That's nice, dear

This blog post is about programming, for people that don't program - at least that's the effect I'm aiming for. The title is in recognition of my tolerant wife, The Inelegant Gardener, who has learnt the appropriate response to my enthusiastic displays of the results of my programming: "That's nice, dear"!.

I started programming a long time ago - in around 1980, at the school computer club, when I was 10. Since then I've been taught odd bits of programming by scientists, and done quite a lot of programming as part of my scientific job. I've started to get more interested in proper software engineering in the last few years. This is a roundabout way of saying I am an enthusiastic amateur.

People associate programming with the mathematically minded, but this isn't necessarily the case: the codebreakers at Bletchley Park, who were amongst the first users of electronic computers, had a range of skills - amongst them were linguists and crossword wizards. I was talking to a Fellow in linguistics, who'd helped write his college's library software - as he pointed out: a very logical view of language is a great benefit for a programmer. Programming is about giving an idiot very exact instructions, if the instructions concern maths then you need to know maths - otherwise you don't.

The core of programming is still what I learned years ago, data (numbers or letters) is stored in "variables" that have names. There are conditional statements: "If [something is true] Then [do this] or else [do the other]". There are looping statements: "Do this 100 times". And there are functions: "add 2 to this number, square it, add the number you first thought of and tell me the answer" or "how many times does the letter a occur in this sentence".

These simple statements are being buried under an increasing depth of additional ideas. Since the 80's the big thing in programming has been "object-orientation". In object-orientated programming you package up data of a particular sort with functions that relate to that data. So if you had data modelling an octopus you would include functions such as "wave-tentacles" and "change colour", such functions would be useless for data describing a horse. The real benefit to this is comprehending larger software systems, because a sea of functions and data is grouped together into logical islands. Beyond this there are design patterns - reoccurring systems of objects which I haven't entirely go the hang of.

In addition to the changes in language, there are changes in the tools used to program: syntax highlighting is nice, it amounts to colouring the verbs, nouns and proper names in programming in different colours - makes it easier to spot mistakes. Auto-completion is another handy tool, in a well-designed language there are only a limited number of next possible statements when you are programming - auto-completion presents you with them as you type. Sites like Stackoverflow are great for asking programming questions, and there no end of function libraries available on the web to help you out.

I have a number of little software projects on the go, you can see them in much the same way as woodworking projects, suduko or crosswords: they keep me out the way, muttering quietly to myself and exercising my brain. It doesn't matter that what I'm doing isn't groundbreaking and new.

Programming does lead to some odd habits; when I started programming it was useful to know binary and hexadecimal number systems, as a consequence I believe that numbers such as 1024 and 128 are nice and round. I've come to appreciate a wide range of bracket styles [] (){} since they are all used for different things and the semi-colon is one of the most important pieces of punctuation in my life. If I program for too long in a stretch I start to forget how to speak to people.

And just to show off the results of my latest fiddlings: maps of the UK election results. I got interested in doing this just after the General Election. The Guardian has published a lovely spreadsheet of election results, including data on every single candidate. You see lots of maps of data of this sort, I wanted to know how it was done. (Technical details beyond the maps.)

First of all the gender of MP's by constituency: constituencies represented by ladies are marked pink, those by men marked blue:

The black constituency in northern England is Thirsk and Malton, which held its election on 27th May, following the death of one of the candidates during the general election campaign.

The population of each constituency is also interesting, here I have coloured the constituencies with 9 different shades of green, the palest shade corresponds to a voting population of between 20,000 and 30,000, the darkest shade corresponds to a population of between 100,000 and 110,000:

The Western Isles (now known by it's Gaelic name: Na h-Eileanan an Iar) has the smallest population at about 22,000 and the Isle of Wight has the largest population with just under 110,000 potential voters. I used ColorBrewer to find a nice set of colours.

Finally here's a map of which party came second in each constituency in the 2010 General Election:

Red for Labour, blue for the Conservatives, orange for Liberal Democrats, yellow for Scottish Nationalists, pale green for Plaid Cymru, dark green for Sinn Fein, blue for Ulster Conservatives and Unionists, and there are a few independents and minor Northern Island parties which are all coloured white. 

Footnotes

So the task is to get the spreadsheet data into a map: To get started I did a bit of memory trawling and googling, a couple of people have written about colouring in maps: this one uses shapefile format map data and the R programming language, whilst this one uses SVG format map data and Python (another programming language). It turns out the shapefile format data for constituencies is a little difficult to get - you have to fill in forms! However enterprising people on Wikipedia have made SVG format constituency maps available. SVG stands for Scaleable Vector Graphics, it's an XML format which means it's plaintext and there are standard means to extract data from it and manipulate it. The only real problem is that the constituency names in the spreadsheet don't exactly match the names inside the SVG format map - I had to resort to some horrible constituency by constituency coding for a load of them. To do this I used the C# programming language, largely because Visual Studio Express C# is a very nice, free development environment which I've used before. To view the SVG maps inside my application I used the Webkit .NET library to provide a webbrowser control (which wraps up the rendering engine used in the Safari and Google Chrome browsers) - the native C# webbrowser control is based on Internet Explorer - which doesn't render SVG. Output to bitmaps is a bit clumsy, Inkscape (a free SVG editor) wasn't keen on displaying the original constituency map, so I resorted to viewing the map in Google Chrome and taking a screen shot (a terrible bodge).

Book review: The World of Gerard Mercator

Once again I have been reading, this time "The World of Gerard Mercator" by Andrew Taylor. As before this blog post could be viewed as a review or, alternatively, as some notes to remind of what I have read. Overall I enjoyed the book, it provides the right amount of background information and doesn't bang on interminably about minutiae. I would have liked to have seen some better illustrations, but I suspect good illustrations of maps of this period are hard to come by and a full description of Mercator's projection was probably not appropriate.

The book starts off with some scene setting: at the beginning of the 16th century the Catholic church were still keen on Ptolemy's interpretation of world geography in fact to defy this interpretation was a heresy and could be severely punished. Ptolemy had put down his thoughts in Geographia produced around 150AD, which combined a discussion of the methods of cartography with a map of the known world. As a precedent Ptolemy's work was excellent, however by the time of the 16th century it was beginning to show it's antiquity. Geographical data, in Ptolemy's time, from beyond the Roman Empire was a little fanciful, and since the known world was a relatively small fraction of the surface of the globe the problems associated with showing the surface of a 3D object on a 2D map were not pressing. Ptolemy was well aware of the spherical nature of the world, Eratothenes had calculated the size of the earth in around 240BC, he stated that a globe would be the best way of displaying a map of the world. However, a globe large enough to display the whole world at sufficient detail would have to be very large, and thus difficult to construct and transport.

