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For people with polycystic kidney disease (PKD), life can be a constant cycle of symptoms: aches and pains, abdominal swelling, kidney stones, high blood pressure. At worst, the disease frequently leads to a suite of major issues, including kidney failure, cysts in the liver and vascular problems, including strokes. According to the National Institutes of Health, PKD is a "fairly common genetic disorder," affecting roughly 600,000 people in the United States, with the more common autosomal dominant (AD) form affecting roughly one in 500 to 1,000 people.

"Most patients will eventually form these big cystic kidneys, and they will need dialysis or a kidney transplant, both of which are not great options," said UC Santa Barbara biochemist Thomas Weimbs, whose research specialty lies in the still somewhat mysterious disease, which has no cure. Meanwhile, treatment of various symptoms and complications put a heavy economic burden on the healthcare system and dramatically lower patients' quality of life.

In a step toward disrupting the cycle that leads to cyst formation in the kidneys, the Weimbs Lab has now uncovered a previously unrecognized mechanism that accelerates cystogenesis. Thought to be a response meant to protect the kidneys, the rapid dilation of the tubules that conduct waste away from the kidneys in the form of urine has been found to be a "third-hit" trigger that results in rapid cyst growth in those with ADPKD.

Their research is published in a paper that appears in the Journal of Clinical Investigation.

The kidneys are the hard-working filtration systems for our blood. Blood enters the nephrons (the kidneys' basic functional unit) where waste and fluid pass through the renal tubules, while cells and proteins stay in the blood. Some fluid and nutrients get reabsorbed into circulation while excess fluid and waste become urine that flows to the bladder. There are about a million such tubules in each human kidney, Weimbs said.

During this filtration process, waste products -- such as calcium oxalate, calcium phosphate and uric acid -- tend to concentrate and precipitate into crystals in the renal tubules. In healthy people, these millions of microscopic crystals form but are flushed away with the urine, while other factors prevent the runaway growth and retention of these crystals in the tubules. The formation and accumulation of these crystals, if left unchecked, could lead to kidney stones.

To prepare to flush out these crystals the renal tubules, it's been found, rapidly dilate, and then return to normal after the crystals have cleared. This dilation is a mechanism that had not been previously recognized, according to Weimbs.

"It was not understood how the bulk of these crystals are flushed out," he said. Until now, stuck crystals were thought to cross through into the kidneys' interstitial tissue to be reabsorbed, he added, but his team's research shows that is not the case for most crystals.

In normal-functioning kidneys, according to the study, the tubule dilation is seen as a protective mechanism. The deposition of oxalate crystals in particular triggers the rapid activation of protein signaling pathways (mTOR and Src/STAT3) that regulate cell growth and proliferation, accompanied by the rapid dilation of the entire tubule system to dislodge the microcrystals.

"In kidneys genetically preconditioned to form these cysts, we found that these crystals can trigger the same dilation, but instead of going back to normal those tubules overshoot and form cysts," Weimbs explained.

In individuals with ADPKD, the rapid and constant tubule dilation is seen as a "third hit" physical injury that results in cyst formation. According to the "third hit" model of cystogenesis, three events must occur to form individual cysts: the first two are genetic mutations, while the third is a physiological damage/repair response, resulting in an overcompensation by the renal tubule that leads to formation of the fluid-filled sacs. Trauma and other assaults to the kidneys are fairly rare, Weimbs said, but the microcrystals could present a persistent and relevant type of injury in ADPKD patients that could trigger the damage/repair response.

The researchers' results suggest that contrary to conventional assumptions that abnormalities in tissue architecture or metabolic abnormalities during ADPKD progression lead to increased kidney stones, the opposite may be the case: More crystals lead to the progression of ADPKD. Additionally, according to the study, it is possible that ADPKD progression and kidney stone formation reinforce each other.

This opens up the possibility that the same well-established practices for keeping kidney stones at bay may also prove effective for slowing the progression of ADPKD. "Our research suggests that the rate of progression could be at least in part determined by something like diet," Weimbs said. Recommendations for preventing kidney stones, such as avoiding certain foods, increasing water intake and prescription citrate therapy, could also prove beneficial for those with polycystic kidney disease, he said.

NASA-NOAA's Suomi NPP satellite passed over Tropical Storm Dorian as it triggered warnings and watches for the  islands of the Eastern Caribbean Sea.

On Monday, August 26, 2019, a Tropical Storm Warning is in effect for Barbados, Martinique, St. Lucia, St. Vincent and the Grenadines. A Tropical Storm Watch is in effect for Dominica, Grenada and its dependencies, Saba and St. Eustatius. A Hurricane Watch is in effect for St. Lucia.

Dorian formed as a tropical depression on Saturday, Aug. 24 about 805 miles (1,300 km) east-southeast of Barbados. By 5 p.m. EDT that day, the depression strengthened into a tropical storm and was named Dorian.

NASA-NOAA's Suomi NPP satellite passed over Tropical Storm Dorian in the western North Atlantic Ocean on Aug. 26 at 1:54 a.m. EDT (0554 UTC). The Visible Infrared Imaging Radiometer Suite (VIIRS) instrument aboard Suomi NPP provided an infrared image of the storm. Infrared imagery reveals cloud top temperatures, and the higher the cloud top, the colder it is, and the stronger the storm. Coldest cloud top temperatures were as cold as minus 70 degrees Fahrenheit (minus 56.6 Celsius) and found around the center of circulation, southwest of the center and in fragmented bands of thunderstorms north of the center. Storms with cloud tops that cold have been found to generate heavy rainfall.

Dorian is a small tropical cyclone. Tropical-storm-force winds only extend outward up to 45 miles (75 km) from the center.

Those areas of strong storms with heavy rainfall potential play into the forecast. NOAA's National Hurricane Center or NHC said that Dorian is expected to produce total rain accumulations of 3 to 8 inches in the Windward Islands from Martinique south to St. Vincent, including Barbados.  Isolated maximum totals of 10 inches are possible across the northern Windward Islands.  Rainfall totals of 1 to 3 inches are expected from the Grenadines, south to Grenada and across Dominica.

Satellite microwave imagery has shown a persistent low-level eye-like feature along with an intermittent mid-level eyewall forming that quickly erodes because of dry air entering the storm in the mid-levels of the atmosphere.

At 11 a.m. EDT (1500 UTC) on Monday, August 26, the center of Tropical Storm Dorian was located near latitude 12.3 degrees north and longitude 57.7 degrees west. The center of Dorian was about 135 miles (220 km) east-southeast of Barbados. The estimated minimum central pressure is 1002 millibars.

Dorian is moving toward the west-northwest near 14 mph (22 kph) and this motion is expected to continue through Tuesday night [Aug. 27], followed by a turn toward the northwest on Wednesday [Aug. 28]. Maximum sustained winds are near 60 mph (95 kph) with higher gusts.

Some strengthening is forecast during the next few days, and Dorian could be near hurricane strength when it passes through the northern Windward Islands on Tuesday, and is expected to be a hurricane when it moves near Puerto Rico and eastern Hispaniola.

