752 research outputs found

    Smoldering Combustion In Porous Media Kinetic Models For Numerical Simulations

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    Tecnologias avançadas para a geração de energia usando combustíveis não convencionais xisto betuminoso e seu semi-coque, areias betuminosas, petróleo extra-pesado e biomassa proveniente de resíduos sólidos urbanos e de lodo de esgoto - têm em comum processos termoquímicos compostos de complexas reações químicas. Este trabalho trata da formulação e otimização de mecanismos químicos normalmente envolvidos na pirólise do xisto betuminoso e na combustão do xisto betuminoso e seu semi-coque. Problemas inversos (usando o algoritmo de Levenberg-Marquardt) foram empregados para minimizar o erro entre os valores estimados e os dados de termogravimétria para os mecanismos de reação de 3 passos para a pirólise do xisto betuminos, e mecanismos de 4 e 3 passos para o xisto betuminoso e seu semi-coque, respectivamente. Os parâmetros cinéticos, tais como ordem de reação, fator pré-exponencial, energia de ativação e os coeficientes estequiométricos que afetam a secagem, as reações de oxidação, pirólise e descarbonatação foram estimadas com sucesso. Além disso, os erros estatísticos e residuais foram avaliados, resultando em um valor razoável para todas as estimativas e o mecanismo cinético proposto e estimado para a combustão do semi-coque foi aplicado em um código em meios porosos. Um estudo paramétrico entre o perfil de temperatura e a velocidade do ar, e o perfil de temperatura e a concentração de carbono fixo foi desenvolvido. Este estudo mostra que o perfil de temperatura é extremamente influenciado por estes parâmetros, confirmando que a propagação da frente é controlada pela injeção de O2. Palavras-chave: Xisto Betuminoso, Semi-Coque, Pirólise, Combustão, Estimação de Parâmetros, Problemas Inversos, Levenberg-Marquardt, Meios Porosos

    A Data-Driven Model of Tonal Chord Sequence Complexity

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    Detection of Earth-like Planets Using Apodized Telescopes

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    The mission of NASA's Terrestrial Planet Finder (TPF) is to find Earth-like planets orbiting other stars and characterize the atmospheres of these planets using spectroscopy. Because of the enormous brightness ratio between the star and the reflected light from the planet, techniques must be found to reduce the brightness of the star. The current favorite approach to doing this is with interferometry: interfering the light from two or more separated telescopes with a π\pi phase shift, nulling out the starlight. While this technique can, in principle, achieve the required dynamic range, building a space interferometer that has the necessary characteristics poses immense technical difficulties. In this paper, we suggest a much simpler approach to achieving the required dynamic range. By simply adjusting the transmissive shape of a telescope aperture, the intensity in large regions around the stellar image can be reduced nearly to zero. This approach could lead to construction of a TPF using conventional technologies, requiring space optics on a much smaller scale than the current TPF approach.Comment: Accepted for publication in ApJ Letters, 9 pages, 6 figure

    Typical and Atypical Symptoms of Petrous Apex Cholesterol Granuloma: Association with Radiological Findings

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    Objective: Petrous apex cholesterol granuloma (PACG) is a lesion that can give rise to different symptoms, and correlations with etiopathology are ambiguous. The aim of this study is to analyze the association between PACG symptoms and radiological findings at presentation, in order to establish a reproduceable pre-operative radiological evaluation and guide the surgical indication. Methods: PACG patients were collected in two tertiary care hospitals. All cases underwent CT/MRI to evaluate the cyst localization and erosion of surrounding structures. Typical and atypical symptoms were then analyzed and compared to radiologic findings established in accordance with the literature. Results: Twenty-nine patients were recruited; the most common symptoms were headache (69%), diplopia (20.7%) and fainting (24.1%), an atypical clinical manifestation related to jugular tubercle involvement. Significant associations between symptoms and radiologic findings were noted in terms of headache and temporal lobe compression (p = 0.04), fainting and jugular tubercle erosion (p < 0.001), vestibular symptoms and internal auditory canal erosion (p = 0.02), facial paresthesia and Meckel’s cave compression (p = 0.03), diplopia and Dorello canal involvement (p = 0.001), and tinnitus and cochlear basal turn erosion (p < 0.001). All patients were treated via an endoscopic–endonasal approach, in which extension was tailored to each case. At a median follow-up of 46 months, 93.1% of patients experienced resolution of symptoms. Conclusions: This clinico-radiological series demonstrates associations between symptoms and anatomical subsites involved with PACG. Hence, it may guide the surgeon at the time of surgical decision, since it asserts that typical and atypical symptoms are actually related to PACG

