Assuntos

RESUMO

[This corrects the article DOI: 10.3389/fnbot.2023.1211570.].

RESUMO

Introduction: We introduce a bio-inspired navigation system for a robot to guide a social agent to a target location while avoiding static and dynamic obstacles. Robot navigation can be accomplished through a model of ring attractor neural networks. This connectivity pattern between neurons enables the generation of stable activity patterns that can represent continuous variables such as heading direction or position. The integration of sensory representation, decision-making, and motor control through ring attractor networks offers a biologically-inspired approach to navigation in complex environments. Methods: The navigation system is divided into perception, planning, and control stages. Our approach is compared to the widely-used Social Force Model and Rapidly Exploring Random Tree Star methods using the Social Individual Index and Relative Motion Index as metrics in simulated experiments. We created a virtual scenario of a pedestrian area with various obstacles and dynamic agents. Results: The results obtained in our experiments demonstrate the effectiveness of this architecture in guiding a social agent while avoiding obstacles, and the metrics used for evaluating the system indicate that our proposal outperforms the widely used Social Force Model. Discussion: Our approach points to improving safety and comfort specifically for human-robot interactions. By integrating the Social Individual Index and Relative Motion Index, this approach considers both social comfort and collision avoidance features, resulting in better human-robot interactions in a crowded environment.

RESUMO

Glaucoma is an eye disease that gradually deteriorates vision. Much research focuses on extracting information from the optic disc and optic cup, the structure used for measuring the cup-to-disc ratio. These structures are commonly segmented with deeplearning techniques, primarily using Encoder-Decoder models, which are hard to train and time-consuming. Object detection models using convolutional neural networks can extract features from fundus retinal images with good precision. However, the superiority of one model over another for a specific task is still being determined. The main goal of our approach is to compare object detection model performance to automate segment cups and discs on fundus images. This study brings the novelty of seeing the behavior of different object detection models in the detection and segmentation of the disc and the optical cup (Mask R-CNN, MS R-CNN, CARAFE, Cascade Mask R-CNN, GCNet, SOLO, Point_Rend), evaluated on Retinal Fundus Images for Glaucoma Analysis (REFUGE), and G1020 datasets. Reported metrics were Average Precision (AP), F1-score, IoU, and AUCPR. Several models achieved the highest AP with a perfect 1.000 when the threshold for IoU was set up at 0.50 on REFUGE, and the lowest was Cascade Mask R-CNN with an AP of 0.997. On the G1020 dataset, the best model was Point_Rend with an AP of 0.956, and the worst was SOLO with 0.906. It was concluded that the methods reviewed achieved excellent performance with high precision and recall values, showing efficiency and effectiveness. The problem of how many images are needed was addressed with an initial value of 100, with excellent results. Data augmentation, multi-scale handling, and anchor box size brought improvements. The capability to translate knowledge from one database to another shows promising results too.

RESUMO

ABSTRACT Deep learning (DL) techniques achieve high performance in the detection of illnesses in retina images, but the majority of models are trained with different databases for solving one specific task. Consequently, there are currently no solutions that can be used for the detection/segmentation of a variety of illnesses in the retina in a single model. This research uses Transfer Learning (TL) to take advantage of previous knowledge generated during model training of illness detection to segment lesions with encoder-decoder Convolutional Neural Networks (CNN), where the encoders are classical models like VGG-16 and ResNet50 or variants with attention modules. This shows that it is possible to use a general methodology using a single fundus image database for the detection/segmentation of a variety of retinal diseases achieving state-of-the-art results. This model could be in practice more valuable since it can be trained with a more realistic database containing a broad spectrum of diseases to detect/segment illnesses without sacrificing performance. TL can help achieve fast convergence if the samples in the main task (Classification) and sub-tasks (Segmentation) are similar. If this requirement is not fulfilled, the parameters start from scratch.

