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Results for “Model explainability”

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At least 451 records · Page 25Linked to original sources

PubMed2026

The Impact of Chatbot Type and Normative Messaging on Chatbot Usage Intention Based on the Health Technology Acceptance Model: Randomized Controlled Trial.

BACKGROUND: Digital health tools, such as health chatbots, may improve access to scalable health support, but adoption remains inconsistent. Existing models do not fully integrate technology acceptance factors with health motivation factors relevant to digital health use. OBJECTIVE: This study proposed and tested the health technology acceptance model and examined whether normative message framing and chatbot type were associated with health motivation, technology acceptance, and intention to use a health chatbot. METHODS: In October 2025, we conducted a 4 × 2 between-participants online experiment with 1000 US adults recruited from a nationally representative YouGov panel. Participants were randomized to 1 of 8 conditions varying norm message type (self-oriented, peer-oriented, expert-oriented, or family-oriented) and chatbot type (AI-powered or rule-based) in a cancer prevention and genetic risk information scenario. Outcomes included descriptive norms, injunctive norms, perceived susceptibility, perceived severity, perceived benefits, self-efficacy, perceived ease of use, trust, privacy concerns, and usage intention. Data were analyzed using a multivariate ANOVA with Bonferroni-adjusted post hoc tests and multiple linear regression. RESULTS: Peer-oriented and family-oriented messages produced higher usage intention than expert-oriented messages, and peer-oriented messages also increased descriptive norms, injunctive norms, self-efficacy, and trust. AI-powered chatbots were associated with higher usage intention (P=.02) and greater trust (P=.008) than rule-based chatbots. In regression analyses, the model explained 50.8% of the variance in usage intention. Usage intention was positively associated with descriptive norms (β=0.087; P=.003), injunctive norms (β=0.078; P=.009), perceived susceptibility (β=0.051; P=.03), perceived benefits (β=0.253; P<.001), and trust (β=0.33; P<.001), and negatively associated with perceived severity (β=-0.047; P=.049) and privacy concerns (β=-0.11; P<.001). Perceived ease of use and self-efficacy were not significant predictors. CONCLUSIONS: The health technology acceptance model was a useful framework for explaining the intention to use a health chatbot by combining technology acceptance and health motivation constructs. Both social design features and chatbot design features shaped adoption-related beliefs, with peer-oriented and family-oriented framing and AI-powered chatbots showing particular promise. Trust and privacy concerns remained central determinants of intended use.

Humans↗

PubMed1997

Evolution and human choice over time.

This chapter reviews previous work on an evolutionary model describing the effect of time delays on human preferences. The model explains why the long-term real interest rate is usually near 3% and why rates of crime and driving accidents are highest among young adults. It does not succeed in explaining the phenomenon of preference reversal. The chapter reports new results on uncertainty and on a more comprehensive model allowing consumption to have simultaneous effects on mortality and fertility.

Adaptation, Psychological↗

PubMed2005

Cell distribution profiles in three-dimensional scaffolds with inverted-colloidal-crystal geometry: modeling and experimental investigations.

Limited ingrowth of stromal cells is observed when a three-dimensionally ordered scaffold possessing inverted-colloidal-crystal geometry is used to culture adherent cells. In this work, a computational model explaining, as well as predicting, experimental cell distributions is developed. It incorporates a modified Contois cell-growth model that includes the effects of nutrient saturation, competitive product inhibition, and cell-contact inhibition to describe the scaffold-cell system. Our results agree with the hypothesis that the rapid growth of cells on the surface of the scaffold depletes the nutrient supply to the core, resulting in the preferential growth on the exterior of the scaffold. When the cells are cultured in a scaffold subjected to a uniform velocity field, they penetrate to a greater extent into the scaffold core. Alternative seeding and culture strategies are suggested and evaluated.

Biocompatible Materials↗

PubMed2001

Energy dissipation in photosynthesis: does the quenching of chlorophyll fluorescence originate from antenna complexes of photosystem II or from the reaction center?

