Helium permeability in Latex

I've spent many hours now trying to find some quantitative data about the permeability of Helium through latex (as in a simple balloon).
If you've any numbers or a reference please let me know.
Thanks. I'm about googled out.
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dave martin wrote:

I remember that in 24 hours, the volume of a latex balloon filled with He would decrease by about one half.
You could ballpark the permeability from some hand calculations knowing the above, and buying a balloon to measure the uninflated membrane thickness and calculate the thickness from blowing it up to about 10 - 13 inches in diameter.
YOu might estimate the pressure from other means, but it is surely less than something like 2 atmospheres.
However, there is nothing like searching real reference books from the rubber industry instead of googling. Or, as has been suggested, contacting (even by phone, for heaven's sake) people working in the industry.
For a lot of things, Google just won't work because nobody will put up all the data for no fee and little reward for doing so. Free data is worth the same as free advice, for the same reasons.
Jim
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...
Actually, the reason for the request is to compare data obtained experimentally with independent sources. In this experiment students are given a He filled balloon & are required to determine the permeability of He in the balloon's membrane by measurements over time.

It is close to one atmosphere and depends on the degree of inflation. Graduate students doing this experiment take the pressure variation with balloon inflation into account. It doesn't make much difference.
Graduate students have also explored the variation of permeability's variation with "stretch".

No question about that.

I disagree. I believe that it is possible to have good data freely available.
I think that NIST or a similar agency should be responsible for publishing all data obtained through federally funded programs. While such data is publically available in principle it is not available in practice.
The marginal cost of such publishing would be small and the benefits to society would be large.
You said "Free data is worth the same as free advice, for the same reasons."
The data I refer to was obtained at relatively high cost to society and should be availible to those who paid for it in the first place.
Further, I argue that while out-of-copyright data is distributable there is little such data actually available. The difficulty here is that the intended finite time period of copyright protections are being destroyed in the interest of protecting commercial interests in trivialities like Mickey Mouse images.
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dave martin wrote:

I hope that someday you learn what copyright means.
Data itself isn't usually copyrighted.
The data in the telephone book is not copyrighted, but the arrangement of the data on the page is covered by copyright.
You can have data be proprietary.
But it is hard to publish data in any form and still complain that it is proprietary.
So, your comments about "public domain" data do not appear to be consistent with current law and practice.
You can extract data from tables of the "Handbook of ......." and freely use it or publish it. You cannot physically copy the table and republish it... without permission. You could reformat it(the data in the phone book), as many several different publishers reformat the data in telephone books, in areas like mine served by three different telephone companies.
"The Handbook of ....." doesn't own the data of the hundreds or thousands of individual researchers who conducted the labor to establish or measure the data.
Perhaps you are inflicting incorrect views of data and copyright on your students.
Jim
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Your comments are helpful.
I hope the following clarifies my thoughts on this topic.
The original intent of the copyright laws is clear; an author's rights to a particular expression should be protected for a finite time period after which that expression passes into the public domain.
I would like to see free public access to out-of-copyright materials like whole tables of data and figures like phase diagrams. Examples I can think of include images of some tables of data from the 1920 edition of the CRC Handbook of Chemistry and Physics or images of individual phase diagrams published in the 1920s.
Cosmetic rearrangement of data tables to avoid copyright protections seems disingenuous to me. While merely retyping a table in a different font or changing column spacing might be sufficient to satisfy a judge, the purpose of the effort was get around the copyright protection, not to create an original expression. The modified expression is clearly intended to be a derivative work.
Perhaps an argument can be made that placing a scanned image of a phase diagram on a publically accessible website is a sufficiently significant alteration of the original expression to be considered an original work. Can we successfully claim that enabling electronic accessibility to the data is a sufficent modification of the expression to warrant release from existing copyrights? Probably not.
Imagine that I make a machine that scans a phase diagram from a printed page, then vectorizes that data and publishes it on a website. Would or should this be OK from a copyright standpoint?
How far do I have to go in modifying the expression of a factual data collection to be legal or ethical?
The age of a particular expression is much easier question to answer. I believe the continual legislative extensions to the period of copyrights which are in effect granting permanent copyrights will ultimately harm society by permanently frustrating access to data which happens to be part of a collection.
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snipped-for-privacy@newarts.com says...

