This century-old mystery has been finally solved by an international joint research team led by LEE Won Chul, Professor of Mechanical Engineering at Hanyang University Erica Campus, JEON Sungho, Postdoctoral Researcher of Mechanical Engineering at Hanyang University Erica Campus, PARK Jungwon, Professor of School of Chemical and Biological Engineering at Seoul National University and Center for Nanoparticle Research within the Institute for Basic Science (IBS), and Peter ERCIUS from Lawrence Berkeley National Laboratory. The joint research team has succeeded in observing the moment of the initial state of nanocrystal nucleation.

The scientists succeeded in filming the process where the gold atoms gather to form nanocrystals. To observe the initial state of the nucleation process, the team synthesized gold nanocrystals by emitting electron beam onto gold cyanide nanoribbons on top of a graphene membrane, which decomposes the nanoribbons into gold atoms. The synthesized specimen was observed with the high-performance transmission electron microscope (TEM) at the Lawrence Berkeley National Laboratory. The process was recorded at an atomic level spatial resolution and an ultra-high temporal resolution on a scale of milliseconds.

The TEM observation showed the abrupt disappearance and reappearance of crystal lattice structures prior to the emergence of a stable crystal structure. Through careful analysis, the team ruled out some factors which may result in such observations such as the orientation, tilt, and fast rotation of nanocrystals. Therefore, the observed results appeared to indicate that the atoms making up the nucleus randomly oscillate between the disordered and crystalline states. This structural fluctuation appeared to occur spontaneously in a stochastic manner. The team’s discovery directly challenged the longstanding nucleation theory as well as a more recent nucleation theory that has been proposed in the last two decades.

In addition, the team found that the stability of the crystalline state increased as the size of the nanocrystals increased. For example, the nanocrystals with 2.0 nm2 areas spent approximately half of the time existing in a crystalline state. When the crystal sizes increased to above 4.0 nm2 in area, the crystals appeared to exist most of the time under a crystalline form.

In order to describe this phenomenon, the team proposed a new thermodynamic theory of crystal nucleation. The study proposed that the energy barrier between crystalline to disordered transformation tends to be very low in the earliest stage of nucleation when the cluster size is small and that it increases as more atoms are added to the structure. This can explain the spontaneous fluctuation between crystalline and disordered states in nascent crystals consisting of a few atoms. The team also pointed out in relatively smaller nanocrystals, even the addition of extra atoms can transfer enough energy into the system to transform the entire structure back to a disordered state. The energy barrier increases as the crystal grows, which reduces the probability of spontaneous reversion and stabilizes the crystalline structures in larger crystals.

Regarding these findings, Prof. Jungwon Park stated that “From a scientific point of view, we discovered a new principle of crystal nucleation process, and we proved it experimentally.” Prof. Won Chul Lee mentioned that “In an engineering point of view, by reproducing the initial state of the deposition process, it can be used to achieve original technology in semiconductor materials, components, and equipment.”

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A study published in the journal Scientific Reports found that some females lay as many as six clutches as far as six miles apart during the same breeding season.

“Nesting females don’t lay all their eggs in one basket. Their reproductive strategy is like investing in a mutual fund. Females divide their resources among many stocks rather than investing everything in a single stock,” said Deby Cassill, biology professor at USF’s St. Petersburg campus and author of the study.

During their 50-year lifetime, a single female loggerhead will produce around 4,200 eggs and scatter them at 40 different sites on the barrier island. This strategy helps reduce the risk of complete reproductive failure by hurricanes and thunderstorms that could wash out or flood all clutches.

“Because females diversify reproduction in unpredictable patterns over time and space, nearly two-thirds of loggerhead sea turtle hatchlings made it into the Gulf of Mexico,” said Cassill.

For the study, Cassill analyzed 17 years of data provided by the Conservancy of Southwest Florida on loggerhead females nesting on Keewaydin Island off the southwestern Gulf coast of Florida. For years, conservancy staff and community volunteers tagged turtles and patrolled the island to monitor and record detailed information on the nesting population.

Though the study shows most sea turtle hatchlings reach the Gulf of Mexico, future impacts due to human encroachment and climate change could affect the population. Increased frequency of extreme storms due to warmer waters and sea-level rise may flood or wash away larger portions of clutches, leading to population declines of the threatened species.

“It’s important to follow individuals over time to really get a glimpse of how they mate, find food and ensure that some of their young survive to maturity. Without knowledge of the sea turtle’s survival and reproductive biology, we cannot develop and implement effective conservation policies,” said Cassill.