Truly global expeditions were starting to occur in the years before Mercator's birth: Columbus had "discovered"  the West Indies in 1492, John Cabot made landfall on the North American landmass in 1497. Bartolomeu Dias had sailed around the Southern tip of Africa in 1488, Vasco da Gama had continued on to India in 1497, around the Cape of Good Hope. The state of the art in geography could be found in Waldseemüller's map of 1507, showing a recognisable view of most of our world. Magellan's expedition would make the first circumnavigation of the globe in the early years of Mercator's life (1519-1522).

Mercator was born in Rupelmonde in Flanders on 5 March 1512, he died 2 December 1594 in Duisburg in what is now Germany at the age of 82. This was a pretty turbulent time in the Netherlands, the country was ruled by Charles V (of Spain) and there appears to have been significant repression of the somewhat rebellious and potentially Protestant population. Mercator was imprisoned for heresy in Rupelmonde in February 1543, remaining in custody until September, many in similar circumstances were executed, however Mercator seems to have avoided this by a combination of moderately powerful friends and a lack of any evidence of heresy.

Mercator's skill was in the collation and interpretation of geographical data from a wide range of sources including his own surveys. In addition he was clearly a very skilled craftsman in the preparation of copperplate engravings. He was commercially successful, manufacturing his globe throughout his life, as well as many maps and scientific instruments for cartographers. He also had a clear insight into the power of patronage.

His early work was in the preparation of maps of the Holy Land (in 1537) and Europe (in 1554), along with a globe produced in 1541. The globe seems to be popular amongst reproducers of antiquities, you can see details of it on the Harvard Map Collection Website.

Mercator is best known for his "projection", in this context a projection is a way of converting the world - which is found on the surface of a 3D sphere into a flat, 2D map. Mercator introduced his eponymous projection for his 1569 map of the world, illustrated at the top of this post. The particular feature of this projection is that if you follow a fixed compass bearing you find yourself following a straight line on the Mercator projected map. This is good news for navigators! The price you pay for this property is that, although all regions are in the correct places relative to each other, their areas are distorted so those regions near the poles appear much larger than those near the equator. Mercator seems to have made little of this discovery, nor described the method by which the projection is constructed - this was done some time later, in 1599, by Edward Wright. Prior to maps following Mercator's projection navigation was a bit hit and miss, basically you headed up to a convenient latitude and then followed it back to your destination - an inefficient way to plan your course. If you're interested in the maths behind the projection see here.

In terms of it's content the 1569 map shows Europe, Africa and a large fraction of Asia much as we would see it today, certainly in terms of outline. The Eastern coast of North and South America is fairly recognisable. The map fails in it's representation of the West coast of America - although to give credit where it is due, it at least has a west coast. The landmasses indicated at the northern and southern poles are close to pure fantasy. The Southern continent had been proposed by Ptolemy as a counterbalance to the known Northern continents - with no supporting evidence. Exploration of the far North was starting to occur during Mercator's life, with expedition such as that of Frobisher.

Mercator is also responsible for the word "atlas" to describe a book containing a set of maps, in this instance he coined the term to describe the volumes of maps he was preparing towards the end of his life, the last of which was published published posthumously by his son, Rumold, in 1595.

Following my efforts on Joseph Banks, I thought I'd make a map of significant locations in Mercator's life. You can find them here in Google Maps, zoom out and you will see the world in Mercator projection - a legacy from a man that lived nearly 500 years ago.

Understanding mayonnaise

Some time ago I wrote a post on confocal microscopy - a way of probing 3D structure at high spatial resolution. This post is about using confocal microscope to understand mayonnaise (and a bunch of other things)

As young scientists we are introduced to the ideas of solids, liquids and gases very early on. We make these distinctions, amongst other things, to understand their mechanical properties, to answer questions such as: How thick do I have to make the legs of my chair to support my weight? How fast will liquid run out of a bucket? How high will my balloon fly?

But what is mayonnaise? It's very soft, and can be made to flow but it's not a proper liquid - you can make a pile of mayonnaise. How do we describe grain in a silo, or an avalanche? In some senses they have properties similar to a liquid: they flow - yet they form heaps which is something a solid does. What about foams -  a pile of shaving foam looks pretty similar to mayonnaise? Starch paste is an even weirder example, it acts like a liquid if you treat it gently but a solid if you try anything quick. (This is known as shear thickening). These mixed systems are known as colloids.

The programme for understanding solids, liquids, gases and these odd systems is to understand the interactions between the "fundamental" particles in the system. For our early courses in solids, liquids, and gases this means understanding what the atoms (or molecules) are doing - how many of them are there in a unit volume, how are they ordered, how do they move and how they interact. Typically there are many "fundamental" particles in whatever you're looking at so rather than trying to work out in detail what all of them are up to you resort to "statistical mechanics": finding the right statistical properties of your collection of particles to inform you of their large scale behaviour.

The distinguishing feature of all of our new systems (mayonnaise, grain piles, avalanches, foams, starch paste) is that they are made from lumps of one phase (gas, liquid, solid) in another. Avalanches and grain piles are solid particles in a gas; mayonnaise is an emulsion: liquid droplets (oil) inside another liquid (water); foams are air inside a liquid and starch paste is a solid inside a liquid. These systems are more difficult to analyse than our traditional gases, solids and liquids: firstly their component parts aren't all simple and aren't all the same. Particles most likely have different sizes and shapes. Atoms and molecules are all the same size and all the same shape. Secondly, they're athermal - ambient temperatures don't jiggle all their bits around to make nice averages.

Confocal microscopy looked like an interesting way to answer some of these important questions about the structures to be found in these complex systems. Mayonnaise turns out not to be a good model system to work with - you can't see through it. However, you can make an emulsion of different combinations of oil and water, and if you're cunning you can make an emulsion with over 50% of droplets by volume which is still transparent. Using even more cunning you can make the distribution of droplet sizes relatively small.

Having spent a fair bit of time getting the emulsions transparent with reasonable droplet size distributions, my student, Jasna, came in with some pictures of an emulsion from the confocal microscope: where the oil droplets touched each other the image was brighter, you can see this in the image at the top of this post. This was rather unexpected, and useful. The thing about squishy balls, is that the amount by which they are squished tells you something about how hard they are being squeezed. The size of the little patches tells you how much force each droplet is feeling. So all we have to do to find the force network in an emulsions is measure the size of the bright patches between them.

In the end our work measured the forces between droplets in a compressed emulsion and we found that these measurements agreed with a theory and some computer simulations. Criticisms of the work were that the relationship between luminous patch size and force was more complicated than we had assumed, and that the force distribution was all very well but the interesting thing was the arrangement of those forces. These criticisms are fair enough. Must have been pretty good though, because someone wrote a paper for Science claiming to have done it first, whilst citing our paper (they had to publish a correction)!

