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Performance Differences (performance + difference)
Selected AbstractsCompressible flow SUPG parameters computed from element matricesINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 9 2005L. Catabriga Abstract We present, for the SUPG formulation of inviscid compressible flows with shocks, stabilization parameters defined based on the element-level matrices. These definitions are expressed in terms of the ratios of the norms of the matrices and take into account the flow field, the local length scales, and the time step size. Calculations of these stabilization parameters are straightforward and do not require explicit expressions for length or velocity scales. We compare the performance of these stabilization parameters, accompanied by a shock-capturing parameter introduced earlier, with the performance of a stabilization parameter introduced earlier, accompanied by the same shock-capturing parameter. We investigate the performance difference between updating the stabilization and shock-capturing parameters at the end of every time step and at the end of every non-linear iteration within a time step. We also investigate the influence of activating an algorithmic option that was introduced earlier, which is based on freezing the shock-capturing parameter at its current value when a convergence stagnation is detected. Copyright © 2005 John Wiley & Sons, Ltd. [source] Accuracy and Fluency in List and Context Reading of Skilled and RD Groups: Absolute and Relative Performance LevelsLEARNING DISABILITIES RESEARCH & PRACTICE, Issue 4 2003Joseph R. Jenkins The purpose of this study was to examine (1) the performance levels and the magnitude of performance difference between students with reading disabilities (RD) and skilled readers when reading a typical classroom text; (2) the hypothesis that students with RD have specific difficulty using context in such a way that reading fluency is affected; and (3) whether RD subtypes may be differentiated according to performance on contextual and context-free reading tasks. Two groups of fourth graders (85 skilled readers and 24 students with RD) completed a standardized test of reading comprehension, read aloud a folktale, and read aloud the folktale's words in a randomly sequenced list. Performance was scored as correct rate and percentage correct. Based on the number of words per idea unit in the passage, we also estimated the rate at which reader groups encountered and processed text ideas. Compared to the RD group, skilled readers read three times more correct words per minute in context, and showed higher accuracy and rates on all measures. Both context and isolated word-reading rates were highly sensitive to impairment. We found no evidence for RD subtypes based on these measures. Results illustrate differences in reading levels between the two groups, the temporal advantage skilled readers have in linking text ideas, how word reading differs as a function of task format and performance dimension, and how limited word-identification skills (not comprehension) produce contextual reading difficulties for students with RD. [source] Antiprogesterone therapy uncouples axonal loss from demyelination in a transgenic rat model of CMT1A neuropathyANNALS OF NEUROLOGY, Issue 1 2007Gerd Meyer zu Horste MD Objective Charcot,Marie,Tooth disease (CMT) is the most common inherited neuropathy, and a duplication of the Pmp22 gene causes the most frequent subform CMT1A. Using a transgenic rat model of CMT1A, we tested the hypothesis that long-term treatment with anti-progesterone (Onapristone) reduces Pmp22 overexpression and improves CMT disease phenotype of older animals, thereby extending a previous proof-of-concept observation in a more clinically relevant setting. Methods We applied placebo-controlled progesterone-antagonist therapy to CMT rats for 5 months and performed grip-strength analysis to assess the motor phenotype. Quantitative Pmp22 RT-PCR and complete histological analysis of peripheral nerves and skin biopsies were performed. Results Anti-progesterone therapy significantly increased muscle strength and muscle mass of CMT rats and reduced the performance difference to wildtype rats by about 50%. Physical improvements can be explained by the prevention of axon loss. Surprisingly, the effects of anti-progesterone were not reflected by improved myelin sheath thickness. Electrophysiology confirmed unaltered NCV, but less reduced CMAP recordings in the treatment group. Moreover, the reduction of Pmp22 mRNA, as quantified in cutaneous nerves, correlated with the clinical phenotype at later stages. Interpretation Progesterone-antagonist treatment. Pmp22 overexpression to a degree at which the axonal support function of Schwann cells is better maintained than myelination. This suggests that axonal loss in CMT1A is not caused by demyelination, but rather by a Schwann cell defect that has been partially uncoupled by anti-progesterone treatment. Pmp22 expression analysis in skin may provide a prognostic marker for disease severity and for monitoring future clinical trials. Ann Neurol 2007;61:61,72 [source] Verbal memory in mania: effects of clinical state