Search results
Results from the WOW.Com Content Network
Ultrastructure (or ultra-structure) is the architecture of cells and biomaterials that is visible at higher magnifications than found on a standard optical light microscope. This traditionally meant the resolution and magnification range of a conventional transmission electron microscope (TEM) when viewing biological specimens such as cells ...
The larger organelles, such as the nucleus and vacuoles, are easily visible with the light microscope. They were among the first biological discoveries made after the invention of the microscope . Not all eukaryotic cells have each of the organelles listed below.
The history of light therapy can be traced back to ancient Egypt and India, where therapy with natural sunlight was first used to treat leucoderma. [3] In the 1850s, Florence Nightingale's advocacy of exposure to clean air and sunlight for health restoration also contributed to the initial development of light therapy for treatments. [4]
However, cellular organelles can be damaged when the photon energy produces chemical and molecular changes rather than being re-emitted. [35] It is believed that the primary culprit in the light-induced toxicity experienced by live cells is a result of free radicals produced by the excitation of fluorescent molecules. [32]
The electron microscope is used to obtain structural information at the nano-scale. Unlike an optical microscope, an electron microscope is able to surpass the diffraction limit of light. This is because the wavelength of accelerated electrons is much shorter than the wavelength of visible light. [5]
Reproduction of an early electron microscope constructed by Ernst Ruska in the 1930s. Many developments laid the groundwork of the electron optics used in microscopes. [2] One significant step was the work of Hertz in 1883 [3] who made a cathode-ray tube with electrostatic and magnetic deflection, demonstrating manipulation of the direction of an electron beam.
An account of the early history of scanning electron microscopy has been presented by McMullan. [2] [3] Although Max Knoll produced a photo with a 50 mm object-field-width showing channeling contrast by the use of an electron beam scanner, [4] it was Manfred von Ardenne who in 1937 invented [5] a microscope with high resolution by scanning a very small raster with a demagnified and finely ...
Similar to the differentiation between "electric" and "electronics," a difference can be made between applications such as therapy and surgery, which use light mainly to transfer energy, and applications such as diagnostics, which use light to excite matter and to transfer information back to the operator. In most cases, the term biophotonics ...