Footnotes
This work can be found in this paper:

Brujic, J., S. F. Edwards, D. V. Grinev, I. Hopkinson, D. Brujic, and H. A. Makse. “3D bulk measurements of the force distribution in a compressed emulsion system.” Faraday  Discussions 123, (2003), 207-220.  (pdf file on Scribd)

Jasna Brujic was the PhD student who did the experimental work, Sir Sam Edwards is a theoretician who works on granular materials, Dmitri Grinev worked with Sir Sam on the theory, I supervised Jasna, Djordje Brujic is Jasna's dad and wrote the image analysis code and Hernan Makse is a computer simulator of granular materials.

Go back to your constituencies and prepare for government!

I think this will be my final political blog post for a while. I've written quite a few over the past month: I started with an explanation as to why I was a member of the Liberal Democrats here. I hunted out some data on the occupations of MP's and made a graph here (what a lot barristers!). Then I wrote a blog post about the statistical errors in opinion polls, which I think was a little prescient (latest reports suggest that the voters that didn't turn out were predominantly LibDem - hence biasing the pre-election polls). Approaching the finishing line, I wrote a post on my plans to stay up late on election night, followed by a post on my crashing gloom of the night itself. Then I made a post on what it might mean as the negotiations for coalition continued.

This post is about coalition, and a look at the debris of the election. My friends at work from Labour and Conservative tendencies called me a "turncoat weasel" today (in a friendly manner) so I have illustrated this post with a picture I took of a weasel.

First up, my take on the agreement between the Liberal Democrat and Conservative Party: remind me not to negotiate with Nick Clegg for anything, I think he's played a blinder on this one. The agreement contains a mix of LibDem and Tory policies, and five positions in cabinet. It's quite clear that the LibDems are a junior partner, but then that's what you'd expect. I'm also pleased Nick Clegg did what he said he would do before the election: go to the party with the largest electoral mandate in the first instance.

Despite the massive apparent differences on Europe, I suspect it won't be a big problem for the coalition. Liberal Democrats have a principled view that power should dissociate to the appropriate level - some things are best handled at a local level, some at a national level, and some to the European level. My guess is that over the next five years there will not be another major treaty moving power towards Europe, and joining the Euro in the next five years, as we all crawl out of recession, would be unwise as far as anyone is concerned. Perhaps David Cameron will value a coalition partner who has not isolated itself in Europe.

I'm wondering whether the Labour Party are trying to take the mantle of "the nasty party", in the background to David Cameron's speech in Downing Street could be heard a chant of "Tory scum". David Blunkett described Nick Clegg as a harlot, amusing coming from an adulterer. And this morning Nick Cohen, left-wing columnist for the Observer and various other places, tweeted:

Here's my writing sorted out, Will crucify every fucker who voted Lib Dem, one by one, in the national press. Better you had voted Tory.

I suppose I should proviso this last one, on the whole I don't believe a single tweet means national news, perhaps Cohen was joking, perhaps he was tired and emotional. But it picks up the tenor of quite a few of the tweets I've seen from Labour supporters today.

Maybe this is why I'm a natural Liberal Democrat, I feel nothing like a visceral hatred for either of the two other main parties. I believe that people are largely in politics for the right reasons, I may think they are wrong but I don't question their faith in what they believe is for the best. Getting a glimpse of how elections work via twitter, I see just how much work is involved in getting elected as an MP (at least in a contestable seat).

It's tickled my fancy that much of the discussion of the last few days has centred around the percentage share of the vote that a different alliances would get, that's lovely and I agree entirely with that line of argument but your past record: opposing proportional representation, tells me that you're a hypocrite if you raise it just now.

I'm still glad I voted Liberal Democrat, I didn't vote Tory because of the social conservatives, Margaret Thatchers "no such thing as society", Michael Howard's blind faith in market solutions, isolationism in Europe, Peter Lilley and his little list, John Major's denial of support to the Iraq rebels after the first Gulf War and the moves of senior Tories into directorships of companies benefiting from their privatisations. The Tories claim to have changed, perhaps they have, perhaps the LibDems will reinforce that strand.

I hope the move for fair votes takes off, in a sense this is one of the key things I'm after long term in politics. Democracy is important, when I go to the ballot box I want my vote to count just as much as yours. Sorting out the deficit is ephemeral, fair votes will be a lasting legacy.

Perhaps the coalition will fall apart before the end of its term, perhaps the LibDems will suffer for this coalition in the next election (there's some suggestion that this happens to smaller coalition parties). But for the first time in 70 years people who call themselves "liberal" are in government.

May you live in interesting times...

It turns out that a chunk of my audience for my last blog post were my colleagues at work, they thought it a bit of a gloomy rant. These days I'm a bit more perky: in contrast to every election since 1974, this time the Liberal Democrats (my party) have something to be cheery about following the despair of election night! Usually post-election we are most definitely not in government, returning wearily to our constituencies to prepare for more time in opposition. This time it's different!

Watching the comments on twitter as events have unfolded has raised a few questions, and clear misconceptions which I thought might try to address from my point of view as a long (21 years) term party member.

What are the Liberal Democrats?
Some Liberal Democrats were carried over from the old style Liberals, some Liberal Democrats split off from the Labour party as the Social Democrat Party, since 1988 they were simply Liberal Democrats. I've always been a Liberal Democrat but my political origins are probably closer to the soft-right of the Tory party. I've never been tribal Labour (or Tory) for that matter. It's fair to say that the majority of the Liberal Democrats are left of centre, but we're in the party for a reason - we don't want to be in any other party.

What is coalition government?
The way people talk you might get the impression that the Liberal Democrats in coalition would simply be there to prop up their coalition partners. Labour seem to view this almost as a right, that the Liberal Democrats are a little turbocharger for those elections where they didn't quite win in their own right. Consequently they believe that a LibCon coalition would simply prop up a Tory government with a Tory agenda. This misses the point of coalition entirely, why on earth would we sign up to such a deal? The point of coalition is to get at least some of your agenda implemented, if you're not in the governing coalition then none of your agenda is implemented.

Proportional Representation
A lot of the discussion at the moment is around proportional representation, personally I think it should be around the economy first: massive deficits don't get reduced by themselves. I don't intend to discuss proportional representation properly here, but simply highlight three systems:
The pure Alternative Vote system is the one proposed by those that don't actually want proportional representation, it doesn't actually provide a proportional output. The Jenkins Commission, set up by the Labour government following the 1997 election, recommended Alternative Vote plus top up (AV+). In AV+ there are constituency elections with a top-up from party lists that provides proportionality, the benefit here is that there are still relatively small constituencies. The output should be pretty proportional. The Electoral Reform Society prefers Single Transferable Vote, this provides broadly proportional output, but requires the use of large constituencies to work.

Labour and Proportional Representation
Labour's new-found enthusiasm for proportional representation leads to hollow laughter amongst Liberal Democrats. For why? Go have a look at the evolution of the Labour commitment to a referendum. Basically a referendum was promised at the 1997 election, this referendum never happened and although it remained in the manifesto for subsequent elections the commitment became ever weaker. You can see why Liberal Democrats don't trust Labour on proportional representation.

