Nanotherapy

Two of the ways in which nanotherapy is being used in medicine will be highlighted here: the encapsulation of existant drugs in polymer coatings, and the usage of magnetic nanomolecules to destroy tumors.

Polymeric encapsulation

The problem with current drug formulations is that they aren't always soluble, and cannot be taken up by our bodies efficiently. Drugs have to pass over membranes and also be transported in the blood stream. Packing drugs into polymeric "packets" make them easier to absorb by the body. The polymers are hydrophilic on one side (water-loving) and hydrophobic on the other (orient themselves away from water) (see below). When the polymers are mixed with the drug particles, they organise themselves around the drug molecules so that the hydrophobic ends surround the drug on the inside, while the hydrophilic ends form the outside shell. This makes the molecule soluble and easier to transport in the blood stream.

These nanomolecules are often adapted with proteins or peptides on the surface in order to target them to the specific area in the body where the drug is supposed to take effect. One way that this is done is by adding antibodies to the shell of the nanomolecule (see below). These antibodies recognise receptors that are expressed specifially on the surface of tumors. This means that, once the nanomolecules have reached the tumor, they bind to the receptors and are taken into the tumor cells by a mechanism called endocytosis. In this way the often highly toxic cancer drugs do not affect other, healthy tissues in the body.

Magnetic nanoparticles

Metal-based nanoparticles can be used to target tumors without affecting other tissues, and without exposing the patient to harmful chemicals used to treat cancer. Magnetic nanoparticles are injected directly into the tumor (such as a brain tumor). The patient is then placed in a magnetic field that makes the magnetic poles of the nanoparticles alternate rapidly, causing an increase in heat. The increased heat causes the nanoparticles to be absorbed into the cancer cells. The magnetic field treatment is repeated, causing a further increase in heat. The particles also oscillate, which destroys the cells. The destroyed cells are excreted by the body. The 1-hour treatment is repeated 6 times, but the nanoparticles are only injected once, which makes this a good alternative to conventional chemotherapy.

Surfing

To know how surfing actually "works", you have to know about planing. You might've heard about cars aquaplaning across pools of water, and drivers thereby losing control of the steering. Planing simply means that an object (like a boat or a car) is lifted up onto the surface of the water and is skimming across it, as opposed to plowing through it. Th object or craft is supported predominantly by hydrodynamic lift (water + movement) rather than hydrostatic lift (bouyancy). As the object moves through the water, it is lifted up, thereby decreasing the contact of the object and the water, decreasing the drag, and allowing greater speed.

Waves are formed by wind blowing on the surface of water. The stronger the wind, and the larger the area it blows on, the bigger the waves are that form. Water molecules closer to the surface move faster than water molecules at depth. This means that the top "layer" of water eventually overruns the lower "layer" of water, creating a wave.


The surf zone (where waves break) is determined by the direction of the swell and the contours of the bottom of the beach. The surf zone forms when the depth of the water is roughly 1.3 times the height of the wave. So a five foot wave will begin to break when the water is about six-and-a-half feet deep.

In order to catch a wave, a surfer has to accelerate up to the speed of the wave (wave velocity). The surfer must place himself further than the position where the waves break, and ensure that his distance from any approaching wave allows him to paddle sufficiently so that he can match his velocity to that of the wave.

After accelerating up to the wave speed, the rider pops up to a standing position and begins planing over the surface of the wave. Since the wave becomes steeper as it advances, the surfer has to move towards the front of the wave where the acceleration is less. Advanced surfers don't simply ride waves straight out to the beach, but travel across waves, in a path that is parallel to the crest. The surfer rides along the position of the wave where the water is starting to rise just before breaking. A surfer can steer a surfboard by shifting their weight between the balls and heels of their feet, along with the help of the fins attached to the bottom of the board.

The native inhabaitants of Hawaii surfed straight out to shore on huge, wooden surf boards that had no fins. When surfing became popular in the USA, modern boards that were a lot lighter, with fins, were developed. In the 80's the short board became popular, and surfers started doing skateboard-inspired jumps on the water.

Alcohol

Ethanol is one of the oldest known drugs. 9000 year-old pottery in China have shown traces of alcohol, indicating that Neolithic humans may have drunk alcoholic beverages.