RESUMEN Las técnicas de Deep Learning (DL) han demostrado un buen desempeño en la detección de anomalías en imágenes de retina, pero la mayoría de los modelos son entrenados en diferentes bases de datos para resolver una tarea en específico. Como consecuencia, actualmente no se cuenta con modelos que se puedan usar para la detección/segmentación de varias lesiones o anomalías con un solo modelo. En este artículo, se utiliza Transfer Learning (TL) con la cual se aprovecha el conocimiento adquirido para determinar si una imagen de retina tiene o no una lesión. Con este conocimiento se segmenta la imagen utilizando una red neuronal convolucional (CNN), donde los encoders o extractores de características son modelos clásicos como VGG-16 y ResNet50 o variantes con módulos de atención. Se demuestra así, que es posible utilizar una metodología general con bases de datos de retina para la detección/ segmentación de lesiones en la retina alcanzando resultados como los que se muestran en el estado del arte. Este modelo puede ser entrenado con bases de datos más reales que contengan una gama de enfermedades para detectar/ segmentar sin sacrificar rendimiento. TL puede ayudar a conseguir una convergencia rápida del modelo si la base de datos principal (Clasificación) se parece a la base de datos de las tareas secundarias (Segmentación), si esto no se cumple los parámetros básicamente comienzan a ajustarse desde cero.

RESUMO

A pipeline is proposed here to describe different features to study brain microcircuits on a histological scale using multi-scale analyses, including the uniform manifold approximation and projection (UMAP) dimensional reduction technique and modularity algorithm to identify neuronal ensembles, Runs tests to show significant ensembles activation, graph theory to show trajectories between ensembles, and recurrence analyses to describe how regular or chaotic ensembles dynamics are. The data set includes ex-vivo NMDA-activated striatal tissue in control conditions as well as experimental models of disease states: decorticated, dopamine depleted, and L-DOPA-induced dyskinetic rodent samples. The goal was to separate neuronal ensembles that have correlated activity patterns. The pipeline allows for the demonstration of differences between disease states in a brain slice. First, the ensembles were projected in distinctive locations in the UMAP space. Second, graphs revealed functional connectivity between neurons comprising neuronal ensembles. Third, the Runs test detected significant peaks of coactivity within neuronal ensembles. Fourth, significant peaks of coactivity were used to show activity transitions between ensembles, revealing recurrent temporal sequences between them. Fifth, recurrence analysis shows how deterministic, chaotic, or recurrent these circuits are. We found that all revealed circuits had recurrent activity except for the decorticated circuits, which tended to be divergent and chaotic. The Parkinsonian circuits exhibit fewer transitions, becoming rigid and deterministic, exhibiting a predominant temporal sequence that disrupts transitions found in the controls, thus resembling the clinical signs of rigidity and paucity of movements. Dyskinetic circuits display a higher recurrence rate between neuronal ensembles transitions, paralleling clinical findings: enhancement in involuntary movements. These findings confirm that looking at neuronal circuits at the histological scale, recording dozens of neurons simultaneously, can show clear differences between control and diseased striatal states: "fingerprints" of the disease states. Therefore, the present analysis is coherent with previous ones of striatal disease states, showing that data obtained from the tissue are robust. At the same time, it adds heuristic ways to interpret circuitry activity in different states.

RESUMO

Background and purposes: The brief Spanish Zung Self-Rating Anxiety Scale is a ten-item tool available; however, there is little information about its psychometric performance. The study aimed to test the dimensionality, internal consistency, nomological validity, and gender differential item functioning of the scale in patients with chronic obstructive pulmonary disease (COPD) in Colombia. Methods: A psychometric study was designed. It participated in 408 COPD patients aged between 40 and 102 years. Results: The confirmatory factor analysis showed both one- and two-dimension structures with acceptable goodness-of-fit indicators. The brief Spanish Zung Self-Rating Anxiety Scale presented high internal consistency, acceptable nomological validity, and non-gender differential functioning. Conclusions: The brief Spanish Zung Self-Rating Anxiety Scale presents some good indicators of validity and reliability, and it can be used in the measurement of anxiety in COPD patients.

