Molecular dynamics study of contact mechanics: contact area and interfacial separation from small to full contact

We report a molecular dynamics study of the contact between a rigid solid with a randomly rough surface and an elastic block with a flat surface. We study the contact area and the interfacial separation from small contact (low load) to full contact (high load). For small load the contact area varies linearly with the load and the interfacial separation depends logarithmically on the load. For high load the contact area approaches to the nominal contact area (i.e., complete contact), and the interfacial separation approaches to zero. The present results may be very important for soft solids, e.g., rubber, or for very smooth surfaces, where complete contact can be reached at moderate high loads without plastic deformation of the solids.Comment: 4 pages,5 figure

Optimal multicopy asymmetric Gaussian cloning of coherent states

We investigate the asymmetric Gaussian cloning of coherent states which produces M copies from N input replicas, such that the fidelity of all copies may be different. We show that the optimal asymmetric Gaussian cloning can be performed with a single phase-insensitive amplifier and an array of beam splitters. We obtain a simple analytical expression characterizing the set of optimal asymmetric Gaussian cloning machines.Comment: 7 pages, 2 figures, RevTeX

Ionization of hydrogen atoms by electron impact at 1eV, 0.5eV and 0.3eV above threshold

We present here triple differential cross sections for ionization of hydrogen atoms by electron impact at 1eV, 0.5eV and 0.3eV energy above threshold, calculated in the hyperspherical partial wave theory. The results are in very good agreement with the available semiclassical results of Deb and Crothers \cite{DC02} for these energies. With this, we are able to demonstrate that the hyperspherical partial wave theory yields good cross sections from 30 eV \cite{DPC03} down to near threshold for equal energy sharing kinematics.Comment: 6 pages, 9 figure

Resilient wheel Patent

Resilient wheel design with woven wire tire and abrasive treads for lunar surface vehicle

Multipartite Asymmetric Quantum Cloning

We investigate the optimal distribution of quantum information over multipartite systems in asymmetric settings. We introduce cloning transformations that take $N$ identical replicas of a pure state in any dimension as input, and yield a collection of clones with non-identical fidelities. As an example, if the clones are partitioned into a set of $M_A$ clones with fidelity $F^A$ and another set of $M_B$ clones with fidelity $F^B$, the trade-off between these fidelities is analyzed, and particular cases of optimal $N \to M_A+M_B$ cloning machines are exhibited. We also present an optimal $1 \to 1+1+1$ cloning machine, which is the first known example of a tripartite fully asymmetric cloner. Finally, it is shown how these cloning machines can be optically realized.Comment: 5 pages, 2 figure

Roll waves in mud

The stability of a viscoplastic fluid film falling down an inclined plane is explored, with the aim of determining the critical Reynolds number for the onset of roll waves. The Herschel–Bulkley constitutive law is adopted and the fluid is assumed two-dimensional and incompressible. The linear stability problem is described for an equilibrium in the form of a uniform sheet flow, when perturbed by introducing an infinitesimal stress perturbation. This flow is stable for very high Reynolds numbers because the rigid plug riding atop the fluid layer cannot be deformed and the free surface remains flat. If the flow is perturbed by allowing arbitrarily small strain rates, on the other hand, the plug is immediately replaced by a weakly yielded ‘pseudo-plug’ that can deform and reshape the free surface. This situation is modelled by lubrication theory at zero Reynolds number, and it is shown how the fluid exhibits free-surface instabilities at order-one Reynolds numbers. Simpler models based on vertical averages of the fluid equations are evaluated, and one particular model is identified that correctly predicts the onset of instability. That model is used to describe nonlinear roll waves

Cloning a Qutrit

We investigate several classes of state-dependent quantum cloners for three-level systems. These cloners optimally duplicate some of the four maximally-conjugate bases with an equal fidelity, thereby extending the phase-covariant qubit cloner to qutrits. Three distinct classes of qutrit cloners can be distinguished, depending on two, three, or four maximally-conjugate bases are cloned as well (the latter case simply corresponds to the universal qutrit cloner). These results apply to symmetric as well as asymmetric cloners, so that the balance between the fidelity of the two clones can also be analyzed.Comment: 14 pages LaTex. To appear in the Journal of Modern Optics for the special issue on "Quantum Information: Theory, Experiment and Perspectives". Proceedings of the ESF Conference, Gdansk, July 10-18, 200

Factors affecting Medicaid funding and implications for health care providers

This paper details several factors that affect Medicaid, the federal program that provides health care reimbursement for millions of low-income Americans. The research presents many challenges to sustaining an equitable welfare system that also produces positive health outcomes. Growing levels of poverty have resulted in increased enrollment in the Medicaid program and projections indicate a continuation of this trend. A decrease in the supply of physicians along with an aging population creates new obstacles to health care access. The Patient Protection and Affordable Care Act (PPACA) introduces additional complexities by expanding Medicaid enrollment, increasing regulatory requirements and reducing payments to health care providers through rate cuts and penalties.Department of Political ScienceMedicaid -- Health care -- Structures and organizations -- Administrative law and regulation -- Reports and projections -- Expectations and challenges.Thesis (M.P.A.