Research Highlights

Our pick of the latest scientific literature

People and birds in front of the Basilica di San Marco, Venice.

Sediment collected from under St Mark’s Basilica in Venice, Italy, reveals details of the city’s birth. Credit: Fabrizio Bensch/REUTERS

Archaeology

Peach stones reveal the origins of Venice

Insight into how and when the Italian city was built come from an unlikely source.

Peach stones recovered from beneath St Mark’s Basilica in the Italian city of Venice have helped to dispel persistent myths about the famous city’s origins.

Albert Ammerman at Colgate University in Hamilton, New York, and his colleagues discovered two peach stones in a sediment core taken from below the cathedral. The sediment was used to fill in canals when people built the city on marshland. When exactly that happened, however, has long eluded researchers because of a lack of documents or archaeological evidence before ad 800. The stones contain a high level of carbon-14, and because there were two right next to each other, the researchers could validate the results and date them with unusual confidence, to between ad 650 and 770.

Together with wood, glass and an animal bone found in other cores extracted from St Mark’s Square, the peach-stone dating indicates that, unlike many of Italy’s other great cities, Venice does not have roots in Roman times, which ended by the fifth century ad.

Specks of catalyst invisible to the human eye are sprinkled on a copper grid for imaging under a microscope.

​​​​​​​Specks of catalyst invisible to the human eye are sprinkled on a copper grid for imaging under a microscope. Credit: EMSL/Pacific Northwest Laboratories

Materials science

Steam-powered catalyst is a cool cleaner

Material can scrub carbon monoxide from low-temperature vehicle exhaust.

A blast of steam can transform a ceramic into a highly effective material for scrubbing pollution from vehicle exhaust gases.

Today’s best catalytic converters operate only when heated to about 250 °C by engine exhaust, and the emissions of more-fuel-efficient vehicles are expected to be much cooler. Abhaya Datye at the University of New Mexico in Albuquerque, Yong Wang at the Pacific Northwest National Laboratory in Richland, Washington, and their colleagues made a catalyst from cerium oxide studded with individual platinum atoms. After the ceramic was exposed to super-heated steam, the catalyst converted all of the carbon monoxide in an exhaust sample to carbon dioxide; it was able to do this for exhaust heated to only 148 °C.

The catalyst also functioned well when heated to 800 °C — the sort of temperature it could be subjected to if a vehicle were straining uphill or a driver were gunning the motor.

Genetic variation helps to determine a person’s response to hundreds of drugs that act on cell-surface proteins.

Genetic variation helps to determine a person’s response to hundreds of drugs that act on cell-surface proteins. Credit: Simon Dawson/Bloomberg/Getty

Cell biology

DNA dictates response to common drugs

Genes affect the shape of proteins targeted by medications.

Variations in genes encoding cell-surface proteins affect how different people respond to common drugs.

About one-third of drugs approved for use in the United States target G-protein-coupled receptors (GPCRs), cell-surface proteins that receive signals from the body and convey directions into the cell. To investigate why people respond differently to drugs targeting these receptors, Alexander Hauser and Madan Babu at the MRC Laboratory of Molecular Biology in Cambridge, UK, and their colleagues analysed genomic data from some 60,000 healthy people. They focused on 108 genes that code for GPCRs targeted by drugs and found that the genes’ sequences differ widely between individuals. Some of this variation affects the shape of the receptors, which can make it more difficult for drugs — such as opioids — to bind to them. 

The authors set up an online database of GPCR variations and say that screening patients’ genomes could allow for more targeted treatments.

The loosely draped skin of this Pacific hagfish (Eptatretus stoutii) and its kin protects its internal organs from the jaws of predators. Credit: Tom McHugh/SPL

Zoology

Baggy skin keeps hagfish safe from danger

Slimy fish’s flaccid covering protects it from predators.

Even a shark bite can’t damage the vital organs of a slimy scavenger called a hagfish, thanks to the fish’s loosely attached, flaccid skin.

After a chomp from a hungry predator, hagfish emit a cloud of goop that repels foes. To find out how a hagfish survives the initial attack, Douglas Fudge at Chapman University in Orange, California, and his colleagues fastened a mako-shark tooth to a makeshift guillotine and plunged it into fresh corpses of both Pacific and Atlantic hagfish (Eptatretus stoutii and Myxine glutinosa, respectively) and the closely related, but taut-skinned sea lamprey (Petromyzon marinus). 

