Abstract The effect of an acute bout of moderate treadmill walking on behavioral and neuroelectric indexes of the cognitive control of attention and applied aspects of cognition involved in ...school-based academic performance were assessed. A within-subjects design included 20 preadolescent participants (age=9.5±0.5 years; eight female) to assess exercise-induced changes in performance during a modified flanker task and the Wide Range Achievement Test 3. The resting session consisted of cognitive testing followed by a cardiorespiratory fitness assessment to determine aerobic fitness. The exercise session consisted of 20 min of walking on a motor-driven treadmill at 60% of estimated maximum heart rate followed by cognitive testing once heart rate returned to within 10% of pre-exercise levels. Results indicated an improvement in response accuracy, larger P3 amplitude, and better performance on the academic achievement test following aerobic exercise relative to the resting session. Collectively, these findings indicate that single, acute bouts of moderately-intense aerobic exercise (i.e. walking) may improve the cognitive control of attention in preadolescent children, and further support the use of moderate acute exercise as a contributing factor for increasing attention and academic performance. These data suggest that single bouts of exercise affect specific underlying processes that support cognitive health and may be necessary for effective functioning across the lifespan.
The aerodynamic design of small wind turbines for the urban setting attracts increasing interest within the scientific community, but the adoption of a proper control strategy may be just as ...important, especially in high turbulent winds, where such energy conversion devices should ideally operate. As a matter of fact, the mere rotor efficiency is meaningless unless the system has also the capability of rapidly changing its angular speed in case of a sudden variation of the wind velocity, to reach a new optimal operating condition. This work will attempt neither to develop dynamic simulation models nor to examine possible turbine control strategies, being the focus much broader, namely, the investigation of operational contexts where the peculiar inertial characteristics of wind turbines would compromise any form of robust control.
Inertial and operational data of commercially available turbines (characterized by both horizontal and vertical-axis architectures), as well as the results disseminated in various literature sources, operational experiences and design best practices, are here collected under one cover and compared, thus deriving some basic and fundamental relations between rotor inertia and angular acceleration, highlighting how, in several cases, a control strategy based on the continuous tracking of the optimal operating condition is most unlikely.
Such considerations raise the question of whether the problem of inertia renders futile many prevailing theories about small wind turbine operation and plans for implementing new control strategies, especially as far as vertical axis architectures are concerned. On the other hand, some constructive advice is also presented, in the form of a means to compare the effective performances of different turbines, in a given installation site, with respect to their nominal (i.e. steady state, or wind tunnel) behaviour. As a final result, a new bound for a reliable estimation of the amount of energy a wind turbine will generate in a specific site is suggested, based on the comparison between a representative time scale of the installation site and the response time of the candidate wind turbine.
•A critical review of the operational contexts where small wind turbines usually work is presented.•Inertial characteristics of small commercial HAWTs and VAWTs are collected under one cover.•In several cases, a control strategy based on the tracking of the optimal operating conditions appears most unlikely.•New parameters are introduced in order to account also for the inertial properties of a turbine during operation.•A new bound for a reliable estimation of the amount of energy a wind turbine will generate in a specific site is suggested.
The Courant–Friedrichs–Lewy (CFL) criterion for the stability of numerical schemes is herein investigated at the conservative interface that divides rotating grids embedded within fixed grids. This ...issue is of specific interest to correctly assess the power coefficient and the energy production of vertical-axis wind turbines (VAWTs).
The CFL number is here manipulated in a convenient form to tackle rotating grids; this manipulation discloses the dependence of the CFL number from the angular location of rotating grid elements and also from the tip speed ratio of the rotating grid. An upper bound of the CFL number that does not depend on the angular location of the rotating grid element is derived. The angular marching step has dramatic effects on the accuracy of results and strongly affects the calculation of the most important integral property (the power coefficient); however, local quantities are affected to a lesser extent and this fact is misleading. Large errors are generated if the angular marching step is too coarse or, in other words, if the CFL criterion is violated. Angular marching steps as small as only 1° do not warrant accurate results, particularly for very small tip speed ratios and fine spatial discretizations. It is found in this study that rotating grids call for a more restrictive (lower) bound (e.g., CFL number less than 0.15) as compared with the literature criterion. This restriction prompts severe limitations to obtain trustable results from numerical simulations of VAWTs.
•Conservative interfaces must fulfill the numerical CFL restriction.•Judgment based on local properties or grid sensitivity analysis is misleading.•A new CFL criterion, useful for rotating grids, is derived as CFL <0.15.•Typical marching steps must not exceed 1/15°.•This restriction is not fulfilled in most of literature investigations.
To assess the effect of a physical activity (PA) intervention on brain and behavioral indices of executive control in preadolescent children.
