2,196 research outputs found
Conversations with authors: Saskya Jain
No full textA 2011 conversation with the author Saskya Jain about her life and the inspiration for her work
Computational electronic structure studies of novel condensed matter phases
No full textThis dissertation compiles the bulk of my work as a PhD student in the research group of Professor Prashant K. Jain at University of Illinois at Urbana-Champaign. My research was exclusively in the field of theoretical chemistry and materials science: I employed high-performance computing tools to perform electronic structure investigations of novel crystalline materials synthesized, some for the very first time, in the group. My placement in the experimentally-focused Jain group afforded multiple opportunities in which the discoveries of my fellow group members prompted me to conduct stand-alone or collaborative theoretical investigations of new nanomaterials. A summary of the experimental backdrop to my work is presented in Chapter 1, along with a description of the theoretical methods that were the mainstay of my PhD research. Chapter 2 presents work in which my density functional theory (DFT) calculations improved our understanding of the metastability of a previously unobserved vacancy ordering in a Cu2Se. Chapter 3 presents a different direction of investigations that we conducted on Cu2Se, this time into its superionic properties. The nucleation, kinetics, and correlation of lattice strain to the order-disorder superionic phase transition were explored through a combination of transmission electron microscopy and DFT. The correlation between lattice strain and superionicity is expanded upon in Chapter 4 where Prashant and I developed a theoretical basis on which to understand compressively strain-stabilized superionicity in Cu2Se and Li2Se. Chapter 5 shifts away from Cu2Se on to HgSe. Additionally, the focus changes from the structure and transport of cations to the structure and transport of electrons, specifically the electron-conducting surface states found in topological phases of matter. Bulk band-structure calculations and charge density character analysis that I carried out led us to hypothesize that a hexagonal phase of HgSe newly-synthesized bny the Jain group was a 3-D topological insulator. The unique topological surface states (TSS) of HgSe and their dependence on strain, crystallographic symmetry, and surface faceting are determined by DFT and presented in Chapter 6. Particularly, the effect of lattice strain on the dispersion and spin texture circles back to the central theme in the studies of super-ionic crystals: that small amounts of strain can significantly alter the charge transport properties of a material.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-05-01The student, Daniel Dumett Torres, accepted the attached license on 2020-04-21 at 14:56.The student, Daniel Dumett Torres, submitted this Dissertation for approval on 2020-04-21 at 15:04.This Dissertation was approved for publication on 2020-04-24 at 13:06.DSpace SAF Submission Ingestion Package generated from Vireo submission #15022 on 2020-08-25 at 17:40:29Made available in DSpace on 2020-08-27T00:49:58Z (GMT). No. of bitstreams: 2
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Jain Rāmāyaṇa Narratives
No full textJain Rāmāyaṇa Narratives: Moral Vision and Literary Innovation traces how and why Jain authors at different points in history rewrote the story of Rāma and situates these texts within larger frameworks of South Asian religious history and literature. The book argues that the plot, characters, and the very history of Jain Rāma composition itself served as a continual font of inspiration for authors to create and express novel visions of moral personhood. In making this argument, the book examines three versions of the Rāma story composed by two authors, separated in time and space by over 800 years and thousands of miles. The first is Raviṣeṇa, who composed the Sanskrit Padmapurāṇa (“The Deeds of Padma”), and the second is Brahma Jinadāsa, author of both a Sanskrit Padmapurāṇa and a vernacular (bhāṣā) version of the story titled Rām Rās (“The Story of Rām”). While the three compositions narrate the same basic story and work to shape ethical subjects, they do so in different ways and with different visions of what a moral person actually is. A close comparative reading focused on the differences between these three texts reveals the diverse visions of moral personhood held by Jains in premodernity and demonstrates the innovative narrative strategies authors utilized in order to actualize those visions. The book is thus a valuable contribution to the fields of Jain studies and religion and literature in premodern South Asia
THE JAIN CENTRE IN LEICESTER
No full textThis dissertation discusses the formative years of the Jain Centre, Leicester, from 1979 when Jain Samaj Leicester, the community body of the Jains in Leicester, bought a dilapidated former chapel and set about converting it into a centre for the community. Central in the plan was the religious dimension which was to unite four "sects" of Jainism under one roof, Svetambara, Digambara, Sthanakvasi and the devotees of Srimad Rajchandra. The prehistory of Jain Samaj is looked at briefly, from the first meetings in members' homes and the formal foundation of Jain Samaj Leicester in 1973. In the main body of the dissertation, in Chapter Three, the approach is largely historical, with the key events being singled out for detailed examination. The account is taken right up-to-date, to 2001. A final chapter analyses the factors which led to the success of this venture.
