The computers connect to the phones using short-range Wi-Fi, requesting web pages as if they were using a wireless router with a wired connection to the internet, and the cellphones use their long-range cellular connection to get the files requested from the net.

Crucially, the system, dubbed , carefully manages the cellphones’ use of battery-hogging wireless to make it practical. Phones and computers all need special software installed to use it.

Battery vampire

Researchers at Microsoft Research India, in Bangalore, first developed the idea in 2007. But , as the system was then called, simply used as many connections as it could from nearby phones to make a computer’s internet connection as fast as possible. Because of this, the heavy power overheads Wi-Fi places on a portable device limited its usefulness.

Now Microsoft researchers and colleagues at the University of California, Santa Barbara, have created Cool-Tether, the first energy-aware technique for forming these on-the-fly hotspots using cellphones.

“Instead of blindly using all the available phones, Cool-Tether determines the optimal number of phones to use to send the contents of the web page,” says , a computer scientist with Microsoft Research India.

Lingering state

Each time a phone transfers a chunk of data by Wi-Fi to a computer, it “lingers in high-power active state for a few seconds” regardless of how much was transferred, Navda explains. This drains a phone’s battery quickly, especially if lots of small transfers are made, as happens when someone browses web pages.

Cool-Tether coordinates the phones to send data in fewer, longer bursts, and to make sure that each “energy tail” is associated with as much data transfer as possible. Cool-Tether uses a quarter as much energy as the previous version of the system, with little loss of downloading speed.

Navda and his colleagues think Cool-Tether is most likely to be of use in poor countries, where it could provide an alternative to an expensive hard-wired connection. In India, for example, 10 times as many people connect to the internet through cellphones as use connections for computers.

of the University of Waterloo in Ontario, Canada, says Cool-Tether incorporates “some neat ideas, [including] burst transmission and a careful analysis of energy”. However, it’s not clear how practical it is today, he argues, because Wi-Fi-enabled cellphones are not yet that common.

A paper on Cool-Tether will be presented this week at the in Rome, Italy.

As scientists start to fill out the picture of a future globe dramatically changed by catastrophic global warming, the use of climate models is increasingly important when forecasting the risks faced by various regions.

Tim Palmer and researchers at the say that running simulations on cheap computer chips that produce results tainted with random noise could improve those models.

Random world

Many climate processes – such as cloud formation or the movement of air currents – are too complex to simulate exactly. Models approximate these processes over a particular region of the planet, dividing it into grids typically around 100 kilometres across.

Different models, however, often fail to precisely match up because they vary in how their approximations are built. While researchers are striving to make the models more realistic, they are limited by the processing power of the supercomputers that run climate models, Palmer says. “That determines how fine of a grid we can solve the equations on, because of the computing cost,” he says.

Try, try again

Adding a degree of randomness to a particular model and running it multiple times could provide a cheaper way to increase realism, Palmer and colleagues argue, as it could be a “poor man’s surrogate for high-resolution models”.

If multiple, slightly different runs of a model come up with the same answer, it provides a hint of the strength of a prediction, according to the team. The technique has already been shown to work for weather forecasting over periods of a few weeks.

“The time is now right to integrate this into climate models,” Palmer says.

Phone chips

Just generating randomness to feed such models can eat up a lot of computing power. A way around this could be to use cheap hardware – low-cost computer chips that generate output with some random noise due to the way electrons bounce through them. Essentially, those chips produce the necessary randomness for free.

“It’s very speculative,” Palmer says. “But if it can be made to work, it would make much more efficient use of power.” The idea of adding randomness into the models is “very interesting and might be helpful for some cases”, says Reto Knutti of the Swiss Federal Institute of Technology in Zurich, “but in my view it will not solve all problems.”

Randomness will work best for well-understood processes such as the movement of air currents, Knutti says. “But for a case where we don’t understand the process in the first place” – such as how climate change will affect plant growth – “it may not help”.

Journal reference: A pre-print of a paper on the proposal is available on the arXiv:

A material with remarkable oil-absorbing properties has been developed by US researchers. It could help develop high-tech “towels” able to soak up oil spills at sea faster, protecting wildlife and human health.

Almost 200,000 tonnes of oil have been spilled at sea in accidents since the start of the decade, according to the .

