Robust, reduced-order, nonstrictly proper state estimation via the optimal projection equations with Petersen—Hollot bounds

A state-estimation design problem involving parametric plant uncertainties is considered. An error bound suggested by recent work of Petersen and Hollot is utilized for guaranteeing robust estimation. Necessary conditions which generalize the optimal projection equations for reduced-order state estimation are used to characterize the estimator which minimizes the error bound. The design equations thus effectively serve as sufficient conditions for synthesizing robust estimators. An additional feature is the presence of a static estimation gain in conjunction with the dynamic (Kalman) estimator, i. e., a nonstrictly proper estimator.     

Reducing the man-machine barrier: the Sequence Analysis Workbench

The conventional software paradigm in which the machine acts as an unintelligent but patient servant often increases the perceived distance between scientist and data. Direct manipulation offers an alternative paradigm in which the scientist uses the computer as a scientific instrument for examining and modifying the data directly, rather than by issuing instructions to an agent. The Sequence Analysis Workbench provides several experimental tools for direct manipulation of sequence data; object-oriented programming makes it possible to construct sophisticated tools quickly, and facilitates critical examination and review of scientific software.     

Near-far resistance of space-time processing for wireless CDMAcommunications

In this letter we evaluate the performance of space-time adaptive processing for wireless code-division multiple access (CDMA) communications through analysis of the near-far resistance. The model assumed is that of a frequency-selective and slow-fading channel. It is shown that while maximum ratio combining is not near-far resistant, optimum combining is near-far resistant when the number of cochannel interferences is less than the system dimensionality     

Actin disassembles reversibly during electrically induced recycling of synaptic vesicles in cultured neurons

We have studied depolarization-induced regulation of actin assembly in exocytotically active areas of dissociated chick sympathetic neurons. Active areas were identified with the fluorescent dye FM1-43 which labels synaptic vesicles that recycle in these regions. Exocytosis (electrically stimulated) was monitored in real time through depletion of FM1-43 fluorescence. To study depolarization-induced disassembly of actin in the FM1-43-stained regions, the cells were fixed after different periods of depolarization and stained with rhodamine phalloidin, which binds preferentially to the filamentous form of actin. In active regions, actin disassembles and reassembles during continuous 2 min depolarization. Actin disassembly that occurs after the first 25 s of depolarization was detected by a reduction in rhodamine phalloidin staining and confirmed by correlative electron microscopy. Immunogold staining revealed that actin is abundant throughout resting terminals. In some experiments, actin filaments were stabilized by loading cells with unlabelled phalloidin before stimulating secretion. Stabilizing the filaments does not alter the initial release but strongly reduces the release rate at later stages. These data are consistent with a model in which partial disassembly of actin filaments is necessary for facilitating the transport of vesicles within the terminal and reassembly is necessary for limiting that movement.     

Crack initiation and near-threshold surface fatigue crack propagation behavior of the iron-base superalloy A-286

The fatigue behavior of the iron-base superalloy A-286 was studied at room temperature in air for three aging conditions: underaged, peak aged, and overaged. A fatigue strength at 10⁷ cycles of about 200 MPa, independent of aging condition, was measured for an applied load ratio ofR =0.1. Surface crack initiation and propagation were measured using hourglass specimens. Surface cracks were invariably initiated in slip bands orientated between 45 and 55 deg to the load axis, and an average ratio of crack depth to crack length of about 0.45 for these semi-elliptical cracks was measured. These earliest observable short surface cracks grew at an accelerated propagation rate in the near-threshold regime but were retarded in a transition stage, resulting in a minimum in crack growth rate. This behavior was correlated to the interaction of the crack with specific microstructure features. Following this minimum, the crack growth accelerated again with increasing ΔK and appeared to converge with the crack growth behavior expected for long through cracks. The crack propagation rate at fixed ΔK was lowest in underaged, compared to peak aged and overaged microstructures. The minimum and trends in crack growth rate appeared to depend on the development of roughness-induced closure. M. A. DAEUBLER, formerly with Carnegie Mellon University     

Proglumide as a morphine adjunct in cancer pain management

PURPOSE: To determine the expression of CD44 isoforms in cultured human trabecular meshwork (HTM) and to discuss their possible relationship with outflow facility. METHODS: CD44 isoform expression in cultured HTM was qualitatively examined using immunohistochemistry and RT-PCR analysis. RESULTS: Immunohistochemistry of cultured HTM showed intense staining with a CD44s antibody, and with antibodies against CD44 exon 7, exon 11-12 and exon 14. By RT-PCR, at least three isoforms of CD44 were expressed in HTM: CD44s, CD44v-III and CD44v-I. CONCLUSIONS: At least three isoforms of CD44 are expressed in the HTM. CD44 may play a role in binding and turnover of hyaluronic acid in the trabecular meshwork, thereby regulating outflow facility.     

A multi-threshold, internal rule representation form used to support user modifiable knowledge-based systems

A flat file (i.e., tabular) internal rule representation suitable for storing expert system rules that can make use of a spread-sheet-like user interface is presented. The representation handles individual rule thresholds, different knowledge evidence procedures, and rule structures which can be represented as network graphs. Such representations: (a) help a system's rule structure to be made relatively accessible for those without significant artificial intelligence training, (b) allow for clear understanding of the extent and nature of a rule, and (c) provide opportunities for consistency checking.     

Role of heat treatment and cathodic charging conditions on the hydrogen embrittlement of HP 7075 aluminum alloy

The response of an equiaxed-grained, high-purity 7075 aluminum alloy to hydrogen as a function of heat treatment and temperature of cathodic charging has been studied. Room-temperature (RT) tensile tests following RT or 120 °C cathodic charging revealed that hydrogen embrittlement susceptibility was dependent on both heat treatment and charging conditions. However, intergranular behavior was only observed following RT charging, limited to a zone a few grains deep from the surface. This fracture appearance has been considered in terms of the possible formation of an aluminum- or magnesium-base hydride at room temperature, compounds which are thermodynamically unstable at the 150 °C charging temperature. Reasons for the observed embrittlement following high-temperature charging are also considered. Formerly with Carnegie Mellon University.     

Studies on the Light Stability of Flordipine Tablets in Amber Blister Packaging Material

Accelerated light conditions have been used in the evaluation of light stability of flordipine tablets. The tablets were subjected to exaggerated light exposure in a fadeometer and to 150 foot candles of fluorescent light in a light cabinet. A comparative study was conducted between tile tablets exposed directly to light and to those covered with amber vinyl sheeting. The color change was evaluated by a tristimulus colorimeter using the Hunter L, a, b scale. The b coordinate was selected for the final evaluation of light stability since it corresponded closely to the visual increase in yellowness with time. The data demonstrated that the amber colored vinyl sheeting had an excellent protective effect on the discoloration of flordipine tablets. Data obtained in the fadeometer in six hours as well as results from exposure in the light cabinet for twenty-nine days, facilitate the comparative evaluation of light stability of flordipine tablets. One hour's exposure to fade oneter was found to be equal to 480 hours in fluorescent light