Spectral weight transfer in a disorder-broadened Landau level

In the absence of disorder, the degeneracy of a Landau level (LL) is $N=BA/\phi_0$, where $B$ is the magnetic field, $A$ is the area of the sample and $\phi_0=h/e$ is the magnetic flux quantum. With disorder, localized states appear at the top and bottom of the broadened LL, while states in the center of the LL (the critical region) remain delocalized. This well-known phenomenology is sufficient to explain most aspects of the Integer Quantum Hall Effect (IQHE) [1]. One unnoticed issue is where the new states appear as the magnetic field is increased. Here we demonstrate that they appear predominantly inside the critical region. This leads to a certain ``spectral ordering'' of the localized states that explains the stripes observed in measurements of the local inverse compressibility [2-3], of two-terminal conductance [4], and of Hall and longitudinal resistances [5] without invoking interactions as done in previous work [6-8].Comment: 5 pages 3 figure

The nature of localization in graphene under quantum Hall conditions

Particle localization is an essential ingredient in quantum Hall physics [1,2]. In conventional high mobility two-dimensional electron systems Coulomb interactions were shown to compete with disorder and to play a central role in particle localization [3]. Here we address the nature of localization in graphene where the carrier mobility, quantifying the disorder, is two to four orders of magnitude smaller [4,5,6,7,8,9,10]. We image the electronic density of states and the localized state spectrum of a graphene flake in the quantum Hall regime with a scanning single electron transistor [11]. Our microscopic approach provides direct insight into the nature of localization. Surprisingly, despite strong disorder, our findings indicate that localization in graphene is not dominated by single particle physics, but rather by a competition between the underlying disorder potential and the repulsive Coulomb interaction responsible for screening.Comment: 18 pages, including 5 figure

GERMINATION OF SEEDS OF Chorisia glaziovii O. Kuntze SUBMITTED TO WATER STRESS AT DIFFERENT TEMPERATURES

Chorisia glaziovii O. Kuntze, da fam\uedlia Bombacaceae \ue9 uma florestal nativa do Nordeste brasileiro, conhecida popularmente como barriguda devido ao tronco bojudo, seus frutos s\ue3o deiscentes e as sementes revestidas por uma estrutura fibrosa (l\ue3) utilizada nas ind\ufastrias de estofados. Por isso objetivou-se avaliar o comportamento germinativo e o vigor das sementes de Chorisia glaziovii, submetidas ao estresse h\ueddrico em diferentes temperaturas. Os tratamentos consistiram dos potenciais de -0,1; -0,2 e -0,3 MPa simulados com polietileno glicol (PEG 6000), al\ue9m do n\uedvel zero (0,0) utilizando apenas \ue1gua destilada, nas temperaturas constantes de 20, 25 e 30\ub0C, em delineamento experimental inteiramente ao acaso. As vari\ue1veis analisadas foram: porcentagem, primeira contagem e \uedndice de velocidade de germina\ue7\ue3o de sementes, al\ue9m do comprimento de ra\uedzes e altura de parte a\ue9rea, e massa seca de ra\uedzes e parte a\ue9rea das pl\ue2ntulas. As maiores porcentagens de germina\ue7\ue3o das sementes de Chorisia glaziovii foram obtidas na aus\ueancia de estresse h\ueddrico independentemente da temperatura, sendo a de 20\ub0C prejudicial \ue0 germina\ue7\ue3o das sementes, com redu\ue7\ue3o para 20% no potencial de -0,1MPa; nas temperaturas mais elevadas, as sementes foram mais tolerantes ao estresse h\ueddrico, com uma porcentagem de 68% neste mesmo potencial. As sementes de Chorisia glaziovii s\ue3o sens\uedveis ao estresse h\ueddrico, com germina\ue7\ue3o totalmente inibida em todas as temperaturas no potencial de -0,3 MPa.Chorisia glaziovii O. Kuntze, the Bombacaceae family is a native forest of northeastern Brazil, popularly known as paunchy, due to bulging trunk. Its fruits are dehiscent and its seeds covered with a fibrous structure (wool) used in upholstery industries. Therefore, it was aimed to evaluate the germination behavior and seed germination of Chorisia glaziovii, subjected to water stress at different temperatures. The treatments consisted of the potential of -0.1; -0.2 And -0.3 MPa simulated with polyethylene glycol (PEG 6000) plus zero (0,0) level using only distilled water, at constant temperatures of 20, 25 and 30 \ub0C in a totally randomized experimental design chance. The analyzed variables were: percentage, first count and rate of germination rate of seeds, plus the length of roots and shoots of height, and dry weight of roots and shoots of seedlings. The highest percentage of germination of Chorisia glaziovii were obtained in the absence of water stress independent of temperature, so the 20 \ub0C detrimental to seed germination, reducing to 20% in potential -0.1MPa; at higher temperatures the seeds were more tolerant to water stress, with a percentageof 68% at this same potential. The seeds of Chorisia glaziovii are sensitive to water stress, with completely inhibited germination at all temperatures in the potential of -0.3 MPa

