A way to make water potable using carbon dioxide

THE world’s thirst for clean drinking water is vast and growing. It is also unslaked, particularly in poor countries. The World Health Organisation estimates that more than 660m people rely on what it calls “unimproved” water sources. A quarter of this is untreated surface water. Moreover, even water that has undergone at least some treatment may not be potable. Across the planet, 1.8bn human beings drink water contaminated with faeces. All this polluted water spreads diseases such as cholera, dysentery and typhoid. Every year, more than half a million people die from waterborne diarrhoea alone. As they describe in a paper in Nature Communications, however, Howard Stone of Princeton University and his colleagues have an idea for a new and cheap way to clean water up by mixing it with a substance normally regarded as a pollutant in its own right—carbon dioxide.

There are many existing ways to make water safe to drink, but each has drawbacks. The…Continue reading
Source: Economist

Cheap illumination’s benefits in remote areas may be limited

But will it help him learn?

FOR sunny places not connected to the electricity grid, the falling price of solar panels and LED lighting promises a bright future. No more smoky, lung-damaging kerosene lamps. Greater security and safety. More ways to connect with the world—even if that involves only something as simple as being able to charge a mobile phone. And, above all, the chance to work or study into the evening and thus improve both a family’s immediate economic circumstances and its children’s future prospects. It is a tale of hope. But as a study just published in Science Advances, by Michaël Aklin of the University of Pittsburgh and his colleagues, shows, these potentially glowing benefits can in some cases amount to not very much at all.

More than 1bn people around the world have no access to electricity. Providing them with off-grid solar power is something almost all development experts agree is A Good Thing. Yet the…Continue reading
Source: Economist

A large-scale cyber-attack highlights the structural dilemma of the NSA

IN BRITAIN, doctors could neither access their patients’ files nor make appointments to see those patients. In Russia, hundreds of the interior ministry’s workers sat idle. In China, students were locked out of their theses. As the latest cyber-attack rippled around the globe, infecting at least 45,000 computers in 74 countries, according to Kaspersky Labs, a Russian cyber-security firm, it seemed for a moment that the world was facing digital apocalypse. In the event, catastrophe was averted when somebody found a kill switch, which stopped the malicious software involved spreading further. The attackers will still make a pretty penny, however, and untold hours will have to be spent cleaning up the mess. What is more galling than that is that all of this was entirely avoidable.

From the victims’ perspective, the Great Cyber Attack of May 12th was a typical, if widespread, example of extortion by “ransomware”, to which users of…Continue reading
Source: Economist

A large-scale cyber attack highlights the structural dilemma of the NSA

IN BRITAIN, doctors could neither gain access their patients’ files nor make appointments to see those patients. In Russia, hundreds of the interior ministry’s workers sat idle. In China, students were locked out of their theses. As the latest cyber attack rippled around the globe, infecting at least 45,000 computers in 74 countries, according to Kaspersky Labs, a Russian cyber-security firm, it seemed for a moment that the world was facing digital apocalypse. In the event, catastrophe was averted when somebody found a kill switch, which stopped the malicious software involved spreading further. The attackers will still make a pretty penny, however, and untold hours will have to be spent cleaning up the mess. What is more galling than that is that all of this was entirely avoidable.

From the victims’ perspective, the Great Cyber Attack of May 12th was a typical, if widespread, example of extortion by “ransomware”, to which users of…Continue reading
Source: Economist

A self-repairing surface that stays clean and dry

THE repulsive powers of lotus leaves are the stuff of legend. Water sprayed onto them forms instantly into silvery beads (see picture) and rolls right off again—carrying any dirt on the leaf’s surface with it.

The physics behind this impressive and beautiful phenomenon is well understood. Lotus leaves repel water because they are covered with minuscule waxy nodules that stop water molecules bonding with a leaf’s surface tissues, meaning those molecules bond with each other instead. That arrangement has been replicated in several man-made materials. Unfortunately, these are easily damaged by abrasion—and, not being alive, cannot regrow and repair themselves. They are thus hard to commercialise, which is a pity, because the self-cleaning, self-drying surfaces they create could be of great value. A technique just described in Langmuir by Jürgen Rühe of the University of Freiburg, in Germany, may, however, fix this problem by giving lotus-like materials the…Continue reading
Source: Economist

Why AI researchers like video games

LAST year Artur Filipowicz, a computer scientist at Princeton University, had a stop-sign problem. Dr Filipowicz is teaching cars how to see and interpret the world, with a view to them being able to drive themselves around unaided. One quality they will need is an ability to recognise stop signs. To that end, he was trying to train an appropriate algorithm. Such training meant showing this algorithm (or, rather, the computer running it) lots of pictures of lots of stop signs in lots of different circumstances: old signs and new signs; clean signs and dirty signs; signs partly obscured by lorries or buildings; signs in sunny places, in rainy places and in foggy ones; signs in the day, at dusk and at night.

