Saturday, August 15, 2020

Captain Lakshmi Sahgal: A beacon of inspiration

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Charvi Trivedi

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Captain Lakshmi Sahgal: A beacon of inspiration

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Global Views 360

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August 15, 2020

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Captain Lakshmi Sahgal in INA Uniform

Captain Lakshmi Sahgal in INA Uniform | Source: Indiatimes

Indian freedom movement has given countless heroes who gave the prime of their lives to see India chart her own destiny by throwing out the Britishers. While there were leaders and fighters like Mahatma Gandhi or Netaji Subhash Chandra Bose, whom everyone knows, there were many other bravehearts who gave up their lives and used every ounce of their strength to free India from the clutches of British Rule. Doctor Lakshmi Sahgal was one of them.

Early Life

Lakshmi Swaminathan was born in Madras (now Chennai), which was under the Madras Presidency, British India, on October 24, 1914. Born to influential parents, Lakshmi was enthused with her mother’s contribution in the field of social work and inherited her father’s intelligence, who was a lawyer, and went on to become a doctor.

She received her MBBS degree from Madras Medical college in the year 1938 and a diploma in Obstetrics and Gynaecology, the following year and was a working doctor in the Kasturba Gandhi Hospital, Chennai. Moreover, she established a clinic in Singapore, a year after getting her diploma, for the under-privileged and Indian migrant labourers.

In Singapore she joined hands with the Indian Independence League, a political body headquartered in Singapore, which prepared Indians living outside of India, to seek independence from the harsh British rule.

Indian National Army days

When the Japanese forces lost the 1942 Battle of Singapore to the British Army, DR. Sahgal played a prominent role in tending to the injured war prisoners. Several of these prisoners had not lost hope yet and wanted to begin an Indian Liberation Army. Their wish was granted when Netaji Subhash Chandra Bose visited Singapore in July, 1943. After listening to Bose’s speeches on wanting to establish an army composed of women to fight against the British forces, Lakshmi quickly set up a meeting with Bose and expressed her desire to be a part of the women regiment. She soon launched the Rani of Jhansi regiment, which was a wonderful opportunity for numerous women to do something for their nation.

Lakshmi Swaminathan turned into Captain Lakshmi, which marked the beginning of her inspiring journey in the freedom struggle. Nearly 50,000 women trained and fought under her command. She also carried the title of Colonel in the women’s army unit, the first one ever to be carried by a female in the entire continent of Asia during that time. Her regiment battled against the British forces along with the Axis Powers.

Unfortunately, she was arrested in 1945 in Burma (now Myanmar) and remained there for a year until she was sent back to India.

Later years

Lakshmi married Colonel Prem Kumar Sahgal in March, 1947 in Lahore, British India. Lakshmi Sahgal moved to Kanpur with her husband and carried on with her medical practice, attending to the needs of evacuees after the Partition of India.

After Independence, Lakshmi entered into the world of policy making and represented her party, The Communist Party of India (Marxist), in Rajya Sabha. During the Bangladesh crisis, she was the one who called for medical aid for thousands of refugees from Bangladesh who came into Calcutta. Moreover, she led a medical team to tend to the victims of the catastrophic Bhopal Gas Tragedy and worked towards refurbishing peace during the anti-Sikh riots, both which took place in the year 1984.

In 2002, she was the only opponent of A.P.J Abdul Kalam when she got elected as a candidate in the Presidential elections, of four leftist parties namely the Revolutionary Socialist Party, All India Forward Bloc, the Communist Party of India and the Communist Party of India (Marxist).

DR. Lakshmi Sahgal was awarded the Padma Vibhushan, the second-highest civilian award, in 1998 for her great achievements, by R.K. Narayan. An airport in Dehat district of Kanpur, Captain Lakshmi Sahgal International Airport, is named in her honour.

She passed away on July, 23, 2012 after suffering from a cardiac arrest, at a good age of 97. Her noble deeds did not stop even after her death as she donated her body to Kanpur Medical College for medical research.

She was a true leader who broke the glass ceiling and barged into the male dominated world of revolutionary army which played a great role in throwing out the Britishers from India. After India’s independence she excelled in another male dominated domain, politics. Hers is an inspiring story that women can be equally brave and fierce as men and can achieve anything by showing perseverance.

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April 13, 2021 2:10 PM

Detecting The Ultra-High Energy Cosmic Rays With Smartphones

Smartphones have become the most commonplace objects in our daily lives. The unimaginable power that we hold in our hands is unrealized by most of us and, more importantly, untapped. Its creativity often gets misused but one can only hope that it’s fascinating abilities would be utilized. For example, did you know that the millions of phones around the globe can be connected to form a particle detector? The following article covers the CRAYFIS (Cosmic RAYs Found in Smartphones) phone-based application developed by the physicists from the University of California—Daniel Whiteson, Michael Mulhearn, and their team. CRAYFIS aims to take advantage of the large network of smartphones around the world and detect the cosmic or gamma rays bursts which enter the Earth’s atmosphere almost constantly.

What Are Cosmic Rays?

Cosmic rays are high velocity subatomic particles bombarding the Earth’s upper atmosphere continuously. Cosmic ray bursts have the highest energy compared to all forms of electro-magnetic radiation. When we say ultra-high energy particles (energy more than 1018^eV), we mean two million times more energetic than the ones that can be produced by the particle colliders on Earth.  These rays are thought to be more powerful than typical supernovae and can release trillions of times more energy than the Sun. They are also highly unpredictable as they can enter Earth’s atmosphere from any direction and the bursts can last for any period of time ranging from a few thousand seconds to several minutes.

