Inverse Optical Cavity Design for Ultrabroadband Light Absorption Beyond the Conventional Limit in Low‐Bandgap Nonfullerene Acceptor–Based Solar Cells

In the subwavelength regime, several nanophotonic configurations have been proposed to overcome the conventional light trapping or light absorption enhancement limit in solar cells also known as the Yablonovitch limit. It has been recently suggested that establishing such limit should rely on computational inverse electromagnetic design instead of the traditional approach combining intuition and a priori known physical effect. In the present work, by applying an inverse full wave vector electromagnetic computational approach, a 1D nanostructured optical cavity with a new resonance configuration is designed that provides an ultrabroadband (≈450 nm) light absorption enhancement when applied to a 107 nm thick active layer organic solar cell based on a low‐bandgap (1.32 eV) nonfullerene acceptor. It is demonstrated computationally and experimentally that the absorption enhancement provided by such a cavity surpasses the conventional limit resulting from an ergodic optical geometry by a 7% average over a 450 nm band and by more than 20% in the NIR. In such a cavity configuration the solar cells exhibit a maximum power conversion efficiency above 14%, corresponding to the highest ever measured for devices based on the specific nonfullerene acceptor used.     

Roosting requirements of Helmeted Guineafowl Numida meleagris on Highveld grain and livestock farms with alien tree groves,Gauteng province,South Africa

This study describes the relationship between Helmeted Guineafowl Numida meleagris and invasive alien trees on livestock and maize farms south-east of Johannesburg, Gauteng province, South Africa. The dependence of the birds on alien trees affects strategies for the removal of these trees. During June to December 2014, Helmeted Guineafowl were recorded weekly on maps along a 42 km transect. Since Helmeted Guineafowl live in cohesive social groups of 15–20 birds, they roost communally in one or two trees during winter rather than spreading across an entire tree grove. The distribution of alien trees across the landscape in patches has enabled Helmeted Guineafowl flocks to reach new feeding patches near to roosting trees, as old feeding patches are depleted. One Helmeted Guineafowl flock of 15–20 birds requires ～0.09 ha covered with mature alien trees for roosting. Suggestions are presented relating to the reduction of alien trees in compliance with the Conservation of Agricultural Resources Act 43 of 1983 and conservation of Helmeted Guineafowl.     

Development of a liquid flow-through system to inhibit browning in callus cultures of guayule (Parthenium argentatum Gray)

Calli of P. argentatum were grown on a newly designed liquid nutrient flow-through system which facilitated the subculturing of calli and delayed browning for 6 weeks. Friable calli were obtained on half-strength Gamborg B5-medium supplemented with 0.05 mgl⁻¹ 2,4-dichlorophenoxyacetic acid. Shoots developed on media supplemented with 0.2 mgl⁻¹ benzylaminopurine but lacking 2,4-dichlorophenocyacetic acid.     

Sulfate assimilation in Rhodopseudomonas globiformis

Rhodopseudomonas globiformis is able to grow on sulfate as sole source of sulfur, but only at concentrations below 1 mM. Good growth was observed with thiosulfate, cysteine or methionine as sulfur sources. Tetrathionate supported slow growth. Sulfide and sulfite were growth inhibitory. Growth inhibition by higher sulfate concentrations was overcome by the addition of O-acetylserine, which is known as derepressor of sulfate-assimilating enzymes, and by reduced glutathione. All enzymes of the sulfate assimilation pathway. ATP-sulfurylase, adenylylphosphate-sulfotransferase, thiosulfonate reductase and O-acetylserine sulfhydrylase are present in R. globiformis. Sulfate was taken up by the cells and the sulfur incorporated into the amino acids cysteine, methionine and homocysteine. It is concluded, that the failure of R. globiformis to grow on higher concentrations of sulfate is caused by disregulation of the sulfate assimilation pathway. Some preliminary evidence for this view is given in comparing the activities of some of the involved enzymes after growth on different sulfur sources and by examining the effect of O-acetylserine on these activities.Abbreviations DTE dl-dithioerythritol - APS adenosine 5-phosphosulfate, adenylyl sulfate - PAPS 3-phosphoadenosine 5-phosphosulfate, 3-phosphoadenylylsulfate     

The glutaredoxin mono- and di-thiol mechanisms for deglutathionylation are functionally equivalent: implications for redox systems biology

Glutathionylation plays a central role in cellular redox regulation and anti-oxidative defence. Grx (Glutaredoxins) are primarily responsible for reversing glutathionylation and their activity therefore affects a range of cellular processes, making them prime candidates for computational systems biology studies. However, two distinct kinetic mechanisms involving either one (monothiol) or both (dithiol) active-site cysteines have been proposed for their deglutathionylation activity and initial studies predicted that computational models based on either of these mechanisms will have different structural and kinetic properties. Further, a number of other discrepancies including the relative activity of active-site mutants and contrasting reciprocal plot kinetics have also been reported for these redoxins. Using kinetic modelling, we show that the dithiol and monothiol mechanisms are identical and, we were also able to explain much of the discrepant data found within the literature on Grx activity and kinetics. Moreover, our results have revealed how an apparently futile side-reaction in the monothiol mechanism may play a significant role in regulating Grx activity in vivo.     

A revised classification of the sister tribes Palicoureeae and Psychotrieae (Rubiaceae) indicates genus-specific alkaloid accumulation

Phytochemistry Reviews - Tribes Palicoureeae and Psychotrieae (Rubiaceae, Gentianales) are complex and speciose sister groups with a pantropical distribution. Since the initial studies on...     

