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Sample records for parametric competing risks

  1. Parametric likelihood inference for interval censored competing risks data.

    PubMed

    Hudgens, Michael G; Li, Chenxi; Fine, Jason P

    2014-03-01

    Parametric estimation of the cumulative incidence function (CIF) is considered for competing risks data subject to interval censoring. Existing parametric models of the CIF for right censored competing risks data are adapted to the general case of interval censoring. Maximum likelihood estimators for the CIF are considered under the assumed models, extending earlier work on nonparametric estimation. A simple naive likelihood estimator is also considered that utilizes only part of the observed data. The naive estimator enables separate estimation of models for each cause, unlike full maximum likelihood in which all models are fit simultaneously. The naive likelihood is shown to be valid under mixed case interval censoring, but not under an independent inspection process model, in contrast with full maximum likelihood which is valid under both interval censoring models. In simulations, the naive estimator is shown to perform well and yield comparable efficiency to the full likelihood estimator in some settings. The methods are applied to data from a large, recent randomized clinical trial for the prevention of mother-to-child transmission of HIV.

  2. Parametric Estimation in a Recurrent Competing Risks Model.

    PubMed

    Taylor, Laura L; Peña, Edsel A

    2013-01-01

    A resource-efficient approach to making inferences about the distributional properties of the failure times in a competing risks setting is presented. Efficiency is gained by observing recurrences of the competing risks over a random monitoring period. The resulting model is called the recurrent competing risks model (RCRM) and is coupled with two repair strategies whenever the system fails. Maximum likelihood estimators of the parameters of the marginal distribution functions associated with each of the competing risks and also of the system lifetime distribution function are presented. Estimators are derived under perfect and partial repair strategies. Consistency and asymptotic properties of the estimators are obtained. The estimation methods are applied to a data set of failures for cars under warranty. Simulation studies are used to ascertain the small sample properties and the efficiency gains of the resulting estimators.

  3. Non-parametric estimation of bivariate failure time associations in the presence of a competing risk.

    PubMed

    Bandeen-Roche, Karen; Ning, Jing

    2008-03-01

    Most research on the study of associations among paired failure times has either assumed time invariance or been based on complex measures or estimators. Little has accommodated competing risks. This paper targets the conditional cause-specific hazard ratio, henceforth called the cause-specific cross ratio, a recent modification of the conditional hazard ratio designed to accommodate competing risks data. Estimation is accomplished by an intuitive, non-parametric method that localizes Kendall's tau. Time variance is accommodated through a partitioning of space into 'bins' between which the strength of association may differ. Inferential procedures are developed, small-sample performance is evaluated and the methods are applied to the investigation of familial association in dementia onset.

  4. Modelling childhood caries using parametric competing risks survival analysis methods for clustered data.

    PubMed

    Stephenson, J; Chadwick, B L; Playle, R A; Treasure, E T

    2010-01-01

    Caries in primary teeth is an ongoing issue in children's dental health. Its quantification is affected by clustering of data within children and the concurrent risk of exfoliation of primary teeth. This analysis of caries data of 103,776 primary molar tooth surfaces from a cohort study of 2,654 British children aged 4-5 years at baseline applied multilevel competing risks survival analysis methodology to identify factors significantly associated with caries occurrence in primary tooth surfaces in the presence of the concurrent risk of exfoliation, and assessed the effect of exfoliation on caries development. Multivariate multilevel parametric survival models were applied at surface level to the analysis of the sound-carious and sound-exfoliation transitions to which primary tooth surfaces are subject. Socio-economic class, fluoridation status and surface type were found to be the strongest predictors of primary caries, with the highest rates of occurrence and lowest median survival times associated with occlusal surfaces of children from poor socio-economic class living in non-fluoridated areas. The concurrent risk of exfoliation was shown to reduce the distinction in survival experience between different types of surfaces, and between surfaces of teeth from children of different socio-economic class or fluoridation status. Clustering of data had little effect on inferences of parameter significance.

  5. Parametric mixture models to evaluate and summarize hazard ratios in the presence of competing risks with time-dependent hazards and delayed entry

    PubMed Central

    Lau, Bryan; Cole, Stephen R.; Gange, Stephen J.

    2010-01-01

    In the analysis of survival data, there are often competing events that preclude an event of interest from occurring. Regression analysis with competing risks is typically undertaken using a cause-specific proportional hazards model. However, modern alternative methods exist for the analysis of the subdistribution hazard with a corresponding subdistribution proportional hazards model. In this paper, we introduce a flexible parametric mixture model as a unifying method to obtain estimates of the cause-specific and subdistribution hazards and hazard ratio functions. We describe how these estimates can be summarized over time to give a single number that is comparable to the hazard ratio that is obtained from a corresponding cause-specific or subdistribution proportional hazards model. An application to the Women’s Interagency HIV Study is provided to investigate injection drug use and the time to either the initiation of effective antiretroviral therapy, or clinical disease progression as a competing event. PMID:21337360

  6. Meta-analysis for aggregated survival data with competing risks: a parametric approach using cumulative incidence functions.

    PubMed

    Bonofiglio, Federico; Beyersmann, Jan; Schumacher, Martin; Koller, Michael; Schwarzer, Guido

    2016-09-01

    Meta-analysis of a survival endpoint is typically based on the pooling of hazard ratios (HRs). If competing risks occur, the HRs may lose translation into changes of survival probability. The cumulative incidence functions (CIFs), the expected proportion of cause-specific events over time, re-connect the cause-specific hazards (CSHs) to the probability of each event type. We use CIF ratios to measure treatment effect on each event type. To retrieve information on aggregated, typically poorly reported, competing risks data, we assume constant CSHs. Next, we develop methods to pool CIF ratios across studies. The procedure computes pooled HRs alongside and checks the influence of follow-up time on the analysis. We apply the method to a medical example, showing that follow-up duration is relevant both for pooled cause-specific HRs and CIF ratios. Moreover, if all-cause hazard and follow-up time are large enough, CIF ratios may reveal additional information about the effect of treatment on the cumulative probability of each event type. Finally, to improve the usefulness of such analysis, better reporting of competing risks data is needed. Copyright © 2015 John Wiley & Sons, Ltd. Copyright © 2015 John Wiley & Sons, Ltd.

  7. Prediction of long-term cumulative incidences based on short-term parametric model for competing risks: application in early breast cancer.

    PubMed

    Cabarrou, B; Belin, L; Somda, S M; Falcou, M C; Pierga, J Y; Kirova, Y; Delord, J P; Asselain, B; Filleron, T

    2016-04-01

    Use of parametric statistical models can be a solution to reduce the follow-up period time required to estimate long-term survival. Mould and Boag were the first to use the lognormal model. Competing risks methodology seems more suitable when a particular event type is of interest than classical survival analysis. The objective was to evaluate the ability of the Jeong and Fine model to predict long-term cumulative incidence. Survival data recorded by Institut Curie (Paris) from 4761 breast cancer patients treated and followed between 1981 and 2013 were used. Long-term cumulative incidence rates predicted by the model using short-term follow-up data were compared to non-parametric estimation using complete follow-up data. 20- or 25-year cumulative incidence rates for loco-regional recurrence and distant metastasis predicted by the model using a maximum of 10 years of follow-up data had a maximum difference of around 6 % compared to non-parametric estimation. Prediction rates were underestimated for the third and composite event (contralateral or second cancer or death). Predictive ability of Jeong and Fine model on breast cancer data was generally good considering the short follow-up period time used for the estimation especially when a proportion of patient did not experience loco-regional recurrence or distant metastasis.

  8. Non-parametric estimation of the case fatality ratio with competing risks data: an application to Severe Acute Respiratory Syndrome (SARS).

    PubMed

    Jewell, Nicholas P; Lei, Xiudong; Ghani, Azra C; Donnelly, Christl A; Leung, Gabriel M; Ho, Lai-Ming; Cowling, Benjamin J; Hedley, Anthony J

    2007-04-30

    For diseases with some level of associated mortality, the case fatality ratio measures the proportion of diseased individuals who die from the disease. In principle, it is straightforward to estimate this quantity from individual follow-up data that provides times from onset to death or recovery. In particular, in a competing risks context, the case fatality ratio is defined by the limiting value of the sub-distribution function, F(1)(t) = Pr(T infinity, where T denotes the time from onset to death (J = 1) or recovery (J = 2). When censoring is present, however, estimation of F(1)(infinity) is complicated by the possibility of little information regarding the right tail of F(1), requiring use of estimators of F(1)(t(*)) or F(1)(t(*))/(F(1)(t(*))+F(2)(t(*))) where t(*) is large, with F(2)(t) = Pr(T parametric estimators of F(1) and F(2). The ideas are illustrated on case fatality data for individuals infected with Severe Acute Respiratory Syndrome (SARS) in Hong Kong in 2003.

  9. Recursive Partitioning Method on Competing Risk Outcomes

    PubMed Central

    Xu, Wei; Che, Jiahua; Kong, Qin

    2016-01-01

    In some cancer clinical studies, researchers have interests to explore the risk factors associated with competing risk outcomes such as recurrence-free survival. We develop a novel recursive partitioning framework on competing risk data for both prognostic and predictive model constructions. We define specific splitting rules, pruning algorithm, and final tree selection algorithm for the competing risk tree models. This methodology is quite flexible that it can corporate both semiparametric method using Cox proportional hazards model and parametric competing risk model. Both prognostic and predictive tree models are developed to adjust for potential confounding factors. Extensive simulations show that our methods have well-controlled type I error and robust power performance. Finally, we apply both Cox proportional hazards model and flexible parametric model for prognostic tree development on a retrospective clinical study on oropharyngeal cancer patients. PMID:27486300

  10. Random survival forests for competing risks

    PubMed Central

    Ishwaran, Hemant; Gerds, Thomas A.; Kogalur, Udaya B.; Moore, Richard D.; Gange, Stephen J.; Lau, Bryan M.

    2014-01-01

    We introduce a new approach to competing risks using random forests. Our method is fully non-parametric and can be used for selecting event-specific variables and for estimating the cumulative incidence function. We show that the method is highly effective for both prediction and variable selection in high-dimensional problems and in settings such as HIV/AIDS that involve many competing risks. PMID:24728979

  11. Competing mortality and fracture risk assessment.

    PubMed

    Leslie, W D; Lix, L M; Wu, X

    2013-02-01

    Failure to account for competing mortality gave higher estimates of 10-year fracture probability than if appropriate adjustment is made for competing mortality, particularly among subgroups with higher mortality. A modified Kaplan-Meier method is easy to implement and provides an alternative approach to existing methods for competing mortality risk adjustment. A unique feature of FRAX(®) is that 10-year fracture probability accounts for mortality as a competing risk. We compared the effect of competing mortality adjustment on nonparametric and parametric methods of fracture probability estimation. The Manitoba Bone Mineral Density (BMD) database was used to identify men and women age ≥50 years with FRAX probabilities calculated using femoral neck BMD (N = 39,063). Fractures were assessed from administrative data (N = 2,543 with a major osteoporotic fracture, N = 549 with a hip fracture during mean 5.3 years follow-up). The following subgroups with higher mortality were identified: men, age >80 years, high fracture probability, and presence of diabetes. Failure to account for competing mortality in these subgroups overestimated fracture probability by 16-56 % with the standard nonparametric (Kaplan-Meier) method and 15-29 % with the standard parametric (Cox) model. When the outcome was hip fractures, failure to account for competing mortality overestimated hip fracture probability by 18-36 % and 17-35 %, respectively. A simple modified Kaplan-Meier method showed very close agreement with methods that adjusted for competing mortality (within 2 %). Failure to account for competing mortality risk gives considerably higher estimates of 10-year fracture probability than if adjustment is made for this competing risk.

  12. Penalized variable selection in competing risks regression.

    PubMed

    Fu, Zhixuan; Parikh, Chirag R; Zhou, Bingqing

    2017-07-01

    Penalized variable selection methods have been extensively studied for standard time-to-event data. Such methods cannot be directly applied when subjects are at risk of multiple mutually exclusive events, known as competing risks. The proportional subdistribution hazard (PSH) model proposed by Fine and Gray (J Am Stat Assoc 94:496-509, 1999) has become a popular semi-parametric model for time-to-event data with competing risks. It allows for direct assessment of covariate effects on the cumulative incidence function. In this paper, we propose a general penalized variable selection strategy that simultaneously handles variable selection and parameter estimation in the PSH model. We rigorously establish the asymptotic properties of the proposed penalized estimators and modify the coordinate descent algorithm for implementation. Simulation studies are conducted to demonstrate the good performance of the proposed method. Data from deceased donor kidney transplants from the United Network of Organ Sharing illustrate the utility of the proposed method.

  13. Multilevel joint competing risk models

    NASA Astrophysics Data System (ADS)

    Karunarathna, G. H. S.; Sooriyarachchi, M. R.

    2017-09-01

    Joint modeling approaches are often encountered for different outcomes of competing risk time to event and count in many biomedical and epidemiology studies in the presence of cluster effect. Hospital length of stay (LOS) has been the widely used outcome measure in hospital utilization due to the benchmark measurement for measuring multiple terminations such as discharge, transferred, dead and patients who have not completed the event of interest at the follow up period (censored) during hospitalizations. Competing risk models provide a method of addressing such multiple destinations since classical time to event models yield biased results when there are multiple events. In this study, the concept of joint modeling has been applied to the dengue epidemiology in Sri Lanka, 2006-2008 to assess the relationship between different outcomes of LOS and platelet count of dengue patients with the district cluster effect. Two key approaches have been applied to build up the joint scenario. In the first approach, modeling each competing risk separately using the binary logistic model, treating all other events as censored under the multilevel discrete time to event model, while the platelet counts are assumed to follow a lognormal regression model. The second approach is based on the endogeneity effect in the multilevel competing risks and count model. Model parameters were estimated using maximum likelihood based on the Laplace approximation. Moreover, the study reveals that joint modeling approach yield more precise results compared to fitting two separate univariate models, in terms of AIC (Akaike Information Criterion).

  14. Frailty-Based Competing Risks Model for Multivariate Survival Data

    PubMed Central

    Gorfine, Malka; Hsu, Li

    2011-01-01

    SUMMARY In this work, we provide a new class of frailty-based competing risks models for clustered failure times data. This class is based on expanding the competing risks model of Prentice et al. (1978, Biometrics 34, 541–554) to incorporate frailty variates, with the use of cause-specific proportional hazards frailty models for all the causes. Parametric and nonparametric maximum likelihood estimators are proposed. The main advantages of the proposed class of models, in contrast to the existing models, are: (1) the inclusion of covariates; (2) the flexible structure of the dependency among the various types of failure times within a cluster; and (3) the unspecified within-subject dependency structure. The proposed estimation procedures produce the most efficient parametric and semiparametric estimators and are easy to implement. Simulation studies show that the proposed methods perform very well in practical situations. PMID:20707868

  15. Cumulative Incidence Association Models for Bivariate Competing Risks Data.

    PubMed

    Cheng, Yu; Fine, Jason P

    2012-03-01

    Association models, like frailty and copula models, are frequently used to analyze clustered survival data and evaluate within-cluster associations. The assumption of noninformative censoring is commonly applied to these models, though it may not be true in many situations. In this paper, we consider bivariate competing risk data and focus on association models specified for the bivariate cumulative incidence function (CIF), a nonparametrically identifiable quantity. Copula models are proposed which relate the bivariate CIF to its corresponding univariate CIFs, similarly to independently right censored data, and accommodate frailty models for the bivariate CIF. Two estimating equations are developed to estimate the association parameter, permitting the univariate CIFs to be estimated either parametrically or nonparametrically. Goodness-of-fit tests are presented for formally evaluating the parametric models. Both estimators perform well with moderate sample sizes in simulation studies. The practical use of the methodology is illustrated in an analysis of dementia associations.

  16. Creating Efficient Instrumentation Networks to Support Parametric Risk Transfer

    NASA Astrophysics Data System (ADS)

    Rockett, P.

    2009-04-01

    The development and institutionalisation of Catastrophe modelling during the 1990s opened the way for Catastrophe risk securitization transactions in which catastrophe risk held by insurers is transferred to the capital markets in the form of a bond. Cat Bonds have been one of the few areas of the capital markets in which the risk modelling has remained secure and the returns on the bonds have held up well through the 2008 Credit Crunch. There are three ways of structuring the loss triggers on bonds: ‘indemnity triggers' - reflecting the actual losses to the issuers; ‘index triggers' reflecting the losses to some index such as reported insurance industry loss and ‘parametric triggers' reflecting the parameters of the underlying catastrophe event itself. Indemnity triggers require that the investors trust that the insurer is reporting all their underlying exposures, while both indemnity and index losses may take 1-2 years to settle before all the claims are reported and resolved. Therefore parametric structures have many advantages, in particular in that the bond can be settled rapidly after an event. The challenge is to create parametric indices that closely reflect the actual losses to the insurer - ie that minimise ‘basis risk'. First generation parametric indices had high basis risk as they were crudely based on the magnitude of an earthquake occurring within some defined geographical box, or the intensity of a hurricane relative to the distance of the storm from some location. Second generation triggers involve taking measurements of ground motion or windspeed or flood depths at many locations and weighting each value so that the overall index closely mimics insurance loss. Cat bonds with second generation parametric triggers have been successfully issued for European Windstorm, UK Flood and California and Japan Earthquake. However the spread of second generation parametric structures is limited by the availability of suitable networks of

  17. Familial Risk and Child Competence.

    ERIC Educational Resources Information Center

    Sameroff, Arnold J.; Seifer, Ronald

    1983-01-01

    Examines components of familial risk in the context of a four-year longitudinal study of children with mentally ill mothers. Risk factors examined were parental mental health, social status, parental perspectives, and family stress. Interactions among risk factors were found to be complex and different for cognitive and social-emotional…

  18. Familial Risk and Child Competence.

    ERIC Educational Resources Information Center

    Sameroff, Arnold J.; Seifer, Ronald

    1983-01-01

    Examines components of familial risk in the context of a four-year longitudinal study of children with mentally ill mothers. Risk factors examined were parental mental health, social status, parental perspectives, and family stress. Interactions among risk factors were found to be complex and different for cognitive and social-emotional…

  19. Minimization of Basis Risk in Parametric Earthquake Cat Bonds

    NASA Astrophysics Data System (ADS)

    Franco, G.

    2009-12-01

    A catastrophe -cat- bond is an instrument used by insurance and reinsurance companies, by governments or by groups of nations to cede catastrophic risk to the financial markets, which are capable of supplying cover for highly destructive events, surpassing the typical capacity of traditional reinsurance contracts. Parametric cat bonds, a specific type of cat bonds, use trigger mechanisms or indices that depend on physical event parameters published by respected third parties in order to determine whether a part or the entire bond principal is to be paid for a certain event. First generation cat bonds, or cat-in-a-box bonds, display a trigger mechanism that consists of a set of geographic zones in which certain conditions need to be met by an earthquake’s magnitude and depth in order to trigger payment of the bond principal. Second generation cat bonds use an index formulation that typically consists of a sum of products of a set of weights by a polynomial function of the ground motion variables reported by a geographically distributed seismic network. These instruments are especially appealing to developing countries with incipient insurance industries wishing to cede catastrophic losses to the financial markets because the payment trigger mechanism is transparent and does not involve the parties ceding or accepting the risk, significantly reducing moral hazard. In order to be successful in the market, however, parametric cat bonds have typically been required to specify relatively simple trigger conditions. The consequence of such simplifications is the increase of basis risk. This risk represents the possibility that the trigger mechanism fails to accurately capture the actual losses of a catastrophic event, namely that it does not trigger for a highly destructive event or vice versa, that a payment of the bond principal is caused by an event that produced insignificant losses. The first case disfavors the sponsor who was seeking cover for its losses while the

  20. Survival analysis in the presence of competing risks.

    PubMed

    Zhang, Zhongheng

    2017-02-01

    Survival analysis in the presence of competing risks imposes additional challenges for clinical investigators in that hazard function (the rate) has no one-to-one link to the cumulative incidence function (CIF, the risk). CIF is of particular interest and can be estimated non-parametrically with the use cuminc() function. This function also allows for group comparison and visualization of estimated CIF. The effect of covariates on cause-specific hazard can be explored using conventional Cox proportional hazard model by treating competing events as censoring. However, the effect on hazard cannot be directly linked to the effect on CIF because there is no one-to-one correspondence between hazard and cumulative incidence. Fine-Gray model directly models the covariate effect on CIF and it reports subdistribution hazard ratio (SHR). However, SHR only provide information on the ordering of CIF curves at different levels of covariates, it has no practical interpretation as HR in the absence of competing risks. Fine-Gray model can be fit with crr() function shipped with the cmprsk package. Time-varying covariates are allowed in the crr() function, which is specified by cov2 and tf arguments. Predictions and visualization of CIF for subjects with given covariate values are allowed for crr object. Alternatively, competing risk models can be fit with riskRegression package by employing different link functions between covariates and outcomes. The assumption of proportionality can be checked by testing statistical significance of interaction terms involving failure time. Schoenfeld residuals provide another way to check model assumption.

  1. Survival analysis in the presence of competing risks

    PubMed Central

    2017-01-01

    Survival analysis in the presence of competing risks imposes additional challenges for clinical investigators in that hazard function (the rate) has no one-to-one link to the cumulative incidence function (CIF, the risk). CIF is of particular interest and can be estimated non-parametrically with the use cuminc() function. This function also allows for group comparison and visualization of estimated CIF. The effect of covariates on cause-specific hazard can be explored using conventional Cox proportional hazard model by treating competing events as censoring. However, the effect on hazard cannot be directly linked to the effect on CIF because there is no one-to-one correspondence between hazard and cumulative incidence. Fine-Gray model directly models the covariate effect on CIF and it reports subdistribution hazard ratio (SHR). However, SHR only provide information on the ordering of CIF curves at different levels of covariates, it has no practical interpretation as HR in the absence of competing risks. Fine-Gray model can be fit with crr() function shipped with the cmprsk package. Time-varying covariates are allowed in the crr() function, which is specified by cov2 and tf arguments. Predictions and visualization of CIF for subjects with given covariate values are allowed for crr object. Alternatively, competing risk models can be fit with riskRegression package by employing different link functions between covariates and outcomes. The assumption of proportionality can be checked by testing statistical significance of interaction terms involving failure time. Schoenfeld residuals provide another way to check model assumption. PMID:28251126

  2. Calibrated predictions for multivariate competing risks models.

    PubMed

    Gorfine, Malka; Hsu, Li; Zucker, David M; Parmigiani, Giovanni

    2014-04-01

    Prediction models for time-to-event data play a prominent role in assessing the individual risk of a disease, such as cancer. Accurate disease prediction models provide an efficient tool for identifying individuals at high risk, and provide the groundwork for estimating the population burden and cost of disease and for developing patient care guidelines. We focus on risk prediction of a disease in which family history is an important risk factor that reflects inherited genetic susceptibility, shared environment, and common behavior patterns. In this work family history is accommodated using frailty models, with the main novel feature being allowing for competing risks, such as other diseases or mortality. We show through a simulation study that naively treating competing risks as independent right censoring events results in non-calibrated predictions, with the expected number of events overestimated. Discrimination performance is not affected by ignoring competing risks. Our proposed prediction methodologies correctly account for competing events, are very well calibrated, and easy to implement.

  3. Non-parametric estimation of spatial variation in relative risk.

    PubMed

    Kelsall, J E; Diggle, P J

    We consider the problem of estimating the spatial variation in relative risks of two diseases, say, over a geographical region. Using an underlying Poisson point process model, we approach the problem as one of density ratio estimation implemented with a non-parametric kernel smoothing method. In order to assess the significance of any local peaks or troughs in the estimated risk surface, we introduce pointwise tolerance contours which can enhance a greyscale image plot of the estimate. We also propose a Monte Carlo test of the null hypothesis of constant risk over the whole region, to avoid possible over-interpretation of the estimated risk surface. We illustrate the capabilities of the methodology with two epidemiological examples.

  4. Number needed to treat for time-to-event data with competing risks.

    PubMed

    Gouskova, Natalia A; Kundu, Suprateek; Imrey, Peter B; Fine, Jason P

    2014-01-30

    The number needed to treat is a tool often used in clinical settings to illustrate the effect of a treatment. It has been widely adopted in the communication of risks to both clinicians and non-clinicians, such as patients, who are better able to understand this measure than absolute risk or rate reductions. The concept was introduced by Laupacis, Sackett, and Roberts in 1988 for binary data, and extended to time-to-event data by Altman and Andersen in 1999. However, up to the present, there is no definition of the number needed to treat for time-to-event data with competing risks. This paper introduces such a definition using the cumulative incidence function and suggests non-parametric and semi-parametric inferential methods for right-censored time-to-event data in the presence of competing risks. The procedures are illustrated using the data from a breast cancer clinical trial. Copyright © 2013 John Wiley & Sons, Ltd.

  5. Risks, risk assessment and risk competence in toxicology

    PubMed Central

    Stahlmann, Ralf; Horvath, Aniko

    2015-01-01

    Understanding the toxic effects of xenobiotics requires sound knowledge of physiology and biochemistry. The often described lack of understanding pharmacology/toxicology is therefore primarily caused by the general absence of the necessary fundamental knowledge. Since toxic effects depend on exposure (or dosage) assessing the risks arising from toxic substances also requires quantitative reasoning. Typically public discussions nearly always neglect quantitative aspects and laypersons tend to disregard dose-effect-relationships. One of the main reasons for such disregard is the fact that exposures often occur at extremely low concentrations that can only be perceived intellectually but not by the human senses. However, thresholds in the low exposure range are often scientifically disputed. At the same time, ignorance towards known dangers is wide-spread. Thus, enhancing the risk competence of laypersons will have to be initially restricted to increasing the awareness of existing problems. PMID:26195922

  6. Competing Risks Regression for Stratified Data

    PubMed Central

    Zhou, Bingqing; Latouche, Aurelien; Rocha, Vanderson; Fine, Jason

    2012-01-01

    Summary For competing risks data, the Fine–Gray proportional hazards model for subdistribution has gained popularity for its convenience in directly assessing the effect of covariates on the cumulative incidence function. However, in many important applications, proportional hazards may not be satisfied, including multicenter clinical trials, where the baseline subdistribution hazards may not be common due to varying patient populations. In this article, we consider a stratified competing risks regression, to allow the baseline hazard to vary across levels of the stratification covariate. According to the relative size of the number of strata and strata sizes, two stratification regimes are considered. Using partial likelihood and weighting techniques, we obtain consistent estimators of regression parameters. The corresponding asymptotic properties and resulting inferences are provided for the two regimes separately. Data from a breast cancer clinical trial and from a bone marrow transplantation registry illustrate the potential utility of the stratified Fine–Gray model. PMID:21155744

  7. Comparison of competing risks models based on cumulative incidence function in analyzing time to cardiovascular diseases.

    PubMed

    Dianatkhah, Minoo; Rahgozar, Mehdi; Talaei, Mohammad; Karimloua, Masoud; Sadeghi, Masoumeh; Oveisgharan, Shahram; Sarrafzadegan, Nizal

    2014-01-01

    Competing risks arise when the subject is exposed to more than one cause of failure. Data consists of the time that the subject failed and an indicator of which risk caused the subject to fail. With three approaches consisting of Fine and Gray, binomial, and pseudo-value, all of which are directly based on cumulative incidence function, cardiovascular disease data of the Isfahan Cohort Study were analyzed. Validity of proportionality assumption for these approaches is the basis for selecting appropriate models. Such as for the Fine and Gray model, establishing proportionality assumption is necessary. In the binomial approach, a parametric, non-parametric, or semi-parametric model was offered according to validity of assumption. However, pseudo-value approaches do not need to establish proportionality. Following fitting the models to data, slight differences in parameters and variances estimates were seen among models. This showed that semi-parametric multiplicative model and the two models based on pseudo-value approach could be used for fitting this kind of data. We would recommend considering the use of competing risk models instead of normal survival methods when subjects are exposed to more than one cause of failure.

  8. Competing risks to breast cancer mortality.

    PubMed

    Rosenberg, Marjorie A

    2006-01-01

    Simulation models analyzing the impact of treatment interventions and screening on the level of breast cancer mortality require an input of mortality from causes other than breast cancer, or competing risks. This chapter presents an actuarial method of creating cohort life tables using published data that removes breast cancer as a cause of death. Mortality from causes other than breast cancer as a percentage of all-cause mortality is smallest for women in their forties and fifties, as small as 85% of the all-cause rate, although the level and percentage of the impact varies by birth cohort. This method produces life tables by birth cohort and by age that are easily included as a common input by the various CISNET modeling groups to predict mortality from other causes. Attention to removing breast cancer mortality from all-cause mortality is worthwhile, because breast cancer mortality can be as high as 15% at some ages.

  9. The effects of misclassification of the actual cause of death in competing risks analysis.

    PubMed

    Ebrahimi, N

    1996-07-30

    The problem of competing risks analysis arises often in public health, demography, actuarial science, industrial reliability applications, and experiments in medical therapeutics. In the classical competing risks scenario one models the risks with a vector (T = (T1, ..., Tk) of non-negative random variables that represents the potential times to death of k risks. One cannot see T directly but sees instead Y = min (T1, ..., Tk) and the actual cause of death. The major difficulty with this analysis is the requirement for the expert to specify the single cause of death that, in fact, may not be the actual cause. This paper addresses competing risks analysis for the situations where one observes Y and the set of several possible causes of death specified by the expert. Many times there are several causes that act together and realistically it is impossible for the expert to assign a death to a single cause. In particular, I provide a likelihood for parametric competing risks analysis when the actual cause of death is possibly misclassified. The data include time to death, Y, and a set of possible causes of death. If misclassification probabilities are unknown, I propose a Baysian analysis based on a prior distribution for the parameters of interest and for the misclassification probabilities.

  10. Accelerated failure time models for semi-competing risks data in the presence of complex censoring.

    PubMed

    Lee, Kyu Ha; Rondeau, Virginie; Haneuse, Sebastien

    2017-04-10

    Statistical analyses that investigate risk factors for Alzheimer's disease (AD) are often subject to a number of challenges. Some of these challenges arise due to practical considerations regarding data collection such that the observation of AD events is subject to complex censoring including left-truncation and either interval or right-censoring. Additional challenges arise due to the fact that study participants under investigation are often subject to competing forces, most notably death, that may not be independent of AD. Towards resolving the latter, researchers may choose to embed the study of AD within the "semi-competing risks" framework for which the recent statistical literature has seen a number of advances including for the so-called illness-death model. To the best of our knowledge, however, the semi-competing risks literature has not fully considered analyses in contexts with complex censoring, as in studies of AD. This is particularly the case when interest lies with the accelerated failure time (AFT) model, an alternative to the traditional multiplicative Cox model that places emphasis away from the hazard function. In this article, we outline a new Bayesian framework for estimation/inference of an AFT illness-death model for semi-competing risks data subject to complex censoring. An efficient computational algorithm that gives researchers the flexibility to adopt either a fully parametric or a semi-parametric model specification is developed and implemented. The proposed methods are motivated by and illustrated with an analysis of data from the Adult Changes in Thought study, an on-going community-based prospective study of incident AD in western Washington State.

  11. The Functional Competency of Elderly at Risk.

    ERIC Educational Resources Information Center

    Stanley, Barbara; And Others

    1988-01-01

    Investigated functional competency to make informed decisions by elderly depressed and cognitively impaired psychiatric patients. Although depressed elderly patients did not appear to experience problems in informed consent process, cognitively impaired patients had difficulty understanding important aspects of consent information. Suggests that…

  12. Intervening on risk factors for coronary heart disease: an application of the parametric g-formula

    PubMed Central

    Taubman, Sarah L; Robins, James M; Mittleman, Murray A; Hernán, Miguel A

    2009-01-01

    Estimating the population risk of disease under hypothetical interventions—such as the population risk of coronary heart disease (CHD) were everyone to quit smoking and start exercising or to start exercising if diagnosed with diabetes—may not be possible using standard analytic techniques. The parametric g-formula, which appropriately adjusts for time-varying confounders affected by prior exposures, is especially well suited to estimating effects when the intervention involves multiple factors (joint interventions) or when the intervention involves decisions that depend on the value of evolving time-dependent factors (dynamic interventions). We describe the parametric g-formula, and use it to estimate the effect of various hypothetical lifestyle interventions on the risk of CHD using data from the Nurses’ Health Study. Over the period 1982–2002, the 20-year risk of CHD in this cohort was 3.50%. Under a joint intervention of no smoking, increased exercise, improved diet, moderate alcohol consumption and reduced body mass index, the estimated risk was 1.89% (95% confidence interval: 1.46–2.41). We discuss whether the assumptions required for the validity of the parametric g-formula hold in the Nurses’ Health Study data. This work represents the first large-scale application of the parametric g-formula in an epidemiologic cohort study. PMID:19389875

  13. A missing data approach to semi-competing risks problems.

    PubMed

    Dignam, James J; Wieand, Kelly; Rathouz, Paul J

    2007-02-20

    For event time data involving multiple mutually exclusive competing causes of failure, classic competing risks results show that marginal survival distributions are not identifiable. In a related instance, one or more failure modes may be observed provided that the failure events occur in a specific order. In such situations, sometimes referred to as semi-competing risks problems, the observations may under realistic assumptions lend information about parameters of interest that would be nonidentifiable in the strict competing risks case. Here, we present an approach that makes use of partially observable multiple modes of failures to obtain an estimate of the marginal distribution of one event type that may occur prior to the occurrence of another event type or be precluded by it. We apply the proposed method to the problem of estimating the distribution of time to tumour recurrence at specific sites among breast cancer patients participating in randomized clinical trials.

  14. Competing risk bias was common in Kaplan-Meier risk estimates published in prominent medical journals.

    PubMed

    van Walraven, Carl; McAlister, Finlay A

    2016-01-01

    Risk estimates from Kaplan-Meier curves are well known to medical researchers, reviewers, and editors. In this study, we determined the proportion of Kaplan-Meier analyses published in prominent medical journals that are potentially biased because of competing events ("competing risk bias"). We randomly selected 100 studies that had at least one Kaplan-Meier analysis and were recently published in prominent medical journals. Susceptibility to competing risk bias was determined by examining the outcome and potential competing events. In susceptible studies, bias was quantified using a previously validated prediction model when the number of outcomes and competing events were given. Forty-six studies (46%) contained Kaplan-Meier analyses susceptible to competing risk bias. Sixteen studies (34.8%) susceptible to competing risk cited the number of outcomes and competing events; in six of these studies (6/16, 37.5%), the outcome risk from the Kaplan-Meier estimate (relative to the true risk) was biased upward by 10% or more. Almost half of Kaplan-Meier analyses published in medical journals are susceptible to competing risk bias and may overestimate event risk. This bias was found to be quantitatively important in a third of such studies. Copyright © 2016 Elsevier Inc. All rights reserved.

  15. Crash risk analysis for Shanghai urban expressways: A Bayesian semi-parametric modeling approach.

    PubMed

    Yu, Rongjie; Wang, Xuesong; Yang, Kui; Abdel-Aty, Mohamed

    2016-10-01

    Urban expressway systems have been developed rapidly in recent years in China; it has become one key part of the city roadway networks as carrying large traffic volume and providing high traveling speed. Along with the increase of traffic volume, traffic safety has become a major issue for Chinese urban expressways due to the frequent crash occurrence and the non-recurrent congestions caused by them. For the purpose of unveiling crash occurrence mechanisms and further developing Active Traffic Management (ATM) control strategies to improve traffic safety, this study developed disaggregate crash risk analysis models with loop detector traffic data and historical crash data. Bayesian random effects logistic regression models were utilized as it can account for the unobserved heterogeneity among crashes. However, previous crash risk analysis studies formulated random effects distributions in a parametric approach, which assigned them to follow normal distributions. Due to the limited information known about random effects distributions, subjective parametric setting may be incorrect. In order to construct more flexible and robust random effects to capture the unobserved heterogeneity, Bayesian semi-parametric inference technique was introduced to crash risk analysis in this study. Models with both inference techniques were developed for total crashes; semi-parametric models were proved to provide substantial better model goodness-of-fit, while the two models shared consistent coefficient estimations. Later on, Bayesian semi-parametric random effects logistic regression models were developed for weekday peak hour crashes, weekday non-peak hour crashes, and weekend non-peak hour crashes to investigate different crash occurrence scenarios. Significant factors that affect crash risk have been revealed and crash mechanisms have been concluded.

  16. Teaching Risk Management: Addressing ACGME Core Competencies.

    PubMed

    Nissen, Kiki; Angus, Steven V; Miller, Wendy; Silverman, Adam R

    2010-12-01

    Risk management is an important aspect of education for all residents. Unfortunately, few curricula currently exist to fulfill this educational need. We developed a curriculum that teaches residents basic principles of risk management with the goals of (1) educating residents about the medical-legal environment in which they operate, (2) helping residents identify common malpractice exposures, and (3) teaching practical risk management/patient safety interventions that can be implemented in their practice that could reduce malpractice exposure and improve patient safety. The curriculum was developed by Medical Risk Management, LLC, a Connecticut-based risk management firm, in conjunction with academic leadership at the University of Connecticut. The program uses 3 learning modalities: live lectures, web-based video modules, and e-mailed learning publications. Gains in resident knowledge through participation in the curriculum were measured using pretests and posttests. Learner satisfaction with the curriculum was measured through web-based surveys. We found a significant improvement in knowledge in residents who took the pretest and posttest (P < .001). Of the survey respondents, 97% said the content was relevant to their specialty practice and 95% responded that these sessions should be held annually. Most respondents indicated they would change their practice as a result of what they learned from the live lectures. This risk management curriculum has been successful in providing our residents with learning activities in risk management, improving their knowledge of risk management principles, and changing their attitudes and behaviors. These improvements may lead to fewer malpractice claims against them and the hospitals they train in.

  17. Competing risk bias in Kaplan-Meier risk estimates can be corrected.

    PubMed

    van Walraven, Carl; Hawken, Steven

    2016-02-01

    Kaplan-Meier (KM) analyses are frequently used to measure outcome risk over time. These analyses overestimate risk whenever competing events are present. Many published KM analyses are susceptible to such competing risk bias. This study derived and validated a model that predicted true outcome risk based on the biased KM risk. We simulated survival data sets having a broad range of 1-year true outcome and competing event risk. Unbiased true outcome risk estimates were calculated using the cumulative incidence function (CIF). Multiple linear regression was used to determine the independent association of CIF-based true outcome risk with the biased KM risk and the proportion of all outcomes that were competing events. The final model found that both the biased KM-based risk and the proportion of all outcomes that were competing events were strongly associated with CIF-based risk. In validation populations that used a variety of distinct survival hazard functions, the model accurately predicted the CIF (R(2) = 1). True outcome risk can be accurately predicted from KM estimates susceptible to competing risk bias. Copyright © 2016 Elsevier Inc. All rights reserved.

  18. Ohio Financial Services and Risk Management. Technical Competency Profile (TCP).

    ERIC Educational Resources Information Center

    Ray, Gayl M.; Wilson, Nick; Mangini, Rick

    This document describes the essential competencies from secondary through post-secondary associate degree programs for a career in financial services and risk management. Ohio College Tech Prep Program standards are described, and a key to profile codes is provided. Sample occupations in this career area, such as financial accountant, loan…

  19. Assessing Talking and Writing: Linguistic Competence for Students at Risk.

    ERIC Educational Resources Information Center

    Montgomery, Judy K

    1998-01-01

    Suggests coordinated assessment and intervention strategies that speech language pathologists, special educators, and general educators, in co-teaching or inclusive settings, can use to assist at-risk students to achieve both oral and written linguistic competence. Proposes a strong link between talking and writing in the normal developmental…

  20. Semi-parametric risk prediction models for recurrent cardiovascular events in the LIPID study

    PubMed Central

    2010-01-01

    Background Traditional methods for analyzing clinical and epidemiological cohort study data have been focused on the first occurrence of a health outcome. However, in many situations, recurrent event data are frequently observed. It is inefficient to use methods for the analysis of first events to analyse recurrent event data. Methods We applied several semi-parametric proportional hazards models to analyze the risk of recurrent myocardial infarction (MI) events based on data from a very large randomized placebo-controlled trial of cholesterol-lowering drug. The backward selection procedure was used to select the significant risk factors in a model. The best fitting model was selected using the log-likelihood ratio test, Akaike Information and Bayesian Information Criteria. Results A total of 8557 persons were included in the LIPID study. Risk factors such as age, smoking status, total cholesterol and high density lipoprotein cholesterol levels, qualifying event for the acute coronary syndrome, revascularization, history of stroke or diabetes, angina grade and treatment with pravastatin were significant for development of both first and subsequent MI events. No significant difference was found for the effects of these risk factors between the first and subsequent MI events. The significant risk factors selected in this study were the same as those selected by the parametric conditional frailty model. Estimates of the relative risks and 95% confidence intervals were also similar between these two methods. Conclusions Our study shows the usefulness and convenience of the semi-parametric proportional hazards models for the analysis of recurrent event data, especially in estimation of regression coefficients and cumulative risks. PMID:20356409

  1. Evaluation of prognostic factors effect on survival time in patients with colorectal cancer, based on Weibull Competing-Risks Model

    PubMed Central

    Moamer, Soraya; Baghestani, Ahmadreza; Pourhoseingholi, Mohamad Amin; Hajizadeh, Nastaran; Ahmadi, Farzaneh; Norouzinia, Mohsen

    2017-01-01

    Aim: The aim of this study was to assess the association between survival of patients with colorectal cancer and prognostic factors in a competing risk parametric model using Weibull distribution. Background: The prognosis of colorectal cancer is relatively good in terms of survival time. In many prognostic studies, patients may be exposed to several types of competing events. These different causes of death are called competing risks. Methods: Data was recorded from 372 patients with colorectal cancer who registered in the Institute for Gastroenterology and Liver Diseases, Shahid Beheshti University of Medical Sciences (Tehran, Iran) from 2004 to 2015 in a retrospective study. Analysis was performed using competing risks model and Weibull distribution. Software used for data analysis was R, and significance level was regarded as 0.05. Results: The result indicated that, at the end of follow-up, 111 (29.8%) deaths were from colorectal cancer and 14 (3.8%) deaths were due to other diseases. The average body mass index (BMI) was 24.61(SD 3.98). The mean survival time for a patient in 372 was 62.05(SD 48.78) month with median equals to 48 months. According to competing-risks method, only stageIII (HR, 1.69; 95% CI, 1.246-2.315 ), stageIV( HR, 4.51; 95% CI,2.91-6.99 ) and BMI( HR, 0.96; 95% CI, 0.96-0.975) have a significant effect on patient’s survival time. Conclusion: This study indicated pathologic stage (III,IV) and BMI as the prognosis, using a Weibull model with competing risks analysis, while other models without the competing events lead to significant predictors which may be due to over-estimation.

  2. Decision-making competence predicts domain-specific risk attitudes

    PubMed Central

    Weller, Joshua A.; Ceschi, Andrea; Randolph, Caleb

    2015-01-01

    Decision-making competence (DMC) reflects individual differences in rational responding across several classic behavioral decision-making tasks. Although it has been associated with real-world risk behavior, less is known about the degree to which DMC contributes to specific components of risk attitudes. Utilizing a psychological risk-return framework, we examined the associations between risk attitudes and DMC. Italian community residents (n = 804) completed an online DMC measure, using a subset of the original Adult-DMC battery. Participants also completed a self-reported risk attitude measure for three components of risk attitudes (risk-taking, risk perceptions, and expected benefits) across six risk domains. Overall, greater performance on the DMC component scales were inversely, albeit modestly, associated with risk-taking tendencies. Structural equation modeling results revealed that DMC was associated with lower perceived expected benefits for all domains. In contrast, its association with perceived risks was more domain-specific. These analyses also revealed stronger indirect effects for the DMC → expected benefits → risk-taking path than the DMC → perceived riskrisk-taking path, especially for behaviors that may be considered more maladaptive in nature. These results suggest that DMC performance differentially impacts specific components of risk attitudes, and may be more strongly related to the evaluation of expected value of a specific behavior. PMID:26029128

  3. Geometry of the q-exponential distribution with dependent competing risks and accelerated life testing

    NASA Astrophysics Data System (ADS)

    Zhang, Fode; Shi, Yimin; Wang, Ruibing

    2017-02-01

    In the information geometry suggested by Amari (1985) and Amari et al. (1987), a parametric statistical model can be regarded as a differentiable manifold with the parameter space as a coordinate system. Note that the q-exponential distribution plays an important role in Tsallis statistics (see Tsallis, 2009), this paper investigates the geometry of the q-exponential distribution with dependent competing risks and accelerated life testing (ALT). A copula function based on the q-exponential function, which can be considered as the generalized Gumbel copula, is discussed to illustrate the structure of the dependent random variable. Employing two iterative algorithms, simulation results are given to compare the performance of estimations and levels of association under different hybrid progressively censoring schemes (HPCSs).

  4. Societal perspectives on risk awareness and risk competence

    PubMed Central

    Koller, Michael; Hoffrage, Ulrich

    2015-01-01

    Medical risks can be assessed by objectifiable therapeutic features; however, these risks are also characterised to a considerable degree by individual and social values. People tend to strive towards both freedom as well as safety; in a medical context, these two aims are taken into account by shared decision-making models and by stricter regulations in the pharmaceutical sector. Media reports on medical risks are caught between providing information and economic interests, and this conflict particularly complicates rational discussions about unexpected risks (for instance, in the field of natural medicine). Thus, it is necessary to create the type of information culture which allows differentiating between real and less pronounced risks. PMID:26195921

  5. Societal perspectives on risk awareness and risk competence.

    PubMed

    Koller, Michael; Hoffrage, Ulrich

    2015-01-01

    Medical risks can be assessed by objectifiable therapeutic features; however, these risks are also characterised to a considerable degree by individual and social values. People tend to strive towards both freedom as well as safety; in a medical context, these two aims are taken into account by shared decision-making models and by stricter regulations in the pharmaceutical sector. Media reports on medical risks are caught between providing information and economic interests, and this conflict particularly complicates rational discussions about unexpected risks (for instance, in the field of natural medicine). Thus, it is necessary to create the type of information culture which allows differentiating between real and less pronounced risks.

  6. Smoking, death, and Alzheimer disease: a case of competing risks.

    PubMed

    Chang, Chung-Chou H; Zhao, Yongyun; Lee, Ching-Wen; Ganguli, Mary

    2012-01-01

    If smoking is a risk factor for Alzheimer disease (AD) but a smoker dies of another cause before developing or manifesting AD, smoking-related mortality may mask the relationship between smoking and AD. This phenomenon, referred to as competing risk, complicates efforts to model the effect of smoking on AD. Typical survival regression models assume that censorship from analysis is unrelated to an individual's probability for developing AD (ie, censoring is noninformative). However, if individuals who die before developing AD are younger than those who survive long enough to develop AD, and if they include a higher percentage of smokers than nonsmokers, the incidence of AD will appear to be higher in older individuals and in nonsmokers. Further, age-specific mortality rates are higher in smokers because they die earlier than nonsmokers. Therefore, if we fail to take into account the competing risk of death when we estimate the effect of smoking on AD, we bias the results and are in fact only comparing the incidence of AD in nonsmokers with that in the healthiest smokers. In this study, we demonstrate that the effect of smoking on AD differs in models that are and are not adjusted for competing risks.

  7. A SAS macro for the joint modeling of longitudinal outcomes and multiple competing risk dropouts.

    PubMed

    Wang, Wei; Wang, Wanmei; Mosley, Thomas H; Griswold, Michael E

    2017-01-01

    The joint modeling of longitudinal and survival data to assess effects of multiple informative dropout mechanisms on longitudinal outcomes inference has received considerable attention during recent years; related statistical programs to apply these methods have been lacking. This paper provides a SAS macro implementation of a shared parameter model to accommodate the analysis of longitudinal outcomes in the presence of multiple competing survival/dropout events. In this macro, we assumed that the associations between the survival and the longitudinal submodels are linked through a set of shared random effects. The submodel for the longitudinal outcome takes the form of a linear mixed effects model, with specifications for the random intercept and/or random slope. The survival submodel allows up to three different competing causes for dropout, each allowing either an exponential or Weibull parametric baseline hazard function. In addition, information criterion fit statistics AIC and BIC are provided to assist with parametric baseline hazard function selection. We illustrate the SAS Macro in a cognitive decline study sensitivity analysis using data from the Atherosclerosis Risk in Communities Neurocognitive Study (ARIC-NCS). In addition, we also conduct a simulation study to show that the joint model provides unbiased parameter estimates when informative dropout exists compared against separate model approach which assumes missing at random dropout mechanisms. We have presented a SAS macro to implement a shared parameter model for a longitudinal outcome and multiple cause-specific dropouts and made the macro code freely available for download. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  8. Parametric estimation of P(X > Y) for normal distributions in the context of probabilistic environmental risk assessment

    PubMed Central

    Bekker, Andriëtte A.; van der Voet, Hilko; ter Braak, Cajo J.F.

    2015-01-01

    Estimating the risk, P(X > Y), in probabilistic environmental risk assessment of nanoparticles is a problem when confronted by potentially small risks and small sample sizes of the exposure concentration X and/or the effect concentration Y. This is illustrated in the motivating case study of aquatic risk assessment of nano-Ag. A non-parametric estimator based on data alone is not sufficient as it is limited by sample size. In this paper, we investigate the maximum gain possible when making strong parametric assumptions as opposed to making no parametric assumptions at all. We compare maximum likelihood and Bayesian estimators with the non-parametric estimator and study the influence of sample size and risk on the (interval) estimators via simulation. We found that the parametric estimators enable us to estimate and bound the risk for smaller sample sizes and small risks. Also, the Bayesian estimator outperforms the maximum likelihood estimators in terms of coverage and interval lengths and is, therefore, preferred in our motivating case study. PMID:26312175

  9. Parametric estimation of P(X > Y) for normal distributions in the context of probabilistic environmental risk assessment.

    PubMed

    Jacobs, Rianne; Bekker, Andriëtte A; van der Voet, Hilko; Ter Braak, Cajo J F

    2015-01-01

    Estimating the risk, P(X > Y), in probabilistic environmental risk assessment of nanoparticles is a problem when confronted by potentially small risks and small sample sizes of the exposure concentration X and/or the effect concentration Y. This is illustrated in the motivating case study of aquatic risk assessment of nano-Ag. A non-parametric estimator based on data alone is not sufficient as it is limited by sample size. In this paper, we investigate the maximum gain possible when making strong parametric assumptions as opposed to making no parametric assumptions at all. We compare maximum likelihood and Bayesian estimators with the non-parametric estimator and study the influence of sample size and risk on the (interval) estimators via simulation. We found that the parametric estimators enable us to estimate and bound the risk for smaller sample sizes and small risks. Also, the Bayesian estimator outperforms the maximum likelihood estimators in terms of coverage and interval lengths and is, therefore, preferred in our motivating case study.

  10. Nonparametric Analysis of Bivariate Gap Time with Competing Risks

    PubMed Central

    Huang, Chiung-Yu; Wang, Chenguang; Wang, Mei-Cheng

    2016-01-01

    Summary This article considers nonparametric methods for studying recurrent disease and death with competing risks. We first point out that comparisons based on the well-known cumulative incidence function can be confounded by different prevalence rates of the competing events, and that comparisons of the conditional distribution of the survival time given the failure event type are more relevant for investigating the prognosis of different patterns of recurrence disease. We then propose nonparametric estimators for the conditional cumulative incidence function as well as the conditional bivariate cumulative incidence function for the bivariate gap times, that is, the time to disease recurrence and the residual lifetime after recurrence. To quantify the association between the two gap times in the competing risks setting, a modified Kendall’s tau statistic is proposed. The proposed estimators for the conditional bivariate cumulative incidence distribution and the association measure account for the induced dependent censoring for the second gap time. Uniform consistency and weak convergence of the proposed estimators are established. Hypothesis testing procedures for two-sample comparisons are discussed. Numerical simulation studies with practical sample sizes are conducted to evaluate the performance of the proposed nonparametric estimators and tests. An application to data from a pancreatic cancer study is presented to illustrate the methods developed in this article. PMID:26990686

  11. Modeling Potential Time to Event Data with Competing Risks

    PubMed Central

    Li, Liang; Hu, Bo; Kattan, Michael W.

    2014-01-01

    Patients receiving radical prostatectomy are at risk of metastasis or prostate cancer related death, and often need repeated clinical evaluations to determine whether additional adjuvant or salvage therapies are needed. Since the prostate cancer is a slowly progressing disease, and these additional therapies come with significant side effects, it is important for clinical decision making purposes to estimate a patient’s risk of cancer metastasis, in the presence of a competing risk by death, under the hypothetical condition that the patient does not receive any additional therapy. In observational studies, patients may receive additional therapy by choice; the time to metastasis without any therapy is often a potential outcome and not always observed. We study the competing risks model of Fine and Gray (1999) with adjustment for treatment choice by inverse probability censoring weighting (IPCW). The model can be fit using standard software for partial likelihood with double IPCW weights. The proposed methodology is used in a prostate cancer study to predict the post-prostatectomy cumulative incidence probability of cancer metastasis without additional adjuvant or salvage therapies. PMID:24061908

  12. Actual and actuarial probabilities of competing risks: apples and lemons.

    PubMed

    Grunkemeier, Gary L; Jin, Ruyun; Eijkemans, Marinus J C; Takkenberg, Johanna J M

    2007-05-01

    The probability of a type of failure that is not inevitable, but can be precluded by other events such as death, is given by the cumulative incidence function. In cardiac research articles, it has become known as the actual probability, in contrast to the actuarial methods of estimation, usually implemented by the Kaplan-Meier (KM) estimate. Unlike cumulative incidence, KM attempts to predict what the latent failure probability would be if death were eliminated. To do this, the KM method assumes that the risk of dying and the risk of failure are independent. But this assumption is not true for many cardiac applications in which the risks of failure and death are negatively correlated (ie, patients with a higher risk of dying have a lower risk of failure, and patients with a lower risk of death have a higher risk of failure, which is a condition called informative censoring). Recent editorials in two cardiac journals have promoted the use of the KM method (actuarial estimate) for competing risk events (specifically for heart valve performance) and criticized the use of the cumulative incidence (actual) estimates. This report has two aims: to explain the difference between these two estimates and to show why the KM is generally not appropriate. In the process we will rely on alternative representations of the KM estimator (using redistribution to the right and inverse probability weighting) to explain the difference between the two estimates and to show how it may be possible to adjust KM to overcome the informative censoring.

  13. Optimising import risk mitigation: anticipating the unintended consequences and competing risks of informal trade.

    PubMed

    Hueston, W; Travis, D; van Klink, E

    2011-04-01

    The effectiveness of risk mitigation may be compromised by informal trade, including illegal activities, parallel markets and extra-legal activities. While no regulatory system is 100% effective in eliminating the risk of disease transmission through animal and animal product trade, extreme risk aversion in formal import health regulations may increase informal trade, with the unintended consequence of creating additional risks outside regulatory purview. Optimal risk mitigation on a national scale requires scientifically sound yet flexible mitigation strategies that can address the competing risks of formal and informal trade. More robust risk analysis and creative engagement of nontraditional partners provide avenues for addressing informal trade.

  14. Risk Taking: A Required Competency for Merger, Acquisitions, and Partnerships.

    PubMed

    Trepanier, Sylvain; Crenshaw, Jeannette T; Yoder-Wise, Patricia S

    2016-01-01

    Today's nurse executive is likely to find himself or herself in the middle of a merger, acquisition, and/or partnership (MAP). This is the result of health care agencies vying for market share in the midst of stiff competition, as well as decreased reimbursement in a rapidly changing payment system. The phenomenon of MAPs is fueled by the focus on care coordination and population health management. To be prepared for the ongoing and increasing MAP activity, nurse executives need to develop the skill of risk taking as an essential competency for leading change. This article emphasizes the need to maintain and improve health care quality and patient safety.

  15. The application of cure models in the presence of competing risks: a tool for improved risk communication in population-based cancer patient survival.

    PubMed

    Eloranta, Sandra; Lambert, Paul C; Andersson, Therese M-L; Björkholm, Magnus; Dickman, Paul W

    2014-09-01

    Quantifying cancer patient survival from the perspective of cure is clinically relevant. However, most cure models estimate cure assuming no competing causes of death. We use a relative survival framework to demonstrate how flexible parametric cure models can be used in combination with competing-risks theory to incorporate noncancer deaths. Under a model that incorporates statistical cure, we present the probabilities that cancer patients (1) have died from their cancer, (2) have died from other causes, (3) will eventually die from their cancer, or (4) will eventually die from other causes, all as a function of time since diagnosis. We further demonstrate how conditional probabilities can be used to update the prognosis among survivors (eg, at 1 or 5 years after diagnosis) by summarizing the proportion of patients who will not die from their cancer. The proposed method is applied to Swedish population-based data for persons diagnosed with melanoma, colon cancer, or acute myeloid leukemia between 1973 and 2007.

  16. Parametric Method for the Noise Risk Assessment of Professional Orchestral Musicians

    PubMed Central

    Bo, Matteo; Clerico, Marina; Pognant, Federica

    2016-01-01

    Background: The Occupational Health and Safety (OH&S) literature shows that noise could represent a risk factor for professional orchestral musicians. The continuative exposition to elevated noise levels and the particular nature of the activity make necessary an “atypical” OH&S approach, which was identified to be necessarily organizational. Materials and Methods: In this study, a parametric-based method for orchestral exposure assessment and management was developed. The goal was to achieve a predictive tool to involve safety in the decision making of concert season program. After setting the parameters, the project's hypothesis was defined and then validated through a yearly-scale monitoring on an important European symphonic orchestra. Moreover, workers’ exposure was assessed from the parametric study by a wide measurement campaign. Results: A general validation of the method was obtained by the verification of the main parameters’ (repertoire, headcount, and disposition) significant influence on the sound pressure levels produced by the orchestra. Exposure levels comparable to the trends in literature for symphonic orchestras were observed, with criticalities among brass musicians, which was the only group exceeding the upper exposure action values. Conclusion: This research has emphasized that the exposure condition of musicians can be critical and requires the implementation of improvement plans. The study has shown that the predictive analysis can be performed on parameters describing the concert's emissive characteristics. The future development of research currently under study will focus on the concert's pieces and the use of parameters as indicators of the exposure context. PMID:27991463

  17. Parametric method for the noise risk assessment of professional orchestral musicians.

    PubMed

    Bo, Matteo; Clerico, Marina; Pognant, Federica

    2016-01-01

    The Occupational Health and Safety (OH&S) literature shows that noise could represent a risk factor for professional orchestral musicians. The continuative exposition to elevated noise levels and the particular nature of the activity make necessary an "atypical" OH&S approach, which was identified to be necessarily organizational. In this study, a parametric-based method for orchestral exposure assessment and management was developed. The goal was to achieve a predictive tool to involve safety in the decision making of concert season program. After setting the parameters, the project's hypothesis was defined and then validated through a yearly-scale monitoring on an important European symphonic orchestra. Moreover, workers' exposure was assessed from the parametric study by a wide measurement campaign. A general validation of the method was obtained by the verification of the main parameters' (repertoire, headcount, and disposition) significant influence on the sound pressure levels produced by the orchestra. Exposure levels comparable to the trends in literature for symphonic orchestras were observed, with criticalities among brass musicians, which was the only group exceeding the upper exposure action values. This research has emphasized that the exposure condition of musicians can be critical and requires the implementation of improvement plans. The study has shown that the predictive analysis can be performed on parameters describing the concert's emissive characteristics. The future development of research currently under study will focus on the concert's pieces and the use of parameters as indicators of the exposure context.

  18. Epidemiology of competence: a scoping review to understand the risks and supports to competence of four health professions

    PubMed Central

    Glover Takahashi, Susan; Nayer, Marla

    2017-01-01

    Objectives This study examined the risks and supports to competence discussed in the literature related to occupational therapists, pharmacists, physical therapists and physicians, using epidemiology as a conceptual model. Design Articles from a scoping literature review, published from 1975 to 2014 inclusive, were included if they were about a risk or support to the professional or clinical competence of one of four health professions. Descriptive and regression analyses identified potential associations between risks and supports to competence and the location of study, type of health profession, competence life-cycle and the domain(s) of competence (organised around the CanMEDS framework). Results A total of 3572 abstracts were reviewed and 943 articles analysed. Most focused on physicians (n=810, 86.0%) and ‘practice’ (n=642, 68.0%). Fewer articles discussed risks to competence (n=418, 44.3%) than supports (n=750, 79.5%). The top four risks, each discussed in over 15% of articles, were: transitions in practice, being an international graduate, lack of clinical exposure/experience (ie, insufficient volume of procedures or patients) and age. The top two supports (over 35%) were continuing education participation and educational information/programme features. About 60% of all the articles discussed medical expert and about 25% applied to all roles. Articles focusing on residents had a greater probability of reporting on risks. Conclusions Articles about physicians were dominant. The majority of articles were written in the last decade and more discussed supports than risks to competence. An epidemiology-based conceptual model offers a helpful organising framework for exploring and explaining the competence of health professions. PMID:28864686

  19. Competing risks to breast cancer mortality in Catalonia

    PubMed Central

    Vilaprinyo, Ester; Gispert, Rosa; Martínez-Alonso, Montserrat; Carles, Misericòrdia; Pla, Roger; Espinàs, Josep-Alfons; Rué, Montserrat

    2008-01-01

    Background Breast cancer mortality has experienced important changes over the last century. Breast cancer occurs in the presence of other competing risks which can influence breast cancer incidence and mortality trends. The aim of the present work is: 1) to assess the impact of breast cancer deaths among mortality from all causes in Catalonia (Spain), by age and birth cohort and 2) to estimate the risk of death from other causes than breast cancer, one of the inputs needed to model breast cancer mortality reduction due to screening or therapeutic interventions. Methods The multi-decrement life table methodology was used. First, all-cause mortality probabilities were obtained by age and cohort. Then mortality probability for breast cancer was subtracted from the all-cause mortality probabilities to obtain cohort life tables for causes other than breast cancer. These life tables, on one hand, provide an estimate of the risk of dying from competing risks, and on the other hand, permit to assess the impact of breast cancer deaths on all-cause mortality using the ratio of the probability of death for causes other than breast cancer by the all-cause probability of death. Results There was an increasing impact of breast cancer on mortality in the first part of the 20th century, with a peak for cohorts born in 1945–54 in the 40–49 age groups (for which approximately 24% of mortality was due to breast cancer). Even though for cohorts born after 1955 there was only information for women under 50, it is also important to note that the impact of breast cancer on all-cause mortality decreased for those cohorts. Conclusion We have quantified the effect of removing breast cancer mortality in different age groups and birth cohorts. Our results are consistent with US findings. We also have obtained an estimate of the risk of dying from competing-causes mortality, which will be used in the assessment of the effect of mammography screening on breast cancer mortality in Catalonia

  20. Risky-Play at School. Facilitating Risk Perception and Competence in Young Children

    ERIC Educational Resources Information Center

    Lavrysen, Ann; Bertrands, Els; Leyssen, Leene; Smets, Lieve; Vanderspikken, Anja; De Graef, Peter

    2017-01-01

    Recent research indicates that risk competence and perception can be improved through the learning environment. The project "Riscki" examined how risk perception and risk competence in young children between three and eight years of age can be observed and measured within the classroom and school context. An intensive package of…

  1. A New Flexible Dependence Measure for Semi-competing Risks

    PubMed Central

    Yang, Jing

    2016-01-01

    Summary Semi-competing risks data are often encountered in chronic disease follow-up studies that record both nonterminal events (eg. disease landmark events) and terminal events (eg. death). Studying the relationship between the nonterminal event and the terminal event can provide insightful information on disease progression. In this paper, we propose a new sensible dependence measure tailored to addressing such an interest. We develop a nonparametric estimator, which is general enough to handle both independent right censoring and left truncation. Our strategy of connecting the new dependence measure with quantile regression enables a natural extension to adjust for covariates with minor additional assumptions imposed. We establish the asymptotic properties of the proposed estimators and develop inferences accordingly. Simulation studies suggest good finite-sample performance of the proposed methods. Our proposals are illustrated via an application to Denmark diabetes registry data. PMID:26916804

  2. Quantifying Cancer Absolute Risk and Cancer Mortality in the Presence of Competing Events after a Myotonic Dystrophy Diagnosis

    PubMed Central

    Gadalla, Shahinaz M.; Pfeiffer, Ruth M.; Kristinsson, Sigurdur Y.; Björkholm, Magnus; Hilbert, James E.; Moxley, Richard T.; Landgren, Ola; Greene, Mark H.

