Researchers have developed a way to create photonic time crystals, showing that these bizarre, artificial materials amplify the light that shines on them. These findings could lead to more efficient and robust wireless communications and significantly improved lasers.

Time crystals were first conceived by Nobel laureate Frank Wilczek in 2012. While conventional natural crystals have a structural pattern that repeats in space, in a time crystal, the pattern repeats in time instead.

Although some physicists were initially skeptical that time crystals could exist, recent experiments have succeeded in creating them. Last year, researchers at Aalto University’s Low Temperature Laboratory created paired time crystals that could be useful for quantum devices.

Now, another team has made photonic time crystals, which are temporal analogues of conventional optical materials. The researchers created photonic time crystals that operate at microwave frequencies and showed that they can amplify electromagnetic waves.

This ability has potential applications in various technologies, including wireless communication, integrated circuits, and lasers. 

So far, research on photonic time crystals has focused on bulk materials – that is, three-dimensional structures. This has proven enormously challenging, and the experiments haven’t gotten past model systems with no practical applications.

Now, the team including researchers from Aalto University, the Karlsruhe Institute of Technology (KIT), and Stanford University tried a new approach: building a two-dimensional photonic time crystal.

‘We found that reducing the dimensionality from a 3D to a 2D structure made the implementation significantly easier, which made it possible to realise photonic time crystals in reality,’ says Xuchen Wang, the study’s lead author, who was a doctoral student at Aalto and is currently at KIT.

The new approach enabled the team to fabricate a photonic time crystal and experimentally verify the theoretical predictions about its behaviour. ‘We demonstrated for the first time that photonic time crystals can amplify incident light with high gain,’ says Wang.

‘In a photonic time crystal, the photons are arranged in a pattern that repeats over time. This means that the photons in the crystal are synchronized and coherent, which can lead to constructive interference and amplification of the light,’ explains Wang. 

Two-dimensional photonic time crystals have a range of potential applications. By amplifying electromagnetic waves, they could make wireless transmitters and receivers more powerful or more efficient.

Wang points out that coating surfaces with 2D photonic time crystals could also help with signal decay, which is a significant problem in wireless transmission. Photonic time crystals could also simplify laser designs by removing the need for bulk mirrors that are typically used in laser cavities.

Another application emerges from the finding that 2D photonic time crystals don’t just amplify electromagnetic waves that hit them from surrounding space but also waves travelling along surfaces. Surface waves are used for communication between electronic components in integrated circuits.

‘When a surface wave propagates, it suffers from material losses, and the signal strength is reduced. With 2D photonic time crystals integrated into the system, the surface wave can be amplified, and communication efficiency enhanced,’ says Professor Viktar Asadchy, who has generated the idea of 2D photonic time crystals.

Source: University of Amsterdam

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A new study’s finding that urban light pollution may disrupt the winter dormancy period for mosquitoes that transmit West Nile virus could be considered both good and bad.

The good news is that the disease-carrying pests may not survive the winter if their plans to fatten up are foiled. The bad news is their dormancy period, known as diapause, may simply be delayed – meaning they’re biting humans and animals longer into the fall. 

“We see the highest levels of West Nile virus transmission in Ohio’s late summer and early fall. If you have mosquitoes postponing or delaying diapause and continuing to be active longer in the year, that’s at a time when the mosquitoes are most likely to be infected with West Nile virus and people could be at greatest risk of contracting it,” said Megan Meuti, senior author of the study and an assistant professor of entomology at The Ohio State University. 

This study and earlier findings by Meuti and her colleagues are among the first to show that artificial light at night could significantly impact mosquito behavior – including effects that aren’t necessarily predictable. 

“We’re finding that the same urban light at night can have very different effects under different seasonal contexts,” she said. 

Meuti conducted the study with first author Matthew Wolkoff and Lydia Fyie, both PhD candidates in entomology at Ohio State. The research was published recently in the journal Insects. 

Diapause for female Northern house mosquitoes (Culex pipiens) is not quite a winter slumber, but rather a period of dormancy when the insects live in caves, culverts, sheds and other semi-protected locations. Prior to winter’s arrival, mosquitoes convert sugary sources, such as plant nectar, into fat.

As days get longer, females begin foraging for blood meals to enable egg production. Some get infected with West Nile virus by feeding on infected birds, and later transmit the virus when they feed on people, horses and other mammals. 

This study builds upon two previous findings from Meuti’s lab: For her dissertation, Meuti found that circadian clock genes differ between diapausing and non-diapausing mosquitoes, strongly suggesting that day length dictates when diapause should start.

