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Kinetic particle simulations in a global toroidal geometry
No full textThe gyrokinetic toroidal code has been upgraded for global simulations by coupling the core and scrape-off layer regions across the separatrix with field-aligned particle-grid interpolations. A fully kinetic particle pusher for high frequency waves (ion cyclotron frequency and beyond) and a guiding center pusher for low frequency waves have been implemented using cylindrical coordinates in a global toroidal geometry. The two integrators correctly capture the particle orbits and agree well with each other, conserving energy and canonical angular momentum. As a verification and application of this new capability, ion guiding center simulations have been carried out to study ion orbit losses at the edge of the DIII-D tokamak for single null magnetic separatrix discharges. The ion loss conditions are examined as a function of the pitch angle for cases without and with a radial electric field. The simulations show good agreement with past theoretical results and with the experimentally observed feature in which high energy ions flow out along the ion drift orbits and then hit the divertor plates. A measure of the ion direct orbit loss fraction shows that the loss fraction increases with the ion energy for DIII-D in the initial velocity space. Finally, as a further verification of the capability of the new code, self-consistent simulations of zonal flows in the core region of the DIII-D tokamak were carried out. All DIII-D simulations were performed in the absence of turbulence
Topological Phases in Hydrogenated Group 13 Monolayers
No full textNontrivial topology of Dirac semi-metals, Weyl semimetals, and nodal line semimetals (NLSMs) is delineated by the novel band crossings near the Fermi level in the bulk and the appearance of exotic surface states. Among them, NLSMs have gained immense interest because of the formation of a one-dimensional nodal ring near the Fermi level. Using density functional theory calculations and an effective two-band k.p model, we report that a two-dimensional (2D) NLSM phase can be hosted on hydrogen-passivated gallenene (gallenane) and on other group 13 elements, without inclusion of spin-orbit coupling (SOC). NLSM in these 2D systems is protected by the presence of crystalline symmetry along with inversion symmetry and time-reversal symmetry. In the presence of SOC, aluminane preserves its topological NLSM phase, while in other hydrogenated group 13 monolayers, a gap opens at the nodal point because of relatively stronger SOC effect. On applying tensile strain along with the inclusion of SOC, gallenane evolves into a quantum spin Hall insulator with an indirect band gap of 28 meV. The appearance of long-range dissipationless linearly dispersive helical edge states and a large gap in gallenane makes it promising for room-temperature spintronic applications
Land surface temperature variability across India: a remote sensing satellite perspective
No full textLand surface temperature (LST) plays a key role in the surface energy budget computation and land surface process studies. The Moderate Resolution Imaging Spectroradiometer (MODIS) sensors onboard the Aqua and Terra satellites provide comprehensive global LST estimates at a fine spatial resolution. The MODIS products were recently upgraded to Collection 6, and shown to be more accurate than its predecessor Collection 5 products. In this study, LST and its variability have been examined across India from Collection 6 of the Aqua MODIS data at 0.05 degrees spatial resolution for the period of 2003 to 2017. All-India mean LST characteristics show distinctive features as compared to the well-documented mean characteristics of near-surface air temperature. All land cover types except permanent snow and ice, and cold desert areas exhibit bimodal peaks in seasonal variations of daytime LST. The daytime LST over the coldest and high-altitude regions of northern India shows anomalous positive linear relationship with NDVI at a monthly scale. However, monthly domain-mean daytime LST of cropland regions is largely negatively correlated with NDVI as compared to other land cover types. Results reveal that about 17% of the Indian landmass received its hottest LST during 2010 followed by 2016. Linear trend analysis for the 15-year period of mean annual LST shows a decrease in diurnal temperature range over most parts of the country due to rather rapid increase in nighttime LST than daytime LST, similar as changes in near-surface air temperature across the country
Diffraction by ruled gratings with variable spacing: fundamental method of intensity calculation
No full textA regular diffraction grating produces intensity patterns that combine waves coming through equispaced slits, so that the waves emerging from any two neighboring slits have identical phase differences. In this paper, we calculate the degradation in the intensity pattern when the grating has irregular spacing. The model of randomness considers the grating spacing and openings as being created by a ``random walk.'' The resolving power of the grating is evaluated in relation to the D lines of sodium. It is shown that as the number of rulings increases, the uniformity of their spacing becomes more important in precision spectroscopic measurements, such as in astrophysical spectroscopy
Synthesis, characterization, and antioxidant activity of thymol-based paracetamol analogues
