One- and Two-Electron Oxidations of β-Amyloid_25-35 by Carbonate Radical Anion (CO₃•-) and Peroxymonocarbonate (HCO₄-):Role of Sulfur in Radical Reactions and Peptide Aggregation

The β-amyloid (Aβ) peptide plays a key role in the pathogenesis of Alzheimer’s disease. The methionine (Met) residue at position 35 in Aβ C-terminal domain is critical for neurotoxicity, aggregation, and free radical formation initiated by the peptide. The role of Met in modulating toxicological properties of Aβ most likely involves an oxidative event at the sulfur atom. We therefore investigated the one- or two-electron oxidation of the Met residue of Aβ25-35 fragment and the effect of such oxidation on the behavior of the peptide. Bicarbonate promotes two-electron oxidations mediated by hydrogen peroxide after generation of peroxymonocarbonate (HCO4−, PMC). The bicarbonate/carbon dioxide pair stimulates one-electron oxidations mediated by carbonate radical anion (CO3•−). PMC efficiently oxidizes thioether sulfur of the Met residue to sulfoxide. Interestingly, such oxidation hampers the tendency of Aβ to aggregate. Conversely, CO3•− causes the one-electron oxidation of methionine residue to sulfur radical cation (MetS•+). The formation of this transient reactive intermediate during Aβ oxidation may play an important role in the process underlying amyloid neurotoxicity and free radical generation

Intersubband Transition Engineering in the Conduction Band of Asymmetric Coupled Ge/SiGe Quantum Wells

n-type Ge/SiGe asymmetric coupled quantum wells represent the building block of a variety of nanoscale quantum devices, including recently proposed designs for a silicon-based THz quantum cascade laser. In this paper, we combine structural and spectroscopic experiments on 20-module superstructures, each featuring two Ge wells coupled through a Ge-rich SiGe tunnel barrier, as a function of the geometry parameters of the design and the P dopant concentration. Through a comparison of THz spectroscopic data with numerical calculations of intersubband optical absorption resonances, we demonstrated that it is possible to tune, by design, the energy and the spatial overlap of quantum confined subbands in the conduction band of the heterostructures. The high structural/interface quality of the samples and the control achieved on subband hybridization are promising starting points towards a working electrically pumped light-emitting device. © 2020 by the authors. Licensee MDPI, Basel, Switzerland

Terahertz absorption-saturation and emission from electron-doped germanium quantum wells

We study radiative relaxation at terahertz frequencies in n-type Ge/SiGe quantum wells, optically pumped with a terahertz free electron laser. Two wells coupled through a tunneling barrier are designed to operate as a three-level laser system with non-equilibrium population generated by optical pumping around the 1→3 intersubband transition at 10 THz. The non-equilibrium subband population dynamics are studied by absorption-saturation measurements and compared to a numerical model. In the emission spectroscopy experiment, we observed a photoluminescence peak at 4 THz, which can be attributed to the 3→2 intersubband transition with possible contribution from the 2→1 intersubband transition. These results represent a step towards silicon-based integrated terahertz emitters

Terahertz absorption-saturation and emission from electron-doped germanium quantum wells

We study radiative relaxation at terahertz frequencies in n-type Ge/SiGe quantum wells, optically pumped with a terahertz free electron laser. Two wells coupled through a tunneling barrier are designed to operate as a three-level laser system with non-equilibrium population generated by optical pumping around the 1→3 intersubband transition at 10 THz. The non-equilibrium subband population dynamics are studied by absorption-saturation measurements and compared to a numerical model. In the emission spectroscopy experiment, we observed a photoluminescence peak at 4 THz, which can be attributed to the 3→2 intersubband transition with possible contribution from the 2→1 intersubband transition. These results represent a step towards silicon-based integrated terahertz emitters