And more recent work led by Fyie found that female mosquitoes exposed to dim light at night averted diapause and became reproductively active – even when short days indicated they should be dormant. 

In the current study authored by Wolkoff, the researchers pursued both lines of inquiry, comparing daily activity and nutrient accumulation by mosquitoes reared in two lab conditions – long days mimicking the insects’ active season and short days that induced dormancy – with and without exposure to artificial light at night. 

The study provided more evidence associated with a circadian pattern to mosquito behavior, showing that insects’ activity decreases during diapause, but the circadian rhythmicity of that activity is sustained even during this dormant period. 

The introduction of artificial light at night was found to affect those activity patterns and to influence mosquitoes’ acquisition of nutrient reserves needed for fattening up and weathering winter temperatures. 

Exposure to light pollution suppressed the amount of water-soluble carbohydrates – sugars that are an essential food source during winter – that were accumulated by mosquitoes in both long- and short-day conditions.

Patterns of accumulation of the sugar glycogen were reversed by exposure to artificial light at night: Under normal conditions, non-dormant mosquitoes had lots of glycogen in their bodies but diapausing bugs did not – but in mosquitoes subjected to light pollution, the long-day mosquitoes didn’t accumulate much glycogen and short-day mosquitoes showed an increase in glycogen accumulation.

The researchers observed consistent trends in activity-related effects of light at night, with slight increased activity among the dormant mosquitoes and slightly suppressed activity among long-day mosquitoes expected to be busy looking for food.

Though the findings weren’t statistically significant, Wolkoff said the combined observations suggest light pollution causes mosquitoes to ward off diapause – perhaps by scrambling signals from their circadian clock.

“This could be bad for mammals in the short term because mosquitoes are potentially biting us later in the season, but it could also be bad for mosquitoes in the long term because they might be failing to fully engage in preparatory activities they need to survive the winter during diapause, and that might reduce their survival rate,” Wolkoff said. 

The researchers plan to carry out field studies to see if these lab findings hold true in the wild.

Source: Ohio State University

After nearly a century of scientific inquiry, scientists have finally characterized a key component in the substance called melanin responsible for giving countless living organisms their color. 

In the study, published online in the journal Nature Chemistry, an international team of researchers isolated a key molecule involved in the synthesis of melanin, a substance in the human body that produces pigmentation in the hair and skin and protects the cells from being damaged by ultraviolet radiation from the sun.

The molecule they studied has many physical properties of eumelanin, a type of melanin that typically produces only black and brown pigments. 

Despite what researchers know about melanin, its chemical structure has remained elusive, said Bern Kohler, an Ohio Eminent Scholar and professor of chemistry and biochemistry at The Ohio State University, one of three senior authors.  

“Melanin is as plain as the nose on our face and we still don’t know exactly what it’s made of and how it works,” said Kohler. “It’s thought to be a material made of large numbers of interacting components, and so what my collaborators and I are trying to get at is, what are melanin’s underlying chemical units and what are the interactions that give rise to its properties?”

In the lab, melanin can be made naturally from just a few simple chemical substances that combine or react to form the pigmented material. Thanks to the efforts of Jean-Philip Lumb of McGill University and Lluis Blancafort of the University of Girona, the team was able to successfully synthesize and analyze one of its molecule-sized ingredients. They found that it had many of the same properties as the final product melanin, even without further transformation.

“Melanin is like a complex dish that you cook from just a few ingredients,” said Kohler. “Given that melanin granules in skin contain billions of atoms, it was surprising to see melanin-like properties emerge in a molecule containing only a few dozen atoms.”

As a spectroscopist – or a scientist who investigates the interactions between matter and light – Kohler said what he finds most remarkable is the brilliant green color of the melanin-like molecule, which is able to absorb deep red light. 

“That’s very hard for a small molecule to do,” said Kohler. “This is one of the smallest organic molecules known that can absorb long wavelengths all the way out into the infrared.”

Its unusual optical and magnetic properties make the melanin-mimicking molecule an attractive prospect for advancing bioelectronics research, a field that aims to connect electronics and living biological materials to fabricate new technologies or therapies for medical treatments, said Kohler.

The study results also suggest that harnessing the power of melanin could be used to change the way humans harvest energy from our environment.

“Like solar energy conversion, part of our strategy for alternative energy is to absorb photons of light from across the solar spectrum,” Kohler said. “That’s what eumelanin does, rather naturally.”

Future research will aim to study melanin-like properties in similar kinds of molecules. Such strides could offer greater accessibility to synthetic biomaterial alternatives, but in the short term, Kohler imagines the team’s work uncovering a melanin-like molecule will inspire other labs to look more closely at how melanin’s properties may emerge from other unexpectedly small molecular units. 

