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PubMed1990

The effect of signal-frequency uncertainty on comodulation masking release.

The aim of this study was to examine whether the scheme of across-frequency comparison underlying comodulation masking release (CMR) is sensitive to the placement of the signal in the array of comodulating bands. This was addressed using the paradigm of signal-frequency uncertainty. In the first experiment, maskers were constructed of linearly spaced sinusoidally amplitude-modulated tones, and the signal was a pure tone presented at one of five frequencies. A small uncertainty effect was observed for the noncomodulated masker, but no significant effect was observed for the comodulated masker. In the second experiment, the maskers were constructed of logarithmically spaced noise bands, and the signal was a pure tone presented at one of seven frequencies. In these conditions, an uncertainty effect was observed in both noncomodulated and comodulated maskers, which was larger than that observed in experiment 1. The results were interpreted as indicating that the mechanism of across-frequency comparison underlying CMR is sensitive to signal location.

Acoustic Stimulation↗
PubMed1991

Listening bandwidths and frequency uncertainty in pure-tone signal detection.

The effect of frequency uncertainty on the detection of tonal signals in noise was studied using a modified probe-signal method. Widths of the listening bands used during detection were measured directly, allowing for an analysis that separates the effects of having to monitor multiple independent bands from those due to limited frequency resolution. Uncertainty was varied by beginning each trial with a cue consisting of one, two, or four randomly chosen, simultaneously presented tones. An expected signal, whose frequency matched one of the components in a cue, was presented on a majority of trials. However, on remaining trials, the signal was a probe, which meant that its frequency differed from one of the components in the cue by a constant ratio. Performance as measured in percent correct declined for probes at increasingly distant ratios from the expected values. The results were converted to dB using individual psychometric functions for expected signals and listening bands were fitted using the rounded exponential filter of Patterson et al. [J. Acoust. Soc. Am. 72, 1788-1803 (1982)]. The obtained bandwidths are comparable to those reported using notched-noise maskers, but there is a small but consistent increase in bandwidth with increased numbers of components in the cues. The primary results is that the effects due to uncertainty are well described by a 1-of-M orthogonal band model, which takes into consideration limitations of the detector, including the widths of the listening bands.

Attention↗
PubMed2005

The importance of acknowledging clinical uncertainty in the diagnosis of epilepsy and non-epileptic events.

BACKGROUND: Failure to recognise diagnostic uncertainty between the epilepsies and non-epileptic events may be a factor in high rates of misdiagnosis. AIMS: To explore the results of acknowledging diagnostic uncertainty in a cohort of children presenting with paroxysmal events. METHODS: Children (29 days-16th birthday) with new presentations of paroxysmal disorders were ascertained through outpatients, admissions, and accident and emergency over a two year period in a district hospital with a catchment population of 500,000. Cases were classified by diagnosis at entry and 6-30 months later. A random selection of cases was independently assessed. RESULTS: A total of 684 cases were ascertained. Attacks were initially classified as febrile seizures (n = 212), acute symptomatic epileptic seizures (n = 5), epilepsies (n = 83), unclassified (possible epilepsy) (n = 90), isolated epileptic seizures (n = 51), and non-epileptic events (n = 243). Case review enabled reclassification of 61 of those initially unclassified--31 to an epilepsy and 27 to non-epileptic events. In 29 the final diagnosis was never clarified. These were 23 cases with confusing or absent histories and six with short lived seizure clusters. Prognosis for these 29 cases was good; 75% had been discharged. None were on long term medication. The diagnosis in the 131 cases confirmed as epilepsy was stable. Independent review of a random sample showed full concordance with one neurologist and 20% uncertainty with another. CONCLUSION: In addition to definite epilepsy or non-epileptic events it is helpful to recognise a group of cases where the diagnosis is uncertain-unclassified paroxysmal events. Reassessment of these cases enables accurate diagnosis and may prevent a hasty and incorrect diagnosis of epilepsy.

Adolescent↗
PubMed1990

Uncertainties in the risk assessment of three mycotoxins: aflatoxin, ochratoxin, and zearalenone.

