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Wake modes of a three-dimensional blunt-based body near a wall are investigated at a Reynolds number
. The targeted modes are the static symmetry-breaking mode and two antisymmetric periodic modes. The static mode orientation is aligned with the horizontal major
-axis of the base and randomly switches between a positive
and a negative
state leading to long-time bistable dynamics of the turbulent wake. The modifications of these modes are studied when continuous blowing is applied at different locations through four slits along the base edges (denoted L for left, R for right, T for top and B for bottom) in either four single asymmetric configurations or two double symmetric configurations (denoted LR and TB). Two regimes, referred to as mass and momentum, are clearly identifiable for all configurations. The mass regime, which is fairly insensitive to blowing momentum and location, is characterized by the growth of the recirculating bubble as the total injected flow rate is increased, and is associated with a base drag reduction and interpreted as resulting from the equilibrium between mass fluxes feeding and emptying the recirculating region. A simple budget model is shown to be in agreement with entrainment velocities measured for isolated turbulent mixing layers. The strength of the static mode is reduced up to 20 % when the bubble length is maximum, whereas no change in the periodic mode frequencies is found. On the other hand, the momentum regime is characterized by the deflating of the recirculating bubble, leading to base drag increase, and it is interpreted by the free shear layer forcing, which increases the entrainment velocity, thus emptying the recirculating bubble. In this regime the static mode orientation is imposed by the blowing symmetry. Lateral L and R (respectively top/bottom T and B) blowing configurations select
states in the horizontal (respectively vertical) direction, while bistable dynamics persists for the symmetric LR and TB configurations. The shape of periodic modes follows the changes in wake static orientation. The transition between the two regimes is governed by both the total injected flow rate and the location of the injection.
Predation by Engytatus varians (Distant) adults on different development stages of the prey species Bactericera cockerelli (Sulcer) (egg, second, and third nymphal instars), Spodoptera exigua (Hübner) and Spodoptera frugiperda (J. E. Smith) (egg, first, and second larval instars) was evaluated using tomato (Solanum lycopersicum L.) leaflets or plants. These insects are the primary pest of several agriculturally important crops. The influence of E. varians age on the predation capacity was also analysed. Engytatus varians females consumed significantly more B. cockerelli eggs and nymphs than males. Additionally, female predators consumed significantly more second than third instar prey at two predator ages, while males consumed significantly more the second instar than third instar prey at all predator ages. In most of the cases, females also consumed significantly more S. exigua and S. frugiperda eggs than males; however, in terms of larvae consumption, this difference was observed only in some predator ages. Females consumed more the first than second instar S. exigua than males, whereas this behaviour was only observed in males when the predators were 15 and 17 days old. No significant differences were observed in the consumption of first and second instar of S. frugiperda for both sexes of the predators. Predator age did not cause any systematic effects on the predation rates of any prey species. Based on these results, we confirmed that E. varians has potential as a biological control agent for B. cockerelli and also for the Spodoptera species bioassayed.
Here we report the results of an experimental study where we measure the hydrodynamic force acting on a plate which is lifted from a water surface, suddenly starting to move upwards with an acceleration much larger than gravity. Our work focuses on the early stage of the plate motion, when the hydrodynamic suction forces due to the liquid inertia are the most relevant ones. Besides the force, we measure as well the acceleration at the centre of the plate and the time evolution of the wetted area. The results of this study show that, at very early stages, the hydrodynamic force can be estimated by a simple extension of the linear exit theory by Korobkin (J. Fluid Mech., vol. 737, 2013, pp. 368–386), which incorporates an added mass to the body dynamics. However, at longer times, the measured acceleration decays even though the applied external force continues to increase. Moreover, high-speed recordings of the disc displacement and the radius of the wetted area reveal that the latter does not change before the disc acceleration reaches its maximum value. We show in this paper that these phenomena are caused by the elastic deflection of the disc during the initial transient stage of water exit. We present a linearised model of water exit that accounts for the elastic behaviour of the lifted body. The results obtained with this new model agree fairly well with the experimental results.
African American youths are overrepresented in the American juvenile justice system relative to Caucasians. Yet, research on antisocial behaviors (ASB) has focused on predominantly Caucasian populations. Furthermore, relatively little is known about how environmental factors, such as supportive parenting (e.g., how close adolescents feel to their parent) and school connectedness (e.g., how supported adolescents feel at school), affect trajectories of ASB in Caucasians versus African Americans. This study mapped developmental trajectories of ASB in Caucasians (n = 10,764) and African Americans (n = 4,091) separately, using four waves of data from the National Longitudinal Study of Adolescent to Adult Health. We then examined supportive parenting and school connectedness on the trajectories of ASB. Four trajectories of ASB were identified for both Caucasians and African Americans: negligible, adolescence-peaked, low-persistence, and high-persistence ASB, although prevalence rates differed by racial-ethnic status. Supportive parenting reduced the risk of membership into the adolescence-peaked trajectory for both Caucasians and African Americans. However, school connectedness was less protective for African Americans than for Caucasians because it only predicted a lower risk of adolescence-peaked membership for African Americans. Findings may reflect the complex social dynamics between race and schools in the development of ASB.
