Tech

ATLANTA--The number of U.S. adults who perceive e-cigarettes to be at as harmful as, or more harmful than, cigarettes has increased between 2017 and 2018, even prior to the national outbreak of vaping-related lung disease and deaths, a study by tobacco researchers from Georgia State University's School of Public Health has found.

The findings, published in JAMA Network Open, augment earlier work by the researchers that found an increase in perceived harm of e-cigarettes relative to cigarettes between 2012 and 2017.

The percentage of adults who perceived e-cigarettes to be less harmful than cigarettes decreased from 29 percent in 2017 to 26 percent in 2018, while the proportion of adults who perceived e-cigarettes to be equally harmful, more harmful, or much more harmful than cigarettes all increased in that time.

In 2018, 43 percent of U.S. adults considered e-cigarettes to be as harmful as cigarettes and 8 percent considered e-cigarettes to be more harmful or much more harmful than cigarettes. This trend was also observed among current smokers of cigarettes, a finding that has implications for smokers' decision-making around switching to e-cigarettes.

"Smokers who perceive too much risk from e-cigarettes may decide against using them to quit smoking and may instead continue with their combustible smoking habit," said Amy L. Nyman, lead author of the study and research associate in the School of Public Health. "The increase in perceived harm of electronic cigarettes may reflect growing concerns about the surge in e-cigarette use among young people, and the subsequent media coverage of the teen vaping epidemic."

Nyman noted that perceived harm of e-cigarettes relative to cigarettes may have increased further since 2018 because of the recent outbreak of vaping-related illnesses, which have resulted in at least 42 deaths nationwide, according to the Centers for Disease Control and Prevention.

The study used data from The Tobacco Products and Risk Perceptions Survey, a national online survey of about 6,000 U.S. adults conducted annually by Georgia State from 2014 through 2018.

NASA's Aqua satellite captured an image of Tropical Depression Kalmaegi in the South China Sea as it was dissipating.

On Nov. 20, Kalmaegi had crossed over Luzon, the northernmost island of the Philippines. The storm then moved into the South China Sea where it encountered stronger wind shear, winds that can tear a storm apart. Kalmaegi is known locally in the Philippines as Tropical Cyclone Ramon.

The Joint Typhoon Warning Center issued the final warning on the storm at 4 p.m. EST (2100 UTC) on Nov. 20. At that time, Kalmaegi was located near latitude 14.1 degrees north and longitude 119.2 degrees east. That is about 109 nautical miles west-southwest of Manila, Philippines. The storm was moving to the southwest, and maximum sustained winds were down to near 75 knots (29 mph/46 kph).

On Nov. 21, the Moderate Imaging Spectroradiometer or MODIS instrument that flies aboard NASA's Aqua satellite provided a visible image of Kalmaegi. The MODIS image revealed a shapeless storm, indicating that the storm had weakened. Kalmaegi is dissipating over the South China Sea.

NASA's Aqua satellite is one in a fleet of NASA satellites that provide data for hurricane research.

Typhoons and hurricanes are the most powerful weather event on Earth. NASA's expertise in space and scientific exploration contributes to essential services provided to the American people by other federal agencies, such as hurricane weather forecasting.

With seemingly endless emails, phone calls and meetings, it's no secret that working in an office environment can be quite stressful. Understanding how stress manifests by exposing the effects of distractions can help unlock an office workers' full potential, according to new data collected by researchers from three university laboratories.

Ioannis Pavlidis, director of the Computational Physiology Laboratory at the University of Houston, along with Ricardo Gutierrez-Osuna from Texas A&M University and Gloria Mark from the University of California Irvine, conducted an experiment using thermal imaging and wearable sensors to better understand the stress and performance patterns of so-called knowledge workers - scientists, engineers, designers and academics. The findings are published in the journal Scientific Data.

Preliminary observations include:

Minute fluctuation of facial sweating emerges as the best way to measure stress during knowledge production and handling.

Presenting views and findings to management is far more stressful than producing them.

Given more relaxed deadlines, many office workers do not write longer reports but spend all the extra time to style them better.

Spell checkers - despite their bad rap in the context of texting - save the day in long writings, which would be riddled with mechanics errors in their absence.

"When you are stressed, you don't realize this, but you perspire small amounts of from your nose. The more you are stressed, the more you sweat," said Pavlidis, Eckhard-Pfeiffer Professor of Computer Science in the UH College of Natural Science and Mathematics, whose focus is human-computer interaction. "We also found people who have neurotic tendencies work better when they are regularly distracted by emails and the highly-educated worker relies too much on computerized tools such as spellcheck."

Sixty-three study participants carried out a series of typical tasks and office activities including writing essays, taking breaks and presenting their findings before their managers. Half of the participants wrote their essays while being regularly distracted by emails while the other half received their emails in batches. This study is the first of a series of studies on knowledge work funded by a $1.2 million grant from the National Science Foundation.

A thermal facial camera tracked perspiration levels around the nose and upper mouth while wearable devices on the chest and wrist monitored heart and breathing rates. Two cameras one on the computer screen and the other tucked in the ceiling - recorded participants' facial expressions and hand activities.

