Locked out of language

by Hansraj Agrawal | Apr 6, 2025 | Science

Going under general anaesthesia is always unnerving. There is this lurking apprehension that you may not emerge out of it.

But anaesthesia could produce some unexpected consequences — something that has caught the fancy of creative writers. For example, in Laughing Gas, PG Wodehouse makes two of his characters — the famous Bertram Wooster and the American child actor Joey Cooley — swap bodies when anaesthetised with nitrous oxide, or ‘laughing gas’, during a dental procedure. Each of their souls gets into the other’s body. What fun!

That is fiction but occasionally reality comes pretty close — as with a 17-year-old Dutch soccer player, who was administered anaesthesia for a knee surgery. The boy woke up alright but no longer remembered his native tongue and only spoke English, a language he had a thin command of. The nurse assumed it was a case of the more common ‘emergence delirium’ but only later did doctors diagnose it as the extremely rare ‘foreign language syndrome’ (FLS). The case has been reported in detail in a 2022 paper titled ‘Lost in another language’.

FLS is extremely rare — only nine reported cases. Another paper, ‘Speaking in tongues’, mentions a 54-year-old Englishman who switched to fluent Spanish after the anaesthesia wore off, and could no longer understand a word of English.

A happy coda to all these cases is that the patients slipped back to their native tongues after a few days — just as Wooster and Cooley went back to themselves. Scientists are saying that the study of FLS could throw light on how languages are stored in the brain.

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Recycling plastic through co-pyrolysis with biomass

by Hansraj Agrawal | Apr 6, 2025 | Science

BURNING ISSUE: Pyrolysis can convert plastic into hydrocarbons such as diesel, naphtha and kerosene
| Photo Credit:
Debu Durlav

Come August, negotiators will congregate in Geneva for yet another round of talks on hammering out a Global Plastics Treaty, under the aegis of the United Nations Environment Programme. They will pick up the thread from the failed negotiations at Busan in December 2024.

An agreement on tackling the plastics problem is delayed by differences over the approach to be taken — limiting the production and use of plastics or recycling it. (India is not in favour of legally binding limits or caps on the production of plastic polymers.)

The plastics problem is fast getting out of hand because it is hard to rein in an industry that is approaching a trillion dollars in size and produces about half a billion tonnes a year, even as the products have become so integral to daily life that they appear to be near irreplaceable. Yet, these polymers are also a growing problem because they pop up almost everywhere, including places where they pose a grave threat — such as human blood and semen, oceans and foods.

Solutions to convert plastic into more benign forms do exist — mostly in technical literature — offering ways to break these long-chain polymers into simpler stuff, such as diesel-like fuel and gas.

The problem, however, lies in the implementation. Only 9 per cent of all plastic waste is being recycled, compared with 12 per cent incinerated and 79 per cent ending up in landfills. The reason is the shortage of recycling infrastructure — the machines can turn only clean, homogenous plastic waste into oils or gas economically but waste collections are typically a mixed bag. In fact, each reactor is designed for a specific type of plastic.

If you can get homogenous plastic waste, you are in business. You can dust off the old pyrolysis technology and put it to use. Pyrolysis is simple enough. It typically involves two-step heating — first up to 230 degrees C to melt the plastic into a liquid and then heating the liquid some more to produce a suite of products, such as diesel, naphtha and kerosene.

Balancing factor

Since it is difficult to get consistent plastic as raw material, members of the scientific community are mooting co-pyrolysis of the two major anthropogenic wastes — plastics and biomass.

This is because biomass helps buffer the process. Biomass typically contains oxygenated compounds. When co-pyrolysed with plastic, which are typically hydrogen-rich, it can help balance the reaction (synergistic effect). The plastic needn’t necessarily be homogenous.

“Combining waste plastic and biomass in the pyrolysis process can improve the quality and yield of the resulting bio-oil, making it a more viable substitute for fossil fuels,” says Saumitra Saxena of the Clean Energy Research Platform, at the King Abdullah University of Science and Technology in Thuwal, Saudi Arabia. In his paper titled ‘Pyrolysis and beyond: Sustainable valorization of plastic waste’, Saxena notes that “plastics typically have higher hydrogen content, which can enhance the deoxygenation of biomass-derived compounds, leading to a higher-quality oil with better fuel properties”.

