Louis, Godfrey; Philip, J(The American Physical Society, 1996)
[+]
[-]
Abstract:
A detailed ultrasonic study of the elastic properties of lithium ammonium sulfate ~LiNH4SO4! or LAS has
been carried out below room temperature. The elastic constants of LAS at room temperature are reported. The
discrepancy present in earlier elastic constant data associated with the different choice of axes for this orthorhombic
system are clarified. The results of the temperature variation study down to 220 K confirm the
ferroelastic phase transition at 285 K and establish a thermal hysteresis of about 2.5 K between the cooling and
heating cycles. Results of the investigation on the suspected weak phase transition at 256 K suggest that this
transition occurs at 242 K on cooling and at 256 K on heating, thus having a thermal hysteresis of about 14 K.
However, since the observed elastic anomaly for this transition is very small, the nature of this transition still
remains unclear
Louis, Godfrey; Santhosh Kumar, A(Springerlink, January 1, 2006)
[+]
[-]
Abstract:
A red rain phenomenon occurred in Kerala, India starting from 25th July 2001,
in which the rainwater appeared coloured in various localized places that are spread
over a few hundred kilometers in Kerala. Maximum cases were reported during
the first 10 days and isolated cases were found to occur for about 2 months. The
striking red colouration of the rainwater was found to be due to the suspension
of microscopic red particles having the appearance of biological cells. These particles have no similarity with usual desert dust. An estimated minimum quantity
of 50,000 kg of red particles has fallen from the sky through red rain. An analysis of this strange phenomenon further shows that the conventional atmospheric
transport processes like dust storms etc. cannot explain this phenomenon. The
electron microscopic study of the red particles shows fine cell structure indicat-
ing their biological cell like nature. EDAX analysis shows that the major elements
present in these cell like particles are carbon and oxygen. Strangely, a test for DNA
using Ethidium Bromide dye fluorescence technique indicates absence of DNA in
these cells. In the context of a suspected link between a meteor airburst event and
the red rain, the possibility for the extraterrestrial origin of these particles from
cometary fragments is discussed.
Louis, Godfrey; Santhosh Kumar, A(Society of Photo-Optical Instrumentation Engineers, 2008)
[+]
[-]
Abstract:
The red cells found in the red rain in Kerala, India are now considered as a possible case of extraterrestrial life form.
These cells can undergo rapid replication even at an extreme high temperature of 300 deg C. They can also be cultured in
diverse unconventional chemical substrates. The molecular composition of these cells is yet to be identified. This paper
reports the unusual autofluorescence characteristic of the cultured red rain cells. A spectrofluorimetric study has been
performed to investigate this, which shows a systematic shift of the fluorescence emission peak wavelength as the
excitation wavelength is increased. Conventional biomolecules are not known to have this property. Details of this
investigation and the results are discussed.
Louis, Godfrey; Varughese, George; Santhosh Kumar, A; Philip, J(Indian Academy of Sciences, 2008)
[+]
[-]
Abstract:
The double sulfate family (ABSO4), where A and B are alkali metal cations, is the object of great
interest owing to the complexity and richness of its sequence of phase transition induced by temperature
variation. A new sulfate salt characterized by the presence of water molecule in the unit cell with the chemical
formula, Li2Na3(SO4)2⋅6H2O (LSSW), was obtained. The ultrasonic velocity measurement was done with pulse
echo overlap technique [PEO]. All the six second order elastic stiffness constants, C11 = C22, C33, C44 = C55, C12,
C14 and C13 = C23 are reported for the first time. The anisotropy in the elastic properties of the crystal are well
explained by the pictorial representation of the polar plots of phase velocity, slowness, Young’s modulus and
linear compressibility in a–b and a–c planes.