Estimation of carbonate concentration and characterization of marine sediments by Fourier Transform Infrared Spectroscopy

Fourier Transform Infrared Spectroscopy (FTIR) is a well established method for the characterization of mineralogical and geochemical properties of marine sediments. Understanding the biogeochemical changes in marine ecosystems is challenging task since it requires adequate analytical techniques and efforts. Biogeochemical characteristics of twenty one marine sediment samples collected off Chennai coast, Bay of Bengal, India were analyzed using FTIR spectroscopy. The FTIR peaks at 1460 cm⁻¹ (stretching vibration) and 880 cm⁻¹ (bending vibration) were used for carbonate determination. To verify the FTIR results, the obtained carbonate data were compared with carbonate values obtained by chemical analyses. The ranges of carbonate in sediments using FTIR and chemical analyses were 4.5–9.6% and 4.8–10%, respectively. The significant positive relationship was obtained between the carbonate results of FTIR and chemical analyses. This study demonstrates that instead of expensive and time consuming chemical methods, FTIR spectroscopic technique is found as a suitable, rapid and effective method for the quantification of carbonate in marine sediments.     

Periodic boundary value problem of functional differential equations with perturbation

By coincidence degree, the existence of solution to the periodic boundary value problem of functional differential equations with perturbation     

图的周长的一个度条件

本文用度和给出一个关于图的最长圈的存在性条件.这一结果是N.Dean和P.Fraisse的相应结论的推广.     

奇异椭圆方程组径向正解的存在性

Abstract. The existence of positive radial solutions to the systems of     

The twisted quantum affine algebra Uq(A2(2)) and correlation functions of the Izergin-Korepin model

We derive the exchange relations of the vertex operators of U_q(A₂⁽²⁾) and show that these vertex operators give the bosonization of the Izergin-Korepin model. We give an integral expression of the correlation functions of the Izergin-Korepin model and derive the difference equations which they satisfy.     

Influence of Ca2+ or Na+ extraframework cations on the thermal dehydration and related kinetic performance of LSX zeolite

Nitrogen adsorption performances of low-silica type X zeolites (LSX) containing Na⁺ or Ca²⁺ ions were studied and compared with Li⁺ ion, and their structural and thermal properties were investigated using various characterizations (XRD, TG-DTG, BET, XPS, SEM, TEM, and EDX with elemental mapping techniques). The kinetics of their thermal dehydration and decomposition was studied using thermogravimetry at three rates (5, 10, and 15 K/min) of linear increase of temperature under non-isothermal heating. Two model free procedures named, Kissinger, and Flynn–Wall–Ozawa (iso-conversional) and one model fitting method called Coats–Redfern based on single TG curves, as well as 41 mechanism functions were used. The kinetic parameters (apparent activation energy E, pre-exponential factor A and model) of the three phases for each sample obtained from the non-isothermal methods were then compared with the results from iso-conversional methods this showed that they strongly depend on the selection of appropriate mechanism function and the corresponding kinetic model from the perspective of crystal structure used. The results demonstrated that the E value obtained at low temperature was lower than that at high temperature, implying that the dehydration process of physisorbed water belongs to diffusion-based control, while decomposition of bonded water (chemisorbed) belongs to kinetic-based control at high temperature. These comparisons allow us to underline the strong effect of cations in association with water and their distribution in the micropores of LSX on the N₂ adsorption performance.