Well this is a bit embarrassing... My apologies to anyone who's followed a direct link to one of my blog entries at supernovacondensate.net (such as my recent post for the toxic carnival or that graphic showing scale images of spacecraft) and ended up here on my main page, instead of where they wanted to be. Livejournal's inadequate attempts at domain hosting seem to be giving me problems again.

Please bear with me while I bother the support staff about this one more time, and hope that it gets fixed rapidly. Apologies for any inconvenience.

Chocolate. Take a minute to think about enjoying a delicious piece of your favourite chocolate, won't you? That moment when you bite and it snaps into your mouth with a light crunch, and the rich warm flavour of it starts to diffuse throughout your mouth. As you inhale, the flavours and aromas flood your olfactory senses. Your brain releases a burst of pleasure chemicals in reaction to the sensations your mouth is enjoying. With each bite, it melts more and more, luxuriously coating your tongue, filling each and every tastebud with luxurious sensations and deep, complex flavours.

Chocolate is a fascinating thing. As with all of the greatest of life's pleasures, it's complex and intricate. And the science of chocolate is a blend of different facets of chemistry and biology no less complex than the flavours it possesses. Similarly intricate is the history chocolate shares with society. Human beings have been enjoying chocolate for at least 4000 years. Coming from the plant genus theobroma (literally meaning "food of the gods"), it was originally used by the Aztecs and Mayans in the ancient Americas. The traditional use was to grind the cocoa beans and brew them into a hot drink, together with chilli and other spices. This drink was known in the Nahuatl language as xocolātl, which is possibly where the word "chocolate" originated. So beloved were the cocoa beans to the people of South America that some cultures even traded them as a form of currency. Since then, chocolate has found its way to the very heart of human culture, and is enjoyed almost everywhere humanity places its feet, including being taken into space by astronauts.

Take a step back, now. A step back to what's happening in your body as you bite into a nice luxurious bar of chocolate. Laced with the alkaloid drugs, caffeine, theobromine and phenethylamine, a the chocolate stimulates your nervous system, latching onto the dopamine and adenosine receptors in your brain. Your pulse rate increases and you start to sweat lightly, as a wave of dopamine washes over your brain. Your muscles contract, your skin starts to tingle, and your senses sharpen. You salivate as the chocolate melts slowly in your mouth. As it continues to do so, your brain continues to release pleasure chemicals. Serotonin and endorphins wash over your senses, relaxing you in spite of the stimulant effects your body is experiencing. Sharpened senses, elevated heart rate, deeper breathing, tensed muscles and dreamy relaxation. All at the same time. No wonder chocolate is so blissful.

Chemically, chocolate is rather interesting too. A dispersion of cocoa solids and milk solids, encased in a soft cocoa butter matrix. Cocoa butter is the fatty oil found in cocoa beans, and it's the magical ingredient that allows chocolate to melt at approximately 3 degrees below human body temperature, allowing that delectable feeling of the chocolate melting as you bite into it. A good chocolatier will work carefully to treat their chocolate to give it that perfect taste and texture. After being fermented and dried, the cocoa nibs are treated with an alkali (often potassium carbonate) prior to roasting them, to improve the flavour (a process known as "ducting"). The amount of alkali needs to be just enough so that it catalyses the Maillard reaction and enriches the flavour, but not too much or the triglycerides in the cocoa butter will start to saponify, ruining the flavour. The cocoa should be roasted carefully so as not to burn it, but enough to enrich the colour as the roasting produces tannins. Those tannins then oxidise, darkening the cocoa still further. These roasted nibs are then ground and liquefied into what's known as chocolate liquor -- the purest most unadulterated form of chocolate!

The chocolate liquor is then blended, with cocoa butter, to whatever extend is desired. The darkest chocolate is virtually pure chocolate liquor with enough cocoa butter to set it. Milk chocolate typically contains vanilla as well as milk, to enrich the flavour, and white chocolate omits the cocoa solids altogether, containing purely cocoa butter and milk. This blend is emulsified and "conched" -- the liquid is swirled around metal beads which grind all the solid particles finely. The finer they are, the smoother the chocolate, and the silkier it feels in your mouth as you savour it. The highest quality chocolate is conched this way for at least 72 hours to ensure it's as perfectly smooth as can be.

