29 results on '"Argha A"'
Search Results
2. Mechanical Tuning of Fluorescence Lifetime and Bandgap in an Elastically Flexible Molecular Semiconductor Crystal.
- Author
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Dar, Arif Hassan, Rahman, Atiqur, Mondal, Srijan, Barman, Argha, Gupta, Monika, Chowdhury, Pramit K., and Thomas, Sajesh P.
- Published
- 2024
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3. Photoinduced [3+2] Cycloaddition of Carbenes and Nitriles: A Versatile Approach to Oxazole Synthesis.
- Author
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Saha, Argha, Sen, Chiranjit, Guin, Srimanta, Das, Chandan, Maiti, Debajit, Sen, Subhabrata, and Maiti, Debabrata
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NITRILES , *CARBENES , *PHOTOLYSIS (Chemistry) , *OXAZOLES , *RADIOLABELING , *RING formation (Chemistry) , *CARBENE synthesis , *DIAZO compounds , *NITRILE oxides - Abstract
We have developed a photoinduced protocol for the synthesis of pharmaceutically important oxazole molecules using diazo‐ and nitrile‐containing reactants. The process involves the initial photolysis of the diazo compound to afford singlet carbenes, which are tapped by nitriles in a [3+2] cycloaddition fashion to give substituted oxazoles. With di‐nitrile compounds, useful bis‐oxazoles were obtained. The applicability of the transformation is showcased through the expedient synthesis of small‐molecule drugs and biologically relevant molecules such as felbinac, pimprinine, texamine, ugnenenazole etc. The protocol is also useful for the generation of 2H and 13C isotope labelled oxazoles. Merging photolysis with continuous‐flow chemistry was demonstrated for scaling up the reaction. The non‐requirement of metal catalysis or photosensitizers to harness the light energy with blue light sufficing the execution of the reaction makes it a versatile and general protocol for the synthesis of structurally diverse oxazoles [ABSTRACT FROM AUTHOR]
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- 2023
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4. A Scaling Relation for Cryoconite Holes.
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Banerjee, Argha, Sarangi, Chandan, Rashid, Irfan, Vijay, Saurabh, Najar, Nadeem Ahmad, and Chandel, Amit Singh
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GLACIERS , *SOLAR radiation , *RADIATION absorption , *ECHO sounding - Abstract
Tiny cryoconite holes are commonly found on glacier surfaces. Despite a long history of research on them, their influence on glacier‐scale mass balance and runoff are not well understood. We model the absorption of solar radiation at the bottom of cylindrical cryoconite holes, incorporating the three‐dimensional geometry. The simulated holes achieve a limiting steady‐state depth, where the daily melt rate at the bottom of the holes matches that at the glacier surface. This implies a feedback loop restricting the excess ice melt due to the presence of dark supraglacial impurities. The modeled steady‐state depth scales approximately linearly with the radius, consistent with in situ observations at several glaciers across the world. Given the areal coverage and radius distribution of cryoconite holes on a glacier, this scaling yields first‐order estimates of their melt contribution. Plain Language Summary: Dark particles deposited on glacier surfaces absorb more solar radiation than the surrounding ice, and melt into the surface to create approximately cylindrical holes with a layer of dark "cryoconite" substance at their bottom. Such cryoconite holes are commonly seen on glacier surfaces all over the world. These holes continue to deepen, reducing the exposure of the dark cryoconite to solar radiation, and eventually leading to a steady‐state depth. We combine modeling and in situ observations to show that the steady depth is approximately proportional to the radius of the hole. This simple geometric property proves useful in estimating the net contribution of all the cryoconite holes present on a glacier to its mass balance and runoff. Our estimates suggest that these holes efficiently negate the melt‐enhancing effects of the dark impurities on glacier surface. Key Points: Effects of shortwave radiation on cryoconite holes modeled in three dimensionsUnder steady clear‐sky conditions, cryoconite holes deepen up to a steady depth which scales with radiusThis depth‐diameter scaling yields estimates of cryoconite‐hole contribution to glacier mass balance [ABSTRACT FROM AUTHOR]
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- 2023
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5. Investigation and Characterization of Graphene/Al, ZnO/Al and Al/Graphene/ZnO Contacts.
