Using Column Generation to Solve Extensions to the Markowitz Model

We introduce a solution scheme for portfolio optimization problems with cardinality constraints. Typical portfolio optimization problems are extensions of the classical Markowitz mean-variance portfolio optimization model. We solve such type of problems using a method similar to column generation. In this scheme, the original problem is restricted to a subset of the assets resulting in a master convex quadratic problem. Then the dual information of the master problem is used in a sub-problem to propose more assets to consider. We also consider other extensions to the Markowitz model to diversify the portfolio selection within the given intervals for active weights.Comment: 16 pages, 3 figures, 2 tables, 1 pseudocod

Physical activity and motor skills in children: A differentiated approach

Being physically active plays an essential role in a child's physical development. While there is ample evidence for a positive association between physical activity (PA) and motor skills in children, the question of how PA should be implemented to optimally foster motor skill proficiency is less clear. To address this gap, the current longitudinal study compared four groups of children with different patterns of leisure-time PA engagement—namely children engaging in either structured PA, unstructured PA, a combination of structured and unstructured PA, or no PA at all—with respect to their gross and fine motor skill development. Results of repeated measures mixed modeling procedures revealed that engaging in structured PA—either exclusively or in combination with unstructured PA—is beneficial for children's gross motor development, whereas engaging in unstructured PA lacks such effectiveness. As to fine motor skills, a beneficial tendency of structured PA was observed as well. Hence, PA seems to be beneficial for motor skill development particularly when implemented in a formal setting with guided opportunities for practice. In conclusion, regularly engaging in structured PA constitutes a promising way to promote motor skills and support motor development over the long term

The effect of video games, exergames and board games on executive functions in kindergarten and 2nd grade: An explorative longitudinal study

We examined the relation between different kinds of play behavior (video games, exergames, board games) in kindergarten (T1) and components of executive function (EF; inhibition, switching, verbal and visuospatial updating) in kindergarten and second grade (T1 and T2). Ninety-seven children participated in this longitudinal study. Parents were asked to complete a questionnaire regarding children's play behavior, reporting frequency, duration, and game type. The results indicate that play behavior is associated with EF development in children; however, only exergames, electronic puzzle games, and board games predicted EF at T2. Additionally, the time spent on electronic games was negatively related to visuospatial updating at T1 but did not predict EF at T2. The results support further investigation of a potential link between board game and exergame play behavior and EF development

The mediating role of self-concept between sports-related physical activity and mathematical achievement in fourth graders

Being physically active has many benefits for children and adolescents. It is essential for various aspects of physical and mental health, and also positively influences academic performance and school achievement. In addressing the still incomplete understanding of the link between physical activity (PA) and academic achievement, the present study scrutinized the open issues regarding different roles of PA type and PA duration within the relation between self-reported PA and objectively measured mathematical achievement in fourth graders. As to the type of PA, the current study distinguished between structured and unstructured sports activities children perform in their leisure time. Moreover, the current study investigated the indirect effect of PA on mathematical achievement by controlling for the mathematical self-concept as a mediating variable. Results showed PA to be positively related to mathematical outcomes if implemented in a structured setting and pursued for at least two hours per week. As to the mediation, the results revealed a full mediation, indicating PA to improve mathematical self-concept, which, in turn, positively affected mathematical achievement. Thus, engaging in structured PA for two hours or more a week may have additional benefits for children’s and adolescents’ self-concept in a way that is favorable and encouraging for promoting their academic achievement

Relationship of aerobic fitness and motor skills with memory and attention in preschoolers (Ballabeina): A cross-sectional and longitudinal study

BACKGROUND: The debate about a possible relationship between aerobic fitness and motor skills with cognitive development in children has recently re-emerged, because of the decrease in children's aerobic fitness and the concomitant pressure of schools to enhance cognitive performance. As the literature in young children is scarce, we examined the cross-sectional and longitudinal relationship of aerobic fitness and motor skills with spatial working memory and attention in preschool children. METHODS: Data from 245 ethnically diverse preschool children (mean age: 5.2 (0.6) years, girls: 49.4%) analyzed at baseline and 9 months later. Assessments included aerobic fitness (20 m shuttle run) and motor skills with agility (obstacle course) and dynamic balance (balance beam). Cognitive parameters included spatial working memory (IDS) and attention (KHV-VK). All analyses were adjusted for age, sex, BMI, migration status, parental education, native language and linguistic region. Longitudinal analyses were additionally adjusted for the respective baseline value. RESULTS: In the cross-sectional analysis, aerobic fitness was associated with better attention (r=0.16, p=0.03). A shorter time in the agility test was independently associated with a better performance both in working memory (r=-0.17, p=0.01) and in attention (r=-0.20, p=0.01). In the longitudinal analyses, baseline aerobic fitness was independently related to improvements in attention (r=0.16, p=0.03), while baseline dynamic balance was associated with improvements in working memory (r=0.15, p=0.04). CONCLUSIONS: In young children, higher baseline aerobic fitness and motor skills were related to a better spatial working memory and/or attention at baseline, and to some extent also to their future improvements over the following 9 months. TRIAL REGISTRATION: clinicaltrials.gov NCT0067454

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Metacognition and self-concept: Elaborating on a construct relation in first-grade children

Self-evaluations play an important role in various fields of study, specifically in research on metacognition and self-concept. Although the assumption that self-evaluations as known from metacognitive monitoring and academic self-concept are related has received wide agreement, the nature of such a relationship has only rarely been investigated. In the current study, the individual-differences approach that has occasionally addressed this association is discussed and extended twofold. For one, a novel way to compare metacognition and self-concept is presented by computing a self-concept bias—analogous to metacognition research. For another, the study targeted a younger population, namely first-grade children. In line with previous studies, the results confirmed a weak relation between metacognitive monitoring and academic self-concept when relating the two constructs at the absolute level of confidence. However, relating the constructs by means of the respective biases revealed a more substantial association. Thus, while previous studies have assumed the common thread between metacognition and self-concept to be best explained by a general confi- dence trait, the present study suggests the accuracy of self-evaluations to be at stake instead. Hence, by introducing a method to quantify a bias in self-concept, the current study proposes a new and promising way to compare and relate the constructs of metacognition and self-concept