Ultrafast laser deposition and microfabrication of thin films for MEMS structures

This thesis is organized into a chapter on literature review, three papers and a chapter on conclusions. The first paper deals with the femtosecond pulsed laser deposition and fabrication of micromotor on Teflon thin films along with a comparison of the traditional excimer deposition. The second paper deals with the femtosecond pulsed laser deposition and fabrication of microgripper on 3C-SiC along with a comparison of films deposited by excimer laser and atmospheric chemical vapor deposition methods. The third paper deals with the details of fabrication of a microgripper on 3C-SiC thin film

Constitutive Activation of NF-κB Pathway in Hematopoietic Stem Cells Causes Loss of Quiescence and Deregulated Transcription Factor Networks

Identifying physiological roles of specific signaling pathways that regulate hematopoietic stem cell (HSC) functions may lead to new treatment strategies and therapeutic interventions for hematologic disorders. Here, we provide genetic evidence that constitutive activation of NF-κB in HSCs results in reduced pool size, repopulation capacities, and quiescence of HSCs. Global transcriptional profiling and bioinformatics studies identified loss of ‘stemness’ and ‘quiescence’ signatures in HSCs with deregulated NF-κB activation. In particular, gene set enrichment analysis identified upregulation of cyclin dependent kinase- Ccnd1 and down regulation of cyclin dependent kinase inhibitor p57kip2. Interestingly, constitutive activation of NF-κB is sufficient to alter the regulatory circuits of transcription factors (TFs) that are critical to HSC self-renewal and functions. Molecular studies identified Junb, as one of the direct targets of NF-κB in hematopoietic cells. In essence, these studies demonstrate that aberrant activation of NF-κB signals impairs HSC quiescence and functions and alters the ‘TF networks’ in HSCs

Vermicomposting of coirpith with cowdung by Eudrilus eugeniae Kinberg and its efficacy on the growth of Cyamopsis tetragonaloba (L) Taub

AbstractIn view of the growing awareness about ecofriendly organic farming and biotechnology, coirpith and cowdung natural sources were used to produce vermicompost which showed enhanced growth promoting effect in the crop Cyamopsis tetragonaloba. Initially, neutral detergent fibre, acid detergent fibre, lignin, cellulose and hemicellulose contents were determined in three different grades of coirpith and in cowdung. Vermicompost was prepared using the earthworm Eudrilus eugeniae with 60days maintenance. During composting N, P, K and C contents were estimated in vermicompost as well as in control compost. N, P and K values were highly increased in vermicompost. C:N was dramatically decreased in vermicomposting during the experimental period. Vermicompost enhanced the growth of tested C. tetragonaloba crop. Vermicompost treated plants were taller by 9cm when compared with the control plant. The use of Vermicompost also led to a marked increase in plant biomass

Antagonistic potential of Trichoderma hamatum against Alternaria porri causing purple blotch disease of onion through Gas chromatography-mass spectrometry (GCMS) analysis

Alternaria porri causing purple blotch disease of onion is a destructive phytopathogen which causes severe loss in productivity. The present study aimed to unravel the antagonistic potential and efficacy of volatile organic compounds produced by various Trichoderma spp. against A. porri causing purple blotch disease of onion through Gas chromatography-mass spectrometry (GCMS) analysis. Ten isolates of Trichoderma species were isolated from the rhizospheric soil of healthy onion plants. Upon paired plate technique, the in vitro efficacy of ten Trichoderma isolates were tested against virulent isolate of Alternaria porri isolated from purple blotch disease infected onion plants. The Trichoderma isolate TIM2 showed 76.29 per cent inhibition on mycelial growth of pathogen. The effective Trichoderma isolate was identified as Trichoderma hamatum through the analysis of the rDNA of internal transcribed spacers (ITS) region and it was subjected to GC-MS analysis.  The result of GCMS analysis indicated the highest peak area and retention time with major antimicrobial bioactive compounds like Tetradecane, 2,6,10-trimethy (20.327), (1.22) and Dodecane, 2-cyclohexyl (20.079), (2.14), Heptadecane (21.222), (9.50), Octadecane (22.379), (3.58), Eicosane, 9-cyclohexyl (22.578), (1.84), 2-Propenoic acid, pentadecyl ester (23.400), (10.37), 2,6,10,14-tetramethyl (23.567), (10.37), Eicosane (27.311), (2.34), Hexadecanoic acid, methyl ester (27.918), (4.43), n-Hexadecanoic acid (29.156), (3.59) and  Tetrapentacontane, 1,54-dibromo (31.906), (3.33). These bioactive compounds identified through GCMS analysis from the crude extracts of Trichoderma hamatum exhibited a stronger antifungal activity against A. porri. Hence the application of T. hamatum for the management of purple blotch disease highly supress growth of the pathogen and reduce the disease incidence.    