Assuntos

RESUMO

RESUMEN Objetivo Diseñar y aplicar objetos virtuales de aprendizaje con énfasis en el estudiante y evaluar los resultados de un curso renovado en el aprendizaje de los métodos y técnicas apropiadas para el análisis de políticas públicas en salud. Metodología El proyecto se concibió como un estudio observacional, comparativo y analítico para establecer la eficacia de las innovaciones pedagógicas. De marzo a julio de 2018 se llevó a cabo el proceso de rediseño pedagógico de cada una de las unidades del curso virtual de Análisis de Políticas Públicas en Salud. El curso renovado se realizó de agosto a diciembre de 2018. Resultados Se introdujeron modificaciones en la estructura y la visualización del curso. Se llevó a cabo una innovación pedagógica por medio de las TIC, que incluyó videos de presentación del curso y de sus unidades, videos de presentación de los docentes, guías en HTML y PDF interactivos, cuestionarios en línea, presentaciones en Prezi, infografías, videoconferencias y evaluaciones en línea. Los indicadores usados muestran un mejoramiento de los logros y competencias en el curso renovado con respecto a los cursos anteriores. Discusión Los resultados del proyecto sugieren que las transformaciones pedagógicas basadas en el uso intensivo de las TIC pueden tener resultados favorables. Esto es significativo para el análisis sobre las transformaciones relevantes del "modelo pedagógico".

ABSTRACT Objective Design and use virtual learning object with particular emphasis on students and evaluate the results of an updated workshop to learn methods and skills to analyze public policies on health. Methodology The project was made like an observational, comparative, and analytical study to stablish the effectiveness of pedagogical innovations. From March to July 2018 the process of pedagogical redesign of every part of the workshop "Análisis de Políticas Públicas en Salud". The renovate course took place from August to December 2018. Results Modifications were made to the course's structure and visualization. A pedagogical innovation was made using ICT (course presentation videos, HTML guides, Interactive PDF, computer graphics, videoconferences, and online examinations). The indicators show an improvement of the achievements and competencies in the renewed course with respect to the previous courses. Discussion The results of the project suggest that the pedagogical changes based on the interactive use of ICT could have favorable outcomes. This is meaningful for the analysis of the relevant changes of the "pedagogical model".

RESUMO

The pre-Bötzinger complex (preBötC), located within the ventral respiratory column, produces inspiratory bursts in varying degrees of synchronization/amplitude. This wide range of population burst patterns reflects the flexibility of the preBötC neurons, which is expressed in variations in the onset/offset times of their activations and their activity during the population bursts, with respiratory neurons exhibiting a large cycle-to-cycle timing jitter both at the population activity onset and at the population activity peak, suggesting that respiratory neurons are stochastically activated before and during the inspiratory bursts. However, it is still unknown whether this stochasticity is maintained while evaluating the coactivity of respiratory neuronal ensembles. Moreover, the preBötC topology also remains unknown. In this study, by simultaneously recording tens of preBötC neurons and using coactivation analysis during the inspiratory periods, we found that the preBötC has a scale-free configuration (mixture of not many highly connected nodes, hubs, with abundant poorly connected elements) exhibiting the rich-club phenomenon (hubs more likely interconnected with each other). PreBötC neurons also produce multineuronal activity patterns (MAPs) that are highly stable and change during the hypoxia-induced reconfiguration. Moreover, preBötC contains a coactivating core network shared by all its MAPs. Finally, we found a distinctive pattern of sequential coactivation of core network neurons at the beginning of the inspiratory periods, indicating that, when evaluated at the multicellular level, the coactivation of respiratory neurons seems not to be stochastic.NEW & NOTEWORTHY By means of multielectrode recordings of preBötC neurons, we evaluated their configuration in normoxia and hypoxia, finding that the preBötC exhibits a scale-free configuration with a rich-club phenomenon. preBötC neurons produce multineuronal activity patterns that are highly stable but change during hypoxia. The preBötC contains a coactivating core network that exhibit a distinctive pattern of coactivation at the beginning of inspirations. These results reveal some network basis of inspiratory rhythm generation and its reconfiguration during hypoxia.

