Determination and confirmation of the amnesic shellfish poisoning toxin, domoic acid, in shellfish from Scotland by liquid chromatography and mass spectrometry

During 1998 and early 1999, shellfish samples from sites in Scotland were found to contain the amnesic shellfish poisoning toxin, domoic acid (DA). Two different techniques, liquid chromatography (LC) with UV diode-array detection and LC with mass spectrometric (MS) detection, were used to detect and confirm DA in shellfish extracts. The LC/UV method was validated for routine monitoring by recovery experiments on spiked mussel and scallop tissues with a certified mussel tissue used as reference material. Crude extracts of selected samples as well as extracts cleaned with strong anion exchange (SAX) were analyzed by both LC/UV and LC/MS. Good correlation (linear regression r2 = 0.996, slope = 0.93) between the 2 methods was found for cleaned extracts. Analyses of crude extracts by LC/UV produced false-positive results in 2 crab samples, whereas LC/MS analyses gave accurate results. It was concluded that LC/UV is a valid approach for routine monitoring of DA in shellfish when cleanup is performed with a SAX cartridge to prevent false positives. A variety of shellfish species were surveyed for DA content, including Pecten maximus (king scallops), Chlamys opercularis (queen scallop), Mytilus edulis (blue mussels), Cancer pugaris (crab), and Ensis ensis (razor fish). The highest concentration of DA was 105 microg/g in Pecten maximus.     

Existence and instability of spike layer solutions to singular perturbation problems

An abstract framework is given to establish the existence and compute the Morse index of spike layer solutions of singularly perturbed semilinear elliptic equations. A nonlinear Lyapunov-Schmidt scheme is used to reduce the problem to one on a normally hyperbolic manifold, and the related linearized problem is also analyzed using this reduction. As an application, we show the existence of a multi-peak spike layer solution with peaks on the boundary of the domain, and we also obtain precise estimates of the small eigenvalues of the operator obtained by linearizing at a spike layer solution.     

Invariant foliations near normally hyperbolic invariant manifolds for semiflows

Let be a compact manifold which is invariant and normally hyperbolic with respect to a semiflow in a Banach space. Then in an -neighborhood of there exist local center-stable and center-unstable manifolds and , respectively. Here we show that and may each be decomposed into the disjoint union of submanifolds (leaves) in such a way that the semiflow takes leaves into leaves of the same collection. Furthermore, each leaf intersects in a single point which determines the asymptotic behavior of all points of that leaf in either forward or backward time.

     

An extension of the Dirac theory of constraints

Constructions introduced by Dirac for singular Lagrangians are extended and reinterpreted to cover cases when kernel distributions are either nonintegrable or of nonconstant rank, and constraint sets need not be closed.     

Differential inhibition of postnatal brain,spinal cord and body growth by a growth hormone antagonist

Background  

Growth hormone (GH) plays an incompletely understood role in the development of the central nervous system (CNS). In this study, we use transgenic mice expressing a growth hormone antagonist (GHA) to explore the role of GH in regulating postnatal brain, spinal cord and body growth into adulthood. The GHA transgene encodes a protein that inhibits the binding of GH to its receptor, specifically antagonizing the trophic effects of endogenous GH.     

Characterisation of different polymorphs of tris(8-hydroxyquinolinato)aluminium(III) using solid-state NMR and DFT calculations

Background  

Organic light emitting devices (OLED) are becoming important and characterisation of them, in terms of structure, charge distribution, and intermolecular interactions, is important. Tris(8-hydroxyquinolinato)-aluminium(III), known as Alq₃, an organomettalic complex has become a reference material of great importance in OLED. It is important to elucidate the structural details of Alq₃ in its various isomeric and solvated forms. Solid-state nuclear magnetic resonance (NMR) is a useful tool for this which can also complement the information obtained with X-ray diffraction studies.     

Electron-ion collisional dissociative recombination at high ambient ammonia densities

A plot of the measured electron—ion recombination coefficient against the number density of ambient ammonia shows an unexpectedly early fall which, it is suggested, may be due to the collisional coupling between the dissociative states and the other states being weakened by the growth in the clustering.     

Absorption spectra of diatomic molybdenum nitride (MoN), molybdenum oxide (MoO), and molybdenum dimer (Mo2) molecules isolated in Ar,Ne, and Kr matrices

MoN and MoO molecules produced in a hollow cathode discharge have been trapped in Ne, Ar, and Kr matrices at 4.2 and 13 K and investigated by optical spectroscopy. Bands attributed to MoN were identified in the red and blue spectral regions and assigned by comparison with gas phase results to the A⁴π → X⁴Σ^? (a) and B⁴Σ → X⁴Σ^? (a) transitions, respectively. The ground state of Mo¹⁴N has been identified as ⁴Σ^? with ω_e = 1040 cm^?1 in an Ar matrix. Absorptions assigned to MoO in the red spectral region form the (0-0) and (1-0) bands of at least one electronic transition, but could not definitely be correlated with the gas phase results. The ground state vibrational frequency for Mo¹⁶O in an Ar matrix is 893.5 cm^?1. Additionally, Mo₂ absorptions centered at 19 305 cm^?1 were shown to be part of a vibrational progression with an average spacing of 181 cm^?1.     

Astronomical speckle imaging

The many methods suggested and (some of them) tried out experimentally and/or observationally for imaging celestial objects through the Earth's atmosphere are reviewed. Their theoretical and physical bases are examined. Most attention is paid to Labeyrie's speckle interferometry and its several extensions devised during the past decade-astrophysical results obtained with the aid of these techniques are listed. Other forms of optical interferometry are discussed, as are related techniques in radio astronomy and ultrasonics.