The study is one in a series of upcoming articles by Cassill pertaining to her “maternal risk management model,” which looks at how natural selection pressures, such as predators, storms and resource scarcity, influence how mothers invest in offspring quantity and quality.

She argues turtles and fish invest in large numbers of offspring when the likelihood their offspring will be killed by predators is high. Mammal mothers like whales and elephants provide extensive care to one offspring at a time when the likelihood their young will starve during seasonal droughts is high.

The model, based on the number and size of offspring produced by a mother, extends Darwin’s theory of natural selection by explaining the fusion of parents and offspring into family units and societies.

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“Marine heatwaves will be more intense and happen more often in the future,” said Dillon Amaya, a CIRES Visiting Fellow and lead author on the study out this week in the Bulletin of the American Meteorological Society‘s Explaining Extreme Events. “And we are now understanding the mechanics of why. When the mixed layer is thin, it takes less heat to warm the ocean more.”

The mixed layer — the water in which temperature remains consistent — blankets the top 20-200 meters of the ocean. Its thickness is responsible for heat events: the thicker it is, the more the layer can act as a buffer to shield the waters below from incoming hot air. But as this armor thins, the mixed layer becomes more susceptible to rapid swings in temperature.

“Think of the mixed layer as boiling a pot of water,” said Amaya. “It will take no time at all for an inch of water to come to a boil, but much longer for a pot filled to the brim to heat through.”

Amaya and his team used a combination of ocean observations and models to estimate the depth of the mixed layer back to 1980, and also project out into the future. They determined that over the last 40 years, the layer has thinned by nearly 3 meters (9 feet) in some regions of the North Pacific. And by 2100, the mixed layer will be 4 meters (12 feet) thinner — 30 percent less than what it is today. This thin mixed layer combined with warmer global temperatures will set the stage for drastic swings in ocean temperatures, leading to much more frequent and extreme heating events, the researchers say.

And it’s already happening. Take the 2019 heatwave in the Northeast Pacific. Weakened winds and higher air temperatures came together to warm Pacific Ocean waters by about 3 degrees C (5.5 F). A thinning mixed layer most likely contributed to this surge of warm waters, the authors found. And it will get worse.

“If you take the same wind and ocean conditions that occurred in 2019 and you apply them to the estimated mixed layer in 2100, you get a marine heatwave that is 6.5 degrees C (12 F) warmer than what we say in 2019,” said Amaya. “An event like that would absolutely devastate sensitive marine ecosystems along the U.S. west coast.”

Amaya also points out that, as climate continues to warm and the mixed layer continues to thin, scientists might start to lose the ability to predict year-to-year ocean surface temperatures. Without the ability to accurately forecast ocean temperatures, fisheries and other coastal operations could be in danger.

Other studies also suggest marine heatwaves will become more common in the future, but not many have explored the root cause: ocean dynamics and physics. “In order to simulate these events in models and help predict them, we must understand the physics of why that’s happening,” said Amaya.

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But existing methods require multiple steps performed at high temperatures over a lengthy period of time in order to produce a catalyst with the needed efficiency. That requires substantial amounts of energy and drives up the cost.

Researchers from the University of Houston have reported an oxygen evolving catalyst that takes just minutes to grow at room temperature on commercially available nickel foam. Paired with a previously reported hydrogen evolution reaction catalyst, it can achieve industrially required current density for overall seawater splitting at low voltage. The work is described in a paper published in Energy & Environmental Science.

Zhifeng Ren, director of the Texas Center for Superconductivity at UH (TcSUH) and corresponding author for the paper, said speedy, low-cost production is critical to commercialization.

“Any discovery, any technology development, no matter how good it is, the end cost is going to play the most important role,” he said. “If the cost is prohibitive, it will not make it to market. In this paper, we found a way to reduce the cost so commercialization will be easier and more acceptable to customers.”

Ren’s research group and others have previously reported a nickel-iron-(oxy)hydroxide compound as a catalyst to split seawater, but producing the material required a lengthy process conducted at temperatures between 300 Celsius and 600 Celsius, or as high as 1,100 degrees Fahrenheit. The high energy cost made it impractical for commercial use, and the high temperatures degraded the structural and mechanical integrity of the nickel foam, making long-term stability a concern, said Ren, who also is M.D. Anderson Professor of physics at UH.

