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Brunei Darussalam Monday, 15 October, 2018 - 22:32

Forests, be it the Amazonian rainforests or the montane forests of the Western Ghats closer home, are astoundingly complex biological systems. For years, enthralled by this complexity, researchers have tried to understand the distribution of the world’s forests with the geography—a field of study called phytogeography. Till date, they have identified six floristic realms—geographical areas with a uniform composition of plant species—across the world, namely Afrotropical, Antarctic, Boreal, Holarctic, Neotropical and Paleotropical realms.

The advent of phylogenetics, or the study of evolutionary relationships among biological entities using genetic data, has aided in establishing new, evolutionary connections among several plant and animal species across the world. In a recent study, published in the Proceedings of the National Academy of Sciences (PNAS) of the United States of America, an international team of researchers have phylogenetically classified the world’s tropical forests into five principal floristic regions—Indo-Pacific, Subtropical, African, American and dry forests that include the famed forests of Andes ranges and Brazilian Cerrado.

“This study is different in the fact that for the first time a global classification of forests based on inventory data using phylogenetic (evolutionary) similarity between tree communities is produced", remarks Dr Ferry Slik, an Associate Professor at the Universiti Brunei Darussalam, Brunei Darussalam, and an author of the study. "The findings highlight historical similarity better than previous analyses that were based on just similarity in species, genus or family", he adds, talking about the novelty of this approach.

Previous classification systems often found the three main tropical continents—America, Africa and Asia—as separate biomes. America stood separated from Africa and Asia, and often there were distinctions between the classical 'New-world' and 'Old-world' tropics. "Our study links most African forests with American forests, while some are linked to Asian forests, i.e. the split runs through Africa”, explains Dr Slik.

The phylogenetic tree, proposed in the current study, included all flowering plants dating back to 140 million years. It was found that the plants from the Late Cretaceous period, as old as 100-66 million years, dominated the present-day tropical forests. The pattern of distribution is further explained by the breakup of an ancient supercontinent, Gondwanaland. The breakup of  Gondwanaland into present-day Africa, South America, Australia, Antarctica, the Indian subcontinent and the Arabian Peninsula, explains the connection between South American and African forests.

“The phylogenetic analysis just calculates the evolutionary distance in years since the last common ancestor between pairs of species in each tree inventory, gathering accurate information on the health and diversity of a forest. Based on that, you can calculate an average similarity between inventories, with more closer inventories having more species in common that split apart more recently”, elucidates Dr Slik.

In the 1970s, two famous botanists, Peter Raven and Daniel Isaac Axelrod, had proposed a link between Africa and America based on plant fossils. The current study provides evidence for the same, thereby confirming the relationship. Also, the study found indications for the existence of a global dry forest region with representative forests in America, Africa, India and Madagascar that are characterised by a deficit of rain and contain deciduous species. A northern hemisphere subtropical forest region was identified within representative field sites from Asia and America providing evidence for their forest linkages.

“There are still many things to discover about tropical forests”, says Dr Slik, adding that there are only a handful of studies that have compared global patterns in forests.

“Such comparisons are important because it has become clear that there are substantial regional differences in tree compositions and forest structure, which are linked to the separate historical developments of all these regional forests. If we can pinpoint these differences, we will also be much better in predicting how these forests will respond to things like climate change, forest fragmentation, and increasing levels of carbon dioxide. It clearly has significant policy implications as well, not just contributing fundamental biological knowledge”, he adds, talking about the implications of such studies.

Section: General, Science, Ecology, Deep-dive Source: Link
Pune Monday, 15 October, 2018 - 15:56

In a recent announcement, Dr Shekhar C. Mande, the current Director of the National Centre for Cell Science (NCCS), Pune has been appointed as the new Director General of the Council of Scientific and Industrial Research (CSIR) and the Secretary of the Department of Scientific and Industrial Research (DSIR), India. He succeeds Dr Girish Sahni, who retired on 31st August 2018. CSIR is one of the world’s largest publicly-funded research and development organisations and is known for its contributions in diverse areas of science.

Dr Mande is a leading structural and computational biologist and has more than 100 publications to his credit. His laboratory at NCCS has been involved in research on the structural characterisation of Mycobacterium tuberculosis proteins and the computational analysis of genome-wide protein: protein interactions.

