IT would seem paradoxical that during the apparent tranquillity of sleep the brain is actually bustling with activity. According to a study by the Washington University School of Medicine in St. Louis, which was published in a recent issue of Nature, during sleep, brain cells produce bursts of electrical pulses that cumulate into rhythmic waves. This is a sign of heightened brain cell function. These waves propel fluid through dense brain tissue, in the process washing it and helping flush waste out of the brain.
On the basis of model studies with sleeping mice, the researchers found that neurons drive cleaning efforts by firing electrical signals in a coordinated fashion to generate these rhythmic waves in the brain, explained Li-Feng Jiang-Xie, a neurobiologist and one of the authors of the study. The team silenced specific brain regions so that neurons in those regions did not create the waves. Without the waves, fresh cerebrospinal fluid could not flow through the silenced brain regions and trapped waste could not leave the brain tissue.
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“These neurons are miniature pumps,” said Jiang-Xie. “Synchronised neural activity powers fluid flow and removal of debris from the brain. If we can build on this process, there is the possibility of delaying or even preventing neurological diseases, including Alzheimer’s and Parkinson’s..., in which excess waste—such as metabolic waste and junk proteins—accumulates in the brain and lead to neurodegeneration.”
To perform energy-demanding tasks, brain cells require fuel. Their consumption of nutrients from food creates metabolic waste. “It is critical that the brain disposes of metabolic waste that can build up and contribute to neurodegenerative diseases,” said Jonathan Kipnis, the senior author of the study. “We knew that sleep is a time when the brain initiates a cleaning process to flush out waste and toxins it accumulates during wakefulness. But we didn’t know how that happens.” Cleaning the dense brain is no simple task. The cerebrospinal fluid enters and weaves through intricate cellular webs in the brain, collecting toxic waste as it travels. Upon exiting the brain, contaminated fluid must pass through a barrier before spilling into the lymphatic vessels in the dura mater—the outer tissue layer enveloping the brain underneath the skull. “We think the brain-cleaning process is similar to washing dishes,” Jiang-Xie said.
Cash-strapped NASA may shut down Chandra
The Chandra X-ray Observatory has been the world’s most powerful X-ray telescope for the past 25 years. It is able to detect sources more than 20 times fainter than any previous X-ray telescope and has a resolution eight times greater. | Photo Credit: NASA/Chandra X-ray Center & J. Vaughan
FOLLOWING significant cuts in its budget for FY2025, NASA has told the US astronomical community that it will gradually shut down the Chandra X-ray Observatory (CXO). Shocked by the news, astronomers have launched a “Save Chandra” campaign.
According to Science, President Joe Biden’s budget request announced on March 11 includes $1.58 billion for NASA’s astrophysics division, which is 3 per cent over the FY2024 appropriations but $2 billion less than what it had asked for. NASA has scaled its budget for Chandra down to $41.1 million for FY2025 against the $68.3 million appropriated in FY2023. NASA plans to reduce it to $26.6 million in FY2026, the journal said. By 2029, it will be down to only $5 million. Astronomers said that despite some ageing issues that have been largely dealt with, the CXO is still as productive as ever and has a functional life for at least a decade.
Named after the Nobel laureate astrophysicist Subrahmanyan Chandrasekhar and launched in 1999, Chandra was originally planned as a five-year mission. Along with the Hubble Space Telescope (1990−), the Compton Gamma Ray Observatory (1991–2000), and the Spitzer Space Telescope (2003–20), the CXO forms part of NASA’s “Great Observatories”. “I’m horrified by the prospect of Chandra being shut down prematurely,” Andrew Fabian, an X-ray astronomer of the University of Cambridge who has been involved with the observatory from before its launch, told Science. “If you start doing deep cuts so abruptly you will lose a whole generation [of X-ray astronomers],” Science quoted Elisa Costantini of the Netherlands Institute for Space Research, who has worked with Chandra data since its launch. It will leave “a hole in our know- ledge” of high-energy astrophysics, she said.
Chandra was the first to detect X-rays from Sagittarius A*, the supermassive black hole at the centre of the Milky Way, and spot shock waves from the nearby supernova 1987A. It discovered that gamma-ray bursts come from star-forming regions in distant galaxies. In 2020, the CXO was the first to find evidence of an exoplanet in another galaxy. In 2006, it found strong evidence that dark matter exists (“Direct proof of dark matter?”, Frontline, October 6, 2006).
A new radiation source for beyond 6G technologies
The electromagnetic spectrum showing the THz region. | Photo Credit: iScience/ScienceDirect.com (2021)
RESEARCHERS at IIT Delhi, in collaboration with a scientist from the National University of Singapore (NUS), have developed a device capable of producing high-intensity radiation at terahertz (THz) frequencies (1012 Hz), which are beyond the capabilities of current 6G communication technologies. While the IITD team of Rahul Mishra, Samaresh Das, and Pinki Yadav at the IITD’s Centre for Applied Research in Electronics spearheaded the design and fabrication of the device, Yang Hyunsoo at the NUS conducted critical measurements.
Called a spintronic terahertz emitter, the device operates through a bilayer system composed of ferromagnetic and non- magnetic materials. The IITD team developed a semimetal material using platinum, which it then paired with a layer of cobalt. This combination enables the device to generate high-intensity pulses in the THz range.
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“Existing sources for this frequency range face limitations such as narrow bandwidths, low emission strength, and the need for low-temperature operations,” said Mishra describing the motivation behind this development. “Our goal was to create an emitter that not only provides enhanced emission strength but also functions efficiently at room temperature, making it suitable for practical, real-time application.”
“Terahertz technology, with its high-frequency radiation emission capabilities, holds the potential to revolutionise various aspects of our daily lives. Its non-invasive nature is particularly advantageous for medical imaging, enabling doctors to visualise the interior of the human body safely, without the risks associated with conventional X-rays,” said Das.
“THz waves can facilitate faster and more secure wireless networks, significantly enhancing the speed and reliability of our Internet connections,” said Yadav.
The work was published in a recent issue of Nano Letters, a journal of the American Chemical Society.
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