No abstract

Nesse artigo, apresentamos vários paradoxos aparentes da relatividade restrita e suas respectivas soluções. Esse paradoxos aparecem desde o advento da relatividade, em 1905, e de fato nunca são paradoxos. Do ponto de vista didático, os paradoxos são uma excelente ferramenta de aprendizado. Eles levam o estudante a confrontar, e abandonar, vários conceitos centrais da teoria Galileana, como a simultaneidade e a rigidez dos corpos extensos. Particularmente, revisaremos uma nova e simples solução para o paradoxo dos gêmeos, encontrada recentemente por um dos presentes autores [1]. Ela não necessita considerar referenciais acelerados ou sinais de luz, que são as soluções apresentadas na literatura.

The treatment of venous vascular malformations with Photo-Derm® is safe and effective as it offered a high degree of patient satisfaction and good results in the disappearance of the lesions.

The following study reports the development of modified electrode with reduced graphene oxide (ErGO) for the voltammetric determination of 17α‐ethinylestradiol (EE2). The structural and morphological characterizations of the rGO were carried out by FTIR, Raman, UV‐Vis, TEM and SEM, and showed the typical formation of the nanomaterial. Electrochemical analyses were performed using Differential Pulse Voltammetry (DPV). Under optimized conditions, an analytical curve was generated for the sensor, which presented a linear dynamic range (LDR) from 0.04 to 8.28 μmol L−1 (R2=0.9999), with limit of detection (LOD) of 6.79 nmol L−1 and limit of quantification (LOQ) of 22.60 nmol L−1. The reproducibility and repeatability studies showed relative standard deviations (RSD) of 2.31 % and 5.23 %, respectively. ErGO was used to determine EE2 in wastewater, tablets, and synthetic urine samples with recovery values between 94.8 % and 110.1 %. The results obtained with ErGO show that the developed sensor can be used for the identification and quantification of EE2 in several matrices, due the excellent analytical performance presented.