Wednesday, March 31, 2010

The Dreamliner did o.k.

Following up on Monday's post, the press release from Boeing states:

"The initial results of the ultimate-load test are positive. More extensive analysis and review are required before the test can be deemed a success."

I can certainly understand the need for more "analysis and review", as composites are not simple materials to understand. At the very least, it doesn't appear that the wing snapped in two, so that's a good thing.

More on DNA Patentability

I've a little more time today to state my opinion on Monday's court decision overturning "DNA Patents". I'm not going to go look at the details - others can do that far better than me. I want to make a much broader based observation that goes far beyond the patents at hand.

What I see here is an attempt to maximize today's gain and forget about the future.

The patents at issue are about testing for the existence of two genes in women. If the women has the genes, she is at much greater risk for breast cancer. The test is quite expensive ($3000) and typically not covered by insurance. Invalidating the patents would open the area up to competition, lower test prices, and more women having invaluable knowledge that could save/extend their lives.

My take however, is that this test exists only because of the patent system we have in place. Given the advanced state of modern analytical technology, keeping the test and the chemicals used in it as a trade secret is pretty much impossible. Development of the test required a risky investment in research and development that may have not paid off at all. Since there are no competitive, alternative tests available, it certainly appears that these patents have stifled innovation, a common complaint against patents in general, but keep in mind that this is only temporary and that the patents will someday expire. Overturning these patents in specific and "DNA Patents" in general would do far more to stifle innovation in these areas and the stifling would be permanent. The long-term loss would in my mind negate any short-term gain. The judge in case is basically saying "It's great that our patent system has gotten us this far. Now let's change the rules so that we can take advantage of these advances today. Tomorrow's advances ? Well, don't ask me about that."

You can easily see this attitude reflected in larger society as well. Here are a couple of divergent examples:

20 years ago, my wife and I first lived settled in Woodbury Minnesota, a suburb on the eastern edge of St. Paul. At that time, only a few thousand people lived there. The town was originally a township (36 square miles) but 90% it or so was farmland. The residential areas continued to expand east into the farmlands, bringing commercial development, a pattern that continues to this day. My wife and I noticed an interesting pattern. Many of the new inhabitants after a few years had gone by would start to complain that the city was continuing to grow, that the growth was too much and that it should be stopped. We summarized this as "Everyone wants to be the last person to move into Woodbury," but it is just a variation of "the system is great today; let me take advantage of what others have done before, and change the rules so that others in the future can't.'

I also see this reflected in many political arguments of the ilk "I'm not going to use that _________________ (insert any construction project using public funds). Why should I pay for it?" The irony of course is most of the people stating this are graduates of public schools that they never paid for, users of public roads that they never paid for...Again, it's a variation of the argument "the system is great today; let me take advantage of what others have done before and change the rules so that others in the future can't."

This blog never has been about politics and I don't plan to start now. I'm only using this political example to illustrate my original argument. Anyone thinking that it is support for any and all public projects needs to reread everything until they get it. Remember, this is a post about the patent system and recent court case.

Tuesday, March 30, 2010

DNA Patentability

This will be all over the news very quickly. A judge in the Southern District of New York has overturned patent law and declared that DNA cannot be patented. This was a crazy lawsuit brought by the ACLU that sought to have DNA/gene patents declared unconstitutional.

I can safely state that the case will be appealed and overturned. (Patent cases are appealed to a special court, the Court of Appeals of the Federal Circuit, that was set up to provide expertise and uniformity in patent cases.) I suspect that the Supreme Court won't even grant the case a hearing after that.

Acrylamide, Toluene and Biologists

Any biologists reading this should stop immediately. Besides being seriously lost on the Web, you probably won’t like the jokes, jibs and jabs that I will make at your expense today. Seeing this headline at Chemical Week, "ECHA Adds Acrylamide to Reach Candidate List" set off a chain of thoughts that reminded me of the quirky thought patterns of biologists.

A few jobs back, I was a lonely little chemist in a microbiology lab. These weren’t just any old microbiologists, they were of the worst ilk – food microbiologists. You know, the type that love to scare you about all the bugs in your dinner that will make you sick and kill you. They never got to me or made me change my eating habits (I still eat hamburgers rare) because they never understood what chemists do: It’s the dose that makes the poison (Paracelsus). So what if there is e. coli in there; is it enough to kill me? i.e., What is the LD50? Of course, that would require a little bit of math, not one of their strong points since they think multiplication and division are the same.

