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Petkau Effect
The Petkau effect is an early counterexample to linear-effect assumptions usually made about radiation exposure. It was found by Dr. Abram Petkau at the Atomic Energy of Canada Whiteshell Nuclear Research Establishment, Manitoba and published in Health Physics March 1972. The Petkau effect was coined by Swiss nuclear hazards commentator Ralph Graeub in 1985 in this book ''Der Petkau-Effekt und unsere strahlende Zukunft'' (The Petkau effect and our Radiating Future). Petkau had been measuring, in the usual way, the radiation dose that would rupture a simulated artificial cell membrane. He found that 3500 rads delivered in hours (26 rad/min = 15.5 Sv/h) would do it. Then, almost by chance, Petkau repeated the experiment with much weaker radiation and found that 0.7 rad delivered in hours (1 millirad/min = 0.61 mSv/h) also ruptured the membrane. This was counter to the prevailing assumption of a linear relationship between total dose or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: * ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ) * ''particle radiation'', such as alpha radiation (α), beta radiation (β), proton radiation and neutron radiation (particles of non-zero rest energy) * '' acoustic radiation'', such as ultrasound, sound, and seismic waves (dependent on a physical transmission medium) * ''gravitational wave, gravitational radiation'', that takes the form of gravitational waves, or ripples in the curvature of spacetime Radiation is often categorized as either ''ionizing radiation, ionizing'' or ''non-ionizing radiation, non-ionizing'' depending on the energy of the radiated particles. Ionizing radiation carries more than 10 electron volt, eV, which is enough to ionize atoms and molecules and break ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Abram Petkau
Abraham, ; ar, , , name=, group= (originally Abram) is the common Hebrew patriarch of the Abrahamic religions, including Judaism, Christianity, and Islam. In Judaism, he is the founding father of the special relationship between the Jews and God; in Christianity, he is the spiritual progenitor of all believers, whether Jewish or non-Jewish; and in Islam, he is a link in the chain of Islamic prophets that begins with Adam (see Adam in Islam) and culminates in Muhammad. His life, told in the narrative of the Book of Genesis, revolves around the themes of posterity and land. Abraham is called by God to leave the house of his father Terah and settle in the land of Canaan, which God now promises to Abraham and his progeny. This promise is subsequently inherited by Isaac, Abraham's son by his wife Sarah, while Isaac's half-brother Ishmael is also promised that he will be the founder of a great nation. Abraham purchases a tomb (the Cave of the Patriarchs) at Hebron to be Sa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Atomic Energy Of Canada
Atomic Energy of Canada Limited (AECL) is a Canadian federal Crown corporation and Canada's largest nuclear science and technology laboratory. AECL developed the CANDU reactor technology starting in the 1950s, and in October 2011 licensed this technology to Candu Energy (a wholly owned subsidiary of SNC-Lavalin). Today AECL develops peaceful applications from nuclear technology through expertise in physics, metallurgy, chemistry, biology and engineering. AECL's activities range from research and development, design and engineering to specialized technology development, waste management and decommissioning. AECL partners with Canadian universities, other Canadian government and private-sector R&D agencies (including Candu Energy), various national laboratories outside Canada, and international agencies such as the IAEA. AECL describes its goal as ensuring that "Canadians and the world receive energy, health, environmental and economic benefits from nuclear science and technol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Whiteshell Nuclear Research Establishment
The Whiteshell Laboratories, originally known as the Whiteshell Nuclear Research Establishment (WNRE) was an Atomic Energy of Canada Limited, Atomic Energy of Canada (AECL) laboratory in Manitoba, northeast of Winnipeg. It was originally built as a home for the experimental WR-1 reactor, but over time came to host a variety of experimental systems, including a SLOWPOKE reactor (the SLOWPOKE Demonstration Reactor) and the Underground Research Laboratory to study nuclear waste disposal. Employment peaked in the early 1970s at about 1,300, but during the 1980s the experiments began to wind down, and in 2003 the decision was made to close the site. the site is undergoing decommissioning with a planned completion date in 2024. History In the late 1950s, Atomic Energy Canada Limited (AECL) was planning an aggressive expansion of their experimental reactor designs. Among a number of proposals were versions of the heavy water reactor concept using alternate cooling arrangements including oi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manitoba
Manitoba ( ) is a Provinces and territories of Canada, province of Canada at the Centre of Canada, longitudinal centre of the country. It is Canada's Population of Canada by province and territory, fifth-most populous province, with a population of 1,342,153 as of 2021, of widely varied landscape, from arctic tundra and the Hudson Bay coastline in the Northern Region, Manitoba, north to dense Boreal forest of Canada, boreal forest, large freshwater List of lakes of Manitoba, lakes, and prairie grassland in the central and Southern Manitoba, southern regions. Indigenous peoples in Canada, Indigenous peoples have inhabited what is now Manitoba for thousands of years. In the early 17th century, British and French North American fur trade, fur traders began arriving in the area and establishing settlements. The Kingdom of England secured control of the region in 1673 and created a territory named Rupert's Land, which was placed under the administration of the Hudson's Bay Company. Rupe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Membrane
