7940 research outputs found
Sort by
Development of Some Efficient Schemes for ECG Signal Quality Assessment and Processing
No full textElCTROCARDIOGRAM (ECG) is a widely utilized tool for the diagnosis of cardiac ailments. However, considering the rapid growth of population as well as poor doctor to patient ratio, the computer-based automated monitoring of ECG signal is efficient as it provides fast processing and precise long term monitoring with less human effort. The main objective of this research work is to improve the performance of a computer-based automated ECG monitoring system incorporating efficient schemes for ECG signal quality assessment and processing, which can enhance the reliability of the medical diagnosis. Some of the existing literature on signal quality assessment (SQA) discuss ECG SQA schemes employing QRS complex morphology and R-peak information based features. But the performance of such techniques degrades due to improper detection of R-peaks. This research attempts to develop an efficient wavelet sub-bands features based ECG SQA scheme. Various wavelet sub-band level signal features are applied to machine learning-based classifier for estimating the ECG signal quality. Further, the filtering of ECG records is essential for precise identification and detection of local components when a considerable amount of noise in ECG records affects the low amplitude P and T waves significantly. Hence this research proposes an efficient ECG denoising methodology based on both empirical mode decomposition (EMD) and adaptive switching mean filter (ASMF) approach. Unlike conventional EMD based techniques, the proposed method reduces the effect of noises simultaneously preserving the high-frequency QRS complex information. For typical low-frequency noises, this method does not meet the achievable performance. Hence, this research is motivated towards developing ECG signal enhancement scheme in a dictionary learning (DL) based sparse representation framework. The proposed method completely enhances the ECG signal quality by removing both low and high-frequency noises. Continuous monitoring of ECG records for better medical diagnosis in telemetry needs a large memory space for storage and also it requires more transmission power. A low power based solution utilising for ECG compression based on beat type dictionary based compressed sensing (CS) scheme is proposed which offers high-quality signal recovery avoiding the training stage of individual ECG record. Effective detection of R-peaks in ECG plays a vital role in the extraction of clinical features in a computer-based automated system. Hence, a wavelet-based R-peak detection scheme using the Hilbert transform is proposed. The efficacy of all the proposed approaches is evaluated through MATLAB simulation based studies by comparing with the existing schemes considering ECG records of standard databases
Nanoparticle Functionalization: Implications in Corona-Modulated Biological Applications
No full textIncreasing growth and necessity of nanotechnology has brought risk to flora and fauna of niche for nanoparticle (NP)-mediated effects, including mortality. Additionally, over the last decade, there have been reports on heavy metal remediation by microbes and plants into harmless forms, which they, some of them, either store or secrete in the form of biocompatible nanocrystals stabilized with host’s biological moieties. The findings have been exploited, here, to fabricate metal nanoparticle with natural moieties as surface functionalities, and investigated for wide range of potential nanoparticle mediated biological applications, like antimicrobial, cytocompatible and adjuvant applications. The NP, when administered in biological milieu, tends to further bind a variety of biomolecules, especially proteins, forming an interfacial corona that provides biological identity to NP. The adopted corona in new biological milieu is anticipated to affect the adsorbed protein conformation depending upon the interaction pattern at the interface, as explored in the thesis using bovine lactoferrin (BLf) and Bacillus anthracis protective antigen (PA) as protein models. BLf shares 69% sequence homology with human lactoferrin, and is a well-studied protein for its conformation. On the other hand, PA protein is a non-virulent factor of anthrax toxin of proteinaceous nature that constitutes the major component of adjuvant vaccine adsorbed (AVA) against anthrax, and has anionic interface unlike BLf. The thesis, mainly, discussed two metal nanoparticle interfaces in this context, i.e. silver nanoparticle (AgNP) and aluminum nanoparticle (AlNP). Upon analyzing the cytotoxic property of the nanoparticles against different spectrum of eukaryotic and prokaryotic cells, thesis investigated change in protein conformation, when it is adsorbed as hard/soft corona, and subsequent effects on the protein function. The interactions of BLf with AgNP, leading to the protein adsorption onto AgNP interface, were mainly contributed by van der Waals interactions and hydrogen bonds. Besides retaining the bacteriostatic function, BLf-adsorbed AgNP (BLf-AgNP) showed relatively lesser cytotoxicity, despite of enhanced internalization in THP-1 cell compared to bare AgNP. In the end, the thesis discusses effect of functionalized AgNP and AlNP interfaces on conformational dynamics of PA, where the interface, depending upon the surface functionalities, showed contrasting effects on PA aggregation propensity. Nevertheless, the biofabricated AlNP (bAlNP) and BLf-AgNP proved better adjuvant for PA-mediated immunization, in vivo. PA adsorbed as soft corona onto bAlNP showed to trigger better humoral and cellular immune responses with enhanced interleukins level in spleen, especially IL4, IL10 and IFN-, compared to immunization with commercially available adjuvant-antigen formulation or with only antigen. Thus, the thesis altogether outlines the importance of surface functionalities in biofabricated metal nanoparticles for its potential prophylactic and therapeutic application
