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Covalent Organic Cage Materials for CO2 Gas Adsorption and Chemosensing Applications
No full textThe rapid growth of industrial development changes the global economy and human life becomes more comfortable while on the other hand, it is releasing harmful gases into the environment. Traditional energy sources such as coal, natural gas, and oil emits drastic amounts of carbon dioxide (CO2) gas into the air during the burning process. Hence, to address the issue of controlling the CO2 gas in the environment, it is important to develop sustainable, environmentally friendly materials for capturing and storing the CO2 gas from the industrial process and is the main important research area in the present. On the other hand it is crucial to develop effective and cheap chemosensory materials for the detection of explosives (Nitroaromatics: NACs) and metal ions to control the air and water pollution that affecting the health of living organisms. Porous materials, particularly, Zeolites, COFs, activated carbons, MOFs and COCs are found to be potential as well as sustainable materials for CO2 gas adsorption and chemosensory applications. Although excellent studies have been carried out on covalent organic cage (COC) materials, still underlying mechanism of making the relation between structure and properties were least understood. In this thesis, various covalent organic cage materials have been synthesized by following lower temperature conditions (0 - 5 °C), room temperature as well as reflux method. Further, the CO2 gas adsorption and chemosensing applications of these materials are studied. In this thesis, the research work has started with simple dialdehydes like meta and para-phthalaldehyde derivatives and synthesized both imine and amine-linked covalent organic cage materials and understood their role in CO2 gas sorption applications. The unusual enhancement in CO2 gas adsorption capacity almost 40% was observed in imine-linked para-pthalaldehyde derivative (COC-PI) when the temperature was increased from 273 to 298 K at pressure 1 bar. The enhancement in CO2 gas adsorption capacity of COC-PI investigated in the direction of the flexibility of the COC molecules in the crystal supported the easy penetration of CO2 outcomes and lattice enlargement. Later in chapter four, synthesized four triazine-based imine-linked cage materials by changing the amine precursor molecule to obtain COCs with the various morphologies. The cage materials were showed a good amount of CO2 gas adsorption capacity at 273 K and 298 K with 1 bar pressure. After that the research work has extended to the synthesis of luminescent COC molecules for chemosensing applications. In this thesis, mainly focused on triphenylamine linker molecules because they showed excellent luminescent properties. By taking this advantage, synthesized the both imine and amine linked cage materials for sensing applications of explosives, metal ions, and small molecule (Chloroform, DCM, DMF, etc.) by fluorescence method. The fluorescent characteristics of the cage molecules were studied in various solvents like non-polar, polar protic, and polar aprotic. One of our cage materials (F-COC) was showed excellent enhanced emission in polystyrene (PS) doped matrix when exposed to chloroform vapours. Finally in this thesis, synthesized a novel fluorescent organic cage material for the detection of metal ions (Co2+) in the solution state with good selectivity and sensing
Phase, Morphology, And Photoluminescence Characteristics Of Europium Doped Zinc Oxide Nanopowders For Luminescent Applications
No full textAmong various inorganic oxides, zinc oxide (ZnO) demonstrates a versatile material due to its high electron mobility, better thermal and chemical stability as well as it acts as an excellent host matrix to accommodate various rare-earth ions, which resulting in different luminescent applications. Trivalent rare-earth activator such as Eu3+-doped ZnO with controllable particle size and shape has gained more interest because of its potential applications in numerous fields, including luminescence. In the past few years, Eu3+-ions in ZnO matrix have been focused for the development of a highly red-emitting Eu3+- doped ZnO phosphor with distinct and well-defined morphology. A well-defined morphology is highly required to obtain the richness of red colour and improve the photoluminescence characteristics of Eu3+-doped ZnO nanophosphor. The prime objective of this research work is to develop deep red-emitting as well as unique and well-established morphology of Eu3+-doped ZnO nanophosphors by considering three different zinc-based precursors such as zincnitrate, zinc-acetate, and zinc-chloride through precipitation route with the help of sodium borohydride. In addition, influence of precursors, calcination temperatures, secondary phases, and dopant concentrations on the photoluminescence characteristics of Eu3+-doped ZnO have been explored. Different characterization such as XRD, FTIR, Raman, DRS, Photoluminescence characteristics (asymmetric ratio, colour coordinates, colour purity, and CCT), luminescence lifetime, and quantum yield have been performed on different samples. Motivation for selecting three different zinc-based precursors has been discussed by comparing the phase and powder morphology of undoped and Eu3+-doped ZnO samples. Further, the influence of calcination temperature on the phase, morphology, and photoluminescence characteristics of 3 mol% Eu3+-doped ZnO samples has been explored. Pure phase ZnO has been observed up to 800 °C. The secondary phases, such as EuBO3 and Eu(BO2)3, were developed due to the presence of borate (BO3 and BO4) and hydroxyl (O-H/B-OH) groups. A broad transition of 5D0―› 7F2 was observed at 613 nm for all samples calcined up to 800 °C. However, it was found splitting in nature and broadened due to non-homogenous Eu3+-ions and secondary phases. Deep red emission was observed