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PubMed2002

Context-tree modeling of observed symbolic dynamics.

Modern techniques invented for data compression provide efficient automated algorithms for the modeling of the observed symbolic dynamics. We demonstrate the relationship between coding and modeling, motivating the well-known minimum description length (MDL) principle, and give concrete demonstrations of the "context-tree weighting" and "context-tree maximizing" algorithms. The predictive modeling technique obviates many of the technical difficulties traditionally associated with the correct MDL analyses. These symbolic models, representing the symbol generating process as a finite-state automaton with probabilistic emission probabilities, provide excellent and reliable entropy estimations. The resimulations of estimated tree models satisfying the MDL model-selection criterion are faithful to the original in a number of measures. The modeling suggests that the automated context-tree model construction could replace fixed-order word lengths in many traditional forms of empirical symbolic analysis of the data. We provide an explicit pseudocode for implementation of the context-tree weighting and maximizing algorithms, as well as for the conversion to an equivalent Markov chain.

Journal Article↗

PubMed2003

Detecting subthreshold events in noisy data by symbolic dynamics.

We show that a symmetric threshold crossing detector can be described by a symbolic dynamics of a static three-symbol encoding which is highly efficient to detect subthreshold events in noisy nonstationary data. After computing instantaneous word statistics and running cylinder entropies, we introduce a mean-field transformation of the three-symbol dynamics considered as a Potts-spin lattice onto a distribution of two symbols. This transformed word statistics enables one to derive an estimator of the signal-to-noise ratio (SNR). Subthreshold events are then proven by a prominent peak of the SNR estimator as a function of the noise intensity.

Entropy↗

PubMed2003

Estimating good discrete partitions from observed data: symbolic false nearest neighbors.

A symbolic analysis of observed time series requires a discrete partition of a continuous state space containing the dynamics. A particular kind of partition, called "generating," preserves all deterministic dynamical information in the symbolic representation, but such partitions are not obvious beyond one dimension. Existing methods to find them require significant knowledge of the dynamical evolution operator. We introduce a statistic and algorithm to refine empirical partitions for symbolic state reconstruction. This method optimizes an essential property of a generating partition, avoiding topological degeneracies, by minimizing the number of "symbolic false nearest neighbors." It requires only the observed time series and is sensible even in the presence of noise when no truly generating partition is possible.

Journal Article↗

PubMed2005

Optimized symbolic dynamics approach for the analysis of the respiratory pattern.

Traditional time domain techniques of data analysis are often not sufficient to characterize the complex dynamics of respiration. In this paper, the respiratory pattern variability is analyzed using symbolic dynamics. A group of 20 patients on weaning trials from mechanical ventilation are studied at two different pressure support ventilation levels, in order to obtain respiratory volume signals with different variability. Time series of inspiratory time, expiratory time, breathing duration, fractional inspiratory time, tidal volume and mean inspiratory flow are analyzed. Two different symbol alphabets, with three and four symbols, are considered to characterize the respiratory pattern variability. Assessment of the method is made using the 40 respiratory volume signals classified using clinical criteria into two classes: low variability (LV) or high variability (HV). A discriminant analysis using single indexes from symbolic dynamics has been able to classify the respiratory volume signals with an out-of-sample accuracy of 100%.

Algorithms↗

PubMed1982

A new symbolic language for diagramming pacemaker/heart interaction.

A new symbolic language is presented that can be used to diagram pacemaker/heart interactions. The language symbolically indicates "normally" conducted and ectopic events; pacemaker stimuli; pacemaker capture of the chamber; triggered pacemaker stimuli by "normal" or ectopic events; as well as such anomalous pacemaker/heart interactions as failure to sense; "crosstalk" between electrodes; and "normal," ectopic, or paced events in one chamber sensed by the electrode in the other chamber. In addition, symbols are provided to represent antegrade and retrograde accessory pathway conduction, and electronic and physiological refractory intervals. A common baseline is used to separate symbols for atrial activity, above the baseline, from those for ventricular activity, below the baseline. Parallel baselines are used to plot refractory intervals. Thus, even complex dual-chamber pacemaker operating modes can be represented with intrinsic and stimulated cardiac response to pacemaker operation. The language can be sketched out informally for description of general concepts or drafted on millimeter grid paper to make precise timing notations. It is especially useful for interdisciplinary communication of ideas about complex pacemaker/heart interactions.

Atrial Function↗

PubMed1998

Change in the word symbol for nurse in Korea.

