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Results for “computational frameworks”

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At least 325 records · Page 18Linked to original sources

PubMed2000

Perceptual organization of two-dimensional patterns.

The perceptual organization of image patterns is considered from 2 standpoints. First, a theoretical framework is presented from which computational models of perceptual organization can be constructed and tested. Second, a specific computational model for perceptual organization of line images is described. In this model, input images are first processed by a dense array of neurons that have properties consistent with recent analyses of single-neuron responses in primary visual cortex. Then, complex image structure is discovered by interleaved pattern-matching and grouping processes constrained by a generalized uniqueness principle. A series of 3-pattern grouping experiments was performed to test a restricted version of the model and to estimate critical parameters. Using the estimated parameters, an extended version of the model was tested by generating predictions for a series of "textbook" perceptual organization demonstrations.

Humans↗

PubMed2000

Computational principles of movement neuroscience.

Unifying principles of movement have emerged from the computational study of motor control. We review several of these principles and show how they apply to processes such as motor planning, control, estimation, prediction and learning. Our goal is to demonstrate how specific models emerging from the computational approach provide a theoretical framework for movement neuroscience.

Animals↗

PubMed1999

Stretching single-domain proteins: phase diagram and kinetics of force-induced unfolding.

Single-molecule force spectroscopy reveals unfolding of domains in titin on stretching. We provide a theoretical framework for these experiments by computing the phase diagrams for force-induced unfolding of single-domain proteins using lattice models. The results show that two-state folders (at zero force) unravel cooperatively, whereas stretching of non-two-state folders occurs through intermediates. The stretching rates of individual molecules show great variations reflecting the heterogeneity of force-induced unfolding pathways. The approach to the stretched state occurs in a stepwise "quantized" manner. Unfolding dynamics and forces required to stretch proteins depend sensitively on topology. The unfolding rates increase exponentially with force f till an optimum value, which is determined by the barrier to unfolding when f = 0. A mapping of these results to proteins shows qualitative agreement with force-induced unfolding of Ig-like domains in titin. We show that single-molecule force spectroscopy can be used to map the folding free energy landscape of proteins in the absence of denaturants.

Amino Acid Sequence↗

PubMed2025

Rethinking GWAS: how lessons from genetic screens and artificial intelligence could reveal biological mechanisms.

MOTIVATION: Modern single-cell omics data are key to unraveling the complex mechanisms underlying risk for complex diseases revealed by genome-wide association studies (GWAS). Phenotypic screens in model organisms have several important parallels to GWAS which the author explores in this essay. RESULTS: The author provides the historical context of such screens, comparing and contrasting similarities to association studies, and how these screens in model organisms can teach us what to look for. Then the author considers how the results of GWAS might be exhaustively interrogated to interpret the biological mechanisms underpinning disease processes. Finally, the author proposes a general framework for tackling this problem computationally, and explore the data, mechanisms, and technology (both existing and yet to be invented) that are necessary to complete the task. AVAILABILITY AND IMPLEMENTATION: There are no data or code associated with this article.

Genome-Wide Association Study↗

PubMed1999

Distributions of transition matrix elements in classically mixed quantum systems.

The quantitative contributions of a mixed phase space to the mean characterizing the distribution of diagonal transition matrix elements and to the variance characterizing the distributions of nondiagonal transition matrix elements are studied. It is shown that the mean can be expressed as the sum of suitably weighted classical averages along an ergodic trajectory and along the stable periodic orbits. Similarly, it is shown that the values of the variance are well reproduced by the sum of the suitably weighted Fourier transforms of classical autocorrelation functions along an ergodic trajectory and along the stable periodic orbits. The illustrative numerical computations are done in the framework of a hydrogen atom in a strong magnetic field, for three different values of the scaled energy.

Journal Article↗

PubMed2003

Farmer health beliefs about an occupational illness that affects farmworkers: the case of green tobacco sickness.