The flexibility of the hagfish’s skin allowed its innards to slip away from the tooth when the skin was punctured. The lamprey suffered a bloodier fate: in every test, its muscle was punctured. The finding showcases the versatility of the hagfish’s saggy skin, which also allows the animal to tie itself in knots and burrow into the sand and mud.

Even the 1.2-metre-tall Emperor penguin is smaller than a newly discovered penguin species that lived some 60 million years ago.

Even the 1.2-metre-tall Emperor penguin is smaller than a newly discovered penguin species that lived some 60 million years ago. Credit: Paul Souders/Getty

Palaeontology

Ancient mega-penguin reached human height

Species’ discovery reveals that giant penguins evolved more than once.

An enormous species of penguin that stood as tall as a human roamed the waters of New Zealand some 60 million years ago, shortly after its first flightless predecessors appeared.

Gerald Mayr at Senckenberg Research Institute and Natural History Museum Frankfurt in Germany and his colleagues analysed the fossilized remains of a giant extinct penguin (Kumimanu biceae) discovered in the Moeraki Formation in Otago, New Zealand. The team estimates that the bird was 1.77 metres tall and weighed more than 100 kilograms, making it one of the largest penguins ever to have lived.

The scientists fitted the new species into the penguin evolutionary tree and found it emerged soon after the first penguins traded flying for diving. Smaller species appear later in the fossil record, before the emergence of modern giants such as the 1.2-metre-tall Emperor penguin (Aptenodytes forsteri), indicating that gigantic size has evolved more than once in these birds.

Latte showing banded layers.

Technique, not espresso quality, conjures up the stripes in a glass of latte. Credit: Pixabay (CC0)

Physics

How warm milk generates latte layers

High-speed espresso injection creates that banded look.

It takes a quick pour to create the stripes in a layered latte.

When a barista makes a latte, distinct horizontal layers sometimes form as the espresso settles into the denser milk. To investigate this process, Howard Stone of Princeton University in New Jersey and his colleagues ran computer simulations and experiments that involved injecting warm dyed water into denser salt water. They found that if espresso is injected fast enough into a glass of warm milk, the espresso–milk mixture closest to the wall of the glass cools, becomes denser and sinks until it reaches a layer of the same density. At that point, it stops sinking and begins to circulate horizontally, forming multiple convection cells that can retain their structure for hours.

The team demonstrated a way to use this technique to create layered gels that could be useful for cell cultures. The method could also be applied in manufacturing and tissue engineering, the authors write.

DREADD-based activation of MSc vGluT2 neurons.

Mice become dainty eaters after a subset of brain cells (left, bright red) is activated (right, red and blue). Credit: Sweeney, P. <i>et al.</i> <i>Proc. Natl Acad. Sci USA</i> http://dx.doi.org/10.1073/pnas.1707228114 (2017).

Neuroscience

Appetite drops off after brain region fires

Brain cells linked to emotion also affect food intake.

Mice lose their appetite in response to activation of a brain area that is involved in emotion and cognition.

Eating is prompted, in part, by brain regions that help to maintain the body’s energy levels. But hunger pangs are not the only motivation for a trip to the snack bar. In an effort to understand how the brain’s emotional and cognitive machinery influences appetite, Yunlei Yang and his colleagues at the State University of New York Upstate Medical University in Syracuse examined the medial septal complex, a group of brain cells that has a role in emotion.

Some of the complex’s cells produce a signalling chemical called glutamate. When the scientists turned on these glutamate-producing cells in mice, the animals ate less than half as much as control mice. That makes the region a good starting point for studies of emotionally triggered eating, the team says.

Wind turbines spin in Wyoming, but warming could markedly cut wind-energy potential in the region.

Wind turbines spin in Wyoming, but warming could markedly cut wind-energy potential in the region. Credit: Pete McBride/Getty

Climate change

​​​​​​​Warming could foil wind energy

​​​​​​​How winds might change should be considered in energy planning.

Global warming could alter the way air moves around the world, ultimately affecting one of the most popular means of generating clean energy: wind turbines.

Kristopher Karnauskas and his colleagues at the University of Colorado Boulder used ten global climate models to explore how winds might change in two warming scenarios. Their results suggest that, in both low- and high-emissions scenarios, wind resources will decrease across the northern mid-latitudes, mainly as a result of weather patterns associated with accelerated warming in the Arctic. In the Southern Hemisphere, high emissions see wind resources increase on average, because of temperature differentials over land and sea. The effects vary by location, however.

