Giant Ice Age species including elephant-sized sloths and powerful sabre-toothed cats that once roamed the windswept plains of Patagonia, southern South America, were finally felled by a perfect storm of a rapidly warming climate and humans, a new study has shown.
Research led by the Australian Centre for Ancient DNA (ACAD) at the University of Adelaide, published today in Science Advances, has revealed that it was only when the climate warmed, long after humans first arrived in Patagonia, did the megafauna suddenly die off around 12,300 years ago.
The timing and cause of rapid extinctions of the megafauna has remained a mystery for centuries.
“Patagonia turns out to be the Rosetta Stone – it shows that human colonisation didn’t immediately result in extinctions, but only as long as it stayed cold,” says study leader Professor Alan Cooper, ACAD Director. “Instead, more than 1000 years of human occupation passed before a rapid warming event occurred, and then the megafauna were extinct within a hundred years.”
The researchers, including from the University of Colorado Boulder, University of New South Wales and University of Magallanes in Patagonia, studied ancient DNA extracted from radiocarbon-dated bones and teeth found in caves across Patagonia, and Tierra del Fuego, to trace the genetic history of the populations. Species such as the South American horse, giant jaguar and sabre-toothed cat, and the enormous one-tonne short-faced bear (the largest land-based mammalian carnivore) were found widely across Patagonia, but seemed to disappear shortly after humans arrived.
The pattern of rapid human colonisation through the Americas, coinciding with contrasting temperature trends in each continent, allowed the researchers to disentangle the relative impact of human arrival and climate change.
“The America’s are unique in that humans moved through two continents, from Alaska to Patagonia, in just 1500 years,” says Professor Chris Turney, from the University of New South Wales. “As they did so, they passed through distinctly different climate states – warm in the north, and cold in the south. As a result, we can contrast human impacts under the different climatic conditions.”
The only large species to survive were the ancestors of today’s llama and alpaca – the guanaco and vicuna ─ and even these species almost went extinct.
“The ancient genetic data show that only the late arrival in Patagonia of a population of guanacos from the north saved the species, all other populations became extinct,” says lead author Dr Jessica Metcalf, from the University of Colorado Boulder.
“In 1936 Fell’s cave, a small rock shelter in Patagonia, was the first site in the world to show that humans had hunted Ice Age megafauna. So it seems appropriate that we’re now using the bones from the area to reveal the key role of climate warming, and humans, in the megafaunal extinctions,” says Dr Fabiana Martin, at the University of Magallanes.
A Stanford University research lab has developed new technologies to tackle two of the world’s biggest energy challenges – clean fuel for transportation and grid-scale energy storage.
The researchers described their findings in two studies published this month in the journals Science Advances and Nature Communications.
Hydrogen fuel has long been touted as a clean alternative to gasoline. Automakers began offering hydrogen-powered cars to American consumers last year, but only a handful have sold, mainly because hydrogen refueling stations are few and far between.
Stanford engineers created arrays of silicon nanocones to trap sunlight and improve the performance of solar cells made of bismuth vanadate (1µm=1,000 nanometers).(Image credit: Wei Chen and Yongcai Qiu)
“Millions of cars could be powered by clean hydrogen fuel if it were cheap and widely available,” said Yi Cui, associate professor of materials science and engineering at Stanford.
Unlike gasoline-powered vehicles, which emit carbon dioxide, hydrogen cars themselves are emissions free. Making hydrogen fuel, however, is not emission free: Today, making most hydrogen fuel involves natural gas in a process that releases carbon dioxide into the atmosphere.
To address the problem, Cui and his colleagues have focused on photovoltaic water splitting. This emerging technology consists of a solar-powered electrode immersed in water. When sunlight hits the electrode, it generates an electric current that splits the water into its constituent parts, hydrogen and oxygen.
Finding an affordable way to produce clean hydrogen from water has been a challenge. Conventional solar electrodes made of silicon quickly corrode when exposed to oxygen, a key byproduct of water splitting. Several research teams have reduced corrosion by coating the silicon with iridium and other precious metals.
