Observational Studies: Cohort and Case-Control Studies

PubMed Central

Song, Jae W.; Chung, Kevin C.

2010-01-01

Observational studies are an important category of study designs. To address some investigative questions in plastic surgery, randomized controlled trials are not always indicated or ethical to conduct. Instead, observational studies may be the next best method to address these types of questions. Well-designed observational studies have been shown to provide results similar to randomized controlled trials, challenging the belief that observational studies are second-rate. Cohort studies and case-control studies are two primary types of observational studies that aid in evaluating associations between diseases and exposures. In this review article, we describe these study designs, methodological issues, and provide examples from the plastic surgery literature. PMID:20697313

Case-Control Studies of Sporadic Enteric Infections: A Review and Discussion of Studies Conducted Internationally from 1990 to 2009

PubMed Central

Fullerton, Kathleen E.; Scallan, Elaine; Kirk, Martyn D.; Mahon, Barbara E.; Angulo, Frederick J.; de Valk, Henriette; van Pelt, Wilfrid; Gauci, Charmaine; Hauri, Anja M.; Majowicz, Shannon; O’Brien, Sarah J.

2015-01-01

Epidemiologists have used case-control studies to investigate enteric disease outbreaks for many decades. Increasingly, case-control studies are also used to investigate risk factors for sporadic (not outbreak-associated) disease. While the same basic approach is used, there are important differences between outbreak and sporadic disease settings that need to be considered in the design and implementation of the case-control study for sporadic disease. Through the International Collaboration on Enteric Disease “Burden of Illness” Studies (the International Collaboration), we reviewed 79 case-control studies of sporadic enteric infections caused by nine pathogens that were conducted in 22 countries and published from 1990 through to 2009. We highlight important methodological and study design issues (including case definition, control selection, and exposure assessment) and discuss how approaches to the study of sporadic enteric disease have changed over the last 20 years (e.g., making use of more sensitive case definitions, databases of controls, and computer-assisted interviewing). As our understanding of sporadic enteric infections grows, methods and topics for case-control studies are expected to continue to evolve; for example, advances in understanding of the role of immunity can be used to improve control selection, the apparent protective effects of certain foods can be further explored, and case-control studies can be used to provide population-based measures of the burden of disease. PMID:22443481

Design and validity of a clinic-based case-control study on the molecular epidemiology of lymphoma

PubMed Central

Cerhan, James R; Fredericksen, Zachary S; Wang, Alice H; Habermann, Thomas M; Kay, Neil E; Macon, William R; Cunningham, Julie M; Shanafelt, Tait D; Ansell, Stephen M; Call, Timothy G; Witzig, Thomas E; Slager, Susan L; Liebow, Mark

2011-01-01

We present the design features and implementation of a clinic-based case-control study on the molecular epidemiology of lymphoma conducted at the Mayo Clinic (Rochester, Minnesota, USA), and then assess the internal and external validity of the study. Cases were newly diagnosed lymphoma patients from Minnesota, Iowa and Wisconsin seen at Mayo and controls were patients from the same region without lymphoma who had a pre-scheduled general medical examination, frequency matched on age, sex and residence. Overall response rates were 67% for cases and 70% for controls; response rates were lower for cases and controls over age 70 years, cases with more aggressive disease, and controls from the local area, although absolute differences were modest. Cases and controls were well-balanced on age, sex, and residence characteristics. Demographic and disease characteristics of NHL cases were similar to population-based cancer registry data. Control distributions were similar to population-based data on lifestyle factors and minor allele frequencies of over 500 SNPs, although smoking rates were slightly lower. Associations with NHL in the Mayo study for smoking, alcohol use, family history of lymphoma, autoimmune disease, asthma, eczema, body mass index, and single nucleotide polymorphisms in TNF (rs1800629), LTA (rs909253), and IL10 (rs1800896) were at a magnitude consistent with estimates from pooled studies in InterLymph, with history of any allergy the only directly discordant result in the Mayo study. These data suggest that this study should have strong internal and external validity. This framework may be useful to others who are designing a similar study. PMID:21686124

Publishing Single-Case Research Design Studies That Do Not Demonstrate Experimental Control

ERIC Educational Resources Information Center

Tincani, Matt; Travers, Jason

2018-01-01

Demonstration of experimental control is considered a hallmark of high-quality single-case research design (SCRD). Studies that fail to demonstrate experimental control may not be published because researchers are unwilling to submit these papers for publication and journals are unlikely to publish negative results (i.e., the file drawer effect).…

Response rates in case-control studies of cancer by era of fieldwork and by characteristics of study design.

PubMed

Xu, Mengting; Richardson, Lesley; Campbell, Sally; Pintos, Javier; Siemiatycki, Jack

2018-04-09

The purpose of this study was to describe time trends in response rates in case-control studies of cancer and identify study design factors that influence response rate. We reviewed 370 case-control studies of cancer published in 12 journals during indicator years in each of the last four decades. We estimated time trends of response rates and reasons for nonresponse in each of the following types of study subjects: cases, medical source controls, and population controls. We also estimated response rates according to characteristics of study context. Median response rates among cases and population controls were between 75% and 80% in the 1970s. Between 1971 and 2010, study response rates declined by 0.31% per year for cases and 0.78% for population controls. Only a minority of studies reported reasons for nonparticipation; subject refusal was the most common reported reason. Studies conducted in North America had lower median response rates than studies conducted in Europe. In-person and telephone interviews elicited higher response rates than mail questionnaires. Response rates from case-control studies of cancer have declined, and this could threaten the validity of results derived from these studies. Copyright © 2018 Elsevier Inc. All rights reserved.

Combining epidemiology and biomechanics in sports injury prevention research: a new approach for selecting suitable controls.

PubMed

Finch, Caroline F; Ullah, Shahid; McIntosh, Andrew S

2011-01-01

Several important methodological issues need to be considered when designing sports injury case-control studies. Major design goals for case-control studies include the accounting for prior injury risk exposure, and optimal definitions of both cases and suitable controls are needed to ensure this. This article reviews methodological aspects of published sports injury case-control studies, particularly with regard to the selection of controls. It argues for a new approach towards selecting controls for case-control studies that draws on an interface between epidemiological and biomechanical concepts. A review was conducted to identify sport injury case-control studies published in the peer-review literature during 1985-2008. Overall, 32 articles were identified, of which the majority related to upper or lower extremity injuries. Matching considerations were used for control selection in 16 studies. Specific mention of application of biomechanical principles in the selection of appropriate controls was absent from all studies, including those purporting to evaluate the benefits of personal protective equipment to protect against impact injury. This is a problem because it could lead to biased conclusions, as cases and controls are not fully comparable in terms of similar biomechanical impact profiles relating to the injury incident, such as site of the impact on the body. The strength of the conclusions drawn from case-control studies, and the extent to which results can be generalized, is directly influenced by the definition and recruitment of cases and appropriate controls. Future studies should consider the interface between epidemiological and biomechanical concepts when choosing appropriate controls to ensure that proper adjustment of prior exposure to injury risk is made. To provide necessary guidance for the optimal selection of controls in case-control studies of interventions to prevent sports-related impact injury, this review outlines a new case-control selection strategy that reflects the importance of biomechanical considerations, which ensures that controls are selected based on the presence of the same global injury mechanism as the cases. To summarize, the general biomechanical principles that should apply to the selection of controls in future case-control studies are as follows: (i) each control must have been exposed to the same global injury mechanism as the case, (e.g. head impact, fall onto outstretched arm); and (ii) intrinsic (individual) factors (e.g. age, sex, skill level) that might modify the person's response to the relevant biomechanical loads are adjusted when either selecting the controls or are in the analysis phase. The same considerations for control selection apply to other study designs such as matched cohort studies or case-crossover studies.

Effects of imperfect test sensitivity and specificity on observational studies of influenza vaccine effectiveness.

PubMed

Jackson, Michael L; Rothman, Kenneth J

2015-03-10

The recently developed test-negative design is now standard for observational studies of influenza vaccine effectiveness (VE). It is unclear how influenza test misclassification biases test-negative VE estimates relative to VE estimates from traditional cohort or case-control studies. We simulated populations whose members may develop acute respiratory illness (ARI) due to influenza and to non-influenza pathogens. In these simulations, vaccination reduces the risk of influenza but not of non-influenza ARI. Influenza test sensitivity and specificity, risks of influenza and non-influenza ARI, and VE were varied across the simulations. In each simulation, we estimated influenza VE using a cohort design, a case-control design, and a test-negative design. In the absence of influenza test misclassification, all three designs accurately estimated influenza VE. In the presence of misclassification, all three designs underestimated VE. Bias in VE estimates was slightly greater in the test-negative design than in cohort or case-control designs. Assuming the use of highly sensitive and specific reverse-transcriptase polymerase chain reaction tests for influenza, bias in the test-negative studies was trivial across a wide range of realistic values for VE. Although influenza test misclassification causes more bias in test-negative studies than in traditional cohort or case-control studies, the difference is trivial for realistic combinations of attack rates, test sensitivity/specificity, and VE. Copyright © 2015 Elsevier Ltd. All rights reserved.

Design and analysis of multiple diseases genome-wide association studies without controls.

PubMed

Chen, Zhongxue; Huang, Hanwen; Ng, Hon Keung Tony

2012-11-15

In genome-wide association studies (GWAS), multiple diseases with shared controls is one of the case-control study designs. If data obtained from these studies are appropriately analyzed, this design can have several advantages such as improving statistical power in detecting associations and reducing the time and cost in the data collection process. In this paper, we propose a study design for GWAS which involves multiple diseases but without controls. We also propose corresponding statistical data analysis strategy for GWAS with multiple diseases but no controls. Through a simulation study, we show that the statistical association test with the proposed study design is more powerful than the test with single disease sharing common controls, and it has comparable power to the overall test based on the whole dataset including the controls. We also apply the proposed method to a real GWAS dataset to illustrate the methodologies and the advantages of the proposed design. Some possible limitations of this study design and testing method and their solutions are also discussed. Our findings indicate that the proposed study design and statistical analysis strategy could be more efficient than the usual case-control GWAS as well as those with shared controls. Copyright © 2012 Elsevier B.V. All rights reserved.

A Multiple Case Study of Faculty Control over Course Design and Its Effect on Faculty Efficacy

ERIC Educational Resources Information Center

King, Tara

2017-01-01

Online education continues to grow and change and different colleges and universities have varying degrees of faculty control over course design. This multiple case study investigated patterns in the efficacy of faculty who teach online courses in relation to the faculty members' involvement in the creation of elements of course design. The…

Study design and hierarchy of evidence for surgical decision making.

PubMed

Sprague, Sheila; McKay, Paula; Thoma, Achilleas

2008-04-01

This article provides a historical overview of the hierarchy of evidence for surgical decision making and discusses key study designs in the hierarchy of evidence. This encompasses meta-analyses, randomized controlled trials, and observational studies, including cohort and case-controlled studies, case series and case reports, and basic science studies. This article also reviews the principles and importance of evidence-based plastic surgery and describes several systems to rate the strength of the scientific evidence.

Biomarker discovery study design for type 1 diabetes in The Environmental Determinants of Diabetes in the Young (TEDDY) study.

PubMed

Lee, Hye-Seung; Burkhardt, Brant R; McLeod, Wendy; Smith, Susan; Eberhard, Chris; Lynch, Kristian; Hadley, David; Rewers, Marian; Simell, Olli; She, Jin-Xiong; Hagopian, Bill; Lernmark, Ake; Akolkar, Beena; Ziegler, Anette G; Krischer, Jeffrey P

2014-07-01

The Environmental Determinants of Diabetes in the Young planned biomarker discovery studies on longitudinal samples for persistent confirmed islet cell autoantibodies and type 1 diabetes using dietary biomarkers, metabolomics, microbiome/viral metagenomics and gene expression. This article describes the details of planning The Environmental Determinants of Diabetes in the Young biomarker discovery studies using a nested case-control design that was chosen as an alternative to the full cohort analysis. In the frame of a nested case-control design, it guides the choice of matching factors, selection of controls, preparation of external quality control samples and reduction of batch effects along with proper sample allocation. Our design is to reduce potential bias and retain study power while reducing the costs by limiting the numbers of samples requiring laboratory analyses. It also covers two primary end points (the occurrence of diabetes-related autoantibodies and the diagnosis of type 1 diabetes). The resulting list of case-control matched samples for each laboratory was augmented with external quality control samples. Copyright © 2013 John Wiley & Sons, Ltd.

Improved minimum cost and maximum power two stage genome-wide association study designs.

PubMed

Stanhope, Stephen A; Skol, Andrew D

2012-01-01

In a two stage genome-wide association study (2S-GWAS), a sample of cases and controls is allocated into two groups, and genetic markers are analyzed sequentially with respect to these groups. For such studies, experimental design considerations have primarily focused on minimizing study cost as a function of the allocation of cases and controls to stages, subject to a constraint on the power to detect an associated marker. However, most treatments of this problem implicitly restrict the set of feasible designs to only those that allocate the same proportions of cases and controls to each stage. In this paper, we demonstrate that removing this restriction can improve the cost advantages demonstrated by previous 2S-GWAS designs by up to 40%. Additionally, we consider designs that maximize study power with respect to a cost constraint, and show that recalculated power maximizing designs can recover a substantial amount of the planned study power that might otherwise be lost if study funding is reduced. We provide open source software for calculating cost minimizing or power maximizing 2S-GWAS designs.

Case-crossover design and its implementation in R

PubMed Central

2016-01-01

Case-crossover design is a variation of case-control design that it employs persons’ history periods as controls. Case-crossover design can be viewed as the hybrid of case-control study and crossover design. Characteristic confounding that is constant within one person can be well controlled with this method. The relative risk and odds ratio, as well as their 95% confidence intervals (CIs), can be estimated using Cochran-Mantel-Haenszel method. R codes for the calculation are provided in the main text. Readers may adapt these codes to their own task. Conditional logistic regression model is another way to estimate odds ratio of the exposure. Furthermore, it allows for incorporation of other time-varying covariates that are not constant within subjects. The model fitting per se is not technically difficult because there is well developed statistical package. However, it is challenging to convert original dataset obtained from case report form to that suitable to be passed to clogit() function. R code for this task is provided and explained in the text. PMID:27761445

CONDUIT: A New Multidisciplinary Integration Environment for Flight Control Development

NASA Technical Reports Server (NTRS)

Tischler, Mark B.; Colbourne, Jason D.; Morel, Mark R.; Biezad, Daniel J.; Levine, William S.; Moldoveanu, Veronica

1997-01-01

A state-of-the-art computational facility for aircraft flight control design, evaluation, and integration called CONDUIT (Control Designer's Unified Interface) has been developed. This paper describes the CONDUIT tool and case study applications to complex rotary- and fixed-wing fly-by-wire flight control problems. Control system analysis and design optimization methods are presented, including definition of design specifications and system models within CONDUIT, and the multi-objective function optimization (CONSOL-OPTCAD) used to tune the selected design parameters. Design examples are based on flight test programs for which extensive data are available for validation. CONDUIT is used to analyze baseline control laws against pertinent military handling qualities and control system specifications. In both case studies, CONDUIT successfully exploits trade-offs between forward loop and feedback dynamics to significantly improve the expected handling, qualities and minimize the required actuator authority. The CONDUIT system provides a new environment for integrated control system analysis and design, and has potential for significantly reducing the time and cost of control system flight test optimization.

Evaluating psychiatric case-control studies using the STROBE (STrengthening the Reporting of OBservational Studies in Epidemiology) statement.

PubMed

Goi, Pedro Domingues; Goi, Julia Domingues; Cordini, Kariny Larissa; Ceresér, Keila Mendes; Rocha, Neusa Sica da

2014-01-01

Case-control studies are important in developing clinical and public health knowledge. The STROBE statement (STrengthening the Reporting of OBservational Studies in Epidemiology) was developed to establish a checklist of items that should be included in articles reporting observational studies. Our aim was to analyze whether the psychiatric case-control articles published in Brazilian journals with CAPES Qualis rating B1/B2 in 2009 conformed with the STROBE statement. Descriptive study on psychiatric papers published in Brazilian journals, within the Postgraduate Medical Program on Psychiatry, at Universidade Federal do Rio Grande do Sul. All psychiatric case-control studies from Brazilian Qualis B1/B2 journals of psychiatry, neurology and public health in 2009 were analyzed. The four most specific items of the STROBE statement were used to evaluate whether these studies fitted within the case-control parameters: 1) selection of cases and controls; 2) controlling for bias; 3) statistical analysis; and 4) presentation of results. Sixteen case-control studies were identified, of which eleven (68.75%) were in psychiatry-focused journals. From analysis using the STROBE statement, all of the articles conformed with item 1; two (12.5%) completely conformed with item 2; none completely conformed with item 3; and only three (18.8%) conformed with item 4. The case-control studies analyzed here did not completely conform with the four STROBE statement items for case-control design. In view of the inadequate methodology of the published studies, these findings justify focusing on research and methodology and expanding the investigations on adherence of studies to their designs.

Analysis of case-parent trios at a locus with a deletion allele: association of GSTM1 with autism.

PubMed

Buyske, Steven; Williams, Tanishia A; Mars, Audrey E; Stenroos, Edward S; Ming, Sue X; Wang, Rong; Sreenath, Madhura; Factura, Marivic F; Reddy, Chitra; Lambert, George H; Johnson, William G

2006-02-10

Certain loci on the human genome, such as glutathione S-transferase M1 (GSTM1), do not permit heterozygotes to be reliably determined by commonly used methods. Association of such a locus with a disease is therefore generally tested with a case-control design. When subjects have already been ascertained in a case-parent design however, the question arises as to whether the data can still be used to test disease association at such a locus. A likelihood ratio test was constructed that can be used with a case-parents design but has somewhat less power than a Pearson's chi-squared test that uses a case-control design. The test is illustrated on a novel dataset showing a genotype relative risk near 2 for the homozygous GSTM1 deletion genotype and autism. Although the case-control design will remain the mainstay for a locus with a deletion, the likelihood ratio test will be useful for such a locus analyzed as part of a larger case-parent study design. The likelihood ratio test has the advantage that it can incorporate complete and incomplete case-parent trios as well as independent cases and controls. Both analyses support (p = 0.046 for the proposed test, p = 0.028 for the case-control analysis) an association of the homozygous GSTM1 deletion genotype with autism.

Analysis of case-parent trios at a locus with a deletion allele: association of GSTM1 with autism

PubMed Central

Buyske, Steven; Williams, Tanishia A; Mars, Audrey E; Stenroos, Edward S; Ming, Sue X; Wang, Rong; Sreenath, Madhura; Factura, Marivic F; Reddy, Chitra; Lambert, George H; Johnson, William G

2006-01-01

Background Certain loci on the human genome, such as glutathione S-transferase M1 (GSTM1), do not permit heterozygotes to be reliably determined by commonly used methods. Association of such a locus with a disease is therefore generally tested with a case-control design. When subjects have already been ascertained in a case-parent design however, the question arises as to whether the data can still be used to test disease association at such a locus. Results A likelihood ratio test was constructed that can be used with a case-parents design but has somewhat less power than a Pearson's chi-squared test that uses a case-control design. The test is illustrated on a novel dataset showing a genotype relative risk near 2 for the homozygous GSTM1 deletion genotype and autism. Conclusion Although the case-control design will remain the mainstay for a locus with a deletion, the likelihood ratio test will be useful for such a locus analyzed as part of a larger case-parent study design. The likelihood ratio test has the advantage that it can incorporate complete and incomplete case-parent trios as well as independent cases and controls. Both analyses support (p = 0.046 for the proposed test, p = 0.028 for the case-control analysis) an association of the homozygous GSTM1 deletion genotype with autism. PMID:16472391

Methods to control for unmeasured confounding in pharmacoepidemiology: an overview.

PubMed

Uddin, Md Jamal; Groenwold, Rolf H H; Ali, Mohammed Sanni; de Boer, Anthonius; Roes, Kit C B; Chowdhury, Muhammad A B; Klungel, Olaf H

2016-06-01

Background Unmeasured confounding is one of the principal problems in pharmacoepidemiologic studies. Several methods have been proposed to detect or control for unmeasured confounding either at the study design phase or the data analysis phase. Aim of the Review To provide an overview of commonly used methods to detect or control for unmeasured confounding and to provide recommendations for proper application in pharmacoepidemiology. Methods/Results Methods to control for unmeasured confounding in the design phase of a study are case only designs (e.g., case-crossover, case-time control, self-controlled case series) and the prior event rate ratio adjustment method. Methods that can be applied in the data analysis phase include, negative control method, perturbation variable method, instrumental variable methods, sensitivity analysis, and ecological analysis. A separate group of methods are those in which additional information on confounders is collected from a substudy. The latter group includes external adjustment, propensity score calibration, two-stage sampling, and multiple imputation. Conclusion As the performance and application of the methods to handle unmeasured confounding may differ across studies and across databases, we stress the importance of using both statistical evidence and substantial clinical knowledge for interpretation of the study results.

Bias correction of risk estimates in vaccine safety studies with rare adverse events using a self-controlled case series design.

PubMed

Zeng, Chan; Newcomer, Sophia R; Glanz, Jason M; Shoup, Jo Ann; Daley, Matthew F; Hambidge, Simon J; Xu, Stanley

2013-12-15

The self-controlled case series (SCCS) method is often used to examine the temporal association between vaccination and adverse events using only data from patients who experienced such events. Conditional Poisson regression models are used to estimate incidence rate ratios, and these models perform well with large or medium-sized case samples. However, in some vaccine safety studies, the adverse events studied are rare and the maximum likelihood estimates may be biased. Several bias correction methods have been examined in case-control studies using conditional logistic regression, but none of these methods have been evaluated in studies using the SCCS design. In this study, we used simulations to evaluate 2 bias correction approaches-the Firth penalized maximum likelihood method and Cordeiro and McCullagh's bias reduction after maximum likelihood estimation-with small sample sizes in studies using the SCCS design. The simulations showed that the bias under the SCCS design with a small number of cases can be large and is also sensitive to a short risk period. The Firth correction method provides finite and less biased estimates than the maximum likelihood method and Cordeiro and McCullagh's method. However, limitations still exist when the risk period in the SCCS design is short relative to the entire observation period.

Nonlinear multivariable design by total synthesis. [of gas turbine engine control systems

NASA Technical Reports Server (NTRS)

Sain, M. K.; Peczkowski, J. L.

1982-01-01

The Nominal Design Problem (NDP) is extended to nonlinear cases, and a new case study of robust feedback synthesis for gas turbine control design is presented. The discussion of NDP extends and builds on earlier Total Synthesis Problem theory and ideas. Some mathematical preliminaries are given in which a bijection from a set S onto a set T is considered, with T admitting the structure of an F-vector space. NDP is then discussed for a nonlinear plant, and nonlinear nominal design is defined and characterized. The design of local controllers for a turbojet and the scheduling of these controls into a global control are addressed.

Clinical Research Methodology 2: Observational Clinical Research.

PubMed

Sessler, Daniel I; Imrey, Peter B

2015-10-01

Case-control and cohort studies are invaluable research tools and provide the strongest feasible research designs for addressing some questions. Case-control studies usually involve retrospective data collection. Cohort studies can involve retrospective, ambidirectional, or prospective data collection. Observational studies are subject to errors attributable to selection bias, confounding, measurement bias, and reverse causation-in addition to errors of chance. Confounding can be statistically controlled to the extent that potential factors are known and accurately measured, but, in practice, bias and unknown confounders usually remain additional potential sources of error, often of unknown magnitude and clinical impact. Causality-the most clinically useful relation between exposure and outcome-can rarely be definitively determined from observational studies because intentional, controlled manipulations of exposures are not involved. In this article, we review several types of observational clinical research: case series, comparative case-control and cohort studies, and hybrid designs in which case-control analyses are performed on selected members of cohorts. We also discuss the analytic issues that arise when groups to be compared in an observational study, such as patients receiving different therapies, are not comparable in other respects.

A sham case-control study of effectiveness of DTP-Hib-hepatitis B vaccine against rotavirus acute gastroenteritis in Kenya

PubMed Central

2014-01-01

Background In many GAVI-eligible countries, effectiveness of new vaccines will be evaluated by case-control methodology. To inform the design and assess selection bias of a future case-control study of rotavirus vaccine effectiveness (VE) in western Kenya, we performed a sham case-control study evaluating VE of pentavalent vaccine (DTP-Hib-HepB) against rotavirus acute gastroenteritis (AGE). Methods From ongoing rotavirus surveillance, we defined cases as children 12 weeks to 23 months old with EIA-confirmed rotavirus AGE. We enrolled one community-based and two hospital-based control groups. We collected vaccination status from cards at enrollment, or later in homes, and evaluated VE by logistic regression. Results We enrolled 91 cases (64 inpatient, 27 outpatient), 252 non-rotavirus AGE facility-based controls (unmatched), 203 non-AGE facility-based controls (age-matched) and 271 community controls (age-matched). Documented receipt of 3 pentavalent doses was 77% among cases and ranged from 81-86% among controls. One percent of cases and 0-2% of controls had no pentavalent doses. The adjusted odds ratio of three versus zero doses for being a case was 3.27 (95% CI 0.01-1010) for community controls and 0.69 (95% CI 0.06-7.75) for non-rotavirus hospital-based AGE controls, translating to VE of -227% and 31%, respectively, with wide confidence intervals. (No facility-based non-AGE controls were unvaccinated.) Similar results were found for ≥2 pentavalent doses and for severe rotavirus AGE. Conclusions The study showed that it is feasible to carry out a real case control in the study area, but this needs to be done as soon as the vaccine is introduced to capture the real impact. Sham case-control or pilot studies before vaccine introduction can be useful in designing case-control VE studies. PMID:24517198

A sham case-control study of effectiveness of DTP-Hib-hepatitis B vaccine against rotavirus acute gastroenteritis in Kenya.

PubMed

Khagayi, Sammy; Tate, Jacqueline E; Onkoba, Reuben; Parashar, Umesh; Odhiambo, Frank; Burton, Deron; Laserson, Kayla; Feikin, Daniel R

2014-02-11

In many GAVI-eligible countries, effectiveness of new vaccines will be evaluated by case-control methodology. To inform the design and assess selection bias of a future case-control study of rotavirus vaccine effectiveness (VE) in western Kenya, we performed a sham case-control study evaluating VE of pentavalent vaccine (DTP-Hib-HepB) against rotavirus acute gastroenteritis (AGE). From ongoing rotavirus surveillance, we defined cases as children 12 weeks to 23 months old with EIA-confirmed rotavirus AGE. We enrolled one community-based and two hospital-based control groups. We collected vaccination status from cards at enrollment, or later in homes, and evaluated VE by logistic regression. We enrolled 91 cases (64 inpatient, 27 outpatient), 252 non-rotavirus AGE facility-based controls (unmatched), 203 non-AGE facility-based controls (age-matched) and 271 community controls (age-matched). Documented receipt of 3 pentavalent doses was 77% among cases and ranged from 81-86% among controls. One percent of cases and 0-2% of controls had no pentavalent doses. The adjusted odds ratio of three versus zero doses for being a case was 3.27 (95% CI 0.01-1010) for community controls and 0.69 (95% CI 0.06-7.75) for non-rotavirus hospital-based AGE controls, translating to VE of -227% and 31%, respectively, with wide confidence intervals. (No facility-based non-AGE controls were unvaccinated.) Similar results were found for ≥2 pentavalent doses and for severe rotavirus AGE. The study showed that it is feasible to carry out a real case control in the study area, but this needs to be done as soon as the vaccine is introduced to capture the real impact. Sham case-control or pilot studies before vaccine introduction can be useful in designing case-control VE studies.

The risk of acute liver injury among users of antibiotic medications: a comparison of case-only studies.

PubMed

Brauer, Ruth; Ruigómez, Ana; Klungel, Olaf; Reynolds, Robert; Feudjo Tepie, Maurille; Smeeth, Liam; Douglas, Ian

2016-03-01

The aims of this study were two-fold: (i) to investigate the effect of exposure to antibiotic agents on the risk of acute liver injury using a self-controlled case series and case-crossover study and (ii) to compare the results between the case-only studies. For the self-controlled case series study relative incidence ratios (IRR) were calculated by dividing the rate of acute liver injury experienced during patients' periods of exposure to antibiotics to patients' rate of events during non-exposed time using conditional Poisson regression. For the case-crossover analysis we calculated Odds Ratios (OR) using conditional logistic regression by comparing exposure during 14- and 30-day risk windows with exposure during control moments. Using the self-controlled case series approach, the IRR was highest during the first 7 days after receipt of a prescription (10.01, 95% CI 6.59-15.18). Omitting post-exposure washout periods lowered the IRR to 7.2. The highest estimate in the case-crossover analysis was found when two 30-day control periods 1 year prior to the 30-day ALI risk period were retained in the analysis: OR = 6.5 (95% CI, 3.95-10.71). The lowest estimate was found when exposure in the 14-day risk period was compared to exposure in four consecutive 14-day control periods immediately prior to the risk period (OR = 3.05, 95% CI, 2.06-4.53). An increased relative risk of acute liver injury was consistently observed using both self-controlled case series and case-crossover designs. Case-only designs can be used as a viable alternative study design to study the risk of acute liver injury, albeit with some limitations. © 2015 The Authors Pharmacoepidemiology and Drug Safety Published by John Wiley & Sons Ltd.

Using public control genotype data to increase power and decrease cost of case-control genetic association studies.

PubMed

Ho, Lindsey A; Lange, Ethan M

2010-12-01

Genome-wide association (GWA) studies are a powerful approach for identifying novel genetic risk factors associated with human disease. A GWA study typically requires the inclusion of thousands of samples to have sufficient statistical power to detect single nucleotide polymorphisms that are associated with only modest increases in risk of disease given the heavy burden of a multiple test correction that is necessary to maintain valid statistical tests. Low statistical power and the high financial cost of performing a GWA study remains prohibitive for many scientific investigators anxious to perform such a study using their own samples. A number of remedies have been suggested to increase statistical power and decrease cost, including the utilization of free publicly available genotype data and multi-stage genotyping designs. Herein, we compare the statistical power and relative costs of alternative association study designs that use cases and screened controls to study designs that are based only on, or additionally include, free public control genotype data. We describe a novel replication-based two-stage study design, which uses free public control genotype data in the first stage and follow-up genotype data on case-matched controls in the second stage that preserves many of the advantages inherent when using only an epidemiologically matched set of controls. Specifically, we show that our proposed two-stage design can substantially increase statistical power and decrease cost of performing a GWA study while controlling the type-I error rate that can be inflated when using public controls due to differences in ancestry and batch genotype effects.

Comparing U.S. Army suicide cases to a control sample: initial data and methodological lessons.

PubMed

Alexander, Cynthia L; Reger, Mark A; Smolenski, Derek J; Fullerton, Nicole R

2014-10-01

Identification of risk and protective factors for suicide is a priority for the United States military, especially in light of the recent steady increase in military suicide rates. The Department of Defense Suicide Event Report contains comprehensive data on suicides for active duty military personnel, but no analogous control data is available to permit identification of factors that differentially determine suicide risk. This proof-of-concept study was conducted to determine the feasibility of collecting such control data. The study employed a prospective case-control design in which control cases were randomly selected from a large Army installation at a rate of four control participants for every qualifying Army suicide. Although 111 Army suicides were confirmed during the study period, just 27 control soldiers completed the study. Despite the small control sample, preliminary analyses comparing suicide cases to controls identified several factors more frequently reported for suicide cases, including recent failed intimate relationships, outpatient mental health history, mood disorder diagnosis, substance abuse history, and prior self-injury. No deployment-related risk factors were found. These data are consistent with existing literature and form a foundation for larger control studies. Methodological lessons learned regarding study design and recruitment are discussed to inform future studies. Reprint & Copyright © 2014 Association of Military Surgeons of the U.S.

Snippets from the past: is Flint, Michigan, the birthplace of the case-control study?

PubMed

Morabia, Alfredo

2013-12-15

In the summer of 1924, an outbreak of scarlet fever occurred in Flint, Michigan. Unable to trace it to the usual causes, particularly fresh milk, the Michigan Department of Health used a novel approach to disentangle the enigma: The 116 cases of scarlet fever were compared with 117 "controls" selected from neighbors of the quarantined cases and from patients at the City Health Center who had been treated for ailments unrelated to scarlet fever. The extraordinary culprit was ice cream, which had a frequent/occasional/none consumption prevalence of 60%, 34%, and 6% among the cases and 24%, 51%, and 25% among the controls, respectively. The 1925 report reads, "Detailed epidemiological investigation, by means of case histories and control histories on well persons, confirmed early suspicions and established the fact that the epidemic was spread by ice cream" (Am J Hyg. 1925;5(5):669-681). This forgotten epidemiologic study is the oldest study using the case-control design to have been resurrected thus far. The case-control study design may have been conceived simultaneously, but independently and for different purposes, in England (Janet Lane-Claypon's 1926 report on the determinants of breast cancer) and the United States.

Waiting list randomized controlled trial within a case-finding design: methodological considerations.

PubMed

Ronaldson, Sarah; Adamson, Joy; Dyson, Lisa; Torgerson, David

2014-10-01

Randomized controlled trials (RCTs) are widely used in health care research to provide high-quality evidence of effectiveness of an intervention. However, sometimes a study does not require an RCT in order to answer its primary objective; a case-finding design may be more appropriate. The aim of this paper was to introduce a new study design that nests a waiting list RCT within a case-finding study. An example of the new study design is the DOC Study, which primarily aims to determine the diagnostic accuracy of lung function tests for chronic obstructive pulmonary disease. It also investigates the impact of lung function tests on smoking behaviour through use of a waiting list design. The first step of the study design is to obtain participants' consent. Individuals are then randomized to one of two groups; either the 'intervention now' group or the 'intervention later' group, that is, participants are placed on a waiting list. All participants receive the same intervention; the only difference between the groups is the timing of the intervention. The design addresses patient preference issues and recruitment issues that can arise in other trial designs. Potential limitations include differential attrition between study groups and potential demoralization for the 'intervention later' group. The 'waiting list case-finding trial' design is a valuable method that could be applied to case-finding studies; the design enables the case-finding component of a study to be maintained while simultaneously exploring additional hypotheses through conducting a trial. © 2014 John Wiley & Sons, Ltd.

Outbreak of Escherichia coli O157:H7 Infections After Petting Zoo Visits, North Carolina State Fair, October-November 2004

USDA-ARS?s Scientific Manuscript database

Objectives: To identify cases, describe the outbreak, implement control measures, and identify factors associated with infection or protection from infection, including contact with animals and hand hygiene practices. Design: Case finding, a case-control study of 45 cases and 188 controls, enviro...

Methodological Issues in Design and Analysis of a Matched Case-Control Study of a Vaccine’s Effectiveness

PubMed Central

Niccolai, Linda M.; Ogden, Lorraine G.; Muehlenbein, Catherine E.; Dziura, James D.; Vázquez, Marietta; Shapiro, Eugene D.

2007-01-01

Objective Case-control studies of the effectiveness of a vaccine are useful to answer important questions, such as the effectiveness of a vaccine over time, that usually are not addressed by pre-licensure clinical trials of the vaccine’s efficacy. This report describes methodological issues related to design and analysis that were used to determine the effects of time since vaccination and age at the time of vaccination. Study Design and Setting A matched case-control study of the effectiveness of varicella vaccine. Results Sampling procedures and conditional logistic regression models including interaction terms are described. Conclusion Use of these methods will allow investigators to assess the effects of a wide range of variables, such as time since vaccination and age at the time of vaccination, on the effectiveness of a vaccine. PMID:17938054

Case-control Studies on the Effectiveness of Breast Cancer Screening: Insights from the UK Age Trial.

PubMed

van der Waal, Daniëlle; Broeders, Mireille J M; Verbeek, André L M; Duffy, Stephen W; Moss, Sue M

2015-07-01

Ongoing breast cancer screening programs can only be evaluated using observational study designs. Most studies have observed a reduction in breast cancer mortality, but design differences appear to have resulted in different estimates. Direct comparison of case-control and trial analyses gives more insight into this variation. Here, we performed case-control analyses within the randomized UK Age Trial. The Age Trial assessed the effect of screening on breast cancer mortality in women ages 40-49 years. In our approach, case subjects were defined as breast cancer deaths between trial entry (1991-1997) and 2004. Women were ages 39-41 years at entry. For every case subject, five control subjects were selected. All case subjects were included in analyses of screening invitation (356 case subjects, 1,780 controls), whereas analyses of attendance were restricted to women invited to screening (105 case subjects, 525 age-matched controls). Odds ratios (OR) were estimated with conditional logistic regression. We used and compared two methods to correct for self-selection bias. Screening invitation resulted in a breast cancer mortality reduction of 17% (95% confidence interval [CI]: -36%, +6%), similar to trial results. Different exposure definitions and self-selection adjustments influenced the observed breast cancer mortality reduction. Depending on the method, "ever screened" appeared to be associated with a small reduction (OR: 0.86, 95% CI: 0.40, 1.89) or no reduction (OR: 1.02, 95% CI: 0.48, 2.14) using the two methods of correction. Recent attendance resulted in an adjusted mortality reduction of 36% (95% CI: -69%, +31%) or 45% (95% CI: -71%, +5%). Observational studies, and particularly case-control studies, are an important monitoring tool for breast cancer screening programs. The focus should be on diminishing bias in observational studies and gaining a better understanding of the influence of study design on estimates of mortality reduction.

On the Analysis of Case-Control Studies in Cluster-correlated Data Settings.

PubMed

Haneuse, Sebastien; Rivera-Rodriguez, Claudia

2018-01-01

In resource-limited settings, long-term evaluation of national antiretroviral treatment (ART) programs often relies on aggregated data, the analysis of which may be subject to ecological bias. As researchers and policy makers consider evaluating individual-level outcomes such as treatment adherence or mortality, the well-known case-control design is appealing in that it provides efficiency gains over random sampling. In the context that motivates this article, valid estimation and inference requires acknowledging any clustering, although, to our knowledge, no statistical methods have been published for the analysis of case-control data for which the underlying population exhibits clustering. Furthermore, in the specific context of an ongoing collaboration in Malawi, rather than performing case-control sampling across all clinics, case-control sampling within clinics has been suggested as a more practical strategy. To our knowledge, although similar outcome-dependent sampling schemes have been described in the literature, a case-control design specific to correlated data settings is new. In this article, we describe this design, discuss balanced versus unbalanced sampling techniques, and provide a general approach to analyzing case-control studies in cluster-correlated settings based on inverse probability-weighted generalized estimating equations. Inference is based on a robust sandwich estimator with correlation parameters estimated to ensure appropriate accounting of the outcome-dependent sampling scheme. We conduct comprehensive simulations, based in part on real data on a sample of N = 78,155 program registrants in Malawi between 2005 and 2007, to evaluate small-sample operating characteristics and potential trade-offs associated with standard case-control sampling or when case-control sampling is performed within clusters.

Misclassification of Case-Control Studies in Neurosurgery and Proposed Solutions.

PubMed

Esene, Ignatius Ngene; Mbuagbaw, Lawrence; Dechambenoit, Gilbert; Reda, Wael; Kalangu, Kazadi K

2018-04-01

Case-control studies (CCS) and cohort studies (CS) are common research designs in neurosurgery. But the term case-control study is frequently misused in the neurosurgical literature, with many articles reported as CCS, even although their methodology does not respect the basic components of a CCS. We sought to estimate the extent of these discrepancies in neurosurgical literature, explore factors contributing to mislabeling, and shed some light on study design reporting. We identified 31 top-ranking pure neurosurgical journals and searched them for articles reported as CCS, either in the title or in the abstract. The articles were read to determine if they really were CCS according to STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) guidelines. Article assessment was conducted in duplicate (agreement [κ statistics] = 99.82%). Two hundred and twenty-four articles met our inclusion criteria, 133 of which (59.38%) correctly labeled the case-control design, whereas 91 (40.62%) misclassified this study design. Cohort studies (CS) were the most common design mislabeled as case-control studies in 76 articles (33.93%), 57 of which (25.45%) were retrospective CS. The mislabeling of CCS impairs the appropriate indexing, classification, and sorting of evidence. Mislabeling CS for CCS leads to a downgrading of evidence as CS represent the highest level of evidence for observational studies. Odds ratios instead of relative risk are reported for these studies, resulting in a distortion of the measurement of the effect size, compounded when these are summarized in systematic reviews and pooled in meta-analyses. Many studies reported as CCS are not true CCS. Reporting guidelines should include items that ensure that studies are labeled correctly. STROBE guidelines should be implemented in assessment of observational studies. Researchers in neurosurgery need better training in research methods and terminology. We also recommend accrued vigilance from reviewers and editors. Copyright © 2018 Elsevier Inc. All rights reserved.

A scan statistic for identifying optimal risk windows in vaccine safety studies using self-controlled case series design.

PubMed

Xu, Stanley; Hambidge, Simon J; McClure, David L; Daley, Matthew F; Glanz, Jason M

2013-08-30

In the examination of the association between vaccines and rare adverse events after vaccination in postlicensure observational studies, it is challenging to define appropriate risk windows because prelicensure RCTs provide little insight on the timing of specific adverse events. Past vaccine safety studies have often used prespecified risk windows based on prior publications, biological understanding of the vaccine, and expert opinion. Recently, a data-driven approach was developed to identify appropriate risk windows for vaccine safety studies that use the self-controlled case series design. This approach employs both the maximum incidence rate ratio and the linear relation between the estimated incidence rate ratio and the inverse of average person time at risk, given a specified risk window. In this paper, we present a scan statistic that can identify appropriate risk windows in vaccine safety studies using the self-controlled case series design while taking into account the dependence of time intervals within an individual and while adjusting for time-varying covariates such as age and seasonality. This approach uses the maximum likelihood ratio test based on fixed-effects models, which has been used for analyzing data from self-controlled case series design in addition to conditional Poisson models. Copyright © 2013 John Wiley & Sons, Ltd.

Case-Cohort Studies: Design and Applicability to Hand Surgery.

PubMed

Vojvodic, Miliana; Shafarenko, Mark; McCabe, Steven J

2018-04-24

Observational studies are common research strategies in hand surgery. The case-cohort design offers an efficient and resource-friendly method for risk assessment and outcomes analysis. Case-cohorts remain underrepresented in upper extremity research despite several practical and economic advantages over case-control studies. This report outlines the purpose, utility, and structure of the case-cohort design and offers a sample research question to demonstrate its value to risk estimation for adverse surgical outcomes. The application of well-designed case-cohort studies is advocated in an effort to improve the quality and quantity of observational research evidence in hand and upper extremity surgery. Copyright © 2018 American Society for Surgery of the Hand. Published by Elsevier Inc. All rights reserved.

Recruitment of participants through community pharmacies for a pharmacogenetic study of antihypertensive drug treatment.

PubMed

van Wieren-de Wijer, Diane B M A; Maitland-van der Zee, Anke-Hilse; de Boer, Anthonius; Stricker, Bruno H Ch; Kroon, Abraham A; de Leeuw, Peter W; Bozkurt, O; Klungel, Olaf H

2009-04-01

To describe the design, recruitment and baseline characteristics of participants in a community pharmacy based pharmacogenetic study of antihypertensive drug treatment. Participants enrolled from the population-based Pharmaco-Morbidity Record Linkage System. We designed a nested case-control study in which we will assess whether specific genetic polymorphisms modify the effect of antihypertensive drugs on the risk of myocardial infarction. In this study, cases (myocardial infarction) and controls were recruited through community pharmacies that participate in PHARMO. The PHARMO database comprises drug dispensing histories of about 2,000,000 subjects from a representative sample of Dutch community pharmacies linked to the national registrations of hospital discharges. In total we selected 31010 patients (2777 cases and 28233 controls) from the PHARMO database, of whom 15973 (1871 cases, 14102 controls) were approached through their community pharmacy. Overall response rate was 36.3% (n = 5791, 794 cases, 4997 controls), whereas 32.1% (n = 5126, 701 cases, 4425 controls) gave informed consent to genotype their DNA. As expected, several cardiovascular risk factors such as smoking, body mass index, hypercholesterolemia, and diabetes mellitus were more common in cases than in controls. Furthermore, cases more often used beta-blockers and calcium-antagonists, whereas controls more often used thiazide diuretics, ACE-inhibitors, and angiotensin-II receptor blockers. We have demonstrated that it is feasible to select patients from a coded database for a pharmacogenetic study and to approach them through community pharmacies, achieving reasonable response rates and without violating privacy rules.

Optimal case-control matching in practice.

PubMed

Cologne, J B; Shibata, Y

1995-05-01

We illustrate modern matching techniques and discuss practical issues in defining the closeness of matching for retrospective case-control designs (in which the pool of subjects already exists when the study commences). We empirically compare matching on a balancing score, analogous to the propensity score for treated/control matching, with matching on a weighted distance measure. Although both methods in principle produce balance between cases and controls in the marginal distributions of the matching covariates, the weighted distance measure provides better balance in practice because the balancing score can be poorly estimated. We emphasize the use of optimal matching based on efficient network algorithms. An illustration is based on the design of a case-control study of hepatitis B virus infection as a possible confounder and/or effect modifier of radiation-related primary liver cancer in atomic bomb survivors.

Epidemiological designs for vaccine safety assessment: methods and pitfalls.

PubMed

Andrews, Nick

2012-09-01

Three commonly used designs for vaccine safety assessment post licensure are cohort, case-control and self-controlled case series. These methods are often used with routine health databases and immunisation registries. This paper considers the issues that may arise when designing an epidemiological study, such as understanding the vaccine safety question, case definition and finding, limitations of data sources, uncontrolled confounding, and pitfalls that apply to the individual designs. The example of MMR and autism, where all three designs have been used, is presented to help consider these issues. Copyright © 2011 The International Alliance for Biological Standardization. Published by Elsevier Ltd. All rights reserved.

Drug and alcohol crash risk : a case-control study.

DOT National Transportation Integrated Search

2016-12-01

This study used a case-control design to estimate the risk of crashes involving drivers using drugs, alcohol or both. Data was collected in Virginia Beach, Virginia, for 20 months. The study obtained biological measures on more than 3,000 crash...

Toxoplasmosis gondii and schizophrenia: a case control study in a low Toxoplasma gondii seroprevalence Mexican population

USDA-ARS?s Scientific Manuscript database

There are conflicting reports concerning the association of T. gondii infection and schizophrenia. Therefore, we determined such association in a Mexican population of Mestizo ethnicity. Through a case-control study design, 50 schizophrenic patients and 150 control subjects matched by gender, age, r...

Multiple imputation of missing data in nested case-control and case-cohort studies.

PubMed

Keogh, Ruth H; Seaman, Shaun R; Bartlett, Jonathan W; Wood, Angela M

2018-06-05

The nested case-control and case-cohort designs are two main approaches for carrying out a substudy within a prospective cohort. This article adapts multiple imputation (MI) methods for handling missing covariates in full-cohort studies for nested case-control and case-cohort studies. We consider data missing by design and data missing by chance. MI analyses that make use of full-cohort data and MI analyses based on substudy data only are described, alongside an intermediate approach in which the imputation uses full-cohort data but the analysis uses only the substudy. We describe adaptations to two imputation methods: the approximate method (MI-approx) of White and Royston () and the "substantive model compatible" (MI-SMC) method of Bartlett et al. (). We also apply the "MI matched set" approach of Seaman and Keogh () to nested case-control studies, which does not require any full-cohort information. The methods are investigated using simulation studies and all perform well when their assumptions hold. Substantial gains in efficiency can be made by imputing data missing by design using the full-cohort approach or by imputing data missing by chance in analyses using the substudy only. The intermediate approach brings greater gains in efficiency relative to the substudy approach and is more robust to imputation model misspecification than the full-cohort approach. The methods are illustrated using the ARIC Study cohort. Supplementary Materials provide R and Stata code. © 2018, The International Biometric Society.

Considerations of study design.

PubMed

Koretz, Ronald L

2007-12-01

Research projects attempt to answer specific questions. The particular study design that is selected will depend in large measure on the nature of the question and the time and resources available. There are 5 common categories of clinical questions; they relate to etiology, prognosis, utility of diagnostic tests, efficacy of proposed interventions, and cost of treatment in specific disease states. A number of study designs can be used. Case reports serve to memorialize unusual or novel aspects of diseases. Retrospective case series are useful for defining natural history. Case-control studies are used by epidemiologists to elucidate potential etiologies of diseases. Prospective cohort studies can be used to assess natural history or to assess potential disease etiologies. Controlled trials are designed to assess the efficacy of therapeutic interventions. Studies that define the sensitivity and specificity of diagnostic tests can be used to assess the utility of those tests. Economic analyses estimate the costs that particular diseases or therapies will require. Each of these study designs has limitations; with the exception of high-quality randomized trials, none of these study designs can establish a causative relationship between putative etiologic (or therapeutic) factors and disease (outcomes).

[The choice of the type of design in the clinical investigation studies. Case and control studies].

PubMed

Posada de la Paz, M

2004-09-01

Case-control studies are appropriate designs in neurology sciences to search for risk factors that have already occurred in a group of patients. In them, the subjects are selected on the basis of whether they have the disease or not and then they are compared in regards to the risk factor or prognosis investigated. These sorts of designs can be performed in a shorter and cheaper way than the regular cohort studies. They are appropriate for the evaluation of rare diseases and can examine multiple etiological factors for a single disease. On the contrary, they are not so efficient when rare exposures are involved. Incidence rates in exposed and non-exposed subjects cannot be calculated and on some occasions, the timing between exposure and outcome can be very difficult to establish. The Odds Ratio and its confident intervals is the measurement used for estimating the risk strength in this design. The clinical neurologist should be familiar with these terms, given the frequency of case-control studies described in neurology science literature, and should know their principal advantages and limitations.

Unconditional analyses can increase efficiency in assessing gene-environment interaction of the case-combined-control design.

PubMed

Goldstein, Alisa M; Dondon, Marie-Gabrielle; Andrieu, Nadine

2006-08-01

A design combining both related and unrelated controls, named the case-combined-control design, was recently proposed to increase the power for detecting gene-environment (GxE) interaction. Under a conditional analytic approach, the case-combined-control design appeared to be more efficient and feasible than a classical case-control study for detecting interaction involving rare events. We now propose an unconditional analytic strategy to further increase the power for detecting gene-environment (GxE) interactions. This strategy allows the estimation of GxE interaction and exposure (E) main effects under certain assumptions (e.g. no correlation in E between siblings and the same exposure frequency in both control groups). Only the genetic (G) main effect cannot be estimated because it is biased. Using simulations, we show that unconditional logistic regression analysis is often more efficient than conditional analysis for detecting GxE interaction, particularly for a rare gene and strong effects. The unconditional analysis is also at least as efficient as the conditional analysis when the gene is common and the main and joint effects of E and G are small. Under the required assumptions, the unconditional analysis retains more information than does the conditional analysis for which only discordant case-control pairs are informative leading to more precise estimates of the odds ratios.

Disease-Concordant Twins Empower Genetic Association Studies.

PubMed

Tan, Qihua; Li, Weilong; Vandin, Fabio

2017-01-01

Genome-wide association studies with moderate sample sizes are underpowered, especially when testing SNP alleles with low allele counts, a situation that may lead to high frequency of false-positive results and lack of replication in independent studies. Related individuals, such as twin pairs concordant for a disease, should confer increased power in genetic association analysis because of their genetic relatedness. We conducted a computer simulation study to explore the power advantage of the disease-concordant twin design, which uses singletons from disease-concordant twin pairs as cases and ordinary healthy samples as controls. We examined the power gain of the twin-based design for various scenarios (i.e., cases from monozygotic and dizygotic twin pairs concordant for a disease) and compared the power with the ordinary case-control design with cases collected from the unrelated patient population. Simulation was done by assigning various allele frequencies and allelic relative risks for different mode of genetic inheritance. In general, for achieving a power estimate of 80%, the sample sizes needed for dizygotic and monozygotic twin cases were one half and one fourth of the sample size of an ordinary case-control design, with variations depending on genetic mode. Importantly, the enriched power for dizygotic twins also applies to disease-concordant sibling pairs, which largely extends the application of the concordant twin design. Overall, our simulation revealed a high value of disease-concordant twins in genetic association studies and encourages the use of genetically related individuals for highly efficiently identifying both common and rare genetic variants underlying human complex diseases without increasing laboratory cost. © 2016 John Wiley & Sons Ltd/University College London.

Case-control studies in neurosurgery.

PubMed

Nesvick, Cody L; Thompson, Clinton J; Boop, Frederick A; Klimo, Paul

2014-08-01

Observational studies, such as cohort and case-control studies, are valuable instruments in evidence-based medicine. Case-control studies, in particular, are becoming increasingly popular in the neurosurgical literature due to their low cost and relative ease of execution; however, no one has yet systematically assessed these types of studies for quality in methodology and reporting. The authors performed a literature search using PubMed/MEDLINE to identify all studies that explicitly identified themselves as "case-control" and were published in the JNS Publishing Group journals (Journal of Neurosurgery, Journal of Neurosurgery: Pediatrics, Journal of Neurosurgery: Spine, and Neurosurgical Focus) or Neurosurgery. Each paper was evaluated for 22 descriptive variables and then categorized as having either met or missed the basic definition of a case-control study. All studies that evaluated risk factors for a well-defined outcome were considered true case-control studies. The authors sought to identify key features or phrases that were or were not predictive of a true case-control study. Those papers that satisfied the definition were further evaluated using the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) checklist. The search detected 67 papers that met the inclusion criteria, of which 32 (48%) represented true case-control studies. The frequency of true case-control studies has not changed with time. Use of odds ratios (ORs) and logistic regression (LR) analysis were strong positive predictors of true case-control studies (for odds ratios, OR 15.33 and 95% CI 4.52-51.97; for logistic regression analysis, OR 8.77 and 95% CI 2.69-28.56). Conversely, negative predictors included focus on a procedure/intervention (OR 0.35, 95% CI 0.13-0.998) and use of the word "outcome" in the Results section (OR 0.23, 95% CI 0.082-0.65). After exclusion of nested case-control studies, the negative correlation between focus on a procedure/intervention and true case-control studies was strengthened (OR 0.053, 95% CI 0.0064-0.44). There was a trend toward a negative association between the use of survival analysis or Kaplan-Meier curves and true case-control studies (OR 0.13, 95% CI 0.015-1.12). True case-control studies were no more likely than their counterparts to use a potential study design "expert" (OR 1.50, 95% CI 0.57-3.95). The overall average STROBE score was 72% (range 50-86%). Examples of reporting deficiencies were reporting of bias (28%), missing data (55%), and funding (44%). The results of this analysis show that the majority of studies in the neurosurgical literature that identify themselves as "case-control" studies are, in fact, labeled incorrectly. Positive and negative predictors were identified. The authors provide several recommendations that may reverse the incorrect and inappropriate use of the term "case-control" and improve the quality of design and reporting of true case-control studies in neurosurgery.

Snippets From the Past: Is Flint, Michigan, the Birthplace of the Case-Control Study?

PubMed Central

Morabia, Alfredo

2013-01-01

In the summer of 1924, an outbreak of scarlet fever occurred in Flint, Michigan. Unable to trace it to the usual causes, particularly fresh milk, the Michigan Department of Health used a novel approach to disentangle the enigma: The 116 cases of scarlet fever were compared with 117 “controls” selected from neighbors of the quarantined cases and from patients at the City Health Center who had been treated for ailments unrelated to scarlet fever. The extraordinary culprit was ice cream, which had a frequent/occasional/none consumption prevalence of 60%, 34%, and 6% among the cases and 24%, 51%, and 25% among the controls, respectively. The 1925 report reads, “Detailed epidemiological investigation, by means of case histories and control histories on well persons, confirmed early suspicions and established the fact that the epidemic was spread by ice cream” (Am J Hyg. 1925;5(5):669–681). This forgotten epidemiologic study is the oldest study using the case-control design to have been resurrected thus far. The case-control study design may have been conceived simultaneously, but independently and for different purposes, in England (Janet Lane-Claypon's 1926 report on the determinants of breast cancer) and the United States. PMID:24064743

Review of the literature on benzene exposure and leukemia subtypes.

PubMed

Schnatter, A Robert; Rosamilia, Kim; Wojcik, Nancy C

2005-05-30

The epidemiologic literature on benzene exposure and leukemia in the MEDLINE and TOXNET databases was examined through October 2004 using the keywords "benzene", "leukemia" and "adverse health effects". This search was complemented by reviewing the reference lists from extant literature reviews and criteria documents on benzene. Published studies were characterized according to the type of industry studied and design, exposure assessment, disease classification, and control for confounding variables. Study design consisted of either cohort studies or case-control studies, which were further categorized into population-based and nested case-control studies. Disease classification considered the source of diagnostic information, whether there was clinical confirmation from medical records or histopathological, morphological and/or cytogenetic reviews, and as to whether the International Classification of Diseases (ICD) or the French-American-British (FAB) schemes were used (no studies used the Revised European-American Lymphoma (REAL) classification scheme). Nine cohort and 13 case-control studies met inclusion criteria for this review. High and significant acute myeloid leukemia risks with positive dose response relationships were identified across study designs, particularly in the "well-conducted" cohort studies and especially in more highly exposed workers in rubber, shoe, and paint industries. Risks for chronic lymphocytic leukemia (CLL) tended to show elevations in nested case-control studies, with possible dose response relationships in at least two of the three studies. However, cohort studies on CLL show no such risks. Data for chronic myeloid leukemia and acute lymphocytic leukemia are sparse and inconclusive.

The Development of the CONDUIT Advanced Control System Design and Evaluation Interface with a Case Study Application to an Advanced Fly by Wire Helicopter Design

NASA Technical Reports Server (NTRS)

Colbourne, Jason

1999-01-01

This report details the development and use of CONDUIT (Control Designer's Unified Interface). CONDUIT is a design tool created at Ames Research Center for the purpose of evaluating and optimizing aircraft control systems against handling qualities. Three detailed design problems addressing the RASCAL UH-60A Black Hawk are included in this report to show the application of CONDUIT to helicopter control system design.

High reprint orders in medical journals and pharmaceutical industry funding: case-control study

PubMed Central

Handel, Adam E; Patel, Sunil V; Pakpoor, Julia; Ebers, George C; Goldacre, Ben

2012-01-01

Objectives To assess the extent to which funding and study design are associated with high reprint orders. Design Case-control study. Setting Top articles by size of reprint orders in seven journals, 2002-09. Participants Lancet, Lancet Neurology, Lancet Oncology (Lancet Group), BMJ, Gut, Heart, and Journal of Neurology, Neurosurgery & Psychiatry (BMJ Group) matched to contemporaneous articles not in the list of high reprint orders. Main outcome measures Funding and design of randomised controlled trials or other study designs. Results Median reprint orders for the seven journals ranged from 3000 to 126 350. Papers with high reprint orders were more likely to be funded by the pharmaceutical industry than were control papers (industry funding versus other or none: odds ratio 8.64, 95% confidence interval 5.09 to 14.68, and mixed funding versus other or none: 3.72, 2.43 to 5.70). Conclusions Funding by the pharmaceutical industry is associated with high numbers of reprint orders. PMID:22745328

A comparison of the test-negative and the traditional case-control study designs for estimation of influenza vaccine effectiveness under nonrandom vaccination.

PubMed

Shi, Meng; An, Qian; Ainslie, Kylie E C; Haber, Michael; Orenstein, Walter A

2017-12-08

As annual influenza vaccination is recommended for all U.S. persons aged 6 months or older, it is unethical to conduct randomized clinical trials to estimate influenza vaccine effectiveness (VE). Observational studies are being increasingly used to estimate VE. We developed a probability model for comparing the bias and the precision of VE estimates from two case-control designs: the traditional case-control (TCC) design and the test-negative (TN) design. In both study designs, acute respiratory illness (ARI) patients seeking medical care testing positive for influenza infection are considered cases. In the TN design, ARI patients seeking medical care who test negative serve as controls, while in the TCC design, controls are randomly selected individuals from the community who did not contract an ARI. Our model assigns each study participant a covariate corresponding to the person's health status. The probabilities of vaccination and of contracting influenza and non-influenza ARI depend on health status. Hence, our model allows non-random vaccination and confounding. In addition, the probability of seeking care for ARI may depend on vaccination and health status. We consider two outcomes of interest: symptomatic influenza (SI) and medically-attended influenza (MAI). If vaccination does not affect the probability of non-influenza ARI, then VE estimates from TN studies usually have smaller bias than estimates from TCC studies. We also found that if vaccinated influenza ARI patients are less likely to seek medical care than unvaccinated patients because the vaccine reduces symptoms' severity, then estimates of VE from both types of studies may be severely biased when the outcome of interest is SI. The bias is not present when the outcome of interest is MAI. The TN design produces valid estimates of VE if (a) vaccination does not affect the probabilities of non-influenza ARI and of seeking care against influenza ARI, and (b) the confounding effects resulting from non-random vaccination are similar for influenza and non-influenza ARI. Since the bias of VE estimates depends on the outcome against which the vaccine is supposed to protect, it is important to specify the outcome of interest when evaluating the bias.

Unconditional or Conditional Logistic Regression Model for Age-Matched Case-Control Data?

PubMed

Kuo, Chia-Ling; Duan, Yinghui; Grady, James

2018-01-01

Matching on demographic variables is commonly used in case-control studies to adjust for confounding at the design stage. There is a presumption that matched data need to be analyzed by matched methods. Conditional logistic regression has become a standard for matched case-control data to tackle the sparse data problem. The sparse data problem, however, may not be a concern for loose-matching data when the matching between cases and controls is not unique, and one case can be matched to other controls without substantially changing the association. Data matched on a few demographic variables are clearly loose-matching data, and we hypothesize that unconditional logistic regression is a proper method to perform. To address the hypothesis, we compare unconditional and conditional logistic regression models by precision in estimates and hypothesis testing using simulated matched case-control data. Our results support our hypothesis; however, the unconditional model is not as robust as the conditional model to the matching distortion that the matching process not only makes cases and controls similar for matching variables but also for the exposure status. When the study design involves other complex features or the computational burden is high, matching in loose-matching data can be ignored for negligible loss in testing and estimation if the distributions of matching variables are not extremely different between cases and controls.

Psychological Factors in Deliberate Self-Harm as Seen in an Urban African Population in Uganda: A Case-Control Study

ERIC Educational Resources Information Center

Kinyanda, Eugene; Hjelmeland, Heidi; Musisi, Seggane

2005-01-01

Psychological factors associated with deliberate self-harm (DSH) as seen in an African population in Uganda are described. A case-control study design was employed in which a Luganda version (predominant language in the study area) of the modified European Parasuicide Interview Schedule I (EPSIS I) was used to collect data. The controls were…

Supporting Affect Regulation in Children with Multiple Disabilities during Psychotherapy: A Multiple Case Design Study of Therapeutic Attachment

ERIC Educational Resources Information Center

Schuengel, C.; Sterkenburg, P. S.; Jeczynski, P.; Janssen, C. G. C.; Jongbloed, G.

2009-01-01

In a controlled multiple case design study, the development of a therapeutic relationship and its role in affect regulation were studied in 6 children with visual disabilities, severe intellectual disabilities, severe challenging behavior, and prolonged social deprivation. In the 1st phase, children had sessions with an experimental therapist…

Reducing selection bias in case-control studies from rare disease registries.

PubMed

Cole, J Alexander; Taylor, John S; Hangartner, Thomas N; Weinreb, Neal J; Mistry, Pramod K; Khan, Aneal

2011-09-12

In clinical research of rare diseases, where small patient numbers and disease heterogeneity limit study design options, registries are a valuable resource for demographic and outcome information. However, in contrast to prospective, randomized clinical trials, the observational design of registries is prone to introduce selection bias and negatively impact the validity of data analyses. The objective of the study was to demonstrate the utility of case-control matching and the risk-set method in order to control bias in data from a rare disease registry. Data from the International Collaborative Gaucher Group (ICGG) Gaucher Registry were used as an example. A case-control matching analysis using the risk-set method was conducted to identify two groups of patients with type 1 Gaucher disease in the ICGG Gaucher Registry: patients with avascular osteonecrosis (AVN) and those without AVN. The frequency distributions of gender, decade of birth, treatment status, and splenectomy status were presented for cases and controls before and after matching. Odds ratios (and 95% confidence intervals) were calculated for each variable before and after matching. The application of case-control matching methodology results in cohorts of cases (i.e., patients with AVN) and controls (i.e., patients without AVN) who have comparable distributions for four common parameters used in subject selection: gender, year of birth (age), treatment status, and splenectomy status. Matching resulted in odds ratios of approximately 1.00, indicating no bias. We demonstrated bias in case-control selection in subjects from a prototype rare disease registry and used case-control matching to minimize this bias. Therefore, this approach appears useful to study cohorts of heterogeneous patients in rare disease registries.

Environment And Genetics in Lung cancer Etiology (EAGLE) study: an integrative population-based case-control study of lung cancer.

PubMed

Landi, Maria Teresa; Consonni, Dario; Rotunno, Melissa; Bergen, Andrew W; Goldstein, Alisa M; Lubin, Jay H; Goldin, Lynn; Alavanja, Michael; Morgan, Glen; Subar, Amy F; Linnoila, Ilona; Previdi, Fabrizio; Corno, Massimo; Rubagotti, Maurizia; Marinelli, Barbara; Albetti, Benedetta; Colombi, Antonio; Tucker, Margaret; Wacholder, Sholom; Pesatori, Angela C; Caporaso, Neil E; Bertazzi, Pier Alberto

2008-06-06

Lung cancer is the leading cause of cancer mortality worldwide. Tobacco smoking is its primary cause, and yet the precise molecular alterations induced by smoking in lung tissue that lead to lung cancer and impact survival have remained obscure. A new framework of research is needed to address the challenges offered by this complex disease. We designed a large population-based case-control study that combines a traditional molecular epidemiology design with a more integrative approach to investigate the dynamic process that begins with smoking initiation, proceeds through dependency/smoking persistence, continues with lung cancer development and ends with progression to disseminated disease or response to therapy and survival. The study allows the integration of data from multiple sources in the same subjects (risk factors, germline variation, genomic alterations in tumors, and clinical endpoints) to tackle the disease etiology from different angles. Before beginning the study, we conducted a phone survey and pilot investigations to identify the best approach to ensure an acceptable participation in the study from cases and controls. Between 2002 and 2005, we enrolled 2101 incident primary lung cancer cases and 2120 population controls, with 86.6% and 72.4% participation rate, respectively, from a catchment area including 216 municipalities in the Lombardy region of Italy. Lung cancer cases were enrolled in 13 hospitals and population controls were randomly sampled from the area to match the cases by age, gender and residence. Detailed epidemiological information and biospecimens were collected from each participant, and clinical data and tissue specimens from the cases. Collection of follow-up data on treatment and survival is ongoing. EAGLE is a new population-based case-control study that explores the full spectrum of lung cancer etiology, from smoking addiction to lung cancer outcome, through examination of epidemiological, molecular, and clinical data. We have provided a detailed description of the study design, field activities, management, and opportunities for research following this integrative approach, which allows a sharper and more comprehensive vision of the complex nature of this disease. The study is poised to accelerate the emergence of new preventive and therapeutic strategies with potentially enormous impact on public health.

An alternative experimental case-control design for genetic association studies on bovine mastitis.

PubMed

Biffani, S; Del Corvo, M; Capoferri, R; Pedretti, A; Luini, M; Williams, J L; Pagnacco, G; Minvielle, F; Minozzi, G

2017-04-01

The possibility of using genetic control strategies to increase disease resistance to infectious diseases relies on the identification of markers to include in the breeding plans. Possible incomplete exposure of mastitis-free (control) animals, however, is a major issue to find relevant markers in genetic association studies for infectious diseases. Usually, designs based on elite dairy sires are used in association studies, but an epidemiological case-control strategy, based on cows repeatedly field-tested could be an alternative for disease traits. To test this hypothesis, genetic association results obtained in the present work from a cohort of Italian Holstein cows tested for mastitis over time were compared with those from a previous genome-wide scan on Italian Holstein sires genotyped with 50k single nucleotide polymorphisms for de-regressed estimated breeding values for somatic cell counts (SCCs) on Bos taurus autosome (BTA6) and BTA14. A total of 1121 cows were selected for the case-control approach (cases=550, controls=571), on a combination of herd level of SCC incidence and of within herd individual level of SCC. The association study was conducted on nine previously identified markers, six on BTA6 and four on BTA14, using the R statistical environment with the 'qtscore' function of the GenABEL package, on high/low adjusted linear score as a binomial trait. The results obtained in the cow cohort selected on epidemiological information were in agreement with those obtained from the previous sire genome-wide association study (GWAS). Six out of the nine markers showed significant association, four on BTA14 (rs109146371, rs109234250, rs109421300, rs109162116) and two on BTA6 (rs110527224 and rs42766480). Most importantly, using mastitis as a case study, the current work further validated the alternative use of historical field disease data in case-control designs for genetic analysis of infectious diseases in livestock.

Estimating risk and rate levels, ratios and differences in case-control studies.

PubMed

King, Gary; Zeng, Langche

2002-05-30

Classic (or 'cumulative') case-control sampling designs do not admit inferences about quantities of interest other than risk ratios, and then only by making the rare events assumption. Probabilities, risk differences and other quantities cannot be computed without knowledge of the population incidence fraction. Similarly, density (or 'risk set') case-control sampling designs do not allow inferences about quantities other than the rate ratio. Rates, rate differences, cumulative rates, risks, and other quantities cannot be estimated unless auxiliary information about the underlying cohort such as the number of controls in each full risk set is available. Most scholars who have considered the issue recommend reporting more than just risk and rate ratios, but auxiliary population information needed to do this is not usually available. We address this problem by developing methods that allow valid inferences about all relevant quantities of interest from either type of case-control study when completely ignorant of or only partially knowledgeable about relevant auxiliary population information.

Case-control analysis in highway safety: Accounting for sites with multiple crashes.

PubMed

Gross, Frank

2013-12-01

There is an increased interest in the use of epidemiological methods in highway safety analysis. The case-control and cohort methods are commonly used in the epidemiological field to identify risk factors and quantify the risk or odds of disease given certain characteristics and factors related to an individual. This same concept can be applied to highway safety where the entity of interest is a roadway segment or intersection (rather than a person) and the risk factors of interest are the operational and geometric characteristics of a given roadway. One criticism of the use of these methods in highway safety is that they have not accounted for the difference between sites with single and multiple crashes. In the medical field, a disease either occurs or it does not; multiple occurrences are generally not an issue. In the highway safety field, it is necessary to evaluate the safety of a given site while accounting for multiple crashes. Otherwise, the analysis may underestimate the safety effects of a given factor. This paper explores the use of the case-control method in highway safety and two variations to account for sites with multiple crashes. Specifically, the paper presents two alternative methods for defining cases in a case-control study and compares the results in a case study. The first alternative defines a separate case for each crash in a given study period, thereby increasing the weight of the associated roadway characteristics in the analysis. The second alternative defines entire crash categories as cases (sites with one crash, sites with two crashes, etc.) and analyzes each group separately in comparison to sites with no crashes. The results are also compared to a "typical" case-control application, where the cases are simply defined as any entity that experiences at least one crash and controls are those entities without a crash in a given period. In a "typical" case-control design, the attributes associated with single-crash segments are weighted the same as the attributes of segments with multiple crashes. The results support the hypothesis that the "typical" case-control design may underestimate the safety effects of a given factor compared to methods that account for sites with multiple crashes. Compared to the first alternative case definition (where multiple crash segments represent multiple cases) the results from the "typical" case-control design are less pronounced (i.e., closer to unity). The second alternative (where case definitions are constructed for various crash categories and analyzed separately) provides further evidence that sites with single and multiple crashes should not be grouped together in a case-control analysis. This paper indicates a clear need to differentiate sites with single and multiple crashes in a case-control analysis. While the results suggest that sites with multiple crashes can be accounted for using a case-control design, further research is needed to determine the optimal method for addressing this issue. This paper provides a starting point for that research. Copyright © 2012 Elsevier Ltd. All rights reserved.

Evaluating efficiency and statistical power of self-controlled case series and self-controlled risk interval designs in vaccine safety.

PubMed

Li, Rongxia; Stewart, Brock; Weintraub, Eric

2016-01-01

The self-controlled case series (SCCS) and self-controlled risk interval (SCRI) designs have recently become widely used in the field of post-licensure vaccine safety monitoring to detect potential elevated risks of adverse events following vaccinations. The SCRI design can be viewed as a subset of the SCCS method in that a reduced comparison time window is used for the analysis. Compared to the SCCS method, the SCRI design has less statistical power due to fewer events occurring in the shorter control interval. In this study, we derived the asymptotic relative efficiency (ARE) between these two methods to quantify this loss in power in the SCRI design. The equation is formulated as [Formula: see text] (a: control window-length ratio between SCRI and SCCS designs; b: ratio of risk window length and control window length in the SCCS design; and [Formula: see text]: relative risk of exposed window to control window). According to this equation, the relative efficiency declines as the ratio of control-period length between SCRI and SCCS methods decreases, or with an increase in the relative risk [Formula: see text]. We provide an example utilizing data from the Vaccine Safety Datalink (VSD) to study the potential elevated risk of febrile seizure following seasonal influenza vaccine in the 2010-2011 season.

National Case-Control Study of Homicide Offending and Methamphetamine Use

ERIC Educational Resources Information Center

Stretesky, Paul B.

2009-01-01

The purpose of this study is to examine the relationship between methamphetamine use and homicide. To carry out this study, data from the National Household Survey on Drug Abuse and Survey of Inmates in State and Federal Correctional Facilities were combined to create a case-control design. The main exposure measure is methamphetamine use and the…

Wind Turbine Control Design to Reduce Capital Costs: 7 January 2009 - 31 August 2009

DOE Office of Scientific and Technical Information (OSTI.GOV)

Darrow, P. J.

2010-01-01

This report first discusses and identifies which wind turbine components can benefit from advanced control algorithms and also presents results from a preliminary loads case analysis using a baseline controller. Next, it describes the design, implementation, and simulation-based testing of an advanced controller to reduce loads on those components. The case-by-case loads analysis and advanced controller design will help guide future control research.

The Family Investigation of Nephropathy and Diabetes (FIND): design and methods.

PubMed

Knowler, William C; Coresh, Josef; Elston, Robert C; Freedman, Barry I; Iyengar, Sudha K; Kimmel, Paul L; Olson, Jane M; Plaetke, Rosemarie; Sedor, John R; Seldin, Michael F

2005-01-01

The Family Investigation of Nephropathy and Diabetes (FIND) is a multicenter study designed to identify genetic determinants of diabetic nephropathy. It is conducted in eight U.S. clinical centers and a coordinating center, and with four ethnic groups (European Americans, African Americans, Mexican Americans, and American Indians). Two strategies are used to localize susceptibility genes: a family-based linkage study and a case-control study using mapping by admixture linkage disequilibrium (MALD). In the family-based study, probands with diabetic nephropathy are recruited with their parents and selected siblings. Linkage analyses will be conducted to identify chromosomal regions containing genes that influence the development of diabetic nephropathy or related quantitative traits such as serum creatinine concentration, urinary albumin excretion, and plasma glucose concentrations. Regions showing evidence of linkage will be examined further with both genetic linkage and association studies to identify genes that influence diabetic nephropathy or related traits. Two types of MALD studies are being done. One is a case-control study of unrelated individuals of Mexican American heritage in which both cases and controls have diabetes, but only the case has nephropathy. The other is a case-control study of African American patients with nephropathy (cases) and their spouses (controls) unaffected by diabetes and nephropathy; offspring are genotyped when available to provide haplotype data. Identification of genes that influence susceptibility to diabetic nephropathy will lead to a better understanding of how nephropathy develops. This should eventually lead to improved treatment and prevention.