Dissipation of light energy was studied in the moss Rhytidiadelphus squarrosus (Hedw.) Warnst., and in leaves of Spinacia oleracea L. and Arabidopsis thaliana (L.) Heynh., using chlorophyll fluorescence as an indicator reaction. Maximum chlorophyll fluorescence of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU)-treated spinach leaves, as produced by saturating light and studied between and -20 degrees C, revealed an activation energy delta E of 0.11 eV. As this suggested recombination fluorescence produced by charge recombination between the oxidized primary donor of photosystem II and reduced pheophytin, a mathematical model explaining fluorescence, and based in part on known characteristics of primary electron-transport reactions, was developed. The model permitted analysis of different modes of fluorescence quenching, two localized in the reaction center of photosystem II and one in the light-harvesting system of the antenna complexes. It predicted differences in the relationship between quenching of variable fluorescence Fv and quenching of basal, so-called F0 fluorescence depending on whether quenching originated from antenna complexes or from reaction centers. Such differences were found experimentally, suggesting antenna quenching as the predominant mechanism of dissipation of light energy in the moss Rhytidiadelphus, whereas reaction-center quenching appeared to be important in spinach and Arabidopsis. Both reaction-center and antenna quenching required activation by thylakoid protonation but only antenna quenching depended on or was strongly enhanced by zeaxanthin. De-protonation permitted relaxation of this quenching with half-times below 1 min. More slowly reversible quenching, tentatively identified as so-called qI or photoinhibitory quenching, required protonation but persisted for prolonged times after de-protonation. It appeared to originate in reaction centers.

Bryopsida↗

PubMed2006

The origin of allometric scaling laws in biology.

The empirical rules relating metabolic rate and body size are described in terms of (i) a scaling exponent, which refers to the ratio of the fractional change in metabolic rate to a change in body size, (ii) a proportionality constant, which describes the rate of energy expenditure in an organism of unit mass. This article integrates the chemiosmotic theory of energy transduction with the methods of quantum statistics to propose a molecular mechanism which, in sharp contrast to competing models, explains both the variation in scaling exponents and the taxon-specific differences in proportionality constants. The new model is universal in the sense that it applies to unicellular organisms, plants and animals.

Animals↗

PubMed2006

Testing a pharmacist-patient relationship quality model among older persons with diabetes.

BACKGROUND: Considering recent changes to the Medicare program, pharmacists will have unique opportunities to be reimbursed for providing Medication Therapy Management Services to older persons with diabetes. A high-quality pharmacist-patient relationship can lay the foundation for effective provision of Medication Therapy Management Services and improved care in this cohort. OBJECTIVE: To test a pharmacist-patient relationship quality model in a group of older persons with diabetes from the patient's perspective. Antecedents to relationship quality were pharmacist participative behavior/patient-centeredness of relationship, patient participative behavior, and pharmacist-patient interpersonal communication. Pharmacist-patient relationship commitment was the outcome of relationship quality studied. METHODS: Data were collected via mailed questionnaire from a random sample of 600 community-dwelling adults in the United States who (1) were 65 years of age and older, (2) had type 1 or type 2 diabetes, (3) used at least one prescription medication to treat their diabetes, and (4) used some type of nonmail order pharmacy as their primary source of obtaining prescription medications. Model relationships were tested using path analysis. RESULTS: The adjusted response rate was 41.6% (221/531). The models explained 47% and 49% of the variance in relationship quality and relationship commitment, respectively. In the relationship quality model, pharmacist participative behavior/patient-centeredness of relationship (beta=.51, P<.001) and pharmacist-patient interpersonal communication (beta=.17, P=.008) had direct effects on relationship quality. In the relationship commitment model, relationship quality had a direct effect on relationship commitment (beta=.60, P<.001). Pharmacist participative behavior/patient-centeredness and pharmacist-patient interpersonal communication had indirect effects on relationship commitment through their effects on relationship quality, which is a mediator in the model. CONCLUSIONS: Results affirm findings from previous research showing that patients' perceptions of pharmacist participative behavior/patient-centeredness of relationship and pharmacist-patient interpersonal communication are positively related to perceptions of relationship quality. Also, relationship quality is a strong mediator between pharmacist participative behavior/patient-centeredness of relationship and relationship commitment, as well as between pharmacist-patient interpersonal communication and relationship commitment.