    2013-01-01

    Recent studies show that patients with myotonic dystrophy (DM) have an increased risk of specific malignancies, but estimates of absolute cancer risk accounting for competing events are lacking. Using the Swedish Patient Registry, we identified 1,081 patients with an inpatient and/or outpatient diagnosis of DM between 1987 and 2007. Date and cause of death and date of cancer diagnosis were extracted from the Swedish Cause of Death and Cancer Registries. We calculated non-parametric estimates of absolute cancer risk and cancer mortality accounting for the high non-cancer competing mortality associated with DM. Absolute cancer risk after DM diagnosis was 1.6% (95% CI=0.4-4%), 5% (95% CI=3-9%) and 9% (95% CI=6-13%) at ages 40, 50 and 60 years, respectively. Females had a higher absolute risk of all cancers combined than males: 9% (95% CI=4-14), and 13% (95% CI=9-20) vs. 2% (95%CI= 0.7-6) and 4% (95%CI=2-8) by ages 50 and 60 years, respectively) and developed cancer at younger ages (median age =51 years, range=22-74 vs. 57, range=43-84, respectively, p=0.02). Cancer deaths accounted for 10% of all deaths, with an absolute cancer mortality risk of 2% (95%CI=1-4.5%), 4% (95%CI=2-6%), and 6% (95%CI=4-9%) by ages 50, 60, and 70 years, respectively. No gender difference in cancer-specific mortality was observed (p=0.6). In conclusion, cancer significantly contributes to morbidity and mortality in DM patients, even after accounting for high competing DM mortality from non-neoplastic causes. It is important to apply population-appropriate, validated cancer screening strategies in DM patients. PMID:24236163

  3. Estimating twin concordance for bivariate competing risks twin data.

    PubMed

    Scheike, Thomas H; Holst, Klaus K; Hjelmborg, Jacob B

    2014-03-30

    For twin time-to-event data, we consider different concordance probabilities, such as the casewise concordance that are routinely computed as a measure of the lifetime dependence/correlation for specific diseases. The concordance probability here is the probability that both twins have experienced the event of interest. Under the assumption that both twins are censored at the same time, we show how to estimate this probability in the presence of right censoring, and as a consequence, we can then estimate the casewise twin concordance. In addition, we can model the magnitude of within pair dependence over time, and covariates may be further influential on the marginal risk and dependence structure. We establish the estimators large sample properties and suggest various tests, for example, for inferring familial influence. The method is demonstrated and motivated by specific twin data on cancer events with the competing risk death. We thus aim to quantify the degree of dependence through the casewise concordance function and show a significant genetic component.

  4. A Method for Evaluating Competency in Assessment and Management of Suicide Risk

    ERIC Educational Resources Information Center

    Hung, Erick K.; Binder, Renee L.; Fordwood, Samantha R.; Hall, Stephen E.; Cramer, Robert J.; McNiel, Dale E.

    2012-01-01

    Objective: Although health professionals increasingly are expected to be able to assess and manage patients' risk for suicide, few methods are available to evaluate this competency. This report describes development of a competency-assessment instrument for suicide risk-assessment (CAI-S), and evaluates its use in an objective structured clinical…

  5. A Method for Evaluating Competency in Assessment and Management of Suicide Risk

    ERIC Educational Resources Information Center

    Hung, Erick K.; Binder, Renee L.; Fordwood, Samantha R.; Hall, Stephen E.; Cramer, Robert J.; McNiel, Dale E.

    2012-01-01

    Objective: Although health professionals increasingly are expected to be able to assess and manage patients' risk for suicide, few methods are available to evaluate this competency. This report describes development of a competency-assessment instrument for suicide risk-assessment (CAI-S), and evaluates its use in an objective structured clinical…

  6. Unconditional and conditional competing risk models of activity duration and activity sequencing decisions: An empirical comparison

    NASA Astrophysics Data System (ADS)

    Leszczyc, Peter T. L. Popkowski; Timmermans, Harry

    This paper reports the results of an empirical comparison of various types of competing risk models in predicting the timing and duration of activities. In particular, three types of models are compared: a non-competing risk model, an unconditional competing risk model, and a conditional competing risk model. The models are applied to an activity diary, collected in the Netherlands. The results of the comparison indicate that the conditional competing risk model performs best, indicating that the choice and timing of activities depends on the nature and duration of the activity conducted previously. The specific structure of these dependent transition probabilities are discussed in detail. Several socio-demographic variables are found to be significantly related to the transition probabilities.

  7. Identifying Factors Associated with Risk Assessment Competencies of Public Health Emergency Responders

    PubMed Central

    Hao, Jiejing; Ren, Jiaojiao; Wu, Qunhong; Hao, Yanhua; Sun, Hong; Ning, Ning; Ding, Ding

    2017-01-01

    This study aimed to better understand the current situation of risk assessment and identify the factors associated with competence of emergency responders in public health risk assessment. The participants were selected by a multi-stage, stratified cluster sampling method in Heilongjiang Centers for Disease Control and Prevention (CDC). The questionnaires that measured their perceptions on risk assessment competences were administered through the face-to-face survey. A final sample of 1889 staff was obtained. Of this sample, 78.6% of respondents rated their own risk assessment competences as “relatively low”, contrasting with 21.4% rated as “relatively high”. Most of the respondents (62.7%) did not participate in any risk assessment work. Only 13.7% and 42.7% of respondents reported participating in risk assessment training and were familiar with risk assessment tools. There existed statistical significance between risk assessment-related characteristics of respondents and their self-rated competences scores. Financial support from the government and administrative attention were regarded as the important factors contributing to risk assessment competences of CDC responders. Higher attention should be given to risk assessment training and enhancing the availability of surveillance data. Continuous efforts should be made to remove the financial and technical obstacles to improve the competences of risk assessment for public health emergency responders. PMID:28587226

  8. Identifying Factors Associated with Risk Assessment Competencies of Public Health Emergency Responders.

    PubMed

    Hao, Jiejing; Ren, Jiaojiao; Wu, Qunhong; Hao, Yanhua; Sun, Hong; Ning, Ning; Ding, Ding

    2017-06-04

    This study aimed to better understand the current situation of risk assessment and identify the factors associated with competence of emergency responders in public health risk assessment. The participants were selected by a multi-stage, stratified cluster sampling method in Heilongjiang Centers for Disease Control and Prevention (CDC). The questionnaires that measured their perceptions on risk assessment competences were administered through the face-to-face survey. A final sample of 1889 staff was obtained. Of this sample, 78.6% of respondents rated their own risk assessment competences as "relatively low", contrasting with 21.4% rated as "relatively high". Most of the respondents (62.7%) did not participate in any risk assessment work. Only 13.7% and 42.7% of respondents reported participating in risk assessment training and were familiar with risk assessment tools. There existed statistical significance between risk assessment-related characteristics of respondents and their self-rated competences scores. Financial support from the government and administrative attention were regarded as the important factors contributing to risk assessment competences of CDC responders. Higher attention should be given to risk assessment training and enhancing the availability of surveillance data. Continuous efforts should be made to remove the financial and technical obstacles to improve the competences of risk assessment for public health emergency responders.

  9. Estimation of distribution function in bivariate competing risk models.

    PubMed

    Sankaran, P G; Lawless, J F; Abraham, B; Antony, Ansa Alphonsa

    2006-06-01

    We consider lifetime data involving pairs of study individuals with more than one possible cause of failure for each individual. Non-parametric estimation of cause-specific distribution functions is considered under independent censoring. Properties of the estimators are discussed and an illustration of their application is given.

  10. Accounting for competing risks in randomized controlled trials: a review and recommendations for improvement

    PubMed Central

    Fine, Jason P.

    2017-01-01

    In studies with survival or time‐to‐event outcomes, a competing risk is an event whose occurrence precludes the occurrence of the primary event of interest. Specialized statistical methods must be used to analyze survival data in the presence of competing risks. We conducted a review of randomized controlled trials with survival outcomes that were published in high‐impact general medical journals. Of 40 studies that we identified, 31 (77.5%) were potentially susceptible to competing risks. However, in the majority of these studies, the potential presence of competing risks was not accounted for in the statistical analyses that were described. Of the 31 studies potentially susceptible to competing risks, 24 (77.4%) reported the results of a Kaplan–Meier survival analysis, while only five (16.1%) reported using cumulative incidence functions to estimate the incidence of the outcome over time in the presence of competing risks. The former approach will tend to result in an overestimate of the incidence of the outcome over time, while the latter approach will result in unbiased estimation of the incidence of the primary outcome over time. We provide recommendations on the analysis and reporting of randomized controlled trials with survival outcomes in the presence of competing risks. © 2017 The Authors. Statistics in Medicine published by John Wiley & Sons Ltd. PMID:28102550

  11. Media influence on risk competence in self-medication and self-treatment

    PubMed Central

    Schweim, Harald; Ullmann, Marcela

    2015-01-01

    Media play an important role in the reception of health risks; thus, media competence is important for enhancing the risk competence of patients and consumers. In addition to life-long health education, risk competence particularly requires careful handling of health information because, at present, the key problem is not the lack of sufficient information on health topics but the quality of such information. Patients and consumers of health procedures and health products also require information which relates to their daily life and matches their life style. PMID:26195923

  12. Media influence on risk competence in self-medication and self-treatment.

    PubMed

    Schweim, Harald; Ullmann, Marcela

    2015-01-01

    Media play an important role in the reception of health risks; thus, media competence is important for enhancing the risk competence of patients and consumers. In addition to life-long health education, risk competence particularly requires careful handling of health information because, at present, the key problem is not the lack of sufficient information on health topics but the quality of such information. Patients and consumers of health procedures and health products also require information which relates to their daily life and matches their life style.

  13. Competing-risk analysis of ESRD and death among patients with type 1 diabetes and macroalbuminuria.

    PubMed

    Forsblom, Carol; Harjutsalo, Valma; Thorn, Lena M; Wadén, Johan; Tolonen, Nina; Saraheimo, Markku; Gordin, Daniel; Moran, John L; Thomas, Merlin C; Groop, Per-Henrik

    2011-03-01

    Patients with both type 1 diabetes and CKD have an increased risk of adverse outcomes. The competing risks of death and ESRD may confound the estimates of risk for each outcome. Here, we sought to determine the major predictors of the cumulative incidence of ESRD and pre-ESRD mortality in patients with type 1 diabetes and macroalbuminuria while incorporating the competing risk for the alternate outcome into a Fine-Gray competing-risks analysis. We followed 592 patients with macroalbuminuria for a median of 9.9 years. During this time, 56 (9.5%) patients died and 210 (35.5%) patients developed ESRD. Predictors of incident ESRD, taking baseline renal function and the competing risk for death into account, included an elevated HbA(1c), elevated LDL cholesterol, male sex, weight-adjusted insulin dose, and a shorter duration of diabetes. By contrast, predictors of pre-ESRD death, taking baseline renal function and the competing risk for ESRD into account, included only age, the presence of established macrovascular disease, and elevated cholesterol levels. This competing-risks approach has potential to highlight the appropriate targets and strategies for preventing premature mortality in patients with type 1 diabetes.

  14. A Comparison of Parametric and Non-Parametric Methods Applied to a Likert Scale.

    PubMed

    Mircioiu, Constantin; Atkinson, Jeffrey

    2017-05-10

    A trenchant and passionate dispute over the use of parametric versus non-parametric methods for the analysis of Likert scale ordinal data has raged for the past eight decades. The answer is not a simple "yes" or "no" but is related to hypotheses, objectives, risks, and paradigms. In this paper, we took a pragmatic approach. We applied both types of methods to the analysis of actual Likert data on responses from different professional subgroups of European pharmacists regarding competencies for practice. Results obtained show that with "large" (>15) numbers of responses and similar (but clearly not normal) distributions from different subgroups, parametric and non-parametric analyses give in almost all cases the same significant or non-significant results for inter-subgroup comparisons. Parametric methods were more discriminant in the cases of non-similar conclusions. Considering that the largest differences in opinions occurred in the upper part of the 4-point Likert scale (ranks 3 "very important" and 4 "essential"), a "score analysis" based on this part of the data was undertaken. This transformation of the ordinal Likert data into binary scores produced a graphical representation that was visually easier to understand as differences were accentuated. In conclusion, in this case of Likert ordinal data with high response rates, restraining the analysis to non-parametric methods leads to a loss of information. The addition of parametric methods, graphical analysis, analysis of subsets, and transformation of data leads to more in-depth analyses.

  15. Predicting Emotional and Social Competence during Early Childhood from Toddler Risk and Maternal Behavior

    PubMed Central

    Blandon, Alysia Y.; Calkins, Susan D.; Keane, Susan P.

    2010-01-01

    The longitudinal associations between maternal parenting behavior and toddler risk with children’s emotional and social competence were examined during the transition to kindergarten, in a sample of 253 children. Toddler risk was characterized by early externalizing behavior and poor emotion regulation skills. Given that we were interested in the multiple pathways that may result in emotional and social competence, we examined the interactions among maternal parenting behavior and toddler risk. There were some significant interactions; although the pattern of results was not consistent across all competence outcomes. Maternal parenting behavior was not directly associated with children’s emotional and social competence. In some instances, maternal control has differential implications for children’s emotional and social competence dependent upon the child’s level of early risk and maternal positive parenting. Specifically, maternal control tended to be more detrimental for children’s emotional competence during the transition to kindergarten, when children exhibit higher levels of risk. Overall, it appears that there are multiple developmental pathways, depending on child and maternal characteristics that lead to early emotional and social competence. PMID:20102651

  16. The Fine–Gray Model Under Interval Censored Competing Risks Data

    PubMed Central

    Li, Chenxi

    2015-01-01

    We consider semiparametric analysis of competing risks data subject to mixed case interval censoring. The Fine–Gray model (Fine & Gray, 1999) is used to model the cumulative incidence function and is coupled with sieve semiparametric maximum likelihood estimation based on univariate or multivariate likelihood. The univariate likelihood of cause-specific data enables separate estimation of cumulative incidence function for each competing risk, in contrast with the multivariate likelihood of full data which estimates cumulative incidence functions for multiple competing risks jointly. Under both likelihoods and certain regularity conditions, we show that the regression parameter estimator is asymptotically normal and semiparametrically efficient, although the spline-based sieve estimator of the baseline cumulative subdistribution hazard converges at a rate slower than root-n. The proposed method is evaluated by simulation studies regarding its finite sample performance and is illustrated by a competing risk analysis of data from an dementia cohort study. PMID:26543275

  17. Competing events in patients with malignant disease who are at risk for recurrent venous thromboembolism.

    PubMed

    Parpia, S; Julian, J A; Thabane, L; Lee, A Y Y; Rickles, F R; Levine, M N

    2011-11-01

    Patients with malignant disease enrolled in trials of thrombotic disorders may experience competing events such as death. The occurrence of a competing event may prevent the thrombotic event from being observed. Standard survival analysis techniques ignore competing risks, resulting in possible bias and distorted inferences. To assess the impact of competing events on the results of a previously reported trial comparing low molecular weight heparin (LMWH) with oral anticoagulant (OAC) therapy for the prevention of recurrent venous thromboembolism (VTE) in patients with advanced cancer, we compare the results from standard survival analysis with those from competing risk techniques which are based on the cumulative incidence function (CIF) and Gray's test. The Kaplan-Meier method overestimates the risk of recurrent VTE (17.2% in the OAC group and 8.7% in the LMWH group). Risk of recurrence using the CIF is 12.0% and 6.0% in the OAC and LMWH groups, respectively. Both the log-rank test (p=0.002) and Gray's test (p=0.006) suggest evidence in favor of LMWH. The overestimation of risk is 30% in each treatment group, resulting in a similar relative treatment effect; using the Cox model the hazard ratio (HR) is 0.48 (95% confidence interval [CI], 0.30 to 0.78) and HR=0.47 (95% CI, 0.29 to 0.74) using the CIF model. Failing to account for competing risks may lead to incorrect interpretations of the probability of recurrent VTE. However, when the distribution of competing risks is similar within each treatment group, standard and competing risk methods yield comparable relative treatment effects.

  18. An approach to evaluating competence in assessing and managing violence risk.

    PubMed

    McNiel, Dale E; Hung, Erick K; Cramer, Robert J; Hall, Stephen E; Binder, Renee L

    2011-01-01

    The authors developed and evaluated a tool for assessing competency in violence risk assessment and management. The Competency Assessment Instrument for Violence Risk (CAI-V) was based on the literature on violence risk assessment, which was complemented by feedback from faculty focus groups. In an objective structured clinical examination, 31 faculty observers used the CAI-V to rate the performance of 31 learners' (26 psychiatry residents and five psychology interns) risk assessments of standardized (simulated) patients. In an interrater reliability study, six faculty members rated video-recorded risk assessments. The CAI-V had good internal consistency reliability (α=.93). Senior learners performed better on the CAI-V than junior learners, supporting the instrument's concurrent validity. Interrater reliability was good (intraclass correlation coefficient=.93). Participants reported that the CAI-V provided a helpful structure for feedback and supervision. The results supported the potential of this new approach for appraising competency in violence risk assessment and management.

  19. Suicide Risk Assessment Training for Psychology Doctoral Programs: Core Competencies and a Framework for Training.

    PubMed

    Cramer, Robert J; Johnson, Shara M; McLaughlin, Jennifer; Rausch, Emilie M; Conroy, Mary Alice

    2013-02-01

    Clinical and counseling psychology programs currently lack adequate evidence-based competency goals and training in suicide risk assessment. To begin to address this problem, this article proposes core competencies and an integrated training framework that can form the basis for training and research in this area. First, we evaluate the extent to which current training is effective in preparing trainees for suicide risk assessment. Within this discussion, sample and methodological issues are reviewed. Second, as an extension of these methodological training issues, we integrate empirically- and expert-derived suicide risk assessment competencies from several sources with the goal of streamlining core competencies for training purposes. Finally, a framework for suicide risk assessment training is outlined. The approach employs Objective Structured Clinical Examination (OSCE) methodology, an approach commonly utilized in medical competency training. The training modality also proposes the Suicide Competency Assessment Form (SCAF), a training tool evaluating self- and observer-ratings of trainee core competencies. The training framework and SCAF are ripe for empirical evaluation and potential training implementation.

  20. Suicide Risk Assessment Training for Psychology Doctoral Programs: Core Competencies and a Framework for Training

    PubMed Central

    Cramer, Robert J.; Johnson, Shara M.; McLaughlin, Jennifer; Rausch, Emilie M.; Conroy, Mary Alice

    2014-01-01

    Clinical and counseling psychology programs currently lack adequate evidence-based competency goals and training in suicide risk assessment. To begin to address this problem, this article proposes core competencies and an integrated training framework that can form the basis for training and research in this area. First, we evaluate the extent to which current training is effective in preparing trainees for suicide risk assessment. Within this discussion, sample and methodological issues are reviewed. Second, as an extension of these methodological training issues, we integrate empirically- and expert-derived suicide risk assessment competencies from several sources with the goal of streamlining core competencies for training purposes. Finally, a framework for suicide risk assessment training is outlined. The approach employs Objective Structured Clinical Examination (OSCE) methodology, an approach commonly utilized in medical competency training. The training modality also proposes the Suicide Competency Assessment Form (SCAF), a training tool evaluating self- and observer-ratings of trainee core competencies. The training framework and SCAF are ripe for empirical evaluation and potential training implementation. PMID:24672588

  1. Analysis of Intravenous Glucose Tolerance Test Data Using Parametric and Nonparametric Modeling: Application to a Population at Risk for Diabetes

    PubMed Central

    Marmarelis, Vasilis Z.; Shin, Dae C.; Zhang, Yaping; Kautzky-Willer, Alexandra; Pacini, Giovanni; D’Argenio, David Z.

    2013-01-01

    Background: Modeling studies of the insulin–glucose relationship have mainly utilized parametric models, most notably the minimal model (MM) of glucose disappearance. This article presents results from the comparative analysis of the parametric MM and a nonparametric Laguerre based Volterra Model (LVM) applied to the analysis of insulin modified (IM) intravenous glucose tolerance test (IVGTT) data from a clinical study of gestational diabetes mellitus (GDM). Methods: An IM IVGTT study was performed 8 to 10 weeks postpartum in 125 women who were diagnosed with GDM during their pregnancy [population at risk of developing diabetes (PRD)] and in 39 control women with normal pregnancies (control subjects). The measured plasma glucose and insulin from the IM IVGTT in each group were analyzed via a population analysis approach to estimate the insulin sensitivity parameter of the parametric MM. In the nonparametric LVM analysis, the glucose and insulin data were used to calculate the first-order kernel, from which a diagnostic scalar index representing the integrated effect of insulin on glucose was derived. Results: Both the parametric MM and nonparametric LVM describe the glucose concentration data in each group with good fidelity, with an improved measured versus predicted r2 value for the LVM of 0.99 versus 0.97 for the MM analysis in the PRD. However, application of the respective diagnostic indices of the two methods does result in a different classification of 20% of the individuals in the PRD. Conclusions: It was found that the data based nonparametric LVM revealed additional insights about the manner in which infused insulin affects blood glucose concentration. PMID:23911176

  2. Analysis of intravenous glucose tolerance test data using parametric and nonparametric modeling: application to a population at risk for diabetes.

    PubMed

    Marmarelis, Vasilis Z; Shin, Dae C; Zhang, Yaping; Kautzky-Willer, Alexandra; Pacini, Giovanni; D'Argenio, David Z

    2013-07-01

    Modeling studies of the insulin-glucose relationship have mainly utilized parametric models, most notably the minimal model (MM) of glucose disappearance. This article presents results from the comparative analysis of the parametric MM and a nonparametric Laguerre based Volterra Model (LVM) applied to the analysis of insulin modified (IM) intravenous glucose tolerance test (IVGTT) data from a clinical study of gestational diabetes mellitus (GDM). An IM IVGTT study was performed 8 to 10 weeks postpartum in 125 women who were diagnosed with GDM during their pregnancy [population at risk of developing diabetes (PRD)] and in 39 control women with normal pregnancies (control subjects). The measured plasma glucose and insulin from the IM IVGTT in each group were analyzed via a population analysis approach to estimate the insulin sensitivity parameter of the parametric MM. In the nonparametric LVM analysis, the glucose and insulin data were used to calculate the first-order kernel, from which a diagnostic scalar index representing the integrated effect of insulin on glucose was derived. Both the parametric MM and nonparametric LVM describe the glucose concentration data in each group with good fidelity, with an improved measured versus predicted r² value for the LVM of 0.99 versus 0.97 for the MM analysis in the PRD. However, application of the respective diagnostic indices of the two methods does result in a different classification of 20% of the individuals in the PRD. It was found that the data based nonparametric LVM revealed additional insights about the manner in which infused insulin affects blood glucose concentration. © 2013 Diabetes Technology Society.

  3. Development of Instructional Competencies for Assessing and Managing Suicide Risk for Baccalaureate Nursing Education: A Modified Delphi Study.

    PubMed

    Kotowski, Abigail; Roye, Carol

    2017-03-01

    Suicide is a major health problem and a leading cause of death throughout the world. A primary goal for suicide prevention is reforming health professional education in order to increase the competence of health professionals in assessing and managing suicide risk. Nursing leadership is involved in this reform, yet nurses frequently lack the competence to care for patients in suicidal crisis. An identified gap in baccalaureate nursing education is instructional competencies for assessing and managing suicide risk. A modified Delphi study was used. The study began with a focus group which was conducted in order to develop the Round I Survey which included forty-four competencies. After scoring these competencies, thirty-four were scored for inclusion, two were dropped and eight were revised according to panel members' comments. The Round II Survey comprised the eight revised competencies which were scored for inclusion, resulting in forty-two competencies in the final set of instructional competencies. Forty-two instructional competencies were developed: fourteen pre-assessment instructional competencies, fifteen assessment instructional competencies, and thirteen management instructional competencies. Incorporating these instructional competencies into baccalaureate nursing education might increase the competence of nursing students, and thus new nurses, in caring for patients at risk for suicide. These instructional competencies provide a first step to address the challenging task of intervening with patients at risk for suicide.

  4. Contextual Risk and Parenting as Predictors of Effortful Control and Social Competence in Preschool Children

    ERIC Educational Resources Information Center

    Lengua, Liliana J.; Honorado, Elizabeth; Bush, Nicole R.

    2007-01-01

    Using a short-term longitudinal design (6 months), this study examined cumulative contextual risk as a predictor of effortful control (EC) and social competence in a community sample of children (N = 80, ages 33-40 months at time 1). Maternal parenting was examined as a mediator of contextual risk. EC was assessed using laboratory tasks, and…

  5. Core Competencies and the Prevention of High-Risk Sexual Behavior

    ERIC Educational Resources Information Center

    Charles, Vignetta Eugenia; Blum, Robert Wm.

    2008-01-01

    Adolescent sexual risk-taking behavior has numerous individual, family, community, and societal consequences. In an effort to contribute to the research and propose new directions, this chapter applies the core competencies framework to the prevention of high-risk sexual behavior. It describes the magnitude of the problem, summarizes explanatory…

  6. Core Competencies and the Prevention of High-Risk Sexual Behavior

    ERIC Educational Resources Information Center

    Charles, Vignetta Eugenia; Blum, Robert Wm.

    2008-01-01

    Adolescent sexual risk-taking behavior has numerous individual, family, community, and societal consequences. In an effort to contribute to the research and propose new directions, this chapter applies the core competencies framework to the prevention of high-risk sexual behavior. It describes the magnitude of the problem, summarizes explanatory…

  7. The competing risks illness-death model under cross-sectional sampling.

    PubMed

    Mandel, Micha

    2010-04-01

    The competing risks illness-death model describes the dynamics of healthy subjects who may move to an "illness" state before entering into one of several competing terminal states. A motivating example concerns patients in a hospital who may acquire infections during their stay, where the competing terminal states are discharged alive and death in the hospital. We consider a cross-sectional sampling of independent competing risks illness-death processes in which data are subject to length bias and censoring and develop estimators for functionals of the underlying distribution such as the joint probability of the terminal state and illness (infection) and cumulative incidence functions. We apply the methodology to infection data obtained in a cross-sectional study of patients hospitalized in intensive care units.

  8. Development and evaluation of the "BRISK Scale," a brief observational measure of risk communication competence.

    PubMed

    Han, Paul K J; Joekes, Katherine; Mills, Greg; Gutheil, Caitlin; Smith, Kahsi; Cochran, Nancy E; Elwyn, Glyn

    2016-12-01

    To develop and evaluate a brief observational measure of clinical risk communication competence. A 4-item checklist-type measure, the BRISK (Brief Risk Information Skill) Scale, was developed by selecting and refining items from a more comprehensive measure of clinical risk communication competence. Six volunteer raters received brief training on the measure and then used the BRISK Scale to evaluate 52 video-recorded encounters between 2nd-year medical students and standardized patients conducted as part of an Observed Structured Clinical Examination (OSCE) involving a risk communication task. Internal consistency reliability, inter-rater reliability, and criterion validity were assessed. Raters reported no difficulties using the BRISK Scale; scores across all raters and subjects ranged from 0 to 16 with a mean score of 6.49 (SD=3.17). The BRISK Scale showed good internal consistency reliability (α=0.64), and inter-rater reliability at the scale level (Intraclass Correlation Coefficient (ICC)=0.79 for consistency, and 0.75 for absolute agreement) and individual-item level (ICC range: 0.62-.91). Novice raters' BRISK Scale scores were highly correlated (r=0.84, p<0.01) with expert raters' scores on the Risk Communication Content measure, a more comprehensive measure of risk communication competence. The BRISK Scale is a promising new brief observational measure of clinical risk communication competence. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  9. Students "At-Risk" Policy: Competing Social and Economic Discourses

    ERIC Educational Resources Information Center

    Mosen-Lowe, Linda Audrey Joy; Vidovich, Lesley; Chapman, Anne

    2009-01-01

    Within a context of global reform agendas that promote economic ideologies in education the discourses surrounding "school failure" have shifted from "individual risk" to "a nation at-risk". Enhancing the quality of schooling through improving educational outcomes and standards for all, and thereby reducing…

  10. Students "At-Risk" Policy: Competing Social and Economic Discourses

    ERIC Educational Resources Information Center

    Mosen-Lowe, Linda Audrey Joy; Vidovich, Lesley; Chapman, Anne

    2009-01-01

    Within a context of global reform agendas that promote economic ideologies in education the discourses surrounding "school failure" have shifted from "individual risk" to "a nation at-risk". Enhancing the quality of schooling through improving educational outcomes and standards for all, and thereby reducing…

  11. Do Health Professionals Need Additional Competencies for Stratified Cancer Prevention Based on Genetic Risk Profiling?

    PubMed Central

    Chowdhury, Susmita; Henneman, Lidewij; Dent, Tom; Hall, Alison; Burton, Alice; Pharoah, Paul; Pashayan, Nora; Burton, Hilary

    2015-01-01

    There is growing evidence that inclusion of genetic information about known common susceptibility variants may enable population risk-stratification and personalized prevention for common diseases including cancer. This would require the inclusion of genetic testing as an integral part of individual risk assessment of an asymptomatic individual. Front line health professionals would be expected to interact with and assist asymptomatic individuals through the risk stratification process. In that case, additional knowledge and skills may be needed. Current guidelines and frameworks for genetic competencies of non-specialist health professionals place an emphasis on rare inherited genetic diseases. For common diseases, health professionals do use risk assessment tools but such tools currently do not assess genetic susceptibility of individuals. In this article, we compare the skills and knowledge needed by non-genetic health professionals, if risk-stratified prevention is implemented, with existing competence recommendations from the UK, USA and Europe, in order to assess the gaps in current competences. We found that health professionals would benefit from understanding the contribution of common genetic variations in disease risk, the rationale for a risk-stratified prevention pathway, and the implications of using genomic information in risk-assessment and risk management of asymptomatic individuals for common disease prevention. PMID:26068647

  12. Do Health Professionals Need Additional Competencies for Stratified Cancer Prevention Based on Genetic Risk Profiling?

    PubMed

    Chowdhury, Susmita; Henneman, Lidewij; Dent, Tom; Hall, Alison; Burton, Alice; Pharoah, Paul; Pashayan, Nora; Burton, Hilary

    2015-06-09

    There is growing evidence that inclusion of genetic information about known common susceptibility variants may enable population risk-stratification and personalized prevention for common diseases including cancer. This would require the inclusion of genetic testing as an integral part of individual risk assessment of an asymptomatic individual. Front line health professionals would be expected to interact with and assist asymptomatic individuals through the risk stratification process. In that case, additional knowledge and skills may be needed. Current guidelines and frameworks for genetic competencies of non-specialist health professionals place an emphasis on rare inherited genetic diseases. For common diseases, health professionals do use risk assessment tools but such tools currently do not assess genetic susceptibility of individuals. In this article, we compare the skills and knowledge needed by non-genetic health professionals, if risk-stratified prevention is implemented, with existing competence recommendations from the UK, USA and Europe, in order to assess the gaps in current competences. We found that health professionals would benefit from understanding the contribution of common genetic variations in disease risk, the rationale for a risk-stratified prevention pathway, and the implications of using genomic information in risk-assessment and risk management of asymptomatic individuals for common disease prevention.

  13. Self-criticism of physicians, patient participation and risk competence.

    PubMed

    Wolffsohn, Michael

    2015-01-01

    Self-criticism of physicians and patient participation are the pillars of modern medical ethics and medical programmes. Patients expect risk minimisation from physicians, mostly without realising how much they could actively do themselves in this respect. But what about the willingness of German people to take risks, how high is it really at present? Direct empirical data are not available, but results from general empirical research show that people's willingness to take risks is probably rather low. Post-heroic societies of welfare states are less likely to take risks than supposedly heroic ones. Therefore, the question whether it is responsible for medical experts to transfer even more responsibility to non-medical laypeople becomes increasingly important in a social context.

  14. Self-criticism of physicians, patient participation and risk competence

    PubMed Central

    Wolffsohn, Michael

    2015-01-01

    Self-criticism of physicians and patient participation are the pillars of modern medical ethics and medical programmes. Patients expect risk minimisation from physicians, mostly without realising how much they could actively do themselves in this respect. But what about the willingness of German people to take risks, how high is it really at present? Direct empirical data are not available, but results from general empirical research show that people’s willingness to take risks is probably rather low. Post-heroic societies of welfare states are less likely to take risks than supposedly heroic ones. Therefore, the question whether it is responsible for medical experts to transfer even more responsibility to non-medical laypeople becomes increasingly important in a social context. PMID:26195919

  15. Statistical analysis of dependent competing risks model from Gompertz distribution under progressively hybrid censoring.

    PubMed

    Shi, Yimin; Wu, Min

    2016-01-01

    Previous studies have mostly considered the competing risks to be independent even when the interpretation of the failure modes implies dependency. This paper studies the dependent competing risks model from Gompertz distribution under Type-I progressively hybrid censoring scheme. We derive the maximum likelihood estimations of the model parameters, and then the asymptotic likelihood theory and Bootstrap method are used to obtain the confidence intervals. The simulation results are provided to investigate the effects of different dependence structures on the estimations of parameters. Finally, one data set was used for illustrative purpose.

  16. Are women as likely to take risks and compete? Behavioural findings from central Vietnam.

    PubMed

    Fletschner, Diana; Anderson, C Leigh; Cullen, Alison

    2010-01-01

    Using controlled experiments to compare the risk attitude and willingness to compete of husbands and wives in 500 couples in rural Vietnam, we find that women are more risk averse than men and that, compared to men, women are less likely to choose to compete, irrespective of how likely they are to succeed. Relevant to development programmes concerned with lifting women out of poverty, our findings suggest that women may be more reluctant to adopt new technologies, take out loans, or engage in economic activities that offer higher expected returns, in order to avoid setups that require them to be more competitive or that have less predictable outcomes.

  17. Trustworthy patient decision aids: a qualitative analysis addressing the risk of competing interests

    PubMed Central

    Elwyn, Glyn; Dannenberg, Michelle; Blaine, Arianna; Poddar, Urbashi; Durand, Marie-Anne

    2016-01-01

    Objective Our aim in this study was to examine the competing interest policies and procedures of organisations who develop and maintain patient decision aids. Design Descriptive and thematic analysis of data collected from a cross-sectional survey of patient decision aid developer's competing interest policies and disclosure forms. Results We contacted 25 organisations likely to meet the inclusion criteria. 12 eligible organisations provided data. 11 organisations did not reply and 2 declined to participate. Most patient decision aid developers recognise the need to consider the issue of competing interests. Assessment processes vary widely and, for the most part, are insufficiently robust to minimise the risk of competing interests. Only half of the 12 organisations had competing interest policies. Some considered disclosure to be sufficient, while others imposed differing levels of exclusion. Conclusions Patient decision aid developers do not have a consistent approach to managing competing interests. Some have developed policies and procedures, while others pay no attention to the issue. As is the case for clinical practice guidelines, increasing attention will need to be given to how the competing interests of contributors of evidence-based publications may influence materials, especially if they are designed for patient use. PMID:27612542

  18. Criteria for use of composite end points for competing risks-a systematic survey of the literature with recommendations.

    PubMed

    Manja, Veena; AlBashir, Siwar; Guyatt, Gordon

    2017-02-01

    Composite end points are frequently used in reports of clinical trials. One rationale for the use of composite end points is to account for competing risks. In the presence of competing risks, the event rate of a specific event depends on the rates of other competing events. One proposed solution is to include all important competing events in one composite end point. Clinical trialists require guidance regarding when this approach is appropriate. To identify publications describing criteria for use of composite end points for competing risk and to offer guidance regarding when a composite end point is appropriate on the basis of competing risks. We searched MEDLINE, CINAHL, EMBASE, The Cochrane's Central & Systematic Review databases including the Health Technology Assessment database, and the Cochrane's Methodology register from inception to April 2015, and candidate textbooks, to identify all articles providing guidance on this issue. Eligible publications explicitly addressed the issue of a composite outcome to address competing risks. Two reviewers independently screened the titles and abstracts for full-text review; independently reviewed full-text publications; and abstracted specific criteria authors offered for use of composite end points to address competing risks. Of 63,645 titles and abstracts, 166 proved potentially relevant of which 43 publications were included in the final review. Most publications note competing risks as a reason for using composite end points without further elaboration. None of the articles or textbook chapters provide specific criteria for use of composite end points for competing risk. Some advocate using composite end points to avoid bias due to competing risks and others suggest that composite end points seldom or never be used for this purpose. We recommend using composite end points for competing risks only if the competing risk is plausible and if it occurs with sufficiently high frequency to influence the interpretation

  19. Contextual risk and parenting as predictors of effortful control and social competence in preschool children.

    PubMed

    Lengua, Liliana J; Honorado, Elizabeth; Bush, Nicole R

    2007-01-01

    Using a short-term longitudinal design (6 months), this study examined cumulative contextual risk as a predictor of effortful control (EC) and social competence in a community sample of children (N = 80, ages 33-40 months at time 1). Maternal parenting was examined as a mediator of contextual risk. EC was assessed using laboratory tasks, and parenting was assessed using observational ratings. Time 1 contextual risk was negatively related to time 2 EC after controlling for time 1 EC. Mothers' limit setting and scaffolding predicted higher time 2 EC and accounted for the effect of contextual risk. Time 1 EC, contextual risk, and parenting predicted time 2 social competence, and contextual risk had an indirect effect on social competence through parenting. Results suggest that contextual risk predicts smaller relative increases in EC and that parenting accounts for this effect. Knowledge of the factors that divert or promote effortful control can provide targets for intervention to enhance effortful control abilities and better adjustment.

  20. Contextual risk and parenting as predictors of effortful control and social competence in preschool children

    PubMed Central

    Lengua, Liliana J.; Honorado, Elizabeth; Bush, Nicole R.

    2011-01-01

    Using a short-term longitudinal design (6 months), this study examined cumulative contextual risk as a predictor of effortful control (EC) and social competence in a community sample of children (N = 80, ages 33–40 months at time 1). Maternal parenting was examined as a mediator of contextual risk. EC was assessed using laboratory tasks, and parenting was assessed using observational ratings. Time 1 contextual risk was negatively related to time 2 EC after controlling for time 1 EC. Mothers’ limit setting and scaffolding predicted higher time 2 EC and accounted for the effect of contextual risk. Time 1 EC, contextual risk, and parenting predicted time 2 social competence, and contextual risk had an indirect effect on social competence through parenting. Results suggest that contextual risk predicts smaller relative increases in EC and that parenting accounts for this effect. Knowledge of the factors that divert or promote effortful control can provide targets for intervention to enhance effortful control abilities and better adjustment. PMID:21687825

  1. Rapid Risk-Based Evaluation of Competing Conceptual Designs

    SciTech Connect

    Bott, T.F.; Butner, J.M.

    1999-08-22

    In this paper, the authors have shown how a qualitative analysis can provide good input to a risk reduction design problem. Traditionally qualitative analyses such as the FMEA can be supplemented by qualitative fault trees and event trees to produce logic models of the accident sequences for the different design options. These models can be compared using rule-based manipulations of qualitative branch point probabilities. A qualitative evaluation of other considerations such as collateral safety effects, operational impacts and worker-safety impacts can provide a more complete picture of the trade-off between options. The authors believe that their risk-reduction analysis approach that combines logic models with qualitative and possibility metrics provides an excellent tool for incorporating safety concerns rapidly and effectively into a conceptual design evaluation.

  2. Social Competence of Students with Learning Disabilities Using a Risk-Resilience Model

    ERIC Educational Resources Information Center

    Benowitz, Alison Joy

    2010-01-01

    Children with learning disabilities (LD) makeup 50.5% of all children identified for special services in the schools. Research has found that children with LD have difficulties in areas of functioning related to social competence. This study is based on a risk and resilience model to explore external protective factors (friendships and social…

  3. Therapeutic risk management of clinical-legal dilemmas: should it be a core competency?

    PubMed

    Simon, Robert I; Shuman, Daniel W

    2009-01-01

    Therapeutic risk management of clinical-legal dilemmas achieves an optimal alignment between clinical competence and an understanding of legal concerns applicable to psychiatric practice. Understanding how psychiatry and law interact in frequently occurring clinical situations is essential for effective patient care. Successful management of clinical-legal dilemmas also avoids unnecessary, counterproductive defensive practices.

  4. Pitfalls in Pathways: Some Perspectives on Competing Risks Event History Analysis in Education Research

    ERIC Educational Resources Information Center

    Scott, Marc A.; Kennedy, Benjamin B.

    2005-01-01

    A set of discrete-time methods for competing risks event history analysis is presented. The approach used is accessible to the practitioner and the article describes the strengths, weaknesses, and interpretation of both exploratory and model-based tools. These techniques are applied to the impact of "nontraditional" enrollment features (working,…

  5. Using La Familia Communication Competency Skills To Empower Hispanic At-Risk Students.

    ERIC Educational Resources Information Center

    Flores, Norma Landa

    Hispanic families can be empowered through parent training workshops focusing on the development of competency based interpersonal communication skills. Nearly 50% of the Latinos in the United States are at risk of dropping out before graduating from high school. They believe that their family obligations come first and that the school system is…

  6. The Effect of Family on the Job Exits of Young Adults: A Competing Risk Model.

    ERIC Educational Resources Information Center

    Koenigsberg, Judy; And Others

    1994-01-01

    Event history analysis and a competing risk model of occupational attainment indicate that, for men, marriage and children at job entry have negative effects on job exits; for women, they negatively affect exits to attend school but positively affect exits for other reasons, suggesting that young women with children may consider parenting their…

  7. Using La Familia Communication Competency Skills To Empower Hispanic At-Risk Students.

    ERIC Educational Resources Information Center

    Flores, Norma Landa

    Hispanic families can be empowered through parent training workshops focusing on the development of competency based interpersonal communication skills. Nearly 50% of the Latinos in the United States are at risk of dropping out before graduating from high school. They believe that their family obligations come first and that the school system is…

  8. Risk of dementia and death in patients with atrial fibrillation: A competing risk analysis of a population-based cohort.

    PubMed

    Marzona, Irene; Baviera, Marta; Vannini, Tommaso; Tettamanti, Mauro; Cortesi, Laura; Riva, Emma; Nobili, Alessandro; Marcon, Gabriella; Fortino, Ida; Bortolotti, Angela; Merlino, Luca; Roncaglioni, Maria Carla

    2016-10-01

    Previous studies have stated that atrial fibrillation (AF) is associated with a higher risk of dementia. However, none have examined the competition between death and incident dementia in patients with AF. We evaluated the risk of incident dementia in patients with AF in comparison to people without this arrhythmia, considering of the competing risk of death. AF and non-AF cohorts were identified using the large administrative database of the Lombardy Region and followed for ten years. Patients with incident dementia were identified if they had an ICD 9 code referring to dementia at hospital discharge or a prescription for any anti-dementia drug. The association of AF with dementia or death was assessed with the multivariable Cox proportional-regression model, sensitivity analysis with a 1:1 propensity score matching and competing-risk analysis. In 2003 a total of 27,431 patients were hospitalized for AF in the Lombardy Region, while the cohort of non-AF counted 1,600,200 people. AF was associated with a higher risk of dementia (17%) and death (51%) at multivariable Cox analysis. These results were confirmed by the model fitted after propensity score matching. However, competing risk analysis found the association between AF and incident dementia was no longer significant (HR 0.99; 95% CI 0.94-1.04). In this real-world population the association between AF and dementia was no longer statistically significant when death was considered a competing risk. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  9. Intelligence quotient discrepancy indicates levels of motor competence in preschool children at risk for developmental delays.

    PubMed

    Yu, Tzu-Ying; Chen, Kuan-Lin; Chou, Willy; Yang, Shu-Han; Kung, Sheng-Chun; Lee, Ya-Chen; Tung, Li-Chen

    2016-01-01

    This study aimed to establish 1) whether a group difference exists in the motor competence of preschool children at risk for developmental delays with intelligence quotient discrepancy (IQD; refers to difference between verbal intelligence quotient [VIQ] and performance intelligence quotient [PIQ]) and 2) whether an association exists between IQD and motor competence. Children's motor competence and IQD were determined with the motor subtests of the Comprehensive Developmental Inventory for Infants and Toddlers and Wechsler Preschool and Primary Scale of Intelligence™ - Fourth Edition. A total of 291 children were included in three groups: NON-IQD (n=213; IQD within 1 standard deviation [SD]), VIQ>PIQ (n=39; VIQ>PIQ greater than 1 SD), and PIQ>VIQ (n=39; PIQ>VIQ greater than 1 SD). The results of one-way analysis of variance indicated significant differences among the subgroups for the "Gross and fine motor" subdomains of the Comprehensive Developmental Inventory for Infants and Toddlers, especially on the subtests of "body-movement coordination" (F=3.87, P<0.05) and "visual-motor coordination" (F=6.90, P<0.05). Motor competence was significantly worse in the VIQ>PIQ group than in the NON and PIQ>VIQ groups. Significant negative correlations between IQD and most of the motor subtests (r=0.31-0.46, P<0.01) were found only in the VIQ>PIQ group. This study demonstrates that 1) IQD indicates the level of motor competence in preschoolers at risk for developmental delays and 2) IQD is negatively associated with motor competence in preschoolers with significant VIQ>PIQ discrepancy. The first finding was that preschoolers with VIQ>PIQ discrepancy greater than 1 SD performed significantly worse on motor competence than did preschoolers without significant IQD and preschoolers with PIQ>VIQ discrepancy greater than 1 SD. However, preschoolers with significant PIQ>VIQ discrepancy performed better on motor competence than did preschoolers without significant IQD, though the

  10. Intelligence quotient discrepancy indicates levels of motor competence in preschool children at risk for developmental delays

    PubMed Central

    Yu, Tzu-Ying; Chen, Kuan-Lin; Chou, Willy; Yang, Shu-Han; Kung, Sheng-Chun; Lee, Ya-Chen; Tung, Li-Chen

    2016-01-01

    Purpose This study aimed to establish 1) whether a group difference exists in the motor competence of preschool children at risk for developmental delays with intelligence quotient discrepancy (IQD; refers to difference between verbal intelligence quotient [VIQ] and performance intelligence quotient [PIQ]) and 2) whether an association exists between IQD and motor competence. Methods Children’s motor competence and IQD were determined with the motor subtests of the Comprehensive Developmental Inventory for Infants and Toddlers and Wechsler Preschool and Primary Scale of Intelligence™ – Fourth Edition. A total of 291 children were included in three groups: NON-IQD (n=213; IQD within 1 standard deviation [SD]), VIQ>PIQ (n=39; VIQ>PIQ greater than 1 SD), and PIQ>VIQ (n=39; PIQ>VIQ greater than 1 SD). Results The results of one-way analysis of variance indicated significant differences among the subgroups for the “Gross and fine motor” subdomains of the Comprehensive Developmental Inventory for Infants and Toddlers, especially on the subtests of “body-movement coordination” (F=3.87, P<0.05) and “visual-motor coordination” (F=6.90, P<0.05). Motor competence was significantly worse in the VIQ>PIQ group than in the NON and PIQ>VIQ groups. Significant negative correlations between IQD and most of the motor subtests (r=0.31–0.46, P<0.01) were found only in the VIQ>PIQ group. Conclusion This study demonstrates that 1) IQD indicates the level of motor competence in preschoolers at risk for developmental delays and 2) IQD is negatively associated with motor competence in preschoolers with significant VIQ>PIQ discrepancy. The first finding was that preschoolers with VIQ>PIQ discrepancy greater than 1 SD performed significantly worse on motor competence than did preschoolers without significant IQD and preschoolers with PIQ>VIQ discrepancy greater than 1 SD. However, preschoolers with significant PIQ>VIQ discrepancy performed better on motor competence than

  11. Oppositionality and socioemotional competence: interacting risk factors in the development of childhood conduct disorder symptoms.

    PubMed

    Mandy, William; Skuse, David; Steer, Colin; St Pourcain, Beate; Oliver, Bonamy R

    2013-07-01

    Oppositional behavior in childhood is a probabilistic risk factor for the subsequent development of more serious conduct problems characteristic of conduct disorder (CD). The capacity to understand the subjective states of others (socioemotional competence) helps regulate antisocial behavior in typical development. We hypothesized that socioemotional competence moderates the developmental relationship between oppositionality and CD symptoms, such that oppositional defiant disorder (ODD) symptoms pose the greatest risk for subsequent CD symptoms in children with poor socioemotional competence. Parent-report data were collected for 6,218 children at 7 and 10 years of age. Bootstrap multiple regression predicting CD symptoms at age 10 was used to test for an interaction between socioemotional competence and ODD symptoms, while also accounting for direct effects and controlling for sex, maternal education, attention-deficit/hyperactivity disorder symptoms, and CD symptoms at 7 years. We further tested whether the interaction applied to both males and females, and to both aggressive and rule-breaking CD symptoms. A significant interaction was found between ODD and socioemotional competence: the association between oppositionality at 7 years and CD traits at 10 years was strongest for children with poor socioemotional capacities. As predicted, this moderation effect was significant in a model predicting aggression, but it was not significant for rule-breaking CD symptoms. Socioemotional competence moderates the developmental relationship between mid-childhood oppositionality and more serious conduct problems in later childhood. A capacity to understand the subjective states of others may buffer the risk posed by oppositionality for later CD symptoms, including aggression. Copyright © 2013 American Academy of Child and Adolescent Psychiatry. Published by Elsevier Inc. All rights reserved.

  12. Comparing multiple competing interventions in the absence of randomized trials using clinical risk-benefit analysis

    PubMed Central

    2012-01-01

    Background To demonstrate the use of risk-benefit analysis for comparing multiple competing interventions in the absence of randomized trials, we applied this approach to the evaluation of five anticoagulants to prevent thrombosis in patients undergoing orthopedic surgery. Methods Using a cost-effectiveness approach from a clinical perspective (i.e. risk benefit analysis) we compared thromboprophylaxis with warfarin, low molecular weight heparin, unfractionated heparin, fondaparinux or ximelagatran in patients undergoing major orthopedic surgery, with sub-analyses according to surgery type. Proportions and variances of events defining risk (major bleeding) and benefit (thrombosis averted) were obtained through a meta-analysis and used to define beta distributions. Monte Carlo simulations were conducted and used to calculate incremental risks, benefits, and risk-benefit ratios. Finally, net clinical benefit was calculated for all replications across a range of risk-benefit acceptability thresholds, with a reference range obtained by estimating the case fatality rate - ratio of thrombosis to bleeding. Results The analysis showed that compared to placebo ximelagatran was superior to other options but final results were influenced by type of surgery, since ximelagatran was superior in total knee replacement but not in total hip replacement. Conclusions Using simulation and economic techniques we demonstrate a method that allows comparing multiple competing interventions in the absence of randomized trials with multiple arms by determining the option with the best risk-benefit profile. It can be helpful in clinical decision making since it incorporates risk, benefit, and personal risk acceptance. PMID:22233221

  13. A Comparison of Parametric and Non-Parametric Methods Applied to a Likert Scale

    PubMed Central

    Mircioiu, Constantin; Atkinson, Jeffrey

    2017-01-01

    A trenchant and passionate dispute over the use of parametric versus non-parametric methods for the analysis of Likert scale ordinal data has raged for the past eight decades. The answer is not a simple “yes” or “no” but is related to hypotheses, objectives, risks, and paradigms. In this paper, we took a pragmatic approach. We applied both types of methods to the analysis of actual Likert data on responses from different professional subgroups of European pharmacists regarding competencies for practice. Results obtained show that with “large” (>15) numbers of responses and similar (but clearly not normal) distributions from different subgroups, parametric and non-parametric analyses give in almost all cases the same significant or non-significant results for inter-subgroup comparisons. Parametric methods were more discriminant in the cases of non-similar conclusions. Considering that the largest differences in opinions occurred in the upper part of the 4-point Likert scale (ranks 3 “very important” and 4 “essential”), a “score analysis” based on this part of the data was undertaken. This transformation of the ordinal Likert data into binary scores produced a graphical representation that was visually easier to understand as differences were accentuated. In conclusion, in this case of Likert ordinal data with high response rates, restraining the analysis to non-parametric methods leads to a loss of information. The addition of parametric methods, graphical analysis, analysis of subsets, and transformation of data leads to more in-depth analyses. PMID:28970438

  14. Competence, risk, and resilience in military families: conceptual commentary.

    PubMed

    Masten, Ann S

    2013-09-01

    This commentary highlights conceptual themes in the opening section of this special issue on military families in relation to a new synthesis of developmental systems theory that emerged from developmental, ecological, and family systems theory, as well as developmental psychopathology and risk/resilience frameworks. Articles in this special issue draw on these concepts to characterize and guide the burgeoning research on military families. This perspective emphasizes that multiple dynamic systems interact across levels to shape individual development, as well as the function of families and military units. Developmental timing is important for understanding how challenges of military life may impact individuals and families. Cascade effects are noted, where stress experienced by one family or service member can influence the function of other individuals or larger systems. Capacity for resilience is distributed across systems, including families and cultures, as well as resources or supports provided by military organizations to foster adaptive responses or recovery. These systems include schools and educational programs that play key roles in fostering and supporting resilience for children. Overall, developmental system concepts have considerable utility for guiding research with military families, particularly in regard to promoting resilience. Moreover, lessons learned from military families and programs may have much broader implications for many other nonmilitary children, families, and organizations that share similar goals and challenges.

  15. A Novel Risk Score to the Prediction of 10-year Risk for Coronary Artery Disease Among the Elderly in Beijing Based on Competing Risk Model.

    PubMed

    Liu, Long; Tang, Zhe; Li, Xia; Luo, Yanxia; Guo, Jin; Li, Haibin; Liu, Xiangtong; Tao, Lixin; Yan, Aoshuang; Guo, Xiuhua

    2016-03-01

    The study aimed to construct a risk prediction model for coronary artery disease (CAD) based on competing risk model among the elderly in Beijing and develop a user-friendly CAD risk score tool. We used competing risk model to evaluate the risk of developing a first CAD event. On the basis of the risk factors that were included in the competing risk model, we constructed the CAD risk prediction model with Cox proportional hazard model. Time-dependent receiver operating characteristic (ROC) curve and time-dependent area under the ROC curve (AUC) were used to evaluate the discrimination ability of the both methods. Calibration plots were applied to assess the calibration ability and adjusted for the competing risk of non-CAD death. Net reclassification index (NRI) and integrated discrimination improvement (IDI) were applied to quantify the improvement contributed by the new risk factors. Internal validation of predictive accuracy was performed using 1000 times of bootstrap re-sampling. Of the 1775 participants without CAD at baseline, 473 incident cases of CAD were documented for a 20-year follow-up. Time-dependent AUCs for men and women at t = 10 years were 0.841 [95% confidence interval (95% CI): 0.806-0.877], 0.804 (95% CI: 0.768-0.839) in Fine and Gray model, 0.784 (95% CI: 0.738-0.830), 0.733 (95% CI: 0.692-0.775) in Cox proportional hazard model. The competing risk model was significantly superior to Cox proportional hazard model on discrimination and calibration. The cut-off values of the risk score that marked the difference between low-risk and high-risk patients were 34 points for men and 30 points for women, which have good sensitivity and specificity. A sex-specific multivariable risk factor algorithm-based competing risk model has been developed on the basis of an elderly Chinese cohort, which could be applied to predict an individual's risk and provide a useful guide to identify the groups at a high risk for CAD among the Chinese adults over 55

  16. A Novel Risk Score to the Prediction of 10-year Risk for Coronary Artery Disease Among the Elderly in Beijing Based on Competing Risk Model

    PubMed Central

    Liu, Long; Tang, Zhe; Li, Xia; Luo, Yanxia; Guo, Jin; Li, Haibin; Liu, Xiangtong; Tao, Lixin; Yan, Aoshuang; Guo, Xiuhua

    2016-01-01

    Abstract The study aimed to construct a risk prediction model for coronary artery disease (CAD) based on competing risk model among the elderly in Beijing and develop a user-friendly CAD risk score tool. We used competing risk model to evaluate the risk of developing a first CAD event. On the basis of the risk factors that were included in the competing risk model, we constructed the CAD risk prediction model with Cox proportional hazard model. Time-dependent receiver operating characteristic (ROC) curve and time-dependent area under the ROC curve (AUC) were used to evaluate the discrimination ability of the both methods. Calibration plots were applied to assess the calibration ability and adjusted for the competing risk of non-CAD death. Net reclassification index (NRI) and integrated discrimination improvement (IDI) were applied to quantify the improvement contributed by the new risk factors. Internal validation of predictive accuracy was performed using 1000 times of bootstrap re-sampling. Of the 1775 participants without CAD at baseline, 473 incident cases of CAD were documented for a 20-year follow-up. Time-dependent AUCs for men and women at t = 10 years were 0.841 [95% confidence interval (95% CI): 0.806–0.877], 0.804 (95% CI: 0.768–0.839) in Fine and Gray model, 0.784 (95% CI: 0.738–0.830), 0.733 (95% CI: 0.692–0.775) in Cox proportional hazard model. The competing risk model was significantly superior to Cox proportional hazard model on discrimination and calibration. The cut-off values of the risk score that marked the difference between low-risk and high-risk patients were 34 points for men and 30 points for women, which have good sensitivity and specificity. A sex-specific multivariable risk factor algorithm-based competing risk model has been developed on the basis of an elderly Chinese cohort, which could be applied to predict an individual's risk and provide a useful guide to identify the groups at a high risk for CAD among the Chinese

  17. Competing risk analysis on outcome after hepatic resection of hepatocellular carcinoma in cirrhotic patients

    PubMed Central

    Cucchetti, Alessandro; Sposito, Carlo; Pinna, Antonio Daniele; Citterio, Davide; Cescon, Matteo; Bongini, Marco; Ercolani, Giorgio; Cotsoglou, Christian; Maroni, Lorenzo; Mazzaferro, Vincenzo

    2017-01-01

    AIM To investigate death for liver failure and for tumor recurrence as competing events after hepatectomy of hepatocellular carcinoma. METHODS Data from 864 cirrhotic Child-Pugh class A consecutive patients, submitted to curative hepatectomy (1997-2013) at two tertiary referral hospitals, were used for competing-risk analysis through the Fine and Gray method, aimed at assessing in which circumstances the oncological benefit from tumour removal is greater than the risk of dying from hepatic decompensation. To accomplish this task, the average risk of these two competing events, over 5 years of follow-up, was calculated through the integral of each cumulative incidence function, and represented the main comparison parameter. RESULTS Within a median follow-up of 5.6 years, death was attributable to tumor recurrence in 63.5%, and to liver failure in 21.2% of cases. In the first 16 mo, the risk of dying due to liver failure exceeded that of dying due to tumor relapse. Tumor stage only affects death from recurrence; whereas hepatitis C infection, Model for End-stage Liver Disease score, extent of hepatectomy and portal hypertension influence death from liver failure (P < 0.05 in all cases). The combination of these clinical and tumoral features identifies those patients in whom the risk of dying from liver failure did not exceed the tumour-related mortality, representing optimal surgical candidates. It also identifies those clinical circumstances where the oncological benefit would be borderline or even where the surgery would be harmful. CONCLUSION Having knowledge of these competing events can be used to weigh the risks and benefits of hepatic resection in each clinical circumstance, separating optimal from non-optimal surgical candidates. PMID:28293094

  18. Improved Method to Stratify Elderly Patients With Cancer at Risk for Competing Events.

    PubMed

    Carmona, Ruben; Zakeri, Kaveh; Green, Garrett; Hwang, Lindsay; Gulaya, Sachin; Xu, Beibei; Verma, Rohan; Williamson, Casey W; Triplett, Daniel P; Rose, Brent S; Shen, Hanjie; Vaida, Florin; Murphy, James D; Mell, Loren K

    2016-04-10

    To compare a novel generalized competing event (GCE) model versus the standard Cox proportional hazards regression model for stratifying elderly patients with cancer who are at risk for competing events. We identified 84,319 patients with nonmetastatic prostate, head and neck, and breast cancers from the SEER-Medicare database. Using demographic, tumor, and clinical characteristics, we trained risk scores on the basis of GCE versus Cox models for cancer-specific mortality and all-cause mortality. In test sets, we examined the predictive ability of the risk scores on the different causes of death, including second cancer mortality, noncancer mortality, and cause-specific mortality, using Fine-Gray regression and area under the curve. We compared how well models stratified subpopulations according to the ratio of the cumulative cause-specific hazard for cancer mortality to the cumulative hazard for overall mortality (ω) using the Akaike Information Criterion. In each sample, increasing GCE risk scores were associated with increased cancer-specific mortality and decreased competing mortality, whereas risk scores from Cox models were associated with both increased cancer-specific mortality and competing mortality. GCE models created greater separation in the area under the curve for cancer-specific mortality versus noncancer mortality (P < .001), indicating better discriminatory ability between these events. Comparing the GCE model to Cox models of cause-specific mortality or all-cause mortality, the respective Akaike Information Criterion scores were superior (lower) in each sample: prostate cancer, 28.6 versus 35.5 versus 39.4; head and neck cancer, 21.1 versus 29.4 versus 40.2; and breast cancer, 24.6 versus 32.3 versus 50.8. Compared with standard modeling approaches, GCE models improve stratification of elderly patients with cancer according to their risk of dying from cancer relative to overall mortality. © 2016 by American Society of Clinical Oncology.

  19. Improved Method to Stratify Elderly Patients With Cancer at Risk for Competing Events

    PubMed Central

    Carmona, Ruben; Zakeri, Kaveh; Green, Garrett; Hwang, Lindsay; Gulaya, Sachin; Xu, Beibei; Verma, Rohan; Williamson, Casey W.; Triplett, Daniel P.; Rose, Brent S.; Shen, Hanjie; Vaida, Florin; Murphy, James D.

    2016-01-01

    Purpose To compare a novel generalized competing event (GCE) model versus the standard Cox proportional hazards regression model for stratifying elderly patients with cancer who are at risk for competing events. Methods We identified 84,319 patients with nonmetastatic prostate, head and neck, and breast cancers from the SEER-Medicare database. Using demographic, tumor, and clinical characteristics, we trained risk scores on the basis of GCE versus Cox models for cancer-specific mortality and all-cause mortality. In test sets, we examined the predictive ability of the risk scores on the different causes of death, including second cancer mortality, noncancer mortality, and cause-specific mortality, using Fine-Gray regression and area under the curve. We compared how well models stratified subpopulations according to the ratio of the cumulative cause-specific hazard for cancer mortality to the cumulative hazard for overall mortality (ω) using the Akaike Information Criterion. Results In each sample, increasing GCE risk scores were associated with increased cancer-specific mortality and decreased competing mortality, whereas risk scores from Cox models were associated with both increased cancer-specific mortality and competing mortality. GCE models created greater separation in the area under the curve for cancer-specific mortality versus noncancer mortality (P < .001), indicating better discriminatory ability between these events. Comparing the GCE model to Cox models of cause-specific mortality or all-cause mortality, the respective Akaike Information Criterion scores were superior (lower) in each sample: prostate cancer, 28.6 versus 35.5 versus 39.4; head and neck cancer, 21.1 versus 29.4 versus 40.2; and breast cancer, 24.6 versus 32.3 versus 50.8. Conclusion Compared with standard modeling approaches, GCE models improve stratification of elderly patients with cancer according to their risk of dying from cancer relative to overall mortality. PMID:26884579

  20. Competing risk analysis of mortality in prostate cancer treated with radical prostatectomy.

    PubMed

    Ruiz-Cerdá, J L; Soto-Poveda, A; Luján-Marco, S; Loras-Monfort, A; Trassierra-Villa, M; Rogel-Bertó, R; Boronat-Tormo, F

    To determine the risk of cancer-specific mortality (CSM) versus the competing risk of mortality by other causes (MOC) in patients with localised prostate cancer (LPC) treated with radical prostatectomy (RP). An observational cohort study of 982 patients with LPC treated with RP selected from our department's PC registry database. A competing risk analysis was performed, calculating the probability of CSM in the presence of the competing risk of MOC. Cumulative incidence curves were constructed, and point estimates were performed at 5, 10 and 15 years. The analysis was stratified by age (≤65 vs. >65 years) and risk group: low (Gleason score ≤6 and pT2abc); intermediate (Gleason score of 7 and pT2abc) and high (Gleason score of 8-10 or pT3ab). With a median follow-up of 60 months, the overall probability of dying from PC was 3.5%, and the probability of dying from other causes was 9%. A competing effect for MOC was observed. The risk of MOC was almost 3 times greater than that of CSM. This effect remained for all risk groups, although its magnitude decreased progressively according to the risk group level. At 10 years, CSM was only 0%, 1% and 2% for the low, intermediate and high-risk groups, respectively, while the likelihood of MOC was 4%, 4% and 10%, respectively. The mortality risk was shown after 10years of follow-up and was higher for other causes not attributable to PC and for patients older than 65years. The benefit of RP might be overestimated, given that the risk of MOC is greater than that of CSM, regardless of the age group and risk group, especially after 10years of follow-up. The only parameter that varied was the magnitude of the CSM/MOC ratio. This information could help in choosing the active treatment for patients with LPC and short life expectancies. Copyright © 2016 AEU. Publicado por Elsevier España, S.L.U. All rights reserved.

  1. Quantifying the predictive accuracy of time-to-event models in the presence of competing risks.

    PubMed

    Schoop, Rotraut; Beyersmann, Jan; Schumacher, Martin; Binder, Harald

    2011-02-01

    Prognostic models for time-to-event data play a prominent role in therapy assignment, risk stratification and inter-hospital quality assurance. The assessment of their prognostic value is vital not only for responsible resource allocation, but also for their widespread acceptance. The additional presence of competing risks to the event of interest requires proper handling not only on the model building side, but also during assessment. Research into methods for the evaluation of the prognostic potential of models accounting for competing risks is still needed, as most proposed methods measure either their discrimination or calibration, but do not examine both simultaneously. We adapt the prediction error proposal of Graf et al. (Statistics in Medicine 1999, 18, 2529–2545) and Gerds and Schumacher (Biometrical Journal 2006, 48, 1029–1040) to handle models with competing risks, i.e. more than one possible event type, and introduce a consistent estimator. A simulation study investigating the behaviour of the estimator in small sample size situations and for different levels of censoring together with a real data application follows.