The effects of particulate air pollution on daily deaths: a multi-city case crossover analysis

PubMed Central

Schwartz, J

2004-01-01

Background: Numerous studies have reported that day-to-day changes in particulate air pollution are associated with day-to-day changes in deaths. Recently, several reports have indicated that the software used to control for season and weather in some of these studies had deficiencies. Aims: To investigate the use of the case-crossover design as an alternative. Methods: This approach compares the exposure of each case to their exposure on a nearby day, when they did not die. Hence it controls for seasonal patterns and for all slowly varying covariates (age, smoking, etc) by matching rather than complex modelling. A key feature is that temperature can also be controlled by matching. This approach was applied to a study of 14 US cities. Weather and day of the week were controlled for in the regression. Results: A 10 µg/m3 increase in PM10 was associated with a 0.36% increase in daily deaths from internal causes (95% CI 0.22% to 0.50%). Results were little changed if, instead of symmetrical sampling of control days the time stratified method was applied, when control days were matched on temperature, or when more lags of winter time temperatures were used. Similar results were found using a Poisson regression, but the case-crossover method has the advantage of simplicity in modelling, and of combining matched strata across multiple locations in a single stage analysis. Conclusions: Despite the considerable differences in analytical design, the previously reported associations of particles with mortality persisted in this study. The association appeared quite linear. Case-crossover designs represent an attractive method to control for season and weather by matching. PMID:15550600

Effect of Supported Employment on Vocational Rehabilitation Outcomes of Transition-Age Youth with Intellectual and Developmental Disabilities: A Case Control Study

ERIC Educational Resources Information Center

Wehman, Paul; Chan, Fong; Ditchman, Nicole; Kang, Hyun-Ju

2014-01-01

The purpose of this study was to examine the effect of supported employment intervention on the employment outcomes of transition-age youth with intellectual and developmental disabilities served by the public vocational rehabilitation system using a case-control study design. Data for this study were extracted from the Rehabilitation Services…

Proton pump inhibitors and the risk of pneumonia: a comparison of cohort and self-controlled case series designs

PubMed Central

2013-01-01

Background To compare the results of a new-user cohort study design and the self-controlled case series (SCCS) design using the risk of hospitalisation for pneumonia in those dispensed proton pump inhibitors compared to those unexposed as a case study. Methods The Australian Government Department of Veterans’ Affairs administrative claims database was used. Exposure to proton pump inhibitors and hospitalisations for pneumonia were identified over a 4 year study period 01 Jul 2007 -30 Jun 2011. The same inclusion and exclusion criteria were applied to both studies, however, the SCCS study included subjects with a least one hospitalisation for pneumonia. Results There were 105,467 subjects included in the cohort study and 6775 in the SCCS. Both studies showed an increased risk of hospitalisations for pneumonia in the three defined risk periods following initiation of proton pump inhibitors compared to baseline. With the highest risk in the first 1 to 7 days (Cohort RR, 3.24; 95% CI (2.50, 4.19): SCCS: RR, 3.07; 95% CI (2.69, 3.50)). Conclusions This study has shown that the self-controlled case series method produces similar risk estimates to a new-users cohort study design when applied to the association of proton pump inhibitors and pneumonia. Exposure to a proton pump inhibitor increases the likelihood of being admitted to hospital for pneumonia, with the risk highest in the first week of treatment. PMID:23800078

Experimental comparison of conventional and nonlinear model-based control of a mixing tank

DOE Office of Scientific and Technical Information (OSTI.GOV)

Haeggblom, K.E.

1993-11-01

In this case study concerning control of a laboratory-scale mixing tank, conventional multiloop single-input single-output (SISO) control is compared with model-based'' control where the nonlinearity and multivariable characteristics of the process are explicitly taken into account. It is shown, especially if the operating range of the process is large, that the two outputs (level and temperature) cannot be adequately controlled by multiloop SISO control even if gain scheduling is used. By nonlinear multiple-input multiple-output (MIMO) control, on the other hand, very good control performance is obtained. The basic approach to nonlinear control used in this study is first to transformmore » the process into a globally linear and decoupled system, and then to design controllers for this system. Because of the properties of the resulting MIMO system, the controller design is very easy. Two nonlinear control system designs based on a steady-state and a dynamic model, respectively, are considered. In the dynamic case, both setpoint tracking and disturbance rejection can be addressed separately.« less

Design, methodological issues and participation in a multiple sclerosis case-control study.

PubMed

Williamson, D M; Marrie, R A; Ashley-Koch, A; Schiffer, R; Trottier, J; Wagner, L

2012-09-01

This study was conducted to determine whether the risk of developing multiple sclerosis (MS) was associated with certain environmental exposures or genetic factors previously reported to influence MS risk. This paper describes the methodological issues, study design and characteristics of the study population. Individuals with definite MS were identified from a prevalence study conducted in three geographic areas. The target number of cases was not reached, so an additional study area was added. Identifying clinic controls was inefficient, so controls were recruited using random digit dialing. All study participants completed a detailed questionnaire regarding environmental exposures using computer-assisted telephone interviewing, and blood was collected for genetic analysis. In total, 276 cases and 590 controls participated, but participation rates were low, ranging from 28.4% to 38.9%. Only one-third (33.6%) of individuals identified in the prevalence study agreed to participate in the case-control study. Cases were more likely to be non-Hispanic white and older than their source populations as identified in the preceding prevalence study (P < 0.05). Most participants provided a blood sample for genotyping (91%; n = 789). Epidemiological studies play a key role in identifying genetic and environmental factors that are associated with complex diseases like MS. Methodological issues arise in every study, and investigators need to be able to detect, respond to and correct problems in a timely and scientifically valid manner. © 2011 John Wiley & Sons A/S.

An experimental study on the effects of a simulation game on students' clinical cognitive skills and motivation.

PubMed

Dankbaar, Mary E W; Alsma, Jelmer; Jansen, Els E H; van Merrienboer, Jeroen J G; van Saase, Jan L C M; Schuit, Stephanie C E

2016-08-01

Simulation games are becoming increasingly popular in education, but more insight in their critical design features is needed. This study investigated the effects of fidelity of open patient cases in adjunct to an instructional e-module on students' cognitive skills and motivation. We set up a three-group randomized post-test-only design: a control group working on an e-module; a cases group, combining the e-module with low-fidelity text-based patient cases, and a game group, combining the e-module with a high-fidelity simulation game with the same cases. Participants completed questionnaires on cognitive load and motivation. After a 4-week study period, blinded assessors rated students' cognitive emergency care skills in two mannequin-based scenarios. In total 61 students participated and were assessed; 16 control group students, 20 cases students and 25 game students. Learning time was 2 h longer for the cases and game groups than for the control group. Acquired cognitive skills did not differ between groups. The game group experienced higher intrinsic and germane cognitive load than the cases group (p = 0.03 and 0.01) and felt more engaged (p < 0.001). Students did not profit from working on open cases (in adjunct to an e-module), which nonetheless challenged them to study longer. The e-module appeared to be very effective, while the high-fidelity game, although engaging, probably distracted students and impeded learning. Medical educators designing motivating and effective skills training for novices should align case complexity and fidelity with students' proficiency level. The relation between case-fidelity, motivation and skills development is an important field for further study.

Epidemiologic study of residential proximity to transmission lines and childhood cancer in California: description of design, epidemiologic methods and study population

PubMed Central

Kheifets, Leeka; Crespi, Catherine M; Hooper, Chris; Oksuzyan, Sona; Cockburn, Myles; Ly, Thomas; Mezei, Gabor

2015-01-01

We conducted a large epidemiologic case-control study in California to examine the association between childhood cancer risk and distance from the home address at birth to the nearest high-voltage overhead transmission line as a replication of the study of Draper et al. in the United Kingdom. We present a detailed description of the study design, methods of case ascertainment, control selection, exposure assessment and data analysis plan. A total of 5788 childhood leukemia cases and 3308 childhood central nervous system cancer cases (included for comparison) and matched controls were available for analysis. Birth and diagnosis addresses of cases and birth addresses of controls were geocoded. Distance from the home to nearby overhead transmission lines was ascertained on the basis of the electric power companies’ geographic information system (GIS) databases, additional Google Earth aerial evaluation and site visits to selected residences. We evaluated distances to power lines up to 2000 m and included consideration of lower voltages (60–69 kV). Distance measures based on GIS and Google Earth evaluation showed close agreement (Pearson correlation >0.99). Our three-tiered approach to exposure assessment allowed us to achieve high specificity, which is crucial for studies of rare diseases with low exposure prevalence. PMID:24045429

Evaluating hospital design from an operations management perspective.

PubMed

Vos, Leti; Groothuis, Siebren; van Merode, Godefridus G

2007-12-01

This paper describes an evaluation method for the assessment of hospital building design from the viewpoint of operations management to assure that the building design supports the efficient and effective operating of care processes now and in the future. The different steps of the method are illustrated by a case study. In the case study an experimental design is applied to assess the effect of used logistical concepts, patient mix and technologies. The study shows that the evaluation method provides a valuable tool for the assessment of both functionality and the ability to meet future developments in operational control of a building design.

Case-control studies in cancer patients as a surveillance system of occupational exposure in the European Community. European Community Working Party.

PubMed Central

Rona, R J; Taub, N A; Rasmussen, S

1993-01-01

STUDY OBJECTIVE--The main aim was to detect known relationships between lung and blood cancers and various occupational exposures (using job titles as proxies) using a case-control design. The suitability of this system for routine surveillance could then be assessed. DESIGN--A case-control study was carried out in 1989. SETTING--Hospitals in eight European Community countries. SUBJECTS--Men aged 25 to 75 years with incident and prevalent cancer of the lung (190 cases), haematopoietic system (210 cases), or gastrointestinal tract (245 controls) were studied. MEASUREMENTS AND MAIN RESULTS--The crude estimate of the overall odds ratio exposure (OR) for relevant occupational exposure of lung cancer relative to gastrointestinal cancer was 1.20 (95% confidence interval (CI) 0.82, 1.77). In a logistic regression analysis adjusting for country, age at diagnosis, smoking, and alcohol consumption, the overall OR was not greatly changed. A significant interaction of occupational exposure and age at diagnosis showed that lung cancer patients diagnosed at a younger age had a higher OR than patients diagnosed at an older age. Thus, the overall, insignificant result may have been due to a low reliability of occupational history in older age or to a selective mechanism related to age. The overall OR for occupational exposure of cancer of the blood relative to gastrointestinal cancer was 0.88 (95% CI 0.60, 1.31). The logistic regression analysis did not alter these results. CONCLUSION--A surveillance based on a case-control design using job titles would not be sensitive enough to detect possible occupational risks. PMID:8228771

Child Maltreatment as a Risk Factor for Opioid Dependence: Comparison of Family Characteristics and Type and Severity of Child Maltreatment with a Matched Control Group

ERIC Educational Resources Information Center

Conroy, Elizabeth; Degenhardt, Louisa; Mattick, Richard P.; Nelson, Elliot C.

2009-01-01

Objective: To examine the prevalence, characteristics and risk factors for child maltreatment among opioid-dependent persons compared to a community sample of similar social disadvantage. Method: The study employed a case-control design. Cases had a history of opioid pharmacotherapy. Controls were frequency matched to cases with regard to age, sex…

Steep discounting of delayed monetary and food rewards in obesity: a meta-analysis.

PubMed

Amlung, M; Petker, T; Jackson, J; Balodis, I; MacKillop, J

2016-08-01

An increasing number of studies have investigated delay discounting (DD) in relation to obesity, but with mixed findings. This meta-analysis synthesized the literature on the relationship between monetary and food DD and obesity, with three objectives: (1) to characterize the relationship between DD and obesity in both case-control comparisons and continuous designs; (2) to examine potential moderators, including case-control v. continuous design, money v. food rewards, sample sex distribution, and sample age (18 years); and (3) to evaluate publication bias. From 134 candidate articles, 39 independent investigations yielded 29 case-control and 30 continuous comparisons (total n = 10 278). Random-effects meta-analysis was conducted using Cohen's d as the effect size. Publication bias was evaluated using fail-safe N, Begg-Mazumdar and Egger tests, meta-regression of publication year and effect size, and imputation of missing studies. The primary analysis revealed a medium effect size across studies that was highly statistically significant (d = 0.43, p < 10-14). None of the moderators examined yielded statistically significant differences, although notably larger effect sizes were found for studies with case-control designs, food rewards and child/adolescent samples. Limited evidence of publication bias was present, although the Begg-Mazumdar test and meta-regression suggested a slightly diminishing effect size over time. Steep DD of food and money appears to be a robust feature of obesity that is relatively consistent across the DD assessment methodologies and study designs examined. These findings are discussed in the context of research on DD in drug addiction, the neural bases of DD in obesity, and potential clinical applications.

Evaluating the Impact of Database Heterogeneity on Observational Study Results

PubMed Central

Madigan, David; Ryan, Patrick B.; Schuemie, Martijn; Stang, Paul E.; Overhage, J. Marc; Hartzema, Abraham G.; Suchard, Marc A.; DuMouchel, William; Berlin, Jesse A.

2013-01-01

Clinical studies that use observational databases to evaluate the effects of medical products have become commonplace. Such studies begin by selecting a particular database, a decision that published papers invariably report but do not discuss. Studies of the same issue in different databases, however, can and do generate different results, sometimes with strikingly different clinical implications. In this paper, we systematically study heterogeneity among databases, holding other study methods constant, by exploring relative risk estimates for 53 drug-outcome pairs and 2 widely used study designs (cohort studies and self-controlled case series) across 10 observational databases. When holding the study design constant, our analysis shows that estimated relative risks range from a statistically significant decreased risk to a statistically significant increased risk in 11 of 53 (21%) of drug-outcome pairs that use a cohort design and 19 of 53 (36%) of drug-outcome pairs that use a self-controlled case series design. This exceeds the proportion of pairs that were consistent across databases in both direction and statistical significance, which was 9 of 53 (17%) for cohort studies and 5 of 53 (9%) for self-controlled case series. Our findings show that clinical studies that use observational databases can be sensitive to the choice of database. More attention is needed to consider how the choice of data source may be affecting results. PMID:23648805

Adaptation of Chain Event Graphs for use with Case-Control Studies in Epidemiology.

PubMed

Keeble, Claire; Thwaites, Peter Adam; Barber, Stuart; Law, Graham Richard; Baxter, Paul David

2017-09-26

Case-control studies are used in epidemiology to try to uncover the causes of diseases, but are a retrospective study design known to suffer from non-participation and recall bias, which may explain their decreased popularity in recent years. Traditional analyses report usually only the odds ratio for given exposures and the binary disease status. Chain event graphs are a graphical representation of a statistical model derived from event trees which have been developed in artificial intelligence and statistics, and only recently introduced to the epidemiology literature. They are a modern Bayesian technique which enable prior knowledge to be incorporated into the data analysis using the agglomerative hierarchical clustering algorithm, used to form a suitable chain event graph. Additionally, they can account for missing data and be used to explore missingness mechanisms. Here we adapt the chain event graph framework to suit scenarios often encountered in case-control studies, to strengthen this study design which is time and financially efficient. We demonstrate eight adaptations to the graphs, which consist of two suitable for full case-control study analysis, four which can be used in interim analyses to explore biases, and two which aim to improve the ease and accuracy of analyses. The adaptations are illustrated with complete, reproducible, fully-interpreted examples, including the event tree and chain event graph. Chain event graphs are used here for the first time to summarise non-participation, data collection techniques, data reliability, and disease severity in case-control studies. We demonstrate how these features of a case-control study can be incorporated into the analysis to provide further insight, which can help to identify potential biases and lead to more accurate study results.

Real-time simulation model of the HL-20 lifting body

NASA Technical Reports Server (NTRS)

Jackson, E. Bruce; Cruz, Christopher I.; Ragsdale, W. A.

1992-01-01

A proposed manned spacecraft design, designated the HL-20, has been under investigation at Langley Research Center. Included in that investigation are flight control design and flying qualities studies utilizing a man-in-the-loop real-time simulator. This report documents the current real-time simulation model of the HL-20 lifting body vehicle, known as version 2.0, presently in use at NASA Langley Research Center. Included are data on vehicle aerodynamics, inertias, geometries, guidance and control laws, and cockpit displays and controllers. In addition, trim case and dynamic check case data is provided. The intent of this document is to provide the reader with sufficient information to develop and validate an equivalent simulation of the HL-20 for use in real-time or analytical studies.

Online Case-Based Learning Design for Facilitating Classroom Teachers' Development of Technological, Pedagogical, and Content Knowledge

ERIC Educational Resources Information Center

Saltan, Fatih

2017-01-01

The aim of this study is to investigate whether, and if so how, online case-based learning influence pre-service classroom teachers' self-confidence on technological pedagogical content knowledge (TPACK). To achieve the goal, a control group pretest-posttest quasi experimental design was used. Participants of the study consisted of 160 pre-service…

The Mortality Penalty of Incarceration: Evidence from a Population-based Case-control Study of Working-age Males.

PubMed

Pridemore, William Alex

2014-06-01

There is a growing body of research on the effects of incarceration on health, though there are few studies in the sociological literature of the association between incarceration and premature mortality. This study examined the risk of male premature mortality associated with incarceration. Data came from the Izhevsk (Russia) Family Study, a large-scale population-based case-control design. Cases (n = 1,750) were male deaths aged 25 to 54 in Izhevsk between October 2003 and October 2005. Controls (n = 1,750) were selected at random from a city population register. The key independent variable was lifetime prevalence of incarceration. I used logistic regression to estimate mortality odds ratios, controlling for age, hazardous drinking, smoking status, marital status, and education. Seventeen percent of cases and 5 percent of controls had been incarcerated. Men who had been incarcerated were more than twice as likely as those who had not to experience premature mortality (odds ratio = 2.2, 95 percent confidence interval: 1.6-3.0). Relative to cases with no prior incarceration, cases who had been incarcerated were more likely to die from infectious diseases, respiratory diseases, non-alcohol-related accidental poisonings, and homicide. Taken together with other recent research, these results from a rigorous case-control design reveal not only that incarceration has durable effects on illness, but that its consequences extend to a greater risk of early death. I draw on the sociology of health literature on exposure, stress, and social integration to speculate about the reasons for this mortality penalty of incarceration. © American Sociological Association 2014.

Association between the 2008-09 seasonal influenza vaccine and pandemic H1N1 illness during Spring-Summer 2009: four observational studies from Canada.

PubMed

Skowronski, Danuta M; De Serres, Gaston; Crowcroft, Natasha S; Janjua, Naveed Z; Boulianne, Nicole; Hottes, Travis S; Rosella, Laura C; Dickinson, James A; Gilca, Rodica; Sethi, Pam; Ouhoummane, Najwa; Willison, Donald J; Rouleau, Isabelle; Petric, Martin; Fonseca, Kevin; Drews, Steven J; Rebbapragada, Anuradha; Charest, Hugues; Hamelin, Marie-Eve; Boivin, Guy; Gardy, Jennifer L; Li, Yan; Kwindt, Trijntje L; Patrick, David M; Brunham, Robert C

2010-04-06

In late spring 2009, concern was raised in Canada that prior vaccination with the 2008-09 trivalent inactivated influenza vaccine (TIV) was associated with increased risk of pandemic influenza A (H1N1) (pH1N1) illness. Several epidemiologic investigations were conducted through the summer to assess this putative association. (1) test-negative case-control design based on Canada's sentinel vaccine effectiveness monitoring system in British Columbia, Alberta, Ontario, and Quebec; (2) conventional case-control design using population controls in Quebec; (3) test-negative case-control design in Ontario; and (4) prospective household transmission (cohort) study in Quebec. Logistic regression was used to estimate odds ratios for TIV effect on community- or hospital-based laboratory-confirmed seasonal or pH1N1 influenza cases compared to controls with restriction, stratification, and adjustment for covariates including combinations of age, sex, comorbidity, timeliness of medical visit, prior physician visits, and/or health care worker (HCW) status. For the prospective study risk ratios were computed. Based on the sentinel study of 672 cases and 857 controls, 2008-09 TIV was associated with statistically significant protection against seasonal influenza (odds ratio 0.44, 95% CI 0.33-0.59). In contrast, estimates from the sentinel and three other observational studies, involving a total of 1,226 laboratory-confirmed pH1N1 cases and 1,505 controls, indicated that prior receipt of 2008-09 TIV was associated with increased risk of medically attended pH1N1 illness during the spring-summer 2009, with estimated risk or odds ratios ranging from 1.4 to 2.5. Risk of pH1N1 hospitalization was not further increased among vaccinated people when comparing hospitalized to community cases. Prior receipt of 2008-09 TIV was associated with increased risk of medically attended pH1N1 illness during the spring-summer 2009 in Canada. The occurrence of bias (selection, information) or confounding cannot be ruled out. Further experimental and epidemiological assessment is warranted. Possible biological mechanisms and immunoepidemiologic implications are considered.

Case-spouse control design in practice: an experience in estimating smoking and chronic obstructive pulmonary disease deaths in Chinese adults.

PubMed

Jiang, Jingmei; Liu, Boqi; Sitas, Freddy; Zeng, Xianjia; Chen, Junshi; Han, Wei; Zou, Xiaonong; Wu, Yanping; Zhao, Ping; Li, Junyao

2010-05-01

We assessed the effect of smoking on death from chronic obstructive pulmonary disease (COPD) in China by employing a large population-based, case-spouse control study design using data from a nationwide survey of mortality. During 1989-1991, a nationwide retrospective survey of mortality was conducted in China. For approximately 1,000,000 adults dying from all causes during 1986-1988, their surviving spouses or other informants provided detailed information about their own as well as the deceased person's smoking history. For this study, 183,393 individuals who died of COPD at age > or = 40 years were taken as cases, while 272,984 sex-matched surviving spouses of subjects who died from any cause were taken as controls. COPD death rates for smokers were more than twice as high as those of non-smokers, with a dose-response risk pattern, despite the fact that COPD death rates varied widely by region and age. Tobacco accounted for 41.4% of COPD deaths in men, but only 13.5% of those in women, who had a lower rate of smoking. A case-spouse control study, as an alternative design, is valid and feasible in utilizing information from population-based, retrospective mortality survey data for an analytical epidemiological study of disease etiology. Copyright 2010 Formosan Medical Association & Elsevier. Published by Elsevier B.V. All rights reserved.

A retrospective likelihood approach for efficient integration of multiple omics factors in case-control association studies.

PubMed

Balliu, Brunilda; Tsonaka, Roula; Boehringer, Stefan; Houwing-Duistermaat, Jeanine

2015-03-01

Integrative omics, the joint analysis of outcome and multiple types of omics data, such as genomics, epigenomics, and transcriptomics data, constitute a promising approach for powerful and biologically relevant association studies. These studies often employ a case-control design, and often include nonomics covariates, such as age and gender, that may modify the underlying omics risk factors. An open question is how to best integrate multiple omics and nonomics information to maximize statistical power in case-control studies that ascertain individuals based on the phenotype. Recent work on integrative omics have used prospective approaches, modeling case-control status conditional on omics, and nonomics risk factors. Compared to univariate approaches, jointly analyzing multiple risk factors with a prospective approach increases power in nonascertained cohorts. However, these prospective approaches often lose power in case-control studies. In this article, we propose a novel statistical method for integrating multiple omics and nonomics factors in case-control association studies. Our method is based on a retrospective likelihood function that models the joint distribution of omics and nonomics factors conditional on case-control status. The new method provides accurate control of Type I error rate and has increased efficiency over prospective approaches in both simulated and real data. © 2015 Wiley Periodicals, Inc.

A comparison of estimators from self-controlled case series, case-crossover design, and sequence symmetry analysis for pharmacoepidemiological studies.

PubMed

Takeuchi, Yoshinori; Shinozaki, Tomohiro; Matsuyama, Yutaka

2018-01-08

Despite the frequent use of self-controlled methods in pharmacoepidemiological studies, the factors that may bias the estimates from these methods have not been adequately compared in real-world settings. Here, we comparatively examined the impact of a time-varying confounder and its interactions with time-invariant confounders, time trends in exposures and events, restrictions, and misspecification of risk period durations on the estimators from three self-controlled methods. This study analyzed self-controlled case series (SCCS), case-crossover (CCO) design, and sequence symmetry analysis (SSA) using simulated and actual electronic medical records datasets. We evaluated the performance of the three self-controlled methods in simulated cohorts for the following scenarios: 1) time-invariant confounding with interactions between the confounders, 2) time-invariant and time-varying confounding without interactions, 3) time-invariant and time-varying confounding with interactions among the confounders, 4) time trends in exposures and events, 5) restricted follow-up time based on event occurrence, and 6) patient restriction based on event history. The sensitivity of the estimators to misspecified risk period durations was also evaluated. As a case study, we applied these methods to evaluate the risk of macrolides on liver injury using electronic medical records. In the simulation analysis, time-varying confounding produced bias in the SCCS and CCO design estimates, which aggravated in the presence of interactions between the time-invariant and time-varying confounders. The SCCS estimates were biased by time trends in both exposures and events. Erroneously short risk periods introduced bias to the CCO design estimate, whereas erroneously long risk periods introduced bias to the estimates of all three methods. Restricting the follow-up time led to severe bias in the SSA estimates. The SCCS estimates were sensitive to patient restriction. The case study showed that although macrolide use was significantly associated with increased liver injury occurrence in all methods, the value of the estimates varied. The estimations of the three self-controlled methods depended on various underlying assumptions, and the violation of these assumptions may cause non-negligible bias in the resulting estimates. Pharmacoepidemiologists should select the appropriate self-controlled method based on how well the relevant key assumptions are satisfied with respect to the available data.

On the use of an Arduino-based controller to control the charging process of a wind turbine

NASA Astrophysics Data System (ADS)

Mahmuddin, Faisal; Yusran, Ahmad Muhtam; Klara, Syerly

2017-02-01

In order to avoid an excessive charging voltage which can damage power storage when converting wind energy using a turbine, it is necessary to control the charging voltage of the turbine generator. In the present study, a charging controller which uses an Arduino microcontroller, is designed. 3 (three) indicator lights are installed to indicate the battery charging process, power diversion to dummy load and battery power level. The performance of the designed controller is evaluated by simulating 3 cases. In this simulation, a battery with maximum voltage of 12.4 V is used. Case 1 is performed with input voltage equals the one set in Arduino which is 10 V. In this case, the battery is charged up to 10.8 V. In case 2, the input voltage is 13 V while the maximum voltage set in Arduino is also 13 V. In this case, the battery is charged up to maximum voltage of the battery. Moreover, the dummy load indicator is ON and charging indicator is OFF after the maximum charging voltage is reached because the electricity is flowed to the dummy load. In the final case, the input voltage is set to be 16 V while the maximum voltage set in Arduino is 13 V. In this case, the charging indicator is OFF and dummy load indicator is ON which means that the Arduino has successfully switched the power to be flowed to dummy load. From the 3 (three) cases, it can be concluded that the designed controller works perfectly to control the charging process of the wind turbine. Moreover, the charging time needed in each case can also be determined.

Effect of sulfasalazine use on the presence of Pneumocystis organisms in the lung among patients with rheumatoid arthritis: A test-negative design case-control study with PCR tests.

PubMed

Nunokawa, Takahiro; Yokogawa, Naoto; Shimada, Kota; Sugii, Shoji

2018-05-03

To evaluate the effect of sulfasalazine (SSZ) on the presence of Pneumocystis jirovecii (P. jirovecii) in the lungs of rheumatoid arthritis (RA) patients. We retrospectively studied episodes of suspected P. jirovecii pneumonia (PJP) which were examined for P. jirovecii with polymerase chain reaction (PCR). We employed a test negative design case-control study; the cases were episodes of suspected PJP that were positive for PCR, and the controls were episodes of suspected PJP that were negative for PCR. The odds ratio for the positive PCR result associated with SSZ use was estimated by Firth's logistic regression. Between 2003 and 2017, 36 cases and 83 controls were identified. While none of the cases received SSZ before the episode, 18 of the controls received the drug. In the primary analysis involving all the episodes, SSZ use was negatively associated with PCR positivity (adjusted odds ratio, 0.087; confidence interval, <0.001-0.789). The sensitivity analysis, excluding those who received PJP prophylaxis, showed the same association as the primary analysis (adjusted odds ratio 0.085, 95% CI <0.001-0.790). This study demonstrated that SSZ use is associated with the absence of P. jirovecii in the lung, suggesting the preventive efficacy of the drug against PJP.

A systematic review of occupational safety and health business cases.

PubMed

Verbeek, Jos; Pulliainen, Marjo; Kankaanpää, Eila

2009-12-01

Business cases are commonly developed as means to rationalize investment. We systematically reviewed 26 reported cases on occupational safety and health (OSH) interventions to assess if health and productivity arguments make a good business case. To be included in the review, studies had to analyze the costs and benefits, including productivity, of an OSH intervention at the enterprise level. We searched Medline and Embase for studies and used Google search in addition. Two reviewers independently selected studies and extracted data. The intervention profitability was calculated in euros (euro in 2008) as the first year's benefits minus the total intervention costs per worker. The payback period was calculated as the intervention costs divided by the first year's benefits. We found three ex-ante and 23 ex-post cases. In 20 cases, the study design was a before-after comparison without a control group. Generally a 100% reduction of injuries or sickness absence was assumed. In two cases, productivity and quality increases were very large. The main benefit was avoided sick leave. Depreciation or discounting was applied only in a minority of cases. The intervention profitability was negative in seven studies, up to euro 500 per employee in 12 studies and more than euro 500 per employee in seven studies. The payback period was less than half a year for 19 studies. Only a few studies included sensitivity analyses. Few ex-ante business cases for management decisions on OSH are reported. Guidelines for reporting and evaluation are needed. Business cases need more sound assumptions on the effectiveness of interventions and should incorporate greater uncertainty into their design. Ex-post evaluation should be based preferably on study designs that control for trends at a time different from that of the intervention.

Optimal design of studies of influenza transmission in households. I: case-ascertained studies.

PubMed

Klick, B; Leung, G M; Cowling, B J

2012-01-01

Case-ascertained household transmission studies, in which households including an 'index case' are recruited and followed up, are invaluable to understanding the epidemiology of influenza. We used a simulation approach parameterized with data from household transmission studies to evaluate alternative study designs. We compared studies that relied on self-reported illness in household contacts vs. studies that used home visits to collect swab specimens for virological confirmation of secondary infections, allowing for the trade-off between sample size vs. intensity of follow-up given a fixed budget. For studies estimating the secondary attack proportion, 2-3 follow-up visits with specimens collected from all members regardless of illness were optimal. However, for studies comparing secondary attack proportions between two or more groups, such as controlled intervention studies, designs with reactive home visits following illness reports in contacts were most powerful, while a design with one home visit optimally timed also performed well.

Case studies on design, simulation and visualization of control and measurement applications using REX control system

NASA Astrophysics Data System (ADS)

Ozana, Stepan; Pies, Martin; Docekal, Tomas

2016-06-01

REX Control System is a professional advanced tool for design and implementation of complex control systems that belongs to softPLC category. It covers the entire process starting from simulation of functionality of the application before deployment, through implementation on real-time target, towards analysis, diagnostics and visualization. Basically it consists of two parts: the development tools and the runtime system. It is also compatible with Simulink environment, and the way of implementation of control algorithm is very similar. The control scheme is finally compiled (using RexDraw utility) and uploaded into a chosen real-time target (using RexView utility). There is a wide variety of hardware platforms and real-time operating systems supported by REX Control System such as for example Windows Embedded, Linux, Linux/Xenomai deployed on SBC, IPC, PAC, Raspberry Pi and others with many I/O interfaces. It is modern system designed both for measurement and control applications, offering a lot of additional functions concerning data archiving, visualization based on HTML5, and communication standards. The paper will sum up possibilities of its use in educational process, focused on control of case studies of physical models with classical and advanced control algorithms.

Association between the 2008–09 Seasonal Influenza Vaccine and Pandemic H1N1 Illness during Spring–Summer 2009: Four Observational Studies from Canada

PubMed Central

Skowronski, Danuta M.; De Serres, Gaston; Crowcroft, Natasha S.; Janjua, Naveed Z.; Boulianne, Nicole; Hottes, Travis S.; Rosella, Laura C.; Dickinson, James A.; Gilca, Rodica; Sethi, Pam; Ouhoummane, Najwa; Willison, Donald J.; Rouleau, Isabelle; Petric, Martin; Fonseca, Kevin; Drews, Steven J.; Rebbapragada, Anuradha; Charest, Hugues; Hamelin, Marie-Ève; Boivin, Guy; Gardy, Jennifer L.; Li, Yan; Kwindt, Trijntje L.; Patrick, David M.; Brunham, Robert C.

2010-01-01

Background In late spring 2009, concern was raised in Canada that prior vaccination with the 2008–09 trivalent inactivated influenza vaccine (TIV) was associated with increased risk of pandemic influenza A (H1N1) (pH1N1) illness. Several epidemiologic investigations were conducted through the summer to assess this putative association. Methods and Findings Studies included: (1) test-negative case-control design based on Canada's sentinel vaccine effectiveness monitoring system in British Columbia, Alberta, Ontario, and Quebec; (2) conventional case-control design using population controls in Quebec; (3) test-negative case-control design in Ontario; and (4) prospective household transmission (cohort) study in Quebec. Logistic regression was used to estimate odds ratios for TIV effect on community- or hospital-based laboratory-confirmed seasonal or pH1N1 influenza cases compared to controls with restriction, stratification, and adjustment for covariates including combinations of age, sex, comorbidity, timeliness of medical visit, prior physician visits, and/or health care worker (HCW) status. For the prospective study risk ratios were computed. Based on the sentinel study of 672 cases and 857 controls, 2008–09 TIV was associated with statistically significant protection against seasonal influenza (odds ratio 0.44, 95% CI 0.33–0.59). In contrast, estimates from the sentinel and three other observational studies, involving a total of 1,226 laboratory-confirmed pH1N1 cases and 1,505 controls, indicated that prior receipt of 2008–09 TIV was associated with increased risk of medically attended pH1N1 illness during the spring–summer 2009, with estimated risk or odds ratios ranging from 1.4 to 2.5. Risk of pH1N1 hospitalization was not further increased among vaccinated people when comparing hospitalized to community cases. Conclusions Prior receipt of 2008–09 TIV was associated with increased risk of medically attended pH1N1 illness during the spring–summer 2009 in Canada. The occurrence of bias (selection, information) or confounding cannot be ruled out. Further experimental and epidemiological assessment is warranted. Possible biological mechanisms and immunoepidemiologic implications are considered. Please see later in the article for the Editors' Summary PMID:20386731

A matched case-control study of convenience store robbery risk factors.

PubMed

Hendricks, S A; Landsittel, D P; Amandus, H E; Malcan, J; Bell, J

1999-11-01

Convenience store clerks have been shown to be at high risk for assault and homicide, mostly owing to robbery or robbery attempts. Although the literature consistently indicates that at least some environmental designs are effective deterrents of robbery, the significance of individual interventions and policies has differed across past studies. To address these issues, a matched case-control study of 400 convenience store robberies in three metropolitan areas of Virginia was conducted. Conditional logistic regression was implemented to evaluate the significance of various environmental designs and other factors possibly related to convenience store robbery. Findings indicate that numerous characteristics of the surrounding environment and population were significantly associated with convenience store robbery. Results also showed that, on a univariate level, most crime prevention factors were significantly associated with a lower risk for robbery. Using a forward selection process, a multivariate model, which included cash handling policy, bullet-resistant shielding, and numerous characteristics of the surrounding area and population, was identified. This study addressed numerous limitations of the previous literature by prospectively collecting extensive data on a large sample of diverse convenience stores and directly addressing the current theory on the robbers' selection of a target store through a matched case-control design.

Importance of relationship context in HIV transmission: results from a qualitative case-control study in Rakai, Uganda.

PubMed

Higgins, Jenny A; Mathur, Sanyukta; Eckel, Elizabeth; Kelley, Laura; Kelly, Laura; Nakyanjo, Neema; Sekamwa, Richard; Namatovu, Josephine; Ddaaki, William; Nakubulwa, Rosette; Namakula, Sylvia; Nalugoda, Fred; Santelli, John S

2014-04-01

We present results from life history interviews with 60 young adults from southern Uganda. Using a novel qualitative case-control design, we compared newly HIV-positive cases with HIV-negative controls matched on age, gender, marital status, and place of residence. Relationship context was the most salient theme differentiating cases from controls. Compared with HIV-negative respondents, recent seroconverters described relationships marked by poorer communication, greater suspicion and mistrust, and larger and more transitory sexual networks. Results highlight the importance of dyadic approaches to HIV and possibly of couple-based interventions. Using HIV-matched pairs allowed additional understanding of the factors influencing transmission. This hybrid methodological approach holds promise for future studies of sexual health.

Importance of Relationship Context in HIV Transmission: Results From a Qualitative Case-Control Study in Rakai, Uganda

PubMed Central

Mathur, Sanyukta; Eckel, Elizabeth; Kelly, Laura; Nakyanjo, Neema; Sekamwa, Richard; Namatovu, Josephine; Ddaaki, William; Nakubulwa, Rosette; Namakula, Sylvia; Nalugoda, Fred; Santelli, John S.

2014-01-01

We present results from life history interviews with 60 young adults from southern Uganda. Using a novel qualitative case-control design, we compared newly HIV-positive cases with HIV-negative controls matched on age, gender, marital status, and place of residence. Relationship context was the most salient theme differentiating cases from controls. Compared with HIV-negative respondents, recent seroconverters described relationships marked by poorer communication, greater suspicion and mistrust, and larger and more transitory sexual networks. Results highlight the importance of dyadic approaches to HIV and possibly of couple-based interventions. Using HIV-matched pairs allowed additional understanding of the factors influencing transmission. This hybrid methodological approach holds promise for future studies of sexual health. PMID:24524490

Risk of acute liver injury associated with use of antibiotics. Comparative cohort and nested case-control studies using two primary care databases in Europe.

PubMed

Brauer, Ruth; Douglas, Ian; Garcia Rodriguez, Luis Alberto; Downey, Gerald; Huerta, Consuelo; de Abajo, Francisco; Bate, Andrew; Feudjo Tepie, Maurille; de Groot, Mark C H; Schlienger, Raymond; Reynolds, Robert; Smeeth, Liam; Klungel, Olaf; Ruigómez, Ana

2016-03-01

To assess the impact of varying study designs, exposure and outcome definitions on the risk of acute liver injury (ALI) associated with antibiotic use. The source population comprised of patients registered in two primary care databases, in the UK and in Spain. We identified a cohort consisting of new users of antibiotics during the study period (2004-2009) and non-users during the study period or in the previous year. Cases with ALI were identified within this cohort and classified as definite or probable, based on recorded medical information. The relative risk (RR) of ALI associated with antibiotic use was computed using Poisson regression. For the nested case-control analyses, up to five controls were matched to each case by age, sex, date and practice (in CPRD) and odds ratios (OR) were computed with conditional logistic regression. The age, sex and year adjusted RRs of definite ALI in the current antibiotic use periods was 10.04 (95% CI: 6.97-14.47) in CPRD and 5.76 (95% CI: 3.46-9.59) in BIFAP. In the case-control analyses adjusting for life-style, comorbidities and use of medications, the OR of ALI for current users of antibiotics was and 5.7 (95% CI: 3.46-9.36) in CPRD and 2.6 (95% CI: 1.26-5.37) in BIFAP. Guided by a common protocol, both cohort and case-control study designs found an increased risk of ALI associated with the use of antibiotics in both databases, independent of the exposure and case definitions used. However, the magnitude of the risk was higher in CPRD compared to BIFAP. Copyright © 2016 John Wiley & Sons, Ltd.

Estimates of 2012/13 influenza vaccine effectiveness using the case test-negative control design with different influenza negative control groups.

PubMed

Nunes, Baltazar; Machado, Ausenda; Guiomar, Raquel; Pechirra, Pedro; Conde, Patrícia; Cristovão, Paula; Falcão, Isabel

2014-07-31

In recent years several reports of influenza vaccine effectiveness (VE) have been made early for public health decision. The majority of these studies use the case test-negative control design (TND), which has been showed to provide, under certain conditions, unbiased estimates of influenza VE. Nevertheless, discussions have been taken on the best influenza negative control group to use. The present study aims to contribute to the knowledge on this field by comparing influenza VE estimates using three test-negative controls: all influenza negative, non-influenza respiratory virus and pan-negative. Incident ILI patients were prospectively selected and swabbed by a sample of general practitioners. Cases were ILI patients tested positive for influenza and controls ILI patients tested negative for influenza. The influenza negative control group was divided into non-influenza virus control group and pan-negative control group. Data were collected on vaccination status and confounding factors. Influenza VE was estimated as one minus the odds ratio of been vaccinated in cases versus controls adjusted for confounding effect by logistic regression. Confounder adjusted influenza VE against medically attended laboratory-confirmed influenza was 68.4% (95% CI: 20.7-87.4%) using all influenza negatives controls, 82.1% (95% CI: 47.6-93.9%) using non-influenza controls and 49.4% (95% CI: -44.7% to 82.3%) using pan-negative controls. Influenza VE estimates differed according to the influenza negative control group used. These results are in accordance with the expected under the hypothesis of differential viral interference between influenza vaccinated and unvaccinated individuals. Given the wide importance of TND study further studies should be conducted in order to clarify the observed differences. Copyright © 2014 Elsevier Ltd. All rights reserved.

Effectiveness of inactivated quadrivalent influenza vaccine in the 2015/2016 season as assessed in both a test-negative case-control study design and a traditional case-control study design.

PubMed

Kimiya, Takahisa; Shinjoh, Masayoshi; Anzo, Makoto; Takahashi, Hiroki; Sekiguchi, Shinichiro; Sugaya, Norio; Takahashi, Takao

2018-04-21

Both traditional case-control studies (TCCSs) and test-negative case-control studies (TNCCSs) are commonly used to assess influenza vaccine effectiveness (VE). To compensate for the fact that observational studies are susceptible to bias, we combined both methods to assess VE in one geographical area during the 2015/2016 season, when influenza A (H1N1)pdm was dominant. Our TNCCS covered 331 children aged 6 months to 15 years who visited our hospital with fever, including 182 with influenza, and our TCCS covered 812 pediatric outpatients aged 6 months to 15 years, including 214 with influenza. Influenza infection and vaccination history were reviewed, and VE was calculated as (1 - odds ratio) × 100. In the TNCCS, VE against influenza A was 68% (95% CI 47-81) overall, and 70% (48-83) for those given two doses; against influenza B, VE was 37% (- 12-64) overall and 49% (2-74) for two doses. In the TCCS, VE against influenza A was 44% (15-63) overall and 44% (13-64) for two doses, and VE against influenza B was 24% (- 19-52) overall and 41% (3-64) for two doses. Both studies confirmed significant VE against influenza A, significant two-dose VE against influenza B, and better two-dose VE than one-dose VE. What is Known: • Influenza vaccine effectiveness (VE) varies from year to year. • Observational studies are conventionally used for VE assessment. However, they are inherently susceptible to bias and confounding. What is New: • This is the first report of influenza VE assessment using more than one observational study and performed in a specific area during the same season. • VE estimates obtained in our traditional case-control study were lower than those in our test-negative case-control study, but both studies found significant VE against influenza.

Models in the Design and Validation of Eddy Current Inspection for Cracking in the Shuttle Reaction Control System Thruster

NASA Technical Reports Server (NTRS)

Aldrin, John C.; Williams, Phillip A.; Wincheski, Russell (Buzz) A.

2008-01-01

A case study is presented for using models in eddy current NDE design for crack detection in Shuttle Reaction Control System thruster components. Numerical methods were used to address the complex geometry of the part and perform parametric studies of potential transducer designs. Simulations were found to show agreement with experimental results. Accurate representation of the coherent noise associated with the measurement and part geometry was found to be critical to properly evaluate the best probe designs.

Propensity score matching for selection of local areas as controls for evaluation of effects of alcohol policies in case series and quasi case-control designs.

PubMed

de Vocht, F; Campbell, R; Brennan, A; Mooney, J; Angus, C; Hickman, M

2016-03-01

Area-level public health interventions can be difficult to evaluate using natural experiments. We describe the use of propensity score matching (PSM) to select control local authority areas (LAU) to evaluate the public health impact of alcohol policies for (1) prospective evaluation of alcohol policies using area-level data, and (2) a novel two-stage quasi case-control design. Ecological. Alcohol-related indicator data (Local Alcohol Profiles for England, PHE Health Profiles and ONS data) were linked at LAU level. Six LAUs (Blackpool, Bradford, Bristol, Ipswich, Islington, and Newcastle-upon-Tyne) as sample intervention or case areas were matched to two control LAUs each using PSM. For the quasi case-control study a second stage was added aimed at obtaining maximum contrast in outcomes based on propensity scores. Matching was evaluated based on average standardized absolute mean differences (ASAM) and variable-specific P-values after matching. The six LAUs were matched to suitable control areas (with ASAM < 0.20, P-values >0.05 indicating good matching) for a prospective evaluation study that sought areas that were similar at baseline in order to assess whether a change in intervention exposure led to a change in the outcome (alcohol related harm). PSM also generated appropriate matches for a quasi case-control study--whereby the contrast in health outcomes between cases and control areas needed to be optimized in order to assess retrospectively whether differences in intervention exposure were associated with the outcome. The use of PSM for area-level alcohol policy evaluation, but also for other public health interventions, will improve the value of these evaluations by objective and quantitative selection of the most appropriate control areas. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

Does high flexion after total knee replacement really improve our patients' quality of life at a short-term follow-up? : a comparative case-control study with hyperflex PFC Sigma versus a Triathlon knee series.

PubMed

Mencière, Maxime L; Epinette, Jean-Alain; Gabrion, Antoine; Arnalsteen, Damien; Mertl, Patrice

2014-10-01

A full range of motion after total knee arthroplasty has become more and more requested by our patients, leading to novel designs of knee implants, the so-called "hyperflex" knees. The aim of the present study was to confirm whether or not hyperflexion of operated knees really improves the patients' quality of life. A retrospective comparative case-control study has been carried out to compare clinical results shown in two types of knee prosthesis, from two homogeneous paired groups of patients including 45 cases of a "hyperflex" model (RP-F), while the control group consisted of 43 cases of a "regular design" model (Triathlon) in terms of expected postoperative flexion. The hyperflex group demonstrated significant higher mean values of passive flexion at 119.9° in the RP-F group versus 111.1° in the Triathlon group. However, global results in the "regular" control group were significantly better than the "hyperflex" study group, in both IKS knee and functional scores at 84.4 points (RP-F) vs. 89.8 points (Triathlon), and 84.6 points (RP-F) vs. 89.5 points (Triathlon), respectively. Moreover, the self-administered KOOS questionnaire was significantly in favor of the control group, with 73.5 points in RP-F knees versus 86.0 points for Triathlon knees at global KOOS postoperative scores. The quality of life of operated patients after TKA obviously would be considered as the main priority, which was better obtained by a "regular design" in our study. Hence "high flexion" cannot be considered as an absolute target when choosing a model for total knee arthroplasty.

Utilising family-based designs for detecting rare variant disease associations.

PubMed

Preston, Mark D; Dudbridge, Frank

2014-03-01

Rare genetic variants are thought to be important components in the causality of many diseases but discovering these associations is challenging. We demonstrate how best to use family-based designs to improve the power to detect rare variant disease associations. We show that using genetic data from enriched families (those pedigrees with greater than one affected member) increases the power and sensitivity of existing case-control rare variant tests. However, we show that transmission- (or within-family-) based tests do not benefit from this enrichment. This means that, in studies where a limited amount of genotyping is available, choosing a single case from each of many pedigrees has greater power than selecting multiple cases from fewer pedigrees. Finally, we show how a pseudo-case-control design allows a greater range of statistical tests to be applied to family data. © 2014 The Authors. Annals of Human Genetics published by John Wiley & Sons Ltd/University College London.

Risk factors associated with asbestos-related diseases: a community-based case-control study.

PubMed

Rosell-Murphy, Magdalena-Isabel; Abós-Herràndiz, Rafael; Olivella, Josep Tarrés; Alberti-Casas, Constança; Allas, Isabel García; Artés, Xavier Martinez; Günther, Ilona Krier; Malet, Isidre Grimau; Martínez, Ramon Orriols; Canela-Soler, Jaume

2013-08-06

Asbestos is a first level carcinogen. However, few epidemiological studies analyse the risk and protective factors associated with asbestos-related diseases and follow up these conditions in the general population. Pleural mesothelioma, caused by inhalation of asbestos fibres at work, at home or in the environment, is the most representative asbestos-related disease.The objectives of this study are to analyse the risk and protective factors associated with asbestos-related diseases and to investigate the incidence of new clinical manifestations in patients already diagnosed with some form of ARD. We have designed a matched case-control study with follow up of both cohorts from a population of a health district of the Barcelona province that has been exposed to asbestos for a period of 90 years. A better understanding of asbestos-related diseases should improve i) the clinical and epidemiological follow up of patients with this condition; ii) the design of new treatment strategies; iii) and the development of preventive activities. At the end of the study, the two cohorts created in this study (affected cases and healthy controls) will constitute the basis for future research.

Obstacles to action in arthritis: a community case-control study.

PubMed

Hutton, Ingrid; Gamble, Greg; McLean, Grant; Butcher, Hugh; Gow, Peter; Dalbeth, Nicola

2009-07-01

Despite the benefits of physical activity, people with arthritis are less active than the general population. The aim of this study was to determine the motivators and obstacles to physical activity for adults with arthritis. Participants were identified from the Obstacles to Action Study, a community based study of 8163 adults, which explored barriers and motivators to physical activity. A 1:1 case-control study was designed; cases were identified as those participants who reported arthritis (n = 1106). Each case was matched with an age, sex and ethnicity-matched non-arthritis control (n = 1106). Cases were less likely to achieve recommended physical activity targets (58.8% vs. 68.1% P = 0.00001). Furthermore, fewer people with arthritis believed that physical activity would help them lead healthy lives (86.7% vs. 91.3% P = 0.006) or viewed physical activity as a priority (53.8% vs. 59.8% P = 0.005). Cases were less confident in their abilities to try a new activity (37.1% vs. 43.7% P = 0.002) or maintain a healthy weight (65.0% vs. 74.3% P = 0.00001). Cases also reported greater negative impact scores for barriers to activity, particularly arthritis, accessibility, cost and discomfort while exercising. Motivators and environmental barriers to activity were similar for cases and controls. These findings persisted after adjusting for educational level, body mass index and comorbidities. People with arthritis are less active and demonstrate different attitudes toward physical activity. Although people with arthritis identify similar environmental barriers, they have different psychosocial barriers. In order to design effective physical activity programs for people with arthritis, these barriers must be specifically addressed.

Maximum likelihood estimation for Cox's regression model under nested case-control sampling.

PubMed

Scheike, Thomas H; Juul, Anders

2004-04-01

Nested case-control sampling is designed to reduce the costs of large cohort studies. It is important to estimate the parameters of interest as efficiently as possible. We present a new maximum likelihood estimator (MLE) for nested case-control sampling in the context of Cox's proportional hazards model. The MLE is computed by the EM-algorithm, which is easy to implement in the proportional hazards setting. Standard errors are estimated by a numerical profile likelihood approach based on EM aided differentiation. The work was motivated by a nested case-control study that hypothesized that insulin-like growth factor I was associated with ischemic heart disease. The study was based on a population of 3784 Danes and 231 cases of ischemic heart disease where controls were matched on age and gender. We illustrate the use of the MLE for these data and show how the maximum likelihood framework can be used to obtain information additional to the relative risk estimates of covariates.

Optimization under variability and uncertainty: a case study for NOx emissions control for a gasification system.

PubMed

Chen, Jianjun; Frey, H Christopher

2004-12-15

Methods for optimization of process technologies considering the distinction between variability and uncertainty are developed and applied to case studies of NOx control for Integrated Gasification Combined Cycle systems. Existing methods of stochastic optimization (SO) and stochastic programming (SP) are demonstrated. A comparison of SO and SP results provides the value of collecting additional information to reduce uncertainty. For example, an expected annual benefit of 240,000 dollars is estimated if uncertainty can be reduced before a final design is chosen. SO and SP are typically applied to uncertainty. However, when applied to variability, the benefit of dynamic process control is obtained. For example, an annual savings of 1 million dollars could be achieved if the system is adjusted to changes in process conditions. When variability and uncertainty are treated distinctively, a coupled stochastic optimization and programming method and a two-dimensional stochastic programming method are demonstrated via a case study. For the case study, the mean annual benefit of dynamic process control is estimated to be 700,000 dollars, with a 95% confidence range of 500,000 dollars to 940,000 dollars. These methods are expected to be of greatest utility for problems involving a large commitment of resources, for which small differences in designs can produce large cost savings.

Network-based regularization for matched case-control analysis of high-dimensional DNA methylation data.

PubMed

Sun, Hokeun; Wang, Shuang

2013-05-30

The matched case-control designs are commonly used to control for potential confounding factors in genetic epidemiology studies especially epigenetic studies with DNA methylation. Compared with unmatched case-control studies with high-dimensional genomic or epigenetic data, there have been few variable selection methods for matched sets. In an earlier paper, we proposed the penalized logistic regression model for the analysis of unmatched DNA methylation data using a network-based penalty. However, for popularly applied matched designs in epigenetic studies that compare DNA methylation between tumor and adjacent non-tumor tissues or between pre-treatment and post-treatment conditions, applying ordinary logistic regression ignoring matching is known to bring serious bias in estimation. In this paper, we developed a penalized conditional logistic model using the network-based penalty that encourages a grouping effect of (1) linked Cytosine-phosphate-Guanine (CpG) sites within a gene or (2) linked genes within a genetic pathway for analysis of matched DNA methylation data. In our simulation studies, we demonstrated the superiority of using conditional logistic model over unconditional logistic model in high-dimensional variable selection problems for matched case-control data. We further investigated the benefits of utilizing biological group or graph information for matched case-control data. We applied the proposed method to a genome-wide DNA methylation study on hepatocellular carcinoma (HCC) where we investigated the DNA methylation levels of tumor and adjacent non-tumor tissues from HCC patients by using the Illumina Infinium HumanMethylation27 Beadchip. Several new CpG sites and genes known to be related to HCC were identified but were missed by the standard method in the original paper. Copyright © 2012 John Wiley & Sons, Ltd.

Graph theoretic framework based cooperative control and estimation of multiple UAVs for target tracking

NASA Astrophysics Data System (ADS)

Ahmed, Mousumi

Designing the control technique for nonlinear dynamic systems is a significant challenge. Approaches to designing a nonlinear controller are studied and an extensive study on backstepping based technique is performed in this research with the purpose of tracking a moving target autonomously. Our main motivation is to explore the controller for cooperative and coordinating unmanned vehicles in a target tracking application. To start with, a general theoretical framework for target tracking is studied and a controller in three dimensional environment for a single UAV is designed. This research is primarily focused on finding a generalized method which can be applied to track almost any reference trajectory. The backstepping technique is employed to derive the controller for a simplified UAV kinematic model. This controller can compute three autopilot modes i.e. velocity, ground heading (or course angle), and flight path angle for tracking the unmanned vehicle. Numerical implementation is performed in MATLAB with the assumption of having perfect and full state information of the target to investigate the accuracy of the proposed controller. This controller is then frozen for the multi-vehicle problem. Distributed or decentralized cooperative control is discussed in the context of multi-agent systems. A consensus based cooperative control is studied; such consensus based control problem can be viewed from the algebraic graph theory concepts. The communication structure between the UAVs is represented by the dynamic graph where UAVs are represented by the nodes and the communication links are represented by the edges. The previously designed controller is augmented to account for the group to obtain consensus based on their communication. A theoretical development of the controller for the cooperative group of UAVs is presented and the simulation results for different communication topologies are shown. This research also investigates the cases where the communication topology switches to a different topology over particular time instants. Lyapunov analysis is performed to show stability in all cases. Another important aspect of this dissertation research is to implement the controller for the case, where perfect or full state information is not available. This necessitates the design of an estimator to estimate the system state. A nonlinear estimator, Extended Kalman Filter (EKF) is first developed for target tracking with a single UAV. The uncertainties involved with the measurement model and dynamics model are considered as zero mean Gaussian noises with some known covariances. The measurements of the full state of the target are not available and only the range, elevation, and azimuth angle are available from an onboard seeker sensor. A separate EKF is designed to estimate the UAV's own state where the state measurement is available through on-board sensors. The controller computes the three control commands based on the estimated states of target and its own states. Estimation based control laws is also implemented for colored noise measurement uncertainties, and the controller performance is shown with the simulation results. The estimation based control approach is then extended for the cooperative target tracking case. The target information is available to the network and a separate estimator is used to estimate target states. All of the UAVs in the network apply the same control law and the only difference is that each UAV updates the commands according to their connection. The simulation is performed for both cases of fixed and time varying communication topology. Monte Carlo simulation is also performed with different sample noises to investigate the performance of the estimator. The proposed technique is shown to be simple and robust to noisy environments.

Differentiation of African components of ancestry to stratify groups in a case-control study of a Brazilian urban population.

PubMed

Silbiger, Vivian N; Hirata, Mario H; Luchessi, Andre D; Genvigir, Fabiana D V; Cerda, Alvaro; Rodrigues, Alice C; Willrich, Maria A V; Arazi, Simone S; Dorea, Egidio L; Bernik, Marcia M S; Faludi, Andre A; Bertolami, Marcelo C; Santos, Carla; Carracedo, Angel; Salas, Antonio; Freire, Ana; Lareu, Maria Victoria; Phillips, Christopher; Porras-Hurtado, Liliana; Fondevila, Manuel; Hirata, Rosario D C

2012-06-01

Balancing the subject composition of case and control groups to create homogenous ancestries between each group is essential for medical association studies. We explored the applicability of single-tube 34-plex ancestry informative markers (AIM) single nucleotide polymorphisms (SNPs) to estimate the African Component of Ancestry (ACA) to design a future case-control association study of a Brazilian urban sample. One hundred eighty individuals (107 case group; 73 control group) self-described as white, brown-intermediate or black were selected. The proportions of the relative contribution of a variable number of ancestral population components were similar between case and control groups. Moreover, the case and control groups demonstrated similar distributions for ACA <0.25 and >0.50 categories. Notably a high number of outlier values (23 samples) were observed among individuals with ACA <0.25. These individuals presented a high probability of Native American and East Asian ancestral components; however, no individuals originally giving these self-described ancestries were observed in this study. The strategy proposed for the assessment of ancestry and adjustment of case and control groups for an association study is an important step for the proper construction of the study, particularly when subjects are taken from a complex urban population. This can be achieved using a straight forward multiplexed AIM-SNPs assay of highly discriminatory ancestry markers.

Applying Matched Sampling to Evaluate a University Tutoring Program for First-Year Students

ERIC Educational Resources Information Center

Walvoord, Mark E.; Pleitz, Jacob D.

2016-01-01

Our study used a case-control matching design to assess the influence of a voluntary tutoring program in improving first-year students' Grade Point Averages (GPA). To evaluate program effectiveness, we applied case-control matching to obtain 215 pairs of students with or without participation in tutoring, but matched on high school GPA and…

Field investigation of influenza vaccine effectiveness on morbidity.

PubMed

Carrat, F; Tachet, A; Rouzioux, C; Housset, B; Valleron, A J

1998-01-01

Our objective was to evaluate influenza vaccine effectiveness during an influenza epidemic by means of a matched case-control study. The study was performed by 35 general practitioners who collected specimens for influenza virus testing from 610 patients who consulted for infectious syndrome: 168 (28%) were influenza-positive. Two designs were used for selecting controls to take into account the high incidence-rate of influenza-like illness and the various possible protective effects of the vaccine. A first disease-free control matched for age and sex was selected during the same week as the case. A second control matched for age and sex was selected at the end of the epidemic period, irrespective of disease history during the epidemic period. Upper and lower bounds of vaccine effectiveness can be derived from these case-control designs. After adjustment for chronic conditions and exposure to an index case, analysis of the matched-pairs whose case was influenza-positive showed, with the first group of controls, an influenza vaccine effectiveness of 68% (95% CI, 10% to 88%) and, in the second group, 53% (95% CI, -19% to 82%). Among the pairs whose case was negative for influenza, vaccine effectiveness was, respectively, 31% (95% CI, -17% to 59%) and 12% (95% CI, -47% to 47%). Vaccine effectiveness was highest for the H3N2 subtype whose vaccine strain was identical to that of the wild-type strain. The results suggest that influenza vaccine is effective in the field in preventing influenza morbidity.

Research Methods in Healthcare Epidemiology and Antimicrobial Stewardship-Observational Studies.

PubMed

Snyder, Graham M; Young, Heather; Varman, Meera; Milstone, Aaron M; Harris, Anthony D; Munoz-Price, Silvia

2016-10-01

Observational studies compare outcomes among subjects with and without an exposure of interest, without intervention from study investigators. Observational studies can be designed as a prospective or retrospective cohort study or as a case-control study. In healthcare epidemiology, these observational studies often take advantage of existing healthcare databases, making them more cost-effective than clinical trials and allowing analyses of rare outcomes. This paper addresses the importance of selecting a well-defined study population, highlights key considerations for study design, and offers potential solutions including biostatistical tools that are applicable to observational study designs. Infect Control Hosp Epidemiol 2016;1-6.

What's in a Name? The Incorrect Use of Case Series as a Study Design Label in Studies Involving Dogs and Cats.

PubMed

Sargeant, J M; O'Connor, A M; Cullen, J N; Makielski, K M; Jones-Bitton, A

2017-07-01

Study design labels are used to identify relevant literature to address specific clinical and research questions and to aid in evaluating the evidentiary value of research. Evidence from the human healthcare literature indicates that the label "case series" may be used inconsistently and inappropriately. Our primary objective was to determine the proportion of studies in the canine and feline veterinary literature labeled as case series that actually corresponded to descriptive cohort studies, population-based cohort studies, or other study designs. Our secondary objective was to identify the proportion of case series in which potentially inappropriate inferential statements were made. Descriptive evaluation of published literature. One-hundred published studies (from 19 journals) labeled as case series. Studies were identified by a structured literature search, with random selection of 100 studies from the relevant citations. Two reviewers independently characterized each study, with disagreements resolved by consensus. Of the 100 studies, 16 were case series. The remaining studies were descriptive cohort studies (35), population-based cohort studies (36), or other observational or experimental study designs (13). Almost half (48.8%) of the case series or descriptive cohort studies, with no control group and no formal statistical analysis, included inferential statements about the efficacy of treatment or statistical significance of potential risk factors. Authors, peer-reviewers, and editors should carefully consider the design elements of a study to accurately identify and label the study design. Doing so will facilitate an understanding of the evidentiary value of the results. Copyright © 2017 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.

Research designs and making causal inferences from health care studies.

PubMed

Flannelly, Kevin J; Jankowski, Katherine R B

2014-01-01

This article summarizes the major types of research designs used in healthcare research, including experimental, quasi-experimental, and observational studies. Observational studies are divided into survey studies (descriptive and correlational studies), case-studies and analytic studies, the last of which are commonly used in epidemiology: case-control, retrospective cohort, and prospective cohort studies. Similarities and differences among the research designs are described and the relative strength of evidence they provide is discussed. Emphasis is placed on five criteria for drawing causal inferences that are derived from the writings of the philosopher John Stuart Mill, especially his methods or canons. The application of the criteria to experimentation is explained. Particular attention is given to the degree to which different designs meet the five criteria for making causal inferences. Examples of specific studies that have used various designs in chaplaincy research are provided.

A fuzzy control design case: The fuzzy PLL

NASA Technical Reports Server (NTRS)

Teodorescu, H. N.; Bogdan, I.

1992-01-01

The aim of this paper is to present a typical fuzzy control design case. The analyzed controlled systems are the phase-locked loops (PLL's)--classic systems realized in both analogic and digital technology. The crisp PLL devices are well known.

Unconditional or Conditional Logistic Regression Model for Age-Matched Case–Control Data?

PubMed Central

Kuo, Chia-Ling; Duan, Yinghui; Grady, James

2018-01-01

Matching on demographic variables is commonly used in case–control studies to adjust for confounding at the design stage. There is a presumption that matched data need to be analyzed by matched methods. Conditional logistic regression has become a standard for matched case–control data to tackle the sparse data problem. The sparse data problem, however, may not be a concern for loose-matching data when the matching between cases and controls is not unique, and one case can be matched to other controls without substantially changing the association. Data matched on a few demographic variables are clearly loose-matching data, and we hypothesize that unconditional logistic regression is a proper method to perform. To address the hypothesis, we compare unconditional and conditional logistic regression models by precision in estimates and hypothesis testing using simulated matched case–control data. Our results support our hypothesis; however, the unconditional model is not as robust as the conditional model to the matching distortion that the matching process not only makes cases and controls similar for matching variables but also for the exposure status. When the study design involves other complex features or the computational burden is high, matching in loose-matching data can be ignored for negligible loss in testing and estimation if the distributions of matching variables are not extremely different between cases and controls. PMID:29552553

A case-control study of domestic kitchen microbiology and sporadic Salmonella infection.

PubMed

Parry, S M; Slader, J; Humphrey, T; Holmes, B; Guildea, Z; Palmer, S R

2005-10-01

The microbiology of domestic kitchens in the homes of subjects who had suffered sporadic Salmonella infection (cases) was compared with control domestic kitchens. Case and control dishcloths and refrigerator swabs were examined for the presence of Salmonella spp., total Enterobacteriaceae counts and total aerobic colony counts. Salmonella spp. were isolated from both case and control dishcloths and refrigerators but there were no significant differences between the two groups. Colony counts were similar in case and control dishcloths and refrigerator swabs. There was no relationship between the total counts and presence of Salmonella . There was no evidence that cases of Salmonella infection were more likely to have kitchens which were contaminated with these bacteria or have higher bacterial counts than controls. Total bacterial counts were poor indicators of Salmonella contamination of the domestic kitchen environment. Further factors which could not be identified by a study of this design may increase risk of Salmonella food poisoning. These factors may include individual susceptibility of the patient. Alternatively, sporadic cases of Salmonella food poisoning may arise from food prepared outside the home.

Adaptive control using neural networks and approximate models.

PubMed

Narendra, K S; Mukhopadhyay, S

1997-01-01

The NARMA model is an exact representation of the input-output behavior of finite-dimensional nonlinear discrete-time dynamical systems in a neighborhood of the equilibrium state. However, it is not convenient for purposes of adaptive control using neural networks due to its nonlinear dependence on the control input. Hence, quite often, approximate methods are used for realizing the neural controllers to overcome computational complexity. In this paper, we introduce two classes of models which are approximations to the NARMA model, and which are linear in the control input. The latter fact substantially simplifies both the theoretical analysis as well as the practical implementation of the controller. Extensive simulation studies have shown that the neural controllers designed using the proposed approximate models perform very well, and in many cases even better than an approximate controller designed using the exact NARMA model. In view of their mathematical tractability as well as their success in simulation studies, a case is made in this paper that such approximate input-output models warrant a detailed study in their own right.

A general regression framework for a secondary outcome in case-control studies.

PubMed

Tchetgen Tchetgen, Eric J

2014-01-01

Modern case-control studies typically involve the collection of data on a large number of outcomes, often at considerable logistical and monetary expense. These data are of potentially great value to subsequent researchers, who, although not necessarily concerned with the disease that defined the case series in the original study, may want to use the available information for a regression analysis involving a secondary outcome. Because cases and controls are selected with unequal probability, regression analysis involving a secondary outcome generally must acknowledge the sampling design. In this paper, the author presents a new framework for the analysis of secondary outcomes in case-control studies. The approach is based on a careful re-parameterization of the conditional model for the secondary outcome given the case-control outcome and regression covariates, in terms of (a) the population regression of interest of the secondary outcome given covariates and (b) the population regression of the case-control outcome on covariates. The error distribution for the secondary outcome given covariates and case-control status is otherwise unrestricted. For a continuous outcome, the approach sometimes reduces to extending model (a) by including a residual of (b) as a covariate. However, the framework is general in the sense that models (a) and (b) can take any functional form, and the methodology allows for an identity, log or logit link function for model (a).

Research Design Options for Intervention Studies.

PubMed

Lobo, Michele A; Kagan, Sarah H; Corrigan, John D

2017-07-01

To review research designs for rehabilitation. Single-case, observational, and qualitative designs are highlighted in terms of recent advances and ability to answer important scientific questions about rehabilitation. Single-case, observational, and qualitative designs can be conducted in a systematic and rigorous manner that provides important information that cannot be acquired using more common designs, such as randomized controlled trials. These less commonly used designs may be more feasible and effective in answering many research questions in the field of rehabilitation. Researchers should consider these designs when selecting the optimal design to answer their research questions. We should improve education about the advantages and disadvantages of existing research designs to enable more critical analysis of the scientific literature we read and review to avoid undervaluing studies not within more commonly used categories.

Use of case-time-control design in pharmacovigilance applications: exploration with high-risk medications and unplanned hospital admissions in the Western Australian elderly.

PubMed

Price, Sylvie D; Holman, C D'Arcy J; Sanfilippo, Frank M; Emery, Jon D

2013-11-01

To use a case-time-control design to derive preliminary estimates of unplanned hospitalisations attributable to suspected high-risk medications in elderly Western Australians. Using pharmaceutical claims linked to inpatient and other health records, the study applied a case-time-control design and conditional logistic regression to estimate odds ratios (ORs) for unplanned hospital admissions associated with anticoagulants, antirheumatics, opioids, corticosteroids and four major groups of cardiovascular drugs. Attributable fractions (AFs) were derived from the ORs to estimate the number and proportion of admissions associated with drug exposure. Results were compared with those obtained from a more conventional method using International Classification of Diseases (ICD) external cause codes to identify admissions related to adverse drug events. The study involved 1 899 699 index hospital admissions. Six of the eight drug groups were associated with an increased risk of unplanned hospitalisation, opioids (adjusted OR = 1.81, 95%CI 1.75-1.88; AF = 44.9%) and corticosteroids (1.48, 1.42-1.54; 32.2%) linked with the highest risks. For all six, the estimated number of hospitalisations attributed to the medication in the exposed was higher (two to 31-fold) when derived from the case-time-control design compared with identification from ICD codes. This study provides an alternative approach for identifying potentially harmful medications and suggests that the use of ICD external causes may underestimate adverse drug events. It takes drug exposure into account, can be applied to individual medications and may overcome under-reporting issues associated with conventional methods. The approach shows great potential as part of a post-marketing pharmacovigilance monitoring system in Australia and elsewhere. Copyright © 2013 John Wiley & Sons, Ltd.

DHM simulation in virtual environments: a case-study on control room design.

PubMed

Zamberlan, M; Santos, V; Streit, P; Oliveira, J; Cury, R; Negri, T; Pastura, F; Guimarães, C; Cid, G

2012-01-01

This paper will present the workflow developed for the application of serious games in the design of complex cooperative work settings. The project was based on ergonomic studies and development of a control room among participative design process. Our main concerns were the 3D human virtual representation acquired from 3D scanning, human interaction, workspace layout and equipment designed considering ergonomics standards. Using Unity3D platform to design the virtual environment, the virtual human model can be controlled by users on dynamic scenario in order to evaluate the new work settings and simulate work activities. The results obtained showed that this virtual technology can drastically change the design process by improving the level of interaction between final users and, managers and human factors team.

A standardized mean difference effect size for multiple baseline designs across individuals.

PubMed

Hedges, Larry V; Pustejovsky, James E; Shadish, William R

2013-12-01

Single-case designs are a class of research methods for evaluating treatment effects by measuring outcomes repeatedly over time while systematically introducing different condition (e.g., treatment and control) to the same individual. The designs are used across fields such as behavior analysis, clinical psychology, special education, and medicine. Emerging standards for single-case designs have focused attention on methods for summarizing and meta-analyzing findings and on the need for effect sizes indices that are comparable to those used in between-subjects designs. In the previous work, we discussed how to define and estimate an effect size that is directly comparable to the standardized mean difference often used in between-subjects research based on the data from a particular type of single-case design, the treatment reversal or (AB)(k) design. This paper extends the effect size measure to another type of single-case study, the multiple baseline design. We propose estimation methods for the effect size and its variance, study the estimators using simulation, and demonstrate the approach in two applications. Copyright © 2013 John Wiley & Sons, Ltd.

Robust dynamic inversion controller design and analysis (using the X-38 vehicle as a case study)

NASA Astrophysics Data System (ADS)

Ito, Daigoro

A new way to approach robust Dynamic Inversion controller synthesis is addressed in this paper. A Linear Quadratic Gaussian outer-loop controller improves the robustness of a Dynamic Inversion inner-loop controller in the presence of uncertainties. Desired dynamics are given by the dynamic compensator, which shapes the loop. The selected dynamics are based on both performance and stability robustness requirements. These requirements are straightforwardly formulated as frequency-dependent singular value bounds during synthesis of the controller. Performance and robustness of the designed controller is tested using a worst case time domain quadratic index, which is a simple but effective way to measure robustness due to parameter variation. Using this approach, a lateral-directional controller for the X-38 vehicle is designed and its robustness to parameter variations and disturbances is analyzed. It is found that if full state measurements are available, the performance of the designed lateral-directional control system, measured by the chosen cost function, improves by approximately a factor of four. Also, it is found that the designed system is stable up to a parametric variation of 1.65 standard deviation with the set of uncertainty considered. The system robustness is determined to be highly sensitive to the dihedral derivative and the roll damping coefficients. The controller analysis is extended to the nonlinear system where both control input displacements and rates are bounded. In this case, the considered nonlinear system is stable up to 48.1° in bank angle and 1.59° in sideslip angle variations, indicating it is more sensitive to variations in sideslip angle than in bank angle. This nonlinear approach is further extended for the actuator failure mode analysis. The results suggest that the designed system maintains a high level of stability in the event of aileron failure. However, only 35% or less of the original stability range is maintained for the rudder failure case. Overall, this combination of controller synthesis and robustness criteria compares well with the mu-synthesis technique. It also is readily accessible to the practicing engineer, in terms of understanding and use.

A Data Management System for Multi-Phase Case-Control Studies

PubMed Central

Gibeau, Joanne M.; Steinfeldt, Lois C.; Stine, Mark J.; Tullis, Katherine V.; Lynch, H. Keith

1983-01-01

The design of a computerized system for the management of data in multi-phase epidemiologic case-control studies is described. Typical study phases include case-control selection, abstracting of data from medical records, and interview of study subjects or next of kin. In consultation with project personnel, requirements for the system were established: integration of data from all study phases into one data base, accurate follow-up of subjects through the study, sophisticated data editing capabilities, ready accessibility of specified programs to project personnel, and generation of current status and exception reports for project managment. SIR (Scientific Information Retrieval), a commercially available data base management system, was selected as the foundation of this system. The system forms a comprehensive data management system applicable to many types of public health research studies.

Case studies on design, simulation and visualization of control and measurement applications using REX control system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ozana, Stepan, E-mail: stepan.ozana@vsb.cz; Pies, Martin, E-mail: martin.pies@vsb.cz; Docekal, Tomas, E-mail: docekalt@email.cz

REX Control System is a professional advanced tool for design and implementation of complex control systems that belongs to softPLC category. It covers the entire process starting from simulation of functionality of the application before deployment, through implementation on real-time target, towards analysis, diagnostics and visualization. Basically it consists of two parts: the development tools and the runtime system. It is also compatible with Simulink environment, and the way of implementation of control algorithm is very similar. The control scheme is finally compiled (using RexDraw utility) and uploaded into a chosen real-time target (using RexView utility). There is a widemore » variety of hardware platforms and real-time operating systems supported by REX Control System such as for example Windows Embedded, Linux, Linux/Xenomai deployed on SBC, IPC, PAC, Raspberry Pi and others with many I/O interfaces. It is modern system designed both for measurement and control applications, offering a lot of additional functions concerning data archiving, visualization based on HTML5, and communication standards. The paper will sum up possibilities of its use in educational process, focused on control of case studies of physical models with classical and advanced control algorithms.« less

Interrelationships of Hormones, Diet, Body Size and Breast Cancer Among Hispanic Women

DTIC Science & Technology

2006-09-01

faculty, and 2) to design and conduct a clinic-based case-control study to include completion of a questionnaire, anthropometry and a blood draw...clinic-based case- control study to include completion of a questionnaire, anthropometry and a blood draw, 3) to disseminate findings to the Texas...Psychosocial stress, coping and prostate cancer. Ethnicity Dis (In Press). Sanderson M, Coker AL, Perez A, Du XL , Peltz G, Fadden MK. A

Overview of clinical research design.