Describing co-pyrolysis of waste plastic and biomass as “an emerging area in waste management”, he notes that the process “can significantly reduce the environmental footprint compared to separate pyrolysis of plastics and biomass”. Biomass can help crack long-chain hydrocarbons in plastics, reducing the formation of undesirable byproducts, such as char and tar.

In another paper, scientists of the King Fahd University of Petroleum & Minerals, Saudi Arabia, note that co-pyrolysis of waste plastic and biomass “greatly enhances the properties of fuel” due to the synergetic effect.

“It is well known that plastic waste has a low oxygen-to-carbon and high hydrogen-to-carbon ratio whereas biomass has a high O-C and low H-C ratio. The co-pyrolysis process supports solid biomass inherently and increases the product quality and uniformity while minimising coke deposition caused by pure plastic waste pyrolysis,” says the paper authored by Ahmad Nawaz and Shaikh Abdur Razzak.

Despite the advantages, commercial implementation of co-pyrolysis technology is still nascent, observes Saxena, adding that largescale adoption requires further research and development to overcome technical and economic barriers.

“Key focus areas include improving reactor designs, enhancing process efficiency and developing robust supply chains for feedstock collection and preprocessing,” the paper says.

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Visible connectivity: Let there be Li-Fi!

by Hansraj Agrawal | Apr 6, 2025 | Science

The Wi-Fi we use today is based on radio waves, which is a long wavelength, low-frequency electromagnetic radiation. Instead of radio waves, can we use light, which is also electromagnetic radiation but of higher frequency? After all, higher frequency implies higher data rates, so “Li-Fi” should be better than Wi-Fi, right?

Yes, say scientists. Research is on to bring in light-fidelity or Li-Fi to replace Wi-Fi. IIT-Delhi’s Prof Abhishek Dixit is working on ‘visible light communication’ (VLC). He says that the modest LED (light emitting diode) lamp found in most houses today can be used to transfer data via light by electrically switching it on and off to arrive at combinations of 1s and 0s (1 is presence and 0, absence of light).

One of the challenges in using the visible range is the directional nature of light. Unlike in the case of radio frequency signals, which spread out, in the case of light the user should have an ‘optimum field of view in the coverage area of the light source’ to receive the signal. To address this shortcoming, Prof Dixit’s team has designed optics that spread the light in an optimal way, aiming for uniform distribution and minimal interference between multiple LEDs within a room. The team has applied for a patent for this design.

To overcome the challenge of limited bandwidth in visible light LEDs, compared with infrared diodes, Dixit has developed ‘equalisation’ circuits to significantly increase the bandwidth of LEDs (say, from 3 to 80 MHz).

What is equalisation? Much like the wind interferes with how far your voice can travel in the open, in telecom the communication channel can distort signals. Equalisation helps undo the distortion.

The team is also exploring higher-order modulation to achieve bigger data rates over limited bandwidth. It is also working to develop a Li-Fi network, whereby users can maintain Internet connectivity even while moving within a room.

Li-Fi vs Wi-Fi

VLC currently offers data rates of 200-400 Mbps per access point. Infrared LED-based solutions can go up to 1-2 Gbps.

The visible light LED-based solutions can also go up to a range of 1 Gbps but “our current set-ups are targeting 200 Mbps”, says Prof Dixit. However, it must be noted that achieving high data rates via visible light LED is more difficult compared with IR LED-based solutions.

While a single Wi-Fi access point may offer high bandwidth (say 1 Gbps), this is shared among all connected devices, potentially reducing speeds for individual users.

So, if a single room has 10-20 Li-Fi access points and a single Wi-Fi access point, the available bandwidth per room for Li-Fi is 10-20 Gbps or higher, while for Wi-Fi it would be 1 Gbps.

A changeover from Wi-Fi to Li-Fi would necessitate rewiring existing LED lamps in the house or a user-cluster in a setting such as a hotel to connect to the Internet. You would also need a receiver, likely a dongle with a photodiode, to convert light signals back into electrical signals for devices like mobile phones or laptops.

The existing LED lamps in a home could be used for both illumination and communication, and hence Li-Fi is an energy-efficient solution.

Prof Abhijit Mitra of IIIT-Delhi says LEDs work as transmitters while photodetectors (sensors that detect and convert light into electrical signals) can function as ‘receivers’.

Mitra and his team are working on switching speeds of LEDs. Despite the large bandwidth available, the bottleneck would be the speeds at which LEDs can be turned on and off. For digital communication, fast switching is crucial to transmit data at high rates. Each on-off cycle can represent a bit of information.

