Today I learned ...

Economics

2008-03-11T23:55:00.003Z

I am a real dummy when it comes to Economics. So much that I often have problems understanding current affairs, political decisions, etc. Therefore I decided to buy a book Economics for dummies and I really enjoy it. In my opinion, Economics should be thought in school. It would definitely be much more useful to have, say, at least one hour of Economics a week, than three hours of Art every week. I seriously can't believe we had THREE hours of Art per week!

Anyway, the book says that "Economics is all about humanity's struggle to achieve happiness in a world full of constraints." I never thought about economics like this. This first sentence got me in, and I've fully enjoyed reading the book since then. And to be honest, it sounds much more interesting than Wikipedia's first sentence which says: "Economics is the social science that studies the production, distribution, and consumption of goods and services."

If you want to know more about Economics and you are a complete beginner, I would thoroughly recommend this book.

Progenitor cell

2008-03-02T19:29:00.002Z

The term progenitor cell is used in cell biology and developmental biology to refer to immature or undifferentiated cells, typically found in post-natal animals. While progenitor cells share many common features with stem cells, the term is far less restrictive.

Like stem cells, progenitor cells have a capacity for self-renewal and differentiation, although these properties may be limited.

Stem cells: Unlimited self-renewal and are pluripotent.
Progenitor cells: Self-renewal can be limited and are unipotent or multipotent.

Ionophore

2008-03-02T15:58:00.002Z

A ionophore is a lipid-soluble molecule usually synthesized by microorganisms to transport ions across the lipid bilayer of the cell membrane.

(Source: Wikipedia)

Some Chinese statistics

2008-02-17T15:31:00.002Z

I couldn't believe it. Apparently more than 1.1 billion Chinese people (around 85% of China's population) share just 129 surnames. This, it's not hard to believe, makes them a lot of problems when publishing scientific papers, where authors publish under abreviated names, e.g. X. Wang.

(Source: Nature 451, 14th Feb 2008)

A short course in human relations

2008-02-15T23:43:00.004Z

The six most important words: "I admit, I made a mistake."
The five most important words: "You did a good job."
The four most important words: "What is your opinion?"
The three most important words: "Would you mind?"
The two most important words: "Thank you."
The one most important word: "We."

The least important word: "I."

(Source: Dealing with difficult people (Roy Lilley))

Cytokine receptors

2008-02-14T10:45:00.007Z

Cytokines are a group of proteins and peptides that are signalling compounds produced by cells to communicate with one another. They act via cell-surface cytokine receptors. Due to their central role in the immune system, cytokines are involved in a variety of immunological, inflammatory, and infectious diseases. They are also involved in embryonal development of the organism. Known cytokines include the interleukines (IL), erythropoietin, growth hormone, interferons (INF), and tumor necrosis factor (TNF).

Type I cytokine receptors are transmembrane receptors, expressed on the surface of cells that recognize and respond to cytokines with four α-helical strands. These receptors are also known under the name hemopoietin receptors, and share a common amino acid motif (WSXWS). Members of the type I cytokine receptor family are involved in ligand/cytokine interaction and in signal transduction. Type I cytokine receptors include interleukin receptors, colony stimulating factor (e.g. erythropoietin) receptors, and other cytokine receptors (e.g. growth hormone receptor).

Type II cytokine receptors are similar to type I cytokine receptors except they do not possess the signature sequence WSXWS.

(Sources: Wikipedia and Biochemistry of signal transduction and regulation (Gerhard Krauss))

The Greeks

2008-02-13T23:09:00.002Z

No, not the nation :) This is a nice and interesting name for something in mathematical finance. Read on ...

In mathematical finance, the Greeks are the quantities representing the market sensitivities of options or other derivatives. Each "Greek" measures a different aspect of the risk in an option position, and corresponds to a parameter on which the value of an instrument or portfolio of financial instrument is dependent. The name is used because the parameters are often denoted by Greek letters.

The Delta measures the sensitivity to changes in the price of the underlying asset (the first derivative). The second derivative with respect to spot is called Gamma and the process is called Gamma-hedging. It measures the rate of change in the Delta. The derivative with respect to the short rate, r, is called Rho. The derivative with respect to time, t, is called Theta. The derivative with respect to volatility is known as Vega, or (on unreasonable grounds that vega is not a letter in the Greek alphabet) by some people, Kappa.

