916 research outputs found
C. C. Mehta
No full textOn the life and works of Chandravadan Chimanlal Mehta, b. 1901, Gujarati author
Mobilities in Religious Knowledge: Phiroz Mehta and the Logics of Transreligiosity in 1970s–80s South London
No full textThis paper examines transreligiosity in the context of the transmission of South Asian concepts of spirituality to the UK in the 20th century. Between the 1920s and 1990s, Indian teacher and author Phiroz Mehta (1902–1994) crossed borders in a colonial and postcolonial shuttling between India and the UK but also transgressed conceptual and practice borders of religion, teaching Indian religious concepts to post-Christian spiritual seekers in 1970s–80s South London. Mehta cultivated an elasticity between many religious and philosophical traditions, recognising the post-institutional fatigue of subjects who sought alternative forms of ‘belonging without believing’. Privileging the domestic space for teaching, as well as transitory ‘camp’ gatherings in the UK and Germany, Mehta often operated in the social margins, combining teachings from Hinduism, Buddhism, and Christianity with Zoroastrianism, Judaism (specifically Kabbalah), and Daoism. He offered his tutees the freedom to practice religion in whatever way they chose by drawing on a broad range of traditions concurrently to create a transreligiosity. This paper examines Panagiotopoulos and Roussou’s ‘transgressional webs of practising individualised forms of alternative spirituality’ in relation to Mehta’s followers in the 1970s-1980s and asks how transreligiosity relates to other theoretical analyses, such as religious exoticism, bricolage, religious appropriation, cultural re-articulation or assemblage. This paper focuses on qualitative interviews with original members of the Mehta community conducted between 2021 and 2022.</p
Design and development of a mechatronic training simulator for adult ECMO
No full textWidespread adoption of Extracorporeal Membrane Oxygenation (ECMO) in adults has been limited by unfamiliarity with the procedure, including cannulation and safe handling of the ECMO equipment. We present the design and development of a mechatronic training simulator for ECMO that can help medical professionals acquire the needed skills, gain familiarity, and reduce errors by practicing before performing the procedure on real patients. The trainer is designed as an ultrasound-compatible, wholesome simulator with realistic components such as synthetic blood vessels, cannulation pads, and a color-changing blood simulant to simulate oxygenation and deoxygenation. The simulator is integrated with a mathematical model of human physiology to simulate real-time patient vitals and training scenarios, and to control the trainer hardware. We present results related to successful cannulation under ultrasound scanning and a simple patient scenario of hypovolemia.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2021-05-01The student, Iti Mehta, accepted the attached license on 2019-04-24 at 10:58.The student, Iti Mehta, submitted this Thesis for approval on 2019-04-24 at 11:11.This Thesis was approved for publication on 2019-04-24 at 12:45.DSpace SAF Submission Ingestion Package generated from Vireo submission #13873 on 2019-08-22 at 15:08:02Made available in DSpace on 2019-08-23T20:36:09Z (GMT). No. of bitstreams: 2
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Previous issue date: 2019-04-24Embargo set by: Seth Robbins for item 112203
Lift date: 2021-08-23T20:36:18Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 112203 on 2021-08-24T09:15:24Z
Synthesis Of Medium Ring Carbasugar Analogues And Terpenoid Natural Products
No full textNature’s expertise in creating breathtaking structural wonders which are vital for sustenance of life on this planet has astonished and inspired many synthetic chemists. We too have been attracted towards understanding, exploring and mimicking a few of these magnificent molecular entities. Our efforts are directed towards the synthesis of two types of molecular assembles of contemporary interest; first of them are medium ring carbohydrate mimetics which are unnatural compounds inspired by Nature and other class consisted of the terpenoid natural products which are conceived and assembled by Nature in ever increasing numbers.
The spectacular development of carbohydrate mimetics, prompted primarily by their properties as glycosidase inhibitors, has led to the conception and synthesis of a wide variety of novel structures, the most significant ones belonging to the families of imino sugars and carbasugars. Major advances in diverse subjects such as chemical synthesis, analytical chemistry, structural biology, cell-surface recognition, molecular modeling and spectroscopy have made carbohydrate mimetics embraced by scientific community with increasing vigor.
