SEARCH · Search PubMed

Results for “Fuzzy Logic”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 487 records · Page 27Linked to original sources

PubMed1998

Agonistic screams and the classification of dominance relationships: are monkeys fuzzy logicians?

Scream vocalizations of group-living rhesus macaques provoked by higher-ranking aggressors were examined in two contexts: encounters in which the rank difference between opponents was either large or small. Such vocalizations are important in eliciting support from the caller's allies in the group (usually matrilineal kin). Five acoustically distinct recruitment screams encode specific information about features of the agonistic context, for example, relative rank of the opponent and the severity of the attack. Against higher-ranking opponents, noisy screams are most likely to be given during encounters that involve contact aggression, and tonal or undulated screams are most likely for non-contact aggression. We predicted that scream bouts directed to small rank difference opponents would be more likely to comprise calls from scream classes other than the expected type, and that scream bouts from large rank difference encounters would be more in accord with the expected class. For large rank difference bouts, on average 74.2% of calls were of the expected class; for small rank difference bouts, a significantly smaller per cent (53.8%) of calls was accurately predicted. In the large rank difference encounters, 65.6% (55/84) of bouts were composed entirely of expected scream types, but only 47.6% (39/82) were uniformly correct for small rank difference encounters. Large rank difference interactions also yielded significantly fewer bouts where none of the screams produced by the victim of attack belonged to the predicted class. We suggest that a multi-valued or fuzzy logic system, that is one with more than two truth values, might be a more realistic way to conceptualize the categorization of certain referents of monkey vocalizat. Copyright 1998 The Association for the Study of Animal Behaviour.

Journal Article↗

PubMed1994

Children's integration of speech and pointing gestures in comprehension.

We examined 4- and 9-year-old's referential comprehension when given pointing gestures and spoken labels, in two types of contextually ambiguous situations. In one situation, speech/gesture discordance was produced in conditions where labels for one of four objects being referred to sounded either alike, or different from each other. In the other, the contextual set contained the same two objects, and ambiguity was produced by factorially combining speech on a continuum ranging between /bcl/ and /dcl/ with a pointing gesture from a continuum ranging between an unambiguous point to a ball and to a doll. Results showed that the speech modality had a far greater influence on word comprehension than gestures. Second, the influence of gestures was greater for the older children. Mathematical models of speech-gesture understanding were tested against the data. Selection models assume that one dimension of information is used on a given trial, and that the selection of a modality depends on the ambiguity of information encoded on the dominant dimension. The Fuzzy Logical Model of Perception (FLMP) assumes that both modalities are evaluated independently of one another and then integrated to achieve comprehension. The results from both age groups were best described by the assumptions of the FLMP. Results are related to general claims about perceptual development during childhood concerning the quality of representations formed and dimensional selectivity of visual-spoken language.

Auditory Perception↗

PubMed1998

Broadening the Tests of Learning Models.

For many years psychological studies of the learning process have used a simulated medical diagnosis task in which symptom configurations are probabilistically related to diseases. Participants are given a set of symptoms and asked to indicate which disease is present, and feedback is given on each trial. We enrich this standard laboratory task in four different ways. First, the symptoms have four possible values (low, medium low, medium high, and high) rather than just two. Second, symptom configurations are generated from an expanded factorial design rather than a simple factorial design. Third, subjects are asked to make a continuous judgment indicating their confidence in the diagnosis, rather than simply a binary judgment. Fourth, cumulated performance scores, payoffs, and the availability of a historical summary of the outcomes are varied in order to assess how these treatments modulate performance. These enrichments provide a broader data set and more challenging tests of the models. Using 123 subjects each in 480 trials, we compare five existing learning models plus several variants, including the well-known Bayesian, fuzzy logic, connectionist, exemplar, and ALCOVE models. We find that the subjects do learn to distinguish the symptom configurations, that subjects are quite heterogeneous in their response to the task, and that only a small part of the variation across subjects arises from the differences in treatments. The most striking finding is that the model that best predicts subjects' behavior is a simple Bayesian model with a single fitted parameter for prior precision to capture individual differences. We use rolling regression techniques to elucidate the behavior of this model over time and find some evidence of over-response to current stimuli. Copyright 1998 Academic Press.

Journal Article↗

PubMed2000

Accuracy, Scope, and Flexibility of Models.

