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Results for “Model interpretability”

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PubMed2002

A haemodynamic model for the physiological interpretation of in vivo measurements of the concentration and oxygen saturation of haemoglobin.

We present a model that describes the effect of physiological parameters such as the speed of blood flow, local oxygen consumption, capillary recruitment, and vascular dilation/constriction on the concentration and oxygen saturation of haemoglobin in tissue. This model can be used to guide the physiological interpretation of haemodynamic and oximetric data collected in vivo with techniques such as optical imaging, near-infrared spectroscopy and functional magnetic resonance imaging. In addition to providing a formal description of well-established results (exercise-induced hyperemia, reperfusion hyperoxia, decrease in the concentration of deoxyhaemoglobin induced by brain activity, measurement of arterial saturation by pulse oximetry, etc.), this model suggests that the superposition of asynchronous contributions from the arterial, capillary and venous haemoglobin compartments may be at the origin of observed out-of-phase oscillations of the oxyhaemoglobin and deoxyhaemoglobin concentrations in tissue.

Hemodynamics↗

PubMed2003

Model selection for the interpretation of protein side chain methyl dynamics.

A number of different dynamics models are considered for fitting (13)C and (2)H side chain methyl relaxation rates. It is shown that in cases where nanosecond time scale dynamics are present the extended Lipari-Szabo model which is explicitly parameterized to include the effects of slow motions can produce wide distributions of fitting parameters even in cases where the errors are relatively small and large numbers of relaxation rates are considered. In contrast, fits of (15)N backbone dynamics using this model are far more robust. The origin of this difference is analyzed and can be explained by the different functional forms of the spectral density in these two cases. The utility of a number of models for the analysis of methyl side chain dynamics is presented.

Amino Acids↗

PubMed1989

A model for multisystem evaluation, interpretation, and treatment of individuals with neurologic dysfunction.

We have presented a model that can be used to organize current concepts of neuroanatomy, neurophysiology, and motor control theory into a clinically relevant context. This model can be used to postulate the causal relationship among pathology, impairments, and disabilities. Knowledge of the insult often provides predictive information regarding stability of the disability, progression of the disease, and possibly recovery. Knowledge of neuropathology should guide the clinician regarding the types of impairments that are expected. Thus, by knowing the type and location of the lesion, the clinician already has a perspective regarding which evaluative tests should be emphasized and what treatment strategies will be most effective. In the absence of known pathology, knowledge of motor control theory, neuroanatomy, and neuropathology can still help the clinician make educated judgments regarding the interrelationship of the patient's impairments. In this model, we separate impairments that result directly from neuropathology and those that arise indirectly to help the clinician keep the total patient in perspective and to focus intervention. This separation emphasizes the applicability and limitations of motor control theories in the treatment of neurologically impaired individuals. Motor control theory helps to identify the relationship between direct impairments and their likely consequences; motor control theory does not address the very real issue of impairments that arise indirectly in systems such as the musculoskeletal and cardiopulmonary systems. Impairments that occur as a composite effect of multiple causes are identified as a separate category. Some of the causes of these impairments can often be addressed by physical therapy intervention, and some cannot.(ABSTRACT TRUNCATED AT 250 WORDS)

Cerebrovascular Disorders↗

PubMedDate not supplied

[Socio-economic inequalities and mental health. I. Concepts, theories, and interpretations].

AIMS: Reconstructing the models used for approaching the inequalities issues in health, identifying the most relevant theoretical and conceptual contributions. METHOD: Literature electronic-search on Medline, Psyclit, Econlit, Social Science Index and SocioSearch using the key-words inequalities, deprivation, poverty, socio-economic status, social class, occupational class, mental health for the period 1965-2002; integrated with manual search. The material was classified according to the conceptual and theoretical interpretative models or to the analyses of the association 'inequalities-health' where health was expressed as mortality, morbidity or services utilisation. RESULTS: Four different interpretative models about the genesis of inequalities were identified. Further theoretical developments overcome the distinction among conceptuals contrapositions selection versus causation, statistic artefactual versus real differences, individual behaviours versus material context. Since the 80's the concept of material deprivation has been enlarged to include social deprivation to explain health inequalities. The social exclusion is related to material deprivation and to social fragility enlarging the traditional aspects of poverty. The theories that better adapt to the psychiatric field are the social selection and social causation. CONCLUSIONS: The social exclusion and the new methodologies for measuring the inequalities seems to be an effective way for understanding of the inexplored aspects of the mental health inequalities.

