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

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

Podcast: Soundscape of the deep ocean

A new form of bioengineering ditches the cell and could speed up innovation. Five…Continue reading
Source: Economist

Cell-free biotech will make for better products

THE stuff of life comes wrapped in tiny bags called cells. Inside are DNA molecules that carry the instructions for how to run the cell, to make it grow, and to cause it, ultimately, to divide into two cells, if that is to be its fate. Messages made of a slightly different molecule, RNA, carry these instructions to molecular machines called ribosomes. A ribosome’s job is to read the RNA messages and translate them into proteins, the workhorse molecules of cells. Those proteins then supervise and execute the running, the growing and the dividing.

It is a system that has worked well over the 4bn years that life has existed on Earth. To some biotechnologists, though, the cell is old hat. They approve of the machinery of DNA, RNA, ribosomes and proteins, which can be engineered to make useful chemicals, ranging from drugs to the building-blocks of plastics. But they want to get rid of the bags that contain it, retaining only the part of the protoplasmic “gloop” inside a cell needed to do their bidding.

In this way they hope to control, far more precisely than is possible by conventional genetic engineering (or even by improved methods of gene modification,…Continue reading
Source: Economist

How to build an artificial womb

Sheep may safely laze

THESE days, in rich countries, premature birth is the main cause of infant mortality. A baby born at 23 weeks—just over half way through a normal pregnancy—has a fighting chance of survival. But underdeveloped lungs struggle to cope with breathing air. External pumps used to circulate blood impose potentially fatal stresses on tiny hearts. Those that do pull through are often left with lifelong problems that range from brain damage to blindness. In a paper just published in Nature Communications, a team of doctors at the Children’s Hospital of Philadelphia, led by Alan Flake, describe an artificial womb that, they hope, could improve things dramatically, boosting the survival rate of the most premature babies while reducing the chance of lasting disabilities.

The device, which looks a bit like a high-tech jiffy bag, is designed to mimic a real womb as closely as possible (see picture above, of a fetus after 28 days in the artificial womb). The fetus—a lamb in the team’s trials—is surrounded in a substitute for the amniotic fluid that keeps the animal’s lungs filled with liquid in a real uterus….Continue reading
Source: Economist

Spyware that can identify what films you are watching

We know what you’re doing

REMEMBER that racy film you probably should not have enjoyed on Netflix last weekend? Eran Tromer’s algorithms can tell what it was. Although videos streamed from services such as Netflix, Amazon and YouTube are encrypted in various ways to ensure privacy, all have one thing in common: they leak information. Dr Tromer, of Tel Aviv university, his colleague Roei Schuster and Vitaly Shmatikov of Cornell have worked out how those leaks can identify the film you are watching—even if they cannot directly observe the stream of bits delivering it, or obtain access to the device on which you are watching it.

Videos streamed over the internet are usually transmitted using a standard called MPEG-DASH. This chops a data stream up into segments that are then encrypted and fetched one at a time by the machine playing the video. The result is an on-off, “bursty” pattern of data arrival. But not all segments are equal. One depicting the mating habits of sloths will contain less information than another showing a car chase. Streaming services use something called variable bit-rate (VBR) compression to take advantage of this….Continue reading
Source: Economist

The first humans in America may not have been Homo sapiens

WHEN did the first human beings arrive in the Americas? Though there are arguments about the details, the consensus is that it was around 15,000 years ago, when retreating glaciers at the end of the last ice age permitted travellers from Asia to cross what is now the Bering strait but was then dry land.

This makes sense. The evidence suggests that, recent migrants from Africa and their progeny aside, people now alive in Asia, Australia, Europe and the Americas are descended from a handful of Africans who left the continent of their birth about 70,000 years ago. This fits nicely with the conventional date for America’s colonisation, by giving time for the heirs of these African émigrés to make it to eastern Asia, ready for the hop to the New World when conditions permitted.

What, then, to make of a discovery, reported in this week’s Nature, by Thomas Deméré of the San Diego Natural History Museum and his colleagues? They have just dated an archaeological site found in California in 1992, which seems to be a place where human beings used stone tools to dismember a mastodon, a now-extinct type of elephant. Unfortunately for existing theories, the…Continue reading
Source: Economist

Plastic-eating caterpillars could save the planet

MOST scientific research follows a logical progression, with one experiment following up on the findings of another. Every now and then, however, serendipity plays a part. Such is the case with a paper just published in Current Biology, which reveals to the world a moth that is capable of chewing up plastic.

The experiment behind the paper was inspired when Federica Bertocchini, an amateur beekeeper who is also a biologist at Cantabria University, in Spain, was looking at some of the honeycombs in her hives and noticed caterpillars chewing holes through the beeswax and lapping up the honey. Such pests are not uncommon, so to be certain of what she was dealing with, she collected some of the caterpillars and took them home in a plastic shopping bag for subsequent examination. She assumed the larvae would be unable to escape from this bag, but she was wrong. When, a few hours later, she got around to looking at her captives she found the bag pierced by holes and the caterpillars roaming around her house.

After rounding them up, she identified them as the larvae of the greater wax moth, a well-known pest of bee hives. On considering their escape from their…Continue reading
Source: Economist