Traditionally, models are compared on the basis of their accuracy, their scope, and their simplicity. Simplicity is often represented by parameter counts; the fewer the parameters, the simpler the model. Arguments are presented here suggesting that simplicity has little place in discussions of modeling; instead, the concept of flexibility should be substituted. When comparing two models one should be wary of the possibility of their differential flexibility. Several methods for assessing relative flexibility are possible, as represented in this special issue of the Journal of Mathematical Psychology. Here, the method of cross-validation is applied in the comparison of two models, a linear integration model (LIM) and the fuzzy-logical model of perception (FLMP), in the fitting of 44 data sets concerning the perception of layout seen among three panels with the presence or absence of four sources of information for depth. Prior to cross-validation the two models performed about equally well; after cross-validation LIM was statistically superior to FLMP, but the overall pattern of fits remained nearly the same for both models. Copyright 2000 Academic Press.

Journal Article↗

PubMed1998

Mafia behaviour and the evolution of facultative virulence.

Some organisms enforce "maladaptive" behaviours on others of the same or different species by imposing costs in the absence of compliance. Such enforcement is used by the enforcer to obtain benefits in the possession of the enforced individual. This mechanism is known as mafia behaviour in humans, but may be widespread in parasite-host relationships in nature, from the cellular level to societies. In this paper we describe the evolution of such mafia mechanisms, and we propose a fuzzy logic model where the mafia mechanism is based on enforcement of hosts by exponentially increasing the cost of resistance to the parasite. The benefits of host resistance can be counteracted by parasite virulence, or even a decrease in response to an increment in its resistance. This parasite response to the host defence increment can be used for the parasite to teach the host that it is better to pay part of its benefits than increase its extremely costly defence. This model differs from others because it takes into account the evolution of host defence related to the evolution of parasite virulence (host-parasite coevolution) and points out an optimum in host defence related to the facultative virulence of the parasite. We provide several potential examples of facultative virulence depending on the antiparasite responses of hosts, and we suggest that this kind of mafia behaviour may be a widespread mechanism in biological processes at a number of different levels.

Animals↗

PubMed1993

A new approach to analysis and display of local lipophilicity/hydrophilicity mapped on molecular surfaces.

A new method for display and analysis of lipophilic/hydrophilic properties on molecular surfaces is presented. The present approach is based on the concept of Crippen and coworkers that the overall hydrophobicity of a molecule (measured as the logarithm of the partition coefficient in an octanol/water system) can be obtained as a superposition of single atom contributions. It is also based on the concept of molecular lipophilicity potentials (MLP) first introduced by Audry and coworkers in order to establish a 3D lipophilicity potential profile in the molecular environment. Instead of using a l/r- or an exponential distance law between the atomic coordinates and a point on the molecular surface, a new distance dependency is introduced for the calculation of an MLP-value on the solvent-accessible surface of the molecule. In the present formalism the Crippen values (introduced for atoms in their characteristic structural environment) are 'projected' onto the van der Waals surface of the molecule by a special weighting procedure. This guarantees that only those atomic fragments contribute significantly to the surface values that are in the close neighbourhood of the surface point. This procedure not only works for small molecules but also allows the characterization of the surfaces of biological macromolecules by means of local lipophilicity. Lipophilic and hydrophilic domains can be recognized by visual inspection of computer-generated images or by computational procedures using fuzzy logic strategies. Local hydrophobicities on different molecular surfaces can be quantitatively compared on the basis of the present approach.

Alcohols↗

PubMed2004

Reduction of false arterial blood pressure alarms using signal quality assessment and relationships between the electrocardiogram and arterial blood pressure.

The paper presents an algorithm for reducing false alarms related to changes in arterial blood pressure (ABP) in intensive care unit (ICU) monitoring. The algorithm assesses the ABP signal quality, analyses the relationship between the electrocardiogram and ABP using a fuzzy logic approach and post-processes (accepts or rejects) ABP alarms produced by a commercial monitor. The algorithm was developed and evaluated using unrelated sets of data from the MIMIC database. By rejecting 98.2% (159 of 162) of the false ABP alarms produced by the monitor using the test set of data, the algorithm was able to reduce the false ABP alarm rate from 26.8% to 0.5% of ABP alarms, while accepting 99.8% (441 of 442) of true ABP alarms. The results show that the algorithm is effective and practical, and its use in future patient monitoring systems is feasible.

