Stability of the k=3 Read-Rezayi state in chiral two-dimensional systems with tunable interactions

The k=3 Read-Rezayi (RR) parafermion quantum Hall state hosts non-Abelian excitations which provide a platform for the universal topological quantum computation. Although the RR state may be realized at the filling factor \nu=12/5 in GaAs-based two-dimensional electron systems, the corresponding quantum Hall state is weak and at present nearly impossible to study experimentally. Here we argue that the RR state can alternatively be realized in a class of chiral materials with massless and massive Dirac-like band structure. This family of materials encompasses monolayer and bilayer graphene, as well as topological insulators. We show that, compared to GaAs, these systems provide several important advantages in realizing and studying the RR state. Most importantly, the effective interactions can be tuned {\it in situ} by varying the external magnetic field, and by designing the dielectric environment of the sample. This tunability enables the realization of RR state with controllable energy gaps in different Landau levels. It also allows one to probe the quantum phase transitions to other compressible and incompressible phases.Comment: 12 pages, 5 figures; to appear in New Journal of Physics, Focus on Topological Quantum Computatio

The Impact of Parenting on First-Time Mothers Mental Health and Sense of Competence: A Mixed-Method Study

Early adverse childhood experiences impact the psychosocial functioning of individuals when they become parents themselves including links to postnatal mental health problems. Previous research primarily focused broadly on attachments styles or the impact of abuse on parenting. This mixed-method study will look at both negative and positive day-to-day parenting interactions that mothers experienced with their own parents. A community sample of 212 first time mothers of infants under 12-months old completed questionnaires relating to perceptions of being parented, parenting stress, parenting sense of competence, postnatal depression and postnatal anxiety. 25 of these mothers were then interviewed 1:1 to explore at a deeper level the transition to motherhood and aspects of their own parenting that they draw upon. Quantitative data was analysed using PROCESS for moderating and mediating relationships and qualitative data was analysed using reflexive thematic analysis. Results showed that both positive and negative experiences of being parented affect mothers’ sense of competence and that this relationship is mediated by mental health disorders such as depression and anxiety. Stress moderated some of these relationships. Reflexive thematic analysis generated themes explaining how mothers’ made sense of and responded to their own experiences of being parented in order to manage their own mental health and develop their own parenting styles. These findings have implications for postnatal mental health services and parenting programs

Modelling of fatigue damage in aluminum cylinder heads

International audienceCar manufacturers are very much concerned with thermal fatigue ....

Quantum Hall Effects in Graphene-Based Two-Dimensional Electron Systems

In this article we review the quantum Hall physics of graphene based two-dimensional electron systems, with a special focus on recent experimental and theoretical developments. We explain why graphene and bilayer graphene can be viewed respectively as J=1 and J=2 chiral two-dimensional electron gases (C2DEGs), and why this property frames their quantum Hall physics. The current status of experimental and theoretical work on the role of electron-electron interactions is reviewed at length with an emphasis on unresolved issues in the field, including assessing the role of disorder in current experimental results. Special attention is given to the interesting low magnetic field limit and to the relationship between quantum Hall effects and the spontaneous anomalous Hall effects that might occur in bilayer graphene systems in the absence of a magnetic field

Numerical studies of the fractional quantum Hall effect in systems with tunable interactions

The discovery of the fractional quantum Hall effect in GaAs-based semiconductor devices has lead to new advances in condensed matter physics, in particular the possibility for exotic, topological phases of matter that possess fractional, and even non-Abelian, statistics of quasiparticles. One of the main limitations of the experimental systems based on GaAs has been the lack of tunability of the effective interactions between two-dimensional electrons, which made it difficult to stabilize some of the more fragile states, or induce phase transitions in a controlled manner. Here we review the recent studies that have explored the effects of tunability of the interactions offered by alternative two-dimensional systems, characterized by non-trivial Berry phases and including graphene, bilayer graphene and topological insulators. The tunability in these systems is achieved via external fields that change the mass gap, or by screening via dielectric plate in the vicinity of the device. Our study points to a number of different ways to manipulate the effective interactions, and engineer phase transitions between quantum Hall liquids and compressible states in a controlled manner.Comment: 9 pages, 4 figures, updated references; review for the CCP2011 conference, to appear in "Journal of Physics: Conference Series

A Peptide from the Beta-strand Region of CD2 Protein that Inhibits Cell Adhesion and Suppresses Arthritis in a Mouse Model

This is the peer reviewed version of the following article: Satyanarayanajois, S. D., Büyüktimkin, B., Gokhale, A., Ronald, S., Siahaan, T. J. and Latendresse, J. R. (2010), A Peptide from the Beta-strand Region of CD2 Protein that Inhibits Cell Adhesion and Suppresses Arthritis in a Mouse Model. Chemical Biology & Drug Design, 76: 234–244. doi:10.1111/j.1747-0285.2010.01001.x, which has been published in final form at http://doi.org/10.1111/j.1747-0285.2010.01001.x. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Cell adhesion molecules play a central role at every step of the immune response. The function of leukocytes can be regulated by modulating adhesion interactions between cell adhesion molecules to develop therapeutic agents against autoimmune diseases. Among the different cell adhesion molecules that participate in the immunological response, CD2 and its ligand CD58 (LFA-3) are two of the best-characterized adhesion molecules mediating the immune response. To modulate the cell adhesion interaction, peptides were designed from the discontinuous epitopes of the β-strand region of CD2 protein. The two strands were linked by a peptide bond. β-Strands in the peptides were nucleated by inserting a β-sheet-inducing Pro-Gly sequence with key amino acid sequences from CD2 protein that binds to CD58. Using a fluorescence assay, peptides that exhibited potential inhibitory activity in cell adhesion were evaluated for their ability to bind to CD58 protein. A model for peptide binding to CD58 protein was proposed based on docking studies. Administration of one of the peptides, P3 in collagen-induced arthritis (CIA) in the mouse model, indicated that peptide P3 was able to suppress rheumatoid arthritis in mice

Energy gaps at neutrality point in bilayer graphene in a magnetic field

Utilizing the Baym-Kadanoff formalism with the polarization function calculated in the random phase approximation, the dynamics of the $\nu=0$ quantum Hall state in bilayer graphene is analyzed. Two phases with nonzero energy gap, the ferromagnetic and layer asymmetric ones, are found. The phase diagram in the plane $(\tilde{\Delta}_0,B)$, where $\tilde{\Delta}_0$ is a top-bottom gates voltage imbalance, is described. It is shown that the energy gap scales linearly, $\Delta E\sim 14 B[T]K, with magnetic field.Comment: 5 pages, 3 figures, title changed, references added, JETP Letters versio

Coulomb impurity under magnetic field in graphene: a semiclassical approach

We address the problem of a Coulomb impurity in graphene in the presence of a perpendicular uniform magnetic field. We show that the problem can be solved below the supercritical impurity magnitude within the WKB approximation. Without impurity the semiclassical energies correctly reproduce the Landau level spectrum. For a given Landau level the WKB energy depends on the absolute value of angular momentum in a way which is consistent with the exact diagonalization result. Below the supercritical impurity magnitude, the WKB solution can be expanded as a convergent series in powers of the effective fine structure constant. Relevance of our results to validity of the widely used Landau level projection approximation is discussed.Comment: 10 pages, 5 figure