After university cafeterias expanded their vegetarian selections, more diners chose meatless items. Credit: Getty
Human behavior
Dining-hall data suggest that a rise in vegetarian options leads customers to embrace meat-free meals.
Dining establishments can nudge consumers to eat less meat by offering more vegetarian choices, according to a study of university-cafeteria sales.
Emma Garnett and her colleagues at the University of Cambridge, UK, collected data on more than 94, 000 meals sold in 3 of the cafeterias at the university in 2017. When the proportion of meatless options doubled from one to two of four choices, overall sales remained about constant. But sales of meat-containing meals dropped, and sales of vegetarian meals, such as “wild mushroom, roasted butternut squash and sun blushed tomato risotto with parmesan”, rose – 80%.
Increases in plant-based dining were largest among people with the lowest baseline rates of vegetarian-meal consumption. The researchers found no evidence that higher sales of vegetarian dishes at lunch led to lower vegetarian sales at dinner.
Other variables that influenced dining choices included the relative prices of vegetarian and non-vegetarian options, and the outdoor temperature.
The authors suggest that an increase in vegetarian options could encourage consumers to move away from meat-heavy diets, potentially reducing greenhouse-gas emissions linked to animal-derived food.
A coal-fired power plant in Huainan, China. Similar facilities now on the drawing board in Asia could struggle as climate change limits the availability of cooling water. Credit: Shutterstock
Climate change
Climate change could force prospective coal-burning facilities to cut output.
Future water shortages in Asia threaten the coal-fired power plants planned for the region.
By 2030, construction of new power plants will add more than 400 gigawatts of coal-fired generating capacity in 11 rapidly developing Asian nations. Operating the plants’ cooling systems will require lots of water, which will probably be drawn from local waterways.
Environmental concern has focused mostly on the facilities’ expected emissions of carbon dioxide and other pollutants. But Yaoping Wang at the University of Tennessee in Knoxville and her colleagues studied whether there would be enough water available to support the new power plants.
The scientists analyzed how streamflow and water temperatures would change if global temperatures rose up to 3 ° C above pre-industrial levels. They found that, as a result of changing weather patterns, streamflow will drop in new coal-fired plant locations – which include Mongolia and parts of India and China.
The shortage makes it likely that new plants will have to scale back operations on days when water is scarce.
It looks like an eel, but this fish (Phoebodus saidselachus) lived more than 380 million years ago and is closely related to much bigger and more fearsome predators – today’s sharks. Credit: L. Freyet al./Proc. R. Soc. B
Palaeontology
A fish species dated to about 383 million years ago is the earliest known member of the group that includes sharks.
A strange-looking ancient fish that was closely related to modern sharks had an eel-like body and might have gulped small marine creatures whole.
Sharks belong to a group of fishes called elasmobranchs, which have skeletons of cartilage rather than bone. Because cartilage rarely fossilizes, scientists know little about this group’s early members.
Christian Klug at the University of Zurich in Switzerland and his colleagues found the nearly complete skeleton – including preserved cartilage and muscle – of a new species of fish (Phoebodus saidselachus) that lived around 383 million years ago. It is the oldest known cartilage-based fish with an eel-shaped body, and its discovery pushes back the emergence of elasmobranchs 10 million years earlier than previously thought.
The creature’s jaw shape suggests that it had a weak bite compared with other early sharks. The skeleton closely resembles that of the modern-day frilled shark (Chlamydoselachus anguineus). The authors suggest thatPhoebodus, like the frilled shark, might have swallowed marine invertebrates and small fishes whole.
Neonatal intensive-care units are vulnerable to outbreaks ofKlebsiellabacteria, which become more deadly if they acquire a newly identified package of genes. Credit: Roberto Schmidt / AFP / Getty
Public health
An easily transmitted piece of DNA cranks up the virulence ofKlebsiellabacteria, a major cause of infections in hospitals.