Aged↗

PubMed2005

Evo-devo and the search for homology ("sameness") in biological systems.

Developmental biology and evolutionary studies have merged into evolutionary developmental biology ("evo-devo"). This synthesis already influenced and still continues to change the conceptual framework of structural biology. One of the cornerstones of structural biology is the concept of homology. But the search for homology ("sameness") of biological structures depends on our favourite perspectives (axioms, paradigms). Five levels of homology ("sameness") can be identified in the literature, although they overlap to some degree: (i) serial homology (homonomy) within modular organisms, (ii) historical homology (synapomorphy), which is taken as the only acceptable homology by many biologists, (iii) underlying homology (i.e., parallelism) in closely related taxa, (iv) deep evolutionary homology due to the "same" master genes in distantly related phyla, and (v) molecular homology exclusively at gene level. The following essay gives emphasis on the heuristic advantages of seemingly opposing perspectives in structural biology, with examples mainly from comparative plant morphology. The organization of the plant body in the majority of angiosperms led to the recognition of the classical root-shoot model. In some lineages bauplan rules were transcended during evolution and development. This resulted in morphological misfits such as the Podostemaceae, peculiar eudicots adapted to submerged river rocks. Their transformed "roots" and "shoots" fit only to a limited degree into the classical model which is based on either-or thinking. It has to be widened into a continuum model by taking over elements of fuzzy logic and fractal geometry to accommodate for lineages such as the Podostemaceae.

Animals↗

PubMed2000

Model complexity: the fit to random data reconsidered.

A recent controversy in the field of depth perception has highlighted an important aspect of model testing concerning a model's complexity, defined as the prior propensity of the model to fit arbitrary data sets. The present article introduces an index of complexity, called the mean minimum distance, defined as the average squared distance between an arbitrary data point and the prediction range of the model. It may also be expressed as a dimensionless quantity called the scaled mean minimum distance. For linear models, theoretical values for the scaled mean minimum distance and the variance of the scaled minimum distance can be readily obtained and compared against empirical estimates obtained from fits to random data. The approach is applied to resolving the question of the relative complexity of the Linear Integration model and the Fuzzy Logic of Perception model, both of which have been the subject of controversy in the field of depth perception. It is concluded that the two models are equally complex.

Humans↗

PubMed2003

Understanding clay minerals with fuzzy mathematics.

A long-existing geochemical problem is the lack of a means of chemically defining non-stoichiometric complex minerals such as clays, which have no distinct composition and no clear compositional boundaries. We propose here a novel approach for describing the chemical nature of clay minerals using fuzzy logic. This non-conventional mathematical approach allows us to quantify compositional vagueness in such systems. We show that a clay mineral can be described in terms of how compositionally representative it is, of its own type ("belonging-ness") and to what extent it resembles other types (compositional overlap). Many clay minerals are seen to be far from the ideal, and most minerals are also to a lesser (and sometimes greater) extent, close to types other than their own. This has provided a means of grading such minerals, evaluating how "good" a sample is, and defining the extent of transition to other phases. We have derived here the fundamental methodology for such computations, which could be a framework for the analysis of other complex chemical systems, especially in the fields of geology and metallurgy.

Journal Article↗

PubMed2006

Application of kaolin to improve citric acid production by a thermophilic Aspergillus niger.

Citric acid production by a thermophilic strain of the filamentous fungus Aspergillus niger IIB-6 in a medium containing blackstrap cane molasses was improved by the addition of kaolin to the fermentation medium. The fermentation was run in a 7.5-l stirred bioreactor (60% working volume). The optimal sugar concentration was found to be 150 g/l. Kaolin (1.0 ml) was added to the fermentation medium to enhance volumetric production. The best results in terms of product formation were observed when 15 parts per million (ppm) kaolin was added 24 h after inoculation. With added kaolin, citric acid production was enhanced 2.34-fold, compared to a control fermentation without added kaolin. The length of incubation to attain this product yield was shortened from 168 to 96 h. The comparison of kinetic parameters showed improved citrate synthase activity of the culture (Y (p/x)=7.046 g/g). When the culture grown at various kaolin concentrations was monitored for Q (p), Q (s), and q (p), there was significant improvement in these variables over the control. Specific production by the culture (q (p)=0.073 g/g cells/h) was improved several fold. The addition of kaolin substantially improved the enthalpy (DeltaH (D)=74.5 kJ/mol) and entropy of activation (DeltaS=-174 J/mol/K) for citric acid production, free energies for transition state formation, and substrate binding for sucrose hydrolysis. The performance of fuzzy logic control of the bioreactor was found to be very promising for an improvement ( approximately 4.2-fold) in the production of citric acid (96.88 g/l), which is of value in commercial applications.

