Indian Institute of Science Bangalore
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Structural and Electrochemical Investigation of Bisulfate and Hydroxysulfate based Polyanionic Cathodes
No full textThe discovery of LiFePO4 cathode for Li-ion battery ushered intensive study on polyanionic high-voltage battery insertion materials. Polyanionic materials offer rich crystal chemistry, robust framework, voltage tunability, and high redox potential based on the inductive effect due to the polyanionic unit [(XO4)mn-, X = S, P, Si, W, Mo, etc.] [1]. Among them, SO4-based polyanionic systems have the advantage of higher redox potential and ease/versatility of low temperature synthesis. In this spirit, I have investigated bisulfate [A2-xM(SO4)2: A= Li, Na, K; x= 0,1] and hydroxysulfate [AMSO4OH: A = Li] type sulfate-based polyanionic frameworks. Few salient features of my thesis work are:
(i) Spray drying route was used to discover a metastable monoclinic polymorph of Li2NiII(SO4)2 (s.g. P21/c). As per first principle calculations, it can work as a 5.5 V (vs. Li+/Li) cathode for Li-ion battery coupling both cationic (Ni2+/Ni3+) and anionic (O-) redox activity. The crystal chemistry, phase stability landscape and the ground state magnetic structure (A-type Antiferromagnetic spin ordering) of this novel compound have been examined [2,3].
(ii) Mineralogical exploration and synthetic preparation of naturally found minerals are strategically used to unveil battery electrode materials. Following, saranchinaite Na2Cu(SO4)2 and its hydrated derivative kröhnkite Na2Cu(SO4)2.2H2O bisulfate minerals have been prepared using the facile spray drying synthesis route. The thermodynamic phase stability landscape has been explored along with the structural effects on the Na+ ion mobility. While the presence of Cu makes them unsuitable for insertion ion chemistry, they have been reported as potential conversion type battery electrodes [4].
(iii) The eldfellite NaVIII(SO4)2 (s.g. C2/m) is demonstrated as a versatile novel cathode material for both Li-ion (2.57 V, 80 mAh/g) and Na-ion (2.28 V, 70 mAh/g) battery at current rate of C/20 and based on solid solution reaction mechanism.
(iv) Hydrothermally prepared orthorhombic polymorph of FeIIISO4OH (s.g. Pnma) has been examined as a 3.2 V (110 mAh/g, C/20) Li-ion battery cathode. I have further demonstrated the first reversible Na-ion (de)insertion in monoclinic FeIIISO4OH at ~2.9 V based on solid solution reaction mechanism with a discharge capacity of 85 mAh/g (C/100) [5,6].
Overall, this work can be suitably placed in the materials science tetrahedron encompassed by “structure-property-processing-performance”. I will elaborate the above-mentioned sulfate based polyanionic battery insertion materials.Ministry of Human Resource Developmen
Itaconate Based Novel Amphiphilic Polymer Architectures
No full textAmphiphiles are natural or synthetic molecules consisting of hydrophilic polar head group and hydrophobic non-polar hydrocarbon tail. Beyond a certain concentration, known as critical micellar concentration (CMC), amphiphilic molecules can self-assemble into a large variety of morphologies, such as spherical micelles, cylindrical micelles, reverse micelles, vesicles, lamellae etc.1 The idea of self-assembly is not limited to small molecule amphiphiles, but it can also be extended to the macromolecular amphiphiles often referred to as amphiphilic polymers, wherein both hydrophilic and hydrophobic segments are typically polymeric in nature. There is another type of amphiphile carrying a polymerizable unit at the junction of the immiscible segments, the polymerization of which results in the formation of amphiphilic brush type of polymers. In this context, I have utilized a biosourced starting material namely, itaconic acid to prepare several types of polymerizable amphiphiles, which upon polymerization leads to the formation of amphiphilic brush polymers with different architectures. In my presentation, I will discuss about few of those architecturally different amphiphilic brush polymers based on itaconate.
First, I will talk about the crystallization induced gelation in amphiphilic double-brush polymers, where we show that the gel-sol transition temperature as well as mechanical properties can be easily tuned by varying the length of the hydrocarbon side chain from C12 to C18.2 Finally, as these gels are biocompatible, we have shown that insulin can be encapsulated within the hydrogel and can be released in sustained manner for diabatic treatment.