A chunk of genetic material can slip into microbes that are an important cause of hospital-acquired infections – and make the organisms more deadly.
Klebsiellabacteria cause bloodstream infections and pneumonia, and easily spread through health-care facilities, such as neonatal intensive-care units. Antibiotic-resistantKlebsiellathreaten human health worldwide.
Sheng Chen at the City University of Hong Kong in Kowloon and his colleagues isolated a strain ofKlebsiellafrom a patient in a Chinese hospital. The strain contained a ring-shaped piece of DNA called a plasmid, which can travel from one bacterium to another. The new-found plasmid includes genes that make bacteria more dangerous.
When the scientists infected mice with aKlebsiellastrain that lacked this plasmid, the animals survived. But when the mice were infected with the same strain after it had acquired the plasmid, all of the animals died. Further experiments showed that the plasmid can easily enter other strains ofKlebsiellaand enhance their lethality.
The Andromeda galaxy (center) belongs to a group of ordinarily sedate galaxies. Six similar galaxies have morphed to become flamboyantly bright. Credit: Alan Dyer / VWPics / Alamy
Astronomy and astrophysics
Sedate objects ‘change their look’ after the abrupt awakening of their black holes.
Six galaxies have been caught in a dramatic transformation as the black holes at their centers suddenly developed voracious appetites.
A quasar is an extremely bright galaxy with a gluttonous black hole at its core. The black hole’s consumption of gas and dust emits large amounts of light, producing the quasar’s dazzling luminosity. Quasars fall into one of two categories depending on the spectrum of the light that they emit. Strangely, some quasars can switch between the two types, a mysterious process known as ‘changing their look’.
By comparing recent observations with archival data, Sara Frederick at the University of Maryland in College Park and her colleagues found six galaxies that brightened into quasars over less than a decade as their relatively dormant black holes suddenly became active. One galaxy needed less than three months to light up. During this process, the galaxies also changed their look.
Follow-up observations suggest that these are part of a new category of galaxies capable of suddenly consuming vast amounts of material, the authors write. Further study could help reveal why some galaxies can change their look.
) An earthquake and the landslides it triggered devastated the Indonesian village of Perumnas Balaroa (pictured) in 2018. Credit: Mohd Rasfan / AFP / Getty
Geology
Crop irrigation saturated soil, helping to set off Indonesian slides that killed thousands of people.
Irrigation of rice paddies led to many of the 4, 000 – plus deaths during the powerful earthquake that struck Palu, Indonesia, in September 2018. The waterlogged ground shook during the magnitude-7.5 quake and slid downhill, according to two teams that studied the aftermath of the disaster.
The landslides surprised many scientists because the slopes in the Palu Valley are so gentle. To investigate, Kyle Bradley at Nanyang Technological University in Singapore and his colleagues mapped four of the big landslides and evaluated the ground that had collapsed.
) The team found that wet rice paddies had saturated the sandy soil. When the earthquake hit, that soil liquefied and flowed across the landscape. Had the ground been dry, the landslides would probably not have happened.
Separately, Ian Watkinson and Robert Hall at Royal Holloway University of London in Egham, UK, studied buildings that had been carried away by the landslides. They confirmed that the slides happened only on irrigated ground.
The studies suggest that even gentle slopes, when irrigated, could pose a serious landslide risk in other earthquake-prone parts of the world.
Observations by the Subaru telescope (silver and white) helped to pinpoint a primordial cluster of 12 galaxies. Credit: NAOJ
Astronomy and astrophysics
Telescopes detect a ‘protocluster’ that had already formed less than one billion years after the Big Bang.
Astronomers have found the earliest known protocluster – a mass of gas that contains the seeds of a cluster of galaxies.
Insights into how galaxy clusters form could help scientists understand the evolution of structure in the Universe. But many of the clusters near the Milky Way have already matured, making it difficult to spot these bodies in their early stages. This has led astronomers to search for distant protoclusters from the early universe.
