Small Differences In Performance Research Articles

Forecasting and Evaluating Network Growth

This research assesses the implications of existing trends on future network investment, comparing alternative scenarios concerning budgets and investment rules. The main scenarios compare “stated decision rules”, processes encoded in flowcharts and weights developed from official documents or by discussion with agency staff, with “revealed decision rules”, weights estimated statistically based on observed historical behavior. This research specifies the processes necessary to run the network forecasting models with various decision rules. We find that given the relatively small amount of funds available for network growth in a mature system, alternative decision rules make only small differences in overall system performance, though they direct investments to very different locations and affect the trip time and spatial accessibility in a significantly different way.

Does Mission Matter? An Analysis of Private School Achievement Differences

Using student achievement data from British Columbia, Canada, this study is an exploration of the differences that lie within the private school sector using hierarchical linear modeling to analyze the data. The analysis showed that when controlling for language, parents' level of educational attainment, and prior achievement, the private school subsectors had small but important differences in average performance compared to one another and to public schools. The study suggests that mission might matter more in parental school choice decisions than academic achievement and implications of this for school choice are explored.

Issues in the design, analysis and interpretation of condom functionality studies

Background Male condom functionality studies are typically crossover trials in which enrolled couples use both experimental and latex control condoms for sexual intercourse. Noninferiority of the experimental type is assessed using confidence intervals for differences in breakage and slippage probabilities. Seemingly straightforward, the design, analysis and interpretation of functionality studies are complicated by the choice of noninferiority criterion, study population and the potential for learning effects. Methods Power calculations, secondary data analyses and simulations were used to illustrate concerns and make recommendations. Results The probability of failure can be too low to draw meaningful conclusions in certain population subgroups. Learning effects among inexperienced users can exaggerate differences in performance and undermine power. A product which is, on average, inferior to latex may still be a viable prophylactic for a large percentage of couples. Conclusions Heterogeneity of failure probabilities, combined with small acceptable differences in performance, requires care when selecting study participants. Pilot data, adequate training on condom use and reasonable expectations regarding performance of a new condom type are essential to maximizing the chance of identifying a noninferior product.

Effects of Wake Rollup on Formation-Flight Aerodynamics

The aerodynamic performance of two high aspect-ratio wings flying in formation is investigated with particular interest in the importance of considering wake rollup in making aerodynamic predictions. For this purpose, formations of various separations were investigated using a drag-free, fixed-wake model as well as a force-free, relaxed one. In all cases the aircraft were trimmed for roll and the follower aircraft pitch attitude was adjusted to match the lift coefficient of the lead aircraft. Both wake representations result in similar induced-drag minima for the follower aircraft which result when the lateral overlaps of the two aircraft are around 10% of a wingspan. Computations with the fixed-wake model, however, predict a wider region of lateral separations having the lowest induced drag than do the simulations with wake rollup. A small performance difference due to the wake model also exists when one aircraft follows directly behind the other. Independent of the wake model used, trimming the aircraft in roll and pitch can have a significant influence on their performance, although the required control-input solutions for trim are essentially not affected by the choice of wake representation.

Comparison of Three Multiobjective Optimization Algorithms for Inverse Modeling of Vadose Zone Hydraulic Properties

Inverse modeling has become increasingly popular for estimating effective hydraulic properties across a range of spatial scales. In recent years, many different algorithms have been developed to solve complex multiobjective optimization problems. In this study, we compared the efficiency of the Nondominated Sorting Genetic Algorithm (NSGA‐II), the Multiobjective Shuffled Complex Evolution Metropolis algorithm (MOSCEM‐UA), and AMALGAM, a multialgorithm genetically adaptive search method for multiobjective estimation of soil hydraulic parameters. In our analyses, we implemented the HYDRUS‐1D model and used observed pressure head data at three different depths from the Spydia experimental field site in New Zealand. Our optimization problem was posed in a multiobjective context by simultaneously using three complementary RMSE criteria at each depth. We analyzed the trade‐off between these criteria and the adherent Pareto uncertainty. The results demonstrate that all three algorithms were able to find a good approximation of the Pareto set of solutions, but differed in the rate of convergence to this distribution. Small differences in performance of the various algorithms were observed because of the relative high dimension of the optimization problem in combination with the presence of multiple local optimal solutions within the three‐objective search space. The Pareto parameter sets yielded satisfactory results when simulating the transient tensiometric pressure at predetermined observation points in the investigated vadose zone profile. The overall best parameter set was found by AMALGAM with RMSE values of 0.14, 0.11, and 0.17 m at the 0.4‐, 1.0‐, and 2.6‐m depths, respectively. In contrast, the fit errors were substantially higher at these respective depths, with RMSE values ranging from 0.87 to 1.49 m, when using soil hydraulic parameters derived from laboratory analysis of small vadose zone cores.

