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15 ore fa · In quantum mechanics, perturbation theory is a set of approximation schemes directly related to mathematical perturbation for describing a complicated quantum system in terms of a simpler one. The idea is to start with a simple system for which a mathematical solution is known, and add an additional "perturbing" Hamiltonian representing a weak disturbance to the system.
15 ore fa · 1923 - Roscoe Dickinson and Albert Raymond, and independently, H.J. Gonell and Hermann Mark, first showed that an organic molecule, specifically hexamethylenetetramine, could be characterized by x-ray crystallography. [64] [65] 1923 - William H. Bragg and Reginald E. Gibbs elucidated the structure of quartz.
15 ore fa · Modeling indicates that the transient condensed water films on the surface should be transported to lower depths (≈10 m) potentially transporting nitrates, where subsurface microorganisms could thrive. In contrast, phosphate, one of the chemical nutrients thought to be essential for life, is readily available on Mars. Low pressure
