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At least 955 records · Page 53Linked to original sources
PubMed2005

The value of site-specific information and the environment: technology adoption and pesticide use under uncertainty.

Remote sensing technology offers an opportunity to significantly increase the amount of site-specific information about field characteristics such as pest populations. Coupled with variable rate application technologies, this added information has the potential to provide environmental benefits through reduced pesticide applications. However, producers face a complicated adoption decision because output prices and crop yields are uncertain. A model is developed to examine the potential value of remote sensing information to pesticide applications in an option-value framework under uncertainty. Simulations suggest that remote sensing information could decrease pesticide use, but uncertainty and irreversibility are likely to limit technological adoption by farmers. Potential cost-share subsidies are discussed.

Agriculture↗
PubMed2006

Toward quantifying the effectiveness of water trading under uncertainty.

This paper presents a methodology for quantifying the effectiveness of water-trading under uncertainty, by developing an optimization model based on the interval-parameter two-stage stochastic program (TSP) technique. In the study, the effectiveness of a water-trading program is measured by the water volume that can be released through trading from a statistical point of view. The methodology can also deal with recourse water allocation problems generated by randomness in water availability and, at the same time, tackle uncertainties expressed as intervals in the trading system. The developed methodology was tested with a hypothetical water-trading program in an agricultural system in the Swift Current Creek watershed, Canada. Study results indicate that the methodology can effectively measure the effectiveness of a trading program through estimating the water volume being released through trading in a long-term view. A sensitivity analysis was also conducted to analyze the effects of different trading costs on the trading program. It shows that the trading efforts would become ineffective when the trading costs are too high. The case study also demonstrates that the trading program is more effective in a dry season when total water availability is in shortage.

Agriculture↗
PubMed2005

Sensor fault diagnosis for nonlinear processes with parametric uncertainties.

This paper addresses the problem of detecting, discriminating, and reconstructing sensor faults for nonlinear systems with known model structure but uncertainty in the parameters of the process. The convenience of the proposed technique lies in the fact that historical operational data and/or a priori fault information is not required to achieve accurate fault reconstruction except for fixed, short intervals. The overall fault diagnosis algorithm is composed of a series of nonlinear estimators, which estimates parameter and a fault isolation and identification filter. Parameter estimation and fault reconstruction cannot be performed accurately since faults and parametric uncertainty interact with each other. Therefore, these two tasks are performed at different time scales, where the fault diagnosis takes place at a more frequent rate than the parameter estimation. It is shown that the fault can be reconstructed under some realistic assumptions and the performance of the proposed methodology is evaluated on a simulated chemical process exhibiting nonlinear dynamic behavior.

Algorithms↗
PubMed2006

Uncertainty in descriptions of biosocial phenomena and the schism between preventionists and moralists.

Biosocial systems are dual-natured phenomena. A relationship between social and biological parameters of any biosocial system may be described by an uncertainty principle: it is not possible to measure both types of parameters exactly and simultaneously. A full description of dual-natured phenomenon requires two mutually exclusive (complementary) concepts. Preventionists and moralists use complementary descriptions of HIV/AIDS epidemic, sexual behavior and drug addiction. That is why they do not understand each other. The "compromise" may be defined as taking into consideration both types of descriptions. The compromise determines approximate values of complementary sets of parameters somewhere between their extreme alternative or complementary descriptions. A compromise is reached within the framework of the complex interplay of complementary descriptions and currently existing norms and generates new social norms and new intersectoral partnerships. The existing schism between preventionists and moralists concerning HIV/AIDS and similar issues is a result of uncertainty of complementary descriptions of complex biosocial systems and should be resolved through compromises which may vary in different countries.

Acquired Immunodeficiency Syndrome↗
PubMed2006

Encoding uncertainty in the hippocampus.