for calcined (400 °C) nitrate-based sample as well as calcined (800 °C) acetate and chloride-based samples with better colour purity. The involvement of crystalline nature of secondary phases at higher temperature does not hinder, rather moderately improve the photoluminescence characteristics. To find out the nucleation of these secondary phases and its effect on photoluminescence properties, all precursor-based samples with 5 mol % Eu3+ dopant have been analysed at 800 °C. The nucleation of secondary phases was not properly crystallized for acetate and chloride-based samples; however, it was significantly evolved for nitrate-based samples. Flower-like morphology with larger particle size may induce fewer defects and decrease the nonradiative rate, resulting in an increase in the emission intensity of acetate-based samples. It was also found that the induced secondary phases do not hamper but considerably achieved a better R/O ratio, colour coordinates, and colour purity. Furthermore, influence of dopant concentration on the phase, morphology, and photoluminescence behaviour of Eu3+-doped ZnO samples has also been explored in this research work. Distinct morphologies were formed in Eu3+-doped ZnO samples by varying the dopant concentration at different temperatures. The electric dipole transition 5D0 7F2 (613 nm) was more intense than the intensity of magnetic dipole transition 5D0 7F1 for all the samples. The emission intensity has been dependent on the dopant concentration and morphology as well as particle size. Additionally, the 3 mol% based Eu3+-doped ZnO samples calcined (at 400 °C, 600 °C, and 800 °C) exhibited the colour coordinates in red/deep red region with better colour purity as compared to the other composition (Eu3+-dopant) at different temperatures. Finally, this research work demonstrated the prototype applications by utilizing the appropriate precursor-based red-emitting Eu3+-doped ZnO sample by considering the valuable photoluminescence characteristics in the latent fingerprint detection and anti-counterfeiting. Latent fingerprint has been explored on multiple surfaces and compared with scanned fingerprints. Besides, QR-code was printed by screen printing technique and applied for anti-counterfeiting
Analytical and Numerical Solutions of Fractional Differential Equations
No full textDifferential equations are often used to explain the behaviours of real-life phenomena, and those are usually modelled by various differential equations with integer orders. Sometimes the behaviours of the physical problems may be advantageous to understand using non-integer order derivatives. In this regard, fractional calculus (FC) was introduced. Due to its hereditary and the description of memory properties, fractional-order models are more realistic and best suited in real phenomena than the integer-order models. The subject of fractional calculus has gained considerable popularity and importance during the past three decades mainly due to its validated applications in various fields. It deals with the differential and integral operators with non-integral powers. The fractional derivative has been used in various physical problems, such as frequency-dependent damping behaviour of structures, motion of a plate in a Newtonian fluid, controller for the control of dynamical systems, etc. The mathematical models in electromagnetics, rheology, viscoelasticity, electrochemistry, control theory, Brownian motion, signal and image processing, fluid dynamics, financial mathematics, and material science are well defined by fractional-order differential equations. D PI One of the most notable features of fractional derivatives is their distinctive nonlocal properties. This property allows to forecast the behaviours of phenomena by looking at their progress from the past to the present. Mostly used definitions of fractional calculus are Riemann-Liouville (RL) and Caputo fractional operators, defined by the convolution and the Power decay functions as kernel. Several researchers have extended the principles of fractional differential and integral operators to the fields related to various science and engineering problems using power-law distribution. However, when the fractional order is less than 1, this power-law distribution has no statistical significance. The fractional differential operators based on the power-law kernel meet certain classical conditions, such as index law, classical mechanical law, and singular kernels. It suggests that those operators based on the power-law kernel are physically weak and may not deal with more complex phenomena. Another problem is singularity which is challenging to explain in different natural phenomena. In order to address these problems, two important fractional derivatives, namely Caputo-Fabrizio and Atangana-Baleanu are developed. Although, these modern derivatives do not work under a power distribution, but they have nonsingular kernels. A generalized Mittag-Leffler function is used for Atangana–Baleanu derivative, and the Caputo-Fabrizio operator relies on the exponential law. Such operators have been able to model several scientific processes. Further, a new kind of operator was developed to represent two forms of fractional order, which reflect the fractional-order and the fractal dimension. The definitions of fractal-fractional differential and integral operators seem superior to the present fractional operators. One may obtain the fractal differential and integral operators when the fractional order is removed in the fractal-fractional differential and integral operators. Further, when the fractal dimension is neglected, then fractional derivatives and integrals are obtained. Hence, these fractal-fractional operators may catch more complexities than current operators as they have both exact and self-similar properties. Further, the uncertainties or randomness of the parameters and variables involved in the fractional systems are of serious concern. Investigations