After completing his M.Sc. in Physics from Nagpur University in 1984, Dr Mande obtained his PhD in Molecular Biophysics from the Indian Institute of Science, Bengaluru, in 1991 under the supervision of Prof. M. Vijayan. He started his postdoctoral research at Rijksuniversiteit Groningen, in the Netherlands in 1991 and joined as a senior fellow at the University of Washington, Seattle, USA in 1992.

After returning to India, he joined the Institute of Microbial Technology, Chandigarh, as a scientist and continued till 2001 when he was selected as a Staff Scientist at the Centre for DNA Fingerprinting and Diagnostics, Hyderabad. In 2011, Dr Mande was appointed as the Director of NCCS, Pune, an autonomous Institute of the Department of Biotechnology, Government of India. He also served in various advisory committees for the Government of India.

Dr Mande has several honours and awards to his credit. He is the fellow of all the three major science academies of India—the Indian National Science Academy (INSA), the National Academy of Sciences India (NASI), and the Indian Academy of Sciences (IAS). He received the prestigious Shanti Swarup Bhatnagar Prize for Biological Sciences in 2005.

Expressing his commitment to this new role, Dr Mande responded, “I am personally excited with this opportunity to work with great institutions...” and that “...CSIR will strive to contribute to the growth on Indian society, as it has gloriously done in the last 75 years.”

Section: General, Science, News Source:
Bengaluru Monday, 15 October, 2018 - 08:00

Looking up at the clear moonless sky gives one a glimpse of the breathtaking view presented by a part of our galaxy, the Milky Way, as a starry strip across the sky. Whether you are stargazing casually or observing with a pair of binoculars or a telescope, you are always in for a treat whenever you point your ‘eyes’ at the beautiful star clusters, nebulae and the dusty dark lanes. However, beyond the myriad stars and nebulae, exists a complex system of a star cluster near the massive black hole at the very centre of our galaxy. Most of these central ‘nuclear’ stars are old, but there are some young and luminous stars that appear to be distributed in a disc very close to the black hole. Unlike most other stars that are formed by dense clumps of molecular gas, these young stars are thought to have originated when the gas around the massive black hole fragmented to form locally dense regions. In this case, their orbits at formation would have been close to circular shape, inherited from the parent gas flow. But the young stars at the galactic center have orbits that are much more elongated or eccentric than expected.

In a recent study, researchers from the Raman Research Institute (RRI), Bengaluru and their collaborators at Leiden University, Netherlands, and the American University of Beirut, Lebanon, have delved deeper into the lives of these nuclear stars, and how gravity influences their orbits. They have identified instabilities, driven by the gravitational interactions between the stars themselves and the central black hole, which can drive a disc full of stars on nearly circular orbits into a state where the disc has more elongated orbits.

To describe how the change happens, we need to introduce the orbital energy and angular momentum of a star. The energy is a measure of the size of the orbit, and the angular momentum is a measure of how circular the orbit is. Astronomers study the orbits of stars in galaxies because the nature of the orbits of individual stars is one of the factors, which probe the internal structure of galaxies.

Physically, these orbits look oval-shaped with two centers or ‘foci’ with two unequal diameters called the minor and major axes. The degree of such elongation, known as the ‘eccentricity’ of the orbit, governs its shape. However, in the center of our Galaxy, a tightly packed system of many stars in their orbits interact with each other due to gravity, often leading to an exchange of their orbital angular momenta, while their semi-major axes which is the most extended radius, are constant. Thus, any decrease in the angular momentum of a star implies an increase in its eccentricity, causing these stars to have elongated orbits.

So, can gravitational interactions between the stars lead to an increase in the range of elongations of orbits as observed in our Galactic center? This question is difficult to answer since there are millions of stars in our Galaxy, and gravity is a long-range, purely attractive force. Hence, it is a challenge to disentangle the cumulative effect of each of these stars.

In this study, Dr. Karamveer Kaur and Prof. S. Sridhar from RRI, and their collaborators Mher Kazandjian from Leiden and Jihad Touma from Beirut, present a simple analytical model that tries to solve this question. The model assumes a razor-thin disc in which each star has an elliptical orbit with a massive black hole at one of its foci. Since the physical problem concerns exchange of angular momenta, they consider all the stars to have the same semi-major axis. So, in this model, each stellar orbit will have just its angular momentum and the angle along which it is elongated in the disc plane.

