Comparison between experiment and computer modeling for simple MILOconfigurations

The MILO is a crossed-field HPM, high power microwave source which uses its self-generated magnetic field to cut off electron flow to the anode. A detailed comparison of experimental results and a computer simulation has been made for a number of simple axisymmetric MILO structures designed to operate at 1 GHz. The structures were built from demountable components which enabled the number of cavities and their dimensions to be rapidly altered. Measurements were made of the fluctuating magnetic fields at the end of each cavity. The amplitude and depth of RF modulation of the magnetic fields, although repeatable, changed drastically from one configuration to the next; these parameters were compared with predictions from VIPER, a 2-D electromagnetic PIC code. Good quantitative agreement was obtained between experiments and the simulation in most situations, although, late in the current pulse, after about 100 ns, the level of RF began to decay; a phenomenon which became more pronounced as the applied voltage was increased. The decay was attributed to plasma formation on the cavity vanes and subsequent electron emission; this explanation was verified by computer modeling electron emission and by using vanes make from polished stainless steel in place of aluminum vanes     

Fattening complex manifolds: Curvature and Kodaira—Spencer maps

We present a calculus whereby the curvature of a geometry arising from any generalized twistor correspondence is related to an obstruction-theoretic classification of the infinitesimal neighborhoods of submanifolds of its twistor space. The crux of the argument involves a relation between Kodaira—Spencer maps and the Penrose transform.     

Marine vehicles and offshore installations: Laser diagnostics of machinery health

For reasons of both safety and economy it is desirable to avoid the breakdown at sea of heavy machinery in marine transport and offshore installations. Unscheduled loss of production or power during ‘downtime’ enhances vulnerability and often carries severe financial penalties. This has led to an increasing interest in the concept of monitoring machinery health to detect impending failure. This paper demonstrates how applied optics and laser technology can be used to address the problem of diagnosing failure in viscous shear torsional dampers which are normally fitted to the crankshaft of large marine propulsion diesels and generator sets. The method allows condition diagnosis to be achieved while the engine is running and avoids the need for ‘downtime’ associated with traditional fluid sampling methods.     

Synthesis and mesomorphic behaviour of novel light-emitting liquid crystals

We report the results of a systematic study of the structure-mesomorphic behaviour relationships of a diverse range of light-emitting liquid crystals, but especially nematic 2,7-disubstituted-9,9-dialkylfluorenes. The dependence of the mesomorphic behaviour and transition temperatures on the nature and length of the terminal chains, the nature, position and number of lateral substituents and the number and nature of aromatic rings with and without heteroatoms in the central core is studied. The results of these studies are used to design polymerizable, light-emitting crystals (reactive mesogens) with a nematic phase having a high clearing point and a melting point below room temperature for facile OLED fabrication.     

Infrared spectrometry field-method for identification of natural seep-oils

An infrared field-method has been developed which is capable of distinguishing between oils originating from natural seepage in the Santa Barbara (California) Channel region and closely similar oils from onshore drilling platforms. The technique involves a minimum of sample preparation and the use of simple infrared instrumentation which can be operated by non-technical personnel. Natural seep-oil samples were collected from the surface of the water, underwater, and from beaches in the area. The non-seep oils were obtained from production wells which were located in the same geographical areas as the seepage and were from several different well depths corresponding to different geological zones. Natural seep-oils are more aromatic than the production oils, and this difference is evidenced by observed differences in the spectra for both weathered and unweathered oils. These spectral differences between seep and non-seep oils have been found to persist after exposure to weathering for a week.     

High performance liquid chromatographic measurement of bisoprolol in plasma

A simple high performance liquid chromatographic method has been devised for the measurement of bisoprolol in plasma or serum. The sample (200 microL) is vortex mixed for 30 s with 2 M Tris solution (50 microL), aqueous internal standard (benzimidazole, 2.0 mg/L, 50 microL) and methyl t-butyl ether (200 microL). After centrifugation (9950 x g, 2 min), a portion of the resulting extract is analysed on a microparticulate (5 microns) silica column using 1 mM camphorsulphonic acid in methanol as the mobile phase. Detection is by fluorescence at an excitation wavelength of 215 nM. The lower limit of accurate measurement for the assay is 10 micrograms/L (CV% = 8.9, n = 9) with a lower limit of detection of 5 micrograms/L. There is minimal interference from either commonly prescribed drugs or endogenous compounds.     

Extracting invariants of isolated hypersurface singularities from their moduli algebras

We use classical invariant theory to construct invariants of complex graded Gorenstein algebras of finite vector space dimension. As a consequence, we obtain a way of extracting certain numerical invariants of quasi-homogeneous isolated hypersurface singularities from their moduli algebras, which extends an earlier result due to the first author. Furthermore, we conjecture that the invariants so constructed solve the biholomorphic equivalence problem in the homogeneous case. The conjecture is easily verified for binary quartics and ternary cubics. We show that it also holds for binary quintics and sextics. In the latter cases the proofs are much more involved. In particular, we provide a complete list of canonical forms of binary sextics, which is a result of independent interest.