Electron population dynamics in optically pumped asymmetric coupled Ge/SiGe quantum wells: experiment and models

n-type doped Ge quantum wells with SiGe barriers represent a promising heterostructure system for the development of radiation emitters in the terahertz range such as electrically pumped quantum cascade lasers and optically pumped quantum fountain lasers. The nonpolar lattice of Ge and SiGe provides electron–phonon scattering rates that are one order of magnitude lower than polar GaAs. We have developed a self-consistent numerical energy-balance model based on a rate equation approach which includes inelastic and elastic inter- and intra-subband scattering events and takes into account a realistic two-dimensional electron gas distribution in all the subband states of the Ge/SiGe quantum wells by considering subband-dependent electronic temperatures and chemical potentials. This full-subband model is compared here to the standard discrete-energy-level model, in which the material parameters are limited to few input values (scattering rates and radiative cross sections). To provide an experimental case study, we have epitaxially grown samples consisting of two asymmetric coupled quantum wells forming a three-level system, which we optically pump with a free electron laser. The benchmark quantity selected for model testing purposes is the saturation intensity at the 1→3 intersubband transition. The numerical quantum model prediction is in reasonable agreement with the experiments and therefore outperforms the discrete-energy-level analytical model, of which the prediction of the saturation intensity is off by a factor 3

Avaliação química e sensorial de blends de Coffea canephora Pierre e Coffea arabica L.

The coffee blend of C. arabica and C. canephora species, made by roasting with the strategy of uniting the sensory characteristics of these prominent coffee are called blends. Considering the diversity of coffees that can be obtained, depending on the type of processing, in the preparation of the blends is important to consider the correct proportion of coffee to ensure both the quality of the final product. The objective of the present work is to analyze blends in different proportions of the species C. canephora and C. arabica, by sensory and chemical evaluations. Data were subjected to analysis of variance and regression analysis later. Significant differences were detected for all variables chemical analysis and sensory attributes of blends with higher proportions of coffee canephora, observing the change in attributes fragrance, aroma and acidity and changes in attributes bitterness and body.A mistura dos cafés das espécies C. arábica e C. canephora, realizados pelas torrefadoras com a estratégia de unir as características sensoriais de destaque desses cafés são denominadas blends. Considerando a diversidade de cafés que podem ser obtidos, em função do tipo de processamento, na elaboração dos blends é importante considerar a correta proporção de ambos os cafés para assegurar a qualidade final do produto. Objetivou-se com o presente trabalho analisar blends em diferentes proporções das espécies C. canephora e C. arabica, por meio de avaliações químicas e sensoriais. Os dados foram submetidos à análise de variância e posteriormente à análise de regressão. Foram detectadas diferenças significativas para todas as variáveis das análises químicas e nos atributos sensoriais dos blends com maiores proporções de café canephora, observando-se a mudança nos atributos fragrância, aroma e acidez e alterações nos atributos amargor e corpo

n-type Ge/SiGe multi quantum-wells for a THz quantum cascade laser

Exploiting intersubband transitions in Ge/SiGe quantum cascade devices provides a way to integrate terahertz light emitters into silicon-based technology. With the view to realizing a Ge/SiGe Quantum Cascade Laser, we present the optical and structural properties of n-type strain-symmetrized Ge/SiGe asymmetric coupled quantum wells grown on Si(001) substrates by means of ultrahigh vacuum chemical vapor deposition. We demonstrate the high material quality of strain-symmetrized structures and heterointerfaces as well as control over the inter-well coupling and electron tunneling. Motivated by the promising results obtained on ACQWs, which are the basic building block of a cascade structure, we investigate, both experimentally and theoretically, a Ge/SiGe THz QCL design, optimized through a non-equilibrium Green's function formalism

Estudos de validação de diagnósticos de enfermagem em pacientes com insuficiência cardíaca: revisão integrativa / Validation studies of nursing diagnoses in patients with heart failure: integrative review

As doenças crônicas não transmissíveis constituem-se um problema de saúde pública, responsáveis por 74% das mortes em todo mundo, sendo as doenças cardiovasculares as primeiras causas, destacando a insuficiência cardíaca como integrante dessa causa. A insuficiência cardíaca como uma síndrome complexa concebe um grande desafio para a equipe de saúde constituindo-se uma das principais causas de hospitalizações. O enfermeiro implementa o Processo de Enfermagem para elaborar um plano de cuidados clínicos, aplicar esse conhecimento para a identificação dos sinais e sintomas, considerando a fisiopatologia da insuficiência cardíaca, tendo o Diagnóstico de Enfermagem viabilizar a individualização do cuidado e fundamenta a escolha das intervenções de enfermagem  adequadas para atingir as metas, resultados de enfermagem.Através da revisão integrativa da literatura, este estudo objetivou analisar a produção do conhecimento de estudos de validação de diagnósticos de enfermagem em pacientes com insuficiência cardíaca. O resultado deste estudo trouxe sete artigos, sendo a maioria produzidos por pesquisadores brasileiros. Concluiu-se há uma escassez de publicações de trabalhos de validação de diagnósticos de enfermagem para pessoas com insuficiência cardíaca e que também a validação de diagnósticos de enfermagem para populações específicas fornece base para orientar intervenções e resultados que possam ajudar a controlar o processo da doença, aperfeiçoar o tratamento e melhorar a qualidade de vida e sobrevivência.

