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At least 127 records · Page 7Linked to original sources
PubMed2000

Gray-scale skeletonization of small vessels in magnetic resonance angiography.

Interpretation of magnetic resonance angiography (MRA) is problematic due to complexities of vascular shape and to artifacts such as the partial volume effect. We present new methods to assist in the interpretation of MRA. These include methods for detection of vessel paths and for determination of branching patterns of vascular trees. They are based on the ordered region growing (ORG) algorithm that represents the image as an acyclic graph, which can be reduced to a skeleton by specifying vessel endpoints or by a pruning process. Ambiguities in the vessel branching due to vessel overlap are effectively resolved by heuristic methods that incorporate a priori knowledge of bifurcation spacing. Vessel paths are detected at interactive speeds on a 500-MHz processor using vessel endpoints. These methods apply best to smaller vessels where the image intensity peaks at the center of the lumen which, for the abdominal MRA, includes vessels whose diameter is less than 1 cm.

Algorithms↗
PubMed1996

Developmental dyslexia: a motor-articulatory feedback hypothesis.

Reading is mediated by parallel and widely distributed modular systems. There are, therefore, multiple loci in these systems where dysfunction may lead to developmental dyslexia. However, most normal children learn to read using the alphabetic system. Learning to use this system requires awareness that words are comprised of a system of speech sounds (phonological awareness) and the knowledge of how to convert letters (graphemes) into these speech sounds (phonemes). Most dyslexic children have deficient phonological awareness and have difficulty converting graphemes into phonemes. Studies of patients with acquired lesions who are unable to convert graph-emes into phonemes, as well as positron emission tomographic studies of normal subjects, suggest that the left inferior frontal lobe is important in phonologic reading. Phonetic gestures are represented in the brain as invariant motor commands that program the articulators. Phonologic reading may activate the left inferior frontal lobe because grapheme-to-phoneme conversion requires activation of these motor-articulatory gestures. Dyslexic children are unaware of the position of their articulators during speech. The inability to associate the position of their articulators with speech sounds may impair the development of phonological awareness and the ability to convert graphemes to phonemes. Unawareness of their articulators may be related to programming or feedback deficits.

Auditory Pathways↗
PubMed2000

Verbal and visual causal arguments.

The present paper analyzes how verbalizations and visualizations can be used to justify and dispute causal claims. The analysis is based on a taxonomy of 27 causal arguments as they appear in ordinary language. It is shown how arguments from spatio-temporal contiguity, covariation, counterfactual necessity, and causal mechanisms, to name only a few, are visualized in persuasive uses of tables, graphs, time series, causal diagrams, drawings, maps, animations, photos, movies, and simulations. The discussion centers on how these visual media limit the argumentative moves of justifying, disputing, and qualifying claims; how they constrain the representation of observational, explanatory, and abstract knowledge in the premises of causal arguments; and how they support and externalize argument-specific inferences, namely generalizations, comparisons, mental simulations, and causal explanations.

Humans↗
PubMedDate not supplied

Automatic derivation of initial match points for paired digital images of skin.

Computerized matching of skin images has been suggested as a means of screening for changes indicative of malignant melanoma. Matching or "registering" each lesion in a pair of images plays an important role in this process. Point-pattern matching algorithms based upon correlation or geometric transformations of the image pairs have been shown to be effective for this registration but require knowledge of one or more "initial match" points which are known to be the same on both images. A method is described for automatically finding these initial match points with a high degree of success. Our algorithm uses the so-called "Gabriel graph" representation of the paired images to select sets of probable matching points. Performance of the algorithm has been measured in realistic trials, using images of patients with large numbers of pigmented lesions. Results show that the single best match chosen is correct greater than 99% of the time, while over 93% of the first three consecutive matches will be chosen correctly. It is likely that these results can be improved through the use of additional nonpositional information or additional image processing.

Algorithms↗
PubMed2000

A pattern catalogue of surgical interventions for computer-supported operation planning.

In this paper we present a new operation planning system which was evaluated in the clinic for Cranio-Maxillo-Facial-Surgery at the University of Heidelberg. In opposite to commercial systems our goal was, that the system considers the complete surgical intervention and not only a single procedure of it. A second goal was, that the system enables managing of complex operations, independent of which way the intervention will be intraoperatively performed (without technical support, with passive navigation support or active support by robots). Our system supports the surgeon during the preoperative planning as well as during the intraoperative execution phase. Therefore we developed a course model by which the managing of surgical interventions is possible. The focus of this paper is on this course model. At first we introduce instruction graphs and describe the structure of each activity observing its attributes and their context. Additionally, various surgical scopes will be presented which enable the surgeon to select one view among different ones of the individual operation procedures in accordance to medical and technical knowledge as well as in accordance to different degrees of abstraction. At last we demonstrate operation patterns, used as expert knowledge.

