Calculation of chemical and phase equilibria via simulated annealing

We present a new class of techniques for the solution of the chemical and phase equilibria problem for reacting species in a closed system. The minimisation of the Gibbs free energy for all the species in the system is conducted using the technique of simulated annealing (SA). The SA objective function incorporates non‐ideal equations of state. This new approach is demonstrably able to solve multi‐species and multi‐phase LTCE problems in ideal‐gas solutions, ideal solutions and mixtures of ideal and non‐ideal solutions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Structure elucidation and spectral assignment of analogs of navelbine® (8′-noranhydrovinblastine)

During the development of the bis-indole alkaloid anticancer drug Navelbine® (vinorelbine), several chemical degradants of the drug were isolated and identified. These included 7′-nor-6′,9′-secovinorelbine (7′,8′-bisnor-6′,9′-secoanhydrovinblastine) and 4-deacetyl-8′-vinorelbine (4-deacetyl-8′-noranhydrovinblastine). The elucidation of the structure of 7′-nor-6′,9′-secovinorelbine is described; the assignment of the proton and carbon spectra of both compounds is contrasted to the shift assignments of Navelbine.     

3,4-Alkylenedioxypyrroles: functionalized derivatives as monomers for new electron-rich conducting and electroactive polymers

New functionalized derivatives of 3,4-ethylenedioxypyrrole (EDOP, 5a) and 3,4-(1,3-propylenedioxy)pyrrole (ProDOP, 5b) as especially electron-rich monomers which yield highly electroactive and stable conducting polymers useful for a diverse set of applications have been synthesized. N-Alkylations of ProDOP were carried out to yield a variety of ProDOP derivatives having alkyl, sulfonatoalkoxy, glyme, and glyme alcohol pendant chains. Iodization of EDOP and ProDOP via iodo-decarboxylation afforded iodo-functionalized derivatives useful for subsequent aryl coupling chemistry. N-Protection and formylation of EDOP, followed by Knoevenagel condensation of the resultant 2-formyl-EDOP with aryl acetonitrile derivatives, led to 1-cyano-2-(2-(3,4-ethylenedioxypyrryl))-1-(2-thienyl)vinylene (23) (Th-CNV-EDOP) and 1-cyano-2-(2-(3,4-ethylenedioxypyrryl))-1-(2-(3,4-ethylenedioxythienyl)vinylene (26) (EDOT-CNV-EDOP). A 14-crown-4-ether 34 based dioxypyrrole was synthesized with a cavity potentially useful for lithium ion coordination and sensing in the resultant electroactive polymer. C-Alkylated ProDOPs (43a, 43b, and 43c) containing octyl, ethylhexyl, and dioctyl substituents appended to the central methylene of the propylene bridge, were prepared as monomers for potentially soluble pi-conjugated polymers.     

Fluorescence and Absorption Contrast Mechanisms for Biomedical Optical Imaging Using Frequency-Domain Techniques

Abstract— The ability to optically image or detect diseased tissue volumes located deep within tissues depends upon the degree of contrast provided by differences in local optical properties. In this report, we show that the exogenous contrast offered by fluorescent compounds is superior to that provided by nonfluorescing, light-absorbing compounds when time-dependent measurements are employed. In addition, we show that the induced contrast is not only moderated by the preferential uptake of fluorescent agents into diseased tissue volumes of interest but also by the fluorescent optical properties and the fluorescence dynamics in the specific tissue volume. Using tissue phantom studies, we demonstrated experimentally that near-infrared-absorbing and fluorescent dyes such as in-docyanine green can provide detection of diseased tissue volumes from fluorescence measurements made at the periphery of tissue when there is perfect, 100-fold and 10-fold partitioning in diseased tissues over that in surrounding normal tissues. Experimental results of common laser dyes show the contrast is also mediated by the quantum yield and lifetime parameters that may be dependent upon the local tissue environment.     

Functionalization of colloidal silica and silica surfaces via silylation reactions

A series of trialkoxysilane compounds tipped with primary amine groups were used to functionalize the surfaces of glass and colloidal silica. Streaming potential and microelectrophoretic mobility measurements were used to monitor the stability of the functionalized surfaces.Hydrolytic breakdown of the surface-to-silane coupling was induced by either successively increasing and decreasing the pH of the solution in contact with the surface, or by aging the derivatised surfaces in aqueous solution over prolonged periods of time. The chemistry of the spacer units between the trialkoxysilane group and the primary amine tip had a major influence on the subsequent hydrolytic stability. Large hydrophobic spacer groups showed small changes in the electrokinetic properties on storage, but large changes when successively titrated with acid and base through the pH range. The behavior observed with small hydrophobic spacer groups was that large changes in electrokinetic properties were obtained on storage and with pH titration.     

Improving fast atom bombardment mass spectra: The influence of some controllable parameters on spectral quality

The relative effects of adjustable fast atom bombardment (FAB) parameters (choice of matrix, primary atom flux, and primary atom energy) on the appearance of FAB spectra (including signal-to-noise, signal-to-background, and signal-to-matrix ratios) of several organic dyes have been investigated. Beam-induced chemical damage is minimized by lowering the primary atom flux, by raising the primary atom energy, and by selecting a matrix with radical scavenging properties (e.g., m-nitrobenzyl alcohol). The relative importance in minimizing this chemical damage is choice of matrix > primary atom flux > (nominal) primary atom energy, but optimization of the parameters involves a trade-off between sensitivity and damage. The effect of these parameters on thermal damage (fragmentation) is much less. It can be concluded from comparison of the dyes that the extent of beam damage does not depend simply on the standard reduction potential of the analyte.     

Tautomerism in malonic ester derivatives of s-triazine

Pmr and uv spectra of tris-, bis- and monomalonic ester derivatives of s-triazine were studied in chloroform, dioxane, methanol, water, acetonitrile, dimethylsulfoxide, dimethylformamide, and cyclohexylamine. The results indicate that the enaminic structures (I, II and III) predominate in chloroform, dioxane, methanol and water. A small amount of enolate is present in acetonitrile and a larger amount of enolate is present in dimethylsulfoxide, dimethylformamide and cyclohexylamine in the case of the tris- and bismalonic ester derivatives of s-triazine. The conclusion is reached that for these latter compounds in basic solvent, a tautomeric equilibrium exists between the enaminic form and resonance-stabilized enolate ions.     

Coupled map lattice techniques for simulating interfacial phenomena in reaction-diffusion systems

Interfacial patterns arise due to the dynamical evolution of phase boundaries in physical, chemical and biological systems. Coupled map lattices (CML) offer a useful tool for the simulation of such systems, being able to naturally accommodate the disparate length and time scales inherent in the dynamics of these processes. We illustrate this idea by reviewing work done on applying CML methods to crystal growth and to excitable media.