National Institute of Technology Rourkela

Not a member yet
    7542 research outputs found

    Analytical and Numerical Solutions of Fractional Differential Equations

    No full text
    Differential 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

    On the Development of Improved Mammogram Detection System using Machine Learning Approaches

    No full text
    In recent years, breast cancer has become one of the most prevalent causes of death among women. Once the malignant cells are developed in the breast, it spreads to different body organs very quickly. Detection at the early stages and diagnosis is the only way to prevent mortality. Mammography, a noninvasive, non-radioactive imaging technique, has been widely used in diagnosing breast tissue abnormalities. Manual diagnosis based on visual inspection of mammograms is time-consuming, inconvenient, and necessitates skilled supervision. Thus, automated detection using modern imaging, machine learning, and deep learning approaches has become vital for quick, reliable, and correct conclusions. In the last decade, the development of automated computer-aided diagnosis/detection (CAD) models has progressed remarkably. However, there is still an opportunity for improvement in terms of automation, usability, and accuracy. This dissertation is aimed at designing automated CAD frameworks that will help radiologists validate their clinical diagnoses. This research primarily proposes various feature extraction techniques and classifiers for detecting breast tumors in mammography images. The first contribution consists of three frameworks with various feature extraction techniques like discrete wavelet transform (DWT), lifting wavelet transform (LWT), and fast curvelet transforms (FCT). For all frameworks, a combined feature reduction technique such as principal component analysis (PCA) and linear discriminant analysis (LDA) has been employed for feature vector computation. Finally, a simple and flexible learning scheme called the extreme learning algorithm (ELM), back-propagation neural network, k-nearest neighbors, and support vector machine have been used separately to obtain the classification accuracy. This contribution describes an empirical analysis of ELM with other classifiers. In the second contribution, a set of innovative hybrid classification systems proposes to reduce the bottleneck caused by extreme learning machines and contemporary meta-heuristic optimization techniques to classify mammogram images. The optimization techniques have been utilized to obtain the hidden node parameters of the ELM. Here, the same feature reduction technique is used as in the previous contribution. Different hybrid classification systems have examined the three handcrafted feature extraction techniques: DWT, LWT, and FCT. The third contribution is about designing a framework based on non-handcrafted features. Here, deep learning algorithms are used to solve the challenge of manually selecting appropriate features for mammogram classification. The different deep CNN models such as VGG-16, ResNet-50, and Inception-V3 have been utilized for feature extraction, and the same feature reduction method is applied as previous frameworks. Finally, various hybrid classifiers are used for the classification task. The final contribution involves designing a customized CNN model for multiclass mammogram images. This model is designed to extract high-level features from mammogram images automatically. End-to-end learning is facilitated by the proposed deep architectures, which aid in generating promising results. To evaluate the efficiency of each suggested CAD framework, a significant number of experiments have been conducted individually utilizing binary and multiclass mammogram classification. Various performance measurements have been used to compare the suggested CAD frameworks with existing standard techniques. Experimental results demonstrate that the proposed methodologies are superior to existing binary and multiclass breast cancer detection models. The customized CNN model removes manual handcrafted feature extraction issues and avoids feature reduction tasks. As a result, the proposed CAD frameworks are faster and can be used as an enhanced tool by clinicians to validate their diagnoses

    Microstructural Correlation of Creep, Tensile and Corrosion Behaviour of AZ91 Magnesium Alloy with Bi, Ca and Sr Additions

