Graphene joins the race to redefine the ampere

May 12, 2013 ? A new joint innovation by the National Physical Laboratory (NPL) and the University of Cambridge could pave the way for redefining the ampere in terms of fundamental constants of physics. The world's first graphene single-electron pump (SEP), described in a paper today in Nature Nanotechnology, provides the speed of electron flow needed to create a new standard for electrical current based on electron charge.

The international system of units (SI) comprises seven base units (the metre, kilogram, second, Kelvin, ampere, mole and candela). Ideally these should be stable over time and universally reproducible. This requires definitions based on fundamental constants of nature which are the same wherever you measure them.

The present definition of the Ampere, however, is vulnerable to drift and instability. This is not sufficient to meet the accuracy needs of present and certainly future electrical measurement. The highest global measurement authority, the Conf?rence G?n?rale des Poids et Mesures, has proposed that the ampere be re-defined in terms of the electron charge.

The frontrunner in this race to redefine the ampere is the single-electron pump (SEP). SEPs create a flow of individual electrons by shuttling them in to a quantum dot -- a particle holding pen -- and emitting them one at a time and at a well-defined rate. The paper published today describes how a graphene SEP has been successfully produced and characterised for the first time, and confirms its properties are extremely well suited to this application.

A good SEP pumps precisely one electron at a time to ensure accuracy, and pumps them quickly to generate a sufficiently large current. Up to now the development of a practical electron pump has been a two-horse race. Tuneable barrier pumps use traditional semiconductors and have the advantage of speed, while the hybrid turnstile utilises superconductivity and has the advantage that many can be put in parallel. Traditional metallic pumps, thought to be not worth pursuing, have been given a new lease of life by fabricating them out of the world's most famous super-material -- graphene.

Previous metallic SEPs made of aluminium are very accurate, but pump electrons too slowly for making a practical current standard. Graphene's unique semimetallic two-dimensional structure has just the right properties to let electrons on and off the quantum dot very quickly, creating a fast enough electron flow -- at near gigahertz frequency -- to create a current standard. The Achillies heel of metallic pumps, slow pumping speed, has thus been overcome by exploiting the unique properties of graphene.

The scientist at NPL and Cambridge still need to optimise the material and make more accurate measurements, but today's paper marks a major step forward in the road towards using graphene to redefine the ampere.

The realisation of the ampere is currently derived indirectly from resistance or voltage, which can be realised separately using the quantum Hall effect and the Josephson Effect. A fundamental definition of the ampere would allow a direct realisation that National Measurement Institutes around the world could adopt. This would shorten the chain for calibrating current-measuring equipment, saving time and money for industries billing for electricity and using ionising radiation for cancer treatment.

Current, voltage and resistance are directly correlated. Because we measure resistance and voltage based on fundamental constants -- electron charge and Planck's constant -- being able to measure current would also allow us to confirm the universality of these constants on which many precise measurements rely.

Graphene is not the last word in creating an ampere standard. NPL and others are investigating various methods of defining current based on electron charge. But today's paper suggests graphene SEPs could hold the answer. Also, any redefinition will have to wait until the Kilogram has been redefined. This definition, due to be decided soon, will fix the value of electronic charge, on which any electron-based definition of the ampere will depend.

Today's paper will also have important implications beyond measurement. Accurate SEPs operating at high frequency and accuracy can be used to make electrons collide and form entangled electron pairs. Entanglement is believed to be a fundamental resource for quantum computing, and for answering fundamental questions in quantum mechanics.

Malcolm Connolly, a research associate based in the Semiconductor Physics group at Cambridge, says: "This paper describes how we have successfully produced the first graphene single-electron pump. We have work to do before we can use this research to redefine the ampere, but this is a major step towards that goal. We have shown that graphene outperforms other materials used to make this style of SEP. It is robust, easier to produce, and operates at higher frequency. Graphene is constantly revealing exciting new applications and as our understanding of the material advances rapidly, we seem able to do more and more with it."

