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Shearography is an interferometric method that overcomes several limitations of holography by eliminating the reference beam. It greatly simplifies the optical setup and has much higher tolerance to environmental disturbances. Consequently, the technique has received considerable industrial acceptance, particularly for nondestructive testing. Shearography, however, is generally not applicable to the measurement of an obstructed area, as the area to be measured must be accessible to both illumination and imaging. We present an algorithm based on the principle of tomography that permits the reconstruction of the unavailable phase distribution in an obstructed area from the measured boundary phase distribution. In the process, a set of imaginary rays is projected from many different directions across the area. For each ray, integration of the phase directional derivative along the ray is equal to the phase difference between the boundary points intercepted by the ray. Therefore, a set of linear equations can be established by considering the multiple rays. Each equation expresses the unknown phase derivatives in the obstructed area in terms of the measured boundary phase. Solution of the set of simultaneous equations yields the unknown phase distribution in the blind area. While its applications to shearography are demonstrated, the technique is potentially applicable to all full-field optical measurement techniques such as holography, speckle interferometry, classical interferometry, thermography, moire, photoelasticity, and speckle correlation techniques. OCIS codes: 100.6950, 090.2880, 100.3190, 100.3020.

By using the natural birefringence of an a-cut Nd:GdV[O.sub.4] crystal, we experimentally investigate laser operation under different light polarizations ([pi] and [sigma]-polarized emissions) and compare their performance. The laser performance is further compared with a diode-pumped c-cut Nd:GdV[O.sub.4] laser of the same parameters. We show experimentally that the c-cut Nd:GdV[O.sub.4] laser could have good passively Q-switched performance in a low-pump-power region but is influenced by other intrinsic laser effects, such as the thermally induced cavity losses; its performance is severely degraded under high pump power. The best passively Q-switched performance obtained in our experiments is from the a-cut [pi]-polarized laser, which gives the narrowest pulse of 5.4 ns with the highest peak power of 20 kW. Our experimental results show that, to achieve the best performance of the passively Q-switched laser operation, an overall consideration of laser parameters is important. OCIS codes: 140.3540, 260.5430, 140.3480.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.solener.2005.08.004 Byline: Michael K.H. Leung (a), S.M. Tang (a), Ringo C.W. Lam (a), Dennis Y.C. Leung (a), W.C. Yam (b), S.P. Ng (b), Lilian L.P. Vrijmoed (c) Keywords: Solar; Photocatalytic; Parallel-plate photoreactor; Design optimization Abstract: This study focused on modeling and optimization of a photoreactor packed with parallel glass plates coated with sol-gel TiO.sub.2 thin films on both sides. The photoreactor design has great potential for solar photocatalytic air purification. Borosilicate glass substrate was selected because its high transmissivity facilitated the transmission and distribution of exterior solar radiation onto interior immobilized photocatalyst. Flat-plate configuration was adopted because a TiO.sub.2-coated plate could be easily set up for effective ion implantation treatment to extend the activating spectral range from UV to visible light for a higher solar photonic efficiency. In the analytical study of this research, a semi-empirical correlation model was formulated for prediction of the photoreactor performance. The correlation coefficients were obtained based on the results of photocatalytic air purification experiments conducted. Additional experimental tests were carried out for validation of the model. In the photoreactor design optimization analysis, the semi-empirical correlation model was used as an optimizer to determine the number of parallel TiO.sub.2-coated plates needed for efficient photocatalytic air purification. It was found that the optimal number of plates was dependent of the incident irradiance. The modeling and optimization methods developed for solar photocatalytic air purification are equally applicable for solar photocatalytic water purification. Author Affiliation: (a) Department of Mechanical Engineering, The University of Hong Kong, 7/F Haking Wong Building, Pokfulam Road, Hong Kong, China (b) Department of Microbiology, The University of Hong Kong, Hong Kong, China (c) Department of Biology and Chemistry, City University of Hong Kong, Hong Kong, China Article History: Received 19 May 2005; Accepted 16 August 2005 Article Note: (miscellaneous) Communicated by: Associate Editor Gion Calzaferri