The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (the extracellular space). The cell membrane consists of a lipid bilayer, made up of two layers of phospholipids with cholesterols (a lipid component) interspersed between them, maintaining appropriate membrane fluidity at various temperatures. The membrane also contains membrane proteins, including integral proteins that span the membrane and serve as membrane transporters, and peripheral proteins that loosely attach to the outer (peripheral) side of the cell membrane, acting as enzymes to facilitate interaction with the cell's environment. Glycolipids embedded in the outer lipid layer serve a similar purpose. The cell membrane controls the movement of substances in and out of cells and organelles, being selectively permeable to ions a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rad (unit)
The rad is a unit of absorbed radiation dose, defined as 1 rad = 0.01 Gy = 0.01 J/kg. It was originally defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by one gram of matter. The material absorbing the radiation can be human tissue or silicon microchips or any other medium (for example, air, water, lead shielding, etc.). It has been replaced by the gray (Gy) in SI derived units, but is still used in the United States, although this is "strongly discouraged" in Chapter 5.2 of the ''Guide to the SI'', which was written and published by the U.S. National Institute of Standards and Technology. However, the numerically equivalent SI unit, the centigray, is widely used to report absorbed doses within radiotherapy. The roentgen, used to quantify the radiation exposure, may be related to the corresponding absorbed dose by use of the F-factor. Health effects A dose of under 100 rad will typically produce no immediate symptoms other than blood ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Military Medical Academy (Serbia)
The Military Medical Academy ( sr, Војномедицинска академија, Vojnomedicinska akademija; abbr. VMA), is a military hospital center in the Banjica neighborhood of Belgrade, Serbia. Founded in 1844, it is a part of the Ministry of Defence (Serbia), Serbian Ministry of Defence and is generally intended to serve the personnel of the Serbian Armed Forces and Ministry of Defence, although it is open for civilians as well. It is known for its high standard in medical practice and is generally considered to be among the best medical institution in the country. In 2011, Medical School of Military Medical Academy is formed as part of the newly-established University of Defence. History The Military Medical Academy was founded on 2 March 1844. On that day, Alexander Karađorđević, Prince of Serbia, Prince Alexander Karađorđević signed a decree establishing the first "Central Military Hospital" on the foundations of the military hospital in Belgrade. In 1909 beg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oxygen
Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is Earth's most abundant element, and after hydrogen and helium, it is the third-most abundant element in the universe. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula . Diatomic oxygen gas currently constitutes 20.95% of the Earth's atmosphere, though this has changed considerably over long periods of time. Oxygen makes up almost half of the Earth's crust in the form of oxides.Atkins, P.; Jones, L.; Laverman, L. (2016).''Chemical Principles'', 7th edition. Freeman. Many major classes of organic molecules in living organisms contain oxygen atoms, such as proteins, nucleic acids, carbohydrates, and fats, as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Concentration
In chemistry, concentration is the abundance of a constituent divided by the total volume of a mixture. Several types of mathematical description can be distinguished: '' mass concentration'', ''molar concentration'', ''number concentration'', and ''volume concentration''. The concentration can refer to any kind of chemical mixture, but most frequently refers to solutes and solvents in solutions. The molar (amount) concentration has variants, such as normal concentration and osmotic concentration. Etymology The term concentration comes from the word concentrate, from the French , from con– + center, meaning “to put at the center”. Qualitative description Often in informal, non-technical language, concentration is described in a qualitative way, through the use of adjectives such as "dilute" for solutions of relatively low concentration and "concentrated" for solutions of relatively high concentration. To concentrate a solution, one must add more solute (for example, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Non-monotonic Logic
A non-monotonic logic is a formal logic whose conclusion relation is not monotonic. In other words, non-monotonic logics are devised to capture and represent defeasible inferences (cf. defeasible reasoning), i.e., a kind of inference in which reasoners draw tentative conclusions, enabling reasoners to retract their conclusion(s) based on further evidence. Most studied formal logics have a monotonic entailment relation, meaning that adding a formula to a theory never produces a pruning of its set of conclusions. Intuitively, monotonicity indicates that learning a new piece of knowledge cannot reduce the set of what is known. A monotonic logic cannot handle various reasoning tasks such as reasoning by default (conclusions may be derived only because of lack of evidence of the contrary), abductive reasoning (conclusions are only deduced as most likely explanations), some important approaches to reasoning about knowledge (the ignorance of a conclusion must be retracted when the concl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superoxide Dismutase
Superoxide dismutase (SOD, ) is an enzyme that alternately catalyzes the dismutation (or partitioning) of the superoxide () radical into ordinary molecular oxygen (O2) and hydrogen peroxide (). Superoxide is produced as a by-product of oxygen metabolism and, if not regulated, causes many types of cell damage. Hydrogen peroxide is also damaging and is degraded by other enzymes such as catalase. Thus, SOD is an important antioxidant defense in nearly all living cells exposed to oxygen. One exception is ''Lactobacillus plantarum'' and related lactobacilli, which use a different mechanism to prevent damage from reactive . Chemical reaction SODs catalyze the disproportionation of superoxide: : 2 HO2 → O2 + H2O2 In this way, is converted into two less damaging species. The pathway by which SOD-catalyzed dismutation of superoxide may be written, for Cu,Zn SOD, with the following reactions: * Cu2+-SOD + → Cu+-SOD + O2 (reduction of copper; oxidation of superoxide) * Cu+-S ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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