Let’s get back to the acrylamide. Biologists use it all the time to make their electrophoresis gels used to separate DNA, RNA, proteins,…The monomer is being linked to cancer (hence the headline above) and made the news a few years ago because it is found in fried foods. Despite this, they have no problem working with a suspected carcinogen. It's just fine. But get this: I could clear a room if I even showed them a bottle of toluene. Somehow every last one of them was absolutely convinced that it was a carcinogen. It’s not. Not even close. In their minds, acrylamide, a suspected carcinogen is fine, while toluene is not. Why?

Monday, March 29, 2010

Injection Molding Tradeoffs

Just a one-liner: “The Materials Analyst” article in this month’s (March 2010) Injection Molding Magazine is very good. I’ve butted heads in the past with the author on other subjects, but this article is one of his best. It’s a thorough discussion of the tradeoffs in processing ease vs. physical properties. Injection molding is pretty much nothing but tradeoffs, so understanding the fundamentals behind the tradeoffs is key to learning and understanding. Short of that, nothing is carried forward for the future.

And that’s my 5-sentence one-liner. It reminds me of the joke: There are three types of mathematicians; those who can count and those who can’t.”

Jet Plane Testing

The Boeing Dreamliner, the commercial plane closest to being all plastic, has a critical test to pass today – the “Ultimate Load Test” – in which the wings will have a stress of 150% of the expected maximum applied to for 3 seconds. The test will obviously be run on the ground and not in the air.

“In programs past, with traditional aluminum planes, Boeing has generally passed the ultimate-load test and then taken the pressure higher until the wing does break, to see where that point is, Gunter said.

That’s not planned today, however, because the reinforced composite wings are expected to be stronger and would need an amount of force that’s too risky to the equipment and personnel, she said.”

Those are some seriously large forces to be working with (maybe the Mythbusters can run the test some day in their typically schlocky fashion). I do find it somewhat strange that the test is defined in terms of the total deformation time (3 seconds) and that there is not a deformation rate associated with it. Composite materials certainly would show a change in deformation values with the stress rate, not just the total stress. Mid-air turbulence and other stresses have a higher frequency than 1/3 s-1. It is quite apparent that this test was originally designed for aluminum planes and is being grandfathered in. Worse yet, I found this line about the Airbus 380 disturbing:

”The FAA mandates that the aircraft survive three seconds of 150 percent stress in the “ultimate load test,” creating enough pressure to potentially snap the wings in two. That’s what happened with the Airbus SAS A380 in 2006. While the breakage was a “black eye” for the Toulouse, France-based planemaker, Airbus was able to convince authorities it knew exactly what the problem was and could fix it, without having to repeat the test, Weber said.”

While some such test is needed, the specifics should get a review as composite planes are not going to disappear anytime soon.

If the video is ever released, it would be fascinating to watch. A few years ago, Rolls Royce released video of engine testing that was reassuring but also personally troublesome. While the engine past the test so well, it was disturbing as it opened my eyes to a potential failure mode that I had never thought of before.

Thursday, March 25, 2010

What are the Odds?

Being that I work for a company owned by Andersen Corporation, maker of Andersen Windows, I've heard through the grapevine about windows concentrating and reflecting sunlight onto neighboring houses and in many cases causing damage. (Sorry, I don't have any inside knowledge or access to damaging "internal memos" or any other smoking guns that a class-action attorney would sell out his best hunting dog for. If any lawyers are reading this, go subpoena sumebody else.) Plastics News had a article on it recently, but this has been going on for a few years.

What is thought to occur is that with a sealed, double-paned window, pressure differences between the sealed interior and the exterior can give the window glass a concave geometry of sorts, which can then serve to concentrate sunlight. Low-E glass is particularly troublesome in this regards. The reflected and concentrated sunlight can then heat and soften vinyl siding on neighboring houses.

I'd love to run a Monte Carlo simulation on this sometime to see how it plays out. Or maybe a derivation of the Drake equation would be better. Think about what has to work out just right for this to occur. First the right pressure differential has to be there, not an easy set up to control. External atmospheric pressure is constantly changing as is the pressure inside the window due to changes in temperature. Then once you have the concavity, you have to have sunlight. And then the 3-D geometry of the sun, window and neighboring house has to be just right. And then the focal length of the lens has to match (not exactly, but close enough) the distance to the siding. My gut feeling is that this would be a "one-in-a-million" type problem, comparable to winning the lottery, but apparently not.