"This study was a comprehensive microcosm of all things happening in a 21st century office," Pavlidis explained. "Crowdsourced data analysis is expected to lead to personalized recommendations for handling email interruptions and a deeper understanding of how people cope with different office activities. If the initial analysis we did is an indicator, the conclusion is that people who work at the office in knowledge professions have far more diverse responses than people in other professions we studied in the past."

Adjusting the water flow rate in a river can prevent invasive species from moving upstream and expanding their range. An applied mathematician at UT has developed a partial differential equation model to find the desired flow rate to reduce invasive populations.

The model is detailed in a new paper by Suzanne Lenhart, Chancellor's Professor and James R. Cox Professor of Mathematics, published in Mathematics.

"Invasives pose a serious threat to native habitats and species, especially in aquatic environments," said Lenhart. "Using optimal control techniques in a model with realistic hydrology features, we illustrated how to adjust the flow rate in a river to keep an invasive species from moving upstream."

Mathematical models like the PDE model in this study, which represents an invasive population in a river, can give insight into new management strategies. Current strategies to prevent upstream expansion of invasive species include electric fences or nets in the river, but these are not the only management actions that can be taken.

River flow affects species survival success in habitats. Lower flow rates increase the chance of a species persisting, and higher flow rates inhibit success by limiting the species's range and chance of survival. This study investigates how water discharge rates, controlled by water release mechanisms like dams, can force the invasive populations downstream while minimizing the cost of management.

"With our model, we show how far the invasive population moves upstream with no control, constant control, and optimal control of water discharge," said Lenhart. "As expected, the populations with no control are able to move further upstream, and we can manipulate the control levels to find the desired flow rate."

"In the future, we hope to apply these results with new data to a particular invasive species like Asian carp," said Lenhart.

A review of the literature led by researchers from the University of Florida attempts to provide clarification and analysis on various aspects of what a controlled environment system entails and the extent to which differing food production approaches can be applied to the many current and hopeful endeavors of Urban Agriculture.

Before land and labor shortages prompted by the Industrial Revolution forced food production to move away from cities, agriculture was central to urban environments and their planning. Now, certain shifts in consumption habits and preferences are allowing urban agriculture to make a comeback to address sustainability issues in our food system and promote social and environmental cohesion by reducing dependence of fossil fuels and increasing food security.

Celina Gómez and her fellow researchers delved into the likelihood that controlled environments will revolutionize urban food systems and exactly what techniques can be employed for them to do so. Their full analysis is detailed in their article "Controlled Environment Food Production for Urban Agriculture" published in HortScience.

The push for more effective urban agriculture is as much a desire as it is a need. There has been a calculable increased market demand for locally grown produce that has helped generate interest in the application of techniques developed for the controlled environment agriculture industry. These systems and methods have the potential to contribute to year-round crop production and to decrease food costs within an urban setting.

Controlled environments provide advantages to predict plant responses and increase production efficiency, optimize plant yield, and improve plant quality. Among the topics described by the researchers, soilless culture systems allow plants to grow in nonconventional spaces. Light-emitting diodes help reduce energy consumption and improve product quality. Greenhouses built on vacant rooftops of city buildings can capitalize on sunlight to produce plants in close proximity to consumers. Plus, these greenhouse systems can be customized to fit unique needs requiring special construction materials, including photovoltaic systems and rainwater harvesting strategies, increasing their potential to expand sustainability. Controlled environments provide many opportunities to help expand and maximize urban agriculture.

For urban farmers to benefit from controlled environment agriculture, analysis will need consideration of local demand and supply of food, location, population density, facility design, and crops produced. Preliminary research suggests that sustainability for these urban farms hinges on capital investment and operating costs, production volume, product quality and consistency, and local market trends.

Indoor urban farms demonstrate more challenges, due in part to their heavy reliance on electricity. However, these added challenges are not insurmountable, and in considering the factors of food-safety issues and environmental or seasonal limitations, they may easily be deemed worth it.

Says Gómez, "Establishing scalable approaches that support urban agriculture has significant potential to reduce food and nutritional insecurity in urban and peri-urban spaces. More importantly, well-designed business plans can help boost local economies by creating job opportunities and may help contribute to support community-based education programs."

The researchers have offered a detailed examination of multiple facets of the controlled environment: carbon dioxide enrichment, humidity control, water and soil cycling and the environmental footprint, food safety, economic factors, electric lighting, and quite a bit more.

The applicability of controlled environment agriculture within urban settings as a solution to current challenges in our food-supply chain will be context-dependent. They offer different guarantees to the farmer as advantages over traditional field-based production systems. Although large-scale outdoor farms will continue to be instrumental in being able to deliver fresh produce to the areas needing it, urban farms will increase in importance as populations move into cities and the demand for local food increases.

Adds Gómez, "Consumers today have tremendous opportunities to get involved with many aspects of the food production process, and controlled environments will play a central role as cities continue to be transformed by fostering urban agriculture."

NASA's Terra satellite captured a visible image of Tropical Storm Sebastien that showed wind shear had pushed the bulk of its clouds and showers to the southeast of the center.

