Litty, Mathew Irimpan; Radhakrishnan, P; Nampoori, V P N(International School of Photonics, June , 2008)
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Abstract:
The spectral and nonlinear optical characteristics of nano ZnO and its composites are investigated. The fluorescence behaviour of nano colloids of ZnO has been studied as a function of the excitation wavelength and there is a red shift in emission peak with excitation wavelength. Apart from the observation of the reported ultra violet and green emissions, our results reveal that additional blue emissions at 420 nm and 490 nm are developed with increasing particle size. Systematic studies on nano ZnO have indicated the presence of luminescence due to excitonic emissions when excited with 255 nm as well as significant contribution from surface defect states when excited with 325 nm. In the weak confinement regime, the third-order optical susceptibility χ(3) increases with increasing particle size (R) and annealing temperature (T) and a R2 and T2.5 dependence of χ(3) is obtained for nano ZnO. ZnO nanocolloids exhibit induced absorption whereas the self assembled films of ZnO exhibit saturable absorption due to saturation of linear absorption of ZnO defect states and electronic effects. ZnO nanocomposites exhibit negative nonlinear index of refraction which can be attributed to two photon absorption followed by weak free carrier absorption. The increase of the third-order nonlinearity in the composites can be attributed to the enhancement of exciton oscillator strength. The nonlinear response of ZnO nanocomposites is wavelength dependent and switching from induced absorption to saturable absorption has been observed at resonant wavelengths. Such a change-over is related to the interplay of plasmon/exciton band bleach and optical limiting mechanisms. This study is important in identifying the spectral range and the composition over which the nonlinear material acts as an optical limiter. ZnO based nanocomposites are potential materials for enhanced and tunable light emission and for the development of nonlinear optical devices with a relatively small optical limiting threshold.
Shahul,Hameed T S; Dr.Baba, M(Cochin University of Science And Technology, March , 1989)
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Abstract:
Some investigations on the spectral and statistical
characteristics of deep water waves are available for Indian
waters. But practically no systematic investigation on the
shallow water wave spectral and probabilistic characteristics
is made for any part of the Indian coast except for a
few restricted studies. Hence a comprehensive study of the
shallow water wave climate and their spectral and statistical
characteristics for a location (Alleppey) along the southwest coast of India is undertaken based on recorded
data. The results of the investigation are presented in this thesis.The thesis comprises of seven chapters
Seena, E B; Prathapachandra Kurup, M R(Elsevier, 2007)
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Abstract:
Three copper(II) complexes of salicylaldehyde N(4)-phenyl thiosemicarbazone (H2L1) and two copper(II) complexes of N(4)-cyclohexyl thiosemicarbazone (H2L2) have been synthesized and characterized by different physicochemical techniques like magnetic studies and electronic, infrared and EPR spectral studies. The complexes View the MathML source and [(CuL2)2] (4) having dimeric structure. The thiosemicarbazones bind to the metal as dianionic ONS donor ligand in all the complexes, except in the complex [Cu(HL1)2] · H2O (2). In complex 2, the ligand moieties are coordinated as monoanionic (HL−) ones. Two of the complexes [CuL1dmbipy] · H2O (3) and [CuL2dmbipy] (5) have been found to possess the stoichiometry [CuLB], where B = 4,4′-dimethyl-2,2′-bipyridine (dmbipy). The coordination geometry around copper(II) in 5 is trigonal bipyramidal distorted square based pyramidal (TBDSBP), as obtained by X-ray diffraction studies.
