Archive for: April, 2011

On Guest Bloggery

Apr 09 2011 Published by under Uncategorized

Quite typically for the blogger version of me, I get to the end of a 2 week guest blogging spell here at Scientopia and think 'damn, I meant to write about a, b and c as well'.  I do this all the time - think up things during the day that would make a fantastic blog post (to me anyways), then forget to write it, or decide to think about it some more, and then it just doesn't get done.  I guess I need a bit of self-discipline, but then I spend every day exerting a large quantity of self-discipline, mainly to avoid yet another mug of hot chocolate, but also to get marking or some such teaching chore done.

Spring Break!

On the other hand, its our equivalent of spring break now, the end of term and the possibility of a few slightly less hectic months.  The end of the academic year is in sight, just, if you squint and look slightly to the left of the pile of marking that is, and the summer stretches out beyond that.  In addition to writing here, I submitted my first major solo grant application over the last fortnight,  spent 3 nights recovering from said submission in a very nice hotel, and enjoying views like this:

Derwentwater, Lake District National Park, Cumbria, England, UK

 

I'll echo Émilie and Patrice's sentiments - this has been a great experience, and my thanks go to all involved in sorting it out, and to you all for taking the trouble to read.      I'll head back over to Endless Possibilities now which feels a bit like heading home after a nice wee break - hopefully things haven't gotten too dusty!

Cheers!

Katherine

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The end !

Apr 09 2011 Published by under Uncategorized

We are now completing our 2-week period as guest bloggers here at Scientopia. We would like to take this opportunity to thank the individuals responsible for this access to Scientopia's readership. This was a very good experience and I hope that you, dear readers, enjoyed it as well.

We'll continue blogging in French and in English over at Le Physiologiste. Don't hesitate to come visit us !

Émilie et Patrice

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Real Life 'What Am I?'.

Apr 07 2011 Published by under Uncategorized

Today has been quite an interesting day - I've spent the morning with 10 very smart A-level chemistry students (that's second to last year of high school in non-England school systems).  We were analysing the contents of jars in a pharmacy exhibit.  It turned out to be a real life 'what am I?' but instead of being confronted by several chemical structures and working out what the household item was, we were confronted by 14 samples of solids and liquids with labels that did not make much sense.  Do you know what pulv rhei  is?  No, we didn't either this morning.

Lets backtrack a wee bit and explain.  Ironbridge Gorge is a World Heritage Site not too far from Keele.  Amongst the wonderful museums there is Blists Hill Victorian Town which is a village sized museum where you can visit Victorian style shops and buy things, either with modern money, or you can change your money for olde worlde money.  One of the shops is a pharmacy that was recently used as part of the set for a BBC TV series 'The Victorian Pharmacy'.

The inside of the pharmacy shop, photocredit Calotype46

It looks pretty typical for a museum version of a Victorian Pharmacy with one exception - most museums just have empty, clean jars.  This one doesn't - about 300 of the jars along the back shelves are filled with substances that may or maynot be those detailed on the label.  The museum got in touch with one of my colleagues last year about the potential safety issues surrounding unknown chemicals - what if they were spilled? What action should be taken?  We agreed to carry out an assessment of the chemicals and try to identify as many as possible.  On one level, that involves looking up the labels on the internet or in various Pharmacopoeia and working out that Pulv Rhei may well be powdered (pulverised) rhubarb.  On another level that involves a series of wet and analytical chemistry techniques to determine if the contents are what they say they are.  Over recent years, various curators of this collection have made substitutions of the jar contents, replacing substances like boric acid with salt or sugar.  Unfortunately little documentation has been carried out so we're trying to change that.  A few weeks ago a group of students went with my colleague and did some testing on site, and started the task of sampling the jars.  Today the A-level students came up to use our chemistry labs to analyse the contents.

Why are we using school children for this task?  Actually, analysing these unknowns is good fun and an excellent open ended experiment.  We thought it would make an excellent outreach activity, making a good contribution to the project.  Today we provided the students with a sample each and let them come up with a plan for analysis.  We offered them various wet chemical techniques such as flame tests to identify metals like copper, pH tests to confirm acid or base, reaction with acid to generate CO2 gas (turns lime water cloudy) if we thought it was a carbonate.  We also let them use our infrared and NMR spectrometers to further analyse samples.   We also provided known, modern versions of chemicals where we could identify them. The students really enjoyed the problem solving type activity although the biggest criticism was that we couldn't tell them for definite at the end if their answer was correct or not.

And what of Pulv Rhei?  We provided a stalk of rhubarb for comparison and the student pulverised that with table salt before running an infrared spectrum.  That showed a lot of water.  The actual sample was a crystalline white powder so we suspected it might by oxalic acid, a chemical known to be in rhubarb, particularly the leaves.  We ran the IR of the original sample and the oxalic acid but it wasn't that either.  Searching the IR library indicated some similarities with the spectrum of sucrose.  A simple wet chemical test using Benedict's reagent confirmed the presence of a sugar.

