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Dmitry Shintyakov
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It takes twice the man to ride half the bike
It takes twice the man to ride half the bike

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Сrystals of a compound I discovered experimentally.

It was prepared by mixing warm saturated solutions of copper beta-alaninate and urea. Unknown product is less soluble than its constituents, and forms violet crystalline precipitate. Crystals on the photo were obtained by recrystallization of the original precipitate. Unlike pure copper beta-alaninate, which is extremely prone to dehydration, this urea adduct is completely stable. Apparently, it contains no water of crystallization.

Crystals have very dark, violet-blue color, characteristic for amino-complexes of Cu(II). Their shape is very distorted octahedron, with all three axes different. This suggests orthorhombic crystal system, though I am not sure.

Regarding its chemical composition, my guess is:

Cu(βAla)₂·xCO(NH₂)₂

where βAla is beta-alanine anion, C₃H₆NO₂, and CO(NH₂)₂ is urea. From the experimental stoichiometry data, x is probably 1 or 2.

Speaking of the nature of the compound, I think that it is a molecular adduct (held by hydrogen bonds) rather than a product of reaction, because it formed very quickly and in mild conditions.

Growth time of the biggest crystals is about 10 days. They grow slowly because of relatively low solubility of the compound, around 10g/100ml
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Recently I bought a jar of beta-alanine in the sport food shop, and made a few experiments with it. Here is one of them: copper salt of beta-alanine.

The compound was prepared by reacting copper hydroxycarbonate with beta-alanine in water solution. It is very well soluble in water. Solution has dark blue color characteristic for amino complexes of copper. It is much darker then coper sulfate solution, saturated solution is almost black.

I don't know the exact formula. From the common sense, I expect it to be chelate, Cu(βA)₂·xH₂O, where βA is β-alanine anion, C₃H₆NO₂.

However, two equivalents of β-alanine was not enough for complete dissolution of copper hydroxocarbonate, even after prolonged heating. Between 3 or 4 equivalents required in my experiment. Two explanations are possible: either the compound has more β-alanine molecules (possibly acting as ligand), or it is not stable in water solution without excess of β-alanine.

Crystal was grown using slow evaporation method, for 2 weeks approximately.

It has very deep blue-violet color, which is not reproduced well by a monitor (can't get that violet tinge even after adjusting colors).

Unfortunately, it is very unstable on air: dehydration starts in few minutes. At the end of the photo session, it already developed small white spots on the surface. This suggests that it has many molecules of crystalline water.
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This scarf with cellular automaton pattern is seamless: after many steps initial pattern returns to its original state, (flipped, because it is Mobius loop)
Here's another piece from the Bridges 2018 art gallery, a scarf with a cellular automaton pattern by Elisabetta Matsumoto, +Henry Segerman, and Fabienne Serriere. This one looks to be Rule 150. The part that raises this above the level of "just another use of cellular automata to create decorative patterns", though, is that they carried out a search for an initial seed pattern that would return to itself, in reversed form, at the right length to form a nice Möbius-band scarf. So (except possibly for any unevenness in actually fabricating the join) the pattern is seamless.
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Crystals of a rare hexagonal shape.
The compound is a double salt, guanidinium aluminium sulfate hexahydrate:

C(NH2)3Al(SO4)2*6H2O

These are not final crystals, just nice samples obtained during recrystallization of the crude compound. I am going to grow larger samples later.

I learned about this compound from this page: http://www.myttex.net/forum/Thread-Solfato-di-guanidina-e-alluminio-III-esaidrato-Sintesi
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I prepared this compound for another experiment, but during recrystallization step noticed that it easily forms large crystals, so used part of the solution to grow a single crystal.

The formula is (probably) Na3[Al(C2O4)3]*5H2O

Some sources state that it has 3 molecules of H2O, but it seems to be a mistake due to potassium analog.

It is aluminium analog of sodium ferrioxalate

which has very similar though more vividly colored crystals.

Again, similarly to its ferric sibling, it has high solubility exceeding 50g per 100ml and grows easily, but is not stable on air: after few days of exposure to air, it would lose transparency and turn white. I am currently storing it under a layer of liquid paraffin.

Crystal size is about 4cm along the longest face, growing method was slow evaporation (I rarely have success with other methods), growth time is less than 2 weeks.

Preparation

To prepare this compound, I dissolved Al metal in NaOH solution, then added stoichiometric amount of oxalic acid and heated while stirring until complete dissolution of precipitate. Total equation is:

2 Al + 6 NaOH + 6 H2C2O4 = 2 Na3[Al(C2O4)3] + 6 H2O + 3 H2(g)
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A month ago there was a large bicycle parade in my city.
Today I have discovered that someone painted me!

Artist name is Mikhail Bazarov (Михаил Базаров)
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Oh, that's clever.

I've got interested in Minkowski geometry recently, after reading Greg Egan's "Dichronauts", but never realized that fractals could have negative dimensions in it.

It is quite obvious in the hindsight though: the more "jagged" the path is, the smaller its total pseudo-length.
Here's a funny way to get negative fractional dimensions. We look at time-like curves in 2+1D Minkowski space-time. So using special relativity and looking at the temporal dimension: how much the proper elapsed time scales with temporal resolution. In other words, how much time passes for you as you get closer and closer to approximating the trajectory in question.

If the path length gets longer with increasing resolution then your velocity gets closer to that of light and your elapsed time decreases, this can give a negative dimensional curve:

https://tglad.blogspot.com.au/2017/08/negative-dimensional-curves.html

The pic shows the Minkowski time-like equivalent of a Levy C curve. As the dimension decreases the spatial curve gets noticibly smoother. However, the motion itself isn’t really getting smoother, it is just getting closer to light speed, so you can’t see the variation as easily, but the boosts are actually getting ‘rougher’.

It is interesting that the case where the dimension is 0 also seems to be the case where it is smooth. Is it really two circular arcs in the 0+0D case? Is this significant? Or is it obvious?

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A good one.
I spent half of the day and five pages of paper, but solved it without hints. Retrospectively, it was not that hard though.
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Take A and B, big square matrix with iid normally distributed complex entries.
Let F(t) = A+0.1*exp(2*pi*i*t)*B
Plot the eigenvalues of F(t) in the complex plane as t varies from 0 to 1 over 4 seconds (roughly).

BTW Note that even though the animation has a period of 4 seconds, the individual points follow paths that often take longer than 4 seconds to close the loop.

Motivated by +Terence Tao and Vu: https://projecteuclid.org/euclid.acta/1485892530
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Crystals of lithium ferric EDTA, a lithium analog of this compound: https://photos.app.goo.gl/iTWDMDqw531YZrFg2

I obtained these crystals experimentally and have no literature references.

The formula is Li[Fe(edta)], where edta stands for ethylenediaminetetraacetate ligand.

Compared to the sodium analog, lithium compound has the same dark brown color, but crystal shape is very different, crystals being almost cubic. Solubility is significantly higher, around 51 g/100ml at room temperature.

Crystals are stable on air.

Preparation: take 1 mol of EDTA acid suspended in water (it has low solubility), add 1 mol of LiOH, then 1 mol of Fe(OH)3 and heat with stirring until complete dissolution of solids.
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