Saturday, June 10, 2006

Number of the day: 9

When we do arithmetic, we should normally check our work. There are several ways to do this. Our first step should be to ask, "Is the answer reasonable?" Sometimes the answer is way too big, or way too small, or has the wrong number of decimal places. If it looks reasonable, then we check the work. One way is to re-do the arithmetic. This doesn't always catch our errors, as we may make the same mistake, in the same place. Humans are prone to that kind of mistake. A better way is to re-do the arithmetic, in a different order. Add a column of numbers, from bottom to top. Or, have someone else do the arithmetic.

One method, of checking our work, is called "Casting out nines". We convert each number into its casting-out-nines equivalent, and then redo the arithmetic. The casting-out-nines equivalent of this answer should be the casting-out-nines equivalent of the original answer. We get the casting-out-nines equivalent of a number by adding up its digits, and then adding up those digits, until you get a one digit number. If our answer is 9, then that becomes 0. As a short cut, we don't have to add in any of the 9's in our work, as these are the equivalent of 0. We can just "cast out" those 9's. For example, 19 becomes 1, without even adding 1 and 9 and getting 10, and then adding 1 and 0 and getting 1. As a further short cut, we can group numbers together which add up to 9, and replace them with 0. 2974 becomes 4, because we can cast out the 9 and the 2+7 (which is also 9 or 0). Well, let's try an arithmetic problem:

   137892     3
+ 92743 + 7
------ --
230635 1

We converted the first number to 3, by casting out nines (We threw out the 9 and the 7+2 and the 8+1, leaving the 3). The next number became a 7, for similar reasons. The answer became a 1. And, to check our answer, we add the 3 and 7, getting 10, which is 1. It checks out. We get the same answer in both directions.

We can use the same method for subtraction, multiplication, and division (check the division backwards, by doing the multiplication). It doesn't always catch our error. Many numbers reduce to 1. So, we have 8 chances in 9 of catching an error. 1/9 of all our errors will go uncaught. That is pretty good, really. Here's a multiplication problem:

    137     2
x 92 x 2
--- --
12604 4

Again, we get the same answer in both directions. We can be moderately confident of our answer.


For more exploring, click here.


Hong Kong's climate is sub-tropical, tending towards temperate for nearly half the year. During November and December there are pleasant breezes, plenty of sunshine and comfortable temperatures. Many people regard these as the best months of the year.

January and February are more cloudy, with occasional cold fronts followed by dry northerly winds. It is not uncommon for temperatures to drop below 10 ºC in urban areas. The lowest temperature recorded at the Observatory is 0 ºC, although sub-zero temperatures and frost occur at times on high ground and in the New Territories.

Clouds over Hong Kong Convention and Exhibition Centre, Wanchai

March and April can also be very pleasant although there are occasional spells of high humidity. Fog and drizzle can be particularly troublesome on high ground which is exposed to the southeast, and air traffic and ferry services are occasionally disrupted because of reduced visibility.

May to August are hot and humid with occasional showers and thunderstorms, particularly during the mornings. Afternoon temperatures often exceed 31 ºC whereas at night, temperatures generally remain around 26 ºC with high humidity. There is usually a fine dry spell in July which may possibly last for one to two weeks, or for even longer in some years.

Wind and rain in Times Square, Causeway Bay

September is the month during which Hong Kong is most likely to be affected by tropical cyclones, although gales are not unusual at any time between May and November. On average, about 31 tropical cyclones form in the western North Pacific or China Seas every year, and about half of them reach typhoon strength (maximum winds of 118 kilometres per hour or more).

When a tropical cyclone is about 700 to 1000 kilometres southeast of Hong Kong, the weather is usually fine and exceptionally hot, but isolated thunderstorms sometimes occur in the evenings. If the centre comes closer to Hong Kong, winds will increase and rain can become heavy and widespread. Heavy rain from tropical cyclones may last for a few days and subsequent landslips and flooding sometimes cause considerably more damage than the winds.

Typhoon Chanchu sweeps over Hong Kong

The mean annual rainfall ranges from around 1300 millimetres at Waglan Island to more than 3000 millimetres in the vicinity of Tai Mo Shan. About 80 percent of the rain falls between May and September. The wettest month is August, when rain occurs about four days out of seven and the average monthly rainfall at the Observatory is 391.4 millimetres. The driest month is January, when the monthly average is only 23.4 millimetres and rain falls only about six days a month.