Computer Simulation↗
PubMed2002

Computational approaches to the prediction of the blood-brain distribution.

This review attempts to summarise present knowledge related to the theoretical modelling of drug transport across the blood-brain barrier. Several computational protocols are described ranging from quantum mechanics-based approaches through molecular mechanics-related techniques to simple and fast procedures based on only the 2-D graph of the investigated structures. Amazingly, few descriptors have been shown to influence the derived relationships in a significant manner and a cornerstone in most of the described models are terms describing hydrogen bonding. A very quick quantitative assessment of the brain partitioning of a compound has also been devised using the following two rules: If N+O (the number of nitrogen and oxygen atoms) in a molecule is less than or equal to five, it has a high chance of entering the brain. The second rule predicts that if log P-(N+O) is positive then log BB is positive.

Algorithms↗
PubMedDate not supplied

The application of the Transtheoretical Model of Change to adolescent sexual decision-making.

The Transtheoretical Model of Change (TTM) was examined for its applicability to the study of adolescent sexual abstinence behaviors. This investigation involved a cross-sectional secondary analysis of 7th grade students (N = 694) participating is a school-based program funded by the Virginia State Abstinence Initiative. The purpose was to explore the relationships among the concepts and variables of the TTM in an adolescent population with regard to sexual decision-making in abstinence behaviors. The relationship of the different stages of change among virgins and nonvirgins to the decisional balance variable was examined. Results demonstrated significant difference in the decisional balance variable among virgin adolescents in the precontemplation, contemplation, preparation, and action stages of sexual abstinence using ANOVA testing. However, these differences were not seen in the nonvirgin subjects. The virgins followed a highly predictable pattern of sexual decision-making following the graphing of T scores, but this decision-making pattern was not apparent in the nonvirgin subjects. These results support the applicability of the TTM to the behavior of sexual abstinence. Nurses must be aware of the differences in adolescent decision-making processes and incorporate a knowledge of these differences into intervention strategies. Future research will focus on the replication of results in older adolescents and the development of stage-matched interventions to promote healthy sexual behaviors.

Adolescent↗
PubMed2026

Evolution of maize recombination landscape during domestication.

Despite the plethora of knowledge about the benefits of meiotic recombination and numerous theoretical studies examining how recombination rates evolve, there is a general lack of empirical support and consensus across species. To fill this knowledge gap, we characterized the evolution of recombination landscape in maize during its domestication from teosinte and related the observed changes to established theoretical frameworks. Through examining recombination in experimental populations of maize and teosinte and the population genomics approach of identifying historical recombination events using ancestral recombination graph inference to generate saturated maize and teosinte recombination maps, we found that during domestication, maize experienced a 12% increase in its genome-wide recombination rate. Furthermore, maize evolved higher recombination rates on the long arms of chromosomes in regions closer to centromeres, where recombination is generally very low. The repatterning of crossover events came from changes in global crossover positioning rather than alterations in cis-acting chromatin factors. Consequently, we found evidence of selection acting on trans-acting recombination modifiers affecting crossover interference and controlling the interference-dependent class I crossover pathway. We show that CO repatterning was likely beneficial for maize fitness, as significant recombination rate increases were predominantly in gene-rich regions, which harbor domestication-related variation. This work suggests genomic and mechanistic processes leading to the evolution of meiotic recombination landscape in response to directional selection pressure and provides evidence for the evolutionary advantage of recombination.

Zea mays↗
PubMed1986

A graphical method for forecasting radiation exposure from multi-aged fallout from nuclear weapons.

After a nuclear attack it may be necessary for emergency workers, such as firemen, utility workers and medical personnel, to perform urgent tasks in areas highly contaminated by radioactive fallout. To assist the control of radiation exposure of these workers, it will be useful to provide means to forecast radiation exposures both inside and outside the fallout shelter. The method described in this paper is intended for use during the first few days to weeks after the attack, after which time more sophisticated methods may become available. This method requires only a radiation-rate meter, special graph paper, and a timepiece. Communications with Emergency Operating Centers or other sources of information are not necessary. The method permits the determination of the age of fallout and future exposure rates for a location that might be subjected to a number of different fallout clouds, without requiring knowledge of the weapon yields or times of detonation. This method will provide results with less accuracy if different-aged fallout clouds arrive simultaneously. The method is self-correcting so that if the actual decay rate is different than that which is assumed, the forecasted rates will have less error than results obtained by previous methods.

