Characterization of oligosorbents and application to the purification of ochratoxin A from wheat extracts

The aim of this work was to optimize the preparation of an anti-ochratoxin A (OTA) oligosorbent (OS), a solid-phase extraction sorbent based on OTA aptamers covalently immobilized on sepharose. Different syntheses were carried out by modifying the side of the oligonucleotide chain bound to the sepharose, the length of the spacer arm between the aptamer and the sepharose and the amount of the aptamers introduced during the covalent grafting. Indeed, the capacity of OSs prepared using 3′- or 5′-amino-modified sequences with a C6 or a C12 was studied. In the best conditions, the concentration of aptamers sequence used during their grafting was increased and a capacity close to 40 nmol g^?1 of OS was reached. The potential of the resulting OSs was also studied in pure media. For this, their selectivity was checked by comparing them to a control sorbent prepared without immobilizing aptamers. Extraction recoveries close to 100 % were obtained on all OSs, while no retention was observed on the control sorbent. OS does not demonstrate any cross-reactivity towards OTA metabolites, i.e., ochratoxin B and ochratoxin hydroquinone. The oligosorbent was finally applied to the clean-up of OTA from wheat sample extracts. Extraction recoveries were not affected by matrix interferences and the resulting chromatogram clearly highlights the selectivity of the sorbent that allows the removal of matrix components thus improving the reliability of the quantitation of OTA in real samples.     

Functionalisation of mesoporous silica nanoparticles with 3-isocynatopropyltrichlorosilane

The functionalisation of Mesoporous Silica Nanoparticles (MSN) with the isocyanate group was carried out. The excellent reactivity of 3-isocynanatopropyltrichlorosilane allowed its grafting on the surface of MSN in mild conditions. Further reaction with different nucleophiles bearing primary amino groups led to the formation of a urea linkage and thus the covalent grafting of the nucleophiles to the MSN surface.     

A second-order boundary value problem with impulsive effects on an unbounded domain

We study a second-order nonlinear differential equation on an unbounded domain with solutions subject to impulsive conditions and the Sturm–Liouville type boundary conditions. The existence results are obtained via applications of Krasnosel’ski?’s fixed point theorem for the sum of a completely continuous operator and a contraction.     

Multistability,bifurcations, and biological neural networks: A synaptic drive firing model for cerebral cortex transition in the induction of general anesthesia

This paper focuses on multistability theory for discontinuous dynamical systems having a set of multiple isolated equilibria and/or a continuum of equilibria. Multistability is the property whereby the solutions of a dynamical system can alternate between two or more mutually exclusive Lyapunov stable and convergent equilibrium states under asymptotically slowly changing inputs or system parameters. In this paper, we extend the definition and theory of multistability to discontinuous autonomous dynamical systems. In particular, nontangency Lyapunov-based tests for multistability of discontinuous systems with Filippov and Carathéodory solutions are established. The results are then applied to excitatory and inhibitory biological neuronal networks to explain the underlying mechanism of action for anesthesia and consciousness from a multistable dynamical system perspective, thereby providing a theoretical foundation for general anesthesia using the network properties of the brain.     

Synthesis, magnetic properties, and magnetic structure of a natrochalcite structural variant, KM(II)2D3O2(MoO4)2 (M = Mn, Fe, or Co)