He says conventional LEDs can achieve switching speeds of a few megabits per second, but that is not enough for high-bandwidth applications like downloading a 10-GB movie or real-time high-definition video streaming (requiring around 100 Mbps).

To increase the data rate, advanced modulation techniques help. “Instead of just switching the LED fully on or off to represent one bit per cycle, these techniques involve sending one ‘symbol’ per second, where each symbol can encode multiple bits of information,” he says. Pulse amplitude modulation (PAM) is one such technique, where multiple levels of voltage (and thus light intensity) are used to represent different combinations of bits.

There are some obvious advantages with Li-Fi. Light cannot penetrate walls and is hence secure from ‘eavesdropping; Wi-Fi and cellular use radio frequency, which can pass through walls.

Additionally, light spectrum is free to use currently, making it cheaper.

Mitra’s research interest includes the use of solar panels as communication receivers.

With rooftop solar finding more takers today, it could help accelerate the rollout of Li-Fi technology. “Solar panels are sensitive to light, which can be used to detect the rapid switching of a light signal carrying information.”

Apart from doing away with the need for a separate photodetector, solar panels lend themselves to long-distance communication as well. For receiving information (downlink): Information could be relayed from a base station (possibly via free space optics, or FSO links — a point-to-point light-based communication) to a rooftop solar panel equipped with a ‘bandwidth enhancement circuit’ (a small piece of hardware that can detect changes in light intensity). The data received by the solar panel would then be routed through in-home networks (like Ethernet and Wi-Fi) to the user’s device.

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How senior Indians can build resilience against frailty

by Hansraj Agrawal | Apr 6, 2025 | Science

WELLNESS BUFFERS: Aerobic exercise and social engagement
| Photo Credit:
triloks

A viral infection. A fall. A minor surgery. Most people can recover from these in a few days. For senior citizens, however, each of these could be a major setback to health and lifestyle.

In 2011, the country had 104 million seniors, or 10 per cent of the population. By 2050, that number will jump to 340 million, or 20 per cent of the population. This would mean that many more elderly Indians will face heightened health vulnerabilities in the coming decades.

A recent paper from doctors at Vardhman Mahavir Medical College (VMMC) and Safdarjung Hospital in New Delhi analyses the prevalence of frailty among India’s older adults using data from sources that include national surveys, research articles and primary data collection. It reports that 36 per cent of Indian seniors are frail, and 48 per cent are in the pre-frailty stage. This suggests many seniors may be on the cusp of a decline in health and independence.

Frailty is not simply about getting older. In some ways, the body’s “reserve tank” is running low — even small health challenges can cause major problems when there is less reserve strength to fight back.

Measuring frailty

Signs of frailty include loss of muscle mass, walking more slowly, feeling exhausted easily and becoming less active. This happens when multiple body systems gradually decline over time, leaving a person more vulnerable to health setbacks.

The paper mentions that several methods can be used to measure frailty. The Fried Phenotype, for instance, looks for physical signs like unintended weight loss, slow walking and exhaustion. Studies using this approach found 31 per cent of Indian seniors are frail.

Alternatively, researchers and doctors use the Frailty Index, which looks at 40-70 variables such as activity level and mobility, vision, hearing and ability to complete daily activities and cognitive tasks. The finding here is that nearly 50 per cent of Indian senior citizens are frail.

The paper notes that several factors increase frailty risk. Women show higher rates (45 per cent) compared with men (34 per cent). Poor nutrition, low physical activity and low BMI are the other major contributors. Medical conditions like diabetes, hearing problems, cognitive decline and depression are contributing factors. Living alone correlates with higher frailty rates.

The study found that regions with poorer healthcare infrastructure show higher frailty prevalence, suggesting system-level factors play an important role.

For individuals in their 50s and 60s, regular physical activity, combining strength training and aerobic exercise, is essential. Maintaining proper nutrition, particularly adequate protein intake, builds resilience against frailty. Social engagement appears protective as well.

Response to frailty

For policymakers, addressing frailty requires both individual and systemic approaches. Early screening can identify those at risk, focusing on the 48 per cent who are pre-frail and can still recover. Healthcare worker training in frailty management and community-based prevention programmes are needed, especially in States with higher prevalence.

Research priorities include developing India-specific assessment tools and conducting longitudinal studies. Understanding frailty’s economic impact could help guide resource allocation as India’s population ages.

