Manoj, Easwaran potti; Prathapachandra Kurup, M R; Fun, Hoong-Kun(Elsevier, 2007)
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Abstract:
A novel N4O coordination mode offers carbohydrazone ligands as a building block for interesting frameworks through self-assembly. Bridging mode of oxygen of bis(2-benzoylpyridine ketone) carbohydrazone (H2L) with metal centers facilitates the formation of the macrocyclic molecular square [Zn(HL)]4(BF4)4 · 10H2O, offers wide range of applications for carbohydrazones.
Swapna S, Nair; Rajesh, S; Abraham, V S; Anantharaman, M R; Nampoori, V P N(Elsevier, 2006)
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Abstract:
Fine magnetic particles (size≅100 Å) belonging to the series ZnxFe1−xFe2O4 were synthesized by cold co-precipitation methods and their structural properties were evaluated using X-ray diffraction. Magnetization studies have been carried out using vibrating sample magnetometry (VSM) showing near-zero loss loop characteristics. Ferrofluids were then prepared employing these fine magnetic powders using oleic acid as surfactant and kerosene as carrier liquid by modifying the usually reported synthesis technique in order to induce anisotropy and enhance the magneto-optical signals. Liquid thin films of these fluids were prepared and field-induced laser transmission through these films was studied. The transmitted light intensity decreases at the centre with applied magnetic field in a linear fashion when subjected to low magnetic fields and saturate at higher fields. This is in accordance with the saturation in cluster formation. The pattern exhibited by these films in the presence of different magnetic fields was observed with the help of a CCD camera and was recorded photographically.
Rosamma, Philip; Sreedevi N, Kutty(John Wiley & Sons, 2008)
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Abstract:
Yeasts are ubiquitous in their distribution and populations mainly depend on the
type and concentration of organic materials. The distribution of species, as well as
their numbers and metabolic characteristics were found to be governed by existing
environmental conditions. Marine yeasts were first discovered from the Atlantic
Ocean and following this discovery, yeasts were isolated from different sources, viz.
seawater, marine deposits, seaweeds, fish, marine mammals and sea birds. Nearshore
environments are usually inhabited by tens to thousands of cells per litre of
water, whereas low organic surface to deep-sea oceanic regions contain 10 or fewer
cells/litre. Aerobic forms are found more in clean waters and fermentative forms in
polluted waters. Yeasts are more abundant in silty muds than in sandy sediments.
The isolation frequency of yeasts fell as the depth of the sampling site is increased.
Major genera isolated in this study were Candida, Cryptococcus, Debaryomyces and
Rhodotorula. For biomass estimation ergosterol method was used. Classification and
identification of yeasts were performed using different criteria, i.e. morphology, sexual
reproduction and physiological/biochemical characteristics. Fatty acid profiling or
molecular sequencing of the IGS and ITS regions and 28S gene rDNA ensured
accurate identification.
Rajasree, K; Vidyalal, V; Radhakrishnan, P; Nampoori, V P N; Vallabhan, C P G(American Institute of Physics, August 1, 1993)
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Abstract:
Laser‐induced damage and ablation thresholds of bulk superconducting samples of Bi2(SrCa)xCu3Oy(x=2, 2.2, 2.6, 2.8, 3) and Bi1.6 (Pb)xSr2Ca2Cu3 Oy (x=0, 0.1, 0.2, 0.3, 0.4) for irradiation with a 1.06 μm beam from a Nd‐YAG laser have been determined as a function of x by the pulsed photothermal deflection technique. The threshold values of power density for ablation as well as damage are found to increase with increasing values of x in both systems while in the Pb‐doped system the threshold values decrease above a specific value of x, coinciding with the point at which the Tc also begins to fall.
Bindhu, C V; Harilal, S S; Geetha K, Varier; Issac, Riju C; Nampoori, V P N; Vallabhan, C P G(IOP, 1996)
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Abstract:
The dual-beam thermal lens technique has been found to be very
effective for the measurement of fluorescence quantum yields of dye solutions. The
concentration-dependence of the quantum yield of rhodamine B in methanol is
studied here using this technique. The observed results are in line with the
conclusion that the reduction in the quantum yield in the quenching region is
essentially due to the non-radiative relaxation of the absorbed energy. The thermal
lens has been found to become abberated above 40 mW of pump laser power.
This low value for the upper limit of pump power is due to the fact that the medium
is a resonantly absorbing one.
Vidyalal, V; Rajasree, K; Vallabhan, C P G(World Scientific Publishing Company, 1996)
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Abstract:
A simple experimental set-up is described to measure the electromagnetic shielding property of high Tc superconducting samples. Measurements were performed using HTSC materials in the form of laser ablated thin films, powders and sintered pellets. Samples used were Gd-123 in pure and doped form as well as a few Bi-based superconducting ceramics. For comparison, similar measurements were carried out on metals like aluminium, copper and μ metal. Very effective shielding was observed for HTSC materials compared to the conventional materials mentioned above. However it also depended on the sample types and poor shielding was observed for powdered HTSC material in comparison to thin films prepared by laser ablation.
