Roughness of Retinal Layers, A New Alzheimer’s Biomarker (Neuroscience)

Over recent years, the retina has established its position as one of the most promising biomarkers for the early diagnosis of Alzheimer’s. Moving on from the debate as to the retina becoming thinner or thicker, researchers from the Universidad Complutense de Madrid and Hospital Clínico San Carlos are focusing their attention on the roughness of the ten retinal layers.

The study, published in Scientific Reports, “proves innovative” in three aspects according to José Manuel Ramírez, Director of the IIORC (Ramón Castroviejo Institute of Ophthalmologic Research) at the UCM. “This is the first study to propose studying the roughness of the retina and its ten constituent layers. They have devised a mathematical method to measure the degree of wrinkling, through the fractal dimension, and have discovered that in some layers of the retina these measurements indicate that wrinkling begins at very early stages of Alzheimer’s disease,” explains the IIORC expert.

To undertake the study, launched six years ago, the researchers developed computer programs allowing them to separate each layer of the retina. Following this subdivision, the problem which arose was how to distinguish the roughness of one layer from that of the neighbouring layers.

“As each is in contact with the others, the wrinkling of one layer is transmitted to the adjacent layers, and their roughness becomes blurred. The solution was to flatten each layer mathematically on each side and study the roughness remaining on the other side,” indicates Lucía Jáñez, the lead author of the publication.

Software development to calculate roughness

The second problem faced in the research was to find a procedure to measure roughness. “The solution lay in calculating the fractal dimension of the side of each retinal layer studied,” explains Luis Jáñez, researcher at the UCM’s ITC (Institute of Knowledge Technology).

“A flat surface has only two dimensions: length and width, but if it is folded or wrinkled it progressively takes on body and begins to appear a three-dimensional solid object. The fractal dimension adopts fractional values between 2 and 3, and so is suitable to measure the degree of wrinkling of retinal layers,” he adds.

The final step taken by the group was to incorporate the technology they had developed within the Optical Coherence Tomography (OCT) currently available on the market, using mathematical analysis to express this in software which calculates the roughness of each retinal layer, and establishes the boundary between health/illness.

For the patient, this is a simple, quick and low-cost test. “No prior preparation is required. They simply turn up for an ophthalmology appointment, sit facing the machine and spend about 4 seconds looking at a dot of light inside: that generates the OCT image. The analysis of the roughness of the image is performed by a computer program in less than one minute,” the ITC researcher indicates.

After a decade working in this field, researchers understand how the eyesight of patients with Alzheimer’s evolves, and the changes in retinal thickness. “From now on, with this new technique we can research how to use retinal roughness to monitor and ascertain the stage of Alzheimer’s disease,” predicts the IIORC researcher Elena Salobrar García.

As well as being used in Alzheimer’s, the methods they have developed could be applied in studying other diseases, such as ALS or Parkinson’s, “the effects of which on the retina we are now beginning to understand. As well as contributing to advances in neuroscience, this might also be useful in ophthalmology,” concludes Omar Bachtoula, researcher at the UCM Psychology Faculty.


Reference: Jáñez-García, L., Bachtoula, O., Salobrar-García, E. et al. Roughness of retinal layers in Alzheimer’s disease. Sci Rep 11, 11804 (2021). https://doi.org/10.1038/s41598-021-91097-3


Provided by UCM

Study Reveals Formation Mechanism of First Carbon-carbon Bond in MTO Process (Chemistry)

A joint research team led by Prof. LIU Zhongmin, Prof. WEI Yingxu, and Prof. XU Shutao from the Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) revealed the mechanism underlying the formation of the first carbon-carbon (C-C) bond formation during the methanol-to-olefins (MTO) process.

This study was published in Chem on June 23.

Prof. ZHENG Anmin’s group from Innovation Academy for Precision Measurement Science and Technology of CAS was also involved in the study.

The first C-C bond in the MTO process is formed at the initial stage of the reaction. There is no direct method to elucidate the bond formation /reaction mechanism due to the difficulty in capturing intermediate species.

“We investigated the direct C-C bond formation mechanism during the initial MTO reaction over HSSZ-13 zeolite with an 8-membered ring and a chabazite topological structure,” said Prof. XU.

They detected the evolution of the organic species on the SSZ-13 catalyst surface during the methanol conversion. For the first time, they directly captured the surface ethoxy species (SES), the critical species containing the initial C-C bond under real MTO reaction conditions at the initial reaction stage.

