Heterogeneous Chemistry of Iron at the Liquid/Solid and Air/Solid Interfaces

Hematite is one of the common and stable phases of iron oxide that is ubiquitous in nature. It is involved in many heterogeneous reactions through liquid-solid and gas-solid interfacial interactions in aquatic geochemical systems. Moreover, the interfacial chemistry of metal-oxide and organic matter plays a significant role in the mobility and bioavailability of iron and other components such as arsenic in the soil and aquatic systems. The interactions of organic matter with metal oxide surfaces occur through several mechanisms in aquatic environment. Chapter 2 of this thesis describes the interactions of low molecular weight model organics that include citric acid (CA), oxalic acid (OA) and pyrocatechol (PC) on hematite nanoparticles that have been investigated and characterized by in situ attenuated total internal reflectance Fourier transform infrared spectroscopy (ATR-FTIR) measurements. H2O/D2O (H/D) exchange experiments were performed to observe the effect of hydration. It was found that strong hydration influenced the spectra for both CA and OA whereas less in the case of PC. Chapter 3 illustrates the initial binding kinetics of arsenicals such as dimethyl arsinate (DMA) onto hematite nanoparticles pre-exposed to low molecular weight organics such as OA and PC. These kinetic experiments were conducted using ATR-FTIR with an emphasis on the role that electrolytes (KCl, NaCl, and KBr) play in the adsorption process. It was concluded that the rate of adsorption for the arsenical onto pre-exposed model organic-hematite surface was found greater in the presence of electrolytes, based on the initial kinetic rate of adsorption for arsenical. Chapter 4 focuses on the investigation of the hygroscopic properties of organic and organometallic polymeric particles, namely polycatechol, polyguaiacol, Fe-polyfumarte, and Fe-polymuconate. These particles are efficiently formed in iron-catalyzed reactions with aromatic and aliphatic dicarboxylic acid compounds detected in field-collected Secondary Organic Aerosol (SOA). The structure of surface water was studied using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), and the uptake of gas water was quantified using quartz crystal microbalance (QCM) as a function of relative humidity. Spectroscopic data show that water bonding with organic functional groups acting as hydrogen bond acceptors causes shifts in their vibrational modes. Analysis of the hydroxyl group stretching region revealed weak and strong hydrogen bonding networks that suggest cluster formation reflecting water-water and water-organics interactions, respectively. A modified Type II multilayer Brunauer-Emmett-Teller (BET) adsorption model described the adsorption isotherm on the nonporous materials, polycatechol, polyguaiacol, and Fe-polymuconate. However, water adsorption on porous Fe-polyfumarate was best described using a Type V adsorption model, namely the Langmuir-Sips model that accounts for condensation in pores. It was found that the organic polymers are more hydrophobic than the Fe-containing organometallic polymers. In Chapter 5, the efficiency of iron-containing materials such as Fe-BTC (BTC = 1,3,5-benzenetricarboxylate) metal-organic frameworks (MOFs) and CoFe2O4 nanomaterials was examined to explore their performance in reducing NOx in NH3-SCR (Selective Catalytic Reduction) by DRIFTS. Urea was used as an in situ production of NH3(g) as a reductant agent for NO(g). It appeared that the rate of conversion of NO(g) in the presence of CoFe2O4 nanomaterials (2.3±0.03 ppm·meter-2·min-1) is better than that of Fe-BTC MOFs (0.22±0.04 ppm·meter-2·min-1)

Assessing sustainable development of flood mitigation projects using an innovative sustainability assessment framework

Sustainability assessments of flood mitigation projects are crucial for achieving sustainable development of floodplains. This article presents the application of an innovative sustainability assessment (SA) framework for flood mitigation projects throughout its life. The research employed a literature review, consultation with experts, and a case study of a flood mitigation project in Australia. The sustainability assessment framework includes five stages: (a) contextualizing the project; (b) SA at the planning and implementation stage; (c) SA during a flood event; (d) SA at regular intervals; and (e) SA during a change or modification phase. The results of the sustainability assessment at the first two stages of the flood mitigation project suggest how the sustainability index (SI) could be used to choose the best design options. Also, the study presents how the achievement toward sustainability of the finally constructed project could be compared with the planned project using the SI score. Sustainability assessment at Stages 3–5, carried out with possible scenarios, demonstrates that the project's sustainability could be hindered by the growing number of vulnerable population and property development in the floodplain without an upgrade of the project. The findings suggest the applicability of the SA framework for better decision‐making for sustainable flood risk management

Development of breeding and fingerling production techniques for endangered long-whiskered catfish Sperata aor in captivity

