RSTV: SCIENCE MONITOR- 29.08.2020

• As a landmark achievement in Space missions, Indian Astronomers have discovered one of the farthest Star galaxies in the universe.
• AstroSat is India’s first multi-wavelength space telescope, which has five telescopes seeing through different wavelengths simultaneously — visible, near UV, far UV, soft X-ray and hard X-ray.
• Onboard the AstroSat is a 38-cm wide UltraViolet Imaging Telescope (UVIT), which is capable of imaging in far and near-ultraviolet bands over a wide field of view.
• AstroSat was launched on 28 September 2015 by ISRO into a near-Earth equatorial orbit.
• It is a multi-institute collaborative project, involving IUCAA, ISRO, Tata Institute of Fundamental Research (Mumbai), Indian Institute of Astrophysics (Bengaluru), and Physical Research Laboratory (Ahmedabad), among others.
• The galaxy called AUDFs01 was discovered by a team of Astronomers .
• The importance and uniqueness of this original discovery can be made out from the fact that it has been reported in the leading international journal “Nature Astronomy” published from Britain.
• India’s AstroSat/UVIT was able to achieve this unique feat because the background noise in the UVIT detector is much less than one on the Hubble Space Telescope of US based NASA.
• This discovery is a very important clue to how the dark ages of the Universe ended and there was light in the Universe.

ARCI developed high-performance tin anodes for lithium-ion battery used in Electric Vehicles:

• Lithium-ion battery or Li-ion battery is a type of rechargeable battery.
• Li-ion batteries use an intercalated (Intercalation is the reversible inclusion or insertion of a molecule into materials with layered structures) lithium compound as one electrode material, compared to the metallic lithium used in a non-rechargeable lithium battery.
• The battery consists of electrolyte, which allows for ionic movement, and the two electrodes are the constituent components of a lithium-ion battery cell.
• Lithium ions move from the negative electrode to the positive electrode during discharge and back when charging.
• They are one of the most popular types of rechargeable batteries used for military, battery electric vehicle and aerospace applications.
• Scientists at the International Advanced Research Centre for Powder Metallurgy and New Materials (ARCI), an autonomous institute under the Department of Science & Technology have developed low-cost micron Tin based anodes which proved to be high-performance and stable anode material for Lithium-ion batteries (LIBs) used in electric vehicles.
• Electric vehicle (EV) technology demands LIBs with high energy density, long cycle life, and fast charging capability. Existing LIBs use graphite as an anode due to its low operating potential with respect to lithium, high thermal conductivity, and minimal volume expansion (12%) during charge/discharge cycling. However, they have a moderate capacity (372 mAhg^-1) and limited fast-charging capability. Tin (Sn) with its low-cost high capacity (993 mAhg^-1) and fast charging capability is considered a replacement for graphite anodes in LIBs.
• The electrode preparation for LIBs involves coating of slurry of the material on to a metallic foil in a roll-to-roll fashion. In the process of fabricating Sn-based anode, the slurry has to be made using micron-sized Sn (bulk form) powders. However, usage of micron-sized Sn is not recommended due to its high-volume expansion (300%) during charge/discharge cycling, as it leads to cracking of electrodes and drastic erosion of capacity within a few cycles.
• To circumvent such high-volume expansion, nano-size Sn has been used in various studies, which showed a significant enhancement in the cyclic stability. But, it involves a cost-intensive synthesis methodology and low production yields. Switching from nano-Sn to micron-Sn could result in significant cost reduction of the electrode fabrication process almost by 20 times.

Centre for Nano and Soft Matter Sciences has developed an invisible and flexible electromagnetic interference shield using Copper metal mesh:

• Scientists have now achieved a feat by designing a metal mesh structure instead of continuous film on desired transparent substrates to make it a transparent shield for electromagnetic interference (EMI).
• The invisible shield can be used in various military stealth applications and can cover electromagnetic wave emitter or absorber devices without compromising their aesthetics.
• Scientists from Centre for Nano and Soft Matter Sciences (CeNS), Bengaluru, an autonomous institute of the Department of Science & Technology, Govt. of India have fabricated these transparent and flexible EMI shields made of metal meshes using the crack templating method via spray coating which is pioneered in their laboratory.
• The CeNS team has developed a copper metal mesh on polyethylene terephthalate (PET) sheet as its substrate, which exhibited a visible transmittance (T), a parameter of visible transparency of about 85% and sheet resistance (R_s) ~ 0.83 ohm per square. These transparent and flexible EMI shields made of metal mesh coatings on desired transparent substrate they have developed through their research published in the journal ‘Bulletin of Materials Science’ showed remarkably high values for total EMI shielding (SE_T), with the average value being ~ 41 dB over a wide spectral range of the Ku band (12 to 18 GHz).
• Instead of continuous film of metal (Cu) coating on any transparent substrate (glass, PET) where transparency can be compromised. In this method, the CeNS team has deposited metal mesh networks on the substrate, which covers only 7% area of substate, unlike 100% coverage of continuous film. This makes metal mesh transparent compare to continuous metal film. Metal mesh provides better electromagnetic shielding compare to same thickness of continuous metal film where transparency can be compromised.
• This metal mesh can be created on any desired substrates such as acrylic, polycarbonate, glass, etc. without compromising the conductivity of the electrodes.

Modelling water levels of northwestern India in response to improved irrigation use efficiency:

• The groundwater crisis in northwestern India is the result of over-exploitation of groundwater resources for irrigation.
• The Government of India has targeted a 20 percent improvement in irrigation groundwater use efficiency.
• In this perspective, and using a regional-scale calibrated and validated three-dimensional groundwater flow model, this research provides the first forecasts of water levels in the study area up to the year 2028, both with and without this improvement in use efficiency.
• Future water levels without any mitigation efforts are anticipated to decline by up to 2.8 m/year in some areas.
• A simulation with a 20 percent reduction in groundwater abstraction shows spatially varied aquifer responses. Tangible results are visible in a decade, and the water-level decline rates decrease by 36–67 percent in over-exploited areas.
• Although increasing irrigation use efficiency provides tangible benefits, an integrated approach to agricultural water management practice that incorporates use efficiency along with other measures like water-efficient cropping patterns and rainwater harvesting may yield better results in a shorter period.