    No full text
    In the present investigation, five new alloys AZ91+1.0Ca (AZX911), AZ91+0.5Bi (AZB910), AZ91+1.0Ca+0.5Bi (AZXB9110), AZ91+1.0Ca+1.0Bi (AZXB9111), AZ91+2.0Ca+0.5Bi (AZXB9120) (wt.%) have been fabricated by squeeze-cast. The first part of the thesis investigates the influence of combined additions of Ca and Bi on the microstructure, creep, tensile, and corrosion behaviour of the squeeze-cast AZ91 alloy. The same is also studied on the AZ91 alloy with and without single additions of Ca and Bi for comparison. Another three new alloys AZ91+0.5Bi+0.25Sr, AZ91+0.5Bi+0.5Sr, AZ91+1.0Bi+0.5Sr (wt.%) have also been fabricated by squeeze-cast. The second part of the thesis investigates the influence of combined additions of Bi and Sr on the microstructure and creep behaviour of the AZ91 alloy. The creep behaviour of all the alloys is evaluated using impression creep tests in the temperature and stress ranges of 423 to 523 K and 300 to 480 MPa, respectively. The tensile tests of the Ca and Bi added AZ91 alloys are performed at 298, 423, and 473 K with a strain rate of 8.33×10-5 s-1. The corrosion behaviour of the Ca and Bi added AZ91 alloys is studied by immersion, hydrogen evolution, and electrochemical corrosion tests at 0.5 wt.% NaCl solution (pH 7) at room temperature. Both the single and mixed contents of Ca and Bi in the AZ91 alloy refine the grain size of α-Mg and reduce the volume fraction of the β-Mg17Al12 phase considerably. The effect is more noticeable in combined additions than in individual additions. The reticular-shaped Al2Ca and needle-shaped Mg3Bi2 phases additionally form with the α-Mg and β-Mg17Al12 phases because of the sole Ca and Bi additions in the AZ91 alloy. The Al2Ca and Bi3Ca5 phases are formed when Ca and Bi are added together, suppressing the Mg3Bi2 phase formation. The modified AZ91-based alloys containing Ca and/or Bi exhibit improved creep behaviour than the AZ91 alloy at all the stress and temperature levels tested. The individual additions of the elements in the AZ91 alloy show a higher creep rate than the combined additions. The individual Ca addition is better than Bi addition for resisting creep deformation in the AZ91 alloy as the Al2Ca phase in the AZX911 alloy has superior thermal stability compared to that of the Mg3Bi2 phase in the AZB910 alloy. The AZXB9120 exhibits the best creep performance owing to the lower volume fraction of the β-Mg17Al12 phase and the existence of a larger quantity of thermally stable Al2Ca and Bi3Ca5 phases. The values of stress exponents and activation energies conclude that the dominant creep mechanism for all the alloys is dislocation climb aided by pipe diffusion. The microstructural investigation following creep indicates that the β-Mg17Al12 phase is broken into small pieces. In contrast, the thermally stable Al2Ca, Mg3Bi2, and Bi3Ca5 phases preserve their continuity, which results in piled-up dislocations and tangling of dislocations in the interior of the α-Mg grains that leads to the improved resistance to creep deformation of the modified AZ91 alloys. The values of yield strength (YS) are higher, and ductility is lower of all the modified alloys. The ultimate tensile strength (UTS) of the modified AZ91 alloys is lower except at 473 K. The UTS values decrease with an increase in test temperature for all the alloys. The improved YS of the modified alloys is owing to reduced grain size. The brittle Mg3Bi2, Al2Ca, and Bi3Ca5 phases in the modified alloys reduce their UTS and ductility. The transgranular cleavage fracture at 298 K changes to quasi-cleavage fracture at 473 K. Several dislocations piled up around the β-Mg17Al12 and Al2Ca phases are seen. All the modified alloys exhibit better corrosion resistance than the base AZ91 alloy. The AZX911 alloy unveils better corrosion resistance than the AZB910 alloy owing to the Al2Ca phase formation. The combined Ca and Bi added AZ91 alloys acquire better corrosion resistance than the individual Ca or Bi added AZ91 alloys. The AZXB9120 and AZXB9111 alloys exhibit the lowest and the highest corrosion rates among the combined additions. The combined Bi and Sr additions form the Al4Sr and Sr2Bi phases besides the α-Mg and β-Mg17Al12 phases and improve the creep resistance of the AZ91 alloy. The AZ91+1.0Bi+0.5Sr alloy reveals the best creep resistance among the alloys. The stress exponent and activation energy values of all the alloys confirm the pipe diffusion-controlled dislocation creep as the governing creep mechanism. The post creep microstructural study reveals several dislocations pile-ups around the Al4Sr and Sr2Bi phases resulting in improved creep resistance of the modified AZ91 alloys. To conclude, the additions of Ca and/or Bi improve the creep, tensile, and corrosion behaviour of the squeeze-cast AZ91 alloy. The effect is more significant with combined additions. The combined Bi and Sr additions also improve the creep behaviour of the AZ91 alloy. Therefore, the additions of Ca, Bi, and Sr to the AZ91 alloy are beneficial