But with the final stage, there's more left than just pouring it into a mould and allowing it to set. Just as a master blacksmith has to make sure steel is the perfect consistency as it cools, a master chocolatier ensures that chocolate is just right. Both work in the same way. Chocolate is tempered, just as metal is. Cocoa butter is actually capable of existing in 6 different crystalline forms, and in order to make sure it crystallises just right, care must be taken to heat treat it properly. Only one of those crystal forms gives the best chocolate. Get the temperature wrong and it will melt too easily, or taste gritty. At just the right temperature, the chocolate needs to be worked, to create the right kind of seed crystals -- phase V crystals. Only once there are enough phase V seed crystals in the mixture, can it be left to cool and solidify into the perfect chocolate. Smooth, glossy, and crisp. Blissful.

Images from parsectraveller and gnuf on flickr.

Just a quick post, because I'm supposed to be doing something else right now... But it isn't every day you get to watch history being made, streamed live over the internet.



As I type this, the SpaceX Dragon capsule is in the process of docking with the ISS, in orbit high above our heads. It isn't yet fully berthed, but it has now been captured by the robot arm of the ISS to help guide it into place. Currently, they're still running a few checks prior to docking. All the same, capturing the dragon with the robot arm was a historic moment in itself, bringing about jubilation in the control room and prompting astronaut Don Pettit (who was operating the arm at the time) to utter a phrase which should almost certainly go down in history: "Houston, it looks like we've got us a dragon by the tail."

All in all, SpaceX's dragon is turning out to be a highly capable little craft. SpaceX are such an inspiration to me...



"It's a beautiful day in space."

Did you know that there's a twitter feed called molecule of the day? So now, courtesy of twitter, I get a text message every day containing one randomly selected interesting molecule. This is now one of my new favourite things on the internets -- I believe the appropriate word would be NERDGASM!

*ahem*

But anyway, todays molecule caught my attention, because it's relevant to my interests. This is caryophyllene, and it's found in both hops and black pepper! Suddenly, I'm tempted to brew beer from peppercorns.

Anyway, I did a little background reading on it and rapidly discovered that this interesting little molecule shows its tiny carbonaceous face in a lot of places. It's a main component in the essential oils of rosemary and cloves too, as well as basil, oregano, caraway, west african pepper, and cinnamon. I'd speculate that shared compounds like this are why several of those herbs taste good together. It's most notable in black pepper particularly, though, because caryophyllene is one of the things that makes pepper spicy.

Oh yes, and it's also found plentifully in err... cannabis sattiva. Amusingly enough. In fact it even binds to cannabinoid receptors. But not those cannabinoid receptors. Please no one go away and try smoking peppercorns. And if you do, please don't say that some blogger on the internet told you to, ok?

(via @dailymolecule)

Ugh... I'm just going to cut this one immediately, so anyone who doesn't want to hear me whining about wavelength calibration can go on about their business!

( Gratuitous, yet cathartic whining )

I'm genuinely honoured to have a guest blog post today in Nature's Soapbox Science blog about the repurcussions of the recent plug being pulled on the ATHENA X-ray telescope. I'm quite proud of this one. Please do go over and take a look!

(You also get to see what I actually look like, in case you're curious...)

Isaac Newton taught us that every action has an equal and opposite reaction. What he didn’t mention, however, was the fact that this is true for more than just physics. It’s an unfortunate fact in the academic world, that science costs money. Typically, the better or more exciting the feat being attempted, the more expensive it is. While as scientists we all have to learn to accept this, it still comes as little consolation to those who get caught in the aftermath of cancelled projects. ...

In other news, SpaceX has officially made history. The Dragon capsule is currently in orbit around planet Earth. The first orbital spacecraft the world has ever known, which was fully developed and launched by a private company.



