Himalayan Physics 2021-10-08T15:10:46+00:00 Mr Kul Prasad Dahal Open Journal Systems <p>Published by the Department of Physics, Prithvi Narayan Campus, Pokhara and the Nepal Physical Society, Western Regional Chapter, Nepal. Full text articles available.</p> Metal Organic Frameworks (MOFs) as efficient carrier for targeted nanodrug delivery 2021-09-29T16:07:26+00:00 Ravi Karki Dipak Adhikari Kapil Adhikari Nurapati Pantha <p>A controllable and targeted drug delivery system development is imperative and important to reduce side effects and enhance the therapeutic efficacy of drugs. Metal-organic frameworks (MOFs), an emerging type of hybrid porous materials synthesized from metal ions or clusters abridged by organic linkers. They have attracted increasing attention in the recent years owing to the unique physical structures possessed, and the potential for wide range of applications. The superior properties of MOFs, such as well-defined pore aperture, tailorable composition and structure, tunable size, versatile functionality, high agent loading, and improved biocompatibility, have made them promising candidates as drug delivery hosts. MOFs for drug encapsulation and delivery is of great interest and many very promising results have been found, indicating that these porous solids exhibit several advantages over existing systems. This review highlights the recent advances in the synthesis, functionalization, and applications of MOFs in nanodrug delivery, and has classified them using drug loading strategies.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2021 A Density Functional Theory Study on Paracetamol-Oxalic Acid Co-Crystal 2021-09-30T11:48:21+00:00 Punya Paudel Krishna Raj Adhikari Kapil Adhikari <p>Paracetamol (PCA) has two well-known polymorphic forms, monoclinic (form I) and orthorhombic (form II). The parallel packing of flat hydrogen bonded layers in the metastable form II results in compaction properties superior to the thermodynamic stable form I which contains corrugated hydrogen bonded layers of molecules. In this study, the structure of Paracetamol (PCA)-Oxalic acid (OXA) co-crystal has been analyzed and found layered structure similar to PCA form II which enhance ability to form tablet. The Density Functional Theory (DFT) has been conducted to find some physicochemical properties of co-crystal. It was observed that the lattice energy of co-crystal is more than that of PCA form II showing more stability on co-crystal. The energy gap between highest occupied molecular orbital and lowest unoccupied molecular orbital (HOMO-LUMO gap) in co-crystal was found less than PCA form II showing bigger enhancement of reactivity.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics First-principles study of C cites vacancy defects in water adsorbed Graphene 2021-09-30T12:38:39+00:00 Hari Krishna Neupane Narayan Prasad Adhikari <p>&nbsp;The electronic and magnetic properties of water adsorbed graphene (w<sub>ad </sub>– G), single carbon (1C) atom vacancy defects in water adsorbed graphene (1C<sub>atom-vacancy </sub>– w<sub>ad </sub>– G) and double carbon (2C) atoms vacancy defects in water adsorbed graphene (2C<sub>atom-vacancy </sub>– w<sub>ad </sub>– G) materials are studied by first-principles calculations within the frame work of density functional theory (DFT) using computational tool Quantum ESPRESSO (QE) code. We have calculated the binding energy of w<sub>ad </sub>– G, 1C<sub>atom-vacancy </sub>– w<sub>ad </sub>– G and 2C<sub>atom-vacancy </sub>– w<sub>ad </sub>– G materials, and then found that non-defects geometry is more compact than vacancy defects geometries. From band structure calculations, we found that w<sub>ad </sub>– G is zero band gap semiconductor, but 1C<sub>atom-vacancy </sub>– w<sub>ad </sub>– G and, 2C<sub>atom-vacancy </sub>– w<sub>ad </sub>– G materials have metallic properties. Hence, zero band gap semiconductor changes to metallic nature due to C sites vacancy defects in its structures. We have investigated the magnetic properties of w<sub>ad </sub>– G and its C sites vacancy defects materials by using Density of States (DOS) and Partial Density of States (PDOS) calculations. We found that w<sub>ad </sub>– G is non- magnetic material. 