Brick Kiln Workers from Rural Odisha, India: An Analytical Study of Seasonal Migration
No full textThe economic reforms and neo-liberal policies of late nineties have brought about irreversible transformations in the agrarian mode of production and have led to irresistible conflict over the allocation and distribution of natural resources. Around 70 percent of the rural population in the country depends on agriculture for their livelihood. The agricultural sector has been experiencing a negative growth, including decline in the size of landholdings, crop yields and labour force engaged in agriculture. The context and area of work transformed with the growing changes in the economic and agrarian structure but the relationship of dominance and servitude continued to exist between the owners and labourers. Agricultural labourers are presently bonded to various sources of debt contracted from different agro-industry and construction sectors. Migrant labour gets recruited in informal sectors such as textiles, construction, stone quarries and mines, brick-kilns, small scale industry, agro based industries, sugarcane cutting, plantations, rickshaw pulling, food processing including fish and prawn processing, salt panning, domestic work, security services, sex work, small hotels and roadside restaurants and tea shops and street vending.
Brick manufacturing is one such informal sector which recruits poor and miserable agricultural farmers who are indebted to the labour contractors. Brick kilns are small scale labour intensive manufacturing units located on the outskirts of cities, which draws labour from economically underdeveloped regions. Women and children become the worst sufferers in this process of migration. They work as an extended family labour and are deprived of health, housing, sanitation and education facilities in the work site. Brick industries work till the onset of monsoon season, so it recruits seasonal agricultural labourers, who can leave the industry and return to their native place during the rainy season. The labourers from native villages receive advances from the brokers of the brick kiln. Then they migrate to the brick industry to pay off the debt.
The study was conducted in three districts of KBK region of Odisha, India.300 brick kiln migrant workers, 21 labour contractors and 6 owners of the brick kilns were interviewed for the purpose of the study. To explore the various factors affecting the migration decisions, an Exploratory Factor Analysis followed by Multiple Regression was done. It was found that social factors affected the migration decisions more in the presence of other economic and non-economic factors. It was observed that the social network played a major role in organizing the migration. This network provides information about the work and wages at the destination. It was observed that the networks are based on trust and mutual reciprocity. 59 percent of the migrant households were provided information about the work contract through the migration brokers. The process of migration was embedded in the structure of migration which involved four stages: stage of alliance, stage of mobilisation, stage of work and stage of feedback movement. Migration was a never ending process rooted in debts and dependency.
To assess the impact of seasonal migration on the livelihood of the migrants, the DFID Sustainable Livelihood Framework was adopted. It was found that there was improvement in the possession of physical and financial assets among the migrants. The annual income of the migrant household has risen above 20,000/- after migration. Agricultural asset possession like plough, tractors have declined, but other assets like mobile phones, televisions have increased. But the migration has a negative impact on the social, human and natural capital. In order to understand the migrant and state’s relationship Giddens ’Structuration approach is utilized. Various policies and schemes of the government for controlling and regulating migration were reviewed. ISMWA act (labour registration), MGNREGA (wage employment) and PDS (food security) were overviewed. Even the NGO initiatives for resolving the migrant’s problem were also reviewed. It was found that the government policies suffered from poor implementation, lack of awareness, inadequate staffing and funds. Most of the migration was not registered and documented. Thus a collaborative effort of government and non-government organisations is required to deal with the problems of migration at the origin and destination
Deciphering the epigenetic mechanism of gene regulation and evaluation of medicinal plant products in modulation of chromatin modifications in cancer.
