How Exactly Do We Spread Droplets As We Talk? Engineers Found Out (Engineering / Medicine)

For the first time, researchers have directly visualized how speaking produces and expels droplets of saliva into the air. The smallest droplets can be inhaled by other people and are a primary way that respiratory infections like COVID-19 spread from person to person.

Princeton’s Howard Stone and CNRS’s Manouk Abkarian have directly visualized how speech and breath produce and expel droplets of saliva into the air. © Illustration byMatilda Luk, Office of Communications.

Using high-speed imaging, the researchers showed that when our mouths open to produce speech sounds, a film of lubricating saliva initially spreads across the lips. As the lips part, the liquid film then breaks into filaments. Outward airflow from the lungs stretches and thins the filaments until they eventually rupture and disperse into the air as miniscule droplets — all within fractions of a second.

This droplet-producing mechanism is especially pronounced for so-called stop-consonants or “plosives” like “p” and “b,” which require the lips to firmly press together when forming the vocalized sound. Other sounds known as denti-alveolar plosives, such as “t” and “d” which involve the tongue touching the upper teeth and the jaw ridge just behind the teeth, likewise produce droplets at a much greater rate than when forming vowel sounds.

A deeper understanding of this droplet formation and dispersal process should lead to new and better mitigation strategies, helping to slow down the current coronavirus pandemic along with future outbreaks.

The researchers used this laser sheet to illuminate the saliva droplets. The laser light, originating at the left, is expanded to form a “sheet” going from left to right and about a meter high. The research subject (usually Manouk Abkarian of CNRS) would stand in front of the sheet or next to it, depending on the experiment. Drops from their speech or breath that crossed the sheet would produce flashes that they photographed and counted. Some experiments added a Halloween fog machine to see how the subject’s breath or speech droplets interact with the movement of ambient fog droplets.
Photo by Manouk Abkarian.

“We have made the first direct visualization of the mechanism that produces droplets in the oral cavity during everyday speech,” said Howard Stone, the Donald R. Dixon ’69 and Elizabeth W. Dixon Professor of Mechanical and Aerospace Engineering. “Our study provides insights into the origin of droplets when people talk, which can aid in curbing the spread of diseases like COVID-19.”

The study appeared Oct. 2 in the journal Physical Review Fluids. Stone coauthored the study with Manouk Abkarian, a research director at the French National Centre for Scientific Research’s (CNRS), in the Centre de Biologie Structurale of Montpellier. Abkarian had come to Princeton on a planned, short sabbatical in the beginning of March 2020, coincidentally just before the University (and much of the rest of the world) went into a pandemic lockdown.

In those early weeks as COVID-19 infection rates soared, researchers from a wide range of disciplines began focusing on how the virus was transmitted. Likewise concerned, Stone and Abkarian wanted to bring their expertise in fluid mechanics to bear on the problem. The researchers zeroed in on asymptomatic transmission; that is, by people who were not coughing and sneezing and explosively emitting pathogen-laden, airborne particles.

“We wrote a grant proposal in April to investigate the fluid mechanics involved in asymptomatic transmission through the role of speech, when people who aren’t apparently sick are just normally interacting and talking,” said Stone.

To pursue the study, Stone and Abkarian received permission from the University, including the Institutional Review Board, to access his campus lab to pursue this urgent work while observing a strict social distancing protocol. There, Abkarian performed most of the experiments on himself, with some additional imaging of Stone speaking. The experimental setup involved Abkarian sitting in a chair a room filled with mist from a fog machine. He vocalized various phonetics while speaking toward a laser sheet, which is a flat and thin plane of laser light. The laser sheet revealed any particles leaving Abkarian’s mouth due to the light-scattering effect they cause when crossing the sheet. A high-speed camera captured this scattering, enabling the researchers to gauge the level of droplet production per spoken sound.

Researchers used high speed cameras to analyze how speech produces small droplets. ©Photo by the researchers.

To visualize the formation of the droplets during speech, the same camera zoomed in on the speaker’s mouth. The camera recorded at an extremely detail-revealing 5000 frames per second under strong illumination. The millisecond-level, frame-by-frame perspective showed the deposition of a microscopic, lubricating, salivary layer on the lips as the lips press together prior to issuing a plosive consonant. The liquid layer draws into a vertical thin film as the lips separate. The film becomes unstable within a millisecond as it expands to about a millimeter in width. The film splits into numerous filaments that thin and quickly extend over centimeters in length to break finally into drops blown outward by air leaving the speaker’s mouth.