Two hundred twenty-one children (7-9 years) were randomly ...assigned to a 9-month afterschool PA program or a wait-list control. In addition to changes in fitness (maximal oxygen consumption), electrical activity in the brain (P3-ERP) and behavioral measures (accuracy, reaction time) of executive control were collected by using tasks that modulated attentional inhibition and cognitive flexibility.
Fitness improved more among intervention participants from pretest to posttest compared with the wait-list control (1.3 mL/kg per minute, 95% confidence interval CI: 0.3 to 2.4; d = 0.34 for group difference in pre-to-post change score). Intervention participants exhibited greater improvements from pretest to posttest in inhibition (3.2%, 95% CI: 0.0 to 6.5; d = 0.27) and cognitive flexibility (4.8%, 95% CI: 1.1 to 8.4; d = 0.35 for group difference in pre-to-post change score) compared with control. Only the intervention group increased attentional resources from pretest to posttest during tasks requiring increased inhibition (1.4 µV, 95% CI: 0.3 to 2.6; d = 0.34) and cognitive flexibility (1.5 µV, 95% CI: 0.6 to 2.5; d = 0.43). Finally, improvements in brain function on the inhibition task (r = 0.22) and performance on the flexibility task correlated with intervention attendance (r = 0.24).
The intervention enhanced cognitive performance and brain function during tasks requiring greater executive control. These findings demonstrate a causal effect of a PA program on executive control, and provide support for PA for improving childhood cognition and brain health.
We investigated the relationship between age, aerobic fitness, and cognitive function by comparing high- and low-fit preadolescent children and adults.
Twenty-four children (mean age = 9.6 yr) and 27 ...adults (mean age = 19.3 yr) were grouped according to their fitness (high, low) such that four approximately equal groups were compared. Fitness was assessed using the Fitnessgram test, and cognitive function was measured by neuroelectric and behavioral responses to a stimulus discrimination task.
Adults exhibited greater P3 amplitude at Cz and Pz sites, and decreased amplitude at the Oz site compared with children. High-fit children had greater P3 amplitude compared with low-fit children and high- and low-fit adults. Further, adults had faster P3 latency compared with children, and high-fit participants had faster P3 latency compared with low-fit participants at the Oz site. Adults exhibited faster reaction time than children; however, fitness interacted with age such that high-fit children had faster reaction time than low-fit children.
These findings suggest that fitness was positively associated with neuroelectric indices of attention and working memory, and response speed in children. Fitness was also associated with cognitive processing speed, but these findings were not age-specific. These data indicate that fitness may be related to better cognitive functioning in preadolescents and have implications for increasing cognitive health in children and adults.
The global epidemic of childhood obesity has become a major public health concern. Yet, evidence regarding the association between childhood obesity and cognitive health has remained scarce. This ...study examined the relationship between obesity and cognitive control using neuroelectric and behavioral measures of action monitoring in preadolescent children. Healthy weight and obese children performed compatible and incompatible stimulus-response conditions of a modified flanker task, while task performance and the error-related negativity (ERN) were assessed. Analyses revealed that obese children exhibited a longer reaction time (RT) relative to healthy weight children for the incompatible condition, whereas no such difference was observed for the compatible condition. Further, obese children had smaller ERN amplitude relative to healthy weight children with lower post-error response accuracy. In addition, healthy weight children maintained post-error response accuracy between the compatible and incompatible conditions with decreased ERN amplitude in the incompatible condition, whereas obese children exhibited lower post-error response accuracy for the incompatible relative to the compatible condition with no change in ERN amplitude between the compatibility conditions. These results suggest that childhood obesity is associated with a decreased ability to modulate the cognitive control network, involving the prefrontal cortex and anterior cingulate cortex, which supports action monitoring.
Most of the experimental research on vertical axis wind turbines was carried out during 1970–1980s but, recently, the potential of wind energy harvesting in new environments has renewed the interest ...on VAWT technology. Unfortunately, this interest still collides with an immaturity of aerodynamic modelling tools and detailed experimental analyses are now highly recommended to convert flow field comprehension into novel design techniques.
This paper critically revises the main extensive wind tunnel campaigns conducted on VAWTs during the last 15 years. Moreover, a direct comparison between two widely adopted lift-driven rotor architectures, i.e. H-shaped and troposkien, characterized by the same swept area and blade section, is presented. After being instrumented to characterize aerodynamic performance and thrust as well as flow characteristics in the wake, the rotors were tested in the Politecnico di Milano wind tunnel using an open configuration, allowing real-scale measurements of micro wind turbines. A complete characterization was obtained by recording steady-state torque, thrust and flow velocity in the wake as a function of the unperturbed wind speed, while the angular velocity of the rotors was kept constant. The measurements were conducted with high accuracy and can represent a useful experimental benchmark for the validation of computational tools.