Age Factors↗

PubMedDate not supplied

In silico studies toward the discovery of new anti-HIV nucleoside compounds with the use of TOPS-MODE and 2D/3D connectivity indices. 1. Pyrimidyl derivatives.

Computational approaches are developed to design or rationally select, from structural databases, pyrimidyl nucleosides with anti-HIV activity. A data set of 141 nucleoside derivatives was selected from literature, and a discriminant function was derived with the use of TOPS-MODE descriptors. The model is able to classify correctly 83% of the compounds in a training set and 88.5% in a cross-validation set. The use of an external prediction set selected from the most recent literature proved that the model has good predictive ability, with a good classification of 85% of the compounds in this set. This model permitted the structural interpretation of the anti-HIV activity of these nucleoside analogues. This interpretation is formulated as several rules concerning the influence of several structural features on the activity/inactivity of such compounds. A QSAR model for the most active compounds was developed with the combined use of 2D and 3D connectivity indices. This model explains 88% of the variance in the activity of these compounds in MT4 assay. The combination of both models will permit the selection of pyrimidyl nucleoside leads and their optimization to improve the potency of the selected ones.

Anti-HIV Agents↗

PubMedDate not supplied

Comparative protein modeling of 1-deoxy-D-xylulose-5-phosphate reductoisomerase enzyme from Plasmodium falciparum: a potential target for antimalarial drug discovery.

Plasmodium falciparum 1-deoxy-D-xylulose-5-phosphate reductoisomerase (Pf-DXR) is a potential target for antimalarial chemotherapy. The three-dimensional model (3D) of this enzyme was determined by means of comparative modeling through multiple alignment followed by intensive optimization, minimization, and validation. The resulting model demonstrates a reasonable topology as gauged from the Ramachandran plot and acceptable three-dimensional structure compatibility as assessed by the Profiles-3D score. The modeled monomeric subunit consists of three domains: (1) N-terminal NADPH binding domain, (2) connective or linker domain (with most of the active site residues located in this domain), and (3) a C-terminal domain. This structure proved to be consistent with known DXR crystal structures from other species. The predicted active site compared favorably with those of the templates and appears to have an active site with a highly conserved architecture. Additionally, the model explains several site-directed mutagenesis data. Besides using several protein structure-checking programs to validate the model, a set of known inhibitors of DXR were also docked into the active site of the modeled Pf-DXR. The docked scores correlated reasonably well with experimental pIC50 values with a regression coefficient (R2) equal to 0.84. Results of the current study should prove useful in the early design and development of inhibitors by either de novo drug design or virtual screening of large small-molecule databases leading to development of new antimalarial agents.

Aldose-Ketose Isomerases↗

PubMed2002

A reaction-diffusion model for interference in meiotic crossing over.

One crossover point between a pair of homologous chromosomes in meiosis appears to interfere with occurrence of another in the neighborhood. It has been revealed that Drosophila and Neurospora, in spite of their large difference in the frequency of crossover points, show very similar plots of coincidence-a measure of the interference-against the genetic distance of the interval, defined as one-half the average number of crossover points within the interval. We here propose a simple reaction-diffusion model, where a "randomly walking" precursor becomes immobilized and matures into a crossover point. The interference is caused by pair-annihilation of the random walkers due to their collision and by annihilation of a random walker due to its collision with an immobilized point. This model has two parameters-the initial density of the random walkers and the rate of its processing into a crossover point. We show numerically that, as the former increases and/or the latter decreases, plotted curves of the coincidence vs. the genetic distance converge on a unique curve. Thus, our model explains the similarity between Drosophila and Neurospora without parameter values adjusted finely, although it is not a "genetic model" but is a "physical model," specifying explicitly what happens physically.