The National Hurricane Center noted, "Hurricane conditions are possible tonight and early Tuesday within the Hurricane Watch area in the Lesser Antilles. Tropical storm conditions are likely in the warning area by late today. Tropical storm conditions are possible within the tropical storm watch area by tonight or Tuesday. Swells generated by Dorian will be affecting portions of the Lesser Antilles by late today. These swells could cause life-threatening surf and rip current conditions."

On the forecast track, the center of Dorian is expected to be near the Windward Islands late today and tonight, and move into the eastern Caribbean Sea on Tuesday. Dorian is expected to pass near or south of Puerto Rico on Wednesday and approach eastern Hispaniola Wednesday night.

This summer, Alaska has experienced record high temperatures and devastating wildfires. If such events become more frequent, how might that impact our northernmost forests? A team of researchers led by the Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab) projected that the combination of climate change and increased wildfires will cause the iconic evergreen conifer trees of Alaska to get pushed out in favor of broadleaf deciduous trees, which shed their leaves seasonally.

Using a well-tested ecosystem model called ecosys, they predicted that by the year 2100 the relative dominance of evergreen conifer trees (black spruce) will decline by 25% and non-woody herbaceous plants such as moss and lichen will decline by 66%, while broadleaf deciduous trees (aspen) will become dominant, nearly doubling in prevalence. With such large declines, this shift in vegetation will highly likely have reverberations for the entire ecosystem and climate.

"Expansion of the deciduous broadleaf forests in a warmer climate may result in several ecological and climatic feedbacks that affect the carbon cycle of northern ecosystems," said Zelalem Mekonnen, a Berkeley Lab postdoctoral fellow who was first author of the study.

The paper, "Expansion of High-Latitude Deciduous Forests Driven by Interactions Between Climate Warming and Fire," was published today in Nature Plants. The study was funded as part of DOE's Office of Science through the Next-Generation Ecosystem Experiment--Arctic project and included co-authors from UC Irvine, the University of Alberta, and Woods Hole Research Center. NGEE-Arctic seeks to gain a predictive understanding of the Arctic terrestrial ecosystem's feedback to climate and is a collaboration among scientists at Oak Ridge National Laboratory, Berkeley Lab, Los Alamos National Laboratory, Brookhaven National Laboratory, and the University of Alaska Fairbanks.

"We predict the forest system will remain a net sink for carbon, meaning it will absorb more carbon than it emits," said co-author William J. Riley, a senior scientist in Berkeley Lab's Earth & Environmental Sciences Area. "But will it be more or less of a sink? Our next study will quantify the carbon and surface energy budgets. This study focused more on how vegetation types are expected to change."

Changes in forest cover type will affect many important ecosystem processes. For example, an increase in deciduous broadleaf trees, which lose their leaves every year, unlike evergreens, could result in more rapid microbial decomposition and increased transpiration (the loss of moisture through leaves); both of these processes introduce amplifying feedbacks to climate warming. On the other hand, higher surface reflectance may have a cooling effect when more snow is exposed because of fewer evergreen trees; what's more, deciduous trees are less flammable than evergreen trees. The researchers predicted modest effects on net carbon budgets and will analyze that further in future work.

Riley added that the study included many steps to confirm that the results from ecosys were valid. "We evaluated model performance against many current observations of forest cover and carbon cycling measurements, and against long-term changes under natural climate variation," he said.

Combo of fire plus climate warming could alter forests in 40 years

Climate change is hitting the northern latitudes especially hard due to the phenomenon of Arctic amplification, a positive feedback that causes temperatures to rise faster than the global average. While average global temperatures are projected to rise about 4 degrees Celsius by 2100 in a "business as usual" scenario, some recent studies are predicting much larger increases for the Arctic.

The extent to which fires will increase is even more uncertain. So the researchers modeled four scenarios, from a zero increase in burn area up to a 150% increase by 2100. The scenarios were taken from published studies that accounted for factors such as warmer temperatures and increases in lightning strikes.

What is known about fires are the impacts they have on the forest ecosystem. "Fires deepen the active layer, which is the zone of soil that remains unfrozen," said Riley. "That leads to an increase in soil nutrients available for plants. Increases in soil nutrients favor deciduous plants, which is one reason why we predict they will do so well under a warming climate. Higher deciduous tree cover has happened under previous climates; paleoecological studies of the last 10,000 years suggest that Alaskan forests have undergone similar shifts in dominant tree species."

Another factor that favors broadleaf deciduous over evergreen conifer trees is that their leaves decompose more rapidly, leading to more rapid carbon turnover, which determines the available nutrients in the ecosystem. "As you get more rapid turnover, you get more deciduous plants," Riley said. "It's a self-reinforcing mechanism."

Although previous studies have examined how climate change will impact boreal forests, Riley said this was the first to consider the complex interactions among plants, soil, and nutrients - both above and below ground - and how they evolve over time. "This study is a more detailed and mechanistic explanation of these processes," he said.

Other factors that favor broadleaf deciduous trees in a future warmer climate are their greater ability for post-fire seedling regeneration and their ability to grow fast and thus compete for light. "Plants have different strategies to survive under different environmental conditions," Mekonnen said.

The study found that both climate change and increased fire were required to produce broadleaf deciduous trees' dominance. Across the fire scenarios tested where fires increased, that shift was projected to occur around the year 2058. If warming occurred without increased fire or vice versa, the model found that evergreen conifers remained the dominant Alaskan tree type through the 21st century.

Another forest component that will be affected is wildlife. "Broadleaf deciduous trees have a large canopy which covers underlying vegetation, potentially decreasing herbaceous plant cover. Those plants, especially moss, are very important forage for wildlife," Mekonnen said.

What's more, the modeling technique can be used to study how climate change and fire will affect other geographic areas. "Our modeling approach is applicable to other northern regions because the fundamental mechanisms that control these dynamics are similar everywhere," Mekonnen said.

The oceans act as a carbon sink and have already absorbed more than 40% of anthropogenic carbon emissions. The majority of this CO2 has been taken up by the Southern Ocean making these waters hotspots of ocean acidification (OA).

Lead author of the paper published in Nature Climate Change, Dr Katherina Petrou from the University of Technology Sydney, said that although changes in ocean pH have been shown to impact marine calcifying organisms, the consequences for non-calcifying marine phytoplankton are less clear.

"Previous studies reported a range of responses to OA [in phytoplankton] yet rarely considered how environmental pH shifts might affect silicification rates in diatoms," she says.

"Diatoms are unique phytoplankton in that they need silicic acid to produce silica cell walls. Under the microscope they look like beautiful glass jewellery boxes, but importantly, this dense, glass-like armour promotes sinking, which makes diatoms an important conduit for transport of carbon to the deep ocean where it can be stored for millennia."

Diatoms are responsible for around 40% of ocean productivity which means they play a major role in supporting marine food webs, sustaining life for millions of creatures, including humans.