Obtaining all these images from photo libraries would have been hard. Going out into the world and shooting them in person would have been tedious. Instead, Dr Filipowicz turned to “Grand Theft Auto V”, the most recent release of a well-known series of video games. “Grand Theft…Continue reading
Source: Economist

Modern violins are better than 300-year-old ones

Goodbye to old times?

FOR a work of art by a genius, $16m might not seem an outrageous price. And that is what is believed to have been paid, in 2012, for the Vieuxtemps Guarneri—a violin made in the 18th century, in Cremona, Italy, which thus became the most expensive fiddle in the world. The Vieuxtemps’s owner remains anonymous, but he or she has made it available for life to Anne Akiko Meyers, an American violinist pictured playing it.

Violins crafted by members of the Guarneri family and their Cremonese contemporaries, the Stradivari and the Amati, regularly fetch millions, because players like Ms Meyers value them so highly. But a violin is not, by itself, a work of art. It is, rather, a means of creating one—in other words, a piece of technology. An instrument. And for an instrument to be worth that much, it had better be the best in its class.

Unfortunately for the shades of Cremona’s master luthiers, evidence is growing that their…Continue reading
Source: Economist

How to protect women against both HIV and pregnancy

Ringing the changes

PLENTY of progress has been made in the fight against AIDS. Deaths peaked in 2005, at around 2m people. By 2015 that number had fallen to 1.1m. One big reason is that, of the 36.7m people currently infected with HIV, 18.2m are taking antiretroviral drugs that can hold the virus back for decades. Their number has risen more than twentyfold since the turn of the century.

But not all the statistics are so encouraging. Around 1.9m adults contracted HIV in 2015. That number has hardly budged since 2010. The great bulk of those infections, about 1.3m in 2015, happen in sub-Saharan Africa. They happen more often to women than to men: 58% of HIV-infected people in the region are female. Women between 15 and 24 are infected at almost eight times the rate of men of the same age.

There are several reasons why women contract HIV more often than men. Some are biological: women have a higher chance of contracting HIV from a given act of unprotected sex than men do. But cultural factors matter too, especially in poor countries. As in other aspects of society, it is often men who call the shots in the bedroom. Even if a woman…Continue reading
Source: Economist

The link between pollution and heart disease

WHY air pollution causes lung disease is obvious. Why it also causes heart disease is, though, a conundrum. One suggestion is that tiny particles of soot migrate through the lungs, into the bloodstream and thence to the walls of blood vessels, where they cause damage. Until now, this has remained hypothetical. But a study published in ACS Nano, by Mark Miller of Edinburgh University, suggests not only that it is correct, but also that those particles are specifically carried to parts of blood vessels where they will do maximum damage—the arterial plaques associated with cardiovascular disease.

One reason the particle-migration hypothesis has proved hard to confirm is that it is tricky to follow soot around the body. Soot is made of carbon, and that element, when finely divided and at low concentration, is difficult to isolate in biological material. Instead, Dr Miller and his colleagues used soot-sized particles of gold for their experiments. These are easy to detect, even at low concentrations, by means such as mass spectroscopy and Raman spectroscopy. Also, gold is chemically inert and therefore unlikely to be toxic. This is important, because…Continue reading
Source: Economist

Tourists really do seem to help to preserve wild animals

WHICH countries have the best wildlife-conservation records? That was the question posed by a group of biologists led by Peter Lindsey of the University of Pretoria, in South Africa. Their conclusions, just published in Global Ecology and Conservation and summarised in the map below, suggest one determinant is the economic value of wildlife to a country, with nature-tourism destinations in east, central and southern Africa, led by Botswana, dominating the list of high performers.

The team looked at megafauna, defined as terrestrial mammals weighing 15kg or more as adults, if carnivores, or 100kg or more, if herbivores or omnivores. For each of 152 countries examined, they constructed a megafauna-conservation index composed of three elements. The first was, for every relevant species, the fraction of the country it inhabited. The second was the percentage of megafauna habitat which had legal protection. The third was the percentage of GDP a country devoted to…Continue reading
Source: Economist