PubMed

Hartung, Daniel M; Touchette, Daniel

2009-02-15

Basic concepts and terminology of clinical research design are presented for new clinical investigators. Clinical research, research involving human subjects, can be described as either observational or experimental. The findings of all clinical research can be threatened by issues of bias and confounding. Biases are systematic errors in how study subjects are selected or measured, which result in false inferences. Confounding is a distortion in findings that is attributable to mixing variable effects. Uncontrolled observation research is generally more prone to bias and confounding than experimental research. Observational research includes designs such as the cohort study, case-control study, and cross-sectional study, while experimental research typically involves a randomized controlled trial (RCT). The cohort study, which includes the RCT, defines subject allocation on the basis of exposure interest (e.g., drug, disease-management program) and follows the patients to assess the outcomes. The case-control study uses the primary outcome of interest (e.g., adverse event) to define subject allocation, and different exposures are assessed in a retrospective manner. Cross-sectional research evaluates both exposure and outcome concurrently. Each of these design methods possesses different strengths and weaknesses in answering research questions, as well as underlying many study subtypes. While experimental research is the strongest method for establishing causality, it can be difficult to accomplish under many scenarios. Observational clinical research offers many design alternatives that may be appropriate if planned and executed carefully.

Roundabouts : an Arizona case study and design guidelines

DOT National Transportation Integrated Search

2003-07-01

The roundabouts controlling traffic at the I-17/Happy Valley Road interchange represent Arizona's first application of modern roundabout traffic control in this manner. The construction of roundabouts at this interchange location served to alleviate ...

User-only design to assess drug effectiveness in clinical practice: application to bisphosphonates and secondary prevention of fractures.

PubMed

Corrao, Giovanni; Ghirardi, Arianna; Segafredo, Giulia; Zambon, Antonella; Della Vedova, Gianluca; Lapi, Francesco; Cipriani, Francesco; Caputi, Achille; Vaccheri, Alberto; Gregori, Dario; Gesuita, Rosaria; Vestri, Annarita; Staniscia, Tommaso; Mazzaglia, Giampiero; Di Bari, Mauro

2014-08-01

Different strategies applicable to control for confounding by indication in observational studies were compared in a large population-based study regarding the effect of bisphosphonates (BPs) for secondary prevention of fractures. The cohort was drawn from healthcare utilization databases of 13 Italian territorial units. Patients aged 55 years or more who were hospitalized for fracture during 2003-2005 entered into the cohort. A nested case-control design was used to compare BPs use in cohort members who did (cases) and who did not experience (controls) a new fracture until 2007 (outcome). Three designs were employed: conventional-matching (D1 ), propensity score-matching (D2 ), and user-only (D3 ) designs. They differed for (i) cohort composition, restricted to patients who received BPs straight after cohort entry (D3 ); (ii) using propensity score for case-control matching (D2 ); and (iii) compared groups of BPs users versus no users (D1 and D2 ) and long-term versus short-term users (D3 ). Bisphosphonate users had odds ratios (95% confidence interval) of 1.20 (1.01 to 1.44) and 0.95 (0.74 to 1.24) by applying D1 and D2 designs, respectively. Statistical evidence that long-term BPs use protects the outcome onset with respect to short-term use was observed for user-only design (D3 ) being the corresponding odds ratio (95% confidence interval) 0.64 (0.44 to 0.93). User-only design yielded closer results to those seen in RCTs. This approach is one possible strategy to account for confounding by indication. Copyright © 2014 John Wiley & Sons, Ltd.

Improving power and robustness for detecting genetic association with extreme-value sampling design.

PubMed

Chen, Hua Yun; Li, Mingyao

2011-12-01

Extreme-value sampling design that samples subjects with extremely large or small quantitative trait values is commonly used in genetic association studies. Samples in such designs are often treated as "cases" and "controls" and analyzed using logistic regression. Such a case-control analysis ignores the potential dose-response relationship between the quantitative trait and the underlying trait locus and thus may lead to loss of power in detecting genetic association. An alternative approach to analyzing such data is to model the dose-response relationship by a linear regression model. However, parameter estimation from this model can be biased, which may lead to inflated type I errors. We propose a robust and efficient approach that takes into consideration of both the biased sampling design and the potential dose-response relationship. Extensive simulations demonstrate that the proposed method is more powerful than the traditional logistic regression analysis and is more robust than the linear regression analysis. We applied our method to the analysis of a candidate gene association study on high-density lipoprotein cholesterol (HDL-C) which includes study subjects with extremely high or low HDL-C levels. Using our method, we identified several SNPs showing a stronger evidence of association with HDL-C than the traditional case-control logistic regression analysis. Our results suggest that it is important to appropriately model the quantitative traits and to adjust for the biased sampling when dose-response relationship exists in extreme-value sampling designs. © 2011 Wiley Periodicals, Inc.

Mechatronic system design course for undergraduate programmes

NASA Astrophysics Data System (ADS)

Saleem, A.; Tutunji, T.; Al-Sharif, L.

2011-08-01

Technology advancement and human needs have led to integration among many engineering disciplines. Mechatronics engineering is an integrated discipline that focuses on the design and analysis of complete engineering systems. These systems include mechanical, electrical, computer and control subsystems. In this paper, the importance of teaching mechatronic system design to undergraduate engineering students is emphasised. The paper offers the collaborative experience in preparing and delivering the course material for two universities in Jordan. A detailed description of such a course is provided and a case study is presented. The case study used is a final year project, where students applied a six-stage design procedure that is described in the paper.

A case control study of senile cataract in a hospital based population.

PubMed

Badrinath, S S; Sharma, T; Biswas, J; Srinivas, V

1996-12-01

A case-control study (244 cases and 264 controls) was done during 1986-89 on a hospital based population to evaluate the risk factors associated with the etiology of senile cataract. Patient with age between 40-60 years, visual acuity of 6/9 or less, and presence of lenticular opacity of senile origin were included as cases. Age matched individuals with absence of lenticular opacity made up the controls. Multivariate logistic regression analysis revealed that higher systolic BP and number of meals were significantly (P < or = 0.05) associated with presence of senile cataract; whereas higher weight, education and income, and utilization of cooking water had a significant protective effect against senile cataract. The present study helps the clinician to understand the possible risk factors associated with the development of senile cataract and could be helpful in designing a intervention strategy in future.

Medical Conditions in the First Years of Life Associated with Future Diagnosis of ASD in Children

ERIC Educational Resources Information Center

Alexeeff, Stacey E.; Yau, Vincent; Qian, Yinge; Davignon, Meghan; Lynch, Frances; Crawford, Phillip; Davis, Robert; Croen, Lisa A.

2017-01-01

This study examines medical conditions diagnosed prior to the diagnosis of autism spectrum disorder (ASD). Using a matched case control design with 3911 ASD cases and 38,609 controls, we found that 38 out of 79 medical conditions were associated with increased ASD risk. Developmental delay, mental health, and neurology conditions had the strongest…

A novel double loop control model design for chemical unstable processes.

PubMed

Cong, Er-Ding; Hu, Ming-Hui; Tu, Shan-Tung; Xuan, Fu-Zhen; Shao, Hui-He

2014-03-01

In this manuscript, based on Smith predictor control scheme for unstable process in industry, an improved double loop control model is proposed for chemical unstable processes. Inner loop is to stabilize integrating the unstable process and transform the original process to first-order plus pure dead-time dynamic stable process. Outer loop is to enhance the performance of set point response. Disturbance controller is designed to enhance the performance of disturbance response. The improved control system is simple with exact physical meaning. The characteristic equation is easy to realize stabilization. Three controllers are separately design in the improved scheme. It is easy to design each controller and good control performance for the respective closed-loop transfer function separately. The robust stability of the proposed control scheme is analyzed. Finally, case studies illustrate that the improved method can give better system performance than existing design methods. © 2013 ISA Published by ISA All rights reserved.

Adopting an Evidence-Based Lifestyle Physical Activity Program: Dissemination Study Design and Methods.

PubMed

Dunn, Andrea L; Buller, David B; Dearing, James W; Cutter, Gary; Guerra, Michele; Wilcox, Sara; Bettinghaus, Erwin P

2012-06-01

BACKGROUND: There is a scarcity of research studies that have examined academic-commercial partnerships to disseminate evidence-based physical activity programs. Understanding this approach to dissemination is essential because academic-commercial partnerships are increasingly common. Private companies have used dissemination channels and strategies to a degree that academicians have not, and declining resources require academicians to explore these partnerships. PURPOSE: This paper describes a retrospective case-control study design including the methods, demographics, organizational decision-making, implementation rates, and marketing strategy for Active Living Every Day (ALED), an evidence-based lifestyle physical activity program that has been commercially available since 2001. Evidence-based public health promotion programs rely on organizations and targeted sectors to disseminate these programs although relatively little is known about organizational-level and sector-level influences that lead to their adoption and implementation. METHODS: Cases (n=154) were eligible if they had signed an ALED license agreement with Human Kinetics (HK), publisher of the program's textbooks and facilitator manuals, between 2001 and 2008. Two types of controls were matched (2:2:1) and stratified by sector and region. Active controls (Control 1; n=319) were organizations that contacted HK to consider adopting ALED. Passive controls (Control 2; n=328) were organizations that received unsolicited marketing materials and did not initiate contact with HK. We used Diffusion of Innovations Theory (DIT) constructs as the basis for developing the survey of cases and controls. RESULTS: Using the multi-method strategy recommended by Dillman, a total of n=801 cases and controls were surveyed. Most organizations were from the fitness sector followed by medical, nongovernmental, governmental, educational, worksite and other sectors with significantly higher response rates from government, educational and medical sectors compared with fitness and other sectors, (p=0.02). More cases reported being involved in the decision to adopt ALED (p<0.0001). Data indicate that a low percentage of controls had ever heard of ALED despite repeated marketing and offering other types of physical activity programs and services. Finally, slightly over half of the adopters reported they had actually implemented the ALED program. CONCLUSION: Dissemination research requires new perspectives and designs to produce valid insights about the results of dissemination efforts. This study design, survey methods and theoretically-based questions can serve as a useful model for other evidence-based public health interventions that are marketed by commercial publishers to better understand key issues related to adoption and implementation of evidence-based programs.

Design-Filter Selection for H2 Control of Microgravity Isolation Systems: A Single-Degree-of-Freedom Case Study

NASA Technical Reports Server (NTRS)

Hampton, R. David; Whorton, Mark S.

2000-01-01

Many microgravity space-science experiments require active vibration isolation, to attain suitably low levels of background acceleration for useful experimental results. The design of state-space controllers by optimal control methods requires judicious choices of frequency-weighting design filters. Kinematic coupling among states greatly clouds designer intuition in the choices of these filters, and the masking effects of the state observations cloud the process further. Recent research into the practical application of H2 synthesis methods to such problems, indicates that certain steps can lead to state frequency-weighting design-filter choices with substantially improved promise of usefulness, even in the face of these difficulties. In choosing these filters on the states, one considers their relationships to corresponding design filters on appropriate pseudo-sensitivity- and pseudo-complementary-sensitivity functions. This paper investigates the application of these considerations to a single-degree-of-freedom microgravity vibration-isolation test case. Significant observations that were noted during the design process are presented. along with explanations based on the existent theory for such problems.

Economic comparison of fabric filters and electrostatic precipitators for particulate control on coal-fired utility boilers

NASA Technical Reports Server (NTRS)

Cukor, P. M.; Chapman, R. A.

1978-01-01

The uncertainties and associated costs involved in selecting and designing a particulate control device to meet California's air emission regulations are considered. The basic operating principles of electrostatic precipitators and fabric filters are discussed, and design parameters are identified. The size and resulting cost of the control device as a function of design parameters is illustrated by a case study for an 800 MW coal-fired fired utility boiler burning a typical southwestern subbituminous coal. The cost of selecting an undersized particulate control device is compared with the cost of selecting an oversized device.

Genetic polymorphisms for estimating risk of atrial fibrillation: a literature-based meta-analysis

PubMed Central

Smith, J. Gustav; Almgren, Peter; Engström, Gunnar; Hedblad, Bo; Platonov, Pyotr G.; Newton-Cheh, Christopher; Melander, Olle

2013-01-01

Objectives Genome-wide association studies have recently identified genetic polymorphisms associated with common, etiologically complex diseases, for which direct-to-consumer genetic testing with provision of absolute genetic risk estimates is marketed by commercial companies. Polymorphisms associated with atrial fibrillation (AF) have shown relatively large risk estimates but the robustness of such estimates across populations and study designs has not been studied. Design A systematic literature review with meta-analysis and assessment of between-study heterogeneity was performed for single nucleotide polymorphisms (SNPs) in the six genetic regions associated with AF in genome-wide or candidate gene studies. Results Data from 18 samples of European ancestry (n=12,100 cases; 115,702 controls) were identified for the SNP on chromosome 4q25 (rs220733), 16 samples (n=12,694 cases; 132,602 controls) for the SNP on 16q22 (rs2106261) and 4 samples (n=5,272 cases; 59,725 controls) for the SNP in KCNH2 (rs1805123). Only the discovery studies were identified for SNPs on 1q21 and in GJA5 and IL6R, why no meta-analyses were performed for those SNPs. In overall random-effects meta-analyses, association with AF was observed for both SNPs from genome-wide studies on 4q25 (OR 1.67, 95% CI=1.50–1.86, p=2×10−21) and 16q22 (OR 1.21, 95% CI=1.13–1.29, p=1×10−8), but not the SNP in KCNH2 from candidate gene studies (p=0.15). There was substantial effect heterogeneity across case-control and cross-sectional studies for both polymorphisms (I2=0.50–0.78, p<0.05), but not across prospective cohort studies (I2=0.39, p=0.15). Both polymorphisms were robustly associated with AF for each study design individually (p<0.05). Conclusions In meta-analyses including up to 150,000 individuals, polymorphisms in two genetic regions were robustly associated with AF across all study designs but with substantial context-dependency of risk estimates. PMID:22690879

The Ethnic/Racial Variations of Intracerebral Hemorrhage (ERICH) Study Protocol

PubMed Central

Woo, Daniel; Rosand, Jonathan; Kidwell, Chelsea; McCauley, Jacob L.; Osborne, Jennifer; Brown, Mark W.; West, Sandra E.; Rademacher, Eric W.; Waddy, Salina; Roberts, Jamie N.; Koch, Sebastian; Gonzales, Nicole R.; Sung, Gene; Kittner, Steven J.; Birnbaum, Lee; Frankel, Michael; Daniel Testai, Fernando; Hall, Christiana E.; Elkind, Mitchell S. V.; Flaherty, Matthew; Coull, Bruce; Chong, Ji Y.; Warwick, Tanya; Malkoff, Marc; James, Michael L.; Ali, Latisha K.; Worrall, Bradford B.; Jones, Floyd; Watson, Tiffany; Leonard, Anne; Martinez, Rebecca; Sacco, Ralph I; Langefeld, Carl D.

2013-01-01

Background and Purpose Epidemiologic studies of intracerebral hemorrhage (ICH) have consistently demonstrated variation in incidence, location, age at presentation, and outcomes among non-Hispanic white, black, and Hispanic populations. We report here the design and methods for this large, prospective, multi-center case-control study of ICH. Methods The ERICH study is a multi-center, prospective case-control study of ICH. Cases are identified by hot-pursuit and enrolled using standard phenotype and risk factor information and include neuroimaging and blood sample collection. Controls are centrally identified by random digit dialing to match cases by age (+/−5 years), race, ethnicity, gender and metropolitan region. Results As of March 22, 2013, 1,655 cases of ICH had been recruited into the study which is 101.5% of the target for that date and 851 controls had been recruited which is 67.2% of the target for that date (1,267 controls) for a total of 2,506 subjects which is 86.5% of the target for that date (2,897 subjects). Of the 1,655 cases enrolled, 1,640 cases had the case interview entered into the database of which 628 (38%) were non-Hispanic black, 458 (28%) were non-Hispanic white and 554 (34%) were Hispanic. Of the 1,197 cases with imaging submitted, 876 (73.2%) had a 24 hour follow-up CT available In addition to CT imaging, 607 cases have had MRI evaluation. Conclusion The ERICH study is a large, case-control study of ICH with particular emphasis on recruitment of minority populations for the identification of genetic and epidemiologic risk factors for ICH and outcomes after ICH. PMID:24021679

Estimating the Occurrence of Child Maltreatment and Risk-Factor Effects: Benefits of a Mixed-Design Strategy in Epidemiologic Research.

ERIC Educational Resources Information Center

Bertolli, Jeanne; And Others

1995-01-01

This article discusses methodologic limitations of four observational study designs (ecologic, case-control, cross-sectional, and cohort) that dominate the child abuse and neglect literature and identifies key features of an "ideal" study of child maltreatment. It proposes a new mixed-design strategy, which improves ability to identify child…

Evaluating the case-positive, control test-negative study design for influenza vaccine effectiveness for the frailty bias.

PubMed

Talbot, H Keipp; Nian, Hui; Chen, Qingxia; Zhu, Yuwei; Edwards, Kathryn M; Griffin, Marie R

2016-04-04

Previous influenza vaccine effectiveness studies were criticized for their failure to control for frailty. This study was designed to see if the test-negative study design overcomes this bias. Adults ≥ 50 years of age with respiratory symptoms were enrolled from November 2006 through May 2012 during the influenza season (excluding the 2009-2010 H1N1 pandemic season) to perform yearly test-negative control influenza vaccine effectiveness studies in Nashville, TN. At enrollment, both a nasal and throat swab sample were obtained and tested for influenza by RT-PCR. Frailty was calculated using a modified Rockwood Index that included 60 variables ascertained in a retrospective chart review giving a score of 0 to 1. Subjects were divided into three strata: non frail (≤ 0.08), pre-frail (> 0.08 to < 0.25), and frail (≥ 0.25). Vaccine effectiveness was calculated using the formula [1-adjusted odds ratio (OR)] × 100%. Adjusted ORs for individual years and all years combined were estimated by penalized multivariable logistic regression. Of 1023 hospitalized adults enrolled, 866 (84.7%) participants had complete immunization status, molecular influenza testing and covariates to calculate frailty. There were 83 influenza-positive cases and 783 test-negative controls overall, who were 74% white, 25% black, and 59% female. The median frailty index was 0.167 (Interquartile: 0.117, 0.267). The frailty index was 0.167 (0.100, 0.233) for the influenza positive cases compared to 0.183 (0.133, 0.267) for influenza negative controls (p = 0.07). Vaccine effectiveness estimates were 55.2% (95%CI: 30.5, 74.2), 60.4% (95%CI: 29.5, 74.4), and 54.3% (95%CI: 28.8, 74.0) without the frailty variable, including frailty as a continuous variable, and including frailty as a categorical variable, respectively. Using the case positive test negative study design to assess vaccine effectiveness, our measure of frailty was not a significant confounder as inclusion of this measure did not significantly change vaccine effectiveness estimates. Copyright © 2016 Elsevier Ltd. All rights reserved.

Estimating the influenza vaccine effectiveness in elderly on a yearly basis using the Spanish influenza surveillance network--pilot case-control studies using different control groups, 2008-2009 season, Spain.

PubMed

Savulescu, Camelia; Valenciano, Marta; de Mateo, Salvador; Larrauri, Amparo

2010-04-01

We conducted a case-control and screening method studies to estimate influenza vaccine effectiveness (IVE) in the age group >or=65 years, based on the Spanish Influenza Sentinel Surveillance System (SISSS). Cases (influenza laboratory-confirmed) were compared to influenza-negative ILI patients (test-negative) and patients without ILI since the beginning of the season (non-ILI). For the screening method, cases' vaccination coverage was compared to the vaccination coverage of the GPs' catchment population. The results suggested a protective effect of the vaccine against laboratory-confirmed influenza in elderly in 2008-2009. The screening method and the test-negative control designs enable estimating IVE using exclusively SISSS data. (c) 2010 Elsevier Ltd. All rights reserved.

Dermatoglyphic patterns in dementia of the Alzheimer type: a case-control study.

PubMed Central

Berr, C; Okra-Podrabinek, N; Feteanu, D; Taurand, S; Hervy, M P; Forette, F; Piette, F; Sebag-Lanoe, R; Alperovitch, A

1992-01-01

STUDY OBJECTIVE--The aim was to compare digital and palmar dermatoglyphics in subjects with dementia of Alzheimer type and in mentally healthy elderly controls. DESIGN--This design was a case-control study. SETTING--The study was carried out in geriatric units and retirement communities in the Paris area. PARTICIPANTS--Cases were women with clinically diagnosed Alzheimer type dementia according to DSM III-R criteria (n = 82), mainly with late onset of the disease. Controls were women aged 85 years or older without cognitive deterioration (n = 76). MEASUREMENTS AND MAIN RESULTS--Finger and palm prints obtained from both hands by the classical ink method were examined. Fingerprints were classified into four types of figures. On palms, palmar flexion creases, palmar axial triradii, true patterns of the hypothenar area, and main line terminations were described. Examinations were performed by two examiners blind to the subjects's diagnostic category. For the different patterns studied, no major differences between dementia patients and elderly controls were found. Nor was there evidence of high frequencies of features commonly observed in Down's syndrome (trisomy 21), which have previously, though sporadically, been reported. CONCLUSIONS--On one of the largest samples of Alzheimer dementia patients studied, and with evaluation blind to diagnosis, no evidence has been found that particular dermatoglyphic patterns occur like those observed in Down's syndrome, a disease which is related to dementia of the Alzheimer type. PMID:1479321

Matched samples logistic regression in case-control studies with missing values: when to break the matches.

PubMed

Hansson, Lisbeth; Khamis, Harry J

2008-12-01

Simulated data sets are used to evaluate conditional and unconditional maximum likelihood estimation in an individual case-control design with continuous covariates when there are different rates of excluded cases and different levels of other design parameters. The effectiveness of the estimation procedures is measured by method bias, variance of the estimators, root mean square error (RMSE) for logistic regression and the percentage of explained variation. Conditional estimation leads to higher RMSE than unconditional estimation in the presence of missing observations, especially for 1:1 matching. The RMSE is higher for the smaller stratum size, especially for the 1:1 matching. The percentage of explained variation appears to be insensitive to missing data, but is generally higher for the conditional estimation than for the unconditional estimation. It is particularly good for the 1:2 matching design. For minimizing RMSE, a high matching ratio is recommended; in this case, conditional and unconditional logistic regression models yield comparable levels of effectiveness. For maximizing the percentage of explained variation, the 1:2 matching design with the conditional logistic regression model is recommended.

Study design and "evidence" in patient-oriented research.

PubMed

Concato, John

2013-06-01

Individual studies in patient-oriented research, whether described as "comparative effectiveness" or using other terms, are based on underlying methodological designs. A simple taxonomy of study designs includes randomized controlled trials on the one hand, and observational studies (such as case series, cohort studies, and case-control studies) on the other. A rigid hierarchy of these design types is a fairly recent phenomenon, promoted as a tenet of "evidence-based medicine," with randomized controlled trials receiving gold-standard status in terms of producing valid results. Although randomized trials have many strengths, and contribute substantially to the evidence base in clinical care, making presumptions about the quality of a study based solely on category of research design is unscientific. Both the limitations of randomized trials as well as the strengths of observational studies tend to be overlooked when a priori assumptions are made. This essay presents an argument in support of a more balanced approach to evaluating evidence, and discusses representative examples from the general medical as well as pulmonary and critical care literature. The simultaneous consideration of validity (whether results are correct "internally") and generalizability (how well results apply to "external" populations) is warranted in assessing whether a study's results are accurate for patients likely to receive the intervention-examining the intersection of clinical and methodological issues in what can be called a medicine-based evidence approach. Examination of cause-effect associations in patient-oriented research should recognize both the strengths and limitations of randomized trials as well as observational studies.

Morphological Features in Children with Autism Spectrum Disorders: A Matched Case-Control Study

ERIC Educational Resources Information Center

Ozgen, Heval; Hellemann, Gerhard S.; Stellato, Rebecca K.; Lahuis, Bertine; van Daalen, Emma; Staal, Wouter G.; Rozendal, Marije; Hennekam, Raoul C.; Beemer, Frits A.; van Engeland, Herman

2011-01-01

This study was designed to examine morphological features in a large group of children with autism spectrum disorder versus normal controls. Amongst 421 patients and 1,007 controls, 224 matched pairs were created. Prevalence rates and odds ratios were analyzed by conditional regression analysis, McNemar test or paired t-test matched pairs.…

A case-control study of syphilis among men who have sex with men in New York City: association With HIV infection.

PubMed

Paz-Bailey, Gabriela; Meyers, Andrea; Blank, Susan; Brown, James; Rubin, Steve; Braxton, Jim; Zaidi, Akbar; Schafzin, Josh; Weigl, Susan; Markowitz, Laurie E

2004-10-01

The objective of this study was to determine factors associated with syphilis among men who report sex with other men in New York City. DESIGN, SETTING AND STUDY SUBJECTS: We conducted a case-control study among 88 men who reported sex with men in the previous year, 18 to 55 years old and diagnosed with primary or secondary syphilis during 2001; and 176 control subjects frequently matched by age and type of health provider. HIV prevalence among syphilis cases was 48% compared with 15% among control subjects (P <0.001). Variables associated with syphilis in a multivariate model were HIV infection (odds ratio [OR], 7.3; 95% confidence interval [CI], 3.5-15.4), income >$30,000 per year (OR, 2.7; CI, 1.4-5.2), and barebacking (OR, 2.6; CI, 1.4-4.8). The median time since HIV diagnosis for HIV-positive was 6 years for cases and 7 years for control subjects (P = 0.70). Among HIV-infected participants, syphilis cases were more likely than control subjects to report being on antiretroviral therapy (69% vs. 44%, P = 0.05) and to report having undetectable viral load (58% vs. 24%, P = 0.02). HIV infection was strongly associated with syphilis in this study. High-risk behavior reported by both cases and control subjects indicates the potential for increased HIV transmission.

[Design of sponge city and its inspiration to landscape ecology: A case of Liaodong Bay area of Panjin City, Northeast China].

PubMed

Sui, Jin Ling; Liu, Miao; Li, Chun Lin; Hu, Yuan Man; Wu, Yi Lin; Liu, Chong

2017-03-18

With the expansion of urban area, many cities are facing urban water environment issues, i.e., water resources shortage, lack of groundwater reserves, water pollution, urban waterlogging. For resolving these urban issues, 'sponge city' was proposed in 2015 in China. Liaodong Bay area of Panjin City in Liaoning Province of China was chosen as case study. Based on 'Sponge City Construction Technology Guide: Low Impact Development Rainwater System Building (Trial)', the underlying surface and types of land use in the typical area were analyzed. Sponge city plan of the study area was designed through combining topography, hydrology, rainfall intensity and other factors, and selecting LID measures. The results showed that when the study area reached the ove-rall target control rate (the control rate of the total annual runoff was ＞75%), the subsidence greenbelt rate was 1%-31%, with a total area of 13.73 km 2 ; the pervious pavement rate was 1%-13%, with a total area of 2.29 km 2 . This study could provide a case study for planning and designing of 'sponge city', proposing new ideas and methods for the research on landscape pattern and process.

Dietary Cholesterol Intake and Risk of Lung Cancer: A Meta-Analysis.

PubMed

Lin, Xiaojing; Liu, Lingli; Fu, Youyun; Gao, Jing; He, Yunyun; Wu, Yang; Lian, Xuemei

2018-02-08

Multiple epidemiologic studies have evaluated the relationship between dietary cholesterol and lung cancer risk, but the association is controversial and inconclusive. A meta-analysis of case-control studies and cohort studies was conducted to evaluate the relationship between dietary cholesterol intake and lung cancer risk in this study. A relevant literature search up to October 2017 was performed in Web of Science, PubMed, China National Knowledge Infrastructure, Sinomed, and VIP Journal Integration Platform. Ten case-control studies and six cohort studies were included in the meta-analysis, and the risk estimates were pooled using either fixed or random effects models. The case-control studies with a total of 6894 lung cancer cases and 29,736 controls showed that dietary cholesterol intake was positively associated with lung cancer risk (Odds Ratio = 1.70, 95% Confidence Interval: 1.43-2.03). However, there was no evidence of an association between dietary cholesterol intake and risk of lung cancer among the 241,920 participants and 1769 lung cancer cases in the cohort studies (Relative Risk = 1.08, 95% Confidence Interval: 0.94-1.25). Due to inconsistent results from case-control and cohort studies, it is difficult to draw any conclusion regarding the effects of dietary cholesterol intake on lung cancer risk. Carefully designed and well-conducted cohort studies are needed to identify the association between dietary cholesterol and lung cancer risk.

Changes to Hospital Inpatient Volume After Newspaper Reporting of Medical Errors.

PubMed

Fukuda, Haruhisa

2017-06-30

The aim of this study was to investigate the influence of medical error case reporting by national newspapers on inpatient volume at acute care hospitals. A case-control study was conducted using the article databases of 3 major Japanese newspapers with nationwide circulation between fiscal years 2012 and 2013. Data on inpatient volume at acute care hospitals were obtained from a Japanese government survey between fiscal years 2011 and 2014. Panel data were constructed and analyzed using a difference-in-differences design. Acute care hospitals in Japan. Hospitals named in articles that included the terms "medical error" and "hospital" were designated case hospitals, which were matched with control hospitals using corresponding locations, nurse-to-patient ratios, and bed numbers. Medical error case reporting in newspapers. Changes to hospital inpatient volume after error reports. The sample comprised 40 case hospitals and 40 control hospitals. Difference-in-differences analyses indicated that newspaper reporting of medical errors was not significantly associated (P = 0.122) with overall inpatient volume. Medical error case reporting by newspapers showed no influence on inpatient volume. Hospitals therefore have little incentive to respond adequately and proactively to medical errors. There may be a need for government intervention to improve the posterror response and encourage better health care safety.

Estimating the influenza vaccine effectiveness against medically attended influenza in clinical settings: a hospital-based case-control study with a rapid diagnostic test in Japan.

PubMed

Suzuki, Motoi; Yoshimine, Hiroyuki; Harada, Yoshitaka; Tsuchiya, Naho; Shimada, Ikumi; Ariyoshi, Koya; Inoue, Kenichiro

2013-01-01

Influenza vaccine effectiveness (VE) studies are usually conducted by specialized agencies and require time and resources. The objective of this study was to estimate the influenza VE against medically attended influenza using a test-negative case-control design with rapid influenza diagnostic tests (RIDT) in a clinical setting. A prospective study was conducted at a community hospital in Nagasaki, western Japan during the 2010/11 influenza season. All outpatients aged 15 years and older with influenza-like illnesses (ILI) who had undergone RIDT were enrolled. A test-negative case-control design was applied to estimate the VEs: the cases were ILI patients with positive RIDT results and the controls were ILI patients with negative RIDT results. Information on patient characteristics, including vaccination histories, was collected using questionnaires and medical records. Between December 2010 and April 2011, 526 ILI patients were tested with RIDT, and 476 were eligible for the analysis. The overall VE estimate against medically attended influenza was 47.6%, after adjusting for the patients' age groups, presence of chronic conditions, month of visit, and smoking and alcohol use. The seasonal influenza vaccine reduced the risk of medically attended influenza by 60.9% for patients less than 50 years of age, but a significant reduction was not observed for patients 50 years of age and older. A sensitivity analysis provided similar figures. The test-negative case-control study using RIDT provided moderate influenza VE consistent with other reports. Utilizing the commonly used RIDT to estimate VE provides rapid assessment of VE; however, it may require validation with more specific endpoint.

Adaptive sliding mode control for a class of chaotic systems

DOE Office of Scientific and Technical Information (OSTI.GOV)

Farid, R.; Ibrahim, A.; Zalam, B., E-mail: ramy5475@yahoo.com

2015-03-30

Chaos control here means to design a controller that is able to mitigating or eliminating the chaos behavior of nonlinear systems that experiencing such phenomenon. In this paper, an Adaptive Sliding Mode Controller (ASMC) is presented based on Lyapunov stability theory. The well known Chua's circuit is chosen to be our case study in this paper. The study shows the effectiveness of the proposed adaptive sliding mode controller.

The posttraumatic stress disorder project in Brazil: neuropsychological, structural and molecular neuroimaging studies in victims of urban violence.

PubMed

Bressan, Rodrigo A; Quarantini, Lucas C; Andreoli, Sérgio B; Araújo, Celia; Breen, Gerome; Guindalini, Camila; Hoexter, Marcelo; Jackowski, Andrea P; Jorge, Miguel R; Lacerda, Acioly L T; Lara, Diogo R; Malta, Stella; Moriyama, Tais S; Quintana, Maria I; Ribeiro, Wagner S; Ruiz, Juliana; Schoedl, Aline F; Shih, Ming C; Figueira, Ivan; Koenen, Karestan C; Mello, Marcelo F; Mari, Jair J

2009-06-01

Life trauma is highly prevalent in the general population and posttraumatic stress disorder is among the most prevalent psychiatric consequences of trauma exposure. Brazil has a unique environment to conduct translational research about psychological trauma and posttraumatic stress disorder, since urban violence became a Brazilian phenomenon, being particularly related to the rapid population growth of its cities. This research involves three case-control studies: a neuropsychological, a structural neuroimaging and a molecular neuroimaging study, each focusing on different objectives but providing complementary information. First, it aims to examine cognitive functioning of PTSD subjects and its relationships with symptomatology. The second objective is to evaluate neurostructural integrity of orbitofrontal cortex and hippocampus in PTSD subjects. The third aim is to evaluate if patients with PTSD have decreased dopamine transporter density in the basal ganglia as compared to resilient controls subjects. This paper shows the research rationale and design for these three case-control studies. Cases and controls will be identified through an epidemiologic survey conducted in the city of São Paulo. Subjects exposed to traumatic life experiences resulting in posttraumatic stress disorder (cases) will be compared to resilient victims of traumatic life experiences without PTSD (controls) aiming to identify biological variables that might protect or predispose to PTSD. In the neuropsychological case-control study, 100 patients with PTSD, will be compared with 100 victims of trauma without posttraumatic stress disorder, age- and sex-matched controls. Similarly, 50 cases and 50 controls will be enrolled for the structural study and 25 cases and 25 controls in the functional neuroimaging study. All individuals from the three studies will complete psychometrics and a structured clinical interview (the Structured Clinical Interview for DSM-IV and the Clinician-Administered PTSD Scale, Beck Anxiety Inventory, Beck Depression Inventory, Global Assessment of Function, The Social Adjustment Scale, Medical Outcomes Study 36-Item Short-Form Health Survey, Early Trauma Inventory, Clinical global Impressions, and Peritraumatic Dissociative Experiences Questionnaire). A broad neuropsychological battery will be administered for all participants of the neuropsychological study. Magnetic resonance scans will be performed to acquire structural neuroimaging data. Single photon emission computerized tomography with [(99m)Tc]-TRODAT-1 brain scans will be performed to evaluate dopamine transporters. This study protocol will be informative for researchers and clinicians interested in considering, designing and/or conducting translational research in the field of trauma and posttraumatic stress disorder.

An employer's experience with infertility coverage: a case study.

PubMed

Silverberg, Kaylen; Meletiche, Dennis; Del Rosario, Gina

2009-12-01

A case study of Southwest Airlines, a Fortune 500 company, demonstrates that a well-designed infertility coverage plan can control resource use. This successful model could be used by employers who wish to ensure that their employees have access to high-quality, cost-effective infertility services in a managed-care environment.

Effect of socio-cultural factors on spontaneous abortion in Burdur, Turkey: A population based case-control study.

PubMed

Catak, Binali; Oner, Can; Sutlu, Sevinc; Kilinc, Selcuk

2016-01-01

To determine the sociocultural factors that have effect on spontaneous abortion in Burdur, Turkey. Study was designed as case-control study. The case group consist of 257 women whose pregnancies ended with spontaneous abortion. The control group consisted of 514 women whose pregnancy continued since 22 weeks and more during the study. Chi-square, and backward LR logistic regression were utilized in analyses. In multifactorial-analyses it was determined that four factors (educational status of women, employment status of women, exposure to physical violence and non-receipt of ANC) created independent risk on spontaneous abortions. Pregnant women with these risk factors should be followed up more frequently and in a more qualified way in primary and secondary and tertiary health institutions.

Using short-range and long-range functional connectivity to identify schizophrenia with a family-based case-control design.

PubMed

Guo, Wenbin; Liu, Feng; Chen, Jindong; Wu, Renrong; Li, Lehua; Zhang, Zhikun; Chen, Huafu; Zhao, Jingping

2017-06-30

Abnormal short-range and long-range functional connectivities (FCs) have been implicated in the neurophysiology of schizophrenia. This study was conducted to examine the potential of short-range and long-range FCs for differentiating the patients from the controls with a family-based case-control design. Twenty-eight first-episode, drug-naive patients with schizophrenia, 28 unaffected siblings of the patients (family-based controls, FBCs), and 40 healthy controls (HCs) underwent resting-state functional magnetic resonance imaging (fMRI) scans. The data were analyzed by short-range and long-range FC analyses, receiver operating characteristic curve (ROC) and support vector machine (SVM). Compared with the FBCs/HCs, the patients exhibit increased short-range positive FC strength (spFCS) and/or long-range positive FC strength (lpFCS) in the default-mode network (DMN) and decreased spFCS and lpFCS in the sensorimotor circuits. Furthermore, a combination of the spFCS values in the right superior parietal lobule and the lpFCS values in the left fusiform gyrus/cerebellum VI can differentiate the patients from the FBCs with high sensitivity and specificity. The findings highlight the importance of the DMN and sensorimotor circuits in the pathogenesis of schizophrenia. Combining with family-based case-control design may be a viable option to limit the confounding effects of environmental risk factors in neuroimaging studies of schizophrenia. Copyright © 2017 Elsevier Ireland Ltd. All rights reserved.

The use of relative incidence ratios in self-controlled case series studies: an overview.

PubMed

Hawken, Steven; Potter, Beth K; Little, Julian; Benchimol, Eric I; Mahmud, Salah; Ducharme, Robin; Wilson, Kumanan

2016-09-23

The self-controlled case series (SCCS) is a useful design for investigating associations between outcomes and transient exposures. The SCCS design controls for all fixed covariates, but effect modification can still occur. This can be evaluated by including interaction terms in the model which, when exponentiated, can be interpreted as a relative incidence ratio (RIR): the change in relative incidence (RI) for a unit change in an effect modifier. We conducted a scoping review to investigate the use of RIRs in published primary SCCS studies, and conducted a case-study in one of our own primary SCCS studies to illustrate the use of RIRs within an SCCS analysis to investigate subgroup effects in the context of comparing whole cell (wcp) and acellular (acp) pertussis vaccines. Using this case study, we also illustrated the potential utility of RIRs in addressing the healthy vaccinee effect (HVE) in vaccine safety surveillance studies. Our scoping review identified 122 primary studies reporting an SCCS analysis. Of these, 24 described the use of interaction terms to test for effect modification. 21 of 24 studies reported stratum specific RIs, 22 of 24 reported the p-value for interaction, and less than half (10 of 24) reported the estimate of the interaction term/RIR, the stratum specific RIs and interaction p-values. Our case-study demonstrated that there was a nearly two-fold greater RI of ER visits and admissions following wcp vaccination relative to acp vaccination (RIR = 1.82, 95 % CI 1.64-2.01), where RI estimates in each subgroup were clearly impacted by a strong healthy vaccinee effect. We demonstrated in our scoping review that calculating RIRs is not a widely utilized strategy. We showed that calculating RIRs across time periods is useful for the detection of relative changes in adverse event rates that might otherwise be missed due to the HVE. Many published studies of vaccine-associated adverse events could have missed/underestimated important safety signals masked by the HVE. With further development, our application of RIRs could be an important tool to address the HVE, particularly in the context of self-controlled study designs.

Bias reduction in repeated-measures observational studies by the use of propensity score: the case of enteral sedation for critically ill patients.

PubMed

Umbrello, Michele; Mistraletti, Giovanni; Corbella, Davide; Cigada, Marco; Salini, Silvia; Morabito, Alberto; Iapichino, Gaetano

2012-12-01

Within the evidence-based medicine paradigm, randomized controlled trials represent the "gold standard" to produce reliable evidence. Indeed, planning and implementing randomized controlled trials in critical care medicine presents limitations because of intrinsic and structural problems. As a consequence, observational studies still occur frequently. In these cases, propensity score (PS) (probability of receiving a treatment conditional on observed covariates) is an increasingly used technique to adjust the results. Few studies addressed the specific issue of a PS correction of repeated-measures designs. Three techniques for correcting the analysis of nonrandomized designs (matching, stratification, regression adjustment) are presented in a tutorial form and applied to a real case study: the comparison between intravenous and enteral sedative therapy in the intensive care unit setting. After showing the results before and after the use of PS, we suggest that such a tool allows to partially overcoming the bias associated with the observational nature of the study. It permits to correct the estimates for any observed covariate, while unobserved confounders cannot be controlled for. Propensity score represents a useful additional tool to estimate the effects of treatments in nonrandomized studies. In the case study, an enteral sedation approach was equally effective to an intravenous regime, allowing for a lower level of sedation and spare of resources. Copyright © 2012 Elsevier Inc. All rights reserved.

Time Pressure and Creativity in Industrial Design

ERIC Educational Resources Information Center

Hsiao, Shih-Wen; Wang, Ming-Feng; Chen, Chien-Wie

2017-01-01

Creativity is a critical aspect of competitiveness in all trades and professions. In the case of designers, creativity is of the utmost importance. Based on the perspective of industrial design, the relationship between creativity and time pressure was investigated in this study using control and experimental groups. In the first part of the…

A general U-block model-based design procedure for nonlinear polynomial control systems

NASA Astrophysics Data System (ADS)

Zhu, Q. M.; Zhao, D. Y.; Zhang, Jianhua

2016-10-01

The proposition of U-model concept (in terms of 'providing concise and applicable solutions for complex problems') and a corresponding basic U-control design algorithm was originated in the first author's PhD thesis. The term of U-model appeared (not rigorously defined) for the first time in the first author's other journal paper, which established a framework for using linear polynomial control system design approaches to design nonlinear polynomial control systems (in brief, linear polynomial approaches → nonlinear polynomial plants). This paper represents the next milestone work - using linear state-space approaches to design nonlinear polynomial control systems (in brief, linear state-space approaches → nonlinear polynomial plants). The overall aim of the study is to establish a framework, defined as the U-block model, which provides a generic prototype for using linear state-space-based approaches to design the control systems with smooth nonlinear plants/processes described by polynomial models. For analysing the feasibility and effectiveness, sliding mode control design approach is selected as an exemplary case study. Numerical simulation studies provide a user-friendly step-by-step procedure for the readers/users with interest in their ad hoc applications. In formality, this is the first paper to present the U-model-oriented control system design in a formal way and to study the associated properties and theorems. The previous publications, in the main, have been algorithm-based studies and simulation demonstrations. In some sense, this paper can be treated as a landmark for the U-model-based research from intuitive/heuristic stage to rigour/formal/comprehensive studies.

A review of published analyses of case-cohort studies and recommendations for future reporting.

PubMed

Sharp, Stephen J; Poulaliou, Manon; Thompson, Simon G; White, Ian R; Wood, Angela M

2014-01-01

The case-cohort study design combines the advantages of a cohort study with the efficiency of a nested case-control study. However, unlike more standard observational study designs, there are currently no guidelines for reporting results from case-cohort studies. Our aim was to review recent practice in reporting these studies, and develop recommendations for the future. By searching papers published in 24 major medical and epidemiological journals between January 2010 and March 2013 using PubMed, Scopus and Web of Knowledge, we identified 32 papers reporting case-cohort studies. The median subcohort sampling fraction was 4.1% (interquartile range 3.7% to 9.1%). The papers varied in their approaches to describing the numbers of individuals in the original cohort and the subcohort, presenting descriptive data, and in the level of detail provided about the statistical methods used, so it was not always possible to be sure that appropriate analyses had been conducted. Based on the findings of our review, we make recommendations about reporting of the study design, subcohort definition, numbers of participants, descriptive information and statistical methods, which could be used alongside existing STROBE guidelines for reporting observational studies.

Risk factors for childhood burns: a case-control study of Ghanaian children.

PubMed Central

Forjuoh, S N; Guyer, B; Strobino, D M; Keyl, P M; Diener-West, M; Smith, G S

1995-01-01

STUDY OBJECTIVE--To study risk factors for childhood burns in order to identify possible preventive strategies. DESIGN--Case-control design with pair matching of controls to cases in relation to age, sex, and area of residence. The cases and controls were identified by a community based, multisite survey. The effects of host and socioenvironmental variables reported by mothers were investigated in a multivariate analysis using conditional logistic regression. SETTING--A developing country setting the Ashanti Region in Ghana. PARTICIPANTS--These comprised 610 cases aged 0-5 years who had been burned (as evidenced by a visible scar) and 610 controls with no burn history. MAIN RESULTS--The presence of a pre-existing impairment in a child was the strongest risk factor in this population (OR = 6.71; 95% CI 2.78, 16.16). Other significant risk factor included: sibling death from a burn (OR = 4.41; 95% CI 1.16, 16.68); history of burn in a sibling (OR = 1.79; 95% CI 1.24, 2.58); and storage of a flammable substance in the home (OR = 1.51; 95% CI 1.03; 2.21). Maternal education had a protective effect against childhood burns, although this effect was not strong (OR = 0.76; 95% CI 0.55, 1.05). CONCLUSIONS--Community programmes to ensure adequate child supervision and general child wellbeing, particularly for those with impairments, as well as parental education about burns are recommended, to reduce childhood burns in this region of Ghana. The public should bed advised against storing flammable substances in the home. PMID:7798049

Robust blood-glucose control using Mathematica.

PubMed

Kovács, Levente; Paláncz, Béla; Benyó, Balázs; Török, László; Benyó, Zoltán

2006-01-01

A robust control design on frequency domain using Mathematica is presented for regularization of glucose level in type I diabetes persons under intensive care. The method originally proposed under Mathematica by Helton and Merino, --now with an improved disturbance rejection constraint inequality--is employed, using a three-state minimal patient model. The robustness of the resulted high-order linear controller is demonstrated by nonlinear closed loop simulation in state-space, in case of standard meal disturbances and is compared with H infinity design implemented with the mu-toolbox of Matlab. The controller designed with model parameters represented the most favorable plant dynamics from the point of view of control purposes, can operate properly even in case of parameter values of the worst-case scenario.

Comments on: blood product transfusion in emergency department patients: a case control study of practice patterns and impact on outcome.

PubMed

Karami, Manoochehr; Khazaei, Salman

2017-12-06

Clinical decision makings according studies result require the valid and correct data collection, andanalysis. However, there are some common methodological and statistical issues which may ignore by authors. In individual matched case- control design bias arising from the unconditional analysis instead of conditional analysis. Using an unconditional logistic for matched data causes the imposition of a large number of nuisance parameters which may result in seriously biased estimates.

Control of Macromolecular Architectures for Renewable Polymers: Case Studies

NASA Astrophysics Data System (ADS)

Tang, Chuanbing

The development of sustainable polymers from nature biomass is growing, but facing fierce competition from existing petrochemical-based counterparts. Controlling macromolecular architectures to maximize the properties of renewable polymers is a desirable approach to gain advantages. Given the complexity of biomass, there needs special consideration other than traditional design. In the presentation, I will talk about a few case studies on how macromolecular architectures could tune the properties of sustainable bioplastics and elastomers from renewable biomass such as resin acids (natural rosin) and plant oils.

Tuberculosis stigma in Gezira State, Sudan: a case-control study.

PubMed

Ahmed Suleiman, M M; Sahal, N; Sodemann, M; El Sony, A; Aro, A R

2013-03-01

To evaluate the prevalence of tuberculosis (TB) stigma and to determine the relation between socio-demographic characteristics and TB stigma among TB cases and their controls in Gezira State, Sudan. A case-control study design was used. New smear-positive TB patients registered in Gezira State in 2010 (n = 425) and controls who attended the same health facility for other reasons (n < 850) formed the study population. Stigma was measured using a standard modified World Health Organization TB KAP (knowledge, attitudes, practice) instrument. TB stigma did not differ between TB cases and controls; mild stigma was found in both groups. The higher degree of stigma among both groups was significantly associated with higher age, lower level of education, residence in rural areas, unemployment and poor TB awareness, while sex had no association with the degree of stigma in either group. Although TB stigma among the Gezira population was found to be mild, it can affect treatment adherence. Empowering both TB patients and communities by increasing their knowledge through proper education programmes could effectively contribute to the effort of controlling TB in the state.

Case studies of power and control related to tobacco use during pregnancy.

PubMed

Greaves, Lorraine; Kalaw, Cecilia; Bottorff, Joan L

2007-01-01

The objective was to identify and describe elements of power and control evident in couple tobacco-related interaction patterns during pregnancy. Using a case study approach, elements of the Duluth Abuse Intervention Project Power and Control Wheel were used to examine women's experiences of tobacco reduction during pregnancy and post partum. Three cases were selected from a larger qualitative sample, using a maximum variation sampling approach. Although no direct evidence of partner abuse or violence accompanying partner efforts to influence women's smoking was described, most of the elements of power and control were present in the case study, and appeared to cause an emotional toll and a negative impact on women's ability to freely express their views about their own tobacco use. Elements of power and control, however subtle, are potentially important and unrecognized dimensions of women's tobacco reduction experiences. Additional care and attention should be taken in designing tobacco reduction interventions and policies directed at pregnant and post partum women and their partners to reduce the possibility that these interventions may contribute to the use of power and control.

Rotavirus vaccine effectiveness in low-income settings: An evaluation of the test-negative design.

PubMed

Schwartz, Lauren M; Halloran, M Elizabeth; Rowhani-Rahbar, Ali; Neuzil, Kathleen M; Victor, John C

2017-01-03

The test-negative design (TND), an epidemiologic method currently used to measure rotavirus vaccine (RV) effectiveness, compares the vaccination status of rotavirus-positive cases and rotavirus-negative controls meeting a pre-defined case definition for acute gastroenteritis. Despite the use of this study design in low-income settings, the TND has not been evaluated to measure rotavirus vaccine effectiveness. This study builds upon prior methods to evaluate the use of the TND for influenza vaccine using a randomized controlled clinical trial database. Test-negative vaccine effectiveness (VE-TND) estimates were derived from three large randomized placebo-controlled trials (RCTs) of monovalent (RV1) and pentavalent (RV5) rotavirus vaccines in sub-Saharan Africa and Asia. Derived VE-TND estimates were compared to the original RCT vaccine efficacy estimates (VE-RCTs). The core assumption of the TND (i.e., rotavirus vaccine has no effect on rotavirus-negative diarrhea) was also assessed. TND vaccine effectiveness estimates were nearly equivalent to original RCT vaccine efficacy estimates. Neither RV had a substantial effect on rotavirus-negative diarrhea. This study supports the TND as an appropriate epidemiologic study design to measure rotavirus vaccine effectiveness in low-income settings. Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Cancer and Blood Concentrations of the Co-mutagen Harmane in Essential Tremor

PubMed Central

Louis, Elan D.; Pellegrino, Kathryn M.; Factor-Litvak, Pam; Rios, Eileen; Jiang, Wendy; Henchcliffe, Claire; Zheng, Wei

2008-01-01

Background Blood concentrations of harmane, a tremor-producing neurotoxin, are elevated in essential tremor (ET). Harmane is also a co-mutagen. Objective To compare the prevalence of cancer in ET cases vs. controls, and determine whether blood harmane concentrations are elevated among ET cases with cancer. Methods Case-control design. Results 66/267 (24.7%) ET cases vs. 55/331 (16.6%) controls had cancer (adjusted OR 1.52, 95% CI 1.01 – 2.30, p = 0.04). Among specific cancer types, colon cancer was more prevalent in ET cases than controls (2.6% vs. 0.6%, p = 0.04). Log blood harmane concentration was higher in ET cases vs. controls (p = 0.02) and in participants with vs. without cancer (p = 0.02). Log blood harmane concentration was highest in ET cases with cancer when compared with other groups (p = 0.009). Discussion These links between cancer and ET and between high blood harmane and cancer in ET deserve further study. PMID:18709680

Cancer and blood concentrations of the comutagen harmane in essential tremor.

PubMed

Louis, Elan D; Pellegrino, Kathryn M; Factor-Litvak, Pam; Rios, Eileen; Jiang, Wendy; Henchcliffe, Claire; Zheng, Wei

2008-09-15

Blood concentrations of harmane, a tremor-producing neurotoxin, are elevated in essential tremor (ET). Harmane is also a comutagen. Using a case-control design, we compared the prevalence of cancer in ET cases vs. controls, and determined whether blood harmane concentrations are elevated among ET cases with cancer. 66/267 (24.7%) ET cases vs. 55/331 (16.6%) controls had cancer (adjusted OR 1.52, 95% CI 1.01-2.30, P = 0.04). Among specific cancer types, colon cancer was more prevalent in ET cases than controls (2.6% vs. 0.6%, P = 0.04). Log blood harmane concentration was higher in ET cases vs. controls (P = 0.02) and in participants with vs. without cancer (P = 0.02). Log blood harmane concentration was highest in ET cases with cancer when compared with other groups (P = 0.009). These links between cancer and ET and between high blood harmane and cancer in ET deserve further study. (c) 2007 Movement Disorder Society.

Analgesics use and ESRD in younger age: a case-control study

PubMed Central

van der Woude, Fokke J; Heinemann, Lothar AJ; Graf, Helmut; Lewis, Michael; Moehner, Sabine; Assmann, Anita; Kühl-Habich, Doerthe

2007-01-01

Background An ad hoc peer-review committee was jointly appointed by Drug Authorities and Industry in Germany, Austria and Switzerland in 1999/2000 to review the evidence for a causal relation between phenacetin-free analgesics and nephropathy. The committee found the evidence as inconclusive and requested a new case-control study of adequate design. Methods We performed a population-based case-control study with incident cases of end-stage renal disease (ESRD) under the age of 50 years and four age and sex-matched neighborhood controls in 170 dialysis centers (153 in Germany, and 17 in Austria) from January 1, 2001 to December 31, 2004. Data on lifetime medical history, risk factors, treatment, job exposure and intake of analgesics were obtained in a standardized face-to-face interview using memory aids to enhance accuracy. Study design, study performance, analysis plan, and study report were approved by an independent international advisory committee and by the Drug Authorities involved. Unconditional logistic regression analyses were performed. Results The analysis included 907 cases and 3,622 controls who had never used phenacetin-containing analgesics in their lifetime. The use of high cumulative lifetime dose (3rd tertile) of analgesics in the period up to five years before dialysis was not associated with later ESRD. Adjusted odds ratios with 95% confidence intervals were 0.8 (0.7 – 1.0) and 1.0 (0.8 – 1.3) for ever- compared with no or low use and high use compared with low use, respectively. The same results were found for all analgesics and for mono-, and combination preparations with and without caffeine. No increased risk was shown in analyses stratifying for dose and duration. Dose-response analyses showed that analgesic use was not associated with an increased risk for ESRD up to 3.5 kg cumulative lifetime dose (98 % of the cases with ESRD). While the large subgroup of users with a lifetime dose up to 0.5 kg (278 cases and 1365 controls) showed a significantly decreased risk, a tiny subgroup of extreme users with over 3.5 kg lifetime use (19 cases and 11 controls) showed a significant risk increase. The detailed evaluation of 22 cases and 19 controls with over 2.5 kg lifetime use recommended by the regulatory advisors showed an impressive excess of other conditions than analgesics triggering the evolution of ESRD in cases compared with controls. Conclusion We found no clinically meaningful evidence for an increased risk of ESRD associated with use of phenacetin-free analgesics in single or combined formulation. The apparent risk increase shown in a small subgroup with extreme lifetime dose of analgesics is most likely an indirect, non-causal association. This hypothesis, however, cannot be confirmed or refuted within our case-control study. Overall, our results lend support to the mounting evidence that phenacetin-free analgesics do not induce ESRD and that the notion of "analgesic nephropathy" needs to be re-evaluated. PMID:18053232

Thermal Control Subsystem Design for the Avionics of a Space Station Payload

NASA Technical Reports Server (NTRS)

Moran, Matthew E.

1996-01-01

A case study of the thermal control subsystem development for a space based payload is presented from the concept stage through preliminary design. This payload, the Space Acceleration Measurement System 2 (SAMS-2), will measure the acceleration environment at select locations within the International Space Station. Its thermal control subsystem must maintain component temperatures within an acceptable range over a 10 year life span, while restricting accessible surfaces to touch temperature limits and insuring fail safe conditions in the event of loss of cooling. In addition to these primary design objectives, system level requirements and constraints are imposed on the payload, many of which are driven by multidisciplinary issues. Blending these issues into the overall system design required concurrent design sessions with the project team, iterative conceptual design layouts, thermal analysis and modeling, and hardware testing. Multiple tradeoff studies were also performed to investigate the many options which surfaced during the development cycle.

Proteomic Approach for Diagnostic Applications in Head and Neck Cancer — EDRN Public Portal

Cancer.gov

To evaluate the test characteristics of a panel of biomarkers for identifying patients with early stage head and neck squamous cell carcinoma (HNSCC). The primary endpoints are sensitivity, specificity and accuracy of the marker panel. This study of the test characteristics of a modeling strategy for diagnosing HNSCC uses a case-control design, with several types of cases and several types of controls.

A case study of ISO 11064 in control centre design in the Norwegian petroleum industry.

PubMed

Aas, Andreas Lumbe; Skramstad, Torbjørn

2010-12-01

In 2006-2008 we performed a case study for the purpose of assessing the industrial application of the seven part Control Centre (CC) design standard ISO 11064 to identify positive and negative experiences among stakeholders in the Norwegian petroleum sector. We mainly focussed on ISO 11064 Part 1, because this was the most commonly used among the identified stakeholders. ISO 11064 is generally appreciated and applied in the industry, but we did observe a significant variance in use between the different parts of the standard. We also identified potential areas for improvements, like scope and application adaptation. Thus we suggest a more goal-based approach based on one normative part only. Copyright © 2010 Elsevier Ltd. All rights reserved.

Comparison of two control groups for estimation of oral cholera vaccine effectiveness using a case-control study design.

PubMed

Franke, Molly F; Jerome, J Gregory; Matias, Wilfredo R; Ternier, Ralph; Hilaire, Isabelle J; Harris, Jason B; Ivers, Louise C

2017-10-13

Case-control studies to quantify oral cholera vaccine effectiveness (VE) often rely on neighbors without diarrhea as community controls. Test-negative controls can be easily recruited and may minimize bias due to differential health-seeking behavior and recall. We compared VE estimates derived from community and test-negative controls and conducted bias-indicator analyses to assess potential bias with community controls. From October 2012 through November 2016, patients with acute watery diarrhea were recruited from cholera treatment centers in rural Haiti. Cholera cases had a positive stool culture. Non-cholera diarrhea cases (test-negative controls and non-cholera diarrhea cases for bias-indicator analyses) had a negative culture and rapid test. Up to four community controls were matched to diarrhea cases by age group, time, and neighborhood. Primary analyses included 181 cholera cases, 157 non-cholera diarrhea cases, 716 VE community controls and 625 bias-indicator community controls. VE for self-reported vaccination with two doses was consistent across the two control groups, with statistically significant VE estimates ranging from 72 to 74%. Sensitivity analyses revealed similar, though somewhat attenuated estimates for self-reported two dose VE. Bias-indicator estimates were consistently less than one, with VE estimates ranging from 19 to 43%, some of which were statistically significant. OCV estimates from case-control analyses using community and test-negative controls were similar. While bias-indicator analyses suggested possible over-estimation of VE estimates using community controls, test-negative analyses suggested this bias, if present, was minimal. Test-negative controls can be a valid low-cost and time-efficient alternative to community controls for OCV effectiveness estimation and may be especially relevant in emergency situations. Copyright © 2017. Published by Elsevier Ltd.

How to study the aetiology of burn injury: the epidemiological approach.

PubMed

Bouter, L M; Knipschild, P G; van Rijn, J L; Meertens, R M

1989-06-01

Effective prevention of burn injury should be based on sound aetiological knowledge. This article deals with epidemiological methods to study the incidence of burn injury as a function of its risk factors. Central methodological issues are comparability of baseline prognosis, comparability of measurements (of effects in cohort studies and of risk factors in case-control studies), and comparability of external circumstances. These principles are clarified with a number of fictitious examples of risk factors for burn injury. It is explained that in preventive trials comparability may be achieved by randomization, blinding and placebo intervention. The main tools in non-experimental studies are deliberate selection and multivariate analysis. Special attention is given to the definition of the source population and to reducing measurement incomparability in case-control studies. Some well-designed case-control studies following these principles might bring effective prevention of burn injury some steps nearer.

Heart Disease, Hypertension, Gestational Diabetes Mellitus, and Preeclampsia/Eclampsia in Mothers With Juvenile Arthritis: A Nested Case-Control Study.

PubMed

Feldman, Debbie E; Vinet, Évelyne; Bérard, Anick; Duffy, Ciarán; Hazel, Beth; Meshefedjian, Garbis; Sylvestre, Marie-Pierre; Bernatsky, Sasha

2017-02-01

To determine whether women with a history of juvenile arthritis are at higher risk for heart disease and hypertension and for developing adverse maternal outcomes: gestational diabetes mellitus, maternal hypertension, and preeclampsia/eclampsia. We designed a nested case-control study from a cohort of first-time mothers with prior physician billing codes suggesting juvenile arthritis, and a matched comparison group without juvenile arthritis. For the nested case-control design, we selected 3 controls for each case for the outcomes of heart disease (n = 403), prepregnancy hypertension (n = 66), gestational diabetes mellitus (n = 285), maternal hypertension (n = 561), and preeclampsia/eclampsia (n = 236). We used conditional logistic regression, adjusting for maternal age and education. Having juvenile arthritis was associated with heart disease (odds ratio [OR] 2.44 [95% confidence interval (95% CI) 1.15-5.15]) but not with gestational hypertension, diabetes mellitus, or preeclampsia/eclampsia. All 66 cases of prepregnancy hypertension had juvenile arthritis. Having prepregnancy hypertension was strongly associated with preeclampsia/eclampsia (OR 8.05 [95% CI 2.69-24.07]). Women with a history of juvenile arthritis had a higher risk of heart disease. This risk signals the potential importance of cardiac prevention strategies in juvenile arthritis. As this was a retrospective study, it was not possible to correct for some relevant potential confounders. Further studies should assess the impact of medications, disease severity, and other factors (e.g., obesity) on cardiac outcomes in juvenile arthritis. © 2016, American College of Rheumatology.

Statistical inferences for data from studies conducted with an aggregated multivariate outcome-dependent sample design

PubMed Central

Lu, Tsui-Shan; Longnecker, Matthew P.; Zhou, Haibo

2016-01-01

Outcome-dependent sampling (ODS) scheme is a cost-effective sampling scheme where one observes the exposure with a probability that depends on the outcome. The well-known such design is the case-control design for binary response, the case-cohort design for the failure time data and the general ODS design for a continuous response. While substantial work has been done for the univariate response case, statistical inference and design for the ODS with multivariate cases remain under-developed. Motivated by the need in biological studies for taking the advantage of the available responses for subjects in a cluster, we propose a multivariate outcome dependent sampling (Multivariate-ODS) design that is based on a general selection of the continuous responses within a cluster. The proposed inference procedure for the Multivariate-ODS design is semiparametric where all the underlying distributions of covariates are modeled nonparametrically using the empirical likelihood methods. We show that the proposed estimator is consistent and developed the asymptotically normality properties. Simulation studies show that the proposed estimator is more efficient than the estimator obtained using only the simple-random-sample portion of the Multivariate-ODS or the estimator from a simple random sample with the same sample size. The Multivariate-ODS design together with the proposed estimator provides an approach to further improve study efficiency for a given fixed study budget. We illustrate the proposed design and estimator with an analysis of association of PCB exposure to hearing loss in children born to the Collaborative Perinatal Study. PMID:27966260

Modelling the role of dietary habits and eating behaviours on the development of acute coronary syndrome or stroke: aims, design, and validation properties of a case-control study.

PubMed

Kastorini, Christina-Maria; Milionis, Haralampos J; Goudevenos, John A; Panagiotakos, Demosthenes B

2010-09-14

In this paper the methodology and procedures of a case-control study that will be developed for assessing the role of dietary habits and eating behaviours on the development of acute coronary syndrome and stroke is presented. Based on statistical power calculations, 1000 participants will be enrolled; of them, 250 will be consecutive patients with a first acute coronary event, 250 consecutive patients with a first ischaemic stroke, and 500 population-based healthy subjects (controls), age and sex matched to the cases. Socio-demographic, clinical, dietary, psychological, and other lifestyle characteristics will be measured. Dietary habits and eating behaviours will be evaluated with a special questionnaire that has been developed for the study.

Effectiveness of the live attenuated rotavirus vaccine produced by a domestic manufacturer in China studied using a population-based case-control design.

PubMed

Zhen, Shan-Shan; Li, Yue; Wang, Song-Mei; Zhang, Xin-Jiang; Hao, Zhi-Yong; Chen, Ying; Wang, Dan; Zhang, Yan-Hong; Zhang, Zhi-Yong; Ma, Jing-Chen; Zhou, Peng; Zhang, Zhen; Jiang, Zhi-Wei; Zhao, Yu-Liang; Wang, Xuan-Yi

2015-10-01

A universal rotavirus (RV) immunization program is a potentially cost-effective measure for preventing RV infection in China. However, the efficacy of the only licensed RV vaccine (Lanzhou lamb rotavirus vaccine, LLR), which is made by a domestic manufacturer, has not been proven by a properly designed clinical trial. In October 2011 to March 2012, to measure the potential protection provided by LLR, a case-control study nested in a population-based active diarrhea surveillance study of children <5 years of age was conducted in rural Zhengding county. During the study period, 308 episodes of diarrhea were identified as being caused by RV infection, resulting in an incidence rate of 48.0/1000 people/year. The predominant RV serotype was G3 (61.5%), followed by G1 (15.2%), and G9 (6.5%). Overall, a protection of 35.0% (95% confidence interval (CI), 13.0%-52.0%) was identified, and higher protection was found among moderate RV gastroenteritis cases caused by the serotype G3 (52.0% 95% CI: 2.0%-76.1%). A concurrently conducted case-control study comparing non-RV viral diarrheal cases with non-diarrheal controls in the same population found that the RV vaccine offered no protection against non-RV diarrhea. Even under a less ideal immunization schedule, the oral LLR conferred a certain level of protection against RV gastroenteritis. However, further studies are needed to understand the full characteristics of the LLR, including its efficacy when administered following the optimal regimen, the potential risk of inducing intussusception, and the direct and indirect protective effects of LLR.

Quasi-experimental designs in practice-based research settings: design and implementation considerations.

PubMed

Handley, Margaret A; Schillinger, Dean; Shiboski, Stephen

2011-01-01

Although randomized controlled trials are often a gold standard for determining intervention effects, in the area of practice-based research (PBR), there are many situations in which individual randomization is not possible. Alternative approaches to evaluating interventions have received increased attention, particularly those that can retain elements of randomization such that they can be considered "controlled" trials. Methodological design elements and practical implementation considerations for two quasi-experimental design approaches that have considerable promise in PBR settings--the stepped-wedge design, and a variant of this design, a wait-list cross-over design, are presented along with a case study from a recent PBR intervention for patients with diabetes. PBR-relevant design features include: creation of a cohort over time that collects control data but allows all participants (clusters or patients) to receive the intervention; staggered introduction of clusters; multiple data collection points; and one-way cross-over into the intervention arm. Practical considerations include: randomization versus stratification, training run in phases; and extended time period for overall study completion. Several design features of practice based research studies can be adapted to local circumstances yet retain elements to improve methodological rigor. Studies that utilize these methods, such as the stepped-wedge design and the wait-list cross-over design, can increase the evidence base for controlled studies conducted within the complex environment of PBR.

Systematic design of membership functions for fuzzy-logic control: A case study on one-stage partial nitritation/anammox treatment systems.

PubMed

Boiocchi, Riccardo; Gernaey, Krist V; Sin, Gürkan

2016-10-01

A methodology is developed to systematically design the membership functions of fuzzy-logic controllers for multivariable systems. The methodology consists of a systematic derivation of the critical points of the membership functions as a function of predefined control objectives. Several constrained optimization problems corresponding to different qualitative operation states of the system are defined and solved to identify, in a consistent manner, the critical points of the membership functions for the input variables. The consistently identified critical points, together with the linguistic rules, determine the long term reachability of the control objectives by the fuzzy logic controller. The methodology is highlighted using a single-stage side-stream partial nitritation/Anammox reactor as a case study. As a result, a new fuzzy-logic controller for high and stable total nitrogen removal efficiency is designed. Rigorous simulations are carried out to evaluate and benchmark the performance of the controller. The results demonstrate that the novel control strategy is capable of rejecting the long-term influent disturbances, and can achieve a stable and high TN removal efficiency. Additionally, the controller was tested, and showed robustness, against measurement noise levels typical for wastewater sensors. A feedforward-feedback configuration using the present controller would give even better performance. In comparison, a previously developed fuzzy-logic controller using merely expert and intuitive knowledge performed worse. This proved the importance of using a systematic methodology for the derivation of the membership functions for multivariable systems. These results are promising for future applications of the controller in real full-scale plants. Furthermore, the methodology can be used as a tool to help systematically design fuzzy logic control applications for other biological processes. Copyright © 2016 Elsevier Ltd. All rights reserved.

Towards non-conventional methods of designing register-based epidemiological studies: An application to pediatric research.

PubMed

Gong, Tong; Brew, Bronwyn; Sjölander, Arvid; Almqvist, Catarina

2017-07-01

Various epidemiological designs have been applied to investigate the causes and consequences of fetal growth restriction in register-based observational studies. This review seeks to provide an overview of several conventional designs, including cohort, case-control and more recently applied non-conventional designs such as family-based designs. We also discuss some practical points regarding the application and interpretation of family-based designs. Definitions of each design, the study population, the exposure and the outcome measures are briefly summarised. Examples of study designs are taken from the field of low birth-weight research for illustrative purposes. Also examined are relative advantages and disadvantages of each design in terms of assumptions, potential selection and information bias, confounding and generalisability. Kinship data linkage, statistical models and result interpretation are discussed specific to family-based designs. When all information is retrieved from registers, there is no evident preference of the case-control design over the cohort design to estimate odds ratios. All conventional designs included in the review are prone to bias, particularly due to residual confounding. Family-based designs are able to reduce such bias and strengthen causal inference. In the field of low birth-weight research, family-based designs have been able to confirm a negative association not confounded by genetic or shared environmental factors between low birth weight and the risk of asthma. We conclude that there is a broader need for family-based design in observational research as evidenced by the meaningful contributions to the understanding of the potential causal association between low birth weight and subsequent outcomes.

Developing a quality by design approach to model tablet dissolution testing: an industrial case study.

PubMed

Yekpe, Ketsia; Abatzoglou, Nicolas; Bataille, Bernard; Gosselin, Ryan; Sharkawi, Tahmer; Simard, Jean-Sébastien; Cournoyer, Antoine

2018-07-01

This study applied the concept of Quality by Design (QbD) to tablet dissolution. Its goal was to propose a quality control strategy to model dissolution testing of solid oral dose products according to International Conference on Harmonization guidelines. The methodology involved the following three steps: (1) a risk analysis to identify the material- and process-related parameters impacting the critical quality attributes of dissolution testing, (2) an experimental design to evaluate the influence of design factors (attributes and parameters selected by risk analysis) on dissolution testing, and (3) an investigation of the relationship between design factors and dissolution profiles. Results show that (a) in the case studied, the two parameters impacting dissolution kinetics are active pharmaceutical ingredient particle size distributions and tablet hardness and (b) these two parameters could be monitored with PAT tools to predict dissolution profiles. Moreover, based on the results obtained, modeling dissolution is possible. The practicality and effectiveness of the QbD approach were demonstrated through this industrial case study. Implementing such an approach systematically in industrial pharmaceutical production would reduce the need for tablet dissolution testing.

Point process methods in epidemiology: application to the analysis of human immunodeficiency virus/acquired immunodeficiency syndrome mortality in urban areas.

PubMed

Quesada, Jose Antonio; Melchor, Inmaculada; Nolasco, Andreu

2017-05-26

The analysis of spatio-temporal patterns of disease or death in urban areas has been developed mainly from the ecological studies approach. These designs may have some limitations like the ecological fallacy and instability with few cases. The objective of this study was to apply the point process methodology, as a complement to that of aggregated data, to study HIV/AIDS mortality in men in the city of Alicante (Spain). A case-control study in residents in the city during the period 2004-2011 was designed. Cases were men who died from HIV/AIDS and controls represented the general population, matched by age to cases. The risk surfaces of death over the city were estimated using the log-risk function of intensities, and we contrasted their temporal variations over the two periods. High risk significant areas of death by HIV/AIDS, which coincide with the most deprived areas in the city, were detected. Significant spatial change of the areas at risk between the periods studied was not detected. The point process methodology is a useful tool to analyse the patterns of death by HIV/AIDS in urban areas.

Integrated Application of Quality-by-Design Principles to Drug Product Development: A Case Study of Brivanib Alaninate Film-Coated Tablets.

PubMed

Badawy, Sherif I F; Narang, Ajit S; LaMarche, Keirnan R; Subramanian, Ganeshkumar A; Varia, Sailesh A; Lin, Judy; Stevens, Tim; Shah, Pankaj A

2016-01-01

Modern drug product development is expected to follow quality-by-design (QbD) paradigm. At the same time, although there are several issue-specific examples in the literature that demonstrate the application of QbD principles, a holistic demonstration of the application of QbD principles to drug product development and control strategy, is lacking. This article provides an integrated case study on the systematic application of QbD to product development and demonstrates the implementation of QbD concepts in the different aspects of product and process design for brivanib alaninate film-coated tablets. Using a risk-based approach, the strategy for development entailed identification of product critical quality attributes (CQAs), assessment of risks to the CQAs, and performing experiments to understand and mitigate identified risks. Quality risk assessments and design of experiments were performed to understand the quality of the input raw materials required for a robust formulation and the impact of manufacturing process parameters on CQAs. In addition to the material property and process parameter controls, the proposed control strategy includes use of process analytical technology and conventional analytical tests to control in-process material attributes and ensure quality of the final product. Copyright © 2016. Published by Elsevier Inc.

Outcomes of preterm neonates with frontal horn cysts: a retrospective study.

PubMed

Trawber, Rory; Rao, Shripada; Srinivasjois, Ravisha; Thonell, Sven; Nagarajan, Lakshmi; French, Noel; Jacoby, Peter; McMichael, Judy

2010-11-01

Isolated paraventricular frontal horn cysts are sometimes encountered on cranial ultrasound examinations of preterm neonates. The etiology and clinical significance of these lesions are unclear. The authors aimed to identify antenatal/intrapartum risk factors associated with the occurrence of these cysts and to assess developmental outcomes of preterm neonates with isolated frontal horn cysts. A retrospective cohort study with matched control design was used. A total of 28 cases were matched for gestation with 56 controls. No antenatal/intrapartum factors were associated with these cysts. At corrected age of 1 year, there was no difference in the mean general quotient between cases and controls (97.75 ± 17.28 vs 94.94 ± 9.86; P = .410). In all, 1 case and no controls had a diagnosis of cerebral palsy and 1 case and 3 controls had general quotients less than 80. The authors conclude that isolated paraventricular frontal horn cysts are benign, with no effect on neurodevelopment.

Observational studies are complementary to randomized controlled trials.

PubMed

Grootendorst, Diana C; Jager, Kitty J; Zoccali, Carmine; Dekker, Friedo W

2010-01-01

Randomized controlled trials (RCTs) are considered the gold standard study design to investigate the effect of health interventions, including treatment. However, in some situations, it may be unnecessary, inappropriate, impossible, or inadequate to perform an RCT. In these special situations, well-designed observational studies, including cohort and case-control studies, may provide an alternative to doing nothing in order to obtain estimates of treatment effect. It should be noted that such studies should be performed with caution and correctly. The aims of this review are (1) to explain why RCTs are considered the optimal study design to evaluate treatment effects, (2) to describe the situations in which an RCT is not possible and observational studies are an adequate alternative, and (3) to explain when randomization is not needed and can be approximated in observational studies. Examples from the nephrology literature are used for illustration. Copyright 2009 S. Karger AG, Basel.