    Covalent Organic Cage Materials for CO2 Gas Adsorption and Chemosensing Applications

    No full text
    The 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

    Studies on Dynamics of Wind Turbine Rotor Blade System

    No full text
    The use of wind turbines offers a pollution-free, sustainable, and economically workable alternative to the provision of energy. Though substantial progress has already been made in the area of the wind industry, the performances of small wind harvesters can still be enhanced. It is essential to conduct additional research on the aerodynamics of wind turbines and their interaction with fluid flow. It is thus necessary to know various methods that can enhance the potential of a wind turbine. Over the last three decades, the size of the wind turbine blades has increased significantly. This growing size along with the associated mechanical behaviour, results in the generation of aeroelastic effects caused by the fluid-structure interaction (FSI). Effective FSI modelling of rotor blades is highly essential for the research of large-scale wind turbines. These large-scale wind turbines, on the other hand, are incapable of powering small devices, especially in remote locations where such small devices are used to monitor temperature, traffic, cyber security, etc. A small-scale energy harvester that can be used effectively in low-power devices must be investigated. Accommodating the aforementioned statements, this research work has implemented a numerical technique to enhance wind turbine output using different modifications and configurations. The fluid-structure interaction (FSI) analysis is also performed for wind turbine blades using composite materials. Furthermore, an attempt has been made to examine the functioning of a small lab-scaled wind turbine experimentally inside the wind tunnel. To execute these techniques, the fluent solver has been used with the help of the finite-volume method. In this work, four different types of airfoils were investigated, i.e., NREL (National Renewable Energy Laboratory) S809, S818, S825, and S826. Moreover, this work covers two configurations of a wind turbine: one the two-bladed turbine and the other the three-bladed turbine. For the two-bladed turbine NREL phase VI model has been considered to carry out the numerical investigation. For a three-bladed turbine, three kinds of the turbine have been designed and are listed below. 1) Design of the turbine by changing the two-bladed NREL phase VI to the three-bladed turbine. 2) Design of the turbine by using the dimension of GE 1.5 MW and considering S818 airfoil, S825 airfoil, and S826 airfoil. 3) Design of in-house laboratory-scale wind turbine by considering S818 airfoil, S825 airfoil, and S826 airfoil. An FSI simulation was performed for a blade by taking four composite materials in turns. CFD is used to compute the aerodynamic loads, whereas FEA is used to determine the blade structural reactions. The investigation was conducted using commercially available ANSYS packages. The performance of the turbine has been studied in terms of power, torque, deformation, and Von-Mises stress under varying conditions, and the most efficient conditions are outlined. Experiments on small-sized wind turbines have been executed inside the subsonic wind tunnel. Performance parameters are checked by varying wind speeds and loads. An electromechanical model has been developed. The results of the experiments have been compared with the electromechanical model. The experimental outcomes indicate that the designed wind turbine is capable of powering micro-devices

    Genesis of Gold Mineralization in the South Kolar and Gadag Greenstone Belts, Dharwar Craton: Constraints from Hydrothermal Alteration, Tourmaline Chemistry, Fluid Inclusion and Stable Isotope Studies

