Friday, May 11, 2007

Double Pendulum by Mai Yifan

Go here. Beautiful animation of the chaotic motion of a double pendulum. Done by Mai Yifan, 06S7E.

Tuesday, February 27, 2007

Interesting article

Read this a long time ago and recently rediscovered it on the net... If everyone were to be thinking students like the student in the story below, what an exciting class that would be! Don't you agree, fellow teachers and students?

Incidentally, those who enjoy the story will enjoy reading Richard Feynman, who is a "thinking man's physicist". Pick up any of the books about him in the school library -- you'll be enthralled.
(Books are: Surely You're Joking, Mr Feynman; What Do You Care What Other People Think?; Genius by James Gleick.... and a few others)

Mr Koh

PS: After reading the article, post your responses to this question: "What is the conventional answer to the test question?" You'll only fully appreciate the alternative answers if you also know the conventional one...


Angels on a Pin

A Modern Parable
by Alexander Calandra
Saturday Review, Dec 21, 1968.

Some time ago I received a call from a colleague who asked if I would be the referee on the grading of an examination question. He was about to give a student a zero for his answer to a physics question, while the student claimed he should receive a perfect score and would if the system were not set up against the student: The instructor and the student agreed to submit this to an impartial arbiter, and I was selected.

I went to my colleague's office and read the examination question: "Show how it is possible to determine the height of a tall building with the aid of a barometer."

The student had answered: "Take a barometer to the top of the building, attach a long rope to it, lower the barometer to the street and then bring it up, measuring the length of the rope. The length of the rope is the height of the building."

I pointed out that the student really had a strong case for full credit since he had answered the question completely and correctly. On the other hand, if full credit was given, it could well contribute to a high grade for the student in his physics course. A high grade is supposed to certify competence in physics, but the answer did not confirm this. I suggested that the student have another try at answering the question I was not surprised that my colleague agreed, but I was surprised that the student did.

I gave the student six minutes to answer the question with the warning that the answer should show some knowledge of physics. At the end of five minutes, he had not written anything. I asked if he wished to give up, but he said no. He had many answers to this problem; he was just thinking of the best one. I excused myself for interrupting him and asked him to please go on. In the next minute he dashed off his answer which read:

"Take the barometer to the top of the building and lean over the edge of the roof. Drop that barometer, timing its fall with a stopwatch. Then using the formula S = ½at², calculate the height of the building.

At this point I asked my colleague if he would give up. He conceded, and I gave the student almost full credit.

In leaving my colleague's office, I recalled that the student had said he had many other answers to the problem, so I asked him what they were. "Oh yes," said the student. "There are a great many ways of getting the height of a tall building with a barometer. For example, you could take the barometer out on a sunny day and measure the height of the barometer and the length of its shadow, and the length of the shadow of the building and by the use of a simple proportion, determine the height of the building."

"Fine," I asked. "And the others?"

"Yes," said the student. "There is a very basic measurement method that you will like. In this method you take the barometer and begin to walk up the stairs. As you climb the stairs, you mark off the length of the barometer along the wa]l. You then count the number of marks, and this will give you the height of the building in barometer units. A very direct method."

"Of course, if you want a more sophisticated method, you can tie the barometer to the end of a string, swing it as a pendulum, and determine the value of `g' at the street level and at the top of the building. From the difference of the two values of `g' the height of the building can be calculated."

Finally, he concluded, there are many other ways of solving the problem. "Probably the best," he said, "is to take the barometer to the basement and knock on the superintendent's door. When the superintendent answers, you speak to him as follows: "Mr. Superintendent, here I have a fine barometer. If you tell me the height of this building, I will give you this barometer."

At this point I asked the student if he really did know the conventional answer to this question. He admitted that he did, said that he was fed up with high school and college instructors trying to teach him how to think, using the "scientific method," and to explore the deep inner logic of the subject in a pedantic way, as is often done in the new mathematics, rather than teaching him the structure of the subject. With this in mind, he decided to revive scholasticism as an academic lark to challenge the Sputnik-panicked classrooms of America.


