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Model Variables (model + variable)
Selected AbstractsIndividual-based Computational Modeling of Smallpox Epidemic Control StrategiesACADEMIC EMERGENCY MEDICINE, Issue 11 2006Donald S. Burke MD In response to concerns about possible bioterrorism, the authors developed an individual-based (or "agent-based") computational model of smallpox epidemic transmission and control. The model explicitly represents an "artificial society" of individual human beings, each implemented as a distinct object, or data structure in a computer program. These agents interact locally with one another in code-represented social units such as homes, workplaces, schools, and hospitals. Over many iterations, these microinteractions generate large-scale macroscopic phenomena of fundamental interest such as the course of an epidemic in space and time. Model variables (incubation periods, clinical disease expression, contagiousness, and physical mobility) were assigned following realistic values agreed on by an advisory group of experts on smallpox. Eight response scenarios were evaluated at two epidemic scales, one being an introduction of ten smallpox cases into a 6,000-person town and the other an introduction of 500 smallpox cases into a 50,000-person town. The modeling exercise showed that contact tracing and vaccination of household, workplace, and school contacts, along with prompt reactive vaccination of hospital workers and isolation of diagnosed cases, could contain smallpox at both epidemic scales examined. [source] Validation of a prediction rule to maximize curative (R0) resection of early-stage pancreatic adenocarcinomaHPB, Issue 7 2009Philip Bao Abstract Background:, The surgeon's contribution to patients with localized pancreatic adenocarcinoma (PAC) is a margin negative (R0) resection. We hypothesized that a prediction rule based on pre-operative imaging would maximize the R0 resection rate while reducing non-therapeutic intervention. Methods:, The prediction rule was developed using computed tomography (CT) and endoscopic ultrasound (EUS) data from 65 patients with biopsy-proven PAC who underwent attempted resection. The rule classified patients as low or high risk for non-R0 outcome and was validated in 78 subsequent patients. Results:, Model variables were: any evidence of vascular involvement on CT; EUS stage and EUS size dichotomized at 2.6 cm. In the validation cohort, 77% underwent resection and 58% achieved R0 status. If only patients in the low-risk group underwent surgery, the prediction rule would have increased the resection rate to 92% and the R0 rate to 73%. The R0 rate was 40% higher in low-risk compared with high-risk patients (P < 0.001). High risk was associated with a 67% rate of non-curative surgery (unresectable disease and metastases). Conclusion:, The prediction rule identified patients most likely to benefit from resection for PAC using pre-operative CT and EUS findings. Model predictions would have increased the R0 rate and reduced non-therapeutic interventions. [source] Linking trust to use intention for technology-enabled bank channels: The role of trusting intentions,PSYCHOLOGY & MARKETING, Issue 8 2010Sergios Dimitriadis The present research is an attempt to better understand the role of trust in the adoption of technology-based service channels, namely Internet and phone banking. The study conceptualizes and measures trust, distinguishing the cognitive and affective component of trust (the trusting beliefs), the behavioral component of trust (trusting intentions), and the purchase behavior (intention to use), suggesting a mediating role of trusting intentions. Then it tests a model that combines the effect of trusting beliefs and trusting intentions together with the Technology Acceptance Model variables, privacy, and security as well as individual characteristics. Results from 762 retail bank customers revealed a strong mediating role of trusting intention on the intention to use and similar patterns of relationship for the two technology-based bank channels. Several implications for managers and further research are discussed. © 2010 Wiley Periodicals, Inc. [source] GENETIC STUDY: The dopamine D4 Receptor (DRD4) gene exon III polymorphism, problematic alcohol use and novelty seeking: direct and mediated genetic effectsADDICTION BIOLOGY, Issue 2 2009Lara A. Ray ABSTRACT The present study sought to integrate convergent lines of research on the associations among the dopamine D4 receptor (DRD4) gene, novelty seeking and drinking behaviors with the overall goal of elucidating genetic influences on problematic drinking in young adulthood. Specifically, this study tested a model in which novelty seeking mediated the relationship between DRD4 variable number of tandem repeats (VNTR) genotype and problematic alcohol use. Participants (n = 90, 40 females) were heavy-drinking college students. Analyses using a structural equation modeling framework suggested that the significant direct path between DRD4 VNTR genotype and problematic alcohol use was reduced to a trend level in the context of a model that included novelty seeking as a mediator, thereby suggesting that the effects of DRD4 VNTR genotype on problematic alcohol use among heavy-drinking young adults were partially mediated by novelty seeking. Cross-group comparisons indicated that the relationships among the model variables were not significantly different in models for men versus women. These results extend recent findings of the association between this polymorphism of the DRD4 receptor gene, problematic