Nonplanar ion acoustic solitary waves with superthermal electrons and positrons

The properties of cylindrical and spherical ion acoustic solitary waves (IASWs) are investigated in a three-component unmagnetized, collisionless plasma consisting of warm ion fluid and superthermally distributed electrons and positrons in a nonplanar cylindrical or spherical geometry. Using the reductive perturbation technique, the nonplanar cylindrical and spherical Korteweg-de Vries (KdV) equations are derived. The effects of spectral index of electron and positron, and other plasma parameters are studied. It is found that both negative as well as positive solitary potential structures are formed in nonplanar geometries. The numerical solution shows that amplitude of the soliton is large in spherical geometry in comparison with cylindrical geometry. Numerical results indicate that the amplitude of the soliton is large in spherical geometry in comparison with cylindrical geometry.     

Determination of nitrogen dioxide in ambient air employing diffuse reflectance Fourier transform infrared spectroscopy

This paper presents the development of a simple and precise analytical method for the determination of nitrogen dioxide in ambient air. In this method nitrogen dioxide is determined in the form of nitrite. The determination of nitrogen dioxide needs no reagents except for a solution of sodium hydroxide mixed with sodium arsenite (NaOH–Na₂As₂O₃) which is used as an absorbing reagent for trapping the nitrogen dioxide from the atmosphere in the form of nitrite, i.e., a prior analysis step. The determination of submicrogram levels of nitrogen dioxide is based on the selection of a strong and sharp quantitative analytical peak at 1380 cm^− 1 using diffuse reflectance infrared spectroscopy (DRS-FTIR). The limit of detection (LOD) and the limit of quantification of the method are found to be 0.008 μg g^− 1 NO₂⁻ and 0.05 μg g^− 1 NO₂⁻, respectively. The precision in terms of standard deviation and relative standard deviation value at a level of 2 μg NO₂⁻ / 0.1 g KBr for n = 10 is found to be 0.036 μg NO₂⁻ and 1.8%, respectively. The relative standard deviation (n = 10) for the determination of nitrogen dioxide in ambient air was observed to be in the range 2.6–3.8%. The method proposed is time-saving and eliminates the slow and cumbersome steps of pH maintenance of the reaction mixture and color formation of the EPA recommended spectrophotometric and other methods for quantitative determination of nitrogen dioxide.     

Identification of pre-seismic anomalies of soil radon-222 signal using Hilbert–Huang transform

Concentration of Rn-222 in soil has been monitored continuously at Ravangla in the Sikkim Himalayan Region of eastern India for about 7 months from October 2015 to May 2016 to detect earthquake-induced anomalies. The recorded data clearly show that various physical and meteorological parameters influence the soil radon concentration, leading to very complex soil Rn-222 time series. The components due to such external influences have been removed from the present time series, and Hilbert–Huang transform (HHT) applied for analysis of the data. Two radon anomalies caused due to earthquakes of magnitude M _b = 5.0 that occurred on 19 November 2015 and 5 April 2016 within an epicentral distance of 500 km from the monitoring station have been identified on the soil Rn-222 time series. These two precursory anomalies occurred 9 and 10 days, respectively, before the occurrence of the earthquakes. The absence of spurious signals or missing anomalies demonstrates that HHT is advantageous for analysis of nonlinear non-stationary data, and hence, it is a promising technique to analyse soil radon behaviour for predicting the possibility of occurrence of earthquakes.     

The simulation of heavy rainfall episode over Mumbai: impact of horizontal resolutions and cumulus parameterization schemes

In this study, the simulation of an extreme weather event like heavy rainfall over Mumbai (India) on July 26, 2005 has been attempted with different horizontal resolutions using the Advanced Research Weather Research Forecast model version 2.0.1 developed at the National Center for Atmospheric Research (NCAR), USA. The study uses the Betts–Miller–Janjic (BMJ) and the Grell–Devenyi ensemble (GDE) cumulus parameterization schemes in single and nested domain configurations. The model performance was evaluated by examining the different predicted parameters like upper and lower level circulations, moisture, temperature, and rainfall. The large-scale circulation features, moisture, and temperature were compared with the National Centers for Environmental Prediction analyses. The rainfall prediction was assessed quantitatively by comparing rainfall from the Tropical Rainfall Measuring Mission products and the observed station values reported in the Indian Daily Weather Reports from India Meteorological Department (IMD). The quantitative validation of the simulated rainfall was done by calculating the categorical skill scores like frequency bias, threat scores (TS), and equitable threat scores (ETS). It is found that in all simulations, both in single and nested domains, the GDE scheme has outperformed the BMJ scheme for the simulation of rainfall for this specific event.     