  2. Accounting for death as a competing risk in cancer-associated thrombosis studies.

    PubMed

    Campigotto, Federico; Neuberg, Donna; Zwicker, Jeffrey I

    2012-04-01

    In recent years, clinical investigation in the field of cancer-associated thrombosis has identified a number of potential biomarkers to predict the risk of developing a thrombotic event. Similarly, large randomized clinical trials have demonstrated the benefit of low molecular weight heparins in the treatment as well as prevention of venous thromboembolic events (VTE) in cancer patients. However, the most common statistical methodology to evaluate the occurrence of VTE has been the Kaplan-Meier approach. When used to estimate the cumulative incidence of VTE in cancer studies, the Kaplan-Meier method over-estimates the cumulative incidence function due to failure to account for death as a competing risk for the development of VTE. A more appropriate statistical estimate of cumulative incidence of VTE in cancer studies is the competing risk model. This review describes the theoretical and mathematical basis for estimating the cumulative incidence function by the competing risk model for the analysis of VTE outcomes in cancer-associated thrombosis.

  3. Non-parametric estimation of relative risk in survival and associated tests.

    PubMed

    Wakounig, Samo; Heinze, Georg; Schemper, Michael

    2015-12-01

    We extend the Tarone and Ware scheme of weighted log-rank tests to cover the associated weighted Mantel-Haenszel estimators of relative risk. Weighting functions previously employed are critically reviewed. The notion of an average hazard ratio is defined and its connection to the effect size measure P(Y > X) is emphasized. The connection makes estimation of P(Y > X) possible also under censoring. Two members of the extended Tarone-Ware scheme accomplish the estimation of intuitively interpretable average hazard ratios, also under censoring and time-varying relative risk which is achieved by an inverse probability of censoring weighting. The empirical properties of the members of the extended Tarone-Ware scheme are demonstrated by a Monte Carlo study. The differential role of the weighting functions considered is illustrated by a comparative analysis of four real data sets.

  4. Analysis and design of randomised clinical trials involving competing risks endpoints

    PubMed Central

    2011-01-01

    Background In randomised clinical trials involving time-to-event outcomes, the failures concerned may be events of an entirely different nature and as such define a classical competing risks framework. In designing and analysing clinical trials involving such endpoints, it is important to account for the competing events, and evaluate how each contributes to the overall failure. An appropriate choice of statistical model is important for adequate determination of sample size. Methods We describe how competing events may be summarised in such trials using cumulative incidence functions and Gray's test. The statistical modelling of competing events using proportional cause-specific and subdistribution hazard functions, and the corresponding procedures for sample size estimation are outlined. These are illustrated using data from a randomised clinical trial (SQNP01) of patients with advanced (non-metastatic) nasopharyngeal cancer. Results In this trial, treatment has no effect on the competing event of loco-regional recurrence. Thus the effects of treatment on the hazard of distant metastasis were similar via both the cause-specific (unadjusted csHR = 0.43, 95% CI 0.25 - 0.72) and subdistribution (unadjusted subHR 0.43; 95% CI 0.25 - 0.76) hazard analyses, in favour of concurrent chemo-radiotherapy followed by adjuvant chemotherapy. Adjusting for nodal status and tumour size did not alter the results. The results of the logrank test (p = 0.002) comparing the cause-specific hazards and the Gray's test (p = 0.003) comparing the cumulative incidences also led to the same conclusion. However, the subdistribution hazard analysis requires many more subjects than the cause-specific hazard analysis to detect the same magnitude of effect. Conclusions The cause-specific hazard analysis is appropriate for analysing competing risks outcomes when treatment has no effect on the cause-specific hazard of the competing event. It requires fewer subjects than the subdistribution hazard

  5. Treatment should be considered a competing risk when predicting natural conception in subfertile women.

    PubMed

    Van Geloven, N; Broeze, K A; Bossuyt, P M M; Zwinderman, A H; Mol, B W

    2012-03-01

    Prediction of natural conception in subfertile couples can help to differentiate between couples who should have immediate treatment and couples who can aim for natural conception for some time. Natural conception rates are often estimated using standard techniques such as Kaplan-Meier or Cox proportional hazard models. These estimates can be biased by incorrect handling of data from women who start assisted reproductive technology therapy before the end of the follow-up period. This paper discusses the validity and the impact of the assumption of non-informative censoring as used in the Kaplan-Meier and Cox models. In a cohort of 5360 subfertile couples with suspected tubal pathology, the probability of natural conception and the prognostic value of additional tests for tubal pathology were estimated using traditional methods and with a competing risks analysis. The estimated probability of natural conception within 3 years was almost 2-fold higher when assuming non-informative censoring compared with the competing risks model, 41 versus 22%. The prognostic value of tests was more conservative using the competing risks model than with the traditional methods, the fecundity rate ratio for Chlamydia antibody testing was 0.72 versus 0.67, for hysterosalpingography, 0.83 versus 0.71 and for diagnostic laparoscopy, 0.89 versus 0.74. Given the improbable validity of the non-informative censoring assumption, the predictions of natural conception and of the prognostic value of tests are likely to be overestimated by the traditional analytic methods. We suggest the use of competing risks models as an alternative, more conservative, form of analysis when predicting natural conception and evaluating prognostic fertility tests.

  6. Analyzing semi-competing risks data with missing cause of informative terminal event.

    PubMed

    Zhou, Renke; Zhu, Hong; Bondy, Melissa; Ning, Jing

    2017-02-28

    Cancer studies frequently yield multiple event times that correspond to landmarks in disease progression, including non-terminal events (i.e., cancer recurrence) and an informative terminal event (i.e., cancer-related death). Hence, we often observe semi-competing risks data. Work on such data has focused on scenarios in which the cause of the terminal event is known. However, in some circumstances, the information on cause for patients who experience the terminal event is missing; consequently, we are not able to differentiate an informative terminal event from a non-informative terminal event. In this article, we propose a method to handle missing data regarding the cause of an informative terminal event when analyzing the semi-competing risks data. We first consider the nonparametric estimation of the survival function for the terminal event time given missing cause-of-failure data via the expectation-maximization algorithm. We then develop an estimation method for semi-competing risks data with missing cause of the terminal event, under a pre-specified semiparametric copula model. We conduct simulation studies to investigate the performance of the proposed method. We illustrate our methodology using data from a study of early-stage breast cancer. Copyright © 2016 John Wiley & Sons, Ltd.

  7. Variable selection in subdistribution hazard frailty models with competing risks data

    PubMed Central

    Do Ha, Il; Lee, Minjung; Oh, Seungyoung; Jeong, Jong-Hyeon; Sylvester, Richard; Lee, Youngjo

    2014-01-01

    The proportional subdistribution hazards model (i.e. Fine-Gray model) has been widely used for analyzing univariate competing risks data. Recently, this model has been extended to clustered competing risks data via frailty. To the best of our knowledge, however, there has been no literature on variable selection method for such competing risks frailty models. In this paper, we propose a simple but unified procedure via a penalized h-likelihood (HL) for variable selection of fixed effects in a general class of subdistribution hazard frailty models, in which random effects may be shared or correlated. We consider three penalty functions (LASSO, SCAD and HL) in our variable selection procedure. We show that the proposed method can be easily implemented using a slight modification to existing h-likelihood estimation approaches. Numerical studies demonstrate that the proposed procedure using the HL penalty performs well, providing a higher probability of choosing the true model than LASSO and SCAD methods without losing prediction accuracy. The usefulness of the new method is illustrated using two actual data sets from multi-center clinical trials. PMID:25042872

  8. Covariate adjustment of cumulative incidence functions for competing risks data using inverse probability of treatment weighting.

    PubMed

    Neumann, Anke; Billionnet, Cécile

    2016-06-01

    In observational studies without random assignment of the treatment, the unadjusted comparison between treatment groups may be misleading due to confounding. One method to adjust for measured confounders is inverse probability of treatment weighting. This method can also be used in the analysis of time to event data with competing risks. Competing risks arise if for some individuals the event of interest is precluded by a different type of event occurring before, or if only the earliest of several times to event, corresponding to different event types, is observed or is of interest. In the presence of competing risks, time to event data are often characterized by cumulative incidence functions, one for each event type of interest. We describe the use of inverse probability of treatment weighting to create adjusted cumulative incidence functions. This method is equivalent to direct standardization when the weight model is saturated. No assumptions about the form of the cumulative incidence functions are required. The method allows studying associations between treatment and the different types of event under study, while focusing on the earliest event only. We present a SAS macro implementing this method and we provide a worked example. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  9. A computer program for the generalized chi-square analysis of competing risks grouped survival data (CRISCAT).

    PubMed

    Stanish, W M; Chi, G Y; Johnson, W D; Koch, G G; Landis, J R; Liu-Chi, S

    1978-09-01

    CRISCAT is a computer program for the analysis of grouped survival data with competing risks via weighted least squares methods. Competing risks adjustments are obtained from general matrix operations using many of the strategies employed in a previously developed program (GENCAT) for multivariate categorical data. CRISCAT computes survival rates at several time points for multiple causes of failure, where each rate is adjusted for other causes in the sense that failure due to thes other causes has been eliminated as a risk. The program can generate functions of the adjusted survival rates, to which asymptotic regression models may be fit. CRISCAT yields test statistics for hypotheses involving either these functions or estimated model parameters. Thus, this computational algorithm links competing risks theory to linear models methods for contingency table analysis and provides a unified approach to estimation and hypothesis testing of functions involving competing risks adjusted rates.

  10. A method for evaluating competency in assessment and management of suicide risk.

    PubMed

    Hung, Erick K; Binder, Renée L; Fordwood, Samantha R; Hall, Stephen E; Cramer, Robert J; McNiel, Dale E

    2012-01-01

    Although health professionals increasingly are expected to be able to assess and manage patients' risk for suicide, few methods are available to evaluate this competency. This report describes development of a competency-assessment instrument for suicide risk-assessment (CAI-S), and evaluates its use in an objective structured clinical examination (OSCE). The authors developed the CAI-S on the basis of the literature on suicide risk-assessment and management, and consultation with faculty focus groups from three sites in a large academic psychiatry department. The CAI-S structures faculty ratings regarding interviewing and data collection, case formulation and presentation, treatment-planning, and documentation. To evaluate the CAI-S, 31 faculty members used it to rate the performance of 31 learners (26 psychiatric residents and 5 clinical psychology interns) who participated in an OSCE. After interviewing a standardized patient, learners presented their risk-assessment findings and treatment plans. Faculty used the CAI-S to structure feedback to the learners. In a subsidiary study of interrater reliability, six faculty members rated video-recorded suicide risk-assessments. The CAI-S showed good internal consistency, reliability, and interrater reliability. Concurrent validity was supported by the finding that CAI-S ratings were higher for senior learners than junior learners, and were higher for learners with more clinical experience with suicidal patients than learners with less clinical experience. Faculty and learners rated the method as helpful for structuring feedback and supervision. The findings support the usefulness of the CAI-S for evaluating competency in suicide risk-assessment and management.

  11. A Competence-Based Science Learning Framework Illustrated through the Study of Natural Hazards and Disaster Risk Reduction

    ERIC Educational Resources Information Center

    Oyao, Sheila G.; Holbrook, Jack; Rannikmäe, Miia; Pagunsan, Marmon M.

    2015-01-01

    This article proposes a competence-based learning framework for science teaching, applied to the study of "big ideas", in this case to the study of natural hazards and disaster risk reduction (NH&DRR). The framework focuses on new visions of competence, placing emphasis on nurturing connectedness and behavioral actions toward…

  12. The Learning and Competency Development of Master Teachers in Alternative High Schools for At-Risk Youth: A Case Study

    ERIC Educational Resources Information Center

    Williams, Nida W.

    2012-01-01

    This qualitative case study was designed to explore how master teachers in transfer high schools learn the competencies they perceive are required to engage at-risk students so that they persist and graduate. The study is based on the following assumptions: (1) The requisite teacher competencies can be defined and identified and, in fact,…

  13. From Reading Readiness to Reading Competence: The Role of Self-Regulation in At-Risk Children

    ERIC Educational Resources Information Center

    Smith, Leann E.; Borkowski, John G.; Whitman, Thomas L.

    2008-01-01

    This study investigated how self-regulation contributes to the development of reading competence in an at-risk sample of 157 children born to adolescent mothers. It was hypothesized that reading readiness at age 5 would shape self-regulation at age 10, which in turn would influence reading competence at age 14. Based on structural equation…

  14. A Competence-Based Science Learning Framework Illustrated through the Study of Natural Hazards and Disaster Risk Reduction

    ERIC Educational Resources Information Center

    Oyao, Sheila G.; Holbrook, Jack; Rannikmäe, Miia; Pagunsan, Marmon M.

    2015-01-01

    This article proposes a competence-based learning framework for science teaching, applied to the study of "big ideas", in this case to the study of natural hazards and disaster risk reduction (NH&DRR). The framework focuses on new visions of competence, placing emphasis on nurturing connectedness and behavioral actions toward…

  15. A semi-parametric censoring bias model for estimating the cumulative risk of a false-positive screening test under dependent censoring

    PubMed Central

    Hubbard, Rebecca A.; Miglioretti, Diana L.

    2012-01-01

    Summary False-positive test results are among the most common harms of screening tests and may lead to more invasive and expensive diagnostic testing procedures. Estimating the cumulative risk of a false-positive screening test result after repeat screening rounds is therefore important for evaluating potential screening regimens. Existing estimators of the cumulative false-positive risk are limited by strong assumptions about censoring mechanisms and parametric assumptions about variation in risk across screening rounds. To address these limitations, we propose a semi-parametric censoring bias model for cumulative false-positive risk that allows for dependent censoring without specifying a fixed functional form for variation in risk across screening rounds. Simulation studies demonstrated that the censoring bias model performs similarly to existing models under independent censoring and can largely eliminate bias under dependent censoring. We used the existing and newly proposed models to estimate the cumulative false-positive risk and variation in risk as a function of baseline age and family history of breast cancer after 10 years of annual screening mammography using data from the Breast Cancer Surveillance Consortium. Ignoring potential dependent censoring in this context leads to underestimation of the cumulative risk of false-positive results. Models that provide accurate estimates under dependent censoring are critical for providing appropriate information for evaluating screening tests. PMID:23383717

  16. Outcome after Reconstruction of the Proximal Tibia – Complications and Competing Risk Analysis

    PubMed Central

    Puchner, Stephan E.; Kutscha-Lissberg, Paul; Kaider, Alexandra; Panotopoulos, Joannis; Puchner, Rudolf; Böhler, Christoph; Hobusch, Gerhard; Windhager, Reinhard; Funovics, Philipp T.

    2015-01-01

    Background and Objectives The proximal tibia (pT) is a common site for bone tumors. Improvements in imaging, chemotherapy and surgical technique made limb salvage surgery the treatment of choice. Yet, reconstructions of the pT have been associated with less favorable outcome compared to other parts of the extremities. The aim of this study was to evaluate the outcome of patients with a modular endoprosthetic reconstruction of the pT. Methods Eighty-one consecutive patients with an average age of 29 years underwent endoprosthetic reconstruction of the pT. Postoperative complications were categorized according to the ISOLS classification, and revision-free survival until first complication (any Type 1–5), soft tissue failure (Type 1), aseptic loosening (Type 2), structural failure (Type 3), infection (Type 4), and local tumor progression (Type 5) was estimated by using a Fine-Gray model for competing risk analyses for univariate and multivariable regression with Firth’s bias correction. Results A total of 45 patients (56%) had at least one complication. Cumulative incidence for complication Types 1 to 5 at 5 years with death and amputation as competing events revealed a risk of 41% for the first complication, 14% for Type 1, 16% for Type 2, 11% for Type 3, 17% for Type 4, and 1% for Type 5. Conclusion Despite inclusion of amputation and death as strong competing events, pT replacements are still associated with a high risk of postoperative failures. The results suggest that infection and soft tissue failures (Type 1 and 5) seem to depend from each other. Sufficient soft tissue reconstruction and closure allow better function and reduce the risk of infection as the most prominent complication. The use of a rotating hinge design has significantly reduced structural failures over time. PMID:26270336

  17. Competing risk of atherosclerotic risk factors for arterial and venous thrombosis in a general population: the Tromso study.

    PubMed

    Brækkan, Sigrid K; Hald, Erin M; Mathiesen, Ellisiv B; Njølstad, Inger; Wilsgaard, Tom; Rosendaal, Frits R; Hansen, John-Bjarne

    2012-02-01

    To investigate and compare the impact of traditional atherosclerotic risk factors for the risk of arterial and venous thrombosis, taking into account competing risks. In 1994-1995, 26,185 subjects were screened in the Tromsø study. Information on traditional atherosclerotic risk factors was obtained by physical examination, blood samples, and questionnaires. Subjects were followed to the first incident event of myocardial infarction (MI) or venous thromboembolism (VTE), or December 31, 2005. During a median of 10.8 years of follow-up, there were 1279 cases of incident MI and 341 VTE events. Advancing age and high body mass index were both associated with MI and VTE. Hazard ratio per decade of age was 2.34 (95% CI: 2.25-2.43) for MI and 1.87 (1.74-2.01) for VTE, and 3 kg/m(2) increase in body mass index was associated with 1.16 (1.11-1.21) and 1.20 (1.12-1.29) increased risk of MI and VTE, respectively. Blood pressure, high levels of triglycerides and total cholesterol, low HDL cholesterol, self-reported diabetes, and smoking were all associated with increased risk of MI but not associated with VTE. Our findings imply that traditional atherosclerotic risk factors, such as smoking, hypertension, dyslipidemia, and diabetes mellitus are not shared by arterial and venous thrombosis.

  18. Evaluation of Death among the Patients Undergoing Permanent Pacemaker Implantation: A Competing Risks Analysis

    PubMed Central

    GHAEM, Haleh; GHORBANI, Mohammad; ZARE DORNIANI, Samira

    2017-01-01

    Background: Permanent artificial pacemaker is one of the important therapies for treatment of cardiac conduction system problems. The present study aimed to determine the association between some predictive variables and all-cause and cause-specific mortality in the patients who had undergone pacemaker implantation. Methods: This study was conducted on 1207 patients who had undergone permanent pacemaker implantation in the hospitals affiliated with Shiraz University of Medical Sciences, Iran, from Mar 2002 to Mar 2012. The variables that existed in the patients’ medical records included sex, diabetes mellitus, obesity, cerebrovascular accident, cardiomegaly, smoking, hypertension, ischemic heart disease, congenital heart disease, sick sinus syndrome, and atrial fibrillation. Competing risks model was used to assess the association between the predictive variables and cause-specific (i.e., cardiac and vascular) mortality. Results: The patients’ mean age was 66.32±17.92 yr (70.62±14.45 yr in the patients with single-chamber pacemakers vs. 61.91±17.69 yr in those with two-chamber pacemakers) (P<0.001). Sick sinus syndrome and age increased the risk of all-cause mortality, while two-chamber pacemaker decreased this risk. Obesity increased the risk of cardiac death, and diabetes mellitus and heart valve disease increased the risk of vascular death. Conclusion: The variables predicting mortality in all-cause model were completely different from those in cause-specific model. Moreover, death in such patients may occur due to reasons other than pacemaker. Therefore, future studies, particularly prospective ones, are recommended to use competing risks models. PMID:28828325

  19. Evaluation of Death among the Patients Undergoing Permanent Pacemaker Implantation: A Competing Risks Analysis.

    PubMed

    Ghaem, Haleh; Ghorbani, Mohammad; Zare Dorniani, Samira

    2017-06-01

    Permanent artificial pacemaker is one of the important therapies for treatment of cardiac conduction system problems. The present study aimed to determine the association between some predictive variables and all-cause and cause-specific mortality in the patients who had undergone pacemaker implantation. This study was conducted on 1207 patients who had undergone permanent pacemaker implantation in the hospitals affiliated with Shiraz University of Medical Sciences, Iran, from Mar 2002 to Mar 2012. The variables that existed in the patients' medical records included sex, diabetes mellitus, obesity, cerebrovascular accident, cardiomegaly, smoking, hypertension, ischemic heart disease, congenital heart disease, sick sinus syndrome, and atrial fibrillation. Competing risks model was used to assess the association between the predictive variables and cause-specific (i.e., cardiac and vascular) mortality. The patients' mean age was 66.32±17.92 yr (70.62±14.45 yr in the patients with single-chamber pacemakers vs. 61.91±17.69 yr in those with two-chamber pacemakers) (P<0.001). Sick sinus syndrome and age increased the risk of all-cause mortality, while two-chamber pacemaker decreased this risk. Obesity increased the risk of cardiac death, and diabetes mellitus and heart valve disease increased the risk of vascular death. The variables predicting mortality in all-cause model were completely different from those in cause-specific model. Moreover, death in such patients may occur due to reasons other than pacemaker. Therefore, future studies, particularly prospective ones, are recommended to use competing risks models.

  20. Analysing multicentre competing risks data with a mixed proportional hazards model for the subdistribution.

    PubMed

    Katsahian, Sandrine; Resche-Rigon, Matthieu; Chevret, Sylvie; Porcher, Raphaël

    2006-12-30

    In the competing-risks setting, to test the effect of a covariate on the probability of one particular cause of failure, the Fine and Gray model for the subdistribution hazard can be used. However, sometimes, competing risks data cannot be considered as independent because of a clustered design, for instance in registry cohorts or multicentre clinical trials. Frailty models have been shown useful to analyse such clustered data in a classical survival setting, where only one risk acts on the population. Inclusion of random effects in the subdistribution hazard has not been assessed yet. In this work, we propose a frailty model for the subdistribution hazard. This allows first to assess the heterogeneity across clusters, then to incorporate such an effect when testing the effect of a covariate of interest. Based on simulation study, the effect of the presence of heterogeneity on testing for covariate effects was studied. Finally, the model was illustrated on a data set from a registry cohort of patients with acute myeloid leukaemia who underwent bone marrow transplantation.

  1. Competing risks analysis of microsatellite instability as a prognostic factor in colorectal cancer.

    PubMed

    Toh, J; Chapuis, P H; Bokey, L; Chan, C; Spring, K J; Dent, O F

    2017-08-01

    Despite an extensive literature suggesting that high microsatellite instability (MSI-H) enhances survival and protects against recurrence after colorectal cancer resection, such effects remain controversial as many studies show only a weak bivariate association or no multivariable association with outcome. This study examined the relationship between MSI status and colorectal cancer outcomes with adjustment for death from other causes as a competing risk. A hospital database of patients following colorectal cancer resection was interrogated for clinical, operative, pathology, adjuvant therapy and follow-up information. MSI-H status was determined by immunohistochemistry for mismatch repair protein deficiency. The cumulative incidence of recurrence and colorectal cancer-specific death was evaluated by competing risks methods. Among 1009 patients who had a resection between August 2002 and December 2008, and were followed to at least December 2013, there were 114 (11·3 per cent) with MSI-H (72·8 per cent aged at least 70 years; 63·2 per cent women). After potentially curative resection, with adjustment for non-colorectal cancer death as a competing risk and adjustment for 22 clinical, operative and pathological variables, there was no association between MSI-H and recurrence (hazard ratio (HR) 0·81, 95 per cent c.i. 0·42 to 1·57) or colorectal cancer-specific death (HR 0·73, 0·39 to 1·35) in this patient population. For palliative resections, there was no association between MSI-H and colorectal cancer-specific death (HR 0·65, 0·21 to 2·04). MSI-H was associated with non-colorectal cancer death after both curative (HR 1·55, 1·04 to 2·30) and palliative (HR 3·80, 1·32 to 11·00) resections. Microsatellite instability status was not an independent prognostic variable in these patients. © 2017 BJS Society Ltd Published by John Wiley & Sons Ltd.

  2. Practical recommendations for reporting Fine-Gray model analyses for competing risk data.

    PubMed

    Austin, Peter C; Fine, Jason P

    2017-09-15

    In survival analysis, a competing risk is an event whose occurrence precludes the occurrence of the primary event of interest. Outcomes in medical research are frequently subject to competing risks. In survival analysis, there are 2 key questions that can be addressed using competing risk regression models: first, which covariates affect the rate at which events occur, and second, which covariates affect the probability of an event occurring over time. The cause-specific hazard model estimates the effect of covariates on the rate at which events occur in subjects who are currently event-free. Subdistribution hazard ratios obtained from the Fine-Gray model describe the relative effect of covariates on the subdistribution hazard function. Hence, the covariates in this model can also be interpreted as having an effect on the cumulative incidence function or on the probability of events occurring over time. We conducted a review of the use and interpretation of the Fine-Gray subdistribution hazard model in articles published in the medical literature in 2015. We found that many authors provided an unclear or incorrect interpretation of the regression coefficients associated with this model. An incorrect and inconsistent interpretation of regression coefficients may lead to confusion when comparing results across different studies. Furthermore, an incorrect interpretation of estimated regression coefficients can result in an incorrect understanding about the magnitude of the association between exposure and the incidence of the outcome. The objective of this article is to clarify how these regression coefficients should be reported and to propose suggestions for interpreting these coefficients. © 2017 The Authors. Statistics in Medicine published by John Wiley & Sons Ltd.

  3. Proportional hazards model for competing risks data with missing cause of failure

    PubMed Central

    Hyun, Seunggeun; Sun, Yanqing

    2012-01-01

    We consider the semiparametric proportional hazards model for the cause-specific hazard function in analysis of competing risks data with missing cause of failure. The inverse probability weighted equation and augmented inverse probability weighted equation are proposed for estimating the regression parameters in the model, and their theoretical properties are established for inference. Simulation studies demonstrate that the augmented inverse probability weighted estimator is doubly robust and the proposed method is appropriate for practical use. The simulations also compare the proposed estimators with the multiple imputation estimator of Lu and Tsiatis (2001). The application of the proposed method is illustrated using data from a bone marrow transplant study. PMID:22468017

  4. [Determination of the Association Between Smoking and Recurrence of Ischemic Stroke using a Competing Risks Model].

    PubMed

    Zhan, Feng-yu; Yan, Pei-jing; Zhang, Juan; Ran, Meng-dong; Zhu, Cai-rong

    2015-09-01

    To determine the association between smoking and ischemic stroke recurrence. We conducted a prospective follow-up study of patients with first incidence of stroke. A competing risks model was used to establish the association between smoking and stroke recurrence. A total of 594 stroke patients were recruited. Among the 361 male patients, 59 recurrent events and 13 competing events occurred. Among the 233 female patients (all were non-smokers), 49 recurrent events and 11 competing events occurred. Adjusted for confounding factors, male nonsmokers exposed to passive smoking had a SHR of 3. 040 in comparison with those without exposure to smoking and the P value was borderline significant. Those who smoked 100-200 cigarettes a year had a SHR of 0. 947. The other groups with exposure to smoking had a greater than 1 SHR, but without statistical significance. Moreover, no significant associations between recurrence of ischemic stroke and smoking index/cumulative smoking were found. The female nonsmokers who had exposure to passive smoking only at follow-ups had a SHR of 1. 4 (and all other groups had less than 1 SHR). But no statistical significances were found in the comparisons. Further research with a larger sample size is needed to establish the association between smoking and recurrence of ischemic stroke.

  5. Multiple primary tumours: incidence estimation in the presence of competing risks

    PubMed Central

    Rosso, Stefano; Terracini, Lea; Ricceri, Fulvio; Zanetti, Roberto

    2009-01-01

    Background Estimating the risk of developing subsequent primary tumours in a population is difficult since the occurrence probability is conditioned to the survival probability. Methods We proposed to apply Markov models studying the transition intensities from first to second tumour with the Aalen-Johansen (AJ) estimators, as usually done in competing risk models. In a simulation study we applied the proposed method in different settings with constant or varying underlying intensities and applying age standardisation. In addition, we illustrated the method with data on breast cancer from the Piedmont Cancer Registry. Results The simulation study showed that the person-years approach led to a sensibly wider bias than the AJ estimators. The largest bias was observed assuming constantly increasing incidence rates. However, this situation is rather uncommon dealing with subsequent tumours incidence. In 9233 cases with breast cancer occurred in women resident in Turin, Italy, between 1985 and 1998 we observed a significant increased risk of 1.91 for subsequent cancer of corpus uteri, estimated with the age-standardised Aalen-Johansen incidence ratio (AJ-IRstand), and a significant increased risk of 1.29 for cancer possibly related to the radiotherapy of breast cancer. The peak of occurrence of those cancers was observed after 8 years of follow-up. Conclusion The increased risk of a cancer of the corpus uteri, also observed in other studies, is usually interpreted as the common shared risk factors such as low parity, early menarche and late onset of menopause. We also grouped together those cancers possibly associated to a previous local radiotherapy: the cumulative risk at 14 years is still not significant, however the AJ estimators showed a significant risk peak between the eighth and the ninth year. Finally, the proposed approach has been shown to be reliable and informative under several aspects. It allowed for a correct estimation of the risk, and for investigating

  6. Confidence interval procedures for system reliability and applications to competing risks models.

    PubMed

    Hong, Yili; Meeker, William Q

    2014-04-01

    System reliability depends on the reliability of the system's components and the structure of the system. For example, in a competing risks model, the system fails when the weakest component fails. The reliability function and the quantile function of a complicated system are two important metrics for characterizing the system's reliability. When there are data available at the component level, the system reliability can be estimated by using the component level information. Confidence intervals (CIs) are needed to quantify the statistical uncertainty in the estimation. Obtaining system reliability CI procedures with good properties is not straightforward, especially when the system structure is complicated. In this paper, we develop a general procedure for constructing a CI for the system failure-time quantile function by using the implicit delta method. We also develop general procedures for constructing a CI for the cumulative distribution function (cdf) of the system. We show that the recommended procedures are asymptotically valid and have good statistical properties. We conduct simulations to study the finite-sample coverage properties of the proposed procedures and compare them with existing procedures. We apply the proposed procedures to three applications; two applications in competing risks models and an application with a k-out-of-s system. The paper concludes with some discussion and an outline of areas for future research.

  7. A general joint model for longitudinal measurements and competing risks survival data with heterogeneous random effects

    PubMed Central

    Li, Gang; Elashoff, Robert M.; Pan, Jianxin

    2011-01-01

    This article studies a general joint model for longitudinal measurements and competing risks survival data. The model consists of a linear mixed effects sub-model for the longitudinal outcome, a proportional cause-specific hazards frailty sub-model for the competing risks survival data, and a regression sub-model for the variance–covariance matrix of the multivariate latent random effects based on a modified Cholesky decomposition. The model provides a useful approach to adjust for non-ignorable missing data due to dropout for the longitudinal outcome, enables analysis of the survival outcome with informative censoring and intermittently measured time-dependent covariates, as well as joint analysis of the longitudinal and survival outcomes. Unlike previously studied joint models, our model allows for heterogeneous random covariance matrices. It also offers a framework to assess the homogeneous covariance assumption of existing joint models. A Bayesian MCMC procedure is developed for parameter estimation and inference. Its performances and frequentist properties are investigated using simulations. A real data example is used to illustrate the usefulness of the approach. PMID:20549344

  8. A review of methods to estimate cause-specific mortality in presence of competing risks

    USGS Publications Warehouse

    Heisey, Dennis M.; Patterson, Brent R.

    2006-01-01

    Estimating cause-specific mortality is often of central importance for understanding the dynamics of wildlife populations. Despite such importance, methodology for estimating and analyzing cause-specific mortality has received little attention in wildlife ecology during the past 20 years. The issue of analyzing cause-specific, mutually exclusive events in time is not unique to wildlife. In fact, this general problem has received substantial attention in human biomedical applications within the context of biostatistical survival analysis. Here, we consider cause-specific mortality from a modern biostatistical perspective. This requires carefully defining what we mean by cause-specific mortality and then providing an appropriate hazard-based representation as a competing risks problem. This leads to the general solution of cause-specific mortality as the cumulative incidence function (CIF). We describe the appropriate generalization of the fully nonparametric staggered-entry Kaplan–Meier survival estimator to cause-specific mortality via the nonparametric CIF estimator (NPCIFE), which in many situations offers an attractive alternative to the Heisey–Fuller estimator. An advantage of the NPCIFE is that it lends itself readily to risk factors analysis with standard software for Cox proportional hazards model. The competing risks–based approach also clarifies issues regarding another intuitive but erroneous "cause-specific mortality" estimator based on the Kaplan–Meier survival estimator and commonly seen in the life sciences literature.

  9. Vertical modelling: Analysis of competing risks data with missing causes of failure.

    PubMed

    Nicolaie, M A; van Houwelingen, H C; Putter, H

    2015-12-01

    We propose vertical modelling as a natural approach to the problem of analysis of competing risks data when failure types are missing for some individuals. Under a natural missing-at-random assumption for these missing failure types, we use the observed data likelihood to estimate its parameters and show that the all-cause hazard and the relative hazards appearing in vertical modelling are indeed key quantities of this likelihood. This fact has practical implications in that it suggests vertical modelling as a simple and attractive method of analysis in competing risks with missing causes of failure; all individuals are used in estimating the all-cause hazard and only those with non-missing cause of failure for relative hazards. The relative hazards also appear in a multiple imputation approach to the same problem proposed by Lu and Tsiatis and in the EM algorithm. We compare the vertical modelling approach with the method of Goetghebeur and Ryan for a breast cancer data set, highlighting the different aspects they contribute to the data analysis.

  10. Frailty modeling for clustered competing risks data with missing cause of failure.

    PubMed

    Lee, Minjung; Ha, Il Do; Lee, Youngjo

    2017-02-01

    Competing risks data often occur within a center in multi-center clinical trials where the event times within a center may be correlated due to unobserved factors across individuals. In this paper, we consider the cause-specific proportional hazards model with a shared frailty to model the association between the event times within a center in the framework of competing risks. We use a hierarchical likelihood approach, which does not require any intractable integration over the frailty terms. In a clinical trial, cause of death information may not be observed for some patients. In such a case, analyses through exclusion of cases with missing cause of death may lead to biased inferences. We propose a hierarchical likelihood approach for fitting the cause-specific proportional hazards model with a shared frailty in the presence of missing cause of failure. We use multiple imputation methods to address missing cause of death information under the assumption of missing at random. Simulation studies show that the proposed procedures perform well, even if the imputation model is misspecified. The proposed methods are illustrated with data from EORTC trial 30791 conducted by European Organization for Research and Treatment of Cancer (EORTC).

  11. A competing risk analysis of sequential complication development in Asian type 2 diabetes mellitus patients.

    PubMed

    Cheng, Li-Jen; Chen, Jeng-Huei; Lin, Ming-Yen; Chen, Li-Chia; Lao, Chun-Huan; Luh, Hsing; Hwang, Shang-Jyh

    2015-10-28

    This retrospective cohort study investigated the progression risk of sequential complication in Asian type 2 diabetes (T2D) patients using the Taiwan Pay-for-Performance Diabetes Registry and claim data from November 2003 to February 2009. 226,310 adult T2D patients without complication were followed from diagnosis to complications, including myocardial infarction (MI), other ischemic heart disease (IHD), congestive heart failure (CHF), stroke, chronic kidney disease (CKD), retinopathy, amputation, death or to the end of study. Cumulative incidences (CIs) of first and second complications were analyzed in 30 and 4 years using the cumulative incidence competing risk method. IHD (29.8%), CKD (24.5%) and stroke (16.0%) are the most common first complications. The further development of T2D complications depends on a patient's existing complication profiles. Patients who initially developed cardiovascular complications had a higher risk (9.2% to 24.4%) of developing IHD or CKD, respectively. All-cause mortality was the most likely consequence for patients with a prior MI (12.0%), so as stroke in patients with a prior MI (10.8%) or IHD (8.9%). Patients with CKD had higher risk of developing IHD (16.3%), stroke (8.9%) and all-cause mortality (8.7%) than end-stage renal disease (4.0%). Following an amputation, patients had a considerable risk of all-cause mortality (42.1%).

  12. Death Does Matter--Cancer Risk in Patients With End-Stage Renal Disease: A Nationwide Population-Based Study With Competing Risk Analyses.

    PubMed

    Weng, Shih-Feng; Chiu, Yu-Hsien; Jan, Ren-Long; Chen, Yi-Chen; Chien, Chih-Chiang; Wang, Jhi-Joung; Chu, Chin-Chen

    2016-01-01

    Patients with end-stage renal disease (ESRD) have a high mortality rate. We hypothesized that not accounting for death as a competing risk overestimates the event rate caused by ESRD. Thus, we examined the cancer risk for patients with ESRD (ESRD) after death as a competing risk event had been adjusted for. Patients with newly diagnosed ESRD (n = 64,299) between 1999 and 2007, together with age- and sex-matched controls without ESRD (ESRD) (n = 128,592) were enrolled (1:2). In a Cox proportional hazards model that included death as a competing risk, ESRD patients in Taiwan had a lower overall incidence (subdistribution hazard ratio [sdHR] = 1.29) of cancer than did ESRD patients in a Cox model that did not include death as a competing risk (HR = 1.70). After competing mortality had been adjusted for, ESRD patients ≥70 (sdHR = 0.82) and ESRD patients on long-term dialysis (> 5 follow-up years, sdHR = 0.62), had a lower risk for developing cancer than did ESRD patients. This finding supported our hypothesis that standard survival analyses overestimate the event rate, especially when the mortality rate is high. It also showed that ESRD patients, when they grow older, were far less likely to develop cancer and far more likely to die because of underlying illnesses that might also affect the risk of death because of ESRD.

  13. Sociodemographic Risk, Developmental Competence, and PTSD Symptoms in Young Children Exposed to Interpersonal Trauma in Early Life

    PubMed Central

    Enlow, Michelle Bosquet; Blood, Emily; Egeland, Byron

    2014-01-01

    Children under age six years are disproportionately exposed to interpersonal trauma, including maltreatment and witnessing intimate partner violence (IPV), and may be particularly susceptible to negative sequelae. However, young children have generally been neglected from trauma research; thus, little is known about the factors influencing vulnerability to traumatic stress responses and other negative outcomes in early life. This study examined associations among interpersonal trauma exposure, sociodemographic risk, developmental competence, and posttraumatic stress disorder (PTSD) symptoms in 200 children assessed prospectively from birth to 1st grade via home and laboratory observations, record reviews, and maternal and teacher interviews. Greater trauma exposure and sociodemographic risk and lower developmental competence predicted more severe PTSD symptoms. Developmental competence partially mediated the association between exposures and symptoms. Trauma exposure fully mediated the association between sociodemographic risk and symptoms. Neither sociodemographic risk nor developmental competence moderated trauma exposure effects on symptoms. The findings suggest that (a) exposure to maltreatment and IPV has additive effects on posttraumatic stress risk in early life, (b) associations between sociodemographic adversity and poor mental health may be attributable to increased trauma exposure in disadvantaged populations, and (c) early exposures have a negative cascade effect on developmental competence and child mental health. PMID:24490247

  14. Risk management in laboratory medicine: quality assurance programs and professional competence.

    PubMed

    Sciacovelli, Laura; Secchiero, Sandra; Zardo, Lorena; D'Osualdo, Alessandra; Plebani, Mario

    2007-01-01

    To guarantee excellent performance and service, the process of identifying and treating error risks must be integrated into the total testing process. Quality Assurance Programs (QAPs) represent an important tool that allows us to identify errors and pinpoint any need for further systematic investigations, and to rectify procedures to improve the inputs and processes by which the service is delivered. The models used by the laboratory to assure quality and manage the risk of errors have been modified in line with an approach in which the identification of quality goals and the redefinition of professionals duties and responsibilities are indispensable. Error risk is currently high in some areas of laboratory activity, and QAP is needed now more than ever. The present paper provides some descriptive examples of an approach that can be followed to manage an External Quality Assessment Scheme (EQAS) and quality indicators (QIs), the main tools used by laboratories to assure the quality of their service, for the prevention of error risk. In particular, we describe the correct approach to choose EQAS, to use information from the EQAS report, to design a QI model, and to analyze any QI data. The examples highlight that any well-designed quality system can be ineffective if it is not managed by highly competent professionals with a deep sense of responsibility.

  15. A competing-risk-based score for predicting twenty-year risk of incident diabetes: the Beijing Longitudinal Study of Ageing study

    PubMed Central

    Liu, Xiangtong; Chen, Zhenghong; Fine, Jason Peter; Liu, Long; Wang, Anxin; Guo, Jin; Tao, Lixin; Mahara, Gehendra; Yang, Kun; Zhang, Jie; Tian, Sijia; Li, Haibin; Liu, Kuo; Luo, Yanxia; Zhang, Feng; Tang, Zhe; Guo, Xiuhua

    2016-01-01

    Few risk tools have been proposed to quantify the long-term risk of diabetes among middle-aged and elderly individuals in China. The present study aimed to develop a risk tool to estimate the 20-year risk of developing diabetes while incorporating competing risks. A three-stage stratification random-clustering sampling procedure was conducted to ensure the representativeness of the Beijing elderly. We prospectively followed 1857 community residents aged 55 years and above who were free of diabetes at baseline examination. Sub-distribution hazards models were used to adjust for the competing risks of non-diabetes death. The cumulative incidence function of twenty-year diabetes event rates was 11.60% after adjusting for the competing risks of non-diabetes death. Age, body mass index, fasting plasma glucose, health status, and physical activity were selected to form the score. The area under the ROC curve (AUC) was 0.76 (95% Confidence Interval: 0.72–0.80), and the optimism-corrected AUC was 0.78 (95% Confidence Interval: 0.69–0.87) after internal validation by bootstrapping. The calibration plot showed that the actual diabetes risk was similar to the predicted risk. The cut-off value of the risk score was 19 points, marking mark the difference between low-risk and high-risk patients, which exhibited a sensitivity of 0.74 and specificity of 0.65. PMID:27849048

  16. Competing Risk Analysis for Evaluation of Dalteparin Versus Unfractionated Heparin for Venous Thromboembolism in Medical-Surgical Critically Ill Patients.

    PubMed

    Li, Guowei; Cook, Deborah J; Levine, Mitchell A H; Guyatt, Gordon; Crowther, Mark; Heels-Ansdell, Diane; Holbrook, Anne; Lamontagne, Francois; Walter, Stephen D; Ferguson, Niall D; Finfer, Simon; Arabi, Yaseen M; Bellomo, Rinaldo; Cooper, D Jamie; Thabane, Lehana

    2015-09-01

    Failure to recognize the presence of competing risk or to account for it may result in misleading conclusions. We aimed to perform a competing risk analysis to assess the efficacy of the low molecular weight heparin dalteparin versus unfractionated heparin (UFH) in venous thromboembolism (VTE) in medical-surgical critically ill patients, taking death as a competing risk.This was a secondary analysis of a prospective randomized study of the Prophylaxis for Thromboembolism in Critical Care Trial (PROTECT) database. A total of 3746 medical-surgical critically ill patients from 67 intensive care units (ICUs) in 6 countries receiving either subcutaneous UFH 5000 IU twice daily (n = 1873) or dalteparin 5000 IU once daily plus once-daily placebo (n = 1873) were included for analysis.A total of 205 incident proximal leg deep vein thromboses (PLDVT) were reported during follow-up, among which 96 were in the dalteparin group and 109 were in the UFH group. No significant treatment effect of dalteparin on PLDVT compared with UFH was observed in either the competing risk analysis or standard survival analysis (also known as cause-specific analysis) using multivariable models adjusted for APACHE II score, history of VTE, need for vasopressors, and end-stage renal disease: sub-hazard ratio (SHR) = 0.92, 95% confidence interval (CI): 0.70-1.21, P-value = 0.56 for the competing risk analysis; hazard ratio (HR) = 0.92, 95% CI: 0.68-1.23, P-value = 0.57 for cause-specific analysis. Dalteparin was associated with a significant reduction in risk of pulmonary embolism (PE): SHR = 0.54, 95% CI: 0.31-0.94, P-value = 0.02 for the competing risk analysis; HR = 0.51, 95% CI: 0.30-0.88, P-value = 0.01 for the cause-specific analysis. Two additional sensitivity analyses using the treatment variable as a time-dependent covariate and using as-treated and per-protocol approaches demonstrated similar findings.This competing risk analysis yields no

  17. Competing Risk Analysis for Evaluation of Dalteparin Versus Unfractionated Heparin for Venous Thromboembolism in Medical-Surgical Critically Ill Patients

    PubMed Central

    Li, Guowei; Cook, Deborah J.; Levine, Mitchell A.H.; Guyatt, Gordon; Crowther, Mark; Heels-Ansdell, Diane; Holbrook, Anne; Lamontagne, Francois; Walter, Stephen D.; Ferguson, Niall D.; Finfer, Simon; Arabi, Yaseen M.; Bellomo, Rinaldo; Cooper, D. Jamie; Thabane, Lehana

    2015-01-01

    Abstract Failure to recognize the presence of competing risk or to account for it may result in misleading conclusions. We aimed to perform a competing risk analysis to assess the efficacy of the low molecular weight heparin dalteparin versus unfractionated heparin (UFH) in venous thromboembolism (VTE) in medical-surgical critically ill patients, taking death as a competing risk. This was a secondary analysis of a prospective randomized study of the Prophylaxis for Thromboembolism in Critical Care Trial (PROTECT) database. A total of 3746 medical-surgical critically ill patients from 67 intensive care units (ICUs) in 6 countries receiving either subcutaneous UFH 5000 IU twice daily (n = 1873) or dalteparin 5000 IU once daily plus once-daily placebo (n = 1873) were included for analysis. A total of 205 incident proximal leg deep vein thromboses (PLDVT) were reported during follow-up, among which 96 were in the dalteparin group and 109 were in the UFH group. No significant treatment effect of dalteparin on PLDVT compared with UFH was observed in either the competing risk analysis or standard survival analysis (also known as cause-specific analysis) using multivariable models adjusted for APACHE II score, history of VTE, need for vasopressors, and end-stage renal disease: sub-hazard ratio (SHR) = 0.92, 95% confidence interval (CI): 0.70–1.21, P-value = 0.56 for the competing risk analysis; hazard ratio (HR) = 0.92, 95% CI: 0.68–1.23, P-value = 0.57 for cause-specific analysis. Dalteparin was associated with a significant reduction in risk of pulmonary embolism (PE): SHR = 0.54, 95% CI: 0.31–0.94, P-value = 0.02 for the competing risk analysis; HR = 0.51, 95% CI: 0.30–0.88, P-value = 0.01 for the cause-specific analysis. Two additional sensitivity analyses using the treatment variable as a time-dependent covariate and using as-treated and per-protocol approaches demonstrated similar findings. This competing risk analysis

  18. Patient death as a censoring event or competing risk event in models of nursing home placement.

    PubMed

    Szychowski, Jeff M; Roth, David L; Clay, Olivio J; Mittelman, Mary S

    2010-02-10

    Participant death is often observed in studies that examine predictors of events, such as hospitalization or institutionalization, in older adult populations. The Cox proportional hazards modeling of the target event, whereby death is treated as a censoring event, is the standard analysis in this competing risks situation. However, the assumption of noninformative censoring applied to a frequently occurring competing event like death may be invalid and complicate interpretation in terms of the probability of the event. Multiple cause-specific hazard (CSH) models can be estimated, but ambiguities may arise when interpreting covariate effects across multiple CSH models and in terms of the cumulative incidence function (CIF). Alternatively, one can model the proportional hazards of the subdistribution of the CIF and evaluate the covariate effects on the CIF directly. We examine and compare these two approaches with nursing home (NH) placement data from a randomized controlled trial of a counseling and support intervention for spouse-caregivers of patients with Alzheimer's disease. CSHs for NH placement (where death is treated as a censoring event) and death (where NH placement is treated as a censoring event) and subdistribution hazards of the CIF for NH placement are modeled separately. In the presence of multiple covariates, the intervention effect is significant in both approaches, but the interpretation of the covariate effects requires joint evaluation of all estimated models.

  19. Competing event risk stratification may improve the design and efficiency of clinical trials: Secondary analysis of SWOG 8794

    PubMed Central

    Zakeri, Kaveh; Rose, Brent S.; Gulaya, Sachin; D'Amico, Anthony V.; Mell, Loren K.

    2012-01-01

    Background Composite endpoints can be problematic in the presence of competing risks when a treatment does not affect events comprising the endpoint equally. Methods We conducted secondary analysis of SWOG 8794 trial of adjuvant radiation therapy (RT) for high-risk post-operative prostate cancer. The primary outcome was metastasis-free survival (MFS), defined as time to first occurrence of metastasis or death from any cause (competing mortality (CM)). We developed separate risk scores for time to metastasis and CM using competing risks regression. We estimated treatment effects using Cox models adjusted for risk scores and identified an enriched subgroup of 75 patients at high risk of metastasis and low risk of CM. Results The mean CM risk score was significantly lower in the RT arm vs. control arm (p=0.001). The effect of RT on MFS (HR 0.70; 95% CI, 0.53–0.92; p=0.010) was attenuated when controlling for metastasis and CM risk (HR 0.76; 95% CI, 0.58–1.00; p=0.049), and the effect of RT on overall survival (HR 0.73; 95% CI, 0.55–0.96; p=0.02) was no longer significant when controlling for metastasis and CM risk (HR 0.80; 95% CI, 0.60–1.06; p=0.12). Compared to the whole sample, the enriched subgroup had the same 10-year incidence of MFS (40%; 95% CI, 22–57%), but a higher incidence of metastasis (30% (95% CI, 15–47%) vs. 20% (95% CI, 15–26%)). A randomized trial in the subgroup would have achieved 80% power with 56% less patients (313 vs. 709, respectively). Conclusion Stratification on competing event risk may improve the efficiency of clinical trials. PMID:23063467

  20. Competing event risk stratification may improve the design and efficiency of clinical trials: secondary analysis of SWOG 8794.

    PubMed

    Zakeri, Kaveh; Rose, Brent S; Gulaya, Sachin; D'Amico, Anthony V; Mell, Loren K

    2013-01-01

    Composite endpoints can be problematic in the presence of competing risks when a treatment does not affect events comprising the endpoint equally. We conducted secondary analysis of SWOG 8794 trial of adjuvant radiation therapy (RT) for high-risk post-operative prostate cancer. The primary outcome was metastasis-free survival (MFS), defined as time to first occurrence of metastasis or death from any cause (competing mortality (CM)). We developed separate risk scores for time to metastasis and CM using competing risks regression. We estimated treatment effects using Cox models adjusted for risk scores and identified an enriched subgroup of 75 patients at high risk of metastasis and low risk of CM. The mean CM risk score was significantly lower in the RT arm vs. control arm (p=0.001). The effect of RT on MFS (HR 0.70; 95% CI, 0.53-0.92; p=0.010) was attenuated when controlling for metastasis and CM risk (HR 0.76; 95% CI, 0.58-1.00; p=0.049), and the effect of RT on overall survival (HR 0.73; 95% CI, 0.55-0.96; p=0.02) was no longer significant when controlling for metastasis and CM risk (HR 0.80; 95% CI, 0.60-1.06; p=0.12). Compared to the whole sample, the enriched subgroup had the same 10-year incidence of MFS (40%; 95% CI, 22-57%), but a higher incidence of metastasis (30% (95% CI, 15-47%) vs. 20% (95% CI, 15-26%)). A randomized trial in the subgroup would have achieved 80% power with 56% less patients (313 vs. 709, respectively). Stratification on competing event risk may improve the efficiency of clinical trials. Copyright © 2012 Elsevier Inc. All rights reserved.

  1. Comparing predictions among competing risks models with time-dependent covariates

    PubMed Central

    Cortese, Giuliana; Gerds, Thomas A.; Andersen, Per K.

    2013-01-01

    Prediction of cumulative incidences is often a primary goal in clinical studies with several end-points. We compare predictions among competing risks models with time-dependent covariates. For a series of landmark time points we study the predictive accuracy of a multi-state regression model, where the time-dependent covariate represents an intermediate state and two alternative landmark approaches (Cortese & Andersen, 2010). At each landmark time point, the prediction performance is measured as the t-year expected Brier score where pseudovalues are constructed in order to deal with right censored event times. We apply the methods to data from a bone marrow transplant study where graft versus host disease (GvHD) is considered a time-dependent covariate for predicting relapse and death in remission. PMID:23494745

  2. Nonparametric analysis of competing risks data with event category missing at random.

    PubMed

    Gouskova, Natalia A; Lin, Feng-Chang; Fine, Jason P

    2017-03-01

    In competing risks setup, the data for each subject consist of the event time, censoring indicator, and event category. However, sometimes the information about the event category can be missing, as, for example, in a case when the date of death is known but the cause of death is not available. In such situations, treating subjects with missing event category as censored leads to the underestimation of the hazard functions. We suggest nonparametric estimators for the cumulative cause-specific hazards and the cumulative incidence functions which use the Nadaraya-Watson estimator to obtain the contribution of an event with missing category to each of the cause-specific hazards. We derive the propertied of the proposed estimators. Optimal bandwidth is determined, which minimizes the mean integrated squared errors of the proposed estimators over time. The methodology is illustrated using data on lung infections in patients from the United States Cystic Fibrosis Foundation Patient Registry.

  3. CURRENT STATUS DATA WITH COMPETING RISKS: LIMITING DISTRIBUTION OF THE MLE

    PubMed Central

    Groeneboom, Piet; Maathuis, Marloes H.; Wellner, Jon A.

    2009-01-01

    We study nonparametric estimation for current status data with competing risks. Our main interest is in the nonparametric maximum likelihood estimator (MLE), and for comparison we also consider a simpler ‘naive estimator’. Groeneboom, Maathuis and Wellner [8] proved that both types of estimators converge globally and locally at rate n1/3. We use these results to derive the local limiting distributions of the estimators. The limiting distribution of the naive estimator is given by the slopes of the convex minorants of correlated Brownian motion processes with parabolic drifts. The limiting distribution of the MLE involves a new self-induced limiting process. Finally, we present a simulation study showing that the MLE is superior to the naive estimator in terms of mean squared error, both for small sample sizes and asymptotically. PMID:19888358

  4. On assessing surrogacy in a single trial setting using a semi-competing risks paradigm

    PubMed Central

    Ghosh, Debashis

    2009-01-01

    Summary There has been a recent emphasis on the identification of biomarkers and other biologic measures that may be potentially used as surrogate endpoints in clinical trials. We focus on the setting of data from a single clinical trial. In this paper, we consider a framework in which the surrogate must occur before the true endpoint. This suggests viewing the surrogate and true endpoints as semi-competing risks data; this approach is new to the literature on surrogate endpoints and leads to an asymmetrical treatment of the surrogate and true endpoints. However, such a data structure also conceptually complicates many of the previously considered measures of surrogacy in the literature. We propose novel estimation and inferential procedures for the relative effect and adjusted association quantities proposed by Buyse and Molenberghs (1998, Biometrics, 1014 – 1029). The proposed methodology is illustrated with application to simulated data, as well as to data from a leukemia study. PMID:18759839

  5. The use of group sequential designs with common competing risks tests

    PubMed Central

    Logan, Brent R.; Zhang, Mei-Jie

    2012-01-01

    Clinical trials are often performed using a group sequential design in order to allow investigators to review the accumulating data sequentially and possibly terminate the trial early for efficacy or futility. Standard methods for comparing survival distributions have been shown under varying levels of generality to follow an independent increments structure. In the presence of competing risks, where the occurrence of one type of event precludes the occurrence of another type of event, researchers may be interested in inference on the cumulative incidence function, which describes the probability of experiencing a particular event by a given time. This manuscript shows that two commonly used tests for comparing cumulative incidence functions, a pointwise comparison at a single point, and Gray's test, also follow the independent increments structure when used in a group sequential setting. A simulation study confirms the theoretical derivations even for modest trial sample sizes. Two examples of clinical trials in hematopoietic cell transplantation are used to illustrate the techniques. PMID:22945865

  6. Flexible parametric modelling of cause-specific hazards to estimate cumulative incidence functions

    PubMed Central

    2013-01-01

    Background Competing risks are a common occurrence in survival analysis. They arise when a patient is at risk of more than one mutually exclusive event, such as death from different causes, and the occurrence of one of these may prevent any other event from ever happening. Methods There are two main approaches to modelling competing risks: the first is to model the cause-specific hazards and transform these to the cumulative incidence function; the second is to model directly on a transformation of the cumulative incidence function. We focus on the first approach in this paper. This paper advocates the use of the flexible parametric survival model in this competing risk framework. Results An illustrative example on the survival of breast cancer patients has shown that the flexible parametric proportional hazards model has almost perfect agreement with the Cox proportional hazards model. However, the large epidemiological data set used here shows clear evidence of non-proportional hazards. The flexible parametric model is able to adequately account for these through the incorporation of time-dependent effects. Conclusion A key advantage of using this approach is that smooth estimates of both the cause-specific hazard rates and the cumulative incidence functions can be obtained. It is also relatively easy to incorporate time-dependent effects which are commonly seen in epidemiological studies. PMID:23384310

  7. Connection between competence, usability, environment and risk of falls in elderly adults.

    PubMed

    Leiva-Caro, José Alex; Salazar-González, Bertha Cecilia; Gallegos-Cabriales, Esther Carlota; Gómez-Meza, Marco Vinicio; Hunter, Kathleen F

    2015-01-01

    To determine connections between competence, usability, environment and risk of falls in elderly adults. Correlational descriptive study, 123 elderly adults, both male and female, aged 70 years and older were included. Data was collected via the Tinetti Scale, CESD-7 Scale, Montreal Cognitive Assessment, Usability Questionnaire on Housing and Housing Enabler; and sociodemographic and health background certificate data. For data analysis, descriptive and inferential statistics were used, multivariate linear and logistic regression models were adjusted. 42.0% of the elderly adults had presented with falls, with a higher prevalence in women, and in the group of 70-75 years. The physical environment of the house, gait, and usability were set as risk factors for falls. A negative relationship between usability and depressive symptoms, cognitive health, balance, gait, the social and physical environment was found, p <0.05; and a strong positive correlation between walking and balance, p <0.05. This study helps to better understand the phenomenon of falling, to find a connection between usability with the risk of falls, and other variables.

  8. Connection between competence, usability, environment and risk of falls in elderly adults

    PubMed Central

    Leiva-Caro, José Alex; Salazar-González, Bertha Cecilia; Gallegos-Cabriales, Esther Carlota; Gómez-Meza, Marco Vinicio; Hunter, Kathleen F.

    2015-01-01

    Objective: to determine connections between competence, usability, environment and risk of falls in elderly adults. Method: correlational descriptive study, 123 elderly adults, both male and female, aged 70 years and older were included. Data was collected via the Tinetti Scale, CESD-7 Scale, Montreal Cognitive Assessment, Usability Questionnaire on Housing and Housing Enabler; and sociodemographic and health background certificate data. For data analysis, descriptive and inferential statistics were used, multivariate linear and logistic regression models were adjusted. Results: 42.0% of the elderly adults had presented with falls, with a higher prevalence in women, and in the group of 70-75 years. The physical environment of the house, gait, and usability were set as risk factors for falls. A negative relationship between usability and depressive symptoms, cognitive health, balance, gait, the social and physical environment was found, p <0.05; and a strong positive correlation between walking and balance, p <0.05. Conclusion: this study helps to better understand the phenomenon of falling, to find a connection between usability with the risk of falls, and other variables. PMID:26626006

  9. Diet-Induced Overweight and Obesity and Periodontitis Risk: An Application of the Parametric G-Formula in the 1982 Pelotas Birth Cohort.

    PubMed

    Nascimento, Gustavo G; Peres, Marco A; Mittinty, Murthy N; Peres, Karen G; Do, Loc G; Horta, Bernardo L; Gigante, Denise P; Corrêa, Marcos B; Demarco, Flávio F

    2017-03-15

    We aimed to estimate hypothetical effects of habits (smoking, alcohol consumption, and fat and carbohydrates consumption) combined with diet-induced overweight/obesity on the risk of periodontitis. The risk of any periodontitis, moderate/severe periodontitis, and the combination of bleeding on probing (BOP) and clinical attachment loss (CAL) was estimated using the parametric g-formula in adults aged 31 years from the 1982 Pelotas Birth Cohort in Brazil. Individuals in this cohort have been followed since birth. Hypothetical conditions were set independently for each risk factor and in combination for the entire population. A total of 539 participants had oral examinations in 2013. The cumulative 31-year risk under no intervention was 33.3% for any periodontitis, 14.3%, for moderate/severe periodontitis, and 14.7%, for BOP and CAL. According to our statistical approach, diet-induced overweight/obesity increased the risk of all outcomes: 11% (overweight) and 22% (obesity) higher risk of periodontitis; 12% (overweight) and 27% (obesity) higher risk of moderate/severe periodontitis; 21% (overweight) and 57% (obesity) higher risk of CAL and BOP. When overweight/obesity was combined with other unhealthy habits, the risk was even greater. Our findings suggest that the combination of diet-induced obesity with other risk factors may increase the risk of periodontitis. Further research in the field is required to corroborate our study. © The Author 2017. Published by Oxford University Press on behalf of the Johns Hopkins Bloomberg School of Public Health. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  10. Examining the role of methamphetamine in permanency: A competing risks analysis of reunification, guardianship, and adoption.

    PubMed

    Akin, Becci A; Brook, Jody; Lloyd, Margaret H

    2015-03-01

    Parental methamphetamine use has drawn significant attention in recent years. Despite prior research that shows that parental substance abuse is a risk factor for lengthy foster care stay, little is known about the effect of specific types of substance use on permanency. This study sought to compare the impact of parental methamphetamine use to alcohol use, other drug use, and polysubstance use on the timing of 3 types of permanency: reunification, guardianship, and adoption. Using an entry cohort of 16,620 children who had entered foster care during a 5-year period, competing risks event history models were conducted for each permanency type. Findings showed that, after controlling for several case characteristics, parent illicit drug use significantly impacted the timing of the 3 types of permanency, but alcohol use did not. Methamphetamine, other drug, and polysubstance with methamphetamine use were associated with lower rates of reunification and higher rates of adoption. Guardianship was also predicted by other drug and polysubstance use without methamphetamine; however, methamphetamine use was not associated with guardianship. Notably, the methamphetamine groups comprised the youngest children and had the shortest median time to adoption. Results suggest that type of parental substance use is predictive of permanency exits and that parental illicit drug use may require tailored strategies for improving permanency outcomes. Further implications of the findings are discussed. (c) 2015 APA, all rights reserved).

  11. Cumulative Risk, the Mother-Child Relationship, and Social-Emotional Competence in Latino Head Start Children

    ERIC Educational Resources Information Center

    Martí, Maria; Bonillo, Albert; Jané, Maria Claustre; Fisher, Elisa M.; Duch, Helena

    2016-01-01

    Research Findings: Supportive mother-child interactions promote the development of social-emotional competence. Poverty and other associated psychosocial risk factors have a negative impact on mother-child interaction. In spite of Latino children being disproportionately represented among children living in poverty, research on mother-child…

  12. Cumulative Risk, the Mother-Child Relationship, and Social-Emotional Competence in Latino Head Start Children

    ERIC Educational Resources Information Center

    Martí, Maria; Bonillo, Albert; Jané, Maria Claustre; Fisher, Elisa M.; Duch, Helena

    2016-01-01

    Research Findings: Supportive mother-child interactions promote the development of social-emotional competence. Poverty and other associated psychosocial risk factors have a negative impact on mother-child interaction. In spite of Latino children being disproportionately represented among children living in poverty, research on mother-child…

  13. Sensation Seeking: A Potential Factor Influencing Perceived Risk and Perceived Competence in an Introductory Scuba Diving Course

    ERIC Educational Resources Information Center

    Morgan, Cass

    2009-01-01

    This study examined the relationship between the sensation-seeking personality trait to changes in perceived risk and perceived competence during an adventure experience. Participants (n = 57) were enrolled in a 14-week introductory scuba diving course offered at a university in eastern North Carolina in 2006. The data was analyzed using a…

  14. A Proportional Hazards Regression Model for the Sub-distribution with Covariates Adjusted Censoring Weight for Competing Risks Data

    PubMed Central

    HE, PENG; ERIKSSON, FRANK; SCHEIKE, THOMAS H.; ZHANG, MEI-JIE

    2015-01-01

    With competing risks data, one often needs to assess the treatment and covariate effects on the cumulative incidence function. Fine and Gray proposed a proportional hazards regression model for the subdistribution of a competing risk with the assumption that the censoring distribution and the covariates are independent. Covariate-dependent censoring sometimes occurs in medical studies. In this paper, we study the proportional hazards regression model for the subdistribution of a competing risk with proper adjustments for covariate-dependent censoring. We consider a covariate-adjusted weight function by fitting the Cox model for the censoring distribution and using the predictive probability for each individual. Our simulation study shows that the covariate-adjusted weight estimator is basically unbiased when the censoring time depends on the covariates, and the covariate-adjusted weight approach works well for the variance estimator as well. We illustrate our methods with bone marrow transplant data from the Center for International Blood and Marrow Transplant Research (CIBMTR). Here cancer relapse and death in complete remission are two competing risks. PMID:27034534

  15. Environmental risk assessment of replication competent viral vectors applied in clinical trials: potential effects of inserted sequences.