In general, wind shear is a measure of how the speed and direction of winds change with altitude. Tropical cyclones are like rotating cylinders of winds. Each level needs to be stacked on top each other vertically in order for the storm to maintain strength or intensify. Wind shear occurs when winds at different levels of the atmosphere push against the rotating cylinder of winds, weakening the rotation by pushing it apart at different levels.

On Nov. 20, the Moderate Resolution Imaging Spectroradiometer or MODIS instrument that flies aboard NASA's Terra satellite provided a visible image of Tropical Storm Sebastien. The MODIS image showed the center of circulation appeared to be surrounded by wispy clouds, and that northwesterly wind shear had pushed the bulk of Sebastien's clouds and showers southeast of the center. In addition, the low-level center of circulation was exposed to outside winds.

On Nov. 21, the National Hurricane Center Sebastien said that the storm continues to produce a large area of deep convection over the eastern semicircle of the circulation, but the banding features are not very well defined.

On Nov. 21 at 10 a.m. EST (1500 UTC), the center of Tropical Storm Sebastien was located near latitude 23.5 degrees north and longitude 60.5 degrees west about 405 miles (650 km) north-northeast of the Northern Leeward Islands.

Sebastien is moving toward the north-northeast near 8 mph (13 kph).  A faster northeastward motion is expected during the next few days. The estimated minimum central pressure is 999 millibars.

Maximum sustained winds are near 60 mph (95 kph) with higher gusts. Sebastien is forecast to become a hurricane by tonight, but a weakening trend is expected to begin by late Friday. The system is likely to become an extratropical cyclone by Saturday when it is forecast to become embedded in a frontal zone.

Most mammals walk at slow speeds and run or trot at intermediate speeds because these movement strategies are energetically optimal, according to a study published in PLOS Computational Biology by Delyle Polet and John Bertram of the University of Calgary in Alberta, Canada.

When unconstrained at a given speed, members of a quadrupedal species will generally select a common gait, which is seldom unique to that species alone. With few exceptions, mammals choose a walk at slow speeds, a running trot at intermediate speeds, and a gallop at high speeds. The consistency of gait choice is remarkable, given how many alternatives exist. In the new study, Polet and Bertram explore why quadrupedal mammals move in such consistent ways, when so many options are available. They tackled this problem by determining energetically optimal gaits using a simple computational model of a four-legged animal.

The model can use virtually any (physics-permitting) pattern of movement but selects movement strategies observed in nature as energetically optimal. The researchers compared the simulation results to empirical data on dogs, but they anticipate the results are more broadly applicable across quadrupedal mammals. The similarities between the computer-based predictions and natural animal movement are striking, and suggest mammals utilize movement strategies that optimize energy use when they move.

"We didn't tell the computer what gait it should choose, but it found natural gaits anyway," says Polet. "It was surreal to essentially plug some physics into a computer program, press play, and see it 'decide' to walk like a dog."

In particular, the results provide evidence for the global optimality of walking at low speeds and running or trotting at intermediate speeds, at least for a dog-like morphology. According to the authors, this strongly suggests that these gaits are globally optimal strategies at their respective speeds.

RESEARCH TRIANGLE PARK, N.C. (Nov. 21, 2019) -- An Army-funded project may boost 5G and mm-Wave technologies, improving military communications and sensing equipment.

Carbonics, Inc., partnered with the University of Southern California to develop a carbon nanotube technology that, for the first time, achieved speeds exceeding 100GHz in radio frequency applications. The milestone eclipses the performance -- and efficiency -- of traditional Radio Frequency Complementary Metal-Oxide Semiconductor, known as RF-CMOS technology, that is ubiquitous in modern consumer electronics, including cell phones.

"This milestone shows that carbon nanotubes, long thought to be a promising communications chip technology, can deliver," said Dr. Joe Qiu, program manager, solid state and electromagnetics at the Army Research Office. "The next step is scaling this technology, proving that it can work in high-volume manufacturing. Ultimately, this technology could help the Army meet its needs in communications, radar, electronic warfare and other sensing applications."

The research was published in the journal Nature Electronics.

The work, funded by ARO, an element of U.S. Army Combat Capabilities Development Command's Army Research Laboratory, is a part of a Small Business Technology Transfer Program. The program focuses on feasibility studies leading to prototype demonstration of technology for specific applications.

For nearly two decades, researchers have theorized that carbon nanotubes would be well suited as a high-frequency transistor technology due to its unique one-dimensional electron transport characteristics. The engineering challenge has been to assemble the high-purity semiconducting nanotubes into densely aligned arrays and create a working device out of the nanomaterial.

Carbonics, a venture backed start-up, and USC, successfully overcame this challenge. Projections based on scaling single carbon nanotube device metrics suggest the technology could ultimately far exceed the top-tier incumbent RF technology, Gallium Arsenide.

Carbonics employs a deposition technology called ZEBRA that enables carbon nanotubes to be densely aligned and deposited onto a variety of chip substrates including silicon, silicon-on-insulator, quartz and flexible materials. This allows the technology to be directly integrated with traditional CMOS digital logic circuits, overcoming the typical problem of heterogeneous integration.

"With this exciting accomplishment, the timing is ripe to leverage our CMOS-compatible technology for the 5G and mm-Wave defense communication markets," said Carbonics' CEO Kos Galatsis. "We are now engaged in licensing and technology transfer partnerships with industry participants, while we continue to advance this disruptive RF technology."

