Recursive retrospective revaluation of causal judgments.

Recursive causal evaluation is an iterative process in which the evaluation of a target cause, T, is based on the outcome of the evaluation of another cause, C, the evaluation of which itself depends on the evaluation of a 3rd cause, D. Retrospective revaluation consists of backward processing of information as indicated by the fact that the evaluation of T is influenced by subsequent information that is not concerned with T directly. Two experiments demonstrate recursive retrospective revaluation with contingency information presented in list format as well as with trial-by-trial acquisition. Existing associative models are unable to predict the results. The model of recursive causal disambiguation that conceptualizes the revaluation as a recursive process of disambiguation predicts the pattern of results correctly. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Modeling Associative Recognition: A Comparison of Two-High-Threshold, Two-High-Threshold Signal Detection, and Mixture Distribution Models.

A 2-high-threshold signal detection (HTSDT) model, a mixture distribution (SON) model, and 2-highthreshold (HT) models with responses distributed over 1 or several response categories were fit to results of 6 experiments from 2 studies on associative recognition: R. Kelley and J. T. Wixted (2001) and A. P. Yonelinas (1997). HTSDT assumes that associative recognition is based on conscious recollection and familiarity assessment, whereas according to SON and HT, associative information results in a shift of familiarity. The modeling results cast doubt on the prominent role of conscious recollection, and as far as models are valid, parameter estimation suggests 2 processes in associative recognition: a shift in familiarity that is due to associative information and the determination of the source of familiarity of pairs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Feature sampling in detection: Implications for the measurement of perceptual independence.

The article presents the feature sampling signal detection (FS-SDT) model, an extension of the multivariate signal detection (SDT) model. The FS-SDT model assumes that, because of attentional shifts, different subsets of features are sampled for different presentations of the same multidimensional stimulus. Contrary to the SDT model, the FS-SDT model enables the estimation of pure perceptual effects that are uncontaminated by strategic attention shifts. The consideration of feature sampling in detection and identification opens a new perspective on the problem of measuring, respectively, the separability and integrality of stimulus dimensions. Disregarding feature sampling as a component process in detection and identification usually results in biased estimations of perceptual independence concepts relevant for judgments of whether stimulus dimensions are processed independently. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Obtaining configuration space and singularity maps for parallel manipulators

The aim of this paper is to describe a general methodology to obtain the entire set of positions that a parallel manipulator can reach and the workspace regions where the robot is controllable. The workspace is computed using a hybrid analytical-discrete procedure. Next the singularity maps are traced by carrying out a kinematic analysis of the positions obtained. To perform the latter a systematic method has been introduced to obtain the corresponding Jacobian matrices. The result of the whole process is the computation of singularity-free workspace regions, associated with certain working and assembly modes. After that, strategies to enlarge the accessible space are easier to plan and implement. This methodology is based on disassembling the manipulator into a mobile platform and a set of kinematic chains.     

Ion-selective electrodes using carbon nanotubes as ion-to-electron transducers

This study developed a new type of all-solid-state ion-selective electrode based on a transducing layer of a network of single-walled carbon nanotubes. The extraordinary capacity of carbon nanotubes to promote electron transfer between heterogeneous phases made the presence of electroactive polymers or any other ion-to-electron-transfer promoter unnecessary. The new transducer layer was characterized by environmental scanning electron microscopy and electrochemical impedance spectroscopy. The stability of the electrical potential of the new solid-contact electrode was examined by performing current-reversal chronopotentiometry, and the influence of the interfacial water film was assessed by the potentiometric water layer test. The performance of the new electrode was evaluated by determining K+ with an ion-selective membrane that contained the well-known valinomycin ion carrier. The new electrode had a Nernstian slope (58.4 mV/decade), dynamic ranges of four logarithmic units, and selectivities and limits of detection comparable to other solid-contact electrodes. The short response time (less than 10 s for activities higher than 10(-5.5) M) and the stability of the signal over several days makes these new electrodes very promising candidates for attaining true miniaturization.     