Since there are many stars in the disc, the researchers used a 'water bag' model to simplify the model.  A water bag model is analogous to water in a container having constant density inside but zero outside. Thus, despite all angles of elongation being equally probable in an initially circular disc of stars, this could evolve into a disc, which is non-symmetric about the axis (non-axisymmetric) wherein only some angles of elongation are more heavily represented.

The stellar orbits evolve over long timescales (though smaller than the average lifespan of stars) to result in a transformation from an initial planar configuration into a stable complex system of orbits with broad eccentricities. The critical part of this result stems from simulations performed using different combinations of angular momenta values and tracing the evolution of the model over different timescales. The simulations successfully demonstrated that the thin disc of stars experiences various non-axisymmetric, linearly unstable, long-term disturbances as a result of gravitational interaction between them. In the one particular case, it appears that the non-axisymmetric features eventually damp, and the disc settles into a new circular state, with a much wider distribution of eccentricities than in the original circular disc.

“The water bag instabilities for stellar discs are the first of their kind. Earlier known instabilities were mainly associated with counter-rotating systems. These non-axisymmetric instabilities open a way for stellar discs in the vicinity of massive black holes to accelerate in their eccentricity distribution on much shorter timescales. This phenomenon might be a possible channel via which stars in the young stellar disc at the galactic center got excited in eccentricities within their lifespan”, says Dr. Kaur, explaining their results in a nutshell.

The findings of the study have a crucial impact on our understanding of the Milky Way’s center and the processes that occur within it. An incredibly simple construct like this is a first step towards explaining the nature of the orbits of the nuclear stars. Exciting follow-up investigations are planned which would involve updating the disc models to mimic the real physical system, incorporating detailed properties of the nuclear stars like their ages.

“The assumption of a flat disc is a restriction that needs to be lifted to allow for fully three-dimensional stellar orbits. Our interest is to see if the eccentric instabilities we found will trigger inclination oscillations, perhaps leading to an eccentric and warped final state”, comments S. Sridhar, explaining the future research direction. 

Section: General, Science, Deep-dive Source: Link
Bengaluru Friday, 12 October, 2018 - 09:11

In a recent study, scientists have reported that the extract of the plant Toxicodendron pubescens, commonly called the Atlantic poison oak, could help alleviate neuropathic pain caused by nerve damage. The study included researchers from the R. C. Patel Institute of Pharmaceutical Education and Research, Kalinga Institute of Industrial Technology, SVKM’s Institute of Pharmacy, Janmangal Homeopathy and Wellness Centre and UAE University. It was published in the journal Scientific Reports.

Neuropathic pain is caused by damage or disease in parts of our nervous system perceiving various sensations. Thanks to the increase in the ageing population, survivors from cancer chemotherapy and the incidence of diabetes, this condition is now prevalent. Although there are a few anti-neuropathic drugs, they are not effective for pain management and pose various side effects. “The efficacy of available anti-neuropathic drugs is limited due to occurrence of several side effects and inadequate or delayed pain relief”, say the researchers.

For their study, the researchers, induced a neuropathic pain-like condition in laboratory rats by surgical lesions and treated them with the extract of the Atlantic poison oak. The extracts of the plant has been already used in alternative system of medicines, like homeopathy, for treating inflammatory conditions, rheumatic pain and typhoid fever. This is the first such attempt to test their efficacy on neuropathic pain.

What causes nerve injury and pain? Oxidative stress—an imbalance between harmful free radicals generated in the body and our ability to detoxify their effects, and inflammation, are some factors that could lead to nerve injury and persistent pain in the nerves. Enzymes like catalase, which catalyses the decomposition of hydrogen peroxide into water and oxygen, and superoxide dismutase, an antioxidant enzyme, protect us from oxidative stress by scavenging the harmful free radicals. When there is a nerve injury, the levels of these enzyme decrease in the body.

The study found that the extract of the Atlantic poison oak had antioxidant and anti-inflammatory properties that could alleviate neuropathic pain. When the injured rats were treated with the plant extract, it could revive the levels of catalase and superoxide dismutase. The researchers also observed that some cytokines (signaling molecules) of the immune system, which are released following nerve injury and contribute to the development of neuropathic pain, were also inhibited by the plant extract.

