Paul Sutton @zleap@qoto.org

2021-03-26, 19:05, Friday

I promised a few paragraphs about x-ray diffraction, so here it goes. This is mostly unedited because I'm tired and lazy.

Basically, light has a property to undergo what's called diffraction: shine a laser beam on a grated piece of plastic and beam will split into an uneven number of new beams. Using this pattern and some trigonometry you can calculate the wavelength of light if you know how fine the grating is and the angle between beams. This works only when wavelength is a few times smaller than the grating size.

Now, the important bit is that atoms in crystal sort of work like grating. Light reflects from different layers of atoms differently and this forms the same diffraction pattern. Since the distance between atomic layers determines the structure of the crystal, we can now measure it using light and some math called Bragg's law. The only thing we need is a light source with fixed, well-known and very small wavelength. Now, the "grating" in our case is approximately 2-4*10^-10 m, or 2-5 angstrem.

Conveniently, metallic anode, when put in a vacuum and under high voltage, emits high energy photones, generally of a fixed wavelength, corresponding to the valent electron's excited state. And if we use copper, this wavelength is roughly 1.51 angstrem, which is about what we need.

Now that all elements are in place, we just need to build a complex machinery that will hold our sample, put a piece of copper under a few kilovolts, cool it down simultaneously, while also rotating a detector to capture light intensities under a range of angles. Different lattices will give different diffraction patterns, and one can be calculated from another.

And this is more or less how x-ray diffraction works.

#qotojournal #science #xrd #materialsciences

Leaked Apple Training Videos Show How It Undermines Third-Party Repair https://www.vice.com/en/article/5dbv83/leaked-apple-training-videos-show-how-it-undermines-third-party-repair

There is NO training on Sunday 17th October. Trojans Rookie camp starts on 24th October.

http://torbaytrojans.co.uk/

Ageing Well Festival 2022

https://www.torbaycdt.org.uk/whats-on/

@zleap 12 yo +/- 1

@icedquinn @lucifargundam @TechUr

Videos from our recent LibreOffice Conference 2021 are now also available on PeerTube! Check them out here: https://peertube.opencloud.lu

@icedquinn

The quote actually originated with Rutherford and was later repeated in another form by Einstein, feynman adopted it as a technique.

Rutherford said "it should be possible to explain the laws of physics to a barmaid."

Einstein said, while referencing Rutherford in a conversation with de Broglie in france: "that all physical theories, their mathematical expressions apart ought to lend themselves to so simple a description that even a child could understand them."

So Einstein coined the phrase and idea in reference to a child.

The Feynman technique was explicitly inspired by Einstein and is a 4 step technique:

1) Pick the subject of interest
2) explain the concept as if to a 6th grader
3) Identify the holes in your understanding
4) Study the parts you couldnt explain simply

While the Feynman technique is based off observations in Feynmans study habits he never taught the technique formally nor did he define it.

@lucifargundam @TechUr

Second beta of Krita 5 released! https://krita.org/en/item/second-beta-for-krita-5-0/ Please help us test it and report those pesky bugs!

@zleap @feditips i mean i don't like facebook especially but it was a frickin' mistake in the algorithm
They reverted it already c'mon

Huh, it’s like he’s above the law! Like he’s a Prince or something 🤔 https://twitter.com/i/events/1447485253862387715

Exciting EU study on open source software:

> strongly contributes to GDP
> avoids vendor lock-in
> reduces costs & maintenance
> drives state-of-the-art tech
> fosters competition, interoperability & tech-neutrality

https://digital-strategy.ec.europa.eu/en/library/study-about-impact-open-source-software-and-hardware-technological-independence-competitiveness-and