Ancient storms

A Chinese library is an unlikely place to go looking for catastrophic hurricanes, but a US geography professor reckons that he can unearth ancient storms by trawling the archives of China dating back to the time of the Song Dynasty.

Kam-biu Liu of Louisiana State University in Baton Rouge made the news two years ago when his work on core samples from coastal lakes and shorelines revealed that catastrophic hurricanes hit the US Gulf Coast every three centuries or so. Now, he is getting to the core of archaic weather via a different route.

Kam-biu Liu

Kam-biu Liu

Liu’s previous work involved carbon-dating coastal core samples to find out when prehistoric storm surges washed sand into the lakes. His detailed studies of cores dating back five millennia have given birth to a new field of science – paleotempestology – the study of past tropical cyclone activities using geological methods.

But, historical records from Guangdong Province on the southeastern coast of China, have now revealed details of some 1,133 typhoons that led to serious loss of life and property in this area. Liu has spotted clusters of very powerful storms happening in a fifty-year cycle in this region. The period studied spans 1,025 years beginning in 975 AD, and, according to Liu is the longest documentary record of tropical cyclone activity ever compiled.

First Song Emperor Taizu

First Song Emperor Taizu

The significance of the discovery that major tropical cyclone activity occurs every fifty years has not been lost on the Chinese government. Guangdong Province is now one of the most rapidly expanding economic regions in China and its long and exposed coastline makes it highly vulnerable to catastrophic storm surges and coastal flooding. Some 158 cyclones blasted Guangdong between 1949 and 1988, with thirty-three of those gusting at wind speeds above 73 mph making them typhoons. If a typhoon the strength of Hurricane Camille were to hit Guangdong Province today, the destruction and possible loss of life would be immense, Liu suggests, The logical question to ask is, what is causing these cycles?

Super Typhoon Winnie (1997) approaching China

Super Typhoon Winnie (1997) approaching China

The answer could lie in Chinese dynastic histories. In North America the record is very short, Liu explains, Even after Columbus it’s very sketchy for the first hundred years. And the Gulf Coast has virtually nothing before the 17th century. Contrast the American records with the meticulous historical records kept as an official history by each dynasty over the last three millennia. These dynastic histories carry with them details of natural disasters, including typhoons.

1997’s Typhoon Chebi

1997’s Typhoon Chebi

Studying in Hong Kong and Beijing libraries Liu and his team have worked their way through hundreds of records highlighting entries such as the following from the Zhenhai County Gazette: In the sixth lunar month of the sixth year of the Emperor Chongzhen (1633 AD), a typhoon struck. Torrential rain fell for ten days. Houses collapsed. Naval battleships were drifting in the sea; eight or nine out of ten were destroyed, drowning numerous soldiers. Since the first year of Chongzhen there was no year without typhoon strikes. The damage was especially serious this year. It was widely believed the culprit was a mischievous dragon.

Liu and his team checked the reliability of the historical record by comparing it with a 26-year period, from 1884 to 1909, when the historical record overlapped with instrumental observations. The historical record, it seems, under-reported the number of tropical cyclones. But, the under-reporting is much smaller if only typhoons are counted. Liu points out that the year-by-year accounts in these Chinese records are far more accurate than any sedimentary core research. The sedimentary records are accurate only to between 100 and 200 years. They can reveal the major storm cycles, but the historical record is essentially at a much higher resolution and shows annual activity within these major cycles.

Researchers believe that a colder climate and a lower sea surface temperature are at the root of reduced hurricane activity and intensity. However, a peak in landfall activity occurred between 1660 and 1680, which was the coldest and driest period the Northern Hemisphere had experienced over the last 500 years. Liu conjectures that climatic changes merely shift the path of tropical cyclones further south so that they cause more landfalls in Guangdong Province. But, in order to find out what causes storms to follow their cycles, Liu and his colleagues are working their way through library records along the coast of China, and plan to branch out into the historical records of Japan and the Philippines. Integrating the historical data will help us understand the climatological mechanisms that control these activities, Liu explains. Once we understand those, it will help us predict these storms.

One clue to the storm cycles that can be revealed by a modern scientific approach is that the periods of greatest storm activity and typhoon landfalls occur when there is very little sunspot activity. Indeed, such a period occurred between 1660 and 1680, which was marked by very low sunspot activity. The relationship between sunspot activity and earth’s climate is still very unclear, but revelations in Chinese dynastic history could play a role in finding new answers to the ancient problem of predicting seriously stormy weather.

Further reading

Kam-biu Liu
http://www.ga.lsu.edu/liu.htm

Suggested searches

Paleotempestology
Hurricanes
Climatology

Sparks fly no more

One of the world’s biggest van de Graaff electrostatic accelerators is to be shut down amidst protests from European nuclear physicists. The two-million-volt Vivitron facility in Strasbourg, France, is set to close even though researchers point out that the successor to this technology is yet to be built.

France’s National Institute of Nuclear and Particle Physics made the decision to close the Vivitron purely for financial reasons. According to a report in the journal Nature, the move to close the facility will drive some exotic nuclear researchers out of the field for good.