This study shows how the extract of Toxicodendron pubescens, also called Rhus Tox (RT), can help control neuropathic pain in laboratory rats. The researchers suggest the need for further pre-clinical and clinical studies to confirm its potential therapeutic use in humans.  “Results of the present study are suggestive of the effect of RT extract against neuropathic pain and deserve further validation of its effectiveness in various painful conditions”, conclude the researchers.

Section: General, Science, News Source: Link
Mumbai Friday, 12 October, 2018 - 00:34

During my visit to my grandma’s place near Aravali in the Konkan region of Maharashtra, a trip to the closest hot spring was a routine. The spring acted as the source of hot water to the locals, and the water was said to have medicinal properties. Thermal springs, such as this, are a part of the geothermal fluids that occur below the surface of the earth to depths of about a kilometre. In a recent study, Dr Trupti Chandrashekhar from the Indian Institute of Technology Bombay (IIT Bombay), and her collaborators from the Indian Institute of Technology Hyderabad, Rajiv Gandhi Institute of Petroleum Technology, Amethi, and other institutes from Italy, have explored the origins of the hot springs along the Western Ghats. They have found that these springs evolved from rocks millions of years old, and marine sediments played a crucial role in their evolution.

There is more to the hot springs than just the famous spas around them. Geothermal fluids, in general, are used in aquaculture, horticulture, space heating and power generation. “Geothermal fluids act as the source and feedstock for geothermal power plants, just like coal for a coal power plant, or wind for a wind power plant. India has an immense potential for geothermal resource development and has the potential to generate over 10,000 MW of power using geothermal resources,” says Dr Chandrashekhar. The quality, quantity, temperature, pressure and grading of these fluids decide the type of geothermal power plants that can be built.

What forms geothermal fluids? Surface water on earth percolates deeper through faults and fissures in the rocks. As the temperature rises gradually below the surface, this water is subjected to heat and pressure and finds its way out to the surface again through faults in the rocks, in the form of geysers and springs. Depending on the path of circulation and the rocks it interacts with, the water obtains specific chemical properties that are characteristic of its evolution and origin.

Geothermal fluids contain a wide variety of dissolved constituents including carbonates, nitrates, zinc, copper and boron. By studying these constituents, scientists decipher the fundamental processes like water-rock interactions, the origin of thermal fluids and also the environmental impacts of their exploitation.

The Deccan plateau, formed millions of years ago as a result of volcanic activity, has a layer of basalt on the top with varying thickness. Basalt is a type of rock of volcanic origin. Below this are sedimentary layers of sandstone, called the Kadalgi sediments. Underneath them are rocks formed billions of years ago, called the Precambrian granite and gneiss. Long tectonic faults in the Deccan volcanic flows run in the north-south direction in the Konkan region of Maharashtra, almost parallel to the west coast. The springs in places like Sativli, Mandangad, Aravali, Anjaneri, Rajapur and others, form a cluster of hot springs found in these rock formations. 

“The geothermal springs along the western coast of Maharashtra flow along linear faults that lie parallel to the west coast. They formed about 65 million years ago when the whole of western India experienced intense volcanic activity,” explains Dr Chandrashekhar.

The researchers of this study collected 15 thermal springs water samples, eight groundwater samples and two river water samples along a 350 km stretch. They then studied the chemical composition, temperature, salinity and electrical conductivity of the samples to understand the ascent of thermal fluids. They also studied rock and water interactions in the laboratory, at high temperature and pressure, to simulate the reaction of rock and water deep inside the earth. The researchers also carried out an investigation on the boron isotopes for the first time on Indian thermal springs.

The study found that the Deccan basalts, the Kaladgi sediments, and the Precambrian granites play a significant role in the evolution of the thermal springs along the west coast. The chemical analysis of elements like calcium, sodium and chlorine, and the boron isotope studies, indicated that the geothermal water from all these places, except those at Rajapur and Math, originated from locations that were influenced by marine sediments deposited millions of years ago.

The study points to a possibility of geothermal power project development in Maharashtra and proposes splitting it into short-term, mid-term and long-term plans. The short-term plan could focus on uses like space heating, dehydration units for perishable food products, aquaculture or natural health spas, which could promote sustainable small to medium enterprise businesses.

“Mid and long-term development plan could be centred around the use of geothermal energy for generating cheap, clean and base power generation systems, beginning with the drilling of ten to fifteen deep exploration along the identified locations,” concludes Dr Chandrashekhar.

