Cortisol Reactivity to Social Stress as a Mediator of Early Adversity on Risk and Adaptive Outcomes

Children chronically exposed to stress early in life are at increased risk for maladaptive outcomes, though the physiological mechanisms driving these effects are unknown. Cortisol reactivity was tested as a mediator of the relation between prenatal substance exposure and/or early adversity on adaptive and maladaptive outcomes. Data were drawn from a prospective longitudinal study of prenatal substance exposure (N = 860). Cortisol reactivity was assessed at age 11. Among African Americans, prenatal substance exposure exerted an indirect effect through early adversity and cortisol reactivity to predict externalizing behavior, delinquency, and a positive student–teacher relationship at age 11. Decreased cortisol reactivity was related to maladaptive outcomes, and increased cortisol reactivity predicted better executive functioning and a more positive student–teacher relationship.     

The Hit & Turn Tennis Test: an acoustically controlled endurance test for tennis players

This study was conducted to validate and evaluate the "Hit & Turn Tennis Test", an acoustically progressive on-court endurance test for tennis players. Ninety-eight competitive tennis players (53 males, 45 females) of different age groups participated in the study. For validation, the adult male players completed three Hit & Turn tests, one on a clay court and two on a carpet surface, a tennis-specific ball machine test and an incremental treadmill run in a randomized order. A stronger correlation between maximal performance (r = 0.81, P < 0.01) and maximal oxygen uptake (r = 0.96, P < 0.01) was observed between the Hit & Turn test and the ball machine test, than between the Hit & Turn test and the treadmill test. For test-retest, we found a significant correlation between maximal performance on the same (r = 0.83, P < 0.01) and on different surfaces (r = 0.74, P < 0.01). During test evaluation, maximal performance was higher in males than in females (P < 0.01) and increased by consecutive age group in boys (P < 0.01) but not in girls (P = 0.97). In conclusion, Hit & Turn maximum test performance can be recommended as a valid and reliable indicator for tennis-specific endurance.     

Towards the use of multidimensional performance indicators in football small-sided games: the effects of pitch orientation

This study aimed to compare youth football players’ performance during two small-sided games with different pitch orientation: i) 40x30m and ii) 30x40m formats. Twenty under-15 players (age = 14.1 ± 0.5 years) participated in nine GK+4vs4+GK situations in each format, with the duration of six minutes each. Positional data were collected using individual GPS units, and computed for tactical and physical performance indicators. The SSG were video recorded, using notational analysis for collecting technical indicators. A novel method that incorporates time dependent notational information with spatiotemporal data was used to compute multidimensional parameters. Standardised effect sizes and non-clinical magnitude-based inferences were used to compare formats. Results showed that players covered more distance at higher intensities, presented more passes and dribbles and were more synchronised in the longitudinal axis while playing in the 40x30m pitch. In the 30x40m pitch, results showed a lower distance between team centroids, higher number of shots, more lateral passes and a wider team positioning. Multidimensional indicators, as players position and distance to the closest defender while shooting, revealed a more constant distance between attacker and defender in the 40x30m pitch. These results highlight the importance of integrating information from different indicators for a contextually valid information.     

The Macro and Micro Scale of Open Access Predation

Having found a business opportunity in exploiting the open access publishing model, predatory journals and publishers have been spamming authors with emails, inviting them to submit articles for publication. Authors may be misled by the names of prestigious authors and editors that predatory journals and publishers use to advertise their publishing services, either by claims that those scientists serve on the editorial boards or by sending invitations in their names. Given the fact that detailed knowledge of a journal is required to make an informed decision of whether the inviting journal is predatory or not, junior scientists are not likely to possess the knowledge or skill to make such decisions. In addition, analysis of the details of new suspicious journals and publishers can be a lengthy process or even a waste of time. Therefore, in this paper, we provide an analysis of a likely scenario that many authors are facing nowadays when they take on the difficult task of studying the details of suspicious journals as possible venues for the publication of their research findings. The analysis takes the form of an analysis of the Kenkyu Publishing Group, which is listed on Jeffrey Beall’s list of “predatory” open access publishers.     

Dissipative observers for discrete-time nonlinear systems

This paper addresses the problem of designing a state observer for a class of nonlinear discrete-time systems using the dissipativity theory. We show that the dissipative observation methodology, originally proposed by one of the authors for continuous-time nonlinear systems, can be extended to the discrete-time case. For constructing a convergent observer, the methodology is applied to the nonlinear estimation error dynamics, which is decomposed into a discrete-time Linear Time-Invariant (LTI) subsystem in the forward loop, connected to a time-varying static nonlinearity in the feedback loop. In order to assure asymptotic stability of the closed-loop, complementary dissipativity conditions are imposed on each of the subsystems: (i) the static nonlinearity is required to be dissipative with respect to a quadratic supply rate, and (ii) the observer gains are designed such that the LTI system is dissipative with respect to a complementary supply rate. As in the continuous time framework, the proposed method includes as special cases, unifies and generalizes some observer design methods proposed previously in the literature. A great advantage of the Dissipative Observer Design Method proposed here is that it leads to Matrix Inequalities for the design of the observer gains, and these can be usually converted into Linear Matrix Inequalities (LMI’s). The results are illustrated using Chua’s Chaotic system.     

Learning to live together on a small planet

International understanding, once a humanitarian virtue, is now a dramatic, urgent necessity: the interdependence of the different regions and countries of the world and the strain on limited resources are such that without understanding leading to co-operation there will be disaster. The following article by Lester Brown, head of the Worldwatch Institute, should serve to remind our readers that unless we all become educated to the grave problems facing humanity, the technical skills and general knowledge imparted by our shool and university systems may well become superfluous. [Ed.]D. C.-based non-profit research organization created to analyse and to focus attention on global problems. Author of In the Human Interestand The Twenty Ninth Day: Accommodating Human Needs and Numbers to the Earth's Resources.