A team led by Yuichi Harikane, at the University of Tokyo, used the Subaru telescope at the summit of Mauna Kea, Hawaii, to look for regions of the night sky with more galaxies than expected. The researchers made follow-up observations of one such region to measure how far away its galaxies were, thereby mapping them in 3D.
This revealed a protocluster of a dozen galaxies that existed 13 billion years ago, less than one billion years after the Big Bang – making it the earliest known protocluster of that size.
Further analysis showed that its galaxies are forming stars at a rate at least five times faster than the average for galaxies with similar masses.
Human norovirus readily multiplies in zebrafish larvae (above), providing scientists with an efficient animal model for infection with the pathogen. Credit: Steve Gschmeissner / SPL
Virology
Small and easy to keep, zebrafish larvae provide a useful system for studying norovirus.
The first reliable small-animal model for human norovirus infection, a notorious cause of the illness known as stomach flu, should help researchers to better understand the biology of these pathogens – and might lead to treatments .
Noroviruses are the leading cause of food-borne illness, and the vomiting, nausea, diarrhoea and stomach cramps that go with it. Every year, the viruses cause around 700 million infections and kill more than 200, 000 people – at the expense of US $ 60 billion in lost productivity and healthcare costs. Until now, the only animal models, including large animals such as chimpanzees and pigs, have been unsuitable.
Now Joana Rocha-Pereira, at KU Leuven in Belgium, and her colleagues report successfully cultivating human noroviruses in the larvae of zebrafish (Danio rerio), a freshwater minnow that shares many genes with humans and is a well-established animal model of human disease.
The model should help to identify the key determinants for human norovirus infection, and – to the relief of many parents – expedite the development of antiviral drugs.
Pulling into the first open spot is the least efficient option, according to models of a highly simplified parking scenario. Credit: Orbon Alija / Getty
Mathematics and computing
Two strategies for choosing a parking spot save far more time than a third, according to researchers ’estimates.
Physicists have compared three typical strategies for finding a parking spot to determine which saves the most time – at least in a highly simplified parking scenario.
Paul Krapivsky at Boston University in Massachusetts and Sidney Redner at the Santa Fe Institute in New Mexico modelled an idealized car park in which the parking spots are in a single row between the entrance to the park and the drivers’ ultimate destination, such as a building.
An ‘optimistic’ strategy, which aims to minimize the time spent walking, is to drive straight to the destination and then backtrack to find a spot. Drivers using a ‘meek’ strategy try to reduce the time spent driving by picking the spot immediately before the first parked car that they come across. An intermediate, or ‘prudent’, strategy is to park in the first encountered gap between two cars.
The authors calculated that the prudent strategy is on average slightly more efficient – in terms of time spent walking and driving – than the optimistic one; the meek strategy was a distant third. Still, even the prudent strategy left many good spots near the target empty.
This resident of a Florida zoo belongs to the newly identified speciesCrocodylus halli.It was previously living incognito as a member of the similar speciesCrocodylus novaeguineae. Credit: ASIH
Biodiversity
Analysis reveals that specimens of New Guinean freshwater crocodile belong to two species rather than one.
Dozens of skulls tucked away in museums have yielded a toothy surprise: a new species of crocodile that measures some 3 meters long and is very much alive.
Researchers routinely discover new species of ant and frog, but undocumented large species turn up only rarely. Christopher Murray at Southeastern Louisiana University in Hammond and his colleagues tracked down one such animal by investigating reports that individuals in the northern and southern populations of the New Guinea crocodile (Crocodylus novaeguineae) do not look the same.
The team examined skulls of 51 museum specimens and found anatomical variations that were linked to the animals’ region of origin. For example, crocs from the south of the island of New Guinea tend to have shorter snouts than do northern animals.
Skull bones of the newly named speciesCrocodylus halli.Credit: ASIH
The researchers concluded that the southern animals are a separate species, which they dubbedCrocodylus halli.
