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

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

Quantificação de sorgoleone em extratos e raízes de sorgo sob diferentes períodos de armazenamento.

Neste trabalho, foi realizada a purificação, a obtenção do padrão de sorgoleone (2 ? hidroxi ? 5 ? metoxi ? 3 ? [(8?Z,11?Z)-8',11',14'-pentadecatrieno]-p-benzoquinona) e a quantificação desse marcador em raízes primárias de sorgo. As sementes de sorgo foram desinfectadas, colocadas em placas gerbox opacas e acondicionadas em câmara de germinação a 30 o C durante sete dias no escuro. Posteriormente, a extração foi feita mergulhando-se as raízes por 5 min em solução de ácido acético glacial em diclorometano 0,0025% v/v. A quantificação de sorgoleone nos extratos obtidos foi feita por cromatografia líquida de alta eficiência (HPLC), utilizando-se uma curva de calibração. Foi avaliado o efeito do armazenamento de extratos e de raízes, utilizando-se três repetições para cada tratamento. Os extratos de raízes recém-coletadas foram armazenados a -20 o C por 0, 1, 3, 5, 7, 14 e 21 dias. As raízes foram coletadas e imediatamente congeladas (20 o C) e armazenadas pelo mesmo período, quando foram submetidas à extração. Não foi observada diferença significativa entre a quantidade de sorgoleone em extratos armazenados e a de não armazenados, sendo observado o mesmo resultado em extratos obtidos de raízes frescas e armazenadas. Os resultados obtidos mostram que o armazenamento por até 21 dias não altera o conteúdo de sorgoleone nos extratos.Número especial

ENERGY RECOVERY FROM MUNICIPAL SOLID WASTE: OPPORTUNITIES AND CHALLENGES IN THE BRAZILIAN SCENARIO

Municipal solid waste has always been an undesirable asset in society, and its generation grows every year. Inadequate waste disposal may cause many problems, either by the contamination of the environment or by its capacity to serve as a vector for a series of pathogenic elements. The COVID-19 pandemic drew the world’s attention to these challenges and made it clear how they impact society in an unprecedented way. The higher amount of waste and safety supplies discarded, such as masks and facial shields, require an analysis of the current situation of solid waste management along with solutions to increase the capacity for resource recovery. Methods of treating, collecting, transporting, and disposing of municipal solid waste must be integrated with the other levels of the waste hierarchy (prevention, reuse and preparing for reuse, recycling, other recovery (including energy recovery), and disposal). The scientific literature on this subject was verified in this paper, serving as a subsidy for the implementation of possible processes to be used in companies in the area of basic sanitation and city halls, which can benefit from investments that will incur in the generation of products of added value, creating a new link in its business chain. The production and application of integrated municipal solid waste management systems, including energy recovery from refuse derived fuel, can reduce the volume and expenses of municipal administrations with inadequate waste disposal in landfills and promote more sustainable practices in the circular economy scenario. Therefore, this paper sought to highlight the main activities related to municipal solid waste management with an aim to energy recovery

Feature selection and novelty in computational aesthetics

[Abstract] An approach for exploring novelty in expression-based evolutionary art systems is presented. The framework is composed of a feature extractor, a classifier, an evolutionary engine and a supervisor. The evolutionary engine exploits shortcomings of the classifier, generating misclassified instances. These instances update the training set and the classifier is re-trained. This iterative process forces the evolutionary algorithm to explore new paths leading to the creation of novel imagery. The experiments presented and analyzed herein explore different feature selection methods and indicate the validity of the approach.Portugal. Fundação para a Ciência e a Tecnologia; PTDC/EIA–EIA/115667/2009Galicia.Consellería de Innovación, Industria e Comercio ; PGIDIT10TIC105008P

Emergent hydrodynamics in non-equilibrium quantum systems

A tremendous amount of recent attention has focused on characterizing the dynamical properties of periodically driven many-body systems. Here, we use a novel numerical tool termed `density matrix truncation' (DMT) to investigate the late-time dynamics of large-scale Floquet systems. We find that DMT accurately captures two essential pieces of Floquet physics, namely, prethermalization and late-time heating to infinite temperature. Moreover, by implementing a spatially inhomogeneous drive, we demonstrate that an interplay between Floquet heating and diffusive transport is crucial to understanding the system's dynamics. Finally, we show that DMT also provides a powerful method for quantitatively capturing the emergence of hydrodynamics in static (un-driven) Hamiltonians; in particular, by simulating the dynamics of generic, large-scale quantum spin chains (up to L = 100), we are able to directly extract the energy diffusion coefficient.Comment: 6+21 pages, 4+23 figure

Emergent Hydrodynamics in Nonequilibrium Quantum Systems

A tremendous amount of recent attention has focused on characterizing the dynamical properties of periodically driven many-body systems. Here, we use a novel numerical tool termed “density matrix truncation” (DMT) to investigate the late-time dynamics of large-scale Floquet systems. We find that DMT accurately captures two essential pieces of Floquet physics, namely, prethermalization and late-time heating to infinite temperature. Moreover, by implementing a spatially inhomogeneous drive, we demonstrate that an interplay between Floquet heating and diffusive transport is crucial to understanding the system’s dynamics. Finally, we show that DMT also provides a powerful method for quantitatively capturing the emergence of hydrodynamics in static (undriven) Hamiltonians; in particular, by simulating the dynamics of generic, large-scale quantum spin chains (up to L=100), we are able to directly extract the energy diffusion coefficient