Accurate Multi-physics Numerical Analysis of Particle Preconcentration Based on Ion Concentration Polarization

This paper studies mechanism of preconcentration of charged particles in a straight micro-channel embedded with permselective membranes, by numerically solving coupled transport equations of ions, charged particles and solvent fluid without any simplifying assumptions. It is demonstrated that trapping and preconcentration of charged particles are determined by the interplay between drag force from the electroosmotic fluid flow and the electrophoretic force applied trough the electric field. Several insightful characteristics are revealed, including the diverse dynamics of co-ions and counter ions, replacement of co-ions by focused particles, lowered ion concentrations in particle enriched zone, and enhanced electroosmotic pumping effect etc. Conditions for particles that may be concentrated are identified in terms of charges, sizes and electrophoretic mobilities of particles and co-ions. Dependences of enrichment factor on cross-membrane voltage, initial particle concentration and buffer ion concentrations are analyzed and the underlying reasons are elaborated. Finally, post priori a condition for validity of decoupled simulation model is given based on charges carried by focused charge particles and that by buffer co-ions. These results provide important guidance in the design and optimization of nanofluidic preconcentration and other related devices.Comment: 18 pages, 11 firgure

Ion Channels in Epilepsy: Blasting Fuse for Neuronal Hyperexcitability

Voltage-gated ion channels (VGICs), extensively distributed in the central nervous system (CNS), are responsible for the generation as well as modulation of neuroexcitability and considered as vital players in the pathogenesis of human epilepsy, with regulating the shape and duration of action potentials (APs). For instance, genetic alterations or abnormal expression of voltage-gated sodium channels (VGSCs), Kv channels, and voltage-gated calcium channels (VGCCs) are proved to be associated with epileptogenesis. This chapter aims to highlight recent discoveries on the mutations in VGIC genes and dysfunction of VGICs in epilepsy, especially focusing on the pathophysiological and pharmacological properties. Understanding the role of epilepsy-associated VGICs might not only contribute to clarify the mechanism of epileptogenesis and genetic modifiers but also provide potential targets for the precise treatment of epilepsy

Non-equilibrium behaviour in coacervate-based protocells under electric-field-induced excitation

Although numerous strategies are now available to generate rudimentary forms of synthetic cell-like entities, minimal progress has been made in the sustained excitation of artificial protocells under non-equilibrium conditions. Here we demonstrate that the electric field energization of coacervate microdroplets comprising polylysine and short single strands of DNA generates membrane-free protocells with complex, dynamical behaviours. By confining the droplets within a microfluidic channel and applying a range of electric field strengths, we produce protocells that exhibit repetitive cycles of vacuolarization, dynamical fluctuations in size and shape, chaotic growth and fusion, spontaneous ejection and sequestration of matter, directional capture of solute molecules, and pulsed enhancement of enzyme cascade reactions. Our results highlight new opportunities for the study of non-equilibrium phenomena in synthetic protocells, provide a strategy for inducing complex behaviour in electrostatically assembled soft matter microsystems and illustrate how dynamical properties can be activated and sustained in microcompartmentalized media.</p

Excellent performance of Pt-C/TiO2 for methanol oxidation:contribution of mesopores and partially coated carbon

Partial deposition of carbon onto mesoporous TiO2 (C/TiO2) were prepared as supporting substrate for Pt catalyst development. Carbon deposition is achieved by in-situ carbonization of furfuryl alcohol. The hybrid catalysts were characterized by XRD, Raman, SEM and TEM and exhibited outstanding catalytic activity and stability in methanol oxidation reaction. The heterogeneous carbon coated on mesoporous TiO2 fibers provided excellent electrical conductivity and strong interfacial interaction between TiO2 support and Pt metal nanoparticles. Methanol oxidation reaction results showed that the activity of Pt-C/TiO2 is 3.0 and 1.5 times higher than that of Pt-TiO2 and Pt-C, respectively. In addition, the Pt-C/TiO2 exhibited a 6.7 times enhanced stability compared with Pt-C after 2000 cycles. The synergistic effect of C/TiO2 is responsible for the enhanced activity of Pt-C/TiO2, and its excellent durability could be ascribed to the strong interfacial interaction between Pt nanoparticles and C/TiO2 support

Scorpion Toxins from <em>Buthus martensii</em> Karsch (BmK) as Potential Therapeutic Agents for Neurological Disorders: State of the Art and Beyond

Scorpions are fascinating creatures which became residents of the planet well before human beings dwelled on Earth. Scorpions are always considered as a figure of fear, causing notable pain or mortality throughout the world. Their venoms are cocktails of bioactive molecules, called toxins, which are responsible for their toxicity. Fortunately, medical researchers have turned the life-threatening toxins into life-saving therapeutics. From Song Dynasty in ancient China, scorpions and their venoms have been applied in traditional medicine for treating neurological disorders, such as pain, stroke, and epilepsy. Neurotoxins purified from Chinese scorpion Buthus Martensii Karsch (BmK) are considered as the main active ingredients, which act on membrane ion channels. Long-chain toxins of BmK, composed of 58–76 amino acids, could specifically recognize voltage-gated sodium channels (VGSCs). Short-chain BmK toxins, containing 28–40 amino acids, are found to modulate the potassium or chloride channels. These components draw attention as useful scaffolds for drug-design in order to tackle the emerging global medical threats. In this chapter, we aim to summarize the most promising candidates that have been isolated from BmK venoms for drug development

