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Formal power series products appear in nonlinear control theory when systems modeled by Chen-Fliess series are interconnected to form new systems. In fields like adaptive control and learning systems, the coefficients of these formal power series are estimated sequentially with real-time data. The main goal is to prove the continuity and analyticity of such products with respect to several natural (locally convex) topologies on spaces of locally convergent formal power series in order to establish foundational properties behind these technologies. In addition, it is shown that a transformation group central to describing the output feedback connection is in fact an analytic Lie group in this setting with certain regularity properties., Author(s): W. Steven Gray [sup.1] , Mathias Palmstrøm [sup.2] , Alexander Schmeding [sup.3] Author Affiliations: (1) grid.261368.8, 0000 0001 2164 3177, Old Dominion University, , 23529, Norfolk, VA, USA (2) [...]

Tumor cells can engage in a process called collective invasion, in which cohesive groups of cells invade through interstitial tissue. Here, we identified an epigenetically distinct subpopulation of breast tumor cells that have an enhanced capacity to collectively invade. Analysis of spheroid invasion in an organotypic culture system revealed that these 'trailblazer' cells are capable of initiating collective invasion and promote non-trailblazer cell invasion, indicating a commensal relationship among subpopulations within heterogenous tumors. Canonical mesenchymal markers were not sufficient to distinguish trailblazer cells from non-trailblazer cells, suggesting that defining the molecular underpinnings of the trailblazer phenotype could reveal collective invasion-specific mechanisms. Functional analysis determined that DOCK10, ITGA11, DAB2, PDFGRA, VASN, PPAP2B, and LPAR1 are highly expressed in trailblazer cells and required to initiate collective invasion, with DOCK10 essential for metastasis. In patients with triple-negative breast cancer, expression of these 7 genes correlated with poor outcome. Together, our results indicate that spontaneous conversion of the epigenetic state in a subpopulation of cells can promote a transition from in situ to invasive growth through induction of a cooperative form of collective invasion and suggest that therapeutic inhibition of trailblazer cell invasion may help prevent metastasis., Introduction The hollow tubular architecture of epithelial tissue is fundamentally disrupted during malignant progression, culminating with the invasion of neoplastic cells into the surrounding stromal tissue (1). Once out of [...]

This paper analyzes the output tracking performance of a Boeing 737 aircraft in closed loop with a Recoverable Computer System (RCS) operating in a high intensity neutron environment at the Los Alamos National Laboratory. A stochastic hybrid model, validated by simulated-neutron experiments done at the NASA Langley Research Center, is used to theoretically predict the outcome of the experiment. In particular, this model predicts and the data confirms that the recoverable digital flight control system, when functioning as designed, will provide accurate output tracking performance in the presence of neutron-induced single-event upsets (SEUs) at normal atmospheric levels.

To purchase or authenticate to the full-text of this article, please visit this link: http://dx.doi.org/10.1111/j.1540-5931.2007.00428.x Byline: W. RUSSEL GRAY (1) Author Affiliation: (1)Princeton, Pennsylvania

A novel method was developed for engineering an oligomeric protein to a monomeric, biologically active protein to understand the self-association property of apolipoprotein (apo AI) required for its lipoprotein binding activity. It showed that apoAI mutant is a monomeric, active apoAI useful for structural determination.

The combined use of deuteration of Synechococcus lividus PS II and pulsed high-frequency (130 GHz) saturation-recovery EPR spectroscopy to measure directly the spin-spin interaction of the Car(super +) and Chl(super +) radicals with other paramagnetic centers of PS II is presented. The relative location of Car(super +) and Chl(super +) radicals determined provides valuable insight into the sequence of electron transfers in the alternate electron-donation pathways of PS II.

The motion detection problem occurs frequently in many applications connected with computer vision. Researchers have studied motion detection based on naturally occurring biological circuits for over a century. In this paper, we propose and analyze a motion detection circuit which is based on nerve membrane conduction. It consists of two unidirectional neural networks connected in an opposing fashion. Volterra input - output (I-O) models are then derived for the network so that velocity estimation can be cast as a parameter estimation problem. The technique is demonstrated through simulation. Index Terms - Image motion analysis, neural network architecture, nonlinear systems, parameter estimation, Volterra series.

