On Thu, Sep 20, 2012 Anders Sandberg <span dir="ltr"><<a href="mailto:anders@aleph.se" target="_blank">anders@aleph.se</a>></span> wrote:<br><div class="gmail_quote"><br><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote">
<blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote">>>Well, if molecule X and molecule Y got together and produced
molecule Z and you find Z then you can deduce that X and Y must
have existed and been close together at a previous time<br></blockquote></blockquote><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote"><br></blockquote>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">
> But if W and U can also react and make Z? </div></blockquote><div><br>If W and U are molecules not normally found in the brain, or if they were found in the brain but judging by the surrounding structure it didn't make sense for them to be at that particular spot then you can rule them out; and even if it is reasonable for them to be there you still might be able to make a good educated guess because the XY and WU reactions probably don't proceed at the same rate, so one is more likely than the other. However if they do both proceed at the same rate and its equally reasonable for all 4 to be found at that point and if X,Y,W and U are important molecules then you could have a serious problem.<br>
</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">> That is where the entropy
comes in. </div></blockquote><div><br>Yes, entropy seems to sneak its way into just about everything. Even if the universe was as deterministic as Newton thought it was if XY and WU both made Z at the same rate then you could predict the future but you couldn't figure out what the past was. <br>
</div><div><br></div><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div bgcolor="#FFFFFF" text="#000000">> Now you don't know whether there was XY or WU.</div>
</blockquote><div bgcolor="#FFFFFF" text="#000000"><br>If you used the plastic infusion method one of those 4 chemicals was probably introduced by you. <br><br><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote">
> Receptors can be bound or unbound: this changes due to synaptic
potentiation. It likely matters a lot to get the right number, since
this partially sets the synaptic strength. But if freezing makes
some unbound you cannot deduce the original number, unless the
unbinding has some very simple regularities. <br></blockquote><div><br>Yes simple regularities is the name of the game, or if not simple at least not astronomically complex as with turbulence.<br></div><div class="im">
<br></div><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote">
> There are thousands of different chemicals around, not all react by
fixing. And some things might not fix properly, like g-proteins or
high energy compounds. <br></blockquote><div class="im">
<br>Yes there are lots of unknowns, but the question is which method has the fewer unknowns, plastic or freezing? <br><br>
<blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote"><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote">
>> The real enemy is chaotic fluid flow,
turbulence.<br></blockquote><blockquote type="cite">
</blockquote>> You *really* mean fluid flow, and not just as a metaphor?! <br></blockquote><div><br>Yes, if the brain always acted as a solid there really wouldn't be any problem and preserving it would be easy, or at least easier, but we know that isn't the case and after death the parts of it refuse to stay put because they are battered around by fluid; we don't want that fluid flow to be chaotic. <br>
</div>
</div><br><blockquote style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex" class="gmail_quote">> But the
Reynolds numbers in tissues are *far* into the laminar! There *is no
turbulence*, except maybe in some bigger blood vessels. <br></blockquote><div><br>if true then that is very good news for both methods.<br><br> John K Clark<br><br><br> <br></div><br></div></div>