Magnetic moments

A CLASSIC experiment beloved of scientifically inclined children is to cover a magnet with a piece of paper and sprinkle iron filings onto the paper. This reveals the field lines that connect the magnet’s north and south poles. Try something similar with some of the new types of magnets now being made using additive manufacturing (3D printing), and a rather different image might appear. Unlike the simple bars and horseshoes of children’s magnets, the 3D-printed variety can be made in all manner of shapes. Their fields can thus be tailored into patterns far more complex than a simple north-south alignment. 

These unconventional magnets have huge value in the design and performance of many products that rely on magnetic components: from hospital body-scanners to audio speakers, and from hard disks to wind turbines. In particular, anything that involves an electric motor or a generator also uses magnets. A modern car, for instance, contains a hundred or more electric motors of various sorts, to open and close the windows, adjust the seats, run the heating and, increasingly, to turn the wheels. All require magnets to make them work. The unconventional…Continue reading
Source: Economist

Where’s the catch?

ABOUT 90% of the world’s fish stocks are being fished either to their limit or beyond it. Monitoring fish numbers reliably, though, is no easy matter. Official catch data are often incomplete and sometimes untrustworthy. Moreover, large tracts of the sea are not monitored at all. In order to know which species to conserve, and where, it would be handy to be able to establish fish numbers cheaply and reliably. Now, as they write in PLOS ONE, Philip Thomsen of the Natural History Museum of Denmark, in Copenhagen, and his colleagues think they have taken a step towards this goal.

Scientific surveys of deepwater fish are often carried out by trawling the ocean bed. This means towing a net over a set distance and then hauling it up to count the catch within. That, when due allowance is made for the size of the net’s mouth, yields a figure for the number of each fish species per square kilometre.

Every year a research vessel called Paamiut carries out surveys of this sort in the Davis Strait off south-west Greenland. This year it also had one of Dr Thomsen’s colleagues on board. At each of the 21 places Paamiut dropped her nets, he collected two litres of seawater from the bottom. The team’s aim was not to sample sea life directly, but rather to examine the fragments of floating DNA…Continue reading
Source: Economist

Not so lonely sea in the sky

A great hole in Pluto

IS THE solar system about to get another ocean? So far, besides Earth, six bodies are known or suspected to harbour oceans. These are Europa, Callisto and Ganymede (all moons of Jupiter), Enceladus and Titan (both moons of Saturn) and Triton (a moon of Neptune). The latest candidate is Pluto, the most famous inhabitant of the Kuiper belt, a girdle of asteroids that orbit the sun beyond Neptune.

Pluto’s claim to an ocean, argued this week in two papers published in Nature, is based on data collected in 2015 by New Horizons, a robotic spacecraft that zoomed past it in July of that year. The ocean in question, if it exists, is beneath Pluto’s surface. That makes it unlike Earth’s ocean, but like those of the other six bodies. To human sensibilities that is, perhaps, a funny sort of ocean. But add it to the other six and it is Earth’s surface ocean that looks anomalous, rather than Pluto’s buried one.

The argument for a Plutonic ocean—advanced by teams led by Francis Nimmo of the University of California, Santa Cruz, and James Keane, of…Continue reading
Source: Economist

The biter bit

KILLING mosquitoes of the genus Anopheles, the sort that transmit malaria, is a serious business—so serious that some doctors would like to do it by using people as bait. Their idea is to dose those in malarious areas with a drug called ivermectin. This will not protect the dosees directly, for it does not act on the parasite that causes the disease. But it may protect them indirectly, by making their blood poisonous to Anopheles. Mosquitoes do not tend to fly far from the place they hatch, and experiments suggest that if most of a village’s inhabitants were to take ivermectin they could collectively do serious damage to the local Anopheles population. That would substantially reduce the number of cases of malaria in an area.

Whether this is ethical is debated. Ivermectin is used routinely to treat filariasis, river blindness, scabies and several other diseases. But drugging healthy people is generally frowned on. At the moment, though, there is a more practical objection. Ivermectin does not hang around in the body long enough to make a concerted…Continue reading
Source: Economist

No news like fake news

Source: Economist

The year of your birth affects your resistance to flu

WHEN it comes to infectious diseases, Ebola and Zika have hogged the headlines of late. But the rise of exotic pathogens does not make more familiar ones less dangerous. Epidemiologists are therefore keeping a close eye on two versions of influenza, known as H5N1 and H7N9 (the “H” and the “N” refer to proteins in the viral coat, and the numbers to particular versions of those proteins). Either of these, they fear, might become pandemic.

