130,432 research outputs found
Cooperative self-assembly process involving Giant Polyoxometakate as trans-membrane-like component into 2D bilayer Structure-type
No full textInternational audienceCHAOTROPIC EFFECT AS AN ASSEMBLY MOTIF IN POLYOXOMETALATE SUPRAMOLECULAR CHEMISTRYSoumaya Khlifi,1 Clément Falaise,1 Mohamed Haouas,1 Nathalie Leclerc,1 Pierre Bauduin2 and Emmanuel Cadot,11 ILV, UVSQ, Université Paris-Saclay, Versailles, France2 ICSM, CEA, CNRS, ENSCM, Université Montpellier, 34199 Marcoule, FranceAbstract. The ability of biochemical substances such as phospholipids, glycans, or proteins to interact with discrete inorganic species is essential for some biological functions.[1] Then, designing supramolecular hybrid architectures including dynamics and responsive behavior requires a fine balance between the conglomerate of weak forces such as electrostatic, ion-dipole, dipole-dipole, hydrogen-bonding, dispersion, etc., that drives the aggregation processes. Recent reports highlight the intriguing properties of certain inorganic polynuclear anions, such as polyoxometalates (POMs) or polynuclear clusters for their extremely high propensity to interact strongly in aqueous solution with non-ionic organic components such as macrocycles or surfactants.[2,3,4] This striking driving force has been identified as a strong solvent effect arising from chaotropic nature of the polyoxometalates in aqueous solution. In this communication, we will highlight the origin of this effect by proposing a classification of the chaotropic character of a large series of polyoxometalates, ranging from the Keggin type ions to the large nanoscopic ring-shape molybdenum blue. However, we will give some relevant examples showing how the chaotropic effect can be used to monitor supramolecular hybrid assemblies such as molecular core-shell, supramolecular MOFs or POM-containing bilayer type membrane. [1]Zhong, W.; Alexeev, D.; Harvey, I.; Guo, M.; Hunter, D. J. B.; Zhu, H.; Campopiano, D. J.; Sadler, P. J.. Angew. Chem. Int. Ed. 2004, 43 (44), 5914–5918.[2] Assaf, K. I.; Ural, M. S.; Pan, F.; Georgiev, T.; Simova, S.; Rissanen, K.; Gabel, D.; Nau, W. M. Angew. Chem. Int. Ed. 2015, 54 (23), 6852–6856.[3]Moussawi, M. A.; Haouas, M.; Floquet, S.; Shepard, W. E.; Abramov, P. A.; Sokolov, M. N.; Fedin, V. P.; Cordier, S.; Ponchel, A.; Monflier, E.; Marrot, J.; Cadot, E. J. Am. Chem. Soc. 2017, 139 (41), 14376–14379.[4]Falaise, C.; Khlifi, S.; Bauduin, P.; Schmid, P.; Shepard, W.; Ivanov, A. A.; Sokolov, M. N.; Shestopalov, M. A.; Abramov, P. A.; Cordier, S.; Marrot, J.; Haouas, M.; Cadot, E. Angew. Chem. Int. Ed. 2021, 60 (25), 14146–14153
Cooperative self-assembly process involving Giant Polyoxometakate as trans-membrane-like component into 2D bilayer Structure-type
No full textInternational audienceCHAOTROPIC EFFECT AS AN ASSEMBLY MOTIF IN POLYOXOMETALATE SUPRAMOLECULAR CHEMISTRYSoumaya Khlifi,1 Clément Falaise,1 Mohamed Haouas,1 Nathalie Leclerc,1 Pierre Bauduin2 and Emmanuel Cadot,11 ILV, UVSQ, Université Paris-Saclay, Versailles, France2 ICSM, CEA, CNRS, ENSCM, Université Montpellier, 34199 Marcoule, FranceAbstract. The ability of biochemical substances such as phospholipids, glycans, or proteins to interact with discrete inorganic species is essential for some biological functions.[1] Then, designing supramolecular hybrid architectures including dynamics and responsive behavior requires a fine balance between the conglomerate of weak forces such as electrostatic, ion-dipole, dipole-dipole, hydrogen-bonding, dispersion, etc., that drives the aggregation processes. Recent reports highlight the intriguing properties of certain inorganic polynuclear anions, such as polyoxometalates (POMs) or polynuclear clusters for their extremely high propensity to interact strongly in aqueous solution with non-ionic organic components such as macrocycles or surfactants.[2,3,4] This striking driving force has been identified as a strong solvent effect arising from chaotropic nature of the polyoxometalates in aqueous solution. In this communication, we will highlight the origin of this effect by proposing a classification of the chaotropic character of a large series of polyoxometalates, ranging from the Keggin type ions to the large nanoscopic ring-shape molybdenum blue. However, we will give some relevant examples showing how the chaotropic effect can be used to monitor supramolecular hybrid assemblies such as molecular core-shell, supramolecular MOFs or POM-containing bilayer type membrane. [1]Zhong, W.; Alexeev, D.; Harvey, I.; Guo, M.; Hunter, D. J. B.; Zhu, H.; Campopiano, D. J.; Sadler, P. J.. Angew. Chem. Int. Ed. 2004, 43 (44), 5914–5918.[2] Assaf, K. I.; Ural, M. S.; Pan, F.; Georgiev, T.; Simova, S.; Rissanen, K.; Gabel, D.; Nau, W. M. Angew. Chem. Int. Ed. 2015, 54 (23), 6852–6856.[3]Moussawi, M. A.; Haouas, M.; Floquet, S.; Shepard, W. E.; Abramov, P. A.; Sokolov, M. N.; Fedin, V. P.; Cordier, S.; Ponchel, A.; Monflier, E.; Marrot, J.; Cadot, E. J. Am. Chem. Soc. 2017, 139 (41), 14376–14379.[4]Falaise, C.; Khlifi, S.; Bauduin, P.; Schmid, P.; Shepard, W.; Ivanov, A. A.; Sokolov, M. N.; Shestopalov, M. A.; Abramov, P. A.; Cordier, S.; Marrot, J.; Haouas, M.; Cadot, E. Angew. Chem. Int. Ed. 2021, 60 (25), 14146–14153