Another Inorganic Molecule to Look at

Following up on Tuesday's post, there is this new beauty to study, a record for the largest coordination number - 15.

Less anyone think I am going rogue and leaving the true, the pure and the proud - the organikers, no, I am not. I always carry a copy of this periodic table in my lab notebook, although I certainly would reinsert sulfur. My ANTEC presentation this year in on thiol-ene chemistry - I need that S.

Wednesday, March 24, 2010

ANTEC Bound, I think

So apparently I am going to be presenting a paper at the Society of Plastics Engineers (SPE) ANTEC Conference this year. I don't have details on timing yet, as I haven't even received a formal letter of acceptance despite my paper being submitted in early January. (I only have been told of the acceptance because a colleague called to find out what was going on.)

The sloppy organization doesn't surprise me as I have had a slew of bad experiences with the SPE. The last time I went (2005, Boston), I had submitted two papers. One was accepted and one was rejected. Imagine my surprise upon finding out at registration that the rejected paper had been rejected as an oral presentation but had been then been accepted as a poster without anyone notifying me. That meant I had to scramble to put a poster together - getting a colleague back home to find and email me a copy of the submitted paper, converting it to a poster, find a print shop that could make the poster and then getting it printed. This fiasco caused me to miss a number of talks that I had been looking forward to.

After I got back from the conference, I wrote an email to the organizers about the problems. They were sympathetic and promised a CD of the proceedings, which I never received. For group that has been hurting for membership, they certainly make it difficult to continue as a member. Anyone else had similar problems?

When I find out more details, I'll post them. Maybe we can have a meet-the-blogger session at a watering hole some evening.

Tuesday, March 23, 2010

Is this a Dagwood?

Can they keep alternating the Cd/Lu metal centers? How high can they go?

Automotive Plastics

As I see it, applications for plastics in automobiles can be broken into three categories:
  • the easy ones, which generally means that a non-plastic alternative is difficult to find. These include dashboards, seats, carpeting.
  • The moderately challengin ones, where the demands are higher but not outrageous. These include plastic side panels, windows and HDPE gas tanks.
  • And then there are the "you-must-be-crazy" applications, mostly under the hood (i.e., bonnet for the readers in the U.K.) where you have the engine throwing out a lot of heat via conduction, convection and radiation. Plastic air intake manifolds have been around for a while, but now DuPont has a some new nylons that it is targeting for oil pans and mufflers
  • .
    Think about having to develop a platic for that - hot oil in constant contact with your candidates, all day long. Hot exhause gases constantly blowing over your plastic. And since these are both along the bottom of the car, there is a large temperature differential (especially in Northern winters) that is trying to warp the parts more than dilithium crystals twisted space for the USS Enterprise.

    As I've mentioned before, plastics are going to continue to be needed in automobiles in order to increase mileage. I'm just glad someone else is working on these developments.

    Friday, March 19, 2010

    Another use for FTIR in the Medical Lab

    Not quite a year ago I wrote about using an FTIR to detect myocardial infarctions - heart attacks. Well, your FTIR is revealing itself to be even more useful in medical testing - now it can diagnose cancer.

    So what's next for this super-analytical technique? Genetic testing? Alzheimer's? Psychic abilities?

    Thursday, March 18, 2010

    Real World Recycling Issues

    I mentioned a few weeks ago that I had found a package that was labeled with the recycling code #7 - other, but also stated that it was compatible with #5 - polyproplyene, and I questioned the validity of the codes.

    Apparently it is a very real problem. The linked article describes a similar package being labeled as "PET compatible".

    The article also answer a number of tacit questions that I previously had. Use of the recycling codes is governed by a patchwork of 39 state laws of varying content - clearly national standards are needed, as recycling of polymers is becoming more important all the time.

    My heart goes out to recyclers out there having to deal with the dirty input streams.

    Wednesday, March 17, 2010

    Why I hate PVC

    If PVC had only been invented yesterday, the inventors would have published a nice paper about it and that would be the end of it. Maybe they would have saved a few samples for posterity, but the rest should have gone right into the dumpster and that would have been it. Done. Gone. Good riddance.

    "PVC, how do I hate thee? Let me count the ways."