on a variety of fractional models are usually done by taking deterministic or crisp parameters, but the truth is quite diverse. The primary causes of the spread of uncertainty or randomness are defects in measurement, observations, environmental conditions, etc., which hinder the behaviour of models. As a matter of fact, these investigation anomalies indicate that the fractional models may not have the capability to demonstrate their normal behaviours. The influence of uncertainties becomes much more profound in the case of physical and structural problems due to the possibility of errors in the experiments or observations. In fact, several fractional physical and structural dynamics studies also support the claim of the possible inclusion of uncertainties in various parameters and initial conditions. In view of the above, the objective of this thesis has been to investigate a variety of fractional and fractal-fractional order models arise in i) wave dynamics, ii) fluid dynamics, iii) structural dynamics, iv) biology, v) economics, and vi) interpersonal relationship. In some of the problems, initial conditions and involved parameters are also considered as uncertain. Various computationally efficient analytical or numerical methods (where appropriate) are used/developed to investigate the models accordingly. Although a few methods have been developed by other researchers to analyse the above problems, but often those are problem dependent and are not efficient
Transfer of Vertically Aligned Silicon Nanowires Array Fabricated Using Metal-assisted Chemical Etching
No full textBulk silicon (Si) possesses an indirect bandgap and low surface area to volume Si ratio. Silicon nanowires (SiNWs), a derived material of Si, overcomes the drawbacks of Si and promises improvement in energy conversion (e.g., solar cell) and storage (e.g., lithium-ion battery) devices, gas sensors, medical diagnostics, drug delivery. The SiNWs-based devices have optical, electronic, and physical properties that can outperform their traditional counterparts in various ways because the SiNWs have a high surface Si area to volume ratio and unique quasi-one-dimensional electronic structure. The metal-assisted chemical etching (MACE) produces the SiNWs using an electrolyte composed of hydrofluoric acid (HF), hydrogen peroxide (H2O2), and a metal salt. Effect of MACE parameters, such as H2O2 concentration (i.e., 0.1 M to 0.3 M), etching time (i.e., 30 minutes to 60 minutes), Si wafer resistivity, HF concentration (i.e., from 0.48M to 9.6M), and etching temperature (i.e., 25℃ to 85℃), on the morphological characteristics (especially length) of SiNWs are compared and thoroughly discussed. Additionally, MACE parameters on the length of SiNWs using Si and porous Si substrates are discussed. The cross-sectional view of FESEM confirms the variation of the length of SiNWs for the variation of MACE parameters. The Raman line broadening and peak shift are due to FANTUM (FANo + quanTUM) effect (i.e., Fano effect and quantum confinement effect), amorphous content (⁓15-20%), and stress in the SiNWs. The tensile strain remains ⁓0.25%, and the crystallinity volume fraction of ⁓80% provides a range of MACE parameter variation to fabricate the SiNWs according to various device applications. The SiNWs, however, need to be transferred to a better substrate for additional flexibility, lesser cost, and transparency compared to Si substrate resulting in improved device functionality. This part explores, optimizes, and compares two techniques to transfer SiNWs to glass: the gluing technique and the two-step electro-assisted technique. The objective is to preserve the length of nanowires on a larger transfer area. Gluing technique spin-coats an adhesive layer made of polyvinyl acetate (PVAc) and methanol solution. The gluing method studies the effect of variation in MACE time on the percentage transfer ratio for the optimized PVAc layer. The electro-assisted technique detaches the vertically aligned SiNWs array with the aid of a sacrificial porous Si layer for variation in anodization time. The yield of the gluing and electro-assisted technique is optimized for MACE and anodization time. The transferred layer is characterized by various parameters, such as the percentage transferred length (%TRL), total transfer area, crystallinity, strain, and morphology of the SiNWs. For optimized values, the gluing method achieved %TRL = 68.2% while transferring 0.95 cm2 of the film area, whereas the electro-assisted technique achieves %TRL = 7.4% for an area of 19 cm2
Deciphering the Aggregation Behaviour of CHAPS, a Steroidal Zwitterionic Surfactant, and its Interaction with Biologically Important Molecules and Macromolecules: A Spectroscopic Approach
No full textSteroidal biosurfactants, particularly bile salts have been the centre of attraction among the researchers due to their peculiar structure, aggregation pattern and a wide range of applications. The unconventional amphiphilic nature of bile salts is responsible for their surface-active property and thus responsible for the solubilization and absorption of cholesterol, lipids, dietary fats, and hydrophobic drugs. Bile salts have also been largely investigated as building blocks for the construction of supramolecular aggregates for drug delivery purposes. Moreover, the applications of biosurfactants in the field of proteomics have increased exponentially in recent years. Though bile salts provide alternatives to conventional surfactants by avoiding undesirable aggregations in proteins, yet their anionic nature can alter the native charge properties of proteins. In this regard, looking at the advantages of zwitterionic surfactants over the charged ones due to their mildness and neutral character, CHAPS (3-[(3-cholamidopropyl)-dimethylamino]-1-propanesulfonate), the zwitterionic derivative of cholic acid was conceptualized. CHAPS was originally synthesized in the 1980s, for the purification of membrane proteins