Density dependence of Anaphes sordidatus (Hymenoptera: Mymaridae) parasitism on eggs of Listronotus oregonensis (Coleoptera: Curculionidae)

Listronotus oregonensis (LeConte) (Coleoptera: Curculionidae) oviposits in carrot leaves and the larvae feed in carrot roots. Its eggs are parasitized by Anaphes sordidatus (Girault) (Hymenoptera: Mymaridae) throughout its oviposition period. This parasitoid is the major biotic mortality factor for L. oregonensis. Parasitism by A. sordidatus was studied for three years in sequentially sown plots of carrots, Daucus carota var. sativa. Over the scason, significantly fewer L. oregonensis eggs were oviposited in later sown carrots than in earlier sown carrots because oviposition started later in late sown plots of carrots. A positive temporal density-dependent relationship was observed each year between parasitism rates and host densities. This positive density dependence occurred in early and mid-summer for earlysown carrots where host density reached 1–2 host eggs per plant but disappeared in late summer when host density decreased while parasitism remained high. Latesown carrots had low host egg density (0.2 host egg per plant) and contributed little to the total number of eggs. In these late sown plots, parasitism increased rapidly to over 80% but no density dependence was observed. Spatially, few statistically significant regressions were found but all indicated a positive spatial density-dependence. Most non-significant regressions occurred because the range of egg density was too small between plots for a given date.     

Cognition,behaviour and academic skills after cognitive rehabilitation in Ugandan children surviving severe malaria: a randomised trial

Background  

Infection with severe malaria in African children is associated with not only a high mortality but also a high risk of cognitive deficits. There is evidence that interventions done a few years after the illness are effective but nothing is known about those done immediately after the illness. We designed a study in which children who had suffered from severe malaria three months earlier were enrolled into a cognitive intervention program and assessed for the immediate benefit in cognitive, academic and behavioral outcomes.     

Accessing the Two‐Electron Charge Storage Capacity of MnO2 in Mild Aqueous Electrolytes

Rechargeable batteries based on MnO₂ cathodes, able to operate in mild aqueous electrolytes, have attracted attention due to their appealing features for the design of low‐cost stationary energy storage devices. However, the charge/discharge mechanism of MnO₂ in such media is still a matter of debate. Here, an in‐depth quantitative spectroelectrochemical analysis of MnO₂ thin‐films provides a set of unrivaled mechanistic insights. A major finding is that charge storage occurs through the reversible two‐electron faradaic conversion of MnO₂ into Mn²⁺ in the presence of a wide range of weak Brønsted acids, including the [Zn(H₂O)₆]²⁺ or [Mn(H₂O)₆]²⁺ complexes present in aqueous Zn/MnO₂ batteries. Furthermore, it is shown that buffered electrolytes loaded with Mn²⁺ are ideal to achieve highly reversible conversion of MnO₂ with both high gravimetric capacity and remarkably stable charging/discharging potentials. In the most favorable case, a record gravimetric capacity of 450 mA·h·g^?1 is obtained at a high rate of 1.6 A·g^?1, with a Coulombic efficiency close to 100% and a MnO₂ utilization of 84%. Overall, the present results challenge the common view on MnO₂ the charge storage mechanism in mild aqueous electrolytes and underline the benefit of buffered electrolytes for high‐performance rechargeable aqueous batteries.     

Perovskite Solar Cells go Outdoors: Field Testing and Temperature Effects on Energy Yield

Perovskite solar cells (PSC) have shown that under laboratory conditions they can compete with established photovoltaic technologies. However, controlled laboratory measurements usually performed do not fully resemble operational conditions and field testing outdoors, with day‐night cycles, changing irradiance and temperature. In this contribution, the performance of PSCs in the rooftop field test, exposed to real weather conditions is evaluated. The 1 cm² single‐junction devices, with an initial average power conversion efficiency of 18.5% are tracked outdoors in maximum power point over several weeks. In parallel, irradiance and air temperature are recorded, allowing us to correlate outside factors with generated power. To get more insight into outdoor device performance, a comprehensive set of laboratory measurements under different light intensities (10% to 120% of AM1.5) and temperatures is performed. From these results, a low power temperature coefficient of ?0.17% K^?1 is extracted in the temperature range between 25 and 85 °C. By incorporating these temperature‐ and light‐dependent PV parameters into the energy yield model, it is possible to correctly predict the generated energy of the devices, thus validating the energy yield model. In addition, degradation of the tested devices can be tracked precisely from the difference between measured and modelled power.     

Surprising low diversity of the plant pathogen Phytophthora in Amazonian forests

The genus Phytophthora represents a group of plant pathogens with broad global distribution. The majority of them cause the collar and root-rot of diverse plant species. Little is known about Phytophthora communities in forest ecosystems, especially in the Neotropical forests where natural enemies could maintain the huge plant diversity via negative density dependence. We characterized the diversity of soil-borne Phytophthora communities in the North French Guiana rainforest and investigated how they are structured by host identity and environmental factors. In this little-explored habitat, 250 soil cores were sampled from 10 plots hosting 10 different plant families across three forest environments (Terra Firme, Seasonally Flooded and White Sand). Phytophthora diversity was studied using a baiting approach and metabarcoding (High-Throughput Sequencing) on environmental DNA extracted from both soil samples and baiting-leaves. These three approaches revealed very similar communities, characterized by an unexpected low diversity of Phytophthora species, with the dominance of two cryptic species close to Phytophthora heveae. As expected, the Phytophthora community composition of the French Guiana rainforest was significantly impacted by the host plant family and environment. However, these plant pathogen communities are very small and are dominated by generalist species, questioning their potential roles as drivers of plant diversity in these Amazonian forests.