and task requirementsBIPOLAR DISORDERS, Issue 5 2003David E Fleck Objectives: Manic patients exhibit impaired verbal learning and memory, particularly following longstanding illness. However, it is unclear whether recognition and recall performance are differentially influenced by a manic mood state. Methods: To examine this issue, we administered the California Verbal Learning Test and symptom-rating scales to inpatients with pure or mixed mania, euthymic outpatients, and healthy comparison subjects. Results: An overall performance difference was identified between groups. Manic and euthymic patients performed more poorly than healthy subjects on recall. However, manic patients performed more poorly than euthymic patients and healthy subjects on recognition. Conclusions: These results suggest that verbal retrieval deficits are stable vulnerability indicators in bipolar disorder, whereas verbal encoding deficits are manic episode indicators. The known subcortical dysfunction in this disorder may produce stable retrieval deficits while acute mood symptoms attenuate encoding during affective episodes only. [source] Performance comparison of MPI and OpenMP on shared memory multiprocessorsCONCURRENCY AND COMPUTATION: PRACTICE & EXPERIENCE, Issue 1 2006Géraud Krawezik Abstract When using a shared memory multiprocessor, the programmer faces the issue of selecting the portable programming model which will provide the best performance. Even if they restricts their choice to the standard programming environments (MPI and OpenMP), they have to select a programming approach among MPI and the variety of OpenMP programming styles. To help the programmer in their decision, we compare MPI with three OpenMP programming styles (loop level, loop level with large parallel sections, SPMD) using a subset of the NAS benchmark (CG, MG, FT, LU), two dataset sizes (A and B), and two shared memory multiprocessors (IBM SP3 NightHawk II, SGI Origin 3800). We have developed the first SPMD OpenMP version of the NAS benchmark and gathered other OpenMP versions from independent sources (PBN, SDSC and RWCP). Experimental results demonstrate that OpenMP provides competitive performance compared with MPI for a large set of experimental conditions. Not surprisingly, the two best OpenMP versions are those requiring the strongest programming effort. MPI still provides the best performance under some conditions. We present breakdowns of the execution times and measurements of hardware performance counters to explain the performance differences. Copyright © 2005 John Wiley & Sons, Ltd. [source] A Risk Adjusted Method for Comparing Adverse Outcomes among Practitioners in Pediatric and Congenital Cardiac CatheterizationCONGENITAL HEART DISEASE, Issue 4 2008Lisa Bergersen MD ABSTRACT Objective., We sought to develop a method to adjust for case mix diversity and allow comparison of adverse outcome rates among practitioners in pediatric and congenital cardiac catheterization. Patients and Methods., A single institutional database that captured demographic and procedural data was used to identify patient and procedural characteristics associated with adverse events (AE) and any high severity event classified as preventable or possibly preventable (P/PP). Diagnostic and procedural risk groups were created and indicators of hemodynamic vulnerability were defined. Expected event rates by the practitioners adjusting for case mix were calculated. Standardized adverse event ratios (SAER), defined as the observed rate divided by the expected rate for each practitioner were calculated with 95% confidence intervals. Results., The database included 1727 hemodynamic (30%) and interventional (70%) cases performed by seven practitioners in 18 months. During 147 cases, at least one P/PP AE occurred; among the seven practitioners observed, event rates ranged from 3.2 to 14.2%. In multivariable analysis, risk factors for all P/PP events included highest procedure risk group (odds ratio [OR] 2.1 for group 2, and 2.8 for group 3, relative to group 1, P = .001 and P < .001, respectively) and weight less than 4 kg (OR 2.8, P < .001). High severity P/PP events occurred in 67 cases with rates ranging from 2.0 to 6.6% by the practitioners. For these events, risk factors included: highest procedure risk group (OR 4.5 for group 2, and 4.9 for group 3, both P < .001) and an indicator of hemodynamic vulnerability (OR 1.8, P = .026). For the seven practitioners, the SAER ranged from 0.41 to 1.32 for any P/PP AE and from 0.69 to 1.44 for P/PP high severity events. In this cohort, we did not identify any statistically significant performance differences. Conclusion., Despite wide variations in case mix complexity in pediatric and congenital cardiac catheterization, this study demonstrates a method for risk adjustment which allows equitable comparisons among practitioners at a single institution. [source] Exploring the Link between Dominant Logic and Company PerformanceCREATIVITY AND INNOVATION MANAGEMENT, Issue 2 2000Georg Von Krogh To revitalize the discussion on dominant logic our paper aims to establish the forgotten link between dominant logic and firm performance. To do so, the concept is enhanced conceptually