Direct iminization of PEEK

Semi-crystalline poly(ether ketone)s are important high-temperature engineering thermoplastics, but are difficult to characterize at the molecular level because of their insolubility in conventional organic solvents. Here we report that polymers of this type, including PEEK, react cleanly at high temperatures with low-volatility aralkyl amines to afford stable, noncrystalline poly(ether-imine)s, which are readily soluble in solvents such as chloroform, THF and DMF and so characterizable by conventional size-exclusion chromatography

Impacts de l’intensification agricole et de la structure du paysage sur les relations tri – trophiques entre un oiseau hôte, des mouches ectoparasites et leur parasitoïdes

L’intensification des pratiques agricoles a été identifiée comme cause majeure du déclin de la biodiversité. Plusieurs études ont documenté l’impact de la fragmentation du paysage naturel et de l’agriculture intensive sur la diversité des espèces, mais très peu ont quantifié le lien entre la structure du paysage et les interactions trophiques, ainsi que les mécanismes d’adaptation des organismes. J’ai étudié un modèle biologique à trois niveaux trophiques composé d’un oiseau hôte, l’hirondelle bicolore Tachycineta bicolor, de mouches ectoparasites du genre Protocalliphora et de guêpes parasitoïdes du genre Nasonia, au travers d’un gradient d’intensification agricole dans le sud du Québec. Le premier objectif était de déterminer l’abondance des espèces de mouches ectoparasites et de leurs guêpes parasitoïdes qui colonisent les nids d’hirondelles dans la zone d’étude. La prévalence de nids infectés par Protocalliphora spp. était de 70,8% en 2008 et 34,6% en 2009. Le pourcentage de nids comprenant des pupes de Protocalliphora parasitées par Nasonia spp. était de 85,3% en 2008 et 67,2% en 2009. Trois espèces de Protocalliphora ont été observées (P. sialia, P. bennetti et P. metallica) ainsi que deux espèces de Nasonia (N. vitripennis et N. giraulti). Il s’agit d’une première mention de P. bennetti et de N. giraulti dans la province de Québec. Mon deuxième objectif était d’évaluer l’impact de l’intensification agricole et de la structure du paysage sur les relations tri-trophiques entre les organismes à l’étude. Les résultats révèlent que les réponses à la structure du paysage de l’hirondelle, de l’ectoparasite et de l’hyperparasite dépendantent de l’échelle spatiale. L’échelle spatiale fonctionnelle à laquelle les espèces répondent le plus varie selon le paramètre du paysage modélisé. Les analyses démontrent que l’intensification des pratiques agricoles entraîne une diminution des populations d’oiseaux, d’ectoparasites et d’hyperparasites. De plus, les populations de Protocalliphora et de Nasonia sont menacées en paysage intensif puisque la dégradation du paysage associée à l’intensification des pratiques agricoles agit directement sur leurs populations et indirectement sur les populations de leurs hôtes. Mon troisième objectif était de caractériser les mécanismes comportementaux permettant aux guêpes de composer avec la variabilité de la structure du paysage et de la qualité des hôtes. Nos résultats révèlent que les femelles Nasonia ajustent la taille de leur ponte en fonction de la taille de la pupe hôte et de l’incidence d’hyperparasitisme. Le seul facteur ayant une influence déterminante sur le ratio sexuel est la proportion de paysage dédié à l’agriculture intensive. Aucune relation n’a été observée entre la structure du paysage et la taille des filles et des fils produits par les femelles Nasonia fondatrices. Ce phénomène est attribué aux comportements d’ajustement de la taille de la ponte et du ratio sexuel. En ajustant ces derniers, minimisant ainsi la compétition entre les membres de leur progéniture, les femelles fondatrices sont capables de maximiser la relation entre la disponibilité des ressources et la valeur sélective de leur progéniture. En conclusion, ce travail souligne l’importance de considérer le contexte spatial des interactions trophiques, puisqu’elles influencent la biodiversité locale et le fonctionnement de l’écosystème.Landscape fragmentation and homogenization are considered to be the main causes of the worldwide decline in biological diversity. The degradation of habitat quality is mainly caused by the expansion and intensification of human land-use activities, primarily for agricultural purposes. Many studies documented the impact of landscape fragmentation and agricultural intensification on the overall fitness of animals across various taxa, but few works have studied this phenomenon in relation to trophic interactions. Here, we investigated the effects of landscape structure on the tri-trophic interactions between a bird host (the Tree Swallow Tachycineta bicolor (Vieillot)), its blowfly ectoparasites (Protocalliphora Hough), and their parasitoid wasps (Nasonia Walker) along a gradient of agricultural intensification covering 10, 200 km2 in southern Québec, Canada. The first objective was to describe the assemblages of Protocalliphora and Nasonia species found in Tree Swallow nests within our system. The prevalence of nest infestation by Protocalliphora was of 70.8% in 2008 and 34.6% in 2009. The percentage of nests containing Protocalliphora pupae parasitized by Nasonia spp. was of 85.3 % in 2008 and 67.2% in 2009. Three species of Protocalliphora were collected (P. sialia, P. bennetti and P. metallica) and two species of Nasonia (N. vitripennis and N. giraulti). Secondly, I evaluated the impact of landscape structure and agricultural intensification on the number of Tree Swallow fledglings, number of Protocalliphora per nest and the level of hyperparasitism by Nasonia. Our results revealed that organisms from different trophic levels perceived the landscape at distinctive spatial extents. This perception, however, differed based on whether the proportions of intensive or extensive culture in the landscape were considered. Furthermore, the number of Tree Swallow fledglings, the abundance of P. sialia and the level of hyperparasitism by N. vitripennis all decreased with an increase in the proportion of intensive culture in the landscape. Protocalliphora and Nasonia were more susceptible to extinction within highly intensive landscapes as they are confronted with both the direct effect of habitat degradation on their populations and the indirect effect of habitat degradation on their host populations. The last objective was to investigate how parasitoid wasps respond to environmental variability. We showed that the size of the P. sialia pupae hosts decreased in more intensive landscapes. Wasps clutch size was shown to increase within increasing host size and the sex ratio of offspring produced by N. vitripennis became more male biased as the proportion of intensive culture increased in the landscape. In addition, both female and male size was influenced by resource availability (size of host and number of competitors). Our data indicate that by producing smaller male biased clutches in the smaller hosts within intensive landscapes, females were able to respond to poor environments and maximize the size of their offspring. To conclude, this work highlights the importance of considering the landscape context of trophic interactions, as these interactions dictate local biodiversity and ecosystem function

