Synchronization of complex networks with time‐varying inner coupling and outer coupling matrices

Synchronization of complex networks with time‐varying coupling matrices is studied in this paper. Two kinds of time‐varying coupling are taken into account. One is the time‐varying inner coupling in the node state space and the other is the time‐varying outer coupling in the network topology space. By respectively setting linear controllers and adaptive controllers, time‐varying complex networks can be synchronized to a desired state. Meanwhile, different influences of the control parameters of linear controllers and adaptive controllers on the synchronization have also been investigated. Based on the Lyapunov function theory, we construct appropriate positive‐definite functions, and several sufficient synchronization criteria are obtained. Numerical simulations further illustrate the effectiveness of conclusions. Copyright © 2017 John Wiley & Sons, Ltd.     

Composition algebras and outer automorphisms of algebraic groups via triality

In this note, we establish an equivalence of categories between the category of all eight-dimensional composition algebras with any given quadratic form n over a field k of characteristic not two, and a category arising from an action of the projective similarity group of n on certain pairs of automorphisms of the group scheme PGO⁺(n) defined over k. This extends results recently obtained in the same direction for symmetric composition algebras. We also derive known results on composition algebras from our equivalence.     

Protein environmental effects on iron‐sulfur clusters: A set of rules for constructing computational models for inner and outer coordination spheres

The structural properties and reactivity of iron‐sulfur proteins are greatly affected by interactions between the prosthetic groups and the surrounding amino acid residues. Thus, quantum chemical investigations of the structure and properties of protein‐bound iron‐sulfur clusters can be severely limited by truncation of computational models. The aim of this study was to identify, a priori, significant interactions that must be included in a quantum chemical model. Using the [2Fe‐2S] accessory cluster of the FeFe‐hydrogenase as a demonstrative example with rich electronic structural features, the electrostatic and covalent effects of the surrounding side chains, charged groups, and backbone moieties were systematically mapped through density functional theoretical calculations. Electron affinities, spin density differences, and delocalization indexes from the quantum theory of atoms in molecules were used to evaluate the importance of each interaction. Case studies for hydrogen bonding and charged side‐chain interactions were used to develop selection rules regarding the significance of a given protein environmental effect. A set of general rules is proposed for constructing quantum chemical models for iron‐sulfur active sites that capture all significant interactions from the protein environment. This methodology was applied to our previously used models in galactose oxidase and the 6Fe‐cluster of FeFe‐hydrogenase. © 2016 Wiley Periodicals, Inc.     

Electrodialytic separation of potassium ions from sodium ions in the presence of crown ether using a cation-exchange membrane

The separation of potassium and sodium ions from their mixture was performed by electrodialyzing a mixed solution of potassium chloride and sodium chloride in the presence of 18-crown-6 using a commercial cation-exchange membrane. After 18-crown-6 had been impregnated in the membrane, the mixed solution containing 18-crown-6 was electrodialyzed as the desalting-side solution. The permeation of potassium ions through the membrane decreased remarkably and the electrical resistance of the membrane increased during electrodialysis with increasing concentration of 18-crown-6 in the solution. Because potassium ions form a more stable complex with 18-crown-6 than sodium ions and because the complex permeated through the membrane with difficulty, sodium ions are thought to selectively permeate through the membrane. The current efficiency in electrodialysis was greater than 97.0%. Received: 1 June 1999/Accepted in revised form: 13 August 1999     

Sorption and pervaporation properties of crosslinked membranes of poly(ethylene oxide imide) segmented copolymer to aromatic/nonaromatic hydrocarbon mixtures

Poly(ethylene oxide imide) segmented copolymer (PEO‐PI) membranes were crosslinked by the chemical reaction between ethylene glycol diglycidyl ether and benzylalcohol groups of diamine moieties in polyimide segments at high temperatures. Sorption and diffusion of penetrants took place in poly(ethylene oxide) segment microdomains. Sorption and desorption behavior of pure vapors such as benzene (Bz), cyclohexane (Cx) and n‐hexane (Hx) was classified as the Fickian diffusion. Sorption isotherms of binary liquid mixtures could be represented by the Flory–Rehner model, but the model overpredicted the sorption amounts of Cx and Hx, leading to small predictions of sorption selectivity α_S for Bz/Cx and Bz/Hx systems. UNIFAC‐FV model fairly well predicted the sorption amounts of aromatic hydrocarbons, but significantly overestimated those of nonaromatic ones, leading to too small predictions of α_S. Pervaporation (PV) behavior of PEO‐PI membranes was governed by sorption behavior followed by membrane swelling. Diffusion coefficient weakly depended on the minimum cross section of a penetrant. The diffusivity selectivity α_D hardly depended on the feed composition and was about 1.4 and 0.75 for Bz/Cx and Bz/Hx, respectively. PV selectivity α_PV was larger for Bz/Hx than for Bz/Cx because of larger α_S. PEO‐PI membranes displayed high specific permeation flux Ql and reasonably high α_PV for aromatic/nonaromatic hydrocarbons; for example, Ql = 60 Kg μm/(m² h) and α_PV = 8 for a feed mixture containing Bz, Tol, Hx, n‐Ot and i‐Ot of 20 wt % at 353 K. © 2000 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 38: 1800–1811, 2000     

Contribution of cell-surface components to Cu2+ adsorption by Pseudomonas putida 5-x

