Tuesday, May 25, 2010

Solar System Dating

Astronomy with Radioactivities: (An Introduction to Astrophysics with
Decaying Isotopes)

This chapter presents a (partial) review of the information we can derive on the early history of the Solar System from radioactive nuclei of very different half-life, which were recognized to have been present alive in pristine solids. In fact, radioactivities open for us a unique window on the evolution of the solar nebula and provide tools for understanding the crucial events that determined and accompanied the formation of the Sun. Discussing these topics will require consideration of (at least) the following issues. i) The determination of an age for solar system bodies, as it emerged especially from the application of radioactive dating. ii) A synthetic account of the measurements that proved the presence of radioactive nuclei (especially those of half-life lower than about 100 Myr) in the Early Solar System (hereafter ESS). iii) An explanation of their existence in terms of galactic nucleosynthesis, and/or of local processes (either exotic or in-situ) preceding and accompanying the formation of the Sun. This will also need some reference to the present scenarios for star formation, as applied to the ESS

Monday, May 24, 2010

Grand Unified Theories

The Algebra of Grand Unified Theories
The Standard Model of particle physics may seem complicated and arbitrary, but it has hidden patterns that are revealed by the relationship between three "grand unified theories": theories that unify forces and particles by extending the Standard Model symmetry group U(1) x SU(2) x SU(3) to a larger group. These three theories are Georgi and Glashow's SU(5) theory, Georgi's theory based on the group Spin(10), and the Pati-Salam model based on the group SU(2) x SU(2) x SU(4). In this expository account for mathematicians, we explain only the portion of these theories that involves finite-dimensional group representations. This allows us to reduce the prerequisites to a bare minimum while still giving a taste of the profound puzzles that physicists are struggling to solve.

Sunday, May 23, 2010

Flow My Tears, the Policeman Said

Flow My Tears, the Policeman Said is a paranoid science fiction novel by Philip K. Dick.
Scrutinizing him, she said, 'Maybe your're not a celebrity; maybe I've reverted back to my delusional period. They said I probably would, sometime. Sooner or later. Maybe it's later now.'
'That,' he pointed out, 'would make me a hallucination of yours. Try harder; I don't feel completely real.'
She laughed.

The Big Sleep

The Big Sleep is a detective novel by Raymond Chandler.

"You know what Canino will do? Beat my teeth out and kick me in the stomach for mumbling."

See The Simple of Art of Murder for a previous post about Raymond Chandler.

A Simple Heart

A Simple Heart is a story by Gustave Flaubert, it's one of my favorites. Sad, funny, droll - a person, place and time that has no particular intrinsic interest but despite that (or perhaps because of it) a great story.

Wednesday, May 19, 2010

Terahertz Lenses

X-Ray Vision, Without the Radiation in Science. "X-ray–like imaging without the harmful radiation and cell phones with more bandwidth are closer to reality now that researchers have developed a novel type of lens that works with terahertz frequencies. The new lens is a metamaterial, an artificial material with a structure made from many tiny parts, and it could drastically expand what lenses can do. "

Sunday, May 16, 2010

Thursday, May 13, 2010

The Inner Core

Hemispherical anisotropic patterns of the Earth’s inner core in PNAS.
It has been shown that the Earth’s inner core has an axisymmetric anisotropic structure with seismic waves traveling ∼3% faster along polar paths than along equatorial directions. Hemispherical anisotropic patterns of the solid Earth’s core are rather complex, and the commonly used hexagonal-close-packed iron phase might be insufficient to account for seismological observations. We show that the data we collected are in good agreement with the presence of two anisotropically specular east and west core hemispheres. The detected travel-time anomalies can only be disclosed by a lattice-preferred orientation of a body-centered-cubic iron aggregate, having a fraction of their [111] crystal axes parallel to the Earth’s rotation axis. This is compelling evidence for the presence of a body-centered-cubic Fe phase at the top of the Earth’s inner core

Ultrasmall Archaea

Enigmatic, ultrasmall, uncultivated Archaea in PNAS.
Metagenomics has provided access to genomes of as yet uncultivated microorganisms in natural environments, yet there are gaps in our knowledge—particularly for Archaea—that occur at relatively low abundance and in extreme environments. Ultrasmall cells (< 500 nm in diameter) from lineages without cultivated representatives that branch near the crenarchaeal>/euryarchaeal divide have been detected in a variety of acidic ecosystems.

Monday, May 10, 2010

Manta Rays

Once again I've had the good fortune to visit the Manta Rays of San Benedicto Island, in the Pacific off the coast of Mexico. Thanks again to Gregory Colbert, his film crew and friends, and the crew of the Nautilus Explorer for another wonderful trip.
I haven't been able to find a reference to the tubes just above the corners of the manta's mouth pictured below. Thanks to Sten Johansson of the Nautilus Explorer for the photos and for pointing out this interesting feature. Please comment if you can identify these structures, a reference or link to the literature would be especially welcome!

Newton and the Counterfeiter

Newton and the Counterfeiter: The Unknown Detective Career of the World's Greatest Scientist a book by Thomas Levenson is about Isaac Newton and William Chaloner a notorious counterfeiter that Newton prosecuted when he was Warden of the Royal Mint.
While Newton was perhaps the greatest scientific genius of all time, and even a very competent functionary - as detailed in this book - he was strictly mortal in the realm of financial investments. He lost a fortune in the South Sea Bubble of 1720 which rankled him greatly, admitting "that he could not calculate the madness of the people."