In my second chapter, I will talk about core-shell type of amphiphilic brush polymers, wherein, I will discuss about the bulk properties of two types of core-shell type of polymers; in one case the hydrophilic segments at the core and hydrophilic segments at the shell, in another case the amphiphilicity is reversed.
In chapter 3, I will present multiple attempts to generate 2 dimensionally crosslinked polymer nanosheet structures based on itaconate followed by investigation of their thermal as well as morphological properties.
In the final chapter, I will talk about a different class of amphiphilic polymers with multiblock architecture carrying a diacetylene unit at the middle of the hydrophobic alkyl segment and explored the possibility of topochemical polymerization of the diacetylene within a single folded polymer chain with limited success
Understanding the role of paraspeckle components NEAT1 and PSPC1 in HCV life cycle and pathogenesis
No full textHepatitis C virus (HCV) is an enveloped, small, icosahedral, positive-sense single-stranded RNA virus that belongs to the Hepacivirus genus and the Flaviviridae family. HCV causes acute and chronic hepatitis which can range in severity from a moderate condition to a serious life-long condition involving liver cirrhosis and cancer. Around 1.5 million new cases of the hepatitis C virus are reported each year, with an estimated 58 million people worldwide carrying the infection. According to the WHO report, 2,90,000 people died of hepatitis C infection in 2019, primarily due to cirrhosis and hepatocellular carcinoma (HCC). HCV infection causes dysregulation of various host factors and signaling pathways, which might result in HCC. Several cellular entities, including paraspeckle components, are involved in the viral life cycle, pathogenesis, and disease progression. Paraspeckles are subnuclear bodies, composed of proteins like Paraspeckle Component 1 (PSPC1), Splicing Factor Proline and Glutamine Rich (PSF), and Non-POU Domain Containing Octamer Binding (NONO), etc. that bind to lncRNA Nuclear Paraspeckle Assembly Transcript 1 (NEAT1) and form a paraspeckle. They trap various proteins and mRNAs, hindering their function and thereby affecting the cell’s continued response to stress.
To understand the molecular basis of HCC, we have studied some of the key components of paraspeckle, the lncRNA NEAT1 and PSPC1 protein in HCV life cycle and pathogenesis. The specific aims of this study are:
1a. Understanding the role of NEAT1 in HCV-induced Hepatocellular Carcinoma
1b. Elucidation of the role of NEAT1 on the HCV life cycle
2. Possible role of paraspeckle protein PSPC1 in the HCV life cycle
Part 1a: Understanding the role of NEAT1 in HCV-induced Hepatocellular Carcinoma
NEAT1 lncRNA is a major component of paraspeckles that has been linked to several malignancies. Analysis of ‘The Cancer Genome Atlas (TCGA)’ database and validation in HCV-induced HCC tissue and serum samples showed significant high expression of NEAT1 in patients with liver cancer. Moreover, it was observed that NEAT1 levels increased with HCV infection, along with the size and number of the paraspeckles. To further understand the mechanism of NEAT1-induced HCC progression, we selected one of its targets, miR-9-5p, which regulates Beta Ig-H3 (BGH3) mRNA levels. Interestingly, miR-9-5p levels were found to be downregulated upon HCV infection, whereas BGH3 levels were upregulated showing a reverse correlation. Partial knockdown of NEAT1 increased miR-9-5p levels and decreased BGH3 levels, corroborating our initial findings. BGH3 levels were also found to be upregulated in HCV-induced HCC which is consistent with TCGA data and could be directly correlated with NEAT1 levels. As a known oncogene, BGH3 is directly linked to HCC progression mediated by NEAT1. Direct-acting antiviral (DAA)-based treatment is likely to minimize the progression of liver disease and liver-related mortality linked to HCV infection. However, in cirrhotic patients, the risk of HCC persists even after HCV treatment. Elevated levels of NEAT1 were found in serum samples of patients even after treatment with direct-acting antivirals (DAA), indicating that NEAT1 might be a molecular trigger that promotes pathogenesis. Collectively, these findings provide molecular insights into HCV-induced HCC progression via the NEAT1-miR-9-BGH3 axis.
