BIBECHANA

Characterization of carbon derived from candle by flame-soot method for counter electrodes of dye-sensitized solar cells

Prakash Joshi, Umesh Lawaju, Anupam K.C., Mim Nakarmi, Ramani Pradhan — Fri, 01 Dec 2023 00:00:00 +0000

Candle soot, carbon samples prepared by flame-soot method, was characterized and investigated for its catalytic ability for the reduction of tri-iodide ions aiming to substitute expensive platinum based electrode used in dye-sensitized solar cells (DSCs). The Energy Dispersive X-ray Spectroscopy of the candle soot samples revealed that the soot contains 96% carbon. Similarly, Scanning Electron Microscopy images show that the candle soot consists of interconnected carbon nanoparticles of size ∼50 nm. Furthermore, X-ray Diffraction and Raman spectroscopy showed that the candle soot consists of disordered and ordered graphitic carbons in a comparable proportion. The catalytic ability of the candle soot was compared with that of platinum by Electrochemical Impedance Spectroscopy of the symmetrical electrochemical cells. The charge transfer resistance (Rct) at the candle soot-electrolyte interface was observed to be ∼4.42 Ω cm² compared to ∼ 5.04 Ω cm² that of the platinum-electrolyte interface. The candle soot was prepared by a simple method using low-cost material; hence, it can be a low-cost and efficient counter electrode material alternate to the platinum used in counter electrodes of DSCs.

The Correlative study of Aerosol Optical Depth with Precipitable water over five AERONET station across the world

Santosh Sapkota, Sabin Gautam, Aayush Gautam, Bhairab Ale — Thu, 30 Nov 2023 00:00:00 +0000

Ground-based measurements were taken at various locations, including Kathmandu Bode, Beijing, Gandhi College (located in South Asian zone, highly polluted area), Canberra, and UNC Gaitan (located in South Eastern zone, low polluted area), from January to December 2016. The study investigated the seasonal and inter-annual AOD that were obtained using CIMEL Sunphotometer, as a part of the Aerosol Robotic Network (AERONET). The data showed that Kathmandu (0.45±0.01), Gandhi College (0.45±0.02 and Beijing (0.85±0.03) had higher AOD values compared to other stations, with Kathmandu being a high-altitude site. The analysis found that pre-monsoon AOD were higher over Kathmandu (0.45±0.01), Gandhi College (0.45±0.02), UNC Gaitan (0.28±0.001), and Canberra (0.06±0.002). On the other hand, the monsoon AOD was higher over Beijing (0.85±0.03). The study identified various factors contributing to the higher AOD values in specific regions. Beijing, Gandhi College, and Kathmandu, located in Asian monsoon regions, experienced high aerosol loading due to economic activities, vehicles, urbanization, vegetation fire, land clearing for crop cultivation, as well as winter biomass burning, heating needs, and pollution from bricks kilns, factories, and vehicles. Canberra and UNC Gaitan had higher AOD values primarily due to biomass burning and dust. AOD values are higher for shorter wavelength and vice-versa. We conducted a correlation analysis between AOD and perceptible water at different wavelengths and observed one to one correspondence. The columnar water vapor (CWV) exhibited a high correlation with AOD in Canberra (Coefficient of determination, R² = 0.61) at 1640 nm but had no relationship with AOD in Gandhi College (Coefficient of determination, R² = 0) at 1640nm. There is weak negative correlation between AOD and preceptable water over Kathmandu and UNC Gaitan, but have positive correlation in Canberra, Beijing and Gandhi College

Electronic and magnetic performance of MoS2 monolayer via Tc & Nb impurities defect and water adsorption

Hari Neupane, Prakash Khatri, Arun Devkota, Narayan Prasad Adhikari — Thu, 30 Nov 2023 00:00:00 +0000