Factors Associated with Tuberculosis Treatment Default in an Endemic Area of the Brazilian Amazon: A Case Control-Study

PubMed Central

Garrido, Marlucia da Silva; Penna, Maria Lucia; Perez-Porcuna, Tomàs M.; de Souza, Alexandra Brito; Marreiro, Leni da Silva; Albuquerque, Bernardino Claudio; Martínez-Espinosa, Flor Ernestina; Bührer-Sékula, Samira

2012-01-01

Setting Treatment default is a serious problem in tuberculosis control because it implies persistence of infection source, increased mortality, increased relapse rates and facilitates the development of resistant strains. Objective This study analyzed tuberculosis treatment default determinants in the Amazonas State to contribute in planning appropriate control interventions. Design Observational study with a retrospective cohort using Brazilian Disease Notification System data from 2005 to 2010. A nested case control study design was used. Patients defaulting from treatment were considered as ‘cases’ and those completing treatment as ‘controls’. In the analysis, 11,312 tuberculosis patients were included, 1,584 cases and 9,728 controls. Results Treatment default was observed to be associated to previous default (aOR 3.20; p<0.001), HIV positivity (aOR 1.62; p<0.001), alcoholism (aOR 1.51; p<0.001), low education level (aOR 1.35; p<0.001) and other co-morbidities (aOR 1.31; p = 0.05). Older patients (aOR 0.98; p = 0.001) and DOT (aOR 0,72; p<0.01) were considered as protective factor for default. Conclusions Associated factors should be considered in addressing care and policy actions to tuberculosis control. Information on disease and treatment should be intensified and appropriate to the level of education of the population, in order to promote adherence to treatment and counter the spread of multidrug resistance to anti-TB drugs. PMID:22720052

The determination of the operating range of a twin-grip control yoke through biomechanical means

NASA Technical Reports Server (NTRS)

Gaertner, K. P.

1978-01-01

A twin-grip control yoke was designed as an ergonomic case study that allows dual axis control inputs, both axes being rotational. Inputs are effected by rotating the grips. How the handles were designed with respect to their shape and size and how the angular range of the control yoke in both rotational axes was evaluated. The control yoke which requires two-hand operation was tested to determine its operating range. The intention of this investigation was to find out the optimal form of the control yoke and the maximum permissible range in both rotating axes. In these experiments controls had no spring resistance.

Electrocardiographic features of sudden unexpected death in epilepsy.

PubMed

Chyou, Janice Y; Friedman, Daniel; Cerrone, Marina; Slater, William; Guo, Yu; Taupin, Daniel; O'Rourke, Sean; Priori, Silvia G; Devinsky, Orrin

2016-07-01

Sudden unexpected death in epilepsy (SUDEP) is the most common cause of epilepsy-related mortality. We hypothesized that electrocardiography (ECG) features may distinguish SUDEP cases from living subjects with epilepsy. Using a matched case-control design, we compared ECG studies of 12 consecutive cases of SUDEP over 10 years and 22 epilepsy controls matched for age, sex, epilepsy type (focal, generalized, or unknown/mixed type), concomitant antiepileptic, and psychotropic drug classes. Conduction intervals and prevalence of abnormal ventricular conduction diagnosis (QRS ≥110 msec), abnormal ventricular conduction pattern (QRS <110 msec, morphology of incomplete right or left bundle branch block or intraventricular conduction delay), early repolarization, and features of inherited cardiac channelopathies were assessed. Abnormal ventricular conduction diagnosis and pattern distinguished SUDEP cases from matched controls. Abnormal ventricular conduction diagnosis was present in two cases and no controls. Abnormal ventricular conduction pattern was more common in cases than controls (58% vs. 18%, p = 0.04). Early repolarization was similarly prevalent in cases and controls, but the overall prevalence exceeded that of published community-based cohorts. Wiley Periodicals, Inc. © 2016 International League Against Epilepsy.

The effects of polycystic ovary syndrome on gestational diabetes mellitus.

PubMed

Aktun, Hale Lebriz; Yorgunlar, Betul; Acet, Mustafa; Aygun, Banu Kumbak; Karaca, Nilay

2016-01-01

The aim of this study was to explore the inter-relationship between polycystic ovary syndrome and gestational diabetes mellitus, and demonstrate maternal and fetal outcomes. This was a case-control study in 1360 pregnant women who received a diagnosis of gestational diabetes mellitus between 24 and 28 weeks of gestational age. Among all diagnosed with gestational diabetes mellitus, 150 pregnant women had received a polycystic ovary syndrome, and 160 women who did not have polycystic ovary syndrome were designated as controls. The incidence of pregnancy-induced hypertension was 26.3% and 12% in the case and control groups, respectively. Preeclampsia was seen at an incidence of 12% and 6% in case and in control groups, respectively. The difference in neonatal hypoglycemia between the two groups was statistically significant, with an incidence of 17% and 5% in the case and in control groups, respectively. This study demonstrated that the presence of polycystic ovary syndrome along with gestational diabetes mellitus increases the risk of pregnancy induced hypertension by 2.4 fold, preeclampsia by 2 fold and neonatal hypoglycemia by 3.2 fold, compared to gestational diabetes mellitus alone.

Validity and power of association testing in family-based sampling designs: evidence for and against the common wisdom.

PubMed

Knight, Stacey; Camp, Nicola J

2011-04-01

Current common wisdom posits that association analyses using family-based designs have inflated type 1 error rates (if relationships are ignored) and independent controls are more powerful than familial controls. We explore these suppositions. We show theoretically that family-based designs can have deflated type-error rates. Through simulation, we examine the validity and power of family designs for several scenarios: cases from randomly or selectively ascertained pedigrees; and familial or independent controls. Family structures considered are as follows: sibships, nuclear families, moderate-sized and extended pedigrees. Three methods were considered with the χ(2) test for trend: variance correction (VC), weighted (weights assigned to account for genetic similarity), and naïve (ignoring relatedness) as well as the Modified Quasi-likelihood Score (MQLS) test. Selectively ascertained pedigrees had similar levels of disease enrichment; random ascertainment had no such restriction. Data for 1,000 cases and 1,000 controls were created under the null and alternate models. The VC and MQLS methods were always valid. The naïve method was anti-conservative if independent controls were used and valid or conservative in designs with familial controls. The weighted association method was generally valid for independent controls, and was conservative for familial controls. With regard to power, independent controls were more powerful for small-to-moderate selectively ascertained pedigrees, but familial and independent controls were equivalent in the extended pedigrees and familial controls were consistently more powerful for all randomly ascertained pedigrees. These results suggest a more complex situation than previously assumed, which has important implications for study design and analysis. © 2011 Wiley-Liss, Inc.

Comparison of transhumeral socket designs utilizing patient assessment and in vivo skeletal and socket motion tracking: a case study.

PubMed

Resnik, Linda; Patel, Tarpit; Cooney, Shane G; Crisco, Joseph J; Fantini, Christopher

2016-01-01

This case study compares the impact of two prosthetic socket designs, a "traditional" transhumeral (TH) socket design and a Compression Released Stabilized (CRS) socket. A CRS socket was compared to the existing socket of two persons with transhumeral amputation. Comparisons included assessments of patient comfort and satisfaction with fit, as well as dynamic kinematic assessment using a novel high-speed, high-resolution, bi-plane video radiography system (XROMM, for X-ray Reconstruction of Moving Morphology). Subjects were more satisfied with the comfort of the traditional sockets, although they had positive impressions about aspects of the fit and style of the CRS socket, and thought that it provided better control. Dynamic kinematic assessment revealed that the CRS socket provided better control of the residual limb within the socket, and had less slippage as compared to a traditional TH socket design. The TH CRS socket provided better control of the residual limb within the socket, and had less slippage. However, participants were less satisfied with the comfort and overall utility of the CRS socket, and stated that additional fitting visits/modifications to the CRS socket were needed. It is possible that satisfaction with the CRS socket may have improved with prosthetic adjustment and more acclimation time. Implications for Rehabilitation A comfortable, good fitting prosthetic socket is the key factor in determining how long (or if) an upper limb amputee can tolerate wearing a prosthesis. This case series was a comparison of two socket designs, a 'traditional' socket design and a Compression Released Stabilized (CRS) socket design in persons with transhumeral amputation. The CRS socket provided better control of the residual limb within the socket, and had less slippage. However, its tightness made it more difficult to don. Both subjects were less satisfied with the comfort and overall utility of the CRS socket. However, satisfaction might have been improved with additional fitting visits and more acclimation time.

Asthma in changing environments - chances and challenges of international research collaborations between South America and Europe - study protocol and description of the data acquisition of a case-control-study

PubMed Central

2010-01-01

Background Asthma in children is an emerging public health problem in South America. So far, research in this part of the world is limited. This paper presents the methodology and description of the data acquisition of an asthma case-control study conducted in the Central South of Chile. Methods/Design A hospital-based case-control study about asthma (188 cases, 294 controls) in children (6-15 years) was carried out in Valdivia, Chile between November 2008 and December 2009. Data on asthma risk factors were collected by computer-assisted personal interview using validated questions from e.g. ISAAC phase II. Data on household dust exposure (endotoxin, allergen analyses), skin prick tests to most common allergens, stool examinations for parasitic infection, and blood samples (total IgE, genetics) were collected. Additionally, 492 randomly chosen blood donors were recruited in order to assess allele frequencies in the population of Valdivia. Discussion Overall 1,173 participants were contacted. Response was 82% among cases and 65% among controls. Atopic sensitization was high (78% among cases, 47% among controls). Cases had a statistically significantly (p < .0001) increased self-reported 12-month prevalence of symptoms of rhinitis (82% vs. 51%) and wheeze (68% vs. 16%). The study is well placed to address current hypotheses about asthma and its correlates in the South American context. Results of this study might help develop novel, innovative and individualized prevention strategies in countries in transition with respect to the South American context. PMID:20718949

New ideas for shallow gas well control

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bourgoyne, A.T.; Kelly, O.A.; Sandoz, C.L.

1996-06-01

Flow from an unexpected shallow gas sand is one of the most difficult well control problems faced by oil and gas well operators during drilling operations. Current well control practice for bottom-supported marine rigs usually calls for shutting in the well when a kick is detected, if sufficient casing has been set to keep any flow underground. However, when shallow gas is encountered, casing may not be set deep enough to keep the underground flow from broaching to surface near the platform foundations. Once the flow reaches surface, craters are sometimes formed which can lead to loss of the rigmore » and associated marine structures. This short article overviews an ongoing study by Louisiana State University of the breakdown resistance of shallow marine sediments, using leak-off test data and geotechnical reports provided by Unocal. Such study is important for improving the characterization of shallow marine sediments to allow more reliable shallow casing designs, as the authors will conclude. This study has already proven that sediment failure mechanisms that lead to cratering have been poorly understood. In addition, there has been considerable uncertainty as to the best choices of well design parameters and well control contingency plans that will minimize risks associated with a shallow gas flow.« less

Job Rotation Designed to Prevent Musculoskeletal Disorders and Control Risk in Manufacturing Industries: A Systematic Review

PubMed Central

Padula, Rosimeire Simprini; Comper, Maria Luiza Caires; Sparer, Emily H.; Dennerlein, Jack T

2017-01-01

To better understand job rotation in the manufacturing industry, we completed a systematic review asking the following questions: 1) How do job-rotation programs impact work-related musculoskeletal disorders (MSDs) and related risk control for these MSDs, as well as psychosocial factors? and 2) How best should the job rotation programs be designed? We searched MEDLINE, EMBASE, Business Source Premier, ISI Web of Knowledge, CINAHL, PsyINFO, Scopus, and SciELO databases for articles published in peer-reviewed journals. Eligible studies were examined by two independent reviewers for relevance (population of manufacturing workers, outcomes of musculoskeletal disease, physical factors, psychosocial factors, and strategies used in job-rotation implantation) and methodological quality rating. From 10,809 potential articles, 71 were read for full text analysis. Of the 14 studies included for data extraction, two were non-randomized control trial studies, one was a case-control study, and 11 were cross-sectional comparisons. Only one, with a case-control design, was scored with good methodological quality. Currently, weak evidence exists supporting job rotation as a strategy for the prevention and control of musculoskeletal disorders. Job rotation did not appear to reduce the exposure of physical risk factors; yet, there are positive correlations between job rotation and higher job satisfaction. Worker training has been described as a crucial component of a successful job-rotation program. The studies reported a range of parameters used to implement and measure job-rotation programs. More rigorous studies are needed to better understand the full impact of job rotation on production and health. PMID:27633235

Impact of waning acquired immunity and asymptomatic infections on case-control studies for enteric pathogens.

PubMed

Havelaar, Arie H; Swart, Arno

2016-12-01

Case-control studies of outbreaks and of sporadic cases of infectious diseases may provide a biased estimate of the infection rate ratio, due to selecting controls that are not at risk of disease. We use a dynamic mathematical model to explore biases introduced in results drawn from case-control studies of enteric pathogens by waning and boosting of immunity, and by asymptomatic infections, using Campylobacter jejuni as an example. Individuals in the population are either susceptible (at risk of infection and disease), fully protected (not at risk of either) or partially protected (at risk of infection but not of disease). The force of infection is a function of the exposure frequency and the exposure dose. We show that the observed disease odds ratios are indeed strongly biased towards the null, i.e. much lower than the infection rate ratio, and furthermore even not proportional to it. The bias could theoretically be controlled by sampling controls only from the reservoir of susceptible individuals. The population at risk is in a dynamic equilibrium, and cannot be identified as those who are not and have never experienced disease. Individual-level samples to measure protective immunity would be required, complicating the design, cost and execution of case-control studies. Copyright © 2016 The Author(s). Published by Elsevier B.V. All rights reserved.

Polymorphisms of the lipoprotein lipase gene as genetic markers for stroke in colombian population: a case control study.

PubMed

Velásquez Pereira, Leydi Carolina; Vargas Castellanos, Clara Inés; Silva Sieger, Federico Arturo

2016-12-30

To analyze if there is an association between the presence of polymorphisms in the LPL gene (rs320, rs285 and rs328) with development of acute ischemic stroke in Colombian population. In a case control design, 133 acute ischemic stroke patients (clinical diagnosis and x-ray CT) and 269 subjects without stroke as controls were studied. PCR -RFLP technique was used to detect rs320, rs285 and rs328 polymorphisms in the LPL gene. In the present research was not found any association between any of the LPL gene polymorphism and acute ischemic stroke in the population studied; the allele and genotypic frequencies of the studied polymorphisms were similar in cases and controls and followed the Hardy-Weinberg equilibrium. The study was approved by the IRB and each subject signed the informed consent. LPL gene polymorphisms are not genetic markers for the development of stroke in the Colombian sample used.

Effectiveness of Case-Based Learning Instruction on Epistemological Beliefs and Attitudes Toward Chemistry

NASA Astrophysics Data System (ADS)

Çam, Aylin; Geban, Ömer

2011-02-01

The purpose of the study was to investigate the effectiveness of case-based learning instruction over traditionally designed chemistry instruction on eleventh grade students' epistemological beliefs and their attitudes toward chemistry as a school subject. The subjects of this study consisted of 63 eleventh grade students from two intact classes of an urban high school instructed with same teacher. Each teaching method was randomly assigned to one class. The experimental group received case-based learning and the control group received traditional instruction. At the experimental group, life cases were presented with small group format; at the control group, lecturing and discussion was carried out. The results showed that there was a significant difference between the experimental and control group with respect to their epistemological beliefs and attitudes toward chemistry as a school subject in favor of case-based learning method group. Thus, case base learning is helpful for development of students' epistemological beliefs and attitudes toward chemistry.

Genome-wide association analysis of secondary imaging phenotypes from the Alzheimer's disease neuroimaging initiative study.

PubMed

Zhu, Wensheng; Yuan, Ying; Zhang, Jingwen; Zhou, Fan; Knickmeyer, Rebecca C; Zhu, Hongtu

2017-02-01

The aim of this paper is to systematically evaluate a biased sampling issue associated with genome-wide association analysis (GWAS) of imaging phenotypes for most imaging genetic studies, including the Alzheimer's Disease Neuroimaging Initiative (ADNI). Specifically, the original sampling scheme of these imaging genetic studies is primarily the retrospective case-control design, whereas most existing statistical analyses of these studies ignore such sampling scheme by directly correlating imaging phenotypes (called the secondary traits) with genotype. Although it has been well documented in genetic epidemiology that ignoring the case-control sampling scheme can produce highly biased estimates, and subsequently lead to misleading results and suspicious associations, such findings are not well documented in imaging genetics. We use extensive simulations and a large-scale imaging genetic data analysis of the Alzheimer's Disease Neuroimaging Initiative (ADNI) data to evaluate the effects of the case-control sampling scheme on GWAS results based on some standard statistical methods, such as linear regression methods, while comparing it with several advanced statistical methods that appropriately adjust for the case-control sampling scheme. Copyright © 2016 Elsevier Inc. All rights reserved.

Risk factors for nonspecific low-back pain in Chinese adolescents: a case-control study.

PubMed

Yao, WeiGuang; Luo, ChenLing; Ai, FuZhi; Chen, Qing

2012-05-01

The objective of this study was to gain a basic understanding of the influential factors for nonspecific low-back pain (LBP) among adolescents of southern China. The study was designed as a school-based case control study. Nonspecific LBP is a common health problem in adolescence. Although some behaviors and socio-demographic factors are believed to contribute to the disorder, influential factors of LBP remain undefined. Moreover, until now there is no available information of influential factors for LBP in Chinese adolescents. A total of 1,214 adolescents were involved in the study, including 607 cases with nonspecific LBP and 607 controls without history of nonspecific LBP. A self-administered questionnaire was designed for epidemiological survey to investigate the risk factors for nonspecific LBP. All cases and controls were investigated for their family histories of nonspecific LBP, physical activities, sedentary activities, schoolbag weights, school performances, living conditions, and etc. A 1:1 matched case-control study was conducted on 1,214 adolescents from an elementary school and a secondary school in Guangzhou City, southern China. Family history (odds ratio [OR] 2.57, 95% confidence interval [CI] 1.85-3.58), long duration of carrying schoolbag (OR 1.38, 95% CI 1.11-1.72) and rest position between classes (OR 1.18, 95% CI 1.01-1.39) were positively correlated with self-reported nonspecific LBP. Students regularly playing basketball (OR 1.58, 95% CI 1.09-2.30) was found to be significantly more likely to have LBP. Also, students who feel schoolbag uncomfortable (OR 1.38, 95% CI 1.11-1.72) was found to experience more LBP. Family history, feeling schoolbag uncomfortable, duration of schoolbag carrying, basketball playing and rest position between classes are the major risk factors for nonspecific LBP in adolescents. Wiley Periodicals, Inc.

Statins and Risk of Lower Limb Revision Surgery: The Influence of Differences in Study Design Using Electronic Health Records From the United Kingdom and Denmark

PubMed Central

Lalmohamed, Arief; van Staa, Tjeerd P.; Vestergaard, Peter; Leufkens, Hubertus G. M.; de Boer, Anthonius; Emans, Pieter; Cooper, Cyrus; de Vries, Frank

2016-01-01

Abstract Previous observational studies on statins have shown variable results based on the methodology used. Our objective was to study the association between statins and orthopedic implant failure and to explore the influence of methodological differences in study design. Our study base consisted of patients with a primary total joint replacement in Denmark and the United Kingdom (n = 189,286; 1987–2012). We used 4 study designs: 1) case-control (each patient with revision surgery matched to 4 controls), 2) time-dependent cohort (postoperative statin use as a time-varying exposure variable), 3) immortal time cohort (misclassifying the time postoperatively before statin use), and 4) time-exclusion cohort (excluding the time postoperatively before statin use). Cox proportional hazards models and logistic regression were used to estimate incidence rate ratios. In the time-dependent cohort design, statin use was associated with a decreased risk of revision surgery (adjusted incidence rate ratio (IRR) = 0.90, 95% confidence interval (CI): 0.85, 0.96), which was similar to our case-control results (IRR = 0.87, 95% CI: 0.81, 0.93). In contrast, both time-fixed cohort designs yielded substantially lower risk estimates (IRR = 0.36 (95% CI: 0.34, 0.38) and IRR = 0.65 (95% CI: 0.63, 0.68), respectively). We discourage the use of time-fixed cohort studies, which may falsely suggest protective effects. The simple choice of how to classify exposure can substantially change results from biologically plausible to implausible. PMID:27317693

Natural gas operations: considerations on process transients, design, and control.

PubMed

Manenti, Flavio

2012-03-01

This manuscript highlights tangible benefits deriving from the dynamic simulation and control of operational transients of natural gas processing plants. Relevant improvements in safety, controllability, operability, and flexibility are obtained not only within the traditional applications, i.e. plant start-up and shutdown, but also in certain fields apparently time-independent such as the feasibility studies of gas processing plant layout and the process design of processes. Specifically, this paper enhances the myopic steady-state approach and its main shortcomings with respect to the more detailed studies that take into consideration the non-steady state behaviors. A portion of a gas processing facility is considered as case study. Process transients, design, and control solutions apparently more appealing from a steady-state approach are compared to the corresponding dynamic simulation solutions. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

Psychiatric comorbidity may not predict suicide during and after hospitalization. A nested case-control study with blinded raters.

PubMed

Walby, Fredrik A; Odegaard, Erik; Mehlum, Lars

2006-06-01

To investigate the differential impact of DSM-IV axis-I and axis-II disorders on completed suicide and to study if psychiatric comorbidity increases the risk of suicide in currently and previously hospitalized psychiatric patients. A nested case-control design based on case notes from 136 suicides and 166 matched controls. All cases and controls were rediagnosed using the SCID-CV for axis-I and the DSM-IV criteria for axis-II disorders and the inter-rater reliability was satisfactory. Raters were blind to the case and control status and the original hospital diagnoses. Depressive disorders and bipolar disorders were associated with an increased risk of suicide. No such effect was found for comorbidity between axis-I disorders and for comorbidity between axis-I and axis-II disorders. Psychiatric diagnoses, although made using a structured and criteria-based approach, was based on information recorded in case notes. Axis-II comorbidity could only be investigated at an aggregated level. Psychiatric comorbidity did not predict suicide in this sample. Mood disorders did, however, increase the risk significantly independent of history of previous suicide attempts. Both findings can inform identification and treatment of patients at high risk for completed suicide.

Vitamin E Intake and Risk of Renal Cell Carcinoma: A Meta-Analysis of 7 Case-Control Studies.

PubMed

Shang, Yonggang; Yi, Shanhong; Cui, Dong; Han, Guangwei; Liu, Chengcheng

2015-07-01

Vitamin E intake may reduce the risk of renal cell carcinoma, but the results were inconsistent. Hence, we conducted a meta-analysis to assess the association between dietary vitamin E intake and the risk of renal cell carcinoma. We searched PubMed to identify the relevant case-control studies up to June 2014. Reference lists of retrieved articles were also reviewed. Odds ratios and corresponding 95% confidence intervals were used to estimate the association between dietary vitamin E intake and the risk of renal cell carcinoma. We identified 7 case-control studies regarding dietary vitamin E intake and risk of renal cell carcinoma, involving 5789 cases and 14866 controls. The odds ratio of renal cell carcinoma for the highest compared with the lowest dietary vitamin E intake was 0.75 (95% confidence interval: 0.59-0.91), and heterogeneity was observed across studies. The association between dietary vitamin E intake and the risk of renal cell carcinoma was not significantly differed by gender, but this association were inconsistent in the North American and European populations. Our study provided a evidence that there was a significant inverse association of dietary vitamin E intake with risk of renal cell carcinoma. However, this finding was based on the case-control studies, more well-designed cohort studies are needed. Copyright © 2015 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.

Inflammasomes make the case for littermate-controlled experimental design in studying host-microbiota interactions.

PubMed

Mamantopoulos, Michail; Ronchi, Francesca; McCoy, Kathy D; Wullaert, Andy

2018-04-19

Several human diseases are thought to evolve due to a combination of host genetic mutations and environmental factors that include alterations in intestinal microbiota composition termed dysbiosis. Although in some cases, host genetics may shape the gut microbiota and enable it to provoke disease, experimentally disentangling cause and consequence in such host-microbe interactions requires strict control over non-genetic confounding factors. Mouse genetic studies previously proposed Nlrp6/ASC inflammasomes as innate immunity regulators of the intestinal ecosystem. In contrast, using littermate-controlled experimental setups, we recently showed that Nlrp6/ASC inflammasomes do not alter the gut microbiota composition. Our analyses indicated that maternal inheritance and long-term separate housing are non-genetic confounders that preclude the use of non-littermate mice when analyzing host genetic effects on intestinal ecology. Here, we summarize and discuss our gut microbiota analyses in inflammasome-deficient mice for illustrating the importance of littermate experimental design in studying host-microbiota interactions.

Risk assessment as standard work in design.

PubMed

Morrill, Patricia W

2013-01-01

This case study article examines a formal risk assessment as part of the decision making process for design solutions in high risk areas. The overview of the Failure Modes and Effects Analysis (FMEA) tool with examples of its application in hospital building projects will demonstrate the benefit of those structured conversations. This article illustrates how two hospitals used FMEA when integrating operational processes with building projects: (1) adjacency decision for Intensive Care Unit (ICU); and (2) distance concern for handling of specimens from Surgery to Lab. Both case studies involved interviews that exposed facility solution concerns. Just-in-time studies using the FMEA followed the same risk assessment process with the same workshop facilitator involving structured conversations in analyzing risks. In both cases, participants uncovered key areas of risk enabling them to take the necessary next steps. While the focus of this article is not the actual design solution, it is apparent that the risk assessment brought clarity to the situations resulting in prompt decision making about facility solutions. Hospitals are inherently risky environments; therefore, use of the formal risk assessment process, FMEA, is an opportunity for design professionals to apply more rigor to design decision making when facility solutions impact operations in high risk areas. Case study, decision making, hospital, infection control, strategy, work environment.

A genuine nonlinear approach for controller design of a boiler-turbine system.

PubMed

Yang, Shizhong; Qian, Chunjiang; Du, Haibo

2012-05-01

This paper proposes a genuine nonlinear approach for controller design of a drum-type boiler-turbine system. Based on a second order nonlinear model, a finite-time convergent controller is first designed to drive the states to their setpoints in a finite time. In the case when the state variables are unmeasurable, the system will be regulated using a constant controller or an output feedback controller. An adaptive controller is also designed to stabilize the system since the model parameters may vary under different operating points. The novelty of the proposed controller design approach lies in fully utilizing the system nonlinearities instead of linearizing or canceling them. In addition, the newly developed techniques for finite-time convergent controller are used to guarantee fast convergence of the system. Simulations are conducted under different cases and the results are presented to illustrate the performance of the proposed controllers. Copyright © 2011 ISA. Published by Elsevier Ltd. All rights reserved.

Association of Serum Retinol-Binding Protein 4 Concentration With Risk for and Prognosis of Amyotrophic Lateral Sclerosis.

PubMed

Rosenbohm, Angela; Nagel, Gabriele; Peter, Raphael S; Brehme, Torben; Koenig, Wolfgang; Dupuis, Luc; Rothenbacher, Dietrich; Ludolph, Albert C

2018-05-01

Knowledge about the metabolic states of patients with amyotrophic lateral sclerosis (ALS) may provide a therapeutic approach. To investigate the association between the onset and prognosis of ALS and serum retinol-binding protein 4 (RBP4) concentration as a biomarker for insulin resistance and vitamin A metabolism. Case-control design for risk factors of ALS; cohort design for prognostic factors within ALS cases. Between October 1, 2010, and June 30, 2014, a population-based case-control study with randomly selected controls was established based on the ALS Registry Swabia in southern Germany, with a target population of 8.4 million inhabitants. Response rates were 64.8% among the cases and 18.7% among the controls. The dates of analysis were April 2016 to May 2017. Serum samples were measured for RBP4. Information on covariates was assessed by an interview-based standardized questionnaire. Main outcomes and measures were adjusted odds ratios for risk of ALS associated with serum RBP4 concentration, as well as time to death associated with RBP4 concentration at baseline in ALS cases only. Conditional logistic regression was applied to calculate multivariable odds ratios for risk of ALS. Survival models were used in cases only to appraise their prognostic value. Data from 289 patients with ALS (mean [SD] age, 65.7 [10.5] years; 172 [59.5%] male) and 504 controls (mean [SD] age, 66.3 [9.8] years; 299 [59.3%] male) were included in the case-control study. Compared with controls, ALS cases were characterized by lower body mass index, less educational attainment, smoking, light occupational work intensity, and self-reported diabetes. The median serum RBP4 concentration was lower in ALS cases than in controls (54.0 vs 59.5 mg/L). In the multivariable model, increasing RBP4 concentration was associated with reduced odds for ALS (top vs bottom quartile odds ratio, 0.36; 95% CI, 0.22-0.59; P for trend <.001), which persisted after further adjustment for renal function and for leptin and adiponectin. Among 279 ALS cases during a median follow-up of 14.5 months, 104 died (mean [SD] age, 68.9 [10.3] years; 56 [53.9%] male). In this ALS cohort, an inverse association was found between serum RBP4 concentration as a continuous measure and survival. RBP4 was inversely related to risk for and prognosis of ALS, suggesting that vitamin A metabolism or impaired insulin signaling could be involved. Further research, including a prospective design and other biological markers, is necessary to clarify the role of insulin resistance in the pathogenesis of ALS.

Making medical decisions in dependence of genetic background: estimation of the utility of DNA testing in clinical, pharmaco-epidemiological or genetic studies.

PubMed

Nguyen, Thuy Trang; Schäfer, Helmut; Timmesfeld, Nina

2013-05-01

An index measuring the utility of testing a DNA marker before deciding between two alternative treatments is proposed which can be estimated from pharmaco-epidemiological case-control or cohort studies. In the case-control design, external estimates of the prevalence of the disease and of the frequency of the genetic risk variant are required for estimating the utility index. Formulas for point and interval estimates are derived. Empirical coverage probabilities of the confidence intervals were estimated under different scenarios of disease prevalence, prevalence of drug use, and population frequency of the genetic variant. To illustrate our method, we re-analyse pharmaco-epidemiological case-control data on oral contraceptive intake and venous thrombosis in carriers and non-carriers of the factor V Leiden mutation. We also re-analyse cross-sectional data from the Framingham study on a gene-diet interaction between an APOA2 polymorphism and high saturated fat intake on obesity. We conclude that the utility index may be helpful to evaluate and appraise the potential clinical and public health relevance of gene-environment interaction effects detected in genomic and candidate gene association studies and may be a valuable decision support for designing prospective studies on the clinical utility. © 2013 Wiley Periodicals, Inc.

Dental care of autistic children within the non-specialized Public Dental Service.

PubMed

Fahlvik-Planefeldt, C; Herrström, P

2001-01-01

Children with an autistic disorder may need more dental care and may also be more difficult to treat than healthy children. This study compared oral health in autistic and healthy children. Also explored was the dental management of autistic children within the non-specialized Public Dental Service. The study was designed as a case-control study with all cases of autistic disorders aged 3-19 years identified within a primary care area in southwest Sweden. One dentist did a clinical investigation of cases and one control per case. The patients, or their parents, answered a questionnaire. 28 patients were identified and 20 (71%) agreed to participate in the study. Cases and controls had a similar prevalence of fillings, caries, gingivitis and degree of oral hygiene. However, the need of orthodontic treatment seemed to be greater among the autistic children. According to a standardised assessment, autistic children were less able to cooperate in the dental treatment. Approximately 30% of the cases had occasionally been subjected to specialized dental care. The results of this study indicate that the care provided to autistic children within the non-specialized Public Dental Service is satisfactory, provided that there is access to a paediatric dentist when necessary.

Disease-modifying anti-rheumatic drug use in pregnant women with rheumatic diseases: a systematic review of the risk of congenital malformations.

PubMed

Baldwin, Corisande; Avina-Zubieta, Antonio; Rai, Sharan K; Carruthers, Erin; De Vera, Mary A

2016-01-01

Despite the high incidence of rheumatic diseases during the reproductive years, little is known about the impact of disease-modifying anti-rheumatic drug (DMARD) use during pregnancy. Our objective was to systematically review and appraise evidence in women with rheumatic disease on the use of traditional and biologic DMARDs during pregnancy and the risk of congenital malformation outcomes. We conducted a systematic search of MEDLINE, EMBASE, and INTERNATIONAL PHARMACEUTICAL ABSTRACTS databases. Inclusion criteria were: 1) study sample including women with rheumatic disease; 2) use of traditional and/or biologic DMARDs during pregnancy; and 3) congenital malformation outcome(s) reported. We extracted information on study design, data source, number of exposed pregnancies, type of DMARD, number of live births, and number of congenital malformations. Altogether, we included 79 studies; the majority were based on designs that did not involve a comparison group, including 26 case reports, 17 case series, 20 cross-sectional studies, and 4 surveys. Studies that had a comparator group included 1 case control, 10 cohort studies, and 1 controlled trial. Hydroxychloroquine and azathioprine represent the most studied traditional DMARD exposures and, among biologics, most of the reports were on infliximab and etanercept. This is the first systematic review on the use of both traditional and biologic DMARDs during pregnancy among women with rheumatic diseases and congenital malformation outcomes, with a focus on study design and quality. Findings confirm the limited number of studies, as well as the need to improve study designs.

Statistical inferences for data from studies conducted with an aggregated multivariate outcome-dependent sample design.

PubMed

Lu, Tsui-Shan; Longnecker, Matthew P; Zhou, Haibo

2017-03-15

Outcome-dependent sampling (ODS) scheme is a cost-effective sampling scheme where one observes the exposure with a probability that depends on the outcome. The well-known such design is the case-control design for binary response, the case-cohort design for the failure time data, and the general ODS design for a continuous response. While substantial work has been carried out for the univariate response case, statistical inference and design for the ODS with multivariate cases remain under-developed. Motivated by the need in biological studies for taking the advantage of the available responses for subjects in a cluster, we propose a multivariate outcome-dependent sampling (multivariate-ODS) design that is based on a general selection of the continuous responses within a cluster. The proposed inference procedure for the multivariate-ODS design is semiparametric where all the underlying distributions of covariates are modeled nonparametrically using the empirical likelihood methods. We show that the proposed estimator is consistent and developed the asymptotically normality properties. Simulation studies show that the proposed estimator is more efficient than the estimator obtained using only the simple-random-sample portion of the multivariate-ODS or the estimator from a simple random sample with the same sample size. The multivariate-ODS design together with the proposed estimator provides an approach to further improve study efficiency for a given fixed study budget. We illustrate the proposed design and estimator with an analysis of association of polychlorinated biphenyl exposure to hearing loss in children born to the Collaborative Perinatal Study. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

A Framework for the Design of Service Systems

NASA Astrophysics Data System (ADS)

Tan, Yao-Hua; Hofman, Wout; Gordijn, Jaap; Hulstijn, Joris

We propose a framework for the design and implementation of service systems, especially to design controls for long-term sustainable value co-creation. The framework is based on the software support tool e3-control. To illustrate the framework we use a large-scale case study, the Beer Living Lab, for simplification of customs procedures in international trade. The BeerLL shows how value co-creation can be achieved by reduction of administrative burden in international beer export due to electronic customs. Participants in the BeerLL are Heineken, IBM and Dutch Tax & Customs.

A boundedness result for the direct heuristic dynamic programming.

PubMed

Liu, Feng; Sun, Jian; Si, Jennie; Guo, Wentao; Mei, Shengwei

2012-08-01

Approximate/adaptive dynamic programming (ADP) has been studied extensively in recent years for its potential scalability to solve large state and control space problems, including those involving continuous states and continuous controls. The applicability of ADP algorithms, especially the adaptive critic designs has been demonstrated in several case studies. Direct heuristic dynamic programming (direct HDP) is one of the ADP algorithms inspired by the adaptive critic designs. It has been shown applicable to industrial scale, realistic and complex control problems. In this paper, we provide a uniformly ultimately boundedness (UUB) result for the direct HDP learning controller under mild and intuitive conditions. By using a Lyapunov approach we show that the estimation errors of the learning parameters or the weights in the action and critic networks remain UUB. This result provides a useful controller convergence guarantee for the first time for the direct HDP design. Copyright © 2012 Elsevier Ltd. All rights reserved.

Culture, risk factors and suicide in rural China: a psychological autopsy case control study.

PubMed

Zhang, J; Conwell, Y; Zhou, L; Jiang, C

2004-12-01

Previous research on sociocultural factors for Chinese suicide have been basically limited to single case studies or qualitative research with ethnographic methodology. The current study examines the major risk factors and some cultural uniqueness related to Chinese rural suicide using a quantitative design. This is a case control study with 66 completed suicides and 66 living controls obtained from psychological autopsy interviews in rural China. Both bivariate analyses and the multiple regression model have found that the Chinese rural suicide patterns are basically similar to those in most other cultures in the world: strong predictors of rural Chinese suicide are the psychopathological, psychological, and physical health variables, followed by social support and negative and stressful life events. Other significant correlates include lower education, poverty, religion, and family disputes. Culture has an important impact on suicide patterns in a society.

Culture, risk factors and suicide in rural China: a psychological autopsy case control study

PubMed Central

Zhang, J.; Conwell, Y.; Zhou, L.; Jiang, C.

2009-01-01

Objective Previous research on sociocultural factors for Chinese suicide have been basically limited to single case studies or qualitative research with ethnographic methodology. The current study examines the major risk factors and some cultural uniqueness related to Chinese rural suicide using a quantitative design. Method This is a case control study with 66 completed suicides and 66 living controls obtained from psychological autopsy interviews in rural China. Results Both bivariate analyses and the multiple regression model have found that the Chinese rural suicide patterns are basically similar to those in most other cultures in the world: strong predictors of rural Chinese suicide are the psychopathological, psychological, and physical health variables, followed by social support and negative and stressful life events. Other significant correlates include lower education, poverty, religion, and family disputes. Conclusion Culture has an important impact on suicide patterns in a society. PMID:15521827

Associations of daily pediatric asthma emergency department visits with air pollution in Newark, NJ: utilizing time-series and case-crossover study designs.

PubMed

Gleason, Jessie A; Fagliano, Jerald A

2015-10-01

Asthma is one of the most common chronic diseases affecting children. This study assesses the associations of ozone and fine particulate matter (PM2.5) with pediatric emergency department visits in the urban environment of Newark, NJ. Two study designs were utilized and evaluated for usability. We obtained daily emergency department visits among children aged 3-17 years with a primary diagnosis of asthma during April to September for 2004-2007. Both a time-stratified case-crossover study design with bi-directional control sampling and a time-series study design were utilized. Lagged effects (1-d through 5-d lag, 3-d average, and 5-d average) of ozone and PM2.5 were explored and a dose-response analysis comparing the bottom 5th percentile of 3-d average lag ozone with each 5 percentile increase was performed. Associations of interquartile range increase in same-day ozone were similar between the time-series and case-crossover study designs (RR = 1.08, 95% CI 1.04-1.12) and (OR = 1.10, 95% CI 1.06-1.14), respectively. Similar associations were seen for 1-day lag and 3-day average lag ozone levels. PM2.5 was not associated with the outcome in either study design. Dose-response assessment indicated a statistically significant and increasing association around 50-55 ppb consistent for both study designs. Ozone was statistically positively associated with pediatric asthma ED visits in Newark, NJ. Our results were generally comparable across the time-series and case-crossover study designs, indicating both are useful to assess local air pollution impacts.

Controlling hazardous reactions during voltage reversal of high energy lithium cells

NASA Technical Reports Server (NTRS)

Domeniconi, M.

1983-01-01

The roll of general cell design characteristics in preventing hazardous reactions during voltage reversal of lithium cells is discussed. Anode limited versus cathode limited design and case positive versus case negative design are addressed.

Incidence and risk factors of aplastic anemia in Latin American countries: the LATIN case-control study

PubMed Central

Maluf, Eliane; Hamerschlak, Nelson; Cavalcanti, Alexandre Biasi; Júnior, Álvaro Avezum; Eluf-Neto, José; Falcão, Roberto Passetto; Lorand-Metze, Irene G.; Goldenberg, Daniel; Santana, Cézar Leite; de Oliveira Werneck Rodrigues, Daniela; da Motta Passos, Leny Nascimento; Rosenfeld, Luis Gastão Mange; Pitta, Marimilia; Loggetto, Sandra; Feitosa Ribeiro, Andreza A.; Velloso, Elvira Deolinda; Kondo, Andrea Tiemi; de Miranda Coelho, Erika Oliveira; Pintão, Maria Carolina Tostes; de Souza, Hélio Moraes; Borbolla, José Rafael; Pasquini, Ricardo

2009-01-01

Background Associations between aplastic anemia and numerous drugs, pesticides and chemicals have been reported. However, at least 50% of the etiology of aplastic anemia remains unexplained. Design and Methods This was a case-control, multicenter, multinational study, designed to identify risk factors for agranulocytosis and aplastic anemia. The cases were patients with diagnosis of aplastic anemia confirmed through biopsy or bone marrow aspiration, selected through an active search of clinical laboratories, hematology clinics and medical records. The controls did not have either aplastic anemia or chronic diseases. A total of 224 patients with aplastic anemia were included in the study, each case was paired with four controls, according to sex, age group, and hospital where the case was first seen. Information was collected on demographic data, medical history, laboratory tests, medications, and other potential risk factors prior to diagnosis. Results The incidence of aplastic anemia was 1.6 cases per million per year. Higher rates of benzene exposure (≥30 exposures per year) were associated with a greater risk of aplastic anemia (odds ratio, OR: 4.2; 95% confidence interval, CI: 1.82–9.82). Individuals exposed to chloramphenicol in the previous year had an adjusted OR for aplastic anemia of 8.7 (CI: 0.87–87.93) and those exposed to azithromycin had an adjusted OR of 11.02 (CI 1.14–108.02). Conclusions The incidence of aplastic anemia in Latin America countries is low. Although the research study centers had a high coverage of health services, the underreporting of cases of aplastic anemia in selected regions can be discussed. Frequent exposure to benzene-based products increases the risk for aplastic anemia. Few associations with specific drugs were found, and it is likely that some of these were due to chance alone. PMID:19734415

XPAT: a toolkit to conduct cross-platform association studies with heterogeneous sequencing datasets.

PubMed

Yu, Yao; Hu, Hao; Bohlender, Ryan J; Hu, Fulan; Chen, Jiun-Sheng; Holt, Carson; Fowler, Jerry; Guthery, Stephen L; Scheet, Paul; Hildebrandt, Michelle A T; Yandell, Mark; Huff, Chad D

2018-04-06

High-throughput sequencing data are increasingly being made available to the research community for secondary analyses, providing new opportunities for large-scale association studies. However, heterogeneity in target capture and sequencing technologies often introduce strong technological stratification biases that overwhelm subtle signals of association in studies of complex traits. Here, we introduce the Cross-Platform Association Toolkit, XPAT, which provides a suite of tools designed to support and conduct large-scale association studies with heterogeneous sequencing datasets. XPAT includes tools to support cross-platform aware variant calling, quality control filtering, gene-based association testing and rare variant effect size estimation. To evaluate the performance of XPAT, we conducted case-control association studies for three diseases, including 783 breast cancer cases, 272 ovarian cancer cases, 205 Crohn disease cases and 3507 shared controls (including 1722 females) using sequencing data from multiple sources. XPAT greatly reduced Type I error inflation in the case-control analyses, while replicating many previously identified disease-gene associations. We also show that association tests conducted with XPAT using cross-platform data have comparable performance to tests using matched platform data. XPAT enables new association studies that combine existing sequencing datasets to identify genetic loci associated with common diseases and other complex traits.

A network control theory approach to modeling and optimal control of zoonoses: case study of brucellosis transmission in sub-Saharan Africa.

PubMed

Roy, Sandip; McElwain, Terry F; Wan, Yan

2011-10-01

Developing control policies for zoonotic diseases is challenging, both because of the complex spread dynamics exhibited by these diseases, and because of the need for implementing complex multi-species surveillance and control efforts using limited resources. Mathematical models, and in particular network models, of disease spread are promising as tools for control-policy design, because they can provide comprehensive quantitative representations of disease transmission. A layered dynamical network model for the transmission and control of zoonotic diseases is introduced as a tool for analyzing disease spread and designing cost-effective surveillance and control. The model development is achieved using brucellosis transmission among wildlife, cattle herds, and human sub-populations in an agricultural system as a case study. Precisely, a model that tracks infection counts in interacting animal herds of multiple species (e.g., cattle herds and groups of wildlife for brucellosis) and in human subpopulations is introduced. The model is then abstracted to a form that permits comprehensive targeted design of multiple control capabilities as well as model identification from data. Next, techniques are developed for such quantitative design of control policies (that are directed to both the animal and human populations), and for model identification from snapshot and time-course data, by drawing on recent results in the network control community. The modeling approach is shown to provide quantitative insight into comprehensive control policies for zoonotic diseases, and in turn to permit policy design for mitigation of these diseases. For the brucellosis-transmission example in particular, numerous insights are obtained regarding the optimal distribution of resources among available control capabilities (e.g., vaccination, surveillance and culling, pasteurization of milk) and points in the spread network (e.g., transhumance vs. sedentary herds). In addition, a preliminary identification of the network model for brucellosis is achieved using historical data, and the robustness of the obtained model is demonstrated. As a whole, our results indicate that network modeling can aid in designing control policies for zoonotic diseases.

A Network Control Theory Approach to Modeling and Optimal Control of Zoonoses: Case Study of Brucellosis Transmission in Sub-Saharan Africa

PubMed Central

Roy, Sandip; McElwain, Terry F.; Wan, Yan

2011-01-01

Background Developing control policies for zoonotic diseases is challenging, both because of the complex spread dynamics exhibited by these diseases, and because of the need for implementing complex multi-species surveillance and control efforts using limited resources. Mathematical models, and in particular network models, of disease spread are promising as tools for control-policy design, because they can provide comprehensive quantitative representations of disease transmission. Methodology/Principal Findings A layered dynamical network model for the transmission and control of zoonotic diseases is introduced as a tool for analyzing disease spread and designing cost-effective surveillance and control. The model development is achieved using brucellosis transmission among wildlife, cattle herds, and human sub-populations in an agricultural system as a case study. Precisely, a model that tracks infection counts in interacting animal herds of multiple species (e.g., cattle herds and groups of wildlife for brucellosis) and in human subpopulations is introduced. The model is then abstracted to a form that permits comprehensive targeted design of multiple control capabilities as well as model identification from data. Next, techniques are developed for such quantitative design of control policies (that are directed to both the animal and human populations), and for model identification from snapshot and time-course data, by drawing on recent results in the network control community. Conclusions/Significance The modeling approach is shown to provide quantitative insight into comprehensive control policies for zoonotic diseases, and in turn to permit policy design for mitigation of these diseases. For the brucellosis-transmission example in particular, numerous insights are obtained regarding the optimal distribution of resources among available control capabilities (e.g., vaccination, surveillance and culling, pasteurization of milk) and points in the spread network (e.g., transhumance vs. sedentary herds). In addition, a preliminary identification of the network model for brucellosis is achieved using historical data, and the robustness of the obtained model is demonstrated. As a whole, our results indicate that network modeling can aid in designing control policies for zoonotic diseases. PMID:22022621

Do consanguineous parents of a child affected by an autosomal recessive disease have more DNA identical-by-descent than similarly-related parents with healthy offspring? Design of a case-control study

PubMed Central

2010-01-01

Background The offspring of consanguineous relations have an increased risk of congenital/genetic disorders and early mortality. Consanguineous couples and their offspring account for approximately 10% of the global population. The increased risk for congenital/genetic disorders is most marked for autosomal recessive disorders and depends on the degree of relatedness of the parents. For children of first cousins the increased risk is 2-4%. For individual couples, however, the extra risk can vary from zero to 25% or higher, with only a minority of these couples having an increased risk of at least 25%. It is currently not possible to differentiate between high-and low-risk couples. The quantity of DNA identical-by-descent between couples with the same degree of relatedness shows a remarkable variation. Here we hypothesize that consanguineous partners with children affected by an autosomal recessive disease have more DNA identical-by-descent than similarly-related partners who have only healthy children. The aim of the study is thus to establish whether the amount of DNA identical-by-descent in consanguineous parents of children with an autosomal recessive disease is indeed different from its proportion in consanguineous parents who have healthy children only. Methods/Design This project is designed as a case-control study. Cases are defined as consanguineous couples with one or more children with an autosomal recessive disorder and controls as consanguineous couples with at least three healthy children and no affected child. We aim to include 100 case couples and 100 control couples. Control couples are matched by restricting the search to the same family, clan or ethnic origin as the case couple. Genome-wide SNP arrays will be used to test our hypothesis. Discussion This study contains a new approach to risk assessment in consanguineous couples. There is no previous study on the amount of DNA identical-by-descent in consanguineous parents of affected children compared to the consanguineous parents of healthy children. If our hypothesis proves to be correct, further studies are needed to obtain different risk figure estimates for the different proportions of DNA identical-by-descent. With more precise information about their risk status, empowerment of couples can be improved when making reproductive decisions. PMID:20637082

On the dynamics of a generalized predator-prey system with Z-type control.

PubMed

Lacitignola, Deborah; Diele, Fasma; Marangi, Carmela; Provenzale, Antonello

2016-10-01

We apply the Z-control approach to a generalized predator-prey system and consider the specific case of indirect control of the prey population. We derive the associated Z-controlled model and investigate its properties from the point of view of the dynamical systems theory. The key role of the design parameter λ for the successful application of the method is stressed and related to specific dynamical properties of the Z-controlled model. Critical values of the design parameter are also found, delimiting the λ-range for the effectiveness of the Z-method. Analytical results are then numerically validated by the means of two ecological models: the classical Lotka-Volterra model and a model related to a case study of the wolf-wild boar dynamics in the Alta Murgia National Park. Investigations on these models also highlight how the Z-control method acts in respect to different dynamical regimes of the uncontrolled model. Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.

Sample size for positive and negative predictive value in diagnostic research using case–control designs

PubMed Central

Steinberg, David M.; Fine, Jason; Chappell, Rick

2009-01-01

Important properties of diagnostic methods are their sensitivity, specificity, and positive and negative predictive values (PPV and NPV). These methods are typically assessed via case–control samples, which include one cohort of cases known to have the disease and a second control cohort of disease-free subjects. Such studies give direct estimates of sensitivity and specificity but only indirect estimates of PPV and NPV, which also depend on the disease prevalence in the tested population. The motivating example arises in assay testing, where usage is contemplated in populations with known prevalences. Further instances include biomarker development, where subjects are selected from a population with known prevalence and assessment of PPV and NPV is crucial, and the assessment of diagnostic imaging procedures for rare diseases, where case–control studies may be the only feasible designs. We develop formulas for optimal allocation of the sample between the case and control cohorts and for computing sample size when the goal of the study is to prove that the test procedure exceeds pre-stated bounds for PPV and/or NPV. Surprisingly, the optimal sampling schemes for many purposes are highly unbalanced, even when information is desired on both PPV and NPV. PMID:18556677

Helicopter internal noise control: Three case histories

NASA Technical Reports Server (NTRS)

Edwards, B. D.; Cox, C. R.

1978-01-01

Case histories are described in which measurable improvements in the cabin noise environments of the Bell 214B, 206B, and 222 were realized. These case histories trace the noise control efforts followed in each vehicle. Among the design approaches considered, the addition of a fluid pulsation damper in a hydraulic system and the installation of elastomeric engine mounts are highlighted. It is concluded that substantial weight savings result when the major interior noise sources are controlled by design, both in altering the noise producing mechanism and interrupting the sound transmission paths.

Using genetic prediction from known complex disease Loci to guide the design of next-generation sequencing experiments.

PubMed

Jostins, Luke; Levine, Adam P; Barrett, Jeffrey C

2013-01-01

A central focus of complex disease genetics after genome-wide association studies (GWAS) is to identify low frequency and rare risk variants, which may account for an important fraction of disease heritability unexplained by GWAS. A profusion of studies using next-generation sequencing are seeking such risk alleles. We describe how already-known complex trait loci (largely from GWAS) can be used to guide the design of these new studies by selecting cases, controls, or families who are most likely to harbor undiscovered risk alleles. We show that genetic risk prediction can select unrelated cases from large cohorts who are enriched for unknown risk factors, or multiply-affected families that are more likely to harbor high-penetrance risk alleles. We derive the frequency of an undiscovered risk allele in selected cases and controls, and show how this relates to the variance explained by the risk score, the disease prevalence and the population frequency of the risk allele. We also describe a new method for informing the design of sequencing studies using genetic risk prediction in large partially-genotyped families using an extension of the Inside-Outside algorithm for inference on trees. We explore several study design scenarios using both simulated and real data, and show that in many cases genetic risk prediction can provide significant increases in power to detect low-frequency and rare risk alleles. The same approach can also be used to aid discovery of non-genetic risk factors, suggesting possible future utility of genetic risk prediction in conventional epidemiology. Software implementing the methods in this paper is available in the R package Mangrove.

Dissociation between facial and bodily expressions in emotion recognition: A case study.

PubMed

Leiva, Samanta; Margulis, Laura; Micciulli, Andrea; Ferreres, Aldo

2017-12-21

Existing single-case studies have reported deficit in recognizing basic emotions through facial expression and unaffected performance with body expressions, but not the opposite pattern. The aim of this paper is to present a case study with impaired emotion recognition through body expressions and intact performance with facial expressions. In this single-case study we assessed a 30-year-old patient with autism spectrum disorder, without intellectual disability, and a healthy control group (n = 30) with four tasks of basic and complex emotion recognition through face and body movements, and two non-emotional control tasks. To analyze the dissociation between facial and body expressions, we used Crawford and Garthwaite's operational criteria, and we compared the patient and the control group performance with a modified one-tailed t-test designed specifically for single-case studies. There were no statistically significant differences between the patient's and the control group's performances on the non-emotional body movement task or the facial perception task. For both kinds of emotions (basic and complex) when the patient's performance was compared to the control group's, statistically significant differences were only observed for the recognition of body expressions. There were no significant differences between the patient's and the control group's correct answers for emotional facial stimuli. Our results showed a profile of impaired emotion recognition through body expressions and intact performance with facial expressions. This is the first case study that describes the existence of this kind of dissociation pattern between facial and body expressions of basic and complex emotions.

Known glioma risk loci are associated with glioma with a family history of brain tumours -- a case-control gene association study.

PubMed

Melin, Beatrice; Dahlin, Anna M; Andersson, Ulrika; Wang, Zhaoming; Henriksson, Roger; Hallmans, Göran; Bondy, Melissa L; Johansen, Christoffer; Feychting, Maria; Ahlbom, Anders; Kitahara, Cari M; Wang, Sophia S; Ruder, Avima M; Carreón, Tania; Butler, Mary Ann; Inskip, Peter D; Purdue, Mark; Hsing, Ann W; Mechanic, Leah; Gillanders, Elizabeth; Yeager, Meredith; Linet, Martha; Chanock, Stephen J; Hartge, Patricia; Rajaraman, Preetha

2013-05-15

Familial cancer can be used to leverage genetic association studies. Recent genome-wide association studies have reported independent associations between seven single nucleotide polymorphisms (SNPs) and risk of glioma. The aim of this study was to investigate whether glioma cases with a positive family history of brain tumours, defined as having at least one first- or second-degree relative with a history of brain tumour, are associated with known glioma risk loci. One thousand four hundred and thirty-one glioma cases and 2,868 cancer-free controls were identified from four case-control studies and two prospective cohorts from USA, Sweden and Denmark and genotyped for seven SNPs previously reported to be associated with glioma risk in case-control designed studies. Odds ratios were calculated by unconditional logistic regression. In analyses including glioma cases with a family history of brain tumours (n = 104) and control subjects free of glioma at baseline, three of seven SNPs were associated with glioma risk: rs2736100 (5p15.33, TERT), rs4977756 (9p21.3, CDKN2A-CDKN2B) and rs6010620 (20q13.33, RTEL1). After Bonferroni correction for multiple comparisons, only one marker was statistically significantly associated with glioma risk, rs6010620 (ORtrend for the minor (A) allele, 0.39; 95% CI: 0.25-0.61; Bonferroni adjusted ptrend , 1.7 × 10(-4) ). In conclusion, as previously shown for glioma regardless of family history of brain tumours, rs6010620 (RTEL1) was associated with an increased risk of glioma when restricting to cases with family history of brain tumours. These findings require confirmation in further studies with a larger number of glioma cases with a family history of brain tumours. Copyright © 2012 UICC.

Control-oriented modelization of a satellite with large flexible appendages and use of worst-case analysis to verify robustness to model uncertainties of attitude control

NASA Astrophysics Data System (ADS)

Gasbarri, Paolo; Monti, Riccardo; Campolo, Giovanni; Toglia, Chiara

2012-12-01

The design of large space structures (LSS) requires the use of design and analysis tools that include different disciplines. For such a kind of spacecrafts it is in fact mandatory that mechanical design and guidance navigation and control (GNC) design are developed within a common framework. One of the key-points in the development of LSS is related to the dynamic phenomena. These phenomena usually lead to two different interpretations. The former one is related to the overall motion of the spacecraft, i.e., the motion of the centre of gravity and motion around the centre of gravity. The latter one is related to the local motion of the elastic elements that leads to oscillations. These oscillations have in turn a disturbing effect on the motion of the spacecraft. From an engineering perspective, the structural model of flexible spacecrafts is generally obtained via FEM involving thousands of degrees of freedom (DOFs). Many of them are not significant from the attitude control point of view. One of the procedures to reduce the structural DOFs is tied to the modal decomposition technique. In the present paper a technique to develop a control-oriented structural model will be proposed. Starting from a detailed FE model of the spacecraft and using a special modal condensation approach, a continuous model is defined. With this transformation the number of DOFs necessary to study the coupled elastic/rigid dynamic is reduced. The final dynamic model will be suitable for the control design implementation. In order to properly design a satellite controller, it is important to recall that the characteristic parameters of the satellite are uncertain. The effect that uncertainties have on control performance must be investigated. A possible solution is that, after the attitude controller is designed on the nominal model, a Verification and Validation (V&V) process is performed to guarantee a correct functionality under a large number of scenarios. The V&V process can be very lengthy and expensive: difficulty and cost do increase because of the overall system dimension that depends on the number of uncertainties. Uncertain parameters have to be parametrically investigated to determine robust performance of the control laws via gridding approaches. In particular in this paper we propose to consider two methods: (i) a conventional Monte Carlo analysis, and (ii) a worst-case analysis, i.e., an optimization process to find an estimation of the true worst-case behaviour. Both techniques allow to verify that the design is robust enough to meet the system performance specification in case of uncertainties.

Use and interpretation of logistic regression in habitat-selection studies

USGS Publications Warehouse

Keating, Kim A.; Cherry, Steve

2004-01-01

 Logistic regression is an important tool for wildlife habitat-selection studies, but the method frequently has been misapplied due to an inadequate understanding of the logistic model, its interpretation, and the influence of sampling design. To promote better use of this method, we review its application and interpretation under 3 sampling designs: random, case-control, and use-availability. Logistic regression is appropriate for habitat use-nonuse studies employing random sampling and can be used to directly model the conditional probability of use in such cases. Logistic regression also is appropriate for studies employing case-control sampling designs, but careful attention is required to interpret results correctly. Unless bias can be estimated or probability of use is small for all habitats, results of case-control studies should be interpreted as odds ratios, rather than probability of use or relative probability of use. When data are gathered under a use-availability design, logistic regression can be used to estimate approximate odds ratios if probability of use is small, at least on average. More generally, however, logistic regression is inappropriate for modeling habitat selection in use-availability studies. In particular, using logistic regression to fit the exponential model of Manly et al. (2002:100) does not guarantee maximum-likelihood estimates, valid probabilities, or valid likelihoods. We show that the resource selection function (RSF) commonly used for the exponential model is proportional to a logistic discriminant function. Thus, it may be used to rank habitats with respect to probability of use and to identify important habitat characteristics or their surrogates, but it is not guaranteed to be proportional to probability of use. Other problems associated with the exponential model also are discussed. We describe an alternative model based on Lancaster and Imbens (1996) that offers a method for estimating conditional probability of use in use-availability studies. Although promising, this model fails to converge to a unique solution in some important situations. Further work is needed to obtain a robust method that is broadly applicable to use-availability studies.

Vaccine testing for emerging infections: the case for individual randomisation

PubMed Central

Eyal, Nir; Lipsitch, Marc

2017-01-01

During the 2014–2015 Ebola outbreak in Guinea, Liberia and Sierra Leone, many opposed the use of individually randomised controlled trials to test candidate Ebola vaccines. For a raging fatal disease, they explained, it is unethical to relegate some study participants to control arms. In Zika and future emerging infections, similar opposition may hinder urgent vaccine research, so it is best to address these questions now. This article lays out the ethical case for individually randomised control in testing vaccines against many emerging infections, including lethal infections in low-income countries, even when at no point in the trial do the controls receive the countermeasures being tested. When individual randomisation is feasible—and it often will be—it tends to save more lives than alternative designs would. And for emerging infections, individual randomisation also tends as such to improve care, access to the experimental vaccine and prospects for all participants relative to their opportunities absent the trial, and no less than alternative designs would. That obtains even under placebo control and without equipoise—requiring which would undermine individual randomisation and the alternative designs that opponents proffered. Our arguments expound four often-neglected factors: benefits to non-participants, benefits to participants once a trial is over including post-trial access to the study intervention, participants’ prospects before randomisation to arms and the near-inevitable disparity between arms in any randomised controlled trial. PMID:28396558

Neurocognitive performance in family-based and case-control studies of schizophrenia.

PubMed

Gur, Ruben C; Braff, David L; Calkins, Monica E; Dobie, Dorcas J; Freedman, Robert; Green, Michael F; Greenwood, Tiffany A; Lazzeroni, Laura C; Light, Gregory A; Nuechterlein, Keith H; Olincy, Ann; Radant, Allen D; Seidman, Larry J; Siever, Larry J; Silverman, Jeremy M; Sprock, Joyce; Stone, William S; Sugar, Catherine A; Swerdlow, Neal R; Tsuang, Debby W; Tsuang, Ming T; Turetsky, Bruce I; Gur, Raquel E

2015-04-01

Neurocognitive deficits in schizophrenia (SZ) are established and the Consortium on the Genetics of Schizophrenia (COGS) investigated such measures as endophenotypes in family-based (COGS-1) and case-control (COGS-2) studies. By requiring family participation, family-based sampling may result in samples that vary demographically and perform better on neurocognitive measures. The Penn computerized neurocognitive battery (CNB) evaluates accuracy and speed of performance for several domains and was administered across sites in COGS-1 and COGS-2. Most tests were included in both studies. COGS-1 included 328 patients with SZ and 497 healthy comparison subjects (HCS) and COGS-2 included 1195 patients and 1009 HCS. Demographically, COGS-1 participants were younger, more educated, with more educated parents and higher estimated IQ compared to COGS-2 participants. After controlling for demographics, the two samples produced very similar performance profiles compared to their respective controls. As expected, performance was better and with smaller effect sizes compared to controls in COGS-1 relative to COGS-2. Better performance was most pronounced for spatial processing while emotion identification had large effect sizes for both accuracy and speed in both samples. Performance was positively correlated with functioning and negatively with negative and positive symptoms in both samples, but correlations were attenuated in COGS-2, especially with positive symptoms. Patients ascertained through family-based design have more favorable demographics and better performance on some neurocognitive domains. Thus, studies that use case-control ascertainment may tap into populations with more severe forms of illness that are exposed to less favorable factors compared to those ascertained with family-based designs.

A novel approach to exploring potential interactions among single-nucleotide polymorphisms of inflammation genes in gliomagenesis: an exploratory case-only study.

PubMed

Amirian, E Susan; Scheurer, Michael E; Liu, Yanhong; D'Amelio, Anthony M; Houlston, Richard S; Etzel, Carol J; Shete, Sanjay; Swerdlow, Anthony J; Schoemaker, Minouk J; McKinney, Patricia A; Fleming, Sarah J; Muir, Kenneth R; Lophatananon, Artitaya; Bondy, Melissa L

2011-08-01

Despite extensive research on the topic, glioma etiology remains largely unknown. Exploration of potential interactions between single-nucleotide polymorphisms (SNP) of immune genes is a promising new area of glioma research. The case-only study design is a powerful and efficient design for exploring possible multiplicative interactions between factors that are independent of one another. The purpose of our study was to use this exploratory design to identify potential pair wise SNP-SNP interactions from genes involved in several different immune-related pathways for investigation in future studies. The study population consisted of two case groups: 1,224 histologic confirmed, non-Hispanic white glioma cases from the United States and a validation population of 634 glioma cases from the United Kingdom. Polytomous logistic regression, in which one SNP was coded as the outcome and the other SNP was included as the exposure, was utilized to calculate the ORs of the likelihood of cases simultaneously having the variant alleles of two different SNPs. Potential interactions were examined only between SNPs located in different genes or chromosomes. Using this data mining strategy, we found 396 significant SNP-SNP interactions among polymorphisms of immune-related genes that were present in both the U.S. and U.K. study populations. This exploratory study was conducted for the purpose of hypothesis generation, and thus has provided several new hypotheses that can be tested using traditional case-control study designs to obtain estimates of risk. This is the first study, to our knowledge, to take this novel approach to identifying SNP-SNP interactions relevant to glioma etiology. ©2011 AACR.

Application of Probabilistic Methods for the Determination of an Economically Robust HSCT Configuration

NASA Technical Reports Server (NTRS)

Mavris, Dimitri N.; Bandte, Oliver; Schrage, Daniel P.

1996-01-01

This paper outlines an approach for the determination of economically viable robust design solutions using the High Speed Civil Transport (HSCT) as a case study. Furthermore, the paper states the advantages of a probability based aircraft design over the traditional point design approach. It also proposes a new methodology called Robust Design Simulation (RDS) which treats customer satisfaction as the ultimate design objective. RDS is based on a probabilistic approach to aerospace systems design, which views the chosen objective as a distribution function introduced by so called noise or uncertainty variables. Since the designer has no control over these variables, a variability distribution is defined for each one of them. The cumulative effect of all these distributions causes the overall variability of the objective function. For cases where the selected objective function depends heavily on these noise variables, it may be desirable to obtain a design solution that minimizes this dependence. The paper outlines a step by step approach on how to achieve such a solution for the HSCT case study and introduces an evaluation criterion which guarantees the highest customer satisfaction. This customer satisfaction is expressed by the probability of achieving objective function values less than a desired target value.

On Problem of Synthesis of Control System for Quadrocopter

NASA Astrophysics Data System (ADS)

Larin, V. B.; Tunik, A. A.

2017-05-01

An algorithm for designing a control for a quadrocopter is given. Two cases of control of the horizontal motion of a vehicle are considered. Terminal location is given in one case, and cruise speed is given in the other case. The results are compared with those obtained by other authors

Thromboembolism Following Shoulder Arthroscopy

PubMed Central

Schick, Cameron W.; Westermann, Robert W.; Gao, Yubo; Abboud, Joseph A.; Wolf, Brian R.

2014-01-01

Background: Thromboembolism following shoulder arthroscopy is considered an uncommon complication, with fewer than 50 cases reported in the literature. Arthroscopy of the shoulder is one of the most commonly performed orthopaedic procedures, with low associated risks. Purpose: To identify potential risk factors for the development of venous thromboembolism (VTE) following shoulder arthroscopy and to determine the overall incidence of this complication. Study Design: Case-control study; Level of evidence, 3. Methods: A retrospective case-control review was performed of patients who developed symptomatic deep venous thrombosis (DVT) or pulmonary embolism (PE) following shoulder arthroscopy. Multiple surgeons from across North America were queried. For every case of DVT or PE identified, 2 control cases of shoulder arthroscopy were analyzed. The incidence of DVT/PE following shoulder arthroscopy was determined. A univariate analysis and a multivariate logistic regression model were conducted to identify any potential risk factors for the development of VTE following shoulder arthroscopy. Results: A total of 17 surgeons participated in this study and had performed a total of 15,033 cases of shoulder arthroscopy from September 2002 through August 2011. Eleven of the 17 participating surgeons had had a patient with a VTE complication during this time frame. The incidence of VTE in the 15,033 cases was 0.15%; 22 patients of the 15,033 patients had a DVT (n = 15) and/or PE (n = 8). Forty-four control cases were also analyzed. Univariate and multivariate analyses were performed. No significant risk factors were identified other than patient positioning. All cases and controls were positioned in the beach-chair position for surgery. Conclusion: The results of this study show that although rare, VTE occurs following shoulder arthroscopy at a rate of 0.15%. The variables analyzed in the cases of VTE compared with the control cases did not show any significant risk factors. All cases were positioned in the beach-chair position. Further analysis of future cases is warranted. PMID:26535285

A Conceptual Design Model for CBT Development: A NATO Case Study

ERIC Educational Resources Information Center

Kok, Ayse

2014-01-01

CBT (computer-based training) can benefit from the modern multimedia tools combined with network capabilities to overcame traditional education. The objective of this paper is focused on CBT development to improve strategic decision-making with regard to air command and control system for NATO staff in virtual environment. A conceptual design for…

Performance Appraisal in an Academic Library: A Case Study.

ERIC Educational Resources Information Center

George, Verna E.

Well-designed performance appraisals should provide employees with feedback concerning their performance, serve as a basis for modifying behavior toward more effective work habits, and provide managers with data which they can use to judge future job assignments and compensation. Poorly-designed ones, used as short-term control systems, can create…

Designing Case-Control Studies: Decisions About the Controls

PubMed Central

Hodge, Susan E.; Subaran, Ryan L.; Weissman, Myrna M.; Fyer, Abby J.

2014-01-01

The authors quantified, first, the effect of misclassified controls (i.e., individuals who are affected with the disease under study but who are classified as controls) on the ability of a case-control study to detect an association between a disease and a genetic marker, and second, the effect of leaving misclassified controls in the study, as opposed to removing them (thus decreasing sample size). The authors developed an informativeness measure of a study’s ability to identify real differences between cases and controls. They then examined this measure’s behavior when there are no misclassified controls, when there are misclassified controls, and when there were misclassified controls but they have been removed from the study. The results show that if, for example, 10% of controls are misclassified, the study’s informativeness is reduced to approximately 81% of what it would have been in a sample with no misclassified controls, whereas if these misclassified controls are removed from the study, the informativeness is only reduced to about 90%, despite the reduced sample size. If 25% are misclassified, those figures become approximately 56% and 75%, respectively. Thus, leaving the misclassified controls in the control sample is worse than removing them altogether. Finally, the authors illustrate how insufficient power is not necessarily circumvented by having an unlimited number of controls. The formulas provided by the authors enable investigators to make rational decisions about removing misclassified controls or leaving them in. PMID:22854929

Effects of Buckling Knockdown Factor, Internal Pressure and Material on the Design of Stiffened Cylinders

NASA Technical Reports Server (NTRS)

Lovejoy, Andrew E.; Hilburger, Mark W.; Chunchu, Prasad B.

2010-01-01

A design study was conducted to investigate the effect shell buckling knockdown factor (SBKF), internal pressure and aluminum alloy material selection on the structural weight of stiffened cylindrical shells. Two structural optimization codes were used for the design study to determine the optimum minimum-weight design for a series of design cases, and included an in-house developed genetic algorithm (GA) code and PANDA2. Each design case specified a unique set of geometry, material, knockdown factor combinations and loads. The resulting designs were examined and compared to determine the effects of SBKF, internal pressure and material selection on the acreage design weight and controlling failure mode. This design study shows that use of less conservative SBKF values, including internal pressure, and proper selection of material alloy can result in significant weight savings for stiffened cylinders. In particular, buckling-critical cylinders with integrally machined stiffener construction can benefit from the use of thicker plate material that enables taller stiffeners, even when the stiffness, strength and density properties of these materials appear to be inferior.

Co-Prevalence of Tremor with Spasmodic Dysphonia: A Case-Control Study

PubMed Central

White, Laura; Klein, Adam; Hapner, Edie; Delgaudio, John; Hanfelt, John; Jinnah, H. A.; Johns, Michael

2011-01-01

OBJECTIVES/HYPOTHESIS The aim of this study was to define the co-prevalence of tremor with spasmodic dysphonia (SD). STUDY DESIGN A single institution prospective, case-control study was performed from May 2010 to July 2010. METHODS Consecutive patients with SD (cases) and other voice disorders (controls) were enrolled prospectively. Each participant underwent a voice evaluation and an evaluation for tremor. RESULTS 146 voice disorder controls and 128 patients with SD were enrolled. 26% of patients with SD had vocal tremor, 21% had non-vocal tremor. Patients with SD were 2.8 times more likely to have co-prevalent tremor than the control group (OR = 2.81; 95% CI, 1.55 to 5.08) and only 35% of patients with SD had been seen by a neurologist for the evaluation of dystonia and tremor. CONCLUSIONS Tremor is highly prevalent in patients with SD. It is important for each patient diagnosed with SD to undergo an evaluation for tremor, this is especially important in patients diagnosed with vocal tremor. Level of evidence 3b. PMID:21792965

A re-evaluation of a case-control model with contaminated controls for resource selection studies

Treesearch

Christopher T. Rota; Joshua J. Millspaugh; Dylan C. Kesler; Chad P. Lehman; Mark A. Rumble; Catherine M. B. Jachowski

2013-01-01

A common sampling design in resource selection studies involves measuring resource attributes at sample units used by an animal and at sample units considered available for use. Few models can estimate the absolute probability of using a sample unit from such data, but such approaches are generally preferred over statistical methods that estimate a relative probability...

Promoting Distance Learners' Cognitive Engagement and Learning Outcomes: Design-Based Research in the Costa Rican National University of Distance Education

ERIC Educational Resources Information Center

Joo, K. P.; Andrés, Carmen; Shearer, Rick

2014-01-01

To explore effective learning design for students' cognitive engagement, a design-based case study was conducted in a quality control course in the Costa Rican National University of Distance Education between the 2011 and 2012 academic years. The course was revised for the 2012 provision in terms of the assignment structure, the number of…

Are steroids useful to treat cerebral venous thrombosis?

PubMed

Canhão, Patrícia; Cortesão, Ana; Cabral, Marta; Ferro, José M; Stam, Jan; Bousser, Marie-Germaine; Barinagarrementeria, Fernando

2008-01-01

No randomized controlled trial has evaluated the efficacy of steroids in acute cerebral venous thrombosis (CVT). We aimed to analyze the effect of steroids on the outcome of patients in the International Study on Cerebral Veins and Dural Sinus Thrombosis (ISCVT). ISCVT is a prospective observational study that included 624 CVT patients. Death or dependence at 6 months was compared between cases (patients treated with steroids) and controls (patients not treated with steroids), using 3 designs: (1) Matched case-control study (each case matched with a control for prognostic factors); (2) Nonmatched case-control study of the ISCVT cohort; (3) Case-control study in different strata according to the number of poor prognostic variables in each patient. One hundred and fifty (24%) patients were treated with steroids. (1) In the matched case-control study, poor outcome was similar in the two groups of patients (26/146 versus 17/149, OR=1.7; 95% CI 0.9 to 3.3, P=0.119). (2) In the ISCVT cohort, no significant difference in poor outcomes was found whether patients were treated with steroids or not (26/146 versus 60/469, OR=1.5; 95% CI 0.9 to 2.4). Patients without parenchymal lesions treated with steroids had worse prognosis than those treated without steroids (8/45 versus 9/184, OR=4.2, 95% CI 1.6 to 11.6, P=0.008). (3) Treatment with steroids was not associated with a better outcome in any strata of patients according to the number of poor prognostic factors. Steroids in the acute phase of CVT were not useful and were detrimental in patients without parenchymal cerebral lesions. These results do not support the use of steroids in CVT (evidence level III).

Sleep problems and suicide attempts among adolescents: a case-control study.

PubMed

Koyawala, Neel; Stevens, Jack; McBee-Strayer, Sandra M; Cannon, Elizabeth A; Bridge, Jeffrey A

2015-01-01

This study used a case-control design to compare sleep disturbances in 40 adolescents who attempted suicide with 40 never-suicidal adolescents. Using hierarchical logistic regression analyses, we found that self-reported nighttime awakenings were significantly associated with attempted suicide, after controlling for antidepressant use, antipsychotic use, affective problems, and being bullied. In a separate regression analysis, the parent-reported total sleep problems score also predicted suicide attempt status, controlling for key covariates. No associations were found between suicide attempts and other distinct sleep problems, including falling asleep at bedtime, sleeping a lot during the day, trouble waking up in the morning, sleep duration, and parent-reported nightmares. Clinicians should be aware of sleep problems as potential risk factors for suicide attempts for adolescents.