An experiment was undertaken to develop a suitable seed production technique for Sperata aor in captivity. Naturally produced fry of aor was reared at different densities in nine nursery ponds 0.012 ha in size with an average depth of 0.8 m each. Three stocking densities tested, each of which was triplicated. Fry of aor stocked at 100,000/ha was designated as treatment-1 (T1), 150,000/ha as treatment-2 (T2) and 200,000/ha as treatment-3 (T3). All stocked fry were from the same age group with mean length and weight of 1.78 ± 0.28 cm and 0.24 ± 0.05 g, respectively. Fry in all the treatments were fed with SABINCO nursery feed (32.06% crude protein) for the first 14 days and starter-I (31.53% crude protein) for days 15 to 56. Physico-chemical parameters and plankton population of pond water were within the optimal level being better in T1 than those in T2 and T3. Growth in terms of final weight and length, weight and length gain, specific growth rate, daily growth rate, and survival of fingerlings were significantly higher in T1 followed by T2 and T3. Food conversion rate was significantly lower in T1 than in T2 and T3. Significantly higher number of fingerlings was produced in T3 than those in T2 and T1. Despite this, consistently higher net benefits were achieved from T1 than from T2 and T3. This is the first time report that stocking of 100,000 fry/ha appears to be the most suitable density for rearing of aor fingerlings in nursery ponds

Effects of temperature on the embryonic and early larval development in tropical species of black sea urchin, Diadema setosum (Leske, 1778)

Influence of temperature on the embryonic and early development and growth performance of larva in tropical sea urchin, Diadema setosum was investigated in water temperature ranging between 16 and 34?C under controlled laboratory conditions. The critical lower and higher temperature for embryonic development was found at 16 and 34?C, respectively. Embryos reared in both of these two temperatures exhibited 100% abnormality within 48 hrs post-insemination. The time required to reach these embryonic and larval stages increased with temperature from 28 followed by 31, 25, 22 and 19?C in that order. The developmental times of 2-cell stage until 4-arm pluteus larva showed significant differences (P 0.05). Among them, 28?C was found to be the best temperature with respect of the highest larval growth and development at all stages. The findings of the study will not only be helpful to understand the critical limits of temperature, but also to identify the most appropriate temperature for optimum growth and development of embryos and larvae, as well as to facilitate the development of captive breeding and mass seed production of D. setosum and other important sea urchins for commercial aquaculture

Development of captive breeding and seed production techniques for Giant River Catfish Sperata seenghala

The Giant River Catfish Sperata seenghala, locally known as “Guizza Air” (and hereafter referred to as just Guizza), has significant aquacultural and conservational values, but closer monitoring of the fish is now badly needed. To protect the species from extinction, an experiment was undertaken to breed and produce seed of Guizza in a captive-rearing system. In our study, Guizza were successfully bred and the naturally produced fry were reared at different stocking densities in nine earthen nursery ponds having an area of 0.012 ha each with an average depth of 0.8 m. Three stocking densities were evaluated in three replicates each. Fry produced from natural propagation that were stocked at 100,000/ha were defined as treatment 1 (T1), those stocked at 150,000/ha as treatment 2 (T2), and those stocked at 200,000/ha as treatment 3 (T3). At stocking, all reared fry were of the same age-group with a mean±SD length and weight of 1.74±0.27 cm and 0.20±0.03 g, respectively. Fry in all the experimental ponds were reared with commercial Saudi Bangla (SABINCO) nursery feed (32.06% crude protein) for the first 14 d and starter-I (31.53% crude protein) for days 15–56. Growth (final weight, final length, weight gain, length gain, and specific growth rate) and survival of the fingerlings were significantly higher in T1 than in T2 and T3. Feed conversion rate was significantly lower in T1 than in T2 and T3. Moreover, the physicochemical measurements and plankton population of the pond water were within the optimal level for fish culture, with plankton abundance being higher in T1 than in T2 and T3. Consistently higher net benefits were obtained from T1 than from T2 and T3. Hence, of the three stocking densities, 100,000 fry/ha was the most suitable density for rearing Guizza fingerlings in nursery ponds

Ischemic Strokes: Observations from a Hospital Based Stroke Registry in Bangladesh.