Severe weather phenomena that can affect Hong Kong include tropical cyclones, strong winter monsoon winds, and thunderstorms with associated squalls that are most frequent from April to September. Waterspouts and hailstorms occur infrequently, while snow and tornadoes are rare.

Photographs from HK Digital Vision
Text from Hong Kong Observatory

Difficult yet simple: Part 2

(See Question.)



Now work out which of the three identities above match the following graphs:

404 error?

On any given web server, numerical codes are used to represent various server (or website) errors.

The 404 error represents a website's failure to find a page sought by a visitor. Generally, there are two causes for a 404 error:

1. The page does not exist at all, or

2. The page name was misspelled by the visitor on his/her browser.

The 404 error page is thus the web page that displays on a browser whenever the error is triggered.

Some hilarious 404 error pages:

Friday, June 09, 2006

Gloomy glow

The view from my window:

Hong Kong, 10 am

An active trough of low pressure is bringing unsettled weather to the south China coastal areas. Locally, there were heavy rain and thunderstorms today. More than 100 millimetres of rainfall were generally recorded over the territory. Those recorded at Tsuen Wan, Sai Kung and Tuen Mun even exceeded 180 millimetres.

Weather forecast for tonight and tomorrow:

Cloudy to overcast with occasional heavy rain and squally thunderstorms. Temperatures will range between 24 and 27 degrees. Moderate west to southwesterly winds.

Outlook : Still showery in the following two days.

Weather report from Hong Kong Observatory


My website as a graph (as of June 8, 2006):

I probably need to simplify my website, lol.


blue: for links (the A tag)
red: for tables (TABLE, TR and TD tags)
green: for the DIV tag
violet: for images (the IMG tag)
yellow: for forms (FORM, INPUT, TEXTAREA, SELECT and OPTION tags)
orange: for linebreaks and blockquotes (BR, P, and BLOCKQUOTE tags)
black: the HTML tag, the root node
grey: all other tags

From Website as Graphs

Intelligence quiz

Your Dominant Intelligence is Logical-Mathematical Intelligence

You are great at finding patterns and relationships between things.
Always curious about how things work, you love to set up experiments.
You need for the world to make sense - and are good at making sense of it.
You have a head for numbers and maths... and you can solve almost any logic puzzle.

You would make a great scientist, engineer, or researcher.

Thursday, June 08, 2006

Polymer #4: Poly(tetrafluoroethene)

(Also known as poly(tetrafluoroethylene) or PTFE.)

Tetrafluoroethene is an example of a fluorocarbon, a compound of fluorine and carbon. In the molecule, all four hydrogen atoms of ethene have been replaced by fluorine atoms.

Molecular structure of PTFE

Fluorocarbon compounds constitute almost another world from organic and inorganic chemistry, in part because the C-F bond is so strong that it almost totally ignores attack by other molecules. In the small fluorine atoms, the highly charged fluorine nucleus exerts such tight control over the electrons in its vicinity that they take much less part in weak intermolecular bonding than do the electrons in hydrocarbons. As a result, fluorocarbons are generally more volatile than the corresponding hydrocarbons.

Fluorocarbons came into prominence after World War II, when the nuclear industries grew and supplies of fluorine became available (fluorine is used in the manufacture of uranium hexafluoride, UF6, a volatile solid used in the separation of uranium isotopes). Tetrafluoroethene is a colourless, odourless, tasteless gas; its principle destination is polymerisation to give the fluorocarbon analogue of poly(ethene).

PTFE consists of very long chains, composed of about 50000 -CF2- groups each, with very little cross-linking between them. As a result, the molecules pack together to give a dense, compact solid with a high melting point. Even when the material is molten, the chains are so closely packed that they flow past each other only very slowly. Molten PTFE is so viscous that most PTFE articles are made by heating and compressing the powder to obtain a dense, strong, homogeneous lump.

The chemical and thermal stability of PTFE can be traced to two features. One is the considerable strength of the C-C and C-F bonds, which keeps the molecules from decomposing even they are moderately heated. The second feature is the match between the sizes of the fluorine and carbon atoms, which results in the fluorine atoms forming an almost continous sheath around the chain of carbon atoms, protecting it from chemical attack. In effect, the fluorine atoms act as chemical insulation around the carbon-atom 'wire'.

Grease and oil do not form bonds with PTFE, so surfaces coated in it are 'non-stick'; that is, PTFE is an abherent coating, the opposite of an adherent substance like glue. Because fats and oils do not form bonds with the alien PTFE molecules, PTFE feels slippery to the touch. Its molecules pack together so densely that the solid does not absorb water, making it an excellent electrical insulator.

