Some Fixed Point Result in Metric Spaces for Rational Expression

In the present paper we establish some fixed point theorems in complete metric space taking rational expression. Our Result Generalize the result of many authors. Key words: Fixed point, common fixed point, rational expression

Interfacial Mechanism for Efficient Resistive Switching in Ruddlesden-Popper Perovskites for Non-volatile Memories

Ion migration, one origin of current–voltage hysteresis, is the bane of halide perovskite optoelectronics. Herein, we leverage this unwelcome trait to unlock new opportunities for resistive switching using layered Ruddlesdsen–Popper perovskites (RPPs) and explicate the underlying mechanisms. The ON/OFF ratio of RPP-based devices is strongly dependent on the layers and peaks at n̅ = 5, demonstrating the highest ON/OFF ratio of ∼104 and minimal operation voltage in 1.0 mm2 devices. Long data retention even in 60% relative humidity and stable write/erase capabilities exemplify their potential for memory applications. Impedance spectroscopy reveals a chemical reaction between migrating ions and the external contacts to modify the charge transfer barrier at the interface to control the resistive states. Our findings explore a new family of facile materials and the necessity of ionic population, migration, and their reactivity with external contacts in devices for switching and memory applications

Hybrid Perovskite-Based Memristor Devices

Modern electronic devices are being developed for cutting-edge applications, as a result of recent developments in artificial intelligence (AI) and machine learning (ML). The demand for “universal memory” devices with exceptional qualities, such as high data transmission speed, storage capacity, non-volatility, and low operation voltage has increased as a result of the industry’s ability to sustain such a high growth rate. In this chapter, we elaborate on the history of the evaluation of novel memristor structures, various switching mechanisms, and materials for developing memristor devices. The current state of the art of the memristor for various applications, such as data storage, artificial synapse, light-induced resistive switching, logic gates, and mimicking human behavior is also systematically summarized

Hot carrier extraction in CH3NH3PbI3 unveiled by pump-push-probe spectroscopy

Halide perovskites are promising materials for development in hot carrier (HC) solar cells, where the excess energy of above-bandgap photons is harvested before being wasted as heat to enhance device efficiency. Presently, HC separation and transfer processes at higher-energy states remain poorly understood. Here, we investigate the excited state dynamics in CH3NH3PbI3 using pump-push-probe spectroscopy. It has its intrinsic advantages for studying these dynamics over conventional transient spectroscopy, albeit complementary to one another. By exploiting the broad excited-state absorption characteristics, our findings reveal the transfer of HCs from these higher-energy states into bathophenanthroline (bphen), an energy selective organic acceptor far above perovskite's band edges. Complete HC extraction is realized only after overcoming the interfacial barrier formed at the heterojunction, estimated to be between 1.01 and 1.08 eV above bphen's lowest unoccupied molecular orbital level. The insights gained here are essential for the development of a new class of optoelectronics

Morphology dependent photophysics in bulk heterojunction organic solar cells

The morphology of organic active layer plays a crucial role in the performance of organic solar cell devices. Understanding of charge carrier mechanism governed by the distinct morphologies of the active blend systems is required to enhance the power conversion efficiencies in solar cells. In this work, we have investigated the ultrafast photophysics in a wide range of active blend systems and correlated with their nano-morphology and optoelectronic properties in solar cell devices. External electric field treatment, inclusion of the solvent additive and solvent vapour annealing of the active layer were adopted as three different processing methods to modify the morphology of the active blend system in bulk heterojunction solar cells. External electric field treatment on the active layers based on semicrystalline donor polymers (i.e. P3HT and P3BT) promotes self-organization in the system and enhances the exciton/polaron generation, which results in improved device efficiency. On the other hand, inability of self-organization, complex molecular structure and larger molecular size of the amorphous donor polymers (i.e. PTB7 and PCPDTBT) make this approach unsuitable, resulting in invariant optoelectronic performance. Addition of a small fraction of poor solvent in P3HT:PCBM blend system is a room temperature processing approach to improve the device efficiency, which is suitable for roll-to-roll applications. The performance enhancement by solvent additive is comparable to the thermally annealed devices, however certain additives cause strong phase separation of the donor and acceptor, which result in higher charge carrier recombination. Similar to conjugated polymer systems, the suppression of charge carrier losses is also important in solution processed small molecule blend system. Solvent vapour annealing of DRCN5T:PCBM active blend layer helps to reduce the predominant monomolecular recombination in the finely mixed system. Hence, this improved the performance from 3.3 % to 10%. This work provides new in-depth understanding on the morphology dependent charge carrier dynamics, which will lead to further improvements in organic solar cell devices.​Doctor of Philosophy (SPMS

microRNAs as potential tools for ‘miR’aculous CHO cell phenotypes in Bioprocessing systems