Section: General, Science, Deep-dive Source: Link
Guwahati Wednesday, 10 October, 2018 - 21:44

If you ever happen to visit a hospital, hope that you do not bring home the bacterium Methicillin-Resistant Staphylococcus aureus (MRSA). This notorious bacterium can survive most of the antibiotics flung at it—penicillin, cephalosporin or methicillin and hence is difficult to treat. In a recent study, researchers from the Institute of Advanced Study in Science and Technology, Guwahati, Assam, have used a combination of cutting-edge nanotechnology, antibiotics and enzymes, to punch holes in the defences of this bacterium and kill it.

Found in crowded places like hospitals, prisons and nursing homes, MRSA is a more dangerous pathogenic strain of the otherwise 'friendly' Staphylococcus aureus, which mostly lives harmoniously with other microbes in our upper respiratory tract and skin. Sometimes, this friendly bacterium acquires specific antibiotic resistant genes from other bacteria and turn into its adamant, nasty MRSA avatar. The first symptom of infection from MRSA is an innocent-looking pimple or a boil on the skin, which soon escalates into its dreadful form that is resilient to many antibiotics.

The researchers of the current study, published in the journal Scientific Reports, prepared a ‘concoction’ of gold nanoclusters, the antibiotic ampicillin and a lysozyme enzyme. When this combination was used on animal model infected by MRSA, it not only reduced the systemic infection in mice and cleared infection from diabetic wounds of rat but also solved the age-old problem of antibiotic resistance in this bacteria.

“The unique ultra-small size, stability and multiple modes of action of the nanohybrid combination are what makes it so successful,” says Dr Sanjeeb Kalita and Dr. Raghuram Kandimalla, the lead authors of the study. The research was supported by the Department of Science and Technology.

Ampicillin is an antibiotic which binds to and inhibits an enzyme required to build bacterial cell walls during cell division. However, when this drug is administered directly, the dosage that could enter inside a bacterium might not be sufficient to kill it, giving it a chance to develop resistance. In this study, the researchers coated ampicillin on gold nanoclusters. Nanoclusters are microscopic particles smaller than nanoparticles and can easily penetrate the cell wall of the bacteria. Since nanoclusters have a higher surface area, they can be loaded with higher concentrations of ampicillin, providing more sites of interaction with the bacteria at a time. This ability increases the efficacy of the drug against the bacteria.

Most antibiotic-resistant bacteria pump out the antibiotics from the interior of the cell using specific proteins in the cell membrane. The gold nanoclusters, used in the study, block this action, thereby choking the bacteria with a high dose of antibiotics that is present inside. In certain bacteria that have a thicker cell wall (gram-positive bacteria), the antibiotics cannot penetrate easily. Hence, the researchers have combined the nanoclusters with an enzyme called lysozyme, which degrades the bacterial cell wall by punching holes into it and making it susceptible. Besides, gold ions released from the nanoclusters may inhibit specific enzymes in the bacteria.

The researchers also point out that using nanoclusters, instead of nanoparticles, is less toxic to our cells. Nanoparticles are taken into our cells through a process called ‘cell eating’ or phagocytosis. However, since nanoclusters are smaller in size, they enter the cells through pinocytosis or ‘cell drinking’, which allows only small doses inside at a time making it less toxic says Dr. Sarathi Kundu and Ashim Chandra Bhowal.

When researchers used the ampicillin and lysosome coated gold nanoclusters on MRSA, they found that these bacteria, which were proven to be resistant to antibiotics previously, were killed altogether. They further observed that even after repeated exposure (15 times) to these nanoclusters, the bacteria could not develop resistance—a finding that could solve the most critical problem of antibiotic resistance. Also, just topical application of these nanoclusters on a diabetic wound eradicated MRSA infection, leading to quicker wound healing. On testing the nanoclusters in MRSA infected rat, the researchers observed that it cleared the infection and increased the lifespan of the rat.

“The reported nanohybrid system overcomes the resistance behaviour of MRSA through exploiting the physical barriers, which are not bacteria-specific. Through its versatility, it can be potentially effective against most of the other resistant bacterial types too,” remarks Dr Kalita and Dr. Kandimalla, adding that this approach can be replicated on other drug resistant bacteria.

