LIAD-fs scheme for studies of ultrafast laser interactions with gas phase biomolecules

Laser induced acoustic desorption (LIAD) has been used for the first time to study the parent ion production and fragmentation mechanisms of a biological molecule in an intense femtosecond (fs) laser field. The photoacoustic shock wave generated in the analyte substrate (thin Ta foil) has been simulated using the hydrodynamic HYADES code, and the full LIAD process has been experimentally characterised as a function of the desorption UV-laser pulse parameters. Observed neutral plumes of densities >10(9) cm(-3) which are free from solvent or matrix contamination demonstrate the suitability and potential of the source for studying ultrafast dynamics in the gas phase using fs laser pulses. Results obtained with phenylalanine show that through manipulation of fundamental femtosecond laser parameters (such as pulse length, intensity and wavelength), energy deposition within the molecule can be controlled to allow enhancement of parent ion production or generation of characteristic fragmentation patterns. In particular by reducing the pulse length to a timescale equivalent to the fastest vibrational periods in the molecule, we demonstrate how fragmentation of the molecule can be minimised whilst maintaining a high ionisation efficiency.     

13C NMR spectra of polymethoxy- and methylenedioxyflavonols

The ¹³C NMR spectra of 20 polymethoxy- and/or methylenedioxyflavonols are reported. In key cases assignments have been made by examination of fully coupled spectra.     

A study of oxygen self-diffusion in the C-direction of rutile using a nuclear technique

Oxygen-18 has been used as a tracer to study diffusion in the c-direction of rutile single crystals in the temperature range 1173–1473K. The distribution of the tracer was determined by means of a nuclear technique. The diffusion coefficient can be represented in this temperature range by the equation $\text{D = 2.4 × 10}{}^{\mathrm{?6}}\text{exp}\text{?}\text{(2.826 ± 0.05) × 10}{}^5\text{RT}\text{m}{}^2\text{s}{}^{\mathrm{?1}}$. A diffusion coefficient obtained at 1673 K using a different technique agrees well with the value obtained by extrapolation from the other results. Consideration of the results from specimens with different impurity concentrations leads to the conclusion that the diffusion which has been studied is extrinsic.The results obtained in this investigation are in good agreement with those of Haul and Dümbgen[l] and (by extrapolation) Gruenwald and Gordon [2] but not with those of Doskocil and Pospisil[3] and Bagshaw and Hyde[4].     

Biomimetic Processing of Gel Glasses and Organic-Inorganic Hybrids

Biological hard tissues like bone and shell show combinations of strength and toughness that are hard to duplicate with synthetic materials. These properties are attained by a composite of organic and inorganic phases with very organized microstructures. The structures are hierarchical in that several different scales of organization contribute to the final properties.Biological systems form by chemical precipitation at room temperature in contrast to synthetic processing, which usually depends on thermal solidification. In principle, chemical solidification can give much more control over composition and structure but is limited by the time taken for diffusion processes in any solid component.A family of solid freeform fabrication methods have recently been developed which allow parts to be built under the direct control of a 3-dimensional CAD drawing without the need for a mold. These methods also offer a way of building composite structures, with full control of structure and composition at the scale of 100 m and up. Since this is a layerwise process, like biological growth, diffusion paths are short and so chemical processing of large parts is feasible.We have been developing an SFF system based on extrusion of a reactive slurry through a 300 m needle. The needle is moved on three axes so as to build up a part. The application of this method to the formation of components from sol-gel glasses and organic-inorganic hybrids is described.     

Determination of lincomycin and tylosin residues in honey using solid-phase extraction and liquid chromatography-atmospheric pressure chemical ionization mass spectrometry

An analytical method for the determination of residues of the antibiotic drugs lincomycin and tylosin in honey was developed. The procedure employed a solid-phase extraction for the isolation of lincomycin and tylosin from diluted honey samples. The antibiotic residues were subsequently analyzed by reversed-phase HPLC with atmospheric pressure chemical ionization mass spectrometric detection. Average analyte recoveries for lincomycin and tylosin ranged from 84 to 107% in replicate sets of honey samples fortified with drug concentrations of 0.01, 0.5, and 10 microg/g. The method detection limits were determined to be 0.007 and 0.01 microg/g for lincomycin and tylosin, respectively.     

Crystal structure of β-CaNi5D0.77 by rietveld analysis of neutron powder-diffraction data

β-CaNi₅D_0.77 is orthorhombic (a = 8.6033(13) b = 5.0810(9) c = 7.8557(15)Å, Pmcm, Z = 4, D_x = 6.48 g cm^?3, V = 343.4ų, FW = 1339.8 amu. Rietveld analysis of a neutron powder-diffraction pattern shows that D atoms occupy the centers of [Ni₄Ca₂] square dipyramids (“octahedra”) linked through the Ca atoms at opposite apices and forming chains. About 80% of the deuterium atoms occupy fairly regular sites (DNi = 1.53, 1.80, 1.86, 1.86 Å; DCa = 2.42, 2.45 Å). The remaining 20% occupy very distorted sites (DNi = 1.21, 1.38, 2.07, 2.07 Å; DCa = 2.54, 2.60 Å). The average DD distance in a chain is 4.3 Å.     

On the Compactness of the Nonlinear Evolution Operator in a Banach Space

Let X be a real Banach space and let A(t): X 2^x be dissipativefor all t(0, T). Assume that {A(t)} generates an evolution operatorU(t, s) of type (D, , f). Necessary and sufficient conditionsare given for the compactness of U(t, s) for 0 s < t <T.     

Spontaneous and self-assembled line formations on silicon substrates with vanadium pentoxide sol-gels

A simple one-pot method has been developed to deposit discreet nanometer line formations on silicon substrates without any surface pretreatment starting with vanadium pentoxide sol-gels. These vanadium suspensions were made by hydrolyzing amorphous V2O5 in water. The properties of the vanadium clusters were determined through X-ray diffraction, elemental analyses, pH calculations, and concentration calculations. Morphology of the lines was examined with optical microscopy, atomic force microcoscopy, and scanning electron microscopy. Infrared spectroscopy was used to inspect the organic components. The vanadium sol-gel used formed discreet and regular lines with high reproducibility and on the same order of magnitude as other patterning techniques. Previous research with a low solubility, 8 g/L, metal oxide for line, ring, or helix formation has not been found in the literature; this work could lead to novel applications of metal oxides such as porous catalysts, battery materials, and resistive electronic materials.