Alcohol is a depressant - it temporarily diminishes the function of the central nervous system. Alcohol "works" by affecting more than one system in the body, but it has been determined that alcohol stimulates certain receptors in the brain. These receptors (including GABA receptors) decrease neuron activity when a molecule is bound to it. It is also believed that some of these receptors control fear and anxiety, and therefore they are the target of a number of anti-anxiety drugs, like valium.

Ethanol is metabolised in the body like any foodstuff, as it contains sugars and other foodstuffs. Removal of alcohol by the liver is rate-limited, meaning there is a maximal rate that the liver can metabolise alcohol, and after that alcohol will start accumulating in the body untill the liver is given enough time to metabolise all of it.

Space blankets

Space blankets (also called mylar blankets) consist of a thin layer of plastic (often PET), with an extremely thin layer of metal (usually aluminium) over it. The blanket is wrapped around a person with the metallic, reflective side on the inside. The metal reflects visible light as well as infrared light - this is how it reflects body heat back onto the person around which it is wrapped.

Space blankets are also very light and take up very little space. They're wind- and waterproof too, so will keep you dry and warm even when the wind is blowing, or it's raining.

The space blanket was developed by NASA in the 1960's for the US space program. These days it's used in emergencies, first aid, and for camping.

Titanium prosthetic limbs

When a bone in the body has to be replaced, the best material to use is a type of metal. The environment inside your body is not ideal for any sort of metal though - metals corrode and rust. Some metals also cause an allergic reaction.

Many prosthetics these days contain Titanium, as it has a good strength to density ratio. Titanium is also strong, tough, resists corrosion, and is biologically compatible (it doesn't cause allergic reactions). It can be strengthened by alloying it with other elements like aluminium or vanadium. These alloys are used in hip and knee joint replacements, dental implants, and pacemaker cases. It is also used in procedures where the metal is allowes to join the surrounding tissue (see a recent entry in my sister blog).

Economics

The Credit Crunch was partially characterised by people who didn't want to cut their losses and sell, refusing to show a loss. Is this sort of behaviour part of a thought-out plan, or is it instinct?

It turns out that economics "work" in a way that is predictable and hard-wired into our brains. In an experiment where monkeys were taught to use money, the monkeys made decisions that directly reflected decisions that contributed to the Credit Crunch.

Monkeys were taught to use coins in order to buy grapes from laboratory "salesmen".

In the first experiment the monkeys could choose between two options: one salesman sometimes doubled the number of grapes after the sale was made, and sometimes he didn't; the other salesman always added one grape after the sale was made. The second salesman therefore represented a *safe* option with a certain increase in product, while the first salesman represented a *risky* option. Most monkeys bought from the *safe* salesman, preferring a sure increase in the product they bought.

In the second experiment the monkeys had two different choices: one salesman would always sell two grapes, but remove one before handing the grapes over to the monkeys; the other salesman started with three grapes, and either removed two, or none. The first salesman again represented a *safe* option as he always did the same thing, while the second salesman represented a *risky* option as he sometimes handed over less grapes than could be bought from his competitor. Most monkeys bought from the *risky* salesman here, preferring the choice of potentially getting a lot more grapes than they would get from salesman number one.

In the first experiment the monkeys had, in effect, a small amount of money which they could increase by a defined amount (always getting one extra grape), or by an unsure amount (getting no extra grapes, or two extra grapes). Monkeys chose to increase their money by a defined amount.

In the second experiment monkeys had, in effect, a large amount of money which they could have decreased by a defined amount (always getting one less grape than they bought), or by an unsure amount (getting two less grapes than they bought, or not losing any grapes at all). Monkeys chose to avoid the certain loss of money here, and took a risk by buying from the *risky* salesman.

In the Credit Crunch (and in economics in general!) the behaviour of people follow the model highlighted by the monkeys here: when people start off with a small amount of money, they're less likely to take risks with it, rather choosing to increase their money by a defined amount. When people start off with a very large amount of money, they don't want to lose any of it, so they're more likely to take risks with it. They do this even when it is obvious that they might make a massive loss. This is why people are reluctant to sell falling stock or put their houses on the market when prices are dropping. People hate the idea of losing what they have, almost regardless of the implications.