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Sen, Suchismita, Sarkar, Argha, Chakraborty, Pinaki, Teja, Neeruganti Vikram, and Kundu, Mayuri
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ZINC oxide films , *GRAPHENE , *ZINC oxide , *SCHOTTKY barrier , *SPIN coating , *THIN films - Abstract
In this paper, investigation has been made on the electrical properties of graphene/Al contact, ZnO/Al contact and Al/graphene/ZnO contacts in detail. Al metallization is considered, and it is performed via thermal vacuum coating technique under strict monitoring of the rate of thickness of the metal. Spin coating method and shadow masking are done for depositing fabricated graphene and ZnO on the thin film. Comparative analysis has been made on the parameters like saturation current, Barrier height and ideality factors which are calculated using Schottky barrier height (SBH) method. I–V characteristics are analyzed using the key‐sight B2029A semiconductor parameter analyzer. It is seen that the ZnO/Al contact has more ideality factor nearly 0.059 and exhibits Schottky behavior. Meanwhile, maximum saturation current is obtained for Graphene/Al contact whereas maximum barrier height is for ZnO/Al contact. © 2023 Institute of Electrical Engineer of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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6. Comparison of continuous wave and pulsed mode plasma polymerization of glycidol for storage‐stable coatings for biomolecule immobilization.
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Chakraborty, Argha, Jasieniak, Marek, Coad, Bryan R., and Griesser, Hans J.
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PLASMA polymerization , *PLASMA instabilities , *POLYMERS , *X-ray photoelectron spectroscopy , *CASPOFUNGIN , *SECONDARY ion mass spectrometry , *SURFACE coatings , *INSECT flight - Abstract
Plasma polymers from glycidol vapors are of interest for direct covalent grafting of molecules bearing amine or thiol groups. The question of whether pulsed plasma operation might lead to a higher surface density of epoxide groups and a higher density of grafted molecules is studied using the antifungal drug caspofungin. X‐ray photoelectron spectroscopy and Time of flight‐secondary ions mass spectrometry analysis followed by caspofungin grafting revealed that both continuous wave and pulsed plasmas led to surface epoxides but with higher densities upon pulsing. Investigations into stability suggested that glycidol plasma polymer coatings were still able to immobilize caspofungin after 2 years of storage, making them suitable for applications where grafting of molecules needs to be done immediately before usage of a device. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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7. Substrate‐Rhodium Cooperativity in Photoinduced ortho‐Alkynylation of Arenes.
- Author
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Saha, Argha, Ghosh, Animesh, Guin, Srimanta, Panda, Sanjib, Mal, Dibya Kanti, Majumdar, Abhirup, Akita, Munetaka, and Maiti, Debabrata
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AROMATIC compounds , *OXIDATIVE addition , *CHARGE exchange , *TRANSITION metals - Abstract
In the realm of metallaphotocatalytic C−H activation strategy, the direct excitation of the transition metal which plays the dual role of light energy harnessing alongside performing the bond breaking and forming is a rare phenomenon. In this context we have developed the first photo‐induced Rh‐catalyzed ortho‐alkynylation under ambient conditions without the requirement of silver salt, photocatalyst (PC) or any engineered substrate or catalyst. The transformation functions by the specific cooperative effect of a six‐membered rhodacycle which is the photo‐responsive species. The catalytic system allows the conjugation of arenes with sp3‐rich pharmacophoric fragments. The control experiments as well as the computational studies resolve the mechanistic intricacies for this transformation. An outer sphere electron transfer process from Rh to alkynyl radical is operative for the present photo‐induced transformation over the more common oxidative addition or 1,2‐migratory insertion pathways. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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8. Approaches to 1,4‐Disubstituted Cubane Derivatives as Energetic Materials: Design, Theoretical Studies and Synthesis.
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Lal, Sohan, Bhattacharjee, Argha, Chowdhury, Arindrajit, Kumbhakarna, Neeraj, and Namboothiri, Irishi N. N.
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BAND gaps - Abstract
Novel 1,4‐disubstituted cubane derivatives have been designed and selected ones have been successfully synthesized and characterized by various analytical and spectroscopic techniques, including single‐crystal X‐ray analysis. A detailed computational study at B3LYP/6‐311++G(d,p) level of theory revealed that all newly designed 1,4‐disubstituted cubane derivatives possess higher densities, higher density‐specific impulse and superior ballistic properties when compared to conventional fuels, for example, RP‐1. These compounds also exhibit acceptable kinetic and thermodynamic stabilities which were evaluated in terms of their HOMO‐LUMO energy gap and bond dissociation energies, respectively, and are superior to TEX and many other compounds containing explosophoric groups. These results provide novel insights into the possible application of cubane‐based energetic materials. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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9. Emerging Approaches for Enabling RNAi Therapeutics.
