The Transition between Nonorthogonal Polarization Modes in PSR B2016+28 at 1404 MHz

Polarization observations of the radio emission from PSR B2016+28 at 1404 MHz reveal properties that are consistent with two, very different, interpretations of the pulsar's viewing geometry. The pulsar's average polarization properties show a rapid change in position angle (PA) near the pulse center, suggesting that the observer's sightline nearly intersects the star's magnetic pole. But single pulse, polarization observations of the pulsar show nearly orthogonal modes of polarization following relatively flat and parallel PA trajectories across the pulse, suggesting that the sightline is far from the pole. Additionally, PA histograms reveal a "modal connecting bridge", of unknown origin, joining the modal PA trajectories over much of the pulse and following the rapid PA change shown in the average data. The nonorthogonality of polarization modes is incorporated in a statistical model of radio polarization to account for the deviations from mode orthogonality that are observed in the pulsar. The model is used to interpret the rapid PA change and modal connecting bridge as a longitudinally-resolved transition between modes of nonorthogonal polarization. Thus, the modal PA trajectories are argued to reflect the pulsar's true viewing geometry. This interpretation is consistent with the pulsar's morphological classification, preserves the Radhakrishnan & Cooke model of pulsar radio emission, and avoids the complication that the modal connecting bridge might be produced by some other emission mechanism. The statistical model's ability to simulate the rich variety of polarization properties observed in the emission lends additional support to the model's applicability and its underlying assumption that the polarization modes occur simultaneously.Comment: Accepted for publication in Ap

Influence of an Internal Magnetar on Supernova Remnant Expansion

Most of the proposed associations between magnetars and supernova remnant suffer from age problems. Usually, supernova remnants ages are determined from an approximation of the Sedov-Taylor phase relation between radius and age, for a fixed energy of the explosion ~ 10^{51} erg. Those ages do not generally agree with the characteristic ages of the (proposed) associated magnetars. We show quantitatively that, by taking into account the energy injected on the supernova remnant by magnetar spin-down, a faster expansion results, improving matches between characteristic ages and supernova remnants ages. However, the magnetar velocities inferred from observations would inviabilize some associations. Since characteristic ages may not be good age estimators, their influence on the likelihood of the association may not be as important. In this work we present simple numerical simulations of supernova remnants expansion with internal magnetars, and apply it to the observed objects. A short initial spin period, thought to be important for the very generation of the magnetic field, is also relevant for the modified expansion of the remnant. We next analyze all proposed associations case-by-case, addressing the likelyhood of each one, according to this perspective. We consider a larger explosion energy and reasses the characteristic age issue, and conclude that about 50% of the associations can be true ones, provided SGRs and AXPs are magnetars.Comment: 30 pages, AAStex, 5 figures, format fixe

The Use of a Learning Community and Online Evaluation of Utilization for SPECT Myocardial Perfusion Imaging

Resource-sensitive and quality-centered imaging begins with the selection of the appropriate patient and test. Appropriate use criteria have been developed to aid clinicians but are often not available in an easily accessible format. FOCUS (Formation of Optimal Cardiovascular Utilization Strategies), a Web-based community and quality improvement instrument, was developed to increase the feasibility of measuring and improving practice patterns based on the appropriate use criteria. The FOCUS instrument proposed to reduce inappropriate imaging by 15% in 1 year and by 50% within 3 years. Between April 2010 and December 2011, data were voluntarily collected through the FOCUS radionuclide imaging performance improvement module (PIM). Appropriateness rates were compared between phases of the PIM. For the 55 participating sites that had completed the PIM by December 2011, the proportion of inappropriate cases decreased from 10% to 5% (p < 0.0001). These preliminary data from initial participating sites suggest that through the use of a self-directed, quality improvement software and an interactive community, physicians may be able to significantly decrease the proportion of tests not meeting appropriate use criteria

Niacin therapy and the risk of new-onset diabetes: a meta-analysis of randomized controlled trials