This caught-on-camera evidence contrasts with previous, mostly unsupported hypotheses regarding the formation of aerosolized droplets. Droplet formation has been presumed to occur in two ways: from thin films bursting deep in the lungs, or from airflow shearing droplets off of saliva-coated surfaces in the upper airway, which includes the throat and mouth. The jury remains out on whether those other proposed mechanisms play a role beyond the mechanism documented by Stone and Abkarian.

“No one has been able to obtain direct measurements or visualizations of droplet formation in the lungs or upper airway before,” said Abkarian. “Now with our study, there is compelling evidence that the stretching and breakup of saliva filaments during speech is behind aerosol formation.”

Wearing masks, as is near-universally recommended by public health experts and mandated in many jurisdictions, should effectively contain a significant portion of expelled aerosols, the researchers pointed out. Stone and Abkarian further suggested that the simple intervention of wearing lip balm should cut down on droplet formation during speaking.

When pandemic conditions allow, Stone and Abkarian would like to extend the imaging in their study to more participants to confirm that the droplet generation mechanism they documented is a general characteristic of human speech.

The researchers also are interested in differences between languages in terms of the variety and frequency of sounds their articulation invokes. It is possible that speakers of certain languages with many hard consonants, for instance, will tend to produce more droplets than speakers of languages featuring greater use of softer vowel sounds. People who do produce more spittle when they speak—dubbed “superemitters”—may not necessarily be superspreaders of COVID-19 or other saliva-borne diseases, however. That is because the infectiousness of any given droplet is likely based on the amount of virus it contains, and a person infected with COVID-19 who just happens to produce copious droplets may not also have a high viral load in their saliva or respiratory tract.

“We’re still learning an awful lot about how COVID-19 is transmitted,” said Stone. “Our hope is that this study will help in the overall fight against this devastating pandemic.”

References: “Stretching and break-up of saliva filaments during speech: A route for pathogen aerosolization and its potential mitigation” by M. Abkarian and H. A. Stone was published in Physical Review Fluids on Oct. 2 DOI: 10.1103/PhysRevFluids.5.102301

Provided by Princeton University

Move It Or Lose It: Saving Species In A Changing Climate (Biology)

Humans will need to physically relocate many species to ensure their survival in the face of climate change, University of Queensland-led research recommends.

The mountain pygmy-possum, which also lives in alpine habitats, is another species that would benefit from being moved to a different environment. Researchers at UNSW have developed a plan to translocate them to lowland areas, as the species currently exists at the edge of what would have been a much wider range, and so can be acclimatised to other environments. ©University of Queensland

UQ School of Earth and Environmental Sciences researcher Dr Nathalie Butt said that conservationists must seriously consider expanding their species translocation strategy to stop mass extinctions.

“One in six species could become extinct as a result of climate change,” Dr Butt said.

“And the impacts of climate change, such as increasing temperatures or rising sea levels, mean that some habitats are already becoming unsuitable for species.

“We know that at least 40 per cent of amphibian species, 30 per cent of reef-forming coral species, and a third of all marine mammal species are now threatened with extinction.

Archey’s frog is a tiny, rare terrestrial amphibian for which translocation outside its current climate envelope is likely to be required to ensure its survival. It is easily contained in in-situ locations, as its capacity to move any distance is limited, and is currently captive-bred at Auckland Zoo, New Zealand, making it an ideal candidate for testing out assisted migration, as conditions of possible new sites could be mimicked as closely as possible, in the zoo or other ex-situ locations, to examine the effects on breeding and survival to test whether assisted migration would be feasible. ©University Of Queensland

“Many species faced with climate change will not be able to adapt and survive in place – they simply won’t be able move to somewhere more suitable on their own because of physical barriers, like cities, or being on top of a mountain.

“If we’re going to protect as many species as possible, we’re going to have to intervene.”

One such species is the Mount Claro rock wallaby, endemic to Australia’s Great Dividing Range.

The Mount Claro Rock Wallaby ©University of Queensland

It’s just one of 26 species on the Range projected to lose its habitat due to increased temperatures.