A major area of interest of organic chemistry is the total synthesis of complex natural products conceived and created by Nature. As a result of refinements in isolation and purification techniques and recent advances in spectroscopy and crystallography, unravelling of natural products from exotic species such as wild plants to microorganisms and from geographic locations ranging from mountain tops to the ocean floors, has made identification and structural elucidation of complex natural products a fairly routine exercise. Among natural products, terpenoids are considered as masterpieces of structural diversity with their bewildering carbocyclic arrangements and diverse functionalities embedded in them.
The present thesis entitled “Synthesis of medium ring carbasugar analogues and terpenoid natural products” is an effort to design and synthesise natural and unnatural molecular entities either conceived by human mind or inspired by Nature. The research described in this thesis has been organized under three chapters.
Chapter I: Design and synthesis of cyclooctanoid and cyclononanoid carbasugar analogues. Chapter II: A total synthesis of putative structure of sesquiterpenoid natural product dichomitol. Chapter III: A total synthesis of diterpenoid natural product guanacastepene C.
A brief overview of each of these three chapters is presented below.(For Equations and Figures Refer PDF File)
Chapter I: Design and synthesis of cyclooctanoid and cyclononanoid carbasugar
analogues
In recent years, the search for new therapeutically useful glycosidase inhibitors, mimicking carbohydrates 1, has extended beyond the realm of five and six membered cyclitols 2 (carbasugars), and targeted towards the medium-sized carbocyclic cores. In this context, we have conceptulised a new family of novel cyclooctanoid 3 and cyclononanoid 4 carbasugar analogues in order to study the effect of the enhanced flexibility and of new spatial distribution displayed by these structures on their adaptability in the active site of the enzymes.
We have developed a versatile synthesis of cyclooctane based polyols 3 from commercially available hydrocarbon cyclooctatetraene 5. It was visualised that a bicyclo[4.2.1]nona-2,4,7-trien-9-one 6 is a functionally locked cyclooctatetraene with dispensed and differentiated double bonds and a masked C9 cycloocta-carbasugar from which the eight membered ring can be extracted through oxidative C1-C9 bond scission, Scheme 1. Several transformations in 6, leading to a range of polyhydroxylated cyclooctanoids was envisaged.
Bayer-villiger oxidation in ketone 6 was smooth and led to a δ-lactone which on catalytic OsO4 dihydroxylation furnished diol 7. Further acetylation on 7 delivered a rearranged γ-lactone 8. LAH reduction in 8 and peracetylation furnished diene 9. Controlled catalytic hydrogenation in 8 furnished 1:1 mixture of 10 and 11, which on hydride reduction gave tetrols 12 and 13, respectively, Scheme 2. Protection of vic diol in 12 led to 14. Hydroboration-oxidation of 14 and peracetylation furnished three diastereomeric mixture of acetonide triacetates in 9:4:1 ratio and they were hydrolysed to give 15-17, Scheme 3.
Interestingly, pentahydroxy 16 is an eight membered analogue of α-talose.
Reagents and conditions: i) m-CPBA, DCM, 60% ii) OsO4, NMMO, acetone-H2O, 75% iii) Ac2O, Py, 90% iv) LAH, THF v) Ac2O, Py, 36% (2 steps) vii) H2, Pd/C, EtOAc, 95% viii) LAH, THF, 40%.
Reagents and conditions: i) acetone, amberlyst-15, 80% ii) BH3-THF, NaOH, H2O2 iii) Ac2O, Py, 54% (2 steps) iv) 2N, HCl, 76%.
Acetylation of 12 led to tertraacetate 18 which on OsO4-dihydroxylation and acetylation furnished two diastereomeric hexaacetates in 1:1 ratio. Hydrolysis of these hexaacetates with base furnished 19-20, Scheme 4.
Reagents and conditions: i) Ac2O, Py, 90% ii) OsO4, NMMO, acetone-H2O iii) Ac2O, Py, 72% (2 steps) iv) NaOMe, MeOH, 75%.