    Interventions addressing the adolescent HIV continuum of care in South Africa: a systematic review and modified Delphi analysis

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    INTRODUCTION: Compared with adults, adolescents in South Africa have larger gaps at each step of the HIV continuum of care resulting in low levels of viral suppression. METHODS: We conducted a systematic review and modified Delphi analysis of interventions addressing the HIV continuum of care for adolescents in South Africa. We searched PubMed, Science Direct, and Google Scholar and online conference proceedings from the International AIDS Society, the International AIDS Conference, and the Conference on Retrovirology and Opportunistic Infections from 1 January 2010 to 30 September 2020. We then conducted a modified Delphi analysis with 29 researchers involved in the National Institutes of Health's Fogarty International-supported Adolescent HIV Implementation Science Alliance-South Africa to evaluate interventions for efficacy, feasibility and potential for scale-up. RESULTS: We identified nine initial published articles containing interventions addressing the adolescent HIV continuum of care in South Africa, including five interventions focused on HIV diagnosis, two on antiretroviral therapy adherence and two on retention in care. No studies addressed linkage to care or transition from paediatric to adult care. Two studies discussed intervention costs. In-home and HIV self-testing, community-based adherence support, and provision of adolescent-friendly services were the most impactful and scalable interventions addressing the adolescent HIV continuum of care. CONCLUSION: Future interventions should work comprehensively across the adolescent HIV continuum of care and be tailored to the specific needs of adolescents

    Emissão de metano por decomposição de resíduo florestal inundado.

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    A construção de represas pode aumentar a emissão de gases do efeito estufa (GEE), principalmente metano (CH4) pela decomposição anaeróbica dos resíduos florestais, como galhos, ramos, folhas e miscelânea inundados. Objetivou-se, neste estudo, avaliar a emissão de CH4 após a inundação do solo coberto com resíduos florestais. Unidades experimentais foram construídas com tubos de PVC contendo solo e diferentes combinações de dose (0; 21,2; 42,3 e 64,1 Mg ha-1) e tipo de resíduos (folhas, ramos e miscelânea, galhos e composição original) e água de rio. O delineamento experimental foi inteiramente casualizado com arranjo fatorial e três repetições. As taxas de emissão de CH4 foram monitoradas em 19 eventos durante um ano (Fevereiro/2012 a Março/2013). Cerca de 75 dias após a incubação do solo com resíduos florestais verificou-se aumento das emissões de CH4, ocorrendo dois picos de emissão, aos 111 e aos 249 dias. A emissão acumulada de CH4 no primeiro ano de alagamento foi de 200 g C m-2 na dose zero, passando a valores próximos a 400 g C m-2 nas doses de 21,2 Mg ha-1 e maiores, não havendo efeito do tipo de resíduo, apenas da dose, como fator isolado

    Early Detection of Prostate Cancer: The Role of Scent

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    Prostate cancer (PCa) represents the cause of the second highest number of cancer-related deaths worldwide, and its clinical presentation can range from slow-growing to rapidly spreading metastatic disease. As the characteristics of most cases of PCa remains incompletely understood, it is crucial to identify new biomarkers that can aid in early detection. Despite the prostate-specific antigen serum (PSA) levels, prostate biopsy, and imaging representing the actual gold-standard for diagnosing PCa, analyzing volatile organic compounds (VOCs) has emerged as a promising new frontier. We and other authors have reported that highly trained dogs can recognize specific VOCs associated with PCa with high accuracy. However, using dogs in clinical practice has several limitations. To exploit the potential of VOCs, an electronic nose (eNose) that mimics the dog olfactory system and can potentially be used in clinical practice was designed. To explore the eNose as an alternative to dogs in diagnosing PCa, we conducted a systematic literature review and meta-analysis of available studies. PRISMA guidelines were used for the identification, screening, eligibility, and selection process. We included six studies that employed trained dogs and found that the pooled diagnostic sensitivity was 0.87 (95% CI 0.86–0.89; I2, 98.6%), the diagnostic specificity was 0.83 (95% CI 0.80–0.85; I2, 98.1%), and the area under the summary receiver operating characteristic curve (sROC) was 0.64 (standard error, 0.25). We also analyzed five studies that used an eNose to diagnose PCa and found that the pooled diagnostic sensitivity was 0.84 (95% CI, 0.80–0.88; I2, 57.1%), the diagnostic specificity was 0.88 (95% CI, 0.84–0.91; I2, 66%), and the area under the sROC was 0.93 (standard error, 0.03). These pooled results suggest that while highly trained dogs have the potentiality to diagnose PCa, the ability is primarily related to olfactory physiology and training methodology. The adoption of advanced analytical techniques, such as eNose, poses a significant challenge in the field of clinical practice due to their growing effectiveness. Nevertheless, the presence of limitations and the requirement for meticulous study design continue to present challenges when employing eNoses for the diagnosis of PCa

