| Abstract: | Antioxidants are substances that when present at low concentrations compared to that of an oxidisable substrate significantly delays or inhibits oxidation of that substrate in food products or in living systems. Antioxidants are either endogenous to the body or derived from the diet. Several types of synthetic antioxidants like BHT, BHA, TBHQ etc. are also used in the food industry. However, findings and subsequent publicity has fostered significant consumer resistance to the use of synthetic food additives as antioxidants, colourants etc. and therefore food industry is in search of potential natural antioxidants from edible sources.The major dietary sources of antioxidant phytochemicals are cereals, legumes, fruits, vegetables, oilseeds, beverages, spices and herbs. In the present study, we have focused on rice bran and its byproducts. Rice is one of the oldest of food crops and has been a staple food in India from very ancient times. It is also the staple food for about 60% of the world's population. Rice bran is a byproduct of the rice milling industry and is a potential commercial source of a healthy edible oil viz. rice bran oil and a variety of bio-active phytochemicals.Defatted rice bran (DRB), a byproduct of rice bran oil extraction, is also a good source of insoluble dietary fiber, protein, phytic acid, inosito I, vitamin B and a variety of other phytochemicals. Though the antioxidant potential of DRB has been demonstrated, it still remained a relatively unexplored source material, which demanded further investigation especially with regard to its detailed phytochemical profile leading to practical application. The focus of the present investigation therefore has been on DRB primarily to establish its phytochemical status and feasibility of using it as a source of bio-active phytochemicals and natural antioxidants leading to value addition of DRB otherwise used as cattle feed. To gain a better understanding of the value of rice bran as a source of phytochemicals, five popular rice varieties of the region viz. PTB 50, PTB 39, PTB 38, JA Y A, and MO 10 and a wild variety (oryza nivara) that is mainly used for medicinal applications in traditional ayurvedic system were characterized along with commercial samples of rice bran. The present study also explains the feasibility of a process for the extraction, enrichment, and isolation of antioxidant compounds from DRB. The antioxidant potential of the extracts were evaluated both in bulk oils and in food relevant model emulsions, using standard in vitro models. Radical scavenging effects, indicative of possible biological effects, were also evaluated. |
| URI: | http://dyuthi.cusat.ac.in/purl/2378 |
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| Dyuthi-T0650.pdf | (8.546Mb) |
| Description: | Dept.of Applied Chemistry,Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2157 |
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| Dyuthi-T0516.pdf | (7.090Mb) |
| Description: | Department of Physics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2572 |
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| Dyuthi-T0701.pdf | (6.292Mb) |
| Description: | Department of Applied Chemistry, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2374 |
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| Dyuthi-T0646.pdf | (5.798Mb) |
| Abstract: | In this thesis, we report our endeavours in the synthesis of a few polycyclic compounds. We were interested in the synthesis of a few bicyclic compounds designed to undergo interesting photochemical transformations including tripletmediated di-π-methane rearrangement and/or competing singlet-mediated electrocyclic reactions. Our target molecules have "inbuilt" structural features which will potentially alter the photochemistry of the substrate under consideration.The present investigation was undertaken to test our hypothesis on selective intramolecular quenching of singlet or triplet excited states of molecules.We adopted Dies-Alder reaction for the synthesis of several of the bicyclic compounds we were interested in. Some of the precursor dienes synthesised by us are capable of undergoing intramolecular cycloaddition reactions as well. So, it was important to delineate the conditions and structural features that will enable a particular molecule to undergo intermolecular and intramolecular Dies-Alder reaction when treated with a suitable dienophile.Though, the main focus of this thesis is on the synthesis of bicyclic and tricyclic systems capable of undergoing di-π-methane rearrangement, in the last chapter of this thesis, we describe our findings on the synthesis of a few dispirocompounds. These systems were encountered as unexpected products in the attempted synthesis of novel dibenzoylalkene-type systems. Consequently, a brief survey on the synthesis and transformations of dibenzoylalkenes is also included as an integral part of this thesis. |
| Description: | Department of Applied Chemistry, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/2054 |
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| Dyuthi-T0477.pdf | (4.280Mb) |