A series of short-isora-fiber-reinforced natural
rubber composites were prepared by the incorporation of
fibers of different lengths (6, 10, and 14 mm) at 15 phr loading
and at different concentrations (10, 20, 30, and 40 phr) with a
10 mm fiber length. Mixes were also prepared with 10 mm
long fibers treated with a 5% NaOH solution. The vulcanization
parameters, processability, and stress-strain properties
of these composites were analyzed. Properties such as tensile
strength, tear strength, and tensile modulus were found to be
at maximum for composites containing longitudinally oriented
fibers 10 mm in length. Mixes containing fiber loadings of 30 phr with bonding agent (resorcinol-formaldehyde [RF]
resin) showed mechanical properties superior to all other
composites. Scanning electron microscopy (SEM) studies
were carried out to investigate the fiber surface morphology,
fiber pullout, and fiber-rubber interface. SEM studies showed
that the bonding between the fiber and rubber was improved
with treated fibers and with the use of bonding agent.
Joseph Mathai, C; Anantharaman, M R; Venkitachalam, S; Jayalekshmi, S(Elsevier, September , 2002)
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Abstract:
Polyfurfural thin films lying in the thickness range of 1300–2000 A˚ were prepared by ac plasma polymerization technique.
The current–voltage characteristics in symmetric and asymmetric electrode configuration were studied with a view to determining
the dominant conduction mechanism.It was found that the Schottky conduction mechanism is dominant in plasma polymerized
furfural thin films.The predominance of Schottky mechanism was further confirmed based on the thermally stimulated current
measurements.
Anantaraman, R; Sugunan, S(Indian Journal of Chemistry, August , 1982)
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Abstract:
Kinetics of mercuric chloride catalysed solvolysis of benzyl chloride have been studied in water. 10% aq. ethanol, 10,20 and
30% aq. acetone and 20% aq. DMSO. The results confirm the operation of a mass law effect.
Ambika, G; Nandakumaran, V M; Babu Joseph, K(World Scientific Publishing Company, 1991)
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Abstract:
We consider a resistively shunted Josephson junction with a resistance that depends inversely on voltage. It is shown that such a junction in the underdamped case can give rise to extremely long-lived metastable states even in the absence of external noise. We investigate numerically this metastable state and its transition to a chaotic state. The junction voltages corresponding to these states are studied.
Senoy, Thomas; Jinesh, Mathew; Radhakrishnan, P; Nampoori, V P N; George, A K; Al-Harthi, S H; Ramanujan, R V; Anantharaman, M R(Elsevier, 2010)
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Abstract:
Metallic glass alloy Metglas 2826 MB based amorphous magnetic thin films were fabricated by the thermal evaporation technique. Transmission electron micrographs and electron diffraction pattern showed the amorphous nature of the films. Composition of the films was analyzed employing X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy techniques. The film was integrated to a long period fibre grating. It was observed that the resonance wavelength of the fibre grating decreased with an increase in the magnetic field. Change in the resonance wavelength was minimal at higher magnetic fields. Field dependent magnetostriction values revealed the potential application of these films in magnetostrictive sensor devices.
V P N Nampoori; Senoy,Thomas; Jinesh,Mathew; Radhakrishnan,P; George,A K; Al-Harthi,R V; Ramanujan; Anantharaman,M R(Sensors and Actuators: A Physical, May 11, 2010)
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Abstract:
Metallic glass alloy Metglas 2826 MB based amorphous magnetic thin films were
fabricated by the thermal evaporation technique. Transmission electron micrographs and
electron diffraction pattern showed the amorphous nature of the films. Composition of
the films was analyzed employing x-ray photoelectron spectroscopy and energy
dispersive x-ray spectroscopy techniques. The film was integrated to a long period fibre
grating. It was observed that the resonance wavelength of the fibre grating decreased with
an increase in the magnetic field. Change in the resonance wavelength was minimal at
higher magnetic fields. Field dependent magnetostriction values revealed the potential
application of these films in magnetostrictive sensor devices
Sudha Kartha,C(Taylor and francis, October 20, 2003)
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Abstract:
Polymer materials find application in optical storage technology,
namely in the development of high information density and fast access type
memories. A new polymer blend of methylene blue sensitized polyvinyl alcohol
(PVA) and polyacrylic acid (PAA) in methanol is prepared and characterized
and its comparison with methylene blue sensitized PVA in methanol and
complexed methylene blue sensitized polyvinyl chloride (CMBPVC) is presented.
