Jayaprasad, P N; Dr.Johnson, T P(Cochin University of Science And Technology, January 6, 2014)
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Abstract:
One can do research in pointfree topology in two ways. The rst is
the contravariant way where research is done in the category Frm but
the ultimate objective is to obtain results in Loc. The other way is the
covariant way to carry out research in the category Loc itself directly.
According to Johnstone [23], \frame theory is lattice theory applied to
topology whereas locale theory is topology itself". The most part of this
thesis is written according to the rst view. In this thesis, we make an
attempt to study about
1. the frame counterparts of maximal compactness, minimal Hausdor -
ness and reversibility,
2. the automorphism groups of a nite frame and its relation with the
subgroups of the permutation group on the generator set of the frame
Description:
Department of Mathematics
Cochin University of Science and Technology
Dhanya., R; Dr. P. Jayamurthy(Cochin University of Science and Technology, February 22, 2016)
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Abstract:
The incidence of diabetes is rapidly increasing and by 2030 an expected 592 million individuals
are projected to be affected (WHO report). Hyperglycaemic condition is recognized as the causal
link between diabetes and its complications. The chronic hyperglycemia resulting from diabetes
brings about a rise in oxidative stress due to overproduction of reactive oxygen species (ROS) as
a result of glucose auto oxidation and protein glycosylation. Generation of ROS leads to
oxidative damage of the structural components (such as lipids, DNA and proteins) of cells and
potentiate diabetes related complications. Oxidative insult in cells is also created by the
impairment in functioning of endogenous antioxidant enzymes because of their non enzymatic
glycosylation and oxidation. The prolonged exposure of oxidative stress may cause insulin
resistance by triggering an alteration in cellular redox balance. Several lines of evidence suggest
that oxidative stress occurs in diabetes and could have a role in the development of insulin
resistance. The cause and cellular mechanism responsible for this abnormality is not fully
understand despite of intense investigative efforts. However it is unknown whether it is the cause
or consequence of diabetes. Despite strong experimental evidence indicating that oxidative stress
may determine the onset and progression of late-diabetic complications, controversy exists
between the cause and associative relationship between oxidative stress and diabetes mellitus.
Disruption of glucose homeostasis is a characteristic feature of Non-insulin dependent diabetes
mellitus (NIDDM) and is associated with some complications including cardiovascular disease
and renal failure. Glucose transport, the rate limiting step in glucose metabolism, can be activated
in peripheral tissues by two distinct pathways. One stimulated by insulin through IRS-1/PI3K,
Preface
Page 2
the other by muscle contraction/exercise through the activation of AMPK. Both pathways also
increase the phosphorylation and activity of MAPK family components of which p38 MAPK
participates in the full activation of GLUT4.Insulin exerts its biological effect upon binding with the insulin receptor (IR) thereby activating
the downstream signaling that lead to enhanced glucose uptake. In skeletal muscle, it potentiates
glucose transport through PI3K mediated or non-PI3K mediated pathways. Alterations or defects
in its signal transduction pathway was found in diabetic patients associated with decreased levels
of IRb, IRS-1, and PI3K. In the insulin signaling, PI3K is a key molecule and inhibition of PI3K
completely abolish insulin stimulated uptake. Akt or Pkb is an important downstream target of
insulin stimulated glucose transport and metabolism.Impairment in fuel metabolism occurs in obesity, and this impairment is a leading pathogenic
factor in type 2 diabetes. The insulin resistance associated with type 2 diabetes is most profound
at the level of skeletal muscle as this is the primary site of glucose and fatty acid utilization.
Therefore, an understanding of how to activate AMPK in skeletal muscle would offer significant
pharmacologic benefits in the treatment of type 2 diabetes. Metformin and the thiazolidinedione
drugs exert the effects via activation of AMPK. Activation of AMPK occurs in response to
exercise, an activity known to have significant benefit for type 2 diabetics. AMPK serves as
sensor of energy status whose activity is triggered in response to changes in nutritional status in
order to modulate tissue-specific metabolic pathways
Krishna, C; Dr.Chandrasekaran,M(Cochin University of Science and Technology, August , 1995)
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Abstract:
A critical survey of the fruits and vegetable
markets of the towns and cities in South India reveals that
banana fruit stalk wastes share a dominant proportion among
the solid wastes generated. In the light of the review of
literature presented in the foregoing section, few reports are
available on the utilisation of banana waste for the
production of alcoholic beverages, biogas, and single cell
protein. However, it is not yet tried for the production of
industrial enzymes. Moreover, preliminary fermentation
studies conducted under uncontrolled conditions revealed that
banana fruit stalk could be aptly utilised as solid substrate?
for the industrial production of microbial amylases and
cellulases at a cheaper cost. Therefore, it was proposed to conduct a detailed study towards the development of a suitable fermentation process for the production of industrial enzymes using banana fruit stalk wastes, which is rich in carbohydrate, as solid substrate, employing bacteria, under SSF.
