Transport between edge states in multilayer integer quantum Hall systems: exact treatment of Coulomb interactions and disorder

A set of stacked two-dimensional electron systems in a perpendicular magnetic field exhibits a three-dimensional version of the quantum Hall effect if interlayer tunneling is not too strong. When such a sample is in a quantum Hall plateau, the edge states of each layer combine to form a chiral metal at the sample surface. We study the interplay of interactions and disorder in transport properties of the chiral metal, in the regime of weak interlayer tunneling. Our starting point is a system without interlayer tunneling, in which the only excitations are harmonic collective modes: surface magnetoplasmons. Using bosonization and working perturbatively in the interlayer tunneling amplitude, we express transport properties in terms of the spectrum for these collective modes, treating electron-electron interactions and impurity scattering exactly. We calculte the conductivity as a function of temperature, finding that it increases with increasing temperature as observed in recent experiments. We also calculate the autocorrelation function of mesoscopic conductance fluctuations induced by changes in a magnetic field component perpendicular to the sample surface, and its dependence on temperature. We show that conductance fluctuations are characterised by a dephasing length that varies inversely with temperature.Comment: 13 pages, 10 figures, minor changes made for publicatio

Population-Based Pragmatic Trial of Advance Care Planning in Primary Care in the University of California Health System.

Introduction: Varying intensity of advance care planning (ACP) interventions at the population level has not been compared among seriously ill patients in primary care. This project will implement, test, and disseminate real-world scalable ACP interventions among primary care clinics across three University of California Health systems. The three ACP interventions are (1) distribution of an advance directive (AD) with targeted ACP messaging, (2) the AD, messaging, plus prompting patients to engage with the Prepare For Your Care website (PREPARE), and (3) the AD, messaging, PREPARE, plus Care Coordinator engagement with patients and clinicians. Methods: We will identify a population cohort of seriously ill primary care patients and implement the ACP interventions using electronic health record (EHR) patient portals and postal mailings. Forty-five clinics across the three health systems will be cluster randomized to one of the three ACP interventions. The primary outcome for the population cohort is AD or Physician Orders for Life-Sustaining Treatment documentation in the EHR. A subset of the population cohort will be surveyed to assess patient-centered outcomes, including care consistent with goals at baseline, 12 months, and 24 months. Caregivers will be interviewed if patients are unable to be surveyed or die. ACP documentation, goal concordant care, and among decedents, health care utilization will be compared among intervention arms. Study Implementation: Challenges and Contributions: The project is guided by a Study Advisory Group and Community Advisory Groups at each site to ensure rigorous patient-centered methods and consistency of implementation. Intervention fidelity will be evaluated using the Reach, Efficacy, Adoption, Implementation, and Maintenance (RE-AIM) framework. Challenges to implementation of this three-site health system trial and to intervention fidelity stem from site/clinic/system cultures, increasing attention to end-of-life care from payers and regulators, and growing pressures by health systems to implement ACP interventions. Stakeholder engagement is required to ensure consistent interventions across sites

A review of source tracking techniques for fine sediment within a catchment

Excessive transport of fine sediment, and its associated pollutants, can cause detrimental impacts in aquatic environments. It is therefore important to perform accurate sediment source apportionment to identify hot spots of soil erosion. Various tracers have been adopted, often in combination, to identify sediment source type and its spatial origin; these include fallout radionuclides, geochemical tracers, mineral magnetic properties and bulk and compound-specific stable isotopes. In this review, the applicability of these techniques to particular settings and their advantages and limitations are reviewed. By synthesizing existing approaches, that make use of multiple tracers in combination with measured changes of channel geomorphological attributes, an integrated analysis of tracer profiles in deposited sediments in lakes and reservoirs can be made. Through a multi-scale approach for fine sediment tracking, temporal changes in soil erosion and sediment load can be reconstructed and the consequences of changing catchment practices evaluated. We recommend that long-term, as well as short-term, monitoring of riverine fine sediment and corresponding surface and subsurface sources at nested sites within a catchment are essential. Such monitoring will inform the development and validation of models for predicting dynamics of fine sediment transport as a function of hydro-climatic and geomorphological controls. We highlight that the need for monitoring is particularly important for hilly catchments with complex and changing land use. We recommend that research should be prioritized for sloping farmland-dominated catchments

Will I Get In? Using Predictive Analytics to Develop Student-Facing Tools to Estimate University Admissions Decisions

A sizable number of low-income high school graduates enroll in colleges less selective than their academic qualifications would allow or forgo postsecondary altogether despite being college-ready. One potential cause of this “undermatching” is that some students have limited access to information about their college options. We hypothesize that providing students with more and better information about the relationship between their academic preparation and college options may promote college-going. The purpose of this study was to develop a predictive model of admissions to public 4-year institutions using data from Texas’ statewide longitudinal data system in order to build a student-facing tool that predicts admissions decisions. We sought to include only variables for which students have some control over, namely academic characteristics, but compared the predictive accuracy of this reduced model to more complex models that include demographic variables commonly used in higher education research. We show the reduced model successfully predicts admissions decisions for approximately 85% of applications. The addition of demographic variables, despite showing a statistically significant better fit of the data, do not substantively change the predictive accuracy of the model. We include a demonstration of a data visualization tool built on this predictive model using the open-source R statistical software that can be used by students, parents, and educators. We also discuss causes for both optimism and caution when using predictive modeling to develop student-facing tools