Parametric Study and Optimization for Welding Processes Using Machine Learning

Optimization facilitates in attainment of maximum strength, efficiency, reliability, productivity and longevity. In this work, data from three material joining processes - Ultrasonic welding of polymers, arc welding as Metal Inert Gas and Tungsten Inert Gas are analysed for establishing quantitative relationship between the process parameters and for prediction of weld features using Multivariate Linear Regression algorithm. The various dependency coefficients and characteristics generated with the ML algorithms are in agreement with the inherent dependency as obtained from experimental data and simulation results. This investigation is a preliminary attempt with a limited set of data to manifest the suitability of machine learning techniques; nevertheless, the results are far from conclusive owing to small data set and hence may be extended to precisely model joining processes with higher number of process parameters, degree of freedom and responses

Simulation Study of Critical Aspects of MIAB Welding for Analysis of Potential Factors Governing the Performance of Weld Formation

Magnetically Impelled Arc Butt (MIAB) welding, is a solid-state welding technique. The magnetic system of this technique is pivotal for the generation of the Lorentz force, which impels an arc to rotate along the periphery of the weld tubes and thus facilitates the heating of faying surfaces. The magnetic arrangement and the arc dynamics significantly impact the effectiveness of the welding process, eventually dictating the efficiency. This study case investigates the impact of the magnetic arrangement on the arc rotation and possible factors that cause irregularities in the (MIAB) welding through COMSOL simulation. The COMSOL simulation has served as a powerful tool to comprehensively analyse various arc dynamics and magnetic systems and extrapolate the observations to analyse the arc dynamics and magnetic systems involved in MIAB welding. By employing simulation studies, the research aims to unravel critical insights for an efficient design of the MIAB welding system. This work includes a study of the effect of magnetic forces on arc dynamics using various models and attempts to develop an analogy to the MIAB welding process. This is further utilized to explain the process variations in the form of arc displacement, electric potential distribution, and the possibility of self-demagnetization of AlNiCo magnets. Thus, it provides a foundation for advancing the technological aspects of MIAB welding to overcome the limitations and irregularities. This research is instrumental in enhancing the understanding of magnetic interactions involved in the MIAB process, which can further pave the way for improved welding machine designs and consequently, enable research on these lines that can help in establishing an optimized parametric window

Climate nutrient management for various sources and levels of fertilizers on soil nutrients, growth and yield of maize (Zea mays l.) in Madurai district, Tamil Nadu, India

Global climate change is expected to soil processes and properties, which are important for restoring soil fertility and low productivity. The field experiment was conducted at Research Farm, Agricultural College, and Research Institute, Madurai district, Tamil Nadu, during Kharif season 2021 to study of various sources and fertilizers' levels to influence under deficit and excess water conditions on soil fertility, growth, and yield of maize (Zea mays). The study revealed that excess and deficit water condition in moisture regime irrigations at Irrigation water / Cumulative Pan Evaporation (IW/CPE) ratio of 1.0 along with nutrient management practices (N8) 125 % Soil Test Crop Response (STCR) - NPK soil application by 1 % foliar spray of micronutrient mixture. Significantly higher of mean values available nitrogen (225 kg ha-1), available phosphorous (20.81 kg ha-1), available potassium (351 kg ha-1), dry matter production (DMP) (16,404 kg ha-1), plant height (250 cm) and yield (9,030 kg ha-1) and was comparable with IW/CPE ratio of 0.8, 0.6 along with others nutrient management practices at 100 % and 75 % STCR - NPK followed by foliar sprays 2 % NPK (19:19:19) and Pink-pigmented facultative methylotrophs (PPFM) 1 %. Hence, under a normal water availability situation, irrigation at an IW/CPE ratio of 0.8 was good enough to produce a higher yield, while under deficit and excess water conditions IW/CPE ratio of 1.0 along with125 % STCR-NPK by foliar spray of micronutrient mixture of 1 % was suitable for obtaining optimum nutrient management for enhancing soil fertility, growth and yield of maize