Moreover, the researchers employed the ab initio molecular dynamics (AIMD) theoretical calculation simulation to predict and present the visualized and complete process of initial C-C bond formation starting from the C1 reactants and C1 intermediates.

Based on the experimental and theoretical evidence, they established the complete and feasible initial C-C bond formation routes, namely, surface methoxy species (SMS)/trimethoxyonium (TMO) mediated methanol/dimethyl ether (DME) activation with a synergistic effect from SMS and the negatively charged framework oxygen atoms to form SES.

“Our study not only sheds light on the controversial issue of the first C-C bond formation in the MTO process, but also enriches the fundamental theory of C1 catalytic chemistry,” said Prof. WEI.

This work was supported by the National Natural Science Foundation of China, Strategic Priority Research Program of the Chinese Academy of Sciences, iChEM, the Youth Innovation Promotion Association of the Chinese Academy of Sciences and Liaoning Revitalization Talents Program.

Featured image: Revealing the whole first C-C bond formation processes in MTO reaction: based on the in situ NMR spectroscopic evidences and advanced ab initio molecular dynamics (AIMD) theoretical calculation method © DICP


Reference: Shutao Xu, Yuchun Zhi, Jingfeng Han, Wenna Zhang, Xinqiang Wu, Tantan Sun, Yingxu Wei, Zhongmin Liu, Chapter Two – Advances in Catalysis for Methanol-to-Olefins Conversion, Editor(s): Chunshan Song, Advances in Catalysis, Academic Press, Volume 61, 2017, Pages 37-122, ISSN 0360-0564, ISBN 9780128120781, https://doi.org/10.1016/bs.acat.2017.10.002. (https://www.sciencedirect.com/science/article/pii/S0360056417300056)


Provided by DICP

Low-cost Imaging Technique Shows How Smartphone Batteries Could Charge in Minutes (Chemistry)

Researchers have developed a simple lab-based technique that allows them to look inside lithium-ion batteries and follow lithium ions moving in real time as the batteries charge and discharge, something which has not been possible until now.

Using the low-cost technique, the researchers identified the speed-limiting processes which, if addressed, could enable the batteries in most smartphones and laptops to charge in as little as five minutes.

The researchers, from the University of Cambridge, say their technique will not only help improve existing battery materials, but could accelerate the development of next-generation batteries, one of the biggest technological hurdles to be overcome in the transition to a fossil fuel-free world. The results are reported in the journal Nature.

While lithium-ion batteries have undeniable advantages, such as relatively high energy densities and long lifetimes in comparison with other batteries and means of energy storage, they can also overheat or even explode, and are relatively expensive to produce. Additionally, their energy density is nowhere near that of petrol. So far, this makes them unsuitable for widespread use in two major clean technologies: electric cars and grid-scale storage for solar power.

“A better battery is one that can store a lot more energy or one that can charge much faster – ideally both,” said co-author Dr Christoph Schnedermann, from Cambridge’s Cavendish Laboratory. “But to make better batteries out of new materials, and to improve the batteries we’re already using, we need to understand what’s going on inside them.”

To improve lithium-ion batteries and help them charge faster, researchers need to follow and understand the processes occurring in functioning materials under realistic conditions in real time. Currently, this requires sophisticated synchrotron X-ray or electron microscopy techniques, which are time-consuming and expensive.

“To really study what’s happening inside a battery, you essentially have to get the microscope to do two things at once: it needs to observe batteries charging and discharging over a period of several hours, but at the same time it needs to capture very fast processes happening inside the battery,” said first author Alice Merryweather, a PhD student at Cambridge’s Cavendish Laboratory.

The Cambridge team developed an optical microscopy technique called interferometric scattering microscopy to observe these processes at work. Using this technique, they were able to observe individual particles of lithium cobalt oxide (often referred to as LCO) charging and discharging by measuring the amount of scattered light.

They were able to see the LCO going through a series of phase transitions in the charge-discharge cycle. The phase boundaries within the LCO particles move and change as lithium ions go in and out. The researchers found that the mechanism of the moving boundary is different depending on whether the battery is charging or discharging.

