Tuesday, 26 March 2013

Chemistry Dictionary: Adrenaline (epinephrine)

Adrenaline (epinephrine)

Adrenaline is a hormone, which is a chemical messenger in the body.  When the body is panicked, adrenaline is released into the bloodstream, and it acts on many parts of the body.  It tells the liver to release glucose (sugar) into the bloodstream; it tells the heart to pump faster, and tells the airways to open to get more air into the lungs and more oxygen into the bloodstream.  This is called the ‘fight or flight’ response, as the body prepares to respond to a perceived threat.

The shape of the adrenaline molecule fits into specific ‘receptors’, called adrenergic receptors, found on the cells in the heart, liver and lungs (and many other organs too), and when the adrenaline molecule fits into one of these receptors, it activates the receptor and tells the organs (through further messages) to respond in their own specific way.

Adrenaline was first artificially synthesised in 1904, and since then has become a common treatment for anaphylactic shock. It can be quickly administered to people showing signs of severe allergic reactions, and some people with known severe allergies carry epinephrine auto-injectors in case of an emergency.  Adrenaline is also one of the main drugs used to treat patients who have a low cardiac output — the amount of blood the heart pumps — and cardiac arrest. It can stimulate the muscle and increases the person's heart rate.

It's also a useful starting point for many drugs, because it has a wide range of effects on the body.  For example, its effect on the lungs means that a variation on adrenaline can be used to treat asthma.  One particularly successful drug is salbutamol, and the salbutamol molecule has a lot in common with adrenaline.

The differences between salbutamol and adrenaline make salmeterol more "specific" - in other words, salmeterol is designed (or adapted) to make it target just the soft tissue in the lungs and wind-pipe, and affect the heart less strongly.  If you think of adrenaline as a super key that can open many doors, than salbutamol is an adapted key that's only able to open some doors.

You may recall diagrams such as these from from school chemistry classes - chemicals and molecules being illustrated by a series of carbon, oxygen and hydrogen atoms joined together by little lines.  The manufacturers of pharmaceutical compounds pay very close attention to these diagrams.  After all, the difference between a successful drug and a dangerous, toxic or addictive one is often just a hydrogen atom here, a carbon atom there.  Any drug which is released and authorised for sale in the UK has gone through rigorous checking to ensure that it is effective and that any side effects are also known.  Adrenaline is an ideal starting point for drugs, given its widespread effect on the human body; however, it's possible to begin with other starting points, and look to achieve different effects.

Sadly, in the UK, there has recently been an explosion of compounds which mimic the effects of popular illegal drugs such as cocaine, ecstasy and cannabis, but are chemically different enough to avoid being illegal.  Keeping up with the new highs is difficult. Chemical compounds are effectively legal until they are banned, which means the UK Government has no choice but to be reactive once a chemical hits the market, and must move switfly to determine if it is legal.  A recent report from the European Monitoring Centre for Drugs and Drug Addiction, stated that one new legal high was being “discovered” every week in 2011. Additionally, the number of online shops offering at least one psychoactive substance rose from 314 in 2011 to 690 in 2012.

Chemistry moleculemolecule

Thursday, 21 March 2013

Film Review: Wing Commander

I only played Wing Commander on a PC once; maybe twice.  I didn't own the game, and played it on a friend's PC. First-person space shooters have never ever appealed to me, since I never understood the three-dimensional radar readouts, and if I should press Up or Down to catch the enemy.  As a result, I never got into the original game, or any of the subsequent Wing Commander series.

However, Wing Commander was widely recognised as a very good example of its genre, and had a working plot and back story, based around mankind's war against the feline-looking Kilrathi.  So, it was only a matter of time before a Wing Commander film was made.  I'm still waiting for a Command and Conquer film crossover, and I acknowledge my optimism on that score!

Coming from a generation where movies were made into computer games, I was interested to see how a computer game could be made into a movie. The DVD blurb describes the film as Starship Troopers meets Top Gun, and the film is a blend of sci-fi, testosterone and a large fistful of cliches.  And you'd better pay attention during the opening credits, as the voice-overs are going to give you all the back-story in case you've only played the Wing Commander game a few times.

The plot:  Earth's distant Vega outpost is attacked by the Kilrathi, and they break into the outpost and steal a Navcom AI unit.  This will enable them to carry out a series of hyperspace jumps to Earth.  I'm sure there's more to it than that, but that's the gist of it.  As far as back-stories go, Wing Commander has one, which was becoming the de facto standard for 90s computer games.

A security 'breech', and more serious than the breach of spelling.  Note Nokia's product placement - this IS the 1990s, after all.

