New approaches on composite designs for Response Surface Methodology.

Recent attention has increasingly focused on the significance of Definitive Screening Designs (DSDs), originally introduced by Jones and Nachtsheim (2011), as a compelling alternative to traditional designs bib Response Surface Methodology (RSM). This paper introduces two novel composite techniques aimed at enhancing design efficiency and elevating D-values. By utilizing orthogonal matrices and integrating axial components from either simple orthogonal designs or the block orthogonal designs detailed in the work of Alrweili et al. (2020), new design matrices are constructed based on established composite design principles. Notably, the novel designs presented in this manuscript surpass previously documented designs in the existing literature in terms of design efficiency and robustness.

Discrete choice experiments: An overview on constructing D-optimal and near-optimal choice sets.

Discrete choice experiments (DCEs) are frequently used to estimate and forecast the behavior of an individual's choice. DCEs are based on stated preference; therefore, underlying experimental designs are required for this type of study. According to psychologists, DCE designs consist of a small number of choice sets with a limited size in the number of alternatives within a choice set to increase the response efficiency in the questionnaire. Even though algorithmic constructions (known as efficient designs) become quite common for practitioners, optimal designs (sometimes so-called orthogonal designs) continue to be used in choice experiment studies, particularly in the case that prior information about the extent of the population preference is not available. Various approaches have been developed to construct DCE designs with fewer choice sets. However, the question in many practitioners' minds is which techniques perform better (i.e. given small designs with high efficiency) in a given circumstance. In this paper and to address these concerns, we conducted an overview of the constructions of discrete choice experiments in the literature for models with only main effects. The various ways of constructing optimal and near-optimal designs were compared in terms of their ability to minimize the number of choice sets in the survey. Our findings shed light on the optimal sample sizes needed for efficient experimentation which then can help the researchers to design more effective experiments in this area.

Carotid ultrasonography improves residual risk stratification in guidelines-defined high cardiovascular risk patients.

AIMS: The clinical value of carotid atherosclerosis markers for residual risk stratification in high atherosclerotic cardiovascular disease (ASCVD) risk patients is not established. We aimed to derive and validate optimal values of markers of carotid subclinical atherosclerosis improving risk stratification in guidelines-defined high ASCVD risk patients. METHODS AND RESULTS: We consecutively analysed high or very high ASCVD risk patients from a cardiovascular (CV) prevention registry (n = 751, derivation cohort) and from the Atherosclerosis Risk in Communities (ARIC) study (n = 2,897, validation cohort). Baseline ASCVD risk was defined using the 2021 European Society of Cardiology guidelines (clinical ESCrisk). Intima-media thickness excluding plaque, average maximal (avg.maxWT), maximal wall thickness (maxWT) and number of sites with carotid plaque were assessed. As primary endpoint of the study was defined the composite of cardiac death, acute myocardial infarction and revascularization after a median of 3.4 years in both cohorts and additionally for 16.7 years in the ARIC cohort. RESULTS: MaxWT > 2.00 mm and avg.maxWT > 1.39 mm provided incremental prognostic value, improved discrimination and correctly reclassified risk over the clinical ESCrisk both in the derivation and the validation cohort (P < 0.05 for net reclassification index, integrated discrimination index and Delta Harrell's C index). MaxWT < 0.9 mm predicted very low probability of CV events (negative predictive value = 97% and 92% in the derivation and validation cohort, respectively). These findings were additionally confirmed for very long-term events in the validation cohort. CONCLUSION: Integration of carotid ultrasonography in guidelines-defined risk stratification may identify patients at very high-risk in need for further residual risk reduction or at very low probability for events.

Survival estimation through the cumulative hazard with monotone natural cubic splines using convex optimization-the HCNS approach.

BACKGROUND AND OBJECTIVES: In survival analysis both the Kaplan-Meier estimate and the Cox model enjoy a broad acceptance. We present an improved spline-based survival estimate and offer a fully automated software for its implementation. We explore the use of natural cubic splines that are constrained to be monotone. Apart from its superiority over the Kaplan Meier estimator our approach overcomes limitations of other known smoothing approaches and can accommodate covariates. Unlike other spline methods, concerns of computational problems and issues of overfitting are resolved since no attempt is made to maximize a likelihood once the Kaplan-Meier estimator is obtained. An application to laryngeal cancer data, a simulation study and illustrations of the broad application of the method and its software are provided. In addition to presenting our approaches, this work contributes to bridging a communication gap between clinicians and statisticians that is often apparent in the medical literature. METHODS: We employ a two-stage approach: first obtain the stepwise cumulative hazard and then consider a natural cubic spline to smooth its steps under restrictions of monotonicity between any consecutive knots. The underlying region of monotonicity corresponds to a non-linear region that encompasses the full family of monotone third-degree polynomials. We approximate it linearly and reduce the problem to a restricted least squares one under linear restrictions. This ensures convexity. We evaluate our method through simulations against competitive traditional approaches. RESULTS: Our method is compared to the popular Kaplan Meier estimate both in terms of mean squared error and in terms of coverage. Over-fitting is avoided by construction, as our spline attempts to approximate the empirical estimate of the cumulative hazard itself, and is not fitted directly on the data. CONCLUSIONS: The proposed approach will enable clinical researchers to obtain improved survival estimates and valid confidence intervals over the full spectrum of the range of the survival data. Our methods outperform conventional approaches and can be readily utilized in settings beyond survival analysis such as diagnostic testing.