“We found that there are different speed limits for lithium-ion batteries, depending on whether it’s charging or discharging,” said Dr Akshay Rao from the Cavendish Laboratory, who led the research. “When charging, the speed depends on how fast the lithium ions can pass through the particles of active material. When discharging, the speed depends on how fast the ions are inserted at the edges. If we can control these two mechanisms, it would enable lithium-ion batteries to charge much faster.”

“Given that lithium-ion batteries have been in use for decades, you’d think we know everything there is to know about them, but that’s not the case,” said Schnedermann. “This technique lets us see just how fast it might be able to go through a charge-discharge cycle. What we’re really looking forward to is using the technique to study next-generation battery materials – we can use what we learned about LCO to develop new materials.”

“The technique is a quite general way of looking at ion dynamics in solid state materials, so you can use it on almost any type of battery material,” said Professor Clare Grey, from Cambridge’s Yusuf Hamied Department of Chemistry, who co-led the research.

The high throughput nature of the methodology allows many particles to be sampled across the entire electrode and, moving forward, will enable further exploration of what happens when batteries fail and how to prevent it.

“This lab-based technique we’ve developed offers a huge change in technology speed so that we can keep up with the fast-moving inner workings of a battery,” said Schnedermann. “The fact that we can actually see these phase boundaries changing in real time was really surprising. This technique could be an important piece of the puzzle in the development of next-generation batteries.”


Reference: Merryweather, A.J., Schnedermann, C., Jacquet, Q. et al. Operando optical tracking of single-particle ion dynamics in batteries. Nature 594, 522–528 (2021). https://doi.org/10.1038/s41586-021-03584-2


Provided by University of Cambridge

Pleistocene Sediment DNA from Denisova Cave (Paleontology)

Sediment DNA tracks 300,000 years of hominin and animal presence at Denisova Cave

Denisova Cave is located in the Altai Mountains in southern Siberia and is famous for the discovery of Denisovans, an extinct form of archaic humans that is thought to have occupied large parts of central and eastern Asia. Neandertal remains have also been found at the site, as well as a bone from a child who had a Neandertal mother and Denisovan father, showing that both groups met in the region. However, only eight bone fragments and teeth of Neandertals and Denisovans have been recovered so far from the deposits in Denisova Cave, which cover a time span of over 300,000 years. These are too few fossils to reconstruct the occupational history of the site in detail, or to link the different types of stone tools and other artefacts found in Denisova Cave to specific hominin groups. For example, the discovery of jewelry and pendants typical of the so-called Initial Upper Palaeolithic culture in approximately 45,000-year-old layers has prompted debates as to whether Denisovans, Neandertals or modern humans were the creators of these artefacts.

Michael Shunkov of the Siberian Branch of the Russian Academy of Sciences, who leads the excavations at Denisova Cave, assembled an interdisciplinary team of archaeologists, geneticists, geochronologists and other scientists to study this unique site. The team has now performed the largest analysis ever of sediment DNA from a single excavation site. “The analysis of sediment DNA provides a wonderful opportunity to combine the dates that we previously determined for the deposits in Denisova Cave with molecular evidence for the presence of people and fauna”, says Richard ‘Bert’ Roberts from the University of Wollongong in Australia. The team of geochronologists led by him and Zenobia Jacobs collected more than 700 sediment samples in a dense grid from the exposed sediment profiles in the cave. “Just collecting the samples from all three chambers in the cave, and documenting their precise locations, took us more than a week”, Jacobs says.

Traces of DNA in the sediment

Researchers Zenobia Jacobs, Bo Li and Kieran O’Gorman collecting sediment samples in the Main Chamber. © Richard G. Roberts

When the samples arrived at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Elena Zavala, the lead author of the study, spent another two years in the lab to extract and sequence small traces of ancient hominin and animal mitochondrial DNA from this huge collection of samples. “These efforts paid off and we detected the DNA of Denisovans, Neandertals or ancient modern humans in 175 of the samples”, Zavala says.

When matching the DNA profiles with the ages of the layers, the researchers found that the earliest hominin DNA belonged to Denisovans, indicating that they produced the oldest stone tools at the site between 250,000 and 170,000 years ago. The first Neandertals arrived towards the end of this time period, after which both Denisovans and Neandertals frequented the site – except between 130,000 and 100,000 years ago, when no Denisovan DNA was detected in the sediments. The Denisovans who came back after this time carried a different mitochondrial DNA, suggesting that a different population arrived in the region.

