920 resultados para Frontiers


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Carbons are the main electrode materials used in supercapacitors, which are electrochemical energy storage devices with high power densities and long cycling lifetimes. However, increasing their energy density capacity will improve their potential for commercial implementation.
In this regard, the use of high surface area carbons and high voltage electrolytes are well known strategies to increase the attainable energy density, and lately ionic liquids have been explored as promising alternatives to current state of the art acetonitrile-based electrolytes. Also, in terms of safety and sustainability ionic liquids are attractive electrolyte materials for supercapacitors. In addition, it has been shown that the matching of the carbon pore size with the electrolyte ion size further increases the attainable electrochemical double layer (ECDL) capacitance and energy density.
The use of pseudocapacitive reactions can significantly increase the attainable energy density, and quinonic-based materials offer a potentially sustainable and cost effective research avenue for both the electrode and the electrolyte.
This perspective will provide an overview of the current state of the art research on supercapacitors based on combinations of carbons, ionic liquids and quinonic compounds, highlighting performances and challenges and discussing possible future research avenues. In this regard, current interest is mainly focused on strategies which may ultimately lead to commercially competitive sustainable high performance supercapacitors for different applications including those requiring mechanical flexibility and biocompatibility.

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Foraminifera are an important faunal element of the benthos in oxygen-depleted settings such as Oxygen Minimum Zones (OMZs) where they can play a relevant role in the processing of phytodetritus. We investigated the uptake of phytodetritus (labeled with 13C and 15N) by cal-careous foraminifera in the 0-1 cm sediment horizon under different oxygen concentrations within the OMZ in the eastern Arabian Sea. The in situ tracer experiments were carried out along a depth transect on the Indian margin over a period of 4 to 10 days. The uptake of phy-todetrital carbon within 4 days by all investigated species shows that phytodetritus is a rele-vant food source for foraminifera in OMZ sediments. The decrease of total carbon uptake from 540 to 1100 m suggests a higher demand for carbon by species in the low-oxygen core region of the OMZ or less food competition with macrofauna. Especially Uvigerinids showed high uptake of phytodetrital carbon at the lowest oxygenated site. Variation in the ratio of phytodetrital carbon to nitrogen between species and sites indicates that foraminiferal carbon and nitrogen use can be decoupled and different nutritional demands are found between spe-cies. Lower ratio of phytodetrital carbon and nitrogen at 540 m could hint for greater demand or storage of food-based nitrogen, ingestion or hosting of bacteria under almost anoxic condi-tions. Shifts in the foraminiferal assemblage structure (controlled by oxygen or food availabil-ity) and in the presence of other benthic organisms account for observed changes in the pro-cessing of phytodetritus in the different OMZ habitats. Foraminifera dominate the short-term processing of phytodetritus in the OMZ core but are less important in the lower OMZ bounda-ry region of the Indian margin as biological interactions and species distribution of foraminifera change with depth and oxygen levels.

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The role of insulin-like growth factor binding protein 2 (IGFBP2) in cancer is unclear. In general, IGFBP2 is considered to be oncogenic and its expression is often observed to be elevated in cancer. However, there are a number of conflicting reports in vitro and in vivo where IGFBP2 acts in a tumor suppressor manner. In this mini-review, we discuss the factors influencing the variation in IGFBP2 expression in cancer and our interpretation of these findings.

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Anthrax is an endemic infection in many countries, particularly in the developing world. The causative agent, Bacillus anthracis, mediates disease through the secretion of binary exotoxins. Until recently, research into adaptive immunity targeting this bacterial pathogen has largely focused on the humoral response to these toxins. There is, however, growing recognition that cellular immune responses involving IFNγ producing CD4+ T cells also contribute significantly to a protective memory response. An established concept in adaptive immunity to infection is that during infection of host cells, new microbial epitopes may be revealed, leading to immune recognition of so called 'cryptic' or 'subdominant' epitopes. We analyzed the response to both cryptic and immunodominant T cell epitopes derived from the toxin component lethal factor and presented by a range of HLA-DR alleles. Using IFNγ-ELISpot assays we characterized epitopes that elicited a response following immunization with synthetic peptide and the whole protein and tested their capacities to bind purified HLA-DR molecules in vitro. We found that DR1 transgenics demonstrated T cell responses to a greater number of domain III cryptic epitopes than other HLA-DR transgenics, and that this pattern was repeated with the immunodominant epitopes, as a greater proportion of these epitopes induced a T cell response when presented within the context of the whole protein. Immunodominant epitopes LF457-476 and LF467-487 were found to induce a T cell response to the peptide, as well as to the whole native LF protein in DR1 and DR15, but not in DR4 transgenics. The analysis of Domain I revealed the presence of several unique cryptic epitopes all of which showed a strong to moderate relative binding affinity to HLA-DR4 molecules. However, none of the cryptic epitopes from either domain III or I displayed notably high binding affinities across all HLA-DR alleles assayed. These responses were influenced by the specific HLA alleles presenting the peptide, and imply that construction of future epitope string vaccines which are immunogenic across a wide range of HLA alleles could benefit from a combination of both cryptic and immunodominant anthrax epitopes.

