Tessy,Maliekal T; Sudha,B; Paulose,C S(Department of Biotechnology, February 14, 1997)
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Abstract:
The role of thyroid hormones in DNA synthesis and in the activity of Thymidille
kinase (TK), a key regulatory enzyme of DNA synthesis was studied in proliferating
hepatocytes in vivo. Liver regeneration after partial hepatectomy was used as a
model for controlled cell division in rats having different thyroid status - euthyroid,
hypothyroid and 3,3',5'-triiodo-L-thyronine (T))-heated hypothyroid. Partial
hepatectomy caused a significant elevation of DNA synthesis (p<0.01) in all the three
groups compared to their sham-operated counterparts. Hypothyroid liepatectomised
animals showed significantly lower (p<0.01) level of DNA synthesis than euthyroid
hepatectomised animals. A single subcutaneous close of 1'3 to hypothyroid shamoperated
animals resulted in a significant increase (p<0.01) of DNA synthesis in the
intact liver. 17tis was comparable to the level of DNA synthesis occurring in
regenerating liver of euthyroid animals. In hypothyroid hepatectomised animals, "1'3
showed an additive effect on l)NA synthesis and this group exhibited maximum level
of DNA synthesis (p<0.0I ). Studies of the kinetic parameters of TK show that the
Michelis-Menten constant, (K111) of TK for thymidine was altered by the thyroid
status. K11 increased significantly (p<0.01) in untreated hypothyroid animals when
compared to the euthyroid rats. '13 treatment of hypothyroid animals reversed this
effect and this group showed the lowest value for K111 (p<0.01). Thus our results
indicate that thyroid hormones can influence DNA synthesis during liver regeneration
and they may regulate the activity of enzymes such as 17rymidine kinase which are
important for DNA synthesis and hence cell division.
Nithyaja, B; Jisha, V K; Tintu, R; Saramma, A V; V P N Nampoori(Laser Physics, 2009)
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Abstract:
The growth kinetics of an aerial bacterial colony on solid agar media was studied using laser
induced fluorescence technique. Fluorescence quenching of Rhodamin B by the bacterial colony was utilized
for the study. The lag phase, log phase, and stationary phase of growth curve of bacterial colony was identified
by measuring peak fluorescence intensity of dye doped bacterial colony.
Seema,P V; Sudha,B; Pius S,Padayatti; Asha,Abraham; Raghu,K G; Paulose,C S(Department of Biotecnology, June , 1996)
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Abstract:
The functional basis of diabetes-mellitus to a certain extent,
can be elucidated by studying diabetes-induced changes
in metabolic enzymes. Malate dehydrogenase (MDH),
is an enzyme directly involved in glucose metabolism. The
kinetic parameters of MDH and its purified cytosolic isozyme,
S-MDH, have been studied in the liver of streptozotocin-
diabetic rats; also the potential of the leaf extract of A.
marmelose as an was investigated. The
Km of the liver enzyme increased significantly, in both
crude and purified preparations in the diabetic state when
compared to Lhe respective controls. Insulin as well as leaf-
•extract treatment of the diabetic rats brought about a reversal
of K. values to near normal. Vmax of purified S-MDH
was significantly higher in the diabetic state when compared
to the control. Insulin and leaf extract treatment did not
reverse this change. Since MDH is an important enzyme in
glucose metabolism, the variation in its quantitative and
qualitative nature may contribute to the pathological status
of diabetes. The fact that leaf extract of A. marmelose
was found to be as effective as insulin in restoration of blood
glucose and body weight to normal levels, the use of A.
marmelose as potential hypoglycemic agent is suggested.
Thomas,P T; George,K K(Department of Applied Economics, September , 1994)
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Abstract:
It is hoped that the present study by analysing the
dynamics of agrarian change and peasant mobility may contribute
to the on-going debate on this issue in India and other developing
countries. It may also help to throw light on the validity of some
of the theories formulated on the basis of experience in different
regions and at different times. The study is likely to be of
special importance as it covers an area which has one of the
highest densities of population. The area has also witnessed
sweeping changes in agrarian structure as a result of the most
radical land reforms among the Indian states.