Strange metals make interesting bedfellows for a phenomenon known as high-temperature superconductivity, which allows materials to carry electricity with zero loss.

Both are rule-breakers. Strange metals don't behave like regular metals, whose electrons act independently; instead their electrons behave in some unusual collective manner. For their part, high-temperature superconductors operate at much higher temperatures than conventional superconductors; how they do this is still unknown.

In many high-temperature superconductors, changing the temperature or the number of free-flowing electrons in the material can flip it from a superconducting state to a strange metal state or vice versa.

Scientists are trying to find out how these states are related, part of a 30-year quest to understand how high-temperature superconductors work so they can be developed for a host of potential applications, from maglev trains to perfectly efficient power transmission lines.

In a paper published today in Science, theorists with the Stanford Institute for Materials and Energy Sciences (SIMES) at the Department of Energy's SLAC National Accelerator Laboratory report that they have observed strange metallicity in the Hubbard model. This is a longstanding model for simulating and describing the behavior of materials with strongly correlated electrons, meaning that the electrons join forces to produce unexpected phenomena rather than acting independently.

Although the Hubbard model has been studied for decades, with some hints of strange metallic behavior, this was the first time strange metallicity had been seen in Monte Carlo simulations, in which billions of separate and slightly different calculations are averaged to produce an unbiased result. This is important because the physics of these systems can change drastically and without warning if any approximations are introduced.

The SIMES team was also able to observe strange metallicity at the lowest temperatures ever explored with an unbiased method - temperatures at which the conclusions from their simulations are much more relevant for experiments.

The scientists said their work provides a foundation for connecting theories of strange metals to models of superconductors and other strongly correlated materials.

Fentanyl overdoses cluster geographically more than non-fentanyl overdoses, according to a study just released by Columbia University Mailman School of Public Health. The findings suggest that fentanyl-involved overdoses are concentrated in resource deprived neighborhoods over and above what data show for opioid and polydrug overdoses. This is one of few studies to examine the local geographic distribution of drug overdoses and associated neighborhood-level risk factors. The results are published online in the American Journal of Public Health.

The researchers examined geographic trends in the distribution of fentanyl-involved overdose deaths in Cook County, Ill, the second most populous county in the U.S. Data were collected from 2014 to 2018 through the County Medical Examiner's office, which includes Chicago and the surrounding suburbs. The Medical Examiner's Office began routinely testing for fentanyl in June 2015.

"Much of the work to date has used large geographic units such as zip codes or counties on a national scale, noted Elizabeth Nesoff, PhD, postdoctoral fellow in the Department of Epidemiology and first author. "Our research using census block group-level data provides a window into the broader neighborhood context not fully explained by demographics."

The odds of a fentanyl-involved overdose were significantly increased for men, Blacks, Latinos, and younger individuals as well as resource deprived neighborhoods. For example, a larger proportion of non-fentanyl overdoses were White, 53% vs. fentanyl: 43.0%), while a larger proportion of fentanyl overdoses were men (78% vs. non-fentanyl, 73%). These findings echo prior studies of risk for crack-cocaine use, which identified socioeconomic disadvantage as a fundamental cause of racial disparities in crack use.

According to Drug Enforcement Administration data, the number of seized drug samples testing positive for fentanyl more than doubled from 2015 to 2016, rising from 14,440 to 34,119; this increase continued into 2017. Potency of fentanyl -- which is increasingly found in counterfeit medications -- has also increased.

While some people who use drugs seek out fentanyl and fentanyl-adulterated drugs, there is evidence that many people who consume fentanyl may be unaware they are consuming fentanyl, the authors note. One theory is that fentanyl is significantly cheaper to produce than heroin.

"Our study provides a unique perspective on overdose locations, and shows that fentanyl does not follow the same geographic distribution as that of the general drug-using population," said Silvia Martins, MD, PhD, associate professor of epidemiology and director of PHIOS (Policies and Health Initiatives on Opioids and Other Substances) at Columbia Mailman School, and senior author. "This finding was supported by the fact that population density was not a significant factor." One area in particular showed notably elevated risk for fentanyl overdoses located in two specific neighborhoods of Chicago.

Earlier research by Department of Epidemiology Chair Charles Branas, PhD, Gelman Endowed Professor, and a study co-author, showed that neighborhood risk factors for drug use could be modified through targeted infrastructure improvements or other community development strategies, such as park-making or building renovation, but this research has not been extended to overdose prevention. "For example, vacant lot remediation has been shown to significantly reduce gun violence and improve residents' mental health in cities; this presents a possible strategy for reducing drug use in resource deprived neighborhoods. We believe that further inquiry into specific aspects of neighborhood deprivation which can be used to create actionable policy and interventions for harm reduction and overdose prevention is warranted."

Brazil is the world's largest producer of niobium and holds about 98% of the active reserves on the planet. This chemical element is used in metal alloys, especially high-strength steel, and in an almost unlimited array of high-tech applications from cell phones to aircraft engines. Brazil exports most of the niobium it produces in the form of commodities such as ferroniobium.

