Faridul Islam

Sluggish oxygen reduction reaction (ORR) of electrodes is one of the main challenges in fuel cell systems. This study explored the kinetics of the ORR reaction mechanism, which enables us to understand clearly the electrochemical activity of the electrode. In this research, electrocatalysts were synthesized from platinum (Pt) catalyst with multi-walled carbon nanotubes (MWCNTs) coated by three polymers (polybenzimidazole (PBI), sulfonated tetrafluoroethylene (Nafion), and polytetrafluoroethylene (PTFE)) as the supporting materials by the polyol method while hexachloroplatinic acid (H₂PtCl₆) was used as a catalyst precursor. The oxygen reduction current of the synthesized electrocatalysts increased that endorsed by linear sweep voltammetry (LSV) curves while increasing the rotation rates of the disk electrode. Additionally, MWCNT-PBI-Pt was attributed to the maximum oxygen reduction current densities at −1.45 mA/cm² while the minimum oxygen reduction current densities of MWCNT-Pt were obtained at −0.96 mAcm². However, the ring current densities increased steadily from potential 0.6 V to 0.0 V due to their encounter with the hydrogen peroxide species generated by the oxygen reduction reactions. The kinetic limiting current densities (J_K) increased gradually with the applied potential from 1.0 V to 0.0 V. It recommends that the ORR consists of a single step that refers to the first-order reaction. In addition, modified MWCNT-supported Pt electrocatalysts exhibited high electrochemically active surface areas (ECSA) at 24.31 m²/g of MWCNT-PBI-Pt, 22.48 m²/g of MWCNT-Nafion-Pt, and 20.85 m²/g of MWCNT-PTFE-Pt, compared to pristine MWCNT-Pt (17.66 m²/g). Therefore, it can be concluded that the additional ionomer phase conducting the ionic species to oxygen reduction in the catalyst layer could be favorable for the ORR reaction.

The aim of the study was to characterize the chemical constituents and determine antibacterial and antioxidant activities of essential oils and three different extracts of Dryopteris marginalis. The root had essential oil yield of 0.36 % (w/w) in which 12 organic compounds representing 97.22% of the root oils were identified. Tyranton was found as the most abundant component with 77.571 % of the total concentration in the essential oil. The zones of inhibition of different organic extracts against the tested bacteria were found in the range of 6.5-15 mm. Pseudomonas was the most vulnerable with MICs of 15.62 μg/mL by both ethyl acetate and petroleum ether extract producing 3.8 mm zone of inhibition. The essential oils extracted from roots of Dryopteris marginalis showed maximum 85.29 % inhibition of radical scavenging at 2 mg/mL concentration. Among all root extracts, methanol extract exhibited 41.11 % inhibition at 2 mg/mL concentration.

In this study, green coloured Cu(II) and red coloured Fe(III) complexes of pyridine were prepared and the elemental characterization confirmed their composition. The pyridine complexes of Cu(II) and Fe(III) were found very interesting and attractive as potential candidates with antimicrobial activity. Along with this, melting point, molar conductivity measurement, magnetic moment determination, electronic and FTIR spectroscopy were also measured to characterize the prepared complexes. Pyridine acts as monodentate which resulted in formation of square planar and octahedral structure of Cu(II) and Fe(III) complexes, respectively with the nitrogen atom pyridine ring by coordination bond. For antimicrobial activity studies Alternaria alternata, Bacillus cerelus, Botrgodiplodia theobromal, Colletotrichums corcolei, Escherichia coli, Fusarium equiseti, Macrophomina phaseolina, Salmonell typhi and Shigella dysenteriae were used. The prepared complexes showed inhibition against mycelial growth. Although the complexes showed satisfactory inhibition against the tested bacteria and fungi species, both of the complexes were comparatively better against bacteria than fungi compared to ligand.

A total number of 50 crossbred duck (indigenous × exotic crossbred) farmers from 15 villages under Noakhali district in Bangladesh were selected from April to May 2017 to explore information about crossbred duck farming. Data were collected by door to door visit using a pre-structured questionnaire and collected data were analyzed using SAS software. Fifty percent of the respondents used commercial ready feed to supplement the feed and 90.00% farmers maintained own water reservoirs to swim and scavenge of their crossbred duck with prepared mixed feed. In 90.00 % farms, housewives took care of the crossbred duck and spent the money earned from farming. Most of the farmers vaccinated (90.00%) and de-wormed (94.00%) their crossbred ducks. Natural uncontrolled flock mating system was exercised (100.00%) during study period. About 62.00% farmers selected higher egg producer and 74.00% farmers used to hatch crossbred duck eggs to produce day old ducklings. Khaki color crossbred duck (166±1.54 pcs) laid the highest number of eggs and this was followed by mixed (156 ±0.88 pcs) and white plumage colored duck (151±1.39 pcs). But, Khaki color crossbred ducks (2.06 ±0.02 kg) were heavier than those of white (1.72 ±0.04 kg) and mixed plumage colored (1.68±0.05 kg) ones. It is suggested that crossbred Khaki color ducks were better performer in the village women driven duck farms but farmers were not aware of inbreeding problems. Bangladesh J. Sci. Ind. Res.53(1), 47-52, 2018

ObjectiveTo explore the antidiabetic and the antidiarrhoeal effects of ethanolic extracts of Cynodon dactylon Pers. aerial parts (EECA) in Wistar rats.MethodsTo assess the antidiabetic activity of EECA, oral glucose tolerance test (OGTT) model and alloxan induced diabetic test (AIDT) model were performed. The EECA was used at the doses of 2 g/kg, 1 g/kg and 500 mg/kg body weight in OGTT model and 1.5 g/kg was used for AIDT model. Castor oil-induced diarrhoeal model and gastrointestinal motility test with barium sulphate milk model were performed for evaluating the antidiarrhoeal effects at doses of 1 g/kg, 750 mg/kg respectively.ResultsThe dose 2 g/kg in OGTT and 1.5 g/kg in AIDT model blood glucose levels decreased significantly (P < 0.01) in Wistar rats that showed antidiabetic effect of EECA. After administration of EECA at the dose of 1 g/kg, the extract showed significant (P < 0.05) antidiarrhoeal activity in castor oil-induced diarrhoeal model. The results were also significant (P < 0.05) in barium sulphate milk model for the same dose by using above mentioned animals.ConclusionsIt is concluded that EECA contains both antidiabetic and the antidiarrhoeal properties