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PubMed1996

Characterization of a Class of Sigmoid Functions with Applications to Neural Networks.

We study two classes of sigmoids: the simple sigmoids, defined to be odd, asymptotically bounded, completely monotone functions in one variable, and the hyperbolic sigmoids, a proper subset of simple sigmoids and a natural generalization of the hyperbolic tangent. We obtain a complete characterization for the inverses of hyperbolic sigmoids using Euler's incomplete beta functions, and describe composition rules that illustrate how such functions may be synthesized from others. These results are applied to two problems. First we show that with respect to simple sigmoids the continuous Cohen-Grossberg-Hopfield model can be reduced to the (associated) Legendre differential equations. Second, we show that the effect of using simple sigmoids as node transfer functions in a one-hidden layer feedforward network with one summing output may be interpreted as representing the output function as a Fourier series sine transform evaluated at the hidden layer node inputs, thus extending and complementing earlier results in this area. Copyright 1996 Elsevier Science Ltd

Journal Article↗
PubMed2001

Age of the emergence of negative attitudes toward strabismus.

INTRODUCTION: Strabismus impacts a variety of psychosocial variables in both children and adults. Poor self-esteem, lack of confidence, altered interpersonal relationships, and difficulty with employment procurement have been reported. The purpose of this study was to determine the age at which children perceive strabismus in dolls and to evaluate their reactions. METHODS: Three identical dolls were altered so that one was orthotropic, one esotropic, and one exotropic. Thirty-four naïve children between 3 and 7 years of age were individually placed in a waiting room with the 3 dolls as the only toys with which to play. A one-way mirror allowed a hidden observer to tabulate the number of positive and negative behaviors exhibited toward each doll. After a 10-minute observation period, the children were asked a short series of questions about their preferences and attitudes toward the dolls. Odds ratios were then determined for both the observed behaviors and the expressed responses to the strabismic dolls compared with the orthotropic dolls. RESULTS: Children aged 5(3/4) years and older were 73 times more likely than younger children to express a negative feeling about the strabismic dolls when asked (P =.003). Additionally, when comparing the strabismic dolls with the orthotropic doll, children aged 3 to 4(1/4) years did not notice a difference, children aged 4(1/2) to 5(1/4) years tended to describe the eyes as "different," and children aged 5(3/4) years or older almost uniformly gave a negative description of the strabismic dolls. CONCLUSIONS: A negative attitude toward strabismus appears to emerge at approximately 6 years of age. The biopsychosocial determinants of dislike and hostility toward ocular deviations are apparently acquired, learned responses.

Age Factors↗
PubMed2003

Domestic violence in South Australia: a population survey of males and females.

OBJECTIVE: To determine the self-reported prevalence of domestic violence in South Australian adults and to examine the associated risk factors, demographic factors and related health issues using computer-aided telephone interviewing (CATI) methodology. SAMPLE: A representative random sample of South Australian adults aged 18 years and over selected from the Electronic White Pages. Overall, 6,004 interviews were completed (73.1% response rate). RESULTS: In total, 17.8% of adults in South Australia reported some form of domestic violence by a current or an ex-partner. Demographic factors such as low household income, unemployment or part-time employment and health variables such as poor to fair self-reported health status and alcohol abuse problems were found to have a significant relationship with domestic violence. CONCLUSIONS: Approximately one in five South Australian adults report physical and emotional abuse from current or ex-partners, of whom the majority are women who are separated, divorced or never married and on lower incomes. Telephone interviewing is a cost-effective method of identifying prevalence estimates of domestic violence when compared with data collection by way of police reports or hospital emergency statistics. IMPLICATIONS: Domestic violence is a serious public health concern often 'hidden' by the lack of appropriate data. This study has shown that domestic violence is frequent and has important social, economic and health consequences.

Adult↗
PubMed2005

An evolutionary space-time model with varying among-site dependencies.

It is now widely accepted that sites in a protein do not undergo independent evolutionary processes. The underlying assumption is that proteins are composed of conserved and variable linear domains, and thus rates at neighboring sites are correlated. In this paper, we comprehensively examine the performance of an autocorrelation model of evolutionary rates in protein sequences. We further develop a model in which the level of correlation between rates at adjacent sites is not equal at all sites of the protein. High correlation is expected, for example, in linear functional domains. On the other hand, when we consider nonlinear functional regions (e.g., active sites), low correlation is expected because the interaction between distant sites imposes independence of rates in the linear sequence. Our model is based on a hidden Markov model, which accounts for autocorrelation at certain regions of the protein and rate independence at others. We study the differences between the novel model and models which assume either independence or a fixed level of dependence throughout the protein. Using a diverse set of protein data sets we show that the novel model better fits most data sets. We further analyze the potassium-channel protein family and illustrate the relationship between the dependence of rates at adjacent sites and the tertiary structure of the protein.

