BIBECHANA

A brief review on preparation and application of MWCNT-based polymer nanocomposites

Jyoti Giri, Rameshwar Adhikari — Wed, 05 Apr 2023 00:00:00 +0000

Technological advancementalways seeks new materials with improved functional properties, particularly for smart applications. In this regard, nanotechnology is offering today wide range of novel material designs fabricated by compounding nanofillers into the polymer matrix. Different allotropic forms of carbon can reinforce the properties of polymers for various applications. Reinforcement depends on the dimension, shape, size and compatibility of the nanofiller with the polymer matrix. Chemical modification of filler surfaces and the matrix can selectively localize the filler in the hybrid composites in the desired phase or at the interface by melt mixing or solution casting method, during compounding procedure. In this regard, the conducting nature of the additioin of multiwalled carbon nanotubes (MWCNTs) into a polymer matrix fosters the conductivity into the materials. Such nanocomposites can be used for numerous applications such as conducting materials, super-capacitors, light emitting devices, medical purposes etc,. This review paper focuses on different methods of preparation of MWCNT/polymer nanocomposites, their surface properties, and microbial properties etc,.

Study of aerosol optical properties in Lumbini, Nepal

Wed, 05 Apr 2023 00:00:00 +0000

The mixture of different sized particles (fine and coarse) with air composition forms aerosols. Increased economic activities, vehicles, and rapid urbanization made Lumbini one of the heavily polluted regions in Nepal. Data are extracted from AERONET websites between 2013 to 2019 with standard deviation. We are mainly focused on understanding variations in aerosol optical properties: aerosol optical depth (AOD), angstrom parameter (α and β), visibility, single-scattering albedo (SSA), refractive index (real and imaginary), and asymmetry parameter (AP) in the Lumbini region. The maximum value of AOD (675nm) in Lumbini occurred mostly during post-monsoon season (0.61 ± 0.38) whereas, the values of AOD were found to be lower during the monsoon season (0.18 ± 0.12). Most of the AOD values are found to be greater than 0.4, indicating the higher level of pollution in the study area. There is a positive correlation between perceptible water and AOD, maximum correlation (0.4) occurs at the lowest AOD (440nm) while the minimum (0.1) at the highest AOD (1020nm). The turbidity coefficient (β) has an adverse effect on visibility. The Visibility over Lumbini was found to be highest (20 km) during monsoon. Single-scattering albedo (SSA) accretions occur at wavelengths between 440 and 675 nm, but the pattern changes from 675 to 1020 nm. All parameters were found to be distinct and seasonal fluctuations among this station are mainly due to the different aerosols availability such as biomass burning, mixed aerosols, and anthropogenic aerosols over the Lumbini site.

Porous activated carbon materials from Triphala seed stones for high-performance supercapacitor applications

Wed, 05 Apr 2023 00:00:00 +0000

Porous activated carbon materials derived from biomass could be the suitable materials for high-rate performance electrochemical supercapacitors as it exhibits high surface area due to well-defined pore structure. Here, we report the novel porous activated carbon from Triphala seed stones by chemical activation with zinc chloride at different carbonization temperature (400-700 °C) under the nitrogen gas atmosphere. The activated carbon was characterized by Fourier transform-infrared (FTIR) spectroscopy, Raman scattering and scanning electron microscopy (SEM). Nitrogen adsorption-desorption measurements was used to study the surface properties (effective surface areas, pore volumes and pore size distributions). The electrochemical measurements were performed in an aqueous 1 M sulphuric acid (H₂SO₄) solution in a three-electrode cell set up. Triphala seed stones-derived porous carbon materials with well-defined micro- and mesopores exhibit high specific surface area ranges from 878.7 to 1233.3 m² g^-1 and total pore volume ranges from 0.439 to 0.626 cm³ g^-1. The specific capacitance obtained by electrochemical measurement experiment was 208.7 F g^-1 at 1 A g^-1. These results indicate that the prepared nanoporous activated carbon material from Triphala seed stones would have significant possibility as supercapacitor electrode material for high-energy-storage supercapacitor applications.