PTFE non-stick cookware

Tetrafluoroethene is often copolymerised with other fluorocarbons to produce the range of plastics widely known as Teflons (a Du Pont trade name). One Teflon is PTFE itself. Another, Teflon-FEP (fluorinated ethene-propene), is a copolymer of tetrafluoroethene and the fully fluorinated version of propene (CF3-CF=CF2). The -CF3 groups of the fluoropropene molecule are bumps on the -CF2- backbone of the copolymer and result in less close packing. As may be suspected, the solid melts at a lower temperature than does PTFE and forms a liquid with a lower viscosity. It can therefore be moulded by conventioonal (injection) techniques but retains the desirable thermal and chemical stability of PTFE.

Brain booster

I've ordered these textbooks as no one would teach these modules at our school; so I will have to self-study :)

  • Combinations of random variables
  • Sampling
  • Estimation, confidence intervals and tests
  • Goodness of fit and contingency tables
  • Regression and correlation

  • Hyperbolic functions
  • Differentation (of hyperbolic functions etc.)
  • Integration (of hyperbolic functions etc.)
  • Coordinate systems (parabola, ellipse, hyperbola, rectangular hyperbola, and their properties; insintric coordinates)

Buy them here.

Don't be geeks with no brains.

Wednesday, June 07, 2006

Polymer #3: Poly(chloroethene)

(Also known as poly(vinyl chloride) or PVC.)

Now we let the ethene molecule acquire a bit more personality by replacing a hydrogen atom with a chlorine atom. At first sight, the new personality is unattractive, for chloroethene (or vinyl chloride) is a carcinogenic gas. Nevertheless, it is manufactured (from ethene) in huge amounts each year, since it can be polymerised to form PVC, one of the most useful and adaptable of all plastics.

Molecular structure of PVC

Because of the big chlorine atoms present on the chains, PVC molecules do not pack together so well that they form a rigid solid. However, to increase the flexibility of the solid, commercially produced PVC molecules do contains large organic molecules (including esters of alcohols containing about ten carbon atoms) that act as plasticisers that lubricate the PVC molecules and allow them to move easily past each other when the solid is bent. These lubricants are not bound chemically to the polymer chains and slowly migrate to the surface. There they are lost and, as a result, the plastic becomes brittle and stiff. Since some bacteria enjoy a good meal of hydrocarbon chains and will eat parts of the plasticiser molecules, biocides are somtimes incorporated into PVC.

PVC pipes

PVC is produced in such huge amounts because it is so versatile. It can be mixed with a very wide range of additives chosen to tailor its properties to many different applications. When it is properly protected by its additives, it is also chemically resistant to attack and degradation.

How lucky we are

Tuesday, June 06, 2006

Particles and pulley: Question

Two particles E and F of masses 0.5 kg and 0.7 kg respectively are connected by a light inextensible string.
Particle E rests on a smooth horizontal table, 1 m from a fixed smooth pulley at the edge of the table.
The string passes over the pulley and F hangs freely 0.75 m above the floor.
The system is released from rest with the string taut.
After 0.5 s the string breaks.


(a) the distance the particles have moved when the string breaks
(b) the velocity of the particles when the string breaks
(c) the further time that elapses before E hits the floor, given that the table is 0.9 m high


- assume g = 9.8 ms^-2
- parts (a) and (b) are relatively easy, part (c) quite difficult.

Rotating snakes

Enlarge the following picture by clicking on it:

Beware: you will start to rotating...

Shades of blue: Question

Why did you have to leave? Why did you have to set me free? Why did you have to go? I will wait for you, here in all these shades of blue...

Which shade of blue should go in the blank square (4 , 3)?

Monday, June 05, 2006

Bubble on bubble

Ask Frank Morgan, a leading researcher in optimal geometry, "What happens when one soap bubble likes another soap bubble?" and he'll answer with effervescent enthusiasm. "They meet to make a double bubble. And they always meet at angles of 120 degrees."

Will these two bubbles form a double bubble?

Although the question may sound like a riddle, it involves complex mathematics and science. Every time two soap bubbles form a double bubble, they demonstrate the best -- or optimal -- geometric figure for enclosing two separate volumes of air within the least amount of surface area. It took mathematicians centuries to arrive at the proof, which was announced in 2000. Further research using techniques from that proof could enhance our understanding of the physical properties of structures ranging in size from the nanoscale to the galactic.