Background. Stroke is an important morbidity for low and middle income countries like Bangladesh. We established the first stroke registry in Bangladesh. Methods. Data was collected from stroke patients who were admitted in Department of Neurology of BIRDEM with first ever stroke, aged between 30 and 90 years. Patients with intracerebral hemorrhage, subarachnoid and subdural hemorrhage, and posttrauma features were excluded. Results. Data was gathered from 679 stroke patients. Mean age was 60.6 years. Almost 68% of patients were male. Small vessel strokes were the most common accounting for 45.4% of all the patients followed by large vessel getting affected in 32.5% of the cases. Only 16 (2.4%) died during treatment, and 436 (64.2%) patients had their mRS score of 3 to 5. Age greater than 70 years was associated with poor outcome on discharge [OR 1.79 (95% CI: 1.05 to 3.06)] adjusting for gender, duration of hospital stay, HDL, and pneumonia. Age, mRS, systolic blood pressure, urinary tract infection, pneumonia, and stroke severity explained the Barthel score. Conclusion. Mortality was low but most of patient had moderate to severe disability at discharge. Age, mRS, systolic blood pressure, urinary tract infection, pneumonia, and stroke severity influenced the Barthel score

Review of some biological aspects and fisheries of grey-eel catfish Plotosus canius (Hamilton, 1822)

Plotosus canius, the grey-eel catfish belonging to the family Plotosidae is endemic to the south-east Asia and Australia. Primarily the fish is found in marine environment but at times may be found in brackish or fresh water environments. Despite the vast research that have been conducted on various catfish species, both marine and freshwater; little attention has been paid to P. canius. This study reviewed published information on the distribution, biology and fisheries of this economically important fish species

Riverbank erosion and rural food security in Bangladesh

The erosion of riverbanks has a negative impact on many nations across the world, costing them land, buildings, food, fish, and other living things, which forces people to relocate. Both the frequency and severity of riverbank erosion are alarming in Bangladesh. In Zajira Upazila, a baseline investigation was carried out to evaluate the effects of river erosion on the local availability of food. The results show how erosion threatens the majority of residents in the research territory. Additionally, as a consequence of the depletion of farmland brought on by the disaster and its effects, crop production is steadily dropping. Occasionally, people lose whole properties, leaving them with few employment options and little spending power. As a result, they are always in danger of experiencing a shortage of food. The suffering people use various coping strategies to deal with these challenging circumstances, such as shifting to cheaper or less appealing eating options. Despite the fact that local governing bodies have put in place various programs to help them, including food assistance and social protection programs, these are inadequate because of the government’s constrained organizational assets and competence The study’s findings will aid scientists and decision-makers in Bangladesh and abroad in better comprehending the requirements of vulnerable riverine populations and in designing programs that would increase those societies’ food safety Therefore, these results imply that developing and implementing efficient rural development strategies could increase the food security of those residing in Bangladeshi regions threatened by riverbank erosion

Influence of salinity variations on the embryonic and early larval development of long-spined black sea urchin (Diadema Setosum)

Effects of salinity on fertilization, embryonic, and early larval development and growth performances of long-spined black sea urchin (Diademasetosum) were investigated in a controlled laboratory condition. The experiment was carried out with seven salinity treatments (22, 25, 28, 31, 34, 37 and 40ppt), each of which was triplicated. Significantly highest fertilization success was achieved at 31 ppt (97.33%), followed by those at 34, 37, 28, 25 and 40 ppt, and the lowest value at 22 ppt, decreased with increasing and decreasing salinities (P 0.05) were recognized among these four salinity levels on prism larval length and width. However, significant differences (P> 0.05) were noted in morphometric characteristics of 2-arm and 4-arm pluteus larvae. The finding of the study indicated that D.setosum is a stenohaline echinoid that could not be able to survive and develop if the salinity range is less than28 or more than 37 ppt

Antitumor Activity of 2,9-Di-\u3cem\u3eSec\u3c/em\u3e-Butyl-1,10-Phenanthroline

The anti-tumor effect of a chelating phen-based ligand 2,9-di-sec-butyl-1,10-phenanthroline (dsBPT) and its combination with cisplatin were examined in both lung and head and neck cancer cell lines and xenograft animal models in this study. The effects of this agent on cell cycle and apoptosis were investigated. Protein markers relevant to these mechanisms were also assessed. We found that the inhibitory effect of dsBPT on lung and head and neck cancer cell growth (IC50 ranged between 0.1–0.2 μM) was 10 times greater than that on normal epithelial cells. dsBPT alone induced autophagy, G1 cell cycle arrest, and apoptosis. Our in vivo studies indicated that dsBPT inhibited tumor growth in a dose-dependent manner in a head and neck cancer xenograft mouse model. The combination of dsBPT with cisplatin synergistically inhibited cancer cell growth with a combination index of 0.3. Moreover, the combination significantly reduced tumor volume as compared with the untreated control (p = 0.0017) in a head and neck cancer xenograft model. No organ related toxicities were observed in treated animals. Our data suggest that dsBPT is a novel and potent antitumor drug that warrants further preclinical and clinical development either as a single agent or in combination with known chemotherapy drugs such as cisplatin