and operationalized by developing a framework including firms' conceptualization of the business (external environment) and of themselves (internal environment) and performance. The framework is applied to a longitudinal study of two consumer electronics firms. The empirical evidence shows that differences in dominant logic lead to different strategic reactions to developments in the industry, and thus result in performance differences. [source] An Investigation of Localization as an Element of Cognitive Fit in Accounting Model RepresentationsDECISION SCIENCES, Issue 1 2001Cheryl Dunn Abstract Cognitive fit, a correspondence between task and data representation format, has been demonstrated to lead to superior task performance by individual users and has been posited as an explanation for performance differences among users of various problem representations such as tables, graphs, maps, and schematic faces. The current study extends cognitive fit to accounting models and integrates cognitive fit theory with the concept of localization to provide additional evidence for how cognitive fit works. Two accounting model representations are compared in this study, the traditional DCA (Debit-Credit-Account) accounting model and the REA (Resources-Events-Agents) accounting model. Results indicate that the localization of relevant objects or linkages is important in establishing cognitive fit. [source] A comparison of invasive and non-invasive dayflowers (Commelinaceae) across experimental nutrient and water gradientsDIVERSITY AND DISTRIBUTIONS, Issue 5-6 2004Jean H. Burns ABSTRACT Little is known about the traits and mechanisms that determine whether or not a species will be invasive. Invasive species are those that establish and spread after being introduced to a novel habitat. A number of previous studies have attempted to correlate specific plant traits with invasiveness. However, many such studies may be flawed because they fail to account for shared evolutionary history or fail to measure performance directly. It is also clear that performance is context dependent. Thus, an approach that corrects for relatedness and incorporates multiple experimental conditions will provide additional information on performance traits of invasive species. I use this approach with two or three pairs of invasive and closely related non-invasive species of Commelinaceae grown over experimental gradients of nutrient and water availability. Invasive species have been introduced, established, and spread outside their native range; non-invasive species have been introduced, possibly (but not necessarily) established, but are not known to have spread outside their native range. The invasive species had higher relative growth rates (RGR) than non-invasive congeners at high nutrient availabilities, but did not differ from non-invasive species at low nutrient availabilities. This is consistent with a strategy where these particular invasive species are able to rapidly use available resources. Relative growth rates were also higher for two out of three invasive species across a water availability gradient, but RGR did not differ in plasticity between the invasive and non-invasive species. This suggests that nutrient addition, but not changes in water availability, might favour invasion of dayflowers. This approach is novel in comparing multiple pairs of invasive and non-invasive congeners across multiple experimental conditions and allows evaluation of the robustness of performance differences. It also controls for some of the effects of relatedness that might confound multispecies comparisons. [source] HETEROSIS AND OUTBREEDING DEPRESSION IN DESCENDANTS OF NATURAL IMMIGRANTS TO AN INBRED POPULATION OF SONG SPARROWS (MELOSPIZA MELODIA)EVOLUTION, Issue 1 2002Amy B. Marr Abstract We studied heterosis and outbreeding depression among immigrants and their descendants in a population of song sparrows on Mandarte Island, Canada. Using data spanning 19 generations, we compared survival, seasonal reproductive success, and lifetime reproductive success of immigrants, natives (birds with resident-hatched parents and grandparents), and their offspring (F1s, birds with an immigrant and a native parent, and F2s, birds with an immigrant grandparent and resident-hatched grandparent in each of their maternal and paternal lines). Lifetime reproductive success of immigrants was no worse than that of natives, but other measures of performance differed in several ways. Immigrant females laid later and showed a tendency to lay fewer clutches, but had relatively high success raising offspring per egg produced. The few immigrant males survived well but were less likely to breed than native males of the same age that were alive in the same year. Female F1s laid earlier than expected based on the average for immigrant and native females, and adult male F1s were more likely to breed than expected based on the average for immigrant and native males. The performance differences between immigrant and native females and between F1s and the average of immigrants and natives are consistent with the hypothesis that immigrants were disadvantaged by a lack of site experience and that immigrant offspring