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.
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.