Source: http://feeds.sciencedaily.com/~r/sciencedaily/~3/_n1XFFUNADE/130512141212.htm

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Snow's melting: Time to find budget hiking boots

By Kara Reinhardt, Cheapism.com

The Merrell Moab Ventilator is a low-cut hiking shoe, an increasingly popular and affordable alternative to higher-cut boots.

April showers and spring snowmelt signal that it?s time to trade in ski boots and snowshoes for hiking boots. Of course, those harbingers of warm weather also turn hiking trails to muck. Opt for a cut-rate pair of boots, and you could easily wind up with wet, blistered feet and a muddy rump. You could also wind up with a high-quality hiking shoe or even a reliable mid-cut boot for under $100.

Cheapism.com has highlighted four top picks, all of which come in men?s and women?s versions.

• The Merrell Moab Ventilator (starting at $72) has been labeled an excellent value in side-by-side comparisons by outdoor gear experts. This is a supportive hiking shoe that grips the trail with deep 5-millimeter lugs, or treads, yet it?s lightweight and very comfortable, according to online reviews. While the Ventilator is not waterproof (pricier Moab models are), it has a highly breathable mesh upper that allows it to dry out quickly in warm weather. The namesake ventilation further helps prevent blisters by airing out hot, sweaty feet. (Where to buy)
• The Keen Alamosa WP (starting at $72) caters to hikers who prefer a waterproof shoe. In this price range the term is often used loosely, but reviewers verify that the waterproof membrane that lines this shoe prevents water from leaking through. They also note the sturdy yet extremely lightweight construction, including durable, suede-like nubuck leather and a rubber bumper on the toe. (Where to buy)
• The mid-cut L.L. Bean Waterproof Trail Model Hikers (starting at $90) are classic hiking boots that come up higher on the ankle to provide additional support and protection. The mid-cut design alone is often enough to price a shoe over $100 and this budget pair is waterproof to boot (no pun intended). Again, numerous reviewers vouch for the effectiveness of the waterproof lining. (Where to buy)
• The Salomon Synapse (starting at $60) is uniquely designed for trail running, or for covering a lot of ground quickly. The midsole is tilted downward, toward the toe, to propel the wearer forward. A record holder who completed the fastest end-to-end hike of the Appalachian Trail wore these inexpensive shoes to accomplish her feat. Novices, too, have found them durable and supremely comfortable. (Where to buy)

Light hiking shoes dominate the low end of the market and have become a popular alternative to heavy-duty backpacking boots. A multi-day trip with a heavy pack over rough, uneven terrain calls for a burly boot with a higher price tag. But for day hikes that don?t venture off the trail, many hikers prefer nimbler footwear. While that often means a low-cut shoe, a few mid-cut boots, such as L.L. Bean?s Trail Model Hikers, offer similarly light weight and low cost.

Another hallmark of this type of shoe is a sole that?s supportive without being too stiff. All four pairs listed above manage to walk that line, reviewers say. They feature foot beds made from cushy EVA, or ethylene vinyl acetate. However, nothing will make a boot comfortable if it doesn?t fit correctly. Outside magazine explains exactly how to find the right one for you.

Related from Cheapism:
Cheap hiking boots buying guide
Cheap tent recommendations
The best cheap binoculars
Sleeping bag reviews and recommendations

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Your instant coffee may be about to go gourmet, for the same price

Marcy Nicholson , Reuters ? ? ? 6 hrs.

Instant coffee drinkers may soon be getting a more gourmet brew than they realize at no extra cost as roasters consider adding higher-quality arabica beans into their blends.

Soaring demand for instant coffee in emerging markets has caused demand growth for caffeine-rich robusta coffee, widely used in soluble coffee, to outpace that for arabica beans, which dominate the gourmet ground-coffee market. That has pushed the typically cheaper and lower-quality beans to almost par with some arabicas.

