Three Large-Scale Changes To The Medicare Program Could Curb Its Costs But Also Reduce Enrollment

With Medicare spending projected to increase to 24 percent of all federal spending and to equal 6 percent of the gross domestic product by 2037, policy makers are again considering ways to curb the program's spending growth. We used a microsimulation approach to estimate three scenarios: imposing a means-tested premium for Part A hospitalinsurance, introducing a premium support credit to purchase health insurance, and increasing the eligibility age to sixty-seven.We found thatthe scenarios would lead to reductions in cumulative Medicare spending in 2012 -- 36 of 2.4 -- 24.0 percent. However, the scenarios also would increase out-of-pocket spending for enrollees and, in some cases, causemillions of seniors not to enroll in the program and to be left without coverage. To achieve substantial cost savings without causing substantial lack of coverage among seniors, policy makers should consider benefitchanges in combination with other options, such as some of those now being contemplated by the Obama administration and Congress

Some open questions on anti-de Sitter geometry

We present a list of open questions on various aspects of AdS geometry, that is, the geometry of Lorentz spaces of constant curvature -1. When possible we point out relations with homogeneous spaces and discrete subgroups of Lie groups, to Teichm\"uller theory, as well as analogs in hyperbolic geometry.Comment: Not a research article in the usual sense but rather a list of open questions. 19 page

Lift-off dynamics in a simple jumping robot

We study vertical jumping in a simple robot comprising an actuated mass-spring arrangement. The actuator frequency and phase are systematically varied to find optimal performance. Optimal jumps occur above and below (but not at) the robot's resonant frequency $f_0$. Two distinct jumping modes emerge: a simple jump which is optimal above $f_0$ is achievable with a squat maneuver, and a peculiar stutter jump which is optimal below $f_0$ is generated with a counter-movement. A simple dynamical model reveals how optimal lift-off results from non-resonant transient dynamics.Comment: 4 pages, 4 figures, Physical Review Letters, in press (2012

Learning Terrain Dynamics: A Gaussian Process Modeling and Optimal Control Adaptation Framework Applied to Robotic Jumping

The complex dynamics characterizing deformable terrain presents significant impediments toward the real-world viability of locomotive robotics, particularly for legged machines. We explore vertical, robotic jumping as a model task for legged locomotion on presumed-uncharacterized, nonrigid terrain. By integrating Gaussian process (GP)-based regression and evaluation to estimate ground reaction forces as a function of the state, a 1-D jumper acquires the capability to learn forcing profiles exerted by its environment in tandem with achieving its control objective. The GP-based dynamical model initially assumes a baseline rigid, noncompliant surface. As part of an iterative procedure, the optimizer employing this model generates an optimal control strategy to achieve a target jump height. Experiential data recovered from execution on the true surface model are applied to train the GP, in turn, providing the optimizer a more richly informed dynamical model of the environment. The iterative control-learning procedure was rigorously evaluated in experiment, over different surface types, whereby a robotic hopper was challenged to jump to several different target heights. Each task was achieved within ten attempts, over which the terrain's dynamics were learned. With each iteration, GP predictions of ground forcing became incrementally refined, rapidly matching experimental force measurements. The few-iteration convergence demonstrates a fundamental capacity to both estimate and adapt to unknown terrain dynamics in application-realistic time scales, all with control tools amenable to robotic legged locomotion

Witten's 2+1 gravity on R x (Klein bottle)

Witten's formulation of 2+1 gravity is investigated on the nonorientable three-manifold R x (Klein bottle). The gauge group is taken to consist of all four components of the 2+1 Poincare group. We analyze in detail several components of the classical solution space, and we show that from four of the components one can recover nondegenerate spacetime metrics. In particular, from one component we recover metrics for which the Klein bottles are spacelike. An action principle is formulated for bundles satisfying a certain orientation compatibility property, and the corresponding components of the classical solution space are promoted into a phase space. Avenues towards quantization are briefly discussed.Comment: 33 pages, REVTeX v3.0, 3 figures in a separate PostScript fil