Welding of High Entropy Alloys A Review

High-entropy alloy (HEA) offers great flexibility in materials design with 3–5 principal elements and a range of unique advantages such as good microstructure stability, mechanical strength over a broad range of temperatures and corrosion resistance, etc. Welding of high entropy alloy, as a key joining method, is an important emerging area with significant potential impact to future application-oriented research and technological developments in HEAs. The selection of feasible welding processes with optimized parameters is essential to enhance the applications of HEAs. However, the structure of the welded joints varies with material systems, welding methods and parameters. A systemic understanding of the structures and properties of the weldment is directly relevant to the application of HEAs as well as managing the effect of welding on situations such as corrosion that are known to be a service life limiting factor of welded structures in conditions such as marine environments. In this paper, key recent work on welding of HEAs is reviewed in detail focusing on the research of main HEA systems when applying different welding techniques. The experimental details including sample preparation, sample size (thickness) and welding conditions reflecting energy input are summarized and key issues are highlighted. The microstructures and properties of different welding zones, in particular the fusion zone (FZ) and the heat affected zones (HAZ), formed with different welding methods are compared and presented in details and the structure-property relationships are discussed. The work shows that the weldability of HEAs varies with the HEA composition groups and the welding method employed. Arc and laser welding of AlCoCrFeNi HEAs results in lower hardness in the FZ and HAZ and reduced overall strength. Friction stir welding results in higher hardness in the FZ and achieves comparable/higher strength of the welded joints in tensile tests. The welded HEAs are capable of maintaining a reasonable proportion of the ductility. The key structure changes including element distribution, the volume fraction of face centered cubic (FCC) and body centered cubic (BCC) phase as well as reported changes in the lattice constants are summarized and analyzed. Detailed mechanisms governing the mechanical properties including the grain size-property/hardness relationship in the form of Hall–Petch (H–P) effect for both bulk and welded structure of HEAs are compared. Finally, future challenges and main areas to research are highlighted

Non-Destructive Testing of Magnetically Impelled Arc Butt Welding of Mild Steel Tubes

This paper presents the results of Non-Destructive Testing on Magnetically Impelled Arc Butt (MIAB) welded mild steel tubes of 27mm OD and 1.5mm thickness. As part of this work, the tests covered were radiography, liquid penetrant, and magnetic particle testing. The testing results indicate that porosity, penetration levels and the defects found are within acceptable limits as per standard. For this experimental work, the selection of parameters was based on trial and error adopted in preliminary trials. The irregularities found in the non-destructive testing samples have enabled the fine-tuning of process parameters. The optimum values of hydraulic pressure, weld time and weld current are assessed to be 30-35bar, 5.5s and 150 A, respectively 270 A for this dimension of tubes. This work focuses on the experimental observations of MIAB welding and Non-destructive testing results for MS tubes of the selected dimension, which have not been reported in the existing literature. The achieved input forms the database for the parametric study of this process. The optimum parametric ranges obtained from the results can be extrapolated to be used for joining tubes of different dimensions and can also form the inputs for reaching parameter and response dependency equations

Thermo-tolerance characterization and bioassay of selected entomopathogenic fungal (EPF) isolates on larva of Spodoptera litura Fab.

Entomopathogenic fungi viz. Metarizhium anisoplae and Beauveria bassiana are well characterized in respect to pathogenicity to several insects and have been used for biological control of agriculture pests worldwide. Despite their potential, several factors like low resistance to elevated temperature have hindered widespread adoption of fungi as part of biological control regimes. In this study, five isolates of B. bassiana (Bb 01, Bb 02, Bb 03, Bb 04 and Bb 05) and two isolates of M. anisoplae (Ma 01 and Ma 02) were evaluated for thermotolerance capacity and bioefficacy against third instar of Spodoptera litura. Among the isolates studied, Bb 04 recorded the higher temperature tolerance up to 34oC with mean spore germination of 35.00 percent and mean dry mycelial weight of 443.38 mg. Further, in the bioassay studies, Bb 04 caused significantly (@ P<0.01%) higher percent mortality of S. litura larva at 1×108 spores ml-1 on fifth day (80.00 %) with LT50 value of 4.08 days and LC50 value of 2.07×104 conidia ml-1 at five days. Investigation results indicated that BB 04 is a suitable EPF isolate for management of S. litura where higher temperature prevails. &nbsp