“The Mount Claro rock-wallaby lives in high, cool areas,” Dr Butt said.

“A lot of its habitat is used by humans for forestry and agriculture, so it will be difficult for the wallaby to move across these landscapes to higher altitudes without help.

“Conservation managers need to actively get involved with these rescues, and soon.

“We can’t simply wait until their habitat is lost.

“A small rodent once found in northern Queensland called the Bramble Cay melomys became the first documented climate change extinction due to rising sea levels.”

In marine environments, coral reefs often bear the brunt of climate change, resulting in coral bleaching or death. A new method to help them recover is being tried out on the Great Barrier Reef, where surviving polyps are being propagated and moved to repopulate areas that were destroyed by warming seas. Find out more from National Geographic. Credit: Michaela Skovranova.

Griffith University’s Dr Alienor Chauvenet said the research team was advocating for conservationists and policy-makers to reconsider their strategies to prevent more climate extinctions.

“While hundreds of articles mention species translocation and assisted migration as tools to adapt to climate change, it is rarely practiced,” Dr Chauvenet said.

“Most actions are designed to keep species in their current native locations, with protections applied to their reserves, habitat restorations, tree and vegetation plantings.

In the Wet Tropics, in northern Australia, the white lemuroid possum is getting closer to extinction due to increasing heatwaves driven by climate change. The species has no mechanisms for body-cooling, and so high temperatures are fatal, and they are rapidly losing suitable habitat. The nearest rainforest is 1,000 km distant, and they would not be able to reach it unassisted. ©University of Queensland

“While this is effective and appropriate in many instances, there are plenty of instances where this kind of strategy alone will lead to extinct species.

“There are many barriers to this thinking in the conservation community, such as the risk of introducing an invasive species, socio-political pushback, getting the timing wrong and a lack of understanding.

“We’re advocating for assisted migrations at small scales, translocating species with little invasion risk, adopting robust monitoring protocols that trigger an active response, and promoting political and public support.

“If we can change how conservationists approach translocation of species, we might be able to seriously increase how many animals can survive a climate catastrophe.”

References: Butt, N., Chauvenet, A.L., Adams, V.M., Beger, M., Gallagher, R.V., Shanahan, D.F., Ward, M., Watson, J.E. and Possingham, H.P. (2020), Importance of species translocations under rapid climate change. Conservation Biology. doi:10.1111/cobi.13643

Provided by University Of Queensland

Oxford Scientists Develop Extremely Rapid Diagnostic Test For Covid-19 (Medicine)

Scientists from Oxford University’s Department of Physics have developed an extremely rapid diagnostic test that detects and identifies viruses in less than five minutes.

The method, published on the preprint server MedRxiv, is able to differentiate with high accuracy SARS-CoV-2, the virus responsible for COVID-19, from negative clinical samples, as well as from other common respiratory pathogens such as influenza and seasonal human coronaviruses.

The test uses a convolutional neural network to classify microscopy images of single intact particles of different viruses © University Of Oxford

Working directly on throat swabs from COVID-19 patients, without the need for genome extraction, purification or amplification of the viruses, the method starts with the rapid labelling of virus particles in the sample with short fluorescent DNA strands. A microscope is then used to collect images of the sample, with each image containing hundreds of fluorescently-labelled viruses.

Machine-learning software quickly and automatically identifies the virus present in the sample. This approach exploits the fact that distinct virus types have differences in their fluorescence labeling due to differences in their surface chemistry, size, and shape.

The scientists have worked with clinical collaborators at the John Radcliffe Hospital in Oxford to validate the assay on COVID-19 patient samples which were confirmed by conventional RT-PCR methods.

Professor Achilles Kapanidis, at Oxford’s Department of Physics, says: ‘Unlike other technologies that detect a delayed antibody response or that require expensive, tedious and time-consuming sample preparation, our method quickly detects intact virus particles; meaning the assay is simple, extremely rapid, and cost-effective.’

DPhil student Nicolas Shiaelis, at the University of Oxford, says: ‘Our test is much faster than other existing diagnostic technologies; viral diagnosis in less than 5 minutes can make mass testing a reality, providing a proactive means to control viral outbreaks.’