The research was carried out the Australian Antarctic base, Davis station, by a team of scientists from the University of Technology Sydney (UTS), Southern Cross University (SCU), the Australian Antarctic Division (AAD) and the University of Tasmania. Using large 650 L experimental tanks, a temperature controlled 40-foot container and natural coastal water, their research was designed to investigate the effects of predicted future changes in ocean acidity on the community structure of the Antarctic phytoplankton.

"We were alarmed to find that diatoms were so negatively affected, with some species likely to have diminished silica production before the end of this century," says Dr Petrou.

In the context of global climate change, these findings are important because they reveal that OA can notonly alter phytoplankton community composition, but also reduce diatom ballast (sinking ability), adds SCU based Kai Schulz. Loss of silica production and thus ballast could mean that fewer diatoms end up on the ocean floor, resulting in less atmospheric CO2 being removed from our atmosphere and transported for storage in the deep ocean.

"The only genuine way to circumvent this outcome, is to cut our greenhouse gas emissions and limit the acidification of our oceans," the researchers say.

At about the same rate that your heart beats, a Utah rock formation called Castleton Tower gently vibrates, keeping time and keeping watch over the sandstone desert. Swaying like a skyscraper, the red rock tower taps into the deep vibrations in the earth--wind, waves and far-off earthquakes.

New research from University of Utah geologists details the natural vibration of the tower, measured with the help of two skilled rock climbers. Understanding how this and other natural rock forms vibrate, they say, helps us keep an eye (or ear) on their structural health and helps us understand how human-made vibrations affect seemingly unmovable rocks. The results are published in the Bulletin of the Seismological Society of America.

"We often view such grand and prominent landforms as permanent features of our landscape, when in reality, they are continuously moving and evolving," says Riley Finnegan, a graduate student and co-author on the paper.

"A stoic power"

Castleton Tower is a spire of Wingate Sandstone nearly 400 feet (120 m) tall that stands over Utah's Castle Valley. First climbed in 1961, Castleton Tower became a widely renowned classic destination after appearing as one of two Utah climbs in the 1979 book "Fifty Classic Climbs of North America." It's one of the largest freestanding rock towers.

"Most people are in awe of its static stability, in its dramatic freestanding nature perched at the end of a ridge overlooking Castle Valley," says geologist Jeff Moore, who led the study. "It has a kind of stoic power in its appearance."

Moore and his colleagues study the vibrations of rock structures, including arches and bridges, to understand what natural forces act on these structures. They also measure the rocks' resonance, or the way the structures amplify the energy that passes through them. Sources of this energy can be as local as wind gusts or traffic on a nearby road or as distant as far-off earthquakes and even ocean waves. "Because nothing is truly static, there is always energy propagating throughout the earth, which serves as a constant vibration source for the rock," Finnegan says.

Moore, Finnegan and graduate student Paul Geimer have been developing and refining their methods of measuring rock structures as they've surveyed arches, bridges and hoodoos, which are small spire-like formations--towers on a smaller scale. They use seismometers to measure even the slightest movement in three dimensions. For some of their measurements, they've sped up the low-frequency seismic data into audible sound--allowing you to listen to the voice of a rock.

Hear Castleton Tower here.

As part of the research, Geimer has led an effort to collect 3-D imagery of the rock structures to precisely measure the rocks' dimensions--helping the researchers learn even more about what makes these rocks rumble.

"As of just a few years ago there were almost no measurements of the kind in existence," Moore says, "so every feature we measure is something new."

"Something we couldn't just walk up to"

Placing a seismometer at the top of Castleton Tower, however, required someone ascending to the top to install and retrieve the equipment. Fortunately, two professional climbers on a seasonal break from their employment offered their skills and equipment. "They were all in." Moore says. The research team jumped at the chance.

To get the needed data, the climbers trekked to the base of the tower and placed a seismometer to serve as a reference. Geimer says that on the day of the experiment, in March 2018, the weather was good and the climbing route up the popular tower was filled with a consistent stream of climbers. "I can imagine both anxiety and excitement levels spiked when the team walked away from the reference and began the climb to the top," Geimer says, "knowing that it would be hours before returning safely to the base and verifying a successful measurement."

The climbers carried another heavy seismometer to the top and ran measurements for three hours before returning both instruments to the research team. "Their skills provided us an opportunity to measure something we couldn't just walk up to," Finnegan says.

Just as predicted

From their earlier work, the team was able to predict some of the properties of the tower. Finnegan says that larger structures like Castleton Tower vibrate at lower frequencies than smaller structures. "Think of it like a guitar string," she says. "The thick ones have lower pitches, and the thin ones have higher pitches."

Geimer adds that the geometry of the tower is relatively simple, making it suitable for fundamental models that characterize how it might respond to vibrations, including seismic events.

Analyzing the data, the researchers found that the tower's two primary resonance modes were at frequencies of 0.8 and 1.0 hertz, respectively. One hertz is equal to one cycle per second, so these results mean that the tower naturally sways around once per second. And that small sway is constant, Geimer says. "The distant sources that excite the unique resonance of Castleton Tower are always active and transferring energy into the rock mass."

A geological checkup

Castleton Tower is the largest rock structure that Moore, Finnegan and Geimer have studied. So far, the team is collecting baseline measurements about the rocks' movements. Geimer will use the data to see if repeated measurements can assess damage to the structures, while Finnegan is studying how vibrational energy, both from natural and human sources, may impact the structural integrity of structures like Castleton Tower. "While some forces humans create might appear minor," Moore says, "our research is addressing the long-term effects of these forces on the rate of erosion and structural degradation over time." So far, the team can tell that Castleton Tower's vibrational modes sit in a quiet part of the frequency spectrum, relatively unaffected by traffic or even small earthquakes.

"I hope that climbers and anyone who is fortunate enough to stand in the shadow of this stone giant will see it in a new light moving forward," Geimer says. "As with the desert landscape in which it resides, Castleton Tower is dynamic and energetic, subtly responding to changes in the surrounding environment."

Researchers from The Westmead Institute for Medical Research (WIMR) have discovered how fatty liver disease develops in lean people, aiding the development of potential treatments for these patients.

Fatty liver disease - a condition characterised by a build-up of fat in the liver - affects a quarter of the world's population. Although it commonly develops in overweight and obese people, many individuals with a body-mass index of less than 25kg/m2 will develop the disease, and tend to have worse outcomes compared to obese patients.

Professor Jacob George, co-lead researcher of the study said, "Cases of lean fatty liver disease are considered a bit of a mystery, as we don't know how and why the disease develops and progresses.

"Our research team compared the metabolism, gut bacteria and genetic profiles of patients with lean and non-lean fatty liver disease to determine factors that contribute to disease development and progression.

"Interestingly, lean fatty liver patients have a very distinct metabolism compared to non-lean ones, which can explain some of the differences we see in disease progression.

"Compared to non-lean patients, lean patients had higher levels of bile acids, which play a role in the digestion of fats, and a protein called fibroblast growth factor 19 (FGF19). Bile acids and FGF19 increase energy expenditure, which can explain why lean individuals with fatty liver disease stay lean. This suggests that lean patients with a fatty liver may have an 'obesity-resistant' profile, and better adaptation to an excess intake of calories."