    PubMed

    van den Akker, Eric; van der Vlugt, Cecile J B; Bleijs, Diederik A; Bergmans, Hans E

    2013-12-01

    Risk assessments of clinical applications involving genetically modified viral vectors are carried out according to general principles that are implemented in many national and regional legislations, e.g., in Directive 2001/18/EC of the European Union. Recent developments in vector design have a large impact on the concepts that underpin the risk assessments of viral vectors that are used in clinical trials. The use of (conditionally) replication competent viral vectors (RCVVs) may increase the likelihood of the exposure of the environment around the patient, compared to replication defective viral vectors. Based on this assumption we have developed a methodology for the environmental risk assessment of replication competent viral vectors, which is presented in this review. Furthermore, the increased likelihood of exposure leads to a reevaluation of what would constitute a hazardous gene product in viral vector therapies, and a keen interest in new developments in the inserts used. One of the trends is the use of inserts produced by synthetic biology. In this review the implications of these developments for the environmental risk assessment of RCVVs are highlighted, with examples from current clinical trials. The conclusion is drawn that RCVVs, notwithstanding their replication competency, can be applied in an environmentally safe way, in particular if adequate built-in safeties are incorporated, like conditional replication competency, as mitigating factors to reduce adverse environmental effects that could occur.

  16. Resource effects of training general practitioners in risk communication skills and shared decision making competences.

    PubMed

    Cohen, David; Longo, M F; Hood, Kerenza; Edwards, Adrian; Elwyn, Glyn

    2004-08-01

    Involving patients more in decisions about their own care requires doctors to be trained in effective ways of communicating information and in developing competences to negotiate levels of patient involvement which are most appropriate for each case. The aim of this study was to determine the cost of such training and identify which service resource variables are subsequently affected. An explanatory cluster randomized crossover trial was carried out which involved training general practitioners (GPs) in the use of risk communication (RC) tools, shared decision making (SDM) competences or both. Continuing care by GPs of patients with one of four chronic conditions (menopausal symptoms, menorrhagia, atrial fibrillation, prostatism) was reviewed before and after training. Cost of training was assessed by prospective monitoring of resources used. Data on prescribing, referrals and investigations were collected via questionnaires to participating practitioners. Data on follow-up GP consultations were extracted from medical records. Three two-level logistic models were performed to investigate the probability of training having an effect on prescribing, referrals and investigations ordered at the review consultation. Training cost pound 1218 per practitioner which increased the cost of a consultation by pound 2.89. Training in SDM or combined with RC significantly affected the probability of a prescription being issued to women with menopausal symptoms and menorrhagia (although RC on its own had no effect) but did not significantly affect prescribing for patients with prostatism or atrial fibrillation. It did not significantly affect the probability of investigations, referrals or follow-up GP visits for any of the conditions. Unless training has a major influence on consultation length, it is unlikely to have any major impacts on cost.

  17. A parametric method for cumulative incidence modeling with a new four-parameter log-logistic distribution

    PubMed Central

    2011-01-01

    Background Competing risks, which are particularly encountered in medical studies, are an important topic of concern, and appropriate analyses must be used for these data. One feature of competing risks is the cumulative incidence function, which is modeled in most studies using non- or semi-parametric methods. However, parametric models are required in some cases to ensure maximum efficiency, and to fit various shapes of hazard function. Methods We have used the stable distributions family of Hougaard to propose a new four-parameter distribution by extending a two-parameter log-logistic distribution, and carried out a simulation study to compare the cumulative incidence estimated with this distribution with the estimates obtained using a non-parametric method. To test our approach in a practical application, the model was applied to a set of real data on fertility history. Conclusions The results of simulation studies showed that the estimated cumulative incidence function was more accurate than non-parametric estimates in some settings. Analyses of real data indicated that the proposed distribution showed a much better fit to the data than the other distributions tested. Therefore, the new distribution is recommended for practical applications to parameterize the cumulative incidence function in competing risk settings. PMID:22074546

  18. Subsequent fracture in nursing home residents with a hip fracture: a competing risks approach.

    PubMed

    Berry, Sarah D; Samelson, Elizabeth J; Ngo, Long; Bordes, Malynda; Broe, Kerry E; Kiel, Douglas P

    2008-10-01

    To determine the incidence and predictors of subsequent fracture in nursing home residents with a hip fracture, accounting for the competing risk of death. Dynamic cohort study. Hebrew Rehabilitation Center, a 725-bed, long-term care facility in Boston, Massachusetts. Long-term care residents with a surgically repaired hip fracture (1999-2006) followed through June 30, 2007, for the occurrence of subsequent fracture at any skeletal site. Information on age, sex, anatomic location, type of repair, body mass index (BMI), comorbidities, functional status, cognitive status, and medication use were evaluated as potential risk factors for subsequent fracture. The study included 184 residents with a baseline hip fracture. Thirty-nine residents (7 men, 32 women) experienced a subsequent fracture over a median follow-up of 1.1 years. After the baseline hip fracture, 6% of residents experienced a subsequent fracture within 6 months, 12% within 1 year, and 21% within 5 years. In addition, 23% of residents died within 6 months, 31% within 1 year, and 60% within 5 years. High functional status was associated with a five times greater risk of subsequent fracture (high vs low functional status, hazard ratio=5.10, P<.005). Age, sex, BMI, comorbidities, cognitive status, and medication use were not associated with subsequent fracture. Hip fractures are a sentinel event in nursing home residents, with a high incidence of subsequent fracture and death occurring within 1 year. Identification of prefracture characteristics and postfracture complications associated with mortality should help guide secondary prevention efforts in nursing home residents.

  19. Impact of Competing Risk of Mortality on Association of Weight Loss With Risk of Central Body Fractures in Older Men: A Prospective Cohort Study.

    PubMed

    Ensrud, Kristine E; Harrison, Stephanie L; Cauley, Jane A; Langsetmo, Lisa; Schousboe, John T; Kado, Deborah M; Gourlay, Margaret L; Lyons, Jennifer G; Fredman, Lisa; Napoli, Nicolas; Crandall, Carolyn J; Lewis, Cora E; Orwoll, Eric S; Stefanick, Marcia L; Cawthon, Peggy M

    2017-03-01

    To determine the association of weight loss with risk of clinical fractures at the hip, spine, and pelvis (central body fractures [CBFs]) in older men with and without accounting for the competing risk of mortality, we used data from 4523 men (mean age 77.5 years). Weight change between baseline and follow-up (mean 4.5 years between examinations) was categorized as moderate loss (loss ≥10%), mild loss (loss 5% to <10%), stable (<5% change) or gain (gain ≥5%). Participants were contacted every 4 months after the follow-up examination to ascertain vital status (deaths verified by death certificates) and ask about fractures (confirmed by radiographic reports). Absolute probability of CBF by weight change category was estimated using traditional Kaplan-Meier method and cumulative incidence function accounting for competing mortality risk. Risk of CBF by weight change category was determined using conventional Cox proportional hazards regression and subdistribution hazards models with death as a competing risk. During an average of 8 years, 337 men (7.5%) experienced CBF and 1569 (34.7%) died before experiencing this outcome. Among men with moderate weight loss, CBF probability was 6.8% at 5 years and 16.9% at 10 years using Kaplan-Meier versus 5.7% at 5 years and 10.2% at 10 years using a competing risk approach. Men with moderate weight loss compared with those with stable weight had a 1.6-fold higher adjusted risk of CBF (HR 1.59; 95% CI, 1.06 to 2.38) using Cox models that was substantially attenuated in models accounting for competing mortality risk and no longer significant (subdistribution HR 1.16; 95% CI, 0.77 to 1.75). Results were similar in analyses substituting hip fracture for CBF. Older men with weight loss who survive are at increased risk of CBF, including hip fracture. However, ignoring the competing mortality risk among men with weight loss substantially overestimates their long-term fracture probability and relative fracture risk. © 2016 American

  20. Estimation of the Standardized Risk Difference and Ratio in a Competing Risks Framework: Application to Injection Drug Use and Progression to AIDS After Initiation of Antiretroviral Therapy

    PubMed Central

    Cole, Stephen R.; Lau, Bryan; Eron, Joseph J.; Brookhart, M. Alan; Kitahata, Mari M.; Martin, Jeffrey N.; Mathews, William C.; Mugavero, Michael J.; Cole, Stephen R.; Brookhart, M. Alan; Lau, Bryan; Eron, Joseph J.; Kitahata, Mari M.; Martin, Jeffrey N.; Mathews, William C.; Mugavero, Michael J.

    2015-01-01

    There are few published examples of absolute risk estimated from epidemiologic data subject to censoring and competing risks with adjustment for multiple confounders. We present an example estimating the effect of injection drug use on 6-year risk of acquired immunodeficiency syndrome (AIDS) after initiation of combination antiretroviral therapy between 1998 and 2012 in an 8-site US cohort study with death before AIDS as a competing risk. We estimate the risk standardized to the total study sample by combining inverse probability weights with the cumulative incidence function; estimates of precision are obtained by bootstrap. In 7,182 patients (83% male, 33% African American, median age of 38 years), we observed 6-year standardized AIDS risks of 16.75% among 1,143 injection drug users and 12.08% among 6,039 nonusers, yielding a standardized risk difference of 4.68 (95% confidence interval: 1.27, 8.08) and a standardized risk ratio of 1.39 (95% confidence interval: 1.12, 1.72). Results may be sensitive to the assumptions of exposure-version irrelevance, no measurement bias, and no unmeasured confounding. These limitations suggest that results be replicated with refined measurements of injection drug use. Nevertheless, estimating the standardized risk difference and ratio is straightforward, and injection drug use appears to increase the risk of AIDS. PMID:24966220

  1. Estimation of the standardized risk difference and ratio in a competing risks framework: application to injection drug use and progression to AIDS after initiation of antiretroviral therapy.

    PubMed

    Cole, Stephen R; Lau, Bryan; Eron, Joseph J; Brookhart, M Alan; Kitahata, Mari M; Martin, Jeffrey N; Mathews, William C; Mugavero, Michael J

    2015-02-15

    There are few published examples of absolute risk estimated from epidemiologic data subject to censoring and competing risks with adjustment for multiple confounders. We present an example estimating the effect of injection drug use on 6-year risk of acquired immunodeficiency syndrome (AIDS) after initiation of combination antiretroviral therapy between 1998 and 2012 in an 8-site US cohort study with death before AIDS as a competing risk. We estimate the risk standardized to the total study sample by combining inverse probability weights with the cumulative incidence function; estimates of precision are obtained by bootstrap. In 7,182 patients (83% male, 33% African American, median age of 38 years), we observed 6-year standardized AIDS risks of 16.75% among 1,143 injection drug users and 12.08% among 6,039 nonusers, yielding a standardized risk difference of 4.68 (95% confidence interval: 1.27, 8.08) and a standardized risk ratio of 1.39 (95% confidence interval: 1.12, 1.72). Results may be sensitive to the assumptions of exposure-version irrelevance, no measurement bias, and no unmeasured confounding. These limitations suggest that results be replicated with refined measurements of injection drug use. Nevertheless, estimating the standardized risk difference and ratio is straightforward, and injection drug use appears to increase the risk of AIDS.

  2. Regression analysis for cumulative incidence probability under competing risks and left-truncated sampling.

    PubMed

    Shen, Pao-sheng

    2012-01-01

    The cumulative incidence function provides intuitive summary information about competing risks data. Via a mixture decomposition of this function, Chang and Wang (Statist. Sinca 19:391-408, 2009) study how covariates affect the cumulative incidence probability of a particular failure type at a chosen time point. Without specifying the corresponding failure time distribution, they proposed two estimators and derived their large sample properties. The first estimator utilized the technique of weighting to adjust for the censoring bias, and can be considered as an extension of Fine's method (J R Stat Soc Ser B 61: 817-830, 1999). The second used imputation and extends the idea of Wang (J R Stat Soc Ser B 65: 921-935, 2003) from a nonparametric setting to the current regression framework. In this article, when covariates take only discrete values, we extend both approaches of Chang and Wang (Statist Sinca 19:391-408, 2009) by allowing left truncation. Large sample properties of the proposed estimators are derived, and their finite sample performance is investigated through a simulation study. We also apply our methods to heart transplant survival data.

  3. Risk factors for reporting poor cultural competency among patients with diabetes in safety net clinics.

    PubMed

    Seligman, Hilary K; Fernandez, Alicia; Stern, Rachel J; Weech-Maldonado, Robert; Quan, Judy; Jacobs, Elizabeth A

    2012-09-01

    The Consumer Assessment of Healthcare Providers and Systems Cultural Competency Item Set assesses patient perceptions of aspects of the cultural competence of their health care. To determine characteristics of patients who identify the care they receive as less culturally competent. Cross-sectional survey consisting of face-to-face interviews. Safety-net population of patients with type 2 diabetes (n=600) receiving ongoing primary care. Participants completed the Consumer Assessment of Healthcare Providers and Systems Cultural Competency and answered questions about their race/ethnicity, sex, age, education, health status, depressive symptoms, insurance coverage, English proficiency, duration of relationship with primary care provider, and comorbidities. In adjusted models, depressive symptoms were significantly associated with poor cultural competency in the Doctor Communication--Positive Behaviors domain [odds ratio (OR) 1.73, 95% confidence interval, 1.11-2.69]. African Americans were less likely than whites to report poor cultural competence in the Doctor Communication--Positive Behaviors domain (OR 0.52, 95% CI, 0.28-0.97). Participants who reported a longer relationship (≥ 3 y) with their primary care provider were less likely to report poor cultural competence in the Doctor Communication--Health Promotion (OR 0.35, 95% CI, 0.21-0.60) and Trust domains (OR 0.4, 95% CI, 0.24-0.67), whereas participants with lower educational attainment were less likely to report poor cultural competence in the Trust domain (OR 0.51, 95% CI, 0.30-0.86). Overall, however, sociodemographic and clinical differences in reports of poor cultural competence were insignificant or inconsistent across the various domains of cultural competence examined. Cultural competence interventions in safety-net settings should be implemented across populations, rather than being narrowly focused on specific sociodemographic or clinical groups.

  4. Transferable Competences of Young People with a High Dropout Risk in Vocational Training in Germany

    ERIC Educational Resources Information Center

    Frey, Andreas; Balzer, Lars; Ruppert, Jean-Jacques

    2014-01-01

    This paper examines whether the subjective beliefs on their competences of 409 trainees in machinery, sales, and logistics constitute a reliable and valid way to measure transferable competences. The analysis of results attributes satisfactory to good reliability values to the assessment procedure. Furthermore, it could be shown that young people…

  5. Transferable Competences of Young People with a High Dropout Risk in Vocational Training in Germany

    ERIC Educational Resources Information Center

    Frey, Andreas; Balzer, Lars; Ruppert, Jean-Jacques

    2014-01-01

    This paper examines whether the subjective beliefs on their competences of 409 trainees in machinery, sales, and logistics constitute a reliable and valid way to measure transferable competences. The analysis of results attributes satisfactory to good reliability values to the assessment procedure. Furthermore, it could be shown that young people…

  6. Predictors of competing mortality in early breast cancer.

    PubMed

    Mell, Loren K; Jeong, Jong-Hyeon; Nichols, Michael A; Polite, Blase N; Weichselbaum, Ralph R; Chmura, Steven J

    2010-12-01

    Death in the absence of disease recurrence (competing mortality) is an important determinant of disease-free survival (DFS) in early breast cancer. The authors sought to identify predictors of this event using competing risks modeling. A cohort study was made of 1231 consecutive women with stage I to II invasive breast cancer diagnosed between 1986 and 2004, treated with breast conservation therapy. Median follow-up was 82 months. The authors used a parametric competing risks regression model to analyze factors associated with the cumulative incidence of competing mortality. They generated a risk score from the model coefficient estimates and stratified patients according to low and high risk score for analysis. Ten-year DFS was 69.7% (95% confidence interval [CI], 66.2%-72.9%). The 10-year cumulative incidence of locoregional recurrence (LRR) was 4.4% (95% CI, 3.0%-5.8%), distant recurrence was 7.1% (95% CI, 5.4%-8.9%), and competing mortality was 18.7% (95% CI, 15.9%-21.6%). On multivariate analysis, competing mortality was associated with increasing age (hazard ratio [HR], 1.83 per 10 years; 95% CI, 1.58-2.12), black race (HR, 1.71; 95% CI, 1.17-2.51), and comorbid disease (HR, 1.93, 95% CI, 1.40-2.65). Ten-year cumulative incidences of competing mortality, locoregional recurrence, and distant recurrence for patients at low (n=638) versus high (n=593) risk of competing mortality were 7.2% versus 30.6% (P<.001), 4.4% versus 4.4% (P=.97), and 8.6% versus 5.6% (P=.12), respectively. Competing mortality is an important event influencing 10-year DFS in early breast cancer and is associated with increasing age, black race, and comorbid disease. Stratifying patients according to competing mortality risk may be useful in designing clinical trials. Copyright © 2010 American Cancer Society.

  7. Risk Factors for Reporting Poor Cultural Competency Among Patients with Diabetes in Safety-Net Clinics

    PubMed Central

    Seligman, Hilary K.; Fernandez, Alicia; Stern, Rachel J.; Weech-Maldonado, Robert; Quan, Judy; Jacobs, Elizabeth A.

    2012-01-01

    Background The Consumer Assessment of Healthcare Providers and Systems Cultural Competency (CAHPS-CC) Item Set assesses patient perceptions of aspects of the cultural competence of their health care. Objective To determine characteristics of patients who identify the care they receive as less culturally competent Research Design Cross-sectional survey consisting of face-to-face interviews Subjects Safety-net population of patients with type 2 diabetes (n=600) receiving ongoing primary care Measures Participants completed the CAHPS-CC and answered questions about their race/ethnicity, gender, age, education, health status, depressive symptoms, insurance coverage, English proficiency, duration of relationship with primary care provider, and co-morbidities. Results In adjusted models, depressive symptoms were significantly associated with poor cultural competency in the Doctor Communication – Positive Behaviors domain (OR 1.73, 95%CI 1.11, 2.69). African-Americans were less likely than Whites to report poor cultural competence in the Doctor Communication – Positive Behaviors domain (OR 0.52, 0.28–0.97). Participants who reported a longer relationship (≥3 years) with their primary care provider were less likely to report poor cultural competence in the Doctor Communication – Health Promotion (OR 0.35, 0.21–0.60) and Trust domains (OR 0.4, 0.24–0.67), while participants with lower educational attainment were less likely to report poor cultural competence in the Trust domain (OR 0.51, 0.30–0.86). Overall, however, sociodemographic and clinical differences in reports of poor cultural competence were insignificant or inconsistent across the various domains of cultural competence examined. Conclusions Cultural competence interventions in safety-net settings should be implemented across populations, rather than being narrowly focused on specific sociodemographic or clinical groups. PMID:22895232

  8. Flexible parametric modelling of the cause-specific cumulative incidence function.

    PubMed

    Lambert, Paul C; Wilkes, Sally R; Crowther, Michael J

    2017-04-30

    Competing risks arise with time-to-event data when individuals are at risk of more than one type of event and the occurrence of one event precludes the occurrence of all other events. A useful measure with competing risks is the cause-specific cumulative incidence function (CIF), which gives the probability of experiencing a particular event as a function of follow-up time, accounting for the fact that some individuals may have a competing event. When modelling the cause-specific CIF, the most common model is a semi-parametric proportional subhazards model. In this paper, we propose the use of flexible parametric survival models to directly model the cause-specific CIF where the effect of follow-up time is modelled using restricted cubic splines. The models provide smooth estimates of the cause-specific CIF with the important advantage that the approach is easily extended to model time-dependent effects. The models can be fitted using standard survival analysis tools by a combination of data expansion and introducing time-dependent weights. Various link functions are available that allow modelling on different scales and have proportional subhazards, proportional odds and relative absolute risks as particular cases. We conduct a simulation study to evaluate how well the spline functions approximate subhazard functions with complex shapes. The methods are illustrated using data from the European Blood and Marrow Transplantation Registry showing excellent agreement between parametric estimates of the cause-specific CIF and those obtained from a semi-parametric model. We also fit models relaxing the proportional subhazards assumption using alternative link functions and/or including time-dependent effects. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

  9. A competing risks approach for time estimation of household WEEE disposal

    SciTech Connect

    Gutierrez, E.; Adenso-Diaz, B.; Lozano, S.; Gonzalez-Torre, P.

    2010-08-15

    The recent growth in the number of electrical and electronic devices is viewed as one the priority waste streams in European Union waste management policy. This paper presents the findings of a survey to study domestic habits with respect to Waste Electrical and Electronic Equipment (WEEE) in Spain. A specific problem when performing this estimation arises from the fact that consumers quite often store old appliances at home when they are no longer used. Focusing on four different types of appliance, survival analysis (SA) is used to study both the usage span and the reasons for no longer using each device. The time that the discarded products were kept at home before being disposed of was studied using competing risks (CR) analysis. The results of the analysis provide information on the distribution of the studied variables for the different outcomes as well as the influence exerted by the socio-demographic variables considered. Relations between these characteristics and the storage time of the appliances before disposal emerge based on survey data. For instance, the CR model finds that the storage time of the some appliances (i.e. refrigerator) is related to these social-demographics factors. However, other appliances (i.e. microwave oven) are less influenced by these factors. The attitude and motivation of the respondents to the survey as regards the End-of-Life of appliances were also analysed. A majority of respondents do not store discarded appliances at home. The first reason for storing appliances at home is the possibility of it being useful in the future and the second that the respondents did not know what to do with them.

  10. A competing risks approach for time estimation of household WEEE disposal.

    PubMed

    Gutiérrez, E; Adenso-Díaz, B; Lozano, S; González-Torre, P

    2010-01-01

    The recent growth in the number of electrical and electronic devices is viewed as one the priority waste streams in European Union waste management policy. This paper presents the findings of a survey to study domestic habits with respect to Waste Electrical and Electronic Equipment (WEEE) in Spain. A specific problem when performing this estimation arises from the fact that consumers quite often store old appliances at home when they are no longer used. Focusing on four different types of appliance, survival analysis (SA) is used to study both the usage span and the reasons for no longer using each device. The time that the discarded products were kept at home before being disposed of was studied using competing risks (CR) analysis. The results of the analysis provide information on the distribution of the studied variables for the different outcomes as well as the influence exerted by the socio-demographic variables considered. Relations between these characteristics and the storage time of the appliances before disposal emerge based on survey data. For instance, the CR model finds that the storage time of the some appliances (i.e. refrigerator) is related to these social-demographics factors. However, other appliances (i.e. microwave oven) are less influenced by these factors. The attitude and motivation of the respondents to the survey as regards the End-of-Life of appliances were also analysed. A majority of respondents do not store discarded appliances at home. The first reason for storing appliances at home is the possibility of it being useful in the future and the second that the respondents did not know what to do with them.

  11. Competing risk models in reliability systems, a weibull distribution model with bayesian analysis approach

    NASA Astrophysics Data System (ADS)

    Iskandar, Ismed; Satria Gondokaryono, Yudi

    2016-02-01

    In reliability theory, the most important problem is to determine the reliability of a complex system from the reliability of its components. The weakness of most reliability theories is that the systems are described and explained as simply functioning or failed. In many real situations, the failures may be from many causes depending upon the age and the environment of the system and its components. Another problem in reliability theory is one of estimating the parameters of the assumed failure models. The estimation may be based on data collected over censored or uncensored life tests. In many reliability problems, the failure data are simply quantitatively inadequate, especially in engineering design and maintenance system. The Bayesian analyses are more beneficial than the classical one in such cases. The Bayesian estimation analyses allow us to combine past knowledge or experience in the form of an apriori distribution with life test data to make inferences of the parameter of interest. In this paper, we have investigated the application of the Bayesian estimation analyses to competing risk systems. The cases are limited to the models with independent causes of failure by using the Weibull distribution as our model. A simulation is conducted for this distribution with the objectives of verifying the models and the estimators and investigating the performance of the estimators for varying sample size. The simulation data are analyzed by using Bayesian and the maximum likelihood analyses. The simulation results show that the change of the true of parameter relatively to another will change the value of standard deviation in an opposite direction. For a perfect information on the prior distribution, the estimation methods of the Bayesian analyses are better than those of the maximum likelihood. The sensitivity analyses show some amount of sensitivity over the shifts of the prior locations. They also show the robustness of the Bayesian analysis within the range

  12. Outcomes of Peritoneal Dialysis Patients and Switching to Hemodialysis: A Competing Risks Analysis

    PubMed Central

    Pajek, Jernej; Hutchison, Alastair J.; Bhutani, Shiv; Brenchley, Paul E.C.; Hurst, Helen; Perme, Maja Pohar; Summers, Angela M.; Vardhan, Anand

    2014-01-01

    ♦ Background: We performed a review of a large incident peritoneal dialysis cohort to establish the impact of current practice and that of switching to hemodialysis. ♦ Methods: Patients starting peritoneal dialysis between 2004 and 2010 were included and clinical data at start of dialysis recorded. Competing risk analysis and Cox proportional hazards model with time-varying covariate (technique failure) were used. ♦ Results: Of 286 patients (median age 57 years) followed for a median of 24.2 months, 76 were transplanted and 102 died. Outcome probabilities at 3 and 5 years respectively were 0.69 and 0.53 for patient survival (or transplantation) and 0.33 and 0.42 for technique failure. Peritonitis caused technique failure in 42%, but ultrafiltration failure accounted only for 6.3%. Davies comorbidity grade, creatinine and obesity (but not residual renal function or age) predicted technique failure. Due to peritonitis deaths, technique failure was an independent predictor of death hazard. When successful switch to hemodialysis (surviving more than 60 days after technique failure) and its timing were analyzed, no adverse impact on survival in adjusted analysis was found. However, hemodialysis via central venous line was associated with an elevated death hazard as compared to staying on peritoneal dialysis, or hemodialysis through a fistula (adjusted analysis hazard ratio 1.97 (1.02 - 3.80)). ♦ Conclusions: Once the patients survive the first 60 days after technique failure, the switch to hemodialysis does not adversely affect patient outcomes. The nature of vascular access has a significant impact on outcome after peritoneal dialysis failure. PMID:24497601

  13. Changes over calendar time in the risk of specific first AIDS-defining events following HIV seroconversion, adjusting for competing risks

    PubMed Central

    Babiker, Abdel; Darbyshire, Janet; Pezzotti, Patrizio; Porter, Kholoud; Rezza, Giovanni; Walker, Sarah A; Beral, Valerie; Coutinho, Roel; Del Amo, Julia; Gill, Noël; Lee, Christine; Meyer, Laurence; Tyrer, Freya; Dabis, François; Thiébaut, Rodolphe; Lawson-Aye, Sylvie; Boufassa, Faroudy; Hamouda, Osamah; Fischer, Klaus; Pezzotti, Patrizio; Touloumi, Giota; Hatzakis, Angelos; Karafoulidou, Anastasia; Katsarou, Olga; Brettle, Ray; Del Romero, Jorge; Prins, Maria; Van Benthem, Birgit; Kirk, Ole; Pederson, Court; Hernández Aguado, Idelfonso; Pérez-Hoyos, Santiago; Eskild, Anne; Bruun, Johan N; Sannes, Mette; Sabin, Caroline; Johnson, Anne M; Phillips, Andrew N; Francioli, Patrick; Vanhems, Philippe; Egger, Mathias; Rickenbach, Martin; Cooper, David; Kaldor, John; Ashton, Lesley; Vizzard, Jeanette; Muga, Roberto; Day, Nicholas E; De Angelis, Daniela

    2002-01-01

    Background Although studies have reported large reductions in the risks of AIDS and death since the introduction of potent anti-retroviral therapies, few have evaluated whether this has been similar for all AIDS-defining diseases. We wished to evaluate changes over time in the risk of specific AIDS-defining diseases, as first events, using data from individuals with known dates of HIV seroconversion. Methods Using a competing risks proportional hazards model on pooled data from 20 cohorts (CASCADE), we evaluated time from HIV seroconversion to each first AIDS-defining disease (16 groups) and to death without AIDS for four calendar periods, adjusting for exposure category, age, sex, acute infection, and stratifying by cohort. We compared results to those obtained from a cause-specific hazards model. Results Of 6941, 2021 (29%) developed AIDS and 437 (6%) died without AIDS. The risk of AIDS or death remained constant to 1996 then reduced; relative hazard = 0.89 (95% CI: 0.77–1.03); 0.90 (95% CI: 0.81–1.01); and 0.32 (95% CI: 0.28–0.37) for 1979–1990, 1991–1993, and 1997–2001, respectively, compared to 1994–1996. Significant risk reductions in 1997–2001 were observed in all but two AIDS-defining groups and death without AIDS in a competing risks model (with similar results from a cause-specific model). There was significant heterogeneity in the risk reduction across events; from 96% for cryptosporidiosis, to 17% for death without AIDS (P < 0.0001). Conclusion These findings suggest that studies reporting a stable trend for particular AIDS diseases over the period 1979–2001 may not have accounted for the competing risks among other events or lack the power to detect smaller trends. PMID:12435766

  14. Medical language proficiency: A discussion of interprofessional language competencies and potential for patient risk.

    PubMed

    Hull, Melodie

    2016-02-01

    In increasingly multilingual healthcare environments worldwide, ensuring accurate, effective communication is requisite. Language proficiency is essential, particularly medical language proficiency. Medical language is a universal construct in healthcare, the shared language of health and allied health professions. It is highly evolved, career-specific, technical and cultural-bound-a language for specific purposes. Its function differs significantly from that of a standard language. Proficiency requires at minimum, a common understanding of discipline-specific jargon, abstracts, euphemisms, abbreviations; acronyms. An optimal medical language situation demands a level of competency beyond the superficial wherein one can convey or interpret deeper meanings, distinguish themes, voice opinion, and follow directions precisely. It necessitates the use of clarity, and the ability to understand both lay and formal language-characteristics not essential to standard language. Proficiency influences professional discourse and can have the potential to positively or negatively affect patient outcomes. While risks have been identified when there is language discordance between care provider and patient, almost nothing has been said about this within care teams themselves. This article will do so in anticipation that care providers, regulators, employers, and researchers will acknowledge potential language-based communication barriers and work towards resolutions. This is predicated on the fact that the growing interest in language and communication in healthcare today appears to be rested in globalization and increasingly linguistically diverse patient populations. Consideration of the linguistically diverse healthcare workforce is absent. An argument will be posited that if potential risks to patient safety exist and there are potentials for disengagement from care by patients when health providers do not speak their languages then logically these language-based issues can

  15. Risk Management. Unit 20. Level 3. Instructor Guide. PACE: Program for Acquiring Competence in Entrepreneurship. Third Edition. Research & Development Series No. 303-20.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This instructor guide for a unit on risk management in the PACE (Program for Acquiring Competence in Entrepreneurship) curriculum includes the full text of the student module and lesson plans, instructional suggestions, and other teacher resources. The competencies that are incorporated into this module are at Level 3 of learning--starting and…

  16. Risk Management. Unit 20. Level 2. Instructor Guide. PACE: Program for Acquiring Competence in Entrepreneurship. Third Edition. Research & Development Series No. 302-20.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This instructor guide for a unit on risk management in the PACE (Program for Acquiring Competence in Entrepreneurship) curriculum includes the full text of the student module and lesson plans, instructional suggestions, and other teacher resources. The competencies that are incorporated into this module are at Level 2 of learning--planning for a…

  17. Response to 'Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort'.

    PubMed

    Hoffmann, S; Sobotzki, C

    2017-03-23

    Lindqvist et al. [1] recently published a mortality analysis in a prospective cohort of 29 518 Sweden-born women. Using a competing risk framework, the authors observed an increased mortality by cardiovascular disease (CVD) and noncancer/non-CVD for women who avoided sun exposure. A. Torres, the president of the American Academy of Dermatology, already addressed a number of limitations which are important in the interpretation of this study [2]. This article is protected by copyright. All rights reserved.

  18. Prediction of skull fracture risk for children 0-9 months old through validated parametric finite element model and cadaver test reconstruction.

    PubMed

    Li, Zhigang; Liu, Weiguo; Zhang, Jinhuan; Hu, Jingwen

    2015-09-01

    Skull fracture is one of the most common pediatric traumas. However, injury assessment tools for predicting pediatric skull fracture risk is not well established mainly due to the lack of cadaver tests. Weber conducted 50 pediatric cadaver drop tests for forensic research on child abuse in the mid-1980s (Experimental studies of skull fractures in infants, Z Rechtsmed. 92: 87-94, 1984; Biomechanical fragility of the infant skull, Z Rechtsmed. 94: 93-101, 1985). To our knowledge, these studies contained the largest sample size among pediatric cadaver tests in the literature. However, the lack of injury measurements limited their direct application in investigating pediatric skull fracture risks. In this study, 50 pediatric cadaver tests from Weber's studies were reconstructed using a parametric pediatric head finite element (FE) model which were morphed into subjects with ages, head sizes/shapes, and skull thickness values that reported in the tests. The skull fracture risk curves for infants from 0 to 9 months old were developed based on the model-predicted head injury measures through logistic regression analysis. It was found that the model-predicted stress responses in the skull (maximal von Mises stress, maximal shear stress, and maximal first principal stress) were better predictors than global kinematic-based injury measures (peak head acceleration and head injury criterion (HIC)) in predicting pediatric skull fracture. This study demonstrated the feasibility of using age- and size/shape-appropriate head FE models to predict pediatric head injuries. Such models can account for the morphological variations among the subjects, which cannot be considered by a single FE human model.

  19. Risk

    PubMed Central

    Cole, Stephen R.; Hudgens, Michael G.; Brookhart, M. Alan; Westreich, Daniel

    2015-01-01

    The epidemiologist primarily studies transitions between states of health and disease. The purpose of the present article is to define a foundational parameter for such studies, namely risk. We begin simply and build to the setting in which there is more than 1 event type (i.e., competing risks or competing events), as well as more than 1 treatment or exposure level of interest. In the presence of competing events, the risks are a set of counterfactual cumulative incidence functions for each treatment. These risks can be depicted visually and summarized numerically. We use an example from the study of human immunodeficiency virus to illustrate concepts. PMID:25660080

  20. Parametric Cost Deployment

    NASA Technical Reports Server (NTRS)

    Dean, Edwin B.

    1995-01-01

    Parametric cost analysis is a mathematical approach to estimating cost. Parametric cost analysis uses non-cost parameters, such as quality characteristics, to estimate the cost to bring forth, sustain, and retire a product. This paper reviews parametric cost analysis and shows how it can be used within the cost deployment process.

  1. Predictors of progression to chronic dialysis in survivors of severe acute kidney injury: a competing risk study

    PubMed Central

    2014-01-01

    Background Survivors of acute kidney injury are at an increased risk of developing irreversible deterioration in kidney function and in some cases, the need for chronic dialysis. We aimed to determine predictors of chronic dialysis and death among survivors of dialysis-requiring acute kidney injury. Methods We used linked administrative databases in Ontario, Canada, to identify patients who were discharged from hospital after an episode of acute kidney injury requiring dialysis and remained free of further dialysis for at least 90 days after discharge between 1996 and 2009. Follow-up extended until March 31, 2011. The primary outcome was progression to chronic dialysis. Predictors for this outcome were evaluated using cause-specific Cox proportional hazards models, and a competing risk approach was used to calculate absolute risk. Results We identified 4 383 patients with acute kidney injury requiring temporary in-hospital dialysis who survived to discharge. After a mean follow-up of 2.4 years, 356 (8%) patients initiated chronic dialysis and 1475 (34%) died. The cumulative risk of chronic dialysis was 13.5% by the Kaplan-Meier method, and 10.3% using a competing risk approach. After accounting for the competing risk of death, previous nephrology consultation (subdistribution hazard ratio (sHR) 2.03; 95% confidence interval (CI) 1.61-2.58), a history of chronic kidney disease (sHR3.86; 95% CI 2.99-4.98), a higher Charlson comorbidity index score (sHR 1.10; 95% CI 1.05-1.15/per unit) and pre-existing hypertension (sHR 1.82; 95% CI 1.28-2.58) were significantly associated with an increased risk of progression to chronic dialysis. Conclusions Among survivors of dialysis-requiring acute kidney injury who initially become dialysis independent, the subsequent need for chronic dialysis is predicted by pre-existing kidney disease, hypertension and global comorbidity. This information can identify patients at high risk of progressive kidney disease who may benefit from

  2. Core Competency Modification. A Manual for Working with At-Risk/Special Needs Students.

    ERIC Educational Resources Information Center

    Loess Hills Area Education Agency 13, Council Bluffs, IA.

    This manual assists teachers in providing adaptations for disabled and disadvantaged students to ensure their success in the regular vocational classroom and to meet requirements of the new vocational education standards in Iowa, which call for a competency-based curriculum. Introductory pages include strategies for teaching special needs…

  3. Instructional Climates in Preschool Children Who Are At-Risk. Part II: Perceived Physical Competence

    ERIC Educational Resources Information Center

    Robinson, Leah E.; Rudisill, Mary E.; Goodway, Jacqueline D.

    2009-01-01

    In Part II of this study, we examined the effect of two 9-week instructional climates (low-autonomy [LA] and mastery motivational climate [MMC]) on perceived physical competence (PPC) in preschoolers (N = 117). Participants were randomly assigned to an LA, MMC, or comparison group. PPC was assessed by a pretest, posttest, and retention test with…

  4. Core Competency Modification. A Manual for Working with At-Risk/Special Needs Students.

    ERIC Educational Resources Information Center

    Loess Hills Area Education Agency 13, Council Bluffs, IA.

    This manual assists teachers in providing adaptations for disabled and disadvantaged students to ensure their success in the regular vocational classroom and to meet requirements of the new vocational education standards in Iowa, which call for a competency-based curriculum. Introductory pages include strategies for teaching special needs…

  5. Risk and Protective Factors for Children of Adolescents: Maternal Depression and Parental Sense of Competence

    ERIC Educational Resources Information Center

    Knoche, Lisa L.; Givens, Jami E.; Sheridan, Susan M.

    2007-01-01

    We investigated the relationship between depression and parental sense of competence to child cognitive outcomes for a sample of 49 adolescent mothers and their young children ("Mean age" = 9 1/2 months) enrolled in a student parenting program. Cognitive development of the infants and toddlers was assessed using the Bayley Scales of Infant…

  6. Instructional Climates in Preschool Children Who Are At-Risk. Part II: Perceived Physical Competence

    ERIC Educational Resources Information Center

    Robinson, Leah E.; Rudisill, Mary E.; Goodway, Jacqueline D.

    2009-01-01

    In Part II of this study, we examined the effect of two 9-week instructional climates (low-autonomy [LA] and mastery motivational climate [MMC]) on perceived physical competence (PPC) in preschoolers (N = 117). Participants were randomly assigned to an LA, MMC, or comparison group. PPC was assessed by a pretest, posttest, and retention test with…

  7. Type 2 diabetes, adiposity and cancer morbidity and mortality risk taking into account competing risk of noncancer deaths in a prospective cohort setting.

    PubMed

    Drake, Isabel; Gullberg, Bo; Sonestedt, Emily; Stocks, Tanja; Bjartell, Anders; Wirfält, Elisabet; Wallström, Peter; Orho-Melander, Marju

    2017-09-15

    Type 2 diabetes (T2D) and adiposity associate with increased risk of several cancers, but the impact of competing risk of noncancer deaths on these associations is not known. We prospectively examined participants in the Malmö Diet and Cancer Study aged 44-73 years with no history of cancer at baseline (n = 26,953, 43% men). T2D was ascertained at baseline and during follow-up, and body mass index (BMI) and waist circumference (WC) at baseline. Multivariable cause-specific hazard ratios (HR) and subdistribution hazard ratios (sHR), taking into account noncancer deaths, were estimated using Cox- and competing risk regression. During follow-up (mean 17 years), 7,061 incident cancers (3,220 obesity-related cancer types) and 2,848 cancer deaths occurred. BMI and WC were associated with increased risk of obesity-related cancer incidence and cancer mortality. In T2D subjects, risk of obesity-related cancer was elevated among men (HR = 1.31, 95% CI: 1.12-1.54; sHR = 1.29, 95% CI: 1.10-1.52), and cancer mortality among both men and women (HR = 1.34, 95% CI: 1.20-1.49; sHR = 1.30, 95% CI: 1.16-1.45). There was no elevated actual risk of cancer death in T2D patients with long disease duration (sHR = 1.00, 95% CI: 0.83-1.20). There was a significant additive effect of T2D and adiposity on risk of obesity-related cancer and cancer mortality. In conclusion, detection bias may partially explain the increased risk of cancer morbidity among T2D patients. Both excess risk of competing events among patients with T2D and depletion of susceptibles due to earlier cancer detection will lower the actual risk of cancer, particularly with longer diabetes duration and at older ages. © 2017 The Authors International Journal of Cancer published by John Wiley & Sons Ltd on behalf of UICC.

  8. Risk communication as a core public health competence in infectious disease management: Development of the ECDC training curriculum and programme.

    PubMed

    Dickmann, Petra; Abraham, Thomas; Sarkar, Satyajit; Wysocki, Piotr; Cecconi, Sabrina; Apfel, Franklin; Nurm, Ülla-Karin

    2016-01-01

    Risk communication has been identified as a core competence for guiding public health responses to infectious disease threats. The International Health Regulations (2005) call for all countries to build capacity and a comprehensive understanding of health risks before a public health emergency to allow systematic and coherent communication, response and management. Research studies indicate that while outbreak and crisis communication concepts and tools have long been on the agenda of public health officials, there is still a need to clarify and integrate risk communication concepts into more standardised practices and improve risk communication and health, particularly among disadvantaged populations. To address these challenges, the European Centre for Disease Prevention and Control (ECDC) convened a group of risk communication experts to review and integrate existing approaches and emerging concepts in the development of a training curriculum. This curriculum articulates a new approach in risk communication moving beyond information conveyance to knowledge- and relationship-building. In a pilot training this approach was reflected both in the topics addressed and in the methods applied. This article introduces the new conceptual approach to risk communication capacity building that emerged from this process, presents the pilot training approach developed, and shares the results of the course evaluation.

  9. Communication Competencies.

    ERIC Educational Resources Information Center

    Boileau, Don M.

    Aware of the societal problems stemming from a lack of communication skills, the American public is pressing for instruction in speaking and listening in the schools. This response is reflected in the speaking and listening competency recommendations in many national reform reports. Such reports include "A Nation at Risk" by the National…

  10. A Competence-Based Science Learning Framework Illustrated Through the Study of Natural Hazards and Disaster Risk Reduction

    NASA Astrophysics Data System (ADS)

    Oyao, Sheila G.; Holbrook, Jack; Rannikmäe, Miia; Pagunsan, Marmon M.

    2015-09-01

    This article proposes a competence-based learning framework for science teaching, applied to the study of 'big ideas', in this case to the study of natural hazards and disaster risk reduction (NH&DRR). The framework focuses on new visions of competence, placing emphasis on nurturing connectedness and behavioral actions toward resilience and sustainability. The framework draws together competences familiarly expressed as cognitive knowledge and skills, plus dispositions and adds connectedness and action-related behaviors, and applies this by means of a progression shift associated with NH&DRR from abilities to capabilities. The target is enhanced scientific literacy approached through an education through science focus, amplified through the study of a big idea, promotion of sustained resilience in the face of disaster and the taking of responsibilities for behavioral actions. The framework is applied to a learning progression for each interrelated education dimension, thus serving as a guide for both the development of abilities and as a platform for stimulating student capabilities within instruction and assessment.

  11. Slow Gait Speed and Risk of Long-Term Nursing Home Residence in Older Women, Adjusting for Competing Risk of Mortality: Results from the Study of Osteoporotic Fractures.

    PubMed

    Lyons, Jennifer G; Ensrud, Kristine E; Schousboe, John T; McCulloch, Charles E; Taylor, Brent C; Heeren, Timothy C; Stuver, Sherri O; Fredman, Lisa

    2016-12-01

    To determine whether slow gait speed increases the risk of costly long-term nursing home residence when accounting for death as a competing risk remains unknown. Longitudinal cohort study using proportional hazards models to predict long-term nursing home residence and subdistribution models with death as a competing risk. Community-based prospective cohort study. Older women (mean age 76.3) participating in the Study of Osteoporotic Fractures who were also enrolled in Medicare fee-for-service plans (N = 3,755). Gait speed was measured on a straight 6-m course and averaged over two trials. Long-term nursing home residence was defined using a validated algorithm based on Medicare Part B claims for nursing home-related care. Participants were followed until long-term nursing home residence, disenrollment from Medicare plan, death, or December 31, 2010. Over the follow-up period (median 11 years), 881 participants (23%) experienced long-term nursing home residence, and 1,013 (27%) died before experiencing this outcome. Slow walkers (55% of participants with gait speed <1 m/s) were significantly more likely than fast walkers to reside in a nursing home long-term (adjusted hazards ratio (aHR) = 1.79, 95% confidence interval (CI) = 1.54-2.09). Associations were attenuated in subdistribution models (aHR = 1.52, 95% CI = 1.30-1.77) but remained statistically significant. Older community-dwelling women with slow gait speed are more likely to experience long-term nursing home residence, as well as mortality without long-term residence. Ignoring the competing mortality risk may overestimate long-term care needs and costs. © 2016, Copyright the Authors Journal compilation © 2016, The American Geriatrics Society.

  12. Competing Risk Approach (CRA) for Estimation of Disability Adjusted Life Years (DALY’s) for Female Breast Cancer in India

    PubMed Central

    Thirthahalli, Chethana; Nooyi, Shalini Chandrashekar; Shivaraj, NS; Murthy, Nandagudi Srinivasa

    2015-01-01

    Background Competing Risk Approach (CRA) has been used to compute burden of disease in terms of Disability Adjusted Life Years (DALYs) based on a life table for an initially disease-free cohort over time. Objective To compute Years of Life Lost (YLL) due to premature mortality, Years of life lost due to Disability (YLD), DALYs and loss in expectation of life (LEL) using competing risk approach for female breast cancer patients for the year 2008 in India. Materials and Methods The published data on breast cancer by age & sex, incidence & mortality for the year 2006-2008 relating to six population based cancer registries (PBCR) under Indian Council of Medical Research (ICMR), general mortality rates of 2007 in India, published in national health profile 2010; based on Sample Registration System (SRS) were utilized for computations. Three life tables were constructed by applying attrition of factors: (i) risk of death from all causes (‘a’; where a is the general death rate); (ii) risk of incidence and that of death from causes other than breast cancer (‘b-a+c’; where ‘b’ is the incidence of breast cancer and ‘c’ is the mortality of breast cancer); and (iii) risk of death from all other causes after excluding cancer mortality (‘a-c’). Taking the differences in Total Person Years Lived (TPYL), YLD and YLL were derived along with LEL. Results CRA revealed that the DALYs were 40209 per 100,000 females in the life time of 0-70+ years with a LEL of 0.11 years per person. Percentage of YLL to DALYs was 28.20% in the cohort. Conclusion The method of calculation of DALYs based on the CRA is simple and this will help to identify the burden of diseases using minimal information in terms of YLL, YLD, DALYs and LEL. PMID:26557544

  13. Conceptualizing and Re-Evaluating Resilience across Levels of Risk, Time, and Domains of Competence

    ERIC Educational Resources Information Center

    Vanderbilt-Adriance, Ella; Shaw, Daniel S.

    2008-01-01

    This article examines potential theoretical constraints on resilience across levels of risk, time, and domain of outcome. Studies of resilience are reviewed as they relate to the prevalence of resilience across levels of risk (e.g., single life events vs. cumulative risk), time, and domains of adjustment. Based on a thorough review of pertinent…

  14. Risks, dangers and competing clinical decisions on venous thromboembolism prophylaxis in hospital care.

    PubMed

    Boiko, Olga; Sheaff, Rod; Child, Susan; Gericke, Christian A

    2014-07-01

    Drawing on wider sociologies of risk, this article examines the complexity of clinical risks and their management, focusing on risk management systems, expert decision-making and safety standards in health care. At the time of this study preventing venous thromboembolism (VTE) among in-patients was one of the top priorities for hospital safety in the English National Health Service (NHS). An analysis of 50 interviews examining hospital professionals' perceptions about VTE risks and prophylaxis illuminates how National Institute for Health and Clinical Excellence (NICE) guidelines influenced clinical decision-making in four hospitals in one NHS region. We examine four themes: the identification of new risks, the institutionalisation and management of risk, the relationship between risk and danger and the tensions between risk management systems and expert decision-making. The implementation of NICE guidelines for VTE prevention extended managerial control over risk management but some irreducible clinical dangers remained that were beyond the scope of the new VTE risk management systems. Linking sociologies of risk with the realities of hospital risk management reveals the capacity of these theories to illuminate both the possibilities and the limits of managerialism in health care. © 2014 The Authors. Sociology of Health & Illness © 2014 Foundation for the Sociology of Health & Illness/John Wiley & Sons Ltd.

  15. Prediagnostic serum glucose and lipids in relation to survival in breast cancer patients: a competing risk analysis.

    PubMed

    Wulaningsih, Wahyu; Vahdaninia, Mariam; Rowley, Mark; Holmberg, Lars; Garmo, Hans; Malmstrom, Håkan; Lambe, Mats; Hammar, Niklas; Walldius, Göran; Jungner, Ingmar; Coolen, Anthonius C; Van Hemelrijck, Mieke

    2015-11-17

    Abnormal glucose and lipids levels may impact survival after breast cancer (BC) diagnosis, but their association to other causes of mortality such as cardiovascular (CV) disease may result in a competing risk problem. We assessed serum glucose, triglycerides (TG) and total cholesterol (TC) measured prospectively 3 months to 3 years before diagnosis in 1798 Swedish women diagnosed with any type of BC between 1985 and 1999. In addition to using Cox regression, we employed latent class proportional hazards models to capture any heterogeneity of associations between these markers and BC death. The latter method was extended to include the primary outcome (BC death) and competing outcomes (CV death and death from other causes), allowing latent class-specific hazard estimation for cause-specific deaths. A lack of association between prediagnostic glucose, TG or TC with BC death was observed with Cox regression. With latent class proportional hazards model, two latent classes (Class I and II) were suggested. Class I, comprising the majority (81.5 %) of BC patients, had an increased risk of BC death following higher TG levels (HR: 1.87, 95 % CI: 1.01-3.45 for every log TG increase). Lower overall survival was observed in Class II, but no association for BC death was found. On the other hand, TC positively corresponded to CV death in Class II, and similarly, glucose to death from other causes. Addressing cohort heterogeneity in relation to BC survival is important in understanding the relationship between metabolic markers and cause-specific death in presence of competing outcomes.

  16. The role of verbal competence and multiple risk on the internalizing behavior problems of Costa Rican youth.

    PubMed

    Corapci, Feyza; Smith, Julia; Lozoff, Betsy

    2006-12-01

    This longitudinal study examined internalizing behavior problems (anxiety/depression) in early adolescence in relation to adversity in early childhood and child verbal competence. We hypothesized that verbal competence would act as a protective factor in the face of early adversity, that is, high verbal IQ would predict relatively lower internalizing problems in early adolescence primarily for those children who experienced the greatest adversity. The sample was based on 191 Costa Rican children and their mothers, who were recruited in infancy from an urban community and assessed again at 5 and 11-14 years. Families were generally lower-middle to working class. A total of 165 children (94 boys) participated in the early adolescent follow-up (mean age = 12.3 years). Internalizing problems were based on maternal report (Spanish Child Behavior Checklist). Our cumulative risk index (CRI)_of adversity in early childhood consisted of home environment quality (HOME score), socioeconomic status, maternal depressed mood (CESD), and maternal IQ. Controlling for the effects of age, gender, internalizing problems at 5 years, and verbal IQ at 5 years, there was a significant interaction between early adversity and verbal IQ at age 11-14 years in predicting internalizing problems in early adolescence. Youth with high verbal IQ had comparable levels of internalizing problems regardless of high or low adversity in early childhood. In contrast, youth with low verbal IQ received higher internalizing problem ratings if they experienced high adversity early in life. The results raise the possibility that interventions to improve verbal competence might help lower the risk of internalizing problems in the face of early adversity.

  17. Competing-risks regression models in analysis of biomarkers as predictors of high-risk human papillomavirus (HPV) infection outcomes and incident CIN in the LAMS cohort.

    PubMed

    Syrjänen, Stina; Longhato-Filho, Adhemar; Sarian, Luis O; Naud, Paulo; Derchain, Sophie; Rottelli-Martins, Cecilia; Tatti, Silvio; Branca, Margherita; Eržen, Mojca; Hammes, Luciano S; Matos, Jean; Gontijo, Renata; Bragança, Joana; Arlindo, Francisco C; Maeda, Mariana Y S; Costa, Silvano; Syrjänen, Kari

    2013-07-01

    To assess the prediction potential of a 5-biomarker panel for detecting high-risk human papillomavirus (HR-HPV) infections and/or cervical intraepithelial neoplasia (CIN) progression. Five biomarkers, lipocalin, plasminogen activator inhibitor-2, p300, interleukin-10, and stratifin, were assessed in cervical biopsies from 225 women of the Latin American Screening Study. Competing-risks regression models were constructed to assess their predictive power for (i) HR-HPV outcomes (negative, transient, or persistent infection) and (ii) CIN outcomes (no progression, incident CIN1, CIN2, or CIN3). p300, LCN2, stratifin were significantly associated with prevalent HR-HPV but lost their significance in multivariate analysis. In the multivariate model, only p300 was an independent predictor of CIN3 (odds ratio=2.63; 95% confidence interval, 1.05-6.61; P=0.039). In univariate competing-risks regression, lipocalin predicted permanent HR-HPV-negative status, but in the multivariate model, IL-10 emerged as a independent predictor of HPV-negative status (subhazard ratio=4.04; 95% confidence interval, 1.81-9.01; P=0.001). The clinical value of the panel in predicting longitudinal outcomes of HR-HPV infection and/or incident CIN is limited.

  18. Sparse representation of multi parametric DCE-MRI features using K-SVD for classifying gene expression based breast cancer recurrence risk

    NASA Astrophysics Data System (ADS)

    Mahrooghy, Majid; Ashraf, Ahmed B.; Daye, Dania; Mies, Carolyn; Rosen, Mark; Feldman, Michael; Kontos, Despina

    2014-03-01

    We evaluate the prognostic value of sparse representation-based features by applying the K-SVD algorithm on multiparametric kinetic, textural, and morphologic features in breast dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI). K-SVD is an iterative dimensionality reduction method that optimally reduces the initial feature space by updating the dictionary columns jointly with the sparse representation coefficients. Therefore, by using K-SVD, we not only provide sparse representation of the features and condense the information in a few coefficients but also we reduce the dimensionality. The extracted K-SVD features are evaluated by a machine learning algorithm including a logistic regression classifier for the task of classifying high versus low breast cancer recurrence risk as determined by a validated gene expression assay. The features are evaluated using ROC curve analysis and leave one-out cross validation for different sparse representation and dimensionality reduction numbers. Optimal sparse representation is obtained when the number of dictionary elements is 4 (K=4) and maximum non-zero coefficients is 2 (L=2). We compare K-SVD with ANOVA based feature selection for the same prognostic features. The ROC results show that the AUC of the K-SVD based (K=4, L=2), the ANOVA based, and the original features (i.e., no dimensionality reduction) are 0.78, 0.71. and 0.68, respectively. From the results, it can be inferred that by using sparse representation of the originally extracted multi-parametric, high-dimensional data, we can condense the information on a few coefficients with the highest predictive value. In addition, the dimensionality reduction introduced by K-SVD can prevent models from over-fitting.

  19. Ordinary risks and accepted fictions: how contrasting and competing priorities work in risk assessment and mental health care planning.

    PubMed

    Coffey, Michael; Cohen, Rachel; Faulkner, Alison; Hannigan, Ben; Simpson, Alan; Barlow, Sally

    2017-06-01

    Communication and information sharing are considered crucial to recovery-focused mental health services. Effective mental health care planning and coordination includes assessment and management of risk and safety. Using data from our cross-national mixed-method study of care planning and coordination, we examined what patients, family members and workers say about risk assessment and management and explored the contents of care plans. Thematic analysis of qualitative research interviews (n = 117) with patients, family members and workers, across four English and two Welsh National Health Service sites. Care plans were reviewed (n = 33) using a structured template. Participants have contrasting priorities in relation to risk. Patients see benefit in discussions about risk, but cast the process as a worker priority that may lead to loss of liberty. Relationships with workers are key to family members and patients; however, worker claims of involving people in the care planning process do not extend to risk assessment and management procedures for fear of causing upset. Workers locate risk as coming from the person rather than social or environmental factors, are risk averse and appear to prioritize the procedural aspects of assessment. Despite limitations, risk assessment is treated as legitimate work by professionals. Risk assessment practice operates as a type of fiction in which poor predictive ability and fear of consequences are accepted in the interests of normative certainty by all parties. As a consequence, risk adverse options are encouraged by workers and patients steered away from opportunities for ordinary risks thereby hindering the mobilization of their strengths and abilities. © 2016 The Authors. Health Expectations Published by John Wiley & Sons Ltd.

  20. Parametrically defined differential equations

    NASA Astrophysics Data System (ADS)

    Polyanin, A. D.; Zhurov, A. I.

    2017-01-01

    The paper deals with nonlinear ordinary differential equations defined parametrically by two relations. It proposes techniques to reduce such equations, of the first or second order, to standard systems of ordinary differential equations. It obtains the general solution to some classes of nonlinear parametrically defined ODEs dependent on arbitrary functions. It outlines procedures for the numerical solution of the Cauchy problem for parametrically defined differential equations.

  1. Conceptualizing and Re-Evaluating Resilience Across Levels of Risk, Time, and Domains of Competence

    PubMed Central

    Shaw, Daniel S.

    2009-01-01

    This article examines potential theoretical constraints on resilience across levels of risk, time, and domain of outcome. Studies of resilience are reviewed as they relate to the prevalence of resilience across levels of risk (e.g., single life events vs. cumulative risk), time, and domains of adjustment. Based on a thorough review of pertinent literature, we conclude that resilience, as a global construct, appears to be rare at the highest levels of risk, and that resilience may benefit from a narrower conceptualization focusing on specific outcomes at specific timepoints in development. The implication of this conclusion for future research and intervention efforts is then discussed. PMID:18379875

  2. The Relation Between Adolescent Social Competence and Young Adult Delinquency and Educational Attainment Among At-Risk Youth: The Mediating Role of Peer Delinquency

    PubMed Central

    Stepp, Stephanie D; Pardini, Dustin A; Loeber, Rolf; Morris, Nancy A

    2015-01-01

    Objective We examined trajectories of adolescent social competence as a resilience factor among at-risk youth. To examine potential mechanisms of this resilience process, we investigated the putative mediating effect of peer delinquency on the relation between adolescent social competence and young adult delinquency seriousness and educational attainment. Method Participants (n = 257) were screened to be at risk for antisocial behaviour at age 13 years. Data were derived from an ongoing longitudinal study of the development of antisocial and delinquent behaviour among inner-city boys, the Pittsburgh Youth Study. We used data collected from participants when aged 13 years until they were aged 25.5 years for our study. Results Results indicated that boys with high levels of social competence decreased their involvement with deviant peers throughout adolescence, which, in turn, predicted less serious forms of delinquency in early adulthood. Social competence had a direct effect on educational attainment in early adulthood, as boys who developed social competencies in adolescence went further in school irrespective of their involvement with delinquent peers. Conclusions Results suggest that promoting the development of social competencies and reducing involvement with delinquent peers will protect at-risk youth from engaging in serious delinquency in early adulthood while increasing their educational success. PMID:21878156

  3. Nurturing Cognitive Competence in Preschoolers: A Longitudinal Study of Intergenerational Continuity and Risk

    ERIC Educational Resources Information Center

    Saltaris, Christina; Serbin, Lisa A.; Stack, Dale M.; Karp, Jennifer A.; Schwartzman, Alex E.; Ledingham, Jane E.

    2004-01-01

    The current investigation was designed to examine the provision of cognitive stimulation to preschool-aged children from high-risk families. Participants were drawn from the Concordia Longitudinal Risk Project, a prospective, longitudinal investigation of individuals recruited in 1976-77 from lower SES neighbourhoods who were rated by childhood…

  4. Nurturing Cognitive Competence in Preschoolers: A Longitudinal Study of Intergenerational Continuity and Risk

    ERIC Educational Resources Information Center

    Saltaris, Christina; Serbin, Lisa A.; Stack, Dale M.; Karp, Jennifer A.; Schwartzman, Alex E.; Ledingham, Jane E.

    2004-01-01

    The current investigation was designed to examine the provision of cognitive stimulation to preschool-aged children from high-risk families. Participants were drawn from the Concordia Longitudinal Risk Project, a prospective, longitudinal investigation of individuals recruited in 1976-77 from lower SES neighbourhoods who were rated by childhood…

  5. Is Resilience Only Skin Deep? Rural African Americans’ Preadolescent Socioeconomic Status-Related Risk and Competence and Age 19 Psychological Adjustment and Allostatic Load

    PubMed Central

    Brody, Gene H.; Yu, Tianyi; Chen, Edith; Miller, Gregory E.; Kogan, Steven M.; Beach, Steven R. H.

    2012-01-01

    Many African American youth may develop high levels of allostatic load (AL), a measure of physiological wear and tear on the body as a function of developing psychosocial competence under conditions of high SES-related risk. The current study was designed to test hypotheses based on John Henryism theory about such physiological costs. We tested these hypotheses with a representative sample of 489 African American youth living in the rural South. Cumulative SES-related risks and teacher-reported competence were assessed when the youth were 11 to 13 years of age; depressive symptoms, externalizing behavior, and AL were assessed at age 19. The results revealed that rural African American preadolescents who evinced high psychosocial competence under conditions of high cumulative SES-related risk displayed low levels of adjustment problems along with high AL at age 19. These results suggest that, for many rural African Americans, resilience may indeed be only “skin deep.” PMID:23722980

  6. A competing risk survival analysis model to assess the efficacy of filling carious primary teeth.

    PubMed

    Stephenson, J; Chadwick, B L; Playle, R A; Treasure, E T

    2010-01-01

    In recent years a strategy of selective, symptom-based intervention of carious primary teeth has been developed amongst some British general dental practitioners. Practice-based studies appear to provide evidence that policies of restoration of symptomless carious primary teeth do not confer any significant benefits above those associated with non-restorative care. However, results from these studies contrast with those of many clinical trials and prospective studies of primary molar restorations. In the current investigation, cohort study data from 5,168 carious primary molar teeth from 2,654 British children aged 4-5 years at baseline, augmented with Dental Practice Board treatment data, was utilised to assess the effect of restorative treatment on the likelihood of carious teeth subsequently progressing to either exfoliation or extraction. The effect of demographic and tooth level covariates on the fate of these teeth was also assessed. Multivariate multilevel parametric survival models were applied to the analysis of the carious-exfoliation and carious-extraction transitions to which the teeth were subject, assuming an underlying data hierarchy with teeth nested within individuals. Time of occurrence of caries affected survival experience, with teeth in which caries occurred later in life being associated with higher survival rates to extraction. Amongst filled teeth, later fillings were also associated with higher survival rates to extraction. Demographic and tooth level variables had a limited effect on survival experience. Treatment was found to be significantly associated with survival with respect to extraction, with survival rates of over 80% at 14 years, double those of untreated teeth.

  7. Planning and evaluating clinical trials with composite time-to-first-event endpoints in a competing risk framework.

    PubMed

    Rauch, G; Beyersmann, J

    2013-09-20

    Composite endpoints combine several events of interest within a single variable. These are often time-to-first-event data, which are analyzed via survival analysis techniques. To demonstrate the significance of an overall clinical benefit, it is sufficient to assess the test problem formulated for the composite. However, the effect observed for the composite does not necessarily reflect the effects for the components. Therefore, it would be desirable that the sample size for clinical trials using composite endpoints provides enough power not only to detect a clinically relevant superiority for the composite but also to address the components in an adequate way. The single components of a composite endpoint assessed as time-to-first-event define competing risks. We consider multiple test problems based on the cause-specific hazards of competing events to address the problem of analyzing both a composite endpoint and its components. Thereby, we use sequentially rejective test procedures to reduce the power loss to a minimum. We show how to calculate the sample size for the given multiple test problem by using a simply applicable simulation tool in SAS. Our ideas are illustrated by two clinical study examples. Copyright © 2013 John Wiley & Sons, Ltd.

  8. Parametric Resonance Revisited

    NASA Astrophysics Data System (ADS)

    van den Broeck, C.; Bena, I.

    The phenomenon of parametric resonance is revisited. Several physical examples are reviewed and an exactly solvable model is discussed. A mean field theory is presented for globally coupled parametric oscillators with randomly distributed phases. A new type of collective instability appears, which is similar in nature to that of noise induced phase transitions.