Dr Nicole Robb, formerly a Royal Society Fellow at the University of Oxford and now at Warwick Medical School, says: ‘A significant concern for the upcoming winter months is the unpredictable effects of co-circulation of SARS-CoV-2 with other seasonal respiratory viruses; we have shown that our assay can reliably distinguish between different viruses in clinical samples, a development that offers a crucial advantage in the next phase of the pandemic.’

The researchers aim to develop an integrated device that will eventually be used for testing in sites such as businesses, music venues, airports etc., to establish and safeguard COVID-19-free spaces.

They are currently working with Oxford University Innovation (OUI) and two external business/finance advisors to set up a spinout, and are seeking investment to accelerate the translation of the test into a fully integrated device to be deployed as a real-time diagnostic platform capable of detecting multiple virus threats.

They hope to incorporate the company by the end of the year, start product development in early 2021, and have an approved device available within 6 months of that time.

References: Nicolas Shiaelis, Alexander Tometzki, Leon Peto, Andrew McMahon, Christof Hepp, Erica Bickerton, Cyril Favard, Delphine Muriaux, Monique Andersson, Sarah Oakley, Alison Vaughan, Philippa C Matthews, Nicole Stoesser, Derrick Crook, Achillefs N Kapanidis, Nicole C Robb, “Virus detection and identification in minutes using single-particle imaging and deep learning”, medRxiv 2020.10.13.20212035; doi: link:

Provided by University Of Oxford

Wheat Gluten Can Be Used To Make Sustainable Diaper Material (Material Science)

Most of the billions of diapers used each year are made with petroleum-based absorbent material. That could change with the development of new sustainable materials like the one recently reported by researchers at KTH.

More sustainable diapers are one possible use for a new bio-based material that researchers in Sweden are developing. The superabsorbent material is made with wheat gluten proteins from wheat starch processing, without directly competing with food resources.


Antonio Capezza , a researcher in at KTH Royal Institute of Technology and SLU Swedish University of Agricultural Sciences, says the material is capable of swelling up to 4,000 percent in water and 600 percent in saline solution.

The worldwide disposable diaper market is expected to reach more than $55 billion by 2025, and many of these products consist of fossil-based absorbent components. “This is an opportunity to increase the use of renewable materials in diapers and meet the growing need for health and hygiene products,” Capezza says.

“… We need to use raw materials that are renewable and that are not going to interfere with the main food production chain.” Researcher Antonio Capezza in the laboratory working with wheat gluten proteins. (Photo: courtesy of Antonio Capezza)

Capezza says the next step is to scale up production of the material so that the researchers’ industrial partners can test it in different applications. “By developing bio-based solutions then we are contributing toward a circular bio-economy and possibly new business opportunities and partnerships,” he says.

In order to create a fully sustainable alternative, the researchers are focusing only on agricultural side-streams, or co-products. “If we want to be sustainable, we need to use raw materials that are renewable and that are not going to interfere with the main food production chain in the future,” he says.

The water absorbency of the new material matches that of other bio-based alternatives. This includes products made with raw materials that are not obtained as a co-product, Capezza says. A research paper, which was published in Advanced Sustainable Systems, indicates that the material could be further engineered to eventually match the absorbency of petroleum-based synthetics.

The market for superabsorbent materials extends beyond disposable diapers, but Capezza says that diapers are the most demanding in terms of urine absorption properties. “By aiming to match or exceed the absorbency performance of petroleum-based superabsorbents used in many disposable diapers, we can meet the standards for most other applications that require superabsorbents.”

Highly absorbent materials are used in personal care and medical products, as well as in flood water mitigation and rain water retention for agriculture, among other formats. Capezza says the next step is to scale up production of the material so that the researchers’ industrial partners can test it in different applications.

A co-product from industrial production of wheat starch and ethanol production, wheat gluten is composed of proteins that make it a promising material for absorbency applications. The researchers enhanced the swelling potential of the wheat gluten polymer by changing the chemistry of the gluten to more resemble that of synthetic material, and crosslinking the molecules with plant extracts from the fruit of gardenia jasminoides.

Working with the researchers from KTH were colleagues at SLU and Kyoto University in Japan. The project was founded by VINNOVA, in collaboration with Lantmännen and Essity.