Brain Structure and Function Differences in Monozygotic Twins: Possible Effects of Breast Cancer Chemotherapy

Adjuvant chemotherapy has been associated with mild cognitive decline among a subset of breast cancer survivors. Late cognitive effects after chemotherapy can have a deleterious impact on survivor quality of life and functional health; however, the etiology of chemotherapy-related cognitive dysfunction remains unknown. We present a case of monozygotic twins who are discordant for breast cancer and chemotherapy exposure (ie, one twin contracted breast cancer and underwent chemotherapy, and the other had no breast cancer). As part of a larger study, each was evaluated with standardized, self-report measures of cognitive function, standard neuropsychological tests, and structural and functional magnetic resonance imaging (MRI). Results indicated small differences in neuropsychological test performance but striking contrasts in self-reported cognitive complaints and structural and functional MRI images. Specifically, the twin who underwent chemotherapy had substantially more subjective cognitive complaints, more white matter hyperintensities on MRI, and an expanded spatial extent of brain activation during working memory processing than her nonaffected twin. This case illustrates possible physiologic mechanisms that could produce long-term cognitive complaints among chemotherapy recipients and help formulate hypotheses for further empirical study in the area of chemotherapy-associated cognitive dysfunction.

System for assessing Aviation’s Global Emissions (SAGE), Part 2: Uncertainty assessment

This paper focuses on assessing and applying the Federal Aviation Administration’s System for assessing Aviation’s Global Emissions (SAGE), Version 1.5, to evaluate global aircraft fuel consumption and emissions. The model is capable of computing fuel burn and emissions on a flight-by-flight, fleet and global basis. Here, a parametric study was conducted to rank-order the effects that the modeling uncertainties had on estimates of fuel burn and emissions. Statistical methods were applied to analyze both the random and systematic errors of the model. Also, applying the model to a sample policy analysis case allowed an examination of more stringent engine certification standards for mitigating aviation emissions. Uncertainties of the model were carefully accounted for in the fuel burn and emissions scenarios of the policy options. Results show that for some applications, SAGE may be used to resolve small differences in fleet emissions performance. Although the absolute uncertainty in flight-by-flight NO x predictions from the model are of the order of 40%, results show that it is well within the current capabilities of the model to distinguish between the fleet average NO x emissions associated with the typical NO x stringency options considered in policy analyses.

Parallel evolution in sympatric, hybridizing species: performance ofColiasbutterflies on their introduced host plants

AbstractShared ancestry and introgression can contribute to genetic similarity between hybridizing species, and it is generally difficult to disentangle these causes. However, shared ancestry plays a more limited role in traits that have recently undergone parallel directional selection in the two species, permitting the role of introgression to be better understood. The butterfliesColias eurytheme(Boisduval) andColias philodice(Godart) (Lepidoptera, Pieridae) are native to North America and have shifted their host ranges in parallel onto several introduced weedy and agricultural legumes. These butterflies hybridize at moderate rates throughout their range, and there is a strong possibility that they could be sharing host‐associated adaptations. We split families of each species among nine introduced, prospective hosts and measured survivorship, larval duration, pupal weight, and a new variable, effective daily growth rate (DGR), analogous to a compound daily interest rate in economics. We found strong effects of host, sex, and family (species), but negligible effects of the host*species interaction that would indicate species‐specific differences in performance on different hosts. We found species‐specific life‐history differences:C. eurythemematured significantly later and reached a significantly larger body size thanC. philodicewhile growing at the same DGR. Protandry was strong, and males, in addition to pupating sooner than females, grew significantly faster than females as measured by DGR. We measured broad‐sense heritabilities and genetic correlations for host‐associated performance variables. Most pairwise comparisons of performance among hosts and most pairwise comparisons between performance variables showed positive genetic correlations, except survivorship where little heritability was found. Nevertheless, a factorial multivariate analysis of variance of G‐matrices showed highly significant species, host, and host*species interactions, suggesting differentially evolving genetic architectures underlying host adaptation in these two species, despite the small differences in overall performance. At least some of the genes affecting host performance inColiasare likely to be in the small, species‐diagnostic regions and not shared via introgression between these hybridizing species. For biologists interested in the evolutionary ecology of their host associations, including applied biologists managing their agricultural pest potential,C. eurythemeandC. philodiceare most usefully studied as if they were a single polymorphic species wherever they co‐exist. In studying species that hybridize readily with a sympatric congener, it may often be necessary to include the second species in the experimental design.