The article is by Alexander Calandra and appeared first in "The Saturday Review" (December 21, 1968, p 60). It is also in the collection "More Random Walks in Science" by
R.L.Weber, The Institute of Physics, 1982.

Calandra was born in 1911, started at Washington University (St. Louis) in 1950 as Associate Prof. of Physics. B.S. from Brooklin College and Ph.D. in statistics from New York Univ. Consultant, tv teacher and has been AIP regional counselor for Missouri.

Monday, February 19, 2007

Organic Synthesis

I'm sure many of you will know who I am... so leave you all to guess if you don't know.

I'm posting because poor Mr Koh is the lonely one posting only to dunno-who's-reading. So allow me to contribute my fair share of knowledge on Science ===> Chemistry.

You get headache... what do you eat? Panadol? Do you know what's in your panadol that makes it work? (If you don't know start reading the contents of every drug you come across.) Well, it's called paracetamol (allright I've told you). But do you know how it works? And more importantly (to me), do you know how to synthesize it?

Organic synthesis was, and is, a very important field in science today. Back in the past, the importance was to be able to synthesize alkaloids e.g. quinine (for anti-malaria) so that we need not be overly reliant on the raw materials from trees, but could instead use simpler raw materials that are readily available, and can thus produce the alkaloid in larger quantities.

So what's the significance today? Simple. You know bird flu? Avian Influenze H5N1? (For your information, H stands for Hemagglutinin subtype 5 and Neuraminidase subtype 1 (out of 14 and 9 respectively). They are cell-surface glycoproteins. (Don't know? Go read up!)) What's the drug that Roche produced to treat Avian flu? Oseltamivir (a.k.a. Tamiflu). How does it work? I don't know. But more importantly, if it works, then get more of it! But how on earth do you get more of it when it comes from star anise, and you can buy up all the star anise in the world yet it's still not enough to produce enough pills for everyone in America and Europe? The answer lies in retrosynthesis and organic synthesis. Using strategies to make bonds etc. and using all available organic reactions known till date, you get now not 1 or 2, but 3 different ways to make Tamiflu. Wanna see the reaction scheme?


Ok so tell me what you feel. *What the... what is this?* or *Lost...* or *Oh my god this is SO cool!!!* (yea right... -.-")? I do believe many of you will feel overwhelmed by this huge reaction scheme, when most of you barely learnt much organic chemistry in sec3/4. This is a teaser to show you the peak of organic chemistry, the application to serve mankind most directly. But of course to be able to do all this you need to first digest many Chemistry textbooks and notes with Muggase (Note that muggase is produced by your brain, and not your stomach.) and pass all your chemistry tests and exams.

Hard work isn't it all? But I dare tell you that half of you will find organic chemistry the easiest out of all the chemistry components in A-level Chemistry (*looks left... looks right... Ok Mr Sam Lee not here... continue!) What you will learn this 2 years will barely scratch the reactions shown above. But then again, it's a teaser for you all.

The point in showing all these is that organic chemistry is 1. fun, 2. visual (compared to crunching equations for physical chemistry (Mr Teo dun come after me pls...)) 3. important in terms of applications. If you look up the Nobel Chemistry prizes, you will learn that so many of the awardees received it because of organic chemistry (and biology fields. amazing? protein structure!) To date organic chemists have synthesized countless alkaloids, all for the hope of making drugs and stuff so that man will live a better and longer life with lessened pain. Lemeshow you how difficult organic synthesis can be. Many of you should know Vancomycin, the last line of defence against bacterial diseases. This is the structure of Vancomycin:


Complicated right... this is the kind of complexity that many of us have to grapple with to find pathways to synthesize. But if we don't tackle such challenges, then we'd have one less drug to treat diseases and infections. Vancomycin is a very important drug, as is Tamiflu.