Evolution, Molecular↗
PubMed2000

Application of neural computing methods for interpreting phospholipid fatty acid profiles of natural microbial communities.

The microbial community compositions of surface and subsurface marine sediments and sediments lining burrows of marine polychaetes and hemichordates from the North Inlet estuary (near Georgetown, S.C. ) were analyzed by comparing ester-linked phospholipid fatty acid (PLFA) profiles with a back-propagating neural network (NN). The NNs were trained to relate PLFA inputs to sediment type outputs (e.g., surface, subsurface, and burrow lining) and worm species (e.g., Notomastus lobatus, Balanoglossus aurantiacus, and Branchyoasychus americana). Sensitivity analysis was used to determine which of the 60 PLFAs significantly contributed to training the NN. The NN architecture was optimized by changing the number of hidden neurons and calculating the cross-validation error between predicted and actual outputs of training and test data. The optimal NN architecture was found to be four hidden neurons with 60-input neurons representing the 60 PLFAs, and four output neurons coding for both sediment types and worm species. Comparison of cross-validation results using NNs and linear discriminant analysis (LDA) revealed that NNs had significantly fewer incorrect classifications (2.7%) than LDA (8.4%). For the NN cross-validation, both sediment type and worm species had 3 incorrect classifications out of 112. For the LDA cross-validation, sediment type and worm species had 7 and 12 incorrect classifications out of 112, respectively. Sensitivity analysis of the trained NNs revealed that 17 fatty acids explained 50% of variability in the data set. These PLFAs were highly different among sediments and burrow types, indicating significant differences in the microbiota.

Animals↗
PubMed1995

Extraversion: a "hidden" personality factor in coping?

Recent evidence suggests a larger role for personality determinants of the coping response than has been traditionally held. In the two studies presented here, we examined the influence of personality on the use of social support and other coping strategies in samples of undergraduate students. The first study surveyed a range of coping responses to naturally occurring stressors and found that Extraversion was related to social support seeking, optimism (identified as germane to coping in prior research) was related to problem solving, and both dispositions were negatively related to avoidance. The second study used an experimental approach and multiple personality measures to correct for possible methodological problems in the first. Extraversion again proved to be associated with help seeking; moreover, this relationship accounted for that of another disposition, self-esteem--a construct considered crucial in the literature. The utility of personality variables, particularly Extraversion, in predicting and explaining the choice of a coping strategy is discussed.

Adaptation, Psychological↗
PubMed1991

Methods for knowledge extraction from a clinical database on liver diseases.

We performed exploratory data analysis (EDA) to examine the hidden structure in liver disease data. The purpose was to demonstrate the potential of statistical techniques for extracting knowledge from an active HIS (hospital information system) database with decision support. The goal is to give strong support to the creation of new rules or "tuning" of old rules in the knowledge base. This would facilitate utilization of large patient databases, now commonly available, to help build/update decision support systems for improved patient care. Several statistical techniques were investigated. Stepwise discriminant analysis was found to be a good method in discriminating among different disease classes. Results showed that classification strength of a few (3) variables was similar to all the available (19) variables. Other important issues in the work are treatment of missing values as well as atypical values in medical databases. In estimating missing values we utilized both statistical methods and artificial intelligence approaches. Both these approaches were promising in the estimation of missing values. The study showed that several statistical approaches are possible for knowledge extraction from clinical data collected retrospectively.

Artificial Intelligence↗
PubMed2003

Estimation of the inbreeding coefficient through use of genomic data.

Many linkage studies are performed in inbred populations, either small isolated populations or large populations with a long tradition of marriages between relatives. In such populations, there exist very complex genealogies with unknown loops. Therefore, the true inbreeding coefficient of an individual is often unknown. Good estimators of the inbreeding coefficient (f) are important, since it has been shown that underestimation of f may lead to false linkage conclusions. When an individual is genotyped for markers spanning the whole genome, it should be possible to use this genomic information to estimate that individual's f. To do so, we propose a maximum-likelihood method that takes marker dependencies into account through a hidden Markov model. This methodology also allows us to infer the full probability distribution of the identity-by-descent (IBD) status of the two alleles of an individual at each marker along the genome (posterior IBD probabilities) and provides a variance for the estimates. We simulate a full genome scan mimicking the true autosomal genome for (1) a first-cousin pedigree and (2) a quadruple-second-cousin pedigree. In both cases, we find that our method accurately estimates f for different marker maps. We also find that the proportion of genome IBD in an individual with a given genealogy is very variable. The approach is illustrated with data from a study of demyelinating autosomal recessive Charcot-Marie-Tooth disease.

Charcot-Marie-Tooth Disease↗
PubMed2006

An artificial neural network-based expert system for the appraisal of two-car crash accidents.