The risk assessment of mycotoxins is made up of two major components: an exposure assessment and a hazard assessment. There are many uncertainties in both of these components. This paper will briefly discuss the various aspects of the risk assessment process as it applies to mycotoxins and will then focus mainly on some of the uncertainties in the hazard assessment component of several carcinogenic mycotoxins. To arrive at an estimated "safe dose" (end point of the hazard assessment), we have previously used two major approaches: the no observed effect level (NOEL) divided by a safety factor approach and a mathematical (robust linear) extrapolation to a "virtual safe dose." Both of these approaches use only points from the no observed effect region of the dose-response curve and ignore valuable data from the response region. It is proposed to use the dose at which 50% of the animals would have developed tumors (the TD50) divided by a large safety factor of 50,000 as an additional estimate of "safe dose". For many studies, the TD50 lies within the observed response region of the dose-response curve and may have more validity. It is also suggested in certain cases that some of the uncertainties regarding the NOEL can be reduced if one uses a statistically derived no effect level (NEL).

Aflatoxins↗
PubMed2005

Decision making in the face of uncertainty and resource constraints: examples from trauma imaging.

The purpose of this review is to illustrate how tools and concepts from decision and cost-effectiveness analyses can be used to help make decisions in the face of uncertainty and resource constraints, select appropriate subjects for imaging, choose between competing imaging modalities, and prioritize future research. Examples from trauma imaging illustrate the use of the presented tools. The author advocates the PROACTIVE approach in deciding which imaging strategies are cost-effective (PRO for defining the problem, reframing the problem from multiple perspectives, and focusing on the objective; ACT for expanding the alternatives, considering the consequences and associated chances of each alternative, and identifying the trade-offs involved; IVE for integrating the evidence and values, optimizing the value of interest, and exploring uncertainty). Simulation models play an important role in the assessment of imaging strategies by helping to identify alternative strategies and to integrate the best-available evidence related to risks, benefits, patient values, and costs. Exploring the uncertainty in the evidence and assessing the value of obtaining more information can help prioritize future research and guide study design.

Cerebral Angiography↗
PubMed2003

Mathematical models of renal fluid and electrolyte transport: acknowledging our uncertainty.

Mathematical models of renal tubular function, with detail at the cellular level, have been developed for most nephron segments, and these have generally been successful at capturing the overall bookkeeping of solute and water transport. Nevertheless, considerable uncertainty remains about important transport events along the nephron. The examples presented include the role of proximal tubule tight junctions in water transport and in regulation of Na(+) transport, the mechanism by which axial flow in proximal tubule modulates solute reabsorption, the effect of formate on proximal Cl(-) transport, the assessment of potassium transport along collecting duct segments inaccessible to micropuncture, the assignment of pathways for peritubular Cl(-) exit in outer medullary collecting duct, and the interaction of carbonic anhydrase-sensitive and -insensitive pathways for base exit from inner medullary collecting duct. Some of these uncertainties have had intense experimental interest well before they were cast as modeling problems. Indeed, many of the renal tubular models have been developed based on data acquired over two or three decades. Nevertheless, some uncertainties have been delineated as the result of model exploration and represent communications from the modelers back to the experimental community that certain issues should not be considered closed. With respect to model refinement, incorporating more biophysical detail about individual transporters will certainly enhance model reliability, but ultimate confidence in tubular models will still be contingent on experimental development of critical information at the tubular level.

Absorption↗
PubMed2002

A methodology for missile countermeasures optimization under uncertainty.

The missile countermeasures optimization problem is a complex strategy optimization problem that combines aircraft maneuvers with additional countermeasures in an attempt to survive attack from a single surface-launched, anti-aircraft missile. Classic solutions require the evading aircraft to execute specific sequences of maneuvers at precise distances from the pursuing missile and do not effectively account for uncertainty about the type and/or current state of the missile. This paper defines a new methodology for solving the missile countermeasures optimization problem under conditions of uncertainty. The resulting genetic programming system evolves programs that combine maneuvers with such countermeasures as chaff, flares, and jamming to optimize aircraft survivability. This methodology may be generalized to solve strategy optimization problems for intelligent, autonomous agents operating under conditions of uncertainty.

Aircraft↗
PubMed1998

Sources of diagnostic uncertainty for chronically psychotic cocaine abusers.