benefited from heterosis. However, we could not exclude the possibility that immigrants had a different strategy for optimizing reproductive success or that they experienced ecological compensation for life-history parameters. For example, the offspring of immigrants may have survived well because immigrants laid later and produced fewer clutches, thereby raising offspring during a period of milder climatic conditions. Although sample sizes were small, we found large performance differences between F1s and F2s, which suggested that either heterosis was associated with epistasis in F1s, that F2s experienced outbreeding depression, or that both phenomena occurred. These findings indicate that the performance of dispersers may be affected more by fine-scale genetic differentiation than previously assumed in this and comparable systems. [source] DIFFERENTIAL PERFORMANCE AMONG LDH-B GENOTYPES IN RANA LESSONAE TADPOLESEVOLUTION, Issue 5 2000Hansjürg Hotz Abstract The European pool frog, Rana lessonae, is widely polymorphic for two common alleles (b, e) at the lactate dehydrogenase-B (LDH-B) locus. We compared fitness-related larval life-history traits among LDH-B genotypes, which originated from segregation in heterozygous parents, in an artificial pond experiment where tadpoles of R. lessonae from a Swiss population were raised together with tadpoles of the hemiclonal hybrid R. esculenta at two densities. In R. lessonae, LDH-B e/e homozygotes at each density had a higher proportion of metamorphs among survivors, reached metamorphosis earlier, and were heavier at metamorphosis than b/b homozygotes; b/e heterozygotes had intermediate values. That e/e individuals were superior to b/b in both time to and mass at metamorphosis is surprising because these two life-history traits are thought to reflect a performance trade-off; e/e genotypes apparently compensated for shorter time to metamorphosis by a higher growth rate. The two alleles showed the same performance ranking when combined in hybrids with a R. ridibunda allele: When R. esculenta from Swiss populations reared in the same ponds had received the e allele rather than the b allele from their R. lessonae parent, they reached metamorphosis earlier, but did not differ in mass at metamorphosis. The degree of linkage disequilibrium in the source population of the eight R. lessonae used as parents of the R. lessonae tadpoles is unknown, so we cannot exclude the possibility that the performance differences are caused by some anonymous tightly linked gene, rather than the LDH-B locus, that constitutes the genomically localized target of natural selection. A causal involvement of LDH-B is plausible, nevertheless, because this enzyme takes part in the central energy-metabolizing processes and has been reported to underlie fitness differences in other animals; also, differential performance of LDH-B genotypes has been observed in R. lessonae larvae from another population. The present results suggest strong directional selection for allele e; the sum of available data, including an independent laboratory experiment, suggests that partial environment-dependent overdominance combined with balancing selection favoring e/e homozygotes under some and b/b homozygotes under other conditions may be partially responsible for the broad maintenance of the LDH-B polymorphism in R. lessonae. [source] Strategic orientation and performance of internet-based businessesINFORMATION SYSTEMS JOURNAL, Issue 1 2004Varun Grover Abstract., Many of the pure internet-based businesses that proliferated over the past 5 years have encountered serious problems as their lofty valuations have plunged. Industry observers have attributed this phenomenon to a variety of factors, generally framed in terms of poor conceptualization or implementation of the ,business model'. This study explores an often-used concept in strategic management called ,strategic orientation' and applies it to internet-based businesses. Based on an analysis of over 100 public businesses, firms that cluster together with similar strategic orientation are observed. These strategic groups are then analysed for performance differences. The results are discussed with the intent of learning from the dot-burn effects as we evolve to the next generation of internet-based business. [source] Evaluating cognition in an elderly cohort via telephone assessmentINTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 5 2010Effie M. Mitsis Abstract Objective Longitudinal neuropsychological assessment provides the opportunity to observe the earliest transition to cognitive impairment in healthy, elderly individuals. We examined the feasibility, and its comparability to in-person assessment, of a telephone administered battery of established neuropsychological measures of cognitive functioning in healthy, elderly women. Methods Fifty-four women (age,=,79,±,7.7; education,=,15.4,±,3.3) who were in self-reported good health were recruited from senior centers and other community sources. A two-way cross-over design was used in which participants were randomly assigned to receive either (1) in-person neuropsychological assessment followed by telephone assessment and (2) telephone assessment