Friday, June 09, 2006

Miscellaneous links, 2006-06-09

Once again, a link fest...

Probing the antiworld
A free access article from the October 2005 issue of Physics World. (There's at least one in each issue, and it's usually worth the read.) This article describes how antimatter (antihydrogen) is actuall made in the lab. The ultimate goal is to allow a test of the CPT theorem by measuring the spectrum of antihydrogen.

Universe reveals its dark side
Another article from Physics World, the May 2005 issue. It provides a quick overview of what dark matter might be, and more detail on various experimental approaches to detecting dark matter. (Additional evidence is discussed here.)

Relativity at the centenary
One more article from Physics World, January 2005. Most physicists do not seriously doubt either special relativity or general relativity -- at least, not in almost all circumstances. But since relativity does not comport well with the other foundation of modern physics, quantum mechanics, there's plenty of reason to search for minuscule effects where relativity is not quite correct. The hope is that understanding such effets -- if they exist -- may give clues to how relativity needs to change in order to fit better with quantum mechanics. For instance, tests for violations of "Lorentz invariance", a key feature of special relativity, could tell us something about possible theories of quantum gravity, such as string theory. In another direction, tests of the inverse square law of gravitational attraction at small distances (under 10 mm) could indicate the existence of more than 3 spatial dimensions.

Brain's Darwin Machine
April 11, 2006 article from the Los Angeles Times. It describes a fascinating recent research finding. Every human brain contains roughly 100 billion (1011) neurons. Brains of 3-year-olds actually contain twice as many neurons, and half of them die by adulthood. But even in adulthood, thousands of new neurons form every day and play a role in building new memories. Amazingly, most neurons are genetically different from all others. The new discovery is that this difference seems to be due to the insertion of a short sequence of DNA, called a "long interspersed nuclear element", at random locations in the genome. The distinctness of most neurons may help account for the vast amount of information and experience that brains are capable of encoding.

Regrow Your Own
April 11, 2006 article from the New York Times. Regenerative medicine is about discovering how to induce human bodies to regrow damaged parts, just as some amphibians and fish can. Experimental stem cell therapies receive the most attention in this field, but there's an alternative: employing the same (or similar) genetic programs that the amphibians and fish use. This involves mature cells at the location of damage reverting to a more immature state, forming a cell mass called a "blastema", which in turn develops into the appropriate body part. Humans may have the necessary genes to do this, but for unknown reasons they are not switched on. There is reason to hope for a way around this, because in fact there is one organ that actually can regenerate after substantial damage: the liver.

Fighting Cancer Through the Study of Sarcomas
Here's an article from the September-October 2005 issus of American Scientist. A sarcoma is a cancerous tumor of bone, fat, or muscle tissue. Sarcomas are less common than cancers of the blood or internal organs, but exhibit the same abnormalities. It's often noted that cancer is really a large number of different diseases, each reflecting some different combination of genetic damage. Such genetic problems tend to be studied in more detail in sarcomas, leading to diverse kinds of experimental treatments. The article gives a number of examples, which illustrate a variety of the different abnormalities that lead to cancer.

This is the only link in this collection to a whole site rather than a single article. BioCarta is a commercial enterprise that supplies "uniquely sourced and characterized reagents and assays for biopharmaceutical and academic research." Their customers are generally engaged in the field of "proteomics", which is the study of how proteins interact with each other and thereby control all processes in and between living cells. But BioCarta's site is less about their business than it is a fascinating catalog of known "pathways", which are biological programs made up of sequences of protein interactions that drive a particular cellular function, such as "apoptosis" (cell death) or regulation of the "cell cycle". Each pathway is described with both text and high-quality graphics. For example: the p53 signalling pathway -- p53 is a protein that has a key role in regulating the cell cycle, in order to prevent cell division if the cell's DNA has been damaged. Mutations in the p53 gene so that its protein malfunctions are very common in many types of cancer.


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