Ohmic contacts for organic optoelectronic devices

In last three decades, great progress has been made in the field of organic electronics. Researchers have put tremendous efforts to make new materials and device architectures, which has resulted in a great commercial success of organic light emitting diodes in mobile phone and television display screens. Despite that, still today it is challenging to make organic electronic devices that are efficient in performance, stable in operation and are economical in production at the same time. The objective of this thesis is to understand fundamental charge transport properties of small molecules based organic semiconductors and to develop novel organic electronic device architectures. One of the prime requirements for efficient organic optoelectronic devices is to have ohmic charge injection contacts. Therefore, first a charge injection strategy for making ohmic hole contacts is developed. Using this strategy, ohmic hole contacts are achieved on organic semiconductors with an ionization energy up to 6 eV. As a result, the hole transport in a wide range of organic small molecules with ionization energy between 5 to 6 eV could be investigated. Despite the difference in their chemical structures, similar bulk hole mobilities in the range of $1\times10^{-4}$ cm$^{2}$V$^{-1}$s$^{-1}$ were observed for all molecules. The hole transport was also investigated using molecular multiscale simulations, an excellent agreement was obtained with the experimental results. Despite fullerene derivatives being known as electron conductors, It was found that the fullerene derivative ICBA has a very good hole mobility of $1.4\times10^{-3}$ cm$^{2}$V$^{-1}$s$^{-1}$ which is the same as bulk electron mobility, demonstrating the intrinsic bipolar charge-trasnport character of organic semiconductors. It is found that charge trapping is causing the frequently observed unipolarity in organic semiconductors, causing preferential conduction of either holes or electrons. This limits the efficiencies and stabilities of the organic optoelectronic devices. By investigating charge trapping in a wide range of organic semiconductors, we have identified that when the electron affinity is lower than 3.6 eV, electron transport becomes trap limited and when ionization energy is higher than 6 eV hole transport becomes trap limited. As a result, within this energy window of about 2.4 eV trap-free charge transport is observed. Combining this energy window for trap-free transport with our developed charge injection strategy, an efficient and stable single layer OLED based on a neat thermally activated delayed fluorescence emitter is demonstrated. The OLED has a maximum external quantum efficiency of 19% at a luminance of $500$ cdm$^{-2}$and a lifetime to 50% of initial luminance of $1000$ cdm$^{-2}$ of 1,880 h. It has an exceptionally low operating voltage of 2.9 V at a luminance of $10,000$ cdm$^{-2}$, which resulted in a maximum power efficiency of $87$ lmW$^{-1}$

"'राजवल्लभ' અને 'शिल्पस्मृतिवास्तुविद्यायाम्' નું તુલનાત્મક અધ્યયન"

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Identification of clinker formation in power station boilers – CFD based approach

Pulverised coal combustion continues to be one of the main conventional methods of producing electricity over the last several decades. Mineral matter present in coal is usually present as free ions, salts, organically bound inorganic and hard minerals. During coal combustion these minerals partly vaporized, coalesce or fragment. The mineral matter in coal transforms into ash during combustion and deposition on wall surfaces causing problems such as fouling and slagging. The deposited lumps called clinkers, mainly in radiation zone directly exposed to flame radiation resulting to slagging, while sintered deposit in convection zone not directly exposed by flame radiation called fouling. The scope of this work encompasses identification of slagging and clinker formation areas in a typical 330 MW boiler using commercial code FLUENT and several available empirical indices. The propensity of the slagging with the used coal is calculated by several thermal indices. Temperature distributions, velocity profiles and particle trajectories were analysed and utilised to predict the most probable zones likely to experience clinker formation. Most probable spots for slagging were found in the radiation zone near to the nose of furnace and left-top side of superheater tube sections which agrees closely with the plant observations. However, the propensity of deposited ash obtained from the plant is seemed low to medium using several indices.Results from the current investigation demonstrate the usefulness of modelling approach in identifying the probable zones of clinker formation which can prove to be valuable for power utilities to adopt corrective measures for soot blowing to clean the ash deposits before it grows bigger in size

Drug Repurposing: Scopes in Herbal/Natural Products-based Drug Discovery and Role of in silico Techniques

