SEARCH · PubMed Health

Results for “Model interpretability”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 1,243 records · Page 69Linked to original sources

PubMed2003

A nonlinear rheological assessment of muscle recovery from eccentric stretch injury.

PURPOSE: To better understand the mechanical behavior of healing skeletal muscle; specifically the tissue's response after acute eccentric stretch injury. METHODS: Rabbit tibialis anterior (TA) muscle tendon units were subjected to an in vivo single stretch (eccentric) injury and mechanically evaluated (constant rate elongation to failure) at 1, 3, and 7 d postinjury. In addition to a traditional linear analysis (linear stiffness and failure load), an existing nonlinear rheological model was modified to interpret the experimental load-to-failure data. The models' performance were evaluated and discussed. RESULTS: No significant injury effect was observed, either within or between groups, across the 7-d healing interval, using the linear analysis. However, interpretation of the data using our nonlinear phenomenological model identified significant changes in mechanical behavior that went undetected by linear analyses. Percent differences, between injured and contralateral control limbs, of model parameter estimates were analyzed. Nonparametric statistical analysis illustrated significant changes in the first-order stiffness (k1) throughout the 7-d healing interval. Model simulations using mean values of each parameter revealed increased low-load tissue compliance after injury, with a decrease in linear slope that recovered steadily toward control values by day 7. At 7 d postinjury, virtually no differences were observed between injured and sham control tissues. CONCLUSIONS: Our findings suggest that acute eccentric injury increases the muscle's compliance 24 h after injury, with a steady recovery to uninjured values by the 7th day, yet these changes went undetected by linear analysis. Therefore, nonlinear analysis is necessary to recognize valuable information contained in the low-load region and to quantify important biomechanical phenomena of stretch-injured healing skeletal muscle.

Animals↗

PubMed1998

Age-period-cohort analysis of chronic disease rates. I: Modelling approach.

Age-Period-cohort models are widely used by epidemiologists to analyse trends in disease incidence and mortality. The interpretation of such models is fraught with difficulty in view of the exact linear dependency between the three variables. It is the purpose of this paper to review, compare and contrast some of the more common approaches to this problem based on Poisson regression and a linear model for the log rates. Also the results of using the different approaches on a single series of data on breast cancer incidence among females in Scotland from 1960-1989 are presented for comparison. Recommendations as to the merits and drawbacks of the approaches are also given in the conclusions. Models which are based upon the estimable contrasts such as local curvatures and deviations from linearity are most suitable.

Adolescent↗

PubMed2004

A growth kinetic model of Kluyveromyces marxianus cultures on cheese whey as substrate.

This work presents a multi-route, non-structured kinetic model for determination of microbial growth and substrate consumption in an experimental batch bioreactor in which beta-galactosidase is produced by Kluyveromyces marxianus growing on cheese whey. The main metabolic routes for lactose, and oxygen consumption, cell growth, and ethanol production are derived based on experimental data. When these individual rates are combined into a single growth rate, by rewriting the model equations, the model re-interpretation has a complexity similar to that of the usual variations of the Monod kinetic model, available in the literature. Furthermore, the proposed model is in good agreement with the experimental data for different growth temperatures, being acceptable for dynamic simulations, processes optimization, and implementations of model-based control technologies.

Bioreactors↗

PubMed1998

Modeling carcinogenesis under a time-changing exposure.

A model of carcinogenesis for fractionated and continuous exposure is developed. The model is discussed from two points of view. First a "surface" statistical model is introduced by making assumptions about the hazard function for the time of tumor latency. Later it is shown that the model can be interpreted in a mechanistic sense as a discrete and a mixed discrete/continuous counterpart of a model of carcinogenesis recently proposed by Yakovlev and Polig [A. Yakovlev, E. Polig, Math. Biosci. 132 (1996) 1]. Two counteracting effects are combined: a protective multiplicative effect of the exposure on the hazard function along with an additive effect of cancer induction responsible for an additional hazard. The model is used to revisit the analysis by Yakovlev et al. [A. Yakovlev, W. Müller. L. Pavlova, E. Polig, Math. Biosci. 142 (1997) 107] of lymphoma-free survival in irradiated mice under acute and fractionated exposure.