Writing in the June 17 edition of Sciences Advances, Cui and his colleagues presented a new approach using bismuth vanadate, an inexpensive compound that absorbs sunlight and generates modest amounts of electricity.
“Bismuth vanadate has been widely regarded as a promising material for photoelectrochemical water splitting, in part because of its low cost and high stability against corrosion,” said Cui, who is also an associate professor of photon science at SLAC National Accelerator Laboratory. “However, the performance of this material remains well below its theoretical solar-to-hydrogen conversion efficiency.”
Bismuth vanadate absorbs light but is a poor conductor of electricity. To carry a current, a solar cell made of bismuth vanadate must be sliced very thin, 200 nanometers or less, making it virtually transparent. As a result, visible light that could be used to generate electricity simply passes through the cell.
To capture sunlight before it escapes, Cui’s team turned to nanotechnology. The researchers created microscopic arrays containing thousands of silicon nanocones, each about 600 nanometers tall.
“Nanocone structures have shown a promising light-trapping capability over a broad range of wavelengths,” Cui explained. “Each cone is optimally shaped to capture sunlight that would otherwise pass through the thin solar cell.”
In the experiment, Cui and his colleagues deposited the nanocone arrays on a thin film of bismuth vanadate. Both layers were then placed on a solar cell made of perovskite, another promising photovoltaic material.
When submerged, the three-layer tandem device immediately began splitting water at a solar-to-hydrogen conversion efficiency of 6.2 percent, already matching the theoretical maximum rate for a bismuth vanadate cell.
“The tandem solar cell continued generating hydrogen for more than 10 hours, an indication of good stability,” said Cui, a principal investigator at the Stanford Institute for Materials and Energy Sciences. “Although the efficiency we demonstrated was only 6.2 percent, our tandem device has room for significant improvement in the future.”
Rechargeable zinc battery
In a second study published in the June 6 edition of Nature Communications, Cui and Shougo Higashi, a visiting scientist from Toyota Central R&D Labs Inc., proposed a new battery design that could help solve the problem of grid-scale energy storage.
“Solar and wind farms should be able to provide around-the-clock energy for the electric grid, even when there’s no sunlight or wind,” Cui said. “That will require inexpensive batteries and other low-cost technologies big enough to store surplus clean energy for use on demand.”
A conventional zinc (Zn) battery (left) short circuits when dendrites growing from the zinc anode make contact with the metal cathode. Stanford scientists redesigned the battery (right) using plastic and carbon insulators to prevent zinc dendrites from reaching the cathode. (Image credit: Shougo Higashi)
In the study, Cui, Higashi and their co-workers designed a novel battery with electrodes made of zinc and nickel, inexpensive metals with the potential for grid-scale storage.
A variety of zinc-metal batteries are available commercially, but few are rechargeable, because of tiny fibers called dendrites that form on the zinc electrode during charging. Theses dendrites can grow until they finally reach the nickel electrode, causing the battery to short circuit and fail.
The research team solved the dendrite problem by simply redesigning the battery. Instead of having the zinc and nickel electrodes face one another, as in a conventional battery, the researchers separated them with a plastic insulator and wrapped a carbon insulator around the edges of the zinc electrode.
“With our design, zinc ions are reduced and deposited on the exposed back surface of the zinc electrode during charging,” said Higashi, lead author of the study. “Therefore, even if zinc dendrites form, they will grow away from the nickel electrode and will not short the battery.”
To demonstrate stability, the researchers successfully charged and discharged the battery more than 800 times without shorting.
“Our design is very simple and could be applied to a wide range of metal batteries,” Cui said.
Other co-authors of the Nature Communicationsstudy, “Avoiding short circuits from zinc metal dendrites in anode by backside-plating configuration,” are Seok Woo Lee and Jang Soo Lee of Stanford, and Kensuke Takechi of Toyota Central R&D Labs Inc.
