Archive for the ‘interesting’ Category

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Lazy cat

August 15, 2008

Yesterday I had to defend my internship report; everything went better than I could’ve expected. I almost couldn’t stop talking, and my presentation was between 45-50 minutes (while 20 minutes was sufficient). Anyway, the questions afterwards were not that difficult, and all in all they were happy with the way I had worked during my internship.

Now I’m at my parents for a few days, and when I was goofing around with one of our cats, I had the chance to stare right into the belly of the beast:

Straight into the belly of the beast

Straight into the belly of the beast

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Cosmic background radiation

September 1, 2007

I finally finished my course on Quantum Optics; in the book we used was a question about the “number of photons per unit volume excited in a cavity at temperature T” (Loudon, Quantum Theory of Light). After deriving a formula for this, you can show that the cosmic background radiation contains about 4-5*10^5 photons per litre.
I always got stuck at the same point, but now I finally know how to solve this.

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Read the attached pdf if you want to know the solution.

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Hurricanes and global warming

July 19, 2007

There’s an article in Scientific American (July 2007) about the relation between global warming and hurricanes. I learned a few things from this:
A cyclone, typhoon and hurricane are the same thing; they only differ in the region where they are observed.

How do hurricanes form?

  • The sun raises the Sea Surface Temperature (SST)
  • Water is evaporated to release the excess heat
  • The moisture raises and condenses into rain
  • When raindrops are formed, latent energy is released
  • The heat goes up and creates ‘updrafts and thunderclouds’
  • Beneath this area, a low pressure zone is created which ‘sucks up’ moist air
  • Due to Coriolis forces due to the earth’s rotation a vortex is created
  • “The eye” is a low pressure area at the bottom of this vortex
  • Due to the circling hot air, the rising air dries and gains energy
  • Some of this air is absorbed again in the eye, and some of the air ‘spirals out’ over a large area (many kilometres)

How hurricanes form - Copyright Scientific American

The different seasons play a role as well:
The energy released when raindrops form heats the atmosphere

  • In winter, the heat goes up and radiates into space
  • In summer, the heat rises to higher altitudes in tropical areas

Further ingredients needed to start a hurricane:

  • high SST (>26 degrees Celsius); SST may rise due to the greenhouse effect
  • plentiful water vapour
  • low pressure at the ocean’s surface
  • weak wind shear between low and high altitudes (strong winds destroy emerging vortices)

The rising SST may (partly) originate from the greenhouse effect. However, in 2004 and 2005 we saw a lot of hurricanes, but 2006 was a quiet year.

Some scientists believe this is due to the “Atlantic Multidecadal Oscillation” (AMO), which is basically a cycle in which temperatures rise and fall. But simulation shows that this can’t be the whole story (the temperature difference is only 0.5 degrees Celsius). The models do show (as far as they are correct; which is difficult to assess) that human action is likely a cause of the rising SST. Approximately 0.6 degrees Celsius can be attributed to human action (probably without the AMO) since 1970. It is noted that this may sound small, but only one degree can change the storm’s intensity to a higher category. This may well explain the rise in the number of ‘high’ category hurricanes.

The fact that 2006 was a quiet year (in stark contrast to 2004 and 2005) is due to a different factor. In 2004/2005, El Nino warmed the ocean. La Nina cooled the ocean the subsequent year. This is explained in the remainder of the article.

The article concludes that the hurricane threats are likely to get more severe.

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Huntington’s disease

May 6, 2007

In the April/May 2006 (Yes, it’s an oldie, but I’m just catching up) edition of Scientific American Mind, there’s an interesting article written by Juergen Andrich and Joerg T. Epplen about Huntington’s disease.

It starts with simple incidents, such as forgetting a familiar address, or dropping a cup. But they are not incidents. Not clumsiness, forgetfulness or overreaction either. At least, when you have Huntington’s disease, an inherited disease of which the mutating gene was discovered in 1993. It leads to “progressive destruction of the brain, crippling muscles and mental function“. This mutation wreaks havoc inside the brain.

A single gene on chromosome 4 (the huntingtin gene (no misspelling)) is the cause. DNA consists of 4 bases: Cytosine, Adenine, Guanine and Thymine. If the CAG sequence on this gene occurs more than 35 to 40 times (instead of the regular 28 times), this chain becomes too long and causes trouble. The longer the chain of CAG-sequences, the earlier the disease starts showing, and the more severe it gets.

The symptoms usually show up when at age 35-45, but this also depends on the length of the chain.

Saint Vitus dance, an “involuntary movement disorder“, is characterized by “brief, irregular contractions that are not repetitive or rhythmic, but appear to flow from one muscle to the next. These ‘dance-like’ movements of chorea (from the same root word as “choreography”) often occur with athetosis, which adds twisting and writhing movements.” This is also seen in Huntington’s disease. But mental symptoms often occur before the physical problems, which also leads to social problems (relatives, friends, etc.), and even suicide. Before 1993 (when the responsible gene was discovered) people were often misdiagnosed as “mentally ill or alcoholic”.

What follows is something I don’t fully understand and therefore may not be very clear, but I’ve included it nonetheless:
When the elongated protein starts binding with other proteins, the function of those proteins is in danger.
Glutamate is a neurotransmitter, a chemical which helps a neuron “talk” with another cell. Synapses allow the neurons to form a network and communicate, and function as a system.
Via some complex process, some neurotransmitters won’t be removed “such as glutamate from the synapses“, resulting in “adjacent neurons continually excited” which will damage the cell.
Because of some other difficult process, it’s inpossible for the huntingtin protein to bind to the HIP-1 protein: “the neurons are driven to kill themselves.”