    Designing cascades of electron transfer processes in multicomponent graphene conjugates

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    A novel family of nanocarbon-based materials was designed, synthesized, and probed within the context of charge-transfer cascades. We integrated electron-donating ferrocenes with light-harvesting/electron-donating (metallo)porphyrins and electron-accepting graphene nanoplates (GNP) into multicomponent conjugates. To control the rate of charge flow between the individual building blocks, we bridged them via oligo-p-phenyleneethynylenes of variable lengths by β-linkages and the Prato-Maggini reaction. With steady-state absorption, fluorescence, Raman, and XPS measurements we realized the basic physico-chemical characterization of the photo- and redox-active components and the multicomponent conjugates. Going beyond this, we performed transient absorption measurements and corroborated by single wavelength and target analyses that the selective (metallo)porphyrin photoexcitation triggers a cascade of charge transfer events, that is, charge separation, charge shift, and charge recombination, to enable the directed charge flow. The net result is a few nanosecond-lived charge-separated state featuring a GNP-delocalized electron and a one-electron oxidized ferrocenium

    Exploration of Gate Trench Module for Vertical GaN devices

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    The aim of this work is to present the optimization of the gate trench module for use in vertical GaN devices in terms of cleaning process of the etched surface of the gate trench, thickness of gate dielectric and magnesium concentration of the p-GaN layer. The analysis was carried out by comparing the main DC parameters of devices that differ in surface cleaning process of the gate trench, gate dielectric thickness, and body layer doping. . On the basis of experimental results, we report that: (i) a good cleaning process of the etched GaN surface of the gate trench is a key factor to enhance the device performance, (ii) a gate dielectric >35-nm SiO2 results in a narrow distribution for DC characteristics, (iii) lowering the p-doping in the body layer improves the ON-resistance (RON). Gate capacitance measurements are performed to further confirm the results. Hypotheses on dielectric trapping/detrapping mechanisms under positive and negative gate bias are reported.Comment: 5 pages, 10 figures, submitted to Microelectronics Reliability (Special Issue: 31st European Symposium on Reliability of Electron Devices, Failure Physics and Analysis, ESREF 2020

    Sensory and chemical profile of a phenolic extract from olive mill waste waters in plant-base food with varied macro-composition

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    Phenols from olive mill waste water (OMWW) represent valuable functional ingredients. The negative impact on sensory quality limits their use in functional food formulations. Chemical interactions phenols/biopolymers and their consequences on bioactivity in plant-base foods have been widely investigated, but no studies to date have explored the variation of bitterness, astringency and pungency induced by OMWW phenols as a function of the food composition. The aim of the paper was to profile the sensory and chemical properties of phenols from OMWW in plant-base foods varied in their macro-composition. Four phenol concentrations were selected (0.44, 1.00, 2.25, 5.06 g/kg) to induce significant variations of bitterness, sourness, astringency and pungency in three plant-base food: proteins/neutral pH \u2013 bean pur\ue9e (BP), starch/neutral pH \u2013 potato pur\ue9e (PP), fiber/low pH \u2013 tomato juice (TJ). The macro-composition affected the amount of the phenols recovered from functionalized food. The highest recovery was from TJ and the lowest from BP. Two groups of 29 and 27 subjects, trained to general Labelled Magnitude Scale and target sensations, participated in the evaluation of psychophysical curves of OMWW phenols and of functionalized plant-base foods, respectively. Target sensations were affected by the food macro-composition. Bitterness increased with phenol concentration in all foods. Astringency and sourness slightly increased with concentration, reaching the weak-moderate intensity at the highest phenol concentration in PP and TJ only. Pungency was suppressed in BP and perceived at weak-moderate intensity in PP and TJ sample at the highest phenol concentration. Proteins/neutral pH plant-food (BP) resulted more appropriate to counteract the impact of added phenol on negative sensory properties thus allowing to optimize the balance between health and sensory properties
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