alcohol use and novelty seeking. These findings may also help elucidate the specific pathways of risk associated with genetic influences on alcohol use and abuse phenotypes. [source] The costs and benefits of lifelong learning: The case of the NetherlandsHUMAN RESOURCE DEVELOPMENT QUARTERLY, Issue 2 2002Marko J. van Leeuwen This article deals with costs and benefits related to on-the-job training. For calculating costs and benefits of on-the-job training at the sector and macroeconomic levels, a model is developed. Model parameters are estimated using information from a survey of employers and employees in the Netherlands. Exogenous model variables are taken from the survey as well as from several official statistical sources. The model is used for running a baseline scenario and several policy scenarios. The policy scenarios describe proposed policy measures for stimulating lifelong learning in the Netherlands. The model calculates detailed costs and benefits for players in the market for on-the-job training and the macroeconomic consequences. It is shown that the differences in cost-effectiveness of policy measures can be large. Another important conclusion is that the results may differ strongly among employers, employees, and the government. [source] High-dimensional model representation for structural reliability analysisINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 4 2009Rajib Chowdhury Abstract This paper presents a new computational tool for predicting failure probability of structural/mechanical systems subject to random loads, material properties, and geometry. The method involves high-dimensional model representation (HDMR) that facilitates lower-dimensional approximation of the original high-dimensional implicit limit state/performance function, response surface generation of HDMR component functions, and Monte Carlo simulation. HDMR is a general set of quantitative model assessment and analysis tools for capturing the high-dimensional relationships between sets of input and output model variables. It is a very efficient formulation of the system response, if higher-order variable correlations are weak, allowing the physical model to be captured by the first few lower-order terms. Once the approximate form of the original implicit limit state/performance function is defined, the failure probability can be obtained by statistical simulation. Results of nine numerical examples involving mathematical functions and structural mechanics problems indicate that the proposed method provides accurate and computationally efficient estimates of the probability of failure. Copyright © 2008 John Wiley & Sons, Ltd. [source] High dimensional model representation for piece-wise continuous function approximationINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING, Issue 12 2008Rajib Chowdhury Abstract High dimensional model representation (HDMR) approximates multivariate functions in such a way that the component functions of the approximation are ordered starting from a constant and gradually approaching to multivariance as we proceed along the terms like first-order, second-order and so on. Until now HDMR applications include construction of a computational model directly from laboratory/field data, creating an efficient fully equivalent operational model to replace an existing time-consuming mathematical model, identification of key model variables, global uncertainty assessments, efficient quantitative risk assessments, etc. In this paper, the potential of HDMR for tackling univariate and multivariate piece-wise continuous functions is explored. Eight numerical examples are presented to illustrate the performance of HDMR for approximating a univariate or a multivariate piece-wise continuous function with an equivalent continuous function. Copyright © 2007 John Wiley & Sons, Ltd. [source] Associations of Sexual Victimization, Depression, and Sexual Assertiveness with Unprotected Sex: A Test of the Multifaceted Model of HIV Risk Across GenderJOURNAL OF APPLIED BIOBEHAVIORAL RESEARCH, Issue 1 2009Patricia J. Morokoff This study examined whether the Multifaceted Model of HIV Risk (MMOHR) would predict unprotected sex based on predictors including gender, childhood sexual abuse (CSA), sexual victimization (SV), depression, and sexual assertiveness for condom use. A community-based sample of 473 heterosexually active men and women, aged 18,46 years completed survey measures of model variables. Gender predicted several variables significantly. A separate model for women demonstrated excellent fit, while the model for men demonstrated reasonable fit. Multiple sample model testing supported the use of MMOHR in both men and women, while simultaneously highlighting areas of gender difference. Prevention interventions should focus on sexual assertiveness, especially for CSA and SV survivors, as well as targeting depression, especially among men. [source] A comparison of cloud-resolving model simulations of trade wind cumulus with aircraft observations taken during RICOTHE QUARTERLY JOURNAL OF THE ROYAL METEOROLOGICAL SOCIETY, Issue 624 2007S. J. Abel Abstract This paper presents results from simulations of trade wind cumulus with the Met Office Large Eddy Model (LEM) based on observed environmental profiles from the Rain In Cumulus over the Ocean (RICO) field experiment. Comparisons of updraught core parameters are made with the in situ data collected onboard the three research aircraft that participated in RICO. The default set-up of the LEM was unable to produce sufficient amounts of rainwater content when