References: Capezza, A.J., Cui, Y., Numata, K., Lundman, M., Newson, W.R., Olsson, R.T., Johansson, E. and Hedenqvist, M.S. (2020), Superabsorbent Polymers: High Capacity Functionalized Protein Superabsorbents from an Agricultural Co‐Product: A Cradle‐to‐Cradle Approach (Adv. Sustainable Syst. 9/2020). Adv. Sustainable Syst., 4: 2070018. doi:10.1002/adsu.202070018

Provided by KTH

Making New Materials Using AI (Material Science)

There is an old saying, “If rubber is the material that opened the way to the ground, aluminum is the one that opened the way to the sky.” New materials were always discovered at each turning point that changed human history. Materials used in memory devices are also drastically evolving with the emergence of new materials such as doped silicon materials, resistance changing materials, and materials that spontaneously magnetize and polarize. How are these new materials made? A research team from POSTECH has revealed the mechanism behind making materials used in new memory devices by using artificial intelligence.

The research team led by Professor Si-Young Choi of Department of Materials Science and Engineering and the team led by Professor Daesu Lee of the Department of Physics at POSTECH have together succeeded in synthesizing a novel substance that produces electricity by causing polarization (a phenomenon in which the position of negative and positive charges is separated from the negative and positive charges within the crystal) at room temperature and confirmed its variation in the crystal structure by applying deep neural network analysis. This paper was published in the recent issue of Nature Communications.

The atomic structures of perovskite oxides are often distorted and their properties are determined by the oxygen octahedral rotation (OOR) accordingly. In fact, there are only a few stable OOR patterns present at equilibrium and this inevitably limits the properties and functions of perovskite oxides.

The joint research team focused on a perovskite oxide called CaTiO3 [1] which remains nonpolar (or paraelectric) even at the absolute temperature of 0K. Based on the ab-initio calculations, however, the team found that a unique OOR pattern [2] that does not naturally exist would be able to facilitate the ferroelectricity, a powerful polarization at room temperature.

In this light, the research team succeeded in synthesizing a novel material (heteroepitaxial CaTiO3) that possesses the ferroelectricity by applying interface engineering [3] that controls the atomic structures at the interface and accordingly its physical property.

In addition, deep neural network analysis was applied to examine the fine OOR and the variation of a few decades of picometer in the atomic structures, and various atomic structures were simulated and data were utilized for AI analysis to identify artificially controlled OOR patterns.

“We have confirmed that we can create new physical phenomena that do not naturally occur by obtaining the unique OOR pattern through controlling the variation in its atomic structure,” remarked Professor Daesu Lee. “It is especially significant to see that the results of the convergent research of physics and new materials engineering enable calculations for material design, synthesis of novel materials, and analysis to understand new phenomena.”

Professor Si-Young Choi explained, “By applying the deep machine learning to materials research, we have successfully identified atomic-scale variations on tens of picometers that are difficult to identify with the human eye.” He added, “It could be an advanced approach for materials analysis that can help to understand the mechanism for creating new materials with unique physical phenomena.”

The findings are the result of convergence research conducted by the Department of Physics and the Department of Materials Science and Engineering at POSTECH and Seoul National University’s Center for Correlated Electron Systems. It was conducted with the support from the Mid-career Researcher Program and the Global Frontier Hybrid Interface Materials Program of the National Research Foundation of Korea and the POSTECH-Samsung Electronics Industry-Academia Cooperative Research Center.


  1. CaTiO3
    Oxygen octahedral structure defined as a-b+a-
  2. Oxygen octahedral rotation pattern
    Having an oxygen octahedral structure defined as a-a-a-
  3. Interface engineering
    The boundary between two substances of different materials is called interface. Interface engineering is the study of the conditions and properties of this interface and its surrounding materials.

Provided by POSTECH

Radiative Cooler That Cools Down Even Under Sunlight (Engineering)

Now that autumn is upon us, there is a large temperature gap between day and night. This is due to the temperature inversion caused by radiative cooling on the Earth’s surface. Heat from the sun during the day causes its temperature to rise and when the sun sets during the night, its temperature cools down. Recently, a joint research team from POSTECH and Korea University has demonstrated a daytime radiative cooling effect which exhibits lower temperatures than its surroundings even during the day.