Chinese Hamster Ovary (CHO) cells are the biopharmaceutical industry’s “mini biofactories” for the production of complex, post-translationally modified therapeutic proteins. In order to address the ever-growing market need for these recombinant proteins, various genetic engineering tools have been employed. Here, we describe genetic approaches to improve CHO cell culture longevity, with a view to increasing overall process yield via the manipulation of two miRNAs: Let-7a and miR-7. Previous miRNA profiling studies in our laboratory and in the published literature helped in the identification of these miRNAs, which have shown to be disregulated in various tumor types and are key regulators of the cell cycle. Therefore, this stimulated the interest of our research group to manipulate these miRNAs in CHO cells with a view to positively impact bioprocess-relevant CHO cell phenotypes. In the first approach, we used a Let-7 sponge decoy vector to deplete endogenous Let-7 levels with a view to increasing culture longevity and productivity of CHO-K1 SEAP expressing cells. Despite let-7 having a recognised role in deregulated cell growth no improvement was observed in stable, sponge-transfected clones. Out of a panel of 40 clones, we observed only two with improved cellular viability in 24 well plate format, however, the results were not reproduced in a 5 mL scale-up batch study. In the second approach, we targeted a previously verified miRNA for improved CHO cell growth and productivity i.e. miR-7, using a bacterial genome-editing tool, CRISPR-Cas9. A considerable amount of optimisation work was performed to establish the CRISPR system for use in the lab, initially using eGFP as model target gene in CHO cells. Finally we designed single guide RNAs to target Cas9 to the miR-7a-5p genomic locus to disrupt miR-7 in order to enhance growth of a CHO-K1 cell line producing an IgG-1. We estimated ~ 40% targeting efficiency of miRNAs using this approach. After an extensive screen, one stable clone was identified with what appeared to be a heterozygous deletion of one miR-7a copy. We demonstrate that CRISPR-Cas9 can be successfully used to target miRNA loci in the CHO genome but that functional knockout may be more difficult compared to protein coding genes

Clinicohistopathological profile of 85 pediatric patients attending skin outpatient department: A retrospective analysis at a municipal hospital of middle-east region of Ahmedabad

Introduction: Skin diseases are a major health problem in pediatric age group. Skin biopsy and histopathological examination are required in clinically challenging situation to clinch the correct diagnosis. Aims and Objectives: To recognize clinical and histopathological relevance in different pediatric dermatoses and to compare the results. Materials and Methods: A total of 85 skin biopsies were taken over a period of 3 years between August 1, 2012, and July 31, 2015, at our tertiary care hospital and were analyzed by histopathological study. Results: A total of 85 pediatric patients were included in this study. Of these, female were 48 (56.47%). Main diseases diagnosed during the study were bacterial diseases – 20 (23.52%), noninfectious papulosquamous lesions – 13 (15.29%); nevi, vascular tumors and malformations, and viral diseases were 6 (7.05%) each. Conclusion: The histopathologic diagnosis inturn is used as an adjuvant to clinical diagnoses to aid in the management of patients

Viscoelastic-augmented trabeculectomy: A newer concept

Purpose: Comparison of conventional trabeculectomy (CT) and viscoelastic-augmented trabeculectomy (VAT) in primary open-angle glaucoma. Methods: A total of 65 primary open-angle glaucoma cases were taken for each of the two groups, i.e., CT and VAT. Viscoelastic-augmented trabeculectomy constituted lamellar scleral flap, deep scleral flap, penetrating trabeculectomy, peripheral iridectomy, filling of the anterior chamber with viscoelastic (sodium hyaluronate) and balanced salt solution, movement of visco in bleb, and tight flap closure. Success criteria included intraocular pressure (IOP) <14 mmHg with no devastating complications. P < 0.05 was considered statistically significant. Results: Mean IOP was significantly lower after VAT compared to CT at 6 weeks, 12 weeks, and 6 months postoperatively. Target IOP was achieved in 60% cases in VAT group compared to 36.92% in CT group. Conclusion: VAT is effective in reducing IOP to the target level for advanced glaucoma with lower postoperative complications

Compositional and morphological changes in water-induced early-stage degradation in lead halide perovskites

With tremendous improvements in lead halide perovskite-based optoelectronic devices ranging from photovoltaics to light-emitting diodes, the instability problem stands as the primary challenge in their development. Among all factors, water is considered as one of the major culprits to the degradation of halide perovskite materials. For example, CH3NH3PbI3 (MAPbI3) and CH(NH2)2PbI3 (FAPbI3) decompose into PbI2 in days under ambient conditions. However, the intermediate changes of this degradation process are still not fully understood, especially the changes in early stage. Here we perform an in-situ investigation of the early-stage MAPbI3 and FAPbI3 degradation under high water vapor pressure. By probing the surface and bulk of perovskite samples using near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) and XRD, our findings clearly show that PbI2 formation surprisingly initiates below the top surface or at grain boundaries, thus offering no protection as a water-blocking layer on surface or grain boundaries to slow down the degradation process. Meanwhile, significant morphological changes are observed in both samples after water vapor exposure. In comparison, the integrity of MAPbI3 film degrades much faster than the FAPbI3 film against water vapor. Pinholes and large voids are found in MAPbI3 film while only small number of pinholes can be found in FAPbI3 film. However, the FAPbI3 film suffers from its phase instability, showing a fast α-to-δ phase transition. Our results highlight the importance of the compositional and morphological changes in the early stage degradation in perovskite materials.NRF (Natl Research Foundation, S’pore)MOE (Min. of Education, S’pore)Published versio