Optimal geometry is concerned with geometric figures and their properties, and specifically: what shape or configuration of shapes best meets a situation's given constraints.

Throughout his career, Morgan, a professor at Williams College, has studied soap bubbles, films and double bubbles for insight into the interplay of area and volume. He and three other mathematicians -- Michael Hutchings of the University of California at Berkeley, and Manuel Ritoré and Antonio Ros of Universidad de Granada in Spain -- proved that the common double soap bubble is the most efficient structure for containing two separate volumes of air within the least amount of surface area. The National Science Foundation and the Spanish scientific research foundation DirecciÓn General de InvestigaciÓn CientÍfica y TÉcnica supported their work.

The team's solution of the Double Bubble Conjecture was announced in March 2000 before the Undergraduate Mathematics Conference at the Rose-Hulman Institute of Technology, and has been heralded as a "mathematical milestone" by the American Mathematical Society.

"Double soap bubbles have known what they’re doing all along," says Morgan. "But it's taken us since the geometry of Euclid and Archimedes to prove it."

Ultimately, the proof of the Double Bubble Conjecture was gained by the team’s use of novel instability and rotation arguments, and built upon earlier research accomplishments by distinguished mathematicians as well as undergraduate students mentored by Morgan in the 1990s.

Morgan describes the team’s instability argument, stretching and shrinking the bubble like Silly Putty in a way to preserve the volume constraints but decrease the surface area: "Our method involved rotating the bubble, half one way and half the other way, dividing it in half very carefully so that where you split it in half, the bubble is already going in the direction of the rotation, so it just stretches it instead of breaking it."

Soap films and bubbles are examples of what mathematicians refer to as minimal surfaces or area-minimizing shapes. When a bubble wand is dipped into a soapy solution, the soap film that forms is a surface that spans the given curves with the least area. This is why individual soap bubbles are always round. The surface tension of the soap film and the air pressure inside reach equilibrium by virtue of the bubble adopting the shape of a sphere, the geometric figure with the least surface area for a given volume.

The Double Bubble Conjecture is an example of what mathematicians call a problem in "calculus of variations": finding the best configuration that maximizes or minimizes some quantity given geometrical constraints. The range of applications of such methods is enormous, and has a famous history that includes the story of Queen Dido’s Problem.

Scientists commonly observe that nature often seems to work along optimization principles -- trying to get the most benefit for the least cost, preferring solutions that minimize the use of energy and materials. The team's proof provided fresh evidence that nature holds key insights for solving the world’s future optimization problems.

"Optimization problems are universal and extremely complicated," says Morgan. "If you think about it, that's what we human beings work on doing -- trying to maximize profit or enjoyment while minimizing time, energy, or suffering. What math shows us is that any problem can be viewed geometrically. The way to understand things is to investigate the underlying principles and look at simple examples like the soap bubble."

Mathematicians believe that the insights provided by the proof of the Double Bubble Conjecture and their further investigations of optimal geometry have much to contribute toward helping us solve other essential questions -- such as how can we best design new materials, what are the optimal mechanisms of cellular transport, what efficiency secrets can we learn from the growth patterns of crystals, what is the optimal configuration of an information network, how are black holes structured and how do optimization principles affect the shape of the universe?

"Whether it's soap bubbles or materials or black holes or human cells -- these structures meet in certain ways. So we ask -- how do they fit, how do they pack, on the very small scale and on the very largest of scales. To solve the minimization problems of humanity, we start with a simple example, and that’s hard enough," says Morgan.

Moira Burns

Sunday, June 04, 2006

Meiosis demystified: Summary

Diploid organisms contain two copies of each gene in each of their cells. In sexual reproduction, gametes are formed containing one copy of each gene. Each offsping receives two copies of each gene, one from each of its parents.

Gametes are haploid cells, and they are formed from diploid cells by meiosis. Meiosis consists of two divisions. The first division, meiosis I, separates the homologous chromosomes, so that each cell now has only one of each pair. The second division, meiosis II, separates the chromatids of each chromosome. Meiotic division therefore produces four cells, each with one complete set of chromosomes.

The cell produced by meiosis are genetically different from each other and from their parent cell. This results from independent assortment of the chromosomes as the bivalents line up on the equator during metaphase I, and also from crossing over between the chromatids of homologous chromosomes during prophase I.

Genetic variation also results from random fertilisation, as gametes containing different varieties of genes fuse together to form a zygote.

