Hexbyte Glen Cove Stabilized blue phase crystals could lead to new optical technologies

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Stabilized blue phase liquid crystals, developed by Prof. Juan de Pablo and his team, can reflect blue and green light, and can be switched on and off incredibly quickly, opening the door to faster response times in optical technologies. Credit: Wikimedia Commons

Liquid crystals already provide the basis for successful technologies like LCD displays, and researchers continue to create specific kinds of liquid crystals for even better optical devices and applications.

Juan de Pablo, Liew Family Professor of Molecular Engineering at the Pritzker School of Molecular Engineering (PME) at the University of Chicago, and his team have now found a way to create and stabilize so-called “blue phase liquid crystals,” which have the properties of both liquids and crystals, and can in some cases reflect better than ordinary liquid crystals.

The results, published in ACS Nano, could lead to new optical technologies with better response times.

A new method for stabilizing blue phase crystals

Thanks to their uniform molecular orientation, liquid crystals are already the basis for many display technologies, including those in digital displays for computers and televisions. In this research, de Pablo and his team were interested in chiral liquid crystals, which have a certain asymmetrical “handedness”—like right-handedness or left-handedness—that allows them to exhibit a wider and more interesting range of optical behaviors.

Importantly, these crystals can form blue phase crystals, which because of their unique structure, can reflect blue and green light, and can be switched on and off incredibly quickly. But these crystals only exist in a small range of temperatures and are inherently unstable: Heating them up even one degree can destroy their properties. That has limited their use in technologies.

Through simulation and experiments, the team was able to stabilize the blue phase crystals through the formation of so-called double emulsions. They used a small core droplet of a water-based solution surrounded by an outer droplet of an oily chiral , thereby creating a “core and shell” structure. That structure was itself suspended in another water-based liquid, unmixable with the liquid crystal. Over the appropriate range of temperatures, they were able to trap the chiral liquid crystal in the shell in a “blue phase” state. They then formed a polymer network within the shell, which stabilized the blue crystal without destroying its properties.

Creating perfect crystals

The team then showed that they could change the temperature of the blue phase crystal by 30 degrees without destroying it. Not only that, the process formed perfect, uniform blue phase crystals, which allowed the researchers to better predict and control their behavior.

“Now that we understand these materials and can control them, we can take advantage of their unique optical properties,” de Pablo said. “The next step is deploying them in devices and to demonstrate their usefulness.”

Potential applications include display technologies that could be turned on and off with very small changes in size, temperature, or exposure to light, or sensors that can detect radiation within a certain wavelength.

More information:
Monirosadat Sadati et al, Control of Monodomain Polymer-Stabilized Cuboidal Nanocrystals of Chiral Nematics by Confinement, ACS Nano (2021). DOI: 10.1021/acsnano.1c04231

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Hexbyte Glen Cove A sequence change in a single protein allowed a tomato virus to become a global crop pandemic

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Tomato plants (cv. Moneymaker) (upper panel) and leaves (lower panel) homozygous to the tm-2 or Tm-22 allele infected with ToMV and ToMVMP-ToBRFV. Credit: Hagit Hak and Ziv Spiegelman

In the last years, a new viral tomato disease has emerged, threatening tomato production worldwide. This is caused by the Tomato brown rugose fruit virus (ToBRFV), a member of a devastating group of plant viruses called tobamoviruses. ToBRFV overcomes all known tobamovirus resistance in tomato, including the one conferred by Tm-22, a resistance gene responsible for the stable resistance to these viruses for more than 60 years. In a study recently published in the Molecular Plant-Microbe Interactions (MPMI), journal, Dr. Ziv Spiegelman and Dr. Hagit Hak explored the molecular mechanism by which this emerging virus was able to successfully break this resistance and become a devastating global crop pandemic.

“Tm-22 encodes a plant immune receptor protein, which recognizes a viral-encoded protein named movement protein, triggering an against a wide range of tobamoviruses. ToBRFV is the first virus that was able to overcome the durable Tm-22 ,” said Spiegelman. “We found that the ToBRFV movement protein harbored sequence changes that allow it to evade Tm-22. We confirmed this by introducing this new sequence to another virus (the tomato mosaic virus) that normally cannot infect plants harboring Tm-22, which resulted in a virulent virus.”