    No full text
    South Kolar greenstone belt (SKGB) in the Eastern Dharwar Craton (EDC) and Gadag greenstone belt (GGB) in the Western Dharwar Craton (WDC) are well known for Neoarchean orogenic gold deposits in India. Chigargunta (CG) and Bisanatham (BN) deposits with contrasting host rocks such as Champion gneiss and metabasalt respectively within the SKGB reflect almost similar steeply dipping structural attitudes (0–10/74W– 87E) that controls the emplacements of auriferous lodes. On the other hand, third generation deformations along the NW-SE were the key structural control for major gold mineralization in turbidite hosted Gadag gold field (GGF) in the GGB. Hydrothermal alteration mineral assemblages i.e., quartz + carbonate + muscovite + chlorite + sericite + tourmaline (± biotite) are common in both the SKGB and GGF deposits irrespective of their host rock compositions, deformation settings and P-T conditions of alteration. Although, mineralogically they are similar, alteration mineral chemistry and substantial mobility of elements during alteration of two contrasting lithounits from the CG (Champion gneiss) and BN (metabasalt) typically fingerprint the host rock chemistry. Abridged activity-activity [(aMg2+/aH+) vs. (aK+/aH+) and (aNa+/aH+) vs. (aK+/aH+)] diagrams corroborate the observed alteration-induced mineralogical changes, in accordance with the isocon plot and constrain the possible fluid composition. Occurrences of native gold in association with sulfides are more common in the SKGB while both invisible lattice bound refractory as well as native gold are observed in the GGF. Hydrothermally precipitated tourmalines intimately associated with/without sulfides, in the alteration zones, from the gold deposits of the CG, BN and GGF belong to dravite or oxy-dravite group. A significant fluctuation in chemical compositions (XFe, Mg, Ca) from proximal to inner zone and strong chemical zoning of tourmaline grains without changes in Na content reflect no changes in fluid salinity in the CG and suggest ore fluid evolution with multiple pulses in a cyclic fluid flow event. Such notable change in fluid chemistry is attributed to the result of fluctuation of fluid pressure during seismic fracture propagation accompanying gold mineralization event. The intra-deposit chemical fluctuation within tourmaline in the BN and GGF are insignificant. The low salinity and reduced nature of the ore fluid are consistent throughout all the deposits inferred from low to medium Na, medium to high X-site vacancy and low Fe3+/Fe2+ ratio. Detailed fluid inclusion study from the mineralized quartz-carbonate veins reveals low to medium saline (CG: 0.5–13.3 wt% NaCl equiv.; BN: 1. 6–6.4 wt% NaCl equiv; GGF: 0.04–9.6 wt% NaCl equiv.) H2O-NaCl-CO2±CH4±N2 primary fluid. Estimated P-T conditions (CG: 1.7–3.5 kbar/285–378 ℃; BN: 0.8–1.2 kbar/365405 ℃; GGF: 1.62.9 kbar/296333 ℃) by combining fluid inclusion, chlorite and arsenopyrite thermometry reflect greenschist facies conditions of alteration and mineralization at the SKGB and GGF. Alteration mineral assemblages, tourmaline chemistry and fluid inclusion study confirm that the low saline, reduced fluid transported gold as Au(HS)2 − complex and precipitated gold as a consequence of pressure drop induced phase separation as well as wall rock interaction processes rather than fluid mixing. Sulfur isotopic compositions of the ore fluid (34SH2S) (CG: –0.4 to +2.4‰, BN: +0.3 to +2.3‰ and GGF: +1.0 to +3.4‰) are indicative of average crustal sulfur source. The 34S (+1.5 to +4.5‰) values of mineralized sulfides overlap with host-rock early pyrites (–1.0 to +7.5‰) in the GGF. Thus, it can be inferred that the sulfur in the mineralizing fluid most likely have derived either by desulfidation and/or dissolution of early pyrites during the continuous fluid flux along the shear zone. Carbon (δ13CCO2) isotopic compositions of ore fluid deduced from δ13C of carbonates furnish a range from –2.4 to +3.3‰ in the CG, – 2.1 to +1.4‰ in the BN and –5.9 to +1.6‰ in the GGF. Such inferred narrow ranges signify that the carbonates in ore forming fluid could have possibly been derived by decarbonation or dissolution of marine carbonates during the metamorphic devolatilization of the greenstone belts. Hence, the metamorphic source of ore-forming fluid is postulated for the gold mineralization at the SKGB and GGF and it is comparable with other orogenic gold hosting greenstone belts in the Dharwar Craton and elsewhere in the world

    Development of IoT-based Wireless Sensor System for Slope Stability Monitoring in Open-cast mines

    No full text
    Slope 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

    Polysaccharide-based Oil-in-water Emulsion Systems for the Prolonged Efficacy of Hydrophobic Antimicrobial Compounds