No full textThe development and progression of cancer is predominantly regulated by both tumor suppressor genes as well as oncogenes. Either gene mutation causes hyper-activation of ‘oncogenes’ and suppression of ‘cell cycle control and tumor suppressor genes’; or alleles of these sets of genes expression profiles are modulated by epigenetic mechanisms. Hence, cancer is the manifestation of both genetic and epigenetic alternations modulating the metabolic profile and cellular homeostasis. Since cellular metabolism is mostly controlled by enzymatic activities and enhanced during the disease progression, chemo-preventive bioactive molecules from edible and medicinal plants are being increasingly evaluated which could be one of the desired ‘toxicity free’ therapeutic strategies against cancer. This thesis attempts to investigate the anticancer and epigenetic regulatory activity of Paederia foetida (P. foetida) and its active constituents; lupeol and β-sitosterol. The regulation mechanism(s) of tumor suppressor gene E-cadherin (CDH1) is tested considering multiple modalities of epigenetic modulations; like, DNA methylation, histone methylation, acetylation and phosphorylation. The cellular environment(s)/metabolism(s) were experimentally modulated by ectopic application of drugs and/or H2O2 with the cell culture media/buffer executing in vitro cell cultures. Crude methanolic leaf extract of P. foetida (MEPL) and two of the identified products, lupeol and β-sitosterol exhibit anticancer activity through inhibition of ‘cellular viability and migration’ by up regulation of CDH1 gene expression. Along with this, it also induces apoptosis through up regulation of pro-apoptotic gene Bax and down regulation of the anti-apoptotic gene Bcl2 in human prostate (PC-3 and DU-145) and breast cancer (MCF-7 and MDA-MB-231) cell lines. Ectopic applications of MEPL, lupeol and β-sitosterol also significantly down regulated the expression of DNMTs and HDACs as well as reduced the total DNMT and HDAC activity.
Loss of CDH1 protein and epithelial to mesenchymal transition (EMT) are key steps in cancer progression. Reactive oxygen species (ROS) within cells are the products of metabolic reactions and play some crucial roles in cellular metabolism, physiological functions and homeostasis. Roles of E-cadherin, EMT and ROS are discretely and intriguingly illustrated in many cancers focusing their collective concert during cancer progression. We report that hydrogen peroxide (H2O2) treatment modulate CDH1 gene expression by epigenetic modification(s). Sublethal dosage of H2O2 treatment decrease of E-cadherin, increase DNMT1, HDAC1, Snail, Slug and enrich H3K9me3 and H3K27me3 in the CDH1 promoter. The effect of H2O2 was attenuated by ROS scavengers; NAC, lupeol and β-sitosterol. DNMT inhibitor, AZA prevented the H2O2induced promoter-CpG-island methylation of CDH1. Treatment of cells with U0126 (inhibitor of ERK) reduced the expression of DNMT1, Snail and Slug, increased CDH1. This implicates that CDH1 is synergistically repressed by histone methylation, DNA methylation and histone deacetylation mediated chromatin remodelling and activation of Snail and Slug through ERK pathway. Increased ROS leads to activation of epigenetic machineries and EMT activators Snail/Slug which in their course of action inactivates CDH1 gene and lack of E-cadherin protein promotes EMT in breast cancer cells. ROS and ERK signaling facilitate epigenetic silencing and support the fact that subtle increase of ROS above basal level act as key cell signaling molecules. Free radical scavengers, lupeol and β-sitosterol may be tested for therapeutic intervention of breast cancer.