followed by in-person assessment, separated by approximately 4 weeks. Linear regression models were used to determine whether there were performance differences by method (in-person vs. telephone), and equivalence testing assessed comparability of the two methods. Results There were no statistically significant differences in performance between in-person and telephone assessments on most neuropsychological tests, with the exception of digit span backward, Oral Trail Making Test Part A, and delayed recall on the SRT, the latter likely related to non-comparable exposure (6-trials in-person vs. 3-trials telephone). Equivalence testing differences fell in the pre-specified clinical equivalence zones, providing evidence of comparability of the two methods. Conclusions These pilot data support telephone administration of a neuropsychological battery that yields comparable performance to in-person assessment with respect to most instruments. Significant differences in scores on some measures suggest care should be taken in selecting specific measures used in a neuropsychological battery administered by telephone. Copyright © 2009 John Wiley & Sons, Ltd. [source] Effect of molecular relaxation of acrylic elastomers on impact toughening of polybutylene terephthlateJOURNAL OF APPLIED POLYMER SCIENCE, Issue 4 2007Nafih Mekhilef Abstract In this study, we examined the performance of two core-shell acrylic-based impact modifiers (AIM) prepared by emulsion polymerization. The rubber core was prepared from ethyl hexyl acrylate (EHA) and n -octyl acrylate (n -OA). In such as process, the particle size and particle-size distribution of the modifiers were precisely controlled, so that performance differences observed in polybutylene terephthlate (PBT), used as matrix resin, could only be interpreted in terms of the nature of the elastomeric component of the modifiers. When isolated, the rubber core of the modifiers showed identical glass transition temperatures (Tg) by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA) despite the fact that they were made from two different acrylic monomers. Temperature-frequency superposition principle inferred from the classical WLF equation showed that the rubber components exhibit the same Tg at all frequencies including at the time scale at which mechanical impact typically occurs. However, significant differences in low temperature impact performance measured at ,30°C using notched Izod impact test according to ASTM D 256 were obtained even though their rubber components had identical Tg. Such differences were attributed to the dynamic relaxation behavior of the rubber components and identified as inherent properties of the elastomers due to the structure of the monomers' repeat units. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007 [source] Profitability differences between MNE subsidiaries and domestic firms: The case of the food industry in GreeceAGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 1 2004George Anastassopoulos This report analyzes determinants of profitability differences between subsidiaries of Multinational Enterprises (MNEs) and Domestic Enterprises (DMEs) in the Greek food industry using company level data. Previous studies have tested the hypothesis that ownership-specific advantages are a major determinant of performance differences. This study analyzes the processed food sector (SIC = 20), using a panel data set for 75 firms and 5 years. The model is evaluated using a random effects model. The results indicate that the determinants of profitability differ between MNEs subsidiaries and DMEs. MNEs' profitability depends on their market share, knowledge, and experience of the local market; training intensity; and product differentiation through the use of technological inputs from abroad and local advertising. DMEs' profitability depends on their market share and product differentiation, through local advertising and local R&D. Size has a negative effect on profitability for both groups of companies. Even after allowing for all of these determinants of profitability, ownership has an independent effect on profitability (namely higher for MNE subsidiaries than DMEs). [EconLit citations: F23, L66, L69]. © 2004 Wiley Periodicals, Inc. Agribusiness 20: 45,60, 2004. [source] Increased Activation of the ACC During a Spatial Working Memory Task in Alcohol-Dependence Versus Heavy Social DrinkingALCOHOLISM, Issue 5 2010Sabine Vollstädt-Klein Background:, Activation of the anterior cingulate cortex (ACC) in a spatial working memory task has been associated with risk factors for alcohol use disorders such as low alcohol effects and positive alcohol expectations in adolescents. To transfer these results into adults, we used the same task in adults. Methods:, During functional magnetic resonance imaging, 12 light social, 7 heavy social, and 11 non-abstinent-dependent alcohol drinkers performed a spatial working memory task and completed measures of automatic alcohol-related thoughts and behavior (Obsessive,Compulsive Drinking Scale,OCDS), alcohol use of the last 90 days, and general intelligence. Results:, Behavioral performance in the spatial working memory task was not significantly different