Aspergillus niger↗

PubMed2003

Decision support for road system analysis and modification on the Tahoe National Forest.

The United States Forest Service is required to analyze road systems on each of the national forests for potential environmental impacts. We have developed a novel and inexpensive way to do this using the Ecosystem Management Decision Support program (EMDS). We used EMDS to integrate a user-developed fuzzy logic knowledge base with a grid-based geographic information system to evaluate the degree of truth for assertions about a road's environmental impact. Using spatial data for natural and human processes in the Tahoe National Forest (TNF, California, USA), we evaluated the assertion "the road has a high potential for impacting the environment." We found a high level of agreement between the products of this evaluation and ground observations of a TNF transportation engineer, as well as occurrences of road failures. We used the modeled potential environmental impact to negatively weight roads for a least-cost path network analysis to 1573 points of interest in the forest. The network analysis showed that out of 8233 km of road analyzed in the forest, 3483 km (42%) must be kept in a modified road network to ensure access to these points. We found that the modified network had improved patch characteristics, such as significantly fewer "cherry stem" roads intruding into patches, an improved area-weighted mean shape index, and larger mean patch sizes, as compared to the original network. This analysis system could be used by any public agency to analyze infrastructure for environmental or other risk and included in other mandated analyses such as risks to watersheds.

Conservation of Natural Resources↗

PubMed2006

Critical sampling points methodology: case studies of geographically diverse watersheds.

Only with a properly designed water quality monitoring network can data be collected that can lead to accurate information extraction. One of the main components of water quality monitoring network design is the allocation of sampling locations. For this purpose, a design methodology, called critical sampling points (CSP), has been developed for the determination of the critical sampling locations in small, rural watersheds with regard to total phosphorus (TP) load pollution. It considers hydrologic, topographic, soil, vegetative, and land use factors. The objective of the monitoring network design in this methodology is to identify the stream locations which receive the greatest TP loads from the upstream portions of a watershed. The CSP methodology has been translated into a model, called water quality monitoring station analysis (WQMSA), which integrates a geographic information system (GIS) for the handling of the spatial aspect of the data, a hydrologic/water quality simulation model for TP load estimation, and fuzzy logic for improved input data representation. In addition, the methodology was purposely designed to be useful in diverse rural watersheds, independent of geographic location. Three watershed case studies in Pennsylvania, Amazonian Ecuador, and central Chile were examined. Each case study offered a different degree of data availability. It was demonstrated that the developed methodology could be successfully used in all three case studies. The case studies suggest that the CSP methodology, in form of the WQMSA model, has potential in applications world-wide.

Ecosystem↗

PubMed2005

A Grid-based HIV expert system.

OBJECTIVES: This paper addresses Grid-based integration and access of distributed data from infectious disease patient databases, literature on in-vitro and in-vivo pharmaceutical data, mutation databases, clinical trials, simulations and medical expert knowledge. METHODS: Multivariate analyses combined with rule-based fuzzy logic are applied to the integrated data to provide ranking of patient-specific drugs. In addition, cellular automata-based simulations are used to predict the drug behaviour over time. Access to and integration of data is done through existing Internet servers and emerging Grid-based frameworks like Globus. Data presentation is done by standalone PC based software, Web-access and PDA roaming WAP access. The experiments were carried out on the DAS2, a Dutch Grid testbed. RESULTS: The output of the problem-solving environment (PSE) consists of a prediction of the drug sensitivity of the virus, generated by comparing the viral genotype to a relational database which contains a large number of phenotype-genotype pairs. CONCLUSIONS: Artificial Intelligence and Grid technology are effectively used to abstract knowledge from the data and provide the physicians with adaptive interactive advice on treatment applied to drug resistant HIV. An important aspect of our research is to use a variety of statistical and numerical methods to identify relationships between HIV genetic sequences and antiviral resistance to investigate consistency of results.

Biometry↗

PubMed2006

Thrombophilia in ischemic stroke subtypes: implications for treatment.

