Concerning the electrosynthesis of hydrogen peroxide and peroxodisulfates. Section 2: Optimization of electrolysis cells using an electrolyzer for peroxodisulfuric acid as an example

The model is presented of an electrolyzer for peroxodisulfuric acid, and it is analyzed mathematically. Its application for engineering and economic optimization is investigated in detail. The mathematical analysis leads to conclusions concerning the change in position of the optimum with respect to the various target functions due to changes of the individual design-caused and economic parameters

Modeling and technical use of gas evolving electrodes. Part 2: Modeling of gas-evolving electrolyzers with free electrolyte circulation

In an electrochemical reactor with gas-evolving electrodes, the transporting action of the gas bubbles can be used to move the electrolyte in a cycle flow, when the structure of the flow channels is suitable. For an electrolysis cell with such a circulation system a mathematic model was set up and evaluated. It is shown that in this manner, a rapid flow through the electrode gap can be achieved without additional energy consumption, in addition to a low gas fraction and a low cell voltage. The cell voltage and the attainable cycle spread are investigated as a function of the geometric parameters for their optimum values

Bayesian Phylogenetic Estimation of Clade Ages Supports Trans-Atlantic Dispersal of Cichlid Fishes

Divergence-time estimation based on molecular phylogenies and the fossil record has provided insights into fundamental questions of evolutionary biology. In Bayesian node dating, phylogenies are commonly time calibrated through the specification of calibration densities on nodes representing clades with known fossil occurrences. Unfortunately, the optimal shape of these calibration densities is usually unknown and they are therefore often chosen arbitrarily, which directly impacts the reliability of the resulting age estimates. As possible solutions to this problem, two nonexclusive alternative approaches have recently been developed, the "fossilized birth-death" (FBD) model and "total-evidence dating." While these approaches have been shown to perform well under certain conditions, they require including all (or a random subset) of the fossils of each clade in the analysis, rather than just relying on the oldest fossils of clades. In addition, both approaches assume that fossil records of different clades in the phylogeny are all the product of the same underlying fossil sampling rate, even though this rate has been shown to differ strongly between higher level taxa. We here develop a flexible new approach to Bayesian age estimation that combines advantages of node dating and the FBD model. In our new approach, calibration densities are defined on the basis of first fossil occurrences and sampling rate estimates that can be specified separately for all clades. We verify our approach with a large number of simulated data sets, and compare its performance to that of the FBD model. We find that our approach produces reliable age estimates that are robust to model violation, on par with the FBD model. By applying our approach to a large data set including sequence data from over 1000 species of teleost fishes as well as 147 carefully selected fossil constraints, we recover a timeline of teleost diversification that is incompatible with previously assumed vicariant divergences of freshwater fishes. Our results instead provide strong evidence for transoceanic dispersal of cichlids and other groups of teleost fishes. [Bayesian inference; calibration density; Cichlidae; fossil record; marine dispersal; phylogeny; relaxed molecular clock]

Uncoupling GP1 and GP2 expression in the Lassa virus glycoprotein complex: implications for GP1 ectodomain shedding

<p>Abstract</p> <p>Background</p> <p>Sera from convalescent Lassa fever patients often contains antibodies to Lassa virus (LASV) glycoprotein 1 (GP1), and glycoprotein 2 (GP2); Immunization of non-human primates with viral vectors expressing the arenaviral glycoprotein complex (GPC) confers full protective immunity against a lethal challenge with LASV. Thus, the development of native or quasi native recombinant LASV GP1 and GP2 as soluble, uncoupled proteins will improve current diagnostics, treatment, and prevention of Lassa fever. To this end, mammalian expression systems were engineered for production and purification of secreted forms of soluble LASV GP1 and GP2 proteins.</p> <p>Results</p> <p>Determinants for mammalian cell expression of secreted uncoupled Lassa virus (LASV) glycoprotein 1 (GP1) and glycoprotein 2 (GP2) were established. Soluble GP1 was generated using either the native glycoprotein precursor (GPC) signal peptide (SP) or human IgG signal sequences (s.s.). GP2 was secreted from cells only when (1) the transmembrane (TM) domain was deleted, the intracellular domain (IC) was fused to the ectodomain, and the gene was co-expressed with a complete GP1 gene in <it>cis</it>; (2) the TM and IC domains were deleted and GP1 was co-expressed in <it>cis</it>; (3) expression of GP1 was driven by the native GPC SP. These data implicate GP1 as a chaperone for processing and shuttling GP2 to the cell surface. The soluble forms of GP1 and GP2 generated through these studies were secreted as homogeneously glycosylated proteins that contained high mannose glycans. Furthermore, observation of GP1 ectodomain shedding from cells expressing wild type LASV GPC represents a novel aspect of arenaviral glycoprotein expression.</p> <p>Conclusion</p> <p>These results implicate GP1 as a chaperone for the correct processing and shuttling of GP2 to the cell surface, and suggest that native GPC SP plays a role in this process. In the absence of GP1 and GPC SP the GP2 protein may be processed by an alternate pathway that produces heterogeneously glycosylated protein, or the polypeptide may not fully mature in the secretory cascade in mammalian cells. The expression constructs developed in these studies resulted in the generation and purification of soluble, uncoupled GP1 and GP2 proteins from mammalian cells with quasi-native properties. The observation of GP1 ectodomain shedding from cells expressing wild type LASV GPC establishes new correlates of disease progression and highlights potential opportunities for development of diagnostics targeting the early stages of Lassa fever.</p