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Mallick, Argha M., Tripathi, Archana, Mishra, Sukumar, Mukherjee, Asmita, Dutta, Chiranjit, Chatterjee, Ananya, and Sinha Roy, Rituparna
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THERAPEUTICS , *RARE diseases , *SMALL interfering RNA , *METASTASIS , *GENETIC disorders - Abstract
RNA interference (RNAi) is a primitive evolutionary mechanism developed to escape incorporation of foreign genetic material. siRNA has been instrumental in achieving the therapeutic potential of RNAi by theoretically silencing any gene of interest in a reversible and sequence‐specific manner. Extrinsically administered siRNA generally needs a delivery vehicle to span across different physiological barriers and load into the RISC complex in the cytoplasm in its functional form to show its efficacy. This review discusses the designing principles and examples of different classes of delivery vehicles that have proved to be efficient in RNAi therapeutics. We also briefly discuss the role of RNAi therapeutics in genetic and rare diseases, epigenetic modifications, immunomodulation and combination modality to inch closer in creating a personalized therapy for metastatic cancer. At the end, we present, strategies and look into the opportunities to develop efficient delivery vehicles for RNAi which can be translated into clinics. [ABSTRACT FROM AUTHOR]
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- 2022
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10. High Thermopower and Optical Properties of A2MoS4 (A = K, Rb, Cs) and Cs2MoSe4.
- Author
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Roy, Argha Jyoti, Sharma, Vineet Kumar, and Kanchana, Venkatakrishanan
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OPTICAL properties , *THERMOELECTRIC power , *ALKALI metals , *TRANSITION metal chalcogenides , *COMPUTATIONAL physics , *ISOTROPIC properties - Abstract
The current work analyzes the electronic, structural, mechanical, thermoelectric (TE), and optical properties of alkali‐based transition metal chalcogenides A2MoS4 (A = K, Rb, Cs) and Cs2MoSe4 using methods based on first principles. The electronic, structural, and mechanical properties are analyzed using projected augmented wave (PAW) potentials. The electronic structure calculations show them to be direct bandgap semiconductors. From the TE properties, it is found that all the compounds possess huge thermopower especially for the holes, and this along with low lattice thermal conductivity enables us to predict A2MoS4 (A = K, Rb, Cs) and Cs2MoSe4 to be a good class of material for TE applications. Also, the optical properties are found to be nearly isotropic in the low energy region, which also might fetch potential applications in the visible range. The nearly isotropic optical properties along with giant thermopower are the highlights of the current study, which sets a platform for exploring future device applications. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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11. High Thermopower and Optical Properties of A2MoS4 (A = K, Rb, Cs) and Cs2MoSe4.
- Author
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Roy, Argha Jyoti, Sharma, Vineet Kumar, and Kanchana, Venkatakrishanan
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OPTICAL properties ,THERMOELECTRIC power ,ALKALI metals ,TRANSITION metal chalcogenides ,COMPUTATIONAL physics ,ISOTROPIC properties - Abstract
The current work analyzes the electronic, structural, mechanical, thermoelectric (TE), and optical properties of alkali‐based transition metal chalcogenides A2MoS4 (A = K, Rb, Cs) and Cs2MoSe4 using methods based on first principles. The electronic, structural, and mechanical properties are analyzed using projected augmented wave (PAW) potentials. The electronic structure calculations show them to be direct bandgap semiconductors. From the TE properties, it is found that all the compounds possess huge thermopower especially for the holes, and this along with low lattice thermal conductivity enables us to predict A2MoS4 (A = K, Rb, Cs) and Cs2MoSe4 to be a good class of material for TE applications. Also, the optical properties are found to be nearly isotropic in the low energy region, which also might fetch potential applications in the visible range. The nearly isotropic optical properties along with giant thermopower are the highlights of the current study, which sets a platform for exploring future device applications. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
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12. Studies on prospect of HTV silicone rubber as dielectric material when reinforced with TiO2 nano particles.
- Author
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Pal, Argha Kamal, Baral, Arijit, and Lahiri, Abhijit
- Abstract
The present work aims to improve both the thermal and dielectric properties at power frequency of millable high temperature vulcanized silicone rubber (HTV SR) so that it can be used as housing material for transformer bushings or as a substitute to ceramic and glass insulators. For this purpose, nano sized titanium dioxide (TiO2) particles have been incorporated into HTV SR. Samples of HTV SR, filled with different percentages by weight of nano TiO2 fillers have been synthesized along with one HTV SR sample without filler loading referred here as blank HTV SR sample in the subsequent sections. Morphological characterizations of these nano filler impregnated samples are carried out. Thermal, electrical and mechanical characterizations are performed and the results are compared with those obtained for blank HTV SR samples. Results showed that at lower filler concentrations, dielectric properties and thermal stability of HTV SR/TiO2 nanocomposites have improved to a considerable extent while retaining the mechanical properties. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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13. Investigation of Quantum Droplets: An Analytical Approach.