 

One of the A-level students contemplating an unknown unknown!

We analysed 14 different samples this morning and managed to work out about 10 of them.  Many weren't what they said on the label.  Some samples had deteriorated with age (potassium permanganate for example), others had been substituted for new unknowns.  That leaves us about 200+ samples still to do, but fortunately the school are eager to come back to analyse more in June, and we have a couple of other school groups interested in the project.  The real question is which of us is volunteering to take the compounds in the poison cupboard for analysis!  I suspect that may be my job for July.

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Reduced orthostatic tolerance in athletes: it's all in their heads !

Apr 06 2011 Published by under Uncategorized

Dear athletes, did you ever experience light headedness or dizziness following a sudden change in position, i.e. from the sitting to the standing position? These symptoms of brain hypoperfusion are known to be a consequence of orthostatic hypotension (sudden reduction in arterial pressure when standing up), and surprisingly, aerobic fitness seems to be associated with reduced orthostatic tolerance !

While the higher prevalence of orthostatic hypotension in athletes could be explained by factors such as the presence of a more important amount of blood volume in the legs due to improved leg compliance (change in volume for a given change in pressure), it may also be the consequence of an impaired capacity of the cerebral vasculature to efficiently deal with changes in arterial pressure.

A group of Danish researchers was interested by this specific issue and recently published interesting results in the Journal of Applied Physiology.

The aim of the study was to investigate whether trained individuals have less efficient regulation of cerebral vascular resistance compared to untrained individuals. They studied cerebral autoregulation (that reflects dilatation or constriction of resistance vessels of the brain to a reduction or an elevation in perfusion pressure, respectively, in order to maintain cerebral blood flow relatively constant) in 9 highly-trained subjects and 9 untrained subjects with similar baseline characteristics, except for body weight and maximal oxygen uptake (VO2max). Cerebral autoregulation was evaluated by the thigh cuff method (see below) and transfer function analysis. For the need of this post, we’ll focus on the section of the article using the former method.

Several parameters such as mean arterial pressure, heart rate, cardiac output, cerebral blood flow and cerebrovascular conductance (ratio of cerebral blood flow and mean arterial pressure) were continuously measured for a period of 5 min before (baseline), 2.5 min during and 5 min following the inflation of thigh cuffs at a pressure of 300 mmHg. In the figure below, you can see (no matter what line you’re looking at) that the sudden release of the cuffs (0 s) leads to a reduction in both mean arterial pressure (MAP) and cerebral blood flow (MCA Vmean). Following a few seconds, the cerebrovascular conductance (CvCi) starts to increase back to baseline values.

After the release of the cuffs, the rate of decline in MAP and MCA Vmean was faster in trained (black lines) compared to untrained subjects (dotted lines). In addition, the time at which CvCi started to increase (that represents the onset of cerebral autoregulation) was delayed in trained compared to untrained subjects. Once initiated, this autoregulatory response was similar between groups. Consequently, recovery of MCA Vmean and CvCi to baseline values was slower for the trained subjects.

According to the authors, the post-ischemic legs of the athletes may require a more important proportion of the cardiac output, compromising blood flow to other organs such as the brain. Also, a delayed onset of autoregulation in the trained subjects could be related to higher cerebrovascular tone (basal state of vasoconstriction), which could make the cerebral vessels of these subjects more vulnerable to a rapid reduction in blood pressure (although that higher cerebrovascular tone could, on the other hand, protect them from surges in arterial pressure such as during exercise).

Although exercise training is associated with an impressive amount of benefits, further studies are clearly warranted to better understand the long-term effects of exercise on the brain vessels. While researchers have focused on the increased ability to pool blood in the lower legs and/or the reduced ability of baroreceptors to maintain MAP to explain the higher prevalence of symptoms related to orthostatic hypotension in athletes, this study suggests that aerobic fitness affects cerebral autoregulation and could increase the risk of cerebral hypoperfusion during a sudden lowering in arterial pressure.

So, dear athletes, next time that you are feeling dizzy or light headed in response to a sudden change of position, well, it’s all in your head !

Patrice

Lind-Holst M, Cotter JD, Helge JW, Boushel R, Augustesen H, van Lieshout JJ, Pott FC. Cerebral autoregulation dynamics in endurance-trained individuals. J Appl Physiol 2011 (Epub ahead of print) PMID: 21372098

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What Am I? 14

Apr 05 2011 Published by under Uncategorized

Below I’ve listed the key chemicals found in a commonly available  product.  I’ve drawn the chemical structures of principal components where simple and appropriate; given the E number or CAS number (however tempting Sigma-Aldrich catalogue numbers would be) if no simple chemical structure exists for an additive; and given the chemical formulae or name if neither of the above make sense.  See if you can guess what this is!  If no one gets it within 24 hours, I will post a clue.


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I've already reached that stage...

