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Shamla, Ahammed; Dr. Prema, P (Cochin University of Science and Technology, May 3, 2002)[+][-]
Abstract: The continually growing worldwide hazardous waste problem is receiving much attention lately. The development of cost effective, yet efficient methods of decontamination are vital to our success in solving this problem.Bioremediation using white rot fungi, a group of basidiomycetes characterized by their ability to degrade lignin by producing extracellular LiP, MnP and laccase have come to be recognized globally which is described in detail in Chapter 1.These features provide them with tremendous advantages over other micro-organisms.Chapter 2 deals with the isolation and screening of lignin degrading enzyme producing micoro-organisms from mangrove area. Marine microbes of mangrove area has great capacity to tolerate wide fluctuations of salinitie.Primary and secondary screening for lignin degrading enzyme producing halophilic microbes from mangrove area resulted in the selection of two fungal strains from among 75 bacteria and 26 fungi. The two fungi, SIP 10 and SIP ll, were identified as penicillium sp and Aspergillus sp respectively belonging to the class Ascomycetes .Specific activity of the purified LiP was 7923 U/mg protein. The purification fold was 24.07 while the yield was 18.7%. SDS PAGE of LiP showed that it was a low molecular weight protein of 29 kDa.Zymogram analysis using crystal violet dye as substrate confirmed the peroxidase nature of the purified LiP.The studies on the ability of purified LiP to decolorize different synthetic dyes was done. Among the dyes studied, crystal violet, a triphenyl methane dye was decolorized to the greatest extent. Description: Biochemical Processing Division, Regional Research Laboratory, Trivandrum URI: http://dyuthi.cusat.ac.in/purl/3116 Files in this item: 1
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Shamala,Ahammed; Prema,P (CSIR & CUSAT,Faculty of Science, 2002)[+][-]
Abstract: In this thesis, the production and characterization of ligninolytic enzymes using the fungi isolated from mangrove area are studied. The objective of the present work are isolation and screening of dye decolorizing micro-organisms from mangrove area, screening of the selected microorganisms for the production of lignin degrading enzymes, identification of the potent micro-organisms, characterization of the crude enzyme, lignin peroxidase, of the selected fungi—Aspergillus sp. SIP 11 and Penicillium sp. SIP 10 etc. This included the determination of the optimum pH, temperature, veratryl alcohol and H2O2 concentration. Besides the stability of crude LiP at different pHs and temperatures were studied. The immense applications, particularly in bioremediation, to which the lignin degrading micro-organisms could be used make this study important, the ascomycetes and deuteromycetes fungi, especially form the marine environment were studied with respect to their ligninolytic enzyme system making this study an initial step in unraveling the vast hidden potential of these microbes in bioremediation, the marine microbes are halophilic in nature which make them better suited to cope with the high salinity of industrial effluents thereby giving them added advantage in the filed of bioremediation. The thesis deals with the isolation and screening of lignin degrading enzyme-producing microbes from mangrove area. The identification of the most potent fungal isolates and characterization of LiP from these are also done. URI: http://dyuthi.cusat.ac.in/purl/24 Files in this item: 1
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Beena, P S; Dr.Chandrasekaran,M; Dr.Sarita,Bhat G (Cochin University of Science & Technology, January , 2010)[+][-]
Abstract: Marine fungi remain totally unexplored as a source of industrial enzyme and prospective applications. Further tannase production by a marine organism has so far not been established. The primary objective of this study included the evaluation of the potential of Aspergillus awamori isolated from sea water as part of an earlier study and available in the culture collection of the Microbial technology laboratory for tannase production through different fermentation methods, optimization of bioprocess variables by statistical methods, purification and characterization of the enzyme, genetic study, and assessment of its potential applications. Description: Department of Biotechnology, Cochin University of Science and Technology URI: http://dyuthi.cusat.ac.in/xmlui/purl/2020 Files in this item: 1
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Korak, Saha; Dr. Parameswaran, K (Space Physics Laboratory, Vikram Sarabhai Space Centre, July , 2008)[+][-]
Abstract: Global Positioning System (GPS), with its high integrity, continuous availability and reliability, revolutionized the navigation system based on radio ranging. With four or more GPS satellites in view, a GPS receiver can find its location anywhere over the globe with accuracy of few meters. High accuracy - within centimeters, or even millimeters is achievable by correcting the GPS signal with external augmentation system. The use of satellite for critical application like navigation has become a reality through the development of these augmentation systems (like W AAS, SDCM, and EGNOS, etc.) with a primary objective of providing essential integrity information needed for navigation service in their respective regions. Apart from these, many countries have initiated developing space-based regional augmentation systems like GAGAN and IRNSS of