Earth's battle fleet are too far away to prevent the impending attack on Earth, so it falls to one surviving battleship to save the day. The message is passed from Earth central command to the one surviving battleship in the area, the Tiger Claw, by a young hot shot pilot, Lieutenant Christopher Blair.  They relay the message, and one battleship is set to face-off against a vast and overwhelming Kilrathi army.  Who will win?  Is Earth safe?

Of course, Blain's father served with many of the Tiger Claw's senior staff (very Top Gun).  He's on board a carrier ship which is taking him out to active duty, and which is piloted by a crusty old captain who is secretly an expert in space combat, and is one of the "Pilgrims", a sort of human under-class with special space-faring abilities.  Are you counting the cliches yet?  And does Blair have some previously undiscovered special space-faring abilities as well?

To quote a conversation on the Tiger Claw:
"Lieutenant, you wouldn't be related to Arnold Blair, would you?"
"He was my father, sir."
"He married a Pilgrim woman, didn't he?"

"Pilgrims don't think like us."
"You won't have to worry sir, they're both dead."

So let's add 'orphan' to the list of cliches.  And while this scene is playing out, remember to have a go at "What have they been in since (or before)?" - there's David "Poirot" Suchet, and David Warner (Tron, Star Trek VI), and Hugh Quarshie (Holby City) just for starters.

Fortunately, Wing Commander does have a few novelties: the senior flying officer (played with a genuine British accent by Saffron Burrows) is female, and a slightly better-developed character; a few of the other fighter pilots are female too, so the film just manages to dodge much of the testosterone-laden dialogue that completely overwhelmed Top Gun.  This film is a PG, so it's all toned down.  The worst example here:  Blair, to the senior flying officer Lieutenant Commander Deveraux (I mean Wing Commander, of course I do),  "If I'm locked on, there's no such thing as evasive action," delivered with a smile that's wider than the Andromeda galaxy.  She puts him in his place with some witticisms, thankfully.  This forms the basis of the usual mistaken identity moment where "It turns out that the mechanic is actually the commanding officer," and you know as soon as Blair has demonstrated his immaturity and lack of flying experience to Deveraux that they'll be kissing before the final credits.  Predictable?  Absolutely.  

Wing Commander features the pilot hot shot rivalry that is par for the course with any military action film, but thankfully it only occurs in a couple of scenes, as Blair and his colleague have to find their places in the pecking order on the Tiger Claw.  A few cross words and a bit of fist waving, and it's all done and dusted.  That's a relief.

There is also the death of a colleague, which was a little surprising for a computer game crossover, but standard issue in Top Gun etc.  I should have seen it coming, I know.  The death of one of the characters requires more depth in the characters who should adjust to it, but the script and the story just don't have the extra dimension that's needed.  Subsequently, Matthew Lillard's character Todd Marshall comes off looking underwritten (or under-acted - I'll be honest, I can't decide).  The colleague's death is his fault, but by the end of the film he still looks as hot-headed and stupid as he did at the start.

Otherwise, it's a by-the-numbers shoot-em-up...  there are a few variations on the theme:  in Top Gun, it's "If you can't find somebody to fly on your wing, I will," whereas in Wing Commander, it goes like this:

Deveraus: "Let's make them bleed.  Mount up.  Blair, you'll take Hunter's wing."
Hunter: "Ma'am, I'd as soon you assign me another wingman."
Deveraux:  "You have a problem I should be aware of?"
Hunter: "Yes, ma'am, I do. I don't fly with Pilgrims."
Deveraux (to Blair): "You'll fly my wing."
Blair: "Are you sure?"
Deveraux:  "Did I give a suggestion or an order?"
Blair: "I got your wing, ma'am."

The space setting is used to good effect, with a nebula and a black hole (named Scylla and Charybdis) and massive 'distortions in space-time' (i.e. a very massive star) providing some mild jeopardy at the start of the film, and a way to defeat the Kilrathi battleship towards the end.  Although how the Kilrathi failed to see the very bright star just in front of them until it was too late is a mystery to me.  There's a good battle scene in an asteroid field, where the debate that Blair and Deveraux about fighting the enemy is enacted in real life.  Foreshadowing?  Predictability?  Not sure.

For me, the one major disappointment is the Kilrathi.  I know it's a strange disappointment, but I've always read, seen and understood from Wing Commander reviews, magazine articles and conversations that they were feline (or felinoid, to quote the Wing Commander wiki).  However, here, the costuming is way off, and they look like they're reptilian... or at best, bald cats.  They have no fur or hair; their faces look too unrealistic to be believable and they come off looking unintelligent.  They only get a few lines of dialogue too, spoken in Kilrathi and subtitled, so the end result is that they look like men in costumes that are so poorly designed that the actors inside them can't be heard properly.  And these are the villains of this piece:  some characterisation other than "bent on total intergalactic domination" would have been good.

