MEMBRANE PHOTOMODIFICATION OF CARDIAC MYOCYTES: POTASSIUM AND LEAKAGE CURRENTS

Cardiac myocytes were isolated from the atria of frogs (Rana pipiens) and whole cell potassium (IK) and "leakage" (Ileak) currents were monitored using the patch clamp technique. Cells were photosensitized by exposure to Rose Bengal (0.125-0.5 microM). Illumination produced an exponential decrease in IK, and an increase in Ileak. Current modifications varied with light intensity and sensitizer concentration. IK stabilized when illumination ceased, while Ileak continued to increase at a slower rate after illumination ended. The exponential nature of IK modification suggests that potassium channels are photomodified with single hit kinetics. The stabilization of IK following illumination suggests (1) that the photomodification of the potassium channel does not involve long lasting (minutes) radical chain reactions and (2) that this photomodification is not repaired in the course of a few minutes.     

PHOTOCHEMICAL OXIDATIONS—IV. THE PHOTOOXIDATION OF CYCLOHEXANE WITH OXYGEN

Abstract— –For the photooxidation of cyclohexane, data on the rates of formation of cyclohexanol (I), cyclohexanone (II), and cyclohexylhydroperoxide (III) are presented. There are induction periods for the formation of I and II but not for III. The alcohol (I) is not the precursor of II in this reaction. The photooxidation does not occur when optical filters eliminate wavelengths of 260 nm or less from the incident light, and therefore the contact charge transfer absorption is responsible for the initiation of the reaction. Ozone is not involved to any significant extent in this reaction. The photodecomposition of III produces I and II, and this decomposition is first order during the initial stages. An overall 11 step mechanism is suggested for the photooxidation.     

Adsorption of Hydrazoic Acid on Pristine Graphyne Sheet: A Computational StudySCI北大核心CSCD

Herein we have investigated the interaction between hydrazoic acid(HN3) and a pristine graphyne system based on density functional theory(DFT) method using generalized gradient approximation. The van der Waals dispersion correction is also considered for predicting the possibility of using the graphyne system for detection of hydrazoic acid. Pristine graphyne has a band gap of 0.453 eV, which decreases to 0.424 eV when HN3 is adsorbed on graphyne. The electrical conductivity of HN3-adsorbed graphyne is greater than that of its pristine counterpart. Charge transfer analysis reveals that the HN3-adsorbed graphyne system behaves as an n-type semiconductor; however, its pristine analogue acts as an intrinsic semiconductor. Pristine graphyne has zero dipole moment; however, its interaction with HN3 increases its dipole moment. The electronic properties of graphyne is significantly influenced by the presence of HN3, leading to the possibility of designing graphyne-based sensors for HN3 detection.     

Theoretical calculation of the structure of a polarizable-ionic fluid

Much theory of the structures of fluids depends on the assumption of pair-additive forces between the particles. Simulations and experiments have shown that many molten salts, molecular fluids and other systems have structures that depend sensitively on polarization of their electron clouds, or on other internal distortions. In such cases, the forces are not pair additive and the theoretical calculation of structure, expressed as a radial distribution function, g(r), is not possible using the ordinary methods. Part of the problem is that the internal structure is quantum mechanical. A theoretical method for the calculation of the structure of a fluid of polarizable particles is presented here, in a form that may be applied to any one of many structure theories in common use. The method is inspired by work on the simulation of polarizable fluids. It is applied to a simple model of a molten salt with polarizable ions. The theory is applicable to particles carrying any combination of induced electrical multipole moments, along with charges and permanent moments.     

Permeation of ions through a model biological channel: effect of periodic boundary conditions and cell size

The effect of the simulation cell size and periodic boundary conditions on non-equilibrium molecular dynamics simulations of the structure and dynamics with explicit water molecules and ions in and near a model channel in a biological membrane is considered. The approach seems satisfactory. In particular, the presence of image channels that often contain image ions seems to have little effect on the average structure, channel content, or current for this system.     

Error Bounds for Hermite Interpolation by Quadratic Splines on an {alpha}-Triangulation

For l, an -triangulation F of a planar domain is such that,for every T F, there holds 1 R_T/2r_T , where R_T (resp. r_T)denotes the radius of the circumscribed (resp. inscribed) circleof the triangle T. When T is varying in F the centre of itsinscribed circle is varying in a compact interior to T and itsorthogonal projections on the sides are varying in compact intervalsinterior to these sides. Precise results are given about thesizes of these compacts and are used for the computation oferror constants in the problem of Hermite interpolation by Powell-Sabinquadratic finite elements, bringing to the fore their dependenceon the parameter .     

A transferable representation of the induced multipoles in ionic crystals

Electronic structure calculations of the induced dipole and quadrupole moments on a fluoride ion at low symmetry sites in a model crystalline environments are described. The results are used to characterize the short range contributions to the induced multipoles on the F^? ion that arise from overlap between the wavefunctions of the ions. These are represented by general functions of the positions of the surrounding ions, suitable for use in a computationally tractable simulation model. The present calculations are designed to test the transferability to other classes of materials of this representation which, to date, largely has been deduced from calculations on distorted alkali halide crystals. First, the induced multipoles in mixed crystals of the alkali halides are considered, in order to check that they are predicted reliably by combining the representations deduced for the corresponding pure materials. Second, polarization effects in the alkaline earth fluorides MgF₂, and CaF₂, in a locally distorted fluorite crystal structure are examined. It is found that the material-specific parameters in the representation are related through simple functions of the ionic radii. This relationship holds between MgF₂, and CaF₂, in the fluorite structure, but also extends to the alkali fluorides previously studied. In order to illustrate the significance of polarization effects, the polarization model for CaF₂ is combined with an ab initio pair potential for the repulsion and dispersion interactions and used in a molecular dynamics simulation. Inclusion of the polarization term improves greatly the calculated phonon frequencies in the crystal.     

Beyond the LAN: Ethernet’s Evolution into the Public Network

This article details the evolution of Ethernet into Gigabit Ethernet and how this LAN-based technology has undergone major transformations over time. From its data rates and distances to supported media and functionality, Ethernet has greatly improved, enabling it to surmount many of its former limitations and in so doing to expand beyond the LAN into the MAN and now even the WAN. In this article, Pioneer Consulting explores the evolution further by focusing on some of the major technological directions in the Ethernet equipment industry.