Just pretty pictures today; the post I had been planning on for today is turning out a bit more complicated than I had figured. This will probably happen again. That's the thing about learning new stuff... it always takes longer than you think it will.
Sao Paolo
Syria
There's nothing quite like standing on top of a tank in the hot summer sun, surrounded by other tanks all reflecting the heat back up at you. Except, maybe, if you're wearing a full face gas mask and taking samples of a gas that is just about everything bad you can call a chemical.
Toxic, corrosive, flammable, explosive, carcinogenic… The whole system ran at a slight negative pressure, so that if there were any leaks air would go in instead of toxic gas leaking out, and they monitored it carefully to keep the concentration out of the explosive range.
I was testing the performance of a new scrubber which was taking the gas in question out of the exhaust, so I had to climb up to the top of the tanks then up on a scaffold, carrying a vacuum flask, to stand next to the exhaust stack and suck a sample out of the flow. All around me were explosion hatches; small explosions ("puffs") were undesirable but routine, and there was a well-established procedure for re-starting the system after it shut itself down following a puff.
For all that, it was pretty safe: as safe as it could be, considering the material. One day when I was taking a sample, a puff happened while I was on top, and I barely noticed it. I think I heard a bang as the explosion hatches jumped, but by the time I turned to look they had fallen back into place and re-sealed the tank, exactly as they were designed to do.
The gas mask was uncomfortable, but I was happy to be wearing it. It sealed all around my face, forehead to chin, and the sweat it generated improved the seal. I couldn't wipe the sweat off my face however, and it's no fun to get sweat in your eyes while you're climbing around a scaffolding system.
After a couple of weeks of this (I could only take one in/out sample set per day, and if there was a process upset that day I had to throw my results out) I noticed that my hair smelled … strange. For all it was a treated gas stream, with low levels of the toxic chemical, I had been spending enough time exposed to it that the gas had started doing something to my hair. The smell was that sickly-sweet smell of rotting fruit, and it lingered for a week or so after I finished that particular project. It took a few washes before the smell finally went away.
That smell in my hair was the only effect the gas had on me. Gas masks are wonderful things.
I'm in trouble now…
I recently discovered a black hole as deep as the internet for losing time in, but which is much more edifying - so I don't feel so bad about all the time spent there because I'm learning stuff.
How useful that stuff is has yet to be determined.
We begin with Google Scholar. This is a corner of google's search engine that is focussed exclusively on technical journals and peer-reviewed publications. It's fantastic if you're looking for technical information about something that is also for sale; regular Google would be massively polluted by people selling that something, or asking for help about that something, or reviews of that something, or blogging about that something. There's just one catch, and it's a big one: the journals are almost all pay sites.
Oh, they let you read the abstract, and sometimes you're just doing an overview and that's enough. But at $30 per article or more, it can get expensive really fast if you're actually trying to dig into a subject. On top of that, if you're looking for something specific like the solubility of a relatively obscure compound (by 'obscure' I mean it's not on wikipedia), the information may not be in the abstract.
Then I remembered from my student days that the university library had a proxy which students could log in with and which would give full, free, institutional access to most of these pay sites. Of course the university would have a subscription! Of course, I'm not a student anymore.
After a bit of investigating, I discovered that my old student number was still in the university's system, and I successfully logged in to the proxy and downloaded a few papers that I'd put on my "to get" list.
Next thing I knew, it was three hours later, I'd downloaded a dozen related papers, was having a grand time reading them and following references—and I was still at work.
Fortunately, I was looking up information related to one of my projects at work and some of the interesting stuff I'd read might help the project, so I knew the boss wouldn't mind. Too much.
Now I have a bookmark to Google Scholar via the library proxy in my browser's bookmark bar which takes me to the proxy login page then to the search engine, so that every link I click on in the results goes straight to the full article.
I think I'm in love.
The Chinook wind is a warm dry wind that comes down from the Rocky Mountains into Alberta, and can turn a winter day into short-sleeve weather in the space of hours. But what heats up the air? It wasn’t that warm on the BC side of the rockies, before it crossed the mountain range. Well, I decided that I was going to calculate it. Let's see if this works.
Let’s say the air comes off the ocean at about 10 degrees Centigrade and 90% relative humidity, which isn't actually typical for a dreary Vancouver winter day—but that's because the Chinook is powered by the Pineapple Express, which is warm, wet air coming inland from Hawaii. It travels inland, raining on Vancouver as it goes, until it hits the coast mountain range, and is forced to rise.
You’ve probably noticed, if you’ve ever changed altitude quickly, that it gets colder the higher you are. Well, that wind from the ocean is going to do exactly that.
To do the math, we’ll look at a small piece of the wind, pretend it stays together to simplify things, and follow it over the mountains.
