Random Quantization of Hamiltonian Systems

Doklady Mathematics - A quantization of a Hamiltonian system is an ambiguous procedure. Accordingly, we introduce the notion of random quantization, related random variables with values in the set...     

In situ imaging of usnic acid in selected Cladonia spp. by vibrational spectroscopy

In this study, we demonstrate the first in situ detection of usnic acid (UA) in selected species of the lichen Cladonia, using FPA-FTIR imaging and Raman microscopy. Fruticose lichens present a variety of defensive mechanisms, one of which is the production of UA. This polyketide secondary metabolite, produced by certain lichenized fungi, has a protective function for the lichen that includes a strong absorption in the ultraviolet range. Upon confirming the distinct spectral signature of UA in lichen tissue, we mapped its distribution in Cladonia arbuscula, Cladonia uncialis and Cladonia sulphurina tissues. Spectroscopic images were obtained from cryosectioned lichen fragments embedded in media and from hand-sectioned fragments that were media-free. UA was present in the pycnidia, and younger walls of C. arbuscula and C. uncialis, the spore-producing region of a C. uncialis apothecium, and in both the younger and older soredia of C. sulphurina. The localization of UA in lichens is an important precursor to future work that includes the identification of the gene cluster responsible for its biosynthesis. Our results show that FTIR and Raman imaging can be an effective way to study the distribution of natural products in lichens with micron-scale precision.     

Structural and charge‐transfer properties of indolylfulgides

The structural and electronic properties of a photochromic molecule dictate their potential photochemical activity. To gain insight into these influences, the ground‐state structure and excited state properties of six indolylgulgides were calculated using several time dependent‐density functional theory (DFT) (TD‐DFT)//DFT methods, second‐order M?ller–Plesset (MP2), and CIS(D). These methods simulated the charge‐transfer properties and the conformation of the ground‐state structure for each molecule. Generally, TD‐DFT accurately simulated the expected charge‐transfer state. The degree of spatial overlap of the occupied and virtual molecular orbitals involved in the S₁ transition of indolylfulgides quantitatively assessed their charge‐transfer character and was qualitatively useful in assessing their photochromic activity. The M06, M06‐2X, and M11 structures were quite similar to those calculated by MP2. Structural differences, similarities, and functional trends are compared and discussed. © 2013 Wiley Periodicals, Inc.     

Simplified methods for the inversion of thermophysical data

Simplified inversion techniques are described which enable the potential energy functions of molecules to be determined directly from thermophysical data without recourse to additional information. The accuracy of the methods is confirmed by applying them to the data for krypton, a substance for which the potential energy function is well established.     

Three dimensional finite element analysis of the flow of polymer melts

The finite element simulation of a selection of two- and three-dimensional flow problems is presented, based upon the use of four different constitutive models for polymer melts (Oldroyd-B, Rolie-Poly, Pom-Pom and XPP). The mathematical and computational models are first introduced, before their application to a range of visco-elastic flows is described. Results demonstrate that the finite element models used here are able to re-produce predictions made by other published numerical simulations and, significantly, by carefully conducted physical experiments using a commercial-grade polystyrene melt in a three-dimensional contraction geometry. The paper also presents a systematic comparison and evaluation of the differences between two- and three-dimensional simulations of two different flow regimes: flow of an Oldroyd-B fluid around a cylinder and flow of a Rolie-Poly fluid into the contraction geometry. This comparison allows new observations to be made concerning the relatively poor quality of two-dimensional simulations for flows in even quite deep channels.     

Laser-Stark spectroscopy of fluoromethane in a molecular beam

The laser-Stark spectrum of the ν₃ vibration of fluoromethane in a molecular beam is recorded using bolometric detection methods. The resolution of the spectra is limited by the homogeneity of the applied electric field to one part in 3000 of the Stark shift required to tune a transition into resonance. The observation of several field induced transitions of fluoromethane is reported.     

Models for dielectric relaxation of biopolymers: Myoglobin in aqueous solution,a five dispersion fit

The dielectric relaxation spectrum of 20% aqueous solutions of myoglobin is reported for frequencies between 10 kHz and 4 GHz and temperatures between 4° and 50°C. Nonlinear regression analysis suggests the best representation of the results to be given by a model comprising five simple Debye dispersions. Two at lower frequencies are associated with the overall reorientational motion of the protein and two at higher frequencies are associated with motion of the water. The fifth, at intermediate frequencies and of small amplitude, may possibly be associated, although not unequivocally, with motional relaxation of the protein side chains. The results suggest the activation energy for the bound water relaxation to be near 5 kcal-mol^?1 — a value somewhat lower than literature values for other similar systems.     

On pseudo-clathrate hydrate structure in aqueous solutions of tetrahydrofuran

Dielectric relaxation in aqueous solutions of tetrahydrofuran is reported and the results interpreted in terms of the pseudo-clathrate hydrate model of the structure of the liquid state. The lifetime of any given pseudo-clathrate configuration is 10^–11 sec.Issued as NRCC Publication No. 17436