Uncoupling protein-2 mRNA expression in mice subjected to intermittent hypoxia

Objetivo: Investigar o efeito da hipóxia intermitente com um modelo de apneia obstrutiva do sono (AOS) sobre a expressão de uncoupling protein-2 (UCP2), assim como sobre perfis glicêmicos e lipídicos, em camundongos C57BL. Métodos: Camundongos C57BL machos foram expostos a hipóxia intermitente ou hipóxia simulada (grupo controle) 8 h/dia durante 35 dias. A condição de hipóxia intermitente envolveu a exposição dos camundongos a uma atmosfera de 92% de N e 8% de CO2 por 30 s, com redução progressiva de fração de O2 inspirado até 8 ± 1%, seguida por exposição a ar ambiente por 30 s e repetições do ciclo (480 ciclos no período experimental de 8 h). Os pâncreas foram dissecados para isolar as ilhotas. Foi realizada PCR em tempo real utilizando o método TaqMan. Resultados: A expressão do mRNA da UCP2 nas ilhotas pancreáticas foi 20% maior no grupo controle que no grupo hipóxia (p = 0,11). A insulina sérica de jejum foi maior no grupo hipóxia do que no grupo controle (p = 0,01). O modelo de avaliação da homeostase de resistência à insulina indicou que, em comparação com os camundongos controle, aqueles expostos à hipóxia intermitente apresentaram 15% menor resistência à insulina (p = 0,09) e 21% maior função das células beta (p = 0,01). A coloração das ilhotas pancreáticas por imuno-histoquímica não mostrou diferenças significativas entre os grupos em termos da área ou da intensidade das células alfa e beta, marcadas por insulina e glucagon. Conclusões: Segundo nosso conhecimento, esta é a primeira descrição do efeito da hipóxia intermitente sobre a expressão da UCP2. Nossos achados sugerem que UCP2 regula a produção de insulina na AOS. Futuras investigações sobre o papel da UCP2 no controle glicêmico em pacientes com AOS são justificadas.Objective: To investigate the effect of intermittent hypoxia—a model of obstructive sleep apnea (OSA)—on pancreatic expression of uncoupling protein-2 (UCP2), as well as on glycemic and lipid profiles, in C57BL mice. Methods: For 8 h/day over a 35-day period, male C57BL mice were exposed to intermittent hypoxia (hypoxia group) or to a sham procedure (normoxia group). The intermittent hypoxia condition involved exposing mice to an atmosphere of 92% N and 8% CO2 for 30 s, progressively reducing the fraction of inspired oxygen to 8 ± 1%, after which they were exposed to room air for 30 s and the cycle was repeated (480 cycles over the 8-h experimental period). Pancreases were dissected to isolate the islets. Real-time PCR was performed with TaqMan assays. Results: Expression of UCP2 mRNA in pancreatic islets was 20% higher in the normoxia group than in the hypoxia group (p = 0.11). Fasting serum insulin was higher in the hypoxia group than in the normoxia group (p = 0.01). The homeostasis model assessment of insulin resistance indicated that, in comparison with the control mice, the mice exposed to intermittent hypoxia showed 15% lower insulin resistance (p = 0.09) and 21% higher pancreatic β-cell function (p = 0.01). Immunohistochemical staining of the islets showed no significant differences between the two groups in terms of the area or intensity of α- and β-cell staining for insulin and glucagon. Conclusions: To our knowledge, this is the first report of the effect of intermittent hypoxia on UCP2 expression. Our findings suggest that UCP2 regulates insulin production in OSA. Further study of the role that UCP2 plays in the glycemic control of OSA patients is warranted

THz Intersubband Emitter based on Silicon

We present THz quantum cascade emitters realized on a Si substrate. The emission centered at 3.4 and 4.9 THz originates from L-valley transitions in strain-compensated n-type Ge/SiGe heterostructures. This is an important step towards the realization of Si-based THz quantum cascade lasers