I'm sure you've all heard the story of how vitamin C either prevents or cures the common cold. Some of you may also remember that vitamin C prevents or cures scurvy. But what exactly does it do for our bodies? I decided to do a bit of searching and find out.
Clues to what vitamin C does for us can be found in the symptoms of vitamin C deficiency itself. Scurvy is not just the disease where your teeth fall out, though that is one of the symptoms. Bleeding gums, bleeding under the skin (bruising), bleeding in the joints (joint pain), bleeding at hair follicles, and bleeding at previously healed scars start off the list of visible symptoms. Before those is fatigue; after those is death.
All of those bleeding symptoms demonstrate that the body is falling apart and can't keep its blood inside anymore. Quite literally: vitamin C is required for the production of collagen, the structural support cables of our body. They're found basically everywhere, including in bones and teeth, where they're mixed with minerals. Lose the ability to make new cables, and you lose the ability to repair routine damage day to day - and over time you lose the microscale structural integrity that keeps the blood inside your veins, among other things.
Fatigue is so general a symptom it can't really be used to diagnose anything. Besides, you probably just stayed up too late. But even here, it seems that vitamin C plays a role. In addition to being crucial to making collagen, it's also crucial to making dopamine, norepinephrine and epinephrine (adrenaline), and carnitine.
Carnitine is an escort for fatty acids into the mitochondria, according to the link above. Basically it's the fuel injection system for the motors that power our cells. While we get most of our carnitine from our diets, particularly from meat, if we're so low on vitamin C we're suffering from scurvy, we probably have low carnitine intake as well, a double-whammy.
But carnitine is in meat, and vitamin C is in oranges and other tasty veggies and fruits, right? How could the inuit survive on a meat-only diet? Actually, there's vitamin C in meat, too: mostly in organ meat, and the inuit do just fine without vegetables, on their traditional diet.
In fact, it looks like just by eating a reasonably healthy mix of food, you'll get enough vitamin C. Not everybody manages this, but I guess scurvy is rare enough now that people forget about the whole "it keeps you alive" part and instead spend their time thinking about some of its very minor effects.
As for curing the common cold? survey says… taking it when cold symptoms appear does no better than a placebo; taking it every day reduces cold duration by maybe 10%; and if you're physically stressed (i.e., working in a cold climate or running marathons, not just worried) then taking it every day can be justified because it gives significantly more than a 10% benefit.
Activated carbon is a pretty amazing material. It's just carbon, the same stuff as in charcoal, diamond, and the carbon black that shows up on the bottom of pans and kettles used over flame, for those who have gas stoves or enjoy camping. At the same time, it's an incredibly important material for purification, because one of the neat things that activated carbon does is trap toxic stuff by adsorption. It doesn't catch everything, but it catches so many different things that it's often used in gas masks when you don't know what toxic gas you might encounter - for a HazMat team, for example, those who aren't using SCBA tanks.
One unfortunate problem with any filtration system is that the filter itself has a limit to how much crap it can capture from the water or air that's passing through - and the filter can't tell you when it's getting full. How do you know when it's time to change your Brita filter? How does a HazMat team know when their gas masks stop working? In a plant situation with large equipment, you can install sensors to monitor for breakthrough, but that's not practical, and sometimes not even possible, on small portable filtration systems.
A team from the University of California San Diego recently published in the journal Advanced Materials a paper on the production of carbon nanofiber photonic crystals. These are a special crystal form of carbon which, once they've captured toxins, change colour. No power required, no special equipment required, no extra weight for HazMat to carry. These crystals can be embedded right in the activated carbon filter, so they see exactly the same level of toxin as the filter itself. If you embed them at varying depths in the filter, you could actually watch the adsorption front as it moved through the filter, and know with certainty when your filter is getting close to breakthrough, and thus when it needs to be changed.
In honour of today's shuttle launch, I thought I'd start off with a bang, or at least a roar of fire: rocket fuel!
The shuttle uses two different styles of rockets with two very different types of fuel: liquid and solid. The shuttle itself has three big rocket engines that run on liquid hydrogen and liquid oxygen, stored in the big orange external tank, while the rest of the thrust is provided by solid fuel in the solid rocket boosters, a mixture of ammonium perchlorate (NH4ClO4), aluminum, iron oxide, and some binders to hold it in its moulded shape.
The liquid fuel engines fire first; they are the controllable ones. If there's a problem, they can be shut down. Once the solid fuel starts burning, they only stop by running out of fuel - and the solid rockets provide the majority of the boost to get the shuttle off the ground.
And since this is a chemical engineer's blog, I'm going to do some calculations around the chemistry of those engines. Of course, this won't be nearly enough to design your own rocket engine from, but then I'm just doing this for fun, I'm not a rocket scientist.