Key Features of Intertidal Food Webs That Support Migratory Shorebirds

The migratory shorebirds of the East Atlantic flyway land in huge numbers during a migratory stopover or wintering on the French Atlantic coast. The Brouage bare mudflat (Marennes-Oléron Bay, NE Atlantic) is one of the major stopover sites in France. The particular structure and function of a food web affects the efficiency of carbon transfer. The structure and functioning of the Brouage food web is crucial for the conservation of species landing within this area because it provides sufficient food, which allows shorebirds to reach the north of Europe where they nest. The aim of this study was to describe and understand which food web characteristics support nutritional needs of birds. Two food-web models were constructed, based on in situ measurements that were made in February 2008 (the presence of birds) and July 2008 (absence of birds). To complete the models, allometric relationships and additional data from the literature were used. The missing flow values of the food web models were estimated by Monte Carlo Markov Chain – Linear Inverse Modelling. The flow solutions obtained were used to calculate the ecological network analysis indices, which estimate the emergent properties of the functioning of a food-web.The total activities of the Brouage ecosystem in February and July are significantly different. The specialisation of the trophic links within the ecosystem does not appear to differ between the two models. In spite of a large export of carbon from the primary producer and detritus in winter, the higher recycling leads to a similar retention of carbon for the two seasons. It can be concluded that in February, the higher activity of the ecosystem coupled with a higher cycling and a mean internal organization, ensure the sufficient feeding of the migratory shorebirds.     

Oxidized phospholipids are more potent antagonists of lipopolysaccharide than inducers of inflammation

Polyunsaturated fatty acids are precursors of multiple pro- and anti-inflammatory molecules generated by enzymatic stereospecific and positionally specific insertion of oxygen, which is a prerequisite for recognition of these mediators by cellular receptors. However, nonenzymatically oxidized free and esterified polyunsaturated fatty acids also demonstrate activities relevant to inflammation. In particular, phospholipids containing oxidized fatty acid residues (oxidized phospholipids; OxPLs) were shown to induce proinflammatory changes in endothelial cells but paradoxically also to inhibit inflammation induced via TLR4. In this study, we show that half-maximal inhibition of LPS-induced elevation of E-selectin mRNA in endothelial cells developed at concentrations of oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (OxPAPC) 10-fold lower than those required to induce proinflammatory response. Similar concentration difference was observed for other classes and molecular species of OxPLs. Upon injection into mice, OxPAPC did not elevate plasma levels of IL-6 and keratinocyte chemoattractant but strongly inhibited LPS-induced upregulation of these inflammatory cytokines. Thus, both in vitro and in vivo, anti-LPS effects of OxPLs are observed at lower concentrations than those required for their proinflammatory action. Quantification of the most abundant oxidized phosphatidylcholines by HPLC/tandem mass spectrometry showed that circulating concentrations of total oxidized phosphatidylcholine species are close to the range where they demonstrate anti-LPS activity but significantly lower than that required for induction of inflammation. We hypothesize that low levels of OxPLs in circulation serve mostly anti-LPS function and protect from excessive systemic response to TLR4 ligands, whereas proinflammatory effects of OxPLs are more likely to develop locally at sites of tissue deposition of OxPLs (e.g., in atherosclerotic vessels).     

The presence of a haloarchaeal type tyrosyl-tRNA synthetase marks the opisthokonts as monophyletic

Lateral gene transfer plays an important role in the evolution of life. Events of ancient gene transfer can transmit genetic novelties to descendent lineages and subsequently shape their genetic systems. We here present the analyses of the gene encoding tyrosyl-tRNA synthetase (tyrRS), which reveal two eukaryotic tyrRS lineages, one including the opisthokonts and the other the remaining eukaryotes. The different origins of tyrRS lineages between the opisthokonts and the remaining eukaryotes indicate a likely case of ancient lateral gene transfer of tyrRS from an archaeon to the opisthokonts, which lends further support for the monophyly of the latter group. Ancient paralogy followed by differential gene loss is an alternative, albeit less parsimonious explanation for the distribution of the two eukaryotic tyrRS types. In either case, the presence of a haloarchaeal tyrRS type in the opisthokonts marks this group as monophyletic. This finding also points to the potential utility of ancient gene transfer events as molecular markers for major organismal lineages.     

Direct Cloning from Enrichment Cultures, a Reliable Strategy for Isolation of Complete Operons and Genes from Microbial Consortia

Enrichment cultures of microbial consortia enable the diverse metabolic and catabolic activities of these populations to be studied on a molecular level and to be explored as potential sources for biotechnology processes. We have used a combined approach of enrichment culture and direct cloning to construct cosmid libraries with large (>30-kb) inserts from microbial consortia. Enrichment cultures were inoculated with samples from five environments, and high amounts of avidin were added to the cultures to favor growth of biotin-producing microbes. DNA was extracted from three of these enrichment cultures and used to construct cosmid libraries; each library consisted of between 6,000 and 35,000 clones, with an average insert size of 30 to 40 kb. The inserts contained a diverse population of genomic DNA fragments isolated from the consortia organisms. These three libraries were used to complement the Escherichia coli biotin auxotrophic strain ATCC 33767 Δ(bio-uvrB). Initial screens resulted in the isolation of seven different complementing cosmid clones, carrying biotin biosynthesis operons. Biotin biosynthesis capabilities and growth under defined conditions of four of these clones were studied. Biotin measured in the different culture supernatants ranged from 42 to 3,800 pg/ml/optical density unit. Sequencing the identified biotin synthesis genes revealed high similarities to bio operons from gram-negative bacteria. In addition, random sequencing identified other interesting open reading frames, as well as two operons, the histidine utilization operon (hut), and the cluster of genes involved in biosynthesis of molybdopterin cofactors in bacteria (moaABCDE).