Covariance Control Research Articles

Active vaccination inhibits the acquisition of methamphetamine self-administration in rats

Active vaccination inhibits the acquisition of methamphetamine self-administration in rats

MP6-04 THE IMPACT OF TRAINING DENSITY ON PROSTATE CANCER DETECTION: AN ANALYSIS OF OVER 2000 PROSTATE BIOPSY CASES PERFORMED BY UROLOGY RESIDENTS

INTRODUCTION AND OBJECTIVES: There is wide variability in the number of prostate biopsies performed by residents. Residency programs reported a vast range in number of cases per trainee in 2010 and 2011 (13-540, 17-329, respectively). This study investigates the impact of caseload density (number of biopsies completed over a given time period) on the likelihood of a positive biopsy result. METHODS: We examined 2,046 prostate biopsy procedures performed by first-year urology residents. Residents were divided into high-density (HD; first 10 cases in 15 days) and low-density (LD; first 10 cases in >15 days) training groups. The primary endpoint was the likelihood of cancer diagnosis. The frequency of cancer detection in the initial 10 cases was compared to that of the subsequent cases using generalized estimating equation models that account for correlated observations and control for multiple covariates. RESULTS: High-density training achieved significantly more consistent results compared to LD training. In the HD group, the odds ratios (OR) of detecting cancer ranged from 0.83 (p1⁄40.50) to 1.09 (p1⁄40.84) when comparing the first 10 cases with subsequent sets of 10 cases up to 50 cases (Figure). The cancer detection rate was unchanged comparing the first 50 cases with the subsequent 50-100 cases (OR1⁄41.40, p1⁄40.06) and >100 cases (OR1⁄41.17, p1⁄40.16). In contrast, LD residents showed significant and progressive improvement in their ability to detect prostate cancer during the first 50 procedures (OR up to 2.54, p1⁄40.018) before reaching a plateau at 41-50 cases. CONCLUSIONS: Training density may play an important role in medical and surgical residency education. For prostate biopsy, high-density training (first ten cases within 15 days) appears to result in more consistent cancer detection rate during subsequent procedures. We conclude that high-density training is likely to achieve earlier attainment of proficiency thereby obviating the need for large case numbers and allowing residents more time to master other procedures.

Neighborhood Socioeconomic Status in Relation to Cancer Mortality in the Black Women's Health Study, 1995–2011

Abstract Neighborhood socioeconomic status has been associated with a range of cancer health outcomes, but longitudinal data in African Americans, who tend to live in more deprived neighborhoods, is lacking. We assessed the relation of neighborhood socioeconomic status (SES) to cancer mortality in a prospective cohort of African American women. Participants enrolled in the Black Women's Health Study in 1995 by completing mailed questionnaires. Exposure information and incident diagnoses are updated through biennial questionnaires. Neighborhood SES was measured by a factor score based on census block group data for 6 indicators of income and education – median household income, median housing value, percent of households receiving interest/dividend/rental income, percent of adults who are college graduates, percent of white-collar workers, and percent of households not headed by a single female. Deaths through 2011 and cause of death were identified through linkage to the National Death Index. Cox proportional hazard models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) with control for age, education, marital status, cigarette smoking, physical activity, time spent watching TV, and dietary pattern. Based on 819 cancer deaths that occurred from 1995–2011, neighborhood SES was inversely associated with cancer mortality. The age-adjusted HR for lowest quartile of neighborhood SES relative to highest quartile was 1.63, 95% CI 1.33–2.00; control for covariates reduced the HR to 1.29, 95% CI 1.05–1.60. In analyses restricted to participants with 16 or more years of education, the multivariable HR for lowest relative to highest quartile of neighborhood SES was 1.38 (95% CI 1.01–1.90). Our results suggest that neighborhood SES is associated with an individual's risk of cancer mortality and that the association is mediated in part by diet, physical activity, and sedentary behavior. The finding that this association was present even among college graduates is of particular relevance to African Americans, who are more likely to live in disadvantaged neighborhoods regardless of their individual income or educational attainment.

