Showing posts with label X-ray. Show all posts
Showing posts with label X-ray. Show all posts

Sunday, August 12, 2012

Perhaps this time it may be right - taking a big chance

I wrote a while back how Shiva's measurements gave 0.29eV as the binding energies in our polymer/dye material (with an experimental uncertainty of 0.02 eV) which is responsible for forming domains that are at the heart of our theory of self-hearing .  I tried to figure out what interactions between molecules and polymer would give this energy and came up with a possibility.  But because I read the data tables incorrectly, I wrongly thought I had solved the problem.

When preparing my talk for SPIE a couple days ago, I drew the PMMA polymer chain with a molecule drawing program and added a few DO11 tautomer molecules to see where they would fit.  Miraculously, as a plopped the DO11 molecules on the page, I immediately saw that the NH from the DO11 tautomer cozies up to one oxygen in the PMMA polymer chain while the OH group naturally attaches itself to another oxygen in the chain, as shown above.  And he energy?  You got it; the sum of the two hydrogen bound energies is 0.30eV, a match.  The table below shows the energies of four types of hydrogen bonds.




There are always other possibilities that we have not yet considered, but this smells right.  Perhaps we are onto something.  Future experimentalists will allow us to test this hypothesis and zero in on what is going on when a molecule self heals.

This project has been one huge puzzle, were each new experiment presents to us a new piece.  It reminds me of how the discovers of the structure of DNA (Crick, Watson, and Wilson  ) pieced together cardboard cutouts of molecules to guess its molecular structure, and confirmed their results using x-ray scattering data from  Rosalind Franklin.  Incidentally, the story behind Franklin's contributions to the discovery of DNA and not being recognized  at the time makes for interesting reading.  I also recommend readers to check out Schrodinger's guess as the structure of DNA using simple physics principles.  The title of his very thin but fascinating book is

"What Is Life?: with 'Mind and Matter' and 'Autobiographical Sketches'"


I can imagine the thrill of discovery experienced by Crick, Wason, Wilson, and Farklin.  From little cardboard pieces and an "X" on a piece of film from an x-ray scattering experiment (shown above), they revolutionized our understanding of the workings of DNA.  Ironically, the forces that hold together the double helix reside in the hydrogen bond, the very forces that seem to be at work in our molecule/polymer system.

I am preparing my talks this morning, and plan to go on a limb proposing stating that the interaction between a DO11 molecule and a polymer chain  through hydrogen bonding underpins the phenomena of self healing.  I am not a chemist and have a naive view of the intricacies of how molecules interact.  But, I hope that my bold proposal will result in good feedback form my audience that will help us fine tune our models of the mechanisms of self healing.

I have been very excited in recent months by all of the discoveries that we are making.   Even if they end up being wrong, the process of the search for the truth is exhilarating.  Gotta run.  Too much to do.  And again, sorry for the typos!

Monday, July 18, 2011

A silver lining

We have been on the east coast visiting with family in the Philadelphia area. What should have been a fun time has for me been colored with sadness and anxiety. First, there is the issue of what to do with my 95-year-old father.

He is highly independent, living on his own, cooking for himself, and competently driving a car. In fact, in the summer, he and his buddies (all younger than him) routinely drive to Cape May - a Victorian beach town - for a day of walking on the beach and eating out.

He is so energetic that he volunteers twice a week to work at the senior lunch, collecting the $1.50 cost of the meal, and making sure that the books are balanced. He even helps deliver food to the eighty-year-olds who need walkers.

Ten years ago, we decided to build an addition to our home so that my father could move in with us. He refused. I don't blame him. He has friends and activities to keep him busy. He routinely takes part in activities at the Ukrainian Church and the Ukrainian Center in the Fox Chase area of north of Philly. Pullman, on the other hand, has for all practical purposes zero Ukrainians for him to befriend. Though we are here for him, work is a large part of our days, so he would be bored to death without our company. In Philly, he is an active part of his micro-community.

My father is concerned that his driver's license will not be renewed, making his present lifestyle impossible. We are also concerned that as he gets older, he will be less able to take care of himself. Our agonizing decision comes down to a choice between him continuing to live alone with the chance that he may injure himself, but otherwise have a happy life; or, moving him to Pullman, and dooming him to certain misery. In my mind, both choices are far from ideal.

Our concerns were renewed a few days ago when my father fell (when alone in his apartment) as a result of a dizzy spell. He was bruised but otherwise seemed unharmed. However, it was painful for him to walk, and his nurse (who visits him occasionally at home for blood tests), recommended that he get an X-ray to make sure that he did not fracture his hip. Fortunately, we had made plans to have lunch with good friends of ours from Yardley. After lunch, John - an orthopedic surgeon, and Camille - a physical therapist, checked my fathers injuries and felt that they were not serious, but ordered X-rays just in case. We went to a local hospital in an expedited process - care of our friends. He was indeed not badly injured

This whole process reminded us of my father's precarious situation and the decisions that would have to be made. Unfortunately, every option, other than the status quo, is unacceptable to my father. No senior living homes, no roommates, no moving to Pullman, etc. So for now, we are trying to find ways to make his life simpler in his present living arrangements.

In the meantime, we have been driving extensively to get between my fathers place, and the various in-laws. As a result, I have been feeling depressed and anxious about not having time to work, not to mention my motion sickness. Yesterday afternoon, after arriving at my sister-in-law's vacation home in Delaware, I finally sat down at my computer to work, only to come down with a migraine headache moments later. My symptoms put me out of commission for the rest of the evening.

This morning, I awoke feeling physically well, but mentally exhausted with thoughts of the piles of work that has accumulated. As I was working, I got two pieces of good news within a few minutes of each other.

First, I was notified that my NSF proposal on sum rules has been recommended for funding. However, there are several questions that I first need to address before approval. This will be my first priority, so my other work will need to wait. Hope my graduate students understand my inaccessibility during this period of time.

Secondly, while reading through the email from NSF, my email dinged with a message that a third paper was accepted in our series of papers on Nathan's work on photo mechanical liquid crystal elastomers. An excerpt of comments from each reviewer follows.

REVIEWER 1

The manuscript provides an in-depth model and related discussion on the deformation mechanism of azo containing liquid crystal elastomer upon a light trigger. The authors incorporated in the model heat effects as related to absorption and diffusion during and after exposure in the absorption band of the azo compound. To my opinion this was the first time that it was described so extensively rather than mentioning that heat effects might also play role next to the photo-isomerization reaction. For this reason it is my opinion that the paper should be published in the Journal of the Optical Society of America...

REVIEWER 2
In the manuscript “Modeling the mechanisms of the photomechanical response of a nematic liquid crystal elastomer”, authors have done the modeling to explain the plausible mechanisms involved in photomechanical response of nematic liquid crystal elastomer. In the previous report: N. J. Dawson et al., J. Opt. Soc. Am. B 28, 1916 (2011), authors have reported the experimental determination of mechanisms of photomechanical effects in a nematic liquid crystal elastomer in a particular device geometry. More interestingly, in the present report the models have been initially proposed and then used to compare with experimental results and to evaluate related material parameters. Undoubtedly, the theoretical modeling, comparison with experimental results and related explanations are up to the mark. Moreover, the report does not only demonstrate the fundamental mechanisms but also provide the platform for design of optical devices based on photomechanical effect and hence seems to be greatly useful for liquid crystal community as well as other related fields.
On the basis of the originality and novelty of the work presented in this report, I feel that it would be really of worth to keep this article in JOSA B. Therefore, I recommend it for the publication in JOSA B.

I have to run!