Aerosol particulate matter (PM 10 and PM 2.5 ) and trace gases (SO 2 , NO 2 , CO and O 3 ) were sampled at five locations in greater Dhaka, Bangladesh, between January and April 2006. Particulate matter was collected on microfiber filters with a low-volume sampler, and trace gases (SO 2 , NO 2 , and O 3 ) were collected with an impinger equipped with PM samplers. Carbon monoxide was determined using the Indicator Tube method. The total average concentrations of SO 2 , NO 2 , CO, and O 3 were 48.3, 21.0, 166.0 and 28 μg m -3 , respectively. The total average concentrations of SO 2 and NO 2 were much lower than the annual average guideline values of the World Health Organization (WHO). The total average O 3 concentration was also much lower than the daily maximum values established by WHO (average of 100 μg m -3 for an 8-h sample). The total average concentrations of five sites were 263, 75.5 and 66.2 μg m -3 for SPM, PM 10 and PM 2.5 , respectively. The mass of PM 2.5 is approximately 88% of the PM 10 mass, indicating that fossil fuel is the main source of PM in Dhaka. An atomic absorption spectrophotometer was used to determine the heavy metal concentrations in the PM 2.5 size fraction. The total average concentrations of As, Cd, Cu, Fe, Pb, and Zn in PM 2.5 were 6.3, 13, 94, 433, 204, and 381 ng m -3 , respectively. The Pb concentration in Dhaka shows a decreasing tendency, presumably due to the ban on the use of leaded fuel. The overall trace metal concentrations in Dhaka are higher than those in European (e.g., Spain, Norway) and East Asian (e.g., Taiwan) locations, but lower than those measured in Southeast Asian (Kanpur, Delhi, Mumbai, India; Lahore, Pakistan) cities.

An in vitro experiment was conducted to find out the optimum hormonal supplement and sucrose level for the bulb production of Hippeastrum. Murashige and Skoog medium supplemented with different hormone concentrations of BAP (0.0, 2.0, 4.0, 6.0 and 8.0 mg/L) and CCC (0.0, 125, 250 and 500 mg/L) and sucrose levels (30, 60, 80, 90 and 110 g/L) were used in this study. Sucrose level at 90 g/L produced the maximum average weight as well as the highest regeneration percentage. The increasing rate of CCC increased the number and average weight of bulb. The maximum bulb formation observed in media supplement with 6.0 mg/L BAP and 500 mg/L CCC fortified with 90 g/L sucrose.

The aim of this study was to identify the content of secondary Science curriculum excluded in teaching and learning activities, the reasons behind the omission and its impact on students' learning in the context of Bangladesh. This study used qualitative methodology. Eight teachers were selected and interviewed to investigate what they excluded from their teaching and what the reasons behind the exclusion were. Data were collected from participating teachers' students using a focus group discussion. Data collected from students and teachers were analyzed first. Then purposefully selected curriculum developers, textbook authors and teacher educators were interviewed to understand the impact of the null curriculum on students' learning. Analysis of data revealed that all the participant teachers excluded a chapter in grades IX-X General Science textbook. This chapter included information about reproductive organs, physical and psychological changes during puberty, pregnancy, evolution and related topics. Teachers argued that the topics were uncomfortable for them to teach, contradicted with religion, and students might misinterpret and practice unethical relationships if these topics were taught. However, the curriculum developers and the textbook authors asserted that including these topics would solve problems like adolescent mistakes, child rape, child pregnancy and distorted fantasies. This study concluded that excluding the chapter on adolescence, sexual and reproductive health and evolution obstructs achievement of students' scientific literacy.

Genetic variation and relationship among 28 mango germplasm were analyzed using Random Amplified Polymorphic DNA (RAPD). Out of 20 primers screened, four were selected, which gave 50 clear and bright fragments, out of which 48 fragments were considered polymorphic. The proportion of polymorphic loci and gene diversity values across all loci were 96% and 0.29, respectively. The UPGMA dendrogram based on genetic distance segregated the 28 mango germplasm into two main clusters. Sukul alone formed one cluster and the rest germplasm were grouped together into another cluster. Mallika and Amrapali cultivar pair was very close to each other with the highest intervarietal similarity index (87.30%) and lowest genetic distance (0.08). On the other hand, Sukul and Meghnath pair was more distant to each other with the lowest intervarietal similarity index (14.29%) and highest genetic distance (0.87). The results of the present study indicated that the RAPD analysis could be utilized by breeders for further improvement of mango varieties.

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