New tools

Researchers Zenobia Jacobs, Bo Li and Kieran O’Gorman collecting sediment samples in the South Chamber. © Credit: Dr. Richard G. Roberts

Modern human mitochondrial DNA first appears in the layers containing Initial Upper Palaeolithic tools and other objects, which are much more diverse than in the older layers. “This provides not only the first evidence of ancient modern humans at the site, but also suggests that they may have brought new technology into the region with them”, says Zavala.

The scientists studied animal DNA and identified two time periods where changes occurred in both animal and hominin populations. The first, around 190,000 years ago, coincided with a shift from relatively warm (interglacial) conditions to a relatively cold (glacial) climate, when hyaena and bear populations changed and Neandertals first appeared in the cave. The second major change occurred between 130,000 and 100,000 years ago, along with a shift in climate from relatively cold to relatively warm conditions. During this period, Denisovans were absent and animal populations changed again.

“I believe that our Russian colleagues who excavate this amazing site have set the standards for many future archaeological excavations with their careful collection of many samples from each archaeological layer for DNA analysis”, says Svante Pääbo who initiated the study with the Russian team. “Being able to generate such dense genetic data from an archaeological site is like a dream come true, and these are just the beginnings”, says Matthias Meyer, the senior author on the study. “There is so much information hidden in sediments – it will keep us and many other geneticists busy for a lifetime.”

Featured image: The entrance to Denisova Cave, the famous site in southern Siberia where remains of both Neandertals and their Asian relatives, the Denisovans, have been found. © Richard G. Roberts


Reference: Elena Zavala et al.Pleistocene sediment DNA reveals hominin and faunal turnovers at Denisova CaveNature, 23 June 2021, DOI: 10.1038/s41586-021-03675-0


Provided by Max Planck Institute for Evolutionary Anthropology

Outstanding Organic Solar Cells’ Performance Achieved By Using New Technology (Chemistry)

Organic solar elements with the self-assembling molecular-thin layer (SAM) of hole-transporting material, the technology, which was used in producing a record-breaking tandem solar cell, achieved 18.4 power conversion efficiency. The invention of Lithuanian chemists working at Kaunas University of Technology (KTU), commercialized by several global companies proved versatile and applicable to different solar technologies.

Organic solar cells are made of common organic elements such as carbon, hydrogen, nitrogen, fluorine, oxygen, and sulphur. Their raw materials are cheap, abundant, and can be easily recycled. Although the organic photovoltaic (OPV) elements are lighter, more flexible and cheaper to produce, their efficiency still falls behind that of other photovoltaic technologies, including silicone, perovskite and tandem solar cells. And yet, this aspect may soon change.

Solar cells developed in Lithuania and Saudi Arabia

At the end of 2018, a group of Lithuanian chemists from Kaunas University of Technology synthesised a material, which self-assembles into a molecule-thick layer, aka monolayer, can cover a variety of surfaces and function as a hole-transporting layer in a solar element. Until recently, the self-assembling monolayers (SAMs) have been used to produce record-breaking perovskite/silicon and CIGS/perovskite tandem solar cells. However, the technology also proved very efficient – reaching nearly record-breaking 18.4 power conversion – when used in an organic solar cell, produced by the group of researchers headed by Professor Thomas Anthopoulos at the KAUST University in Saudi Arabia.

Dr Artiom Magomedov, c0-author of the invention © KTU

“We made some modifications in the material used in SAM formation to tailor it for organic solar elements. However, our technology, offering a breakthrough approach towards photovoltaic elements’ production remains the same: the surface is dipped into a solution and a molecule-thick semiconductor layer is formed. The technology is cheap, efficient and versatile”, says Dr Artiom Magomedov of KTU Faculty of Chemical Technology, the co-author of the invention.

Organic solar cell achieved 18.4 efficiency

As the materials synthesised by KTU chemists are now commercialised and freely available in the market for research groups and companies all over the world, the discovery continues to advance the development of photovoltaic technologies.

“Last year, we noticed an article published by the researchers from KAUST, where they described the achieved very high efficiency of an organic solar cell while using our SAMs. We contacted the scientists and offered to collaborate in enhancing the capacities of the material. Due to the pandemic restrictions, all cooperation was remote – we sent the synthesised materials by post and our colleagues in Saudi Arabia built the organic solar cells and measured their properties”, explains Dr Magomedov.

