Channel-like Domain Research Articles

The NaClO4-water eutectic electrolyte for environmentally friendly electrical double-layer capacitors operating at low temperature

Herein, owing to its remarkable ionic conductivity, the 8.84 mol kg−1 NaClO4 water-in-salt (WIS) eutectic electrolyte is suggested for the low temperature operation of electrical double-layer capacitors down to -35 °C. Molecular dynamic simulations reveal that the local structure of the solution remains relatively stable from RT to -35 °C, with distinct channel-like domains formed by hydrogen-bonded water molecules, which facilitate the ionic diffusion within the bulk of the electrolyte. Interestingly, on activated carbon (AC) electrodes, the electrolyte demonstrates an electrochemical stability window (ESW) increasing from 1.8 V to 2.1 V as temperature decreases from 25 °C to -35 °C. The high ESW of this electrolyte is due to i) pH close to neutrality enabling high overpotential of water reduction on porous AC electrodes; ii) WIS characteristics with a reduced amount of free water in the Stern layer under positive polarization of AC; iii) higher oxidation potential at low temperature ascribed to the enhanced immobilization of the ClO4− anions in the Stern layer as well as reduced diffusion of water molecules in the AC electrode porosity. The electrochemical investigations on laminate AC//AC cells in the NaClO4-water electrolyte demonstrate low values of their resistive components down to -30 °C, while the devices can operate with rated voltage of 2.0 V and 1.7 V at -30 °C and RT, respectively. At -30 °C and under discharge power as high as 10 kW kg−1, the AC//AC capacitor in the NaClO4-water electrolyte outperforms the specific output energy of a traditional AC//AC cell in the 1 M TEABF4/ACN electrolyte. Hence, for sub-ambient temperatures, the presented environmentally friendly EDLC holds promise to compete with traditional devices implementing an organic electrolyte.

Global attractors of the delay 2D Navier-Stokes equations on unbounded Channel-like domains

This paper studies the global attractors of 2D Navier-Stokes equations with delay defined in unbounded Channel-like domains. We establish the uniform tail-ends estimates of the solutions by establishing all the solutions are uniformly small for overcome the non-compactness of the solutions.

Role of the CagY antenna projection in Helicobacter pylori Cag type IV secretion system activity.

Helicobacter pylori strains containing the cag pathogenicity island (PAI) are associated with the development of gastric adenocarcinoma and peptic ulcer disease. The cag PAI encodes a secreted effector protein (CagA) and a type IV secretion system (Cag T4SS). Cag T4SS activity is required for the delivery of CagA and non-protein substrates into host cells. The Cag T4SS outer membrane core complex (OMCC) contains a channel-like domain formed by helix-loop-helix elements (antenna projections, AP) from 14 copies of the CagY protein (a VirB10 ortholog). Similar VirB10 antenna regions are present in T4SS OMCCs from multiple bacterial species and are predicted to span the outer membrane. In this study, we investigated the role of the CagY antenna region in Cag T4SS OMCC assembly and Cag T4SS function. An H. pylori mutant strain with deletion of the entire CagY AP (∆AP) retained the capacity to produce CagY and assemble an OMCC, but it lacked T4SS activity (CagA translocation and IL-8 induction in AGS gastric epithelial cells). In contrast, a mutant strain with Gly-Ser substitutions in the unstructured CagY AP loop retained Cag T4SS activity. Mutants containing CagY AP loops with shortened lengths were defective in CagA translocation and exhibited reduced IL-8-inducing activity compared to control strains. These data indicate that the CagY AP region is required for Cag T4SS activity and that Cag T4SS activity can be modulated by altering the length of the CagY AP unstructured loop.

Uniform tail-ends estimates of the Navier-Stokes equations on unbounded channel-like domains

This paper deals with the asymptotic compactness of the solutions of the two-dimensional Navier-Stokes equations defined in unbounded channel-like domains. In order to overcome the non-compactness of Sobolev embeddings in unbounded domains, we establish the uniform tail-ends estimates of solutions by showing all the solutions are uniformly small outside a sufficiently large bounded domain for all large time and bounded initial data, which implies the asymptotic compactness and hence the existence of global attractors in the natural energy space. The uniform tail-ends estimates are derived by the scalar stream function of the Navier-Stokes equations which is distinct from the reaction-diffusion equation due to the divergence free condition.

Boundary stabilizing actuators for multi-phase fluids in a channel

This work is devoted to the problem of boundary stabilization of a mixture of two viscous and incompressible fluids in a three dimensional channel-like domain (x,y,z)∈R×(0,1)×R. The model consists of the Navier-Stokes equations, governing the fluid velocity, coupled with a convective Cahn-Hilliard equation for the relative density of the atoms of one of the fluids. The feedback stabilizing controller, we design here, is with actuation only on the tangential component of the velocity field on both walls y=0,1. Moreover, it is given in a simple and explicit form, easy to manipulate from the computational point of view.

A firehose for phospholipids.