“Our team is excited that further progress at understanding the structure of melanin can succeed by studying tailorable small molecules like the one we write about in this paper,” he said. “The chemistry is still tremendously complex, but interest should grow in small molecules as melanin models and the promise they hold for generating new, melanin-inspired materials.”

Source: Ohio State University

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In a message posted on the Telegram social network, the Ministry of Defense of Belarus presented a video saying that its military pilots of Su-25s have completed additional training under the supervision of instructors from the Russian Federation in order to be able to use armaments of a “special designation”.

The video does not say precisely what kind of weapons they had in mind, but defense experts unanimously agree that “special designation” explicitly means nuclear weapon.

This course of action was expected since the meeting of Belarusian and Russian presidents in August 2022. Then, Belarusian President Aleksander Lukashenko disclosed that Russia has upgraded a certain number of jets from his country’s military fleet to enable them to carry tactical nuclear weapons.

The only serious technical issue is that the Su-25 attack aircraft is just a subsonic vehicle with velocities that are sub-optimal for the use of nuclear weapons.

Theoretically, Su-25 could deliver free-falling bombs from their maximum flight altitude, but with a substantial risk that the aircraft together with the pilot would be destroyed during the attack.

Previously, both Russian and Belarusian media assumed that this attack capability was reserved for the Su-24 bomber plane which was specially designed for this kind of tasks. But after the latest announcement, it became obvious that these will be Su-25s, not Su-24s.

The Su-25 was developed in the former USSR and even then it was out of the question that this aircraft could become a nuclear-capable carrier.

Su-24. These planes are much faster than Su-25. Image credit: Armed Forces of Russia

The method for using nuclear munitions requires that the plane flies at a relatively low altitude at its maximum possible speed, drops the bomb, and withdraws in the opposite direction as fast as possible, to avoid being hit by a nuclear explosion.

For this purpose, the Soviet Union built Yak-28 bomber in the 1950s which had a maximum speed of 1830 km/h. Later it was replaced by Su-24 which could reach 1700 km/h, and even at low altitudes, it could fly at velocities up to 1400 km/h. Currently, the Russian Federation has Su-34 reaching 1400-1900 km/h depending on the flight altitude.

Meanwhile, the top speed of the Su-25 is does not exceed 1000 km/h.

PH-40 tactical nuclear bomb. It could fit on Su-25, but the plane still would not be able to lfy fast enough to escape its destruction.

From the structural perspective, Su-25 could take off the ground with a nuclear bomb onboard, such as 30-kiloton PH-40. But would it be able to escape safely after dropping it?

Defense Express notes that Su-25 which appeared in the Belarusian video was not covered in special light-colored “anti-atomic” coating which should protect the aircraft from light radiation during a nuclear explosion.

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The Russian T-90A main battle tank that was spotted in Louisiana sparked lots of heated debates and discussions about the reason why and also how this machine appeared in the United States.

The images circulating on social networks were taken quite freshly. But the tank itself was apparently captured by Ukraine last year, writes The Drive.

The fact of the tank’s capture by the Ukrainian Armed Forces was confirmed by the open source intelligence (OSINT) trackers. The trailer carrying this vehicle was photographed at a truck stop on the southernmost cross-country highway Interstate 10.

The T-90A is considered one of the most modern Russian combat machines among those used during their invasion of Ukraine. As with all tanks, it is also exceptionally heavy – according to the publication, the truck that was hauling this huge load experienced problems with its transmission.

Russian tank spotted in the USA, Louisiana. Namely the T-90A, which the Ukrainian military captured last year in the Kharkiv region. Now it looks like Russian tank was handed over to the Americans for research. https://t.co/YXbBOLYiyL pic.twitter.com/Nplhao1LEj

— Special Kherson Cat 🐈🇺🇦 (@bayraktar_1love) April 13, 2023

The tank itself does not contain its full equipment and add-on systems – for example, its machine guns and fire control systems have been removed. However, some explosive reactive armor containers have been left on the gun turret.

The exact reason why T-90A appears in the United States remains unknown. The experts, however, say that the U.S. Military may have brought this tank to the United States to thoroughly analyze its features in order to gain insights into its capabilities and potential vulnerabilities.

We could expect that later the results of this analysis could be handed over to Ukrainian defenders in order to improve their defensive capabilities against this machine and similar military equipment.

Oryx, an open source intelligence community, reports that the Ukrainian Army has captured at least 549 Russian tanks to this date, not counting those units that were destroyed in combat.

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