We present a novel method for three-dimensional optical data storage that has submicrometer size resolution, provides a large contrast in index of refraction, and is applicable to a wide range of transparent materials. Bits are recorded by use of a 0.65-N.A. objective to focus 100-fs laser pulses inside the material. The laser pulse produces a submicrometer-diameter structurally altered region with high contrast in index of refraction. We record binary information by writing such bits in multiple planes and read it out with a microscope objective with a short depth of field. We demonstrate data storage and retrieval with 2-microm in-plane bit spacing and 15-microm interplane spacing (17 Gbits/cm(3)). Scanning electron microscopy and atomic force microscopy show structural changes confined to an area 200 nm in diameter.

We compared student learning from different modes of presenting classroom demonstrations to determine how much students learn from traditionally presented demonstrations, and whether learning can be enhanced by simply changing the mode of presentation to increase student engagement. We find that students who passively observe demonstrations understand the underlying concepts no better than students who do not see the demonstration at all, in agreement with previous studies. Learning is enhanced, however, by increasing student engagement; students who predict the demonstration outcome before seeing it, however, display significantly greater understanding.

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Objectives: This European Society for Pediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) position statement provides a comprehensive guide for health care providers to manage percutaneous endoscopic gastrostomy tubes in a safe, effective, and appropriate way. Methods: Relevant literature from searches of PubMed, CINAHL, and recent guidelines was reviewed. In the absence of evidence, recommendations reflect the expert opinion of the authors. Final consensus was obtained by multiple e-mail exchange and during 3 face-to-face meetings of the gastroenterology committee of the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition. Results: Endoscopically placed gastrostomy devices are essential in the management of children with feeding and nutritional problems. The article focuses on practical issues such as indications and contraindications. Conclusions:The decision to place an endoscopic gastrostomy has to be made by an appropriate multidisciplinary team, which then provides active follow-up and care for the child and the device.

Time-resolved measurements of the spectral dielectric function reveal new information about ultrafast phase transitions induced by femtosecond laser pulses in Sb-rich amorphous GeSb films. The excitation generates a nonthermal phase within 200 fs. The dielectric function of this phase differs from that of the crystalline phase, contrary to previous suggestions of a disorder-to-order transition. The observed dielectric function is close to that of the liquid phase, indicating an ultrafast transition from the amorphous phase to a different disordered state.

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