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Debnath, Argha and Khan, Ayan
- Abstract
Recent observations of droplets in dipolar and binary Bose–Einstein condensate (BEC) gives motivation to study the theory of droplet formation in detail. Specifically, the authors are interested in investigating the possibility of droplet formation in a quasi‐1D geometry. Recent observations have suggested that droplets are stabilized by competition between effective mean‐field and beyond mean‐field interaction. Hence, it is possible to map the effective equation of motion to a cubic‐quartic nonlinear Schrödinger equation (CQNLSE). Two analytical solutions of the modified Gross–Pitaevskii equation or CQNLSE are obtained and they are verified numerically. Based on their stability, the parameter regime for which droplets can form is investigated. The effective potential allows for conclusions about the regions of soliton domination and self‐bound droplet formations. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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14. Evaluation of a Tubulin‐Targeted Pyrimidine Indole Hybrid Molecule as an Anticancer Agent.
- Author
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Bose, Chandra, Banerjee, Priyanjalee, Kundu, Jayanta, Dutta, Biswadeb, Ghosh, Indranil, Sinha, Shreya, Ghosh, Argha, Barua, Abhishek, Gupta, Shalini, Das, Ujjal, Jana, Siddhartha S., and Sinha, Surajit
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EPITHELIAL-mesenchymal transition ,ANTINEOPLASTIC agents ,SMALL molecules ,INDOLE ,CANCER cell migration ,ANTIMITOTIC agents - Abstract
Several small molecules targeting microtubule dynamics have been developed because microtubules are considered to be one of the most successful cancer chemotherapeutic targets. In this regard, taxol is most worthy to mention which stabilizes microtubule polymer thereby causing defectsinmitotic spindle assembly, chromosome segregation and cell division resulting in cancer inhibition. In this direction, we have earlier reported a small molecule called Pyrimidine‐Indole‐Hybrid (PIH (P)) which was found to inhibit ciliogenesis by inhibiting both the acetylation and polymerization of tubulin subunits. Here, we have evaluated the anticancer activities of PIH (P) and its water soluble derivatives. Three water soluble derivatives of PIH (P) namely 6 A, 6B and 6 C were synthesized. Among PIH (P) series of compounds, PIH (P) and 6 C were found to be the most potent compounds showing anti‐proliferative and cytoskeletal disrupting activities against MCF‐7 cells. Not only that, PIH (P) and 6 C also showed a promising effect in preventing cancer cell migration, invasion and colony‐formation and helped to reduce spheroid formation by several‐folds. They have potential to inhibit the activity of proteins (N‐Cadherin, Vimentin) responsible for Epithelial to Mesenchymal Transition (EMT). Hence, this class of compound could be a new antimitotic agent that is different from taxol with respect to mechanism, particularly by destabilizing tubulin rather than causing stabilization. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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15. Para‐Selective Cyanation of Arenes by H‐Bonded Template.
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Pimparkar, Sandeep, Bhattacharya, Trisha, Maji, Arun, Saha, Argha, Jayarajan, Ramasamy, Dutta, Uttam, Lu, Gang, Lupton, David W., and Maiti, Debabrata
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AROMATIC compounds ,MOIETIES (Chemistry) ,MODIFICATIONS - Abstract
The significance of site selective functionalization stands upon the superior selectivity, easy synthesis and diverse product utility. In this work, we demonstrate the para‐selective introduction of versatile nitrile moiety, enabled by a detachable and reusable H‐bonded auxiliary. The methodology holds its efficiency irrespective of substrate electronic bias. The conspicuous shift in the step energetics was probed by both experimental and computational mechanistic tools, which heralds the inception of para‐deuteration. The synthetic impact of the methodology was highlighted with reusability of directing group and post synthetic modifications. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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16. Sliding‐mode fault‐tolerant control using the control allocation scheme.
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Argha, Ahmadreza, Su, Steven W., Zheng, Wei Xing, and Celler, Branko G.
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ROBUST control , *ACTUATORS , *VECTOR control , *IMAGE reconstruction algorithms , *PIEZOELECTRIC actuators - Abstract
Summary: This paper is devoted to the design of a novel fault‐tolerant control (FTC) using the combination of a robust sliding‐mode control (SMC) strategy and a control allocation (CA) algorithm, referred to as a CA‐based sliding‐mode FTC (SMFTC). The proposed SMFTC can also be considered a modular‐design control strategy. In this approach, first, a high‐level SMC, designed without detailed knowledge of systems' actuators/effectors, commands a vector of virtual control signals to meet the overall control objectives. Then, a CA algorithm distributes the virtual control efforts among the healthy actuators/effectors using the real‐time information obtained from a fault detection and reconstruction mechanism. As the underlying system is not assumed to have a rank‐deficient input matrix, the control allocator module is visible to the SMC module resulting in an uncertainty. Hence, the virtual control, in this scheme, is designed to be robust against uncertainties emanating from the visibility of the control allocator to the controller and imperfections in the estimated effectiveness gain. The proposed CA‐based SMFTC scheme is a unified FTC, which does not need to reconfigure the control system in the case of actuator fault or failure. Additionally, to cope with actuator saturation limits, a novel redistributed pseudoinverse‐based CA mechanism is proposed. The effectiveness of the proposed schemes is discussed with a numerical example. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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17. Static output feedback fault tolerant control using control allocation scheme.