Associate Professor Mohammed Eslam, co-lead researcher added, "Importantly, the favourable profile of lean patients did not protect them from liver fat accumulation.

"We also identified changes in particular gut bacteria and novel genes that can influence the development of fatty liver disease in lean patients. For example, we identified that a variant in the gene TM6SF2, previously linked to fatty liver disease, is more common in lean patients."

Without treatment, fatty liver disease can result in liver scarring, liver cirrhosis and, in severe cases, liver failure.

Associate Professor Mohammed Eslam said, "The metabolic adaptive mechanisms in lean fatty liver disease tend to be lost in the late stages of the disease. This could explain why these patients have worse disease outcomes compared to their obese counterparts."

"Now that we know more about the metabolic profile and processes behind fatty liver disease in lean people, we can work towards more targeted treatments for these patients."

Professor George concluded, "Our research is now focused on understanding more about the condition, so that we can prevent its progression, and develop more personalised treatment regimens."

Metal Matrix Nanocomposites (MMNCs) are increasingly used in industries such as automotive, aerospace and military due to their excellent combination of high strength, thermal stability, ductility and isotropy. However, despite MMNCs' superior properties and growing interest, the complex processing and inadequate economic efficiency have limited the applications of MMNCs. High energy consumption is still essential to disperse the reinforcement to achieve microstructural homogeneity and advanced mechanical properties in these materials.

Selective laser melting (SLM), also known as laser powder bed fusion (L-PBF), is an additive manufacturing (AM) technology applied to metals and ceramics, and has shown promising potential for fabrication of unique structures and properties such as MMNCs. Using high power laser, SLM allows for quick production of three-dimensional (3D) parts with complicated shapes directly from powder materials without the time-consuming mold design process. This reduces production cost and lead time while delivering customized MMNCs parts for automotive, aerospace, electronics and biomedical industries.

However, due to the lack of comprehensive understanding of the defects unique to SLM as well as the fabrication and performance of nanocomposites with SLM, researchers from Singapore University of Technology and Design (SUTD) and their research collaborators set out to gain a thorough understanding of the scientific and technological knowledge. They reviewed state of the art research from the perspective of materials and SLM processing parameters. Their paper was published in Progress in Materials Science, a journal that publishes authoritative reviews of recent advances in the science of materials.

An in-depth review of the fabrication considerations related to nanocomposites was also conducted including the materials and SLM processing parameters, emphasizing on physical properties and preparation of powders (refer to image). Thereafter, mechanical properties of MMNCs and the corresponding enhancing mechanisms were addressed to provide a deeper understanding of MMNCs.

"MMNCs have always been a huge interest for material scientists. With the advancement in advanced manufacturing, particularly additive manufacturing, there is now greater potential in achieving high quality MMNCs. In our review, laser powder bed fusion is chosen as the process in focus as it has proven its capabilities in fabricating functional parts from metals and ceramics," explained principal investigator and co-author Professor Chua Chee Kai from SUTD.

The review paper also addressed the defects unique to SLM technology associated with nanoparticles. The applications of MMNCs especially those fabricated with SLM processing were also listed and compared.

"One of the key challenges in AM is the lack of 'printable' materials. We believe this comprehensive review provides a timely overview and understanding of SLM for MMNCs by focusing on the merits while not ignoring the limitations. This hopefully will encourage more researchers to explore this highly interesting area," said co-author Dr Sing Swee Leong from Nanyang Technological University.

Solar cells that rely on perovskites to harvest sunlight are bound to gain in energy conversion efficiency thanks to an atomic-level understanding of the structure-property relationship of these photovoltaic materials. Researchers from the KAUST Solar Center monitored the impact of compositional changes on the structural organization and photovoltaic properties of perovskite thin films in situ1, 2.

Hybrid perovskites have emerged as key components in low-cost, high-efficiency solar cells because they are cheaper and easier to process than traditional silicon-based solar cell materials. In addition, they exhibit unique optoelectronic characteristics, including high light absorption and a defect tolerance that lead to solar cells with maximum power-conversion efficiencies of 24 to 28 percent when used alone or in tandem combination with silicon. They also outperform single-junction silicon solar cells.

Solar cell performance and stability depend on the morphology of the thin films, especially their ability to crystallize in the so-called photoactive α-phase. Perovskites containing lead tend to combine various halides, such as the anionic forms of bromine and iodine, with mixtures of methylammonium, formamidinium, cesium and other cations. These have led to record conversion efficiencies and thermal stabilities compared with their single-halide, single-cation analogs. However, these mixed-halide, mixed-cation perovskite films have been characterized only through ex-situ postdeposition techniques. This limits the understanding of the mechanisms that govern their growth from their sol-gel precursor to their solid state and stalls attempts to improve device performance and stability.

Now, Stefaan De Wolf, his postdoc Kai Wang and coworkers have investigated the impact of cations, halides and antisolvent dripping on mixed-halide, mixed-cation perovskite films. The team tracked the films' structural evolution during the spin-coating deposition process using an in situ X-ray scattering technique. The X-ray technique probed the films at the atomic scale from their sol-gel precursor to the solid state and provided information about the formation of crystalline intermediates during the solidification. The researchers also incorporated the films into solar cells and evaluated the performance and stability of the resulting devices.

"Our study provides critical insights into the crystallization of the multicomponent systems toward high-performance perovskite solar cells," Wang says. Changes in the compositions of the halide and cation dramatically affected the solidification of the perovskite precursors during spin coating and the subsequent formation of the desired α-phase upon antisolvent addition.

The period needed to generate high-quality films by antisolvent addition ended when the sol-gel structure collapsed to produce crystalline by-products depending on the precursor mixture. Consequently, tuning the halide-cation mixture could delay this collapse, widening the antisolvent dripping window from a few seconds to several minutes. As well, simultaneously incorporating cesium and rubidium cations in the perovskite synergistically stimulated the formation of the α-phase. The length of this window showed little effect on resulting solar cell performance as long as the antisolvent was added within this period.

These findings suggest new directions for the development of perovskite formulations that can further stabilize the sol-gel state and promote its conversion to the desirable perovskite phase. "This is critical in achieving better-performing, reproducible, cost-efficient and scalable manufacturing of perovskite solar cells," Wang says.

The team is working on transferring this knowledge to other deposition technologies to progress toward market-ready perovskite solar cells.

The Sustainable Development Goals and the Paris Agreement on Climate Change call for deep transformations that require complementary actions by governments, civil society, science, and business. IIASA contributed to a new study outlining six major transformations that will be required to achieve these ambitious goals.