In aggressive tumors, there is increase expression of enhancer of zeste homologue (EZH2) and silencing of CDH1 genes. EZH2 is histone-lysine N-methyltransferase enzyme encoded by EZH2 gene. It participates in histone methylation and, ultimately, transcriptional repression. EZH2 specifically catalyses the addition of methyl groups to histone H3 at lysine 27(H3K27). The role of oxidative stress upon EZH2 and EZH2 mediated CDH1 regulation is still not explored. To decipher this, this thesis aimed to investigate the effect of H2O2 induced ROS on EZH2 expression. Data obtained reveals the induced expression of EZH2 in H2O2 treated cells suggesting the role of oxidative stress in EZH2 expression. Again treatment with EZH2 siRNA results in enhanced expression of CDH1 and reduced expression of EZH2 suggesting the role of EZH2 in negative regulation of CDH1 (CDH1) expression. Simultaneous treatment with EZH2 siRNA and H2O2 results in enhanced CDH1 (CDH1) expression and decrease expression of EZH2 which reveals the involvement of oxidative stress in enhanced expression of EZH2 and thus reduced the expression of CDH1 in breast cancer. Moreover, other studies also demonstrate the regulation of CDH1 and EZH2 by DNA methylation and histone modifications. DNMT1 is overexpressed and inversely correlated with CDH1 expression in breast cancer. Our thesis here demonstrates the negative regulation of CDH1 by EZH2. Most importantly it was found that, by inhibiting DNMT1 with 5-AZA-cytidine, it induced the expression of CDH1 indicating DNA methylation as well as EZH2 methylation is responsible for CDH1 down regulation in breast cancer. H3K27me3 also helps in the methylation of EZH2 and EZH2 mediated trimethylation of H3K27 is a prerequisite for promoter DNA methylation. This thesis demonstrates the expression of EZH2 and occupancy H3K27me3 is notably higher in untreated control cells as compared to EZH2 siRNA treated cells suggesting that CDH1 expression is regulated by higher expression of EZH2 thus results in H3K27 hyper-methylation. Inhibition of histone deacetylation by TSA (HDAC inhibitor) also restores the expression of CDH1 by inhibiting the EZH2 expression. This suggests that, histone deacetylation also plays an important role in regulation of EZH2 expression.
Collectively, this work broadens the amplitude of the epigenome, enhance the understanding of the modulation of the epigenome and open avenues for investigations on conjoint effects of canonical and intrinsic metabolite signaling and epigenetic modulations of genes during tumor development and cancer progression
Information Measures for Truncated Random Variables
No full textThe concept of entropy plays a crucial role in information theory. Many authors obtained several properties of entropy and its various generalizations so far. The divergence measure was proposed to measure the inefficiency of taking an approximate distribution when the actual distribution is known. In reliability theory we often get random observations which are truncated in nature. The purpose of the thesis is to study properties of various information measures in truncated domain. First, we consider measures based on the probability density functions. These are Shannon’s entropy, weighted Shannon’s entropy, weighted generalized entropy, weighted Kullback-Leibler divergence and weighted generalized divergence. In these cases, we study various properties. Mainly, we obtain characterizations, inequalities, bounds, uncertainty orders and the effect of monotone transformations. Nonparametric classes based on monotonicity property of the uncertainty measures are introduced. The measures based on the density functions have some drawbacks. So, we consider weighted cumulative residual entropy, weighted cumulative entropy and their generalizations. These measures are based on the distribution function and the survival function. We obtain several characterizations. The importance of the characterization result is that it determines the distribution function uniquely under certain conditions. Always it is not an easy task to obtain a closed-form expression of the proposed measure. Therefore, we obtain various bounds and inequalities. The effect of monotone transformations is discussed. New uncertainty orders and classes of lifetime distributions are introduced. In addition, we propose estimators for the case of weighted extended cumulative residual entropy and weighted generalized cumulative entropy using empirical approach. Large sample property of the proposed estimators is studied. It is noticed that there are distributions such as power-Pareto and Govindarajulu which do not have closed-form distribution functions though these have closed-form quantile functions. Motivated by this, we consider quantile-based inaccuracy measure and its dynamic versions. Various results including characterization, effect of transformation and bounds are derived. Few examples are considered to illustrate the results
On Some Signal Processing Algorithms Applicable to Cognitive Radio Communication