Assuntos

RESUMO

OBJECTIVES: The objective was to identify the presence of the capacity for reflexive-critical thinking or similar, in Nursing Curricula in Iberian America. METHODS: The article gathers the results of one of the objectives of the macro-project developed by the Iberian American Network on Nursing Education Research, titled Strategies to develop reflective and critical thinking in nursing students: Iberian America situation. To achieve this, a descriptive and exploratory research was conducted with qualitative approach. An instrument created for this project was used, along with some guiding questions to focus the information. RESULTS: Eight countries participated (Bolivia, Brazil, Colombia, Ecuador, Spain, Mexico, Peru, and Venezuela), which contributed information from 189 curricular plans. The R&CT was found in the majority of the curricula, although with diverse denominations. The principal learning strategies used were problem-based learning, group dynamics, reflective reading, clinical practice, and simulation laboratories. The evaluation methods used are the knowledge test, case analysis, and practical exam. CONCLUSIONS: Significant stress exists in the discourse and curricular organization. Incongruences were found and a clear inclination toward the formation of professionals with broad technical skills under a traditional, memory, banking and knowledge accumulation education.

Assuntos

RESUMO

Objective. The objective was to identify the presence of the capacity for reflexive-critical thinking or similar, in Nursing Curricula in Iberian America. Methodology. The article gathers the results of one of the objectives of the macro-project developed by the Iberian American Network on Nursing Education Research, titled Strategies to develop reflective and critical thinking in nursing students: Iberian America situation. To achieve this, a descriptive and exploratory research was conducted with qualitative approach. An instrument created for this project was used, along with some guiding questions to focus the information. Results. Eight countries participated (Bolivia, Brazil, Colombia, Ecuador, Spain, Mexico, Peru, and Venezuela), which contributed information from 189 curricular plans. The R&CT was found in the majority of the curricula, although with diverse denominations. The principal learning strategies used were problem-based learning, group dynamics, reflective reading, clinical practice, and simulation laboratories. The evaluation methods used are the knowledge test, case analysis, and practical exam. Conclusion. Significant stress exists in the discourse and curricular organization. Incongruences were found and a clear inclination toward the formation of professionals with broad technical skills under a traditional, memory, banking and knowledge accumulation education.

Objetivo. Identificar la presencia de la competencia de pensamiento reflexivo-crítico o afines en los currículos de Enfermería en Iberoamérica. Metodología: El artículo recoge los resultados de uno de los objetivos del macro-proyecto que desarrolla la Red Iberoamericana de Investigación en Educación en Enfermería (RIIEE) titulado Estrategias para desarrollar en el estudiante de enfermería el pensamiento reflexivo y crítico (PRyC): situación Iberoamérica. Para lograrlo se realizó una investigación descriptiva y exploratoria con abordaje cualitativo. Se empleó un instrumento creado para este proyecto y algunas preguntas orientadoras para focalizar la información. Resultados. Participaron ocho países (Bolivia, Brasil, Colombia, Ecuador, España. México, Perú y Venezuela) que aportaron la información de 189 planes curriculares. El PRyC se encontró en la mayoría de los currículos, aunque con diversas denominaciones. Las principales estrategias de aprendizaje empleadas fueron: el aprendizaje basado en problemas, las dinámicas grupales, la lectura reflexiva, la práctica clínica y los laboratorios de simulación. Los métodos de evaluación utilizados son el examen de conocimientos, el análisis de casos y el examen práctico. Conclusión. Existe una tensión significativa en el discurso y la organización curricular. Se encuentran incongruencias y una clara inclinación hacia la formación de profesionales con amplias capacidades técnicas bajo una educación tradicional, memorística, bancaria y de acúmulo de conocimientos.