Furthermore, they came up with an interesting observation from an evolutionary point of view. “Viral movement proteins allow the virus to spread from cell to cell and infect the entire plant. We found that the elements that enabled the movement protein to avoid Tm-22 recognition likely resulted in reduced viral movement. This suggests that the virus pays a penalty for evading host resistance, which is a reduced cell-to-cell transport. This finding may explain the high durability of Tm-22 resistance, which had remained unbroken for over half a century,” stated Spiegelman.

More information:
Hagit Hak et al, The Tomato Brown Rugose Fruit Virus Movement Protein Overcomes Tm-22 Resistance in Tomato While Attenuating Viral Transport, Molecular Plant-Microbe Interactions (2021). DOI: 10.1094/MPMI-01-21-0023-R

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American Phytopathological Society

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Hexbyte Glen Cove Researchers move closer to controlling two-dimensional graphene

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The TOS-doped graphene is highly conductive but absorbs very little of the infrared light in the resonator—a combination of properties that makes this material unique and promising for opto-electronic applications. Credit: Ipshita Datta, Lipson Nanophotonics Group, Columbia University

The device you are currently reading this article on was born from the silicon revolution. To build modern electrical circuits, researchers control silicon’s current-conducting capabilities via doping, which is a process that introduces either negatively charged electrons or positively charged “holes” where electrons used to be. This allows the flow of electricity to be controlled and for silicon involves injecting other atomic elements that can adjust electrons—known as dopants—into its three-dimensional (3D) atomic lattice.

Silicon’s 3D lattice, however, is too big for next-generation electronics, which include ultra-thin transistors, new devices for optical communication, and flexible bio-sensors that can be worn or implanted in the human body. To slim things down, researchers are experimenting with materials no thicker than a single sheet of atoms, such as . But the tried-and-true method for doping 3D silicon doesn’t work with 2D graphene, which consists of a single of carbon atoms that doesn’t normally conduct a current.

Rather than injecting dopants, researchers have tried layering on a “charge-transfer layer” intended to add or pull away electrons from the graphene. However, previous methods used “dirty” materials in their charge-transfer layers; impurities in these would leave the graphene unevenly doped and impede its ability to conduct electricity.

Now, a new study in Nature Electronics proposes a better way. An interdisciplinary team of researchers, led by James Hone and James Teherani at Columbia University, and Won Jong Yoo at Sungkyungkwan University in Korea, describe a clean technique to dope graphene via a charge-transfer layer made of low-impurity tungsten oxyselenide (TOS).

The team generated the new “clean” layer by oxidizing a single atomic layer of another 2D material, tungsten selenide. When TOS was layered on top of graphene, they found that it left the graphene riddled with electricity-conducting holes. Those holes could be fine-tuned to better control the materials’ electricity-conducting properties by adding a few atomic layers of tungsten selenide in between the TOS and the graphene.

The researchers found that graphene’s electrical mobility, or how easily charges move through it, was higher with their new doping method than previous attempts. Adding tungsten selenide spacers further increased the mobility to the point where the effect of the TOS becomes negligible, leaving mobility to be determined by the intrinsic properties of graphene itself. This combination of high doping and high mobility gives graphene greater electrical conductivity than that of highly conductive metals like copper and gold.

As the got better at conducting electricity, it also became more transparent, the researchers said. This is due to Pauli blocking, a phenomenon where charges manipulated by doping block the material from absorbing light. At the infrared wavelengths used in telecommunications, the graphene became more than 99 percent transparent. Achieving a high rate of transparency and conductivity is crucial to moving information through light-based photonic devices. If too much light is absorbed, information gets lost. The team found a much smaller loss for TOS-doped graphene than for other conductors, suggesting that this method could hold potential for next-generation ultra-efficient photonic devices.

“This is a new way to tailor the properties of graphene on demand,” Hone said. “We have just begun to explore the possibilities of this new technique.”

