Measuring valley polarization in two-dimensional materials with second-harmonic spectroscopy

A population imbalance at different valleys of an electronic system lowers its effective rotational symmetry. We introduce a technique to measure such imbalance - a valley polarization - that exploits the unique fingerprints of this symmetry reduction in the polarization-dependent second-harmonic generation (SHG). We present the principle and detection scheme in the context of hexagonal two-dimensional crystals, which include graphene-based systems and the family of transition metal dichalcogenides, and provide a direct experimental demonstration using a 2H-MoSe$_{2}$ monolayer at room temperature. We deliberately use the simplest possible setup, where a single pulsed laser beam simultaneously controls the valley imbalance and tracks the SHG process. We further developed a model of the transient population dynamics which analytically describes the valley-induced SHG rotation in very good agreement with the experiment. In addition to providing the first experimental demonstration of the effect, this work establishes a conceptually simple, com-pact and transferable way of measuring instantaneous valley polarization, with direct applicability in the nascent field of valleytronics

Adaptation of Ancient Techniques to Recreate ‘Wines’ and ‘Beverages’ Using Withered Grapes of Muscat of Alexandria

The production of wines using ancient techniques is a present trend with commercial interest among consumers valorising their historical background. Therefore, the objective of the present work was to recreate wines and piquettes produced from dehydrated grapes, vinified according to the techniques described in classical Roman agricultural manuals. Muscat of Alexandria grapes were harvested and subjected to greenhouse drying under ambient temperature for 7 days, during the 2020 and 2021 harvests. When weight loss was approximately 30%, grapes were processed according to different protocols, including a rehydration step using saltwater or white wine (2020 harvest). Fermentation was conducted with the addition of commercial yeast without sulphur dioxide supplementation. The piquettes were obtained from the pressed pomaces diluted with water solution (5 g/L tartaric acid). The 2020 wines showed alcoholic content and residual sugar ranging from 14.8 to 17.0% (v/v), and 0.8 g/L to 18 g/L, respectively. Volatile acidity was less than 1 g/L (as acetic acid) in all wines, except for the fermentation of crushed grapes alone, which yielded 2.3 g/L volatile acidity. The fermentation of dehydrated crushed grapes in the semi-industrial trial run in the harvest of 2021 yielded 1.1 g/L volatile acidity. The piquettes analysis showed ethanol ranging from 10.2% (v/v) to 16.0% (v/v), reducing substances less than 2 g/L and volatile acidity less than 0.8 g/L. Overall, the physicochemical analysis showed that it was possible to recreate ancient winemaking techniques that may be further improved to produce commercially and legally acceptable winesinfo:eu-repo/semantics/publishedVersio

Seedless Cu electroplating on Co-W thin films in low pH electrolyte: early stages of formation

The use of Ta/TaN barrier bilayer systems in electronic applications has been ubiquitous over the last decade. Alternative materials such as Co-W or Ru-W alloys have gathered interest as possible replacements due to their conjugation of favourable electrical properties and barrier layer efficiency at reduced thicknesses while enabling seedless Cu electroplating. The microstructure, morphology, and electrical properties of Cu films directly electrodeposited onto Co-W or Ru-W are important to assess, concomitant with their ability to withstand the electroplating baths/conditions. This work investigates the effects of the current application method and pH value of the electroplating solution on the electrocrystallisation behaviour of Cu deposited onto a Co-W barrier layer. The film structure, morphology, and chemical composition were studied by X-ray diffraction, scanning electron microscopy and atomic force microscopy, as well as photoelectron spectroscopy. The results show that the electrolyte solution at pH 1.8 is incapable of creating a compact Cu film over the Co-W layer in either pulsed or direct-current modes. At higher pH, a continuous film is formed. A mechanism is proposed for the nucleation and growth of Cu on Co-W, where a balance between Cu nucleation, growth, and preferential Co dissolution dictates the substrate area coverage and compactness of the electrodeposited films.Portugal 2020 through European Regional Development Fund (FEDER) in the frame of Operational Competitiveness and Internationalisation Programme (POCI) and in the scope of the project USECoIN with grant number PTDC/CTM-CTM/31953/2017. This work was also supported by FCT, through IDMEC, under LAETA project UIDB/50022/202

The Monocarboxylate Transporter Inhibitor α-Cyano-4-Hydroxycinnamic Acid Disrupts Rat Lung Branching