A Note on Close Elections and Regression Analysis of the Party Incumbency Advantage

Much research has recently been devoted to understanding the effects of party incumbency following close elections, typically using a regression discontinuity design. Researchers have demonstrated that close elections in the United States may systematically favor certain types of candidates, and that a research design that focuses on close elections may therefore be inappropriate for estimation of the incumbency advantage. We demonstrate that any issues raised with the study of close elections may be equally applicable to the ordinary least squares analysis of electoral data, even when the sample contains all elections. When vote share is included as part of a covariate control strategy, the estimate produced by an ordinary least squares regression that includes all elections either exactly reproduces or approximates the regression discontinuity estimate.

Fuzzy Stabilization for Nonlinear Discrete Ship Steering Stochastic Systems Subject to State Variance and Passivity Constraints

For nonlinear discrete-time stochastic systems, a fuzzy controller design methodology is developed in this paper subject to state variance constraint and passivity constraint. According to fuzzy model based control technique, the nonlinear discrete-time stochastic systems considered in this paper are represented by the discrete-time Takagi-Sugeno fuzzy models with multiplicative noise. Employing Lyapunov stability theory, upper bound covariance control theory, and passivity theory, some sufficient conditions are derived to find parallel distributed compensation based fuzzy controllers. In order to solve these sufficient conditions, an iterative linear matrix inequality algorithm is applied based on the linear matrix inequality technique. Finally, the fuzzy stabilization problem for nonlinear discrete ship steering stochastic systems is investigated in the numerical example to illustrate the feasibility and validity of proposed fuzzy controller design method.

A Note on Close Elections and Regression Analysis of the Party Incumbency Advantage

AbstractMuch research has recently been devoted to understanding the effects of party incumbency following close elections, typically using a regression discontinuity design. Researchers have demonstrated that close elections in the US House of Representatives may systematically favor certain types of candidates, and that a research design that focuses on close elections may therefore be inappropriate for estimation of the incumbency advantage. We demonstrate that any issues raised with the study of close elections may be equally applicable to the ordinary least squares analysis of electoral data, even when the sample contains all elections. When vote share is included as part of a covariate control strategy, the estimate produced by an ordinary least squares regression that includes all elections either exactly reproduces or approximates the regression discontinuity estimate.

Cerebral Regional Oxygen Saturation and Serum Neuromarkers for the Prediction of Adverse Neurologic Outcome in Pediatric Cardiac Surgery

The aim of this study is to determine the utility of non-invasive bedside neuromonitoring, including cerebral regional oxygen saturation (rSO2) measured by near-infrared spectroscopy and serum biomarkers, in identifying children at risk from adverse neurological outcome after heart surgery. Prospective observational study including 39 consecutive children undergoing heart surgery with cardiopulmonary bypass (CPB) and normal neurologic exam prior to surgery. Cerebral rSO2 was measured at baseline (prior to surgery) and then continuously during surgery and for the first 16 h post-operatively. Neuromarkers [neuron-specific enolase (NSE), S100β, glial fibrillary acidic protein (GFAP), and brain-derived neurotrophic factor (BDNF)] were measured in serum at baseline, immediately after CPB and at 16 h post-operatively. Adverse neurological outcome was defined as an abnormal pediatric cerebral performance category (PCPC) scale score at 12 months after surgery. Sixteen children (41 %) had an abnormal PCPC scale score at the 12-month evaluation after surgery. In children with unfavorable neurological outcomes, mean cerebral rSO2 values were lower and the area-under-the-curve below a threshold of 40 and 20% below baseline were also increased. No significant differences were found in serum neuromarkers between groups at the time points that were assessed. Bedside determination of cerebral rSO2 may have some utility in identifying children at risk for adverse neurological outcome after heart surgery in children. Additional studies that are sufficiently powered to control for the many covariates in this patient population will be required to fully interrogate this important question. The role of serum neuromarkers in the immediate post-operative period do not appear to be helpful in this question, though more thorough interrogation of delayed periods may ultimately demonstrate some utility in answering this question.