considering its nondenaturing and disaggregating properties. Owing to its unique structure having a rigid steroid and a long zwitterionic tail, the aggregation behaviour of CHAPS cannot be explained through conventional micellization models. Hence, the micellization process of CHAPS has garnered ample curiosity; however, compared to bile salts, surface chemical research on CHAPS is only limited and it still remains an open question to be addressed. The extensive use of CHAPS in biochemical research necessitates a proper understanding of its aggregation behaviour at a molecular level. CHAPS being an electrically neutral surfactant over a large pH range can offer a better alternative to the bile salt-based delivery systems. Further, the successful applications of CHAPS as a drug carrier requires a comprehensive understanding on its interaction with the carrier proteins like serum albumins. With this motivation, the objective of the present thesis is to investigate the aggregation behaviour of CHAPS and to understand its interaction with certain biologically important small molecules and macromolecules. Chapter 1 introduces different types of conventional surfactants, their micellization pattern and applications. It highlights the importance of biosurfactants particularly the bile salts, the unique class of steroidal surfactants; their structure, amphiphilicity, aggregation patterns and applications have also been discussed. Owing to the widespread applications of bile salts, various derivatives of the bile salt variants with enhanced functionality have been synthesized, which have also been discussed. The present chapter also introduces CHAPS, the zwitterionic derivative of cholic acid. The surge in the application of zwitterionic moieties in the field of proteomics and pharmaceutics necessitates the understanding of the aggregation behaviour of CHAPS. Due to its biodegradable, biocompatible nature, and mild character, it can be a better alternative to the bile salts in the field of drug delivery. Hence an in-depth knowledge is required regarding the aggregation behaviour of this unique surfactant and its interaction with drugs and biological macromolecules like proteins. The present chapter also provides a summary of the literature regarding the aggregation behaviour and applications of CHAPS. Keeping the knowledge gap in mind the objectives of the present thesis have been articulated. Chapter 2 offers the information on the materials used and the methodologies employed for the studies. Chapter 3 deals with the understanding of the aggregation of CHAPS in aqueous solution using the modulation in the photophysical properties of Coumarin 1 (C1) and Coumarin 466 (C466). These two 7-aminocoumarins offer a large scope for research in both biological and chemical sciences due to the efficient intra-molecular charge transfer (ICT) process upon photoexcitation, which makes them highly sensitive to the local environment in terms of the polarity, viscosity, pH, and hydrogen bonding. They offer various fluorescence parameters such as emission intensity (quantum yield), energy, anisotropy, and lifetime to get insight into the aggregation behaviour and properties of surfactants. The present work contributes significantly to the general understanding of the microenvironment provided by the surfactant aggregates to the guest molecules. This chapter comprises of two parts: Part I focuses on the investigation of the aggregation behaviour of CHAPS under different physiological conditions by employing C1 as a fluorescent molecular reporter. Modulation in the photophysics of C1 has been utilized for making structural comparisons and in determining local structure variation of this unconventional surfactant and the cholates, its structural bile salt analogues. CHAPS exhibits a relatively speedier self-assembly and faster growth with slightly critical and cooperative micellization unlike the cholates, which is known to aggregate in a non-critical self-association manner i.e., the intermolecular interactions are less cooperative and occur in a progressive fashion over a
wide concentration range. The effect of salt concentration and temperature on the self-assembly process and micellar properties of CHAPS has been investigated. The effect of sodium cholate (NaC) and sodium taurocholate (NaTC) as co-surfactants has also been monitored to understand the formation of mixed micelles. The various photophysical parameters reveal that CHAPS micelles offer a relatively more hydrophobic, compact, and non-polar microenvironment to C1 as compared to the cholates, indicating efficient packing of CHAPS molecules in the micelles. Part II deals with the studies on the effect of CHAPS and different bile salts namely sodium deoxycholate (NaDC), sodium taurodeoxycholate (NaTDC), NaC, and NaTC, on the photophysical behaviour of C466 to understand the role of surfactants’ structure on the aggregation behaviour and micellar properties. This part also involves a comparative study on the aggregation behaviour and properties of these structurally different steroidal surfactants using C466 as a fluorescent molecular reporter. The photophysical properties of C466 have been found to be very sensitive towards the aggregation of CHAPS and the bile salts variants and their self-association has been reflected in the different fluorescence parameters. Though CHAPS shares maximum homology with the cholates, yet its aggregation behaviour is more inclined towards that of the deoxycholates and follows Small’s model of aggregation with three distinct stages: (i) pre-micellar range, (ii) micellization range, and (iii) stable primary micelles. The micellar properties such as hydrophobicity and rigidity of CHAPS aggregates are almost comparable to that of the deoxycholates and are significantly higher than the cholates. CHAPS has also been observed to form relatively larger micelles as compared to the bile salts. This chapter suggests a superior nature of CHAPS