The hydrogen bond, and the structure and properties of H20 and (H20)2

The properties of a hydrogen bond are reviewed. We consider the H₂0 molecule in its ground electronic state since this has to be the starting point for a study of water, ice and aqueous solutions. The water dimer, (H₂0)₂, and the hydrogen fluoride dimer, (HF)₂, are discussed. The electrostatic nature of the hydrogen bond is emphasized.     

A mathematical model of aging-related and cortisol induced hippocampal dysfunction

Background  

The hippocampus is essential for declarative memory synthesis and is a core pathological substrate for Alzheimer's disease (AD), the most common aging-related dementing disease. Acute increases in plasma cortisol are associated with transient hippocampal inhibition and retrograde amnesia, while chronic cortisol elevation is associated with hippocampal atrophy. Thus, cortisol levels could be monitored and managed in older people, to decrease their risk of AD type hippocampal dysfunction. We generated an in silicomodel of the chronic effects of elevated plasma cortisol on hippocampal activity and atrophy, using the systems biology mark-up language (SBML). We further challenged the model with biologically based interventions to ascertain if cortisol associated hippocampal dysfunction could be abrogated.     

Large-Order Asymptotics for Multiple-Pole Solitons of the Focusing Nonlinear Schrödinger Equation

Journal of Nonlinear Science - We analyze the large-n behavior of soliton solutions of the integrable focusing nonlinear Schrödinger equation with associated spectral data consisting of a...     

Definition and measurement of the normalized electrical impedance of lossy piezoelectric resonators for ultrasonic transducers

Relevant equivalent circuit parameters and values of material constants of a piezoelectric resonator can be determined from measurements of its electrical input impedance as a function of frequency. The complex electrical impedance curves and the associated critical frequencies are the basis of this characterization by the piezoelectric resonance method. In this paper, the previously introduced concept of normalized electrical impedance of the lossy resonator, extended to include piezoelectric losses, is applied to the analysis of the effects of different types of intrinsic losses on peak values, bandwidths and characteristic frequencies. The resulting impedance patterns depend solely on the electromechanical coupling coefficient and the loss tangents, providing a useful tool for the analysis of low-Q resonators. The normalized impedance is experimentally evaluated from the basic data provided by an HP 4194A impedance analyser by means of specifically developed ASP programs.     

Microscale Ionic Diodes: An Overview

Ionic rectifier membranes or devices generate uni-directional ion transport to convert an alternating current (AC) ion current input into stored energy or direct current (DC) in the form of ion/salt gradients. Electrochemical experiments 80 years ago were conducted on biological membrane rectifier systems, but today a plethora of artificial ionic rectifier types has been developed and electroanalytical tools are employed to explore mechanisms and performance. This overview focuses on microscale ionic rectifiers with a comparison to nano- and macroscale ionic rectifiers. The potential is surveyed for applications in electrochemical analysis, desalination, energy harvesting, electrochemical synthesis, and in selective ion extraction.     

Investigation of electric-field-gradient-induced birefringence in H2 and D2

An ab initio computational investigation of the electric–field–gradient–induced birefringence in H₂ and D₂ is presented. The quadrupole moment and all linear and non-linear optical properties contributing to the induced anisotropy of the refractive index are computed by means of Coupled Cluster Singles and Doubles response theory. The latter leads for these systems to Full Configuration Interaction results. Vibrational averaging, centrifugal distortion due to rotation, isotope effects and differences between ortho and para species are also considered.