Tamsulosin treatment for benign prostatic hyperplasia and risk of severe hypotension in men aged 40-85 years in the United States: risk window analyses using between and within patient methodology

Objective To characterize risk of hypotension requiring admission to hospital in middle aged and older men treated with tamsulosin for benign prostatic hyperplasia.Design Population based retrospective cohort study (between patient...

Social Cohesion and Mortality: A Survival Analysis of Older Adults in Japan

We examined the association between social cohesion and mortality in a sample of older adults in Japan. Data were derived from a cohort study of elderly individuals (65-84 years) in Shizuoka Prefecture; 14 001 participants were enrolled at baseline (1999) and followed up in 2002, 2006, and 2009. Among the 11 092 participants for whom we had complete data, 1427 had died during follow-up. We examined the association between social cohesion (assessed at both the community and individual levels) and subsequent mortality after control for baseline and time-varying covariates. We used clustered proportional hazard regression models to estimate hazard ratios (HRs) and confidence intervals (CIs). After control for individual characteristics, individual perceptions of community cohesion were associated with a reduced risk of all-cause mortality (HR = 0.78; 95% CI = 0.73, 0.84) as well as mortality from cardiovascular disease (HR = 0.75; 95% CI = 0.67, 0.84), pulmonary disease (HR = 0.66; 95% CI = 0.58, 0.75), and all other causes (HR = 0.76; 95% CI = 0.66, 0.89). However, no statistically significant relationship was found between community cohesion and mortality risk. Among the elderly in Japan, more positive individual perceptions of community cohesion are associated with reduced risks of all-cause and cause-specific mortality.

Is the association between education and depressiveness mediated by work stress and social isolation and moderated by regional unemployment rate? - A confirmatory moderated lower level mediation model of the lidA (leben in der Arbeit)-study

Introduction/Background: As a consequence of the demographic change the German work force is ageing and shrinking. Therefore older employees are of rising value to hold up the German productivity, competitiveness and welfare state. Goal of the lidA-study is to identify factors which keep ageing German employees healthy and motivated at work. Depressiveness is one of the leading reasons for days absent from work, loss of productivity and early retirement. Social differences to the disadvantage of lower status groups in depressiveness are well known. Our question was by which pathways these differences could be explained. We hypothesized that part of the social differences in depressiveness could be explained by work-related stress and social isolation and there may be regional differences in this association which could be explained by regional unemployment rate. Data/Methods: This confirmatory analysis was conducted on the 6339 employees of the first wave of the lidA-cohort study. Work-related stress was parameterized by effort-reward imbalance (ERI-ratio), depressiveness by the short version of the Becks depression inventory (BDI-V). Education was measured by a combined score of school education and vocational training, social isolation by a simple item sum score. Regional unemployment rate came from the Federal Statistical Office. First level mediation was defined according to the criteria of Baron and Kenny (1986). Moderated lower level mediation was analyzed by the method of Bauer et al (2006). The multilevel-model was adjusted for gender, negative affectivity and overcommitment. Age-specific differences were analysed by age-stratification. Results: There was a stronger relationship between educational level and depressiveness in the younger age cohort. Whereas in the younger age cohort education was both, directly and indirectly (i.e. mediated by work stress), significantly inversely associated with depressiveness in the older age cohort only the indirect association was significant. In both cohorts social isolation was a significant non-work related mediator in the association between education and depressiveness after control for covariates. Considering the total effect there was a clear inverse association between education and depressiveness in the younger but not in the older cohort. Regional variation between work-related stress and depressiveness was observed for both age cohorts. Yet, the regional variation was not explained by regional unemployment. No regional variation was found for the association between education and depressiveness or education and work-related stress. Discussion/Conclusion: Our results indicate that younger employees with lower SES might have a higher probability of showing depressive symptoms. There was also a stronger indirect association between educational level and depressiveness mediated by work-related stress in the younger cohort. This observation could be of preventive value as a social gradient in depressiveness could be reduced by preventive measures lowering work-related stress. Regarding the stronger direct association between educational level and depressiveness in the younger age group improvements in vocational training in younger lower educated employees could have an additional preventive effect in the long run. Both preventive actions could be worthwhile with regard to preservation of work power and competitiveness of an ageing and shrinking German work force.