The current understanding of thrombogenesis is modeled on Virchow's triad: stasis, hypercoagulability, and vessel wall injury. There is a dynamic (always changing) nonlinear interaction between the vascular wall, blood components, and flow, which at times defined "pathologic" leads to thrombosis or hemorrhage, at other times called "healthy" to normal hemostasis. The triad named after Virchow was not designated as such in Virchow's work. Instead, Virchow showed that thrombosis itself leads to endothelial damage, hypercoagulability, and stasis. Thus, cause and effect regarding the elements of Virchow's triad and thrombosis become indistinguishable if linearity is considered mandatory. Considering a nonlinear relation solves this problem. In the real patient, each element is present to a degree. At every moment in time, the direction of coagulation (toward hemostasis, thrombosis, or hemorrhage) and the dynamic of interaction of the elements of the triad change. The complexity and nonlinearity of the thrombotic context is evident. These facts suggest a new venue for diagnostic classification of stroke (ischemic and hemorrhagic) by causation and have implications for its prevention and treatment. Clinical and laboratory evidence can be gathered for the elements of Virchow's triad as well as for fibrinolysis and thrombosis. Mathematical methods other than probability-based statistics can represent the measured presence of these elements to a degree and their nonlinear relationship. These include, but may not be limited to, Riemannian geometry, fuzzy logic, cellular automata, and infinitesimals, all proscribed by evidence-based medicine. However, by using these methods, diagnosis and treatment measures for stroke can be built on a causal rather than risk methodology, individualizing medical decisions to the patient. All current clinical guidelines are based on linear methods of probability-based statistics and group-based data. The therapeutic choice of antithrombotic therapy in the individual patient for whom measured elements of thrombogenesis are available rests on the knowledge and expertise of the treating physician.

Journal Article↗

PubMed1996

Information integration in cross-modal pattern recognition: an argument for acquired modularity.

Three experiments addressed the issue of whether modularized operations (Fodor, 1983) in pattern recognition could be acquired. In Experiment 1, blind and sighted individuals were compared in the speech-tactile domain of pattern recognition. The results were inconsistent with the assumptions of the fuzzy logical model of perception (FLMP) (Oden and Massaro, 1978) and with the assumptions of modularized pattern recognition processes, but were consistent with the assumptions of 'penetrability' into non-modularized operations. Experiments 2 and 3 compared sighted individuals across speech-visual and speech-tactile domains, revealing fundamentally different patterns of performance that we argue demonstrate modularized and non-modularized FLMP operations in pattern recognition, respectively.

Adolescent↗

PubMed1991

Integration versus interactive activation: the joint influence of stimulus and context in perception.

Empirical results from both reading and speech perception indicate that stimulus and context information have independent influences on perceptual recognition. Massaro (1989) argued that these data are inconsistent with an interactive activation and competition (IAC) model (McClelland & Rumelhart, 1981), and consistent with the fuzzy logical model of perception (FLMP) (Massaro, 1979; 1989). McClelland (1991) than modified the interactive activation model to be stochastic rather than deterministic and to use a best one wins (BOW) decision rule, allowing it to predict independent influences of stimulus and context. When tested against real data, however, the network proposed by McClelland and extended by us gives a poorer description of actual empirical results than the FLMP. To account for the dynamics of information processing, the SIAC model, an interactive model based on the Boltzmann machine, and the FLMP are formulated to make quantitative predictions of performance as a function of processing time. It is shown that the dynamic FLMP provides a better description of the time course of perceptual processing than does interactive activation. The SIAC and Boltzmann models have difficulty predicting 1) context effects given little processing time and 2) a strong stimulus influence given substantial processing time. Finally, we demonstrate that the FLMP predicts that context can improve the accuracy of performance, in addition to providing a bias to respond with the alternative supported by context. In summary, there is now both empirical and theoretical evidence in favor of the FLMP over SIAC models of pattern recognition. We therefore argue that interactive activation is both less consistent with empirical results and not necessary to describe the joint influence of stimulus and context in language perception.

Algorithms↗

PubMed1977

Some observations on fuzzy diagnosis and medical computing.

Wechsler has advocated the use of fuzzy logic for medical diagnosis, but it is pointed out that simpler systems have proved more successful than is apparent from his paper. The proposal raises a broad range of issues concerning the role of sophisticated information-processing techniques in the development of medical computing. These issues are discussed and it is suggested that a more evolutionary view of this development would be of greater benefit in the long run.

Bayes Theorem↗