1,724,214 research outputs found
Engineering Pt-Pt coordination environment to enhance the four-electron oxygen reduction reaction
No full textThe oxygen reduction reaction (ORR) in proton exchange membrane fuel cells plays an important role in the H2 economy. Pt-based alloy catalysts with tuned d-band centres are widely regarded as the most efficient catalysts. Here we report that the average size of Pt domains in a Pt-Pd alloy, described as the Pt-Pt coordination number (C.N.), may measure the coordination environment of Pt and its effect on the d-states, to serve as a key geometric descriptor for the ORR activity. The decrease of Pt-Pt C.N. from 10.8 in commercial Pt nanoparticles to 1.33 in Pt1Pd493 alloy leads to an exponential increase in the Pt mass activity from 0.18 to 4.86 A/mgPt. Density functional theory calculations show that low C.N. sites of Pt within the Pd host have low O-O dissociation barriers, favouring the four-electron dissociative pathway. The precise engineering of Pt-Pt C.N. in an alloy is critical for optimising metal use in the activation of chemically stable compounds, particularly in the context of catalysis for renewable energy
Unprecedented Pt-Pt Bonded Trimer {[Pt2Cu4(CºCPh)8]}3 showing Unusual Near-Infrared Luminescence
Get PDFThe homoleptic high-nuclearity platinum-copper acetylide complex of stoichiometry [PtCu2-(C≡CPh)4] crystallizes in at least three different polymorphic forms. Dark violet-green crystals with metallic reflectance have been shown by an X-ray diffraction study to be formed by discrete trimers of an hexanuclear octahedral cluster unit {[Pt2Cu4(C≡CPh)8]}3 stabilized by two unsupported Pt-Pt interactions [2.995(1) Å]. The photoluminescence behavior of this complex which is dramatically influenced by strong axial Pt⋯Pt interactions either in solid state or in solution (CH2Cl2 298, 77 K) has been studied
The FYVE domain in Smad anchor for receptor activation (SARA) is sufficient for localization of SARA in early endosomes and regulates TGF-beta/Smad signalling
No full textBACKGROUND: Transforming growth factor-beta (TGF-beta) initiates intracellular signalling by inducing the formation of a heteromeric complex between TGF-beta type I (TbetaR-I) and TGF-beta type II serine/threonine kinase receptors (TbetaR-II). After the activation of TbetaR-I kinase by TbetaR-II kinase, specific receptor-regulated Smads (R-Smads) are phosphorylated by TbetaR-I kinase. Smad anchor for receptor activation (SARA), which contains a FYVE finger domain, regulates the subcellular localization of R-Smads and presents them to TbetaR-I. However, it is unclear where SARA is localized in the cell and which phospholipid(s) interacts with its FYVE domain. RESULTS: Wild-type SARA and the FYVE domain of SARA (FYVE(SARA)) reveal a punctate staining pattern and co-localize with the early endosomal markers, early endosomal antigen-1 (EEA1) and hepatic growth factor-regulated tyrosine kinase substrate (Hrs). The ectopic expression of dominant negative rab5, a critical regulatory molecule in endosome function, redistributes SARA from punctate to a diffuse cytosolic staining pattern. A lipid binding assay demonstrated that the recombinant FYVE domain from SARA predominantly interacts with phosphatidylinositol 3-phosphate (PtdIns(3)P). Consistent with this result, wortmannin, a PI3 kinase inhibitor, resulted in both a redistribution of SARA from the endosomal compartment to the cytosol and the attenuation of both TGF-beta-induced R-Smad phosphorylation and transcriptional activation. Ectopic expression of the FYVE domain of SARA also induced the redistribution of wild-type SARA and inhibited TGF-beta as well as BMP/Smad-induced transcriptional responses. CONCLUSION: The FYVE domain is sufficient and necessary for the early endosomal localization of SARA, probably through its interaction with PtdIns(3)P. Moreover, the localization of SARA in early endosomes is required for efficient TGF-beta/Smad signalling
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
PT-PT synthetic speech detection
No full textRecent developments in the field of artificial intelligence (AI) have led to the creation of powerful generative models. These models have demonstrated such capabilities that it becomes nearly impossible for a human to distinguish between generated and human utterances, between synthetic and natural speech. A relatively recent example of this fact is the deepfake video of former U.S. President Barack Obama [1]. This video not only serves as a demonstration of the capabilities of AI models but also highlights the potential for misinformation, as these models can deceive individuals into believing in fabricated scenarios. This extends to the realm of synthetic speech, where models like Google Duplex [2], leveraging WaveNet technology, a deep neural network for seamless speech creation, exhibit an impressive degree of realism and naturalness. For this reason, two situations may arise. The first is related to new business opportunities, such as the creation of realistic voiceovers for films and animations or enhancement in the communication for individuals with hearing or speech impairments [3]. The other, raises concerns about privacy and security since voice impersonation is easily achievable with today’s tools. Given this fact, an analysis of approaches applied in the ASVspoof challenge [4] was carried on. The ultimate goal is to develop a system capable of distinguishing between real voices and cloned voices, by adapting the research done on this chal lenge to the portuguese from Portugal (PT-PT) language. For this purpose, we first created a PT-PT dataset using both text-to-speech (TTS) and speech-to-speech (STS). Then, we employed and implemented some models from the literature and tested in several datasets that encompass both english and PT-PT voices, to evaluate their per formance and reach conclusions. From this, we found out that while this is a difficult task, by augmenting the data with different impulse response devices (IRs) and com pressions codecs, there was an improvement in the generalization to different attacks from different datasets. Overall, after the evaluation process the best models found through statistical anal ysis were the ResNet-OC and ECAPA-TDNN. Being our goal tailored to PT-PT, by fine-tuning them, we further improved their performance. At the end future steps are highlighted, one of which may be very important to complement the work made so far, which is the integration of the fraud detection componentOs recentes desenvolvimentos na área de inteligência artificial (IA) levaram à criação de poderosos modelos generativos. Estes modelos demonstraram tais capacidades que torna quase impossível para um humano a tarefa de distinguir entre afirmações geradas na IA e humanas. Um exemplo relativamente recente deste facto é o do vídeo falso do ex-Presidente dos Estados Unidos, Barack Obama [1]. Este vídeo não serve apenas como uma demonstração das capacidades dos modelos de IA, mas também destaca o potencial de desinformação, uma vez que estes modelos podem induzir indivíduos a acreditar em cenários "fabricados". Isto estende-se ao domínio da fala sintética, onde modelos como o Google Duplex [2], que aproveitando a tecnologia WaveNet, uma rede neuronal profunda que serve para a criação perfeita de um discurso, exibem um elevado grau de realismo e naturalidade. Por este motivo, podemo-nos deparar com duas situações: a primeira está ligada à oportunidade para novos negócios, como a criação de dobragens realistas para filmes e animações [3], enquanto que a outra, abre caminho a problemas relacionados com a privacidade e segurança, uma vez que a falsificação da voz é de fácil execução com as ferramentas que existem hoje em dia. Dado este fato, foi realizada uma análise das abordagens aplicadas no desafio ASVspoof [4]. O objetivo final é desenvolver um sistema capaz de distinguir entre vozes reais e vozes clonadas, adaptando a investigação realizada no mesmo, para a língua portuguesa de Portugal (PT-PT). Para este fim, primeiro criámos um conjunto de dados PT-PT usando tanto a conversão de texto-para-fala como a conversão de fala-para-fala. Em seguida, utilizámos e implementámos alguns modelos da literatura e testámos em vários conjuntos de dados, que englobam tanto vozes em inglês como em PT-PT, para avaliar o seu desempenho e tirar conclusões. Desta forma, descobrimos que, embora esta seja uma tarefa difícil, ao aumentar os dados com diferentes dispositivos de resposta ao impulso e tipos de compressões, houve uma melhoria na generalização para diferentes ataques de diferentes conjuntos de dados. No geral, após a fase de testes, os melhores modelos encontrados através da análise estatística foram o ResNet-OC e o ECAPA-TDNN. Sendo o nosso objetivo focado para PT-PT, ao refiná-los, conseguimos melhorar ainda mais o desempenho dos dois. No final, são destacados os passos futuros, um dos quais pode vir a ser muito importante para complementar o trabalho feito até ao momento que é a incorporação da componente de deteção de fraude
Electrochemical behavior of allyl alcohol, malenoid and fumaric acids on Pd/Pt and Pt/Pt electrodes
No full textElectrochemical behavior of Pd-Pt and Pt/Pt electrodes in acidic water solutions of allyl alcohol, fumaric and malenoid acids has been studied. The results obtained at Pd/Pt and Pt/Pt electrodes were analyzed, and it was found that surface absorption ability of Pd/Pt electrode increases in the row fumaric acid-malenoid acid-allyl alcohol. Absorption activity of Pt/Pt electrode is higher than that of Pd/Pt one
Nucleobase Stacking Sustained by Pt−Pt Interactions
No full textAbstract This article reports the use of metal–metal interactions as a way to induce nucleobase stacking in a dinucleotide chain. We synthetized and study a series of C,N‐cyclometallated platinum(II) binuclear complexes derived from 6‐phenylpurine dinucleotide 1 as proligand, and β‐diketonates, 2,2'‐bipyridines and 1,10‐phenanthroline as ancillary ligands. The X‐ray diffraction analysis revealed that the diketonate derivatives 7 and 8 are chiral helixes sustained by Pt−Pt intramolecular interactions that allow the nucleobase stacking. The folded helical structures are maintained in solution, as demonstrated by the appearance of metal–metal‐to‐ligand charge‐transfer (MMLCT) transitions in the UV‐vis spectra. The influence of the ancillary ligand in the molecular structure was evidenced by the absence of bands derived from M−M interactions in the absorption spectra of 2,2’‐bipyridine and and 1,10‐phenanthroline derivatives 12–14. The existence of Pt−Pt in the complexes of this study can be also detected by electrochemistry
Electrochemical behavior of allyl alcohol, malenoid and fumaric acids on Pd/Pt and Pt/Pt electrodes
No full textElectrochemical behavior of Pd-Pt and Pt/Pt electrodes in acidic water solutions of allyl alcohol, fumaric and malenoid acids has been studied. The results obtained at Pd/Pt and Pt/Pt electrodes were analyzed, and it was found that surface absorption ability of Pd/Pt electrode increases in the row fumaric acid-malenoid acid-allyl alcohol. Absorption activity of Pt/Pt electrode is higher than that of Pd/Pt one
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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