BITS Faculty Publications
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Item Atomistic modeling of two-dimensional electronic spectra and excited-state dynamics for a light harvesting 2 complex(ACS, 2015-01) Prajapati, Jigneshkumar DahyabhaiThe Light Harvesting 2 (LH2) complex is a vital part of the photosystem of purple bacteria. It is responsible for the absorption of light and transport of the resulting excitations to the reaction center in a highly efficient manner. A general description of the chromophores and the interaction with their local environment is crucial to understand this highly efficient energy transport. Here we include this interaction in an atomistic way using mixed quantum-classical (molecular dynamics) simulations of spectra. In particular, we present the first atomistic simulation of nonlinear optical spectra for LH2 and use it to study the energy transport within the complex. We show that the frequency distributions of the pigments strongly depend on their positions with respect to the protein scaffold and dynamics of their local environment. Furthermore, we show that although the pigments are closely packed the transition frequencies of neighboring pigments are essentially uncorrelated. We present the simulated linear absorption spectra for the LH2 complex and provide a detailed explanation of the states responsible for the observed two-band structure. Finally, we discuss the energy transfer within the complex by analyzing population transfer calculations and 2D spectra for different waiting times. We conclude that the energy transfer from the B800 ring to the B850 ring is mediated by intermediate states that are delocalized over both rings, allowing for a stepwise downhill energy transport.Item Characterization of ciprofloxacin permeation pathways across the Porin OmpC using metadynamics and a string method(ACS, 2017-08) Prajapati, Jigneshkumar DahyabhaiThe rapid spreading of antimicrobial resistance in Gram-negative bacteria has become a major threat for humans as well as animals. As one of the main factors involved, the permeability of the outer membrane has attracted a great deal of attention recently. However, the knowledge regarding the translocation mechanisms for most available antibiotics is so far rather limited. Here, a theoretical study concerning the diffusion route of ciprofloxacin across the outer membrane porin OmpC from E. coli is presented. To this end, we establish a protocol to characterize meaningful permeation pathways by combining metadynamics with the zero-temperature string method. It was found that the lowest-energy pathway requires a reorientation of ciprofloxacin in the extracellular side of the porin before reaching the constriction region with its carboxyl group ahead. Several affinity sites have been identified, and their metastability has been evaluated using unbiased simulations. Such a detailed understanding is potentially very helpful in guiding the development of next generation antibiotics.Item Intelligent Virtual Laboratory Development and Implementation using the RASA Framework(IEEE, 2023-04) Bhatt, Upendra MohanVirtual environments for learning with intelligent support are in high demand right now. This is due to the fact that smart e-learning environments must be built internally in order to increase students' hands-on abilities. Through inquiry and demonstration in a smart e-lab environment, these talents are linked to several disciplines of science and engineering. Students and instructors may make the transition from working in virtual environments to doing experiments using actual materials. Lab assistants often spend the bulk of their time making the same mistakes. As a result, this research looked at the technology, proposed approach, and implementation of an intelligent virtual C programming laboratory. This ensures that virtual assistants employ chatbots to fix student faults. The environment is based on his NLP (natural language processing) and machine learning models, with web application development using his MERN stack and virtual assistant production using the RASA, Artificial Intelligence (AI) framework.Item Meta Effect of Absorption Energy in Donor–Acceptor Substituted Benzenoids: A Computational Study of Its Dependence on Acceptor Strength, Solvent Polarity, and Conjugation Length(ACS, 2014-08) Pati, Avik K.The present work focuses on theoretical understanding of electronic absorption energies of N,N-dimethylaniline with different ortho-, meta-, and para-substituted acceptor groups. The meta isomers exhibit the lowest absorption energy compared to the ortho and para derivatives. This unusual behavior of absorption energies of the meta isomers is related to the “meta effect” well-known in organic photochemical reactions. The meta effect of absorption energy of the derivatives is found to depend on the strength of acceptors, solvent polarity, and conjugation length. The meta derivatives with strong acceptor groups generally exhibit the lowest absorption energy over the other isomers irrespective of solvent polarity. However, the meta isomers with weak acceptor groups exhibit the meta effect only in highly polar solvents. The trend of the lowest absorption energies of the meta isomers is observed to change if the acceptor group is bridged through π conjugation unit (n) with the core moiety. The normal pattern of absorption energy that is the para isomer is of lowest energy is observed to occur for the derivatives where the repeated conjugation units (n) are between 2 and 4. The normal pattern of absorption energy is continued to observe from n > 4 for all the derivatives.Item Colossal Power Extraction from Active Cyclic Brownian Information Engines(ACS, 2022-07) Dutta, SandipanBrownian information engines can extract work from thermal fluctuations by utilizing information. To date, the studies on Brownian information engines consider the system in a thermal bath; however, many processes in nature occur in a nonequilibrium setting, such as the suspensions of self-propelled microorganisms or cellular environments called an active bath. Here, we introduce an archetypal model for a Maxwell-demon type cyclic Brownian information engine operating in a Gaussian correlated active bath capable of extracting more work than its thermal counterpart. We obtain a general integral fluctuation theorem for the active engine that includes additional mutual information gained from the active bath with a unique effective temperature. This effective