Health Services Accessibility↗

PubMed2002

From heart attacks to melanoma: do common sense models of somatization influence symptom interpretation for female victims?

Common sense models regarding gender and stress influenced how laypeople responded to information about symptoms in 3 experiments. In Study 1, medical intervention was perceived to be less important for female targets reporting chest pain and stressful events than for male targets experiencing identical symptoms and stressors. In addition, chest pain was less likely to be attributed to cardiac causes for female targets. This gender-based stress-discounting effect was replicated for symptoms of gallstones and melanoma in Study 2, where participants again were less likely to recommend medical care for female than for male targets. Recognition memory for information about a somatizing target was tested in Study 3; results suggested that laypeople hold stereotypes associating somatization with female gender. The authors' findings provide insight into the naive theories that shape symptom interpretation and self-referral behavior.

Adolescent↗

PubMed1991

Improved methods for building protein models in electron density maps and the location of errors in these models.

Map interpretation remains a critical step in solving the structure of a macromolecule. Errors introduced at this early stage may persist throughout crystallographic refinement and result in an incorrect structure. The normally quoted crystallographic residual is often a poor description for the quality of the model. Strategies and tools are described that help to alleviate this problem. These simplify the model-building process, quantify the goodness of fit of the model on a per-residue basis and locate possible errors in peptide and side-chain conformations.

Chemical Phenomena↗

PubMed2006

Analysis of the electromeniscus phenomenon using a different interpretation of the Maxwell model applied to three-dimensional molecular orientations.

An electrohydrodynamic phenomenon called the electromeniscus is analyzed. This phenomenon is closely related to the oscillation of a microscale liquid and is analyzed using an interpretation of the Maxwell model coupled with a variational principle. The analysis clearly shows that the electromeniscus phenomenon is generated as a result of mass transformation of the oscillating liquid in order to transform the electric energy at the electrode to kinetic energy of the liquid most efficiently through their resonance. Mass transformation is a characteristic phenomenon of a liquid, and control of this phenomenon demonstrates great potential for self-aligning nanoscale materials and production of functional polymers characterized by specific molecular orientations.

Journal Article↗

PubMed1985

The use of a logistic model for the quantitative interpretation of indirect sandwich enzyme labelled immunosorbent assays (ELISA) for antibodies and antigens in foot and mouth disease.

A three parameter logistic model is described for the analysis of profiles of optical density vs log dose for indirect sandwich ELISA tests in foot and mouth disease. The model describes the observed phenomenon of saturability with increasing dose, and its parameters can be interpreted in terms of molecular binding events. A computer program to fit the model is described. An approximate statistical test is developed which can be used to test for departures from equivalence for replicate profiles. It is found that correlation of the optical density values to a standard reference reaction considerably improves reproducibility.

Animals↗

PubMed2003

Topology of gene expression networks as revealed by data mining and modeling.

MOTIVATION: Interpretation of high-throughput gene expression profiling requires a knowledge of the design principles underlying the networks that sustain cellular machinery. Recently a novel approach based on the study of network topologies has been proposed. This methodology has proven to be useful for the analysis of a variety of biological systems, including metabolic networks, networks of protein-protein interactions, and gene networks that can be derived from gene expression data. In the present paper, we focus on several important issues related to the topology of gene expression networks that have not yet been fully studied. RESULTS: The networks derived from gene expression profiles for both time series experiments in yeast and perturbation experiments in cell lines are studied. We demonstrate that independent from the experimental organism (yeast versus cell lines) and the type of experiment (time courses versus perturbations) the extracted networks have similar topological characteristics suggesting together with the results of other common principles of the structural organization of biological networks. A novel computational model of network growth that reproduces the basic design principles of the observed networks is presented. Advantage of the model is that it provides a general mechanism to generate networks with different types of topology by a variation of a few parameters. We investigate the robustness of the network structure to random damages and to deliberate removal of the most important parts of the system and show a surprising tolerance of gene expression networks to both kinds of disturbance.

Algorithms↗

PubMed2006

A flexible computational framework for detecting, characterizing, and interpreting statistical patterns of epistasis in genetic studies of human disease susceptibility.

