Fabrication and Characterization of Al / AlOx / Al Josephson Junctions

This thesis works deals with the fabrication and characterization of Josephson Junctions. An upgrade over the existing fabricating process with the aim of integrating Josephson Junctions with hetero-structure based HEMT devices was the main aim of this research work. In order to achieve this, new fabrication technique with aim of fabricating small area overlap junction is presented. Josephson Junctions are a Metal-Insulator-Metal capacitor, with both of its electrodes as superconductor metals having femto Farad capacitance and low resistance. The current transfer mechanism across very thin junctions was discussed and the related tunneling current equations were deduced after extracting the equations from the Wentzel-Kramers-Brillouin (WKB) approximation. These junctions are prone to various kinds of tunneling current phenomenon. A relationship between the room temperature tunneling current for a Metal-Insulator-Metal (MIM) capacitor and that to the resistance of the Josephson Junctions above its critical temperature was derived. A new fabrication method consists of a side-wall overlap area was presented in order to fabricate these Josephson Junctions. The dielectric / insulator layer was also deposited using a relatively new approach of Atomic Layer Deposition technique. Using this new fabrication approach, Josephson Junctions with the small area overlap, lower capacitance and resistance values were obtained. Capacitances for these devices were measured using an E4980 Agilent Precision LSR meter system with a 2 point probe setup. The same setup was used in order to obtain Current (I) vs. Voltage (V) sweep values for the Josephson Junctions, in order to identify the tunneling mechanism occurring in the junctions. Barrier height and effective mass of the dielectric were calculated from these tunneling plots. It was observed that these junctions had an area overlap of ~ 0.75 μm^2 with capacitance ~ 100 fF and resistance ~ 150 Ω μm^2. These values where in the same range to the value from literature which utilized the dolan bridge fabrication technique. Hence, this concluded that the step-edge technique is better approach towards fabrication of small overlap Josephson Junctions with the aim of integrating them with HEMT based devices

Duality of locally quasi-convex convergence groups

[EN] In the realm of the convergence spaces, the generalisation of topological groups is the convergence groups, and the corresponding extension of the Pontryagin duality is the continuous duality. We prove that local quasi-convexity is a necessary condition for a convergence group to be c-reflexive. Further, we prove that every character group of a convergence group is locally quasi-convex.We thank Prof. H.-P. Butzmann and the anonymous reviewers for their many insightful comments and suggestions.Sharma, P. (2021). Duality of locally quasi-convex convergence groups. Applied General Topology. 22(1):193-198. https://doi.org/10.4995/agt.2021.14585OJS193198221L. Außenhofer, Contributions to the Duality Theory of Abelian Topological Groups and to the Theory of Nuclear Groups, Dissertationes mathematicae. Institute of Mathematics, Polish Academy of Sciences, 1999.W. Banaszczyk, Additive Subgroups of Topological Vector Spaces, Lecture Notes in Matheatics, Springer Berlin Heidelberg, 1991. https://doi.org/10.1007/BFb0089147R. Beattie and H.-P. Butzmann, Convergence Structures and Applications to Functional Analysis, Bücher, Springer Netherlands, 2013.M. Bruguera, Topological groups and convergence groups: Study of the Pontryagin duality, Thesis, 1999.H.-P. Butzmann, Über diec-Reflexivität von Cc (X), Comment. Math. Helv. 47, no. 1 (1972), 92-101. https://doi.org/10.1007/BF02566791H.-P. Butzmann, Duality theory for convergence groups, Topology Appl. 111, no. 1 (2000), 95-104. https://doi.org/10.1016/S0166-8641(99)00188-1M. J. Chasco and E. Martín-Peinador, Binz-Butzmann duality versus Pontryagin duality, Arch. Math. (Basel) 63, no. 3 (1994), 264-270. https://doi.org/10.1007/BF01189829M. J. Chasco, D. Dikranjan and E. Martín-Peinador, A survey on reflexivity of abelian topological groups, Topology Appl. 159, no. 9 (2012), 2290-2309. https://doi.org/10.1016/j.topol.2012.04.012S. Dolecki and F. Mynard, Convergence Foundations of Topology, World Scientific Publishing Company, 2016. https://doi.org/10.1142/9012E. Martín-Peinador, A reflexive admissible topological group must be locally compact, Proc. Amer. Math. Soc. 123, no. 11 (1995), 3563-3566. https://doi.org/10.2307/2161108E. Martín-Peinador and V. Tarieladze, A property of Dunford-Pettis type in topological groups, Proc. Amer. Math. Soc. 132, no. 6 (2004), 1827-1837. https://doi.org/10.1090/S0002-9939-03-07249-6P. Sharma, Locally quasi-convex convergence groups, Topology Appl. 285 (2020), 107384. https://doi.org/10.1016/j.topol.2020.107384P. Sharma and S. Mishra, Duality in topological and convergence groups, Top. Proc., to appear