With the price of some arabicas near that of robusta, some instant coffee makers have already taken the rare step of adding the typically more expensive arabica to their highly secretive blends, coffee buyers said.

The move marks a possible a precursor that other coffee makers who currently use robusta in their blends may be reverting their blends to include more higher quality arabica beans, a change that could soften the current surge in robusta demand. This is coming less than two years after several shifted in the other direction.

"Since early this year, we are seeing roasters replacing robusta for low grade arabica in the lower quality soluble coffees," said Freddie Schol, trading manager for Nedcoffee in Amsterdam.

Soluble, or instant coffee, is usually made from robusta beans, known for acidic flavors and higher caffeine content.

The taste for instant coffee in Asia has surged, with consumers in China buying more than 40,000 metric tons (44,092 tons) of it in 2012, up 9 percent from 2011 and up 43 percent from 2008, Euromonitor International data showed.

That equates to roughly 59 million cups a day of instant brew, more than double the instant coffee purchases in the United States, where demand is relatively flat.

Robusta usage has also risen after the 2011 arabica rally forced many roasters to adjust or create new blends with higher robusta content.

Nedcoffee, a large coffee trading company headquartered in Amsterdam, buys 150,000 metric tons (2.5 million 60-kilogram bags) of coffee annually, with 99 percent of this being robusta, an amount that equates to roughly 10 percent of Vietnam's entire crop. It has procurement and processing plants in Ivory Coast, India, Indonesia and Vietnam.

Arabica gets cheaper
On the physical market, prices of some low grade arabica beans have fallen to below high-quality robusta, importers said.

Uganda drugar beans, an unwashed and low-quality arabica, stored in U.S. warehouses, recently fetched roughly $1.15 per lb while Uganda standard robusta was valued at about $1.18 per lb, U.S. importers said.

Instant coffee processors do not appear to be the only ones adding arabica beans their blends.

"(Roasters) are thinking about it now and some of them are already doing it, but it's going to be gradual," said Ernesto Alvarez, chief executive of COEX Coffee Group in Miami.

There is no data available to show this trend, but Alvarez said that he has already started selling some discounted mild arabica beans to a company that had previously increased its usage of robusta in its blends due to the rally in arabicas.

"As the arbitrage narrows, it makes natural sense that they would begin to shift at these levels back into arabica in the future," said one U.S. coffee buyer, who spoke on the condition of anonymity, referring to the difference in price between arabica and robusta beans.

Coffee has been volatile since arabica prices on ICE Futures U.S. more than doubled over 11 months to above $3 per lb in May 2011 as speculators piled into the market.

The rally pushed the arabica premium on the futures market over robusta to nearly $1.90 per lb in 2011, well above the premium that ranged between 35 and 85 cents in 2009 and 2010. In March it dropped to around 35 cents, the lowest level in four years, and a level many dealers consider historically normal.

While several coffee dealers expect the premium will drop further to 20 cents, others anticipate it will rise. On Tuesday, the premium sat around 45 cents.

So far the switch in beans is limited in scale. A blend change is easier for instant coffee makers or small roasters than the large roasters, several coffee buyers said.

Analysts said arabica's premium would need to be around 35 cents for months before larger roasters would adjust their blends, a process that involves extensive research to ensure the taste profile isn't significantly altered.

"I don't think we're at the point where we can definitely say there's massive shifting happening, but incrementally we have to believe that it's happening behind the scenes," the U.S. buyer said.

Americans drink more robusta
While U.S. instant coffee consumption has flatlined, Americans are drinking more brewed coffee made from robusta beans, adding to mounting pressure on global supplies.

Total consumption of robusta in brewed coffee climbed by 7 percent in the United States in 2012, up from 3.9 percent growth in 2011 and 3.6 percent in 2010, according to StudyLogic, a U.S. market research firm.