At a time when pharma companies are hesitating to uncover and develop new antibiotics, the way forward could be to use old antibiotics combined with new sophisticated technology to counter antibacterial resistance. “An estimated 700 000 people die annually from infection with drug-resistant microbes. On the other hand, due to uncertainty in the path to market and profitability, a majority of the pharmaceutical companies are abandoning antibiotic development programs. The yield of the gold nanocluster is significantly high, and we believe that the cost-benefit ratio is maintained by taking account of this drug resistance crisis”, Dr Kalita and Dr. Kandimalla signs off.

Section: General, Science, Health, Deep-dive Source: Link
Bengaluru Wednesday, 10 October, 2018 - 18:12

Last week, the world enthusiastically awaited one of the year’s exciting announcements—the Nobel Prize in the fields of Physiology or Medicine, Physics, and Chemistry. First of them to be announced was the Nobel Prize in Physiology or Medicine, jointly awarded to James P. Allison, Professor at the University of Texas MD Anderson Cancer Center, USA, and Tasuku Honjo, Professor at Kyoto University, Japan. They were considered for this prestigious honour for their contributions to cancer therapy using our body’s immune system to attack cancer cells.

“Allison and Honjo showed how different strategies for inhibiting the brakes on the immune system can be used in the treatment of cancer. The seminal discoveries by the two Laureates constitute a landmark in our fight against cancer”, reads the press release from the Nobel Committee.

Our immune system is a robust defence system that protects our body from invaders. However, cancer cells escape its action by blocking some cells from acting against them. Cancer immunotherapy, the concept of using our well-defending immune system against cancer cells, releases these cells to unleash their prowess and kill the cancer cells. Although research in cancer immunotherapy started in the later-half of the 19th century, the pathbreaking works of Prof. James P. Allison and Prof. Tasuku Honjo have turned it to reality now.

In one of our archives, Research Matters had covered the field of immunotherapy in detail, with a feature on how research by Dr Udupi Ramagopal, Associate Professor and Structural Biologist at the Poornaprajna Institute of Scientific Research, Bengaluru, could make immunotherapeutic drugs affordable for all. In summary, these drugs bind to the T-cells, a type of white blood cell in our body, which play an active role in destroying the invaders.

Prof. James P. Allison, also the winner of the 2014 Breakthrough Prize, studied a protein called CTLA-4 that functions as a brake on the T cells and prevents its action against the cancer cells. He developed an antibody that could bind to CTLA-4 and block its function. Prof. Tasuku Honjo discovered another protein called PD-1 on the surface of the T cells which also act as a brake. Although therapy against PD-1 has proven to be more powerful, a combination therapy targeting both these brakes could be even more effective.

Thanks to these efforts, we now have drugs like ipilimumab, sold under the brand name Yervoy, and nivolumab, marketed as Opdivo, which are referred to as ‘checkpoint inhibitors’, bringing a smile to the faces of many patients who are fighting cancer. If the ‘made in India’ drug soon sees the light of the day, it could bring an immunotherapy drug on the aisles of the pharmacy at a fraction of today’s cost! 

Section: General, Science, News Source:
Mumbai Tuesday, 9 October, 2018 - 22:36

As electronic gadgets dominate many aspects of our lives, smaller devices that pack more functionality and consume lower power are increasingly becoming popular. Transistors—one of the basic building blocks of these devices—dictate their size, speed, efficiency and battery life. In a recent study, Ms Poonam Jangid, Mr Dawuth Pathan and Prof.Anil Kottantharayil from the Indian Institute of Technology Bombay (IIT Bombay) have developed a technique to fabricate graphene transistors as small as 20 nanometers wide (5000 times smaller than the thickness of a sheet of paper). These graphene transistors consume less power in the standby state and can facilitate faster circuit operations. 

Silicon and similar semiconductor materials have been traditionally used to build transistors. However, there are significant challenges to making smaller but faster silicon transistors. An alternative is graphene, which is a crystalline form of carbon that is made up of a single layer of carbon atoms. In its pure form, graphene is a conductor. But, by altering its structure, it can be turned into a semiconductor, making it an ideal candidate for next-generation transistors and other electronic devices.