  9. Twitter as a Potential Disaster Risk Reduction Tool. Part IV: Competency-based Education and Training Guidelines to Promote Community Resiliency

    PubMed Central

    Yeager, Violet; Cooper, Guy Paul; Burkle, Frederick M.; Subbarao, Italo

    2015-01-01

    Twitter can be an effective tool for disaster risk reduction but gaps in education and training exist in current public health and disaster management educational competency standards.  Eleven core public health and disaster management competencies are proposed that incorporate Twitter as a tool for effective disaster risk reduction.  Greater funding is required to promote the education and training of this tool for those in professional schools and in the current public health and disaster management workforce.  PMID:26203398

  10. A collaborative national model to assess competencies for medical students, residents, and other healthcare practitioners in gait and falls risk evaluation.

    PubMed

    Atkinson, Hal H; Tan, Zaldy S; Brennan, Maura; Granville, Lisa

    2014-06-01

    To ensure that the healthcare workforce is adequately prepared to care for the growing population of older adults, minimum competencies in geriatrics have been published for medical students and primary care residents. Approaches to teaching and assessing these competencies are needed to guide medical schools, residencies, and continuing medical education programs. With sponsorship by the Education Committee and Teachers Section of the American Geriatrics Society (AGS), geriatrics educators from multiple institutions collaborated to develop a model to teach and assess a major domain of student and resident competency: Gait and Falls Risk Evaluation. The model was introduced as a workshop at annual meetings of the AGS and the American College of Physicians in 2011 and 2012. Participants included medical students, residents, geriatrics fellows, practicing physicians, and midlevel practitioners. At both national meetings, participants rated the experience highly and reported statistically significant gains in overall competence in gait and falls risk evaluation. The largest gains were observed for medical students, residents, and practicing physicians (P < .001 for all); geriatrics fellows reported a higher level of baseline competence and therefore had a lower magnitude of improvement, albeit still significant (P = .02). Finally, the majority of participants reported intent to disseminate the model in their institutions. This article describes the design, implementation, and evaluation of this collaborative national model. A number of institutions have used the model, and the goal of this article is to aid in further dissemination of this successful approach to teaching and assessing geriatrics competencies.

  11. Reducing psychosocial risks through supervisors' development: a contribution for a brief version of the "Stress Management Competency Indicator Tool".

    PubMed

    Toderi, Stefano; Gaggia, Andrea; Balducci, Cristian; Sarchielli, Guido

    2015-06-15

    With the recent changes in the world of work psychosocial risks are increasingly prevalent, causing work stress and physical and mental illnesses, which have a tremendous impact on public health and social participation. Supervisors' behaviour development was proposed as an innovative intervention that can reduce psychosocial risks. The "Stress Management Competency Indicator Tool" is one of the most important questionnaires that assess managers' preventive behaviour. However, its psychometric properties have never been evaluated and the length of the questionnaire (66 items) limits its practical applicability. The aim of this study was to contribute to the development of the questionnaire by providing psychometric evidence on a brief version of the tool focusing on the "Managing and Communicating existing and future Work" cluster of behaviours, which has been found to be the crucial one in terms of stress prevention. A questionnaire was administered to 178 employees of two Italian public organizations (a municipality and a hospital), measuring the supervisors' "Managing and Communicating existing and future Work" competency, and the affective well-being and work team effectiveness. The results showed excellent psychometric properties of the supervisors' behaviour scale and confirmed the expected relationships with criterion outcomes (affective well-being and team effectiveness). Overall, the factorial structure and dimensionality, the construct validity and reliability, and the concurrent validity of the tool were strongly supported by this study. We concluded that the brief version of the scale is a valid and reliable measure that can be easily used in practice and that can contribute to the development of research and practice on this topic. Copyright © 2015 Elsevier B.V. All rights reserved.

  12. ESHOL study reanalysis: All-cause mortality considered by competing risks and time-dependent covariates for renal transplantation.

    PubMed

    Maduell, Francisco; Moreso, Francesc; Mora-Macià, Josep; Pons, Mercedes; Ramos, Rosa; Carreras, Jordi; Soler, Jordi; Torres, Ferrán

    2016-01-01

    The ESHOL study showed that post-dilution online haemodiafiltration (OL-HDF) reduces all-cause mortality versus haemodialysis. However, during the observation period, 355 patients prematurely completed the study and, according to the study design, these patients were censored at the time of premature termination. The aim of this study was to investigate the outcome of patients who discontinued the study. During follow-up, 207 patients died while under treatment and 47 patients died after discontinuation of the study. Compared with patients maintained on haemodialysis, those randomised to OL-HDF had lower all-cause mortality (12.4 versus 9.46 per 100 patient-years, hazard ratio and 95%CI: 0.76; [0.59-0.98], P= 0.031). For all-cause mortality by time-dependent covariates and competing risks for transplantation, the time-dependent Cox analysis showed very similar results to the main analysis with a hazard ratio of 0.77 (0.60-0.99, P= 0.043). The results of this analysis of the ESHOL trial confirm that post-dilution OL-HDF reduces all-cause mortality versus haemodialysis in prevalent patients. The original results of the ESHOL study, which censored patients discontinuing the study for any reason, were confirmed in the present ITT population without censures and when all-cause mortality was considered by time-dependent and competing risks for transplantation. Copyright © 2015 Sociedad Española de Nefrología. Published by Elsevier España, S.L.U. All rights reserved.

  13. Advantage of the modified Lunn-McNeil technique over Kalbfleisch-Prentice technique in competing risks

    NASA Astrophysics Data System (ADS)

    Lukman, Iing; Ibrahim, Noor A.; Daud, Isa B.; Maarof, Fauziah; Hassan, Mohd N.

    2002-03-01

    Survival analysis algorithm is often applied in the data mining process. Cox regression is one of the survival analysis tools that has been used in many areas, and it can be used to analyze the failure times of aircraft crashed. Another survival analysis tool is the competing risks where we have more than one cause of failure acting simultaneously. Lunn-McNeil analyzed the competing risks in the survival model using Cox regression with censored data. The modified Lunn-McNeil technique is a simplify of the Lunn-McNeil technique. The Kalbfleisch-Prentice technique is involving fitting models separately from each type of failure, treating other failure types as censored. To compare the two techniques, (the modified Lunn-McNeil and Kalbfleisch-Prentice) a simulation study was performed. Samples with various sizes and censoring percentages were generated and fitted using both techniques. The study was conducted by comparing the inference of models, using Root Mean Square Error (RMSE), the power tests, and the Schoenfeld residual analysis. The power tests in this study were likelihood ratio test, Rao-score test, and Wald statistics. The Schoenfeld residual analysis was conducted to check the proportionality of the model through its covariates. The estimated parameters were computed for the cause-specific hazard situation. Results showed that the modified Lunn-McNeil technique was better than the Kalbfleisch-Prentice technique based on the RMSE measurement and Schoenfeld residual analysis. However, the Kalbfleisch-Prentice technique was better than the modified Lunn-McNeil technique based on power tests measurement.

  14. Evaluating the competing risks of HIV acquisition and maternal mortality in Africa: a decision analysis.

    PubMed

    Rodriguez, M I; Reeves, M F; Caughey, A B

    2012-08-01

    To model the risk of HIV acquisition and maternal mortality for women in four African countries in the light of previous data on risk of HIV acquisition and hormonal contraceptive use. Decision analysis. Chad, Kenya, South Africa and Uganda. Women of reproductive age, at risk of HIV, who do not desire pregnancy. A decision analysis model was built to compare the consequences of removing progestin injectables from use, assuming an increased risk of HIV acquisition. Three scenarios were considered in four African countries: replacement of progestin injectables with no method, with combined oral contraceptives (COC) or with an intrauterine device (IUD). Health outcomes measured include: life-years, maternal mortality, HIV acquisition and unsafe abortion. Sensitivity analysis, including Monte Carlo simulation, was performed around all variables. HIV acquisition, maternal mortality and life-years. If progestin injectables are removed from use, without a minimum of 70-100% of women switching to an IUD or COCs, up to nine additional maternal deaths will occur for every case of HIV averted. Sensitivity analysis demonstrated that this finding persisted across a broad range of variables. Contraception is critical to preserving life for women in Africa. In the absence of clear evidence regarding hormonal contraception and HIV acquisition, policy decisions must not overlook the very real risk of maternal mortality. © 2012 World Health Organization BJOG An International Journal of Obstetrics and Gynaecology © 2012 RCOG.

  15. Types of oral contraceptives and breast cancer survival among women enrolled in Medicaid: A competing-risk model.

    PubMed

    Samson, Marsha E; Adams, Swann Arp; Mulatya, Caroline M; Zhang, Jiajia; Bennett, Charles L; Hebert, James; Steck, Susan E

    2017-01-01

    Oral contraceptive pills have been implicated in the pathophysiology of breast cancer. Although many studies have examined the relationship between combined oral contraceptives (COCs) and breast cancer, there is a paucity of literature that discusses progestin-only oral contraceptives (POCs) and breast cancer. The purpose of this investigation is to examine potential associations between different types of oral contraceptives and breast cancer mortality in the South Carolina Medicaid population among different racial/ethnic groups. Subjects included 4816 women diagnosed with breast cancer between 2000 and 2013. Kaplan-Meier curves were calculated to determine time-to-mortality rates among users of oral contraceptives. Competing-risks models and Cox multivariate survival models were used to estimate the hazard ratios (HRs) and 95% confidence intervals (CIs) of breast cancer and other-cause mortality, as well as all-cause mortality. POCs were associated with a significantly decreased risk of breast cancer mortality (HR: 0.07; 95% CI: 0.01, 0.52) and a non-significant increased risk of all-cause mortality (HR: 1.04; 95% CI: 0.52, 2.07). COCs increased the risk of breast cancer mortality (HR: 1.61; 95% CI: 1.14, 2.28) and all-cause mortality (HR: 1.83; 95% CI: 1.30, 2.57). Use of POCs may be associated with a decreased risk of breast cancer mortality. Due to the small sample size of POC users in the current study, additional research is needed to confirm these findings. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  16. Usefulness of parametric renal clearance images in the assessment of basic risk factors for renalnal clearance images in the assessment of basic risk factors for renal scarring in children with recurrent urinary tract infections.

    PubMed

    Pietrzak-Stelasiak, Ewa; Bieńkiewicz, Małgorzata; Woźnicki, Wojciech; Bubińska, Krystyna; Kowalewska-Pietrzak, Magdalena; Płachcińska, Anna; Kuśmierek, Jacek

    2017-01-01

    Clinically confirmed incidents of acute pyelonephritis (APN) following recurrent infections of urinary tract (UTI) form basic risk factors for renal scarring in children. Vesico-uretheral reflux (VUR) of higher grade is additional risk factor for this scarring. Opinions on diagnostic value of summed sequential images of renal uptake phase (SUM) of dynamic renal scintigraphy in detection of renal scars are diverse. However, several publications point to higher diagnostic efficacy of clearance parametric images (PAR) generated from this study. To establish a clinical value of parametric renal clearance images in detection of renal scarring. A prospective study was performed in a group of 91 children at the age of 4 to 18 years with recurrent UTI. Clinically documented incidents of APN were noted in 32 children: in 8 cases - one and in the remaining 24 - 2 to 5 (mean 3) incidents. In the remaining 59 patients only infections of the lower part of urinary tract were diagnosed. Static renal 99mTc-DMSA SPECT study and after 2-4 days dynamic renal studies (99mTc-EC) were performed in every patient not earlier than 6 months after the last documented incident of UTI. PAR images generated from a dynamic study by in-house developed software and SUM images were compared with a gold standard SPECT study. Percentages of children with detected renal scar(s) with SPECT and PAR methods amounted to 55% and 54%, respectively and were statistically significantly higher (p < 0.0001) than with SUM method - 31%. Scars in children with history of APN detected with SPECT and PAR methods were significantly more frequent than with infections of only lower part of urinary tract (72% vs. 46%; p = 0.017 and 69% vs. 46%; p = 0.036, respectively). A SUM method did not reveal statistically significant differences between frequencies of detection of scars in groups specified above - 38% vs. 27% (p = 0.31). Both SPECT and PAR methods showed also that frequencies of occurrence of renal scars in

  17. Socioenvironmental Risk and Adjustment in Latino Youth: The Mediating Effects of Family Processes and Social Competence

    ERIC Educational Resources Information Center

    Prelow, Hazel M.; Loukas, Alexandra; Jordan-Green, Lisa

    2007-01-01

    The direct and mediated effects of socioenvironmental risk on internalizing and externalizing problems among Latino youth aged 10-14 were examined using prospective analyses. Participants in this study were 464 Latino mother and child dyads surveyed as part of the "Welfare, Children & Families: A Three City Study." It was hypothesized that…

  18. Child Care Providers' Competence and Confidence in Referring Children at Risk for Developmental Delays

    ERIC Educational Resources Information Center

    Branson, Diane; Bingham, Ann

    2017-01-01

    Despite the benefits of early intervention for children, the majority of children with developmental delays are not identified prior to the age of 5 years. Child care providers could aid in recognition of children at risk for developmental delays; however, there is little research on this topic. This article reports on a qualitative research study…

  19. A Multivariate Investigation of Maternal Risks and Their Relationship to Low-Income, Preschool Children's Competencies

    ERIC Educational Resources Information Center

    Perry, Marlo A.; Fantuzzo, John W.

    2010-01-01

    Utilizing a developmental-ecological framework, the purpose of this study was to understand the unique impact of multiple maternal risks across time on ethnically diverse, low-income, preschool children's cognitive skills, pro-social behaviors, and behavior problems. Additionally, this study sought to understand the variability of maternal risks…

  20. Resilience and Risk Competence in Schools: Theory/Knowledge and International Application in Project REBOUND

    ERIC Educational Resources Information Center

    Brown, Joel H.; Jean-Marie, Gaetane; Beck, Jerome

    2010-01-01

    Despite a 50-year interdisciplinary and longitudinal research legacy--showing that nearly 80% of young people considered most "at risk" thrive by midlife--only recently have practitioners/researchers engaged in the explicit, prospective facilitation of "resilience" in educational settings. Here, theory/knowledge distinguishing…

  1. Parental Beliefs and Values Related to Family Risk, Educational Intervention, and Child Academic Competence.

    ERIC Educational Resources Information Center

    Campbell, Frances A.; And Others

    1991-01-01

    Studied the relation of child-rearing beliefs and values of parents of children entering kindergarten to children's academic achievements. Examined effects of a child-centered educational preschool program for socioeconomically disadvantaged children on parents' beliefs and values. Parents of children at risk differed from other parents in beliefs…

  2. Resilience and Risk Competence in Schools: Theory/Knowledge and International Application in Project REBOUND

    ERIC Educational Resources Information Center

    Brown, Joel H.; Jean-Marie, Gaetane; Beck, Jerome

    2010-01-01

    Despite a 50-year interdisciplinary and longitudinal research legacy--showing that nearly 80% of young people considered most "at risk" thrive by midlife--only recently have practitioners/researchers engaged in the explicit, prospective facilitation of "resilience" in educational settings. Here, theory/knowledge distinguishing…

  3. A Multivariate Investigation of Maternal Risks and Their Relationship to Low-Income, Preschool Children's Competencies

    ERIC Educational Resources Information Center

    Perry, Marlo A.; Fantuzzo, John W.

    2010-01-01

    Utilizing a developmental-ecological framework, the purpose of this study was to understand the unique impact of multiple maternal risks across time on ethnically diverse, low-income, preschool children's cognitive skills, pro-social behaviors, and behavior problems. Additionally, this study sought to understand the variability of maternal risks…

  4. Child Care Providers' Competence and Confidence in Referring Children at Risk for Developmental Delays

    ERIC Educational Resources Information Center

    Branson, Diane; Bingham, Ann

    2017-01-01

    Despite the benefits of early intervention for children, the majority of children with developmental delays are not identified prior to the age of 5 years. Child care providers could aid in recognition of children at risk for developmental delays; however, there is little research on this topic. This article reports on a qualitative research study…

  5. Socioenvironmental Risk and Adjustment in Latino Youth: The Mediating Effects of Family Processes and Social Competence

    ERIC Educational Resources Information Center

    Prelow, Hazel M.; Loukas, Alexandra; Jordan-Green, Lisa

    2007-01-01

    The direct and mediated effects of socioenvironmental risk on internalizing and externalizing problems among Latino youth aged 10-14 were examined using prospective analyses. Participants in this study were 464 Latino mother and child dyads surveyed as part of the "Welfare, Children & Families: A Three City Study." It was hypothesized that…

  6. [Biological risk in health. Risk to third parties: medical-legal focus. Responsible behavior of the competent physician].

    PubMed

    Rodriguez, Daniele

    2010-01-01

    The responsibility of the occupational physician (OP) is discussed within the particular topic of biological risk generated by health care workers (HCW) versus third parties in health care settings. The present contribution offers keys of interpretation regarding current Italian legislation and passed sentences, taking into account principles of occupational medicine, the ICOH code of ethics for occupational health professionals, as well as duties and tasks of OP, employers and employees. Most of the responsibilities stand on employers, but OP has a primary duty of information and to judge fitness for work. It is underlined the difficult interpretation of the current legislation and indications. Behaviour of the OP could be censored in case of particular fitness for work or in case of inadequate information, as well as if the comprehension of information is not verified or when indication to minimize the risk are not controlled.

  7. The EARLY ALLIANCE prevention trial: an integrated set of interventions to promote competence and reduce risk for conduct disorder, substance abuse, and school failure.

    PubMed

    Dumas, J E; Prinz, R J; Smith, E P; Laughlin, J

    1999-03-01

    Describes the EARLY ALLIANCE interventions, an integrated set of four programs designed to promote competence and reduce risk for early-onset conduct disorder, substance abuse, and school failure. These interventions are evaluated as part of a prevention trial that begins at school entry and targets child functioning and socializing practices across multiple contexts (school, peer group, family) and multiple domains (affective, social, and achievement coping-competence). The paper presents the conceptual foundation of the four interventions, including a synopsis of the risk and protective factors associated with conduct disorder and related outcomes, and of the coping-competence model driving EARLY ALLIANCE. The developmental rationale, intended impact, and procedures are described for each intervention: a universally administered classroom program and indicated, peer, reading-mentoring, and family programs. Interventions are currently being tested in a prevention trial, which is briefly summarized.

  8. Unifying framework for decomposition models of parametric and non-parametric image registration

    NASA Astrophysics Data System (ADS)

    Ibrahim, Mazlinda; Chen, Ke

    2017-08-01

    Image registration aims to find spatial transformations such that the so-called given template image becomes similar in some sense to the reference image. Methods in image registration can be divided into two classes (parametric or non-parametric) based on the degree of freedom of the given method. In parametric image registration, the transformation is governed by a finite set of image features or by expanding the transformation in terms of basis functions. Meanwhile, in non-parametric image registration, the problem is modelled as a functional minimisation problem via the calculus of variations. In this paper, we provide a unifying framework for decomposition models for image registration which combine parametric and non-parametric models. Several variants of the models are presented with focus on the affine, diffusion and linear curvature models. An effective numerical solver is provided for the models as well as experimental results to show the effectiveness, robustness and accuracy of the models. The decomposition model of affine and linear curvature outperforms the competing models based on tested images.

  9. Competence, Self-Esteem, and Coping Efficacy as Mediators of Ecological Risk and Depressive Symptoms in Urban African American and European American Youth

    ERIC Educational Resources Information Center

    Prelow, Hazel M.; Weaver, Scott R.; Swenson, Rebecca R.

    2006-01-01

    Structural equation modeling was used to test [Sandler, "American Journal of Community Psychology" 29: 19-61.] a theoretical model of risk and resilience in an urban sample of African American and European American adolescents. The aims of the present study were to examine whether self-system processes (i.e., competence, self-esteem, and coping…

  10. Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort.

    PubMed

    Lindqvist, P G; Epstein, E; Nielsen, K; Landin-Olsson, M; Ingvar, C; Olsson, H

    2016-10-01

    Women with active sunlight exposure habits experience a lower mortality rate than women who avoid sun exposure; however, they are at an increased risk of skin cancer. We aimed to explore the differences in main causes of death according to sun exposure. We assessed the differences in sun exposure as a risk factor for all-cause mortality in a competing risk scenario for 29 518 Swedish women in a prospective 20-year follow-up of the Melanoma in Southern Sweden (MISS) cohort. Women were recruited from 1990 to 1992 (aged 25-64 years at the start of the study). We obtained detailed information at baseline on sun exposure habits and potential confounders. The data were analysed using modern survival statistics. Women with active sun exposure habits were mainly at a lower risk of cardiovascular disease (CVD) and noncancer/non-CVD death as compared to those who avoided sun exposure. As a result of their increased survival, the relative contribution of cancer death increased in these women. Nonsmokers who avoided sun exposure had a life expectancy similar to smokers in the highest sun exposure group, indicating that avoidance of sun exposure is a risk factor for death of a similar magnitude as smoking. Compared to the highest sun exposure group, life expectancy of avoiders of sun exposure was reduced by 0.6-2.1 years. The longer life expectancy amongst women with active sun exposure habits was related to a decrease in CVD and noncancer/non-CVD mortality, causing the relative contribution of death due to cancer to increase. © 2016 The Association for the Publication of the Journal of Internal Medicine.

  11. Competing risks model in screening for preeclampsia by maternal characteristics and medical history.

    PubMed

    Wright, David; Syngelaki, Argyro; Akolekar, Ranjit; Poon, Leona C; Nicolaides, Kypros H

    2015-07-01

    The purpose of this study was to develop a model for preeclampsia based on maternal demographic characteristics and medical history. This was a screening study of 120,492 singleton pregnancies at 11-13 weeks' gestation, including 2704 pregnancies (2.2%) that experienced preeclampsia. A survival-time model for the gestational age at delivery with preeclampsia was developed from variables of maternal characteristics and history. This approach assumes that, if the pregnancy was to continue indefinitely, all women would experience preeclampsia and that whether they do so or not before a specified gestational age depends on competition between delivery before or after development of preeclampsia. A 5-fold cross validation study was conducted to compare the performance of the new model with the National Institute for Health and Clinical Excellence (NICE) guidelines. In the new model, increased risk for preeclampsia, with a consequent shift in the Gaussian distribution of the gestational age at delivery with preeclampsia to the left, is provided by advancing maternal age, increasing weight, Afro-Caribbean and South Asian racial origin, medical history of chronic hypertension, diabetes mellitus and systemic lupus erythematosus or antiphospholipid syndrome, family history and personal history of preeclampsia, and conception by in vitro fertilization. The risk for preeclampsia decreases with increasing maternal height and in parous women with no previous preeclampsia; in the latter, the protective effect, which is related inversely to the interpregnancy interval, persists beyond 15 years. At a screen-positive rate of 11%, as defined by NICE, the new model predicted 40%, 48%, and 54% of cases of total preeclampsia and preeclampsia requiring delivery at <37 and <34 weeks' gestation, respectively, which were significantly higher than the respective values of 35%, 40%, and 44% achieved by application of NICE guidelines. A new model that is based on maternal characteristics and

  12. Prognostic factors and impact of adjuvant treatments on local and metastatic relapse of soft-tissue sarcoma patients in the competing risks setting.

    PubMed

    Italiano, Antoine; Le Cesne, Axel; Mendiboure, Jean; Blay, Jean-Yves; Piperno-Neumann, Sophie; Chevreau, Christine; Delcambre, Corinne; Penel, Nicolas; Terrier, Philippe; Ranchere-Vince, Dominique; Lae, Marick; Le Guellec, Sophie; Michels, Jean-Jacques; Robin, Yves Marie; Bellera, Carine; Bonvalot, Sylvie

    2014-11-01

    In the medical literature many analyses of outcomes of sarcoma patients were performed without regard to the problem of "competing risks." We analyzed local relapse-free and metastasis-free survival in a population of 3255 adult patients with a primary soft-tissue sarcoma (STS) included in the French Sarcoma Group database. Cumulative incidence of local and metastatic relapse was estimated by accounting for death as a competing event. On multivariate analysis, age, tumor site, histological subtype, and grade were independent adverse prognostic factors for local relapse, whereas tumor depth and size had no influence. Histological subtype, tumor depth, tumor size, and grade were independent adverse prognostic factors for metastatic relapse. Despite a higher incidence of competing deaths in patients managed with adjuvant radiotherapy than in patients not receiving radiotherapy, adjuvant radiotherapy was associated with a significant benefit in terms of local relapse-free survival. Despite a similar cumulative incidence of competing deaths in patients with grade 2 and grade 3 disease, we found that the benefit of adjuvant chemotherapy was present only in patients with grade 3 and not in patients with grade 2 disease. In the setting of competing risks, tumor biology reflected by histological grade is a crucial predictor of local relapse, whereas tumor depth and size have poor if any influence. Grade could also predict the benefit of adjuvant chemotherapy in patients with STS. © 2014 American Cancer Society.

  13. Competing-Risks Mortality After Radiotherapy vs. Observation for Localized Prostate Cancer: A Population-based Study

    SciTech Connect

    Abdollah, Firas; Sun, Maxine; Schmitges, Jan; Thuret, Rodolphe; Tian, Zhe; Shariat, Shahrokh F.; Briganti, Alberto; Jeldres, Claudio; Perrotte, Paul; Montorsi, Francesco; Karakiewicz, Pierre I.

    2012-09-01

    Purpose: Contemporary patients with localized prostate cancer (PCa) are more frequently treated with radiotherapy. However, there are limited data on the effect of this treatment on cancer-specific mortality (CSM). Our objective was to test the relationship between radiotherapy and survival in men with localized PCa and compare it with those treated with observation. Methods: A population-based cohort identified 68,797 men with cT1-T2 PCa treated with radiotherapy or observation between the years 1992 and 2005. Propensity-score matching was used to minimize potential bias related to treatment assignment. Competing-risks analyses tested the effect of treatment type (radiotherapy vs. observation) on CSM, after accounting to other-cause mortality. All analyses were carried out within PCa risk, baseline comorbidity status, and age groups. Results: Radiotherapy was associated with more favorable 10-year CSM rates than observation in patients with high-risk PCa (8.8 vs. 14.4%, hazard ratio [HR]: 0.59, 95% confidence interval [CI]: 0.50-0.68). Conversely, the beneficial effect of radiotherapy on CSM was not evident in patients with low-intermediate risk PCa (3.7 vs. 4.1%, HR: 0.91, 95% CI: 0.80-1.04). Radiotherapy was beneficial in elderly patients (5.6 vs. 7.3%, HR: 0.70, 95% CI: 0.59-0.80). Moreover, it was associated with improved CSM rates among patients with no comorbidities (5.7 vs. 6.5%, HR: 0.81, 95% CI: 0.67-0.98), one comorbidity (4.6 vs. 6.0%, HR: 0.87, 95% CI: 0.75-0.99), and more than two comorbidities (4.2 vs. 5.0%, HR: 0.79, 95% CI: 0.65-0.96). Conclusions: Radiotherapy substantially improves CSM in patients with high-risk PCa, with little or no benefit in patients with low-/intermediate-risk PCa relative to observation. These findings must be interpreted within the context of the limitations of observational data.

  14. Efficient Estimation of Semiparametric Transformation Models for the Cumulative Incidence of Competing Risks.

    PubMed

    Mao, Lu; Lin, D Y

    2017-03-01

    The cumulative incidence is the probability of failure from the cause of interest over a certain time period in the presence of other risks. A semiparametric regression model proposed by Fine and Gray (1999) has become the method of choice for formulating the effects of covariates on the cumulative incidence. Its estimation, however, requires modeling of the censoring distribution and is not statistically efficient. In this paper, we present a broad class of semiparametric transformation models which extends the Fine and Gray model, and we allow for unknown causes of failure. We derive the nonparametric maximum likelihood estimators (NPMLEs) and develop simple and fast numerical algorithms using the profile likelihood. We establish the consistency, asymptotic normality, and semiparametric efficiency of the NPMLEs. In addition, we construct graphical and numerical procedures to evaluate and select models. Finally, we demonstrate the advantages of the proposed methods over the existing ones through extensive simulation studies and an application to a major study on bone marrow transplantation.

  15. Evaluating predictors of competing risk outcomes when censoring depends on time-dependent covariates, with application to safety and efficacy of HIV treatment.

    PubMed

    Lok, Judith J; Hughes, Michael D

    2016-06-15

    We propose a prediction model for the cumulative incidence functions of competing risks, based on a logit link. Because of a concern about censoring potentially depending on time-varying covariates in our motivating human immunodeficiency virus (HIV) application, we describe an approach for estimating the parameters in the prediction models using inverse probability of censoring weighting under a missingness at random assumption. We then illustrate the application of this methodology to identify predictors of the competing outcomes of virologic failure, an efficacy outcome, and treatment limiting adverse event, a safety outcome, among human immunodeficiency virus-infected patients first starting antiretroviral treatment. Copyright © 2016 John Wiley & Sons, Ltd.

  16. On the importance of accounting for competing risks in pediatric cancer trials designed to delay or avoid radiotherapy: I. Basic concepts and first analyses.

    PubMed

    Tai, Bee-Choo; Grundy, Richard G; Machin, David

    2010-04-01

    In trials designed to delay or avoid irradiation among children with malignant brain tumor, although irradiation after disease progression is an important event, patients who have disease progression may decline radiotherapy (RT), or those without disease progression may opt for elective RT. To accurately describe the cumulative need for RT in such instances, it is crucial to account for these distinct events and to evaluate how each contributes to the delay or advancement of irradiation via a competing risks analysis. We describe the summary of competing events in such trials using competing risks methods based on cumulative incidence functions and Gray's test. The results obtained are contrasted with standard survival methods based on Kaplan-Meier curves, cause-specific hazard functions and log-rank test. The Kaplan-Meier method overestimates all event-specific rates. The cause-specific hazard analysis showed reduction in hazards for all events (A: RT after progression; B: no RT after progression; C: elective RT) among children with ependymoma. For event A, a higher cumulative incidence was reported for ependymoma. Although Gray's test failed to detect any difference (p = 0.331) between histologic subtypes, the log-rank test suggested marginal evidence (p = 0.057). Similarly, for event C, the log-rank test found stronger evidence of reduction in hazard among those with ependymoma (p = 0.005) as compared with Gray's test (p = 0.086). To evaluate treatment differences, failing to account for competing risks using appropriate methodology may lead to incorrect interpretations.

  17. Negotiating competency, professionalism and risk: the integration of complementary and alternative medicine by nurses and midwives in NHS hospitals.

    PubMed

    Cant, Sarah; Watts, Peter; Ruston, Annmarie

    2011-02-01

    This qualitative interview study examined the use of complementary and alternative medicine (CAM) by nurses and midwives in NHS hospital settings in 2008 in the UK. It showed that the groundswell of interest in CAM in the 1990s had diminished by this time due to changes to policy and funding, and increasingly stringent clinical governance. Nevertheless, CAM provided an opportunity for committed and self-motivated practitioners to extend their therapeutic repertoire and develop affective dimensions of practice. However, the integration of CAM did not afford the autonomy, status and material gains traditionally associated with a collective professional project. In practice, occupational strategies were individualistic, and grounded in the assertion of competency through expressions of professionalism rather than the credentialism which underpins classic professionalisation. Central to these strategies was CAM related risk, which became a means by which to claim occupational space. However, the extent to which the adoption of CAM enhanced the nurses' and midwives' roles was limited by traditional medical authority; the uncertain status of CAM knowledge; and the absence of collective strategies - which together often left practitioners in a position of vulnerability.

  18. Fine and Gray competing risk regression model to study the cause-specific under-five child mortality in Bangladesh.

    PubMed

    Mohammad, Khandoker Akib; Fatima-Tuz-Zahura, Most; Bari, Wasimul

    2017-01-28

    The cause-specific under-five mortality of Bangladesh has been studied by fitting cumulative incidence function (CIF) based Fine and Gray competing risk regression model (1999). For the purpose of analysis, Bangladesh Demographic and Health Survey (BDHS), 2011 data set was used. Three types of mode of mortality for the under-five children are considered. These are disease, non-disease and other causes. Product-Limit survival probabilities for the under-five child mortality with log-rank test were used to select a set of covariates for the regression model. The covariates found to have significant association in bivariate analysis were only considered in the regression analysis. Potential determinants of under-five child mortality due to disease is size of child at birth, while gender of child, NGO (non-government organization) membership of mother, mother's education level, and size of child at birth are due to non-disease and age of mother at birth, NGO membership of mother, and mother's education level are for the mortality due to other causes. Female participation in the education programs needs to be increased because of the improvement of child health and government should arrange family and social awareness programs as well as health related programs for women so that they are aware of their child health.

  19. Proximal femoral replacement in the management of acute periprosthetic fractures of the hip: a competing risks survival analysis

    PubMed Central

    Colman, Matthew; Choi, Lisa; Chen, Antonia; Crossett, Lawrence; Tarkin, Ivan; McGough, Richard

    2014-01-01

    To examine the mortality and implant survivorship of proximal femoral replacement (PFR), revision total hip arthroplasty (REV) and open reduction internal fixation (ORIF) in the treatment of acute periprosthetic fractures of the proximal femur, we retrospectively reviewed 97 consecutive acute periprosthetic proximal femoral fractures from 2000–2010. Three groups were defined: PFR (n=21), REV (n=19), and ORIF (n=57). Outcome measures were all-cause mortality, implant failure, and reoperation. Competing Risks survival analysis of overall mortality during the mean 35-month follow-up showed no statistical difference between the three groups (p=0.65; 12 and 60 month mortality for PFR: 37%, 45%; REV: 16%, 46%; ORIF: 14%, 100%). Implant survival was worse for the PFR group (p=0.03, 12 and 60-month implant failure rate for PFR: 5%, 39%; REV: 7%, 7%; ORIF 2%, 2%). We conclude that PFR as compared with REV or ORIF may have worse medium-term implant survival, primarily due to instability and dislocation. PMID:23856062

  20. Proximal femoral replacement in the management of acute periprosthetic fractures of the hip: a competing risks survival analysis.

    PubMed

    Colman, Matthew; Choi, Lisa; Chen, Antonia; Crossett, Lawrence; Tarkin, Ivan; McGough, Richard

    2014-02-01

    To examine the mortality and implant survivorship of proximal femoral replacement (PFR), revision total hip arthroplasty (REV) and open reduction internal fixation (ORIF) in the treatment of acute periprosthetic fractures of the proximal femur, we retrospectively reviewed 97 consecutive acute periprosthetic proximal femoral fractures from 2000 to 2010. Three groups were defined: PFR (n=21), REV (n=19), and ORIF (n=57). Outcome measures were all-cause mortality, implant failure, and reoperation. Competing Risks survival analysis of overall mortality during the mean 35-month follow-up showed no statistical difference between the three groups (P=0.65; 12 and 60 month mortality for PFR: 37%, 45%; REV: 16%, 46%; ORIF: 14%, 100%). Implant survival was worse for the PFR group (P=0.03, 12 and 60-month implant failure rate for PFR: 5%, 39%; REV: 7%, 7%; ORIF 2%, 2%). We conclude that PFR as compared with REV or ORIF may have worse medium-term implant survival, primarily due to instability and dislocation.

  1. AAOHN Competencies.

    PubMed

    2015-11-01

    The AAOHN Competency document is one of the core documents that define occupational health nursing practice. This article provides a description of the process used to update the competencies, as well as a description of the new competencies.

  2. Intern Boot Camp: Feasibility and impact of a 1-hour session to ensure graduating medical student competency in falls risk assessment.

    PubMed

    Omlor, Rebecca L; Watkins, Franklin S; Lawlor, Janice S; Lovato, James F; Fino, Nora F; Atkinson, Hal H

    2017-01-01

    The authors evaluated the feasibility of a 1-hour session to ensure competency in gait and falls risk assessment for medical students at their institution. The session included a history and exam with faculty and staff as standardized patients, gait recognition videos, and case evaluation for falls risk assessment and prevention. Student perceptions were evaluated using a retrospective pre-post survey, scored on a 5-point Likert-type scale. Wilcoxon signed-rank tests were used to assess change and Kruskal-Wallis tests were used to analyze differences by residency choice. A range of five to 11 faculty and staff certified 238 medical students during eight 1-hour sessions. Overall self-perception of competence in falls risk assessment and prevention improved (p ≤ .001), and did not differ by residency choice, both before and after the training program (p = .73 and p = .25). Feedback was positive. This session is a feasible way to teach and assess the competency for falls risk assessment with modest time commitment.

  3. Conceptualization and Pilot Testing of a Core Competency-Based Training Workshop in Suicide Risk Assessment and Management: Notes From the Field.

    PubMed

    Cramer, Robert J; Bryson, Claire N; Eichorst, Morgam K; Keyes, Lee N; Ridge, Brittany E

    2017-03-01

    As professional psychology training programs and continuing education have moved toward competency based approaches, it has become equally important to develop uniform, evidence-based approaches for suicide risk assessment and management. The present article presents a workshop curriculum based on established core competencies in suicide risk assessment and management. Drawing on theories suicide risk formation, the workshop features an integration of didactic, process, and experiential components. We present pilot data from 2 small group workshops (n = 17): 1 from a clinical psychology doctoral program and 1 from a university counseling center. Workshop participation yielded increases in (a) the ability to recognize appropriate clinician responses to suicidal client statements, (b) self-perceptions of general capacity to interface with suicidal patients and mastery of the 10 core competencies, (c) factual knowledge concerning suicide risk assessment and management, and (d) the self-rated ability to assess and manage a suicidal patient. We discuss statistical and generalizability limitations as well as implications for future modification, implementation, and provision of this training method. © 2016 Wiley Periodicals, Inc.

  4. Quantifying intrinsic and extrinsic control of single-cell fates in cancer and stem/progenitor cell pedigrees with competing risks analysis

    PubMed Central

    Cornwell, J. A.; Hallett, R. M.; der Mauer, S. Auf; Motazedian, A.; Schroeder, T.; Draper, J. S.; Harvey, R. P.; Nordon, R. E.

    2016-01-01

    The molecular control of cell fate and behaviour is a central theme in biology. Inherent heterogeneity within cell populations requires that control of cell fate is studied at the single-cell level. Time-lapse imaging and single-cell tracking are powerful technologies for acquiring cell lifetime data, allowing quantification of how cell-intrinsic and extrinsic factors control single-cell fates over time. However, cell lifetime data contain complex features. Competing cell fates, censoring, and the possible inter-dependence of competing fates, currently present challenges to modelling cell lifetime data. Thus far such features are largely ignored, resulting in loss of data and introducing a source of bias. Here we show that competing risks and concordance statistics, previously applied to clinical data and the study of genetic influences on life events in twins, respectively, can be used to quantify intrinsic and extrinsic control of single-cell fates. Using these statistics we demonstrate that 1) breast cancer cell fate after chemotherapy is dependent on p53 genotype; 2) granulocyte macrophage progenitors and their differentiated progeny have concordant fates; and 3) cytokines promote self-renewal of cardiac mesenchymal stem cells by symmetric divisions. Therefore, competing risks and concordance statistics provide a robust and unbiased approach for evaluating hypotheses at the single-cell level. PMID:27250534

  5. DWPF Welder Parametric Study

    SciTech Connect

    Plodinec, M.J.

    1998-11-20

    After being filled with glass, DWPF canistered waste forms will be welded closed using an upset resistance welding process. This final closure weld must be leaktight, and must remain so during extended storage at SRS. As part of the DWPF Startup Test Program, a parametric study (DWPF-WP-24) has been performed to determine a range of welder operating parameters which will produce acceptable welds. The parametric window of acceptable welds defined by this study is 90,000 + 15,000 lb of force, 248,000 + 22,000 amps of current, and 95 + 15 cycles* for the time of application of the current.

  6. DWPF welder parametric study

    SciTech Connect

    Eberhard, B.J.; Harbour, J.R.; Plodinec, M.J.

    1994-06-01

    As part of the DWPF Startup Test Program, a parametric study has been performed to determine a range of welder operating parameters which will produce acceptable final welds for canistered waste forms. The parametric window of acceptable welds defined by this study is 90,000 {plus_minus} 15,000 lb of force, 248,000 {plus_minus} 22,000 amps of current, and 95 {plus_minus} 15 cycles (@ 60 cops) for the time of application of the current.

  7. Parametric Rietveld refinement

    PubMed Central

    Stinton, Graham W.; Evans, John S. O.

    2007-01-01

    In this paper the method of parametric Rietveld refinement is described, in which an ensemble of diffraction data collected as a function of time, temperature, pressure or any other variable are fitted to a single evolving structural model. Parametric refinement offers a number of potential benefits over independent or sequential analysis. It can lead to higher precision of refined parameters, offers the possibility of applying physically realistic models during data analysis, allows the refinement of ‘non-crystallographic’ quantities such as temperature or rate constants directly from diffraction data, and can help avoid false minima. PMID:19461841

  8. Cluster B personality symptoms in persons at genetic risk for schizophrenia are associated with social competence and activation of the right temporo-parietal junction during emotion processing.

    PubMed

    Goldschmidt, Micaela Giuliana; Villarreal, Mirta Fabiana; de Achával, Delfina; Drucaroff, Lucas Javier; Costanzo, Elsa Yolanda; Castro, Mariana Nair; Pahissa, Jaime; Camprodon, Joan; Nemeroff, Charles; Guinjoan, Salvador Martín

    2014-01-30

    Personality disorders are common in nonpsychotic siblings of patients with schizophrenia, and some personality traits in this group may be associated with an increased risk for full-blown psychosis. We sought to establish if faulty right-hemisphere activation induced by social cognitive tasks, as previously described in patients with schizophrenia, is associated with specific personality symptoms in their unaffected siblings. We observed that cluster B personality symptoms in this group were inversely related to activation in the right temporo parietal junction (rTPJ, a structure critical in social cognitive processing) in response to a basic emotion processing task and also to social competence, whereas in contrast to our initial hypothesis, cluster A traits were not associated with right hemisphere activation during emotion processing or with social competence. These findings suggest the existence of clinical traits in at-risk individuals which share a common neurobiological substrate with schizophrenia, in regards to social performance.

  9. Education methods for maintaining nursing competency in low-volume, high-risk procedures in the rural setting: bridging the theory to practice gap.

    PubMed

    Banks, Cassie M; Gilmartin, Heather; Fink, Regina M

    2010-01-01

    Nurses practicing in the rural setting have faced a unique challenge in maintaining competency in low-volume, high-risk procedures. This study assessed the effectiveness of a focused, multifaceted educational intervention on the retention of nursing knowledge related to central venous access devices care and maintenance. A pretest-posttest intervention study design was used at a 58-bed rural healthcare facility in a Western state. This study demonstrates a statistically significant increase in functional nursing knowledge in the postintervention period.

  10. First incident hospitalisation for Australian women aged 70 and beyond: A 10 year examination using competing risks.

    PubMed

    Harris, Melissa L; Dolja-Gore, Xenia; Kendig, Hal; Byles, Julie E

    2016-01-01

    There are increasing concerns regarding high hospital use among older adults and the capacity to manage the economic impact of the ageing population trend on healthcare systems. First hospitalisation in old age may act as a catalyst for ongoing intensification of health problems and acute care use. This study examined factors associated with first incident hospitalisation in women aged over 70, accounting for the health inequalities associated with geographic location. Survey data from 3780 women from the 1921 to 1926 cohort of the Australian Longitudinal Study on Women's Health were matched with the Admitted Patients Data Collection and National Death Index. Days to first event (hospitalisation or death) were modelled using competing risks methods. A total of 3065 (80.3%) women had at least one hospital admission. More than half of the top 15 reasons for first hospitalisation were related to cardiovascular disease, with atrial fibrillation the most common. Proportional subdistribution hazards models showed that first hospital admission was driven by enabling and need factors including asthma/bronchitis diagnosis (HR=1.16; p=0.047), private health insurance (HR=1.16; p=0.004) more than two prescribed medications in previous month (HR=1.31; p=0.001), more than four general practitioner visits in previous year (HR=1.50; p=0.034), lower physical functioning (HR=0.99; p<0.001) and living in an inner regional area (HR=1.17; p=0.003). First overnight hospitalisation was primarily related with potentially preventable and treatable chronic diseases. Primary and secondary strategies aimed at chronic disease generally, and better chronic disease management particularly for cardiovascular and respiratory diseases, may play a vital role in disease prevention or delay in readmissions among this population. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

  11. Parametric Differentiation and Integration

    ERIC Educational Resources Information Center

    Chen, Hongwei

    2009-01-01

    Parametric differentiation and integration under the integral sign constitutes a powerful technique for calculating integrals. However, this topic is generally not included in the undergraduate mathematics curriculum. In this note, we give a comprehensive review of this approach, and show how it can be systematically used to evaluate most of the…

  12. Parametric Interpretation in Yorktalk.

    ERIC Educational Resources Information Center

    Ogden, Richard

    The method of parametric interpretation used in the computer program "Yorktalk," software that creates synthetic parameter files from phonological representations of speech, is explained. First, the design of the program is described, and the concept of "exponency" in prosodic analysis is explained as it is applied in the…

  13. Parametric Differentiation and Integration

    ERIC Educational Resources Information Center

    Chen, Hongwei

    2009-01-01

    Parametric differentiation and integration under the integral sign constitutes a powerful technique for calculating integrals. However, this topic is generally not included in the undergraduate mathematics curriculum. In this note, we give a comprehensive review of this approach, and show how it can be systematically used to evaluate most of the…

  14. Families, Risk, and Competence.

    ERIC Educational Resources Information Center

    Lewis, Michael, Ed.; Feiring, Candice, Ed.

    The problems of studying families arise from the difficulty in studying systems in which there are multiple elements interacting with each other and with the child. This book attests to the growing sophistication of the conceptualization and measurement techniques for understanding family processes. Chapters in the first part of the book,…

  15. Families, Risk, and Competence.

    ERIC Educational Resources Information Center

    Lewis, Michael, Ed.; Feiring, Candice, Ed.

    The problems of studying families arise from the difficulty in studying systems in which there are multiple elements interacting with each other and with the child. This book attests to the growing sophistication of the conceptualization and measurement techniques for understanding family processes. Chapters in the first part of the book,…

  16. Parametric instability of pressurized propellant tanks

    NASA Astrophysics Data System (ADS)

    Albus, Jochen; Dieker, Stefan; Őry, Huba; Rittweger, Andreas

    2008-01-01

    Pressurized propellant tanks might become dynamically unstable with detrimental dynamic responses if a dynamic excitation leads to a coupling of pressure oscillations (especially due to the response of axisymmetric modes) with very low damped ovalizing modes. This phenomenon can be described and identified as the so-called parametric instability. During the dynamic qualification test campaign of the new Ariane 5 Cryogenic Upper Stage ESC-A, a parametric instability was observed for sinusoidal tests under certain test conditions with low static pressure in the propellant tank. The parametric instability was identified and an analytical simulation was performed that confirmed the instability. During flight, harmonic excitations might occur due to pressure oscillations within the solid rocket booster. However, the application of the analytical model on flight conditions indicates that the flight behaviour will be stable. This was confirmed by results from additional tests. This paper describes the phenomenon of the parametric instability of pressurized propellant tanks and presents an analytical methodology to assess the risk of the occurrence of a parametric instability.

  17. Repeated testing improves achievement in a blended learning approach for risk competence training of medical students: results of a randomized controlled trial.

    PubMed

    Spreckelsen, C; Juenger, J

    2017-09-26

    Adequate estimation and communication of risks is a critical competence of physicians. Due to an evident lack of these competences, effective training addressing risk competence during medical education is needed. Test-enhanced learning has been shown to produce marked effects on achievements. This study aimed to investigate the effect of repeated tests implemented on top of a blended learning program for risk competence. We introduced a blended-learning curriculum for risk estimation and risk communication based on a set of operationalized learning objectives, which was integrated into a mandatory course "Evidence-based Medicine" for third-year students. A randomized controlled trial addressed the effect of repeated testing on achievement as measured by the students' pre- and post-training score (nine multiple-choice items). Basic numeracy and statistical literacy were assessed at baseline. Analysis relied on descriptive statistics (histograms, box plots, scatter plots, and summary of descriptive measures), bootstrapped confidence intervals, analysis of covariance (ANCOVA), and effect sizes (Cohen's d, r) based on adjusted means and standard deviations. All of the 114 students enrolled in the course consented to take part in the study and were assigned to either the intervention or control group (both: n = 57) by balanced randomization. Five participants dropped out due to non-compliance (control: 4, intervention: 1). Both groups profited considerably from the program in general (Cohen's d for overall pre vs. post scores: 2.61). Repeated testing yielded an additional positive effect: while the covariate (baseline score) exhibits no relation to the post-intervention score, F(1, 106) = 2.88, p > .05, there was a significant effect of the intervention (repeated tests scenario) on learning achievement, F(1106) = 12.72, p < .05, d = .94, r = .42 (95% CI: [.26, .57]). However, in the subgroup of participants with a high initial numeracy score no similar

  18. Constrained parametric model for simultaneous inference of two cumulative incidence functions.

    PubMed

    Shi, Haiwen; Cheng, Yu; Jeong, Jong-Hyeon

    2013-01-01

    We propose a parametric regression model for the cumulative incidence functions (CIFs) commonly used for competing risks data. The model adopts a modified logistic model as the baseline CIF and a generalized odds-rate model for covariate effects, and it explicitly takes into account the constraint that a subject with any given prognostic factors should eventually fail from one of the causes such that the asymptotes of the CIFs should add up to one. This constraint intrinsically holds in a nonparametric analysis without covariates, but is easily overlooked in a semiparametric or parametric regression setting. We hence model the CIF from the primary cause assuming the generalized odds-rate transformation and the modified logistic function as the baseline CIF. Under the additivity constraint, the covariate effects on the competing cause are modeled by a function of the asymptote of the baseline distribution and the covariate effects on the primary cause. The inference procedure is straightforward by using the standard maximum likelihood theory. We demonstrate desirable finite-sample performance of our model by simulation studies in comparison with existing methods. Its practical utility is illustrated in an analysis of a breast cancer dataset to assess the treatment effect of tamoxifen, adjusting for age and initial pathological tumor size, on breast cancer recurrence that is subject to dependent censoring by second primary cancers and deaths.

  19. The Prospective, Observational, Multicenter, Major Trauma Transfusion (PROMMTT) Study: Comparative Effectiveness of a Time-varying Treatment with Competing Risks

    PubMed Central

    Holcomb, John B.; del Junco, Deborah J.; Fox, Erin E.; Wade, Charles E.; Cohen, Mitchell J.; Schreiber, Martin A.; Alarcon, Louis H.; Bai, Yu; Brasel, Karen J.; Bulger, Eileen M.; Cotton, Bryan A.; Matijevic, Nena; Muskat, Peter; Myers, John G.; Phelan, Herb A.; White, Christopher E.; Zhang, Jiajie; Rahbar, Mohammad H.

    2013-01-01

    Context Hemorrhagic shock is the leading potentially preventable cause of death after injury. Transfusion of early and increased ratios of plasma and platelets to red blood cells (RBCs) has been associated with decreased mortality; however conflicting reports and the time-varying nature of transfusions and hemorrhagic death raise concern for the validity of the clinical conclusions drawn from the retrospective data. Objective To relate in-hospital mortality to: 1) early transfusion of plasma and/or platelets and 2) time-varying plasma:RBC and platelet:RBC ratios. Design Prospective cohort study documenting the timing of transfusions during active resuscitation and patient outcomes. Data were analyzed using time-dependent proportional hazards models. Setting Ten US Level 1 trauma centers. Patients Adult trauma patients surviving for 30 minutes after admission, transfused at least 1 unit RBC within 6 hours of admission (n=1245, the original study group) and at least 3 total units (of RBC, plasma or platelets) within 24 hours (n=905, the analysis group). Main outcome measure In-hospital mortality Results Plasma:RBC and platelet:RBC ratios were not constant over the first 24 hours (p<.001 for both). In a multivariable time-dependent Cox model, increased ratios of plasma:RBC (adjusted hazard ratio, HR=0.31, 95% CI=0.16–0.58) and platelets:RBC (adjusted HR=0.55, 95% CI=0.31–0.98) were independently associated with decreased 6-hour mortality, when hemorrhagic death predominated. In the first 6 hours, patients with ratios < 1:2 were 3–4 times more likely to die than patients with ratios ≥1:1. After 24 hours, plasma and platelet ratios were unassociated with mortality, when competing risks from non-hemorrhagic causes prevailed. Conclusions Higher plasma and platelet ratios early in resuscitation were associated with decreased mortality in patients transfused at least three units of blood products during the first 24 hours after admission. Among survivors at 24 hours

  20. Competency Index. [Health Technology Cluster.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This competency index lists the competencies included in the 62 units of the Tech Prep Competency Profiles within the Health Technologies Cluster. The unit topics are as follows: employability skills; professionalism; teamwork; computer literacy; documentation; infection control and risk management; medical terminology; anatomy, physiology, and…

  1. Competency Index. [Health Technology Cluster.

    ERIC Educational Resources Information Center

    Ohio State Univ., Columbus. Center on Education and Training for Employment.

    This competency index lists the competencies included in the 62 units of the Tech Prep Competency Profiles within the Health Technologies Cluster. The unit topics are as follows: employability skills; professionalism; teamwork; computer literacy; documentation; infection control and risk management; medical terminology; anatomy, physiology, and…

  2. Heat Transfer Parametric System Identification

    DTIC Science & Technology

    1993-06-01

    Transfer Parametric System Identification 6. AUTHOR(S Parker, Gregory K. 7. PERFORMING ORGANIZATION NAME(S) AND AOORESS(ES) 8. PERFORMING ORGANIZATION...distribution is unlimited. Heat Transfer Parametric System Identification by Gregory K. Parker Lieutenant, United States Navy BS., DeVry Institute of...Modeling Concept ........ ........... 3 2. Lumped Parameter Approach ...... ......... 4 3. Parametric System Identification ....... 4 B. BASIC MODELING

  3. Different survival analysis methods for measuring long-term outcomes of Indigenous and non-Indigenous Australian cancer patients in the presence and absence of competing risks.

    PubMed

    He, Vincent Y F; Condon, John R; Baade, Peter D; Zhang, Xiaohua; Zhao, Yuejen

    2017-01-17

    Net survival is the most common measure of cancer prognosis and has been used to study differentials in cancer survival between ethnic or racial population subgroups. However, net survival ignores competing risks of deaths and so provides incomplete prognostic information for cancer patients, and when comparing survival between populations with different all-cause mortality. Another prognosis measure, "crude probability of death", which takes competing risk of death into account, overcomes this limitation. Similar to net survival, it can be calculated using either life tables (using Cronin-Feuer method) or cause of death data (using Fine-Gray method). The aim of this study is two-fold: (1) to compare the multivariable results produced by different survival analysis methods; and (2) to compare the Cronin-Feuer with the Fine-Gray methods, in estimating the cancer and non-cancer death probability of both Indigenous and non-Indigenous cancer patients and the Indigenous cancer disparities. Cancer survival was investigated for 9,595 people (18.5% Indigenous) diagnosed with cancer in the Northern Territory of Australia between 1991 and 2009. The Cox proportional hazard model along with Poisson and Fine-Gray regression were used in the multivariable analysis. The crude probabilities of cancer and non-cancer methods were estimated in two ways: first, using cause of death data with the Fine-Gray method, and second, using life tables with the Cronin-Feuer method. Multivariable regression using the relative survival, cause-specific survival, and competing risk analysis produced similar results. In the presence of competing risks, the Cronin-Feuer method produced similar results to Fine-Gray in the estimation of cancer death probability (higher Indigenous cancer death probabilities for all cancers) and non-cancer death probabilities (higher Indigenous non-cancer death probabilities for all cancers except lung cancer and head and neck cancers). Cronin-Feuer estimated much lower

  4. On the Importance of Accounting for Competing Risks in Pediatric Cancer Trials Designed to Delay or Avoid Radiotherapy: I. Basic Concepts and First Analyses

    SciTech Connect

    Tai, Bee-Choo; Grundy, Richard G.; Machin, David

    2010-04-15

    Purpose: In trials designed to delay or avoid irradiation among children with malignant brain tumor, although irradiation after disease progression is an important event, patients who have disease progression may decline radiotherapy (RT), or those without disease progression may opt for elective RT. To accurately describe the cumulative need for RT in such instances, it is crucial to account for these distinct events and to evaluate how each contributes to the delay or advancement of irradiation via a competing risks analysis. Methods and Materials: We describe the summary of competing events in such trials using competing risks methods based on cumulative incidence functions and Gray's test. The results obtained are contrasted with standard survival methods based on Kaplan-Meier curves, cause-specific hazard functions and log-rank test. Results: The Kaplan-Meier method overestimates all event-specific rates. The cause-specific hazard analysis showed reduction in hazards for all events (A: RT after progression; B: no RT after progression; C: elective RT) among children with ependymoma. For event A, a higher cumulative incidence was reported for ependymoma. Although Gray's test failed to detect any difference (p = 0.331) between histologic subtypes, the log-rank test suggested marginal evidence (p = 0.057). Similarly, for event C, the log-rank test found stronger evidence of reduction in hazard among those with ependymoma (p = 0.005) as compared with Gray's test (p = 0.086). Conclusions: To evaluate treatment differences, failing to account for competing risks using appropriate methodology may lead to incorrect interpretations.

  5. Competent psychopharmacology.

    PubMed

    Gardner, David M

    2014-08-01

    There is little doubt that undergraduate and post-graduate training of physicians, pharmacists, and nurses is insufficient to prepare them to use psychotropics safely and effectively, especially in the context of their expanded off-label uses. Therefore, the development of competencies in psychotropic prescribing needs to be approached as a long-term, practice-based learning commitment. Proposed are the abilities and knowledge components necessary for safe and effective use of psychotropics. Typical challenges in prescribing for chronic and recurrent illnesses include highly variable responses and tolerability, drug interactions, and adverse effects that can be serious, irreversible, and even fatal. Prescribing psychotropics is further complicated by negative public and professional reports and growing patient concerns about the quality of care, and questions about the efficacy, safety, and addictive risks of psychotropics. Increased efforts are needed to enhance clinical training and knowledge in psychopharmacology among trainees and practising clinicians, with more comprehensive and sustained attention to the assessment of individual patients, and greater reliance on patient education and collaboration. Improved competence in psychotropic prescribing should lead to more informed, thoughtful, and better-targeted applications as one component of more comprehensive clinical care.

  6. Competent Psychopharmacology

    PubMed Central

    Gardner, David M

    2014-01-01

    There is little doubt that undergraduate and post-graduate training of physicians, pharmacists, and nurses is insufficient to prepare them to use psychotropics safely and effectively, especially in the context of their expanded off-label uses. Therefore, the development of competencies in psychotropic prescribing needs to be approached as a long-term, practice-based learning commitment. Proposed are the abilities and knowledge components necessary for safe and effective use of psychotropics. Typical challenges in prescribing for chronic and recurrent illnesses include highly variable responses and tolerability, drug interactions, and adverse effects that can be serious, irreversible, and even fatal. Prescribing psychotropics is further complicated by negative public and professional reports and growing patient concerns about the quality of care, and questions about the efficacy, safety, and addictive risks of psychotropics. Increased efforts are needed to enhance clinical training and knowledge in psychopharmacology among trainees and practising clinicians, with more comprehensive and sustained attention to the assessment of individual patients, and greater reliance on patient education and collaboration. Improved competence in psychotropic prescribing should lead to more informed, thoughtful, and better-targeted applications as one component of more comprehensive clinical care. PMID:25161064

  7. A general framework for parametric survival analysis.

    PubMed

    Crowther, Michael J; Lambert, Paul C

    2014-12-30

    Parametric survival models are being increasingly used as an alternative to the Cox model in biomedical research. Through direct modelling of the baseline hazard function, we can gain greater understanding of the risk profile of patients over time, obtaining absolute measures of risk. Commonly used parametric survival models, such as the Weibull, make restrictive assumptions of the baseline hazard function, such as monotonicity, which is often violated in clinical datasets. In this article, we extend the general framework of parametric survival models proposed by Crowther and Lambert (Journal of Statistical Software 53:12, 2013), to incorporate relative survival, and robust and cluster robust standard errors. We describe the general framework through three applications to clinical datasets, in particular, illustrating the use of restricted cubic splines, modelled on the log hazard scale, to provide a highly flexible survival modelling framework. Through the use of restricted cubic splines, we can derive the cumulative hazard function analytically beyond the boundary knots, resulting in a combined analytic/numerical approach, which substantially improves the estimation process compared with only using numerical integration. User-friendly Stata software is provided, which significantly extends parametric survival models available in standard software. Copyright © 2014 John Wiley & Sons, Ltd.

  8. Chalcogenide optical parametric oscillator.

    PubMed

    Ahmad, Raja; Rochette, Martin

    2012-04-23

    We demonstrate the first optical parametric oscillator (OPO) based on chalcogenide glass. The parametric gain medium is an As(2)Se(3) chalcogenide microwire coated with a layer of polymer. The doubly-resonant OPO oscillates simultaneously at a Stokes and an anti Stokes wavelength shift of >50 nm from the pump wavelength that lies at λ(P) = 1,552 nm. The oscillator has a peak power threshold of 21.6 dBm and a conversion efficiency of >19%. This OPO experiment provides an additional application of the chalcogenide microwire technology; and considering the transparency of As(2)Se(3) glass extending far in the mid-infrared (mid-IR) wavelengths, the device holds promise for realizing mid-IR OPOs utilizing existing optical sources in the telecommunications wavelength region.

  9. Parametric Explosion Spectral Model

    SciTech Connect

    Ford, S R; Walter, W R

    2012-01-19

    Small underground nuclear explosions need to be confidently detected, identified, and characterized in regions of the world where they have never before occurred. We develop a parametric model of the nuclear explosion seismic source spectrum derived from regional phases that is compatible with earthquake-based geometrical spreading and attenuation. Earthquake spectra are fit with a generalized version of the Brune spectrum, which is a three-parameter model that describes the long-period level, corner-frequency, and spectral slope at high-frequencies. Explosion spectra can be fit with similar spectral models whose parameters are then correlated with near-source geology and containment conditions. We observe a correlation of high gas-porosity (low-strength) with increased spectral slope. The relationship between the parametric equations and the geologic and containment conditions will assist in our physical understanding of the nuclear explosion source.

  10. Parametric surface denoising

    NASA Astrophysics Data System (ADS)

    Kakadiaris, Ioannis A.; Konstantinidis, Ioannis; Papadakis, Manos; Ding, Wei; Shen, Lixin

    2005-08-01

    Three dimensional (3D) surfaces can be sampled parametrically in the form of range image data. Smoothing/denoising of such raw data is usually accomplished by adapting techniques developed for intensity image processing, since both range and intensity images comprise parametrically sampled geometry and appearance measurements, respectively. We present a transform-based algorithm for surface denoising, motivated by our previous work on intensity image denoising, which utilizes a non-separable Parseval frame and an ensemble thresholding scheme. The frame is constructed from separable (tensor) products of a piecewise linear spline tight frame and incorporates the weighted average operator and the Sobel operators in directions that are integer multiples of 45°. We compare the performance of this algorithm with other transform-based methods from the recent literature. Our results indicate that such transform methods are suited to the task of smoothing range images.

  11. Access to Heart Transplantation: A Proper Analysis of the Competing Risks of Death and Transplantation Is Required to Optimize Graft Allocation.

    PubMed

    Cantrelle, Christelle; Legeai, Camille; Latouche, Aurélien; Tuppin, Philippe; Jasseron, Carine; Sebbag, Laurent; Bastien, Olivier; Dorent, Richard

    2017-08-01

    Heart allocation systems are usually urgency-based, offering grafts to candidates at high risk of waitlist mortality. In the context of a revision of the heart allocation rules, we determined observed predictors of 1-year waitlist mortality in France, considering the competing risk of transplantation, to determine which candidate subgroups are favored or disadvantaged by the current allocation system. Patients registered on the French heart waitlist between 2010 and 2013 were included. Cox cause-specific hazards and Fine and Gray subdistribution hazards were used to determine candidate characteristics associated with waitlist mortality and access to transplantation. Of the 2053 candidates, 7 variables were associated with 1-year waitlist mortality by the Fine and Gray method including 4 candidate characteristics related to heart failure severity (hospitalization at listing, serum natriuretic peptide level, systolic pulmonary artery pressure, and glomerular filtration rate) and 3 characteristics not associated with heart failure severity but with lower access to transplantation (blood type, age, and body mass index). Observed waitlist mortality for candidates on mechanical circulatory support was like that of others. The heart allocation system strongly modifies the risk of pretransplant mortality related to heart failure severity. An in-depth competing risk analysis is therefore a more appropriate method to evaluate graft allocation systems. This knowledge should help to prioritize candidates in the context of a limited donor pool.

  12. The effect of duration of follow-up and presence of competing risk on lifespan-gain from implantable cardioverter defibrillator therapy: who benefits the most?