India, MSAS and QZSS of Japan, COMPASS of China, etc. In future, these regional systems will operate simultaneously and emerge as a Global Navigation Satellite System or GNSS to support a broad range of activities in the global navigation sector.Among different types of error sources in the GPS precise positioning, the propagation delay due to the atmospheric refraction is a limiting factor on the achievable accuracy using this system. The WADGPS, aimed for accurate positioning over a large area though broadcasts different errors involved in GPS ranging including ionosphere and troposphere errors, due to the large temporal and spatial variations in different atmospheric parameters especially in lower atmosphere (troposphere), the use of these broadcasted tropospheric corrections are not sufficiently accurate. This necessitated the estimation of tropospheric error based on realistic values of tropospheric refractivity. Presently available methodologies for the estimation of tropospheric delay are mostly based on the atmospheric data and GPS measurements from the mid-latitude regions, where the atmospheric conditions are significantly different from that over the tropics. No such attempts were made over the tropics. In a practical approach when the measured atmospheric parameters are not available analytical models evolved using data from mid-latitudes for this purpose alone can be used. The major drawback of these existing models is that it neglects the seasonal variation of the atmospheric parameters at stations near the equator. At tropics the model underestimates the delay in quite a few occasions. In this context, the present study is afirst and major step towards the development of models for tropospheric delay over the Indian region which is a prime requisite for future space based navigation program (GAGAN and IRNSS). Apart from the models based on the measured surface parameters, a region specific model which does not require any measured atmospheric parameter as input, but depends on latitude and day of the year was developed for the tropical region with emphasis on Indian sector.Large variability of atmospheric water vapor content in short spatial and/or temporal scales makes its measurement rather involved and expensive. A local network of GPS receivers is an effective tool for water vapor remote sensing over the land. This recently developed technique proves to be an effective tool for measuring PW. The potential of using GPS to estimate water vapor in the atmosphere at all-weather condition and with high temporal resolution is attempted. This will be useful for retrieving columnar water vapor from ground based GPS data. A good network of GPS could be a major source of water vapor information for Numerical Weather Prediction models and could act as surrogate to the data gap in microwave remote sensing for water vapor over land. URI: http://dyuthi.cusat.ac.in/purl/2715 Files in this item: 1
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Balakrishna Warrier, K; Dr.Purushothaman, C (Cochin University of Science and Technology, January , 1982)[+][-]
Abstract: The present thesis deals with the theoretical investigations on the effect of anisotropy on various properties of magnetically doped superconductors described by fihiba — Rusinov model.Chapter 1 is introductory. It contains a brief account of the current status of theory of superconductivity. In’ chapter 2 we give the formulation of the problem. Chapter 2.1 gives the BCS theory. The effect of magnetic impurities in superconductors as described by A8 theory is given in chapter 2.2A and that described by SR model is discussed in chapter 2.28. Chapter 2.2c deals with Kondo effect. In chapter 2.3 the anisotropy problem is reviewed. Our calculations, results and discussions are given in chapter 3. Chapter 3.1 deals with Josephson tunnel effect. In chapter 3.2 the thermodynamic critical field H62 is described. Chtpter 3.3 deals with the density of states. The ultrasonic attenuation coefficient and ufitlear spin relaxation are given in chapter 3.4 and 3.5 respectively. In chapter 3.6 we give the upper critical field calculations and chapter 3.7 deals with the response function. The Kondo effect is given in chapter 3.8. In chapter 4 we give the sumary of our results Description: Department of Physics, Cochin University of science and Technology URI: http://dyuthi.cusat.ac.in/purl/3566 Files in this item: 1
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Preeth, M; Dr.Unnikrishnan Nair, N (Cochin University of Science and Technology, June , 2014)[+][-]
Abstract: The present work is intended to discuss various properties and reliability aspects of higher order equilibrium distributions in continuous, discrete and multivariate cases, which contribute to the study on equilibrium distributions. At first, we have to study and consolidate the existing literature on equilibrium distributions. For this we need some basic concepts in reliability. These are being discussed in the 2nd chapter, In Chapter 3, some identities connecting the failure rate functions and moments of residual life of the univariate, non-negative continuous equilibrium distributions of higher order and that of the baseline distribution are derived. These identities are then used to characterize the generalized Pareto model, mixture of exponentials and gamma distribution. An approach using the characteristic functions is also discussed with illustrations. Moreover, characterizations of ageing classes using stochastic orders has been discussed. Part of the results of this chapter has been reported in Nair