Parametric retrieval model for estimating aerosol size distribution via the AERONET, LAGOS station

The size characteristics of atmospheric aerosol over the tropical region of Lagos, Southern Nigeria were investigated using two years of continuous spectral aerosol optical depth measurements via the AERONET station for four major bands i.e. blue, green, red and infrared. Lagos lies within the latitude of 6.465�N and longitude of 3.406�E. Few systems of dispersion model was derived upon specified conditions to solve challenges on aerosols size distribution within the Stokes regime. The dispersion model was adopted to derive an aerosol size distribution (ASD) model which is in perfect agreement with existing model. The parametric nature of the formulated ASD model shows the independence of each band to determine the ASD over an area. The turbulence flow of particulates over the area was analyzed using the unified number (Un). A comparative study via the aid of the Davis automatic weather station was carried out on the Reynolds number, Knudsen number and the Unified number. The Reynolds and Unified number were more accurate to describe the atmospheric fields of the location. The aerosols loading trend in January to March (JFM) and August to October (ASO) shows a yearly 15% retention of aerosols in the atmosphere. The effect of the yearly aerosol retention can be seen to partly influence the aerosol loadings between October and February.The size characteristics of atmospheric aerosol over the tropical region of Lagos, Southern Nigeria were investigated using two years of continuous spectral aerosol optical depth measurements via the AERONET station for four major bands i.e. blue, green, red and infrared. Lagos lies within the latitude of 6.465�N and longitude of 3.406�E. Few systems of dispersion model was derived upon specified conditions to solve challenges on aerosols size distribution within the Stokes regime. The dispersion model was adopted to derive an aerosol size distribution (ASD) model which is in perfect agreement with existing model. The parametric nature of the formulated ASD model shows the independence of each band to determine the ASD over an area. The turbulence flow of particulates over the area was analyzed using the unified number (Un). A comparative study via the aid of the Davis automatic weather station was carried out on the Reynolds number, Knudsen number and the Unified number. The Reynolds and Unified number were more accurate to describe the atmospheric fields of the location. The aerosols loading trend in January to March (JFM) and August to October (ASO) shows a yearly 15% retention of aerosols in the atmosphere. The effect of the yearly aerosol retention can be seen to partly influence the aerosol loadings between October and February

Aerosol Optical Depth Trends over Different Regions of Nigeria: Thirteen Years Analysis

Recurrent challenges of the theoretical estimation of aerosol optical thickness (AOT) are traceable to bogus assumption in its mathematical model. The objective of this paper is to propound a model that could describe the aerosol distribution sizes per time. The physics of the salient properties of aerosol within the Stokes regime was discussed. The mathematical model was applied to six locations within 335 ˟ 230 Km2 area of a selected portion of south-west, Nigeria. Though the climatic change is evident via thirteen years ground data set assimilation, the sensitivity of the proposed model was proven to increase by 0.1%. The research affirmed the use of some parameters (e.g. minimum temperature, cloud cover, relative humidity and rainfall) to estimate aerosol optical thickness and by extension the aerosol distribution size over an area

"Spectra of water dimer from ab initio calculations"

International audienc

Ab Initio Water Pair Potential with Flexible Monomers

A potential energy surface for the water dimer with explicit dependence on monomer coordinates is presented. The surface was fitted to a set of previously published interaction energies computed on a grid of over a quarter million points in the 12-dimensional configurational space using symmetry-adapted perturbation theory and coupled-cluster methods. The present fit removes small errors in published fits, and its accuracy is critically evaluated. The minimum and saddle-point structures of the potential surface were found to be very close to predictions from direct ab initio optimizations. The computed second virial coefficients agreed well with experimental values. At low temperatures, the effects of monomer flexibility in the virial coefficients were found to be much smaller than the quantum effects

Thiocyanate-induced N-activation and nucleophilic 1,2-dearomatization of pyridinedicarbonyl dichloride: a synthetic route to a novel 1,2-dihydropyridine-based heterocyclic compound

The 1,2-dearomatized pyridine derivatives are among the most beneficial scaffolds for synthetic and medicinal chemistry and have along with others substantially contributed to pharmaceutical research. We report uncatalyzed thiocyanate-induced N-activation and nucleophilic 1,2-dearomatization of pyridinedicarbonyl dichloride with further addition of diphenylamine leading to the novel 1,2-dihydropyridine-based heterocyclic compound; ( +/-) 2 '-(diphenylamino)-3-thioxo-2,3-dihydro-1H,4 ' H-spiro[imidazo[1,5-a]pyridine-5,5 '-thiazole]-1,4 '-dione (1). The previously reported dearomatizations of pyridine and its derivatives usually demand a specific catalyst. Therefore, uncatalyzed 1,2-dearomatization of pyridinedicarbonyl dichloride observed in this study is unusual. Heterocyclic compound 1 will act as potential mother reagent for the synthetic route to a variety of novel heterocyclic compounds derivative to 1,2-dihydropyridine. The purity of the product was assessed by Ultraperformance Liquid Chromatography (UPLC), and the structural characterization was achieved by H-1 NMR, C-13 NMR, DEPT-135-NMR, IR, Liquid Chromatography Mass Spectrometry (ESI-MS), single crystal X-ray crystallography and density function theory (DFT)