    I don't even know where to start, although I know not to start with any arguments about the negative environmental impact of the chlorine and how it creates dioxin when burned and how plasticizers are killing us all or...

    Instead, let's look at it from the point of view of an engineer. How about all the endless additives that are needed? The first of these are of course plasticizers, although they certainly are not a necessity as unplasticized PVC is widely used, but when plasticizers are used, they can often be added in very high loadings ( > 100 phr). And what about the internal and external lubricants? And the various heat stabilizers (lead, tin, cadmium...)? There can be still more additive too such as pigments, impact modifiers, UV absorbers, flame retardants, fillers... [1] Face it, without additives, PVC is nothing.

    And then once added, the plasticizers won't stay put [2]. They come oozing out over time, gumming up adhesive labels on the surface or anything in contact with the plastic.

    Proceesing PVC is a real treat too. We run quite a bit here of it here at Aspen Research (including some with wood flour added) and need special fire training because if an extruder overheats, HCl is one of the products. A room with high levels of HCl is just not something you want to run into without a partner to drag you out if you go down and an independent air supply.

    Running rheology tests on the material is a joy too. I can't heat the material too high (see above) and have to work quickly because it has less ability to handle even moderate heat for long periods of time. In short, dynamic mechanical analysis of the stuff is not my favorite way to spend a week.

    The one amusingly redeeming quality of PVC is the color change that sometimes occurs in white PVC. Instead of the oxidation --> chain breaking reaction that occurs in olefins, in the pinking reaction H + Cl is removed from the repeat units and a double bond forms along the backbone. When the double bonds are alternate with single bonds, conjugation occurs. If the conjugation is long enough, the material will absorb visible light, starting with the blue end of the spectra and moving towards green and yellow, leaving on the red. Given the initial white color, white + red --> pink. Pink!

    But PVC is here to stay (despite the efforts of Greenpeace). I have no problem with it or products made from it. But you can make me happy if you ask someone else to work with it instead of me. It's just too much of a struggle without an appropriate reward.

    [1]To be fair, this last list of additives are often added to polymers in general and are not unique to PVC.

    [2] I've always suspected but have never been able to confirm that this occurs because of a thermodynamic incompatibility between the PVC and the plasticizers. It is not simply because of the high loading per se. Pressure-sensitive adhesives can have similarly high levels of tackifiers added and yet I am not familiar with any similar migration of the tackifiers. Can anybody confirm my suspicions?

    Tuesday, March 16, 2010

    Another cold shoulder for polypropylene

    So after this mornings entry, in my mail box is the March 2010 issue of "Hydrocarbon Processing", and on the cover is a lead-in title "On Purpose" Propylene. [1]
    Oh the disrespect!

    Propylene has been such an unloved child that the polymer industry could get by on the scraps of the gasoline industry, and now since demand is getting higher, someone is going to have to make propylene 'on purpose' and not by accident. And this is worth mentioning on the cover of "Hydrocarbon Processing.[2]

    So is there a conspiracy here? Are there black helicopters flying overhead to watch if anyone is talking up polypropylene? Will I be posting tomorrow, or will I be whisked off to a super-double-secret prison in a foreign land and subjected to polyethylene boarding until I talk?

    [1] (As of right now, the article is not online - the February 2010 issue is the "current issue").

    [2] And elsewhere too. (13,000 hits.) Somebody is making a big deal about all this.

    Cold, cold polypropylene

    Some polymers just have a bad rap. I’m not talking about PVC (I’ll give that polymer the business sometime soon, but not for the reasons that most people expect), but instead about PP a.k.a. polypropylene, a.k.a. polyethylene’s high class cousin.

    The most common misconception of PP is that it doesn’t perform well in cold temperatures. I’ve heard this from previous colleagues as well as current clients. The listed Tg of about -10 oC is the culprit, which many take as a sign of absolute limit – go colder than that and it will break upon impact. Depending where you are in the world, -10 oC can be ungodly cold, a mildly cold winter morning, or a heat wave, but if you are designing a product for large portions of the world, temperatures this low are certainly possible.

    And yet car batteries, loaded with concentrated sulfuric acid, use PP as the case, knowing full well that the battery is most likely to fail to start the car at temperatures of -10 oC or lower, and also knowing full well that the people replacing the battery in that cold, most concerned with getting the job over with quickly and then getting someplace warm, are going to be banging the case around as it is being pulled out of the car and dropped on the ground.