description modifies the generalized second law and provides a new upper bound for the extracted work. Unlike the passive information engine operating in a thermal bath, the active information engine extracts colossal power that peaks at the finite cycle period. Our study provides fundamental insights into the design and functioning of synthetic and biological submicrometer motors in active baths under measurement and feedback control.Item Conformational Polymorphism in Sulfonylurea Drugs: Electronic Structure Analysis(ACS, 2010-08) Sundriyal, SandeepQuantum chemical calculations have been performed using HF, B3LYP, and MP2 methods on the model sulfonylurea PhSO2NHC(═O)NHMe to understand the conformational and tautomeric preferences. The results indicate that a conformer with intramolecular hydrogen bond SLU-1 (hitherto not considered) is more stable than the conformer SLU-2 (which is generally considered) for sulfonylureas. The energy difference between these two conformers is about 4 kcal/mol in the gas phase; however, the energy differences between the two rotamers become negligible in the solvent phase. Iminol tautomeric forms of sulfonylurea (which were also not studied until now) are only about 5−6 kcal/mol higher in energy as per both gas-phase and solvent-phase analyses, indicating easy accessibility of tautomeric states in sulfonylureas. Quantum chemical analysis has also been carried out on the possible dimeric structures of these three important isomers of sulfonylurea, and correlations have been made to the known crystal structures of polymorphic states of sulfonylurea drugsItem A numerical investigation of the heat transfer characteristics of water-based mango bark nanofluid flowing in a double-pipe heat exchanger(Elsevier, 2019) Bhattacharyya, SuvanjanIn this study, the heat transfer characteristics of a new class of nanofluids made from mango bark was numerically simulated and studied during turbulent flow through a double pipe heat exchanger. A range of volume fractions was considered for a particle size of 100 nm. A two-phase flow was considered using the mixture model. The mixture model governing equations of continuity, momentum, energy and volume fraction were solved using the finitevolume method. The results showed an increase of the Nusselt number by 68% for a Reynolds number of 5,000 and 45% for a Reynolds number of 13 000, and the heat transfer coefficient of the nanofluid was about twice that of the base fluid. In addition, the Nusselt number decreased by an average value of 0.76 with an increase of volume fraction by 1%. It was also found that there was a range of Reynolds numbers in which the trend of the average heat transfer coefficient of the nanofluid was completely reversed, and several plots showing zones of higher heat transfer which if taken advantage of in design will lead to higher heat transfer while avoiding other zones that have low heat transfer. It is hoped that these results will influence the thermal design of new heat exchangers.Item Comparing Environmental Impact of Various Energy Sources Powering Data Centres’s at Indian Candidate Locations(Springer, 2021-08) Srinivasan, P.While major 21st century developments are data-intensive, the use and storage of such high volumes of data are processed through datacentres. Though Datacentres (DC) are typically high-power consumption applications, the percentage of energy consumption is even higher in developing economies such as India. This paper studies the net environmental impact of energy supply to such datacentres, at four candidate locations, by examining their net Green House Gas Emissions per kWh and land usage per kW. The study analyses various sources of energy such as thermal, wind, and solar plus battery systems to provide a comprehensive view of environmental impacts caused by the power supply.Item A Machine Vision-based Cyber-Physical Production System for Energy Efficiency and Enhanced Teaching-Learning Using a Learning Factory(Elsevier, 2021) Sangwan, Kuldip Singh; Kumar, RajneeshMachine vision (MV) can help in achieving real-time data analysis in a manufacturing environment. This can be implemented in any industry to achieve real-time monitoring of workpieces for geometric defects and material irregularities. Identification of defects, sorting of workpieces based on their physical parameters, and analysis of process abnormalities can be achieved by using the real-time data from simple and cost-effective raspberry pi with camera and open source machine learning platform TensorFlow to run convolutional neural network (CNN) model. The proposed cyber-physical production system enables to develop a MV based system for data acquisition integrating physical entities of learning factory (LF) with the cyber world. Nowadays, LFs are widely used to train the workforce for developing competencies for emerging technologies and challenges faced due to technological advancements in Industry 4.0. This paper demonstrates the application of a cost-effective MV system in a learning factory environment to achieve real-time data acquisition and energy efficiency. The proposed low-cost machine vision is found to detect geometric irregularities, colours and surface defects. The simple cost effective MV system has enhanced the energy efficiency and reduced the total carbon footprint by 18.37 % and 78.83 % depending upon the location of MV system along the flow. The teaching-learning experience is also enhanced through action-based learning strategies. This not only ensures less rework, better control, unbiased decisions, 100% quality assurance but also the need of workers/operators can be reduced.Item Traceless Directing Groups in Radical Cascades: From Oligoalkynes to Fused Helicenes without Tethered Initiators(ACS, 2014-12-24) Banerjee, TanmayWe report the first example of a traceless directing group in a radical cascade. The chemo- and regioselectivity of the initial attack in skipped oligoalkynes is controlled by propargyl OR moiety. Radical translocations lead to the boomerang return of the radical center to the site of initial attack where it assists the elimination of the directing functionality via β-scission in the last step of the cascade. The Bu3Sn moiety continues further via facile reactions with electrophiles as well as Stille and Suzuki cross-coupling reactions. This selective radical transformation opens a new approach for the controlled transformation of skipped oligoalkynes into polycyclic ribbons of tunable dimensions.