Bacterial-based systems for expression and purification of recombinant Lassa virus proteins of immunological relevance

<p>Abstract</p> <p>Background</p> <p>There is a significant requirement for the development and acquisition of reagents that will facilitate effective diagnosis, treatment, and prevention of Lassa fever. In this regard, recombinant Lassa virus (LASV) proteins may serve as valuable tools in diverse antiviral applications. Bacterial-based systems were engineered for expression and purification of recombinant LASV nucleoprotein (NP), glycoprotein 1 (GP1), and glycoprotein 2 (GP2).</p> <p>Results</p> <p>Full-length NP and the ectodomains of GP1 and GP2 were generated as maltose-binding protein (MBP) fusions in the Rosetta strains of <it>Escherichia coli </it>(<it>E. coli</it>) using pMAL-c2x vectors. Average fusion protein yields per liter of culture for MBP-NP, MBP-GP1, and MBP-GP2 were 10 mg, 9 mg, and 9 mg, respectively. Each protein was captured from cell lysates using amylose resin, cleaved with Factor Xa, and purified using size-exclusion chromatography (SEC). Fermentation cultures resulted in average yields per liter of 1.6 mg, 1.5 mg, and 0.7 mg of purified NP, GP1 and GP2, respectively. LASV-specific antibodies in human convalescent sera specifically detected each of the purified recombinant LASV proteins, highlighting their utility in diagnostic applications. In addition, mouse hyperimmune ascitic fluids (MHAF) against a panel of Old and New World arenaviruses demonstrated selective cross reactivity with LASV proteins in Western blot and enzyme-linked immunosorbent assay (ELISA).</p> <p>Conclusion</p> <p>These results demonstrate the potential for developing broadly reactive immunological assays that employ all three arenaviral proteins individually and in combination.</p

Stable species boundaries despite ten million years of hybridisation in tropical eels

Genomic evidence is increasingly underpinning that hybridization between taxa is commonplace, challenging our views on the mechanisms that maintain their boundaries. Here, we focus on seven catadromous eel species (genus Anguilla) and use genome-wide sequence data from more than 450 individuals sampled across the tropical Indo-Pacific, morphological information, and three newly assembled draft genomes to compare contemporary patterns of hybridization with signatures of past introgression across a time-calibrated phylogeny. We show that the seven species have remained distinct for up to 10 million years and find that the current frequencies of hybridization across species pairs contrast with genomic signatures of past introgression. Based on near-complete asymmetry in the directionality of hybridization and decreasing frequencies of later-generation hybrids, we suggest cytonuclear incompatibilities, hybrid breakdown, and purifying selection as mechanisms that can support species cohesion even when hybridization has been pervasive throughout the evolutionary history of clades

Ticket to spawn: Combining economic and genetic data to evaluate the effect of climate and demographic structure on spawning distribution in Atlantic cod