Nuclear Warfare↗
PubMedDate not supplied

Symbolic anatomic knowledge representation in the Read Codes version 3: structure and application.

The Read Thesaurus (Version 3 of the Read Codes) is a controlled medical vocabulary produced during the Clinical Terms Projects with the involvement of over 2,000 health care professionals from all United Kingdom specialties. In addition to allowing the transfer of clinical information in a meaningful way, it supports analysis of this information and provides a basis for the development of shareable medical knowledge bases. The thesaurus includes a comprehensive, dynamic set of over 7,000 gross anatomic concepts richly linked in a network with over 16,000 operative procedures and 40,000 disorders. The representation of anatomic concepts aims to balance the requirements for expressivity, clearness, and simplicity. The underlying directed acyclic graph hierarchy is independent of the alphanumeric code and enables continued refinement and expansion. A template table allows semantic definition, qualification, and linkage of concepts.

Anatomy↗
PubMed1990

A computer system for contact dermatitis: graphical representation of data.

An overview is given of the computer applications we have developed over the last twelve years in the field of contact dermatitis. The dissemination of exposure lists to sensitised individuals and the development of a knowledge-based system are mentioned only briefly. Priority here is given to the explanation of the graphical representation of the patient data collected since 1978 on 12,000 patients referred to three contact dermatitis units. More than a hundred parameters of each patient have been collected in a database. Several graphs are given of these data and are discussed in detail.

Adolescent↗
PubMed1992

Dynamics for communications data.

To create a complex dynamical model for a complex system, it is normally necessary to have a directed graph of the network, a dynamical model for each node, and a coupling function for each directed edge. But in many applications, the only observable data consists of communications from one node to another. In this situation, the modeler may infer a complex dynamical model for the network without any explicit knowledge of the independent dynamical behavior of the component systems (nodes). Here we present one procedure for this type of modeling problem, inspired by the attractor reconstruction procedure of chaos theory. Part of this proposal consists of a strategy for computer graphic presentation of the interactive dynamics of the complex system (or social network of dynamical schemes) called a netscope. We can imagine applications to diverse situations, such as decision groups, management, forecasting, international relations, classroom monitoring, therapy (personal, family, group, etc.) and distributed processors, to name a few.

Communication↗
PubMed1983

The case report. I. Guidelines for preparation.

A case report, if prepared properly, is a valuable educational device to describe an unusual clinical syndrome, association, reaction, or treatment. If a case advances basic understanding of a disorder, increases clinical skill, or suggests useful research, it is worthy of publication. Conciseness is paramount. The description of the case should contain only pertinent positive and negative findings. Irrelevant material or excessive detail can obscure the essence of a report and repel editors and readers. The discussion should emphasize the salient features of the case, show their relation to previous knowledge, interpret their significance, draw conclusions or generalizations about future cases when warranted by the evidence presented, or suggest further possible studies. Information withheld by the patient and unjustified speculation can nullify the value of a case report. Illustrations add visual appeal and enhance the educational value of a report. Tables and graphs should reduce any statistical data to readily interpretable form. All visual supplements should be simple, compact, and self-contained. Appropriate documentation is desirable, but only essential citations need be included, and the author should have carefully reviewed and verified all references used. Begin with a clear title and end with an informative Summary. A useful case report is factual, concise, logically organized, clearly presented, and readable. The three primary principles to remember: (1) Make sure the case warrants publication. (2) Include only pertinent information. (3) Be concise.

Humans↗
PubMed1996

A knowledge-based model construction approach to medical decision making.

We present a framework for representing the probabilistic effects of actions and contingent treatment plans. Our language has a well-defined declarative semantics and we have developed an implemented algorithm (named BNG) that generates Bayesian networks (BN) to compute the posterior probabilities of queries. In this paper we address the problem of projecting a contingent treatment plan by automatically constructing a structure of interrelated BNs, which we call a BN-graph, and applying the available propagation procedures on it. To address the optimal plan generation, we base our approach on the observation that normally the target plan space has a well-defined structure. We provide a language to describe plan spaces which resembles a programming language with loops and conditionals. We briefly present the procedures for finding the optimal plan(s) from such specified plan spaces.