Graphene nanoribbons are strips of graphene made by creating parallel channels on its surface by removing some carbon atoms. Previous studies have shown that the conductivity of graphene can be controlled by changing the width and structure of the edge of the channel; the narrower the width of the ribbon, lesser is the conductivity. “Compared to silicon transistors, graphene transistors can be 100 times faster," says Prof. Kottantharayil.

So far, graphene nanoribbons are synthesised either through chemical processes or by etching on graphene films using nanocrystals of metals like nickel, copper or iron. However, neither chemical synthesis nor any known method of etching yields graphene nanoribbons with a smooth and desirable edge structure. In this study, published in the journal Carbon, the researchers have fabricated graphene nanoribbons by etching graphene films using platinum nanocrystals. Since platinum is a nearly-inert material and is a useful chemical catalyst, it yielded good quality graphene nanoribbons, with a width of 10-20 nm and smooth edges. The process was carried out at a temperature of about 1000oC in the presence of a mixture of hydrogen and argon gas.

Transistors act as switches that allow current to flow when they are turned on and stop it when they are switched off. However, in practice, a small, negligible current, called leakage current (IOFF), flows even when the transistor is off. It is because of this leakage current that electronic devices consume battery power even in the standby mode. Ideally, an efficient transistor would aim at having the lowest possible value for the leakage current. A higher value of the current passing through a transistor when it's on (ION) indicates that the device has a higher conductivity, and can be turned on and off faster.

“ION/IOFF is a figure of merit for the switching efficacy of transistors. High ION results in faster circuits and low IOFF is desirable for low standby power,” explains Prof  Kottantharayil.

The new graphene transistor designed by the researchers showed a high ION/IOFF ratio of 600 at room temperature and a high conductivity compared to not only traditional transistors but also to graphene nanoribbon transistors made by other methods. Although graphene nanoribbon transistors fabricated using nickel nanocrystal-based etching have a higher ION/IOFF ratio of 5000 at room temperature, they have very low conductivity, which may tend to heat the device, reducing its efficiency.

Although the findings of the study are exciting, graphene nanoribbon transistors are still far away from reality. “To be used in nanoscale circuits, it is essential to fabricate graphene nanoribbons on a large scale with lesser defects. Graphene nanoribbons are at least ten years, if not farther, from widespread applications,” says Prof Kottantharayil.

A major drawback of synthesising graphene nanoribbons by etching is that they contain many defects. Hence, to produce nanoribbons on a large scale, non-etching based techniques need to be developed.

“Some possible research direction include directed movement of catalyst nanoparticles that are deposited or grown at specific locations of interest. Some of the techniques used in our research along with etching based techniques could be interesting to study,” Prof. Kottantharayil signs off.

Section: General, Science, Technology, Deep-dive Source:
New Delhi Tuesday, 9 October, 2018 - 18:10

In a recent study published in the journal Scientific Reports, researchers from the Jawaharlal Nehru University, India, and Louisiana State University, USA, have analysed the differences in the genome of a variety of weedy rice, with that of two cultivated rice varieties. Weedy rice, as the name suggests, is a variety of rice that grows like weed in paddy fields. Also called ‘red rice’, they produce far fewer grains than their cultivated counterparts, compete with them and pose a significant threat to rice production across the world.

Although it is believed that weedy rice evolved from cultivated rice and wild rice, so far there was limited knowledge of the variations in their genome, which have differentiated them from their cultivated counterparts. In this study, the researchers have compared the genetic differences between the weedy rice accession ‘PSRR-1’ and two cultivated rice accessions, ‘Bengal’ and ‘Nona Bokra’, belonging to rice subspecies japonica and indica, respectively.

“Analysing the genome level DNA polymorphisms between the weedy and cultivated rice is crucial to elucidate the molecular basis of weedy and agronomic traits, which in turn can enhance our ability to control weedy rice and its utilization for rice improvement,” say the researchers about the importance of this study.

The researchers identified 11546 genetic variations affecting 5673 genes in the weedy rice variety that differed from the cultivated rice varieties. They also found that a high degree of similarity in the genetic variations present in the genomes of the weedy rice with the indica cultivar, indicating that weedy rice might have originated from indica. “Despite its morphological similarity with cultivated rice, differences between weedy and cultivated rice at the whole genome level shed some light on the genome organization in weedy rice compared to the cultivated rice”, say the researchers, commenting in the findings.