Meiosis demystified: Part 3

Microscope slides:
Stages of meiosis in an animal cell
Locust (x 350)

Interphase nucleus (not part of meiosis)

Meiosis I
Early prophase I
: chromosomes condensing and becoming visible

Prophase I: homologous chromosomes have paired up, forming bivalents, and crossing over or chromatis is ocurring; members of each pair of chromosomes are repelling each other but are held at the crossing-over points (chiasmata, plural of chiasma)

Metaphase I: bivalents line up across the equator of the spindle; the spindle is not visible in the photo

Anaphase I: homologous chromosomes move to opposite poles of the spindle

Telophase I and cytokinesis

Meiosis II
Metaphase II: single chromosomes line up across the equator of a new spindle

Anaphase II: chromatids separate and move to opposite poles of the new spindle

Late anaphase II

Telophase II

From Biology 2, Cambridge Advanced Sciences

Meiosis demystified: Part 2

The process of meiosis is best described by means of annotated diagrams (below). An animal cell is shown where 2n = 4, and different colours represent maternal and paternal chromosomes.

Unlike mitosis, meiosis involves two divisions, meiosis I and meiosis II. Meiosis I is a reduction division, resulting in two daughter nuclei with half the number of chromosomes of the parent nucleus. In meiosis II, the chromosomes behave as in mitosis, so that each of the haploid daughter nuclei divides again. Meiosis therefore results in a total of four haploid nuclei. Note that it is the behaviour of the chromosomes in meiosis I that is particularly important and contrasts with mitosis.

Meiosis and cytokinesis in an animal cell

Two of the events that take place during meiosis help to produce genetic variation between the daughter cells that are produced. These are independent assortment of the homologous chromosomes, and crossing over, which happens between the chromatids of homologous chromosomes. When these genetically different gametes fuse, randomly, at fertilisation, yet more variation is produced among the offspring.

From Biology 2, Cambridge Advanced Sciences

Meiosis demystified: Part 1

All species of living organisms are able to reproduce. Reproduction may be asexual or sexual. In asexual reproduction, a single organism produces offspring that are genetically identical to itself. The cells of the new organisms are formed as a result of mitosis in eukaryotes or binary fusion in prokaryotes.

However, in sexual reproduction, the offspring that are produced are genetically different from each other and from their parent or parents. Each parent produces specialised reproductive cells, known as gametes, that fuse together in fertilisation to produce the first cell of the new organism - a zygote.

If a life cycle involves sexual reproduction, then it is necessary for the number of chromosomes to be halved at some point. This is done by a special type of cell division called meiosis. In animals such as humans, for example, meiosis occurs as gametes are formed inside the testes and ovaries (precisely, the germinal epithelium of ovary, and the germinal epithelium of seminiferous tubule). The cells from which the gametes will be produced are normal diploid (2n) cells, each containing two complete sets of chromosomes. As a result of meiosis, the gametes contain only half the normal number of chromosomes, and they are said to be haploid (n) cells. Thus, when two gametes fuse together at fertilisation. the zygote that is formed obtains two complete sets of chromosomes, returning to the diploid condition.

Outline of the life cycle of an animal

Meiosis does more than halve the number of chromosomes in a cell. Meiosis also introduces genetic variation into the gametes and therefore the zygotes that are produced. Genetic variation may also arise as a result of mutation, which can occur at any stage in a life cycle. Such variation is the raw material on which natural selection has worked to produce the huge range of species that live on Earth.

From Biology 2, Cambridge Advanced Sciences

Work hard, sleep hard

Written by Jann Yee Chin

As a medical student, there have been many times when I wished sleep was unnecessary: the desperate moments cramming, hoping it will be enough for the exam the next morning. Yet each hopeless attempt ends in a cowardly retreat to bed, overpowered by that desire to sleep. We find ourselves increasingly burdened by the need to balance a successful career and secure finances against social and family lives. The frequent outcome — sleep deprivation — impairs our efficiency and causes mental and physical disorders. Whether sleep deprivation is a global problem or not has become a hot topic of debate.

Sleep is vital to all mental and physical human activities, and so it is recommended that we have 7–9 hours of it a night in order to guarantee our good health, safety and optimal performance. The UK has little representative data on sleeping patterns in comparison to the US. However, in 2004 the Surrey Sleep Research Centre carried out a cross-sectional survey. Through face-to-face interviews of 2,000 British adults, aged 16–93 and randomly selected at national sampling points, 59% reported sleeping problems in the previous week, with 18% admitting that they do not sleep sufficiently on the majority of nights. The youngest participants, aged 16–24, slept one hour longer than the average of 7 hours calculated from the entire sample. There was no discernible difference between men and women.

