Force exertion by light-fueled self-assembly:synthetic polymer motors

Vital cellular functions rely on dynamic soft materials known as microtubules and actin filaments. The role of these polymerization motors consists in converting the free energy of supramolecular polymerization into mechanical forces, through which purposeful motion can be generated, for example chromosomes separation or cell movement. The goal of this PhD project is to create fully artificial and waste-free polymerization motors capable of converting light into mechanical forces at the nanoscale and beyond. The first challenge is to control the aqueous supramolecular polymerization of dynamic tubular self-assemblies (artificial microtubules) and dynamic networks of helical supramolecular polymers (artificial actin networks) by light. The second challenge is to demonstrate the exertion of mechanical forces generated by their light-fueled self-assembly

Hypoglycemic Activity of Hydro-Acetonic and HydroMethanolic Leaf and Bark Extracts of Bauhinia rufescens Lam in mice

The purpose of this study was to determine the hypoglycaemic effects of leaf and bark extracts of Bauhinia rufescens Lam, used in traditional medicine for diabetes in Senegal. Phytochemical screening of hydromethanolic and hydro-acetonic extracts obtained from leaves and barks were carried out according to standard analytical methods. Experiments were carried out on normoglycemic and diabetic mice. These were obtained after injection of a single dose of glucose (4 g/kg of body weight). The results showed that polyphenolic compounds, tannins and flavonoids were the main phytochemical constituents of the extracts. Then the oral administration of the different extracts of Bauhinia rufescens Lam at doses of 500, 700 and 1000 mg/kg of body weight led to a significant reduction in blood sugar (p < 0.05), similarly to antidiabetic action of glibenclamide (10 mg/kg of body weight). Whatever the organ and the extraction solvent, the doses of 500 and 700 mg/kg of body weight induced dose-dependent hypoglycemia, just like glibenclamide. These results show that the metabolites revealed in the extracts could be responsible for its hypoglycemic effects. Thus, supported by a complete chemical study with a view to isolating the active substances responsible for the antidiabetic effect is possible. It will allowed to formulate from a phytomedicine with potential for diabetes which make possible their uses by populations for treatment of diabetes.&nbsp

Quantitative analysis of behaviour phase difference in locusts with the examination of spatial distribution patterns

The use of cameras to analyze locust activity, attraction / repulsion is an innovation that is increasingly used in behavioral studies. It allows to simultaneously collect information without interacting with the locusts and to observe more discrete behaviors which are not visually noticeable. Although the technique is complementary to the one focused on the analysis of the individual response to a group of stimuli, it offers an improvement in the observation methods of groups of individuals through the application of spatial statistics. In our present study, we did laboratory analysis of locust spatial distribution patterns in a circular arena for characterizing phase status. With spatial statistics, we examined the temporal variations of nearest neighbor distances as a criterion of attraction / repulsion between individuals raised either in isolation or in groups in order to induce phase behavior. Also, the successive changes of position of the individuals because of their activity in the circular arena were interpreted as criterion of differentiation between solitarious and gregarious locust phases. Tests were carried out, first with the sequences of photographs taken at regular intervals on 3rd instar hoppers of Desert Locust, Schistocerca gregaria, and secondly with the help of video tracking on 3rd instar hoppers of the Migratory Locust, Locusta migratoria. Making inferences on the underlying process that generates the temporal variations of the positions of the hoppers in the arena, we found that there was a larger nearest neighbor distance between isolated-rearedhoppers (indicating repulsion) in contrast to crowd-rearedhoppers, which showed an attraction with their conspecifics. From the analysis of walked distances in both tests, we found a greater activity of crowd-rearedhoppers compared to isolated-rearedhoppers. This method of quantitative analysis of locust phase differences appears to be more effective in saving time and providing more insight into as yet unclear aspects of behavioral phase studies

Relationships between anthocyanins and other compounds and sensory acceptability of Hibiscus drinks