Targeting Neuroglial Sodium Channels in Neuroinflammatory Diseases

The Hodgkin-Huxley model, at its 66th anniversary, remains a footing stone of neuroscience, which describes how the action potential (AP) is generated. As the core player of AP initiation, voltage-gated sodium channels (VGSCs) are always considered to be required for electrogenesis in excitable cells. Cells which are not traditionally been considered to be excitable, including glial cells, also express VGSCs in physiological as well as pathological conditions. The dysfunction of glial VGSCs is seemingly not related to abnormal excitation of neurons, but of importance in the astrogliosis and M1 polarization of microglia, which could induce refractory neuroinflammatory diseases, such as multiple sclerosis, stroke, epilepsy, and Alzheimer’s and Parkinson’s diseases. Therefore, in this chapter, we aim to describe the physiological and pathological roles of VGSCs contributing to the activity of glial cells and discuss whether VGSC subtypes could be used as a novel drug target, with an eye toward therapeutic implications for neuroinflammatory diseases

A Simple High-Order Shear Deformation Triangular Plate Element with Incompatible Polynomial Approximation

The High-order Shear Deformation Theories (HSDTs) which can avoid the use of a shear correction factor and better predict the shear behavior of plates have gained extensive recognition and made quite great progress in recent years, but the general requirement of C1 continuity in approximation fields in HSDTs brings difficulties for the numerical implementation of the standard finite element method which is similar to that of the classic Kirchhoff-Love plate theory. As a strong complement to HSDTs, in this work, a series of simple High-order Shear Deformation Triangular Plate Elements (HSDTPEs) using incompatible polynomial approximation are developed for the analysis of isotropic thick-thin plates, cracked plates, and through-thickness functionally graded plates. The elements employ incompatible polynomials to define the element approximation functions u/v/w, and a fictitious thin layer to enforce the displacement continuity among the adjacent plate elements. The HSDTPEs are free from shear-locking, avoid the use of a shear correction factor, and provide stable solutions for thick and thin plates. A variety of numerical examples are solved to demonstrate the convergence, accuracy, and robustness of the present HSDTPEs

ACCURATE MULTI-PHYSICS NUMERICAL ANALYSIS OF PARTICLE PRECONCENTRATION BASED ON ION CONCENTRATION POLARIZATION

© 2017 World Scientific Publishing Europe Ltd. This paper studies the mechanism of preconcentration of charged particles in a straight microchannel embedded with permselective membranes by numerically solving the coupled transport equations of ions, charged particles and solvent fluid without any simplifying assumptions. It is demonstrated that trapping and preconcentration of charged particles are determined by the interplay between drag force from the electroosmotic fluid flow and the electrophoretic force applied through the electric field. Several insightful characteristics are revealed, including the diverse dynamics of co-ions and counter ions, replacement of co-ions by focused particles, lowered ion concentrations in particle-enriched zone, and enhanced electroosmotic pumping effect, etc. Conditions for particles that can be concentrated are identified in terms of charges, sizes and electrophoretic mobilities of particles and co-ions. Dependences of enrichment factor on cross-membrane voltage, initial particle concentration and buffer ion concentrations are analyzed and the underlying reasons are elaborated. Finally, post priori condition for the validity of decoupled simulation model is given based on the charges carried by focused particles and buffer co-ions. These results provide an important guidance in the design and optimization of nanofluidic preconcentration and other related devices

Effects of ionic hydration and hydrogen bonding on flow resistance of ionic aqueous solutions confined in molybdenum disulfide nanoslits: Insights from molecular dynamics simulations

Single-layer molybdenum disulfide (MoS2) is a novel two-dimensional material that has attracted considerable attention because of its excellent properties. In this work, molecular dynamics simulations were performed to investigate the effect of different kinds of alkali metal ions (Li+, Na+, and K+) on the flow resistance of ionic aqueous solutions confined in MoS2 nanoslits under shearing. Three slit widths (i.e. 1.2, 1.6, and 2.0 nm) were investigated. Simulation results showed that the friction coefficient followed the order of K+ < Na+ < Li+. The friction coefficient decreased with the increasing of slit width. Unique confined spatial distributions of different types of ionic aqueous solutions led to different confined ionic hydrations for different cations. These differences lead to different orientations of surrounding water molecules and then form different hydrogen bond (HB) networks. The friction coefficient was greatly dependent on the number of HBs per water; i.e., the larger the number of HBs formed, the lower was the flow resistance