Objetivo. O objetivo foi identificar a presença da competência de pensamento reflexivo e crítico ou relacionado, nos currículos de enfermagem na América Latina. Métodos. O artigo reúne os resultados de um dos objetivos do macroprojeto desenvolvido pela Rede Ibero-americana de Pesquisa em Educação em Enfermagem (RIIEE) intitulado Estratégias para Desenvolver o Pensamento Reflexivo e Crítico em Estudantes de Enfermagem (PRyC): a situação ibero-americana. Para conseguir, foi realizada uma pesquisa descritiva e exploratória com abordagem qualitativa. Um instrumento criado para este projeto e algumas perguntas orientadas para enfocar as informações. Resultados. Participaram oito países (Bolívia, Brasil, Colômbia, Equador, Espanha, México, Peru e Venezuela) que contribuíram com informações de 189 planos curriculares. O PRyC foi encontrado na maioria dos currículos, embora com nomes diferentes. As principais estratégias de aprendizagem utilizadas foram: aprendizagem baseada em problemas, dinâmica de grupo, leitura reflexiva, prática clínica e laboratórios de simulação. Os métodos de avaliação utilizados são o teste de conhecimentos, a análise de casos e o teste prático. Conclusão. Existe uma tensão significativa no discurso e na organização do currículo. Há incongruências e uma clara inclinação para a formação de profissionais com amplas capacidades técnicas sob uma educação tradicional, de memória, bancária e de acumulação de conhecimento.

Assuntos

RESUMO

RESUMEN El fibroadenoma gigante juvenil es un tumor de mama benigno y una variante rara de los fibroadenomas. La presentación clínica suele ser una masa tumoral unilateral, de crecimiento rápido e indolora. En este artículo presentamos el caso de un fibroadenoma gigante juvenil de 12 cm de diámetro en la mama de una niña de 13 años. Se realiza estudio radiológico e histológico de la lesión siendo categorizada como un fibroadenoma gigante juvenil por lo que se realiza tumorectomía completa con remodelación mamaria posterior. A los dos meses de seguimiento, la paciente se encuentra sin signos de recidiva, con buena situación general y a la espera de cirugía de remodelación mamaria.

ABSTRACT Juvenile giant fibroadenoma is a benign breast tumor and a rare variant of fibroadenomas. The clinical presentation is usually a painless, fast growing, unilateral tumor mass. In this article we present the case of a giant juvenile fibroadenoma of 12 cm in diameter in the breast of a 13-year-old girl. A radiological and histological study of the lesion was carried out and it was categorized as a juvenile giant fibroadenoma, so a complete lumpectomy with posterior breast remodeling was performed. After two months of follow-up, the patient is without signs of recurrence, in good general condition and waiting for the breast remodeling surgery.

Assuntos

RESUMO

Recently, oxytocin (OT) has been studied as a potential modulator of endogenous analgesia by acting upon pain circuits at the spinal cord and supraspinal levels. Yet the detailed action mechanisms of OT are still undetermined. The present study aimed to evaluate the action of OT in the spinal cord dorsal horn network under nociceptive-like conditions induced by the activation of the N-methyl-d-aspartate (NMDA) receptor and formalin injection, using calcium imaging techniques. Results demonstrate that the spontaneous Ca2+-dependent activity of the dorsal horn cells was scarce, and the coactivity of cells was mainly absent. When NMDA was applied, high rates of activity and coactivity occurred in the dorsal horn cells; these rates of high activity mimicked the activity dynamics evoked by a neuropathic pain condition. In addition, although OT treatment increased activity rates, it was also capable of disrupting the conformation of coordinated activity previously consolidated by NMDA treatment, without showing any effect by itself. Altogether, our results suggest that OT globally prevents the formation of coordinated patterns previously generated by nociceptive-like conditions on dorsal horn cells by NMDA application, which supports previous evidence showing that OT represents a potential therapeutic alternative for the treatment of chronic neuropathic pain.

