Kunjomana, A G; Dr.Elizabeth, Mathai(Cochin University Of Science And Technology, August 10, 1992)
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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
Ajimsha, R S; Jayaraj, M K(Department of Physics, February , 2008)
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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,
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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.
Sreeja, R; Dr.Jayaraj, M K(Cochin University Of Science And Technology, July 6, 2011)
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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
Joy, C M; Dr.Balakrishnan, K P(Cochin University of Science and Technology, April , 1989)
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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.
Bindu Bhaskaran, A B; Dr.Mohammed Salih,K Y(Cochin University Of Science And Technology, March 14, 2011)
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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
Annies, Joseph; Dr.Rosamma,Philip(Cochin University of Science and Technology, July , 2008)
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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
Selven,S; Dr.Rosamma,Philip(Cochin University of Science and Technology, May , 2008)
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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.
Suresh, K; Dr.Mohandas, A(Cochin University of Science And Technology, January , 1988)
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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