Attracting shallow donors: Hydrogen passivation in (Al,Ga,In)-doped ZnO

The hydrogen interstitial and the substitutional Al_Zn, Ga_Zn and In_Zn are all shallow donors in ZnO and lead to n-type conductivity. Although shallow donors are expected to repel each other, we show by first principles calculations that in ZnO these shallow donor impurities attract and form a complex, leading to a donor level deep in the band gap. This puts a limit on the n-type conductivity of (Al,Ga,In)-doped ZnO in the presence of hydrogen.Comment: 4 pages, 5 figure

Adolescent Development in Context: Social, Psychological, and Neurological Foundations

This project was funded by KU Libraries’ Parent’s Campaign with support from the David Shulenburger Office of Scholarly Communication & Copyright and the Open Educational Resources Working Group in the University of Kansas Libraries.Increasingly, there is a tendency to characterize the teenage years as a time of general moral degeneration and deviance. This is unfortunate because the teenage years represent a key developmental period of the typical human lifespan, and from an evolutionary point of view, the actual characteristics that define adolescence represent critical learning opportunities. The increased sensitivity to social influences, identity formation, and social-emotional skills are just a few of such opportunities that require appropriate environments and contexts for optimal, healthy outcomes. Research in the field of adolescent development has not been immune to the negative stereotypes surrounding adolescence, and it is common to see researchers, either implicitly or explicitly, refer to adolescence as a high-risk, anomalous developmental stage that must be controlled, managed, or simply endured until adult-level abilities emerge spontaneously as a result of having survived an intrinsically tumultuous developmental time. More enlightened views of adolescence recognize that all biological adaptations have a cause and a purpose, and that the purpose of adolescence can be discerned from understanding the complex evolutionary history of humans as a group-based, family-based, highly social, sometimes competitive, abstract-thinking species. Understanding the biological foundations of adolescence is meaningless if one does not also consider how biology and environment interact. In humans, these interactions are highly complex and involve not only immediate physical realities, but also social, cultural, and historical realities that create complex contexts and webs of interactions. Therefore, this textbook seeks to reconcile the biological and neurological foundations of human development with the psychological and sociological mechanisms that formed and continue to influence human developmental trajectories. To this end, we have divided the textbook into three main sections. The first, Foundations of Adolescent Development, introduces the historical science of studying adolescence and the biological foundations of puberty. The second section, Contexts of Adolescent Development, considers the primary contextual factors that influence developmental outcomes during adolescence. These include work and employment, peers, in-school and out-of-school contexts, leisure time, and the family. The final section, Milestones of Adolescent Development, addresses the primary psychological milestones that represent healthy adjustment to adult roles and responsibilities in society. The domains of these milestones include cognition and decision-making; identity, meaning, and purpose, moral development, and sexuality. From an educational point of view, the objective of this textbook is to provide a resource that is capable of fostering advanced conceptual change and learning in the field of adolescent development in order to go beyond stereotypical portrayals of adolescence as a pathological condition. Organized in a manner designed to scaffold increasingly complex ideas, the textbook redefines adolescence a sensitive period of development characterized by phylogenetically derived experience-expectant states and complex interactions of biological, psychological, and social factors. The textbook draws from the latest advances in neuroscience and psychology to construct a practical framework for use in a wide range of academic and professional contexts, and it presents historical as well as contemporary research to accomplish a radical redefining of an often misunderstood and maligned developmental period

The effects of disorder and interactions on the Anderson transition in doped Graphene

We undertake an exact numerical study of the effects of disorder on the Anderson localization of electronic states in graphene. Analyzing the scaling behaviors of inverse participation ratio and geometrically averaged density of states, we find that Anderson metal-insulator transition can be introduced by the presence of quenched random disorder. In contrast with the conventional picture of localization, four mobility edges can be observed for the honeycomb lattice with specific disorder strength and impurity concentration. Considering the screening effects of interactions on disorder potentials, the experimental findings of the scale enlarges of puddles can be explained by reviewing the effects of both interactions and disorder.Comment: 7 pages, 7 figure