All lipid transport proteins in eukaryotes are thought to shuttle lipids between cellular membranes. In this issue, Li et al. (2020. J. Cell Biol.https://doi.org/10.1083/jcb.202001161) show that Vps13 has a channel-like domain that may allow lipids to flow between closely apposed membranes at contact sites.

Hydrodynamic and thermodiffusive instability effects on the evolution of laminar planar lean premixed hydrogen flames

AbstractNumerical simulations with single-step chemistry and detailed transport are used to study premixed hydrogen/air flames in two-dimensional channel-like domains with periodic boundary conditions along the horizontal boundaries as a function of the domain height. Both unity Lewis number, where only hydrodynamic instability appears, and subunity Lewis number, where the flame propagation is strongly affected by the combined effect of hydrodynamic and thermodiffusive instabilities are considered. The simulations aim at studying the initial linear growth of perturbations superimposed on the planar flame front as well as the long-term nonlinear evolution. The dispersion relation between the growth rate and the wavelength of the perturbation characterizing the linear regime is extracted from the simulations and compared with linear stability theory. The dynamics observed during the nonlinear evolution depend strongly on the domain size and on the Lewis number. As predicted by the theory, unity Lewis number flames are found to form a single cusp structure which propagates unchanged with constant speed. The long-term dynamics of the subunity Lewis number flames include steady cell propagation, lateral flame movement, oscillations and regular as well as chaotic cell splitting and merging.

Strong Solutions to Non-stationary Channel Flows of Heat-Conducting Viscous Incompressible Fluids with Dissipative Heating

We study an initial-boundary-value problem for time-dependent flows of heat-conducting viscous incompressible fluids in channel-like domains on a time interval (0,T). For the parabolic system with strong nonlinearities and including the artificial (the so called do nothing) boundary conditions, we prove the local in time existence, global uniqueness and smoothness of the solution on a time interval (0,T ?), where 0<T ??T.

Instability of two-phase flows: A lower bound on the dimension of the global attractor of the Cahn–Hilliard–Navier–Stokes system

We consider a model for the flow of a mixture of two viscous and incompressible fluids in a two or three dimensional channel-like domain. The model consists of the Navier–Stokes equations governing the fluid velocity coupled with a convective Cahn–Hilliard equation for the relative density of atoms of one of the fluids. We prove the instability of certain stationary solutions for such a system endowed with periodic boundary conditions on elongated domains (0,2π/α0)×(0,2π) or (0,2π/α0)×(0,2π)×(0,2π/β0) for a special class of periodic body forces, provided that α0 and β0 are small enough. As a consequence, we deduce a lower bound for the Hausdorff dimension of the global attractor.

Subunit stoichiometry and channel pore structure of ion channels: all for one, or one for one?

Subunit stoichiometry and channel pore structure of ion channels: all for one, or one for one?

Magmatic structures in the Krkonoše–Jizera Plutonic Complex, Bohemian Massif: evidence for localized multiphase flow and small-scale thermal–mechanical instabilities in a granitic magma chamber

The present paper examines magmatic structures in the Jizera and Liberec granites of the Krkonoše–Jizera Plutonic Complex, Bohemian Massif. The magmatic structures are here interpreted to preserve direct field evidence for highly localized magma flow and other processes in crystal-rich mushes, and to capture the evolution of physical processes in an ancient granitic magma chamber. We propose that after chamber-wide mixing and hybridization, as suggested by recent petrological studies, laminar magma flow became highly localized to weaker channel-like domains within the higher-strength crystal framework. Mafic schlieren formed at flow rims, and their formation presumably involved gravitational settling and velocity gradient flow sorting coupled with interstitial melt escape. Local thermal or compositional convection may have resulted in the formation of vertical schlieren tubes and ladder dikes whereas subhorizontal tubes or channels formed during flow driven by lateral gradients in magma pressure. After the cessation or deceleration of channel flow, gravity-driven processes (settling of crystals and enclaves, gravitational differentiation, development of downward dripping instabilities), accompanied by compaction, filter pressing and melt segregation, dominated in the crystal mush within the flow channels. Subsequently, magmatic folds developed in schlieren layers and the magma chamber recorded complex, late magmatic strains at high magma crystallinities. Late-stage magma pulsing into localized submagmatic cracks represents the latest events of magmatic history of the chamber prior to its final crystallization. We emphasize that the most favorable environments for the formation and preservation of magmatic structures, such as those hosted in the Jizera and Liberec granites, are slowly cooling crystal-rich mushes. Therefore, where preserved in plutons, these structures may lend strong support for a “mush model” of magmatic systems.