Diene 9 on exhaustive stereoselective double dihydroxylation and base hydrolysis led to octahydroxycyclooctane 21, Scheme 5. A cyclooctane derivative bearing eight oxygen atoms has been prepared for the first time.
Reagents and conditions: i) OsO4, NMMO, acetone-H2O ii) NaOMe, MeOH, 56% (2 steps).
In an unconventional but interesting enterprise, commercially available hydrocarbon cyclooctatetraene 5 has been elaborated to a rare hexose sugar (DL)-β-allose and its 2C branched analogue. The main theme in this approach was to generate a cyclic acetal moiety, a structural characteristic of sugars through ozonolytic cleavage of an appropriately crafted olefin and in situ intramolecular acetalisation, Scheme 6.
Acetonide protection in 7 led to 22. LAH reduction in 22 liberated the diol and selective primary alcohol protection as TBS derivative furnished 23. Ozonolysis of 23 and PCC oxidation of the resulting lactal 24 led to lactone 25. Methoxide mediated lactone opening in 25 and protection of anomeric hydroxyl group as methyl ether led to 26. LAH reduction of ester led to 27 and further deprotections furnished (DL)-methyl-2-deoxy-2C-hydroxymethyl-β-allose 28. Protected hexose homologue 27 was converted via a mesylate to the terminal olefin 29 through a series of functional group transformations. Ozonolysis of 29 furnished hemiacetal 30, which on sodium borohydride reduction and acetonide deprotection delivered (DL)-methyl-β-allopyranoside 31, Scheme 7.
Motivated and encouraged by the synthesis of cyclooctane carbasugar analogues, it was decided to venture into the synthesis of cyclononane carbasugar analogues. It was visualized that appropriately functionalized bicyclo[4.3.1]decane system 32, can serve as a masked C10 cyclononane carbasugar from which the nine membered ring can be extracted through the C1-C10 bond scission, Scheme 8.
Reagents and conditions: i) 2,2-DMP, CSA, 65% ii) LAH, THF, 80% iii) TBSCl, imidazole, 54% iv) O3, DCM-MeOH, DMS v) PCC, DCM, 40% (2 steps) vi) NaOMe, MeOH vii) MeI, Ag2O, 73% (2 steps) viii) LAH, THF, 85% ix) TBAF, THF, 70% x) amberlyst-15, MeOH, 65% xi) Ac2O, DMAP, 92% xii) TBAF, THF, 74% xii) MsCl, DCM, 65% xiv) KOtBu, DMSO, 70% xv) O3, DCM, 75% xvi) NaBH4, MeOH, 80% xvii) amberlyst-15, MeOH, 60%.
The bridged dienone 32 was readily prepared from cyclohexanone following a literature protocol. Ketone 32 on Bayer-Villiger oxidation furnished lactone 33 in moderate
yield, and further exhaustive double dihydroxylation furnished two unanticipated rearranged products δ-lactone 34 and γ-lactone 35 in 5:3 ratio. Both, the novel lactones 34 and 35 were further elaborated to the corresponding hexahydroxy cyclononane carbasugar analogues 36 and 37, Scheme 9. These novel medium ring carbasugar analogues involving a nine memebered carbocycle have been synthesized for the first time.
Reagents and conditions: i) m-CPBA, DCM, 60% ii) OsO4, NMMO, acetone-H2O, 54% of 34 and 32% of 35 iii) acetone, PPTS, 98% iv) LAH, THF, 90% v) 2N HCl, 88% vi) acetone, PPTS, 92% vii) LiBH4, THF, 50% viii) 2N HCl, 88%.
All the details of our synthetic efforts towards several novel carbasugar analogues which have been synthesised for the first time, along with the synthesis of some interesting polyoxygenated carbocyclic intermediates, unusual products from rearrangements, incisive NMR studies and X-ray analyses to solve the stereochemical puzzles, along with enzyme inhibition studies will be presented in this chapter of the thesis.
