Richard Dixon Oldham (July 31, 1858 – July 15, 1936) was an Irish geologist and seismologist who discovered evidence for the existence of the Earth's liquid core in 1906.
In studying seismograms of the great 1897 Indian Earthquake he identified P (primary) and S (secondary) waves. It is interesting that he did not get a clue to the presence of the core from the S waves, which are actually incapable of being transmitted through the liquid of the outer core. (The liquid core does not transmit the shear wave energy released during an earthquake.)
Rather he noted the existence of a shadow zone in which P waves from an earthquake in the opposite hemisphere of the earth failed to appear. From Today in Science History
Saturday, July 31, 2010
Friday, July 30, 2010
Evolution of The Inner Ear
Fossil evidence on evolution of inner ear cochlea in Jurassic mammals. 2010. Zhe-Xi Luo, et al. Proc. Of the Royal Soc. B. Published online before print July 28.
Click to enlarge
Abstract: The coiled cochlea is a key evolutionary innovation of modern therian mammals. We report that the Late Jurassic mammal Dryolestes, a relative to modern therians, has derived bony characteristics of therian-like innervation, but its uncoiled cochlear canal is less derived than the coiled cochlea of modern therians. This suggests a therian-like innervation evolved before the fully coiled cochlea in phylogeny.
The embryogenesis of the cochlear nerve and ganglion in the inner ear of mice is now known to be patterned by neurogenic genes, which we hypothesize to have influenced the formation of the auditory nerve and its ganglion in Jurassic therian evolution, as shown by their osteological correlates in Dryolestes, and by the similar base-to-apex progression in morphogenesis of the ganglion in mice, and in transformation of its canal in phylogeny. The cochlear innervation in Dryolestes is the precursory condition in the curve-to-coil transformation of the cochlea in mammalian phylogeny.
This provides the timing of the evolution, and where along the phylogeny the morphogenetic genes were co-opted into patterning the cochlear innervation, and the full coiling of the cochlea in modern therians. link
Click to enlarge
Abstract: The coiled cochlea is a key evolutionary innovation of modern therian mammals. We report that the Late Jurassic mammal Dryolestes, a relative to modern therians, has derived bony characteristics of therian-like innervation, but its uncoiled cochlear canal is less derived than the coiled cochlea of modern therians. This suggests a therian-like innervation evolved before the fully coiled cochlea in phylogeny.
The embryogenesis of the cochlear nerve and ganglion in the inner ear of mice is now known to be patterned by neurogenic genes, which we hypothesize to have influenced the formation of the auditory nerve and its ganglion in Jurassic therian evolution, as shown by their osteological correlates in Dryolestes, and by the similar base-to-apex progression in morphogenesis of the ganglion in mice, and in transformation of its canal in phylogeny. The cochlear innervation in Dryolestes is the precursory condition in the curve-to-coil transformation of the cochlea in mammalian phylogeny.
This provides the timing of the evolution, and where along the phylogeny the morphogenetic genes were co-opted into patterning the cochlear innervation, and the full coiling of the cochlea in modern therians. link
Sunday, July 25, 2010
Southern Alberta Dinosaur Project 2010 Photos #2
On yet another rainy day we drove to Eastend, SK, to check out the T. rex Discovery Centre.
Touring the T. rex Centre. That's CMNH Kirtlandia, Geoff Goodman, above.
Eastend also has a small cultural museum downtown with a nice Triceratops skull and Torosaurus frill, as well as other displays, such as the above.
Nic C. collects part of a tyrannosaurid skull.
Finishing up field jackets in camp. Magdeline, U of Calgary Phrynosoma researcher, looks on from above.
CWRU Work Study student, Matt Clemens, is unsure of the wisdom of defying the storm gods today.
The students tour Dinosaur Provincial Park. At the Centrosaurus BB, top row: Geoff, Kentaro, Eric the CO; Bottom row: Matt, Evan, David Lloyd (RTMP Tech), Danielle D. (Carleton U.).
Chris Magarity, U of T grad student and summer RTMP tech, works on his thesis at the museum in the off hours. Chris and his wonderful wife, Kelly, spent much of their days off helping us out in the field.
Born This Day: Rosalind Franklin
Rosalind Franklin (July 25, 1920 - Apr. 16, 1958) was an English scientist who contributed to the discovery of the molecular structure of deoxyribonucleic acid (DNA), a constituent of chromosomes that serves to encode genetic information.
Beginning in 1951, she made careful X-ray diffraction photographs of DNA, leading her to suspect the helical form of the molecule, at least under the conditions she had used.
Beginning in 1951, she made careful X-ray diffraction photographs of DNA, leading her to suspect the helical form of the molecule, at least under the conditions she had used.
Thursday, July 22, 2010
Born This Day: Gregor Mendel
From Today In Science History:
Mendel (July 22, 1822 – Jan. 6, 1884) was an Austrian pioneer in the study of heredity. He spent his adult life with the Augustinian monastery in Brunn, where as a geneticist,
botanist and plant experimenter, he was the first to lay the mathematical foundation of the science of genetics, in what came to be called Mendelism.
Over the period 1856-63, Mendel grew and analyzed over 28,000 pea plants. He carefully studied for each their plant height, pod shape, pod color, flower position, seed color, seed shape and flower color. He made two very important generalizations from his pea experiments, known today as the Laws of Heredity. Mendel coined the present day terms in genetics: recessiveness and dominance.
Mendel (July 22, 1822 – Jan. 6, 1884) was an Austrian pioneer in the study of heredity. He spent his adult life with the Augustinian monastery in Brunn, where as a geneticist,
botanist and plant experimenter, he was the first to lay the mathematical foundation of the science of genetics, in what came to be called Mendelism.
Over the period 1856-63, Mendel grew and analyzed over 28,000 pea plants. He carefully studied for each their plant height, pod shape, pod color, flower position, seed color, seed shape and flower color. He made two very important generalizations from his pea experiments, known today as the Laws of Heredity. Mendel coined the present day terms in genetics: recessiveness and dominance.
Friday, July 02, 2010
Southern Alberta Dinosaur Project 2010 Photos
I'm back in the field with David Evans from the ROM, hence the lack of posts for the past few weeks. Here are few recent photos:
Reopening a theropod quarry
Collecting a hadrosaur femur from the Milk River Ridge
Students mapping in the ceratopsid bone bed.
Nic Campione hard at work.
Prepping on a rainy day.
Reopening a theropod quarry
Collecting a hadrosaur femur from the Milk River Ridge
Students mapping in the ceratopsid bone bed.
Nic Campione hard at work.
Prepping on a rainy day.
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