No full textConvergence of Wireless communication and Internet has leveraged for mammoth expansion of wireless radio access techniques leading to overcrowding of spectrum. Additionally there is need for large bandwidth to accommodate high data rate demand. In spite of intensive research and development efforts scarcity of available radio spectrum is a critical limitation. Opportunistic dynamic spectrum access (DSA) and cognitive radio (CR) techniques have received increasing attention as potential solutions to spectrum shortage issue in 5G wireless communication systems. Recently, spectrum sensing and identification have been considered critical functionalities to accommodate DSA. Spectrum sensing, enables CRs to identify spectral holes without interfering with licensed primary user maintaining quality of service of secondary user. On other hand, expanding wireless communication usage has rendered for radio access techniques(RATs) with various modulation, antenna systems, hardware architectures and channel scenario. Hence, there is a requirement to investigate robust spectrum sensing and radio access identification methods. This thesis, focuses on two important aspects of spectrum sensing. One is identifying the occupancy of spectrum and other is differentiate different users occupying the spectrum on basis of modulation type and RATs classification. Hence, by this process efficient management of interference mitigation and DSA is possible in the emerging heterogeneous networks. Realization of both the subtask leads to addressing various challenges. One of the important challenge is quickly identifying occupancy of spectrum without any priori information about primary user by using very few samples of data. Next traditional spectrum sensing algorithms become unsuitable when real time wireless communication signals passed through harsh channel impairment in presence of hardware imperfections due to non-stationary nature of signal. Last challenge is related to radio signal classification in which there is no single optimal solution to classify all the types modulation techniques and RATs signals in emerging next generation wireless communication systems. This thesis address the first challenge by proposing a blind eigenvalue based signal processing solutions that work under sample starving environment to enhance spectral detection efficiency. Two modified eigenvalue based spectrum sensing (SS) techniques called corrected John’s test (CJT) and higher order eigenvalue-moment ratio (HO-EMR) based techniques are proposed. Further to increase robustness of sensing a dual stage SS is adopted as per IEEE 802.22 CR standard, with the use of energy detection and EMR based techniques. Dual SS possess the capability to estimate the noise variance and enhance prediction accuracy by combining superior features of both detection algorithms. To counter the dynamic nature of emerging radio signal, time frequency based spectrum sensing is proposed. These have been historically used for non-stationary radar signal detection. Various TF distribution based SS are also proposed and comparative analysis carried out. Later, to make the CR intelligent, applicability of combination TF distribution and recent trends of machine learning in form of deep learning techniques are used for modern modulation detection and radio access techniques (RAT) identification. Deep learning based network are data driven classifiers and they avoid need for manual expert feature design, which is a necessity in traditional feature based classifiers. Their performance are analyzed in terms of classification accuracy with recently proposed DL architectures. Overall thesis proposes novel spectrum sensing and radio signal classification algorithms that assist in imbibing cognitive capability among emerging next generation wireless networks
Development and Characterisation of Metal Matrix Composite Using Cenosphere for Wear Resistant Applications
No full textEnvironmental pollution is the major problem associated with rapid industrialisation, urbanisation, and rise in living standards of people. However, industrialisation, on the other hand, causes serious problems relating to environmental pollution. Industrial wastes seems to be a hindrance on the path of industrial growth. The major generators of the industrial solid waste are the thermal power plants producing fly ash. Fly ash is an inexpensive resource material. Continuous efforts have been made by different researchers worldwide, for proper utilisation of fly ash for various applications. The small scale of fly ash has successfully utilised for making building materials. However, large-scale utilisation is yet to take off. In the last few years, considerable development has occurred for potential use of this waste in the area of metal matrix composites for automotive applications. Considerable trials have been done on the use of metal matrix composites like aluminium-silicon carbide composites for connecting rods, brake rotors, drive shafts and several other components. However, cost still remains a major barrier in designing aluminium composite components for wider applications in automotive industries. In order to reduce the cost of composites, the fly ash particles, a waste by-product from power plants, have been incorporated in molten aluminium alloy to make low cost aluminium–fly ash composites. In these composites, fly ash generally acts as a filler replacing energy intensive metal without deleterious loss of desirable properties.