aggregates and better shielding of guest molecules inside the aggregates due to which, CHAPS based colloids could be promising candidates as potential drug delivery systems. Chapter 4 evaluates and compares CHAPS and the four bile salts namely NaDC, NaTDC, NaC, and NaTC, as potential drug carriers for curcumin under different physiological conditions to address the two major challenges that limit the practical applications of curcumin i.e., its poor aqueous solubility and lack of stability leading to low bioavailability. Various fluorescence parameters such as emission intensity, emission energy, fluorescence anisotropy, quantum yield, and fluorescence lifetime of curcumin are compared in the presence of these steroidal surfactants to get a comprehensive idea about the microenvironment of curcumin in these aggregates. The extent of increase in the fluorescence parameters of curcumin has been observed to be considerably higher in the presence of CHAPS and the two conjugated bile salts NaTDC and NaTC, in comparison to that of the unconjugated bile salts i.e., NaDC and NaC. The presence of the basic carboxylate end group in the side chain of NaDC and NaC introduces an additional non-radiative decay pathway due to the possibility of excited-state proton transfer (ESPT) between curcumin and the carboxylate end group. In this chapter, the concentration of maximum solubilized curcumin inside the aggregates of CHAPS and the bile salts has also been estimated, and CHAPS is found to solubilize the maximum amount of curcumin as compared to the bile salts. The effect of physiological conditions such as pH, ionic strength, and temperature on the stability of curcumin in these biosurfactants has been studied and among these steroidal surfactants, CHAPS has been found to offer better stability to curcumin under all conditions. The biological activity of curcumin loaded micelles has also been evaluated in the presence of these surfactants. The present study reveals that CHAPS based colloids are promising candidates as potential delivery systems for biomedical applications. Chapter 5 deals with the effect of CHAPS on the structure and function of the two widely studied serum albumins BSA (Bovine serum albumin) and HSA (Human serum albumin). The two proteins, BSA and HSA with two and one tryptophan residues respectively, provide an opportunity for an interesting comparison of tryptophan fluorescence behaviour on interaction with CHAPS. To understand the effect of CHAPS on protein conformation, different spectroscopic techniques have been utilized along with molecular docking. From the fluorescence studies, a significant difference has been observed in the fluorescence parameters of the two homologous proteins in the presence of CHAPS. The different fluorescence parameters of BSA exhibit considerably larger changes than those of HSA, which can probably be due to the involvement of the additional tryptophan in the subdomain IB i.e., tryptophan 134 of BSA in interaction process. From the binding analysis, a sequential interaction between CHAPS and BSA occurring in three different stages depending on the concentrations of CHAPS has been identified. Stage I: up to 1 mM concentration, CHAPS binds at the highly specific and energetic sites of the serum protein; Stage II: In the concentration range of 18 mM, CHAPS interacts cooperatively with BSA; Stage III: in the concentration range of 832 mM of CHAPS, a plateau in tryptophan fluorescence is observed, which indicates that the protein is either almost saturated with CHAPS and further binding may not be consequential or the binding of CHAPS happens at the low-affinity sites in such a manner that the microenvironment of tryptophan residues remains unaffected. Moreover, in this concentration range, self-aggregation of CHAPS has already commenced and there is possible adsorption of CHAPS micelles on the surface of BSA. Unlike BSA-CHAPS system, a bimodal variation is observed in different fluorescence parameters of HSA in the studied concentration range of CHAPS and the changes are significantly smaller in comparison to that of BSA. Studies are also carried out in the presence of two well-known site markers, Warfarin, and Ibuprofen, to perceive the effect of CHAPS on the two principal drug binding sites. The effect of CHAPS on the secondary structure of the proteins has also been studied from the far-UV CD profiles of the two serum albumins. A comparison has been carried out between CHAPS and its bile salt analogues NaC and NaTC in terms of their interaction with the two serum albumins in order to understand the role of the surfactants’ structure on the interaction process. The present study reveals the mildness of CHAPS towards these drug-binding proteins in comparison to its bile salt analogues, which makes CHAPS a better alternative to the bile salts as a drug delivery. Chapter 6 provides a summary of the important findings in the present work and also discusses the future scope
A Comprehensive Study on the Microstructure, Texture, and Mechanical Properties of Mg and its Alloys during Grain Growth