We report the syntheses, crystal structures, and magnetic properties of KMn(2)(H(3)O(2))(MoO(4))(2) (MnH), KMn(2)(D(3)O(2))(MoO(4))(2) (MnD), KFe(2)(H(3)O(2))(MoO(4))(2) (FeH), KFe(2)(D(3)O(2))(MoO(4))(2) (FeD), KCo(2)(H(3)O(2))(MoO(4))(2) (CoH), and KCo(2)(D(3)O(2))(MoO(4))(2) (CoD), and the magnetic structures of MnD and FeD. They belong to the structural variant (space group I2/m) of the mineral natrochalcite NaCu(2)(H(3)O(2))(SO(4))(2) (space group C2/m) where the diagonal within the ac-plane of the latter become one axis of the former. The structure of MnD, obtained from Rietveld refinement of a high-resolution neutron pattern taken at 300 K, consists of chains of edge-sharing octahedra bridged by MoO(4) and D(3)O(2) to form layers, which are connected to K through the oxygen atoms to form the three-dimensional (3D)-network. The X-ray powder diffraction patterns of the other two compounds were found to belong to the same space group with similar parameters. The magnetic susceptibilities of MnH and FeH exhibit long-range ordering of the moments at a Ne?el temperature of 8 and 11 K, respectively, which are accompanied by additional strong Bragg reflections in the neutron diffraction in the ordered state, consistent with antiferromagnetism. Analyses of the neutron data for MnD and FeD reveal the presence of both long- and short-range orderings and commensurate magnetic structures with a propagation vector of (?, 0, ?). The moments are antiferromagnetically ordered within the chains with alternation between chains to generate four nonequivalent nuclear unit cells. For MnD the moments are perpendicular to the chain axis (b-axis) while for FeD they are parallel to the b-axis. The overall total is a fully compensated magnetic structure with zero moment in each case. Surprisingly, for KCo(2)(D(3)O(2))(MoO(4))(2) neither additional peaks nor increase of the nuclear peaks' intensities were observed in the neutron diffraction patterns below the magnetic anomaly at 12 K which was identified to originate from a small quantity of a ferromagnetic compound, Co(2)(OH)(2)MoO(4).     

Coupled fused silica capillaries for rapid capillary zone electrophoresis of proteins

A novel two-dimensional electrophoretic system for the control of electroosmosis in capillary zone electrophoresis has been developed and evaluated for rapid separations of proteins. The system comprises uncoated and polyether-coated fused silica capillaries coupled in series. An equation relating the average electroosmotic flow velocity in the coupled capillaries to the intrinsic electroosmotic velocities of the connected segments and their corresponding lengths has been derived and verified experimentally. This approach has the advantage of enabling the electroosmotic flow to be tuned independently of the applied voltage. As a consequence, rapid protein analysis at relatively low field strength was achieved without sacrificing the high separation efficiencies obtained with surface-modified capillaries.     

Sur le groupe affine d'un corps local

Let G be the affine group of a local field and $A(G)$ be its Fourier algebra. We prove some properties for G of which the principal is the following: if G is Archimedian and $f\in A(G)$ with compact support for which the Fourier cotransform is of finite rank, then $f=0$. To cite this article: W. Nasserddine, C. R. Acad. Sci. Paris, Ser. I 342 (2006).     

Complex structured singular value analysis using fixed-structure dynamic D-scales

Models of systems are always inexact. Hence, to better predict the performance of a system it is necessary to take into account uncertainty in a nominal model of a system. The structured singular value was developed to nonconservatively analyze robust stability and performance for systems with multiple-block uncertainty. In practice, optimization techniques are used to compute an upper bound on the structured singular value. For dynamic uncertainty with bounded magnitude and arbitrary phase (i.e., "complex uncertainty"), the standard approach to computing an upper bound involves finding diagonal scaling matrices D(jω) that minimize σ_max (D(jω)G(jω)D^-1(jω)) over a (theoretically) infinite number of frequencies. The order of the corresponding stable, minimum phase, rational function D(s) (if it exists) is hence arbitrary, which can lead to very high order controllers when D(s) is used for controller synthesis. This paper develops a fixed-structure approach to computing an upper bound for the complex structured singular value. In particular, by relying on results from mixed-norm H₂/H_∞ analysisD(s) is a priori constrained to be a rational matrix function of a chosen order and a new approach to computing an upper bound on the structured singular value is developed. The results are illustrated using two examples which clearly demonstrate the suboptimality of standard curve fitting. The proposed approach can be extended to mixed uncertainty and structured singular value controller synthesis without D — K type iteration.     

Three Point Boundary Value Problems on Time Scales

This work formulates existence theorems for solutions to three-point boundary value problems on time scales. The ideas are based on a relationship between the three point boundary conditions, lower and upper solutions and topological degree theory.     

Facile electrodeposition of ZnO on graphitic substrate for photocatalytic application: degradation of antibiotics in a continuous stirred-tank reactor

Journal of Solid State Electrochemistry - This work discusses the possibility of obtaining ZnO film on graphite, which can be widely used for photocatalysis, photocells, photodetectors, etc. The...