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Greater Dispersion (greater + dispersion)
Selected AbstractsCharacterization of the Electroanatomical Substrate in Human Atrial Fibrillation: The Relationship between Changes in Atrial Volume, Refractoriness, Wavefront Propagation Velocities, and AF BurdenJOURNAL OF CARDIOVASCULAR ELECTROPHYSIOLOGY, Issue 3 2007PIPIN KOJODJOJO M.R.C.P. Introduction: Progressive remodeling occurs in experimental models of AF whereby slowing of conduction, shortening of refractoriness, and atrial dilatation are associated with an increased vulnerability to atrial fibrillation (AF). This study investigates the relative changes in atrial geometry and electrophysiology with increasing AF burden in humans. Methods and Results: Patients undergoing ablation of AF or left-sided accessory pathways were recruited. Atrial volumes were determined by echocardiography. Wavefront propagation velocities (WPV), specifically in the direction of activation, were calculated from pre-ablation activation (CartoÔ) maps of both atria. Dispersion, adaptation of, and effective refractoriness (ERP) were measured at 3 sites. A composite arrhythmogenic index (Atrial Volume/WPV × ERP) was derived to compare the degree of electroanatomical remodeling with AF burden. Fifty-nine patients (22 paroxysmal AF, 19 recurrent persistent AF, and 18 controls) were recruited. AF subjects had slower right atrial WPV (P = 0.01), but no difference in left atrial WPV compared with controls. ERP was reduced globally (P < 0.05), with increased dispersion (P < 0.05). WPV and ERP did not distinguish between patients with paroxysmal or persistent AF. Biatrial volumes were greater only in patients with persistent AF (P < 0.01). There was a stepwise increase in the AI with increasing AF burden (P < 0.0001). Conclusion: An arrhythmogenic substrate exists in human AF, characterized by globally decreased refractoriness with greater dispersion, slower right atrial conduction, and atrial dilatation. Persistence of AF is not accompanied by any further electrical remodeling, but only atrial dilatation. The degree of electroanatomical remodeling is associated with the clinical pattern of AF. [source] The Dimensionality of DSM-IV Alcohol Use Disorders Among Adolescent and Adult Drinkers and Symptom Patterns by Age, Gender, and Race/EthnicityALCOHOLISM, Issue 5 2009Thomas C. Harford Background:, There is limited information on the validity of Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV) alcohol use disorders (AUD) symptom criteria among adolescents in the general population. The purpose of this study is to assess the DSM-IV AUD symptom criteria as reported by adolescent and adult drinkers in a single representative sample of the U.S. population aged 12 years and older. This design avoids potential confounding due to differences in survey methodology when comparing adolescents and adults from different surveys. Methods:, A total of 133,231 current drinkers (had at least 1 drink in the past year) aged 12 years and older were drawn from respondents to the 2002 to 2005 National Surveys on Drug Use and Health. DSM-IV AUD criteria were assessed by questions related to specific symptoms occurring during the past 12 months. Factor analytic and item response theory models were applied to the 11 AUD symptom criteria to assess the probabilities of symptom item endorsements across different values of the underlying trait. Results:, A 1-factor model provided an adequate and parsimonious interpretation for the 11 AUD criteria for the total sample and for each of the gender,age groups. The MIMIC model exhibited significant indication for item bias among some criteria by gender, age, and race/ethnicity. Symptom criteria for "tolerance,""time spent," and "hazardous use" had lower item thresholds (i.e., lower severity) and low item discrimination, and they were well separated from the other symptoms, especially in the 2 younger age groups (12 to 17 and 18 to 25). "Larger amounts,""cut down,""withdrawal," and "legal problems" had higher item thresholds but generally lower item discrimination, and they tend to exhibit greater dispersion at higher AUD severity, particularly in the youngest age group (12 to 17). Conclusions:, Findings from the present study do not provide support for the 2 separate DSM-IV diagnoses of alcohol abuse and dependence among either adolescents or adults. Variations in criteria severity for both abuse and dependence offer support for a dimensional approach to diagnosis which should be considered in the ongoing development of DSM-V. [source] Spatial Distribution of Repolarization Times in Patients with Coronary Artery DiseasePACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 8 2003PETER VAN LEEUWEN The potential clinical value of QT dispersion (QTd), a measure of the interlead range of QT interval duration in the surface 12-lead ECG, remains ambiguous. The aim of the study was the temporal and spatial analysis of the QT interval in healthy subjects and in patients with coronary artery disease (CAD) using magnetocardiography (MCG) and surface ECG. Standard 12-lead ECG and 37-channel MCG were performed in 20 healthy subjects, 23 patients with CAD without prior myocardial infarction (MI), 31 MI patients and 11 MI patients with ventricular tachycardia (VT). QTd was increased in CAD without MI compared to normals (ECG46.1 ± 6.0vs42.8 ± 5.0, P < 0.05; MCG66.8 ± 20.3vs49.7 ± 10.8, P < 0.01) and in VT compared to MI (ECG66.8 ± 16.5vs51.9 ± 16.6, P < 0.05; MCG93.6 ± 29.6vs66.8 ± 20.8, P < 0.005). In MCG, spatial distribution of QT intervals in patient groups differed from those in healthy subjects in three ways: (1) greater dispersion, (2) greater local variability, and (3) a change in overall pattern. This was quantified on the basis of smoothness indexes (SI). Normalized SI was higher in CAD without MI compared to normals (3.8 ± 1.1vs2.7 ± 0.6, P < 0.001) and in VT compared to MI (6.4 ± 1.6vs4.2 ± 1.4, P < 0.0005). For the normal-CAD comparison a sensitivity of 74% and a specificity of 80% was obtained, for MI-VT, 100% and 77%, respectively. The results suggest that examining the spatial interlead variability in multichannel MCG may aid in the initial identification of CAD patients with unimpaired left ventricular function and the identification of post-MI patients with augmented