The medial temporal lobe may play a critical role in binding successive events into memory while encoding contextual information in implicit and explicit memory tasks. Information theory provides a quantitative basis to model contextual information engendered by conditional dependence between, or conditional uncertainty about, consecutive events in a sequence. We show that information theoretic indices characterizing contextual dependence within a sequential reaction time task (SRTT) predict regional responses, measured by fMRI, in areas associated with sequence learning and navigation. Specifically, activity of a distributed paralimbic system, centered on the left hippocampus, correlated selectively with predictability as measured with mutual information. This is clear evidence that the brain is sensitive to the probabilistic context in which events are encountered. This is potentially important for theories about how the brain represents uncertainty and makes perceptual inferences, particularly those based on predictive coding and hierarchical Bayes.

Adult↗
PubMed2005

An inexact fuzzy two-stage stochastic model for quantifying the efficiency of nonpoint source effluent trading under uncertainty.

Reduction of nonpoint source (NPS) pollution from agricultural lands is a major concern in most countries. One method to reduce NPS pollution is through land retirement programs. This method, however, may result in enormous economic costs especially when large sums of croplands need to be retired. To reduce the cost, effluent trading can be employed to couple with land retirement programs. However, the trading efforts can also become inefficient due to various uncertainties existing in stochastic, interval, and fuzzy formats in agricultural systems. Thus, it is desired to develop improved methods to effectively quantify the efficiency of potential trading efforts by considering those uncertainties. In this respect, this paper presents an inexact fuzzy two-stage stochastic programming model to tackle such problems. The proposed model can facilitate decision-making to implement trading efforts for agricultural NPS pollution reduction through land retirement programs. The applicability of the model is demonstrated through a hypothetical effluent trading program within a subcatchment of the Lake Tai Basin in China. The study results indicate that the efficiency of the trading program is significantly influenced by precipitation amount, agricultural activities, and level of discharge limits of pollutants. The results also show that the trading program will be more effective for low precipitation years and with stricter discharge limits.

Agriculture↗
PubMed2005

Communicating risk and uncertainty in relation to development and implementation of disease control policies.

Scientific evidence is one of the key factors to be considered in the development of disease control policies. It is generated using investigations into cause-effect relationships, which usually produce results that are associated with a varying degree of uncertainty. Experience has shown that taking account of these uncertainties can become a formidable challenge for policy makers when devising the strategies and when communicating them to stakeholders. The situation has been further complicated by a reduction in public trust in scientific evidence. It is now recognised that this challenge cannot be managed by simply providing more information, but it is also necessary to consider the influence that variation in risk perception amongst stakeholders has on their response to and commitment towards the policies.

Animals↗
PubMed2004

Stochastic modelling of landfill leachate and biogas production incorporating waste heterogeneity. Model formulation and uncertainty analysis.

A mathematical model simulating the hydrological and biochemical processes occurring in landfilled waste is presented and demonstrated. The model combines biochemical and hydrological models into an integrated representation of the landfill environment. Waste decomposition is modelled using traditional biochemical waste decomposition pathways combined with a simplified methodology for representing the rate of decomposition. Water flow through the waste is represented using a statistical velocity model capable of representing the effects of waste heterogeneity on leachate flow through the waste. Given the limitations in data capture from landfill sites, significant emphasis is placed on improving parameter identification and reducing parameter requirements. A sensitivity analysis is performed, highlighting the model's response to changes in input variables. A model test run is also presented, demonstrating the model capabilities. A parameter perturbation model sensitivity analysis was also performed. This has been able to show that although the model is sensitive to certain key parameters, its overall intuitive response provides a good basis for making reasonable predictions of the future state of the landfill system. Finally, due to the high uncertainty associated with landfill data, a tool for handling input data uncertainty is incorporated in the model's structure. It is concluded that the model can be used as a reasonable tool for modelling landfill processes and that further work should be undertaken to assess the model's performance.

Biodegradation, Environmental↗
PubMed2005

Quantifying the uncertainty of on-line sensors at WWTPs during field operation.

