| Description: | Department of Physics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2135 |
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| Dyuthi-T0496.pdf | (4.844Mb) |
| Description: | Department of Physics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/2136 |
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| Dyuthi-T0497.pdf | (3.650Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/5210 |
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| Dyuthi T-2225.pdf | (22.25Mb) |
| Abstract: | The physical properties of solid matter are basically influenced by the existence of lattice defects; as a result the study of crystal defects has assumed a central position in solid state physics and materials science. The study of dislocations ixa single crystals can yield a great deal of information on the mechanical properties of materials. In order to secure a full understanding of the processes taking place in semiconducting materials, it is important to investigate the microhardness of these materials-—the most reliable method of determining the fine structure of crystals, the revelation of micro—inhomogenities in the distribution of impurities, the effect of dislocation density on the mechanical properties of crystals etc. Basically electrical conductivity in single crystals is a defect controlled phenomenon and hence detailed investigation of the electrical properties of these materials is one of the best available methods for the study of defects in them. In the present thesis a series of detailed studies carried out in Te—Se system, Bi2Te3 and In2Te3 crystals using surface topographical, dislocation and microindentation analysis as well as electrical measurements are presented |
| Description: | Department of Physics, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3611 |
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| Dyuthi-T1569.pdf | (58.55Mb) |
| Abstract: | Transparent conducting oxides (TCO’s) have been known and used for technologically important applications for more than 50 years. The oxide materials such as In2O3, SnO2 and impurity doped SnO2: Sb, SnO2: F and In2O3: Sn (indium tin oxide) were primarily used as TCO’s. Indium based oxides had been widely used as TCO’s for the past few decades. But the current increase in the cost of indium and scarcity of this material created the difficulty in obtaining low cost TCO’s. Hence the search for alternative TCO material has been a topic of active research for the last few decades. This resulted in the development of various binary and ternary compounds. But the advantages of using binary oxides are the easiness to control the composition and deposition parameters. ZnO has been identified as the one of the promising candidate for transparent electronic applications owing to its exciting optoelectronic properties. Some optoelectronics applications of ZnO overlap with that of GaN, another wide band gap semiconductor which is widely used for the production of green, blue-violet and white light emitting devices. However ZnO has some advantages over GaN among which are the availability of fairly high quality ZnO bulk single crystals and large excitonic binding energy. ZnO also has much simpler crystal-growth technology, resulting in a potentially lower cost for ZnO based devices. Most of the TCO’s are n-type semiconductors and are utilized as transparent electrodes in variety of commercial applications such as photovoltaics, electrochromic windows, flat panel displays. TCO’s provide a great potential for realizing diverse range of active functions, novel functions can be integrated into the materials according to the requirement. However the application of TCO’s has been restricted to transparent electrodes, ii notwithstanding the fact that TCO’s are n-type semiconductors. The basic reason is the lack of p-type TCO, many of the active functions in semiconductor originate from the nature of pn-junction. In 1997, H. Kawazoe et al reported the CuAlO2 as the first p-type TCO along with the chemical design concept for the exploration of other p-type TCO’s. This has led to the fabrication of all transparent diode and transistors. Fabrication of nanostructures of TCO has been a focus of an ever-increasing number of researchers world wide, mainly due to their unique optical and electronic properties which makes them ideal for a wide spectrum of applications ranging from flexible displays, quantum well lasers to in vivo biological imaging and therapeutic agents. ZnO is a highly multifunctional material system with highly promising application potential for UV light emitting diodes, diode lasers, sensors, etc. ZnO nanocrystals and nanorods doped with transition metal impurities have also attracted great interest, recently, for their spin-electronic applications This thesis summarizes the results on the growth and characterization of ZnO based diodes and nanostructures by pulsed laser ablation. Various ZnO based heterojunction diodes have been fabricated using pulsed laser deposition (PLD) and their electrical characteristics were interpreted using existing models. Pulsed laser ablation has been employed to fabricate ZnO quantum dots, ZnO nanorods and ZnMgO/ZnO multiple quantum well structures with the aim of studying the luminescent properties. |
| URI: | http://dyuthi.cusat.ac.in/purl/666 |
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| Dyuthi-T0331.pdf | (2.957Mb) |