    PubMed

    Raphael, Claire E; Finegold, Judith A; Barron, Anthony J; Whinnett, Zachary I; Mayet, Jamil; Linde, Cecilia; Cleland, John G F; Levy, Wayne C; Francis, Darrel P

    2015-07-07

    In at-risk patients with left ventricular dysfunction, implantable cardioverter defibrillators (ICDs) prolong life. Implantable cardioverter defibrillators are increasingly implanted for primary prevention and therefore into lower risk patients. Trial data have demonstrated the benefit of these devices but does not provide an estimate of potential lifespan-gain over longer time periods, e.g. a patient's lifespan. Using data from landmark ICD trials, lifespan-gain was plotted against baseline annual mortality in the individual trials. Lifespan-gain was then extrapolated to a time-horizon of >20 years while adjusting for increasing 'competing' risk from ageing and non-sudden cardiac death (pump failure). At 3 years, directly observed lifespan-gain was strongly dependent on baseline event rate (r = 0.94, P < 0.001). However, projecting beyond the duration of the trial, lifespan-gain increases rapidly and non-linearly with time. At 3 years, it averages 1.7 months, but by 10 years up to 9-fold more. Lifespan-gain over time horizons >20 years were greatest in lower risk patients (∼5 life-years for 5% baseline mortality, ∼2 life-years for 15% baseline mortality). Increased competing risks significantly reduce lifespan-gain from ICD implantation. While high-risk patients may show the greatest short-term gain, the dramatic growth of lifespan-gain over time means that it is the lower risk patients, e.g. primary prevention ICD implantation, who gain the most life-years over their lifetime. Benefit is underestimated when only trial data are assessed as trials can only maintain randomization over limited periods. Lifespan-gain may be further increased through advances in ICD device programming. Published on behalf of the European Society of Cardiology. All rights reserved. © The Author 2015. For permissions please email: journals.permissions@oup.com.

  13. Linking the Prevention of Problem Behaviors and Positive Youth Development: Core Competencies for Positive Youth Development and Risk Prevention

    ERIC Educational Resources Information Center

    Guerra, Nancy G.; Bradshaw, Catherine P.

    2008-01-01

    In this chapter, we present a brief review of the developmental literature linking healthy adjustment to five core competencies: (1) positive sense of self, (2) self-control, (3) decision-making skills, (4) a moral system of belief, and (5) prosocial connectedness. A central premise of this chapter and the rest of the volume is that promoting…

  14. Linking the Prevention of Problem Behaviors and Positive Youth Development: Core Competencies for Positive Youth Development and Risk Prevention

    ERIC Educational Resources Information Center

    Guerra, Nancy G.; Bradshaw, Catherine P.

    2008-01-01

    In this chapter, we present a brief review of the developmental literature linking healthy adjustment to five core competencies: (1) positive sense of self, (2) self-control, (3) decision-making skills, (4) a moral system of belief, and (5) prosocial connectedness. A central premise of this chapter and the rest of the volume is that promoting…

  15. Typical Classroom Experiences in First Grade: The Role of Classroom Climate and Functional Risk in the Development of Social Competencies

    ERIC Educational Resources Information Center

    Wilson, H. Kent; Pianta, Robert C.; Stuhlman, Megan

    2007-01-01

    In this study we examined the relation between children's social competence and their first-grade classroom environment. Drawing from data from the NICHD Study of Early Child Care and Youth Development, we used cluster analysis to identify 4 types of typical classrooms based on observed classroom emotional and instructional supports. The 4 types…

  16. Sex Offender Situational Competency Test (SOSCT) Pretreatment and Posttreatment Effects for Inpatient Sex Offenders in Hypothetical High-Risk Situations

    ERIC Educational Resources Information Center

    Reddon, John R.; Takacs, Shelly; Hogan, Stephen

    2013-01-01

    The purpose of the study was to evaluate relapse prevention skill acquisition within the context of a comprehensive treatment program involving group psychotherapy, relapse prevention programming, and other essential psychoeducational components. The Sex Offender Situational Competency Test (SOSCT) was administered pretreatment and posttreatment…

  17. Sex Offender Situational Competency Test (SOSCT) Pretreatment and Posttreatment Effects for Inpatient Sex Offenders in Hypothetical High-Risk Situations

    ERIC Educational Resources Information Center

    Reddon, John R.; Takacs, Shelly; Hogan, Stephen

    2013-01-01

    The purpose of the study was to evaluate relapse prevention skill acquisition within the context of a comprehensive treatment program involving group psychotherapy, relapse prevention programming, and other essential psychoeducational components. The Sex Offender Situational Competency Test (SOSCT) was administered pretreatment and posttreatment…

  18. Professional Development for ECEC Practitioners with Responsibilities for Children at Risk: Which Competences and In-Service Training Are Needed?

    ERIC Educational Resources Information Center

    Peeters, Jan; Sharmahd, Nima

    2014-01-01

    There is growing evidence among researchers and international organisations that quality of Early Childhood Education and Care (ECEC), and ultimately the outcomes for children and families--especially disadvantaged ones--is dependent on well-educated and competent staff, and that a lack of higher pre-service training can be partly compensated by…

  19. Competing risks and the development of adaptive management plans for water resources: Field reconnaissance investigation of risks to fishes and other aquatic biota exposed to endocrine disrupting chemicals (edcs) in lake mead, Nevada USA

    USGS Publications Warehouse

    Linder, G.; Little, E.E.

    2009-01-01

    The analysis and characterization of competing risks for water resources rely on a wide spectrum of tools to evaluate hazards and risks associated with their management. For example, waters of the lower Colorado River stored in reservoirs such as Lake Mead present a wide range of competing risks related to water quantity and water quality. These risks are often interdependent and complicated by competing uses of source waters for sustaining biological resources and for supporting a range of agricultural, municipal, recreational, and industrial uses. USGS is currently conducting a series of interdisciplinary case-studies on water quality of Lake Mead and its source waters. In this case-study we examine selected constituents potentially entering the Lake Mead system, particularly endocrine disrupting chemicals (EDCs). Worldwide, a number of environmental EDCs have been identified that affect reproduction, development, and adaptive behaviors in a wide range of organisms. Many EDCs are minimally affected by current treatment technologies and occur in treated sewage effluents. Several EDCs have been detected in Lake Mead, and several substances have been identified that are of concern because of potential impacts to the aquatic biota, including the sport fishery of Lake Mead and endangered razorback suckers (Xyrauchen texanus) that occur in the Colorado River system. For example, altered biomarkers relevant to reproduction and thyroid function in fishes have been observed and may be predictive of impaired metabolism and development. Few studies, however, have addressed whether such EDC-induced responses observed in the field have an ecologically significant effect on the reproductive success of fishes. To identify potential linkages between EDCs and species of management concern, the risk analysis and characterization in this reconnaissance study focused on effects (and attendant uncertainties) that might be expressed by exposed populations. In addition, risk reduction

  20. Competing Uses of Underground Systems Related to Energy Supply: Applying Single- and Multiphase Simulations for Site Characterization and Risk-Analysis

    NASA Astrophysics Data System (ADS)

    Kissinger, A.; Walter, L.; Darcis, M.; Flemisch, B.; Class, H.

    2012-04-01

    Global climate change, shortage of resources and the resulting turn towards renewable sources of energy lead to a growing demand for the utilization of subsurface systems. Among these competing uses are Carbon Capture and Storage (CCS), geothermal energy, nuclear waste disposal, "renewable" methane or hydrogen storage as well as the ongoing production of fossil resources like oil, gas, and coal. Besides competing among themselves, these technologies may also create conflicts with essential public interests like water supply. For example, the injection of CO2 into the underground causes an increase in pressure reaching far beyond the actual radius of influence of the CO2 plume, potentially leading to large amounts of displaced salt water. Finding suitable sites is a demanding task for several reasons. Natural systems as opposed to technical systems are always characterized by heterogeneity. Therefore, parameter uncertainty impedes reliable predictions towards capacity and safety of a site. State of the art numerical simulations combined with stochastic approaches need to be used to obtain a more reliable assessment of the involved risks and the radii of influence of the different processes. These simulations may include the modeling of single- and multiphase non-isothermal flow, geo-chemical and geo-mechanical processes in order to describe all relevant physical processes adequately. Stochastic approaches have the aim to estimate a bandwidth of the key output parameters based on uncertain input parameters. Risks for these different underground uses can then be made comparable with each other. Along with the importance and the urgency of the competing processes this may lead to a more profound basis for a decision. Communicating risks to stake holders and a concerned public is crucial for the success of finding a suitable site for CCS (or other subsurface utilization). We present and discuss first steps towards an approach for addressing the issue of competitive

  1. Parametric Trace Slicing

    NASA Technical Reports Server (NTRS)

    Rosu, Grigore (Inventor); Chen, Feng (Inventor); Chen, Guo-fang; Wu, Yamei; Meredith, Patrick O. (Inventor)

    2014-01-01

    A program trace is obtained and events of the program trace are traversed. For each event identified in traversing the program trace, a trace slice of which the identified event is a part is identified based on the parameter instance of the identified event. For each trace slice of which the identified event is a part, the identified event is added to an end of a record of the trace slice. These parametric trace slices can be used in a variety of different manners, such as for monitoring, mining, and predicting.

  2. Multicast Parametric Synchronous Sampling

    DTIC Science & Technology

    2011-09-01

    28, No. 23, pp. 3478-3487 (2010). [7] S. Moro, E. Myslivets, J.R. Windmiller, N. Alic, J.M. Chavez Boggio , S. Radic “Synthesis of Equalized...Broadband Parametric Gain by Localized Dispersion Mapping” IEEE Photonics Technology Letters, Vol. 20, No. 23, pp. 1971 – 1973 (2008). [8] J.C. Boggio , S...21 No. 10, pp. 612-614 (2009). [9] C.S. Bres, J.M. Chavez- Boggio , N. Alic, S. Radic, “1-to-40 10-Gb/s Channel Multicasting and Amplification in

  3. Optical parametric loop mirror

    NASA Astrophysics Data System (ADS)

    Mori, K.; Morioka, T.; Saruwatari, M.

    1995-06-01

    A novel configuration for four-wave mixing (FWM) is proposed that offers the remarkable feature of inherently separating the FWM wave from the input pump and signal waves and suppressing their background amplified stimulated emission without optical filtering. In the proposed configuration, an optical parametric loop mirror, two counterpropagating FWM waves generated in a Sagnac interferometer interfere with a relative phase difference that is introduced deliberately. FWM frequency-conversion experiments in a polarization-maintaining fiber achieved more than 35 dB of input-wave suppression against the FWM wave.

  4. Greater decision-making competence is associated with greater expected-value sensitivity, but not overall risk taking: an examination of concurrent validity.

    PubMed

    Parker, Andrew M; Weller, Joshua A

    2015-01-01

    Decision-making competence reflects individual differences in the susceptibility to committing decision-making errors, measured using tasks common from behavioral decision research (e.g., framing effects, under/overconfidence, following decision rules). Prior research demonstrates that those with higher decision-making competence report lower incidence of health-risking and antisocial behaviors, but there has been less focus on intermediate processes that may impact real-world decisions, and, in particular, those implicated by normative models. Here we test the associations between measures of youth decision-making competence (Y-DMC) and one such process, the degree to which individuals make choices consistent with maximizing expected value (EV). Using a task involving hypothetical gambles, we find that greater EV sensitivity is associated with greater Y-DMC. Higher Y-DMC scores are associated with (a) choosing risky options when EV favors those options and (b) avoiding risky options when EV favors a certain option. This relationship is stronger for gambles that involved potential losses. The results suggest that Y-DMC captures decision processes consistent with standard normative evaluations of risky decisions.

  5. Progress in optical parametric oscillators

    NASA Technical Reports Server (NTRS)

    Fan, Y. X.; Byer, R. L.

    1984-01-01

    It is pointed out that tunable coherent sources are very useful for many applications, including spectroscopy, chemistry, combustion diagnostics, and remote sensing. Compared with other tunable sources, optical parametric oscillators (OPO) offer the potential advantage of a wide wavelength operating range, which extends from 0.2 micron to 25 microns. The current status of OPO is examined, taking into account mainly advances made during the last decade. Attention is given to early LiNbO3 parametric oscillators, problems which have prevented wide use of parametric oscillators, the demonstration of OPO's using urea and AgGaS2, progress related to picosecond OPO's, a breakthrough in nanosecond parametric oscillators, the first demonstration of a waveguide and fiber parametric amplification and generation, the importance of chalcopyrite crystals, and theoretical work performed with the aim to understand the factors affecting the parametric oscillator performance.

  6. Toward core inter-professional health promotion competencies to address the non-communicable diseases and their risk factors through knowledge translation: curriculum content assessment.

    PubMed

    Dean, Elizabeth; Moffat, Marilyn; Skinner, Margot; Dornelas de Andrade, Armele; Myezwa, Hellen; Söderlund, Anne

    2014-07-14

    To increase the global impact of health promotion related to non-communicable diseases, health professionals need evidence-based core competencies in health assessment and lifestyle behavior change. Assessment of health promotion curricula by health professional programs is a first step. Such program assessment is a means of 1. demonstrating collective commitment across health professionals to prevent non-communicable diseases; 2. addressing the knowledge translation gap between what is known about non-communicable diseases and their risk factors consistent with 'best' practice; and, 3. establishing core health-based competencies in the entry-level curricula of established health professions. Consistent with the World Health Organization's definition of health (i.e., physical, emotional and social wellbeing) and the Ottawa Charter, health promotion competencies are those that support health rather than reduce signs and symptoms primarily. A process algorithm to guide the implementation of health promotion competencies by health professionals is described. The algorithm outlines steps from the initial assessment of a patient's/client's health and the indications for health behavior change, to the determination of whether that health professional assumes primary responsibility for implementing health behavior change interventions or refers the patient/client to others.An evidence-based template for assessment of the health promotion curriculum content of health professional education programs is outlined. It includes clinically-relevant behavior change theory; health assessment/examination tools; and health behavior change strategies/interventions that can be readily integrated into health professionals' practices. Assessment of the curricula in health professional education programs with respect to health promotion competencies is a compelling and potentially cost-effective initial means of preventing and reversing non-communicable diseases. Learning evidence

  7. Toward core inter-professional health promotion competencies to address the non-communicable diseases and their risk factors through knowledge translation: Curriculum content assessment

    PubMed Central

    2014-01-01

    Background To increase the global impact of health promotion related to non-communicable diseases, health professionals need evidence-based core competencies in health assessment and lifestyle behavior change. Assessment of health promotion curricula by health professional programs is a first step. Such program assessment is a means of 1. demonstrating collective commitment across health professionals to prevent non-communicable diseases; 2. addressing the knowledge translation gap between what is known about non-communicable diseases and their risk factors consistent with ‘best’ practice; and, 3. establishing core health-based competencies in the entry-level curricula of established health professions. Discussion Consistent with the World Health Organization’s definition of health (i.e., physical, emotional and social wellbeing) and the Ottawa Charter, health promotion competencies are those that support health rather than reduce signs and symptoms primarily. A process algorithm to guide the implementation of health promotion competencies by health professionals is described. The algorithm outlines steps from the initial assessment of a patient’s/client’s health and the indications for health behavior change, to the determination of whether that health professional assumes primary responsibility for implementing health behavior change interventions or refers the patient/client to others. An evidence-based template for assessment of the health promotion curriculum content of health professional education programs is outlined. It includes clinically-relevant behavior change theory; health assessment/examination tools; and health behavior change strategies/interventions that can be readily integrated into health professionals’ practices. Summary Assessment of the curricula in health professional education programs with respect to health promotion competencies is a compelling and potentially cost-effective initial means of preventing and reversing non

  8. Combining parametric, semi-parametric, and non-parametric survival models with stacked survival models.

    PubMed

    Wey, Andrew; Connett, John; Rudser, Kyle

    2015-07-01

    For estimating conditional survival functions, non-parametric estimators can be preferred to parametric and semi-parametric estimators due to relaxed assumptions that enable robust estimation. Yet, even when misspecified, parametric and semi-parametric estimators can possess better operating characteristics in small sample sizes due to smaller variance than non-parametric estimators. Fundamentally, this is a bias-variance trade-off situation in that the sample size is not large enough to take advantage of the low bias of non-parametric estimation. Stacked survival models estimate an optimally weighted combination of models that can span parametric, semi-parametric, and non-parametric models by minimizing prediction error. An extensive simulation study demonstrates that stacked survival models consistently perform well across a wide range of scenarios by adaptively balancing the strengths and weaknesses of individual candidate survival models. In addition, stacked survival models perform as well as or better than the model selected through cross-validation. Finally, stacked survival models are applied to a well-known German breast cancer study.

  9. The risks for adolescents of negatively biased self-evaluations of social competence: the mediating role of social support.

    PubMed

    Bédard, Karine; Bouffard, Thérèse; Pansu, Pascal

    2014-08-01

    This study conducted among 544 adolescents (M = 15.1 years, SD = .82) examined whether perceived social support from parents and peers mediated the relationship between biased self-evaluations of social competence and internalizing problems. The results showed negative links between bias in self-evaluation and depressive symptoms, social anxiety and social avoidance. Bias in self-evaluation of social competence was more strongly related to perceived peer support than perceived parental support. Gender differences were observed in the mediating role of social support. Among boys, parental support was a partial mediator only of the link between bias in self-evaluation and depressive symptoms. While perceived peer support was a partial mediator of the links between bias in self-evaluation and depressive symptoms, social anxiety and social avoidance in girls, this was the case only for social avoidance in boys. These findings suggest that girls may show vulnerability to peer emotional support at an earlier age than boys.

  10. Enhancing Key Competencies of Health Professionals in the Assessment and Care of Adults at Risk of Suicide Through Education and Technology.

    PubMed

    Ryan, Kathryn; Tindall, Claudia; Strudwick, Gillian

    This article describes efforts undertaken to improve the clinical competencies of health professionals in the area of suicide risk assessment, documentation, and care planning. Best practices that fit the mental health and addictions setting were identified from the Registered Nurses' Association of Ontario Best Practice Guideline on Assessment and Care of Adults at Risk for Suicidal Ideation and Behaviour. A variety of methods were used to implement the guidelines at the Centre for Addiction and Mental Health in Toronto, Ontario, Canada. These included 3 in-person educational modules, an e-learning module, and the creation of an electronic health record suicide risk assessment documentation form. Results showed that interprofessional team members improved their suicide awareness and increased their confidence and knowledge in suicide risk assessment and the identification of interventions for clients at risk. Organizational level performance and quality improvement activities after implementation of the education and the electronic suicide risk assessment documentation form are being implemented through a collaboration between performance improvement, clinical education and informatics, and professional practice. The success of an interprofessional educational program of this nature is dependent on the collaboration of a number of stakeholders from a variety of areas of the organization.

  11. On the Importance of Accounting for Competing Risks in Pediatric Brain Cancer: II. Regression Modeling and Sample Size

    SciTech Connect

    Tai, Bee-Choo; Grundy, Richard; Machin, David

    2011-03-15

    Purpose: To accurately model the cumulative need for radiotherapy in trials designed to delay or avoid irradiation among children with malignant brain tumor, it is crucial to account for competing events and evaluate how each contributes to the timing of irradiation. An appropriate choice of statistical model is also important for adequate determination of sample size. Methods and Materials: We describe the statistical modeling of competing events (A, radiotherapy after progression; B, no radiotherapy after progression; and C, elective radiotherapy) using proportional cause-specific and subdistribution hazard functions. The procedures of sample size estimation based on each method are outlined. These are illustrated by use of data comparing children with ependymoma and other malignant brain tumors. The results from these two approaches are compared. Results: The cause-specific hazard analysis showed a reduction in hazards among infants with ependymoma for all event types, including Event A (adjusted cause-specific hazard ratio, 0.76; 95% confidence interval, 0.45-1.28). Conversely, the subdistribution hazard analysis suggested an increase in hazard for Event A (adjusted subdistribution hazard ratio, 1.35; 95% confidence interval, 0.80-2.30), but the reduction in hazards for Events B and C remained. Analysis based on subdistribution hazard requires a larger sample size than the cause-specific hazard approach. Conclusions: Notable differences in effect estimates and anticipated sample size were observed between methods when the main event showed a beneficial effect whereas the competing events showed an adverse effect on the cumulative incidence. The subdistribution hazard is the most appropriate for modeling treatment when its effects on both the main and competing events are of interest.

  12. On the importance of accounting for competing risks in pediatric brain cancer: II. Regression modeling and sample size.

    PubMed

    Tai, Bee-Choo; Grundy, Richard; Machin, David

    2011-03-15

    To accurately model the cumulative need for radiotherapy in trials designed to delay or avoid irradiation among children with malignant brain tumor, it is crucial to account for competing events and evaluate how each contributes to the timing of irradiation. An appropriate choice of statistical model is also important for adequate determination of sample size. We describe the statistical modeling of competing events (A, radiotherapy after progression; B, no radiotherapy after progression; and C, elective radiotherapy) using proportional cause-specific and subdistribution hazard functions. The procedures of sample size estimation based on each method are outlined. These are illustrated by use of data comparing children with ependymoma and other malignant brain tumors. The results from these two approaches are compared. The cause-specific hazard analysis showed a reduction in hazards among infants with ependymoma for all event types, including Event A (adjusted cause-specific hazard ratio, 0.76; 95% confidence interval, 0.45-1.28). Conversely, the subdistribution hazard analysis suggested an increase in hazard for Event A (adjusted subdistribution hazard ratio, 1.35; 95% confidence interval, 0.80-2.30), but the reduction in hazards for Events B and C remained. Analysis based on subdistribution hazard requires a larger sample size than the cause-specific hazard approach. Notable differences in effect estimates and anticipated sample size were observed between methods when the main event showed a beneficial effect whereas the competing events showed an adverse effect on the cumulative incidence. The subdistribution hazard is the most appropriate for modeling treatment when its effects on both the main and competing events are of interest. Copyright © 2011 Elsevier Inc. All rights reserved.

  13. Monolithic optical parametric oscillators

    NASA Astrophysics Data System (ADS)

    Breunig, Ingo; Beckmann, Tobias; Buse, Karsten

    2012-02-01

    Stability and footprint of optical parametric oscillators (OPOs) strongly depend on the cavity used. Monolithic OPOs tend to be most stable and compact since they do not require external mirrors that have to be aligned. The most straightforward way to get rid of the mirrors is to coat the end faces of the nonlinear crystal. Whispering gallery resonators (WGRs) are a more advanced solution since they provide ultra-high reflectivity over a wide spectral range without any coating. Furthermore, they can be fabricated out of nonlinear-optical materials like lithium niobate. Thus, they are ideally suited to serve as a monolithic OPO cavity. We present the experimental realization of optical parametric oscillators based on whispering gallery resonators. Pumped at 1 μm wavelength, they generate signal and idler fields tunable between 1.8 and 2.5 μm wavelength. We explore different schemes, how to phase match the nonlinear interaction in a WGR. In particular, we show improvements in the fabrication of quasi-phase-matching structures. They enable great flexibility for the tuning and for the choice of the pump laser.

  14. A probabilistic strategy for parametric catastrophe insurance

    NASA Astrophysics Data System (ADS)

    Figueiredo, Rui; Martina, Mario; Stephenson, David; Youngman, Benjamin

    2017-04-01

    Economic losses due to natural hazards have shown an upward trend since 1980, which is expected to continue. Recent years have seen a growing worldwide commitment towards the reduction of disaster losses. This requires effective management of disaster risk at all levels, a part of which involves reducing financial vulnerability to disasters ex-ante, ensuring that necessary resources will be available following such events. One way to achieve this is through risk transfer instruments. These can be based on different types of triggers, which determine the conditions under which payouts are made after an event. This study focuses on parametric triggers, where payouts are determined by the occurrence of an event exceeding specified physical parameters at a given location, or at multiple locations, or over a region. This type of product offers a number of important advantages, and its adoption is increasing. The main drawback of parametric triggers is their susceptibility to basis risk, which arises when there is a mismatch between triggered payouts and the occurrence of loss events. This is unavoidable in said programmes, as their calibration is based on models containing a number of different sources of uncertainty. Thus, a deterministic definition of the loss event triggering parameters appears flawed. However, often for simplicity, this is the way in which most parametric models tend to be developed. This study therefore presents an innovative probabilistic strategy for parametric catastrophe insurance. It is advantageous as it recognizes uncertainties and minimizes basis risk while maintaining a simple and transparent procedure. A logistic regression model is constructed here to represent the occurrence of loss events based on certain loss index variables, obtained through the transformation of input environmental variables. Flood-related losses due to rainfall are studied. The resulting model is able, for any given day, to issue probabilities of occurrence of loss

  15. Quantifying and comparing dynamic predictive accuracy of joint models for longitudinal marker and time-to-event in presence of censoring and competing risks.

    PubMed

    Blanche, Paul; Proust-Lima, Cécile; Loubère, Lucie; Berr, Claudine; Dartigues, Jean-François; Jacqmin-Gadda, Hélène

    2015-03-01

    Thanks to the growing interest in personalized medicine, joint modeling of longitudinal marker and time-to-event data has recently started to be used to derive dynamic individual risk predictions. Individual predictions are called dynamic because they are updated when information on the subject's health profile grows with time. We focus in this work on statistical methods for quantifying and comparing dynamic predictive accuracy of this kind of prognostic models, accounting for right censoring and possibly competing events. Dynamic area under the ROC curve (AUC) and Brier Score (BS) are used to quantify predictive accuracy. Nonparametric inverse probability of censoring weighting is used to estimate dynamic curves of AUC and BS as functions of the time at which predictions are made. Asymptotic results are established and both pointwise confidence intervals and simultaneous confidence bands are derived. Tests are also proposed to compare the dynamic prediction accuracy curves of two prognostic models. The finite sample behavior of the inference procedures is assessed via simulations. We apply the proposed methodology to compare various prediction models using repeated measures of two psychometric tests to predict dementia in the elderly, accounting for the competing risk of death. Models are estimated on the French Paquid cohort and predictive accuracies are evaluated and compared on the French Three-City cohort. © 2014, The International Biometric Society.

  16. Bayesian joint modeling of bivariate longitudinal and competing risks data: An application to study patient-ventilator asynchronies in critical care patients.

    PubMed

    Rué, Montserrat; Andrinopoulou, Eleni-Rosalina; Alvares, Danilo; Armero, Carmen; Forte, Anabel; Blanch, Lluis

    2017-08-11

    Mechanical ventilation is a common procedure of life support in intensive care. Patient-ventilator asynchronies (PVAs) occur when the timing of the ventilator cycle is not simultaneous with the timing of the patient respiratory cycle. The association between severity markers and the events death or alive discharge has been acknowledged before, however, little is known about the addition of PVAs data to the analyses. We used an index of asynchronies (AI) to measure PVAs and the SOFA (sequential organ failure assessment) score to assess overall severity. To investigate the added value of including the AI, we propose a Bayesian joint model of bivariate longitudinal and competing risks data. The longitudinal process includes a mixed effects model for the SOFA score and a mixed effects beta regression model for the AI. The survival process is defined in terms of a cause-specific hazards model for the competing risks death or alive discharge. Our model indicates that the SOFA score is strongly related to vital status. PVAs are positively associated with alive discharge but there is not enough evidence that PVAs provide a more accurate indication of death prognosis than the SOFA score alone. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Avoiding the parametric roll

    NASA Astrophysics Data System (ADS)

    Acomi, Nicoleta; Ancuţa, Cristian; Andrei, Cristian; Boştinǎ, Alina; Boştinǎ, Aurel

    2016-12-01

    Ships are mainly built to sail and transport cargo at sea. Environmental conditions and state of the sea are communicated to vessels through periodic weather forecasts. Despite officers being aware of the sea state, their sea time experience is a decisive factor when the vessel encounters severe environmental conditions. Another important factor is the loading condition of the vessel, which triggers different behaviour in similar marine environmental conditions. This paper aims to analyse the behaviour of a port container vessel in severe environmental conditions and to estimate the potential conditions of parametric roll resonance. Octopus software simulation is employed to simulate vessel motions under certain conditions of the sea, with possibility to analyse the behaviour of ships and the impact of high waves on ships due to specific wave encounter situations. The study should be regarded as a supporting tool during the decision making process.

  18. Parametric light generation.

    PubMed

    Ebrahimzadeh, M

    2003-12-15

    Since its invention more than 40 years ago, the laser has become an indispensable optical tool, capable of transforming light from its naturally incoherent state to a highly coherent state in space and time. Yet, due to fundamental limitations, operation of the laser remains confined to restricted spectral and temporal regions. Nonlinear optics can overcome this limitation by allowing access to new spectral and temporal regimes through the exploitation of suitable dielectric materials in combination with the laser. In particular, optical parametric oscillators are versatile coherent light sources with unique flexibility that can provide optical radiation across an entire spectral range from the ultraviolet to the far-infrared and over all temporal scales from continuous wave to the ultrafast femtosecond domain.

  19. Parametric lattice Boltzmann method

    NASA Astrophysics Data System (ADS)

    Shim, Jae Wan

    2017-06-01

    The discretized equilibrium distributions of the lattice Boltzmann method are presented by using the coefficients of the Lagrange interpolating polynomials that pass through the points related to discrete velocities and using moments of the Maxwell-Boltzmann distribution. The ranges of flow velocity and temperature providing positive valued distributions vary with regulating discrete velocities as parameters. New isothermal and thermal compressible models are proposed for flows of the level of the isothermal and thermal compressible Navier-Stokes equations. Thermal compressible shock tube flows are simulated by only five on-lattice discrete velocities. Two-dimensional isothermal and thermal vortices provoked by the Kelvin-Helmholtz instability are simulated by the parametric models.

  20. Nanoscale electromechanical parametric amplifier

    SciTech Connect

    Aleman, Benjamin Jose; Zettl, Alexander

    2016-09-20

    This disclosure provides systems, methods, and apparatus related to a parametric amplifier. In one aspect, a device includes an electron source electrode, a counter electrode, and a pumping electrode. The electron source electrode may include a conductive base and a flexible conductor. The flexible conductor may have a first end and a second end, with the second end of the flexible conductor being coupled to the conductive base. A cross-sectional dimension of the flexible conductor may be less than about 100 nanometers. The counter electrode may be disposed proximate the first end of the flexible conductor and spaced a first distance from the first end of the flexible conductor. The pumping electrode may be disposed proximate a length of the flexible conductor and spaced a second distance from the flexible conductor.

  1. Mechanical Parametric Oscillations and Waves

    ERIC Educational Resources Information Center

    Dittrich, William; Minkin, Leonid; Shapovalov, Alexander S.

    2013-01-01

    Usually parametric oscillations are not the topic of general physics courses. Probably it is because the mathematical theory of this phenomenon is relatively complicated, and until quite recently laboratory experiments for students were difficult to implement. However parametric oscillations are good illustrations of the laws of physics and can be…

  2. Mechanical Parametric Oscillations and Waves

    ERIC Educational Resources Information Center

    Dittrich, William; Minkin, Leonid; Shapovalov, Alexander S.

    2013-01-01

    Usually parametric oscillations are not the topic of general physics courses. Probably it is because the mathematical theory of this phenomenon is relatively complicated, and until quite recently laboratory experiments for students were difficult to implement. However parametric oscillations are good illustrations of the laws of physics and can be…

  3. Parametric binary dissection

    NASA Technical Reports Server (NTRS)

    Bokhari, Shahid H.; Crockett, Thomas W.; Nicol, David M.

    1993-01-01

    Binary dissection is widely used to partition non-uniform domains over parallel computers. This algorithm does not consider the perimeter, surface area, or aspect ratio of the regions being generated and can yield decompositions that have poor communication to computation ratio. Parametric Binary Dissection (PBD) is a new algorithm in which each cut is chosen to minimize load + lambda x(shape). In a 2 (or 3) dimensional problem, load is the amount of computation to be performed in a subregion and shape could refer to the perimeter (respectively surface) of that subregion. Shape is a measure of communication overhead and the parameter permits us to trade off load imbalance against communication overhead. When A is zero, the algorithm reduces to plain binary dissection. This algorithm can be used to partition graphs embedded in 2 or 3-d. Load is the number of nodes in a subregion, shape the number of edges that leave that subregion, and lambda the ratio of time to communicate over an edge to the time to compute at a node. An algorithm is presented that finds the depth d parametric dissection of an embedded graph with n vertices and e edges in O(max(n log n, de)) time, which is an improvement over the O(dn log n) time of plain binary dissection. Parallel versions of this algorithm are also presented; the best of these requires O((n/p) log(sup 3)p) time on a p processor hypercube, assuming graphs of bounded degree. How PBD is applied to 3-d unstructured meshes and yields partitions that are better than those obtained by plain dissection is described. Its application to the color image quantization problem is also discussed, in which samples in a high-resolution color space are mapped onto a lower resolution space in a way that minimizes the color error.

  4. Adjudicative Competence

    PubMed Central

    Dawes, Sharron E.; Palmer, Barton W.; Jeste, Dilip V.

    2008-01-01

    Purpose of review Although the basic standards of adjudicative competence were specified by the U.S. Supreme Court in 1960, there remain a number of complex conceptual and practical issues in interpreting and applying these standards. In this report we provide a brief overview regarding the general concept of adjudicative competence and its assessment, as well as some highlights of recent empirical studies on this topic. Findings Most adjudicative competence assessments are conducted by psychiatrists or psychologists. There are no universal certification requirements, but some states are moving toward required certification of forensic expertise for those conducting such assessments. Recent data indicate inconsistencies in application of the existing standards even among forensic experts, but the recent publication of consensus guidelines may foster improvements in this arena. There are also ongoing efforts to develop and validate structured instruments to aid competency evaluations. Telemedicine-based competency interviews may facilitate evaluation by those with specific expertise for evaluation of complex cases. There is also interest in empirical development of educational methods to enhance adjudicative competence. Summary Adjudicative competence may be difficult to measure accurately, but the assessments and tools available are advancing. More research is needed on methods of enhancing decisional capacity among those with impaired competence. PMID:18650693

  5. Distinct variation in vector competence among nine field populations of Aedes aegypti from a Brazilian dengue-endemic risk city.

    PubMed

    Gonçalves, Caroline M; Melo, Fabrício F; Bezerra, Juliana M T; Chaves, Bárbara A; Silva, Breno M; Silva, Luciana D; Pessanha, José E M; Arias, Jorge R; Secundino, Nágila F C; Norris, Douglas E; Pimenta, Paulo F P

    2014-07-11

    In Brazil, dengue epidemics erupt sporadically throughout the country and it is unclear if outbreaks may initiate a sustainable transmission cycle. There are few studies evaluating the ability of Brazilian Aedes aegypti populations to transmit dengue virus (DENV). The aim of this study was to compare DENV susceptibility of field-captured Ae. aegypti populations from nine distinct geographic areas of the city of Belo Horizonte in 2009 and 2011. Infection Rate (IR), Vector Competence (VC) and Disseminated Infection Rate (DIR) were determined. Aedes aegypti eggs from each region were collected and reared separately in an insectary. Adult females were experimentally infected with DENV-2 and the virus was detected by qPCR in body and head samples. Data were analyzed with the Statistical Package for the Social Sciences version 17. IR varied from 40.0% to 82.5% in 2009 and 60.0% to 100.0% in 2011. VC ranged from 25.0% to 77.5% in 2009 and 25.0% to 80.0% in 2011. DIR oscillated from 68.7% to 100.0% in 2009 and 38.4% to 86.8 in 2011. When the results were evaluated by a logistic model using IR as covariate, North, Barreiro, South-Central and Venda Nova showed the strongest association in 2009. In 2011, a similar association was observed for South-Central, Venda Nova, West and Northeast regions. Using VC as covariate, South-Central and Venda Nova showed the most relevant association in 2009. In 2011, South-Central, Venda Nova and Barreiro presented the greatest revelation associations. When DIR data were analyzed by logistic regression models, Pampulha, South-Central, Venda Nova, West, Northeast and East (2009) as well as South-Central, Venda Nova and West (2011) were the districts showing the strongest associations. We conclude that Ae. aegypti populations from Belo Horizonte exhibit wide variation in vector competence to transmit dengue. Therefore, vector control strategies should be adapted to the available data for each region. Further analysis should be conducted to

  6. Dynamic Assessment of Seismic Risk (DASR) by Multi-parametric Observations: Preliminary Results of PRIME experiment within the PRE-EARTHQUAKES EU-FP7 Project

    NASA Astrophysics Data System (ADS)

    Tramutoli, V.; Inan, S.; Jakowski, N.; Pulinets, S. A.; Romanov, A.; Filizzola, C.; Shagimuratov, I.; Pergola, N.; Ouzounov, D. P.; Papadopoulos, G. A.; Parrot, M.; Genzano, N.; Lisi, M.; Alparlsan, E.; Wilken, V.; Tsybukia, K.; Romanov, A.; Paciello, R.; Zakharenkova, I.; Romano, G.

    2012-12-01

    The integration of different observations together with the refinement of data analysis methods, is generally expected to improve our present knowledge of preparatory phases of earthquakes and of their possible precursors. This is also the main goal of PRE-EARTHQUAKES (Processing Russian and European EARTH observations for earthQUAKE precursors Studies) the FP7 Project which, to this aim, committed together, different international expertise and observational capabilities, in the last 2 years. In the learning phase of the project, different parameters (e.g. thermal anomalies, total electron content, radon concentration, etc.), measured from ground and satellite systems and analyzed by using different data analysis approaches, have been studied for selected geographic areas and specific seismic events in the past. Since July 2012 the PRIME (PRE-EARTHQUAKES Real-time Integration and Monitoring Experiment) started attempting to perform, on the base of independent observations collected and integrated in real-time through the PEG (PRE-EARTHQUAKES Geo-portal), a Dynamic Assessment of Seismic Risk (DASR) on selected geographic areas of Europe (Italy-Greece-Turkey) and Asia (Kamchatka, Sakhalin, Japan). In this paper, results so far achieved as well as the potential and opportunities they open for a worldwide Earthquake Observation System (EQuOS) - as a dedicated component of GEOSS (Global Earth Observation System of Systems) - will be presented.

  7. Parametric Timing Analysis

    SciTech Connect

    Vivancos, E; Healy, C; Mueller, F; Whalley, D

    2001-05-09

    Embedded systems often have real-time constraints. Traditional timing analysis statically determines the maximum execution time of a task or a program in a real-time system. These systems typically depend on the worst-case execution time of tasks in order to make static scheduling decisions so that tasks can meet their deadlines. Static determination of worst-case execution times imposes numerous restrictions on real-time programs, which include that the maximum number of iterations of each loop must be known statically. These restrictions can significantly limit the class of programs that would be suitable for a real-time embedded system. This paper describes work-in-progress that uses static timing analysis to aid in making dynamic scheduling decisions. For instance, different algorithms with varying levels of accuracy may be selected based on the algorithm's predicted worst-case execution time and the time allotted for the task. We represent the worst-case execution time of a function or a loop as a formula, where the unknown values affecting the execution time are parameterized. This parametric timing analysis produces formulas that can then be quickly evaluated at run-time so dynamic scheduling decisions can be made with little overhead. Benefits of this work include expanding the class of applications that can be used in a real-time system, improving the accuracy of dynamic scheduling decisions, and more effective utilization of system resources. This paper describes how static timing analysis can be used to aid in making dynamic scheduling decisions. The WCET of a function or a loop is represented as a formula, where the values affecting the execution time are parameterized. Such formulas can then be quickly evaluated at run-time so dynamic scheduling decisions can be made when scheduling a task or choosing algorithms within a task. Benefits of this parametric timing analysis include expanding the class of applications that can be used in a real-time system

  8. Elderly Peritoneal Dialysis Compared with Elderly Hemodialysis Patients and Younger Peritoneal Dialysis Patients: Competing Risk Analysis of a Korean Prospective Cohort Study

    PubMed Central

    Kim, Hyunsuk; An, Jung Nam; Kim, Dong Ki; Kim, Myoung-Hee; Kim, Ho; Kim, Yong-Lim; Park, Ki Soo; Oh, Yun Kyu; Lim, Chun Soo; Kim, Yon Su; Lee, Jung Pyo

    2015-01-01

    The outcomes of peritoneal dialysis (PD) in elderly patients have not been thoroughly investigated. We aimed to investigate the clinical outcomes and risk factors associated with PD in elderly patients. We conducted a prospective observational nationwide adult end-stage renal disease (ESRD) cohort study in Korea from August 2008 to March 2013. Among incident patients (n = 830), patient and technical survival rate, quality of life, and Beck’s Depression Inventory (BDI) scores of elderly PD patients (≥65 years, n = 95) were compared with those of PD patients aged ≤49 years (n = 205) and 50~64 years (n = 192); and elderly hemodialysis (HD) patients (n = 315). The patient death and technical failure were analyzed by cumulative incidence function. Competing risk regressions were used to assess the risk factors for survival. The patient survival rate of elderly PD patients was inferior to that of younger PD patients (P<0.001). However, the technical survival rate was similar (P = 0.097). Compared with elderly HD patients, the patient survival rate did not differ according to dialysis modality (P = 0.987). Elderly PD patients showed significant improvement in the BDI scores, as compared with the PD patients aged ≤49 years (P = 0.003). Low albumin, diabetes and low residual renal function were significant risk factors for the PD patient survival; and peritonitis was a significant risk factor for technical survival. Furthermore, low albumin and hospitalization were significant risk factors of patient survival among the elderly. The overall outcomes were similar between elderly PD and HD patients. PD showed the benefit in BDI and quality of life in the elderly. Additionally, the technical survival rate of elderly PD patients was similar to that of younger PD patients. Taken together, PD may be a comparable modality for elderly ESRD patients. PMID:26121574

  9. Parametric scramjet analysis

    NASA Astrophysics Data System (ADS)

    Choi, Jongseong

    The performance of a hypersonic flight vehicle will depend on existing materials and fuels; this work presents the performance of the ideal scramjet engine for three different combustion chamber materials and three different candidate fuels. Engine performance is explored by parametric cycle analysis for the ideal scramjet as a function of material maximum service temperature and the lower heating value of jet engine fuels. The thermodynamic analysis is based on the Brayton cycle as similarly employed in describing the performance of the ramjet, turbojet, and fanjet ideal engines. The objective of this work is to explore material operating temperatures and fuel possibilities for the combustion chamber of a scramjet propulsion system to show how they relate to scramjet performance and the seven scramjet engine parameters: specific thrust, fuel-to-air ratio, thrust-specific fuel consumption, thermal efficiency, propulsive efficiency, overall efficiency, and thrust flux. The information presented in this work has not been done by others in the scientific literature. This work yields simple algebraic equations for scramjet performance which are similar to that of the ideal ramjet, ideal turbojet and ideal turbofan engines.

  10. Parametric Transformation Analysis

    NASA Technical Reports Server (NTRS)

    Gary, G. Allan

    2003-01-01

    Because twisted coronal features are important proxies for predicting solar eruptive events, and, yet not clearly understood, we present new results to resolve the complex, non-potential magnetic field configurations of active regions. This research uses free-form deformation mathematics to generate the associated coronal magnetic field. We use a parametric representation of the magnetic field lines such that the field lines can be manipulated to match the structure of EUV and SXR coronal loops. The objective is to derive sigmoidal magnetic field solutions which allows the beta greater than 1 regions to be included, aligned and non-aligned electric currents to be calculated, and the Lorentz force to be determined. The advantage of our technique is that the solution is independent of the unknown upper and side boundary conditions, allows non-vanishing magnetic forces, and provides a global magnetic field solution, which contains high- and low-beta regimes and is consistent with all the coronal images of the region. We show that the mathematical description is unique and physical.

  11. Parametric Mass Reliability Study

    NASA Technical Reports Server (NTRS)

    Holt, James P.

    2014-01-01

    The International Space Station (ISS) systems are designed based upon having redundant systems with replaceable orbital replacement units (ORUs). These ORUs are designed to be swapped out fairly quickly, but some are very large, and some are made up of many components. When an ORU fails, it is replaced on orbit with a spare; the failed unit is sometimes returned to Earth to be serviced and re-launched. Such a system is not feasible for a 500+ day long-duration mission beyond low Earth orbit. The components that make up these ORUs have mixed reliabilities. Components that make up the most mass-such as computer housings, pump casings, and the silicon board of PCBs-typically are the most reliable. Meanwhile components that tend to fail the earliest-such as seals or gaskets-typically have a small mass. To better understand the problem, my project is to create a parametric model that relates both the mass of ORUs to reliability, as well as the mass of ORU subcomponents to reliability.

  12. The influence of the perceived consequences of refusing to share injection equipment among injection drug users: Balancing competing risks

    PubMed Central

    Wagner, Karla D.; Lankenau, Stephen E.; Palinkas, Lawrence A.; Richardson, Jean L.; Chou, Chih-Ping; Unger, Jennifer B.

    2011-01-01

    Injection drug users (IDUs) are at risk for HIV and other bloodborne pathogens through receptive syringe sharing (RSS) and receptive paraphernalia sharing (RPS). Research into the influence of the perceived risk of HIV infection on injection risk behavior has yielded mixed findings. One explanation may be that consequences other than HIV infection are considered when IDUs are faced with decisions about whether or not to share equipment. We investigated the perceived consequences of refusing to share injection equipment among 187 IDUs recruited from a large syringe exchange program in Los Angeles, California, assessed their influence on RSS and RPS, and evaluated gender differences. Two sub-scales of perceived consequences were identified: structural/external consequences and social/internal consequences. In multiple linear regression, the perceived social/internal consequences of refusing to share were associated with both RSS and RPS, after controlling for other psychosocial constructs and demographic variables. Few statistically significant gender differences emerged. Assessing the consequences of refusing to share injection equipment may help explain persistent injection risk behavior, and may provide promising targets for comprehensive intervention efforts designed to address both individual and structural risk factors. PMID:21498004

  13. Parametric Equations, Maple, and Tubeplots.

    ERIC Educational Resources Information Center

    Feicht, Louis

    1997-01-01

    Presents an activity that establishes a graphical foundation for parametric equations by using a graphing output form called tubeplots from the computer program Maple. Provides a comprehensive review and exploration of many previously learned topics. (ASK)

  14. Setting priorities for private land conservation in fire-prone landscapes: Are fire risk reduction and biodiversity conservation competing or compatible objectives?

    USGS Publications Warehouse

    Syphard, Alexandra D.; Butsic, Van; Bar-Massada, Avi; Keeley, Jon E.; Tracey, Jeff A.; Fisher, Robert N.

    2016-01-01

    Although wildfire plays an important role in maintaining biodiversity in many ecosystems, fire management to protect human assets is often carried out by different agencies than those tasked for conserving biodiversity. In fact, fire risk reduction and biodiversity conservation are often viewed as competing objectives. Here we explored the role of management through private land conservation and asked whether we could identify private land acquisition strategies that fulfill the mutual objectives of biodiversity conservation and fire risk reduction, or whether the maximization of one objective comes at a detriment to the other. Using a fixed budget and number of homes slated for development, we simulated 20 years of housing growth under alternative conservation selection strategies, and then projected the mean risk of fires destroying structures and the area and configuration of important habitat types in San Diego County, California, USA. We found clear differences in both fire risk projections and biodiversity impacts based on the way conservation lands are prioritized for selection, but these differences were split between two distinct groupings. If no conservation lands were purchased, or if purchases were prioritized based on cost or likelihood of development, both the projected fire risk and biodiversity impacts were much higher than if conservation lands were purchased in areas with high fire hazard or high species richness. Thus, conserving land focused on either of the two objectives resulted in nearly equivalent mutual benefits for both. These benefits not only resulted from preventing development in sensitive areas, but they were also due to the different housing patterns and arrangements that occurred as development was displaced from those areas. Although biodiversity conflicts may still arise using other fire management strategies, this study shows that mutual objectives can be attained through land-use planning in this region. These results likely

  15. Impact of Increasing Age on Cause-Specific Mortality and Morbidity in Patients With Stage I Non-Small-Cell Lung Cancer: A Competing Risks Analysis.

    PubMed

    Eguchi, Takashi; Bains, Sarina; Lee, Ming-Ching; Tan, Kay See; Hristov, Boris; Buitrago, Daniel H; Bains, Manjit S; Downey, Robert J; Huang, James; Isbell, James M; Park, Bernard J; Rusch, Valerie W; Jones, David R; Adusumilli, Prasad S

    2017-01-20

    Purpose To perform competing risks analysis and determine short- and long-term cancer- and noncancer-specific mortality and morbidity in patients who had undergone resection for stage I non-small-cell lung cancer (NSCLC). Patients and Methods Of 5,371 consecutive patients who had undergone curative-intent resection of primary lung cancer at our institution (2000 to 2011), 2,186 with pathologic stage I NSCLC were included in the analysis. All preoperative clinical variables known to affect outcomes were included in the analysis, specifically, Charlson comorbidity index, predicted postoperative (ppo) diffusing capacity of the lung for carbon monoxide, and ppo forced expiratory volume in 1 second. Cause-specific mortality analysis was performed with competing risks analysis. Results Of 2,186 patients, 1,532 (70.1%) were ≥ 65 years of age, including 638 (29.2%) ≥ 75 years of age. In patients < 65, 65 to 74, and ≥ 75 years of age, 5-year lung cancer-specific cumulative incidence of death (CID) was 7.5%, 10.7%, and 13.2%, respectively (overall, 10.4%); noncancer-specific CID was 1.8%, 4.9%, and 9.0%, respectively (overall, 5.3%). In patients ≥ 65 years of age, for up to 2.5 years after resection, noncancer-specific CID was higher than lung cancer-specific CID; the higher noncancer-specific, early-phase mortality was enhanced in patients ≥ 75 years of age than in those 65 to 74 years of age. Multivariable analysis showed that low ppo diffusing capacity of lung for carbon monoxide was an independent predictor of severe morbidity ( P < .001), 1-year mortality ( P < .001), and noncancer-specific mortality ( P < .001), whereas low ppo forced expiratory volume in 1 second was an independent predictor of lung cancer-specific mortality ( P = .002). Conclusion In patients who undergo curative-intent resection of stage I NSCLC, noncancer-specific mortality is a significant competing event, with an increasing impact as patient age increases.

  16. Association of Cervical Cancer Screening with Knowledge of Risk Factors, Access to Health Related Information, Health Profiles, and Health Competence Beliefs among Community-Dwelling Women in Japan

    PubMed

    Oba, Shino; Toyoshima, Masato; Ogata, Hiromitsu

    2017-08-27

    Objective: The aim of this study was to evaluate the past attendance for cervical cancer screening with knowledge of risk factors, access to health-related information, health profiles and health competence beliefs among Japanese women. Methods: Women ages 25, 30, 35, 40, 45, 50, 55, and 60 were contacted cross-sectionally as part of a project for the Japanese Ministry of Health, Labour and Welfare in Nikaho, Akita prefecture Japan between June 2010 and March 2011, and 249 women were analyzed for the current study. The questionnaire asked about past cervical cancer screening. Knowledge of each cervical cancer risk factor was determined on a four-point scale. A barriers to information access scale was utilized to assess the degree of difficulty in accessing health-related information. Health profiles were measured using the EuroQOL EQ-5D. Perceived health competence was measured using a scale (PHCS). The association was evaluated with odds ratios with 95% confidence interval were calculated from a logistic regression analysis after adjustment for age and potential confounders. The trend across the level was also assessed. Results: Women who knew that sexual intercourse at young age was a risk factor were significantly more likely to have participated in cervical cancer screening sometime in their lives (p for trend =0.02). Women who had pain/discomfort and those who had anxiety/depression were significantly more likely to have participated in cervical screening within the past two years (odds ratio [OR]: 2.02, 95% confidence interval [CI]: 1.04–3.94; OR: 2.32, 95% CI: 1.05–5.16, respectively). Women with higher PHCS were significantly more likely to have attended for cervical screened at some point in their lives (p=0.04). Conclusion: This study observed that specific knowledge of cervical cancer risk factors, health profiles and PHCS were associated with the past attendance for cervical cancer screening among women in a community. Further researches are

  17. Prevention for Preschoolers at High Risk for Conduct Problems: Immediate Outcomes on Parenting Practices and Child Social Competence

    ERIC Educational Resources Information Center

    Brotman, Laurie Miller; Gouley, Kathleen Kiely; Chesir-Teran, Daniel; Dennis, Tracy; Klein, Rachel G.; Shrout, Patrick

    2005-01-01

    This study investigated the immediate impact of an 8-month center- and home-based prevention program for preschoolers at high risk for conduct problems. We report immediate program effects on observed and self-rated parenting practices and observed child behavior with peers. Ninety-nine preschool-age siblings of adjudicated youths and their…

  18. Theme: Coping with Competencies.

    ERIC Educational Resources Information Center

    Brown, Daniel; And Others

    1989-01-01

    Consists of five articles on the topic of competencies in vocational agriculture. Topics covered include (1) competency-based instruction, (2) competencies for agricultural recordkeeping, (3) competencies in hydroponics, and (4) competencies in agribusiness. (CH)

  19. Theme: Coping with Competencies.

    ERIC Educational Resources Information Center

    Brown, Daniel; And Others

    1989-01-01

    Consists of five articles on the topic of competencies in vocational agriculture. Topics covered include (1) competency-based instruction, (2) competencies for agricultural recordkeeping, (3) competencies in hydroponics, and (4) competencies in agribusiness. (CH)

  20. Denervated Myocardium Is Preferentially Associated With Sudden Cardiac Arrest in Ischemic Cardiomyopathy: A Pilot Competing Risks Analysis of Cause-Specific Mortality.

    PubMed

    Fallavollita, James A; Dare, Jonathan D; Carter, Randolph L; Baldwa, Sunil; Canty, John M

    2017-08-01

    Previous studies have identified multiple risk factors that are associated with total cardiac mortality. Nevertheless, identifying specific factors that distinguish patients at risk of arrhythmic death versus heart failure could better target patients likely to benefit from implantable cardiac defibrillators, which have no impact on nonsudden cardiac death. We performed a pilot competing risks analysis of the National Institutes of Health-sponsored PAREPET trial (Prediction of Arrhythmic Events with Positron Emission Tomography). Death from cardiac causes was ascertained in subjects with ischemic cardiomyopathy (n=204) eligible for an implantable cardiac defibrillator for the primary prevention of sudden cardiac arrest after baseline clinical evaluation and imaging at enrollment (positron emission tomography and 2-dimensional echo). Mean age was 67±11 years with an ejection fraction of 27±9%, and 90% were men. During 4.1 years of follow-up, there were 33 sudden cardiac arrests (arrhythmic death or implantable cardiac defibrillator discharge for ventricular fibrillation or ventricular tachycardia >240 bpm) and 36 nonsudden cardiac deaths. Sudden cardiac arrest was correlated with a greater volume of denervated myocardium (defect of the positron emission tomography norepinephrine analog (11)C-hydroxyephedrine), lack of angiotensin inhibition therapy, elevated B-type natriuretic peptide, and larger left ventricular end-diastolic volume index. In contrast, nonsudden cardiac death was associated with a higher resting heart rate, older age, elevated creatinine, larger left atrial volume index, and larger left ventricular end-diastolic volume index. Distinct clinical, laboratory, and imaging variables are associated with cause-specific cardiac mortality in primary-prevention candidates with ischemic cardiomyopathy. If prospectively validated, these multivariable associations may help target specific therapies to those at the greatest risk of sudden and nonsudden cardiac

  1. Parametric design using IGRIP

    SciTech Connect

    Baker, C.

    1994-10-01

    The Department of Energy`s (DOE) Hanford site near Richland, Washington is being cleaned up after 50 years of nuclear materials production. One of the most serious problems at the site is the waste stored in single-shell underground storage tanks. There are 149 of these tanks containing the spent fuel residue remaining after the fuel is dissolved in acid and the desired materials (primarily plutonium and uranium) are separated out. The tanks are upright cylinders 75 ft. in diameter with domed tops. They are made of reinforced concrete, have steel liners, and each tank is buried under 7--12 ft. of overburden. The tanks are up to 40-ft. high, and have capacities of 500,000, 750,000, or 1,000,000 gallons of waste. As many as one-third of these tanks are known or suspected to leak. The waste form contained in the tanks varies in consistency from liquid supernatant to peanut-butter-like gels and sludges to hard salt cake (perhaps as hard as low-grade concrete). The current waste retrieval plan is to insert a large long-reach manipulator through a hole cut in the top of the tank, and use a variety of end-effectors to mobilize the waste and remove it from the tank. PNL has, with the assistance of Deneb robotics employees, developed a means of using the IGRIP code to perform parametric design of mechanical systems. This method requires no modifications to the IGRIP code, and all design data are stored in the IGRIP workcell. The method is presented in the context of development of a passive articulated mechanism that is used to deliver down-arm services to a gantry robot. The method is completely general, however, and could be used to design a fully articulated manipulator. Briefly, the method involves using IGCALC expressions to control manipulator joint angles, and IGCALC variables to allow user control of link lengths and offsets. This paper presents the method in detail, with examples drawn from PNL`s experience with the gantry robot service-providing mechanism.

  2. The Dangers of Parametrics

    NASA Technical Reports Server (NTRS)

    Prince, Frank A.

    2017-01-01

    Building a parametric cost model is hard work. The data is noisy and often does not behave like we want it to. We need statistics to give us an indication of the goodness of our models, but; statistics can be manipulated and mislead. On top of all of that, our own very human biases can lead us astray; causing us to see patterns in the noise and draw false conclusions from the data. Yet, it is the data itself that is the foundation for making better cost estimates and cost models. I believe the mistake we often make is we believe that our models are representative of the data; that our models summarize the experiences, the knowledge, and the stories contained in the data. However, it is the opposite that is true. Our models are but imitations of reality. They give us trends, but not truth. The experiences, the knowledge, and the stories that we need in order to make good cost estimates is bound up in the data. You cannot separate good cost estimating from a knowledge of the historical data. One final thought. It is our attempts to make sense out of the randomness that leads us astray. In order to make progress as cost modelers and cost estimators, we must accept that there are real limitations on our ability to model the past and predict the future. I do not believe we should throw up our hands and say this is the best we can do. Rather, to see real improvement we must first recognize these limitations, avoid the easy but misleading solutions, and seek to find ways to better model the world we live in. I don't have any simple solutions. Perhaps the answers lie in better data or in a totally different approach to simulating how the world works. All I know is that we must do our best to speak truth to ourselves and our customers. Misleading ourselves and our customers will, in the end, result in an inability to have a positive impact on those we serve.

  3. Rephasing invariant parametrization of flavor mixing

    NASA Astrophysics Data System (ADS)

    Lee, Tae-Hun

    A new rephasing invariant parametrization for the 3 x 3 CKM matrix, called (x, y) parametrization, is introduced and the properties and applications of the parametrization are discussed. The overall phase condition leads this parametrization to have only six rephsing invariant parameters and two constraints. Its simplicity and regularity become apparent when it is applied to the one-loop RGE (renormalization group equations) for the Yukawa couplings. The implications of this parametrization for unification of the Yukawa couplings are also explored.

  4. Competing-risks model in screening for pre-eclampsia in twin pregnancy by maternal characteristics and medical history.

    PubMed

    Francisco, C; Wright, D; Benkő, Z; Syngelaki, A; Nicolaides, K H

    2017-10-01

    A survival-time regression model for gestational age at delivery with pre-eclampsia (PE) in singleton pregnancy, using maternal demographic characteristics and medical history, was reported previously. The objective of this study was to extend this model to dichorionic (DC) and monochorionic (MC) twin pregnancy. The study population included 1789 DC and 430 MC twin pregnancies and 93 297 singleton pregnancies. A survival-time model for gestational age at delivery with PE was developed from variables of maternal characteristics and medical history. The risk of PE with delivery < 37 weeks and < 42 weeks in twin pregnancies was determined and compared with that in singleton pregnancies. In singleton pregnancies comprising women of Caucasian racial origin, mean weight of 69 kg at 12 weeks' gestation, mean height of 164 cm, nulliparous, with spontaneous conception, no family history of PE and no history of diabetes mellitus, systemic lupus erythematosus or antiphospholipid syndrome, the mean of the Gaussian distribution of gestational age at delivery with PE was 55 weeks. In DC twins with PE, mean gestational age at delivery was shifted to the left by 8.2 (95% CI, 7.2-9.1) weeks and in MC twins it was shifted to the left by 10.0 (95% CI, 8.5-11.4) weeks. The risk of delivery with PE occurring at, or before, a specified gestational age is given by the area under the fitted distribution curve. For a reference population with the above characteristics, the estimated risk of PE < 37 weeks' gestation, assuming no other cause of delivery, was 0.6% for singletons, 9.0% for DC twins and 14.2% for MC twins; the respective values for PE < 42 weeks were 3.6%, 27.0% and 36.5%. A model based on maternal characteristics and medical history has been developed for estimation of patient-specific risks for PE in DC and MC twin pregnancy. Such estimation of the a-priori risk for PE is an essential first step in the use of Bayes' theorem to combine maternal

  5. Observing and Planning for Play and Competence.

    ERIC Educational Resources Information Center

    Neumann, Eva A.

    This paper presents a framework useful for preschool and elementary teachers in developing a basic understanding of competency and play and their interrelationship. Specific guidelines are given for observing and planning toward increasing opportunities for competency and play. Competency is viewed as consisting of growth, risk-taking, and a…

  6. Estimating Loss to Follow-Up in HIV-Infected Patients on Antiretroviral Therapy: The Effect of the Competing Risk of Death in Zambia and Switzerland

    PubMed Central

    Mwango, Albert; Stringer, Jeffrey; Ledergerber, Bruno; Mulenga, Lloyd; Bucher, Heiner C.; Westfall, Andrew O.; Calmy, Alexandra; Boulle, Andrew; Chintu, Namwinga; Egger, Matthias; Chi, Benjamin H.

    2011-01-01

    Background Loss to follow-up (LTFU) is common in antiretroviral therapy (ART) programmes. Mortality is a competing risk (CR) for LTFU; however, it is often overlooked in cohort analyses. We examined how the CR of death affected LTFU estimates in Zambia and Switzerland. Methods and Findings HIV-infected patients aged ≥18 years who started ART 2004–2008 in observational cohorts in Zambia and Switzerland were included. We compared standard Kaplan-Meier curves with CR cumulative incidence. We calculated hazard ratios for LTFU across CD4 cell count strata using cause-specific Cox models, or Fine and Gray subdistribution models, adjusting for age, gender, body mass index and clinical stage. 89,339 patients from Zambia and 1,860 patients from Switzerland were included. 12,237 patients (13.7%) in Zambia and 129 patients (6.9%) in Switzerland were LTFU and 8,498 (9.5%) and 29 patients (1.6%), respectively, died. In Zambia, the probability of LTFU was overestimated in Kaplan-Meier curves: estimates at 3.5 years were 29.3% for patients starting ART with CD4 cells <100 cells/µl and 15.4% among patients starting with ≥350 cells/µL. The estimates from CR cumulative incidence were 22.9% and 13.6%, respectively. Little difference was found between naïve and CR analyses in Switzerland since only few patients died. The results from Cox and Fine and Gray models were similar: in Zambia the risk of loss to follow-up and death increased with decreasing CD4 counts at the start of ART, whereas in Switzerland there was a trend in the opposite direction, with patients with higher CD4 cell counts more likely to be lost to follow-up. Conclusions In ART programmes in low-income settings the competing risk of death can substantially bias standard analyses of LTFU. The CD4 cell count and other prognostic factors may be differentially associated with LTFU in low-income and high-income settings. PMID:22205933

  7. Incorporating parametric uncertainty into population viability analysis models

    USGS Publications Warehouse

    McGowan, Conor P.; Runge, Michael C.; Larson, Michael A.

    2011-01-01

    Uncertainty in parameter estimates from sampling variation or expert judgment can introduce substantial uncertainty into ecological predictions based on those estimates. However, in standard population viability analyses, one of the most widely used tools for managing plant, fish and wildlife populations, parametric uncertainty is often ignored in or discarded from model projections. We present a method for explicitly incorporating this source of uncertainty into population models to fully account for risk in management and decision contexts. Our method involves a two-step simulation process where parametric uncertainty is incorporated into the replication loop of the model and temporal variance is incorporated into the loop for time steps in the model. Using the piping plover, a federally threatened shorebird in the USA and Canada, as an example, we compare abundance projections and extinction probabilities from simulations that exclude and include parametric uncertainty. Although final abundance was very low for all sets of simulations, estimated extinction risk was much greater for the simulation that incorporated parametric uncertainty in the replication loop. Decisions about species conservation (e.g., listing, delisting, and jeopardy) might differ greatly depending on the treatment of parametric uncertainty in population models.

  8. Identifying at risk individuals for drug and alcohol dependence: teaching the competency to students in classroom and clinical settings.

    PubMed

    Kane, Irene; Mitchell, Ann M; Puskar, Kathryn R; Hagle, Holly; Talcott, Kimberly; Fioravanti, Marie; Droppa, Mandy; Luongo, Peter F; Lindsay, Dawn

    2014-01-01

    Alcohol use and other drug use affect patient healthcare outcomes. This article describes a classroom-to-clinical approach teaching nursing students to utilize motivational interviewing techniques to support patient behavior change. Through the lens of a universal prevention method, nursing students learned about reward circuit activation leading to risky substance use and the difference between addiction and at-risk use. Specific assessment tools and motivational interviewing techniques were presented in the classroom. Students then applied their knowledge in simulation laboratories and clinical rotations.

  9. Parametric Resonance for Material Characterization

    NASA Astrophysics Data System (ADS)

    Adler, Laszlo; Rokhlin, Stanislav I.