Professor Junsuk Rho and Ph.D. candidate Dasol Lee of departments of mechanical engineering and chemical engineering and Professor Jin Kon Kim and Ph.D. candidate Myeongcheol Go in the Department of Chemical Engineering at POSTECH have conducted a joint study with Professor Heon Lee of Materials Science Engineering at Korea University to successfully realized an energy-free radiative cooling technology using silica-coated porous anodic aluminum oxide. The study was published in the latest online edition of Nano Energy, an international journal in the energy sector.

With growing interest in energy consumption, such as environmental pollution and limitations in using fossil fuels, attempts to lower the temperature without consuming energy continue. Radiative cooling is an example of structures installed on windows or walls to reduce the building temperature by reflecting sunlight or by absorbing and radiating far-infrared light. Radiative cooling is a technology that allows objects to receive less energy from the sun and lower temperatures by emitting radiative heat.

Unlike conventional cooling systems, radiative cooling is difficult to apply to large areas, although it has the advantage of significantly reducing energy consumption like electricity. Research to overcome this issue is being actively carried out around the world but it is still challenging to commercialize the technology.

To this, the joint research team found a very simple solution. Just by coating the porous anodic aluminum with a thin film of silica [1], it has been confirmed that there is a cooling effect that exhibits a lower temperature than the surroundings even under direct sunlight. Experiments have confirmed that an optimized structure can have a reflectivity [2] of 86% in the solar spectral region and a high emissivity [3] of 96% in the atmospheric window (8-13 μm). In addition, the radiative cooling material – produced in centimeters – showed a cooling efficiency of up to 6.1°C during the day when the sunlight was strong.

“This newly developed radiative cooling material can be easily produced,” explained POSTECH Professor Junsuk Rho. He added optimistically, “It will help solve environmental problems if applied to heating and cooling systems since it can be readily applied to large areas.”

This research was supported by POSCO’s Green Science Program, the Future Materials Discovery Program, Mid-career Researcher, Global Frontier, Regional Leading Research Center, and the Research Leader programs of the National Research Foundation of Korea funded by the Ministry of Science and ICT of Korea and the Global PhD Fellowship from the Ministry of Education of Korea.


  1. Silica (silicon dioxide)
    The most commonly present component in the earth’s crust, present in almost all rocks as a silicate mineral combined with other elements.
  2. Reflectivity
    The ratio of the energy of the reflected light to the energy of the incidental light. It indicates what extent several types of radiation waves, including light, are reflected from the surface of an object, which depends on the type of material and the condition of the surface.
  3. Emissivity
    The efficiency of energy released on the surface of an object in thermal radiation. It depends on the type and thickness of the object, surface condition, temperature, and wavelength of heat radiation.

Provided by POSTECH

Symmetry and the Laws of Nature (Quantum)

Not until the 17th century did humans seriously think of the possibility that a body of laws exists that would explain all the observed physical reality. Galileo Galilei, René Descartes, and in particular Isaac Newton demonstrated for the first time that a handful of mathematical laws can explain a wealth of phenomena, ranging from falling apples and ocean tides to the motion of the planets. In the 19th century, Michael Faraday and James Clerk Maxwell were able to do the same for electricity and magnetism.

The Hubble Ultra Deep Field. Almost 10,000 galaxies. Looking back to when the universe was less than a billion years old.Source: Credit: NASA, ESA, and S. Beckwith (STScI) and the HUDF Team/Public Domain

Then the 20th century witnessed the birth of not one but two scientific revolutions. First, Einstein’s theories of Special Relativity and General Relativity inextricably linked the concepts of space and time, and suggested that gravity is not some mysterious force that acts across distance, but rather a manifestation of the warping of the fabric of space-time by masses, a bit like a trampoline sagging under the weight of a person standing on it. Second, Quantum Mechanics asserted that we can only determine the probabilities of outcomes of experiments, not the outcomes themselves. To paraphrase Einstein, God does appear to play dice with the world.

With every step along this path of a deeper understanding of the universe, the role of symmetry as the foundation for the laws of nature has become increasingly appreciated. A symmetry of the laws means that when we observe phenomena from different points of view, we discover that they are governed precisely by the same laws. For example, the law of gravity takes precisely the same form whether we are here on Earth, on the Moon, or in a galaxy ten billion light-years away. This is an example of symmetry under translation. If the laws of physics were not symmetric under translation (that is, they were changing from place to place), it would have been impossible to understand the cosmos.

