Ask a physicist anything. (5)

[mzungu]

It seems to me you want to apply "steady state" to things that are not state variables.

By all means please enlighten me. After all I did express ignorance on the subject and will be more than happy to learn if you would care to explain it to me?

Where is the physicist when you most need him; Out on a tea break again?

 

[Wiccan_Child]

By all means please enlighten me. After all I did express ignorance on the subject and will be more than happy to learn if you would care to explain it to me?

Where is the physicist when you most need him; Out on a tea break again?

Walking my dog, actually

 

[selfinflikted]

Royalty is like English cooking: almost always unappetizing, hard on the digestion, and leaving a bad smell.

[bless and do not curse][bless and do not curse][bless and do not curse] NOE.

2 Reasons:

1) bangers and mash. (Yum!)

2) Bubble and squeak. (Yum!)

That is all.

 

[mzungu]

I don't believe so.

Thermodynamically, a steady state is one which is largely consistent over time: its pressure, volume, temperature, chemical potential, etc, are constant. But this doesn't mean that it can be dynamic.

I see, but, When you say through time it sounds very vague. What about entropy? If what you say is correct then how did the big bang arise? Unless of course by time you mean a specific time?

I could look it up but that would spoil the fun of asking a physicist anything rather than going over to physicsforum.com

 

[Wiccan_Child]

I see, but, When you say through time it sounds very vague.

Well, time is a variable, and if pressure, volume, temperature, etc, don't change as that variable increases, then the system is in a steady state.

What about entropy?

Entropy, as a rule, tends to a maximum. There's nothing to stop it being constant, however, especially if it's already reached its maximum.

If what you say is correct then how did the big bang arise? Unless of course by time you mean a specific time?

Well, not all systems must be in a steady state. I could easily create a system, then inject some more air into it, thus changing the chemical potential and upsetting the steady state.

Plus, the Big Bang is/was a singularly unique event, it's not even clear that the laws of thermodynamics would apply.

I could look it up but that would spoil the fun of asking a physicist anything rather than going over to physicsforum.com

Bah, they steal all my fun!

Also I noticed a typo in my previous post; it should say "But this doesn't mean that it can't be dynamic."

 

[mzungu]

Also I noticed a typo in my previous post; it should say "But this doesn't mean that it can't be dynamic."

Good gad man! off you go to my study. Six of the best should straighten things up.

 

[GrowingSmaller]

Why do things "behave" rather than e.g. float upwards?

I know theres gravity etc, but heck, why bother with regularised patterns of behaviour?

 

[Wiccan_Child]

Why do things "behave" rather than e.g. float upwards?

I know theres gravity etc, but heck, why bother with regularised patterns of behaviour?

Because particles interact with other particles in the same way - an electron will interact with an antiquark in the same way as any other electron. So, regular behaviour is whether two particles are interacting in the same way. Electricity works because electrons are all interacting with the wire in the same way.

But why do they interact in that particular way, and why always in the same way? No idea

 

[mzungu]

Because particles interact with other particles in the same way - an electron will interact with an antiquark in the same way as any other electron. So, regular behaviour is whether two particles are interacting in the same way. Electricity works because electrons are all interacting with the wire in the same way.

But why do they interact in that particular way, and why always in the same way? No idea

Perhaps because they abide by the laws of the constants? And what of the constants?

NATURE DID IT CASE CLOSED
​

 

[TheReasoner]

Another serious question for you...

Some archaea live in temperatures well in excess of 100°C.
Yet DNA melts (the G-C and A-T hydrogen bonds break) at well below this.

So: How can archaea live in such conditions?

 

[mzungu]

Another serious question for you...

Some archaea live in temperatures well in excess of 100°C.
Yet DNA melts (the G-C and A-T hydrogen bonds break) at well below this.

So: How can archaea live in such conditions?

Here in an excerpt from a very interesting site:

[FONT=verdana, geneva, arial, helvetica]Thermophiles are adapted to temperatures above 60 degrees in a variety of ways. Often thermophiles have a high G + C content in their DNA such that the melting point of the DNA (the temperature at which the strands of the double helix separate) is at least as high as the organism's maximum T for growth. But this is not always the case, and the correlation is far from perfect, so thermophile DNA must be stabilized in these cells by other means. The membrane fatty acids of thermophilic bacteria are highly saturated allowing their membranes to remain stable and functional at high temperatures. The membranes of hyperthermophiles, virtually all of which are Archaea, are not composed of fatty acids but of repeating subunits of the C5 compound, phytane, a branched, saturated, "isoprenoid" substance, which contributes heavily to the ability of these bacteria to live in superheated environments. The structural proteins (e.g. ribosomal proteins, transport proteins (permeases) and enzymes of thermophiles and hyperthermophiles are very heat stable compared with their mesophilic counterparts. The proteins are modified in a number of ways including dehydration and through slight changes in their primary structure, which accounts for their thermal stability.

Read more here: Nutrition and Growth of Bacteria
[/FONT]

 

[Wiccan_Child]

Another serious question for you...

Some archaea live in temperatures well in excess of 100°C.
Yet DNA melts (the G-C and A-T hydrogen bonds break) at well below this.

So: How can archaea live in such conditions?

