Metal oxides of resistive memories investigated by electron and ion backscattering

The memristor is one of the most promising devices being studied for multiple uses in future electronic systems, with applications ranging from nonvolatile memories to artificial neural networks. Its working is based on the forming and rupturing of nano-scaled conductive filaments, which drastically alters the device’s resistance. These filaments are formed by oxygen vacancy accumulation, hence a deep understanding of the self-diffusion of oxygen in these systems is necessary. Accurate measurements of oxygen self-diffusion on metal oxides was achieved with the development of a quantitative analysis of the energy spectrum of the backscattering of electrons. The novel technique called Electron Rutherford Backscattering Spectroscopy (ERBS) uses the scattering of high energy electrons ( 40 keV) to probe the sample’s near surface (10–100 nm). Measurements of the high energy loss region – called Reflection High-Energy Electron Loss Spectroscopy (RHEELS) – also exhibit characteristics of the material’s electronic structure. A careful procedure was developed for the fitting of ERBS spectra, which was then applied on the analysis of multi-layered samples of Si3N4/TiO2, and measurements of the band gap of common oxides, such as SiO2, CaCO3 and Li2CO3. Monte Carlo simulations were employed to study the effects of multiple elastic scatterings in ERBS spectra, and a dielectric function description of inelastic scatterings extended the simulation to also consider the plasmon excitation peaks observed in RHEELS. These analysis tools were integrated into a package named PowerInteraction. With its use, a series of measurements of oxygen self-diffusion in TiO2 were conducted. The samples were composed of two sputtered deposited TiO2 layers, one of which was enriched with the 18 mass oxygen isotope. After thermal annealing, diffusion profiles were obtained by tracking the relative concentration of oxygen isotopes in both films. From the logarithmic temperature dependence of the diffusion coefficients, an activation energy of 1.05 eV for oxygen self-diffusion in TiO2 was obtained. Common ion beam analysis, such as RBS and NRA/NRP (Nuclear Reaction Analysis/Profiling), were also used to provide complementary information.O memristor é um dos dispositivos mais promissores sendo estudados para múltiplos usos em sistemas eletrônicos, com aplicações desde memórias não voláteis a redes neurais artificiais. Seu funcionamento é baseado na formação e ruptura de filamentos condutores nanométricos, o que altera drasticamente a resistência do dispositivo. Estes filamentos são formados pela acumulação de vacâncias de oxigênio, portanto um profundo entendimento da autodifusão de oxigênio nestes sistemas é necessário. Medidas acuradas da difusão em óxidos metálicos foi obtida com o desenvolvimento de uma análise quantitativa do espectro em energia de elétrons retroespalhados. A inovadora técnica de RBS de elétrons (ERBS) utiliza elétrons de alta energia ( 40 keV) para investigar a região próxima a superfície (10–100 nm). Medidas da região de alta perda de energia – chamada de Spectroscopia de Perda de Alta-Energia de Elétrons Refletidos (RHEELS) – também exibe características da estrutura eletrônica dos materiais. Um procedimento cuidadoso para o ajuste de espectros de ERBS foi desenvolvido, e então aplicado na análise de amostras multi camada de Si3N4/TiO2, e medidas de band gap de alguns óxidos, como SiO2, CaCO3 e Li2CO3. Simulações de Monte Carlo foram empregadas no estudo dos efeitos de espalhamento múltiplo nos espectros de ERBS, e uma descrição dielétrica dos espalhamentos inelásticos extendeu as simulação para também considerarem os picos de exitação plasmônica observados em RHEELS. Estas ferramentas de análise foram integradas em um pacote chamado PowerInteraction. Com o uso deste, uma série de medidas de autodifusão de oxigênio em TiO2 foram conduzidas. As amostras eram compostas por dois filmes de TiO2 depositados por sputtering, um dos quais enriquecido com isótopo 18 de oxigênio. Após tratamentos térmicos, perfis de difusão foram obtidos pelo rastreio das concentrações relativas dos isótopos de oxigênio nos dois filmes. Do comportamento logarítmico dos coeficientes de difusão em relação à temperatura, uma energia de ativação de 1.05 eV para a autodifusão de oxigênio em TiO2 foi obtida. Análises por feixes de íons, como RBS e NRA/NRP (Análise/Perfilometria por Reação Nuclear), também forneceram informações complementares