I'd like to present a slightly heretical opinion for a Liberal Democrat: an absence of a commitment for a referendum on proportional representation should not be a deal breaker. My reasoning: I don't believe either Tory or Labour party could currently deliver a majority in parliament for such a referendum. It is possible that a referendum would not require a parliamentary vote, but let's assume it does. A commission on electoral reform means that at least the Tories will have to start thinking about it on their own terms, something they haven't been doing, even if it is a self-evident kick into the long grass. The next time there's a hung parliament we will then have fruitless electoral reform documents from both Labour and Tory parties, but here's the good thing: that means that they can't really ask for another one. Furthermore there appears to be a groundswell of opinion in favour of electoral reform, and I don't think it's party political. Over the coming parliament, and at the next election I really hope this groundswell is directed into contact with politicians, we shouldn't be hearing "This isn't an issue on the doorstep" next time.

Under proportional representation coalition government is likely to become a fact of life so a successful Lib-Con coalition in the absence of a deal on PR would be worth having. I must admit the green shoots of coalition are promising. Rather than a pointless exercise in taking chunks out of each other we are starting to see politicians talk about what they agree on.

In a way we have nothing to lose, what's the worst that can happen? Things fall apart and an election is called where we lose some percentage share of the vote leading to a reduction in seats - unpredictably fewer due to first-past-the-post system. We'd still be an opposition party with little power in parliament, so in a place broadly similar to the one we found ourselves in before this election campaign. What's different now is that there is a broader movement for electoral reform, that may be the thing we won at this election.

In posting this now (5:30pm on Monday 10th May) I am very aware that I may be overtaken by events!

Footnotes

• The Jenkins Commission Report
• Ministry of Justice: Review of Voting Systems: the experience of new voting systems in the United Kingdom since 1997
• Vernon Bogdanor's report on referenda

I was up for Evan Harris

This is a graph that shows you the number of seats (actual seats) each of the three main parties will get*, and the number of seats (proportional seats) they would get under a pure proportional system. You notice for the Labour and Conservative parties the number of seats they actually get is more than the number of seats in proportion to their votes, for the Liberal Democrats the opposite is true and by a very substantial margin.

When Liberal Democrats went into the polling stations yesterday they were given a single polling card, their Labour and Conservative comrades had three. Look them in the eye, ask them:

What is it about you that makes your vote three times more powerful, three times heavier, three times more important than mine?

What is special about you but not about me?

Explain to me how this is fair.

Explain to me how this is democracy.

To put it another way, every Labour or Conservative seat requires about 33,000 votes to win, a Liberal Democrat one requires 100,000 votes. We are the Great Ignored.

We have come to accept this inequity, it's happened in every election since the early 80's. As a country we just accept it as part of the way things are. It's the defining feeling of being a Liberal Democrat, seeing the overall share of our vote creep up election by election and receiving the same feeble, disproportionate harvest in seats. The sinking feeling in the middle of the night that, no, of course there has been no breakthrough. It's not because we perform poorly, it is because we have one polling card each, the others have three.

In 1997 the defining moment was Michael Portillo losing his seat to Stephen Twigg. My defining moment for this election was seeing Evan Harris lose his Oxford West and Abingdon seat. "I was up for Evan Harris", I had a tear in my eye.

Footnote
*This is based on the exit poll (see entry at 23:11), which looks consistent with the results of the actual election as of 10:30am May 7th which are Conservative 291, Labour 247, Liberal Democrat 51 616 of 650 seats declared. Under pure proportionality UKIP would receive 20 seats, the BNP 12.

No sleep 'til Batley!

I'm planning on staying up late tonight, watching the results of the general election come in, this is an occasion for a graph. The chaps at tweetminster have uploaded a list of predicted declaration times here. I've rearranged the data a bit to plot it, the height of each bar tells you the number of constituencies declaring during the hour starting at the time indicated at the bottom of the bar. As you can see, things don't really get going until about 2am. Key times for me are the declaration in my own constituency, City of Chester, at 3am and Dr Evan Harris' Oxford West and Abingdon at 2:30am. Batley & Spen declares at around 5am hence the title of this blog post.

This has been the most exciting election campaign, and election night, in quite sometime. I spent the 1997 election at a friends house in Darlington, I remember stumbling out into the early morning with "Things can only get better" ringing in my ears. For a few years that seemed to be the case. 1992 was interesting in that we all thought John Major was going to lose, and then he won to the surprise of everyone (including John Major). 2001 and 2005 were rather dull.

As a seasoned Liberal Democrat I'm used to my party getting pretty good percentage poll scores overall and winning pitiably few seats, so to the newcomers out there - welcome to my world! I can only hope that this time things will be different.

Economics: The physics of money?

Today I'm off visiting the economists, this is a bit of a different sort of visit since I haven't found that many to follow on twitter, instead I must rely on their writings.

I've been reading Tim Harford's "The Undercover Economist" which is the main topic of this post, in the past I've also read "Freakonomics" by Levitt and Dubner. Harford's book is more about classical economics whilst "Freakonomics" is more about the application of quantitative methods to the analysis of social data. This is happy territory for a physicist such as myself: there are numbers, there are graphs and there are mathematical models.

David Ricardo pops up a few times, it would seem fair to compare him to the Newton of economics, he lived 1772-1823.

I learnt a whole bunch of things from Tim Harford's book, including what shops are up to: working out how to persuade everyone to pay as much as they are willing to pay, by means such as "Value" and "Finest" ranges whose price differences don't reflect their cost differences, similar pricing regimes are found in fancy coffee. In a way income tax bypasses this, it replaces willingness to pay with ability to pay - I'm sure shops would love to be able to do this! Scarcity power allows a company to change more for its goods or services, and a company's profits are indication that this might be happening.

Another important concept is market "efficiency": perfect efficiency is achieved when no-one can be made better off without someone else losing out, this is not the same as fairness. In theory a properly operating market should be efficient but not necessarily fair. Externalities are the things outside the market to which a monetary value needs to be attached in order for them to be included in the efficiency calculation, this includes things like pollution and congestion in the case of traffic. This sounds rather open-ended since I imagine externality costing can be extremely disputed.

There's an interesting section on inside / asymmetric information, and how this prevents markets from operating properly. The two examples cited are second-hand car sales and health insurance, in the first case the seller knows the quality of the car he his selling whilst the buyer struggles to get this information. Under these circumstances the market struggles to operate efficiently because the buyer doesn't know whether he is buying a 'peach' (a good car) or a 'lemon' (a bad car), this reduces the amount he is willing to pay - the seller struggles to find a mechanism to transmit trusted quality information to the buyer. Work on information asymmetry won a Nobel Prize for Economics for George Akerlof, Michael Spence, and Joseph Stiglitz in 2001.