This study examined the effect of Tc & Nb impurity atoms on MoS₂ (Tc-MoS₂ & Nb-MoS₂ ), and adsorption of water molecule on impurities defected MoS₂ (Tc-W-MoS₂ & Nb-W-MoS₂) material from first-principles calculations. By the estimation of their ground state energy and binding energy, they are stable 2D materials. From band structure and density of states (DoS) calculations, Tc & Nb
impurities affect the nature of pristine MoS₂. It is found that Tc-MoS₂ has n-type & Nb-MoS₂ has p-type semiconducting nature. Water interaction on Tc-MoS₂ & Nb-MoS₂ slightly changes the electronic properties and impacts the bandgap, which enhanced the electronic performance of material than that of pristine MoS₂. The magnetic properties of Tc-MoS₂, Nb-MoS₂, Tc-W-MoS₂, and Nb-W-MoS₂ are analyzed and found to exhibit an uneven distribution of up-spin and down-spin states of electrons in the orbital of atoms near the Fermi level. It reflects that they have magnetic properties. The non-magnetic MoS₂ material changes in to weak magnetic defected-MoS₂ materials due to the presence of Tc, Nb and adsorbed water molecule. It means, impurity defects add to magnetic properties of pristine MoS₂. Magnetic properties on defected MoS₂ occurred due to the dominant contributions of spin states of 4d-orbital of Mo, Tc, Nb atoms, and 3p-orbital of S atoms in the structures. This study highlights the impact of Tc & Nb impurity atoms and adsorbed water molecule on impurities defected MoS₂. The studied materials have potential applications in the fields of catalysis, nanoelectronics, biomedicine, and magnetic sensors on the basis of their electronic and magnetic properties.

Phytochemistry, Biological Activities, and Chemical Profiling of Berberis asiatica

Keshab Bhattarai, Devendra Dhakal, Indira Pandey, Bimala Subba, Khaga Raj Sharma — Thu, 30 Nov 2023 00:00:00 +0000

This study focused on chemical profiling and assessed the total phenolic and flavonoid content as well as the antioxidant and antibacterial effect of the medicinal plant Berberis asiatica. The results revealed that this plant has high concentrations of TPC (Total phenol content) and TFC (Total flavonoid content) of 37.686 ± 2.728 mg GAE/g and 115.568 ± 8.012 mg QE/g, respectively. The DPPH free radical scavenging assay demonstrated strong inhibition, with an IC₅₀ of 205.7 ± 5.353 μg/mL, and also showed robust antibacterial properties against Staphylococcus aureus and Klebsiella pneumoniae with a zone of inhibition (ZOI) of 14 mm and 19 mm, respectively. The extract exhibited an excellent inhibitory potential against S. aureus, and K. pneumoniae with an MIC (Minimum inhibitory concentration) of 0.39 mg/mL, and 3.125 mg/mL respectively, indicating significant inhibitory action. Furthermore, the MBC (Minimum bactericidal concentration) for both S. aureus and K. pneumoniae was found to be 6.25 mg/mL, emphasizing the extract's consistent bactericidal effectiveness against these bacteria. These findings underscore the potential utility of the methanolic extract of Berberis asiatica as a natural antibacterial agent. GC-MS analysis of hexane fraction indicates the plant is rich in secondary metabolites, specifically 2,2-dimethyl-3-pentanol, 2-methyl-2-pentanol, 2,5-dimethyl-4-hydroxy-3-hexanone, 3-hexanol, 4-methyl-2-pentanol are identified. Overall, this study highlights the importance of plant-based natural products as potential sources of antioxidants and antibacterial agents that contributes to the future drug development process.

Time and Space Domain Prediction of Water Quality Parameters of Bagmati River Using Deep Learning Methods

Pujan Bashyal, Mandira Adhikari, Nanda Bikram Adhikari — Thu, 30 Nov 2023 00:00:00 +0000