| Abstract: | In natural systems phytoplankton interact with planktonic (free living) and attached epiphytic bacteria both synergistically and antagonistically. The specificity of the association with micro algae and bacteria differs in terms of adhesion mechanisms and metabolic cooperation. Present research was carried out to study the effect of bacterial isolates namely Bacillus sp. and Pseudomonas sp. from algal culture systems on the growth of micro algae such as Chaetoceros calcitrans and Nannochloropsis oculata. C. calcitrans (F= 15.34; P<0.05) and N. oculata (F=12.52; P<0.05) showed significantly higher growth, in treatments with Bacillus sp. and Pseudomonas sp when compared to control. |
| Description: | Int.J.Curr.Microbiol.App.Sci (2014) 3(4): 352-359 |
| URI: | http://dyuthi.cusat.ac.in/purl/3950 |
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| Growth enhancem ... cted bacterial strains.pdf | (1.187Mb) |
| Abstract: | Nonlinear optics has been a rapidly growing field in recent decades since the invention of lasers. The systematic progress in the laser technology increases our efficiency in the generation and control of coherent optical radiations. Nonlinear optics is based on the study ofeffects and phenomena related to the interaction of intense coherent light radiation with matter. Compared to other light sources laser radiation can provide high directionality, high monochromaticiry, high brightness and high photon degeneracy. At such a very intense incident beam, the matter responds in a nonlinear manner to the incident radiation fields, which endows the media :1 characteristic to change the refractive index or absorption coe fflcient of the media or the wavelength, or the frequency of the incident electromagnetic waves. This thesis encompasses the fabrication of nonlinear optical devices based on semiconductor and metal nanostructures. The presented work focus on the experimental and theoretical discussions on nonlinear optical effects especially nonlinear absorption and refraction exhibitted by metal and semiconductor nanostructures |
| Description: | Optoelectronic Devices Laboratory Department of Physics Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3730 |
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| Dyuthi-T1695.pdf | (10.84Mb) |
| Abstract: | Zinc oxide (ZnO) thin films were deposited on quartz, silicon, and polymer substrates by pulsed laser deposition (PLD) technique at different oxygen partial pressures (0.007 mbar to 0.003 mbar). Polycrystalline ZnO films were obtained at room temperature when the oxygen pressure was between 0.003 mbar and .007 mbar, above and below this pressure the films were amorphous as indicated by the X-ray diffraction (XRD). ZnO films were deposited on Al2O3 (0001) at different substrate temperatures varying from 400oC to 600oC and full width half maximum (FWHM) of XRD peak is observed to decrease as substrate temperature increases. The optical band gaps of these films were nearly 3.3 eV. A cylindrical Langmuir probe is used for the investigation of plasma plume arising from the ZnO target. The spatial and temporal variations in electron density and electron temperature are studied. Optical emission spectroscopy is used to identify the different ionic species in the plume. Strong emission lines of neutral Zn, Zn+ and neutral oxygen are observed. No electronically excited O+ cations are identified, which is in agreement with previous studies of ZnO plasma plume. |
| URI: | http://dyuthi.cusat.ac.in/purl/789 |
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| SPIE paper.pdf | (1.287Mb) |
| Abstract: | The thesis entitled Growth Response of Phytoplankton Exposed to Industrial Effluents in River Periyar. The present investigation has been conducted in two phases: field observation and algal assays. The monthly distribution of hydrographic features is represented graphically. The sampling year has been divided into three seasons: monsoon (June to September), postmonsoon (October to January) and premonsoon (February to May). The data were analysed using Student's t-test to find whether there was any significant difference between surface and bottom samples. The spatial variation of the variables was assessed by Page's L (trend) test (Ray Meddis, 1975). The standard procedure for algal toxicity test (Ward and Parrish, 1982) was followed throughout the study. Statistical analysis (Page's L (trend) test) showed that there was no significant difference in Secchi disc transparency between the stations. The field observations as well as the laboratory assays confirm that the rate of discharge in river Periyar during premonsoon is insufficient to effect dilution of wastewater received in the industrial zone. |
| Description: | School of Environmental Studies, Cochin University of Science and Technology. |
| URI: | http://dyuthi.cusat.ac.in/purl/3243 |
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| Dyuthi-T1217.pdf | (1.997Mb) |
