The graphene sheet versus the 2DEG: a relativistic Fano spin-filter via STM and AFM tips

We explore theoretically the density of states (LDOS) probed by an STM tip of 2D systems hosting an adatom and a subsurface impurity,both capacitively coupled to AFM tips and traversed by antiparallel magnetic fields. Two kinds of setups are analyzed, a monolayer of graphene and a two-dimensional electron gas (2DEG). The AFM tips set the impurity levels at the Fermi energy, where two contrasting behaviors emerge: the Fano factor for the graphene diverges, while in the 2DEG it approaches zero. As result, the spin-degeneracy of the LDOS is lifted exclusively in the graphene system, in particular for the asymmetric regime of Fano interference. The aftermath of this limit is a counterintuitive phenomenon, which consists of a dominant Fano factor due to the subsurface impurity even with a stronger STM-adatom coupling. Thus we find a full polarized conductance, achievable just by displacing vertically the position of the STM tip. To the best knowledge, our work is the first to propose the Fano effect as the mechanism to filter spins in graphene. This feature arises from the massless Dirac electrons within the band structure and allows us to employ the graphene host as a relativistic Fano spin-filter

Microplastic incorporation into soil in agroecosystems

Background: We live in a plastic age (Thompson et al., 2009), with microplastic (typically defined as plastic particles < 5 mm) becoming an increasingly appreciated aspect of environmental pollution. Research has been overwhelmingly focused on aquatic systems, especially the oceans, but there is a current shift to more strongly consider terrestrial ecosystems (Rillig, 2012; Horton et al., 2017). In particular agroecosystems are coming into focus as a major entry point for microplastics in continental systems (Nizzetto et al., 2016b), where contamination might occur via different sources as sludge amendment or plastic mulching (Steinmetz et al., 2016). Given the central role of agroecosystems, including their soil biodiversity (Rillig et al., 2016), in food production, such numbers are potential cause for concern. Field data on measured microplastic presence in agricultural soils are still not widely available, but nevertheless this material is certain to arrive at the soil surface. The fate of material deposited at the soil surface is not clear: particles may be removed by wind or water erosion, becoming airborne, or may be lost by surface runoff (Nizzetto et al., 2016a). Nevertheless, a substantial part of the microplastic (or nanoplastic following further disintegration) is expected to enter the soil. The degree of hazard represented by microplastic to various soil biota is not clear. Direct evidence comes from experimental work on earthworms, on which microbeads had negative effects (Huerta Lwanga et al., 2016; also reviewed in Horton et al., 2017). Data on impacts on other soil biota groups are not available. However, Kiyama et al. (2012) have shown that polystyrene beads can be taken up by the nematode Caenorhabditis elegans; this means the material could also accumulate in the soil food web (Rillig, 2012). Movement into soil is an important aspect of assessing risk: will soil biota be exposed to microplastics? Here, we sketch what is known about movement of such particles in soil, which players and factors could influence this, and we chart avenues for research aimed at the movement and distribution of microplastic in agricultural soils

Cost-effectiveness analysis of a state funded programme for control of severe asthma

<p>Abstract</p> <p>Background</p> <p>Asthma is one of the most common chronic diseases and a major economical burden to families and health systems. Whereas efficacy of current therapeutical options has been clearly established, cost-effectiveness analysis of public health interventions for asthma control are scarce.</p> <p>Methods</p> <p>81 patients with severe asthma (12–75 years) joining a programme in a reference clinic providing free asthma medication were asked retrospectively about costs and events in the previous 12 months. During 12 months after joining the programme, information on direct and indirect costs, asthma control by lung function, symptoms and quality of life were collected. The information obtained was used to estimate cost-effectiveness of the intervention as compared to usual public health asthma management. Sensitivity analysis was conducted.</p> <p>Results</p> <p>64 patients concluded the study. During the 12-months follow-up within the programme, patients had 5 fewer days of hospitalization and 68 fewer visits to emergency/non scheduled medical visits per year, on average. Asthma control scores improved by 50% and quality of life by 74%. The annual saving in public resources was US$387 per patient. Family annual income increased US$512, and family costs were reduced by US$733.</p> <p>Conclusion</p> <p>A programme for control of severe asthma in a developing country can reduce morbidity, improve quality of life and save resources from the health system and patients families.</p

Catching the Bound States in the Continuum of a Phantom Atom in Graphene

We explore theoretically the formation of bound states in the continuum (BICs) in graphene hosting two collinear adatoms situated at different sides of the sheet and at the center of the hexagonal cell, where a phantom atom of a fictitious lattice emulates the six carbons of the cell. We verify that in this configuration the local density of states (LDOS) near the Dirac points exhibits two characteristic features: i) the cubic dependence on energy instead of the linear one for graphene as found in New J. Phys. 16, 013045 (2014) and ii) formation of BICs as aftermath of a Fano destructive interference assisted by the Coulomb correlations in the adatoms. For the geometry where adatoms are collinear to carbon atoms, we report absence of BICs