    No full text
    Prevalence of foodborne pathogens and its associated disease outbreaks are major causes of concern for public health globally. Significant efforts have been taken to resolve this issue, among which the use of antimicrobials is a major approach. Antimicrobial compounds have been used alone or in combinations to achieve enhanced functionality within food systems. Natural antimicrobials such as essential oils used in food preservation by conventional techniques are prone to rapid depletion owing to their volatile nature, hydrophobic properties, enzymatic hydrolysis, specific interactions with surrounding food components and alteration of flavor profile at higher usage levels. One strategy for prolonged protection of antimicrobial compounds is through designing a suitable carrier vehicle. In this study, the overall goal is to design oil-in-water emulsion systems for the sustained protection of various antimicrobial compounds against targeted foodborne pathogens. The first part of the work was carried out in model testing system such as Brain heart infusion (BHI) broth, where the effective concentration of antimicrobial emulsions prepared through ultrasonication and stabilized with gum arabic were evaluated. The oil phase of formulated emulsions was constituted with geraniol and carvacrol, incorporated at various ratios of 1:0, 2:1, 1:1, 1:2, and 0:1 (v/v). These emulsion systems were characterized for mean particle diameter, polydispersity index (PDI), ζ-potential, storage stability, creaming index, and microstructural parameters (confocal laser scanning microscopy (CLSM) and transmission electron microscopy (TEM)). In addition, Time-kill assay for the formulated emulsions was tested against model bacterial pathogens, Gram-positive bacteria B. cereus MTCC 430 and Gram-negative bacteria Escherichia coli MTCC 443. The results demonstrated that among all the formulations, higher stability was displayed by combined oil, geraniol: carvacrol (1:1) emulsion with no visible separation of cream. Further, the microstructural analysis confirmed the presence of stable emulsion. Analysis of time-kill assay showed prolonged antibacterial efficacy for the combined essential oil-based emulsion against both the model bacterial pathogens. In the second part of the work, the antimicrobial emulsions incorporated with geraniol and carvacrol at the selected oil phase ratios were stabilized with Tween 80 and Gum arabic (coating solution). These emulsion-based coating solutions were used to extend the shelf life of goat meat. They were characterized for mean particle diameter, PDI, ζ-potential, storage stability and creaming index, and microstructural parameters. Evaluation of the antimicrobial activity of the functional emulsions was carried out against Gram-positive bacteria B. cereus MTCC 430 and Gram-negative bacteria Escherichia coli MTCC 443. The study showed that the emulsion-entrapped formulations could prolong the antimicrobial efficacy of geraniol and carvacrol till nine days as compared to treatments performed with non-emulsion formulations on a goat meat model. The final part of the work was focused towards using two volatile essential oils, d-limonene and trans-cinnamaldehyde stabilized by Tween-20 and Starch-Octenyl Succinic Anhydride (OSA), for the preparation and characterization of oil-in-water type emulsions (coating solution). The impact of this delivery system on the antimicrobial retention was studied against the model bacterial pathogens using fresh-cut papaya as the model food. It was found that the emulsion-based coating solutions could prolong the antimicrobial efficacy of d-limonene and trans-cinnamaldehyde against both B. cereus MTCC 430 and Escherichia coli MTCC 443 on fresh-cut papaya. Overall, the emulsion-based carrier systems demonstrated effective retention of antimicrobials in the model testing system (BHI broth) and a potential application of these delivery systems to extend the shelf-life of goat meat and fresh-cut fruits was identified

    Study on Membrane Parameters Involved in ZnONP Penetration and Amyloid Beta Interaction in Neurodegeneration