Chapter One provides essential introductory orientation on the Jains, both as a community and as followers of an ancient religion, relating this to the situation of the Jains in Leicester. In a second part of this chapter sources and methodology are outlined. Primary sources comprise
(a) Information from members of the Jain community,
(b) Participant observation by the author over a quarter of a century,
(c) A large collection of written material put together over the years and comprising letters, notices and much more from Jain Samaj and others, and runs of the newsletters and journal published by Jain Samaj, as well as news cuttings, particularly from the local press.
These three sources have been of roughly equal weight.
Secondary sources are the author's own collection of some 200 books and pamphlets on Jainism and the Jains, together with the resources of other libraries particularly that of the School of Oriental and African Studies.
Chapter Two provides a description of the Jain Centre and examines some aspects of its functioning. Chapter Four is devoted to the temple, its architecture and iconography, and the religious life centred there.
Finally, in Chapter Five an analysis is made of some key aspects of the Centre's history, and a tentative forecast of the future is attempted
Exploring condensed phases in engineered semiconducting nanocrystals
No full textThe Jain lab employs a topotactic method called cation exchange to produce semiconductor nanocrystals (NCs) in novel morphologies, compositions, and crystallographic phases. My dissertation research focuses on the understanding of the physical properties and phase transitions of these new nanomaterials prepared by cation exchange. In Chapter 1, I describe the countless possibilities of the exploration of physicochemical properties and applications of molecularly precise semiconductor nanoclusters, a class of materials that we were able to expand with the help of cation exchange. In Chapter 2, I discuss how ultrasmall copper selenide (Cu2-xSe) NCs prepared by cation exchange of cadmium selenide NCs exhibit a disordered cationic sub-lattice under ambient conditions. This behavior is quite unlike larger NCs or the bulk, suggesting an interesting effect of crystallite size and strain on the stability of super-ionic phases. In Chapter 3, I describe my investigations of Li-doping of Cu2-xSe NCs and how this doping influences the crystal structure and consequently the phase transition behavior. A close-to-ambient-temperature transition from the non-superionic to superionic phase transition also appears to be present in the final lithium selenide (Li2Se) NCs formed from this doping reaction. In Chapter 4, I explain on the basis of optical spectra measurements and density functional theory (DFT) calculations how HgSe NCs, prepared using cation exchange in a novel wurtzite phase, differ from their natural zinc-blende counterparts. The latter is a semi-metal, whereas the newer phase obtained from cation exchange is found to have an inverted band structure along with a finite band-gap, making it a potential 3D topological insulator. In Chapter 5, I extend the understanding of ion exchange reactions to an “anion exchange” process in zinc oxide (ZnO) NCs. As a detour from the central thesis of my dissertation, in Chapter 6, I present my work on electrodynamic simulations of optical properties of nanostructures, which helped demonstrate that localized surface plasmons can be imaged in real space with nanometer resolution using a scanning tunneling microscope (STM) coupled to a laser.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2020-12-01The student, Progna Banerjee, accepted the attached license on 2018-11-23 at 13:07.The student, Progna Banerjee, submitted this Dissertation for approval on 2018-11-23 at 13:29.This Dissertation was approved for publication on 2018-11-27 at 08:38.DSpace SAF Submission Ingestion Package generated from Vireo submission #13088 on 2019-02-08 at 11:38:51Made available in DSpace on 2019-02-08T18:39:46Z (GMT). No. of bitstreams: 4
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Modeling Neutron Damage in Silicon Detectors for High Energy Physics Experiments