Chapter II: A total synthesis of putative structure of sesquiterpenoid natural product Dichomitol
This chapter describes the first total synthesis of the putative structure of the sesquiterpenoid natural product dichomitol 55 bearing a novel triquinane framework, and reported in 2004 from the bascidiomycete fungi Dichomitus squalens by a group of Chinese researchers. Dichomitol 55 not only represented a novel skeletal-type among linear triquinanes but was also biogenetically quite intriguing as it was suggested to be related to hirsutanes through an unusual methyl shift. This unusual positioning of methyl group in
Reagents and conditions: i) CO(OCH3)2, THF, 82% ii) MeI, THF, 90% iii) ethanedithiol, PTSA, 75%, iv) Raney-Ni, EtOH, 90% v) PCC, DCM, 90% vi) LHMDS, THF, -78 °C; Pd(OAc)2, CH3CN, 86% vii) MeLi, ether viii) PCC, DCM, 84% (2 steps) ix) Mg, 4-bromobutene, CuBr-DMS, THF; AcOH, 95% x) LHMDS, THF, -78 °C; Pd(OAc)2, CH3CN, 80% xi) DBU, KOtBu, PTSA, RhCl3.
dichomitol 55 which probably originated through a Wagner-Meerwein rearrangement of a corresponding ceratopicane derivative aroused our interest, curiosity (and suspicion) towards this natural product and it was decided to undertake its total synthesis.
Our synthesis commenced from the known bicyclic ketone 39 readily accessible from commercially available 1,5-cyclooctadiene 38 through a sequence previously developed in our laboratory. Successive α- carbomethoxylation and α-methylation correctly installed C-11 centre in 40. Carbonyl group in 40 was protected as its thioketal to furnish 41 which on reductive desulphurization with simultaneous benzyl deprotection and further oxidation led to ketone 42. Following Saegusa protocol, 42 was converted into enone 43. Alkylative transposition in 43 furnished enone 44, which on Cu(I) mediated 1,4-conjugate addition delivered 45 with desired methyl stereochemistry with preferred addition from the exo-face. Kende cyclization in 45 smoothly delivered tricyclic 46, a C5-C6 double bond isomer of the desired tricyclic precursor of the natural product. Several attempts to isomerise the C5-C6 double bond in 46 to the required C6-C7 position failed to deliver 47, Scheme 11.
Reagents and conditions: i) ethyleneglycol, PTSA, C6H6, 97% ii) LAH, THF, 96% iii) amberlyst-15, acetone, 95% iv) TBSCl, imidazole, DCM, 98% v) OsO4, NMMO, acetone-H2O, 90% vi) TBSCl, imidazole, DCM, 86% vii) IBX, DMSO-toluene, 78% viii) LHMDS, THF, -78 °C, 40% ix) Martin sulfurane, CHCl3, 40% x) DIBAL-H, DCM, 90% xi) TBAF, THF, 85%.
At this stage it was decided to pursue an aldol based approach as it may help to install the tetrasubstituted C6-C7 double bond. Bicyclic ketone 45 was protected as its ethylene ketal, ester group was reduced with LAH and ketal deprotection furnished 48. The primary hydroxyl protection in 48 led to 49. Dihydroxylation on the butenyl arm gave diol 50, wherein the primary hydroxyl was protected as TBS derivative and secondary hydroxyl group was oxidized to furnish 51. Employing LHMDS as a base, key aldol reaction was carried out on 51 to give three aldol products in which the required compound 52 was the major product. The tertiary hydroxyl group in 52 when subjected to dehydration using Martin sulfurane delivered the required 53 with correctly installed C6-C7 double bond, only in trace amounts, along with two other regioisomeric dehydration products. DIBAL-H reduction on 53 stereoselectively delivered 54 and TBS deprotection furnished a product 55 bearing the structure assigned for the natural product ‘dichomitol’, Scheme 12. Significant variation in the spectral characteristics of our synthetic product 55 and those reported for ‘dichomitol’ necessitates a reinvestigation of the structure of natural product.
All the details of our synthetic efforts, problems and challenges encountered enroute and the synthetic insights used to address them will be presented in this chapter of the thesis.