Fractionation of oxygen isotopes in phosphate during its interactions with iron oxides

Iron (III) oxides are ubiquitous in near-surface soils and sediments and interact strongly with dissolved phosphates via sorption, co-precipitation, mineral transformation and redox-cycling reactions. Iron oxide phases are thus, an important reservoir for dissolved phosphate, and phosphate bound to iron oxides may reflect dissolved phosphate sources as well as carry a history of the biogeochemical cycling of phosphorus (P). It has recently been demonstrated that dissolved inorganic phosphate (DIP) in rivers, lakes, estuaries and the open ocean can be used to distinguish different P sources and biological reaction pathways in the ratio of ¹⁸O/¹⁶O (δ¹⁸O_P) in PO₄³⁻. Here we present results of experimental studies aimed at determining whether non-biological interactions between dissolved inorganic phosphate and solid iron oxides involve fractionation of oxygen isotopes in PO₄. Determination of such fractionations is critical to any interpretation of δ¹⁸O_P values of modern (e.g., hydrothermal iron oxide deposits, marine sediments, soils, groundwater systems) to ancient and extraterrestrial samples (e.g., BIF’s, Martian soils). Batch sorption experiments were performed using varied concentrations of synthetic ferrihydrite and isotopically-labeled dissolved ortho-phosphate at temperatures ranging from 4 to 95 °C. Mineral transformations and morphological changes were determined by X-Ray, Mössbauer spectroscopy and SEM image analyses.Our results show that isotopic fractionation between sorbed and aqueous phosphate occurs during the early phase of sorption with isotopically-light phosphate (P¹⁶O₄) preferentially incorporated into sorbed/solid phases. This fractionation showed negligible temperature-dependence and gradually decreased as a result of O-isotope exchange between sorbed and aqueous-phase phosphate, to become insignificant at greater than ∼100 h of reaction. In high-temperature experiments, this exchange was very rapid resulting in negligible fractionation between sorbed and aqueous-phase phosphate at much shorter reaction times. Mineral transformation resulted in initial preferential desorption/loss of light phosphate (P¹⁶O₄) to solution. However, the continual exchange between sorbed and aqueous PO₄, concomitant with this mineralogical transformation resulted again in negligible fractionation between aqueous and sorbed PO₄ at long reaction times (>2000 h). This finding is consistent with results obtained from natural marine samples. Therefore, ¹⁸O values of dissolved phosphate (DIP) in sea water may be preserved during its sorption to iron-oxide minerals such as hydrothermal plume particles, making marine iron oxides a potential new proxy for dissolved phosphate in the oceans.     

Atmospheric ionic species in PM2.5 and PM1 aerosols in the ambient air of eastern central India

This study elucidates the characteristics of ambient PM_2.5 (fine) and PM₁ (submicron) samples collected between July 2009 and June 2010 in Raipur, India, in terms of water soluble ions, i.e. Na⁺, NH ₄ ⁺ , K⁺, Mg²⁺, Ca²⁺, Cl^?, NO ₃ ^? and SO ₄ ^2? . The total number of PM_2.5 and PM₁ samples collected with eight stage cascade impactor was 120. Annual mean concentrations of PM_2.5 and PM₁ were 150.9?±?78.6 μg/m³ and 72.5?±?39.0 μg/m³, respectively. The higher particulate matter (PM) mass concentrations during the winter season are essentially due to the increase of biomass burning and temperature inversion. Out of above 8 ions, the most abundant ions were SO ₄ ^2? , NO ₃ ^? and NH ₄ ⁺ for both PM_2.5 and PM₁ aerosols; their average concentrations were 7.86?±?5.86 μg/m³, 3.12?±?2.63 μg/m³ and 1.94?±?1.28 μg/m³ for PM_2.5, and 5.61?±?3.79 μg/m³, 1.81?±?1.21 μg/m³ and 1.26?±?0.88 μg/m³ for PM₁, respectively. The major secondary species SO ₄ ^2? , NO ₃ ^? and NH ₄ ⁺ accounted for 5.81%, 1.88% and 1.40% of the total mass of PM_2.5 and 11.10%, 2.68%, and 2.48% of the total mass of PM₁, respectively. The source identification was conducted for the ionic species in PM_2.5 and PM₁ aerosols. The results are discussed by the way of correlations and principal component analysis. Spearman correlation indicated that Cl^? and K⁺ in PM_2.5 and PM₁ can be originated from similar type of sources. Principal component analysis reveals that there are two major sources (anthropogenic and natural such as soil derived particles) for PM_2.5 and PM₁ fractions.     

