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There has been substantial interest in determining the thermo-physical properties of hydrocarbon fluids. We have used three different experimental techniques: ultrasonic interferometry to determine the velocity of compressional wave, differential scanning calorimetry to determine the specific heat and the Anton Paar density meter to determine the density of crude oil sample over a wide range of temperatures varying from 20 to 70 °C. These data are used in thermodynamic relations to evaluate the specific heat ratio, the Grüneisen parameter, the Debye temperature and the long wavelength limit of the structure factor. The packing fraction obtained for crude oil is found to be closer to the values of other dense liquid fluids.

Lindamann's formula is extended to investigate the pressure dependence of the melting temperature, T m (P ). The important ingredient is the pressure dependence of the Debye temperature which has been determined from the measured data of acoustic longitudinal and transverse waves velocities. It is shown that Lindemann's type relation can be utilized to obtain an empirical relation for T m (P ) in terms of the Grüneisen parameter and the bulk modulus. Computed values of T m (P ) for alumina, Heusler alloy, and gabbro (an igneous rock) are presented.

a b s t r a c tMetallic 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.

In this paper, we describe the use of an open cell photoacoustic configuration for the evaluation of the thermal effusivity of liquid crystals. The feasibility, precision and reliability of the method are initially established by measuring the thermal effusivities of water and glycerol, for which the effusivity values are known accurately. In order to demonstrate the use of the present method in the thermal characterization of liquid crystals, we have measured the thermal effusivity values in various mesophases of 4-cyano-4octyloxybiphenyl (8OCB) and 4-cyano-4-heptyloxybiphenyl (7OCB) liquid crystals using a variable temperature open photoacoustic cell. A comparison of the measured values for the two liquid crystals shows that the thermal effusivities of 7OCB in the nematic and isotropic phases are slightly less than those of 8OCB in the corresponding phases.

A spinning-drop technique was used to study the thermal variation of surface tension of two nematic liquid crystals at the interface with an isotropic fluid. A sharp increase in interfacial tension was observed in the vicinity of the nematic-isotropic transition. The interfacial tension-temperature characteristics, unlike monotonically decreasing dependence found in most isotropic fluids, showed regions of positive slope, both in the isotropic and anisotropic phases. A positive slope in the isotropic region of the liquid crystal is interesting since it implies that excess order has developed at the surface while the buk interior remains isotropic.

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