The impulses that lead us are evident in our monkey cousins. This implies that our decision-making skills, and our relationship with risk-taking, was formed many millions of years ago. We have failed to "evolve" out of this particular way of acting and reacting, but this isn't unusual. We also have a great love of fat and sugar, even though over-consumption of these foods lead sto health problems. The one thing that we *do* have is the intellectual capacity to consider situations and make reasoned and considered decisions. Therefore we aren't hostages to our natural instincts.

The research cited in this post was done by Laurie Santos at Yale University. For a 20-minute run-down on her research, be sure to watch her captivating and engaging lecture at http://www.ted.com/talks/laurie_santos.html.

Sustained release drugs

Usually when you eat or drink something, it's digested and absorbed straight away. In the past this was also true for medication. However, a lot of drugs these days are treated or packaged in a way that means the drug is released slowly into the blood stream. This means that you don't have to take the drug as frequently as before. Some of the drugs that work like this include hayfever treatment, pain medication, and anti-depressants. The method is called sustained release.

The simplest way of making a drug sustained-release is by packaging it in some kind of polymer (figure 1). Each grain of medication is coated in a material that dissolves slowly. The granules can be compressed into a tablet, or packed into a capsule. The thickness and type of material determine how slow the drug release will be.




Another way is to mix the drug with an insoluble material (figure 2). The drug gets released as it slowly diffuses out of the insoluble material.











A third method mixes the previous two techniques: the drug is packaged in a material that is partially soluble (figure 3). Parts of the membrane around the drug dissolves, and the drug diffuses out of the coating in this way.















Recently an additional material has been developed, called hydrogel (figure 4). A drug can be packaged in a hydrogel, which will safely transport the drug through the stomach without dissolving. Then, when the hydrogel is in a specific environment (for example, a specific pH), it swells up and the drug can diffuse through pores formed in the coating.










It is important to remember to follow the instructions for taking a specific drug. For example, if you chewed a tablet that was designed to be slow release using technique number 1, as described here, you would destroy its slow-release ability.

The contraceptive implant, Implanon, contains the hormone progestogen. This hormone is released slowly over 3 years. It is imbedded in a polymer called evatane, and the release of the hormone is further controlled by a membrane that ensures a consistent daily dose.

Freckles

Skin colour is determined by a pigment called melanin. When skin is exposed to sunlight, ultraviolet (UV) radiation triggers the production of more melanin. The melanin functions to protect the skin from damage that may be caused by the UV radiation.

There are two types of melanin, namely red pheomelanin and black eumelanin, both of which are present in human skin. However, only eumelanin protects skin from UV damage, while pheomelanin can actually generate free radicals which might contribute to skin damage.

Not every cell in the body produces melanin - skin cells that do, are called melanocytes. In most people melanocytes are spread evenly across the skin, but some people have melanocytes in clumps in the skin. These clumped melanocytes don't produce the UV-protective eumelanin, as they have a mutation in a gene that is essential for regulating the proportions of pheomelanin and eumelanin. Usually this proportion is controlled by a hormone called melanocyte stimulating hormone (MSH). This hormone binds to a specific receptor on the surface of the melanocyte cell called MC1R (A in the illustration on the right). When MSH binds to MC1R signals are sent into the cell to turn pheomelanin into eumelanin. When there is a mutation in MC1R, the MSH can't bind to it, and pheomelanin isn't turned into eumelanin (B in the illustration on the right). This causes the reddish colour of freckles.

The MC1R mutation is dominant, meaning that you only need one copy of the gene to have freckles. However, red hair is a recessive trait, which means that you need two copies of the MC1R gene to have red hair.

A recent interesting paper has determined that variations in MC1R caused variation in hair and skin pigmentation in Neanderthals on a scale that is observed in modern humans.¹


Photo above: Cyclist's tan with freckles. The skin is freckle-free where a watch fits around the wrist and on the hand where cycling gloves cover the skin.

If you want further information on skin pigmentation and melanoma (cancer), you can go here.



¹ Lalueza-Fox C et al.
A Melanocortin 1 Receptor Allele Suggests Varying Pigmentation Among Neanderthals

Cycling

How do you remain upright on a bike? How does steering work? How about those nifty fixie-riders and their track stands at red lights?

