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[Foundation of the bineme model for eukaryote chromosome].

The fitness of two alternative chromosome models (unineme and bineme) to the vast body of biochemical, genetic, radiobiological and ultrastructural data is tested. Unineme model postulates the existence of only one DNA molecule (Watson--Crick double helix) per higher eukaryote chromosome at the G1 stage of the cell cycle. The bineme model postulates that eukaryotic G1-chromosome in higher eukaryotes consists of two homologous DNA molecules connected at the telomere and thus forming a circle. Comparative analysis shows that contemporary data favour the bineme model and disagree considerably with the unineme model.

Animals↗

Ontological foundations for biology knowledge models.

This paper analyzes the ontological requirements for representing biology knowledge, and identifies several areas where current knowledge representation (KR) paradigms need to be extended. We focus on the representation of experimental materials and methods, and the reasoning task of intelligent information retrieval; however, the ontological issues we raise apply to biology (and experimental sciences) in general. We have identified two important concept types in molecular biology that cause problems for standard knowledge models: 1) complex substances such as mixtures and nucleic acid sequences; 2) transformations (such as biochemical reactions) that convert one substances into another. We describe these problems, propose solutions for some of them, and given examples of the need for such knowledge representations in intelligent information retrieval.

Models, Biological↗

Multimodel ranking and inference in ground water modeling.

Uncertainty of hydrogeologic conditions makes it important to consider alternative plausible models in an effort to evaluate the character of a ground water system, maintain parsimony, and make predictions with reasonable definition of their uncertainty. When multiple models are considered, data collection and analysis focus on evaluation of which model(s) is(are) most supported by the data. Generally, more than one model provides a similar acceptable fit to the observations; thus, inference should be made from multiple models. Kullback-Leibler (K-L) information provides a rigorous foundation for model inference that is simple to compute, is easy to interpret, selects parsimonious models, and provides a more realistic measure of precision than evaluation of any one model or evaluation based on other commonly referenced model selection criteria. These alternative criteria strive to identify the true (or quasi-true) model, assume it is represented by one of the models in the set, and given their preference for parsimony regardless of the available number of observations the selected model may be underfit. This is in sharp contrast to the K-L information approach, where models are considered to be approximations to reality, and it is expected that more details of the system will be revealed when more data are available. We provide a simple, computer-generated example to illustrate the procedure for multimodel inference based on K-L information and present arguments, based on statistical underpinnings that have been overlooked with time, that its theoretical basis renders it preferable to other approaches.

Evaluation Studies as Topic↗

Health care organization and incentives under emerging models of elderly health care.

Health providers are rapidly establishing integrated delivery systems to prepare for managed care and capitation. However, acute and primary services for the elderly continue to be reimbursed through DRGs or fee-for-service (FFS) payments. Different incentives and care patterns are described for providers caring for elderly populations and younger, capitated groups. Pilot programs to provide Medicare services to the elderly may become models or foundations for a future, capitated health system for the elderly. Existing models of elderly health care that receive capitated payments are described in this article, including Social HMOs, TEFRA HMOs. and PACE programs. The potential significance of these programs for the synchrony of operational incentives, comprehensiveness of health care, volume of institutional services, and primary care orientation is analyzed.

Aged↗

Exploring the possible reasons why the UK Government commended the EFQM (European Foundation for Quality Management) excellence model as the framework for delivering governance in the new NHS.

A brief introduction into recent developments of the EFQM Excellence Model and the United Kingdom (UK) Government's agenda for ensuring that quality is at the heart of all decision making is given. In view of the Government explicitly commending the use of the EFQM Excellence Model to all organisations within the National Health Service, the author decides to explore the possible reasons behind the commendation. When comparing the EFQM Excellence Model with the Government's vision for quality, the former emerges as a more than ideal tool for any organisation wishing to commence or strengthen their journey on the road to quality and/or excellence; particularly as the EFQM Excellence Model is based on the principles of self-assessment, continuous improvement, learning and innovation, teamwork and a culture totally focused on the customer. Finally, ten possible reasons behind the Government commending the use of the Model are given.

Benchmarking↗

Modeling multiphase migration of organic chemicals in groundwater systems--a review and assessment.

Over the past two decades, a number of models have been developed to describe the multiphase migration of organic chemicals in the subsurface. This paper presents the state-of-the-art with regard to such modeling efforts. The mathematical foundations of these models are explored and individual models are presented and discussed. Models are divided into three groups: a) those that assume a sharp interface between the migrating fluids; b) those that incorporate capillarity; and c) those that consider interphase transport of mass. Strengths and weaknesses of each approach are considered along with supporting data for model validation. Future research directions are also highlighted.

Capillary Action↗

The North Carolina Breast Cancer Screening Program: foundations and design of a model for reaching older, minority, rural women.