The Sex Specificity of Navigational Strategies in Alzheimer Disease

Alzheimer disease (AD) is associated with navigational impairments that limit functional independence. We have now examined the role of cognitive and perceptual mechanisms in the navigational impairment of AD to test the hypothesis that men and women with AD may focus on different navigational cues. We conducted navigational, neuropsychologic, and psychophysical testing in men and women from 3 groups: older normal controls, patients with mild cognitive impairment, and patients with AD. Men and women showed parallel declines in navigational capacities from the older normal control, to the mild cognitive impairment, to the AD groups with men and women making similar numbers of errors but different types of errors. There were small sex differences in neuropsychologic and psychophysical performance but large sex differences in how those measures related to navigational capacity: men showed strong links between visual motion processing and navigation. Women showed strong links between verbal capacities and navigation. The findings of these cross-sectional comparisons suggest that there may be sex differences in the progressive navigational decline of AD: men and women who are impaired to the same degree may suffer somewhat different patterns of decline with men relying more on visuospatial processing and women relying more on verbal mediation.

Water Potential Characteristics of Transgenic Petunias Over-expressing Two Arabidopsis C-repeat Binding Factor cDNAs

Petunia × hybrida `Electric Purple' plants, genetically transformed (Selecta Klemm Co.) via Agrobacterium tumefaciens to constitutively express the Cauliflower Mosaic Virus 35S promoter (CaMV35S) fused to two separate Arabidopsis c-repeat binding factor cDNAs (CBF3 & CBF4), were utilized to evaluate water relations. Non-stressed plants followed a classical stomatal conductance pattern, with maximum conductance between 1000 hr and 1400 hr. CBF3 and CBF4 plants showed an increase in transpiration rates and a decrease in stomatal resistance at 1230 hr, compared to `Electric Purple'. Transpiration rates (per unit leaf area) were similar in CBF3 and `Electric Purple' plants, but CBF4 plants were 12% less than `Electric Purple'. Xylem water potentials at visible wilt were between –1.4 and –1.5 MPa and there were no significant differences between line or irrigation treatment. A fourth experiment observed differential plant responses to stress cycles. Under non-stress irrigation conditions, CBF4 plants showed an increase in stomatal resistance and a decrease in transpiration rate compared to `Electric Purple' plants. There were no differences in the xylem water potential at visible wilt for the first and third stress cycles, but, for the second cycle, xylem water potentials at wilt were –1.9, –1.7 and –1.4 Mpa for CBF4, `Electric Purple' and CBF3 plants, respectively. CBF3 and CBF4 plants showed small differences in performance as compared to `Electric Purple' and under mild stress conditions as imposed in these experiments apparent heterologous overexpression of the Arabidopsis CBF3 & 4 transgenes may not be sufficient for conferring drought tolerance in petunia.

