Polarizabilities of Push-Pull Carbon Nanotubes: Semi-Empirical PM6 Study

A series of push-pull armchair (5,5) single-walled carbon nanotubes (D-CNTs-NO2) nbspsaturated with hydrogen at the ends have been studied using semi-empirical PM6 methods. As a result, it is found that the polarizability strongly depends on the strength of Pi-electron donor substituent. Particularly, for both static and dynamic polarizabilities the largest increment of Deltaalpha is seen to be due to - NMe2 donor group (Deltaalpha =100 a.u.). Miller QSAR-polarizability, empirical models based on molecular volumes(Vm) and electrons number (Ne) correlatenbsp well (Rgt0.97) with PM6 polarizabilities results

Short-term effect of sawdust biochar and bovine manure on the physiological behavior of turnip (Brassica rapa L.) grown in open fields in the Algiers region

ArticleThis study was designed to determine the effect of different doses of biochar (B) 5.10, 20tha-1alone and mixed with manure (F) 10tha-1on turnips. The results showed that the OM (organic matter) rate had a maximum of 93.7% for (B20*F) and a minimum of 14.5% for (F); the CEC (cation exchange capacity) showed a maximum of 32.2% for (B10*F) and a minimum of 0.2% with (B5*F) compared to the control (T) and finally the pH to be increased with a maximum value of 11.2% for (B20*F) and a minimum value of 1.7% for (F) compared to (T) (≤0.01).For the chemical parameters of the turnip, the maximum nitrogen rate was 93.8% with (B10) and 2% for (B20). The highest value for phosphorus was recorded in (F) and a minimal value in (B5) (≤0.01).The potassium level was high 4.2% for the treatment (B20*F) with the lowest value of 4.4% for (B5) and (B10) compared to (T) (0.05).For the yield components, thefresh weight of the most important bulb was obtained with (F) with the value of 116.8% and minimum weight of 0.4% in the treatment (B5). The highest bulb length value was 36.8% in (F) and the lowest was 0.5% obtained with (B20*F). The bulb diameter was the largest in the treatment (F) and the smallest was 4.8% in (B20). Finally, the fresh weight of the leaves showed a maximum of 106.9% in (F) and an increase of 6% in (B20) compared to (T) (≤0.01)

Pathogenicity of proteinase 3-anti-neutrophil cytoplasmic antibody in granulomatosis with polyangiitis: Implications as biomarker and future therapies

Granulomatosis with polyangiitis (GPA) is a rare but serious necrotizing auto-immune vasculitis. GPA is mostly associated with the presence of Anti-Neutrophil Cytoplasmic Antibody (ANCA) targeting proteinase 3 (PR3-ANCA), a serine protease contained in neutrophil granules but also exposed at the membrane. PR3-ANCAs have a proven fundamental role in GPA: they bind neutrophils allowing their auto-immune activation responsible for vasculitis lesions. PR3-ANCAs bind neutrophil surface on the one hand by their Fab binding PR3 and on the other by their Fc binding Fc gamma receptors. Despite current therapies, GPA is still a serious disease with an important mortality and a high risk of relapse. Furthermore, although PR3-ANCAs are a consistent biomarker for GPA diagnosis, relapse management currently based on their level is inconsistent. Indeed, PR3-ANCA level is not correlated with disease activity in 25% of patients suggesting that not all PR3-ANCAs are pathogenic. Therefore, the development of new biomarkers to evaluate disease activity and predict relapse and new therapies is necessary. Understanding factors influencing PR3-ANCA pathogenicity, i.e. their potential to induce auto-immune activation of neutrophils, offers interesting perspectives in order to improve GPA management. Most relevant factors influencing PR3-ANCA pathogenicity are involved in their interaction with neutrophils: level of PR3 autoantigen at neutrophil surface, epitope of PR3 recognized by PR3-ANCA, isotype and glycosylation of PR3-ANCA. We detailed in this review the advances in understanding these factors influencing PR3-ANCA pathogenicity in order to use them as biomarkers and develop new therapies in GPA as part of a personalized approach

MIL-91(Ti), a small pore metal-organic framework which fulfils several criteria : an upscaled green synthesis, excellent water stability, high CO2 selectivity and fast CO2 transport