One promising direction is to alter graphene’s electronic and optical properties by changing the pattern of the TOS, and to imprint electrical circuits directly on the graphene itself. The team is also working to integrate the doped material into novel photonic devices, with potential applications in transparent electronics, telecommunications systems, and quantum computers.

More information:
Min Sup Choi et al, High carrier mobility in graphene doped using a monolayer of tungsten oxyselenide, Nature Electronics (2021). DOI: 10.1038/s41928-021-00657-y

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Hexbyte Glen Cove Better models of atmospheric ‘detergent’ can help predict climate change

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Credit: CC0 Public Domain

Earth’s atmosphere has a unique ability to cleanse itself by way of invisible molecules in the air that act as minuscule cleanup crews. The most important molecule in that crew is the hydroxyl radical (OH), nicknamed the “detergent of the atmosphere” because of its dominant role in removing pollutants. When the OH molecule chemically interacts with a variety of harmful gases, including the potent greenhouse gas methane, it is able to decompose the pollutants into forms that can be removed from Earth’s atmosphere.

It is difficult to measure OH, however, and it is not directly emitted. Instead, researchers predict the presence of OH based on its chemical production from other “precursor” . To make these predictions, researchers use computer simulations.

In a new paper published in the journal PNAS, Lee Murray, an assistant professor of earth and environmental sciences at the University of Rochester, outlines why computer models used to predict future levels of OH—and, therefore, how long air pollutants and reactive greenhouse gases last in the —have traditionally produced widely varying forecasts. The study is the latest in Murray’s efforts to develop models of the dynamics and composition of Earth’s atmosphere and has important implications in advancing policies to combat .

“We need to understand what controls changes in in Earth’s atmosphere in order to give us a better idea of the measures we need to take to rid the atmosphere of pollutants and reactive greenhouse gases,” Murray says.

Building accurate computer models to predict OH levels is similar to baking: Just as you must add precise ingredients in the proper amounts and order to make an edible cake, precise data and metrics must be input into computer models to make them more accurate.

The various existing computer models used to predict OH levels have traditionally been designed with data input involving identical emissions levels of OH precursor gases. Murray and his colleagues, however, demonstrated that OH levels strongly depend on how much of these precursor emissions are lost before they react to produce OH. In this case, different bakers follow the same recipe of ingredients (emissions), but end up with different sizes of cake (OH levels) because some bakers throw out different portions of batter in the middle of the process.

“Uncertainties in future predictions are primarily driven by uncertainties in how models implement the fate of reactive gases that are directly emitted,” Murray says.

As Murray and his colleagues show, the computer models used to predict OH levels must evaluate the loss processes of reactive precursor gases, before they may be used for accurate future predictions.

But more data is needed about these processes, Murray says.

“Performing new measurements to constrain these processes will allow us to provide more accurate data about the amount of hydroxyl in the atmosphere and how it may change in the future,” he says.

More information:
Lee T. Murray et al, Large uncertainties in global hydroxyl projections tied to fate of reactive nitrogen and carbon, Proceedings of the National Academy of Sciences (2021). DOI: 10.1073/pnas.2115204118

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Hexbyte Glen Cove Team develops real-time diagnostic for Liquid Metal Jetting 3D printing

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Credit: CC0 Public Domain

As 3D printing continues to grow and evolve, diagnostics capable of monitoring builds in real-time have become essential tools for producing quality parts, particularly in emerging printing technologies such as Liquid Metal Jetting (LMJ).

In LMJ, tiny molten metal droplets are ejected from a nozzle at high speeds to 3D print a part in layers, similar to inkjet printers on the consumer market. Unlike laser-based metal 3D printing processes, the technology doesn’t require , which can be hazardous to handle and wasteful of material. Diagnostics used today to ensure high-quality LMJ prints largely rely on high-speed videography, which requires expensive equipment, can be difficult to set up, and generates large amounts of data. While adequate for evaluating a few seconds of a test printing, it isn’t a feasible solution for longer builds.

