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We study surface-enhanced Raman scattering (SERS) in fully dielectric periodic structures supporting Bloch surface waves. We demonstrate a lower bound for the SERS enhancement of 50 when the optical pump is resonantly coupled to the Bloch surface wave supported by the structure. A corresponding photoluminescence experiment shows an emission enhancement of more than two orders of magnitude, suggesting that the actual SERS enhancement is ∼200. Analogous conclusions are obtained by means of a semiclassical theoretical model. These results suggest an alternative to plasmonic materials to enhance Raman scattering at a surface and are of interest to those working in the field of Raman as well as fluorescence spectroscopy.

FePt nanoparticles with uniform compositions were synthesized by a modified coreduction process of FeCl2·4H2O and Pt(acac)2and then rapidly annealed in a vacuum under temperatures ranging from 500 to 700 °C. We found that the coercivities of the FePt nanoparticles were greatly enhanced by the rapid annealing in a vacuum. Negative peaks on δMcurves for the annealed FePt nanoparticles demonstrate that the predominant interparticle interactions are dipolar-type rather than exchange coupling ones, which indicates that the rapid annealing in a vacuum can prevent the agglomeration of the nanoparticles. Through the heat treatment of annealing in a vacuum, monodispersed Fe46Pt54nanoparticles with a high coercivity of 9230 Oe were successfully fabricated.

This study develops and demonstrates a realistic x-ray imaging simulator with computerized observers to maximize lesion detectability and minimize patient exposure. A software package, ViPRIS, incorporating two computational patient phantoms, has been developed for simulating x-ray radiographic images. A tomographic phantom, VIP-Man, constructed from Visible Human anatomical colour images is used to simulate the scattered portion using the ESGnrc Monte Carlo code. The primary portion of an x-ray image is simulated using the projection ray-tracing method through the Visible Human CT data set. To produce a realistic image, the software simulates quantum noise, blurring effects, lesions, detector absorption efficiency and other imaging artefacts. The primary and scattered portions of an x-ray chest image are combined to form a final image for computerized observer studies and image quality analysis. Absorbed doses in organs and tissues of the segmented VIP-Man phantom were also obtained from the Monte Carlo simulations. Approximately 25?000 simulated images and 2500?000 data files were analysed using computerized observers. Hotelling and Laguerre-Gauss Hotelling observers are used to perform various lesion detection tasks. Several model observer tasks were used including SKE/BKE, MAFC and SKEV. The energy levels and fluence at the minimum dose required to detect a small lesion were determined with respect to lesion size, location and system parameters.

The origin of three kinds of scatter centers in KDP and DKDP crystals and their relations were investigated. The results have shown that solid inclusions will form liquid and gas inclusions in KDP (DKDP) crystals. The effect of scatter centers on Laser Damage Threshold of the crystals is not same because their sizes are different. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Scatter centers in rapidly grown KDP crystal were detected with Ultra‐microscopy and TEM. The results have been compared with those obtained from traditional technique. In this paper, the difference is shown and a corresponding mechanism is proposed and discussed.

Pyrophosphate doped KDP crystal was grown from aqueous solution by the temperature lowering method. Light scatter in KDP crystal was detected with an ultramicroscopic method. It has been proved that light scatter in KDP crystal aggravated when pyrophosphate was doped into the growth solution, which distributed non‐uniformly in prism and pyramidal sectors of the KDP crystal. The different effects of pyrophosphate on prism and pyramidal sector of KDP crystals can explain this case. The method of eliminating light scatter in pyrophosphate doped KDP crystal is discussed.

A new set of fluence-to-absorbed dose and fluence-to-effective dose conversion coefficients have been calculated for neutrons below 20 MeV using a whole-body anatomical model, VIP-Man, developed from the high-resolution transverse colour photographic images of the National Library of Medicine's Visible Human Project®. Organ dose calculations were performed using the Monte Carlo code MCNP for 20 monoenergetic neutron beams between 1×10-9MeV and 20 MeV under six different irradiation geometries: anterior-posterior, posterior-anterior, right lateral, left lateral, rotational and isotropic. The absorbed dose for 24 major organs and effective dose results based on the realistic VIP-Man are presented and compared with those based on the simplified MIRD-based phantoms reported in the literature. Effective doses from VIP-Man are not significantly different from earlier results for neutrons in the energy range studied. There are, however, remarkable deviations in organ doses due to the anatomical differences between the image-based and the earlier mathematical models.

