Layers Of Maturation In Cortical Hierarchies

Hierarchies form critical scaffolds for top-down processing but are often multiplex. In the brain, multiple layers of complex hierarchies intersect, dissociate, and re-converge over the lifespan. Although aspects of local hierarchical organizations are well-mapped for sensory systems, the fashion by which hierarchical organization extends globally is unknown. Human neuroimaging provides a means by which to observe both the developmental emergence and functions of global neurohierarchical organization. Here, we leveraged these advances to distill multiple layers of hierarchical formation across diverse brain-tissue quantifications. We demonstrate that these layers form common and dissociable biomarkers of the developmental emergence of complex cognition. Our results indicate that multiplex neurocognitive development both processes across a normative hierarchical pattern and contributes to engraining the pattern into cortical function. Further, our results suggest that neurocognitive development is largely contemporaneous with neurocognitive aging in an integrated, flexible lifespan sequence

Impurity-Induced Quasiparticle Transport and Universal Limit Wiedemann-Franz Violation in d-Wave Superconductors

Due to the node structure of the gap in a d-wave superconductor, the presence of impurities generates a finite density of quasiparticle excitations at zero temperature. Since these impurity-induced quasiparticles are both generated and scattered by impurities, prior calculations indicate a universal limit (\Omega -> 0, T -> 0) where the transport coefficients obtain scattering-independent values, depending only on the velocity anisotropy v_f/v_2. We improve upon prior results, including the contributions of vertex corrections and Fermi liquid corrections in our calculations of universal limit electrical, thermal, and spin conductivity. We find that while vertex corrections modify electrical conductivity and Fermi liquid corrections renormalize both electrical and spin conductivity, only thermal conductivity maintains its universal value, independent of impurity scattering or Fermi liquid interactions. Hence, low temperature thermal conductivity measurements provide the most direct means of obtaining the velocity anisotropy for high T_c cuprate superconductors.Comment: 22 pages, 6 figures; revised version to be published in Phys Rev

Quasiparticle excitations in relativistic quantum field theory

We analyze the particle-like excitations arising in relativistic field theories in states different than the vacuum. The basic properties characterizing the quasiparticle propagation are studied using two different complementary methods. First we introduce a frequency-based approach, wherein the quasiparticle properties are deduced from the spectral analysis of the two-point propagators. Second, we put forward a real-time approach, wherein the quantum state corresponding to the quasiparticle excitation is explicitly constructed, and the time-evolution is followed. Both methods lead to the same result: the energy and decay rate of the quasiparticles are determined by the real and imaginary parts of the retarded self-energy respectively. Both approaches are compared, on the one hand, with the standard field-theoretic analysis of particles in the vacuum and, on the other hand, with the mean-field-based techniques in general backgrounds.Comment: 53 pages, 4 figures. Version accepted for publication in Ann. Phy

Clinical exigencies, psychosocial realities: negotiating HIV preâ exposure prophylaxis beyond the cascade among gay, bisexual and other men who have sex with men in Canada

IntroductionNotwithstanding the efficacy of oral preâ exposure prophylaxis (PrEP) in clinical trials, a number of obstacles exist to achieving populationâ level impact among gay, bisexual and other men who have sex with men (GBM). However, few studies have explored the subjective experiences of GBM PrEP users and nonâ users in the community, outside of clinical trials. The objectives of this study were to explore GBM’s experiences of considering, accessing and using (or not using) PrEP, and to understand emerging sexual health, social and community issues among GBM in the PrEP era.MethodsFrom October 2015 to March 2016, we purposively sampled PrEPâ naïve and PrEPâ experienced GBM from community organizations and health centres in Toronto, Canada. Inâ depth, 45â to 90â minute semiâ structured interviews explored PrEP perspectives and decisionâ making, access, initiation, use over time, sexual practices and psychosocial considerations. Interviews were recorded, transcribed verbatim, uploaded into NVIVO, reviewed using thematic analysis and then contrasted with the PrEP cascade.ResultsParticipants included PrEP users (n = 15) and nonâ users (n = 14) (mean age = 36.7 years; SD = 8.2), largely gayâ identified (86.2%), cisgender male (89.7%) and white (79.3%). Themes indicate not only correspondences, but also limitations of the PrEP cascade by complicating a user/nonâ user binary and challenging the unilateral presupposition that HIV risk perception leads to PrEP acceptance. Findings further call into question assumptions of a linear stage progression and retention in care as a universal endpoint, instead revealing alternate trajectories of seasonal or intermittent PrEP use and, for some, an end goal of terminating PrEP. GBM’s narratives also revealed potent psychological/affective experiences of untethering sex from HIV anxiety; multifaceted PrEP stigma; and challenges to sexual norms and practices that complicate existing behavioural prevention strategies and sexual and social relationships.ConclusionsAn expanded PrEP cascade should consider alternate trajectories of use based on dynamic relationships and behavioural risks that may call for seasonal or intermittent use; systemic barriers in access to and sustaining PrEP; and multiple end goals including PrEP maintenance and discontinuation. Incorporating GBM’s lived experiences, evolving preferences, and psychosocial and communityâ level challenges into PrEP implementation models, rather than a circumscribed biomedical approach, may more effectively support HIV prevention and GBM’s broader sexual and psychological health.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/146595/1/jia225211_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/146595/2/jia225211.pd

Doing good buffers against feeling bad: Prosocial impact compensates for negative task and self-evaluations

Although evidence suggests that negative task and self-evaluations are associated with emotional exhaustion, little research has examined factors that buffer against these affects. We propose that perceived prosocial impact, the experience of helping others, compensates for negative task and self-evaluations by focusing attention on positive outcomes for others. In Study 1, perceived prosocial impact attenuated the associations of low intrinsic motivation and core self-evaluations with emotional exhaustion among professional fundraisers. Study 2 replicated these results among public sanitation employees and extended them to supervisor performance ratings. Mediated moderation analyses indicated that by protecting against emotional exhaustion, perceived prosocial impact compensated for low intrinsic motivation and core self-evaluations to predict higher performance ratings. Our studies extend theory and research on burnout, helping, and citizenship

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

Digital game elements, user experience and learning

The primary aim of this paper is to identify and theoretically validate the relationships between core game design elements and mechanics, user motivation and engagement and consequently learning. Additionally, it tries to highlight the moderating role of player personality traits on learning outcomes and acceptance and suggest ways to incorporate them in the game design process. To that end, it outlines the role of narrative, aesthetics and core game mechanics in facilitating higher learning outcomes through intrinsic motivation and engagement. At the same time, it discusses how player goal orientation, openness to experience, conscientiousness, sensation seeking and need for cognition influence the translation of the gameplay experience into valuable learning outcomes and user acceptance of the technology