Challenges and prospects about the graphene role in the design of photoelectrodes for sunlight-driven water splitting.

Graphene and its derivatives have emerged as potential materials for several technological applications including sunlight-driven water splitting reactions. This review critically addresses the latest achievements concerning the use of graphene as a player in the design of hybrid-photoelectrodes for photoelectrochemical cells. Insights about the charge carrier dynamics of graphene-based photocatalysts which include metal oxides and non-metal oxide semiconductors are also discussed. The concepts underpinning the continued progress in the field of graphene/photoelectrodes, including different graphene structures, architecture as well as the possible mechanisms for hydrogen and oxygen reactions are also presented. Despite several reports having demonstrated the potential of graphene-based photocatalysts, the achieved performance remains far from the targeted benchmark efficiency for commercial application. This review also highlights the challenges and opportunities related to graphene application in photoelectrochemical cells for future directions in the field.

Comparison and validation of seven white matter hyperintensities segmentation software in elderly patients.

BACKGROUND: Manual segmentation is currently the gold standard to assess white matter hyperintensities (WMH), but it is time consuming and subject to intra and inter-operator variability. PURPOSE: To compare automatic methods to segment white matter hyperintensities (WMH) in the elderly in order to assist radiologist and researchers in selecting the most relevant method for application on clinical or research data. MATERIAL AND METHODS: We studied a research dataset composed of 147 patients, including 97 patients from the Alzheimer's Disease Neuroimaging Initiative (ADNI) 2 database and 50 patients from ADNI 3 and a clinical routine dataset comprising 60 patients referred for cognitive impairment at the Pitié-Salpêtrière hospital (imaged using four different MRI machines). We used manual segmentation as the gold standard reference. Both manual and automatic segmentations were performed using FLAIR MRI. We compared seven freely available methods that produce segmentation mask and are usable by a radiologist without a strong knowledge of computer programming: LGA (Schmidt et al., 2012), LPA (Schmidt, 2017), BIANCA (Griffanti et al., 2016), UBO detector (Jiang et al., 2018), W2MHS (Ithapu et al., 2014), nicMSlesion (with and without retraining) (Valverde et al., 2019, 2017). The primary outcome for assessing segmentation accuracy was the Dice similarity coefficient (DSC) between the manual and the automatic segmentation software. Secondary outcomes included five other metrics. RESULTS: A deep learning approach, NicMSlesion, retrained on data from the research dataset ADNI, performed best on this research dataset (DSC: 0.595) and its DSC was significantly higher than that of all others. However, it ranked fifth on the clinical routine dataset and its performance severely dropped on data with artifacts. On the clinical routine dataset, the three top-ranked methods were LPA, SLS and BIANCA. Their performance did not differ significantly but was significantly higher than that of other methods. CONCLUSION: This work provides an objective comparison of methods for WMH segmentation. Results can be used by radiologists to select a tool.

Convolutional neural networks for classification of Alzheimer's disease: Overview and reproducible evaluation.

Numerous machine learning (ML) approaches have been proposed for automatic classification of Alzheimer's disease (AD) from brain imaging data. In particular, over 30 papers have proposed to use convolutional neural networks (CNN) for AD classification from anatomical MRI. However, the classification performance is difficult to compare across studies due to variations in components such as participant selection, image preprocessing or validation procedure. Moreover, these studies are hardly reproducible because their frameworks are not publicly accessible and because implementation details are lacking. Lastly, some of these papers may report a biased performance due to inadequate or unclear validation or model selection procedures. In the present work, we aim to address these limitations through three main contributions. First, we performed a systematic literature review. We identified four main types of approaches: i) 2D slice-level, ii) 3D patch-level, iii) ROI-based and iv) 3D subject-level CNN. Moreover, we found that more than half of the surveyed papers may have suffered from data leakage and thus reported biased performance. Our second contribution is the extension of our open-source framework for classification of AD using CNN and T1-weighted MRI. The framework comprises previously developed tools to automatically convert ADNI, AIBL and OASIS data into the BIDS standard, and a modular set of image preprocessing procedures, classification architectures and evaluation procedures dedicated to deep learning. Finally, we used this framework to rigorously compare different CNN architectures. The data was split into training/validation/test sets at the very beginning and only the training/validation sets were used for model selection. To avoid any overfitting, the test sets were left untouched until the end of the peer-review process. Overall, the different 3D approaches (3D-subject, 3D-ROI, 3D-patch) achieved similar performances while that of the 2D slice approach was lower. Of note, the different CNN approaches did not perform better than a SVM with voxel-based features. The different approaches generalized well to similar populations but not to datasets with different inclusion criteria or demographical characteristics. All the code of the framework and the experiments is publicly available: general-purpose tools have been integrated into the Clinica software (www.clinica.run) and the paper-specific code is available at: https://github.com/aramis-lab/AD-DL.