Chemical composition of Hibiscus drinks (Koor and Vimto varieties, commercial and traditional, infusions and syrups) was related to sensory evaluation and acceptance. Significant correlations between chemical composition and sensory perception of drinks were found (i.e. anthocyanin content and Hibiscus taste). Consumers (n=160) evaluated drink acceptability on a 9-point verbal hedonic scale. Three classes of behaviour were identified: a) those who preferred syrup (43% of consumers); b) those who preferred infusion (36%); and c) those who preferred all of the samples (21%). Acceptability of ‘syrup likers‘ was positively correlated to sweet taste, reducing sugar content and inversely correlated to acidic taste and titrable acidity. Acceptability of ‘infusion likers’ was positively correlated to the taste of Hibiscus drink and anthocyanin content. The study shows that the distinctions between the acceptability groups are very clear with respect to the chemical composition and rating of sensory attributes

From no whinge scenarios to viability tree

Avoiding whinges from various and potentially conflicting stakeholders is a major challenge for sustainable development and for the identification of sustainability scenarios or policies for biodiversity and ecosystem services. It turns out that independently complying with whinge thresholds and constraints of these stakeholders is not sufficient because dynamic ecological-economic interactions and uncertainties occur. Thus more demanding no whinge standards are needed. In this paper, we first argue that these new boundaries can be endogenously exhibited with the mathematical concepts of viability kernel and viable controls. Second, it is shown how these no whinge kernels have components, such as harvesting of resources, that should remain within safe corridor while some other components, in particular biodiversity, have only lower conservation limits. Thus, using radar charts, we show how this no whinge kernels can take the shape of a tree that we name viability tree. These trees of viability capture the idea that the unbounded renewal potential of biodiversity combined with a bounded use of the different ecosystem services are crucial ingredients for the sustainability of socio-ecosystems and the design of no whinge policies reconciling the different stakeholders involved

Gradual emergence followed by exponential spread of the SARS-CoV-2 Omicron variant in Africa.

The geographic and evolutionary origins of the SARS-CoV-2 Omicron variant (BA.1), which was first detected mid-November 2021 in Southern Africa, remain unknown. We tested 13,097 COVID-19 patients sampled between mid-2021 to early 2022 from 22 African countries for BA.1 by real-time RT-PCR. By November-December 2021, BA.1 had replaced the Delta variant in all African sub-regions following a South-North gradient, with a peak Rt of 4.1. Polymerase chain reaction and near-full genome sequencing data revealed genetically diverse Omicron ancestors already existed across Africa by August 2021. Mutations, altering viral tropism, replication and immune escape, gradually accumulated in the spike gene. Omicron ancestors were therefore present in several African countries months before Omicron dominated transmission. These data also indicate that travel bans are ineffective in the face of undetected and widespread infection

Retraction.

This is a retraction of 'Gradual emergence followed by exponential spread of the SARS-CoV-2 Omicron variant in Africa' 10.1126/science.add873

Bradford quantification of Glomalin-Related Soil Protein in coloured extracts of forest soils

Glomalin-related soil protein (GRSP) is thought to represent a fraction of recalcitrant organic matter in soil. But it is recognized that the autoclaved-citrate extraction procedure causes the co-extraction of humic substances which interfere (directly and indirectly) with the Bradford colorimetric assay. The aim of this work was to propose a reliable quantification method of GRSP from forest soil, very rich in organic matter and therefore in colour. We estimated the quantities of GRSP in the topsoil (0–10 cm) of 102 French forests using five methods: i) direct calibration, reasoned dilution with colour correction, ii) direct calibration, reasoned dilution but no colour correction, iii) direct calibration, 1:2 dilution, no colour correction, iv) indirect calibration and v) dilution method. Our results concur that the interference caused by the co-extracted compounds is not related simply to either the colour of the extracts or total soil organic matter content. These findings suggest that for improved accuracy of GRSP estimates using the Bradford method, extracts should be diluted, and the pH-specific absorbance of coloured extracts should be subtracted