| Description: | Department of Applied Chemistry, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1964 |
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| Dyuthi-T0478.pdf | (44.66Mb) |
| Abstract: | Preparation of simple and mixed ferrospinels of nickel, cobalt and copper and their sulphated analogues by the room temperature coprecipitation method yielded fine particles with high surface areas. Study of the vapour phase decomposition of cyclohexanol at 300 °C over all the ferrospinel systems showed very good conversions yielding cyclohexene by dehydration and/or cyclohexanone by dehydrogenation, as the major products. Sulphation very much enhanced the dehydration activity over all the samples. A good correlation was obtained between the dehydration activities of the simple ferrites and their weak plus medium strength acidities (usually of the Brφnsted type) determined independently by the n-butylamine adsorption and ammonia-TPD methods. Mixed ferrites containing copper showed a general decrease in acidities and a drastic decrease in dehydration activities. There was no general correlation between the basicity parameters obtained by electron donor studies and the ratio of dehydrogenation to dehydration activities. There was a leap in the dehydrogenation activities in the case of all the ferrospinel samples containing copper. Along with the basic properties, the redox properties of copper ion have been invoked to account for this added activity. |
| URI: | http://dyuthi.cusat.ac.in/purl/2278 |
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| Dyuthi-SS61.pdf | (215.1Kb) |
| Description: | Department of Statistics, Cochin University of Sciene ans Technology |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1994 |
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| Dyuthi-T0480.pdf | (671.8Kb) |
| Abstract: | In this thesis, the concept of reversed lack of memory property and its generalizations is studied.We we generalize this property which involves operations different than the ”addition”. In particular an associative, binary operator ” * ” is considered. The univariate reversed lack of memory property is generalized using the binary operator and a class of probability distributions which include Type 3 extreme value, power function, reflected Weibull and negative Pareto distributions are characterized (Asha and Rejeesh (2009)). We also define the almost reversed lack of memory property and considered the distributions with reversed periodic hazard rate under the binary operation. Further, we give a bivariate extension of the generalized reversed lack of memory property and characterize a class of bivariate distributions which include the characterized extension (CE) model of Roy (2002a) apart from the bivariate reflected Weibull and power function distributions. We proved the equality of local proportionality of the reversed hazard rate and generalized reversed lack of memory property. Study of uncertainty is a subject of interest common to reliability, survival analysis, actuary, economics, business and many other fields. However, in many realistic situations, uncertainty is not necessarily related to the future but can also refer to the past. Recently, Di Crescenzo and Longobardi (2009) introduced a new measure of information called dynamic cumulative entropy. Dynamic cumulative entropy is suitable to measure information when uncertainty is related to the past, a dual concept of the cumulative residual entropy which relates to uncertainty of the future lifetime of a system. We redefine this measure in the whole real line and study its properties. We also discuss the implications of generalized reversed lack of memory property on dynamic cumulative entropy and past entropy.In this study, we extend the idea of reversed lack of memory property to the discrete set up. Here we investigate the discrete class of distributions characterized by the discrete reversed lack of memory property. The concept is extended to the bivariate case and bivariate distributions characterized by this property are also presented. The implication of this property on discrete reversed hazard rate, mean past life, and discrete past entropy are also investigated. |
| Description: | Department of Statistics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2356 |
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| Dyuthi-T0629.pdf | (629.2Kb) |
| Description: | Department of Physics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1960 |
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| Dyuthi-T0481.pdf | (7.945Mb) |
| Abstract: | Titania, sulfated titania and chromium loaded sulfated titania were prepared by sol–gel method and characterized using different technique. Phenol is nitrated regioselectively by nitric acid using chromium loaded sulfated titania catalysts. A remarkable ortho selectivity is observed in solid state nitration to yield exclusively ortho-nitrophenol. Compared to the conventional process, phenol nitration over solid acid catalyst is a clean and environment friendly process. Catalytic activity well correlates with the Brönsted acid sites of these catalysts. |
| URI: | http://dyuthi.cusat.ac.in/purl/2320 |
