Thermionic Emission and Radiation and Half-Lifes
For the write-up section of my coursework I went on a trip to the Kent
and Canterbury Hospital in order to look at the application of physics
within the field of medicine. I intend to spend time explaining two
physics principles which have uses in this scientific field, and
illustrate how they are used, either within the diagnosis or treatment
of a patient.
Two principles:
1. Thermionic emission.
2. Radiation and half-lives.
Thermionic emission
Thermionic emission is a phenomenon by which electrons are emitted
from the surface of a metal or metal oxide. The flow of these
electrons can only occur when the thermal vibrational energy of the
matrix overcomes the electrostatic forces preventing the electrons
leaving the surface.
Thermionic emission is entirely reliant upon the 'sea of free
electrons'. This is the collective name given to the one or two
electrons per atom, in any metal, which are free to move around and
are not bound to the atom. The velocities of these free electrons
follow a statistical distribution, and occasionally an electron will
have enough velocity to overcome the electrostatic retaining forces.
The minimum amount of energy required for one of these electrons to
escape is called the work function. The work function varies within
different materials.
The process can occur at any temperature above absolute zero but it is
extremely inefficient, therefore when ever thermionic emission is
being used or tested the material is heated to a very high
temperature. Another method used in increasing the amount of
thermionic emission taking pl...
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carrier molecule, to which isotopes can be bound, which target
specific organs or disease states, and carry technetium-99m or other
radionuclides to the sites in the body that want imaging. Once this
binding has occurred the substance is termed a radiopharmaceutical and
can be administered in three different ways depending on where it must
end up. It can be swallowed, injected or inhaled.
The picture is created by a tomography using gamma receptors
(photomultipliers) which change the colour of their crystals depending
upon the amount of gamma radiation it receives. After this the colour
change occurs larger photomultipliers send a signal to a computer
where the picture is built up in slices (cross-sectional of a
horizontal body) the brighter areas are where there is a higher level
of gamma radiation coming from.
Jocelin Of Brakelond. Chronicles of the Abbey of Bury St Edmunds. trans. Diana Greenway and Jane Sayers (Oxford University Press,1989)
3 "DoverLock and Key of the Kingdom." The Golden Arrow. http://www.dover-kent.co.uk/transport/golden_arrow.htm (accessed April 10, 2014).
be biased or lie. We can see in the maps of Sailsbury and Hereford the
“London.” Lloyd’s Evening Post. 9 August. 1773- 11 August. 1773. Gale Cenage Learning. Web. 29 March. 2014.
Lambdin, Laura C. and Robert T. Lambdin, ed. Chaucer's Pilgrims: An Historical Guide to the Pilgrims in the Canterbury Tales. London: Greenwood Press, 1996.
In 1950, a man, Enrico Fermi, during a lunch break conversation he causally asked his co-workers an interesting question, “where is everybody”. (Howell, 2014) By which he meant, since there are over a million planets which are proficient enough to support life and possibly some sort of intelligent species, so how come no one has visited earth? This became known as The Fermi Paradox, which came from his surname and two Greek words, para meaning contrary and Doxa meaning opinion, about a 100 years ago. (Webb 2002) A paradox arises when you set undisputable evidence and then a certain conclusion contradicts the idea. For example, Fermi realized that extra-terrestrials have had a large amount of time to appear
Gull, John. The Oxford Illustrated History of Brittan. Great Brittan: Butler & Tanner Ltd, Frome, Somerset., 1984. Print.
“Go from Corlears Hook to Coenties Slip, and from thence, by Whitehall, northward. What do you see?- Posted like silent sentinels all around the town, stand thousands upon thousands of mortal men fixed in ocean reveries. Some leaning against the spiles; some seated upon the pier-heads; some looking over the bulwarks of ships from China; some high aloft in the rigging, as if striving to get a still better seaward peep. But these are all landsmen; of week days pent up in lath and plaster- tied to counters, nailed to benches...
Radiation is the emission of electromagnetic energy that is given off in the form of high speed particles that cause ionization. During ionization radiation hits and knocks electrons from an atom creating charged ions. Due to the electron being stripped away from the atom this break the chemical bond. Living tissue within the human body is damaged and attempts to repair it but sometimes the damage is beyond repair.
The setting is London in 1854, which is very different to anything we know today. Johnson’s description of this time and place makes it seem like a whole other world from the here and now....
England now, as I once was, and had but this fish painted, not a holiday
“John Constable, The Haywain, 1821” as per the John Constable and book point of view freshly perceived landscapes
Van Nortwick, Thomas. Somewhere I have travelled: the hero's journey. New York: Oxford University Press, 1996.
In nature radioactive material occurs either as naturally in the form of radioactive isotopes in rocks or as a consequence of human release such as during nuclear testing, normal maintenance of nuclear power plants and nuclear accidents such as those at Chernobyl and Fukushima Dallchi. Natural level of radiation sometime exceeds low baseline levels in uncontaminated areas by several hundred fold (Ghiassi-Nejad et al. 2002) resulting in significant rates of diseases in human (Lubin and Boice, 1997) and to other organisms can result in reproductive failure and death (Lubin and Boice, 1997; Ghiassi-Nejad et al. 2002).
I am planning a trip to my dream destination, the United Kingdom! I have always dreamed of going to London and exploring all of the beautiful landscapes the country has to offer. On my voyage I will be accompanied by my boyfriend, Damian, and my younger sister, Taylor. Before we can begin our journey we have to do the proper research so our trip will be everything we want it to be.