No full textSilicon detectors are expected to experience an unprecedented neutron flux in the future upgrades of the detectors at the Large Hadron Collider (LHC). The challenging radiation environment of these experiments will severely affect the performance of silicon detectors. An irradiation campaign is generally carried out, followed by measurements, to develop radiation-hard silicon detectors. Device modeling complements the measurement results for the detailed understanding of the silicon detectors. Our Group at the University of Delhi successfully developed the radiation damage model for proton irradiation. However, a similar model for neutron irradiation has been missing. In the present work, a Technology Computer-Aided Design (TCAD) simulation software—Silvaco, has been used to study the effects of neutron irradiation on silicon detectors. The effects of radiation damage are incorporated using an effective two-trap model. A trap level is characterized by a number of trap parameters, e.g. trap type, trap energy level, introduction rate of acceptors and donors, and carrier (electrons and holes) capture cross section for that particular trap level. A systematic study of the sensitivity of various macroscopic parameters of silicon detectors to these trap parameters has been performed. The simulation results on leakage current (ILEAK), full depletion voltage (VFD) and charge collection efficiency (CCE), using the neutron damage model, are found to be in good agreement with the measurement results
Tracking the evolution of photoexcitations in strongly light absorbing systems
No full textAuthor requested closed access (OA after 2yrs) in Vireo ETD systemLimitedThis dissertation consists of the work done towards a Ph.D. degree in the research group of Professor Prashant K. Jain at the University of Illinois at Urbana-Champaign. Here, I describe the study of the conversion of light energy using hybrid perovskite and noble metal-based semiconductor nanoparticles. The large surface-area-to-volume ratios and superlative ability to absorb visible light make these materials worthy candidates for solar energy harvesting. The primary questions I have asked in my research are: what is the fate of photoexcitation in a nanostructured material and how can we channel such photo-excitations in an efficient and selective manner? Chapter 1 of this dissertation introduces some of the theoretical backdrops to my studies of strongly light-absorbing plasmonic nanoparticulate systems. This chapter elucidates what follows and introduces the concepts and terms used. Chapter 2 presents my investigation of hybrid organic-inorganic perovskite materials for potential uses towards light trapping and emission. We discovered that commonly observed luminescence from microcrystals of these materials showed a spectrum that varied with sample morphology and location on the sample. The origin of this spectral heterogeneity was then traced to the phenomenon of luminescence self-absorption, which is prevalent due to the overlapping absorption and emission, i.e., small Stokes-shift, in these materials. Then we explored light-to-chemical-energy conversion in perovskite materials, but they proved to be photochemically unstable; so, we turned our attention to noble metal nanoparticles, which have strong plasmon resonance absorption and high photostability. Chapter 3 describes the investigation of light-to-chemical energy conversion in colloidal gold (Au) nanoparticles In particular, we studied the effect of visible-light excitation of Au nanoparticles in the presence of an electron acceptor (HAuCl4) and a hole acceptor (short-chain alcohol). This led to the discovery of a hitherto unknown photoreaction, which involves the splitting and chlorination of the alcohol
generating a chloroalkane and an aldehyde. This reaction was found to take place with several alcohols, which led us to a general reaction mechanism that is catalyzed synergistically by the photoexcited nanoparticle and the Lewis acidic HAuCl4. In the specific case of 2-butanol as the hole acceptor, we found a substantial difference between the product distributions of the light-driven reaction as compared to a thermal reaction. This finding represents an example of light-driven-control of catalytic selectivity. Finally, as presented in Chapter 4, the insights gained from the study described in Chapter 3 led me to a new, simple chemical process for low-temperature chlorination of methane in a non-corrosive aqueous environment. The kinetics and mechanism of this reaction were studied. Methane chlorination is at the heart of natural-gas upgradation, so this new finding represents an ideal culmination of my dissertation. An outlook and potential future directions are presented in Chapter 5.Submission published under a 24 month embargo labeled 'Closed Access', the embargo will last until 2022-12-01The student, Varun Mohan, accepted the attached license on 2020-12-01 at 18:31.The student, Varun Mohan, submitted this Dissertation for approval on 2020-12-01 at 18:50.This Dissertation was approved for publication on 2020-12-04 at 10:01.DSpace SAF Submission Ingestion Package generated from Vireo submission #16022 on 2021-03-04 at 16:33:11Made available in DSpace on 2021-03-05T21:47:26Z (GMT). No. of bitstreams: 8
