Tuesday, December 13, 2011

She chills me out - thanks to my oxytocin receptor gene

Can your girlfriend help chill you out before some stressful activity? It probably depends on whether you have the G allele of the rs53576 single nucleotide polymorphism of the oxytocin receptor gene, according to this study in PNAS: Common oxytocin receptor gene (OXTR) polymorphism and social support interact to reduce stress in humans . See a previous blog post You're Nice, He's a Jerk - is it because of your Oxycotin receptor genes? for more fascinating research about the behavioral differences attributed to different variants of this gene.

Monday, December 12, 2011

Step up to the bar - the Milky Way bar

Apparently there's a bar/box shaped concentration of stars in the center of our Milky Way galaxy.

This central bar is oriented about 20 degrees from our line of sight to the center of the galaxy - so the diagram above doesn't look quite right to me. The bar seems to rotate like a cylinder - rigidly. This type of structure is typical of many galaxies, not just ours. There's evidence that our bar is a fairly uniform population, there's no real evidence of recent mergers. That's inconsistent with a model of galaxy formation by merger, which seemed to work well for elliptical galaxies. Our Milky Way is a barred spiral - different from ellipticals - but it was thought for a while that the central bulge of spirals might have formed a similar manner. Now that no longer appears to be true.
For some scientific details see The Bulge Radial Velocity Assay (BRAVA): II. Complete Sample and Data Release and OUR MILKY WAY AS A PURE-DISK GALAXY—A CHALLENGE FOR GALAXY FORMATION.

Saturday, December 10, 2011


Magma is melted rock, when it reaches the surface it's called lava. Magma comes from deep underground where it's much hotter, so the rock down there is melted, isn't it? Well not really. Beneath the earth's crust is the mantle and it's by and large solid too. The difference between the crust and the mantle is mainly chemical, they are both solid.
So then, where does magma come from, how does all that rock melt and create such appalling displays at volcanic eruptions?

As it turns out, magma forms by decompression melting. Not only is the temperature higher deep underground in the mantle, the pressure is also terrifically greater. We usually think of solids melting when the temperature rises, but they can also melt when the pressure decreases. Peridotite the mantle rock, is solid at the high pressures and temperatures found down in the mantle, but it will melt when the pressure is released by an opening to the surface - a volcano.

The Mid-Pleistocene Transition

Before 1.2 million years ago, glacial cycles had a 40,000 year periodicity. But in the past 700,000 years the ice-age cycle has been around 100,000 years. There was a transitional period in between. See Atmospheric Carbon Dioxide Concentration Across the Mid-Pleistocene Transition from 2009 in Science magazine. There is a 41,000 year periodicity in the earth's orbit which could explain the earlier periodicity (see Milankovitch cycles), but the the transition to the more recent 100,000 year cycle is currently rather mysterious.

Tuesday, December 06, 2011

Type Ia Supernovae and the discovery of Cosmic Acceleration

It's not so easy to figure out the distance to far away objects in the sky - see an older post on the cosmic distance ladder. However, it's possible for even beginning astronomy students to climb the First Three Rungs of the Cosmological Distance Ladder. The top of the ladder isn't so easy though. The 2011 Nobel Prize in Physics was awarded for "for the discovery of the accelerating expansion of the Universe through observations of distant supernovae". A key element of that discovery was the use of Type Ia supernova to determine distances. Type Ia supernova are supposed to the explosion of a white dwarf star, conveniently it seems to be possible to determine the absolute luminosity of those explosions, which indicates the actual distance.

The preprint Type Ia Supernovae and the discovery of the Cosmic Acceleration is a nice explanation of the history of this discovery by Alejandro Clocchiatti a member of one of the groups which made the discovery - the High-z Supernova Search Team.

Kepler's supernova

Monday, December 05, 2011

Hank Paulson: Facts and Figures - or Fiction?

Henry Paulson has had a distinguished career as CEO of Goldman Sachs and U.S. Secretary of the Treasury under President George W. Bush. As Treasury Secretary he was a key figure in the 2007-2009 financial crisis.
He's also known as an avid nature lover. In the article Birds and Bankers in the New Yorker he's quoted as saying, "The Amazon dumps enough fresh water in the ocean every hour to fill one Lake Superior.”
However, according to Wikipedia:
the water volume of Lake Superior is 12,000 cubic kilometers;
the average discharge of the Amazon River is approximately 209,000 cubic meters per second.
Based on those figures, according to my calculations it would actually take approximately 15,948 hours (1.82 years) for the Amazon River to discharge enough fresh water to fill Lake Superior.
I hope Secretary Paulson had superior sources of information while discharging his duties during the financial crisis.

Sunday, December 04, 2011

You're Nice, He's a Jerk - is it because of your Oxycotin receptor genes?

A study published in PNAS: Thin-slicing study of the oxytocin receptor (OXTR) gene and the evaluation and expression of the prosocial disposition indicates that individual differences in social behavior are correlated with variants of their Oxycotin receptor genes. Previously, another study in PNAS: Oxytocin receptor gene (OXTR) is related to psychological resources indicated that variation in this gene was also related to other personality traits. Forget about horoscopes, find out whether your potential mate has the A or G allele of the oxytocin receptor (OXTR) SNP rs53576!
Oxytocin is the "love hormone" associated with maternal and sexual behavior.