The very limited instrumental record makes extensive analyses of the natural variability of global tropical cyclone activities difficult in most of the tropical cyclone basins. However, in the two regions where reasonably reliable records exist (the North Atlantic and the western North Pacific), substantial multidecadal variability (particularly for intense Atlantic hurricanes) is found, but there is no clear evidence of long-term trends. Efforts have been initiated to use geological and geomorphological records and analysis of oxygen isotope ratios in rainfall recorded in cave stalactites to establish a paleoclimate of tropical cyclones, but these have not yet produced definitive results. Recent thermodynamical estimation of the maximum potential intensities (MPI) of tropical cyclones shows good agreement with observations. Although there are some uncertainties in these MPI approaches, such as their sensitivity to variations in parameters and failure to include some potentially important interactions such as ocean spray feedbacks, the response of upper-oceanic thermal structure, and eye and eyewall dynamics, they do appear to be an objective tool with which to predict present and future maxima of tropical cyclone intensity. Recent studies indicate the MPI of cyclones will remain the same or undergo a modest increase of up to 10%-20%. These predicted changes are small compared with the observed natural variations and fall within the uncertainty range in current studies. Furthermore, the known omissions (ocean spray, momentum restriction, and possibly also surface to 300-hPa lapse rate changes) could all operate to mitigate the predicted intensification. A strong caveat must be placed on analysis of results from current GCM simulations of the 'tropical-cyclone-like' vortices. Their realism, and hence prediction skill (and also that of 'embedded' mesoscale models), is greatly limited by the coarse resolution of current GCMs and the failure to capture environmental factors that govern cyclone intensity. Little, therefore, can be said about the potential changes of the distribution of intensities as opposed to maximum achievable intensity. Current knowledge and available techniques are too rudimentary for quantitative indications of potential changes in tropical cyclone frequency. The broad geographic regions of cyclogenesis and therefore also the regions affected by tropical cyclones are not expected to change significantly. It is emphasized that the popular belief that the region of cyclogenesis will expand with the 26 [degrees] C SST isotherm is a fallacy. The very modest available evidence points to an expectation of little or no change in global frequency. Regional and local frequencies could change substantially in either direction, because of the dependence of cyclone genesis and track on other phenomena (e.g., ENSO) that are not yet predictable. Greatly improved skills from coupled global ocean-atmosphere models are required before improved predictions are possible.

Recently, Chair and Varshney have solved the data fusion problem for fixed binary local detectors with statistically independent decisions. We generalize their solution by using the Bahadur-Lazarsfeld expansion of probability density functions. The optimal data fusion rule is developed for correlated local binary decisions, in terms of the conditional correlation coefficients of all orders. We show that when all these coefficients are zero, the rule coincides with the original Chair-Varshney design.

Electrocatalytic reduction of protons to dihydrogen is achieved by protonation of nickel containing metalloenzymes in a nonaqueous solution of DMF with any hydrogenase as a catalyst. This reaction has two steps involving two sequential one-electron reductions. The first is a ligand reduction to form a nickel-ligand (NiIIL)+ cation complex, and the second is used to form an (NiIL)0 complex at the metal center. Cyclic voltammetric and square wave voltammetric processes are used for electrochemical measurements.

A monomeric, biologically active, full length apolipoprotein E (apoE) is generated using protein-engineering techniques. Cross-linking experiments indicate that this mutant is nearly 95-100% monomeric at 20 mg/mL.

In this paper a set of sufficient conditions is developed in terms of controllability and observability functions under which a given state-space realization of a formal power series is minimal. Specifically, it is shown that positivity of these functions, in addition to a stability requirement and a few technical conditions, implies minimality. Using the nonlinear analogue of the Kalman decomposition, connections are then established between minimality, singular value functions, balanced realizations, and various notions of teachability and observability for nonlinear systems. Index Terms--Controllability and observability functions, formal power series, minimal realizations, nonlinear systems.

High intensity electromagnetic radiation has been demonstrated to be a source of computer upsets in commercially available digital flight control systems. Such upsets can degrade the quality of the control signal ranging from a perturbation error over a few sample periods to a permanent error mode or computer failure. Under these conditions, the primary concern of the control engineer is to insure that the closed-loop system remains stable. A stochastic disturbance model and a set of associated stability assessment tools are introduced for determining stability robustness of a nominal closed-loop system subject to electromagnetic disturbances. The focus is primarily on flight control applications, but the methodology is suitable for any application where highly reliable digital control is needed. The technique is demonstrated on a simple test example and on a stabilizing controller for the longitudinal dynamics of the AFTI/F-16 aircraft.