Another substance Brazil also has in copious quantities but underuses is glycerol, a byproduct of oil and fat saponification in the soap and detergent industry, and of transesterification reactions in the biodiesel industry. In this case the situation is even worse because glycerol is often discarded as waste, and proper disposal of large volumes is complex.

A study performed at the Federal University of the ABC (UFABC) in São Paulo State, Brazil, combined niobium and glycerol in a promising technological solution to the production of fuel cells. An article describing the study, entitled "Niobium enhances electrocatalytic Pd activity in alkaline direct glycerol fuel cells", is published in ChemElectroChem and featured on the cover of the journal.

"In principle, the cell will work like a glycerol-fueled battery to recharge small electronic devices such as cell phones or laptops. It can be used in areas not covered by the electricity grid. Later the technology can be adapted to run electric vehicles and even to supply power to homes. There are unlimited potential applications in the long run," chemist Felipe de Moura Souza, first author of the article told. Souza has a direct doctorate scholarship from São Paulo Research Foundation - FAPESP.

In the cell, chemical energy from the glycerol oxidation reaction in the anode and air oxygen reduction in the cathode is converted into electricity, leaving only carbon gas and water as residues. The complete reaction is C3H8O3 (liquid glycerol) + 7/2 O2 (oxygen gas) ? 3 CO2 (carbon gas) + 4 H2O (liquid water). A schematic representation of the process is shown below.

"Niobium [Nb] participates in the process as a co-catalyst, assisting the action of the palladium [Pd] used as the fuel cell anode. The addition of niobium enables the amount of palladium to be halved, lowering the cost of the cell. At the same time it significantly increases the power of the cell. But its main contribution is a reduction in the electrolytic poisoning of the palladium that results from the oxidation of intermediates that are strongly adsorbed in long-term operation of the cell, such as carbon monoxide," said Mauro Coelho dos Santos, a professor at UFABC, thesis adviser for Souza's direct doctorate, and principal investigator for the study.

From the environmental standpoint, which more than ever should be a decisive criterion for technological choices, the glycerol fuel cell is considered a virtuous solution because it can replace combustion engines powered by fossil fuels.

An international team led by researchers at Princeton University has directly observed a surprising quantum effect in a high-temperature iron-containing superconductor.

Superconductors conduct electricity without resistance, making them valuable for long-distance electricity transmission and many other energy-saving applications. Conventional superconductors operate only at extremely low temperatures, but certain iron-based materials discovered roughly a decade ago can superconduct at relatively high temperatures and have drawn the attention of researchers.

Exactly how superconductivity forms in iron-based materials is something of a mystery, especially since iron's magnetism would seem to conflict with the emergence of superconductivity. A deeper understanding of unconventional materials such as iron-based superconductors could lead eventually to new applications for next-generation energy-saving technologies.

The researchers probed the behavior of iron-based superconductors when impurities - namely atoms of cobalt - are added to explore how superconductivity forms and dissipates. Their findings led to new insights into a 60-year old theory of how superconductivity behaves. The study was published in the journal Physical Review Letters this week.

Adding impurities is a useful way to learn about the behavior of superconductors, said M. Zahid Hasan, the Eugene Higgins Professor of Physics at Princeton University, who led the research team. "It is like the way we probe the wave behavior of water in the lake by throwing a stone," he said. "The way the superconducting properties react to the impurity reveals their secrets with quantum-level detail."

A longstanding idea known as Anderson's theorem predicts that although adding impurities can introduce disorder into a superconductor, in many cases, it will not destroy the superconductivity. The theorem was put forth in 1959 by Nobel Prize-winning physicist Philip Anderson, Princeton's Joseph Henry Professor of Physics, Emeritus. But there are always exceptions to the rule.

Cobalt appears to be one of these exceptions. Contrary to the theory, the addition of cobalt forces the iron-based superconductor to lose its superconducting ability and become like an ordinary metal, in which electricity flows with resistance and wastes its energy as heat.

Until now, it has been unclear how this happens.

To explore this phenomenon, the Princeton team of researchers used a technique known as scanning tunneling microscopy, which is capable of imaging individual atoms, to study an iron-based superconductor made from lithium, iron and arsenic.

They introduced non-magnetic impurities in the form of cobalt atoms into the superconductor to see how it behaved.

The researchers measured a large number of samples at extremely low temperatures, about minus 460 degrees Fahrenheit (400 degrees milliKelvin), which is colder than outer space by almost ten degrees Fahrenheit. Under these conditions, the researchers located and identified each cobalt atom in the crystal lattice, and then directly measured the effect it had on the superconductivity at both the atomically local scale and the global superconducting properties of the sample.

To do this, the researchers studied over 30 crystals across eight different concentrations at these extremely low temperatures with atomic-level resolution. "There's no guarantee that any given crystal will give us the high-quality data we need," said Songtian Sonia Zhang, a graduate student and co-first author of the study.

As a result of this extensive experiment, the team discovered that each cobalt atom has a limited local impact that vanishes an atom or two in distance away from the impurity. However, there is a strong, systematic evolution through a phase transition into a normal, non-superconducting state as the cobalt concentration increases. The superconductivity is eventually fully destroyed by introducing more cobalt atoms.

