Ultrasonic pulse induced mechanoluminescence of europium doped strontium aluminate micro-crystals

When rare earth doped strontium aluminate micro-crystals are exposed to ultrasonic pulse, then mechanumnescence (ML) is induced. The intensity of ML is proportional to the power of ultrasonic pulse used for ML excitation. The ML in europium doped strontium aluminate micro-crystals can be understood on the basis of the piezoelectrically induced electron detrapping model. On the basis of the piezoelectrically-induced electron detrapping model, expressions are derived for the general kinetics of ML intensity, rise of ML intensity, peak ML intensity and decay of ML intensity, in which good agreement is found between the theoretical and experimental results. A linear relation between the ML intensity and the ultrasonic power can also be understood on the basis of the proposed theory. The present investigation shows that the ML can be used to detecting the presence of ultrasonic waves and also for the measurement of ultrasonic power.&nbsp

Prevalence of seroreactivity among blood donors in rural population

The seroreactivity pattern amongst blood donors in rural population was studied at S.R.T. Rural Medical College and Hospital, Ambajogai (M. S.). The study period was from January 1996 to December 2001. A total number of 12,240 blood donors were screened. The voluntary donation was 36.98% and replacement donors were 63.02%. No professional donor is bled in our blood bank. The HIV seroreactivity among voluntary donors was 1.56% and 2.11% in replacement donors. The HBsAg seroreactivity was 2.78% in voluntary donors and 4.84% in replacement donors. VDRL seroreactivity is 1.12% in replacement donors. No malarial parasite and HCV seroreactive donor was found in our study period. We have found the magnitude of hepatitis to be far more than that of HIV. Hence testing for HCV routinely is mandatory, besides HBsAg

Structural characterization of MCM-41 over a wide range of length scales

In the present work the meso- and macrostructural characteristics of the recently developed model mesoporous adsorbent MCM-41, of different pore diameters, prepared in our laboratory, have been estimated with the help of various techniques. The structure is found to comprise four different length scales-those of the mesopores, the crystallites, the grains, and the particles. It was also found that the surface area estimated by the use of small angle scattering techniques is higher, while that estimated by mercury porosimetry is much lower, than that obtained from gas adsorption methods. On the basis of the macropore characterization by mercury porosimetry, and the considerable macropore area determined, it is seen that the actual mesopore area of MCM-41 may be significantly lower than the BET area. TEM studies indicated that even though MCM-41 does not have an ideal mesopore structure (because of the presence of curved pore channels), it may still be treated as a model mesoporous material for gas adsorption studies because of the large radius of curvature of the channels

Modeling of adsorption and nucleation in infinite cylindrical pores by two-dimensional density functional theory

In this paper, we present an analysis of argon adsorption in cylindrical pores having amorphous silica structure by means of a nonlocal density functional theory (NLDFT). In the modeling, we account for the radial and longitudinal density distributions, which allow us to consider the interface between the liquidlike and vaporlike fluids separated by a hemispherical meniscus in the canonical ensemble. The Helmholtz free energy of the meniscus was determined as a function of pore diameter. The canonical NLDFT simulations show the details of density rearrangement at the vaporlike and liquidlike spinodal points. The limits of stability of the smallest bridge and the smallest bubble were also determined with the canonical NLDFT. The energy of nucleation as a function of the bulk pressure and the pore diameter was determined with the grand canonical NLDFT using an additional external potential field. It was shown that the experimentally observed reversibility of argon adsorption isotherms at its boiling point up to the pore diameter of 4 nm is possible if the potential barrier of 22kT is overcome due to density fluctuations

Modeling nitrogen adsorption in spherical pores of siliceous materials by density functional theory

Adsorption of nitrogen in spherical pores of FDU-1 silica at 77 K is considered by means of a nonlocal density functional theory (NLDFT) accounting for a disordered structure of pore walls. Pore size distribution analysis of various FDU-1 samples subject to different temperatures of calcination revealed three distinct groups of pores. The principal group of pores is identified as ordered spherical mesopores connected with each other by smaller interconnecting pores and irregular micropores present in the mesopore walls. To account for the entrances (connecting pores) into spherical mesopores, a concept of solid mass distribution with respect to the apparent density was introduced. It is shown that the introduction of the aforementioned distribution was sufficient to quantitatively describe experimental adsorption isotherms over the entire range of relative pressures spanning six decades