Objective Previous studies have suggested that niacin treatment raises glucose levels in patients with diabetes and may increase the risk of developing diabetes. We undertook a meta-analysis of published and unpublished data from randomised trials to confirm whether an association exists between niacin and new-onset diabetes. Methods We searched Medline, EMBASE and the Cochrane Central Register of Controlled Trials, from 1975 to 2014, for randomised controlled trials of niacin primarily designed to assess its effects on cardiovascular endpoints and cardiovascular surrogate markers. We included trials with ≥50 non-diabetic participants and average follow-up of ≥24 weeks. Published data were tabulated and unpublished data sought from investigators. We calculated risk ratios (RR) for new-onset diabetes with random-effects meta-analysis. Heterogeneity between trials was assessed using the I2 statistic. Results In 11 trials with 26 340 non-diabetic participants, 1371 (725/13 121 assigned niacin; 646/13 219 assigned control) were diagnosed with diabetes during a weighted mean follow-up of 3.6 years. Niacin therapy was associated with a RR of 1.34 (95% CIs 1.21 to 1.49) for new-onset diabetes, with limited heterogeneity between trials (I2=0.0%, p=0.87). This equates to one additional case of diabetes per 43 (95% CI 30 to 70) initially non-diabetic individuals who are treated with niacin for 5 years. Results were consistent regardless of whether participants received background statin therapy (p for interaction=0.88) or combined therapy with laropiprant (p for interaction=0.52). Conclusions Niacin therapy is associated with a moderately increased risk of developing diabetes regardless of background statin or combination laropiprant therapy

Coccolithophore Relief: An Art and Science Interrogation of Ocean Acidification

Organisms that remove carbon from the world’s carbon cycle are becoming ever more important as we try to constrain our carbon emissions to slow climate change. Marine phytoplankton, like coccolithophores, are responsible for 50 percent of global carbon fixation. Through photosynthesis, which also produces oxygen as a by-product, they fix carbon dioxide throughout their lives in the surface waters of the ocean. Even in their death, they help remove carbon from the system. Coccolithophores make armoured plates (coccoliths, hereafter referred to as ‘liths’) from calcium carbonate, which together form a sort of external skeleton for each organism. When they die, they sink and join bottom sediments, in effect exporting and burying carbon in deep-sea sediments.We decided to share the story of coccolithophores, including their important environmental role and their sensitivity to ocean acidification, with the public. We intentionally developed a project involving social arts practice to help people reflect on the importance of these small things. This included the beauty of the tiny liths that make up the  coccolithophore’s amour, the importance of each little lith to collectively make a healthy organism (that in turn has an important global role), and the effect of our individual small actions contributing to climate change. Engaging communities in social arts practice, by involving hands-on making with cognitive activity, gives time and space for such criticalreflection.5 Joining key features of the scientific narrative with congruent aspects of the art-making can serve to reinforce understanding and potential behaviour change

Atomistic studies of transformation pathways and energetics in plutonium

One of the most challenging problems in understanding the structural phase transformations in Pu is to determine the energetically favored, continuous atomic pathways from one crystal symmetry to another. This problem involves enumerating candidate pathways and studying their energetics to garner insight into instabilities and energy barriers. The purpose of this work is to investigate the energetics of two transformation pathways for the delta to alpha' transformation in Pu that were recently proposed [Lookman et al., Phys. Rev. Lett. 100:145504, 2008] on the basis of symmetry. These pathways require the presence of either an intermediate hexagonal closed-packed (hcp) structure or a simple hexagonal (sh) structure. A subgroup of the parent fcc and the intermediate hexagonal structure, which has trigonal symmetry, facilitates the transformation to the intermediate hcp or sh structure. Phonons then break the translational symmetry from the intermediate hcp or sh structure to the final monoclinic symmetry of the alpha' structure. We perform simulations using the modified embedded atom method (MEAM) for Pu to investigate these candidate pathways. Our main conclusion is that the path via hcp is energetically favored and the volume change for both pathways essentially occurs in the second step of the transformation, i.e. from the intermediate sh or hcp to the monoclinic structure. Our work also highlights the deficiency of the current state-of-the-art MEAM potential in capturing the anisotropy associated with the lower symmetry monoclinic structure.Comment: 12 pages, 5 figures, accepted for publication in Philos. Ma

