Mathew, K T; Biju Kumar, S; Anil, Lonappan; Joe, Jacob; Jacob, Samuel; Thommachan, Xavier; Thomas, Kurian(Elsevier Science, October , 2002)
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Abstract:
Ionic polymers (ionomers) with interesting characteristics are emerging as important commercial polymers. Ionomers have
the unique ability to behave as cross-linked materials at ambient temperatures and to melt and flow at elevated temperatures like
thermoplastics. The complex permittivity and conductivity of a class of ionomers at microwave frequencies are determined
using the cavity perturbation technique and the results are presented.
Bindu, G; Anil, Lonappan; Vinu, Thomas; Anandan, C K; Mathew, K T(Progress In Electromagnetics Research, 2006)
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Abstract:
Permittivity and conductivity studies of corn syrup in
various concentrations are performed using coaxial cavity perturbation
technique over a frequency range of 250 MHz–3000 MHz. The results
are utilized to estimate relaxation time and dipole moments of the
samples. The stability of the material over the variations of time is
studied. The measured specific absorption rate of the material complies
with the microwave power absorption rate of biological tissues. This
suggests the feasibility of using corn syrup as a suitable, cost effective
coupling medium for microwave breast imaging. The material can also
be used as an efficient breast phantom in microwave breast imaging
studies.
Bindu, G; Anil, Lonappan; Vinu, Thomas; Anandan, C K; Mathew, K T(Springer, November 1, 2006)
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Abstract:
Phantoms that exhibit complex dielectric
properties similar to low water content biological tissues
over the electromagnetic spectrum of 2–3 GHz
have been synthesized from carbon black powder,
graphite powder and polyvinyl-acetate-based adhesive.
The materials overcome various problems that are
inherent in conventional phantoms such as decomposition
and deterioration due to the invasion of bacteria
or mold. The absorption coefficients of the materials
for various compositions of carbon black and graphite
powder are studied. A combination of 50% polyvinylacetate-
based adhesive, 20% carbon black powder and
30% graphite powder exhibits high absorption coefficient,
which suggests another application of the material
as good microwave absorber for interior lining of
tomographic chamber in microwave imaging. Cavity
perturbation technique is adopted to study the dielectric
properties of the material.
V P N Nampoori; Radhakrishnan, P; Kailasnath, M; Nishant Kumar; Bikas, Ranjan(PHOTONICS-2008: International Conference on Fiber Optics and Photonics, December , 2008)
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Abstract:
The direction dependant wavelength selective transmission mechanism in poly (methyl
methacrylate)(PMMA) rods doped with C 540 dye and C 540:Rh.B dye mixture as a combination has been
investigated. When a polished slice of pure C 540 doped polymer rod was used side by side with a C540:Rh B
doped rod with acceptor concentration [A] = 7x10-4 m/l , we could notice more than 100% change in the
transmitted intensity along opposite directions at the C 540, Rh B emission and the excitation wavelengths . A
blue high bright LED emitting at a peak wavelength 465nm was used as the excitation source.
Radhakrishnan, P; V P N Nampoori; Kailasnath, M; Nishant Kumar; Bikas, Ranjan(PHOTONICS-2008: International Conference on Fiber Optics and Photonics, December , 2008)
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Abstract:
The direction dependant wavelength selective transmission mechanism in poly (methyl
methacrylate)(PMMA) rods doped with C 540 dye and C 540:Rh.B dye mixture as a combination has been
investigated. When a polished slice of pure C 540 doped polymer rod was used side by side with a C540:Rh B
doped rod with acceptor concentration [A] = 7x10-4 m/l , we could notice more than 100% change in the
transmitted intensity along opposite directions at the C 540, Rh B emission and the excitation wavelengths . A
blue high bright LED emitting at a peak wavelength 465nm was used as the excitation source.
Kailasnath, M; V P N Nampoori; Radhakrishnan, P; Nishant Kumar; Bikas, Ranjan(PHOTONICS-2008: International Conference on Fiber Optics and Photonics IIT Delhi, India, December , 2008)
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Abstract:
The direction dependant wavelength selective transmission mechanism in poly (methyl
methacrylate)(PMMA) rods doped with C 540 dye and C 540:Rh.B dye mixture as a combination has been
investigated. When a polished slice of pure C 540 doped polymer rod was used side by side with a C540:Rh B
doped rod with acceptor concentration [A] = 7x10-4 m/l , we could notice more than 100% change in the
transmitted intensity along opposite directions at the C 540, Rh B emission and the excitation wavelengths . A
blue high bright LED emitting at a peak wavelength 465nm was used as the excitation source.