Detecting, characterizing, and interpreting gene-gene interactions or epistasis in studies of human disease susceptibility is both a mathematical and a computational challenge. To address this problem, we have previously developed a multifactor dimensionality reduction (MDR) method for collapsing high-dimensional genetic data into a single dimension (i.e. constructive induction) thus permitting interactions to be detected in relatively small sample sizes. In this paper, we describe a comprehensive and flexible framework for detecting and interpreting gene-gene interactions that utilizes advances in information theory for selecting interesting single-nucleotide polymorphisms (SNPs), MDR for constructive induction, machine learning methods for classification, and finally graphical models for interpretation. We illustrate the usefulness of this strategy using artificial datasets simulated from several different two-locus and three-locus epistasis models. We show that the accuracy, sensitivity, specificity, and precision of a naïve Bayes classifier are significantly improved when SNPs are selected based on their information gain (i.e. class entropy removed) and reduced to a single attribute using MDR. We then apply this strategy to detecting, characterizing, and interpreting epistatic models in a genetic study (n = 500) of atrial fibrillation and show that both classification and model interpretation are significantly improved.

Atrial Fibrillation↗

PubMed1995

A linear modelling approach to automatic interpretation of quality control measurements in mammography.

An approach to the automated interpretation of quality control data is described in which the relationship between small changes in system performance and the resulting small changes in the measured quality control test results are approximated as a set of linear equations in matrix form. The inverse of this forward matrix is then used to identify causal changes from the set of measured changes. This approach has been investigated for the case of mammographic screening quality assurance and shown to provide a potentially useful tool to assist in the interpretation task.

Autoanalysis↗

PubMed1997

Fourier models and the loci of adaptation.

First measures of sensitivity and the need for a model to interpret them are addressed. Then modeling in the Fourier domain is promoted by a demonstration of how much an approach explains spatial sensitization and its dependence on luminance. Then the retinal illuminance and receptor absorptions produced by various stimuli are derived to foster interpretation of the neural mechanisms underlying various psychophysical phenomena. Finally, the sequence and the anatomical loci of the processes controlling visual sensitivity are addressed. It is concluded that multiplicative adaptation often has effects identical to response compression followed by subtractive adaptation and that, perhaps as a consequence, there is no evidence of retinal gain changes in human cone vision until light levels are well above those available in natural scenes and in most contemporary psychophysical experiments; that contrast gain control fine tunes sensitivity to patterns at all luminances; and that response compression, modulated by subtractive adaptation, predominates in the control of sensitivity in human cone vision.

Adaptation, Physiological↗

PubMed1999

Electrostatic Contribution to the Enthalpy of Charging at Hematite/Electrolyte Interface.

A calorimetry study of hematite surface reactions is reported, with special emphasis on the estimation of the electrostatic contribution to the enthalpy of charging. The calorimetry titrations were performed outside the point of zero charge region where the electrostatic contribution is significant. The results were interpreted by the surface complexation model. The interpretation enabled the evaluation of standard protonation and deprotonation enthalpies as well as the electrostatic contribution to these quantities. Copyright 1999 Academic Press.

Journal Article↗

PubMed1994

The GALEN project.

The GALEN project is developing language independent concept representation systems as the foundations for the next generation of multilingual coding systems. It aims to support the flexibility required to cope with the diversity amongst medical applications, while ensuring the coherence necessary for integration and re-use of terminologies. GALEN is developing a fully compositional and generative formal system for modelling concepts: the GALEN Representation and Integration Language (GRAIL) Kernel. Its goal is to overcome many of the problems with traditional coding and classification systems, in particular the combinatorial explosion of terms in enumerative systems and the generation of nonsensical terms in partially compositional systems. It will also provide a clean separation between the concept model and linguistic mechanisms which interpret that model (i.e., the words in a specific language, syntax, alternative phrasings, etc.) in order to allow the development of multilingual systems. GRAIL aims to be formally sound and produce models that are verifiable and contain no contradictions or ambiguities, with realistic human effort. A Coding Reference (CORE) Model of medical terminology covering is being developed which aims to represent the core concepts in for example pathology, anatomy and therapeutics, that have widespread applicability in medical applications. It should also provide the basis for specialist extensions according to the formal principles of GRAIL. The main results of GALEN will be delivered as a Terminology Server (TeS) which encapsulates and coordinates the functionality of the concept module, multilingual module, and code conversion module, and also provides a uniform applications programming interface and network services for use by external applications.