1C atom vacancy defects in graphene surface of w<sub>ad </sub>– G is induced magnetization by the re-bonding of two dangling bonds and acquiring significant magnetic moment (0.11 µB/ cell) through remaining unsaturated dangling bond. But, 2C atoms vacancy defects in graphene surface of w<sub>ad </sub>– G induced low value of magnetic moment (+0.03 µB/ cell) than 1C atom vacancy defects in structure, which is due to no dangling bonds present in the structure. Therefore, non-magnetic, w<sub>ad </sub>– G changes to magnetic, 1C<sub>atom-vacancy </sub>– w<sub>ad </sub>– G and, 2C<sub>atom-vacancy </sub>– w<sub>ad </sub>– G materials due to C sites vacancy defects in w<sub>ad </sub>– G structure. The 2p orbital of carbon atoms has main contribution of magnetic moment in defects structures.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics Diffusion of fructose in water: a molecular dynamics study 2021-09-30T13:02:39+00:00 Santosh Bhusal Nurapati Pantha <p>Present work carries the molecular dynamics (MD) simulation to study the self-diffusion coefficients of fructose (C<sub>6</sub>H<sub>12</sub>O<sub>6</sub>) and SPC/E (Extended Simple Point Charge) water (H<sub>2</sub>O) along with their binary diffusion coefficients at different temperature (298.15 K, 303.15 K, 308.15 K and 312.15 K). A dilute solution of 3 molecules of fructose (solute, mole fraction 0.0018) and 1624 molecules of water (solvent, mole fraction 0.9982) has been taken for making it relevant to the previously reported experiment. The structural analysis of the mixture has been estimated by using the radial distribution function (RDF) of its constituents. Mean square displacement (MSD) and Einstein’s relation have been used to find the self-diffusion coefficients of both the solute and solvent. Furthermore, Darken’s relation finds the binary diffusion coefficients. The temperature dependence of diffusion coefficients follows the Arrhenius behavior which further calculates activation energy of diffusion. The results from the present work agree well with the previously reported experimental values.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics Study of Affecting Factors of Meteorological Parameters on Solar Radiation on Pokhara 2021-09-30T13:02:40+00:00 Prakash M. Shrestha Jeevan Regmi Usha Joshi Khem N. Poudyal Narayan P. Chapagain Indra B. Karki <p>Solar radiation data are of great significance for solar energy systems. This study aimed to estimate monthly and seasonal average of daily global solar radiation on a horizontal surface in Pokhara (Lat.:28.21<sup>o </sup>N, Long.: 84<sup>o</sup> E and alt. 827 m above sea level), Nepal, by using CMP6 pyranometer in 2015. As a result of this measurement, monthly and yearly mean solar radiation values were 20.37 ±5.62 MJ/m<sup>2</sup>/ day in May, 11.37 ± 2.38 MJ/m<sup>2</sup>/ day in December and 16.82 ±5.24 MJ/m<sup>2</sup>/ day respectively. Annual average of clearness index and extinction coefficient are 0.51±0.14 and 0.53±0.31 respectively. There is positive correlation of maximum temperature and negative correlation of with global solar radiation.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics Variation of mean value of velocity of ion with different obliqueness of magnetized plasma sheath 2021-09-30T13:19:29+00:00 B.R. Adhikari H.P. Lamichhane R. Khanal <p>Plasma sheath, which forms between a material wall and incoming plasma, plays an important role in controlling particle and energy fluxes to the wall. The problem of plasma sheath is one of the oldest in plasma and still draws attention, especially in magnetized plasmas. In this work velocity of ions in a magnetized plasma sheath has been studied using a kinetic trajectory simulation model for varying obliqueness of the field. Any change in obliqueness of the field causes the velocities to change. The change in mean value of the component normal to the wall is comparatively small whereas the other two components of velocity vary sinusoidally, nearly complementary to each other with nearly equal amplitudes.