Researchers at Lawrence Livermore National Laboratory (LLNL) are attempting to solve the problem with a new diagnostic tool that can determine the quality of metal droplets and monitor LMJ prints in real time. The approach uses low frequency, electromagnetic near-field detection to capture metal droplet dynamics that when combined with simulation, provide information on droplet features based on signal amplitude and phase alone.

Researchers said the ability to characterize the droplets using just one parameter significantly reduces the amount of necessary data, making processing and feedback of longer-term LMJ prints possible. The work was published online by the Journal of Applied Physics, where editors selected it as a Featured Article.

“Our results demonstrate that in situ monitoring of Liquid Metal Jetting is possible with millimeter-wave detection methods,” said lead author and LLNL engineer Tammy Chang. “This is exciting because it means we could replace computationally expensive high-speed, high-resolution optical diagnostics to enable real-time performance evaluation and feedback control, to ensure high quality printed metal parts.”

With the new technique, they discovered large-scale trends such as print variation and anomalies at the nozzle, as well as micro-level attributes about the droplets, including size, position and dynamics. The team used electromagnetic simulations to model droplet properties, allowing the team to understand the physics of the electromagnetic scattering and how variations in the magnitude and phase of the detected signals affected droplet features, Chang said.

The result of the research is a “compact and non-invasive” diagnostic able to distinguish droplets in LMJ machines at higher print rates than possible before, as well as the capability to detect additional features of the print system, researchers said. The ability to capture droplet properties based on one parameter alone ultimately shows promise for feedback systems in which rapid, real-time processing can be used to adjust print settings and guarantee part quality, they concluded.

“Getting a clean ejection of a single drop that falls straight down is key to achieving good print quality,” said LLNL engineer Andy Pascall, a co-author on the paper. “High-speed videography works well in a lab-scale environment where we are testing new print parameters, but will never work in production. The millimeter-wave diagnostic is a huge improvement because it can be integrated into the , doesn’t require optical access and provides data that can be analyzed in real time to determine if high-quality droplets are being generated. This type of diagnostic will be very useful in a production environment.”

In the future, researchers said signal processing techniques could be used to correlate optical and millimeter-wave and predict droplet properties based on millimeter-wave results alone. Processing efforts developed by the LLNL researchers and their collaborators are currently under review.

The work is part of a three-year Laboratory Directed Research and Development (LDRD) project aimed at developing acoustic and electromagnetic monitoring approaches for metal additive manufacturing. It supports LLNL’s droplet-on-demand Liquid Metal Jetting work led by Pascall and physicist Jason Jeffries.

Lab staff scientist and Nondestructive Evaluation Group Leader Joe Tringe devised the original foundational idea for the diagnostic, as well as the broader LDRD Exploratory Research project for acoustic and electromagnetic for metal additive manufacturing.

Co-authors on the paper included LLNL scientists and engineers Saptarshi Mukherjee, Nicholas Watkins, Edward Benavidez, Abigail Gilmore and principal investigator David Stobbe.

More information:
T. Chang et al, Millimeter-wave electromagnetic monitoring for liquid metal droplet-on-demand printing, Journal of Applied Physics (2021). DOI: 10.1063/5.0065989

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Hexbyte Glen Cove Last seven years on track to be hottest on record: UN

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Recent years have seen an onslaught of extreme weather, including wildfires made more intense by climate change.

The years from 2015 to 2021 are on track to be the seven hottest on record, the World Meteorological Organization said on Sunday, warning that the planet was heading into “uncharted territory”.

The preliminary WMO state of the report, launched as the UN COP26 climate conference opens, said that from greenhouse gas emissions threatens “far-reaching repercussions for current and future generations”.

Based on data for the first nine months of the year, the WMO said 2021 was likely to be between the fifth and seventh on record—despite the cooling effect of the La Nina phenomenon that lowered temperatures at the beginning of the year.

“From the ocean depths to mountain tops, from melting glaciers to relentless extreme weather events, ecosystems and communities around the globe are being devastated,” said United Nations Secretary-General Antonio Guterres in a statement on the report.