BACKGROUND/AIMS: The human embryo develops in a hypoxic environment. In this way, cells have to rely on the glycolytic pathway for energy supply, leading to an intracellular accumulation of monocarboxylates such as lactate and pyruvate. These acids have an important role in cell metabolism and their rapid transport across the plasma membrane is crucial for the maintenance of intracellular pH homeostasis. This transport is mediated by a family of transporters, designated by monocarboxylate transporters (MCTs), namely isoforms 1 and 4. MCT1/4 expression is regulated by the ancillary protein CD147.The general aim of this study was to characterize the expression pattern of MCT1/4, CD147 and the glucose transporter GLUT1 during human fetal lung development and elucidate the role of MCTs in lung development. METHODS: The expression pattern of MCT1/4 and GLUT1 was characterized by immunohistochemistry and fetal lung viability and branching were evaluated by exposing rat fetal lung explants to CHC, an inhibitor of MCT activity. RESULTS: Our findings show that all the biomarkers are differently expressed during fetal lung development and that CHC appears to have an inhibitory effect on lung branching and viability, in a dose dependent way. CONCLUSION: We provide evidence for the role of MCTs in embryo lung development, however to prove the dependence of MCT activity further studies are waranted.This work was supported by the Life and Health Sciences Research Institute, University of Minho, Portugal, and Fundacao para a Ciencia e Tecnologia (SFRH/BD/33503/2010 to S.G., SFRH/BD/87139/2012 to F.M.S. and SFRH/BD/51997/2012 to V.M.G.

Strain sensors based on knocked down carbon nanotubes and bucky papers thin films

Recently, carbon nanotubes (CNTs) thin films have been widely applied in sensing applications due to their piezoresistive response. Furthermore, CNT anisotropic electric properties, due to its alignment, can provide useful information regarding strain direction. We present a comparative study between knocked down vertically aligned CNT based sensor, reported in our previous work [1], and CNT bucky papers (BP) based sensors. For this purpose, commercial multi-wall carbon nanotubes (MWCNTs) were dispersed in two different solvents, dimethylformamide (DMF) and ethanol, vacuum filtrated and dried. From these freestanding BP thin films, 10x10 mm squares were cut off and transferred to polyimide (PI) films. The relative electric resistance response and sensitivity of the strained samples was measured and compared with the knocked down CNT/PI based sensor. Moreover, the morphology of the samples was characterized by scanning electron microscopy (SEM). The results showed a high sensitivity to strain, however knocked down CNT/PI based sensor presented better mechanical performance and an anisotropic behaviour that can be used to infer strain direction.FCT, Programa MIT Portugal, projeto "IAMAT (Introduction of Advanced Materials Technologies into New Product Development for the Mobility Industries

Effect of carbon nanotubes on methane production in pure cultures of methanogens and in a syntrophic co-culture

ICBM-3 - 3rd International Conference on Biogas MicrobiologyConductive materials have been reported to enhance methane production by anaerobic microbial communities from a wide diversity of substrates 1 . The mechanisms involved are far from being fully understood. Many studies suggest that these materials facilitate direct interspecies electron transfer (DIET) between electrogenic bacteria and methanogens and that this mechanism is even dominant over interspecies hydrogen and formate transfer 2,3. The effect of conductive materials in pure cultures of methanogens or in co-cultures of typical fatty acid-degrading syntrophs with methanogenic partners was never studied. In this work, the effect of carbon nanotubes (CNT) on the activity of pure cultures of Methanobacterium formicicum, Methanospirillum hungatei, Methanosarcina mazei and Methanosaeta concilii, and in the co-culture of Syntrophomonas wolfei and Methanospirillum hungatei was evaluated. The results showed that CNT affect methane production by methanogens. Initial methane production rate (MPR) increased 17 and 6 times when M. formicicum and M. hungatei were incubated with 5g·L-1 CNT, respectively. M. mazei and M. concilii‘ activities were higher when exposed to CNT concentrations of 0.1 to 1g·L-1 , but lower with 5g·L-1 . Increasing CNT concentrations resulted in more negative redox potentials, which correlated with the increased methanogenic activity. Remarkably, in the absence of a reducing agent, but in the presence of CNT, the MPR was higher than in incubations with reducing agent, while no growth was observed without reducing agent and without CNT. MPR from butyrate increased 1.5 fold in the presence of CNT (5g.L-1 ), showing a positive effect of CNT on the syntrophic coculture. Indications of DIET by the presence CNT were not obtained. Rather, CNT directly affects the activity of methanogens, which creates new opportunities to improve methane production from waste and wastewater in anaerobic digesters.info:eu-repo/semantics/publishedVersio

Breakdown of universality in three-dimensional Dirac semimetals with random impurities

Dirac-Weyl semimetals are unique three-dimensional (3D) phases of matter with gapless electrons and novel electrodynamic properties believed to be robust against weak perturbations. Here, we unveil the crucial influence of the disorder statistics and impurity diversity in the stability of incompressible electrons in 3D semimetals. Focusing on the critical role played by rare impurity configurations, we show that the abundance of low-energy resonances in the presence of diluted random potential wells endows rare localized zero-energy modes with statistical significance, thus lifting the nodal density of states. The strong nonperturbative effect here reported converts the 3D Dirac-Weyl semimetal into a compressible metal even at the lowest impurity densities. Our analytical results are validated by high-resolution real-space simulations in record-large 3D lattices with up to 536 000 000 orbitals

Mitochondrial haplogroup H1 is protective for ischemic stroke in Portuguese patients