Defect States Control Effective Band Gap and Photochemistry of Graphene Quantum Dots.

Graphene quantum dots (GQDs) have emerged as a new group of quantum-confined semiconductors in recent years, with possible applications as light absorbers, luminescent labels, electrocatalysts, and photoelectrodes for photoelectrochemical water splitting. However, their semiconductor characteristics, such as the effective band gap, majority carrier type, and photochemistry, are obscured by defects in this material. Herein, we use surface photovoltage spectroscopy (SPS) in combination with photoelectrochemical measurements to determine the parameters that are essential to the use of GQDs as next-generation semiconductor devices and photocatalysts. Our results show that ordered GQDs (1-6 nm) behave as p-type semiconductors, based on the positive photovoltage in the SPS measurements on Al, Au, and fluorine-doped tin oxide substrates, and generate mobile charge carriers under excitation of defect states at 1.80 eV and under band gap excitation at 2.62 eV. Chemical reduction with hydrazine removes some defects and increases the effective band gap to 2.92 eV. SPS measurements in the presence of sacrificial electron donor and acceptors show that photochemical charge carriers can be extracted and promote redox reactions. A reduced GQDs photocathode supports an unprecedented photocurrent of 50 µA cm-2 using K3Fe(CN)6 as sacrificial electron acceptor. Additionally, while pristine GQDs do not photoreduce protons under visible light, hydrazine-treated GQDs generate H2 from aqueous methanol under visible and UV light (0.04% quantum efficiency at 375 nm) without added co-catalysts. These findings are relevant to the use of GQDs in photochemical and photovoltaic energy-conversion systems.

Surface Photovoltage Measurements on a Particle Tandem Photocatalyst for Overall Water Splitting.

Surface photovoltage spectroscopy (SPS) is used to measure the photopotential across a Ru-SrTiO3:Rh/BiVO4 particle tandem overall water splitting photocatalyst. The tandem is synthesized from Ru-modified SrTiO3:Rh nanocrystals and BiVO4 microcrystals by electrostatic assembly followed by thermal annealing. It splits water into H2 and O2 with an apparent quantum efficiency of 1.29% at 435 nm and a solar to hydrogen conversion efficiency of 0.028%. According to SPS, a photovoltage develops above 2.20 eV, the effective band gap of the tandem, and reaches its maximal value of -2.45 V at 435 nm (2.44 mW cm-2), which corresponds to 96% of the theoretical limit of the photocatalyst film on the fluorine-doped tin-oxide-coated glass (FTO) substrate. Charge separation is 82% reversible with 18% of charge carriers being trapped in defect states. The unusually strong light intensity dependence of the photovoltage (1.16 V per decade) is attributed to depletion layer changes inside of the BiVO4 microcrystals. These findings promote the understanding of solar energy conversion with inorganic particle photocatalysts.

Energetic features of copper and lead sorption by innovative aminoalcohol-functionalized cobalt phyllosilicates.

Inorganic-organic cobalt phyllosilicate hybrids were synthesized by the sol-gel procedure under mild non-hydrothermal conditions with a silicon precursor, formed through individual reactions between the silane 3-glycidoxypropyltriethoxysilane and the aminoalcohols ethanol- or diethanolamine. These procedures generated talc-like phyllosilicates containing pendant organic chains with nitrogen and oxygen basic centres located in the interlamellar region. For organofunctionalized phyllosilicates the lamellar structure obtained through the sol-gel method was confirmed by X-ray powder diffraction, while elemental analysis indicated that the densities of the organic groups attached to the new matrices were 3.31 ± 0.05 and 3.08 ± 0.07 mmol g(-1) for hybrids functionalized with ethanol- and diethanolamines, respectively. Infrared spectroscopy and nuclear magnetic resonance in the solid state for (13)C and (29)Si showed that the organic groups are indeed covalently bonded to the inorganic structures and the process of functionalization did not affect the original structures of the silylating agents employed. The thermally stable hybrids presented well-formed particles with a homogeneous distribution of cobalt and nitrogen atoms. Their abilities for copper removal from aqueous solutions gave maximum capacities of sorption of 2.01 ± 0.11 and 2.55 ± 0.15 mmol g(-1) for phyllosilicates containing ethanol- and diethanolamine groups, respectively. For lead sorption the values of 2.59 ± 0.11 and 2.43 ± 0.12 mmol g(-1) were found for this same sequence. These sorption data were adjusted to the non-linear regression of the Langmuir equation. Energetic features related to the interactions between the cations and the pendant basic centres were determined through calorimetric titrations. The acid-basic interactions reflect the spontaneity of the reactions, which are also enthalpically and entropically favourable for these chelating processes at the solid-liquid interface.

