Recent comments in /f/askscience

ZakeDude t1_jbrvfx6 wrote

Reply to How do impurities affect superconductivity? by Infferno122

Really depends on the impurity and the material.

Some increase or decrease the critical temperature. Some affect the critical magnetic field (see Ta or Ti in Nb3Sn) by changing the normal state resistance. You can also increase the amount of current that can pass through the material by increasing the number of microstructural features -- smaller grains, say, or bits of non-superconducting material.

Source: working on a degree in superconducting wires

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SwitchingtoUbuntu t1_jbrq3ya wrote

Reply to How do impurities affect superconductivity? by Infferno122

It totally depends on the superconducting metal and the impurity.

Superconductors have a tendency of "proximatizing" other materials, making them superconducting by being near to them.

For example, a 1nm thin film of a normal metal on top of a 100nm thick film of superconducting Niobium will likely superconduct.

Similarly, some superconducting metals when deposited with non-metals actually can become better superconductors. For example, Aluminum that has a little oxygen in it (granular aluminum, or dirty aluminum) actually has a higher superconducting critical temperature than clean aluminum.

That said, if you get too much copper or gold in your superconducting film, it just won't superconduct at all.

The interactions are all really complex and involve the coupling between the lattice of the superconducting metal and the charge carriers.

Look up "BCS theory" for more info!

Source: PhD working in superconducting qubits.

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Elladan71 t1_jbrnlfg wrote

Reply to comment by dave-the-scientist in I just learned that the known shortest DNA in an “organism” is about 1700 base pairs in a certain virus. Is there a minimum amount of “code” required for an organism (or virus) to function in any capacity? by mcbergstedt

I think you're on the right track, here. A virus needs a cell to function. A bacterium needs a nutrient-rich environment to function. An animal needs gravity oxygen, water, and food. Plants and animals are *environments for other kinds of life, so it's no wonder that the question is difficult to answer. When asked in the other direction, you're confronted with whether the Earth itself is alive.

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Elladan71 t1_jbrmf6j wrote

Reply to comment by TheNorthComesWithMe in I just learned that the known shortest DNA in an “organism” is about 1700 base pairs in a certain virus. Is there a minimum amount of “code” required for an organism (or virus) to function in any capacity? by mcbergstedt

This is undeniable. But when we're talking about definitions, aren't we talking about human constructs, attempts to approximate truth? Isn't it the same impulse that birthed the scientific method? Drawing lines between things is *useful!

Plus, anything that provides conversation like this thread is worth talking about, if you ask me.

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