Bacteria may be the key to turning graphene into a semiconductor

SINCE its discovery in 2004 graphene, a form of carbon made of sheets a single atom thick, has been an invention in search of an application. In particular, it has fired engineers’ imaginations with the possibility of making thin, flexible, semi-transparent electronics. But it has always promised more than it has delivered because, although it is an excellent conductor of electricity, its other electronic properties are lacklustre. First, instead of being easily channelled, electric current moves across a graphene sheet randomly and in all directions. Second, graphene does not have a bandgap—a property needed to create the distinct “on” and “off” electronic states that transistors rely on to work, and which is induced in a material by disrupting the way its electrons are distributed.

One way to open up a bandgap is to introduce atoms of other elements into a substance. For graphene, however, this reduces the conductivity that is one of its attractive features. Another approach is to modify the atomic sheets’ shapes by, for example, wrinkling them—but existing methods of doing this do not control where the wrinkles form or how they are…Continue reading
Source: Economist

Their time has come

A cage for battery ions

BATTERIES are notoriously hard to improve. Nowhere was this more apparent than at the opening last week, on July 29th, of Tesla’s Gigafactory, a massive battery plant in Nevada. According to its boss Elon Musk, Tesla built the factory because wringing more efficiency out of batteries is far more difficult than optimising the process by which they are made.

It is an ironic coincidence, therefore, that last week also saw the publication, in Nature Energy, of a paper outlining a way of making a battery whose prototype stores twice as much juice as the lithium-ion cells the Gigafactory will turn out, and which could eventually do better than that. The new battery, brainchild of Ju Li of the Massachusetts Institute of Technology, is some way from commercialisation, but its design is such that commercialising it should not be hard.

The fundamental idea behind Dr Li’s device is not new. It is a version of what is known as a lithium-air battery, something that has been a desideratum of energy-storage research since the 1970s. In theory, such batteries could hold more than four times the energy per…Continue reading
Source: Economist

Seek, but shall ye find?

DURING war games played off the coast of Florida last year, a nuclear-powered French attack submarine, Saphir, eluded America’s sub-hunting aircraft and vessels with enough stealth to sink (fictitiously) a newly overhauled American aircraft-carrier, Theodore Roosevelt, and most of her escort. An account of the drill on a French defence-ministry website was promptly deleted, but too late for it to go unnoticed. 

Nor was this French victory a fluke. In 2006, in what was very far from being a war game, a Chinese diesel-electric submarine surfaced near Okinawa within torpedo range of another American carrier, Kitty Hawk, without having been detected by that carrier’s escort of more than a dozen vessels and anti-submarine aircraft. And, from the point of view of carrier-deploying navies, things are threatening to get worse. Saphir, launched in 1981, hardly represents the state of the art in underwater undetectability; in the decade since the Okinawa incident diesel-electrics have become even quieter. For an inkling of the silence of the new generation…Continue reading
Source: Economist

What is unbearable?

“A FATE worse than death” is a journalistic cliché, used this week alone to describe a visit to the dentist (in a British newspaper) and the plot arc of a character in J.K. Rowling’s new “Harry Potter” play (in an American magazine). But for the terminally ill, such fates do exist: death really can seem preferable to a lifetime of pain and suffering. A growing movement, including this newspaper, thus seeks to legalise—with stringent safeguards—doctor-assisted suicide around the world.

Yet doctors are taught to keep patients alive regardless of the circumstances, says Emily Rubin of the University of Pennsylvania. A paper by her and her colleagues, just published in JAMA Internal Medicine, attempts to give statistical rigour to scientific hunches about end-of-life care. Over an eight-month period, beginning in July 2015, her team surveyed 180 patients who had been admitted to a hospital in Philadelphia suffering from serious illnesses, including lung and heart disease. All participants were over 60, and were asked by medical staff to hypothesise whether they would prefer to die than be in progressively worse vegetative states.

As the chart shows, half or more said that they would consider being incontinent, being unable to get out of bed or relying on a breathing machine to stay alive as fates worse than death. Being so…Continue reading
Source: Economist

Didi overtakes Uber

Source: Economist

Researchers have built an artificial neuron

SINCE nobody really knows how brains work, those researching them must often resort to analogies. A common one is that a brain is a sort of squishy, imprecise biological version of a digital computer. But analogies work both ways, and computer scientists have a long history of trying to improve their creations by taking ideas from biology. The trendy and rapidly developing branch of artificial intelligence known as “deep learning”, for instance, takes much of its inspiration from the way biological brains are put together.

