New insights on the molecular features and electrophysiological properties of dinotefuran, imidacloprid and acetamiprid neonicotinoid insecticides

Structural features and hydrogen-bond interactions of dinotefuran (DIN), imidacoloprid (IMI) and acetamiprid (ACE) have been investigated experimentally through analyses of new crystal structures and observations in structural databases, as well as by Density Functional Theory quantum chemical calculations. Several conformations are observed experimentally in the solid state, highlighting the large flexibility of these compounds. This feature is confirmed by the theoretical calculations in the gas phase, the numerous and different energetic minima of the three neonicotinoids being located within a 10kJ/mol range. Comparisons of the observed and simulated data sheds light on the hydrogen-bond (HB) strength of the functional group at the tip of the electronegative fragment of each pharmacophore (NO(2) for DIN and IMI and CN for ACE). This effect originates in the \u27push-pull\u27 nature of these fragments and the related extensive electron delocalization. Molecular electrostatic potential calculations provide a ranking of the two fragments of the three neonicotinoid in terms of HB strength. Thus, the NO(2) group of DIN is the strongest HB acceptor of the electronegative fragment, closely followed by the cyano group of ACE. These two groups are significantly more potent than the NO(2) group of IMI. With respect to the other fragments of the three neonicotinoids, the nitrogen atom of the pyridine of IMI and ACE are stronger HB acceptors than the oxygen atom of the furanyl moiety of DIN. Finally, compared to electrophysiological studies obtained from cockroach synaptic and extrasynaptic receptors, DIN appears more effective than IMI and ACE because it strongly increases dose-dependently the ganglionic depolarisation and the currents amplitudes. These data suggest that DIN, IMI and ACE belong to two subgroups which act differently as agonists of insect nicotinic receptors

Drying of microalga Spirulina platensis in a rotary dryer with inert bed

[EN] The aim of this work is investigate the use of a rotary dryer with inert bed for drying of microalga Spirulina platensis. The influence of air temperature, feed rate, rotation speed and inerts filling degree was quantified. The contents of main bioactive compounds were also analyzed. The results shown that the used drying system proved to be an interesting alternative for a possible use of this microalga, if performed under adequate conditions. It was identified conditions with high drying performance and with the preservation of product qualitySilva, NC.; Silva, TC.; Santos, AO.; Graton, IS.; Duarte, CR.; Barrozo, M. (2018). Drying of microalga Spirulina platensis in a rotary dryer with inert bed. En IDS 2018. 21st International Drying Symposium Proceedings. Editorial Universitat Politècnica de València. 1535-1542. https://doi.org/10.4995/IDS2018.2018.7457OCS1535154

Predictive Models for Halogen-bond Basicity of Binding Sites of Polyfunctional Molecules

© 2016 Wiley-VCH Verlag GmbH & Co. KGaA.Halogen bonding (XB) strength assesses the ability of an electron-enriched group to be involved in complexes with polarizable electrophilic halogenated or diatomic halogen molecules. Here, we report QSPR models of XB of particular relevance for an efficient screening of large sets of compounds. The basicity is described by pKBI2, the decimal logarithm of the experimental 1 : 1 (B :I2) complexation constant K of organic compounds (B) with diiodine (I2) as a reference halogen-bond donor in alkanes at 298K. Modeling involved ISIDA fragment descriptors, using SVM and MLR methods on a set of 598 organic compounds. Developed models were then challenged to make predictions for an external test set of 11 polyfunctional compounds for which unambiguous assignment of the measured effective complexation constant to specific groups out of the putative acceptor sites is not granted. At this stage, developed models were used to predict pKBI2 of all putative acceptor sites, followed by an estimation of the predicted effective complexation constant using the ChemEqui program. The best consensus models perform well both in cross-validation (root mean squared error RMSE=0.39-0.47logKBI2 units) and external predictions (RMSE=0.49). The SVM models are implemented on our website (http://infochim.u-strasbg.fr/webserv/VSEngine.html) together with the estimation of their applicability domain and an automatic detection of potential halogen-bond acceptor atoms

Microstructural evolution and trace element mobility in Witwatersrand pyrite

Microstructural analysis of pyrite from a single sample of Witwatersrand conglomerate indicates a complex deformation history involving components of both plastic and brittle deformation. Internal deformation associated with dislocation creep is heterogeneously developed within grains, shows no systematic relationship to bulk rock strain or the location of grain boundaries and is interpreted to represent an episode of pyrite deformation that predates the incorporation of detrital pyrite grains into the Central Rand conglomerates. In contrast, brittle deformation, manifest by grain fragmentation that transects dislocation-related microstructures, is spatially related to grain contacts and is interpreted to represent post-depositional deformation of the Central Rand conglomerates. Analysis of the low-angle boundaries associated with the early dislocation creep phase of deformation indicates the operation of {100} slip systems. However, some orientation boundaries have geometrical characteristics that are not consistent with simple {100} deformation.These boundaries may represent the combination of multiple slip systems or the operation of the previously unrecognized {120} slip system. These boundaries are associated with order of magnitude enrichments in As, Ni and Co that indicate a deformation control on the remobilization of trace elements within pyrite and a potential slip system control on the effectiveness of fast-diffusion pathways. The results confirm the importance of grain-scale elemental remobilization within pyrite prior to their incorporation into the Witwatersrand gold-bearing conglomerates. Since the relationship between gold and pyrite is intimately related to the trace element geochemistry of pyrite, the results have implications for the application of minor element geochemistry to ore deposit formation, suggest a reason for heterogeneous conductivity and localized gold precipitation in natural pyrite and provide a framework for improving mineral processing

A New Simulation Approach for Performance Prediction of Vertically Integrated Nanogenerators

International audienceThe vertically integrated nanogenerator (VING) is one of the most used designs in mechanical energy harvesting using piezoelectric nanowires, dueto its easiest manufacturing process. Here, a new modeling approach is presented in order to reduce the computation time of a whole VING finiteelement simulation. In this work, the effect of the polymer layer (Parylene C), in which nanowires are immersed, on the electromechanical behavior of the whole VING is taken into account. The active part of the VING (nanowires–polymer composite) is considered as a 1–3 piezocomposite. It isformed with ZnO piezoelectric nanowires; however, this study can be applied to any type of piezoelectric nanowires (PZT, GaN, PVDF, etc.) and matrix materials (PDMS, PMMA, Al2O3, etc.). The present method relies on the finite element method applied to a single nanowire-composite cell in open-circuit condition, combined with an analytical modeling of the full VING. This approach allows the computation time to be drastically reduced without inducing significant approximation errors. The expected maximum power, internal capacitance, and optimum resistance can be deduced thanks to this efficient modeling tool, offering wide perspectives for the optimization of such VING devices