This paper employs artificial neural network (ANN) to develop an accident appraisal expert system. Two ANN models-- party-based and case-based-- with different hidden neurons are trained and validated by k-fold (k=3) cross validation method. A total of 537 two-car crash accidents (1074 parties involved) are randomly and equally divided into three subsets. For the comparison, a discrimination analysis (DA) model is also calibrated. The results show that the ANN model can achieve a high correctness rate of 85.72% in training and 77.91% in validation and a low Schwarz's Bayesian information criterion (SBC) of -0.82 in training and 0.13 in validation, which indicates that the ANN model is suitable for accident appraisal. Furthermore, in order to measure the importance of each explanatory variable, a general influence (GI) index is computed based on the trained weights of ANN. It is found that the most influential variable is right-of-way, followed by location and alcoholic use. This finding concurs with the prior knowledge in accident appraisal. Thus, for the fair assessment of accident liabilities the correctness of these three key variables is of critical importance to police investigation reports.

Accidents, Traffic↗
PubMed2003

Apomixis in flowering plants: an overview.

Apomixis is a common feature of perennial plants, which occurs in ca. 60% of the British flora, but has been largely ignored by reproductive theoreticians. Successful individuals may cover huge areas, and live to great ages, favoured by 'symmetrical' selection. Apomixis is favoured by colonizing modes, for instance post-glacially. Despite its theoretical advantages, apomixis usually coexists with sexuality, suggesting 'hidden' disadvantages. Agamospermy (apomixis by seed) is relatively uncommon, but gains from the attributes of the seed. It pays agamospermy genes, which discourage recombination, to form co-adapted linkage groups, so that they become targets for disadvantageous recessive mutant accumulation. Consequently, agamospermy genes cannot succeed in diploids and agamosperms are hybrid and highly heterotic. Agamospermous endosperm may suffer from genomic imbalance, so that nutritious ovules, which can support embryos without endosperm, may be preadapted for agamospermy. When primary endosperm nucleus fertilization ('pseudogamy') continues as a requirement for many aposporous agamosperms, selfing sex becomes preadaptive and archesporial sex remains an option. Apomictic populations can be quite variable although apomictic families are much less variable than sexuals. Only in some diplosporous species does sex disappear completely, and in those species some release of variability may persist through somatic recombination. The search for an agamospermy gene suitable for genetic modification should target fertile sexuals with a single localized agamospermy (A) gene, which therefore lack a genetic load. The A gene should coexist alongside sexuality, so that it would be easy to select seedlings of sexual and asexual origins. Plants with sporophytic agamospermy provide all these attributes.

Magnoliopsida↗
PubMed1999

Asthma visits to emergency rooms and soybean unloading in the harbors of Valencia and A Coruña, Spain.

Soybean unloading in the harbor of Barcelona, Spain, has been associated with large increases in the numbers of asthma patients treated in emergency departments between 1981 and 1987. In this study, the association between asthma and soybean unloading in two other Spanish cities, Valencia and A Coruña, was assessed. Asthma admissions were retrospectively identified for the period 1993-1995, and harbor activities were investigated in each location. Two approaches were used to assess the association between asthma and soybean unloading: One used unusual asthma days (days with an unusually high number of emergency room asthma visits) as an effect measure, and the other estimated the relative increase in the daily number of emergency room visits by autoregressive Poisson regression, adjusted for meteorologic variables, seasonality, and influenza incidence. No association between unusual asthma days and soya unloading was observed in either Valencia or A Coruña, except for one particular dock in Valencia. When the association between unloaded products and the daily number of emergency asthma visits was studied, a statistically significant association was observed for unloading of soya husk (relative risk = 1.50, 95% confidence interval 1.16-1.94) and soybeans (relative risk = 1.31, 95% confidence interval 1.08-1.59) in A Coruña. In Valencia, a statistical association was found only for the unloading of soybeans at two particular docks. Although these findings support the notion that asthma outbreaks are not a common hidden condition in most harbors where soybeans are unloaded, the weak associations reported are likely to be causal. Therefore, appropriate control measures should be implemented to avoid soybean dust emissions, particularly in harbors with populations living in the vicinity.

Air Pollutants↗
PubMed1994

Contrasting population structure from nuclear intron sequences and mtDNA of humpback whales.

Powerful analyses of population structure require information from multiple genetic loci. To help develop a molecular toolbox for obtaining this information, we have designed universal oligonucleotide primers that span conserved intron-exon junctions in a wide variety of animal phyla. We test the utility of exon-primed, intron-crossing amplifications by analyzing the variability of actin intron sequences from humpback, blue, and bowhead whales and comparing the results with mitochondrial DNA (mtDNA) haplotype data. Humpback actin introns fall into two major clades that exist in different frequencies in different oceanic populations. It is surprising that Hawaii and California populations, which are very distinct in mtDNAs, are similar in actin intron alleles. This discrepancy between mtDNA and nuclear DNA results may be due either to differences in genetic drift in mitochondrial and nuclear genes or to preferential movement of males, which do not transmit mtDNA to offspring, between separate breeding grounds. Opposing mtDNA and nuclear DNA results can help clarify otherwise hidden patterns of structure in natural populations.