PURPOSE: To analyze the 1987 change in the written symbol for the work "nurse" in Korea, engendered by Mo Im Kim. DESIGN: Descriptive historical and narrative analysis. METHODS: Data were collected from documents in four libraries 1992-1996 in Seoul, Korea and Dallas, Texas. Kim and 20 of her friends, colleagues, and associates were interviewed. Findings from the interviews were compared with historical nursing documents and letters. FINDINGS: Kim's work with her colleagues and their joint endeavors resulted in a change in nursing's status and responsibilities through an alteration of the Korean symbol for nursing. The symbol change resulted in the definition of nursing moving from that of manual laborer to that of teacher or professional. CONCLUSIONS: Changing the symbol for nurse reflected the shift in nursing's responsibilities and caused a legal change in the official civil service classification of nurse. This, in turn, has changed the status of nursing and led to more professional practice.

History of Nursing↗

PubMed2005

Is vision screening in 3-year-old children feasible? Comparison between the Lea Symbol chart and the HVOT (LM) chart.

PURPOSE: The aim of this prospective study was to compare visual screening at the age of 3 years with screening at 4 years using two different charts. METHODS: A total of 478 3-year-old children were tested at four child health care centres (CHCCs). Of these children, 440 were tested again at the age of 4 years. A third group, a control group, consisting of 229 children, was examined only at the age of 4 years. All children were tested with both the HVOT chart and the Lea Symbol chart. RESULTS: Testability rates for 3-year-olds were almost the same with the Lea Symbol chart and the HVOT chart (82.8% and 84.8%, respectively). The corresponding rates for the same children tested at 4 years of age were 96.5% and 97.0%, and for the 4-year-olds not previously tested 92.9% and 92.8%. The mean testing time was somewhat shorter for the Lea Symbol chart in all three groups, but the difference was not statistically significant. The difference in the assessment of visual acuity between the two charts was small and less than 1/10th of a line. The positive predictive value was lower at 3 years (58%) than has previously been found at 4 years (74.6%). CONCLUSION: Three-year-old children co-operate well in visual acuity testing. However, the examination time is a little longer and the testability rate is about 10% lower than at 4 years. Both 3-year-old and 4-year-old children can be tested equally well with the HVOT and the Lea Symbol charts.

Amblyopia↗

PubMed2006

Sensitivity and specificity of a visual acuity screening protocol performed with the Lea Symbols 15-line folding distance chart in preschool children.

PURPOSE: The aim of this study was to assess the feasibility of a visual acuity (VA) test using the Lea Symbols 15-line folding distance chart and its diagnostic validity in detecting VA deficiency in preschool children. METHODS: A group of 149 children aged 38-54 months underwent VA examination performed with the Lea 15-line folding optotype at a distance of 3 metres, according to a test protocol described in the Methods section. After the VA test, a complete ophthalmological examination, including cycloplegic retinoscopy, a cover test and examination of the anterior and posterior segments, was performed on each child in order to detect any VA-threatening ocular abnormality. The Lea Symbols test's sensitivity, specificity, positive and negative likelihood ratios (LR +, LR -) and the receiver operating characteristic (ROC) curve were calculated by means of standard procedures using each VA level of the chart from 0.1 to 1 (1-0 logMAR) as a cut-off point. RESULTS: The Lea Symbols test could be successfully used in 95.9% of the population. The most useful cut-off points for screening preschool children were found to be 0.8 (LR + 5.73, LR - 0.05) or 0.63 (LR + 11.7, LR - 0.23). CONCLUSION: The Lea Symbols test proved to be clinically useful in detecting VA deficiency in preschool children. The choice between the two best performing cut-off levels should be made according to the expected cost-effectiveness of the screening programme.

Child, Preschool↗

PubMed2002

Examination of young children with Lea symbols.

