Exact-exchange density-functional theory for quasi-two-dimensional electron gases

A simple exact-exchange density-functional method for a quasi-two-dimensional electron gas with variable density is presented. An analytical expression for the exact-exchange potential with only one occupied subband is provided, without approximations. When more subbands are occupied the exact-exchange potential is obtained numerically. The theory shows that, in contradiction with LDA, the exact-exchange potential exhibits discontinuities and the system suffers a zero-temperature first-order transition each time a subband is occupied. Results suggesting that the translational symmetry might be spontaneously broken at zero temperature are presented. An extension of the theory to finite temperatures allows to describe a drop in the intersubband spacing in good quantitative agreement with recent experiments.Comment: 14 pages, 3 figure

Pre- and Postharvest Strategies for Pleurotus ostreatus Mushroom in a Circular Economy Approach

Publisher Copyright: © 2024 by the authors.Mushroom cultivation presents a viable solution for utilizing agro-industrial byproducts as substrates for growth. This process enables the transformation of low-economic-value waste into nutritional foods. Enhancing the yield and quality of preharvest edible mushrooms, along with effectively preserving postharvest mushrooms, stands as a significant challenge in advancing the industry. Implementing pre- and postharvest strategies for Pleurotus ostreatus (Jacq.) P. Kumm (oyster mushroom) within a circular economy framework involves optimizing resource use, minimizing waste, and creating a sustainable and environmentally friendly production system. This review aimed to analyze the development and innovation of the different themes and trends by bibliometric analysis with a critical literature review. Furthermore, this review outlines the cultivation techniques for Pleurotus ostreatus, encompassing preharvest steps such as spawn production, substrate preparation, and the entire mushroom growth process, which includes substrate colonization, fruiting, harvesting, and, finally, the postharvest. While novel methodologies are being explored for maintaining quality and extending shelf-life, the evaluation of the environmental impact of the entire mushroom production to identify areas for improvement is needed. By integrating this knowledge, strategies can be developed for a more sustainable and circular approach to Pleurotus ostreatus mushroom cultivation, promoting environmental stewardship and long-term viability in this industry.publishersversionpublishe

Challenges of dosimetry of ultra-short pulsed very high energy electron beams

Very high energy electrons (VHEE) in the range from 100–250 MeV have the potential of becoming an alternative modality in radiotherapy because of their improved dosimetric properties compared with 6-20 MV photons generated by clinical linear accelerators (LINACs). VHEE beams have characteristics unlike any other beams currently used for radiotherapy: femtosecond to picosecond duration electron bunches, which leads to very high dose per pulse, and energies that exceed that currently used in clinical applications. Dosimetry with conventional online detectors, such as ionization chambers or diodes, is a challenge due to non-negligible ion recombination effects taking place in the sensitive volumes of these detectors. FLUKA and Geant4 Monet Carlo (MC) codes have been employed to study the temporal and spectral evolution of ultrashort VHEE beams in a water phantom. These results are complemented by ion recombination measurements employing an IBA CC04 ionization chamber for a 165 MeV VHEE beam. For comparison, ion recombination has also been measured using the same chamber with a conventional 20 MeV electron beam. This work demonstrates that the IBA CC04 ionization chamber exhibits significant ion recombination and is therefore not suitable for dosimetry of ultrashort pulsed VHEE beams applying conventional correction factors. Further study is required to investigate the applicability of ion chambers in VHEE dosimetry