    No full text
    Ferroelectric materials are widely employed in electronic devices such as sensors, actuators, and non-volatile random access memory (NVRAM), etc. due to their multifunctional properties. In these device applications, the ferroelectric materials are subjected to different loading cycles. This results in fatigue behaviour, which becomes a serious issue and restricts their commercial applications. This fatigue factor determines the stability and lifetime of ferroelectric devices. Among many ferroelectric materials, perovskite-based PbZr0.52Ti0.48O3 (PZT) and bismuth layered-based SrBi2Ta2O9 have been widely investigated for their use in non-volatile memory applications. Lead-based systems, despite their superior ferroelectric characteristics, are prohibited from being used in device applications owing to health and environmental concerns. Among various lead-free ferroelectrics, Na0.5Bi0.5TiO3 (NBT) system promises to be a potential replacement for lead-based perovskites. However, certain drawbacks of NBT system such as poor fatigue resistance and high coercive field need to be addressed. Though SrBi2Ta2O9 system has better fatigue resistance, the low switchable polarization (2Pr) and high processing temperature to synthesize this system make them incompatible to be used in device applications. Synthesis of NBT and SrBi2Ta2O9 based materials by conventional solid-state reaction route necessitates high processing temperatures, which may result in the loss of volatile components due to their high volatilities, resulting in deterioration of material properties. Therefore, to lower the processing temperature and time, microwave processing technique is used. XRD study revealed that the optimal calcination and sintering temperatures for microwave synthesized NBT ceramics are 800 oC for 15 minutes and 1000 oC for 30 minutes. Whereas, the optimal calcination and sintering temperatures for conventionally synthesized NBT ceramics are 850 oC for 4 hours and 1150 oC for 4 hours, respectively. Similarly, for microwave synthesized Sr0.8Bi2.15Ta2O9 (SBT) ceramics, optimal calcination and sintering temperatures are 950 oC for 30 minutes and 1100 oC for 30 minutes, respectively, which is significantly lower than the same system synthesized by conventional processing routes. Because the processing temperature and time of microwave processing technique differ noticeably and lower than those of conventional synthesis processes, microwave processing technique offers a potential benefit in terms of time and energy savings. Dense microstructure with smaller and fine grains distribution was observed in microwave processed NBT and SBT based ceramics. Microwave processed NBT and SBT based ceramics showed lower loss and lower leakage current density that can be associated to their increased density. There have been several attempts to enhance the characteristics of NBT system by different ionic substitution or doping at A or B-sites for wider applications. Donor doping has been shown to improve the ferroelectric characteristics of materials. To investigate the effect of doping, several dopants, based on their ionic radii and valency, to replace A and B-sites were chosen. Microwave-assisted solid-state reaction method was used to synthesize NBT doped systems with varying mol % of dopants, as given below, 1. (Na0.5Bi0.5)(1-x)LaxTi(1-x/4)O3 (where x=0.01,0.02,0.03) 2. (Na0.5Bi0.5)(1-x)SmxTi(1-x/4)O3 (where x=0.01,0.02,0.03) 3. (Na0.5Bi0.5)(1-x/2)Ti(1-x)NbxO3 (where x=0.005, 0.01, 0.015) 4. (Na0.5Bi0.5)(1-x)Ti(1-x)WxO3 (where x=0.005, 0.01, 0.015) XRD analysis of A-site and B-site doped NBT systems indicated that the solubility limits of B-site dopants (around 1 mol %) were lower than those of A-site dopants (around 3 mol %). XRD patterns of both A-site and B-site doped NBT systems with single perovskite phase were matched with JCPDS file- 36-0340 of NBT having rhombohedral structure. Rietveld refinement indicated no structural change with doping, however, doping induced lattice deformation due to differences in dopant ionic radii and host atom radii. Substitution of La3+ and Sm3+ ions at A-sites tends to shrink the lattice due to their lower ionic radii than Na1+ and Bi3+ of host A-site ions. Whereas occupancy of Nb5+ and W6+ ions at B-site expands the lattice a little due to their comparable but slightly larger ionic radii than Ti4+ of host B-site ions. Density of all the doped systems was found to be lower than the parent system. Thus, higher sintering temperature is required to get densified modified NBT ceramics. Incorporation of donor dopants resulted in reduction in grain size as the cation vacancies accumulates at grain boundary, which inhibited grain growth, thus, all the dopants act as grain growth inhibitors in modified NBT systems. Minimal decrease in leakage current density was observed up to 2 mol% of A-site and 1 mol% of B-site doping and all the modified ceramics displayed Ohmic type conduction behaviour. Overall, 1mol% Sm-doped NBT (abbreviated as NBST1) showed the better ferroelectric characteristics among all the doped ceramics with 2Pr and Ec of ~20.65 μC/cm2and ~20.23 kV/cm, respectively compared to ~13.37 μC/cm2 and ~23.84 kV/cm for NBT. Hence NBST1 system was chosen as the matrix to synthesize composites with SBT system as filler. Some researchers have put an effort to develop composites of efficient lead-free perovskite material with an appropriate bismuth-layered material to compensate for the required properties. In the present study, composites of perovskite NBST1 system and bismuth layered based SBT system have been prepared by microwave-assisted solid-state reaction route to improve their overall fatigue as well as ferroelectric properties. Two parent systems were prepared individually and were mixed by varying wt.% of each phase to produce the composite systems. The composites synthesized by microwave-assisted solid-state reaction route are; (1-x) NBST1-xSBT (where x= 0, 4, 8, 12, 16wt.%) X-ray diffraction patterns of (1-x)NBST1-xSBT composites revealed the coexistence of both perovskite and bismuth layered phases in all the composites. Change in peak intensity was thought to be induced by a change in composition, i.e., when SBT content increases, the peak intensity of the NBST1 perovskite phase decreased while the peak intensity of the bismuth layered SBT phase slowly increased. Density of all the composites was between that of matrix NBST1 (~5.28 g/cm3) system and filler SBT (~8.92 g/cm3) system. It was observed that well-developed grains of various sizes were densely distributed throughout the surface of ceramics. From the room temperature dielectric study, it was found that both dielectric constant and loss decreased with the increase of SBT content in composites. Increase in internal stress in composites owing to adjustment of two separate systems with considerably differing lattice parameters was evidenced by decrease in transition temperatures. Leakage current density and ferroelectric parameters like remnant polarization and coercive field decreased with the incorporation of SBT system in composites. Polarization fatigue study confirmed that fatigue endurance increased with the increase of SBT content. Among the studied (1-x)NBST1-xSBTcomposites, composite with x= 8 wt.% appeared to be the best in terms of dielectric, ferroelectric, and fatigue resistance for multifunctional device applications, especially for ferroelectric memory