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Argha, Ahmadreza, Su, Steven W., and Celler, Branko G.
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FAULT tolerance (Engineering) , *ARTIFICIAL intelligence , *MATHEMATICAL models , *NUMERICAL analysis , *ROBUST control - Abstract
Summary: This paper describes two novel schemes for fault tolerant control using robust suboptimal static output feedback design methods. These schemes can also be employed as actuator redundancy management for overactuated uncertain linear systems. In contrast to many existing methods in the literature that assume the control input matrix (i) is not of full‐rank such that it can be factorized into two matrices and (ii) it does not involve uncertainty, these schemes can be applied to systems whose control input matrix cannot be factorized and/or involve uncertainty. The so‐called virtual control, in these schemes, is calculated using suboptimal H2‐based static output feedback design schemes constructed to be robust against uncertainties emanating from inherent input matrix uncertainty and visibility of the control allocator to the controller. Then, using two proposed control allocation schemes (fixed and on‐line), the obtained virtual control signal is redistributed among remaining (redundant or nonfaulty) set of actuators. As the proposed schemes are modular‐based, they can be employed as real‐time fault tolerant control schemes with no need to reconfigure the controller in the case of actuator faults or failures. The effectiveness of the proposed schemes is discussed and compared with numerical examples. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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18. Evaluation of different large‐scale predictor‐based statistical downscaling models in simulating zone‐wise monsoon precipitation over India.
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Akhter, Javed, Das, Lalu, Meher, Jitendra Kumar, and Deb, Argha
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MONSOONS ,METEOROLOGICAL precipitation ,DOWNSCALING (Climatology) ,CALIBRATION - Abstract
Selection of suitable predictors for downscaling local‐scale precipitation from the wide range of large‐scale predictors available in National Center for Atmospheric Research/National Centers for Environmental Prediction (NCAR/NCEP) reanalysis is a challenging task because of the existence of the complex interactions between local‐scale predictands and large‐scale predictor fields. An attempt was made to assess how well different large‐scale predictors were able to reproduce local‐scale monsoon precipitation over seven homogeneous zones of India through statistical downscaling. For calibration of downscaling (DS) models, the principal component (PC)‐based multiple linear regression approach was adopted where each raw grid‐point predictor field transformed into PCs using empirical orthogonal function (EOF) analysis. The predictors consistently producing better downscaled results across four nonoverlapping calibration and validation periods were identified as "superior predictor" (SP). It was found that some common predictors like precipitable water; specific and relative humidity at different levels have emerged as SP predictors over several zones. In general, SP predictors have not been much sensitive with small changes in the domain size. However, a decline in performances of DS models was noticed for the majority of SP predictors for a large increase in the size of domains. Especially, the largest South Asia domain has been the most inappropriate domain as very few predictors found to be suitable for downscaling. In general, about 40% out of 36 numbers of combined predictors were identified as potential SP predictors over the majority of the zones. Several numbers of combined SP predictors have also produced slightly superior skills compared to single SP predictors. In many cases, predictors showing poor performance as single predictors have produced improved performances when combined with other predictors. A schematic diagram of downscaling for assessing the performances of different predictors in simulating precipitation. Over a selected domain, empirical orthogonal function analysis was performed on the predictor field. Principal components (PCs) explaining 99% variances were retained. Downscaling (DS) models were calibrated with these PCs through multiple linear regressions. Prediction was made during the validation period using the DS model. For assessing predictor performances R2, AIC values during calibration and R, RSR values during validation were estimated. [ABSTRACT FROM AUTHOR]
- Published
- 2019
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19. Application of a new reduced‐complexity assessment tool to estimate CO2 and brine leakage from reservoir and above‐zone monitoring interval (AZMI) through an abandoned well under geologic carbon storage conditions.