The researchers examined three live crocodiles at a Florida zoo and concluded that all three, although previously identified asC. novaeguinea, are in factC. halli.
Researchers inflated a balloon to fabricate the bowl-shaped electronic circuit in this ‘smart’ contact lens. Credit: C. Yu et al./Nat. Electron.
Materials science
Balloon technique throws circuit manufacturers a curve.
A process that uses an ordinary balloon as a stamp for printing electronics can make all sorts of curved devices, from domed arrays of light sensors to ‘smart’ contact lenses.
Many electronic devices are 3D, but most methods of manufacturing circuits produce only flat, 2D arrays that don’t easily fit on curved surfaces. To build a millimeter-scale circuit that would hug a complex surface, Cunjiang Yu at the University of Houston, Texas, and his colleagues first manufactured a silicon circuit. The team then inflated a latex balloon, coated it with a commercially available urethane rubber and pressed it against the circuit, which stuck to the balloon. When the researchers then pressed the balloon to a dome made of silicone, the circuit transferred onto the dome.
To demonstrate the technique, the authors built a convex array of light sensors for a wide-angle camera, a hemispherical solar cell that can pick up more light than a flat model, and a prototype contact lens that measures levels of the bodily substance lactate in tears.
Cats seek comfort and confidence from their caregivers, suggesting that the cat – human tie can be as strong as that between toddlers and the adults who tend them. Credit: miodrag ignjatovic / iStock / Getty
Animal behavior
A test shows that a majority of felines are well attached to their caregivers.
Domestic cats have a reputation for being aloof and emotionally distant from the humans in their lives. Thus it came as a surprise to Kristyn Vitale at Oregon State University in Corvallis and her colleagues that felines are as firmly bonded to their owners as young children are to their primary caregivers.
In a standard experiment on humans, a caregiver briefly leaves their child alone in an unfamiliar environment and then returns. Securely attached kids tend to check in with the returning adult and then resume calmly exploring the space. Those with less secure attachments either ignore their returning caregiver or cling to them nervously. These experiments show that about 65% of human children are ‘securely attached’ to their caregivers.
When Vitale and her team ran a similar experiment with 70 Kittens, 64 .3% approached their owners and gazed at or nuzzled them. These animals were categorized as securely attached. A follow-up experiment involving 38 older cats found that nearly the same proportion were securely attached. Maybe our cats actually love us after all – or most of them do, anyhow.
A diamond chip (above) can store 10 qubits, the quantum equivalent of the bits used in conventional computers. Credit: QuTech
Quantum information
Tiny device holds an unprecedented number of quantum units of information.
Quantum memories built of ‘qubits’, the quantum equivalent of computer bits, could make possible technologies from ultra-secure communication systems to quantum computers far faster than today’s machines. Now physicists have created a diamond-based quantum memory that holds 10 qubits and stores information for 75 seconds – both records for such a device.
Qubits exploit quirks of quantum mechanics to store more information than ordinary computer bits. To harness this capability, Tim Taminiau at Delft University of Technology in the Netherlands and his collaborators started with an artificial diamond crystal embedded with nitrogen atoms. The researchers used radio waves to ‘program’ one of a nitrogen atom’s electrons as a qubit and then prodded the electron to interact with some of the diamond’s carbon nuclei.
That created nine additional qubits and allowed as many as seven qubits to be ‘entangled’, meaning that they share a common quantum state. Entanglement is a crucial step for most applications of qubits, including quantum computing; previously, a maximum of three qubits had been entangled in similar devices.
Long-lasting qubits built in diamond crystals could help to build a future ‘quantum Internet’ that could be virtually un-hackable.
Immune cells called T cells (pictured; artificially colored) multiply after vaccination in the middle of the day. Credit: Stocktrek Images / Alamy
Immunology
Immune cells’ built-in timepieces affect response to inoculation.