Preparation of high-T c oxide films via flaming solvent spray

Thick films of the high-temperature superconductors YBa₂Cu₃O_7?x and Bi_1.7Pb_0.3Sr₂Ca₂Cu₃O₁₀ have been prepared by spraying an ignited ethanol, ethylene glycol, or liquid ammonia solution of stoichiometric amounts of the metal nitrates (or acetates) onto polycrystalline MgO. The flaming spray is mechanically forced to traverse a region directly in front of the substrates. This new method is simple and inexpensive, and eliminates the problem of substrate cooling encountered in normal spray pyrolysis methods. Since decomposition of the solvent and metal salts occurs before deposition, the resulting films are relatively free of craters and nonuniformities common with spray methods. The method can be adapted to coat large areas and irregular or nonplanar shapes (i.e., cylinders), which could have useful magnetic shielding properties. The films were characterized by XRD and show single-phase material with preferredc-axis orientation. For YBa₂Cu₃O_7?x , resistance vs. temperature measurements show aT _c onset at 90 K and aT _c 0 at 76 K. Silver nitrate has been added to some of the solutions in an attempt to improve contact among individual grains.     

Tachycardia preconditions infarct size in dogs: role of adenosine and protein kinase C

BACKGROUND: Myocardial ischemic preconditioning is a well-known phenomenon, however there is scant information in regard to nonischemic preconditioning. METHODS AND RESULTS: We studied in anesthetized dogs the preconditioning effect of tachycardia and the mediation of adenosine and protein kinase C in this process. In a control group the anterior descending coronary artery was occluded for 60 minutes and reperfused for 270 minutes. Heart rate was kept constant at 120 +/- 5 cycles/min and aortic pressure changes were damped. The infarct size (necrotic volume/risk region volume x 100) was 15.8 +/- 1.5%. In another group of dogs a similar protocol was followed, but five periods of tachycardia (213 +/- 12 cycles/min), 5 minutes in duration each, with 5 minutes of intervening periods at control heart rate, were induced previous to the coronary occlusion. The infarct size was reduced by 46% (P<.001) with respect to the nonpreconditioned group. This effect was not due to changes in collateral flow nor risk region size. During tachycardia, myocardial interstitial adenosine increased about twofold (P<.05); no metabolic, hemodynamic, or ECG evidences of ischemia were observed and the transmural vasodilatory reserve was preserved. The blockade of adenosine receptors with 8 phenyltheophylline, before or after the preconditioning tachycardia, reverted its protecting effect but it did not modify infarct size in nonpreconditioned dogs. No changes in cytosolic or particulate protein kinase C activity or translocation of alpha-, beta-, epsilon-, and zeta- protein kinase C isozyme by effect of tachycardia or ischemia were observed between preconditioned and nonpreconditioned dogs. CONCLUSIONS: Tachycardia, in the absence of ischemia, mimics the preconditioning effect of ischemia in the dog. This effect is mediated by adenosine but not by changes in protein kinase C activity or its translocation.     

Preparation of high-Tc oxide films via flaming solvent spray

Thick films of the high-temperature superconductors YBa₂Cu₃O_7–x and Bi_1.7Pb_0.3Sr₂Ca₂Cu₃O₁₀ have been prepared by spraying an ignited ethanol, ethylene glycol, or liquid ammonia solution of stoichiometric amounts of the metal nitrates (or acetates) onto polycrystalline MgO. The flaming spray is mechanically forced to traverse a region directly in front of the substrates. This new method is simple and inexpensive, and eliminates the problem of substrate cooling encountered in normal spray pyrolysis methods. Since decomposition of the solvent and metal salts occurs before deposition, the resulting films are relatively free of craters and nonuniformities common with spray methods. The method can be adapted to coat large areas and irregular or nonplanar shapes (i.e., cylinders), which could have useful magnetic shielding properties. The films were characterized by XRD and show single-phase material with preferredc-axis orientation. For YBa₂Cu₃O_7–x , resistance vs. temperature measurements show aT _c onset at 90 K and aT _c 0 at 76 K. Silver nitrate has been added to some of the solutions in an attempt to improve contact among individual grains.     

Incorporating Danckwerts’ boundary conditions into the solution of the stochastic differential equation

The one-dimensional dispersion model has been solved analytically as well as numerically to describe flow in continuous “closed” boundary systems using the celebrated Danckwerts boundary conditions. Nevertheless, a continuous state stochastic approach can sometimes be more appropriate especially in cases when input fluctuations are of the same order as the time scale of the system and in such cases an accurate treatment of the boundary conditions is indispensable for the successful application of the method. A deterministic approach was carried out in which the differential equation was solved using Fourier's method and the Laplace transform. These solutions were used as a yardstick to assess the precision of the stochastic solution with its proposed boundary conditions conforming to Danckwerts’ boundary conditions. Our problem is somehow simplified if we assume that the convection term and the dispersion term are constants independent of space and time. A stochastic differential equation was thus employed, governed by the Wiener process and solved using the Euler-Maruyama method.