Speeding up the solution of the Bethe-Salpeter equation by a double-grid method and Wannier interpolation

The Bethe-Salpeter equation is a widely used approach to describe optical excitations in bulk semiconductors. It leads to spectra that are in very good agreement with experiment, but the price to pay for such accuracy is a very high computational burden. One of the main bottlenecks is the large number of k-points required to obtain converged spectra. In order to circumvent this problem we propose a strategy to solve the Bethe-Salpeter equation based on a double-grid technique coupled to a Wannier interpolation of the Kohn-Sham band structure. This strategy is then benchmarked for a particularly difficult case, the calculation of the absorption spectrum of GaAs, and for the well studied case of Si. The considerable gains observed in these cases fully validate our approach, and open the way for the application of the Bethe-Salpeter equation to large and complex systems.Comment: 5 pages, 3 figures. Accepted for Phys. Rev.

Stomach contents of Brazilian non-passerine birds

We report on the stomach contents of 70 individuals belonging to 36 species and 12 families of non-passerine birds of the Ornithological Collection Marcelo Bagno, University of Brasilia, Brazil. The stomachs, mostly collected during the rainy season and in the Cerrado area, were opened and their food items sorted to the nearest taxonomic level. Virtually all stomachs contained food items consistent with the literature. Galbula ruficauda, however, had plant material in its stomach, although it is considered insectivorous. It is interesting to mention that species considered omnivorous, such as Rhynchotus rufescens, Nothura maculosa and Ramphastos toco, contained only animal material in their stomachs. Columbina talpacoti, Leptotila verreauxi and Leptotila rufaxilla, which can supplement their diet with arthropods, ate only vegetable material, reinforcing items of animal origin as unusual in their diet. Geotrygon montana, C. talpacoti, L. verreauxi, N. maculosa, Aratinga aurea and Aratinga cactorum had stones in their stomachs, which can help to macerate food items. This study covers non-passerines poorly sampled in the literature and can assist in improving the knowledge about the diet of these species

Methodology based on collaborative problem solving implemented in a high academic achievement group

[EN] The High Academic Achievement (ARA, by its acronym in Spanish) group began its course in the 2011/12 academic year to reinforce the potential of the most outstanding students since the beginning of their university studies. In order to improve the employability of this students, at least 50% of basic or compulsory credits of the degree are taught in English. In addition, a series of language training aids are provided, which also has advantages in obtaining Erasmus scholarships. The ARA group only offers 25 places each academic course. Being a small group, personalized teaching is enhanced while the schedule is compacted. In this contribution the methodology used in the subject of Signals and Systems of the Degree in Sound and Image in Telecommunication Engineering of the Alicante University (Spain) is presented. The methodology emphasizes the practical application of the subject and its direct applicability in real systems.Ferrando-Rocher, M.; Marini, S.; Galiana-Merino, J.; Carbajo, J. (2020). Methodology based on collaborative problem solving implemented in a high academic achievement group. En 6th International Conference on Higher Education Advances (HEAd'20). Editorial Universitat Politècnica de València. (30-05-2020):555-560. https://doi.org/10.4995/HEAd20.2020.11105OCS55556030-05-202

Design Strategy and Considerations to Improve Corona Discharge Breakdown in Groove Gap Waveguides

Paper submitted to the 15th European Conference on Antennas and Propagation (EuCAP), 22-26 March 2021.This paper studies the corona discharge breakdown thresholds in groove gap waveguides, and proposes a design strategy to enhance its peak power handling capability (PPHC). The theoretical analysis is focused on the study of the quasi-TE 10 mode, and on the PPHC at different frequencies and multiple arrangements of the pin dimensions of the bed of nails. Next, the geometrical parameters width, length and separation of such pins are optimized for improving peak power limits. Finally, the simulated results show reasonably good performance with respect to the equivalent rectangular waveguide power limit.This work has been supported by the University of Alicante through the fellowship grant UAFPU2018-054 and by the ”Ministerio de Ciencia e Innovación” through research projects PID2019-103982RB-C41 and PID2019-103982RB-C43

In-depth Study of the Corona Discharge Breakdown Thresholds in Groove Gap Waveguides and Enhancement Strategies for Inductive Bandpass Filters