In the second case, health insurance, the buyer purportedly knows the risk they present whilst the seller doesn't, this doesn't quite ring true to me, it seems the observed behaviour in the US private healthcare system matches this model though. In a private insurance system the people who are well (and are likely to remain well) will not buy insurance, whilst those that believe themselves to be ill, or at serious risk of being ill will be offered expensive insurance because there is not a large population of healthy buyers to support them. Harford recommends the Singapore model for health care, which has compulsory saving for health care costs, price controls and universal insurance for very high payouts. This gives the consumer some interest in making most efficient use of the money they have available for health care.

You might recall the recent auctions of radio spectrum for mobile phone and other applications, this turns out to be a fraught process for the organiser - in the US and New Zealand this process went poorly with the government receiving few bids and less cash then they expected. In the UK the process went very well for the government, essentially through a well designed auction system. The theoretical basis for such auctions is in game theory, with John von Neumann and John Nash important players in the field (both recognised as outstanding mathematicians).

Tim Harford did wind me up a bit in this book, repeatedly referring to the market as "the world of truth", and taxes as "lies". This is a straightforward bit of framing: that's to say the language used means anyone arguing against him is automatically in the "arguing against the truth" camp irrespective of the validity of the arguments. The formulation that taxes represent information loss is rather more interesting and he seems to stick with this more often than not. In this instance I feel the "world of truth" is ever so slightly tongue in cheek, but in the real world free-markets are treated very much as a holy "world of truth" by some political factions with little regard to the downsides: such as a complete ignorance of fairness, the problems of inside information and the correct costing of externalities.

A not inconsiderable number of physicists end up doing something in finance or economics: As Tom Lehrer says in the preamble to "In old Mexico": "He soon became a specialist, specializing in diseases of the rich". It turns out you get paid more if the numbers you're fiddling with represent money, rather than the momentum of an atom. Looking at these descriptions of economic models, I can't help thinking of toy physics models which assume no friction, and are at equilibrium. These things are very useful when building understanding, but for practical applications they are inadequate. Presumably more sophisticated economic models take this things into account. From a more physical point of view, it doesn't seem unreasonable to model economics through concepts such as conservation (of cash) and equilibrium, but physics doesn't have to concern itself with self-awareness - i.e. physical systems can't act wilfully once given knowledge of a model of their behaviour. I guess this is where game theory comes in.

The interesting question is whether I should see economics as a science, like physics, which is used by politicians for their own ends or whether I should see them as being rather more on the inside. Economics as a whole seems to be tied up with political philosophy. Observing economists in the media there seem to be much wider range of what is considered possibly correct than you observe in scientific discussion.

Opinion polls and experimental errors

I thought I might make a short post about opinion polls, since there's a lot of them about at the moment, but also because they provide an opportunity to explain experimental errors - of interest to most scientists.

I can't claim great expertise in this area, physicists tend not to do a great deal of statistics unless you count statistical mechanics which is a different kettle of fish to opinion polling. Really you need a biologist or a consumer studies person. Physicists are all very familiar with experimental error, in a statistical sense rather than the "oh bollocks I just plugged my 110 volt device into a 240 volt power supply" or "I've dropped the delicate critical component of my experiment onto the unyielding floor of my lab" sense. 

There are two sorts of error in the statistical sense: "random error" and "systematic error". Let's imagine I'm measuring the height of a group of people, to make my measurement easier I've made them all stand in a small trench, whose depth I believe I know. I take measurements of the height of each person as best I can but some of them have poor posture and some of them have bouffant hair so getting a true measure of their height is a bit difficult: if I were to measure the same person ten times I'd come out with ten slightly different answers. This bit is the random error.

To find out everybody's true height I also need to add the depth of the trench to each measurement, I may have made an error here though - perhaps a boiled sweet was stuck to the end of my ruler when I measured the depth of the trench. In this case my mistake is added to all of my other results and is called a systematic error. 

This leads to a technical usage of the words "precision" and "accuracy". Reducing random error leads to better precision, reducing systematic error leads to better accuracy.

This relates to opinion polling: I want to know the result of the election in advance, one way to do this would be to get everyone who was going to vote to tell me in advance what their voting intentions. This would be fairly accurate, but utterly impractical. So I must resort to "sampling": asking a subset of the total voting population how they are going to vote and then by a cunning system of extrapolation working out how everybody's going to vote. The size of the electorate is about  45million, the size of a typical sampling poll is around 1000. That's to say one person in a poll represents 45,000 people in a real election.

To get this to work you need to know about the "demographics" of your sample and the group you're trying to measure. Demographics is stuff like age, sex, occupation, newspaper readership and so forth - all things that might influence the voting intentions of a group. Ideally you want the demographics of your sample to be the same as the demographics of the whole voting population, if they're not the same you will apply "weightings" to the results of your poll to adjust for the different demographics. You will, of course, try to get the right demographics in the sample, but people may not answer the phone or you might struggle to find the right sort of person in the short time you have available.The problem is you don't know for certain what demographic variables are important in determining the voting intentions of a person. This is a source of systematic error, and some embarrassment for pollsters. 

Although the voting intentions of the whole population may be very definite (and even that's not likely to be the case), my sampling of that population is subject to random error. You can improve your random error by increasing the number of people you sample but the statistics are against you because the improvement in error goes as one over the square root of the sample size. That's to say a sample which is 100 times bigger only gives you 10 times better precision. The systematic error arises from the weightings, problems with systematic errors are difficult to track down in polling as in science.

So after this lengthy preamble I come to the decoration in my post, a graph: This is a representation of a recent opinion poll result shown in the form of probability density distributions, the area under each curve (or part of each curves) indicates the probability that the voting intention lies in that range. The data shown is from the YouGov poll published on 27th April. The full report on the poll is here, you can find the weighting they applied on the back page of the report. The "margin of error" of which you very occasionally hear talk gives you a measure of the width of these distributions (I assumed 3% in this case, since I couldn't find it in the report), the horizontal location of the middle of each peak tells you the most likely result for that party.

For the Conservatives I have indicated the position of the margin of error, the polling organisation believe that the result lies in the range indicated by the double headed arrow with 95% probability. However there is a 5% chance (1 in 20) that it lies outside this range. This poll shows that the Labour and Liberal Democrat votes are effectively too close to call and the overlap with with the Conservative peak indicates some chance that they do not truly lead the other two parties. And this is without considering any systematic error. For an example of systematic error causing problems for pollsters see these wikipedia article on The Shy Tory Factor.

Actually for these data it isn't quite as simple as I have presented since a reduction in the percentage polled of one party must appear as an increase in the percentages polled of other parties.

On top of all this the first-past-the-post electoral systems means that the overall result in terms of seats in parliament is not simply related to the percentage of votes cast. 

Occupations of MPs

Ever alert to the possibility of finding some data to play with I was interested in an article in the Times regarding the number of MP's with scientific backgrounds in parliament. First I found data on occupations in the population as a whole here (Office of National Statistics) and data on MP's here, published by parliament. I thought it would be interesting to compare the two sets of figures, this turns out to be rather difficult because they define occupations very differently so I had to do a bit of playing about to get them into roughly comparable form.