This compares with a small 1.9 percent climb in demand for brewed arabica in 2012, versus a year-over-year increase of 4.1 percent in 2011 and 5.4 percent rise in 2010.

Global robusta exports jumped a whopping 24 percent to 46.6 million 60-kilogram bags in the 2012 calendar year, versus 2011, while arabica exports dropped by 0.8 percent to 66.5 million bags, International Coffee Organization data showed.

Several U.S. importers have said they are concerned about securing robusta supplies later this year, with one wondering if he will have problems as early as August if demand continues to climb at its current pace.

"There's too much demand for coffee. At the rate we're going, I don't know how that's going to be met," said COEX's Alvarez.

Copyright 2013 Thomson Reuters.

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Senate to cast first gun-control votes on Thursday (reuters)

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Family Tree Trailer: HBO is Forcing You to Buy HBO | Slog

HBO has been killing it lately?with of course Game of Thrones, Veep, the upcoming Liberace biopic [WATCH THAT TRAILER!!!] and now a new comedy series from Christopher Guest called Family Tree, starring Chris Dowd and every single person from every Christopher Guest movie ever. It debuts Sun May 12 at 10:30 pm and it looks very funny. WATCH THAT TRAILER!!!

Source: http://slog.thestranger.com/slog/archives/2013/04/09/family-tree-trailer-hbo-is-forcing-you-to-buy-hbo

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Top admiral: US can intercept a North Korean missile

While testifying before the Senate Armed Services Committee, Adm. Samuel Locklear, Commander of the US military's Pacific Command, says he's confident missile defenses are capable of intercepting a ballistic missile launched by North Korea towards the U.S. — or any of its allies.

By Jim Miklaszewski and Courtney Kube, NBC News

If North Korea decides to launch a missile, the United States is ready to respond and is capable of intercepting it, a top U.S. military commander told Congress on Tuesday.

The Commander of U.S. Pacific Command also said that he cannot recollect a more tense time between the U.S., South Korea, and North Korea since the end of the Korean War.

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Responding to Sen. John McCain's statement that he doesn't know a time of greater tension in the decades since the war, Admiral Sam Locklear said that "I would agree that in my recollection I don't know a greater time."

Locklear told members of the Senate Armed Services Committee that the U.S. is ready to respond to a North Korean missile launch or other threat.

"I am satisfied that we are ready today, yes," Locklear said.

South Korean official have said since Sunday that a missile launch by the North could come as early as Wednesday but U.S. military and intelligence officials have seen no movement or preparations that would indicate that a launch of the Musudan missiles from the launch site on North Korea's east coast is imminent.

Locklear acknowledged that the U.S. believes North Korea has placed a Musadan missile on that coast, adding the missile has a range of roughly 1,800 to 2,100 miles, with a minimum range of about 400 miles.

He said it does not threaten the mainland United States or Hawaii, but it could put Guam at risk. He added that the U.S. has "capability in place" to protect Guam.

Asked specifically whether U.S. forces can intercept a missile from North Korea, Locklear said, "I believe we have a credible ability to defend the homeland, to defend Hawaii, defend Guam, to defend our forward-deployed forces and defend our allies."

He went on to say that the U.S. could intercept a missile even if it happens in the next several days.

Locklear said he would not recommend intercepting a missile, however, until the U.S. is certain what the target is.

"If the missile was in defense of the homeland, I would certainly recommend that action. And if it was defense of our allies, I would recommend that action," he said.

He added that they will know "pretty quickly" where the missile is going and "what we need to do about it."

Locklear also acknowledged that China, the North's only diplomatic and financial ally, could play a key role in stopping the rhetoric from North Korea.

Asked whether the Chinese government has done enough to restrain North Korea, Locklear said, "I think they could do more."

The admiral's comments come as world leaders have shown alarm at the prospects of a conflict involving a reclusive state that claims to be developing a nuclear weapon.

South Koreans expect Pyongyang to launch a medium-range missile near the border as North Korea warned foreigners in South Korea to be prepared to evacuate. NBC's Richard Engel reports.