Bagmati river is biologically, geologically, religiously and historically significant among the river systems of the Kathmandu Valley. The river is affected by five major tributaries, including Manohara, Dhobi Khola, Tukucha, Bishnumati, and Balkhu Khola, which significantly impact the water chemistry inside the Kathmandu Valley. The data of water quality parameters pH, dissolved oxygen, turbidity, temperature, oxygen reduction potential, conductivity, total dissolved solids, salinity among others was collected using fixed sensors (in period of 5 seconds) and mobile sensors (with latitude and longitude) along the river. The observation is important for two reasons, one because it was collected in real-time and fine scale, which is not normally possible with traditional ways, and next such observation was done for the first time in Bagmati River. The aim of this study was to predict water quality parameters of the Bagmati River using machine learning time series models, specifically ARIMA and LSTM. The LSTM model was designed with one input layer, one encoder layer, one repeat layer, one decoder layer, and one output dense layer to separate the output into temporal slices. Additionally, a DNN model was employed for location-based prediction, utilizing two input layers for latitude and longitude and seven output layers for the seven water quality parameters considered for study. The models demonstrated promising performance, but further data collection and parameter variation are recommended for continued optimization.

An accurate theoretical formula for linear momentum, force and kinetic energy

Chandra Bahadur Khadka — Thu, 30 Nov 2023 00:00:00 +0000

The paper demonstrates that the existing mathematical formulas of linear momentum, force and kinetic energy in physics are incomplete, since such formulas have been formulated without incorporation of mass-energy equivalence relation E = mc². Therefore, new reformulations of the main equations of linear momentum, force and kinetic energy in the realm of special relativity are proposed. The proposed formulas provide same mathematical outcomes as the old formulas, displaying same behavior of the system when velocity approaches to speed of light, but, most importantly, comprise only velocity of the light and mass of object to provide well-defined expressions. [Formulae available with the full text]. These formulas vividly reveal that every physical variable depends solely on relativistic mass. Therefore, it modifies Newton’s second law of motion and states that the force depends on rate of change of relativistic mass of object rather than its velocity. In this highly interesting topic, primary purpose here has been to present a succinct and the carefully reasoned account of a new aspect of the Newton’s second law of motion which properly allows to derive the new mathematical formulas of linear momentum, force and kinetic energy.

Machine learning driven prediction of lattice constants in transition metal dichalcogenides

Bhupendra Sharma, Laxman Chaudhary, Rajendra Adhikari, Madhav Prasad Ghimire — Thu, 30 Nov 2023 00:00:00 +0000

Machine learning represents an emerging branch of artificial intelligence, centering on the enhancement of algorithms in computer programs through the utilization of data and the accumulation of research-driven knowledge. The requirement for artificial intelligence in materials science is essential due to the significant need for innovative high-performance materials on a large scale. In this report, the gradient boosting regression tree model of machine learning was applied to predict the lattice constants of cubic and trigonal MX₂ systems (M=transition metal and X=chalcogen atoms). The theoretical/experimental values of the materials were compared to the predicted values to calculate the standard errors such as RMSE (root mean square error) and MAE (mean absolute error). The features used to predict lattice constants were ionic radius, lattice angles, bandgap, formation energy, total magnetic moment, density and oxidation states. The features versus contribution barplot has been drawn to reveal the contribution level of each parameter in the degree of [0,1] to obtain the predictions. This report provides a precise account of the prediction methodology for lattice parameters of the transition metal dichalcogenides family, a process that was previously not reported.

Cr3+ substitution effect on Co-Cu and Cu-Co nano ferrites on structural and morphological properties

D. Parajuli, N. Murali, K. Samatha — Thu, 30 Nov 2023 00:00:00 +0000

The Cr³⁺ substituted Co-Cu (Co_0.7Cu_0.3Fe_2-xCr_xO₄) and Cu-Co (Cu_0.7Co_0.3Fe_2-xCr_xO₄) where x = 0.0, 0.05, 0.1, 0.15, 0.2 and 0.25 nano ferrite composite were prepared with the sol-gel approach. Their structural, dc electrical resistivity, and magnetic properties were analyzed. XRD shows the single-phase spinel ferrite. Adding Cr³⁺ ions decreases the lattice volume and the size of the crystallite respectively. FESEM images show non-spherical particles on a largely uniform surface shape with decreasing grain size on doping Cr³⁺. The FTIR pattern supports the XRD patterns for spinel ferrite.