The present study examined the association between high-quality diet (using the Mediterranean diet (MD) as an example) and well-being cross-sectionally and prospectively in Spanish children and adolescents. Participants included 533 children and 987 adolescents at baseline and 527 children and 798 adolescents at 2-year follow-up, included in the UP&DOWN study (follow-up in schoolchildren and adolescents with and without Down’s syndrome). The present study excluded participants with Down’s syndrome. Adherence to an MD was assessed using the KIDMED index. Well-being was measured using the Positive and Negative Affect Schedule and the KIDSCREEN-10 questionnaire. Associations between MD adherence and well-being were assessed using multi-level, mixed-effects linear regression. At baseline, MD adherence was positively related to health-related quality of life in secondary school girls and boys (β=0·41, se 0·10, P<0·001; β=0·46, se 0·10, P<0·001, respectively) and to positive affect in secondary school girls and boys (β=0·16, se 0·05, P=0·006; β=0·20, se 0·05, P<0·001, respectively) and in primary school boys (β=0·20, se 0·08, P=0·019). At 2-year follow-up, MD adherence was negatively related to negative affect in secondary school adolescent girls and boys (β=–0·15, se 0·07, P=0·047; β=–0·16, se 0·06, P=0·019, respectively), and MD adherence was associated with higher positive affect scores in secondary school girls (β=0·30, se 0·06, P<0·001) and in primary school boys (β=0·20, se 0·09, P=0·023). However, MD adherence at baseline did not predict well-being indicators at 2-year follow-up. In conclusion, higher MD adherence was found to behave as a protective factor for positive well-being in cross-sectional analysis.
The Asian chestnut gall wasp, Dryocosmus kuriphilus, is an invasive pest causing significant damage to chestnut trees (Castanea spp., Fagaceae). Originating from China, it has recently invaded a wide range of regions in Europe and North America. Understanding the population genetic structure of important invasive pests is very useful for improving the knowledge concerning routes of expansion and colonizing capacity. Despite its economic importance, limited attention has been given to D. kuriphilus origin and spread, or to its genetic structure. In this study, D. kuriphilus populations sampled in eight European countries were screened using both mitochondrial (cytochrome c oxidase subunit 1; COI) and nuclear (internal transcribed spacer 2; ITS2) sequences, and Amplified Fragment Length Polymorphism (AFLP) markers. The molecular markers COI and ITS2 highlighted the presence of a single haplotype in all the studied populations. The recorded mitochondrial haplotype was identical to one of the most widespread haplotypes occurring in the native area (China). AFLP results indicated that D. kuriphilus individuals belong to two genetically distinct clusters without any further geographic clustering. These results suggest that D. kuriphilus populations in Europe could be the result of a single introduction of a Chinese founder population characterized by two genetically distinct lineages that subsequently spread rapidly across Europe. However, the possibility that populations originated from multiple introductions of the same Chinese mitochondrial haplotype cannot be excluded. The reported results provide useful information concerning this invasive species, potentially facilitating integrated pest management.
For more than 60 years, Colombia experienced an armed conflict involving government forces, guerrillas, and other illegal armed groups. Violence, including torture and massacres, has caused displacement of entire rural communities to urban areas. Lack of information on the problems displaced communities face and on their perceptions on potential solutions to these problems may prevent programs from delivering appropriate services to these communities. This study explores the problems of Afro-Colombian survivors from two major cities in Colombia; the activities they do to take care of themselves, their families, and their community; and possible solutions to these problems.
This was a qualitative, interview-based study conducted in Quibdó and Buenaventura (Colombia). Free-list interviews and focus groups explored the problems of survivors and the activities they do to take care of themselves, their families, and their community. Key-informant interviews explored details of the identified mental health problems and possible solutions.
In Buenaventura, 24 free-list interviews, one focus group, and 17 key-informant interviews were completed. In Quibdó, 29 free-list interviews, one focus group, and 15 key-informant interviews were completed. Mental health problems identified included: (1) problems related to exposure to torture/violent events; (2) problems with adaptation to the new social context; and (3) problems related to current poverty, lack of employment, and ongoing violence. These problems were similar to trauma symptoms and features of depression and anxiety, as described in other populations. Solutions included psychological help, talking to friends/family, relying on God’s help, and getting trained in different task or jobs.
Afro-Colombian survivors of torture and violence described mental health problems similar to those of other trauma-affected populations. These results suggest that existing interventions that address trauma-related symptoms and current ongoing stressors may be appropriate for improving the mental health of survivors in this population.
Santaella-TenorioJ, Bonilla-EscobarFJ, Nieto-GilL, Fandiño-LosadaA, Gutiérrez-MartínezMI, BassJ, BoltonP. Mental Health and Psychosocial Problems and Needs of Violence Survivors in the Colombian Pacific Coast: A Qualitative Study in Buenaventura and Quibdó. Prehosp Disaster Med. 2018;33(6):567–574.
Pathological worry is a hallmark feature of generalised anxiety disorder (GAD), associated with dysfunctional emotional processing. The ventromedial prefrontal cortex (vmPFC) is involved in the regulation of such processes, but the link between vmPFC emotional responses and pathological v. adaptive worry has not yet been examined.
To study the association between worry and vmPFC activity evoked by the processing of learned safety and threat signals.
In total, 27 unmedicated patients with GAD and 56 healthy controls (HC) underwent a differential fear conditioning paradigm during functional magnetic resonance imaging.
Compared to HC, the GAD group demonstrated reduced vmPFC activation to safety signals and no safety–threat processing differentiation. This response was positively correlated with worry severity in GAD, whereas the same variables showed a negative and weak correlation in HC.
Poor vmPFC safety–threat differentiation might characterise GAD, and its distinctive association with GAD worries suggests a neural-based qualitative difference between healthy and pathological worries.