Addressing North Korea's latest saber-rattling that warned foreigners to leave South Korea, the White House on Tuesday called the rhetoric "unhelpful" and "provocative."

President Barack Obama called North Korea's nuclear test in February "highly provocative." Russian President Vladimir Putin has said?hostilities?could create a cataclysm worse than the 1986 Chernobyl nuclear disaster.?

Yet in South Korea, where most of the harsh rhetoric is aimed, people?numbed by years of threats?are calmly going about their business. Restaurants and hotels are full in Seoul - a mere 30 miles from 700,000 North Korean soldiers -- and no emergency supplies such as gas mask or drugs are being distributed.

Admiral Locklear meanwhile referred to North Korean leader Kim Jung Un as the "impetuous young leader" who "continues to focus on provocation rather than on his own people.?

Locklear said that Kim Jung Un is more unpredictable that his father or grandfather who "always figured into their provocation cycle an off ramp of how to get out of it."

"It's not clear to me that he has thought through how to get out of it. And so, this is what makes this scenario, I think, particularly challenging," Locklear said.

As to any potential missile launch, U.S. officials say that they firmly believe that missiles would be aimed out to open sea, not at South Korea, Japan or Guam.

And despite the taunts from North Korea, which?include a call for foreigners to leave the South, the U.S. State Department hasn?t issued any new security warnings to Americans in South Korea or planning to travel there.

At the State dept. briefing today, Spokesperson Patrick Ventrell said that no new security warnings are being issued to Americans in South Korea or planning to travel to South Korea based on recent taunts from North Korea.

"There's no specific information to suggest imminent threat to U.S. citizens or facilities in the Republic of Korea,? State Department spokesman Patrick Ventrell said on Tuesday. ?So the U.S. embassy has not changed its security posture. We have not recommended that U.S. citizens who reside in or plan to visit the Republic of Korea take special security precautions at this time."

NBC News' Jim Maceda and Jeff Black contributed to this report.

Related:

Google+ Hangout: Richard Engel answers questions on North Korea

North Korea warns foreigners to leave South

Who is North Korea's secretive leader? Here is what we know

'Positive thinking' after years of threats keeps South Koreans going

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Beyonce and Jay-Z's trip to Cuba was sanctioned

By Anna Chan and Gael Fashingbauer Cooper, NBCNews.com

Ramon Espinosa / AP

Beyonce and Jay-Z spent their fifth anniversary in Cuba.

The U.S. Department of the Treasury on Thursday confirmed that Beyonce and Jay-Z's controversial trip to Cuba last week was indeed sanctioned.

"It is our understanding that the travelers in question traveled to Cuba pursuant to an educational exchange trip organized by a group authorized by (the Office of Foreign Assets Control) to sponsor and organize programs to promote people-to-people contact in Cuba," Alastair M. Fitzpayne, the Treasury's assistant secretary for legislative affairs, wrote in a letter to Reps. Ileana Ros-Lehtinen and Mario Diaz-Balart.

The letter also notes that "OFAC's regulations and guidelines require that such trips involve a full-time schedule of educational exchange activities that result in meaningful interaction between the U.S. travelers and individuals of Cuba." Visitors are allowed to "engage in non-educational activities off-hours."

The Florida representatives had contacted the Treasury with concerns about the singers' trip, writing that the U.S. travel restrictions are in place to prevent American tourism dollars being spent to support a "murderous regime."

Americans can travel?to Cuba if they first obtain a license for an academic, religious, journalistic or cultural exchange trip, but may not travel there simply for tourism.

The celebrity couple was pictured visiting the island on their fifth wedding anniversary. They toured historic Old Havana and dined at an elegant Havana restaurant, and Jay-Z was photographed smoking one of Cuba's famed cigars. The stars' presence created such a stir that police were called in.

-- With additional reporting by Kelly O'Donnell

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