Positioning system for radiotherapy

A system (1) for positioning a patient for radiotherapy in accordance with patient specific data including a first volumetric image (e.g. a pCT image) of the patient comprising tissue label data and dose specification data is provided that comprises an imaging device (2), a positioning device (3) and an optimization controller (4). The imaging device (2) is configured to provide a second volumetric image (e.g. an rCT image) of the patient including a designated part of the patient to be treated. The positioning device (3) is provided to hold the patient in a variable position and/or orientation in the beam of radiation for an accurate intervention to a designated part of the patient. The optimization controller (4) comprises a dose based control module configured to provide registration control data (ΔP) to guide the positioning device (3) so that the actually applied treatment dose optimally matches the planned treatment dose

Positioning system for radiotherapy

A system (1) for positioning a patient for radiotherapy in accordance with patient specific data including a first volumetric image (e.g. a pCT image) of the patient comprising tissue label data and dose specification data is provided that comprises an imaging device (2), a positioning device (3) and an optimization controller (4). The imaging device (2) is configured to provide a second volumetric image (e.g. an rCT image) of the patient including a designated part of the patient to be treated. The positioning device (3) is provided to hold the patient in a variable position and/or orientation in the beam of radiation for an accurate intervention to a designated part of the patient. The optimization controller (4) comprises a dose based control module configured to provide registration control data (ΔP) to guide the positioning device (3) so that the actually applied treatment dose optimally matches the planned treatment dose

Positioning system for radiotherapy

A system (1) for positioning a patient for radiotherapy in accordance with patient specific data including a first volumetric image (e.g. a pCT image) of the patient comprising tissue label data and dose specification data is provided that comprises an imaging device (2), a positioning device (3) and an optimization controller (4). The imaging device (2) is configured to provide a second volumetric image (e.g. an rCT image) of the patient including a designated part of the patient to be treated. The positioning device (3) is provided to hold the patient in a variable position and/or orientation in the beam of radiation for an accurate intervention to a designated part of the patient. The optimization controller (4) comprises a dose based control module configured to provide registration control data (ΔP) to guide the positioning device (3) so that the actually applied treatment dose optimally matches the planned treatment dose

Positioning system for radiotherapy

A system (1) for positioning a patient for radiotherapy in accordance with patient specific data including a first volumetric image (e.g. a pCT image) of the patient comprising tissue label data and dose specification data is provided that comprises an imaging device (2), a positioning device (3) and an optimization controller (4). The imaging device (2) is configured to provide a second volumetric image (e.g. an rCT image) of the patient including a designated part of the patient to be treated. The positioning device (3) is provided to hold the patient in a variable position and/or orientation in the beam of radiation for an accurate intervention to a designated part of the patient. The optimization controller (4) comprises a dose based control module configured to provide registration control data (ΔP) to guide the positioning device (3) so that the actually applied treatment dose optimally matches the planned treatment dose

Positioning system for radiotherapy

A system (1) for positioning a patient for radiotherapy in accordance with patient specific data including a first volumetric image (e.g. a pCT image) of the patient comprising tissue label data and dose specification data is provided that comprises an imaging device (2), a positioning device (3) and an optimization controller (4). The imaging device (2) is configured to provide a second volumetric image (e.g. an rCT image) of the patient including a designated part of the patient to be treated. The positioning device (3) is provided to hold the patient in a variable position and/or orientation in the beam of radiation for an accurate intervention to a designated part of the patient. The optimization controller (4) comprises a dose based control module configured to provide registration control data (ΔP) to guide the positioning device (3) so that the actually applied treatment dose optimally matches the planned treatment dose

