Thursday, 5 October 2017

A lighter side to Carbon!

Illuminating the composition of carbon-based ancient materials

Carbon can take various forms depending on the function of the molecule in which it is placed, each with its own distinct ‘species’. The ‘speciation’ of carbonaceous materials is generally obtained by methods requiring destructive sampling or through surface analysis methods such as optical Raman spectrometry, infrared microscopy or X-ray absorption spectroscopy (XAS). The last technique is routinely available at synchrotron facilities, however a limitation remains in the use of the XAS method for many carbonaceous compounds: the strong interaction of these soft X-rays at the carbon absorption edge imposes severe limitations on the sample and its environment. In particular, its application is limited for complex, heterogeneous, fragile and/or rare samples, such as heritage objects or paleontological specimens, as these systems might have contaminated surfaces and cannot be put in a vacuum environment.

An unexpected application of X-ray Raman scattering
An international team of researchers from France (Paris–Saclay, Sorbonne Universités, and Grenoble), Manchester in the United Kingdom and the United States (Stanford, Columbia, and Charleston) have adapted X-ray Raman scattering (XRS) to these systems. This method, which has been previously applied to study the structure of carbon speciation related to fossil fuels, utilizes more penetrating harder (higher energy) X-rays. In XRS, a small fraction of the X-ray energy is transferred to the electrons by inelastic scattering, yielding a detectable signal to diagnose compositional chemistry of a sample. Therefore, it is possible to carry out measurements similar to that achievable with XAS but at an energy more than 20 times higher. This makes it possible to work at ambient conditions and with bulk probe depth avoiding many of the limitations of the conventional soft X-ray methods like XAS.

X-ray Raman spectroscopy was used to study a fragment of skin of a woolly mammoth from the Lyakhov Islands. The specimen (MNHN.F.MAQ 287), is held at the Paris National Museum of Natural History and reveals exceptional preservation at the chemical level.

Characterizing historical and ancient materials
The results are published in the journal Analytical Chemistry and involve three international synchrotron facilities: SOLEIL, where experiments were carried out on the GALAXIES beamline, as well as the ESRF in France and the Stanford Synchrotron Radiation Lightsource in the US, where preliminary studies were performed. The scientists conducted the work during the invited visit of one of the team members, Uwe Bergmann, to IPANEMA (Paris-Saclay), funded by Fondation des Sciences du Patrimoine and SLAC National Accelerator Laboratory. The team demonstrated the use of XRS for the study of artistic samples (carbon-based pigments), archaeological, and paleontological samples (fossils). This research shows how XRS successfully provides a new way to image ancient worlds. The pivotal role that carbon plays in life can now be further scrutinized using the extreme bright X-rays from modern synchrotron light sources.  

Publication reference:
Pierre Gueriau, Jean-Pascal Rueff, Sylvain Bernard, Josiane A. Kaddissy, Sarah Goler, Christoph J. Sahle, Dimosthenis Sokaras, Roy A. Wogelius, Phillip L. Manning, Uwe Bergmann & Loïc Bertrand, Noninvasive synchrotron-based X-Ray Raman scattering discriminates carbonaceous compounds in ancient and historical materials, Analytical Chemistry, 2017. doi : 10.1021/acs.analchem.7b02202

Saturday, 29 July 2017

Tyrannosaurus rex couldn’t run says new research

·       T. rex could not run due to its size and weight
·       T. rex was unable to pursue prey at high speeds
·       Even walking speed was limited due its impact on the skeleton
·       This changes the way we have to think about the way T. rex behaved
It is a classic chase scene in modern cinematic history. The image of a rampant Tyrannosaurus rex (T. rex) chasing Jeff Goldblum as he sits injured in the back of a 4x4 vehicle in Stephen Spielberg’s original Jurassic Park.
But could a T. rex actually move that fast, or even run at all?
New research from the University of Manchester says the sheer size and weight of T. rex means it couldn’t move at high speed, as its leg-bones would have buckled under its own weight load.
The research, in collaboration with the N8 High Performance Computer (NPC) research partnership, looks extensively into the gait and biomechanics of the world’s most famous Dinosaur and, using the latest in high performance computing technology, has created a new simulation model to test its findings.
Led by Prof William Sellers from the School of Earth and Environmental Sciences, the researchers have combined two separate biomechanical techniques, known as multibody dynamic analysis (MBDA) and skeletal stress analysis (SSA), into one simulation model, creating a new more accurate one.
Prof Sellers says the results demonstrate any running gaits for T. rex would probably lead to ‘unacceptably high skeletal loads’. Meaning, in layman’s terms, any running would simply break the dinosaur’s legs. This contradicts the running speeds predicted by previous biomechanical models which can suggest anything up to 45mph.
He explains: ‘the running ability of T. rex and other similarly giant dinosaurs has been intensely debated amongst palaeontologist for decades. However, different studies using differing methodologies have produced a very wide range of top speed estimates and we say there is a need to develop techniques that can improve these predictions.
‘Here we present a new approach that combines two separate biomechanical techniques to demonstrate that true running gaits would probably lead to unacceptably high skeletal loads in T. rex.’

The results also mean that the T. rex couldn’t pursue its prey in a high-speed chase as previously thought. He added: ‘Being limited to walking speeds contradicts arguments of high-speed pursuit predation for the largest bipedal dinosaurs like T. rex and demonstrates the power of Multiphysics approaches for locomotor reconstructions of extinct animals.’
Although the research focuses on the T. rex, the findings also means running at high speeds were probably highly unlikely for other large two-legged dinosaurs such as, Giganotosaurus, Mapusaurus, and Acrocanthosaurus.  
Dr Sellers adds: ‘Tyrannosaurus rex is one of the largest bipedal animals to have ever evolved and walked the earth. So it represents a useful model for understanding the biomechanics of other similar animals. Therefore, these finding may well translate to other long-limbed giants so but this idea should be tested alongside experimental validation work on other bipedal species.’
This isn’t the first time MBDA and SSA have been used to measure the walking and running ability of dinosaurs. However, it is the first time they have been used together to literally create a more accurate picture.

Dr Sellers explains: ‘Our previous simulations of theropod bipedal running did not directly consider the skeletal loading but these new simulations do calculate all the forces in the limb bones and these can be used directly to estimate the bone loading on impact.’
The fact that T. rex was restricted to walking also supports arguments of a less athletic lifestyle. This means the results could change the way we view the effects of how the size and shape of T. rex and other large bipedal dinosaurs alters as they grow.  Previous studies have suggested the torso became longer and heavier whereas the limbs became proportionately shorter and lighter as T. rex grew. These changes would mean that the running abilities of T. rex would also change as the animal grew with adults likely to be less agile than younger individuals.

But Dr Sellers says these new findings show this probably wasn’t the case and we should apply this new model even wider: ‘It would be very valuable not only to investigate the gait of other species, but also apply our multiphysics approach to different growth stages within that species.’
You can download this paper for FREE from PeerJ, click this LINK