Part 1b: Elucidation of the role of NEAT1 on the HCV life cycle
The expression of NEAT1 gets elevated in response to viral infection as a stress-induced lncRNA upregulation strategy. However, there are no reports on how NEAT1 or paraspeckles are involved in HCV infection. Interestingly, siRNA-mediated partial silencing of NEAT1 in Huh 7.5 cells increased both positive and negative-strand viral RNA, suggesting that NEAT1 negatively affects the HCV life cycle. NEAT1 resides in the paraspeckles, where it is associated with the proteins, PSF, NONO, and PSPC1. Several reports have indicated that in normal cells, PSF protein is bound to the promoter of several immune-responsive genes and represses their transcription. Upon viral infection, increased NEAT1 level sequesters PSF from the promoter of immune-related genes, thereby increasing their expression. PSF can bind to the DDX60 promoter and inhibit its transcription. We observed that DDX60 level decreases upon silencing of NEAT1 in the background of HCV infection. It appears, upon HCV infection, NEAT1 sequesters PSF from the DDX60 promoter, and hence DDX60 transcription increases. DDX60 is known to inhibit HCV RNA replication, which is regulated by NEAT1, and PSF. Results suggest that NEAT1 regulates HCV RNA by regulating DDX60 levels.
Part 2: Possible role of paraspeckle protein PSPC1 in the HCV life cycle
Paraspeckle protein PSPC1 (Paraspeckle Component 1) binds to poly(A), poly(G), and poly(U) RNA homopolymers, transports lipid-related genes from nucleus to cytoplasm and increases cell proliferation. PSPC1 is also known for regulating the life cycle of different viruses, but no reports are available on its role during HCV infection. We investigated the role of PSPC1 in HCV life cycle. Earlier, from our lab, we reported several RNA binding proteins of the host, such as HuR, La, and PTB, which relocalizes from the nucleus to the cytoplasm, bind to HCV RNA, and affect its life cycle. Similarly, PSPC1 protein was also found to be relocalized to cytoplasm upon HCV infection. Partial silencing of PSPC1 increased HCV RNA levels, suggesting negative regulation by PSPC1. Immuno-pulldown using anti-PSPC1 antibody followed by RT-qPCR suggested the binding of PSPC1 protein to HCV RNA. Bioinformatics analysis and UV-crosslinking experiments validated the binding of PSPC1 in the HCV 5’ UTR in the SLIV region. Competition UV-crosslinking experiment using cytoplasmic extract (S10) of Huh7.5 cells suggested that PSPC1 can replace host factors from the HCV 5’ UTR. We further observed that PSPC1 protein levels gradually decreased upon HCV infection. It appears, that as a host response, PSPC1 reduces HCV RNA level, and to prevent that as a viral response, HCV decreases PSPC1 protein level.
Taken together, in this study the NEAT1/miR-9-5p/BGH3 axis has been linked to the disease progression. Results put forward the idea of using the NEAT1 level as a potential biological marker for disease prognosis to help better strategize the follow-up treatment approaches. Also, the study unravels the dual control of the HCV life cycle by the Paraspeckle components, NEAT1, and PSPC1, which in turn contributes to viral pathogenesis.CSIR for Fellowshi
Prediction of Dynamical Systems by Constraining the Dynamics on the Observational Manifold
No full textEvolution models of dynamical systems posed as differential equations generally do not include all the factors affecting the system. This leads to a mismatch between the model prediction and the observations. In this work, an approach is developed where the observations are treated as constraints on the system dynamics. This problem is posed as a Differential-Algebraic Equation (DAE) system and the algebraic constraints are obtained from the system observation data. This leads to evaluation of extra forcing terms for keeping the dynamics on the observation constraints manifold by using Lagrange multipliers. The Lagrange multipliers generate the instances of the unmodelled forcing terms which, in turn, are used to modify the evolution rule to improve the prediction capability of the original nominal model.
Orbit prediction of Global Navigation Satellite System (GNSS) satellites which is essential for positioning has been studied to elucidate the above approach. In this context, this work studies the GNSS data and some techniques for mitigating the errors and biases in the raw measurements. Using the first principles, the constrained dynamical system equations are derived for the dynamics of the satellites in orbit. The DAE approach outlined in first paragraph is applied to predict orbit of a geostationary satellite of the BeiDou satellite constellation using historical International GNSS Services' precise ephemeris data. In our example, we observe a reduction in the predicted orbital position error by roughly 88% as compared to the nominal
gravitational model.
In another illustrative application, temperature predictions are done for a one-dimensional heat conduction system. This problem presents itself with a challenge of limited sampling in the temperature domain. The observed data is used to generate instances of extra terms in the evolution model. These instances are fitted to a regression model which is used during prediction.