Natural products and their derivatives are the most promising and prolific resources in identifying the therapeutic small compounds with potential therapeutic activity. Nowadays, working with herbal or natural products can be boosted by collecting the data available for their chemical, pharmacological, and biological characteristics properties. Using in silico tools and methods, we can enhance the chances of getting a better result in a precise way. It can support experiments to emphasis their sources in fruitful directions. Though due to their limitations with respect to current knowledge, quality, quantity, relevance of the present data as well as the scope and limitations of cheminformatics methods, herbal product-based drug discovery is limited. The pharmaceutical re-profiling is done with the main objective to establish strategies by using approved drugs and rejected drug candidates in the diagnosis of new diseases. Drug repurposing offers safety lower average processing cost for already approved, withdrawn drug candidates. In silico methods could be oppressed for discovering the actions of un-investigated phytochemicals by identification of their molecular targets using an incorporation of chemical informatics and bioinformatics along with systems biological approaches, hence advantageous for small-molecule drug identification. The methods like rule-based, similarity-based, shape-based, pharmacophore-based, and network-based approaches and docking and machine learning methods are discussed

Pharmacovigilance study of beta adrenergic receptor antagonists in patients visiting department of medicine of a tertiary care hospital, Surendranagar, Gujarat, India

Background: The objective of this study was to evaluate incidence, patterns, and severity of Beta blockers induced adverse drug reactions (ADR).Methods: A total of 500 patients taking Beta blockers were enrolled in the study by taking an informed consent. Reporting of all Beta blockers-induced ADRs was done by filling CDSCO ADR form. All ADR reports were evaluated according to WHO-UMC causality assessment scale.Results: A total of 64 ADRs (48 males and 18 females) was observed in 500 patients taking beta blockers. Of 64 ADRs, 20 (31.25%) were mild, 34 (53.13%) were moderate, and 10 (15.62%) were classified as severe. 26 (40.62%) ADRs were classified as Probable, followed by 22 (34.38%) ADRs were in Possible category, 8 (12.5%) were in certain category, 4 (6.25%) ADRs were unlikely and 4(6.25%) ADRs were Conditional. Among 64 ADRs, 22 (3.43%) patients developed bronchospasm, 10 (1.56%) bradycardia, 8 (1.25%) fatigue, 8 (1.25%) nausea/GI upset, 4 (0.62%) erectile dysfunction, 4 (0.62%) dry cough, altered lipid profile, insomnia, night mares and diarrhea are other rare ADRs.Conclusions: Incidence of ADRs by beta blockers is 12.80% with bronchospasm as the most common ADR followed by bradycardia. As atenolol is most frequently used beta blocker, ADRs due to atenolol are more common

Pharmacovigilance study of angiotensin-converting enzyme inhibitors in patients visiting Department of Medicine of a Tertiary Care Hospital, Surendranagar, Gujarat

Background: The objective of this study was to evaluate incidence, patterns, and severity of angiotensin-converting enzyme inhibitor (ACEI) induced adverse drug reactions (ADR).Methods: A total of 500 hypertensive patients taking ACEI was enrolled in the study by taking an informed consent. Reporting of all ACEI-induced ADRs was done by filling CDSCO ADR form. All ADR reports were evaluated according to WHO-UMC causality assessment scale.Results: A total of 53 ADRs (31 males and 22 females) was observed in 500 hypertensive patients taking ACEI. Of 53 ADRs, 22 (41.51%) were mild, 28 (52.83%) were moderate, and only 3 (5.66%) were classified as severe. 7 ADRs (13.21%) were classified as certain, 30 ADRs (56.60%) were in probable category, 8 (15.09%) were in possible category, 4 (7.55%) in unlikely category, 3 (5.66%) in conditional category (unclassified), and 1 ADR was in unassessable (unclassifiable) category. Among 53 ADRs, 24 (4.80%) patients developed dry cough, 8 (1.60%) hypotension, 2 (0.40%) headache, 2 (0.40%) dizziness, 3 (0.60%) nausea/bowel upset, 3 (0.60%) rashes, 2 (0.40%) developed angioedema, 3 (0.60%) dysgeusia, hyperkalemia, acute renal failure, proteinuria are rare.Conclusions: Incidence of ADRs by ACEIs is 10.60% with cough as the most common ADR followed by hypotension. As enalapril is most frequently used ACEI, ADRs due to enalapril are more common