Acute Disease↗
PubMed1993

Hierarchical functional organization of formal biological systems: a dynamical approach. III. The concept of non-locality leads to a field theory describing the dynamics at each level of organization of the (D-FBS) sub-system.

In paper I, the construction of the graph of interactions, called (O-FBS), was deduced from the 'self-association hypothesis'. In paper II, a criterion of evolution during development for the (O-FBS), which represents the topology of the biological system, was deduced from an optimum principle leading to specific dynamics. Experimental verification of the proposed extremum hypothesis is possible because precise knowledge of the dynamics is not necessary; only knowledge of the monotonic variation of the number of sinks is required for given initial conditions. Essentially, the properties of the (O-FBS) are based on the concept of non-symmetry of functional interactions, as shown by the 'orgatropy' function (paper II). In this paper, a field theory is proposed to describe the (D-FBS), i.e. the physiological processes expressed by functional interactions: (i) physiological processes are conceived as the transport of a field variable submitted to the action of a field operator; (ii) because of hierarchy, this field theory is based on the concept of non-locality, and includes a non-local and non-symmetric interaction operator; (iii) the geometry of the structure contributes to the dynamics via the densities of structural units; and (iv) because a physiological process evolves on a particular timescale, it is possible to classify the levels of organization according to distinct timescales, and, therefore, to obtain a 'decoupling' of dynamics at each level. Thus, a property of structurality for a biological system is proposed, which is based on the finiteness of the velocity of the interaction, thus, with distinct values of timescales for the construction of the hierarchy of the system. Three axioms are introduced to define the fields associated with the topology of the system: (i) the existence of the fields; (ii) the decoupling of the dynamics; and (iii) the ability of activation-inhibition. This formulation leads to a self-coherent definition of auto-organization: an FBS is self-organized if it goes from one stable state for the (D-FBS) to another under the influence of certain modifications of its topology, i.e. a modification of the (O-FBS). It is shown that properties deduced with this formalism give the relationship between topology and geometry in an FBS, and particularly, the geometrical re-distribution of units.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1979

[Activation of student cognitive activities in the process of teaching medical microbiology].

The main trends of methodical work conducted at the chair of microbiology of Orenburng Medical Institute are presented. For the purpose of activation of cognition activity of students during medical microbiology teaching the following methods were applied: presentation of the teaching material, creation of visual teaching methods in a single methodical plan in accordance with the logic structure graphs of the subject as a whole, its individual sections and themes; introduction of problem teaching method, solution of practical tasks of the II and III learning level; introduction of scientific achievements of the chair into the teaching process. Result of evaluation of the efficacy of the teaching-methodical work of the chair carried out demonstrated that knowledge of the principal microbiology problems in the students and interns persisted for long periods of time.

Cognition↗
PubMed1982

An approach to completely automatic comparison of two-dimensional electrophoresis gels.

The problem addressed is that of determining the similarities and differences appearing in a sequence of two-dimensional polyacrylamide gels where we have no a priori knowledge of the intensity and spatial distribution of the protein spots. It is assumed that the gels are not in precise registration. An attempt is being made to develop a completely automatic program for use in genetic studies, which will compare a sequence of three gels run on samples from father, mother, and child. The program constructs a graph by using as nodes those spot cues that exceed a given intensity threshold. The graphs are then compared to determine an initial subset of spots that are common to all three gels. From this subset of common spots the program then determines whether the remaining graph differences are real or result from quantitative variation causing spots to fall below threshold.

Adult↗
PubMedDate not supplied

[Pressure distribution on the sole of the human foot while standing and walking, barefoot and with shoes].

For more than a century, scientists and practicians of orthopedic shoe production have been increasing their knowledge on the normal statics and dynamics of the lower extremities as well as on innate or often acquired posture anomalies and foot deformities. Even amongst young adults, barely half of one percent has so-called "inconspicuous" feet without restrictive signs of foot deformities. Consequently, the resulting primary illnesses and secondary injuries must be treated. Quantitative pressure distribution graphs in isobaric representation at the heel barefoot when standing and walking were determined by means of an improved, locally fixed device by Elftman and Helm. For the first time, a newly developed mobile measuring process allows measuring pressures at the heel inside the shoe while standing as well as while walking, running or jumping. The rolloff motion of the heel allowed the determination of a "maximum pressure line." Orthopedic recommendations for the production of true-to-form and true-to-function shoes for walking and sports shoes are included.

Biomechanical Phenomena↗