181,571 research outputs found

    Estimation of the mean of a discrete parameter, covariance stationary, stochastic process in rotation sampling

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    Constrained optimization procedure for deriving linear estimator of population mean in rotation samplin

    Uncertainty in Soft Temporal Constraint Problems:A General Framework and Controllability Algorithms forThe Fuzzy Case

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    In real-life temporal scenarios, uncertainty and preferences are often essential and coexisting aspects. We present a formalism where quantitative temporal constraints with both preferences and uncertainty can be defined. We show how three classical notions of controllability (that is, strong, weak, and dynamic), which have been developed for uncertain temporal problems, can be generalized to handle preferences as well. After defining this general framework, we focus on problems where preferences follow the fuzzy approach, and with properties that assure tractability. For such problems, we propose algorithms to check the presence of the controllability properties. In particular, we show that in such a setting dealing simultaneously with preferences and uncertainty does not increase the complexity of controllability testing. We also develop a dynamic execution algorithm, of polynomial complexity, that produces temporal plans under uncertainty that are optimal with respect to fuzzy preferences

    Reactivation of contraction in detergent-lysed teleost retinal cones.

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    Teleost retinal cones contract in the light and elongate in the dark. In the green sunfish, Lepomis cyanellus, the necklike myoid region of the cone contracts from as much as 120 micrometers (midnight dark-adapted) to 6 micrometers in fully light-adapted state. When dark-adapted fish are exposed to light (1.4 lux), cone myoids contract with a linear rate of 1.5 +/- 0.1 micrometers/min. We report here that detergent-lysed motile models of teleost retinal cones exhibit calcium- and ATP-dependent reactivated contraction, with morphology and rate comparable to that observed in vivo. For reactivation studies isolated dark-adapted retinas were lysed with nonionic detergent Brij-58 (0.1-1.0%). In reactivation medium containing 10(-5) M free calcium and 4 mM ATP, the lysed cones contracted with normal morphology at in vivo rates (1.4 +/- 1 micrometer/min). Little contraction was observed if ATP or detergent was deleted from the medium or if free calcium levels were less than 10(-8) M. Ultrastructural examination of cone models lysed with 1% Brij-58 revealed that, in spite of extensive extraction of the cytoplasmic matrix, cytoskeletal components (thin filaments, intermediate filaments, microtubules) were still present. Thus we have produced extensively extracted motile models of teleost retinal cones which undergo calcium- and ATP-dependent reactivated contraction with normal morphology at physiological rate

    Kinematics of a large-scale intraplate extending lithosphere: The Basin-Range

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    Upper lithospheric structure of the Cordilleran Basin Range (B-R) is characterised by an E-W symmetry of velocity layering. The crust is 25 km thick on its eastern active margin, thickening to 30 km within the central portion and thinning to approx. 25 km on the west. Pn velocities of 7.8 to 7.9 km/s characterize the upper mantle low velocity cushion, 7.4 km/s to 7.5 km/s, occurs at a depth of approx. 25 km in the eastern B-R and underlies the area of active extension. An upper-crustal low-velocity zone in the eastern B-R shows a marked P-wave velocity inversion of 7% at depths of 7 to 10 km also in the area of greatest extension. The seismic velocity models for this region of intraplate extension suggest major differences from that of a normal, thermally underformed continental lithosphere. Interpretations of seismic reflection data demonstrate the presence of extensive low-angle reflections in the upper-crust of the eastern B-R at depths from near-surface to 7 to 10 km. These reflections have been interpreted to represent low-angle normal fault detachments or reactivated thrusts. Seismic profiles across steeply-dipping normal faults in unconsolidated sediments show reflections from both planar to downward flatening (listric) faults that in most cases do not penetrate the low-angle detachments. These faults are interpreted as late Cenozoic and cataclastic mylonitic zones of shear displacement

    A structural, spectroscopic and theoretical study of the triphenylphosphine chalcogenide complexes of tungsten carbonyl, [W(XPPh3)(CO)5], X=O, S, Se