(Sources: Wikipedia and The concepts and practice of mathematical finance (Mark Joshi))

Charles Bukowski

2008-02-13T09:41:00.000Z

Charles Bukowski (1920 - 1994), an influential poet and novelist.

He seems to be an idol of a popular Slovenian blogger Fetalij, and there's where I heard about him. I searched for some of his poems, to see what it's all about. And just when I was about to write that I don't like any of his poems, I found one that is good. To be honest, I haven't spend much time searching, so I might as well be doing him injustice. I checked online, there's one of his books in our library and I might check it out one day.

Alone with everybody (Charles Bukowski)

the flesh covers the bone

and they put a mind

in there and

sometimes a soul,

and the women break

vases against the wall

sand the men drink too

much

and nobody finds the

one

but keep

looking

crawling in and out

of beds.

flesh covers

the bone and the

flesh searches

for more than

flesh.

there’s no chance

at all:

we are all trapped

by a singular

fate.

nobody ever finds

the one.

the city dumps fill

the junkyards fill

the madhouses fill

the hospitals fill

the graveyards fill

nothing else

fills.

Winehouse: For my Blake incarcerated

2008-02-13T00:01:00.000Z

Amy Winehouse, who scored 5 Grammies yesterday, dedicated them to (among others) her Blake incarcerated. It was the first time I heard this word and I found what she said quite strange and unnatural... is this word often used?

From Cambridge dictonary:

incarcerate = to put or keep someone in prison or in a place used as a prison

Example: Thousands of dissidents have been interrogated or incarcerated.

People are different

2008-02-12T00:58:00.000Z

I often say to my friends that I've only recently realized that people are different. I've always thought that everyone thinks in the same way than I do. That everyone has the same values. That good is good for everyone and bad is bad for everyone. How wrong. What I just wrote may seem funny and obvious, but I've also realized I'm by far not the only person with this beliefs.

Things are changing now, but there are still traces in these beliefs in me. I should interact with other people as much as possible to learn more, understand relationships and, what's most important, myself.

Financial markets: vocabulary

2008-02-09T00:37:00.000Z

I've been a total ignorant about economics, stock exchange, financial markets and all these kind of things. It's time to learn some basics. Wikipedia is a good place for this. I'll start by some common vocabulary.

In economics, a financial market is a mechanism that allows people to easily buy and sell (trade) financial securities (such as stocks and bonds), commodities (such as precious metals or agricultural goods), and other fungible items of value at low transaction costs and at prices that reflect the efficient market hypothesis.

Dividends are payments made by a company to its shareholders. When a company earns a profit, that money can be put to two uses: it can either be re-invested in the business (called retained earnings), or it can be paid to the shareholders of the company as a dividend.

A mortgage is a method of using property (real or personal) as security for the performance of an obligation, usually the payment of a debt.

A good example of a financial market is a stock exchange. A company can raise money by selling shares to investors and its existing shares can be bought or sold. A stock exchange, share market or bourse is a corporation which provides facilities for stock brokers and traders, to trade company stocks and other securities.

Relationship between lenders and borrowers
Lenders	Financial intermediaries	Financial Markets	Borrowers
Individuals Companies	Banks Insurance Companies Pension Funds Mutual Funds	Interbank Stock Exchange Money Market Bond Market Foreign Exchange	Individuals Companies Central Government Municipalities Public Corporations

Governments borrow by issuing bonds. Government debt seems to be permanent. Indeed the debt seemingly expands rather than being paid off. One strategy used by governments to reduce the value of the debt is to influence inflation.

The money market is the global financial market for short-term borrowing and lending. Companies tend to be borrowers of capital. When companies have surplus cash that is not needed for a short period of time, they may seek to make money from their cash surplus by lending it via short term markets called money markets.

Many borrowers have difficulty raising money locally. They need to borrow internationally with the aid of Foreign Exchange Markets.

The term financial intermediary may refer to an institution, firm or individual who performs intermediation between two or more parties in a financial context. Typically the first party is a provider of a product or service and the second party is a consumer or customer.