No full textIn the present study, the microstructure, and texture evolution during grain growth of pure Mg and its alloys, such as AM30 (Mg 3 wt.% Al 0.3 wt.% Mn) and AME300 (Mg 3 wt.% Al 0.3 wt.% Mn 0.2 wt.% Ce) have been investigated. The objective of the present study has also been to establish the correlation between microstructure, texture, and mechanical properties in these materials. Hot rolled pure Mg samples were subjected to isothermal annealing at temperatures of 150, 200, 300 and 400 °C for different soaking times ranging from 1 min to 1440 min (i.e., from 1 min to 1 day). A grain growth exponent of n = 13 was observed and the activation energy for grain growth kinetics was found to be 95.6 kJmol. Further, broadening of the normalized grain size distributions, indicating abnormal grain growth, was also observed at all temperatures of annealing. The samples had dominant basal texture before and after annealing. However, alleviation of basal texture was observed in the samples after annealing up to a temperature of 300 °C. Annealing further at a temperature of 400 C formed a strong basal texture in the samples. The mobility of high angle grain boundaries, which is proportional to correlated misorientation distribution, was observed to be responsible for texture strengthening of the material. The boundary mobility changes during grain growth led to the growth of either small or large grains. It was further observed that the growth of small grains caused the formation of basal fiber and large grains led to the weakening of basal texture. AM30 alloy samples were subjected to annealing at temperatures ranging from 200 to 450 °C for different time periods of 1 1440 min respectively. The effects of both annealing temperature, T, and time, t, on the overall grain growth process have been evaluated. A grain growth exponent of n = 9 and activation energy of Q = 105.6 kJmol were observed. It was also observed that the presence of precipitates, such as Mg17 Al12, Al11 Mn4, and Al8 Mn5, in the alloy significantly affect the grain growth kinetics during annealing. Both the volume fraction and the average size of the precipitates decreased as a function of annealing temperature/time. The precipitates were further appeared to be dissolved at a temperature of 450 °C of annealing and this led to the abnormal grain growth of the samples during annealing. The effects of solute drag and dislocation density on the grain growth behavior were found to be insignificant during annealing, as estimated through a mesoscale model based on cellular automata. The strong basal texture in the starting material was observed to be weakened up to 480 min of annealing. However, annealing for 1440 min regained the basal texture which may be attributed due to the abnormal grain growth in the samples. AME300 alloy samples were subjected to annealing at temperatures ranging from 200 to 450 °C for different periods to evaluate the microstructure and texture developments in the alloy. The grain growth exponent of n = 13 and the activation energy for grain growth, Q = 75 kJmol were observed. A large number of precipitates were observed in the samples. They were found to be Mg17 Al12, Al8 Mn5, Al11 Mn4, Al11 Ce3, Al3Ce, Al4 Ce, Mg17 Ce2, Al10 Mn7 Ce2, Mg2 Ce, Mg3 Ce, and Mg12 Ce, as confirmed by electron probe microanalysis (EPMA) and X-ray Diffraction (XRD). The precipitates were further found to be dissolved or disappeared with an increase in the temperature of annealing. As a result, the grain boundary mobility was enhanced during annealing at high temperatures and increased the grain growth of the samples. The initial basal texture in the alloy was observed to be tilted (by ~ 30°) towards the transverse direction of the samples during annealing. Such a texture weakening in the alloy during annealing was attributed to the nucleation and growth of new grains formed in the deformed zone surrounding the precipitates. The correlation between microstructures, textures, and mechanical properties of pure Mg, AM30 and AME300 alloys was further investigated in the present study. The results revealed that the ductility of pure Mg is dependent on the reduction in basal texture intensity. However, its tensile strength is dependent on the average grain sizes of the samples. The same has also been observed in AM30 and AME300 alloys after annealing at higher temperatures of 400 and 450 °C. However, annealing at lower temperatures (i.e., 200 and 300 °C) did not show any correlation between grain size, texture, and mechanical properties of the alloys. This has been attributed to the presence of precipitates in the alloys. It was further found that AME300 alloy had the best combination of tensile strength and ductility compared to AM30 and pure Mg after annealing
Development of Membrane Filtration Process Protocol for Reduction of Astringency and Retention of Bioactive Compounds in Cashew Apple (Anacardium occidentale L.) Juice
No full textIndia is one of the largest producers of cashew fruits in the world. The fruit consists of cashew apple and the nut. The cashew nut has high commercial value. However, despite a high concentration of bioactive compounds, the cashew apple is still an underutilized by- product of the cashew processing industry. The cashew apple contains a high amount of tannin that gives an astringent taste and has low consumer acceptability. The traditional method of removing tannin and further processing of cashew apple juice involves thermal treatment, which results in the loss of many bioactive compounds, including polyphenols and ascorbic acid. The heat treatment changes the colour and aroma of the juice. It also imparts a 'cooked flavour' to the juice and the value-added products. Hence, it is necessary to develop a non-thermal process protocol to reduce the astringency and retention of the bioactive compounds in the juice. For this purpose, different properties of the cashew apple fruit have been determined. The result showed that this fruit has a high moisture content of 85.62% (w.b.), which is the main reason for its high softness and perishability. The fruit resembled an oblate-ellipsoid shape (sphericity: 0.85) with an average dimension of length (50.34 mm), width (42.78 mm), and thickness (36.08 mm). The pH, total sugar, phenolic content, protein and ascorbic acid of this yellowish colour fruit were 4.37, 10.57%, 365.30 mg/100 g GAE, 1.13% and 218.93 mg/100 g, respectively. Later, juice from the cashew apple was extracted using the enzymatic hydrolysis technique. The effect of pectinase, cellulase, and tannase enzymes on the yield and physicochemical quality of juice was studied to find the most suitable enzyme for enzyme-assisted juice extraction. After considering the optimum processing condition and juice quality, the cellulase enzyme with an optimum incubation time of 27 min, incubation temperature