Balancing on a bike

The best comparison I've read about balancing on a bicycle is the one that compares it to balancing a stick on your hand, vertically. The moment the stick seems to tilt over right, you move your hand to the right (and slightly over) in order to get the stick to tilt back again. This adjustment is done continuously and leads to the stick "balancing" on your hand. Cycling is the same. As you ride, you fall slightly to the right or left. As you fall to the right, you steer the bike to the right in order to get the wheels under you again. As you fall to the left, you steer left. And so cycling is a continuous adjustment from a tilted position to an upright position - you're actually turning left and right the whole time (albeit small turns). When you look at the track created by a bike you will see these left-and-right swerves created by the wheels.

Track stands

Fixed-gear bikes don't have a freewheel. This means that if you stop pedalling, the wheels stop moving, and if you pedal backwards, the bike moves backwards. When you see a fixie rider standing still at a red light, he always has his wheel turned sharply to one side or the other. What he (or she!) is doing is moving slightly forward or back, or side to side, compensating for the bike leaning in any direction or moving forward or back, in order to stand still. I believe this is a lot easier on a fixed-gear bike as you can control both forward and backward motion.

Steering your bike

When you turn your bike right, centrifugal forces will try to push you towards the left. So in order to turn right, you have to lean your bicycle to the right to counteract the centrifugal forces (see diagram).

If you want to lean your bicycle to the right, you have to actually turn the bars to the left. When you turn the bars to the left, your hips naturally shift towards the right, and the bike leans right. This is called countersteering.

When you turn your bike, this all happens automatically without you having to think about it!

Hygro-, baro-, and thermometers (dial-style)

You might've seen one of these in someone's house, or on a boat. It's a mini weather station consisting of a hygrometer, barometer, and thermometer. The hygrometer measures the relative humidity of the air, barometer measures the air pressure, and thermometer obviously tells you how warm (or cold) it is.

But how do they work? What turns the little dial on the indicator and what acutally measures the moisture, pressure, and temperature? Well, it's all down to really basic physics.

The hygrometer

The hygrometer uses a measuring element - this can be any material that expands when humidity increases, and contracts when humidity decreases. The hygrometer measures and shows the change in length of this element. Since the element is attached to the dial (through a number of levers and axles), the dial turns as humidity changes.
The measuring element is usually a human hair, thread, or paper.

The barometer

The barometer uses a metal capsule called a diaphragm. When air pressure increases, the diaphragm is pressed together, and when air pressure decreases, the diaphragm expands - sort of like a balloon being deflated or inflated. The change in the diaphragm is transformed into a turn of the dial on the meter's face with the help of levers.

The thermometer

You might know thermometers that use mercury or other liquids inside them. When the temperatur of the liquid increases, it expands and moves up in the tube. But dial-type thermometers use a spiral spring made of two different metals. The metals contract with decreasing temperature and expand with increasing temperature, but to different extents. Because the one is less reactive than the other, the spring makes accurate, defined rotating movements. This movement is directly transferred to the dial which indicates what the temperature is.

Reflective material

In the UK cyclists must have a white front light and red rear light to cycle at night. This is required by law. However, these lights are often not sufficient, and so it's advisable to wear clothing with reflective strips on them.

But how does reflective technology work? 3M makes a lot of these products using their Scotchlite technology. They use glass beads and prismatic technology to reflect light rays in a way called "retro reflection".

When a ray of light strikes a reflective surface straight on (at a 90 degree angle), the light is reflected straight back along the same path. However, when light hits the surface at an angle, it's reflected at an angle in an opposite direction. Retro-reflectivity occurs when the reflected ray returns in the direction of the light source, regardless of the angle at which it strikes the reflective surface. This reflection can be obtained in one of two ways:

With the use of three mirrors that are perpendicular to each other.



Or with special beads that bend and reflect light rays in a specific way.


Retro-reflective material reflect the largest amount of light of all reflective materials. The strength of reflective light is measured in candela. White material performs at 0.3 candela while retro-reflective material can measure up to 500 candela.

Hawk-Eye

After watching some Wimbledon and what with the controversy of the World Cup, I asked myself how Hawk Eye actually works. This is the system that tracks the ball as it moves around the court (or football pitch) and determines whether a ball is in or out, and where it might've gone if not it wasn't caught or hit (especially important in leg-before-wicket decisions in cricket. Hawk-Eye was invented by Paul Hawkins and David Sherry at Roke Manor Research in the UK, with the initial main aim of being used in cricket.