He added that the two-week COP26 climate conference “must be a turning point for people and planet”.

The WMO found that the average temperature for 2021 was around 1.09 degrees Celsius higher than pre-industrial levels.

And the average temperature over the last 20 years (2002-2021) for the first time exceeded the symbolic threshold of 1C above the mid-19th century, when humans began burning on an industrial scale.

This will “focus the minds of delegates at COP26 aspiring to keep global temperature rise to within the limits agreed in Paris six years ago”, said Stephen Belcher, chief scientist at Britain’s Met Office.

The 2015 Paris Agreement saw countries agree to cap global warming at “well below” 2C above pre-industrial levels, and 1.5C if possible.

Since then the world has seen a litany of weather disasters including record-shattering wildfires across Australia and Siberia, a once-in-a-thousand-years heatwave in North America and extreme rainfall that caused massive flooding in Asia, Africa, the US and Europe.

“Extreme events are the new norm,” said WMO Secretary-General Petteri Taalas.

“There is mounting that some of these bear the footprint of human-induced .”

‘Unimaginable’ consequences

The state of the climate report is a snapshot of planetary health, including temperatures, extreme weather, glacier retreat and ice melt.

Ocean acidification due to the absorption of carbon dioxide by the seas was “unprecedented” in at least 26,000 years, the WMO said, adding that this will lessen the ability of the oceans to take in more C02.

Meanwhile, sea level rise—mainly caused by the expansion of warming sea water and the melting of ice on land—was at a new high.

The report is “shocking and deeply disturbing and yet another wake-up call to world leaders that time has run out for talk”, said Jonathan Bamber, Director of the Bristol Glaciology Centre, in comments to the Science Media Centre.

He said on the current trajectory, sea level rise could exceed two metres (more than six feet) by 2100, which could displace some 630 million people worldwide.

“The consequences of that are unimaginable,” said Bamber.

“What is required now is profound and comprehensive action by every nation and state actor to limit further and deeper climate breakdown.”

© 2021 AFP

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Hexbyte Glen Cove COP26 climate summit ‘last, best hope’ to meet 1.5C target

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Climate protesters including from Extinction Rebellion have gathered in Glasgow to keep up the pressure.

Global COP26 climate negotiations are the “last, best hope” to keep the goal of limiting global warming to 1.5C alive, said summit president Alok Sharma as he opened the meeting on Sunday.

The Glasgow gathering, which runs to November 12, comes as an accelerating onslaught of extreme weather events across the world underscores the devastating impacts of climate change from 150 years of burning fossil fuels.

“We know that our shared planet is changing for the worse,” Sharma said at the opening ceremony, as protesters gathered in the Scottish city to pile pressure on governments.

Experts warn that only transformative action in the next 10 years will help stave off far more cataclysmic impacts.

And the warming of the planet did not pause for the Covid-19 pandemic, which caused the UN meeting to be delayed by a year.

The last year alone has seen a once-in-a-thousand-years heatwave and scorching wildfires in North America, extreme rainfall and flooding in Asia, Africa, the US and Europe and severe drought in Madagascar, which Sharma said has been referred to as the “first climate-induced famine”.

In a stark reminder of what is at stake, the World Meteorological Organization said Sunday the years from 2015 to 2021 were on track to be the seven hottest on record.

Climate impacts in the last year include a record-shattering heatwave in North America and severe wildfires.

‘Precious planet’

COP26 inherits its central goal from the landmark 2015 Paris Agreement, which saw countries agree to cap global warming at “well below” 2C above pre-industrial levels, and 1.5C if possible.

That deal left many crucial details to be worked out, while emissions reductions remain woefully insufficient to avert global warming.

In August a bombshell “code red” report from the world’s top climate science body warned that Earth’s average temperature will hit the 1.5C threshold around 2030, a decade earlier than projected only three years ago.

And last week a UN report said even the latest, most ambitious carbon-cutting commitments would still lead to “catastrophic” warming of 2.7C.

COP26 now marks the “last, best hope to keep 1.5C in reach”, Sharma said.

“If we act now and we act together we can protect our precious planet,” he said.