of 34 ºC, and cellulose concentration of 0.091% was the best enzyme for cashew apple juice extraction. Subsequently, technology has been developed with optimum process conditions for clarifying cashew apple juice using centrifugation, microfiltration, and ultrafiltration. At the optimum conditions of 7532 rpm rotational speed and 52.6 min time, the centrifugation removed large suspended particles and improved the clarity of the juice. Similarly, at the optimum conditions of microfiltration (0.2 μm membrane pore size and 138 kPa transmembrane pressure) and ultrafiltration (30 kDa molecular weight cut-off and 138 kPa transmembrane pressure), the steady-state flux obtained was 74.87 L/m2h and 16.55 L/m2h, respectively. The membrane clarification removed all microorganisms, and reduced turbidity, viscosity and total tannin content of the juice. It also increased the colour intensity, improved the clarity, and preserved the ascorbic acid content of the juice. The clarified juice was later concentrated using a reverse osmosis membrane. The optimum process condition for concentration was achieved as 30 bar transmembrane pressure with a steady-state flux of 25.79 L/m2h. The juice concentrated at this condition had a 97% reduction in turbidity, 87% reduction in total tannin, 15% reduction in viscosity, 94% reduction in colour intensity, and 97% increase in clarity. The concentrated juice retained 89% of the ascorbic acid content. A storage study of the concentrated juice at 4 ºC in glass bottles was taken up. The analyzed quality parameters, including the sensory and microbial qualities, confirmed that the juice concentrate could be stored for 12 weeks. In addition, the cost analysis revealed that the manufacturing cost of the developed cashew apple concentrate is ₹1050.31 per L, which is comparable to the current market price of the commercial concentrated juices. The results suggest that the membrane filtration process is suitable for developing astringent-free, clarified cashew apple concentrate and could be scaled up for industrial use
Performance Evaluation of Solar PV System for Power Generation in Surface Mines
No full textThis thesis presents a study of Solar Photo-Voltaic (PV) energy system from the environmental impact analysis and its effects point of view and the enhancement factors affecting the Solar Photovoltaic (PV) module by the tilt angles variation on power output of MPPT and dust accumulation on solar PV panel. For the energy utilization in mining industry this thesis proposes a hybrid technique to recover the efficiency of solar photovoltaic (PV) energy system from the environmental impacts and the approach to improve the performance of photovoltaic (PV) system and track the maximum power from the system. For this, the proposed Hybrid techniques followed is the combination of sparrow search algorithm (SSA) and gradient boosting decision tree; thus, it is named as SSA-GBDT method and the combination of Tunicate Swarm Algorithm (TSA) and Radial Basis Function Neural Network (RBFNN), hence it is called TSA-RBFNN. The purpose of the proposed techniques is to improve the efficiency of solar PV energy system and maximization of power removal from PV arrays and to “achieve the best output from solar system by tilt angles variations and environmental effects, like dust accumulation, water drops, partial shading, and maximum power point tracking (MPPT) of the solar PV panel. Here, tilt angle and orientation angles are important factor for obtaining the maximal power of the photovoltaic system with consequently the power fed to load in the PV system. The voltage, current, and PV system power are used to analyze the effect of any particle size and any weight of dust for the performance of PV modules. An Experimental study and a specific investigation on dust deposition effect on the solar photovoltaic (PV) panel, its power loss and overall efficiency of the solar panel are made. The Scanning Electron Microscope (SEM) analysis is carried out for the collected dust samples from the mines, and obtained images are also analyzed. A specific investigation on dust samples like Iron ore, Coal, Limestone, Sandstone of different weights, and three different irradiation levels of 500,700,900W/m2 is done and the following data collected. In this study, measuring of voltage current, power in the solar photovoltaic (PV) panel is also done. According to the accumulation of dust particles on the solar panel the minimum power of the solar panel is observed for deposition of coal dust on the solar PV panel and the maximum power of the solar PV panel is observed for deposition of iron ore dust on the solar PV module. The performance of PV under normal condition, dust accumulation condition, water drops condition and partial shading conditions are the considered cases. In these cases, photovoltaic irradiance and temperature, PV current, voltage and generated power, active and reactive power, grid current and voltage, inverter power are also evaluated. In addition, the determination of cleaning frequency is also developed for dirty PV modules depending upon the dust deposition velocity, then the correlation among deposited dust density including power performance of photovoltaic module. Then, the proposed techniques are implemented on the MATLAB/Simulink platform and the performance is compared with existing techniques. Furthermore, optimum solutions for proposed technique, the current, voltage, power are also analyzed
Development of IoT-based Wireless Sensor System for Slope Stability Monitoring in Open-cast mines