Hawk-Eye requires a minimum of 4 cameras around the playing field (cricket uses 6, see illustration below). The cameras are normal video cameras and thus take a series of shots of what they see, called frames. Each frame is sent to a data processing unit (a computer) where the computer has to firstly identify the ball and calculate its position in the frame. Once the computer has done this for all 4 cameras, it calculates a 3D position of the ball in space using all the data gathered from all the cameras. After this, the computer can draw the path that the ball has taken, as well as predict a path that the ball might take, based on the change of position of the ball in successive frames. The computer can then map this path and compare it to the rules of the game to determine whether a ball was in or out, or a player was LBW. The computer can also work as a statistics generator, recording and storing information about ball track, size, and velocity. This is particularly useful if cricket commentators want to discuss ball delivery.


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Yesterday I spent some time at the Royal Society's Summer Exhibition and learned a lot about shape-shifting materials, viruses, how the brain works, and land mine detection technology - things I'll definitely be writing about soon!

How to visit the Old Bailey

As a bonus to my first post, here's a very simple little "how it works", and it's practical in nature.

How to view court cases at the Central Criminal Court in London, England

The Central criminal Court in London is known as the Old Bailey - named after the street it's situated in. It's just around the corner from St. Paul's cathedral, and it seems that very few people know they can just walk in and observe cases free of charge.

The Old Bailey is open from 9:45 each day to the public. You're not allowed to take in mobile phones,cameras, bags or food. If you want to make it easy on yourself, drop your bag off at the Old Bailey Cafe diagonally opposite the Old Bailey for £1. Go into the building via the Public Entrance (to the right of the building if you're standing in front of it; it looks like a tunnel). Go early - there are often school groups taking up all the seats. Don't just barge in, but ask the guards at the doors just off the stairwell if there's a case that you can watch. If possible, find someone who goes a lot and latch onto them - the guards are a lot friendlier with regulars.

A large part of the fun is patching together the story as the arguments unfold. If you're lucky, you'll also witness an ace solicitor cross-examining a witness and playing to the gallery. And you get used to those silly silly wigs pretty quickly, believe me.

Inaugural post - paternity testing.

Welcome to my blog, in which I'll attempt to explain how things work! As someone with a fairly broad field of interest, I intend to cover a large amount of subjects - from genetics and cycling, to ocean waves and selling cars. However, as a trained scientist I predict that I'll post a bit more about science-related stuff. My goal is to try and make complicated things a lot easier to understand.

So, without further ado:

Paternity testing

Every person has DNA in the cells of his or her body. Half of your DNA comes from your father, and the other half comes from your mother. Scientists have developed techniques to compare the DNA of a child with that of their parents.

In particular, small bits of DNA that we know are often different between individuals, are copied thousands of times so we can discriminate these important bits from unimportant DNA. These bits of DNA differ in size between different people, so scientists just need to separate the DNA bits (fragments) to compare their sizes. DNA is separated in a slab of gel which works like a series of sieves where the biggest DNA fragments get stuck towards the top, while smaller fragments move towards the bottom where they get stuck. Each person's DNA is analysed separately.

This is a gel being loaded with DNA. The DNA is suspended in a coloured dye before the fragments are separated. The DNA is separated with an electric current.

After the DNA fragments are separated, you can stain the DNA with a dye that is visible under UV light, and this will show you where the DNA fragments are in the gel. This is how it might look:


In column 1 there is a "ruler" that you can use to compare the size of DNA. Next to column 1 you can see DNA sizes. "bp" stands for "base pair", a unit in which DNA is measured. As you can see the largest fragments (23130 bp) are at the top, while the small fragments (564 bp) are at the bottom. Columns 2, 3, and 4 contain DNA samples from different sources.







Say we get DNA from Jane, her baby, and two men who claim to be the father. Who do you think is the father?

The baby shares one DNA fragment with Jane (second from the top). The baby also shares two DNA fragments with Man 2, but none with Man 1. Therefore Man 2 must be the baby's father!









This sort of technique is also used by scientists to identify contamination in foodstuffs (for example, if canned meat is contaminated with other meats that aren't supposed to be in the can), to identify plant and animal species, and to identify bacteria, viruses, and fungi - especially when they are causing disease.