We present a study where the energy loss function of Ta 2 O 5 , initially derived in the optical limit for a limited region of excitation energies from reflection electron energy loss spectroscopy (REELS) measurements, was improved and extended to the whole momentum and energy excitation region through a suitable theoretical analysis using the Mermin dielectric function and requiring the fulfillment of physically motivated restrictions, such as the f-and KK-sum rules. The material stopping cross section (SCS) and energy-loss straggling measured for 300−2000 keV proton and 200− 6000 keV helium ion beams by means of Rutherford backscattering spectrometry (RBS) were compared to the same quantities calculated in the dielectric framework, showing an excellent agreement, which is used to judge the reliability of the Ta 2 O 5 energy loss function. Based on this assessment, we have also predicted the inelastic mean free path and the SCS of energetic electrons in Ta 2 O 5 .
As blindagens são uma parte fundamental na radioproteção. A construção de curvas de transmissão para um material utilizado como blindagem é importante para a definição da espessura necessária da blindagem. O principal objetivo deste trabalho é desenvolver um método para caracterizar novos materiais para blindagem de fótons usando a ferramenta computacional Geant4. As amostras irradiadas, denominadas Traço A, B e C, foram produzidas no Laboratório de Resistência de Materiais da UCPel. As validações experimentais de caracterização das amostras foram realizadas pelo teste da camada semirredutora (CSR), medida de kerma e medidas de Rutherford Backscattering Spectrometry (RBS), sendo os dois primeiros validados por meio de simulações. Os resultados de RBS e do imageamento mostraram a influência da granularidade dos agregados do concreto na homogeneidade e reprodutibilidade das amostras. A validação da aplicação foi feita por meio da verificação dos espectros teóricos e simulados, da geometria de radiação e caracterização do material. Os espectros teóricos e simulados foram validados por testes estatísticos, sendo considerados equivalentes. A geometria de radiação foi validada utilizando um visualizador e as ferramentas de verificação da geometria disponibilizadas pelo Geant4. Espera-se, com esses resultados, fazer medidas experimentais e criar curvas de transmissão simuladas para aplicações na radiologia diagnóstica e radioterapia.
In this study, it is investigated the anti-adhesive effectiveness of ZrN/Ti and TiN/Ti, deposited by magnetron sputtering, as coating materials of electrosurgical electrodes of steel in protein adhesion tests. Stoichiometry and the thickness of the systems were assessed with Rutherford backscattering spectrometry measurements. Vertical surface deviations were evaluated with the five-point mean height and the arithmetic average height and correlations between the amount of adhered protein in the electrosurgical electrodes and measurements of wettability and electrical resistivity were investigated. The quality of both coatings was put to the test through protein adhesion tests at high temperatures. Cuts with electrosurgical electrodes were performed in an abdominal flap for different electric power and cutting times. The results indicate less adhesion of protein on both proposed coatings, compared to the traditional electrodes of stainless steel, proving to be cheaper alternatives for the surgical industry than other massive anti-adherent electrodes as Au and Ti.
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