17-Jun-2021: Space-time induces neutrino oscillations
Scientists have shown that the geometry of space-time can cause neutrinos to oscillate. Neutrinos are mysterious particles, produced copiously in nuclear reactions in the Sun, stars, and elsewhere. They also "oscillate"-- meaning that different types of neutrinos change into one another – as has been found in many experiments. Probing of oscillations of neutrinos and their relations with mass are crucial in studying the origin of the universe.
Neutrinos interact very weakly with everything else – trillions of them pass through every human being every second without anyone noticing; a neutrino’s spin always points in the opposite direction of its motion, and until a few years ago, neutrinos were believed to be massless. It is now generally believed that the phenomenon of neutrino oscillations require neutrinos to have tiny masses.
Professor Amitabha Lahiri of S N Bose National Centre for Basic Sciences (SNBNCBS) an autonomous institute under the Department of Science & Technology (DST), Government of India showed in a paper published along with Subhasish Chakrabarty, his student, that the geometry of space-time can cause neutrino oscillations through quantum effects even if neutrinos are massless. It was published in the journal ‘European Physical Journal C’.
Einstein’s theory of general relativity says that gravitation is the manifestation of space-time curvature. According to the SNBNCBS team, neutrinos, electrons, protons and other particles which are in the category of fermions show a certain peculiarity when they move in presence of gravity. Space-time induces a quantum force in addition to gravity between every two fermions. This force can depend on the spin of the particles, and causes massless neutrinos to appear massive when they pass through matter, like the Sun’s corona or the Earth’s atmosphere. Something similar happens for electroweak interactions, and together with the geometrically induced mass it is enough to cause oscillation of neutrinos.
15-Jun-2021: Researchers find an improved method of imaging objects through fog
Imaging of objects in foggy weather conditions may now be clearer. Researchers have found a method that can improve the images captured on such days. The technique involves modulating the light source and demodulating them at the observer’s end.
Scientists have long attempted to use the physics of scattering and computer algorithms to process the resulting data and improve the quality of images. Whereas the improvements are not stark in some cases, computer algorithms require processing large volumes of data, involving ample storage and significant processing time.
Research by a team has offered a solution for improving the image quality without heavy computations. The team from the Raman Research Institute (RRI), Bengaluru, an autonomous institute of the Department of Science and Technology; Space Applications Centre, Indian Space Research Organisation, Ahmedabad; Shiv Nadar University, Gautam Buddha Nagar; and Université Rennes and Université Paris-Saclay, CNRS, France, modulated the light source and demodulated them at the observer’s end to achieve sharper images. The research was published in the journal ‘OSA Continuum’.
The researchers have demonstrated the technique by conducting extensive experiments on foggy winter mornings at Shiv Nadar University, Gautam Buddha Nagar, Uttar Pradesh. They chose ten red LED lights as the source of light. Then, they modulated this source of light by varying the current flowing through the LEDs at a rate of about 15 cycles per second.
The researchers kept a camera at a distance of 150 metres from the LEDs. The camera captured the image and transmitted it to a desktop computer. Then, computer algorithms used the knowledge of the modulation frequency to extract the characteristics of the source. This process is called ‘demodulation’. The demodulation of the image had to be done at a rate that was equal to the rate of modulation of the source of light to get a clear image.
The team saw a marked improvement in the image quality using the modulation-demodulation technique. The time the computer takes to execute the process depends on the image’s size. “For a 2160 × 2160 image, the computational time is about 20 milliseconds,” shares Bapan Debnath, PhD scholar at RRI and a co-author of the study. That is roughly the size of the image containing the LEDs. His colleagues had estimated the rate in 2016.
The team repeated the experiment a few times and observed the improvement each time. Once, when the fog varied in intensity during the observation, they did not record a marked improvement in the image quality. In this case, there was a strong wind, and they observed fog trails across the scene. The density of the water droplets in the air changed as time passed, which rendered the modulation-demodulation technique less effective.
Next, the researchers changed the experimental setup. They made an external material, a piece of cardboard kept at a distance of 20 centimetres from the LEDs, to reflect the light to the camera. The distance between the cardboard and the camera was 75 metres. The modulated light reflected from the cardboard travelled through the fog and was then captured by the camera. They demonstrated how their technique still significantly improved the quality of the resulting image.
Repeating the experiment under sunny conditions, they found that after performing the demodulation of the source, the image quality was high enough to distinguish the LEDs from the strongly reflected sunlight.
The study was partially funded by the Department of Science and Technology, Ministry of Science and Technology, Government of India.
