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At least 1,225 records · Page 68Linked to original sources
PubMed1981

Risk taking behavior: decision making in the face of genetic uncertainty.

Clients of genetic counseling frequently are called on to choose courses of action which may place themselves, their families, or their future offspring at some physical and/or emotional risk. This paper focuses on the nature of decision making in the face of such uncertainties. Evidence is presented from both research with clients making decision as well as from basic social psychological investigations of decision making which indicates the emotional and cognitive strains involved in making judgments under uncertainty. A framework for social work intervention is suggested that emphasizes prevention of deficiencies in information processing and decision making.

Decision Making↗
PubMed2002

Calibration and uncertainty estimation of erythemal radiometers in the argentine ultraviolet monitoring network.

The erythemal radiometers of the Ultraviolet Monitoring Network of the Argentine Servicio Meteorológico Nacional were calibrated in an extensive in situ campaign from October 1998 to April 1999 with Austrian reference instruments. Methods to correct the influence of the location's horizon and long-term detector changes are applied. The different terms that contribute to the measurement uncertainty are analyzed. The expanded uncertainty is estimated to be +/- 10% at 70 degrees solar zenith angle (SZA) and +/-6% for a SZA of <50 degrees. We observed significant changes for some detectors over hours and days, reaching a maximum diurnal drift of +/-5% at a SZA of 70 degrees and a maximum weekly variation of +/-4%.

Journal Article↗
PubMed2005

Uncertainty analysis in the measurement of the spatial responsivity of infrared antennas.

The measurement of a two-dimensional spatial responsivity map of infrared antennas can be accomplished by use of an iterative deconvolution algorithm. The inputs of this algorithm are the spatial distribution of the laser beam irradiance illuminating the antenna-coupled detector and a map of the measured detector response as it moves through the illuminating beam. The beam irradiance distribution is obtained from knife-edge measurements of the beam waist region; this data set is fitted to a model of the beam. The uncertainties, errors, and artifacts of the measurement procedure are analyzed by principal-component analysis. This study has made it possible to refine the measurement protocol and to identify, classify, and filter undesirable sources of noise. The iterative deconvolution algorithm stops when a well-defined threshold is reached. Spatial maps of mean values and uncertainties have been obtained for the beam irradiance distribution, the scanned spatial response data, and the resultant spatial responsivity of the infrared antenna. Signal-to-noise ratios have been defined and compared, and the beam irradiance distribution characterization has been identified as the statistically weakest part of the measurement procedure.

Journal Article↗
PubMed2006

Reducing the uncertainty in laser beam size measurement with a scanning edge method.

A modification in the analysis of a conventional laser beam spot size measurement method has been developed. The new analysis significantly decreases the uncertainty in the estimation of the beam-spot size. A conventional beam scanning approach was used in the measurement, but instead of differentiating the data and fitting the result to a Gaussian function, the data were fit to an analytical approximation to the complementary error function. As a result, fitted parameters were obtained that were consistent with the standard differentiation approach, but with considerably smaller uncertainty.

Journal Article↗
PubMed1996

Uncertainty experiments support the roles of second-order mechanisms in spatial frequency and orientation discriminations.

Previous studies of spatial frequency and orientation discrimination [Vision Res. 32, 1885 (1992)] suggest the existence of two second-order cortical mechanisms: one that mediates spatial frequency discriminations and sums signals across orientations and one that mediates orientation discriminations and sums signals across spatial frequency bands. The existence of each mechanism is tested in an uncertainty experiment in which the observer does not know which of two hypothetically pooled signals deviates from the standard but must judge whether the deviation is an increment or a decrement. No uncertainty effect is expected if the signals are completely pooled. Observed effects are compared with this expectation and with both theoretical and empirical estimates of the effects expected if the signals are processed separately. Results support the existence of the first mechanism, but not its exclusive role in mediating spatial frequency judgments, and support the exclusive role of the second mechanism in mediating orientation judgments.

Humans↗
PubMed1985

Simultaneous measurement of spatial-frequency summation and uncertainty effects.

The predictions for summation and uncertainty effects from several multiple-spatial-frequency-channels models were calculated. The models differed in their assumptions about the shape of the channels' underlying probability-density functions and in the decision rule used to combine the channels' outputs. Varying these assumptions resulted in quite different predictions about the magnitudes of these effects. Simultaneous summation and uncertainty experiments measured the detectability of gratings containing one (simple) or two (compound) spatial frequencies. Performance was assessed in two types of blocks of trials: either each stimulus was in a separate block or three stimuli (two simple gratings and their compound) were randomly intermixed in one block. Quantitative comparisons of the models with the data showed that the increasing-variance Gaussian models (in which the decision variable is the sum of the monitored channels' outputs) provided the best overall fit.

