Month: February 2016

Biology: protists: diatoms

The tutor mentions a few points about diatoms. In my Feb 4 post I introduced protists, which constitute a kingdom of eukaryotic, mainly single-celled organisms. Protists are divided into plantlike and animal-like ones. Diatoms, from phylum Chrysophyta, are among the

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Math & Comp Sci: Graph theory: what is an elementary subdivision?

The tutor shows the easy concept, from graph theory, of elementary subdivision. An elementary subdivision on a graph replaces one edge by two, with a new vertex installed between them. Consider the following two graphs: Graph 1 Graph 2 Graph

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Math & Comp Sci: Graph theory: what is a cut set?

The tutor defines cut set with a couple of examples. When one imagines a cut set, one imagines removing edges from a graph, but not the vertices they connect. In this context, we are thinking of undirected graphs. A cut

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Physics: models of the atom

The tutor reviews the progress of thought about atoms through the ages. Democritus, a Greek philosopher living around 400 BC, is credited as the first promoter of the concept of the atom. He proposed that all matter consists of tiny,

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Math: graph theory: a textbook example

The tutor offers a solution to a textbook graph theory question. On page 556 (Grimaldi) is the following question: Let G be a loop-free connected undirected 3-regular graph (every vertex has degree 3), such that |E| = 2|V| – 6

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Physics: friction force: how far will the curling stone glide?

The tutor gives an example with friction force. I’ve never been curling. Even so, I can imagine the following question resonates with many curlers and spectators: A curling stone is released at 1.2m/s. If the coefficient of friction between the

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Physics: calculating force of friction

The tutor shows a basic example of calculating friction. The force of friction, Ff, on a flat surface is given by Ff = μFN where μ = coefficient of friction (often looked up from a table, or given) FN =

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Math: counting: pigeonhole principle, yet another example

The tutor attempts to strip the pigeonhole principle to bare wires with a simple problem. I discussed the pigeonhole principle in my May 23/14 and Oct 29/14 posts. The concept is that, with n+1 pigeons going to n pigeonholes, one

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Math & Comp Sci: Symbolic Logic: contradiction

The tutor defines, in the context of symbolic logic, contradiction, with a couple of examples. For those new to symbolic logic, my previous post leads back to others that will fill the gaps. A contradiction is a compound statement that

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Math & Comp Sci: Symbolic Logic: another tautology

The tutor follows up about tautology with another example. For grounding about the symbols, etc, readers may want to refer to my Feb 12 post. In my Feb 13 post I defined tautology with a simple example. Today, I’ll give

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