Animals↗

PubMed2003

Cerebral hemispheric specialization for spatial attention: spatial distribution of search-related eye fixations in the absence of neglect.

The "specialization" of the right hemisphere for spatial attention is widely accepted but poorly understood. While several theories have been supported by studies of patients with acute hemispatial neglect, generalizability beyond this population remains unclear. In this study, we compared the predictions of two attention models [Brain 119 (1996) 841; Trans. Am. Neurol. Assoc. 95 (1970) 143] when applied to data obtained from subjects with unilateral right- or left-cerebral lesions, but without clinical evidence of neglect during a visual search task. Both Left Lesion and Right Lesion subjects detected fewer targets in the contralesional hemispace. However, the Right Lesion subjects also made fewer visual fixations and longer saccades in the contralesional hemispace, suggesting a fundamental alteration in the architecture of visual search. The spatial distribution of fixations made by Right Lesion subjects more closely fits the prediction of a "salience" model than of the strict interpretation of a linear "gradient" model. These data support the long-standing notion of right hemisphere dominance for spatial attention, especially for the top-down processes entailed in self-directed visual search, and extend this to lesion patients without clinically evident neglect. A theoretical model based on the salience of extrapersonal space appears useful for understanding alterations of attentional allocation, particularly after recovery from stroke.

Adult↗

PubMed1999

Is there a Gulf War syndrome?

BACKGROUND: UK veterans of the Gulf War report more ill health than servicemen who were not deployed to the Gulf War. We investigated whether the pattern of symptom reporting by veterans of the Gulf War differed from that in active servicemen who had not fought in the Gulf War or who had fought in other conflicts. METHODS: We used a population-based cross-sectional design. We sent a standardised survey that asked about 50 physical symptoms to three UK military cohorts; men who had served in the Gulf War, those who had served in the Bosnia conflict, and men who had been in active service but not deployed to the Gulf War (Era cohort). We used exploratory factor analysis to identify underlying factors and describe the factor structure of the symptoms reported in the Gulf War cohort. Confirmatory factor analysis was used to test the fit of this factor structure in the Bosnia and Era cohorts. FINDINGS: Three factors in the Gulf War cohort together accounted for about 20% of the common variance. We labelled the factors mood, respiratory system, and peripheral nervous system, according to the symptoms that loaded on to them. In the confirmatory factor analysis, the factor structure identified in the Gulf War cohort fitted reasonably well in the Bosnia and Era cohorts. INTERPRETATION: Although results from complex modelling procedures need to be interpreted with caution, our findings do not support a unique Gulf War syndrome. The mechanisms behind increased self-reporting of symptoms need further investigation.

Bosnia and Herzegovina↗

PubMed2005

Protolytic surface reactions of a fluorapatite-maghemite mixture in aqueous suspension.

Synthetically prepared maghemite and fluorapatite, characterized with BET, SEM, XRD, FT-IR, and FT-Raman, are used to investigate the protolytic properties and surface characteristics in a mixed system of maghemite and fluorapatite by means of potentiometric titrations and surface complex modeling. Titrations were performed in the pH range of 7.3-10.5 at 25 +/- 0.2 degrees C in ionic media of 0.10 mol dm(-3) NaNO3 with 0.0100 mol dm(-3) HNO3 and 0.0100 mol dm(-3) NaOH used as titrants. The constant capacitance model (CCM) was applied to interpret the titration data. Two models with different surface equilibria were tested. In the first model, the mixed system was treated as a one-component system with a total surface area of 40.04 +/- 5.2 m2 g(-1) without any consideration to the subsystems. The surface equilibria, triple bond XOH + H+ <==> triple bond XOH2+, beta(s)(-11)(int) = 6.74 +/- 0.07; XOH <==> triple bond XO- + H+, beta(s)(-11)(int) = -7.75 +/- 0.07, were found to represent an accurate model for the system, and the specific capacitance was optimized to 2.0 F m(-2). The number of active surface sites N(s) was found to be 1.2 sites nm(-2). This model has, however, no relation to the subsystems of maghemite and fluorapatite. The second model is related to the subsystems and displays the surface equilibria, triple bond S2OH<==> triple bond S2O- + H+, beta(s)(-101)(int) = -9.12 +/- 0.01; triple bond FeOH + H+<==> triple bond FeOH2+, lg beta(s)(-11)(int) = 6.80 +/- 0.01; triple bond FeOH<==>FeO- + H+, beta(s)(-11)(int) = -7.77 +/- 0.01, where S2OH is related to fluorapatite and FeOH is representing maghemite. Fluorapatite corresponds to the dominating active surface in the system. The specific capacitance was optimized to 18 F m(-2). The N(s) values were found to be 2.27 sites nm(-2) for fluorapatite and 0.80 sites nm(-2) for maghemite. The N(s) values together with evidence from the FT-Raman and SEM investigations reveal that interactions between maghemite and fluorapatite surfaces occur during the titration. The acid-base properties and surface characteristics of the subsystems maghemite-H+ and fluorapatite-OH- using the CCM have been published earlier.

