Few layer graphene on SiC, pyrolitic graphite and graphene: a Raman scattering study

The results of micro-Raman scattering measurements performed on three different ``graphitic'' materials: micro-structured disks of highly oriented pyrolytic graphite, graphene multi-layers thermally decomposed from carbon terminated surface of 4H-SiC and an exfoliated graphene monolayer are presented. Despite its multi-layer character, most parts of the surface of the graphitized SiC substrates shows a single-component, Lorentzian shape, double resonance Raman feature in striking similarity to the case of a single graphene monolayer. Our observation suggests a very weak electronic coupling between graphitic layers on the SiC surface, which therefore can be considered to be graphene multi-layers with a simple (Dirac-like) band structure.Comment: 4 pages, 3 Figures Structure of the paper strongly modified, small changes in Fig 2 and 3. Same interpretation and same result

Moire bands in twisted double-layer graphene

A moire pattern is formed when two copies of a periodic pattern are overlaid with a relative twist. We address the electronic structure of a twisted two-layer graphene system, showing that in its continuum Dirac model the moire pattern periodicity leads to moire Bloch bands. The two layers become more strongly coupled and the Dirac velocity crosses zero several times as the twist angle is reduced. For a discrete set of magic angles the velocity vanishes, the lowest moire band flattens, and the Dirac-point density-of-states and the counterflow conductivity are strongly enhanced

Validación del diagnóstico de enfermería Angustia Espiritual: análisis por especialistas

OBJETIVO: Realizar a validação de conteúdo do diagnóstico de enfermagem Angústia espiritual. MÉTODOS: Utilizando o referencial metodológico proposto por Fehring, foi empregado um questionário semi-estruturado, respondido por uma amostra de 72 enfermeiros, para avaliação do título, definição e características definidoras do diagnóstico Angústia espiritual, bem como, sua disposição na Taxonomia II da North American Nursing Diagnosis Association. RESULTADOS: O melhor domínio para classificação do diagnóstico em estudo, segundo os enfermeiros peritos, é o Domínio 10; no entanto, suas classes requerem revisão. Espiritualidade prejudicada demonstrou ser um título adequado ao conceito investigado. A validação das características definidoras identificou sete delas como importantes indicadores clínicos do diagnóstico e apenas a característica não se interessa pela natureza foi considerada pouco relevante. O escore total do diagnóstico foi 0,72, sendo, portanto, considerado validado. CONCLUSÃO: Uma nova proposta apresentada ao fenômeno em estudo foi considerada pertinente. Este estudo pode oferecer subsídios para a validação clínica do diagnóstico investigado.OBJECTIVE: To validate the nursing diagnosis Spiritual anguish. METHODS: Using the methodological framework proposed by Fehring was utilized a semi-structured questionnaire answered by a sample of 72 nurses, to evaluate the title, definition and defining characteristics of the diagnosis Spiritual anguish, as well as the classification in the Taxonomy II North American Nursing Diagnosis Association. RESULTS: The best area to classify the studied diagnosis according to the expert nurses was the Domain 10; however the Domain classes need to be reviewed. Spirituality impaired proved to be a fitting title for the investigated concept. The validation identified seven defining characteristics as important indicators of clinical diagnosis; the feature - is not interested in nature - was considered little relevant. The total score of diagnosis was 0.72, therefore was considered validated. CONCLUSION: The new proposal submitted to explaining the phenomenon under study was considered relevant. This study may provide insight to validate clinically, diagnostics investigated.OBJETIVO: Realizar la validación de contenido del diagnóstico de enfermería Angustia espiritual. MÉTODOS: Utilizando el marco metodológico propuesto por Fehring, fue empleado un cuestionario semi-estructurado, respondido por una muestra de 72 enfermeros, para evaluar el título, definición y características definidoras del diagnóstico Angustia espiritual, así como, la clasificación en la Taxonomía II de la North American Nursing Diagnosis Association. RESULTADOS: El mejor dominio para la clasificación del diagnóstico en estudio, según los enfermeros peritos, es el Dominio 10; sin embargo, sus clases requieren revisión. La Espiritualidad perjudicada demostró ser un título adecuado para el concepto investigado. La validación de las características definidoras identificó siete de ellas como importantes indicadores clínicos del diagnóstico y apenas la característica no se interesa por la naturaleza fue considerada poco relevante. El puntaje total del diagnóstico fue 0,72, siendo, por tanto, considerado validado. CONCLUSIÓN: La nueva propuesta presentada para el fenómeno en estudio fue considerada pertinente. Este estudio puede ofrecer subsidios para la validación clínica del diagnóstico investigado