Bounds on the Number of Measurements for Reliable Compressive Classification

This paper studies the classification of high-dimensional Gaussian signals from low-dimensional noisy, linear measurements. In particular, it provides upper bounds (sufficient conditions) on the number of measurements required to drive the probability of misclassification to zero in the low-noise regime, both for random measurements and designed ones. Such bounds reveal two important operational regimes that are a function of the characteristics of the source: 1) when the number of classes is less than or equal to the dimension of the space spanned by signals in each class, reliable classification is possible in the low-noise regime by using a one-vs-all measurement design; 2) when the dimension of the spaces spanned by signals in each class is lower than the number of classes, reliable classification is guaranteed in the low-noise regime by using a simple random measurement design. Simulation results both with synthetic and real data show that our analysis is sharp, in the sense that it is able to gauge the number of measurements required to drive the misclassification probability to zero in the low-noise regime.This work was supported by Royal Society International Exchanges Scheme IE120996. The work of H. Reboredo was supported by the Fundação para a Ciência e Tecnologia, Portugal, under Doctoral Grant SFRH/BD/81543/2011. ˆ The work of F. Renna was carried out in part when he was in the Department of Electronic and Electrical Engineering of University College London, and was supported by the European Union’s Horizon 2020 Research and Innovation Programme under the Marie Skłodowska-Curie Grant 655282. The work of R. Calderbank was supported in part by AFOSR under Award FA 9550-13-1-0076. The work of M. R. D. Rodrigues was supported by the EPSRC under Research Grant EP/K033166/1

Elemental Composition of Commercial Herbal Tea Plants and Respective Infusions

Funding Information: Funding: This work received funding support from national funds from Fundação para a Ciência e a Tecnologia, I.P. (FCT), Portugal, through the research units UIDB/04035/2020 (GeoBioTec) and UIDB/00239/2020 (CEF). Publisher Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland.This study evaluated the elemental composition of 25 herbal tea plants commonly used in infusions by Portuguese consumers and the contribution to the elemental daily intake of some essential elements. Hydrocotyle asiatica (L.), Matricaria chamomilla (L.), and Melissa officinalis (L.) samples are a rich source of K with around 6.0 mg g−1 while the Asteraceae Silybum marianum (L.) and Echinacea angustifolia (DC.) exhibited 4.9 and 5.6 mg g−1 Ca, respectively. The highest concentrations of S and Zn were noted in Hydrocotyle asiatica (L.), while the highest concentration of Sr was found in Cassia angustifolia (Vahl.). In general, a large variability in the concentrations among different families and plant organs had been observed, except Cu with levels around 30 µg g−1. The principal component analysis (PCA) showed positive correlations between Zn and S and Sr and Ca, also revealing that Hydrocotyle asiatica (L.), Echinacea angustifolia (DC.), Silybum marianum (L.), and Cassia angustifolia (Vahl.) samples, stands out about all other samples regarding the enrichment of macro and micronutrients. The elemental solubility of macronutrients in the infusion is greater than the micronutrient solubility, despite the contribution to the recommended daily intake was weak. As a whole, Cynara scolymus (L.) and Hibiscus sabdariffa (L.) are the species with the best elemental solubilities, followed by Hydrocotyle asiatica (L.). No harmful elements, such as As and Pb, were observed in both the raw material and the infusions.publishersversionpublishe

Elemental Composition of Commercial Herbal Tea Plants and Respective Infusions

This study evaluated the elemental composition of 25 herbal tea plants commonly used in infusions by Portuguese consumers and the contribution to the elemental daily intake of some essential elements. Hydrocotyle asiatica (L.), Matricaria chamomilla (L.), and Melissa officinalis (L.) samples are a rich source of K with around 6.0 mg g-1 while the Asteraceae Silybum marianum (L.) and Echinacea angustifolia (DC.) exhibited 4.9 and 5.6 mg g-1 Ca, respectively. The highest concentrations of S and Zn were noted in Hydrocotyle asiatica (L.), while the highest concentration of Sr was found in Cassia angustifolia (Vahl.). In general, a large variability in the concentrations among different families and plant organs had been observed, except Cu with levels around 30 g g-1. The principal component analysis (PCA) showed positive correlations between Zn and S and Sr and Ca, also revealing that Hydrocotyle asiatica (L.), Echinacea angustifolia (DC.), Silybum marianum (L.), and Cassia angustifolia (Vahl.) samples, stands out about all other samples regarding the enrichment of macro and micronutrients. The elemental solubility of macronutrients in the infusion is greater than the micronutrient solubility, despite the contribution to the recommended daily intake was weak. As a whole, Cynara scolymus (L.) and Hibiscus sabdariffa (L.) are the species with the best elemental solubilities, followed by Hydrocotyle asiatica (L.). No harmful elements, such as As and Pb, were observed in both the raw material and the infusionsinfo:eu-repo/semantics/publishedVersio