The organic solar cell using Br-2PACz molecule-thin coating as a hole-transporting layer achieved a power conversion efficiency of 18.4 per cent, which is currently among the highest in OPV technologies. Moreover, the electrode constructed was chemically stable, and after removal of the SAM, it could be recycled and reused to construct fresh highly-performing OPV cells.

All solar technologies will find their niches

The researchers emphasise that the use of similar SAMs could be potentially extended in other applications including light-emitting diodes, photodetectors or organic transistors. According to Dr Magomedov, all different solar technologies, which are currently being developed, will find their niches in the market – as OPV cells are lighter, can be made transparent and flexible, they can be used for charging drones, household electronics, for indoor photovoltaics. Currently, no OPV elements are mass-produced.

Professor Vytautas Getautis © KTU

“The semiconducting properties of organic elements are lower than those of non-organic materials. Therefore, the achieved efficiency results are very impressive for everyone working in the field. After the publication, a Swedish company “Dyenamo” has already obtained the licence to produce our materials tailored for the organic solar elements, as they see the potential of this technology”, says Professor Vytautas Getautis, the Head of the KTU research group behind the invention.

Featured image: Chemists from Kaunas University of Technology synthesised a material, which self-assembles into a molecule-thick layer, aka monolayer, can cover a variety of surfaces and function as a hole-transporting layer in a solar element. © KTU


Reference: Lin, Y., Magomedov, A., Firdaus, Y., Kaltsas, D., El-Labban, A., Faber, H., Naphade, D.R., Yengel, E., Zheng, X., Yarali, E., Chaturvedi, N., Loganathan, K., Gkeka, D., AlShammari, S.H., Bakr, O.M., Laquai, F., Tsetseris, L., Getautis, V. & Anthopoulos, T.D. 18.4% Organic solar cells using a high ionization energy self‐assembled monolayer as hole extraction interlayer, ChemSusChem 2021, 14, 1– 1. Article accessible here.


Provided by KTU

Asian Elephants Do More Than Just Trumpet- They Buzz Their Lips to Squeak (Biology)

The animals’ sound production does not only come from the trunk

Communication is crucial for elephants that live in complex multi-tiered social systems. Apart from their iconic trumpets uttered through the trunk, Asian elephants also produce species-specific squeaks by buzzing their lips. This demonstrates once again the elephant’s flexibility in sound production. These results are presented in a publication in “BMC Biology” by behavioural biologist Veronika Beeck from the University of Vienna and colleagues.

Everybody from a child knows that elephants trumpet. Over the past decades research in general and at the University of Vienna has mainly studied the elephants low-frequency rumble. Its fundamental frequency reaches into the infrasonic range below the human hearing threshold. This call is produced by the elephant´s massive vocal folds. Much less was known about how elephants produce their higher pitched sounds, trumpets and squeaks.

The following rule generally applies to sound production in mammals: the larger the vocal fold, the lower the calls fundamental frequency. Conversely the size of the vocal folds sets an upper limit to the fundamental frequencies that can be reached. The high-pitched squeak only Asian but not African elephants produce when aroused, do not fit within that spectrum.

In her recent study Veronika Beeck, who is part of the FWF doctorate school Cognition and Communication at the Department of Behavioural and Cognitive Biology at the University of Vienna and her supervisor Angela Stöger, together with Gunnar Heilmann and Micheal Kerscher from gfai tech, Berlin, studied the squeak sounds of Asian elephants in Nepal.

The researchers used an acoustic camera with an array of 48 microphones that visualises sounds in colours similar to a thermic camera. In this way the sound source was precisely located. “Our images clearly demonstrate that the squeaks are emitted by the mouth and not the trunk”, Veronika Beeck explains. 

According to the researcher’s theory the Asian elephants produce squeaks by pressing air through their tensed lips inducing the lip´s vibration. This technique equals the human brass players lip buzzing to produce a complex sound whose harmonic overtones are subsequently resonated by the instrument, resulting in its characteristic brassy sound. “Apart from human brass players this technique of lip buzzing to produce sounds has, to our knowledge, not been described in any other animal species and is thus considered unique in the animal kingdom”, says Veronika Beeck.

The elephants iconic trumpet on the other hand is produced by a blast of air through the trunk. Here again, however, the vibrating anatomic sound source is not yet conclusively studied.