This work focuses on the study of the corona discharge breakdown in groove gap waveguides (GGWs) and inductive bandpass filters (BPFs) based on this technology. With the main aim of improving the peak power handling capability (PPHC), the location of the maximum normalized electric field strength (|Ê MAX |) as a function of the geometrical parameters is analyzed. First, the research deals with wave-guiding structures, comparing the distribution of the transverse electric TE10-like mode of a GGW to that of an equivalent rectangular waveguide (RW). Next, a design strategy based on the adjustment of the geometrical dimensions of the bed of nails is proposed, thus achieving a considerable reduction of |Ê MAX |. The second part of this paper aims for vertically polarized GGW BPFs, where the inductive irises become the most critical part of the component. By a simple modification of their dimensions, a second design criterion is suggested for improving the PPHC. Finally, several Ku-band BPFs centered at 14 GHz and 16 GHz have been manufactured and experimentally verified at the European High-Power Radiofrequency Space Laboratory. This measurement campaign shows peak power thresholds up to 1.09 kW and 3.59 kW at 600 mbar for the non- and full-optimized GGW BPFs, respectively, thereby demonstrating a PPHC enhancement up to 5.16 dB in the high-pressure range when both strategies, proposed in this work, are used.The authors would like to thank the European Space Agency (ESA) and Val Space Consortium (VSC) —Laboratories funded by the European Regional Development Fund—A way of making Europe, and the Antennas and Propagation Lab (APL – iTEAM UPV) for their contributions

Variabilidade genética de Conopophaga lineata (Conopophagidae) em fragmentos florestais da Mata Atlântica

ABSTRACT: Forest fragmentation affects bird populations in many ways, modifying the composition of communities and favouring open country species. The Atlantic Forest is considered one of the most important biomes in the world, due to its great biodiversity, accelerated rates of deforestation, and high endemism. Despite these characteristics, few studies have evaluated the effects of forest fragmentation in the genetic structure of Atlantic forest bird populations. So, this study aims to verify the effects of forest fragmentation in the genetic population structure of Conopophaga lineata, through RAPD markers. To achieve this goal, 89 C. lineata individuals were captured in nine Atlantic Forest fragments in Minas Gerais State. The RAPD data indicate that forest fragmentation has not affected the genetic variation of C. lineata populations (Mann-Whitney U = 3.50; p = 0.11). Great part of the genetic variability of this species is found within populations and it was not observed a correlation between genetic and geographic distance (Mantel test t = 0.6250; p = 073). UPGMA analyses did not show defined clades and all branches showed low statistical support. The low population differentiation observed in this species can be due to a high gene flow among populations or a recent fragmentation. Thus, the current diversity status of C. lineata populations indicates that this species is not significantly affected by fragmentation. However, more genetic studies are essential to improve conservation strategies of Brazilian Atlantic Forest birds. __________________________________________________________________________________ RESUMOA fragmentação florestal afeta populações de aves de muitas maneiras, modificando a composição das comunidades e favorecendo espécies de áreas abertas. A Mata Atlântica é considerada um dos biomas mais importantes do mundo, devido à sua grande biodiversidade, aos altos níveis endemismo e de desmatamento. Apesar destas características, poucos estudos avaliaram os efeitos da fragmentação florestal na estrutura genética de populações de aves desse ecossistema. Dessa forma, este estudo visa verificar os efeitos da fragmentação florestal na variabilidade genética de Conopophaga lineata, através de marcadores RAPD. Assim, foram capturados 89 indivíduos de C. lineata em nove fragmentos florestais da Mata Atlântica do Estado de Minas Gerais. Os dados de RAPD indicam que a fragmentação florestal não afetou a variabilidade genética de Conopophaga lineata (Mann-Whitney U = 3,50; p = 0,11). Grande parte da variabilidade dessa espécie se encontra dentro das populações e não foi observada correlação entre a distância geográfica e a distância genética (Teste de Mantel t = 0,6250; p = 0.73). A análise UPGMA não mostrou clados definidos e todos os ramos apresentaram baixo suporte estatístico. A reduzida diferenciação populacional observada nessa espécie pode ser devida a intenso fluxo gênico entre as populações ou à recente fragmentação na região. Assim, a situação atual das populações de C. lineata indica que essa espécie não é significativamente afetada pela fragmentação. Entretanto, futuros estudos genéticos são essenciais para melhorar as estratégias de conservação da avifauna da Mata Atlântica do Brasil