Electrostatics of Gapped and Finite Surface Electrodes

We present approximate methods for calculating the three-dimensional electric potentials of finite surface electrodes including gaps between electrodes, and estimate the effects of finite electrode thickness and an underlying dielectric substrate. As an example we optimize a radio-frequency surface-electrode ring ion trap, and find that each of these factors reduces the trapping secular frequencies by less than 5% in realistic situations. This small magnitude validates the usual assumption of neglecting the influences of gaps between electrodes and finite electrode extent.Comment: 9 pages, 9 figures (minor changes

Temporal Quantum Control with Graphene

We introduce a novel strategy for controlling the temporal evolution of a quantum system at the nanoscale. Our method relies on the use of graphene plasmons, which can be electrically tuned in frequency by external gates. Quantum emitters (e.g., quantum dots) placed in the vicinity of a graphene nanostructure are subject to the strong interaction with the plasmons of this material, thus undergoing time variations in their mutual interaction and quantum evolution that are dictated by the externally applied gating voltages. This scheme opens a new path towards the realization of quantum-optics devices in the robust solid-state environment of graphene.Comment: 5 pages, 2 figure

A late Pleistocene long pollen record from Lake Urmia, NW Iran

A palynological study based on two 100-m long cores from Lake Urmia in northwestern Iran provides a vegetation record spanning 200 ka, the longest pollen record for the continental interior of the Near East. During both penultimate and last glaciations, a steppe of Artemisia and Poaceae dominated the upland vegetation with a high proportion of Chenopodiaceae in both upland and lowland saline ecosystems. While Juniperus and deciduous Quercus trees were extremely rare and restricted to some refugia, Hippophaë rhamnoides constituted an important phanerophyte, particularly during the upper last glacial sediments. A pronounced expansion in Ephedra shrub-steppe occurred at the end of the penultimate late-glacial period but was followed by extreme aridity that favoured an Artemisia steppe. Very high lake levels, registered by both pollen and sedimentary markers, occurred during the middle of the last glaciation and upper part of the penultimate glaciation. The late-glacial to early Holocene transition is represented by a succession of Hippophaë, Ephedra, Betula, Pistacia and finally Juniperus and Quercus. The last interglacial period (Eemian), slightly warmer and moister than the Holocene, was followed by two interstadial phases similar in pattern to those recorded in the marine isotope record and southern European pollen sequences

Implementing Zn²⁺ ion and pH-value control into artificial mussel glue proteins by abstracting a His-rich domain from preCollagen

A His-rich domain of preCollagen-D found in byssal threads is derivatized with Cys and Dopa flanks to allow for mussel-inspired polymerization. Artificial mussel glue proteins are accessed that combine cysteinyldopa for adhesion with sequences for pH or Zn2+ induced β-sheet formation. The artificial constructs show strong adsorption to Al2O3, the resulting coatings tolerate hypersaline conditions and cohesion is improved by activating the β-sheet formation, that enhances E-modulus up to 60%

Anderson Transition in Disordered Graphene

We use the regularized kernel polynomial method (RKPM) to numerically study the effect disorder on a single layer of graphene. This accurate numerical method enables us to study very large lattices with millions of sites, and hence is almost free of finite size errors. Within this approach, both weak and strong disorder regimes are handled on the same footing. We study the tight-binding model with on-site disorder, on the honeycomb lattice. We find that in the weak disorder regime, the Dirac fermions remain extended and their velocities decrease as the disorder strength is increased. However, if the disorder is strong enough, there will be a {\em mobility edge} separating {\em localized states around the Fermi point}, from the remaining extended states. This is in contrast to the scaling theory of localization which predicts that all states are localized in two-dimensions (2D).Comment: 4 page