many recent analyses disregard real synapomorphies and discover clades by phenetic rather than phylogenetic principles. We take the opportunity to refute this claim and assert that matrix-based analyses, whether parametric or nonparametric, satisfy the basic tenets of Hennig’s methods, resulting in monophyletic groups confirmed by synapomorphies
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