Latino migrant and seasonal farmworkers, like all agricultural workers, experience high rates of occupational illness and injury. Interventions to reduce occupational injury among farmworkers must attend to the health beliefs of agricultural employers as well as employees, as employers control many aspects of the work environment. Occupational safety programs for Latino migrant and seasonal farmworkers must also be conceptually based in health behavior change and health disparities theories. We examine health beliefs of tobacco farmers about green tobacco sickness (GTS) to show the importance of delineating employer beliefs in agricultural safety. GTS is a highly prevalent occupational illness among tobacco workers that results from nicotine poisoning through dermal absorption of nicotine during cultivation and harvesting. We use qualitative methods structured by the Explanatory Models of Illness approach to identify farmer beliefs about the etiology, onset, pathophysiology, course, and treatment of GTS. Data were collected through semi-structured in-depth interviews with 15 North Carolina tobacco farmers. A computer-assisted, systematic qualitative analysis framework was applied to the interview transcripts. While tobacco farmers were generally knowledgeable about GTS, their explanatory models for this occupational illness often mis-identified its causes (heat and bending rather than nicotine) and minimized its seriousness. These models included methods of prevention that are not proven (e.g., use of anti-nausea drugs) or are more harmful than GTS (smoking cigarettes). The need for medical treatment was also discounted. Addressing each of these beliefs is important in any program to prevent GTS among farmworkers. Documenting and understanding the beliefs and knowledge of agricultural employers is an important undertaking in our efforts to reduce occupational injury and illness among farmworkers.

Adult↗

PubMed2002

Ecological interface design: progress and challenges.

Ecological interface design (EID) is a theoretical framework for designing human-computer interfaces for complex sociotechnical systems. Its primary aim is to support knowledge workers in adapting to change and novelty. This literature review shows that in situations requiring problem solving, EID improves performance when compared with current design approaches in industry. EID has been applied to industry-scale problems in a broad variety of application domains (e.g., process control, aviation, computer network management, software engineering, medicine, command and control, and information retrieval) and has consistently led to the identification of new information requirements. An experimental evaluation of EID using a full-fidelity simulator with professional workers has yet to be conducted, although some are planned. Several significant challenges remain as obstacles to the confident use of EID in industry. Promising paths for addressing these outstanding issues are identified. Actual or potential applications of this research include improving the safety and productivity of complex sociotechnical systems.

Data Display↗

PubMed2000

Virtual training simulator--designer of EEG signals for tutoring students and doctors to methods of quantitative EEG analysis (qEEG).

Within the framework of the system for computer diagnostics of EEG (qEEG) NeuroResearcher 5.2 is created virtual training simulator--designer of EEG signals and models multidimensional neurodynamic systems of the brain. It is intended for tutoring with minimum engaging of mathematical formulas of doctors and students to comprehension of essence of mathematical methods (classical correlation and spectral analysis and newest methods of multi-dimensional analysis of neurodynamic systems of the brain), which are successfully used for quantitative EEG (qEEG).

Computer Simulation↗

PubMedDate not supplied

Characterizing the use of health care services delivered via computer networks.

OBJECTIVE: Evaluators must develop methods to characterize the use of the rapidly proliferating electronic networks that link patients with health services. In this article the 4-S framework is proposed for characterizing the use of health services delivered via computer networks. The utility of the 4-S framework is illustrated using data derived from a completed, randomized field experiment in which 47 caregivers of persons who had Alzheimer's disease accessed ComputerLink, a special computer network providing information, communication, and decision support to homebound caregivers of persons who have Alzheimer's disease. DESIGN: Human-computer interaction theories characterize the use of health services delivered via computer networks in behavioral terms. The 4-S framework incorporates perspectives based on user (subject) behavior: access to and use of the total system, use of specific services, behavior within single sessions, and enduring behavioral characteristics. The 4-S framework was tested in a secondary analysis of data from over 3,800 uses of ComputerLink. MEASUREMENT: The 4-S framework was instantiated using data obtained from the ComputerLink evaluation. Three types of secondary data were obtained. A passive monitor of access to the computer network provided quantitative information, such as time of day when access occurred, duration of access, and sequence of services used. Full-text messages were available from the public message postings. Subjective appraisal of use was obtained from self-reporting by users at the end of the experiment. RESULTS: The components of the 4-S framework were suitable to characterize operational aspects of ComputerLink use by Alzheimer's disease caregivers. Through application of the 4-S framework, an understanding of both quantitative use and qualitative use emerged (e.g., insight was gained into the differential use of specific services). CONCLUSIONS: The 4-S framework provided a mechanism for combining various measures of use into a coherent whole. The framework promotes a precise characterization of use and thereby facilitates evaluation of health services delivered via computer networks. It is suitable for evaluation of user satisfaction, measurement of needs resolution, and ascertainment of selected clinical outcomes.