AIMS: In order to establish normal values and interocular differences of visual acuity, Lea symbols were applied to neurologically and ophthalmologically normal children. METHODS: 385 children (21-93 months old) were examined, within a routine check up in an urban paediatric practice where Lea symbol acuity (LS) was measured. Of these children, 90 were re-examined in hospital comparing Lea symbol acuity (LS) and Landolt C acuity (LC). Strabismus, ametropia, and any organic eye disease were excluded. RESULTS: In the paediatric practice, LS could be measured on both eyes in 54% of the children. In the age group above 36 and 48 months the success rate was 76% and 95%, respectively. Acuity in the paediatric practice ranged from 0.1 to 2.0 (median 1.25) in the whole group. Interocular acuity difference was one line or less in 80%. In the hospital, LS and LC could be measured on both eyes of 77% and 48% of the 90 children, respectively. Cooperation increased with age. LS in the hospital ranged from 0.32 to 2.0 (median 1.0) and LC from 0.16 to 1.25 (median 0.8). Interocular difference of LS acuity was one line or less in 90%. CONCLUSION: Lea symbols were found to be useful for visual acuity assessment in early childhood. Significant variability of visual acuity in this age group is caused by cooperation. When monocular measurements are possible on both eyes, however, the intraindividual interocular difference of visual acuity usually does not exceed one line.

Child, Preschool↗

PubMed2000

Use of tangential visual symbols to increase the long-term learning process: applications of linkage in teaching pharmacological principles of addiction.

Medieval and Renaissance teaching techniques using linkage between course content and tangentially related visual symbols were applied to the teaching of the pharmacological principles of addiction. Forty medical students randomly divided into two blinded groups viewed a lecture. One lecture was supplemented by symbolic slides, and the second was not. Students who viewed symbolic slides had significantly higher scores in a written 15-question multiple-choice test 30 days after the lecture. These results were consistent with learning and semiotic models. These models hypothesize a linkage between conceptual content and perception of visual symbols that thereby increases conceptual retention. Recent neurochemical research supports the existence of a linkage between two chemically distinct memory systems. Simultaneous stimulation of both chemical systems by teaching formats similar to those employed in the study can augment neurochemical signaling in the neocortex.

Adult↗

PubMed2002

LCD versus CRT displays: a comparison of visual search performance for colored symbols.

Visual search performance for tactical symbols was examined with liquid-crystal (LCD) and cathode-ray tube (CRT) displays. Twenty-four adult participants (19 men, 5 women; mean age 41 years) searched for navy tactical display symbols on a map background. LCD and CRT displays of similar size and resolution (52 cm diagonal, 1280 x 1024 pixels) were used. Viewing angle (0 degrees vs. 60 degrees of azimuth), set size, target color (blue, red, or white), target presence, and search type (feature vs. conjunction) were also manipulated. Participants showed reduced sensitivity for red and blue symbols viewed 60 degrees off axis with the LCD relative to on-axis LCD, or to the CRT on or off axis. Colored symbols viewed off axis on the LCD produced longer response times in feature search and lower search efficiency in conjunction search. The results argue against the use of current LCD technology when off-axis viewing is likely and color coding is used.

Adult↗

PubMed2004

A fully symbolic design and modeling of nonlinear glucose control with Control System Professional Suite (CSPS) of Mathematica.

In this case study a fully symbolic design and modeling method are presented for blood glucose control of diabetic patients under intensive care using Mathematica. The analysis is based on a modified two-compartment model proposed by Bergman et al. The applied feedback control law decoupling even the nonlinear model leads to a fully symbolic solution of the closed loop equations. The effectivity of the applied symbolic procedures being mostly built-in the new version of Control System Professional Suite (CSPS) Application of Mathematica have been demonstrated for controller design in case of a glucose control for treatment of diabetes mellitus and also presented for a numerical situation described in Juhász. The results are in good agreement with the earlier presented symbolic-numeric analysis by Benyó et al.

Algorithms↗

PubMed1976

Reaction times and Digit Symbol Test scores of girls identified as daydreamers by their teachers.

Reaction times and Digit Symbol scores of 14 9-yr.-old girls identified as "daydreamers" by their teachers were compared with those of 14 9-yr.-old girls not so identified. Daydreamers tended to have longer mean reaction times under all test conditions but the differences were small. The daydreamers completed significantly less of the Digit Symbol test than did the non daydreamers and also recalled significantly fewer symbols. The daydreamers had significantly larger variances for three of the four measures of outcome of the Digit Symbol test. These data support the hypothesis that girls identified as daydreamers on a questionnaire completed by their teachers did less well on certain tests of attention than girls not so identified.

Acoustic Stimulation↗

PubMed1985

A noncoding motoric equivalent measures most of what the digit symbol does, including age changes.