compared to measurements by the aircraft. As a main aim of RICO was to quantify the importance of precipitation in the trade cumulus regime, we test the sensitivity of the model to changes in the rain microphysics, the large-scale forcing, and horizontal resolution. By changing these model variables we are able to obtain reasonably good agreement with the observations of updraught core vertical velocity, cloud and rainwater contents. Furthermore, the LEM produces comparable surface precipitation rates to those derived from radar measurements during RICO in a previous study. This gives us some confidence in the ability of the LEM to simulate realistic precipitating trade cumulus. Copyright © 2007 Royal Meteorological Society [source] Structural Validity and Generalisability of a Referent Cognitions Model of Turnover IntentionsAPPLIED PSYCHOLOGY, Issue 4 2009David G. Allen A model proposed and empirically tested by Aquino, Griffeth, Allen, and Hom (1997) using employees of a hospital in the northeastern United States was replicated in samples of Korean factory workers from two divisions of a large organisation. Results in both samples suggested that the relationships among model variables and relationships with withdrawal cognitions replicated quite closely. Results also suggested that the way people are treated in an organisation by their supervisors exerts a powerful effect on their turnover-related responses. Most importantly, the results of this study in combination with the earlier results from Aquino et al. (1997) highlight the impact of employee expectations of future job advancement on turnover-related responses. Employees who perceive that their present situation will improve are more satisfied with their present outcomes and their supervisors. They are also less likely to consider quitting even when being unsatisfied with their present situation. Un modèle proposé et testé empiriquement par Aquino, Griffeth, Allen, and Hom (1997) sur des employés d'un hôpital du nord des Etats-Unis a été réutilisé auprès de plusieurs échantillons de travailleurs d'une usine coréenne appartenant à deux divisions d'une grande organisation. Les résultats sur les deux échantillons montrent que les relations entre les variables du modèle et les relations avec les cognitions défaillantes reproduisent de très près ceux du modèle original. Les résultats montrent aussi que la façon dont les salariés sont traités dans une organisation par leurs supérieurs a de fortes retombées sur leurs réponses concernant les démissions. Plus important encore, les résultats de cette étude en concordance avec ceux initiaux obtenus par Aquino et al. (1997), soulignent l'impact des attentes des employés à propos de leur avancement dans leur futur emploi sur leurs réponses concernant les démissions. Les employés qui perçoivent que leur situation présente va s'améliorer sont plus satisfaits de leur rémunération présente et de leurs supérieurs. Ils sont aussi moins enclins à envisager de démissionner même s'ils sont insatisfaits de leur situation présente. [source] A Goodness-of-Fit Test for Multinomial Logistic RegressionBIOMETRICS, Issue 4 2006Jelle J. Goeman Summary This article presents a score test to check the fit of a logistic regression model with two or more outcome categories. The null hypothesis that the model fits well is tested against the alternative that residuals of samples close to each other in covariate space tend to deviate from the model in the same direction. We propose a test statistic that is a sum of squared smoothed residuals, and show that it can be interpreted as a score test in a random effects model. By specifying the distance metric in covariate space, users can choose the alternative against which the test is directed, making it either an omnibus goodness-of-fit test or a test for lack of fit of specific model variables or outcome categories. [source] Mortality at 120 days after prostatic biopsy: A population-based study of 22,175 menINTERNATIONAL JOURNAL OF CANCER, Issue 3 2008Andrea Gallina Abstract Trans-rectal ultrasound guided biopsy of the prostate represents the diagnostic standard for prostate cancer, but its mortality rate has never been examined. We performed a population-based study of 120-day mortality after prostate biopsy in 22,175 patients, who underwent prostate biopsy between 1989 and 2000. The control group consisted of 1,778 men aged 65,85 years (median 69.5), who did not undergo a biopsy. Univariable and multivariable logistic regression analyses were performed in 11,087 of 22,175 (50%) men subjected to prostate biopsy, to identify predictors of 120-day mortality. Variables were age at biopsy, baseline Charlson comorbidity index and cumulative number of biopsy procedures. We externally validated the model's predictors in the remaining 50% of men. Overall 120-day mortality after biopsy was 1.3% versus 0.3% (p < 0.001) in the control group. Of men aged ,60 years, 0.2% died within 120 days versus 2.5% aged 76,80. Zero Charlson comorbidity score yielded 0.7% mortality versus 2.2%, if 3,4. First ever biopsy procedures carried a higher mortality risk than subsequent procedures (1.4 vs. 0.8 vs. 0.6%). In the multivariable model, first ever biopsy, increasing age and comorbidity predicted higher mortality. Overall, the model's variables were 79% accurate in predicting the probability of 120-day mortality after biopsy. In conclusion, our data suggest that prostate biopsy might predispose to higher mortality rate. The certainty of this association remains to be proven. © 2008 Wiley-Liss, Inc. [source] | ||||||||||||||||