As a further elucidation, estimation of the coefficients of a nominal differential equation model from observed data of the system is briefly studied
A Relational Study of Personality Traits, Learning Styles, Learning Competencies, Learning Methods, and Assessment Methods for Engineering and Management Students Studying the Internet of Things Related Knowledge Areas
No full textAccording to India's Human Resource Development Ministry, as of 2019, 6000 plus engineering institutions across India enrolled 2.9 million students every year. They also mentioned that nearly 1.5 million students graduated and entered the job market every year. Of these, 30% were employable, and only 7% were skilled. In this era of technology-intensive organizations and automation, the expectations set by the industries on the higher educational institutions have been to have the students quite well-skilled and partially industry-ready. Hence, the government of India suggested that higher educational institutions consider the academic requirements of the workforce developing intelligent technologies and thereby facilitate such required knowledge areas using appropriate learning methodologies.
As per Gartner's Hype Cycle, one such intelligent technology in this industry 4.0 era, considered for my study, is the Internet of Things (IoT). Courses revolving around the IoT are currently offered to engineering and management students as there is a demand for technology developers and managers in the industries. Further, given the learning process, students exhibit different ways of learning with regards to their learning styles and learning methods. It is observed that personality traits play an essential role in the preferred learning styles, and the learning methods are significantly related to the assessment methods of the students. It is also observed that the learning styles are significantly related to the learning methods, and the learning competencies have a significant impact on the learning methods in an educational setting. Hence, a clear understanding of the associations mentioned above is pivotal. By examining these relationships for those students studying the Internet of Things related knowledge areas, the current study is a step forward in engineering and management education as it could potentially lead to better learning outcomes.
Subsequently, the following four objectives are framed to address the research study:
1. To assess and relate the personality traits with the learning styles
2. To assess and relate the learning methods with the assessment methods
3. To relate the learning styles and the learning competencies with the learning methods
4. To provide recommendations in the process of learning and assessment methodologies
The objective of the study is to understand the relationship between constructs. The hypotheses are then postulated wherein their validity is accepted or rejected based on the statistical tests. This study has adopted the primary data collection method by using a 5-point Likert scale-based questionnaire as the primary research instrument. The sample respondents selected were final year engineering students pursuing their studies in programs such as computer science, information science, electronics and communications, and final year management students pursuing their studies in programs such as industrial engineering management, data sciences, information systems, and business management. Students for the study were selected from those colleges that offered the IoT related knowledge areas as core courses in their respective engineering and management programs. A total of 2315 respondents studying the IoT related knowledge areas were sampled, of which 1588 were from the engineering program, and 727 were from the management program. Those students selected for the study were from colleges across the state of Karnataka in the southern part of India.
Descriptive statistics facilitate the summarization of the recorded data by describing the association between variables within the sample. The application of the descriptive statistics method assisted in analyzing the constructs items-wise and dimension-wise for engineering and management students. After descriptive statistics, an independent t-test was applied for testing the proposed hypotheses. The t-test for this study assisted in understanding the significant difference in the path of the constructs among engineering and management students. Further, a correlation matrix was developed between the constructs for both engineering and management students. This test in the study assisted in understanding the degree of association between the independent and the dependent variables among engineering and management students. In the end, the application of PLS-SEM was performed to evaluate the relationship frameworks with the constructs under the study. This test for the study assisted in establishing the reliability and the validity of the constructs, outer model loadings of the reflective constructs, explanatory power between the constructs, and the significance of the relationship between the constructs through bootstrapping analysis.
The study shows a significant relationship between the constructs for all the above associations for engineering and management students. The study also shows the impact of learning competencies over learning styles on the learning methods for students. However, the study shows no significant difference in the path of the relationship between the constructs among engineering and management students.
Understanding the linkages between personality traits and learning styles, learning methods and assessment methods, and learning styles and learning competencies with learning methods assist the students in their learning process. This research in the future could help educators grasp the complex nature of student diversity and relate them to different kinds of assessments that could potentially enhance the students' learning outcomes. Instructors who recognize the importance of personality traits, learning styles, and learning competencies and consider them vital for effective learning may design courses, assignments, and other teaching and learning approaches that encourage students to adopt required learning methods.