No full textSlope stability in open-cast mines is one of the dominant topics of geological interest. The slopes of open-cast mines need to be monitored consistently so that one has prior knowledge of any slope failure. An early-warning system is necessary for the open-cast mines so that loss of human lives and property is prevented. Both Internet of things (IoT) and wireless sensor system (WSS) have emerged as an aid for real-time monitoring systems. Using WSS, one can monitor the concrete environmental structures by sensing their changes whereas IoT communicates this sensed data from the real-time applications to the application for additional analysis. In real-time monitoring scenarios, power consumption and long-range coverage are of high concern. That is the reason, technologies like WSS, Long Range (LoRa), and IoT have to be collaboratively used to build a slope monitoring system. To monitor slope failure first, slope deformation has to be tracked so that a prediction can be made based on the pattern and generate an alarm that failure is to happen. A coaxial cable along with Time-domain reflectometry (TDR) is used to measure slope deformation based on the reflection principle. This TDR sensor with coaxial cable is set up in slope areas that are more susceptible to failure. Test through open-cast model experiment and shear testing experiment was performed with two types of coaxial cables calibrated with TDR – RG-6 and RG-213 out of which RG-6 was found to be most suitable. Both coaxial cable and TDR are present at the sensing end of the WSS. LoRa acts as a framework for IoT. Since mines are situated in extreme environmental conditions, it is not practical for the mine personnel to be physically present at the mine site to monitor the slopes. The existing slope monitoring systems do not provide the flexibility to monitor slopes independently. Slope monitoring is an exhaustive and risky task for the miners and mine officials if it has to be done physically since any time loss of life may happen due to slope failure. By incorporating LoRa, a wide area is covered and with WSS and IoT slope can be continuously monitored. LoRa operates on various SF out of which SF7 is chosen for this work. This is because, with the increase of SF value, the coverage distance also increases but the signal fades away. The field test results of LoRa with SF7 in open space or non-line of sight (NLoS) areas offered coverage of 2.3 km whereas in the mine site coverage of 1.7 km was obtained without any packet loss. This proved helpful for this research work in open-cast mines because the distance from the mine slope to the mine office is around 1 km. The data which comes from the real-time slope monitoring system has to be processed somewhere so that an early warning can be generated hinting at the occurrence of slope failure. For this purpose, fog computing comes into the picture. Instead of depending on the cloud for every computation, the sensed or monitored data is computed in fog and the outcome is provided to the user. Since the mine environment is uncertain, slope failure can happen within a fraction of a second. For such a scenario, latency-free processing, and delay-free data transmission is required which is offered by fog computing. Besides, it also brings the cloud functionalities nearer to the sensing layer which gives the user the flexibility and eases to use cloud services without any delay. With these motivations and aims, developed and implemented a novel real-time slope monitoring system in this research work is known as Fog-IoT Slope Monitoring (FIoTSM) system to monitor slopes and generate warnings of its failure
Deciphering the Role of MTP18 in Mitophagy and its Targeting for Apoptosis Induction in Oral Squamous Cell Carcinoma
No full textMTP18, a novel human nuclear-encoded protein with a molecular weight of 18 kDa, localized to the inner mitochondrial membrane, has a vital role in maintaining mitochondrial morphology and cell survival. In this study, we have investigated the role of MTP18 in mitophagy activation to clear dysfunctional mitochondria and its physiological significance in cell survival of oral squamous cell carcinoma (OSCC). Our study identified MTP18 as a mitophagy receptor to target damaged mitochondria into the autophagosomes for elimination and degradation. Interestingly, MTP18 interacts with LC3 through its LC3 interacting region (LIR) to induce mitochondrial autophagy, and mutation in the LIR motif inhibits this interaction leading to suppress mitophagy. Further, we established that Parkin-mediated proteasomal degradation of the outer mitochondrial membrane is essential for the interaction of LC3 and MTP18 to successful mitophagy. In this setting, we conclude MTP18 provides a survival advantage to the OSCC in exposure to cellular stress, and inhibition of MTP18-dependent mitophagy effectively reduces cell growth and induces cell death in OSCC. In addition, we have identified a novel inhibitor for MTP18 named S28, which promotes stress-induced mitochondrial hyperfusion (SIMH) in OSCC by limiting MTP18 mediated mitochondrial fission. Mechanistically, S28-mediated SIMH triggers loss of mitochondrial membrane potential, leading to the generation of mitochondrial superoxide followed by apoptosis. Intriguingly, it showed that S28-stimulated mitochondrial superoxide enhances lysosomal membrane permeabilization, resulting in decreased lysosomal pH, which entertained impairment of autophagosome-lysosome fusion. Furthermore, S28 in the combination of FDA-approved anticancer drugs inhibits cell viability and displays enhanced apoptosis suggesting the anticancer drugs exhibit better therapeutic response in MTP18 inhibition conditions in OSCC. In addition, our study unraveled that Abrus agglutinin (AGG), a plant lectin, promotes autophagy through inhibition in the expression of MTP18 in OSCC. We found that AGG-induced autophagy triggers loss of p62 and Nrf2 expression in OSCC. It showed that Nrf2 expression is restored in the presence of 3-methyladenine and Bafilomycin-A1, establishing the role of autophagy in the modulation of Nrf2 through p62. Moreover, we found that Nrf2 inhibition by AGG results in ROS accumulation followed by apoptosis and subsequently inhibits tumor growth in DMBA-induced oral carcinogenesis. Hence, targeting MTP18 may serve as a potential therapeutic for oral cancer treatment