A mutual fund (collective investment scheme) is a way of investing money with other people to participate in a wider range of investments than may be feasible for an individual investor, and to share the costs of doing so.

There's lots more to explore and learn.

(Source: Wikipedia)

Self-harm

2008-02-08T21:06:00.000Z

What is self-harm?

Self-harm describes a wide range of things that people do to themselves in a deliberate and usually hidden way (cutting, burning, scalding, scratching one's own body, breaking bones, hair pulling, ingesting toxic substances or objects).

Why do young people self-harm?

Young people who self-harm mainly do so because they have no other way of coping with problems and emotional distress in their lives. However, this is not a good way of dealing with such problems, as it only provides a temporary relief and does not deal with the underlying issue.

Some statistics

Self-harm is a very common problem, and many people are struggling to deal with it. Research shows that 1 in 15 young people in Britain have harmed themselves. Most young people who harm themselves are aged between 11 and 25. The age at which most people start is 12.

There are lots of internet resources providing help for those who are self harming or whose children or friends are self harming:

www.siari.co.uk
www.youthnet.org
www.lifesigns.org.uk
www.selfharm.org.uk

(Source: Camelot Foundation brochure)

Ageing

2008-02-08T09:00:00.000Z

Life expectancy in humans has raised surprisingly in the last decade and apparently it is still increasing by about 5 hours per day. This means that we wake up in the morning to a 29 hour day, but that we store 5 hours for later in our lives. (Well, it actually means that we wake up tomorrow to a 29 hour day, the day after tomorrow to a 34 hour day etc.) Unbelievable, ha?

Ageing has been a subject of extensive research. A part of scientific community believes that old age is associated with disease, but does not cause it. The other part tries to separate ageing and diseases and identify biological pathways responsible for ageing.

The following are the damages in cells that may contribute to ageing:

DNA damage (copying errors, telomere shortening, gene disruptions by viruses and transposons)
RNA damage (transcription errors, aberrant splicing)
Protein damage (misfolding, synthesis erros, impaired protein turnover, aberrant post-translational modifications)
Membrane damage (oxidation)

(Source: T. B. L. Kirkwood, Nature 451, 7th Feb 2008)

Aberrant

2008-02-07T22:51:00.000Z

From Cambridge dictionary:

aberrant = different from what is typical or usual, especially in an unacceptable way

Example: aberrant behaviour/sexuality

Laudable

2008-02-06T22:00:00.000Z

According to Cambridge dictionary:

laudable = deserving praise, even if there is little or no success

laudable effort, laudable aim, laudable pursuit

I've read this word in my colleague's report which says "The authors' attempt to reconstruct the hidden transcription factor activity profile from observable times series microarray data is laudable."

Mathematical finance: Options

2008-02-03T21:54:00.001Z

An option is an instrument which gives the holder the right to buy or sell a quantity of some fixed asset during a specified period of time at a price fixed today. The important point is that there is no obligation to buy or sell.

An option to buy is called a call option. If we buy an option with strike price K in time T, we have the right to buy stock for price K instead of price S (which is the stock's price at time T). So if S>K, we will exercise the option and if K>S we won't.

Put option with strike price K is an option to sell. This means that we have an option to (the right to) sell the stock for K. So if the stock price (S) will be higher than K, we will not exercise the option, but will sell at S. If the stock price will be lower than K, we will exercise our right to sell the stock for K.

Mathematical finance: Bonds

2008-02-03T21:43:00.000Z

The simplest and the least risky asset is a government bond, issued by a reliable government. The bond is issues for, say, 30 years and every year it pays a sum called the cupon. The original investment is called the principal. The day that the investor gets the principal back (the bond is said to mature) is called the date of maturity. The effective interest rate implied by the market price is called the yield of the bond and this can be very different from the cupon. (Don't really understand this last definition.)

A zero-cupon bond is a bond which pays no interest but instead just returns the investor his investment on the date of maturity.

Infidelity and copulation

2008-01-31T17:57:00.001Z

Today I learned two new English words: infidelity and copulation. I've been such a good girl that I've never come across these words before. Until today, when I studied some method of statistical analysis on sperm count data.