in all 3 groups. Controlling for differences in general intelligence alcohol-dependent participants showed a higher task-related activation of the dorsal ACC (dACC) in comparison with light and heavy social drinkers. Measures of the OCDS were positively correlated with the activation in the left hippocampus and right thalamus in all participants. Conclusions:, Our results support the findings of increased dACC activation during a spatial working memory task as a risk factor for alcohol dependence. Increased task-related activation in the dACC was only observed in alcohol-dependent participants and not in heavy social drinkers with comparable alcohol consumption. Furthermore, the absence of behavioral performance differences between groups as well as an association between dACC activation and working memory performance indicates subtle working memory deficits. Low capacity of working memory has been linked to more automatic and less self-regulated behavior in studies on natural reward processing. Therefore, additional neural activation during performance of the non-alcohol-related working memory task in participants with higher OCDS values in the left hippocampus and the right thalamus may be a consequence of decreased neural capacity because of distracting alcohol-related thoughts. [source] Strategic group membership and nonprofit organization performanceNONPROFIT MANAGEMENT & LEADERSHIP, Issue 1 2009Dan Marlin This study analyzed the resource characteristics of a sample of university foundations and identified five distinct strategic groups. We found significant performance differences among them. Specifically, the group that focused most heavily on fundraising activities had the highest financial performance. Also performing well was the group with the highest ratio of contributions to total revenues combined with the highest level of slack. The research and managerial implications of this study's findings are discussed. [source] Clinical performance of electronic, head-mounted, low-vision devicesOPHTHALMIC AND PHYSIOLOGICAL OPTICS, Issue 4 2004Louise E. Culham Abstract This study compared four electronic head-mounted devices (HMDs) (Jordy, Flipperport, Maxport and NuVision) with conventional optical low-vision aids (LVAs). The aim was to determine any performance differences for laboratory-based clinical measurements and practical visual tasks for patients with macular disease. Possible factors influencing success were explored. Ten patients with early onset macular disease (EOMD) and 10 with age-related macular disease (AMD) used the four HMDs, habitual spectacles and previously prescribed optical LVAs to complete a range of clinical measurements and everyday visual tasks. The clinical measurements were distance, intermediate and near acuities, and contrast sensitivity. The visual tasks were to read text of three sizes, to write a cheque and to identify grocery items on a shelf. Following the initial evaluation, each subject took home two randomly selected HMD devices for 2 weeks, after which performance measures were repeated. No single HMD stood out as being superior overall. Flipperport and Jordy provided significantly better distance and intermediate acuity than the previously prescribed optical LVAs but near acuity and contrast sensitivity were not consistently better with any of the HMDs. Practice at home provided some improvement in performance with HMDs, nevertheless, optical aids remained the best devices for optimum functioning for the majority of tasks. Younger patients and those with better distance acuity were more likely to benefit from HMDs, particularly when reading small print. In low vision clinics, practitioners should continue to show patients conventional optical aids and demonstrate these electronic HMDs only when appropriate for the individual patient. [source] Variability in Implantable Cardioverter Defibrillator Pulse Generator Longevity Between ManufacturersPACING AND CLINICAL ELECTROPHYSIOLOGY, Issue 1p1 2003PATRICK T. ELLINOR ELLINOR, P.T., et al.: Variability in Implantable Cardioverter Defibrillator Pulse Generator Longevity Between Manufacturers.ICDs are used frequently to treat malignant ventricular arrhythmias. Despite the expanding role of these devices, little is known about the manufacturer variability in the performance of ICD generators. The purpose of this study is to explore the indications for ICD pulse generator replacement and to examine performance differences between the three major manufacturers of ICDs in the United States. The authors performed a retrospective review of ICD pulse generators that were implanted and replaced at Massachusetts General Hospital between February 1998 and March 2002. During the study period, 50 (7%) of the 707 devices in the study cohort were replaced. The most common indication for pulse generator replacement was related to battery performance followed by device recall, upgrade to a dual chamber device, and pulse generator malfunction. After exclusion of the recalled devices, a significantly higher number of pulse generators manufactured by St. Jude Medical (14/229) required replacement for battery depletion or prolonged charge times during the study period compared