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Transmission electron microscope (TEM)

The original form of electron microscope, the transmission electron microscope (TEM) uses a high voltage electron beam to create an image. The electrons are emitted by an electron gun, commonly fitted with a tungsten filament cathode as the electron source. The electron beam is accelerated by an anode typically at +100 keV (40 to 400 keV) with respect to the cathode, focused by electrostatic and electromagnetic lenses, and transmitted through the specimen that is in part transparent to electrons and in part scatters them out of the beam. When it emerges from the specimen, the electron beam carries information about the structure of the specimen that is magnified by the objective lens system of the microscope. The spatial variation in this information (the "image") is viewed by projecting the magnified electron image onto a fluorescent viewing screen coated with a phosphor or scintillator material such as zinc sulfide. The image can be photographically recorded by exposing a photographic film or plate directly to the electron beam, or a high-resolution phosphor may be coupled by means of a lens optical system or a fibre optic light-guide to the sensor of a CCD (charge-coupled device) camera. The image detected by the CCD may be displayed on a monitor or computer.

Resolution of the TEM is limited primarily by spherical aberration, but a new generation of aberration correctors have been able to partially overcome spherical aberration to increase resolution. Hardware correction of spherical aberration for the High Resolution TEM (HRTEM) has allowed the production of images with resolution below 0.5 Ångström (50 picometres)^[5] at magnifications above 50 million times.^[6] The ability to determine the positions of atoms within materials has made the HRTEM an important tool for nano-technologies research and development.^[7]

(NBC) - A dog-gone special award for a German shepherd credited with leading state troopers to his owner's burning property. In a dash cam video from a state trooper's cruiser in Alaska you can see the German shepherd, "Buddy," running in front of the cruiser, even turning around to make sure the trooper is still behind him. His owner's property was engulfed in flames Buddy's owner was burned, but he'll be ok.For his heroic actions Buddy will be awarded an engraved silver-plated dog bowl.

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