| Abstract: | In the present study we address the issue on gut associated lactic acid bacteria (LAB) isolated from the intestine of estuarine fish Mugil cephalus using de Man Rogossa and Sharpe (MRS) agar. LAB isolates were identified biochemically and screened for their ability to inhibit in vitro growth of various fish, shrimp and human pathogens. Most of the LAB isolates displayed an improved antagonism against fish pathogens compared to shrimp and human pathogens. Selected representative strains displaying high antibacterial activity were identified using 16S rRNA gene sequence analysis. Of the selected strains Lactobacillus brevis was the most predominant. Four other species of Lactobacillus, Enterobacter hormaechei and Enterobacter ludwigii were also identified. It was also observed that even among same species, considerable diversity with respect to substrate utilization persisted. Considering the euryhaline nature of grey mullet (Mugil cephalus), the LAB isolated from the gut possessed good tolerance to varying salt concentrations. This finding merits further investigation to evaluate whether the isolated LAB could be used as probiotics in various fresh and sea water aquaculture |
| Description: | International Journal of Aquaculture, 2014, Vol.4, No.01 |
| URI: | http://dyuthi.cusat.ac.in/purl/3930 |
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| Gut Associated ... e Estuarine Fish Mugil.pdf | (148.6Kb) |
| Abstract: | Habitat ecology and food and feeding of the herring bow crab, Varuna litterata of Cochin Backwaters, Kerala, India were investigated for a period of one year (April 2011-March 2012). Among the 15 stations surveyed, the crabs were found to occur only in 4 stations, which had a close proximity to the sea. Sediment analysis of the stations revealed that the substratum of these stations is sandy in nature and is rich in organic carbon content (0.79% to 1.07%). These estuarine crabs is euryhaline and are found to be distributed in areas with a sandy substratum, higher organic carbon content and more tidal influx. The stomach contents analysis of crabs examined showed that their diet included crustacean remains, plants, sand and debris, fishes, miscellaneous group and unidentified matter. In adults and sub-adults, crustaceans formed the dominant food group, while in juveniles, sand and debris formed the dominant group. From the present study, V. litterata was found to be a predatory omnivore capable of ingesting both animal and plant tissues |
| Description: | Arthropods, 2013, 2(4): 172-188 |
| URI: | http://dyuthi.cusat.ac.in/purl/4664 |
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| habitat-ecology ... -crab-Varuna-litterata.pdf | (213.5Kb) |
| Abstract: | Fishes are one of the most important members of the aquatic food chain, and through them some toxicants may reach human beings as well. The selection of organisms for toxicity test is mainly based on certain criteria like its ecological status, position within the food chain, suitability for laboratory studies, genetically stable, uniform populations and adequate background data on the organism (Buikema et al., 1982). The species selected for the present study Etroplus maculatus satisfy most of the above protocols. Rechten (1980) opined it as a laboratory favorite of fish researchers. However, there are difficulties in the rise of fishes for pollution assessment impact. Most important of these is our limited understanding of the mechanism of toxicity. The interpretation of the significance or specificity of a measured biological response could there for become difficult. Not withstanding these limitations, attempts have been made to the normal haematology and to analyze the impact of heavy metal at realistic levels to the experimental media, on the haematology, and enzymatic activity and histology of Etroplus maculatus |
| Description: | Dept. of Marine Biology, Microbiology and Biochemistry Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3670 |
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| Dyuthi-T1627.pdf | (9.669Mb) |
| Description: | Department of Marine Biology, Microbiology and Biochemistry, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/1961 |
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| Dyuthi-T0413.pdf | (2.588Mb) |
| Abstract: | This thesis Entitled Haematological responses of penaeus monodon to environmental alterations and pathogenic invasion. Thesis concluded from the present study that stress is accompanied by alterations in haemolymph metabolic variables and immune responses that influences the susceptibility of P. monodon to infection. Acute salinity variations were proved to be a stress condition that enhances the susceptibility of P. monodon to V. harveyi and WSSV infection. Ambient Cu at 0.1 mg 1" and ambient Zn at 1.0 mg 1" proved immunostimulatory in increasing the immunocompetence of P. monodon to WSSV infection and higher concentrations of Cu and Zn proved immunosuppressive. Haemolymph total protein, total carbohydrates and total lipids showed the highest relation with immune responses. THC, PO, ACP and ALP that greatly correlated with the survival rate proposed as reliable biomarkers of health in P. monodon. The study highlights the need for proper management practices and regular health monitoring to be adopted to avoid mass mortality in shrimp culture ponds. |
| Description: | Department of Marine Biology, Microbiology and Biochemistry, School of Ocean Science and T echnology, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3033 |
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| Dyuthi-T1007.pdf | (6.565Mb) |
| Description: | School of Environmental Studies, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/xmlui/purl/2057 |
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| Dyuthi-T0414.pdf | (4.384Mb) |