The UN Sustainable Development Goals (SDGs) focus on time-bound targets for prosperity, people, planet, peace, and partnership - collectively known as the five Ps. By adopting the 2030 Agenda with its 17 SDGs and the Paris Climate Agreement, UN member states effectively created a framework for national action and global cooperation on sustainable development, while the Paris Agreement committed signatory countries to achieving net-zero greenhouse gas emissions by the middle of the century. SDG 13 on climate change specifically links to the Paris Agreement noting that the UN Framework Convention on Climate Change "is the primary international, intergovernmental forum for negotiating the global response to climate change." Despite the interconnectivity and clear aims of these global goals, stakeholders seem to lack a shared understanding of how the 17 SDGs can be operationalized.

Building on previous work by The World in 2050 - a global research initiative established by IIASA - the authors of the study published in the journal Nature Sustainability propose six transformations to organize SDG interventions through a semi-modular action agenda that can be designed by discrete, yet interacting, parts of government. According to the paper, the proposed framework may be operationalized within the structures of governments while still respecting the strong interdependencies across the 17 SDGs. The authors also outline an action agenda for science to provide the knowledge required for designing, implementing, and monitoring the SDG Transformations.

"The 2030 Agenda and the Paris Agreement have given the world an aspirational narrative and an actionable agenda to achieve a just, safe, and sustainable future for all within planetary boundaries. The six transformations provide an integrated and holistic framework for action that reduces the complexity, yet encompasses the 17 SDGs, their 169 targets, and the Paris Agreement. They provide a new approach to shift from incremental to transformational change; to identify synergies using sustainable development pathways; formulate actionable roadmaps; and a focus on inter-relationships to uncover multiple benefits and synergies," explains study co-author Nebojsa Nakicenovic, executive director of The World in 2050 (TWI2050) research initiative at IIASA.

In their paper the researchers considered which key interventions would be necessary to achieve the SDG outcomes and how their implementation might be organized into a limited set of six transformations namely education, gender, and inequality; health, wellbeing, and demography; energy decarbonization and sustainable industry; sustainable food, land, water, and oceans; sustainable cities and communities; and digital revolution for sustainable development. To simplify the discussion of interlinkages between interventions and SDGs, the authors further identified intermediate outputs generated by combinations of interventions, which in turn contribute to the achievement of each SDG. Each SDG transformation describes a major change in societal structure (economic, political, technological, and social) to achieve long-term sustainable development, while also each contributing to multiple SDGs. Excluding any of them would make it virtually impossible to achieve the SDGs.

Pursuing the six transformations will require deep, deliberate, long-term structural changes in resource use, infrastructure, institutions, technologies, and social relations, which have to happen in a relatively short time window. Previous societal transformations, like industrialization in 19th century Europe, were initiated by technological changes like the steam engine and were largely undirected, while 20th century technologies like semiconductors, the Internet and Global Positioning Systems, were promoted through directed innovation to meet military aims. The authors emphasize that it is crucial that SDG transformations are formally directed in order to meet time-bound, quantitative targets, such as net-zero carbon emissions by mid-century.

"By achieving change in these six key areas, we can save both people and planet. To deliver on both ambitious climate targets and meet all the Sustainable Development Goals, we identify very concrete levers that governments can pull. For instance, investing in agriculture with known technologies and management practices can enable both food security, human health, and climate mitigation. Investing in young children's education is another example. It improves human wellbeing, increases economic development, and stabilizes population growth," says study co-author Johan Rockström from the Potsdam Institute for Climate Impact Research in Germany. "The six transformations in this paper have the ultimate goal of enhancing human prosperity and reducing inequalities. This is of course not easy. In fact, it is the largest human endeavor of all time. Science is here to provide governments with a fact-based framework. If political leadership fails to act, however, we would face unprecedented risks for the stability of societies, and for our Earth system."

Hogweed, which has grown over vast territories of Russia, can be useful as a material for batteries. Scientists from NUST MISIS have investigated the possibilities of fibrous substances in the plant stems. They have turned them into electrodes -- elements of devices capable of storing energy. It was experimentally proven that the treated dangerous plant can successfully replace traditional sources of energy without compromising the quality of the batteries.

Supercapacitors are storage devices. They are distinguished from traditional batteries by their high power, long shelf life, and long service life. Such properties are partly explained by the fact that activated carbons with a highly developed surface with a large number of pores of different sizes, act as the electrode material. These pores provide an increase in the area of the electrodes, on which the maximum volume of the accumulated charge directly depends. Scientists are currently trying to receive carbon materials from various plant raw materials, especially from agricultural waste -- from the coconut, almond and walnut shells, husk remaining after cereal processing, etc.

Researchers from NUST MISIS have suggested that the optimal electrode properties can be found in hogweed stems. They consist of a firm bark and a soft inner core, similar to a sponge, forming a diverse porous structure. This design is effective for using carbon material as the basis of electrodes for supercapacitors. In order to turn hogweed stalks into a material suitable for use as electrodes, it was necessary to find the optimal processing technology for them.

The dry stalks of the hogweed were cut into bars about a centimeter long. Then, to remove various inorganic compounds contained in the stems, they were treated with hydrochloric acid, washed and dried. To obtain a carbon material, crushed hogweed stems were saturated with carbon dioxide at a temperature of 400 ° C. In the next stage, the obtained material was mixed with potassium hydroxide and activated, that is, the appeared pores were opened in an argon atmosphere at various temperatures.

Processing the primary carbon material at a temperature of 900° ? led to the formation of a surface with a large number of pores 2-4 nm in size.

"The main parameter of the supercapacitor is capacity, which means a measure of the ability to accumulate an electric charge, -- Oleg Levin, associate professor at the Department of Electrochemistry of St. Petersburg State University, explained. -- The capacity obtained from hogweed stems is at the same level as the one obtained from the other materials. Of course, when using, for example, graphene, it will be higher. However, the use of plant waste material for the production of active carbon is without a doubt a global trend. From this perspective, the work of scientists is promising and deserves attention".

However, the leader of the project, the head of the Department of Physical Chemistry at NUST MISIS Professor Mikhail Astakhov emphasizes that the use of hogweed stems for the production of electrodes on an ongoing basis may encounter great difficulties. Indeed, to obtain raw materials you will have to travel all over the country, cutting down the plant and taking it to the enterprise, since it is unreasonable to create sown areas for a dangerous wild plant. Sooner or later, the reserves of the "wild" hogweed may run low. In this case, the technology created for its processing will simply not be needed.

On the other hand, at present, areas covered by powerful hogweed that inhibits the development of other seeds that have fallen into the soil are only increasing.

HOUSTON -- (Aug. 26, 2019) -- Physicists studying the strange behavior of metal alloys called heavy fermions have made a surprising discovery that could be useful in safeguarding the information stored in quantum bits, or qubits, the basic units of encoded information in quantum computers.

In a study in the Proceedings of the National Academy of Sciences, researchers from Rice University and the Vienna University of Technology (TU Wien) in Austria examined the behavior of an intermetallic crystal of cerium, palladium and silicon as it was subjected to extreme cold and a strong magnetic field. To their surprise, they found they could transform the quantum behavior of the material in two unique ways, one in which electrons compete to occupy orbitals and another where they compete to occupy spin states.

