A sumptuous rendezvous

It was well past the time for my evening tea, and I had not realized. We just got out of the adventure zone at Thenmala – there was enough chest thumping and adrenaline pumping in the couple of hours that we spent inside the park. For the size it was, the adventure zone could have been maintained a little better. Neither helmets were given for games where you are mid-air, nor life jackets given while boating. And mind you, some games were quite challenging. We were seven of us and only one managed to succeed in all the games.

By the time we got out, we were not only just tired from the games but sweaty too from the humid air that hugs Kerala tight. I needed tea. Cold water simply does not satiate my thirst. I mean, it never does. Even under the heat of sweltering summer, I always needed tea to feel better. It pacifies me and no wonder, I call it the elixir of my life. I told my friends that we must stop somewhere for a cup of tea on the way to our next stop – the Kollam Sengottai branch line. I was assured we would stop at a chai kada as soon as we see one. I sat next to the driver just to make sure that he stopped for tea.

We all were on the way towards our next halt. On the way, I saw Kerala State Transport Corporation buses plying to and from Tenkasi, a small town in the Tirunelveli district of Tamilnadu. I have not been to the town myself, but it reminded me of the Courtallam waterfalls that is situated close to Tenkasi. Since the time of actor M. G. Ramachandran, renowned by his initials as MGR, Tamil cinema has been singing its praise. Both MGR and Courtallam have thus become household names in most Tamil families. I simply forgot about my tea and instead, began humming some songs on Courtallam.

Soon, we reached our destination. With thirteen arches and spanning a length of half a kilometer, the bridge was larger than I expected. I was upset about not having a cup of tea. Suddenly, aroma of fresh prawns deep fried in coconut oil wafted through the air. Oh, My!! Oh, My!! I took long and deep breathes to inhale more of that spicy aroma. It had ginger, garlic, peppercorns, and prawns. Now, I needed more than tea – a plate of chemeen porichathu, as the locals fondly call it. That sumptuous aroma wafted from a chai kada nestled under one of the arches. This is what is called destiny, I thought.  It was a small shop run by a couple in their mid-forties. It appeared like the shop also served as their house.

We ordered chai and lime soda, helped ourselves to some chikkis and arisi murukku from the bottles placed on a table in the shop. When I saw that the dish was being prepared in a small kada, I guessed it was being made as an evening snack for the family. I noticed that my friends were not at all excited about the aroma of the prawns fried in coconut oil. I had to let go of my idea of having prawns with chai. The prawns were still being fried and the aroma lured me much more. Well, that’s it.

I initiated a conversation with the chechi.

“Will you be selling those prawns?”

“Illa, for the family.”

“Okay.”.

I smiled at my friends who were already giggling at my uncontrollable urge to taste those prawns.

The hot tea was amazing too. Nothing too special – just the right amount of milk, sugar, and decoction. I had my tea and while cheta was busy making lime soda, I asked chechi.

“Can I take a picture of your chemeen fry?”

She laughed and nodded. I instantly stepped in and took a picture. The prawns were small and had curled in the heat of the coconut oil in which they were being fried. I was reminded of my granny after seeing those prawns with some shards of garlic. Granny has told me that the smallest of prawns often tastes the best. It was then time for us to leave when someone called me from the back.

Chechi handed me a plate with some prawns and asked me to taste it. My joy knew no bounds. I took a mouthful of prawns and my eyes lit up. It was heavenly. The prawns were crisp on the outside and soft inside. There was the right amount of salt and spice. Again, nothing too complex about it but it was such a splendid preparation. Noticing my contented look, my friends laughed uncontrollably and joyously.

I thanked chechi and would thank her another million times for that delicacy.

That’s the thing about some days – it ends in a simple way with simple people, the heart  fulfilled with contentment.

Body cells to bird flocks: Decoding glassiness

It might be baffling to think that tissues, comprising of motile cells, behave like glass. But, did you know that many living systems, like armies of ants, flocks of birds, and cancerous cells are also glass-like? One thing that is common to all these systems is that the others in the system severely restrict the movement of one of the constituent units. In a recent study, researchers from Bengaluru’s Indian Institute of Science (IISc), National Centre for Biological Sciences (NCBS), International Centre for Theoretical Sciences (ICTS) and Israel’s Weizmann Institute of Science, have successfully developed a model to explain the dynamics of collective systems that are motile at high density.

What makes such collective systems glassy? Imagine some motile cells confined to a small region. When there are far too many ants, there would be multiple head-on collisions between them, leading to a significant rise in the ‘cellular traffic’. On a larger scale, the increase in traffic could bring some regions to a standstill, without any movement. Some parts that do not have many encounters, on the other hand, continue to have a fluid-like motion. The solid-like and fluid-like regions may interchange their positions over time. This behaviour is akin to glass—a state of matter that behaves like a solid for short periods of time but relaxes to a liquid state over an infinitely long time.