This is what I came up with in the end:

It's a "representation factor", that's to say I take the fraction of MP's in parliament having a particular occupation and I divide it by the fraction of that occupation in the general population. If that occupation is over-represented in parliament then the number is bigger than one and if they are under-represented then it's smaller than one. It would seem barristers, journalists and career politicians are massively over-represented. Lecturers, civil servants and teachers are a little over-represented. Business people are about as expected and doctors are under-represented (along with manual workers and white collar workers).

I think from all of this the figure on doctors is the most surprising. It does make you wonder about how useful the outside interests of MP's are in guiding their deliberations since most occupations are grossly under-represented. You shouldn't really expect to see the House of Commons faithfully representing the overall working population, but I expected the balance amongst professionals to be a bit more uniform.

The House of Commons library document on "Social background of MPs" from which I got the MP occupation data is rather interesting, in particular the age profile (table 1) appears to be shifting upwards despite the greater youth of the party leaders. The educational background (table 7) is quite striking too.

One of the glories of the internet is that data monkeys like me can find tasty fruit to pick and consume.

Book review: Joseph Banks by Patrick O'Brian

Once again I venture into my own idiosyncratic version of the book review: more reading notes than review. This time I'm reading the biography of Joseph Banks by Patrick O'Brian. Joseph Banks has popped up regularly in my recent reading about the Royal Society and the Age of Wonder. He was on Captain Cooks trip to Tahiti, and then went on to serve as President of the Royal Society for 42 years - the longest term of any President. The Inelegant Gardener has been reading about Kew and various plant hunters, and Sir Joseph crops up there too. Despite his many talents, there are relatively few biographies of Banks, and he is relatively unknown.

Sir Joseph was born of a wealthy family from Lincolnshire, he was educated at Harrow, Eton and then Oxford University. At some point in his school years he became passionately interested in botany, and whilst at Oxford he went to the lengths of recruiting a botany lecturer from Cambridge University to teach him. The lecturer was Daniel Solander, a very talented student of Carl Linnaeus, who would later accompany Banks on his trip around the world with Captain Cook, they would remain close friends until Solanders death in 1782.

Sir Joseph's first trip abroad was to Newfoundland and Labrador in 1766. The area had been ceded to Britain by France, but there was an international fleet of fishing boats operating in it's waters. Banks made his trip as a guest Constantine John Phipps on HMS Niger, which was sent to the area to keep an eye on things. It seems fairly common for gentleman to travel as guests on navy ships of the time: this was broadly the scheme by which Charles Darwin would later join HMS Beagle on his trip around the world.

1768-1771 finds Banks circumnavigating the world on Captain James Cook's ship, HMS Endeavour, in Cook's first such expedition. This voyage was funded by George III following an appeal from the Royal Society for a mission to Tahiti in order to observe the transit of Venus. Banks paid for the contingent of naturalists from his own funds. The stay in Tahiti is much written about largely, I suspect, because they remained there some time. Following their stay in Tahiti, they continued on to New Zealand, which they sailed around rather thoroughly but seemed to land on infrequently as a result of hostile responses from the inhabitants. They then sailed along the East coast of Australia, stopping off on the way at various locations but most particularly Botany Bay. At the time the the existence of Australia was somewhat uncertain in European minds. There's a rather fine map of their course here and Banks' journals are available here.

Through the chapters on both these voyages, O'Brian makes heavy use of the diaries of Banks, quoting from them extensively and often between block quotes further quoting Banks' own words. This may work well for those of a more historical bent, but I felt the need for more interpretation and context. It often feels that O'Brian is more interested in the boats than the botany.

The next episode is somewhat odd: Banks was planning a second trip around the world with Captain Cook but he never went. At almost the last minute he withdrew on the grounds that the Admiralty would not provide adequate accommodation for him and his team scientists. The odd thing is that, despite what appears a fractious falling out, Banks appeared to remain very good friends with both Cook and Lord Sandwich, First Lord of the Admirality at the time. I wonder whether Banks, remembering the 50% mortality rate of his previous voyage with Cook, understandably got cold feet. As a consolation he went off to Iceland in 1772 for a little light botanising, where he scaled Hekla.

Despite recording an extensive journal, collecting a considerable number of anthropological, botanical and zoological specimens as well as a large number of drawings by his naturalist team Banks never published a full report of his Tahiti voyage. He showed the artefacts at his home in Soho Square and prepared a substantial manuscript, with many fine plates but seems to have lost interest in publishing close to the end of the exercise. Throughout his life he produced relatively few publications, this may be a reflection of his dilettante nature: he was skilled in many areas but not deeply expert and so published relatively little.

Banks was elected to the Royal Society whilst on his world tour, and later become President for a 42 year term, until his death in 1820. He made some effort to improve the election procedures of the Society, at the time of his election being in the right social class appeared to be more important than being a scientist. As part of his role as President he was heavily involved in providing advice to government including a proposal to use Australia as a colony for convicts. He was also heavily involved in arranging the return of scientists and others caught up in the wars following the French revolution. In addition to his work at the Royal Society, he also helped found the Africa Association and the Royal Academy.

Kew gardens was created a few years before Joseph Banks became it's unofficial superintendent (in around 1773) and then director. He had a pivotal role in building the collection: commissioning plant collectors to travel the world, all backed by George III. I must admit that my recent reading has led me to see George III in a new light: as an enthusiastic supporter of scientific enterprises, rather than a mad-man. George III and Banks also collaborated on a programme to introduce merino sheep from Spain, which had potentially huge commercial implications. Banks was seen as a loyal courtier.

Through his life it's estimated that Banks wrote an average of 50 letters per week almost entirely in his own hand, although they were fantastically well organised during his life, on his death they were rather poorly treated and dispersed. Warren R. Dawson produced a calendar of the remaining correspondence. I've not found this resource online but a treatment like this Republic of Letters would be fantastic.

I suspect a comprehensive biography of Joseph Banks is exceedingly difficult to write; this one seemed to cover voyaging well but I felt was lacking in botany and his scientific activities at the Royal Society. Perhaps the answer is that a comprehensive biography is impossible, since he had interests and substantial impacts in so many areas. There was simply no end to his talents!

Footnote
In the style of a school project I have made a Google Map with some key locations in Joseph Banks' life.

Lasers go oooooommmmmmm

In a previous post I mentioned, in passing, surface quasi-elastic light scattering (SQELS). SQELS is a fancy way of measuring the surface tension of a liquid using light, it has some advantages over the alternative method: sticking something into the surface of the liquid and measuring the pull but it is technically challenging to do.

