Metastable Ionic Diodes Derived from an Amine‐Based Polymer of Intrinsic Microporosity

A highly rigid amine‐based polymer of intrinsic microporosity (PIM), prepared by a polymerization reaction involving the formation of Tröger’s base, is demonstrated to act as an ionic diode with electrolyte‐dependent bistable switchable states.     

Localization of Non-Relativistic Particles

This paper is a contribution to the problem of particle localization in non-relativistic Quantum Mechanics. Our main results will be (1) to formulate the problem of localization in terms of invariant subspaces of the Hilbert space, and (2) to show that the rigged Hilbert space incorporates particle localization in a natural manner.     

Resonance expansions in quantum mechanics

The goal of this contribution is to discuss various resonance expansions that have been proposed in the literature. Presented at the 3rd International Workshop “Pseudo-Hermitian Hamiltonians in Quantum Physics”, Istanbul, Turkey, June 20–22, 2005.     

Density functional studies of molecular structures of N-methyl formamide, N,N-dimethyl formamide, and N,N-dimethyl acetamide

Density functional theory was applied to the calculation of molecular structures of N-methyl formamide (NMF), N,N-dimethyl formamide (DMF), and N,N-dimethyl acetamide (DMA). DFT calculations on NMF, DMF, and DMA were performed using a combination of the local functional of Vosko, Wilk, and Nusair (VWN) with the nonlocal exchange functional of Becke and the nonlocal correlational functional of Lee, Yang, and Parr (BLYP). The adiabatic connection method (ACM) of Becke has also been used, for the first time, for the calculation of molecular structures of NMF, DMF, and DMA. The calculated molecular structures are in excellent agreement with the experimental geometries of NMF and DMA derived from gas-phase electron-diffraction studies. Sparse experimental data on the gas-phase geometry of DMF reported in the literature compares well with the DFT results on DMF. DFT emerges as a powerful method to calculate molecular structures.     

Antiphytopathogenic activity of Psoralea glandulosa (Fabaceae) against Botrytis cinerea and Phytophthora cinnamomi

The resinous exudate, three meroterpenes, namely bakuchiol (1), 3-hydroxybakuchiol (2), 12-hydroxyisobakuchiol (3), and one furanocoumarin, psoralen (4), were isolated from the leaves of culen (Psoralea glandulosa). In addition to these, two semi-synthetic derivatives, bakuchiol acetate (5) and bakuchiol methyl eter (6), were obtained from 1, and were subsequently evaluated in vitro for the inhibitory effect of resin and compounds on the mycelial growth of Botrytis cinerea Pers.: Fr. and Phytophthora cinnamomi Rands. The resinous exudate inhibited the mycelial growth of both the pathogens, while bakuchiol (1) exhibited an inhibitory effect on the mycelial growth of B. cinerea up to 94% at a concentration of 150 mg/L and psoralen (4) reduced the mycelial growth of P. cinnamomi up to 80% at a concentration of 150 mg/L. These compounds have the ability of blocking the development of mycelial growth and may be used as a potential biopesticide in the agricultural sector once the in vivo test results have been validated.     

Approximate reduction of non-linear discrete models with two time scales

The aim of this work is to present a general class of nonlinear discrete time models with two time scales whose dynamics is susceptible of being approached by means of a reduced system. The reduction process is included in the so-called approximate aggregation of variables methods which consist of describing the dynamics of a complex system involving many coupled variables through the dynamics of a reduced system formulated in terms of a few global variables. For the time unit of the discrete system we use that of the slow dynamics and assume that fast dynamics acts a large number of times during it. After introducing a general two-time scales nonlinear discrete model we present its reduced accompanying model and the relationships between them. The main result proves that certain asymptotic behaviours, hyperbolic asymptotically stable (A.S.) periodic solutions, to the aggregated system entail that to the original system.     

The negative sign and exponential expressions: Unveiling students’ persistent errors and misconceptions

The purpose of this study was to determine whether or not certain errors made when simplifying exponential expressions persist as students progress through their mathematical studies. College students enrolled in college algebra, pre-calculus, and first- and second-semester calculus mathematics courses were asked to simplify exponential expressions on an assessment. Persistent errors are identified and characterized. Using quantitative and qualitative methods, we found that the concept of negativity played a prominent role in most of the students’ errors. We theorize that an underdeveloped conception of additive and multiplicative inverses is the root of these errors.