Plants were regenerated from callus induced from leaf disc explants of a tomato F, hybrid heterozygous
for three marker loci (a), without anthocyanin (aw), and hairless (hl). Regenerants
were studied for somaclonal variation at the phenotypic level by scoring for variation in the marker loci,
and at the DNA level by probing geomic DNA blots with a chlorophyll a/b binding protein (Cab-3C)
cDNA sequence. While no variation was observed at the phenotypic level in over 950 somaclones studied,
DNA polymorphism for the Cab locus could be detected in two out of 17 somaclones tested. Tissue
culture induced variation at the phenotypic level for specific loci is very low (less than 0.001 for a, awor
hl) but DNA sequence changes are induced at much greater frequency (- 0.1 for a multicopy gene family
such as Cab).
Eswar Shankar,P N; Santhosh,K T; Paulose,C S(Department of Biotechnology, March , 2006)
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Abstract:
The stimulatory effect of dopamine through dopamine 1)2
receptor on glucose - induced insulin secretion was studied in the
pancreatic islets in nitro. I)oparnilie signifieanlly stimula(ed insulin
secretion at a concentration of 10 a N1 in the presence of
high,glucose ( 20 nii1 ). ' fhe higher concentrations of dopamine
(111 -1() 4) inhibited glucose- induced insulin secretion in the
presence of both 4 mM1 and 20 m M glucose. Stimulatory and
inhibitory effect of dopamine on glucose - induced insulin secretion
was reverted by the addition of dopamine 1)2 receptor antagonists
such as butaclamol and sulpiride . Norepinephrine (NE) at 111 4 11
concentration inhibited the dopamine uptake as well as its
stimulatory effect at 11) - 8 IN1 concentration on glucose induced
insulin secretion. Our results suggest that dopamine exerts a
differential effect on glucose -induced insulin secretion through
dopamine D2 receptor and it is essential for the regulation of
glucose-induced insulin secretion by pancreatic islets.
Epilepsy is a syndrome of episodic brain dysfunction characterized by recurrent unpredictable, spontaneous
seizures. Cerebellar dysfunction is a recognized complication of temporal lobe epilepsy and it is associated
with seizure generation, motor deficits and memory impairment. Serotonin is known to exert a modulatory
action on cerebellar function through 5HT2C receptors. 5-HT2C receptors are novel targets for developing anticonvulsant
drugs. In the present study, we investigated the changes in the 5-HT2C receptors binding and gene
expression in the cerebellum of control, epileptic and Bacopa monnieri treated epileptic rats. There was a
significant down regulation of the 5-HT content (pb0.001), 5-HT2C gene expression (pb0.001) and 5-HT2C
receptor binding (pb0.001) with an increased affinity (pb0.001). Carbamazepine and B. monnieri treatments
to epileptic rats reversed the down regulated 5-HT content (pb0.01), 5-HT2C receptor binding (pb0.001) and
gene expression (pb0.01) to near control level. Also, the Rotarod test confirms the motor dysfunction and
recovery by B. monnieri treatment. These data suggest the neuroprotective role of B. monnieri through the
upregulation of 5-HT2C receptor in epileptic rats. This has clinical significance in the management of epilepsy
Sona,Kundukulam O; Manju,Paulson; Aanandan,C K; Mohanan,P; Vasudevan,K(Microwave and Optical Technology Letters, June 5, 2000)
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Abstract:
Experimental studies on a compact dual frequency microstrip
antenna are presented. This antenna configuration provides an
area reduction of 40% compared to a standard rectangular antenna
operating at the same frequency without much degradation of the gain.
The antenna structure can be modified to achieve the desired ratio
between the two resonant frequencies
Binoy,G S; Aanandan,C K; Mohanan,P; Vasudevan,K(International Journal of Electronics, January 12, 2002)
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Abstract:
A new design of' a dual-frequency dual-polarized square microsh'ip antenna fed
along the diagonal, embedded with a square slot having three extended stubs for
frequency tuning, is introduced. The proposed antenna was fabricated using a
standard photolithographic method and the antenna was tested using the HP
3510(:; Vector Network Analyser. The antenna is capable of generating dual
resonant frequencies with mutually perpendicular polarizations and broad
radiation pattern characteristics. Such dual-frequency designs find wide
applications in personal mobile handsets combining GSM and CDS 1800 modes,
and applications in which different frequencies are used for emission and reception
such as personal satellite communications and cellular network systems.