Breast cancer screening programs do not reach all women at the same rate. Screening mammography use varies according to sociodemographic characteristics; mammography utilization is highest among women in their fifties but then decreases with age. In North Carolina, breast cancer is a particular burden for Black and lower-income women. Black women are more likely to be diagnosed with late stage disease, and their rate of breast cancer mortality is higher than it is for White women even though the incidence in White women is greater. Older, Black, and low-income women are less likely to obtain screening by mammography and clinical breast examination. The Black-White gap is even more pronounced among rural women, in part because they are more likely to be poor. The North Carolina Breast Cancer Screening Program (NC-BCSP) was established to increase the rate of regular mammography screening by an absolute 20% in 3 years among older Black women ages 50 and older in five rural counties in the eastern part of the state. In this paper, we describe the genesis of this comprehensive community intervention model, highlighting the behavioral science constructs, health education principles, and theories of behavioral and organizational change that form its conceptual foundation. NC-BCSP's theoretical foundations include the social ecological perspective, the PRECEDE model of health promotion, the Health Belief Model of individual change, and the "stages of change" transtheoretical model. We also review the experiences and lessons learned from two previous outreach initiatives in North Carolina that provided valuable "lessons" in the development of the NC-BCSP intervention model. In the second half of the paper, we describe the actual NC-BCSP interventions, activities, and evaluation tools, citing specific examples of how the underlying theories are implemented. NC-BCSP's goal goes beyond individual behavior change to raise low mammography screening rates among Black women in rural North Carolina. Its ultimate objective is to create linkages across agencies, and between agencies and communities, that will endure after the research project ends.

Adult↗

Computer generated track and field scoring tables: II. Theoretical foundation and development of a model.

An investigation is made into the subject of scoring tables for track and field with emphasis on the application of computers to calculate and output the tables. The resulting scoring tables represent an attempt to describe the effective quality of performance for track and field events. This paper is published in three parts. The first portion reviewed the historical development of scoring tables. This part concerns the theoretical foundation and development of a mathematical model. A set of underlying principles and construction guidelines are established as a basis for all scoring tables. In order to satisfy the goals, a model which includes an exponential term is developed. The concept of a zero offset is introduced as a boundary value for the low-level performances. The final part concerns an evaluation of the model and an analysis of the point scores for different events.

Computers↗

The relation between income and mortality in U.S. blacks and whites.

Differential mortality exists in the United States both between racial/ethnic groups and along gradients of socioeconomic status. The specification of statistical models for processes underlying these observed disparities has been hindered by the fact that social and economic quantities are distributed in a highly nonrandom manner throughout the population. We sought to provide a substantive foundation for model development by representing the shape of the income-mortality relation by racial/ethnic group. We used data on black and white men and women from the longitudinal component of the National Health Interview Survey (NHIS), 1986-1990, which provided 1,191,824 person-years of follow-up and 12,165 mortal events. To account for family size when considering income, we used the ratio of annual family income to the federal poverty line for a family of similar composition. To avoid unnecessary categorizations and prior assumptions about model form, we employed kernel smoothing techniques and calculated the continuous mortality surface across dimensions of adjusted income and age for each of the gender and racial/ethnic groups. Representing regions of equal mortality density with contour plots, we observed interactions that need to be accommodated by any subsequent statistical models. We propose two general theories that provide a foundation for more elaborate and testable hypotheses in the future.

Adolescent↗

The intention to give up smoking: disease versus social dimensions.

An expanded protection motivation model was used to investigate the intention to give up smoking. Because smoking has both physiological and social-psychological foundations, the model was expanded to include the social dimensions as well as the original disease dimensions as predictors of health behavior. The participants were 96 current smokers (35 male and 61 female) in Australia; 44 were young adults (age < 22 years), and 52 were adults (age > 34 years). Data were analyzed by multiple regression with hierarchical entry, first of disease dimensions, then of social dimensions. For both the young and the adult smokers, the disease dimensions contributed significantly to the results of the regression equations. Addition of the social dimensions yielded a significant F change only for young smokers and increased the amount of variance explained from 23% to 38%.

Adult↗

An open benchmark and language models for AI in aging biology.

Over the past two decades, human aging has been characterized across DNA methylation, transcriptomic, proteomic, and clinical modalities, yet no benchmark evaluates whether AI systems can interpret these heterogeneous data types in the context of aging biology. We introduce LongevityBench, an open suite of 17 tasks spanning five biodata domains, and use it to assess 18 frontier AI systems from six developer teams. Despite recent advances in AI, no single model dominates all tasks, with omics-based age prediction being the hardest task regardless of scale. To test whether these gaps can be closed without frontier-scale resources, we fine-tuned a family of five multitask Longevity-LLMs on domain-specific aging data. The compact (0.6B-9B parameters) Longevity-LLMs matched or exceeded far larger frontier systems on LongevityBench, showing that general-purpose language models can be adapted to structured-omics tasks. We publicly release the benchmark, models, and Longevity Claw, an agentic research interface for aging researchers.