Assuntos

RESUMO

Resumen Introducción. El derecho a la salud es reconocido constitucionalmente en Sudamérica; sin embargo, se desconoce si el respeto a este derecho tiene relación directa con los indicadores básicos de salud en la población. Objetivo. Hacer una aproximación al derecho a la salud en los países de Sudamérica. Materiales y métodos. A partir de la indagación del derecho a la salud en el marco constitucional y tratados internacionales adoptados en cada país, relacionándolo con algunos indicadores básicos en salud y teniendo en cuenta los conceptos de derecho constitucional y salud como servicio público, se realizó una revisión narrativa de tipo cualitativo de fuente secundaria indexada sobre las categorías "Derecho en salud dentro del marco legal en cada país" e "Indicadores Básicos en Salud". Resultados. Los indicares básicos en salud comparados en los países de estudio son un reflejo de las políticas adoptadas que muestran su relación con el derecho a la salud en su contexto legislativo. Conclusiones. Las tendencias de los comportamientos sanitarios permitieron asociar los impactos encontrados con un avance positivo en el ejercicio del derecho sanitario.

Abstract Introduction: The right to health is constitutionally recognized in South America; however, it is not known whether respect for this right is directly related to the basic health indicators of the population. Objective: To approach to the right to health in South American countries. Materials and methods: A qualitative review of secondary sources was carried out based on a research on the right to health as addressed in the constitutions and international treaties adopted by each country. This was done associating the right to health with some basic health indicators and taking into account the concepts of constitutional right and health as a public service. The following concepts were considered for conducting the review: "Right to health within the legal framework in each country" and "Basic Indicators on Health". Results: The basic health indicators compared in the study countries reflect the adopted policies by country that are associated with the right to health in their legislative context. Conclusions: Trends in health behavior allowed associating the impacts found as a positive progress regarding the practice of health law.

RESUMO

A novel thermosensitive hydrogel consisting of phosphorylated ß-cyclodextrin (ßCD-PH), ß-cyclodextrin (ßCD) and chitosan was prepared by embedding ßCD and ßCD-PH, into the well-studied chitosan/αß-glycerophosphate system (CS/αßGP). The relevance of this work is the use of ßCD-PH to partially substitute αßGP as the gelling agent. The role of ßCD and ßCD-PH on the rheological properties of hydrogels, gelation time, and gelation temperature were investigated. The gelation time for all the samples (CS/αßGP, CS/αßGP/ßCD, and CS/αßGP/ßCD-PH) was less than a minute at 37 °C, which is suitable for biomedical applications. The gelation temperature for hydrogel CS/αßGP/ßCD-PH increased linearly with the addition of ßCD-PH within the interval 31.8-37.3 °C, at ratios CS:ßCD-PH of 1:0.5, 1:1, 1:1.5 and 1:2 (w/w). The hydrogel thus obtained has potential applications in dual drug delivery (hydrophilic and hydrophobic).

RESUMO

Lepisosteoids are known for their evolutionary conservatism, and their body plan can be traced at least as far back as the Early Cretaceous, by which point two families had diverged: Lepisosteidae, known since the Late Cretaceous and including all living species and various fossils from all continents, except Antarctica and Australia, and Obaichthyidae, restricted to the Cretaceous of northeastern Brazil and Morocco. Until now, the oldest known lepisosteoids were the obaichthyids, which show general neopterygian features lost or transformed in lepisosteids. Here we describe the earliest known lepisosteoid (Nhanulepisosteus mexicanus gen. and sp. nov.) from the Upper Jurassic (Kimmeridgian - about 157 Myr), of the Tlaxiaco Basin, Mexico. The new taxon is based on disarticulated cranial pieces, preserved three-dimensionally, as well as on scales. Nhanulepisosteus is recovered as the sister taxon of the rest of the Lepisosteidae. This extends the chronological range of lepisosteoids by about 46 Myr and of the lepisosteids by about 57 Myr, and fills a major morphological gap in current understanding the early diversification of this group.