with devices from Guidant (2/220) or Medtronic (0/273),P = 0.003andP < 0.0001, respectively. This difference was attributable to reduced longevity in the Angstrom series of defibrillators. (PACE 2003; 26[Pt. I]:71,75) [source] Measures of skill and value of ensemble prediction systems, their interrelationship and the effect of ensemble sizeTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 577 2001David S. Richardson Abstract Ensemble forecasts provide probabilistic predictions for the future state of the atmosphere. Usually the probability of a given event E is determined from the fraction of ensemble members which predict the event. Hence there is a degree of sampling error inherent in the predictions. In this paper a theoretical study is made of the effect of ensemble size on forecast performance as measured by a reliability diagram and Brier (skill) score, and on users by using a simple cost-loss decision model. The relationship between skill and value, and a generalized skill score, dependent on the distribution of users, are discussed. The Brier skill score is reduced from its potential level for all finite-sized ensembles. The impact is most significant for small ensembles, especially when the variance of forecast probabilities is also small. The Brier score for a set of deterministic forecasts is a measure of potential predictability, assuming the forecasts are representative selections from a reliable ensemble prediction system (EPS). There is a consistent effect of finite ensemble size on the reliability diagram. Even if the underlying distribution is perfectly reliable, sampling this using only a small number of ensemble members introduces considerable unreliability. There is a consistent over-forecasting which appears as a clockwise tilt of the reliability diagram. It is important to be aware of the expected effect of ensemble size to avoid misinterpreting results. An ensemble of ten or so members should not be expected to provide reliable probability forecasts. Equally, when comparing the performance of different ensemble systems, any difference in ensemble size should be considered before attributing performance differences to other differences between the systems. The usefulness of an EPS to individual users cannot be deduced from the Brier skill score (nor even directly from the reliability diagram). An EPS with minimal Brier skill may nevertheless be of substantial value to some users, while small differences in skill may hide substantial variation in value. Using a simple cost-loss decision model, the sensitivity of users to differences in ensemble size is shown to depend on the predictability and frequency of the event and on the cost-loss ratio of the user. For an extreme event with low predictability, users with low cost-loss ratio will gain significant benefits from increasing ensemble size from 50 to 100 members, with potential for substantial additional value from further increases in number of members. This sensitivity to large ensemble size is not evident in the Brier skill score. A generalized skill score, dependent on the distribution of users, allows a summary performance measure to be tuned to a particular aspect of EPS performance. [source] DIFFERENCES IN FINANCIAL PERFORMANCE AMONGST SPANISH SMES ACCORDING TO THEIR CAPITAL-OWNERSHIP STRUCTURE: A DESCRIPTIVE ANALYSISANNALS OF PUBLIC AND COOPERATIVE ECONOMICS, Issue 1 2010Zuray Melgarejo ABSTRACT,:,The purpose of this paper is to assess whether financial performance differences between labour-managed (LOFs) and mercantile (PCFs) firms are due to differences in their capital-ownership configuration or to the particular measurement indexes commonly used to quantify performance. The empirical evidence rests upon a 1994,2003 data set of LOFs and PCFs that operate in the Industrial and Services sectors of the economy of Navarre, Spain. The results do not detect significant differences in financial performance between LOFs and PCFs, especially in the long-term and suggest the need to develop performance indices more akin to the special nature of the LOFs. [source] Comparison of the swimming performance of farmed and wild gilthead sea bream, Sparus aurataAQUACULTURE RESEARCH, Issue 5 2007Fatih Basaran Abstract Farmed gilthead sea bream, Sparus aurata, frequently escape from the sea cages and interact with wild populations. The impact of these interactions on the wild populations will depend, in part, on differences in performance of the bream. This study compared the swimming performance of the wild and farmed fish in a current channel. The absolute critical swimming speed (Ucrit) increased with increasing size while the relative Ucrit decreased. Even at the same length there were noticeable performance differences between the individuals. The wild sea bream have significantly higher (P<0.05) absolute Ucrit performance (0.86±0.01 m s,1) than the farmed fish (0.79±0.01 m s,1) and significantly higher (P<0.05) relative Ucrit performance (4.52±0.05 BL s,1) than the farmed fish (4.21±0.05 BL s,1). The present study suggests that cultured sea bream may not have the ability to compete with wild sea bream in native seawaters. [source] | ||||||||||||||||||||||||||||||||||