Aging↗

Pharmacokinetics of 2-methoxyethanol and 2-methoxyacetic acid in the pregnant mouse: a physiologically based mathematical model.

A physiologically based pharmacokinetic (PBPK) model was created to describe the disposition of 2-methoxyethanol (2-ME) and its teratogenic metabolite, 2-methoxyacetic acid (2-MAA), in the pregnant CD-1 mouse. The model's foundation is a mathematical description of the physiological changes that occur during gestation (O'Flaherty et al., Toxicol. Appl. Pharmacol. 112, 245-256, 1992). The PBPK model was developed and validated with data collected on Gestation Day (GD) 11. Absorption, distribution, and oxidation of 2-ME to 2-MAA and ethylene glycol (EG) were simulated. Flow-limited disposition of 2-ME in maternal tissues was described using in vitro-determined tissue partition coefficients (PCs). The maximum velocity (Vmax) of 2-ME oxidation to 2-MAA was calculated from literature-based in vitro data. Vmax for EG formation, and Michaelis constants for 2-MAA and EG pathways, were estimated from optimized simulations of plasma 2-ME and metabolite levels obtained after intravenous injection of 5-600 mg 2-ME.kg-1.2-MAA disposition and elimination in the dam were described by a nonphysiological one-compartment model, which was linked to the 2-ME model, based on the volume of distribution (0.510 liters.kg-1) and overall elimination rate constant (0.124 hr-1) calculated from iv 2-MAA plasma concentration-time courses. Transfer of 2-MAA between the placenta and conceptus was described as a diffusion-limited process to more accurately simulate the higher concentrations of 2-MAA determined in embryonic compartments compared with maternal plasma levels. Subsequent 2-MAA disposition within the embryo proper and surrounding fluid of the GD 11 conceptus was adequately described using embryo/blood (0.94) and extraembryonic fluid/blood (1.33) PCs. Extension of the PBPK model to oral and subcutaneous 2-ME administrations required optimization of first-order absorption rates; model simulations agreed closely with measured 2-ME/2-MAA levels. With refinements and further validation, the PBPK model of 2-ME/2-MAA disposition should prove helpful for extrapolation throughout gestation and between species.

Acetates↗

A life span model of successful aging.

To lay the foundation for our model, we first describe existing conceptions of successful aging, underlying assumptions of development, and criteria for success. The model presented extends the discourse on this topic in three directions: (a) It frames the discussion of successful aging in the broader context of life course development; (b) it accounts for both normative and nonnormative (i.e., exceptional) success; and (c) it integrates motivational processes into a theory of successful aging. Successful aging is equated with the development and maintenance of primary control throughout the life course, which is achieved through control-related processes that optimize selection and failure compensation functions. Selection processes regulate the choice of action goals so that diversity is maintained and positive and negative trade-offs between performance domains and life stages are taken into account. Compensation mechanisms serve to maintain, enhance, and remediate competencies and motivational resources after failure experiences. Both compensation and selection processes are motivated by desires for primary control and can be characterized in terms of primary and secondary control processes.

Activities of Daily Living↗

Evolution after gene duplication: models, mechanisms, sequences, systems, and organisms.

Gene duplication is postulated to have played a major role in the evolution of biological novelty. Here, gene duplication is examined across levels of biological organization in an attempt to create a unified picture of the mechanistic process by which gene duplication can have played a role in generating biodiversity. Neofunctionalization and subfunctionalization have been proposed as important processes driving the retention of duplicate genes. These models have foundations in population genetic theory, which is now being refined by explicit consideration of the structural constraints placed upon genes encoding proteins through physical chemistry. Further, such models can be examined in the context of comparative genomics, where an integration of gene-level evolution and species-level evolution allows an assessment of the frequency of duplication and the fate of duplicate genes. This process, of course, is dependent upon the biochemical role that duplicated genes play in biological systems, which is in turn dependent upon the mechanism of duplication: whole genome duplication involving a co-duplication of interacting partners vs. single gene duplication. Lastly, the role that these processes may have played in driving speciation is examined.

Animals↗

Stochastic Dynamic Models of Response Time and Accuracy: A Foundational Primer.

A large class of statistical decision models for performance in simple information processing tasks can be described by linear, first-order, stochastic differential equations (SDEs), whose solutions are diffusion processes. In such models, the first passage time for the diffusion process through a response criterion determines the time at which an observer makes a decision about the identity of a stimulus. Because the assumptions of many cognitive models lead to SDEs that are time inhomogeneous, classical methods for solving such first passage time problems are usually inapplicable. In contrast, recent integral equation methods often yield solutions to both the one-sided and the two-sided first passage time problems, even in the presence of time inhomogeneity. These methods, which are of particular relevance to the cognitive modeler, are described in detail, together with illustrative applications. Copyright 2000 Academic Press.

Journal Article↗