Fly ash is a coal combustion by-product, which consists primarily of aluminosilicates, and the oxides or mixed oxides of silicon, aluminium, iron, calcium. Small amounts of other oxides of common elements such as magnesium and titanium are also present. Fly ash particles generally contain either solid spheres called precipitator fly ash or hollow spheres termed cenosphere fly ash. Precipitator fly ash often has pores and its density ranges from 2.1 to 2.6 gm/cm3. While cenosphere fly ash particles have density in the range of 0.4 to 0.6 gm/cm3.
Aluminium matrix composites are not a single material but a family of materials whose stiffness, strength, density, thermal and electrical properties can be tailored by varying the type of reinforcement material, its volume, shape, location and fabrication method can all be varied to achieve required properties. The present work includes Aluminium alloy (LM6) as metal matrix. LM6 matrix alloy has good casting characteristics. The major alloying element in LM6 is silicon. The alloy has good fluidity and hot tearing properties that make to produce thick and thin casting sections. It has a high strength, which can be used for structural components in the automobile industry.
The present thesis deals with the mechanical and tribological behaviour of LM6-cenosphere metal matrix composites. The composites are fabricated using two types of casting processes viz. stir casting and squeeze casting. The volume fraction of reinforcement (wt. %) is varied from 5-12% for stir casting and 5-15% for squeeze casting with an increment of 2.5 during the fabrication process.
The work presented in this dissertation involves investigation of three distinct problems of LM6-cenosphere composites.
•Study of favourable mechanical properties with various characterisation analyses of both stir and squeeze cast composites.
•An experimental investigation of abrasive wear behaviour of both stir and squeeze cast composites.
•An experimental investigation of erosive wear behaviour of squeeze cast composites.
To study the mechanical properties of the composites, with various volume fraction of reinforcement (wt. %) varied from 5-15%. The composites are synthesised through the stir casting and squeeze casting methods. The microstructure analyses of the composites are carried out using optical microscope. The hardness test of the composites are carried out using Vickers micro hardness tester. It was found that the squeeze cast composites shows fine microstructure compare to stir cast composites. The hardness of the squeeze cast composites are higher than the stir cast composites.
The abrasive wear behaviour of stir cast and squeeze cast composites are carried out using pin-on-disc wear tester as per ASTM standards with various experimental parameters such as sliding velocity, sliding distance, track radius, applied load etc. It has been concluded that the wear resistance of the squeeze cast composites are better than the stir cast composites.
The erosive wear behaviour of squeeze cast composites are performed on an air-jet erosion tester as per ASTM standards with various parameter like impingement angle, impact velocity, standoff distance, abrasive particles, flow rate, pressure etc. The solid particle erosion test clearly indicates that the composites behaviour is semi-ductile in nature.