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Zhang, Liwei, Dilmore, Robert, Huerta, Nicolas, Soong, Yee, Vasylkivska, Veronika, Namhata, Argha, Wang, Yan, and Li, Xiaochun
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CARBON dioxide ,SALT ,RESERVOIRS ,LEAKAGE ,PERMEABILITY - Abstract
Abstract: This study employs a combination of detailed simulations and reduced‐complexity models in the Well Leakage Analysis Tool (WLAT), developed by the National Risk Assessment Partnership (NRAP), US Department of Energy, to investigate how the rates of CO
2 and brine leakage through an abandoned well under geologic CO2 storage conditions are affected by various factors. The factors considered in this study include depth of well penetration into the storage system, location relative to the point of injection, and effective permeability of the abandoned well. Location is the primary factor used to identify high‐ and low‐risk abandoned wells. For the typical CO2 injection scenario considered in this study, the potential impact of CO2 and brine leakage through an abandoned well is very low if the abandoned well is 6.2 km or further away from the CO2 injector. Due to the buoyancy of CO2 relative to formation brine, wells intersecting (i.e., accepting flow from) the top of the above‐zone monitoring interval (AZMI), which is the interval immediately above the seal, have a higher chance to become a pathway for CO2 than wells intersecting the bottom of the AZMI. If the permeability of an abandoned well is 10−14 m2 or less, the risk of CO2 and brine leakage through the well becomes very low. Due to the combined effect of pressure increase and buoyancy, the CO2 leakage rate is higher than brine leakage rate within the CO2 plume extent. Specific values reported in this study are site‐specific results and cannot be regarded as general findings. © 2018 Society of Chemical Industry and John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]- Published
- 2018
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20. Metal‐Free Deoxygenation and Reductive Disilylation of Nitroarenes by Organosilicon Reducing Reagents.
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Bhattacharjee, Argha, Hosoya, Hiromu, Ikeda, Hideaki, Nishi, Kohei, Tsurugi, Hayato, and Mashima, Kazushi
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DEOXYGENATION , *SILYLATION , *ORGANOSILICON compounds , *CHEMICAL reagents , *FUNCTIONAL groups - Abstract
Abstract: A metal‐free deoxygenation and reductive disilylation of nitroarenes was achieved using N,N′‐bis(trimethylsilyl)‐4,4′‐bipyridinylidene (1) under mild and neutral reaction conditions, and a broad functional group tolerance was possible in this reaction. Mono‐deoxygenation, giving a synthetically valuable N,O‐bis(trimethylsilyl)phenylhydroxylamine (7 a) as a readily available and safe phenylnitrene source from nitrobenzene, and double‐deoxygenation, giving N,N‐bis(trimethylsilyl)anilines 8, were easily controlled by varying the amounts of 1 and reaction temperature as well as adding dibenzothiophene (DBTP). Reaction of 2‐arylnitrobenzenes with 1 resulted in the formation of the corresponding carbazoles 14 via in situ‐generated phenylnitrene species derived by thermolysis of N,O‐bis(trimethylsilyl)phenylhydroxylamines 7, followed by their subsequent intramolecular C−H insertion. In addition, the intramolecular N−N coupling reaction proceeded in the reduction of 2,2′‐dinitrobiphenyl derivatives by 1, giving the corresponding benzo[c]cinnolines. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
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21. Prevalence of Power Law Profiles in Passive Margin Escarpments.
- Author
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Banerjee, Argha, Shirsat, Tejal, and Kumari, Reshama
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LANDFORMS ,CLIFFS ,MEDIAN (Mathematics) ,POWER law (Mathematics) ,PSYCHOPHYSICS - Abstract
An analysis of elevation data from several great escarpment regions across the globe revealed a prevalence of inverse power law forms among the escarpment profiles. The best fit power law exponent varies among profiles and has a global median value of 0.9 and standard deviation of 1.8. The power law form is consistent with the shape of a detachment‐limited escarpment that is retreating headward while maintaining a constant shape. Such a constant‐shape evolution requires the local denudation rate to be equal to the product of escarpment retreat rate and local slope. The available basin‐averaged denudation rate data from several great escarpment regions are consistent with this constraint, and this allows estimation of the recent retreat rates of the escarpments within the constant‐shape assumption. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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22. Novel frameworks for the design of fault‐tolerant control using optimal sliding‐mode control.
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Argha, Ahmadreza, Su, Steven W., Savkin, Andrey, and Celler, Branko G.
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ACTUATORS , *MOTION control devices , *EIGENVALUES , *WEYL'S problem , *EIGENFREQUENCIES - Abstract
Summary: This paper describes 2 schemes for a fault‐tolerant control using a novel optimal sliding‐mode control, which can also be employed as actuator redundancy management for overactuated uncertain linear systems. By using the effectiveness level of the actuators in the performance indexes, 2 schemes for redistributing the control effort among the remaining (redundant or nonfaulty) set of actuators are constructed based on an ℋ 2‐based optimal sliding‐mode control. In contrast to the current sliding‐mode fault‐tolerant control design methods, in these new schemes, the level of control effort required to maintain sliding is penalised. The proposed optimal sliding‐mode fault‐tolerant control design schemes are implemented in 2 stages. In the first stage, a state feedback gain is derived using an LMI‐based scheme that can assign a number of the closed‐loop eigenvalues to a known value whilst satisfying performance specifications. The sliding function matrix related to the particular state feedback derived in the first stage is obtained in the second stage. The difference between the 2 schemes proposed for the sliding‐mode fault‐tolerant control is that the second one includes a separate control allocation module, which makes it easier to apply actuator constraints to the problem. Moreover, it will be shown that, with the second scheme, we can deal with actuator faults or even failures without controller reconfiguration. We further discuss the advantages and disadvantages of the 2 schemes in more details. The effectiveness of the proposed schemes are illustrated with numerical examples. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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23. H2-based optimal sparse sliding mode control for networked control systems.
