Linear Control Theory with an ℋ∞ Optimality Criterion

This expository paper sets out the principal results in ℋ∞ control theory in the context of continuous-time linear systems. The focus is on the mathematical theory rather than computational methods

Curve Shortening and the Rendezvous Problem for Mobile Autonomous Robots

If a smooth, closed, and embedded curve is deformed along its normal vector field at a rate proportional to its curvature, it shrinks to a circular point. This curve evolution is called Euclidean curve shortening and the result is known as the Gage-Hamilton-Grayson Theorem. Motivated by the rendezvous problem for mobile autonomous robots, we address the problem of creating a polygon shortening flow. A linear scheme is proposed that exhibits several analogues to Euclidean curve shortening: The polygon shrinks to an elliptical point, convex polygons remain convex, and the perimeter of the polygon is monotonically decreasing.Comment: 15 pages, 18 figure

State-space solutions to standard H2 and H∞ control problems

Simple state-space formulas are derived for all controllers solving the following standard H∞ problem: For a given number γ>0, find all controllers such that the H∞ norm of the closed-loop transfer function is (strictly) less than γ. It is known that a controller exists if and only if the unique stabilizing solutions to two algebraic Riccati equations are positive definite and the spectral radius of their product is less than γ2. Under these conditions, a parameterization of all controllers solving the problem is given as a linear fractional transformation (LFT) on a contractive, stable, free parameter. The state dimension of the coefficient matrix for the LFT, constructed using the two Riccati solutions, equals that of the plant and has a separation structure reminiscent of classical LQG (i.e. H2) theory. This paper is intended to be of tutorial value, so a standard H2 solution is developed in parallel

The oral mucosal and salivary microbial community of Behçet's syndrome and recurrent aphthous stomatitis.

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License, permitting all non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.Behçet's syndrome (BS) is a multisystem immune-related disease of unknown etiology. Recurrent aphthous stomatitis (RAS) is characterized by the presence of idiopathic oral ulceration without extraoral manifestation. The interplay between the oral microbial communities and the immune response could play an important role in the etiology and pathogenesis of both BS and RAS

Japanese encephalitis virus-specific proliferative responses of human peripheral blood T lymphocytes

The T lymphocytes play an important role in prevention and recovery from viral infections. To characterize T lymphocyte responses to Japanese encephalitis (JE) virus infections, we analyzed JE virus-specific T lymphocytes in peripheral blood mononuclear cells (PBMC) obtained from seven JE patients and 10 vaccinees who had received a formalin-inactivated, purified JE virus vaccine (Biken vaccine). These PBMC were examined for proliferative responses against live JE virus, a glutaraldehyde-fixed lysate of cells infected with JE virus, and extracellular particles (EPs; subviral membrane vesicles released from cells infected with recombinant vaccinia viruses encoding the JE virus premembrane and envelope proteins). Japanese encephalitis virus-specific T cell proliferation was demonstrated with PBMC from both patients and vaccinees after stimulation with infectious JE virus or the lysate of JE virus-infected cells. Proliferating PBMC included CD4+ T lymphocytes and CD8+ T lymphocytes in responses to either form of JE viral antigens. Responses to EPs were observed only with PBMC from some American vaccinees whose PBMC also responded to the virus and lysate. These results indicate that JE virus infection and immunization with an inactivated JE vaccine induce JE virus-specific CD4+ and CD8+ T memory lymphocytes that can be induced to proliferate by infectious JE virus and noninfectious JE antigens

High levels of interferon alpha in the sera of children with dengue virus infection

We measured the levels of interferon alpha (IFN alpha) in the sera of Thai children hospitalized with dengue hemorrhagic fever (DHF) or dengue fever (DF) to examine the role of IFN alpha in dengue virus infections of humans. The percentage of patients who had detectable levels of IFN alpha ( \u3e or = 3 U/ml) was higher in patients with DHF (80%, P \u3c 0.001) and in patients with DF (60%, P \u3c 0.001) than in healthy Thai children (7%). The levels of IFN alpha were higher in patients with DHF and in patients with DF on the first few days after the onset of fever than in healthy Thai children. The average levels of IFN alpha in patients with DHF were high two days before defervescence, decreasing gradually until the day of defervescence. There was a subset of patients with DHF who had increasing levels of IFN alpha after defervescence. However, the levels of IFN alpha in patients with DF were not high after fever subsided. The levels of IFN alpha were not different among children with DHF grades 1, 2 and 3. Among patients with DHF, T lymphocytes were activated to a higher degree in high IFN alpha producers than in low IFN alpha producers. These results indicate that similarly high levels of IFN alpha are produced in vivo during the acute stages of DHF and DF, and that high levels of IFN alpha remain after fever subsides in some patients with DHF, but not in patients with DF

Statistical Mechanics of Kinks in (1+1)-Dimensions

We investigate the thermal equilibrium properties of kinks in a classical $\phi^4$ field theory in $1+1$ dimensions. The distribution function, kink density, and correlation function are determined from large scale simulations. A dilute gas description of kinks is shown to be valid below a characteristic temperature. A double Gaussian approximation to evaluate the eigenvalues of the transfer operator enables us to extend the theoretical analysis to higher temperatures where the dilute gas approximation fails. This approach accurately predicts the temperature at which the kink description breaks down.Comment: 8 pages, Latex (4 figures available on request), LA-UR-92-399

Forage Quality and Performance of Yearlings Grazing Switchgrass Strains Selected for Differing Digestibility

Switchgrass (Panicum virgatum) is a native, perennial warm-season grass commonly used as summer pasture. Three strains of switchgrass with different in vitro DM disappearance (IVDMD) values were evaluated with yearling cattle (Bos taurus) in three replicated grazing trials All strains were similar in genetic background, maturity and yield potential. \u27Trailblazer\u27 (high-IVDMD) resulted in higher (P \u3c .05) ADG than \u27Pathfinder\u27 and \u27low-IVDMD\u27. Available forage of Trailblazer had higher IVDMD than Pathfinder and low-IVDMD. The IVDMD differences among strains were similar throughout the season; IVDMD declined between .3 and .5 percentage units per day. Forage availability, CP, NDF and ADF, permanganate lignin and ash were similar among strains. This study documents that plant breeders can select switchgrass plants for higher IVDMD and that strains consisting of progeny of these plants can result in higher animal gains than strains consisting of progeny of unselected or low-IVDMD plants with similar genetic background, forage yield, maturity, morphology and chemical composition

Foraging Quality and Performance of Yearlings Grazing Switchgrass Strains Selected for Differing Digestibility

Switchgrass (Panicum virgatum) is a native, perennial warm-season grass commonly used as summer pasture. Three strains of switchgrass with different in vitro DM disappearance (IVDMD) values were evaluated with yearling cattle (Bos taurus) in three replicated grazing trials. All strains were similar in genetic background, maturity and yield potential. \u27Trailblazer\u27 (high-IVDMD) resulted in higher (P \u3c .05) ADG than \u27Pathfinder\u27 and \u27low-IVDMD\u27. Available forage of Trailblazer had higher IVDMD than Pathfinder and low-IVDMD. The IVDMD differences among strains were similar throughout the season; IVDMD declined between 0.3 and 0.5 percentage units per day. Forage availability, CP, NDF and ADF, permanganate lignin and ash were similar among strains. This study documents that plant breeders can select switchgrass plants for higher IVDMD and that strains consisting of progeny of these plants can result in higher animal gains than strains consisting of progeny of unselected or low-IVDMD plants with similar genetic background, forage yield, maturity, morphology and chemical composition