V P N Nampoori; Radhakrishnan, P; Girijavallabhan, C P; Geetha, K; Rajesh, M(Journal of Optics A: Pure and Applied Optics, Institute of Physics Publishing, January 13, 2006)
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Abstract:
We present a compact solid-state laser based on leaky mode propagation
from a dye-doped polymer free-standing film waveguide. The edge emitted
spectrum clearly indicated the existence of periodic resonant modes. The
reflections from the lateral faces of the free-standing film provided the
optical feedback thus giving rise to a Fabry–Perot like optical cavity. This
together with the guidance through the gain medium gave rise to intense
narrow emission lines. For a pump energy of 1.82 mJ/pulse, an intense line
with FWHM ∼0.4 nmwas observed at 576.5 nm.
Radhakrishnan, P; V P N Nampoori; Girijavallabhan, C P; Geetha, K; Rajesh, M(Journal of Optics A: Pure and Applied Optics, Institute of Physics Publishing, January 13, 2006)
[+]
[-]
Abstract:
We present a compact solid-state laser based on leaky mode propagation
from a dye-doped polymer free-standing film waveguide. The edge emitted
spectrum clearly indicated the existence of periodic resonant modes. The
reflections from the lateral faces of the free-standing film provided the
optical feedback thus giving rise to a Fabry–Perot like optical cavity. This
together with the guidance through the gain medium gave rise to intense
narrow emission lines. For a pump energy of 1.82 mJ/pulse, an intense line
with FWHM ∼0.4 nmwas observed at 576.5 nm.
Girijavallabhan, C P; Radhakrishnan, P; V P N Nampoori; Geetha, K; Rajesh, M(Journal of Optics A: Pure and Applied Optics, Institute of Physics Publishing, January 13, 2006)
[+]
[-]
Abstract:
We present a compact solid-state laser based on leaky mode propagation
from a dye-doped polymer free-standing film waveguide. The edge emitted
spectrum clearly indicated the existence of periodic resonant modes. The
reflections from the lateral faces of the free-standing film provided the
optical feedback thus giving rise to a Fabry–Perot like optical cavity. This
together with the guidance through the gain medium gave rise to intense
narrow emission lines. For a pump energy of 1.82 mJ/pulse, an intense line
with FWHM ∼0.4 nmwas observed at 576.5 nm.
Santhi Ani, Joseph; Gaurav, Sharma; Misha, Hari; Mathew, S; Radhakrishnan, P; Nampoori, V P N(Optical Society of America, 2010)
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Abstract:
We demonstrate the possibility of realizing, all-optical switching in gold nanosol. Two overlapping laser beams are used for this purpose, due to which a low-power beam passing collinear to a high-power beam will undergo cross phase modulation and thereby distort the spatial profile. This is taken to advantage for performing logic operations. We have also measured the threshold pump power to obtain a NOT gate and the minimum response time of the device. Contrary to the general notion that the response time of thermal effects used in this application is of the order of milliseconds, we prove that short pump pulses can result in fast switching. Different combinations of beam splitters and combiners will lead to the formation of other logic functions too.
Optical fiber based laser induced fluorescence (LIF)
measurements were carried out using Rhodamine B to analyze
two different species of bacteria , a Gram-positive bacteria
namely Bacillus smithii , and fibrin alginolvticus, a Gram-
negative bacteria . The fiber sensor was clearly able to distinguish
between the two species of bacteria . Quenching effect of the dye
Rhodamine B by Bacillus smithii was observed . The effect of dye
on the samples was also studied in detail.
V P N Nampoori(Wiley Inter Science, March 27, 2007)
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Abstract:
Optical fiber based laser induced fluorescence (LIF)
measurements were carried out using Rhodamine B to analyze
two different species of bacteria , a Gram-positive bacteria
namely Bacillus .cmithii , and fibrin alginolvticus, a Gram-'
negative bacteria . The fiber sensor was clearly able to distinguish
between the two species of bacteria . Quenching effect of the dye
Rhodamine B by Bacillus smitltii was observed . The effect of dye
on the samples was also studied in detail.