The HABP2 G534E Variant Is an Unlikely Cause of Familial Nonmedullary Thyroid Cancer

PubMed Central

Sahasrabudhe, Ruta; Stultz, Jacob; Williamson, John; Lott, Paul; Estrada, Ana; Bohorquez, Mabel; Palles, Claire; Polanco-Echeverry, Guadalupe; Jaeger, Emma; Martin, Lynn; Echeverry, Maria Magdalena; Tomlinson, Ian

2016-01-01

Context: A recent study reported the nonsynonymous G534E (rs7080536, allele A) variant in the HABP2 gene as causal in familial nonmedullary thyroid cancer (NMTC). Objective: The objective of this study was to evaluate the causality of HABP2 G534E in the TCUKIN study, a multicenter population-based study of NMTC cases from the British Isles. Design and Setting: A case-control analysis of rs7080536 genotypes was performed using 2105 TCUKIN cases and 5172 UK controls. Participants: Cases comprised 2105 NMTC cases. Patient subgroups with papillary (n = 1056), follicular (n = 691), and Hürthle cell (n = 86) thyroid cancer cases were studied separately. Controls comprised 5172 individuals from the 1958 Birth Cohort and the National Blood Donor Service study. The controls had previously been genotyped using genome-wide single nucleotide polymorphism arrays by the Wellcome Trust Case Control Consortium study. Outcome Measures: Association between HABP2 G534E (rs7080536A) and NMTC risk was evaluated using logistic regression. Results: The frequency of the HABP2 G534E was 4.2% in cases and 4.6% in controls. We did not detect an association between this variant and NMTC risk (odds ratio [OR] = 0.896; 95% confidence interval, 0.746–1.071; P = .233). We also failed to detect an association between the HABP2 G534E and cases with papillary (1056 cases; G534E frequency = 3.5%; OR = 0.74; P = .017), follicular (691 cases; G534E frequency = 4.7%; OR = 1.00; P = 1.000), or Hürthle cell (86 cases; G534E frequency = 6.3%; OR = 1.40; P = .279) histology. Conclusions: We found that HABP2 G534E is a low-to-moderate frequency variant in the British Isles and failed to detect an association with NMTC risk, independent of histological type. Hence, our study does not implicate HABP2 G534E or a correlated polymorphism in familial NMTC, and additional data are required before using this variant in NMTC risk assessment. PMID:26691890

Generalisability of vaccine effectiveness estimates: an analysis of cases included in a postlicensure evaluation of 13-valent pneumococcal conjugate vaccine in the USA

PubMed Central

Link-Gelles, Ruth; Westreich, Daniel; Aiello, Allison E; Shang, Nong; Weber, David J; Rosen, Jennifer B; Motala, Tasneem; Mascola, Laurene; Eason, Jeffery; Scherzinger, Karen; Holtzman, Corinne; Reingold, Arthur L; Barnes, Meghan; Petit, Susan; Farley, Monica M; Harrison, Lee H; Zansky, Shelley; Thomas, Ann; Schaffner, William; McGee, Lesley; Whitney, Cynthia G; Moore, Matthew R

2017-01-01

Objectives External validity, or generalisability, is the measure of how well results from a study pertain to individuals in the target population. We assessed generalisability, with respect to socioeconomic status, of estimates from a matched case–control study of 13-valent pneumococcal conjugate vaccine effectiveness for the prevention of invasive pneumococcal disease in children in the USA. Design Matched case–control study. Setting Thirteen active surveillance sites for invasive pneumococcal disease in the USA. Participants Cases were identified from active surveillance and controls were age and zip code matched. Outcome measures Socioeconomic status was assessed at the individual level via parent interview (for enrolled individuals only) and birth certificate data (for both enrolled and unenrolled individuals) and at the neighbourhood level by geocoding to the census tract (for both enrolled and unenrolled individuals). Prediction models were used to determine if socioeconomic status was associated with enrolment. Results We enrolled 54.6% of 1211 eligible cases and found a trend toward enrolled cases being more affluent than unenrolled cases. Enrolled cases were slightly more likely to have private insurance at birth (p=0.08) and have mothers with at least some college education (p<0.01). Enrolled cases also tended to come from more affluent census tracts. Despite these differences, our best predictive model for enrolment yielded a concordance statistic of only 0.703, indicating mediocre predictive value. Variables retained in the final model were assessed for effect measure modification, and none were found to be significant modifiers of vaccine effectiveness. Conclusions We conclude that although enrolled cases are somewhat more affluent than unenrolled cases, our estimates are externally valid with respect to socioeconomic status. Our analysis provides evidence that this study design can yield valid estimates and the assessing generalisability of observational data is feasible, even when unenrolled individuals cannot be contacted. PMID:28851801

Control selection and confounding factors: A lesson from a Japanese case-control study to examine acellular pertussis vaccine effectiveness.

PubMed

Ohfuji, Satoko; Okada, Kenji; Nakano, Takashi; Ito, Hiroaki; Hara, Megumi; Kuroki, Haruo; Hirota, Yoshio

2017-08-24

When using a case-control study design to examine vaccine effectiveness, both the selection of control subjects and the consideration of potential confounders must be the important issues to ensure accurate results. In this report, we described our experience from a case-control study conducted to evaluate the effectiveness of acellular pertussis vaccine combined with diphtheria-tetanus toxoids (DTaP vaccine). Newly diagnosed pertussis cases and age- and sex-matched friend-controls were enrolled, and the history of DTaP vaccination was compared between groups. Logistic regression models were used to calculate odds ratios (ORs) and 95% confidence intervals (CIs) of vaccination for development of pertussis. After adjustment for potential confounders, four doses of DTaP vaccination showed a lower OR for pediatrician-diagnosed pertussis (OR=0.11, 95% CI, 0.01-0.99). In addition, the decreasing OR of four doses vaccination was more pronounced for laboratory-confirmed pertussis (OR=0.07, 95%CI, 0.01-0.82). Besides, positive association with pertussis was observed in subjects with a history of steroid treatment (OR=5.67) and those with a recent contact with a lasting cough (OR=4.12). When using a case-control study to evaluate the effectiveness of vaccines, particularly those for uncommon infectious diseases such as pertussis, the use of friend-controls may be optimal due to the fact that they shared a similar experience for exposure to the pathogen as the cases. In addition, to assess vaccine effectiveness as accurately as possible, the effects of confounding should be adequately controlled with a matching or analysis technique. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Lower limb biomechanics during running in individuals with achilles tendinopathy: a systematic review

PubMed Central

2011-01-01

Background Abnormal lower limb biomechanics is speculated to be a risk factor for Achilles tendinopathy. This study systematically reviewed the existing literature to identify, critique and summarise lower limb biomechanical factors associated with Achilles tendinopathy. Methods We searched electronic bibliographic databases (Medline, EMBASE, Current contents, CINAHL and SPORTDiscus) in November 2010. All prospective cohort and case-control studies that evaluated biomechanical factors (temporospatial parameters, lower limb kinematics, dynamic plantar pressures, kinetics [ground reaction forces and joint moments] and muscle activity) associated with mid-portion Achilles tendinopathy were included. Quality of included studies was evaluated using the Quality Index. The magnitude of differences (effect sizes) between cases and controls was calculated using Cohen's d (with 95% CIs). Results Nine studies were identified; two were prospective and the remaining seven case-control study designs. The quality of 9 identified studies was varied, with Quality Index scores ranging from 4 to 15 out of 17. All studies analysed running biomechanics. Cases displayed increased eversion range of motion of the rearfoot (d = 0.92 and 0.67 in two studies), reduced maximum lower leg abduction (d = -1.16), reduced ankle joint dorsiflexion velocity (d = -0.62) and reduced knee flexion during gait (d = -0.90). Cases also demonstrated a number of differences in dynamic plantar pressures (primarily the distribution of the centre of force), ground reaction forces (large effects for timing variables) and also showed reduced peak tibial external rotation moment (d = -1.29). Cases also displayed differences in the timing and amplitude of a number of lower limb muscles but many differences were equivocal. Conclusions There are differences in lower limb biomechanics between those with and without Achilles tendinopathy that may have implications for the prevention and management of the condition. However, the findings need to be interpreted with caution due to the limited quality of a number of the included studies. Future well-designed prospective studies are required to confirm these findings. PMID:21619710

Using the entire history in the analysis of nested case cohort samples.

PubMed

Rivera, C L; Lumley, T

2016-08-15

Countermatching designs can provide more efficient estimates than simple matching or case-cohort designs in certain situations such as when good surrogate variables for an exposure of interest are available. We extend pseudolikelihood estimation for the Cox model under countermatching designs to models where time-varying covariates are considered. We also implement pseudolikelihood with calibrated weights to improve efficiency in nested case-control designs in the presence of time-varying variables. A simulation study is carried out, which considers four different scenarios including a binary time-dependent variable, a continuous time-dependent variable, and the case including interactions in each. Simulation results show that pseudolikelihood with calibrated weights under countermatching offers large gains in efficiency if compared to case-cohort. Pseudolikelihood with calibrated weights yielded more efficient estimators than pseudolikelihood estimators. Additionally, estimators were more efficient under countermatching than under case-cohort for the situations considered. The methods are illustrated using the Colorado Plateau uranium miners cohort. Furthermore, we present a general method to generate survival times with time-varying covariates. Copyright © 2016 John Wiley & Sons, Ltd. Copyright © 2016 John Wiley & Sons, Ltd.

CONTROL FUNCTION ASSISTED IPW ESTIMATION WITH A SECONDARY OUTCOME IN CASE-CONTROL STUDIES.

PubMed

Sofer, Tamar; Cornelis, Marilyn C; Kraft, Peter; Tchetgen Tchetgen, Eric J

2017-04-01

Case-control studies are designed towards studying associations between risk factors and a single, primary outcome. Information about additional, secondary outcomes is also collected, but association studies targeting such secondary outcomes should account for the case-control sampling scheme, or otherwise results may be biased. Often, one uses inverse probability weighted (IPW) estimators to estimate population effects in such studies. IPW estimators are robust, as they only require correct specification of the mean regression model of the secondary outcome on covariates, and knowledge of the disease prevalence. However, IPW estimators are inefficient relative to estimators that make additional assumptions about the data generating mechanism. We propose a class of estimators for the effect of risk factors on a secondary outcome in case-control studies that combine IPW with an additional modeling assumption: specification of the disease outcome probability model. We incorporate this model via a mean zero control function. We derive the class of all regular and asymptotically linear estimators corresponding to our modeling assumption, when the secondary outcome mean is modeled using either the identity or the log link. We find the efficient estimator in our class of estimators and show that it reduces to standard IPW when the model for the primary disease outcome is unrestricted, and is more efficient than standard IPW when the model is either parametric or semiparametric.

Job rotation designed to prevent musculoskeletal disorders and control risk in manufacturing industries: A systematic review.

PubMed

Padula, Rosimeire Simprini; Comper, Maria Luiza Caires; Sparer, Emily H; Dennerlein, Jack T

2017-01-01

To better understand job rotation in the manufacturing industry, we completed a systematic review asking the following questions: 1) How do job-rotation programs impact work-related musculoskeletal disorders (MSDs) and related risk control for these MSDs, as well as psychosocial factors? and 2) How best should the job rotation programs be designed? We searched MEDLINE, EMBASE, Business Source Premier, ISI Web of Knowledge, CINAHL, PsyINFO, Scopus, and SciELO databases for articles published in peer-reviewed journals. Eligible studies were examined by two independent reviewers for relevance (population of manufacturing workers, outcomes of musculoskeletal disorders, physical factors, psychosocial factors, and strategies used in job-rotation implantation) and methodological quality rating. From 10,809 potential articles, 71 were read for full text analysis. Of the 14 studies included for data extraction, two were non-randomized control trial studies, one was a case-control study, and 11 were cross-sectional comparisons. Only one, with a case-control design, was scored with good methodological quality. Currently, weak evidence exists supporting job rotation as a strategy for the prevention and control of musculoskeletal disorders. Job rotation did not appear to reduce the exposure of physical risk factors; yet, there are positive correlations between job rotation and higher job satisfaction. Worker training has been described as a crucial component of a successful job-rotation program. The studies reported a range of parameters used to implement and measure job-rotation programs. More rigorous studies are needed to better understand the full impact of job rotation on production and health. CRD42014013319. Copyright © 2016 Elsevier Ltd. All rights reserved.

Critical issues in ALS case-control studies: the case of the Euro-MOTOR study.

PubMed

D'Ovidio, Fabrizio; Rooney, James P K; Visser, Anne E; Vermeulen, Roel C H; Veldink, Jan H; Van Den Berg, Leonard H; Hardiman, Orla; Logroscino, Giancarlo; Chiò, Adriano; Beghi, Ettore

2017-08-01

Backround: Political and sociocultural differences between countries can affect the outcome of clinical and epidemiological studies in ALS. Cross-national studies represent the ideal process by which risk factors can be assessed using the same methodology in different geographical areas. A survey of three European countries (The Netherlands, Ireland and Italy) has been conducted in which incident ALS patients and matched controls were recruited in a population-based study based on age, gender and area of residency, under the Euro-MOTOR systems biology programme of research. We have identified strengths and limitations during the trajectory of the Euro-MOTOR study, from the research design to data analysis. We have analysed the implications of factors including cross-national differences in healthcare systems, sample size, types of matching, the definition of exposures and statistical analysis. Addressing critical methodological aspects of the design of the Euro-MOTOR project minimises bias and will facilitate scientific assessment of the independent role of well-defined exposures.

Neuromuscular assessment in elderly workers with and without work related shoulder/neck trouble: the NEW-study design and physiological findings.

PubMed

Sjøgaard, G; Søgaard, K; Hermens, H J; Sandsjö, L; Läubli, T; Thorn, S; Vollenbroek-Hutten, M M R; Sell, L; Christensen, H; Klipstein, A; Kadefors, R; Merletti, R

2006-01-01

Musculoskeletal disorders in the neck and shoulder area are a major occupational concern in the European countries especially among elderly females. The aim was to assess these disorders based on quantitative EMG indicators and functional tests. 252 female computer users (45-68 years) were recruited from four European countries in two contrast groups: (1) 88 neck/shoulder (NS) cases reporting trouble in the neck and/or shoulder region for more than 30 days during the last year, and (2) 164 NS-controls reporting such trouble for no more than 7 days. Questionnaires, functional/clinical tests, and physiological recordings were performed in workplace related field studies. The results showed no differences in anthropometrics but NS-cases reported more strained head positions and more eye problems than controls. The psychosocial working factors were similar, although, NS-controls had slightly better scores on working conditions, general health, and vitality compared to cases. The NS-cases had lower maximal voluntary contraction (MVC) during shoulder elevation (mean (SD) 310 (122) N) compared to the controls (364 (122) N). During 30% MVC electromyography (EMGrms) in the trapezius muscle was lower in NS-cases (194 (105) muV) than in controls (256 (169) muV), while no differences were found regarding endurance time. Estimated conduction velocity was not different between NS-cases and -controls. Four functional computer tests were performed equally well by NS-cases and -controls, and the corresponding EMG variables also did not differ. A major finding in this large-scale epidemiological study is the significantly lower MVC in NS-cases compared with NS-controls together with lower EMGrms value at 30% MVC, while computer tasks were performed at similar relative muscle activation. The study was unable to reveal quantitative EMG indicators and functional tests that could objectively assess disorders in NS-cases.

A novel framework for virtual prototyping of rehabilitation exoskeletons.

PubMed

Agarwal, Priyanshu; Kuo, Pei-Hsin; Neptune, Richard R; Deshpande, Ashish D

2013-06-01

Human-worn rehabilitation exoskeletons have the potential to make therapeutic exercises increasingly accessible to disabled individuals while reducing the cost and labor involved in rehabilitation therapy. In this work, we propose a novel human-model-in-the-loop framework for virtual prototyping (design, control and experimentation) of rehabilitation exoskeletons by merging computational musculoskeletal analysis with simulation-based design techniques. The framework allows to iteratively optimize design and control algorithm of an exoskeleton using simulation. We introduce biomechanical, morphological, and controller measures to quantify the performance of the device for optimization study. Furthermore, the framework allows one to carry out virtual experiments for testing specific "what-if" scenarios to quantify device performance and recovery progress. To illustrate the application of the framework, we present a case study wherein the design and analysis of an index-finger exoskeleton is carried out using the proposed framework.

Learning-based position control of a closed-kinematic chain robot end-effector

NASA Technical Reports Server (NTRS)

Nguyen, Charles C.; Zhou, Zhen-Lei

1990-01-01

A trajectory control scheme whose design is based on learning theory, for a six-degree-of-freedom (DOF) robot end-effector built to study robotic assembly of NASA hardwares in space is presented. The control scheme consists of two control systems: the feedback control system and the learning control system. The feedback control system is designed using the concept of linearization about a selected operating point, and the method of pole placement so that the closed-loop linearized system is stabilized. The learning control scheme consisting of PD-type learning controllers, provides additional inputs to improve the end-effector performance after each trial. Experimental studies performed on a 2 DOF end-effector built at CUA, for three tracking cases show that actual trajectories approach desired trajectories as the number of trials increases. The tracking errors are substantially reduced after only five trials.

Jiangsu Four Cancers Study: a large case-control study of lung, liver, stomach, and esophageal cancers in Jiangsu Province, China.

PubMed

Zhao, Jin-Kou; Wu, Ming; Kim, Claire H; Jin, Zi-Yi; Zhou, Jin-Yi; Han, Ren-Qiang; Yang, Jie; Zhang, Xiao-Feng; Wang, Xu-Shan; Liu, Ai-Ming; Gu, Xiaoping; Su, Ming; Hu, Xu; Sun, Zheng; Li, Gang; Li, Liming; Mu, Lina; Zhang, Zuo-Feng

2017-07-01

Cancer is a major public health burden both globally and in China. The most common cancer-related deaths in China are attributable to cancers of the lung, liver, stomach, and esophagus. Previous epidemiologic studies on cancer in China have often been limited by small sample sizes, inconsistent measurements, and lack of precise and accurate data. The Jiangsu Four Cancers (JFC) Study is a population-based case-control study carried out in an effort to obtain consistent and high-quality data to investigate the life style, behavioral, environmental, and genetic factors associated with the four major cancers in China. The aim of this paper is to describe the overall design of the JFC Study and report selected findings on the major risk factors for cancers. Epidemiologic data were collected from 2003 to 2010 through in-person interviews using a structured questionnaire and blood samples were drawn. Unconditional logistic regression was used to estimate the associations of putative risk factors with risks of cancers of the lung, liver, stomach, and esophagus. The study included 2871 lung cancer cases, 2018 liver cancer cases, 2969 esophageal cancer cases, 2216 stomach cancer cases, and 8019 community controls. Low educational level, low income level, tobacco smoking, alcohol drinking, and family history of cancer were confirmed as risk factors for these major cancers. The JFC Study is one of the largest case-control studies of cancers in the Chinese population and will serve as a rich resource for future research on the four major cancers in China.

Stall Flutter Control of a Smart Blade Section Undergoing Asymmetric Limit Oscillations

DOE PAGES

Li, Nailu; Balas, Mark J.; Nikoueeyan, Pourya; ...

2016-01-01

Stall flutter is an aeroelastic phenomenon resulting in unwanted oscillatory loads on the blade, such as wind turbine blade, helicopter rotor blade, and other flexible wing blades. While the stall flutter and related aeroelastic control have been studied theoretically and experimentally, microtab control of asymmetric limit cycle oscillations (LCOs) in stall flutter cases has not been generally investigated. This paper presents an aeroservoelastic model to study the microtab control of the blade section undergoing moderate stall flutter and deep stall flutter separately. The effects of different dynamic stall conditions and the consequent asymmetric LCOs for both stall cases are simulatedmore » and analyzed. Then, for the design of the stall flutter controller, the potential sensor signal for the stall flutter, the microtab control capability of the stall flutter, and the control algorithm for the stall flutter are studied. Lastly, the improvement and the superiority of the proposed adaptive stall flutter controller are shown by comparison with a simple stall flutter controller.« less

Maternal DNA hypomethylation and congenital heart defects

PubMed Central

Chowdhury, Shimul; Cleves, Mario A.; MacLeod, Stewart L.; James, S. Jill; Zhao, Weizhi; Hobbs, Charlotte A.

2011-01-01

Background Congenital heart defects (CHDs) are among the most prevalent and serious of birth defects. Multiple maternal factors are thought to contribute to CHD development including folate intake. Maternal DNA methylation, which is dependent on folate metabolism, may impact the risk of CHDs. Objective Our study was designed to determine whether maternal long interspersed nucleotide elements-1 (LINE-1) DNA hypomethylation is associated with increased occurrence of non-syndromic CHDs and whether maternal folate-dependent metabolites are correlated with DNA methylation status. Design Using a case-control study design, we measured global DNA methylation status among mothers whose pregnancies were affected by non-syndromic CHDs (n=180) and mothers of unaffected pregnancies (n=187). Methylation of LINE-1 was used as a surrogate marker of global DNA methylation status. The association between DNA methylation and CHD risk was determined while adjusting for selected lifestyle factors. Results LINE-1 DNA methylation was significantly lower in cases compared with controls (p=0.049). After covariate adjustments, a significant difference between cases and controls remained (p=0.010). Among women with LINE-1 methylation in the lowest decile of DNA methylation, the estimated risk of having a CHD-affected pregnancy was almost twice that of women in all other deciles (OR=1.91; 95% CI: 1.03, 3.58). Conclusions Our findings indicate that maternal LINE-1 DNA hypomethylation is associated with an increased risk of CHDs. Future studies investigating the association between maternal DNA methylation patterns and CHDs should be pursued. PMID:21254366

Energy absorption in aluminum extrusions for a spaceframe chassis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Logan, R.W.; Perfect, S.A.; Parkinson, R.D.

1994-09-19

This work describes the design, finite-element analysis, and verifications performed by LLNL and Kaiser Aluminum for the prototype design of the CALSTART Running Chassis purpose-built electric vehicle. Component level studies, along with our previous experimental and finite-element works, provided the confidence to study the crashworthiness of a complete aluminum spaceframe. Effects of rail geometry, size, and thickness were studied in order to achieve a controlled crush of the front end structure. These included the performance of the spaceframe itself, and the additive effects of the powertrain cradle and powertrain (motor/controller in this case) as well as suspension. Various design iterationsmore » for frontal impact at moderate and high speed are explored.« less

Exposure enriched outcome dependent designs for longitudinal studies of gene-environment interaction.

PubMed

Sun, Zhichao; Mukherjee, Bhramar; Estes, Jason P; Vokonas, Pantel S; Park, Sung Kyun

2017-08-15

Joint effects of genetic and environmental factors have been increasingly recognized in the development of many complex human diseases. Despite the popularity of case-control and case-only designs, longitudinal cohort studies that can capture time-varying outcome and exposure information have long been recommended for gene-environment (G × E) interactions. To date, literature on sampling designs for longitudinal studies of G × E interaction is quite limited. We therefore consider designs that can prioritize a subsample of the existing cohort for retrospective genotyping on the basis of currently available outcome, exposure, and covariate data. In this work, we propose stratified sampling based on summaries of individual exposures and outcome trajectories and develop a full conditional likelihood approach for estimation that adjusts for the biased sample. We compare the performance of our proposed design and analysis with combinations of different sampling designs and estimation approaches via simulation. We observe that the full conditional likelihood provides improved estimates for the G × E interaction and joint exposure effects over uncorrected complete-case analysis, and the exposure enriched outcome trajectory dependent design outperforms other designs in terms of estimation efficiency and power for detection of the G × E interaction. We also illustrate our design and analysis using data from the Normative Aging Study, an ongoing longitudinal cohort study initiated by the Veterans Administration in 1963. Copyright © 2017 John Wiley & Sons, Ltd. Copyright © 2017 John Wiley & Sons, Ltd.

Aerodynamic Shape Optimization of Supersonic Aircraft Configurations via an Adjoint Formulation on Parallel Computers

NASA Technical Reports Server (NTRS)

Reuther, James; Alonso, Juan Jose; Rimlinger, Mark J.; Jameson, Antony

1996-01-01

This work describes the application of a control theory-based aerodynamic shape optimization method to the problem of supersonic aircraft design. The design process is greatly accelerated through the use of both control theory and a parallel implementation on distributed memory computers. Control theory is employed to derive the adjoint differential equations whose solution allows for the evaluation of design gradient information at a fraction of the computational cost required by previous design methods. The resulting problem is then implemented on parallel distributed memory architectures using a domain decomposition approach, an optimized communication schedule, and the MPI (Message Passing Interface) Standard for portability and efficiency. The final result achieves very rapid aerodynamic design based on higher order computational fluid dynamics methods (CFD). In our earlier studies, the serial implementation of this design method was shown to be effective for the optimization of airfoils, wings, wing-bodies, and complex aircraft configurations using both the potential equation and the Euler equations. In our most recent paper, the Euler method was extended to treat complete aircraft configurations via a new multiblock implementation. Furthermore, during the same conference, we also presented preliminary results demonstrating that this basic methodology could be ported to distributed memory parallel computing architectures. In this paper, our concern will be to demonstrate that the combined power of these new technologies can be used routinely in an industrial design environment by applying it to the case study of the design of typical supersonic transport configurations. A particular difficulty of this test case is posed by the propulsion/airframe integration.

A Pilot Study to Examine Maturation of Body Temperature Control in Preterm Infants

PubMed Central

Knobel, Robin B.; Levy, Janet; Katz, Laurence; Guenther, Bob; Holditch-Davis, Diane

2013-01-01

Objective To test instrumentation and develop analytic models to use in a larger study to examine developmental trajectories of body temperature and peripheral perfusion from birth in extremely low birth weight (EBLW) infants. Design A case study design. Setting The study took place in a level four neonatal intensive care unit (NICU) in North Carolina. Participants Four ELBW infants, less than 29 weeks gestational age at birth. Methods Physiologic data were measured every minute for the first 5 days of life: peripheral perfusion using perfusion index by Masimo and body temperature using thermistors. Body temperature was also measured using infrared thermal imaging. Stimulation and care events were recorded over the first 5 days using video which was coded with Noldus Observer software. Novel analytical models using the state space approach to time series analysis were developed to explore maturation of neural control over central and peripheral body temperature. Results/Conclusion Results from this pilot study confirmed the feasibility of using multiple instruments to measure temperature and perfusion in ELBW infants. This approach added rich data to our case study design and set a clinical context with which to interpret longitudinal physiological data. PMID:24004312

Active vibration absorber for CSI evolutionary model: Design and experimental results

NASA Technical Reports Server (NTRS)

Bruner, Anne M.; Belvin, W. Keith; Horta, Lucas G.; Juang, Jer-Nan

1991-01-01

The development of control of large flexible structures technology must include practical demonstration to aid in the understanding and characterization of controlled structures in space. To support this effort, a testbed facility was developed to study practical implementation of new control technologies under realistic conditions. The design is discussed of a second order, acceleration feedback controller which acts as an active vibration absorber. This controller provides guaranteed stability margins for collocated sensor/actuator pairs in the absence of sensor/actuator dynamics and computational time delay. The primary performance objective considered is damping augmentation of the first nine structural modes. Comparison of experimental and predicted closed loop damping is presented, including test and simulation time histories for open and closed loop cases. Although the simulation and test results are not in full agreement, robustness of this design under model uncertainty is demonstrated. The basic advantage of this second order controller design is that the stability of the controller is model independent.

Pattern-Based Design of Insider Threat Programs

DTIC Science & Technology

2014-12-01

also applied these models to develop best practices and technical controls for mitigating insider threat. In some cases of in- sider threat...departing insiders might take valuable IP with them. One set of practices and controls designed to reduce the risk of insider IP theft is based on case data...describing this set of practices and controls helps to balance the costs of monitoring employee behavior for suspicious actions against the risk of

Identifying Etiological Agents Causing Diarrhea in Low Income Ecuadorian Communities

PubMed Central

Vasco, Gabriela; Trueba, Gabriel; Atherton, Richard; Calvopiña, Manuel; Cevallos, William; Andrade, Thamara; Eguiguren, Martha; Eisenberg, Joseph N. S.

2014-01-01

Continued success in decreasing diarrheal disease burden requires targeted interventions. To develop such interventions, it is crucial to understand which pathogens cause diarrhea. Using a case-control design we tested stool samples, collected in both rural and urban Ecuador, for 15 pathogenic microorganisms. Pathogens were present in 51% of case and 27% of control samples from the urban community, and 62% of case and 18% of control samples collected from the rural community. Rotavirus and Shigellae were associated with diarrhea in the urban community; co-infections were more pathogenic than single infection; Campylobacter and Entamoeba histolytica were found in large numbers in cases and controls; and non-typhi Salmonella and enteropathogenic Escherichia coli were not found in any samples. Consistent with the Global Enteric Multicenter Study, focused in south Asia and sub-Saharan Africa, we found that in Ecuador a small group of pathogens accounted for a significant amount of the diarrheal disease burden. PMID:25048373

Identification of patients with gout: elaboration of a questionnaire for epidemiological studies.

PubMed

Richette, P; Clerson, P; Bouée, S; Chalès, G; Doherty, M; Flipo, R M; Lambert, C; Lioté, F; Poiraud, T; Schaeverbeke, T; Bardin, T

2015-09-01

In France, the prevalence of gout is currently unknown. We aimed to design a questionnaire to detect gout that would be suitable for use in a telephone survey by non-physicians and assessed its performance. We designed a 62-item questionnaire covering comorbidities, clinical features and treatment of gout. In a case-control study, we enrolled patients with a history of arthritis who had undergone arthrocentesis for synovial fluid analysis and crystal detection. Cases were patients with crystal-proven gout and controls were patients who had arthritis and effusion with no monosodium urate crystals in synovial fluid. The questionnaire was administered by phone to cases and controls by non-physicians who were unaware of the patient diagnosis. Logistic regression analysis and classification and regression trees were used to select items discriminating cases and controls. We interviewed 246 patients (102 cases and 142 controls). Two logistic regression models (sensitivity 88.0% and 87.5%; specificity 93.0% and 89.8%, respectively) and one classification and regression tree model (sensitivity 81.4%, specificity 93.7%) revealed 11 informative items that allowed for classifying 90.0%, 88.8% and 88.5% of patients, respectively. We developed a questionnaire to detect gout containing 11 items that is fast and suitable for use in a telephone survey by non-physicians. The questionnaire demonstrated good properties for discriminating patients with and without gout. It will be administered in a large sample of the general population to estimate the prevalence of gout in France. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

Systematic review of sensory integration therapy for individuals with disabilities: Single case design studies.

PubMed

Leong, H M; Carter, Mark; Stephenson, Jennifer

2015-12-01

Sensory integration therapy (SIT) is a controversial intervention that is widely used for people with disabilities. Systematic analysis was conducted on the outcomes of 17 single case design studies on sensory integration therapy for people with, or at-risk of, a developmental or learning disability, disorder or delay. An assessment of the quality of methodology of the studies found most used weak designs and poor methodology, with a tendency for higher quality studies to produce negative results. Based on limited comparative evidence, functional analysis-based interventions for challenging behavior were more effective that SIT. Overall the studies do not provide convincing evidence for the efficacy of sensory integration therapy. Given the findings of the present review and other recent analyses it is advised that the use of SIT be limited to experimental contexts. Issues with the studies and possible improvements for future research are discussed including the need to employ designs that allow for adequate demonstration of experimental control. Copyright © 2015 Elsevier Ltd. All rights reserved.

Full Envelope Reconfigurable Control Design for the X-33 Vehicle

NASA Technical Reports Server (NTRS)

Cotting, M. Christopher; Burken, John J.; Lee, Seung-Hee (Technical Monitor)

2001-01-01

In the event of a control surface failure, the purpose of a reconfigurable control system is to redistribute the control effort among the remaining working surfaces such that satisfactory stability and performance are retained. An Off-line Nonlinear General Constrained Optimization (ONCO) approach was used for the reconfigurable X-33 control design method. Three example failures are shown using a high fidelity 6 DOF simulation (case I ascent with a left body flap jammed at 25 deg.; case 2 entry with a right inboard elevon jam at 25 deg.; and case 3, landing (TAEM) with a left rudder jam at -30 deg.) Failure comparisons between responses with the nominal controller and reconfigurable controllers show the benefits of reconfiguration. Single jam aerosurface failures were considered, and failure detection and identification is considered accomplished in the actuator controller. The X-33 flight control system will incorporate reconfigurable flight control in the baseline system.

Long term outcome of neonatal meningitis

PubMed Central

Stevens, J; Eames, M; Kent, A; Halket, S; Holt, D; Harvey, D

2003-01-01

Objectives: To quantify long term impairment after neonatal meningitis. Design: Longitudinal case-control study over 9–10 years. Subjects and methods: A total of 111 children who had suffered neonatal meningitis were seen and compared with 113 matched controls from their birth hospital and 49 controls from general practices. Assessments included the WISC IIIUK , movement assessment battery for children (mABC), audiometry, vision testing, and social and medical data. Statistical analysis was by multiple regression, analysis of variance, and χ2 tests. Results: Some 10.8% of cases had a severe and 9% a moderate overall outcome compared with 0% and 1.8% for the hospital controls. The mean intelligence quotient (IQ) of the cases (88.8) was significantly less than that of the hospital controls (99.4) or the GP controls (99.6) . The mABC score was significantly worse for the cases (7.08) than the hospital (5) or GP (4) controls. Some 3.6% of cases had sensorineural hearing loss, 2.7% had persisting hydrocephalus; no controls did. Some 5.4% of cases and 1.7% of hospital controls had treatment for seizures. Conclusions: Severe neurodisability and milder motor and psychometric impairment result from neonatal meningitis. Both clinical follow up and comprehensive developmental assessment are needed after this disease. PMID:12719389

Risk factors and study designs used in research of youths' suicide behaviour-an epidemiological discussion with focus on level of evidence.

PubMed

Christiansen, Erik; Larsen, Kim Juul; Agerbo, Esben; Bilenberg, Niels; Stenager, Elsebeth

2014-11-01

Abstract Introduction: Many different epidemiology study designs have been used to analyse risk factors for suicide behaviour. The purpose of this study was to obtain an insight into the current study design used in research on youths' risk factors for suicide behaviour and to rank the studies according to level of evidence (LoE). We searched PubMed and psycINFO in order to identify relevant individual studies. We included 36 studies of children and youth on suicidal behaviour and ideation-many rank low on LoE. For suicide, cohort design was often used, and mental illness (depression, substance abuse and severity of mental illness) was the most common risk factor. Cohort studies are ranked 2b, which is high according to LoE. For suicide attempts, survey was often used, and psychopathology, substance abuse and being exposed to suicidal behaviour were the most common risk factors. For suicidal ideation, survey was the only design used, and substance abuse and psychopathology the most common risk factors. Surveys are ranked 4, which are low according to LoE. Many risk factors were broad and unspecific, and standard definitions of outcome and exposure were rarely used. A good study of risk factors for suicidal behaviour would need a high LoE, as a high-powered longitudinal epidemiological study (cohort or case-control) of very specific risk factors. The factors would have high prevention potential, compared with more broad and unspecific risk factors, to which many people are exposed. We would recommend a cohort design (in high-risk populations) or a case-control design to identify risk factors, using clinical and/or register data instead of self-reported information, reporting adjusted estimates and using standard definition of suicidal outcome and risk factors.

[Design requirements for clinical trials on re-evaluation of safety and efficacy of post-marketed Chinese herbs].

PubMed

Xie, Yanming; Wei, Xu

2011-10-01

Re-evaluation of post-marketed based on pharmacoepidemiology is to study and collect clinical medicine safety in large population under practical applications for a long time. It is necessary to conduct re-evaluation of clinical effectiveness because of particularity of traditional Chinese medicine (TCM). Right before carrying out clinical trials on re-evaluation of post-marketed TCM, we should determine the objective of the study and progress it in the assessment mode of combination of disease and syndrome. Specical population, involving children and seniors who were excluded in pre-marketed clinical trial, were brought into drug monitoring. Sample size needs to comply with statistical requirement. We commonly use cohort study, case-control study, nested case-control, pragmatic randomized controlled trials.

Risk factors for tuberculosis among health care workers in South India: a nested case-control study.

PubMed

Mathew, Anoop; David, Thambu; Thomas, Kurien; Kuruvilla, P J; Balaji, V; Jesudason, Mary V; Samuel, Prasanna

2013-01-01

The epidemiology of tuberculosis (TB) among health care workers (HCWs) in India remains under-researched. This study is a nested case-control design assessing the risk factors for acquiring TB among HCWs in India. It is a nested case-control study conducted at a tertiary teaching hospital in India. Cases (n = 101) were HCWs with active TB. Controls (n = 101) were HCWs who did not have TB, randomly selected from the 6,003 subjects employed at the facility. Cases and controls were compared with respect to clinical and demographic variables. The cases and controls were of similar age. Logistic regression analysis showed that body mass index (BMI) <19 kg/m(2) (odds ratio [OR]: 2.96, 95% confidence interval [CI]: 1.49-5.87), having frequent contact with patients (OR: 2.83, 95% CI: 1.47-5.45) and being employed in medical wards (OR: 12.37, 95% CI: 1.38-110.17) or microbiology laboratories (OR: 5.65, 95% CI: 1.74-18.36) were independently associated with increased risk of acquiring TB. HCWs with frequent patient contact and those with BMI <19 kg/m(2) were at high risk of acquiring active TB. Nosocomial transmission of TB was pronounced in locations, such as medical wards and microbiology laboratories. Surveillance of high-risk HCWs and appropriate infrastructure modifications may be important to prevent interpersonal TB transmission in health care facilities. Copyright © 2013 Elsevier Inc. All rights reserved.

Influenza vaccine effectiveness estimates in the Dutch population from 2003 to 2014: The test-negative design case-control study with different control groups.

PubMed

van Doorn, Eva; Darvishian, Maryam; Dijkstra, Frederika; Donker, Gé A; Overduin, Pieter; Meijer, Adam; Hak, Eelko

2017-05-15

Information about influenza vaccine effectiveness (IVE) is important for vaccine strain selection and immunization policy decisions. The test-negative design (TND) case-control study is commonly used to obtain IVE estimates. However, the definition of the control patients may influence IVE estimates. We have conducted a TND study using the Dutch Sentinel Practices of NIVEL Primary Care Database which includes data from patients who consulted the General Practitioner (GP) for an episode of acute influenza-like illness (ILI) or acute respiratory infection (ARI) with known influenza vaccination status. Cases were patients tested positive for influenza virus. Controls were grouped into those who tested (1) negative for influenza virus (all influenza negative), (2) negative for influenza virus, but positive for respiratory syncytial virus, rhinovirus or enterovirus (non-influenza virus positive), and (3) negative for these four viruses (pan-negative). We estimated the IVE over all epidemic seasons from 2003/2004 through 2013/2014, pooled IVE for influenza vaccine partial/full matched and mismatched seasons and the individual seasons using generalized linear mixed-effect and multiple logistic regression models. The overall IVE adjusted for age, GP ILI/ARI diagnosis, chronic disease and respiratory allergy was 35% (95% CI: 15-48), 64% (95% CI: 49-75) and 21% (95% CI: -1 to 39) for all influenza negative, non-influenza virus positive and pan-negative controls, respectively. In both the main and subgroup analyses IVE estimates were the highest using non-influenza virus positive controls, likely due to limiting inclusion of controls without laboratory-confirmation of a virus causing the respiratory disease. Copyright © 2017 Elsevier Ltd. All rights reserved.

A Performance Management Framework for Civil Engineering

DTIC Science & Technology

1990-09-01

cultural change. A non - equivalent control group design was chosen to augment the case analysis. Figure 3.18 shows the form of the quasi-experiment. The...The non - equivalent control group design controls the following obstacles to internal validity: history, maturation, testing, and instrumentation. The...and Stanley, 1963:48,50) Table 7. Validity of Quasi-Experiment The non - equivalent control group experimental design controls the following obstacles to

Human Engineering of Space Vehicle Displays and Controls

NASA Technical Reports Server (NTRS)

Whitmore, Mihriban; Holden, Kritina L.; Boyer, Jennifer; Stephens, John-Paul; Ezer, Neta; Sandor, Aniko

2010-01-01

Proper attention to the integration of the human needs in the vehicle displays and controls design process creates a safe and productive environment for crew. Although this integration is critical for all phases of flight, for crew interfaces that are used during dynamic phases (e.g., ascent and entry), the integration is particularly important because of demanding environmental conditions. This panel addresses the process of how human engineering involvement ensures that human-system integration occurs early in the design and development process and continues throughout the lifecycle of a vehicle. This process includes the development of requirements and quantitative metrics to measure design success, research on fundamental design questions, human-in-the-loop evaluations, and iterative design. Processes and results from research on displays and controls; the creation and validation of usability, workload, and consistency metrics; and the design and evaluation of crew interfaces for NASA's Crew Exploration Vehicle are used as case studies.

Risk of Liver Injury Associated with Chinese Herbal Products Containing Radix bupleuri in 639,779 Patients with Hepatitis B Virus Infection

PubMed Central

Lee, Chang-Hsing; Wang, Jung-Der; Chen, Pau-Chung

2011-01-01

Background Chinese herbal products (CHPs) containing Radix bupleuri are often prescribed for chronic hepatitis. There have been no epidemiological studies in populations with hepatitis B virus (HBV) infection. Our study was conducted to determine the association between the use of CHPs containing Radix bupleuri and the risk of hospitalisation related to liver injury among HBV-infected patients in Taiwan. Methods From a total of 639,779 patients with diagnoses related to HBV infection, we included hospitalised adult cases with a primary diagnosis of liver injury in the database of Taiwan's national health insurance during the period 1997–2004. Case-control and case-crossover designs were used to assess the risk of hospitalisation with conditional logistic regression models constructed and adjusted for 270 conventionally hepatotoxic drugs. Cumulative doses of these CHPs and Radix bupleuri were assessed for any dose-response relationship. Findings In total, we collected 1,080 cases fulfilled the inclusion criteria. In the case-control design, the adjusted odds ratio was 1.90 (95% confidence interval [CI]: 1.30 to 2.77). The risks from prescribing the CHPs Xiao-Chai-Hu-Tang and Long-Dan-Xie-Gan-Tang were significantly high, and dose-response relationships were found. The risk of adding each 19 gm dose of Radix bupleuri was 2.19 (95% CI: 1.66 to 2.89). The results using the case-crossover design remained similar. Conclusions Prescribing Xiao-Chai-Hu-Tang, Long-Dan-Xie-Gan-Tang, or CHPs containing more than 19 gram of Radix bupleuri in HBV-infected patients might increase their risks of liver injury. Further studies are indicated to corroborate the above findings. PMID:21264326

Does Cannabis Onset Trigger Cocaine Onset? A Case-Crossover Approach

PubMed Central

O’Brien, Megan S.; Comment, Leah Andrews; Liang, Kung Yee; Anthony, James C.

2016-01-01

Psychiatric researchers tend to select the discordant co-twin design when they seek to hold constant genetic influence while estimating exposure-associated disease risk. The epidemiologic case-crossover research design developed for the past two decades represents a viable alternative, not often seen in psychiatric studies. Here, we turn to the epidemiologic case-crossover approach to examine the idea that cannabis onset is a proximal trigger for cocaine use, with the power of ‘subject-as-own-control’ research used to hold constant antecedent characteristics of the individual drug user, including genetic influence and other traits experienced up to the time of the observed hazard and control intervals. Data are from newly incident cocaine users identified in the 2002–2006 U.S. National Surveys on Drug Use and Health. Among these cocaine users, 48 had both cannabis onset and cocaine onset in the same month-long hazard interval; the expected value is 30 users, based on the control interval we had pre-specified for case-crossover estimation (estimated relative risk, RR = 1.6; exact mid-p = 0.042). Within the framework of a subject-as-own-control design, the evidence is consistent with the hypothesis that cannabis onset is a proximal trigger for cocaine use, with genetic influences (and many environmental conditions and processes) held constant. Limitations are noted and implications discussed. PMID:22228642

Injury case-control studies using "other injuries" as controls.

PubMed

Marshall, Stephen W

2008-03-01

Studies of event-related (or "event-phase") interventions (such as ski helmets) can address injury at a specific body site (such as the head) by using as controls a group of people who experienced the same event (fall) and suffered injuries at other body sites (other than the head). The research question addressed by this type of study is the effect of an exposure or intervention (helmet) during the event phase (fall) of the causal chain. However, this is a valid case-control design only if the controls (skiers with other injuries) provide a reasonable proxy for the prevalence of exposure (helmet-wearing) in the underlying event-phase source population (skiers who fell). This assumption needs to be carefully assessed. Factors associated with both helmet-wearing and injury given a fall (eg, previous injury history, skiing inexperience, or risk-taking behavior) have considerable potential to create bias.

Facilitating Case Studies in Massage Therapy Clinical Education

PubMed Central

Baskwill, Amanda

2013-01-01

The integration of evidence into reflective health care practice has been on the rise in recent years and is a phenomenon that has affected all health care professions, including massage therapy. Clinical case studies are a research design that follows one patient or subject, making the studies ideal for use in clinical practice. They are valuable for communicating information from clinical practice to the broader community. Case studies have face validity that may be more valuable to individual practitioners than homogeneous randomized controlled trials, as the practitioner may recognize a complex patient in the case report. At Humber College, Student Massage Therapists (SMTs) create, conduct, and communicate results of a clinical case study prior to graduation. This article describes the process and experience. PMID:23730397

Linear Parameter Varying Control Synthesis for Actuator Failure, Based on Estimated Parameter

NASA Technical Reports Server (NTRS)

Shin, Jong-Yeob; Wu, N. Eva; Belcastro, Christine

2002-01-01

The design of a linear parameter varying (LPV) controller for an aircraft at actuator failure cases is presented. The controller synthesis for actuator failure cases is formulated into linear matrix inequality (LMI) optimizations based on an estimated failure parameter with pre-defined estimation error bounds. The inherent conservatism of an LPV control synthesis methodology is reduced using a scaling factor on the uncertainty block which represents estimated parameter uncertainties. The fault parameter is estimated using the two-stage Kalman filter. The simulation results of the designed LPV controller for a HiMXT (Highly Maneuverable Aircraft Technology) vehicle with the on-line estimator show that the desired performance and robustness objectives are achieved for actuator failure cases.

Design considerations for case series models with exposure onset measurement error.

PubMed

Mohammed, Sandra M; Dalrymple, Lorien S; Sentürk, Damla; Nguyen, Danh V

2013-02-28

The case series model allows for estimation of the relative incidence of events, such as cardiovascular events, within a pre-specified time window after an exposure, such as an infection. The method requires only cases (individuals with events) and controls for all fixed/time-invariant confounders. The measurement error case series model extends the original case series model to handle imperfect data, where the timing of an infection (exposure) is not known precisely. In this work, we propose a method for power/sample size determination for the measurement error case series model. Extensive simulation studies are used to assess the accuracy of the proposed sample size formulas. We also examine the magnitude of the relative loss of power due to exposure onset measurement error, compared with the ideal situation where the time of exposure is measured precisely. To facilitate the design of case series studies, we provide publicly available web-based tools for determining power/sample size for both the measurement error case series model as well as the standard case series model. Copyright © 2012 John Wiley & Sons, Ltd.

Genetic variations in the Dravidian population of South West coast of India: Implications in designing case-control studies.

PubMed

D'Cunha, Anitha; Pandit, Lekha; Malli, Chaithra

2017-06-01

Indian data have been largely missing from genome-wide databases that provide information on genetic variations in different populations. This hinders association studies for complex disorders in India. This study was aimed to determine whether the complex genetic structure and endogamy among Indians could potentially influence the design of case-control studies for autoimmune disorders in the south Indian population. A total of 12 single nucleotide variations (SNVs) related to genes associated with autoimmune disorders were genotyped in 370 healthy individuals belonging to six different caste groups in southern India. Allele frequencies were estimated; genetic divergence and phylogenetic relationship within the various caste groups and other HapMap populations were ascertained. Allele frequencies for all genotyped SNVs did not vary significantly among the different groups studied. Wright's FSTwas 0.001 per cent among study population and 0.38 per cent when compared with Gujarati in Houston (GIH) population on HapMap data. The analysis of molecular variance results showed a 97 per cent variation attributable to differences within the study population and <1 per cent variation due to differences between castes. Phylogenetic analysis showed a separation of Dravidian population from other HapMap populations and particularly from GIH population. Despite the complex genetic origins of the Indian population, our study indicated a low level of genetic differentiation among Dravidian language-speaking people of south India. Case-control studies of association among Dravidians of south India may not require stratification based on language and caste.

The Case for Use of Simple Difference Scores to Test the Significance of Differences in Mean Rates of Change in Controlled Repeated Measurements Designs

ERIC Educational Resources Information Center

Overall, John E.; Tonidandel, Scott

2010-01-01

A previous Monte Carlo study examined the relative powers of several simple and more complex procedures for testing the significance of difference in mean rates of change in a controlled, longitudinal, treatment evaluation study. Results revealed that the relative powers depended on the correlation structure of the simulated repeated measurements.…

The Application of a Resilience Assessment Approach to Promote Campus Environmental Management: A South African Case Study

ERIC Educational Resources Information Center

Muller, Irene; Tempelhoff, Johann

2016-01-01

Purpose: This paper aims to outline the benefits of using resilience assessment instead of command and control mechanisms to evaluate sustainable campus environments. Design/Methodology/Approach: An exploratory mixed-method design was followed for the purposes of the project. During the first qualitative phase, a historical timeline of the focal…

Determinants of Preventive Health Behavior in Relation to Cervical Cancer Screening among the Female Population of Belgrade

ERIC Educational Resources Information Center

Matejic, Bojana; Vukovic, Dejana; Pekmezovic, Tatjana; Kesic, Vesna; Markovic, Milica

2011-01-01

Identifying the factors that deter or stimulate the women to participate in screening activities is very important in order to design effective education and motivation strategies, particularly in the countries without an organized system. The study employed a case-control design. The participants were recruited in four primary health care…

A methodology for identification and control of electro-mechanical actuators

PubMed Central

Tutunji, Tarek A.; Saleem, Ashraf

2015-01-01

Mechatronic systems are fully-integrated engineering systems that are composed of mechanical, electronic, and computer control sub-systems. These integrated systems use electro-mechanical actuators to cause the required motion. Therefore, the design of appropriate controllers for these actuators are an essential step in mechatronic system design. In this paper, a three-stage methodology for real-time identification and control of electro-mechanical actuator plants is presented, tested, and validated. First, identification models are constructed from experimental data to approximate the plants’ response. Second, the identified model is used in a simulation environment for the purpose of designing a suitable controller. Finally, the designed controller is applied and tested on the real plant through Hardware-in-the-Loop (HIL) environment. The described three-stage methodology provides the following practical contributions: • Establishes an easy-to-follow methodology for controller design of electro-mechanical actuators. • Combines off-line and on-line controller design for practical performance. • Modifies the HIL concept by using physical plants with computer control (rather than virtual plants with physical controllers). Simulated and experimental results for two case studies, induction motor and vehicle drive system, are presented in order to validate the proposed methodology. These results showed that electromechanical actuators can be identified and controlled using an easy-to-duplicate and flexible procedure. PMID:26150992

A methodology for identification and control of electro-mechanical actuators.

PubMed

Tutunji, Tarek A; Saleem, Ashraf

2015-01-01

Mechatronic systems are fully-integrated engineering systems that are composed of mechanical, electronic, and computer control sub-systems. These integrated systems use electro-mechanical actuators to cause the required motion. Therefore, the design of appropriate controllers for these actuators are an essential step in mechatronic system design. In this paper, a three-stage methodology for real-time identification and control of electro-mechanical actuator plants is presented, tested, and validated. First, identification models are constructed from experimental data to approximate the plants' response. Second, the identified model is used in a simulation environment for the purpose of designing a suitable controller. Finally, the designed controller is applied and tested on the real plant through Hardware-in-the-Loop (HIL) environment. The described three-stage methodology provides the following practical contributions: •Establishes an easy-to-follow methodology for controller design of electro-mechanical actuators.•Combines off-line and on-line controller design for practical performance.•Modifies the HIL concept by using physical plants with computer control (rather than virtual plants with physical controllers). Simulated and experimental results for two case studies, induction motor and vehicle drive system, are presented in order to validate the proposed methodology. These results showed that electromechanical actuators can be identified and controlled using an easy-to-duplicate and flexible procedure.

Childhood risk factors in Korean women with anorexia nervosa: two sets of case-control studies with retrospective comparisons.

PubMed

Kim, Youl-Ri; Heo, Si Young; Kang, Heechan; Song, Ki Jun; Treasure, Janet

2010-11-01

The aim of this study was to investigate the characteristics of the risk factors for anorexia nervosa (AN) in Korean women. Two sets of case-control comparisons were conducted, in which 52 women with lifetime AN from Seoul, S. Korea, were compared with 108 Korean healthy controls and also with 42 women with lifetime AN from the UK in terms of their childhood risk factors. A questionnaire designed to conduct a retrospective assessment of the childhood risk factors was administered to all participants. The Korean AN women were more likely to report premorbid anxiety, perfectionism, and emotional undereating and were less likely to report having supportive figures in their childhood than the Korean healthy controls. There were no overall differences in the childhood risk factors between the Korean and British women with AN. Premorbid anxiety, perfectionism, less social support, and emotional undereating merit attention as risk factors in Korean AN. The current results are informative, but an epidemiologically robust prospective case-control study would be needed to validate these findings. © 2009 by Wiley Periodicals, Inc.

Method for evaluating multiple mediators: mediating effects of smoking and COPD on the association between the CHRNA5-A3 variant and lung cancer risk.

PubMed

Wang, Jian; Spitz, Margaret R; Amos, Christopher I; Wu, Xifeng; Wetter, David W; Cinciripini, Paul M; Shete, Sanjay

2012-01-01

A mediation model explores the direct and indirect effects between an independent variable and a dependent variable by including other variables (or mediators). Mediation analysis has recently been used to dissect the direct and indirect effects of genetic variants on complex diseases using case-control studies. However, bias could arise in the estimations of the genetic variant-mediator association because the presence or absence of the mediator in the study samples is not sampled following the principles of case-control study design. In this case, the mediation analysis using data from case-control studies might lead to biased estimates of coefficients and indirect effects. In this article, we investigated a multiple-mediation model involving a three-path mediating effect through two mediators using case-control study data. We propose an approach to correct bias in coefficients and provide accurate estimates of the specific indirect effects. Our approach can also be used when the original case-control study is frequency matched on one of the mediators. We employed bootstrapping to assess the significance of indirect effects. We conducted simulation studies to investigate the performance of the proposed approach, and showed that it provides more accurate estimates of the indirect effects as well as the percent mediated than standard regressions. We then applied this approach to study the mediating effects of both smoking and chronic obstructive pulmonary disease (COPD) on the association between the CHRNA5-A3 gene locus and lung cancer risk using data from a lung cancer case-control study. The results showed that the genetic variant influences lung cancer risk indirectly through all three different pathways. The percent of genetic association mediated was 18.3% through smoking alone, 30.2% through COPD alone, and 20.6% through the path including both smoking and COPD, and the total genetic variant-lung cancer association explained by the two mediators was 69.1%.

Youth Attitude Tracking Study II, Fall 1983.

DTIC Science & Technology

1983-01-01

one - group pretest - posttest design." In this, though a . "before" group of the same individuals is introduced...there is no control group that is not exposed to the event. S Both the one -shot case study and the one - group pretest - posttest design are subject to a...segmentation analysis -A identified five Recruiting Priority Groups on the basis of educational status and average grades earned in high school.

Reconfigurable Control Design for the Full X-33 Flight Envelope

NASA Technical Reports Server (NTRS)

Cotting, M. Christopher; Burken, John J.

2001-01-01

A reconfigurable control law for the full X-33 flight envelope has been designed to accommodate a failed control surface and redistribute the control effort among the remaining working surfaces to retain satisfactory stability and performance. An offline nonlinear constrained optimization approach has been used for the X-33 reconfigurable control design method. Using a nonlinear, six-degree-of-freedom simulation, three example failures are evaluated: ascent with a left body flap jammed at maximum deflection; entry with a right inboard elevon jammed at maximum deflection; and landing with a left rudder jammed at maximum deflection. Failure detection and identification are accomplished in the actuator controller. Failure response comparisons between the nominal control mixer and the reconfigurable control subsystem (mixer) show the benefits of reconfiguration. Single aerosurface jamming failures are considered. The cases evaluated are representative of the study conducted to prove the adequate and safe performance of the reconfigurable control mixer throughout the full flight envelope. The X-33 flight control system incorporates reconfigurable flight control in the existing baseline system.

Design, analysis, fabrication and test of the Space Shuttle solid rocket booster motor case

NASA Technical Reports Server (NTRS)

Kapp, J. R.

1978-01-01

The motor case used in the solid propellant booster for the Space Shuttle is unique in many respects, most of which are indigenous to size and special design requirements. The evolution of the case design from initial requirements to finished product is discussed, with increased emphasis of reuse capability, special design features, fracture mechanics and corrosion control. Case fabrication history and the resulting procedure are briefly reviewed with respect to material development, processing techniques and special problem areas. Case assembly, behavior and performance during the DM-1 static firing are reviewed, with appropriate comments and conclusions.

Design and rationale for Home Blood Pressure Telemonitoring and Case Management to Control Hypertension (HyperLink): a cluster randomized trial.

PubMed

Margolis, Karen L; Kerby, Tessa J; Asche, Stephen E; Bergdall, Anna R; Maciosek, Michael V; O'Connor, Patrick J; Sperl-Hillen, JoAnn M

2012-07-01

Patients with high blood pressure (BP) visit a physician an average of 4 times or more per year in the U.S., yet BP is controlled in fewer than half. Practical, robust and sustainable models are needed to improve BP in patients with uncontrolled hypertension. The Home Blood Pressure Telemonitoring and Case Management to Control Hypertension study (HyperLink) is a cluster-randomized trial designed to determine whether an intervention that combines home BP telemonitoring with pharmacist case management improves BP control compared to usual care at 6 and 12 months in patients with uncontrolled hypertension. Secondary outcomes are maintenance of BP control at 18 months, patient satisfaction with their health care, and costs of care. HyperLink enrolled 450 hypertensive patients with uncontrolled BP from 16 primary care clinics. Eight clinics were randomized to provide usual care (UC) to their patients (n=222) and 8 were randomized to provide the telemonitoring intervention (TI) (n=228). TI patients received home BP telemonitors that internally store and electronically transmit BP data to a secure database. Pharmacist case managers adjust antihypertensive therapy based on the home BP data under a collaborative practice agreement with the clinics' primary care teams. The length of the intervention is 12 months, with follow-up to 18 months to determine the durability of the intervention. We will test in a real primary care setting whether combining BP telemonitoring and pharmacist case management can achieve and maintain high rates of BP control compared to usual care. Copyright © 2012 Elsevier Inc. All rights reserved.

Role of Surgical Margin on Local Recurrence in High Risk Extremity Osteosarcoma: A Case-Controlled Study

PubMed Central

Song, Won Seok; Kong, Chang-Bae; Cho, Wan Hyeong; Cho, Sang Hyun; Lee, Jeong Dong; Lee, Soo-Yong

2013-01-01

Background The relationship between surgical margin and local recurrence (LR) in osteosarcoma patients with poor responses to chemotherapy is unclear. Moreover, the incidences of LR according to three different resection planes (bone, soft tissue, and perineurovascular) are not commonly known. Methods We evaluated the incidence of LR in three areas. To assess whether there is a role of surgical margin on LR in patients resistant to preoperative chemotherapy, we designed a case (35 patients with LR) and control (70 patients without LR) study. Controls were matched for age, location, initial tumor volume, and tumor volume change during preoperative chemotherapy. Results LR occurred at the soft tissues in 18 cases (51.4%), at the perineurovascular tissues in 11 cases (31.4%), and at the bones in six cases (17.2%). The proportion of inadequate perineurovascular margin was higher in the case group than in the control group (p = 0.01). Within case-control group (105 patients), a correlation between each margin status and LR at corresponding area was found in the bone (p < 0.001) and perineurovascular area (p = 0.001). Conclusions LR is most common in soft tissues. In patients showing similar unfavorable responses to chemotherapy, the losses of perineurovascular fat plane on preoperative magnetic resonance imaging may be a valuable finding in predicting LR. PMID:24009908

Childhood Adversities Increase the Risk of Psychosis: A Meta-analysis of Patient-Control, Prospective- and Cross-sectional Cohort Studies

PubMed Central

Varese, Filippo; Smeets, Feikje; Drukker, Marjan; Lieverse, Ritsaert; Lataster, Tineke; Viechtbauer, Wolfgang; Read, John; van Os, Jim; Bentall, Richard P.

2012-01-01

Evidence suggests that adverse experiences in childhood are associated with psychosis. To examine the association between childhood adversity and trauma (sexual abuse, physical abuse, emotional/psychological abuse, neglect, parental death, and bullying) and psychosis outcome, MEDLINE, EMBASE, PsychINFO, and Web of Science were searched from January 1980 through November 2011. We included prospective cohort studies, large-scale cross-sectional studies investigating the association between childhood adversity and psychotic symptoms or illness, case-control studies comparing the prevalence of adverse events between psychotic patients and controls using dichotomous or continuous measures, and case-control studies comparing the prevalence of psychotic symptoms between exposed and nonexposed subjects using dichotomous or continuous measures of adversity and psychosis. The analysis included 18 case-control studies (n = 2048 psychotic patients and 1856 nonpsychiatric controls), 10 prospective and quasi-prospective studies (n = 41 803) and 8 population-based cross-sectional studies (n = 35 546). There were significant associations between adversity and psychosis across all research designs, with an overall effect of OR = 2.78 (95% CI = 2.34–3.31). The integration of the case-control studies indicated that patients with psychosis were 2.72 times more likely to have been exposed to childhood adversity than controls (95% CI = 1.90–3.88). The association between childhood adversity and psychosis was also significant in population-based cross-sectional studies (OR = 2.99 [95% CI = 2.12–4.20]) as well as in prospective and quasi-prospective studies (OR = 2.75 [95% CI = 2.17–3.47]). The estimated population attributable risk was 33% (16%–47%). These findings indicate that childhood adversity is strongly associated with increased risk for psychosis. PMID:22461484

Community participation in disease control.

PubMed

Bermejo, A; Bekui, A

1993-05-01

The main determinants of community participation in disease control programmes are identified and a framework with eleven variables is developed. Attention is drawn to the political background, community characteristics, the managerial capacity of the provider and the epidemiology of the disease. The framework is designed to guide health professionals in the systematic assessment and monitoring of participation in disease control programmes. Analysis of the Ghanaian Guinea Worm Eradication Programme and the Nicaraguan Tuberculosis Control Programme are presented as case studies. They show that political support does not guarantee community participation in disease control programmes and stress the importance of other determinants such as commitment to PHC, intersectoral coordination, the project approach and human resources. The relevance of the epidemiology of the disease in determining what degree of community participation will be most effective is highlighted by the case studies.

Considerations for the Systematic Analysis and Use of Single-Case Research

ERIC Educational Resources Information Center

Horner, Robert H.; Swaminathan, Hariharan; Sugai, George; Smolkowski, Keith

2012-01-01

Single-case research designs provide a rigorous research methodology for documenting experimental control. If single-case methods are to gain wider application, however, a need exists to define more clearly (a) the logic of single-case designs, (b) the process and decision rules for visual analysis, and (c) an accepted process for integrating…

Regulatory RNA design through evolutionary computation and strand displacement.

PubMed

Rostain, William; Landrain, Thomas E; Rodrigo, Guillermo; Jaramillo, Alfonso

2015-01-01

The discovery and study of a vast number of regulatory RNAs in all kingdoms of life over the past decades has allowed the design of new synthetic RNAs that can regulate gene expression in vivo. Riboregulators, in particular, have been used to activate or repress gene expression. However, to accelerate and scale up the design process, synthetic biologists require computer-assisted design tools, without which riboregulator engineering will remain a case-by-case design process requiring expert attention. Recently, the design of RNA circuits by evolutionary computation and adapting strand displacement techniques from nanotechnology has proven to be suited to the automated generation of DNA sequences implementing regulatory RNA systems in bacteria. Herein, we present our method to carry out such evolutionary design and how to use it to create various types of riboregulators, allowing the systematic de novo design of genetic control systems in synthetic biology.

How State-Funded Home Care Programs Respond to Changes in Medicare Home Health Care: Resource Allocation Decisions on the Front Line

PubMed Central

Corazzini, Kirsten

2003-01-01

Objective To examine how case managers in a state-funded home care program allocate home care services in response to information about a client's Medicare home health care status, with particular attention to the influence of work environment. Data Sources/Study Setting Primary data collected on 355 case managers and 26 agency directors employed in June 1999 by 26 of the 27 regional agencies administering the Massachusetts Home Care Program for low-income elders. Study Design Data were collected in a cross-sectional survey study design. A case manager survey included measures of work environment, demographics, and factorial survey vignette clients (N=2,054), for which case managers assessed service eligibility levels. An agency director survey included measures of management practices. Data Collection/Extraction Methods Hierarchical linear models estimated the effects of work environment on the relationship between client receipt of Medicare home health care and care plan levels while controlling for case-mix differences in agencies' clients. Principal Findings Case managers did not supplement extant Medicare home health services, but did allocate more generous service plans to clients who have had Medicare home health care services recently terminated. This finding persisted when controlling for case mix and did not vary by work environment. Work environment affected overall care plan levels. Conclusions Study findings indicate systematic patterns of frontline resource allocation shaping the relationships among community-based long-term care payment sources. Further, results illustrate how nonuniform implementation of upper-level initiatives may be partially attributed to work environment characteristics. PMID:14596390

Neurocognitive performance in family-based and case-control studies of schizophrenia

PubMed Central

Gur, Ruben C.; Braff, David L.; Calkins, Monica E.; Dobie, Dorcas J.; Freedman, Robert; Green, Michael F.; Greenwood, Tiffany A.; Lazzeroni, Laura C.; Light, Gregory A.; Nuechterlein, Keith H.; Olincy, Ann; Radant, Allen D.; Seidman, Larry J.; Siever, Larry J.; Silverman, Jeremy M.; Sprock, Joyce; Stone, William S.; Sugar, Catherine A.; Swerdlow, Neal R.; Tsuang, Debby W.; Tsuang, Ming T.; Turetsky, Bruce I.; Gur, Raquel E.

2014-01-01

Background Neurocognitive deficits in schizophrenia (SZ) are established and the Consortium on the Genetics of Schizophrenia (COGS) investigated such measures as endophenotypes in family-based (COGS-1) and case-control (COGS-2) studies. By requiring family participation, family-based sampling may result in samples that vary demographically and perform better on neurocognitive measures. Methods The Penn computerized neurocognitive battery (CNB) evaluates accuracy and speed of performance for several domains and was administered across sites in COGS-1 and COGS-2. Most tests were included in both studies. COGS-1 included 328 patients with SZ and 497 healthy comparison subjects (HCS) and COGS-2 included 1195 patients and 1009 HCS. Results Demographically, COGS-1 participants were younger, more educated, with more educated parents and higher estimated IQ compared to COGS-2 participants. After controlling for demographics, the two samples produced very similar performance profiles compared to their respective controls. As expected, performance was better and with smaller effect sizes compared to controls in COGS-1 relative to COGS-2. Better performance was most pronounced for spatial processing while emotion identification had large effect sizes for both accuracy and speed in both samples. Performance was positively correlated with functioning and negatively with negative and positive symptoms in both samples, but correlations were attenuated in COGS-2, especially with positive symptoms. Conclusions Patients ascertained through family-based design have more favorable demographics and better performance on some neurocognitive domains. Thus, studies that use case-control ascertainment may tap into populations with more severe forms of illness that are exposed to less favorable factors compared to those ascertained with family-based designs. PMID:25432636

Efficacy and Safety of Gabapentin in the Treatment of Chronic Cough: A Systematic Review.

PubMed

Shi, Guanglin; Shen, Qin; Zhang, Caixin; Ma, Jun; Mohammed, Anaz; Zhao, Huan

2018-06-19

Despite recent clinical guidelines, the optimal therapeutic strategy for the management of refractory chronic cough is still a challenge. The present systematic review was designed to assess the evidence for efficacy and safety of gabapentin in the treatment of chronic cough. A systematic search of PubMed, Embase, Cochrane Library databases, and publications cited in bibliographies was performed. Articles were searched by two reviewers with a priori criteria for study selection. Seven relevant articles were identified, including two randomized controlled trials, one prospective case-series designed with consecutive patients, one retrospective case series of consecutive patients, one retrospective case series with unknown consecutive status, and two case reports comprising six and two patients, respectively. Improvements were detected in cough-specific quality of life (Leicester Cough Questionnaire score) and cough severity (visual analogue scale score) following gabapentin treatment in randomized controlled trials. The results of prospective case-series showed that the rate of overall improvement of cough and sensory neuropathy with gabapentin was 68%. Gabapentin treatment of patients with chronic cough showed superior efficacy and a good safety record compared with placebo or standard medications. Additional randomized and controlled trials are needed. Copyright©2018. The Korean Academy of Tuberculosis and Respiratory Diseases.

Three ADIPOR1 Polymorphisms and Cancer Risk: A Meta-Analysis of Case-Control Studies.

PubMed

Ye, Jiaxiang; Jiang, Li; Wu, Changliang; Liu, Aiqun; Mao, Sufei; Ge, Lianying

2015-01-01

Studies have come to conflicting conclusions about whether polymorphisms in the adiponectin receptor 1 gene (ADIPOR1) are associated with cancer risk. To help resolve this question, we meta-analyzed case-control studies in the literature. PubMed, EMBASE, Cochrane Library, the Chinese Biological Medical Database and the Chinese National Knowledge Infrastructure Database were systematically searched to identify all case-control studies published through February 2015 examining any ADIPOR1 polymorphisms and risk of any type of cancer. Pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated. A total of 13 case-control studies involving 5,750 cases and 6,762 controls were analyzed. Analysis of the entire study population revealed a significant association between rs1342387(G/A) and overall cancer risk using a homozygous model (OR 0.82, 95%CI 0.72 to 0.94), heterozygous model (OR 0.84, 95%CI 0.76 to 0.93), dominant model (OR 0.85, 95%CI 0.75 to 0.97) and allele contrast model (OR 0.88, 95%CI 0.80 to 0.97). However, subgroup analysis showed that this association was significant only for Asians in the case of colorectal cancer. No significant associations were found between rs12733285(C/T) or rs7539542(C/G) and cancer risk, either in analyses of the entire study population or in analyses of subgroups. Our meta-analysis suggests that the ADIPOR1 rs1342387(G/A) polymorphism, but not rs12733285(C/T) or rs7539542(C/G), may be associated with cancer risk, especially risk of colorectal cancer in Asians. Large, well-designed studies are needed to verify our findings.

Does case misclassification threaten the validity of studies investigating the relationship between neck manipulation and vertebral artery dissection stroke? No.

PubMed

Murphy, Donald R; Schneider, Michael J; Perle, Stephen M; Bise, Christopher G; Timko, Michael; Haas, Mitchell

2016-01-01

The purported relationship between cervical manipulative therapy (CMT) and stroke related to vertebral artery dissection (VAD) has been debated for several decades. A large number of publications, from case reports to case-control studies, have investigated this relationship. A recent article suggested that case misclassification in the case-control studies on this topic resulted in biased odds ratios in those studies. Given its rarity, the best epidemiologic research design for investigating the relationship between CMT and VAD is the case-control study. The addition of a case-crossover aspect further strengthens the scientific rigor of such studies by reducing bias. The most recent studies investigating the relationship between CMT and VAD indicate that the relationship is not causal. In fact, a comparable relationship between vertebral artery-related stroke and visits to a primary care physician has been observed. The statistical association between visits to chiropractors and VAD can best be explained as resulting from a patient with early manifestation of VAD (neck pain with or without headache) seeking the services of a chiropractor for relief of this pain. Sometime after the visit the patient experiences VAD-related stroke that would have occurred regardless of the care received. This explanation has been challenged by a recent article putting forth the argument that case misclassification is likely to have biased the odds ratios of the case-control studies that have investigated the association between CMT and vertebral artery related stroke. The challenge particularly focused on one of the case-control studies, which had concluded that the association between CMT and vertebral artery related stroke was not causal. It was suggested by the authors of the recent article that misclassification led to an underestimation of risk. We argue that the information presented in that article does not support the authors' claim for a variety of reasons, including the fact that the assumptions upon which their analysis is based lack substantiation and the fact that any possible misclassification would not have changed the conclusion of the study in question. Current evidence does not support the notion that misclassification threatens the validity of recent case-control studies investigating the relationship between CMT and VAD. Hence, the recent re-analysis cannot refute the conclusion from previous studies that CMT is not a cause of VAD.

Indoor radon and childhood leukaemia.

PubMed

Raaschou-Nielsen, Ole

2008-01-01

This paper summarises the epidemiological literature on domestic exposure to radon and risk for childhood leukaemia. The results of 12 ecological studies show a consistent pattern of higher incidence and mortality rates for childhood leukaemia in areas with higher average indoor radon concentrations. Although the results of such studies are useful to generate hypotheses, they must be interpreted with caution, as the data were aggregated and analysed for geographical areas and not for individuals. The seven available case-control studies of childhood leukaemia with measurement of radon concentrations in the residences of cases and controls gave mixed results, however, with some indication of a weak (relative risk < 2) association with acute lymphoblastic leukaemia. The epidemiological evidence to date suggests that an association between indoor exposure to radon and childhood leukaemia might exist, but is weak. More case-control studies are needed, with sufficient statistical power to detect weak associations and based on designs and methods that minimise misclassification of exposure and provide a high participation rate and low potential selection bias.

Bayes and empirical Bayes methods for reduced rank regression models in matched case-control studies.

PubMed

Satagopan, Jaya M; Sen, Ananda; Zhou, Qin; Lan, Qing; Rothman, Nathaniel; Langseth, Hilde; Engel, Lawrence S

2016-06-01

Matched case-control studies are popular designs used in epidemiology for assessing the effects of exposures on binary traits. Modern studies increasingly enjoy the ability to examine a large number of exposures in a comprehensive manner. However, several risk factors often tend to be related in a nontrivial way, undermining efforts to identify the risk factors using standard analytic methods due to inflated type-I errors and possible masking of effects. Epidemiologists often use data reduction techniques by grouping the prognostic factors using a thematic approach, with themes deriving from biological considerations. We propose shrinkage-type estimators based on Bayesian penalization methods to estimate the effects of the risk factors using these themes. The properties of the estimators are examined using extensive simulations. The methodology is illustrated using data from a matched case-control study of polychlorinated biphenyls in relation to the etiology of non-Hodgkin's lymphoma. © 2015, The International Biometric Society.

Multicriteria Gain Tuning for Rotorcraft Flight Controls (also entitled The Development of the Conduit Advanced Control System Design and Evaluation Interface with a Case Study Application Fly by Wire Helicopter Design)

NASA Technical Reports Server (NTRS)

Biezad, Daniel

1997-01-01

Handling qualities analysis and control law design would seem to be naturally complimenting components of aircraft flight control system design, however these two closely coupled disciplines are often not well integrated in practice. Handling qualities engineers and control system engineers may work in separate groups within an aircraft company. Flight control system engineers and handling quality specialists may come from different backgrounds and schooling and are often not aware of the other group's research. Thus while the handling qualities specifications represent desired aircraft response characteristics, these are rarely incorporated directly in the control system design process. Instead modem control system design techniques are based on servo-loop robustness specifications, and simple representations of the desired control response. Comprehensive handling qualities analysis is often left until the end of the design cycle and performed as a check of the completed design for satisfactory performance. This can lead to costly redesign or less than satisfactory aircraft handling qualities when the flight testing phase is reached. The desire to integrate the fields of handling qualities and flight,control systems led to the development of the CONDUIT system. This tool facilitates control system designs that achieve desired handling quality requirements and servo-loop specifications in a single design process. With CONDUIT, the control system engineer is now able to directly design and control systems to meet the complete handling specifications. CONDUIT allows the designer to retain a preferred control law structure, but then tunes the system parameters to meet the handling quality requirements.