"The effect is so pronounced with one degree of freedom that it ends up liberating the other one," said Rice's Qimiao Si, co-corresponding author of the study and the director of the Rice Center for Quantum Materials (RCQM). "You can essentially tune the system to maximize damage to one of these, leaving the other well-defined."

Si said the result could be important for companies like Google, IBM, Intel and others who are competing to develop quantum computers. Unlike today's digital computers, which use electricity or light to encode bits of information, quantum computers use the quantum states of subatomic particles like electrons to store information in qubits. A practical quantum computer could outperform its digital counterpart in many ways, but the technology is still in its infancy, and one of the chief obstacles is the fragility of the quantum states inside the qubits.

"You need a well-defined quantum state if you wish to be assured that the information that is stored in a qubit will not change due to background interference," Si said.

Every electron acts like a spinning magnet, and its spin is described in one of two values, up or down. In many qubit designs, information is encoded in these spins, but these states can be so fragile that even tiny amounts of light, heat, vibration or sound can cause them to flip from one state to another. Minimizing the information that's lost to such "decoherence" is a major concern in qubit design, Si said.

In the new study, Si worked with longtime collaborator Silke Paschen of TU Wien to study a material where the quantum states of electrons were scrambled not just in terms of their spins but also in terms of their orbitals.

"We designed a system, realized in some theoretical models and concurrently realized in a material, where spins and orbitals are almost on an equal footing and are strongly coupled together," he said.

From previous research in 2012, Si, Paschen and colleagues knew that electrons in the compound could be made to interact so strongly that the material would undergo a dramatic change at a critically cold temperature. On either side of this "quantum critical point," electrons in key orbitals would arrange themselves in a completely different way, with the shift occurring solely due to the quantum interactions between them.

The earlier study invoked a well-known theory Si and collaborators developed in 2001 that prescribes how the spins of these localized electrons, which are part of atoms inside the alloy, strongly couple with free-flowing conduction electrons at the quantum critical point. According to this "local quantum critical" theory, as the material is cooled and approaches the critical point, the spins of localized electrons and conduction electrons begin to compete to occupy particular spin states. The quantum critical point is the tipping point where this competition destroys the ordered arrangement of the localized electrons and they instead become completely entangled with the conduction electrons.

Even though Si has studied quantum criticality for almost 20 years, he was surprised by the results of Paschen's latest experiments.

"The new data was completely baffling to all of us," he said. "That is, until we realized that the system contained not only spins but also orbitals as active degrees of freedom."

With that realization, Si's team, including Rice graduate student Ang Cai, built a theoretical model that contains both the spins and orbitals. Their detailed analysis of the model revealed a surprising form of quantum criticality that provided a clear understanding of the experiments.

"It was a shock to me, both from the theoretical model perspective and the experiments," he said. "Even though this is a soup of things -- spins, orbitals that are all strongly coupled to each other and to background conduction electrons -- we could resolve two quantum critical points in this one system under the tuning of one parameter, which is the magnetic field. And at each one of the quantum critical points, only the spin or the orbital is driving the quantum criticality. The other one is more or less a bystander."

Si is the Harry C. and Olga K. Wiess Professor in Rice's Department of Physics and Astronomy.

The study's co-lead authors are Cai and Valentina Martelli, formerly of TU Wien and now with the University of São Paulo in Brazil. Additional co-authors include Chia-Chuan Liu and Hsin-Hua Lai, both of Rice; Emilian Nica, formerly of Rice and currently at the University of British Columbia; Rong Yu, formerly of Rice and currently at Renmin University of China; Mathieu Taupin, Andrey Prokofiev, Diana Geiger, Jonathan Haenel and Julio Larrea, all of TU Wien; Kevin Ingersent of the University of Florida; Robert Küchler of the Max Planck Institute for Chemical Physics of Solids in Dresden, Germany; and Andre Strydom of the University of Johannesburg in South Africa.

The research was supported by the National Science Foundation (DMR-1920740, CNS-1338099, PHY-1607611, DMR-1508122), the Robert A. Welch Foundation (C-1411), the Army Research Office (ARO-W911NF-14-1-0525, ARO-W911NF-14-1-0496), the Austrian Science Fund (P29296-N27, DK W1243), the European Research Council (Advanced Grant 227378), the Carlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro (201.755/2015), the National Natural Science Foundation of China (11674392), the Ministry of Science and Technology of China (2016YFA0300504), the South African National Research Foundation (93549), the University of Johannesburg and RCQM.

RCQM leverages global partnerships and the strengths of more than 20 Rice research groups to address questions related to quantum materials. RCQM is supported by Rice's offices of the provost and the vice provost for research, the Wiess School of Natural Sciences, the Brown School of Engineering, the Smalley-Curl Institute and the departments of Physics and Astronomy, Electrical and Computer Engineering, and Materials Science and NanoEngineering.

Allergic reactions are common side effects of tattoos and pigments have been blamed for this. Now researchers prove, for the first time, that particles wear from the needle during the tattooing process and contain the allergens nickel and chromium and therefore could also induce allergies.

The number of tattooed people has increased substantially in recent years, with some countries revealing to have up to 24% of the population with a tattoo. Adverse reactions from tattoos are common and until now, researchers believed only inks were to blame.
"There is more to tattoos than meet the eye. It is not only about the cleanliness of the parlour, the sterilization of the equipment or even about the pigments. Now we find that the needle wear also has an impact in your body", explains Hiram Castillo, one of the authors of the study and scientist at the ESRF.

Today, in a new study published in the journal Particle and Fibre Toxicology, scientists have shown that, surprisingly, chromium and nickel particles coming from tattoo needle wear are distributed towards the lymph nodes. Usually tattoo needles contain nickel (6-8%) and chromium (15-20%) both of which prompt a high rate of sensitization in the general population and may therefore play a role in tattoo allergies. Two years ago, the same team of researchers found that the pigments and their metal impurities are transported to the lymph nodes in a nanoform, where they can be found years after the placement of the tattoos.

Ines Schreiver, corresponding author of the research and scientist at the Federal Institute for Risk Assessment in Germany, explains how their detective work led them to the needles. "We were following up on our previous study, by trying to find the link between iron, chromium and nickel and the colouring of the inks. After studying several human tissue samples and finding metallic components, we realized that there must be something else. We also tested around 50 ink samples without finding such metal particles and made sure that we hadn't contaminated the samples during sample preparation. Then we thought of testing the needle and that was our 'eureka' moment".

The team, led by researchers at the Federal Institute for Risk Assessment in Germany, included scientists from the European Synchrotron (ESRF), Grenoble, (France), Xploraytion GmbH, Physikalisch-Technische Bundesanstalt, Technical University Berlin, Helmut Fischer GmbH, Ludwig-Maximilians University, (Germany), the University of Regensburg, a dermatologist from Belgium and CNRS/Sorbonne Université (France). They came to the ESRF - one of the world's most intense X-ray sources - to carry out the analysis of the samples using synchrotron nano-X-ray fluorescence and nano- X-ray absorption near-edge structure on beamlines ID21 and ID16B. The results showed that when the tattoo ink contains titanium dioxide (a white pigment often mixed in bright colours such as green, blue and red), it abrades the needle. This does not happen when using carbon black ink. The team also studied a needle before and after the tattoo process using scanning electron microscopy, which showed the abrasion it had undergone. "It is beyond doubt that the metal particles derive from the tattoo needle as result of pure mechanical grinding", says Bernhard Hesse, of Xploraytion and visiting scientist at the ESRF. It is known that titanium dioxide is very abrasive due to its high density and hardness compared to carbon black.