By use of dynamic subtraction it is feasible to adopt phase-sensitive detection with a CCD camera to reduce long-term optical background drift. We report on a two-order improvement of the signal-to-noise ratio. The improved system is used to image terahertz field distribution generated by an optically rectified electro-optic crystal with a modulation depth as small as 10^-4. We also introduce a modified detection geometry that realizes near-field imaging capability with greatly improved spatial resolution.

Abstract:  A method to determine the velocity components in the third direction for steady-non-axisymmetric nozzle flow experiments has been developed in addition to the two components that could be directly measured by a one-or two-component laser-Doppler anemometer. With the aid of this method, rotation for either the test rig or the anemometer become unnecessary. Results obtained by this approach were used to compare with those directly measured in the downstream wake of a co-axial nozzle with a central five-lobe forced mixer where the flow is non-axisymmetric. Good agreement could be obtained with maximum discrepancy at about 5%. The present approach can be readily applied to many other non-axisymmetric nozzle flow situations with only some minor modifications.

In this paper, the effect of the combination of hydrophilic nano-SiO2 with a particle size of 80 nm and gaffix VC-713 polymer (VC-713) on their hydrate inhibition was investigated at 4.0degC and 6.0 MPa, and the underlying influence mechanism was analysed by a multiple scales of the meso-structural observation experiments. Experimental results indicated that the combination doesn't exhibit any synergistic inhibition effect on the formation of CH4 hydrate, but it weakens the hydrate inhibition abilities of both components. Moreover, with the increase of the VC-713 content to 0.75 wt% and 1.00 wt%, the inhibition of hydrophilic nano-SiO2 completely disappears.

Based on borehole instability problems, a new kind of composite plugging agent for oil-based drilling fluids was developed, and the influence of plugging agent on shale stability was evaluated. The results indicated that the oil-based drilling fluids containing composite plugging agent could produce an ultra-thin, tight and relatively impenetrable mud cake, and consequently provided an excellent sealing effect. The core displacement experiment indicated that this plugging agent could reduce the shale permeability by a significant amount, and thus stop fluid invasion and improve wellbore stability. Using this plugging agent to seal the shale is a very powerful and economical approach to address borehole instability problem in troublesome shale formations. This plugging agent is suitable for the drilling of long sections of horizontal laterals. In the future, this plugging agent might hold great promise to resolve shale instability problem.

Half-metallic Co-based full Heusler alloys have been qualified as promising functional materials in spintronic devices due to their high spin polarization. The lack of perpendicular magnetic anisotropy (PMA) is one of the biggest obstacles restricting their application in next generation ultrahigh density storage such as magnetic random access memory (MARM). How to induce the PMA in Co-based full Heusler alloy thin films has attracted much research interest of scientists. This paper presents an overview of recent progress in this research area. We hope that this paper would provide some guidance and ideas to develop highly spin-polarized Co-based Heusler alloy thin films with PMA.

A new set of fluence-to-absorbed dose and fluence-to-effective dose conversion coefficients has been calculated for high-energy protons using the whole-body anatomical model VIP-Man, which was developed from the high-resolution transverse colour photographic images of the National Library of Medicine's Visible Human Project. For 10 monoenergetic proton beams between 20 and 10,000 MeV, organ dose calculations were performed using the Monte Carlo code MCNPX under six different irradiation geometries: anterior–posterior, posterior–anterior, left lateral, right lateral, isotropic and rotational. The absorbed dose results for 24 major organs of VIP-Man are presented and compared with those based on mathematical phantoms reported in the literature. The discrepancies (generally within 40%) in organ dose and effective dose estimates are attributed to the use of different transport models employed by different Monte Carlo codes.