A broadband polymeric foil transducer

If a 0.001 in (0.025 mm) thick foil of polyethylene teraphthalate is metallized upon one side and a dc voltage is applied to the metallizing, then the foil will adhere firmly by electrostatic attraction to any conducting surface. In acoustic emission experiments with such a foil as a capacitance detector it was observed that by cycling the polarizing voltage it was possible to increase the sensitivity of the device until it was only 30 dB below that of a damped pzt transducer. Such an enhanced response probe has been found to have a frequency response which is flat from 10 kHz to 5 MHz. It also has the advantages of being lightweight; needs no coupling agent when applied to conducting substrates; is stable over long periods; can be made in any shape or array of shapes and will conform to curved surfaces     

Fluorescence of fly ash samples: Implications for in situ and remote detection

A study of the fluorescence spectra of fly ash samples from different sources has shown that each samples has a characteristic fluorescence and excitation spectrum which could be used to identify and monitor its presence. Fluorescence lifetime studies of samples from different sources have demonstrated characteristic features which can be used for identification. The fluorescence method should be useful for in situ and remote monitoring applications.     

Twistors and linearized Einstein theory on plane-fronted impulsive wave backgrounds

The spinor form of linearized gravitation on a curved vacuum background is obtained from the Bianchi identities. There are no Buchdahl constraints to be satisfied, and for a flat background the approach reduces to the usual massless spin 2 theory. The equations are specialized to the plane-fronted impulsive gravitational wave backgrounds which include the ultrarelativistic limit of a moving black hole. Given a solution of the resulting system, it is possible to construct the metric perturbations up to gauge terms. It is shown that this linearized scheme is equivalent to the proposed twistor Hamiltonian formalism. As an example, colliding plane impulsive waves are considered, and the model compares well with the known exact solution. A discussion is given of the application of these methods to ultrarelativistic black-hole encounters.     

Temperature-dependent infrared absorption cross sections of methyl cyanide (acetonitrile)

Pressure broadened (1 atm. N₂) absorption cross sections and integrated band intensities have been derived from laboratory spectra of CH₃CN, recorded at 276, 298, and 323 K, covering 600-. The spectra were recorded at a resolution of using a commercial Fourier transform spectrometer and a custom flowing sample delivery system. We report integrated absorption cross sections for intervals corresponding to the most prominent bands, compare the results with previously reported values, and discuss error sources, which are estimated as ∼7% with systematic error the largest error source.     

Micron-sized atom traps made from magneto-optical thin films

We have produced magnetic patterns suitable for trapping and manipulating neutral atoms on a 1-m length scale. The required patterns are made in Co/Pt thin films on a silicon substrate, using the heat from a focused laser beam to induce controlled domain reversal. In this way we draw lines and paint shaped areas of reversed magnetisation with sub-micron resolution. These structures produce magnetic microtraps above the surface that are suitable for holding rubidium atoms with trap frequencies as high as 1 MHz. PACS 39.25.+k; 03.75.Be; 75.50.Ss; 75.70.-i     

A charge-transfer-induced spin transition in the discrete cyanide-bridged complex [[Co(tmphen)2]3[Fe(CN)6]2

A charge-transfer-induced spin transition (CTIST) is observed in the discrete cyanide-bridged complex, {[Co(tmphen)2]3[Fe(CN)6]2}. Single-crystal X-ray diffraction, 57Fe M?ssbauer spectroscopy, and magnetic susceptibility were used collectively to describe the oxidation states of the Co and Fe ions in this cluster as a function of temperature. This pentanuclear complex represents the first example of a CTIST at the discrete molecular level.     

Structure of optical vortices

Helical modes of light can be focused into toroidal optical traps known as optical vortices, which are capable of localizing and applying torques to small volumes of matter. Measurements of optical vortices created with the dynamic holographic optical tweezer technique reveal an unsuspected dependence of their structure and angular momentum flux on their helicity. These measurements also provide evidence for a novel optical ratchet potential in practical optical vortices.     

Glycosylation of the Arg-gingipains of Porphyromonas gingivalis and comparison with glycoconjugate structure and synthesis in other bacteria

Post-translational modification of proteins by covalent attachment of sugars to the protein backbone (protein glycosylation) is the most common post-translational modification in the eucaryotic cell. However, the addition of carbohydrates to proteins of Eubacteria and Archaea has been demonstrated and accepted only recently. There is now a rapidly expanding list of bacterial glycoproteins that have been characterised from a variety of different organisms including many important pathogens. The Arg-gingipains of Porphyromonas gingivalis are recent additions to this list. In this review we present a summary of our investigations on the structure of the glycan additions to these proteolytic enzymes, the genetics of the glycosylation process and some of the effects on enzyme function and recognition. These findings are placed in the context of the current status of understanding of glycoconjugate structure and synthesis in other bacteria. Given the importance of glycosylation of eucaryotic proteins to their stability, structure, resistance to proteolysis and recognition, the modifications to the proteases described in the present report are likely to have a functional role in the properties of these enzymes in periodontal disease.     

Halo structure of (14)Be

The two-neutron halo nucleus (14)Be has been investigated in a kinematically complete measurement of the fragments ((12)Be and neutrons) produced in dissociation at 35 MeV/nucleon on C and Pb targets. Two-neutron removal cross sections, neutron angular distributions, and invariant mass spectra were measured, and the contributions from electromagnetic dissociation (EMD) were deduced. Comparison with three-body model calculations suggests that the halo wave function contains a large nu(2s(1/2))(2) admixture. The EMD invariant mass spectrum exhibited enhanced strength near threshold consistent with a nonresonant soft-dipole excitation.