BIBECHANA

Seasonal variations of disasters in Nepal

Pitri Bhakta Adhikari — 2024-03-08

Among the natural disasters, landslides, flood, thunderstorm, fire, are major destructive disaster. In every season, fire is the main cause of the death of the people which frequently occurred in spring and winter seasons. The landslide seems to be very destructive in the summer season, flood is also in the summer season, and thunderbolt occurs frequently in spring and summer seasons (pre-monsoon period). The different disaster occurred in different season frequently and have more effect on human, animals, and huge loss of property due to it. Due to the geographical structure of our scenario, the destruction seems to be high in Nepal. Hence, the disasters can’t be stopped, but can be reduced and awareness program should be conducted to mitigate its effects.

Lattice thermal conductivity in half-Heusler compounds XNiSn (X=Ti, Zr, Hf) using Slack's model

Prakash Khatri — 2024-03-08

Reducing lattice thermal conductivity (κ_l) that reflects the material’s heat-carrying capacity through lattice phonon vibrations is crucial for optimizing the figure of merit (zT). Using density functional theory (DFT) and density functional perturbation theory (DFPT), present work considers the structural, electronic, magnetic, and phonon properties of the XNiSn (X=Ti, Zr, Hf ) half Heusler (hH) compounds. TiNiSn, ZrNiSn, and HfNiSn are identified as semiconductors with indirect band gaps of 0.43 eV, 0.47 eV and 0.39 eV, respectively, exhibiting dynamical stability. The temperature- dependent κ_l of hH XNiSn are compared using Slack’s model with two approaches for analyzing phonon velocity: elastic constants from quasi- harmonic approximation (QHA) as implemented in the Thermo_pw code and slope of phonon bands based on DFPT. At room temperature, TiNiSn, ZrNiSn and HfNiSn have κ_l values of 28.61 Wm⁻¹K⁻¹, 34.61 Wm⁻¹K⁻¹ and 29.85 Wm⁻¹K⁻¹ respectively using phonon velocity from slopes of phonon bands based on DFPT. These values show deviation of 1.48%, 6.29%, and 5.82% to those κl values 29.01 Wm⁻¹K^−1’, 36.79 Wm⁻¹K⁻¹ and 31.59 Wm⁻¹K⁻¹ for TiNiSn, ZrNiSn and HfNiSn respectively using QHA.

An investigation of vibrational analysis, thermodynamics properties and electronic properties of Formaldehyde and its stretch by substituent acetone, acetyl chloride and methyl acetate using first principles analysis

Susmita Limbu — 2024-03-08

This study finds the equilibrium configuration, vibrational analysis, thermodynamic properties, and electronic properties of formaldehyde and its derivatives, namely acetone, acetyl chloride, and methyl acetate, using First Principles Analysis. It emphasizes the impact of substituents on the carbonyl group and the need for this comprehensive analysis. The computational methods employed in this work are Gaussian DFT), GaussSum and Moltran calculations. For formaldehyde, the optimization step starts from the energy of -114.51282 Hartree and gets optimized in the energy -114.5129634 Hartree. Similarly for Acetone, Acetyl chloride and Methyl acetate, optimization step start from -193.74375 Hartree, -613.26 Hartree, -266.805 Hartree and gets optimized in the energy -193.1744033 Hartree, -613.2941798 Hartree, -266.8358066 Hartree. Infrared (IR) spectroscopy is used to analyze vibrational frequencies. The C-H and C=O vibrations are highlighted, showing characteristic peaks for each compound. Heat capacity at constant volume (Cv), heat capacity at constant pressure (Cp), internal energy (U), enthalpy (H), entropy (S) and Gibb’s free energy (G) with change in temperature sharply increase from 10 K to 50 K and decreases the increase in rate from 50 K to 500 K. In the derivative of Formaldehyde, Methyl Acetate has the highest energy gap (i.e. -7.4222 eV) and Acetyl Chloride has the small energy gap (i.e. 5.6137 eV). The Chemical parameters like ionization potential, electron affinity, chemical hardness, chemical potential, electronegativity, electrophilicity index, and chemical softness have been also calculated. Electrostatic Potential (ESP) Surfaces, Molecular Electrostatic Potential (MEP), and Electron Density (ED) are visualized to understand charge distribution and reactivity regions. DOS spectra illustrate the density of electron states per unit energy.