Decrease in health-related quality of life associated with awareness of hepatitis C virus infection among people who inject drugs in Scotland

Chronic hepatitis C virus (HCV) infection can significantly reduce health-related quality of life (QoL), but it is not clear if reduction is associated with the infection or with being aware of one's infection status. Understanding the impact of a HCV diagnosis on QoL is essential to inform decision-making regarding screening/testing and treatment. Using a cross-sectional design, we assessed QoL in 2898 people who inject drugs (PWID), surveyed in Scotland during 2010 using EQ-5D. Multifactorial regression compared self-reported QoL between PWID who were (i) chronically HCV-infected and aware of their infected status, (ii) chronically HCV-infected but unaware, and (iii) not chronically infected. Median time since onset of injecting was 10years; not chronically infected PWID were younger and had shorter injecting careers than chronically infected PWID. Median EQ-5D was highest for the not chronically infected and the chronic/unaware groups (0.73) compared with the chronic/aware group (0.66). After adjustment for demographic and behavioural co-factors, QoL was significantly reduced in chronic/aware compared with chronic/unaware PWID (adjusted B=-0.09, p=0.005); there was no evidence for a difference in QoL between not chronically infected and chronic/unaware PWID (adjusted B=-0.03, p=0.13). Awareness of one's chronic HCV status was associated with reduced health-related QoL, but there was no evidence for further reduction attributable to chronic infection itself after adjusting for important covariate differences

Tests of a multichannel photometer based on silicon diode detectors

A breadboard photometer was constructed that demonstrates a precision of 2 times 10 to the 4th power in the laboratory and scintillation-limited performance when used with an 0.5 m aperture telescope. Because the detectors and preamps are not cooled, only stars with m sub v approx. less than 4 are bright enough to allow the photometer to attain a precision of 1 times 10 to the 3rd power for three minute observations with an 0.5 m aperature telescope. Cooling the telescope should allow much fainter stars to be observed. Increasing the aperture of the telescope will allow higher precision and the observation of fainter stars

Magnetic Fields in the Center of the Perseus Cluster

We present Very Long Baseline Array (VLBA) observations of the nucleus of NGC 1275, the central, dominant galaxy in the Perseus cluster of galaxies. These are the first observations to resolve the linearly polarized emission from 3C84, and from them we determine a Faraday rotation measure (RM) ranging from 6500 to 7500 rad/m^2 across the tip of the bright southern jet component. At 22 GHz some polarization is also detected from the central parsec of 3C84, indicating the presence of even more extreme RMs that depolarize the core at lower frequencies. The nature of the Faraday screen is most consistent with being produced by magnetic fields associated with the optical filaments of ionized gas in the Perseus Cluster.Comment: Accepted for publication in MNRA

A citation analysis of the Cambridge Crystallographic Data Centre

Citation analysis has been widely used to quantify the influence of research articles on the development of science. This paper reports a citation analysis of ten highly cited papers associated with the Cambridge Crystallographic Data Centre (CCDC), covering the variation of citation with time, the journals in which citations occur, and the types of organization and the geographic regions that use the Cambridge Structural Database. The ten most highly cited papers, comprising four database descriptions (CSD), two geometrical tabulations (TAB) and four basic research papers (RES), received a total of 8494 citations over the period 1981-1998, with more than half of these citations occurring in the literature published from 1995 onwards. The high citation rates of the database descriptions (3573 of 8494) indicate the value of crystallographic data. However, the large number of citations of the geometrical tables (3172) and the research papers (1767) indicate that this value resides not just in the raw data held in the Cambridge Structural Database, but also in the structural knowledge that can be derived from it. In the most recent years covered by the analysis (1995-1998), these ten CCDC publications have received more than 1000 citations per annum (CSD 507, TAB 398 and RES 153 citations per annum) and the detailed analysis shows that these papers, and the data that they discuss, are used not only by crystallographers but also by researchers across the entire range of the chemical sciences