It remains an ongoing task to quantify the uncertainty of continuous measuring systems at WWTPs during field operation. The commonly used methods are based on lab experiments under standardized conditions and are only suitable for characterizing the measuring device itself. For measuring devices under field conditions, a knowledge of the response time, trueness and precision is equally important. A method is proposed which can be used to characterize newly installed on-line sensors or to evaluate monitoring data which may contain systematic errors. The concept is based on comparative measurements between the sensor and a reference. A linear regression is used to differentiate between trueness and precision. Various statistical tests are conducted to validate the preconditions of linear regression. The information about the trueness and precision of the measuring system under field conditions helps to adapt control strategies more effectively to the relevant processes and permits sophisticated control concepts. Moreover, the concept can help to define guidelines for evaluating the uncertainties of effluent quality monitoring to overcome the concerns about on-line sensors, improve the trust in these systems and to allow the use of continuously measuring systems for legislative purposes. The approach is discussed in detail in this paper and all statistical tests and formulas are listed in the Appendix.

Linear Models↗
PubMed2003

Back pain and the resolution of diagnostic uncertainty in illness narratives.

In this paper I consider 30 Finnish women's written narratives about the process of getting back pain diagnosed. From the beginning of the early discomfort of back pain, the women were sure of its bodily and subjective reality. They struggled repeatedly to be taken seriously, and only after years of medical disparagement did they encounter medical professionals who were able solve the riddle and give it a name, a diagnosis. Since back pain is a baffling problem and challenges the central biomedical epistemology-objective knowledge and measurable findings separate from subjective experience-it allowed the doctors to show a disrespectful attitude toward back pain sufferers. The moral essence of the women's common story was the stigmatizing experience when doctors did not take subjective pain seriously. Instead, doctors' neglectful attitudes became part of the prolonged problem. During the long-lasting uncertainty, women tried multiple coping strategies to ease their lives and developed mental attitudes to endure the pain. Since the protagonists did not give up the lived certainty of back pain they were gradually able to challenge medical uncertainty and to demand a thorough medical examination, and/or through random circumstance they encountered doctors who were willing to take their symptoms seriously. This triggered turning points that immediately or very soon resulted in solving the riddle of the puzzling pain. To be finally diagnosed was a great relief. However, to be taken seriously as a person was considered to be the greatest relief.

Adaptation, Psychological↗
PubMed2003

Human variability in CYP3A4 metabolism and CYP3A4-related uncertainty factors for risk assessment.

CYP3A4 constitutes the major liver cytochrome P450 isoenzyme and is responsible for the oxidation of more than 50% of all known drugs. Human variability in kinetics for this pathway has been quantified using a database of 15 compounds metabolised extensively (>60%) by this CYP isoform in order to develop CYP3A4-related uncertainty factors for the risk assessment of environmental contaminants handled via this route. Data were analysed from published pharmacokinetic studies (after oral and intravenous dosing) in healthy adults and other subgroups using parameters relating primarily to chronic exposure [metabolic and total clearances, area under the plasma concentration-time curve (AUC)] and acute exposure (Cmax). Interindividual variability in kinetics was greater for the oral route (46%, 12 compounds) than for the intravenous route (32%, 14 compounds). The physiological and molecular basis for the difference between these two routes of exposure is discussed. In relation to the uncertainty factors used for risk assessment, the default kinetic factor of 3.16 would be adequate for adults, whereas a CYP3A4-related factor of 12 would be required to cover up to 99% of neonates, which have lower CYP3A4 activity.

Adult↗
PubMed2002

Obsessions and compulsions and intolerance for uncertainty in a non-clinical sample.

It has been hypothesized that decision-making difficulties in patients with obsessive-compulsive disorder may arise from intolerance for uncertainty. We investigated the relationship between obsessivity and intolerance for uncertainty (defined in terms of need for cognitive closure), controlling for state and trait anxiety and depression. We tested nonclinical subjects through the Need for Closure Scale (NFCS), the Padua Inventory Revised (PI-R), the Beck Depression Inventory (BDI), and the State-Trait Anxiety Inventory (Form-Y; STAI-Y). A principal component analysis showed a lack of correlation between the PI-R and the NFCS subscales. A set of multiple regression analyses performed on PI-R subscales showed that the need for cognitive closure cannot be considered as a strong predictor of obsessions and compulsions. These results speak against the hypothesis that people with high obsessivity have difficulties in taking decisions because of a cognitive need for certainty. We instead argue that difficulties in taking decisions may be related to other specific cognitive beliefs or meta-beliefs.

