Bombs that can recognise their targets are back in fashion

---

IT IS easy to forget, given the ubiquity of satellite-navigation devices in cars and mobile phones, that the Global Positioning System (GPS) of orbiting satellites on which they rely was originally—and, indeed, remains—a military technology. The system is, for instance, relied upon by the JDAM (joint direct-attack munition) kits that America’s air force attaches to its free-fall bombs to turn them into smart weapons that can be guided with precision to their targets. 

But JDAM and similar systems work only when they can receive signals from GPS satellites. And such signals are weak—approximately as powerful as a standard television transmission would be if the transmitter were five times as far away as the Moon is. They are thus easily jammed. For obvious reasons, details of the capabilities of jammers are hard to come by, but a Russian system called Pole-21, for instance, may be able to suppress GPS signals as much as 80km (50 miles) away.

One way to get around this—and to guide weapons automatically to their targets without relying on satellites—is to give weapons a map. That has been done in the past. The cruise-missile…Continue reading
Source: Economist

Why disrupted body clocks trigger liver cancer

---

DRINKING too much and eating too much are both good ways of getting liver cancer. But there is a third. The disrupted circadian rhythms caused by working shifts or crossing time zones also seem to induce the disease. Precisely how and why meddling with day and night cycles has such a dire effect on the liver remains an enigma, but a study just published in Cancer Cell by Loning Fu and David Moore at the Baylor College of Medicine, in Texas, sheds some light on the matter.

Among the liver’s many jobs is making bile, a substance secreted into the intestine to break down the fats and oils in food. One of bile’s main components is bile acid, a derivative of cholesterol. Dr Fu and Dr Moore knew from their previous research that disrupting the circadian rhythms of mice causes the rodents’ livers to overproduce this substance. They also knew that liver cancer commonly appears in mice engineered to lack certain genes required for the management of day-night cycles. This led them to suspect a link between liver cancer and too much bile acid. To take a closer look, they set up an experiment.

Working with a team of colleagues, the two researchers…Continue reading
Source: Economist

Machines are learning to find concealed weapons in X-ray scans

---

EVERY day more than 8,000 containers flow through the Port of Rotterdam. But only a fraction are selected to pass through a giant x-ray machine to check for illicit contents. The machine, made by Rapiscan, an American firm, can capture images as the containers move along a track at 15kph (9.3mph). But it takes time for a human to inspect each scan for anything suspicious—and in particular for small metallic objects that might be weapons. (Imagine searching an image of a room three metres by 14 metres crammed to the ceiling with goods.) To increase this inspection rate would require a small army of people.

A group of computer scientists at University College London (UCL), led by Lewis Griffin, may soon speed up the process by employing artificial intelligence. Dr Griffin is being sponsored by Rapiscan to create software that uses machine-learning techniques to scan the x-ray images. Thomas Rogers, a member of the UCL team, estimates that it takes a human operator about ten minutes to examine each X-ray. The UCL system can do it in 3.5 seconds.

Dr Griffin’s team trained its system on…Continue reading
Source: Economist

Ocean acidification: a natural experiment

---

GLOBAL warming is not the only environmental change that is being wrought by rising emissions of carbon dioxide. This gas, acidic when dissolved in water, is also lowering the pH of the world’s sea water—a phenomenon known as ocean acidification.

How much to worry about this acidification (or, strictly, reduction in alkalinity, for there is no risk of the sea actually becoming acidic) is a matter of debate. The threat most talked of is to creatures that make shells out of calcium carbonate. As school chemistry experiments with chalk and vinegar demonstrate, calcium carbonate dissolves in acid, so an ocean less alkaline than it used to be might make life harder for shell-forming animals. Numerous laboratory experiments agree. There is also evidence that the shells of several widespread marine species are thinner and weaker now than they were a few decades ago. What there has not been, though, is a controlled study in the wild—at least, not until now.

The gap has been plugged by Miles Lamare of the University of Otago, in New Zealand, and his colleagues, who have just published their study…Continue reading
Source: Economist