Determining the band gap and mean kinetic energy of atoms from reflection electron energy loss spectra

Reflection electron energy loss spectra from some insulating materials (CaCO3, Li2CO3, and SiO2) taken at relatively high incoming electron energies (5-40 keV) are analyzed. Here, one is bulk sensitive and a well-defined onset of inelastic excitations is observed from which one can infer the value of the band gap. An estimate of the band gap was obtained by fitting the spectra with a procedure that includes the recoil shift and recoil broadening affecting these measurements. The width of the elastic peak is directly connected to the mean kinetic energy of the atom in the material (Doppler broadening). The experimentally obtained mean kinetic energies of the O, C, Li, Ca, and Si atoms are compared with the calculated ones, and good agreement is found, especially if the effect of multiple scattering is taken into account. It is demonstrated experimentally that the onset of the inelastic excitation is also affected by Doppler broadening. Aided by this understanding, we can obtain a good fit of the elastic peak and the onset of inelastic excitations. For SiO2, good agreement is obtained with the well-established value of the band gap (8.9 eV) only if it is assumed that the intensity near the edge scales as (E - Egap)1.5. For CaCO3, the band gap obtained here (7 eV) is about 1 eV larger than the previous experimental value, whereas the value for Li2CO3 (7.5 eV) is the first experimental estimate

Impacto do rastreamento genético em crianças e adultos jovens com neoplasia endócrina múltipla tipo 2A : vinte anos de experiência de um centro de referência