The biological clock ticking within some immune cells can influence how well they respond to vaccination, a study in mice has found.
Cells have molecular clocks that dial gene activity up or down in a daily cycle. These clocks can affect immunity. Nathalie Labrecque at the Maisonneuve-Rosemont Hospital Research Center in Montreal, Canada, and Nicolas Cermakian at the Douglas Mental Health University Institute, also in Montreal, and their colleagues investigated how the circadian clock affects the way that immune cells called CD8 T cells respond to vaccination.
The team found that vaccination stimulated the production of more CD8 T cells during the middle of the day than at other time points. Genes associated with the activation of these T cells were also expressed at higher levels at the middle of the day than at night. Mice that lacked the key clock geneBmal1within CD8 T cells did not show this rhythmic response.
DNA tags could help scientists to study ion channels (yellow), which allow specific ions to pass through the membrane of nerve cells (green). Credit: Patrick Landmann / SPL
Chemistry
Fluorescent tag can be affixed to proteins or genetic structures of interest.
A glowing tag made of DNA can be used to label a single target molecule in a cell.
Today’s advanced microscopes allow physicists to image individual molecules, and even arrange them in simple patterns. But such equipment is not very useful for biologists, because biological structures are complex and easily damaged by microscope probes.
Mingjie Dai and Peng Yin at Harvard Medical School in Boston, Massachusetts, and their colleagues developed a technique that uses fluorescent DNA strands to label biological molecules in a cell. First the label’s DNA binds to a matching strand on a target molecule. Then a fluorescent-dye particle attached to the label glows under illumination. This ‘blink’ switches on a laser, which triggers a chemical element embedded in the DNA label to form a tight bond with the target molecule.
The researchers tagged nanometre-scale synthetic DNA structures with a 65% success rate. They also used the technique to tag protein filaments called microtubules inside cultured cells.
The tags could be used to ferry activating molecules to cell- membrane proteins called ion channels, which are crucial for transmitting nerve-cell messages. This would reveal the workings of an individual channel in a cell, the authors say.
Champagne stored at 20 ° C releases a blueish plume when the cork is popped. Credit: Equipe Effervescence / CNRS / Univ. Reims
Physics
On opening, a bottle of bubbly releases a carbon dioxide plume that travels faster than the speed of sound.
The ‘pop’ of a champagne cork unleashes a supersonic jet of freezing gas.
As the pressurized carbon dioxide in the neck of the bottle is released, the gas cools and condenses, forming a cloudy jet. To investigate this phenomenon in detail, Gérard Liger-Belair at the University of Reims Champagne – Ardenne in France and his colleagues used a camera that records 12, 000 frames per second to film corks bursting from the necks of champagne bottles.
The footage revealed that characteristic shock waves called Mach disks form in the CO (2) jet – indicating that the gas is traveling faster than the speed of sound. Mach disks are also seen in the exhaust trails of fighter jets.
The team found that changing the champagne’s temperature altered the CO (2) jet’s appearance. The jet from a champagne bottle stored at 30 formedC formed large CO (2) ice crystals that scattered light in a manner similar to clouds, and appeared white or gray. But ice crystals in the jet from a bottle cooled to 20 ºC were finer and preferentially scattered blue light, resulting in an evanescent blue plume.
The Australian marsupialPalorchestes azael(artist’s impression), which died off thousands of years ago, could have weighed more than 1, 000 kilogrammes. Credit: Roman Uchytel
Palaeontology
A now-extinct Australian animal was even bigger than previously thought and had joints that are unique among mammals.
A weird species of ancient Australian marsupial had enormous claws, and elbows that were almost completely rigid – a characteristic found in no other mammal, living or extinct.
Large marsupials called palorchestids thrived in Australia for some 25 million years, until as recently as 50, 000 years ago. Scientists long mistook them for ancient kangaroos, but eventually realized that these animals were more similar to horse-sized versions of wombats.