and Preeth (2009). Various properties of equilibrium distributions of non-negative discrete univariate random variables are discussed in Chapter 4. Then some characterizations of the geo- metric, Waring and negative hyper-geometric distributions are presented. Moreover, the ageing properties of the original distribution and nth order equilibrium distribu- tions are compared. Part of the results of this chapter have been reported in Nair, Sankaran and Preeth (2012). Chapter 5 is a continuation of Chapter 4. Here, several conditions, in terms of stochastic orders connecting the baseline and its equilibrium distributions are derived. These conditions can be used to rede_ne certain ageing notions. Then equilibrium distributions of two random variables are compared in terms of various stochastic orders that have implications in reliability applications. In Chapter 6, we make two approaches to de_ne multivariate equilibrium distribu- tions of order n. Then various properties including characterizations of higher order equilibrium distributions are presented. Part of the results of this chapter have been reported in Nair and Preeth (2008). The Thesis is concluded in Chapter 7. A discussion on further studies on equilib- rium distributions is also made in this chapter. URI: http://dyuthi.cusat.ac.in/purl/4939 Files in this item: 1
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Rajeshmon, V G; Dr.Vijayakumar, K P (Cochin University Of Science And Technology, November 4, 2013)[+][-]
Abstract: This thesis is devoted to the development of a relatively new, rapidly developing quaternary semiconducting material (viz., Cu2ZnSnS4) used for photovoltaic applications. This semiconductor, commonly known as CZTS, is closely related to a family of materials that have been used for solar cell applications. It is a compound semiconductor made of copper, zinc, tin and sulfur, which are sufficiently abundant elements; none of them is harmful to the environment even at large scale usage. Aim of this study is to fabricate CZTS solar cells through chemical spray pyrolysis (CSP) technique. At first the influence of various spray parameters like substrate temperature, spray rate, precursor ratio etc. on the opto-electronic properties of CZTS films will be studied in detail. Then the fabrication of CZTS/In2S3 hetero junctions and various ways to improve the performance parameters will be tried Description: Department of Physics Cochin University of Science and Technology URI: http://dyuthi.cusat.ac.in/purl/3535 Files in this item: 1
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Manjula, R; Chandrasekaran, M (Cochin University of Science And Technology, May 19, 2014)
[+][-]Abstract: The present study led to the recognition of Natrinema sp. BTSH 10 isolated from saltern ponds, as an ideal candidate species for production of gelatinase, which was noted as a halozyme capable of showing enzyme activity in the presence of 15% NaCl. Results obtained during the course of the present study indicated potential for application of this enzyme in industrial catalysis that are performed in the presence of high concentrations of salt. The enzyme characteristics noted with this gelatinase also indicate the scope for probable applications in leather industry, meat tenderization, production of fish sauce and soy sauce. Since halophilic proteases are tolerant to organic solvents, they could be used in antifouling coating preparations used to prevent biofouling of submarine equipments. The gelatinase from haloarchaea could be considered as a probable candidate for peptide synthesis. However, further studies are warranted on this haloarcheal gelatinase particularly on structure elucidation and enzyme engineering to suit a wide range of applications. There is immense scope for developing this halozyme as an industrial enzyme once thorough biochemistry of this gelatinase is studied and a pilot scale study is conducted towards industrial production of this enzyme under fermentation is facilitated. Based on the present study it is concluded that haloarchaea Natrinema sp. that inhabit solar saltern ponds are ideal source for deriving industrially important halozymes and molecular studies on enzymes are prerequisite for their probable industrial applications. This is the first time this species of archaea is recognized as a source of gelatinase enzyme that has potential for industrial applications. URI: http://dyuthi.cusat.ac.in/purl/4968 Files in this item: 2
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Archana, Kishore; Dr.Sarita,Bhat G (Cochin University of Science and Technology, March , 2007)[+][-]
Abstract: The temperate, filamentous phage ФMV -5 isolated from Mangalavanam mangrove of Kochi, using the environmental strain of Vibrio sp. MV-5 shares many similar properties with other marine phage isolates, while also remaining unique. The study has revealed that the interaction of temperate phages and the microbial population in the marine environment may contribute significantly to microbial genetic diversity and composition by conversion and transduction and which requires greater study.Prophages contribute a substantial share of the mobile DNA of their bacterial hosts and seem to influence the short-term evolution of pathogenic bacteria. Automated methods for systematic investigation of prophages and other mobile DNA elements in the available bacterial genome sequences will be necessary to understand their role in bacterial genome evolution. In the past, phages were mainly investigated as the simplest model systems in molecular biology. Now it is increasingly