Implementation and evaluation of data compression of MR images

A full-frame bit-allocation technique of data compression has been implemented using the existing computer facilities of an MR imager. Images reconstructed from compressed data files have been compared with the original image and changes in noise and pixel value measured to evaluate any image degradation introduced by the compression process. A 256 x 256 x 8 bit brain image can be compressed in 20 seconds with a compression ratio of greater than 4:1 without significant loss of information.     

Diffraction of bending waves

This paper is a discussion of the theory of diffraction and scattering of bending waves by mass-impedance loadings of an infinite plane plate. Emphasis is placed on the case of heavy loadings, at which deflexions of the plate are precluded and the scattering is the strongest possible. Examples treated in detail include the diffraction grating, diffraction by a semi-infinite rib, and diffraction by a comb of semi-inifinite ribs.     

The gas phase structure of some protonated and ethylated aromatic amines

The fundamental processes of protonation and ethylation, occurring in a methane chemical ionization source, have been investigated for a variety of aromatic amines. The positions of protonation and ethylation on the substrate amines were determined by generating isomeric ions either by protonation of neutral ethyl substituted amines or by ethylation of the amines themselves. The product ions were investigated for structural differences via collision induced dissociation and subsequent analysis via mass analysed ion kinetic energy spectrometry. Similarities and differences between mass analysed ion kinetic energy/collision induced dissociation spectra of these isomeric ions were used to determine protonation and ethylation sites for imidazole, benzimidazole, indazole, pyrrole, pyridine and aniline.     

Gamma-ray spectra and level structure of Cr from thermal neutron capture in Cr

Gamma-ray measurements have been made of the ⁵⁴Cr(n, γ)⁵⁵ Cr reaction at the Livermore reactor. Spectra were taken with Ge(Li) Compton-suppression and pair-coincidence spectrometers. A total of 83 observed γ-rays are attributed to capture in ⁵⁴Cr, of which 26 are assigned to specific transitions among 10 inferred levels in ⁵⁵Cr. The neutron binding energy is determined to be 6246.3 ± 0.4 keV.     

Effect of expression of manganese superoxide dismutase in baculovirus-infected insect cells

It has previously been demonstrated that baculovirus infection of the Spodoptera frugiperda Sf-9 (Sf-9) and Trichoplusia ni BTI-Tn-5B1-4 (Tn-5B1-4) insect cell lines leads to oxidative stress as measured by protein and membrane lipid oxidation and that this oxidative damage contributes to cell death. As a result of these findings, it was hypothesized that baculovirus infection stimulates superoxide radical (O ₂ ^·— synthesis in the mitochondria and that the resulting O ₂ ^·— accumulation overwhelms the cells’ antioxidant defenses. We investigated the ability of manganese superoxide dismutase (MnSOD) expression (which reduces O ₂ ^·— to H₂O₂) to overcome the oxidative damage caused by baculovirus infection. It was found that MnSOD expression significantly reduced oxidative damage in baculovirus-infected Tn-5B1-4 cells but had no significant effect on oxidative damage in baculovirus-infected Sf-9 cells. The results are consistent with the hypothesis that O ₂ ^·— accumulation in the mitochondria is at least partially responsible for the oxidative damage resulting from the baculovirus infection of insect cells.     

Plastic Versus Glass Support for an Immunoassay on Metal-Coated Surfaces in Optically Dense Samples Utilizing Directional Surface Plasmon-Coupled Emission

We compared plastic (polycarbonate) and high-quality glass support materials for gold-coated slides, when performing a model immunoassay against rabbit IgG using fluorescently labeled (AlexaFluor-647) anti-rabbit IgG, and detecting surface plasmon-coupled emission (SPCE) signals. Both, glass and plastic slides were simultaneously coated with a 48-nm layer of gold and protected with a 10-nm layer of silica. The maximum SPCE signal of AlexaFluor-647 was only two- to three-fold smaller on plastic slides than on glass slides. A small difference in the SPCE angles on glass (θ _F = 55°) and plastic (θ _F = 52.5°) slides was observed and can be explained with a slightly smaller refractive index of the plastic. We have not found any difference in the angle distribution (sharpness of the fluorescence signal at optimal SPCE angle) for the plastic slide compared to the glass slide. The kinetics of binding was monitored on the plastic slide as well as on the glass slide. Optically dense samples, a 4% red blood cell suspension and a 15% hemoglobin solution, are causing a reduction in the immunoassay SPCE signal by approximately 15% and three times, respectively, and the percentage of the reduction is the same for plastic and for glass slides. We believe that plastic substrates can be readily used in any SPCE assay, with only marginally lower total signal compared to high-quality glass slides.     

On the role of separation in compression wave generation by a train entering a tunnel hood with a window

An approximate analytical theory is proposed for calculatingthe compression wave generated when a train enters a tunnelfitted with an entrance hood with an open window. The pressurerise ahead of the entering train causes air to exhaust fromthe window in the form of a high-speed jet. The profile of thecompression wave transmitted into the tunnel is modified by theinteraction of the train nose with the window, by multiple reflectionsof wave energy between the window and the hood portal priorto transmission into the tunnel, and in addition by the productionof a pressure pulse by the jet. The wave generation problemcan be formulated in a quasi-one-dimensional manner, wherebythe pressure field generated in front of and to the sides ofthe train in the absence of the window is assumed to be scatteredby the window. A self-consistent solution is obtained by evaluatingthe jet flow from the window using a nonlinear empirical quationproposed and validated by Cummings (1984, Amer. Inst. Aeron.Astron. J., 22, 786–792; 1986, J. Acoust. Soc. Amer.,79, 942–951) for the velocity in the window-exit plane.Predictions are found to be in excellent agreement with measurementsof compression wave profiles obtained in model scale experimentsreported by Howe et al. (2003, J. Fluid Mech., 487, 211–243)at train speeds 350 km h^–1.     

Ultrafast optical delay line by use of a time-prism pair

We demonstrate an all-fiber, programmable, ultrafast optical delay line based on reversible frequency conversion by use of a time-prism pair. Using electro-optic phase modulators to provide the time-prism phase profile, we show a record scanning rate of 0.5 GHz and a delay range of 19.0 ps. Computer modeling suggests that aberration correction in the time-prism system can extend the delay range to 28.0 ps. Finally, limitations and potential improvement of our techniques are discussed.