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Science and Law – Part 3

April 30, 2007

-Read part 0 here
-Read part 1 here
-Read part 2 here

Genetic Science and Truth
As with fingerprinting the uniqueness of a profile, be it a DNA profile or a fingerprint, is an important component in the legal inquiry. However, this should not be confused with the ‘attribution question’. Jasanoff argues that the attribution question molds into the unniqueness question, indicating “how faith in science’s truth-telling capability can distort both the logic and the normative function of legal inquiry.”

Especially with the amount of information gained from genetic science, overreliance on the implications of genetic studies can be troublesome. As more and more genes are mapped by the Human Genome Project, the focus on predictors of physical traits (eye / hair color, diseases, mental conditions) shifts to behavioral characteristics (agression, thrill-seeking), paving the way for eugenetics (leading to the racial rationale in the Nazi regime). This mapping of genes doesn’t eliminate the ‘nature vs. nurture’ -debate, as behavioral characteristics are heavily influenced by surroundings. However, as is noted by the author, money is still spent on research for finding “biological solutions to deep social problems“, as a faster solution for the various (slow) social policies to solve poverty and inequality (e.g. just let the intelligent people survive, to create a more balanced society. Or is there a genetic marker only existent in violent people?).

Science is used as a tool to repair human behaviour and mental conditions. But, as results from the Human Genome Project indicate, because the relative low amount of genes in the human species (only about twice as much as a fruit fly), the explanation of human behaviour doesn’t come from the genes alone.

Extreme care should be taken in explaining human behaviour on the basis of genetic information, or in extending results beyond what the research question.

Jasanoff ends with the article with:
In a court of law, science cannot hold itself out as simply science, the source of transcendental truths; more modestly, and with appropriate caveats, it can be the source of just evidence.

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Science and Law – Part 2

April 28, 2007

-Read part 0 here

-Read part 1 here

Law Enforcement Science
It’s impossible to completely dismiss the possibility of human error. Some mistakes are easy to detect and correct, others are almost impossible to find. Mistakes can result from pressure, insufficient quality control mechanisms, fraud, etc.

Through the act of “normalization of deviance“, people anticipate on common problems and compensate them without starting all over again, which would be costly and time-consuming. Visibility of a high profile case can lead to cover-ups because of fear of public opinion (e.g., a mistake is made, but due to high public pressure the mistake is never admitted).
Also, even in the scientific community, researchers “seduced by the lure of success” are able to make up results, and it may take quite some time before the “organized skepticism” works as it should have. Examples are the various claims that AIDS can be cured, cloning embryonic stemcells, cold fusion, etc. But this fraud is not limited to the scientific community; fabricating evidence (e.g. by law officers) is something that can be done easily, even subconsciously. For example, when comparing two fingerprints, it’s easy to say that the two prints match even if they don’t, just because the need for a suspect. The need for “organized skepticism” is enormous, especially when someone’s life is at stake.
Jasanoff expresses it beautifully: “When the purpose is to free a presumably innocent, wrongfully convicted prisoner, forensic scientists have every incentive to produce the most reliable and persuasive results within their power. By contrast, when the purpose is to convict the guilty, extraordinary pressures may exist to produce results that will satisfy the prosecutor’s and the public’s desire for speedy convictions.

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Science and Law – Part 1

April 26, 2007

-Read part 0 here

Truth in Science and Law

Science as a independent research topic, and science used in the aid of convicting both look for truth. The difference between the two activities is the context:
For the most part, facts produced to serve the aims of litigation do not grow out of, nor play a part in, the same kinds of social interactions as do the facts produced in basic research science or even in regulatory science.
Because of the different contexts, there’s also a difference in what is regarded as “truth”. A simple illustration is in the judiciary: to convict a suspect, facts have to be “proved” beyond reasonable doubt. In a strict sense this is not a proof, as doubt may always exist. It’s not a mathematical formula that can be proven. So, in short, what is true for the law, doesn’t need to be true for science.
There are four differences between Truths in science and law:

  • A truth in science should be valid in a general case, whereas truths in the law is only of interest in specific cases. With this notion, it immediately becomes clear that the way the scientific community eastablished facts doesn’t work in law: in most cases there’s no peer review, hence no replications of the fact. Also, the purpose of science is to advance the knowledge, so that that knowledge of today can be used tomorrow. In contrast, the purpose of science in the law is to use the knowledge of today for things that happened in the past. This leads to enormous costs in order to reduce any doubt, needed for a just process. Those resources could be used more efficiently.
  • Delay. Among with the enormous cost comes a long delay to iron out all the doubts. But it is necessary; otherwise the defense can easily punch a hole in the argument: “In civil cases, plaintiffs need only demonstrate by a perponderance of the evidence that their version of the case is more likely than not to be true. In criminal cases, the defendant needs the quantum of evidence that produces a reasonable doubt in the jury’s mind in order to be acquitted. Legal evidence, in other words, need not and should not be held to scientific standards of robustness.
  • It’s “ethically and practically questionable” that foolproof science can be used to remove any doubt, as it’s mostly “the poor, the disadvantaged, and the racially makred who are actually executed.” Especially in an adversarial system like the US, the judge doesn’t have an active role in finding the truth. He / she listens to both parties, and hopefully tries to distill the truth from that. A good (expensive) defense lawyer is essential in the creation of doubt; in this way the poor aren’t likely to be acquitted.
  • Law has the final word in the conviction (situation in the US). This is illustrated by a 1993 Suppreme Court decision, “which held that a claim of actual innocence is not enough to reopen a criminal conviction based on a fair trial; the prisoner, who is no longer entitled to a presumption of innocence, must also show constitutional error.” Or, to put it differently, science can be used to convict someone, but it can’t be used to free an already convicted prisoner (unless there’s a constitutional error). In the Netherlands this is a little different, but comparable (Puttense moordzaak). Therefore, a scientific truth and a legal truth aren’t the same.