Later, a forced-choice questionnaire was given to all the students in the sample. The forced-choice questionnaire consisted of preferences that were opted by the students. One set of preferences consisted of existing practices in the process of learning and assessment methodologies, and the other set of preferences consisted of possible changes to the existing practices suggested by the literature and the faculties. Based on the students' preferences and the faculties' feedback, possible changes to the learning and assessment methodologies framework are recommended. With the implementation of this framework, the potential impact on the students towards enabling their learning effectiveness and the possible institutional outcomes towards enhancing the research output are highlighted. Further, universities in India could use this proposed learning and assessment methodologies framework for further validation and studies for other programs. They could have a control group and a test group to see which one of the two, i.e., existing practices or proposed framework for learning and assessment, enables better learning and research outcomes
Post translational modification and DNA binding studies with two nucleoid associated proteins of Mycobacterium tuberculosis
No full textGenome in prokaryotes is found in a small confinement called nucleoid. The nucleoid compaction is brought about by the combined action of topoisomerases and Nucleoid associated proteins (NAPs). Topoisomerases maintain topological homeostasis of bacterial chromosomes by catalysing changes in DNA linking number by supercoiling, relaxation and decatenation. NAPs are small basic proteins that bind to the DNA and bring about coating, wrapping, and bridging of the genome. Unlike many well studied prokaryotes like Escherichia coli, Mycobacterium tuberculosis (M. tuberculosis) has underrepresentation of NAPs. Earlier work carried out in the laboratory has shown that NAPs collaborate with other NAPs, other proteins such as Topoisomerase I, as well as show different post translational modifications that alter their DNA binding properties, in order to cope up with the situation. The work shows the effect of acylation on the properties of mycobacterial NAP MtHU. It also covers the occupancy of Rv3852, a unique NAP, on the mycobacterial genome and its effect.HU is one of the abundant NAPs in mycobacteria. It is a histone like protein that undergoes post translational modification, as previously reported by the laboratory. Study was carried out to elucidate the effect of post translational modification of HU, specifically acylation, upon its DNA binding properties. Two modifiers, belonging to GNAT superfamily of proteins, namely Rv2416c (Eis) and Rv0802c, were found to acetylate as well as succinylate MtHU. Eis could acetylate as well as succinylate HU very effectively. However, Rv0802c was found to show better succinyltransferase activity than acetyltransferase activity. Both these modifications modulated the DNA binding properties of HU. Ectopic expression of Eis in Mycobacterium smegmatis (M. smegmatis) caused decompaction of genome, unlike ectopic expression of Rv0802c. Rv1151c is the only characterized Sirtuin like protein in M. tuberculosis. The gene was cloned, expressed and protein was purified. Rv1151c catalysed deacetylation as well as desuccinylation of HU in the presence of NAD. Its activity was however inhibited in the presence of nicotinamide, a known inhibitor of NAD-dependent deacetylases. Deacetylation restored the DNA binding properties of HU. However, its ectopic expression in M. smegmatis didn’t have any effect on the compaction status of the genome.
Rv3852 is a unique NAP found only in slow growing mycobacteria. Although thought to be the mycobacterial counter part of H-NS, the studies from the laboratory showed that Rv3852 is unique in the sense that it binds to the genome as well as tethers to the membrane through its carboxyl terminal region. Genome-wide binding study of Rv3852 on M. tuberculosis was carried out by chromatin immunoprecipitation followed by sequencing. It was found to bind to DNA in a sequence non-specific manner. By binding to genome, it seems to regulate the expression of genes associated with iron homeostasis, polyketide synthases and genes associated with the synthesis of pthiocerol dimycocerosates
Stop codon readthrough of NNAT mRNA and its role in neuronal differentiation
No full textProtein synthesis terminates at the first stop codon encountered by the ribosome. In stop codon readthrough, translation termination is suppressed, enabling the ribosomes to continue translation beyond the canonical stop codon upto a downstream in-frame stop codon resulting in a C-terminally extended polypeptide. Several cis- or trans-acting elements contribute to a programmed stop codon readthrough event. Evidence of stop codon readthrough and the functional significance of the readthrough isoforms have been reported for VEGFA, AGO1, AMD1, AQP4, LDH, MDH, MTCH2 and VDR. The first evidence of functionally relevant, programmed stop codon readthrough was reported in VEGFA. In the same study, genome-wide bioinformatic based analysis was done to identify other potential readthrough candidates. NNAT (encodes Neuronatin), the focus of this study, was one of the potential readthrough candidates identified.
