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Mahanty, Biswanath,Kim, Subin,Kim, Chang Gyun Springer-Verlag 2013 Microbial ecology Vol.65 No.3
<P>To evaluate how native soil microorganism and nutrients interact in a bioaugmented or biostimulated calcification process, batch experiments were conducted in saturated soil extract either amended with Bacillus pasteurii and/or NB-NH4Cl media (nutrient broth, 3.0 g/L; NH4Cl, 10.0 g/L; NaHCO3, 2.12 g/L). The NB-NH4Cl medium was chosen out of three potential candidates, where B. pasteurii precipitated the maximum amount of calcium (>95 %) as calcite in 12 h of incubation. The addition of B. pasteurii into saturated soil extract marginally improved the calcification to 4.26 % compared to the unamended control (3.2 %). Calcification with B. pasteurii in autoclaved soil extract was even better (18.75 %). However, the addition of the NB-NH4Cl medium into the soil extract could significantly improve the calcification irrespective of whether B. pasteurii was added (88.46 %) or not (77.04 %). It suggests that soil microbial activity was not limiting even though soil nutrient was inadequate. It also indicates a possible negative interaction between soil microorganisms and B. pasteurii under nutrient-limited conditions.</P>
Effect of soil acidification on <i>n</i>‐hexane extractable PAH fractions
Mahanty, B.,Kim, C.‐,G. Blackwell Publishing Ltd 2016 European journal of soil science Vol.67 No.1
<P><B>Summary</B></P><P>This study was designed to assess the effect of soil acidification on the extractability of polycyclic aromatic hydrocarbons (PAHs) distributed across various soil organic matter fractions. Phenanthrene, anthracene and pyrene (each at 3.2 mg kg<SUP>−1</SUP> soil) were applied to a natural soil and to an artificially acidified soil, and the samples were incubated for 10 days. Several solvents were tested for the recovery of PAHs from soil, and <I>n</I>‐hexane was the best for extraction efficiency. Soil was treated with hydroxypropyl‐β‐cyclodextrin (HPCD), pyrophosphate or pyrophosphate‐HPCD in sequence followed by the recovery of residual PAHs in <I>n</I>‐hexane. Recovery of PAHs by a single‐step non‐exhaustive <I>n</I>‐hexane extraction from acidified soil was significantly less than that from the original non‐acidified soil (<I>P</I> = 0.023). Based on the sequential extraction, the pool of <I>n</I>‐hexane extractable PAHs was classified operationally into four fractions: one portion that is shared with HPCD (HS), one shared with pyrophosphate (PS) and one with both HPCD and pyrophosphate (HPS), and one that is not shared (US). The sum of PAHs recovered from acidified soil was significantly less than that for non‐acidified soil when compared for PS fractions (5.37 and 14.42%, respectively, with <I>P</I> = 0.003) or US fractions (47.76 and 54.00%, respectively, <I>P</I> < 0.001). In contrast, soil acidification increased the sum of PAHs recovered in HS (from 4.29% (non‐acidic) to 5.39% (acidified), <I>P</I> = 0.014) and HPS fractions (from 23.8% (non‐acidic) to 30% (acidified), <I>P</I> < 0.001). The results suggest that soil acidification reduces the pool of PAHs that is accessible exclusively by organic solvents, but increases the fraction that can be extracted with HPCD or pyrophosphate or both. Spectroscopic analysis (Fourier transform infrared spectroscopy and ultraviolet–visible analysis) of isolated humic substances reveals their greater aromaticity when extracted from acidified soil, which might explain the larger proportion of surface‐adsorbed PAHs in soil organic matter that can be dissolved by an aqueous extractant.</P>
Mahanty, B.,Yoon, S.U.,Kim, C.G. Elsevier 2016 Chemometrics and intelligent laboratory systems Vol.154 No.-
Spectrophotometric quantitation of formazan in tetrazolium-based nanoparticle (NP) toxicity assay requires a robust calibration model immune to optical interference. For the first time, variant of partial least squares (PLS) regression models, such as, full-spectrum (250-700nm) PLS, interval PLS (iPLS), backward interval PLS (biPLS), and synergy interval PLS (siPLS) models have been adopted for formazan quantitation. Models were evaluated based on root mean square error of cross-validation (RMSECV), and prediction (RMSEP). The spectral variables in optimal iPLS, biPLS and siPLS models, as well as variables retained above a selection frequency threshold (for all intervals), were further refined in a genetic algorithm (GA). The results suggest that the optimal biPLS (140 variables, 5 LVs, RMSECV: 0.4438, RMSEP: 0.2936) and siPLS (88 variables, 5 LVs, RMSECV: 0.4401, RMSEP: 0.316) models were superior either to the full-spectrum PLS (4 LVs, RMSECV: 0.9674, RMSEP: 0.4618) or traditional single wavelength calibration (414nm, RMSECV: 2.0864, RMSEP: 2.1628). Minimum RMSEP (0.2976) was observed when GA was performed on spectral variables retained (above a threshold frequency) from the cumulative frequency distribution of all siPLS models. Finally, applicability of the selected PLS regression models in real NP toxicity assay is demonstrated.
Prasun Mahanti,Mark Southwick Robinson,David Carl Humm,Robert Vernon Wagner,Nicholas Michael Estes,Jean-Pierre Williams 한국우주과학회 2023 Journal of Astronomy and Space Sciences Vol.40 No.4
Lunar permanently shadowed regions (PSRs) never see direct sunlight and are illuminated only by secondary illumination - light reflected from nearby topography. The ShadowCam imaging experiment onboard the Korea Pathfinder Lunar Orbiter is acquiring images of these PSRs. We characterize and discuss the nature of secondary illumination for the Shackleton PSR from ShadowCam radiance-calibrated images. We also use modeling to understand the magnitude and direction of the secondary illumination. Results from our analysis highlight the non-homogeneous, dynamic, and complex nature of PSR secondary lighting. Knowledge of the direction of the secondary illumination is crucial for reli-able interpretation of contrasts observed in ShadowCam images. This preliminary analysis of the floor of Shackleton crater from images acquired over multiple secondary illumination conditions does not reveal indications of exposed surface ice, even though temperatures are constantly below 110K.
Kinetics of Oxidation of Nitrotoluenes by Acidic Hexacyanoferrate (Ⅲ)
Bhattacharjee, A. K.,Mahanti, M. K. Korean Chemical Society 1983 Bulletin of the Korean Chemical Society Vol.4 No.3
The reaction of hexacyanoferrate (Ⅲ) with nitrotoluenes in aqueous acetic acid containing perchloric acid(1.0 M) at $50^{\circ}C$ gave the corresponding aldehyde as the major product. The order with respect to each of the reactants ― substrate, oxidant and acid ― was found to be unity. The Hammett plot yielded a ${\sigma}^+$ value of -1.30, and the kinetic isotope effect gave a $k_H/k_D$ value of 6.2. The pathway for the conversion of the nitrotoluenes to the products has been mechanistically visualized as proceeding through the benzylic radical intermediate, formed in the rate determining step of the reaction.