Hydration of neurotransmitters: a computational and spectroscopic study of a noradrenaline analogue, 2-amino-1-phenyl-ethanol

Singly and multiply hydrated clusters of the noradrenaline analogue, 2-amino-I-phenyl-ethanol (APE) have been studied using a combination of resonant two-photon ionization time of flight spectroscopy (R2PI-TOF), infrared ion-dip spectroscopy and ab initio quantum chemical calculation. Singly hydrated clusters populate two distinct structures: the water molecule either hydrogen-bonds to the ethanol group in the extended AG conformer (leaving the intramolecular OH → N hydrogen bond intact) or inserts into the intramolecular hydrogen bond in the (distorted) ethanolamine side chain (promoting a weak NH → O bond). The observed doubly and triply hydrated clusters both display insertion structures only, with the water molecules arrayed as linear chains, hydrogen bonded to the functional groups of the side-chain and again promoting a weak NH → O bond along the distorted ethanolamine side-chain. The infrared spectrum of the 1:4 cluster of APE, which is very similar to that of the corresponding cluster of ephedrine, includes new features in the ‘window region’ (3500–3700 cm^?1), indicating the onset of a three-dimensional assembly. Comparisons with ab initio computed spectra favour a structure that incorporates a cyclic water tetramer linked to the two functional groups on the ethanolamine side-chain.     

The classical partition function of a bound three-particle cluster

The task of computing the classical partition function for a bound aggregate of three particles is reduced to that of performing a 2-dimensional quadrature. A simple, analytical formula is obtained in the special case of three identical particles for which the mutual interactions are given by pair-additive square-well potentials.     

The FeH radical: rotational assignment of the a6A Δ(ν = 2) and b6II (ν = 1) levels

A dispersed fluorescence study of the FeH radical at near ambient (～450 K) temperature has identified the g⁶Φ-a ⁶δ (0, 2) and g⁶Φ-b⁶II (0, 1) bands in the orange region of the spectrum. The corresponding bands with upper state e⁶II are located at about 640nm in the red. High resolution measurements in LIF have enabled the assignment of around 275 lines to these four transitions. Analysis of these bands has provided a second vibrational interval for the a⁶δ state and a first vibrational interval for the b⁶II state as 1536cm^?1 and 1542cm^?1, respectively. Term values have also been measured for a set of levels with a tentative assignment to c⁴Φ_9/2 (ν = 1).     

Complexation in dense gases: concentrations of argon monomers,dimers and trimers

A classical statistical mechanical cluster formalism is presented for computing the thermodynamic properties and equilibrium state of aggregation of a fluid composed of structureless monomeric units which are capable of forming weakly bound van der Waals complexes. The general procedure is not restricted to any particular definition of the clusters, provided that the definition used satisfies certain reasonable criteria. The formalism is illustrated by applying it to two different cluster definitions. Calculations based on these definitions have been performed for the concentrations of argon monomers, dimers and trimers. It is found that gas imperfections due to cluster-cluster interactions can significantly affect the calculated values of these concentrations.     

Dielectric relaxation of α-cyclodextrin-polyiodide complexes (α-cyclodextrin)2 · BaI2 · I2 · 8H2O and (α-cyclodextrin)2 · KI3 · I2 · 8H2O

The frequency and temperature dependence of the real (ε′) and imaginary (ε″) parts of the dielectric constant of the polycrystalline complexes (α-CD)₂ · Bal₂ · I₂ · 8H₂O and (α-CD)₂ · KI₃ · I₂ · 8H₂O (α-CD = α-cyclodetrin) have been investigated over the frequency and temperature ranges 0–100 kHz and 120–300 K, respectively. The temperature dependences of ε′, ε″ and the phase shift φ show two steps, two peaks and two minima, respectively, revealing the existence of two kinds of water molecule, the tightly bound and the easily movable water molecules, in both complexes. The first peak of (T) or the first minimum of φ(T) presents the transformation of flip-flop hydrogen bonds to the normal state. The second ε″ (T) peak or φ(T) minimum corresponds to the easily movable water molecules or to a partial transformation of tightly bound to easily movable water molecules. For T > 270K both samples show semiconductive behaviour with energy gaps of 1.84eV for the (α-CD)₂ · BaI₂ · I₂ · 8H₂O complex and 1.36eV for the (α-CD)₂ · KI₃ · I₂ · 8H₂O complex. The conductivity at room temperature decreases in the order: (α-CD)₂ · BaI₂ · I₂ · 8H₂O > (α-CD)₂ · LiI₃ · I₂ · 8H₂O > (α-CD)₂ · KI₃ · I₂ · 8H₂O > (α-CD)₂ · Cd_0.5 · I₅ · 26H₂O. The relaxation time varies in a Λ-like curve (from 120 to 250 K) and rises rapidly for temperatures greater than 250 K, indicating the process of ionic movements. The activation energies around the transition temperature 0.98–1.09 k _B T _trans for (α-CD)₂ · BaI₂ · I₂ · 8H₂O and 1.06-1.55 k _B T _trans for (α-CD)₂ · KI₃ · I₂ · 8H₂O reveal the greater stability of the α-K complex against that of the α-Ba complex.     

Some properties of electronic non-adiabatic coupling terms

Analytical expressions are obtained for the Born-Oppenheimer non-adiabatic coupling terms formed by a given distribution of conical intersections. The gauge-dependent formulae contain explicitly the boundary conditions that have to be obtained by ab initio calculations performed along a circle in the close vicinity of each conical intersection.     

Continuous-Time Stochastic Calculus: A Survey of Applications in Finance and Accountancy

In recent years, the methods of stochastic calculus have beenincreasingly applied in both the finance and accountancy literatures.To the uninitiated the techniques of stochastic calculus areconfusing and counterintuitive, since few of the rules of ordinarycalculus appear to be satisfied. The present paper providesa simple and somewhat heuristic introduction to the basic concepts,with special attention being paid to applications in the financeand accountancy disciplines. After introducing the concept ofwhite noise, the standard Brownian, Ehrenfest, and tied-downor bridge processes are explained in a discrete-time binomialcontext. Limits are then taken to obtain the continuous-timeanalogues. The paper also provides a brief introduction to theimportant topic of Ito calculus and its applications in accountancyand finance.     

An error bound for the finite element approximation of a model for phase separation of a multi-component alloy

An error bound is proved for a fully practical piecewise linearfinite element approximation, using a backward-Euler time discretization,of a model for phase separation of a multi-component alloy.Numerical experiments with three components in one and two spacedimensions are also presented.     

PHOTOSENSITIZATION OF CONDUCTION IN MOLECULAR SOLIDS*

Abstract— The mechanism of spectral sensitization of conduction in molecular photoconductors has been investigated in systems in which sensitizer and photoconductor form separate layers. The efficiency of sensitization is strongly influenced by external fields, approaching 100 per cent at 10⁶ V/cm in certain cases. The spectral response, efficiency, and field dependence are characteristic primarily of the sensitizer, while the transport characteristics are largely determined by the photoconductor. These results are considered in the light of available information concerning the molecular energy levels of the materials studied. They support the view that light absorption produces mobile electronic charge carriers in the sensitizer, which may be separated, injected, and transported across the photoconductor under an applied electric field. This mechanism is consistent with the interpretation of work on electrolyte-photoconductor contacts, and appears to account for all that is presently known about optical sensitization of molecularly bonded photoconductors.