Analytical Performance and Diagnostic Accuracy of Immunometric Assays for the Measurement of Circulating Oxidized LDL

Oxidized LDL (ox-LDL) plays an important role in the pathogenesis of coronary heart disease (CHD). Several tests for circulating ox-LDL have been published. We believe it is critical to carefully evaluate these assays because small differences in performance may have profound effects when results are compared; we therefore compared the analytical and clinical performances of 2 assays: one developed in our laboratory and a commercial assay (Mercodia) that uses the same monoclonal antibody (4E6). We determined the variance of ox-LDL in both tests, including its longitudinal stability (n = 225; 3 time points per person) and its diagnostic accuracy, by ROC analysis of 95 consecutive CHD patients and 20 controls. The between-person variability was 77% for the in-house assay (with the remaining 23% being within-person and analytical variance) and 74% for the commercial assay. For comparison, previously reported values were 66% for high-sensitivity C-reactive protein and 82% for total cholesterol. The areas under the curves for CHD in the 2 assays were identical (0.85). The odds ratios (logistic regression) for CHD among persons with high ox-LDL (>or=15 mg/L) compared with persons with low ox-LDL were not different: 4.3 (95% confidence interval, 1.4-12) for the in-house assay and 3.3 (1.1-10) for the commercial assay. The longitudinal stability of ox-LDL, as assessed by multiple measures in people over time, is similar to that of total cholesterol and high-sensitivity C-reactive protein. Both assays tested similarly distinguish between healthy controls and CHD patients.

Finance training can be fun and effective

PurposeThis paper's purpose is to address the fact that many intelligent and experienced managers in industry do not really understand about business finance, how profits are generated and what they can do to improve them. This paper shows how the traditional perception problems of dryness, difficulty and irrelevance of finance training can be overcome. Furthermore the paper covers how managers can create action plans within their own areas of interest to have an impact on the company performance.Design/methodology/approachThis paper describes how physical, board‐based simulations can be used to give a learning experience of finance and business in an effective and time efficient way. The paper lists the problems of finance training, explains the means by which a good simulation overcomes these problems, and shows how small performance differences can make a.significant impact.FindingsThe post‐training research shows that participants find the experience of finance in a simulation to be very effective in the use of their time, compared to other methods of training. The feedback is also that their knowledge has substantially improved on the key business issues of finance reports, making choices about the use of resources and the need to work together with others to achieve results.Originality/valueThe paper contains important messages for Learning and Development departments about the methods of finance training and also to operations directors about the ways managers can create action plans to improve the results through a deeper understanding of business.

Auditory Localization Abilities in Bilateral Cochlear Implant Recipients

To quantify binaural advantage for auditory localization in the horizontal plane by bilateral cochlear implant (CI) recipients. Also, to determine whether the use of dual microphones with one implant improves localization. Twenty subjects from the UK multicenter trial of bilateral cochlear implantation with Nucleus 24 K/M device were recruited. Sound localization was assessed in an anechoic room with an 11-loudspeaker array under four test conditions: right CI, left CI, binaural CI, and dual microphone. Two runs were undertaken for each of five stimuli (speech, tones, noise, transients, and reverberant speech). Order of conditions was counterbalanced across subjects. Mean localization error with bilateral implants was 24 degrees compared with 67 degrees for monaural implant and dual microphone conditions (chance performance is 65 degrees). Normal controls average 2 to 3 degrees in similar conditions. Binaural performance was significantly better than monaural performance for all subjects, for all stimulus types, and for different sound sources. Only small differences in performance with different stimuli were observed. Bilateral cochlear implantation with the Nucleus 24 device provides marked improvement in horizontal plane localization abilities compared with unilateral CI use for a range of stimuli having different spectral and temporal characteristics. Benefit was obtained by all subjects, for all stimulus types, and for all sound directions. However, binaural performance was still worse than that obtained by normal hearing listeners and hearing aid users with the same methodology. Monaural localization performance was at chance. There is no benefit for localization with dual microphones.

Neuropsychological and educational problems at school age associated with neonatal encephalopathy

Background: Adverse cognitive and educational outcomes are often ascribed to perinatal hypoxia without good evidence. Objective: To investigate neurocognitive and behavioural outcomes after neonatal encephalopathy. Methods: Sixty five children with...