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics Study of Dust Properties of two Far Infrared Cavities near by Asymptotic Giant Branch stars under Infrared Astronomical Satellite Maps 2021-10-02T03:14:19+00:00 M. Tiwari S.P. Gautam A. Silwal S. Subedi A. Paudel A.K. Jha <p>The physical properties such as dust color temperature, dust mass, visual extinction, and Planck function with their distribution in the core region of two far-infrared cavities, namely FIC16-37 (size ~ 4.79 pc x 3.06 pc) located at R.A. (J2000): 16<sup>h</sup> 33<sup>m</sup> 57.25<sup>s</sup> &amp; Dec. (J2000): -37<sup>d</sup> 47<sup>m</sup> 04.3<sup>s</sup>, and FIC12-58 (size ~ 22.54 pc x 14.84 pc) located at R.A. (J2000): 12<sup>h</sup> 52<sup>m</sup> 50.08<sup>s</sup> &amp; Dec. (J2000): -58<sup>d</sup> 08<sup>m</sup> 55.02<sup>s</sup>, found within a galactic plane -10<sup>o</sup>&nbsp; to +10<sup>o</sup>&nbsp; nearby Asymptotic Giant Branch (AGB) stars namely AGB15-38 (R.A. (J2000): 15<sup>h </sup>37<sup>m</sup> 40.74<sup>s</sup> &amp; Dec. (J2000): -38<sup>d</sup> 20<sup>m</sup> 24.6<sup>s</sup>), and AGB12-57 (R.A (J2000): 12<sup>h</sup> 56<sup>m</sup> 38.50<sup>s</sup> &amp; Dec. (J2000): -57<sup>d</sup> 54<sup>m</sup> 34.70<sup>s</sup>), respectively were studied using Infrared Astronomical Satellite (IRAS) survey. The dust color temperature was found to lie in the range of 23.95 ± 0.25 K to 23.44 ± 0.27 K with an offset about 0.5 K for FIC16-37, and 24.88 ± 0.27 K to 23.63 ± 0.98 K with an offset about 1 K for FIC12-58. The low offset in the dust color temperature indicated the symmetric distribution of density and temperature. The total mass of the cavities FIC16-37 and FIC12-58 were found to be 0.053 M☉ and 0.78 M☉, respectively. The contour plots of mass distribution of both of the cavities was found to follow the cosmological principle, suggesting the homogeneous and isotropic distribution of dust masses. The plot between temperature and visual extinction showed a negative correlation, suggesting that higher temperature has lower visual extinction and vice-versa. The distribution of Planck function along major and minor diameters of both of the cavities was found to be non-uniform, indicating oscillation of dust particles to get dynamical equilibrium. It further suggested the role of pressure-driven events nearby both cavities and suggested that dust particles are not in thermal equilibrium along the diameters.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics An Experimental Study on Irradiated Interface of Silicon 2021-10-01T03:24:40+00:00 Min Raj Lamsal <p>Atomic Force Microscopic (AFM) studies of Mega electron-volt (MeV) ions irradiated silicon surface morphology has been studied to a fluence of 5 x 10<sup>8</sup> ions/cm<sup>2</sup>. Interesting features of cracks of 50 nm in depth and 100 nm in width have been observed on the irradiated surface. The features seemed to have been caused by the irradiation-induced stress in the irradiated regions of the target surface. The observed feature of crack seems to be mainly due to the high electronic energy loss of the irradiated ions on the surface that induces the stress in it. It confirms that the coarseness of the microstructure of a material directly affect the mechanical properties.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics Calculation of energy loss of proton beam on thyroid tumor 2021-10-02T03:49:49+00:00 K. Giri B. Paudel B.R. Gautam <p>Proton beam therapy is an emerging technique in radiotherapy. The Bragg peak of a proton enables it to lose most of its energy to the targeted tissue like tumor cells, with less impact of healthy tissues and organs. This property of a proton beam makes it ideal for clinical applications. When organ safekeeping is our priority then proton beam therapy is the most effective tool to damage nearby affected tissues. For efficient treatment planning in thyroid tumor, the maximal energy loss of proton beam in its tissues must be exactly calculated. The method of computer simulation is employed for the calculation of energy loss by energized proton beam irradiation on thyroid tumor at a depth of 22 mm. The stopping power and range data agrees with standard reference data. Of the 50 MeV energy of proton beam, the most of the energy is absorbed on various layers viz. skin, adipose tissue, skeletal muscles and thyroid which are approximately 1.5 MeV, 5.3 MeV, 10.5 MeV and 33.5 MeV respectively. In total 99.96% of energy of proton beam is absorbed by the targeted tissues.