Supersonic wing and wing-body shape optimization using an adjoint formulation

NASA Technical Reports Server (NTRS)

Reuther, James; Jameson, Antony

1995-01-01

This paper describes the implementation of optimization techniques based on control theory for wing and wing-body design of supersonic configurations. The work represents an extension of our earlier research in which control theory is used to devise a design procedure that significantly reduces the computational cost by employing an adjoint equation. In previous studies it was shown that control theory could be used toeviseransonic design methods for airfoils and wings in which the shape and the surrounding body-fitted mesh are both generated analytically, and the control is the mapping function. The method has also been implemented for both transonic potential flows and transonic flows governed by the Euler equations using an alternative formulation which employs numerically generated grids, so that it can treat more general configurations. Here results are presented for three-dimensional design cases subject to supersonic flows governed by the Euler equation.

Use of advanced modeling techniques to optimize thermal packaging designs.

PubMed

Formato, Richard M; Potami, Raffaele; Ahmed, Iftekhar

2010-01-01

Through a detailed case study the authors demonstrate, for the first time, the capability of using advanced modeling techniques to correctly simulate the transient temperature response of a convective flow-based thermal shipper design. The objective of this case study was to demonstrate that simulation could be utilized to design a 2-inch-wall polyurethane (PUR) shipper to hold its product box temperature between 2 and 8 °C over the prescribed 96-h summer profile (product box is the portion of the shipper that is occupied by the payload). Results obtained from numerical simulation are in excellent agreement with empirical chamber data (within ±1 °C at all times), and geometrical locations of simulation maximum and minimum temperature match well with the corresponding chamber temperature measurements. Furthermore, a control simulation test case was run (results taken from identical product box locations) to compare the coupled conduction-convection model with a conduction-only model, which to date has been the state-of-the-art method. For the conduction-only simulation, all fluid elements were replaced with "solid" elements of identical size and assigned thermal properties of air. While results from the coupled thermal/fluid model closely correlated with the empirical data (±1 °C), the conduction-only model was unable to correctly capture the payload temperature trends, showing a sizeable error compared to empirical values (ΔT > 6 °C). A modeling technique capable of correctly capturing the thermal behavior of passively refrigerated shippers can be used to quickly evaluate and optimize new packaging designs. Such a capability provides a means to reduce the cost and required design time of shippers while simultaneously improving their performance. Another advantage comes from using thermal modeling (assuming a validated model is available) to predict the temperature distribution in a shipper that is exposed to ambient temperatures which were not bracketed during its validation. Thermal packaging is routinely used by the pharmaceutical industry to provide passive and active temperature control of their thermally sensitive products from manufacture through end use (termed the cold chain). In this study, the authors focus on passive temperature control (passive control does not require any external energy source and is entirely based on specific and/or latent heat of shipper components). As temperature-sensitive pharmaceuticals are being transported over longer distances, cold chain reliability is essential. To achieve reliability, a significant amount of time and resources must be invested in design, test, and production of optimized temperature-controlled packaging solutions. To shorten the cumbersome trial and error approach (design/test/design/test …), computer simulation (virtual prototyping and testing of thermal shippers) is a promising method. Although several companies have attempted to develop such a tool, there has been limited success to date. Through a detailed case study the authors demonstrate, for the first time, the capability of using advanced modeling techniques to correctly simulate the transient temperature response of a coupled conductive/convective-based thermal shipper. A modeling technique capable of correctly capturing shipper thermal behavior can be used to develop packaging designs more quickly, reducing up-front costs while also improving shipper performance.

Robust parameter design for automatically controlled systems and nanostructure synthesis

NASA Astrophysics Data System (ADS)

Dasgupta, Tirthankar

2007-12-01

This research focuses on developing comprehensive frameworks for developing robust parameter design methodology for dynamic systems with automatic control and for synthesis of nanostructures. In many automatically controlled dynamic processes, the optimal feedback control law depends on the parameter design solution and vice versa and therefore an integrated approach is necessary. A parameter design methodology in the presence of feedback control is developed for processes of long duration under the assumption that experimental noise factors are uncorrelated over time. Systems that follow a pure-gain dynamic model are considered and the best proportional-integral and minimum mean squared error control strategies are developed by using robust parameter design. The proposed method is illustrated using a simulated example and a case study in a urea packing plant. This idea is also extended to cases with on-line noise factors. The possibility of integrating feedforward control with a minimum mean squared error feedback control scheme is explored. To meet the needs of large scale synthesis of nanostructures, it is critical to systematically find experimental conditions under which the desired nanostructures are synthesized reproducibly, at large quantity and with controlled morphology. The first part of the research in this area focuses on modeling and optimization of existing experimental data. Through a rigorous statistical analysis of experimental data, models linking the probabilities of obtaining specific morphologies to the process variables are developed. A new iterative algorithm for fitting a Multinomial GLM is proposed and used. The optimum process conditions, which maximize the above probabilities and make the synthesis process less sensitive to variations of process variables around set values, are derived from the fitted models using Monte-Carlo simulations. The second part of the research deals with development of an experimental design methodology, tailor-made to address the unique phenomena associated with nanostructure synthesis. A sequential space filling design called Sequential Minimum Energy Design (SMED) for exploring best process conditions for synthesis of nanowires. The SMED is a novel approach to generate sequential designs that are model independent, can quickly "carve out" regions with no observable nanostructure morphology, and allow for the exploration of complex response surfaces.

Home pesticide exposures and risk of childhood leukemia: Findings from the Childhood Leukemia International Consortium

PubMed Central

Bailey, Helen D; Infante-Rivard, Claire; Metayer, Catherine; Clavel, Jacqueline; Lightfoot, Tracy; Kaatsch, Peter; Roman, Eve; Magnani, Corrado; Spector, Logan G; Petridou, Eleni; Milne, Elizabeth; Dockerty, John D; Miligi, Lucia; Armstrong, Bruce K; Rudant, Jérémie; Fritschi, Lin; Simpson, Jill; Zhang, Luoping; Rondelli, Roberto; Baka, Margarita; Orsi, Laurent; Moschovi, Maria; Kang, Alice Y; Schüz, Joachim

2015-01-01

Some previous studies have suggested that home pesticide exposure before birth and during a child's early years may increase the risk of childhood leukemia. To further investigate this, we pooled individual level data from 12 case-control studies in the Childhood Leukemia International Consortium (CLIC). Exposure data were harmonized into compatible formats. Pooled analyses were undertaken using multivariable unconditional logistic regression. The odds ratio (ORs) for acute lymphoblastic leukaemia (ALL) associated with any pesticide exposure shortly before conception, during pregnancy and after birth were 1.39 (95% confidence interval (CI) 1.25, 1.55) (using (2,785 cases, 3635 controls), 1.43 (95% CI 1.32, 1.54) (5,055 cases, 7,370 controls) and 1.36 (95% CI 1.23, 1.51) (4,162 cases 5,179 controls), respectively. Corresponding ORs for risk of acute myeloid leukaemia (AML) were 1.49 (95% CI 1.02, 2.16) (173 cases, 1,789 controls), 1.55 (95% CI 1.21, 1.99) (344 cases, 4,666 controls) and 1.08 (95% CI 0.76, 1.53) (198 cases, 2,655 controls) respectively. There was little difference by type of pesticide used. The relative similarity in ORs between leukaemia types, time periods and pesticide types may be explained by similar exposure patterns and effects across the time periods in ALL and AML, participants’ exposure to multiple pesticides, or recall bias. Although some recall bias is likely, until a better study design can be found to investigate associations between home pesticide use and childhood leukaemia in an equally large sample, it would appear prudent to limit the use of home pesticides before and during pregnancy, and during childhood. PMID:26061779

Lack of Association Between Cytomegalovirus Infection and Hypertensive Disorders in Pregnancy: A Case-Control Study in Durango, Mexico.

PubMed

Alvarado-Esquivel, Cosme; Sandoval-Carrillo, Ada A; Vazquez-Alaniz, Fernando; Salas-Pacheco, José M; Hernández-Tinoco, Jesús; Sánchez-Anguiano, Luis Francisco; Antuna-Salcido, Elizabeth Irasema

2017-09-01

It is not clear whether infection with cytomegalovirus (CMV) is associated with hypertensive disorders in pregnant women. Through a case-control study design, 146 women suffering from hypertensive disorders in pregnancy (cases) and 146 age-matched normotensive pregnant women (controls) were examined for the presence of anti-CMV IgG and IgM antibodies with enzyme-linked immunoassays. IgM seropositive samples were further assayed by enzyme-linked fluorescent assay (ELFA). Anti-CMV IgG antibodies were found in 138 (94.5%) controls and in 136 (93.2%) cases (odds ratio [OR] = 0.78; 95% confidence interval [CI]: 0.30-2.05; P = 0.62). High (>18 IU/ml) levels of anti-CMV IgG antibodies were found in 37.7% of the 138 seropositive controls and in 34.6% of the 136 seropositive cases (OR = 0.87; 95% CI: 0.53-1.43; P = 0.59). Anti-CMV IgM antibodies were found in 1 (0.7%) of the controls but in none of the cases using ELFA ( P = 1.0). Seropositivity to CMV was not associated with a previous preeclampsia and was similar among cases regardless their mean systolic and diastolic blood pressures, and mean arterial blood pressure. No serological evidence of an association between CMV infection and hypertensive disorders of pregnancy was found. Further research to elucidate the role of CMV in hypertensive disorders in pregnancy should be conducted.

Allowing for population stratification in case-only studies of gene-environment interaction, using genomic control.

PubMed

Yadav, Pankaj; Freitag-Wolf, Sandra; Lieb, Wolfgang; Dempfle, Astrid; Krawczak, Michael

2015-10-01

Gene-environment interactions (G × E) have attracted considerable research interest in the past owing to their scientific and public health implications, but powerful statistical methods are required to successfully track down G × E, particularly at a genome-wide level. Previously, a case-only (CO) design has been proposed as a means to identify G × E with greater efficiency than traditional case-control or cohort studies. However, as with genotype-phenotype association studies themselves, hidden population stratification (PS) can impact the validity of G × E studies using a CO design. Since this problem has been subject to little research to date, we used comprehensive simulation to systematically assess the type I error rate, power and effect size bias of CO studies of G × E in the presence of PS. Three types of PS were considered, namely genetic-only (PSG), environment-only (PSE), and joint genetic and environmental stratification (PSGE). Our results reveal that the type I error rate of an unadjusted Wald test, appropriate for the CO design, would be close to its nominal level (0.05 in our study) as long as PS involves only one interaction partner (i.e., either PSG or PSE). In contrast, if the study population is stratified with respect to both G and E (i.e., if there is PSGE), then the type I error rate is seriously inflated and estimates of the underlying G × E interaction are biased. Comparison of CO to a family-based case-parents design confirmed that the latter is more robust against PSGE, as expected. However, case-parent trios may be particularly unsuitable for G × E studies in view of the fact that they require genotype data from parents and that many diseases with an environmental component are likely to be of late onset. An alternative approach to adjusting for PS is principal component analysis (PCA), which has been widely used for this very purpose in past genome-wide association studies (GWAS). However, resolving genetic PS properly by PCA requires genetic data at the population level, the availability of which would conflict with the basic idea of the CO design. Therefore, we explored three modified Wald test statistics, inspired by the genomic control (GC) approach to GWAS, as an alternative means to allow for PSGE. The modified statistics were benchmarked against a stratified Wald test assuming known population affiliation, which should provide maximum power under PS. Our results confirm that GC is capable of successfully and efficiently correcting the PS-induced inflation of the type I error rate in CO studies of G × E.

New controller for functional electrical stimulation systems.

PubMed

Fisekovic, N; Popovic, D B

2001-07-01

A novel, self-contained controller for functional electrical stimulation systems has been designed. The development was motivated by the need to have a general purpose, easy to use controller capable of stimulating many muscle groups, thus restoring complex motor functions (e.g. standing, walking, reaching, and grasping). The designed controller can regulate the frequency, pulse duration, and charge balance on up to 16 channels, and execute pre-programmed and sensory-driven control operations. The controller supports up to eight analog and six digital sensors, and comprises a memory block for including history of the sensory data (time series). Five independent timers provide the basis for the multi-modal and multi-level control of movement. The PC compatible interface is realised via an IR serial communication channel. The PC based software is user friendly and fully menu driven. This paper also presents a case study where the controller was implemented to restore walking in a paraplegic subject. The assistive system comprised the novel controller, the power and output stages of an eight-channel FES system (IEEE Trans Rehabil Eng, TRE-2 (1994) 234), ankle-foot orthoses, and a rolling walker. Stimulation was applied with surface electrodes positioned over the motoneurons that innervate muscles responsible for the hip and knee flexion and extension. The sensory system included goniometers at knee and hip joints, force-sensing resistors built in the shoe insoles, and digital accelerometers at the hips. A rule-based control algorithm was generated following a two-step procedure: (1) simulation and (2) machine learning as described in earlier studies (IEEE Trans Rehab Eng, TRE-7 (1999) 69). The paraplegic subject walked faster, and with less physiological effort, when automatic control was applied as compared to hand-control. This case study, as well as a previous one for assisting grasping (The design and testing of a new programmable electronic stimulator. N. Fisekovic, MS thesis. University of Belgrade, Belgrade, 2000) indicate that the novel control unit is effectively applicable to FES systems.

Prediction of Gut Wall Integrity Loss in Viral Gastroenteritis by Non-Invasive Marker

PubMed Central

Elnady, Hala G.; Sherif, Lobna S.; Saleh, Maysa T.; El-Alameey, Inas R.; Youssef, Mai M.; El Shafie, Amal I.; Helwa, Iman; Raouf, Haiam Abdel; EL-Taweel, Ahmed N.

2015-01-01

BACKGROUND: Intestinal fatty acid binding proteins (I-FABPs) are mainly expressed in the intestinal villi, which are the initial site of destruction in viral gastroenteritis. AIM: This study was designed to assess serum I-FABPs as a predictor of gut wall integrity loss in viral gastroenteritis. PATIENTS AND METHODS: This case-control cross-sectional study was conducted on 93 cases of acute viral gastroenteritis. Twenty-eight healthy children matching in age were recruited as control group. Serum I-FABPs were measured using ELISA technique. Viral detection and typing were done by PCR for adenovirus, and by Reverse transcriptase PCR for rotavirus, astrovirus and norovirus. RESULTS: Serum I-FABPs level was significantly higher in the cases compared to the controls and was also higher in the 46 rotavirus gastroenteritis cases compared to other viral gastroenteritis cases. Serum I- FABPs level was significantly higher in severely dehydrated cases as compared to mildly dehydrated ones (P=0.037). CONCLUSION: Serum I-FABPs could be used as an early and sensitive predictor marker of gut wall integrity loss in children with viral gastroenteritis and its level can indicate case severity. PMID:27275194

ME 5620 Fracture Mechanics in Engineering Design. Case Study Project

DTIC Science & Technology

2011-04-03

14 UNCLASSIFIED References 1 . A First Course in the Finite Element Method, 4th edition, by D.L. Logan, Thomson Engineering, 2006. 2. Altair ...collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources...currently valid OMB control number. 1 . REPORT DATE 03 APR 2011 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Case Study

JPL Thermal Design Modeling Philosophy and NASA-STD-7009 Standard for Models and Simulations - A Case Study

NASA Technical Reports Server (NTRS)

Avila, Arturo

2011-01-01

The Standard JPL thermal engineering practice prescribes worst-case methodologies for design. In this process, environmental and key uncertain thermal parameters (e.g., thermal blanket performance, interface conductance, optical properties) are stacked in a worst case fashion to yield the most hot- or cold-biased temperature. Thus, these simulations would represent the upper and lower bounds. This, effectively, represents JPL thermal design margin philosophy. Uncertainty in the margins and the absolute temperatures is usually estimated by sensitivity analyses and/or by comparing the worst-case results with "expected" results. Applicability of the analytical model for specific design purposes along with any temperature requirement violations are documented in peer and project design review material. In 2008, NASA released NASA-STD-7009, Standard for Models and Simulations. The scope of this standard covers the development and maintenance of models, the operation of simulations, the analysis of the results, training, recommended practices, the assessment of the Modeling and Simulation (M&S) credibility, and the reporting of the M&S results. The Mars Exploration Rover (MER) project thermal control system M&S activity was chosen as a case study determining whether JPL practice is in line with the standard and to identify areas of non-compliance. This paper summarizes the results and makes recommendations regarding the application of this standard to JPL thermal M&S practices.

Using Virtual Reality and Videogames for Traumatic Brain Injury Rehabilitation: A Structured Literature Review.

PubMed

Pietrzak, Eva; Pullman, Stephen; McGuire, Annabel

2014-08-01

This article reviews the available literature about the use of novel methods of rehabilitation using virtual reality interventions for people living with posttraumatic brain injuries. The MEDLINE, EMBASE, SCOPUS, and Cochrane Library databases were searched using the terms "virtual reality" OR "video games" AND "traumatic brain injury." Included studies investigated therapeutic use of virtual reality in adults with a brain trauma resulting from acquired closed head injury, reported outcomes that included measures of motor or cognitive functionality, and were published in a peer-reviewed journal written in English. Eighteen articles fulfilled inclusion criteria. Eight were case studies, five studies had a quasi-experimental design with a pre-post comparison, and five were pilot randomized control trials or comparative studies. The virtual reality systems used were commercial or custom designed for the study and ranged from expensive, fully immersive systems to cheap online games or videogames. In before-after comparisons, improvements in balance were seen in four case studies and two small randomized control trials. Between-group comparisons in these randomized control trials showed no difference between virtual reality and traditional therapy. Post-training improvements were also seen for upper extremity functions (five small studies) and for various cognitive function measures (four case studies and one pilot randomized control trial). Attitudes of participants toward virtual reality interventions was more positive than for traditional therapy (three studies). The evidence that the use of virtual reality in rehabilitation of traumatic brain injury improves motor and cognitive functionality is currently very limited. However, this approach has the potential to provide alternative, possibly more affordable and available rehabilitation therapy for traumatic brain injury in settings where access to therapy is limited by geographical or financial constraints.

Control allocation for gimballed/fixed thrusters

NASA Astrophysics Data System (ADS)

Servidia, Pablo A.

2010-02-01

Some overactuated control systems use a control distribution law between the controller and the set of actuators, usually called control allocator. Beyond the control allocator, the configuration of actuators may be designed to be able to operate after a single point of failure, for system optimization and/or decentralization objectives. For some type of actuators, a control allocation is used even without redundancy, being a good example the design and operation of thruster configurations. In fact, as the thruster mass flow direction and magnitude only can be changed under certain limits, this must be considered in the feedback implementation. In this work, the thruster configuration design is considered in the fixed (F), single-gimbal (SG) and double-gimbal (DG) thruster cases. The minimum number of thrusters for each case is obtained and for the resulting configurations a specific control allocation is proposed using a nonlinear programming algorithm, under nominal and single-point of failure conditions.

Engineering and Economic Analysis of an Advanced Ultra-Supercritical Pulverized Coal Power Plant with and without Post-Combustion Carbon Capture Task 7. Design and Economic Studies

DOE Office of Scientific and Technical Information (OSTI.GOV)

Booras, George; Powers, J.; Riley, C.

2015-09-01

This report evaluates the economics and performance of two A-USC PC power plants; Case 1 is a conventionally configured A-USC PC power plant with superior emission controls, but without CO 2 removal; and Case 2 adds a post-combustion carbon capture (PCC) system to the plant from Case 1, using the design and heat integration strategies from EPRI’s 2015 report, “Best Integrated Coal Plant.” The capture design basis for this case is “partial,” to meet EPA’s proposed New Source Performance Standard, which was initially proposed as 500 kg-CO 2/MWh (gross) or 1100 lb-CO 2/MWh (gross), but modified in August 2015 tomore » 635 kg-CO 2/MWh (gross) or 1400 lb-CO 2/MWh (gross). This report draws upon the collective experience of consortium members, with EPRI and General Electric leading the study. General Electric provided the steam cycle analysis as well as v the steam turbine design and cost estimating. EPRI performed integrated plant performance analysis using EPRI’s PC Cost model.« less

Randomised Controlled Trials in Education Research: A Case Study of an Individually Randomised Pragmatic Trial

ERIC Educational Resources Information Center

Torgerson, Carole J.

2009-01-01

The randomised controlled trial (RCT) is an evaluative method used by social scientists in order to establish whether or not an intervention is effective. This contribution discusses the fundamental aspects of good RCT design. These are illustrated through the use of a recently completed RCT which evaluated an information and communication…

A performance analysis method for distributed real-time robotic systems: A case study of remote teleoperation

NASA Technical Reports Server (NTRS)

Lefebvre, D. R.; Sanderson, A. C.

1994-01-01

Robot coordination and control systems for remote teleoperation applications are by necessity implemented on distributed computers. Modeling and performance analysis of these distributed robotic systems is difficult, but important for economic system design. Performance analysis methods originally developed for conventional distributed computer systems are often unsatisfactory for evaluating real-time systems. The paper introduces a formal model of distributed robotic control systems; and a performance analysis method, based on scheduling theory, which can handle concurrent hard-real-time response specifications. Use of the method is illustrated by a case of remote teleoperation which assesses the effect of communication delays and the allocation of robot control functions on control system hardware requirements.

Medication safety research by observational study design.

PubMed

Lao, Kim S J; Chui, Celine S L; Man, Kenneth K C; Lau, Wallis C Y; Chan, Esther W; Wong, Ian C K

2016-06-01

Observational studies have been recognised to be essential for investigating the safety profile of medications. Numerous observational studies have been conducted on the platform of large population databases, which provide adequate sample size and follow-up length to detect infrequent and/or delayed clinical outcomes. Cohort and case-control are well-accepted traditional methodologies for hypothesis testing, while within-individual study designs are developing and evolving, addressing previous known methodological limitations to reduce confounding and bias. Respective examples of observational studies of different study designs using medical databases are shown. Methodology characteristics, study assumptions, strengths and weaknesses of each method are discussed in this review.

Two Birds With One Stone: Estimating Population Vaccination Coverage From a Test-negative Vaccine Effectiveness Case-control Study.

PubMed

Doll, Margaret K; Morrison, Kathryn T; Buckeridge, David L; Quach, Caroline

2016-10-15

Vaccination program evaluation includes assessment of vaccine uptake and direct vaccine effectiveness (VE). Often examined separately, we propose a design to estimate rotavirus vaccination coverage using controls from a rotavirus VE test-negative case-control study and to examine coverage following implementation of the Quebec, Canada, rotavirus vaccination program. We present our assumptions for using these data as a proxy for coverage in the general population, explore effects of diagnostic accuracy on coverage estimates via simulations, and validate estimates with an external source. We found 79.0% (95% confidence interval, 74.3%, 83.0%) ≥2-dose rotavirus coverage among participants eligible for publicly funded vaccination. No differences were detected between study and external coverage estimates. Simulations revealed minimal bias in estimates with high diagnostic sensitivity and specificity. We conclude that controls from a VE case-control study may be a valuable resource of coverage information when reasonable assumptions can be made for estimate generalizability; high rotavirus coverage demonstrates success of the Quebec program. © The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail journals.permissions@oup.com.

Anorexia nervosa versus bulimia nervosa: differences based on retrospective correlates in a case-control study.

PubMed

Machado, Bárbara C; Gonçalves, Sónia F; Martins, Carla; Brandão, Isabel; Roma-Torres, António; Hoek, Hans W; Machado, Paulo P

2016-06-01

This study is the result of two Portuguese case-control studies that examined the replication of retrospective correlates and preceding life events in anorexia nervosa (AN) and bulimia nervosa (BN) development. This study aims to identify retrospective correlates that distinguish AN and BN METHOD: A case-control design was used to compare a group of women who met Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for AN (N = 98) and BN (N = 79) with healthy controls (N = 86) and with other psychiatric disorders (N = 68). Each control group was matched with AN patients regarding age and parental social categories. Risk factors were assessed by interviewing each person with the Oxford Risk Factor Interview. Compared to AN, women with BN reported significantly higher rates of paternal high expectations, excessive family importance placed on fitness/keeping in shape, and negative consequences due to adolescent overweight and adolescent objective overweight. Overweight during adolescence emerged as the most relevant retrospective correlate in the distinction between BN and AN participants. Family expectations and the importance placed on keeping in shape were also significant retrospective correlates in the BN group.

Epidemiology of shivering (shivers) in horses.

PubMed

Draper, A C E; Bender, J B; Firshman, A M; Baird, J D; Reed, S; Mayhew, I G; Valberg, S J

2015-03-01

Investigating the epidemiology of shivering in horses. The purpose of this study was to characterise the signalment, clinical signs and management factors associated with shivering (also known as shivers), a relatively rare, poorly defined movement disorder in horses. Web-based case series survey and case-control study. A Web-based survey was used to obtain information from owners, worldwide, who suspected that their horse had shivering. Survey respondents were asked to answer standardised questions and to provide a video of the horse. Authors reviewed the surveys and videos, and horses were diagnosed with shivering if they displayed normal forward walking, with difficulty during manual lifting of the hoof and backward walking due to hyperflexion or hyperextension of the pelvic limbs. Cases confirmed by video were designated 'confirmed shivering', while those with compatible clinical signs but lacking video confirmation were designated 'suspected shivering'. Owners of confirmed shivering horses were asked to provide information on 2 horses without signs of shivering (control group). Three hundred and five surveys and 70 videos were received; 27 horses were confirmed shivering (50 controls), 67 were suspected shivering and the rest had a variety of other movement disorders. Suspected shivering horses resembled confirmed shivering cases, except that the suspected shivering group contained fewer draught breeds and fewer horses with exercise intolerance. Confirmed shivering signs often began at <5 years of age and progressed in 74% of cases. Owner-reported additional clinical signs in confirmed cases included muscle twitching (85%), muscle atrophy (44%), reduced strength (33%) and exercise intolerance (33%). Shivering horses were significantly taller (confirmed shivering, mean ∼173 cm; control horses, ∼163 cm) with a higher male:female ratio (confirmed shivering, 3.2:1 vs. control, 1.7:1). No potential triggering factors or effective treatments were reported. Shivering is a chronic, often gradually progressive movement disorder that usually begins before 7 years of age and has a higher prevalence in tall male horses. © 2014 EVJ Ltd.

Simplified filtered Smith predictor for MIMO processes with multiple time delays.

PubMed

Santos, Tito L M; Torrico, Bismark C; Normey-Rico, Julio E

2016-11-01

This paper proposes a simplified tuning strategy for the multivariable filtered Smith predictor. It is shown that offset-free control can be achieved with step references and disturbances regardless of the poles of the primary controller, i.e., integral action is not explicitly required. This strategy reduces the number of design parameters and simplifies tuning procedure because the implicit integrative poles are not considered for design purposes. The simplified approach can be used to design continuous-time or discrete-time controllers. Three case studies are used to illustrate the advantages of the proposed strategy if compared with the standard approach, which is based on the explicit integrative action. Copyright © 2016 ISA. Published by Elsevier Ltd. All rights reserved.

School Effectiveness in the Dominican Republic.

ERIC Educational Resources Information Center

British Columbia Univ., Vancouver. Faculty of Education.

Characteristics distinguishing more effective from less effective public primary (grades 1 to 8) schools in Santo Domingo were studied, using a comparative case study design. The effectiveness of the school was determined by expert nomination and achievement tests in reading, mathematics, and writing. Socioeconomic status was controlled and three…

Aerodynamic Shape Optimization of Supersonic Aircraft Configurations via an Adjoint Formulation on Parallel Computers

NASA Technical Reports Server (NTRS)

Reuther, James; Alonso, Juan Jose; Rimlinger, Mark J.; Jameson, Antony

1996-01-01

This work describes the application of a control theory-based aerodynamic shape optimization method to the problem of supersonic aircraft design. The design process is greatly accelerated through the use of both control theory and a parallel implementation on distributed memory computers. Control theory is employed to derive the adjoint differential equations whose solution allows for the evaluation of design gradient information at a fraction of the computational cost required by previous design methods (13, 12, 44, 38). The resulting problem is then implemented on parallel distributed memory architectures using a domain decomposition approach, an optimized communication schedule, and the MPI (Message Passing Interface) Standard for portability and efficiency. The final result achieves very rapid aerodynamic design based on higher order computational fluid dynamics methods (CFD). In our earlier studies, the serial implementation of this design method (19, 20, 21, 23, 39, 25, 40, 41, 42, 43, 9) was shown to be effective for the optimization of airfoils, wings, wing-bodies, and complex aircraft configurations using both the potential equation and the Euler equations (39, 25). In our most recent paper, the Euler method was extended to treat complete aircraft configurations via a new multiblock implementation. Furthermore, during the same conference, we also presented preliminary results demonstrating that the basic methodology could be ported to distributed memory parallel computing architectures [241. In this paper, our concem will be to demonstrate that the combined power of these new technologies can be used routinely in an industrial design environment by applying it to the case study of the design of typical supersonic transport configurations. A particular difficulty of this test case is posed by the propulsion/airframe integration.

Risk factors for idiopathic intracranial hypertension in men: a case-control study

PubMed Central

Fraser, J. Alexander; Bruce, Beau B.; Rucker, Janet; Fraser, Lisa-Ann; Atkins, Edward J.; Newman, Nancy J.; Biousse, Valérie

2009-01-01

Objective To identify risk factors for idiopathic intracranial hypertension (IIH) in men Design Case-control study. A 96-item telephone questionnaire, answered retrospectively, with cases recalling at the age of their diagnosis and controls recalling at the age of their corresponding case's diagnosis. Setting Outpatient clinics in two US tertiary care centers Participants The characteristics of 24 men with IIH were compared to those of 48 controls matched for sex, age, race, and World Health Organization body mass index (BMI) category. Main Outcome Measures Two previously validated questionnaires: the ADAM (Androgen Deficiency in Aging Males) questionnaire for testosterone deficiency and the Berlin questionnaire for obstructive sleep apnea (OSA), embedded within the telephone questionnaire. Analysis with Mantel-Haenszel odds ratios and mixed-effects logistic regression models accounted for matching. Results Cases and controls had similar enrollment matching characteristics. Although matching was successful by BMI category, there was a small difference between BMI values of cases and controls (cases: median 31.7, controls: median 29.9; p=0.03). After adjustment by BMI value, men with IIH were significantly more likely than controls to have a positive ADAM questionnaire for testosterone deficiency (OR: 17.4, 95% CI: 5.6-54.5; p<0.001) and significantly more likely to have either a positive Berlin questionnaire for OSA or history of diagnosed OSA (OR: 4.4, 95% CI: 1.5-12.9; p=0.03). Conclusions Men with IIH are more likely than controls to have symptoms associated with testosterone deficiency and OSA. These associations suggest a possible role for sex hormones and OSA in the pathogenesis of IIH in men. PMID:19945715

The Design of Case Products’ Shape Form Information Database Based on NURBS Surface

NASA Astrophysics Data System (ADS)

Liu, Xing; Liu, Guo-zhong; Xu, Nuo-qi; Zhang, Wei-she

2017-07-01

In order to improve the computer design of product shape design,applying the Non-uniform Rational B-splines(NURBS) of curves and surfaces surface to the representation of the product shape helps designers to design the product effectively.On the basis of the typical product image contour extraction and using Pro/Engineer(Pro/E) to extract the geometric feature of scanning mold,in order to structure the information data base system of value point,control point and node vector parameter information,this paper put forward a unified expression method of using NURBS curves and surfaces to describe products’ geometric shape and using matrix laboratory(MATLAB) to simulate when products have the same or similar function.A case study of electric vehicle’s front cover illustrates the access process of geometric shape information of case product in this paper.This method can not only greatly reduce the capacity of information debate,but also improve the effectiveness of computer aided geometric innovation modeling.

The MOBI-Kids Study Protocol: Challenges in Assessing Childhood and Adolescent Exposure to Electromagnetic Fields from Wireless Telecommunication Technologies and Possible Association with Brain Tumor Risk.

PubMed

Sadetzki, Siegal; Langer, Chelsea Eastman; Bruchim, Revital; Kundi, Michael; Merletti, Franco; Vermeulen, Roel; Kromhout, Hans; Lee, Ae-Kyoung; Maslanyj, Myron; Sim, Malcolm R; Taki, Masao; Wiart, Joe; Armstrong, Bruce; Milne, Elizabeth; Benke, Geza; Schattner, Rosa; Hutter, Hans-Peter; Woehrer, Adelheid; Krewski, Daniel; Mohipp, Charmaine; Momoli, Franco; Ritvo, Paul; Spinelli, John; Lacour, Brigitte; Delmas, Dominique; Remen, Thomas; Radon, Katja; Weinmann, Tobias; Klostermann, Swaantje; Heinrich, Sabine; Petridou, Eleni; Bouka, Evdoxia; Panagopoulou, Paraskevi; Dikshit, Rajesh; Nagrani, Rajini; Even-Nir, Hadas; Chetrit, Angela; Maule, Milena; Migliore, Enrica; Filippini, Graziella; Miligi, Lucia; Mattioli, Stefano; Yamaguchi, Naohito; Kojimahara, Noriko; Ha, Mina; Choi, Kyung-Hwa; Mannetje, Andrea 't; Eng, Amanda; Woodward, Alistair; Carretero, Gema; Alguacil, Juan; Aragones, Nuria; Suare-Varela, Maria Morales; Goedhart, Geertje; Schouten-van Meeteren, A Antoinette Y N; Reedijk, A Ardine M J; Cardis, Elisabeth

2014-01-01

The rapid increase in mobile phone use in young people has generated concern about possible health effects of exposure to radiofrequency (RF) and extremely low frequency (ELF) electromagnetic fields (EMF). MOBI-Kids, a multinational case-control study, investigates the potential effects of childhood and adolescent exposure to EMF from mobile communications technologies on brain tumor risk in 14 countries. The study, which aims to include approximately 1,000 brain tumor cases aged 10-24 years and two individually matched controls for each case, follows a common protocol and builds upon the methodological experience of the INTERPHONE study. The design and conduct of a study on EMF exposure and brain tumor risk in young people in a large number of countries is complex and poses methodological challenges. This manuscript discusses the design of MOBI-Kids and describes the challenges and approaches chosen to address them, including: (1) the choice of controls operated for suspected appendicitis, to reduce potential selection bias related to low response rates among population controls; (2) investigating a young study population spanning a relatively wide age range; (3) conducting a large, multinational epidemiological study, while adhering to increasingly stricter ethics requirements; (4) investigating a rare and potentially fatal disease; and (5) assessing exposure to EMF from communication technologies. Our experience in thus far developing and implementing the study protocol indicates that MOBI-Kids is feasible and will generate results that will contribute to the understanding of potential brain tumor risks associated with use of mobile phones and other wireless communications technologies among young people.

A Case Study on the Application of a Structured Experimental Method for Optimal Parameter Design of a Complex Control System

NASA Technical Reports Server (NTRS)

Torres-Pomales, Wilfredo

2015-01-01

This report documents a case study on the application of Reliability Engineering techniques to achieve an optimal balance between performance and robustness by tuning the functional parameters of a complex non-linear control system. For complex systems with intricate and non-linear patterns of interaction between system components, analytical derivation of a mathematical model of system performance and robustness in terms of functional parameters may not be feasible or cost-effective. The demonstrated approach is simple, structured, effective, repeatable, and cost and time efficient. This general approach is suitable for a wide range of systems.

Dietary habits after myocardial infarction - results from a cross-sectional study.

PubMed

Wallström, P; Mattisson, I; Tydén, P; Berglund, G; Janzon, L

2005-04-01

Comparing habitual nutrient intakes in persons with a history of acute myocardial infarction (AMI), and age-matched controls. Design. Cross-sectional study. Subjects. Men and women (525 cases and 1890 matched controls), aged 47-73 years, of the population-based Malmö Diet and Cancer cohort. Nutrient intakes were assessed by a validated modified diet history method. Body fatness was assessed by bioimpedance analysis. Case ascertainment was provided by national and regional registries. Men and women were analysed separately. Median time since AMI was 5.5 years in men and 3.8 years in women. Cases reported lower energy intakes (EIs) than controls, despite having similar basal metabolic rates. After adjustment for total EI, both male and female cases had lower fat intake and higher intake of several micronutrients, such as ascorbic acid, folate, and vitamin E, than controls, the difference being largest in men. Most of the cases reporting dietary change quoted 'disease' as their main reason for change. They had lower EI and lower energy-adjusted intake of fat than other cases. Survivors of AMI reported dietary habits more in line with current recommendations, particularly those who afterwards reported having changed their dietary habits. The possible bias introduced by social desirability is discussed.

New Whole-House Case Study: William Ryan Homes, Tampa, Florida

DOE Office of Scientific and Technical Information (OSTI.GOV)

none,

The builder worked with Consortium for Advanced Residential Buildings to design HERS-65 homes with energy-efficient heat pumps and programmable thermostats with humidity controls, foam-filled concrete block walls, draining house wrap, and airsealed kneewalls.

Factors associated with unreported tuberculosis cases in Spanish hospitals.

PubMed

Morales-García, Concepción; Rodrigo, Teresa; García-Clemente, Marta M; Muñoz, Ana; Bermúdez, Pilar; Casas, Francisco; Somoza, María; Milá, Celia; Penas, Antón; Hidalgo, Carmen; Casals, Martí; Caylá, Joan A

2015-07-29

Under-reporting of tuberculosis (TB) cases complicates disease control, hinders contact tracing and alters the accuracy of epidemiological data, including disease burden. The objective of the present study is to evaluate the proportion of unreported TB cases in Spanish healthcare facilities and to identify the associated factors. A multi-center retrospective study design was employed. The study included TB cases diagnosed in 16 facilities during 2011-2012. These cases were compared to those reported to the corresponding public health departments. Demographic, microbiological and clinical data were analyzed to determine the factors associated with unreported cases. Associated factors were analyzed on a bivariate level using the x(2) test and on a multivariate level using a logistic regression. Odds ratios (OR) and 95 % confidence intervals (CI) were calculated. Of the 592 TB cases included in the study, 85 (14.4 %) were not reported. The percentage of unreported cases per healthcare center ranged from 0-45.2 %. The following variables were associated to under-reporting at a multivariate level: smear-negative TB (OR = 1.87; CI:1.07-3.28), extrapulmonary disease (OR = 2.07; CI:1.05-4.09) and retired patients (OR = 3.04; CI:1.29-7.18). A nurse case manager was present in all of the centers with 100 % reporting. The percentage of reported cases among the smear-positive cases was 9.4 % and 19.4 % (p = 0.001) among the rest of the study population. Smear-positive TB was no associated to under-reporting. It is important that TB Control Programs encourage thorough case reporting to improve disease control, contact tracing and accuracy of epidemiological data. The help from a TB nurse case manager could improve the rate of under-reporting.

Space tug thermal control. [design criteria and specifications

NASA Technical Reports Server (NTRS)

1974-01-01

It was determined that space tug will require the capability to perform its mission within a broad range of thermal environments with currently planned mission durations of up to seven days, so an investigation was conducted to define a thermal design for the forward and intertank compartments and fuel cell heat rejection system that satisfies tug requirements for low inclination geosynchronous deploy and retrieve missions. Passive concepts were demonstrated analytically for both the forward and intertank compartments, and a worst case external heating environment was determined for use during the study. The thermal control system specifications and designs which resulted from the research are shown.

Optimum aerodynamic design via boundary control

NASA Technical Reports Server (NTRS)

Jameson, Antony

1994-01-01

These lectures describe the implementation of optimization techniques based on control theory for airfoil and wing design. In previous studies it was shown that control theory could be used to devise an effective optimization procedure for two-dimensional profiles in which the shape is determined by a conformal transformation from a unit circle, and the control is the mapping function. Recently the method has been implemented in an alternative formulation which does not depend on conformal mapping, so that it can more easily be extended to treat general configurations. The method has also been extended to treat the Euler equations, and results are presented for both two and three dimensional cases, including the optimization of a swept wing.

An approach to checking case-crossover analyses based on equivalence with time-series methods.

PubMed

Lu, Yun; Symons, James Morel; Geyh, Alison S; Zeger, Scott L

2008-03-01

The case-crossover design has been increasingly applied to epidemiologic investigations of acute adverse health effects associated with ambient air pollution. The correspondence of the design to that of matched case-control studies makes it inferentially appealing for epidemiologic studies. Case-crossover analyses generally use conditional logistic regression modeling. This technique is equivalent to time-series log-linear regression models when there is a common exposure across individuals, as in air pollution studies. Previous methods for obtaining unbiased estimates for case-crossover analyses have assumed that time-varying risk factors are constant within reference windows. In this paper, we rely on the connection between case-crossover and time-series methods to illustrate model-checking procedures from log-linear model diagnostics for time-stratified case-crossover analyses. Additionally, we compare the relative performance of the time-stratified case-crossover approach to time-series methods under 3 simulated scenarios representing different temporal patterns of daily mortality associated with air pollution in Chicago, Illinois, during 1995 and 1996. Whenever a model-be it time-series or case-crossover-fails to account appropriately for fluctuations in time that confound the exposure, the effect estimate will be biased. It is therefore important to perform model-checking in time-stratified case-crossover analyses rather than assume the estimator is unbiased.

Power controller 28Vdc load switching (N. O. SPST). Final report, 31 August 1977-21 January 1980

DOE Office of Scientific and Technical Information (OSTI.GOV)

McMackin, J.B.

1980-01-21

A solid state power controller has been designed in four ratings to switch 28Vdc power to selected loads upon remote command. The four ratings trip out at currents of 10, 5, 2 and 1/2 amps. The design allows for wide variations in load and supply voltage and will not trip out on short load transients of up to 1000% of rated load current. In case of failure of the controller circuitry, an internal fuse protects the load from excessive current. The control current which operates the controller also provides a sensing function so that the state of the controller canmore » be determined remotely. The controllers are designed to operate over a case temperature range of -54 C to 120 C. A quantity of 100 units have been fabricated, tested, and supplied to the Navy.« less

Effectiveness of 13-Valent Pneumococcal Conjugate Vaccine Against Hospitalization for Community-Acquired Pneumonia in Older US Adults: A Test-Negative Design.

PubMed

McLaughlin, John M; Jiang, Qin; Isturiz, Raul E; Sings, Heather L; Swerdlow, David L; Gessner, Bradford D; Carrico, Ruth M; Peyrani, Paula; Wiemken, Timothy L; Mattingly, William A; Ramirez, Julio A; Jodar, Luis

2018-05-21

Following universal recommendation for use of 13-valent pneumococcal conjugate vaccine (PCV13) in US adults aged ≥65 years in September 2014, we conducted the first real-world evaluation of PCV13 vaccine effectiveness (VE) against hospitalized vaccine-type community-acquired pneumonia (CAP) in this population. Using a test-negative design, we identified cases and controls from a population-based surveillance study of adults in Louisville, Kentucky, who were hospitalized with CAP. We analyzed a subset of CAP patients enrolled 1 April 2015 through 30 April 2016 who were aged ≥65 years and consented to have their pneumococcal vaccination history confirmed by health insurance records. Cases were defined as hospitalized CAP patients with PCV13 serotypes identified via culture or serotype-specific urinary antigen detection assay. Remaining CAP patients served as test-negative controls. Of 2034 CAP hospitalizations, we identified PCV13 serotypes in 68 (3.3%) participants (ie, cases), of whom 6 of 68 (8.8%) had a positive blood culture. Cases were less likely to be immunocompromised (29.4% vs 46.4%, P = .02) and overweight or obese (41.2% vs 58.6%, P = .01) compared to controls, but were otherwise similar. Cases were less likely to have received PCV13 than controls (3/68 [4.4%] vs 285/1966 [14.5%]; unadjusted VE, 72.8% [95% confidence interval, 12.8%-91.5%]). No confounding was observed during adjustment for patient characteristics, including immunocompromised status, body mass index, and history of influenza and pneumococcal polysaccharide vaccination (adjusted VE range, 71.1%-73.3%). Our study is the first to demonstrate real-world effectiveness of PCV13 against vaccine-type CAP in adults aged ≥65 years following introduction into a national immunization program.

Sensori-Motor Learning with Movement Sonification: Perspectives from Recent Interdisciplinary Studies.

PubMed

Bevilacqua, Frédéric; Boyer, Eric O; Françoise, Jules; Houix, Olivier; Susini, Patrick; Roby-Brami, Agnès; Hanneton, Sylvain

2016-01-01

This article reports on an interdisciplinary research project on movement sonification for sensori-motor learning. First, we describe different research fields which have contributed to movement sonification, from music technology including gesture-controlled sound synthesis, sonic interaction design, to research on sensori-motor learning with auditory-feedback. In particular, we propose to distinguish between sound-oriented tasks and movement-oriented tasks in experiments involving interactive sound feedback. We describe several research questions and recently published results on movement control, learning and perception. In particular, we studied the effect of the auditory feedback on movements considering several cases: from experiments on pointing and visuo-motor tracking to more complex tasks where interactive sound feedback can guide movements, or cases of sensory substitution where the auditory feedback can inform on object shapes. We also developed specific methodologies and technologies for designing the sonic feedback and movement sonification. We conclude with a discussion on key future research challenges in sensori-motor learning with movement sonification. We also point out toward promising applications such as rehabilitation, sport training or product design.

40 CFR 63.53 - Application content for case-by-case MACT determinations.

Code of Federal Regulations, 2012 CFR

2012-07-01

... identified emission point or group of affected emission points, an identification of control technology in... on the design, operation, size, estimated control efficiency and any other information deemed... CATEGORIES Requirements for Control Technology Determinations for Major Sources in Accordance With Clean Air...

40 CFR 63.53 - Application content for case-by-case MACT determinations.

Code of Federal Regulations, 2014 CFR

2014-07-01

... identified emission point or group of affected emission points, an identification of control technology in... on the design, operation, size, estimated control efficiency and any other information deemed... CATEGORIES Requirements for Control Technology Determinations for Major Sources in Accordance With Clean Air...

40 CFR 63.53 - Application content for case-by-case MACT determinations.

Code of Federal Regulations, 2013 CFR

2013-07-01

... identified emission point or group of affected emission points, an identification of control technology in... on the design, operation, size, estimated control efficiency and any other information deemed... CATEGORIES Requirements for Control Technology Determinations for Major Sources in Accordance With Clean Air...

40 CFR 63.53 - Application content for case-by-case MACT determinations.

Code of Federal Regulations, 2011 CFR

2011-07-01

... identified emission point or group of affected emission points, an identification of control technology in... on the design, operation, size, estimated control efficiency and any other information deemed... CATEGORIES Requirements for Control Technology Determinations for Major Sources in Accordance With Clean Air...

The Association Between Neurocysticercosis and Hippocampal Atrophy is Related to Age

PubMed Central

Del Brutto, Oscar H.; Issa, Naoum P.; Salgado, Perla; Del Brutto, Victor J.; Zambrano, Mauricio; Lama, Julio; García, Héctor H.

2017-01-01

Neurocysticercosis (NCC) has been associated with hippocampal atrophy, but the prevalence and pathogenic mechanisms implicated in this relationship are unknown. Using a population-based, case–control study design, residents in a rural village (Atahualpa) aged ≥ 40 years with calcified NCC were identified as cases and paired to NCC-free individuals (control subjects) matched by age, sex, and level of education. Cases and control subjects underwent magnetic resonance imaging for hippocampal rating according to the Scheltens' scale for medial temporal atrophy and were interviewed to identify those with a clinical seizure disorder. The prevalence of hippocampal atrophy was compared between cases and control subjects by the use of the McNemar's test for correlated proportions. Seventy-five individuals with calcified NCC and their matched control subjects were included in the analysis. Hippocampal atrophy was noted in 26 (34.7%) cases and nine (12%) control subjects (odds ratio: 4.4; 95% confidence interval: 1.6–14.9, P < 0.0021). Stratification of pairs according to tertiles of age revealed an age-related trend in this association, which became significant only in those aged ≥ 68 years (P = 0.027). Only five cases and one control had recurrent seizures (P = 0.221); three of these five cases had hippocampal atrophy, and the single control subject had normal hippocampi. This study confirms an association between NCC and hippocampal atrophy, and shows that this association is stronger in older age groups. This suggests that NCC-related hippocampal atrophy takes a long time to develop. PMID:28077750

Importance of temperature control for HEFLEX, a biological experiment for Spacelab 1. [plant gravitational physiology study

NASA Technical Reports Server (NTRS)

Chapman, D. K.; Brown, A. H.

1979-01-01

The importance of temperature control to HEFLEX, a Spacelab experiment designed to measure kinetic properties of Helianthis nutation in a low-g environment, is discussed. It is argued that the development of the HEFLEX experiment has been severely hampered by the inadequate control of ambient air temperature provided by the spacecraft module design. A worst case calculation shows that delivery of only 69% of the maximum yield of useful data from the HEFLEX system is guaranteed; significant data losses from inadequate temperature control are expected. The magnitude of the expected data losses indicates that the cost reductions associated with imprecise temperature controls may prove to be a false economy in the long term.

Packed red blood cell transfusion is not associated with increased risk of necrotizing enterocolitis in premature infants

PubMed Central

Sharma, R; Kraemer, DF; Torrazza, RM; Mai, V; Neu, J; Shuster, JJ; Hudak, ML

2015-01-01

OBJECTIVE Recent reports have posited a temporal association between blood transfusion with packed red blood cells (BT) and necrotizing enterocolitis (NEC). We evaluated the relationship between BT and NEC among infants at three hospitals who were consented at birth into a prospective observational study of NEC. STUDY DESIGN We used a case–control design to match each case of NEC in our study population of infants born at <33 weeks postmenstrual age (PMA) to one control infant using hospital of birth, PMA, birth weight and date of birth. RESULT The number of transfusions per infant did not differ between 42 NEC cases and their controls (4.0 ± 4.6 vs 5.4 ± 4.1, mean ± s.d., P = 0.063). A matched-pair analysis did not identify an association of transfusion with NEC in either the 48-h or 7-day time periods before the onset of NEC. Stratifying on matched-sets, the Cox proportional hazard model did not identify any difference in the total number of BTs between the two groups (hazard ratio 0.78, 95% confidence interval 0.57 to 1.07, P = 0.11). CONCLUSION In contrast to previous studies, our case–control study did not identify a significant temporal association between BT and NEC. Additional large prospective randomized studies are needed to clarify the relationship between BT and NEC. PMID:25144159

Optimizing the construction of devices to control inaccesible surfaces - case study

NASA Astrophysics Data System (ADS)

Niţu, E. L.; Costea, A.; Iordache, M. D.; Rizea, A. D.; Babă, Al

2017-10-01

The modern concept for the evolution of manufacturing systems requires multi-criteria optimization of technological processes and equipments, prioritizing associated criteria according to their importance. Technological preparation of the manufacturing can be developed, depending on the volume of production, to the limit of favourable economical effects related to the recovery of the costs for the design and execution of the technological equipment. Devices, as subsystems of the technological system, in the general context of modernization and diversification of machines, tools, semi-finished products and drives, are made in a multitude of constructive variants, which in many cases do not allow their identification, study and improvement. This paper presents a case study in which the multi-criteria analysis of some structures, based on a general optimization method, of novelty character, is used in order to determine the optimal construction variant of a control device. The rational construction of the control device confirms that the optimization method and the proposed calculation methods are correct and determine a different system configuration, new features and functions, and a specific method of working to control inaccessible surfaces.

Case-control geographic clustering for residential histories accounting for risk factors and covariates.

PubMed

Jacquez, Geoffrey M; Meliker, Jaymie R; Avruskin, Gillian A; Goovaerts, Pierre; Kaufmann, Andy; Wilson, Mark L; Nriagu, Jerome

2006-08-03

Methods for analyzing space-time variation in risk in case-control studies typically ignore residential mobility. We develop an approach for analyzing case-control data for mobile individuals and apply it to study bladder cancer in 11 counties in southeastern Michigan. At this time data collection is incomplete and no inferences should be drawn - we analyze these data to demonstrate the novel methods. Global, local and focused clustering of residential histories for 219 cases and 437 controls is quantified using time-dependent nearest neighbor relationships. Business address histories for 268 industries that release known or suspected bladder cancer carcinogens are analyzed. A logistic model accounting for smoking, gender, age, race and education specifies the probability of being a case, and is incorporated into the cluster randomization procedures. Sensitivity of clustering to definition of the proximity metric is assessed for 1 to 75 k nearest neighbors. Global clustering is partly explained by the covariates but remains statistically significant at 12 of the 14 levels of k considered. After accounting for the covariates 26 Local clusters are found in Lapeer, Ingham, Oakland and Jackson counties, with the clusters in Ingham and Oakland counties appearing in 1950 and persisting to the present. Statistically significant focused clusters are found about the business address histories of 22 industries located in Oakland (19 clusters), Ingham (2) and Jackson (1) counties. Clusters in central and southeastern Oakland County appear in the 1930's and persist to the present day. These methods provide a systematic approach for evaluating a series of increasingly realistic alternative hypotheses regarding the sources of excess risk. So long as selection of cases and controls is population-based and not geographically biased, these tools can provide insights into geographic risk factors that were not specifically assessed in the case-control study design.

Rare variant association analysis in case-parents studies by allowing for missing parental genotypes.

PubMed

Li, Yumei; Xiang, Yang; Xu, Chao; Shen, Hui; Deng, Hongwen

2018-01-15

The development of next-generation sequencing technologies has facilitated the identification of rare variants. Family-based design is commonly used to effectively control for population admixture and substructure, which is more prominent for rare variants. Case-parents studies, as typical strategies in family-based design, are widely used in rare variant-disease association analysis. Current methods in case-parents studies are based on complete case-parents data; however, parental genotypes may be missing in case-parents trios, and removing these data may lead to a loss in statistical power. The present study focuses on testing for rare variant-disease association in case-parents study by allowing for missing parental genotypes. In this report, we extended the collapsing method for rare variant association analysis in case-parents studies to allow for missing parental genotypes, and investigated the performance of two methods by using the difference of genotypes between affected offspring and their corresponding "complements" in case-parent trios and TDT framework. Using simulations, we showed that, compared with the methods just only using complete case-parents data, the proposed strategy allowing for missing parental genotypes, or even adding unrelated affected individuals, can greatly improve the statistical power and meanwhile is not affected by population stratification. We conclude that adding case-parents data with missing parental genotypes to complete case-parents data set can greatly improve the power of our strategy for rare variant-disease association.

Management Information Systems for Higher Education. Studies in Institutional Management in Higher Education.

ERIC Educational Resources Information Center

Hussain, K. M., Ed.

Contents include an introduction to information systems (basic concepts and life-cycle); development of an information system (design, implementation, testing, and conversion); operation (evaluation and maintenance, quality control, and economics); and case studies of such systems at the New University of Lisbon, Bath University, Laval University…

Is Infertility Associated with Childhood Autism?

ERIC Educational Resources Information Center

Grether, Judith K.; Qian, Yinge; Croughan, Mary S.; Wu, Yvonne W.; Schembri, Michael; Camarano, Loretta; Croen, Lisa A.

2013-01-01

Concerns persist about a possible link between infertility and risk of autism spectrum disorders (ASD). Interpretation of existing studies is limited by racial/ethnic homogeneity of study populations and other factors. Using a case-control design, we evaluated infertility history and treatment documented in medical records of members of Kaiser…

Designing Biomimetic Materials from Marine Organisms.

PubMed

Nichols, William T

2015-01-01

Two biomimetic design approaches that apply biological solutions to engineering problems are discussed. In the first case, motivation comes from an engineering problem and the key challenge is to find analogous biological functions and map them into engineering materials. We illustrate with an example of water pollution remediation through appropriate design of a biomimetic sponge. In the second case, a biological function is already known and the challenge is to identify the appropriate engineering problem. We demonstrate the biological approach with marine diatoms that control energy and materials at their surface providing inspiration for a number of engineering applications. In both cases, it is essential to select materials and structures at the nanoscale to control energy and materials flows at interfaces.

Design and implementation of multichannel global active structural acoustic control for a device casing

NASA Astrophysics Data System (ADS)

Mazur, Krzysztof; Wrona, Stanislaw; Pawelczyk, Marek

2018-01-01

The paper presents the idea and discussion on implementation of multichannel global active noise control systems. As a test plant an active casing is used. It has been developed by the authors to reduce device noise directly at the source by controlling vibration of its casing. To provide global acoustic effect in the whole environment, where the device operates, it requires a number of secondary sources and sensors for each casing wall, thus making the whole active control structure complicated, i.e. with a large number of interacting channels. The paper discloses all details concerning hardware setup and efficient implementation of control algorithms for the multichannel case. A new formulation is presented to introduce the distributed version of the Switched-error Filtered-reference Least Mean Squares (FXLMS) algorithm together with adaptation rate enhancement. The convergence rate of the proposed algorithm is compared with original Multiple-error FXLMS. A number of hints followed from many years of authors' experience on microprocessor control systems design and signal processing algorithms optimization are presented. They can be used for various active control and signal processing applications, both for academic research and commercialization.

Is bisphosphonate therapy for benign bone disease associated with impaired dental healing? A case-controlled study

PubMed Central

2011-01-01

Background Bisphosphonates are common first line medications used for the management of benign bone disease. One of the most devastating complications associated with bisphosphonate use is osteonecrosis of the jaws which may be related to duration of exposure and hence cumulative dose, dental interventions, medical co-morbidities or in some circumstances with no identifiable aggravating factor. While jaw osteonecrosis is a devastating outcome which is currently difficult to manage, various forms of delayed dental healing may be a less dramatic and, therefore, poorly-recognised complications of bisphosphonate use for the treatment of osteoporosis. It is hypothesised that long-term (more than 1 year's duration) bisphosphonate use for the treatment of post-menopausal osteoporosis or other benign bone disease is associated with impaired dental healing. Methods/Design A case-control study has been chosen to test the hypothesis as the outcome event rate is likely to be very low. A total of 54 cases will be recruited into the study following review of all dental files from oral and maxillofacial surgeons and special needs dentists in Victoria where potential cases of delayed dental healing will be identified. Potential cases will be presented to an independent case adjudication panel to determine if they are definitive delayed dental healing cases. Two hundred and fifteen controls (1:4 cases:controls), matched for age and visit window period, will be selected from those who have attended local community based referring dental practices. The primary outcome will be the incidence of delayed dental healing that occurs either spontaneously or following dental treatment such as extractions, implant placement, or denture use. Discussion This study is the largest case-controlled study assessing the link between bisphosphonate use and delayed dental healing in Australia. It will provide invaluable data on the potential link between bisphosphonate use and osteonecrosis of the jaws. PMID:21477374

Health Care Needs and Support for Patients Undergoing Treatment for Prosthetic Joint Infection following Hip or Knee Arthroplasty: A Systematic Review.

PubMed

Kunutsor, Setor K; Beswick, Andrew D; Peters, Tim J; Gooberman-Hill, Rachael; Whitehouse, Michael R; Blom, Ashley W; Moore, Andrew J

2017-01-01

Hip and knee arthroplasty are common interventions for the treatment of joint conditions, most notably osteoarthritis. Although many patients benefit from surgery, approximately 1% of patients develop infection afterwards known as deep prosthetic joint infection (PJI), which often requires further major surgery. To assess support needs of patients undergoing treatment for PJI following hip or knee arthroplasty and to identify and evaluate what interventions are routinely offered to support such patients. Systematic review. MEDLINE, EMBASE, Web of Science, PsycINFO, Cinahl, Social Science Citation Index, The Cochrane Library, and reference lists of relevant studies from January 01, 1980 to October 05, 2016. Observational (prospective or retrospective cohort, nested case-control or case-control) studies, qualitative studies, or clinical trials conducted in patients treated for PJI and/or other major adverse occurrences following hip or knee arthroplasty. Data were extracted by two independent investigators and consensus was reached with involvement of a third. Given the heterogeneous nature of study designs, methods, and limited number of studies, a narrative synthesis is presented. Of 4,213 potentially relevant citations, we identified one case-control, one prospective cohort and two qualitative studies for inclusion in the synthesis. Patients report that PJI and treatment had a profoundly negative impact affecting physical, emotional, social and economic aspects of their lives. No study evaluated support interventions. The findings demonstrate that patients undergoing treatment for PJI have extensive physical, psychological, social and economic support needs. The interpretation of study results is limited by variation in study design, outcome measures and the small number of relevant eligible studies. However, our review highlights a lack of evidence about support strategies for patients undergoing treatment for PJI and other adverse occurrences following hip or knee arthroplasty. There is a need to design, implement and evaluate interventions to support these patients. PROSPERO 2015: CRD42015027175.

Epidemiology of fetal alcohol syndrome in a South African community in the Western Cape Province.

PubMed Central

May, P A; Brooke, L; Gossage, J P; Croxford, J; Adnams, C; Jones, K L; Robinson, L; Viljoen, D

2000-01-01

OBJECTIVES: This study determined the characteristics of fetal alcohol syndrome in a South African community, and methodology was designed for the multidisciplinary study of fetal alcohol syndrome in developing societies. METHODS: An active case ascertainment, 2-tier methodology was used among 992 first-grade pupils. A case-control design, using measures of growth, development, dysmorphology, and maternal risk, delineated characteristics of children with fetal alcohol syndrome. RESULTS: A high rate of fetal alcohol syndrome was found in the schools--40.5 to 46.4 per 1000 children aged 5 to 9 years--and age-specific community rates (ages 6-7) were 39.2 to 42.9. These rates are 18 to 141 times greater than in the United States. Rural residents had significantly more fetal alcohol syndrome. After control for ethnic variation, children with fetal alcohol syndrome had traits similar to those elsewhere: poor growth and development, congruent dysmorphology, and lower intellectual functioning. CONCLUSIONS: This study documented the highest fetal alcohol syndrome rate to date in an overall community population. Fetal alcohol syndrome initiatives that incorporate innovative sampling and active case ascertainment methods can be used to obtain timely and accurate data among developing populations. PMID:11111264

Consortium on the Genetics of Schizophrenia (COGS) assessment of endophenotypes for schizophrenia: an introduction to this Special Issue of Schizophrenia Research.

PubMed

Swerdlow, Neal R; Gur, Raquel E; Braff, David L

2015-04-01

The COGS is a multi-site NIMH-sponsored investigation of the genetic basis of 12 primary and multiple secondary quantitative endophenotypes in schizophrenia. Since 2003, COGS has completed studies using a family-based ascertainment strategy (COGS-1), and a case-control ascertainment strategy (COGS-2) (cumulative "n">4000). COGS-1 family study confirmed robust deficits in, and heritability of, these endophenotypes in schizophrenia, and provided evidence for a coherent genetic architecture underlying the risk for neurocognitive and neurophysiological deficits in this disorder. COGS-2 case-control findings, many reported herein, establish a foundation for fine genomic mapping and other analyses of these endophenotypes and risk genes for SZ. Several reports in this Special Issue compare findings of endophenotype deficits generated by fundamentally different COGS-1 vs. COGS-2 ascertainment strategies. Despite the expectation that family-based and case-control designs would establish demographically and potentially biologically distinct patient cohorts, findings generally revealed comparable patterns of endophenotype deficits across studies. The COGS-2 case-control design facilitated the accrual of a larger "n", permitting detailed analyses of factors moderating endophenotype performance. Some COGS-2 endophenotypes not assessed in COGS-1 are also reported, as is a new factor analytic strategy for identifying shared vs. unique factors among the COGS endophenotypes which can be used to develop composite variables with distinct genetic signatures. The path to date of COGS-1 endophenotype and genetic findings, followed by replication and extension in COGS-2, establishes benchmarks for endophenotype deficits in SZ and their moderation by specific factors, and clear expectations for informative findings from upcoming COGS-2 genetic analyses. Published by Elsevier B.V.

Early incidence of occupational asthma among young bakers, pastry-makers and hairdressers: design of a retrospective cohort study

PubMed Central

2010-01-01

Background Occupational exposures are thought to be responsible for 10-15% of new-onset asthma cases in adults, with disparities across sectors. Because most of the data are derived from registries and cross-sectional studies, little is known about incidence of occupational asthma (OA) during the first years after inception of exposure. This paper describes the design of a study that focuses on this early asthma onset period among young workers in the bakery, pastry making and hairdressing sectors in order to assess early incidence of OA in these "at risk" occupations according to exposure duration, and to identify risk factors of OA incidence. Methods/Design The study population is composed of subjects who graduated between 2001 and 2006 in these sectors where they experience exposure to organic or inorganic allergenic or irritant compounds (with an objective of 150 subjects by year) and 250 young workers with no specific occupational exposure. A phone interview focusing on respiratory and 'Ear-Nose-Throat' (ENT) work-related symptoms screen subjects considered as "possibly OA cases". Subjects are invited to participate in a medical visit to complete clinical and lung function investigations, including fractional exhaled nitric oxide (FENO) and carbon monoxide (CO) measurements, and to collect blood samples for IgE (Immunoglobulin E) measurements (total IgE and IgE for work-related and common allergens). Markers of oxidative stress and genetic polymorphisms exploration are also assessed. A random sample of 200 "non-cases" (controls) is also visited, following a nested case-control design. Discussion This study may allow to describ a latent period between inception of exposure and the rise of the prevalence of asthma symptoms, an information that would be useful for the prevention of OA. Such a time frame would be suited for conducting screening campaigns of this emergent asthma at a stage when occupational hygiene measures and adapted therapeutic interventions might be effective. Trial registration Clinical trial registration number is NCT01096537. PMID:20420675

Intrahousehold resource allocation and child growth in Mozambique: an ethnographic case-control study.

PubMed

Pfeiffer, J; Gloyd, S; Ramirez Li, L

2001-07-01

This study examines the effect of intrahousehold cash income control and decision-making patterns on child growth in the rural town of Sussundenga in Manica Province, Mozambique. A case-control study design was used to examine the influence of men's and women's disaggregated cash incomes on child growth. The research tested whether greater maternal share of household cash income was associated with (1) increased maternal decision-making and bargaining power in the household, and (2) better child growth. Fifty case households, with children 1-4 years old exhibiting poor growth, were matched with 50 control households of similar socioeconomic status in which all children under five demonstrated healthy growth. Data were gathered on gender-specific income generation and expenditure, specific intrahousehold allocation processes, diet, and sociodemographic variables using a formal survey. Key informant interviews, focus groups, and observation over one year provided ethnographic context for the case-control findings. Case-control differences were analyzed using McNemar's test, paired t-test, and conditional logistic regression. In spite of matching households for socioeconomic status, control household incomes were still slightly greater than cases. Male spouse income was also higher among controls while maternal income, and maternal proportion of household income, were not significantly different. Household meat, fish and poultry consumption, and maternal education were significantly greater among control households than cases. Greater maternal share of household income was not associated with greater maternal decision-making around cash. However, mothers must spend what little cash they earn on daily food supplies and usually request additional cash from spouses to cover these costs. There is evidence that if mothers earn enough to cover these socially prescribed costs, they can spend cash for other needs. Above this threshold, women's earnings may confer more bargaining power. The research also revealed a nuclearization of households, attenuation of community bonds of mutual aid, and increasing importance of cash for survival.

Analyzing self-controlled case series data when case confirmation rates are estimated from an internal validation sample.

PubMed

Xu, Stanley; Clarke, Christina L; Newcomer, Sophia R; Daley, Matthew F; Glanz, Jason M

2018-05-16

Vaccine safety studies are often electronic health record (EHR)-based observational studies. These studies often face significant methodological challenges, including confounding and misclassification of adverse event. Vaccine safety researchers use self-controlled case series (SCCS) study design to handle confounding effect and employ medical chart review to ascertain cases that are identified using EHR data. However, for common adverse events, limited resources often make it impossible to adjudicate all adverse events observed in electronic data. In this paper, we considered four approaches for analyzing SCCS data with confirmation rates estimated from an internal validation sample: (1) observed cases, (2) confirmed cases only, (3) known confirmation rate, and (4) multiple imputation (MI). We conducted a simulation study to evaluate these four approaches using type I error rates, percent bias, and empirical power. Our simulation results suggest that when misclassification of adverse events is present, approaches such as observed cases, confirmed case only, and known confirmation rate may inflate the type I error, yield biased point estimates, and affect statistical power. The multiple imputation approach considers the uncertainty of estimated confirmation rates from an internal validation sample, yields a proper type I error rate, largely unbiased point estimate, proper variance estimate, and statistical power. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The impact of overactive bladder, incontinence and other lower urinary tract symptoms on quality of life, work productivity, sexuality and emotional well-being in men and women: results from the EPIC study.

PubMed

Coyne, Karin S; Sexton, Chris C; Irwin, Debra E; Kopp, Zoe S; Kelleher, Con J; Milsom, Ian

2008-06-01

To examine the effect overactive bladder (OAB) and other lower urinary tract symptoms (LUTS) on health-related quality of life (HRQoL) in a population sample, as OAB often occurs in conjunction with many other LUTS. A nested case-control analysis was performed on men and women with (cases) and without (controls) OAB, from the EPIC study. OAB was assessed using 2002 International Continence Society definitions. Based on their responses to questions about LUTS, cases were classified into five groups; continent OAB, OAB with incontinence, OAB + postmicturition, OAB + voiding, and OAB + postmicturition + voiding. Both cases and controls were asked questions about symptom bother (OAB-q), generic QoL (EQ-5D), work productivity (Work Productivity and Activity Impairment, WPAI), depressive symptoms (Center for Epidemiologic Studies Depression Scale), sexual satisfaction, and erectile dysfunction (men only) using the Massachusetts Male Aging Study. Cases answered additional condition-specific questions HRQoL (OAB-q short form), Patient Perception of Bladder Condition and work productivity related to a specific health problem (WPAI-SHP). General linear models were used to evaluate group differences. Of the EPIC participants, 1434 identified OAB cases were matched by age, gender and country, with 1434 participants designated as controls. Cases and controls were primarily Caucasian (96.2% and 96.7%, respectively), and most (65%) were female; the mean age was 53.8 and 53.7 years, respectively. Comorbid conditions differed significantly by case/control status, with cases reporting significantly greater rates of chronic constipation, asthma, diabetes, high blood pressure, bladder or prostate cancer, neurological conditions and depression. There were significant differences between the cases and controls in all reported LUTS. The OAB + postmicturition + voiding group reported significantly greater symptom bother, worse HRQoL, higher rates of depression and decreased enjoyment of sexual activity, than the other subgroups. OAB has a substantial, multidimensional impact on patients; OAB with additional LUTS has a greater impact. The diagnosis and treatment of OAB should be considered in conjunction with other LUTS, to maximize treatment options and optimize patient outcomes.

Controlled-Root Approach To Digital Phase-Locked Loops

NASA Technical Reports Server (NTRS)

Stephens, Scott A.; Thomas, J. Brooks

1995-01-01

Performance tailored more flexibly and directly to satisfy design requirements. Controlled-root approach improved method for analysis and design of digital phase-locked loops (DPLLs). Developed rigorously from first principles for fully digital loops, making DPLL theory and design simpler and more straightforward (particularly for third- or fourth-order DPLL) and controlling performance more accurately in case of high gain.

Investigation of Maternal Effects, Maternal-Fetal Interactions and Parent-of-Origin Effects (Imprinting), Using Mothers and Their Offspring

PubMed Central

Ainsworth, Holly F; Unwin, Jennifer; Jamison, Deborah L; Cordell, Heather J

2011-01-01

Many complex genetic effects, including epigenetic effects, may be expected to operate via mechanisms in the inter-uterine environment. A popular design for the investigation of such effects, including effects of parent-of-origin (imprinting), maternal genotype, and maternal-fetal genotype interactions, is to collect DNA from affected offspring and their mothers (case/mother duos) and to compare with an appropriate control sample. An alternative design uses data from cases and both parents (case/parent trios) but does not require controls. In this study, we describe a novel implementation of a multinomial modeling approach that allows the estimation of such genetic effects using either case/mother duos or case/parent trios. We investigate the performance of our approach using computer simulations and explore the sample sizes and data structures required to provide high power for detection of effects and accurate estimation of the relative risks conferred. Through the incorporation of additional assumptions (such as Hardy-Weinberg equilibrium, random mating and known allele frequencies) and/or the incorporation of additional types of control sample (such as unrelated controls, controls and their mothers, or both parents of controls), we show that the (relative risk) parameters of interest are identifiable and well estimated. Nevertheless, parameter interpretation can be complex, as we illustrate by demonstrating the mathematical equivalence between various different parameterizations. Our approach scales up easily to allow the analysis of large-scale genome-wide association data, provided both mothers and affected offspring have been genotyped at all variants of interest. Genet. Epidemiol. 35:19–45, 2011. © 2010 Wiley-Liss, Inc. PMID:21181895

Transmitted cardiovascular pulsations on high resolution esophageal impedance manometry, and their significance in dysphagia.

PubMed

Chaudhry, Naueen A; Zahid, Kamran; Keihanian, Sara; Dai, Yunfeng; Zhang, Qing

2017-11-28

To investigate the behavior of pulsatile pressure zones (PPZ's) as noted on high resolution esophageal impedance manometry (HREIM), and determine their association with dysphagia. Retrospective, single center case control design screening HREIM studies for cases (dysphagia) and controls (no dysphagia). Thoracic radiology studies were reviewed further in cases for (thoracic cardiovascular) thoracic cardiovascular (TCV) structures in esophageal proximity to compare with HREIM findings. Manometric data was collected for number, location, axial length, PPZ pressure and esophageal clearance function (impedance). Among 317 screened patients, 56% cases and 64% controls had PPZ's. Fifty cases had an available thoracic radiology comparison. The distribution of PPZ's in these 50 cases and 59 controls was similar (average 1.4 PPZ/patient). Controls (mean 31.2 ± SD 12 years) were a significantly younger population than cases (mean 67.3 ± SD 14.9 years) with P < 0.0001. The upright posture PPZ pressure was higher in controls (15.7 ± 10.0 mmHg) than cases (10.8 ± 9.7 mmHg). Although statistically significant ( P = 0.005), it was a weak predictor using logistic regression and ROC model (AUC = 0.65). Three dysphagia patients had partial compression from external TCV on radiology (1 aberrant subclavian artery, 2 dilated left atrium). The posture (supine vs upright) with more prominent PPZ's impaired bolus clearance in 9 additional cases by > 20%. Transmitted TCV pulsations observed in HREIM bear no significant impact on swallowing. However, in older adults with dysphagia, evidence of impaired bolus clearance on impedance should be evaluated for external TCV compression. These associations have never been explored previously in literature, and are novel.

Transmitted cardiovascular pulsations on high resolution esophageal impedance manometry, and their significance in dysphagia

PubMed Central

Chaudhry, Naueen A; Zahid, Kamran; Keihanian, Sara; Dai, Yunfeng; Zhang, Qing

2017-01-01

AIM To investigate the behavior of pulsatile pressure zones (PPZ’s) as noted on high resolution esophageal impedance manometry (HREIM), and determine their association with dysphagia. METHODS Retrospective, single center case control design screening HREIM studies for cases (dysphagia) and controls (no dysphagia). Thoracic radiology studies were reviewed further in cases for (thoracic cardiovascular) thoracic cardiovascular (TCV) structures in esophageal proximity to compare with HREIM findings. Manometric data was collected for number, location, axial length, PPZ pressure and esophageal clearance function (impedance). RESULTS Among 317 screened patients, 56% cases and 64% controls had PPZ’s. Fifty cases had an available thoracic radiology comparison. The distribution of PPZ’s in these 50 cases and 59 controls was similar (average 1.4 PPZ/patient). Controls (mean 31.2 ± SD 12 years) were a significantly younger population than cases (mean 67.3 ± SD 14.9 years) with P < 0.0001. The upright posture PPZ pressure was higher in controls (15.7 ± 10.0 mmHg) than cases (10.8 ± 9.7 mmHg). Although statistically significant (P = 0.005), it was a weak predictor using logistic regression and ROC model (AUC = 0.65). Three dysphagia patients had partial compression from external TCV on radiology (1 aberrant subclavian artery, 2 dilated left atrium). The posture (supine vs upright) with more prominent PPZ’s impaired bolus clearance in 9 additional cases by > 20%. CONCLUSION Transmitted TCV pulsations observed in HREIM bear no significant impact on swallowing. However, in older adults with dysphagia, evidence of impaired bolus clearance on impedance should be evaluated for external TCV compression. These associations have never been explored previously in literature, and are novel. PMID:29209125

The effect of maternal subclinical hypothyroidism on IQ in 7- to 8-year-old children: A case-control review.