Activists have mobilised in Glasgow to urge the delegates on, with Extinction Rebellion campaigners kicking off the proceedings on Saturday in a march of protesters in white face paint and flamboyant robes.

Severe drought in Madagascar is causing what some have called the first climate-induced famine, Sharma said.

Greta Thunberg also arrived in the Scottish city late Saturday on a train that was mobbed by waiting journalists.

But others hoping to arrive in eco-friendly style were thwarted by severe rail delays.

‘Investing in extinction’

Much of the world’s hopes for wrestling down emissions rest on the G20 richer nations—whose leaders met in Rome at the weekend and whose economies account for about 80 percent of carbon pollution.

They committed to the key goal of limiting global warming to 1.5C and pledged to bring a halt to international funding for coal plants without emissions capture facilities.

They also pledged to reach a target of net zero carbon emissions “by or around mid-century”, falling short of setting a clear 2050 date, as campaigners and summit host Italy were hoping for.

The world’s focus on decarbonisation has sharpened in the face of increasingly dire warnings from scientists, central banks and security services about the threat posed by climate change, as well as global youth protests.

But governments under pressure to reboot their Covid-lashed economies continue to subsidise fossil fuels, even as they tout renewables.

Sharma urged all countries to work together.

UN climate chief Patricia Espinosa told the Glasgow opening ceremony that nations must turn away from business as usual or accept that “we are investing in our own extinction”.

More than 120 heads of state and government will make the trip to Glasgow for the UN meeting, including US President Joe Biden, France’s Emmanuel Macron, India’s Narendra Modi and Australia’s Scott Morrison.

But President Xi Jinping of China, the world’s largest emitter, has not left his country during the pandemic and will not be travelling to Glasgow.

Vladimir Putin of Russia, another major polluter, will also be a no-show.

Sharma said more than 21,000 representatives from governments were registered, as well as nearly 14,000 observers and 4,000 media representatives.

With poorer nations least responsible for greenhouse gas emissions hit hardest by its impacts, inequality overshadows the COP26 negotiations.

The failure of rich countries to cough up $100 billion a year starting in 2020 to help developing nations lower emissions and adapt—a pledge first made in 2009—will complicate the already fraught talks.

© 2021 AFP

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Hexbyte Glen Cove G20 disappoints on key climate target as eyes turn to Glasgow

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G20 nations emit nearly 80 percent of carbon emissions.

The G20 major economies committed on Sunday to the key goal of limiting global warming to 1.5 degrees Celsius, but disappointed leaders warned more was needed to make a success of UN climate talks beginning in Glasgow.

British Prime Minister Boris Johnson, the host of the COP26 summit that opened on Sunday, said the pledge from after two days of talks in Rome was “not enough”, and warned of the dire consequences for the planet.

“If Glasgow fails, the whole thing fails,” he told reporters, saying the G20 commitments were “drops in a rapidly warming ocean”.

UN Secretary General Antonio Guterres also expressed disappointment at the outcome of the G20 summit, saying he left Rome “with my hopes unfulfilled—but at least they are not buried”.

The G20 nations between them emit nearly 80 percent of , and a firm commitment on action was viewed as vital for the success of the UN’s COP26.

In a final communique, the G20 reaffirmed its support for the goals in the landmark 2015 Paris climate accords, to keep “the global average temperature increase well below 2 degrees and to pursue efforts to limit it to 1.5 degrees above pre-industrial levels”.

They said this would require “meaningful and effective actions and commitment by all countries, taking into account different approaches”, while they also promised action on coal.

But experts say meeting the 1.5 degree target means slashing global emissions nearly in half by 2030 and to “net-zero” by 2050—and the G20 set no firm date, speaking only of reaching the goal of net zero “by or around mid century”.

Italian Prime Minister Mario Draghi, who hosted the G20 talks, said he was “proud of these results, but we must remember that it’s only the start”.

Eyes now turn to Glasgow, where more than 120 heads of state and government, including US President Joe Biden, India’s Narendra Modi and Australia’s Scott Morrison, were heading from Rome.