OBJECTIVE: This study determined the sources and frequency of diagnostic uncertainty for patients with chronic psychosis and active cocaine abuse or dependence and assessed the usefulness of prospective follow-up in clarifying diagnosis. METHODS: A total of 165 male patients with chronic psychoses and cocaine abuse or dependence on inpatient units of a Veterans Affairs medical center were evaluated using the Structured Clinical Interview for DSM-III-R (SCID-R), urine tests, hospital records, and interviews with collateral sources. An algorithm allowing key SCID-R items and diagnostic criteria to be designated as provisionally met or uncertain was applied, resulting in a provisional diagnosis and a list of alternate diagnoses. The assessment was repeated 18 months later in an attempt to resolve diagnostic uncertainty. RESULTS: In 30 cases (18 percent), initial assessment produced a definitive diagnosis, including 21 cases of schizophrenia, six of schizoaffective disorder, and three of psychostimulant-induced psychotic disorder. In the other 135 cases, a definitive diagnosis could not be reached because of one or more sources of diagnostic uncertainty, including insufficient periods of abstinence (78 percent), poor memory (24 percent), and inconsistent reporting (20 percent). Reassessment at 18 months led to definitive diagnoses in 12 additional cases. CONCLUSIONS: It was frequently difficult to distinguish schizophrenia from chronic substance-induced psychoses. Rather than concluding prematurely that psychotic symptoms are, or are not, substance induced, clinicians should initiate treatment of both psychosis and the substance use disorder in uncertain cases. The persistence or resolution of psychosis during abstinence and additional history from the stabilized patient or collateral sources may clarify the diagnosis.

Adult↗
PubMedDate not supplied

Net health benefits: a new framework for the analysis of uncertainty in cost-effectiveness analysis.

In recent years, considerable attention has been devoted to the development of statistical methods for the analysis of uncertainty in cost-effectiveness (CE) analysis, with a focus on situations in which the analyst has patient-level data on the costs and health effects of alternative interventions. To date, discussions have focused almost exclusively on addressing the practical challenges involved in estimating confidence intervals for CE ratios. However, the general approach of using confidence intervals to convey information about uncertainty around CE ratio estimates suffers from theoretical limitations that render it inappropriate in many situations. The authors present an alternative framework for analyzing uncertainty in the economic evaluation of health interventions (the "net health benefits" approach) that is more broadly applicable and that avoids some problems of prior methods. This approach offers several practical and theoretical advantages over the analysis of CE ratios, is straightforward to apply, and highlights some important principles in the theoretical underpinnings of CE analysis.

Confidence Intervals↗
PubMed1996

Uncertainty and coping in fathers of children with cancer.

Limited research has been conducted regarding the father's relationship with the chronically ill child, particularly the child with cancer. How fathers cope with their child's illness and treatment is relatively unknown. The purpose of this study was to describe uncertainty and consequential coping patterns in fathers of children with cancer. The sample for this descriptive study was obtained from a computerized, nonalphabetized list of children currently undergoing treatment. The fathers were sent a packet of information that contained a letter introducing the study, a demographic data sheet, Mishel's Parent Perception of Uncertainty Scale, and the Jalowiec Coping Scale. Thirty-one of 150 eligible fathers completed the study. The age of the father, the age of the child, and the length of time since diagnosis showed direct correlation to paternal uncertainty and coping. Fathers used coping styles described as evasive, optimistic, and emotive.

Adaptation, Psychological↗
PubMed2001

The relationship between disability and depression in multiple sclerosis: the role of uncertainty, coping, and hope.

The relationship between disability and depression was studied in 188 patients with clinically definite multiple sclerosis (MS). Patients were administered the Zung Self-Rating Depression Scale, Ways of Coping, Uncertainty of Illness Scale, and Hope Scale during their regular clinic appointments. Their current level of disability was rated by the attending physician using the Expanded Disability Status Scale. Even when the depression measure was corrected for items overlapping with other symptoms or consequences of MS, depression was correlated with disability. Depression was also correlated with an array of psychological variables, including uncertainty concerning ones illness, hope, and the use of various emotion-centered, though not problem-centered coping strategies. Multiple regression analyses revealed that none of these psychological correlates mediated or moderated the relationship between disability and depression. Instead, disability, uncertainty, hope, and emotion-centered coping were significant independent predictors of depression, together accounting for approximately 40% of the variance in patients' self-reported depression. The relationship between disability and depression in MS is usually interpreted as evidence that depression is psychogenic and reactive to the demands and limitations of this disease. The demonstration that this relationship is not diminished when an array of potentially intervening psychological variables are included in the analysis raises questions concerning the validity of this interpretation.