Attention↗
PubMed2003

Cramér-Rao analysis of orientation estimation: influence of target model uncertainties.

We explore the use of Cramér-Rao bound calculations for predicting fundamental limits on the accuracy with which target characteristics can be determined by using imaging sensors. In particular, estimation of satellite orientation from high-resolution sensors is examined. The analysis role that such bounds provide for sensor/experiment design, operation, and upgrade is discussed. Emphasis is placed on the importance of including all relevant target/sensor uncertainties in the analysis. Computer simulations are performed that illustrate that uncertainties in target features (e.g., shape, reflectance, and relative orientation) have a significant impact on the bounds and provide considerable insight as to how details of the three-dimensional target structure may influence the estimation process. The simulations also address the impact that a priori information has on the bounds.

Journal Article↗
PubMed1998

Do clinical practice guidelines define good medical care? The need for good science and the disclosure of uncertainty when defining 'best practices'.

Practice guidelines, although important in promoting quality, can also be harmful if they do not advocate the best options for patients. The latter can occur because of uncertainties in scientific evidence, biases in guideline development, and patient heterogeneity. Guidelines must therefore accurately describe the quality of the evidence and the degree of uncertainty that underlie recommendations. Proper methods for developing practice guidelines are reviewed.

Decision Support Techniques↗
PubMed2005

Fluorescence polarization/anisotropy approaches to study protein-ligand interactions: effects of errors and uncertainties.

Fluorescence techniques are widely used in the study of protein-ligand interactions because of their inherent sensitivity, and the fact that they can be implemented at true equilibrium conditions. Fluorescence polarization/anisotropy methodologies, in particular, are now extensively utilized in biotechnology and clinical chemistry. In this chapter, we shall discuss both theoretical and practical aspects of polarization/anisotropy methods. We shall also focus attention on considerations of errors and uncertainties in such measurements, and how these uncertainties affect the ultimate estimation of ligand-protein dissociation constants.

Fluorescence Polarization↗
PubMed2002

Use of measurement uncertainty analysis to assess accuracy of carbon mass balance closure for a cellulase production process.

Closing carbon mass balances is a critical and necessary step for verifying the performance of any conversion process. We developed a methodology for calculating carbon mass balance closures for a cellulase production process and then applied measurement uncertainty analysis to calculate 95% confidence limits to assess the accuracy of the results. Cellulase production experiments were conducted in 7-L fermentors using Trichoderma reesei grown on pure cellulose (Solka-floc), glucose, or lactose. All input and output carbon-containing streams were measured and carbon dioxide in the exhaust gas was quantified using a mass spectrometer. On Solka-floc, carbon mass balances ranged from 90 to 100% closure for the first 48 h but increased to 101 to 135% closure from 72 h to the end of the cultivation at 168 h. Carbon mass balance closures for soluble sugar substrates ranged from 92 to 127% over the entire course of the cultivations. The 95% confidence intervals (CIs) for carbon mass balance closure were typically +/-11 to 12 percentage points after 48 h of cultivation. Many of the carbon mass balance results did not bracket 100% closure within the 95% CIs. These results suggest that measurement problems with the experimental or analytical methods may exist. This work shows that uncertainty analysis can be a useful diagnostic tool for identifying measurement problems in complex biochemical systems.

Biotechnology↗
PubMed1998

The uncertainty associated with the predictive value of test results.

The uncertainty associated with predictive value of test results was taken into consideration, as concerns both sampling error (related to the size of the statistical reference samples) and analytical imprecision (unavoidably involved by the measurement itself). A software package, developed for the statistical calculations, was used for the treatment of the results obtained for serum free thyroxin in euthyroid and dysthyroid subjects, assumed as an experimental model. Examples are shown for the obtainable functions predictive value vs. estimate and the related uncertainty regions. These data could help in comparing test results and, in particular, in preparing fully informative laboratory reports. The difficulties involved by an extensive application of the procedure are discussed.

Humans↗
PubMed1980

Uncertainty reduction, conditioned reinforcement, and observing.

