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This paper concerns the three-dimensional (3-D) numerical simulation and experimental investigation of fiber laser butt welding AISI 304 stainless steel. On the basis of the 3-D finite element method (FEM) model the temperature distributions of the weld bead at different times are simulated using a double ellipsoid heat source model. The time-temperature profiles of different points are analysed, showing that the temperature is sharply decreased away from the weld bead centre. To verify the simulation results the corresponding fiber laser welding experiments are carried out. The results show that the cross-section microstructures of welded joint are mainly composed of molten pool, narrow heat affected zone (HAZ) and stainless steel substrate. The wineglass-like molten pool shape shows good agreement with the simulated results. And the finer microstructure in the weld bead is resulted from the rapid cooling rate of laser welding which is confirmed by the FEM calculation. The finer microstructures of columnar and equiaxed dendrites are formed in the peripheral and central region of the molten pool. [ABSTRACT FROM AUTHOR]

We observed that a number of patients with severe acute respiratory syndrome (SARS) developed affective psychosis during the acute phase of their illness. We reviewed all SARS- related psychiatric consultations in Hong Kong and investigated the risk factors for psychosis among patients with SARS in a matched case-control study. Patients with SARS- related psychosis received higher total doses of steroids and had higher rates of family history of psychiatric illness. The findings of the present study suggest that steroid toxicity, personal vulnerability, and, probably, psychosocial stressors jointly contributed to the development of psychosis in patients with SARS. [ABSTRACT FROM AUTHOR]

Our experimental results demonstrate that full-field hard-X-ray microscopy is finally able to investigate the internal structure of cells in tissues. This result was made possible by three main factors: the use of a coherent (synchrotron) source of X-rays, the exploitation of contrast mechanisms based on the real part of the refractive index and the magnification provided by high-resolution Fresnel zone-plate objectives. We specifically obtained high-quality microradiographs of human and mouse cells with 29 nm Rayleigh spatial resolution and verified that tomographic reconstruction could be implemented with a final resolution level suitable for subcellular features. We also demonstrated that a phase retrieval method based on a wave propagation algorithm could yield good subcellular images starting from a series of defocused microradiographs. The concluding discussion compares cellular and subcellular hard-X-ray microradiology with other techniques and evaluates its potential impact on biomedical research., (Copyright © 2012 Elsevier Inc. All rights reserved.)

We report an experimental investigation of the optical transfer functions for an X-ray microscope operated in defocus phase-contrast mode. The results are compared with a theoretical model of partially coherent image formation and are found to be in excellent agreement.