    2009-03-01

    While studying finite amplitude ultrasonic wave resonance in a one dimensional liquid filled cavity, formed by a narrow band transducer and a plane reflector, fractional harmonics of the driver's frequency were observed in addition to the expected high harmonics. Subsequently it was realized that the system was one of the many examples where parametric resonance takes place and the observed fractional harmonics are parametrically generated. Parametric resonance occurs in any physical system which has a periodically modulated natural frequency. The generation mechanism also requires a sufficiently high threshold value of the driving amplitude and the system becomes nonlinear. Further increase of the driving amplitude above the threshold produces additional fractional harmonics and at a certain value an almost continuous spectrum is produced and the phenomenon becomes chaotic. Our recently developed frequency modulated angle beam ultrasonic method for adhesive bond evaluation is an additional example of the use of a resonance parametric system. The acoustic resonator is formed by an adhesive layer with the resonance frequency affected by the bond quality between the adhesive and the substrates. In this case the interfacial stresses (due to an external low frequency excitation) may or may not produce parametric shift of the resonance depending on the quality of the interfacial bond.

  10. Parametric functional principal component analysis.

    PubMed

    Sang, Peijun; Wang, Liangliang; Cao, Jiguo

    2017-09-01

    Functional principal component analysis (FPCA) is a popular approach in functional data analysis to explore major sources of variation in a sample of random curves. These major sources of variation are represented by functional principal components (FPCs). Most existing FPCA approaches use a set of flexible basis functions such as B-spline basis to represent the FPCs, and control the smoothness of the FPCs by adding roughness penalties. However, the flexible representations pose difficulties for users to understand and interpret the FPCs. In this article, we consider a variety of applications of FPCA and find that, in many situations, the shapes of top FPCs are simple enough to be approximated using simple parametric functions. We propose a parametric approach to estimate the top FPCs to enhance their interpretability for users. Our parametric approach can also circumvent the smoothing parameter selecting process in conventional nonparametric FPCA methods. In addition, our simulation study shows that the proposed parametric FPCA is more robust when outlier curves exist. The parametric FPCA method is demonstrated by analyzing several datasets from a variety of applications. © 2017, The International Biometric Society.

  11. Potential risk of re-emergence of urban transmission of Yellow Fever virus in Brazil facilitated by competent Aedes populations.

    PubMed

    Couto-Lima, Dinair; Madec, Yoann; Bersot, Maria Ignez; Campos, Stephanie Silva; Motta, Monique de Albuquerque; Santos, Flávia Barreto Dos; Vazeille, Marie; Vasconcelos, Pedro Fernando da Costa; Lourenço-de-Oliveira, Ricardo; Failloux, Anna-Bella

    2017-07-07

    Yellow fever virus (YFV) causing a deadly viral disease is transmitted by the bite of infected mosquitoes. In Brazil, YFV is restricted to a forest cycle maintained between non-human primates and forest-canopy mosquitoes, where humans can be tangentially infected. Since late 2016, a growing number of human cases have been reported in Southeastern Brazil at the gates of the most populated areas of South America, the Atlantic coast, with Rio de Janeiro state hosting nearly 16 million people. We showed that the anthropophilic mosquitoes Aedes aegypti and Aedes albopictus as well as the YFV-enzootic mosquitoes Haemagogus leucocelaenus and Sabethes albiprivus from the YFV-free region of the Atlantic coast were highly susceptible to American and African YFV strains. Therefore, the risk of reemergence of urban YFV epidemics in South America is major with a virus introduced either from a forest cycle or by a traveler returning from the YFV-endemic region of Africa.

  12. Relationship influences on teachers’ perceptions of academic competence in academically at-risk minority and majority first grade students

    PubMed Central

    Hughes, Jan N.; Gleason, Katie A.; Zhang, Duan

    2010-01-01

    This study examined the associations among child demographic variables, teacher perceptions of parent–teacher and student–teacher relationship quality, and teacher perceptions of children’s academic abilities in an ethnically diverse sample of 607 academically at-risk first grade children. Relative to relationships with African American children and parents, teachers rated their relationships with White and Hispanic children and parents more positively. Measures of relationship quality added unique variance to teachers’ perceptions of children’s abilities, controlling for parent educational level and measured ability. Relationship variables fully mediated the association between African American status and teachers’ perceptions of children’s abilities. Implications of the findings for teacher in-service and professional development and for parent involvement programs are discussed. PMID:20401185

  13. Parametric infrared tunable laser system

    NASA Technical Reports Server (NTRS)

    Garbuny, M.; Henningsen, T.; Sutter, J. R.

    1980-01-01

    A parametric tunable infrared laser system was built to serve as transmitter for the remote detection and density measurement of pollutant, poisonous, or trace gases in the atmosphere. The system operates with a YAG:Nd laser oscillator amplifier chain which pumps a parametric tunable frequency converter. The completed system produced pulse energies of up to 30 mJ. The output is tunable from 1.5 to 3.6 micrometers at linewidths of 0.2-0.5 /cm (FWHM), although the limits of the tuning range and the narrower line crystals presently in the parametric converter by samples of the higher quality already demonstrated is expected to improve the system performance further.

  14. Media Competency.

    ERIC Educational Resources Information Center

    Curtis, Ron

    The need to teach media competency in the schools in a systematic way has been largely unrecognized. The Media Now course of study provides an example of the type of instruction needed to teach the knowledge and skills necessary for informed media consumption and skilled media production. The course, which has been thoroughly tested and validated…

  15. Creative Competences.

    ERIC Educational Resources Information Center

    Henry, Jane

    1992-01-01

    A common way to teach creative thinking is through creative problem solving. Outlines the stages of problem solving: problem exploration, idea development, implementation, and selected activities for developing creative problem solving competences. Discusses the role of attitude, experience, and motivation. Concludes that creativity training is…

  16. Raman-Suppressing Coupling for Optical Parametric Oscillator

    NASA Technical Reports Server (NTRS)

    Savchenkov, Anatoliy; Maleki, Lute; Matsko, Andrey; Rubiola, Enrico

    2007-01-01

    A Raman-scattering-suppressing input/ output coupling scheme has been devised for a whispering-gallery-mode optical resonator that is used as a four-wave-mixing device to effect an all-optical parametric oscillator. Raman scattering is undesired in such a device because (1) it is a nonlinear process that competes with the desired nonlinear four-wave conversion process involved in optical parametric oscillation and (2) as such, it reduces the power of the desired oscillation and contributes to output noise. The essence of the present input/output coupling scheme is to reduce output loading of the desired resonator modes while increasing output loading of the undesired ones.

  17. Differential mortality and the excess burden of end-stage renal disease among First Nations people with diabetes mellitus: a competing-risks analysis

    PubMed Central

    Jiang, Ying; Osgood, Nathaniel; Lim, Hyun-Ja; Stang, Mary Rose; Dyck, Roland

    2014-01-01

    Background: Diabetes-related end-stage renal disease disproportionately affects indigenous peoples. We explored the role of differential mortality in this disparity. Methods: In this retrospective cohort study, we examined the competing risks of end-stage renal disease and death without end-stage renal disease among Saskatchewan adults with diabetes mellitus, both First Nations and non–First Nations, from 1980 to 2005. Using administrative databases of the Saskatchewan Ministry of Health, we developed Fine and Gray subdistribution hazards models and cumulative incidence functions. Results: Of the 90 429 incident cases of diabetes, 8254 (8.9%) occurred among First Nations adults and 82 175 (90.9%) among non–First Nations adults. Mean age at the time that diabetes was diagnosed was 47.2 and 61.6 years, respectively (p < 0.001). After adjustment for sex and age at the time of diabetes diagnosis, the risk of end-stage renal disease was 2.66 times higher for First Nations than non–First Nations adults (95% confidence interval [CI] 2.24–3.16). Multivariable analysis with adjustment for sex showed a higher risk of death among First Nations adults, which declined with increasing age at the time of diabetes diagnosis. Cumulative incidence function curves stratified by age at the time of diabetes diagnosis showed greatest risk for end-stage renal disease among those with onset of diabetes at younger ages and greatest risk of death among those with onset of diabetes at older ages. Interpretation: Because they are typically younger when diabetes is diagnosed, First Nations adults with this condition are more likely than their non–First Nations counterparts to survive long enough for end-stage renal disease to develop. Differential mortality contributes substantially to ethnicity-based disparities in diabetes-related end-stage renal disease and possibly to chronic diabetes complications. Understanding the mechanisms underlying these disparities is vital in developing

  18. Polarization mixing optical parametric oscillator.

    SciTech Connect

    Pearl, Shaul; Smith, Arlee Virgil; Arie, Ady; Blau, Pinhas; Kalmani, Gal

    2005-05-01

    We report the experimental realization of a new type of optical parametric oscillator in which oscillation is achieved by polarization rotation in a linear retarder, followed by nonlinear polarization mixing. The mixing is performed by a type II degenerate parametric downconversion in a periodically poled KTP crystal pumped by a 1064 nm pulsed Nd:YAG pump. A single, linearly polarized beam, precisely at the degenerate wavelength is generated. The output spectrum has a narrow linewidth (below the instrumentation bandwidth of 1 nm) and is highly stable with respect to variations in the crystal temperature.

  19. Biological Parametric Mapping WITH Robust AND Non-Parametric Statistics

    PubMed Central

    Yang, Xue; Beason-Held, Lori; Resnick, Susan M.; Landman, Bennett A.

    2011-01-01

    Mapping the quantitative relationship between structure and function in the human brain is an important and challenging problem. Numerous volumetric, surface, regions of interest and voxelwise image processing techniques have been developed to statistically assess potential correlations between imaging and non-imaging metrices. Recently, biological parametric mapping has extended the widely popular statistical parametric mapping approach to enable application of the general linear model to multiple image modalities (both for regressors and regressands) along with scalar valued observations. This approach offers great promise for direct, voxelwise assessment of structural and functional relationships with multiple imaging modalities. However, as presented, the biological parametric mapping approach is not robust to outliers and may lead to invalid inferences (e.g., artifactual low p-values) due to slight mis-registration or variation in anatomy between subjects. To enable widespread application of this approach, we introduce robust regression and non-parametric regression in the neuroimaging context of application of the general linear model. Through simulation and empirical studies, we demonstrate that our robust approach reduces sensitivity to outliers without substantial degradation in power. The robust approach and associated software package provide a reliable way to quantitatively assess voxelwise correlations between structural and functional neuroimaging modalities. PMID:21569856

  20. Biological parametric mapping with robust and non-parametric statistics.

    PubMed

    Yang, Xue; Beason-Held, Lori; Resnick, Susan M; Landman, Bennett A

    2011-07-15

    Mapping the quantitative relationship between structure and function in the human brain is an important and challenging problem. Numerous volumetric, surface, regions of interest and voxelwise image processing techniques have been developed to statistically assess potential correlations between imaging and non-imaging metrices. Recently, biological parametric mapping has extended the widely popular statistical parametric mapping approach to enable application of the general linear model to multiple image modalities (both for regressors and regressands) along with scalar valued observations. This approach offers great promise for direct, voxelwise assessment of structural and functional relationships with multiple imaging modalities. However, as presented, the biological parametric mapping approach is not robust to outliers and may lead to invalid inferences (e.g., artifactual low p-values) due to slight mis-registration or variation in anatomy between subjects. To enable widespread application of this approach, we introduce robust regression and non-parametric regression in the neuroimaging context of application of the general linear model. Through simulation and empirical studies, we demonstrate that our robust approach reduces sensitivity to outliers without substantial degradation in power. The robust approach and associated software package provide a reliable way to quantitatively assess voxelwise correlations between structural and functional neuroimaging modalities. Copyright © 2011 Elsevier Inc. All rights reserved.

  1. Competing risks model in screening for preeclampsia by maternal factors and biomarkers at 11-13 weeks gestation.

    PubMed

    O'Gorman, Neil; Wright, David; Syngelaki, Argyro; Akolekar, Ranjit; Wright, Alan; Poon, Leona C; Nicolaides, Kypros H

    2016-01-01

    Preeclampsia affects approximately 3% of all pregnancies and is a major cause of maternal and perinatal morbidity and death. In the last decade, extensive research has been devoted to early screening for preeclampsia with the aim of reducing the prevalence of the disease through pharmacologic intervention in the high-risk group starting from the first trimester of pregnancy. The purpose of this study was to develop a model for preeclampsia based on maternal demographic characteristics and medical history (maternal factors) and biomarkers. The data for this study were derived from prospective screening for adverse obstetric outcomes in women who attended for their routine first hospital visit at 11-13 weeks gestation in 2 maternity hospitals in England. We screened 35,948 singleton pregnancies that included 1058 pregnancies (2.9%) that experienced preeclampsia. Bayes theorem was used to combine the a priori risk from maternal factors with various combinations of uterine artery pulsatility index, mean arterial pressure, serum pregnancy-associated plasma protein-A, and placental growth factor multiple of the median values. Five-fold cross validation was used to assess the performance of screening for preeclampsia that delivered at <37 weeks gestation (preterm-preeclampsia) and ≥37 weeks gestation (term-preeclampsia) by models that combined maternal factors with individual biomarkers and their combination with screening by maternal factors alone. In pregnancies that experienced preeclampsia, the values of uterine artery pulsatility index and mean arterial pressure were increased, and the values of serum pregnancy-associated plasma protein-A and placental growth factor were decreased. For all biomarkers, the deviation from normal was greater for early than late preeclampsia; therefore, the performance of screening was related inversely to the gestational age at which delivery became necessary for maternal and/or fetal indications. Combined screening by maternal

  2. HIV and infant feeding: to breastfeed or not to breastfeed: the dilemma of competing risks. Part 2.

    PubMed

    Morrison, P

    1999-11-01

    The discovery of the human immunodeficiency virus (HIV) in breastmilk in 1985, and subsequent research, supports the hypothesis that breastfeeding provides a route of transmission to the nursing baby. Various routes of infection and relative rates of transmission have been studied in many parts of the world, leading to the blanket guideline that babies of HIV-infected mothers should not be breastfed, if a safe alternative can be provided. However, due to the limits inherent in various studies and various testing methods, the exact frequency of breastmilk transmission of HIV during the course of lactation remains unknown, and the conclusions drawn are thus conflicting and confusing. Replacement feeding of young babies with non-human milks and other foods may be hazardous in poverty-stricken populations in Africa and elsewhere, and still more research suggests that there are several properties in human milk that may provide specific protection to the baby of an infected mother. The possibility of providing the mother's own treated expressed breastmilk to the baby at risk of HIV infection via breastfeeding is an alternative which has yet to be fully explored and ways that this could be accomplished are examined. Those of us working with mothers and babies need more information before we can assist mothers living with HIV to make truly informed decisions about the safest way to feed their babies. Topics requiring urgent further attention are outlined.

  3. HIV and infant feeding: to breastfeed or not to breastfeed: the dilemma of competing risks. Part 1.

    PubMed

    Morrison, P

    1999-07-01

    The discovery of the human immunodeficiency virus (HIV) in breastmilk in 1985, and subsequent research, supports the hypothesis that breastfeeding provides a route of transmission to the nursing baby. Various routes of infection and relative rates of transmission have been studied in many parts of the world, leading to the blanket guideline that babies of HIV-infected mothers should not be breastfed, if a safe alternative can be provided. However, due to the limits inherent in various studies and various testing methods, the exact frequency of breastmilk transmission of HIV during the course of lactation remains unknown, and the conclusions drawn are thus conflicting and confusing. Replacement feeding of young babies with non-human milks and other foods may be hazardous in poverty-stricken populations in Africa and elsewhere, and still more research suggests that there are several properties in human milk that may provide specific protection to the baby of an infected mother. The possibility of providing the mother's own treated expressed breastmilk to the baby at risk of HIV infection via breastfeeding is an alternative which has yet to be fully explored and ways that this could be accomplished are examined. Those of us working with mothers and babies need more information before we can assist mothers living with HIV to make truly informed decisions about the safest way to feed their babies. Topics requiring urgent further attention are outlined.

  4. HDAC1 and HDAC2 independently predict mortality in hepatocellular carcinoma by a competing risk regression model in a Southeast Asian population

    PubMed Central

    LER, SER YENG; LEUNG, CAROL HO WING; KHIN, LAY WAI; LU, GUO-DONG; SALTO-TELLEZ, MANUEL; HARTMAN, MIKAEL; IAU, PHILIP TSAU CHOONG; YAP, CELESTIAL T.; HOOI, SHING CHUAN

    2015-01-01

    Histone deacetylases (HDACs) are enzymes involved in transcriptional repression. We aimed to examine the significance of HDAC1 and HDAC2 gene expression in the prediction of recurrence and survival in 156 patients with hepatocellular carcinoma (HCC) among a South East Asian population who underwent curative surgical resection in Singapore. We found that HDAC1 and HDAC2 were upregulated in the majority of HCC tissues. The presence of HDAC1 in tumor tissues was correlated with poor tumor differentiation. Notably, HDAC1 expression in adjacent non-tumor hepatic tissues was correlated with the presence of satellite nodules and multiple lesions, suggesting that HDAC1 upregulation within the field of HCC may contribute to tumor spread. Using competing risk regression analysis, we found that increased cancer-specific mortality was significantly associated with HDAC2 expression. Mortality was also increased with high HDAC1 expression. In the liver cancer cell lines, HEP3B, HEPG2, PLC5, and a colorectal cancer cell line, HCT116, the combined knockdown of HDAC1 and HDAC2 increased cell death and reduced cell proliferation as well as colony formation. In contrast, knockdown of either HDAC1 or HDAC2 alone had minimal effects on cell death and proliferation. Taken together, our study suggests that both HDAC1 and HDAC2 exert pro-survival effects in HCC cells, and the combination of isoform-specific HDAC inhibitors against both HDACs may be effective in targeting HCC to reduce mortality. PMID:26352599

  5. [Mortality in early-stage, surgically resected non-small cell lung cancer less than 3 cm of size: Competing risk analysis].

    PubMed

    Jordá Aragón, Carlos; Peñalver Cuesta, Juan Carlos; Mancheño Franch, Nuria; de Aguiar Quevedo, Karol; Vera Sempere, Francisco; Padilla Alarcón, José

    2015-09-07

    Survival studies of non-small cell lung cancer (NSCLC) are usually based on the Kaplan-Meier method. However, other factors not covered by this method may modify the observation of the event of interest. There are models of cumulative incidence (CI), that take into account these competing risks, enabling more accurate survival estimates and evaluation of the risk of death from other causes. We aimed to evaluate these models in resected early-stage NSCLC patients. This study included 263 patients with resected NSCLC whose diameter was ≤ 3 cm without node involvement (N0). Demographic, clinical, morphopathological and surgical variables, TNM classification and long-term evolution were analysed. To analyse CI, death by another cause was considered to be competitive event. For the univariate analysis, Gray's method was used, while Fine and Gray's method was employed for the multivariate analysis. Mortality by NSCLC was 19.4% at 5 years and 14.3% by another cause. Both curves crossed at 6.3 years, and probability of death by another cause became greater from this point. In multivariate analysis, cancer mortality was conditioned by visceral pleural invasion (VPI) (P=.001) and vascular invasion (P=.020), with age>50 years (P=.034), smoking (P=.009) and the Charlson index ≥ 2 (P=.000) being by no cancer. By the method of CI, VPI and vascular invasion conditioned cancer death in NSCLC >3 cm, while non-tumor causes of long-term death were determined. Copyright © 2014 Elsevier España, S.L.U. All rights reserved.

  6. Graphical functions in parametric space

    NASA Astrophysics Data System (ADS)

    Golz, Marcel; Panzer, Erik; Schnetz, Oliver

    2016-12-01

    Graphical functions are positive functions on the punctured complex plane Csetminus {0,1} which arise in quantum field theory. We generalize a parametric integral representation for graphical functions due to Lam, Lebrun and Nakanishi, which implies the real analyticity of graphical functions. Moreover, we prove a formula that relates graphical functions of planar dual graphs.

  7. Global, Multi-Objective Trajectory Optimization With Parametric Spreading

    NASA Technical Reports Server (NTRS)

    Vavrina, Matthew A.; Englander, Jacob A.; Phillips, Sean M.; Hughes, Kyle M.

    2017-01-01

    Mission design problems are often characterized by multiple, competing trajectory optimization objectives. Recent multi-objective trajectory optimization formulations enable generation of globally-optimal, Pareto solutions via a multi-objective genetic algorithm. A byproduct of these formulations is that clustering in design space can occur in evolving the population towards the Pareto front. This clustering can be a drawback, however, if parametric evaluations of design variables are desired. This effort addresses clustering by incorporating operators that encourage a uniform spread over specified design variables while maintaining Pareto front representation. The algorithm is demonstrated on a Neptune orbiter mission, and enhanced multidimensional visualization strategies are presented.

  8. Parametric Identification of Systems Via Linear Operators.

    DTIC Science & Technology

    1978-09-01

    A general parametric identification /approximation model is developed for the black box identification of linear time invariant systems in terms of... parametric identification techniques derive from the general model as special cases associated with a particular linear operator. Some possible

  9. Computing Optimal Stochastic Portfolio Execution Strategies: A Parametric Approach Using Simulations

    NASA Astrophysics Data System (ADS)

    Moazeni, Somayeh; Coleman, Thomas F.; Li, Yuying

    2010-09-01

    Computing optimal stochastic portfolio execution strategies under appropriate risk consideration presents great computational challenge. We investigate a parametric approach for computing optimal stochastic strategies using Monte Carlo simulations. This approach allows reduction in computational complexity by computing coefficients for a parametric representation of a stochastic dynamic strategy based on static optimization. Using this technique, constraints can be similarly handled using appropriate penalty functions. We illustrate the proposed approach to minimize the expected execution cost and Conditional Value-at-Risk (CVaR).

  10. Parametric Model Checking with VerICS

    NASA Astrophysics Data System (ADS)

    Knapik, Michał; Niewiadomski, Artur; Penczek, Wojciech; Półrola, Agata; Szreter, Maciej; Zbrzezny, Andrzej

    The paper presents the verification system verICS, extended with the three new modules aimed at parametric verification of Elementary Net Systems, Distributed Time Petri Nets, and a subset of UML. All the modules exploit Bounded Model Checking for verifying parametric reachability and the properties specified in the logic PRTECTL - the parametric extension of the existential fragment of CTL.

  11. Religious competence as cultural competence

    PubMed Central

    2012-01-01

    Definitions of cultural competence often refer to the need to be aware and attentive to the religious and spiritual needs and orientations of patients. However, the institution of psychiatry maintains an ambivalent attitude to the incorporation of religion and spirituality into psychiatric practice. This is despite the fact that many patients, especially those from underserved and underprivileged minority backgrounds, are devotedly religious and find much solace and support in their religiosity. I use the case of mental health of African Americans as an extended example to support the argument that psychiatric services must become more closely attuned to religious matters. I suggest ways in which this can be achieved. Attention to religion can aid in the development of culturally competent and accessible services, which in turn, may increase engagement and service satisfaction among religious populations. PMID:22421686

  12. Parametric sonars for seafloor characterization

    NASA Astrophysics Data System (ADS)

    Caiti, Andrea; Bergem, Oddbjorn; Dybedal, Johnny

    1999-12-01

    Parametric sonars are instruments capable of transmitting acoustic signals in the water with a very narrow beam and almost no sidelobes. These features are exploited in this paper to define a methodology for quantitative estimation of the geo-acoustic and morphological properties of the uppermost seafloor sediment layer. The three major components of the approach are the parametric instrument itself; the modelling of the forward-propagation problem, with the use of the Kirchhoff approximation for surface scattering and of the small-perturbation theory for the volume scattering; and the definition of a criterion for comparison between data and model predictions, which is accomplished by a generalized time-frequency analysis. In this way the estimation becomes one of a model-based identification, or a model-based inverse problem. Results from a field trial in a shallow water area of the Mediterranean are shown, and compared with independently gathered ground truth.

  13. Frequency domain optical parametric amplification

    PubMed Central

    Schmidt, Bruno E.; Thiré, Nicolas; Boivin, Maxime; Laramée, Antoine; Poitras, François; Lebrun, Guy; Ozaki, Tsuneyuki; Ibrahim, Heide; Légaré, François

    2014-01-01

    Today’s ultrafast lasers operate at the physical limits of optical materials to reach extreme performances. Amplification of single-cycle laser pulses with their corresponding octave-spanning spectra still remains a formidable challenge since the universal dilemma of gain narrowing sets limits for both real level pumped amplifiers as well as parametric amplifiers. We demonstrate that employing parametric amplification in the frequency domain rather than in time domain opens up new design opportunities for ultrafast laser science, with the potential to generate single-cycle multi-terawatt pulses. Fundamental restrictions arising from phase mismatch and damage threshold of nonlinear laser crystals are not only circumvented but also exploited to produce a synergy between increased seed spectrum and increased pump energy. This concept was successfully demonstrated by generating carrier envelope phase stable, 1.43 mJ two-cycle pulses at 1.8 μm wavelength. PMID:24805968

  14. Experience with parametric binary dissection

    NASA Technical Reports Server (NTRS)

    Bokhari, Shahid H.

    1993-01-01

    Parametric Binary Dissection (PBD) is a new algorithm that can be used for partitioning graphs embedded in 2- or 3-dimensional space. It partitions explicitly on the basis of nodes + (lambda)x(edges cut), where lambda is the ratio of time to communicate over an edge to the time to compute at a node. The new algorithm is faster than the original binary dissection algorithm and attempts to obtain better partitions than the older algorithm, which only takes nodes into account. The performance of parametric dissection with plain binary dissection on 3 large unstructured 3-d meshes obtained from computational fluid dynamics and on 2 random graphs were compared. It was showm that the new algorithm can usually yield partitions that are substantially superior, but that its performance is heavily dependent on the input data.

  15. Joint modeling of repeated multivariate cognitive measures and competing risks of dementia and death: a latent process and latent class approach.

    PubMed

    Proust-Lima, Cécile; Dartigues, Jean-François; Jacqmin-Gadda, Hélène

    2016-02-10

    Joint models initially dedicated to a single longitudinal marker and a single time-to-event need to be extended to account for the rich longitudinal data of cohort studies. Multiple causes of clinical progression are indeed usually observed, and multiple longitudinal markers are collected when the true latent trait of interest is hard to capture (e.g., quality of life, functional dependency, and cognitive level). These multivariate and longitudinal data also usually have nonstandard distributions (discrete, asymmetric, bounded, etc.). We propose a joint model based on a latent process and latent classes to analyze simultaneously such multiple longitudinal markers of different natures, and multiple causes of progression. A latent process model describes the latent trait of interest and links it to the observed longitudinal outcomes using flexible measurement models adapted to different types of data, and a latent class structure links the longitudinal and cause-specific survival models. The joint model is estimated in the maximum likelihood framework. A score test is developed to evaluate the assumption of conditional independence of the longitudinal markers and each cause of progression given the latent classes. In addition, individual dynamic cumulative incidences of each cause of progression based on the repeated marker data are derived. The methodology is validated in a simulation study and applied on real data about cognitive aging obtained from a large population-based study. The aim is to predict the risk of dementia by accounting for the competing death according to the profiles of semantic memory measured by two asymmetric psychometric tests. Copyright © 2015 John Wiley & Sons, Ltd.

  16. PHAZE. Parametric Hazard Function Estimation

    SciTech Connect

    Atwood, C.L.

    1990-09-01

    Phaze performs statistical inference calculations on a hazard function ( also called a failure rate or intensity function) based on reported failure times of components that are repaired and restored to service. Three parametric models are allowed: the exponential, linear, and Weibull hazard models. The inference includes estimation (maximum likelihood estimators and confidence regions) of the parameters and of the hazard function itself, testing of hypotheses such as increasing failure rate, and checking of the model assumptions.

  17. Parametric and non-parametric modeling of short-term synaptic plasticity. Part II: Experimental study.

    PubMed

    Song, Dong; Wang, Zhuo; Marmarelis, Vasilis Z; Berger, Theodore W

    2009-02-01

    This paper presents a synergistic parametric and non-parametric modeling study of short-term plasticity (STP) in the Schaffer collateral to hippocampal CA1 pyramidal neuron (SC) synapse. Parametric models in the form of sets of differential and algebraic equations have been proposed on the basis of the current understanding of biological mechanisms active within the system. Non-parametric Poisson-Volterra models are obtained herein from broadband experimental input-output data. The non-parametric model is shown to provide better prediction of the experimental output than a parametric model with a single set of facilitation/depression (FD) process. The parametric model is then validated in terms of its input-output transformational properties using the non-parametric model since the latter constitutes a canonical and more complete representation of the synaptic nonlinear dynamics. Furthermore, discrepancies between the experimentally-derived non-parametric model and the equivalent non-parametric model of the parametric model suggest the presence of multiple FD processes in the SC synapses. Inclusion of an additional set of FD process in the parametric model makes it replicate better the characteristics of the experimentally-derived non-parametric model. This improved parametric model in turn provides the requisite biological interpretability that the non-parametric model lacks.

  18. Parametric Modeling for Fluid Systems

    NASA Technical Reports Server (NTRS)

    Pizarro, Yaritzmar Rosario; Martinez, Jonathan

    2013-01-01

    Fluid Systems involves different projects that require parametric modeling, which is a model that maintains consistent relationships between elements as is manipulated. One of these projects is the Neo Liquid Propellant Testbed, which is part of Rocket U. As part of Rocket U (Rocket University), engineers at NASA's Kennedy Space Center in Florida have the opportunity to develop critical flight skills as they design, build and launch high-powered rockets. To build the Neo testbed; hardware from the Space Shuttle Program was repurposed. Modeling for Neo, included: fittings, valves, frames and tubing, between others. These models help in the review process, to make sure regulations are being followed. Another fluid systems project that required modeling is Plant Habitat's TCUI test project. Plant Habitat is a plan to develop a large growth chamber to learn the effects of long-duration microgravity exposure to plants in space. Work for this project included the design and modeling of a duct vent for flow test. Parametric Modeling for these projects was done using Creo Parametric 2.0.

  19. Population-based absolute risk estimation with survey data

    PubMed Central

    Kovalchik, Stephanie A.; Pfeiffer, Ruth M.

    2013-01-01

    Absolute risk is the probability that a cause-specific event occurs in a given time interval in the presence of competing events. We present methods to estimate population-based absolute risk from a complex survey cohort that can accommodate multiple exposure-specific competing risks. The hazard function for each event type consists of an individualized relative risk multiplied by a baseline hazard function, which is modeled nonparametrically or parametrically with a piecewise exponential model. An influence method is used to derive a Taylor-linearized variance estimate for the absolute risk estimates. We introduce novel measures of the cause-specific influences that can guide modeling choices for the competing event components of the model. To illustrate our methodology, we build and validate cause-specific absolute risk models for cardiovascular and cancer deaths using data from the National Health and Nutrition Examination Survey. Our applications demonstrate the usefulness of survey-based risk prediction models for predicting health outcomes and quantifying the potential impact of disease prevention programs at the population level. PMID:23686614

  20. Bayesian adjustment for covariate measurement errors: a flexible parametric approach.

    PubMed

    Hossain, Shahadut; Gustafson, Paul

    2009-05-15

    In most epidemiological investigations, the study units are people, the outcome variable (or the response) is a health-related event, and the explanatory variables are usually environmental and/or socio-demographic factors. The fundamental task in such investigations is to quantify the association between the explanatory variables (covariates/exposures) and the outcome variable through a suitable regression model. The accuracy of such quantification depends on how precisely the relevant covariates are measured. In many instances, we cannot measure some of the covariates accurately. Rather, we can measure noisy (mismeasured) versions of them. In statistical terminology, mismeasurement in continuous covariates is known as measurement errors or errors-in-variables. Regression analyses based on mismeasured covariates lead to biased inference about the true underlying response-covariate associations. In this paper, we suggest a flexible parametric approach for avoiding this bias when estimating the response-covariate relationship through a logistic regression model. More specifically, we consider the flexible generalized skew-normal and the flexible generalized skew-t distributions for modeling the unobserved true exposure. For inference and computational purposes, we use Bayesian Markov chain Monte Carlo techniques. We investigate the performance of the proposed flexible parametric approach in comparison with a common flexible parametric approach through extensive simulation studies. We also compare the proposed method with the competing flexible parametric method on a real-life data set. Though emphasis is put on the logistic regression model, the proposed method is unified and is applicable to the other generalized linear models, and to other types of non-linear regression models as well. (c) 2009 John Wiley & Sons, Ltd.

  1. Stimulated Parametric Emission Microscope Systems

    NASA Astrophysics Data System (ADS)

    Itoh, Kazuyoshi; Isobe, Keisuke

    2006-10-01

    We present a novel microscopy technique based on the fourwave mixing (FWM) process that is enhanced by two-photon electronic resonance induced by a pump pulse along with stimulated emission induced by a dump pulse. A Ti:sapphire laser and an optical parametric oscillator are used as light sources for the pump and dump pulses, respectively. We demonstrate that our FWM technique can be used to obtain two-dimensional microscopic images of an unstained leaf of Camellia sinensis and an unlabeled tobacco BY2 Cell.

  2. Whispering gallery optical parametric oscillators

    NASA Astrophysics Data System (ADS)

    Breunig, Ingo; Buse, Karsten

    2013-12-01

    Whispering gallery optical parametric oscillators (WGR OPOs) are monolithic sources for tunable coherent and non-classical light. They are based on total internal reflection. Since reflection losses are negligible, their oscillation threshold can be far below one milliwatt. With sub-millimeter diameters, they are the most compact OPOs demonstrated so far. Recent experimental results demonstrate that WGR OPOs emit coherent light tunable over hundreds of nanometers. Operation in the visible as well as in the near-infrared has been demonstrated with up to 30 % conversion efficiency. These results indicate a great potential of WGR OPOs for spectroscopic and sensing applications.

  3. Competing-risk analysis of death and dialysis initiation among elderly (≥80 years) newly referred to nephrologists: a French prospective study

    PubMed Central

    2013-01-01

    Background Reasons underlying dialysis decision-making in Octogenarians and Nonagenarians have not been further explored in prospective studies. Methods This regional, multicentre, non-interventional and prospective study was aimed to describe characteristics and quality of life (QoL) of elderly (≥80 years of age) with advanced chronic kidney disease (stage 3b-5 CKD) newly referred to nephrologists. Predictive factors of death and dialysis initiation were also assessed using competing-risk analyses. Results All 155 included patients had an estimated glomerular filtration rate (eGFR) below 45 ml/min/1.73 m2. Most patients had a non anaemic haemoglobin level (Hb) with no iron deficiency, and normal calcium and phosphate levels. They were well-fed and had a normal cognitive function and a good QoL. The 3-year probabilities of death and dialysis initiation reached 27% and 11%, respectively. The leading causes of death were cardiovascular (32%), cachexia (18%), cancer (9%), infection (3%), trauma (3%), dementia (3%), and unknown (32%). The reasons for dialysis initiation were based on uncontrolled biological abnormalities, such as hyperkalemia or acidosis (71%), uncontrolled digestive disorders (35%), uncontrolled pulmonary or peripheral oedema (29%), and uncontrolled malnutrition (12%). No patients with acute congestive heart failure or cancer initiated dialysis. Predictors of death found in both multivariate regression models (Cox and Fine & Gray) included acute congestive heart failure, age, any walking impairment and Hb <10 g/dL. Regarding dialysis initiation, eGFR <23 mL/min/1.73 m2 was the only predictor found in the Cox multivariate regression model whereas eGFR <23 mL/min/1.73 m2 and diastolic blood pressure were both independently associated with dialysis initiation in the Fine & Gray analysis. Such findings suggested that death and dialysis were independent events. Conclusions Octogenarians and Nonagenarians newly referred to nephrologists by

  4. Parametric nanomechanical amplification at very high frequency.

    PubMed

    Karabalin, R B; Feng, X L; Roukes, M L

    2009-09-01

    Parametric resonance and amplification are important in both fundamental physics and technological applications. Here we report very high frequency (VHF) parametric resonators and mechanical-domain amplifiers based on nanoelectromechanical systems (NEMS). Compound mechanical nanostructures patterned by multilayer, top-down nanofabrication are read out by a novel scheme that parametrically modulates longitudinal stress in doubly clamped beam NEMS resonators. Parametric pumping and signal amplification are demonstrated for VHF resonators up to approximately 130 MHz and provide useful enhancement of both resonance signal amplitude and quality factor. We find that Joule heating and reduced thermal conductance in these nanostructures ultimately impose an upper limit to device performance. We develop a theoretical model to account for both the parametric response and nonequilibrium thermal transport in these composite nanostructures. The results closely conform to our experimental observations, elucidate the frequency and threshold-voltage scaling in parametric VHF NEMS resonators and sensors, and establish the ultimate sensitivity limits of this approach.

  5. Rosetta stone for parametrized tests of gravity

    NASA Astrophysics Data System (ADS)

    Sampson, Laura; Yunes, Nicolás; Cornish, Neil

    2013-09-01

    Several model-independent parametrizations of deviations from general relativity have been developed to test Einstein’s theory. Although these different parametrizations were developed for different gravitational observables, they ultimately all test the same underlying physics. In this paper, we develop connections between the parametrized post-Newtonian, parametrized post-Keplerian, and the parametrized post-Einsteinian frameworks, developed to carry out tests of general relativity with Solar System, binary pulsar, and gravitational wave observations, respectively. These connections, although only valid under certain assumptions such as energy/momentum conservation, allow us to use knowledge gained from one framework to inform and guide tests using the others. Relating these parametrizations and combining the results from each approach strengthens our tests of general relativity.

  6. Assessment of risk factors affecting recurrence of patients with gastric cancer in the presence of informative censoring in Iran.

    PubMed

    Roshanaei, Ghodratollah; Kazemnejad, Anoshirvan; Sadighi, Sanambar

    2011-01-01

    In some survival studies, several events are taken into consideration. If the events are independent then the ordinary methods such as Kaplan-Meier, Cox or parametric models can be used. If one of the events dependently (informatively) censors the other, the results are biased. The present study was designed to assess the risk factors for recurrence of patients with gastric cancer in the presence of informative censoring using parametric models with a semi-competing risk approach. In a retrospective study, 408 cases of gastric cancer were selected from the patients referred to the Tehran Cancer Institute from March 2003 to March 2007. Gender, age at diagnosis, distant metastasis, tumor size, histology type, tumor grade, pathologic stage, tumor site, and type of treatment were studied as prognostic factors and used in the models. Parametric models such as Weibull, exponential, log-logistic were used with informative right censoring using Akaike Information Criteria (AIC) as criteria to compare models. The data were analyzed using R statistical software. A p-value of less than 0.05 was considered as statistically significant. Based on Akaike information criteria (AIC), the Weibull model best fitted to data. The effect of tumor size and pathologic stage were significant on recurrence in both univariate and multivariate analyses. Tumor site and tumor grade were significant only in univariate analysis. The results showed that semi-competing risk methods perform well in determining risk factors for disease recurrence.

  7. A THEORY FOR BROADBAND VARACTOR PARAMETRIC AMPLIFIERS

    DTIC Science & Technology

    This thesis is concerned with the development of a general and rigorous broadbanding theory for varactor parametric amplifiers . Fundamental gain...bandwidth limitations of a varactor parametric amplifier are obtained which are independent of the equalizer. Results obtained in this theory lead to the...design and synthesis of broadband varactor parametric amplifiers . The circuit considered in this thesis is that of linear variable capacitors embedded

  8. Software for Managing Parametric Studies

    NASA Technical Reports Server (NTRS)

    Yarrow, Maurice; McCann, Karen M.; DeVivo, Adrian

    2003-01-01

    The Information Power Grid Virtual Laboratory (ILab) is a Practical Extraction and Reporting Language (PERL) graphical-user-interface computer program that generates shell scripts to facilitate parametric studies performed on the Grid. (The Grid denotes a worldwide network of supercomputers used for scientific and engineering computations involving data sets too large to fit on desktop computers.) Heretofore, parametric studies on the Grid have been impeded by the need to create control language scripts and edit input data files painstaking tasks that are necessary for managing multiple jobs on multiple computers. ILab reflects an object-oriented approach to automation of these tasks: All data and operations are organized into packages in order to accelerate development and debugging. A container or document object in ILab, called an experiment, contains all the information (data and file paths) necessary to define a complex series of repeated, sequenced, and/or branching processes. For convenience and to enable reuse, this object is serialized to and from disk storage. At run time, the current ILab experiment is used to generate required input files and shell scripts, create directories, copy data files, and then both initiate and monitor the execution of all computational processes.

  9. Developing Social Competence in the Preschool Years.

    ERIC Educational Resources Information Center

    Knight, Bruce Allen; Hughes, Desma

    1995-01-01

    Surveys the literature on the importance of social skills acquisition. Cites factors that influence social competence formation, including parental characteristics and quality of preschool care or interventions. Suggests that students lacking social competence risk peer rejection, academic failure, and later social and emotional problems. Includes…

  10. Future Directions for Research on Core Competencies

    ERIC Educational Resources Information Center

    Bradshaw, Catherine P.; Guerra, Nancy G.

    2008-01-01

    This concluding commentary highlights common themes that emerged across the chapters in this volume. We identify strengths and limitations of the core competencies framework and discuss the importance of context, culture, and development for understanding the role of the core competencies in preventing risk behavior in adolescence. We also outline…

  11. An Exploratory Study of the Relationship among Perceived Personal and Social Competence, Health Risk Behaviors, and Academic Achievement of Selected Undergraduate Students

    ERIC Educational Resources Information Center

    Rhodes, Darson L.

    2009-01-01

    A sample of 656 undergraduate students from multiple sections of an introductory nutrition course, a personal health course, and a physical fitness course at a large Midwestern University completed one of four surveys. Using matrix sampling, each participant completed a survey measuring one of four personal and social competence constructs; coping…

  12. An Exploratory Study of the Relationship among Perceived Personal and Social Competence, Health Risk Behaviors, and Academic Achievement of Selected Undergraduate Students

    ERIC Educational Resources Information Center

    Rhodes, Darson L.

    2009-01-01

    A sample of 656 undergraduate students from multiple sections of an introductory nutrition course, a personal health course, and a physical fitness course at a large Midwestern University completed one of four surveys. Using matrix sampling, each participant completed a survey measuring one of four personal and social competence constructs; coping…

  13. Observation of Parametric Instability in Advanced LIGO

    NASA Astrophysics Data System (ADS)

    Evans, Matthew; Gras, Slawek; Fritschel, Peter; Miller, John; Barsotti, Lisa; Martynov, Denis; Brooks, Aidan; Coyne, Dennis; Abbott, Rich; Adhikari, Rana X.; Arai, Koji; Bork, Rolf; Kells, Bill; Rollins, Jameson; Smith-Lefebvre, Nicolas; Vajente, Gabriele; Yamamoto, Hiroaki; Adams, Carl; Aston, Stuart; Betzweiser, Joseph; Frolov, Valera; Mullavey, Adam; Pele, Arnaud; Romie, Janeen; Thomas, Michael; Thorne, Keith; Dwyer, Sheila; Izumi, Kiwamu; Kawabe, Keita; Sigg, Daniel; Derosa, Ryan; Effler, Anamaria; Kokeyama, Keiko; Ballmer, Stefan; Massinger, Thomas J.; Staley, Alexa; Heinze, Matthew; Mueller, Chris; Grote, Hartmut; Ward, Robert; King, Eleanor; Blair, David; Ju, Li; Zhao, Chunnong

    2015-04-01

    Parametric instabilities have long been studied as a potentially limiting effect in high-power interferometric gravitational wave detectors. Until now, however, these instabilities have never been observed in a kilometer-scale interferometer. In this Letter, we describe the first observation of parametric instability in a gravitational wave detector, and the means by which it has been removed as a barrier to progress.

  14. A Comparison of Parametric versus Nonparametric Statistics.

    ERIC Educational Resources Information Center

    Royeen, Charlotte Brasic

    In order to examine the possible effects of violation of assumptions using parametric procedures, this study is an exploratory investigation into the use of parametric versus nonparametric procedures using a multiple case study design. The case study investigation guidelines outlined by Yin served as the methodology. The following univariate…

  15. Why preferring parametric forecasting to nonparametric methods?

    PubMed

    Jabot, Franck

    2015-05-07

    A recent series of papers by Charles T. Perretti and collaborators have shown that nonparametric forecasting methods can outperform parametric methods in noisy nonlinear systems. Such a situation can arise because of two main reasons: the instability of parametric inference procedures in chaotic systems which can lead to biased parameter estimates, and the discrepancy between the real system dynamics and the modeled one, a problem that Perretti and collaborators call "the true model myth". Should ecologists go on using the demanding parametric machinery when trying to forecast the dynamics of complex ecosystems? Or should they rely on the elegant nonparametric approach that appears so promising? It will be here argued that ecological forecasting based on parametric models presents two key comparative advantages over nonparametric approaches. First, the likelihood of parametric forecasting failure can be diagnosed thanks to simple Bayesian model checking procedures. Second, when parametric forecasting is diagnosed to be reliable, forecasting uncertainty can be estimated on virtual data generated with the fitted to data parametric model. In contrast, nonparametric techniques provide forecasts with unknown reliability. This argumentation is illustrated with the simple theta-logistic model that was previously used by Perretti and collaborators to make their point. It should convince ecologists to stick to standard parametric approaches, until methods have been developed to assess the reliability of nonparametric forecasting.

  16. Pump noise cancellation in parametric wavelength converters.

    PubMed

    Ataie, Vahid; Myslivets, Evgeny; Wiberg, Andereas O J; Alic, Nikola; Radic, Stojan

    2012-12-10

    A novel technique for pump noise effect mitigation in parametric wavelength converters is introduced. The method relies on digital signal processing and effectively takes advantage of the correlation property between the pump and idler, imposed by the parametric interaction. A 4 dB improvement in receiver performance is demonstrated experimentally for the conventional 10 Gbps OOK signal converted over 20 nm.

  17. Parametric Cost Models for Space Telescopes

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip

    2010-01-01

    A study is in-process to develop a multivariable parametric cost model for space telescopes. Cost and engineering parametric data has been collected on 30 different space telescopes. Statistical correlations have been developed between 19 variables of 59 variables sampled. Single Variable and Multi-Variable Cost Estimating Relationships have been developed. Results are being published.

  18. Literary Competence beyond Conventions.

    ERIC Educational Resources Information Center

    Torell, Orjan

    2001-01-01

    Revises the concept of "literary competence" based on the texts produced by two Russian high school students. Shows that literacy competence cannot be reduced to internalized literary conventions, although these are a fundamental component of literary competence, and proposes a model of literary competence. Also explores merits and…

  19. Thermal effects in high average power optical parametric amplifiers.

    PubMed

    Rothhardt, Jan; Demmler, Stefan; Hädrich, Steffen; Peschel, Thomas; Limpert, Jens; Tünnermann, Andreas

    2013-03-01

    Optical parametric amplifiers (OPAs) have the reputation of being average power scalable due to the instantaneous nature of the parametric process (zero quantum defect). This Letter reveals serious challenges originating from thermal load in the nonlinear crystal caused by absorption. We investigate these thermal effects in high average power OPAs based on beta barium borate. Absorption of both pump and idler waves is identified to contribute significantly to heating of the nonlinear crystal. A temperature increase of up to 148 K with respect to the environment is observed and mechanical tensile stress up to 40 MPa is found, indicating a high risk of crystal fracture under such conditions. By restricting the idler to a wavelength range far from absorption bands and removing the crystal coating we reduce the peak temperature and the resulting temperature gradient significantly. Guidelines for further power scaling of OPAs and other nonlinear devices are given.

  20. Calculations of superconducting parametric amplifiers performances

    NASA Astrophysics Data System (ADS)

    Goto, T.; Takeda, M.; Saito, S.; Shimakage, H.

    2017-07-01

    A superconducting parametric amplifier is an electromagnetic wave amplifier with high-quality characteristics such as a wide bandwidth, an extremely low noise, and a high dynamic range. In this paper, we report on the estimations of a YBCO superconducting parametric amplifier characteristic. The YBCO thin films were deposited on an MgO substrate by a pulsed laser deposition method. Based on the measured YBCO thin film parameters, theoretical calculations were implemented for evaluations of kinetic inductance nonlinearities and parametric gains. The nonlinearity of the YBCO thin film was estimated to be stronger than a single crystal NbTiN thin film. It is indicated that the YBCO parametric amplifier has a potential to be realized the amplifier with the high parametric gain. It is also expected that it could be operated in the range of the high frequency band, at the high temperature, and low applied current.

  1. Parametric and non-parametric modeling of short-term synaptic plasticity. Part I: computational study

    PubMed Central

    Marmarelis, Vasilis Z.; Berger, Theodore W.

    2009-01-01

    Parametric and non-parametric modeling methods are combined to study the short-term plasticity (STP) of synapses in the central nervous system (CNS). The nonlinear dynamics of STP are modeled by means: (1) previously proposed parametric models based on mechanistic hypotheses and/or specific dynamical processes, and (2) non-parametric models (in the form of Volterra kernels) that transforms the presynaptic signals into postsynaptic signals. In order to synergistically use the two approaches, we estimate the Volterra kernels of the parametric models of STP for four types of synapses using synthetic broadband input–output data. Results show that the non-parametric models accurately and efficiently replicate the input–output transformations of the parametric models. Volterra kernels provide a general and quantitative representation of the STP. PMID:18506609

  2. [From management competencies to nurse managerial competencies].

    PubMed

    Furukawa, Patrícia de Oliveira; Cunha, Isabel Cristina Kowal Olm

    2010-01-01

    This article is a literature review that aimed to collect more information about the competencies management, understand the concepts of profile and competencies in the managing people; understand the issue of professional competence and its relationship with the organization's competencies; and finally identify the managerial competencies necessary to work of the nurse on the aspect of the labor market. The literature showed that the concept of competence shows great results when applied in the people management arena. It also can provide in the context of health services, benefits for the organizations and for the professionals and patients. For that, it's required that health services to take the ownership of this knowledge as possibility to achieve better results, as well as educational institutions and nurses that seek for information and training to achieve the challenges of the profession and the labor market.

  3. Selected Parametric Effects on Materials Flammability Limits

    NASA Technical Reports Server (NTRS)

    Hirsch, David B.; Juarez, Alfredo; Peyton, Gary J.; Harper, Susana A.; Olson, Sandra L.

    2011-01-01

    NASA-STD-(I)-6001B Test 1 is currently used to evaluate the flammability of materials intended for use in habitable environments of U.S. spacecraft. The method is a pass/fail upward flame propagation test conducted in the worst case configuration, which is defined as a combination of a material s thickness, test pressure, oxygen concentration, and temperature that make the material most flammable. Although simple parametric effects may be intuitive (such as increasing oxygen concentrations resulting in increased flammability), combinations of multi-parameter effects could be more complex. In addition, there are a variety of material configurations used in spacecraft. Such configurations could include, for example, exposed free edges where fire propagation may be different when compared to configurations commonly employed in standard testing. Studies involving combined oxygen concentration, pressure, and temperature on flammability limits have been conducted and are summarized in this paper. Additional effects on flammability limits of a material s thickness, mode of ignition, burn-length criteria, and exposed edges are presented. The information obtained will allow proper selection of ground flammability test conditions, support further studies comparing flammability in 1-g with microgravity and reduced gravity environments, and contribute to persuasive scientific cases for rigorous space system fire risk assessments.

  4. Improvement of Statistical Decisions under Parametric Uncertainty

    NASA Astrophysics Data System (ADS)

    Nechval, Nicholas A.; Nechval, Konstantin N.; Purgailis, Maris; Berzins, Gundars; Rozevskis, Uldis

    2011-10-01

    A large number of problems in production planning and scheduling, location, transportation, finance, and engineering design require that decisions be made in the presence of uncertainty. Decision-making under uncertainty is a central problem in statistical inference, and has been formally studied in virtually all approaches to inference. The aim of the present paper is to show how the invariant embedding technique, the idea of which belongs to the authors, may be employed in the particular case of finding the improved statistical decisions under parametric uncertainty. This technique represents a simple and computationally attractive statistical method based on the constructive use of the invariance principle in mathematical statistics. Unlike the Bayesian approach, an invariant embedding technique is independent of the choice of priors. It allows one to eliminate unknown parameters from the problem and to find the best invariant decision rule, which has smaller risk than any of the well-known decision rules. To illustrate the proposed technique, application examples are given.

  5. Mixed-effects varying-coefficient model with skewed distribution coupled with cause-specific varying-coefficient hazard model with random-effects for longitudinal-competing risks data analysis.

    PubMed

    Lu, Tao; Wang, Min; Liu, Guangying; Dong, Guang-Hui; Qian, Feng

    2016-01-01

    It is well known that there is strong relationship between HIV viral load and CD4 cell counts in AIDS studies. However, the relationship between them changes during the course of treatment and may vary among individuals. During treatments, some individuals may experience terminal events such as death. Because the terminal event may be related to the individual's viral load measurements, the terminal mechanism is non-ignorable. Furthermore, there exists competing risks from multiple types of events, such as AIDS-related death and other death. Most joint models for the analysis of longitudinal-survival data developed in literatures have focused on constant coefficients and assume symmetric distribution for the endpoints, which does not meet the needs for investigating the nature of varying relationship between HIV viral load and CD4 cell counts in practice. We develop a mixed-effects varying-coefficient model with skewed distribution coupled with cause-specific varying-coefficient hazard model with random-effects to deal with varying relationship between the two endpoints for longitudinal-competing risks survival data. A fully Bayesian inference procedure is established to estimate parameters in the joint model. The proposed method is applied to a multicenter AIDS cohort study. Various scenarios-based potential models that account for partial data features are compared. Some interesting findings are presented.

  6. Characteristics of stereo reproduction with parametric loudspeakers

    NASA Astrophysics Data System (ADS)

    Aoki, Shigeaki; Toba, Masayoshi; Tsujita, Norihisa

    2012-05-01

    A parametric loudspeaker utilizes nonlinearity of a medium and is known as a super-directivity loudspeaker. The parametric loudspeaker is one of the prominent applications of nonlinear ultrasonics. So far, the applications have been limited monaural reproduction sound system for public address in museum, station and street etc. In this paper, we discussed characteristics of stereo reproduction with two parametric loudspeakers by comparing with those with two ordinary dynamic loudspeakers. In subjective tests, three typical listening positions were selected to investigate the possibility of correct sound localization in a wide listening area. The binaural information was ILD (Interaural Level Difference) or ITD (Interaural Time Delay). The parametric loudspeaker was an equilateral hexagon. The inner and outer diameters were 99 and 112 mm, respectively. Signals were 500 Hz, 1 kHz, 2 kHz and 4 kHz pure tones and pink noise. Three young males listened to test signals 10 times in each listening condition. Subjective test results showed that listeners at the three typical listening positions perceived correct sound localization of all signals using the parametric loudspeakers. It was almost similar to those using the ordinary dynamic loudspeakers, however, except for the case of sinusoidal waves with ITD. It was determined the parametric loudspeaker could exclude the contradiction between the binaural information ILD and ITD that occurred in stereo reproduction with ordinary dynamic loudspeakers because the super directivity of parametric loudspeaker suppressed the cross talk components.

  7. Using health promotion competencies for curriculum development in higher education.

    PubMed

    Madsen, Wendy; Bell, Tanya

    2012-03-01

    Health promotion core competencies are used for a variety of reasons. Recently there have been moves to gain international consensus regarding core competencies within health promotion. One of the main reasons put forward for having core competencies is to guide curriculum development within higher education institutions. This article outlines the endeavours of one institution to develop undergraduate and postgraduate curricula around the Australian core competencies for health promotion practitioners. It argues that until core competencies have been agreed upon internationally, basing curricula on these carries a risk associated with change. However, delaying curricula until such risks are ameliorated decreases opportunities to deliver dynamic and current health promotion education within higher institutions.

  8. Ionization Cooling using Parametric Resonances

    SciTech Connect

    Johnson, Rolland P.

    2008-06-07

    Ionization Cooling using Parametric Resonances was an SBIR project begun in July 2004 and ended in January 2008 with Muons, Inc., (Dr. Rolland Johnson, PI), and Thomas Jefferson National Accelerator Facility (JLab) (Dr. Yaroslav Derbenev, Subcontract PI). The project was to develop the theory and simulations of Parametric-resonance Ionization Cooling (PIC) so that it could be used to provide the extra transverse cooling needed for muon colliders in order to relax the requirements on the proton driver, reduce the site boundary radiation, and provide a better environment for experiments. During the course of the project, the theoretical understanding of PIC was developed and a final exposition is ready for publication. Workshops were sponsored by Muons, Inc. in May and September of 2007 that were devoted to the PIC technique. One outcome of the workshops was the interesting and somewhat unexpected realization that the beam emittances using the PIC technique can get small enough that space charge forces can be important. A parallel effort to develop our G4beamline simulation program to include space charge effects was initiated to address this problem. A method of compensating for chromatic aberrations by employing synchrotron motion was developed and simulated. A method of compensating for spherical aberrations using beamline symmetry was also developed and simulated. Different optics designs have been developed using the OptiM program in preparation for applying our G4beamline simulation program, which contains all the power of the Geant4 toolkit. However, no PIC channel design that has been developed has had the desired cooling performance when subjected to the complete G4beamline simulation program. This is believed to be the consequence of the difficulties of correcting the aberrations associated with the naturally large beam angles and beam sizes of the PIC method that are exacerbated by the fringe fields of the rather complicated channel designs that have been

  9. Superkids: competent children of psychotic mothers.

    PubMed

    Kauffman, C; Grunebaum, H; Cohler, B; Gamer, E

    1979-11-01

    In a follow-up study of children of psychotic mothers, the authors examined a subgroup of outstandingly talented, colorful, and competent "high-risk" children. These children and their mothers were given a variety of psychological tests and were interviewed individually. They were then compared with a control group of children whose mothers had no psychiatric illness. The 6 most socially and intellectually competent high-risk children were strikingly more competent, colorful, creative, and talented than the 6 highest functioning control children. They more often reported having a best friend and had extensive and positive contact with an extrafamilial adult. Another important variable in the prediction of high social competence among children at high risk is a warm relationship with the mother.

  10. Predictive value of beat-to-beat QT variability index across the continuum of left ventricular dysfunction: competing risks of noncardiac or cardiovascular death and sudden or nonsudden cardiac death.

    PubMed

    Tereshchenko, Larisa G; Cygankiewicz, Iwona; McNitt, Scott; Vazquez, Rafael; Bayes-Genis, Antoni; Han, Lichy; Sur, Sanjoli; Couderc, Jean-Philippe; Berger, Ronald D; de Luna, Antoni Bayes; Zareba, Wojciech

    2012-08-01

    The goal of the present study was to determine the predictive value of beat-to-beat QT variability in heart failure patients across the continuum of left ventricular dysfunction. Beat-to-beat QT variability index (QTVI), log-transformed heart rate variance, normalized QT variance, and coherence between heart rate variability and QT variability have been measured at rest during sinus rhythm in 533 participants of the Muerte Subita en Insuficiencia Cardiaca heart failure study (mean age, 63.1±11.7; men, 70.6%; left ventricular ejection fraction >35% in 254 [48%]) and in 181 healthy participants from the Intercity Digital Electrocardiogram Alliance database. During a median of 3.7 years of follow-up, 116 patients died, 52 from sudden cardiac death (SCD). In multivariate competing risk analyses, the highest QTVI quartile was associated with cardiovascular death (subhazard ratio, 1.67 [95% CI, 1.14-2.47]; P=0.009) and, in particular, with non-SCD (subhazard ratio, 2.91 [1.69-5.01]; P<0.001). Elevated QTVI separated 97.5% of healthy individuals from subjects at risk for cardiovascular (subhazard ratio, 1.57 [1.04-2.35]; P=0.031) and non-SCD in multivariate competing risk model (subhazard ratio, 2.58 [1.13-3.78]; P=0.001). No interaction between QTVI and left ventricular ejection fraction was found. QTVI predicted neither noncardiac death (P=0.546) nor SCD (P=0.945). Decreased heart rate variability rather than increased QT variability was the reason for increased QTVI in the present study. Increased QTVI because of depressed heart rate variability predicts cardiovascular mortality and non-SCD but neither SCD nor extracardiac mortality in heart failure across the continuum of left ventricular dysfunction. Abnormally augmented QTVI separates 97.5% of healthy individuals from heart failure patients at risk.

  11. Predictive Value of Beat-to-Beat QT Variability Index across the Continuum of Left Ventricular Dysfunction: Competing Risks of Non-cardiac or Cardiovascular Death, and Sudden or Non-Sudden Cardiac Death

    PubMed Central

    Tereshchenko, Larisa G.; Cygankiewicz, Iwona; McNitt, Scott; Vazquez, Rafael; Bayes-Genis, Antoni; Han, Lichy; Sur, Sanjoli; Couderc, Jean-Philippe; Berger, Ronald D.; de Luna, Antoni Bayes; Zareba, Wojciech

    2012-01-01

    Background The goal of this study was to determine the predictive value of beat-to-beat QT variability in heart failure (HF) patients across the continuum of left ventricular dysfunction. Methods and Results Beat-to-beat QT variability index (QTVI), heart rate variance (LogHRV), normalized QT variance (QTVN), and coherence between heart rate variability and QT variability have been measured at rest during sinus rhythm in 533 participants of the Muerte Subita en Insuficiencia Cardiaca (MUSIC) HF study (mean age 63.1±11.7; males 70.6%; LVEF >35% in 254 [48%]) and in 181 healthy participants from the Intercity Digital Electrocardiogram Alliance (IDEAL) database. During a median of 3.7 years of follow-up, 116 patients died, 52 from sudden cardiac death (SCD). In multivariate competing risk analyses, the highest QTVI quartile was associated with cardiovascular death [hazard ratio (HR) 1.67(95%CI 1.14-2.47), P=0.009] and in particular with non-sudden cardiac death [HR 2.91(1.69-5.01), P<0.001]. Elevated QTVI separated 97.5% of healthy individuals from subjects at risk for cardiovascular [HR 1.57(1.04-2.35), P=0.031], and non-sudden cardiac death in multivariate competing risk model [HR 2.58(1.13-3.78), P=0.001]. No interaction between QTVI and LVEF was found. QTVI predicted neither non-cardiac death (P=0.546) nor SCD (P=0.945). Decreased heart rate variability (HRV) rather than increased QT variability was the reason for increased QTVI in this study. Conclusions Increased QTVI due to depressed HRV predicts cardiovascular mortality and non-sudden cardiac death, but neither SCD nor excracardiac mortality in HF across the continuum of left ventricular dysfunction. Abnormally augmented QTVI separates 97.5% of healthy individuals from HF patients at risk. PMID:22730411

  12. Self-seeding ring optical parametric oscillator

    DOEpatents

    Smith, Arlee V.; Armstrong, Darrell J.

    2005-12-27

    An optical parametric oscillator apparatus utilizing self-seeding with an external nanosecond-duration pump source to generate a seed pulse resulting in increased conversion efficiency. An optical parametric oscillator with a ring configuration are combined with a pump that injection seeds the optical parametric oscillator with a nanosecond duration, mJ pulse in the reverse direction as the main pulse. A retroreflecting means outside the cavity injects the seed pulse back into the cavity in the direction of the main pulse to seed the main pulse, resulting in higher conversion efficiency.

  13. Airy beam optical parametric oscillator

    NASA Astrophysics Data System (ADS)

    Aadhi, A.; Chaitanya, N. Apurv; Jabir, M. V.; Vaity, Pravin; Singh, R. P.; Samanta, G. K.

    2016-05-01

    Airy beam, a non-diffracting waveform, has peculiar properties of self-healing and self-acceleration. Due to such unique properties, the Airy beam finds many applications including curved plasma wave-guiding, micro-particle manipulation, optically mediated particle clearing, long distance communication, and nonlinear frequency conversion. However, many of these applications including laser machining of curved structures, generation of curved plasma channels, guiding of electric discharges in a curved path, study of nonlinear propagation dynamics, and nonlinear interaction demand Airy beam with high power, energy, and wavelength tunability. Till date, none of the Airy beam sources have all these features in a single device. Here, we report a new class of coherent sources based on cubic phase modulation of a singly-resonant optical parametric oscillator (OPO), producing high-power, continuous-wave (cw), tunable radiation in 2-D Airy intensity profile existing over a length >2 m. Based on a MgO-doped periodically poled LiNbO3 crystal pumped at 1064 nm, the Airy beam OPO produces output power more than 8 W, and wavelength tunability across 1.51–1.97 μm. This demonstration gives new direction for the development of sources of arbitrary structured beams at any wavelength, power, and energy in all time scales (cw to femtosecond).

  14. Airy beam optical parametric oscillator

    PubMed Central

    Aadhi, A.; Chaitanya, N. Apurv; Jabir, M. V.; Vaity, Pravin; Singh, R. P.; Samanta, G. K.

