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We report on a theoretical investigation of the dispersion relation of surface plasmon polaritons (SPPs) on a periodically corrugated semiconductor surface. We assumed Drude's permittivity model of the semiconductor, which accurately describes the loss of these spoof SPPs. In the THz frequency range, the properties of the dispersion and loss of spoof SPPs on corrugated Si surfaces are studied. A low-loss propagation of spoof SPPs can be achieved by an optimum design of the surface structure. It was found that by increasing the lattice constant or by reducing the groove depth, the investigated structure can provide a low guiding attenuation.

X-ray backscatter imaging can be used for a wide range of imaging applications, in particular for industrial inspection and portal security. Currently, the application of this imaging technique to the detection of landmines is limited due to the surrounding sand or soil strongly attenuating the 10s to 100s of keV X-rays required for backscatter imaging. Here, we introduce a new approach involving a 140 MeV short-pulse (< 100 fs) electron beam generated by laser wakefield acceleration to probe the sample, which produces Bremsstrahlung X-rays within the sample enabling greater depths to be imaged. A variety of detector and scintillator configurations are examined, with the best time response seen from an absorptive coated BaF2 scintillator with a bandpass filter to remove the slow scintillation emission components. An X-ray backscatter image of an array of different density and atomic number items is demonstrated. The use of a compact laser wakefield accelerator to generate the electron source, combined with the rapid development of more compact, efficient and higher repetition rate high power laser systems will make this system feasible for applications in the field. Content includes material subject to Dstl (c) Crown copyright (2014). Licensed under the terms of the Open Government Licence except where otherwise stated. To view this licence, visit http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3 or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: psi@ nationalarchives.gsi.gov.uk.

Sixteen Chinese chronic hepatitis B virus (HBV)-infected patients were treated with recombinant interferon-alpha 2a (rIFN-alpha 2a). Of these, 8 made a response to IFN, with titers of neutralizing antibody of 141-4525 as determined by an antiviral neutralization bioassay. To determine whether the immunogenicity of the IFN was directly linked to the patients' genotype, their genomic DNA was analyzed for the presence of the human IFN-alpha 2a gene. None of the patients possessed the gene for IFN-alpha 2a, but only 50% developed neutralizing antibodies. The hypothesis, therefore, of a direct link between antibody formation and genotype cannot be sustained. Alternative explanations of the immunogenicity of IFN-alpha 2a must be sought.

Single photon counting techniques were used with an x-ray CCD camera to measure features of synchrotron-like x-ray spectra generated by betatron oscillations of electrons in a laser wakefield accelerator (LWFA) with different injection techniques. Measurements were made using the Hercules laser system at the University of Michigan. With a single stage gas cell, we demonstrate that pure helium gas in our wakefield accelerator will produce spectra with higher critical energies than when helium mixed with nitrogen is used. This result was not evident when a two stage gas cell was used.