Chapter III: A total synthesis of diterpenoid natural product Guanacastepene C
This chapter describes the first total synthesis of a novel 5,7,6 fused tricyclic diterpenoid natural product guanacastepene C 71 isolated from an unidentified fungus growing on the tree Daphnopsis americana by Clardy in 2001. Besides guanacastepene C 71, fourteen other guanacastepenes A-O have also been isolated and these compounds have evoked unprecedented attention from the synthetic community. In particular, several
Reagents and conditions: i) LAH, THF, 55% ii) a. PMBCl, THF, 67% b. TBSOTf, DCM, 68% c. DDQ, DCM-H2O, 95% iii) IBX, toluene-DMSO, 92% iv) Ph2POCH2COCH2COOEt, THF, 86% v) H2, Pd/C, EtOAc, 99% vi) a. 6N H2SO4, THF-H2O, 80% b. 2,2-DMP, PPTS, 91% vii) PCC, DCM, 80% viii) DBU, C6H6, 82%
guanacastepenes exhibit antibacterial activity against MRSA and VREF. Several total syntheses of guanacastepenes have been reported in the last two years due to their enticing architecture and promising biological activity profile. Our group has also been in the fray and following the early leads, we embarked on an ambitious journey towards the total synthesis of guanacastepene C 71.
The synthetic approach towards guanacastepene C 71, envisaged in this study, was revealed through a retrosynthetic analysis which identified hydroazulene core 57, bearing AB rings of the natural product as an advanced precursor on which ring ‘C’ could be annulated, Scheme 13. Earlier efforts from our group have demonstrated that AB ring precursor 57 can be elaborated from readily available tri-cylcopentadienone 56.
Keto-ester in 57 on LAH reduction led to diol 58 and following a three step protocol of protection-deprotection led to 59 wherein the free primary hydroxyl was oxidized to furnish the required aldehyde 60. It was condensed with appropriate four carbon Horner-Wittig partner to furnish a mixture of keto-enol tautomers 61. Hydrogenation of trans double bond led to 62 and TBS deprotection and concomitant acetonide deprotection followed by acetonide protection furnished the hemiketal 63. PCC oxidation in 63 furnished tricyclic precursor 64 for the key Knoevenagel cyclization. Exposing 64 to DBU delivered 65 embodying complete tricarbocyclic framework of guanacastepene C, Scheme 14. LAH reduction on 65, was stereoselective and led predominantly to the unrequired α- isomer 66.
Reagents and conditions: i) LAH, THF, -78 °C, 65% ii) PPh3, C6H5COOH, DIAD, THF, 78% iii) LAH, THF, 84% iv) Ac2O, DCM, 90% v) 4N H2SO4, THF-H2O, 44% vi) DDQ, THF, 85% vii) K2CO3, MeOH, 70%.
Diol 66 was subjected to standard Mitsunobu protocol to furnish dibenzoate 67 which was hydrolysed and reprotected as diacetate 68 with the desired 5β stereochemistry. Deprotection of acetonide in 68 led to the diol 69. Chemoselective allylic oxidation of vicinal diol employing DDQ furnished guanacastepene C diacetate 70. Finally, careful base hydrolysis of 70 delivered guanacastepene C 71, Scheme 15.
Synthesis of guanacastepene C was a difficult and often frustrating journey. Many trials and tribulations to overcome the synthetic challenges and our persistant and sincere efforts to overcome the hurdles confronted by us during the synthesis and finally attainment of the first total synthesis of guanacastepene C 71 will be the subject matter of the last chapter of this thesis.(For structural formula pl refer pdf file
Optimal Bioeconomic Management Strategies for Prevention and Control of Invasive Alien Species
No full textPaper removed by author. Please see the current version, available online January 8, 2007: Mehta, S.V. et al. Optimal detection and control strategies for invasive species management. Ecological Economics (2007), doi:10.1016/j.ecolecon.2006.10.024Environmental Economics and Policy,
Design and implementation of a phase locked loop for high-speed serial links
No full textThe student, Rushabh Mehta, accepted the attached license on 2016-04-25 at 13:40.The student, Rushabh Mehta, submitted this Thesis for approval on 2016-04-25 at 13:46.This Thesis was approved for publication on 2016-04-27 at 14:52.DSpace SAF Submission Ingestion Package generated from Vireo submission #9475 on 2016-07-07 at 13:50:45Made available in DSpace on 2016-07-07T20:27:59Z (GMT). No. of bitstreams: 2
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Previous issue date: 2016-04-27Recent advances in the semiconductor industry and process technology scaling have increased the demand for fast, robust computing. The thirst for high-processing, low power ICs is ever increasing. This has pushed the demand for high data rates in wireless and wireline communication systems in the multi-Gbps range. With higher data rates, the I/O links need to scale proportionally. However, the I/O channel bandwidth has not scaled appropriately making it the biggest bottleneck in high-speed links. Parallel links have not been able to match this increasing system performance due to issues such as crosstalk, timing skew and packaging costs. Thus there is a need for high-speed serial links. For high-speed transmission of data, there arises a need for high-speed on chip clocking circuits making the use of Phase-Locked Loops (PLLs) imperative.