Clean-up methods have improved in recent years, but separating oil from thousands of gallons of water is still difficult and perhaps the biggest barrier to faster clean ups.

The new water-repellent material is based on manganese oxide nanowires and could provide a blueprint for a new generation of oil-spill cleaners. It is able to absorb up to 20 times its own weight in oil, without sucking up a drop of water.

Oil guzzler

Researchers led by at the Massachusetts Institute of Technology in Cambridge, US, made membranes of tangled manganese oxide nanowires around 50 micrometres thick – about a quarter of the thickness of normal office paper.

The tiny wires are first suspended in liquid, before being strained out into flat sheets. “It’s very similar to the process that makes paper,” Stellacci says.

The manganese oxide nanowires are normally very attractive to water. However, adding a silicon coating switches the material to being strongly water repellent. It also becomes able to guzzle oil. Tests showed the material can suck up 20 times its weight in motor oil, and 10 times its weight in gasoline.

The new material is much more selective than other similar materials, such as those made of polymer or glass fibres, tests showed. Those materials all absorb some water as well as oil.

Heat proof

“Our material can be left in water a month or two, and when you take it out it’s still dry,” Stellacci says. “But if that water contains some hydrophobic [oily] contaminants they will get absorbed.”

The membranes are tough, too, and can withstand being heated to evaporate off any oils. High temperatures remove the silicon coating, but once a new one is applied, the membrane is ready to use again, the researchers showed.

The membrane has “extraordinary selectivity and capacity for the separation of oil from water,” says of the University of Michigan in Ann Arbor, US.

But Lahann points out that manganese oxide may not be the best material for real-world applications because it could be toxic. He says, though, that the new material “clearly provides a blueprint that can guide the design of future nanomaterials for environmental applications.”

Journal reference:

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Geckos are famed for their ability to walk on walls thanks to nanoscopic hairs called setae. Ivy uses another nano-scale trick to defy gravity.

Darwin wrote about ivy at length in his book . He noted tiny disc-shaped projections, called rootlets, on the stem of the plant that secrete a yellowish substance and attach to rough surfaces.

“As the disks can almost immediately adhere firmly to such smooth surfaces as planed and painted wood … this alone would render it probable that some cement is secreted,” Darwin wrote in 1865.

Billions of bonds

Now researchers have done the first in-depth analysis of these secretions and found that they contain tiny globules, each about 70 nanometres across, with extraordinary sticking power. A team led by at University of Tennessee in Knoxville, US, spotted the nanoparticles and ran them through chemical tests, revealing 19 different primary compounds.

Most of these compounds were found to be “polar molecules”. This means there is an imbalance of electric charge within them, making them prone to link with other molecules through hydrogen bonds.

Such bonds are relatively weak, but Zhang notes that, “adding up millions or billions of weak adhesion or hydrogen bonds could be a big force. That is what ivy is doing.”

Slippery paint

Zhang adds that the globules “are very small, and can fit into almost anywhere,” helping the plants stick to many different surfaces.

By understanding what makes the nanoparticles stick, the researchers hope to work out way to counteract it. “We are investigating a paint that may protect walls from damage by climbing ivy,” Zhang says. They are also looking at engineering ivy to produce custom nanoparticles, a process known as “green manufacturing”.

“The idea of looking at ivy attachment at the nanoscale seems novel and emphasises how little we still know about this very common natural phenomenon,” says of University College Dublin in Ireland.

“The work should make people more aware that nature is already utilising nanoparticles,” Jarvis adds. She thinks studying plants like ivy could uncover entirely novel nano-materials.

Journal reference:

Contrary to the widespread view that a warming world will bring more hurricanes, a controversial new study suggests the number of cyclones could actually drop in the North Atlantic.

Hurricanes have become a lightning rod for arguments over what global warming might have in store. Most researchers agree that, since 1950, the number of hurricanes forming over the Atlantic has increased, and that since at least since 1980, they have become fiercer.

Many studies have blamed the increase in Atlantic hurricanes on increasing sea-surface temperatures, which fuel the storms. However, other ocean basins have not seen a similar increase in hurricanes.

Storm predictions

and colleagues at the US National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory in Princeton, US, built a computer model to simulate the formation of North Atlantic hurricanes, based on observed sea-surface temperatures and atmospheric conditions.