•A critical review of the main extensive wind tunnel campaigns conducted on VAWTs is presented.•Real scale open wind tunnel measurements are proposed in full similarity conditions.•An extensive experimental campaign is presented for a both a H-shaped Darrieus rotor and a troposkien one.•A complete set of benchmark data is provided for numerical modellers.•Rotor torque and thrust are measured, as well as velocity and turbulence distributions downstream of the rotors.
Ventral tegmental area dopamine neurons control reward-driven learning, and their dysregulation can lead to psychiatric disorders. Tonic and phasic activity of these dopaminergic neurons depends on ...cholinergic tone and activation of nicotinic acetylcholine receptors (nAChRs), particularly those containing the β2 subunit (β2*-nAChRs). Nuclear peroxisome proliferator-activated receptors type-α (PPARα) tonically regulate β2*-nAChRs and thereby control dopamine neuron firing activity. However, it is unknown how and when PPARα endogenous ligands are synthesized by dopamine cells. Using ex vivo and in vivo electrophysiological techniques combined with biochemical and behavioral analysis, we show that activation of α7-nAChRs increases in the rat VTA both the tyrosine phosphorylation of the β2 subunit of nAChRs and the levels of two PPARα endogenous ligands in a Ca(2+)-dependent manner. Accordingly, in vivo production of endogenous PPARα ligands, triggered by α7-nAChR activation, blocks in rats nicotine-induced increased firing activity of dopamine neurons and displays antidepressant-like properties. These data demonstrate that endogenous PPARα ligands are effectors of α7-nAChRs and that their neuromodulatory properties depend on phosphorylation of β2*-nAChRs on VTA dopamine cells. This reveals an autoinhibitory mechanism aimed at reducing dopamine cell overexcitation engaged during hypercholinergic drive. Our results unveil important physiological functions of nAChR/PPARα signaling in dopamine neurons and how behavioral output can change after modifications of this signaling pathway. Overall, the present study suggests PPARα as new therapeutic targets for disorders associated with unbalanced dopamine-acetylcholine systems.
Maternal infections during pregnancy may increase the risk of psychiatric disorders in offspring. We recently demonstrated that activation of peroxisome proliferator-activate receptor-α (PPARα), with ...the clinically available agonist fenofibrate (FEN), attenuates the neurodevelopmental disturbances induced by maternal immune activation (MIA) in rat offspring. We hypothesized that fenofibrate might reduce MIA-induced cytokine imbalance using a MIA model based on the viral mimetic polyriboinosinic-polyribocytidilic acid poly (I:C). By using the Bio-Plex Multiplex-Immunoassay-System, we measured cytokine/chemokine/growth factor levels in maternal serum and in the fetal brain of rats treated with fenofibrate, at 6 and 24 h after poly (I:C). We found that MIA induced time-dependent changes in the levels of several cytokines/chemokines/colony-stimulating factors (CSFs). Specifically, the maternal serum of the poly (I:C)/control (CTRL) group showed increased levels of (i) proinflammatory chemokine macrophage inflammatory protein 1-alpha (MIP-1α), (ii) tumor necrosis factor-alpha (TNF-α), the monocyte chemoattractant protein-1 (MCP-1), the macrophage (M-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF). Conversely, in the fetal brain of the poly (I:C)/CTRL group, interleukin 12p70 and MIP-1α levels were lower than in vehicle (veh)/CTRL group. Notably, MIP-1α, TNF-α, keratinocyte derived chemokine (GRO/KC), GM-CSF, and M-CSF levels were lower in the poly (I:C)/FEN than in poly (I:C)/CTRL rats, suggesting the protective role of the PPARα agonist. PPARα might represent a therapeutic target to attenuate MIA-induced inflammation.
Aging is a progressive physiological degeneration associated with a decline in chemosensory processes and cognitive abilities and a reduction in synaptic plasticity. The biological bases of ageing ...are still not completely understood, and many theories have been proposed. This study aimed to evaluate the occurrence of age-related changes affecting the chemosensory function (gustatory and olfactory) and general cognitive abilities and their potential associations in women. To this aim, 319 women (the age ranging from 18 to 92 years) were recruited and divided into four different age groups: 18–34 years, 35–49 years, 50–64 years, and ≥65 years. Our results confirmed that in women, gustatory, olfactory, and cognitive functions decline, though in a different manner during aging. Olfactory and cognitive function showed a slight decline along the first three age classes, with a dramatic decrease after age 65 years, while gustatory function decreased more gradually. Olfactory and gustatory deficits may have a high degree of predictivity for general cognitive function as well as for specific cognitive subdomains such as visuospatial/executive abilities, language, memory, and attention. Our study highlighted the importance of using chemosensory assessments for the early diagnosis of cognitive decline and for the development of appropriate personalized risk prevention strategies.
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