So:  if you've played the game and understand the backstory, Wing Commander might be a good film to watch for the nostalgia value.  If you don't mind story-telling cliches and you enjoyed Top Gun, you'll like this (and it's rated PG too).  It's quite clear that the Wing Commander team were going for Top Gun in space, and they play up any possible connections or similarities.  Alternatively, if you're a little more selective about your sci-fi, and you've not yet seen any of the recent Battlestar Galactica TV series, I'd recommend them instead.

Friday, 15 March 2013

Angle of Elevation of a Geostationary Satellite

In a previous post, many months ago, I calculated the height of a geostationary satellite using the laws of physics which relate to gravity and circular motion.  This time, I'll use that information to deduce the angle of elevation of a given geostationary satellite, but I'll take the simplified model where the satellite is at the same angle of longitude as the observer (i.e.on the same meridian).  The maths enters three dimensions when the observer is in Europe but the satellite is geostationary over Central America, instead of North Africa.

Drawing a simple diagram will help to outline the situation, and show how the key parts of the model fit together.

A = centre of the Earth
B = position of observer on the Earth's surface
C = satellite

Angle alpha is the angle of longitude of the observer (how far north, or south, of the equator they are).  For this example, I will be using a longitude of 50 degrees north (northern France/southern England).
The angle at B is 90 degrees (the angle between the radius from A and the horizon) plus the angle of elevation, beta, which we are looking to solve.

Lenth a is the straight-line distance from the observer to the satellite
Length b is the distance from the centre of the earth to the satellite, re (radius of earth) plus rs (altitude of satellite, measured from earth's surface)
Length c is the radius of the earth

We only know two of the lengths (b and c) and the included angle, alpha, so we must start solving the triangle by using the cosine rule:

In order to find angle B, and hence beta, we will first need to find length a.Substituting the known lengths and angle into the cosine rule, we get:

a2 = (re+ rs)2 + re2 - (2 x (re+ rs) x re x cos 50)

a2= 42,164,0002+ 6,378,0002- (2 x 42164000 x 6378000 x 0.6428)
a2= 1.473 x 1015 m2
a = 38,376,585 m

Now that we know all three sides, we can use the sine rule to determine an angle by knowing one other angle and the two opposite sides.  I will calculate angle C and then subtract A + C from 180 degrees to find C.

a / sin A = c / sin C

a = 38,376,585 m (as calculated above)
A = angle of longitude of the observer

c = distance from Earth centre to geostationary satellite, which was calculated previously as 42,164,000 m.
C = angle on diagram; angle at satellite between centre of Earth and observer on the ground.

So, by rearranging, we have

sin A) / a = sin C

If A = 50 degrees, then by substitution C = 7.3143 degrees

Therefore, B = 180 - (50 + 7.3143) = 122.6 degrees, and beta = 122.6 - 90 = 32.6 degrees.

There is an alternative route to finding angle beta, and that's by dividing the triangle ABC into two right-angled triangles by dropping a perpendicular from B onto the line AC, see below.  Angle Z = 90 degrees.

Firstly, calculate the distance BZ, which is common to both triangles ABZ and BCZ.  This can be done by simple trigonometry since angle Z is 90 degrees, and angle A is known (or determined by the observer):

sin A = BZ/ re  and where A = 50 degrees, BZ = 4,885,831 m.

Next, calculate AZ in the same triangle ABZ:

cos A = AZ/ re  and where A = 50 degrees, AZ = 4099699  m.

As we now know AZ, we can calculate CZ, and hence identify two of the sides of triangle BCZ.

CZ = AC (distance from centre of Earth to geostationary satellite) minus AZ
CZ = 42,164,000 - 4,099,699 m = 38,064,300 m

Finally:  angle B in triangle BCZ

tan B = CZ / BZ = 38,064,300 / 4,885,831  = 7.7909
B = 82.685 degrees

Now, we know that angle A = 50 degrees, so angle ABZ = 40 degrees.
Angle ABC = 40 degrees + 82.685 degrees = 122.685 degrees.
We want to know the angle between the observer's horizon and the satellite; since the angle AB and the horizon is 90 degrees ('the angle between a radius and a tangent is 90 degrees') this is simply 122.685 degrees - 90 degrees = 32.685 degrees... which agrees with the result from the first method.

QED :-)