The other property common to both collective living systems and glass is jamming. When a liquid changes to a solid in a slow process at low temperatures,  the atoms have enough time to rearrange themselves in an orderly fashion. However, in the case of glass, this change from liquid to solid is rapid, resulting in a disordered solid through a process called jamming.

Studying the properties of such active systems has many implications. “Developing a proper theoretical framework for such a system should help to understand them within a coherent framework. Beyond biology, activity provides an interesting control parameter for a glassy system. We hope, our work will lead to deeper insights into the glassy systems in general”, says Dr. Saroj Nandi, a Postdoctoral Fellow at the Weizmann Institute of Science, Rehovot, Israel.

The researchers of the current study, published in the Proceedings of the National Academy of Sciences, have used random first-order theory—a fundamental mathematical concept—to understand the behaviour of complex systems. The total energy of the system depends on the surface density and evolves depending on the movement within the collective system. It also influences a thermodynamic property called configurational entropy—the different ways in which constituent particles rearrange within a system. In systems devoid of activity, configurational entropy is determined only by the temperature, the number of constituent particles, and the internal energy.

Since the random first-order approximation applies for systems in equilibrium, the researchers modified it to suit active collective systems that are out of equilibrium. They constructed a new model to incorporate the effects of activity in a collective system. The researchers then validated their model through simulations and showed that the behaviour of active glassy systems depends on the nature of the activity.

Since the random first-order approximation applies for systems in equilibrium, the researchers modified it to suit active collective systems that are out of equilibrium. They constructed a new model to incorporate the effects of activity in a collective system. The researchers then validated their model through simulations and showed that the behaviour of active glassy systems depends on the nature of the activity.

“We have a well-established theory for an equilibrium system. We now extend it for active systems so we can understand the assumptions of the theory. It will also be easier to test and establish the predictions by others. This approach is in contrast to modelling a particular biological system”, says Dr Nandi.

The study is an essential milestone in the exploration of activity-driven glass-like systems. It is funded by the Koshland Foundation, Council of Scientific and Industrial Research (India), and the Harold Perlman Family Foundation, and has broad applications not just in studying the nature of the collective behaviour of biological systems but also in areas such as non-equilibrium thermodynamics and disordered magnetism.

Published in Research Matters

Own a Thanjavur Painting?

Try Raman Spectroscopy

A Thanjavur painting typically adorns many a house in the temple towns of Tamil Nadu. The style originated in Thanjavur during the Maratha reign. The paintings usually depict themes from Hindu iconography. The picture is drawn on a wooden plank and is then decorated with motifs made of gold, precious, and semi-precious stones. Owing to its importance as a classical art form, the Thanjavur painting is distinguished with a geographical indication tag by the Government of India. But, due to its fame, bogus replicas abound. Since fakes are common, art connoisseurs are concerned. Sales outlets and auction houses are plagued with the worry: what if this is not real gold?

Scientists from the Indian Institute of Technology, Varanasi and the SASTRA University, Tamil Nadu have now concocted a way to discriminate fake from real gold in paintings.
The researchers devised the setup based on Raman spectroscopy, a diagnostic tool used to distinguish molecules and atoms with rotational and vibrational modes.

When light falls on such molecules, it scatters depending on the type of rotation or vibration present. The major advantage of using Raman spectroscopy is that it is a non-destructive tool to test the authenticity of gold in the paintings, explains V. Ramanathan, IIT BHU.

To verify their strategy, the researchers used samples of actual and fake gold collected from some artisans in Thanjavur. They cleaned the samples with acetone and ethanol to remove any dirt that might have accumulated during or after painting.

A 532 nm laser from the spectrometer was then shone on the samples. Gold, being a metal, is devoid of vibrational and rotational modes. So samples of real gold do not alter the frequency spectrum of incident light. Fake gold, on the other hand, scatters. This leads to the appearance of additional peaks in the frequency spectrum.

‘The scattering peaks are signatures that the gold used is fake’, says P. J. Arathi, SASTRA University.

The researchers used the same technique to identify the genuineness of the precious and semi-precious stones used in Thanjavur paintings. And that is heart-warming news for art aficionados who can now be sure that their painting is genuine.

The researchers say that it would be beneficial to incorporate such a test into the regulations and frameworks of the committee tagging products with a geographical identity.

CURRENT SCIENCE, VOL. 115, NO. 9, 10 NOVEMBER 2018