Adolescent↗
PubMed2003

Mothers' decisions about gastrostomy tube insertion in children: factors contributing to uncertainty.

The purpose of this study was to explore O'Connor's four factors contributing to mothers' uncertainty concerning gastrostomy tube (G-tube) insertion in their children (lack of information; unclear value trade-offs; lack of support; social pressure) in a substitute decision-making context. Fifty mothers participated in one semi-structured interview at the time of their children's G-tube insertion. Children's ages ranged from 2 weeks to 17 years, slightly more than half were male, and most had a primary diagnosis related to a neurological (n = 27) or cardiac (n = 10) condition. Two-thirds of the mothers identified topics about which they wanted more information, the majority reported both gains and losses associated with their decision, three-quarters reported that they had received support during decision making, and half reported that they had felt pressure from family and health care professionals. Results indicate that mothers' decisions about G-tube insertion are complex and difficult. The existence and importance of O'Connor's factors in this context are confirmed by mothers' accounts. Because these factors are believed to be modifiable, health care professionals have the opportunity to potentially minimize the extent to which the factors contribute to decision uncertainly. It is recommended that health care professionals implement interventions focused on minimizing uncertainty.

Adolescent↗
PubMed2026

Scalable, generalizable and uncertainty-aware integration of spatial multiomics across diverse modalities and platforms with SCIGMA.

Recent advances in spatial omics technologies have enabled simultaneous profiling of transcriptomic, proteomic, epigenomic, metabolomic and imaging data at high spatial resolution, offering unprecedented opportunities to dissect tissue complexity. However, integrating these diverse and large-scale spatial multimodal datasets remains a major computational challenge. We present SCIGMA, a scalable and generalizable deep learning framework for spatial multiomics integration. SCIGMA introduces an uncertainty-aware contrastive learning objective and multiview graph neural networks to preserve modality-specific signals while learning biologically meaningful joint representations. Unlike previous methods, SCIGMA provides spatially resolved uncertainty estimates, interpretably identifying regions of biological or technical heterogeneity. SCIGMA supports integration of up to five modalities, and its modular framework is extensible to future technologies with even more modalities. It also scales to more than 1 million spatial locations, enabling analysis of high-resolution datasets such as Visium HD and Xenium Prime. We evaluated SCIGMA across 19 datasets spanning 8 modalities, 10 tissues and 9 platforms. On benchmarkable datasets, SCIGMA outperformed other methods in spatial domain detection, modality preservation, feature reconstruction and reproducibility. SCIGMA identifies biologically meaningful structures, refined spatial domains and modality-specific regulatory programs, providing a robust, flexible and future-ready solution for scalable spatial multimodal integration.

Multiomics↗
PubMed2006

Scientific rationality, uncertainty and the governance of human genetics: an interview study with researchers at deCODE genetics.

Technology development in human genetics is fraught with uncertainty, controversy and unresolved moral issues, and industry scientists are sometimes accused of neglecting the implications of their work. The present study was carried out to elicit industry scientists' reflections on the relationship between commercial, scientific and ethical dimensions of present day genetics and the resources needed for robust governance of new technologies. Interviewing scientists of the company deCODE genetics in Iceland, we found that in spite of optimism, the informants revealed ambiguity and uncertainty concerning the use of human genetic technologies for the prevention of common diseases. They concurred that uncritical marketing of scientific success might cause exaggerated public expectations of health benefits from genetics, with the risk of backfiring and causing resistance to genetics in the population. On the other hand, the scientists did not address dilemmas arising from the commercial nature of their own employer. Although the scientists tended to describe public fear as irrational, they identified issues where scepticism might be well founded and explored examples where they, despite expert knowledge, held ambiguous or tentative personal views on the use of predictive genetic technologies. The rationality of science was not seen as sufficient to ensure beneficial governance of new technologies. The reflexivity and suspension of judgement demonstrated in the interviews exemplify productive features of moral deliberation in complex situations. Scientists should take part in dialogues concerning the governance of genetic technologies, acknowledge any vested interests, and use their expertise to highlight, not conceal the technical and moral complexity involved.