Neuronatin (NNAT) is a small proteolipid expressed from chromosome 2 in mice and chromosome 20 in humans. The gene encoding NNAT, resides in the opposite strand within the intronic region of a larger gene, BLCAP (Bladder Cancer Associated Protein). Also known as Peg5 (Paternally Expressed Gene 5), NNAT is maternally imprinted and is thus expressed only from the paternal allele. Conservation of the proximal 3ꞌUTR of NNAT upto a second in-frame stop codon in different mammals led us to the hypothesis that NNAT mRNA undergoes stop codon readthrough. In this study, we have demonstrated readthrough in NNAT using luminescence- and fluorescence-based reporters as well as by Western blot. Analysis of previously reported ribosome profiling data coupled with the detection of endogenous NNATx (readthrough isoform) by Western blot using an antibody specific for the C-terminal extension of NNATx, confirmed stop codon readthrough in NNAT. We have also identified several cis-acting factors and an RNA-binding trans-acting factor, NONO/p54nrb, that drive stop codon readthrough in NNAT.
To understand the functional role of the readthrough isoform, NNATx, we have overexpressed the canonical (NNAT) and the readthrough (NNATx) isoforms in a mouse neuroblastoma cell line, Neuro-2a. NNAT increases cytoplasmic Ca2+ levels by inhibiting SERCA2 (Sarco/endoplasmic reticulum Ca2+-ATPase isoform 2). SERCA2, a P-type ATPase, is localized on the membrane of the endoplasmic reticulum and pumps Ca2+ from the cytoplasm to the ER. By inhibiting SERCA2, NNAT increases Ca2+ levels in the cytoplasm and promotes neuronal differentiation. Unlike NNAT, the readthrough isoform, NNATx, fails to interact with SERCA2 and does not increase cytoplasmic Ca2+ levels. As a result, NNATx does not promote neuronal differentiation.
To further understand the specific role of NNATx, we decreased the endogenous expression of NNATx using an antisense oligonucleotide (named as +43 ASO) that targets a region between 43 to 66 nucleotides in the inter stop codon region (the 3ꞌ untranslated region between the 1st and 2nd stop codons) of NNAT. With reduced expression of endogenous NNATx, +43 ASO treated cells showed increased cytoplasmic Ca2+ compared to a non-targeting oligonucleotide treated cells. Thus, by modulating stop codon readthrough of NNAT, we show that NNATx fails to promote neuronal differentiation as it fails to increase cytoplasmic Ca2+ levels.
Overall, these results demonstrate regulation of neuronal differentiation by SCR of NNAT. Importantly, this process can be exogenously regulated using a synthetic antisense oligonucleotide.MHR
Control and Safety of Multi-UAV Systems for Collaborative Payload Transportation and Target Tracking
No full textUnmanned aerial vehicles (UAVs) have been widely used in reconnaissance, remote sensing, disaster relief, and agricultural applications. Many applications require multiple UAVs to cooperate to complete the assigned tasks. Two such applications of interest involving multi-UAV collaboration, which are studied extensively in the existing literature are payload transportation and collective target tracking. In this thesis, we study the design of control laws in the context of these applications. Both the applications involve the guidance of the UAVs to a goal or target, while they mutually interact and fly in a formation. The payload transportation problem addresses the issue of limited lifting capabilities of UAV systems, and the need to aggregate them to provide sufficient thrust to lift the payload. The target tracking problem, however, adds robustness to the target monitoring and estimation task with a team of UAVs. The utilization of multiple UAVs in these applications adds redundancy, and thus robustness to UAV failures. Operating such complex systems requires the design and implementation of practical motion control laws, which in turn warrant the design of simple formulations. Such formulations make the coordination of scaled UAV formations possible, besides providing a framework for accommodating the aspect of their safety in the control design.
We employ a two-pronged approach in the control design for payload transportation and target tracking problems. In the first part of the thesis, we develop distance and bearing-based proportional derivative (PD) motion control laws meeting each identified problem objective in a modular framework. In the second part of the thesis, we address the constraints on the UAVs in a formation, in the context of obstacle and inter-UAV collision avoidance, and actuator saturation. Our multi-objective modular control approach makes it possible to modify the control laws based on the objectives of the formation, making our work applicable to a variety of problems. A pair of UAVs that carry a payload and settle on standoff circles about a virtual target, while maintaining their mutual distance, is considered as an example application to demonstrate our approach. As compared to a leader-follower role assignment in the existing literature, we do not assign any roles to the UAVs, which are assumed to be homogeneous. Additionally, we design the guidance strategy for UAVs to reach a target, independent of the payload, relying on the UAV-payload geometry to guide the attached payload to the target location. We simulate agricultural spraying operations in an annular swathe, and over a field using the lawnmower trajectory, with dynamic UAV and payload models, to illustrate how the modular control design is practically applicable. The modular design is augmented by our utilization of non-smooth control laws using the signum and saturation nonlinearities, which further simplifies the control formulations in the payload transportation application, making real-world implementation practical. Use of such non-smooth motion control laws for UAV formations is not prevalent in the existing work, and thus is a major contribution of the thesis. Further, the Lyapunov stability analyses of the multi-objective smooth and non-smooth control laws using results from non-smooth analysis, illustrate the advantages of our modular control approach in yielding analytical guarantees of kinematic stability.