Sona,Kundukulam O; Manju,Paulson; Aanandan,C K; Mohanan,P(Microwave and Optical Technology Letters, September 20, 2002)
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Abstract:
Experimental and simulated results for a dual-port
dual-polarized microstrip antenna are presented. The antenna excites
two orthogonally polarized resonant frequencies providing an isolation
of -30 dB between the ports. The patch geometry consists of
two circular arcs of different radii with their centers displaced by a
distance. This new design offers an area reduction of -70% coinpared
to it standard rectangular microstrip antenna with a reduction
in gain of 1.7 dB
Parvathi, R; Indic, P; Nampoori, V P N(Elsevier, February 11, 2002)
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Abstract:
Nonlinear time series analysis is employed to study the complex behaviour exhibited by a coupled pair of Rossler systems. Dimensional analysis with emphasis on the topological correlation dimension and the Kolmogorov entropy of the system is carried out in the coupling parameter space. The regime of phase synchronization is identified and the extent of synchronization between the systems constituting the coupled system is quantified by the phase synchronization index. The effect of noise on the coupling between the systems is also investigated. An exhaustive study of the topological, dynamical and synchronization properties of the nonlinear system under consideration in its characteristic parameter space is attempted.
George, K E; Komalan, C; Kumar, P A S; Varughese, K T; Thomas, S(eXPRESS Polymer Letters, 2007)
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Abstract:
The dynamic mechanical properties such as storage modulus, loss modulus and damping properties of blends of
nylon copolymer (PA6,66) with ethylene propylene diene (EPDM) rubber was investigated with special reference to the
effect of blend ratio and compatibilisation over a temperature range –100°C to 150°C at different frequencies. The effect of
change in the composition of the polymer blends on tanδ was studied to understand the extent of polymer miscibility and
damping characteristics. The loss tangent curve of the blends exhibited two transition peaks, corresponding to the glass
transition temperature (Tg) of individual components indicating incompatibility of the blend systems. The morphology of
the blends has been examined by using scanning electron microscopy. The Arrhenius relationship was used to calculate the
activation energy for the glass transition of the blends. Finally, attempts have been made to compare the experimental data
with theoretical models.
Chitra, R Nayak; Kuriakose, V C(Elsevier, June 4, 2007)
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Abstract:
We investigate the effect of the phase difference of appliedfields on the dynamics of mutually coupledJosephsonjunctions. A phase difference between the appliedfields desynchronizes the system. It is found that though the amplitudes of the output voltage values are uncorrelated, a phase correlation is found to exist for small values of applied phase difference. The dynamics of the system is found to change from chaotic to periodic for certain values of phase difference. We report that by keeping the value of phase difference as π, the system continues to be in periodic motion for a wide range of values of system parameters. This result may find applications in devices like voltage standards, detectors, SQUIDS, etc., where chaos is least desired.
Riju C, Issac; Vasudevan Pillai, K; Harilal, S S; Geetha, K Varier; Bindhu, C V; Pramod, Gopinath,; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(Elsevier Science, 1998)
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Abstract:
Laser produced plasma from silver is generated using a Q-switched Nd:YAG laser. Optical emission spectroscopy is used
to carry out time of flight (TOF) analysis of atomic particles. An anomalous double peak profile in the TOF distribution is
observed at low pressure. A collection of slower species emerge at reduced pressure below 4 X lO-3 mbar and this species
has a greater velocity spread. At high pressure the plasma expansion follows the shockwave model with cylindrical
symmetry whereas at reduced pressure it shows unsteady adiabatic expansion (UAE). During UAE the species show a
parabolic increases in the expansion time with radial distance whereas during shock wave expansion the exponent is less
than one. The angular distribution of the ablated species in the plume is obtained from the measurement of optical density of
thin films deposited on to glass substrates kept perpendicular to the plume. There is a sharp variation in the film thickness
away from the film centre due to asymmetries in the plume.
Saratchandran, P P; Nandakumaran, V M; Ambika, G(Springer, November , 1996)
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Abstract:
By introducing a periodic perturbation in the control parameter of the logistic map we have investigated the period locking properties of the map. The map then gets locked onto the periodicity of the perturbation for a wide range of values of the parameter and hence can lead to a control of the chaotic regime. This parametrically perturbed map exhibits many other interesting features like the presence of bubble structures, repeated reappearance of periodic cycles beyond the chaotic regime, dependence of the escape parameter on the seed value and also on the initial phase of the perturbation etc.
Thomas, Kuruvilla; Nandakumaran, V M(Indian Academy of Sciences, March , 2000)
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Abstract:
The effect of coupling two chaotic Nd:YAG lasers with intracavity KTP crystal for frequency doubling is numerically studied for the case of the laser operating in three longitudinal modes. It is seen that the system goes from chaotic to periodic and then to steady state as the coupling constant is increased. The intensity time series and phase diagrams are drawn and the Lyapunov characteristic exponent is calculated to characterize the chaotic and periodic regions.