Three-Dimensional Nets from Star-Shaped Hexakis(arylthio)triphenylene Molecules and Silver(I) Salts

This article reports a number of functional 3D networks based on the coordination bonds between the silver(I) ion and polycyclic aromatic 2,3,6,7,10,11-hexakis(organylthio)triphenylene (HRTT) molecules. First, 2,3,6,7,10,11-hexakis(phenylthio)triphenylene (HPhTT) chelates with AgBF4 (or AgTf, where Tf is triflate) in the presence of hexafluorobenzene to form a 3D network (composition, HPhTT x AgBF4; space group, I4), where each Ag(I) atom is bonded to three HPhTT molecules and acts as a three-connected node that interconnects the trigonal HPhTT ligands. In addition to the relatively rare 8(2) x 10-a topology, the network features distinct channel-like domains that incorporate various solvent molecules (e.g., acetone and tetrahydrofuran). The solvent molecules can be evacuated to produce a stable and crystalline apohost network, in which the solvent-accessible fraction of the cell volume is calculated to be about 16%. Second, chelation of 2,3,6,7,10,11-hexakis(4-methoxyphenylthio)triphenylene (HMOPhTT) and AgSbF6 in a 1:1 ratio results in a 3D network featuring a similar 8(2) x 10-a topology and Ag(I) coordination environment. However, the crystallographic symmetry (space group Cc) is lowered, and the feature of porosity is much less distinct. The 3D networks show strong room-temperature fluorescence bands with lambda(F,max) = 450 nm, due to the pi-electron fragment of the triphenylene group.

Spectral vanishing viscosity method for LES: sensitivity to the SVV control parameters

Where spectral methods are concerned, the spectral vanishing viscosity (SVV) method offers an interesting way of computing high Reynolds number flows since it allows stabilization of the calculations whilst preserving the exponential rate of convergence of the spectral approximation. Here we first show how to implement the SVV method in an existing Navier–Stokes solver and then investigate the sensitivity of the numerical results to its main characteristic parameters, namely the SVV amplitude and the SVV activation mode, by focusing on the computation of a turbulent wake in a cylinder, embedded in a channel-like domain, at Reynolds number Re = 3900.

Existence and dimension of the attractor for the Bénard problem on channel-like domains

The Bénard problem, a system with theNavier-Stokes equations for the velocity field coupled with aconvection-diffusion equation for the temperature is considered.Non-homogeneous boundary conditions, external force and heatsource in dual function spaces, and an arbitrary spatial domain(possibly nonsmooth and unbounded) as long as the Poincaréinequality holds on it (channel-like domain) are allowed. Moreoverour approach, unlike in previous works, avoids the use of themaximum principle which would be problematic in this context. Themathematical formulation of the problem, the existence of globalsolution and the existence and finite dimensionality of the globalattractor are proved.

Potassium and voltage dependence of the inorganic pyrophosphatase of intact vacuoles from Chenopodium rubrum

The activity and the voltage dependence of the inorganic pyrophosphatase (PPase) was measured on intact vacuoles of Chenopodium rubrum cells using the patch-clamp technique. With K + at the cytoplasmic side a negative current representing the forward mode of the pump was measured after addition of pyrophosphate (PP i). The pump was reversed and a positive current was detected after addition of orthophosphate (P i) in the presence of K + at the vacuolar side when a pH gradient across the tonoplast was applied. The PPase operates as a constant current source, because no voltage dependence was observed (−60 to 60 mV). The K + dependence of the PP i-induced current was investigated by substitution of cytoplasmic K + by other cations. The selectivity sequence was: K +≥Rb + > NH 4 + = Cs + > Na + > Li + = choline +, and was independent of the membrane voltage and pH cyt. With Cs + or Li + in the bath and K + inside the vacuole the PP i-induced current became voltage-dependent, and positive currents were observed even if the pump was geared to operate in the forward mode. We suggest a ‘tunneling’ effect through a channel-like domain in the PPase molecule which, under defined electrochemical gradient conditions and in the presence of PP i, allows K + ions to cross the energy barrier usually separating the cytoplasmic from the vacuolar face of the pump.

Unraveling the modular design of glutamate-gated ion channels

Glutamate receptors that function as ligand-gated ion channels are essential components of cell-cell communication in the nervous system. Despite a wealth of information concerning these receptors, details of their structure are just beginning to emerge. We propose that glutamate receptors comprise four modules: two modules that are related to bacterial periplasmic-binding proteins, one module that is related to the pore-forming region of K + channels, and one regulatory module of unknown origin. A K +-channel-like domain inserted into a crucial region of a periplasmic-binding protein-like domain suggests a mechanism for transduction of binding energy to channel opening. This modular design also suggests an evolutionary link between a ligand-gated ion-channel family and voltage-gated ion channels.

The attractor of a Navier-Stokes system in an unbounded channel-like domain

The Navier-Stokes system describes a flow of a fluid in an unbounded planar channel-like domain. It is proved that in the case when an external force decays at infinity, the semigroup generated by this system has a global attractor and its Hausdorff dimension is finite. Estimates in weighted Sobolev spaces are used as a main tool. Asymptotics, as the distance from the origin in the plane tends to infinity, of functions on the attactor is found. This asymptotics show that all dynamics on the attractor decays at infinity and the turbulence generated by the force does not propagate to infinity.