Electrochemical Reduction Of Carbon Dioxide On Carbon Nanostructures: Defect Structures & Electrocatalytic Activity

The advantages of the electrochemical conversion of carbon dioxide to fuels using renewable energy sources are two-fold: (1) it has the potential to accomplish a carbon-neutral energy cycle and (2) it can provide an approach to tackle the environmental challenges caused by anthropogenic carbon dioxide emissions. Although thermodynamically possible, the kinetics of carbon dioxide reduction to fuels remains challenging and therefore, an efficient and robust electrocatalyst is needed to promote the reaction. The ideal catalyst for the electrochemical CO2 reduction must be capable of mediating multiple proton-coupled electron transfer reactions at low overpotentials, suppressing the concurrent hydrogen evolution reaction, converting CO2 to desired chemicals with high selectivity, and achieving long-term stability. Extensive research has been carried out on metallic electrocatalysts during the past three decades; however, none of these materials are simultaneously efficient and stable for practical purposes. This Ph.D. dissertation focuses on the investigation of the electro-reduction of CO2 on carbon nanostructures with a focus on understanding the relationship between defect structures and electrocatalytic activity. The initial focus of this work was to accomplish active performance and durability for electrosynthesis of fuels from CO2 using cost-effective catalysts. N-doped carbon nanotubes (NCNTs) were demonstrated as highly efficient, selective and more importantly, stable catalysts to achieve CO2 conversion to CO. The catalytic activity of these NCNTs was further benchmarked against other metallic catalysts reported in literature (Chapter 2). Compared to noble metals Ag & Au, these NCNTs exhibited a lower overpotential to achieve similar selectivity towards CO formation. The second part of this work was a study of the dependence of catalytic activity, i.e., the overpotential and selectivity for CO formation on the defect structures (pyridinic, graphitic, pyrrolic-N) inside NCNTs. The presence of both pyridinic and graphitic-N was found to significantly decrease the absolute overpotential and increase the selectivity towards CO formation (Chapter 3). The third part of this thesis work was to investigate CO2 reduction on N-doped graphene, in order to explore morphology effects on catalytic activity of NCNTs towards CO formation (Chapter 4). Overall, pyridinic-N defects exhibited the highest catalytic activity; thereby suggesting the directions for developing carbon nanostructures as metal-free electrocatalysts for CO2 reduction

Data-driven Identification and Prediction of Power System Dynamics Using Linear Operators

In this paper, we propose linear operator theoretic framework involving Koopman operator for the data-driven identification of power system dynamics. We explicitly account for noise in the time series measurement data and propose robust approach for data-driven approximation of Koopman operator for the identification of nonlinear power system dynamics. The identified model is used for the prediction of state trajectories in the power system. The application of the framework is illustrated using an IEEE nine bus test system.Comment: Accepted for publication in IEEE Power and Energy System General Meeting 201

Nexus amongst Holding Period, Returns and Risk for Mutual Funds (A Case from India)

Every individual should have savings for the old age and the future uncertainties. However as all individuals come from different backgrounds and thus all of them cannot be expected to have knowledge of finance and investment concepts. In such a situation the best investment avenue available is the mutual fund. But, here also the investors because of their ignorance tend to rely heavily on financial advisors and follow the age old maxims without testing them by themselves. This paper aims to empirically test one of such maxim which states that stretching the investment time horizon would lead to better results in terms of increased returns and reduced risks. This work would be of interest not only to the academicians, students and researchers but also to the industry experts and anybody having general inclination to the subject of mutual fund. It is shown that the investment time period has some nexus with both the risk as well as the returns. The paper used Sharpe ratio to evaluate the performance of the funds at different time span

