Lyapunov‐stable discrete‐time model reference adaptive control

Discrete‐time model reference adaptive control (MRAC) is considered with both least squares and projection algorithm parameter identification. For both cases complete Lyapunov proofs are given for stability and convergence. The results extend the approach of Johansson (Int. J. Control 1989; 50 (3):859–869) to include Lyapunov stability for MRAC when the normalized projection algorithm is used for parameter identification. Copyright © 2005 John Wiley & Sons, Ltd.     

The pattern of inflammation in rat sepsis due to enterotoxin-producing Staphylococcus aureus: a comparison with ischemia-reperfusion injury

Sepsis and trauma have similarities in their immunopathologic profiles. Both conditions can result in multi-system organ failure which is sometimes associated with cytokine generation and inflammatory cell activation. Furthermore, decreases in peripheral blood monocyte expression of HLA-DR have been noted in both human sepsis and trauma. However, the magnitude, onset, and time course of such stimuli are often difficult to ascertain in human studies. Thus, to study a more detailed in vivo immunologic profile in these conditions, rat models were employed. Our aim was to describe and analyze cytokine and peripheral blood immunophenotype patterns in bacterially induced rat sepsis and to compare this to rat ischemia-reperfusion injury. Sprague-Dawley rats underwent either bacterial injection with enterotoxin producing Staphylococcus aureus or hind limb ischemia/ reperfusion. Two bacterial doses which were either lethal or sublethal at 24-48 hours were utilized. Peripheral blood neutrophils and B-lymphocytes were studied for expression of beta-integrins (CD11b and CD11b/c) and I-A, respectively, using flow cytometry. Corresponding plasma levels of TNF alpha and interferon gamma were measured by ELISA. At 24 hr, a lethal bacterial lethal bacterial dose injection resulted in significantly higher levels of neutrophil CD11b/c expression (p < 0.005) compared with ischemia-reperfusion treatment. B-cell I-A expression was also higher in lethal sepsis. Gamma interferon levels were significantly higher in lethal sepsis compared with ischemia-reperfusion (p = 0.005). Studies over time showed that CD11b expression and interferon gamma were both more marked at 6 hr than at 24 hr in lethal sepsis. This pattern was not observed in sublethal sepsis or in ischemia-reperfusion. CD11b/c expression on the other hand remained elevated at comparable levels at 6 and 24 hr in lethal sepsis. B-cell I-A expression in ischemia-reperfusion and sublethal sepsis decreased at 24 hr compared with baseline. Lethal sepsis in rats injected with enterotoxin producing staphylococcus results in phasic alterations in neutrophil CD11b and plasma interferon levels prior to death. In analogy to the findings of monocyte decreases in DR expression observed in human trauma and sepsis, rat B-cell I-A expression showed decreases in sublethal sepsis as well as in ischemia-reperfusion injury. However, this was not observed in lethal sepsis. These findings have implications in understanding the immunologic/inflammatory changes observed in human sepsis and trauma.     

Properties of nitrogen-implanted SOI substrates

Properties of nitrogen-implanted silicon-on-insulator (SOI) substrates prepared by implanting different doses of 200 keV nitrogen into 50-70 Ω-cm, p-type silicon substrates at a temperature of 500°C were studied. The distribution of nitrogen was studied using Auger electron spectroscopy. The electrical properties of the active overlayer were studied using Hall-effect measurements and capacitance-voltage depth profile analysis. The insulating integrity of the buried nitride was studied by directly measuring the leakage current from top to bottom through the substrate. Additionally, electric field strength and surface roughness measurements were performed. Nitrogen concentrations in the buried layer increased from below to above the stoichiometric value for Si₃N₄ for increasing dose in the range studied. Nitrogen-related n-type doping is observed in all samples examined, and the magnitude of the doping increased with the increasing implant dose. Insulating buried nitride layers are formed only in samples implanted with very high doses     

Direct Adaptive Dynamic Compensation for Minimum Phase Systems With Unknown Relative Degree

We consider parameter-monotonic direct adaptive control for single-input-single-output minimum-phase linear time-invariant systems with knowledge of the sign of the high-frequency gain (first nonzero Markov parameter) and an upper bound on the magnitude of the high-frequency gain. The first part of the paper is devoted to fixed-gain analysis of single-parameter high-gain-stabilizing controllers. Two novel fixed-gain dynamic compensators are presented for stabilizing minimum-phase systems. One compensator stabilizes systems with arbitrary-but-known relative degree, while the other utilizes a Fibonacci series construction to stabilize systems with unknown-but-bounded relative degree. Next, we provide a general treatment of parameter-monotonic adaptive control, including a result that guarantees state convergence to zero. This result is then combined with the high-gain-stabilizing controllers to yield parameter-monotonic direct adaptive dynamic compensation for minimum-phase systems with either arbitrary-but-known or unknown-but-bounded relative degree     

Semilinear Duhem model for rate-independent and rate-dependent hysteresis

The classical Duhem model provides a finite-dimensional differential model of hysteresis. In this paper, we consider rate-independent and rate-dependent semilinear Duhem models with provable properties. The vector field is given by the product of a function of the input rate and linear dynamics. If the input rate function is positively homogeneous, then the resulting input-output map of the model is rate independent, yielding persistent nontrivial input-output closed curve (that is, hysteresis) at arbitrarily low input frequency. If the input rate function is not positively homogeneous, the input-output map is rate dependent and can be approximated by a rate-independent model for low frequency inputs. Sufficient conditions for convergence to a limiting input-output map are developed for rate-independent and rate-dependent models. Finally, the reversal behavior and orientation of the rate-independent model are discussed.     

SuperDense Quantum Teleportation

Recent advances in experimental technique make SuperDense Teleportation (SDT) possible only now, ten years after my first proposal at an ISI Torino summer conference on Quantum Computing. The effect uses remote state preparation to send more state-specifying parameters per bit than ordinary quantum teleportation (QT) can transmit. The SDT uses a maximally entangled state to teleport the relative phases of an n-dimensional state with equal amplitudes on every standard basis vector. For n greater than or equal to 3, the SDT sends more of these state-specifying parameters than QT. In the limit of large n the ratio is 2 to 1, hence the nomenclature by analogy with Super Dense Coding. Alice’s measurements and Bob’s transformations are far simpler than their corresponding operations in QT. The roles of Charles who chooses the state and Diana who deploys it are different than in QT. My discussion includes a brief review of the progress and possibilities of realization for several different experimental approaches around the world. This paper is the write-up of my remarks at the Festschrift conference for Anton Zeilinger, for many years a close collaborator in the Hampshire College NSF grant continuing our work with Mike Horne and Danny Greenberger started under Cliff Shull at MIT in the late 20th century.