Journal Article↗

PubMed2000

The importance of language and culture in pediatric care: case studies from the Latino community.

BACKGROUND: Few studies have examined culture's effect on pediatric care. OBJECTIVES: To analyze 3 cases illustrating the importance of culture in pediatrics. METHODS: Case analysis with a cultural competency model. RESULTS: No interpreter was available for the parents of a 3-year-old brought to the emergency department because of abdominal pain; she was discharged twice, returned with an acute abdomen, and was hospitalized for treatment of appendiceal rupture and peritonitis. A 2-year-old fractured her clavicle in a fall but was placed in social services' custody because of a pediatrician's misinterpretation. Parents of a ventilation-dependent 2-week-old with encephalopathy, seizures, and renal failure were unaware of the infant's poor prognosis, despite use of an interpreter. CONCLUSIONS: Culture can have a significant impact on pediatric care; use of a simple model can ensure that pediatricians provide culturally competent care.

Abdominal Pain↗

PubMed2005

The cross-classified multilevel measurement model: an explanation and demonstration.

The link between the hierarchical generalized linear model (HGLM) and the Rasch model's parameterization has already been demonstrated by several researchers. Extensions have been described that include higher clustering levels to model more appropriately the contextual effects that are frequently encountered in educational research. However, pure hierarchies are relatively rare and instead cross-classified data structures are more frequently encountered. Cross-classified random effect modeling (CCREM) is still not commonly used. Use of CCREM in combination with the multilevel measurement model (MMM) has been recently introduced and is described further in the current study. Specifically, the link between the MMM and the CCREM MMM (termed "CCMMM" model) is provided. A dataset was simulated to demonstrate interpretation of the CCMMM model's parameters and to compare results under a CCMMM versus HGLM analysis. An Appendix is provided to demonstrate SAS GLIMMIX code used to estimate HGLM and CCMMM models' parameters.

Data Interpretation, Statistical↗

PubMed1995

The use of decision analysis in the pharmacoeconomic evaluation of an antidepressant: a cost-effectiveness study of nefazodone.

A decision model can be a useful tool for evaluating the cost-effectiveness of a drug during research and development, before the drug is marketed. Decision analysis provides a structured process for comparing the costs and consequences of a new drug with those of standard drug therapy. This article introduces the use of a decision model and discusses the advantages and disadvantages of such a model. A cost-utility study of nefazodone, a new antidepressant, illustrates the application and interpretation of decision models. Decision analyses using data from clinical trials are a great potential source of information on the economic impact of new drugs. However, the development and use of such models require tolerance of uncertainty, the ability to represent complex relationships accurately, awareness of all factors that might influence the results, and a willingness to validate the model to the extent that validation is possible. The disadvantage of clinical decision models is that the findings are only as reliable as the information on which the model is based. Nevertheless, sensitivity analyses can be used to vary any information in question and assess the impact of that variation on the findings of the analyses. The advantage of clinical decision models is that they encourage the consideration and explicit representation of all pertinent inputs and outcomes. They clearly differentiate knowledge supported by data from assumptions, and compel assessment of the effect of those assumptions on the findings. The cost-effectiveness of nefazodone relative to standard treatment for major depression was evaluated using a decision model that simulated the lifetime direct medical costs and health outcomes associated with nefazodone and two comparators, imipramine and fluoxetine. The model included the possible clinical management pathways and the use of medical resources in treating major depression from early adulthood until death. Sensitivity analyses were performed to determine the impact of variation in model parameters on the results of the model. Using the base case assumptions of the model, which included parity of pricing with fluoxetine, nefazodone was found to be a cost-effective treatment for major depression.