    If PP was an amorphous polymer, then the Tg value would be more important, but being a semi-crystalline polymer, it is a lot stronger than just that. The crystals serve as effective crosslinking points where chains from multiple molecules come together and provide strength that an amorphous material can only hope to have. Amorphous polypropylene, which is lacking in crystallinity, is a weak material only good for non-demanding adhesive applications. If your using that, then I would be concerned about the low temperatures.

    Bottom line, polypropylene is plenty tough in the cold. If you are concerned, do the needed testing, but don’t rule it out just because of a number on the spec sheet.

    Monday, March 15, 2010

    Viscoelasticity while Painting

    Paints are a classic example of a viscoelastic fluid – shear thinning is needed so that the paint can be easily applied to the wall (a high shear situation), but not run down it after it is applied (a low shear situation). But there are so many more viscoelastic materials to consider when painting.

    Ceiling paints have a different need entirely, in that gravity is now pulling normal to the film, not along the film. Hence there is a need for controlling the extensional viscosity. Painting a ceiling is difficult enough without having to worry about the paint dripping back down on you.

    But even before the first brush stroke is made, another viscoelastic material is on the job – the pressure-sensitive adhesive with a crepe-paper backing, otherwise known as masking tape. Masking tape typically uses a natural rubber based adhesive that has been modified with a whole gamut of additives to modify the adhesion, not only the initial adhesion, but also the build of adhesion over time, which is why there are so many options available. The adhesive properties of these materials can be related to viscoelastic measurements by the Dahlquist criteria.

    Paint brushes for latex paints have bristles from nylon or polyester or a combination of the two. Regardless, the bristles were formed from a drawn, molten polymer, an obvious example of a non-Newtonian fluid. During the fiber forming operation, the fluid was exposed to a large range of time-dependent shear and extensional stresses, all with a thermal background of varying states.

    (These thoughts were brought to you courtesy of a weekend DIY project. I had to have something to think about while watching paint dry.)

    Casimir Chemistry

    The Casimir effect is not something that you typically learn about in school, at least as chemists. A vacuum is filled with zero-point fluctuations with a wide range of associated wavelengths, but if two solid objects are brought close together (nanometer scale), some of the wavelengths are eliminated. As a result, the energy in the gap is reduced and there is an observable force that attempts to close the gap even further. Consider it a van der Waals force for large objects, if you will.

    The subject is an area of active research, especially with micro- and nano-machines. One popular question asks is it possible to use these fluctuations as an energy source (i.e., free and totally clean energy?)

    A new paper (open access though 8/31//2010) in the Journal of Chemical Physics outlines a number of possible cases where the effect could be used to alter chemical reactions. The paper is quite readable for someone with a junior level of chemistry, so please give it a whirl – and then start experimenting. This looks like a neat area to explore.

    Thursday, March 11, 2010

    Qualitative Science

    Here’s one perspective on the history of science: Ug and Grug found that if they took two stones and banged them together, they got sparks and could make fire. They tried to recreate it with other stones, but found that only certain colored stones worked. Their descendents eventually founded atomic theory, created chemicals reactions to purify materials, measured their purity, and even made predictions (successfully) about what other materials would work too.

    Short and sweet, science has gone from a very qualitative state to an extremely quantitative and predictive state. This is repeated anytime a new field of science is opened. First people find qualitative observations in which they can then begin to observe patterns. This then leads to models that make predictions. Failures in the predictions lead to a refinement of the model, allowing for better predictions. Repeat ad infinitum.

    Every once in a while we get clients that want to go in the opposite direction. Many years ago I was charged with a project involving heat transfer in an electronics case. Because of a number of design elements, we could treat it as a 2-D case. We pulled out our standard heat transfer equations, did some manipulations, calculated a few cases in detail, and made suggestions of what could be done to improve the situation. We thought we had nailed it, and certainly in a technical sense, we had.

    But it wasn’t what they wanted. They wanted a bunch of 3D FEA images. The images, being full colored, certainly looked better than equations and spreadsheets, and non-technically-trained upper management liked looking at pretty pictures more than equations, but this was a complete reversal of 15000 years of scientific development taking us right back to Ug and Grug. I am not surprised that the company has been struggling financially in the intervening years.

    While I’m on the subject of FEA, let me add a few thoughts. What I don’t like about FEA modeling is that it is difficult to take a fundamental learning from the output in both cases of success and failure.