Apr 04 2011 Published by under Uncategorized

One year after the end of my PhD, during a visit at the research center where I did my graduate studies, my former PhD supervisor told me the following without any warning: We miss you here !!

At that time, I told myself: Well, this is very kind of him, but he probably just wanted to say that it was cool having me around… no more than that !

I’ve been thinking about that sentence for several weeks now. Why? Because I’m presently on the other side of the fence. Not so long ago, I’ve met that guy who would become my first graduate student.

Being the two of us in the lab for several months, we’ve had the opportunity to build a special relationship...

We’ve had the opportunity to talk a lot about research...

He’s had the opportunity to have me in his shoes 🙂 What can I say, he was my first graduate student!

I remember being (most likely) more nervous than him during his first talk…especially during the question and answer period !

He worked pretty hard on his master’s degree thesis…

He recently submitted his first manuscript as a first author…

I love that part of the job…to see the development of a graduate student over a couple of years…

Sadly, I've already reached that stage…I now know what my PhD supervisor meant that day…

Why? I'm about to loose my first graduate student...

I'm sure that one day, when he'll pay us a visit at that same research center where he did his graduate studies, I'm the one who will say to him: We miss you here!

Patrice

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My relationship with "him"

Apr 02 2011 Published by under Uncategorized

5 days... it's the duration of our last break.

5 days... it's not that long ... but it was long enough to forget you. It was long enough to forget that sometimes, you are getting me out of my mind!

During those days far from you, I spent some time with "normal" people, people who are not like you... or like me!? This is not the first time that I'm behaving like this.... taking a break from you... and each time it's the same thing: I forget you easily!

When I finally decided to come back, a notice, sent by email, was quietly waiting for me: "Dear friend, your manuscript has been rejected" (arghhh, the second one of the month!). What was that all about ? Some kind of revenge ?? Clearly, that shot was below the belt... I almost left again!

3 days... it's the period of time since my return.

Strangely, I'm coming to work in the morning with a smile... It's seems like I'm passionate about you... it's crazy, huh?!?

Love/hate: That is my relationship with you, my PhD!

What kind of relationship do you have with yours ???

Émilie

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Glue Are You?

Apr 01 2011 Published by under Uncategorized

On my first post below, Bob O’Hara commented that I must be sad at the passing of the inventor of superglue.  Yes, I’m sad but what a legacy to leave behind.  Like many discoveries, superglue was discovered by chance whilst looking for something else.  Two scientists working for the Kodak laboratories in 1942 were trying to find a transparent plastic (which is a polymer with additives in it) that could be used for gun sights.  Dr Harry Coover, who sadly died last week, and Fred Joyner discovered that compounds called cyanoacrylates could stick pretty much anything together.  Cyanoacrylate refers to the key parts of the molecules and a few different variations can be made.  When cyanoacrylates come into contact with small molecules like water, they polymerise up to form long chains.  That’s why superglue has to be kept in a moisture free container.   Polymerisation is the process where lots of small molecules, called monomers, react with one another to form long polymers.  These long chains bond the surfaces together when used as a glue.

Methyl cyanoacrylate.  The 'methyl' bit is the CH3 on the right.  The 'cyano' bit is the N with three lines drawn to the next atom which is a carbon (by convention, not shown, just represented by a bend in the line or a change from multiple bonds to single bonds).  Cyano sounds a bit like cyanide and they have the same elements but are very different in behaviour.  Cyanide is a N, nitrogen atom, with three lines (bonds) to C, carbon and a negative charge.  In this molecule the CN bit is very tightly bonded to the rest of the molecule and therefore very different to cyanide.The acrylate bit is basically the rest of the molecule!

 

 

 

This is what happens when molecules like the one above join up to form a polymer.  The R groups at the bottom can be methyl like above, or another organic group.  These polymers can be very long molecules with molecular masses many hundreds of thousands of times heavier than water.

A lot of people use superglue to seal cuts, and some people may recall an episode of House set at the South Pole where the base medic seals a wound in a workers leg with superglue.  Medical grade superglue is available, and the main difference is a long chain added onto the monomers.  This makes the glue less irritating to the skin when applied.

 

 

2- Octyl acryalte.  This is the monomer that may be used in medical grade products.  The main difference is the methyl group has been replaced by a much longer octyl group that behaves like an oil.

 

 

Superglue is also quite commonly used in forensic science applications where it is used to enhance latent fingerprints on non-porous surfaces like glass or metal.  In this case the monomers are warmed gently (many having boiling points below that of water), and the fumes rise up and react with substances left behind in the fingerprint, and with moisture from the air.  This leaves a thin film of white polymer where contact with the fingerprint substances was made, allowing the ridge detail to be visualised and the print compared to reference prints.

The great thing about people like Dr Harry Coover, and the hundreds of researchers and scientists like him, is that they leave behind things that make small yet measurable differences in people’s lives.  Your world might not end because you can’t stick something back together, but its probably better when you can, because of products like Superglue.

 

 

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