risk for VT. (PACE 2003; 26:1706,1714) [source] Pro arrhythmic Effects of Ibutilide in a Canine Model of Pacing Induced CardiomyopathyPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 2 2000MING-HSIUNG HSIEH The authors developed a canine model of pacing induced cardio my apathy to study the possible mechanisms of ibutilide induced torsades de pointes (TP) in heart failure. Thirteen dogs received intravenous ibutilide after acute AV block for 60 minutes, and after implantation of a VVI pacemaker, with a rate of 270 beats/min for 2,3 weeks. Twelve-lead ECG and right and left ventricle monophasic action potentials were recorded at different right ventricle pacing cycle lengths from 600 ms to 1200 ms during the study. The results showed ibutilide could significantly prolong ventricular repolarization and increase the dispersion in a dose dependent and reverse use dependent manner. Furthermore, after ihutilide administration, cardiomyopathic dogs had a greater dispersion of ventricular repolarization, and also had higher incidences of early afterdepolarizations and spontaneous or pacing induced TP than acute AV block dogs. [source] Western lowland gorillas (Gorilla gorilla gorilla) change their activity patterns in response to frugivoryAMERICAN JOURNAL OF PRIMATOLOGY, Issue 2 2009Shelly Masi Abstract The most important environmental factor explaining interspecies variation in ecology and sociality of the great apes is likely to be variation in resource availability. Relatively little is known about the activity patterns of western lowland gorillas (Gorilla gorilla gorilla), which inhabit a dramatically different environment from the well-studied mountain gorillas (G. beringei beringei). This study aims to provide a detailed quantification of western lowland gorillas' activity budgets using direct observations on one habituated group in Bai Hokou, Central African Republic. We examined how activity patterns of both sexes are shaped by seasonal frugivory. Activity was recorded with 5-min instantaneous sampling between December 2004 and December 2005. During the high-frugivory period the gorillas spent less time feeding and more time traveling than during the low-frugivory period. The silverback spent less time feeding but more time resting than both females and immatures, which likely results from a combination of social and physiological factors. When compared with mountain gorillas, western lowland gorillas spend more time feeding (67 vs. 55%) and traveling (12 vs. 6.5%), but less time resting (21 vs. 34%) and engaging in social/other activities (0.5 vs. 3.6%). This disparity in activity budgets of western lowland gorillas and mountain gorillas may be explained by the more frugivorous diet and the greater dispersion of food resources experienced by western lowland gorillas. Like other apes, western lowland gorillas change their activity patterns in response to changes in the diet. Am. J. Primatol. 71:91,100, 2009. © 2008 Wiley-Liss, Inc. [source] Market Sidedness: Insights into Motives for Trade InitiationTHE JOURNAL OF FINANCE, Issue 1 2009ASANI SARKAR ABSTRACT We infer motives for trade initiation from market sidedness. We define trading as more two-sided (one-sided) if the correlation between the number of buyer- and seller-initiated trades increases (decreases), and assess changes in sidedness (relative to a control sample) around events that identify trade initiators. Consistent with asymmetric information, trading is more one-sided before merger news. Consistent with belief heterogeneity, trading is more two-sided before earnings and macro announcements with greater dispersion in analyst forecasts, and after news with larger announcement surprises. We examine the codeterminacy of sidedness, bid-ask spread, volatility, number of trades, and order imbalance. [source] An Empirical Analysis of Entrant and Incumbent Bidding in Road Construction AuctionsTHE JOURNAL OF INDUSTRIAL ECONOMICS, Issue 3 2003Dakshina G. De Silva This paper explores differences in the bidding patterns of entrants and incumbents in road construction auctions. We find that entrants bid more aggressively and win auctions with significantly lower bids than incumbents. The differences in their bidding patterns are consistent with a model of auctions in which the distribution of an entrant's costs exhibits greater dispersion than that of an incumbent's and relations of stochastic dominance in the distributions do not persist for the entire range of estimated costs. We also find that more efficient firms bid, on average, more aggressively and firms with greater backlogs bid less aggressively. [source] Does the labour supply of wives respond to husbands' wages?CANADIAN JOURNAL OF ECONOMICS, Issue 4 2008Canadian evidence from micro data, grouped data Abstract., Using micro data and grouped data, we assess the extent to which Canadian wives adjusted their labour supply in response to changes in husbands' wages during the period 1980-2000. Grouped data parameters based on weighted least squares and the unbiased-error-in-variables estimator developed by Devereux (2004, 2007a,b) yield cross-wage elasticities that are substantially higher (in absolute value) than those derived from OLS regressions run on micro data. Both grouping estimators indicate that the labour supply of Canadian wives responded strongly to changes in husbands' wages during the 1980s. For the 1990s, our estimates of wives' cross-wage elasticity display greater dispersion. A l'aide de micro données et de données groupées, on établit jusqu'à quel point les épouses canadiennes ont ajusté leur offre de travail en réponse aux changements dans les salaires de leurs époux au cours de la période 1980,2000. Les paramètres (pour les données groupées) dérivés par la méthode des moindres carrés pondérés et de l'estimateur développé par Devereux (2004, 2007a,b) engendrent des élasticités croisées qui sont substantiellement plus grandes (en termes absolus) que ceux dérivés par la méthode des moindres carrés ordinaires en utilisant des micro données. Les deux estimations montrent que l'offre de travail des épouses canadiennes a répondu fortement aux changements dans les salaires des époux au cours des années 80. Pour les années 90, les évaluations des élasticités croisées des salaires montrent une plus grande dispersion. [source] | |||||||||||||