I'm putting all these partly because I like organic chemistry and total synthesis. Organic chemistry is really the easiest to score in chemistry here, and is the most visual side of theoretical chemistry compared to... Schrodinger equation... (we also tackle quantum chemistry... it's no fun =( sad...) I'm also putting all these to stimulate your interest in Chemistry and Organic chemistry, and of course... to encourage you all to join Chemistry olympiad (So now you think you know who I am?). Chemistry can be fun and enjoyable once you get past the dry bits of basics. Inorganic chemistry there's all the colourful complexes that you can make with transition metals etc (the colours are really nice, especially once you crystallize them), and organic chemistry there's all the drawing that you do. Math and physics-inclined people will like physical chemistry. But it's all down to one thing: to serve mankind.

Suggestion to Mr Koh here: perhaps you could organise a trip to GlaxoSmithKline to see their pharmaceutical industry in Singapore, and what really goes on in a pharmaceutical industry. The trip that I went really stimulated my interest in Chemistry.

Chemistry isn't just *n is for the quantum level of your orbitals... there are s,p,d,f orbitals ... ... ... * sian right? Here's something to make chemistry more interesting through jokes and laming:

The romantic Diels-Alder reaction: the diene and the diene-lover.

If you all don't get that... please go Wiki and look up. All images from above are from Wikipedia.

Also, I've included links to papers and articles that you all might want to read up on.

The Art and Science of Total Synthesis (79 pages)

The Essence of Total Synthesis (On the right click Full Text (pfd)) (9 pages)

Molecules of the Month - Oxford (Colourful)

Molecules of the Month - Bristol (This one is more interesting)

Allright, hope you all enjoy! Happy cny!

Hadriel Eeyore

Edit: Arrgh! how to show the full thing? Looks terrible! But anyway, if you want to see the whole thing go Wiki "Oseltamivir total synthesis"

Wednesday, February 14, 2007

Physics and Biology

Hi all, its me again ... :)

Two things to share here...

Science News - where to go
If you're interested in science, but wish to be spared the laborious technical details, go to New York Times Science page -- excellent, first class science journalism there.

Forget Discover and New Scientist -- I find their science reporting too inaccurate in terms of scientific details. However, The Economist (Science reporting) and Scientific American are excellent sources of science news.

Physics in Biology -- Biological Quantum Dots
Anyway, mainly wish to share with you something from (Biological Quantum Dots Go Live, Physicsweb, Mar2003) which is relevant with what has been mentioned during the last two talks -- one by Dr Monica Plisch (on quantum dots) and the other by Prof Mike Starck (bioflourescence imaging).

If you recall, Dr Plisch mentioned that quantum dots are particles that are nanometer sized (10^-9 m) and the size of the particles determine the colour with which they flouresce (rather than their molecular makeup). So a nano-sized gold particle could very well be red rather than, well, gold. :)

Gold Nanoparticles in Colloidal suspension (red, rather than, erm.. gold :)

She spoke about the quantum dots being used in bio-imaging due to their ability to flouresce brightly under UV light, making it suitable as an alternative to organic dyes, which tend to fade with time. Also, the range of wavelengths of light emitted by the organic dyes are spread out, making it difficult to use more than 3 or so dyes. In contrast, the light emitted by quantum dots are monochromatic (single wavelength) and adjustable (just inject different sized quantum dots), making it superior. However, the challenge was that most quantum dots were toxic (see cadmium selenide quantum dots - below) and cannot be used in aqueous medium.

All bottles contain Cadmium Selenide Quantum dots -- but in different particle sizes... Numbers give wavelength of light emitted in nanometers. Do you know which bottle has the smallest/largest quantum dots?

Prof Starck mentioned the jellyfish flourescence gene, which could be inserted into the ...erm, DNA(?)... of a cell, and the replication of that allows researchers to tag a particular part of the DNA and observe it on a large scale --- Bio students/teachers, pls correct me k? cos my bio knowledge stops at Sec4...

So this article on (Best of Physicsweb / Physics in Biology) says that
Biologists have long been eager to probe living cells in full colour over extended periods of time. Such a technique could reveal the complex processes that take place in all living organisms in unprecedented detail, such as the development of embryos.
.... ....

