215 research outputs found

    Encapsulation of Nanostructures in a Dielectric Matrix Providing Optical Enhancement in Ultrathin Solar Cells

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    The incorporation of nanostructures in optoelectronic devices for enhancing their optical performance is widely studied. However, several problems related to the processing complexity and the low performance of the nanostructures have hindered such actions in real-life devices. Herein, a novel way of introducing gold nanoparticles in a solar cell structure is proposed in which the nanostructures are encapsulated with a dielectric layer, shielding them from high temperatures and harsh growth processing conditions of the remaining device. Through optical simulations, an enhancement of the effective optical path length of approximately four times the nominal thickness of the absorber layer is verified with the new architecture. Furthermore, the proposed concept in a Cu(In,Ga)Se2 solar cell device is demonstrated, where the short-circuit current density is increased by 17.4%. The novel structure presented in this work is achieved by combining a bottom-up chemical approach of depositing the nanostructures with a top-down photolithographic process, which allows for an electrical contact.This work was funded in part by the Fundação para a Ciência e a Tecnologia (FCT) under Grants IF/00133/2015, PD/BD/142780/2018 and SFRH/BD/ 146776/2019. The authors also want to acknowledge the European Union’s Horizon 2020 Research and Innovation Programme through the ARCIGS-M project under Grant 720887, the Special Research Fund (BOF) of Hasselt University, the FCT through the project NovaCell (PTDC/CTM-CTM/28075/ 2017), and InovSolarCells (PTDC/FISMAC/29696/2017) co-funded by FCT and the ERDF through COMPETE2020. The authors also want to acknowledge Sandra Maya for the production of images used in this work.info:eu-repo/semantics/publishedVersio

    Reproducibility of arterial spin labeling cerebral blood flow image processing:A report of the ISMRM open science initiative for perfusion imaging (OSIPI) and the ASL MRI challenge

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    Purpose: Arterial spin labeling (ASL) is a widely used contrast-free MRI method for assessing cerebral blood flow (CBF). Despite the generally adopted ASL acquisition guidelines, there is still wide variability in ASL analysis. We explored this variability through the ISMRM-OSIPI ASL-MRI Challenge, aiming to establish best practices for more reproducible ASL analysis. Methods: Eight teams analyzed the challenge data, which included a high-resolution T1-weighted anatomical image and 10 pseudo-continuous ASL datasets simulated using a digital reference object to generate ground-truth CBF values in normal and pathological states. We compared the accuracy of CBF quantification from each team's analysis to the ground truth across all voxels and within predefined brain regions. Reproducibility of CBF across analysis pipelines was assessed using the intra-class correlation coefficient (ICC), limits of agreement (LOA), and replicability of generating similar CBF estimates from different processing approaches. Results: Absolute errors in CBF estimates compared to ground-truth synthetic data ranged from 18.36 to 48.12 mL/100 g/min. Realistic motion incorporated into three datasets produced the largest absolute error and variability between teams, with the least agreement (ICC and LOA) with ground-truth results. Fifty percent of the submissions were replicated, and one produced three times larger CBF errors (46.59 mL/100 g/min) compared to submitted results. Conclusions: Variability in CBF measurements, influenced by differences in image processing, especially to compensate for motion, highlights the significance of standardizing ASL analysis workflows. We provide a recommendation for ASL processing based on top-performing approaches as a step toward ASL standardization.</p

    Genome of the Avirulent Human-Infective Trypanosome—Trypanosoma rangeli

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    Background: Trypanosoma rangeli is a hemoflagellate protozoan parasite infecting humans and other wild and domestic mammals across Central and South America. It does not cause human disease, but it can be mistaken for the etiologic agent of Chagas disease, Trypanosoma cruzi. We have sequenced the T. rangeli genome to provide new tools for elucidating the distinct and intriguing biology of this species and the key pathways related to interaction with its arthropod and mammalian hosts.  Methodology/Principal Findings: The T. rangeli haploid genome is ,24 Mb in length, and is the smallest and least repetitive trypanosomatid genome sequenced thus far. This parasite genome has shorter subtelomeric sequences compared to those of T. cruzi and T. brucei; displays intraspecific karyotype variability and lacks minichromosomes. Of the predicted 7,613 protein coding sequences, functional annotations could be determined for 2,415, while 5,043 are hypothetical proteins, some with evidence of protein expression. 7,101 genes (93%) are shared with other trypanosomatids that infect humans. An ortholog of the dcl2 gene involved in the T. brucei RNAi pathway was found in T. rangeli, but the RNAi machinery is non-functional since the other genes in this pathway are pseudogenized. T. rangeli is highly susceptible to oxidative stress, a phenotype that may be explained by a smaller number of anti-oxidant defense enzymes and heatshock proteins.  Conclusions/Significance: Phylogenetic comparison of nuclear and mitochondrial genes indicates that T. rangeli and T. cruzi are equidistant from T. brucei. In addition to revealing new aspects of trypanosome co-evolution within the vertebrate and invertebrate hosts, comparative genomic analysis with pathogenic trypanosomatids provides valuable new information that can be further explored with the aim of developing better diagnostic tools and/or therapeutic targets