Crossing Over, Genetic↗

PubMed1983

Evidence of the validity of a model of determinants of quality of restorative dental care.

A model describing the relationship between self-reported quality of restorative dentistry and dentist characteristics for 119 Montana general dentists is presented. The best predictors formed a significant model explaining 22% of the variance of the quality measure. Results are contrasted with a previous estimation of the model for 102 Washington general practitioners. Evidence for the external validity of the model is presented.

Adult↗

PubMed2004

Reconcilable differences: a cross-sectional study of the relationship between socioeconomic status and the magnitude of short-acting beta-agonist use in asthma.

STUDY OBJECTIVE: To assess the association between socioeconomic status (SES) and short-acting (SA) beta-agonist use, controlling for asthma severity. DESIGN: Cross-sectional study. SETTING: Vancouver, BC, Canada. PARTICIPANTS: Two hundred two asthmatics between 19 years and 50 years of age and residing in the greater Vancouver regional district. MEASUREMENTS: The quantity of SA beta-agonist used in the previous year was collected by self-report; pulmonary function and beta-receptor genotype were measured on each participant. SES was measured at both the individual and population levels. Five methods of adjustment for asthma severity were used, as follows: the Canadian Asthma Consensus Guidelines, three previously developed asthma-severity scores, and forward stepwise multiple regression modeling. Polychotomous logistic regression was used to assess all relationships. RESULTS: Independent of the method used to measure SES or adjust for asthma severity, lower SES was consistently and significantly associated with the use of greater amounts of SA beta-agonist. Adjusting for severity using the multivariate model explained the most variance of SA beta-agonist use (R(2) adjusted, 0.35 to 0.37). In this model, social assistance recipients were more likely to use greater amounts of SA beta-agonist (odds ratio [OR], 3.4; 95% confidence interval [CI], 1.7 to 6.5). An inverse relationship between SA beta-agonist use and both annual household income (> $50,000; OR, 0.28; 95% CI, 0.13 to 0.60; and $20,000 to $50,000; OR, 0.44; 95% CI, 0.21 to 0.96; relative to <$20,000) and education (completing a bachelor's degree vs no formal education; OR, 0.25; 95% CI, 0.14 to 0.71). Participants living in a neighborhood with higher median household income (OR, 0.91; 95% CI, 0.84 to 0.98 per $1,000 increase) or a higher prevalence of having attained a bachelor's degree (OR, 0.96; 95% CI, 0.84 to 0.98 per 1% increase) were also less likely use greater amounts of SA beta-agonist. Results were consistent for neighborhood unemployment rate. CONCLUSIONS: The social gradient in asthma-related outcomes may be at least partially attributable to poorer asthma control in lower-SES asthmatics.

Adrenergic beta-Agonists↗

PubMed2003

Microbiology's principle of biofilms as a major factor in the pathogenesis of acne vulgaris.

Propionibacterium acnes reside within the pilosebaceous unit in a biofilm. As such, they live in a community of bacteria that encase themselves within an extracellular polysaccharide lining, which the organisms secrete after adherence to the surface. This gylcocalyx polymer acts as a protective exoskeleton and serves as a physical barrier, limiting effective antimicrobial concentrations within the biofilm microenvironment. The gylcocalyx polymer secreted by P. acnes as a biofilm may explain the immunogenicity of the organism as well as the clinical course of the disease. The P. acnes' biofilm model explains many aspects of acne pathogenesis and therapy, including why prolonged antibiotic treatment is needed, why antibiotic resistance is not a reliable assessment of treatment outcome, why accutane offers long-lasting effectiveness, and why benzoyl peroxide radicals are beneficial. This microbiologic principle of biofilms as applied to acne leads to numerous new pathways of assessment and exploration.

Acne Vulgaris↗

PubMed2001

Abdominal visceral fat and fasting insulin are important predictors of 24-hour GH release independent of age, gender, and other physiological factors.