Quantum phase transition triggering magnetic BICs in graphene

Graphene hosting a pair of collinear adatoms in the phantom atom configuration has pseudogap with cubic scaling on energy, $\Delta\propto|\varepsilon|^{3}$ which leads to the appearance of spin-degenerate bound states in the continuum (BICs) [Phys. Rev. B 92, 045409 (2015)]. In the case when adatoms are locally coupled to a single carbon atom the pseudogap scales linearly with energy, which prevents the formation of BICs. In this Letter, we explore the effects of non-local coupling characterized by the Fano factor of interference $q_{0},$ tunable by changing the slope of the Dirac cones in the graphene band-structure. We demonstrate that three distinct regimes can be identified: i) for $q_{0}<q_{c1}$ (critical point) a mixed pseudogap $\Delta\propto|\varepsilon|,|\varepsilon|^{2}$ appears yielding a phase with spin-degenerate BICs; ii) near $q_{0}=q_{c1}$ when $\Delta\propto|\varepsilon|^{2}$ the system undergoes a quantum phase transition in which the new phase is characterized by magnetic BICs and iii) at a second critical value $q_{0}>q_{c2}$ the cubic scaling of the pseudogap with energy $\Delta\propto|\varepsilon|^{3}$ characteristic to the phantom atom configuration is restored and the phase with non-magnetic BICs is recovered. The phase with magnetic BICs can be described in terms of an effective intrinsic exchange field of ferromagnetic nature between the adatoms mediated by graphene monolayer. We thus propose a new type of quantum phase transition resulting from the competition between the states characterized by spin-degenerate and magnetic BICs

Caracterização e análise de acessos do banco ativo de germoplasma de Spondias da Embrapa Mandioca e Fruticultura por meio de descritores morfológicos e agronômicos.

Introdução: O gênero Spondias abriga várias frutíferas arbóreas, com espécies nativas do Brasil. Essas plantas são exploradas por meio do extrativismo, com grande potencial econômico e industrial, visto que apresentam frutos comestíveis, saborosos e com alto teor nutritivo. Contudo, há poucas pesquisas que visam à domesticação ou produção comercial dos frutos de Spondias, dado pela falta de informações genéticas, assim como pela ausência de informações de quem as utiliza. Assim, para utilizar as espécies do gênero Spondias, ampliando seus cultivos, é necessário caracterizar os recursos genéticos. Por isso, a Embrapa conserva essas espécies em um Banco Ativo de Germoplasma (BAG), garantindo a variabilidade genética existente, a fim de serem usadas em programas de melhoramento de plantas. Portanto, a correta caracteri- zação e análise dos acessos são de fundamental importância, podendo ser realizada por meio de descritores morfológicos e agronômicos, permitindo desta forma, a separação entre os acessos. A partir do conhecimen-to da variabilidade genética presente entre os acessos conservados no banco de germoplasma é possível desenvolver produtos pré-tecnológicos, tecnológicos e cultivares de interesse econômico. [...]

Proposta metodológica para unidades demonstrativas e melhoramento participativo de milho e feijão em sistemas agroecológicos.

Ao apresentar esta publicação, reafirmamos a consideração dos autores de que os trabalhos de pesquisa devem se basear, cada vez mais, nas necessi- dades do público que se pretende atingir, notadamente em projetos de pes- quisa e desenvolvimento com enfoque agroecológico, em que ações de ade- quação de métodos de avaliação e de melhoramento participativo devem ser abordados pela importância do desenvolvimento e da produção de sementes agroecológicas. As metodologias de avaliação, utilizadas em sistemas convencionais, devem ser ajustadas para uma avaliação mais precisa e adequada para os sistemas agroecológicos e a estratégias das Unidades Produtivas como uma metodo- logia não somente para demonstração, mas também para avaliação e mos- trar-se uma alternativa viável. Conjuntamente, o desenvolvimento de um novo método de seleção denominado células de seleção permite em um mesmo local a seleção de duas espécies, como o milho e feijão, e rotacionando para um segundo plantio no mesmo ano agrícola, aumentando consideravelmente a eficiência do processo de seleção. O desenvolvimento adequado de estratégias para avaliação e melhoramento para sistemas agroecológicos são fundamentais para os agricultores, bem como para os programas de produção de sementes agroecológicas. Devem- se formular protocolos apropriados junto aos órgãos públicos, tanto para elaboração de legislações apropriadas, como para indicação adequada de cultivares para sistemas de base agroecológica