Antidepressive Agents↗

PubMed2003

A proposal for a goodness-of-fit test to the Arnason-Schwarz multisite capture-recapture model.

In an analysis of capture-recapture data, the identification of a model that fits is a critical step. For the multisite (also called multistate) models used to analyze data gathered at several sites, no reliable test for assessing fit is currently available. We propose a test for the JMV model, a simple generalization of the Arnason-Schwarz (AS) model, in the form of interpretable contingency tables. For the AS model, we suggest complementing the test for the JMV model with a likelihood ratio test of AS vs. JMV. The examination of an example leads us to propose further a partitioning that emphasizes the role of the memory model of Brownie et al. (1993 Biometrics 49, 1173-1187) as a biologically more plausible alternative to the AS model.

Animals↗

PubMed2026

Knowledge-driven interpretable neural networks provide mechanistic insight.

Analyzing omics data in the context of pathway knowledge is critical for understanding the molecular mechanisms underlying pathological changes. However, current pathway analysis methods do not model the detailed mechanistic nature of biological interactions, limiting the understanding of pathway behavior to a relatively shallow level. To address this issue, we present a knowledge-driven machine learning framework that embeds features into pathway graphs and models reactions analytically, producing interpretable feature hierarchies and subnetworks in which functional associations are estimated to model biological interactions. The approach is agnostic to feature selection, enabling the use of full omics data sets without discarding weak signals. Applications to breast cancer microRNA-gene regulation data and COVID-19 metabolomic data highlight immune and metabolic pathways relevant to disease progression. This framework bridges predictive modeling with mechanistic interpretation and offers a foundation for integrative pathway analysis.

Humans↗

PubMed2003

A light distribution model for an internally radiating photobioreactor.

Analysis of light energy distribution in culture is important for maximizing the growth efficiency of photosynthetic cells and the productivity of a photobioreactor. To characterize the irradiance conditions in a photobioreactor, we developed a light distribution model for a single-radiator system and then extended the model to multiple radiators using the concept of parallel translation. Mathematical expressions for the local light intensity and the average light intensity were derived for a cylindrical photobioreactor with multiple internal radiators. The proposed model was used to predict the irradiance levels inside an internally radiating photobioreactor using Synechococcus sp. PCC 6301 as a model photosynthetic microorganism. The effects of cell density and radiator number were interpreted through photographic and model simulation studies. The predicted light intensity values were found to be very close to those obtained experimentally, which suggests that the proposed model is capable of accurately interpreting the local light energy profiles inside the photobioreactor system. Due to the simplicity and flexibility of the proposed model, it was also possible to predict the light conditions in other complex photobioreactors, including optical-fiber and pond-type photobioreactors.

Bioreactors↗

PubMed1981

Strength-interval relations in a chronic canine model of myocardial infarction. Implications for the interpretation of electrophysiologic studies.

Fifteen adult mongrel dogs underwent two-stage occlusion of the mid- or distal left anterior descending coronary artery and then a reperfusion stage. The dogs were studied 3-30 days later to determine strength-interval relations in a canine model of chronic myocardial infarction. These dogs were susceptible to the initiation of sustained ventricular tachyarrhythmias with the introduction of one, two or three ventricular extrastimuli. Using unipolar cathodal stimuli with a pulse width of 2 msec, strength-interval curves were constructed from measurements made at multiple sites in the distribution of occluded and nonoccluded vessels during drive pacing at a cycle length of 300 msec. At 56 normal sites, ventricular refractory periods measured at twice-diastolic-excitability threshold approximated the relative refractory periods (mean absolute difference 3 msec), but were variably longer than effective refractory periods (mean difference 18 msec, range 4-29 msec). At 51 infarct sites, differences between ventricular refractory periods measured at twice-diastolic-excitability threshold and both relative refractory periods (mean difference 13 msec, range -60 to +18 msec) and effective refractory periods (mean difference 28 msec, range 1-60 msec) were markedly disparate. These differences were further exaggerated after administration of i.v. procainamide. These findings suggest limitations in interpreting the results of programmed pacing studies performed using stimuli of twice-threshold intensity.

