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Graphene shows unusual thermoelectric response to light – MIT News Office.

 

Graphene shows unusual thermoelectric response to light

Finding could lead to new photodetectors or energy-harvesting devices.

Given the enormous scale of worldwide energy use, there are limited options for achieving significant reductions in greenhouse gas emissions.

October 20, 2011

Photo: Len Rubenstein

Graphene, an exotic form of carbon consisting of sheets a single atom thick, exhibits a novel reaction to light, MIT researchers have found: Sparked by light’s energy, the material can produce electric current in unusual ways. The finding could lead to improvements in photodetectors and night-vision systems, and possibly to a new approach to generating electricity from sunlight.

This current-generating effect had been observed before, but researchers had incorrectly assumed it was due to a photovoltaic effect, says Pablo Jarillo-Herrero, an assistant professor of physics at MIT and senior author of a new paper published in the journal Science. The paper’s lead author is postdoc Nathaniel Gabor; co-authors include four MIT students, MIT physics professor Leonid Levitov and two researchers at the National Institute for Materials Science in Tsukuba, Japan.

Instead, the MIT researchers found that shining light on a sheet of graphene, treated so that it had two regions with different electrical properties, creates a temperature difference that, in turn, generates a current. Graphene heats inconsistently when illuminated by a laser, Jarillo-Herrero and his colleagues found: The material’s electrons, which carry current, are heated by the light, but the lattice of carbon nuclei that forms graphene’s backbone remains cool. It’s this difference in temperature within the material that produces the flow of electricity. This mechanism, dubbed a “hot-carrier” response, “is very unusual,” Jarillo-Herrero says.

Such differential heating has been observed before, but only under very special circumstances: either at ultralow temperatures (measured in thousandths of a degree above absolute zero), or when materials are blasted with intense energy from a high-power laser. This response in graphene, by contrast, occurs across a broad range of temperatures all the way up to room temperature, and with light no more intense than ordinary sunlight.

The reason for this unusual thermal response, Jarillo-Herrero says, is that graphene is, pound for pound, the strongest material known. In most materials, superheated electrons would transfer energy to the lattice around them. In the case of graphene, however, that’s exceedingly hard to do, since the material’s strength means it takes very high energy to vibrate its lattice of carbon nuclei — so very little of the electrons’ heat is transferred to that lattice.

Because this phenomenon is so new, Jarillo-Herrero says it is hard to know what its ultimate applications might be. “Our work is mostly fundamental physics,” he says, but adds that “many people believe that graphene could be used for a whole variety of applications.”

But there are already some suggestions, he says: Graphene “could be a good photodetector” because it produces current in a different way than other materials used to detect light. It also “can detect over a very wide energy range,” Jarillo-Herrero says. For example, it works very well in infrared light, which can be difficult for other detectors to handle. That could make it an important component of devices from night-vision systems to advanced detectors for new astronomical telescopes.

The new work suggests graphene could also find uses in detection of biologically important molecules, such as toxins, disease vectors or food contaminants, many of which give off infrared light when illuminated. And graphene, made of pure and abundant carbon, could be a much cheaper detector material than presently used semiconductors that often include rare, expensive elements.

The research also suggests graphene could be a very effective material for collecting solar energy, Jarillo-Herrero says, because it responds to a broad range of wavelengths; typical photovoltaic materials are limited to specific frequencies, or colors, of light. But more research will be needed, he says, adding, “It is still unclear if it could be used for efficient energy generation. It’s too early to tell.”

“This is the absolute infancy of graphene photodetectors,” Jarillo-Herrero says. “There are many factors that could make it better or faster,” which will now be the subject of further research.

Philip Kim, an associate professor of physics at Columbia University who was not involved in this research, says the work represents “extremely important progress toward optoelectric and energy-harvesting applications” based on graphene. He adds that because of this team’s work, “we now have better understanding of photo-generated hot electrons in graphene, excited by light.”

The research was supported by the Air Force Office of Scientific Research, along with grants from the National Science Foundation and the Packard Foundation.

This is a harth braking story from Ghana.
I makes me feel sad, last time I was in Ghana, the airport was full of rich foreigners coming into the country smelling the possibility to make lots of money in a short time. Ghana is changing, not to the better, but to the worst. For some people, the country is becoming more and more prosperous and westernized, but for others, it is getting harder and harder to make a living.
GHANA: The Abandoned Offspring of Oil – IPS ipsnews.net

The Abandoned Offspring of Oil
By Paul Carlucci and Sam Mark Essien


TAKORADI-SEKONDI, Ghana, Sep 23, 2011 (IPS) – Kobina’s legs are dappled with scars. He gets them flitting across the beach in Sekondi, in southwest Ghana, slipping in the soot-black mud and clambering over pirogues slippery with fish guts, only to sell a sachet of water or a freshly peeled orange to fishermen working on the shore.

