38 research outputs found

    P/2010A2 LINEAR - I: An impact in the Asteroid Main Belt

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    Comet P/2010A2 LINEAR is a good candidate for membership with the Main Belt Comet family. It was observed with several telescopes (ESO NTT, La Silla; Gemini North, Mauna Kea; UH 2.2m, Mauna Kea) from 14 Jan. until 19 Feb. 2010 in order to characterize and monitor it and its very unusual dust tail, which appears almost fully detached from the nucleus; the head of the tail includes two narrow arcs forming a cross. The immediate surroundings of the nucleus were found dust-free, which allowed an estimate of the nucleus radius of 80-90m. A model of the thermal evolution indicates that such a small nucleus could not maintain any ice content for more than a few million years on its current orbit, ruling out ice sublimation dust ejection mechanism. Rotational spin-up and electrostatic dust levitations were also rejected, leaving an impact with a smaller body as the favoured hypothesis, and ruling out the cometary nature of the object. The impact is further supported by the analysis of the tail structure. Finston-Probstein dynamical dust modelling indicates the tail was produced by a single burst of dust emission. More advanced models, independently indicate that this burst populated a hollow cone with a half-opening angle alpha~40degr and with an ejection velocity v_max ~ 0.2m/s, where the small dust grains fill the observed tail, while the arcs are foreshortened sections of the burst cone. The dust grains in the tail are measured to have radii between a=1-20mm, with a differential size distribution proportional to a^(-3.44 +/- 0.08). The dust contained in the tail is estimated to at least 8x10^8kg, which would form a sphere of 40m radius. Analysing these results in the framework of crater physics, we conclude that a gravity-controlled crater would have grown up to ~100m radius, i.e. comparable to the size of the body. The non-disruption of the body suggest this was an oblique impact.Comment: 15 pages, 11 figures, in pres

    Relationship between blood pressure measurements recorded on patients' charts in family physicians' offices and subsequent 24 hour ambulatory blood pressure monitoring

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    BACKGROUND: In most western countries 20% of adults have hypertension. Reports in the literature suggest that from 31 to 86% of treated patients are not at recommended target levels. However it is important to consider how we are determining whether targets are unmet and the degree to which they are unmet. Our underlying hypothesis is that white coat effect is partially responsible for the reported low rates of control of hypertension by primary care practitioners. METHODS: The study population consists of 1142 patients who are being assessed for enrolment in two community-based randomized controlled trials. Patients must have essential hypertension, be on antihypertensive medication, and must not have met their blood pressure targets. We are reporting on the proportion of patients who have not achieved target, and the degree to which they have not achieved their target. We also report on the mean daytime blood pressures on 24 hour ABPM and compare these to mean blood pressures found on the patients' charts. RESULTS: We identified 3284 patient charts of patients with hypertension. Of these, 1142 were determined to be "out of control" (did not achieve target) and 436 agreed to undergo 24 hour ABPM for final determination of eligibility. Overwhelmingly (95.8% of the time) it was the systolic blood pressure that was not under control. However, most of the patients who had not achieved target according to our criteria were within 10 mmHg of the recommended targets. Isolated systolic blood pressure was the best predictor of elevated mean daytime blood pressure on 24 hour ABPM. CONCLUSIONS: At least 35% of patients had not achieved target blood pressure levels and this is primarily due to lack of control of systolic blood pressure. The best predictor of continuing hypertension on 24 hour ABPM was the mean systolic blood pressure on the patients chart. However, only 69% of patients who were uncontrolled according blood pressures recorded in the chart were uncontrolled according to 24 hour ABPM criteria. This suggests that the white coat effect makes blood pressure measurements in the doctor's offices, at least as currently done, not sufficiently accurate for determining treatment endpoint

    A Protocol for the Secure Linking of Registries for HPV Surveillance

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    In order to monitor the effectiveness of HPV vaccination in Canada the linkage of multiple data registries may be required. These registries may not always be managed by the same organization and, furthermore, privacy legislation or practices may restrict any data linkages of records that can actually be done among registries. The objective of this study was to develop a secure protocol for linking data from different registries and to allow on-going monitoring of HPV vaccine effectiveness.A secure linking protocol, using commutative hash functions and secure multi-party computation techniques was developed. This protocol allows for the exact matching of records among registries and the computation of statistics on the linked data while meeting five practical requirements to ensure patient confidentiality and privacy. The statistics considered were: odds ratio and its confidence interval, chi-square test, and relative risk and its confidence interval. Additional statistics on contingency tables, such as other measures of association, can be added using the same principles presented. The computation time performance of this protocol was evaluated.The protocol has acceptable computation time and scales linearly with the size of the data set and the size of the contingency table. The worse case computation time for up to 100,000 patients returned by each query and a 16 cell contingency table is less than 4 hours for basic statistics, and the best case is under 3 hours.A computationally practical protocol for the secure linking of data from multiple registries has been demonstrated in the context of HPV vaccine initiative impact assessment. The basic protocol can be generalized to the surveillance of other conditions, diseases, or vaccination programs

