Charge Accumulation and Hysteresis in Perovskite‐Based Solar Cells: An Electro‐Optical Analysis

Organic–inorganic hybrid perovskite solar cells based on CH₃NH₃PbI₃ have achieved great success with efficiencies exceeding 20%. However, there are increasing concerns over some reported efficiencies as the cells are susceptible to current–voltage (I–V) hysteresis effects. It is therefore essential that the origins and mechanisms of the I–V hysteresis can clearly be understood to minimize or eradicate these hysteresis effects completely for reliable quantification. Here, a detailed electro‐optical study is presented that indicates the hysteresis originates from lingering processes persisting from sub‐second to tens of seconds. Photocurrent transients, photoluminescence, electroluminescence, quasi‐steady state photoinduced absorption processes, and X‐ray diffraction in the perovskite solar cell configuration have been monitored. The slow processes originate from the structural response of the CH₃NH₃PbI₃ upon E‐field application and/or charge accumulation, possibly involving methylammonium ions rotation/displacement and lattice distortion. The charge accumulation can arise from inefficient charge transfer at the perovskite interfaces, where it plays a pivotal role in the hysteresis. These findings underpin the significance of efficient charge transfer in reducing the hysteresis effects. Further improvements of CH₃NH₃PbI₃‐based perovskite solar cells are possible through careful surface engineering of existing TiO₂ or through a judicious choice of alternative interfacial layers.     

Autonomy,productiveness, and community: the rise of inequality in an Amazonian society

In Amazonian societies, autonomy is said to be a core value motivating egalitarian politics. This article shows how the quest for autonomy and productiveness presently sets in motion processes that encroach upon these very values. Among the Shuar of Amazonian Ecuador, the realization of autonomy and productiveness increasingly depends on the capture of state resources. Shuar interact with the local state as members of relatively recent sedentary communities and through the mediation of elected leaders. In these processes, ‘community’ itself is transformed: being a channel to regenerate domestic livelihoods, it also becomes an end in itself, giving rise to new economistic attitudes while legitimizing inequalities between commoners and leaders. The article suggests that the pursuit of autonomy and productiveness within a process of village formation is central to the transformation of egalitarianism that occurs when small-scale Amazonian polities engage with nation-state politics.     

Are offspring begging levels exaggerated beyond the parental optimum? Evidence from a bidirectional selection experiment

Parental care involves elaborate behavioural interactions between parents and their offspring, with offspring stimulating their parents via begging to provision resources. Thus, begging has direct fitness benefits as it enhances offspring growth and survival. It is nevertheless subject to a complex evolutionary trajectory, because begging may serve as a means for the offspring to manipulate parents in the context of evolutionary conflicts of interest. Furthermore, it has been hypothesized that begging is coadapted and potentially genetically correlated with parental care traits as a result of social selection. Further experiments on the causal processes that shape the evolution of begging are therefore essential. We applied bidirectional artificial selection on begging behaviour, using canaries (Serinus canaria) as a model species. We measured the response to selection, the consequences for offspring development, changes in parental care traits, here the rate of parental provisioning, as well as the effects on reproductive success. After three generations of selection, offspring differed in begging behaviour according to our artificial selection regime: nestlings of the high begging line begged significantly more than nestlings of the low begging line. Intriguingly, begging less benefitted the nestlings, as reflected by on average significantly higher growth rates, and increased reproductive success in terms of a higher number of fledglings in the low selected line. Begging could thus represent an exaggerated trait, possibly because parent–offspring conflict enhanced the selection on begging. We did not find evidence that we co‐selected on parental provisioning, which may be due to the lack of power, but may also suggest that the evolution of begging is probably not constrained by a genetic correlation between parental provisioning and offspring begging.     

Nasal Priming with Lactobacillus rhamnosus CRL1505 Stimulates Mononuclear Phagocytes of Immunocompromised Malnourished Mice: Improvement of Respiratory Immune Response

The effect of Lactobacillus rhamnosus CRL1505 (Lr) on macrophages (Ma) and dendritic cells (DC) in the orchestration of anti-pneumococcal immunity was stud     

The investigation of structure–activity relationship of polyamine-targeted synthetic compounds from different chemical groups

Amino Acids - The polyamine (PA) metabolism is involved in cell proliferation and differentiation. Increased cellular PA levels are observed in different types of cancers. Products of PA oxidation...