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Yanyan Xu,1,2 Tsuneo Yamashiro,1,3 Hiroshi Moriya,3 Shun Muramatsu,3 Sadayuki Murayama1 1Department of Radiology, Graduate School of Medical Science, University of the Ryukyus, Okinawa, Japan; 2Department of Radiology, China-Japan Friendship Hospital, Beijing, People’s Republic of China; 3Department of Radiology, Ohara General Hospital, Fukushima, JapanCorrespondence: Tsuneo YamashiroDepartment of Radiology, Graduate School of Medical Science, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, JapanTel +81-98-895-1162Fax +81-98-895-1420Email clatsune@yahoo.co.jpPurpose: To evaluate the advantages of ultra-high-resolution computed tomography (U-HRCT) scans for the quantitative measurement of emphysematous lesions over conventional HRCT scans.Materials and methods: This study included 32 smokers under routine clinical care who underwent chest CT performed by a U-HRCT scanner. Chronic obstructive pulmonary disease (COPD) was diagnosed in 13 of the 32 participants. Scan data were reconstructed by 2 different protocols: i) U-HRCT mode with a 1024×1024 matrix and 0.25-mm slice thickness and ii) conventional HRCT mode with a 512×512 matrix and 0.5-mm slice thickness. On both types of scans, lesions of emphysema were quantitatively assessed as percentage of low attenuation volume (LAV%,

A model for the photoluminescence (PL) spectra of porous silicon has recently been proposed. The model is applied to two types of experimental results and the properties of PL spectra are investigated. The model assumes that the luminescence spectrum comes from the groups of various size particles distributed in porous silicon. The size of nanoparticles is found to obey the logarithmic normal distribution, instead of the Gaussian distribution.

A hybrid photodetector (HPD) combined with a III-V photocathode is considered to be an ideal photodetector, because the quantum efficiency (QE) is high, the collection efficiency is 100%, and the excess noise factor is negligible. An HPD combined with a GaAs photocathode or a blue enhanced GaAs (BE-GaAs) photocathode has been developed. Presently, the QE is approximately 20% from 550nm to 850nm, which is much higher than that of a conventional multi-alkali (S-20) photocathode. The 100% collection efficiency calculated by the computer simulation is supported by the test result of the flat uniformity. Considering the application in high energy physics using a wavelength shifter, energy resolutions of both the BE-GaAs-HPD and the conventional S20-HPD were measured using a 650nm LED light pulse. The BE-GaAs-HPD shows a resolution of 17%, as against 34% for the S20-HPD. The experimental results are consistent with the theoretical estimation. The QE of the HPD is especially important, because the electron multiplication process is noiseless.

The shift of band edges in porous silicon is studied by simulation based on tight-binding band calculations for model structures mimicking porous silicon. The results are compared with recent measurements of band edge shifts, and the greater shift of the valence band edge compared to the conduction band edge in porous silicon is theoretically confirmed. It is found that the ratio of band edge shifts is related to the positions of the center of the electronic density of states for the first conduction and valence bands in bulk silicon. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]