Description:
Department of Biotechnology, Cochin University of
Science & Technology,
Sreedevi, E P; Dr.Sankaran, P G(Cochin University Of Science And Technology, April 9, 2010)
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Abstract:
there has been much research
on analyzing various forms of competing risks data. Nevertheless, there are several
occasions in survival studies, where the existing models and methodologies are
inadequate for the analysis competing risks data. ldentifiabilty problem and various
types of and censoring induce more complications in the analysis of competing risks
data than in classical survival analysis. Parametric models are not adequate for the
analysis of competing risks data since the assumptions about the underlying lifetime
distributions may not hold well. Motivated by this, in the present study. we develop
some new inference procedures, which are completely distribution free for the
analysis of competing risks data.
Description:
Department of Statistics, Cochin University of Science and
Technology
Hareesh, G; Dr.Balakrishna, N(Cochin University of Science and Technology, August , 2010)
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Abstract:
The thesis has covered various aspects of modeling and analysis of finite mean time series
with symmetric stable distributed innovations. Time series analysis based on Box and
Jenkins methods are the most popular approaches where the models are linear and errors
are Gaussian. We highlighted the limitations of classical time series analysis tools and
explored some generalized tools and organized the approach parallel to the classical set up.
In the present thesis we mainly studied the estimation and prediction of signal plus noise
model. Here we assumed the signal and noise follow some models with symmetric stable
innovations.We start the thesis with some motivating examples and application areas of alpha stable
time series models. Classical time series analysis and corresponding theories based on finite
variance models are extensively discussed in second chapter. We also surveyed the existing
theories and methods correspond to infinite variance models in the same chapter.
We present a linear filtering method for computing the filter weights assigned to the observation
for estimating unobserved signal under general noisy environment in third chapter.
Here we consider both the signal and the noise as stationary processes with infinite variance
innovations. We derived semi infinite, double infinite and asymmetric signal extraction filters
based on minimum dispersion criteria. Finite length filters based on Kalman-Levy
filters are developed and identified the pattern of the filter weights. Simulation studies show that the proposed methods are competent enough in signal extraction for processes
with infinite variance.Parameter estimation of autoregressive signals observed in a symmetric stable noise
environment is discussed in fourth chapter. Here we used higher order Yule-Walker type
estimation using auto-covariation function and exemplify the methods by simulation and
application to Sea surface temperature data. We increased the number of Yule-Walker
equations and proposed a ordinary least square estimate to the autoregressive parameters.
Singularity problem of the auto-covariation matrix is addressed and derived a modified
version of the Generalized Yule-Walker method using singular value decomposition.In fifth chapter of the thesis we introduced partial covariation function as a tool for stable
time series analysis where covariance or partial covariance is ill defined. Asymptotic results
of the partial auto-covariation is studied and its application in model identification of stable
auto-regressive models are discussed. We generalize the Durbin-Levinson algorithm to
include infinite variance models in terms of partial auto-covariation function and introduce
a new information criteria for consistent order estimation of stable autoregressive model.In chapter six we explore the application of the techniques discussed in the previous
chapter in signal processing. Frequency estimation of sinusoidal signal observed in symmetric
stable noisy environment is discussed in this context. Here we introduced a parametric
spectrum analysis and frequency estimate using power transfer function. Estimate of the
power transfer function is obtained using the modified generalized Yule-Walker approach.
Another important problem in statistical signal processing is to identify the number of
sinusoidal components in an observed signal. We used a modified version of the proposed
information criteria for this purpose.
Description:
Department of Statistics,
Cochin University of Science and Technology
Anisha,P; Dr.Sankaran, P G(Cochin University of Science and Technology, May 4, 2012)
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Abstract:
This thesis Entitled “modelling and analysis of recurrent event data with multiple causes.Survival data is a term used for describing data that measures the time to occurrence of an event.In survival studies, the time to occurrence of an event is generally referred to as lifetime.Recurrent event data are commonly encountered in longitudinal studies when individuals are followed to observe the repeated occurrences of certain events. In many practical situations, individuals under study are exposed to the failure due to more than one causes and the eventual failure can be attributed to exactly one of these causes.The proposed model was useful in real life situations to study the effect of covariates on recurrences of certain events due to different causes.In Chapter 3, an additive hazards model for gap time distributions of recurrent event data with multiple causes was introduced. The parameter estimation and asymptotic properties were discussed .In Chapter 4, a shared frailty model for the analysis of bivariate competing risks data was presented and the estimation procedures for shared gamma frailty model, without covariates and with covariates, using EM algorithm were discussed.
In Chapter 6, two nonparametric estimators for bivariate survivor function of paired recurrent event data were developed. The asymptotic properties of the estimators were studied. The proposed estimators were applied to a real life data set. Simulation studies were carried out to find the efficiency of the proposed estimators.
