Computing region moments from boundary representations

The class of all possible formulas for computing arbitrary moments of a region from the region's boundary is derived. The selection of a particular formula depends on the choice of an independent parameter. Several choices of this parameter are explored for region boundaries approximated by polygons. The parameter choice that minimizes computation time for boundaries represented by chain code is derived. Algorithms are presented for computing arbitrary moments for a region from a polygonal approximation of its boundary and for computing low order moments from chain encoded boundaries

Late time tails from momentarily stationary, compact initial data in Schwarzschild spacetimes

An L-pole perturbation in Schwarzschild spacetime generally falls off at late times t as t^{-2L-3}. It has recently been pointed out by Karkowski, Swierczynski and Malec, that for initial data that is of compact support, and is initially momentarily static, the late-time behavior is different, going as t^{-2L-4}. By considering the Laplace transforms of the fields, we show here why the momentarily stationary case is exceptional. We also explain, using a time-domain description, the special features of the time development in this exceptional case.Comment: 7 pages, 5 figure

Exploration of an oculometer-based model of pilot workload

Potential relationships between eye behavior and pilot workload are discussed. A Honeywell Mark IIA oculometer was used to obtain the eye data in a fixed base transport aircraft simulation facility. The data were analyzed to determine those parameters of eye behavior which were related to changes in level of task difficulty of the simulated manual approach and landing on instruments. A number of trends and relationships between eye variables and pilot ratings were found. A preliminary equation was written based on the results of a stepwise linear regression. High variability in time spent on various instruments was related to differences in scanning strategy among pilots. A more detailed analysis of individual runs by individual pilots was performed to investigate the source of this variability more closely. Results indicated a high degree of intra-pilot variability in instrument scanning. No consistent workload related trends were found. Pupil diameter which had demonstrated a strong relationship to task difficulty was extensively re-exmained

Wing flutter calculations with the CAP-TSD unsteady transonic small disturbance program

The application and assessment is described of CAP-TSD (Computational Aeroelasticity Program - Transonic Small Disturbance) code for flutter prediction. The CAP-TSD program was developed for aeroelastic analysis of complete aircraft configurations and was previously applied to the calculation of steady and unsteady pressures. Flutter calculations are presented for two thin, swept-and-tapered wing planforms with well defined modal properties. The calculations are for Mach numbers from low subsonic to low supersonic values, including the transonic range, and are compared with subsonic linear theory and experimental flutter data. The CAP-TSD flutter results are generally in good agreement with the experimental values and are in good agreement with subsonic linear theory when wing thickness is neglected

Health Research Participants' Preferences for Receiving Research Results

BACKGROUND: Participants in health research studies typically express interest in receiving results from the studies in which they participate. However, participants’ preferences and experiences related to receiving results are not well understood. In general, existing studies have had relatively small sample sizes and typically address specific and often sensitive issues within targeted populations. METHODS: The present study used an online survey to explore attitudes and experiences of registrants in ResearchMatch, a large database of past, present, and potential health research participants. Survey respondents provided information related to whether or not they received research results from studies in which they participated, the methods used to communicate results, their satisfaction with results, and when and how they would like to receive research results from future studies. 70,699 ResearchMatch registrants were notified of the study’s topic. Of the 5,207 registrants who requested full information about the study, 3,381 respondents completed the survey. RESULTS: Approximately 33% of respondents with previous health research participation reported receiving results. Approximately half of respondents with previous research participation reported no opportunity to request results. However, almost all respondents said researchers should always or sometimes offer results to participants. Respondents expressed particular interest in results related to their (or a loved one's) health, as well as information about studies’ purposes and any medical advances based on the results. In general, respondents’ most preferred dissemination methods for results were email and website postings. The least desirable dissemination methods for results included Twitter, conference calls, and text messages. Across all results, we compare the responses of respondents with and without previous research participation experience, and those who have worked in research organizations vs. those who have not. Compared to respondents who have previous participation experience, a greater proportion of respondents with no participation experience indicated that results should always be shared with participants. Likewise, respondents with no participation experience placed higher importance on the receipt of each type of results information included in the survey. CONCLUSIONS: We present findings from a survey assessing attitudes and experiences of a broad sample of respondents that addresses gaps in knowledge related to participants’ preferences for receiving results. The study’s findings highlight the potential for inconsistency between respondents’ expressed preferences to receive specific types of results via specific methods and researchers’ unwillingness or inability to provide them. We present specific recommendations to shift the approach of new studies to investigate participants’ preferences for receiving research results