Mindfulness, impulsivity, and moral disengagement as parameters of bullying and victimization at school.

The aim of the present study was to examine the existing association between mindfulness, impulsivity, moral disengagement, and bullying experiences at school. Longitudinal data were collected in three points in time (T1, T2, T3) with 6 months interval between them. Participants were 558 adolescents attending secondary schools in Cyprus, with their ages ranging from 14 to 17 years (M = 15.3; standard deviation = 0.69). Through structural equation modeling, it was found that mindfulness at T1 had a significant negative effect on both impulsivity and moral disengagement at T2 and these, in turn, had a positive effect on bullying and victimization at T3. Thus, mindfulness had an indirect effect on both bullying and victimization, fully mediated by impulsivity and moral disengagement.

Age-dependent association of pulse wave velocity with coronary artery disease and myocardial aging in high-risk patients.

AIMS: Progressive arterial stiffening, as a marker of arterial aging, may reach a plateau in elderly patients and may thus lose its clinical utility. This phenomenon may be more prominent in high-risk patients. We aimed to investigate if carotid-to-femoral pulse wave velocity (cf-PWV) is related to coronary artery disease (CAD) and diastolic dysfunction in elderly high-risk patients as compared to a control group of younger individuals. METHODS: One-hundred and ninety-two high-risk stable patients who underwent coronary artery angiography and assessment of cf-PWV were consecutively recruited. Indices of diastolic dysfunction were also measured by echocardiography, including the volume of the left atrium and the ratio of early transmitral peak velocity (E) to the mitral annular early diastolic velocity (E'). RESULTS: Increased cf-PWV was associated with the presence of CAD [odds ratio (OR) 1.34, P = 0.02], number of diseased coronary vessels (OR 1.17, P = 0.029) and CAD severity (P = 0.023) as assessed by Gensini score, in patients less than 65 years old after adjustment for traditional risk factors. Moreover, cf-PWV correlated with E/E' (P = 0.019) and increased the odds by 16% (OR 1.16, P = 0.048) for more severe diastolic dysfunction in patients aged below 65 years old. None of these outcomes correlated with cf-PWV in the elderly. CONCLUSION: In high cardiovascular risk patients, an age-dependent association of cf-PWV with CAD and diastolic dysfunction was evinced. In contrast to younger patients, these results suggest that measuring arterial stiffness in elderly high-risk patients may lack clinical value.

Semi-continuous anaerobic co-digestion of chicken litter with agricultural and food wastes: A case study on the effect of carbon/nitrogen ratio, substrates mixing ratio and organic loading.

In this study, four agro-industrial substrates, chicken litter (CL), food waste (FW), wheat straw (WS) and hay grass (HG) were assessed as feedstock for anaerobic digestion (AD) under semi-continuous conditions at organic loading rates (OLRs) of 2.0-3.0 g TS/L.d and hydraulic retention time (HRT) of 20 days. Six different substrate mixtures were prepared such that the C/N ratio of each was 20 or more. Using principal component analysis 68.1% of data variability was explained. Biogas production from CL, as a single substrate, was 181.3 ±â€¯9.8mLN biogas/g VSadded at OLR of 2.0gTS/L.d. The optimum substrates mixture was CL:FW:WS 60:20:20, where 73.0%, 167.2% and 116.9% increase in total biogas production at OLR of 2.0, 2.5, 3.0gTS/L.d, respectively, compared to that from CL, was obtained. Digestate sequential fractionation revealed carbohydrate degradation is an important factor that can explain the variation in performance and production of biogas for feedstocks of balanced C/N ratio.

The effect of parental style on bullying and cyber bullying behaviors and the mediating role of peer attachment relationships: A longitudinal study.

The purpose of the present study was the examination of the longitudinal effect of parental style on short-term changes in conventional and cyber forms of bullying/victimization, and the investigation of the mediating role of peer attachment relationships on this effect. The participants were 861 children and adolescents (52% girls, Mage = 11.72 years) attending Cyprus public institutions. Students provided information during three measurement points. There was a six and a 12 week interval among the three measurement points, respectively. The findings of the study indicated that parenting seems to be a significant predictor of all forms of bullying/victimization, conventional and cyber, in early adolescents, even when accounting for bullying/victimization levels eighteen weeks back. More importantly, results showed that the effect of parental style on bullying forms was mediated by peer attachment relationships. Results are discussed in the light of theoretical and practical implications.

Externalizing and internalizing behaviours in adolescence, and the importance of parental behavioural and psychological control practices.