The results indicate that energy planners can’t assume the wind available for electricity generation will remain constant over time, and could help to guide more detailed local and regional analyses. 

Gene therapy

A CRISPR system to turn genes on 

New technique modifies gene expression instead of actual DNA.

A modified version of the genome-editing tool CRISPR–Cas9 has reversed disease symptoms in mice by activating genes.

In typical CRISPR editing, small molecules called guide RNAs bind to a specific DNA sequence in the genome and recruit an enzyme, Cas9, to slice DNA’s double helix. The break allows DNA to be altered, but also opens the door to unwanted mutations — a hurdle for using CRISPR in medicine.

Juan Carlos Izpisua Belmonte of the Salk Institute for Biological Studies in La Jolla, California, and his colleagues modified CRISPR so that it could recognize DNA sequences but not cut them. Instead, the Cas9 enzyme carries a genetically engineered molecular ‘switch’ that turns on the target genes. The researchers tested the system in mice with diabetes, muscular dystrophy or kidney injury. It successfully switched on genes that reversed symptoms — increasing insulin production to battle diabetes, for instance — suggesting that it could eventually prove to be a viable therapy for humans.

Neuroscience

How the brain says ‘stop!’

Coordinated action needed to call a halt.

The split-second decision to stop or change an action that is already underway depends on the coordination of two brain regions — not one, as previously thought.

Susan Courtney at Johns Hopkins University in Baltimore, Maryland, and her colleagues asked people to move their eyes when a circle appeared on a screen. After a short delay, study participants got a signal to either stop or proceed with the eye movement. Those who received the stop signal 100 milliseconds after the circle appeared succeeded in stopping their eye movement more than 75% of the time. But when the signal occurred after 200 milliseconds, the success rate dropped to 50%, illustrating the difficulty of abandoning an action.

By observing brain activity in humans and a rhesus macaque (Macaca mulatta), the team found that successful stopping required coordinated action of the premotor cortex and two areas of the prefrontal cortex. Understanding how people stop or fail to stop actions could help to explain addictive behaviour, the authors say.

Hormone-based birth control pills raise risk of breast cancer.

Hormone-based birth-control pills raise risk of breast cancer. Credit: Jamie Grill/Getty

Cancer

Elevated cancer risk associated with birth control

Nationwide study finds higher rates of breast cancer with current or former use of oral contraceptives.

Women who use hormonal birth control have a higher risk of breast cancer, according to a study of nearly 1.8 million women in Denmark.

Past efforts to evaluate a link between breast-cancer risk and hormonal contraception yielded conflicting results, and often focused on older formulations of the drugs. To learn about the risk of modern birth control, Lina Mørch and Øjvind Lidegaard at the University of Copenhagen and their colleagues analysed data collected from 1995 to 2012, and adjusted for factors such as age and family history of breast cancer. 

They found that the risk of breast cancer was 20% higher in current and recent users of hormonal contraception than in those who had never used the drugs. Risk was lower when birth control was used for less than one year, compared with longer use. 

Overall, the data suggested that hormonal contraceptives are linked to one additional case of breast cancer for every 7,690 women using the drugs for one year.

Gas from a star moving towards black hole

Gas from a star (left) spirals towards a black hole, a pairing similar to the V404 Cygni system. Credit: ESA/ATG medialab

Astronomy and astrophysics

A black hole’s outburst offers clues to its magnetic field

The details illuminate the formation of black-hole jets.

The first precise measurements of a black hole’s magnetic field show that it is surprisingly weak.

In June 2015, a burst of radiation was detected from a black hole in the V404 Cygni system, nearly 2,400 parsecs (7,800 light years) from Earth. Yigit Dallilar and Stephen Eikenberry at the University of Florida in Gainesville and their colleagues used multiple telescopes to observe the flare, which was generated by charged particles — electrons and protons — embedded in the black hole’s magnetic field.

By measuring how quickly the flare dimmed, the team determined that the magnetic field was only about 460 Gauss, just a few times stronger than a typical bar magnet. That is orders of magnitude lower than previous estimates for similar systems.

Magnetic fields are thought to play a part in propelling the jets of charged particles observed shooting away from many black holes. The new finding will help scientists to model the conditions required for jet formation.

The Thames Beater, a fourth-century BC wooden club (top) and modern replica (bottom).