The role of laparoscopy in patients with abdominal trauma

Background: Use of laparoscopy in penetrating trauma has been well established; however, its application in blunt trauma is gaining popularity as a useful diagnostic tool to avoid unnecessary laparotomies where there is diagnostic dilemma. Even though recent case reports seem to suggest that these patients can be managed using laparoscopy, the practice is not yet wildly adopted.Methods: All adult patients who presented with abdominal trauma laparoscopic surgery was considered in patients who were deemed fit for the same in the Department of General Surgery, MMIMSR, Mullana, Ambala during a period of 18 months starting from January 1st 2015 to June 30th 2016. Data was analysed using descriptive statistics.Results: A total of 53 patients with either blunt or penetrating abdominal trauma that required surgery were included in the study. Exploratory laparotomy was performed in 45 patients (84.91%) and laparoscopy was performed in 8 patients (15.09%). Overall mesenteric injury (45.28%) was the most common intra-abdominal injury noted. The most common organ involved in blunt trauma was the spleen (68.97%). The mean operating time of laparoscopy was lesser by 57 minutes as compared to exploratory laparotomy. The use of laparoscopy avoided negative and non-therapeutic laparotomy in 2 patients (25%). Therapeutic laparoscopy was performed in 3 patients with repair of bowel and mesenteric injuries. There was no documented procedure‑related morbidity and mortality.Conclusions: The positive outcomes from the study suggest that laparoscopy can be safe and feasible in both diagnostic and therapeutic interventions in carefully selected blunt abdominal trauma patients

Fabrication and Characterization of Al / AlOx / Al Josephson Junctions

This thesis works deals with the fabrication and characterization of Josephson Junctions. An upgrade over the existing fabricating process with the aim of integrating Josephson Junctions with hetero-structure based HEMT devices was the main aim of this research work. In order to achieve this, new fabrication technique with aim of fabricating small area overlap junction is presented. Josephson Junctions are a Metal-Insulator-Metal capacitor, with both of its electrodes as superconductor metals having femto Farad capacitance and low resistance. The current transfer mechanism across very thin junctions was discussed and the related tunneling current equations were deduced after extracting the equations from the Wentzel-Kramers-Brillouin (WKB) approximation. These junctions are prone to various kinds of tunneling current phenomenon. A relationship between the room temperature tunneling current for a Metal-Insulator-Metal (MIM) capacitor and that to the resistance of the Josephson Junctions above its critical temperature was derived. A new fabrication method consists of a side-wall overlap area was presented in order to fabricate these Josephson Junctions. The dielectric / insulator layer was also deposited using a relatively new approach of Atomic Layer Deposition technique. Using this new fabrication approach, Josephson Junctions with the small area overlap, lower capacitance and resistance values were obtained. Capacitances for these devices were measured using an E4980 Agilent Precision LSR meter system with a 2 point probe setup. The same setup was used in order to obtain Current (I) vs. Voltage (V) sweep values for the Josephson Junctions, in order to identify the tunneling mechanism occurring in the junctions. Barrier height and effective mass of the dielectric were calculated from these tunneling plots. It was observed that these junctions had an area overlap of ~ 0.75 μm^2 with capacitance ~ 100 fF and resistance ~ 150 Ω μm^2. These values where in the same range to the value from literature which utilized the dolan bridge fabrication technique. Hence, this concluded that the step-edge technique is better approach towards fabrication of small overlap Josephson Junctions with the aim of integrating them with HEMT based devices

Ethical issues encountered by medical students during their education

Background: Ethical issues and concerns are becoming more and more important in everyday practice of physicians. The aim of this paper is to explore which issues students have encountered in different fields over the duration of their studies. Methods: A hermeneutic method was used to analyse the essays of 19 students in their sixth year of medical studies. The essays were analysed to look for trends and patterns depicting various ethical themes they witnessed during their experiences. Attention was also given to students perspectives regarding each incident Results: Ethical issues and prevalence of these issues were revealed. Ethical dilemmas that students were placed in, in various scenarios were also brought to light. There was comparison mainly between the more authoritarian and paternalistic approach shown by physicians towards patients and colleagues in certain countries. There was good evidence provided towards hierarchal systems in the healthcare setting, which also hi-lighted the pros and cons of hierarchy. There was a compelling viewpoint that pointed to the changing trends in Croatia from a paternalistic approach to a patient a one which respects patient autonomy. Conclusion: This paper provided a useful insight into how students view medical ethics, as a set of values and a course. The results show that many students found that even before the study of the course medical ethics an innate set of morals was helpful and dictated their relationships with patients. There was also the opportunity to carefully examine students over all appreciation for a good set of morals and ethics as well as the importance of this example being set to them from early in their education