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We report, for the first time, extensive biologically-mediated phosphate removal from wastewater during high-rate anaerobic digestion (AD). A hybrid sludge bed/fixed-film (packed pumice stone) reactor was employed for low-temperature (12°C) anaerobic treatment of synthetic sewage wastewater. Successful phosphate removal from the wastewater (up to 78% of influent phosphate) was observed, mediated by biofilms in the reactor. Scanning electron microscopy and energy dispersive X-ray analysis revealed the accumulation of elemental phosphorus (~2%) within the sludge bed and fixed-film biofilms. 4’, 6-diamidino-2-phenylindole (DAPI) staining indicated phosphorus accumulation was biological in nature and mediated through the formation of intracellular inorganic polyphosphate (polyP) granules within these biofilms. DAPI staining further indicated that polyP accumulation was rarely associated with free cells. Efficient and consistent chemical oxygen demand (COD) removal was recorded, throughout the 732-day trial, at applied organic loading rates between 0.4-1.5 kg COD m-3 d-1 and hydraulic retention times of 8-24 hours, while phosphate removal efficiency ranged from 28-78% on average per phase. Analysis of protein hydrolysis kinetics and the methanogenic activity profiles of the biomass revealed the development, at 12˚C, of active hydrolytic and methanogenic populations. Temporal microbial changes were monitored using Illumina Miseq analysis of bacterial and archaeal 16S rRNA gene sequences. The dominant bacterial phyla present in the biomass at the conclusion of the trial were the Proteobacteria and Firmicutes and the dominant archaeal genus was Methanosaeta. Trichococcus and Flavobacterium populations, previously associated with low temperature protein degradation, developed in the reactor biomass. The presence of previously characterised polyphosphate accumulating organisms (PAOs) such as Rhodocyclus, Chromatiales, Actinobacter and Acinetobacter was recorded at low numbers. However, it is unknown as yet if these were responsible for the luxury polyP uptake observed in this system. The possibility of efficient phosphate removal and recovery from wastewater during AD would represent a major advance in the scope for widespread application of anaerobic wastewater treatment technologies.

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Introduction: Abundant evidence shows that regular physical activity (PA) is an effective strategy for preventing obesity in people of diverse socioeconomic status (SES) and racial groups. The proportion of PA performed in parks and how this differs by proximate neighborhood SES has not been thoroughly investigated. The present project analyzes online public web data feeds to assess differences in outdoor PA by neighborhood SES in St. Louis, MO, USA.
Methods: First, running and walking routes submitted by users of the website MapMyRun.com were downloaded. The website enables participants to plan, map, record, and share their exercise routes and outdoor activities like runs, walks, and hikes in an online database. Next, the routes were visually illustrated using geographic information systems. Thereafter, using park data and 2010 Missouri census poverty data, the odds of running and walking routes traversing a low-SES neighborhood, and traversing a park in a low-SES neighborhood were examined in comparison to the odds of routes traversing higher-SES neighborhoods and higher-SES parks.
Results: Results show that a majority of running and walking routes occur in or at least traverse through a park. However, this finding does not hold when comparing low-SES neighborhoods to higher-SES neighborhoods in St. Louis. The odds of running in a park in a low-SES neighborhood were 54% lower than running in a park in a higher-SES neighborhood (OR = 0.46, CI = 0.17-1.23). The odds of walking in a park in a low-SES neighborhood were 17% lower than walking in a park in a higher-SES neighborhood (OR = 0.83, CI = 0.26-2.61).
Conclusion: The novel methods of this study include the use of inexpensive, unobtrusive, and publicly available web data feeds to examine PA in parks and differences by neighborhood SES. Emerging technologies like MapMyRun.com present significant advantages to enhance tracking of user-defined PA across large geographic and temporal settings.

