Pore morphologies in disordered nanoporous thin films

Materials with nanometer size heterogeneities are commonplace in the chemical and biological sciences (e.g, polymer blends, microemulsions, gels) and often exhibit complex morphologies. Although this morphology has a dramatic effect on the materials' properties, it is often difficult to accurately characterize. We describe a method, using small-angle X-ray scattering data, of generating representative three-dimensional morphologies of isotropic two-phase materials where the morphology is disordered, and we apply this to thin films containing nanometer sized pores with a range of porosities (4-44%). These representations provide a visualization of the pore morphology, give the pore size scale and extent of interconnection, and permit the determination of the transitions from closed pore to interconnected pores to bicontinuous morphology.     

Experimental and Computational Study of the Thermal Decomposition of 3‐Methyl‐3‐buten‐1‐ol in m‐Xylene Solution

An experimental study of the thermal decomposition of a β‐hydroxy alkene, 3‐methyl‐3‐buten‐1‐ol, in m‐xylene solution, has been carried out at five different temperatures in the range of 513.15–563.15 K. The temperature dependence of the rate constants for the decomposition of this compound in the corresponding Arrhenius equation is given by ln k (s^?1) = (25.65 ± 1.52) ? (17,944 ± 814) (kJ·mol^?1)·T^?1. A computational study has been carried out at the M05–2X/6–31+G(d,p) level of theory to calculate the rate constants and the activation parameters by the classical transition state theory. There is a good agreement between the experimental and calculated rate constants and activation Gibbs energies. The bonding characteristics of reactant, transition state, and products have been investigated by the natural bond orbital analysis, which provides the natural atomic charges and the Wiberg bond indices. Based on the results obtained, the mechanism proposed is a one‐step process proceeding through a six‐membered cyclic transition state, being a concerted and slightly asynchronous process. The results have been compared with those obtained previously by us (Struct Chem 2013, 24, 1811–1816) for the thermal decomposition of 3‐buten‐1‐ol, in m‐xylene solution. We can conclude that in the compound studied in this work, 3‐methyl‐3‐buten‐1‐ol, the effect of substitution at position 3 by a weakly activating CH₃ group is the stabilization of the transition state formed in the reaction and therefore a small increase in the rate of thermal decomposition.     

Structural and Kinetic Aspects of Blood Plasma Protein Adsorption on the Surface of Hydrophobic Polymers

Abstract

Due to the wide use of polymers in medicine, researchers are required to solve a very important problem–to understand the interaction between materials of nonphysiological origin and the surrounding biological liquids, and tissues, particularly blood.     

The rate of convergence of parabolic difference schemes with constant coefficients

The paper describes how estimates can be obtained for the rate of convergence of certain parabolic difference schemes. These schemes approximate a Cauchy problem with constant coefficients. Interpolation technique is used for many of the proofs. The results are compared with previous work by several authors.This research was supported in part by the National Science Foundation.     

Generalized ray expansion for pulse propagation and attenuation in fluid-saturated porous media

A theory suitable for studying pulses propagating through a layered fluid-saturated porous medium is presented. Biot's theory is used to describe the constitutive equation of a fluid-saturated porous solid. Since fast and slow compressional waves exist in a Biot solid even at normal incidence, there is mode conversion at the interface and, therefore, the transmission and reflection coefficients are 2x2 matrices. We use matrix methods in developing the solution of the wave propagation problem. A generalized ray expansion algorithm is obtained by using the Gauss-Seidel matrix iterative method. The arrivals of the fast and the slow waves are easily identified. A compact computational algorithm is developed using combinatorial analysis and the Cayley-Hamilton theorem.     

Cell compatible trimethoprim-decorated iron oxide nanoparticles bind dihydrofolate reductase for magnetically modulating focal adhesion of mammalian cells

On the basis of the high affinity binding of trimethoprim (TMP) to Escherichia coli dihydrofolate reductase (eDHFR), TMP-decorated iron oxide nanoparticles bind to eDHFR with high affinity and specificity, which allows magnetic modulation of focal adhesion of mammalian cells adhered to a surface. Besides being the first example of nanoparticles that selectively bind to eDHFR, the biocompatibility of the conjugate of TMP-iron oxide nanoparticles renders a convenient and versatile platform for investigating the cellular responses to specific, mechanical perturbation of proteins via a magnetic force.     

The distribution of the eigenvalues of the discrete Laplacian

We estimate the distribution of the eigenvalues of the discrete Laplacian on a bounded set inR ⁿ . The proof is based on a variational technique similar to that used by Weyl for the Laplacian. As an application of our estimates we prove stability in the maximum norm for the Crank-Nicolson method for the heat equation on a bounded set.The research of the second author was supported in part by National Science Foundation grant GP-30735X.