The size of the particles found in the lymph nodes after being translocated from the tattoos range from 50 nanometres to 2 micrometre. Nanoparticles are more dangerous than micro-sized particles due to their increased surface-to-volume ratio, which consequently leads to a potentially higher release of toxic elements. Nanoparticles can also directly enter cells and are more easily distributed in the body. On a positive note, however, they may also be more readily excreted from the body.

The study provides the first proof that, not only tattoo pigments, but also abraded needle particles are distributed towards the lymph nodes. However, further investigations need to be carried out to clearly assess impact on tattoo allergy formation and systemic sensitization. "The fact that all pigments and wear particles are deposited in lymph nodes calls for special attention to be placed on allergy development. Unfortunately, today, we can't determine the exact impact on human health and possible allergy development deriving from the tattoo needle wear", explains Schreiver. "These are long-term effects which can only be assessed in long-term epidemiological studies that monitor the health of thousands of people over decades", she concludes.

A University of Texas at Dallas physicist has teamed with Texas Instruments Inc. to design a better way for electronics to convert waste heat into reusable energy.

The collaborative project demonstrated that silicon's ability to harvest energy from heat can be greatly increased while remaining mass-producible.

Dr. Mark Lee, professor and head of the Department of Physics in the School of Natural Sciences and Mathematics, is the corresponding author of a study published July 15 in Nature Electronics that describes the results. The findings could greatly influence how circuits are cooled in electronics, as well as provide a method of powering the sensors used in the growing "internet of things."

"Sensors go everywhere now. They can't be constantly plugged in, so they must consume very little power," Lee said. "Without a reliable light source for photovoltaic energy, you're left needing some kind of battery -- one that shouldn't have to be replaced."

Thermoelectric generation is a highly green energy source, converting a difference in temperature into electrical energy.

"In a general sense, waste heat is everywhere: the heat your car engine generates, for example," Lee said. "That heat normally dissipates. If you have a steady temperature difference -- even a small one -- then you can harvest some heat into electricity to run your electronics."

Sensors embedded beneath a traffic intersection provide an example of convenient thermoelectric power.

"The heat from tires' friction and from sunlight can be harvested because the material beneath the road is colder," Lee said. "So no one has to dig that up to change a battery."

The primary hurdles for widespread thermoelectric harvesting have been efficiency and cost, he said.

"Thermoelectric generation has been expensive, both in terms of cost per device and cost per watt of energy generated," Lee said. "The best materials are fairly exotic -- they're either rare or toxic -- and they aren't easily made compatible with basic semiconductor technology."

Silicon, upon which so much technology relies, is the second-most abundant element in Earth's crust. It has been known since the 1950s to be a poor thermoelectric material in its bulk, crystalline form. But in 2008, new research indicated that silicon performed much better as a nanowire -- a filamentlike shape with two of its three dimensions less than 100 nanometers. For comparison, a sheet of paper is about 100,000 nanometers thick.

"In the decade since those experiments, however, efforts to make a useful silicon thermoelectric generator haven't succeeded," Lee said.

One barrier is that the nanowire is too small to be compatible with chip-manufacturing processes. To overcome this, Lee and his team relied on "nanoblades" -- only 80 nanometers thick but more than eight times that in width. While that is still much thinner than a sheet of paper, it's compatible with chip-manufacturing rules.

Study co-author Hal Edwards, a TI Fellow at Texas Instruments, designed and supervised fabrication of the prototype devices. He turned to Lee and UT Dallas to further study what the devices could do.

"A deep dive for these novel measurements, detailed analysis and literature comparisons requires a university group," Edwards said. "Professor Lee's analysis identified key metrics in which our low-cost silicon technology competes favorably with more exotic compound semiconductors."

Lee explained that the nanoblade shape loses some thermoelectric ability relative to the nanowire.

"However, using many at once can generate about as much power as the best exotic materials, with the same area and temperature difference," he said.

The team's circuit-design solution combined an understanding of nanoscale physics with engineering principles. One key realization was that some previous attempts failed because too much material was used.

"When you use too much silicon, the temperature differential that feeds the generation drops," Lee said. "Too much waste heat is used, and, as that hot-to-cold margin drops, you can't generate as much thermoelectric power.

"There is a sweet spot that, with our nanoblades, we're much closer to finding than anyone else. The change in the form of silicon studied changed the game," he added.

Lee said that the advanced silicon-processing technology at Texas Instruments allows for efficient, inexpensive manufacturing of a huge number of the devices.

"You can live with a 40% reduction in thermoelectric ability relative to exotic materials because your cost per watt generated plummets," he said. "The marginal cost is a factor of 100 lower."

Gangyi Hu PhD'19, who finished his doctorate in physics at UT Dallas in May, is the study's lead author. He produced the computer modeling to determine the number of nanoblades per unit area that will produce the most energy without reducing the temperature difference.

"We optimized the configuration of our devices to place them among the most efficient thermoelectric generators in the world," Hu said. "Because it's silicon, it remains low-cost, easy to install, maintenance-free, long-lasting and potentially biodegradable."

Lee said the work was also novel because they used an automated industrial manufacturing line to fabricate the silicon integrated-circuit thermoelectric generators.

"We want to integrate this technology with a microprocessor, with a sensor on the same chip, with an amplifier or radio, and so on. Our work was done in the context of that full set of rules that govern everything that goes into mass-producing chips," Lee said. "Over at Texas Instruments, that's the difference between a technology they can use and one they can't."

Edwards vouched for the multiple advantages of collaborating with UT Dallas, including recruiting.

"I find my collaborations with professor Lee's group to be very valuable," Edwards said. "I also value the opportunity to get to know students well, so that I can help them to find roles within TI. One of my close TI colleagues was professor Lee's PhD student during one of our earlier collaborations."

SAN DIEGO, Aug. 26, 2019 -- In addition to their role in plant fertilization and reproduction, pollens and spores have another, hidden talent: With a simple treatment, these cheap, abundant and renewable grains can be converted into tiny sponge-like particles that can grab on to pollutants and remove them from water, scientists report. Even better, these treated particles don't trigger allergies.

The researchers will present their results today at the American Chemical Society (ACS) Fall 2019 National Meeting & Exposition. ACS, the world's largest scientific society, is holding the meeting here through Thursday. It features more than 9,500 presentations on a wide range of science topics.

A brand-new video on the research is available at www.acs.org/HLS_Pollen_Sponge.