Four lead authors contributed equally to the Science Advancesstudy, “Efficient solar-driven water splitting by nanocone BiVO4-perovskite tandem cells”: Yongcai Qiu, Wei Liu and Wei Chen of Stanford, and Wei Chen of Huazhong University. Other authors are Guangmin Zhou, Po-Chun Hsu, Rufan Zhang and Zheng Liang of Stanford; and Shoushan Fan and Yuegang Zhang of Tsinghua University. Support was provided by the U.S. Department of Energy, Stanford’s Global Climate and Energy Project, the National Natural Science Foundation of China and the Natural Science Foundation of Jiangsu Province in China.
Following earlier reports that the claims for discovery of these elements have been fulfilled [1, 2], the discoverers have been invited to propose names and the following are now disclosed for public review:
Nihonium and symbol Nh, for the element 113,
Moscovium and symbol Mc, for the element 115,
Tennessine and symbol Ts, for the element 117, and
Oganesson and symbol Og, for the element 118.
The IUPAC Inorganic Chemistry Division has reviewed and considered these proposals and recommends these for acceptance. A five-month public review is now set, expiring 8 November 2016, prior to the formal approval by the IUPAC Council.
The guidelines for the naming the elements were recently revised  and shared with the discoverers to assist in their proposals. Keeping with tradition, newly discovered elements can be named after:
(a) a mythological concept or character (including an astronomical object),
(b) a mineral or similar substance,
(c) a place, or geographical region,
(d) a property of the element, or
(e) a scientist.
The names of all new elements in general would have an ending that reflects and maintains historical and chemical consistency. This would be in general “-ium” for elements belonging to groups 1-16, “-ine” for elements of group 17 and “-on” for elements of group 18. Finally, the names for new chemical elements in English should allow proper translation into other major languages.
For the element with atomic number 113 the discoverers at RIKEN Nishina Center for Accelerator-Based Science (Japan) proposed the name nihonium and the symbol Nh. Nihon is one of the two ways to say “Japan” in Japanese, and literally mean “the Land of Rising Sun”. The name is proposed to make a direct connection to the nation where the element was discovered. Element 113 is the first element to have been discovered in an Asian country. While presenting this proposal, the team headed by Professor Kosuke Morita pays homage to the trailblazing work by Masataka Ogawa done in 1908 surrounding the discovery of element 43. The team also hopes that pride and faith in science will displace the lost trust of those who suffered from the 2011 Fukushima nuclear disaster.
For the element with atomic number 115 the name proposed is moscovium with the symbol Mc and for element with atomic number 117, the name proposed is tennessine with the symbol Ts. These are in line with tradition honoring a place or geographical region and are proposed jointly by the discoverers at the Joint Institute for Nuclear Research, Dubna (Russia), Oak Ridge National Laboratory (USA), Vanderbilt University (USA) and Lawrence Livermore National Laboratory (USA).
Moscovium is in recognition of the Moscow region and honors the ancient Russian land that is the home of the Joint Institute for Nuclear Research, where the discovery experiments were conducted using the Dubna Gas-Filled Recoil Separator in combination with the heavy ion accelerator capabilities of the Flerov Laboratory of Nuclear Reactions.
Tennessine is in recognition of the contribution of the Tennessee region, including Oak Ridge National Laboratory, Vanderbilt University, and the University of Tennessee at Knoxville, to superheavy element research, including the production and chemical separation of unique actinide target materials for superheavy element synthesis at ORNL’s High Flux Isotope Reactor (HFIR) and Radiochemical Engineering Development Center (REDC).
For the element with atomic number 118 the collaborating teams of discoverers at the Joint Institute for Nuclear Research, Dubna (Russia) and Lawrence Livermore National Laboratory (USA) proposed the name oganesson and symbol Og. The proposal is in line with the tradition of honoring a scientist and recognizes Professor Yuri Oganessian (born 1933) for his pioneering contributions to transactinoid elements research. His many achievements include the discovery of superheavy elements and significant advances in the nuclear physics of superheavy nuclei including experimental evidence for the “island of stability”.
