Effects of Parental Depressive Symptoms on Child Adjustment Moderated by Hypothalamic Pituitary Adrenal Activity: Within‐ and Between‐Family Risk

Child hypothalamic pituitary adrenal (HPA) activity was investigated as a moderator of parental depressive symptom effects on child behavior in an adoption sample (n = 210 families). Adoptive parents' depressive symptoms and child internalizing and externalizing were assessed at 18, 27, and 54 months, and child morning and evening HPA activity measured through salivary cortisol at 54 months. Children's daily cortisol levels and day‐to‐day variability were tested as moderators of longitudinal associations between parent and child symptoms at within‐ and between‐family levels. Mothers' symptoms related directly to child internalizing, but child evening cortisol moderated effects of fathers' symptoms on internalizing, and of both parents' symptoms on externalizing. Different paths of within‐family risk dynamics versus between‐family risk synergy were found for internalizing versus externalizing outcomes.     

Improving high school students' understanding of potential difference in simple electric circuits

This paper reports two studies into the understanding of the concept of potential difference in the current-potential difference-resistance context among 8th-12th graders (Study 1), and the efficiency of a learning device derived from Social Judgment Theory (Study 2). These two studies showed that: (a) when asked to infer potential difference from resistance and current information, most participants only relied on current and ignored or greatly underestimated the importance of resistance information; (b) exposure to an electricity course did not much alter the way participants infer potential difference from resistance and current information; (c) a simple learning device considerably improved the way participants infer potential difference from resistance and current information; and (d) this observed improvement promised to be durable, at least in the short term.     

Trajectory tracking for a quadrotor under wind perturbations: sliding mode control with state-dependent gains

The problem of position tracking of a mini drone subject to wind perturbations is investigated. The solution is based on a detailed unmanned aerial vehicle (UAV) model, with aerodynamic coefficients and external disturbance components, which is introduced in order to better represent the impact of the wind field. Then, upper bounds of wind-induced disturbances are characterized, which allow a sliding mode control (SMC) technique to be applied with guaranteed convergence properties. The peculiarity of the considered case is that the disturbance upper bounds depend on the control amplitude itself (i.e. the system is nonlinear in control), which leads to a new procedure for the control tuning presented in the paper. The last part of the paper is dedicated to the analysis and reduction of chattering effects, as well as investigation of rotor dynamics issues. Conventional SMC with constant gains, proposed first order SMC, and proposed quasi-continuous SMC are compared. Nonlinear UAV simulator, validated through in-door experiments, is used to demonstrate the effectiveness of the proposed controls.     

Impact of the choice of threshold on physical activity patterns in free living conditions among adolescents measured using a uniaxial accelerometer: The HELENA study

Abstract

The aim of this study was to assess the impact of the choice of threshold on physical activity patterns measured in adolescents under free living conditions (FLC) using a uniaxial accelerometer. The study comprised 2043 adolescents (12.5–17.5 years) participating in the HELENA Study. Participants wore a uniaxial accelerometer for 7 days. The PA patterns were assessed using thresholds determined from six different studies. For each of the thresholds used, the number of adolescents fulfilling the recommendation of 60 min of moderate to vigorous PA (MVPA) per day was also calculated. A significant difference was found between thresholds regardless of the activity level: differences of 38%, 207%, 136%, and 2780% for sedentary, light, moderate, and vigorous intensity PA, respectively (P < 0.001). Time of MVPA varied between methods from 25.3 to 55.2 min · day^–1. The number of adolescents fulfilling the recommendation varied from 5.9% to 37% according to the thresholds used. The kappa coefficient for concordance in the assessment of the number of adolescents achieving the PA recommendations was generally low. The definition of the threshold for PA intensity may considerably affect the PA patterns in FLC when assessed using a uniaxial accelerometer and the number of participants fulfilling the recommendations.     

High school students' understanding of resistance in simple series electric circuits

In view of the lack of work on the understanding of resistance concept, we studied the understanding that high school students (from the eighth to the twelfth grades) were able to develop with regard to the interrelationships between this concept, and the potential difference and current concepts (Ohm's law). In addition, we explored the immediate effects of exposure to electricity courses on the intuitive mastery of these relationships. The participants were presented with information on potential difference and intensity of current and asked to predict the corresponding resistance values. In this current-potential difference context, the resistance concept was difficult to understand. For the majority of participants, resistance was a direct function of both current and potential difference, which is more reminiscent of the concept of power than of the concept of resistance. The systematic teaching of electricity concepts and Ohm's law had only limited, positive as well as negative, effects on the understanding of these relationships. The implications for education are discussed.     

Situated trajectories of learning in vocational training interactions

This paper investigates smaller-scale transitions that are part of the longer-term processes of subjective transformation and adaptation to new professional competencies for learners in the field of vocational education. On the conceptual level, it proposes to view transitions as intermediate states in situated trajectories of learning. The notion of trajectory aims to capture that (a) learning occurs through situated and highly contextualized micro activities and (b) that these activities occur within historical sequences of events, which come to form over time dynamic trajectories. The ingredients constitutive of a trajectory of learning are first defined. The notions presented are next applied to the empirical analysis of one sequence of learning, in which we show the transitions undergone by one object of knowledge as it is being taught to different apprentices in a workshop. On the theoretical plane, the paper thus proposes to view transitions as microdynamics of change. On the methodological plane, it contributes to identifying possible empirical sources and methodological frames to study micro-transitional phenomena.     

Screening the active constituents of Chinese medicinal herbs as potent inhibitors of Cdc25 tyrosine phosphatase, an activator of the mitosis-inducing p34cdc2 kinase

Objective: To screen and evaluate the active constituents of Chinese medicinal herbs as potent inhibitors of Cdc25 phosphatase. Methods: The affinity chromatography purified glutashione-S-transferase/Cdc25A phosphatase fusion protein and Cdc2/cyclin B from the extracts of starfish M phase oocytes are used as the cell cycle-specific targets for screening the antimitotic constituents. We tested 9 extracts isolated from the Chinese medicinal herbs and vegetables including the agents currently used in cancer treatment by measuring the inhibition of Cdc25A phosphatase and Cdc2 kinase activity. The antitumor activity of the extracts was also evaluated by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay and flow cytometry. Results: Cdc25A inhibitory activity and antitumor activity are detected in the extracts isolated from three Chinese medicinal herbs Agrimona pilosa; Herba solani lyrati; Galla chinesis. Conclusion: We found three extracts isolated from Chinese medicinal herbs have potential inhibitory activity of Cdc25 phosphatase using a highly specific mechanism-based screen assay for antimitotic drug discovery.