"Even very low levels of certain compounds, such as hormones, pharmaceuticals or those in household and personal care products, can cause toxic effects. However, they often can escape normal cleanup processes at wastewater treatment plants," says Andrew Boa, Ph.D., whose lab is working on the pollen project. "We're trying to find alternative ways to remove these chemicals from water so we can reduce the amount going into the environment."

The project is part of the larger "Sullied Sediments" program in which Boa and many other scientists are assessing pollutant levels in sediments from European waterways, with a view to assessing dredged sediment, managing sediment reuse and reducing future contaminations. These contaminants include pharmaceuticals such as the pain reliever diclofenac and household chemicals such as triclosan, an antimicrobial compound used in toothpaste, and other personal care products. Some of these chemicals, including triclosan, are either banned or their use heavily restricted. The European Union will begin officially monitoring levels of all of these "Watch List" chemicals from 2020 onwards.

The spore grains used in the study are extracted from Lycopodium clavatum -- the common club moss. In their natural state, each of these microscopic grains carries genetic material inside a hard shell that's coated with an outer layer of wax and proteins, explains Aimilia Meichanetzoglou, a doctoral student in Boa's lab at the University of Hull.

Boa first became interested in pollen thanks to his work with Grahame Mackenzie, Ph.D., a Hull professor (now emeritus) who developed the original method to form non-allergenic, hollowed-out pollen and spore shells. Mackenzie's company, Sporomex, uses the inert shells to encapsulate active ingredients for controlled release in pharmaceutical, food, cosmetic and medical applications.

Boa has taken the concept in an entirely different direction. When he and Meichanetzoglou were studying the empty shells' interactions with a variety of chemicals, they noticed that some of the compounds became adsorbed, or stuck to, the surface of the shells. Boa realized this stickiness could potentially be used to grab low levels of pollutants, and so he pursued this type of application.

Meichanetzoglou uses hydrolysis to rid the pollen of its genetic cargo and waxy coat, which makes the grains hypoallergenic. To target particular pollutants, she can vary the hydrolysis conditions and make modifications to the surface of the grains. For example, to remove phosphate, which is used in many fertilizers, Meichanetzoglou deposits iron oxide on the surface of the shells. Iron oxide reacts with the phosphate to form insoluble iron phosphate, which precipitates out of the water and gets adsorbed onto the grains. The researchers found that the grains could remove almost all of the phosphate from water samples and nearly 80% of several other pollutants.

Treating wastewater will require consideration of various factors, such as scale and the degree of contamination. For example, homes that use a septic tank; particular buildings with a high level of pharmaceuticals in their waste water, such as hospitals or care homes for the elderly; or municipal waste water treatment plants that serve a whole city will all have different requirements. Boa is exploring options with local water authorities for implementation of this technology.

Boa has purposely tried to keep process costs low to make the method commercially feasible. The moss is already harvested for other applications, Boa notes, and it can grow on poor-quality soil, so it won't compete with food crops for arable land. His collaborators have also begun testing the bioavailability of pollutants captured by the grains.

A press conference on this topic will be held Monday, Aug. 26, at 9 a.m. Pacific time in the San Diego Convention Center. Reporters may check-in at the press center, Room 14B, Mezzanine Level, or watch live on Youtube http://bit.ly/acs2019sandiego. To ask questions online, sign in with a Google account.

SAN DIEGO, Aug. 26, 2019 -- A polymer that self-destructs? While once a fictional idea, new polymers now exist that are rugged enough to ferry packages or sensors into hostile territory and vaporize immediately upon a military mission's completion. The material has been made into a rigid-winged glider and a nylon-like parachute fabric for airborne delivery across distances of a hundred miles or more. It could also be used someday in building materials or environmental sensors.

The researchers will present their results today at the American Chemical Society (ACS) Fall 2019 National Meeting & Exposition. ACS, the world's largest scientific society, is holding the meeting here through Thursday. It features more than 9,500 presentations on a wide range of science topics.

A brand-new video on the research is available at http://www.acs.org/HLS_Disappearing_Glider.

"This is not the kind of thing that slowly degrades over a year, like the biodegradable plastics that consumers might be familiar with," says Paul Kohl, Ph.D., whose team developed the material. "This polymer disappears in an instant when you push a button to trigger an internal mechanism or the sun hits it." The disappearing polymers were developed for the Department of Defense, which is interested in deploying electronic sensors and delivery vehicles that leave no trace of their existence after use, thus avoiding discovery and alleviating the need for device recovery.

The key to making a polymer disappear, or break apart, is "ceiling temperature." Below the ceiling temperature, a polymer configuration is favored, but above that temperature, the polymer will break apart into its component monomers. Common polymers, like polystyrene, have a ceiling temperature above ambient temperature and are very stable. And even when they are warmed above their ceiling temperature, some of these materials can take a long time to decompose. For example, thousands of chemical bonds link all of the monomers together in polystyrene, and all of these bonds must be broken for the materials to decompose. But with low ceiling-temperature polymers, such as the cyclic ones Kohl is using, only one bond needs to break, and then all of the other bonds come apart, so the depolymerization happens quickly. The process can be initiated by a temperature spike from an outside or embedded source, or by a light-sensitive catalyst.

For many years, researchers have attempted to make these polymers, but were unsuccessful because of the materials' instability at room temperature. Kohl's research group at the Georgia Institute of Technology discovered that they could overcome this issue if they were careful to remove all impurities formed during the synthesis. In addition, they found a number of aldehydes, including phthalaldehyde, that readily form cyclic polymers. Once they had optimized this polymer's synthesis, they focused on ways to make it disappear.

To do this, the researchers incorporated into the polymer a photosensitive additive, which absorbs light and catalyzes depolymerization. "Initially, we made it photosensitive to just ultraviolet light so we could make the parts in a well-lit room with fluorescent lighting, and it was just fine; it was stable," Kohl says. But when the polymer was placed outside, exposure to sunlight vaporized it (or reverted it back to a liquid, in some cases). A vehicle deployed at night would, therefore, disappear with the sunrise.

Kohl's group has since discovered new additives that can trigger depolymerization at different wavelengths of visible light, so the polymer can decompose indoors. "We have polymers designed for applications in which you come in the room, you turn the light on, and the thing disappears," Kohl says.

The group has also determined how to stall depolymerization. "We have a way to delay the depolymerization for a specific amount of time - one hour, two hours, three hours," he says. "You would keep it in the dark until you were going to use it, but then you would deploy it during the day, and you would have three hours before it decomposes." The team has considered chemical methods to start the decomposition process, as well. In addition, they are testing various copolymers that can be added to phthalaldehyde to change the material's properties without altering its ability to vanish.

Kohl says that this "James Bond"-like material is already being incorporated in military devices by other researchers. But he also sees the potential of the materials for non-military applications. For example, the researchers have made a disappearing epoxy for a temporary adhesive that could be used in building materials. They also imagine the material could be used as sensors for environmental monitoring. Once the sensors are finished collecting data, there is no risk of littering the environment since they can be triggered to vaporize. The material can also be used for delivery vehicles in remote areas where recovery is difficult.