Existing imaging techniques use natural molecules that fluoresce, such as organic dyes and proteins that are found in jellyfish and fireflies.....
.... ....

Inorganic semiconductor nanocrystals - quantum dots - can get round .. problems [faced by using organic dyes]. .... a mixture of quantum dots of different sizes can be excited by a light source with a single wavelength, allowing simultaneous detection and imaging in colour. Turning these ideas from physics into biology, however, has remained a challenge because quantum dots cannot survive in water, and they must remain non-toxic.

Now a team of physicists and biologists led by Albert Libchaber and Ali Brivanlou at Rockefeller University in the US has produced new, biocompatible quantum dots and used them to image a live frog embryo (B Dubertret et al. 2002 Science 298 1759-1762). The researchers were able to "dress" quantum dots in an organic disguise that prevents them from coming into direct contact with the aqueous biological environment.

Showing an example of their successful research:

New biocompatible quantum dots are set to revolutionize biological imaging. In (a) a frog embryo has been imaged using conventional organic-dye techniques, and the signal is seen to fade in time. (b) Specially prepared quantum dots that were injected into another frog embryo at the same time fluoresce brightly for much longer.

I thought that it was interesting to read the article in the light of the talks given by the speakers. (They gave excellent talks, in my opinion. Too bad you didn't take the chance to ask more questions to Prof Starck. Fyi, I spoke to Dr Plisch and she was very impressed by the questions that were raised.)

So it is a current field of research and the interesting thing I feel, is its multi-disciplinary nature. '

  • The physics is in understanding the electronic structure of the quantum dots (i.e. the energy levels of the electrons in the quantum dot) and hence the wavelength of light emitted.

  • The chemistry is in the synthesizing of the quantum dots.

  • The biology is in the application of the above in bio-imaging.

  • And, all research carry socio-economical issues as well... such as its economical or medical potential, or perhaps just the issue of whether the poor frog that gets injected has to live with the quantum dots that doesn't stop glowing... :P
So, think of yourselves as students of science and not just a particular subject like bio or chem or physics... and do take some time to read the article here.


PS: I appreciate comments, your thoughts, etc... do post them here or in the comments part. Else I'll feel like I'm talking to myself here... :)

Why Toasts Always Land Jelly Side Up

Would the person who took the above book during Monday's Physics Enrichment please return it ASAP to Mr Gow? Thank you for your cooperation.

Yong Lin
On Behalf of Mr Gow

Tuesday, February 13, 2007

So you say you are interested in science?

Hi all stp students and teachers!

It's great to see that you have set up this blog -- let's make it a platform to share interesting ideas and things about science you've thot of or seen with each other...

for a start, let me post something interesting here from youtube... it's called a non-newtonian fluid (some of u have seen this already in the physics session)

An explanation in wikipedia here tells us that your moms have been making this non-newtonian fluid for years -- a simple cornstarch with water mixture gives such a fluid. The interesting thing is its shear-thickening property -- i.e. the viscosity increases with applied strain (or applied normal force).

I found it really entertaining, but it also set me thinking "hey, it's really science!" -- and found myself really not understanding fluids! You know how in school, we teach u that liquid molecules are in long chains, slide over each other, not bonded that tightly... but how does this non-newtonian fluid have such properties that we can deduce from its molecular nature, arrangement or whatever?

There's much to learn yet... :)

On a different note, hope you check out my blog and read it! Leave a comment or a tag k? Even if i dun teach u, u r welcome to leave a note in my blog...

Mr Koh Teck Seng

PS: can we add a tagboard? ( or something?)

Also, can we change the name of this blog/forum? to something cooler... erm... like Cool Science Blog! or Science Rocks... or Physics is Phun... haha... :P or something serious but not as nerdy sounding... like Science, Thoughts & Principles or something... suggestions, comments please?!

Saturday, February 10, 2007

STP Blog

This is the new STP blog. Feel free to post interesting videos you find here as well as discuss anything regarding Physics, Chemistry or Biology here. Would anyone care to create a template for us? Start posting!!

Yong Lin
07S6K IT rep