The basic idea of SQELS is this: if you take a liquid surface, even in the absence of breezes or shakes, it is perturbed by tiny waves the properties of which tell you about the surface properties of the liquid. These waves have frequencies of 10kHz, wavelengths of 0.1mm and amplitudes of only a few angstroms. They are driven by the thermal motion that means everything, on a small enough scale, is jiggling away incessantly. To measure these waves laser light is shone on the surface, most of the light is scattered elastically that's to say it stays exactly the same colour. However, some of the light is scattered inelastically (or quasi-elastically since the effect is small) - it changes colour slightly, the power spectrum of the surface waves is imprinted onto the laser light in terms of shifts in its colour. So all we need to do is measure the power spectrum of the light reflected from the surface to find out about the surface properties of the liquid.

It turns out I don't have any photos of the SQELS apparatus in all its glory, so I shall describe it in words. The whole thing is found on an 8 foot by 4 foot by 1 foot thick optical table. A fine, very solid table whose top surface is a sheet of brushed steel, pierced by a grid of threaded holes 25mm apart. The apparatus is in the form of a large U covering two long sides and one short side of the table. A laser is bolted at the start of the U; light heads from the laser along the table through a set of lenses, polarisers, a diffraction grating, then upwards through a periscope before being directed down onto the liquid in Langmuir trough. The Langmuir trough is protected by a cardboard box, decorated in the style of a Freisian cow with holes cut roughly in the sides to allow light in and out. Captured after reflection from the surface of the liquid, the laser light is directed back down to the table surface by a second periscope from where it passes back along the long side of the table into a photomultiplier tube - the detector.

The cardboard box is there to stop air currents disturbing the surface of the liquid, vibration is the enemy for this experiment because the liquid in the Langmuir trough picks up the slightest disturbance and wobbles around. Sitting on an optical table weighing a large fraction of a tonne isn't enough - it needs to be on the ground floor too because buildings wobble and in this instance the Langmuir trough sat on an active anti-vibration table - a bit like noise cancellation headphones but the size of a small coffee table. You can manage without active anti-vibration if you're willing to do your experiments in the dead of night.

The cardboard box is emblematic of a piece of research apparatus: much of it is constructed from pre-fabricated components, some of it is custom-made in the departmental workshop but then there are the finishing touches that depend on your ingenuity and black masking tape. I did have plans to get the cardboard box remade in perspex but the box was just the right size and if I wanted more holes in it I could easily cut them with a knife so it was never worth the effort. I seem to remember a bit of drainpipe being involved too. As an experimental scientist you get your eye tuned in to spot things just right to add to your apparatus.

The laser is a single mode solid-state laser producing light of 532nm wavelength - a brilliant green colour. Three things are important about lasers: firstly, they are fantastically bright; secondly, they produce light of a very pure colour - a single wavelength. Thirdly, lasers go "oooooooommmmmmmmm", whilst conventional light-sources go "pip-pip----pip-pip---pip". Technically this is described as "coherence", we're using a laser in part because we want something to compare against and a conventional light-source isn't going to work for this. If you're measuring a small change, it's very handy to have a "ruler" close at hand, and in this case the elastically scattered light is that ruler.

You'll notice that I've not said anything about the results we obtained using the SQELS; truth be told, despite all the hours spent building the apparatus, doing the experiments and analysing the data the results we obtained told us little more than that which we could get by easier and simpler means that I described in my earlier post. I also had the sneaking suspicion that it would have helped if I knew more about optical engineering.

(I got distracted in the middle of this post, browsing through the Newport optical components catalogue site!)

Reference
Cicuta, P., and I. Hopkinson. “Studies of a weak polyampholyte at the air-buffer interface: The effect of varying pH and ionic strength.” Journal of Chemical Physics 114(19), 2001, 8659-8670. (pdf)

Why I'm voting Liberal Democrat

In a change from usual service I'm writing a political blog post, to cut to the chase: Vote Liberal Democrat! This post tries to explain why.

I've been a member of the Liberal Democrats since I was an undergraduate at Bristol University, 20 years ago. As a student I attended a party conference, did a bit of canvassing and I was also a "teller" a couple of times. Since then I've been in cover, very deep cover, I pay my monthly membership and a bit extra at election time and that's pretty much the limit of my activism.

As a casual Liberal Democrat I don't keep a close eye on party policy, essentially I rely on them being my sort of people and doing the right thing, it's with some relief I can report that I agree entirely with Nick Clegg in his interview with The Observer this week. The whole interview is well worth a read, but I'll pick up on one point: there's a real value in a hung (or balanced) parliament with no party in overall control. Reducing the national debt will be a priority for any incoming government, this is likely to be at least a bit painful and I think it's very obvious this is better done with a government that holds representatives from more than the 40% or less of the popular vote that a majority government is likely to get.  Many other issues will be with us for years to come: care for the elderly, climate change, pensions, the shape of our democratic systems. The solutions that politicians come up with should be robust, and have cross-party support, on recent evidence they need to work on this cooperative aspect of politics. Across the world and the UK, in devolved government and European elections we use a form of proportional representation, the sky has not fallen in. I'm fed up with the "smack of firm government" that first-past-the-post gives us.

The expenses scandal has had a big impact on politics in the last year, the Liberal Democrats came out well on this with relatively few outrageous claims and a very definite plan on how to address the problem which unfortunately was not picked up by the other parties. MPs had an expenses system which begged to be abused, I'm sure that with the same system at the place I work we would see a similar range of behaviour.

I've written in the past about the science policies of the Liberal Democrat, Labour and Conservative parties based around a debate organised by the Campaign for Science and Engineering in the UK. In summary, science has done fairly well by Labour over the last 13 years, with a noticeable wobble at the end over the science advisers, particularly on drugs advice. The Tories seem rather uncommitted to science, and look like they would do no better over science advisers. In the Liberal Democrats we have a champion in the form of Dr Evan Harris, who I really wish was my MP. He has done sterling work on the Science and Technology Select Committee, as well as campaigning on libel reform.

I vote in the City of Chester constituency, pragmatically there is absolutely no point in me turning out to vote. It will have no effect on the outcome, come May 7th not one particle of an MP in parliament after will have my electoral support.

Often party X will tell Liberal Democrats to vote for them to prevent party Y getting in, my response is in the form of an analogy: if I want chocolate cake for pudding the offer of an apple or a plate of cheese and biscuits will not satisfy, and may cause offence and derision. Vote for chocolate cake, vote Liberal Democrat!

Experiments for obsessive compulsives

It feels like I've not really been writing about science very much recently, so I thought I'd return to some work on which I spent a few years, with my former PhD student, Pietro Cicuta.

We looked at the properties of a protein from milk (β-casein) spread on the surface of water: principally the effect that it had on the surface tension as a function of amount of protein. Experimental variables were the acidity and saltiness of the water. We did this using a Langmuir trough which I'll describe below. b-casein is what's known as a random coil protein: in contrast to many proteins, which curl up into a well-defined, unique shape, β-casein flops around like a piece of string. This work is directly relevant to people working in the food industry, and more generally interesting to people who work with polymers (chemists) and proteins (biologists).