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| Dyuthi-P00088.pdf | (363.8Kb) |
| Abstract: | The incorporation of transition metal oxide pillars such as those of iron and chromium along with Al2O3, pillars within the interlayers of a montmorillonite clay is investigated. The surface acidity of these catalysts has been evaluated for the first time employing the equilibrium adsorption of an electron donor, perylene, and the results are compared with those obtained by temperature programmed desorption of ammonia. The principle is based on the ability of a catalyst surface site to accept a single electron from an electron donor like perylene to form charge transfer complexes and the amount of adsorbed species is measured quantitatively by UV-vis spectroscopy. Fina1ly, an attempt has been made to correlate the acidity determined by the two independcnt methods and the catalytic activity of present systems in the benzoylation of toluene with benzoyl chloride. Incorporation of Fe and Cr has changed the properties of AI pitlared montmorillonite. Fe pillared systems have been found to be vcry good catalysts for benzoylation reaction |
| URI: | http://dyuthi.cusat.ac.in/purl/2213 |
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| Dyuthi-SS16.pdf | (817.0Kb) |
| Abstract: | We have investigated the changes in surface acidity/basicity and catalytic pro~erties of samarium oxide due to surface modification by SO42- ion. The acidity/basicity of the catalysts is determined by titration method using Hammett indicators. Esterification of acetic acid by n-butanol is chosen as a test reaction. Sm203, owing to its high basicity and low acidity, does not catalyze the reaction. But sulphated Sm20J catalyzes the esterification reaction effectively. Activation temperature does not have much effect on the acidity of sulphated samaria. |
| URI: | http://dyuthi.cusat.ac.in/purl/2144 |
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| Dyuthi -SS01.pdf | (209.6Kb) |
| Abstract: | The surface acidity/basicity of binary oxides of Zr and La and the ternary oxides of Zr, La and Al are reported. The data have been correlated with their catalytic activity towards liquid phase reduction of cyclohexanone. |
| URI: | http://dyuthi.cusat.ac.in/purl/2308 |
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| Dyuthi-SS76.pdf | (155.8Kb) |
| Abstract: | The surface acidity and basicity of ternary oxides of AI, Ce and Dy have been determined using a set of Hammett indicators. The data have been correlated with the catalytic activity of these oxides towards the liquid phase reduction of cyclohexanone in 2-propanol. The reaction is favoured by the higher basicity of the ternary oxide. |
| URI: | http://dyuthi.cusat.ac.in/purl/2306 |
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| Dyuthi-SS74.pdf | (200.7Kb) |
| Abstract: | The surface acidity and basicity of ternary oxides of La, Ce and AI have been determined using a set of Hammett indicators. The data have been correlated with the catalytic activity of these oxides towards the liquid phase reduction of cycIohexanone in 2-propanol. |
| URI: | http://dyuthi.cusat.ac.in/purl/2291 |
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| Dyuthi-SS73.pdf | (195.6Kb) |
| Abstract: | The surface acidity and basicity of oxides of Sm and Zr and their mixed oxides have been determined using a set of Hammett indicators. The data have been correlated with the catalytic activity of these oxides towards the liquid phase reduction of cyclo-hexanone in 2-propanol. |
| URI: | http://dyuthi.cusat.ac.in/purl/2221 |
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| Dyuthi-SS25.pdf | (170.3Kb) |
| Abstract: | Acid/base strength distribution of Y2O3 and its mixed oxides with alumina catalysts are measured on Hammett acidity function scale and expressed in terms of H0max value. Basicity of Y2O3 increases with increase in activation temperature and for mixed oxides the basicity increases with increase in concentration of Y2O3, in the catalyst. |
| URI: | http://dyuthi.cusat.ac.in/purl/2229 |
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| Dyuthi-SS34.pdf | (165.9Kb) |
| Abstract: | The limit of electron transfer in electron affinity from the oxide surface to the electron acceptor (EA) are reported from the adsorption of EA on DY203, mixed oxides of DY203 with alumina and mixed oxides of Y203 with y-alumina. The extent of electron transfer is understood from magnetic measurements. |
| URI: | http://dyuthi.cusat.ac.in/purl/2275 |
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| Dyuthi-SS55.pdf | (210.7Kb) |
| Abstract: | The electron donating properties, surface acidity/ basicity and catalytic activity of cerium - zirconium mixed oxides at various compositions have been reported at an activation temperature of 500 degree C. The catalytic activity for the esterification of acetic acid with n-butanol has heen correlated with electron donating properties and surface acidity/basicity of the oxides. |
| URI: | http://dyuthi.cusat.ac.in/purl/2145 |
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| Dyuthi-P0003.pdf | (315.6Kb) |
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