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In a recent article (Astuti & Bloch, 2015), cognitive anthropologists Rita Astuti and Maurice Bloch claim that the Malagasy are ambivalent as to whether considerations of intentionality are relevant to moral judgments concerning incest and its presumed catastrophic consequences: when making moral judgments about those who commit incest, the Malagasy take into account whether the incest is intentional or not, but, when making moral judgments relating to incest’s catastrophic consequences, they do not take intentionality into account. Astuti & Bloch explain the irrelevance of intentionality in terms of incest entailing such a fundamental attack on the transcendental social order that the Malagasy become dumbfounded and leave aside considerations of intentionality. Finally, they claim that a similar dumbfound reaction is what is involved in the moral dumbfounding concerning incest that social psychologist Jonathan Haidt has found in the US. In this article, we argue that (i) Astuti & Bloch are unclear about many aspects of their claims (in particular, about the moral judgments at stake), (ii) they do not provide sufficient evidence that considerations of intentionality are deemed irrelevant to moral judgments relating to incest’s presumed catastrophic consequences (and hence for the claim that the Malagasy are ambivalent), (iii) their hypothesis that conceiving of incest as an attack on the transcendental social renders considerations of intentionality irrelevant lacks coherence, and (iv) the extension of their explanatory account to the moral dumfounding of American students in Haidt’s well-known scenario of intentional incest is unwarranted.

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Cross education is the process whereby training of one limb gives rise to increases in the subsequent performance of its opposite counterpart. The execution of many unilateral tasks is associated with increased excitability of corticospinal projections from primary motor cortex (M1) to the opposite limb. It has been proposed that these effects are causally related. Our aim was to establish whether changes in corticospinal excitability arising from prior training of the opposite limb determine levels of interlimb transfer.

We used three vision conditions shown previously to modulate the excitability of corticospinal projections to the inactive (right) limb during wrist flexion movements performed by the training (left) limb. These were: mirrored visual feedback of the training limb; no visual feedback of either limb; and visual feedback of the inactive limb. Training comprised 300 discrete, ballistic wrist flexion movements executed as rapidly as possible. Performance of the right limb on the same task was assessed prior to, at the mid point of, and following left limb training.

There was no evidence that variations in the excitability of corticospinal projections (assessed by transcranial magnetic stimulation (TMS)) to the inactive limb were associated with, or predictive of, the extent of interlimb transfer that was expressed. There were however associations between alterations in muscle activation dynamics observed for the untrained limb, and the degree of positive transfer that arose from training of the opposite limb.

The results suggest that the acute adaptations that mediate the bilateral performance gains realised through unilateral practice of this ballistic wrist flexion task are mediated by neural elements other than those within M1 that are recruited at rest by single-pulse TMS.

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There is lack of consistent evidence as to how well PD patients are able to accurately time their movements across space with an external acoustic signal. For years, research based on the finger-tapping paradigm, the most popular paradigm for exploring the brain's ability to time movement, has provided strong evidence that patients are not able to accurately reproduce an isochronous interval [i.e., Ref. (1)]. This was undermined by Spencer and Ivry (2) who suggested a specific deficit in temporal control linked to emergent, rhythmical movement not event-based actions, which primarily involve the cerebellum. In this study, we investigated motor timing of seven idiopathic PD participants in event-based sensorimotor synchronization task. Participants were asked to move their finger horizontally between two predefined target zones to synchronize with the occurrence of two sound events at two time intervals (1.5 and 2.5 s). The width of the targets and the distance between them were manipulated to investigate impact of accuracy demands and movement amplitude on timing performance. The results showed that participants with PD demonstrated specific difficulties when trying to accurately synchronize their movements to a beat. The extent to which their ability to synchronize movement was compromised was found to be related to the severity of PD, but independent of the spatial constraints of the task.

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O conceito de descontinuidade é abordado em função de valores associáveis à cidade num contexto de mudanças de paradigmas relacionados com o planeamento do território. O impacto que as descontinuidades têm na forma, estrutura e fronteiras urbanas é analisado recorrendo à Área Metropolitana de Lisboa como estudo de caso. Para abordar as descontinuidades, recorre-se à análise de tendências territoriais recentes, malhas e tecidos construídos e planos mais directamente relacionados com o desenho urbano. O trabalho empírico culmina com o aprofundamento do estudo de um território do interior da Península de Setúbal. Com os resultados desta investigação pretende-se articular tendências territoriais, territórios construídos e instrumentos de planeamento na definição do conceito de descontinuidade. Apresenta-se ainda como conclusão um modelo de intervenção com vista à resolução de descontinuidades. Esta conclusão pretende ser também um contributo, sob a forma de resposta, para a questão levantada por Federico Oliva, quando se interroga, a propósito da cidade de Milão, sobre o que resta dos planos na Cidade.