He is a child: just 10 years old. But he earns a living selling food to locals.

Comfort Essuman keeps him company, roaming the area selling porridge and deep-fried sugar bread. Two years older than Kobina, she is less shy and more confident. Whereas Kobina will not offer his last name, Comfort readily pronounces hers.

“My mum says I should keep selling and that I will go to school later,” she says, adding that she has not been to school since grade three. “I sell not less than two Ghanaian cedi (just over one dollar) a day and send the proceeds to my mother.” She lives with her aunt, while her mother is in Central Region, one of the West African country’s 10 regions.

Kids like Comfort and Kobina are all over this Western Region metropolis. They are the skinny and scuffed cherubs of Takoradi’s heralded oil era, a newborn epoch that residents say is bringing more trials than triumphs.

Takoradi and Sekondi are the twin capitals of Ghana’s Western Region with a population of about 335,000. Once just sleepy fishing hollows, they were galvanised late last year when the region started producing oil from the offshore Jubilee field. The Ministry of Energy predicts 250,000 barrels per day by the end of the year, with a quarter century total of one billion barrels. And other finds from nearby fields are expected to come online in 2014.

Local chiefs are demanding 10 percent of the expected one billion dollars in annual government revenue from the oil. To kick-start infrastructure, the normally sluggish federal government passed a three billion dollar loan approval through parliament, earmarking 1.8 billion dollars for infrastructure development in Western Region.

Lured by news of oil-driven prosperity, newcomers arrive in droves, each expecting an employment boom that is yet to come. In the meantime, rent goes up. The cost of food increases. Traffic builds. And social malaise multiplies. It is a hydra-headed problem and many of its victims are children, says Deborah Daisy Kwabia, metropolis director for the Regional Department of Social Welfare.

“A lot of people are streaming into Takoradi-Sekondi in pursuit of greener pastures, whereby it doesn’t exist,” she adds. “It’s voluminous. It’s even increasing.”

For children, marginalisation takes two forms. The first is child labour, which can impact girls and boys differently. Older men may train boys to run drugs or steal from shoppers in Takoradi’s crowded Market Circle. Girls, meanwhile, might cook or wash dishes in ramshackle eateries called chop bars. Or they might move into someone’s house and become a maidservant.

The second is prostitution.

“Because of oil, now they have turned to prostitution,” says Comfort Osei Gerning, a foster mother with Mercy Foundation, a local children’s group. “The girls have turned to prostitution, and we have some boys who have turned to (having sex with men).”

The Zenith Hotel is the seat of downtown Takoradi’s nightlife. It is a bright red building next to a taxi station, and food hawkers crowd its corners late into the evening. Inside, men sip alcohol in a gloomy courtyard while prostitutes cruise the tables.

“Those ones aged 12 to 15, they are a different group,” Gerning says. “They are called the Thousand Girls. They charge cheap because they are kids.”

The name is a reference to Ghana’s old devalued currency. Ten Ghanaian cedi (six dollars) used to be 1,000 Ghanaian cedi. And it is what the girls charge. Apart from the Zenith, child prostitutes are said to haunt the Harbour View bar and the beaches of both Takoradi and Sekondi.

“Before you get to them, you have to pass through some grown-ups,” Gerning says. “They will collect the money from you and show you the place. It is someone’s business.”

This happens despite the existence of Ghana’s 1998 Children’s Act. Its clauses rail against child exploitation.

The act mandates the metropolis’ Social Services Sub-Committee to enforce its labour provisions. No one under 18 is allowed to do hazardous work, like going out to sea. No one under 15 is permitted to do manual labour. And light work is not allowed for anyone under 13. The committee can conduct investigations and recommend police action.

John Davis, representative for the metropolitan electoral area of West Anajy, has been the head of the committee for three months. Though he is aware of both child prostitution and labour in the metropolis, he says there have been no investigations under his tenure, and he is not aware of any conducted by the previous committee.

Davis is not able to offer any statistics at all, though he says assembly members were asked a month ago to gather information in their constituencies.

“We have not given any resources to do it,” he admits. “No resources in terms of vehicles or whatever.”

Instead, the committee will focus on an “education campaign”, speaking about the issue on the radio and elsewhere in public.

A lack of resources characterises much of government’s efforts in upholding the Children’s Act.

Kwaku Agyemang Duah, head of Community Care programmes with the Regional Department of Social Welfare, says the department has about 30 officers at its disposal. It needs a minimum of 80.