The results from the present thesis indicate that addition of cenosphere up to 10 wt. % is very effective in improving its wear resistance with stir casting method; whereas 12.5 wt. % of cenosphere gives better wear resistance in squeeze casting. Also for erosion behaviour of the composite, maximum erosion occurs for different wt. % of cenosphere is in the range of 45º- 60ºwhich indicates that the present material is semi ductile in nature
Development of Superhydrophobic Coatings on Metallic Surfaces for Industrial Applications
Get PDFRecently, several superhydrophobic coatings on metallic surfaces have been developed, but they have not achieved great success in developing on commercial scale. Although these coatings have exceptional properties like self cleaning, anti-corrosive, anti-icing, etc., but these coatings cannot be used successfully in industry due to inability of complete mechanical, chemical and thermal stability data. Therefore, the main challenge is to create cheap, excellent adhesively, environmentally safe, durable, regenerative superhydrophobic coatings on various metallic surfaces. In the current work, various superhydrophobic coatings on metallic surfaces (aluminum, steel, copper, and steel mesh) for various industrial applications were synthesized by simple immersion technique.Superhydrophobic coatings on aluminium surfaces were synthesized using two-step and one-step processes. By using two-step process, two different superhydrophobic coatings were prepared using etchants such as KOH and HCl+HNO3 solutions independently and then by immersion in lauric acid solution for lowering surface energy. One-step process was used to synthesize superhydrophobic coating by immersing aluminium sample in a mixture of KOH etchant and lauric acid solution. Superhydrophobic coatings on steel and steel mesh surfaces were synthesized using two-step process. For the fabrication, first roughness was created by immersing in etchant (HCl+HNO3) and then by dipping the roughened surface in lauric acid low surface energy surface was created. Superhydrophobic coatings on copper surfaces were synthesized using two-step and one-step processes. In this case, after the creation of roughness and lowering the surface energy, the same chemicals were used. For each case, effects of process parameters like etching time and immersion time in lauric acid are studied. The result reveals that surface roughness and water contact angle increase with etching and immersion time. After fabrication, mechanical, thermal, and chemical stability tests were performed to identify the operating range. The SEM studies reveal the presence of a rough micropattern on the treated surfaces and the contact angle measurements confirm the superhydrophobicity. The water droplet dynamics study reveals that the water droplet with low impact velocity bounces from the surface. At critical impact velocity, pinning of water droplet is observed. Splashing of water droplet is observed beyond the critical impact velocity. Furthermore, the coated sample remains in floating condition on the water surface for several weeks, showing excellent water-repellent nature. Coated surface bounces off the high speed water jet stream and then still no change in superhydrophobicity is found. This behaviour confirms the excellent mechanical properties of the coatings. In addition to the above, it is observed that mechanical disturbances due to surface bending and repeated folding and de-folding do not have much effect on the superhydrophobicity. Mechanical durability of coatings was also evaluated by performing adhesive tape peeling and sand paper abrasion tests for the confirmation and quantification of the durability of coatings.
In chemical stability test, superhydrophobic nature remains unaffected after several days of immersion in NaCl solution and shows the excellent chemical stability of coating. Thermal stability of coatings was evaluated by annealing samples in temperature range 40 - 250 °C for one-hour period in hot air oven. It is found that superhydrophobicity of most of the coated samples remains unaffected after annealing in temperature range 40 - 140 °C, and this is considered as the excellent thermal stability of coatings. Coatings are found to be fully damaged after 24 hours annealing at 300 °C and superhydrophobicity of surface turns into superhydrophilicity. However, wettability of the surfaces can be restored by simple immersing the samples again in lauric acid solution. The analysis reveals that superhydrophobicity of the coatings is regained.