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As técnicas estatísticas são fundamentais em ciência e a análise de regressão linear é, quiçá, uma das metodologias mais usadas. É bem conhecido da literatura que, sob determinadas condições, a regressão linear é uma ferramenta estatística poderosíssima. Infelizmente, na prática, algumas dessas condições raramente são satisfeitas e os modelos de regressão tornam-se mal-postos, inviabilizando, assim, a aplicação dos tradicionais métodos de estimação. Este trabalho apresenta algumas contribuições para a teoria de máxima entropia na estimação de modelos mal-postos, em particular na estimação de modelos de regressão linear com pequenas amostras, afetados por colinearidade e outliers. A investigação é desenvolvida em três vertentes, nomeadamente na estimação de eficiência técnica com fronteiras de produção condicionadas a estados contingentes, na estimação do parâmetro ridge em regressão ridge e, por último, em novos desenvolvimentos na estimação com máxima entropia. Na estimação de eficiência técnica com fronteiras de produção condicionadas a estados contingentes, o trabalho desenvolvido evidencia um melhor desempenho dos estimadores de máxima entropia em relação ao estimador de máxima verosimilhança. Este bom desempenho é notório em modelos com poucas observações por estado e em modelos com um grande número de estados, os quais são comummente afetados por colinearidade. Espera-se que a utilização de estimadores de máxima entropia contribua para o tão desejado aumento de trabalho empírico com estas fronteiras de produção. Em regressão ridge o maior desafio é a estimação do parâmetro ridge. Embora existam inúmeros procedimentos disponíveis na literatura, a verdade é que não existe nenhum que supere todos os outros. Neste trabalho é proposto um novo estimador do parâmetro ridge, que combina a análise do traço ridge e a estimação com máxima entropia. Os resultados obtidos nos estudos de simulação sugerem que este novo estimador é um dos melhores procedimentos existentes na literatura para a estimação do parâmetro ridge. O estimador de máxima entropia de Leuven é baseado no método dos mínimos quadrados, na entropia de Shannon e em conceitos da eletrodinâmica quântica. Este estimador suplanta a principal crítica apontada ao estimador de máxima entropia generalizada, uma vez que prescinde dos suportes para os parâmetros e erros do modelo de regressão. Neste trabalho são apresentadas novas contribuições para a teoria de máxima entropia na estimação de modelos mal-postos, tendo por base o estimador de máxima entropia de Leuven, a teoria da informação e a regressão robusta. Os estimadores desenvolvidos revelam um bom desempenho em modelos de regressão linear com pequenas amostras, afetados por colinearidade e outliers. Por último, são apresentados alguns códigos computacionais para estimação com máxima entropia, contribuindo, deste modo, para um aumento dos escassos recursos computacionais atualmente disponíveis.

