19 research outputs found
Determinação de atividade quitinolitica em meio solido utilizando quitina marcada com rbb(quitina-rbb)
44
Stopping and straggling of 60-250-keV backscattered protons on nanometric Pt films
The stopping power and straggling of backscattered protons on nanometric Pt films were measured at low to medium energies (60-250 keV) by using the medium-energy ion scattering technique. The stopping power results are in good agreement with the most recent measurements by Primetzhofer Phy s. Rev. B 86, 094102 (2012) and are well described by the free electron gas model at low projectile energies. Nevertheless, the straggling results are strongly underestimated by well-established formulas up to a factor of two. Alternatively, we propose a model for the energy-loss straggling that takes into account the inhomogeneous electron-gas response, based on the electron-loss function of the material, along with bunching effects. This approach yields remarkable agreement with the experimental data, indicating that the observed enhancement in energy-loss straggling is due to bunching effects in an inhomogeneous electron system. Nonlinear effects are of minor importance for the energy-loss straggling
Métodos ativos de ensino de Física e medidas de autoeficácia discente
Parte da comunidade de pesquisa em ensino de Física tem devotado atenção ao estudo de métodos ativos de ensino que primam pela centralização do processo de ensino-aprendizagem no aluno. Além da aprendizagem conceitual, tais métodos buscam favorecer o desenvolvimento de habilidades associadas ao trabalho colaborativo, à argumentação de ideias e diminuir a evasão estudantil. Contudo, o sucesso de tais iniciativas depende do quanto os alunos se julgam capazes de realizar as atividades propostas pelo professor: depende do nível de autoeficácia dos alunos em realizar determinadas ações. Pesquisas apontam para uma baixa mudança em níveis de autoeficácia em função do uso de métodos ativos. Através de um estudo de caso, argumentamos que um reajuste importante nos níveis de autoeficácia pode estar ocorrendo, despercebido em função do modo como os níveis estão sendo medidos
Characterization of oxygen self-diffusion in TiO2 resistive-switching layers by nuclear reaction profiling
Oxygen self-diffusion was investigated in TiO2 layers employed for resistive-switching memories using resonant nuclear reaction profiling (NRP) and 18O labeling. The layers were grown using physical vapor deposition technique (sputtering) and were polycrystalline. The diffusivity was measured over the temperature range 600–800 °C and the activation energy for oxygen self-diffusion in sputter-deposited TiO2 films determined to be 1.09 ± 0.16 eV, a value consistent with results obtained by previous studies (Marmitt et al., 2017).This study was financed in part by the Coordena de Aperfei oamento
de Pessoal de Nvel Superior – Brasil (CAPES) – Finance Code 001, by
CNPq and PRONEX-FAPERGS. We acknowledge support from the
NCRIS ANFF and Heavy-Ion Accelerator Capabilities, with particular
thanks to Dr. Fouad Karouta for the deposition of the (Si3N4) at ANU.