PubMed

Murphy, Niamh C; Diviney, Mairead M; Donnelly, Jennifer C; Cooley, Sharon M; Kirkham, Colin H; Foran, Adrienne M; Breathnach, Fionnuala M; Malone, Fergal D; Geary, Michael P

2015-10-01

In Ireland, pregnant women are not routinely screened for subclinical hypothyroidism (SCH). Our objective was to compare the intelligence quotient (IQ) of children whose mothers had been diagnosed with SCH prenatally with matched controls using a case-control retrospective study. In a previous study from our group, 1000 healthy nulliparous women were screened anonymously for SCH. This was a laboratory diagnosis involving elevated TSH with normal fT4 or normal TSH with hypothyroxinaemia. We identified 23 cases who agreed to participate. These were matched with 47 controls. All children underwent neurodevelopmental assessment at age 7-8. Wechsler Intelligence Scale for Children IV assessment scores were used to compare the groups. Our main outcome measure was to identify whether there was a difference in IQ between the groups. From the cohort of cases, 23 mothers agreed to the assessment of their children as well as 47 controls. The children in the control group had higher mean scores than those in the case group across Verbal Comprehension Intelligence, Perceptual Reasoning Intelligence, Working Memory Intelligence, Processing Speed Intelligence and Full Scale IQ. Mann-Whitney U-test confirmed a significant difference in IQ between the cases (composite score 103.87) and the controls (composite score 109.11) with a 95% confidence interval (0.144, 10.330). Our results highlight significant differences in IQ of children of mothers who had unrecognised SCH during pregnancy. While our study size and design prevents us from making statements on causation, our data suggest significant potential public health implications for routine prenatal screening. © 2015 The Royal Australian and New Zealand College of Obstetricians and Gynaecologists.

A case report of evaluating a large-scale health systems improvement project in an uncontrolled setting: a quality improvement initiative in KwaZulu-Natal, South Africa.

PubMed

Mate, Kedar S; Ngidi, Wilbroda Hlolisile; Reddy, Jennifer; Mphatswe, Wendy; Rollins, Nigel; Barker, Pierre

2013-11-01

New approaches are needed to evaluate quality improvement (QI) within large-scale public health efforts. This case report details challenges to large-scale QI evaluation, and proposes solutions relying on adaptive study design. We used two sequential evaluative methods to study a QI effort to improve delivery of HIV preventive care in public health facilities in three districts in KwaZulu-Natal, South Africa, over a 3-year period. We initially used a cluster randomised controlled trial (RCT) design. During the RCT study period, tensions arose between intervention implementation and evaluation design due to loss of integrity of the randomisation unit over time, pressure to implement changes across the randomisation unit boundaries, and use of administrative rather than functional structures for the randomisation. In response to this loss of design integrity, we switched to a more flexible intervention design and a mixed-methods quasiexperimental evaluation relying on both a qualitative analysis and an interrupted time series quantitative analysis. Cluster RCT designs may not be optimal for evaluating complex interventions to improve implementation in uncontrolled 'real world' settings. More flexible, context-sensitive evaluation designs offer a better balance of the need to adjust the intervention during the evaluation to meet implementation challenges while providing the data required to evaluate effectiveness. Our case study involved HIV care in a resource-limited setting, but these issues likely apply to complex improvement interventions in other settings.

Mycoplasmataceae Colonizations in Women With Urethral Pain Syndrome: A Case-Control Study.

PubMed

Kyndel, Anna; Elmér, Caroline; Källman, Owe; Altman, Daniel

2016-07-01

To determine if Mycoplasma genitalium, Ureaplasma urealyticum, and Ureaplasma parvum are more common in premenopausal women with urethral pain syndrome than in asymptomatic controls. We used a case-control study design to compare the prevalence of M. genitalium, U. urealyticum, and U. parvum using polymerase chain reaction (PCR) analysis in urine. Urethral pain syndrome was defined as localized urethral pain with or without accompanying lower urinary tract symptoms during the past month or longer and at least one negative urine culture. Among the 28 cases, 46% carried Ureaplasma species compared with 64% of the 92 controls overall (P = 0.09). There were no significant differences in the prevalence of U. parvum and U. urealyticum among controls than in patients with urethral pain syndrome (P = 0.35 and P = 0.33, respectively). Co-colonization with U. parvum and urealyticum was infrequent, and there was only one case of M. genitalium colonization, which occurred among the controls. The symptomatic profile of Ureaplasma carriers with urethral pain syndrome was heterogeneous with no clear pattern and did not differ significantly compared with patients negative for Ureaplasma. We found no evidence to support the notion that M. genitalium, U. parvum, and U. urealyticum are more prevalent in women with urethral pain syndrome than in women without lower urinary tract symptoms.

Improving the power of long term rodent carcinogenicity bioassays by adjusting the experimental design.

PubMed

Jackson, Matthew T

2015-07-01

Since long term rodent carcinogenicity studies are used to test a very large number of potential tumor endpoints, finding a balance between the control of Type 1 and Type 2 error is challenging. As a result, these studies can suffer from very low power to detect effects of regulatory significance. In the present paper, a new design is proposed in order address this problem. This design is a simple modification of the existing standard designs and uses the same number of animals. Where it differs from the currently used designs is that it uses just three treatment groups rather than four, with the animals concentrated in the control and high dose groups, rather than being equally distributed among the groups. This new design is tested, in a pair of simulation studies over a range of scenarios, against two currently used designs, and against a maximally powerful two group design. It consistently performs at levels close to the optimal design, and except in the case of relatively modest effects and very rare tumors, is found to increase power by 10%-20% over the current designs while maintaining or reducing the Type 1 error rate. Published by Elsevier Inc.

Identifying patterns in signs and symptoms preceding the clinical diagnosis of Alzheimer's disease: Retrospective medical record review study and a nested case -control design.

PubMed

Bature, Fidelia; Pang, Dong; Robinson, Anthea; Polson, Norma; Pappas, Yannis; Guinn, Barbara

2018-04-04

Evidence suggests that individuals with Alzheimer's disease (AD) are often diagnosed in the later stages of their disease with a poor prognosis. This study aimed to identify patterns in signs and symptoms preceding the clinical diagnosis of AD to suggest a predictive model for earlier diagnosis of the disease in the primary care. A retrospective medical record review; nested case control design. Participants included one hundred and nine patients from three general practice (GP) surgeries in Milton Keynes and Luton Clinical Commissioning groups (CCG) (37 cases with AD and 72 controls without AD). A retrospective analysis using the logistic regression of the presence of signs and symptoms before the diagnosis of AD was attained. Identification of the timing and sequence of appearance of these presentations as first reported before the clinical diagnosis was measured. Episodic memory with an odds ratio of 1.85 was the most frequent presentation, documented in 1.38% of the controls and 75.6% in cases. Auditory disturbance with an odds ratio of 3.03, which has not previously been noted except in the form of auditory hallucination, could have a diagnostic value. Auditory disturbance, which occurred mostly in the Caucasian females, could discriminate individuals with AD from those without. The symptom, which presented up to 14.5 (mean time) years prior to clinical diagnosis, was identified in Caucasians and mixed race individuals only. Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.

The application of SVR model in the improvement of QbD: a case study of the extraction of podophyllotoxin.

PubMed

Zhai, Chun-Hui; Xuan, Jian-Bang; Fan, Hai-Liu; Zhao, Teng-Fei; Jiang, Jian-Lan

2018-05-03

In order to make a further optimization of process design via increasing the stability of design space, we brought in the model of Support Vector Regression (SVR). In this work, the extraction of podophyllotoxin was researched as a case study based on Quality by Design (QbD). We compared the fitting effect of SVR and the most used quadratic polynomial model (QPM) in QbD, and an analysis was made between the two design spaces obtained by SVR and QPM. As a result, the SVR stayed ahead of QPM in prediction accuracy, the stability of model and the generalization ability. The introduction of SVR into QbD made the extraction process of podophyllotoxin well designed and easier to control. The better fitting effect of SVR improved the application effect of QbD and the universal applicability of SVR, especially for non-linear, complicated and weak-regularity problems, widened the application field of QbD.

Adaptive Neural Network Based Control of Noncanonical Nonlinear Systems.

PubMed

Zhang, Yanjun; Tao, Gang; Chen, Mou

2016-09-01

This paper presents a new study on the adaptive neural network-based control of a class of noncanonical nonlinear systems with large parametric uncertainties. Unlike commonly studied canonical form nonlinear systems whose neural network approximation system models have explicit relative degree structures, which can directly be used to derive parameterized controllers for adaptation, noncanonical form nonlinear systems usually do not have explicit relative degrees, and thus their approximation system models are also in noncanonical forms. It is well-known that the adaptive control of noncanonical form nonlinear systems involves the parameterization of system dynamics. As demonstrated in this paper, it is also the case for noncanonical neural network approximation system models. Effective control of such systems is an open research problem, especially in the presence of uncertain parameters. This paper shows that it is necessary to reparameterize such neural network system models for adaptive control design, and that such reparameterization can be realized using a relative degree formulation, a concept yet to be studied for general neural network system models. This paper then derives the parameterized controllers that guarantee closed-loop stability and asymptotic output tracking for noncanonical form neural network system models. An illustrative example is presented with the simulation results to demonstrate the control design procedure, and to verify the effectiveness of such a new design method.

Dermatoglyphic patterns in dementia of the Alzheimer type: a case-control study.

PubMed

Berr, C; Okra-Podrabinek, N; Feteanu, D; Taurand, S; Hervy, M P; Forette, F; Piette, F; Sebag-Lanoe, R; Alperovitch, A

1992-10-01

The aim was to compare digital and palmar dermatoglyphics in subjects with dementia of Alzheimer type and in mentally healthy elderly controls. This design was a case-control study. The study was carried out in geriatric units and retirement communities in the Paris area. Cases were women with clinically diagnosed Alzheimer type dementia according to DSM III-R criteria (n = 82), mainly with late onset of the disease. Controls were women aged 85 years or older without cognitive deterioration (n = 76). Finger and palm prints obtained from both hands by the classical ink method were examined. Fingerprints were classified into four types of figures. On palms, palmar flexion creases, palmar axial triradii, true patterns of the hypothenar area, and main line terminations were described. Examinations were performed by two examiners blind to the subjects's diagnostic category. For the different patterns studied, no major differences between dementia patients and elderly controls were found. Nor was there evidence of high frequencies of features commonly observed in Down's syndrome (trisomy 21), which have previously, though sporadically, been reported. On one of the largest samples of Alzheimer dementia patients studied, and with evaluation blind to diagnosis, no evidence has been found that particular dermatoglyphic patterns occur like those observed in Down's syndrome, a disease which is related to dementia of the Alzheimer type.

Bladder Pain Syndrome/Interstitial Cystitis Is Associated with Hyperthyroidism

PubMed Central

Liu, Shih-Ping; Lin, Ching-Chun; Lin, Herng-Ching

2013-01-01

Background Although the etiology of bladder pain syndrome/interstitial cystitis (BPS/IC) is still unclear, a common theme with BPS/IC patients is comorbid disorders which are related to the autonomic nervous system that connects the nervous system to end-organs. Nevertheless, no study to date has reported the association between hyperthyroidism and BPS/IC. In this study, we examined the association of IC/BPS with having previously been diagnosed with hyperthyroidism in Taiwan. Design Data in this study were retrieved from the Longitudinal Health Insurance Database. Our study consisted of 736 female cases with BPS/IC and 2208 randomly selected female controls. We performed a conditional logistic regression to calculate the odds ratio (OR) for having previously been diagnosed with hyperthyroidism between cases and controls. Results Of the 2944 sampled subjects, there was a significant difference in the prevalence of prior hyperthyroidism between cases and controls (3.3% vs. 1.5%, p<0.001). The conditional logistic regression analysis revealed that compared to controls, the OR for prior hyperthyroidism among cases was 2.16 (95% confidence interval (CI): 1.27∼3.66). Furthermore, the OR for prior hyperthyroidism among cases was 2.01 (95% CI: 1.15∼3.53) compared to controls after adjusting for diabetes, coronary heart disease, obesity, hyperlipidemia, chronic pelvic pain, irritable bowel syndrome, fibromyalgia, chronic fatigue syndrome, depression, panic disorder, migraines, sicca syndrome, allergies, endometriosis, and asthma. Conclusions Our study results indicated an association between hyperthyroidism and BPS/IC. We suggest that clinicians treating female subjects with hyperthyroidism be alert to urinary complaints in this population. PMID:23991081

Characterizing mammographic images by using generic texture features

PubMed Central

2012-01-01

Introduction Although mammographic density is an established risk factor for breast cancer, its use is limited in clinical practice because of a lack of automated and standardized measurement methods. The aims of this study were to evaluate a variety of automated texture features in mammograms as risk factors for breast cancer and to compare them with the percentage mammographic density (PMD) by using a case-control study design. Methods A case-control study including 864 cases and 418 controls was analyzed automatically. Four hundred seventy features were explored as possible risk factors for breast cancer. These included statistical features, moment-based features, spectral-energy features, and form-based features. An elaborate variable selection process using logistic regression analyses was performed to identify those features that were associated with case-control status. In addition, PMD was assessed and included in the regression model. Results Of the 470 image-analysis features explored, 46 remained in the final logistic regression model. An area under the curve of 0.79, with an odds ratio per standard deviation change of 2.88 (95% CI, 2.28 to 3.65), was obtained with validation data. Adding the PMD did not improve the final model. Conclusions Using texture features to predict the risk of breast cancer appears feasible. PMD did not show any additional value in this study. With regard to the features assessed, most of the analysis tools appeared to reflect mammographic density, although some features did not correlate with PMD. It remains to be investigated in larger case-control studies whether these features can contribute to increased prediction accuracy. PMID:22490545

CASE/A - COMPUTER AIDED SYSTEM ENGINEERING AND ANALYSIS, ECLSS/ATCS SERIES

NASA Technical Reports Server (NTRS)

Bacskay, A.

1994-01-01

Design and analysis of Environmental Control and Life Support Systems (ECLSS) and Active Thermal Control Systems (ATCS) for spacecraft missions requires powerful software that is flexible and responsive to the demands of particular projects. CASE/A is an interactive trade study and analysis tool designed to increase productivity during all phases of systems engineering. The graphics-based command-driven package provides a user-friendly environment in which the engineer can analyze the performance and interface characteristics of an ECLS/ATC system. The package is useful during all phases of a spacecraft design program, from initial conceptual design trade studies to the actual flight, including pre-flight prediction and in-flight anomaly analysis. The CASE/A program consists of three fundamental parts: 1) the schematic management system, 2) the database management system, and 3) the simulation control and execution system. The schematic management system allows the user to graphically construct a system model by arranging icons representing system components and connecting the components with physical fluid streams. Version 4.1 contains 51 fully coded and documented default component routines. New components can be added by the user through the "blackbox" component option. The database management system supports the storage and manipulation of component data, output data, and solution control data through interactive edit screens. The simulation control and execution system initiates and controls the iterative solution process, displaying time status and any necessary diagnostic messages. In addition to these primary functions, the program provides three other important functional areas: 1) model output management, 2) system utility commands, and 3) user operations logic capacity. The model output management system provides tabular and graphical output capability. Complete fluid constituent mass fraction and properties data (mass flow, pressure, temperature, specific heat, density, and viscosity) is generated at user-selected output intervals and stored for reference. The Integrated Plot Utility (IPU) provides plotting capability for all data output. System utility commands are provided to enable the user to operate more efficiently in the CASE/A environment. The user is able to customize a simulation through optional operations FORTRAN logic. This user-developed code is compiled and linked with a CASE/A model and enables the user to control and timeline component operating parameters during various phases of the iterative solution process. CASE/A provides for transient tracking of the flow stream constituents and determination of their thermodynamic state throughout an ECLSS/ATCS simulation, performing heat transfer, chemical reaction, mass/energy balance, and system pressure drop analysis based on user-specified operating conditions. The program tracks each constituent through all combination and decomposition states while maintaining a mass and energy balance on the overall system. This allows rapid assessment of ECLSS designs, the impact of alternate technologies, and impacts due to changes in metabolic forcing functions, consumables usage, and system control considerations. CASE/A is written in FORTRAN 77 for the DEC VAX/VMS computer series, and requires 12Mb of disk storage and a minimum paging file quota of 20,000 pages. The program operates on the Tektronix 4014 graphics standard and VT100 text standard. The program requires a Tektronix 4014 or later graphics terminal, third party composite graphics/text terminal, or personal computer loaded with appropriate VT100/TEK 4014 emulator software. The use of composite terminals or personal computers with popular emulation software is recommended for enhanced CASE/A operations and general ease of use. The program is available on an unlabeled 9-track 6250 BPI DEC VAX BACKUP format magnetic tape. CASE/A development began in 1985 under contract to NASA/Marshall Space Flight Center. The latest version (4.1) was released in 1990. Tektronix and TEK 4014 are trademarks of Tektronix, Inc. VT100 is a trademark of Digital Equipment Corporation.

A meta-analytic review of corridor effectiveness.

PubMed

Gilbert-Norton, Lynne; Wilson, Ryan; Stevens, John R; Beard, Karen H

2010-06-01

Using corridors for conservation is increasing despite a lack of consensus on their efficacy. Specifically, whether corridors increase movement of plants and animals between habitat fragments has been addressed on a case-by-case basis with mixed results. Because of the growing number of well-designed experiments that have addressed this question, we conducted a meta-analysis to determine whether corridors increase movement; whether corridor effectiveness differs among taxa; how recent changes in experimental design have influenced findings; and whether corridor effectiveness differs between manipulative and natural experiments. To conduct our meta-analysis, we analyzed 78 experiments from 35 studies using a conservative hierarchical Bayesian model that accounts for hierarchical and sampling dependence. We found a highly significant result that corridors increase movement between habitat patches by approximately 50% compared to patches that are not connected with corridors. We found that corridors were more important for the movement of invertebrates, nonavian vertebrates, and plants than they were for birds. Recent methodological advances in corridor experiments, such as controlling for the area added by corridors, did not influence whether corridors increased movement, whereas controlling for the distance between source and connected or unconnected recipient patches decreased movement through corridors. After controlling for taxa differences and whether studies controlled for distance in experimental design, we found that natural corridors (those existing in landscapes prior to the study) showed more movement than manipulated corridors (those created and maintained for the study). Our results suggest that existing corridors increase species movement in fragmented landscapes and that efforts spent on maintaining and creating corridors are worthwhile.

Distributed neural network control for adaptive synchronization of uncertain dynamical multiagent systems.

PubMed

Peng, Zhouhua; Wang, Dan; Zhang, Hongwei; Sun, Gang

2014-08-01

This paper addresses the leader-follower synchronization problem of uncertain dynamical multiagent systems with nonlinear dynamics. Distributed adaptive synchronization controllers are proposed based on the state information of neighboring agents. The control design is developed for both undirected and directed communication topologies without requiring the accurate model of each agent. This result is further extended to the output feedback case where a neighborhood observer is proposed based on relative output information of neighboring agents. Then, distributed observer-based synchronization controllers are derived and a parameter-dependent Riccati inequality is employed to prove the stability. This design has a favorable decouple property between the observer and the controller designs for nonlinear multiagent systems. For both cases, the developed controllers guarantee that the state of each agent synchronizes to that of the leader with bounded residual errors. Two illustrative examples validate the efficacy of the proposed methods.

A Cross-Sectional Analysis of Publication Types in Quality Improvement Journals.

PubMed

Wong, Christopher J; White, Andrew A; Merel, Susan E; Brock, Douglas M; Staiger, Thomas O

2016-07-01

Despite widespread engagement in quality improvement activities, little is known about the designs of studies currently published in quality improvement journals. This study's goal is to establish the prevalence of the types of research conducted in articles published in journals dedicated to quality improvement. A cross-sectional analysis was performed of 145 research articles published in 11 quality improvement journals in 2011. The majority of study designs were considered pre-experimental (95%), with a small percentage of quasi-experimental and experimental designs. Of the studies that reported the results of an intervention (n = 60), the most common research designs were pre-post studies (33%) and case studies (25%). There were few randomized controlled trials or quasi-experimental study designs (12% of intervention studies). These results suggest that there are opportunities for increased use of quasi-experimental study designs. © The Author(s) 2015.

Gain-Scheduled Fault Tolerance Control Under False Identification

NASA Technical Reports Server (NTRS)

Shin, Jong-Yeob; Belcastro, Christine (Technical Monitor)

2006-01-01

An active fault tolerant control (FTC) law is generally sensitive to false identification since the control gain is reconfigured for fault occurrence. In the conventional FTC law design procedure, dynamic variations due to false identification are not considered. In this paper, an FTC synthesis method is developed in order to consider possible variations of closed-loop dynamics under false identification into the control design procedure. An active FTC synthesis problem is formulated into an LMI optimization problem to minimize the upper bound of the induced-L2 norm which can represent the worst-case performance degradation due to false identification. The developed synthesis method is applied for control of the longitudinal motions of FASER (Free-flying Airplane for Subscale Experimental Research). The designed FTC law of the airplane is simulated for pitch angle command tracking under a false identification case.

A genome-wide association study to identify genetic susceptibility loci that modify ductal and lobular postmenopausal breast cancer risk associated with menopausal hormone therapy use: a two-stage design with replication

PubMed Central

Dahmen, Norbert; Beckmann, Lars; Lindström, Sara; Schoof, Nils; Czene, Kamila; Mittelstraß, Kirstin; Illig, Thomas; Seibold, Petra; Behrens, Sabine; Humphreys, Keith; Li, Jingmei; Liu, Jianjun; Olson, Janet E.; Wang, Xianshu; Hankinson, Susan E.; Truong, Thérèse; Menegaux, Florence; dos Santos Silva, Isabel; Johnson, Nichola; Chen, Shou-Tung; Yu, Jyh-Cherng; Ziogas, Argyrios; Kataja, Vesa; Kosma, Veli-Matti; Mannermaa, Arto; Anton-Culver, Hoda; Shen, Chen-Yang; Brauch, Hiltrud; Peto, Julian; Guénel, Pascal; Kraft, Peter; Couch, Fergus J.; Easton, Douglas F.; Hall, Per; Chang-Claude, Jenny

2013-01-01

Menopausal hormone therapy (MHT) is associated with an elevated risk of breast cancer in postmenopausal women. To identify genetic loci that modify breast cancer risk related to MHT use in postmenopausal women, we conducted a two-stage genome-wide association study (GWAS) with replication. In stage I, we performed a case-only GWAS in 731 invasive breast cancer cases from the German case-control study Mammary Carcinoma Risk Factor Investigation (MARIE). The 1,200 single nucleotide polymorphisms (SNPs) showing the lowest P values for interaction with current MHT use (within 6 months prior to breast cancer diagnosis), were carried forward to stage II, involving pooled case-control analyses including additional MARIE subjects (1,375 cases, 1,974 controls) as well as 795 cases and 764 controls of a Swedish case-control study. A joint P value was calculated for a combined analysis of stages I and II. Replication of the most significant interaction of the combined stage I and II was performed using 5,795 cases and 5,390 controls from nine studies of the Breast Cancer Association Consortium (BCAC). The combined stage I and II yielded five SNPs on chromosomes 2, 7, and 18 with joint P values <6 × 10−6 for effect modification of current MHT use. The most significant interaction was observed for rs6707272 (P = 3 × 10−7) on chromosome 2 but was not replicated in the BCAC studies (P = 0.21). The potentially modifying SNPs are in strong linkage disequilibrium with SNPs in TRIP12 and DNER on chromosome 2 and SETBP1 on chromosome 18, previously linked to carcinogenesis. However, none of the interaction effects reached genome-wide significance. The inability to replicate the top SNP × MHT interaction may be due to limited power of the replication phase. Our study, however, suggests that there are unlikely to be SNPs that interact strongly enough with MHT use to be clinically significant in European women. PMID:23423446

Vaccine testing for emerging infections: the case for individual randomisation.

PubMed

Eyal, Nir; Lipsitch, Marc

2017-09-01

During the 2014-2015 Ebola outbreak in Guinea, Liberia and Sierra Leone, many opposed the use of individually randomised controlled trials to test candidate Ebola vaccines. For a raging fatal disease, they explained, it is unethical to relegate some study participants to control arms. In Zika and future emerging infections, similar opposition may hinder urgent vaccine research, so it is best to address these questions now. This article lays out the ethical case for individually randomised control in testing vaccines against many emerging infections, including lethal infections in low-income countries, even when at no point in the trial do the controls receive the countermeasures being tested. When individual randomisation is feasible-and it often will be-it tends to save more lives than alternative designs would. And for emerging infections, individual randomisation also tends as such to improve care, access to the experimental vaccine and prospects for all participants relative to their opportunities absent the trial, and no less than alternative designs would. That obtains even under placebo control and without equipoise-requiring which would undermine individual randomisation and the alternative designs that opponents proffered. Our arguments expound four often-neglected factors: benefits to non-participants, benefits to participants once a trial is over including post-trial access to the study intervention, participants' prospects before randomisation to arms and the near-inevitable disparity between arms in any randomised controlled trial. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://www.bmj.com/company/products-services/rights-and-licensing/.

A large case-control study reveals a positive association between bisphosphonate use and delayed dental healing and osteonecrosis of the jaw.

PubMed

Borromeo, Gelsomina L; Brand, Caroline; Clement, John G; McCullough, Michael; Crighton, Lisa; Hepworth, Graham; Wark, John D

2014-06-01

This study sought to investigate, using a case-control study design, the association between bisphosphonate therapy and delayed dental healing and osteonecrosis of the jaw. Identification of potential cases of delayed dental healing was by consecutive screening of Specialist Oral and Maxillofacial and Special Needs Dentist clinic records for patients aged older than 50 years, during a 6-month window, in Victoria, Australia. Cases were confirmed by a case adjudication panel blinded to bisphosphonate status. Cases associated with malignancy or local radiotherapy were excluded. Controls were matched for age, sex, and source of dental referral (1:4, n = 160 controls). Variables of interest were dental precipitants, dental clinic type, smoking history, and medical comorbidities. A total of 4212 of 22,358 patients met inclusion criteria, of which 69 were potential cases with 40 (0.95%) confirmed cases. The odds ratio (OR) for developing delayed dental healing when taking an oral bisphosphonate was 13.1 (95% confidence interval [CI] 4.4 to 39.3; p < 0.001). There were no cases associated with intravenous bisphosphonate use. There was some evidence of an interaction with age, sex, and clinic type. When adjusted for smoking, the estimated odds ratio was 11.6 (95% CI 1.9 to 69.4; p = 0.01). There was an association between having another illness and delayed dental healing (OR = 2.3; 95% CI 1.0 to 5.2). A dental precipitant was present in 39 of 40 (97.5%) delayed dental healing cases. An important association between bisphosphonate use and delayed dental healing in the setting of benign bone disease, predominately in individuals with a dental precipitant, has been demonstrated. © 2014 American Society for Bone and Mineral Research.

High Seroprevalence of Leptospira Exposure in Meat Workers in Northern Mexico: A Case-Control Study.

PubMed

Alvarado-Esquivel, Cosme; Hernandez-Tinoco, Jesus; Sanchez-Anguiano, Luis Francisco; Ramos-Nevarez, Agar; Cerrillo-Soto, Sandra Margarita; Saenz-Soto, Leandro; Martinez-Ramirez, Lucio

2016-03-01

The seroepidemiology of Leptospira infection in workers occupationally exposed to raw meat has been poorly studied. This work aimed to determine the association between Leptospira exposure and the occupation of meat worker, and to determine the seroprevalence association with socio-demographic, work, clinical and behavioral characteristics of the meat workers studied. We performed a case-control study in 124 meat workers and 124 age- and gender-matched control subjects in Durango City, Mexico. Sera of cases and controls were analyzed for anti-Leptospira IgG antibodies using a commercially available enzyme immunoassay. Data of meat workers were obtained with the aid of a questionnaire. The association of Leptospira exposure with the characteristics of meat workers was analyzed by bivariate and multivariate analyses. Anti-Leptospira IgG antibodies were found in 22 (17.7%) of 124 meat workers and in eight (6.5%) of 124 controls (OR = 3.12; 95% CI: 1.33 - 7.33; P = 0.006). Seroprevalence of Leptospira infection was similar between male butchers (17.6%) and female butchers (18.2%) (P = 1.00). Multivariate analysis of socio-demographic, work and behavioral variables showed that Leptospira exposure was associated with duration in the activity, rural residence, and consumption of snake meat and unwashed raw fruits. This is the first case-control study of the association of Leptospira exposure with the occupation of meat worker. Results indicate that meat workers represent a risk group for Leptospira exposure. Risk factors for Leptospira exposure found in this study may help in the design of optimal preventive measures against Leptospira infection.

The clinician in the driver's seat: part 2 - intelligent uses of space in a drag/drop user-composable electronic health record.

PubMed

Senathirajah, Yalini; Kaufman, David; Bakken, Suzanne

2014-12-01

User-composable approaches provide clinicians with the control to design and assemble information elements on screen via drag/drop. They hold considerable promise for enhancing the electronic-health-records (EHRs) user experience. We previously described this novel approach to EHR design and our illustrative system, MedWISE. The purpose of this paper is to describe clinician users' intelligent uses of space during completion of real patient case studies in a laboratory setting using MedWISE. Thirteen clinicians at a quaternary academic medical center used the system to review four real patient cases. We analyzed clinician utterances, behaviors, screen layouts (i.e., interface designs), and their perceptions associated with completing patient case studies. Clinicians effectively used the system to review all cases. Two coding schemata pertaining to human-computer interaction and diagnostic reasoning were used to analyze the data. Users adopted three main interaction strategies: rapidly gathering items on screen and reviewing ('opportunistic selection' approach); creating highly structured screens ('structured' approach); and interacting with small groups of items in sequence as their case review progressed ('dynamic stage' approach). They also used spatial arrangement in ways predicted by theory and research on workplace spatial arrangement. This includes assignment of screen regions for particular purposes (24% of spatial codes), juxtaposition to facilitate calculation or other cognitive tasks ('epistemic action'), and grouping elements with common meanings or relevance to the diagnostic facets of the case (20.3%). A left-to-right progression of orienting materials, data, and action items or reflection space was a commonly observed pattern. Widget selection was based on user assessment of what information was useful or relevant. We developed and tested an illustrative system that gives clinicians greater control of the EHR, and demonstrated its feasibility for case review by typical clinicians. Producing the simplifying inventions, such as user-composable platforms that shift control to the user, may serve to promote productive EHR use and enhance its value as an instrument of patient care. Copyright © 2014 Elsevier Inc. All rights reserved.

The Clinician in the Driver’s Seat: Part 2 – Intelligent Uses of Space in a Drag/Drop User-Composable Electronic Health Record

PubMed Central

Senathirajah, Yalini; Kaufman, David; Bakken, Suzanne

2018-01-01

User-composable approaches provide clinicians with the control to design and assemble information elements on screen via drag/drop. They hold considerable promise for enhancing the electronic-health-records (EHRs) user experience. We previously described this novel approach to EHR design and our illustrative system, MedWISE. The purpose of this paper is to describe clinician users’ intelligent uses of space during completion of real patient case studies in a laboratory setting using MedWISE. Thirteen clinicians at a quaternary academic medical center used the system to review four real patient cases. We analyzed clinician utterances, behaviors, screen layouts (i.e., interface designs), and their perceptions associated with completing patient case studies. Clinicians effectively used the system to review all cases. Two coding schemata pertaining to human-computer interaction and diagnostic reasoning were used to analyze the data. Users adopted three main interaction strategies: rapidly gathering items on screen and reviewing (‘opportunistic selection’ approach); creating highly structured screens (‘structured’ approach); and interacting with small groups of items in sequence as their case review progressed (‘dynamic stage’ approach). They also used spatial arrangement in ways predicted by theory and research on workplace spatial arrangement. This includes assignment of screen regions for particular purposes (24% of spatial codes), juxtaposition to facilitate calculation or other cognitive tasks (‘epistemic action’), and grouping elements with common meanings or relevance to the diagnostic facets of the case (20.3%). A left-to-right progression of orienting materials, data, and action items or reflection space was a commonly observed pattern. Widget selection was based on user assessment of what information was useful or relevant. We developed and tested an illustrative system that gives clinicians greater control of the EHR, and demonstrated its feasibility for case review by typical clinicians. Producing the simplifying inventions, such as user-composable platforms that shift control to the user, may serve to promote productive EHR use and enhance its value as an instrument of patient care. PMID:25445921

Genetic factors in pemphigus.

PubMed

Tron, François; Gilbert, Danièle; Mouquet, Hugo; Joly, Pascal; Drouot, Laurent; Makni, Sondès; Masmoudi, Hatem; Charron, Dominique; Zitouni, Mondher; Loiseau, Pascale; Ben Ayed, Mourad

2005-06-01

Epidemiological studies performed in different ethnic populations and family studies, notably based on a partial phenotype of the autoimmune process, indicate that genetic factors are involved in the occurrence of pemphigus. However, the precise heritability remains uncertain in the absence of twin concordance rate studies. Among the different strategies available to identify genetic factors participating in autoimmune disease susceptibility, only population studies based on case-control design have been performed in pemphigus. These studies consistently showed that MHC locus, in particular HLA class II alleles, are associated with pemphigus vulgaris and pemphigus foliaceus. Other genes of the MHC locus may also participate in disease susceptibility as shown by studies using microsatellite markers across different regions of the MHC. It is likely that other non-MHC genes are involved in the pathogenesis of pemphigus. In particular, involvement of a polymorphic variant of desmoglein 1 gene was shown to be associated with pemphigus foliaceus and to interact in an epistatic manner with MHC class II genes to contribute to the autoimmune process. Other candidate genes to which a role can be assigned in the disease pathogenesis should be considered to design case-control or family-based association studies. Genome scan studies which require a large number of multiplex families to reach statistical power, should also be considered in the endemic form of pemphigus foliaceus because of the high number of familial cases.

Application of IFT and SPSA to servo system control.

PubMed

Rădac, Mircea-Bogdan; Precup, Radu-Emil; Petriu, Emil M; Preitl, Stefan

2011-12-01

This paper treats the application of two data-based model-free gradient-based stochastic optimization techniques, i.e., iterative feedback tuning (IFT) and simultaneous perturbation stochastic approximation (SPSA), to servo system control. The representative case of controlled processes modeled by second-order systems with an integral component is discussed. New IFT and SPSA algorithms are suggested to tune the parameters of the state feedback controllers with an integrator in the linear-quadratic-Gaussian (LQG) problem formulation. An implementation case study concerning the LQG-based design of an angular position controller for a direct current servo system laboratory equipment is included to highlight the pros and cons of IFT and SPSA from an application's point of view. The comparison of IFT and SPSA algorithms is focused on an insight into their implementation.

Design of polynomial fuzzy observer-controller for nonlinear systems with state delay: sum of squares approach

NASA Astrophysics Data System (ADS)

Gassara, H.; El Hajjaji, A.; Chaabane, M.

2017-07-01

This paper investigates the problem of observer-based control for two classes of polynomial fuzzy systems with time-varying delay. The first class concerns a special case where the polynomial matrices do not depend on the estimated state variables. The second one is the general case where the polynomial matrices could depend on unmeasurable system states that will be estimated. For the last case, two design procedures are proposed. The first one gives the polynomial fuzzy controller and observer gains in two steps. In the second procedure, the designed gains are obtained using a single-step approach to overcome the drawback of a two-step procedure. The obtained conditions are presented in terms of sum of squares (SOS) which can be solved via the SOSTOOLS and a semi-definite program solver. Illustrative examples show the validity and applicability of the proposed results.

A modal H∞-norm-based performance requirement for damage-tolerant active controller design

NASA Astrophysics Data System (ADS)

Genari, Helói F. G.; Mechbal, Nazih; Coffignal, Gérard; Nóbrega, Eurípedes G. O.

2017-04-01

Damage-tolerant active control (DTAC) is a recent research area that encompasses control design methodologies resulting from the application of fault-tolerant control methods to vibration control of structures subject to damage. The possibility of damage occurrence is not usually considered in the active vibration control design requirements. Damage changes the structure dynamics, which may produce unexpected modal behavior of the closed-loop system, usually not anticipated by the controller design approaches. A modal H∞ norm and a respective robust controller design framework were recently introduced, and this method is here extended to face a new DTAC strategy implementation. Considering that damage affects each vibration mode differently, this paper adopts the modal H∞ norm to include damage as a design requirement. The basic idea is to create an appropriate energy distribution over the frequency range of interest and respective vibration modes, guaranteeing robustness, damage tolerance, and adequate overall performance, taking into account that it is common to have previous knowledge of the structure regions where damage may occur during its operational life. For this purpose, a structural health monitoring technique is applied to evaluate modal modifications caused by damage. This information is used to create modal weighing matrices, conducting to the modal H∞ controller design. Finite element models are adopted for a case study structure, including different damage severities, in order to validate the proposed control strategy. Results show the effectiveness of the proposed methodology with respect to damage tolerance.

Epidemiological evidence of carcinogenicity of chlorinated organics in drinking water.

PubMed

Cantor, K P

1982-12-01

Concern has recently been voiced over possible chronic toxicity associated with chlorination of public drinking water supplies in the United States. This paper reviews the available evidence and the studies underway to further evaluate hypothesized associations between cancer risk and byproducts of chlorination. Preliminary data from measures of halogenated volatiles and personal exposure histories from respondents in a large epidemiologic study of bladder cancer are presented. These data support the use in epidemiologic studies of categorical measures of exposure and suggest that results from completed case-control studies, based on death certificates, may have underestimated the true risk of exposure to chlorination by-products. The current generation of studies which use a case-control interview design offer many advantages over earlier efforts to evaluate this issue.

Epidemiological evidence of carcinogenicity of chlorinated organics in drinking water.

PubMed Central

Cantor, K P

1982-01-01

Concern has recently been voiced over possible chronic toxicity associated with chlorination of public drinking water supplies in the United States. This paper reviews the available evidence and the studies underway to further evaluate hypothesized associations between cancer risk and byproducts of chlorination. Preliminary data from measures of halogenated volatiles and personal exposure histories from respondents in a large epidemiologic study of bladder cancer are presented. These data support the use in epidemiologic studies of categorical measures of exposure and suggest that results from completed case-control studies, based on death certificates, may have underestimated the true risk of exposure to chlorination by-products. The current generation of studies which use a case-control interview design offer many advantages over earlier efforts to evaluate this issue. PMID:6759108

[Correlation between the genetic polymorphisms of apolipoprotein M with the susceptibility to rheumatic diseases of Chinese Han populastion in Lanzhou].

PubMed

Li, Meiyong; Guo, Xinling; Li, Qiannan; You, Chongge

2016-08-01

Objective To investigate the relationship between the genetic polymorphisms of apolipoprotein M (ApoM) and the susceptibility to rheumatoid arthritis (RA), systemic lupus erythematosus (SLE) and ankylosing spondylitis (AS) among Chinese Han population in Lanzhou. Methods Primers for the two single nucleotide polymorphism (SNP) sites (rs805296 and rs805297) in ApoM gene were designed and their genotyping methods of polymerase chain reaction-high resolution melting (PCR-HRM) assay were established. Case-control studies were performed among the 599 cases of RA, 194 cases of SLE, 179 cases of AS and 273 matched healthy controls to analyze the correlations between the two SNPs and the susceptibility to rheumatic diseases. Results The genotype frequencies of rs805296 were AA 87.0%, AG 12.7%, GG 0.3% in RA cases, AA 84.5%, AG 15.0%, GG 0.5% in SLE cases, AA 91.6%, AG 7.3%, GG 1.1% in AS cases, AA 85.0%, AG 15.0%, GG 0% in healthy controls. The ones of rs805297 were GG 38.2%, GT 51.8%, TT 10.0% in RA cases, GG 44.3%, GT 45.4%, TT 10.3% in SLE cases, GG 37.4%, GT 47.5%, TT 15.1% in AS cases, GG 40.7%, GT 46.1%, TT 13.2% in healthy controls. Statistical analyses showed that only the genotype distribution of rs805296 was significantly different between the AS cases and the healthy controls. Under the dominant model, the G allele carriers of rs805296 (AG heterozygote and GG homozygote) were found to significantly decrease the risk for AS development. Conclusion The established PCR-HRM genotyping assays in the present study can successfully achieve the molecular diagnosis of the two SNPs sites (rs805296 and rs805297) from clinical samples, and the study found a significant association between the SNP of rs805296 and the susceptibility to AS among Chinese Han population in Lanzhou.

Novel application of the matched case-control design to compare food supply chains during an Escherichia coli O157 outbreak, United Kingdom, 2016.

PubMed

Inns, Thomas; Cleary, Paul; Bundle, Nick; Foulkes, Sarah; Sharp, Ashley; Utsi, Lara; McBrien, Chris; Teagle, Rehman; Waldram, Alison; Williams, Chris; McCann, Cathy; Smith, Rob; Saleh, Sepeedeh; McCarthy, Noel; Vivancos, Roberto; Hawker, Jeremy; Decraene, Valerie

2018-05-01

There is a need for innovative methods to investigate outbreaks of food-borne infection linked to produce with a complex distribution network. The investigation of a large outbreak of Escherichia coli O157 PT34 infection in the United Kingdom in 2016 indicated that catering venues associated with multiple cases had used salad leaves sourced from one supplier. Our aim was to investigate whether catering venues linked to cases were more likely to have used salad leaves from this supplier. We conducted a matched case-control study, with catering venues as the units of analysis. We compared venues linked to cases to those without known linked cases. We included 43 study pairs and obtained information on salad leaf products received by each venue. The odds of a case venue being supplied with salad leaves by Supplier A were 7.67 times (95% confidence interval: 2.30-25.53) those of control venues. This association provided statistical evidence to support the findings of the other epidemiological investigations undertaken for this outbreak. This is a novel approach which is labour-intensive but which addresses the challenge of investigating exposures to food across a complex distribution network.

Medical and Non-Medical Factors Influencing Utilization of Delayed Pushing in the Second Stage

PubMed Central

FREY, Heather A.; TUULI, Methodius G.; CORTEZ, Sarah; ODIBO, Anthony O.; ROEHL, Kimberly A.; SHANKS, Anthony L.; MACONES, George A.; CAHILL, Alison G.

2014-01-01

Objective To evaluate factors impacting selection to delayed pushing in the second stage of labor. Study design This case-control study was a secondary analysis of a large retrospective cohort study. Cases included women who delayed pushing for 60 minutes or more in the second stage of labor. Controls began pushing prior to 60 minutes from the time of diagnosis of complete dilation. Demographic, labor, and nonmedical factors were compared among cases and controls. Logistic regression modelling was used to identify factors independently associated with delayed pushing. Results We identified 471 women who delayed pushing and 4,819 controls. Nulliparity, maternal body mass index > 25, high fetal station at complete dilation, regional anesthesia use, and start of second stage during staffing shift change were independent factors associated with increased use of delayed pushing. On the other hand, black race and second stage management during night shift were associated with lower odds of employing delayed pushing. Delayed pushing was more commonly employed in nulliparous women, but 38.9% of multiparous women also delayed pushing. Conclusion We identified multiple factors associated with use of delayed pushing. This study helps to define current patterns of second stage labor management. PMID:23208765

Modifiable Neighborhood Features Associated With Adolescent Homicide

PubMed Central

Culyba, Alison J.; Jacoby, Sara F.; Richmond, Therese S.; Fein, Joel A.; Hohl, Bernadette C.; Branas, Charles C.

2016-01-01

IMPORTANCE Homicide is a leading cause of adolescent mortality. To our knowledge, relatively little has been studied in terms of the association between environmental neighborhood features, such as streets, buildings, and natural surroundings, and severe violent injury among youth. OBJECTIVE To assess associations between environmental neighborhood features and adolescent homicide in order to identify targets for future place-based interventions. DESIGN, SETTING, AND PARTICIPANTS Population-based case-control study conducted in Philadelphia, Pennsylvania, from April 15, 2008, to March 31, 2014. We identified adolescents who died by homicide at 13 to 20 years of age from 2010 to 2012 while residing in Philadelphia. We used incidence-density sampling and random-digit dialing to recruit control participants ages 13 to 20 years matched on sex and indoor-outdoor location at the time of each index case participant’s homicide. EXPOSURES To obtain environmental data about modifiable features that were present in the immediate surroundings of our case and control participants, blinded field researchers used standardized techniques to photograph case and control participant outdoor locations. Photographic data were stitched together to create 360° panoramic images that were coded for 60 elements of the visible environment. MAIN OUTCOME AND MEASURE Adolescent homicide. RESULTS We enrolled 143 homicide case participants (mean [SD] age, 18.4 [1.5] years) and 155 matched control participants (mean [SD] age, 17.2 [2.1] years) who were both outdoors at the time of the homicide. In adjusted analyses, multiple features of Philadelphia streets, buildings, and natural surroundings were associated with adolescent homicide. The presence of street lighting (odds ratio [OR], 0.24; 95% CI, 0.09-0.70), illuminated walk/don’t walk signs (OR, 0.16; 95% CI, 0.03-0.92), painted marked crosswalks (OR, 0.17; 95% CI, 0.04-0.63), public transportation (OR, 0.13; 95% CI, 0.03-0.49), parks (OR, 0.09; 95% CI, 0.01-0.88), and maintained vacant lots (OR, 0.17; 95% CI, 0.03-0.81) were significantly associated with decreased odds of homicide. The odds of homicide were significantly higher in locations with stop signs (OR, 4.34; 95% CI, 1.40-13.45), security bars/gratings on houses (OR, 9.23; 95% CI, 2.45-34.80), and private bushes/plantings (OR, 3.44; 95% CI, 1.18-10.01). CONCLUSIONS AND RELEVANCE Using a population-based case-control design, we identified multiple modifiable environmental features that might be targeted in future randomized intervention trials designed to reduce youth violence by improving neighborhood context. PMID:26954939

Associations of welding and manganese exposure with Parkinson disease

PubMed Central

Borenstein, Amy R.; Nelson, Lorene M.

2012-01-01

Objective: To examine associations of welding and manganese exposure with Parkinson disease (PD) using meta-analyses of data from cohort, case-control, and mortality studies. Methods: Epidemiologic studies related to welding or manganese exposure and PD were identified in a PubMed search, article references, published reviews, and abstracts. Inclusion criteria were 1) cohort, case-control, or mortality study with relative risk (RR), odds ratio (OR), or mortality OR (MOR) and 95 confidence intervals (95% CI); 2) RR, OR, and MOR matched or adjusted for age and sex; 3) valid study design and analysis. When participants of a study were a subgroup of those in a larger study, only results of the larger study were included to assure independence of datasets. Pooled RR/OR estimates and 95% CIs were obtained using random effects models; heterogeneity of study effects were evaluated using the Q statistic and I2 index in fixed effect models. Results: Thirteen studies met inclusion criteria for the welding meta-analysis and 3 studies for the manganese exposure meta-analysis. The pooled RR for the association between welding and PD for all study designs was 0.86 (95% CI 0.80–0.92), with absence of between-study heterogeneity (I2 = 0.0). Effect measures for cohort, case-control, and mortality studies were similar (0.91, 0.82, 0.87). For the association between manganese exposure and PD, the pooled OR was 0.76 (95% CI 0.41–1.42). Conclusions: Welding and manganese exposure are not associated with increased PD risk. Possible explanations for the inverse association between welding and PD include confounding by smoking, healthy worker effect, and hormesis. PMID:22965675

Non-psychotropic medication and risk of suicide or attempted suicide: a systematic review

PubMed Central

Gorton, Hayley C; Webb, Roger T; Kapur, Navneet; Ashcroft, Darren M

2016-01-01

Objectives To establish which non-psychotropic medications have been assessed in relation to risk of suicide or attempted suicide in observational studies, document reported associations and consider study strengths and limitations. Design Systematic review. Methods Four databases (Embase, Medline, PsycINFO and International Pharmaceutical Abstracts) were searched from 1990 to June 2014, and reference lists of included articles were hand-searched. Case–control, cohort and case only studies which reported suicide or attempted suicide in association with any non-psychotropic medication were included. Outcome measures The outcomes eligible for inclusion were suicide and attempted suicide, as defined by the authors of the included study. Results Of 11 792 retrieved articles, 19 were eligible for inclusion. Five studies considered cardiovascular medication and antiepileptics; two considered leukotriene receptor antagonists, isotretinoin and corticosteroids; one assessed antibiotics and another assessed varenicline. An additional study compared multiple medications prescribed to suicide cases versus controls. There was marked heterogeneity in study design, outcome and exposure classification, and control for confounding factors; particularly comorbid mental and physical illness. No increased risk was associated with cardiovascular medications, but associations with other medications remained inconclusive and meta-analysis was inappropriate due to study heterogeneity. Conclusions Whether non-psychotropic medications are associated with increased risk of suicide or attempted suicide remains largely unknown. Robust identification of suicide outcomes and control of comorbidities could improve quantification of risk associated with non-psychotropic medication, beyond that conferred by underlying physical and mental illnesses. PMID:26769782

TREAT (TREe-based Association Test)

Cancer.gov

TREAT is an R package for detecting complex joint effects in case-control studies. The test statistic is derived from a tree-structure model by recursive partitioning the data. Ultra-fast algorithm is designed to evaluate the significance of association between candidate gene and disease outcome

Quality Assessment of Studies Published in Open Access and Subscription Journals: Results of a Systematic Evaluation.

PubMed

Pastorino, Roberta; Milovanovic, Sonja; Stojanovic, Jovana; Efremov, Ljupcho; Amore, Rosarita; Boccia, Stefania

2016-01-01

Along with the proliferation of Open Access (OA) publishing, the interest for comparing the scientific quality of studies published in OA journals versus subscription journals has also increased. With our study we aimed to compare the methodological quality and the quality of reporting of primary epidemiological studies and systematic reviews and meta-analyses published in OA and non-OA journals. In order to identify the studies to appraise, we listed all OA and non-OA journals which published in 2013 at least one primary epidemiologic study (case-control or cohort study design), and at least one systematic review or meta-analysis in the field of oncology. For the appraisal, we picked up the first studies published in 2013 with case-control or cohort study design from OA journals (Group A; n = 12), and in the same time period from non-OA journals (Group B; n = 26); the first systematic reviews and meta-analyses published in 2013 from OA journals (Group C; n = 15), and in the same time period from non-OA journals (Group D; n = 32). We evaluated the methodological quality of studies by assessing the compliance of case-control and cohort studies to Newcastle and Ottawa Scale (NOS) scale, and the compliance of systematic reviews and meta-analyses to Assessment of Multiple Systematic Reviews (AMSTAR) scale. The quality of reporting was assessed considering the adherence of case-control and cohort studies to STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) checklist, and the adherence of systematic reviews and meta-analyses to Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) checklist. Among case-control and cohort studies published in OA and non-OA journals, we did not observe significant differences in the median value of NOS score (Group A: 7 (IQR 7-8) versus Group B: 8 (7-9); p = 0.5) and in the adherence to STROBE checklist (Group A, 75% versus Group B, 80%; p = 0.1). The results did not change after adjustment for impact factor. The compliance with AMSTAR and adherence to PRISMA checklist were comparable between systematic reviews and meta-analyses published in OA and non-OA journals (Group C, 46.0% versus Group D, 55.0%; p = 0.06), (Group C, 72.0% versus Group D, 76.0%; p = 0.1), respectively). The epidemiological studies published in OA journals in the field of oncology approach the same methodological quality and quality of reporting as studies published in non-OA journals.

Quality Assessment of Studies Published in Open Access and Subscription Journals: Results of a Systematic Evaluation

PubMed Central

Pastorino, Roberta; Milovanovic, Sonja; Stojanovic, Jovana; Efremov, Ljupcho; Amore, Rosarita; Boccia, Stefania

2016-01-01

Introduction Along with the proliferation of Open Access (OA) publishing, the interest for comparing the scientific quality of studies published in OA journals versus subscription journals has also increased. With our study we aimed to compare the methodological quality and the quality of reporting of primary epidemiological studies and systematic reviews and meta-analyses published in OA and non-OA journals. Methods In order to identify the studies to appraise, we listed all OA and non-OA journals which published in 2013 at least one primary epidemiologic study (case-control or cohort study design), and at least one systematic review or meta-analysis in the field of oncology. For the appraisal, we picked up the first studies published in 2013 with case-control or cohort study design from OA journals (Group A; n = 12), and in the same time period from non-OA journals (Group B; n = 26); the first systematic reviews and meta-analyses published in 2013 from OA journals (Group C; n = 15), and in the same time period from non-OA journals (Group D; n = 32). We evaluated the methodological quality of studies by assessing the compliance of case-control and cohort studies to Newcastle and Ottawa Scale (NOS) scale, and the compliance of systematic reviews and meta-analyses to Assessment of Multiple Systematic Reviews (AMSTAR) scale. The quality of reporting was assessed considering the adherence of case-control and cohort studies to STrengthening the Reporting of OBservational studies in Epidemiology (STROBE) checklist, and the adherence of systematic reviews and meta-analyses to Preferred Reporting Items for Systematic reviews and Meta-Analysis (PRISMA) checklist. Results Among case-control and cohort studies published in OA and non-OA journals, we did not observe significant differences in the median value of NOS score (Group A: 7 (IQR 7–8) versus Group B: 8 (7–9); p = 0.5) and in the adherence to STROBE checklist (Group A, 75% versus Group B, 80%; p = 0.1). The results did not change after adjustment for impact factor. The compliance with AMSTAR and adherence to PRISMA checklist were comparable between systematic reviews and meta-analyses published in OA and non-OA journals (Group C, 46.0% versus Group D, 55.0%; p = 0.06), (Group C, 72.0% versus Group D, 76.0%; p = 0.1), respectively). Conclusion The epidemiological studies published in OA journals in the field of oncology approach the same methodological quality and quality of reporting as studies published in non-OA journals. PMID:27167982

Design concepts and cost studies for magnetic suspension and balance systems. [wind tunnel apparatus

NASA Technical Reports Server (NTRS)

Bloom, H. L.

1982-01-01

The application of superconducting magnets for suspension and balance of wind tunnel models was studied. Conceptual designs are presented for magnetic suspension and balance system (MSBS) configurations compatible with three high Reynolds number cases representing specified combinations of test conditions and model sizes. Concepts in general met initially specified performance requirements such as duty cycle, force and moment levels, model angular displacement and positioning accuracy with nominal design requirements for support subsystems. Other performance requirements, such as forced model sinusoidal oscillations, and control force magnitude and frequency, were modified so as to alleviate the magnitude of magnet, power, and cryogenic design requirements.

Lecture and Workshop Modes Comparison on Rangeland Developments: The Case of Iran

ERIC Educational Resources Information Center

Shahvali, M.; Poursaeed, A.; Sharifzadeh, M.

2009-01-01

This study investigated the effects of workshop and lecture methods on pastoralists' learning in Ilam Province, west of Iran. A quasi-experimental research method and non-equivalent control group design was used. Sixty pastoralists participated in this study. An open-ended questionnaire was used as the instrument of the study and found to have…

Anthrax Vaccine and the Risk of Rheumatoid Arthritis and Systemic Lupus Erythematosus in the U.S. Military: A Case-Control Study.

PubMed

Bardenheier, Barbara H; Duffy, Jonathan; Duderstadt, Susan K; Higgs, Jay B; Keith, Michael P; Papadopoulos, Patricia J; Gilliland, William R; McNeil, Michael M

2016-10-01

U.S. military personnel assigned to areas deemed to be at high risk for anthrax attack receive Anthrax Vaccine Adsorbed (AVA). Few cases of rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE) have been reported in persons who received AVA. Using a matched case-control study design, we assessed the relationship of RA and SLE with AVA vaccination using the Defense Medical Surveillance System. We identified potential cases using International Classification of Diseases, 9th Revision, Clinical Modification codes and confirmed cases with medical record review and rheumatologist adjudication. Using conditional logistic regression, we estimated odds ratios (OR) for AVA exposure during time intervals ranging from 90 to 1,095 days before disease onset. Among 77 RA cases, 13 (17%) had ever received AVA. RA cases were no more likely than controls to have received AVA when looking back 1,095 days (OR: 1.03; 95% confidence interval [CI]: 0.48-2.19) but had greater odds of exposure in the prior 90 days (OR: 3.93; 95% CI: 1.08-14.27). Among the 39 SLE cases, 5 (13%) had ever received AVA; no significant difference in receipt of AVA was found when compared with controls (OR: 0.91; 95% CI: 0.26-3.25). AVA was associated with recent onset RA, but did not increase the risk of developing RA in the long term. Reprint & Copyright © 2016 Association of Military Surgeons of the U.S.

Rapid Preliminary Design of Interplanetary Trajectories Using the Evolutionary Mission Trajectory Generator

NASA Technical Reports Server (NTRS)

Englander, Jacob

2016-01-01

Preliminary design of interplanetary missions is a highly complex process. The mission designer must choose discrete parameters such as the number of flybys, the bodies at which those flybys are performed, and in some cases the final destination. In addition, a time-history of control variables must be chosen that defines the trajectory. There are often many thousands, if not millions, of possible trajectories to be evaluated. This can be a very expensive process in terms of the number of human analyst hours required. An automated approach is therefore very desirable. This work presents such an approach by posing the mission design problem as a hybrid optimal control problem. The method is demonstrated on notional high-thrust chemical and low-thrust electric propulsion missions. In the low-thrust case, the hybrid optimal control problem is augmented to include systems design optimization.

A psychological autopsy study of suicide among Inuit in Nunavut: methodological and ethical considerations, feasibility and acceptability

PubMed Central

Chachamovich, Eduardo; Haggarty, Jack; Cargo, Margaret; Hicks, Jack; Kirmayer, Laurence J.; Turecki, Gustavo

2013-01-01

Introduction The increasing global prevalence of suicide has made it a major public health concern. Research designed to retrospectively study suicide cases is now being conducted in populations around the world. This field of research is especially crucial in Aboriginal populations, as they often have higher suicide rates than the rest of the country. Objective This article presents the methodological aspects of the first psychological autopsy study on suicide among Inuit in Nunavut. Qaujivallianiq Inuusirijauvalauqtunik (Learning from lives that have been lived) is a large case-control study, including all 120 cases of suicide by Inuit that occurred in Nunavut between 1 January 2003 and 31 December 2006. The article describes the research design, ethical considerations and strategies used to adapt the psychological autopsy method to Nunavut Inuit. Specifically, we present local social and cultural issues; data collection procedures; and the acceptability, reliability and validity of the method. Method A retrospective case-control study using the psychological autopsy approach was carried out in 22 communities in Nunavut. A total of 498 individuals were directly interviewed, and medical and correctional charts were also reviewed. Results The psychological autopsy method was well received by participants as they appreciated the opportunity to discuss the loss of a family member or friend by suicide. During interviews, informants readily identified symptoms of psychiatric disorders, although culture-specific rather than clinical explanations were sometimes provided. Results suggest that the psychological autopsy method can be effectively used in Inuit populations. PMID:23539438

A psychological autopsy study of suicide among Inuit in Nunavut: methodological and ethical considerations, feasibility and acceptability.

PubMed

Chachamovich, Eduardo; Haggarty, Jack; Cargo, Margaret; Hicks, Jack; Kirmayer, Laurence J; Turecki, Gustavo

2013-01-01

The increasing global prevalence of suicide has made it a major public health concern. Research designed to retrospectively study suicide cases is now being conducted in populations around the world. This field of research is especially crucial in Aboriginal populations, as they often have higher suicide rates than the rest of the country. This article presents the methodological aspects of the first psychological autopsy study on suicide among Inuit in Nunavut. Qaujivallianiq Inuusirijauvalauqtunik (Learning from lives that have been lived) is a large case-control study, including all 120 cases of suicide by Inuit that occurred in Nunavut between 1 January 2003 and 31 December 2006. The article describes the research design, ethical considerations and strategies used to adapt the psychological autopsy method to Nunavut Inuit. Specifically, we present local social and cultural issues; data collection procedures; and the acceptability, reliability and validity of the method. A retrospective case-control study using the psychological autopsy approach was carried out in 22 communities in Nunavut. A total of 498 individuals were directly interviewed, and medical and correctional charts were also reviewed. The psychological autopsy method was well received by participants as they appreciated the opportunity to discuss the loss of a family member or friend by suicide. During interviews, informants readily identified symptoms of psychiatric disorders, although culture-specific rather than clinical explanations were sometimes provided. Results suggest that the psychological autopsy method can be effectively used in Inuit populations.

Relative position coordinated control for spacecraft formation flying with communication delays

NASA Astrophysics Data System (ADS)

Ran, Dechao; Chen, Xiaoqian; Misra, Arun K.; Xiao, Bing

2017-08-01

This study addresses a relative position coordinated control problem for spacecraft formation flying subject to directed communication topology. Two different kinds of communication delay cases, including time-varying delays and arbitrarily bounded delays are investigated. Using the backstepping control technique, two virtual velocity control inputs are firstly designed to achieve coordinated position tracking for the kinematic subsystem. Furthermore, a hyperbolic tangent function is introduced to guarantee the boundedness of the virtual controller. Then, a finite-time control algorithm is designed for the dynamic subsystem. It can guarantee that the virtual velocity can be followed by the real velocity after finite time. It is theoretically proved that the proposed control scheme can asymptotically stabilize the closed-loop system. Numerical simulations are further presented that not only highlight closed-loop performance benefiting from the proposed control scheme, but also illustrate its superiority in comparison with conventional formation control schemes.

Association Of Serum Total Bilirubin Level With Diabetic Retinopathy In Type 2 Diabetes Mellitus.

PubMed

Ghaffar, Tahir; Marwat, Zahid Irfan; Ullah, Fahim; Khan, Salman; Hassan Aamir, Aziz Ul

2016-01-01

Serum bilirubin has anti-inflammatory, antioxidant and immunological properties. It is considered a protective substance against atherosclerotic and microvascular complications of diabetes mellitus (DM). This study was designed to find the association between total serum bilirubin concentration and diabetic retinopathy (DR). This case control study was conducted in the Department of Endocrinology, Diabetes and Metabolic Diseases, Hayatabad Medical Complex, Peshawar. Type-2 DM patients more than 18 years of age of either gender with duration of T2DM more than 6 months were included and sub categorized in two groups. Cases (DM with DR) and Controls (DM without DR) while patients with acute and chronic liver diseases, haemolytic anaemia, history of chronic alcohol consumption, use of hepatotoxic drugs (anti-tuberculous, anti-epileptic), women on oral contraceptive pills were excluded. All participants underwent ophthalmic examination at diabetic retinopathy screening clinic followed by pre designed set of investigations. A total of 152 patients, 76 cases and 76 controls were included. Serum bilirubin concentration was found inversely and independently (p 0.000) associated and inversely co related (r -0.345and p 0.000) with prevalence of DR. Cases were concentrated in the lower quartiles of serum bilirubin concentration and vice versa. Low haemoglobin (p 0.00) and longer duration of DM (0.003) were independently and directly associated with prevalence of DR. Serum bilirubin concentration is inversely and independently associated and inversely correlated with the prevalence of DR and may predict progression of DR over time.

Glycemic index, glycemic load and endometrial cancer risk: results from the Australian National Endometrial Cancer study and an updated systematic review and meta-analysis.

PubMed

Nagle, Christina M; Olsen, Catherine M; Ibiebele, Torukiri I; Spurdle, Amanda B; Webb, Penelope M

2013-03-01

The relationship between habitual consumption of foods with a high glycemic index (GI) and/or a diet with a high glycemic load (GL) and risk of endometrial cancer is uncertain, and relatively few studies have investigated these associations. The objectives of this study were to examine the association between GI/GL and risk of endometrial cancer using data from an Australian population-based case-control study and systematically review all the available evidence to quantify the magnitude of the association using meta-analysis. The case-control study included 1,290 women aged 18-79 years with newly diagnosed, histologically confirmed endometrial cancer and 1,436 population controls. Controls were selected to match the expected Australian state of residence and age distribution (in 5-year bands) of cases. For the systematic review, relevant studies were identified by searching PubMed and Embase databases through to July 2011. Random-effects models were used to calculate the summary risk estimates, overall and dose-response. In our case-control study, we observed a modest positive association between high dietary GI (OR 1.43, 95 % CI 1.11-1.83) and risk of endometrial cancer, but no association with high dietary GL (OR 1.15, 95 % CI 0.90-1.48). For the meta-analysis, we collated information from six cohort and two case-control studies, involving a total of 5,569 cases. The pooled OR for the highest versus the lowest intake category of GI was 1.15 (0.95-1.40); however, there was significant heterogeneity (p 0.004) by study design (RR 1.00 [95 % CI 0.87-1.14] for cohort studies and 1.56 [95 % CI 1.21-2.02] for case-control studies). There was no association in the dose-response meta-analysis of GI (RR per 5 unit/day increment of GI 1.00, 95 % CI 0.97-1.03). GL was positively associated with endometrial cancer. The pooled RR for the highest versus the lowest GL intake was 1.21 (95 % CI 1.09-1.33) and 1.06 (95 % CI 1.01-1.11) per 50 unit/day increment of GL in the dose-response meta-analysis. The pooled results from observational studies, including our case-control results, provide evidence of a modest positive association between high GL, but not GI, and endometrial cancer risk.

Making a Case for a Blended Approach: The Need for The Design-Based Case Study

ERIC Educational Resources Information Center

Deaton, Cynthia C. M.; Malloy, Jacquelynn A.

2017-01-01

Design-based case studies address research questions that involve instructional innovations within a bounded system. This blend of case study and design-based research provides a systematic approach to examining instructional innovations that are bounded by perspective, context, and time. Design-based case studies provide a framework for engaging…

Enhancing Information Literacy for Preservice Elementary Teachers: A Case Study from the United States

ERIC Educational Resources Information Center

Ruppel, Margie; Fry, Sara Winstead; Bentahar, Adil

2016-01-01

Through this study, a librarian and faculty team aimed to determine the extent to which a one-credit information literacy course deepened preservice teachers' understanding of information literacy. We employed a treatment and control group design; treatment participants received 15 hours of information literacy instruction while control…

Effect of Rehabilitation Technology Services on Vocational Rehabilitation Outcomes of Individuals with Multiple Sclerosis

ERIC Educational Resources Information Center

Chiu, Chung-Yi; Tansey, Timothy N.; Chan, Fong; Strauser, David; Frain, Michael P.; Arora, Simran

2015-01-01

Objectives: To examine the effect of rehabilitation technology interventions on the employment or job retention outcomes of individuals with multiple sclerosis (MS) served by the state-federal vocational rehabilitation program using a case-control study design. Participants: Data for this study were extracted from the Rehabilitation Services…

Inpatient Suicide in a Chinese Psychiatric Hospital

ERIC Educational Resources Information Center

Li, Jie; Ran, Mao-Sheng; Hao, Yuantao; Zhao, Zhenhuan; Guo, Yangbo; Su, Jinghua; Lu, Huixian

2008-01-01

Little is known about the risk factors for suicide among psychiatric inpatients in China. In this study we identified the risk factors of suicide among psychiatric inpatients at Guangzhou Psychiatric Hospital. All psychiatric inpatients who died by suicide during the 1956-2005 period were included in this study. Using a case-control design, 64…

Adult Day Health Center Participation and Health-Related Quality of Life

ERIC Educational Resources Information Center

Schmitt, Eva M.; Sands, Laura P.; Weiss, Sara; Dowling, Glenna; Covinsky, Kenneth

2010-01-01

Purpose: The purpose of this study was to assess the association between Adult Day Health Center (ADHC) participation and health-related quality of life. Design and Methods: Case-controlled prospective study utilizing the Medical Outcomes Survey Form 36 (SF-36) to compare newly enrolled participants from 16 ADHC programs with comparable…

Risk factors for self-directed violence in US Soldiers: A case-control study.

PubMed

Skopp, Nancy A; Zhang, Ying; Smolenski, Derek J; Reger, Mark A

2016-11-30

Military suicide has escalated in recent years, however almost no research has used military surveillance data to examine suicide risk factors. The aims of the current study were to compare suicide risk factors among US Soldiers who died by suicide, attempted suicide, and controls using a prospective case-control design. Controls were 247 Soldiers completing standard post-deployment assessment procedures. Cases were 276 suicide decedents (n=85) or suicide attempters (n=191), drawn from the Department of Defense Suicide Event Report. Compared to controls, suicide attempters and decedents had greater odds of failed intimate relationships, legal problems, and substance abuse problems in the past 90 days. Suicide attempters and decedents also had greater odds of a history of a mood disorder and prior suicide attempt compared to controls. Suicide decedents had greater odds of exposure to legal problems in the past 90 days and lower odds of ever having an anxiety disorder, compared to suicide attempters. Vigilance toward early detection of modifiable suicide risk factors such as relationship dissolution, mood disorders, substance abuse, and legal problems may help reduce suicide risk among US Soldiers. Published by Elsevier Ireland Ltd.

The assessment of risk factors for the Central/East African Genotype of chikungunya virus infections in the state of Kelantan: a case control study in Malaysia.

PubMed

Yusoff, Ahmad Faudzi; Mustafa, Amal Nasir; Husaain, Hani Mat; Hamzah, Wan Mansor; Yusof, Apandi Mohd; Harun, Rozilawati; Abdullah, Faezah Noor

2013-05-08

The aims of the study were to assess the risk factors in relation to cross border activities, exposure to mosquito bite and preventive measures taken.An outbreak of chikungunya virus (CHIKV) infection in Malaysia has been reported in Klang, Selangor (1998) and Bagan Panchor, Perak (2006). In 2009, CHIKV infection re-emerged in some states in Malaysia. It raises the possibilities that re-emergence is part of the epidemics in neighbouring countries or the disease is endemic in Malaysia. For this reason, A community-based case control study was carried out in the state of Kelantan. Prospective case finding was performed from June to December 2009. Those who presented with signs and symptoms of CHIKV infection were investigated. We designed a case control study to assess the risk factors. Assessment consisted of answering questions, undergoing a medical examination, and being tested for the presence of IgM antibodies to CHIKV. Descriptive epidemiological studies were conducted by reviewing both the national surveillance and laboratory data. Multivariable logistic regression analysis was performed to determine risk factors contributing to the illness. Cases were determined by positive to RT-PCR or serological for antibodies by IgM. CHIKV specificity was confirmed by DNA sequencing. There were 129 suspected cases and 176 controls. Among suspected cases, 54.4% were diagnosed to have CHIKV infection. Among the controls, 30.1% were found to be positive to serology for antibodies [IgM, 14.2% and IgG, 15.9%]. For analytic study and based on laboratory case definition, 95 were considered as cases and 123 as controls. Those who were positive to IgG were excluded. CHIKV infection affected all ages and mostly between 50-59 years old. Staying together in the same house with infected patients and working as rubber tappers were at a higher risk of infection. The usage of Mosquito coil insecticide had shown to be a significant protective factor. Most cases were treated as outpatient, only 7.5% needed hospitalization. The CHIKV infection was attributable to central/east African genotype CHIKV. In this study, cross border activity was not a significant risk factor although Thailand and Malaysia shared the same CHIKV genotype during the episode of infections.

The assessment of risk factors for the Central/East African Genotype of chikungunya virus infections in the state of Kelantan: a case control study in Malaysia

PubMed Central

2013-01-01

Background The aims of the study were to assess the risk factors in relation to cross border activities, exposure to mosquito bite and preventive measures taken. An outbreak of chikungunya virus (CHIKV) infection in Malaysia has been reported in Klang, Selangor (1998) and Bagan Panchor, Perak (2006). In 2009, CHIKV infection re-emerged in some states in Malaysia. It raises the possibilities that re-emergence is part of the epidemics in neighbouring countries or the disease is endemic in Malaysia. For this reason, A community-based case control study was carried out in the state of Kelantan. Methods Prospective case finding was performed from June to December 2009. Those who presented with signs and symptoms of CHIKV infection were investigated. We designed a case control study to assess the risk factors. Assessment consisted of answering questions, undergoing a medical examination, and being tested for the presence of IgM antibodies to CHIKV. Descriptive epidemiological studies were conducted by reviewing both the national surveillance and laboratory data. Multivariable logistic regression analysis was performed to determine risk factors contributing to the illness. Cases were determined by positive to RT-PCR or serological for antibodies by IgM. CHIKV specificity was confirmed by DNA sequencing. Results There were 129 suspected cases and 176 controls. Among suspected cases, 54.4% were diagnosed to have CHIKV infection. Among the controls, 30.1% were found to be positive to serology for antibodies [IgM, 14.2% and IgG, 15.9%]. For analytic study and based on laboratory case definition, 95 were considered as cases and 123 as controls. Those who were positive to IgG were excluded. CHIKV infection affected all ages and mostly between 50–59 years old. Staying together in the same house with infected patients and working as rubber tappers were at a higher risk of infection. The usage of Mosquito coil insecticide had shown to be a significant protective factor. Most cases were treated as outpatient, only 7.5% needed hospitalization. The CHIKV infection was attributable to central/east African genotype CHIKV. Conclusions In this study, cross border activity was not a significant risk factor although Thailand and Malaysia shared the same CHIKV genotype during the episode of infections. PMID:23656634

Evaluation of Lipid Profile in Patients with Cherry Angioma: A Case-Control Study in Guilan, Iran.

PubMed

Darjani, Abbas; Rafiei, Rana; Shafaei, Sareh; Rafiei, Elahe; Eftekhari, Hojat; Alizade, Narges; Gharaei Nejad, Kaveh; Rafiee, Behnam; Najirad, Sara

2018-01-01

Cherry angioma is the most common type of acquired cutaneous vascular proliferation which would increase with aging due to some angiogenic factors but the exact pathogenesis is unknown. Usually angiogenic factors are synthesized in human body to compensate occlusive effects of atherogenic agents such as serum lipids. Our hypothesis was that increased levels of these angiogenic factors could be a trigger for development of cherry angioma. This study has been designed to compare frequency of dyslipidemia in subjects with and without cutaneous cherry angioma. In this case-control study, 122 cases with cherry angioma and 122 control subjects without cherry angioma were enrolled. Demographic characteristics, number of the cherry angioma lesions, and serum lipid profile were collected for all subjects. The data was analyzed using SPSS 18 software. Mean levels of the total cholesterol, triglyceride, low-density lipoprotein, and high-density lipoprotein were higher in patients with cherry angioma compared to control subjects in which differences were significant for total cholesterol, low-density lipoprotein, and triglyceride ( P < 0.05) but not for high-density lipoprotein level. Serum lipids may have a role in producing angiogenic factors and development of cherry angioma and it seems logical to evaluate lipid profile in these cases.

A novel case-control design to estimate the extent of over-diagnosis of breast cancer due to organised population-based mammography screening.

PubMed

Beckmann, Kerri R; Lynch, John W; Hiller, Janet E; Farshid, Gelareh; Houssami, Nehmat; Duffy, Stephen W; Roder, David M

2015-03-15

Debate about the extent of breast cancer over-diagnosis due to mammography screening has continued for over a decade, without consensus. Estimates range from 0 to 54%, but many studies have been criticized for having flawed methodology. In this study we used a novel study design to estimate over-diagnosis due to organised mammography screening in South Australia (SA). To estimate breast cancer incidence at and following screening we used a population-based, age-matched case-control design involving 4,931 breast cancer cases and 22,914 controls to obtain OR for yearly time intervals since women's last screening mammogram. The level of over-diagnosis was estimated by comparing the cumulative breast cancer incidence with and without screening. The former was derived by applying ORs for each time window to incidence rates in the absence of screening, and the latter, by projecting pre-screening incidence rates. Sensitivity analyses were undertaken to assess potential biases. Over-diagnosis was estimated to be 8% (95%CI 2-14%) and 14% (95%CI 8-19%) among SA women aged 45 to 85 years from 2006-2010, for invasive breast cancer and all breast cancer respectively. These estimates were robust when applying various sensitivity analyses, except for adjustment for potential confounding assuming higher risk among screened than non-screened women, which reduced levels of over-diagnosis to 1% (95%CI 5-7%) and 8% (95%CI 2-14%) respectively when incidence rates for screening participants were adjusted by 10%. Our results indicate that the level of over-diagnosis due to mammography screening is modest and considerably lower than many previous estimates, including others for Australia. © 2014 UICC.

Two Reconfigurable Flight-Control Design Methods: Robust Servomechanism and Control Allocation

NASA Technical Reports Server (NTRS)

Burken, John J.; Lu, Ping; Wu, Zheng-Lu; Bahm, Cathy

2001-01-01

Two methods for control system reconfiguration have been investigated. The first method is a robust servomechanism control approach (optimal tracking problem) that is a generalization of the classical proportional-plus-integral control to multiple input-multiple output systems. The second method is a control-allocation approach based on a quadratic programming formulation. A globally convergent fixed-point iteration algorithm has been developed to make onboard implementation of this method feasible. These methods have been applied to reconfigurable entry flight control design for the X-33 vehicle. Examples presented demonstrate simultaneous tracking of angle-of-attack and roll angle commands during failures of the fight body flap actuator. Although simulations demonstrate success of the first method in most cases, the control-allocation method appears to provide uniformly better performance in all cases.

