concurrence, congruence

Study: Speed of Gravity, Light Match

Einstein was right. The speed of gravity matches the speed of light, according to astronomers who took advantage of a rare planetary alignment to measure one of the fundamental forces of nature.

Edward B. Fomalout of the National Radio Astronomy Observatory and Sergei Kopeikin of the University of Missouri measured the amount that light from a distant star was deflected by the gravity of Jupiter as the planet passed in front of the star.

Albert Einstein, who formulated basic theories about space, time and relativity, had assumed that gravity moved with the speed of light, about 186,000 miles per second, "but until now, no one had measured it," said Kopeikin.

"Einstein was right, of course," said Fomalout.

The measurement is one of the last fundamental constants in physics to be established and Fomalout admitted, "gravity is not well understood."

The researchers used 10 radio telescopes scattered across the Earth from Hawaii to Germany to precisely measure how light from a distant quasar, a type of star, was bent as it passed by Jupiter on its way to the Earth. Jupiter is in the precise position for such a measurement only once a decade.

To make the measurement, the instruments had to detect a minute deflection of the light. Fomalout compared the required precision to being able to measure the size of a silver dollar sitting on the moon's surface, or measuring the width of a human hair from 250 miles away.

[...] Fomalout and Kopeikin said their results are accurate within about 20 percent.

Knowing the precise speed of gravity is important to physicists testing such modern ideas as the superstring, which holds that fundamental particles in the universe are made up of small vibrating loops or strings. It also affects some basic space-time theories.

Holy serotonin, Batman!

Mouse Study Reveals Second Serotonin-Making Gene

German scientists have identified a second enzyme that is involved in making serotonin, a brain chemical associated with depression. And the genetic hardware of this newly identified enzyme is detected primarily in the brain, according to their mouse study reported in the January 3rd issue of the journal Science.

The findings suggest that all past efforts to identify genetic reasons for mental disorders linked to abnormal serotonin production have focused on the wrong gene, according to Dr. Diego J. Walther of the Max Delbruck Center for Molecular Medicine in Berlin-Buch.

[...] Serotonin synthesis occurs in a handful of extremely important neurons in the brain and in some cells of the gastrointestinal tract, Walther explained in an interview with Reuters Health.

"This is common knowledge in the serotonin field, but it was believed for decades that only one enzyme commits the rate-limiting step in the biosynthesis in all tissues. However, we have discovered a second tryptophan hydroxylase enzyme," added the researcher. A rate-limiting step is the slowest step involved in a multiple-step chemical reaction; this step determines the rate at which a reaction occurs.

"Moreover, we were able to elucidate that this second enzyme is the source for serotonin in neurons, and not the formerly known enzyme (Tph-1), which we've found to synthesize serotonin most prominently in the gut of adult vertebrates," said Walther.

"Therefore, our findings (have) opened a door to a completely new research area, and to our understanding of the biosynthesis of a compound related to a multitude of mood-controlling effects," he added.

In the study, the investigators generated mice genetically deficient in Tph1. These mice lacked any serotonin outside the brain except in the duodenum, the part of the small intestine closest to the stomach, where levels were only about 4% of normal.

However, brain regions known to generate serotonin expressed normal amounts of the neurotransmitter in the mutant mice, and the animals exhibited behavior similar to that of non-mutant mice in tests associated with serotonin-related behavior.

Moreover, the RNA of a second enzyme, Tph2, was distinct from that of Tph1, according to the report. When examining total RNA from the brain stem of normal mice, they observed that Tph2 was expressed at levels 150 times greater than that of Tph1.

more stuff on my reading shelf

When I went to the library this week, I turned in three books, so I thought it was more than fair if I borrowed the same amount. Just to keep my balance even.

One of the books was The Autobiography of Malcolm X, which I checked out for my uncle. If he finishes it in time, I'll try to start it myself. But, knowing him, he'll probably take the entire three weeks.

For myself, I got Religious Mystery and Rational Reflection by Louis Dupre, and Why Religion Matters: The Fate of the Human Spirit in an Age of Disbelief by Huston Smith. Smith is a very accessible writer; I love reading his stuff.