The contribution of various cell-surface components to Cu²⁺ adsorption by a Gram-negative bacterium, Pseudomonas putida 5-x, that was isolated from local electroplating effluent with a high capability to accumulate heavy metal ions was studied. The cell superficial layer had a negative effect on Cu²⁺ adsorption of the bacterial cells. Cu²⁺ adsorption capacity of the separated cell envelopes was fivefold more than that of the intact cells, owing to the liberation of more and more binding sites during the separation process. Some main components in the cell envelope, such as the peptidoglycan (PEG) layer, outer membrane, and inner membrane, provide the capability for Cu²⁺ adsorption. The content of the components in the cell envelope is in the order inner membrane > outer membrane > PEG layer, and their Cu²⁺ adsorption capacity was in the order PEG layer > outer membrane > inner membrane. The total contribution of the separated PEG layer material to Cu²⁺ adsorption by the cell envelope was no more than 15%, and the outer membrane and inner membrane contributed about 30–35% and 25–30%, respectively. The relatively high phospholipid content in the outer membrane may be the major reason for the higher adsorption capacity of the outer membrane to Cu²⁺ and, hence, such a high Cu²⁺ adsorption capacity of P. putida 5-x cell envelope.     

Influence of the nature of membrane ionogenic groups on water dissociation and electrolyte ion transport: A rotating membrane disk study

Polarization properties of electromembrane systems (EMS) consisting of a heterogeneous membrane, either the MK-41 phosphonic acid membrane or the MK-40 sulfonic acid membrane, and dilute sodium chloride solutions are investigated with the rotating membrane disk method. For the MK-41/0.01 M NaCl and MK-41/0.001 M NaCl EMS, effective ion transport numbers and partial current-voltage curves (CVC) are measured for sodium and hydrogen ions, and limiting-current densities and the diffusion-layer thickness are calculated as functions of the rotation rate of the membrane disk. With the theory of the overlimiting state of EMS, internal parameters of the systems under investigation—the diffusion-layer thickness, the space-charge distribution, and electric-field strengths in the diffusion layer and in the membrane—are calculated from experimentally obtained CVC and the dependence of effective transport numbers on current density. The catalytic influence of ionogenic groups on the dissociation rate of water is analyzed quantitatively. Partial CVC for H⁺ ions are calculated for the space-charge region in MK-40 and MK-41 membranes. Analogous CVC for bipolar membranes containing sulfonic acid and phosphonic acid groups are compared. The dissociation mechanism of water is the same in all EMS and is independent of the membrane type and the nature of the functional groups.     

Development of polyelectrolyte multilayer-coated electrospun cellulose acetate fiber mat as composite membranes

Electrostatic multilayers of chitosan (CHI)/sodium alginate (SA) and CHI/poly(styrene sulfonate) sodium salt (PSS) were alternatively coated on electrospun cellulose acetate (CA) fiber mat. Morphologies of the composite membranes were characterized by scanning electron microscopy. The morphology of the CHI/SA-coated membrane was denser than the CHI/PSS-coated one. The top layers consisted of carboxyl and sulfonic functional groups for SA and PSS layers, respectively. Amino groups of CHI were only presented in slight quantity. X-ray photoelectron spectroscopy (XPS) confirmed the deposition of the amino groups of CHI on the multilayer membrane surface. These composite membranes were characterized for its water permeability where the water flux decreased with an increase in the number of the bilayers. The water flux was in the range of 60 and 40 L m⁻² h⁻¹ for 15 and 25 bilayered membranes, respectively. The sodium chloride (NaCl) solution flux was lower than the pure water flux due to the effect of osmotic pressure, and it decreased with an increase in the NaCl concentration. The rejection of NaCl increased substantially with the number of the bilayers of the polyelectrolytes multilayers. The level of NaCl rejection from this work was in the range of 6% and 15% for 15 and 25 bilayered membranes, respectively.     

Efficient free energy calculation of water across lipid membranes

An efficient free energy (FE) calculation of a water molecule to go across lipid membranes is presented. Both overlapping distribution and cavity insertion Widom methods are complementarily used. The former is useful for a dense region where water molecules are found, i.e., from the interfacial to bulk water region, while the latter works well in the low density region, i.e., the hydrocarbon region. Since both methods evaluate the excess chemical potential of water, the obtained FE profile is free from the fitting problem usually arisen when a FE difference method is used. A diphytanyl phosphatidylcholine bilayer is used for our test calculations. An excellent and fast convergence of the chemical potential is obtained when each method is applied for the appropriate region. The estimated FE barrier using the Ewald method for the electrostatic interaction is approximately 7.2 kcal/mol, which is higher than that using the interaction cutoff of 20 A by about 0.9 kcal/mol.     

TRAJELIX: A Computational Tool for the Geometric Characterization of Protein Helices During Molecular Dynamics Simulations

Summary We have developed a computer program with the necessary mathematical formalism for the geometric characterization of distorted conformations of alpha-helices proteins, such as those that can potentially be sampled during typical molecular dynamics simulations. This formalism has been incorporated into TRAJELIX, a new module within the SIMULAID framework (http://inka.mssm.edu/~mezei/simulaid/) that is capable of monitoring distortions of alpha-helices in terms of their displacement, global and local tilting, rotation around their axes, compression/extension, winding/unwinding, and bending. Accurate evaluation of these global and local structural properties of the helix can help study possible intramolecular and intermolecular changes in the helix packing of alpha-helical membrane proteins, as shown here in an application to the interacting helical domains of rhodopsin dimers. Quantification of the dynamic structural behavior of alpha-helical membrane proteins is critical for our understanding of signal transduction, and may enable structure-based design of more specific and efficient drugs.