Applying black hole perturbation theory to numerically generated spacetimes

Nonspherical perturbation theory has been necessary to understand the meaning of radiation in spacetimes generated through fully nonlinear numerical relativity. Recently, perturbation techniques have been found to be successful for the time evolution of initial data found by nonlinear methods. Anticipating that such an approach will prove useful in a variety of problems, we give here both the practical steps, and a discussion of the underlying theory, for taking numerically generated data on an initial hypersurface as initial value data and extracting data that can be considered to be nonspherical perturbations.Comment: 14 pages, revtex3.0, 5 figure

NLC-2 graph recognition and isomorphism

NLC-width is a variant of clique-width with many application in graph algorithmic. This paper is devoted to graphs of NLC-width two. After giving new structural properties of the class, we propose a $O(n^2 m)$-time algorithm, improving Johansson's algorithm \cite{Johansson00}. Moreover, our alogrithm is simple to understand. The above properties and algorithm allow us to propose a robust $O(n^2 m)$-time isomorphism algorithm for NLC-2 graphs. As far as we know, it is the first polynomial-time algorithm.Comment: soumis \`{a} WG 2007; 12

771-4 Enhancement of Delayed Afterdepolarlzatlons (DADs) and Triggered Activity by E-4031 and Dofetilide In a Cardiac Glycoside Model of Cell Ca2+ Overload

HypothesisSeveral new class III antiarrhythmic drugs, including E-4031 and Dofetilide. are reported to selectively block the rapidly activating delayed rectifier current (iKR). These drugs increase action potential duration (APD) which should load cells with Ca2+ via the Na-Ca exchange mechanism and Ca2+ channels. Thus DADs, which occur in Ca2+ loaded cells, should be enhanced by these drugs.MethodsAction potentials were recorded from sheep Purkinje fibers at pacing cycle lengths (CL) of 990 and 690 ms. Ca2+ overload with DADs were induced by exposing fibers to acetylstrophanthidin (AS, 0.15μM) for 30min. Fibers were then exposed to AS-free Tyrode's containing E-4031 (E, 5.0μM; Group 1, n=5), or Dofetilide (D, 0.5 μM; Group 2, n=5), or no drug (Group 3, n=5) for 30 min.Results1) Both E and 0 enhanced DAD amplitude. With AS exposure for 30min. mean DAD amplitude reached 5.6±1.3 and 4.4±0.7 mV for Groups 1–2, respectively (CL 990ms). After 10min exposure to E or D, DAD amplitude increased to 6.6±1.3 and 6.5±1.0 mV, respectively (p<0.05). In Group 3, after switching from AS to no drug for 10 min, DAD amplitude was decreased by 2.2±0.5 mV (p<0.05). Similar findings were obtained at the 690 ms CL. 2) E and D exerted a biphasic effect on APD, initially shortening it at 10 min of exposure (p<0.05) before it lengthened. 3) E and D prolonged DAD disappearance time (36.0±2.4, 34.0±8.7, and 16.0±2.4 min in Groups 1–3, respectively). 4) E and D occasionally induced triggered action potentials. Lowering [K]&z.omicr; (5.4 to 4.0 mM) worsened these effects. 5) Without prior AS exposure, E caused only prolongation of APD and occasionally the induction of early afterdepolarizations.ConclusionsE and D enhanced DADs and triggered activity. In the presence of AS induced Ca2+ overload, E and D caused shortening of APD. These effects can not be explained solely by selective block of iKR by E and D. Additional drug effects, resembling enhancement of cardiac glycoside toxicity, exist