The cost of the technique is low, requiring only a few LEDs and an ordinary desktop computer, which can execute the technique within a second. The method can improve the landing techniques of aeroplanes by providing the pilot with a good view of beacons on the runway, significantly better than relying only on reflected radio waves as is presently the case. The technique can help reveal obstacles in the path that would otherwise be hidden by fog in rail, sea, and road transportation and would also help spotting lighthouse beacons. More research can demonstrate the effectiveness in such real-life conditions. The team is investigating whether the technique can apply to moving sources.
17-May-2021: Scientists develop magnetometer for low cost, reliable & real-time measurements of magnetic fields
Researchers have demonstrated a low-cost digital system to efficiently measure unknown magnetic fields.
Digital signals are the backbone of communication systems processed by hardware systems that transmit and receive the signals with the help of intermediate systems called ‘digital receiver systems’ or DRS. When magnetic matter creates signals, analysing them with DRS lets scientists study the magnetic fields. Analysing the properties of the signals, for example, how they vary with time, scientists can measure the fields and study their small fluctuations.
In a new study, scientists from Raman Research Institute (RRI), Bengaluru, an autonomous institute of the Department of Science & Technology, Government of India, have devised a more efficient, faster, and low-cost digital receiver system that can make precise measurements of magnetic fields. The study was supported by the Department of Science and Technology and the Ministry of Electronics and Information Technology (MeitY) Government of India. It was published in the journal IEEE Transactions on Instrumentation and Measurement. The system costs less than 350$ for all the silicon-based hardware and associated software.
The hardware of digital receiver systems are built with standard silicon-based memory devices. Computer codes are implemented that make these devices perform mathematical operations on the signal they receive, enabling DRS systems to measure fundamental properties of matter like ‘Spin’. The spin of electrons determines the magnetism of most of the objects around us.
“The electrons’ spin is not constant at room temperatures. They fluctuate,” explains Saptarishi Chaudhuri, associate professor of RRI and a co-author of the study. These spin fluctuations cause what scientists call ‘spin-noise’. By measuring the tiny fluctuations in the magnetic field, the researchers can infer the spin-noise accurately.
The work is an extension of the Ph.D. thesis work of the co-authors Maheswar Swar and Subhajit Bhar of RRI. The researchers heated rubidium atoms to temperatures ranging between 100 and 200 degrees Celsius, causing spin fluctuations. Then, they bombarded the atoms with a laser, which has a property called ‘polarization’. The spin fluctuations caused the laser’s polarization to fluctuate, which the researchers measured using a light detector. The polarization fluctuation is the signal for the digital receiver system. They then designed the system to work in two different modes.
One of them uses a widely-used mathematical function, the ‘Fourier transform’ of the signal, named after its inventor Joseph Fourier. The Fourier transform of the signal lets them calculate how the rubidium atom’s energies vary, from which they can directly infer the magnetic field. A standard method of measuring the magnetic field analyses small frequency ranges of the signal separately. The researchers showed that their method speeds up the calculations compared to the standard method. Their improved method also increased their confidence in how the electrons’ energies vary more than ten times.
Sometimes, while measuring magnetic fields, the DRS may receive signals only for a short time. In such scenarios, it is essential to record the signal as it gets created without losing any part of it. The researchers successfully implemented this ability with the help of a combination of standard hardware and computer codes. They measured a magnetic field of 800 microgauss –– roughly a thousand times smaller than the Earth’s magnetic field, within a tenth of a second.
There was, however, a problem –– electromagnetic interference to the signal the DRS receives. “The source is the power supply to the digital receiver, and radio-frequency signals emanating from other nearby electronic devices, such as the computers, phones, lasers, and other laboratory instruments,” explains V. Mugundhan, another co-author of the study. They got rid of these sources by using a battery bank to power the DRS’s hardware components and shielded them entirely from interference using a 5-millimeter thick layer of mild steel. “We have also developed high-end data processing algorithms to remove the residual interference,” he adds.
The researchers applied an external magnetic field across the heated rubidium atoms. They demonstrated that their measurement of the magnetic field was consistent with what they expected. Thus, they demonstrated that their two-component digital receiver system works as an atomic magnetometer. “Our magnetometer can be deployed to measure unknown magnetic fields,” says Saptarishi.
Having demonstrated the functioning of a digital receiver system to precisely measure atomic magnetic fields, the researchers are open to large-scale manufacturing or commercialisation of the device. Such a step would require partners in the industry to show interest in the project. “There are no bottlenecks in manufacturing our device on large scales,” Saptarishi pointed out.