Superconductivity is due to the pairing of two electrons to form a single quantum state described by a property known as a wave function. This pairing allows the electrons to zip through a material without the typical resistance that happens in everyday metals. The minimum energy required to scatter the electrons and break the pairs is called the "superconducting energy gap."

When cobalt atoms are added, the scattering strength can be described in two ways: the strong (or unitary) limit and the weak (or Born) limit. Scattering at the Born limit, named after physicist Max Born, has the weakest potential to disturb the electron wave functions that are crucial to electron-electron interaction and thus the electron pairing.

By replacing iron atoms, the cobalt atoms behave as Born-limit scatterers. Although Born-limit scatterers have a relatively weak potential to disrupt superconductivity, when many combine they can destroy superconductivity.

The researchers discovered that for the lithium iron arsenide material, scattering at the Born limit is apparently able to violate Anderson's theorem, leading to a quantum phase transition from a superconducting to a non-superconducting state.

Superconducting materials can be described by a feature known as the tunneling spectrum, which provides a description of the behavior of electrons in a material and acts as an electron's energy distribution profile. The lithium iron arsenide material has what is known as a "S-wave" gap characterized by a flat "U-shaped" bottom in the superconducting energy gap. A fully opened superconducting gap indicates the quality of the superconducting materials.

In a surprising twist, the cobalt impurities not only suppress the superconductivity, they also change the nature of the gap as it evolves from a U-shape into a V-shape. The shape of the superconducting gap usually reflects the "order parameter," which describes the nature of the superconductivity. Such a shape is characteristic of order parameters that only occur in a unique number of high-temperature superconductors and hints at extremely unconventional behavior.

The apparent transformation through a change in the order parameter (for example, reflected in the measurements by the changing in the shape of the superconducting gap) only adds to the quantum puzzle.

This evolution is unusual and prompted the researchers to deepen their investigation. By combining theoretical calculations with magnetic measurements, they were able to confirm the non-magnetic nature of the cobalt scattering.

Since Anderson's theorem states that non-magnetic impurities should have little effect on this type of superconductor, the researchers realized that an alternate theory had to be developed.

In iron-based superconductors, scientists have speculated that there is a sign change for the phase of superconducting order parameter at different "Fermi pockets" - the energy countours that form due to the rules by which electrons occupty the crystalline structure.

"Naively, distinguishing between conventional superconductivity and sign-changing superconductivity requires a phase-sensitive measurement of the superconducting order parameter, which can be extremely challenging," said Ilya Belopolski, a postdoctoral researcher in Hasan's group and co-author of the study. "A beautiful aspect of our experiment is that by considering violations of Anderson's theorem, we can get around this requirement."

In fact, the team discovered that by introducing such a sign change in the order parameter of the superconductivity, they were able to reproduce the odd evolution from the cobalt impurities. Going beyond these initial calculations, the team employed a further three state-of-the-art theoretical methods to demonstrate the impact of the non-magnetic cobalt scatterers on this sign-changing superconductor.

"The fact that three different theoretical models all point to the same explanation demonstrates this is a robust conclusion," said Jia-Xin Yin, a postdoctoral research associate and another co-first author of the study. In the quest for solving the mysteries of superconductivity, complicated models are developed that do not always agree with each other. In this case, Yin said, "the model-independent results unambiguously pin down that this is a sign-changing exotic superconductor not originally considered by Anderson's work."

Ann Arbor, November 21, 2019 - According to a new study in the American Journal of Preventive Medicine, published by Elsevier, the share of children and adolescents consuming sugar-sweetened beverages (SSBs) and the calories they consume from SSBs declined significantly between 2003 and 2014.

This decline in consumption was found among children and adolescents in all groups studied, including those participating in the Supplemental Nutrition Assistance Program (SNAP), the US federally funded program that provides food assistance to more than 40 million low-income Americans each month -- half of whom are children. However, the study demonstrated that even with the decline, current levels remain too high, with 61 percent of all children and 75.6 percent of SNAP recipients still consuming an SSB on a typical day.

"While the observed declines in children's sugar-sweetened beverage consumption over the past decade are promising, the less favorable trends among children in SNAP suggest the need for more targeted efforts to reduce sugary drink consumption," explained lead investigator J. Wyatt Koma, Independent Researcher, Washington, DC, USA.

The investigators used nationally representative dietary data for 15,645 children and adolescents (aged 2 to 19 years) from the 2003 to 2014 National Health and Nutrition Examination Surveys (NHANES). They classified children according to self-reported participation in the SNAP program and household income: 27.8 percent were SNAP participants; 15.3 percent were income-eligible but not SNAP participants; 29.7 percent had lower incomes that were ineligible for SNAP; and 27.2 percent had higher incomes that were ineligible for SNAP. The analysis determined the share of children in the various groups who consumed an SSB on a typical day as well as the per capita daily consumption of SSB calories from 2003-2014. SSBs were defined as any non-alcoholic drink with added sugar, including soda, fruit drinks, and flavored milks, consumed on a given day.

This study yielded several significant findings, notably:

From 2003 to 2014, the share of children consuming an SSB on a typical day declined significantly across all SNAP participation groups, primarily driven by declines in soda consumption. Among children who were SNAP participants, the percentage drinking SSBs declined from 84.2 percent to 75.6 percent and per capita daily consumption of SSB calories declined from 267 to 182 calories.