These findings correlate well with the US studies, but in comparison with 40-year-old data reveal no statistically reliable reductions. Nevertheless, the concern surrounding sleep deprivation stems from laboratory studies that suggest that even relatively moderate restrictions on sleep can lead to decreased performance and health. Epidemiological studies have reported associations between sleep and mortality, work safety, and mental and physical health.

Sleep deprivation leads to a number of physiological changes, of which two have been identified as the most important. Researchers from the University of Tennessee showed that sleep-deprived rats become immunocompromised and die primarily of bacterial infection, while a group at the University of Lübeck in Germany saw a similar immunosuppression in humans, with sleep-deprived individuals producing fewer antibodies to vaccinations. The second important change relates to the maintenance of the neural system and the consolidation of memory. Hallucinations, mood swings and mental illness may develop with prolonged sleep deprivation. The majority of sleep deficit effects are thought to be due to dysfunction of the brain’s frontal cortex, which is responsible for cognitive control, orchestrating thoughts with actions, maintaining attention, emotional control, and learning from experience and mistakes. Scientists from the University of Athens studied 22 patients with obstructive sleep apnoea syndrome, a respiratory disease that causes sleep deficiency. Using Magnetic Resonance Spectroscopy, they observed a significant decrease in the activity of the frontal cortex in comparison to healthy individuals. They concluded that less sleep allows less time for the nerve cells to rest and repair, and this results in neural damage by excess metabolic end-products and frontal cortex dysfunction.

There are two processes that control sleep. The first is a biological clock located in a region of the brain called the suprachiasmatic nucleus, which responds to light and controls the timing of sleep, so that we are more active in the daytime and asleep at night. It also controls processes vital for growth and development. Sleep is divided into five stages — a ‘rapid eye movement’ (REM) stage and four stages of non-REM. These stages cycle throughout the night, alternating between non-REM and REM sleep every 90 minutes. The second process relates to the specific neural control of REM and non-REM sleep. The multiple components of REM sleep suggest the interaction of multiple cellular pathways. Researchers confirmed this in 1975, showing two groups of neurons, one controlling the onset of REM sleep, and the other, its offset. The onset is driven by neurons producing the neurotransmitter acetylcholine (called cholinergic neurons), whilst the offset is determined by a different type of neurons, which produce 'aminergic' neurotransmitters and have an inhibitory effect upon the cholinergic cells. The neural activities of both are reciprocally related by a negative feedback loop.

Consistent with the fact that dream sleep is emotionally charged, brain imaging studies indicate that an ‘arousal pathway’ stimulates the hypothalamus and a part of the brain known as the limbic system. Accumulated evidence has shown that non-REM sleep is caused by the inhibition of the pathways that produce this stimulation. In a series of experiments in the 1970s, scientists showed that non-REM sleep resulted in a reduced activity pattern of cells belonging to the reticular activating system (RAS). The RAS involves the basal forebrain area, which sends cholinergic neurons to the frontal cortex.

There has been much interest in the chemicals that can induce sleep. Researchers explored the release of such chemicals, and discovered that the neurons at the base of the forebrain possess receptors for adenosine, an important metabolic chemical. They isolated a class of receptors that, upon binding of adenosine, causes an efflux of positively charged potassium ions. The resulting internal negative charges of the neurons cause reduced cellular activity. Thus, a negative feedback system exists to dampen arousal with increasing stimulation, which explains why over longer periods of being awake, we become increasingly tired.

There has been an equal amount of interest in discovering substances that could bypass altogether the need for sleep. The potentially improved efficiency could open up a world like the one represented in the television drama series 24. Alternatively, we could spread our current physiological workload over a longer time period, which would allow for the social activities we so desire. Caffeine is widely consumed to counter fatigue, to good effect. Its primary mechanism of action is to compete with adenosine at the receptors found in the RAS. The stimulant effects on mood, attention and performance are largely recognised, and extensive research by food and drug associations have shown it to be a safe drug with no health risks. Yet the use of caffeine as a counter-measure is not universally supported. Caffeine delays tiredness but does not inhibit the side-effects of sleep deprivation.

Altering our lifestyles and working habits to ensure healthier living is clearly more beneficial than relying on counter-measures against sleep deprivation. Despite my occasional desperate efforts to stay awake, I welcome the bliss of sleep and leave a world without it for someone else’s dreams.

Jann Yee Chin is a medical student based in Addenbrookes Hospital