The Vivitron facility

The Vivitron facility

The fundamental physics of exotic nuclei, those atomic nuclei whose proton and neutron counts are wildly different from the more common stable nuclei, is a highly energetic research field worldwide. There are, however, many unanswered questions in the field about how protons and neutrons interact that continue to challenge nuclear physicists. Research at the Vivitron facility into exotic nuclei has been at the heart of understanding everything from the stellar synthesis of the chemical elements to our fundamental models of the universe and the forces that hold it together.

Two technical hiccups in the 1990s saw the facility shut down temporarily in 1991 and 1995. The first incident followed pollution with hydrofluoric acid accidentally produced in the sulphur hexafluoride gas drying towers, which led to a 12 month closure. The second involved problems with the suppliers of a new rubber-coated fabric belt which closed the facility for eight months. Despite these setbacks, the Vivitron continued to spark scientific interest.

However, there has been a move away from accelerators of this kind in recent years to carrying out exotic nuclear research with radioactive ions. Marielle Chartier, on leave from the University of Bordeaux, is a lecturer at the University of Liverpool, began an EPSRC Advanced Fellowship in October 2001, and is at the forefront of radioactive beam research.

The predictive power of nuclear models developed for stable nuclei will be greatly improved by extending mass measurements to the most exotic nuclei, explains Chartier. It is radioactive ion beams that are thought to be the best bet for generating the essential data for understanding nuclear physics but facilities based on this concept are still in their infancy or, more to the point, yet to be built.

There are hundreds of Vivitron users outside France who, according to Nature, are planning to challenge the closure. One point of contention is that there are many PhD students working on projects that rely on data from the facility.

Further reading

Suggested searches

Exotic nuclei
Radioactive ion beams
Particle accelerators
van de Graaff electrostatic accelerators

Down the tubes

There seems to be no technology that nanotubes cannot slip into. Researchers are developing them as insulating sheaths to wrap around molecular wires for a future generation of nano-electronics. They already find themselves at the tip of high resolution scanning probe microscopes for taking a close look at tiny structures. And, in the more mundane-seeming world of lubrication, they are turning out to be rather slippery customers. Chemists too are hoping to use nanotubes as reaction vessels inside which novel chemistry could be forced to take place away from the bulky milieu of the standard solution in a glass reaction flask.

Until recently, nanotubes – hollow tubes of carbon that look like a microscopic roll of chicken wire – have tended to be rather strait-laced. The have been described as something half-way between a carbon fibre and the soccerball-shaped all-carbon C60, fullerene molecule.

Nanotube

Nanotube

Now, a team at Rensselaer Polytechnic Institute in Troy, New York State, have created the next generation of carbon-based nanotubes that can be grown up, down, sideways, and in all three dimensions. This new world of nanoscale architecture could open up the possibility of 3D computer chips, integrated circuits, and the tiniest of chemical plants in the form of microelectromechanical (MEMS) devices.

Materials scientists Pulickel Ajayan, Ganapathiraman Ramanath and colleagues at Rensselaer point out that to be useful in devices nanoscale structures must be have well-defined architectures rather than being randomly positioned and pointing in all directions or only one direction. To build integrated systems of the kind needed for MEMS and electronics, there has to be control in the production of nanotubes.

Pulickel Ajayan

Pulickel Ajayan

Ajayan and Ramanath have now brought together two different approaches to help them bring new control to the assembly of nanotubes. They have used a chemical-vapour deposition (CVD) method, in which vapourised carbon from an organic molecule, such as xylene, at 800 Celsius are allowed to condense on a silica surface to form the nanotubes.

Ganapathiraman Ramanath

Ganapathiraman Ramanath

They also use a gas-phase catalyst – a pentamethylferrocene – that can help direct the assembly of the carbon nanotubes. But, instead of allowing the catalysed CVD process to take its own course and result in vertically oriented tubes, they have coupled it with technology that allows them to etch the silica, using standard printing, microlithographic wet/dry techniques from the electronics industry.

More nanotubes

More nanotubes

With this templated surface in place, the growing multiwalled nanotubes have no option but to adopt predetermined orientations on the surface. This has allowed the team to build one-, two- and three-dimensional arrangements of nanotubes. It’s a simple and elegant process that provides unprecedented control over nanotube growth, said Ajayan.

Nanotube process

Nanotube process

The team reckon that what they describe as essentially a simple process for controlled nanotube growth will be brought to market in the next few months for further development by the MEMS and electronics industries hoping to develop lab-on-a-chip devices and other such microscale machines. Our fabrication method can be scaled up to large areas and is compatible with standard silicon microfabrication technology, adds Ajayan.

Ramanath is enthusiastic that the process will be taken far beyond nanotubes. This is the first step toward controllably making complex networks comprised of wire-shaped molecular units, he explains, By manipulating the topography of the silica blocks, and utilizing the selective and directional growth process, we have been able to force nanotubes to grow in predetermined, multiple directions, with a very fine degree of control. No one else has done this.

Further reading

Nature, 416, 495-496 (2002)

DOI: 10.1038/416495a

Suggested searches

Microelectromechanical systems
Nanotubes