An additional benefit of our control approach for multi-UAV applications is in providing a platform for integrating operational and safety constraints. The aspect of safety in collaborative UAV applications has not been properly addressed in the existing literature. Formations often require the UAVs to maintain a safe distance from each other, while collectively staying away from obstacles in the environment. To this end, we design actuator saturation constraints, and safety constraints for obstacle and inter-UAV collision avoidance. Control barrier functions (CBFs) are used to develop and enforce these constraints in a control-optimization problem involving a payload which is rigidly attached to two UAVs which settle on target standoff circles, while navigating an environment with obstacles. We extend this optimization problem further and add control Lyapunov function (CLF) constraints, to a problem involving four UAVs and a semi-flexible payload requiring safe shape-manipulation to navigate between obstacles. We also explore the utilization of barrier Lyapunov functions (BLFs) in target tracking problems, where a formation of UAVs tracks a moving target while maintaining inter-UAV separation within specified bounds. The barrier functions provide implementable constraints that are easily integrated with our modular multi-objective control architecture, to provide real-time solutions for collaborative UAV applications. This is extensively demonstrated using numerical and ROS-Gazebo simulations with dynamic UAV and payload models, using the proposed controllers and constraints. Thus, by incorporating these barrier functions in our analysis, our second major contribution is the safety-critical control design of multi-UAV systems.
To summarize, the thesis contributes by developing simple, scalable, and implementable motion control laws to guide UAV formations towards a target, while maintaining their individual and collective safety in the collaborative payload transportation and target tracking applications
Refractive-Index-Matched Fluorescent Particle Image Velocimetry for Investigation of Flow in Immersed Granular Materials
No full textRefractive-Index-Matched Fluorescent Particle Image Velocimetry for Investigation of Flow in Immersed Granular Materials
The ubiquity of granular materials and their importance in everyday life, industry, and nature make their study imperative for proper manipulation of the flow. As granular materials are opaque, optical imaging experiments are limited to studies at the free surface or transparent boundaries of the flow. Though techniques like magnetic resonance imaging and X-ray tomography have been used to obtain information from the interior of the flow system, these studies are limited to a small class of granular materials. Therefore, a modified yet simple optical imaging technique that can access the bulk of the flow is desirable. Our study employs refractive-index-matched fluorescent particle image velocimetry (RIM FPIV) to obtain information about the bulk of the flow. In RIM FPIV, the system of dry granular materials is made transparent by adding a suitable liquid whose refractive index is close to that of the particles (glass beads). The addition of liquid results in immersed granular materials, in which the particles are completely submerged in the liquid. Reported literature indicates that immersed granular materials exhibit shear banding and rate-independent rheology at slow shear rates, just like dry granular materials. A recent study using discrete element method (DEM) simulations and experiments reports a dilation-driven vortex in dry granular materials in the slow flow regime. However, the opacity of the granular materials restricted the experimental studies to visualizing only the free surface of the flow. By utilizing the similarities between the two media, our study on an immersed granular medium could give us insight into the flow behaviour in the bulk of dry granular systems.
In this thesis, we experimentally study the flow of immersed granular materials and compare our observations with that of dry granular media. We perform experiments on slowly sheared immersed granular materials in a cylindrical Couette and present velocity profiles for the free surface using conventional PIV and the bulk of the flow using RIM FPIV. We observe broadening of the shear band in immersed granular materials and explain how the presence of fluid in interstitial spaces is responsible for such behaviour. We also report increased radial flow in the free surface of immersed granular materials due to enhancement of dilation by the fluid. In our RIM FPIV experiments, the velocity profiles in the bulk of the flow show radially inward flow close to the free surface and radially outward flow close to the bottom of the Couette cell. This observation is consistent with the simulations previously performed on a system of dry granular materials, indicating a circulating axial flow. Therefore, this study is a good starting point for experimentally validating the secondary axial flow in the bulk of both immersed and dry granular materials
2,3-Dideoxy Sugars in Glycoconjugations and Cyclic Oligosaccharide Synthesis
No full text2,3- Dideoxy sugars are versatile synthons for organic synthesis. The
applications are diverse in biological systems and organic synthesis. In the first part of the
thesis, 2,3-unsaturated sugars are used for the glycoconjugation of amino acids, peptides and
proteins. In the later part, 2,3-dideoxy sugar is used to synthesize carbohydrate
macrocycle. Finally, sugar vinyl sulfoxide is used to synthesize substituted pyran via 2,6-
anhydro sugar formation.
