Vector potential theory on nonsmooth domains in R<Superscript>3</Superscript> and applications to electromagnetic scattering

We study boundary value problems for the time-harmonic form of the Maxwell equations, as well as for other related systems of equations, on arbitrary Lipschitz domains in the three-dimensional Euclidean space. The main goal is to develop the corresponding theory for L^p-integrable bounday data for optimal values of p's. We also discuss a number of relevant applications in electromagnetic scattering.     

Observation of a quadrupole plasmon mode for a colloidal solution of gold nanoprisms

The synthesis and optical properties of single crystalline gold nanoprisms have been investigated. A three-step mediated seed growth process in an aqueous solution generated gold nanoprisms with a relatively homogeneous size distribution. The purity of these nanostructures has allowed us to observe a weak quadrupole resonance in addition to a strong dipole resonance associated with these novel structures. The experimental optical spectra agree with discrete dipole approximation calculations that have been modeled from the dimensions of gold nanoprisms produced in this synthesis.     

Amperometric detection of hydrazine by cyclic voltammetry and flow injection analysis using ruthenium modified glassy carbon electrodes

Glassy carbon electrodes modified with (5-amino-1,10-phenanthroline)bis(bipyridine)ruthium(II) chloride hydrate, [(bpy)₂Ru(5-phenNH₂)]Cl₂·H₂O, are shown to oxidize hydrazine with excellent sensitivity. The presence of an amine group on the ruthenium complex facilitates electropolymerization onto the electrode surface. Using cyclic voltammetry, a large catalytic current is observed upon oxidation of hydrazine in phosphate buffer (pH 5.0), compared to the current obtained from the ruthenium-modified electrode with no hydrazine present. The sensitivity of cyclic voltammetry is sufficient for obtaining a linear calibration curve for hydrazine over the range of 10⁻⁵ to 10⁻² M. Hydrodynamic amperometry was used to determine the working potential for flow injection analysis. The limit of detection for hydrazine was determined to be 8.5 μM using FIA. The thickness of these films was shown to increase linearly with the number of electropolymerization cycles, in the range of 1000-2500 nm for 5-20 cycles, respectively, using Rutherford backscattering spectrometry (RBS). RBS analysis also suggests that the film is multilayered with the outermost layers containing a high ruthenium concentration, followed by layers where the concentration of ruthenium decreases linearly and approaches zero at the electrode surface.     

An improved procedure for the preparation of 2-amino-8-alkylpyrido-[2,3-d]pyrimidin-4(3H)-ones (8-alkyl-N5-deazapterins)

We report an improved procedure for the preparation of 8-alkyl-N5-deazapterins which allows clean preparation of all ring-methyl substituted compounds, including 5- and 7-methyl substituted compounds. The procedure was also successfully applied to the preparation of N5-deazapterins with improved yield over previous reports. The uv/visible and pKa data confirm the predicted increased basicity of 8-alkyl-N5-deazapterins compared with the N5-deazapterin parents, and indicate that N5-deazapterins protonate on N8 and 8-alkyl-N5-deazapterins protonate on N3.     

Analysis of inter-ring coupling effects in N-heterobicyclic π-systems using a structural definition of aromaticity

A purely structural definition of aromaticity based on the average ring bond length and -bond order is proposed. The definition is illustrated for N-heterocycles by reference to theoretical STO-3G and 3-21G geometries and charges for some pteridine derivatives. The treatment focuses on the gross structural changes (i.e., ring size, overall degree of π-electron delocalization, and net ring charges), accompanying chemical changes, such as substitution, tautomerization, ring reduction, and deazination, as well as the structural interdependence of the two rings in a bicyclic ring system.     

Cohomology of groups with metacyclic Sylow -subgroups

We determine the cohomology algebras for all groups with a metacyclic Sylow -subgroup. The complete -local stable decomposition of the classifying space is also determined.

     

NMR studies of bond orders in heteroaromatic systems

Fifty-seven values for the ortho-benzylic coupling constant ⁴J_{Me? C?C? H} (henceforth denoted as ⁴J_OB) were obtained for a variety of heteroaromatic systems. It was shown that a good correlation exists between ⁴J_OB when the methyl group is not α to the heteroatom and the SCF-MO bond order. This method can therefore be used as an experimental means of determining bond orders in heteroaromatic systems. An examination of bond alternation in thirteen heteroaromatic systems has given a measure of relative “degree of aromaticity” for a larger number of systems than previously reported by any single method.     

Synthesis of the methanesulfonates of α-(4-chlorophenyl)-α-[1-(2-chlorophenyl)emenyl]-1H-1,2,4-triazole-1-ethanol and α-[1-(2-chlorophenyl)ethenyl]-α-(2,4-difluorophenyl)-1H-1,2,4-triazole-1-ethanol,alpha styryl carbinol antifungal agents

The methanesulfonates of (α-(4-chlorophenyl)-α-[1-(2-chlorophenyl)ethenyl]-1H-1,2,4-triazole-1-ethanol and α-[1-(2-chlorophenyl)ethenyl]-α-(2,4-difluorophenyl)-1H-1,2,4-triazole-1-ethanol ( 1a, b ) are orally effective α-styryl carbinol derivatives developed for the treatment and prevention of systemic fungal infections. Practical new processes amenable for the large-scale production of these compounds are described. Of note is the selection of dichlorostyrene as a convenient precursor of the styryl portion, modification of a sensitive Grignard addition into a realistic preparative reaction and the use of 1,2,4-triazole simultaneously as a base transfer agent and nucleophile.