Adaptation, Psychological↗
PubMed2002

Erythropoietin, uncertainty principle and cancer related anaemia.

BACKGROUND: This study was designed to evaluate if erythropoietin (EPO) is effective in the treatment of cancer related anemia, and if its effect remains unchanged when data are analyzed according to various clinical and methodological characteristics of the studies. We also wanted to demonstrate that cumulative meta-analysis (CMA) can be used to resolve uncertainty regarding clinical questions. METHODS: Systematic Review (SR) of the published literature on the role of EPO in cancer-related anemia. A cumulative meta-analysis (CMA) using a conservative approach was performed to determine the point in time when uncertainty about the effect of EPO on transfusion-related outcomes could be considered resolved. PARTICIPANTS: Patients included in randomized studies that compared EPO versus no therapy or placebo. MAIN OUTCOME MEASURES: Number of patients requiring transfusions. RESULTS: Nineteen trials were included. The pooled results indicated a significant effect of EPO in reducing the number of patients requiring transfusions [odds ratio (OR) = 0.41; 95%CI: 0.33 to 0.5; p < 0.00001;relative risk (RR) = 0.61; 95% CI: 0.54 to 0.68]. The results remain unchanged after the sensitivity analyses were performed according to the various clinical and methodological characteristics of the studies. The heterogeneity was less pronounced when OR was used instead of RR as the measure of the summary point estimate. Analysis according to OR was not heterogeneous, but the pooled RR was highly heterogeneous. A stepwise metaregression analysis did point to the possibility that treatment effect could have been exaggerated by inadequacy in allocation concealment and that larger treatment effects are seen at hb level > 11.5 g/dl. We identified 1995 as the point in time when a statistically significant effect of EPO was demonstrated and after which we considered that uncertainty about EPO efficacy was resolved. CONCLUSION: EPO is effective in the treatment of anemia in cancer patients. This could have already been known in 1995 if a CMA had been performed at that time.

Anemia↗
PubMed2006

Manufactured uncertainty: protecting public health in the age of contested science and product defense.

The strategy of "manufacturing uncertainty" has been used with great success by polluters and manufacturers of dangerous products to oppose public health and environmental regulation. This strategy entails questioning the validity of scientific evidence on which the regulation is based. While this approach is most identified with the tobacco industry, it has been used by producers of asbestos, benzene, beryllium, chromium, diesel exhaust, lead, plastics, and other hazardous products to avoid environmental and occupational health regulation. It is also central to the debate on global warming. The approach is now so common that it is unusual for the science not to be challenged by an industry facing regulation. Manufacturing uncertainty has become a business in itself; numerous technical consulting firms provide a service often called "product defense" or "litigation support." As these names imply, the usual objective of these activities is not to generate knowledge to protect public health but to protect a corporation whose products are alleged to have toxic properties. Evidence in the scientific literature of the funding effect--the close correlation between the results of a study desired by a study's funder and the reported results of that study--suggests that the financial interest of a study's sponsors should be taken into account when considering the study's findings. Similarly, the interpretation of data by scientists with financial conflicts should be seen in this light. Manufacturing uncertainty is antithetical to the public health principle that decisions be made using the best evidence currently available.

Environmental Pollutants↗
PubMed1983

Analysis of air pollution effects: uncertainties in proceeding to standards.

Uncertainties in the collection and assessment of scientific information make ambient air quality standard setting difficult. Uncertainties occur in the estimation of the medical parameters under test due to the inherent random variability encountered in sampling the parameters. The most common method of dealing with random variability is statistical significance testing. The main caution offered in regard to that analysis is to avoid calling a nonsignificant result negative, unless the circumstances are such that the smallest effect which indicates likely harm to health could have been detected with sufficiently high probability. Uncertainties also play a crucial role in evaluating the implications that even statistically significant test results have for human health. A signal-detection model, developed to explain expert performance in evaluating the results of such diagnostic tests as X-rays, is presented as an analogy for the situation facing experts who are evaluating the implications of health data that is being considered for use in setting a standard. If criteria are too strict for accepting data as evidence of harm to health, then it is argued that, as a consequence, the decision process will not have sufficient ability to discriminate against false-negative results. False-negative results are those that incorrectly conclude there is no threat when, in fact, a particular level of pollutant is actually a threat to health.