This new evidence further highlights the elephant´s flexibility in sound production. A few years ago, Angela Stöger-Horwath showed that elephants are capable of learning novel sounds. An Asian elephant in a Korean Zoo, by imitating his trainer, learned to speak some words in Korean. Since only a few elephants in this recent study squeaked the researchers suggest that squeaks might be learned, too.

Featured image: With the acoustic camera´s star-shaped array of microphones placed in front of the elephant the researchers are waiting patiently for her to vocalize while night falls. (© Gunnar Heilmann)


Publication in BMC Biology:

  • A novel theory of Asian elephant high-frequency squeak production.
  • Veronika C. Beeck, Gunnar Heilmann, Michael Kerscher, Angela S. Stoeger
  • DOI: BMCB-D-20-01049

Provided by University of Wien

China’s EarthLab Begins Trials as Country’s First Facility Exploring Earth System Interactions (Earth Science)

The Earth is a sphere, and it comprises spheres: atmosphere, hydrosphere, cryosphere, lithosphere and biosphere — in short, all of the cycles that interact to influence Earth’s weather and climate. Now, to better research how the spheres interact and impact the planet, China is launching EarthLab in Beijing. On June 23, after EarthLab’s opening ceremony, researchers will begin trials to demonstrate the facility’s ability to integrate simulations and observations to more accurately project outcomes and provide a scientific foundation to predict and mitigate such things as natural weather disasters. 

EarthLab PIs and sponsors announce trial run together. (Image by LIN Zheng)  

EarthLab’s research team published an introduction to the facility on June 23 in Advances in Atmospheric Sciences. “Since the earth system is extremely large and complex, traditional theories and observations are too limited to meet the overall requirements of the scientific research community,” said paper corresponding author ZHANG He, EarthLab researcher affiliated with the Institute of Atmospheric Physics  (IAP) at the Chinese Academy of Sciences (CAS). “EarthLab is the first comprehensive virtual earth laboratory in China for simulation the physical climate system, environmental system, ecological system, solid earth system, and space weather system as a whole with a high-performance scientific computing platform.”

Simulation by CAS-ESM 2.0, the key software systems of EarthLab. (Image by ZHANG He) 

In partnership with Tsinghua University, IAP/CAS began construction of EarthLab in 2018. After successful trialing, inspections and approvals, EarthLab is expected to become fully operational — and open to universities and research institutes across the world — in 2022.  

“Other countries, such as the United States and Japan, as well as some European countries, have built specialized numerical simulations facilities,” ZHANG said, noting that China’s vast and complex topography has been difficult to model accurately with various levels of observational and experimental resources across the country. “Weather, climate and environmental disasters occur frequently and seriously with grave losses of life and property. Consequently, a global earth system simulation system, as well as high-precision regional environmental simulation system, are urgently needed to better predict climate and environment variability, to prevent and mitigate natural disasters more effectively, and to formulate relevant national plans more scientifically.” 

According to Zhang, EarthLab will also become a science outreach base for children and students to learn more about Earth sciences. During an IAP outreach day in 2017, children voted on EarthLab’s Chinese name: Huan. The name means “a place as vast as the earth where people live and upon whose land they depend”.  

EarthLab Outreach Hall. (Image by ZHU Jiang)  

“Our ultimate goal is to predict Earth systems on a vast range of time scale, from seconds to hundreds of years, and of spatial scale, from 10 meters to millions of meters,” ZHANG said. “Along with other earth simulators around the world, the development and construction of EarthLab will advance not only the understanding of the Earth’s spheres and their interactions, and Earth’s past, present and future, but also the progress of computational mathematics, high-performance computing and technology, and other broader fields.”


Reference: Chai, Z. Y., and Coauthors, 2021: China’s EarthLab—Forefront of Earth system simulation research. Adv. Atmos. Sci., https://doi.org/10.1007/s00376-021-1175-y


Provided by IAP CAS

Earth-like Biospheres On Other Planets May be Rare (Planetary Science)

A new analysis of known exoplanets has revealed that Earth-like conditions on potentially habitable planets may be much rarer than previously thought. The work focuses on the conditions required for oxygen-based photosynthesis to develop on a planet, which would enable complex biospheres of the type found on Earth. The study is published today in Monthly Notices of the Royal Astronomical Society.

