Enhanced electrocatalytic effects of Pd particles immobilized on GC surface on the nitrite oxidation reactions

Ajuts: Manel del Valle thanks the support from program ICREA Academia.Nitrite (NO 2− ) oxidation reactions (NOR) have been performed using a pristine glassy carbon (GC) electrode and Pd modified GC electrode to investigate catalysis and kinetics of oxidation reaction. The XPS analysis revealed that Pd nanoparticles (NPs) on GC is differed electronically from Pd particles alone. Electrochemical observations entailed that the Pd-GC electrode improved the catalytic efficiency by lowering peak potential and improving peak current compared to those obtained by GC or Pd electrode alone. Additionally, the onset potential (E i ) of kinetic process concerning NOR was appeared at 0.63 V for Pd-GC electrode which is smaller than 0.81 V and 0.75 V observed by GC and Pd electrodes, respectively. These observations suggest that the Pd-GC electrode can obtain faster electron transfer and maximum catalytic sites. The validation of Pd-GC as noble catalyst is also supported by observing least free energy of activation at peak (ΔG p‡ = 0.461 eV). The nitrite ions involve a single electron transfer reaction with NO 2 molecules being the product, which later undergoes through a dispropornation reaction yielding NO 2− and NO 3− as final products. The precise observations by RDE experiments revealed that the charge transfer reaction followed by an irreversible first order kinetics with standard rate constant (k 0 ) of 1.98 × 10 −4 cm/s and formal potential (E o ' ) of 0.03 V

Creek`s Aquaculture Techniques in Rangamati Hill Tracts of Bangladesh

An experiment was conducted in nine suitable (average .10±2 ha) creeks of Rangamati hill tracts Bangladesh viz., of Langadu, Naniarchar and Sadar Upazila for evaluating growth, survival and production performance of Indian major carps (Labeo rohita, Catla catla, Cirrhinus mrigala) in a completely randomized design into three different treatments with three replications for a period of one year. Stocking density, growth, survival was checked periodically and total yield calculated from stocking and harvesting data. A significant spatial variation in specific growth rate (SGR) and yields was found despite uniform stocking densities, attributable to variation in environmental parameters. Among the results rohu was found to have comparatively higher SGR of 1.51±0.55 in Naniarchar where as langadu creek was reported with higher SGR of 1.46±0.94, 1.57±0.41 and 1.46 ±.64 for rohu catla, and mrigal. Rangamati sadar Upazilla creek was found to be conducive to Catla with a SGR of 1.55±.78. In general, higher gross and net productions were reported from Sadar Upazilla, Langadu and Naniarchar creeks, suggestive of its suitability for developing creeks aquaculture technology. However research findings will help the community of Chittagong hill tracts by giving appropriate technology for sustainable fish production in creeks

Impact of land cover changes on land surface temperature and human thermal comfort in Dhaka City of Bangladesh

Urbanization leads to the construction of various urban infrastructures in the city area for residency, transportation, industry, and other purposes, which causes major land use change. Consequently, it substantially affects Land Surface Temperature (LST) by unbalancing the surface energy budget. Higher LST in city areas decreases human thermal comfort for the city dwellers and affects the urban environment and ecosystem. Therefore, a comprehensive investigation is needed to evaluate the impact of land use change on the LST. Remote Sensing (RS) and Geographic Information System (GIS) techniques were used for the detailed investigation. RS data for the years 1993, 2007 and 2020 during summer (March–May) in Dhaka city were used to prepare land cover maps, analyze LST, generate hazard maps and relate the land cover change with LST by using GIS. The results show that the built-up area in Dhaka city increased by 67% from 1993 to 2020 by replacing lowland mainly, followed by vegetation, bare soil and water bodies. LSTs found in the study area were ranged from 23.26 to 39.94 °C, 23.69 to 43.35 °C and 24.44 to 44.58 °C for the years 1993, 2007 and 2020, respectively. The increases of spatially distributed maximum and mean LST were found 4.62 °C and 6.43 °C, respectively, for the study period of 27 years while the change in minimum LST was not substantial. LST increased by around 0.24 °C per year and human thermal discomfort shifted from moderate to strong heat stress for the total study period due to the increase of built-up and bare lands. This study also shows that normalized difference vegetation index (NDVI) and normalized difference water index (NDWI) were negatively correlated with LST while normalized difference built-up Index (NDBI) and normalized difference built-up Index (NDBAI) were positively correlated with LST. The methodology developed in this study can be adapted to other cities around the globe

Numerical simulation of periodic MHD casson nanofluid flow through porous stretching sheet

The perspective of this paper is to characterize a Casson type of Non-Newtonian fluid flow through heat as well as mass conduction towards a stretching surface with thermophoresis and radiation absorption impacts in association with periodic hydromagnetic effect. Here heat absorption is also integrated with the heat absorbing parameter. A time dependent fundamental set of equations, i.e. momentum, energy and concentration have been established to discuss the fluid flow system. Explicit finite difference technique is occupied here by executing a procedure in Compaq Visual Fortran 6.6a to elucidate the mathematical model of liquid flow. The stability and convergence inspection has been accomplished. It has observed that the present work converged at, Pr ≥ 0.447 indicates the value of Prandtl number and Le ≥ 0.163 indicates the value of Lewis number. Impact of useful physical parameters has been illustrated graphically on various flow fields. It has inspected that the periodic magnetic field has helped to increase the interaction of the nanoparticles in the velocity field significantly. The field has been depicted in a vibrating form which is also done newly in this work. Subsequently, the Lorentz force has also represented a great impact in the updated visualization (streamlines and isotherms) of the flow field. The respective fields appeared with more wave for the larger values of magnetic parameter. These results help to visualize a theoretical idea of the effect of modern electromagnetic induction use in industry instead of traditional energy sources. Moreover, it has a great application in lung and prostate cancer therapy