In an attempt to describe the appearance and movements of these little-known marsupials, Hazel Richards at Monash University in Clayton, Australia, and her colleagues examined the limbs of more than 60 fossil specimens from 3 species.
The team’s observations suggest that palorchestids were large creatures that could weigh more than one tonne. They had enormous claws that might have helped them to forage for shoots, twigs and leaves, andPalorchestes azael, the most abundant and latest-surviving species, had elbows that were almost **** fixed in a ‘bent’ position.
The authors hope to learn more about palorchestids as more fossils are unearthed or identified in museum collections.
A cloud that extended over Antarctica’s Ross Ice Shelf (pictured) produced drizzle at temperatures far below freezing. Credit: Dale Lorna Jacobsen / Shutterstock
Atmospheric science
‘Supercooled’ rain falls in the darkness of the long polar winter.
Even at – 25 ° C, it can still drizzle rather than snow.
Israel Silber at Pennsylvania State University in University Park and his colleagues spotted supercooled drizzle at this temperature in August 2016, in clouds above the McMurdo Station research base near the Ross Ice Shelf in Antarctica. The drizzle lasted for more than 7.5 hours.
The scientists used lasers and radar to probe Antarctic clouds. By measuring how the instruments’ signals scattered off cloud particles, the researchers could tell that the water was liquid.
In very cold clouds, water usually freezes around dust particles to form ice. The authors suggest that, in this case, there were probably too few dust particles in the air for ice to form. As a result, the water remained liquid as it fell through the sky.
Supercooled drizzle has been spotted at a few other places on the planet. But it might be widespread over Antarctica and the Southern Ocean, because those regions have just the right combination of low dust levels and chilly temperatures.
A male honeybee mates with a queen in mid-air. The semen that a male transfers to a female degrades her vision – and with it her ability to mate with other males. Credit: Otto Hahn / SPL
Animal behavior
Semen that impairs a female’s eyesight is one weapon in the sexual arms race between male honeybees and queens.
After insemination, honeybee queens lose some of their vision – and often lose their way.
Queen honeybeesApis mellifera)embark on mating flights over the course of several days, often collecting sperm from multiple males to boost their hive’s genetic diversity. Evolutionary theory predicts that a male should attempt to prevent queens from mating with other males. In keeping with that prediction, research has suggested that natural insemination alters the activity of vision-related genes in female bees.
To determine the consequences of such changes, Joanito Liberti at the University of Copenhagen and his colleagues artificially inseminated queen bees and found that they became less responsive to light and were more likely to get lost on mating flights than were queens given saline.
Inseminated queens also tended to leave their hives on mating flights two days earlier than control queens. The researchers propose that this early departure was an attempt to compensate for their poor vision.
Workers inspect drugs at a factory in Wuhan, China. A chemical reaction used in drug manufacturing around the world has had an eco-friendly makeover. Credit: Qilai Shen / Bloomberg / Getty Images
Organic chemistry
Thanks to a catalyst, a crucial chemical process no longer requires an explosive ingredient.
A widely used industrial reaction that produces toxic waste could be replaced by one that yields only one by-product – water.
Chemists often use alcohols when synthesizing drugs, but the alcohol must first be ‘activated’ by the addition of other chemicals. Since 1967, that activation has often been carried out by a process called the Mitsunobu reaction, which requires two activating chemicals – one explosive – and generates two by-products, one of which is toxic.
Seeking a greener version of the Mitsunobu reaction, Ross Denton at the University of Nottingham, UK, and his colleagues used a compound called a phosphine oxide as a catalyst to jump-start the reaction. The team’s version of the reaction eliminates the explosive activator and the toxic by-product, and regenerates the second by-product to make the original catalyst, leaving behind nothing but water.
The researchers say that their catalyst provides a more environmentally friendly way of making both drugs and agrochemicals.
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