realized that phage research will be instrumental in the understanding of bacterial abundance in the environment. One can predict that phage research will impact diverse areas such as geochemistry and medicine. Success will largely depend on integrative multidisciplinary approaches in this field. Clearly, further studies are required to understand how vibriophages interact with Vibrios to promote this organism's acquisition of the critical genes which alter its virulence or adaptation to its environmental niche.It is evident from this study and comparison with those reports cited above that vibriophage ФMV-5 is a previously unreported bacteriophage. It is recommended that the minimum requirement for reporting a new phage should be novel morphological markers and a description of host range, both of which have been achieved in this study. Description: Department of Biotechnology, Cochin University of Science and Technology URI: http://dyuthi.cusat.ac.in/purl/2803 Files in this item: 1
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Rekha Mol, K.R; Dr. Padma Nambisan; Dr. Elyas, K.K (Cochin University of Science and Technology, August 23, 2015)[+][-]
URI: http://dyuthi.cusat.ac.in/purl/5148 Files in this item: 1
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Sreelakshmi, N; Muraleedharan Nair, K R (November 20, 2014)[+][-]
URI: http://dyuthi.cusat.ac.in/purl/4905 Files in this item: 1
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Jacob,K Daniel; Krishnamoorthy,K (Cochin University of Science and Technology, 1985)[+][-]
URI: http://dyuthi.cusat.ac.in/purl/1026 Files in this item: 1
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Ramachandran Nair, V K; Krishnamurthy,A (Cochin University of Science and Technology, 1988)[+][-]
URI: http://dyuthi.cusat.ac.in/purl/1032 Files in this item: 1
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Sreenivasan, C; Dr.Krishnamoorthy,A (Cochin University of Science and Technology, August 16, 2012)[+][-]
Abstract: The objective of the study of \Queueing models with vacations and working vacations" was two fold; to minimize the server idle time and improve the e ciency of the service system. Keeping this in mind we considered queueing models in di erent set up in this thesis. Chapter 1 introduced the concepts and techniques used in the thesis and also provided a summary of the work done. In chapter 2 we considered an M=M=2 queueing model, where one of the two heterogeneous servers takes multiple vacations. We studied the performance of the system with the help of busy period analysis and computation of mean waiting time of a customer in the stationary regime. Conditional stochastic decomposition of queue length was derived. To improve the e ciency of this system we came up with a modi ed model in chapter 3. In this model the vacationing server attends the customers, during vacation at a slower service rate. Chapter 4 analyzed a working vacation queueing model in a more general set up. The introduction of N policy makes this MAP=PH=1 model di erent from all working vacation models available in the literature. A detailed analysis of performance of the model was provided with the help of computation of measures such as mean waiting time of a customer who gets service in normal mode and vacation mode. Description: Department of Mathematics, Cochin University of Science and Technology URI: http://dyuthi.cusat.ac.in/purl/3803 Files in this item: 1
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Sreenivasan, C; Dr.Krishnamoorthy,A (Cochin University of Science and Technology, June 16, 2012)[+][-]
Abstract: The thesis entitled “Queueing Models with Vacations and Working Vacations" consists of seven chapters including the introductory chapter. In chapters 2 to 7 we analyze different queueing models highlighting the role played by vacations and working vacations. The duration of vacation is exponentially distributed in all these models and multiple vacation policy is followed.In chapter 2 we discuss an M/M/2 queueing system with heterogeneous servers, one of which is always available while the other goes on vacation in the absence of customers waiting for service. Conditional stochastic decomposition of queue length is derived. An illustrative example is provided to study the effect of the input parameters on the system performance measures. Chapter 3 considers a similar setup as chapter 2. The model is analyzed in essentially the same way as in chapter 2 and a numerical example is provided to bring out the qualitative nature of the model. The MAP is a tractable class of point process which is in general nonrenewal. In spite of its versatility it is highly tractable as well. Phase type distributions are ideally suited for applying matrix analytic methods. In all the remaining chapters we assume the arrival process to be MAP and service process to be phase type. In chapter 4 we consider a MAP/PH/1 queue with working vacations. At a departure epoch, the server finding the system empty, takes a vacation. A customer arriving during a vacation will be served but at a lower rate.Chapter 5 discusses a MAP/PH/1 retrial queueing system with working vacations.In chapter 6 the setup of the model is similar to that of chapter 5. The signicant dierence in this model is that there is a nite buer for arrivals.Chapter 7 considers an MMAP(2)/PH/1 queueing model with a nite retrial group Description: Department of Mathematics, Cochin University of Science and Technology. URI: http://dyuthi.cusat.ac.in/purl/3154 Files in this item: 1