The statistical analysis was about testing the hypothesis that it is evolutionary advantageous for males to (subcounsciously) increase their sperm count in proportion to the opportunities that their mate may have had for infidelity.

King Tut

2008-01-30T23:36:00.000Z

I've been organizing a trip to see a Tutankhamun exhibition in O2 arena in London for the students and I've been surprised that eveybody is asking me what this is. Tutankhamun, hellooooo? The famous Egyptian king? One of the first things I learned in my history lessons. What's going on? Why have British never heard about it? Maybe they just haven't heard about the exhibition? I was to flabberghasted to ask.

Tutankhamun was an Egyptian Pharaoh that lived 1341 BC - 1323 BC. He died only 19 year old and reigned for 10 years. Can you imagine? He was nine when he became a king!! His original name was Tutankhaten. Tutankhamun is, in modern times, one of the most famous of the pharaohs, and the only one to have a nickname in popular culture (King Tut). In historical terms, Tutankhamun is only moderately significant, and his modern fame and popularity stem from the fact that his tomb in the Valley of the Kings was discovered in 1922 almost completely intact.

For a long time the cause of Tutankhamun's death was unknown, and it is still the root of much speculation. There has been much speculation over the age of the king when he died, whether he suffered from any physical abnormalities, or whether he had been murdered. In early 2005 many questions were answered when the results of a set of scull scans on the mummy were released, but many still remain to be unsolved.

(Source: Wikipedia)

The principle of parsimony

2008-01-29T11:03:00.000Z

In modelling and model selection we always hear about the so-called Principle of parsimony. Today I found a simple explanation of its intuitive meaning. Source: Statistics, An Introduction using R (M. J. Crawley).

Parsimony says that, other things being equal, we prefer:

a model with n-1 parameters to a model with n parameters,
a model with k-1 explanatory variables to a model with k explanatory variables,
a linear model to a model which is curved,
a model without a hump to a model with a hump, and
a model without interactions to a model containing interactions between factors.

Latin hypercube sampling

2008-01-27T15:25:00.000Z

Latin hypercube sampling is an efficent way of sampling from a uniform distribution. An even better version of it is orthogonal sampling, which ensures that the ensemble of random numbers is a very good representative of the real variability.

The cause of sleep

2008-01-27T14:33:00.000Z

Philosophers tried to understand sleep centuries ago. Aristotle (384 BC - 322 BC) thought that we sleep because the gases resulting from food digestion in the stomach come to our brain and sedate them. This is what was commonly believed until the 16th century.

Imagine how many things we believe in right now that will appear to be nonsense in the coming centuries!

New types of small RNA

2008-01-27T13:12:00.000Z

Besides classic RNA (ribonuleic acid, the transcripts of DNA) molecules, which include messenger RNA (mRNA), ribosomal RNA (rRNA) and transfer RNA (tRNA), new types of RNA are being discovered. Recently a very hot research topic are so called small RNAs.

Small RNA have an important role in regulating gene expression, and they are non-coding molecules, which means that they don't translate into protein molecules. They have so far been connected to gene silencing.

The types of small RNA that we know are small interfering RNA (siRNA), microRNA (miRNA) and piRNA (Piwi-associated RNA). The latter ones are the ones I've never heard about before. They are 25-30 nulecotides in length, function in association with the Piwi subfamily of Argonaute proteins, and are essential in development of germ cells.

Shrinkage of coefficients in linear regression

2008-01-25T23:03:00.000Z

Actually it would be better if I first explained what a linear regression is (that's what I'm learning these days), but maybe some other time.

Shrinkage of coefficients in linear regression is done in order to improve the prediction accuracy and to be able to better interpret the outcome of linear regression. The most known are the following three methods: subset selection, ridge regression and lasso. In lasso, for example, the solution to the least sqares problem is

subject to

... how to write LaTex on blogger

2008-01-25T22:47:00.000Z

Thanks to this post I learned how to write text in LaTex on blogger. Here is a test:

I'm going to use this new blog for writing about what I learned. The idea is to learn something new every day. Let it be maths, stats, biology... or anything else, from new english words to what I learn in practice about human relationships.