To address both cost and stability, the researchers discovered a process to use nickel-iron-(oxy)hydroxide on nickel foam, doped with a small amount of sulfur to produce an effective catalyst at room temperature within five minutes. Working at room temperature both reduced the cost and improved mechanical stability, they said.

“To boost the hydrogen economy, it is imperative to develop cost-effective and facile methodologies to synthesize NiFe-based (oxy)hydroxide catalysts for high-performance seawater electrolysis,” they wrote. “In this work, we developed a one-step surface engineering approach to fabricate highly porous self-supported S-doped Ni/Fe (oxy)hydroxide catalysts from commercial Ni foam in 1 to 5 minutes at room temperature.”

In addition to Ren, co-authors include first author Luo Yu and Libo Wu, Brian McElhenny, Shaowei Song, Dan Luo, Fanghao Zhang and Shuo Chen, all with the UH Department of Physics and TcSUH; and Ying Yu from the College of Physical Science and Technology at Central China Normal University.

Ren said one key to the researchers’ approach was the decision to use a chemical reaction to produce the desired material, rather than the energy-consuming traditional focus on a physical transformation.

“That led us to the right structure, the right composition for the oxygen evolving catalyst,” he said.

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Materials provided by University of Houston. Original written by Jeannie Kever. Note: Content may be edited for style and length.

Now a team of scientists from Switzerland, Sweden, the UK, and China may have solved the puzzle. Their results show flowering plants indeed originated in the Jurassic or earlier, that is millions of years earlier than their oldest undisputed fossil evidence, according to a new study published in the scientific journal Nature Ecology & Evolution. The lack of older fossils, according to their results, might instead be the product of low probability of fossilization and the rarity of early flowering plants.

“A diverse group of flowering plants had been living for a very long time shadowed by ferns and gymnosperms, which were dominating ancient ecosystems. This reminds me of how modern mammals lived for a long time laying low in the age of dinosaurs, before becoming a dominant component of modern faunas,” said lead author Dr Daniele Silvestro, from the University of Fribourg in Switzerland.

Flowering plants are by far the most abundant and diverse group of plants globally in modern ecosystems, far outnumbering ferns and gymnosperms, and including almost all crops sustaining human livelihood. The fossil record shows this pattern was established over the past 80-100 million years, while earlier flowering plants are thought to have been small and rare. The new results show that flowering plants have been around for as many as 100 million years before they finally came to dominance.

“While we do not expect our study to put an end to the debate about angiosperm origin, it does provide a strong motivation for what some consider a hunt for the snark — a Jurassic flowering plant. Rather than a mythical artefact of genome-based analyses, Jurassic angiosperms are an expectation of our interpretation of the fossil record,” said co-author Professor Philip Donoghue, from the University of Bristol in the UK.

The research conclusions are based on complex modelling using a large global database of fossil occurrences, which Dr Yaowu Xing and his team at the Xishuangbanna Tropical Botanical Garden compiled from more than 700 publications. These records, amounting to more than 15,000, included members of many groups of plants including representatives of palms, orchids, sunflowers, and peas.

“Scientific debate has long been polarised between palaeontologists who estimate the antiquity of angiosperms based on the age of the oldest fossils, versus molecular biologists who use this information to calibrate molecular evolution to geologic time. Our study shows that these views are too simplistic; the fossil record has to be interpreted,” said co-author Dr Christine Bacon, from the University of Gothenburg in Sweden.

“A literal reading of the fossil record cannot be used to estimate realistically the time of origin of a group. Instead, we had to develop new mathematical models and use computer simulations to solve this problem in a robust way.”

Even 140 years after Darwin’s conundrum about the origin of flowering plants, the debate has maintained a central place in the scientific arena. In particular, many studies based on phylogenetic analyses of modern plants and their genomes estimated that the group originated significantly earlier than indicated by the fossil record, a finding widely disputed in palaeontological research. The new study, which was based exclusively on fossils and did not include genome data or evolutionary trees, shows an earlier age of flowering plants is not an artifact of phylogenetic analyses, but is in fact supported by palaeontological data as well.

Co-author Professor Alexandre Antonelli, Director of Science at the Royal Botanic Gardens, Kew in the UK, added: “Understanding when flowering plants went from being an insignificant group into becoming the cornerstone of most terrestrial ecosystems shows us that nature is dynamic. The devastating human impact on climate and biodiversity could mean that the successful species in the future will be very different to the ones we are accustomed to now.”

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