In this paper, we investigate the abatement of spike-and-wave discharges in a thalamocortical model using a closed-loop brain stimulation method. We first explore the complex states and various transitions in the thalamocortical computational model of absence epilepsy by using bifurcation analysis. We demonstrate that the Hopf and double cycle bifurcations are the key dynamical mechanisms of the experimental observed bidirectional communications during absence seizures through top-down cortical excitation and thalamic feedforward inhibition. Then, we formulate the abatement of epileptic seizures to a closed-loop tracking control problem. Finally, we propose a neural network based sliding mode feedback control system to drive the dynamics of pathological cortical area to track the desired normal background activities. The control system is robust to uncertainties and disturbances, and its stability is guaranteed by Lyapunov stability theorem. Our results suggest that the seizure abatement can be modeled as a tracking control problem and solved by a robust closed-loop control method, which provides a promising brain stimulation strategy.

Pure white-light emission and fluent light-emitting color change can be facilely obtained by codoping isostructural homochiral lanthanide metal–organic frameworks.

No abstract

Curcumin has antioxidant, anti-inflammatory, antimicrobial, and anticarcinogenic activities. However, the clinical application of curcumin has been restricted by the poor water solubility and low bioavailability of this molecule. In this work, hydrophobic porous silicon (pSi) particles were prepared by electrochemical etching method and grafted with the different hydrophobic groups on their surfaces. The loading efficiency of curcumin in pSi has been investigated. The properties of pSi particles have been characterized by scanning electron microscopy (SEM) and Fourier transform-infrared spectroscopy (FTIR). The highest loading efficiency of curcumin can be obtained with pSi surface modified with the octadecyl silane group. The release properties of curcumin in hydrophobic pSi have been researched in vitro and in vivo. The curcumin in the hydrophobic pSi surface keeps a high antioxidant bioactivity. The toxicological evaluation of the hydrophobic pSi particles indicates they have a high in vivo biocompatibility within the observed dose ranges. The hydrophobic pSi particles could provide an effective and controlled release delivery carrier for curcumin, which may provide a new tool platform for the further development of curcumin.

On the basis of amino acid-functionalized isophthalic acids, four interesting homochiral metal–organic frameworks (HMOFs), namely, {[Pb2(HL1)2]·11H2O} n (1), {[Pb2(HL2)2]·12H2O} n (2), {[Cd6(L2)4(H2O)11]­·6H2O} n (3), and [Pb­(HL3)] n (4), were constructed (H3L1 = (S)-5-(((1-carboxyethyl)­amino)­methyl)­isophthalic acid, H3L2 = (S)-5-(((1-carboxy-3-methylbutyl)­amino)­methyl)­isophthalic acid, and H3L3 = (S)-5-(((1-carboxy-2-phenylethyl)­amino)­methyl)­isophthalic acid). In 1, 2, and 4, all PbII ions have hemidirected coordination geometries despite the difference in coordination number, and ligands H3L1–H3L3 in negative bivalent zwitterionic forms adopt various coordination modes to bridge PbII centers into two- and three-dimensional (2D–3D) coordination polymers, respectively. Both 1 and 2 contain two independent 63-topological homochiral layers which further form a unique hydrogen-bonded double-layered HMOF with the stereochemically active lone pairs of all PbII ions pointing inward and the hydrophobic side arms of amino acid groups being located on both sides. For 4, it is a 3D helicate of (42·6·83)­(42·63·8) topology, and the resulting one-dimensional (1D) channels are occupied by the hydrophobic benzyls of amino acid groups in (HL3)2– ligands. Coordination polymer 3 is an intriguing HMOF that contains two independent 2D double-layered (63)­(65·8)-topological helicates with alternating distribution of 1D hydrophilic and hydrophobic helical channels. In 3, all hydrophilic helical channels are occupied by water molecules, while all hydrophobic helical channels are filled by the isobutyls of amino acid groups. Remarkably, these chiral tricarboxylic ligands not only have versatile coordination modes in the construction of HMOFs, but also subtly regulate the crystal structures through the different hydrophobic side arms of amino acids implanted in these ligands. Furthermore, the thermal stabilities and solid-state optical properties, including CD spectra, and nonlinear optical and luminescent properties of these complexes were also investigated. Interestingly enough, in our example, it was found that hemidirected, five-coordinate PbII compounds perhaps have stronger emission than those hemidirected four- or six-coordinate PbII compounds.