The laws of physics are also symmetric under rotations. That is, physics has no preferred direction in space. We discover the same laws whether we determine directions with respect to the north, south, or the nearest Starbucks.

A simple example can help clarify the difference between a symmetry of shapes and a symmetry of the laws. The ancient Greeks believed that the orbits of the planets are circular, because circles were considered perfect, being symmetric under rotation by any angle about an axis passing through the circle’s center and being perpendicular to the circle’s area. When astronomer Johannes Kepler discovered that the orbits are in fact ellipses, even Galileo didn’t believe it, since circles seemed more elegant. Newton later showed that elliptical orbits were a natural product of his universal law of gravitation. The fact that his law was symmetric under rotation simply meant that the orbits could have any orientation in space, not that the shape of the orbit had to be circular.

In 1915, German mathematical physicist Emmy Noether proved a remarkable theorem that now bears her name. She showed that to every continuous symmetry of the laws of physics there is a corresponding conservation law and vice versa. For example, the symmetry of the laws under translation corresponds to conservation of linear momentum (the product of the mass and the velocity), the symmetry with respect to the passing of time (the laws do not change with time) corresponds to the conservation of energy, and so on. Noether’s theorem therefore demonstrated that two of the pillars of physics, symmetries and conservation laws, are really two manifestations of the same fundamental property.

The symmetries I have described so far had to do with things that don’t change when we change our viewpoint in space and time. Many of the symmetries underlying the subatomic world and the basic forces of nature are associated with changing our perspective on the identity of elementary particles. For example, quantum mechanics allows for electrons to be in states that mix them with another elementary particle called a neutrino. In other words, particles can carry the label “electron,” “neutrino,” or a mixture of both. It turns out that the forces of nature are symmetric (take the same form) under any interchange between electrons, neutrinos, or a mixture of the two, and many other such so-called gauge symmetries exist.

Nobody knows yet whether symmetry is truly the most fundamental concept in the workings of the cosmos, but there is no doubt that symmetry principles have been extremely fruitful in our endeavors to decipher the universe.

References: (1) Livio, M. (2005). The Equation That Couldn’t Be Solved. New York: Simon & Schuster. (2) Livio, M. (2020). Galileo and the Science Deniers. New York: Simon & Schuster.

This article is republished here from Psychology Today under common creative licenses

Molecular Design Strategy Reveals Near Infrared-Absorbing Hydrocarbon (Chemistry)

Nagoya University researchers have synthesized a unique molecule with a surprising property: it can absorb near infrared light. The molecule is made only of hydrogen and carbon atoms and offers insights for making organic conductors and batteries. The details were published in the journal Nature Communications.

as-indacenoterrylene is a bowl-shaped compound made only of hydrogen and carbon atoms that can absorb near infrared light. ©Norihito Fukui.

Organic chemist Hiroshi Shinokubo and physical organic chemist Norihito Fukui of Nagoya University work on designing new, interesting molecules using organic, or carbon-containing, compounds. In the lab, they synthesized an aromatic hydrocarbon called methoxy-substituted as-indacenoterrylene. This molecule has a unique structure, as its methoxy groups are located internally rather than at its periphery.

“Initially, we wanted to see if this hydrocarbon demonstrated novel phenomena due to its unique structure,” says Fukui.

But during their investigations, the researchers discovered they could convert it into a new bowl-shaped hydrocarbon called as-indacenoterrylene.

“We were surprised to find that this new molecule exhibits near infrared absorption up to 1300 nanometers,” Shinokubo explains.

What’s unique about as-indacenoterrylene is not that it absorbs near infrared light. Other hydrocarbons can do this as well. as-indacenoterrylene is interesting because it does this despite being made of only 34 carbon and 14 hydrogen atoms, without containing other kinds of stabilizing atoms at its periphery.

When the scientists conducted electrochemical measurements, theoretical calculations, and other tests, they found that as-indacenoterrylene was intriguingly stable and also had a remarkably narrow gap between its highest occupied molecular orbital (HOMO) and its lowest unoccupied molecular orbital (LUMO). This means that the molecule has two electronically different subunits, one that donates and another that withdraws electrons. The narrow HOMO-LUMO gap makes it easier for electrons to become excited within the molecule.

