[en] A survey of self-powered neutron detectors, SPND, which are used as part of the in-core instrumentation of nuclear reactors is presented. Measurements with Co and Er SPND's were made in the IEA-R1 reactor for determining the neutron flux distribution and the integral reactor power. Due to the size of the available detectors, the neutron flux distribution could not be obtained with accuracy. The results obtained in the reactor power measurements demonstrate that the SPND have the linearity and the quick response necessary for a reactor power channel. This work also presents a proposed design of a SPND using Pt as wire emissor. This proposed design is based in the experience gained in building two prototypes. The greatest difficulties encountered include materials and technology to perform the delicate weldings. (author)

[en] Published in summary form only

[en] Tiete River, with 1100 km of extension, is one of the most economically important river of the state of Sao Paulo, Brazil and throughout its length can be found reservoirs formed by damming its waters. This river is considered one of the most polluted rivers in the world, especially when it passes through the city of Sao Paulo. As a result of pollution observed since the 1950's, a project was established with the aim of evaluating the historic concentration of the trace elements As, Ba, Br, Ca, Ce, Co, Cr, Cs, Eu, Fe, Hf, La, Lu, Na, Nd, Rb, Sb, Sc, Sm, Ta, Tb, Th, U, Yb and Zn (mg.kg^-1), in sediment cores dated by ²¹⁰Pb method, sampled is several points of the river, since its source in Salesopolis up the mouth, on the Parana River. This work presents the results obtained by the trace elements above determined in two sediment cores collected in reservoirs in the city of Salesopolis and Pirapora do Bom Jesus. The analytical techniques used for the analysis were instrumental neutron activation analysis and gross beta measurement, respectively. The results obtained for the elements Br, Ce, Cr, Cs, Eu, Nd, Sb, Sm, Th and U are higher than the values of Upper Continental Crust and the sedimentation rate obtained for the reservoir in Salesopolis, 1.53 cm.y^-1, suggest silting processes. The enrichment factor and the geo-accumulation index were used to assess the presence of anthropogenic sources of pollution. Document available in abstract form only. (authors)

[en] In 1918 Joseph Lense and Hans Thirring, discovered the gravitomagnetic effect when studied solutions to the Einstein field equations using the weak field and slow motion approximation of rotating systems. They noted that when a body falls towards a massive object in rotation it feels a force perpendicular to its movement. The equations that they obtained were similar to Maxwell’s equations of electromagnetism, now known as Maxwell’s equations for gravitomagnetism. Some authors affirm that the gravitomagnetic effect can cause precession then in this paper we calculate the precession that gravitomagnetic effect cause in Mercury’s perihelion advance. To make this we calculate the field between dipoles to measure the influence that the Sun has on Mercury, taking into account the gravitomagnetic field that the Sun and Mercury produces when they rotate around themselves. In addition, we calculate the ratio of the dipole force (of all solar system planet’s) and the Newton’s gravitational force to see how much is smaller. (paper)

[en] Highlights: • Pulsed water electrolysis is a method capable of enhancing the current/decreasing the voltage during the on-period. • Bubble removal and replenishment of ions are the main causes of this improvement, as well as the perturbation of the electrical double layer. • Currently, the improvement in current caused by pulsed electrolysis is not high enough to compensate for the off-period. In other words, at a fixed energetic efficiency, the average production rate is lower using the pulsed method. • Pulsed water electrolysis could be used to decrease power input while maintaining the current at a minimum level at which gas cross-over is not an issue. -- Abstract: The application of pulses is a promising method to enhance the efficiency of water electrolysis. In this review, we first present a historical overview with several seminal references on the topic. Then, we give an overview of the last researches. Possible reasons for the efficiency improvement are outlined, including an increase in reactant concentration at the electrode surface, the improvement of bubble detachment from the electrode, and the perturbation of the electrical double layer.

No abstract available

[en] The f(R, T) gravity is a theory whose gravitational action depends arbitrarily on the Ricci scalar, R, and the trace of the stress-energy tensor, T; its field equations also depend on matter Lagrangian, L${}_m$. In the modified theories of gravity where field equations depend on Lagrangian, there is no uniqueness on the Lagrangian definition and the dynamics of the gravitational and matter fields can be different depending on the choice performed. In this /textbf{work}, we have eliminated the L${}_m$ dependence from f(R, T) gravity field equations by generalizing the approach of Moraes in Ref. [1]. We also propose a general approach where we argue that the trace of the energy-momentum tensor must be considered an "unknown" variable of the field equations. The trace can only depend on fundamental constants and few inputs from the standard model. Our proposal resolves two limitations: first the energy-momentum tensor of the f(R, T) gravity is not the perfect fluid one; second, the Lagrangian is not well-defined. As a test of our approach we applied it to the study of the matter era in cosmology, and the theory can successfully describe a transition between a decelerated Universe to an accelerated one without the need for dark energy.

[en] A comparison of linear and non-linear regression method in selecting the optimum isotherm was made to the experimental equilibrium data of methylene blue sorption by activated carbon. The r² was used to select the best fit linear theoretical isotherm. In the case of non-linear regression method, six error functions, namely coefficient of determination (r²), hybrid fractional error function (HYBRID), Marquardt's percent standard deviation (MPSD), average relative error (ARE), sum of the errors squared (ERRSQ) and sum of the absolute errors (EABS) were used to predict the parameters involved in the two and three parameter isotherms and also to predict the optimum isotherm. For two parameter isotherm, MPSD was found to be the best error function in minimizing the error distribution between the experimental equilibrium data and predicted isotherms. In the case of three parameter isotherm, r² was found to be the best error function to minimize the error distribution structure between experimental equilibrium data and theoretical isotherms. The present study showed that the size of the error function alone is not a deciding factor to choose the optimum isotherm. In addition to the size of error function, the theory behind the predicted isotherm should be verified with the help of experimental data while selecting the optimum isotherm. A coefficient of non-determination, K² was explained and was found to be very useful in identifying the best error function while selecting the optimum isotherm