Such an outbreak is the sort of thing that keeps doctors awake at night. Between 1918 and 1920, pandemic “Spanish” influenza killed somewhere between 50m and 100m people. Both H5N1 (detected in 2003) and H7N9 (which came to doctors’ attention in 2013) have already caused hundreds of severe or fatal cases of flu. That neither has yet become pandemic is because, in almost all of these cases, the responsible virus was transmitted to its human victim directly from an avian host such as a duck. So far, neither H5N1 nor H7N9 has evolved the ability to hop easily between people. But this might yet happen. Hence the vigilance. And one result of that vigilance is that researchers have noticed an odd pattern among…Continue reading
Source: Economist

Earth’s plants are countering some of the effects of climate change

A feast in the air

IN 1972, on their way to the Moon, the crew of Apollo 17 snapped what would become one of the most famous photographs ever taken. The “Blue Marble” shows Earth as it looks from space: a blue sphere overlaid by large brown swatches of land, with wisps of white cloud floating above.

But times change, and modern pictures of Earth look different. A wash of greenery is spreading over the globe, from central Africa to Europe and South East Asia. One measurement found that between 1982 and 2009 about 18m square kilometres of new vegetation had sprouted on Earth’s surface, an area roughly twice the size of the United States.

The growth in greenery is a consequence of climate change. As the planet heats up, places that were once too chilly for most plants to grow have become steadily more hospitable. That extra vegetation, in turn, exerts its own effects on the climate. According to a team led by Trevor Keenan of the Lawrence Berkeley National Laboratory, in California, who have just published their findings in Nature Communications, the plant growth caused by climate change…Continue reading
Source: Economist

How to enrol your dog in a cancer-drug trial

An idea with legs

DRUG development is a risky—and costly—business. Many promising compounds fail to cut the mustard when put through clinical trials. One reason is that drugs which work on laboratory animals may not work quite so well in human tests. Being able to pick winners and losers as early as possible would save money, and the One Health Company, based in Philadelphia, thinks it may have found a way. It is offering to help pharmaceutical firms test their wares on sick pets. Its first guinea pigs, as it were, will be dogs suffering from cancer.

There are several benefits, says the firm. By treating animals with existing cancers, it hopes to dodge a problem with modern animal research, which is that the “model” animals and diseases that are used to test drugs are not always good stand-ins for the natural illness. For example, mice used to test cancer drugs may have had their tumours grafted surgically into their bodies, and their immune systems knocked out with drugs or by genetic engineering.

Another plus is that pet owners tend to be dedicated carers who are very knowledgeable about their four-legged…Continue reading
Source: Economist

A bet about a cherished theory of physics may soon pay out

IN 1994, on a warm summer’s evening in Erice, in Sicily, in the midst of a pleasantly well-lubricated dinner, two physicists made a wager on the laws of nature. The bet between Kenneth Lane and David Gross concerned supersymmetry, or “Susy” for short, a theory which stipulates that all known fundamental particles have heavier, supersymmetric counterparts called sparticles.

When the bet was laid, no sparticles had been spotted. Yet plans for a powerful particle accelerator called the Large Hadron Collider (LHC) were being drawn up. Dr Lane proposed that if the new machine found evidence for the theory, he would buy the table dinner at Girardet’s, an expensive restaurant in Switzerland considered by some the best in the world. If not, then dinner would be on Dr Gross. The terms, scribbled on a napkin, stipulated that the bet would be payable once the LHC had produced enough data to be sure of the outcome. The chosen figure, in the obscure units used by physicists, was 50 inverse femtobarns, or roughly 5 quadrillion of the high-energy collisions between particles that the LHC is designed to produce.

Two decades on, Girardet’s is no…Continue reading
Source: Economist

Hunting submarines with magnets

SUBMARINES rely on stealth to do their jobs, whether that is sinking enemy ships or hiding nuclear-tipped missiles beneath the ocean. The traditional way of hunting them is with sonar. Modern sonar is extremely sensitive. But modern submarines are very quiet, and neither side has gained a definitive upper hand.

There are other options. Submarine-spotting aircraft carry “magnetic anomaly detectors” (MAD) which pick up disturbances in the Earth’s magnetic field caused by a submarine’s metal hull. Those disturbances are tiny, which means MAD is only useful at ranges of a few hundred metres.

There may, though, be a better way. Thanks to something called the Debye effect, it might be possible to hunt submarines using the magnetic signatures of their wakes. Seawater is salty, full of ions of sodium and chlorine. Because those ions have different masses, any nudge—such as a passing submarine—moves some farther than others. Each ion carries an electric charge, and the movement of those charges produces a magnetic field.

The Debye effect has been known since 1933, but its effects were thought to be tiny. The American navy set…Continue reading
Source: Economist