“The study offers an effective guideline for the design of hydrocarbons with a narrow HOMO-LUMO gap, which is to fabricate molecules with coexisting electron-donating and electron-withdrawing subunits,” says Fukui. “These molecules will be useful for the development of next-generation solid-state materials, such as organic conductors and organic batteries.”

The team next plans to synthesize other near infrared-absorbing aromatic hydrocarbons based on the design concepts garnered in this current study.

References: Tanaka, Y., Fukui, N. & Shinokubo, H. as-Indaceno[3,2,1,8,7,6-ghijklm]terrylene as a near-infrared absorbing C70-fragment. Nat Commun 11, 3873 (2020).

Provided by Nagoya University

New Species Of The Listeria Genus Discovered And Baptised (Biology)

It is estimated that only 1% of bacteria are pathogenic for humans or animals. Among them, the bacterial genus Listeria has been widely studied as it contains two species, Listeria monocytogenes and Listeria ivanovii, which are pathogenic, causing the disease known as listeriosis. Until now, the genus Listeria consisted of a total of 20 species. Researchers from the CEU Cardenal Herrera University of Valencia (CEU UCH) and the Institut Pasteur have expanded this list with the discovery of a new species: Listeria valentina, named for having been discovered in Valencia.

UCH Professor Juan José Quereda. Credit: Asociación RUVID

As a result of the international collaboration between the group of researchers led by Juan José Quereda Torres, a Spanish specialist in the study of listeriosis from CEU UCH, and the National Reference Centre and WHO Collaborating Centre for Listeria at the Institut Pasteur in Paris led by Professor Marc Lecuit, this new species of the genus Listeria called Listeria valentina (in Latin, “from Valencia”) has been discovered. This finding has just been published in the prestigious International Journal of Systematic and Evolutionary Microbiology. L. valentina has been discovered in feces obtained from sheep as well as on the surface of a trough from the same animals. In this sense, the ProVaginBio research group of CEU UCH, which is specialized in the study of the microbiota of ruminants, also collaborated in the study.

Understanding the infection

According to the professor and Juan José Quereda, who has co-led this study with Professor Marc Lecuit from the Institut Pasteur, “The sequencing of the complete genome of L. valentina has revealed that this bacterium lacks most virulence factors of its relatives L. monocytogenes and L. ivanovii, meaning that a priori it could be considered a new non-pathogenic species. L. valentina will enable a better understanding of the evolution, life and adaptation to different environments of the pathogenic species of the genus.”

The new species L. valentina has been recorded and is stored in the microorganism collections of the Institut Pasteur in Paris and the DSMZ Institute in Germany. This scientific finding is the result of two projects funded by the Generalitat Valenciana (GV/2018/A/183) and by the Ministry of Science and Innovation of Spain (PID2019-110764RA-I00), as well as various French research organizations.

Regarding the discovery of this new species of the genus Listeria in Valencia, CEU UCH Professor Juan José Quereda explains: “Bacteria are the most widespread form of life on earth, they inhabit practically all ecosystems. Spain is one of the European Union countries with the greatest biological diversity due in part to its geographical position and its geological, orographic, edaphic and climatic diversity. These peculiarities make it possible to discover new microorganisms in future studies carried out in our environment.”

Listeriosis: A recent increase in cases

Professor Quereda says, “in 2017 the number of confirmed infections of listeriosis cases in the EU increased to 2,480, and 225 deaths were reported. This data is even more worrying because since 2008 the cases of listeriosis in the European Union are increasing.” Cases of listeriosis can also occur in the form of outbreaks: “The largest outbreak of listeriosis reported in history had 937 cases and 216 deaths, taking place in 2018 in South Africa due to the consumption of a processed meat product.”

Humans, as well as animals, are infected via food by consuming products contaminated with Listeria. The clinical signs of listeriosis are very similar in all susceptible hosts. In immunocompetent humans L. monocytogenes produces febrile gastroenteritis, while in immunocompromised individuals it produces septicaemia and meningoencephalitis. In pregnant women it causes abortions, perinatal mortality, generalised infection and meningitis in the neonate called neonatal listeriosis.

References: Juan J. Quereda et al. Listeria valentina sp. nov., isolated from a water trough and the faeces of healthy sheep, International Journal of Systematic and Evolutionary Microbiology (2020). DOI: 10.1099/ijsem.0.004494

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