Chemical composition and bioactivities of three Chrysanthemum essential oils against Tribolium confusum (du Val) (Coleoptera: Tenebrionidae)
No full textEssential oils from three species of Chrysanthemum growing in Tunisia (C. coronarium, C. fuscatum, and C. grandiflorum) were first analyzed by gas chromatography (GC) and GC/mass spectrometry (MS) and then evaluated for toxicity and antifeeding action against Tribolium confusum. The essential oils obtained from leaves and flowers shared a similar qualitative composition, but the relative proportions of the constituents were quite different. The essential oil of C. grandiflorum was rich in sesquiterpenoids, while those of C. fuscatum and C. coronarium were rich in monoterpenoids. The main common constituents of all the essential oils were α-pinene, myrcene, α-humulene, β-caryophylene, spathulenol, and caryophyllene oxide. The most effective essential oil was obtained from the leaves of C. grandiflorum, that inhibited the relative growth rate (−0.03 mg/mg/d), efficiency of conversion of ingested food (−50.69%), relative consumption rate, caused an antifeeding effect (66.43%) and a high mortality (80%) of T. confusum larvae. Topical application C. grandiflorum essential oil caused a significant insect mortality that attends 27% after 7 days of treatment. While essential oil from C. coronarium flowers has contact and fumigant toxicity with a mortality of 9 and 13%, respectively. Results analysis highlights a relationship between essential oils composition and insecticidal activity against T. confusum. The study showed that each essential oil has specific chemical composition and act differently according to the nature of attributed test. The use of essential oils from different Chrysanthemum species with different methods helps poor farmers who store small amounts of grains to preserve it against pest infestatio
MeSH term explosion and author rank improve expert recommendations
No full textInformation overload is an often-cited phenomenon that reduces the productivity, efficiency and efficacy of scientists. One challenge for scientists is to find appropriate collaborators in their research. The literature describes various solutions to the problem of expertise location, but most current approaches do not appear to be very suitable for expert recommendations in biomedical research. In this study, we present the development and initial evaluation of a vector space model-based algorithm to calculate researcher similarity using four inputs: 1) MeSH terms of publications; 2) MeSH terms and author rank; 3) exploded MeSH terms; and 4) exploded MeSH terms and author rank. We developed and evaluated the algorithm using a data set of 17,525 authors and their 22,542 papers. On average, our algorithms correctly predicted 2.5 of the top 5/10 coauthors of individual scientists. Exploded MeSH and author rank outperformed all other algorithms in accuracy, followed closely by MeSH and author rank. Our results show that the accuracy of MeSH term-based matching can be enhanced with other metadata such as author rank
Insecticidal and anti-appetent activities of four Chrysanthemum species against Tribolium confusum Du Val (Coleoptera: Tenebrionidae)
No full textInsect pests are one of the major factors limiting the production and the storage of agricultural products. The use of synthetic pesticides limits the damage of these pests. However, the effectiveness of these products is continually eroded by the development of resistance in these pests and serious health and ecological disadvantages were detected. It is clear that there is an urgent need for alternative control measures, which must be active against the pests, safe to humans and environmentally friendly. Evaluation of local plants as sources of protectants is one of the promising ways to fulfil this need. In this study the essential oil of four Chrysanthemum species (C. macrotum, C. trifurcatum, C. segetum and C. fuscatum) were evaluated for their insecticidal activity against Tribolium confusum using tow methods: fumigation and consumption. The essential was diluted in acetone to obtain the concentration of 1%. For the fumigant activity, 100 μl of the solution was applied on filter paper (1x2.5 cm), after evaporating the solvent, each filter paper was placed on the underside of the screw cap of a glass vial and was screwed tightly onto the vial containing ten adults of Tribolium confusum. Concerning the evaluation of the anti-appetent activity, 5 μl of each Chrysanthemum species essential oil were applied on flour disc (95% wheat semolina and 5% beer yeast). The control received only acetone and five replicates were set up for each treatment and control. The results showed that essential oil obtained from flowers of C. macrotum and those from leaves of C. trifurcatum have the highest fumigant activity and cause respectively the mortality of 48 and 40% against adults of T. confusum. The study of anti-appetent effect on larvae of T. confusum showed that C. segetum flowers essential oil has the significant feeding deterrent index (92.45±4.61) followed by the leaves essential oil obtained from C. fuscatum (71.20±19.22), without having a significant mortality on this larvae.