This thesis includes an overview of high-speed links along with the need for PLLs. An in-depth understanding of PLL theory, loop dynamics and behavioral and transistor level simulation follows. Performance metrics such as phase noise, random jitter and deterministic jitter are discussed. Finally, this thesis concludes with an insight into All Digital Phase-Locked Loops (ADPLLs).Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2018-05-01Embargo set by: Seth Robbins for item 93174
Lift date: 2018-07-07T20:28:14Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemEmbargo set by: Seth Robbins for item 93174
Lift date: 2018-07-07T20:35:34Z
Reason: Author requested U of Illinois access only (OA after 2yrs) in Vireo ETD systemU of I Only Restriction Lifted for Item 93174 on 2018-07-08T09:15:20Z
Role of zeta potential in micro-carrier process
No full textThe micro-carrier process recently developed at NJIT is a new high rate settling technology for water and wastewater treatment. This process utilizes the micro-cater as a flocculating enhancement agent to achieve rapid removal of colloidal particles. This thesis consist of two parts, namely, 1) A review of the flocculation process utilized in water and wastewater treatment, and 2) An experimental program to evaluate the role of zeta potential in the flocculation process.
The results of this study indicated that the DLVO theory (Darjaguin, Landau, Overbeek, Verwey theory) is applicable to micro-cater process in the absence of polyelectrolytes. The best flocculation was achieved when the zeta potential approached the minimum value. It was observed that in the presence of different polyelectrolytes non-DLVO forces have a significant impact
Visual outcomes of bilateral congenital and developmental cataracts in young children in south India and causes of poor outcome.
No full textCONTEXT: Bilateral pediatric cataracts are important cause of visual impairment in children. AIM: To study the outcome of bilateral pediatric cataract surgery in young children. SETTING AND DESIGN: Retrospective case series in a tertiary center. MATERIALS AND METHODS: Records of pediatric cataracts operated between January 2001 and December 2003, with a minimum follow-up of 3 months, were reviewed retrospectively. STATISTICAL METHODS: Independent sample t-test, Fisher's exact test, and logistic regression using SPSS (Statistical Package for Social Science, Chicago, USA) version 12. RESULTS: 215/257 (83.7%) patients had a minimum follow-up of 3 months. The mean age of presentation to the hospital was 53 months (range: 0-168 months). Congenital cataract was present in 107 patients (58.2%) and developmental cataract in 77 patients (41.8%). The mean age at surgery was 55.2 months (range: 1-168 months). Out of 430 eyes, 269 (62.6%) had an intraocular lens implanted. The mean duration of follow-up was 13.1 months (range: 3-38 months). Pre-operatively, 102 patients (47.3%) had visual acuity 6/18. The most common early post-operative complication was fibrinous uveitis in 57 eyes (13.3%) and the most common delayed post-operative complication was posterior capsular opacification in 118 eyes (27.4%). The most important prognostic factor for poor outcome was congenital cataract (odds ratio [OR]: 26.3; 95% confidence interval [CI], 4.4-158.5) and total cataract (OR: 4.8; 95% CI, 1.3-17). CONCLUSION: Nearly half of the eyes had visual acuity >6/18. The outcome was poorer in congenital cataracts, especially those operated after >1 year of age
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