Databases, Bibliographic↗

PubMed1998

Incorporation of a set enumeration trees-based classifier into a hybrid computer-assisted diagnosis scheme for mass detection.

RATIONALE AND OBJECTIVES: The authors evaluated whether a hybrid classifier of two independent computer-aided diagnosis (CAD) schemes, the set enumeration (SE) trees approach and an artificial neural network (ANN), could improve the detection of masses on digitized mammograms. The potential benefits resulting from the interpretability of the SE trees model was also explored. MATERIALS AND METHODS: Two hundred thirty verified mass regions and 230 negative but suspicious regions were randomly selected from 618 digitized mammograms. Each region was represented by a 24-parameter feature vector. These features were used as input data for the SE trees and ANN-based schemes. After the positive and negative regions were randomly segmented into five exclusive partitions, a fivefold cross-validation method was applied to evaluate and compare the performance of the SE trees, ANN, and hybrid system in the identification of masses. RESULTS: The performance of the SE trees approach was comparable to that of the ANN. The average area under the receiver operating characteristic (ROC) curves for all five partitions was 0.88 (standard deviation, 0.04). Owing to the relatively low correlation between the region-based results of the SE trees and ANN methods, the hybrid classifier yielded a significantly improved performance, with an area under the ROC curve of 0.94 (standard deviation, 0.02; P < .05). CONCLUSION: The hybrid CAD scheme significantly improved performance. The amenability of the SE trees models to interpretation may aid in the assessment of the importance of specific features.

Artificial Intelligence↗

PubMed2005

Dogmas and misconceptions in heterogeneous photocatalysis. Some enlightened reflections.

In a recent article, Ollis analyzed heretofore reported photocatalyst kinetics of surface photochemical reactions that take place in heterogeneous systems and that rely heavily on the Langmuir-Hinshelwood (LH) kinetic model to interpret the experimental observations. This model assumes a fast adsorption/desorption equilibrium step and a subsequent slow surface step. His interesting analysis of the experimental results reported in 2000 by Emeline and co-workers, Xu and Langford, and Martyanov and Savinov prompted our reexamination of the LH kinetic model along with several other dogmas that continue to propagate in the heterogeneous photocatalytic landscape. This short article discusses some of these issues and reexamines certain misinterpretations. Specifically, we reexamine (1) the a priori assumed validity of the LH kinetic model in heterogeneous photocatalysis, (2) the recombination of photogenerated free charge carriers on the solid (metal oxide) photocatalyst by the band-to-band recombination pathway, and (3) the mistaken assertion that the kinetics of a heterogeneous photoreaction are either only first-order dependent or half-order dependent on photon flow (i.e., light irradiance).

Journal Article↗

PubMed1998

Model selection for covariance structures analysis in nursing research.

Covariance structures analysis is often used in nursing research to appraise statistical models reflecting complex human health processes. The model selection approach in covariance structures analysis is designed to select the "best" model from a specified set of theoretically defensible, competing alternatives, all of which are viewed as approximations. Model selection criteria explicitly incorporate both model misfit in the population and sampling error to evaluate the set of models. The result is that interpretability of model parameters and goodness-of-fit are enhanced simultaneously. Relative merits of the model selection approach are identified in light of technical concerns, parsimony, and use of scientific theory in nursing.

Analysis of Variance↗

PubMed2000

Light scattering and absorption model for the quantitative interpretation of human blood platelet spectral data.

Multiwavelength ultraviolet-visible (UV-Vis) transmission spectroscopy is a relatively simple technique that can provide considerable quantitative information on the properties of micron and submicron particle suspensions. Two important particle properties are particle size distribution (PSD) and chemical composition. These properties provide characteristics for the identification and classification of biological systems ranging in size and composition from proteins and nucleic acids to cells. By measuring the complete UV-Vis spectrum, the combined scattering and absorption properties are obtained as a function of wavelength. The quantitative evaluation of the size distribution and chemical composition is accomplished through the application of light-scattering theory. This paper reports on the estimation of the optical properties of human blood platelets and their use in the interpretation of platelet UV-Vis spectra within the context of Mie theory. The model developed herein provides reliable and accurate estimates for the PSD and particle number of platelet suspensions. One potential application of this characterization method is in the analysis of platelet activation by thrombin. Quantification of spectral data with respect to average particle size and particle number provides a real-time description of the dramatic changes that accompany the platelet activation process.

Blood Platelets↗