Characterization of fatty acid esters of okadaic acid and related toxins in blue mussels (Mytilus edulis) from Norway

Marine algal toxins of the okadaic acid group can occur as fatty acid esters in blue mussels, and are commonly determined indirectly by transformation to their parent toxins by alkaline hydrolysis. Some data are available regarding the identity of the fatty acid esters, mainly of palmitic acid (16:0) derivatives of okadaic acid (OA), dinophysistoxin-1 (DTX1) and dinophysistoxin-2 (DTX2). Other fatty acid derivatives have been described, but with limited mass spectral data. In this paper, the mass spectral characterization of the [M-H](-) and [M+Na](+) ions of 16 fatty acid derivatives of each of OA, DTX1 and DTX2 is presented. The characteristic fragmentation of [M+Na](+) ions of OA analogues provided a useful tool for identifying these, and has not been described previously. In addition, a set of negative ion multiple reaction monitoring (MRM) methods was developed for direct determination of 16 fatty acid esters of OA, 16 fatty acid esters of DTX1 and 16 fatty acid esters of DTX2 in shellfish extracts. The MRM methods were employed to study the profiles of fatty acid esters of OA analogues in blue mussels and to compare these with fatty acid ester profiles reported for other groups of marine algal toxins.     

A comprehensive and comparative analysis for MALDI FTMS lipid and phospholipid profiles from biological samples

Described here is a computationally automated method for translating complex accurate mass spectra into biologically relevant and meaningful data. Rapid profiling of detailed high resolution mass spectra resulting from direct analysis of whole cells and tissues by matrix-assisted laser desorption/ionization (MALDI) Fourier transform mass spectrometry (FTMS) is discussed. Lipid and phospholipid ions create complex spectra containing multiple m/z values corresponding to the same fundamental chemical species. A computational approach is employed to sort ions, with mass to charge ratios lower than m/z 1000, into groups of similar lipid and phospholipid compositions for comprehensive and rapid analysis. By sorting or binning ions in this manner, variations in the degree of cation exchange can be avoided, thus increasing the comparability of the data. The result is displayed as a histogram that is easily interpretable and comparable with similar analyses and is particularly useful for direct comparison of similar tissues. Spectra of leaves from a healthy Prunus persica (peach) tree are compared with those from leaves infected by the fungus Taphrina deformans. Although the infection can be seen as a difference in leaf structure and by visual inspection of the mass spectra, the method described here details the chemical difference in phospholipid compositions and their relative abundances.     

Fiber optic cables for undersea communications

Abstract

Areas for potential use of low-loss optical fibers in undersea communications are discussed, along with constraints that should be satisfied in incorporating these fibers into practical cables. Recent progress in construction of optical cable units with low attenuation, small diameter, low specific gravity, high tensile strength, and extended flexural endurance is described. Design concepts for six undersea optical cables, with a variety of diameters and capabilities, are presented in detail. Guidelines are discussed for the design of such cables. Related operational requirements on the cable, such as power transfer, are examined to show how unconventional approaches can allow advantages of the optical data link to be more fully utilized.     

Monte Carlo calculations of reaction rates and energy distributions among reaction products. Reactions of HF and DF with H and D-atoms

Rate coefficients are calculated for the reactions of H and D-atoms with vibrationally excited HF and DF molecules. Three-dimensional classical trajectories of the collision dynamics of these reactions have been calculated by means of the London-Eyring-Polanyi-Sato (LEPS) potential energy surface. The Monte Carlo procedure is used to start each collision trajectory. Results of this study indicate that (a) chemical exchange provides an efficient mechanism for relaxing vibrationally excited HF and DF molecules by H and D-atoms; (b) multiple-quantum transitions are important in the deactivation processes; and (c) both vibration-translation and vibration-rotation energy transfers contribute to vibrational relaxation of vibrationally excited HF and DF molecules by H and D-atoms. The vibrational relaxation of HF (v = 1) by H-atoms is faster than the vibrational relaxation of DF (v = 1) by H-atoms. A similar effect is indicated for D-atoms; i.e. the vibrational relaxation of DF (v = 1) by D-atoms is faster than the vibrational relaxation of HF (v = 1) by D-atoms. Room temperature vibration to translation-rotation (V → T, R) relaxation rates in units of (μsec Torr)^-1 are as follows: 13·8 × 10^-2 for HF (v = 1) by H, 3·1 × 10^-2 for DF (v = 1) by D, 5·5 × 10^-3 for HF (v = 1) by D, and 1·9 × 10^-2 for DF (v = 1) by H. Rates of deactivation of vibrationally excited HF and DF molecules by H and D-atoms are very fast. Rate coefficients are provided for many reactions that have not been measured experimentally.     