Leji, Latheef; Dr.Prathapachandra Kurup,M R(Cochin University of Science & Technology, September , 2007)
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Abstract:
The thesis is an introduction to evaluate the coordination behaviour of a few
compounds of our interest. The crucial aim of these investigations was to
synthesize and characterize some transition metal complexes using the ligands
benzaldehyde, 2-hydroxybenzaldehyde and 4-methoxybenzaldehyde N(4)-ring
incorporated thiosemicarbazones.The study involves a brief foreword of the metal
complexes of thiosemicarbazones including their bonding, stereochemistry and
biological activities.The different analytical and spectroscopic techniques used for
the analysis of the ligands and their complexes are discussed.It also deals with the synthesis and spectral characterization of the
thiosemicarbazones and single crystal X-ray diffraction study of one of them.Chapter 3 describes the synthesis, spectral characterization, single crystal X-ray
diffraction studies of copper(ll) complexes with ONS/NS donor
thiosemicarbazones. Chapter 4 deals with the synthesis, spectral characterization
and single crystal X-ray diffraction studies of nickel(II) complexes. Chapter 5
contains the synthesis, structural and spectral characterization of the cobalt(III)
complexes. Chapters 6 and 7 include the synthesis, structural and spectral
characterization of zinc(II) and cadmium(ll) complexes with ONS/NS donor
thiosemicarbazones.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology
Shreedevi,T T; Padayatti,P S; Kala,M S; Philip, J; Paulose,C S(Department of Biotechnology, May 25, 1994)
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Abstract:
Optical absorption characteristics of rat blood
affected by diabetes has been studied using photoacoustic
(PA) technique. PA spectrum of blood
depends on the molecular structure of haemoglobin.
The peak value ratio ylQ increases with increase in
the diabetic state. Externally added glucose to
normal blood does not show any increase in y//3 ratio
as seen in the diabetic condition . The increase in yl,8
ratio may be due to the decrease in DPG level and
the resultant shift from R -> T conformation of
majority of diabetic haemoglobin.
Radhakrishnan, P; Nampoori, V P N; Girijavallabhan, C P; Nandakumaran, V M; Dann, V J; Mathew, M V(Plasma Science and Technology, August , 2007)
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Abstract:
Optical emission from TiO2 plasma, generated by a nanosecond laser is spectroscopically
analysed. The main chemical species are identified and the spatio-temporal distribution of
the plasma parameters such as electron temperature and density are characterized based on the
study of spectral distribution of the line intensities and their broadening characteristics. The parameters
of laser induced plasma vary quickly owing to its expansion at low background pressure
and the possible deviations from local thermodynamic equilibrium conditions are tested to show
its validity
Nandakumaran, V M; V P N Nampoori; Radhakrishnan, P; Girijavallabhan, C P; Dann, V J; Mathew, M V(Plasma Science and Technology, August , 2007)
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Abstract:
Optical emission from TiO2 plasma, generated by a nanosecond laser is spectroscopically
analysed. The main chemical species are identified and the spatio-temporal distribution of
the plasma parameters such as electron temperature and density are characterized based on the
study of spectral distribution of the line intensities and their broadening characteristics. The parameters
of laser induced plasma vary quickly owing to its expansion at low background pressure
and the possible deviations from local thermodynamic equilibrium conditions are tested to show
its validity.
V P N Nampoori; Radhakrishnan, P; Girijavallabhan, C K; Nandakumaran, V M; Dann, V J; Mathew, M V(Plasma Science and Technology, August , 2007)
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Abstract:
Optical emission from TiO2 plasma, generated by a nanosecond laser is spectroscopically
analysed. The main chemical species are identified and the spatio-temporal distribution of
the plasma parameters such as electron temperature and density are characterized based on the
study of spectral distribution of the line intensities and their broadening characteristics. The parameters
of laser induced plasma vary quickly owing to its expansion at low background pressure
and the possible deviations from local thermodynamic equilibrium conditions are tested to show
its validity.
Girijavallabhan, C P; Radhakrishnan, P; V P N Nampoori; Nandakumaran, V M; Dann, V J; Mathew, M V(Plasma Science and Technology, August , 2007)
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Abstract:
Optical emission from TiO2 plasma, generated by a nanosecond laser is spectroscopically
analysed. The main chemical species are identified and the spatio-temporal distribution of
the plasma parameters such as electron temperature and density are characterized based on the
study of spectral distribution of the line intensities and their broadening characteristics. The parameters
of laser induced plasma vary quickly owing to its expansion at low background pressure
and the possible deviations from local thermodynamic equilibrium conditions are tested to show
its validity.