    SN 2005cs in M51 II. Complete Evolution in the Optical and the Near-Infrared

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    We present the results of the one year long observational campaign of the type II-plateau SN 2005cs, which exploded in the nearby spiral galaxy M51 (the Whirlpool Galaxy). This extensive dataset makes SN 2005cs the best observed low-luminosity, 56Ni-poor type II-plateau event so far and one of the best core-collapse supernovae ever. The optical and near-infrared spectra show narrow P-Cygni lines characteristic of this SN family, which are indicative of a very low expansion velocity (about 1000 km/s) of the ejected material. The optical light curves cover both the plateau phase and the late-time radioactive tail, until about 380 days after core-collapse. Numerous unfiltered observations obtained by amateur astronomers give us the rare opportunity to monitor the fast rise to maximum light, lasting about 2 days. In addition to optical observations, we also present near-infrared light curves that (together with already published UV observations) allow us to construct for the first time a reliable bolometric light curve for an object of this class. Finally, comparing the observed data with those derived from a semi-analytic model, we infer for SN 2005cs a 56Ni mass of about 0.003 solar masses, a total ejected mass of 8-13 solar masses and an explosion energy of about 3 x 10^50 erg.Comment: 18 pages, 18 figures, accepted for publication in MNRA

    Physician privacy concerns when disclosing patient data for public health purposes during a pandemic influenza outbreak

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    Background: Privacy concerns by providers have been a barrier to disclosing patient information for public health\ud purposes. This is the case even for mandated notifiable disease reporting. In the context of a pandemic it has been\ud argued that the public good should supersede an individual’s right to privacy. The precise nature of these provider\ud privacy concerns, and whether they are diluted in the context of a pandemic are not known. Our objective was to\ud understand the privacy barriers which could potentially influence family physicians’ reporting of patient-level\ud surveillance data to public health agencies during the Fall 2009 pandemic H1N1 influenza outbreak.\ud Methods: Thirty seven family doctors participated in a series of five focus groups between October 29-31 2009.\ud They also completed a survey about the data they were willing to disclose to public health units. Descriptive\ud statistics were used to summarize the amount of patient detail the participants were willing to disclose, factors that\ud would facilitate data disclosure, and the consensus on those factors. The analysis of the qualitative data was based\ud on grounded theory.\ud Results: The family doctors were reluctant to disclose patient data to public health units. This was due to concerns\ud about the extent to which public health agencies are dependable to protect health information (trusting beliefs),\ud and the possibility of loss due to disclosing health information (risk beliefs). We identified six specific actions that\ud public health units can take which would affect these beliefs, and potentially increase the willingness to disclose\ud patient information for public health purposes.\ud Conclusions: The uncertainty surrounding a pandemic of a new strain of influenza has not changed the privacy\ud concerns of physicians about disclosing patient data. It is important to address these concerns to ensure reliable\ud reporting during future outbreaks.University of Ottawa Open Access Author Fun

    An asymmetric stream communication system

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    Photometry and model of near-Earth asteroid 2021 DW1 from one apparition

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    Aims. Very small asteroids (VSAs, objects with diameters smaller than about 150 m) can be spun up by the YORP effect to rotation periods as short as tens of seconds. This effect has been observed for many of them. It is also hypothesised, that in the same process their spin axes are asymptotically drawn to the position perpendicular to the orbital plane. So far this effect has been observed only for one VSA and needs further verification. For that, spin axes of several other VSAs should be determined by observing their brightness variations at many different positions on the sky. Methods. On 4 March 2021 at 9 UTC a 30-m in diameter near-Earth asteroid 2021 DW1 passed the Earth at a distance of 570 000 km, reaching the maximum brightness of V = 14.6 mag. We observed it photometrically from 2 March, when it was visible at V = 16.5 mag, until 7 March (V = 18.2 mag). During that time 2021 DW1 swept a 170° long arc in the northern sky, spanning solar phase angles in the range from 36° to 86°. This made it an excellent target for physical characterisation, including spin axis and shape derivation. Results. Convex inversion of the asteroid lightcurves gives a sidereal period of rotation Psid = 0.013760 ± 0.000001 h, and two solutions for the spin axis ecliptic coordinates: (A) λ1 = 57° ± 10°, β1 = 29° ± 10° and (B) λ2 = 67° ± 10°, β2 = −40° ± 10°. The magnitude-phase curve can be fitted with a standard H, G function with H = 24.8 ± 0.5 mag and an assumed G = 0.24. The asteroid colour indices are g − i = 0.79 ± 0.01 mag, and i − z = 0.01 ± 0.02 mag which indicates an S taxonomic class, with an average geometric albedo pV = 0.23 ± 0.02. The asteroid effective diameter, derived from H and pV, is Deff = 30 ± 10 m. Conclusions. It was found that the inclination of the spin axis of 2021 DW1 is not perpendicular to the orbital plane (obliquity ϵ = 54° ± 10° or ϵ = 123° ± 10°). More spin axes of VSAs should be determined to check, if 2021 DW1 is an exception or a typical case.T.K., A.K., and D.O. were supported by a grant No.2017/25/B/ST9/00740 from the National Science Centre, Poland. T. Kim was supported by the Korea Astronomy and Space Science Institute under the R&D program (Project No. 2020-1-600-05) supervised by the Ministry of Science and ICT (MSIT), and the National Research Foundation of Korea (NRF) Grant No. 2020R1A2C3011091, funded by MSIT. The work by T.S.-R. was carried out through a grant APOSTD/2019/046 by Generalitat Valenciana (Spain). He was also supported by the MINECO (Spanish Ministry of Economy) through a grant RTI2018-095076-B-C21 (MINECO/FEDER, UE)
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