The aims of the present study were to explore the impact of parental characteristics (behavioural control and psychological control) on adolescents' expression of externalizing and internalizing behaviours. To address the aim of the study, participants completed quantitative measures; the study included 538 adolescents and their mothers and fathers. Overall, 513 mothers and 464 fathers participated in the study. Adolescents completed the Children's Report on Parent Behaviour Inventory (CRPBI), while parents completed the Child Behaviour Checklist - Parent Report (Short Form; CBCL). Results of the study showed that only maternal and paternal psychological control predicted externalizing and internalizing behaviours. The conclusions have practical applications, as they can provide novel approaches in parent training programmes. Furthermore, results are discussed in relation to the connection with earlier studies and the theoretical contribution.

Smooth ROC curves and surfaces for markers subject to a limit of detection using monotone natural cubic splines.

The use of ROC curves in evaluating a continuous or ordinal biomarker for the discrimination of two populations is commonplace. However, in many settings, marker measurements above or below a certain value cannot be obtained. In this paper, we study the construction of a smooth ROC curve (or surface in the case of three populations) when there is a lower or upper limit of detection. We propose the use of spline models that incorporate monotonicity constraints for the cumulative hazard function of the marker distribution. The proposed technique is computationally stable and simulation results showed a satisfactory performance. Other observed covariates can be also accommodated by this spline-based approach.

Cultural value orientation and authoritarian parenting as parameters of bullying and victimization at school.

The purpose of the present study was to examine the existing association between cultural value orientation, authoritarian parenting, and bullying and victimization at school. The participants (N = 231) were early adolescents, randomly selected from 11 different schools in urban and rural areas of Cyprus. Participants completed self reports measuring cultural value orientation, authoritarian parenting, bullying, and victimization. These instruments were the following: the cultural value scale (CVS), the parental authority questionnaire (PAQ), and the revised bullying and victimization questionnaire (BVQ-R). Structural equation modeling (SEM) was used to examine mediation effects. It was found that vertical individualism acted as a mediator between authoritarian parenting and bullying. Statistically significant positive correlations were found between authoritarian parenting and the vertical dimensions of both cultural value orientations (individualism and collectivism), but not with the horizontal dimensions of either cultural orientation. Further, authoritarian parenting was also positively associated with bullying and victimization at school. The main contribution of the present study is the finding that vertical individualism significantly mediates the relationship between authoritarian parental style and bullying propensity.

Survival estimation through the cumulative hazard function with monotone natural cubic splines.

In this paper we explore the estimation of survival probabilities via a smoothed version of the survival function, in the presence of censoring. We investigate the fit of a natural cubic spline on the cumulative hazard function under appropriate constraints. Under the proposed technique the problem reduces to a restricted least squares one, leading to convex optimization. The approach taken in this paper is evaluated and compared via simulations to other known methods such as the Kaplan Meier and the logspline estimator. Our approach is easily extended to address estimation of survival probabilities in the presence of covariates when the proportional hazards model assumption holds. In this case the method is compared to a restricted cubic spline approach that involves maximum likelihood. The proposed approach can be also adjusted to accommodate left censoring.

Longitudinal associations between adolescent alcohol use and parents' sources of knowledge.

The aim of this study was to test the direction of effect in the relationship between parents' sources of knowledge (parental monitoring and child disclosure) and adolescent alcohol use. The participants were 215 adolescents and their mothers, randomly selected from urban and rural areas in Cyprus. A 3-month, two-timepoint longitudinal design was used in which adolescents completed the alcohol use disorders identification test while mothers completed a parental knowledge questionnaire. The results of this study showed that parental monitoring did not predict subsequent adolescent alcohol use. However, child disclosure at Time 1 negatively predicted adolescent alcohol use at Time 2. Moreover, adolescents' alcohol dependence symptoms at Time 1 negatively predicted both sources of parental knowledge at Time 2.

Bullying and victimization at school: the role of mothers.

BACKGROUND: Social learning literature is used in order to describe the contextual parameters of peer aggression, and specifically bullying and victimization. AIM: The aim of the present study was to examine the influence of maternal characteristics on their child's victimization or bullying experience at school. SAMPLE: The participants were 252 elementary school students (mean age 11.5 years) and their mothers. METHOD: A theoretically driven model was developed and its ability to fit the data was tested. The main factors included in the model were the following: parental style as perceived by the child, self-reported parental involvement, the mother's emotional state and the degree of victimization experienced by the child at school. RESULTS: Through confirmatory factor analysis, it was shown that maternal responsiveness was positively related to the child's adjustment at school (i.e. achievement and social adaptation), while the same factor was negatively related to school aggression (bullying and disrupting behaviour). Overprotective mothering was associated with high degrees of victimization experienced by the child, whereas maternal depressiveness was related to both victimization and bullying behaviour on the part of the child. CONCLUSIONS: Parents should be included in the design of intervention plans aiming at the elimination of bullying at school.