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About Synthetic Biology

Synthetic biology is the use of advanced science and engineering to make or re-design living organisms, such as bacteria, so that they can carry out specific functions. Synthetic biology involves making new genetic code, also known as DNA, that does not already exist in nature.

The Project on Emerging Nanotechnologies is an initiative launched by the Woodrow Wilson International Center for Scholars and The Pew Charitable Trusts in 2005. It is dedicated to helping business, government and the public anticipate and manage possible health and environmental implications of nanotechnology. For more information about the project, log on to

Marine 'dead zones' leave crabs gasping

* 22:00 29 September 2008

* news service

* Catherine Brahic

It's not easy being a fish these days, but it could be even harder being a crab. Research into marine "dead zones" around the world suggests that crustaceans are the first to gasp for air when oxygen levels get low.

The findings, based on a review of 872 published studies of 206 ocean-floor dwelling species, also suggest that a much greater area than we thought is dangerously low on oxygen.

In marine dead zones – also known as hypoxic zones – the amount of dissolved oxygen in the water becomes too low for organisms to survive.

They are usually caused by synthetic fertilisers, which are carried from fields, down rivers, and out to sea, where algal blooms gorge on the extra nutrients. When these phytoplankton die, they fall to the bottom where they are eaten by bacteria that consume all the local oxygen in the process.

Marine biologists generally hold that any area that has less than 2 milligrams of dissolved oxygen per litre of seawater is hypoxic – "dead". The threshold was set by a study in 1983 in the Gulf of Mexico, when marine biologists found that fish and shrimp had deserted bottom waters that had 2 mg/l of oxygen or less.

Now Raquel Vaquer-Sunyer and Carlos Duarte of the Mediterranean Institute for Advanced Studies, Spain, have examined the validity of this threshold.

Local variation

The pair reviewed previously published laboratory experiments where bottom-dwelling animals including fish, crustaceans, molluscs and worms were placed in water containing different levels of oxygen to determine the critical levels.

They found that the minimum oxygen level varies widely between species. Studies suggest the American oyster (Crassostrea virginica) is able to survive for some time in waters that are entirely devoid of oxygen. But the larvae of the rock crab (Cancer irroratus) die if there is any less than 8.6 mg/l.

Overall, says Vaquer-Sunyer, if the aim is to preserve 90% of the bottom-dwelling biodiversity oxygen levels need to be 4.6 mg/l or higher. This is considerably more than the commonly adopted 2 mg/l threshold.

"I can't disagree with the conclusion that 2 mg/l is too low to protect all species. By the time you get to 2 mg/l, you start to see really serious effects," says Robert Diaz of the Virginia Institute of Marine Science.

"At 2.8 mg/l behavioural mechanisms start to kick in," he says. Animals that can flee, such as fast-swimming fish, do; sea urchins stand up as high as possible on their spines to reach a little higher above the sea floor.

Warming threat

Diaz says water-quality thresholds need to be set regionally. In Chesapeake Bay, Virginia – where levels of pollutants such as fertilisers and sewage are also monitored – he advised on a set of standards that vary according to depth and range between 1 mg/l and over 2 mg/l.

"What you want are criteria that are protective of the species in the area," he says.

The Gulf of Mexico, which has one of the world's largest seasonal dead zones, has no such standards.

In a review published in August, Diaz found that more than 245,000 square kilometres of ocean bed world wide have 2.8 mg/l of oxygen per litre of water or less (Science, DOI: 10.1126/science.1156401), making them dead zones.

If Vaquer-Sunyer and Duarte's conclusions are correct, the area affected could be much greater.

The situation is also predicted to get worse with climate change: warmer oceans can hold less dissolved oxygen. A recent study calculated that the area of hypoxic Danish coast could more than double over the coming century (Science, vol 320, p 655).

Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0803833105)

Immigrant children from poor countries academically outperform those from developed countries

Sociological research also shows that children from small immigrant communities and children of politically motivated immigrants are at educational disadvantage

WASHINGTON, DC — Immigrants who seek a better life in Western countries may not be able to escape the influence of their home country when it comes to their children's academic performance, according to findings from the October issue of the American Sociological Review.

Sociologists Mark Levels, Jaap Dronkers and Gerbert Kraaykamp find that large-scale influences such as country of origin, destination country and immigrant community play a role in educational outcomes for immigrant children in their host country.

The research, which looked at the mathematical literacy scores of thousands of 15-year-old immigrants to 13 Western nations from 35 different native countries, indicates that economic development and political conditions in an immigrant's home country impact the child's academic success in his or her destination country. Counter-intuitively, immigrant children from countries with lower levels of economic development have better scholastic performance than comparable children who emigrate from countries with higher levels of economic development.

Children of immigrants from politically unstable countries have poorer scholastic performance compared to other immigrant children. "Adult political immigrants are known to face serious negative consequences that can be related to the political situations in their origin countries," said sociologist Mark Levels, junior researcher in the Department of Sociology at Radboud University, Nijmegen, in the Netherlands. "We found that these consequences carry across generations to affect their children's educational chances as well. Our findings therefore have urgent implications in countries that receive a large number of these immigrants."

"Specific educational programs designed to counter the negative effects of political migration may be essential to ensure that the children of politically motivated immigrants achieve their full potential," Levels said.

The study authors also analyzed the impact of policies and political conditions in destination countries. In traditional immigrant-receiving countries such as Australia and New Zealand, they found that immigrant children academically outperformed their counterparts in other Western nations. The authors theorize that this finding is likely the result of restrictive immigration policies that ensure that better qualified adults emigrate (e.g., those with employment and high levels of education), rather than a receptive climate toward immigrants or education policies designed to meet their needs.

The size and socioeconomic characteristics of immigrant communities also played a role in the academic performance of their children. Children from immigrant communities with higher socioeconomic status relative to the native population had higher scholastic performance than those from other immigrant communities. Likewise, children from large immigrant communities were more likely to perform better academically than children from smaller immigrant communities.

Data for this study came from the 2003 wave of the Project for International Student Assessment (PISA) from the Organization for Economic Co-operation and Development (OECD), the first large cross-national OECD dataset to contain information on the origin of first- and second-generation migrants. The sample was comprised of 7,403 15-year-old immigrant children from 35 different native countries living in 13 destination/host countries. Scholastic performance was based on PISA measurement of mathematical literacy scores.

Jaap Dronkers, professor of social inequality and stratification at the European University Institute in San Domenico di Fiesole, Italy, and Gerbert Kraaykamp, professor of empirical sociology at Radboud University, Nijmegen, co-authored the report with Mark Levels.

The research article, "Immigrant Children's Educational Achievement in Western Countries: Origin, Destination, and Community Effects on Mathematical Performance," is available by request for members of the media. Contact Jackie Cooper, ASA's Media Relations Officer, at or (202) 247-9871.

Treatment window expanded

Stroke patients benefit from dissolving a blood clot in the brain up to 4.5 hours after a stroke

Patients can still benefit up to 4.5 hours after a stroke if a drug that dissolves blood clots in the brain is administered. Thus far, three hours had been considered the useful limit for administering thrombolytic drugs. The results of the “European Cooperative Acute Stroke Study 3” (ECASS 3) have now been published in the “New England Journal of Medicine”.

These new insights will benefit tens of thousands of patients whose cerebral circulation could be restored“, said the study director, Professor Dr. Werner Hacke, Medical Director of the Neurology Clinic at Heidelberg University Hospital, who presented the study at the World Stroke Congress in Vienna.

A total of 826 patients in 130 European stroke centers who were treated in the clinic between 3 and 4.5 hours after a stroke were injected with either the thrombolytic drug alteplase or a placebo. Cerebral hemorrhage as a cause of the stroke was first ruled out by CT scan.

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