Higher Mobility and Carrier Lifetimes in Solution‐Processable Small‐Molecule Ternary Solar Cells with 11% Efficiency

Solution‐processed small molecule (SM) solar cells have the prospect to outperform their polymer‐fullerene counterparts. Considering that both SM donors/acceptors absorb in visible spectral range, higher expected photocurrents should in principle translate into higher power conversion efficiencies (PCEs). However, limited bulk‐heterojunction (BHJ) charge carrier mobility (<10^‐4 cm² V^‐1 s^‐1) and carrier lifetimes (<1 µs) often impose active layer thickness constraints on BHJ devices (≈100 nm), limiting external quantum efficiencies (EQEs) and photocurrent, and making large‐scale processing techniques particularly challenging. In this report, it is shown that ternary BHJs composed of the SM donor DR3TBDTT (DR3), the SM acceptor ICC6 and the fullerene acceptor PC₇₁BM can be used to achieve SM‐based ternary BHJ solar cells with active layer thicknesses >200 nm and PCEs nearing 11%. The examinations show that these remarkable figures are the result of i) significantly improved electron mobility (8.2 × 10^‐4 cm² V^‐1 s^‐1), ii) longer carrier lifetimes (2.4 µs), and iii) reduced geminate recombination within BHJ active layers to which PC₇₁BM has been added as ternary component. Optically thick (up to ≈500 nm) devices are shown to maintain PCEs >8%, and optimized DR3:ICC6:PC₇₁BM solar cells demonstrate long‐term shelf stability (dark) for >1000 h, in 55% humidity air environment.     

Soil Respiration in European Grasslands in Relation to Climate and Assimilate Supply

Soil respiration constitutes the second largest flux of carbon (C) between terrestrial ecosystems and the atmosphere. This study provides a synthesis of soil respiration (R _s) in 20 European grasslands across a climatic transect, including ten meadows, eight pastures and two unmanaged grasslands. Maximum rates of R _s ( ), R _s at a reference soil temperature (10°C; ) and annual R _s (estimated for 13 sites) ranged from 1.9 to 15.9 μmol CO₂ m⁻² s⁻¹, 0.3 to 5.5 μmol CO₂ m⁻² s⁻¹ and 58 to 1988 g C m⁻² y⁻¹, respectively. Values obtained for Central European mountain meadows are amongst the highest so far reported for any type of ecosystem. Across all sites was closely related to . Assimilate supply affected R _s at timescales from daily (but not necessarily diurnal) to annual. Reductions of assimilate supply by removal of aboveground biomass through grazing and cutting resulted in a rapid and a significant decrease of R _s. Temperature-independent seasonal fluctuations of R _s of an intensively managed pasture were closely related to changes in leaf area index (LAI). Across sites increased with mean annual soil temperature (MAT), LAI and gross primary productivity (GPP), indicating that assimilate supply overrides potential acclimation to prevailing temperatures. Also annual R _s was closely related to LAI and GPP. Because the latter two parameters were coupled to MAT, temperature was a suitable surrogate for deriving estimates of annual R _s across the grasslands studied. These findings contribute to our understanding of regional patterns of soil C fluxes and highlight the importance of assimilate supply for soil CO₂ emissions at various timescales.     

Influence of physiological phenology on the seasonal pattern of ecosystem respiration in deciduous forests

Understanding the environmental and biotic drivers of respiration at the ecosystem level is a prerequisite to further improve scenarios of the global carbon cycle. In this study we investigated the relevance of physiological phenology, defined as seasonal changes in plant physiological properties, for explaining the temporal dynamics of ecosystem respiration (R_ECO) in deciduous forests. Previous studies showed that empirical R_ECO models can be substantially improved by considering the biotic dependency of R_ECO on the short‐term productivity (e.g., daily gross primary production, GPP) in addition to the well‐known environmental controls of temperature and water availability. Here, we use a model‐data integration approach to investigate the added value of physiological phenology, represented by the first temporal derivative of GPP, or alternatively of the fraction of absorbed photosynthetically active radiation, for modeling R_ECO at 19 deciduous broadleaved forests in the FLUXNET La Thuile database. The new data‐oriented semiempirical model leads to an 8% decrease in root mean square error (RMSE) and a 6% increase in the modeling efficiency (EF) of modeled R_ECO when compared to a version of the model that does not consider the physiological phenology. The reduction of the model‐observation bias occurred mainly at the monthly time scale, and in spring and summer, while a smaller reduction was observed at the annual time scale. The proposed approach did not improve the model performance at several sites, and we identified as potential causes the plant canopy heterogeneity and the use of air temperature as a driver of ecosystem respiration instead of soil temperature. However, in the majority of sites the model‐error remained unchanged regardless of the driving temperature. Overall, our results point toward the potential for improving current approaches for modeling R_ECO in deciduous forests by including the phenological cycle of the canopy.     

