Search results for "SELECTIVITY"
showing 10 items of 1148 documents
Grand Canonical Monte Carlo Simulations to Determine the Optimal Interlayer Distance of a Graphene Slit-Shaped Pore for Adsorption of Methane, Hydrog…
2021
The adsorption—for separation, storage and transportation—of methane, hydrogen and their mixture is important for a sustainable energy consumption in present-day society. Graphene derivatives have proven to be very promising for such an application, yet for a good design a better understanding of the optimal pore size is needed. In this work, grand canonical Monte Carlo simulations, employing Improved Lennard–Jones potentials, are performed to determine the ideal interlayer distance for a slit-shaped graphene pore in a large pressure range. A detailed study of the adsorption behavior of methane, hydrogen and their equimolar mixture in different sizes of graphene pores is obtained through ca…
Combined effect of solvent content, temperature and pH on the chromatographic behaviour of ionisable compounds.
2008
The organic solvent content and the pH in the mobile phase are the usual main factors in reversed-phase liquid chromatographic separations, owing to their strong effects on retention and/or selectivity. Temperature is often neglected. However, even in cases where the impact of this factor on selectivity is minor, the reduction in analysis time is still an interesting reason to consider it. In addition, ionisable compounds may exhibit selectivity changes, owing to the interaction of organic solvent and/or temperature with pH. The separation of ionisable compounds (nine diuretics: bendroflumethiazide, benzthiazide, bumetanide, chlorthalidone, furosemide, piretanide, probenecid, trichloromethi…
Modulation of retention and selectivity in oil-in-water microemulsion liquid chromatography: A review
2019
Microemulsions (MEs) are stable, isotropically clear solutions consisting of an oil and water stabilized by a surfactant and a co-surfactant. Oil-in-water microemuslion liquid chromatography (MELC) is a relatively new chromatographic mode, which uses an O/W ME as mobile phase. Retention, selectivity and efficiency can be modified by changing the concentration of the ME components and the ratio between the aqueous and oil phases. This work makes a critical survey on the information found in the literature about the mobile phase compositions that lead to the creation of successful O/W ME mobile phases, as well as the effect of pH for ionizable compounds and temperature. The viability of perfo…
Intra-individual variability in task performance after cognitive training is associated with long-term outcomes in children
2020
AbstractThe benefits and mechanistic effects of working memory training in children are the subject of much research and debate. The cumulative evidence indicates that training can alter brain structure and function in the short term and have lasting effects on behaviour. We show that five weeks of working memory training led to greater activity in prefrontal and striatal brain regions, better accuracy, and reduced intra-individual variability in response times. The reduction in intra-individual variability can be explained by changes to the evidence accumulation rates and thresholds in a sequential sampling decision model. Critically, intra-individual variability was more closely associate…
Redox and Catalytic Properties of Promoted NiO Catalysts for the Oxidative Dehydrogenation of Ethane
2017
[EN] NiO and metal-promoted NiO catalysts (M-NiO, with a M/(M+Ni) atomic ratio of 0.08, with M = Nb, Sn, or La) have been prepared, tested in the oxidative dehydrogenation (ODH) of ethane, and characterized by means of XRD, TPR, HRTEM, Raman, XPS, and in situ XAS (using H-2/He, air or C2H6/He mixtures). The selectivity to ethylene during the ODH of ethane decreases according to the following trend: Nb NiO Sn NiO > La NiO > NiO, whereas the catalyst reducibility (determined by both TPR and XAS using H-2/He mixtures) shows the opposite trend. However, different reducibility and catalytic behavior in the absence of oxygen (ethane/He mixtures) have been observed, especially when comparing Nb- a…
Support effects on NiO-based catalysts for the oxidative dehydrogenation (ODH) of ethane
2019
[EN] We report on the effect of NiO-support interactions on the chemical nature of Ni species in a series of supported NiO catalysts for the ODH of ethane. SiO2, TiO2-anatase, a high surface area TiO2 and a porous clay hetero-structure (PCH) with TiO2 and SiO2 pillars were used as supports, which led to a selectivity to ethylene in the range 30-90% over supported NiO catalysts. The catalysts were characterized by means of XRD, N-2-Adsorption, H-2-TPR, XPS and in situ (under H-2 reductive atmosphere) and ex situ XAS spectroscopy. The catalytic performance of supported materials is discussed in terms of their reducibility and specific reduction kinetics, but also taking into account the speci…
Competitive and Selective Csp3Br versus Csp2Br Bond Activation in Palladium-Catalysed Suzuki Cross-Coupling: An Experimental and Theoretical Study …
2010
Phosphine ligands have been demonstrated to have an effect on reactivity and selectivity in the competitive intramolecular palladium-catalysed Suzuki-Miyaura coupling of dibromo sulfoxide 1a possessing two different hybridised electrophilic carbons. It was found that the bromine bond to the sp(3)-hybridised carbon is selectively replaced in the presence of unhindered phosphines such as PPh(3) or xantphos. The use of hindered phosphine ligands such as P(o-tol)(3) and P(1-naphthyl)(3) reversed the selectivity, conducting the cross-coupling at the Csp(2)-Br. Identical trends were observed in external competition experiments carried out with bromomethyl sulfoxide and different substituted bromo…
A doubly bridged isodicyclopentadienyl zirconium complex: bis{N-(3,5-dimethylphenyl)-N-[(η5-isodicyclopentadien-2-yl)dimethylsilyl]amido-κN}zirconium…
2002
Transmetallation of the dilithium salt of (3,5-dimethyphenylamino)(isodicyclopentadienyl)dimethylsilane by treatment with zirconium tetrachloride in a 2:1 ratio leads to the substitution of all four chloride ligands. With the applied stoichiometry, the title complex, [Zr(C(20)H(25)NSi)(2)].C(4)H(10)O, was obtained and crystallized from diethyl ether. X-ray diffraction characterization showed that both isodicyclopentadienyl ligands (alternatively called 4,5,6,7-tetrahydro-4,7-methano-1H-indene) are complexed to the metal on their exo face in a completely stereoselective manner and that they are eta(5)-bonded to the Zr atom.
Event-Based Trajectory Prediction Using Spiking Neural Networks
2021
International audience; In recent years, event-based sensors have been combined with spiking neural networks (SNNs) to create a new generation of bio-inspired artificial vision systems. These systems can process spatio-temporal data in real time, and are highly energy efficient. In this study, we used a new hybrid event-based camera in conjunction with a multi-layer spiking neural network trained with a spike-timing-dependent plasticity learning rule. We showed that neurons learn from repeated and correlated spatio-temporal patterns in an unsupervised way and become selective to motion features, such as direction and speed. This motion selectivity can then be used to predict ball trajectory…
Etude des effets collisionnels dans les molécules tétraédriques. Applications au méthane perturbé par l'argon
1996
This thesis is devoted to the study of relaxational and collisional line-broadening processes in the first vibrational polyads of tetrahedral molecules. In a first part, the particular internal dynamics of such molecules is discussed. The second chapter reviews the literature on phenomena induced by intermolecular interactions involving this type of molecules. More theoretical aspects are developed in the second part. The so-called tetrahedral tensorial formalism adapted to the construction of Hamiltonians and transition moments of tetrahedral molecules is described. Main features of the infrared line-shapes theories and of semi-classical line-broadening and line-shifting calculations are a…