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    The series [W(XPPh3)(CO)5], X=O, S, Se has been structurally determined by X-ray crystallography and fully characterised spectroscopically to provide data for comparing the bonding of the Ph3PX ligands to the metal. The P-X-W angles are 134.3°, 113.2° and 109.2°, respectively, for X=O, S, Se. The bonding has been analysed using EHMO calculations which suggest that lower P-X-W angles depend on the relative importance of σ-bonding, which in turn depends on the chalcogen in the order X=Se > S > O. The effect is enhanced by lower energies of the metal σ and π orbital energies

    Drawing Boundaries

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    In “On Drawing Lines on a Map” (1995), I suggested that the different ways we have of drawing lines on maps open up a new perspective on ontology, resting on a distinction between two sorts of boundaries: fiat and bona fide. “Fiat” means, roughly: human-demarcation-induced. “Bona fide” means, again roughly: a boundary constituted by some real physical discontinuity. I presented a general typology of boundaries based on this opposition and showed how it generates a corresponding typology of the different sorts of objects which boundaries determine or demarcate. In this paper, I describe how the theory of fiat boundaries has evolved since 1995, how it has been applied in areas such as property law and political geography, and how it is being used in contemporary work in formal and applied ontology, especially within the framework of Basic Formal Ontology

    Contralateral inhibition of click- and chirp-evoked human compound action potentials

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    Cochlear outer hair cells (OHC) receive direct efferent feedback from the caudal auditory brainstem via the medial olivocochlear (MOC) bundle. This circuit provides the neural substrate for the MOC reflex, which inhibits cochlear amplifier gain and is believed to play a role in listening in noise and protection from acoustic overexposure. The human MOC reflex has been studied extensively using otoacoustic emissions (OAE) paradigms; however, these measurements are insensitive to subsequent “downstream” efferent effects on the neural ensembles that mediate hearing. In this experiment, click- and chirp-evoked auditory nerve compound action potential (CAP) amplitudes were measured electrocochleographically from the human eardrum without and with MOC reflex activation elicited by contralateral broadband noise. We hypothesized that the chirp would be a more optimal stimulus for measuring neural MOC effects because it synchronizes excitation along the entire length of the basilar membrane and thus evokes a more robust CAP than a click at low to moderate stimulus levels. Chirps produced larger CAPs than clicks at all stimulus intensities (50–80 dB ppeSPL). MOC reflex inhibition of CAPs was larger for chirps than clicks at low stimulus levels when quantified both in terms of amplitude reduction and effective attenuation. Effective attenuation was larger for chirp- and click-evoked CAPs than for click-evoked OAEs measured from the same subjects. Our results suggest that the chirp is an optimal stimulus for evoking CAPs at low stimulus intensities and for assessing MOC reflex effects on the auditory nerve. Further, our work supports previous findings that MOC reflex effects at the level of the auditory nerve are underestimated by measures of OAE inhibition

    The Changing Economic Status of U.S. Disabled Men: Trends and Their Determinants, 1982–1991

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    In this paper, we track the level of economic well-being of the population of men who began receiving Social Security Disability Insurance (SSDI) benefits in 1980–81 from the time just after they became beneficiaries (in 1982) to 1991, nearly a decade later. We present measures of the economic well-being of disabled individuals and their nondisabled peers as indicators of the relative economic position of these two groups. These measures also provide an intertemporal comparison of well-being and hardship as disabled persons and their nondisabled peers age and retire. We first show several economic well-being indicators for this group of new male recipients of disability benefits in 1982 and 1991. Then, we compare their economic position to that of a matched group of nondisabled males with sufficient work histories to have been disability-insured, that is, eligible for SSDI benefits had they been unable to engage in substantial gainful employment. Because labor market changes over this decade have led to a relative deterioration in the position of younger and less-educated workers, we compare men with disabilities to those without disabilities and distinguish different age and educational levels within the groups. In studying these comparative trends in well-being, we focus on the prevalence of poverty and its correlates. We conclude by assessing the antipoverty effectiveness of Social Security income support for both younger and older men who became SSDI recipients in 1980–81.
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