The thing about data is that it's not expression, it's facts. You can no more copyright the fact that water boils at 100deg C and freezes at 0deg C (a very simple example of a data table) than you could copyright the fact that WWII started in 1942.
Going back to the telephone book example from another poster, one of the baby-bells did attempt to assert copyright over the data in the white and yellow pages against competing phone books and reverse phone books. In court it was shown that the competitors were simply scanning the baby-bell's phone books and OCRing the data into a database to generate their phone books, mistakes, omissions, and all. The baby-bells lost, no copyright on data.
Marc
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Big oops below.

> the fact that WWII started in 1942.

If speaking of US involvement, Pearl Harbor was bombed on Dec 7, 1941 and war was declared the following week. Germany actually got their declaration in first. But the war actually began in 1939 with the invasion of Poland.
The big thing in 1942 was our navy trouncing the Japanese fleet at Midway. Some say that was the real turning point for the Japanese could never mount a seriously credible naval threat in the Pacific afterwards
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snipped-for-privacy@spam.edu says...

Yeah, big oops! Thanks.
Marc
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snipped-for-privacy@newarts.com (dave martin) wrote in message

Just a little comment about the extensions to copyright. While Disney ( for example ) certainly benefited from the recent extension, and may well have lobbied for it, that wasn't actually the purpose. In our interconnected modern world it seems and seemed logical that copyright protection should be standardised across countries. The US and most of Europe were at 50 years after the creator's death ( and companies had slightly different rules ). Germany however was at 70 years. When the EU, as part of the Single European Market project standardised copyright protections, it went to the German standard : 70 years. That then led to the US following suit. As I say above, while big corporations may have benefited, it was actually the spread of international trade and the WWW that led to the move to standardise.
There is also one of the odder stories from the UK Parliament. When the bill to standardise came to the House of Lords, one of the " Noble Members " ( I think it was Baroness Trumpington, a rather splendid woman now sadly departed. Think of one of Bertie Wooster's more terrifying Aunts.) reminded the House that the copyright for Peter Pan was actually held by Great Ormond Street Hospital for Children ( having been left to it in JM Barrie's will ). It had run out under the 50 year rule, and would be reinstated under the 70 year one. But it would then run out again shortly. She thought that this was quite clearly a bad idea, and so suggested that Peter Pan alone should have permanent copyright : and included in the speech that " As everyone knows when a child says they don't believe a fairy dies, and it is necessary for us to clap to keep that fairy alive. So I would ask the Noble Members who support this amendment to clap their approval " ( Languid drawls of " Hear Hear " and mass clapping. ) The amendment passed of course.
I saw in the news a few days ago somewhere that a new film of Peter Pan is held up because the Producers do not want to pay Great Ormond St : and while this permanent copyright only covers the Uk, they still want to distribute the film there when made.
Not a lot to do with materials in the above . Sorry.
Tim Worstall
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snipped-for-privacy@2xtreme.net (Tim Worstall) wrote in message

Thanks for the helpful comment..
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The quick and dirty way around copyright is to set up web space in a country that does not respect copyright laws thought a like minded local and post what ever you wish by sending it to him one CDROM and having him put it up on the web page. That method would not leave any tracks.
You could probably get away with renting the web space yourself and posting from here but there would by a trail to follow that lawyers could use to harass you.
Gordon

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snipped-for-privacy@newarts.com (dave martin) wrote:

Chainey M., Wilkinson M.C., Hearn J., Makromol. Chem. Suppl., 10/11, 435-446, 1985.
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