Despite many theoretical hypotheses, the sources of these ultra-high energy cosmic rays are still a mystery to us even after many decades of their discovery. These rays were initially discovered in the 1960’s by the U.S. military when they were doing background checks for gamma rays after nuclear weapon testing. Cosmologists suggest that these bursts could be the result of super massive stars collapsing - leading to hypernova; or can be retraced to collisions of black holes with other black holes or neutron stars.

How Do We Detect Them?

When the high-energy particles collide with the Earth’s atmosphere, the air and the gas molecules cause them to break apart and create massive showers of relatively low-energy particles. Aurora borealis i.e., the Northern and the Southern lights are the lights that are emitted when these cosmic rays interact with the Earth’s magnetic field. Currently, these particles are hitting the Earth at a rate of about one per square meter per second. The showers get scattered to a radius of one or two kilometers consisting mostly of high-energy photons, electrons, positrons and muons. But the fact that these particles can hit the Earth anytime and anywhere is where the problem arises. Since the Earth has a massive area, it is not possible to place a detector everywhere and catch them at the exact moment.

Energetic charged particles known as cosmic rays hit our atmosphere, where they collide with air molecules to produce a shower of secondary particle | Source: CERN

Detecting such a shower requires a very big telescope, which logically means a network of individual particle detectors distributed over a mile or two-wide radius and connected to each other. The Pierre Auger Observatory in South America is the only such arrangement where 1,600 particle detectors have been scattered on 3,000 square kilometers of land. But the construction cost of the same was about $100 million. Yet, only a few cosmic ray particles could be detected using this arrangement. How do we spread this network around the Earth?

In addition to being cost-effective, such a setup must also be feasible. The Earth’s surface cannot possibly be dotted with particle detectors which cost huge fortunes. This is where smartphones come into the picture.

Detecting The Particles Using Smartphones

Smartphones are the most appropriate devices required to solve the problem. They have planet wide coverage, are affordable by most people and are being actively used by more than 1.5 billion users around the planet. Individually, these devices are low and inefficient; but a considerably dense network of such devices can give us a chance to detect cosmic ray showers belonging to the highest energy range.

Previous research has shown that smartphones have the capability of detecting ionizing radiation. The camera is the most sensitive part of the smartphone and is just the device required to meet our expectations. A CMOS (Complementary Metal Oxide Semiconductor) device is present in the camera- in which silicon photodiode pixels produce electron-hole pairs when struck by visible photons (when photons are detected by the CMOS device, it leaves traces of weakly activated pixels). The incoming rays are also laced with other noises and interference from the surroundings.  Although these devices are made to detect visible light, they still have the capability of detecting higher-energy photons and also low-ionizing particles such as the muons.

A screenshot from the app which shows the exposure time, the events- the number of particles recorded and other properties

To avoid normal light, the CRAYFIS application is to be run during nighttime with the camera facing down. As the phone processor runs the application it collects data from its surroundings using a camera as its detector element. The megapixel images (i.e., the incoming particles) are scanned at a speed of 5 to 15 frames per second, depending on the frame-processing speed of the device. Scientists expect that signals from the cosmic rays would occur rarely, i.e., around one in 500 frames. Also, there is the job of removing background data. An algorithm was created to tune the incoming particle shower by setting a threshold frequency at around 0.1 frames per second. Frames containing pixels above the threshold are stored and passed to the second stage which examines the stored frames, saving only the pixels above a second, lower threshold.

The CRAYFIS app is designed to run when the phone is not being used and when it is connected to a power source. The actual performance would be widely affected by the geometry of the smartphone’s camera and the conditions in which the data is being collected. Further, once the application is installed and is in the operating mode, no participation is required from the user, which is required to achieve wide-scale participation. When a Wifi connection is available the collected data would be uploaded to the central server so that it could be interpreted.

There is much complicated math used to trace back the information collected from the application. The most important parameters for the app are the local density of incoming particles, the detection area of the phone and the particle identification efficiency. These parameters are used to find the mean number of candidates (photons or muons) being detected. Further, the probability that a phone will detect no candidates or the probability that a phone will detect one or more candidates is given by Poisson distribution. The density of the shower is directly proportional to the incident particle energy with a distribution in x and y sensitive to the direction in which the particle came from. An Unbinned Likelihood (it is the probability of obtaining a certain data- in this case the distribution of the cosmic rays including their energy and direction, the obtained data is arranged into bins which are very, very small) analysis is used to determine the incident particle energy and direction. To eliminate background interference, a benchmark requirement has been set that at least 5 phones must detect and register a hit to be considered as a candidate.

It is impossible to express just how mind-blowing this innovation is. As the days pass, Science and Technology around us keep on surprising us and challenge us to rack our brains for more and more unique ways to deal with complex problems. The CRAYFIS app is simply beautiful and it would be a dream-come-true to the scientists if the project works out and we are able to detect these high energy, super intimidating cosmic rays with smartphones from our backyard.

Further Reading

The paper by Daniel Whiteson and team can be found here.

An exciting book “We Have No Idea” by Daniel Whiteson and cartoonist Jorge Cham can be found here.

The CRAYFIS app can be found here.

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