RGE and MV further acknowledge the ARC funding program for financial support
Stopping and straggling of 60-250-keV backscattered protons on nanometric Pt films
The stopping power and straggling of backscattered protons on nanometric Pt films were measured at low to medium energies (60-250 keV) by using the medium-energy ion scattering technique. The stopping power results are in good agreement with the most recent measurements by Primetzhofer Phys. Rev. B 86, 094102 (2012) and are well described by the free electron gas model at low projectile energies. Nevertheless, the straggling results are strongly underestimated by well-established formulas up to a factor of two. Alternatively, we propose a model for the energy-loss straggling that takes into account the inhomogeneous electron-gas response, based on the electron-loss function of the material, along with bunching effects. This approach yields remarkable agreement with the experimental data, indicating that the observed enhancement in energy-loss straggling is due to bunching effects in an inhomogeneous electron system. Nonlinear effects are of minor importance for the energy-loss straggling.This study was financed in part by: Coordenação de
Aperfeiçoamento de Pessoal de Nível Superior - Brazil
(CAPES) - Finance Code 001; Conselho Nacional de Desenvolvimento Cientfico e Tecnológico - Brazil (CNPq) Projects
No. 141833/2017-3, No. 160018/2019-6, No. 406750/2016-
5 and No. 404301/2016-9; and PRONEX-FAPERGS. J.M.,
P.L.G., and F.F.S. acknowledge support by RADIATE project
under the Grant Agreement 824096 from the EU Research and
Innovation program HORIZON 2020. M.V. acknowledges
the Australian Research Council - Australia (ARC) funding
program for financial support. P.L.G. and F.F.S. acknowledge
D. Primetzhofer for the enlightening discussion
ARMAZENAGEM REFRIGERADA DE PIMENTAS SOB CONDIÇÃO DE ATMOSFERA NORMAL E MODIFICADA
O cultivo de pimentas pode ser mais uma opção para os produtores diversificarem a produção e aumentarem sua renda. com este objetivo desenvolve-se pesquisas sobre o comportamento e adaptação das cultivares ‘Malagueta’, ‘Chapéu de Bispo’, ‘Cheiro de Luna’, ‘Jalapeño’ e ‘Novo México’ hà região e sua conservação armazenadas em frio em atmosfera normal e atmosfera modificada. O resultado esperado para este trabalho é o de a armazenagem em atmosfera modificada conservar o fruto por mais tempo em relação a armazenagem em atmosfera normal preservando as pimentas
Characterization of soil chemical properties of strawberry fields using principal component analysis
Determinação de atividade quitinolitica em meio solido utilizando quitina marcada com rbb(quitina-rbb)
44
The influence of radiation damage on electrons and ion scattering measurements from PVC films
Polyvinyl chloride (PVC) is a material that decomposes rapidly when irradiated by charged particles. Here we use energy spectra of electrons reflected from the PVC films during electron radiation to monitor this process. This is accomplished by measuring the energy distribution of elastically scattered electrons which depends on the mass of the scattering atoms. Incoming electrons with energy between 5 and 40 keV are used. Information is obtained about both the relative amount of Cl, C and H present in the sample. Especially the Cl concentration decreases quickly during irradiation. At larger energy losses the signature of the band gap is visible in the energy loss spectrum. The number of excitations within the band gap increases rapidly when the composition of the film changes. The H intensity is somewhat less affected by the electron beam than the Cl intensity but accurate determination of the H content is complicated due to the changing background. Medium-energy ion scattering measurements (using 200 keV protons) and Rutherford backscattering measurements (using 2 MeV He ions) showed a strong decrease in the measured Cl intensity with ion fluence used. The Cl concentration as a function of fluence for electrons, protons and He ions can be described in a uniform way by considering the density of electronic excitations produced under the different irradiation conditions.This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) - Finance Code 001, by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and PRONEX-FAPERGS. MV acknowledges the ARC funding program for financial support
Métodos ativos de ensino de Física e medidas de autoeficácia discente
Parte da comunidade de pesquisa em ensino de Física tem devotado atenção ao estudo de métodos ativos de ensino que primam pela centralização do processo de ensino-aprendizagem no aluno. Além da aprendizagem conceitual, tais métodos buscam favorecer o desenvolvimento de habilidades associadas ao trabalho colaborativo, à argumentação de ideias e diminuir a evasão estudantil. Contudo, o sucesso de tais iniciativas depende do quanto os alunos se julgam capazes de realizar as atividades propostas pelo professor: depende do nível de autoeficácia dos alunos em realizar determinadas ações. Pesquisas apontam para uma baixa mudança em níveis de autoeficácia em função do uso de métodos ativos. Através de um estudo de caso, argumentamos que um reajuste importante nos níveis de autoeficácia pode estar ocorrendo, despercebido em função do modo como os níveis estão sendo medidos