    Body weight, metabolism and clock genes

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    Biological rhythms are present in the lives of almost all organisms ranging from plants to more evolved creatures. These oscillations allow the anticipation of many physiological and behavioral mechanisms thus enabling coordination of rhythms in a timely manner, adaption to environmental changes and more efficient organization of the cellular processes responsible for survival of both the individual and the species. Many components of energy homeostasis exhibit circadian rhythms, which are regulated by central (suprachiasmatic nucleus) and peripheral (located in other tissues) circadian clocks. Adipocyte plays an important role in the regulation of energy homeostasis, the signaling of satiety and cellular differentiation and proliferation. Also, the adipocyte circadian clock is probably involved in the control of many of these functions. Thus, circadian clocks are implicated in the control of energy balance, feeding behavior and consequently in the regulation of body weight. In this regard, alterations in clock genes and rhythms can interfere with the complex mechanism of metabolic and hormonal anticipation, contributing to multifactorial diseases such as obesity and diabetes. The aim of this review was to define circadian clocks by describing their functioning and role in the whole body and in adipocyte metabolism, as well as their influence on body weight control and the development of obesity

    Cartografia e diplomacia: usos geopolíticos da informação toponímica (1750-1850)

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    O artigo explora dimensões geopolíticas da toponímia, registradas em documentos cartográficos, desde as reformas empreendidas pelo consulado pombalino em meados do século XVIII, até às primeiras décadas do século XIX, em meio ao processo de afirmação do Estado imperial pós-colonial.This paper explores the geopolitical dimensions of toponymy as registered in cartographic documents dating from the reforms pushed through by the consulate of Marquis of Pombal in the mid 18th century to the early decades of the 19th century, as the post-colonial imperial State established itself

    Para que servem os inventários de fauna?

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    Inventários de fauna acessam diretamente a diversidade de uma localidade, em um determinado espaço e tempo. Os dados primários gerados pelos inventários compõem uma das ferramentas mais importantes na tomada de decisões a respeito do manejo de áreas naturais. Entretanto, vários problemas têm sido observados em diversos níveis relacionados aos inventários de fauna no Brasil e vão desde a formação de recursos humanos até a ausência de padronização, de desenho experimental e de seleção de métodos inadequados. São apresentados estudos de caso com mamíferos, répteis, anfíbios e peixes, nos quais são discutidos problemas como variabilidade temporal e métodos para detecção de fauna terrestre, sugerindo que tanto os inventários quanto os programas de monitoramento devam se estender por prazos maiores e que os inventários devem incluir diferentes metodologias para que os seus objetivos sejam plenamente alcançados.Inventories of fauna directly access the diversity of a locality in a certain period of time. The primary data generated by these inventories comprise one of the most important steps in decisions making regarding the management of natural areas. However, several problems have been observed at different levels related to inventories of fauna in Brazil, and range from the training of humans to the lack of standardization of experimental design and selection of inappropriate methods. We present case studies of mammals, reptiles, amphibians and fishes, where they discussed issues such temporal variability and methods for detection of terrestrial fauna, suggesting that both inventories and monitoring programs should be extended for longer terms and that inventories should include different methodologies to ensure that their goals are fully achieved

    Massive X-ray screening reveals two allosteric drug binding sites of SARS-CoV-2 main protease

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    The coronavirus disease (COVID-19) caused by SARS-CoV-2 is creating tremendous health problems and economical challenges for mankind. To date, no effective drug is available to directly treat the disease and prevent virus spreading. In a search for a drug against COVID-19, we have performed a massive X-ray crystallographic screen of repurposing drug libraries containing 5953 individual compounds against the SARS-CoV-2 main protease (Mpro), which is a potent drug target as it is essential for the virus replication. In contrast to commonly applied X-ray fragment screening experiments with molecules of low complexity, our screen tested already approved drugs and drugs in clinical trials. From the three-dimensional protein structures, we identified 37 compounds binding to Mpro. In subsequent cell-based viral reduction assays, one peptidomimetic and five non-peptidic compounds showed antiviral activity at non-toxic concentrations. Interestingly, two compounds bind outside the active site to the native dimer interface in close proximity to the S1 binding pocket. Another compound binds in a cleft between the catalytic and dimerization domain of Mpro. Neither binding site is related to the enzymatic active site and both represent attractive targets for drug development against SARS-CoV-2. This X-ray screening approach thus has the potential to help deliver an approved drug on an accelerated time-scale for this and future pandemics
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