Bloch Electrons in a Magnetic Field - Why Does Chaos Send Electrons the Hard Way?

We find that a 2D periodic potential with different modulation amplitudes in x- and y-direction and a perpendicular magnetic field may lead to a transition to electron transport along the direction of stronger modulation and to localization in the direction of weaker modulation. In the experimentally accessible regime we relate this new quantum transport phenomenon to avoided band crossing due to classical chaos.Comment: 4 pages, 3 figures, minor modifications, PRL to appea

Convergence properties of the Kalman inverse filter

The Kalman filter has a long history of use in input deconvolution where it is desired to estimate structured inputs or disturbances to a plant from noisy output measurements. However, little attention has been given to the convergence properties of the deconvolved signal, in particular the conditions needed to estimate inputs and disturbances with zero bias. The paper draws on ideas from linear systems theory to understand the convergence properties of the Kalman filter when used for input deconvolution. The main result of the paper is to show that, in general, unbiased estimation of inputs using a Kalman filter requires both an exact model of the plant and an internal model of the input signal. We show that for unbiased estimation, an identified subblock of the Kalman filter that we term the plant model input generator (PMIG) must span all possible inputs to the plant and that the robustness of the estimator with respect to errors in model parameters depends on the eigenstructure of this subblock. We give estimates of the bias on the estimated inputs/disturbances when the model is in error. The results of this paper provide insightful guidance in the design of Kalman filters for input deconvolution

Bridging the Gap: using an interrupted time series design to evaluate systems reform addressing refugee maternal and child health inequalities

BACKGROUND: The risk of poor maternal and perinatal outcomes in high-income countries such as Australia is greatest for those experiencing extreme social and economic disadvantage. Australian data show that women of refugee background have higher rates of stillbirth, fetal death in utero and perinatal mortality compared with Australian born women. Policy and health system responses to such inequities have been slow and poorly integrated. This protocol describes an innovative programme of quality improvement and reform in publically funded universal health services in Melbourne, Australia, that aims to address refugee maternal and child health inequalities. METHODS/DESIGN: A partnership of 11 organisations spanning health services, government and research is working to achieve change in the way that maternity and early childhood health services support families of refugee background. The aims of the programme are to improve access to universal health care for families of refugee background and build organisational and system capacity to address modifiable risk factors for poor maternal and child health outcomes. Quality improvement initiatives are iterative, co-designed by partners and implemented using the Plan Do Study Act framework in four maternity hospitals and two local government maternal and child health services. Bridging the Gap is designed as a multi-phase, quasi-experimental study. Evaluation methods include use of interrupted time series design to examine health service use and maternal and child health outcomes over a 3-year period of implementation. Process measures will examine refugee families' experiences of specific initiatives and service providers' views and experiences of innovation and change. DISCUSSION: It is envisaged that the Bridging the Gap program will provide essential evidence to support service and policy innovation and knowledge about what it takes to implement sustainable improvements in the way that health services support vulnerable populations, within the constraints of existing resources