Kannan, Balakrishnan; Anil, Kumar; Sindhumol, S(Elsevier, July 30, 2013)
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Abstract:
A spectral angle based feature extraction method, Spectral Clustering Independent Component Analysis
(SC-ICA), is proposed in this work to improve the brain tissue classification from Magnetic Resonance
Images (MRI). SC-ICA provides equal priority to global and local features; thereby it tries to resolve the
inefficiency of conventional approaches in abnormal tissue extraction. First, input multispectral MRI is
divided into different clusters by a spectral distance based clustering. Then, Independent Component
Analysis (ICA) is applied on the clustered data, in conjunction with Support Vector Machines (SVM)
for brain tissue analysis. Normal and abnormal datasets, consisting of real and synthetic T1-weighted,
T2-weighted and proton density/fluid-attenuated inversion recovery images, were used to evaluate the
performance of the new method. Comparative analysis with ICA based SVM and other conventional
classifiers established the stability and efficiency of SC-ICA based classification, especially in reproduction
of small abnormalities. Clinical abnormal case analysis demonstrated it through the highest Tanimoto
Index/accuracy values, 0.75/98.8%, observed against ICA based SVM results, 0.17/96.1%, for reproduced
lesions. Experimental results recommend the proposed method as a promising approach in clinical and
pathological studies of brain diseases
Description:
Biomedical Signal Processing and Control 8 (2013) 667– 674
Santhi, A; Vinu V, Namboodiri; Radhakrishnan, P; Nampoori, V P N(American Institute of Physics, 2006)
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Abstract:
Wavelength dependence of saturable absorption (SA) and reverse saturable absorption (RSA) of zinc phthalocyanine was studied using 10 Hz, 8 ns pulses from a tunable laser, in the wavelength range of 520–686 nm, which includes the rising edge of the Q band in the electronic absorption spectrum. The nonlinear response is wavelength dependent and switching from RSA to SA has been observed as the excitation wavelength changes from the low absorption window region to higher absorption regime near the Q band. The SA again changes back to RSA when we further move over to the infrared region. Values of the imaginary part of third order susceptibility are calculated for various wavelengths in this range. This study is important in identifying the spectral range over which the nonlinear material acts as RSA based optical limiter.
Santhi, A; Vinu V, Namboodiri; Radhakrishnan, P; Nampoori, V P N(American Institute of Physics, 2006)
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Abstract:
Wavelength dependence of saturable absorption (SA) and reverse saturable absorption (RSA) of zinc phthalocyanine was studied using 10 Hz, 8 ns pulses from a tunable laser, in the wavelength range of 520–686 nm, which includes the rising edge of the Q band in the electronic absorption spectrum. The nonlinear response is wavelength dependent and switching from RSA to SA has been observed as the excitation wavelength changes from the low absorption window region to higher absorption regime near the Q band. The SA again changes back to RSA when we further move over to the infrared region. Values of the imaginary part of third order susceptibility are calculated for various wavelengths in this range. This study is important in identifying the spectral range over which the nonlinear material acts as RSA based optical limiter.
Padmaja, G; Ravi Kumar, A V; Vidyalal, V; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(Springer, May , 1989)
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Abstract:
Laser induced plasma emission spectra from highT c superconducting samples of YBa2Cu3O7 and GdBa2Cu3O7 obtained with 1.06µm radiation from a Q switched Nd:YAG laser beam has been analysed. The results clearly show the presence of diatomic oxides in addition to ionized species of the constituent metals in the plasma thus produced.
Marthakutty, Joseph; Dr.Prathapachandra Kurup,M R(Cochin University Of Science And Technology, July 19, 2004)
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Abstract:
Aqua complex ions of metals must have existed since the appearance of
water on the earth, and the subsequent appearance of life depended on, and may
even have resulted from the interaction of metal ions with organic molecules.
Studies on the coordinating ability of metal ions with other molecules and anions
culminated in the theories of/\lfred Werner. Thereon the progress in the studies of
metal complex chemistry was rapid. Many factors, like the utility and economic
importance of metal chemistry, the intrinsic interest _in many of the compounds and
the intellectual challenge of the structural problems to be solved, have contributed
to this rapid progress. X—ray diffraction studies further accelerated the progress.