Multivariate bayesian spatial model of preterm birth and cardiovascular disease among georgia women: Evidence for life course social determinants of health

Background: There is epidemiologic evidence that women who experience preterm birth (PTB) are at elevated risk for cardiovascular disease (CVD) later in life. Each outcome independently has noted spatial and socioeconomic gradients; we test for spatial structure in the population correlation of the two.Methods: Exploratory spatial data analysis and multivariate Bayesian spatial models were fit to describe the spatial correlation of PTB with CVD among women in Georgia counties from 2002 to 2006.Results: Global Moran’s I and local-indicators of spatial association statistics suggest significant co-occurrence of CVD and PTB. Bayesian posterior estimates for multivariate correlation of these outcomes range from r=0.11–0.34 for CVD and PTB. Significant spatial correlation persists with control for county covariates among whites but not blacks.Conclusion: Modest evidence for spatial structure of the ecologic correlation of PTB and women’s CVD is consistent with a lifecourse perspective on socially clustered determinants of health.

Combined Use of Waist and Hip Circumference to Identify Abdominally Obese HIV-Infected Patients at Increased Health Risk

ObjectivesTo determine whether for a given waist circumference (WC), a larger hip circumference (HC) was associated with a reduced risk of insulin resistance, type 2 diabetes (T2D), hypertension and cardiovascular disease (CVD) in HIV-infected patients. A second objective was to determine whether, for a given WC, the addition of HC improved upon estimates of abdominal adiposity, in particular visceral adipose tissue (VAT), compared to those obtained by WC alone.MethodsHIV-infected men (N = 1481) and women (N = 841) were recruited between 2005 and 2009. WC and HC were obtained using standard techniques and abdominal adiposity was measured using computed tomography.ResultsAfter control for WC and covariates, HC was negatively associated with risk of insulin resistance (p<0.05) and T2D [Men: OR = 0.91 (95% CI: 0.86–0.96); Women: OR = 0.91 (95% CI: 0.84–0.98)]. For a given WC, HC was also negatively associated with a lower risk of hypertension (p<0.05) and CVD [OR = 0.94 (95% CI: 0.88–0.99)] in men, but not women. Although HC was negatively associated with VAT in men and women after control for WC (p<0.05), the addition of HC did not substantially improve upon the prediction of VAT compared to WC alone.ConclusionsThe identification of HIV-infected individuals at increased health risk by WC alone is substantially improved by the addition of HC. Estimates of visceral adipose tissue by WC are not substantially improved by the addition of HC and thus variation in visceral adiposity may not be the conduit by which HC identifies increased health risk.

Perceived weight, not obesity, increases risk for major depression among adolescents

This study examined the association between major depression, obesity and body image among adolescents. Methods: Participants were 4175 youths 11–17 years of age sampled from the community who were interviewed using the Diagnostic Interview Schedule for Children and Adolescents, Version IV, completed a self-report questionnaire, and had their weight and height measured. There were 2 measures of body image: perceived weight and body satisfaction. Obesity was associated with increased risk of depression, with no controls for covariates. However, when the association was examined in models which included weight, major depression, and body image measures and covariates, there was no association between major depression and body weight, nor between body satisfaction and major depression. Perceived overweight was strongly and independently associated with body weight (O.R. = 2.62). We found no independent association between major depression and body weight. If there is an etiologic link between major depression and body weight among adolescents, it most likely operates through processes involving components of body image. Future research should focus on the role of depression and body image in the etiology of obesity.