Convergence of potential net ecosystem production among contrasting C3 grasslands

Metabolic theory and body size constraints on biomass production and decomposition suggest that differences in the intrinsic potential net ecosystem production (NEP_POT) should be small among contrasting C₃ grasslands and therefore unable to explain the wide range in the annual apparent net ecosystem production (NEP_APP) reported by previous studies. We estimated NEP_POT for nine C₃ grasslands under contrasting climate and management regimes using multiyear eddy covariance data. NEP_POT converged within a narrow range, suggesting little difference in the net carbon dioxide uptake capacity among C₃ grasslands. Our results indicate a unique feature of C₃ grasslands compared with other terrestrial ecosystems and suggest a state of stability in NEP_POT due to tightly coupled production and respiration processes. Consequently, the annual NEP_APP of C₃ grasslands is primarily a function of seasonal and short‐term environmental and management constraints, and therefore especially susceptible to changes in future climate patterns and associated adaptation of management practices.     

Detection of early stages of apoptosis in experimental intestinal ischemia-reperfusion injury

Apoptosis is a form of programmed cell death that plays an important role in small intestine ischemia-reperfusion (IR) injury. The aim of this study was to determine the total proportion of apoptotic cell death (apoptotic index) following injury induced by ischemia and during various subsequent reperfusion periods, total histopathological status and the intestine regeneration dynamics after the IR injury. Experimental animals, Wistar rats (n = 45) were divided into three experimental and one control groups. In the experimental groups 1 h ischemia was followed by 1, 4 and 24 h reperfusion. Intestinal ischemia was induced by superior mesenteric artery (SMA) occlusion. Segments of jejunum were stained with hematoxylin and eosin and studied immunohistochemically using M30 CytoDEATH and in situ TUNEL methods for apoptosis detection. Our experimental data showed that: (i) apoptosis is an important form of cell death in the small intestine after IR injury induced by SMA occlusion; (ii) maximum levels of histopathological damage and apoptotic index of mucosa occurred after 1 h ischemia and 1 h of reperfusion; and (iii) mucosa possesses great regeneration ability. The lowest levels of histopathological damage and apoptotic index were observed in the group with 1 h ischemia and 24 h reperfusion where, however, the highest mitotic index was present.     

Variation in prey-specific consumption rates and patterns of field co-occurrence for two larval predaceous diving beetles

Freshwater predatory insects can exert strong effects on prey, although how multiple similar predators may coexist is not well understood. Larval predaceous diving beetles are often numerically and taxonomically abundant predators in lentic systems, but the proximate mechanisms that explain their high abundance remain unknown. Field surveys were conducted twice in June in ponds in Alberta, Canada to assess the associations between larvae of two genera (Graphoderus, Rhantus), their spatial locations, and correlations with potential prey. Both larvae were common and positively correlated within wetlands although neither varied with pond depth nor distance from edge. Laboratory trials indicated that Graphoderus consumed more prey (corixids) at the surface, whereas Rhantus killed benthic prey (chironomids) and corixids at an equal rate; damselflies were the least consumed prey. Predation also varied with depth, with both larvae feeding at higher rates in the shallowest environments compared to Graphoderus at an intermediate depth. Predator–prey correlations from ponds were mostly congruent with predation trials; Graphoderus was positively correlated with corixids, Rhantus was positively correlated with corixids and chironomids; beetles were uncorrelated with damselflies. Reliance on different prey in different microhabitats may be an important mechanism for the maintenance of high abundance of dytiscid larvae.     

Recurrence of Subdural Haematoma in a Population-Based Cohort – Risks and Predictive Factors

Objectives

To estimate the risks of and identify predictors for recurrent subdural haematoma in surgically and conservatively treated patients.

Methods

The cohort comprised all individuals diagnosed with a first-time subdural hematoma in Denmark 1996–2011. Information on potential predictors was retrieved from the Danish health registers. Cumulative recurrence risks were estimated using the Aalen-Johansen estimator. Rate ratios (RR) were estimated using Poisson regression.

Results

Among 10,158 individuals with a subdural hematoma, 1,555 had a recurrent event. The cumulative risk of recurrent subdural hematoma was 9% at 4 weeks after the primary bleeding, increasing to and stabilising at 14% after one year. Predictors associated with recurrence were: Male sex (RR 1.60, 95% CI:1.43–1.80), older age (>70 years compared to 20–49 years; RR 1.41, 95% CI: 1.21–1.65), alcohol addiction (RR 1.20, 95% CI:1.04–1.37), surgical treatment (RR 1.76, 95% CI:1.58–1.96), trauma diagnoses (RR 1.14, 95% CI:1.03–1.27), and diabetes mellitus (RR 1.40, 95% CI:1.11–1.74). Out of a selected combination of risk factors, the highest cumulative 1-year recurrence risks for subdural hematoma of 25% (compared to 14% for all patients) was found in surgically treated males with diabetes mellitus.

Conclusions

The recurrence risk of subdural hematoma is largely limited to the first year. Patient characteristics including co-morbidities greatly influence the recurrence risk of SDH, suggesting that individualized prognostic guidance and follow-up is needed.