Overall migration of microplastics in mineral water and non-alcoholic beverages

Jagjit Kour, Pratima Bhatt, Shobha Basnet — Wed, 05 Apr 2023 00:00:00 +0000

In today's world, packaging plays a crucial role in enhancing, enclosing, and shielding the materials that are used from procurement to handling and storage, processing, manufacturing and finally to the consumer. Packaging shields a product's contents from contamination, spoiling and makes it simple to store and transfer anywhere. Man-made plastic breaks down into little particles as a result of numerous external pressures. The degradation of plastics produce nano or microplastic. Health issues arise when microplastics (MPs) leak from plastic food packaging and are consumed by people. Though plastic packaging is abundant, consumers from developing nation are not aware of the risk associated with plastic food packaging. The purpose of this study is to demonstrate occurrence of microplastics in plastic food packaging and highlight the risks involved in consumption of microplastics.

In this research, the migration of microplastics from different plastic containers were noted in accordance to the Bureau of Indian Standards IS - 9845-1998. The IS 9845: 1998 method was utilized in this investigation to determine the overall migration of various plastics used to package mineral water and beverages. Distilled water and 3% acetic acid (w/v) were utilized as food simulators for the analysis. The migration of microplastics in mineral water were found to range from 0.38 ppm to 0.54 ppm while in case of non-alcoholic beverages overall migration ranged from 0.29 to 75.75 ppm. Among the 12 samples of non-alcoholic beverages, one sample exceeded the maximum limit of microplastics as specified by WHO standard.microplastics

A systematic study on material properties of water retted Sterculia and Bauhinia fiber

Wed, 05 Apr 2023 00:00:00 +0000

Lignocellulose biomass forms an important component of traditional and next generation composite materials. To obtain desired properties, the biomass needs to be chemo‒mechanically processed at different levels. The raw lignocellulose fiber obtained from Sterculia villosa (Roxb.) and Bauhinia vahlii is traditionally believed to have high water stability; and therefore used in rural areas of South Asian regions to secure objects submerged under water. In this research, we systematically studied several material properties of raw Sterculia and Bauhinia fiber samples retted for 0, 20, 30 and 55 days (n=8). Water retting resulted in significant decrease in lignin and extractives content (p<0.05) and increase in cellulose content. Fiber bundle strength of Sterculia fiber increased with retting time (R²= 0.7) but Bauhinia fiber did not show significant change (p>0.05). Interestingly, water retting resulted in increased thermal stability in both fiber types. These findings suggested that the fiber studied have excellent water stability. The observed trend in mechanical and thermal properties could have resulted from crystallinity change and/or nominal fiber damage as supported by XRD and SEM imaging data; respectively. These findings suggested that Sterculia and Bauhinia fiber biomass could be an important component of biodegradable composite materials which are intended for high wetting and/or humid conditions.

The fatalities and injuries due to avalanche effect in the Himalayan Region, Nepal

Pitri Bhakta Adhikari, Sapana Dawadi, Shanta Nepal — Wed, 05 Apr 2023 00:00:00 +0000

Snow avalanches present the major natural hazard in Himalayan region of Nepal. The loss of human life is the main effect of avalanche. The records and casualties compared with specific Europe countries which help to analyze the hazard in the mountain region and can be recommend to the public people of this area about the avalanche condition, prevention from it and dissemination of information. On analyzing the statistics of avalanche fatality in the high mountain of Asia from 1895 to 2022, the fatality number was 59 at Annapurna and Dhaulagiri mountain Peaks. Different highest peaks of mountains attract tourist and the massive amount of snow create an avalanche in these areas, so Avalanche is one of the most devastating hazards in Western Himalayan. This fatality events, and fatality rates of Nepal and Europe countries from 1971 to 2022 analyzes the collected data from the DesInventar data-set, Disaster Risk Reduction Portal of the government of Nepal. The European Avalanche Warning System is used in the government of Europe using the geographic Information system (ArcGIS) tools. This study recommends the establishment of an Avalanche warning System with proper tools in the western Himalayan to save the life of humans and property.

