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welcome to mission control houston i'm

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here with dr peter voorhees the

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principal investigator of one of the

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experiments on the international space

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station uh this is a rather special run

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for this experiment because

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it's one where we brought the samples up

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on the spacex dragon vehicle and we'll

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be returning them home when the spacex

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dragon comes back on may the 25th so

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it's a very quick run and dr voorhees

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will tell us a little bit more about his

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experiment and why it's important for it

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to come back so quickly welcome to

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mission control thank you it's a

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pleasure to be here now you are here for

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some regular space station program

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science meetings about uh how we

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coordinate all the research on the

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station right that's exactly right that

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meeting starts in a little bit all right

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well we appreciate you taking time to

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join us today tell us a little bit about

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your experiment what do you call it yeah

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so uh what we're interested is in

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studying how the how these structures

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called dendrites evolve

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and dendrites everyone has experience so

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if you go out in the you look at your

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windshield in the winter and you'll see

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frost on your on on the windshield those

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little things are dendrites ice crystals

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are dendrites snow

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and what happens when you make materials

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is they're solidified from a liquid and

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when they solidify they form dendrites

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and the properties of the material are

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inherently linked to the way what these

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dendrites look like

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and what we're studying in space is how

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they evolve so that we can understand

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better how to control these dendritic

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structures on the ground and improve the

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properties of materials

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okay and how long have you been working

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on this kind of research

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oh my first experiment for nasa was

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proposed in 1985.

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and so you did some space shuttle

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experiments too right some space shuttle

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experiments as well so i've transitioned

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from the shuttle now into the space

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station era okay great and tell us the

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name of this particular experiment this

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is called coarsening and solid liquid

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mixtures

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okay and uh what are the

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advantages of learning how these

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dendrites work and solidify in

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microgravity yeah microgravity is really

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essential because what happens is when

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we do the experiments on the ground it's

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just like ice cubes in a drink the ice

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cubes settle to the top

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and so when we do the experiments on the

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ground the dendrites settle to the top

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and that's exactly not what we want we

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want them to be uniformly distributed in

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the liquid

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and so in space there's the absence of

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gravity and they stay approximately

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fixed in space and we can watch these

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things evolve

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in in during the experiment without

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having them settle okay now what

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material are you working with

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the material we're using is lead tin

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this is commonly called solder

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but the nice thing about lead tin is

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that it melted a very low temperature

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it's only 185 degrees centigrade so it's

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easy to do the experiments in space

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okay great the furnace only takes 11

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watts of power all right and so

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again

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you've got a number of these uh

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experiments and samples that have been

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worked on the space station already

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that's right this is a little bit

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different because it went up and it's

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coming back very quickly why is that

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important that this this is one of the i

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think the real highlights of this

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particular mission in the sense that we

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can send the experiments up have them

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done and returned quickly because what

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happens is that the samples degrade once

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they're solidified after they're

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solidified

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and it makes the analysis of the samples

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that much more difficult if we have to

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wait a long period of time before they

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come back

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so the ability to retrieve the samples

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very very quickly is really a really

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real uh plus for us okay and so these

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samples are going to come back on uh may

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the march the 25th when do you expect to

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have them in your hands march the 28th

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wow that's pretty quick return yes after

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a splash down the pacific ocean and then

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they go to the total

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long beach and they take them out out of

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the out of the furnaces at long beach

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and put them into dry ice and send them

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uh to northwestern great and what kind

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of analysis do you do on these yeah what

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what we do when we get them back in the

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laboratory is that my students and

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postdocs will be working on cutting them

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up

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and looking at the insides of the

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samples to look at the dendrite

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structures

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and tell us a little bit more about the

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potential benefits to

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people here on earth from what we

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learned about this

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yeah it turns out that the the

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properties of materials let's say

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aluminum alloys that are used in

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bicycles or used in engine blocks are

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inherently linked to how the what these

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dendrite structures look like in other

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words what these christmas christmas

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tree-like structures uh look like

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and

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them

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then you would understand how to

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improve their strength improve their

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ability to withstand vibrations over

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long periods of time

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and so what we'll do is we'll take this

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information that we get from these

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experiments and use that in in codes

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that that will predict the properties of

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materials so i'm guessing this would

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apply to just about anything that's an

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alloy a mixture of metals absolutely

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that's right that's right there are

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about

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uh

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a billion trillion dendrites produced

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every day in the casting of steels and

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and and aluminum alloys that are used in

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virtually every material that you that

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every application you can think of and

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so it's inherently linked to a lot of

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the properties of these materials and of

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course launching things to space is

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pretty expensive and so we're not

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talking about making a factory to do

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these in microgravity but can you

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translate what you learn into improved

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processes for manufacturing

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that's precisely the whole idea we're

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not manufacturing in space but we're

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using the information to improve what we

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know about the processes and hence

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impact things that we do on the ground

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here in earth okay tell us a little bit

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about you i did you always know you were

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going to be doing research in space um

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no i didn't know when i when i did my

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phd of course i never thought i'd ever

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ever have the opportunity to do

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experiments in space it's just that uh

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the the microgravity environment

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provided by the iss or the shuttle is

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such a unique platform to do these

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experiments and you can act really focus

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on the important issues associated with

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material science in many cases by doing

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experiments in space so we know you're

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at northwestern in the chicago area now

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where are you from originally i grew up

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on stat in staten island new york it's a

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borough of new york city

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and spent some time at

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nist national institute of standards and

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technology in gaithersburg and then

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moved to northwestern

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now almost 20 years 25 years ago so i've

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been there ever since are you missing

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the cold weather yet oh i couldn't

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believe how warm it was when i arrived

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yesterday it's like 88 degrees

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all right well dr peter voorhees thank

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you so much for joining us here in

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mission control today explain a little

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bit about your experiment uh good luck

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in your meetings here and on your

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travels back home and we look forward to

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hearing the results of uh how this

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unique opportunity to get your

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experiment up and down quickly works out