Comparative study of the dust color temperature and dust mass within the isolated dust in W51 giant molecular cloud in IRIS and AKARI data

M.S. Paudel — 2024-03-08

This work presents the comparative study of the properties of dust within the W51 Giant Molecular Cloud (GMC) located at (RA, DEC) (J2000): 290.91°, +14.51°. In the infrared data of Improved Reprocessing of the IRAS (IRIS) the dust structure seems single and isolated having size 0.45°×0.45° but in AKARI infrared survey it breaks into two isolated regions having size 0.15°×0.15° and 0.10°×0.10°, represented by AKARI-I and AKARI-II respectively. In IRIS map, 60 and 100 mm and in AKARI map, 90 and 140 mm image are used for extraction of the infrared flux. The dust color temperature (T_d) and dust mass (M_d) are calculated from the infrared flux and found to 30.34 K in IRIS and 27.40 K and 23.55 K in AKARI-I and AKARI-II. A linear relationship between the infrared flux at two wavelength is found except AKADI-I. The dust mass per pixels in the isolated (core) region is found to be increase compare to total study region. To quantify the relation between flux, dust color temperature and dust mass the regression analysis is used and observed spectrum of relation. A huge SIMBAD background objected is found embedded in the dust cloud which might have been shaping the spatial variation of temperature and mass within dust cloud.

Potential removal of arsenite from contaminated water using a fixed bed column packed with TiO2-impregnated pomegranate peel powder

Bhoj Raj Poudel — 2024-03-08

A dynamic biosorption of arsenite in a fixed bed column packed with TiO₂ impregnated pomegranate peel (PP@TiO₂) has been investigated in this work, which is important to identify the effectiveness and affordability of an adsorbent in actual practice. To create an active adsorption site for As (III) ions, pomegranate peel powder (PP) was impregnated with TiO₂. Under various operating parameters, the performance of a column packed with PP@TiO₂ for adsorbing As (III) ions was evaluated. Breakthrough curve modelling showed that the bed depth service time (BDST) and Thomas models agreed well with the experimental data. The maximum column capacity of PP@TiO₂ using the Thomas model was found to have resembled experimental value with high values of coefficient of determination. Therefore from these results, we may anticipate that PP@TiO₂ can be a strong contender for the treatment of wastewater that has traces amount of the As (III) ion in a fixed bed system.

Synthesis, characterization and antimicrobial study of silver nanoparticles using methanolic fraction of Artemisia vulgaris leaf

Sandhya Parajuli — 2024-03-08

Rational selection of active biomolecules in the synthesis of nanoparticles for reducing the precursor and functionalizing the nanoparticles (NPs) can offer remarkable comeback of biocompatibility and biological applicability. This work aimed at the synthesis of a cost-effective, ecofriendly, and a facile approach of silver nanoparticles (AgNPs) using methanolic leaf extract of Artemisia vulgaris. The phytochemical constituents present in the methanolic extract were characterized by qualitative chemical tests and spectroscopic measurements and employed for the reduction of silver nitrate into silver nanoparticles. Formation of AgNPs was monitored by UV-visible spectroscopic measurement. Fourier transform infrared (FTIR) spectroscopy reflected the presence of characteristic functional groups associated with the phytochemical constituents involved in the formation of nanoparticles. The crystalline phase and morphology of the NPs were assessed form X-ray diffraction (XRD) spectra and field emission scanning electron microscopy (FESEM), respectively. XRD pattern revealed the crystalline nature of nanoparticles with grain size of ∼ 28 nm based on the Debye Scherer formula. Study of antimicrobial activity of AgNPs against Gram-positive bacteria Bacillus subtili, Gram-negative bacteria Escherichia coli, and fungus Candida albicans exhibited good potential to control the bacterial and fungal growth.

Structural and cation distribution analysis of Nickel-Copper/Nickel-Magnesium Substituted Lithium Ferrites

D. Parajuli — 2024-03-08

Lithium ferrite (Li_0.5Fe_2.5O₄) shows significant promise in electrical and electronic engineering. It possesses a crystal spinel crystal structure denoted as AB₂O₄, with "A" and "B" representing specific tetrahedral and octahedral lattice sites respectively. Analysis of X-ray diffraction (XRD) patterns aligns well with the JCPDS card (no. 38-0259), confirming the spinel structure with the Fd3m space group. However, an additional peak at 211 in the basic lithium ferrite suggests a subtle Fd3m to the P4₁32 phase change with a minor secondary hematite phase. Investigating the cation distribution in these ferrites is crucial for further exploration of their magnetic and dielectric properties. These ferrites find widespread applications in microwave technology and magnetic and electric energy storage devices.