Bilayer graphene: gap tunability and edge properties

Bilayer graphene -- two coupled single graphene layers stacked as in graphite -- provides the only known semiconductor with a gap that can be tuned externally through electric field effect. Here we use a tight binding approach to study how the gap changes with the applied electric field. Within a parallel plate capacitor model and taking into account screening of the external field, we describe real back gated and/or chemically doped bilayer devices. We show that a gap between zero and midinfrared energies can be induced and externally tuned in these devices, making bilayer graphene very appealing from the point of view of applications. However, applications to nanotechnology require careful treatment of the effect of sample boundaries. This being particularly true in graphene, where the presence of edge states at zero energy -- the Fermi level of the undoped system -- has been extensively reported. Here we show that also bilayer graphene supports surface states localized at zigzag edges. The presence of two layers, however, allows for a new type of edge state which shows an enhanced penetration into the bulk and gives rise to band crossing phenomenon inside the gap of the biased bilayer system.Comment: 8 pages, 3 fugures, Proceedings of the International Conference on Theoretical Physics: Dubna-Nano200

Localized states at zigzag edges of bilayer graphene

We report the existence of zero energy surface states localized at zigzag edges of bilayer graphene. Working within the tight-binding approximation we derive the analytic solution for the wavefunctions of these peculiar surface states. It is shown that zero energy edge states in bilayer graphene can be divided into two families: (i) states living only on a single plane, equivalent to surface states in monolayer graphene; (ii) states with finite amplitude over the two layers, with an enhanced penetration into the bulk. The bulk and surface (edge) electronic structure of bilayer graphene nanoribbons is also studied, both in the absence and in the presence of a bias voltage between planes.Comment: 4 pages, 5 figure

Institui????es de longa perman??ncia para idosos: um estudo sobre a necessidade de vagas

Trata-se de notas de pesquisa acerca do aumento da participa????o relativa dos idosos na popula????o e, por essa raz??o, a necessidade de atendimento de novos tipos de demandase, com isso, a cria????o de vagas em determinados servi??os p??blicos

Mental health of caregivers of elderly patients: the impact of psychotropic drugs on quality of life, anxiety, depression, and stress

Caregiver burden is a common impairment resulting from coping with the physical dependence and mental incapacity of the care subject. This study aimed to assess the self-perception of formal and informal caregivers of elderly patients regarding burden, quality of life, anxiety and depression, stress, and the impact of psychotropic drugs. The questionnaire was disseminated in nursing homes and caregivers' associations. Statistical analysis was carried out using SPSS V.28, with a significance level of α = 0.05. The questionnaires used were the Sociodemographic Questionnaire, the Depression, Anxiety and Stress Scales, the Zarit Scale, the Satisfaction with Medication Treatment Questionnaire and Quality of Life. The sample consisted mainly of female individuals, with an average ageof 52 years, residing in the northern region of the country and mostly married. Around half of the respondents admitted taking some psychotropic drug, namely selective serotonin reuptake inhibitor(s) or benzodiazepines. Caregivers who use medication report being moderately satisfied with it, and global satisfaction was correlated with the convenience and effectiveness of the medication. Caregivers also demonstrate that being a caregiver has a high impact on their quality of life, and informal caregivers are those who report a more severe state of depression, anxiety, and stress. The current study highlights the need to assess mental health status and the impact of pharmacotherapy on the quality of life of caregivers of elderly patients.info:eu-repo/semantics/publishedVersio

Modern sandy contourites: conceptual and economic implications

Bottom currents are common sedimentary and oceanographic processes in deep-marine settings that affect continental margins worldwide. Contourites are defined as sediments deposited or substantially reworked by the persistent action of bottom currents. Despite numerous efforts to differentiate between contourites and other deep-water deposits in cores, reliable diagnostic criteria are still lacking. This Thesis presents a multidisciplinary study based on grain size and geochemistry of sedimentary facies —reinforced by micro- and ichnofacies— in the Gulf of Cadiz Contourite Depositional System, in the upper continental slope of the Mozambican margin and the eastern flank of the Corsica Trough. Discrimination criteria are put forth for hemipelagites, silty contourites, sandy contourites, bottom current reworked sands, fine-grained turbidites, hyperpycnites and debrites in sediment cores. The stacked vertical variability of these deposits evidences that the contourite drifts, contourite channels and contourite terraces were influenced by the interrelation of hemipelagic, gravitational and bottom current induced depositional processes. The interrelation of sedimentary processes is tied to intermittency in bottom current velocity, observed at different scales. In the Gulf of Cadiz, the intermittency is a consequence of precession-driven changes related to Mediterranean climate variability, punctuated by millennial-scale variability. In the Corsica contourite depositional system, bioclastic sands would have been transported to the slope during sea level lowstands, probably during isolated episodes of reworking and transport of sediments from the shelf. In contrast, the Mozambique contourite terrace occupies shallower locations and lies directly offshore the Zambezi delta, meaning it was continuously supplied from the adjacent continent and shelf and by along-slope currents, especially during sea level highstands. At bed scale, the variability in ichnodiversity, abundance and distribution of bioturbation is linked to intermittent interactions between bottom currents and sediment supply, hence different environmental conditions for tracemakers. Such intermittency reflects brief changes in hydrodynamic conditions during its deposition: shorter-term (centennial) yet higher accumulation rates, lower bioturbation rates, and flow variability. This new model could therefore provide support for basic sedimentological interpretation and petroleum exploration strategies

The impact of the Covid-19 crisis on migration and asylum law and policy in the EU and its member states

Esta dissertação pretende dar algumas respostas sobre a forma como a COVID-19 teve um impacto direto sobre as práticas de Controlo da Migração. Assim, o presente estudo procura ver o possível impacto da crise do COVID-19 na migração global. A questão do Controlo das Migrações é bastante complexa; embora seja prematuro antecipar os efeitos a médio e longo prazo. Nesta dissertação, vou analisar os tipos de ações legais que foram intentadas nos tribunais europeus durante a pandemia. Para alcançar este ponto, vou examinar se as premissas do Direito Internacional dos Direitos Humanos e do Direito Europeu desempenharam um papel fundamental no Controlo das Migrações no contexto da crise da COVID-19. Ao fazê-lo, centrar-me-ei em vários processos jurídicos que foram intentados nos tribunais europeus durante a pandemia, analisando a decisão final e várias violações dos direitos humanos que tiveram lugar na altura.This dissertation intends to provide some answers about how the outbreak of COVID-19 had a direct impact on the practices of Migration Control. Thus, the present study seeks to analyze the possible impact of the COVID-19 crisis on global migration. The issue of Migration Control is quite complex; even though it is premature to anticipate the medium-and long-term effects. In this dissertation, I will analyze the types of legal actions that have been brought before European courts during the pandemic. To achieve this point, I will examine whether the premises under International Human Rights Law and European Law has played a fundamental role in the regulation of Migration Control within the context of the COVID-19 crisis. In doing so, I will focus on several legal actions that have been brought before European courts during the pandemic, by analyzing the final decision and various human rights violations that took place at the time