Alzheimer Disease↗

PubMed2003

From sarcomere to cell: an efficient algorithm for linking mathematical models of muscle contraction.

Two classes of mathematical framework have previously been developed to model active tension generation in contracting muscle. Cross-bridge models of muscle are biophysically based but computationally expensive to solve, and thus unsuitable for embedding in spatially distributed continuum representations. Fading memory models are computationally efficient but provide limited biophysical insight. In this study a novel computational method is proposed for coupling these two frameworks such that biophysical events can be determined and computational tractability maintained. Within the cross-bridge model, the functional forms of the distribution of cross-bridges, as a function of strain in each state, are approximated using the distribution moment approach. Using the variables of area, mean and standard deviation of each distribution, analytic expressions are developed to calculate the temporal dynamics of stiffness, tension and energy. A root finding method is employed to adjust the variables such that the temporal dynamics of the cross-bridge model match those of an equivalent fading memory model. The method is demonstrated for sinusoidal perturbations in length at two frequencies, with an approximate 30-fold increase in computational efficiency over a conventional technique for finding a solution to the cross-bridge model.

Adenosine Triphosphate↗

PubMedDate not supplied

[Effect of the computer-assisted diagnostic system [ADM] on the success and cost of diagnosis (author's transl)].

Taking into account the interest we have in helping physicians arrive at a diagnosis and in choosing the procedures utilized in the computer-assisted diagnostic system (ADM) already described, a study was devised to estimate the efficiency of the system in relation to costs. From 300 patient records, 80 presenting a true diagnostic problem within the framework of the diseases already in computer memory were selected. A comparison was made between the normal procedure, with and without computer help, keeping in mind the diagnoses themselves as well as the performance and the cost. Criteria and evaluation methods were evaluated. The results, even though preliminary, are encouraging and justify the continued development of the system.

Cost-Benefit Analysis↗

PubMed2003

Development and evaluation of a computer-animated tutor for vocabulary and language learning in children with autism.

Using our theoretical framework of multimodal processing, we developed and evaluated a computer-animated tutor, Baldi, to teach vocabulary and grammar for children with autism. Baldi was implemented in a Language Wizard/Player, which allows easy creation and presentation of a language lesson involving the association of pictures and spoken words. The lesson plan includes both the identification of pictures and the production of spoken words. In Experiment 1, eight children were given initial assessment tests, tutorials, and reassessment tests 30 days following mastery of the vocabulary items. All of the students learned a significant number of new words and grammar. A second within-subject design with six children followed a multiple baseline design and documented that the program was responsible for the learning and generalization of new words. The research indicates that children with autism are capable of learning new language within an automated program centered around a computer-animated agent, multimedia, and active participation and can transfer and use the language in a natural, untrained environment.

Autistic Disorder↗

PubMed1994

A computational model for shape from texture.

Shape from texture is best analysed in a two-stage framework analogous to stereopsis and structure from motion: (a) computing the 'texture distortion' from the image; and (b) interpreting the 'texture distortion' to infer the orientation and shape of the scene surface in 3D. We model the texture distortion at a point in any particular direction on the image plane as an affine transformation and derive the relationship between the parameters of the affine transformation and the surface shape and orientation. We have developed a technique for estimating affine transforms between nearby image patches which is based on solving a system of linear constraints derived from a differential analysis. It is not necessary explicitly to identify texels or make restrictive assumptions about the nature of the image texture like isotropy. We have developed two different models for recovering surface orientation (slant and tilt) and shape (principal curvatures and directions) based on the estimated affine transforms in a number of directions. Experimental results are presented on images of planar and curved surfaces under perspective projection.

Animals↗

PubMed2003

A computational basis to object?

To use an object, we must be able to perceive the spatial relationship between the object's parts. The accepted view of how the brain coherently encodes an object is that some neurons in the frontal cortex employ an object-centered coordinate frame. A new computational model challenges this view, using the rich conceptual framework of neural basis functions.

Computational Biology↗

PubMedDate not supplied

Stress distribution on the metal framework of the implant-supported fixed prosthesis using different veneering materials.

