Simple approximation formulae for elliptical dielectric waveguides

A simple method to obtain accurate explicit approximation formulae for the properties of an elliptical dielectric waveguide is explained. As examples, expressions for the propagation constant, geometric birefringence, and generalized two-dimensional Petermann spot-size are derived for step refractive index profiles.     

Analysis of biological reference materials, prepared by microwave dissolution, using inductively coupled plasma mass spectrometry

A procedure has been developed for the analysis of biological materials by inductively coupled plasma mass spectrometry (ICP-MS). Fast, efficient and complete sample digestion is achieved by a combined microwave-nitric acid/open beaker-nitric acid-hydrogen peroxide procedure. The ICP-MS analysis is performed with an on-line five-element internal standard to correct for matrix and instrumental drift effects. Results are presented for 24 elements in three biological reference materials (National Institute of Standards and Technology Standard Reference Materials 5277a Liver and 1566 Oyster and International Atomic Energy Agency Certified Reference Material H4 Animal Muscle). For all elements significantly above the detection limit and reagent blank concentrations, good agreement exists between ICP-MS and certified values.     

Quantum dynamics in simple fluids

We use quantum-correction factors to calculate approximately the quantum velocity time-correlation function (TCF) of supercritical Lennard-Jones argon from the classical TCF. We find that for this quite classical system, several different quantum-correction schemes yield essentially identical results for the real and imaginary parts of the quantum TCF, and also agree well with the recent forward-backward semiclassical dynamics (FBSD) results of Wright and Makri [J. Chem. Phys. 119, 1634 (2003)]. We also consider a more quantum-mechanical fluid of lighter atoms (neon) at a lower temperature. In this case different quantum-correction schemes give different results. FBSD calculations show that the harmonic quantum correction factor works the best for this system     

Pronounced non-Condon effects in the ultrafast infrared spectroscopy of water

In the context of vibrational spectroscopy in liquids, non-Condon effects refer to the dependence of the vibrational transition dipole moment of a particular molecule on the rotational and translational coordinates of all the molecules in the liquid. For strongly hydrogen-bonded systems, such as liquid water, non-Condon effects are large. That is, the bond dipole derivative of an OH stretch depends strongly on its hydrogen-bonding environment. Previous calculations of nonlinear vibrational spectroscopy in liquids have not included these non-Condon effects. We find that for water, inclusion of these effects is important for an accurate calculation of, for example, homodyned and heterodyned three-pulse echoes. Such echo experiments have been "inverted" to obtain the OH stretch frequency time-correlation function, but by necessity the Condon and other approximations are made in this inversion procedure. Our conclusion is that for water, primarily because of strong non-Condon effects, this inversion may not lead to the correct frequency time-correlation function. Nevertheless, one can still make comparison between theory and experiment by calculating the experimental echo observables themselves.     

The preparation and reduction of 5-cyano-3-indolylketones. Synthesis of 5-cyanotryptamines

The acylation of indoles under acidic conditions has been studied. Stannic chloride was shown to be an effective catalyst for the preparation of some 3-acylindoles, notably 5-cyano-3-indolylketones. The various 5-cyano -3 - indolylketones were reduced with sodium borohydride to yield either the 5-cyano-3-carbinols or 5-cyano-3-alkylindoles. 5-Cyanotryptamines were obtained by reduction of appropriate α-dialkylamino and α-azidoketones. A cleavage reaction of the carbinols involving loss of the 3-side chain to yield 5-cyanoindole is also described.     

The enthalpies of formation of bis-(benzene)molybdenum and of bis-(toluene)tungsten

Microcalorimetric measurements at 520–523 K of the heats of thermal decomposition and of iodination of bis-(benzene)molybdenum and of bis-(toluene)tungsten have led to the values (kJ mol^?): ΔH^o_f[Mo(η-C₆H₆)₂, c] = (235.3 ± 8) and ΔH^o_f[W(η⁶-C₇H₈)₂, c] = (242.2 ± 8) for the standard enthalpies of formation at 25°C. The corresponding ΔH^o_f(g) values, using available and estimated enthalpies of sublimation, are (329.9 ± 11) and 352.2 ± 11) respectively, from which the metalligand mean bond-dissociation enthalpies, $\text{D}$(Mo—benzene) = (247.0 ± 6) and $\text{D}$(W—toluene) = (304.0 ± 6) kJ mol^?1, are derived.     

The enthalpies of formation of CH3Mn(CO)5 and of CH3Re(CO)5, and the strengths of the CH3Mn and CH3Re bonds

From measurements of the heats of iodination of CH₃Mn(CO)₅ and CH₃Re(CO)₅ at elevated temperatures using the ‘drop’ microcalorimeter method, values were determined for the standard enthalpies of formation at 25° of the crystalline compounds: ΔH^o_f[CH₃Mn(CO)₅, c] = ?189.0 ± 2 kcal mol^?1 (?790.8 ± 8 kJ mol^?1), ΔH^o_f[Ch₃Re(CO)₅,c] = ?198.0 ± kcal mol^?1 (?828.4 ± 8 kJ mo^?1). In conjunction with available enthalpies of sublimation, and with literature values for the dissociation energies of MnMn and ReRe bonds in Mn₂(CO)₁₀ and Re₂(CO)₁₀, values are derived for the dissociation energies: D(CH₃Mn(CO)₅) = 27.9 ± 2.3 or 30.9 ± 2.3 kcal mol^?1 and D(CH₃Re(CO)₅) = 53.2 ± 2.5 kcal mol^?1. In general, irrespective of the value accepted for D(MM) in M₂(CO)₁₀, the present results require that, D(CH₃Mn) = $\text{1}\text{2}$D(MnMn) + 18.5 kcal mol^?1 and D(CH₃Re) = $\text{1}\text{2}$D(ReRe) + 30.8 kcal mol^?1.     

Quantitative Determination of Carisoprodol and its Metabolites in Equine Urine and Serum by Liquid Chromatography-Tandem Mass Spectrometry

Cefuroxime is a broad-spectrum second-generation bactericidal cephalosporin antibiotic active against β-lactamase-producing strains. Anti-cefuroxime, the geometric isomer of cefuroxime, might be present in cefuroxime dosage forms as a process-related impurity and possible degradation product. In the work discussed in this paper a precise and sensitive micellar liquid chromatographic (MLC) method for stability testing of cefuroxime axetil and anti-cefuroxime axetil in tablets, using benzoic acid as internal standard, was developed and validated. MLC was performed on an XTerra C₁₈ reversed-phase column at 50 °C with 8:92 (v/v) acetonitrile–20 mM sodium dodecyl sulphate, pH 2.5, as mobile phase at a flow rate of 1.5 mL min^?1. Detection was at 280 nm. Under these conditions the retention time and retention factor were of 6.65 min and 4.57, respectively, for cefuroxime axetil and 11.45 min and 8.59, respectively, for anti-cefuroxime axetil, indicating that the compounds were well separated. RSD values for quantification of cefuroxime axetil and anti-cefuroxime axetil were 0.39 and 1.7%, respectively, indicating the precision of the MLC method was good. The method is sensitive—LOD=0.5 μg mL^?1 and LOQ=1.5 μg mL^?1 for anti-cefuroxime axetil—and reproducible, with good recovery values.