    Impact of dietary modulations on the onset of Type 2 Diabetes in Drosophila melanogaster and its treatment mediated by metallic and polymeric nanoparticles

    No full text
    Diabetes mellitus is one of the most prevalent metabolic disorders of the current century. High calorie diet having high glycemic index (GI) are the major contributors of diabetes. Due to the complex nature of this disease, it is difficult to treat and often leads to huge treatment burden. Numerous studies have tried to understand the detailed mechanism of this disease to design new and effective therapeutic approaches. The application of nanotechnology in the field of diabetes have been proven beneficial. The current study aims to investigate the effect of dietary modulation in the onset of diabetes and established the role of anti-diabetic NPs by using Drosophila melanogaster as a model system. The first objective aims to investigate the effects of dietary advanced glycated end products (AGE). Oral feeding of three types of AGE compounds (i.e. AGE glucose, AGE-fructose and AGE-ribose) was found to alter growth and development of the flies. Beside this, the larva and adults showed persistent hyperglycemic condition, excess fat deposition and micronuclei formation in gut and fat body as well as insulin resistance. The flies also showed increased ROS formation via downregulation of the antioxidant enzyme system. Behavioral defects were also evidenced in the larval and adult locomotion, suggesting neuronal damage. The second objective depicts the role of Strontium ferrite, a metallic nanoparticle as a non-toxic anti-diabetic agent. Files fed with a high fat diet (HFD) were used as a diabetic model. The toxicity profile of the nanoparticles was checked, showing no DNA damage or cytotoxicity. Feeding of the NPs to the diabetic flies demonstrated that, the NPs were able to reduce fly weight, metabolic sugar and triglyceride level, reduce the deposition of fat and also reduce ROS level and behavioral abnormalities. In the third objective, the flies were reared on a high sugar diet (HSD), which tremendously affected their growth and development. Beside this, behavioral alterations was also seen. Hyperglycemia followed by excess fat deposition in the gut, fat body and crop confirmed the diabetic phenotype. A novel polymeric nanoparticle, namely polyvinylpyrollidone-curcumin (PVP-C) was checked for antidiabetic potential. Non-cytotoxic and non-genotoxic potential of the nanoparticles were evidenced from no DNA damage, and absence of trypan blue staining, as well as no phenotypic abnormality. Treatment of PVP-C NPs to the diabetic flies showed reduction of metabolic contents and ROS level. Together the study suggests the role of diet in diabetic onset and importance of nanoparticles having potential to be used alone as an anti-diabetic agent or a combination to deliver therapeutic molecules


    full texts


    metadata records
    Updated in last 30 days.
    ethesis@nitr is based in India
    Access Repository Dashboard
    Do you manage Open Research Online? Become a CORE Member to access insider analytics, issue reports and manage access to outputs from your repository in the CORE Repository Dashboard! 👇