Numerous physiological factors modulate GH secretion, but these variables are not independent of one another. We studied 40 younger (20-29 yr.; 21 men and 19 women) and 62 older (57-80 yr.; 35 men and 27 women) adults to determine the contributions of several demographic and physiological factors to the variability in integrated 24-h GH concentrations. Serum GH was measured every 10 min for 24 h in an enhanced sensitivity chemiluminescence assay. The predictor variables included: age group (young or old), gender, abdominal visceral fat (by computed tomography), total body fat mass and percentage body fat by dual-energy x-ray absorptiometry, serum IGF-I, fasting serum insulin, 24-h mean estradiol and testosterone, and peak oxygen uptake by graded exercise (treadmill) testing. Multiple ordinary least squares regression analysis was used to quantitatively assess the individual contribution that each predictive measure made to explain the variability among values of integrated 24-h GH concentrations while in the presence of the remaining predictors. The model explained 65% of the variance in integrated 24-h GH concentrations. Abdominal visceral fat (P < 0.002) and fasting insulin (P < 0.008) were consistently important predictors of integrated 24-h GH concentrations independent of age group, gender, and all other predictor variables. Although serum IGF-I was an important overall predictor of integrated 24-h GH concentrations (P = 0.002), this relationship was present only in the young subjects and was modulated by gender. The remaining variables failed to contribute significantly to the model. We conclude that abdominal visceral fat and fasting insulin are important predictors of integrated 24-h GH concentrations in healthy adults, independent of age and gender. Serum IGF-I is an important predictor of integrated 24-h GH concentrations in young but not older subjects. Bidirectional feedback between each of these three factors and GH secretion may account for the strong relationships observed.

Abdomen↗

PubMed1999

Three-dimensional high-resolution particle tracking for optical tweezers by forward scattered light.

A quadrant photodiode placed in the back-focal plane of the microscope of a laser trap provides a high-resolution position sensor. We show that in addition to the lateral displacement of a trapped sphere, its axial position can be measured by the ratio of the intensity of scattered laser light to the total amount of the light reaching the detector. The addition of the axial information offers true three-dimensional position detection in solution, creating, together with a position control, a photonic force microscope with nanometer spatial and microsecond temporal resolution. The measured position signals are explained as interference of the unscattered trapping laser beam with the laser light scattered by the trapped bead. Our model explains experimental data for trapped particles in the Rayleigh regime (radius a <0.2lambda) for displacements up to the focal dimensions. The cross-talk between the signals in the three directions is explained and it is shown that this cross-talk can be neglected for lateral displacements smaller than 75 nm and axial displacements below 150 nm. The advantages of three-dimensional single-particle tracking over conventional video-tracking are shown through the example of the diffusion of the GPI-anchored membrane protein Thy1.1 on a neurite.

Animals↗

PubMed1994

Statistical model for prediction of retrospective exposure to ethylene oxide in an occupational mortality study.

Since direct measures of individual exposure seldom exist for the entire period of an occupational mortality study, retrospective exposure estimates are necessary. This is often done in a subjective manner involving a consensus of opinion from a panel of epidemiologists and industrial hygienists. An alternative method utilizing a statistical model provides a more objective procedure for retrospective exposure assessment. The development of a weighted multiple regression model is presented for estimation of exposure levels to ethylene oxide (ETO) for inclusion in a cohort mortality study of workers in the sterilization industry. Three steps in development of the model are described: (1) data acquisition and assessment, (2) model building, and (3) evaluation of the model. The final model explained a remarkable 85% of the variability in 205 average measurements of ETO levels. Exposure factors included in the model were exposure category, product type, size of the sterilization unit, selected engineering controls, days after sterilization, and calendar year. The model was evaluated in two ways: against a set of measurement data not used to develop the model and a panel of 11 industrial hygienists representing the sterilization industry. The model predicted ETO exposures within 1.1 ppm of the validation data set with a standard deviation of 3.7 ppm. The arithmetic and geometric means of the 46 measurements in the validation data set were 4.6 and 2.2 ppm, respectively. The model also outperformed the panel of industrial hygienists relative to the validation data in terms of both bias and precision.