Perfusión aislads de extremidades / Isolated limb perfusion

La perfusión aislada de extremidades con melfalan y factor de necrosis tumoral es un procedimiento quirúrgico utilizado en el tratamiento de sarcomas y melanomas con metástasis en tránsito. Esta técnica ha demostrado su utilidad para evitar la amputación de extremidades extensamente afectadas por un tumor. Este artículo busca hacer una aproximación a esta nueva técnica para ser implementada en Colombia. Se revisan aquí los principios farmacológicos, el uso de esta técnica y las indicaciones en cada patología.

Insulinoma del páncreas: reporte de tres casos y discusión / Insulinoma of the pancreas: three cases report and discussion

El insulinoma es un tumor endocrino pancreático raro, su incidencia ha sido estimada en tan solo 4 personas por millón por año. Nosotros reportamos tres casos vistos en el Instituto Nacional de Cancerología con síntomas neuroglicopénicos, perfil bioquímico de hipoglicemia, hiperinsulinémica endógena e imágenes compatibles con insulinoma, quienes fueron llevados a cirugía con resolución completa de la sintomatología. El propósito de este artículo es revisar la presentación clínica, diagnóstico, localización de la lesión y manejo del insulinoma. El temprano reconocimiento y adecuado diagnóstico de este tumor pancreático raro es importante debido a que es potencialmente curable con tratamiento quirúrgico.

Sarna: opçäo de tratamento por via oral / Scabies: via oral optin treatment

Os autores revisam o tema escabiose, dando maior ênfase ao aspecto da sarna crostosa ou norueguesa. Relatam suas experiências, reportando toda a evolução, do diagnóstico ao tratamento, comentando seu mecanismo de ação e, finalmente, sobre a droga ivermectina, com largo espectro de ação, destacando seu valor por via oral em dose única para o tratamento da escabiose em todas as suas formas e estágios

Eficacia de la terapia tetraconjugada para la erradicación de Helicobacter pylori en pacientes con úlcera duodenal y dispepsia no ulcerosa

Helicobacter pylori es la principal causa de gastritis crónica y de úlceras gástricas y duodenales. Igualmente, aunque más discutido y controvertido, ha sido implicado en la etiología de síntomas en pacientes con dispepsia funcional (DF), particularmente de tipo ulceroso. Por estos motivos se han propuesto numerosos esquemas de antimicrobianos para erradicar la bacteria. El concepto actual indica que son necesarios por lo menos dos antibióticos par obtener una eficacia no inferior al 90 por ciento. El tratamiento con la terapia triple clásica (Bismuto+tetraciclina+metronidazol), ha sido consistentemente eficaz cuando no hay resistencia al metronidazol. Sin embargo, al adicionarle un IBP, los resultados son aúun mejores (95-100 por ciento de eficacia) aunque exista resistencia al metronidazol. En el presente trabajo evaluamos la erradicación de H. pylori en 33 pacientes, de los cuales sólo 24 fueron finalmente estudiados (11 con UD y 13 con DF). Se utilizó una terapia cuadruple durante dos semanas, consiste en: omeprazol 20 mg dos veces al día, subsalicilato de bismuto 524 mg 4 veces al día, tetraciclina clorhidrato 500 mg cuatro veces al día y metronidazol 250 mg cuatro veces al día. Se obtuvo una eradicación en 17/24 casos (70.8 por ciento, IC 95; 52-89 por ciento). Hubo efectos colaterales leves a moderados en el 50 por ciento de los casos y dos pacientes abandonaron el tratamiento. La baja tasa de erradicación puede ser debida a la alta resistencia al metronidazol en nuestro medio. Se surgiere que las altenativas terapéuticas en nuestro medio podrían ser una triple terapia con un IBP más dos antibióticos durante 10 días o la triple terapia clásica, reemplazando el metronidazol por furazolidona. Consideramos que la muestra es pequeña y se requieren estudios con mayor número de pacientes