We have examined the propagation of femtosecond laser pulses in an absorbing dye solution through a short to a long range of propagation distance. The transmitted pulses show strong spectral shift and a superluminal to subluminal transition in the propagation velocity keeping its initial shape almost intact. It is verified that the peak velocity is well described by a modified group velocity v(S) defined within the framework of the saddle-point method as well as by a recent prediction of the net group delay of surviving frequency.

Abstract:The chemical, physico-chemical and functional properties of flour and starch from three varieties of jackfruit seed were analyzed in this study. Starch was isolated using distilled water, alkaline and α-amylase enzyme. All varieties of jackfruit seed flour had moisture content 6.28-9.16%, protein 9.19-11.34%, fat 1.18-1.40%, ash 1.53-2.66%, amylose 26.49%-30.21% and starch contents 81.05%-82.52%. Gala variety had highest amount of water soluble index, swelling water capacity and water absorption index than Khaja and Durasha varieties. On the other hand, isolated starch varied 8.39 to 12.20% moisture, 1.09 to 3.67% protein, 1.18 to 1.40% fat, 0.03 to 0.59% ash content. Starch isolated with distilled water had higher protein content, yield, amylose and total starch than starch isolated with alkaline and enzyme. However, purity was depended on the variety and extraction conditions. Enzymatic method gave highest amount of water absorption index and water soluble index as compared to distilled water and alkaline method. Results from this study suggest that jackfruit seed flour can be used as partial replacement of wheat flour and good source of starch.

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The aim of this study was to determine the degree of contamination caused by Cryptosporidium oocyts in regularly consumed salad vegetables sold at various wholesale and retail markets in northern part of Bangladesh. A total number of 165 samples of salad vegetables collected from different wholesale and retail markets were examined for detection of Cryptosporidium oocysts using sucrose flotation medium of 1.18 specific gravity and Ziehl Neelsen staining technique with some modifications. Cryptosporidium oocysts were detected in 47 (30%) of the total examined samples. About 40 Tomato, 35 Cucumber, 20 Lettuce, 35 Carrot and 35 Mint's leaf samples were examined while Lettuce had the highest (40%) contamination rate followed by Tomato (32.5%), Carrot (31.4%), Cucumber (25.7%), and Mint's leaf (22.8%). There was no significant difference (x2 = 2.278; p <0.05) among occurrences of Cryptosporidium oocysts in usually consumed salad vegetables sold at market. This study has shown that salad vegetables sold at wholesale and retail markets in northern part of Bangladesh are contaminated with Cryptosporidium oocysts, may pose a health risk to consumers of such products. This reveals food safety and significance of public health.

Photoluminescence spectra and the reflectivity of incident light were examined in dye molecules in strongly scattering media. With increasing incident light intensity, the spectra show red-and blueshifts depending on the geometry of experiments, and the reflectivity increases nonlinearly. These excitation-power-dependent spectral shifts and nonlinear reflectivity are well explained when we consider saturation absorption in the excitation process and the reabsorption in the luminescence process in dyes. ͓S0163-1829͑99͒14701-5͔