The destructive powers of the Thames Beater, a fourth-century BC wooden club (top), were tested with a modern replica (bottom). Credit: Meaghan Dyer/M. Dyer & L. Fibiger/Antiquity December 2017

Anthropology

What the ‘Thames Beater’  could do to skulls

A team tracked the source of skull fractures in prehistoric Europeans.

Damage to the skulls of some prehistoric Europeans has been linked experimentally to a specific type of weapon: the wooden club.

Numerous human skeletons from the European Neolithic period, which lasted from about 7000 to 2000 bc, bear fractures indicative of violence. Meaghan Dyer and Linda Fibiger at the University of Edinburgh, UK, sought to determine the kind of weapon that could have inflicted the injuries. They had a male assistant wield a replica of the ‘Thames Beater’ — a wooden club from the fourth century bc that was found in London’s River Thames — against multi-layered synthetic spheres designed to replicate the human head.

The cracks made by the 1.2-kilogram club closely matched those on Neolithic skulls that had evidently been crushed by human blows. The researchers say that their results are the first to link Neolithic blunt-force injuries — trauma inflicted with a non-bladed implement — to a specific weapon.

Stem cells collected from a donor

Stem cells destined for a patient with blood cancer are collected from a donor in a London hospital. Credit: In Pictures Ltd./Corbis/Getty

Stem cells

How to grow better stem cells more quickly

A new method could ease donors’ ordeal.

A new drug combination could make it easier to collect high-quality blood stem cells for medical transplants.

Blood-stem-cell transplants can help to treat cancers and other diseases of the blood and bone marrow. Typically, donors receive several injections of a drug that triggers the release of stem cells from the bone marrow into the circulation. But this multi-day process can also cause pain, nausea and even organ damage.

Jonathan Hoggatt at Massachusetts General Hospital in Boston and his colleagues tested a new drug combination in mice, and found that it produced as many stem cells in 15 minutes as the conventional treatment does over multiple days. When the team transplanted the cells into mice whose blood cells had been depleted by radiation, the mice recovered faster than those that received stem cells collected using the conventional regimen.

The researchers plan to test the drugs’ safety and efficacy in humans next.

Loggerhead turtle hatchling swimming.

A loggerhead turtle hatchling (Caretta caretta) plies the waves. Credit: Wild Wonders of Europe/Zankl/NPL

Animal behaviour

Young sea turtles show swimming skills

Junior loggerheads go against the flow to avoid being swept to shore.

Despite weighing only a few hundred grams, young loggerhead sea turtles (Caretta caretta) in the South Atlantic are able to overcome ocean currents.

Before they return to the beach to breed, young sea turtles spend years adrift in the open ocean — but these ‘lost years’ have proved difficult to study. So Katherine Mansfield at the University of Central Florida in Orlando and her colleagues attached satellite-tracking tags to 19 young loggerheads and released the animals into the Atlantic Ocean off the coast of Brazil. In the months after their release, the turtles travelled up to 4,350 kilometres. They followed seasonal currents much of the time, but would also swim against the current to avoid being swept towards shore.

Most turtles released early in the hatching season travelled south, but those released later were more likely to travel north, matching seasonal patterns in the currents. Their flexibility might help turtle populations to be more resilient to environmental change, the authors say.

Medical research

Anti-drink drug fights another deadly scourge

How an old standby for fighting alcohol dependence blitzes cancer cells.

A drug that helps people to overcome alcohol dependence cuts the risk of death from a host of cancers, including tumours of the colon, prostate and breast.

Developing new cancer drugs is costly and time-consuming. A promising alternative is to repurpose drugs that have already been approved to treat other conditions.

Jiri Bartek at the Danish Cancer Society Research Center in Copenhagen and his colleagues studied the records of people with cancer across Denmark. They discovered that individuals who continued taking disulfiram — a long-established alcohol-aversion drug marketed as Antabuse — after their cancer diagnosis had a lower risk of death than those who stopped taking the drug.

Further work showed that, in mice, disulfiram is metabolized into a molecule that immobilizes NPL4–p97, a naturally occuring protein grouping that supports tumour growth. Putting the complex out of action kills cancer cells. 

The authors highlight the p97–NPL4 pathway as a promising therapeutic target, and suggest that disulfiram, which is cheap and safe, could help in the treatment of patients whose tumours resist other chemotherapy.

It couldn’t fly, but Halszkaraptor escuilliei could both walk and swim. Credit: Lukas Panzarin

Palaeontology

A dinosaur with an unusual skill set

Fossil hints that creature swam with the help of stubby ‘arms’.