The research leading to these results has received funding from the European Community Seventh Framework Program (FP7/2007-2013) [grant agreement number 608490] (project M4CO2) and from the ANR ‘CHESDENS’ (ANR-13-SEED-0001-01).A multidisciplinary approach combining advanced experimental and modelling tools was undertaken to characterize the promises of a small-pore type Ti-based metal-organic framework, MIL-91(Ti) for CO2 capture. This material was prepared using two synthesis strategies, i.e. under hydrothermal conditions and under reflux, and its single component adsorption behaviour with respect to CO2, CH4 and N2 was first revealed by gravimetry measurements. This hydrophilic and highly water stable MOF is characterized by a relatively high CO2 adsorption enthalpy. Molecular simulations combined with in situ powder X-ray diffraction evidenced that this is due to the combined interaction of this probe with N-H and P-O groups in the phosphonate linker. High CO2 selectivities in the presence of either N2 or CH4 were also predicted and confirmed by co-adsorption measurements. The possibility to prepare this sample under reflux represents an environmentally friendly route which can easily be upscaled. This green synthesis route, excellent water stability, high selectivities and relatively fast transport kinetics of CO2 are significant points rendering this sample of utmost interest for CO2 capture.PostprintPostprintPeer reviewe

Studies on metal-organic frameworks of Cu(II) with isophthalate linkers for hydrogen storage

Hydrogen (H2) is a promising alternative energy carrier due to its environmental benefits, high energy density and its abundance. However, development of a practical storage system to enable the “Hydrogen Economy” remains a huge challenge. Metal-organic frameworks (MOFs) are an important class of crystalline coordination polymers constructed by bridging metal centers with organic linkers, and show promise for H2 storage due to their high surface area and tuneable properties. We summarize our research on novel porous materials with enhanced H2 storage properties, and describe frameworks derived from 3,5-substituted dicarboxylates (isophthalates) that serve as versatile molecular building blocks for the construction of a range of interesting coordination polymers with Cu(II) ions. A series of materials has been synthesised by connecting linear tetracarboxylate linkers to {Cu(II)2} paddlewheel moieties. These (4,4)-connected frameworks adopt the fof-topology in which the Kagomé lattice layers formed by {Cu(II)2} paddlewheels and isophthalates are pillared by the bridging ligands. These materials exhibit high structural stability and permanent porosity, and the pore size, geometry and functionality can be modulated by variation of the organic linker to control the overall H2 adsorption properties. NOTT-103 shows the highest H2 storage capacity of 77.8 mg g−1 at 77 K, 60 bar among the fof-type frameworks. H2 adsorption at low, medium and high pressures correlates with the isosteric heat of adsorption, surface area and pore volume, respectively. Tri-branched C3-symmetric hexacarboxylate ligands with Cu(II) give highly porous (3,24)-connected frameworks incorporating {Cu(II)2} paddlewheels. These ubt-type frameworks comprise three types of polyhedral cage: a cuboctahedron, truncated tetrahedron and a truncated octahedron which are fused in the solid state in the ratio 1:2:1, respectively. Increasing the length of the hexacarboxylate struts directly tunes the porosity of the resultant material from micro- to mesoporosity. These materials show exceptionally high H2 uptakes owing to their high surface area and pore volume. NOTT-112, the first reported member of this family reported, adsorbs 111 mg g−1 of H2 at 77 K , 77 bar. More recently, enhanced H2 adsorption in these ubt-type frameworks has been achieved using combinations of polyphenyl groups linked by alkynes to give an overall gravimetric gas capacity for NU-100 of 164 mg g−1 at 77 K, 70 bar. However, due to its very low density NU-100 shows a lower volumetric capacity of 45.7 g L-1 compared with 55.9 g L-1 for NOTT-112, which adsorbs 2.3 wt% H2 at 1 bar, 77K. This significant adsorption of H2 at low pressures is attributed to the arrangement of the {Cu24(isophthalate)24} cuboctahedral cages within the polyhedral structure. Free metal coordination positions are the first binding sites for D2, and in these ubt-type frameworks there are two types of Cu(II) centres, one with its vacant site pointing into the cuboctahedral cage and another pointing externally. D2 molecules bind first at the former position, and then at the external open metal sites. However, other adsorption sites between the cusp of three phenyl groups and a Type I pore window in the framework are also occupied. Ligand and complex design feature strongly in enhancing and maximising H2 storage, and, although current materials operate at 77 K, research continues to explore routes to high capacity H2 storage materials that can function at higher temperatures

Methane adsorption in metal-organic frameworks containing nanographene linkers: a computational study

