Negative chemical ionization mass spectrometry of phenols,and their determination in acidic fractions of coal-derived liquids

The use of Freon–113 as a reagent gas in the negative chemical ionization mass spectra of phenolic compounds is reported. The dominant mode of ionization is by chloride attachment producing [M + Cl]^? ions. The application of this technique to the highly phenolic acid fractions from coal-derived liquids gives spectra containing essentially only [M + Cl]^? peaks. This allows relative molecular mass profiles to be obtained. The resultant complex spectra are simplified by dividing them into their homologous series components. Since this is a low-resolution technique, absolute component identification cannot be made; but in conjunction with other analytical methods, tentative identification of series of molecules is possible. Thus, the alkyl-substituent ranges of the different homologous series can be assessed. Comparisons between coal-derived liquids produced under different reaction conditions are made, and composition differences detected.     

Measurement and analysis of the ν4 band of silane

The ν₄ band of silane has been recorded with a resolution of about 0.06 cm⁻¹ in the region from 850 to 950 cm⁻¹. Assignments of all allowed transitions in this range with J′ ≤ 12 have been made on the basis of frequency and relative intensity. Qualitative agreement with theory is good but quantitative agreement begins to break down above J′ = 8. The breakdown is attributed to the effects of the strong Coriolis interaction with nearby ν₂.Lines of ²⁹SiH₄ and ³⁰SiH₄ have been observed in the R branch with constant isotope shifts of −1.334 cm⁻¹ and −2.600 cm⁻¹.     

Highly sensitive indirect photometric detection of cations by capillary electrophoresis with the cationic dye chrysoidine

The cationic dye, chrysoidine, has been used for the first time as a probe for the indirect photometric detection of cations. The dye has been used as a probe at concentrations of 5 mM, which is roughly an order of magnitude higher than for other cationic dyes used previously for the same purpose, in order to minimise electromigrational dispersion. Baseline instability was minimised by a combination of coating the capillary with poly(ethyleneimine), addition of a neutral polymer to the electrolyte, and the application of a small amount (20 mbar) of hydrodynamic pressure during the separation. Separation of a mixture containing alkali metals, alkaline earths, transition metals and lanthanides was achieved by the addition of 2-hydroxyisobutyric and lactic acid as complexing agents. Excellent peak shapes were observed over a wide range of analyte mobilities due to the moderate mobility of the probe. The high absorptivity (26733 l mol(-1) cm(-1)) provided by chrysoidine in comparison with typically used, less absorbing probes, was reflected in limits of detection which were typically less than 0.5 microM. These are amongst the lowest reported using hydrodynamic injection without the use of large volume stacking methods. The use of 2-hydroxyisobutyric and lactic acids as complexing agents at pH values close to their pKa values provided suitable buffering which was highlighted by very good reproducibility of migration time, corrected peak area and peak height.     

Measurement of emulsion droplet sizes using PFG NMR and regularization methods

The droplet size distributions of emulsions have been measured using pulsed field gradient (PFG) nuclear magnetic resonance (NMR) for many years. This technique finds particular application with emulsions that are concentrated and/or opaque, since such emulsion systems are difficult to characterize by other methods. Most studies employing PFG techniques assume a lognormal form when extracting the droplet size distribution from the experimental data. It is clearly desirable to retrieve a droplet size distribution from the experimental data without assuming such a functional form. This is achieved for the first time using regularization techniques. Regularization based on the distribution area and on its second derivative are compared and assessed along with the following techniques for selecting the optimal regularization parameter: the L-curve method, generalized cross validation (GCV), and the discrepancy principle. Regularization is applied to both simulated data sets and experimental data. It is found that when the experimental error can be estimated accurately, the discrepancy principle with area regularization is the best approach. When the error is not known the GCV method, with second derivative regularization and allowing only nonnegative values, is most effective.     

The construction of dispersion approximations to the solution of the vector convective diffusion equation

This paper is the sequel to an earlier paper in which we discover how to construct dispersion approximations to the solution of the vector convective diffusion equation. In this paper we make the construction concrete by providing useful formulas for the important elements of our theory. For definiteness we investigate cylinders of circular cross-section.Notation re() real part of - im() imaginary part of - int[] greatest integer less than or equal to - Z* adjoint of Z - adj Z adjugate of Z - col Z column vector of Z - det Z determinant of Z - Z generalized inverse of Z - Im Z image of Z - [,] generalized inner product - Ker Z kernel of Z - Ker Z* subspace perpendicular to Ker Z* - rank Z rank of Z - (Z) spectral radius of Z - tr Z trace of Z     

Fourier Transform Spectrum and Term Values for the CO-Stretching Mode of CD3OH Methanol

The Fourier transform infrared (FTIR) spectrum of the CO-stretching fundamental band of CD₃OH has been recorded at a resolution of 0.002 cm^-1. Assignments are reported for 35 subbands in the n = 0 ground torsional state, covering K = 0 to 9 for all torsional symmetries plus K = 10 A, and 12 assorted A and E subbands in the n = 1 first excited torsional state ranging from K = 0 up to K = 5. The subband wavenumbers have been fitted to J(J + 1) power-series energy expansions to obtain subband origins and a compact representation of the spectral observations. With the use of known ground-state energies, CO-stretch energy term values have been determined and tabulated. Least-squares fitting of the subband origins to a fourth-order Hamiltonian model for the CO-stretch mode is discussed.     

Red-Light Activation of a Microtubule Polymerization Inhibitor via Amide Functionalization of the Ruthenium Photocage

Photoactivated chemotherapy (PACT) is a promising cancer treatment modality that kills cancer cells via photochemical uncaging of a cytotoxic drug. Most ruthenium-based photocages used for PACT are activated with blue or green light, which penetrates sub-optimally into tumor tissues. Here, we report amide functionalization as a tool to fine-tune the toxicity and excited states of a terpyridine-based ruthenium photocage. Due to conjugation of the amide group with the terpyridine π system in the excited state, the absorption of red light (630 nm) increased 8-fold, and the photosubstitution rate rose 5-fold. In vitro, red light activation triggered inhibition of tubulin polymerization, which led to apoptotic cell death both in normoxic (21 % O₂) and hypoxic (1 % O₂) cancer cells. In vivo, red light irradiation of tumor-bearing mice demonstrated significant tumor volume reduction (45 %) with improved biosafety, thereby demonstrating the clinical potential of this compound.     

Die Bestimmungen kleiner Mengen Blaus?ure

Ohne Zusammenfassung     

Sur quelques récents résultats dans la théorie des surfaces algébriques

Sans résumé