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Quad-band circularly polarized super-wideband MIMO antenna for wireless applications
No full textIn this article, a Super-wideband (2.6–22 GHz) two-elements multiple-input-multiple-output antenna (MIMO) is presented with a dimension of 49 × 54.5 × 1.6 mm3 on an FR-4 substrate. The antenna is also exhibited dual circular polarization (RHCP and LHCP) simultaneously at two separate ports at four frequencies of 5.2, 11.5, 14.66, and 16.75 GHz, which are extensively utilized for WLAN, X, and Ku-band applications. Four EBG cells of various sizes have been installed across the feed line to maintain the antenna's efficiency and control the specific absorption rate (SAR). The antenna has a minimum isolation of 17 dB (20 dB for the important portion) in Super-wideband (SWB) and excellent diversity performance. Simulated results of antenna-like return loss, isolation, and diversity parameters have also been verified experimentally, which are in the acceptable range. Also, the calculated maximum SAR at 10 g is 1.095 W/kg with the head voxel model at 3.5 GHz
The impact of the competence quorum sensing system on Streptococcus pneumoniae biofilms varies depending on the experimental model
No full textBackground: Different models for biofilm in Streptococcus pneumoniae have been described in literature. To permit comparison of experimental data, we characterised the impact of the pneumococcal quorum-sensing competence system on biofilm formation in three models. For this scope, we used two microtiter and one continuous culture biofilm system. Results: In both microtiter models the competence system influences stability and structure of biofilm in the late attachment phase and synthetic competence stimulating peptide (CSP) restored wild type phenotypes in the comC mutants unable to produce the peptide. Early attachment of single cells to well bottoms was found for both systems to be competence independent, while later phases, including microcolony formation correlated to an intact competence system. The continuous culture biofilm model was not affected by mutations in the competence locus, but deletion of capsule had a significant impact in this model. Conclusions: Since biofilm remains a largely uncharacterised multi-parameter phenotype it appears to be advisable to exploit more than one model in order to draw conclusion of possible relevance of specific genotypes on pneumococcal physiology.Claudia Trappetti, Luciana Gualdi, Lorenzo Di Meola, Prashant Jain, Cindy C Korir, Paul Edmonds, Francesco Iannelli, Susanna Ricci, Gianni Pozzi and Marco R Oggion
Interview with S. Lochlann Jain
No full textProf. S. Lochlann Jain (he/him, they/them) is a Professor of Anthropology at Stanford University and Visiting Professor of Global Health and Social Medicine at King’s College London. Jain is an award-winning scholar, artist, and author of three books: Injury (Princeton University Press, 2006), Malignant: How Cancer Becomes Us (University of California Press, 2013), and Things that Art (University of Toronto Press, 2019).
Jain’s work lies at the intersection of science and technology studies, history, political economy, gender and sexuality, biology, and medicine and aims to unsettle some of the deeply held assumptions about objectivity that underlie the politics and history of medical research. His book Malignant traces the contested concepts of cancer that lie at the core of debates over cause, treatment, responsibility, and national progress, aiming to show why cancer remains such an intractable medical, social, and economic problem that takes millions of lives, while it both costs and generates billions of dollars.
Jain has won numerous prizes in anthropology, medical journalism, and science and technology studies, including the Staley Prize, June Roth Memorial Award, Fleck Prize, Edelstein Prize, Victor Turner Prize, and the Diana Forsythe Prize. His work has been supported by Stanford Center for the Advanced Study of Behavioral Sciences, National Endowment for the Humanities Fellowship, and the National Humanities Center
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