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March 2011 Elements that contain unstable nuclei are radioactive; they are called radionuclides. They decay by releasing mostly alpha and beta particles accompanied by gamma rays. An alpha particle has low-energy, is positively charged and consists of two protons and two neutrons, i.e., a helium atom without its 2 electrons; it can be stopped by tissue paper or human skin.  A beta particle is a high-energy, negatively charged electron (negatron) or a positively charged positron; it can be stopped by a sheet of aluminum. Gamma rays are high energy, short-wavelength, electromagnetic radiation; they can be stopped by concrete or lead. The energy released by radionuclides may knock electrons out of their orbits around an atom’s nucleus. This process is called ionizing radiation. Ionizing radiation damages living tissues, leads to changes in constituents of the cell, including the DNA of chromosomes, and results in changes in structure and function of the cells and organ syst...

A series of comparison shots from the showdown of smaller "big" cameras from Canon, Olympus, and Panasonic Canon PowerShot G10, Olympus E-420, Panasonic Lumix G1 Size is an issue with cameras . I miss a lot of good shots when I don't feel like lugging around a hefty SLR (such as my current fav, the Nikon D90). And while my pocket camera (presently a Canon SD800) is easy to tote, the image quality is more for "snapshots" than "photographs." I, and a few other shutterbugs around the office, have been looking into the middle category of cameras : big enough to take good pictures, but not so big that it's a burden. Now is a good time to look, since several camera makers have fresh midsize camera offerings . Recently introduced, the Canon G10 ($450) is the latest in its long-running series of "serious" point-and-shoots. At the heart of the camera is a tiny (about 40 square millimeters) image sensor similar to what you get in a pocket model....