Monday, July 13, 2009

Hominin Evolution

Middle and later Pleistocene hominins in Africa and Southwest Asia in PNAS.
Approximately 700,000 years ago, Homo erectus in Africa was giving way to populations with larger brains accompanied by structural adjustments to the vault, cranial base, and face. Such early Middle Pleistocene hominins were not anatomically modern. Their skulls display strong supraorbital tori above projecting faces, flattened frontals, and less parietal expansion than is the case for Homo sapiens. Postcranial remains seem also to have archaic features. Subsequently, some groups evolved advanced skeletal morphology, and by ca. 200,000 years ago, individuals more similar to recent humans are present in the African record. These fossils are associated with Middle Stone Age lithic assemblages and, in some cases, Acheulean tools. Crania from Herto in Ethiopia carry defleshing cutmarks and superficial scoring that may be indicative of mortuary practices. Despite these signs of behavioral innovation, neither the Herto hominins, nor others from Late Pleistocene sites such as Klasies River in southern Africa and Skhūl/Qafzeh in Israel, can be matched in living populations. Skulls are quite robust, and it is only after ≈35,000 years ago that people with more gracile, fully modern morphology make their appearance. Not surprisingly, many questions concerning this evolutionary history have been raised. Attention has centered on systematics of the mid-Pleistocene hominins, their paleobiology, and the timing of dispersals that spread H. sapiens out of Africa and across the Old World. In this report, I discuss structural changes characterizing the skulls from different time periods, possible regional differences in morphology, and the bearing of this evidence on recognizing distinct species.

An ancient human skull (pictured above) was found in Israel at Skhūl cave!?

Genetic Analysis of Copernicus?

It's impressive that they can now do so much with remains that are over 400 years old. Genetic identification of putative remains of the famous astronomer Nicolaus Copernicus at PNAS.
We report the results of mitochondrial and nuclear DNA analyses of skeletal remains exhumed in 2005 at Frombork Cathedral in Poland, that are thought to be those of Nicolaus Copernicus (1473–1543). The analyzed bone remains were found close to the altar Nicolaus Copernicus was responsible for during his tenure as priest. The mitochondrial DNA (mtDNA) profiles from 3 upper molars and the femurs were identical, suggesting that the remains originate from the same individual. Identical mtDNA profiles were also determined in 2 hairs discovered in a calendar now exhibited at Museum Gustavianum in Uppsala, Sweden. This calendar was the property of Nicolaus Copernicus for much of his life. These findings, together with anthropological data, support the identification of the human remains found in Frombork Cathedral as those of Nicolaus Copernicus. Up-to-now the particular mtDNA haplotype has been observed only 3 times in Germany and once in Denmark. Moreover, Y-chromosomal and autosomal short tandem repeat markers were analyzed in one of the tooth samples, that was much better preserved than other parts of the skeleton. Molecular sex determination revealed that the skeleton is from a male individual, and this result is consistent with morphological investigations. The minimal Y-chromosomal haplotype determined in the putative remains of Nicolaus Copernicus has been observed previously in many countries, including Austria, Germany, Poland, and the Czech Republic. Finally, an analysis of the SNP located in the HERC2 gene revealed the C/C genotype that is predominant in blue-eyed humans, suggesting that Copernicus may have had a light iris color.

See this blog post for more information about the HERC2 gene HERC2 & blue eye color & Danes

B Factories

Future prospects of B physics
In recent years, the CKM picture of flavor and CP violation has been confirmed, mainly due to B decay data. Yet, it is likely that there are small corrections to this picture. We expect to find new physics not much above the weak scale. This new physics could modify flavor changing processes compared to their SM expectations. Much larger B decay data sets, which are expected from LHCb and super-B-factories, will be used to search for these deviations with much improved sensitivity. The combination of low and high energy data will be particularly useful to probe the structure of new physics.

LHCb detector

Hierarchy problems

In particle physics, the Hierarchy problem is the question why the weak force is 10^32 times stronger than gravity. The Cosmological constant problem is that most quantum field theories predict a huge cosmological constant from the energy of the quantum vacuum . The value is off by 120 orders of magnitude, which is said to be the worst prediction in theorectical physics! In the preprint The Concept of a Cosmographical Vacuum we have:
The argument for a novel concept with a not unique, ``Cosmographical Vacuum'' state which generates fermion and weak boson masses is outlined in a brief and concise way.

The following preprint discusses the particle physics hierarchy problem and the problem of the very small but nonzero neutrino masses using the (speculative) possibility of extra dimensions:
Signatures of Singlet Neutrinos in Large Extra Dimensions at the LHC
It is a challenge to explain why neutrinos are so light compared to other leptons. Small neutrino masses can be explained if right-handed fermions propagate in large extra dimensions. Fermions propagating in the bulk would have implications on Higgs boson decays. If the Higgs boson is discovered at the Large Hadron Collider (LHC), a detailed analysis may reveal the presence of large extra dimensions. This paper reviews the status of large extra-dimensional models in the context of the current limits on Higgs boson masses and the fundamental Planck scale in extra dimensions.

Solar Circulation Paradox

Secrets of Magnetohydrodynamic Hell: The Solar Circulation Paradox and the Geodynamo
Differential rotation is widely supposed to be essential for the dynamo effects that sustain solar and planetary magnetic fields, but dynamo effects tend to oppose the flows that drive them, and it is uncertain what drives differential rotation. The relative sign of the differential rotation and meridional circulation is not consistent with simple convection modified by Coriolis forces. We investigate dynamo mechanisms consistent with the observed solar circulation, and discuss how reactive JxB forces would affect such flows. We formulate scaling rules that relate the magnetic field strength to mean rotation and convective heat transport.

On Time Reversal Mirrors

Narcissus by Caravaggio
A friend of mine complained that her boyfriend accused her of never passing a mirror without checking herself out, and that she spent half her life looking at her face in the mirror. Well if that were true and my friend had herself a Time Reversal Mirror, she would never get older! Sorry, that application is not actually discussed in this preprint, despite the promising title: On time reversal mirrors.
Time reversal (TR) is the process of recording the signal, time-reversing and re-propagating the signal. When the signal is from a localized source the time reversed field is expected to focus on the source. Time reversal of acoustic waves has led to applications in ultrasound and underwater acoustics including brain therapy, lithotripsy, nondestructive testing and telecommunications [17]. An even greater potential holds for the time reversal of electro-magnetic waves which is closely related to optical phase conjugation [28].

While it isn't quite the fountain of youth for the narcissists among us, there are exciting applications.

Dorian Gray used a different technology to remain youthful.

The Space Station

Space Station Is Near Completion, Maybe the End Plan to 'De-Orbit' in 2016 Is Criticized - article in the Washington Post. After $100 billion dollars the space station should be completed next year. Then we're going to burn it up over the ocean in 2016. Nice. Essentially no science has ever been done on the space station, though there's supposed to be an experiment brought up on the last shuttle flight in 2010. After that the space station can only be reached by the Russian Soyuz. What a waste. Someone in the article suggested that instead of destroying it we should give it to China!
Photo NASA