Single-bubble and multi-bubble cavitation in water triggered by laser-driven focusing shock waves

In this study a single laser pulse spatially shaped into a ring is focused into a thin water layer, creating an annular cavitation bubble and cylindrical shock waves: an outer shock that diverges away from the excitation laser ring and an inner shock that focuses towards the center. A few nanoseconds after the converging shock reaches the focus and diverges away from the center, a single bubble nucleates at the center. The inner diverging shock then reaches the surface of the annular laser-induced bubble and reflects at the boundary, initiating nucleation of a tertiary bubble cloud. In the present experiments, we have performed time-resolved imaging of shock propagation and bubble wall motion. Our experimental observations of single-bubble cavitation and collapse and appearance of ring-shaped bubble clouds are consistent with our numerical simulations that solve a one dimensional Euler equation in cylindrical coordinates. The numerical results agree qualitatively with the experimental observations of the appearance and growth of bubble clouds at the smallest laser excitation rings. Our technique of shock-driven bubble cavitation opens novel perspectives for the investigation of shock-induced single-bubble or multi-bubble cavitation phenomena in thin liquids

Mirror Furnace for Synchrotron Dark Field X-ray Microscopy Experiments

We present a multi-purpose mirror furnace designed for synchrotron X-ray experiments. The furnace is optimized specifically for dark-field X-ray microscopy (DFXM) of crystalline materials at the beamline ID06 of the ESRF. The furnace can reach up to ~1600{\deg}C with stability better than 2{\deg}C, and heating and cooling rates up to 30{\deg}C/s. The contact-less design enables samples to be heated either in air or in a controlled atmosphere in a capillary tube. The temperature was calibrated via the thermal expansion of an a-iron grain. Temperature profiles in the y and z axes were measured by scanning a thermocouple through the focal spot of the furnace. In the current configuration of the beamline, the furnace can be used for DFXM, near-field X-ray topography, bright field X-ray nanotomography, high resolution reciprocal space mapping, and limited powder diffraction experiments. As a first application, we present a DFXM case study on isothermal heating of a commercially pure Al single crystal

Molecular Information Technology

Molecular materials are endowed with unique properties of unrivaled potential for high density integration of computing systems. Present applications of molecules range from organic semiconductor materials for low-cost circuits to genetically modified proteins for commercial imaging equipment. To fully realize the potential of molecules in computation, information processing concepts that relinquish narrow prescriptive control over elementary structures and functions are needed, and self-organizing architectures have to be developed. Investigations into qualitatively new concepts of information processing are underway in the areas of reaction-diffusion computing, self-assembly computing, and conformation-based computing. Molecular computing is best considered not as a competitor for conventional computing, but as an opportunity for new applications. Microrobotics and bioimmersive computing are among the domains likely to benefit from advances in molecular computing. Progress will depend on both novel computing concepts and innovations in materials. This article reviews current directions in the use of bulk and single molecules for information processing

Machine learning to analyze images of shocked materials for precise and accurate measurements

A supervised machine learning algorithm, called locally adaptive discriminant analysis (LADA), has been developed to locate boundaries between identifiable image features that have varying intensities. LADA is an adaptation of image segmentation, which includes techniques that find the positions of image features (classes) using statistical intensity distributions for each class in the image. In order to place a pixel in the proper class, LADA considers the intensity at that pixel and the distribution of intensities in local (nearby) pixels. This paper presents the use of LADA to provide, with statistical uncertainties, the positions and shapes of features within ultrafast images of shock waves. We demonstrate the ability to locate image features including crystals, density changes associated with shock waves, and material jetting caused by shock waves. This algorithm can analyze images that exhibit a wide range of physical phenomena because it does not rely on comparison to a model. LADA enables analysis of images from shock physics with statistical rigor independent of underlying models or simulations.United States. Office of Naval Research (Grant N00014-16-1-2090)United States. Office of Naval Research (Grant N00014-15-1-2694

Simultaneous 8.2 keV phase-contrast imaging and 24.6 keV X-ray diffraction from shock-compressed matter at the LCLS

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Physicians’ Decisions About Continuing or Stopping Colon Cancer Screening in the Elderly: A Qualitative Study

Experts suggest an individualized approach to colon cancer screening to take into account variation in older adults’ life expectancies and potential to benefit from screening. However, little is known about how physicians make decisions about colon cancer screening in adults age 75 and older