Incorporation of rubber-steel bearing isolation in multi-storey muilding

Base isolation incorporation has moved towards a popular technology in the seismic vulnerable regions. The system mitigates lateral action of tremor hazard providing flexibility of structures. Implementing base isolation on buildings in the soil and seismic condition of medium risk seismicity is currently an important issue. A thorough investigation is of burning need for buildings to be incorporated with base isolator and to carry out dynamic analysis. The study provides incorporation of rubber-steel bearings and focuses on the structural changes. Designs of base isolation bearings are performed along with structural viability check. Lead rubber bearing (LRB) and high damping rubber bearing (HDRB) have been inserted on the corresponding structural bases. In finite-element approach, link element simulates the bearing. Bi-linear hysteretic behaviour is presented for LRB and equivalent linear model simulated HDRB. Linear static, free vibration and dynamic frequency-domain analyses are performed for both isolated and non-isolated buildings under bidirectional site-specific earthquake. The study reveals that for multi-storey buildings, isolation can drastically reduce seismic responses. Furthermore, flexibility of buildings predicts some structural savings for reduced responses. Good agreement has been achieved through rapid solution in frequency-domain approach. In medium risk earthquake-prone area, rubber-steel bearing isolators can be beneficially inserted

Relationship between weather variables and new daily covid-19 cases in Dhaka, Bangladesh

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. The present study investigated the relationship between the transmission of COVID-19 infections and climate indicators in Dhaka, Bangladesh, using coronavirus infections data available from the Institute of Epidemiology, Disease Control and Research (IEDCR), Bangladesh. The Spearman rank correlation test was carried out to study the association of seven climate indicators, including humidity, air quality, minimum temperature, precipitation, maximum temperature, mean temperature, and wind speed with the COVID-19 outbreak in Dhaka, Bangladesh. The study found that, among the seven indicators, only two indicators (minimum temperature and average temperature) had a significant relationship with new COVID-19 cases. The study also found that air quality index (AQI) had a strong negative correlation with cumulative cases of COVID-19 in Dhaka city. The results of this paper will give health regulators and policymakers valuable information to lessen the COVID-19 spread in Dhaka and other countries around the world

Phytotoxic interference of volatile organic compounds and water extracts of Tinospora tuberculata Beumee on growth of weeds in rice fields

Tinospora tuberculata Beumee is an aromatic shrub with pharmacological properties and belongs to the Menispermaceae family. We assessed T. tuberculata for its ability to suppress growth of weeds in rice fields. In seedling bioassays, the rate of seed germination and the radicle and hypocotyl lengths of barnyardgrass, rice and weedy rice seedlings were reduced as the concentration of aqueous water extracts and volatile organic compounds increased compared to the control. In a glasshouse experiment, T. tuberculata leaf powder also exhibited effective reduction in the emergence and growth of weeds in rice fields. Applications at rates of 4 t ha− 1 completely suppressed emergence of barnyardgrass, sprangletop and smallflower umbrella. The chemical compositions of extracts and volatiles were analyzed by GC–MS and HS-SPME-GC–MS. The results showed that 7 of 43 components in the leaf aqueous extract, as compared to 5 of 15 compounds in the stem aqueous extract, are known to be toxic compounds. Moreover, eight main volatile organic compounds were identified, which accounted for 97 and 95% of the whole fresh and dry leaf volatiles, respectively. We observed qualitative and quantitative differences in the compounds present in the dry and fresh leaf. Confocal laser scanning microscope images showed that the volatile emissions and aqueous extracts also inhibited the main root diameter, and the number and elongation of root hairs of tested weeds in rice fields. These results suggest that T. tuberculata contains a significant source of plant growth inhibitors. Hence, it can be used as a mulch to suppress weeds in rice fields and for developing new herbicide based on phytotoxic compounds release by this plant

Inhibition of methane oxidation by nitrogenous fertilizers in a paddy soil

Nitrogenous fertilizers are generally thought to have an important role in regulating methane oxidation. In this study, the effect of ammonium on methane oxidation activity was investigated in a paddy soil using urea at concentrations of 0, 50, 100, 200 and 400 μg N per gram dry weight soil (N/g.d.w.s) and ammonium sulfate at concentrations of 0, 50 and 200 μg N/g.d.w.s. The results of this study demonstrate that urea concentrations of 200 μg N/g.d.w.s. and above significantly inhibit methane oxidation activity, whereas no statistically significant difference was observed in methane oxidation activity among soil microcosms with urea concentrations of less than 200 μg N/g.d.w.s after incubation for 27 days. Similar results were obtained in a sense that methane oxidation activity was inhibited only when the ammonium sulfate concentration was 200 μg N/g.d.w.s in soil microcosms in this study. Phylogenetic analysis of pmoA genes showed that nitrogen fertilization resulted in apparent changes in the community composition of methane-oxidizing bacteria (MOB). Type I MOB displayed an increased abundance in soil microcosms amended with nitrogenous fertilizers, whereas type II MOB dominated the native soil. Furthermore, although no statistically significant relationship was observed between pmoA gene and amoA gene abundances, methane oxidation activity was significantly negatively correlated with nitrification activity in the presence of urea or ammonium sulfate. Our results indicate that the methane oxidation activity in paddy soils might be inhibited when the concentration of ammonium fertilizers is high and that the interactions between ammonia and methane oxidizers need to be further investigated