No full textThymol (2-isopropyl-5-methylphenol) is an important monoterpene phenol occurring in the essential oils isolated from Thymus vulgaris, Thymus zygis, Thymus hyemalis, etc. Thymol and its derivatives show various activities such as antioxidant, antiinflammatory, antibacterial, and antifungal effects. In the present study, a set of new benzamide derivatives (4a-e), which are structurally similar to paracetamol, were synthesized from thymol using a green synthetic approach and characterized by Fourier-transform infrared (FT-IR) and H-1 and C-13 nuclear magnetic resonance (NMR) spectroscopies, liquid chromatography-mass spectrometry (LC-MS), and X-ray single-crystallographic analysis for derivative 4c. These derivatives were subjected to antioxidant testing by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and antibacterial testing against five microorganisms. Molecular docking studies of all the compounds indicated that they are good inhibitors of heme oxygenase-1. These results extend the development of thymol-based benzamide scaffolds as promising antioxidant agents
vdWP-FL: An Improved Thermodynamic Theory for Gas Hydrates with Free-Energy Contributions due to Hydrate Lattice Flexibility
No full textA modification of the original van der Waals and Platteuw (vdWP) theory that accounts for free-energy contributions due to the vibrational and librational movement of water molecules in the hydrate lattice is presented. The modified theory is labeled vdWP-FL. In our previous work, we had presented a method to compute these contributions to the partition function. This was successfully applied to simulated phase equilibria of various gas hydrates. In this work, we apply the vdWP-FL theory to experimental data of gas hydrate phase equilibria and recompute the guest-water potentials. The empty hydrate reference properties are directly computed from molecular simulations. In this implementation of the vdWP-FL theory, only one parameter per guest molecule per cavity type is regressed from the experimental data on gas hydrates. The gas hydrates chosen for this study are methane, ethane, carbon dioxide, propane, iso-butane, and the hydrates formed by their binary mixtures. The vdWP-FL theory gives accurate predictions of the dissociation temperatures and pressures of the above gas hydrates and their mixtures. In addition, it also predicts the hydrate cage occupancy accurately
Paper Stacks for Uniform Rehydration of Dried Reagents in Paper Microfluidic Devices
No full textSpatially uniform reconstitution of dried reagents is critical to the function of paper microfluidic devices. Advancing fluid fronts in paper microfluidic devices drive (convect) and concentrate rehydrated reagents to the edges, causing steep chemical gradients and imperfect mixing. This largely unsolved problem in paper microfluidics is exacerbated by increasing device dimensions. In this article, we demonstrate that mixing of dried reagents with a rehydrating fluid in paper microfluidics may be significantly enhanced by stacking paper layers having different wicking rates. Compared to single-layer paper membranes, stacking reduced the ``non-reactive area'', i.e. area in which the reconstituted reagents did not interact with the rehydrating fluid, by as much as 97% in large (8 cm x 2 cm) paper membranes. A paper stack was designed to collect similar to 0.9 ml liquid sample and uniformly mix it with dried reagents. Applications of this technology are demonstrated in two areas: (i) collection and dry storage of sputum samples for tuberculosis testing, and (ii) salivary glucose detection using an enzymatic assay and colorimetric readout. Maximizing the interaction of liquids with dried reagents is central to enhancing the performance of all paper microfluidic devices; this technique is therefore likely to find important applications in paper microfluidics
Endoplasmic reticulum targeted chemotherapeutics: the remarkable photo-cytotoxicity of an oxovanadium(iv) vitamin-B6 complex in visible light (vol 50, pg 5590, 2014)
No full textCorrection for `Endoplasmic reticulum targeted chemotherapeutics: the remarkable photo-cytotoxicity of an oxovanadium(iv) vitamin-B6 complex in visible light' by Samya Banerjee et al., Chem. Commun., 2014, 50, 5590-5592
Regional stochastic GMPE with available recorded data for active region - Application to the Himalayan region
No full textNew ground motion prediction equation for the active Himalayan region for a wide range of moment magnitude (M-w 4-9) and distance (10-750 km) is developed. For simulating the synthetic ground motions; source, path, and site terms are derived using the Fourier amplitude spectrum of the recorded ground motion data. Uncertainty of input parameters is propagated through simulation by random sampling of the corresponding distribution of input parameters. Synthetic and recorded data are regressed using random-effect maximum likelihood regression algorithm by determining the compatible functional form. Sensitivity analysis is used in determining the impact of uncertainty of each input parameter on standard deviation of the regression residuals about the median prediction equation. Major contribution to total uncertainty is from Kappa factor in case of within-event terms and from stress drop in case of event-to-event variability. Predicted and recorded response spectra is matching within +/- 1 standard deviation for the entire period range