In 2014, nearly one in four children who were income-eligible for the SNAP program consumed a fruit drink on any given day (SNAP participants: 24.8 percent; Income-eligible nonparticipants: 23.4 percent).

The share of SNAP participants consuming a sports/energy drink on any given day tripled from 2003 to 2014 (from 2.6 percent to 8.4 percent).

Although SNAP's success in reducing hunger and food insecurity in the US is well documented, public health attention has more recently turned to the secondary goals of the SNAP program: improving diet quality and preventing obesity among participants.

Senior author Sara N. Bleich, PhD, Department of Health Policy and Management, Harvard T.H. Chan School of Public Health, Boston, MA, USA, observed, "Current policy debates are considering whether the diet quality of SNAP participants can be improved by restricting which items can be purchased with SNAP benefits. Our analysis is important for these discussions. While our results confirm that efforts to decrease SSB consumption over the past decade have been successful, they also suggest that the continued surveillance of children's SSB consumption by beverage type is important, given the consumption trends for sports/energy drinks and non-traditional SSBs like flavored milks. These trends could reduce or eliminate the past decades' achievements limiting SSB consumption."

Globally, in 2016, 81% of 11 to 17-year-old school students did not reach WHO recommendations to do an hour of moderate-to-vigorous physical activity every day.

Girls were less active than boys and this gap has grown between 2001-2016, with rates of physical inactivity remaining similar for girls, while they have improved slightly for boys.

In 2016, in 27 counties, 90% or more of girls did not reach sufficient levels of activity, whereas this was the case for only two countries for boys.

Boys in the Philippines and girls in South Korea were the most inactive, whereas Bangladesh had the lowest rates of physical inactivity for boys and girls.

The first ever global trends for adolescent insufficient physical activity show that urgent action is needed to increase physical activity levels in girls and boys aged 11 to 17 years. The study, published in The Lancet Child & Adolescent Health journal and produced by researchers from the World Health Organization (WHO), finds that more than 80% of school-going adolescents globally did not meet current recommendations of at least one hour of physical activity per day - including 85% of girls and 78% of boys.

The study - which is based on data reported by 1.6 million 11 to 17-year-old students - finds that across all 146 countries studied between 2001-2016 girls were less active than boys in all but four (Tonga, Samoa, Afghanistan and Zambia).

The difference in the proportion of boys and girls meeting the recommendations was greater than 10 percentage points in almost one in three countries in 2016 (29%, 43 of 146 countries), with the biggest gaps seen in the United States of America and Ireland (more than 15 percentage points). Most countries in the study (73%, 107 of 146) saw this gender gap widen between 2001-2016.

Young people's health compromised by insufficient physical activity

The authors say that levels of insufficient physical activity in adolescents continue to be extremely high, compromising their current and future health. "Urgent policy action to increase physical activity is needed now, particularly to promote and retain girls' participation in physical activity," says study author Dr Regina Guthold, WHO. [1]

The health benefits of a physically active lifestyle during adolescence include improved cardiorespiratory and muscular fitness, bone and cardiometabolic health, and positive effects on weight. There is also growing evidence that physical activity has a positive impact on cognitive development and socialising. Current evidence suggests that many of these benefits continue into adulthood.

To achieve these benefits, the WHO recommends for adolescents to do moderate or vigorous physical activity for an hour or more each day [2].

The authors estimated how many 11 to 17-year-olds do not meet this recommendation by analysing data collected through school-based surveys on physical activity levels. The assessment included all types of physical activity, such as time spent in active play, recreation and sports, active domestic chores, walking and cycling or other types of active transportation, physical education and planned exercise.

To improve levels of physical activity among adolescents, the study recommends that:
- Urgent scaling up is needed of known effective policies and programmes to increase physical activity in adolescents;
- Multisectoral action is needed to offer opportunities for young people to be active, involving education, urban planning, road safety and others;
The highest levels of society, including national, city and local leaders, should promote the importance of physical activity for the health and well-being of all people, including adolescents.

"The study highlights that young people have the right to play and should be provided with the opportunities to realise their right to physical and mental health and wellbeing," says co-author Dr Fiona Bull, WHO. "Strong political will and action can address the fact that four in every five adolescents do not experience the enjoyment and social, physical, and mental health benefits of regular physical activity. Policy makers and stakeholders should be encouraged to act now for the health of this and future young generations." [1]

Physical activity trends show slight improvement for boys, none for girls

The new study estimated for the first time how trends changed between 2001-2016-applying the trends from 73 countries who did repeat surveys during that period to all 146 countries.

Globally, the prevalence of insufficient physical activity slightly decreased in boys between 2001 and 2016 (from 80% to 78%), but there was no change over time in girls (remaining around 85%).

The countries showing the greatest decreases in boys being insufficiently active were Bangladesh (from 73% to 63%), Singapore (78% to 70%), Thailand (78% to 70%), Benin (79% to 71%), Ireland (71% to 64%), and the USA (71% to 64%). However, among girls, changes were small, ranging from a 2 percentage-point decrease in Singapore (85% to 83%) to a 1 percentage-point increase in Afghanistan (87% to 88%).

