September 8th, 2020

лошадь, диаграмма, Фейнман

Дележка арбуза по-научному

How to fairly share a watermelon: https://arxiv.org/abs/2009.02325

Timoteo Carletti, Duccio Fanelli, Alessio Guarino
Geometry, calculus and in particular integrals, are too often seen by young students as technical tools with no link to the reality. This fact generates into the students a loss of interest with a consequent removal of motivation in the study of such topics and more widely in pursuing scientific curricula [1-5]. With this note we put to the fore a simple example of practical interest where the above concepts prove central; our aim is thus to motivate students and to inverse the dropout trend by proposing an introduction to the theory starting from practical applications [6-7]. More precisely, we will show how using a mixture of geometry, calculus and integrals one can easily share a watermelon into regular slices with equal volume.
лошадь, диаграмма, Фейнман

Шикарная модележка последовательностей МРТ

A Beginner's Guide to Bloch Equation Simulations of Magnetic Resonance Imaging Sequences: https://arxiv.org/abs/2009.02789
ML Lauzon
Nuclear magnetic resonance (NMR) concepts are rooted in quantum mechanics, but MR imaging principles are well described and more easily grasped using classical ideas and formalisms such as Larmor precession and the phenomenological Bloch equations. Many textbooks provide in-depth descriptions and derivations of the various concepts. Still, carrying out numerical Bloch equation simulations of the signal evolution can oftentimes supplement and enrich one's understanding. And though it may appear intimidating at first, performing these simulations is within the realm of every imager. The primary objective herein is to provide novice MR users with the necessary and basic conceptual, algorithmic and computational tools to confidently write their own simulator. A brief background of the idealized MR imaging process, its concepts and the pulse sequence diagram are first provided. Thereafter, two regimes of Bloch equation simulations are presented, the first which has no radio frequency (RF) pulses, and the second in which RF pulses are applied. For the first regime, analytical solutions are given, whereas for the second regime, an overview of the computationally efficient, but often overlooked, Rodrigues' rotation formula is given. Lastly, various simulation conditions of interest and example code snippets are given and discussed to help demonstrate how straightforward and easy performing MR simulations can be.
Comments: 7 pages of text, 2 appendices, 1 figure, 10 code snippets, 25 references