Precision and accuracy of three alternative instruments for measuring soil water content in two forest soils of the Pacific Northwest

We compared the accuracy and precision of three devices for measuring soil water content in both natural and repacked soils and evaluated their temperature sensitivity. Calibrations were developed for a capacitance instrument (ECH2O), a time domain reflectometry cable tester (CT), and a water content reflectometer (WCR) in soils collected from the Wind River and H.J. Andrews Experimental Forests. We compared these calibrations with equations suggested by manufacturers or commonly used in the literature and found the standard equations predicted soil moisture content 0%–11.5% lower (p < 0.0001) than new calibrations. Each new calibration equation adequately predicted soil moisture from the output for each instrument regardless of location or soil type. Prediction intervals varied, with errors of 4.5%, 3.5%, and 7.1% for the ECH2O, CT, and WCR, respectively. Only the ECH2O system was significantly influenced by temperature for the range sampled: as temperature increased by 1 °C, the soil moisture estimate decreased by 0.1%. Overall, the ECH2O performed nearly as well as the CT, and thanks to its lower cost, small differences in performance might be offset by deployment of a greater number of probes in field sampling. Despite its higher cost, the WCR did not perform as well as the other two systems.

Ultrafiltration of kraft cooking liquors from a continuous cooking process

Two cooking liquors and a black liquor were fractionated by ultrafiltration. The liquors were withdrawn from different stages in a kraft pulp mill employing continuous digestion. The ultrafiltration was performed at 90°C with two ceramic membranes with cut-offs of 5 kDa and 15 kDa. Only small differences in membrane performance were observed when concentrating the three liquors to 90% volume reduction. The average flux was 55 l/m 2 h for the 5 kDa membrane and about 115 l/m 2 h for the 15 kDa membrane. The concentration of lignin was on average 230 and 155 g/L in the retentate from the 5 kDa and 15 kDa cut-off membranes. The ash content was reduced from 37–40 g/g total dry solids to 20–30 g/g after ultrafiltration.

VARIATIONS AMONG HIGH VOLUME SURGEONS IN THE RATE OF COMPLICATIONS AFTER RADICAL PROSTATECTOMY: FURTHER EVIDENCE THAT TECHNIQUE MATTERS

A strong association between surgeon, hospital volume and postoperative morbidity of radical prostatectomy has been demonstrated. While better outcomes are associated with high volume surgeons, the degree of variation in outcomes among surgeons has not been fully examined. Using a linked database from Surveillance, Epidemiology and End Results registries and federal Medicare claims data, we analyzed outcomes of consecutive patients treated with radical prostatectomy between 1992 and 1996. We focused on variations in several measures of morbidity (perioperative complications, late urinary complications and long-term incontinence) among patients of high volume surgeons, defined as those with 20 or more patients in the study period. After adjusting for hospital, surgeon volume and case mix, we examined the extent to which variations in the rates of adverse outcomes differed among surgeons for all 3 end points. Of the 999 surgeons 16% (159) performed 48.7% (5,238) of the 10,737 radical prostatectomies during the study. The 30-day mortality rate was 0.5%, the major postoperative complication rate was 28.6%, late urinary complications 25.2% (major events 16%) and long-term incontinence 6.7%. For all 3 morbidity outcomes the variation among surgeons in the rate of complications was significantly greater than that expected by chance (p =0.001 for each) after adjustment of covariates. Furthermore, surgeons with better (or worse) than average results with regard to 1 outcome were likely to have better (or worse, respectively) results with regard to the other 2 outcome measures. Morbidity end points that directly affect quality of life showed significant variability among high volume providers. Surgeons who performed well in 1 area (eg postoperative complications) performed well in others. These results further suggest that variations in surgical technique and postoperative care lead to variations in outcomes after radical prostatectomy, indicating that outcomes of this operation are sensitive to small differences in performance.

Evaluation of transgenic hybrid corn (VIP3A) in broiler chickens

A 49-d feeding study evaluated whether standard broiler diets prepared with Syngenta Seeds VIP3A transgenic derived corn grain had any unanticipated adverse effects on male or female broiler chickens as compared with diets prepared with nontransgenic (isoline) control corn grain. Two commercial lots of grain grown in North Carolina during the 1999 (NC 1999) and 2000 (NC 2000) seasons were included for reference purposes.Broiler growth was excellent with males reaching 3466 g and females reaching 2882 g at 49 d of age. Final BW of the VIP3A, isoline, and NC 1999 corn groups were within 21.1 g, whereas the NC 2000 group was 42.4 g lower than the lowest of this group. There was no overall corn source effect on adjusted feed conversion ratio (FCR) or mortality to 49 d of age. Carcass analysis demonstrated no differences in percentage yield due to corn source among males and females other than percentage wings in females. Comprehensive clinical chemical analyses of blood taken from representative birds at 49 d of age showed no differences due to corn sources.The transgenic VIP3A hybrid diets numerically supported the most rapid broiler chicken growth, the second lowest mortality rate and best FCR, without practical differences in carcass yield. The few differences found in this study were not unique to a given corn source but instead appeared to be distributed equally across the diet groups evaluated in the study. Although it was not clear whether small differences in performance were attributable to the transgenic corn per se or were due to possible slight differences in overall composition of the formulated diets, it was clear that the transgenic corn had no deleterious effects on broiler performance and carcass yield in this study.