Presumably, either their DNA is held together by more than H-bonds (perhaps the enzymes roaming their DNA include a sticky 'held together stronger' one). Moreover, in eukaryotes at least, DNA is usually split into a tangle of single strands anyway - it's only during mitosis that they come together in the well-known X's.

Plus, what mzungo said.

 

[TheReasoner]

Presumably, either their DNA is held together by more than H-bonds (perhaps the enzymes roaming their DNA include a sticky 'held together stronger' one). Moreover, in eukaryotes at least, DNA is usually split into a tangle of single strands anyway - it's only during mitosis that they come together in the well-known X's.

Plus, what mzungo said.

actually it isn't split apart into single strands. It's still in the double helix. Or is that what you meant? It's only melted during some mutations (for example dimer formation between A and T), repair, replication and transcription. True though, they don't merge into the x-s until mitosis.

I still don't see how DNA consisting of even pure Cs and Gs could withstand such high temperatures. 120 C? That's really high. I suppose if you had some nucleosomes attached to the DNA at all times which were capable of holding the strands together even at such heats it might work. Still leaves a lot of questions I think. Hm.

It's not part of my curriculum, but it's fascinating I think.

 

[Wiccan_Child]

actually it isn't split apart into single strands. It's still in the double helix. Or is that what you meant? It's only melted during some mutations (for example dimer formation between A and T), repair, replication and transcription. True though, they don't merge into the x-s until mitosis.

I meant single chromosomes, as opposed to the classic X-shape.

I still don't see how DNA consisting of even pure Cs and Gs could withstand such high temperatures. 120 C? That's really high. I suppose if you had some nucleosomes attached to the DNA at all times which were capable of holding the strands together even at such heats it might work. Still leaves a lot of questions I think. Hm.

It's not part of my curriculum, but it's fascinating I think.

It could evolve like that, though - higher and higher temperatures mean these 'repair' enzymes are working more and more, until they're always working to keep DNA in check.

I found this article which goes into the chemistry somewhat of thermophiles. With regards to DNA, it's kept stable with:

• Higher levels of salts such as potassium and magnesium which prevent the phosphodiester bonds from degrading
• The DNA of some thermophiles is supercoiled - the double-stranded DNA is further twisted which confers heat stability.

 

[Naraoia]

And by appointment too!

FTW.

I was actually out celebrating the royal wedding at a barbecue while we all wore our poshest suits and dresses. Fun times!

I'm so glad I was home at the time of the wedding. I don't even want to imagine St Andrews on the day

Another serious question for you...

Some archaea live in temperatures well in excess of 100°C.
Yet DNA melts (the G-C and A-T hydrogen bonds break) at well below this.

So: How can archaea live in such conditions?

I have a vague recollection that they keep their DNA in a very compact format, so the strands can't physically separate... but maybe that was Deinococcus Basically, my only guess is "packaged with the right proteins".

Here in an excerpt from a very interesting site:

[FONT=verdana, geneva, arial, helvetica]The membranes of hyperthermophiles, virtually all of which are Archaea, are not composed of fatty acids but of repeating subunits of the C5 compound, phytane, a branched, saturated, "isoprenoid" substance, which contributes heavily to the ability of these bacteria to live in superheated environments.
[/FONT]

I'd like to remind the world that archaea are still not bacteria.

 

[TheReasoner]

I have a vague recollection that they keep their DNA in a very compact format, so the strands can't physically separate... but maybe that was Deinococcus Basically, my only guess is "packaged with the right proteins".

That'd have to be my guess. And they do have packaging proteins, histones of a sort. So I guess that's it, really.

Archaea really fascinate me. They're like Scwartzenegger and Chuck Norris combined in a single cell organism. (well, or rather the people/machines those actors portray) Wherever and whatever no-one else can survive they thrive in. Heat stuff up? Still going strong. Cool stuff down? No problemo!

Of course I find bacteria fascinating too. Just consider extremely toxic environments like poisoned pools left behind after a mine has run dry. Especially older mines where really toxic chemicals were used. Bacteria - and even higher organisms - adapt and find a way to make things we thought were terminal to any and all life a source of food instead.

Just when you think you've nailed down something that can kill them or they can't live off of evolution comes along and says "nope. I can do that. Hang on a couple of generations while I do my thing!"

Fascinating stuff

 

[mzungu]

Of course I find bacteria fascinating too. Just consider extremely toxic environments like poisoned pools left behind after a mine has run dry. Especially older mines where really toxic chemicals were used. Bacteria - and even higher organisms - adapt and find a way to make things we thought were terminal to any and all life a source of food instead.

Just when you think you've nailed down something that can kill them or they can't live off of evolution comes along and says "nope. I can do that. Hang on a couple of generations while I do my thing!"

Fascinating stuff

That's because life always finds a way!

 

[Gracchus]

That's because life always finds a way!

No it doesn't!

 

[mzungu]

No it doesn't!

Microbes have been found living kilometres underground! Yes sir! Life indeed does find a way! The only way to actually totally rid this world of all life is to burn the whole planet like it will happen when our sun becomes a red giant.

 

[Gracchus]

Microbes have been found living kilometres underground! Yes sir! Life indeed does find a way! The only way to actually totally rid this world of all life is to burn the whole planet like it will happen when our sun becomes a red giant.

So it doesn't always find a way, unless extinction is a "way".