    Because of the expense in completing the computations, the outputs are usually limited to only a few images. As such, if the model is successful, there are most often few if any patterns to allow for a generalization to be noted so that future predictions can be made without the use of FEA.

    And on the other hands, as I noted above, failure in the predictions from an equation means that the equation needs more work to understand what is truly occurring, what subtlety has been missed, what nuance needs to be tickled out. Failure of an FEA model prediction could mean any of a number of things – that the software package is bad, that the inputs were bad, that the mesh generated was appropriate… all sorts of possibilities, but not that the underlying science is in need of correction.

    Either way, I usually don’t take much away from the output of an FEA modeling effort.

    Wednesday, March 10, 2010

    The Great Pacific Garbage Patch

    Rise Above Plastics has a new public service video out about plastics in the ocean harming marine life, providing at the end the terse message:

    "Plastics kill 1.5 million marine animals each year."

    I can't seem to find any reference to support this claim, let alone details about how many different species are aggregated in this number, or ultimately how many of each individual species die from plastics. (I'd certainly be willing to settle for a genus or family breakdown - asking species can often be quite demanding.)

    Considering that much of the published hype regarding oceanic garbage patches can be effectively debunked, I would expect that that is also the case with this number.

    Certainly trash in the ocean is wrong, plastic or otherwise. But the solution will be to not put it there in the first place.

    Tuesday, March 09, 2010

    No, not that size...the other size

    In the Giga-hyped world of nano-technology, one of the few materials making the grade are carbon-nano-tubes (CNTs for short). These are the tubular version of buckyballs (which never have amounted to even a nano-portion of their original hype). They are fabulous for boosting the mechanical properties of polymers, but this is all a topic for another day. My only point today regarding CNTs is about their size. They are very small, only a couple of nanometers in diameter. There pretty much at the limit between being a bulk material and being an individual molecule.

    So imagine my surprise when I saw this headline:

    “Nanocyl and 3B-Fibreglass Announce Joint Agreement for Developing CNT-Sized Glass Fibers.”

    Wow! Glass fibers the size of a CNT! Keep in mind that CNT’s are built up in size from atoms, while glass fibers are built down in size from the everyday world (typically by pushing molten glass through a small circular opening and then pulling on it to make it even thinner in diameter.) Individual fiber optic glass strands are about 10 microns in diameter or so, a whole 3 orders of magnitude larger than CNTs. I couldn’t wait to find out about the technology breakthrough that would close that gap.

    And then I realized that I had misunderstood the headline. "Size" refers not only to how large something is, it is also and old-but-still-used papermaking term for a coating applied to the web; the term is also used in other industries such as glass and fiber production. Such is the case here: the CNTs are applied as a sizing to standard glass fibers. Certainly interesting and potentially useful, but quite different from what I initially expected.

    This is not the first time I’ve made that mistake. Many self-wound pressure-sensitive adhesive tapes (such as masking tape) have a sizing on them so that you can unwind the tape. This is often called a low-adhesion backsize. When I first started working at 3M, it took me quite some time for to realize that others were using the term “backsize” and not “backside”.

    Here is the article if you wish to read it.

    Friday, March 05, 2010

    Reductio ad absurdum

    That is the Latin phrase of "reduction to absurdity", used as a way to show the fallacy of an argument.

    I also see a new application of the phrase applying it to physicists who argue that all the other sciences can be reduced to physics. The logic goes that chemistry is all about the electron which can be described by the Schrodinger equation, and since all of biology is chemical reactions, everything can be reduced to physics. (xkcd recently had a slightly different spin on this.) Certainly it can be done, but doing so may actually be counter productive.

    This is because humans have some weird quirks in processing information. An example of this is the refrigerator poetry kits - words with magnetic backings that you slide around on the fridge and make up poems. People are always amazed by how nice a poem they can quickly create despite their belief that they aren't a poet. Now imagine the situation if you were to take the words and cut them into individual letters. Most people would freeze and be unable to create much of anything despite the fact that the exact same set of letters is there in both cases.

    Phyics: chemistry: biology
    Letters: words: paragraphs

    Yes, the originally proposed reduction can be completed, but would it be worthwhile at all? Would anything be learned? What would be lost?

    Notes: 1) The original idea of cutting up the magnetic words was in an article in Nature from about 10+ years ago. I can't provide any citation. The analysis stopped at the idea that humans don't process all information sets the same even if the same data is present in all cases.