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics Study of noise level status at different rice mills in Surkhet Valley, Nepal 2021-10-02T03:57:09+00:00 Dharma Raj Paudel Hom Nath Baral <p>Noise is an unwanted sound. High-intensity noise has a detrimental effect on the health conditions. This study aims to measure noise intensity inside different rice mills in Surkhet valley. Rice mills are spread all over Nepal from village to town. They are among the noisiest environment. Twelve mills are selected at different locations inside the valley. Noise intensities are determined by using a sound-level meter and the health conditions of the workers are concluded using a questionnaire technique. The study shows that noise level status is well above the recommended level set by the World Health Organization (WHO). It also concludes statistically that high intensity of sound causes hearing problems in workers.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics Elliptically polarized laser assisted elastic electron-hydrogen atom collision and differential scattering cross-section 2021-10-02T04:05:20+00:00 Kishori Yadav S.P. Gupta J.J. Nakarmi <p>In the present study, we have investigated scattering of an electron by hydrogen atoms in the presence of the elliptical polarized laser field. We have discussed the polarization effect of laser field on hydrogen atom and effect of the resulted polarized potential on differential scattering cross-section is studied. We assume the scattered electrons having kinetic energy (~3000 eV) and laser field of moderate field strength because it is permitted to treat the scattering process in first Born approximation and the scattering electron was described by Volkov wave function. We found that the differential scattering cross-section area increases with the increase of the kinetic energy of the incident electron and there is no effect of changing the value of polarizing angle on the differential cross-section with kinetic energy. We observed that differential scattering cross-section in elliptical polarization in the high energy region depends upon the laser intensity and the incident energy for a linearly polarized field.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics Geodynamics of Gorkha earthquake (Mw 7.9) and its aftershocks 2021-10-02T04:10:25+00:00 Ram Krishna Tiwari H. Paudyal Paudyal <p>A devastating earthquake (Mw 7.9) occurred in Gorkha region on 25 April 2015 caused loss of 8964 human lives and huge property in Central Nepal and adjoining region. Sequence of aftershocks, including four having magnitude greater than 6 occurred within 18 days, confined in a distance of about 150 km from Gorkha to Dolakha. Main shock and its aftershocks series confined in a depth range of 12 to 21 km. In this study, using 11 CMT solutions of earthquakes with magnitude 5 and above, occurred between 2014.12.18 and 2016.11.27 within 84<sup>o</sup> to 87<sup>o</sup> E and 27<sup>o</sup> to 29<sup>o</sup> N, we analyze faulting pattern of the Gorkha earthquake and associated large aftershocks to reveal recent geodynamics pattern in the central Himalayan region. Nodal planes of mainshock and four large aftershocks have east west orientation and shallow dip (6<sup>o</sup> to 23<sup>o</sup>) towards north, exhibit strong thrust mechanism. Smaller aftershocks scattered within 150 km long rupture zone along NW to SE direction show similar mechanism with large thrust component. Collective dips of nodal plane of ten events indicate northward under thrusting of the Indian plate at shallow angle, though the nodal plane of individual event differ slightly in their orientation. The cross-sectional study of focal mechanism shows the clustering of the seismic events at different depth with diverse faulting pattern. It is inferred that recent seismic activity in central Nepal region is dominated by thrust faulting and the mechanism which were responsible for the formation of Himalaya are still continuing.</p> 2020-12-31T00:00:00+00:00 Copyright (c) 2020 Himalayan Physics