Tropical storms and hurricanes formed spontaneously in the model, following much the same tracks as real storms do.

They also found that the model predicted fairly closely the number of North Atlantic hurricanes over the past 25 years – with 162 predicted storms, as opposed to 143 recorded. The strength of the most severe storms was not predicted, however.

Next they fed the model predictions of how Atlantic waters are likely to warm with climate change.

These were based on an ensemble of climate models in which emissions rise until mid-century, then start to taper off – an optimistic scenario for future carbon-dioxide emissions. Though emissions drop off, the ocean would continue warming through the end of the century and beyond.

Fewer hurricanes

Surprisingly, the model simulated fewer tropical storms as the ocean warmed, and fewer hurricanes. By the end of this century, it predicted, the Atlantic will see a drop in tropical storms of 27%, and a drop in hurricanes of 18%.

“This study does not support the idea there is a large increasing trend [in hurricanes] due to greenhouse warming,” says Knutson.

The model also predicted that the fewer hurricanes that do emerge will become slightly stronger on average, but Knutson is cautious about this finding. “We don’t want to take it quantitatively too seriously because it’s not simulating stronger storms very well,” he says.

Nonetheless, he adds, “it gives more support to the idea that in the tropics in general, hurricanes will be slightly more intense and have more rainfall.”

Other researchers are sceptical about drawing any big conclusions from the study, pointing to the fact that the model did not produce any really strong hurricanes, of category four or five, in either the 20th century or in the coming century.

Low resolution

This “is a major shortcoming,” says of the National Center for Atmospheric Research in Boulder, Colorado, US.

“In this study there is a suggestion that the strongest storms increase, but the model never simulates them in the first place,” Trenberth says. “It could be grossly in error for the strongest storms, which are the ones that do most damage.”

of the Massachusetts Institute of Technology in Cambridge, US agrees. “My only reservation is that the model’s spatial resolution is still too low to allow for intense hurricanes,” he says.

In a with higher resolution, but simpler models, Emanuel and colleagues also found an increase in hurricanes’ intensities in the northern hemisphere.

Journal reference:

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Video: Climbing is a walk in the park for small primates

Climbing stairs can be a slog for us humans, but for smaller primates scampering up trees requires no more energy than strolling along the ground, researchers say.

The new findings suggest a way that small, early primates could have invaded unexploited food niches without using more energy, giving them an advantage over other tree-dwellers.

It has long been known that, kilo for kilo, small animals use more energy to walk along flat ground than big animals do.

Small animals have to take more steps to move a certain distance, and large animals can store proportionately more energy from each step in stretchy tendons, which literally puts a spring in their step, making walking easier.

Equal energy

Now and colleagues at Duke University have rigged up a kind of vertical treadmill to compare various primates’ climbing abilities for the first time.

Their device uses a loop of rope, strung vertically around two pulleys and driven by a motor, to keep the lemurs and lorises in the study climbing in one place.

Putting a box around each animal while on the treadmill allowed them to measure oxygen consumption and estimate their energy expenditure.

They calculated that, for each kilo of bodyweight, it took about the same amount of energy to climb, for all the primates – from the mouse-sized slender loris to the 1.5-kilogram mongoose lemur.

Data from an earlier study of rock climbers suggests that people also use about the same amount of energy, kilo for kilo, as the other primates.

Biological constant

The team also found that, for the smaller primates of 0.5 kg and under, walking and climbing took the same amount of energy. You would think that it would cost more energy to go up, rather than to walk, Hanna says. “It certainly does with humans.”

“We expected the same thing with small primates,” she adds. “But it turned out they didn’t use more energy, so it was counterintuitive.”

It had been thought that when early primates evolved to exploit unused food niches, such as the small twigs at the tips of branches, they were paying an energetic cost to do so.

Not so, says Hanna. Once primates evolved to have grasping paws, rather than claws like squirrels have, they could bound up into trees more easily than larger animals.

“They have hit on a fascinating constant in biology: energy efficiency during climbing is the same for all animals regardless of size,” says of Washington University in St. Louis, US. “This is really interesting, since nearly everything in biology is affected by an animal’s size.”

Journal reference: , DOI: 0.1126/science.1155504

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