The Digit Symbol test and a copying test with identical graphomotor requirements but not visual search, memory, or coding demands were given to 108 normal volunteers and neurologically screened physical rehabilitation patients age 20 to 90 yr. The ratio of coding to copying scores did not change over age, and the high correlations between them were similar across age groups. Little variance was unaccounted for; gross lapses in nonmotoric functions such as memory or attention may prevent Digit Symbol's use with some patients, but subtler decrements need not be invoked to explain age effects. Tentative norms provided here allow evaluation of individual deviations in coding/copying ratios or exploratory use of the copying test to monitor the course of disease or drug titration with patients whose linguistic or perceptual deficits invalidate Digit Symbol or Trail Making tests. If discrepant ratios characterize some groups of patients, the ratios may become useful diagnostic indices. If coding and copying are as closely related for patients with cerebral dysfunction as for normals, the copying test may become a useful alternative to Digit Symbol with patients unable to comply reliably with its requirements.

Adult↗

PubMedDate not supplied

[The informational concept of searching for periodicity in symbol sequences].

Method of informational decomposition has been developed, allowing one to reveal hidden periodicity in any symbol sequences. The informational decomposition is calculated without conversion of a symbol sequence into the numerical one, which facilitates finding periodicities in a symbol sequence. The method permits introducing an analog of the autocorrelation function of a symbol sequence. The method developed by us has been applied to reveal hidden periodicities in nucleotide and amino acid sequences, as well as in different poetical texts. Hidden periodicity has been detected in various genes, testifying to their quantum structure. The functional and structural role of hidden periodicity is discussed.

Algorithms↗

PubMed2003

Ambiguity of human gene symbols in LocusLink and MEDLINE: creating an inventory and a disambiguation test collection.

Genes are discovered almost on a daily basis and new names have to be found. Although there are guidelines for gene nomenclature, the naming process is highly creative. Human genes are often named with a gene symbol and a longer, more descriptive term; the short form is very often an abbreviation of the long form. Abbreviations in biomedical language are highly ambiguous, i.e., one gene symbol often refers to more than one gene. Using an existing abbreviation expansion algorithm,we explore MEDLINE for the use of human gene symbols derived from LocusLink. It turns out that just over 40% of these symbols occur in MEDLINE, however, many of these occurrences are not related to genes. Along the process of making an inventory, a disambiguation test collection is constructed automatically.

Algorithms↗

PubMedDate not supplied

[Are symbolic behaviour and neuroplasticity an example of gene-culture coevolution?].

INTRODUCTION AND DEVELOPMENT: The brain size in the Homo genus not only has not increased during the last 150,000 years but has also experienced a slight reduction in the last 35,000 years. This reduction coincides with the generalization of the symbolic culture that was most likely established during the Upper Palaeolithic. Therefore, the cognitive capacities characteristic in the Homo sapiens could be due to structural and functional changes during the brain evolution, rather than an increase of the brain size. Dependence of symbolic culture probably required an increase of the learning and memory skills, thus demanding, at the same time, an improvement of neuroplasticity. CONCLUSIONS: The epsilon3 and epsilon2 alleles of the apolipoprotein E seem to contribute to a better synaptic repairing, in relation to the ancestral epsilon4 allele. Mutation leading to the epsilon3 allele occurred between 220,000 and 150,000 years ago. Its selection and expansion may have continued until a relatively recent period that coincides with the emergence and expansion of the complex symbolic culture. Other factors favouring neuroplasticity, such as certain polymorphisms and the expression increase of certain proteins as reelin, could also have been selected. Emergence of the symbolic behaviour and increase of its deriving technical and social complexity could have made an intense selective pressure leading to a selection of genes that induced an improvement in neuroplasticity. This would constitute an example of gene-culture coevolution.

Alleles↗

PubMed1984

Perceived variability and symbol use: a common language-cognition interface in children and chimpanzees (Pan troglodytes).

Analysis of two chimpanzees' conversations with their teacher during a tool-use training task demonstrated that chimps use lexigrams, a humanly devised visual symbol system, selectively to encode perceived variability; that is, they generally used their symbols to differentiate alternative possibilities or to represent change or novelty in a situation. In contrast, they tended to leave unsaid what was unchanging, repetitive, or the unique possibility in a situation. Perceived variability influenced not only which symbols were selected but also utterance length: A single dimension of variability in a situation leads to single-lexigram utterances; multiple dimensions are associated with multi-lexigram utterances. This pattern of results indicates that the absence of formal grammatical structure in chimp language does not imply that utterances beyond one word in length are either rote strings or imitations. The chimps' tendency to mention the variable while leaving the constant or redundant unsaid is, moreover, strong support for the position that their use of a humanly devised symbol system is more than a series of conditioned responses.

Animals↗