Transcript Research
Applications of Quantum Mechanics Textbook: pages 203-207 Lasers -produce a light beam -the light is completely monochromatic. That means it is all the same wavelength (and therefore the same colour). -the light is made of coherent waves (that means each photon in line follows the previous one precisely, acting like one continous wave Uses of Lasers Medicine – eye treatment, surgery, kidney stone treatment Research – spectroscopy, microdissection, fluorescence microscopy Forensics – fingerprint identification Military – marking targets, missile defence Product Development – Printers, optical discs, holograms Vary in strength from 1 mW (laser pointer) to recently built 100 kW CO laser. Lasers and Quantum Mechanics -Einstein (1917): a rise in energy level of an electron in an atom requires a specific photon to be absorbed. If a photon of exactly that energy were to hit an atom, already in its excited state, the electron would be “stimulated” to drop back to a lower level. -therefore if the electrons could be held temporarily at an excited state, a single photon could start a chain reaction of photons releasing energy and exciting other photons. Lasers and Quantum Mechanics -all these photons being emitted would be of exactly the same wavelength, and arranged in coherent waves moving in the same direction. Thus the laser. Lasers and Quantum Mechanics Theodore Maiman – taught at Simon Fraser University. Created first laser. Lasers and Quantum Mechanics John C. Polanyi -Canadian chemist -infrared chemiluminescence – the emission of light by an atom in its excited state Diagnosis and Quantum Mechanics X-rays -first X-ray photograph taken by Roentgen in 1895 -first photograph was of his wife’s hand. X-Rays -X-rays are electromagnetic waves, just like light. The difference is that the waves of X-rays carry a lot more energy than light waves. -The high energy waves pass through soft tissue but are absorbed by bone. X-rays -Film is placed behind the patient -The areas not absorbed (i.e. where energy passes) appear black on the film. -Areas where waves are absorbed such as bones appear white on the film. Magnetic Resonance Imaging (MRI) -Living things are made up most of water (H2O). -The human body is full of hydrogen atoms. -Powerful magnet lines up all the protons of hydrogen atoms. -A pulse of radio waves is then sent out. This causes the protons to scatter. -As the protons realign back in place, they emit a signal. -Soft tissues with high water content (e.g. Nervous system) appear more opaque than bone. Can therefore tell tissues apart. -Signals are picked up by computers which generate an image. Magnetic Resonance Imaging (MRI) Computed Tomography (CT) -Produces images through series of thin X-Ray sections through the body. -Patient is moved slowly through the CT machine as X-rays machine rotates around them. -Computer produces high quality images of each section or can be put together to make 3D image. CT versus MRI -MRI better at seeing soft tissues like tendons and ligaments. -CT Scan especially useful for looking at dense materials. It Is useful for detecting ruptured blood vessels. Problems: MRI and CT imaging equipment is expensive to buy, operate, and maintain, so it is usually available only in large urban centres with high demand. In Ontario, these technologies are covered by OHIP. But there is a waiting list. PET Scans -Stands for Positron Emission Tomography -Used in brain research -Can reveal the location of a physiological and biochemical processes in the body. -Inject molecules labelled with radioisotopes into the blood stream. Molecules travel to target area. -Scanner records the energy given off by the particles. Radioisotopes -Isotopes: Different atomic forms of the same element. Same number of protons but different number of neutrons. -Some isotopes are stable, don’t have a tendency to lose particles. -Some isotopes are unstable, or radioactive. The nucleus decays spontaneously, giving off particles and energy. National Research Universal Reactor Chalk River Ontario, 180 Northwest of Ottawa. -Produces the most commonly used radioisotope in imaging (one that decays quickly & can be tagged to pharmaceuticals). -This isotope is made at 5 nuclear reactors around the world. 30-40 percent are made at NRU alone. -All of these reactors are more than 40 years old, periods of shutdown and repair. -NRU shutdown exactly two years ago for maintenance. Created a worldwide shortage of radioisotopes. In 2008 a radioactive leak was discovered at NRU. The leak “stopped” on its own before the source could be Located. NRU was restarted exactly one year ago today. In May it was discovered that the leak had returned, and this time it was much worse. NRU is currently shutdown with spring 2010 the earliest it Will be restarted. This has resulted in a worldwide shortage of radioisotopes. Possible solutions: Manitoba has a facility which could be altered to make radioisotopes. Or purchase 100-150 MRI and CT scanners which don’t require radioisotopes.