Multi-objective control for stochastic model reference systems based on LMI approach and sliding mode control concept

In this article, a multi-objective control u(t) is designed for stochastic model reference systems to achieve the following three objectives simultaneously: the pole placement constraint, H ∞-norm constraint and individual error state variance constraint. Using the invariance property of sliding mode control, the reference model input and the plant error term will disappear on the sliding mode of the error system. By combining the upper bound covariance control theory, pole placement skill and H ∞-norm control theory, a controller, in which the control feedback gain matrix is synthesised utilising linear matrix inequality (LMI) approach, is derived to achieve the above multiple objectives. Furthermore, a practical example for the problem of ship yaw-motion systems is adopted to illustrate the proposed method.

Pretreatment dietary patterns, weight status, and head and neck squamous cell carcinoma prognosis

Few studies have evaluated the association of diet and weight status with head and neck cancer outcomes. The purpose of this study was to determine whether pretreatment dietary patterns and weight status are associated with head and neck cancer prognosis. This was a longitudinal study of 542 patients with newly diagnosed head and neck cancer who completed food-frequency questionnaires and health surveys before treatment. Clinical data were abstracted from medical records and the Social Security Death Index. Dietary patterns were identified by using principal component analysis. Cox proportional hazard models were used to examine the association of derived dietary patterns (fit by quintiles of exposure) and weight status with time to recurrence and survival, with control for covariates. During the study period, there were 229 deaths and 184 recurrences. Two dietary patterns were identified: a whole-foods pattern (characterized by high intakes of vegetables, fruit, fish, poultry, and whole grains) and a Western pattern (characterized by high intakes of red and processed meats, refined grains, potatoes, and French fries). In multivariable analyses, significantly fewer deaths were observed in subjects most adherent to the whole-foods pattern (HR: 0.56; 95% CI: 0.34, 0.92; P-trend = 0.01). Subjects classified as overweight or obese had significantly fewer deaths (HR: 0.65; 95% CI: 0.49, 0.85; P = 0.001) and recurrences (HR: 0.70; 95% CI: 0.52, 0.95; P = 0.02) than did normal-weight or underweight subjects. Consumption of a diet rich in vegetables, fruit, fish, poultry, and whole grains and being overweight before diagnosis with head and neck cancer are associated with a better prognosis.

A novel approach to improve health status measurement in observational claims-based studies of cancer treatment and outcomes

To develop and provide initial validation for amultivariate, claims-based prediction model for disability status (DS), a proxymeasure of performance status (PS), among older adults. The model was designed to augment information on health status at the point of cancer diagnosis in studies using insurance claims to examine cancer treatment and outcomes. We used data from the 2001–2005 Medicare Current Beneficiary Survey (MCBS), with observations randomly split into estimation and validation subsamples. We developed an algorithm linking self-reported functional status measures to a DS scale, a proxy for the Eastern Cooperative Oncology Group (ECOG) PS scale. The DS measure was dichotomized to focus on good [ECOG 0–2] versus poor [ECOG 3–4] PS. We identified potential claims-based predictors, and estimated multivariate logistic regression models, with poor DS as the dependent measure, using a stepwise approach to select the optimal model. Construct validity was tested by determining whether the predicted DS measure generated by the model was a significant predictor of survival within a validation sample from the MCBS. One-tenth of the beneficiaries met the definition for poor DS. The base model yielded high sensitivity (0.79) and specificity (0.92); positive predictive value=48.3% and negative predictive value=97.8%, c-statistic=0.92 and good model calibration. Adjusted poor claims-based DS was associated with an increased hazard of death (HR=3.53, 95% CI 3.18, 3.92). The ability to assess DS should improve covariate control and reduce indication bias in observational studies of cancer treatment and outcomes based on insurance claims.

