Non-collinear magnetic structure and multipolar order in Eu2_2Ir2_2O7_7

The magnetic properties of the pyrochlore iridate material Eu$_2$Ir$_2$O$_7$ (5$d^5$) have been studied based on the first principle calculations, where the crystal field splitting $\Delta$, spin-orbit coupling (SOC) $\lambda$ and Coulomb interaction $U$ within Ir 5$d$ orbitals are all playing significant roles. The ground state phase diagram has been obtained with respect to the strength of SOC and Coulomb interaction $U$, where a stable anti-ferromagnetic ground state with all-in/all-out (AIAO) spin structure has been found. Besides, another anti-ferromagnetic states with close energy to AIAO have also been found to be stable. The calculated nonlinear magnetization of the two stable states both have the d-wave pattern but with a $\pi/4$ phase difference, which can perfectly explain the experimentally observed nonlinear magnetization pattern. Compared with the results of the non-distorted structure, it turns out that the trigonal lattice distortion is crucial for stabilizing the AIAO state in Eu$_2$Ir$_2$O$_7$. Furthermore, besides large dipolar moments, we also find considerable octupolar moments in the magnetic states.Comment: 6 pages, 4 figures, supplemental material is included in the source file, accepted for publication in PR

Weighted selective collapsing strategy for detecting rare and common variants in genetic association study

<p>Abstract</p> <p>Background</p> <p>Genome-wide association studies (GWAS) have been used successfully in detecting associations between common genetic variants and complex diseases. However, common SNPs detected by current GWAS only explain a small proportion of heritable variability. With the development of next-generation sequencing technologies, researchers find more and more evidence to support the role played by rare variants in heritable variability. However, rare and common variants are often studied separately. The objective of this paper is to develop a robust strategy to analyze association between complex traits and genetic regions using both common and rare variants.</p> <p>Results</p> <p>We propose a weighted selective collapsing strategy for both candidate gene studies and genome-wide association scans. The strategy considers genetic information from both common and rare variants, selectively collapses all variants in a given region by a forward selection procedure, and uses an adaptive weight to favor more likely causal rare variants. Under this strategy, two tests are proposed. One test denoted by <it>B_wSC</it>is sensitive to the directions of genetic effects, and it separates the deleterious and protective effects into two components. Another denoted by <it>B_wSCd</it>is robust in the directions of genetic effects, and it considers the difference of the two components. In our simulation studies, <it>B_wSC</it>achieves a higher power when the casual variants have the same genetic effect, while <it>B_wSCd</it>is as powerful as several existing tests when a mixed genetic effect exists. Both of the proposed tests work well with and without the existence of genetic effects from common variants.</p> <p>Conclusions</p> <p>Two tests using a weighted selective collapsing strategy provide potentially powerful methods for association studies of sequencing data. The tests have a higher power when both common and rare variants contribute to the heritable variability and the effect of common variants is not strong enough to be detected by traditional methods. Our simulation studies have demonstrated a substantially higher power for both tests in all scenarios regardless whether the common SNPs are associated with the trait or not.</p

Pressure-Driven Orbital Selective Insulator to Metal Transition and Spin State Crossover in Cubic CoO

The metal-insulator and spin state transitions of CoO under high pressure are studied by using density functional theory combined with dynamical mean-field theory. Our calculations predict that the metal-insulator transition in CoO is a typical orbital selective Mott transition, where the $t_{2g}$ orbitals of Co 3d shell become metallic firstly around 60 GPa while the $e_g$ orbitals still remain insulating until 170 GPa. Further studies of the spin states of Co 3d shell reveal that the orbital selective Mott phase in the intermediate pressure regime is mainly stabilized by the high-spin state of the Co 3d shell and the transition from this phase to the full metallic state is driven by the high-spin to low-spin transition of the Co$^{2+}$ ions. Our results are in good agreement with the most recent transport and x-ray emission experiments under high pressure.Comment: 5+ pages, 4 figure

A Non-cooperative Game Algorithm for Task Scheduling in Wireless Sensor Networks

Scheduling tasks in wireless sensor networks is one of the most challenging problems. Sensing tasks should be allocated and processed among sensors in minimum times, so that users can draw prompt and effective conclusions through analyzing sensed data. Furthermore, finishing sensing task faster will benefit energy saving, which is critical in system design of wireless sensor networks. But sensors may refuse to take pains to carry out the tasks due to the limited energy. To solve the potentially selfish problem of the sensors, a non-cooperative game algorithm (NGTSA) for task scheduling in wireless sensor networks is proposed. In the proposed algorithm, according to the divisible load theory, the tasks are distributed reasonably to every node from SINK based on the processing capability and communication capability. By removing the performance degradation caused by communications interference and idle, the reduced task completion time and the improved network resource utilization are achieved. Strategyproof mechanism which provide incentives to the sensors to obey the prescribed algorithms, and to truthfully report their parameters, leading to an effient task scheduling and execution. A utility function related with the total task completion time and tasks allocating scheme is designed. The Nash equilibrium of the game algorithm is proved. The simulation results show that with the mechanism in the algorithm, selfish nodes can be forced to report their true processing capability and endeavor to participate in the measurement, thereby the total time for accomplishing the task is minimized and the energy-consuming of the nodes is balanced