The optical absorption spectra of the thin films of these polymers
showed a strong and broad absorption region at 670-650 nm, matching the
wavelength of the laser used. A very slow recovery of the dye on irradiation was
observed when a 7:3 blend of polyvinyl alcohol/polyacrylic acid at a pHof 3.8
and a sensitizer concentration of 4.67 10 5 g/ml were used. A diffraction
efficiency of up to 20% was observed for the MBPVA/alcohol system and an
energetic sensitivity of 2000 mJ/cm2 was obtained in the photosensitive films
with a spatial frequency of 588 lines/mm.
Polymer materials find application in optical storage technology,
namely in the development of high information density and fast access type
memories. A new polymer blend of methylene blue sensitized polyvinyl alcohol
(PVA) and polyacrylic acid (PAA) in methanol is prepared and characterized
and its comparison with methylene blue sensitized PVA in methanol and
complexed methylene blue sensitized polyvinyl chloride (CMBPVC) is presented.
The optical absorption spectra of the thin films of these polymers
showed a strong and broad absorption region at 670-650 nm, matching the
wavelength of the laser used. A very slow recovery of the dye on irradiation was
observed when a 7:3 blend of polyvinyl alcohol/polyacrylic acid at a pHof 3.8
and a sensitizer concentration of 4.67 10 5 g/ml were used. A diffraction
efficiency of up to 20% was observed for the MBPVA/alcohol system and an
energetic sensitivity of 2000 mJ/cm2 was obtained in the photosensitive films
with a spatial frequency of 588 lines/mm.
Thomas Lee, S; Aneeshkumar, B; Radhakrishnan, P; Vallabhan, C P G; Nampoori, V P N(Elsevier, May , 2002)
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Abstract:
Optical fiber sensors developed for measuring pH values usually employ an unclad and unstrained section of the fiber. In this paper, we describe the design and fabrication of a microbent fiber optic sensor that can be used for pH sensing. In order to obtain the desired performance, a permanently microbent portion of a plastic optic fiber is coated with a thin film of dye impregnated sol–gel material. The measurements are simultaneously carried out in two independent detection schemes viz., the bright field detection configuration for detecting the core modes and dark field detection configuration, for detecting the cladding modes. The results of measurements of core mode-power and cladding mode-power variation with change in pH of a solution surrounding the coated portion of the fiber is presented. This paper thus demonstrates how a bare plastic fiber can be modified for pH sensing in a simple and cost effective manner.
Thomas Lee, S; Nampoori, V P N; Vallabhan, C P G; Radhakrishnan, P; Geetha, K(Society of Photo-Optical Instrumentation Engineers, 2002)
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Abstract:
Microbent optical fibers are potential candidates for evanescent wave sensing. We investigate the behavior of a permanently microbent fiber optic sensor when it is immersed in an absorbing medium. Two distinct detection schemes, namely, bright-field and dark-field detection configuration, are employed for the measurements. The optical power propagating through the sensor is found to vary in a logarithmic fashion with the concentration of the absorbing species in the surrounding medium. We observe that the sensitivity of the setup is dependent on the bending amplitude and length of the microbend region for the bright-field detection scheme, while it is relatively independent of both for the dark-field detection configuration. This feature can be exploited in compact sensor designs where reduction of the sensing region length is possible without sacrificing sensitivity.
Mridula,S; Jacob,George; Mohanan,P(Microwave and Optical Technology Letters, December 20, 1999)
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Abstract:
A novel antenna configuration comprised of two circular
micro strip antennas (CMAs) resonating in the TMtt and TM2, modes,
producing radiation characteristics suitable for a mobile telephone handset,
is presented. The antennas operating at the same frequency are
placed back to back with a separation comparable to the thickness of a
typical handset. The radiation pattern consists of a region of reduced
radiation intensity, which minimizes the radiation hazards to the user
Jitha, B; Bybi, P C; Aanandan, C K; Mohanan, P(John Wiley & Sons, June , 2008)
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Abstract:
Design of a compact microstrip band reject filter is proposed. The device consists of an Open Loop Rectangular Resonator (OLRR) coupled to a microstrip line. The transmission line has a U-bend which enhances the coupling with the OLRR element and reduces the size of the filter. The filter can be made tunable by mounting variable capacitance to the system. Simulated and experimental results are presented.
Zhongyou,Yan(Microwave Engineering Group,Department of Electronics, January 5, 2002)
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Abstract:
patch resonator with a via connecting ground plane is
proposed and studied experimentally. The resonant frequency of this
patch resonator is tunable up to about 34 % by adjusting the via position
in the center line. The lowest resonant frequency of this patch resonator
has been reduced by more than 64% of the same size patch resonator