“It is a pleasure to see that specific places and names (country, state, city, and scientist) related to the new elements is recognized in these four names. Although these choices may perhaps be viewed by some as slightly self-indulgent, the names are completely in accordance with IUPAC rules”, commented Jan Reedijk, who corresponded with the various laboratories and invited the discoverers to make proposals. “In fact, I see it as thrilling to recognize that international collaborations were at the core of these discoveries and that these new names also make the discoveries somewhat tangible.”
Finally, laboratories are already working on searches for the elements in the 8th row of the periodic table, and they are also working to consolidate the identification of copernicium and heavier elements. To be able to evaluate this work, IUPAC and the International Union of Pure and Applied Physics (IUPAP) are currently reviewing the selection principle and operations of a future Joint Working Party (JWP) and as soon as these principles have been decided a new group will be formed. This new JWP will review new claims and the consistency of new results with those already evaluated by earlier JWPs.
A species of tropical fish has been shown to be able to distinguish between human faces. It is the first time fish have demonstrated this ability.
The research, carried out by a team of scientists from the University of Oxford (UK) and the University of Queensland (Australia), found that archerfish were able to learn and recognize faces with a high degree of accuracy — an impressive feat, given this task requires sophisticated visual recognition capabilities.
First author Dr Cait Newport, Marie Curie Research Fellow in the Department of Zoology at Oxford University, said: ‘Being able to distinguish between a large number of human faces is a surprisingly difficult task, mainly due to the fact that all human faces share the same basic features. All faces have two eyes above a nose and mouth, therefore to tell people apart we must be able to identify subtle differences in their features. If you consider the similarities in appearance between some family members, this task can be very difficult indeed.
‘It has been hypothesized that this task is so difficult that it can only be accomplished by primates, which have a large and complex brain. The fact that the human brain has a specialized region used for recognizing human faces suggests that there may be something special about faces themselves. To test this idea, we wanted to determine if another animal with a smaller and simpler brain, and with no evolutionary need to recognize human faces, was still able to do so.’
The researchers found that fish, which lack the sophisticated visual cortex of primates, are nevertheless capable of discriminating one face from up to 44 new faces. The research provides evidence that fish (vertebrates lacking a major part of the brain called the neocortex) have impressive visual discrimination abilities.
In the study, archerfish — a species of tropical fish well known for its ability to spit jets of water to knock down aerial prey — were presented with two images of human faces and trained to choose one of them using their jets. The fish were then presented with the learned face and a series of new faces and were able to correctly choose the face they had initially learned to recognize. They were able to do this task even when more obvious features, such as head shape and colour, were removed from the images.
The fish were highly accurate when selecting the correct face, reaching an average peak performance of 81% in the first experiment (picking the previously learned face from 44 new faces) and 86% in second experiment (in which facial features such as brightness and colour were standardized).
Dr Newport said: ‘Fish have a simpler brain than humans and entirely lack the section of the brain that humans use for recognizing faces. Despite this, many fish demonstrate impressive visual behaviours and therefore make the perfect subjects to test whether simple brains can complete complicated tasks.
‘Archerfish are a species of tropical freshwater fish that spit a jet of water from their mouth to knock down insects in branches above the water. We positioned a computer monitor that showed images of human faces above the aquariums and trained them to spit at a particular face. Once the fish had learned to recognize a face, we then showed them the same face, as well as a series of new ones.
‘In all cases, the fish continued to spit at the face they had been trained to recognize, proving that they were capable of telling the two apart. Even when we did this with faces that were potentially more difficult because they were in black and white and the head shape was standardized, the fish were still capable of finding the face they were trained to recognize.
‘The fact that archerfish can learn this task suggests that complicated brains are not necessarily needed to recognize human faces. Humans may have special facial recognition brain structures so that they can process a large number of faces very quickly or under a wide range of viewing conditions.’
Human facial recognition has previously been demonstrated in birds. However, unlike fish, they are now known to possess neocortex-like structures. Additionally, fish are unlikely to have evolved the ability to distinguish between human faces.