Lacking ambition

The G20 leaders did agree to end funding for new unabated coal plants abroad—those whose emissions have not gone through any filtering process—by the end of 2021.

But environmental campaign group Greenpeace slammed the final statement as “weak, lacking both ambition and vision”, saying G20 leaders “failed to meet the moment”.

“If the G20 was a dress rehearsal for COP26, then world leaders fluffed their lines,” said Executive Director Jennifer Morgan.

Friederike Roder, senior director at anti-poverty group Global Citizen, told AFP the summit had produced “half-measures rather than concrete actions”.

European leaders pointed out that given the fundamental divisions among the world’s most advanced nations, a joint commitment to what was the most ambitious Paris goal was a step forward.

“I hear all the very alarmed talk on these subjects. I’m myself worried and we are fully mobilised,” said French President Emmanuel Macron.

“But I would like us to take a step back and look at the situation where we were four years ago”, when former US President Donald Trump announced he was pulling out of the treaty.

Draghi said that the needle had moved markedly even in the past few days, including by China—by far the world’s biggest carbon polluter.

Beijing plans to make its economy carbon neutral before 2060, but has resisted pressure to offer nearer-term goals.

India, meanwhile, argues that if net-zero by 2050 is the global goal, then rich countries should be carbon neutral 10 years earlier to allow poorer, emerging nations a larger carbon allowance and more time to develop.

‘Dream big’

Earlier on Sunday, Draghi, Britain’s Prince Charles and Pope Francis had all called on G20 leaders—and by extension, the wider group of world leaders meeting in Glasgow—to think big.

Calling climate change “the defining challenge of our times”, Draghi warned: “Either we act now… or we delay acting, pay a much higher price later, and risk failing.”

Pope Francis, who is outspoken on the issue and received several G20 leaders at the Vatican this weekend, said: “This is a moment to dream big, to rethink our priorities… The time to act, and to act together, is now!”

© 2021 AFP

G20 disappoints on key climate target

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Hexbyte Glen Cove River beds that can shift naturally are more efficient carbon sinks than straightened rivers

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Rio Bermejo. Credit: Kristen Cook

It takes about 8500 years for a grain of sand from the Andes to be washed across the Argentine lowlands into the Río Paraná. The 1200-kilometer journey in the river called Río Bermejo is interrupted by many stops in river floodplains, where the grain is deposited, sometimes over thousands of years, and then washed free again. The sand is accompanied by organic carbon, washed in from soil and plants. The transport in water thus gains relevance for the climate: Rivers carry the carbon, which was previously removed from the atmosphere via photosynthesis, as sediment into the sea, where it is stored for thousands of years without harming the climate.

Researchers at the GFZ German Research Centre for Geosciences have now quantified the individual processes of the journey for the first time and report on them in the journal Nature Geoscience. An important result of the work: It is in particular undisturbed meandering sections of a river where carbon is deposited and reabsorbed, and then transported further into the sea. In river sections with straight, stable banks, on the other hand, only the suspended particle load passes through, while the carbon in the river floodplains is slowly decomposed again to CO2 by microorganisms. GFZ working group leader Dirk Sachse says that “the Río Bermejo was an ideal natural laboratory for us because it has no significant tributaries.” Sachse is also director of the “Landscapes of the Future” topic in the Helmholtz program “Changing Earth—Sustaining Our Future.” He says that “this means that natural river courses that have space to erode floodplains can remove more carbon from the atmosphere than straight river sections. In this respect, straightening of by humans could also contribute to the increase in atmospheric CO2 concentration. What’s exciting now is answering the question of whether we can help the climate by giving rivers more space again and not impeding natural river meandering.”

The international team led by first author Marisa Repasch of GFZ studied the processes in the river and its floodplains with a diverse set of instruments. Analyses of cosmogenic beryllium-10 content, for example, indicated the duration of sediment transport. Dating based on the unstable carbon isotope 14C, in turn, allowed conclusions to be drawn about the age of the particles of organic origin. During fieldwork in Argentina, samples were taken from the river at multiple stations along the source-to-sink pathway. “Naturally meandering rivers erode material from floodplains and transport it to the sea, where it remains for a long time,” says Marisa Repasch, summarizing the results, “in contrast, artificially stabilized river courses are far less effective carbon sinks.”