The work cited in this thesis was carried out by the author in the
Department of Applied Chemistry during 2001-2004. The primary aim of these
investigations was to synthesise and characterize some transition metal complexes
of 2-benzoylpyridine N(4)-substituted thiosemicarbazones and to study the
antimicrobial activities of the ligands and their metal complexes. The work is
divided into eight chapters
Description:
Department of Applied Chemistry
Cochin University of Science and Technology
Reena, T A; Dr.Prathapachandra Kurup,M R(Cochin University of Science & Technology, March , 2011)
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Abstract:
The present work is concentrated on the studies of two novel
semicarbazones, di-2-pyridyl ketone-N4-phenyl-3-semicarbazone (HL1) and
quinoline-2-carboxaldehyde-N4-phenyl-3-semicarbazone (HL2). The compositions
of these semicarbazones were determined by the CHN analyses. For the
characterization of these compounds we have used IR, UV and NMR spectral
studies. The molecular structure of quinoline-2-carboxaldehyde-N4-phenyl-3-
semicarbazone (HL2) was obtained by single crystal X-ray diffraction studies.
Also, we have synthesized Zn(II), Cd(II), Cu(II), Ni(II), Co(II) and Mn(II)
complexes of these semicarbazones, HL1 and HL2. These complexes were
characterized by various spectroscopic techniques, magnetic and conductivity
studies. We could isolate single crystals of some Zn(II) and Cd(II) compounds
suitable for X-ray diffraction studies. For other complexes we could not isolate
single crystals of good quality for single crystal X-ray diffraction studies.
Description:
Department of Applied Chemistry,
Cochin University of Science and Technology
Kumar, G A; Thomas, J; George, N; Nampoori, V P N; Radhakrishnan, P; Vallabhan, C P G(Society of Glass Technology, 2000)
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Abstract:
Optical absorption and emission spectral studies of free and metal naphthalocyanine doped borate glass matrix are reported for the first time. Absorption spectra recorded in the UV- VIS-NIR region show the characteristic absorption bands, namely, the B-band and Q-band of the naphthalocyanine (Nc) molecule. Some of the important spectral parameters, namely, the optical absorption coefficient (α), molar extinction coefficient (ε) and absorption cross section (σa) of the principal absorption transitions are determined. Optical band gap (Eg) of the materials evaluated from the functional dependence of absorption coefficient on photon energy lies in the range 1.6 eV≤Eg≤2.1 eV. All fluorescence spectra except that of EuNc consist of an intense band in the 765 nm region corresponding to the excitation of Q-band. In EuNc the maximum fluorescence intensity band is observed at 824 nm. The intensity of the principal fluorescence band is maximum in ZnNc, whereas it is minimum in H2Nc. Radiative parameters of the principal fluorescence transitions corresponding to the Q-band excitation are also reported for the naphthalocyanine and phthalocyanine based matrices.
Girish Kumar,K; Muthuselvi,R(Department of Applied Chemistry, March 30, 2005)
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Abstract:
A spectrophotometric method employing 2-hydroxybenzaldiminoglycine (HBIG) is proposed for
the determination of chromium(III). The results of the determinations are compared with the standard diphenyl
carbazide method. The presently developed method is direct, simple, rapid, selective, sensitive and precise.
Girish Kumar,K; Devala Rao, G; Chowdary, K P R(Indian Journal Of Pharmaceutical Sciences, February 7, 2001)
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Abstract:
Two simple and sensitive spectrophotometric methods(A and B) in the visible region have been developed for the determination of cefotaxime sodium (DFTS) in bulk and in dosage forms. Method A is based on the reaction of CFTS with nitrous acid under alkaline conditions to form a stable violet colored chromogen with absorption maximum of 560 nm and method B is based on the reaction of CFTS with1,10-phenanthroline and ferric chloride to form a red colored chromogen with the absorption maximum of 520 mm.The color obeyed Beer’s law in the concentration range of 100-500 µg/ml for method A and 1.6-16 µg/ml for method B, respectively.When pharmaceutical preparations containing CFTS were analysed, the results obtained by the proposed methods are in good agreement with the labeled amounts and are comparable with the results obtained using a UV spectrophotometric method.