Measurement of background radiation in Jhapa, Ilam, Panchthar, and Taplejung districts of Nepal

Thu, 30 Nov 2023 00:00:00 +0000

In this study, we investigated the levels of background radiation in different locations across the Eastern part of Koshi province, specifically in Taplejung, Panchthar, Ilam, and Jhapa. We used a portable Geiger Muller counter to collect data from twenty different locations, with five sites taken from each district. The average absorbed dose rate was found to be 0.243±0.035 mSv/y. The highest measured value of absorbed dose was 0.335±0.041 mSv/y at Pathivara temple in Taplejung, and the lowest was found to be 0.197±0.039 mSv/y at Kakarvita, Jhapa. The results suggest that these four districts do not pose any radiation risk because it was below the threshold of risk (1mSv/y). We also measured the variation of absorption dose with altitude which is positively correlated with altitude with a correlation coefficient of +0.57. This might be because of the surge in cosmic radiation with an increase in altitude.

Assessment of the antibacterial activity of lemongrass-extracted essential oil

Thu, 30 Nov 2023 00:00:00 +0000

Lemongrass is one of the medicinal plants having significant applications to cure various diseases. This study aims at extracting essential oils from lemongrass plants and examining their antibacterial activity. The sample of lemongrass for this study was collected from Kailali District, Nepal. The leaves of lemongrass were collected, washed, cut into small pieces, and dried in the sun. Then pieces of lemongrass were steam distilled for about 4 hours using the Clevenger apparatus, and oil was extracted. The extracted essential oil was further utilized to study its antibacterial activity in human pathogens, namely Staphylococcus aureus (S. aureus: gram-positive bacteria), by Agar diffusion and broth dilution methods. It was found that the zone of inhibition for S. aureus in concentrations of 100%, 75%, 50%, and 25% was about 25 mm, 11 mm, 9 mm, and 0 mm, respectively. In addition, it is clear from this study that the gram-positive bacteria were sensitive to essential oils. The lowest and highest zones of inhibition were shown against S. aureus at 25% and 100% concentrations, respectively. The zone of inhibition at 100% concentration is 25 mm and at 25% concentration is 0 mm, so lemongrass oil is effective against drug-resistant organisms only at high concentrations.

Effects of calcination and sintering processes on structural profile parameters of modified BNKT-based ferroelectric ceramics

Ram Prasad Aryal, Binod Kumar Bhattarai, Bhadra Prasad Pokhrel — Thu, 30 Nov 2023 00:00:00 +0000

We have carried out a detailed study of synthesis and variations of structural profile parameters: lattice constants, unit cell volume, densities, porosity, crystallite size, dislocation density and micro-strain of BMZ modified BNKT (1-x) Bi_0.5(Na_0.70K_0.30)_0.5TiO₃-xBiMg_0.5Zr_0.5O₃ for x=0, 0.03, 0.06, 0.09 and 0.12 using x-ray diffraction. The conventional solid-state reaction method was used to synthesize BNKT samples. The BNKT powders were calcined at an optimized temperature of 850 °C for 2 hours. Keeping the calcination temperature fixed, optimized sintering temperature and time were also determined to be 1140⁰C for 2 hours, based on the sharpness of the peaks and densification. The nature of the XRD patterns is qualitatively similar to that observed for calcined powders, however, the reflections are sharper in sintered samples presumably due to an increase in particle size. The XRD profile reveals an almost pure perovskite structure with cubic symmetries for all samples in both calcined powders as well as sintered samples. The crystallite size, dislocation densities, and micro-strain were determined by using William-Hall plots as well as Scherrer formula. It is observed that the maximum bulk density was found to be 5.88 gm/cm³ for x=0.03 which is 96.39 % of the theoretical density. The crystallite size varies from 19.84 - 44.15 nm with compositions for calcined powders and from 57.01- 62.69 nm for sintered samples. The very low value of crystallite sizes of calcined powder indicates that the particle size is comparably very low to that of sintered samples. The dislocation densities and micro-strain for calcined and sintered powders were observed in the range (5.1- 25.4)´10^-4nm^-2, and (2.54 - 3.1) ´10^-4nm^-2 and (1.3 -4.8) ´10^-3 and (8.93 - 9.90) ´10^-4 respectively which are determined using William-Hall plot method. These results are also confirmed by the results obtained from the Scherrer method. Both results show improved profile parameters in sintered compositions than in calcination. This verifies that sintered BMZ-doped BNKT powders are promising candidates for many dielectric-based energy storage applications.