The general idea of building computers to resemble brains is called neuromorphic computing, a term coined by Carver Mead, a pioneering computer scientist, in the late 1980s. There are many attractions. Brains may be slow and error-prone, but they are also robust, adaptable and frugal. They excel at processing the sort of noisy, uncertain data that are common in the real world but which tend to give conventional electronic computers, with their prescriptive arithmetical approach, indigestion.The latest development in this area came on August 3rd, when a group of researchers led by Evangelos Eleftheriou at IBM’s research…Continue reading
Source: Economist

You’ve got a nerve

SINCE nobody really knows how brains work, those researching them must often resort to analogies. A common one is that a brain is a sort of squishy, imprecise, biological version of a digital computer. But analogies work both ways, and computer scientists have a long history of trying to improve their creations by taking ideas from biology. The trendy and rapidly developing branch of artificial intelligence known as “deep learning”, for instance, takes much of its inspiration from the way biological brains are put together.

The general idea of building computers to resemble brains is called neuromorphic computing, a term coined by Carver Mead, a pioneering computer scientist, in the late 1980s. There are many attractions. Brains may be slow and error-prone, but they are also robust, adaptable and frugal. They excel at processing the sort of noisy, uncertain data that are common in the real world but which tend to give conventional electronic computers, with their prescriptive arithmetical approach, indigestion. The latest development in this area came on August 3rd, when a group of researchers led by Evangelos Eleftheriou at IBM’s research…Continue reading
Source: Economist

New Zealand’s war on predators

NO ONE can accuse New Zealand’s government of a lack of ambition for the country’s wildlife. Earlier this year it came up with a new plan to save what might be regarded as the planet’s most unconservable bird—a flightless parrot called the kakapo that is basically a ready-meal with feathers. Now, it proposes to top this by eliminating almost all ground-dwelling predators from the entire archipelago, thus making New Zealand safe not just for kakapos, but for myriad other creatures that evolved there unhunted until humans introduced rats, cats, stoats, possums and so on.

The project, “Predator Free New Zealand”, was announced on July 25th. It will be run by a public-private partnership similar to the one that looks after the kakapo. New Zealand’s taxpayers will seed it with NZ$28m ($20m) on condition that twice this sum is raised elsewhere. The objective is to eliminate three types of introduced predator—rats, weasels and possums—by 2050. To placate the country’s moggy lovers, cats are mostly off the list at the moment, though feral felines living on public land will be legitimate targets.

Eradicating introduced…Continue reading
Source: Economist

Breathtaking

SMOKING a whole packet of cigarettes in a day once or twice a year would certainly make someone feel ill, but probably would not kill him. Smoking even one cigarette every day for decades, though, might do so. That is the difference between acute and chronic exposure, and it is a difference most people understand. What they may not understand is that the same thing applies to air pollution.

On a day-to-day basis, the forecasts most cities offer turn red only when pollution levels rise to a point where they will cause immediate discomfort. That makes sense, for it lets people such as asthmatics take appropriate action. But it might also lead the unwary to assume, if most days in the place he inhabits are green, that the air he is breathing is basically safe. This may well not be the case. In London, for example, a study published last year by researchers at King’s College suggested air pollution shortens the city’s inhabitants’ lives by nine to 16 months.

To investigate the matter, The Economist crunched a year’s worth of data collected from May 2015 onwards in 15 big cities. They were gathered…Continue reading
Source: Economist

Time capsules

OXYGEN makes up a fifth of the atmosphere (20.9%, to be precise), but that has not always been so. For the first 2 billion years of Earth’s existence, before photosynthetic organisms became common, there was no chemically uncombined oxygen in the air at all. Even after that, the gas remained scarce for hundreds of millions of years. By 575m years ago, however—which was when animals whose dimensions are measured in centimetres rather than microns appear—there must have been enough oxygen around to support their respiration. The usual guess is that the gas’s levels began to rise about 700m years ago. But a guess it is.

Now, Nigel Blamey of Brock University, in Ontario, Canada, has brought some evidence to bear on the question. His study, just published in Geology, is the first to measure directly the composition of samples of air from this ancient time. They were trapped in rock salt from the Officer Basin in south-western Australia, laid down by the evaporation of seawater between 830m and 800m years ago.

Previous estimates of oxygen’s past abundance have been made indirectly. In particular, the gas’s…Continue reading
Source: Economist