PURPOSE: This study evaluated stress distribution in metal frameworks constructed on implants under masticatory forces using computer simulations. MATERIALS AND METHODS: Three-dimensional finite element analysis was used to study four different veneering materials-metal framework combinations using Calcitek implants. The veneering materials used in the study were porcelain, heat-polymerized poly(methyl methacrylate) resin, microfilled composite resin, and glass-modified composite resin. All computations were conducted for different levels on the buccal and lingual sides. RESULTS: Changing the veneering material on the prosthesis produced significant effects on stress levels and stress distribution on the metal frameworks. Stresses were concentrated along the marginal area of the prosthesis. Acrylic resin showed greater displacement than porcelain, probably because of its lower modulus of elasticity. CONCLUSION: In comparison to porcelain, more stress is borne by the acrylic resin-veneered metal framework under static loading.

Acrylic Resins↗

PubMed2003

Spectroscopic and computational characterization of the nickel-containing F430 cofactor of methyl-coenzyme M reductase.

Methyl-coenzyme M reductase (MCR) catalyzes the terminal reaction in methanogenesis, the formation of methane from methyl-coenzyme M and coenzyme B. The active site of MCR binds the prosthetic group F(430), a unique nickel hydrocorphin cofactor. Here, spectroscopy and computations are employed in developing detailed electronic descriptions of the Ni(II) and Ni(I) forms of the free cofactor. Absorption, magnetic circular dichroism (MCD), and variable-temperature variable-field MCD data are analyzed within the framework of time-dependent DFT computations to assign key electronic transitions. DFT calculations are further employed to evaluate possible reduced F(430) models-a one-electron reduced Ni(I)F(430) model and a three-electron reduced Ni(I)F(red430) model (possessing a reduced hydrocorphin ligand)-on the basis of excited-state spectra and published EPR/ENDOR parameters. While calculations on both models yield spectroscopic parameters that are consistent with most experimental data, overall better agreement is achieved using the Ni(I)F(430) model, particularly with respect to electronic absorption and (1)H ENDOR. The experimentally validated bonding descriptions generated herein show that in Ni(II)F(430) the occupied Ni 3d orbitals are too low in energy to significantly perturb the dominant electronic transition involving the pi and pi* frontier MOs of the macrocycle (i.e., the HOMO-->LUMO transition). Upon one-electron reduction of the Ni(II) ion, the occupied Ni 3d orbitals are raised in energy, shifting between the HOMO and the LUMO of the oxidized cofactor. These ground-state changes have a dramatic effect on the excited-state structure, causing a blue shift of the dominant pi-->pi* transition and the appearance of numerous Ni 3d-->hydrocorphin pi* charge-transfer features in the vis/near-IR region.

Computational Biology↗

PubMed1997

Cost-effective management of high-risk patients: a case-map approach.

BACKGROUND: The case-management approach to patient care used by most cardiac surgical practices frequently highlights patients designated as high-risk. Increased risk might be because of advanced age, the need for complex reoperations, high risk of bleeding, and renal failure, all of which may be superimposed on poor ventricular performance. METHODS: A small consensus panel of cardiac surgeons, anesthesiologists, perfusionists, cardiac-care nurse managers, and coagulation experts met to assess the potential for development of case-management pathways targeted towards high-risk coronary artery bypass graft patients. The process comprised review of the literature to identify risk factors and strategies most cost-effective in reducing risk. RESULTS: A series of management strategies driven by data from the literature--or by consensus when such information was not available--were developed to cost-effectively manage the high-risk patient. The process was then converted to a multidimensional computer program. This personal computer-driven program served as a framework upon which any institution could impose its own practice style and modify recommendations. The program was designed to be interactive and to allow easy transition from patient-management strategies to support data. A facilitator generally coordinates the interaction between the local patient-care group and the computer information base to evolve a case-management map. CONCLUSIONS: By using stored information based on current literature and easily updated, the system is both educational and product oriented, and provides a case-map approach to the cost-effective management of patients during the preoperative, intraoperative, and postoperative phases of hospital care.

Case Management↗

PubMed1995

A generalizable framework for information systems for physician recruitment/referral.

Hospital information systems have evolved from data processing systems for patient billing and payroll to decision-support systems which support decision making at the middle and upper management levels. With the advancements in the areas of database management, expert systems and networks, important hospital functions such as physician recruitment and referral which historically were performed using traditional procedures, are now performed using these computer-based technologies. Develops a generalizable framework for information systems for physician recruitment and referral using technologies of database management, expert systems and networks. This GIS-PRR system may be used by hospitals and other health-care providers to improve the efficiency and effectiveness of the physician recruitment/referral process.

Database Management Systems↗