<p>Abstract</p> <p>Background</p> <p>The genetic contribution to stroke is well established but it has proven difficult to identify the genes and the disease-associated alleles mediating this effect, possibly because only nuclear genes have been intensely investigated so far. Mitochondrial DNA (mtDNA) has been implicated in several disorders having stroke as one of its clinical manifestations. The aim of this case-control study was to assess the contribution of mtDNA polymorphisms and haplogroups to ischemic stroke risk.</p> <p>Methods</p> <p>We genotyped 19 mtDNA single nucleotide polymorphisms (SNPs) defining the major European haplogroups in 534 ischemic stroke patients and 499 controls collected in Portugal, and tested their allelic and haplogroup association with ischemic stroke risk.</p> <p>Results</p> <p>Haplogroup H1 was found to be significantly less frequent in stroke patients than in controls (OR = 0.61, 95% CI = 0.45–0.83, p = 0.001), when comparing each clade against all other haplogroups pooled together. Conversely, the pre-HV/HV and U mtDNA lineages emerge as potential genetic factors conferring risk for stroke (OR = 3.14, 95% CI = 1.41–7.01, p = 0.003, and OR = 2.87, 95% CI = 1.13–7.28, p = 0.021, respectively). SNPs m.3010G>A, m.7028C>T and m.11719G>A strongly influence ischemic stroke risk, their allelic state in haplogroup H1 corroborating its protective effect.</p> <p>Conclusion</p> <p>Our data suggests that mitochondrial haplogroup H1 has an impact on ischemic stroke risk in a Portuguese sample.</p

Photoelectrodes with titanate nanotubes sensitized by mesoporphyrin derivative from cashew nut shell

Titanate nanotubes (TiNTs) with the chemical composition Na2Ti3O7.nH2O (NaTiNT) were obtained througha hydrothermal method in highly alkaline medium. Protonated titanates nanotubes (H-TiNTs), with the compositionH2Ti3O7.nH2O, were prepared by ion exchange reaction through a suspension of Na2Ti3O7nH2Onanotubes in HCl medium, promoting the exchange of Na+ ions by H+. Both Na2Ti3O7.nH2O andH2Ti3O7.nH2O products, as well the TiO2 used as raw material for the nanotubes processing, were used asstarting material for the solar cells photoelectrodes sensitized using mesoporphyrin extracted from a precursorof cashew nut shell. Exposing the NaTiNT sample to solar radiation of 1258 W/m2, a short-circuit currentdensity (ISC) of 13 A/cm2 and an open-circuit voltage (VOC) of 370 mV were registered and, a current densityof 7.6 A/cm2 and a voltage of 256 mV for the prototype cell based on H-TiNTs. A current density of 1.1A/cm2 and an open-circuit voltage of 1.6 mV were obtained for the cell using TiO2 as electrode.Keywords: Titanate Nanotubes. Ionic exchange. Mesoporphyrin. Dye-sensitized solar cell

Nationwide access to endovascular treatment for acute ischemic stroke in portugal

Publisher Copyright: Copyright Ordem dos M dicos 2021.Introduction: Since the publication of endovascular treatment trials and European Stroke Guidelines, Portugal has re-organized stroke healthcare. The nine centers performing endovascular treatment are not equally distributed within the country, which may lead to differential access to endovascular treatment. Our main aim was to perform a descriptive analysis of the main treatment metrics regarding endovascular treatment in mainland Portugal and its administrative districts. Material and Methods: A retrospective national multicentric cohort study was conducted, including all ischemic stroke patients treated with endovascular treatment in mainland Portugal over two years (July 2015 to June 2017). All endovascular treatment centers contributed to an anonymized database. Demographic, stroke-related and procedure-related variables were collected. Crude endovascular treatment rates were calculated per 100 000 inhabitants for mainland Portugal, and each district and endovascular treatment standardized ratios (indirect age-sex standardization) were also calculated. Patient time metrics were computed as the median time between stroke onset, first-door, and puncture. Results: A total of 1625 endovascular treatment procedures were registered. The endovascular treatment rate was 8.27/100 000 inhabitants/year. We found regional heterogeneity in endovascular treatment rates (1.58 to 16.53/100 000/year), with higher rates in districts closer to endovascular treatment centers. When analyzed by district, the median time from stroke onset to puncture ranged from 212 to 432 minutes, reflecting regional heterogeneity. Discussion: Overall endovascular treatment rates and procedural times in Portugal are comparable to other international registries. We found geographic heterogeneity, with lower endovascular treatment rates and longer onset-to-puncture time in southern and inner regions. Conclusion: The overall national rate of EVT in the first two years after the organization of EVT-capable centers is one of the highest among European countries, however, significant regional disparities were documented. Moreover, stroke-onset-to-first-door times and in-hospital procedural times in the EVT centers were comparable to those reported in the randomized controlled trials performed in high-volume tertiary hospitalspublishersversionpublishe