The tolerance of eucalyptus globulus to soil contamination with arsenic

UID/FIS/04559/2020The contamination of abandoned mining areas is a problem worldwide that needs urgent attention. Phytoremediation emerges as a successful method to extract different contaminants from the soil. In this context, Eucalyptus globulus plants growing in soils artificial contaminated with arsenic (As) were used to access its phytoremediation capabilities. The effects of As on photosynthetic performance were monitored through different physiological parameters, whereas the uptake and translocation of As and the putative effects on calcium, iron, potassium, and zinc levels on plants were evaluated by X-ray fluorescence analysis. Root system is the major accumulator organ, while the translocation to the above-ground organs is poor. In the end of the experiment, the root biomass of plants treated with 200 μg As mL−1 is 27% and 49.7% lower than equivalent biomass from plants treated with 100 μg As mL−1 and control plants, respectively. Each plant can accumulate 8.19 and 8.91 mg As after a 6-month period, when submitted to 100 As and 200 As, respectively. It seems to exist an antagonistic effect of As on Zn root uptake by E. globulus. In general, the tested concentrations do not influence negatively plant metabolism, indicating that this species is suitable for plantation in contaminated areas.publishersversionpublishe

Phenotypic Diversity of Seminal Root Traits in Bread Wheat Germplasm from Different Origins

Publisher Copyright: © 2022 by the authors.Bread wheat (Triticum aestivum L.) is a major staple crop, and more adapted varieties are needed to ensure productivity under unpredictable stress scenarios resulting from climate changes. In the development of new genotypes, root system traits are essential since roots have a key function in water and nutrient uptake, and root architecture determines the plant’s ability to spatially explore the soil resources. Genetic variation in wheat root system may be assessed at the early stages of development. This study evaluates in vitro and at the seedling stage, the genetic diversity of root growth angle (RGA), seminal root number (SRN), and radicle length (RadL) in 30 bread wheat genotypes from different origins and belonging to distinct evolutive or breeding groups. SRN and RadL were analyzed at 1, 2, 3 and 6 days after sowing (DAS) and RGA was measured through the angle between the first pair of seminal roots. A large variability was found in RGA values that ranged from 63° to 122°. Although differences were found between genotypes within the same groups, the narrower angles tended to occur among landraces, while the higher RGA values were observed in advanced lines and Australian varieties. Differences were also observed as regards the SRN (1.0–3.0, 2.7–4.7, 3.2–5.0 and 4.4–6.3 at 1, 2, 3 and 6 DAS, respectively) and RadL (0.1–1.5, 2.1–5.0, 4.0–7.5 and 5.1–13.7 cm at 1, 2, 3 and 6 DAS, respectively). Genetic variability in root traits at seedling stage allows more rapid selection of genotypes better adapted to environmental and soil constraints, necessary to Portuguese Wheat Breeding Program. It will also contribute to the definition of wheat ideotypes with improved performance under Mediterranean climate conditions.publishersversionpublishe

Nutritional Properties of Baobab Pulp from Different Angolan Origins

Publisher Copyright: © 2022 by the authors.The baobab tree (Adansonia digitata L.) is found widely in the forests and savannas of sub-Saharan Africa. The baobab fruit has a sour and slightly sweet taste and is widely consumed by the natives, thus containing a high nutritional value and providing a source of income for rural people. This study aimed to compare the nutritional composition of baobab fruit pulp from different localities in the Namibe province (Angola). Twenty samples of baobab pulp were collected in markets of the four municipalities of Namibe. The results obtained showed that there is some geographic location dependence on nutritional and functional composition. The municipality of Camucuio showed samples with higher fibre content (56.62 g/100 g) and vitamin C (288.9 mg/100 g). Samples from the Virei municipality stood out for their antioxidant activity (1936 mmol TE/100 g), high K content (42.4 mg/g) and higher values of protein (2.42 g/100 g). The samples collected in the municipality of Bibala stood out for their high contents of carbohydrates (28.1 g/100 g), total phenolic compounds (972 mg GAE/100 g) and Ca (3.80 mg/g). Despite the differences in origin, the high nutritional value of baobab fruit has the potential to improve the diet of thousands of people in Africa qualitatively.publishersversionpublishe