| Abstract: | Aquaculture has developed to become one of the fastest growing food producing sectors in the world.Today India is one among the major shrimp producing countries in the world.There are extensive and intensive shrimp culture practices. In extensive shrimp culture, shrimps are stocked at low densities (< 25 PLs m'2)in large ponds or tidal enclosures in which little or no management is exercised or possible. Farmers depend almost entirely on natural conditions in extensive cultures. Intensive shrimp culture is carried out in high densities (>200 PLs m'2). Much of the world shrimp production still comes from extensive culture.There is a growing demand for fish and marine products for human and animal consumption. This demand has led to rapid growth of aquaculture, which some times has been accompanied by ecological impacts and economic loss due to diseases. The expansion of shrimp culture always accompanies local environmental degradation and occurrence of diseases.Disease out breaks is recognised as a significant constraint to aquaculture production. Environmental factors, water quality, pollution due to effluent discharge and pathogenic invasion due to vertical and horizontal transmission are the main causes of shrimp disease out breaks. Nutritional imbalance, toxicant and other pollutants also account for the onset of diseases. pathogens include viruses, bacteria, fungi and parasites.Viruses are the most economically significant pathogens of the cultured shrimps world wide. Disease control in shrimp aquaculture should focus first on preventive measures for eliminating disease promoting factors.ln order to design prophylactic and proactive measures against shrimp diseases, it is mandatory to understand the immune make up of the cultivable species, its optimum culture conditions and the physico chemical parameters of the rearing environment. It has been proven beyond doubt that disease is an end result of complex interaction of environment, pathogen and the host animal. The aquatic environment is abounded with infectious microbes.The transmission of disease in this environment is extremely easy, especially under dense, culture conditions. Therefore, a better understanding of the immune responses of the cultured animal in relation to its environmental alterations and microbial invasions is essential indevising strategic measures against aquaculture loss due to diseases. This study accentuate the importance of proper and regular health monitoring in shrimps employing the most appropriate haematological biomarkers for application of suitable prophylactic measures in order to avoid serious health hazards in shrimp culture systems. |
| URI: | http://dyuthi.cusat.ac.in/purl/3012 |
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| Dyuthi-T0991.pdf | (21.83Mb) |
| Abstract: | It is well known that under certain conditions, populations of oysters and clams are susceptible to destructive epizootics caused by pathogenic micro-organisms. It has also been shown that exposure of mammals to certain heavy metals causes increased susceptibility to and severity of microbial infections (Koller, 1980). Consequently, pollutants that affect haemocyte viability or interfere with internal defence functions of the haemocytes which are considered as the major means of defence in moliuscs against invading foreign organisms and pathogens (Cheng, 1981) may have profound effect on long term survival of molluscan populations. All these justify the significance of the present study in the context of the current status on molluscan culture programme, and how the data on molluscan haematological studies .could be taken as the reliable criteria for pollution monitoring studies. |
| Description: | School of Marine Sciences, Cochin University of Science and Technology |
| URI: | http://dyuthi.cusat.ac.in/purl/3639 |
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| Dyuthi-T1618.pdf | (21.77Mb) |
| URI: | http://dyuthi.cusat.ac.in/purl/1213 |
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| Suresh K 1988.PDF | (705.8Kb) |
| Abstract: | Halobacteria, members of the domain Archaea that live under extremely halophilic conditions, are often considered as dependable source for deriving novel enzymes, novel genes, bioactive compounds and other industrially important molecules. Protein antibiotics have potential for application as preserving agents in food industry, leather industry and in control of infectious bacteria. Halocins are proteinaceous antibiotics synthesized and released into the environment by extreme halophiles, a universal characteristic of halophilic bacteria. Herein, we report the production of halocin (SH10) by an extremely halophilic archeon Natrinema sp. BTSH10 isolated from salt pan of Kanyakumari, Tamilnadu, India and optimization of medium for enhanced production of halocin. It was found that the optimal conditions for maximal halocin production were 42 C, pH 8.0, and 104 h of incubation at 200 rpm with 2% (V/V) inoculum concentration in Zobell’s medium containing 3 M NaCl, Galactose, beef extract, and calcium chloride as additional supplements. Results indicated scope for fermentation production of halocin for probable applications using halophilic archeon Natrinema sp. BTSH10 |
| Description: | saudi journal of biological sciences(2013) 20,205-212 |
| URI: | http://dyuthi.cusat.ac.in/purl/4265 |
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| Halocin SH10 pr ... lt pans of South India.pdf | (733.2Kb) |
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