First-principles calculations of hematite (α-Fe2O3) by self-consistent DFT+U+V

Owing to the confined Fe-3d orbitals and self-interaction error of exchange-correlation functionals, approximate DFT fails to describe iron oxides electronic structure and magnetic properties accurately. Hybrid DFT or DFT + U can solve these problems, but the former is expensive, and the latter only considers on-site interactions. Here, we used DFT + U + V, a DFT + U extension including inter-site interactions, to simulate the structural, magnetic, and electronic properties, along with Fe and O K-edge XAS spectra of α-Fe2O3. Two types of atomic orbital projectors were studied, orthogonalized and non-orthogonalized. DFT + U + V improves the description of the structural, magnetic, and electronic properties of α-Fe2O3 compared to approximate DFT. The accuracy of the correction depends on the orbital projector used. DFT + U + V with orthogonalized projectors achieves the best experimental agreement at a fraction of hybrid DFT cost. This work emphasizes the importance of inter-site interactions and the type of atomic orbital projectors used in the theoretical research of α-Fe2O

Peak Power Handling Capability in Groove Gap Waveguide Filters Based on Horizontally Polarized Resonators and Enhancement Solutions

This letter studies the peak power handling capability (PPHC) in groove gap waveguide filters based on horizontally polarized resonators. Moreover, a modification of the resonant cavity is proposed, where the central pins of the original structure are replaced by a rounded metal block. As a result of this change, the TE₁₀₁-like mode can still be excited, but the maximum electric field strength is shifted to the center of the cavity, which leads to a higher PPHC. The main advantages of the original structure are maintained, and greater robustness in the manufacturing process is achieved. Next, some guidelines for the design of the coupling windows and the dimensions of the blocks are shown to minimize the electric field strength and, consequently, maximize the PPHC. Finally, two third-order bandpass filters (with pins and with blocks) centered at 16 GHz have been manufactured and tested in a measurement campaign, where a PPHC enhancement of 8.7 dB at high pressures is achieved for the novel solution presented in this work.This work was supported in part by the University of Alicante through the Fellowship Grant UAFPU2018-054 and in part by MCIN/AEI/10.13039/501100011033 through the Sub-Projects C41 and C43 of the Coordinated Project under Grant PID2019-103982RB

Padrões de ocupação do javali (Sus scrofa L.) na Mata Atlântica brasileira

Apesar dos grandes impactos da invasão do javali (Sus scrofa) nos ecossistemas naturais, o uso de hábitats por esta espécie nos neotrópicos ainda permanece pouco estudado. Aqui, nós investigamos os efeitos do hábitat local e de covariáveis da paisagem (tipos de vegetação, cursos d'água e estradas) sobre os padrões de ocupação do javali na Mata Atlântica do sul do Brasil. Utilizamos a modelagem de ocupação de estação única para estimar as probabilidades de detecção (p) e de ocupação (ψ) dos javalis, usando monitoramento de armadilha fotográfica por 8 dias em 100 locais. As câmeras detectaram javalis em 64 locais (ocupação ingênua = 64%). Os quatro melhores modelos explicaram 72,7% dos padrões de ocupação, e o melhor modelo (com variável "água") teve um peso de 28,5%. Embora nenhuma das variáveis testadas apresentaram alto poder explicativo na ocupação do javali, a variável água foi a que contribuiu com uma tendência de efeito negativo (β = -1,124; SE = 0,734), com 59% de ocupação quando a água estava presente e 82% quando estava ausente nos pontos de amostragem. Vestígios da presença de javali em diferentes tipos de vegetação revelaram que eles utilizaram plantações de Pinus sp., florestas nativas e culturas de milho e aveia. O padrão de ocupação mostra que o javali é extremamente generalista em nosso local de estudo na Mata Atlântica, sendo encontrado em todos os lugares, o que levanta preocupações ecológicas e econômicas sobre os potenciais efeitos negativos de sua invasão.Despite the great impacts of invasive wild pig (Sus scrofa) to natural ecosystems, habitat use by this species in the neotropics remains poorly studied. Here, we investigated the effects of local habitat and landscape covariates (vegetation types, running watercourses and roads) on occupancy patterns of wild pig in the Atlantic Forest of southern Brazil. We used single season occupancy modeling to estimate detection (p) and occupancy (ψ) probabilities, using 8-day camera-trap monitoring of 100 sampled sites. The cameras detected wild pig in 64 sites (naïve occupancy = 64 %). The four best models explained 72.7 % of the occupancy patterns, and the top model (with "water" variable) had a weight of 28.5 %. Even though none of the tested variables had high explanatory power of wild pig occupancy, the water variable had a negative effect trend (β = -1.124; SE = 0.734), with 59 % of occupancy when water was present and 82 % when it was absent around the sampling sites. Vestiges of the presence of wild pig in different vegetation types revealed that they used plantations of Pinus sp., native forests, and corn and oat crops. The occupation pattern shows that wild pig are generalist at our study site at the Atlantic Forest being found everywhere, raising ecological and economic concerns about the high potential negative effects of its invasion