They also need a shelter for kids with no homes. The nearest one is four hours away in Accra, the country’s capital. And even if there was a shelter, they would need funds for feeding children as well as general maintenance.

“We present a budget every year,” he says, “but what comes out of it is a different story.”

Duah points to his office as a microcosm of the department’s financial straits. The floor looks like a warehouse. He has a desk and a filing cabinet and some rickety chairs. He has no computer and no office phone. The regional director’s office next door is only marginally better.

“I see it as a problem in developing countries,” says Peter Twineboa-Kodua, the regional director at the department. “We have not gone so far to look at the development of the individual as a human resource. Other (government) agencies on the financial side, they get everything they want. You can see their target. But child health, you cannot see the target.”

Unencumbered by bureaucracy, the Mercy Foundation has been able to make strides in addressing the problem. In the days before oil, when child labour was more a result of parents migrating to Ivory Coast to work in those fishing communities, they ran a school that involved 400 at risk children. It was funded by a World Bank grant that ran dry in 2004.

Smaller donations make other projects possible, however. Children have been re-integrated into the government schooling system. Those who were too de-institutionalised were taught vocations.

The Middle East’s New Geopolitical Map » Counterpunch: Tells the Facts, Names the Names

The Middle East’s New Geopolitical Map

by PATRICK SEALE

The Arab Spring is not the only revolution in town. The toppling of dictators in Tunisia, Egypt and Libya; the mounting death toll in Syria and Yemen, where the outcome is still undecided; the revival of long-suppressed Islamic movements demanding a share of power; the struggle by young revolutionaries to re-invent the Arab state — all these dramatic developments have distracted attention from another revolution of equal significance.

It is the challenge being mounted by the region’s heavyweights — Turkey, Saudi Arabia, Egypt and Iran — against the hegemony which the United States and Israel have sought to exercise over them for more than half a century.

When David Ben-Gurion declared Israel’s independence on 14 May 1948, he held the view that the country’s security could be assured only if it were militarily stronger than any possible Arab combination. This became Israel’s security doctrine. The desired hegemony was achieved by the prowess of Israel’s armed forces, but also by Israel’s external alliances first with France, then with the United States.

Military superiority won Israel outstanding victories in the 1948 and 1967 wars, a less resounding victory in 1973, still more contentiously by its invasions of Lebanon in 1978, 1982 and 2006, and more reprehensively by its operation of unashamed brutality against Gaza in 2008-9 — to mention only the most significant among a host of other Israeli attacks, incursions and onslaughts against its neighbours over the past several decades.

In its early years, Israel’s hegemony was reinforced by its so-called ‘periphery’ doctrine — its attempt to neutralise the Arabs by concluding strategic alliances with neighbouring non-Arab states such as Turkey and the Shah’s Iran. Its 1979 peace treaty with Egypt also proved a vital asset over the past three decades, since it removed the most powerful country from the Arab line-up.

The collapse of Soviet power in 1989-91 contributed to the Arabs’ disarray, as did the huge success of pro-Israeli Americans in penetrating almost every institution of the American government, whether at state or federal level, most notably the U.S. Congress. The message these advocates conveyed was that the interests of America and Israel were identical and their alliance ‘unshakable.’

Over the past forty years, the United States has provided Israel with sustained political and diplomatic support, as well as massive financial and military assistance, including a guarantee, enshrined in American law, of Israel’s Qualitative Military Edge (QME) – that is to say a U.S. pledge to guarantee Israel’s ability to defeat any challenge from any of its neighbours.

Even 9/11 was turned to Israel’s advantage in convincing American opinion that Palestinian resistance to Israel was terrorism, no different from that which America itself had suffered. There followed George W. Bush’s catastrophic militarisation of American foreign policy, and the invasion, occupation and destruction of Iraq on fraudulent premises, largely engineered by neo-cons such as Paul Wolfowitz, Douglas Feith and their colleagues at the Pentagon and in the Vice-President’s office, concerned above all to remove any possible threat to Israel from Saddam Hussein’s Iraq.

The United States has sought to protect Israel’s regional nuclear monopoly by harsh sanctions against Iran, because of its nuclear activities, as well as joint U.S.-Israeli sabotage operations, such as the infiltration into Iranian computers of the Stuxnet virus. Washington has turned a blind eye to Israel’s assassination of Iranian scientists, and has followed Israel in demonizing resistance movements such as Hizbullah and Hamas as terrorist organisations.

America’s most grievous mistake, however — the source of great harm to itself, to Israel, and to peace and stability in the Middle East — has been to tolerate Israel’s continued occupation and dispossession of the Palestinians. These policies have aroused intense hate of Israel in the Arab and Muslim world and great anger at its superpower protector.

