Impurity State and Variable Range Hopping Conduction in Graphene

The variable range hopping theory, as formulated for exponentially localized impurity states, does not necessarily apply in the case of graphene with covalently attached impurities. We analyze the localization of impurity states in graphene using the nearest-neighbor, tight-binding model of an adatom-graphene system with Green's function perturbation methods. The amplitude of the impurity state wave function is determined to decay as a power law with exponents depending on sublattice, direction, and the impurity species. We revisit the variable range hopping theory in view of this result and find that the conductivity depends as a power law of the temperature with an exponent related to the localization of the wave function. We show that this temperature dependence is in agreement with available experimental results

A noncontact measurement technique for the density and thermal expansion coefficient of solid and liquid materials

A noncontact measurement technique for the density and the thermal expansion coefficient of refractory materials in their molten as well as solid phases is presented. This technique is based on the video image processing of a levitated sample. Experiments were performed using the high-temperature electrostatic levitator (HTESL) at the Jet Propulsion Laboratory in which 2–3 mm diam samples can be levitated, melted, and radiatively cooled in vacuum. Due to the axisymmetric nature of the molten samples when levitated in the HTESL, a rather simple digital image analysis can be employed to accurately measure the volumetric change as a function of temperature. Density and the thermal expansion coefficient measurements were made on a pure nickel sample to test the accuracy of the technique in the temperature range of 1045–1565 °C. The result for the liquid phase density can be expressed by rho=8.848+(6.730×10^−4)×T (°C) g/cm^3 within 0.8% accuracy, and the corresponding thermal expansion coefficient can be expressed by beta=(9.419×10^−5) −(7.165×10^−9)×T (°C) K^−1 within 0.2% accuracy

Development of a Community-Based Spiritual Life Review Program for Promoting Resilience of Elders Residing in Disaster-Prone Areas

Background: Nowadays disasters are a common occurrence in the world. The elderly are in a vulnerable condition in terms of disasters and need help to recover from the hardship caused if they are caught in such a disaster. Two significant contributors to elderly people having sufficient resilience to be able to deal with such disasters are spiritual support and social support. Purpose: To develop a program specifically for Muslim elderly in Indonesia for promoting resilience. Method: The processes of developing the program were conducted in 2011, and included a critical review of the literature, constructing the elements of the actual program, validating the contents of the program by three experts, revising the program according to the experts‟ suggestions, and finally pilot-tested the final version of the program on a group 12 elders in Banda Aceh, Indonesia. Result: The program protocol established in this program includes five stages: (1) reviewing individual spiritual life experiences using memorable photos; (2) appreciating feelings among group members (3) re-evaluating the participant‟s life by looking to the group‟s album, (4) reconstructing the participants‟ life, and (5) affirming the six spiritual dimensions of the Islamic religion by the religious leader

Born-Infeld Type Extension of (Non-)Critical Gravity

We consider the Born-Infeld type extension of (non-)critical gravity which is higher curvature gravity on Anti de-Sitter space with specific combinations of scalar curvature and Ricci tensor. This theory may also be viewed as a natural extension of three-dimensional Born-Infeld new massive gravity to arbitrary dimensions. We show that this extension is consistent with holographic $c$-theorem and scalar graviton modes are absent in this theory. After showing that ghost modes in the theory can be truncated consistently by appropriate boundary conditions, we argue that the theory is classically equivalent to Einstein gravity at the non-linear level. Black hole solutions are discussed in the view point of the full non-linear classical equivalence between the theory and Einstein gravity. Holographic entanglement entropy in the theory is also briefly commented on.Comment: 1+13 pages, improvements in presentation, references added, accepted to PR

Simple threshold rules solve explore/exploit trade‐offs in a resource accumulation search task

How, and how well, do people switch between exploration and exploitation to search for and accumulate resources? We study the decision processes underlying such exploration/exploitation trade‐offs using a novel card selection task that captures the common situation of searching among multiple resources (e.g., jobs) that can be exploited without depleting. With experience, participants learn to switch appropriately between exploration and exploitation and approach optimal performance. We model participants' behavior on this task with random, threshold, and sampling strategies, and find that a linear decreasing threshold rule best fits participants' results. Further evidence that participants use decreasing threshold‐based strategies comes from reaction time differences between exploration and exploitation; however, participants themselves report non‐decreasing thresholds. Decreasing threshold strategies that “front‐load” exploration and switch quickly to exploitation are particularly effective in resource accumulation tasks, in contrast to optimal stopping problems like the Secretary Problem requiring longer exploration

Avalanches in a Bose-Einstein condensate

Collisional avalanches are identified to be responsible for an 8-fold increase of the initial loss rate of a large 87-Rb condensate. We show that the collisional opacity of an ultra-cold gas exhibits a critical value. When exceeded, losses due to inelastic collisions are substantially enhanced. Under these circumstances, reaching the hydrodynamic regime in conventional BEC experiments is highly questionable.Comment: 4 pages, 2 figures, 1 tabl