Chapter 1 of the thesis is divided into two parts. The first part describes the literature
on unsaturated sugar, especially 2,3-unsaturated sugars, synthesis and their
modifications. Attention is given to their addition reactions with nucleophiles and
conjugation with biomolecules. A brief introduction to glycoconjugation is also reported in
this part. Different glycoconjugation methods are discussed briefly, and the advantages are
compared accordingly. The second part of this chapter elaborates on the synthesis of cyclic
oligosaccharides. The approaches and the difficulties in the respective
approaches are mentioned accordingly. Challenges with synthesising small cyclic
oligosaccharides are cited according to the available literature. Current development
in the field is also covered in the discussion.
Chapter 2 of the thesis deals with the glycoconjugation methods using sugar vinyl
sulfoxide involving Michael addition reaction. Glycoconjugations of amino acids, peptides
and protein, namely lysozyme are demonstrated in benign physiological conditions. The
smaller glycoconjugated molecules are characterized with the help of NMR spectroscopy
and mass spectrometry, while the larger glycoconjugated peptide and protein are
characterized with the help of mass spectrometry. Biophysical studies of glycoconjugated
lysozyme showed increased stability in the presence of trypsin while retaining its antimicrobial
activity. Thus, a benign glycoconjugation method is developed.
Chapter 3 of the thesis unravels further potential of glycoconjugation using sugar vinyl
sulfoxide. PETIM dendrimers of generation zero to three are glycoconjugated with sugar
vinyl sulfoxide. The glycoconjugations of the lower generation dendrimers are confirmed
using NMR spectroscopy and mass spectrometry; for higher generations, only NMR
spectroscopy was employed for the characterization. The first-order reaction rate constant
of the glycoconjugation reaction is also determined using NMR spectroscopy. Further
biological evaluation of the native and glycoconjugated PETIM dendrimer reveals that
PETIM dendrimers show selective antibacterial activity against M. smegmatis, and the
native dendrimers show higher efficacy over the glycoconjugated dendrimer.
Chapter 4 of the thesis describes the synthesis of the cyclic disaccharide molecule
composed of 2,3-dideoxy furanoside monomer units. The synthesis started from protected
glucal molecules and followed a few simple reaction steps, including the Ferrier reaction,
desulfurization reaction, and selective hydroxy group protection and finally,
glycoconjugation reaction. While the formation of the disaccharide is confirmed using NMR
spectroscopy and mass spectrometry, the conformation of the constituting monomeric unit
of the cyclic disaccharide is ascertained through solid state structure determination using
the single crystal X-ray diffraction method. The ring contraction of the pyranoside monomer to
furanoside cyclic disaccharide is explained by two plausible mechanisms involved in the
glycosylation step. Further encapsulation property of the cyclic disaccharide molecule was
evaluated against the 1-aminoadamantane using the ITC method. This experiment allows looking into the thermodynamics of the encapsulation and the encapsulation mode of the
molecule.
Chapter 5 of the thesis shows sugar vinyl sulfoxide's application and potential
as a synthetic intermediate. Intra-molecular Michael addition reaction of the sugar vinyl
sulfoxide in basic condition affords elusive 2,6-anhydro sugar molecules in a single step.
Selective opening of the bicyclic ring of the anhydro sugar converts it to a substituted
pyran. The applicability of this two-step, one-pot reaction is also tested on sugar vinyl
sulfoxide derived from galactal.
The thesis describes the achievement of the diversification of 2,3-unsaturated sugar. A
benign glycoconjugation method is developed and adequately characterized. The synthetic
potential of 2,3-dideoxy sugar is demonstrated through the synthesis of cyclic disaccharide
via a ring contraction of pyranoside to a furanoside. And finally, a two-step reaction
protocol converts pyranoside sugar into a substituted pyran