Avaliação das condições de precipitação do azul da Prússia sobre pó de grafite visando o desenvolvimento de eletrodos de pasta de carbono para a quantificação de nitrito

An amperometric FIA method for nitrite quantification based on nitrite electroreduction and employing a carbon paste electrode (CPE) chemically modified with iron hexacyanoferrate (HCF) as an amperometric detector was developed. The influence of experimental conditions on the preparation of the electrode materials was evaluated and the materials obtained in each study were used for the development of modified electrodes. The electrochemical sensors were prepared by a fast, simple, and inexpensive procedure, and the long-term performance of the electrodes were quite satisfactory as the stability was maintained over one year. HCF was an effective redox mediator for nitrite electroreduction in acidic media, allowing nitrite detection at +0.2 V vs. Ag/AgClsat, which is a potential free of possible interfering species that are normally present in food and water samples. The electrochemical cell used in the FIA system was similar to a batch injection analysis cell, enabling recirculation of the carrier solution. This is an attractive feature because it allows the use of a high flow rate (6 mL min-1) leading to high sensitivity and analysis speed, while keeping reagent consumption low. The proposed method had a detection limit of 9 μmol L-1 and was successfully employed for nitrite quantification in spiked water and sausage samples. The obtained results were in good agreement with those provided by the spectrophotometric official method. At a 95 % confidence level it was not observed statistical differences neither in nitrite content nor in the precision provided by both methods. The experimental conditions for the synthesis of HCF were optimized and the best electrode material was prepared by mixing FeCl3, K4[Fe(CN)6] and carbon powder subjected to an acid and thermal treatment (400 ºC), followed by ultrasonic agitation at 4 °C. This material was used to construct an electrode with improved analytical performance to reduce nitrite, which presented greater stability compared to HCF film electrodeposited on the EPC, showing that the preparation procedure of the electrode material is an effective strategy for the development of HCF modified electrodes.

Avaliação tribológica de novas modificações superficiais para cilindros de laminação a frio

The present work analyzed the tribological behavior of coatings/surface modifications traditionally used in cold rolling mill rolls and new coatings/surface modificationswith potential to replace the carcinogenic hard chrome. The study started with identification of wear mechanisms occurring in real coldrollingmill rolls. Due the high cost and dimensions of the rolls, thereplication technique was used. Replicas were obtained from 4 different rolling millBrazilian companies before and after a normal rolling campaign. Initial sliding tests were conducted using spherical and cylindrical counter bodies in order to verifywhichtribological conditions allowed to reproduce the wear mechanisms found in the replicas. These tests indicated the use of reciprocating sliding tests with cylindrical counter bodies (line contact), normal load of 100 N, and test times of and 1 h and 5 h. Different surface modifications were carried out on samples produced from a fragment of a rolling mill roll. The specimens were heat treated and ground on both sides. After, some specimens were surface textured by electrical discharge texturing (EDT). For both groups (ground and EDT), subsequent treatments of chromium plating, electroless NiP coating and plasma nitriding were carried out. The results of the reciprocating tests showed that specimens with electroless NiP coating presented the lowest friction coefficients, while plasma nitrided specimens showed the highest. In general, previous surface texturing before the coating/surface modification increased the wear of the counter bodies. Oneexceptionwas for EDT with subsequent electroless NiP coating, which presented the lowest counter bodies wear rate. The samples withelectroless NiP coating promoted a tribolayer consisting of Nickel, Phosphorus and Oxygen on both the specimens andthecounter bodies, which was apparently responsible for the reduction of friction coefficient and wear rate. The increase of the test time reduced the wear rate of the samples, apparently due the stability of the tribolayers formed, except for the nitrided samples. For the textured specimens, NiP coating showed the best performance in maintaining the surface topography of the specimens after the sliding tests.

Preparação e caracterização de biomateriais poliméricos para avaliação da viabilidade de uso como phantom biológico

The theoretical and experimental developments in the biomaterials area have been directly applied to different fields of Medicine (odontology, regenerative medicine and radiotherapy). These advances have focused both for diagnosing diseases such as for quantifying degrees of progression. From the perspective of these studies, biomaterials are being designed and manufactured for application in various areas of science, provided advances in diagnostic radiology, radiotherapy dosimetry and calibration of radiotherapy equipment. Develop a phantom from a biomaterial has become a great ally of medicine in the treat patients with oncological diseases, allowing better performance of the equipment in order to reduce damage to healthy tissue due to excessive exposure to radiation. This work used polymers: chitosan and gelatin, for making the polymeric structures and controlled for different types of production and processing, characterizing and evaluating the biopolymer by physical techniques (STL, SEM and DEI) and therefore analyze applicability as phantom mouse lung. It was possible to evaluate the morphology of biomaterials quantitatively by scanning electron microscopy associated with imaging technique. The relevance of this work focuses on developing a phantom from polymeric biomaterials that can act as phantom providing high image contrast when subjected to analysis. Thus, the choice of DEI technique is satisfactory since it is an imaging technique of X-ray high resolution. The images obtained by DEI have shown the details of the internal microstructure of the biomaterial produced which have ≈ 10 μm dimension. The phantoms had made density ranging from 0.08 a 0.13 g/cm3.

Avaliação das Funções Executivas em Dependentes Químicos

The aim of this study was to investigate possible alterations in attentive functions and mental flexibility in individuals diagnosed with Addiction. The sample (n=40) was located for convenience, and included 20 individuals with addiction behaviors (G1), and 20 individuals who do not use harmfully psychoactive substances (G2). Assessment instruments used were: Experimental and Computerized Test of Continuous Performance, and the Wisconsin Card Sorting Test. It was concluded that individuals in the G1 group had a poorer performance in all categories analyzed on the Wisconsin Card Sorting Test and in reaction time on the Experimental and Computerized Test (p<0,05), showing a deficit in mental flexibility and attentive functions, which may have direct implications on addictive behaviors and treatment.

Avaliação do AAM - Active Appearance Model para detecção de regiões de interesse em radiografias carpais na estimativa da idade óssea através do método TW

In several areas of health professionals (pediatricians, nutritionists, orthopedists, endocrinologists, dentists, etc.) are used in the assessment of bone age to diagnose growth disorders in children. Through interviews with specialists in diagnostic imaging and research done in the literature, we identified the TW method - Tanner and Whitehouse as the most efficient. Even achieving better results than other methods, it is still not the most used, due to the complexity of their use. This work presents the possibility of automation of this method and therefore that its use more widespread. Also in this work, they are met two important steps in the evaluation of bone age, identification and classification of regions of interest. Even in the radiography in which the positioning of the hands were not suitable for TW method, the identification algorithm of the fingers showed good results. As the use AAM - Active Appearance Models showed good results in the identification of regions of interest even in radiographs with high contrast and brightness variation. It has been shown through appearance, good results in the classification of the epiphysis in their stages of development, being chosen the average epiphysis finger III (middle) to show the performance. The final results show an average percentage of 90% hit and misclassified, it was found that the error went away just one stage of the correct stage.