Tuesday, April 27, 2010

STALAGMITE REVEALS CARBON FOOTPRINT OF EARLY NATIVE AMERICANS

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A new study led by Ohio University scientists suggests that early Native Americans left a bigger carbon footprint than previously thought, providing more evidence that humans impacted global climate long before the modern industrial era.

Chemical analysis of a stalagmite found in the mountainous Buckeye Creek basin of West Virginia suggests that native people contributed a significant level of greenhouse gases to the atmosphere through land use practices. The early Native Americans burned trees to actively manage the forests to yield the nuts and fruit that were a large part of their diets.

“They had achieved a pretty sophisticated level of living that I don’t think people have fully appreciated,” said Gregory Springer, an associate professor of geological sciences at Ohio University and lead author of the study, which was published a recent issue of the journal The Holocene. “They were very advanced, and they knew how to get the most out of the forests and landscapes they lived in. This was all across North America, not just a few locations.”

Initially, Springer and research collaborators from University of Texas at Arlington and University of Minnesota were studying historic drought cycles in North America using carbon isotopes in stalagmites. To their surprise, the carbon record contained evidence of a major change in the local ecosystem beginning at 100 B.C. This intrigued the team because an archeological excavation in a nearby cave had yielded evidence of a Native American community there 2,000 years ago.

Springer recruited two Ohio University graduate students to examine stream sediments, and with the help of Harold Rowe of University of Texas at Arlington, the team found very high levels of charcoal beginning 2,000 years ago, as well as a carbon isotope history similar to the stalagmite.

This evidence suggests that Native Americans significantly altered the local ecosystem by clearing and burning forests, probably to make fields and enhance the growth of nut trees, Springer said.

This picture conflicts with the popular notion that early Native Americans had little impact on North American landscapes. They were better land stewards than the European colonialists who followed, he said, but they apparently cleared more land and burned more forest than previously thought.

“Long before we were burning fossil fuels, we were already pumping greenhouse gasses into the atmosphere. It wasn’t at the same level as today, but it sets the stage,” Springer said.

This long-ago land clearing would have impacted global climate, Springer added. Ongoing clearing and burning of the Amazon rainforest, for example, is one of the world’s largest sources of greenhouse gas emissions. Prehistoric burning by Native Americans was less intense, but a non-trivial source of greenhouse gases to the atmosphere, he said.

(Photo: Springer, Ohio University)

Ohio University

NEURONS GROWING IN LINE

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In order to be able to understand complex organs such as the brain or the nervous system, simplified model systems are required. A group of scientists led by the Frankfurt brain researcher Erin Schuman has successfully developed a novel method to grow cultured neurons in order to investigate basic mechanisms of memory.

The researchers grew two separate populations of neurons in microfluidic platforms. These neurons extended their processes through tiny grooves, to meet each other and form synaptic connections. Perpendicular to the grooves, a perfusion channel was constructed that allows the researchers to manipulate very small populations of synapses with drugs or neurotransmitters. The chambers are amenable to imaging, allowing researchers to visualize the dynamics of synapses, the movement of molecules within the neurons.

Studying cultured neurons makes it possible to reduce the complex three-dimensional network in living organisms to two dimensions. However, even in the laboratory, cell growth is totally disorganized, which makes a systematic study difficult. Neurons consist of a nucleus whose signals are transmitted to adjacent cells through a long extension (axon). Shorter extensions (dendrites) absorb the incoming signals. While the stimulus transfer along the axon and dendrites occurs electrically, the contact points between two neurons, the synapses, are bridged by biochemical signals. To understand how synapses are formed and which neurotransmitters play a part in their formation is not only an interesting topic for brain research, but may also aid the development of new pharmaceutical agents.

After demonstrating that functional synapses were formed in the approximately 150 microgrooves of the chamber, the brain researchers developed the device further in order to be able to stimulate the synapses directly. Here, they made use of the fact that cultured dendrites have a characteristic length so that the contact points with the axons of the neighboring cell populations could develop in about the same compartment of the microgrooves. There, the group implemented another small perfusion channel pervading the relevant area perpendicular to the "neuronal channels". This supply channel enables a direct manipulation of the synapses via solute substances.