Keeping children safe at home: protocol for three matched case–control studies of modifiable risk factors for falls

PubMed Central

Kendrick, Denise; Stewart, Jane; Clacy, Rose; Coffey, Frank; Cooper, Nicola; Coupland, Carol; Hayes, Mike; McColl, Elaine; Reading, Richard; Sutton, Alex; M L Towner, Elizabeth; Craig Watson, Michael

2012-01-01

Background Childhood falls result in considerable morbidity, mortality and health service use. Despite this, little evidence exists on protective factors or effective falls prevention interventions in young children. Objectives To estimate ORs for three types of medically attended fall injuries in young children in relation to safety equipment, safety behaviours and hazard reduction and explore differential effects by child and family factors and injury severity. Design Three multicentre case–control studies in UK hospitals with validation of parental reported exposures using home observations. Cases are aged 0–4 years with a medically attended fall injury occurring at home, matched on age and sex with community controls. Children attending hospital for other types of injury will serve as unmatched hospital controls. Matched analyses will use conditional logistic regression to adjust for potential confounding variables. Unmatched analyses will use unconditional logistic regression, adjusted for age, sex, deprivation and distance from hospital in addition to other confounders. Each study requires 496 cases and 1984 controls to detect an OR of 0.7, with 80% power, 5% significance level, a correlation between cases and controls of 0.1 and a range of exposure prevalences. Main outcome measures Falls on stairs, on one level and from furniture. Discussion As the largest in the field to date, these case control studies will adjust for potential confounders, validate measures of exposure and investigate modifiable risk factors for specific falls injury mechanisms. Findings should enhance the evidence base for falls prevention for young children. PMID:22628151

Piecewise exponential survival times and analysis of case-cohort data.

PubMed

Li, Yan; Gail, Mitchell H; Preston, Dale L; Graubard, Barry I; Lubin, Jay H

2012-06-15

Case-cohort designs select a random sample of a cohort to be used as control with cases arising from the follow-up of the cohort. Analyses of case-cohort studies with time-varying exposures that use Cox partial likelihood methods can be computer intensive. We propose a piecewise-exponential approach where Poisson regression model parameters are estimated from a pseudolikelihood and the corresponding variances are derived by applying Taylor linearization methods that are used in survey research. The proposed approach is evaluated using Monte Carlo simulations. An illustration is provided using data from the Alpha-Tocopherol, Beta-Carotene Cancer Prevention Study of male smokers in Finland, where a case-cohort study of serum glucose level and pancreatic cancer was analyzed. Copyright © 2012 John Wiley & Sons, Ltd.

The Risk of Infection from Polychlorinated Biphenyl Exposure in the Harbor Porpoise (Phocoena phocoena): A Case–Control Approach

PubMed Central

Hall, Ailsa J.; Hugunin, Kelly; Deaville, Robert; Law, Robin J.; Allchin, Colin R.; Jepson, Paul D.

2006-01-01

The objective of this study was to determine whether the risk of mortality from infectious disease in harbor porpoise in U.K. waters increased with high exposure to polychlorinated biphenyls (PCBs), using a case–control study design. This is the first time that data from a long-term marine mammal strandings scheme have been used to estimate any increase in risk. The exposure odds ratio (OR) from a logistic regression model with infectious disease deaths as cases and physical trauma deaths as controls, after controlling for the effect of confounding factors, was 1.048 [95% confidence interval (CI), 1.02–1.07]. To further adjust for the difference in energetic status between cases and controls and account for the negative relationship between PCBs (sum of 25 chlorobiphenyl congeners) and blubber mass, we also “standardized” the blubber PCBs to an optimal blubber mass. This lowered the OR to 1.02 (95% CI, 1.00–1.03). Thus, for each 1 mg/kg increase in blubber PCBs, the average increase in risk of infectious disease mortality was 2%. A doubling of risk occurred at approximately 45 mg/kg lipid. In this study, we have endeavored to avoid selection bias by using controls that died of physical trauma as representative of the exposure prevalence in the population that gave rise to the cases. In addition, we controlled for the effect of variation in energetic status among the cases and controls. However, as with case–control studies in human and veterinary epidemiology, unforeseen misclassification errors may result in biased risk estimates in either direction. PMID:16675424

Bayesian Estimation of Pneumonia Etiology: Epidemiologic Considerations and Applications to the Pneumonia Etiology Research for Child Health Study.

PubMed

Deloria Knoll, Maria; Fu, Wei; Shi, Qiyuan; Prosperi, Christine; Wu, Zhenke; Hammitt, Laura L; Feikin, Daniel R; Baggett, Henry C; Howie, Stephen R C; Scott, J Anthony G; Murdoch, David R; Madhi, Shabir A; Thea, Donald M; Brooks, W Abdullah; Kotloff, Karen L; Li, Mengying; Park, Daniel E; Lin, Wenyi; Levine, Orin S; O'Brien, Katherine L; Zeger, Scott L

2017-06-15

In pneumonia, specimens are rarely obtained directly from the infection site, the lung, so the pathogen causing infection is determined indirectly from multiple tests on peripheral clinical specimens, which may have imperfect and uncertain sensitivity and specificity, so inference about the cause is complex. Analytic approaches have included expert review of case-only results, case-control logistic regression, latent class analysis, and attributable fraction, but each has serious limitations and none naturally integrate multiple test results. The Pneumonia Etiology Research for Child Health (PERCH) study required an analytic solution appropriate for a case-control design that could incorporate evidence from multiple specimens from cases and controls and that accounted for measurement error. We describe a Bayesian integrated approach we developed that combined and extended elements of attributable fraction and latent class analyses to meet some of these challenges and illustrate the advantage it confers regarding the challenges identified for other methods. © The Author 2017. Published by Oxford University Press for the Infectious Diseases Society of America.

Design of a large span-distributed load flying-wing cargo airplane with laminar flow control

NASA Technical Reports Server (NTRS)

Lovell, W. A.; Price, J. E.; Quartero, C. B.; Turriziani, R. V.; Washburn, G. F.

1978-01-01

A design study was conducted to add laminar flow control to a previously design span-distributed load airplane while maintaining constant range and payload. With laminar flow control applied to 100 percent of the wing and vertical tail chords, the empty weight increased by 4.2 percent, the drag decreased by 27.4 percent, the required engine thrust decreased by 14.8 percent, and the fuel consumption decreased by 21.8 percent. When laminar flow control was applied to a lesser extent of the chord (approximately 80 percent), the empty weight increased by 3.4 percent, the drag decreased by 20.0 percent, the required engine thrust decreased by 13.0 percent, and the fuel consumption decreased by 16.2 percent. In both cases the required take-off gross weight of the aircraft was less than the original turbulent aircraft.

Coffee Consumption and the Risk of Thyroid Cancer: A Systematic Review and Meta-Analysis.

PubMed

Han, Mi Ah; Kim, Jin Hwa

2017-01-27

An inverse association has been reported between coffee consumption and the risk of several cancers. However, the association between coffee and thyroid cancer is controversial. Thus, this study aimed to evaluate the association between coffee consumption and the risk of thyroid cancer through a systematic review and meta-analysis. Published studies were examined from PubMed, Embase, Cochrane Central, and the reference lists of the retrieved articles. The summary odds ratio (OR) for the association between coffee consumption was categorized as highest versus lowest consumption, and thyroid cancer risk was calculated using a fixed effects model. Subgroup analyses by study design, geographic location, source of controls, and adjusted variables were performed. A total of 1039 thyroid cancer cases and 220,816 controls were identified from five case-control studies and two cohort studies. The summary OR for the association between coffee consumption and thyroid cancer risk was 0.88 (95% confidence interval (CI) = 0.71-1.07). There was no significant heterogeneity among the study results (I² = 0%, p = 0.79). However, the beneficial effect of coffee consumption on thyroid cancer was found only in hospital-based case-control studies (OR= 0.59, 95% CI= 0.37-0.93). There was no significant association between coffee consumption and thyroid cancer risk according to our meta-analysis results. These findings should be interpreted with caution because of potential biases and confounding variables. Further prospective studies with a larger number of cases are encouraged to confirm these results.

Timing is everything: methodologic issues locating and recruiting medically underserved women for abnormal mammography follow-up research

PubMed Central

Fair, Alecia Malin; Wujcik, Debra; Lin, Jin-Mann S.; Egan, Kathleen M.; Grau, Ana M.; Zheng, Wei

2008-01-01

Objectives Recruiting underserved women in breast cancer research studies remains a significant challenge. We present our experience attempting to locate and recruit minority and medically underserved women identified in a Nashville, Tennessee public hospital for a mammography follow-up study. Study Design The study design was a retrospective hospital based case-control study. Methods We identified 227 women (88 African American, 65 Caucasian, 36 other minority, 38 race undocumented in the medical record) who had undergone screening mammography and received an abnormal result during 2003–2004. Of the 227 women identified, 159 women were successfully located with implementation of a tracking protocol and more rigorous attempts to locate the women using online directory assistance and public record search engines. Women eligible for the study were invited to participate in a telephone research survey. Study completion was defined as fully finishing the telephone survey. Results An average of 4.6 telephone calls (range 1–19) and 2.7 months (range 1–490 days) were required to reach the 159 women contacted. Within three contact attempts, more cases were located than controls (61% cases vs. 49% controls, p=0.03). African-American women cases were four times likely to be recruited than African-American controls, (OR, 4.07; 95% CI, 1.59–10.30) (p=0.003). After three months of effort, we located 67% of African-American women, 63% of Caucasian women, and 56% of other minorities. Ultimately, after a maximum of 12 attempts to contact women, 77% of African-American women and 71% of Caucasian women were eventually found. Of these, 59% of African-American women, 69% Caucasian women, and 50% other minorities were located and completed the study survey for an overall response rate of 59%, 71%, and 47% respectively. Conclusions Data collection and study recruitment efforts were more challenging in racial and ethnic minorities. Continuing attempts to contact women may increase minority group study participation but does not guarantee retention or study completion. PMID:18289943

Digital redesign of anti-wind-up controller for cascaded analog system.

PubMed

Chen, Y S; Tsai, J S H; Shieh, L S; Moussighi, M M

2003-01-01

The cascaded conventional anti-wind-up (CAW) design method for integral controller is discussed. Then, the prediction-based digital redesign methodology is utilized to find the new pulse amplitude modulated (PAM) digital controller for effective digital control of the analog plant with input saturation constraint. The desired digital controller is determined from existing or pre-designed CAW analog controller. The proposed method provides a novel methodology for indirect digital design of a continuous-time unity output-feedback system with a cascaded analog controller as in the case of PID controllers for industrial control processes with the presence of actuator saturations. It enables us to implement an existing or pre-designed cascaded CAW analog controller via a digital controller effectively.

Lung cancer risk among bricklayers in a pooled analysis of case–control studies

PubMed Central

Consonni, Dario; Matteis, Sara De; Pesatori, Angela C; Bertazzi, Pier Alberto; Olsson, Ann C; Kromhout, Hans; Peters, Susan; Vermeulen, Roel CH; Pesch, Beate; Brüning, Thomas; Kendzia, Benjamin; Behrens, Thomas; Stücker, Isabelle; Guida, Florence; Wichmann, Heinz-Erich; Brüske, Irene; Landi, Maria Teresa; Caporaso, Neil E; Gustavsson, Per; Plato, Nils; Tse, Lap Ah; Yu, Ignatius Tak-sun; Jöckel, Karl-Heinz; Ahrens, Wolfgang; Pohlabeln, Hermann; Merletti, Franco; Richiardi, Lorenzo; Simonato, Lorenzo; Forastiere, Francesco; Siemiatycki, Jack; Parent, Marie-Élise; Tardón, Adonina; Boffetta, Paolo; Zaridze, David; Chen, Ying; Field, John K; 't Mannetje, Andrea; Pearce, Neil; McLaughlin, John; Demers, Paul; Lissowska, Jolanta; Szeszenia-Dabrowska, Neonila; Bencko, Vladimir; Foretova, Lenka; Janout, Vladimir; Rudnai, Peter; Fabiánová, Eleonóra; Stanescu Dumitru, Rodica; Bueno-de-Mesquita, H B(as); Schüz, Joachim; Straif, Kurt

2015-01-01

Bricklayers may be exposed to several lung carcinogens, including crystalline silica and asbestos. Previous studies that analyzed lung cancer risk among these workers had several study design limitations. We examined lung cancer risk among bricklayers within SYNERGY, a large international pooled analysis of case–control studies on lung cancer and the joint effects of occupational carcinogens. For men ever employed as bricklayers we estimated odds ratios (OR) and 95% confidence intervals (CI) adjusted for study center, age, lifetime smoking history and employment in occupations with exposures to known or suspected lung carcinogens. Among 15,608 cases and 18,531 controls, there were 695 cases and 469 controls who had ever worked as bricklayers (OR: 1.47; 95% CI: 1.28–1.68). In studies using population controls the OR was 1.55 (95% CI: 1.32–1.81, 540/349 cases/controls), while it was 1.24 (95% CI: 0.93–1.64, 155/120 cases/controls) in hospital-based studies. There was a clear positive trend with length of employment (p < 0.001). The relative risk was higher for squamous (OR: 1.68, 95% CI: 1.42–1.98, 309 cases) and small cell carcinomas (OR: 1.78, 95% CI: 1.44–2.20, 140 cases), than for adenocarcinoma (OR: 1.17, 95% CI: 0.95–1.43, 150 cases) (p-homogeneity: 0.0007). ORs were still elevated after additional adjustment for education and in analyses using blue collar workers as referents. This study provided robust evidence of increased lung cancer risk in bricklayers. Although non-causal explanations cannot be completely ruled out, the association is plausible in view of the potential for exposure to several carcinogens, notably crystalline silica and to a lesser extent asbestos. What's new? In their work, bricklayers can be exposed to various airborne carcinogens, including crystalline silica and asbestos. Previous studies of cancer risk have not accounted for full employment history or smoking status, and failed to establish a firm relationship between bricklaying and lung cancer. In this study, the authors used data from the largest collection of case-control studies on lung cancer with complete occupational and smoking history existing today, the SYNERGY project. They found clear evidence that lung cancer risk increases in proportion to the length of time spent working as a bricklayer, paving the way for better protection and compensation for those in this occupation. PMID:24861979

On Mixed Data and Event Driven Design for Adaptive-Critic-Based Nonlinear $H_{\\infty}$ Control.

PubMed

Wang, Ding; Mu, Chaoxu; Liu, Derong; Ma, Hongwen

2018-04-01

In this paper, based on the adaptive critic learning technique, the control for a class of unknown nonlinear dynamic systems is investigated by adopting a mixed data and event driven design approach. The nonlinear control problem is formulated as a two-player zero-sum differential game and the adaptive critic method is employed to cope with the data-based optimization. The novelty lies in that the data driven learning identifier is combined with the event driven design formulation, in order to develop the adaptive critic controller, thereby accomplishing the nonlinear control. The event driven optimal control law and the time driven worst case disturbance law are approximated by constructing and tuning a critic neural network. Applying the event driven feedback control, the closed-loop system is built with stability analysis. Simulation studies are conducted to verify the theoretical results and illustrate the control performance. It is significant to observe that the present research provides a new avenue of integrating data-based control and event-triggering mechanism into establishing advanced adaptive critic systems.

Young People's Risk of Suicide Attempts in Relation to Parental Death: A Population-Based Register Study

ERIC Educational Resources Information Center

Jakobsen, Ida Skytte; Christiansen, Erik

2011-01-01

Background: The objective of this study was to examine the association between the death of a biological parent and subsequent suicide attempts by young people (aged 10-22 years), and to explore sociodemographic factors as modifying factors in the process. Methods: The study used a nested case-control design. The full study population was obtained…

The Effect of Breathing Exercises on the Nocturnal Enuresis in the Children with the Sleep-Disordered Breathing

PubMed Central

Khaleghipour, Shahnaz; Masjedi, Mohsen; Kelishadi, Roya

2013-01-01

Background The nocturnal enuresis is one of the most common complaints of childhood. Upper airway obstruction and nocturnal snoring affect the nocturnal enuresis in children. Objectives The aim of this study was to investigate the effects of breathing exercises on the nocturnal enuresis in the children with the sleep-disordered breathing. Patients and Methods This study was conducted in year of 2011 by a semi-experimental design with the control group among 40 children, aged 6 - 12 years, who had the nocturnal enuresis. Participants were examined based on the criteria of nocturnal enuresis, oral breathing, and nocturnal snoring. Subsequently, they were randomly assigned to the case and control groups. In the case group, the breathing exercises were performed for 45 minutes, and were pursued for four weeks in the morning following and prior to sleeping, and subsequently the arterial blood gases were measured and the frequency of enuresis and the respiratory rates (RR) were recorded. Results After intervention the means of PaCO2 and RR in the control group were significantly higher than the case group (P < 0.0001). Likewise, O2sat, PaO2 in the case group were higher than the control group (P < 0.0001). The nocturnal enuresis decreased significantly in the case group, compared to the control group (P < 0.0001). Conclusions This study suggests that the breathing exercises may reduce the frequency of nocturnal enuresis in the patients with the oral breathing and nocturnal snore. The clinical implications of these findings should be verified in the future longitudinal studies. PMID:24719691

Delinquency and Recidivism: A Multicohort, Matched-Control Study of the Role of Early Adverse Experiences, Mental Health Problems, and Disabilities

ERIC Educational Resources Information Center

Barrett, David E.; Katsiyannis, Antonis; Zhang, Dalun; Zhang, Dake

2014-01-01

The authors examined the role of early adverse experiences, mental health problems, and disabilities in the prediction of juvenile delinquency and recidivism, using a matched-control group design. The delinquent group comprised 99,602 youth, born between 1981 and 1988, whose cases had been processed by the South Carolina Department of Juvenile…

Population-based family case-control proband study on familial aggregation of metabolic syndrome: finding from Taiwanese people involved in Keelung community-based integrated screening (KCIS no. 5).

PubMed

Chiu, Yueh-Hsia; Lin, Wen-Yuan; Wang, Po-En; Chen, Yao-Der; Wang, Ting-Ting; Warwick, Jane; Chen, Tony Hsiu-Hsi

2007-03-01

A population-based case-control proband study was undertaken to elucidate familial aggregation, independent environmental factors, and the interaction between them. A total of 7308 metabolic syndrome (MET-S) cases were identified from the Keelung community-based integrated screening programme between 1999 and 2002. The study has a case-control/family sampling design. A total of 1417 case probands were randomly selected from 3225 metabolic syndrome cases and the corresponding 2458 controls selected from 16,519 subjects without metabolic syndrome by matching on sex, age (+/-3 years) and place of residence. The generalized estimation equation model was used to estimate odds ratios and corresponding 95% confidence intervals. The risk for having metabolic syndrome among family members for cases versus control probands was 1.56-fold (1.29-1.89) after controlling for significant environmental factors. Higher risk of metabolic syndrome was found in parents than spouse. Low education against high education had 2.06-fold (1.36-3.13) risk for metabolic syndrome. Betel quid chewing was positively associated with the risk of MET-S, with 1.99-fold (1.13-3.53) risk for 1-9 pieces and 1.76-fold (0.96-3.23) risk for >or=10 pieces compared with non-chewer. Moderate and high intensity of non-occupational exercise led to 21.0% (OR=0.79 (0.63-0.98)) and 26.0% (OR=0.74 (0.59-0.94)) reduction in the risk for metabolic syndrome, respectively. The frequent consumption of vegetable reduced 24.0% (OR=0.76 (0.62-0.92)) risk for MET-S. The frequent consumption of coffee was associated the increased risk for metabolic syndrome (OR=1.32 (1.07-1.64)). The present study confirmed the risk of metabolic syndrome not only has the tendency towards familial aggregation but is affected by independent effect of environmental or individual correlates.

The relationship between urban environment and the inflammatory bowel diseases: a systematic review and meta-analysis.

PubMed

Soon, Ing Shian; Molodecky, Natalie A; Rabi, Doreen M; Ghali, William A; Barkema, Herman W; Kaplan, Gilaad G

2012-05-24

The objective of this study was to conduct a systematic review with meta-analysis of studies assessing the association between living in an urban environment and the development of the Crohn's disease (CD) or ulcerative colitis (UC). A systematic literature search of MEDLINE (1950-Oct. 2009) and EMBASE (1980-Oct. 2009) was conducted to identify studies investigating the relationship between urban environment and IBD. Cohort and case-control studies were analyzed using incidence rate ratio (IRR) or odds ratio (OR) with 95 % confidence intervals (CIs), respectively. Stratified and sensitivity analyses were performed to explore heterogeneity between studies and assess effects of study quality. The search strategy retrieved 6940 unique citations and 40 studies were selected for inclusion. Of these, 25 investigated the relationship between urban environment and UC and 30 investigated this relationship with CD. Included in our analysis were 7 case-control UC studies, 9 case-control CD studies, 18 cohort UC studies and 21 cohort CD studies. Based on a random effects model, the pooled IRRs for urban compared to rural environment for UC and CD studies were 1.17 (1.03, 1.32) and 1.42 (1.26, 1.60), respectively. These associations persisted across multiple stratified and sensitivity analyses exploring clinical and study quality factors. Heterogeneity was observed in the cohort studies for both UC and CD, whereas statistically significant heterogeneity was not observed for the case-control studies. A positive association between urban environment and both CD and UC was found. Heterogeneity may be explained by differences in study design and quality factors.

An H(∞) control approach to robust learning of feedforward neural networks.

PubMed

Jing, Xingjian

2011-09-01

A novel H(∞) robust control approach is proposed in this study to deal with the learning problems of feedforward neural networks (FNNs). The analysis and design of a desired weight update law for the FNN is transformed into a robust controller design problem for a discrete dynamic system in terms of the estimation error. The drawbacks of some existing learning algorithms can therefore be revealed, especially for the case that the output data is fast changing with respect to the input or the output data is corrupted by noise. Based on this approach, the optimal learning parameters can be found by utilizing the linear matrix inequality (LMI) optimization techniques to achieve a predefined H(∞) "noise" attenuation level. Several existing BP-type algorithms are shown to be special cases of the new H(∞)-learning algorithm. Theoretical analysis and several examples are provided to show the advantages of the new method. Copyright © 2011 Elsevier Ltd. All rights reserved.

Do sugar-sweetened beverages cause adverse health outcomes in adults? A systematic review protocol

PubMed Central

2014-01-01

Background Chronic diseases, such as cardiovascular disease and type 2 diabetes, impose significant burden to public health. Most chronic diseases are associated with underlying preventable risk factors, such as elevated blood pressure, blood glucose, and lipids, physical inactivity, excessive sedentary behaviours, overweight and obesity, and tobacco usage. Sugar-sweetened beverages are known to be significant sources of additional caloric intake, and given recent attention to their contribution in the development of chronic diseases, a systematic review is warranted. We will assess whether the consumption of sugar-sweetened beverages in adults is associated with adverse health outcomes and what the potential moderating factors are. Methods/Design Of interest are studies addressing sugar-sweetened beverage consumption, taking a broad perspective. Both direct consumption studies as well as those evaluating interventions that influence consumption (e.g. school policy, educational) will be relevant. Non-specific or multi-faceted behavioural, educational, or policy interventions may also be included subject to the level of evidence that exists for the other interventions/exposures. Comparisons of interest and endpoints of interest are pre-specified. We will include randomized controlled trials, controlled clinical trials, interrupted time series studies, controlled before-after studies, prospective and retrospective comparative cohort studies, case-control studies, and nested case-control designs. The MEDLINE®, Embase, The Cochrane Library, CINAHL, ERIC, and PsycINFO® databases and grey literature sources will be searched. The processes for selecting studies, abstracting data, and resolving conflicts are described. We will assess risk of bias using design-specific tools. To determine sets of confounding variables that should be adjusted for, we have developed causal directed acyclic graphs and will use those to inform our risk of bias assessments. Meta-analysis will be conducted where appropriate; parameters for exploring statistical heterogeneity and effect modifiers are pre-specified. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach will be used for determining the quality of evidence for outcomes. Systematic review registration PROSPERO CRD42014009638 PMID:25248499

Do variations in the theatre team have an impact on the incidence of complications?

PubMed Central

Baylis, Oliver J; Adams, Wendy E; Allen, David; Fraser, Scott G

2006-01-01

Background To examine whether variations in non-medical personnel influence the incidence of complications in a cataract theatre. Methods A retrospective Case-Control study was undertaken in a single-site, designated cataract theatre. Staffing variations within theatre were examined and the incidence of cataract complications was assessed. Results 100 complicated lists and 200 uncomplicated control lists were chosen. At least 7 nurses were present for every list. Mean experience of the nurses was 6.4 years for case lists and 6.5 years for control lists. Average scrub nurse experience in years was 7.6 years for complicated lists and 8.0 years for controls. 26% of complicated case lists were affected by unplanned leave and 17% in control lists. Odds ratio 1.7 (1.0 to 3.1) 95% CI. Conclusion Unplanned leave can have a detrimental effect on the operating list. The impact of this may be modifiable with careful planning. PMID:16542439

Public health case studies in diabetes prevention and control: innovation, partnerships, and funding.

PubMed

Davis, Mary V; Cannon, Margaret M; Reese, April; Lovette, Beth; Porterfield, Deborah S

2011-01-01

In 2006, we conducted case studies of 4 North Carolina local health departments (LHDs) that scored highly on an index of diabetes prevention and control performance, to explore characteristics that may serve as barriers or facilitators of diabetes prevention and control services. Case studies involving in-depth interviews were conducted at 4 LHDs. Sites were selected on the basis of 2 variables, known external funding for diabetes services and population size, that were associated with performance in diabetes prevention and control in a 2005 survey of all North Carolina LHDs. Fourteen interviews (individual and group) were conducted among 17 participants from the 4 LHDs. The main outcome measures were LHD characteristics that facilitate or hinder the performance of diabetes programs and services. Interviews revealed that all 4 high-performing LHDs had received some sort of funding from a source external to the LHD. Case study participants indicated that barriers to additional service delivery included low socioeconomic status of the population and lack of financial resources. Having a diabetes self-management education program that was recognized by the American Diabetes Association appeared to be a facilitator of diabetes services provision. Other facilitators were leadership and staff commitment, which appeared to facilitate the leveraging of partnerships and funding opportunities, leading to enhanced service delivery. The small number of LHDs participating in the study and the cross-sectional study design were limitations. Leadership, staff commitment, partnership leveraging, and funding appear to be associated with LHD performance in diabetes prevention and control services. These factors should be further studied in future public health systems and services research.

The National Birth Defects Prevention Study: a review of the methods

PubMed Central

Reefhuis, Jennita; Gilboa, Suzanne M.; Anderka, Marlene; Browne, Marilyn L.; Feldkamp, Marcia L.; Hobbs, Charlotte A.; Jenkins, Mary M.; Langlois, Peter H.; Newsome, Kimberly B.; Olshan, Andrew F.; Romitti, Paul A.; Shapira, Stuart K.; Shaw, Gary M.; Tinker, Sarah C.; Honein, Margaret A.

2015-01-01

Background The National Birth Defects Prevention Study (NBDPS) is a large population-based multi-center case-control study of major birth defects in the United States. Methods Data collection took place from 1998 through 2013 on pregnancies ending between October 1997 and December 2011. Cases could be live born, stillborn or induced terminations, and were identified from birth defects surveillance programs in Arkansas, California, Georgia, Iowa, Massachusetts, New Jersey, New York, North Carolina, Texas and Utah. Controls were live born infants without major birth defects identified from the same geographical regions and time periods as cases via either vital records or birth hospitals. Computer-assisted telephone interviews were completed with women between 6 weeks and 24 months after the estimated date of delivery. After completion of interviews, families received buccal cell collection kits for the mother, father and infant (if living). Results There were 47,832 eligible cases and 18,272 eligible controls. Among these, 32,187 (67%) and 11,814 (65%) respectively, provided interview information about their pregnancies. Buccal cell collection kits with a cytobrush for at least one family member were returned by 19,065 case and 6,211 control families (65% and 59% of those who were sent a kit). More than 500 projects have been proposed by the collaborators and over 200 manuscripts published using data from the NBDPS through December 2014. Conclusion The NBDPS has made substantial contributions to the field of birth defects epidemiology through its rigorous design, including case classification, detailed questionnaire and specimen collection, large study population, and collaborative activities across Centers. PMID:26033852

The National Birth Defects Prevention Study: A review of the methods.

PubMed

Reefhuis, Jennita; Gilboa, Suzanne M; Anderka, Marlene; Browne, Marilyn L; Feldkamp, Marcia L; Hobbs, Charlotte A; Jenkins, Mary M; Langlois, Peter H; Newsome, Kimberly B; Olshan, Andrew F; Romitti, Paul A; Shapira, Stuart K; Shaw, Gary M; Tinker, Sarah C; Honein, Margaret A

2015-08-01

The National Birth Defects Prevention Study (NBDPS) is a large population-based multicenter case-control study of major birth defects in the United States. Data collection took place from 1998 through 2013 on pregnancies ending between October 1997 and December 2011. Cases could be live born, stillborn, or induced terminations, and were identified from birth defects surveillance programs in Arkansas, California, Georgia, Iowa, Massachusetts, New Jersey, New York, North Carolina, Texas, and Utah. Controls were live born infants without major birth defects identified from the same geographical regions and time periods as cases by means of either vital records or birth hospitals. Computer-assisted telephone interviews were completed with women between 6 weeks and 24 months after the estimated date of delivery. After completion of interviews, families received buccal cell collection kits for the mother, father, and infant (if living). There were 47,832 eligible cases and 18,272 eligible controls. Among these, 32,187 (67%) and 11,814 (65%), respectively, provided interview information about their pregnancies. Buccal cell collection kits with a cytobrush for at least one family member were returned by 19,065 case and 6,211 control families (65% and 59% of those who were sent a kit). More than 500 projects have been proposed by the collaborators and over 200 manuscripts published using data from the NBDPS through December 2014. The NBDPS has made substantial contributions to the field of birth defects epidemiology through its rigorous design, including case classification, detailed questionnaire and specimen collection, large study population, and collaborative activities across Centers. © 2015 Wiley Periodicals, Inc.

Linear control of oscillator and amplifier flows*

NASA Astrophysics Data System (ADS)

Schmid, Peter J.; Sipp, Denis

2016-08-01

Linear control applied to fluid systems near an equilibrium point has important applications for many flows of industrial or fundamental interest. In this article we give an exposition of tools and approaches for the design of control strategies for globally stable or unstable flows. For unstable oscillator flows a feedback configuration and a model-based approach is proposed, while for stable noise-amplifier flows a feedforward setup and an approach based on system identification is advocated. Model reduction and robustness issues are addressed for the oscillator case; statistical learning techniques are emphasized for the amplifier case. Effective suppression of global and convective instabilities could be demonstrated for either case, even though the system-identification approach results in a superior robustness to off-design conditions.

The clinical application of teaching people about pain.

PubMed

Louw, Adriaan; Zimney, Kory; O'Hotto, Christine; Hilton, Sandra

2016-07-01

Teaching people about the neurobiology and neurophysiology of their pain experience has a therapeutic effect and has been referred to as pain neuroscience education (PNE). Various high-quality randomized controlled trials and systematic reviews have shown increasing efficacy of PNE decreasing pain, disability, pain catastrophization, movement restrictions, and healthcare utilization. Research studies, however, by virtue of their design, are very controlled environments and, therefore, in contrast to the ever-increasing evidence for PNE, little is known about the clinical application of this emerging therapy. In contrast, case studies, case series, and expert opinion and perspectives by authorities in the world of pain science provide clinicians with a glimpse into potential "real" clinical application of PNE in the face of the ever-increasing chronic pain epidemic. By taking the material from the randomized controlled trials, systematic reviews, case series, case studies, and expert opinion, this article aims to provide a proposed layout of the clinical application of PNE. The article systematically discusses key elements of PNE including examination, educational content, and delivery methods, merging of PNE with movement, goal setting, and progression. This perspectives article concludes with a call for research into the clinical application of PNE.

Free-Piston Stirling Convertor Controller Development at NASA Glenn Research Center

NASA Technical Reports Server (NTRS)

Regan, Timothy

2004-01-01

The free-piston Stirling convertor end-to-end modeling effort at NASA Glenn Research Center (GRC) has produced a software-based test bed in which free-piston Stirling convertors can be simulated and evaluated. The simulation model includes all the components of the convertor - the Stirling cycle engine, linear alternator, controller, and load. This paper is concerned with controllers. It discusses three controllers that have been studied using this model. Case motion has been added to the model recently so that effects of differences between convertor components can be simulated and ameliorative control engineering techniques can be developed. One concern when applying a system comprised of interconnected mass-spring-damper components is to prevent operation in any but the intended mode. The design mode is the only desired mode of operation, but all other modes are considered in controller design.

Asymptotic Properties of the Sequential Empirical ROC, PPV and NPV Curves Under Case-Control Sampling.

PubMed

Koopmeiners, Joseph S; Feng, Ziding

2011-01-01

The receiver operating characteristic (ROC) curve, the positive predictive value (PPV) curve and the negative predictive value (NPV) curve are three measures of performance for a continuous diagnostic biomarker. The ROC, PPV and NPV curves are often estimated empirically to avoid assumptions about the distributional form of the biomarkers. Recently, there has been a push to incorporate group sequential methods into the design of diagnostic biomarker studies. A thorough understanding of the asymptotic properties of the sequential empirical ROC, PPV and NPV curves will provide more flexibility when designing group sequential diagnostic biomarker studies. In this paper we derive asymptotic theory for the sequential empirical ROC, PPV and NPV curves under case-control sampling using sequential empirical process theory. We show that the sequential empirical ROC, PPV and NPV curves converge to the sum of independent Kiefer processes and show how these results can be used to derive asymptotic results for summaries of the sequential empirical ROC, PPV and NPV curves.

Asymptotic Properties of the Sequential Empirical ROC, PPV and NPV Curves Under Case-Control Sampling

PubMed Central

Koopmeiners, Joseph S.; Feng, Ziding

2013-01-01

The receiver operating characteristic (ROC) curve, the positive predictive value (PPV) curve and the negative predictive value (NPV) curve are three measures of performance for a continuous diagnostic biomarker. The ROC, PPV and NPV curves are often estimated empirically to avoid assumptions about the distributional form of the biomarkers. Recently, there has been a push to incorporate group sequential methods into the design of diagnostic biomarker studies. A thorough understanding of the asymptotic properties of the sequential empirical ROC, PPV and NPV curves will provide more flexibility when designing group sequential diagnostic biomarker studies. In this paper we derive asymptotic theory for the sequential empirical ROC, PPV and NPV curves under case-control sampling using sequential empirical process theory. We show that the sequential empirical ROC, PPV and NPV curves converge to the sum of independent Kiefer processes and show how these results can be used to derive asymptotic results for summaries of the sequential empirical ROC, PPV and NPV curves. PMID:24039313

Is case-based learning an effective teaching strategy to challenge students' alternative conceptions regarding chemical kinetics?

NASA Astrophysics Data System (ADS)

Yalçınkaya, Eylem; Taştan-Kırık, Özgecan; Boz, Yezdan; Yıldıran, Demet

2012-07-01

Background: Case-based learning (CBL) is simply teaching the concept to the students based on the cases. CBL involves a case, which is a scenario based on daily life, and study questions related to the case, which allows students to discuss their ideas. Chemical kinetics is one of the most difficult concepts for students in chemistry. Students have generally low levels of conceptual understanding and many alternative conceptions regarding it. Purpose: This study aimed to explore the effect of CBL on dealing with students' alternative conceptions about chemical kinetics. Sample: The sample consists of 53 high school students from one public high school in Turkey. Design and methods : Nonequivalent pre-test and post-test control group design was used. Reaction Rate Concept Test and semi-structured interviews were used for data collection. Convenience sampling technique was followed. For data analysis, the independent samples t-test and ANOVA was performed. Results : Both concept test and interview results showed that students instructed with cases had better understanding of core concepts of chemical kinetics and had less alternative conceptions related to the subject matter compared to the control group students, despite the fact that it was impossible to challenge all the alternative conceptions in the experimental group. Conclusions: CBL is an effective teaching method for challenging students' alternative conceptions in the context of chemical kinetics. Since using cases in small groups and whole class discussions has been found to be an effective way to cope with the alternative conceptions, it can be applied to other subjects and grade levels in high schools with a higher sample size. Furthermore, the effect of this method on academic achievement, motivation and critical thinking skills are other variables that can be investigated for future studies in the subject area of chemistry.

Case Management in Primary Care for Frequent Users of Health Care Services: A Mixed Methods Study.

PubMed

Hudon, Catherine; Chouinard, Maud-Christine; Dubois, Marie-France; Roberge, Pasquale; Loignon, Christine; Tchouaket, Éric; Lambert, Mireille; Hudon, Émilie; Diadiou, Fatoumata; Bouliane, Danielle

2018-05-01

This study aimed to evaluate the effects of the V1SAGES case management intervention (Vulnerable Patients in Primary Care: Nurse Case Management and Self-management Support) for frequent users of health care services with chronic disease and complex care needs on psychological distress and patient activation. We used a 2-phase sequential mixed methods design. The first phase was a pragmatic randomized controlled trial with intention-to-treat analysis that measured the effects of the intervention compared with usual care on psychological distress and patient activation before and after 6 months. The second phase had a qualitative descriptive design and entailed thematic analysis of in-depth interviews (25 patients, 6 case management nurses, 9 health managers) and focus groups (8 patients' spouses, 21 family physicians) to understand stakeholders' perceived effects of the intervention on patients. A total of 247 patients were randomized into the intervention group (n = 126) or the control group (n = 121). Compared with usual care, the intervention reduced psychological distress (odds ratio = 0.43; 95% CI, 0.19-0.95, P = .04), but did not have any significant effect on patient activation ( P = .43). Qualitative results suggested that patients and their spouses benefitted from the case management intervention, gaining a sense of security, and stakeholders noted better patient self-management of health. Together, our study's quantitative and qualitative results suggest that case management reduces psychological distress, making patients and caregivers feel more secure, whereas impact on self-management is unclear. Case management is a promising avenue to improve outcomes among frequent users of health care with complex needs. © 2018 Annals of Family Medicine, Inc.

Risk factors for near-fatal asthma. A case-control study in hospitalized patients with asthma.

PubMed

Turner, M O; Noertjojo, K; Vedal, S; Bai, T; Crump, S; Fitzgerald, J M

1998-06-01

We prospectively recruited patients admitted to the hospital with severe asthma to comprehensively evaluate the association of historical and physiologic features with the risk of near-fatal asthma (NFA). A case-control study design was used. All patients admitted with NFA (cases) were identified prospectively and compared with asthma patients admitted during the same period without respiratory failure (controls). Nineteen cases (age: 40.2 +/- 12.0 yr) (mean +/- SD) and 80 controls (age: 36 +/- 13.5 yr) were enrolled. Duration of asthma, gender, smoking status, ethnicity, and prevalence of atopy were similar in the case and control groups. More than 80% of patients in both groups reported worsening symptoms for more than 48 h before admission, and more than 50% were worse for longer than 7 d. There was no difference in degree of airways obstruction or bronchial hyperresponsiveness (PC20). Perception of dyspnea was similar in the cases and controls, but among cases the males had greater impairment than the females (Borg score: 1.9 +/- 1. 4 versus 3.9 +/- 1.2: p = 0.05). Univariate analysis identified a history of previous mechanical ventilation (OR: 27.5; 95% CI: 6.60 to 113.7), admission to the intensive care unit (ICU) (OR: 9.9; 95% CI: 3.0 to 32.9), history of worse asthma during January and February (OR: 3.5; 95% CI: 1.0 to 11.8), and use of air-conditioning (OR: 15.0; 95% CI: 1.3 to 166) as risk factors for NFA. Of concern was the dependence of most patients (59.8%) on the emergency department (ED) for initial care, and the small number of cases (16%) in which patients visited a physician before admission to the hospital. We have confirmed risk factors identified previously in retrospective studies of fatal and NFA, and have also shown that hospitalized patients with asthma, irrespective of severity of their asthma, share several characteristics, especially in terms of their failure to respond to worsening asthma.

A case control study: White-collar defendants compared with defendants charged with other nonviolent theft.

PubMed

Poortinga, Ernest; Lemmen, Craig; Jibson, Michael D

2006-01-01

We examined the clinical, criminal, and sociodemographic characteristics of all white-collar crime defendants referred to the evaluation unit of a state center for forensic psychiatry. With 29,310 evaluations in a 12-year period, we found 70 defendants charged with embezzlement, 3 with health care fraud, and no other white-collar defendants (based on the eight crimes widely accepted as white-collar offenses). In a case-control study design, the 70 embezzlement cases were compared with 73 defendants charged with other forms of nonviolent theft. White-collar defendants were found to have a higher likelihood of white race (adjusted odds ratio (adj. OR) = 4.51), more years of education (adj. OR = 3471), and a lower likelihood of substance abuse (adj. OR = .28) than control defendants. Logistic regression modeling showed that the variance in the relationship between unipolar depression and white-collar crime was more economically accounted for by education, race, and substance abuse.

Impact of organised mammography screening on breast cancer mortality in a case–control and cohort study

PubMed Central

Heinävaara, Sirpa; Sarkeala, Tytti; Anttila, Ahti

2016-01-01

Background: The usefulness of case–control studies has been questioned. Our aim was to evaluate the long-term effect of screening on breast cancer mortality within the population-based mammography programme in Finland using a case–control design, and to compare the analyses with the earlier cohort study. Methods: The cases were women invited to screening, diagnosed and died from breast cancer in 1992–2011 while being 50–84 years at death. We chose 10 controls for each case with non-restrictive eligibility criteria. Our data included 1907 cases and 18 978 matched controls. We analysed associations between the screening participation and the risk of breast cancer death using the conditional Cox proportional hazards model. The effect estimates were corrected for self-selection bias. Results: An overall effect of screening was 0.67 (95% confidence interval (CI): 0.49–0.90), and that remained unchanged over time. Analyses with matching criteria comparable to the cohort study yielded an effect (0.70, 95% CI: 0.49–1.00) in 1992–2003 similar to that of the previous cohort analysis (0.72, 95% CI: 0.56–0.88). Conclusions: Organised mammography screening decreases mortality from breast cancer by 33% among the participants. If made comparable, a case–cohort study can yield effect estimates similar to a cohort study. PMID:27010748

Predictors of immunological failure of antiretroviral therapy among HIV infected patients in Ethiopia: a matched case-control study.

PubMed

Teshome, Wondu; Asefa, Anteneh; Assefa, Anteneh

2014-01-01

In resource constrained settings, immunological assessment through CD4 count is used to assess response to first line Highly Active Antiretroviral Therapy (HAART). In this study, we aim to investigate factors associated with immunological treatment failure. A matched case-control study design was used. Cases were subjects who already experienced immunological treatment failure and controls were those without immunological failure after an exactly or approximately equivalent duration of first line treatment with cases. Data were analyzed using SPSS v16.0. Conditional logistic regression was carried out. A total of 134 cases and 134 controls were included in the study. At baseline, the mean age ± 1 SD of cases was 37.5 ± 9.7 years whereas it was 36.9 ± 9.2 years among controls. The median baseline CD4 counts of cases and controls were 121.0 cells/µl (IQR: 47-183 cells/µl) and 122.0 cells/µl (IQR: 80.0-189.8 cells/µl), respectively. The median rate of CD4 cells increase was comparable for the two groups in the first six months of commencing HAART (P = 0.442). However, the median rate of CD4 increase was significantly different for the two groups in the next 6 months period (M6 to M12). The rate of increment was 8.8 (IQR: 0.5, 14.6) and 1.8 (IQR: 8.8, 11.3) cells/µl/month for controls and cases, respectively (Mann-Whitney U test, P = 0.003). In conditional logistic regressions grouped baseline CD4 count (P = 0.028), old age group and higher educational status (P<0.001) were significant predictors of immunological treatment failure. Subjects with immunological treatment failure have an optimal rate of immunological recovery in the first 6 months of treatment with first line HAART, but relative to the non-failing group the rate declines at a later period, notably between 6 and 12 months. Low baseline CD4 count, old age and higher educational status were associated with immunological treatment failure.

A framework to support decision making in the selection of sustainable drainage system design alternatives.

PubMed

Wang, Mingming; Sweetapple, Chris; Fu, Guangtao; Farmani, Raziyeh; Butler, David

2017-10-01

This paper presents a new framework for decision making in sustainable drainage system (SuDS) scheme design. It integrates resilience, hydraulic performance, pollution control, rainwater usage, energy analysis, greenhouse gas (GHG) emissions and costs, and has 12 indicators. The multi-criteria analysis methods of entropy weight and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) were selected to support SuDS scheme selection. The effectiveness of the framework is demonstrated with a SuDS case in China. Indicators used include flood volume, flood duration, a hydraulic performance indicator, cost and resilience. Resilience is an important design consideration, and it supports scheme selection in the case study. The proposed framework will help a decision maker to choose an appropriate design scheme for implementation without subjectivity. Copyright © 2017 Elsevier Ltd. All rights reserved.

Basic principles of test-negative design in evaluating influenza vaccine effectiveness.

PubMed

Fukushima, Wakaba; Hirota, Yoshio

2017-08-24

Based on the unique characteristics of influenza, the concept of "monitoring" influenza vaccine effectiveness (VE) across the seasons using the same observational study design has been developed. In recent years, there has been a growing number of influenza VE reports using the test-negative design, which can minimize both misclassification of diseases and confounding by health care-seeking behavior. Although the test-negative designs offer considerable advantages, there are some concerns that widespread use of the test-negative design without knowledge of the basic principles of epidemiology could produce invalid findings. In this article, we briefly review the basic concepts of the test-negative design with respect to classic study design such as cohort studies or case-control studies. We also mention selection bias, which may be of concern in some countries where rapid diagnostic testing is frequently used in routine clinical practices, as in Japan. Copyright © 2017. Published by Elsevier Ltd.

Reconfigurable Flight Control Designs With Application to the X-33 Vehicle

NASA Technical Reports Server (NTRS)

Burken, John J.; Lu, Ping; Wu, Zhenglu

1999-01-01

Two methods for control system reconfiguration have been investigated. The first method is a robust servomechanism control approach (optimal tracking problem) that is a generalization of the classical proportional-plus-integral control to multiple input-multiple output systems. The second method is a control-allocation approach based on a quadratic programming formulation. A globally convergent fixed-point iteration algorithm has been developed to make onboard implementation of this method feasible. These methods have been applied to reconfigurable entry flight control design for the X-33 vehicle. Examples presented demonstrate simultaneous tracking of angle-of-attack and roll angle commands during failures of the right body flap actuator. Although simulations demonstrate success of the first method in most cases, the control-allocation method appears to provide uniformly better performance in all cases.

[Implementation and (cost-)effectiveness of case management for people with dementia and their informal caregivers: results of the COMPAS study].

PubMed

van Mierlo, Lisa D; MacNeil-Vroomen, Janet; Meiland, Franka J M; Joling, Karlijn J; Bosmans, Judith E; Dröes, Rose Marie; Moll van Charante, Eric P; de Rooij, Sophia E J A; van Hout, Hein P J

2016-12-01

Different forms of case management for dementia have emerged over the past few years. In the COMPAS study (Collaborative dementia care for patients and caregivers study), two prominent Dutch case management forms were studied: the linkage and the integrated care form. Evaluation of the (cost)effectiveness of two dementia case management forms compared to usual care as well as factors that facilitated or impeded their implementation. A mixed methods design with a) a prospective, observational controlled cohort study with 2 years follow-up among 521 dyads of people with dementia and their primary informal caregiver with and without case management; b) interviews with 22 stakeholders on facilitating and impeding factors of the implementation and continuity of the two case management models. Outcome measures were severity and frequency of behavioural problems (NPI) for the person with dementia and mental health complaints (GHQ-12) for the informal caregiver, total met and unmet care needs (CANE) and quality adjusted life years (QALYs). Outcomes showed a better quality of life of informal caregivers in the integrated model compared to the linkage model. Caregivers in the control group reported more care needs than those in both case management groups. The independence of the case management provider in the integrated model facilitated the implementation, while the rivalry between multiple providers in the linkage model impeded the implementation. The costs of care were lower in the linkage model (minus 22 %) and integrated care model (minus 33 %) compared to the control group. The integrated care form was (very) cost-effective in comparison with the linkage form or no case management. The integrated care form is easy to implement.

Clinical factors associated with readmission for postpartum hypertension in women with pregnancy-related hypertension: a nested case control study

PubMed Central

Hirshberg, A; Levine, LD; Srinivas, SK

2017-01-01

Objective To evaluate the association between mode of delivery and length of labor on readmission for postpartum hypertension in women with pregnancy-related hypertension. Study Design Nested case control study within a cohort of 99 women with pregnancy-related hypertension who delivered at our institution between 2005 and 2009. Data were abstracted for clinical and labor information. Mode of delivery and length of labor were compared between women with previously diagnosed pregnancy-related hypertension readmitted within 4 weeks post partum (25 cases) and those not readmitted (74 controls). Categorical and continuous variables were compared using χ2 and T-tests, respectively. Multivariable logistic regression controlled for confounders. Result Hypertension readmission was not associated with mode of delivery (cases: 10(40%) spontaneous vaginal delivery, 15(60%) cesarean delivery; controls: 38(51%) spontaneous vaginal delivery, 36(49%) cesarean delivery, P=0.33). Length of labor appeared longer in cases, with a trend toward significance (median: 15.5 [7,28] h vs 10.75 [5.8,15.9] h, P=0.12) and was significantly associated with readmission after controlling for delivery mode, induction and parity (adjusted odds ratio = 1.06 [1 to 1.12], P = 0.048). Readmitted patients were less likely to have initially been started on antihypertensive medications after controlling for age, race and chronic hypertension (adjusted odds ratio = 0.23 [0.06 to 0.88], P=0.03). Conclusion Postpartum readmission for hypertension in women with known pregnancy-related hypertension is not associated with mode of delivery, appears increased in those with longer length of labor and decreased in those initially started on antihypertensive medications. This provides targets for future research to continue to improve transitions of care and reduce preventable readmissions. PMID:26765549

Population-based multicase-control study in common tumors in Spain (MCC-Spain): rationale and study design.

PubMed

Castaño-Vinyals, Gemma; Aragonés, Nuria; Pérez-Gómez, Beatriz; Martín, Vicente; Llorca, Javier; Moreno, Victor; Altzibar, Jone M; Ardanaz, Eva; de Sanjosé, Sílvia; Jiménez-Moleón, José Juan; Tardón, Adonina; Alguacil, Juan; Peiró, Rosana; Marcos-Gragera, Rafael; Navarro, Carmen; Pollán, Marina; Kogevinas, Manolis

2015-01-01

We present the protocol of a large population-based case-control study of 5 common tumors in Spain (MCC-Spain) that evaluates environmental exposures and genetic factors. Between 2008-2013, 10,183 persons aged 20-85 years were enrolled in 23 hospitals and primary care centres in 12 Spanish provinces including 1,115 cases of a new diagnosis of prostate cancer, 1,750 of breast cancer, 2,171 of colorectal cancer, 492 of gastro-oesophageal cancer, 554 cases of chronic lymphocytic leukaemia (CLL) and 4,101 population-based controls matched by frequency to cases by age, sex and region of residence. Participation rates ranged from 57% (stomach cancer) to 87% (CLL cases) and from 30% to 77% in controls. Participants completed a face-to-face computerized interview on sociodemographic factors, environmental exposures, occupation, medication, lifestyle, and personal and family medical history. In addition, participants completed a self-administered food-frequency questionnaire and telephone interviews. Blood samples were collected from 76% of participants while saliva samples were collected in CLL cases and participants refusing blood extractions. Clinical information was recorded for cases and paraffin blocks and/or fresh tumor samples are available in most collaborating hospitals. Genotyping was done through an exome array enriched with genetic markers in specific pathways. Multiple analyses are planned to assess the association of environmental, personal and genetic risk factors for each tumor and to identify pleiotropic effects. This study, conducted within the Spanish Consortium for Biomedical Research in Epidemiology & Public Health (CIBERESP), is a unique initiative to evaluate etiological factors for common cancers and will promote cancer research and prevention in Spain. Copyright © 2014 SESPAS. Published by Elsevier Espana. All rights reserved.

Periodontitis and risk of psoriasis: a systematic review and meta-analysis.

PubMed

Ungprasert, P; Wijarnpreecha, K; Wetter, D A

2017-05-01

The association between periodontitis and systemic diseases has been increasingly recognized. However, the data on the association between periodontitis and psoriasis are still limited. To summarize all available data on the association between periodontitis and the risk of psoriasis. Two investigators independently searched published studies indexed in MEDLINE and EMBASE databases from inception to July 2016 using a search strategy that included terms for psoriasis and periodontitis. Studies were included if the following criteria were met: (i) case-control or cohort study comparing the risk of psoriasis in subjects with and without periodontitis; (ii) subjects without periodontitis were used as comparators in cohort studies while participants without psoriasis were used as controls in case-control studies; and (iii) effect estimates and 95% confidence intervals (CI) were provided. Point estimates and standard errors from each study were extracted and combined together using the generic inverse variance technique described by DerSimonian and Laird. Two cohort studies and three case-control studies met the inclusion criteria and were included in the meta-analysis. The pooled risk ratio of psoriasis in patients with periodontitis versus comparators was 1.55 (95% CI, 1.35-1.77). The statistical heterogeneity was insignificant with an I 2 of 18%. Subgroup analysis according to study design revealed a significantly higher risk among patients with periodontitis with a pooled RR of 1.50 (95% CI, 1.37-1.64) for cohort studies and a pooled RR of 2.33 (95% CI, 1.51-3.60) for case-control studies. Patients with periodontitis have a significantly elevated risk of psoriasis. © 2016 European Academy of Dermatology and Venereology.

A compendium of controlled diffusion blades generated by an automated inverse design procedure

NASA Technical Reports Server (NTRS)

Sanz, Jose M.

1989-01-01

A set of sample cases was produced to test an automated design procedure developed at the NASA Lewis Research Center for the design of controlled diffusion blades. The range of application of the automated design procedure is documented. The results presented include characteristic compressor and turbine blade sections produced with the automated design code as well as various other airfoils produced with the base design method prior to the incorporation of the automated procedure.

Interpretive Research Aiming at Theory Building: Adopting and Adapting the Case Study Design

ERIC Educational Resources Information Center

Diaz Andrade, Antonio

2009-01-01

Although the advantages of case study design are widely recognised, its original positivist underlying assumptions may mislead interpretive researchers aiming at theory building. The paper discusses the limitations of the case study design for theory building and explains how grounded theory systemic process adds to the case study design. The…

Rarity of the Alzheimer Disease–Protective APP A673T Variant in the United States

PubMed Central

Wang, Li-San; Naj, Adam C.; Graham, Robert R.; Crane, Paul K.; Kunkle, Brian W.; Cruchaga, Carlos; Gonzalez Murcia, Josue D.; Cannon-Albright, Lisa; Baldwin, Clinton T.; Zetterberg, Henrik; Blennow, Kaj; Kukull, Walter A.; Faber, Kelley M.; Schupf, Nicole; Norton, Maria C.; Tschanz, JoAnn T.; Munger, Ronald G.; Corcoran, Christopher D.; Rogaeva, Ekaterina; Lin, Chiao-Feng; Dombroski, Beth A.; Cantwell, Laura B.; Partch, Amanda; Valladares, Otto; Hakonarson, Hakon; St George-Hyslop, Peter; Green, Robert C.; Goate, Alison M.; Foroud, Tatiana M.; Carney, Regina M.; Larson, Eric B.; Behrens, Timothy W.; Kauwe, John S. K.; Haines, Jonathan L.; Farrer, Lindsay A.; Pericak-Vance, Margaret A.; Mayeux, Richard; Schellenberg, Gerard D.

2015-01-01

IMPORTANCE Recently, a rare variant in the amyloid precursor protein gene (APP) was described in a population from Iceland. This variant, in which alanine is replaced by threonine at position 673 (A673T), appears to protect against late-onset Alzheimer disease (AD). We evaluated the frequency of this variant in AD cases and cognitively normal controls to determine whether this variant will significantly contribute to risk assessment in individuals in the United States. OBJECTIVE To determine the frequency of the APP A673T variant in a large group of elderly cognitively normal controls and AD cases from the United States and in 2 case-control cohorts from Sweden. DESIGN, SETTING, AND PARTICIPANTS Case-control association analysis of variant APP A673T in US and Swedish white individuals comparing AD cases with cognitively intact elderly controls. Participants were ascertained at multiple university-associated medical centers and clinics across the United States and Sweden by study-specific sampling methods. They were from case-control studies, community-based prospective cohort studies, and studies that ascertained multiplex families from multiple sources. MAIN OUTCOMES AND MEASURES Genotypes for the APP A673T variant were determined using the Infinium HumanExome V1 Beadchip (Illumina, Inc) and by TaqMan genotyping (Life Technologies). RESULTS The A673T variant genotypes were evaluated in 8943 US AD cases, 10 480 US cognitively normal controls, 862 Swedish AD cases, and 707 Swedish cognitively normal controls. We identified 3 US individuals heterozygous for A673T, including 1 AD case (age at onset, 89 years) and 2 controls (age at last examination, 82 and 77 years). The remaining US samples were homozygous for the alanine (A673) allele. In the Swedish samples, 3 controls were heterozygous for A673T and all AD cases were homozygous for the A673 allele. We also genotyped a US family previously reported to harbor the A673T variant and found a mother-daughter pair, both cognitively normal at ages 72 and 84 years, respectively, who were both heterozygous for A673T; however, all individuals with AD in the family were homozygous for A673. CONCLUSIONS AND RELEVANCE The A673T variant is extremely rare in US cohorts and does not play a substantial role in risk for AD in this population. This variant may be primarily restricted to Icelandic and Scandinavian populations. PMID:25531812

Study protocol for a cluster randomised controlled factorial design trial to assess the effectiveness and feasibility of reactive focal mass drug administration and vector control to reduce malaria transmission in the low endemic setting of Namibia

PubMed Central

Medzihradsky, Oliver F; Kleinschmidt, Immo; Mumbengegwi, Davis; Roberts, Kathryn W; McCreesh, Patrick; Dufour, Mi-Suk Kang; Uusiku, Petrina; Katokele, Stark; Bennett, Adam; Smith, Jennifer; Sturrock, Hugh; Prach, Lisa M; Ntuku, Henry; Tambo, Munyaradzi; Didier, Bradley; Greenhouse, Bryan; Gani, Zaahira; Aerts, Ann; Gosling, Roly; Hsiang, Michelle S

2018-01-01

Introduction To interrupt malaria transmission, strategies must target the parasite reservoir in both humans and mosquitos. Testing of community members linked to an index case, termed reactive case detection (RACD), is commonly implemented in low transmission areas, though its impact may be limited by the sensitivity of current diagnostics. Indoor residual spraying (IRS) before malaria season is a cornerstone of vector control efforts. Despite their implementation in Namibia, a country approaching elimination, these methods have been met with recent plateaus in transmission reduction. This study evaluates the effectiveness and feasibility of two new targeted strategies, reactive focal mass drug administration (rfMDA) and reactive focal vector control (RAVC) in Namibia. Methods and analysis This is an open-label cluster randomised controlled trial with 2×2 factorial design. The interventions include: rfMDA (presumptive treatment with artemether-lumefantrine (AL)) versus RACD (rapid diagnostic testing and treatment using AL) and RAVC (IRS with Acellic 300CS) versus no RAVC. Factorial design also enables comparison of the combined rfMDA+RAVC intervention to RACD. Participants living in 56 enumeration areas will be randomised to one of four arms: rfMDA, rfMDA+RAVC, RACD or RACD+RAVC. These interventions, triggered by index cases detected at health facilities, will be targeted to individuals residing within 500 m of an index. The primary outcome is cumulative incidence of locally acquired malaria detected at health facilities over 1 year. Secondary outcomes include seroprevalence, infection prevalence, intervention coverage, safety, acceptability, adherence, cost and cost-effectiveness. Ethics and dissemination Findings will be reported on clinicaltrials.gov, in peer-reviewed publications and through stakeholder meetings with MoHSS and community leaders in Namibia. Trial registration number NCT02610400; Pre-results. PMID:29374672

Study protocol for a cluster randomised controlled factorial design trial to assess the effectiveness and feasibility of reactive focal mass drug administration and vector control to reduce malaria transmission in the low endemic setting of Namibia.

PubMed

Medzihradsky, Oliver F; Kleinschmidt, Immo; Mumbengegwi, Davis; Roberts, Kathryn W; McCreesh, Patrick; Dufour, Mi-Suk Kang; Uusiku, Petrina; Katokele, Stark; Bennett, Adam; Smith, Jennifer; Sturrock, Hugh; Prach, Lisa M; Ntuku, Henry; Tambo, Munyaradzi; Didier, Bradley; Greenhouse, Bryan; Gani, Zaahira; Aerts, Ann; Gosling, Roly; Hsiang, Michelle S

2018-01-27

To interrupt malaria transmission, strategies must target the parasite reservoir in both humans and mosquitos. Testing of community members linked to an index case, termed reactive case detection (RACD), is commonly implemented in low transmission areas, though its impact may be limited by the sensitivity of current diagnostics. Indoor residual spraying (IRS) before malaria season is a cornerstone of vector control efforts. Despite their implementation in Namibia, a country approaching elimination, these methods have been met with recent plateaus in transmission reduction. This study evaluates the effectiveness and feasibility of two new targeted strategies, reactive focal mass drug administration (rfMDA) and reactive focal vector control (RAVC) in Namibia. This is an open-label cluster randomised controlled trial with 2×2 factorial design. The interventions include: rfMDA (presumptive treatment with artemether-lumefantrine (AL)) versus RACD (rapid diagnostic testing and treatment using AL) and RAVC (IRS with Acellic 300CS) versus no RAVC. Factorial design also enables comparison of the combined rfMDA+RAVC intervention to RACD. Participants living in 56 enumeration areas will be randomised to one of four arms: rfMDA, rfMDA+RAVC, RACD or RACD+RAVC. These interventions, triggered by index cases detected at health facilities, will be targeted to individuals residing within 500 m of an index. The primary outcome is cumulative incidence of locally acquired malaria detected at health facilities over 1 year. Secondary outcomes include seroprevalence, infection prevalence, intervention coverage, safety, acceptability, adherence, cost and cost-effectiveness. Findings will be reported on clinicaltrials.gov, in peer-reviewed publications and through stakeholder meetings with MoHSS and community leaders in Namibia. NCT02610400; Pre-results. © Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.

Risk factors for hematemesis in Hoima and Buliisa Districts, Western Uganda, September-October 2015.

PubMed

Kabwama, Steven Ndugwa; Mafigiri, Richardson; Balinandi, Stephen; Kagirita, Atek; Riolexus, Alex Ario; Zhu, Bao-Ping

2017-01-01

On 17 September 2015, Buliisa District Health Office reported multiple deaths due to haemorrhage to the Uganda Ministry of Health. We conducted an investigation to verify the existence of an outbreak and to identify the disease nature, mode of transmission and risk factors. We defined a suspected case as onset of hematemesis between 1 June 2015 and 15 October 2015 in a resident of Hoima, Buliisa or neighbouring districts. We identified cases by reviewing medical records and actively searching in the community. We interviewed case-patients and health-care workers and performed descriptive epidemiology to generate hypotheses on possible exposures. In a case-control study we compared exposures between 21 cases and 81 controls, matched by age (± 10 years), sex and village of residence. We collected 22 biological specimens from 19 case-patients to test for Viral Haemorrhagic Fevers (VHF). We analysed the data using the Mantel-Haenszel method to account for the matched study design. We identified 56 cases with onset from June to October (attack rate 15/100,000 in Buliisa District and 5.2/100,000 in Hoima District). The age-specific attack rate was highest in persons aged 31-60 years (15/100,000 in Hoima and 47/100,000 in Buliisa); no persons below 15 years of age had the illness. In the case-control study, 42% (5/12) of cases vs. 0.0% (0/77) of controls had liver disease (OR M-H = ∞; 95%CI = 3.7-∞); 71% (10/14) of cases vs. 35% (28/81) of controls had ulcer disease (OR M-H = 13; 95% CI = 1.6-98); 27% (3/11) of cases vs. 14% (11/81) of controls used indomethacin prior to disease onset (OR M-H = 6.0; 95% CI = 1.0-36). None of the blood samples were positive for any of the VHFs. This reported cluster of hematemesis illness was due to predisposing conditions and use of Non-Steroidal Anti-inflammatory Drugs (NSAID). Health education should be conducted on the danger of NSAIDs misuse, especially in persons with pre-disposing conditions.

Development of a Test Facility for Air Revitalization Technology Evaluation

NASA Technical Reports Server (NTRS)

Lu, Sao-Dung; Lin, Amy; Campbell, Melissa; Smith, Frederick

2006-01-01

An active fault tolerant control (FTC) law is generally sensitive to false identification since the control gain is reconfigured for fault occurrence. In the conventional FTC law design procedure, dynamic variations due to false identification are not considered. In this paper, an FTC synthesis method is developed in order to consider possible variations of closed-loop dynamics under false identification into the control design procedure. An active FTC synthesis problem is formulated into an LMI optimization problem to minimize the upper bound of the induced-L2 norm which can represent the worst-case performance degradation due to false identification. The developed synthesis method is applied for control of the longitudinal motions of FASER (Free-flying Airplane for Subscale Experimental Research). The designed FTC law of the airplane is simulated for pitch angle command tracking under a false identification case.

Young people's risk of suicide attempts after contact with a psychiatric department - a nested case-control design using Danish register data.

PubMed

Christiansen, Erik; Larsen, Kim Juul

2012-01-01

There seems to be an increased risk of children and adolescents committing or attempting suicide after contact with a psychiatric department. Children and adolescents living in families with low socio-economic status (SES) might have an especially increased suicide attempt risk. A complete extraction of Danish register data for every individual born in the period 1983-1989 was made. Of these 403,431 individuals, 3,465 had attempted suicide. In order to control for confounder effects from gender, age and calendar-time, a nested case-control study was designed. A total population of 72,765 individuals was used to analyze the risk of suicide attempts after contact with a psychiatric department. The case-control data were analyzed using conditional logistic regression. This study shows that a child/adolescent's risk of suicide attempt peaks immediately after discharge from last contact with a psychiatric department. The risk of suicide attempt is highest for children and adolescents suffering from personality disorders, depression and substance use disorders. Children and adolescents with previous contact with a psychiatric department and parental income in the lowest third have a significantly higher risk of suicide attempt. Suicide attempters were more likely to have been given several different diagnoses and several different psychopharmacological drugs prior to their attempted suicide. The findings in this study highlight the need for psychopathology assessment in every case of attempted suicide. This study also shows that well-known risk factors such as contact with a psychiatric department do not affect all individuals in the same way. Individuals from families with low SES had the highest risk. This suggests that the presence of factors influencing both vulnerability and resiliency, e.g., family level of SES, needs to be included in the assessment. © 2011 The Authors. Journal of Child Psychology and Psychiatry © 2011 Association for Child and Adolescent Mental Health.

Best management practices used by KYTC for on-site erosion control.

DOT National Transportation Integrated Search

2006-11-01

New erosion control procedures (ECP) have recently been implemented by the Kentucky Transportation Cabinet (KYTC). Previously, consultants and designers developed the ECP as a part of the design plans. In many cases these did not work in the field. T...

A Case-Controlled Investigation of Tactile Reactivity in Young Children with and without Global Developmental Delay

ERIC Educational Resources Information Center

Barney, Chantel C.; Tervo, Raymond; Wilcox, George L.; Symons, Frank J.

2017-01-01

Assessing tactile function among children with intellectual, motor, and communication impairments remains a clinical challenge. A case control design was used to test whether children with global developmental delays (GDD; n = 20) would be more/less reactive to a modified quantitative sensory test (mQST) compared to controls (n = 20). Reactivity…

Statistical Design Model (SDM) of satellite thermal control subsystem

NASA Astrophysics Data System (ADS)

Mirshams, Mehran; Zabihian, Ehsan; Aarabi Chamalishahi, Mahdi

2016-07-01

Satellites thermal control, is a satellite subsystem that its main task is keeping the satellite components at its own survival and activity temperatures. Ability of satellite thermal control plays a key role in satisfying satellite's operational requirements and designing this subsystem is a part of satellite design. In the other hand due to the lack of information provided by companies and designers still doesn't have a specific design process while it is one of the fundamental subsystems. The aim of this paper, is to identify and extract statistical design models of spacecraft thermal control subsystem by using SDM design method. This method analyses statistical data with a particular procedure. To implement SDM method, a complete database is required. Therefore, we first collect spacecraft data and create a database, and then we extract statistical graphs using Microsoft Excel, from which we further extract mathematical models. Inputs parameters of the method are mass, mission, and life time of the satellite. For this purpose at first thermal control subsystem has been introduced and hardware using in the this subsystem and its variants has been investigated. In the next part different statistical models has been mentioned and a brief compare will be between them. Finally, this paper particular statistical model is extracted from collected statistical data. Process of testing the accuracy and verifying the method use a case study. Which by the comparisons between the specifications of thermal control subsystem of a fabricated satellite and the analyses results, the methodology in this paper was proved to be effective. Key Words: Thermal control subsystem design, Statistical design model (SDM), Satellite conceptual design, Thermal hardware

Quantifying driver's field-of-view in tractors: methodology and case study.

PubMed

Gilad, Issachar; Byran, Eyal

2015-01-01

When driving a car, the visual awareness is important for operating and controlling the vehicle. When operating a tractor, it is even more complex. This is because the driving is always accompanied with another task (e.g., plough) that demands constant changes of body postures, to achieve the needed Field-of-View (FoV). Therefore, the cockpit must be well designed to provide best FoV. Today, the driver's FoV is analyzed mostly by computer simulations of a cockpit model and a Digital Human Model (DHM) positioned inside. The outcome is an 'Eye view' that displays what the DHM 'sees'. This paper suggests a new approach that adds quantitative information to the current display; presented on three tractor models as case studies. Based on the results, the design can be modified. This may assist the engineer, to analyze, compare and improve the design, for better addressing the driver needs.

Red Cell Distribution Width and Serum BNP Level Correlation in Diabetic Patients with Cardiac Failure: A Cross - Sectional Study.

PubMed

A R, Subhashree

2014-06-01

Red cell distribution width (RDW) is a red cell measurement given by fully automated hematology analyzers. It is a measure of heterogeneity in the size of circulating erythrocytes. Studies have shown that it is a prognostic marker in non - anemic diabetic patients with symptomatic cardiovascular disease but its correlation with cardiac failure in diabetics has not been studied so far. Moreover, studies have also shown that a higher RDW may reflect an underlying inflammatory state. Since Diabetes is a pro inflammatory state there is a possibility that it might have an influence on the RDW values even when there is no cardiac failure, but research data on this aspect is lacking. B-type natriuretic peptide (BNP) is a proven marker for cardiac failure whose values are comparable with echo cardio graphic findings in assessing the left ventricular dysfunction. This study aimed to find out the correlation between RDW% and serum BNP levels in Diabetics with heart failure (cases) when compared to those without failure (controls). Further, we compared the RDW % values of the cases with controls. Settings and Design : The study was approved by institutional ethical and research committee. A cross-sectional study was conducted with patients attending the Diabetes clinic of a tertiary care hospital in Chennai, India, during the period of October to December 2013. Hundred known cases of type II Diabetes mellitus attending Diabetes centre of the Hospital, with clinical and Echo cardio graphic features of cardiac failure were included as cases. Hundred age and gender matched diabetics with negative history of cardiovascular disease and with normal Echo cardio graphic features were included as controls. Informed consent was obtained from all the cases and controls. Demographic data and clinical history were gathered from all the cases and controls by using a standardized self - administered questionnaire. Biochemical and hematological parameters which included Fasting and Postprandial blood sugar, Glycosylated hemoglobin, Complete Blood count including RDW and serum BNP were performed for all the cases and controls. RESULTS were tabulated and analysed using SPSS 20.0 version A statistically significant correlation (p<.001) was found between Red cell Distribution Width % and Serum B type Natriuretic Peptide values in the cases. Further, RDW% showed a statistically significant difference between cases and controls. RDW% can be used as a screening parameter to identify cardiac failure in Diabetic patients similar to non-diabetic cardiac failure. RDW% values are significantly higher in cases of Diabetes with failure in comparison to uncomplicated Diabetes.

Investigation of a Guillain-Barré syndrome cluster in the Republic of Fiji.

PubMed

Pastula, Daniel M; Khan, Aalisha Sahu; Sharp, Tyler M; Biaukula, Viema L; Naivalu, Taina K; Rafai, Eric; Ermias Belay; Staples, J Erin; Fischer, Marc; Kosoy, Olga I; Laven, Janeen J; Bennett, Elizabeth J; Jenney, Adam W J; Naidu, Ravi Narayan; Lanciotti, Robert S; Galloway, Renee L; Nilles, Eric J; Sejvar, James J; Kama, Mike

2017-01-15

In 2014, we investigated a cluster of Guillain-Barre syndrome (GBS) in Fiji that occurred during a dengue epidemic. We designed a case-control study to determine the etiology. Cases were patients meeting Brighton Collaboration criteria for GBS with onset from February 2014 to May 2014. Controls were persons without symptoms of GBS who were matched by age group and location. We collected information on demographics and potential exposures. Serum samples were tested for evidence of recent arboviral or Leptospira spp. infections. Nine cases of GBS were identified for an incidence of five cases per 100,000 population/year. Median age of cases was 27years (range: 0.8-52); five (56%) were male. Six (67%) reported an acute illness prior to GBS onset. Among the 9 cases and 28 controls enrolled, odds ratios for reported exposures or antibodies against various arboviruses or Leptospira spp. were not statistically significant. No clear etiologies were identified for this unusual GBS cluster. There was a temporal association between the GBS cluster and a dengue epidemic, but we were unable to substantiate an epidemiologic or laboratory association. Further study is needed to explore potential associations between arboviral infections and GBS. Copyright © 2016. Published by Elsevier B.V.

An ℋ∞ full information approach for the feedforward controller design of a large blended wing body flexible aircraft

NASA Astrophysics Data System (ADS)

Westermayer, C.; Schirrer, A.; Hemedi, M.; Kozek, M.

2013-12-01

An ℋ∞ full information feedforward design approach for longitudinal motion prefilter design of a large flexible blended wing body (BWB) aircraft is presented. An existing onset is extended such that specifications concerning command tracking, limited control energy, and manoeuvre load reduction can be addressed simultaneously. Therefore, the utilized design architecture is provided and manual tuning aspects are considered. In order to increase controller tuning efficiency, an automated tuning process based on several optimization criteria is proposed. Moreover, two design methodologies for the parameter-varying design case are investigated. The obtained controller is validated on a high-order nonlinear model, indicating the high potential of the presented approach for flexible aircraft control.

Resolvent analysis of suboptimal control for turbulent skin friction drag reduction

NASA Astrophysics Data System (ADS)

Nakashima, Satoshi; Fukagata, Koji; Luhar, Mitul

2017-11-01

We study the drag reduction mechanisms of suboptimal control (Lee et al. 1998) via the resolvent formulation developed by McKeon and Sharma (2010). Under this formulation, the nonlinear term in the Navier-Stokes equations is regarded as a forcing which acts upon the linear dynamics to output a velocity response across Fourier space. This analysis enables targeted analyses of the effects of the control on modes resembling dynamically important coherent structures such as the near-wall (NW) cycle. Suboptimal control generates blowing and suction at the wall that is proportional to the streamwise (Case ST) or spanwise (Case SP) wall shear-stress, with the magnitude of blowing and suction being a design parameter. Both Case ST and SP can suppress resolvent modes resembling the NW cycle. However, for Case ST, the analysis reveals that the control leads to substantial increase in amplification for structures that are long in the spanwise direction. High actuation of such energetic spanwise structures was confirmed by conducting limited direct numerical simulations. In addition to the study of modes resembling the NW cycle, we will discuss modes of varying propagating speed and wavelength to provide insight into the effects of suboptimal control across spectral space. This work was supported through Grant-in-Aid for Scientific Research (C) (No. 25420129) by Japan Society for the Promotion of Science (JSPS).