linkstream2 microblog

https://www.ncbi.nlm.nih.gov/pubmed/19995626

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From its first test scan on a mouse, in 1967, to current medical practice, the CT scanner has become a core imaging tool in thoracic diagnosis. Initially financed by money from Beatles’ record sales, the first patient scan was performed in 1971. Only 8 years later, a Nobel Prize in Physics and Medicine was awarded to Hounsfield and Cormack for their discovery.
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https://en.wikipedia.org/wiki/Allan_MacLeod_Cormack

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Allan MacLeod Cormack (February 23, 1924 – May 7, 1998) was a South African American physicist who won the 1979 Nobel Prize in Physiology or Medicine (along with Godfrey Hounsfield) for his work on X-ray computed tomography (CT).[1]
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https://en.wikipedia.org/wiki/Godfrey_Hounsfield

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Sir Godfrey Newbold Hounsfield CBE FRS[1] (28 August 1919 – 12 August 2004)[2][3][4][5][6] was an English electrical engineer who shared the 1979 Nobel Prize for Physiology or Medicine with Allan McLeod Cormack for his part in developing the diagnostic technique of X-ray computed tomography (CT).[7][8][9][10][11]
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https://en.wikipedia.org/wiki/Wave_equation

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Introduction
The wave equation is a partial differential equation that may constrain some scalar function u = u (x1, x2, …, xn; t) of a time variable t and one or more spatial variables x1, x2, … xn. The quantity u may be, for example, the pressure in a liquid or gas, or the displacement, along some specific direction, of the particles of a vibrating solid away from their resting positions. The equation is

{\displaystyle {\frac {\partial ^{2}u}{\partial
t^{2}}}\;=\;c^{2}\left({\frac {\partial ^{2}u}{\partial
x_{1}^{2}}}+{\frac {\partial ^{2}u}{\partial x_{2}^{2}}}+\cdots +{\frac {\partial ^{2}u}{\partial x_{n}^{2}}}\right)}{\displaystyle {\frac {\partial ^{2}u}{\partial t^{2}}}\;=\;c^{2}\left({\frac {\partial ^{2}u}{\partial x_{1}^{2}}}+{\frac {\partial ^{2}u}{\partial x_{2}^{2}}}+\cdots +{\frac {\partial ^{2}u}{\partial
x_{n}^{2}}}\right)}
where c is a fixed non-negative real coefficient.

Using the notations of Newtonian mechanics and vector calculus, the wave equation can be written more compactly as

{\displaystyle {\ddot {u}}=c^{2}\nabla ^{2}u}{\displaystyle {\ddot {u}}=c^{2}\nabla ^{2}u}
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https://en.wikipedia.org/wiki/Poincar%C3%A9_map

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In mathematics, particularly in dynamical systems, a first recurrence map or Poincaré map, named after Henri Poincaré, is the intersection of a periodic orbit in the state space of a continuous dynamical system with a certain lower-dimensional subspace, called the Poincaré section, transversal to the flow of the system. More precisely, one considers a periodic orbit with initial conditions within a section of the space, which leaves that section afterwards, and observes the point at which this orbit first returns to the section. One then creates a map to send the first point to the second, hence the name first recurrence map. The transversality of the Poincaré section means that periodic orbits starting on the subspace flow through it and not parallel to it.

A Poincaré map can be interpreted as a discrete dynamical system with a state space that is one dimension smaller than the original continuous dynamical system. Because it preserves many properties of periodic and quasiperiodic orbits of the original system and has a lower-dimensional state space, it is often used for analyzing the original system in a simpler way. In practice this is not always possible as there is no general method to construct a Poincaré map. “}}

https://en.wikipedia.org/wiki/Sofya_Kovalevskaya

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Sofya Vasilyevna Kovalevskaya (Russian: Софья Васильевна Ковалевская), born Sofya Vasilyevna Korvin-Krukovskaya (15 January [O.S. 3 January] 1850 – 10 February 1891), was a Russian mathematician who made noteworthy contributions to analysis, partial differential equations and mechanics. She was a pioneer for women in mathematics around the world
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https://en.wikipedia.org/wiki/Sophie_Germain

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When Germain’s correspondence with Gauss ceased, she took interest in a contest sponsored by the Paris Academy of Sciences concerning Ernst Chladni’s experiments with vibrating metal plates.[30] The object of the competition, as stated by the Academy, was “to give the
mathematical theory of the vibration of an elastic surface and to compare the theory to experimental evidence”. Lagrange’s comment that a solution to the problem would require the invention of a new branch of analysis deterred all but two contestants, Denis Poisson and Germain. Then Poisson was elected to the Academy, thus becoming a judge instead of a contestant,[31] and leaving Germain as the only entrant to the competition.[32]
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Also, story about Gauss!

https://en.wikipedia.org/wiki/Heat_equation

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Meaning of the equation
Informally, the Laplacian operator {\displaystyle \nabla ^{2}}\nabla ^{2} gives the difference between the average value of a function in the neighborhood of a point, and its value at that point. Thus, if {\displaystyle u}u is the temperature, {\displaystyle \nabla ^{2}u}{\displaystyle \nabla ^{2}u} tells whether (and by how much) the material surrounding each point is hotter or colder, on the average, than the material at that point.

By the second law of thermodynamics, heat will flow from hotter bodies to adjacent colder bodies, in proportion to the difference of temperature and of the thermal conductivity of the material between them. When heat flows into (or out of) a material, its temperature increases (respectively, decreases), in proportion to the amount of heat divided by the amount (mass) of material, with a proportionality factor called the specific heat capacity of the material.

Therefore, the equation says that the rate {\displaystyle {\dot {u}}}{\displaystyle {\dot {u}}} at which the material at a point will heat up (or cool down) is proportional to how much hotter (or cooler) the surrounding material is. The coefficient {\displaystyle \alpha }\alpha in the equation takes into account the thermal conductivity, the specific heat, and the density of the material.
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