Fabrication of UV sensing transistor based on transparent polycrystalline zinc oxide thin film using polymeric electrolyte gate dielectric

Rishi Ram Ghimire, Yam Prasad Dahal, Krishna Bahadur Rai — Mon, 10 Apr 2023 00:00:00 +0000

The fabrication of electric double layer thin film transistors (EDLTFTs) using polymeric electrolyte as gate dielectric on chemically grown polycrystalline ZnO thin film channel has the lower threshold voltage at 0.4 V and the saturation current at 3 µA in the dark. The lower threshold voltage is -1 V and the saturation current is 10 µA in the UV illumination. In the dark and under UV light, the off state I_D is 1 nA and 0.3 µA respectively and under gate and UV illumination the on current shows more than 3 times enhancement. This improvement in photocurrent is due to the combined effect of gate and UV illumination. The field effect mobility of the TFT is 0.06 cm²/Vs in the dark and 0.16 cm²/Vs under UV illumination. This increase in mobility under illumination and gate bias is due to the increase in carrier concentration and reduction of charged defects in the channel length.

Analysis and characterization of X-ray flare of Mkn 421 using XMM-Newton observation 0658801301

Rajendra Neupane, Niraj Dhital — Wed, 05 Apr 2023 00:00:00 +0000

This research work was carried out to analyze the X-ray flares in Blazar Mkn 421 using data from XMM-Newton observation (Observation ID: 0658801301) that lasted for 8 hours. EPIC/pn data was used for statistical analysis of the light and spectrum curve in energy ranges from 0.3 to 10.0 keV. The best fit model for the spectrum was found to be the additive model (log-parabola + black-body). The measured integrated flux in the energy range of 0.3-2 keV is 5.015x10^-10 ergs cm^-2 s^-1 with an associated uncertainty range of (5.010 – 5.020) x 10^-10 ergs cm^-2 s^-1 at a 90% confidence level. Similarly, the measured integrated flux in the energy range of 2-10 keV is 2.398 x 10^-10 ergs cm^-2 s^-1 with an associated uncertainty range of (2.392 – 2.405) x 10^-10 ergs cm^-2 s^-1 at a 90% confidence level. The fractional variability of 0.444 is relatively high, which indicates that the source is variable. The fall in count per second per energy around 2 keV in the spectrum curve suggests that the intensity of X-rays decreases in a power law manner after a strong flare at this energy. The count-rate distribution of the observation analyzed is best described by a normal distribution which suggests that the emission mechanism in the blazar is governed by additive processes.

Biosorption of Hexavalent Chromium (Cr(VI)) from contaminated water using charred tea waste

Wed, 05 Apr 2023 00:00:00 +0000

The goal of this study is to develop charred tea waste (CTW) via chemical process for the removal of Cr(VI) from contaminated water. Batch adsorption experiments were conducted as a function of pH, initial concentration, contact time and adsorbent dosage. Characterization of the adsorbent was analyzed by FT-IR and XRD. Maximum adsorption capacity (q_m) of the CTW was found to be 85.32 mg/g at optimum pH 2 in 120 minutes. The adsorption on CTW was well fitted to the Langmuir isotherm and the kinetic data is consistent with the pseudo-second order kinetic model. The findings suggest that CTW could be an efficient and promising adsorbent for the removing Cr(VI) from aqueous solution.

Mixing properties of liquid Al-Au alloys

Shashit Kumar Yadav, Upendra Mehta, Ram Prasad Koirala, Ramesh Kumar Gohivar — Wed, 05 Apr 2023 00:00:00 +0000

The thermodynamic and structural properties of liquid Al-Au alloy have been studied in frame-work of R-K polynomial using temperature-dependent energy interaction parameters at different temperatures. Thermodynamic properties, excess free energy of mixing and activity, and in structural properties, concentration fluctuation in long wave-length limit have been computed at temperatures 1338 K, 1500 K and 1600 K. The properties, such as surface tension and surface concentration of the system have been computed at above mentioned temperatures using Butler model. The system shows transformation from segregating to ordering in nature with increase in concentration of Au.