Fear↗
PubMed2006

Use of motion tracking in stereotactic body radiotherapy: Evaluation of uncertainty in off-target dose distribution and optimization strategies.

Spatial accuracy in extracranial radiosurgery is affected by organ motion. Motion tracking systems may be able to avoid PTV enlargement while preserving treatment times, however special attention is needed when fiducial markers are used to identify the target can move with respect to organs at risk (OARs). Ten patients treated by means of the Synchrony system were taken into account. Sparing of irradiated volume and of complication probability were estimated by calculating treatment plans with a motion tracking system (Cyberknife Synchrony, Sunnyvale, CA, USA) and a PTV-enlargement strategy for ten patients. Six patients were also evaluated for possible inaccuracy of estimation of dose to OARs due to relative movement between PTV and OAR during respiration. Dose volume histograms (DVH) and Equivalent Uniform Dose (EUD) were calculated for the organs at risk. In the cases for which the target moved closer to the OAR (three cases of six), a small but significant increase was detected in the DVH and EUD of the OAR. In three other cases no significant variation was detected. Mean reduction in PTV volume was 38% for liver cases, 44% for lung cases and 8.5% for pancreas cases. NTCP for liver reduced from 23.1 to 14.5% on average, for lung it reduced from 2.5 to 0.1% on average. Significant uncertainty may arise from the use of a motion-tracking device in determination of dose to organs at risk due to the relative motion between PTV and OAR. However, it is possible to limit this uncertainty. The breathing phase in which the OAR is closer to the PTV should be selected for planning. A full understanding of the dose distribution would only be possible by means of a complete 4D-CT representation.

Carcinoma↗
PubMed2000

Certainty and uncertainty in genetic counselling: a qualitative case study.

This study examines the communication that occurs during routine genetic counselling sessions. It involves the qualitative analysis of nine consultations with one member of a clinical genetics team. The consultations were characterised by a contrast between the sense of certainty apparent in how the clinicians talked about the power and promise of the new genetics and the uncertainty communicated regarding the actual information produced by genetic tests and their limitations in solving people's problems. There was also a contrast between how the clinician seemed to control the format and agenda of the consultation and the apparently uncontrollable personal and social implications of the topics discussed. We speculate that this may be explained in terms of the clinician giving some order and certainty in an area of inherent uncertainty, and where great promises are as yet unrealised.

Communication↗
PubMed2006

Increasing data transparency and estimating phylogenetic uncertainty in supertrees: Approaches using nonparametric bootstrapping.

The estimation of ever larger phylogenies requires consideration of alternative inference strategies, including divide-and-conquer approaches that decompose the global inference problem to a set of smaller, more manageable component problems. A prominent locus of research in this area is the development of supertree methods, which estimate a composite tree by combining a set of partially overlapping component topologies. Although promising, the use of component tree topologies as the primary data dissociates supertrees from complexities within the underling character data and complicates the evaluation of phylogenetic uncertainty. We address these issues by exploring three approaches that variously incorporate nonparametric bootstrapping into a common supertree estimation algorithm (matrix representation with parsimony, although any algorithm might be used), including bootstrap-weighting, source-tree bootstrapping, and hierarchical bootstrapping. We illustrate these procedures by means of hypothetical and empirical examples. Our preliminary experiments suggest that these methods have the potential to improve the correspondence of supertree estimates to those derived from simultaneous analysis of the combined data and to allow uncertainty in supertree topologies to be quantified. The ability to increase the transparency of supertrees to the underlying character data has several practical implications and sheds new light on an old debate. These methods have been implemented in the freely available program, tREeBOOT.

Classification↗