    2) This is a (partial) apology to biologists for the title of the last post, "Chemical (Biological) Switching". After all, the examples given were biological in nature, not chemical, something I intend to start changing.

    Thursday, March 04, 2010

    Chemical (er... Biological) Switching

    As I mentioned earlier, I get involved in a lot of problems that are outside the realm of a “normal” polymer scientist.

    In one such case now, I’m looking at biological switches as a source of inspiration. Cells and organisms often have a need to be in one of two states, and they need a switching function that is all-or-nothing and yet not overly sensitive to fluctuations in the switching signal. A “normal” reaction of the sort

    Substrate + signaling agent --> Output

    is difficult to control as it relies on first or second order kinetics, and you can't esablish a critical threshold for the reaction to initiate and stay there. Instead, a better choice is to set up two opposing reactions against each other.

    A terrific example is sex determination (open access, but registration might be required). Humans and most other mammals, (platypuses seem to be an exception, which isn’t too surprising as they seem to be the exception to nearly every rule regarding mammals) start out with the potential to become either sex. As the embryo is growing, asexual gonads develop. At some critical point, if the Y gene is present, the SRY gene will encourage the development of the gonads into testes instead of ovaries. However, two other genes are critical in making the switch complete: WNT and FGF9, both of which work in opposite directions when the SRY is present or absent.

    In cases where one or more of these switching genes is absent, then things can get muddled with the result being a mix of sexual traits. But when things work properly, the signal is processed extremely well and most people end up as clearly male or female. (I've greatly simplified all of this - The Scientist article has much more details on sexual determination, and the first two cited articles are great for probing mathematical models of this.)

    Clearly a neat approach to solving chemical switching.

    Wednesday, March 03, 2010

    Who Knew?

    I've not encountered this term before: Nurdle. It's a pellet that has escaped from normal polymer processing sites and become a piece of trash. I'd never heard of it before, and can't seem to get any etymology on the term. Anyone?

    Tuesday, March 02, 2010

    Living without Plastics?

    If you want to rid your life of plastics, it just can't be done short of moving to the wilderness and living off the land. (Just keep in mind that you will have gotten a huge start from polymeric materials already.) Many bloggers seem to be posting about there attempts to reduce plastic use, and some are getting news coverage.

    There is more to plastics in modern life than is discussed in these reduction blogs. What I see missing can be put into three categories:
    1. Polymers that are "invisible" to the eye but still are there
    2. Polymers that are used by others in delivering goods and services
    3. Polymers that are used in more durable items

    Let me expand on these items just a little bit. Don't even begin to think that this is a complete discussion.

    1. While the blog does note of the plastic in window envelopes, there is more plastic in her mail. Inks, pressure sensitive adhesives (most postage stamps) and any type of adhesive in general are all polymer based. The papers themselves could have a polymeric coating.
    2. Large amounts of plastic are used as secondary and tertiary packaging that the blogger never sees. Shrink-wrap on pallets, adhesives on secondary cardboard boxes...All of this is used to help ensure that products arrive at their destination without being damaged and having to be trashed. This is certainly something that a consumer has little or no control over, but it needs to be accounted for nonetheless....
    3. Durable goods made of plastics parts (computers, cars, washing machines...) should be included in the total even if included on some sort of amortization schedule. Not including these plastics is misrepresenting the whole situation, much like a company's financials can be improved in the short term by delaying needed investments and maintenance.

    In the same way that a system is not optimized by optimizing each individual variable, attempting to improve living by going without plastics is nowhere a easy or as simple as it sounds. This link is just one example. And plastics certainly are not going away. The auto industry is being forced to use ever more plastics just to reach the improved mileage requirements.

    Monday, March 01, 2010

    Unusual Recyling Mix

    I've not seen this before - a combination of recycling symbols on the same package.

    The package is a 7 (Other), but it is 5 (polypropylene) compatible. How is this determination made? The SPI website doesn't have anything on classification, so what does it mean to be comparible?

    Certainly I understand polymer comptability from both a practical and thermodynamic viewpoint, but I'm not sure that just any old processor would be willing to take a "polypropylene compatible" bottle from just anybody. That seems like a unworthy risk. The bottle manufacturer can suddenly say that their bottle is compatible with another resin stream? If anybody knows, please inform me as I am quite curious.

    P.S. Today's "Ph.D. Commics" is terrific.