We are now witnessing a rebellion against these policies by the region’s heavyweights — in effect a rebellion against American and Israeli hegemony as spectacular as the Arab Spring itself. The message these regional powers are conveying is that the Palestine question can no longer be neglected. Israel’s land grab on the West Bank and its siege of Gaza must be ended. The Palestinians must at last be given a chance to create their own state. Their plight weighs heavily on the conscience of the world.

Turkey, long a strategic ally of Israel, has now broken with it. Prime Minister Recep Tayyip Erdogan has denounced it as “the West’s spoilt child.” In a passionate speech in Cairo, he warned Israel that it must “pay for its aggression and crimes.” Supporting the Palestinians in their efforts to gain UN recognition as a state was, he declared, not an option but an obligation.

Prince Turki al Faisal, a leading member of the Saudi Royal family and former intelligence chief, has publicly warned the United States that if it casts its veto against the Palestinian bid for statehood, it risks losing an ally. In a widely-noted article in the International Herald Tribune on 12 September, he wrote that “Saudi Arabia would no longer be able to cooperate with America” in the way it has since the Second World War. The “Special Relationship” between the two countries “would increasingly be seen as toxic by the vast majority of Arabs and Muslims, who demand justice for the Palestinian people.”

Last week, the American-brokered 1979 Israeli-Egyptian peace treaty — a key underpinning of Israel’s regional hegemony — came under open criticism from Egypt itself. The treaty was “not a holy book,” said Egypt’s prime minister, Dr. Essam Sharaf. It would need to be revised. Amr Moussa, the leading candidate for the Egyptian presidency, has called for the treaty’s military annexes to be reviewed so as to allow Egyptian troops to be deployed in Sinai.

As for Iran, denunciation of the United States and Israel can be expected from President Ahmadinejad when he addresses the UN General Assembly in the coming days. The failure to engage with Iran — demonising it as a threat to the whole world, rather than working to incorporate it into the security architecture of the Gulf region — has been one of Obama’s gravest policy mistakes.
Turkey, Iran and Egypt, heirs to ancient civilizations, are thus asserting themselves against what they see as an Israeli upstart. Saudi Arabia, the region’s oil and financial giant, guardian of Islam’s holiest sites, is breaking free from the constraints of the American alliance.

Israel stands accused. Will it heed the message or shoot the messenger? If true to its past form, it might well try to fight its way out of the box in which it now finds itself, further destabilising the region and attracting to itself further opprobrium.

As for the United States, bound hand and foot by Israeli interests, it seems to have abdicated the leading role in the Arab-Israeli peace process it has played for so long — but to so little effect. Disillusion with President Barack Obama is now total. Others must now take up the baton. Many believe the time has come to break the dangerous stalemate with some coercive diplomacy. Will Europe take up the challenge?

Patrick Seale is a leading British writer on the Middle East. His latest book is The Struggle for Arab Independence: Riad el-Solh and the Makers of the Modern Middle East (Cambridge University Press).

Copyright © 2011 Patrick Seale .

 

Iranian security forces quash more protests in Tabriz, Oroumiyeh

Iranian security forces quash more protests in Tabriz, Oroumiyeh
Source: Radio Zamaneh

Iranian security forces descended on demonstrations against the drying of Lake Oroumiyeh in Tabriz and Oroumiyeh in northwestern Iran on Saturday, making numerous arrests.


Lake Urmia (Orumieh) is a salt lake in northwestern Iran near Turkey. The lake is between the provinces of East Azarbaijan and West Azarbaijan, west of the southern portion of the similarly shaped Caspian Sea. It is the largest lake inside Iran, and the third salt water lake on earth, with a surface area of approximately 5,200 km square (2,000 mile square).

News outlets linked to ethnic and human rights activists as well as eyewitness reports indicate that security forces were on alert in various Azerbaijan cities in Iran and confronted the crowds with tear gas and batons.

According to HRANA (the Human Rights Activists News Agency), dozens of people were arrested. Some reports indicate that police used plastic bullets, which led to several injuries among protesters.

The Fars semi-official news agency confirmed the unrest but wrote that the demonstrators were rallied by “ethnic” groups, adding that the demonstrators numbered only about 50 people.


Photos: Lake Orumieh Grappling with Death

The Islamic Republic does not let independent and international media cover social and political protests; therefore, it is not possible to confirm details of the published reports.

Protesters maintain that government policies and mismanagement at the local level are the main causes of the rapid decline in the water levels of Lake Oroumiyeh.

Parliament recently voted down a plan to redirect water from the Aras River to Lake Oroumiyeh, which has led to a new wave of protests by environmental and Azerbaijani activists.

Protests in OrumiehAftermath of protests in the northwestern city of Orumieh (Urmia) on August 27.