Relationship between hysterectomy and admixture in African American women

Most studies suggest that hysterectomies are more common in African American women than in other ethnic groups. To assess this ethnic surgical disparity in a novel way, our main goal was to determine whether admixture (the proportion of sub-Saharan African or European origin in individuals) is associated with hysterectomy frequency in African American women in the Women's Health Initiative. In this retrospective study, we used ancestry informative single nucleotide polymorphisms to estimate admixture proportions in >10,000 African American women from the Women's Health Initiative. Logistic regression models were used to assess the association between admixture and self-reported history of hysterectomy with and without controls for relevant covariates. Multinomial logistic regression models were used to assess the association between admixture and self-reported age of hysterectomy. We also considered other potential risk factors (adiposity, hypertension, and education) for hysterectomy accounting for admixture. African admixture was a strong risk factor after the adjustment for multiple covariates (odds ratio, 1.85; P < .0001). The admixture risk for hysterectomy was highest for those procedures that were performed in the 35-39 age range (odds ratio, 3.08; P < .0001) and least evident in oldest ages (≥45 years old). Our analyses also suggest that adiposity, hypertension, and education were associated independently with hysterectomy in this population group. These results suggest that higher African admixture is associated with higher frequencies of hysterectomy and that genetic studies that specifically target African American women and diseases that are associated with hysterectomy may be especially useful in understanding the pathogenesis and underlying cause of this disparity in health outcome.

Variance-Constrained Multiobjective Control and Filtering for Nonlinear Stochastic Systems: A Survey

The multiobjective control and filtering problems for nonlinear stochastic systems with variance constraints are surveyed. First, the concepts of nonlinear stochastic systems are recalled along with the introduction of some recent advances. Then, the covariance control theory, which serves as a practical method for multi-objective control design as well as a foundation for linear system theory, is reviewed comprehensively. The multiple design requirements frequently applied in engineering practice for the use of evaluating system performances are introduced, including robustness, reliability, and dissipativity. Several design techniques suitable for the multi-objective variance-constrained control and filtering problems for nonlinear stochastic systems are discussed. In particular, as a special case for the multi-objective design problems, the mixedH2/H∞control and filtering problems are reviewed in great detail. Subsequently, some latest results on the variance-constrained multi-objective control and filtering problems for the nonlinear stochastic systems are summarized. Finally, conclusions are drawn, and several possible future research directions are pointed out.

Covariance Control Problems over Martingales with Fixed Terminal Distribution Arising from Game Theory

We study several aspects of covariance control problems over martingale processes in ${\mathbb{R}}^d$ with constraints on the terminal distribution, arising from the theory of repeated games with incomplete information. We show that these control problems are the limits of discrete-time stochastic optimization problems called problems of maximal variation of martingales, meaning that sequences of optimizers for problems of length $n$, seen as piecewise constant processes on the uniform partition of $[0,1]$, define relatively compact sequences having all their limit points in the set of optimizers of the control problem. Optimal solutions of this limit problem are then characterized using convex duality techniques, and the dual problem is shown to be an unconstrained stochastic control problem characterized by a second order nonlinear PDE of HJB type. We deduce from this dual relationship that solutions of the control problem are the images by the spatial gradient of the solution of the HJB equation of the solutions of the dual stochastic control problem using tools from optimal transport theory.

Decentralised covariance control of dynamic routing in traffic networks: a covariance feedback approach

In this study, the authors propose a novel decentralised robust routing control strategy for average and covariance of queue length in a data network. The objective is to control the transitional behaviour of the data networks in response to new traffic load. For each node, the authors design a local state feedback controller based on minimising the worst case of the queue length. The authors then propose an innovative model for covariance of the queue length in each node. To control the average of queue length, local delay-dependent robust controllers are designed based on an equivalent descriptor representation and linear matrix inequalities (LMIs). For covariance control of the queue length, the authors first show that the covariance control problem is equivalent to a standard disturbance rejection problem. Then the authors propose a covariance feedback control law. To investigate the effectiveness of the proposed methodology an example is also presented and extensive simulation results are conducted. Simulation results indicate that the proposed method significantly improves the packet loss and system response time and is able to efficiently control the transient conditions in each.