The study of essential oil composition of the four Chrysanthemum species highlighted their richness on mono and sesqueterpenes that are known for their insecticidal activity.
Though these findings are preliminary, they could represent the basis for further investigations on the questions raised in this work. In particular, additional research is needed to investigate the susceptibility of other stages of the insect life, such as pupae and eggs and to improve our understanding of how mono- and sesquiterpenoids act on insects. Practically, in view of a possible use of the most active mono- and sesquiterpenoids, it should be pointed out that longer exposure periods could be needed to bridge the tolerant phases of insects, some of which could be present at the time of application
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Chemical constituents and toxicity of essential oils from three Asteraceae plants against Tribolium confusum
No full textPlants produce a high diversity of secondary metabolites with a prominent function in the protection against pests and pathogens. In this work, we studied the chemical composition and the effect of six essential oils extracted from three Asteraceae species (Heteromera fuscata, Coleostephus myconis and Mauranthemum paludosum) on nutritional indexes, adult emergence and larva and adult toxicity of Tribolium confusum. Flower and leaf essential oils were obtained by hydrodistillation. The study of their chemical composition was carried out by GC-MS. The results showed that they are rich on monoand sesquiterpens. The consumption of essential oils mixed with artificial diet of T. confusum larvae showed that H. fuscata leaf essential oil delayed the insect growth, reduced the food consumption and exhibited significant food deterrent index (0.02 ± 0.01 mg/mg/j, 0.05 ± 0.02 mg/mg/j, and 71.20 ± 19.22%, respectively) on treated larvae. Topical application of Asteraceae essential oils on pupae less than 24 h of age caused malformation on emerged adults. The highest level of malformation (18%) was induced by C. myconis leaf essential. Topical application of those essential oils on T. confusum adults (10 and 14 days-old) showed higher toxicity. The highest mortality of about 41% was recorded 7 days post-treatment on adults treated with essential oils from M. paludosum leaves. These preliminary results could represent the basis for further investigations on the susceptibility of the other
developmental stages and elucidation of the mode of action of mono- and sesquiterpenoids against these insect pest
Comparison of chemical composition and bio-insecticidal activity of three Chrysanthemum species essential oils on Tribolium confusum Du Val (Coleoptera: Tenebrionidae)
No full textIn traditional agriculture, plant extracts were the most effective source to protect the food, but by the nineteenth century this practice was gradually replaced by synthetic products. However, those products are expensive and induce the insect resistance, so researches are oriented to study the insecticidal activity of plant extracts aimed to isolate active (s) compound(s). In this work we studied the insecticidal activity of essential oils of three Chrysanthemum species against Tribolium confusum. Three methods are used, such as ingestion, topical application against adults and nymphs and fumigation against adults. The results analysis showed that ingestion of artificial medium treated by essential oils causes a decrease in larvae consumption and we noticed that C. macrotum essential oil was the most antifeedant one. In addition this oil caused significant mortality (68 %) in treated larvae.
Topical application of essential oils against adults and nymphs beetle showed that C. macrotum essential oil is more toxic against adults (44%) than nymphs (28%). The analysis of fumigation results showed that the highest toxicity (48%) was caused by C. macrotum essential oil and that so it doesn’t exceed 1% in the case of C. trifurcatum and C. fuscatum. These results highlight that C. macrotum essential oil was most effective against T. confusum. Chemical analysis of different essential oils showed that C. macrotum essential oil was very rich in terpenes, where sesquiterpenes are the most abundant compounds. According these results we have determine the species and the chemical
composition of the most toxic essential oil on T. confusum. Further study will be very useful to determine the toxic compound (s)
"Closing the R&D Gap, Evaluating the Sources of R&D Spending"
No full textBoth spending and tax policies have been implemented in the United States with the goal of stimulating private sector research and development (R&D). Karier questions whether current R&D policy, especially the research and experimentation tax credit, can contribute to closing the gap between nondefense expenditures on R&D in the United States and such expenditures in other countries, such as Japan and Germany. He also explores possible changes to our current R&D policy to make it more effective.
Identification d'un dérivé de polyacetilène de spiroketole enol éther du Chrysanthemum macrotum L
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