The researchers also studied the genes responsible for essential characteristics like seed shattering or the dispersal of seeds after ripening, and seed dormancy—the inability of viable seeds to germinate under favourable conditions. They identified some candidate genes responsible for these characteristics.

But not everything about weedy rice varieties is bad. They are considered a valuable genetic resource for crop improvement as they possess the characteristics like rapid growth, early flowering, disease resistance and tolerance to stresses. “The genomic resources generated in this study will accelerate both molecular genetics and molecular breeding investigations in rice”, comment the researchers about the significance of their findings.

Section: General, Science, News Source: Link
Bengaluru Tuesday, 9 October, 2018 - 00:10

We have all been in an aircraft when all of a sudden the captain asks you to fasten your seatbelts because of  'turbulence'. Although you might experience a few bumps because of this turbulence, which is a technical term for unsteady and chaotic airflow, you may think nothing of it. But, guess what? Turbulent flows are ubiquitous -- from stars and supernovae to mixing of air and fuel in an automobile engine to the flow of water in domestic pipelines.

Turbulence enormously increases mixing rates be it in industrial reactors, or in the atmosphere and oceans, although, all of this comes at the expense of an increased energy consumption. A fundamental understanding of turbulence has, however, remained one of the last major challenges in classical physics. Such an understanding would, for instance, allow one to design better aeroplane wings and not only save you a bumpy ride but save enormous amounts of fuel too.

In a recent study, published in the journal Physical Review Letters, a team of researchers , led jointly by Prof. V. Shankar from the Indian Institute of Technology (IIT) Kanpur and Prof. Ganesh Subramanian from the Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR), Bengaluru, have been able to theoretically explain experimental results showing unexpected turbulence in polymer solutions. They have discovered a hitherto unexplored mechanism by which turbulence can arise in such solutions—a feat that could have far-reaching implications in stimulating future studies on turbulence.

The flow of fluids, like water or air, is described by their stickiness or viscosity. An understanding of this stickiness goes back to Isaac Newton who first characterized it in terms of the resistance to the sliding of adjacent fluid layers in a laminar flow. Water and air are thus examples of 'Newtonian fluids'. Adding polymers to such fluids imparts a certain `springiness’ in addition to the stickiness already present. Such fluids which exhibit both viscous and elastic effects are one of the prominent examples of 'non-Newtonian fluids', and are appropriately referred to as 'viscoelastic fluids'.

In the said study, the researchers have the examined the onset of turbulence in polymer solutions, an important class of viscoelastic fluids. It turns out that such fluids are not only of fundamental interest but also have critical industrial applications. “Addition of polymers to crude oil is well-known to reduce pumping costs in the turbulent regime drastically, and this is exploited in the trans-Alaskan oil pipeline,” explains Prof. V. Shankar from IIT Kanpur.

The flow of Newtonian fluids turns turbulent only at very high flow speeds. Experiments in the past have shown that the flow of viscoelastic fluids, on the other hand, turns turbulent at much lower flow speeds. However, the reasons for this so-called `early turbulence’ had never been understood until now.

Many studies carried out over the last century have shown that Newtonian pipe flow stays laminar or smooth when it is subjected to disturbances that are sufficiently small. These flows are said to be ‘linearly stable’ for minor disturbances. The current belief in the fluid dynamics community is based on the extrapolation of this Newtonian scenario to viscoelastic pipe flows as well. “The belief was so ingrained that not even a single attempt was made in the literature to analyse the stability of viscoelastic pipe flow. When we realised this lacuna, Prof. Subramanian and I felt that it is worth exploring this further”, says Prof. Shankar, explaining the motivation behind the study.

The researchers of this study were able to theoretically calculate the motion of the viscoelastic fluid and confirm, for the first time, that the addition of polymers strongly destabilised the laminar flow rendering it susceptible to the tiniest of disturbances.

“To our surprise, we found a linear instability for viscoelastic flows in both circular pipes and channels, and the icing on the cake was the qualitative agreement with experimental observations of transition in viscoelastic flows. We would be able to make reasonable predictions of the flow speeds at which turbulence begins in polymer solutions”, exclaims Prof. Shankar.         

The results of the study have significant ramifications for our understanding of the behaviour of these non-Newtonian fluids and their broader applications. They will also serve as a ‘template' for future theoretical calculations under less idealised conditions and may well end up as a critical ingredient in any future model of turbulent flows of polymeric liquids.

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