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O presente estudo tem por objetivo compreender, no contexto geopolítico de Timor-Leste, quais as imagens, funções e estatutos das línguas que aí circulam e, simultaneamente, percecionar de que modo a Escola gere essa pluralidade linguística. Para o efeito, tivemos em conta as representações/imagens relativamente às línguas, às suas funções e estatutos, não só dos alunos e dos diferentes atores educativos (professores, diretores de escola e formadores do 1.º e 2.º ciclo), mas também aquelas que circulam em contexto social alargado, onde incluímos os intervenientes e os responsáveis pelas políticas educativas e outros elementos da população. Foi deste modo que procurámos perceber de que forma tais representações se influenciam reciprocamente e se refletem na Escola. O estudo realizado foi de cariz etnográfico. Assim, o investigadorobservador, colocado no terreno, foi produzindo um diário do observador e recolhendo informação etnográfica, através da sua convivência com a sociedade timorense (escritos do quotidiano, questionário à polícia, observação de aula, entre outros), auscultando as “vozes” quer dos alunos (por meio de biografias linguísticas e desenhos), quer dos atores educativos (através de biografias linguísticas e entrevistas), quer ainda dos intervenientes nas políticas educativas (com recurso a entrevistas) e de alguns jovens timorenses, recorrendo de novo às entrevistas. Simultaneamente, foi feita uma recolha documental, ao longo de todo o período em que o estudo decorreu, que integrou fontes escritas (documentos oficiais, como sejam os documentos reguladores das políticas linguísticas e os manuais, fontes não oficiais, incluindo documentos vários e testemunhos e fontes estatísticas, como os Censos) e fontes não escritas (imagens e sons registados, estes posteriormente transcritos). Todos estes dados foram classificados em dados primários e secundários, em função da sua relevância para o estudo. Para a sua análise socorremo-nos da análise de conteúdo para as biografias, as entrevistas e os manuais de língua portuguesa, estes no quadro de uma abordagem para a diversidade linguística e cultural, de uma análise documental para os documentos reguladores do Sistema Educativa e outros documentos oficiais relativos às línguas e, finalmente, recorremos a uma análise biográfica (Molinié, 2011) para os desenhos realizados pelos alunos. Os resultados obtidos vieram evidenciar o multilinguismo social e escolar que se vive no país, as imagens e as funções que as línguas desempenham nestes dois contextos, o escolar e o da sociedade alargada, permitindo-nos compreender que a Escola não é apenas um microcosmos dentro da sociedade, mas um espaço de encontro, por vezes de confronto, entre diversas línguas, culturas e identidades. Ela é também espaço onde as questões do plurilinguismo são mais desafiantes na medida em que as línguas não são apenas objeto de ensino aprendizagem, mas desempenham igualmente funções importantes na aquisição dos saberes escolares, na interação social e no desenvolvimento cognitivo dos alunos. Nestes contextos, ocorrem duas situações relevantes, uma é o facto de a Escola ser um lugar onde os repertórios linguísticos plurilingues dos alunos entram em contacto com as línguas de escolarização, o português, o tétum e o malaio indonésio e outra é que saberes escolares e saberes culturais utilizam línguas diferentes, isto é, os primeiros são veiculados em tétum e português, eventualmente em malaio indonésio, mas os saberes culturais são expressos nas línguas autóctones, ameaçadas, porém, por uma crescente expansão do tétum. Contudo, estas línguas criam também espaços privados, identitários e de coesão social dentro da grande cidade que é Díli. São línguas “secretas” e “de defesa.” Por fim, referiremos a urgência para que se tomem medidas no sentido de se criar um consenso sobre a normalização do tétum, que conduza à sua aplicação em contexto educativo e ao seu desenvolvimento funcional, isto é, que leve à planificação do seu estatuto. Visa-se, com este estudo, contribuir para que os atores, acima referidos, possam «repensar» a Escola, em Timor Leste, e, em particular, no que diz respeito à gestão das línguas que nela circulam, através de uma política linguística (educativa) que beneficie o Sistema Educativo, com eventuais repercussões no âmbito do currículo, da produção de materiais e da formação de professores. Face aos resultados obtidos, ainda que consideremos este estudo como parcelar, pelo facto de ter decorrido, sobretudo, na capital timorense, permitimo-nos sugerir a necessidade de esbater fronteiras entre o espaço escolar e as realidades dos alunos, encontrando uma gestão escolar deste plurilinguismo que crie um currículo mais integrador dos saberes linguísticos dos alunos.

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The use of visual cues during the processing of audiovisual (AV) speech is known to be less efficient in children and adults with language difficulties and difficulties are known to be more prevalent in children from low-income populations. In the present study, we followed an economically diverse group of thirty-seven infants longitudinally from 6–9 months to 14–16 months of age. We used eye-tracking to examine whether individual differences in visual attention during AV processing of speech in 6–9 month old infants, particularly when processing congruent and incongruent auditory and visual speech cues, might be indicative of their later language development. Twenty-two of these 6–9 month old infants also participated in an event-related potential (ERP) AV task within the same experimental session. Language development was then followed-up at the age of 14–16 months, using two measures of language development, the Preschool Language Scale and the Oxford Communicative Development Inventory. The results show that those infants who were less efficient in auditory speech processing at the age of 6–9 months had lower receptive language scores at 14–16 months. A correlational analysis revealed that the pattern of face scanning and ERP responses to audiovisually incongruent stimuli at 6–9 months were both significantly associated with language development at 14–16 months. These findings add to the understanding of individual differences in neural signatures of AV processing and associated looking behavior in infants.

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Sound localization can be defined as the ability to identify the position of an input sound source and is considered a powerful aspect of mammalian perception. For low frequency sounds, i.e., in the range 270 Hz-1.5 KHz, the mammalian auditory pathway achieves this by extracting the Interaural Time Difference between sound signals being received by the left and right ear. This processing is performed in a region of the brain known as the Medial Superior Olive (MSO). This paper presents a Spiking Neural Network (SNN) based model of the MSO. The network model is trained using the Spike Timing Dependent Plasticity learning rule using experimentally observed Head Related Transfer Function data in an adult domestic cat. The results presented demonstrate how the proposed SNN model is able to perform sound localization with an accuracy of 91.82% when an error tolerance of +/-10 degrees is used. For angular resolutions down to 2.5 degrees , it will be demonstrated how software based simulations of the model incur significant computation times. The paper thus also addresses preliminary implementation on a Field Programmable Gate Array based hardware platform to accelerate system performance.