    2016-01-01

    Airy beam, a non-diffracting waveform, has peculiar properties of self-healing and self-acceleration. Due to such unique properties, the Airy beam finds many applications including curved plasma wave-guiding, micro-particle manipulation, optically mediated particle clearing, long distance communication, and nonlinear frequency conversion. However, many of these applications including laser machining of curved structures, generation of curved plasma channels, guiding of electric discharges in a curved path, study of nonlinear propagation dynamics, and nonlinear interaction demand Airy beam with high power, energy, and wavelength tunability. Till date, none of the Airy beam sources have all these features in a single device. Here, we report a new class of coherent sources based on cubic phase modulation of a singly-resonant optical parametric oscillator (OPO), producing high-power, continuous-wave (cw), tunable radiation in 2-D Airy intensity profile existing over a length >2 m. Based on a MgO-doped periodically poled LiNbO3 crystal pumped at 1064 nm, the Airy beam OPO produces output power more than 8 W, and wavelength tunability across 1.51–1.97 μm. This demonstration gives new direction for the development of sources of arbitrary structured beams at any wavelength, power, and energy in all time scales (cw to femtosecond). PMID:27143582

  15. Airy beam optical parametric oscillator.

    PubMed

    Aadhi, A; Chaitanya, N Apurv; Jabir, M V; Vaity, Pravin; Singh, R P; Samanta, G K

    2016-05-04

    Airy beam, a non-diffracting waveform, has peculiar properties of self-healing and self-acceleration. Due to such unique properties, the Airy beam finds many applications including curved plasma wave-guiding, micro-particle manipulation, optically mediated particle clearing, long distance communication, and nonlinear frequency conversion. However, many of these applications including laser machining of curved structures, generation of curved plasma channels, guiding of electric discharges in a curved path, study of nonlinear propagation dynamics, and nonlinear interaction demand Airy beam with high power, energy, and wavelength tunability. Till date, none of the Airy beam sources have all these features in a single device. Here, we report a new class of coherent sources based on cubic phase modulation of a singly-resonant optical parametric oscillator (OPO), producing high-power, continuous-wave (cw), tunable radiation in 2-D Airy intensity profile existing over a length >2 m. Based on a MgO-doped periodically poled LiNbO3 crystal pumped at 1064 nm, the Airy beam OPO produces output power more than 8 W, and wavelength tunability across 1.51-1.97 μm. This demonstration gives new direction for the development of sources of arbitrary structured beams at any wavelength, power, and energy in all time scales (cw to femtosecond).

  16. Parametric display of myocardial function.

    PubMed

    Eusemann, C D; Ritman, E L; Bellemann, M E; Robb, R A

    2001-01-01

    Quantitative assessment of regional heart motion has significant potential to provide more specific diagnosis of cardiac disease and cardiac malfunction than currently possible. Local heart motion may be captured from various medical imaging scanners. In this study, 3-D reconstructions of pre-infarct and post-infarct hearts were obtained from the Dynamic Spatial Reconstructor (DSR)[Ritman EL, Robb RA, Harris LD. Imaging physiological functions: experience with DSR. Philadelphia: Praeger, 1985; Robb RA, Lent AH, Gilbert BK, Chu A. The dynamic spatial reconstructor: a computed tomography system for high-speed simultaneous scanning of multiple cross sections of the heart. J Med Syst 1980;4(2):253-88; Jorgensen SM, Whitlock SV, Thomas PJ, Roessler RW, Ritman EL. The dynamic spatial reconstructor: a high speed, stop action, 3-D, digital radiographic imager of moving internal organs and blood. Proceedings of SPIE, Ultrahigh- and High-speed Photography, Videography, Photonics, and Velocimetry 1990;1346:180-91.] (DSR). Using functional parametric mapping of disturbances in regional contractility and relaxation, regional myocardial motion during a cardiac cycle is color mapped onto a deformable heart model to facilitate appreciation of the structure-to-function relationships in the myocardium, such as occurs in regional patterns of akinesis or dyskinesis associated with myocardial ischemia or infarction resulting from coronary artery occlusion.

  17. Parametrically enhanced hidden photon search

    NASA Astrophysics Data System (ADS)

    Graham, Peter W.; Mardon, Jeremy; Rajendran, Surjeet; Zhao, Yue

    2014-10-01

    Many theories beyond the Standard Model contain hidden photons. A light hidden photon will generically couple to the Standard Model through a kinetic mixing term, giving a powerful avenue for detection using "light-shining-through-a-wall"-type transmission experiments with resonant cavities. We demonstrate a parametric enhancement of the signal in such experiments, resulting from transmission of the longitudinal mode of the hidden photon. While previous literature has focused on the production and detection of transverse modes, the longitudinal mode allows a significant improvement in experimental sensitivity. Although optical experiments such as ALPS are unable to take useful advantage of this enhancement, the reach of existing microwave cavity experiments such as CROWS is significantly enhanced beyond their published results. Future microwave cavity experiments, designed with appropriate geometry to take full advantage of the longitudinal mode, will provide a powerful probe of hidden-photon parameter space extending many orders of magnitude beyond current limits, including significant regions where the hidden photon can be dark matter.

  18. Generating Entangled State with Parametric Amplifier

    NASA Astrophysics Data System (ADS)

    Huang, Jian

    2017-04-01

    We present a scheme for generating entangled state with parametric amplifier with different initial states. Its shown that the entangled state is always generated except some special cases by adjusting the coupling strength and the total number of photons.

  19. Ranking Forestry Investments With Parametric Linear Programming

    Treesearch

    Paul A. Murphy

    1976-01-01

    Parametric linear programming is introduced as a technique for ranking forestry investments under multiple constraints; it combines the advantages of simple tanking and linear programming as capital budgeting tools.

  20. Conformally covariant parametrizations for relativistic initial data

    NASA Astrophysics Data System (ADS)

    Delay, Erwann

    2017-01-01

    We revisit the Lichnerowicz-York method, and an alternative method of York, in order to obtain some conformally covariant systems. This type of parametrization is certainly more natural for non constant mean curvature initial data.

  1. Parametrically disciplined operation of a vibratory gyroscope

    NASA Technical Reports Server (NTRS)

    Shcheglov, Kirill V. (Inventor); Hayworth, Ken J. (Inventor); Challoner, A. Dorian (Inventor); Peay, Chris S. (Inventor)

    2008-01-01

    Parametrically disciplined operation of a symmetric nearly degenerate mode vibratory gyroscope is disclosed. A parametrically-disciplined inertial wave gyroscope having a natural oscillation frequency in the neighborhood of a sub-harmonic of an external stable clock reference is produced by driving an electrostatic bias electrode at approximately twice this sub-harmonic frequency to achieve disciplined frequency and phase operation of the resonator. A nearly symmetric parametrically-disciplined inertial wave gyroscope that can oscillate in any transverse direction and has more than one bias electrostatic electrode that can be independently driven at twice its oscillation frequency at an amplitude and phase that disciplines its damping to zero in any vibration direction. In addition, operation of a parametrically-disciplined inertial wave gyroscope is taught in which the precession rate of the driven vibration pattern is digitally disciplined to a prescribed non-zero reference value.

  2. A Parametric k-Means Algorithm

    PubMed Central

    Tarpey, Thaddeus

    2007-01-01

    Summary The k points that optimally represent a distribution (usually in terms of a squared error loss) are called the k principal points. This paper presents a computationally intensive method that automatically determines the principal points of a parametric distribution. Cluster means from the k-means algorithm are nonparametric estimators of principal points. A parametric k-means approach is introduced for estimating principal points by running the k-means algorithm on a very large simulated data set from a distribution whose parameters are estimated using maximum likelihood. Theoretical and simulation results are presented comparing the parametric k-means algorithm to the usual k-means algorithm and an example on determining sizes of gas masks is used to illustrate the parametric k-means algorithm. PMID:17917692

  3. A Parametric k-Means Algorithm.

    PubMed

    Tarpey, Thaddeus

    2007-04-01

    The k points that optimally represent a distribution (usually in terms of a squared error loss) are called the k principal points. This paper presents a computationally intensive method that automatically determines the principal points of a parametric distribution. Cluster means from the k-means algorithm are nonparametric estimators of principal points. A parametric k-means approach is introduced for estimating principal points by running the k-means algorithm on a very large simulated data set from a distribution whose parameters are estimated using maximum likelihood. Theoretical and simulation results are presented comparing the parametric k-means algorithm to the usual k-means algorithm and an example on determining sizes of gas masks is used to illustrate the parametric k-means algorithm.

  4. Competencies: A New Sector.

    ERIC Educational Resources Information Center

    Brophy, Monica; Kiely, Tony

    2002-01-01

    Job analysis of managers in 42 Irish three-star hotels identified the following key management competencies and associated behavioral indicators. The results were used to develop a competency framework for management development. (Contains 29 references.) (SK)

  5. Putting Competencies to Work.

    ERIC Educational Resources Information Center

    Zemke, Ron; Zemke, Susan

    1999-01-01

    Competency modeling is an attempt to describe work and jobs in a broader, more comprehensive way. Some organizations are restructuring their performance-management systems (interviewing, selecting, developing, rewarding, recognizing) around competence models. (SK)

  6. Competencies: A New Sector.

    ERIC Educational Resources Information Center

    Brophy, Monica; Kiely, Tony

    2002-01-01

    Job analysis of managers in 42 Irish three-star hotels identified the following key management competencies and associated behavioral indicators. The results were used to develop a competency framework for management development. (Contains 29 references.) (SK)

  7. The Quantum Theory of Optical Parametric Amplification

    NASA Astrophysics Data System (ADS)

    Hussain, N. A.

    Available from UMI in association with The British Library. Requires signed TDF. The aim of this thesis is to investigate the effect of parametric amplification on various forms of light. In particular we shall consider number and coherent states, but many of the calculations hold for those states whose operators satisfy the properties, < {a}^+{a}^+ >=<{a}{a }> = < {a}^+>=<{a }>=0 e.g. chaotic light. The first chapter lays down the fundamental preliminaries necessary for our calculations and reviews linear amplifier theory. We consider the phase sensitive and insensitive forms of amplifiers modelling the former on the degenerate parametric amplifier and the latter on the non-degenerate and inverted population amplifiers. Chapter 2 deals with balanced homodyne detection of a narrow band coherent state before and after degenerate parametric amplification. In chapter 3 we consider a continuous mode number state produced by atomic emission and parametrically amplified using the formalism of Collett and Gardiner. We give general results for the output flux intensity and also consider the simpler case where the atomic decay rate is much smaller than the parametric cavity decay rate. Also we consider the degree of second order coherence using this simplified theory. Chapters 4 and 5 consider the double amplifier interferometer, using single and continuous mode theories, and enable us to determine the form of amplifier which produces the best visibility and hence lowest noise figures. The travelling-wave parametric amplifier is discussed in chapter 6 and is contrasted with the cavity parametric amplifier discussed in chapters 1 and 2. Finally we consider the much contemplated idea of using amplifiers to boost signals in fibre optic transmission lines using our model of the parametric amplifier and examining the degradation of the signal-to-noise ratio. We consider both coherent and squeezed inputs and our results hold for both cavity and travelling -wave amplifiers.

  8. Chaos control of parametric driven Duffing oscillators

    SciTech Connect

    Jin, Leisheng; Mei, Jie; Li, Lijie

    2014-03-31

    Duffing resonators are typical dynamic systems, which can exhibit chaotic oscillations, subject to certain driving conditions. Chaotic oscillations of resonating systems with negative and positive spring constants are identified to investigate in this paper. Parametric driver imposed on these two systems affects nonlinear behaviours, which has been theoretically analyzed with regard to variation of driving parameters (frequency, amplitude). Systematic calculations have been performed for these two systems driven by parametric pumps to unveil the controllability of chaos.

  9. Chaos control of parametric driven Duffing oscillators

    NASA Astrophysics Data System (ADS)

    Jin, Leisheng; Mei, Jie; Li, Lijie

    2014-03-01

    Duffing resonators are typical dynamic systems, which can exhibit chaotic oscillations, subject to certain driving conditions. Chaotic oscillations of resonating systems with negative and positive spring constants are identified to investigate in this paper. Parametric driver imposed on these two systems affects nonlinear behaviours, which has been theoretically analyzed with regard to variation of driving parameters (frequency, amplitude). Systematic calculations have been performed for these two systems driven by parametric pumps to unveil the controllability of chaos.

  10. NON-PARAMETRIC ESTIMATION UNDER STRONG DEPENDENCE

    PubMed Central

    Zhao, Zhibiao; Zhang, Yiyun; Li, Runze

    2014-01-01

    We study non-parametric regression function estimation for models with strong dependence. Compared with short-range dependent models, long-range dependent models often result in slower convergence rates. We propose a simple differencing-sequence based non-parametric estimator that achieves the same convergence rate as if the data were independent. Simulation studies show that the proposed method has good finite sample performance. PMID:25018572

  11. Theory of Parametric Amplification in Superlattices

    NASA Astrophysics Data System (ADS)

    Hyart, Timo; Shorokhov, Alexey V.; Alekseev, Kirill N.

    2007-06-01

    We consider a high-frequency response of electrons in a single miniband of superlattice subject to dc and ac electric fields. We show that Bragg reflections in miniband result in a parametric resonance which is detectable using ac probe field. We establish theoretical feasibility of phase-sensitive THz amplification at the resonance. The parametric amplification does not require operation in conditions of negative differential conductance. This prevents a formation of destructive domains of high electric field inside the superlattice.

  12. NON-PARAMETRIC ESTIMATION UNDER STRONG DEPENDENCE.

    PubMed

    Zhao, Zhibiao; Zhang, Yiyun; Li, Runze

    2014-01-01

    We study non-parametric regression function estimation for models with strong dependence. Compared with short-range dependent models, long-range dependent models often result in slower convergence rates. We propose a simple differencing-sequence based non-parametric estimator that achieves the same convergence rate as if the data were independent. Simulation studies show that the proposed method has good finite sample performance.

  13. Competency-based training: who benefits?

    PubMed

    Brightwell, Alexandra; Grant, Janet

    2013-02-01

    Competency based training describes progression through training referenced to the demonstrated ability to perform certain tasks. In recent years, this has become the dominant curriculum model. We seek to examine who benefits from a competency based approach to medical education. For the regulators and service, the apparent advantage is in terms of apparent measurable accountability and flexibility. For assessors, the promise of competence based assessments in the workplace to provide a reliable and objective measurement of a trainee's performance has not been demonstrated in practice. For the doctor in training, there is very little evidence to show benefit from competency based training. Competency based training places emphasis on individual skills rather than overall learning experience thus risks diminishing the role of the trainee in the workplace. Any form of medical education that devalues workplace based learning will ultimately harm the profession and, in turn, patient care.

  14. Do Students Expect Compensation for Wage Risk?

    ERIC Educational Resources Information Center

    Schweri, Juerg; Hartog, Joop; Wolter, Stefan C.

    2011-01-01

    We use a unique data set about the wage distribution that Swiss students expect for themselves ex ante, deriving parametric and non-parametric measures to capture expected wage risk. These wage risk measures are unfettered by heterogeneity which handicapped the use of actual market wage dispersion as risk measure in earlier studies. Students in…

  15. Do Students Expect Compensation for Wage Risk?

    ERIC Educational Resources Information Center

    Schweri, Juerg; Hartog, Joop; Wolter, Stefan C.

    2011-01-01

    We use a unique data set about the wage distribution that Swiss students expect for themselves ex ante, deriving parametric and non-parametric measures to capture expected wage risk. These wage risk measures are unfettered by heterogeneity which handicapped the use of actual market wage dispersion as risk measure in earlier studies. Students in…

  16. Competencies in Science Teaching

    ERIC Educational Resources Information Center

    Mathelitsch, Leopold

    2013-01-01

    The role of competencies is discussed with respect to science teaching. In particular, competence models from Germany, Switzerland and Austria are presented and compared. A special topical program, "Competencies in Mathematics and Science Teaching", was started in Austria three years ago. Initial experiences with this program are…

  17. Competencies for Articulation: Drafting.

    ERIC Educational Resources Information Center

    Southeast Community Coll., Lincoln, NE.

    Designed to help articulate vocational education student progress from one level of training to another and to employment, this drafting guide lists competencies for a core curriculum prerequisite to all drafting areas and competencies for machine, architectural, and civil drafting. The format for each competency is task statement, list of…

  18. On Topological Structures of Fuzzy Parametrized Soft Sets

    PubMed Central

    Zorlutuna, İdris

    2014-01-01

    We introduce the topological structure of fuzzy parametrized soft sets and fuzzy parametrized soft mappings. We define the notion of quasi-coincidence for fuzzy parametrized soft sets and investigated its basic properties. We study the closure, interior, base, continuity, and compactness and properties of these concepts in fuzzy parametrized soft topological spaces. PMID:24955386

  19. Application of Parametric Models to a Survival Analysis of Hemodialysis Patients

    PubMed Central

    Montaseri, Maryam; Charati, Jamshid Yazdani; Espahbodi, Fateme

    2016-01-01

    Background Hemodialysis is the most common renal replacement therapy in patients with end stage renal disease (ESRD). Objectives The present study compared the performance of various parametric models in a survival analysis of hemodialysis patients. Methods This study consisted of 270 hemodialysis patients who were referred to Imam Khomeini and Fatima Zahra hospitals between November 2007 and November 2012. The Akaike information criterion (AIC) and residuals review were used to compare the performance of the parametric models. The computations were done using STATA Software, with significance accepted at a level of 0.05. Results The results of a multivariate analysis of the variables in the parametric models showed that the mean serum albumin and the clinic attended were the most important predictors in the survival of the hemodialysis patients (P < 0.05). Among the parametric models tested, the results indicated that the performance of the Weibull model was the highest. Conclusions Parametric models may provide complementary data for clinicians and researchers about how risks vary over time. The Weibull model seemed to show the best fit among the parametric models of the survival of hemodialysis patients. PMID:27896235

  20. Model reduction techniques for fast blood flow simulation in parametrized geometries.

    PubMed

    Manzoni, Andrea; Quarteroni, Alfio; Rozza, Gianluigi

    2012-01-01

    In this paper, we propose a new model reduction technique aimed at real-time blood flow simulations on a given family of geometrical shapes of arterial vessels. Our approach is based on the combination of a low-dimensional shape parametrization of the computational domain and the reduced basis method to solve the associated parametrized flow equations. We propose a preliminary analysis carried on a set of arterial vessel geometries, described by means of a radial basis functions parametrization. In order to account for patient-specific arterial configurations, we reconstruct the latter by solving a suitable parameter identification problem. Real-time simulation of blood flows are thus performed on each reconstructed parametrized geometry, by means of the reduced basis method. We focus on a family of parametrized carotid artery bifurcations, by modelling blood flows using Navier-Stokes equations and measuring distributed outputs such as viscous energy dissipation or vorticity. The latter are indexes that might be correlated with the assessment of pathological risks. The approach advocated here can be applied to a broad variety of (different) flow problems related with geometry/shape variation, for instance related with shape sensitivity analysis, parametric exploration and shape design. Copyright © 2011 John Wiley & Sons, Ltd.

  1. Competing Risk Analysis of Neurologic versus Nonneurologic Death in Patients Undergoing Radiosurgical Salvage After Whole-Brain Radiation Therapy Failure: Who Actually Dies of Their Brain Metastases?

    SciTech Connect

    Lucas, John T.; Colmer, Hentry G.; White, Lance; Fitzgerald, Nora; Isom, Scott; Bourland, John D.; Laxton, Adrian W.; Tatter, Stephen B.; Chan, Michael D.

    2015-08-01

    Purpose: To estimate the hazard for neurologic (central nervous system, CNS) and nonneurologic (non-CNS) death associated with patient, treatment, and systemic disease status in patients receiving stereotactic radiosurgery after whole-brain radiation therapy (WBRT) failure, using a competing risk model. Patients and Methods: Of 757 patients, 293 experienced recurrence or new metastasis following WBRT. Univariate Cox proportional hazards regression identified covariates for consideration in the multivariate model. Competing risks multivariable regression was performed to estimate the adjusted hazard ratio (aHR) and 95% confidence interval (CI) for both CNS and non-CNS death after adjusting for patient, disease, and treatment factors. The resultant model was converted into an online calculator for ease of clinical use. Results: The cumulative incidence of CNS and non-CNS death at 6 and 12 months was 20.6% and 21.6%, and 34.4% and 35%, respectively. Patients with melanoma histology (relative to breast) (aHR 2.7, 95% CI 1.5-5.0), brainstem location (aHR 2.1, 95% CI 1.3-3.5), and number of metastases (aHR 1.09, 95% CI 1.04-1.2) had increased aHR for CNS death. Progressive systemic disease (aHR 0.55, 95% CI 0.4-0.8) and increasing lowest margin dose (aHR 0.97, 95% CI 0.9-0.99) were protective against CNS death. Patients with lung histology (aHR 1.3, 95% CI 1.1-1.9) and progressive systemic disease (aHR 2.14, 95% CI 1.5-3.0) had increased aHR for non-CNS death. Conclusion: Our nomogram provides individual estimates of neurologic death after salvage stereotactic radiosurgery for patients who have failed prior WBRT, based on histology, neuroanatomical location, age, lowest margin dose, and number of metastases after adjusting for their competing risk of death from other causes.

  2. Acetabular revision with impaction bone grafting and a cemented polyethylene acetabular component: comparison of the Kaplan-Meier analysis to the competing risk analysis in 62 revisions with 25 to 30 years follow-up.

    PubMed

    Te Stroet, M A J; Keurentjes, J C; Rijnen, W H C; Gardeniers, J W M; Verdonschot, N; Slooff, T J J H; Schreurs, B W

    2015-10-01

    We present the results of 62 consecutive acetabular revisions using impaction bone grafting and a cemented polyethylene acetabular component in 58 patients (13 men and 45 women) after a mean follow-up of 27 years (25 to 30). All patients were prospectively followed. The mean age at revision was 59.2 years (23 to 82). We performed Kaplan-Meier (KM) analysis and also a Competing Risk (CR) analysis because with long-term follow-up, the presence of a competing event (i.e. death) prevents the occurrence of the endpoint of re-revision. A total of 48 patients (52 hips) had died or had been re-revised at final review in March 2011. None of the deaths were related to the surgery. The mean Harris hip score of the ten surviving hips in ten patients was 76 points (45 to 99). The KM survivorship at 25 years for the endpoint 're-revision for any reason' was 58.0% (95% confidence interval (CI) 38 to 73) and for 're-revision for aseptic loosening' 72.1% (95% CI 51 to 85). With the CR analysis we calculated the KM analysis overestimates the failure rate with respectively 74% and 93% for these endpoints. The current study shows that acetabular impaction bone grafting revisions provide good clinical results at over 25 years.

  3. Parametrizing arbitrary galaxy morphologies: potentials and pitfalls

    NASA Astrophysics Data System (ADS)

    Andrae, René; Jahnke, Knud; Melchior, Peter

    2011-02-01

    Given the enormous galaxy data bases of modern sky surveys, parametrizing galaxy morphologies is a very challenging task due to the huge number and variety of objects. We assess the different problems faced by existing parametrization schemes (CAS, Gini, M20, Sérsic profile, shapelets) in an attempt to understand why parametrization is so difficult and in order to suggest improvements for future parametrization schemes. We demonstrate that morphological observables (e.g. steepness of the radial light profile, ellipticity, asymmetry) are intertwined and cannot be measured independently of each other. We present strong arguments in favour of model-based parametrization schemes, namely reliability assessment, disentanglement of morphological observables and point spread function modelling. Furthermore, we demonstrate that estimates of the concentration and Sérsic index obtained from the Zurich Structure & Morphology catalogue are in excellent agreement with theoretical predictions. We also demonstrate that the incautious use of the concentration index for classification purposes can cause a severe loss of the discriminative information contained in a given data sample. Moreover, we show that, for poorly resolved galaxies, concentration index and M20 suffer from strong discontinuities, i.e. similar morphologies are not necessarily mapped to neighbouring points in the parameter space. This limits the reliability of these parameters for classification purposes. Two-dimensional Sérsic profiles accounting for centroid and ellipticity are identified as the currently most reliable parametrization scheme in the regime of intermediate signal-to-noise ratios and resolutions, where asymmetries and substructures do not play an important role. We argue that basis functions provide good parametrization schemes in the regimes of high signal-to-noise ratios and resolutions. Concerning Sérsic profiles, we show that scale radii cannot be compared directly for profiles of different

  4. Fiber-optic parametric amplifier and oscillator based on intracavity parametric pump technique.

    PubMed

    Luo, Zhengqian; Zhong, Wen-De; Tang, Ming; Cai, Zhiping; Ye, Chenchun; Xiao, Xiaosheng

    2009-01-15

    A cost-effective fiber optical parametric amplifier (FOPA) based on the laser intracavity pump technique has been proposed and demonstrated experimentally. The parametric process is realized by inserting a 1 km highly nonlinear dispersion-shifted fiber (HNL-DSF) into a fiber ring-laser cavity that consists of a high-power erbium-doped fiber (EDF) amplifier and two highly reflective fiber Bragg gratings. Compared with the conventional parametric pump schemes, the proposed pumping technique is free from a tunable semiconductor laser as the pump source and also the pump phase modulation. When the oscillating power of 530 mW in the EDF laser cavity is achieved to pump the HNL-DSF, a peak parametric gain of 27.5 dB and a net gain over 45 nm are obtained. Moreover, a widely tunable fiber-optic parametric oscillator is further developed using the FOPA as a gain medium.

  5. Optimization of noncollinear optical parametric amplification

    NASA Astrophysics Data System (ADS)

    Schimpf, D. N.; Rothardt, J.; Limpert, J.; Tünnermann, A.

    2007-02-01

    Noncollinearly phase-matched optical parametric amplifiers (NOPAs) - pumped with the green light of a frequency doubled Yb-doped fiber-amplifier system 1, 2 - permit convenient generation of ultrashort pulses in the visible (VIS) and near infrared (NIR) 3. The broad bandwidth of the parametric gain via the noncollinear pump configuration allows amplification of few-cycle optical pulses when seeded with a spectrally flat, re-compressible signal. The short pulses tunable over a wide region in the visible permit transcend of frontiers in physics and lifescience. For instance, the resulting high temporal resolution is of significance for many spectroscopic techniques. Furthermore, the high magnitudes of the peak-powers of the produced pulses allow research in high-field physics. To understand the demands of noncollinear optical parametric amplification using a fiber pump source, it is important to investigate this configuration in detail 4. An analysis provides not only insight into the parametric process but also determines an optimal choice of experimental parameters for the objective. Here, the intention is to design a configuration which yields the shortest possible temporal pulse. As a consequence of this analysis, the experimental setup could be optimized. A number of aspects of optical parametric amplifier performance have been treated analytically and computationally 5, but these do not fully cover the situation under consideration here.

  6. Grating lobe elimination in steerable parametric loudspeaker.

    PubMed

    Shi, Chuang; Gan, Woon-Seng

    2011-02-01

    In the past two decades, the majority of research on the parametric loudspeaker has concentrated on the nonlinear modeling of acoustic propagation and pre-processing techniques to reduce nonlinear distortion in sound reproduction. There are, however, very few studies on directivity control of the parametric loudspeaker. In this paper, we propose an equivalent circular Gaussian source array that approximates the directivity characteristics of the linear ultrasonic transducer array. By using this approximation, the directivity of the sound beam from the parametric loudspeaker can be predicted by the product directivity principle. New theoretical results, which are verified through measurements, are presented to show the effectiveness of the delay-and-sum beamsteering structure for the parametric loudspeaker. Unlike the conventional loudspeaker array, where the spacing between array elements must be less than half the wavelength to avoid spatial aliasing, the parametric loudspeaker can take advantage of grating lobe elimination to extend the spacing of ultrasonic transducer array to more than 1.5 wavelengths in a typical application.

  7. Parametric wavelength conversion in photonic crystal fibers

    NASA Astrophysics Data System (ADS)

    Yang, Sigang; Wu, Zhaohui; Yang, Yi; Chen, Minghua; Xie, Shizhong

    2016-11-01

    Nonlinear wavelength conversion provides flexible solutions for generating wideband tunable radiation in novel wavelength band. Parametric process in photonic crystal fibers (PCFs) has attracted comprehensive interests since it can act as broadband tunable light sources in non-conventional wavelength bands. The current state-of-the-art photonic crystal fibers can provide more freedom for customizing the dispersion and nonlinearity which is critical to the nonlinear process, such as four wave mixing (FWM), compared with the traditional fibers fabricated with doping techniques. Here we demonstrate broadband parametric wavelength conversion in our homemade photonic crystal fibers. The zero dispersion wavelength (ZDW) of PCFs is critical for the requirement of phase matching condition in the parametric four wave mixing process. Firstly a procedure of the theoretical design of PCF with the ZDW at 1060 nm is proposed through our homemade simulation software. A group of PCF samples with gradually variable parameters are fabricated according to the theoretical design. The broadband parametric gain around 1060 nm band is demonstrated pumped with our homemade mode locked fiber laser in the anomalous dispersion region. Also a narrow gain band with very large wavelength detune with the pump wavelength in the normal dispersion region is realized. Wavelength conversion with a span of 194 nm is realized. Furthermore a fiber optical parametric oscillator based on the fabricated PCF is built up. A wavelength tunable range as high as 340 nm is obtained. This report demonstrates a systematic procedure to realize wide band wavelength conversion based on PCFs.

  8. Phase noise suppression through parametric filtering

    NASA Astrophysics Data System (ADS)

    Cassella, Cristian; Strachan, Scott; Shaw, Steven W.; Piazza, Gianluca

    2017-02-01

    In this work, we introduce and experimentally demonstrate a parametric phase noise suppression technique, which we call "parametric phase noise filtering." This technique is based on the use of a solid-state parametric amplifier operating in its instability region and included in a non-autonomous feedback loop connected at the output of a noisy oscillator. We demonstrate that such a system behaves as a parametrically driven Duffing resonator and can operate at special points where it becomes largely immune to the phase fluctuations that affect the oscillator output signal. A prototype of a parametric phase noise filter (PFIL) was designed and fabricated to operate in the very-high-frequency range. The PFIL prototype allowed us to significantly reduce the phase noise at the output of a commercial signal generator operating around 220 MHz. Noise reduction of 16 dB (40×) and 13 dB (20×) were obtained, respectively, at 1 and 10 kHz offsets from the carrier frequency. The demonstration of this phase noise suppression technique opens up scenarios in the development of passive and low-cost phase noise cancellation circuits for any application demanding high quality frequency generation.

  9. Parametric resonance in tunable superconducting cavities

    NASA Astrophysics Data System (ADS)

    Wustmann, Waltraut; Shumeiko, Vitaly

    2013-05-01

    We develop a theory of parametric resonance in tunable superconducting cavities. The nonlinearity introduced by the superconducting quantum interference device (SQUID) attached to the cavity and damping due to connection of the cavity to a transmission line are taken into consideration. We study in detail the nonlinear classical dynamics of the cavity field below and above the parametric threshold for the degenerate parametric resonance, featuring regimes of multistability and parametric radiation. We investigate the phase-sensitive amplification of external signals on resonance, as well as amplification of detuned signals, and relate the amplifier performance to that of linear parametric amplifiers. We also discuss applications of the device for dispersive qubit readout. Beyond the classical response of the cavity, we investigate small quantum fluctuations around the amplified classical signals. We evaluate the noise power spectrum both for the internal field in the cavity and the output field. Other quantum-statistical properties of the noise are addressed such as squeezing spectra, second-order coherence, and two-mode entanglement.

  10. Ku band low noise parametric amplifier

    NASA Technical Reports Server (NTRS)

    1976-01-01

    A low noise, K sub u-band, parametric amplifier (paramp) was developed. The unit is a spacecraft-qualifiable, prototype, parametric amplifier for eventual application in the shuttle orbiter. The amplifier was required to have a noise temperature of less than 150 K. A noise temperature of less than 120 K at a gain level of 17 db was achieved. A 3-db bandwidth in excess of 350 MHz was attained, while deviation from phase linearity of about + or - 1 degree over 50 MHz was achieved. The paramp operates within specification over an ambient temperature range of -5 C to +50 C. The performance requirements and the operation of the K sub u-band parametric amplifier system are described. The final test results are also given.

  11. Parametric modelling of a knee joint prosthesis.

    PubMed

    Khoo, L P; Goh, J C; Chow, S L

    1993-01-01

    This paper presents an approach for the establishment of a parametric model of knee joint prosthesis. Four different sizes of a commercial prosthesis are used as an example in the study. A reverse engineering technique was employed to reconstruct the prosthesis on CATIA, a CAD (computer aided design) system. Parametric models were established as a result of the analysis. Using the parametric model established and the knee data obtained from a clinical study on 21 pairs of cadaveric Asian knees, the development of a prototype prosthesis that suits a patient with a very small knee joint is presented. However, it was found that modification to certain parameters may be inevitable due to the uniqueness of the Asian knee. An avenue for rapid modelling and eventually economical production of a customized knee joint prosthesis for patients is proposed and discussed.

  12. Modeling personnel turnover in the parametric organization

    NASA Technical Reports Server (NTRS)

    Dean, Edwin B.

    1991-01-01

    A model is developed for simulating the dynamics of a newly formed organization, credible during all phases of organizational development. The model development process is broken down into the activities of determining the tasks required for parametric cost analysis (PCA), determining the skills required for each PCA task, determining the skills available in the applicant marketplace, determining the structure of the model, implementing the model, and testing it. The model, parameterized by the likelihood of job function transition, has demonstrated by the capability to represent the transition of personnel across functional boundaries within a parametric organization using a linear dynamical system, and the ability to predict required staffing profiles to meet functional needs at the desired time. The model can be extended by revisions of the state and transition structure to provide refinements in functional definition for the parametric and extended organization.

  13. Modeling personnel turnover in the parametric organization

    NASA Technical Reports Server (NTRS)

    Dean, Edwin B.

    1991-01-01

    A model is developed for simulating the dynamics of a newly formed organization, credible during all phases of organizational development. The model development process is broken down into the activities of determining the tasks required for parametric cost analysis (PCA), determining the skills required for each PCA task, determining the skills available in the applicant marketplace, determining the structure of the model, implementing the model, and testing it. The model, parameterized by the likelihood of job function transition, has demonstrated by the capability to represent the transition of personnel across functional boundaries within a parametric organization using a linear dynamical system, and the ability to predict required staffing profiles to meet functional needs at the desired time. The model can be extended by revisions of the state and transition structure to provide refinements in functional definition for the parametric and extended organization.

  14. Use of robust estimators in parametric classifiers

    NASA Technical Reports Server (NTRS)

    Safavian, S. Rasoul; Landgrebe, David A.

    1989-01-01

    The parametric approach to density estimation and classifier design is a well studied subject. The parametric approach is desirable because basically it reduces the problem of classifier design to that of estimating a few parameters for each of the pattern classes. The class parameters are usually estimated using maximum-likelihood (ML) estimators. ML estimators are, however, very sensitive to the presence of outliers. Several robust estimators of mean and covariance matrix and their effect on the probability of error in classification are examined. Comments are made about alpha-ranked (alpha-trimmed) estimators.

  15. Parametric number covariance in quantum chaotic spectra.

    PubMed

    Vinayak; Kumar, Sandeep; Pandey, Akhilesh

    2016-03-01

    We study spectral parametric correlations in quantum chaotic systems and introduce the number covariance as a measure of such correlations. We derive analytic results for the classical random matrix ensembles using the binary correlation method and obtain compact expressions for the covariance. We illustrate the universality of this measure by presenting the spectral analysis of the quantum kicked rotors for the time-reversal invariant and time-reversal noninvariant cases. A local version of the parametric number variance introduced earlier is also investigated.

  16. Use of robust estimators in parametric classifiers

    NASA Technical Reports Server (NTRS)

    Safavian, S. Rasoul; Landgrebe, David A.

    1989-01-01

    The parametric approach to density estimation and classifier design is a well studied subject. The parametric approach is desirable because basically it reduces the problem of classifier design to that of estimating a few parameters for each of the pattern classes. The class parameters are usually estimated using maximum-likelihood (ML) estimators. ML estimators are, however, very sensitive to the presence of outliers. Several robust estimators of mean and covariance matrix and their effect on the probability of error in classification are examined. Comments are made about alpha-ranked (alpha-trimmed) estimators.

  17. Parametric noise squeezing and parametric resonance of microcantilevers in air and liquid environments

    NASA Astrophysics Data System (ADS)

    Prakash, Gyan; Raman, Arvind; Rhoads, Jeffrey; Reifenberger, Ronald G.

    2012-06-01

    In this work, parametric noise squeezing and parametric resonance are realized through the use of an electronic feedback circuit to excite a microcantilever with a signal proportional to the product of the microcantilever's displacement and a harmonic signal. The cantilever's displacement is monitored using an optical lever technique. By adjusting the gain of an amplifier in the feedback circuit, regimes of parametric noise squeezing/amplification and the principal and secondary parametric resonances of fundamental and higher order eigenmodes can be easily accessed. The exceptionally symmetric amplitude response of the microcantilever in the narrow frequency bandwidth is traced to a nonlinear parametric excitation term that arises due to the cubic nonlinearity in the output of the position-sensitive photodiode. The feedback circuit, working in both the regimes of parametric resonance and noise squeezing, allows an enhancement of the microcantilever's effective quality-factor (Q-factor) by two orders of magnitude under ambient conditions, extending the mass sensing capabilities of a conventional microcantilever into the sub-picogram regime. Likewise, experiments designed to parametrically oscillate a microcantilever in water using electronic feedback also show an increase in the microcantilever's effective Q-factor by two orders of magnitude, opening the field to high-sensitivity mass sensing in liquid environments.

  18. Parametric noise squeezing and parametric resonance of microcantilevers in air and liquid environments.

    PubMed

    Prakash, Gyan; Raman, Arvind; Rhoads, Jeffrey; Reifenberger, Ronald G

    2012-06-01

    In this work, parametric noise squeezing and parametric resonance are realized through the use of an electronic feedback circuit to excite a microcantilever with a signal proportional to the product of the microcantilever's displacement and a harmonic signal. The cantilever's displacement is monitored using an optical lever technique. By adjusting the gain of an amplifier in the feedback circuit, regimes of parametric noise squeezing/amplification and the principal and secondary parametric resonances of fundamental and higher order eigenmodes can be easily accessed. The exceptionally symmetric amplitude response of the microcantilever in the narrow frequency bandwidth is traced to a nonlinear parametric excitation term that arises due to the cubic nonlinearity in the output of the position-sensitive photodiode. The feedback circuit, working in both the regimes of parametric resonance and noise squeezing, allows an enhancement of the microcantilever's effective quality-factor (Q-factor) by two orders of magnitude under ambient conditions, extending the mass sensing capabilities of a conventional microcantilever into the sub-picogram regime. Likewise, experiments designed to parametrically oscillate a microcantilever in water using electronic feedback also show an increase in the microcantilever's effective Q-factor by two orders of magnitude, opening the field to high-sensitivity mass sensing in liquid environments.

  19. Trade-offs Between Efficacy and Cardiac Toxicity of Adjuvant Chemotherapy in Early-Stage Breast Cancer Patients: Do Competing Risks Matter?

    PubMed

    Alarid-Escudero, Fernando; Blaes, Anne H; Kuntz, Karen M

    2017-07-01

    Evidence about treatment efficacy and long-term toxicities for adjuvant chemotherapy in patients with early-stage breast cancer is often presented in different formats and studies. This leads to challenges for patients and their physicians to adequately weigh the trade-offs between effectiveness and long-term cardiac toxicity when making decisions about adjuvant chemotherapy. We used a decision-analytic framework to quantify these trade-offs by combining the available evidence into a single, comparable metric. We developed a Markov model to simulate a hypothetical cohort of newly diagnosed breast cancer patients under three scenarios: no treatment, anthracycline (AC)-based adjuvant chemotherapy (more effective but also more cardiotoxic), and non-AC-based adjuvant chemotherapy. We derived the model parameters from medical literature (e.g., clinical trials). Our primary outcome is 10-year mortality, and other metrics such as cause of death; life years (LYs) and quality-adjusted LYs over 10 years were evaluated in sensitivity analysis. For 55-year-old women with a 10-year risk of metastatic recurrence <12.5% no chemotherapy resulted in the preferred strategy. In general, non-AC-based adjuvant chemotherapy resulted in lower 10-year mortality than AC-based chemotherapy. Patients with low risk of metastatic recurrence are better off without adjuvant chemotherapy regardless of the outcome considered (i.e., the risks of cardiac toxicity from chemotherapy outweighed the benefits). Trade-offs between effectiveness and induced cardiac toxicity impact health outcomes. The choice of adjuvant treatment must consider the patient's risk of distant recurrence and the quality of life associated with different health outcomes. © 2017 Wiley Periodicals, Inc.

  20. Long-term results and competing risk analysis of the H89 trial in patients with advanced-stage Hodgkin lymphoma: a study by the Groupe d'Etude des Lymphomes de l'Adulte (GELA).

    PubMed

    Fermé, Christophe; Mounier, Nicolas; Casasnovas, Olivier; Brice, Pauline; Divine, Marine; Sonet, Anne; Bouafia, Fahdela; Bastard-Stamatoullas, Aspasia; Bordessoule, Dominique; Voillat, Laurent; Reman, Oumedaly; Blanc, Michel; Gisselbrecht, Christian

    2006-06-15

    From 1989 to 1996, 533 eligible patients with stage IIIB/IV Hodgkin lymphoma (HL) were randomly assigned to receive 6 cycles of hybrid MOPP/ABV (mechlorethamine, vincristine, procarbazine, prednisone/Adriamycin [doxorubicin], bleomycin, vinblastine; n = 266) or ABVPP (doxorubicin, bleomycin, vinblastine, procarbazine, prednisone; n = 267). Patients in complete remission (CR) or partial response of at least 75% after 6 cycles received 2 cycles of consolidation chemotherapy (CT) (n = 208) or subtotal nodal irradiation (RT) (n = 210). A better survival probability was observed after ABVPP alone: the 10-year overall survival (OS) estimates were 90% for ABVPP x 8, 78% for MOPP/ABV x 8, 82% for MOPP/ABV with RT, and 77% for ABVPP x 6 with RT (P = .03); and the 10-year disease-free survival (DFS) estimates were 70%, 76%, 79%, and 76%, respectively (P = .09). The 10-year DFS estimates for patients treated with consolidation CT or RT were 73% and 78% (P = .07), and OS estimates were 84% and 79%, respectively (P = .29). These results showed that RT was not superior to consolidation CT after a doxorubicin-induced CR in patients with advanced HL. An analysis of competing risks identified age more than 45 years as a significant risk factor for death, relapse, and second cancers. Prospective evaluation of late adverse events may improve the management of patients with HL.

  1. How should paediatricians assess Gillick competence?

    PubMed

    Larcher, Vic; Hutchinson, Anna

    2010-04-01

    Competence is an essential legal requirement for valid consent to medical treatment. Children under 16 may be considered 'Gillick competent' to make treatment decisions, but may need to demonstrate this. Applied tests for competence are wide-ranging and context dependent. Competence is related to cognitive ability and experience and may be enhanced by education, encouragement etc.; there is a general duty for professionals to enhance the competence of children in their care. The need to assess a child's competence may occur when s/he wishes to make a controversial decision whose wisdom others dispute. Potential assessors should have the necessary practical skills and an understanding of the child in their social and medical context. Assessments should be developmentally appropriate, explore systemic influences, and consider the child's emotional state, cognitive development and ability to balance risks and benefits. The involvement of a psychologist or other independent third party should be considered in cases that raise serious concerns about competency, or that involve complex decisions or conflict between the various parties. In rare cases courts may be involved.

  2. Study of parametric instability in gravitational wave detectors with silicon test masses

    NASA Astrophysics Data System (ADS)

    Zhang, Jue; Zhao, Chunnong; Ju, Li; Blair, David

    2017-03-01

    Parametric instability is an intrinsic risk in high power laser interferometer gravitational wave detectors, in which the optical cavity modes interact with the acoustic modes of the mirrors, leading to exponential growth of the acoustic vibration. In this paper, we investigate the potential parametric instability for a proposed next generation gravitational wave detector, the LIGO Voyager blue design, with cooled silicon test masses of size 45 cm in diameter and 55 cm in thickness. It is shown that there would be about two unstable modes per test mass at an arm cavity power of 3 MW, with the highest parametric gain of  ∼76. While this is less than the predicted number of unstable modes for Advanced LIGO (∼40 modes with max gain of  ∼32 at the designed operating power of 830 kW), the importance of developing suitable instability suppression schemes is emphasized.

  3. Non-parametric estimation of state occupation, entry and exit times with multistate current status data.

    PubMed

    Lan, Ling; Datta, Somnath

    2010-04-01

    As a type of multivariate survival data, multistate models have a wide range of applications, notably in cancer and infectious disease progression studies. In this article, we revisit the problem of estimation of state occupation, entry and exit times in a multistate model where various estimators have been proposed in the past under a variety of parametric and non-parametric assumptions. We focus on two non-parametric approaches, one using a product limit formula as recently proposed in Datta and Sundaram(1) and a novel approach using a fractional risk set calculation followed by a subtraction formula to calculate the state occupation probability of a transient state. A numerical comparison between the two methods is presented using detailed simulation studies. We show that the new estimators have lower statistical errors of estimation of state occupation probabilities for the distant states. We illustrate the two methods using a pubertal development data set obtained from the NHANES III.(2).

  4. Social competence of preschool children with epilepsy.

    PubMed

    Rantanen, K; Timonen, S; Hagström, K; Hämäläinen, P; Eriksson, K; Nieminen, P

    2009-02-01

    The aims of this study were to describe the social competence of 3- to 6-year-old children with epilepsy (n=26) compared with that of age- and gender-matched healthy controls (n=26). Social competence was assessed with the Vineland Social Maturity Scale, Conners' Parent Rating Scales-Revised, and the Child Behavior Checklist. The results indicate that the children with epilepsy, especially with complicated epilepsy, had fewer age-appropriate social skills and more attention and behavior problems than the healthy children, as reported by parents. It is possible that the lack of age-appropriate social skills and the presence of attention problems predispose to behavioral problems. Also, epilepsy-related factors impaired the achievement of social competence. This study shows that the preschool children with complicated, early-onset epilepsy are at increased risk of difficulties in social competence.

  5. The Importance of Military Cultural Competence.

    PubMed

    Meyer, Eric G; Writer, Brian W; Brim, William

    2016-03-01

    Military cultural competence has recently gained national attention. Experts have posited that limited outcomes in the treatment of posttraumatic stress disorder and depression in the military may be related to limited familiarity with the military. National surveys have indicated low military cultural competence among providers and limited educational efforts on military culture or pertinent military pathology in medical schools and residency training programs. Military families, with their own unique military cultural identity, have been identified as a population with increased risks associated with deployment. In response to these findings, several curricula regarding military culture have been established and widely distributed. Assessments of military cultural competence have also been developed. The clinical impact of enhanced cultural competence in general has thus far been limited. The military, however, with its highly prescribed cultural identity, may be a model culture for further study.

  6. Quantifying parametric uncertainty in the Rothermel model

    Treesearch

    S. Goodrick

    2008-01-01

    The purpose of the present work is to quantify parametric uncertainty in the Rothermel wildland fire spreadmodel (implemented in software such as fire spread models in the United States. This model consists of a non-linear system of equations that relates environmentalvariables (input parameter groups...

  7. Noise figure of hybrid optical parametric amplifiers.

    PubMed

    Marhic, Michel E

    2012-12-17

    Following a fiber optical parametric amplifier, used as a wavelength converter or in the phase-sensitive mode, by a phase-insensitive amplifier (PIA) can significantly reduce four-wave mixing between signals in broadband systems. We derive the quantum mechanical noise figures (NF) for these two hybrid configurations, and show that adding the PIA only leads to a moderate increase in NF.

  8. New Logic Circuit with DC Parametric Excitation

    NASA Astrophysics Data System (ADS)

    Sugahara, Masanori; Kaneda, Hisayoshi

    1982-12-01

    It is shown that dc parametric excitation is possible in a circuit named JUDO, which is composed of two resistively-connected Josephson junctions. Simulation study proves that the circuit has large gain and properties suitable for the construction of small, high-speed logic circuits.

  9. Measurement selection for parametric IC fault diagnosis

    NASA Technical Reports Server (NTRS)

    Wu, A.; Meador, J.

    1991-01-01

    Experimental results obtained with the use of measurement reduction for statistical IC fault diagnosis are described. The reduction method used involves data pre-processing in a fashion consistent with a specific definition of parametric faults. The effects of this preprocessing are examined.

  10. Holographic Dark Energy Density and JBP Parametrization

    NASA Astrophysics Data System (ADS)

    Saadat, Hassan; Mousavi, S. N.; Saadat, A. M.

    2011-09-01

    In this article we consider the holographic dark energy density. We study dark energy density in Universe with arbitrary spatially curvature described by the Friedmann-Robertson-Walker metric. We use Jassal-Bagla-Padmanabhan parametrization to specify dark energy density.

  11. Parametric Oscillations in High Power Microwave Amplifiers.

    DTIC Science & Technology

    1979-01-01

    report. I j I 1 1) G. Dohler, Parametric Oscillations in High Power Microwave Amplifiers, L Contract No. F49620-77-C-O0 (1979). 2) O. Doehler B. Dohler...IEEE Transactions on Electron Devices, ED 26(10),[ 1602 (19795. 3) 0. Doehler , G. Dohler, International Electron Devices Meeting, I Washington, D.C

  12. A parametric reconstruction of the deceleration parameter

    NASA Astrophysics Data System (ADS)

    Mamon, Abdulla Al; Das, Sudipta

    2017-07-01

    The present work is based on a parametric reconstruction of the deceleration parameter q( z) in a model for the spatially flat FRW universe filled with dark energy and non-relativistic matter. In cosmology, the parametric reconstruction technique deals with an attempt to build up a model by choosing some specific evolution scenario for a cosmological parameter and then estimate the values of the parameters with the help of different observational datasets. In this paper, we have proposed a logarithmic parametrization of q( z) to probe the evolution history of the universe. Using the type Ia supernova, baryon acoustic oscillation and the cosmic microwave background datasets, the constraints on the arbitrary model parameters q0 and q1 are obtained (within 1σ and 2σ confidence limits) by χ 2-minimization technique. We have then reconstructed the deceleration parameter, the total EoS parameter ω _tot, the jerk parameter and have compared the reconstructed results of q( z) with other well-known parametrizations of q( z). We have also shown that two model selection criteria (namely, the Akaike information criterion and Bayesian information criterion) provide a clear indication that our reconstructed model is well consistent with other popular models.

  13. The fast parametric slantlet transform with applications

    NASA Astrophysics Data System (ADS)

    Agaian, Sos S.; Tourshan, Khaled; Noonan, Joseph P.

    2004-05-01

    Transform methods have played an important role in signal and image processing applications. Recently, Selesnick has constructed the new orthogonal discrete wavelet transform, called the slantlet wavelet, with two zero moments and with improved time localization. The discrete slantlet wavelet transform is carried out by an existing filterbank which lacks a tree structure and has a complexity problem. The slantlet wavelet has been successfully applied in compression and denoising. In this paper, we present a new class of orthogonal parametric fast Haar slantlet transform system where the slantlet wavelet and Haar transforms are special cases of it. We propose designing the slantlet wavelet transform using Haar slantlet transform matrix. A new class of parametric filterbanks is developed. The behavior of the parametric Haar slantlet transforms in signal and image denoising is presented. We show that the new technique performs better than the slantlet wavelet transform in denoising for piecewise constant signals. We also show that the parametric Haar slantlet transform performs better than the cosine and Fourier transforms for grey level images.

  14. Robustness analysis for real parametric uncertainty

    NASA Technical Reports Server (NTRS)

    Sideris, Athanasios

    1989-01-01

    Some key results in the literature in the area of robustness analysis for linear feedback systems with structured model uncertainty are reviewed. Some new results are given. Model uncertainty is described as a combination of real uncertain parameters and norm bounded unmodeled dynamics. Here the focus is on the case of parametric uncertainty. An elementary and unified derivation of the celebrated theorem of Kharitonov and the Edge Theorem is presented. Next, an algorithmic approach for robustness analysis in the cases of multilinear and polynomic parametric uncertainty (i.e., the closed loop characteristic polynomial depends multilinearly and polynomially respectively on the parameters) is given. The latter cases are most important from practical considerations. Some novel modifications in this algorithm which result in a procedure of polynomial time behavior in the number of uncertain parameters is outlined. Finally, it is shown how the more general problem of robustness analysis for combined parametric and dynamic (i.e., unmodeled dynamics) uncertainty can be reduced to the case of polynomic parametric uncertainty, and thus be solved by means of the algorithm.

  15. The Effect of GVHD on Long-term Outcomes after Peripheral Blood Allogeneic Stem Cell Transplantation from an HLA-identical Sibling in Adult Acute Lymphocytic Leukemia: A Landmark Analysis Approach in Competing Risks

    PubMed Central

    Jalali, Arash; Alimoghaddam, Kamran; Mohammad, Kazem; Mousavi, Seied Asadollah; Bahar, Babak; Vaezi, Mohammad; Zeraati, Hojjat; Jahani, Mohammad; Ghavamzadeh, Ardeshir

    2014-01-01

    Allogeneic Hematopoietic stem cell transplantation (HSCT) is the most effective therapy to prevent relapse in acute lymphocytic leukemia (ALL). This benefit is affected by non-relapse mortality (NRM) due to complications such as graft versus host disease (GVHD). A new approach in analyzing time-dependent covariates in competing risks is landmark analysis. So, the aim of this study is to evaluate the effect of acute and chronic GVHD on long-term outcomes, relapse and NRM, after allogeneic HSCT in adult ALL using landmark analysis. This study was conducted on 252 ALL patients who were allogeneic transplanted from an HLA-identical sibling with peripheral blood (PB) as the source of stem cell from 2004 to 2012 and were followed-up until 2013. In the first 100 days after transplant, a landmark analysis on days +10, +11, +12, +17, +24, and +31 was applied to assess the effect of acute GVHD on early relapse and NRM. Similarly, for patients alive and event-free at day +100 after transplant, a landmark analysis at time points day +101, months +4, +5, +6, +9, and +12 was applied to evaluate the effect of chronic GVHD on late relapse and NRM. Five-year LFS and OS were 35.0% (95% CI: 29.1, 42.2%) and 37.5% (95% CI: 31.3, 45.0%), respectively. Five-year cumulative incidence of relapse was 44.5% (95% CI: 37.9, 51.0%) while this was 20.4% (95% CI: 15.4, 26.0%) for NRM. The landmark analysis in the first 100 days after transplant showed that the grade III/IV of aGVHD has a lower risk of relapse but higher risk of NRM after adjustment for the EBMT risk score. For patients alive at day +100, cGVHD had no significant effect on relapse. Limited cGVHD had lower risk of NRM and after 6 month post-transplant the risk of NRM decreased and there were not important difference between the groups of cGVHD. Using advanced models enables us to estimate the effects more precisely and ultimately make inference more accurately. PMID:24800032

  16. Analyzing ADN competencies.

    PubMed

    Mitchell, P R

    1989-01-01

    El Paso Community College District, using the DACUM Process, identified 19 major competency areas with 313 specific competencies for AD Nursing. This article provides an overview of the DACUM Process, a discussion of the application to the ADN program, a summary of the results, and future activities.

  17. The Spiritual Competency Scale

    ERIC Educational Resources Information Center

    Robertson, Linda A.

    2010-01-01

    This study describes the development of the Spiritual Competency Scale, which was based on the Association for Spiritual, Ethical and Religious Values in Counseling's original Spiritual Competencies. Participants were 662 counseling students from religiously based and secular universities nationwide. Exploratory factor analysis revealed a 22-item,…

  18. Communicative Competence Reconsidered.

    ERIC Educational Resources Information Center

    Doushaq, Mufeeq

    A discussion of points raised by Dell Hymes in his article "On Communicative Competence" leads to a proposal for a clearer and more comprehensive theory of communicative competence based on two models, a matrix of discourse analysis and a model of communication interaction. Pedagogical implications of the theory are considered, including the…

  19. Assessing and Teaching Competence

    ERIC Educational Resources Information Center

    Grant, Terri

    2004-01-01

    The Professional Communication Unit (PCU) at the University of Cape Town (UCT) recently conducted a business communication needs analysis to determine student perceptions of their communicative competence and the teaching strategies being used to develop such competence. Students felt that the specialist, stand-alone communication program was more…

  20. Competencies and Their Assessment

    ERIC Educational Resources Information Center

    Drisko, James W.

    2014-01-01

    This article explores competencies and methods for their assessment in higher education and in social work's accreditation standards. Many contemporary policy and educational accreditation efforts employ the model of competency assessment. The current emphasis on accountability in higher education, including the Council on Social Work…

  1. Developing Competence at Work

    ERIC Educational Resources Information Center

    Bound, Helen; Lin, Magdalene

    2013-01-01

    In this paper, we explore the relationship between differing conceptualisations of competence, and the implications of these differences for the enacted workplace curriculum and its pedagogical epistemologies. We argue that when competence is understood as a set of stand-alone attributes that reside within an individual, it limits and over…

  2. Core Competence and Education.

    ERIC Educational Resources Information Center

    Holmes, Gary; Hooper, Nick

    2000-01-01

    Outlines the concept of core competence and applies it to postcompulsory education in the United Kingdom. Adopts an educational perspective that suggests accreditation as the core competence of universities. This economic approach suggests that the market trend toward lifetime learning might best be met by institutions developing a core competence…

  3. The Spiritual Competency Scale

    ERIC Educational Resources Information Center

    Robertson, Linda A.

    2010-01-01

    This study describes the development of the Spiritual Competency Scale, which was based on the Association for Spiritual, Ethical and Religious Values in Counseling's original Spiritual Competencies. Participants were 662 counseling students from religiously based and secular universities nationwide. Exploratory factor analysis revealed a 22-item,…

  4. Competencies in Ornamental Horticulture

    ERIC Educational Resources Information Center

    Loewen, Curtis E.

    1974-01-01

    Based on the author's dissertation, this article pertains to the identification of competencies for ornamental horticulture workers in Oregon. Findings were based on interviews with 56 ornamental horticulture business employers regarding 100 competencies. The method used can serve as a model for obtaining occupational information to develop and…

  5. Assessing and Teaching Competence

    ERIC Educational Resources Information Center

    Grant, Terri

    2004-01-01

    The Professional Communication Unit (PCU) at the University of Cape Town (UCT) recently conducted a business communication needs analysis to determine student perceptions of their communicative competence and the teaching strategies being used to develop such competence. Students felt that the specialist, stand-alone communication program was more…

  6. Developing Competence at Work

    ERIC Educational Resources Information Center

    Bound, Helen; Lin, Magdalene

    2013-01-01

    In this paper, we explore the relationship between differing conceptualisations of competence, and the implications of these differences for the enacted workplace curriculum and its pedagogical epistemologies. We argue that when competence is understood as a set of stand-alone attributes that reside within an individual, it limits and over…

  7. Profiles of Algebraic Competence

    ERIC Educational Resources Information Center

    Humberstone, J.; Reeve, R.A.

    2008-01-01

    The algebraic competence of 72 12-year-old female students was examined to identify profiles of understanding reflecting different algebraic knowledge states. Beginning algebraic competence (mapping abilities: word-to-symbol and vice versa, classifying, and solving equations) was assessed. One week later, the nature of assistance required to map…

  8. Curriculum Competencies, 1984.

    ERIC Educational Resources Information Center

    Delaware Technical and Community Coll., Dover. Terry Campus.

    This manual specifies the skills and abilities possessed by the graduates of programs offered by the Terry Campus of Delaware Technical and Community College. First, introductory material discusses the college's competency-based philosophy and the efforts by faculty and administrators to criterion reference the competencies perceived by faculty to…

  9. Communicative Competence Reconsidered.

    ERIC Educational Resources Information Center

    Doushaq, Mufeeq

    A discussion of points raised by Dell Hymes in his article "On Communicative Competence" leads to a proposal for a clearer and more comprehensive theory of communicative competence based on two models, a matrix of discourse analysis and a model of communication interaction. Pedagogical implications of the theory are considered, including the…

  10. Competencies and Their Assessment

    ERIC Educational Resources Information Center

    Drisko, James W.

    2014-01-01

    This article explores competencies and methods for their assessment in higher education and in social work's accreditation standards. Many contemporary policy and educational accreditation efforts employ the model of competency assessment. The current emphasis on accountability in higher education, including the Council on Social Work…

  11. Therapist Multicultural Competence

    ERIC Educational Resources Information Center

    Mandel, Jennifer O.

    2010-01-01

    The results of this qualitative investigation provide a framework for conceptualizing the practice of multiculturally competent therapy, and identify the characteristics of multiculturally competent therapists. Clinic managers employed in clinics or social service agencies in two Midwestern cities each nominated a white clinician on staff whom…

  12. Drafting. Competency Based Curriculum.

    ERIC Educational Resources Information Center

    Everly, Al; And Others

    This competency based drafting curriculum is presented in seven specialization sections with units in each section containing a competency statement, performance objective, learning activities, evaluation, and quiz or problem sheets. Some units also contain answer sheets and/or handout sheets. Sections and number of units presented are (1) basic…

  13. Adult Educators' Core Competences

    ERIC Educational Resources Information Center

    Wahlgren, Bjarne

    2016-01-01

    Which competences do professional adult educators need? This research note discusses the topic from a comparative perspective, finding that adult educators' required competences are wide-ranging, heterogeneous and complex. They are subject to context in terms of national and cultural environment as well as the kind of adult education concerned…

  14. Competencies in HRD. Symposium.

    ERIC Educational Resources Information Center

    2002

    This symposium is comprised of three papers on competencies in human resource development (HRD). "The Development of a Competency Model and Assessment Instrument for Public Sector Leadership and Management Development" (Sharon S. Naquin, Elwood F. Holton III) reports on a streamlined methodology and process used to develop a competency…

  15. Therapist Multicultural Competence

    ERIC Educational Resources Information Center

    Mandel, Jennifer O.

    2010-01-01

    The results of this qualitative investigation provide a framework for conceptualizing the practice of multiculturally competent therapy, and identify the characteristics of multiculturally competent therapists. Clinic managers employed in clinics or social service agencies in two Midwestern cities each nominated a white clinician on staff whom…

  16. Adult Educators' Core Competences

    ERIC Educational Resources Information Center

    Wahlgren, Bjarne

    2016-01-01

    Which competences do professional adult educators need? This research note discusses the topic from a comparative perspective, finding that adult educators' required competences are wide-ranging, heterogeneous and complex. They are subject to context in terms of national and cultural environment as well as the kind of adult education concerned…

  17. Cultural Competence Revisited

    ERIC Educational Resources Information Center

    Garran, Ann Marie; Werkmeister Rozas, Lisa

    2013-01-01

    In 2001, the National Association of Social Workers (NASW) adopted 10 discrete standards of culturally competent practice which undergird our commitment to diversity and social justice. The concept of intersectionality is newly emerging in social work, though, causing us to reflect on our current conceptualizations of cultural competence.…

  18. Administrative competencies for physician organizations with capitation.

    PubMed

    Penner, M

    1999-01-01

    In California, it is common for HMOs to capitate physician organizations (e.g., independent practice organizations and multispecialty medical groups) for all professional and outpatient ancillary services (and to share risk for inpatient care) under professional risk capitation contracts. This arrangement exports most of the financial risk from the HMO to the physician organization. When HMOs and physician organizations contract under these arrangements, HMOs delegate many of their administrative functions to physician organizations--giving the physician organization authority to make the decisions needed to manage capitated risk. As a result, administrators of physician organizations must be competent in such areas as provider network development, financial forecasting, utilization and quality management, contract negotiation, and establishing systems for claims, reporting, authorizations, and the like. In this study four HMO and 22 physician organization administrators were interviewed concerning key administrative competencies for managing capitation contracts. The competencies were assessed as key administrative work activities that required specific knowledge, skill, or ability to perform. Identifying these competencies is important for physician organizations preparing for capitated risk and will be essential for organizations preparing for HMO or Medicare capitation.

  19. Parametric acoustic arrays: A state of the art review

    NASA Technical Reports Server (NTRS)

    Fenlon, F. H.

    1976-01-01

    Following a brief introduction to the concept of parametric acoustic interactions, the basic properties of parametric transmitting and receiving arrays are considered in the light of conceptual advances resulting from experimental and theoretical investigations that have taken place since 1963.

  20. A novel SURE-based criterion for parametric PSF estimation.

    PubMed

    Xue, Feng; Blu, Thierry

    2015-02-01

    We propose an unbiased estimate of a filtered version of the mean squared error--the blur-SURE (Stein's unbiased risk estimate)--as a novel criterion for estimating an unknown point spread function (PSF) from the degraded image only. The PSF is obtained by minimizing this new objective functional over a family of Wiener processings. Based on this estimated blur kernel, we then perform nonblind deconvolution using our recently developed algorithm. The SURE-based framework is exemplified with a number of parametric PSF, involving a scaling factor that controls the blur size. A typical example of such parametrization is the Gaussian kernel. The experimental results demonstrate that minimizing the blur-SURE yields highly accurate estimates of the PSF parameters, which also result in a restoration quality that is very similar to the one obtained with the exact PSF, when plugged into our recent multi-Wiener SURE-LET deconvolution algorithm. The highly competitive results obtained outline the great potential of developing more powerful blind deconvolution algorithms based on SURE-like estimates.