β-casein acts as a surfactant which helps stabilise fat globules in milk. Surfactants are common type of molecule, the name is a contraction of "surface", "active" and "agent", unsurprisingly they are found at surfaces: typically between one liquids, like oil and water, but also at interfaces between liquid and air. Surfaces are important, they keep the inside in, and the outside out. Surfactant molecules help with this important process by stabilising surfaces (the natural tendency of liquids is to form big blobs, surfactants stop this process). Some examples: the cells in your body are surrounded by surfactants, mayonnaise contains surfactants from egg which keep the oil suspended in the water, all manner of cleaning products for clothes, hair, work by using surfactants to stabilise dirt in water, and foams are formed using surfactants.

To achieve this magic surfactants share a common feature: part of the molecule likes oil and part of the molecule likes water, so to keep both parts happy they hang around at interfaces. Most surfactants are like little tadpoles with water-loving heads and water-hating tails. β-casein is a bit different, parts of the string like water, so they try to stick into the water and parts don't like water so they head for the air. However changing the acidity and saltiness of the water changes the strength of the love for water.

In most cases substances love water because they have an electrical charge, and this is why salinity and aciditiy are important in this experiment: if you change the acidity of the water the electrical charge on the protein changes because of the chemistry of the protein, if you change the salinity then how well the water can see the charges changes. It's a bit like fog, when there is no salt in the water it's as if the electric charges are seen through clear air and their influence spreads far and wide, adding salt is like a mist reducing the visibility of charges until ultimately the electric charges can't be seen at all.

A Langmuir trough is a way of probing surfactant properties. It comprises a shallow trough made of Teflon, a barrier made of Teflon (which can be swept across the surface of liquid in the trough) and a surface tension sensor. Teflon is used because water sits on top of it forming a proud meniscus rather than spreading out, damply. The sensor is nothing more than a bit of filter paper attached to a force measuring device, dip it into the water and feel the pull - that's surface tension. The idea with the barrier is that you place the barrier at one end of the trough, drop your molecules on the surface and then slide the barrier along, the molecules on the surface have few places to go so the decreasing the area amounts to increasing the concentration of the molecules at the surface. It's really the 2D version of compressing a gas with a piston. I tried to find a picture of a trough with a single barrier, but couldn't - the principle of the two-barrier trough shown here is the same, the black tower in the middle is the surface tension sensor.

Langmuir trough experiments are ideal for obsessive-compulsives: before you start your actual experiment you have to get the surface of the liquid you're using absolutely clean. To do this you clean your trough, add in the ultrapure water, compress the surface, hoover (with a glass pipette connected to a vacuum pump) contaminants off the surface if there was an upturn in the surface tension, then go back to compressing the surface, hoovering the surface etc. Some times it just doesn't work and you spend a morning trying to get your trough clean. Doing this for an oil/water interface is difficult, much more difficult actually I never succeeded. The core of the problem is that you don't need much material to make a surface dirty, imagine painting a ball - the amount of paint required to cover the surface is much smaller than the volume of the ball.

The Langmuir trough was developed by Irving Langmuir, building on work by Agnes Pockels done towards the end of the 19th century. You'll often see references to the Langmuir-Blodgett trough, the two terms seem to be used interchangeably but my understanding is that the Langmuir-Blodgett device is used to deposit surface active molecules onto a surface (which is not what we were doing). The Blodgett is Katherine Blodgett, who was the first woman to be awarded a PhD in Physics from Cambridge University.

From the surface tension data we extracted two things: firstly, how the protein molecules interact with each other - this comes from the early part of the compression data when the molecules are just starting to touch each other. Secondly, we get some idea of the innards of the protein from what happens when we squeeze the molecule harder and it starts to deform. Think of it like a bunch of eggs if you're bouncing them around in a basket you find out about how bouncy they are, if you grab hold of one and squeeze it really hard you first discover that it has a tough outer shell, then you discover it has a soft squishy inside, then you discover you have egg all over your hands and you forgot to get the kitchen towel out before you started.

We find out this information about interactions and internal properties as a function of acidity and salinity, which we can then compare with theories of charged polymers. This comparison turned out to work quite nicely, and Pietro came up with a neat way of illustrating how bits of the molecule appeared to plunge into the water as the surface layer was compressed.

This is pretty much my most cited piece of work, with just less than 30 citations. So there you go, several years in the lab condensed into just over a 1000 words, although I didn't mention the Surface Quasi-elastic Light Scattering (SQELS).

Reference
Cicuta, P., and I. Hopkinson. “Studies of a weak polyampholyte at the air-buffer interface: The effect of varying pH and ionic strength.” Journal of Chemical Physics 114(19), 2001, 8659-8670. (pdf)

Caerwys - a breezy spring walk

Off to Afon-wen and Caerwys today for a brisk walk featuring steep walking through woods, spring flowers, llamas, highland cows and a newt. You can see the route here:


View Caerwys in a larger map

It's a walk from "Walking in the Clwydian Range" by Carl Rogers, real men make up their own walks from OS maps and scouting missions but I'm lazy. A cool spring day today, in the distance we could still see the odd patch of snow on the hillsides. The trees were bare but the flowers had started to come out:

Clockwise from top left: Primrose, violet, wood anemone, and celandine

There were many birds out, singing away enthusiastically. I was going to show a picture of a woodpecker which we heard tapping away very close by, but we didn't see it so it would really have been a conceptual piece so I'd like you take that conceptuality one step further and imagine a picture of a tree with an unseen woodpecker in it. Caerwys is the home of llamas, which I also treat with a degree of respect, since they spit if you offend them:

Although it's a very rural location there are both signs of modern industrialisation in the from of quarries and sandpits and also the remnants of older work, including this lime kiln:

And also this rather creepy corrugated iron building which put me in mind of "Jeepers Creepers" or "Deliverance":

With a vivid imagination, a walk in the countryside is never boring! We walked through the village of Caerwys, which is quite pretty - many of the houses seem to be well-made from the local limestone. No photos though, mainly because the streets were full of parked cars which are an aesthetic abomination and I don't like photographing people's houses in close up - it seems rude. However, I had no qualms about photographing this fine house across Ysceifiog Lake which was created for fishing by the Earl of Denbigh in 1904:

We next passed through a small nature reserve: Y Ddol Uchaf, which is a designated Site of Special Scientific Interest (SSSI) whose information board promised newts, and lo - I saw that there were newts and it was good:

On the final stretch back to the car we were treated to these handsome chickens:

And some Highland cows, we first sighted some of these in the distance across a field then we passed close by to another group behind a photography unfriendly fence then eventually coming to some easily accessible ones in photogenic mud:

This one, is the bull in the group, I'm a country lad and was easily able to identify him as such by dint of his sizeable testicles (which I refrained from photographing):

So there you go, a memorial of our Easter Sunday walk immortalised for when I am old and incapable of leaving the house.