More information:
Marisa Repasch et al, Fluvial organic carbon cycling regulated by sediment transit time and mineral protection, Nature Geoscience (2021). DOI: 10.1038/s41561-021-00845-7

River beds that can shift naturally are more efficient carbon sinks than straightened rivers (2021, October 29)
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Hexbyte Glen Cove Detector advance could lead to cheaper, easier medical scans

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New ultrafast photon detectors allow for rapid processing of data from positron emission or X-ray scans without the need for tomography to reconstruct images. This image shows a brain phantom (model) scanned by positron emission using the new technology. Credit: Simon Cherry, UC Davis

Researchers in the U.S. and Japan have demonstrated the first experimental cross-sectional medical image that doesn’t require tomography, a mathematical process used to reconstruct images in CT and PET scans . The work, published Oct. 14 in Nature Photonics, could lead to cheaper, easier and more accurate medical imaging.

The advance was made possible by development of new, ultrafast photon detectors, said Simon Cherry, professor of biomedical engineering and of radiology at the University of California, Davis and senior author on the paper.

“We’re literally imaging at the speed of light, which is something of a holy grail in our field,” Cherry said.

Experimental work was led by Sun Il Kwon, project scientist in the UC Davis Department of Biomedical Engineering and Ryosuke Ota at Hamamatsu Photonics, Japan, where the new detector technology was developed. Other collaborators included research groups led by Professor Yoichi Tamagawa at the University of Fukui, and by Professor Tomoyuki Hasegawa at Kitasato University.

The process of tomography is required to mathematically reconstruct cross-sectional images from the data in imaging that uses X-rays or gamma rays. In PET scans, molecules tagged with trace amounts of a radioactive isotope are injected and taken up by organs and tissues in the body. The isotope, such as fluorine-18, is unstable and emits positrons as it decays.

Ultrafast photon detection

Whenever one of these positrons encounters an electron in the body, they annihilate each other and simultaneously give off two annihilation photons. Tracking the origin and trajectory of these photons theoretically creates an image of the tissues tagged with isotopes. But until now, researchers were unable to do that without the extra step of tomographic reconstruction, because detectors were too slow to precisely determine the arrival times of two photons and thus pinpoint their location based on their .

When the annihilation photons strike the detector, they generate Cherenkov photons that produce the signal. Cherry and his fellow researchers figured out how to detect these Cherenkov photonså with an average timing precision of 32 picoseconds. This meant they could determine where the annihilation photons arose with a spatial precision of 4.8 millimeters. This level of speed and accuracy enabled the research team to produce cross-sectional images of a radioactive isotope directly from the annihilation photons without having to use tomography.

In their paper, the researchers describe various tests they conducted with their new technique, including on a test object that mimics the human brain. They feel confident that this procedure is ultimately scalable to the level needed for clinical diagnostics and has the potential to create higher quality images using a lower radiation dose. Images can also be created more quickly with this method, potentially even in real time during the PET scan, as no after-the-fact reconstruction is needed.

PET scans are currently expensive and are technically limited in some ways, as the full information present in the travel time of the annihilation photons is not captured by current clinical scanners. This new discovery involves a compact equipment setup and could lead to inexpensive, easy and accurate scans of the human body using radioactive isotopes.

Additional coauthors are: Eric Berg at UC Davis; Fumio Hashimoto and Tomohide Omura, Hamamatsu Photonics; Kyohei Nakajima and Izumi Ogawa, University of Fukui.

More information:
Sun Il Kwon et al, Ultrafast timing enables reconstruction-free positron emission imaging, Nature Photonics (2021). DOI: 10.1038/s41566-021-00871-2

Detector advance could lead to cheaper, easier medical scans (2021, October 29)
retrieved 30 October 2021
from https://phys.org/news/2021-10-detector-advance-cheaper-easier-medical.html

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