Assuntos

RESUMO

†Sorbinicharax verraesi is a marine teleostean fish from the Upper Cretaceous of Nardò (Italy). It was first attributed to the otophysan order Characiformes, which represents potential evidence for the controversial marine origin of the clade. Through a review of all the available material, we demonstrate that this species is not an otophysan since it lacks key structures that would allow for its inclusion in this group. †Sorbinicharax has a body shape that recalls ground fishes classically assigned to Acanthomorpha. However, no unambiguous feature allows us to relate it to this clade. In fact, the presence of cellular bony tissue supports its exclusion from Eurypterygii. Since no feature permits the definitive attribution of †Sorbinicharax to any teleost group, it remains as Teleostei incertae sedis. We infer that the morphology of †Sorbinicharax indicates a benthic ecology. It displays: an anteriorly wide body with enlarged ribs; large pectoral fins, while anal and dorsal fins are reduced; a large head measuring » of the total body length; and a mouth opening dorsally in a high position. Such morphology was so far undescribed in Nardo. It is surprisingly displayed by a non-eurypterygian teleost fish which means by a fish which does not belong to the clades that diversify since the upper Cretaceous and include the extant families that show ground ecomorphologies.

Assuntos

RESUMO

The nature and size of the real active species of nanoparticulated metal supported catalysts is still an unresolved question. The technique of choice to measure particle sizes at the nanoscale, HRTEM, has a practical limit of 1 nm. This work is aimed to identify the catalytic role of subnanometer species and methods to detect and characterize them. In this frame, we investigated the sensitivity to redox pretreatments of Ag/Fe/TiO2, Ag/Mg/TiO2 and Ag/Ce/TiO2 catalysts in CO oxidation. The joint application of HRTEM, SR-XRD, DRS, XPS, EXAFS and XANES methods indicated that most of the silver in all samples is in the form of Ag species with size <1 nm. The differences in catalytic properties and sensitivity to pretreatments, observed for the studied Ag catalysts, could not be explained taking into account only the Ag particles whose size distribution is measured by HRTEM, but may be explained by the presence of the subnanometer Ag species, undetectable by HRTEM, and their interaction with supports. This result highlights their role as active species and the need to take them into account to understand integrally the catalysis by supported nanometals.

Assuntos

RESUMO

In this paper, the effect of modifiers and pretreatments on the electronic states of 1 nm gold nanoparticles (AuNPs) supported on silica was systematically studied. AuNPs deposited on silica (particle size of 2-4 nm) modified with Ce, La and Fe oxides, were studied by FTIR of adsorbed CO after different redox treatments at 100, 300 and 500 °C. This study was conducted at room temperature to allow detecting the electronic states of gold, which is more likely involved in CO oxidation at the same temperature. AuNP size distribution was measured by HRTEM. It is shown that the electronic state of gold species (Aun(δ-), Au°, Aun(δ+), Au⁺) in 1 nm AuNPs is sensitive to the modifier as well as to the temperatures of redox pretreatments. Supports modified with the same additives but containing larger AuNPs (~3, 4, 5, and 7 nm) were also studied. They showed that Au° remains stable irrespective of additives and redox pretreatments, indicating no significant effect of such treatments on the electronic properties of larger AuNPs. Samples with a predominant AuNP size of 2 nm are an intermediate case between these two groups of materials.

Assuntos

RESUMO

A challenge in neuroscience is to integrate the cellular and system levels. For instance, we still do not know how a few dozen neurons organize their activity and relations in a microcircuit or module of histological scale. By using network theory and Ca(2+) imaging with single-neuron resolution we studied the way in which striatal microcircuits of dozens of cells orchestrate their activity. In addition, control and diseased striatal tissues were compared in rats. In the control tissue, functional connectomics revealed small-world, scale-free and hierarchical network properties. These properties were lost during pathological conditions in ways that could be quantitatively analyzed. Decorticated striatal circuits disclosed that corticostriatal interactions depend on privileged connections with a set of highly connected neurons or "hubs". In the 6-OHDA model of Parkinson's disease there was a decrease in hubs number; but the ones that remained were linked to dominant network states. l-DOPA induced dyskinesia provoked a loss in the hierarchical structure of the circuit. All these conditions conferred distinct temporal sequences to circuit activity. Temporal sequences appeared as particular signatures of disease process thus bringing the possibility of a future quantitative pathophysiology at a histological scale.

Assuntos