On convective entrainment in a mass flux cumulus parameterization

Summary A new entrainment/detrainment formulation in the Tiedtke’s mass flux cumulus parameterization is discussed here. Apart from validating it with observations both in one and three dimensional cases, it is also evaluated in the light of the results from the original Tiedtke scheme and another mass flux scheme due to Emanuel. The proposed analytical profiles of entrainment and detrainment, easier to implement in any mass flux scheme, give reasonable results in GCM experiments.     

Numerical Analysis of Multi Layer Geosynthetic-Reinforced Granular Bed over Soft Fill

In this paper, considering the plain strain conditions, a numerical study has been conducted to investigate the behavior of multi layer geosynthetic-reinforced granular bed overlying a soft soil using the Fast Lagrangian Analysis of Continua (FLAC) program. The granular fill, soft soil, and geosynthetic reinforcements are considered as linear elastic materials. The geosynthetic reinforcements are modeled as cable elements fully bonded with the surrounding soil, thus neglecting any slip. The results obtained from the present investigation showed very close agreement when compared with the results of finite element analysis and lumped parameter modeling. The distribution of vertical, lateral and shear stresses in the soil are greatly affected as the number of reinforcement layers is increased. If the tensile stiffness of geosynthetic layers increases and its value is no more than 4,000–5,000 kN/m, the settlement of the reinforced foundation decreases significantly. The reduction in settlement is insignificant when the tensile strength of the geosynthetics exceed the above value.     

A nonlinear polar coordinate shallow water model for tsunami computation along North Sumatra and Penang Island

A nonlinear shallow water model in cylindrical polar coordinate system is developed, using an explicit finite difference scheme with a very fine resolution, to compute different aspects of tsunami at North Sumatra and the adjacent island Simeulue in Indonesia, and the Penang Island in Peninsular Malaysia. The pole of the frame is placed on the mainland of Penang (100.5°E) and the model area extends up to the west of Sumatra (87.5°E). The model is applied to simulate the propagation of tsunami wave towards North Sumatra, Simeulue and Penang Islands associated with Indonesian tsunami of 26 December 2004. The model is also applied to compute water levels along the coastal belts of those islands. Computed and observed water level data are found to be in good agreement and North Sumatra is found to be vulnerable for very high surges. The computed and observed arrival times of high surges are also in reasonable agreement everywhere. Further studies are carried out to investigate the effect of convective terms and it is found that their effects are insignificant in tsunami propagation and weakly significant for wave amplitude very near to the coast.     

Nonlinear analysis of multilayer extensible geosynthetic-reinforced granular bed on soft soil

The paper presents a model for the analysis of granular foundation beds reinforced with several geosynthetic layers. Such reinforced granular beds are often placed on soft soil strata for an efficient and economical transfer of superstructure load. The granular bed is modeled by the Pasternak shear layer and the geosynthetic reinforcement layers by stretched rough elastic membranes. The soft soil is represented by a series of nonlinear springs. The reinforcement has been considered to be extensible and it is assumed that the deformation at the interface of the reinforcements and soil are same. The nonlinear behavior of the granular bed and the soft soil is considered. Plane strain conditions are considered for the loading and reinforced foundation soil system. An iterative finite difference scheme is applied for obtaining the solution and results are presented in nondimensional form. The results from the proposed model are compared to the results obtained for multilayer inextensible geosynthetic reinforcement system. Significant reduction in the settlement has been observed when the number of reinforcement layer is increased. In case of inextensible reinforcements as the number of reinforcement layer is increased the settlement is decreased with a decreasing rate, but in case of extensible reinforcement the reduction rate is almost constant. Nonlinear behavior of the soft soil decreases as number of reinforcement layer is increased. The effect of the stiffness of the geosynthetic layer on the settlement response becomes insignificant for multilayer reinforced system, but the mobilized tension in the reinforcement layers increases as the stiffness of the geosynthetic layers increases.