With proper intervention, many seniors can avoid the transition from pre-frailty to frailty, maintaining independence and quality of life for more years.

(S Yasaswini is a writer based in Guwahati)

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ISRO successfully completes 1000-hr life test of Stationary Plasma Thruster for satellites

by Hansraj Agrawal | Mar 29, 2025 | Science

ISRO has announced the successful completion of a 1,000-hour life test on its 300mN (millinewton) Stationary Plasma Thruster that is developed for induction in the Electric Propulsion System of satellites.

The Electric Propulsion System is proposed to replace the chemical propulsion system in future satellites of the space agency and pave the way for communication satellites which use only electric propulsion systems for orbit raising and station keeping.

The induction of these thrusters will result in extensive mass savings thereby enabling the enhancement of transponder capacity in communication satellites, it said.

Noting that these thrusters use Xenon as the propellant, the ISRO said the Specific Impulse of the Electric Propulsion System, which is a major performance indicator of a space propulsion system, is at least 6 times that of the conventional propulsion system.

“The life test was carried out under the full power level of 5.4kW in a chamber that simulates the vacuum conditions of space and the erosion of the electrode liners was periodically monitored,” it added.

Highlighting that the erosion data collected during the life test is essential for predicting the future erosion and determining the lifespan of the thruster, ISRO said this information will be an important role in satellite orbit management.

“This test is a major milestone to demonstrate the reliability and robustness of the thrusters before induction into the satellites. The Electric propulsion System is proposed to be inducted and validated in the upcoming Technology Demonstration Satellite (TDS-01) of ISRO and will be used for orbit raising to the Geostationary orbit,” it added.

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New single photon emitter

by Hansraj Agrawal | Mar 23, 2025 | Science

Researchers at Indian Institute of Science, Bengaluru, along with collaborators at the Centre for Nano Science and Engineering (IISc), the National Centre for Scientific Research (France) and the National Institute for Materials Science (Japan), have developed a new approach to generating single photon emitters (SPEs) in a single layer of 2D semiconducting molybdenum disulphide. Led by PhD student Ajit Kumar Dash and assistant professor Akshay Singh, the team used ultra low-energy electron beam irradiation to create stable SPEs with high spatial resolution. This can enable novel fundamental physics concerning defect- defect coupling and electron-matter interactions, says a write-up on the IISc website.

Berkelium-carbon bond

A research team, led by the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab), has discovered ‘berkelocene’, the first organometallic molecule to be characterised as containing the heavy element berkelium.

Organometallic molecules, which consist of a metal ion surrounded by a carbon-based framework, are relatively common for early actinide elements like uranium (atomic number 92) but are scarcely known for later actinides like berkelium (atomic number 97).

“This is the first time that evidence for the formation of a chemical bond between berkelium and carbon has been obtained. The discovery provides new understanding of how berkelium and other actinides behave relative to their peers in the periodic table,” said Stefan Minasian, a scientist in Berkeley Lab’s Chemical Sciences Division and one of the four co-corresponding authors of a new study published in the journal Science.

Synthesised synaptic link

Scientists have developed a new hybrid material that mimics the work of biological synapses — the junction between two nerve cells (neurons), where signals are transmitted — paving the way for more efficient and adaptive AI systems. Inspired by the human brain’s energy-efficient computing, they created memristor devices — electronic components that regulate current flow and replicate neural communication.

A research team from the SN Bose National Centre for Basic Sciences and the National Institute of Technical Teachers’ Training and Research developed a material called AgCN, which combines mesoporous graphitic carbon nitride with silver nanoparticles. This structure enables gradual resistance changes, essential for neuromorphic computing — AI that learns and adapts like the human brain. Their study, published in Advanced Functional Materials, demonstrated AgCN’s ability to replicate Morse code and even mimic associative learning, like Pavlov’s dog experiment.

By strengthening or weakening metallic pathways under an electric field, these devices efficiently process and transmit information, making them ideal for next-gen AI applications, such as image recognition and real-time decision-making. This breakthrough could lead to smarter, faster and more energy-efficient computing.

“The utilisation of biomimicry principles in neuromorphic computing devices has yielded unparalleled capabilities. Contrary to conventional computing systems that employ rigid algorithms, neuromorphic systems emulate the brain’s capacity for learning and adaptation. AgCN-based memristors exhibit remarkable versatility and adaptability in this domain,” says a press note.

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