A Theory-Based Meta-Analysis: Stress Management Interventions for College Students

The purpose of this study was to determine the combined average effect size for the efficacy of stress management interventions in randomized controlled trials with college students. A workplace stress intervention approach guided article selection. A single instrument measured stress. The analysis was a random effects model. The literature search in the spring of 2020 yielded eight qualifying studies, published from 2014-2020. The overall effect size was statistically significant (g = ‒0.41). Especially given pandemic-related stressors, this meta-analysis could serve as a baseline for future research comparisons. It mirrored results of other meta-analyses, discussed in the literature review. No prior meta-analysis to our knowledge has employed the same approach or framework

Adaptable control for electrical generation at irregural wind speeds

The main aims of this work are the development and the validation of one generic algorithm to provide the optimal control of small power wind generators. That means up to 40 kW and blades with fixed pitch angle. This algorithm allows the development of controllers to fetch the wind generators at the desired operational point in variable operating conditions. The problems posed by the variable wind intensity are solved using the proposed algorithm. This is done with no explicit measure of the wind velocity, and so no special equipment or anemometer is required to compute or measure the wind velocity

Optimal methodology for distribution systems reconfiguration based on OPF and solved by decomposition technique

This paper presents a new and efficient methodology for distribution network reconfiguration integrated with optimal power flow (OPF) based on a Benders decomposition approach. The objective minimizes power losses, balancing load among feeders and subject to constraints: capacity limit of branches, minimum and maximum power limits of substations or distributed generators, minimum deviation of bus voltages and radial optimal operation of networks. The Generalized Benders decomposition algorithm is applied to solve the problem. The formulation can be embedded under two stages; the first one is the Master problem and is formulated as a mixed integer non-linear programming problem. This stage determines the radial topology of the distribution network. The second stage is the Slave problem and is formulated as a non-linear programming problem. This stage is used to determine the feasibility of the Master problem solution by means of an OPF and provides information to formulate the linear Benders cuts that connect both problems. The model is programmed in GAMS. The effectiveness of the proposal is demonstrated through two examples extracted from the literature

Science fairs as learning tools

Science fairs are activities well known, in different countries, for their pedagogical relevance. For that reason a 4 years study was developed to evaluate the advantages of this informal teaching method in the context of a basic school in the northwestern Portuguese seaside town of Viana do Castelo. The study included the analysis of the evolution of students that have participated in previous fairs, and also students participating in the present science fair. The motivation of the students was monitored and also the knowledge and skills’ gains achieved. This way, the relevance of this teaching modality is once more demonstrated, not only in what concern the short term, right after student participation, but also the students future attitude towards the school and their motivation to the study of science, as well as in long term knowledge and skills acquisition

The measurement of tritium in water samples with electrolytic enrichment using liquid scintillation counter

Tritium (3H) present in the environment decreased in the last decades and nowadays it has low activity concentrations. Measurement of low-level tritium activities in natural waters, e. g. in precipitation, groundwater, and river water requires special techniques for water pretreatment and detection of low-level radioactivity. In order to increase the tritium concentration to an easily measurable level, electrolytic enrichment must be applied. This paper presents the enrichment method performed by electrolysis in a battery of 18 cells, giving an enrichment factor of 5.84 (calculated from 59 electrolyses). The calculated mean values of the separation factor and enrichment parameter were 4.10 and 0.84, respectively. Results for tritium activity in precipitation and surface water collected in Belgrade during 2008 and 2009 are presented. The Radiation and Environmental Protection Department of the Vinča Institute of Nuclear Sciences, participated in the IAEA TRIC2008 international intercomparison exercise. The participation in the intercomparisons for any laboratory doing low-level 3H measurements in the waters is very important and useful. It is considered the best way to check the entire procedure and methods of the measurements and the reliability of the standard used. The analysis of the reported 3H activity results showed that all results for five intercomparison samples, for which electrolytic enrichment were applied prior to the 3H measurement, are acceptable

Bioaccumulation and Human Risk Assessment of Heavy Metals in Oreochromis niloticus and Clarias gariepinus Fish Species from the Golinga Reservoir, Ghana

The Nile tilapia (Oreochromis niloticus) and African catfish (Clarias gariepinus) from the Golinga reservoir in Northern Ghana are consumed as an  alternative source of protein. In the current study, levels of selected metals (As, Cd, Fe, Co, Cr, Cu, Mn, Mo, Ni and Pb) in the two fish species and the fish  condition were determined, and potential human health effects assessed. The metal concentrations in the edible fish muscles ranged from 0.16 mg kg−1  (Mn) to 101 mg kg−1 (Pb). The weight-length relationships showed that both fish were growing isometrically, and bioaccumulation of metals from the  reservoir was considered insignificant with bioconcentration factors below 100 except for Mn, whose value was 161 in the gills of Oreochromis niloticus.  The health risk assessment showed that Pb, Cd and As had Target Hazard Quotient values above 1 for both fish species, with that of As being as high as  19.6 for Oreochromis niloticus. The target cancer risk values for As, Cd, Cr and Pb were above the non-risk threshold of ≤10−6, indicating the risk of  cancer developing over the years due to fish consumption. The metal concentration in the fish in the reservoir should therefore be constantly monitored  and potential health risks associated with frequent consumption of the fish assessed