Properties of dust in the North - East part of Perseus Cloud within the open cluster IC 348 using data from IRIS and AKARI

Surakshya Bhattarai, Madhu Sudan Paudel, Shiv Narayan Yadav, Ajay Kumar Jha — Wed, 05 Apr 2023 00:00:00 +0000

In this work, we have studied the dust properties of the North-East part of Perseus cloud having a size of 0.5^o × 0.5^o located at RA (ICRS): 56.14^o DEC (ICRS): +32.15^o, within the Open Cluster IC 348, using IRIS and AKARI data. An isolated region of size 0.39^o×0.23^o in IRIS and 0.34^o×0.16^o in AKARI data is detected within it. The infrared fluxes extracted using Aladin v11.0 are used to study the dust temperature and dust mass. The distance of the selected dust structure is calculated using Gaia EDR3, which is 309.98 pc. The infrared flux density is found to be increased for long-wavelength data. The average dust color temperature calculated from short-wavelength IRIS data is more than that calculated from long-wavelength AKARI data, which are 26.34 K±0.11 K for IRIS and 17.63 K±0.02 K for AKARI data. The mass of dust within the entire dust structure is 0.06 M_ʘfor IRIS data and 37.44 M_ʘfor AKARI data. Jeans mass for isolated region gives contradictory results in two surveys, for IRIS survey total mass is smaller than Jeans mass but for AKARI survey the total mass is larger than the Jeans mass. A good correlation between infrared fluxes is noticed for linear regression. The study background sources observed from the SIMBAD database explore the large number of stars, X-ray sources, YSOs, etc., embedded within the dust structure; some of them are responsible for dust heating and some for the contribution of dust mass. The contour map shows the identical distribution between infrared fluxes, dust color temperature and Planck’s function and dissimilar distribution between dust mass and visual extinction in IRIS and AKARI data. The high temperature at the central region suggests that the core of dust structure is thermally active, radiating the large thermal radiation in comparison to the outer region.

Analysis of phytochemicals and biological activities of rhizome of Curcuma longa, aerial parts of Centella asiatica, and corn silk of Zea mays

Ayusha Hyaunmikha, Bimala Subba — Wed, 05 Apr 2023 00:00:00 +0000

Nepal is a storehouse of medicinal plants. Medicinal plants like the rhizome of Curcuma longa, the aerial part of Centella asiatica, and corn silk of Zea mays were used traditionally as medicine for diseases like inflammation, hepatic disorders, cough, etc. In this study, these selected plants were subjected to the analysis of phytochemical constituents, and biological activities following standard methods. Phytochemical analysis of the methanolic extract of these selected plants revealed the presence of different chemical constituents such as polyphenols, flavonoids, glycosides, quinones, saponins, and tannins. C. longa rhizomes also showed the strongest DPPH radical scavenging activity with IC₅₀ of 55.06 µg/mL which was very close to standard ascorbic acid (49.09 µg/mL) than that of the aerial part of C. asiatica (72.56µg/mL) and corn silk of Z. mays (131.96 µg/mL). Total phenolic and total flavonoid content was found highest in C. longa with the values of 195.95 ± 0.899 mg GEA/g and 56.45 ±4.056 mg QE/g respectively. The phenolic and flavonoid content of methanolic extract of aerial parts of C. asiatica was found to be 110.78 ± 1.984 mg GEA/g and 30.00 ± 2.358 mg QE/g and corn silk of Z. mays were found to be 65.92 ± 1.244 mg GEA/g and 18.50 ±1.424 mg QE/g respectively. The methanolic extract of rhizomes of C. longa exhibited high α-amylase inhibitory activity with IC₅₀ values of 382.30 µg/mL than that of C. asiatica with IC₅₀ value of 520.48 µg/mL and Z. mays with IC₅₀ value 593.09 µg/mL.