Animals↗

PubMed2002

Word frequency and receiver operating characteristic curves in recognition memory: evidence for a dual-process interpretation.

Dual-process models of the word-frequency mirror effect posit that low-frequency words are recollected more often than high-frequency words, producing the hit rate differences in the word-frequency effect, whereas high-frequency words are more familiar, producing the false-alarm-rate differences. In this pair of experiments, the authors demonstrate that the analysis of receiver operating characteristic (ROC) curves provides critical information in support of this interpretation. Specifically, when participants were required to discriminate between studied nouns and their plurality reversed complements, the ROC curve was accurately described by a threshold model that is consistent with recollection-based recognition. Further, the plurality discrimination ROC curves showed characteristics consistent with the interpretation that participants recollected low-frequency items more than high-frequency items.

Association Learning↗

PubMedDate not supplied

Model systems of prostate cancer: uses and limitations.

A valid experimental model system reflects the system under study and is reproducible. Model systems of prostate cancer that accurately reflect the different disease stages are necessary to ensure a proper experimental design aimed at increasing our understanding of the biology of the disease and such models are essential tools to accelerate development of new therapies for prostate cancer. Until recently, a limited number of experimental systems were available and more suitable models derived from human specimens have only recently been developed and become available for use. In addition, transgenic techniques have also permitted the development of unique mouse models. The difficulty in establishing model systems may reflect the complex requirements necessary for cancer progression and should lead us to interpret results from model systems with caution. It is unlikely that a single model system that faithfully reflects the whole process of cancer development and progression will be developed. However, thoughtful use of the available model systems will permit the study of a significant portion of prostate cancer progression. In this review we summarize the properties of the prostate cancer model systems in use and defined their utility and limitations. This review will guide the investigator seeking models with which to test specific hypotheses pertaining to prostate cancer.

Animals↗

PubMed2005

Modeling growth of Clostridium perfringens in pea soup during cooling.

Clostridium perfringens is a pathogen that mainly causes food poisoning outbreaks when large quantities of food are prepared. Therefore, a model was developed to predict the effect of different cooling procedures on the growth of this pathogen during cooling of food: Dutch pea soup. First, a growth rate model based on interpretable parameters was used to predict growth during linear cooling of pea soup. Second, a temperature model for cooling pea soup was constructed by fitting the model to experimental data published earlier. This cooling model was used to estimate the effect of various cooling environments on average cooling times, taking into account the effect of stirring and product volume. The growth model systematically overestimated growth of C. perfringens during cooling in air, but this effect was limited to less than 0.5 log N/ml and this was considered to be acceptable for practical purposes. It was demonstrated that the growth model for C. perfringens combined with the cooling model for pea soup could be used to sufficiently predict growth of C. perfringens in different volume sizes of pea soup during cooling in air as well as the effect of stirring, different cooling temperatures, and various cooling environments on the growth of C. perfringens in pea soup. Although fine-tuning may be needed to eliminate inaccuracies, it was concluded that the combined model could be a useful tool for designing good manufacturing practices (GMP) procedures.

Animals↗

PubMed2002

Mathematical models of human CD4+ T-cell population kinetics.

We review how mathematical models help the interpretation of data measuring CD4+ T-cell kinetics by two recently-developed techniques. Mathematical models are developed for the average content of T-cell receptor excision circles (TRECs) and the average telomeric restriction fragment (TRF) in T-cells in the peripheral blood. Changes in the TRECs were supposed to indicate changes in thymic production. The rate at which naive and memory CD4+ T-cells erode their telomeres was supposed to reflect their respective division rates. Analysing the mathematical models, we show that rapid changes in the TRECs per naive T-cell are most likely due to changes in the division rates, and that the rates of telomere erosion fail to reflect naive and memory division rates. The model is applied to explain data showing that rheumatoid arthritis (RA) patients have abnormal TRECs and telomeres.

Arthritis, Rheumatoid↗