Air Pollutants↗
PubMed2006

Lung cancer attributable to indoor radon exposure in france: impact of the risk models and uncertainty analysis.

OBJECTIVE: The inhalation of radon, a well-established human carcinogen, is the principal-and omnipresent-source of radioactivity exposure for the general population of most countries. Scientists have thus sought to assess the lung cancer risk associated with indoor radon. Our aim here is to assess this risk in France, using all available epidemiologic results and performing an uncertainty analysis. METHODS: We examined the exposure-response relations derived from cohorts of miners and from joint analyses of residential case-control studies and considered the interaction between radon and tobacco. The exposure data come from measurement campaigns conducted since the beginning of the 1980s by the Institute for Radiation Protection and Nuclear Safety and the Directorate-General of Health in France. We quantified the uncertainties associated with risk coefficients and exposures and calculated their impact on risk estimates. RESULTS: The estimated number of lung cancer deaths attributable to indoor radon exposure ranges from 543 [90% uncertainty interval (UI) , 75-1,097] to 3,108 (90% UI, 2,996-3,221) , depending on the model considered. This calculation suggests that from 2.2% (90% UI, 0.3-4.4) to 12.4% (90% UI, 11.9-12.8) of these deaths in France may be attributable to indoor radon. DISCUSSION: In this original work we used different exposure-response relations from several epidemiologic studies and found that regardless of the relation chosen, the number of lung cancer deaths attributable to indoor radon appears relatively stable. Smokers can reduce their risk not only by reducing their indoor radon concentration but also by giving up smoking.

Adult↗
PubMed2003

Theoretical measurement uncertainty of white-light interferometry on rough surfaces.

A great advantage of the white-light interferometry is that it can be used for profile objects with a rough surface. A speckle pattern that arises in the image plane allows one to observethe interference; however, this pattern is also the source of the measurement uncertainty. We derive the theoretical limits of the longitudinal uncertainty by virtue of the first-order statistics of thespeckle pattern. It is shown that this uncertainty depends on the surface roughness of the measured object only; it does not depend on the setup parameters.

Journal Article↗
PubMed2006

Effect of bio-optical parameter variability and uncertainties in reflectance measurements on the remote estimation of chlorophyll-a concentration in turbid productive waters: modeling results.

Most algorithms for retrieving chlorophyll-a concentration (Chla) from reflectance spectra assume that bio-optical parameters such as the phytoplankton specific absorption coefficient (aPhi*) or the chlorophyll-a fluorescence quantum yield (eta) are constant. Yet there exist experimental data showing large ranges of variability for these quantities. The main objective of this study was to analyze the sensitivity of two Chla algorithms to variations in bio-optical parameters and to uncertainties in reflectance measurements. These algorithms are specifically designed for turbid productive waters and are based on red and near-infrared reflectances. By means of simulated data, it is shown that the spectral regions where the algorithms are maximally sensitive to Chla overlap those of maximal sensitivity to variations in the above bio-optical parameters. Thus, to increase the accuracy of Chla retrieval, we suggest using spectral regions where the algorithms are less sensitive to Chla, but also less sensitive to these interferences. aPhi* appeared to be one of the most important sources of error for retrieving Chla. However, when the phytoplankton backscattering coefficient (bb,Phi) dominates the total backscattering, as is likely during algal blooms, variations in the specific bb,Phi may introduce large systematic uncertainties in Chla estimation. Also, uncertainties in reflectance measurements, which are due to incomplete atmospheric correction or reflected skylight removal, seem to affect considerably the accuracy of Chla estimation. Instead, variations in other bio-optical parameters, such as eta or the specific backscattering coefficient of total suspended particles, appear to have minor importance. Suggestions regarding the optimal band locations to be used in the above algorithms are finally provided.

Algorithms↗
PubMed2000

Generalized uncertainty relations and coherent and squeezed states.

Characteristic uncertainty relations and their related squeezed states are briefly reviewed and compared in accordance with the generalizations of three equivalent definitions of canonical coherent states. The standard SU(1, 1) coherent states are shown to be the unique states that minimize the Schrödinger uncertainty relation for every pair of the three generators and the Robertson relation for the three generators. The characteristic uncertainty inequalities are naturally extended to the case of several states. It is shown that these inequalities can be written in the equivalent complementary form.

Journal Article↗