Self-cleaning property of the fabricated superhydrophobic aluminium, steel, and copper surfaces was studied. Coating shows the excellent self-cleaning property. No accumulation of moisture from air on the cooled superhydrophobic aluminium, steel, and copper surfaces is observed and this asserts the excellent anti-fogging property of coatings. By electrochemical tests, it is demonstrated anti-corrosion property of coating with low corrosion current density and high corrosion potential. For the replication of industrial applications in laboratory, petroleum ether-water and benzene-water mixtures which are oil-water mixtures were successfully separated from each other by a simple filtration method using the superhydrophobic steel mesh with the separation efficiency above 99%. Oil-water separation using the coated steel mesh is simple, fast, and repeatable for at least 10 times. The aforesaid durable and regenerable superhydrophobic metallic surfaces have potential industrial applications
Synthesis and Characterization of Functionalized Graphene Based Nanocomposites for Biomedical Applications
No full textPresent research focused on the synthesis of stable, water dispersible surface modified multifunctionalized graphene nanocomposites to enhance therapeutic efficacy, anticancer theranostics with reduced toxicity and to get controlled targeted drug action for biomedical applications. The functionalization of graphene oxide can be achieved by PEGylation of green synthesized metal oxide nanoparticles (like CONPs/AgNPs/IONPs) decorated graphene nanocomposites with EDC-NHS activation chemistry. The successful development of RGO-CONPs/AgNPs/IONPs-PEG nanocomposites was investigated in detail by different analytical techniques. Hydrodynamic diameters in nano range and polydispersibility index values closer to 0.05 indicate the nanocomposites expected to have better colloidal stability and aqueous dispersibility. In order to overcome the side effects of doxorubicin (DOX), an anticancer drug, it was incorporated into amino PEGylated RGO-CONPs/AgNPs/IONPs nanocomposites. The higher percentage drug loading and more pH-responsive release of DOX from nanocomposites lead to promising nanocarrier for the anticancer drug. The nanocomposites were found to be able to efficiently transport DOX into acidic microenvironment of the targeted cancerous cells and then brought about cell death. Finally, cytotoxicity activities of the DOX loaded metal decorated nanocomposites were checked to know whether the original cytotoxic property of the pure drug was retained in such nanoformulations. It was found that DOX loaded RGO-IONPs-PEG nanocomposites were superior to others as far as their cytotoxic activities were concerned. Moreover, even AgNPs and CONPs containing nanoformulations were not inferior to the pure drugs due to cytotoxic activity of AgNPs and antioxidant property of CONPs. These results indicate that each DOX loaded nanoformulation was atleast not less cytotoxic than the respective drug. Thus, all the above mentioned information clearly suggests that each of the nanoformulations may be considered as stable, monodispersive and controlled release nanoformulation having satisfactory cytotoxicity. They even retained anticancer activity of the respective drugs. In addition, the RGO-IONPs-PEG nanocomposites were found to have superparamagnetic property which is an essential factor for cancer specific drug delivery with the ability of carrying anti-cancer drugs to targeted sites under an external magnetic field. It may be concluded that targeted drug carriers of PEGylated metal activated functionalized nanographene oxide could avoid the side effects of free DOX in tumor therapy. In this manner, the aims of the present study were fulfilled, i.e., stable, water dispersible surface modified functionalized metal/metal oxide decorated graphene nanocomposites, to enhance therapeutic efficacy and anticancer activity, were developed successfully for biomedical applications
Experimental and Numerical Analysis of Nonlinear Dynamic Behavior of Delaminated Composite Shell Panel under Hygro-thermo-mechanical Loading
No full textThe nonlinear dynamic responses of the delaminated composite shell panel structure under the combined hygro-thermo-mechanical loading have been analyzed using a generic higher-order FE model in this dissertation. To compute the numerical responses (static, frequency and transient deflection), the nonlinear mathematical model has been developed with the help of two different higher-order polynomials (nine and ten degrees of freedom) and a sub-laminate approach for the inclusion of inter-layer separations. Further, to incorporate the realistic material behavior two different approaches are adopted, i.e., the macro and the micromechanical model including Green-Lagrange strain-displacement relations for excess geometrical distortion. Moreover, the current model is capable of solving for two kind of temperature loading (uniform and linear) and two transverse mechanical load (uniform and sinusoidal). The current macro/micromechanical FE model is capable of handling the variable type of structural problems, i.e., the variation in geometrical dimension, geometries (flat/curved) and elastic properties. The finite element solutions are obtained by resolving the structural governing equations (eigenvalue and equilibrium) with the help of the direct iterative method and Newmark’s integration technique. Further, the model accuracy has been established by comparing the current results with open source data evaluated via various techniques (numerical, exact and analytical). Additionally, to improve the confidence on the present numerical solutions, the results are compared with the own experimental data including the experimental elastic properties. Subsequently, the role of single/multiple debonding (size, location and position) and associated design input parameters on the linear and nonlinear structural responses are computed through a series of numerical examples. Finally, the influences of input parameters associated with material, the geometries including the geometrical configurations on the final responses (linear/nonlinear static, frequencies and transient deflections) are evaluated using the present higher-order nonlinear models and the corresponding inferences provided in details