Exploring topological phase transition in Pt2Hg1−xTlxSe3

Deergh Bahadur Shahi, Dipak Bhattarai, Madhav Prasad Ghimire — Thu, 30 Nov 2023 00:00:00 +0000

The transition from trivial to non-trivial phase in two-dimensional materials are called a topological phase transition (TPT). The Berry phase, non-local string order parameter, and edge states define the topological nature of the system. A newly discovered jacutingaite ma- terial Pt₂HgSe₃ is a layered material which occurs naturally in the form of minerals. The material can be exfoliated and was predicted as a quantum spin Hall insulator. Here, on the basis of density functional theory and tight-binding calculations, we explore Pt₂Hg_1−xTl_xSe₃ (x = 0.25, 0.50, 0.75, 1) to understand the electronic and topological properties. We start with the parent material Pt₂HgSe₃ wherein Hg is replaced partially with x amount of Tl, to tune the topological phases. From the electronic structure calculations, Pt₂HgSe₃ is found to be a non-trivial semimetal in it’s bulk. Upon electron doping, the material transforms to strong topological metallic phase. The topological Z₂ invariant calculation shows TPT in Pt₂Hg₁−_xTl_xSe₃ with weak topological insulating state (0;001) for x=0, to strong topological metal (1;000) for x=1, respectively.

Thermodynamic, structural and surface properties of rare earth metallic alloys: Au-La liquid system

Shashit Kumar Yadav — Thu, 30 Nov 2023 00:00:00 +0000

A complete information related to the mixing behaviours of Au alloyed with rare earth metals or lanthanides is very scarce. Therefore, an attempt has been made in this work to compute and study the temperature and concentration dependent thermodynamic, structural and surface properties of Au-La liquid alloy using different theoretical approaches. The thermodynamic properties, such as excess Gibbs free energy of mixing, enthalpy of mixing, excess entropy of mixing and activity of the system were computed using available coefficients of interaction energy parameters in the framework of Redlich-Kister polynomial. Taking these as reference values, model parameters for quasi-lattice model were optimised at 1473 K. The model parameters were then determined at higher temperatures assuming them to be linear temperature-dependent. The thermodynamic and structural properties were then computed in the temperature range 1473 K-1773 K. The surface properties of the system were computed using Bulter’s model using determined values of partial excess Gibbs free energy of its components. Present investigations revealed that the compound forming tendency of the system gradually decreased with increase in temperature of the system.

Comprehensive review of LCA studies in Civil Engineering

Ishwor Thapa, Nirmal Prasad Baral, Krishna Raj Adhikari — Thu, 30 Nov 2023 00:00:00 +0000

This review paper explores the application of Life Cycle Assessment (LCA) within the domain of civil engineering, aiming to provide a comprehensive overview of current research, methodologies, challenges, and future trends. LCA serves as a pivotal tool for assessing the environmental impact of infrastructure projects, yet gaps persist in its integration with socioeconomic dimensions, regional considerations, and dynamic modeling. By analyzing existing literature and scholarly discussions, this review identifies research gaps and proposes directions for enhancing the applicability and effectiveness of LCA in civil engineering. Moreover, it examines future trends such as the integration of advanced technologies, stakeholder engagement, and policy implementation, poised to shape the landscape of LCA practices in the civil engineering sector. Ultimately, this review paper contributes to the understanding of LCA's potential to drive sustainable decision-making in infrastructure development, paving the way for more informed and environmentally conscious practices.