A newly identified dinosaur had flipper-like forelimbs for swimming and a swan-like neck for grabbing dinner.

Andrea Cau at the Giovanni Capellini Geological and Palaeontological Museum in Bologna, Italy, and his colleagues say that the fossil represents a new species, Halszkaraptor escuilliei. It dates to about 71 million to 75 million years ago and belongs to the family of dinosaurs that gave rise to modern birds. On land, it walked erect on two legs. The team reports that the creature could also manoeuvre itself through the water with its forelimbs, and had an elongated neck that helped it to snap up fish. Only one other dinosaur, Spinosaurus aegyptiacus has been described as water-going.

The species is the first known dinosaur that might have swum using its forearms. Its bizarre body shape, which is unlike that of anything else in its family, shows just how much dinosaur diversity may remain to be discovered, the authors say.

Coastal Indonesian village swamped by the sea

A coastal village in Indonesia is swamped by the sea, which is expected to rise by as much as 2.5 metres globally by 2100 as the world warms. Credit: Ulet Ifansasti/Getty

Climate change

A warning of greater warming on the horizon

Forecast heats up with more realistic modelling.

Global warming this century could exceed previous estimates, according to models that accurately account for energy flow at the top of Earth’s atmosphere.

Climate models generally agree that greenhouse-gas emissions will continue to raise global temperatures, but the amount of warming predicted varies considerably. Patrick Brown and Ken Caldeira at the Carnegie Institution for Science in Stanford, California, assessed a plethora of current climate models. They found that some models more accurately simulate the amount of radiation entering and leaving the atmosphere, a flow known as Earth’s energy budget, than others.

The team combined a number of models but reduced the influence of those that less realistically represent the energy budget. Their calculations reveal that, under the worst-case emissions scenario, by 2100 the planet will warm by 15% more — or about 0.5 °C — than predicted by the previous best estimate.

The researchers say that their findings strengthen the urgency of global efforts to mitigate and adapt to climate change.

Diamond tips apply pressure to a superalloy

Scientists used diamond tips to apply enormous pressure to a superconducting alloy. Credit: Max Alexander/SPL

Physics

Super-squeezing can’t crush this superconductor’s powers

Material shrugs off pressures similar to those at Earth’s core.

An exotic alloy conducts electricity when subjected to extreme pressures that would be expected to crush the material’s structure and destroy its electrical properties.

The alloy is a superconductor, a material that offers no resistance to the passage of an electrical current. Such materials are valuable for fabricating specialized magnets and other technology. But extreme pressures distort their atomic arrangements, disrupting their ability to carry current.

Liling Sun at the Chinese Academy of Sciences in Beijing, Robert Cava at Princeton University in New Jersey and their colleagues subjected samples of the alloy to pressures of up to 190 gigapascals — nearly 2 million times the atmospheric pressure at sea level — about the level in Earth’s outer core. The alloy’s superconductivity persisted. That contradicts scientists’ understanding of how such materials should behave, providing a challenge to superconducting theory, the authors say.

Exoplanet 2M1207b

Giant exoplanets such as 2M1207b, seen orbiting its parent star, bear similarities to the objects called brown dwarfs. Credit: ESO

Planetary science

What big planets have in common with failed stars

‘Gas giant’ exoplanets have an uncanny resemblance to galactic oddities called brown dwarfs.

Giant planets probably share a fundamental property with slightly larger bodies called brown dwarfs.

In the past decade, astronomers have found several examples of big planet-like bodies — those measuring up to 13 Jupiter masses  — orbiting young stars. But researchers have struggled to determine whether they formed by coalescing from a disk of gas and dust swirling around the star — as the planets in our Solar System did — or by clumping together directly from a gaseous cloud, as brown dwarfs do. Brown dwarfs are not big enough to produce their own light, earning them the nickname ‘failed stars’.

A team led by Marta Bryan at the California Institute of Technology in Pasadena used the Keck II telescope in Hawaii to examine three planet-like objects, each less than 13 Jupiter masses, located far from their stars. The scientists compared the rotation rates of those objects with the spins of six brown dwarfs up to 20 Jupiter masses in size. All shared some characteristics, such as a stable rotation rate that has probably endured for billions of years.

The results show that the same physical processes could drive the rotation rates of both big planets and brown dwarfs, regardless of how they formed. That gives astronomers a new tool for exploring how gas accretes onto both types of object as they grow.