Reethamma, Thomas; Nampoori, V P N(Elsevier, 1990)
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Abstract:
Fluorescence of BaS: Sm phosphor has been studied using a pulsed Nitrogen laser (337.1 nm) as the excitation source. The spectrum consists of a broad band in the region 540–660nm superposed by the characteristic Sm3+ lines. Energy level splitting pattern of Sm3+ due to crystal field effects has been calculated and relevent field parameters are evaluated. Analysis shows that Sm3+ takes up Ba2+ substitutional sites.
Nibu A, George; Vallabhan, C P G; Nampoori, V P N; George, A K; Radhakrishnan, P(Taylor & Francis, 2001)
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Abstract:
In this paper we report the use of a laser induced phoroacoustic technique for the detection of multiple phase transitions in heptyl-oxy-cyanobiphenyl (70CB) and octyl-oxy-cyanobiphenyl (80CB) liquid crystals. The observed photoacoustic signal amplitude profile carries clear signatures of two tirst order transitions in 70CB and two tirst order and a second order transitions in 80CB. Analysis of the experimental data using Rosencwaig-Gersho theory shows that the sudden decrease in the photoacoustic (PA) signal amplitude during phase transitions is due to a sharp increase in the heat capacity of the samples near the transition temperatures.
Sajan, D George(Cochin University of Science & Technology, November , 2003)
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Abstract:
Discovery of coherent optical sources four decades ago has revolutionized all fields of scientific development. One of the path breaking applications of lasers is the emergence of various thermo optic techniques to unravel some of the mysteries of light matter interactions.Thermo optic technique is a valuable tool to evaluate optical and thermal properties of materials in solid,liquid and gaseous states .This technique can also be employed effectively in nondestructive quality evaluation. In this doctoral thesis , the use of photothermal techniques based on photoacoustic and photothermal deflection phenomena for the study of certain class of photonics materials such as semiconductors, nano metal dispersed ceramics, composites of conducting polymers and liquid crystals is elaborated.
Description:
International School of Photonics,
Cochin University of Science and Technology
Jacob, Philip; Manivannan, S; Dhanuskodi, S; Tiwari, S K(Springer, 2008)
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Abstract:
N-alkyl-2,6-dimethyl-4(1H)-pyridinones, salts of
4-dimethylaminopyridine and 2-amino-5-nitropyridine are considered
to be potential candidates for nonlinear optical (NLO)
applications, in particular for the generation of blue-green laser
radiation. Single crystals were grown following the slow evaporation
technique at constant temperature. Single-shot laserinduced
surface damage thresholds in the range 3–10 GW/cm2
were measured using a 18 ns Q-switched Nd:YAG laser. The
surface morphologies of the damaged crystals were examined
under an optical microscope and the nature of damage identified.
The Vicker’s microhardness was determined at a load of
98.07 mN. The thermal transport properties, thermal diffusivity
(α), thermal effusivity (e), thermal conductivity (K) and heat
capacity (Cp), of the grown crystals were measured by an improved
photopyroelectric technique at room temperature. All
the results are presented and discussed.
V P N Nampoori; Radhakrishnan, P; Girijavallabhan, C P; Sajan, D George; Aji, A Anapara; K G K Warrier(Proceedings of SPIE, 2003)
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Abstract:
In this paper, we report the measurements of thermal diffusivity of nano Ag metal dispersed ceramic alumina
matrix sintered at different temperatures using laser induced non-destructive photoacoustic technique. Measurements of
thermal diffusivity also have been carried out on specimens with various concentration of nano metal. Analysis of the
data is done on the basis of one-dimensional model of Rosencwaig and Gersho. The present measurements on the
thermal diffusivity of nano metal dispersed ceramic alumina shows that porosity has a great influence on the heat
transport and the thermal diffusivity value. The present analysis also shows that the inclusion of nano metal into
ceramic matrix increases its interconnectivity and hence the thermal diffusivity value. The present study on the samples
sintered at different temperature shows that the porosity of the ceramics varies considerably with the change in sintering
temperature. The results are interpreted in terms of phonon assisted heat transfer mechanism and the exclusion of pores
with the increase in sintering temperature