In a concurrent-chains procedure, pigeons chose between equivalent mixed and multiple fixed-interval schedules of reinforcement. In the first experiment, preference for the multiple schedule was higher when the probability of the shorter fixed interval was less than .50 than for complementary points, an outcome consistent with the delay-reduction hypothesis of conditioned reinforcement and observing, but inconsistent with the uncertainty-reduction hypothesis which requires symmetrical preferences with a maximum when the two intervals are equiprobable. A second experiment assessed preference for equivalent mixed and multiple schedules when each choice outcome resulted in two reinforcements, one on the longer and one on the shorter fixed interval. The order of the two fixed intervals was determined probabilistically. Pigeons again preferred multiple to mixed schedules, although multiple-schedule preference did not vary systematically with the likelihood of the shorter fixed interval occurring first. The results from these choice procedures are consistent with those from the observing-response literature in suggesting that the strength of a stimulus cannot be well described as a function of the degree of uncertainty reduction the stimulus provides about reinforcement.

Journal Article↗
PubMedDate not supplied

Simulation evaluation of the effects of non-uniform flow and degradation parameter uncertainty on subsurface-flow constructed wetland performance.

Although constructed wetland treatment systems have been used in a variety of applications, uncertainty in adequately determining flow conditions or hydraulic residence times ("hydraulic efficiencies") and degradation model parameters remains a problem with their design. Breakthrough or impulse-type tracer studies in constructed wetlands often result in residence-time distributions exhibiting long skewed "tails" suggesting multiple flow channels or perhaps unrealistically large dispersion factors. A fractional-flow analysis is developed here to quantify possible flow non-uniformity in a subsurface-flow constructed wetland and is then used to assess the effects of non-uniformity and degradation model parameter variability on constituent (for example, chemical oxygen demand) removal. A model application to tracer data developed previously demonstrates how flow non-uniformity alone can account for significant "tailing" and can be related to even moderate estimated dispersion numbers. From the analysis, it is evident that flow non-uniformity is of greater concern than decay parameter uncertainty, and that, from a constructed wetland design and operation perspective, every effort should be made to ensure relative flow uniformity across the constructed wetland.

Ecosystem↗
PubMed1982

Mentally retarded and normal children's performance on gross motor reaction- and movement-time tasks with varying degrees of uncertainty of movement.

This study evaluated the effect of uncertainty of movement, as a source of environmental stimuli, on the RT and movement time of 8- and 10-yr.-old mildly retarded and normal boys and girls during a 4.6-m run. With uncertainty of movement, retarded subjects (6 boys, 9 girls) displayed significant increases in both RT and movement time. For normal children (10 boys, 10 girls), no change in performance was noted as the task was simple. These results highlighted the notion of skill constancy and the importance of controlling potential stimuli during skill acquisition.

Child↗
PubMed1989

Uncertainty and visual strategies in table tennis.

Ball games are characterized by perceptual uncertainty and time-pressure. Of interest is the visual-search pattern carried out when these characteristics change. This is the case in table-tennis situations when comparing a drill situation, when one kind of stroke is constantly repeated, and a match situation, when the stroke is more often unpredictable. We analysed, during play, the visual-search pattern of five expert table tennis players to examine the effect of uncertainty on visual behavior. Direction of gaze was recorded by a video-oculographic recorder (NAC Eye Mark Recorder IV). Analysis showed that (i) visual fixations towards opponent player were only systematic in a match contrary to drill where they occurred less frequently. (ii) Whatever the situation, only the first part of the ball's trajectory was visually tracked. This occurred immediately after the opponent's release of the ball. Nevertheless, visual tracking was more frequent and of longer duration in a match. (iii) Analysis of motor behavior showed that the duration of the movement preparation was longer in a match while the duration of the execution phase was unchanged.

Eye Movements↗
PubMed1991

Effects of variations in force and stimulus uncertainty on fractionated reaction time.

Previous research has shown that reaction time (RT) and premotor time varied as a function of force even in simple-RT paradigm. The present purpose was to examine whether stimulus uncertainty induced by catch trials would cause programming delay until after the signal to respond. Subjects were required to react and produce a designated peak force as soon as possible after a visual stimulus, with and without catch trials. Five different levels of force were 10, 30, 50, 70, and 90% of the maximum grip strength of subjects. Analysis showed that simple RT and premotor time changed as a function of force, regardless of whether catch trials were removed. These findings suggest that stimulus uncertainty is not a necessary condition for programming delay.

Adult↗