Metal-organic framework (MOF) materials are known to be amenable to expansion through elongation of the parent organic linker. For a family of model (3,24)-connected MOFs with the rht topology, in which the central part of organic linker comprises a hexabenzocoronene unit, the effect of the linker type and length on their structural and gas adsorption properties is studied computationally. The obtained results compare favourably with known MOF materials of similar structure and topology. We find that the presence of a flat nanographene-like central core increases the geometric surface area of the frameworks, sustains additional benzene rings, promotes linker elongation and the efficient occupation of the void space by guest molecules. This provides a viable linker modification method with potential for enhancement of uptake for methane and other gas molecules

Secondary instabilities in Taylor Couette flow of shear thinning fluids

International audienceThe stability of the Taylor vortex flow in Newtonian and shear-thinning fluids is investigated in the case of a wide gap Taylor-Couette system. The considered radius ratio is eta = R-1/R-2 = 0.4. The aspect ratio (length over the gap width) of experimental configuration is 32. Flow visualization and measurements of two-dimensional flow fields with particle image velocimetry are performed in a glycerol aqueous solution (Newtonian fluid) and in xanthan gum aqueous solutions (shear-thinning fluids). The experiments are accompanied by axisymmetric numerical simulations of Taylor-Couette flow in the same gap of a Newtonian and a purely viscous shear-thinning fluid described by the Carreau model. The experimentally observed critical Reynolds and wavenumbers at the onset of Taylor vortices are in very good agreement with that obtained from a linear theory assuming a purely viscous shear-thinning fluid and infinitely long cylinders. They are not affected by the viscoelasticity of the used fluids. For the Newtonian fluid, the Taylor vortex flow (TVF) regime is found to bifurcate into a wavy vortex flow with a high frequency and low amplitude of axial oscillations of the vortices at Re = 5.28 Re-c. At Re = 6.9 Re-c, the frequency of oscillations decreases and the amplitude increases abruptly. For the shear-thinning fluids the secondary instability conserves axisymmetry. The latter is characterized by an instability of the array of vortices leading to a continuous sequence of creation and merging of vortex pairs. Axisymmetric numerical simulations reproduce qualitatively very well the experimentally observed flow behaviour

Écoulement en conduite cylindrique de fluides rhéofluidifiants

International audienceThe pipe flow of purely viscous shear-thinning fluids is studied using numerical simulations. The rheological behavior is described by the Carreau model. The flow field is decomposed as a base flow and a disturbance. The perturbation equations are then solved using a pseudospectral Petrov-Galerkin method. The time marching uses a fourth-order Adams-Bashforth scheme. In the case of an infinitesimal perturbation, a three-dimensional linear stability analysis is performed based on modal and non modal approaches. It is shown that the pipe flow of shear-thinning fluids is linearly stable and that for the range of the rheological parameters considered, streamwise independent vortices are optimally amplified. The nonlinear computations are done for finite amplitude two-dimensional disturbances, which consist of one pair of longitudinal rolls. The numerical results show that for a given wall Reynolds number, the shear-thinning reduces the energy gain of the perturbation. This is due to a reduction of the exchange energy between the base flow and the perturbation. Besides this, the viscous dissipation decreases with increasing the shear-thinning effects.Lʼécoulement de fluides rhéofluidifiants en conduite cylindrique est étudié à lʼaide de simulations numériques. Le comportement rhéofluidifiant est modélisé par la loi de Carreau. Lʼécoulement est décomposé en un écoulement de base et une perturbation. Les équations aux perturbations sont résolues en utilisant une méthode pseudo-spectrale de Petrov–Galerkin. La discrétisation temporelle utilise un schéma dʼAdams–Bashforth dʼordre quatre. Dans le cas dʼune perturbation infinitésimale, une analyse linéaire tridimensionnelle est effectuée suivant une approche modale puis non-modale. Les résultats obtenus montrent que dans la gamme des paramètres rhéologiques considérés, lʼécoulement dʼun fluide rhéofluidifiant est linéairement stable. La perturbation optimale est constituée dʼune paire de rouleaux longitudinaux contra-rotatifs. Des simulations numériques non linéaires sont ensuite effectuées pour une perturbation bidimensionnelle dʼamplitude finie constituée dʼune paire de rouleaux longitudinaux. Les résultats numériques montrent que la réorganisation de lʼécoulement sʼaccompagne dʼune forte modification du profil de viscosité. En outre, pour une valeur donnée du nombre de Reynolds basé sur la viscosité pariétale, la rhéofluidification réduit lʼamplification de lʼénergie de la perturbation. On montre que cela est dû à la réduction des échanges dʼénergie entre lʼécoulement de base et la perturbation. Parallèlement à cela, la dissipation visqueuse décroit avec lʼaugmentation des effets rhéofluidifiants