Highly-ordered graphene for two dimensional electronics

With expanding interest in graphene-based electronics, it is crucial that high quality graphene films be grown. Sublimation of Si from the 4H-SiC(0001) Si-terminated) surface in ultrahigh vacuum is a demonstrated method to produce epitaxial graphene sheets on a semiconductor. In this paper we show that graphene grown from the SiC$(000\bar{1})$ (C-terminated) surface are of higher quality than those previously grown on SiC(0001). Graphene grown on the C-face can have structural domain sizes more than three times larger than those grown on the Si-face while at the same time reducing SiC substrate disorder from sublimation by an order of magnitude.Comment: Submitted to Appl. Phys. Let

The Computational Complexity of Knot and Link Problems

We consider the problem of deciding whether a polygonal knot in 3-dimensional Euclidean space is unknotted, capable of being continuously deformed without self-intersection so that it lies in a plane. We show that this problem, {\sc unknotting problem} is in {\bf NP}. We also consider the problem, {\sc unknotting problem} of determining whether two or more such polygons can be split, or continuously deformed without self-intersection so that they occupy both sides of a plane without intersecting it. We show that it also is in NP. Finally, we show that the problem of determining the genus of a polygonal knot (a generalization of the problem of determining whether it is unknotted) is in {\bf PSPACE}. We also give exponential worst-case running time bounds for deterministic algorithms to solve each of these problems. These algorithms are based on the use of normal surfaces and decision procedures due to W. Haken, with recent extensions by W. Jaco and J. L. Tollefson.Comment: 32 pages, 1 figur

"Infiltrators" or refugees? An analysis of Israel's policy towards African asylum seekers

This article adopts a genealogical approach in examining Israeli immigration policy by focusing on the situation confronting African asylum seekers who have been forced back into Egypt, detained and deported but who have not had their asylum claims properly assessed. Based on immigration policies formulated at the time of Israeli independence, whose principle objective was to secure a Jewish majority state, we argue that Israel’s treatment of African asylum seekers as ‘infiltrators’/economic migrants stems from an insistence on maintaining immigration as a sovereign issue formally isolated from other policy domains. Such an approach is not only in violation of Israel’s commitment to the Refugee Convention, it directly contributes to policies which are ineffective and unduly harsh

Low Temperature Neutron Diffraction Study of MnTe

Investigation of transport and magnetic properties of MnTe at low temperatures sInvestigation of transport and magnetic properties of MnTe at low temperatures showed anomalies like negative coefficient of resistance below 100K and a sharp rise in susceptibility at around 83K similar to a ferromagnetic transition. Low temperature powder neutron diffraction experiments were therefore carried out to understand the underlying phenomena responsible for such anomalous behavior. Our study indicates that the rise in susceptibility at low temperatures is due to strengthening of ferromagnetic interaction within the plane over the inter plane antiferromagnetic interactions.Comment: Appearing in J. Magn. Magn. Mate

The structural properties of the multi-layer graphene/4H-SiC(000-1) system as determined by Surface X-ray Diffraction

We present a structural analysis of the multi-layer graphene-4HSiC(000-1}) system using Surface X-Ray Reflectivity. We show for the first time that graphene films grown on the C-terminated (000-1}) surface have a graphene-substrate bond length that is very short (0.162nm). The measured distance rules out a weak Van der Waals interaction to the substrate and instead indicates a strong bond between the first graphene layer and the bulk as predicted by ab-initio calculations. The measurements also indicate that multi-layer graphene grows in a near turbostratic mode on this surface. This result may explain the lack of a broken graphene symmetry inferred from conduction measurements on this system [C. Berger et al., Science 312, 1191 (2006)].Comment: 9 pages with 6 figure