A further refinement of the test arrangement was reached by restricting the biochemically effective fluid in the supply channel from infiltrating the channels containing the nerve fibers. Schuman and her collaborators managed to do so by letting in a solution on both sides of the main stream shielding the main stream. The three parallel fluid streams have the additional advantage that the perfusate may be exactly dosed by varying the width of the middle stream.

Besides, the amount of the perfusate is also subject to increased temporal control: The supply can be turned on and off within one minute. It is thus possible to imitate the short duration signals that are the language of the nervous system.

Erin Schuman who relocated several months ago from the renowned California Institute of Technology (Caltech) to the Max Planck Institute for Brain Research in Frankfurt is interested in the function of synapses in the context of memory. How do synapses change during the storage of memory? And what happens during these processes at the molecular and cellular level? Years ago, her group discovered that dendrites can make the proteins required to change the functional capacity of synapses. The nucleus transcribes the required information as messenger RNA (mRNA), which is then sent out to the dendrites. When certain signals arrive, the dendrites translate the mRNA into protein using ribosomes present in the dendrite.

Frankfurt is not only appealing to the native-born Californian because of the possibility to run the Max Planck Institute for Brain Research together with her husband, brain researcher Gilles Laurent (the other director is Wolf Singer). The cooperation with scientists of the excellence cluster "Macromolecular Complexes" at Goethe University with which Schuman is associated as "Principle Investigator" also promises many interesting collaborations, for example with the Paul-Ehrlich-Young Academics awardee Amparo Acker-Palmer or with the Heisenberg-Professor Alexander Gottschalk. With respect to the new building of the MPI for Brain Research, the mother of two daughters at the age of ten and seven already has a plan: "Many employees of the institute have children who come into contact with science already at an early age through their parents. We also want to make the new institute family-friendly. We hope to organize Science Saturdays for our kids to see how exciting it is to explore something on their own."

Goethe University

LINK BETWEEN SOLAR ACTIVITY AND THE UK'S COLD WINTERS

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A new report published Thursday 15 April, in IOP Publishing's Environmental Research Letters describes how we are moving into an era of lower solar activity which is likely to result in UK winter temperatures more like those seen at the end of the seventeenth century.

Lead author Mike Lockwood of the University of Reading said: "This year's winter in the UK has been the 14th coldest in the last 160 years and yet the global average temperature for the same period has been the 5th highest. We have discovered that this kind of anomaly is significantly more common when solar activity is low."

The new paper, 'Are cold winters in Europe associated with low solar activity?', differs from previous efforts to explain the UK's recent cold winters by comparing the most comprehensive, but regionally specific, temperature dataset available (the Central England Temperature dataset) to the long-term behaviour of the Sun's magnetic field, and to trends across the entire Northern Hemisphere.

The paper is being published now as the researchers have just had the opportunity to put this year's data to the test and found that this year's results fit well with the trends they have discovered.

The researchers suggest that the anomaly in Northern Europe's winter temperatures could be to do with a phenomenon called 'blocking'.

'Blocking' is related to the jet stream which brings winds from the west, over the Atlantic, and into Northern Europe but, over the past couple of winters, could have lost its way, for weeks at a time, in an 'anticyclone' before it reaches Europe.

The researchers have found strong correlations between weak solar activity and the occurrences of 'blocking'. As the temperature is affected by a weak Sun so the wind's patterns also change and, as the warmer westerly winds fail to arrive, the UK is hit by north-easterlies from the Arctic.

The researchers, from the Department of Meteorology at the University of Reading, the Science and Technology Facilities Council Space Science and Technology Department, and the Max-Planck Institute for Solar System Research in Katlenburg-Lindau, Germany, are keen to stress the regional and seasonal (European and winter) nature of their research.

Professor Mike Lockwood has explained that the trends do not guarantee colder winters but they do suggest that colder winters will become more frequent. He said: "If we look at the last period of very low solar activity at the end of the seventeenth century, we find the coldest winter on record in 1684 but, for example, the very next year, when solar activity was still low, saw the third warmest winter in the entire 350-year record.

"The results do show however that there are a greater number of cold UK winters when solar activity is low."

(Photo: IoP)

IoP

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