Sucesso reprodutivo de Sicalis citrina em cascalheiras abandonadas, região central do Cerrado

A adequação de habitats degradados para reprodução de aves pode ser testada por meio de avaliação das taxas de predação de ninhos. Neste estudo nós estimamos o sucesso de nidificação do canário-rasteiro (Sicalis citrina) e o relacionamos, por meio de modelagem no programa MARK, com diversos fatores que potencialmente afetam a sobrevivência dos ninhos da espécie em antigas áreas de extração de solo (cascalheiras), no Parque Nacional de Brasília, Distrito Federal. Nós monitoramos 73 ninhos da espécie durante a estação reprodutiva de 2007. Predação foi a principal causa da perda de ninhos (n = 48, 66%), enquanto seis foram abandonados (8%) e 19 produziram ao menos um filhote (26%). A taxa diária de sobrevivência e o sucesso total de Mayfield foram 0,94 and 23%, respectivamente. Nossos resultados, obtidos da modelagem de sobrevivência, indicaram que as taxas de sobrevivência diária dos ninhos aumenta linearmente à medida que avança a estação reprodutiva, ao passo que diminui conforme a idade do ninho aumenta. Nenhum dos fatores que testamos – altura do ninhos, tamanho dos ninhos, planta suporte e distância até a borda dos ambientes de cascalheira – mostraram-se importantes como fatores determinantes do sucesso dos ninhos. Entretanto, ninhos construídos nas plantas mais comuns na área de estudo (samambaias) apresentaram maior tendência de sucesso que os demais. Adicionalmente, não houve interferência do observador nas estimativas de sobrevivência dos ninhos. Nossos resultados sugerem que as antigas áreas de cascalheira podem ser adequadas para a reprodução do canário-rasteiro, uma vez que as taxas de sobrevivência que encontramos neste estudo são similares às encontradas em estudos com outras espécies na região central do Cerrado.Suitability of degraded areas as breeding habitats can be tested through assessment of nest predation rates. In this study we estimated nest success in relation to several potential predictors of nest survival in the Stripe-tailed Yellow-finch (Sicalis citrina) breeding in abandoned mining pits at Brasília National Park. We monitored 73 nests during the 2007-breeding season. Predation was the main cause of nest failure (n = 48, 66%); while six nests were abandoned (8%) and 19 nests produced young (26%). Mayfield’s daily survival rates and nest success were 0.94 and 23%, respectively. Our results from nest survival models on program MARK indicated that daily survival rates increase linearly towards the end of the breeding season and decrease as nests aged. None of the nest individual covariates we tested - nest height, nest size, nest substrate, and edge effect - were important predictors of nest survival; however, nests placed on the most common plant tended to have higher survival probabilities. Also, there was no observer effect on daily survival rates. Our study suggests that abandoned mining pits may be suitable alternative breeding habitats for Striped-tailed Yellow-finches since nest survival rates were similar to other studies in the central cerrado region