Description:
Department of Statistics,
Cochin University of Science and Technology
Kesavan Nampoothiri,C; Balakrishna, N(Department of Statistics, Faculty of Science, 2001)
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Abstract:
The thesis deals with some of the non-linear Gaussian and non-Gaussian time models and mainly concentrated in studying the properties and application of a first order autoregressive process with Cauchy marginal distribution. In this thesis some of the non-linear Gaussian and non-Gaussian time series models and mainly concentrated in studying the properties and application of a order autoregressive process with Cauchy marginal distribution. Time series relating to prices, consumptions, money in circulation, bank deposits and bank clearing, sales and profit in a departmental store, national income and foreign exchange reserves, prices and dividend of shares in a stock exchange etc. are examples of economic and business time series. The thesis discuses the application of a threshold autoregressive(TAR) model, try to fit this model to a time series data. Another important non-linear model is the ARCH model, and the third model is the TARCH model. The main objective here is to identify an appropriate model to a given set of data. The data considered are the daily coconut oil prices for a period of three years. Since it is a price data the consecutive prices may not be independent and hence a time series based model is more appropriate. In this study the properties like ergodicity, mixing property and time reversibility and also
various estimation procedures used to estimate the unknown parameters of the process.
Susarla, Raghuram; Dr.Anil, Bhardwaj(Cochin University Of Science And Technology, July , 2013)
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Abstract:
Comets are the spectacular objects in the night sky since the dawn of mankind. Due to
their giant apparitions and enigmatic behavior, followed by coincidental calamities, they
were termed as notorious and called as `bad omens'. With a systematic study of these
objects modern scienti c community understood that these objects are part of our solar
system. Comets are believed to be remnant bodies of at the end of evolution of solar
system and possess the material of solar nebula. Hence, these are considered as most
pristine objects which can provide the information about the conditions of solar nebula.
These are small bodies of our solar system, with a typical size of about a kilometer
to a few tens of kilometers orbiting the Sun in highly elliptical orbits. The solid body
of a comet is nucleus which is a conglomerated mixture of water ice, dust and some
other gases. When the cometary nucleus advances towards the Sun in its orbit the ices
sublimates and produces the gaseous envelope around the nucleus which is called coma.
The gravity of cometary nucleus is very small and hence can not in
uence the motion
of gases in the cometary coma. Though the cometary nucleus is a few kilometers in size
they can produce a transient, extensive, and expanding atmosphere with size several
orders of magnitude larger in space. By ejecting gas and dust into space comets became
the most active members of the solar system. The solar radiation and the solar wind
in
uences the motion of dust and ions and produces dust and ion tails, respectively.
Comets have been observed in di erent spectral regions from rocket, ground and
space borne optical instruments. The observed emission intensities are used to quantify
the chemical abundances of di erent species in the comets. The study of various physical
and chemical processes that govern these emissions is essential before estimating chemical
abundances in the coma. Cameron band emission of CO molecule has been used to derive
CO2 abundance in the comets based on the assumption that photodissociation of CO2
mainly produces these emissions. Similarly, the atomic oxygen visible emissions have
been used to probe H2O in the cometary coma. The observed green ([OI] 5577 A) to
red-doublet emission ([OI] 6300 and 6364 A) ratio has been used to con rm H2O as the
parent species of these emissions. In this thesis a model is developed to understand the
photochemistry of these emissions and applied to several comets. The model calculated
emission intensities are compared with the observations done by space borne instruments
like International Ultraviolet Explorer (IUE) and Hubble Space Telescope (HST) and
also by various ground based telescopes.
Description:
Space Physics Laboratory
Vikram Sarabhai Space Centre
Indian Space Research Organisation
Thiruvananthapuram
Pravinkumar,P A; Dr.Nair, K G(Cochin University of Science and Technology, March 18, 1985)
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Abstract:
With the advent of satellite communication and radio astronomy, the need for large and efficient reflector antennas had triggered a widespread investigation in reflector feed design techniques. Major improvements sought are reduction in spill-over, cross polarization losses and the enhancement of aperture efficiency. The search for such a feed culminated in the corrugated horn. The main idea behind the present work is to use the H-plane sectoral horns fitted with,corrugated flanges as feeds of a paraboloid and see how the secondary pattern
of the reflector antenna varies with different parameters of the feed. An offset paraboloid is used as the secondary reflector in order to avoid the adverse effect of aperture ‘blocking by the feed horn structure on the secondary radiation pattern. The measurements were repeated for three
different H-plane sectoral horns with the same set of corrugated flanges at various X-band frequencies. The following parameters of the whole system are studied: (a) Beam shaping. (b) Gain. (c) Variation of VSWR and (d) Cross polarization
Description:
Department of Physics, Cochin University of Science and Technology