We may not have even noticed it happening, but we live in a different world now. A world where space is within our reach. A world where anyone can develop a spacecraft, and where people can seriously discuss mining asteroids. Perhaps the future really is now...

So I wanted to write a post for the Toxic Carnival but found myself not entirely sure what to write about. I mean... I don't know a huge amount about cool biogenic toxins like tetrodotoxin. Or unicorns, for that matter. But, back in my comfort zone, if we're talking about astronomical molecules then I have poisons-a-plenty to choose from. Some of them in unspeakably huge quantities. So I mused on this for a while... And I realised that, at least in some ways, I'm a physical organic chemist. And while organic things (like ethanol and benzene and people) are based on carbon hydrides, well... A lot of hydrides are rather toxic. So I bring you, without further ado, my 10 favourite toxic hydrides!^★

( Read more... )

^★ What? I'm a chemist, I'm allowed to put the words favourite, toxic, and hydrides together in the same sentence.

It's quite easy to talk me into doing silly things. Actually, if I'm honest, it's very easy. Especially if those silly things are entertaining and tenuously scientific. For instance, I'm writing this because of a conversation (with certain people) about diffracting Cadbury's creme eggs. There's... not a lot more I can say about that really. (I don't know how these things happen, they just do).

Now, when dealing with subatomic particles, any particle of matter actually exhibits wave-particle duality. Confusingly, matter can act like energy and energy can act like matter. Particles act like waves, act like particles, act like waves. It's bizarro concepts like that which, quite frankly, make me love quantum mechanics. But In theory, this can carry on right the way up to the macroscopic scale.

The photograph here shows my scrawl of the De Broglie equation. The right hand term is a little correction if you're dealing with relativistic velocities (that is, significant amounts of the speed of light). We can simplify things here by ignoring that, because at lower velocities, the whole term (root one minus V² over c²) is essentially equal to 1. So it simply comes down to Planck's constant, divided by mass times velocity. Well, I say simply...

So just suppose I was to throw a creme egg at you. A tasty chocolatey treat, filled with gooey sickly fondant, weighing about 39g (incidentally, the ones they sell in the US are apparently slightly lighter). Assuming I threw it at a reasonable speed of about 100 ms^-1 (metres per second) -- ignore the speed of sound in that photograph, by the way. That's just silly. It would have a De Broglie wavelength of about 1.7x10^-34 m. Oh dear. That's only slightly larger than the Planck length (effectively the smallest anything can be). That egg might diffract a very tiny amount at very small scales (if there's even anything small enough to diffract around). But it won't diffract around your head. Effectively, the creme egg I pelt you with won't diffract at all. Errr... sorry about that.

You might think that something might diffract if you throw it faster, but actually it doesn't work that way. Counter intuitively, the equation shows an inversely proportional relationship -- in other words, the higher the mass and/or velocity, the smaller the wavelength. Subatomic particles can diffract only because they're very very small. For macroscopic matter to diffract, it needs to travel very very slowly. So let's crunch some numbers, shall we?

How about 400 nanometres per second (400nm is the wavelength of violet light). That gives us a wavelength of 4.27x10^-26 metres. We're not exactly making progress, are we? So how about if we move our creme egg at 1.1x10^-15 ms^-1? That's the radius of one neutron every second. It's safe to say by now that that's an imperceptibly small velocity, but that would get us a wavelength of 1.54x10^-17 m. I'm pretty sure by now, we're down to scales which have no real names, and it's all getting a but strange and abstract.

I conclude, somewhat whimsically, that if it were ever possible to move a creme egg at a speed of around one neutrino radius per second, it would probably be able to diffract around neutrinos. I guess that's not really much of a result. Perhaps if you acquired a large mass of creme eggs all travelling at one neutrino radius per second and managed to make them all less that one neutrino radius apart from each other, they might agglutinate into a shared quantum state, giving you superfluid creme eggs...?

Nah. I've got nothing this time. Sorry.