Byline: K. L. Chan (1), S. P. Ng (2), K. W. Chan (3), Y. H. Wo (1), P. K. H. Tam (1) Keywords: Pathogenesis; Necrotizing enterocolitis; Rat Abstract: The pathogenesis of neonatal necrotizing enterocolitis (NEC) is unknown. Intestinal dilatation and preferred occurrence of NEC at sites of bacterial overgrowth (colon and ileum) are common findings. The study attempted to produce NEC with increasing intraluminal pressures and bacterial concentrations in two different aged groups of rats. First, 10-cm terminal ileum segments were isolated with intact vascular pedicles in 1-and 3-month-old rats, and a dose of 10.sup.11 E. coli in 1 ml was injected into each segment. Intraluminal pressure was sustained for 1 h at 150, 100, 50 and 0 cmH.sub.20, respectively, in four experimental groups (n=6). The isolated loop was then returned to the abdominal cavity and assessed grossly for NEC after 24 h. Histological examination was performed by a pathologist (KWC) who was blinded to the procedures. Second, the procedure was repeated with doses of 10.sup.8, 10.sup.5 and 0 bacteria/ml (n=6) at intraluminal pressure of 100 cmH.sub.20 in 1-month-old rats. Third, in another experimental group, oxygenation of the pedicled loop was assessed by oximetry as the intraluminal pressure increased and the findings were correlated with aortic blood pressure. The blood pressures (mean+-SD) for 3- and 1-month-old rats were 110+-6 and 72+-4 mmHg, respectively. Hypoxia (&lt 50% oxygen saturation) of the bowel was detected when the intraluminal pressure exceeded the mean blood pressure. The relative incidences of NEC in the bowel with intraluminal pressure above and below mean blood pressure were 100% (6/6) vs. 4% (1/24 P&lt 0.05) in 3-month-old rats, and 100% (12/12) vs. 11% (2/18 P&lt 0.05) in 1-month-old rats. There was no occurrence of NEC in bowel injected with 10.sup.5 E. coli/ml and less at 100 cm intraluminal pressure. Increased intraluminal pressure results in bowel hypoxia and in the presence of adequate bacterial concentration predisposes to the development of NEC. Young age is associated with a lower threshold for increased intraluminal pressure leading to NEC. Author Affiliation: (1) Division of Pediatric Surgery, Department of Surgery, University of Hong Kong Medical Centre, Queen Mary Hospital, Hong Kong SAR, China (2) Department of Microbiology, University of Hong Kong Medical Centre, Queen Mary Hospital, Hong Kong SAR, China (3) Department of Pathology, University of Hong Kong Medical Centre, Queen Mary Hospital, Hong Kong SAR, China Article History: Accepted Date: 06/11/2002 Online Date: 09/10/2003

Research describing germanium nanocrystal growth is presented. In particular the characteristics of growth in silicon oxide film is investigated by x-ray photoelectron spectroscopy and transmission electron microscopy.

The germanium nanocrystals embedded in amorphous silicon oxide films which were synthesized by rapid thermal annealing have been characterized. The samples were prepared by cosputtering germanium and silicon oxide targets by a radio frequency magnetron sputtering machine, and were analyzed by Raman spectroscopy. The results showed a transition spectra from amorphous to nanocrystalline germanium for samples which were annealed between 600 and 750 degrees C. The estimated crystal size was between 29 and 66 angstrom.

The T6 monoclonal antibody capture enzyme-linked immunosorbent assay detects 99% of the Salmonella serogroup A to E strains and 71% of serogroup F strains present in enriched foods cultured in a nonselective medium before the assay. The method has 100% sensitivity, 99% specificity, and detects almost 98% of the Salmonella strains that infect humans. The O-factor-specific monoclonal antibodies differentiate 88% of the Salmonella spp. into their serogroups. The detection time of the assay is between 17 to 29 hrs depending on the process used to enrich the food.