Prior academic background and student performance in assessment in a graduate entry programme

This study aims to identify whether non-science graduates perform as well as science graduates in Basic and Clinical Sciences (B & CS) assessments during Years 1-3 of a four-year graduate-entry programme at the University of Sydney (the 'USydMP'). Students were grouped into five categories: Health Professions (HP), Biomedical Sciences (BMS), Other Biology (BIOL), Physical Sciences (PHYS) or Non-Science (NONS). We examined the performance rank of students in each of the five groups for single best answer (SBA) and modified essay (MEQ) assessments separately, and also calculated the relative risk of failure in the summative assessments in Years 2 and 3. Students with science-based prior degrees performed better in the SBA assessments. The same occurred initially in the MEQs, but the effect diminished with time. The HP students performed consistently better but converged with other groups over time, particularly in the MEQs. Relative performance by the NONS students improved with time in both assessment formats. Overall, differences between the highest and lowest groups were small and very few students failed to meet the overall standard for the summative assessments. HP and BMS students had the lowest failure rate. NONS students were more likely to fail the assessments in Year 2 and 3, but their pass rates were still high. Female students performed significantly better overall at the end of Year 2 and in Year 3. There were only minor differences between Australian resident and International students. While there are small differences in performance in B & CS early in the programme, these lessen with time. The study results will inform decisions regarding timing of summative assessments, selection policy and for providing additional support to students who need it to minimize their risk of failure. Readers should note that this paper refers to student performance in only one of the four curriculum themes, where health professional and science graduates would be expected to have a significant advantage.

VALIDATION OF SIMULATED RUNOFF FROM SIX TERRESTRIAL ECOSYSTEM MODELS: RESULTS FROM VEMAP

Vegetation/Ecosystem Modeling and Analysis Project (VEMAP) Phase 2 model experiments investigated the response of biogeochemical and dynamic global vegetation models (DGVMs) to differences in climate over the conterminous United States. This was accomplished by simulating ecosystem processes using historical climate and atmospheric CO2 records from 1895–1993. We evaluated the behavior of six models (Biome‐BGC, Century, GTEC, LPJ, MC1, and TEM) by comparing simulated runoff in 13 watersheds to gauged streamflow from the Hydro‐Climatic Data Network. Metrics used to assess the “goodness of fit” between simulated and observed values were: (1) Pearson's r to evaluate the overall data set, (2) Kendall's τ to gauge seasonality trends as derived from a time‐series analysis of monthly runoff, and (3) three measures of absolute and relative error.We found small differences in performance among the six models over all watersheds. However, the models yielded highly divergent results depending upon the watershed analyzed. Performance of the ensemble of models in a watershed was positively correlated with observed streamflow: models in the wettest watersheds in this study were associated with the highest model correlations and largest absolute errors, and models in the driest watersheds were associated with the lowest correlations and smallest absolute errors. Mean relative error was small and nearly constant across watersheds. A bias estimator showed that the models tended to underestimate runoff in wet watersheds and overestimate runoff in dry watersheds. Analysis of long‐term trends in runoff using a moving‐average approach demonstrated the ability of the models to reproduce temporal variation in observed data, even though quantitative differences among models were large.Models relying on prescribed vegetation (Biome‐BGC, Century, and TEM) outperformed the two DGVMs (LPJ and MC1); GTEC gave the poorest fit to observations due to the absence of an evaporation function and a snow routine. Across all 13 watersheds, TEM ranked the highest in model performance. The validation results presented here suggest that improvements in the simulation of hydrologic processes in land‐surface models will come, in part, from a more realistic representation of subgrid‐scale soil moisture and from a more detailed understanding and representation of subsurface processes.