The view of teachers on bullying and implications for nursing

Objetivo: Compreender o bullying escolar, na perspectiva dos professores, e refletir sobre as possíveis ações da área da saúde em seu enfrentamento. Para tanto, tomaram- se por base as diretrizes do Programa Saúde na Escola, dos Ministérios da Saúde e da Educação. Método: Estudo de caso qualitativo, realizado com professores de uma escola pública de Minas Gerais. Foram utilizados grupos focais na coleta de dados e o material empírico foi decodificado a partir de técnica de análise temática de conteúdo, resultando em uma categoria analítica: concepções e experiências de professores diante do bullying. Resultados: Foram identificadas percepções pontuais sobre o fenômeno e utilização de recursos de intervenção pouco eficazes. No plano interpretativo, problematizaram-se as contribuições da saúde e da enfermagem no redimensionamento das intervenções e no processo de formação continuada dos professores. Conclusão: Os resultados apontam para a construção de práticas intersetoriais para o enfrentamento do bullying.To understand school bullying from the perspective of teachers and reflect about the possible actions of the health area when coping with it. The guidelines of the School Health Program of the Ministries of Health and Education were used to reach that purpose. Method: A qualitative study carried out with teachers of a public school in Minas Gerais. Focus groups were used to collect data and the empirical material was decoded from thematic analysis of content, resulting in an analytical category: conceptions and experiences of teachers on bullying. Results: Specific perceptions about the phenomenon and the use of ineffective intervention resources were identified. In the interpretive plan were problematized the health and nursing contributions with resizing the interventions and the continuing training process of teachers. Conclusion: The results point to the construction of intersectoral practices forcoping with bullying.Objetivo: Comprender el bullying escolar desde la perspectiva de los profesores, y reflexionar sobre las posibles acciones del área de salud en su enfrentamiento. Tomando como base los lineamientos del Programa de Salud Escolar, de los Ministerios de Salud y de Educación. Método: Estudio de caso cualitativo realizado con los profesores de una escuela pública en Minas Gerais. Para la recolección de datos se utilizaron grupos focales y el material empírico fue decodificado a partir de la técnica de análisis temático de contenido, dando lugar a una categoría analítica: concepciones y experiencias de los profesores sobre el acoso escolar. Resultados: Se identificaron percepciones específicas sobre el fenómeno y la utilización de recursos ineficaces de intervención. En el plano interpretativo, se problematizaron las contribuciones de la salud y de la enfermería en el redimensionamiento de las intervenciones y en el proceso de formación continua de los profesores. Conclusión: Los resultados apuntan a la construcción de prácticas intersectoriales para el enfrentamiento del bullying.CIEC - Centro de Investigação em Estudos da Criança, UM (UI 317 da FCT

Properties of Graphene: A Theoretical Perspective

In this review, we provide an in-depth description of the physics of monolayer and bilayer graphene from a theorist's perspective. We discuss the physical properties of graphene in an external magnetic field, reflecting the chiral nature of the quasiparticles near the Dirac point with a Landau level at zero energy. We address the unique integer quantum Hall effects, the role of electron correlations, and the recent observation of the fractional quantum Hall effect in the monolayer graphene. The quantum Hall effect in bilayer graphene is fundamentally different from that of a monolayer, reflecting the unique band structure of this system. The theory of transport in the absence of an external magnetic field is discussed in detail, along with the role of disorder studied in various theoretical models. We highlight the differences and similarities between monolayer and bilayer graphene, and focus on thermodynamic properties such as the compressibility, the plasmon spectra, the weak localization correction, quantum Hall effect, and optical properties. Confinement of electrons in graphene is nontrivial due to Klein tunneling. We review various theoretical and experimental studies of quantum confined structures made from graphene. The band structure of graphene nanoribbons and the role of the sublattice symmetry, edge geometry and the size of the nanoribbon on the electronic and magnetic properties are very active areas of research, and a detailed review of these topics is presented. Also, the effects of substrate interactions, adsorbed atoms, lattice defects and doping on the band structure of finite-sized graphene systems are discussed. We also include a brief description of graphane -- gapped material obtained from graphene by attaching hydrogen atoms to each carbon atom in the lattice.Comment: 189 pages. submitted in Advances in Physic

Use of barley straw residues to avoid high erosion and runoff rates on persimmon plantations in Eastern Spain under low frequency-high magnitude simulated rainfall events

[EN] Soil and water losses due to agricultural mismanagement are high and non-sustainable in many orchards. An experiment was set up with rainfall simulation at 78 mm h(-1) over 1 hour on 20 paired plots of 2 m(2) (bare and straw covered) in new persimmon plantations in Eastern Spain. Effects of straw cover on the control of soil and water losses were assessed. An addition of 60% straw cover (75 gm(-2)) resulted in delayed ponding and runoff generation and consequently reduced water losses from 60% to 13% of total rainfall. The straw cover reduced raindrop impact and thus sediment detachment from 1014 to 47 g plot(-1) h(-1). The erosion rate was reduced from 5.1 to 0.2 Mg ha-(1) h(-1). The straw mulch was found to be extremely efficient in reducing soil erosion rates.The research projects GL2008-02879/BTE, LEDDRA 243857 and RECARE-FP7 (no. 603498, http://recare-project.eu/) supported this research.Cerdà, A.; González-Pelayo, Ó.; Giménez Morera, A.; Jordán, A.; Pereira, P.; Novara, A.; Brevik, EC.... (2016). Use of barley straw residues to avoid high erosion and runoff rates on persimmon plantations in Eastern Spain under low frequency-high magnitude simulated rainfall events. Soil Research. 54(2):154-165. https://doi.org/10.1071/SR15092S15416554