Climate warming and harvesting affect the dynamics of species across the globe through a multitude of mechanisms, including distribution changes. In fish, migrations to and distribution on spawning grounds are likely influenced by both climate warming and harvesting. The Northeast Arctic (NEA) cod (Gadus morhua) performs seasonal migrations from its feeding grounds in the Barents Sea to spawning grounds along the Norwegian coast. The distribution of cod between the spawning grounds has historically changed at decadal scales, mainly due to variable use of the northern and southern margins of the spawning area. Based on historical landing records, two major hypotheses have been put forward to explain these changes: climate and harvesting. Climate could affect the distribution through, for example, spatial habitat shifts. Harvesting could affect the distribution through impacting the demographic structure. If demographic structure is important, theory predicts increasing spawner size with migration distance. Here, we evaluate these hypotheses with modern data from a period (2000–2016) of increasing temperature and recovering stock structure. We first analyze economic data from the Norwegian fisheries to investigate geographical differences in size of spawning fish among spawning grounds, as well as interannual differences in mean latitude of spawning in relation to changes in temperature and demographic parameters. Second, we analyze genetically determined fish sampled at the spawning grounds to unambiguously separate between migratory NEA cod and potentially smaller sized coastal cod of local origin. Our results indicate smaller spawners farther away from the feeding grounds, hence not supporting the hypothesis that harvesting is a main driver for the contemporary spawning ground distribution. We find a positive correlation between annual mean spawning latitude and temperature. In conclusion, based on contemporary data, there is more support for climate compared to harvesting in shaping spawning ground distribution in this major fish stock in the North Atlantic Ocean

Lassa Fever in Post-Conflict Sierra Leone

Background: Lassa fever (LF), an often-fatal hemorrhagic disease caused by Lassa virus (LASV), is a major public health threat in West Africa. When the violent civil conflict in Sierra Leone (1991 to 2002) ended, an international consortium assisted in restoration of the LF program at Kenema Government Hospital (KGH) in an area with the world's highest incidence of the disease. Methodology/Principal Findings Clinical and laboratory records of patients presenting to the KGH Lassa Ward in the post-conflict period were organized electronically. Recombinant antigen-based LF immunoassays were used to assess LASV antigenemia and LASV-specific antibodies in patients who met criteria for suspected LF. KGH has been reestablished as a center for LF treatment and research, with over 500 suspected cases now presenting yearly. Higher case fatality rates (CFRs) in LF patients were observed compared to studies conducted prior to the civil conflict. Different criteria for defining LF stages and differences in sensitivity of assays likely account for these differences. The highest incidence of LF in Sierra Leone was observed during the dry season. LF cases were observed in ten of Sierra Leone's thirteen districts, with numerous cases from outside the traditional endemic zone. Deaths in patients presenting with LASV antigenemia were skewed towards individuals less than 29 years of age. Women self-reporting as pregnant were significantly overrepresented among LASV antigenemic patients. The CFR of ribavirin-treated patients presenting early in acute infection was lower than in untreated subjects. Conclusions/Significance: Lassa fever remains a major public health threat in Sierra Leone. Outreach activities should expand because LF may be more widespread in Sierra Leone than previously recognized. Enhanced case finding to ensure rapid diagnosis and treatment is imperative to reduce mortality. Even with ribavirin treatment, there was a high rate of fatalities underscoring the need to develop more effective and/or supplemental treatments for LF

Ocean current patterns drive the worldwide colonization of eelgrass (Zostera marina)

publishedVersio

Convergence of gut microbiotas in the adaptive radiations of African cichlid fishes

Ecoevolutionary dynamics of the gut microbiota at the macroscale level, that is, in across-species comparisons, are largely driven by ecological variables and host genotype. The repeated explosive radiations of African cichlid fishes in distinct lakes, following a dietary diversification in a context of reduced genetic diversity, provide a natural setup to explore convergence, divergence and repeatability in patterns of microbiota dynamics as a function of the host diet, phylogeny and environment. Here we characterized by 16S rRNA amplicon sequencing the gut microbiota of 29 cichlid species from two distinct lakes/radiations (Tanganyika and Barombi Mbo) and across a broad dietary and phylogenetic range. Within each lake, a significant deviation between a carnivorous and herbivorous lifestyle was found. Herbivore species were characterized by an increased bacterial taxonomic and functional diversity and converged in key compositional and functional community aspects. Despite a significant lake effect on the microbiota structure, this process has occurred with remarkable parallels in the two lakes. A metabolic signature most likely explains this trend, as indicated by a significant enrichment in herbivores/omnivores of bacterial taxa and functions associated with fiber degradation and detoxification of plant chemical compounds. Overall, compositional and functional aspects of the gut microbiota individually and altogether validate and predict main cichlid dietary habits, suggesting a fundamental role of gut bacteria in cichlid niche expansion and adaptation