- Author
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Argha, Ahmadreza, Li, Li, and Su, Steven W.
- Subjects
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SLIDING mode control , *SPARSE graphs , *LINEAR matrix inequalities , *DISTRIBUTED computing , *PERFORMANCE evaluation - Abstract
This paper is devoted to the problem of designing a sparsely distributed sliding mode control for networked systems. Indeed, this note uses a distributed sliding mode control framework by exploiting (some of) other subsystems' information to improve the performance of each local controller so that it can widen the applicability region of the given scheme. To do so, different from the traditional schemes in the literature, a novel approach is proposed to design the sliding surface, in which the level of required control effort is taken into account during the sliding surface design based on the [ABSTRACT FROM AUTHOR]
- Published
- 2018
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24. Outside Front Cover: Plasma Process. Polym. 7/2023.
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Chakraborty, Argha, Jasieniak, Marek, Coad, Bryan R., and Griesser, Hans J.
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PLASMA materials processing , *PLASMA waves , *PLASMA polymerization - Abstract
Even without an additional layer of pulsed wave glycidol plasma polymer. B Outside Front Cover b : Continuous wave plasma polymerization of glycidol can directly immobilize amine containing anti-fungal biomolecules on substrates such as biomedical devices. This is facilitated by the abundance of epoxide groups on such plasma polymers to undergo ring-opening reaction. [Extracted from the article]
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- 2023
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25. Homology model of the human tRNA splicing ligase RtcB.
- Author
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Nandy, Argha, Saenz‐Méndez, Patricia, Gorman, Adrienne M., Samali, Afshin, and Eriksson, Leif A.
- Abstract
RtcB is an essential human tRNA ligase required for ligating the 2',3'-cyclic phosphate and 5'-hydroxyl termini of cleaved tRNA halves during tRNA splicing and XBP1 fragments during endoplasmic reticulum stress. Activation of XBP1 has been implicated in various human tumors including breast cancer. Here we present, for the first time, a homology model of human RtcB ( hRtcB) in complex with manganese and covalently bound GMP built from the Pyrococcus horikoshii RtcB ( bRtcB) crystal structure, PDB ID 4DWQA. The structure is analyzed in terms of stereochemical quality, folding reliability, secondary structure similarity with bRtcB, druggability of the active site binding pocket and its metal-binding microenvironment. In comparison with bRtcB, loss of a manganese-coordinating water and movement of Asn226 (Asn202 in 4DWQA) to form metal-ligand coordination, demonstrates the uniqueness of the hRtcB model. Rotation of GMP leads to the formation of an additional metal-ligand coordination (Mn-O). Umbrella sampling simulations of Mn binding in wild type and the catalytically inactive C122A mutant reveal a clear reduction of Mn binding ability in the mutant, thus explaining the loss of activity therein. Our results furthermore clearly show that the GTP binding site of the enzyme is a well-defined pocket that can be utilized as target site for in silico drug discovery. [ABSTRACT FROM AUTHOR]
- Published
- 2017
- Full Text
- View/download PDF
26. Stabilising the networked control systems involving actuation and measurement consecutive packet losses.
- Author
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Argha, Ahmadreza, Li Li, Su, Steven, and Hung Nguyen
- Subjects
- *
DISCRETE time filters , *ACTUATORS , *LINEAR matrix inequalities , *MEAN square algorithms , *CLOSED loop systems - Abstract
This study is devoted to the problem of designing a robust output-feedback discrete-time sliding mode control (ODSMC) for the networked systems involving both measuring and actuating data packet losses. Packet losses in the networked control systems (NCSs) have been modelled by utilising the probability and the characteristics of the sources and the destinations. Here, the well-known Bernoulli random binary distribution is used to model consecutive packet losses in the NCSs. In this study, first, a robust observer-based discrete-time sliding mode control is proposed for the NCSs including random packet losses. The packet losses occur in the channels from the sensors to the controller and the channels from the controller to the actuators. Then, using the notion of exponential mean square stability, the boundedness of the obtained closed-loop system is analysed with a linear matrix inequality approach. Our proposed robust ODSMC can be applied to unstable NCSs, and there is no need to stabilise the underlying system in advance. Illustrative examples are presented to show the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]