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Jacob,K Daniel; Dr.Krishnamoorthy,A (Cochin University Of Science And Technology, 1985)[+][-]
Abstract: In this thesis we study the effect of rest periods in queueing systems without exhaustive service and inventory systems with rest to the server. Most of the works in the vacation models deal with exhaustive service. Recently some results have appeared for the systems without exhaustive service. Description: Department Of‘ Mathematics And Statistics,Cochin University Of Science And Technology URI: http://dyuthi.cusat.ac.in/purl/3579 Files in this item: 1
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Varghese,Jacob; Dr.Krishnamoorthy,A; Dr.Narayanan Namboothiri, M N (Cochin University of Science and Technology, June 16, 2012)[+][-]
Abstract: In this thesis we have introduced and studied the notion of self interruption of service by customers. Service interruption in queueing systems have been extensively discussed in literature (see, Krishnamoorthy, Pramod and Chakravarthy [38]) for the most recent survey. So far all work reported deal with cases in which service interruptions are generated by sources other than customers. However, there are situations where interruptions are due to the customers rather than the system. Such situations are especially arise at doctors clinic, banks, reservation counter etc. Our attempt is to quantify a few of such problems. Systematically we have proceed from single server queue (in Chapter 2) to multi-server queues (Chapter 3). In Chapte 4, we have studied a very general multiserver queueing model with service interruption and protection of service phases. We also introduced customer interruption in a retrial setup (in Chapter 5). All models (from Chapter 2 to Chapter 4) that were analyzed involve 'non-preemptive priority' for interrupted customers where as in the model discussed in Chapter 5 interruption of service by customers is not encouraged. So the interrupted customers cannot access the server as long as there are primary customers in the system. In Chapter 5 we have obtained an explicit expression for the stability condition of the system. In all models analyzed in this thesis, we have assumed that no more than one interruption is allowed for a customer while in service. Since the models are not analytically tractable, a large number of numerical illustrations were given in each chapter it illustrate the working of the systems. We can extend the models discussed in this thesis to several directions. For example some of the models can be analyzed with both server induced and customer induced interruptions the results for which are not available till date. Another possible extension of work is to the case where there is no bound on the number of interruptions a customer is permitted to have before service completion. More complex is the case where a customer is permitted to have a nite number (K ≥ 2) of We can extend the models discussed in this thesis to several directions. Description: Department of Mathematics, Cochin University of Science and Technology. URI: http://dyuthi.cusat.ac.in/purl/3137 Files in this item: 1
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Jaya, S; Dr. B Lakshmi (Cochin University of Science and Technology, August 3, 2015)[+][-]
Abstract: In many situations probability models are more realistic than deterministic models. Several phenomena occurring in physics are studied as random phenomena changing with time and space. Stochastic processes originated from the needs of physicists.Let X(t) be a random variable where t is a parameter assuming values from the set T. Then the collection of random variables {X(t), t ∈ T} is called a stochastic process. We denote the state of the process at time t by X(t) and the collection of all possible values X(t) can assume, is called state space URI: http://dyuthi.cusat.ac.in/purl/5043 Files in this item: 1
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Ajayakumar, C B; Dr.Krishnamoorthy,A (Cochin University of Science and Technology, August , 2011)[+][-]
Description: Department of Mathematics, Cochin University of Science and Technology URI: http://dyuthi.cusat.ac.in/purl/2762 Files in this item: 1
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Viswanath C Narayanan; Krishnamoorthy,A (Department of Mathematics, 2005)[+][-]
Abstract: Application of Queueing theory in areas like Computer networking, ATM facilities, Telecommunications and to many other numerous situation made people study Queueing models extensively and it has become an ever expanding branch of applied probability. The thesis discusses Reliability of a ‘k-out-of-n system’ where the server also attends external customers when there are no failed components (main customers), under a retrial policy, which can be explained in detail. It explains the reliability of a ‘K-out-of-n-system’ where the server also attends external customers and studies a multi-server infinite capacity Queueing system where each customer arrives as ordinary but can generate into priority customer which waiting in the queue. The study gives details on a finite capacity multi-server queueing system with self-generation of priority customers and also on a single server infinite capacity retrial Queue where the customer in the orbit can generate into a priority customer and leaves the system if the server is already busy with a priority generated customer; else he is taken for service immediately. Arrival process is according to a MAP and service times follow MSP. URI: http://dyuthi.cusat.ac.in/purl/760 Files in this item: 1
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