The authors note that if these trends continue, the global target of a 15% relative reduction in insufficient physical activity - which would lead to a global prevalence of less than 70% by 2030 - will not be achieved. This target was agreed to by all countries at the World Health Assembly in 2018.

In 2016, Philippines was the country with the highest prevalence of insufficient activity among boys (93%), whereas South Korea showed highest levels among girls (97%) and both genders combined (94%). Bangladesh was the country with the lowest prevalence of insufficient physical activity among boys, girls, and both genders combined (63%, 69% and 66%, respectively).

Some of the lowest levels of insufficient activity in boys were found in Bangladesh, India and the USA. The authors note that the lower levels of insufficient physical activity in Bangladesh and India (where 63% and 72% of boys were insufficiently active in 2016, respectively) may be explained by the strong focus on national sports like cricket. However, the US rates (64%) may be driven by good physical education in schools, pervasive media coverage of sports, and good availability of sports clubs (such as ice hockey, American football, basketball, or baseball).

For girls, the lowest levels of insufficient activity were seen in Bangladesh and India, and are potentially explained by societal factors, such as increased domestic chores in the home for girls.

Insufficient activity among adolescents a major concern

"The trend of girls being less active than boys is concerning," said study co-author Dr Leanne Riley, WHO. "More opportunities to meet the needs and interests of girls are needed to attract and sustain their participation in physical activity through adolescence and into adulthood." [1]

To increase physical activity for young people, governments need to identify and address the many causes and inequities - social, economic, cultural, technological, and environmental - that can perpetuate the differences between boys and girls, the authors said.

"Countries must develop or update their policies and allocate the necessary resources to increase physical activity," says co-author Dr Fiona Bull. "Policies should increase all forms of physical activity, including through physical education that develops physical literacy, more sports, active play and recreation opportunities - as well as providing safe environments so young people can walk and cycle independently. Comprehensive action requires engagement with multiple sectors and stakeholders, including schools, families, sport and recreation providers, urban planners, and city and community leaders." [1]

The authors note some limitations, including that the study only included information from school-going adolescents, due to lack of data for adolescents out of school. School-going adolescents may vary from others of the same age, as adolescents in school may be more likely to come from advantaged backgrounds that may be more focussed on high achievement in other academic disciplines, rather than physical education and sport. Further, while the study covered 81% of the school-going adolescent population, this coverage varied by country income, ranging from 36% in low-income to 86% in high-income countries.

The study used self-reported data only, which may be subject to bias. Data from wearable devices were not used as they could not be compared to self-reported data from surveys.

Writing in a linked Comment, Dr Mark Tremblay, Children's Hospital of Eastern Ontario Research Institute, Canada, says: "The changing world is changing people, with movement being one of the clearest indicators of this change. The electronic revolution has fundamentally transformed people's movement patterns by changing where and how they live, learn, work, play, and travel, progressively isolating them indoors (eg, houses, schools, workplaces, and vehicles), most often in chairs. People sleep less, sit more, walk less frequently, drive more regularly, and do less physical activity than they used to. They are increasingly moving from one country to another, from rural to urban areas, from outdoors to indoors, from standing to sitting, from walking to driving, and from active play to digital play and, at a macroscopic level, countries are moving through epidemiological and economic transitions at varying rates. These changes in the human exposome fundamentally affect our movement behaviours, patterns, and contexts and could have profound effects on human health. These effects and how they vary spatially, temporally, or culturally are important, particularly since physical inactivity is the fourth leading risk factor for premature death worldwide, but remain poorly understood."

When it comes to electronics, bigger usually isn't better. This is especially true for a new generation of wearable communication systems that promise to connect people, machines and other objects in a wireless "internet of things." To make the devices small and comfortable enough to wear, scientists need to miniaturize their components. Now, researchers in ACS Nano have made the tiniest radio-frequency antennas reported yet, with thicknesses of about 1/100 of a human hair.

Antennas that receive and transmit radio waves are usually made of metal conductors, such as aluminum, copper and silver. Although these materials have high electrical conductivity, they do not perform well in ultrathin, lightweight antennas. As a result, most metal-based antennas are thicker than 30 micrometers in diameter, which limits their application in miniaturized electronic devices. To make even tinier antennas, Keun-Young Shin, Ho Seok Park and colleagues wanted to try using extremely thin sheets of a 2D material that consisted of a layer of metallic niobium atoms sandwiched between two layers of selenium atoms (NbSe2).

The researchers made their antenna by spray-coating several layers of NbSe2 nanosheets onto a plastic substrate. They then tested the 885 nm-thick antenna, finding that a 10 × 10 mm2 patch of the ultrathin material performed well, with a radiation efficiency of 70.6%. The device propagated radio frequency waves in all directions. By changing the length of the antenna, the frequency could be tuned from 2.01 to 2.80 GHz, which includes the frequency required by Bluetooth and Wi-Fi technologies. Also, the antenna could be bent and stretched without large changes in its performance. In addition to wearable electronics, the new antennas could someday find applications in deep space communications systems because the material would become a superconductor in the very cold temperatures of outer space, the researchers say.