- Published
- 2016
- Full Text
- View/download PDF
27. Comparative Multifractal Detrended Fluctuation Analysis of Heavy Ion Interactions at a Few GeV to a Few Hundred GeV.
- Author
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Bhoumik, Gopa, Deb, Argha, Bhattacharyya, Swarnapratim, and Ghosh, Dipak
- Subjects
FLUCTUATIONS (Physics) ,MULTIFRACTALS ,PIONS ,SILVER bromide ,HEAVY ions - Abstract
We have studied the multifractality of pion emission process in
16 O-AgBr interactions at 2.1 AGeV and 60 AGeV,12 C-AgBr and24 Mg-AgBr interactions at 4.5 AGeV, and32 S-AgBr interactions at 200 AGeV using Multifractal Detrended Fluctuation Analysis (MFDFA) method which is capable of extracting the actual multifractal property filtering out the average trend of fluctuation. The analysis reveals that the pseudorapidity distribution of the shower particles is multifractal in nature for all the interactions; that is, pion production mechanism has inbuilt multiscale self-similarity property. We have employed MFDFA method for randomly generated events for32 S-AgBr interactions at 200 AGeV. Comparison of expt. results with those obtained from randomly generated data set reveals that the source of multifractality in our data is the presence of long range correlation. Comparing the results obtained from different interactions, it may be concluded that strength of multifractality decreases with projectile mass for the same projectile energy and for a particular projectile it increases with energy. The values of ordinary Hurst exponent suggest that there is long range correlation present in our data for all the interactions. [ABSTRACT FROM AUTHOR]- Published
- 2016
- Full Text
- View/download PDF
28. Restoration of p53/miR-34a regulatory axis decreases survival advantage and ensures Bax-dependent apoptosis of non-small cell lung carcinoma cells.
- Author
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Chakraborty, Samik, Mazumdar, Minakshi, Mukherjee, Shravanti, Bhattacharjee, Pushpak, Adhikary, Arghya, Manna, Argha, Chakraborty, Sreeparna, Khan, Poulami, Sen, Aparna, and Das, Tanya
- Subjects
LUNG cancer treatment ,DRUG resistance in cancer cells ,APOPTOSIS ,SMALL cell lung cancer ,ACETYLCYSTEINE ,DNA damage ,CANCER cells ,CAPSAICIN ,P53 protein - Abstract
Highlights: [•] We examined the apoptotic role of capsaicin on drug resistant A549 lung cancer cells. [•] Capsaicin triggers ROS generation and subsequently exerts DNA-damage. [•] DNA-damage activates p53 and p53 transactivates the pro-apoptotic protein Bax. [•] p53 activates the pro-apoptotic miR-34a to down-regulate the anti-apoptotic Bcl-2. [•] Activation of the intrinsic pathway leads to the initiation of the apoptotic cascade. [ABSTRACT FROM AUTHOR]
- Published
- 2014
- Full Text
- View/download PDF
29. Phytic Acid-Induced Inhibition of Digestive Protease and α-Amylase in Three Indian Major Carps: An in vitro Study.
- Author
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Khan, Argha and Ghosh, Koushik
- Subjects
PHYTIC acid ,AMYLASES ,PROTEOLYTIC enzymes ,INOSITOL ,ROHU ,SODIUM salts ,REGRESSION analysis - Abstract
Antinutritional effects of phytic acid (myoinositol hexaphosphate, IP6) on growth and digestibility in fish have been reported. However, specific effect of IP6 on the digestive enzymes in fish has not been addressed. In this study, inhibitory effect of synthetic IP6 (Phytic acid sodium salt, 90% purity) on the activity of the digestive protease and α-amylase in rohu, Labeo rohita; catla, Catla catla; and mrigal, Cirrhinus mrigala has been investigated in vitro. Graded levels (12.5, 25, 50, 100, 150, and 200 µg/ mL) of IP6 were added to the reaction mixtures containing enzyme extracts and substrate solution in triplicate to detect any change in enzyme activity. Results of the experiment revealed that IP6 significantly inhibit/lower activities of the digestive enzymes in a dose-dependent manner, as evident from the regression equations ( F values significant at P < 0.001 level). Apparently, irrespective of the fish species studied IP6-induced inhibition of α-amylase activity was greater than protease activity. Among the three fish species studied, C. mrigala appeared to be more sensitive to IP6 for both α-amylase and protease activity. Enzyme activity was least affected in C. catla. Results of the study might raise concern while incorporating IP6 rich plant-derived feed ingredients in aqua feed preparation. [ABSTRACT FROM AUTHOR]
- Published
- 2013
- Full Text
- View/download PDF
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