O rastreamento genético identifica carreadores assintomáticos da mutação no proto-oncogene RET, que estão sob risco de desenvolver o câncer medular de tireoide (CMT) hereditário, possibilitando a tireoidectomia precoce e o aumento nas taxas de cura. Contudo, ainda existem controvérsias sobre o momento ideal da realização da tireoidectomia profilática. O objetivo deste estudo é descrever os achados clínicos e oncológicos dos carreadores da mutação no proto-oncogene RET diagnosticados na infância e início da vida adulta em acompanhamento na nossa instituição, bem como avaliar o impacto da idade da tireoidectomia no status da doença a longo prazo e quais os fatores associados a doença persistente. Foi realizado um estudo de coorte incluindo pacientes com NEM2A diagnosticados com idade menor ou igual a 25 anos. Os dados foram obtidos através de revisão de prontuários médicos. O desfecho primário foi o status da doença ao final do seguimento, classificado em resposta excelente, resposta bioquímica, resposta estrutural ou óbito. Foram incluídos 66 pacientes, sendo 47 (71.2%) diagnosticados pelo screening genético (grupo SG) e 19 (28.8%) diagnosticados através de doença clínica (grupo DC). A média de idade ao diagnóstico foi de 12.6 ± 6.7 anos e 65.2% eram do sexo feminino. A mutação mais frequente foi no codon 634, correspondendo a 84.8% dos casos. A mediana (p25-75) da calcitonina basal foi de 29.0 pg/mL (7.4 – 71.6 pg/mL). Cinquenta e oito pacientes foram submetidos à tireoidectomia total, enquanto oito pacientes estão em seguimento clínico. A idade média (±DP) da tireoidectomia foi maior no grupo DC (13.5 vs 18.1 anos, p 0.006). O tamanho do tumor variou de 0.1 a 3.5cm, com uma mediana 2.0cm (0.5-2.7) no grupo DC vs 0.6cm (0.3-1.0) no grupo SG – p0.052. Em relação ao TNM (8ª edição), 40 (75.4%) pacientes tinham doença estagio I, 6 (11.3%) estagio II, 1 (1.9%) estagio III, 3 (5.7%) estagio IVA e 3 (5.7%) estagio IVC. Os dados de seguimento mostram que, após uma média de 13.1 ± 7.8 anos de acompanhamento, 94.7% dos pacientes do grupo SG encontram-se livres de doença baseados no exame físico, ecografia cervical e níveis indetectáveis de calcitonina sérica. No grupo DC, 10/17 (58.8%) pacientes foram classificados com resposta excelente, 1 (5.9%) resposta bioquímica, 5 (29.4%) doença estrutural e 1 (5.9%) paciente foi a óbito. Análise da curva ROC para avaliar a performance da calcitonina pré-operatória (preCTN) como preditor de doença persistente resultou em uma área sob a curva de 0.87 [IC 0.75–0.99], e um valor de preCTN 42.5 pg/mL foi determinado como melhor ponto de corte com sensibilidade de 100% e especificidade de 69%. Em conclusão, apesar de nossos pacientes terem sido submetidos à tireoidectomia em uma idade mais tardia do que a recomendada pelas diretrizes atuais, a maioria se encontra livre de doença após um tempo de seguimento prolongado. Sabendo que a evolução da doença apresenta características individuais, nossos resultados reforçam a possibilidade de retardar o tratamento cirúrgico em pacientes carreadores da mutação RET que possuam níveis baixos de calcitonina sérica.Genetic screening Genetic screening allows the identification of asymptomatic carriers at risk of developing hereditary medullary thyroid carcinoma and early thyroidectomy, increasing cure rates. However, there are still controversies about the ideal timing of prophylactic thyroidectomy. The aim of this study is to describe the clinical and oncological findings of RET mutation carriers diagnosed in childhood and early adulthood, as well as to assess the impact of thyroidectomy age on long-term disease status and what are the factors associated with persistent disease. A cohort study including patients with MEN2A diagnosed aged 25 years or less was performed. Data were obtained through a review of medical records. The primary outcome was disease status at the end of follow-up, classified as excellent response, biochemical response, structural response, or death. A total of 66 patients were included, 47 (71.2%) diagnosed by genetic screening (GS group) and 19 (28.8%) diagnosed through clinical disease (CD group). The mean age at diagnosis was 12.6 ± 6.7 years and 65.2% were female. The most frequent mutation was at codon 634, corresponding to 84.8% of cases. The median (p25-75) of basal calcitonin was 29.0 pg/ml (7.4 – 71.6 pg/ml). Fifty-eight patients underwent total thyroidectomy, while eight patients are in clinical follow-up. The mean age (±SD) of total thyroidectomy was higher in the CD group (13.5 vs 18.1 years, p 0.006). Tumor size ranged from 0.1 to 3.5cm with median 2.0cm (0.5-2.7) in CD group vs 0.6cm (0.3-1.0) in GS group – p0.052. Regarding the TNM (8th edition), 40 (75.4%) patients had stage I disease, 6 (11.3%) stage II, 1 (1.9%) stage III, 3 (5.7%) stage IVA and 3 (5.7%) stage IVC. Follow-up data show that, after a mean of 13.1 ± 7.8 years of follow-up, 94.7% of patients in the SG group are disease-free based on physical examination, cervical ultrasound, and undetectable serum calcitonin levels. In the CD group, 10/17 (58.8%) patients were classified as having an excellent response, 1 (5.9%) biochemical response, 5 (29.4%) structural disease and 1 (5.9%) patient died. ROC curve analysis to assess the performance of preoperative calcitonin (preCTN) as a predictor of persistent disease resulted in an area under the curve of 0.87 [CI 0.75–0.99], and a preCTN value of 42.5 pg/mL was determined to be best cut-off point with 100% sensitivity and 69% specificity. In conclusion, although our patients underwent thyroidectomy later than recommended by current guidelines, most are disease-free after prolonged follow-up. Knowing that the evolution of the disease has individual characteristics, our results reinforce the possibility of delaying surgical treatment in patients carrying the RET mutation who have low levels of serum calcitonin