Characterizing and Predicting Canadian Adolescents’ Internalizing Symptoms In The First Year Of The COVID-19 Pandemic

To date, most longitudinal studies of adolescents’ internalizing symptoms during the COVID-19 pandemic include few time points, limiting knowledge about the long-term course of adolescents’ mental health during the pandemic. Moreover, examining intraindividual variability in symptoms, which may have important implications for adolescents’ adjustment beyond mean or “typical” symptoms, requires multiple time points. We examined the course of internalizing symptoms in 271 Ontario adolescents (mean n = 193 across time points) during the first year of the pandemic (March 2020–April 2021) via mixed-effect location scale models, drawing upon established internalizing symptom risk factors as predictors of mean trends and intraindividual variability. Adolescents’ internalizing symptoms were relatively stable and generally low over the first year of the pandemic, with severity peaking in February and April 2021. Girls showed more symptoms on average and greater intraindividual variability in symptoms. Parents’ depressive symptoms predicted intraindividual variability in adolescents’ anxious and depressive symptoms. Adolescents’ symptoms were stable and generally below clinical cutoffs. However, female adolescents and those whose parents experienced more depressive symptoms were most vulnerable to the stress of the pandemic. Implications for intervention and prevention efforts are discussed

Maternal Depression, Child Temperament, and Early-Life Stress Predict Never-Depressed Preadolescents’ Functional Connectivity During a Negative-Mood Induction

Understanding the development of depression can inform etiology and prevention/intervention. Maternal depression and maladaptive patterns of temperament (e.g., low positive emotionality [PE] or high negative emotionality, especially sadness) are known to predict depression. Although it is unclear how these risks cause depression, altered functional connectivity (FC) during negative-emotion processing may play an important role. We investigated whether maternal depression and age-3 emotionality predicted FC during negative mood reactivity in never-depressed preadolescents and whether these relationships were augmented by early-life stress. Maternal depression predicted decreased medial prefrontal cortex (mPFC)–amygdala and mPFC–insula FC but increased mPFC–posterior cingulate cortex (PCC) FC. PE predicted increased dorsolateral prefrontal cortex–amygdala FC, whereas sadness predicted increased PCC-based FC in insula, orbitofrontal cortex, and anterior cingulate cortex (ACC). Sadness was more strongly associated with PCC–insula and PCC–ACC FC as early stress increased. Findings indicate that early depression risks may be mediated by FC underlying negative-emotion processing

Orbitofrontal cortex grey matter volume is related to children\u27s depressive symptoms

© 2020 The Author(s) Adults with a history of depression show distinct patterns of grey matter volume (GMV) in frontal cortical (e.g., prefrontal cortex, orbitofrontal cortex) and limbic (e.g., anterior cingulate, amygdala, hippocampus, dorsal striatum) structures, regions relevant to the processing and regulation of reward, which is impaired in the context of depression. However, it is unclear whether these GMV associations with depression precede depressive disorder onset or whether GMV is related to early emerging symptoms or familial depression. To address these questions, we used voxel-based morphometry (VBM) to examine GMV in 85 community-dwelling children (M = 11.12 years, SD = 0.63 years) screened for current and lifetime depression. Associations between children\u27s depressive symptoms (self- and mother-report of children\u27s symptoms), children\u27s maternal depression history, and GMV were examined. Although maternal depression history was unrelated to children\u27s GMV, child GMV in the orbitofrontal cortex (OFC) was negatively related to children\u27s self-reported depressive symptoms, using both a priori ROI and whole-brain analyses. Moderated regression analyses indicated that girls’ GMV was negatively related to girls’ depressive symptoms (as indexed by both self- and mother-report of girls’ symptoms), whereas boys’ symptoms were positively related to GMV. Our findings suggest that brain morphology in the OFC, a region with functional roles in processes relevant to depressive symptoms (i.e., reward-based learning and reward processing), is associated with early depressive symptoms prior to the development of clinically significant depression

Children\u27s neural reactivity to maternal praise and criticism: Associations with early depressive symptoms and maternal depression

Caregiving experiences are implicated in children\u27s depression risk; however, children\u27s neural reactivity to positive and negative feedback from mothers, a potential mediator of depression risk, is poorly understood. In a sample of 81 children

Efeito de Beauveria bassiana sobre Cerotoma arcuata (Olivier, 1791) (Coleoptera: chrysomelidae) após exposição de esporos do fungo a tubérculos de taiuiá (Ceratosanthes hilariana).

Isolados do fungo entomógeno Beauveria bassiana (Deuteromycetes, Moniliales), provenientes de várias regiões do Brasil, têm demonstrado, através de bioensaios, alta patogenicidade a adultos de Cerotoma arcuata (0livier, 1791), importante praga de feijão (Phaseolus vulgaris) e caupi ( Vigna unguiculata)