Analysis and interpretation of the first monochromatic X‐ray tomography data collected at the Australian Synchrotron Imaging and Medical beamline

The first monochromatic X‐ray tomography experiments conducted at the Imaging and Medical beamline of the Australian Synchrotron are reported. The sample was a phantom comprising nylon line, Al wire and finer Cu wire twisted together. Data sets were collected at four different X‐ray energies. In order to quantitatively account for the experimental values obtained for the Hounsfield (or CT) number, it was necessary to consider various issues including the point‐spread function for the X‐ray imaging system and harmonic contamination of the X‐ray beam. The analysis and interpretation of the data includes detailed considerations of the resolution and efficiency of the CCD detector, calculations of the X‐ray spectrum prior to monochromatization, allowance for the response of the double‐crystal Si monochromator used (via X‐ray dynamical theory), as well as a thorough assessment of the role of X‐ray phase‐contrast effects. Computer simulations relating to the tomography experiments also provide valuable insights into these important issues. It was found that a significant discrepancy between theory and experiment for the Cu wire could be largely resolved in terms of the effect of the point‐spread function. The findings of this study are important in respect of any attempts to extract quantitative information from X‐ray tomography data, across a wide range of disciplines, including materials and life sciences.     

44-Methylgambierone,a new gambierone analogue isolated from Gambierdiscus australes

A new analogue of gambierone, 44-methylgambierone, was isolated from the benthic dinoflagellate Gambierdiscus australes collected from Raoul Island (Rangitahua/Kermadec Islands). This molecule has been previously reported as maitotoxin-3. The structure of 44-methylgambierone was elucidated using 1D- and 2D-nuclear magnetic resonance spectroscopy and mass spectrometry techniques. The nine-ring polyether backbone (A–I) and functional groups (carbonyl, terminal diol, 1,3-diene and monosulphate) are the same for both compounds with the addition of an olefinic methyl group being the only modification in 44-methylgambierone.     

Determination of iron in cadmium and cadmium telluride

A procedure is described for the determination of iron in the 10(-6)-10(-4)% range in cadmium and cadmium telluride. Acetylacetone is used for the separation of iron from cadmium, and the iron is determined spectrophotometrically with bathophenanthroline.     

Anisotropic fluid in a spherical spacetime: I. Radiation from a compact star

Generalizing work of Misner and Sharp, we develop the general relativistic theory of any spherically symmetric spacetime, allowing for shearing stresses (hence unequal principal pressures) in the matter. Assumptions specific to the system considered are required to determine the time-evolution of the principal pressures. For a gas of noninteracting massless particles, the necessary equations follow from relativistic kinetic theory. The equations for null radiation are solved in the steady-state case, neglecting both: (a) the mass loss of the central body, and (b) the effect of the radiation on the background (Schwarzschild) geometry. Once the velocity-field of the radiation is specified, its energy-momentum tensor follows by integration. The form of the velocity-field cannot be uniquely fixed by the theory because it varies from case to case. Asymptotically, at large distances R, the energy density and principal pressures of null radiation usually fall off as R^?4 while its proper speed increases as R. A one-parameter family of model stars emitting null radiation in flat spacetime is constructed. These differ in how narrow a cone the radiation is beamed into. Radiation emitted isotropically differs markedly from that which is emitted with sharp directionality.