Use of radial basis function networks and near-infrared spectroscopy for the determination of total nitrogen content in soils from Sao Paulo State

Total nitrogen has been determined by using a model developed between the conventional chemical measurements and diffuse reflectance spectra in the near-infrared region. Samples (244) from different types of soils with total nitrogen contents ranging from 0.20 to 13.60% (m/m) were modeled by partial least-squares regression (PLS), multi-layer perceptron feed-forward networks (MLP) and radial basis function networks (RBFN). The RBFN model produced a better square error of prediction (SEP) of 0.048 and R(2) = 0.93 in a procedure that is simpler, faster and less dependent on the initial conditions.     

The effect of gamma radiation on biodegradability of morpholine in aqueous solution

The effect of -radiation on the aqueous solution of morpholine was studied on the basis of UV spectrum measurement, COD /chemical oxygen demand/, TOC /total organic carbon/ and STOD /short-term oxygen demand/ determination and Pitter's kinetic test of biodegradation. The biodegradability of the model solution after irradiation became substantially worse.     

The radiation treatment of waste water solutions containing 2-mercaptobenzothiazole and N-oxydiethylene-2-benzothiazolesulfenamide

The effect of -radiation on waste water solutions containing 2-mercaptobenzothiazole and N-oxydiethylene-2-benzothiazolesulfenamide was studied by UV spectrosocopy, COD, BOD₅ and TOC determination and Pitter's kinetic test of biodegradation. No improvement in biodegradability of model solutions was detected and in case of 2-mercaptobenzothiazole colloidal turbidity removable by coagulation appeared.     

The absorption spectrum of beryllium

Energy terms, dipole oscillator strengths and photoionization cross-sections from the ground state are calculated. Autoionizing state transition energies and line widths for the ¹P⁰ resonances in the continuum are also obtained. The configuration interaction method for initial and final states is used, and atomic orbitals are generated through angular-momentum-dependent, scaled Thomas-Fermi-Dirac potentials.     

Applications of radio and radiation chemistry to chemical evolution studies

The gamma radiolysis of malonic acid, succinic acid and their corresponding nitriles was carried out over a wide interval of radiation doses. The radiolytic products detected were H₂, CO₂, CO, NH₃ and carboxylic acids. The results obtained supported the hypothesis that in the prebiotic milieu, ionizing radiation might have contributed to the synthesis of compounds of relevance in biological systems.     

Determination of copper in water samples by atomic absorption spectrometry after cloud point extraction

Cloud point extraction employing the new reagent 6-[2′-(6′-methyl-benzothiazolylazo)]-1,2-dihydroxy-3,5-benzenedisulfonic acid as complexing agent and Triton X-114 as the surfactant is proposed for copper determination. A sample volume of 10 mL was used. Dilution of the surfactant-rich phase with acidified methanol was performed after phase separation, and the copper contents were measured by flame atomic absorption spectrometry. Variables affecting the system were optimized using factorial design and Doehlert matrix. Signals were measured as peak height using an instrument software. Using the experimental conditions defined in the optimization, the method allowed copper determination with a detection limit of 1.5 μg L⁻¹. The calculated enrichment factor is 14. The effects of foreign ions are reported. The accuracy of the procedure was tested by analyzing certified reference material. The method was successfully applied to copper determination in natural and drinking water samples.     

On Jacobi fields

We define curves on a Riemannian manifold as integrals of generalized Jacobi fields. We show that the force term that deviates the trajectory from the geodesic motion can be constructed as a functional of the metric tensor. These curves can be interpreted as particles (observers) coupled nonminimally with gravitation that can provide a class of residual observers for the inevitable singularity—as shown in the text.This essay received an honorable mention (1976) from the Gravity Research Foundation-Ed.     

ДлИны Boлн и Bepoятнocти пeppexoдoв Для иэoэлeктpoннoЙ пocлeдoбaтэльнocти киcлoпoдa

Energies of the transitions 1s²2s²2p⁴?1s²2s2p⁵?1s²2p⁶ belonging to the isoelectronic sequence of oxygen have been calculated. The Hartre-Fock energy and the correlation energy, as well as relativistic corrections, were taken into account. The results have been compared with experimental data. Agreement was found to be good, thus suggesting that the $\text{(}\text{1}\text{Z}\text{)-}\text{expansion}$ converges rapidly. Perturbation theory was used for calculations of transition probabilities for the transitions 1s²2s²2p⁴?1s²2s2p⁵?1s²2p⁶ of the isoelectronic sequence of oxygen. The results may be useful in interpreting soft X-ray line radiation from these transitions, as observed in the solar corona and in high-temperature laboratory-generated plasmas.     

An interpretation of the mean spherical approximation

The mean spherical approximation is shown to be derivable from a perturbation expansion where the reference system follows the Percur-Yevick approximation. Then the MSA may be interpreted as a first-order expansion in which the perturbation is averaged with respect to the low-density reference distribution function. This represents a generalization of an equivalent interpretation previously made with respect to the free energy of a polar fluid.