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Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Understanding clinical trial outcomes: design, analysis, and interpretation

DERMATOLOGIC THERAPY, Issue 2 2007
Heidi T. Jacobe
ABSTRACT:, Outcomes (a variable intended for comparison between groups) are integral to the design, conduct, and data analysis of a clinical trial. They are broadly divided into four categories: physician based, patient reported, economic based, and technology based. Each is used in dermatology to some degree, but no consensus exists as to what type of outcome or degree of validation should be employed. This is problematical because poor quality outcomes or their incorrect use may invalidate the results of a clinical trial. Despite their importance, outcome measures in dermatology receive little attention. The present authors aim to provide an overview of important considerations for outcome measures and a practical approach to their analysis. [source]

Global carbonate accumulation rates from Cretaceous to Present and their implications for the carbon cycle model

ISLAND ARC, Issue 1 2001
T. Nakamori
Abstract Global carbonate accumulation rates on the surface of the earth, including not only platforms but also continental margin slopes and deep-sea from the Cretaceous to Present, are estimated by compiling previous geologic studies. These rates are revised, taking account of the erosional effect of the sediments on the platform and deep-sea. Long-term model carbonate fluxes from the ocean to the crust are calculated on the basis of the carbon cycle model (GEOCARB of Berner 1991). The rates based on the actual geologic data indicate much lower values than model fluxes, excluding the Pliocene and Quaternary. The discrepancy could be attributed to the two misunderstandings, namely an overestimate of carbonate accumulation rate for the Quaternary and an incorrect use of the higher Quaternary rate for a boundary condition of the model. The carbonate accumulation rate for the Pliocene to Quaternary is lowered from 29.8 × 1018 mol/Ma (modified from Opdyke & Wilkinson 1988) to 14.8 × 1018 mol/Ma in the present study, assuming that the rate from Quaternary to Pliocene is almost the same as the Miocene value. New model fluxes are recalculated with the new boundary condition in the Quaternary (14.8 × 1018 mol/Ma). Revised model fluxes show general trends of high rates in 120 Ma or 130 Ma, and a low rate in 0 Ma, and are in agreement with the accumulation rate pattern. [source]

Bootstrap diagnostics and remedies

THE CANADIAN JOURNAL OF STATISTICS, Issue 1 2006
Angelo J. Canty
Abstract Bootstrap diagnostics are used to assess the reliability of bootstrap calculations and may suggest useful modified calculations when these are possible. Concern focuses on susceptibility to peculiarities in data, incorrectness of a resampling model, incorrect use of resampling simulation output, and inherent inaccuracy of the bootstrap approach. The last involves issues such as inconsistency of a bootstrap method, the order of correctness of a consistent bootstrap method, and approximate pivotality. The authors review here some of these problems, provide workable diagnostic methods where possible, and discuss fast and simple ways to effect the necessary computations. Diagnostiques et remedes pour le bootstrap Les diagnostiques bootstrap sont des techniques qui permettent d'évaluer la fiabilité des calculs effectués par rééchantillonnage et qui conduisent à l'occasion à des modifications utiles dans les modes de calcul. Parmi les sources d'ennuis communes, on note la sensibilité aux idiosyncrasies des données, l'inexactitude d'un modèle de rééchantillonnage, une utilisation fautive des résultats de la méthode bootstrap, et l'imprécision inhérente à cette approche, à savoir l'éventuelle non-convergence de la procédure, son degré de précision lorsqu'elle converge, ainsi que sa pivotalité approximative. Les auteurs passent ici en revue certaines de ces questions, fournissent des méthodes diagnostiques lorsqu'ils le peuvent, et présentent des procédures de calcul simples et efficaces. [source]

Survey on small animal anaesthesia

AUSTRALIAN VETERINARY JOURNAL, Issue 9 2001
A NICHOLSON
Objective To ascertain anaesthetic practices used currently for dogs and cats in Australia. Methods A questionnaire was distributed to 4800 veterinarians throughout Australia, seeking data on numbers of dogs and cats anaesthetised per week; drug preferences for anaesthetic premedication, induction and maintenance; use of tracheal intubation, supplemental O2, nitrous oxide and anaesthetic antagonists; and types of vaporisers, breathing systems and anaesthetic monitoring devices used or available. Additional questions concerned proportions of different animal types seen in the practice, and the respondent's university and year of graduation. Results The response rate was 19%; 95% of respondents graduated from Australian universities, about half since 1985. Most responses (79%) came from mainly small animal practices. On average 16 dogs and 12 cats were anaesthetised each week. Premedication was used more often in dogs than cats, with acepromazine and atropine most favoured in both species. For anaesthetic induction, thiopentone was most preferred in dogs and alphaxalone/alphadolone in cats. Inhaled agents, especially halothane, were preferred for maintenance in both species. Most respondents usually employed tracheal intubation when using inhalational anaesthetic maintenance, but intubation rates were lower during injectable anaesthetic maintenance and a minority of respondents provided supplemental O2. Nitrous oxide was administered regularly by 13% of respondents. The agents most frequently used to speed recovery from anaesthesia were doxapram and yohimbine. The most widely used vaporisers were the Fluotec Mark III and the Stephens machine. Most (95%) respondents used a rebreathing circuit for large dogs and a non-rebreathing system was used for small dogs by 68% of respondents. Most respondents (93%) indicated some form of aid was available to monitor general anaesthesia: the three most mentioned were an apnoea alarm, oesophageal stethoscope and electrocardiogram. Conclusion Diverse approaches were evident, but there appeared to be less variation in anaesthetising dogs: premedication was more frequent and less varied in type, while thiobarbituates dominated for induction and inhalants for maintenance. Injectable maintenance techniques had substantial use in cats, but little in dogs. Evident disparity between vaporisers available and circuits used suggested either confusion in terminology or incorrect use of some vaporisers in-circuit. While most respondents used monitoring equipment or a dedicated observer to invigilate anaesthesia, the common reliance on apnoea alarms is of concern, because of unproven reliability and accuracy. [source]