The number of confirmed planets in our own Milky Way galaxy now numbers into the thousands. However planets that are both Earth-like and in the habitable zone – the region around a star where the temperature is just right for liquid water to exist on the surface – are much less common.

At the moment, only a handful of such rocky and potentially habitable exoplanets are known. However the new research indicates that none of these has the theoretical conditions to sustain an Earth-like biosphere by means of ‘oxygenic’ photosynthesis – the mechanism plants on Earth use to convert light and carbon dioxide into oxygen and nutrients.

Only one of those planets comes close to receiving the stellar radiation necessary to sustain a large biosphere: Kepler−442b, a rocky planet about twice the mass of the Earth, orbiting a moderately hot star around 1,200 light years away.

The study looked in detail at how much energy is received by a planet from its host star, and whether living organisms would be able to efficiently produce nutrients and molecular oxygen, both essential elements for complex life as we know it, via normal oxygenic photosynthesis.

By calculating the amount of photosynthetically active radiation (PAR) that a planet receives from its star, the team discovered that stars around half the temperature of our Sun cannot sustain Earth-like biospheres because they do not provide enough energy in the correct wavelength range. Oxygenic photosynthesis would still be possible, but such planets could not sustain a rich biosphere.

Planets around even cooler stars known as red dwarfs, which smoulder at roughly a third of our Sun’s temperature, could not receive enough energy to even activate photosynthesis. Stars that are hotter than our Sun are much brighter, and emit up to ten times more radiation in the necessary range for effective photosynthesis than red dwarfs, however generally do not live long enough for complex life to evolve.

“Since red dwarfs are by far the most common type of star in our galaxy, this result indicates that Earth-like conditions on other planets may be much less common than we might hope,” comments Prof. Giovanni Covone of the University of Naples, lead author of the study.

He adds: “This study puts strong constraints on the parameter space for complex life, so unfortunately it appears that the “sweet spot” for hosting a rich Earth-like biosphere is not so wide.”

Future missions such as the James Webb Space Telescope (JWST), due for launch later this year, will have the sensitivity to look to distant worlds around other stars and shed new light on what it really takes for a planet to host life as we know it.

Featured image: An artistic representation of the potentially habitable planet Kepler 422-b (left), compared with Earth (right). © Ph03nix1986 / Wikimedia Commons Licence type: Attribution-ShareAlike (CC BY-SA 4.0)


Further information

The new work appears in, “Efficiency of the oxygenic photosynthesis on Earth-like planets in the habitable zone”, G. Covone, R.M. Ienco, L. Cacciapuoti and L. Inno, Monthly Notices of the Royal Astronomical Society (2021), in press (DOI: 10.1093/mnras/stab1357).


Provided by Royal Astronomical Society

Synthesis of A Near-infrared Light Absorbing Macrocyclic Aromatic Compound (Chemistry)

Selective synthesis of ring-expanded porphyrinoids comprising nine pyrroles

Profs. Okujima and Uno at Ehime University, in collaboration with Prof. Kobayashi at Shinshu University, reported the selective synthesis, the molecular structure, optical properties and electronic structure of cyclo[9]pyrrole, a ring-expanded porphyrin consisting of directly connected pyrrole rings.

Porphyrins, which are well-known natural porphyrin molecules, e.g. heme and chlorophyll, are attractive for use in practical materials because of the easy optimization of their optical and physical properties by conjugation expansion and functionalization. In 2002, Sessler reported the first synthesis of cyclo[n]pyrrole (n: the number of pyrrole rings). Peripheral alkyl-substituted cyclo[8]pyrroles were obtained via an oxidative coupling of 2,2′-bipyrrole, and showed an intense L band at ca. 1,100 nm.

We successfully synthesized a good yield of cyclo[9]pyrroles via the oxidative coupling of terpyrrole. A relatively distorted structure with a C2-like symmetry was clarified by NMR and X-ray diffraction analyses. Intense absorption was observed at ca. 1,740 nm. We analyzed the optical and electronic structures using magnetic circular dichroism spectroscopy and time-dependent density functional theory calculations. Comparison of cyclo[8], [9], and [10]pyrroles showed the electronic structures don’t significantly depend on the number of pyrroles.

Our findings were published on April 15, 2021 in Organic Letters.

Featured image: Selective Synthesis of Cyclo[9]pyrroles Based on an Oxidative Coupling © Tetsuo Okujima, Ehime University


Provided by Ehime University

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