Swimming in circles: Motion of bacteria near solid boundaries

Near a solid boundary, E. coli swims in clockwise circular motion. We provide a hydrodynamic model for this behavior. We show that circular trajectories are natural consequences of force-free and torque-free swimming, and the hydrodynamic interactions with the boundary, which also leads to a hydrodynamic trapping of the cells close to the surface. We compare the results of the model with experimental data and obtain reasonable agreement. In particular, we show that the radius of curvature of the trajectory increases with the length of the bacterium body.Comment: Also available at http://people.deas.harvard.edu/~lauga

Bioabsorbable metal zinc differentially affects mitochondria in vascular endothelial and smooth muscle cells

Zinc is an essential trace element having various structural, catalytic and regulatory interactions with an estimated 3000 proteins. Zinc has drawn recent attention for its use, both as pure metal and alloyed, in arterial stents due to its biodegradability, biocompatibility, and low corrosion rates. Previous studies have demonstrated that zinc metal implants prevent the development of neointimal hyperplasia, which is a common cause of restenosis following coronary intervention. This suppression appears to be smooth muscle cell-specific, as reendothelization of the neointima is not inhibited. To better understand the basis of zinc\u27s differential effects on rat aortic smooth muscle (RASMC) versus endothelial (RAENDO) cells, we conducted a transcriptomic analysis of both cell types following one-week continuous treatment with 5 µM or 50 µM zinc. This analysis indicated that genes whose protein products regulate mitochondrial functions, including oxidative phosphorylation and fusion/fission, are differentially affected by zinc in the two cell types. To better understand this, we performed Seahorse metabolic flux assays and quantitative imaging of mitochondrial networks in both cell types. Zinc treatment differently affected energy metabolism and mitochondrial structure/function in the two cell types. For example, both basal and maximal oxygen consumption rates were increased by zinc in RASMC but not in RAENDO. Zinc treatment increased apparent mitochondrial fusion in RASMC cells but increased mitochondrial fission in RAENDO cells. These results provide some insight into the mechanisms by which zinc treatment differently affects the two cell types and this information is important for understanding the role of zinc treatment in vascular cells and improving its use in biodegradable metal implants

Cervical dystonia incidence and diagnostic delay in a multiethnic population.

BackgroundCurrent cervical dystonia (CD) incidence estimates are based on small numbers in relatively ethnically homogenous populations. The frequency and consequences of delayed CD diagnosis is poorly characterized.ObjectivesTo determine CD incidence and characterize CD diagnostic delay within a large, multiethnic integrated health maintenance organization.MethodsWe identified incident CD cases using electronic medical records and multistage screening of more than 3 million Kaiser Permanente Northern California members from January 1, 2003, to December 31, 2007. A final diagnosis was made by movement disorders specialist consensus. Diagnostic delay was measured by questionnaire and health utilization data. Incidence rates were estimated assuming a Poisson distribution of cases and directly standardized to the 2000 U.S. census. Multivariate logistic regression models were employed to assess diagnoses and behaviors preceding CD compared with matched controls, adjusting for age, sex, and membership duration.ResultsCD incidence was 1.18/100,000 person-years (95% confidence interval [CI], 0.35-2.0; women, 1.81; men, 0.52) based on 200 cases over 15.4 million person-years. Incidence increased with age. Half of the CD patients interviewed reported diagnostic delay. Diagnoses more common in CD patients before the index date included essential tremor (odds ratio [OR] 68.1; 95% CI, 28.2-164.5), cervical disc disease (OR 3.83; 95% CI, 2.8-5.2), neck sprain/strain (OR 2.77; 95% CI, 1.99-3.62), anxiety (OR 2.24; 95% CI, 1.63-3.11) and depression (OR 1.94; 95% CI, 1.4-2.68).ConclusionsCD incidence is greater in women and increases with age. Diagnostic delay is common and associated with adverse effects. © 2019 International Parkinson and Movement Disorder Society