Ethylene Oxide↗

PubMed1986

Genetics of a wild population of rhesus monkeys (Macaca mulatta): II. The Dunga Gali population in species-wide perspective.

Genetic variability in a population of wild rhesus monkeys near the village of Dunga Gali, Northwest Frontier Province, Pakistan (Melnick et al., Am. J. Phys. Anthropol. 63:341-360, 1984) was compared to similar variation in other wild-caught rhesus monkeys. Regional samples of rhesus from different parts of Asia all displayed similar amounts of variation (i.e., P and Hi) and were consistently more variable than the Dunga Gali local population. Despite these differences in the level of genetic variation, genetic diversity is fairly evenly distributed across the species range. Thus only 3-9% of the total gene diversity of Macaca mulatta can be attributed to differences among major regions. The differences that do exist tend toward a weak geographic cline with clustering of populations into an eastern and a western group. Both selection and drift/migration models explain this general genetic homogeneity. More genetic (protein and DNA) and zoogeographic data are necessary to choose between these models.

Alleles↗

PubMed1999

Prediction of visceral adipose tissue from simple anthropometric measurements in youths with obesity.

OBJECTIVE: Although visceral adipose tissue (VAT) is the component of body composition most highly associated with cardiovascular risk factors, its measurement requires expensive procedures, such as magnetic resonance imaging. This study examined the ability of simple demographic and anthropometric measurements to predict magnetic resonance imaging-derived VAT in 76 apparently healthy, black and white youths with obesity who were 7 years to 16 years of age. RESEARCH METHODS AND PROCEDURES: Stepwise multiple linear regression was used to develop a prediction equation for VAT based on 13 simple anthropometric variables (height, weight, body mass index, triceps skinfold, calf skinfold, sagittal diameter, waist circumference, hip circumference, thigh circumference, waist/hip ratio, waist/thigh ratio, sagittal diameter/thigh ratio, and percent body fat from the sum of calf and triceps skinfolds) and three demographic variables (age, gender and ethnicity). RESULTS: The stepwise multiple regression procedure yielded a final model that included two anthropometric variables (sagittal diameter and waist/hip ratio) and one demographic variable (ethnicity). The prediction equation was: VAT = - 124.06+ 16.67 (ethnicity)+4.15 (sagittal diameter)+100.89 (waist/hip ratio), where ethnicity was coded as 0= black and 1 = white. The model explained 63% of the variance in VAT and was associated with a measurement error of 23.9%. DISCUSSION: Although the model seems to lack sufficient explanatory power for routine use in clinical settings with individual patients, it may have some utility in epidemiological studies given its relatively small (<25%) standard error of estimate.

Adipose Tissue↗

PubMed1996

Diet and plasma lipids in women. I. Macronutrients and plasma total and low-density lipoprotein cholesterol in women: the Framingham nutrition studies.

This study examined relationships between diet and plasma total and LDL cholesterol levels in a population-based sample of 695 premenopausal and 727 postmenopausal women participating in the Framingham Offspring/Spouse Study. Regression analyses controlled for age, caloric intake, apolipoprotein E isoform type, estrogen use, and important CVD risk factors indicated that plasma total and LDL-cholesterol levels were directly associated with consumption of saturated fat and inversely associated with total calorie intake. In contrast, dietary cholesterol was not a predictor of plasma total or LDL cholesterol levels. Total cholesterol levels were also directly associated with total fat, oleic acid, and animal fat, and inversely associated with carbohydrate intake. Stepwise regressions with key nutrients indicated that saturated fat was consistently associated with total and LDL cholesterol levels in Framingham women. These analyses suggest that diet explains 2% of the variability in these lipid levels in a cross-sectional sample of women; the full model explains 22-27%.

Adult↗