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Chlorophyll plays a pivotal role in the plant physiology and its productivity. Cultivation of plants in crude oil contaminated soil has a great impact on the synthesis of chlorophyll pigment. Morpho-anatomy of the experimental plant also shows structural deformation in higher concentrations. Keeping this in mind, a laboratory investigation has been carried out to study the effect of crude oil on chlorophyll content and morpho-anatomy of Cyperus brevifolius plant. Fifteen-day-old seedling of the plant was planted in different concentrations of the crude oil mixed soil (i.e., 10,000, 20,000, 30,000, 40,000, and 50,000 ppm). A control setup was also maintained without adding crude oil. Results were recorded after 6 months of plantation. Investigation revealed that there is a great impact of crude oil contamination on chlorophyll content of the leaves of the experimental plant. It also showed that chlorophyll a, chlorophyll b, and total chlorophyll content of leaves grown in different concentrations of crude oil were found to be lower than those of the control plant. Further, results also demonstrated that chlorophyll content was lowest in the treatment that received maximum dose of crude oil. It also showed that chlorophyll content was decreased with increased concentration of crude oil. Results also demonstrated that there was a reduction in plant shoot and root biomass with the increase of crude oil concentration. Results also revealed that the shoot biomass is higher than root biomass. Morphology and anatomy of the experimental plant also show structural deformation in higher concentrations. Accumulation of crude oil on the cuticle of the transverse section of the leaves and shoot forms a thick dark layer. Estimation of the level of pollution in an environment due to oil spill is possible by the in-depth study of the harmful effects of oil on the morphology and anatomy and chlorophyll content of the plants grown in that particular environment.

Stabilizing mechanism of silica nanoparticles on gelled foam prepared with a very low concentration of polymer (xanthan gum) and surfactant (α-olefin sulfonate) is reported in the present study. The morphology of the foam at optimized composition reveals its improved stability, owing to the adsorption of silica nanoparticles on the bubble interface, which was further confirmed by microscopic images. The foam decay experiments confirmed the slower drainage of liquids through the strong and rough bubble interface in the presence of nanoparticles. The synergistic effects of nanoparticles–polymer–surfactant help to improvise rheology, viscoelastic properties and enhanced static proppant suspension capacity of the foam. Addition of nanoparticles helps in reducing the polymer concentration in the foam fluid without compromising in stability criterion. Thus, the prepared gelled foam offers less formation damage with improved rheology, and proppant carrying capacity without any limitation to low-temperature application.

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Pseudomonas aeruginosa RS29, the native biosurfactant‐producing strain isolated from the oil fields of Assam, India was used to investigate the influence of the carbon nitrogen ratio on production of the biosurfactant. The biosurfactant producing ability of the strain was measured based on surface tension (ST) reduction of the culture medium and the emulsification (E24) index. Production was greatly influenced by the sources of nitrogen and carbon as well as the carbon to nitrogen (C/N) ratio. Sodium nitrate was the best nitrogen source and the water miscible carbon source, glycerol was observed as the best carbon source for maximum biosurfactant production. The C/N ratio 12.5 allowed the maximum production of biosurfactant by the RS29 strain. At this C/N ratio, 55 % ST of the culture medium was reduced by the produced biosurfactant. Concentrations of crude and rhamnolipid biosurfactant obtained at this particular C/N ratio were 5.6 and 0.8 g/l respectively. The RS29 strain was novel as it was able to produce a sufficient amount of biosurfactant utilizing a much lower amount of the water miscible carbon source, glycerol. Extraction of the biosurfactant by a chloroform–methanol (2:1) mixture was the best method to obtain the highest biosurfactant from the culture medium of the strain. The biosurfactant was confirmed as a mixture of mono and di‐rhamnolipid congeners, Rha–C10–C10–CH3 being the most abundant one. The biosurfactant was a good foaming and emulsifying agent.

Starting from the past or medieval period to the present day situation, history clearly indicates that the development of a region was and even today is function of a good transportation network. In the present day, society demands for an efficient and unobstructed road network after experiencing major issues or problems like traffic congestion, delay, pollution, increased vehicle operating cost and road accidents. Keeping in mind the above needs and constraints to traffic movement, an analysis of a digitized road network of the concerned city/town can be one of the best remedy to solve the problems. Such analysis is best suited in ArcGIS, Geographic Information System (GIS) software for creating, analyzing and compiling maps for obtaining information. In the present study an effort was made to prepare a road network map of Guwahati city and to find the shortest route between two places by proper analysis and digitization of its existing road network system in order to solve the traffic related problems to great extent. Network Analyst is a special analysis tool in ArcGIS which not only scrutinize the closest facility available in network of digitized interconnected lines but also facilitates in optimizing route during floods and emergency responses. One of the best models that can be generated through Network Analysis is the shortest route between required origin and destination points. The analysis is done based on input of certain network attributes like traversing distance, time and cost of travel, barriers, vehicle restrictions etc. All the important roads connecting each other within the Guwahati City were digitized in the GIS environment and proceeded further to serve the purpose.

Water quality and phytoplankton diversity were investigated in Gopeswar temple pond of Assam, India. Altogether 45 species of phytoplankton were recorded representing Chlorophyceae (16), Cyanophyceae (10), Bacillariophyceae (14), Euglenophyceae (3), Chrysophyceae (1) and Dinophyceae (1). Phytoplankton peaks were observed in summer and monsoon periods. Correlations of phytoplankton density with different water quality parameters were evaluated and the water body was found to be moderately polluted. Presence of Microcystis aeruginosa along with Navicula cryptocephala throughout the year also indicated its cultural eutrophication and hence, needs management intervention DOI: http://dx.doi.org/10.3329/bjb.v41i2.13446 Bangladesh J. Bot. 41(2): 181-185, 2012 (December)