289 research outputs found

    Domain Patterns in the Microwave-Induced Zero-Resistance State

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    It has been proposed that the microwave-induced ``zero-resistance'' phenomenon, observed in a GaAs two-dimensional electron system at low temperatures in moderate magnetic fields, results from a state with multiple domains, in which a large local electric field \bE(\br) is oriented in different directions. We explore here the questions of what may determine the domain arrangement in a given sample, what do the domains look like in representative cases, and what may be the consequences of domain-wall localization on the macroscopic dc conductance. We consider both effects of sample boundaries and effects of disorder, in a simple model, which has a constant Hall conductivity, and is characterized by a Lyapunov functional.Comment: 19 pages, 5 figures; submitted to a special issue of Journal of Statistical Physics, in honor of P. C. Hohenberg and J. S. Lange

    Training-induced inversion of spontaneous exchange bias field on La1.5Ca0.5CoMnO6

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    In this work we report the synthesis and structural, electronic and magnetic properties of La1.5Ca0.5CoMnO6 double-perovskite. This is a re-entrant spin cluster material which exhibits a non-negligible negative exchange bias effect when it is cooled in zero magnetic field from an unmagnetized state down to low temperature. X-ray powder diffraction, X-ray photoelectron spectroscopy and magnetometry results indicate mixed valence state at Co site, leading to competing magnetic phases and uncompensated spins at the magnetic interfaces. We compare the results for this Ca-doped material with those reported for the resemblant compound La1.5Sr0.5CoMnO6, and discuss the much smaller spontaneous exchange bias effect observed for the former in terms of its structural and magnetic particularities. For La1.5Ca0.5CoMnO6, when successive magnetization loops are carried, the spontaneous exchange bias field inverts its sign from negative to positive from the first to the second measurement. We discuss this behavior based on the disorder at the magnetic interfaces, related to the presence of a glassy phase. This compound also exhibits a large conventional exchange bias, for which there is no sign inversion of the exchange bias field for consecutive cycles

    Correlation between the Extraordinary Hall Effect and Resistivity

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    We study the contribution of different types of scattering sources to the extraordinary Hall effect. Scattering by magnetic nano-particles embedded in normal-metal matrix, insulating impurities in magnetic matrix, surface scattering and temperature dependent scattering are experimentally tested. Our new data, as well as previously published results on a variety of materials, are fairly interpreted by a simple modification of the skew scattering model

    Results of the 2016 Indianapolis Biodiversity Survey, Marion County, Indiana

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    Surprising biodiversity can be found in cities, but urban habitats are understudied. We report on a bioblitz conducted primarily within a 24-hr period on September 16 and 17, 2016 in Indianapolis, Indiana, USA. The event focused on stretches of three waterways and their associated riparian habitat: Fall Creek (20.6 ha; 51 acres), Pleasant Run (23.5 ha; 58 acres), and Pogue’s Run (27.1 ha; 67 acres). Over 75 scientists, naturalists, students, and citizen volunteers comprised 14 different taxonomic teams. Five hundred ninety taxa were documented despite the rainy conditions. A brief summary of the methods and findings are presented here. Detailed maps of survey locations and inventory results are available on the Indiana Academy of Science website (https://www.indianaacademyofscience.org/)

    Lessons Learned from Testing the Quality Cost Model of Advanced Practice Nursing (APN) Transitional Care

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    Purpose To describe the development, testing, modification, and results of the Quality Cost Model of Advanced Practice Nurses (APNs) Transitional Care on patient outcomes and health care costs in the United States over 22 years, and to delineate what has been learned for nursing education, practice, and further research. Organizing Construct The Quality Cost Model of APN Transitional Care. Methods Review of published results of seven randomized clinical trials with very low birth-weight (VLBW) infants; women with unplanned cesarean births, high risk pregnancies, and hysterectomy surgery; elders with cardiac medical and surgical diagnoses and common diagnostic related groups (DRGs); and women with high risk pregnancies in which half of physician prenatal care was substituted with APN care. Ongoing work with the model is linking the process of APN care with the outcomes and costs of care. Findings APN intervention has consistently resulted in improved patient outcomes and reduced health care costs across groups. Groups with APN providers were rehospitalized for less time at less cost, reflecting early detection and intervention. Optimal number and timing of postdischarge home visits and telephone contacts by the APNs and patterns of rehospitalizations and acute care visits varied by group. Conclusions To keep people well over time, APNs must have depth of knowledge and excellent clinical and interpersonal skills that are the hallmark of specialist practice, an in-depth understanding of systems and how to work within them, and sufficient patient contact to effect positive outcomes at low cost

    Structural Attributes and Photodynamics of Visible Spectrum Quantum Emitters in Hexagonal Boron Nitride

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    Newly discovered van der Waals materials like MoS2, WSe2, hexagonal boron nitride (h-BN), and recently C2N have sparked intensive research to unveil the quantum behavior associated with their 2D structure. Of great interest are 2D materials that host single quantum emitters. h-BN, with a band gap of 5.95 eV, has been shown to host single quantum emitters which are stable at room temperature in the UV and visible spectral range. In this paper we investigate correlations between h-BN structural features and emitter location from bulk down to the monolayer at room temperature. We demonstrate that chemical etching and ion irradiation can generate emitters in h-BN. We analyze the emitters' spectral features and show that they are dominated by the interaction of their electronic transition with a single Raman active mode of h-BN. Photodynamics analysis reveals diverse rates between the electronic states of the emitter. The emitters show excellent photo stability even under ambient conditions and in monolayers. Comparing the excitation polarization between different emitters unveils a connection between defect orientation and the h-BN hexagonal structure. The sharp spectral features, color diversity, room-temperature stability, long-lived metastable states, ease of fabrication, proximity of the emitters to the environment, outstanding chemical stability, and biocompatibility of h-BN provide a completely new class of systems that can be used for sensing and quantum photonics applications

    Health Care Consumers: Choices and Constraints

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    This article summarizes the research and data currently available on different dimensions of consumer choice. These dimensions include not only whether to participate in a health care plan and which plan to select if given a choice but also the decisions that lead to having a choice and the implications of making the choice. Data are presented on what choices consumers face, how many are given what kinds of choices, what constraints they face, what we know about how they make these choices, and what information they are given and what they use. The majority of Americans are offered some kind of health insurance plan either through their place of employment or as a dependent on someone else’s employer-sponsored health plan. About half of those offered health insurance are offered a choice, usually of only two or three plans. The majority elect to participate in one of those plans.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/68465/2/10.1177_107755879905600102.pd
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