Animals↗
PubMed1997

Dimensions and density of dendritic spines from rat dentate granule cells based on reconstructions from serial electron micrographs.

In the hippocampus, most excitatory synapses are located on dendritic spines. It has been postulated that the geometry of spines and/or postsynaptic density (PSD) influences synaptic efficiency and may contribute to the expression of plastic processes such as learning or long-term potentiation (LTP). Based on three-dimensional reconstructions of dentate granule cell dendrites from serial electron micrographs, we have measured head dimensions, neck cross-sectional areas, neck length, and PSD area and form of 115 spines of dentate granule cells in the medial perforant path termination zone. All dimensions showed a large variability, with up to 100-fold differences in values. A calculated diffusion index for transport of molecules through the reconstructed neck varied over a 100-fold range. The neck and head dimensions were moderately positively correlated, whereas the PSD area was strongly correlated with head volume. Distribution histograms and scatter plots of various spine dimensions did not reveal any systematic clustering, suggesting that there is a continuum of spine geometries rather than distinct classes for granule cell dendritic spines in the middle molecular layer. Transversely (n = 13) and longitudinally (n = 27) sectioned dendrites had mean spine densities of 2.66 and 1.01 spines/microns, respectively, uncorrected for so-called hidden spines. Bifurcating spines made up 2.1% of the total spine number in transversely and 2.3% in longitudinally sectioned dendrites. The twin spine heads never shared the same presynaptic bouton. Fenestrated or split PSDs shared the same presynaptic element in all but two cases, arguing against PSD division as an intermediate step in synapse formation.

Animals↗
PubMed1999

Revisited measles and chickenpox dynamics through orthogonal transformation.

The question addressed is whether or not childhood epidemics such as measles and chickenpox are characterized by low-dimensional chaos. We propose a new method for the detection and extraction of hidden periodic components embedded in an irregular cyclical series, and study the characterization of the epidemiological series in terms of the characteristic features or periodicity attributes of the extracted components. It is shown that the measles series possesses two periodic components each having a period of one year. Both the periodic components have time-varying pattern, and the process is nonlinear and deterministic; there is no evidence of strong chaoticity in the measles dynamics. The chickenpox series has one seasonal component with stable pattern, and the process is deterministic but linear, and hence non-chaotic. We also propose surrogate generators based on null hypotheses relating to the variability of the periodicity attributes to analyse the dynamics in the epidemic series. The process dynamics is also studied using seasonally forced SEIR epidemic model, and the characterization performance of the proposed schemes is assessed.

Chickenpox↗
PubMed2000

Nurse practitioners' perceptions of their caring behaviors.

PURPOSE: To explore nurse practitioners' (NPs) perceptions of their own caring behaviors, the relationship between sociodemographic variables, environmental factors, and NP's perceptions of their caring behaviors. DATA SOURCES: A mailed survey to a systematic random sample of 200 members of an Illinois NP group. CONCLUSIONS: The top ten caring behaviors in rank order were appreciating the patient as a human being, showing respect for the patient, being sensitive to the patient, talking with the patient, treating patient information confidentially, treating the patient as an individual, encouraging the patient to call with problems, being honest with the patient, and listening attentively to the patient. IMPLICATIONS FOR PRACTICE: The quality of instruction in the biomedical aspect of nursing education is relatively easily assessed. Caring is nurses' hidden work that may go unrecognized except when the caring behaviors are missed by the patients or their families.

Adult↗
PubMed2003

Psoriatic arthritis.

AIM OF THE STUDY: To evaluate the clinical pattern of psoriatic arthritis in patients attending a tertiary referral centre in South India. METHODOLOGY: Case records of one hundred and sixteen patients with psoriatic arthritis (PsA) who had attended our Rheumatology Department were analysed using demographic, clinical, laboratory and radiographic variables and the data were compared with other studies. RESULTS: Among 116 patients, 78 were males and 38 were females (ratio 2:1). Peak incidence (69%) was in the fourth and fifth decades. One patient had juvenile psoriatic arthritis (onset <16 years of age). Symmetric polyarthritis (48.3%) was the commonest subtype. Arthritis followed the skin lesions in 50.8% of patients, preceded in 12.1% and occurred simultaneously in 37.1%. Knee (66.4%) was the commonest joint involved. Extra-articular features like sausage digits (19%), enthesitis (7.8%) and eye manifestations (1.7%) like conjunctivitis and uveitis were observed. Psoriasis vulgaris (81%) was the commonest psoriatic lesion. Scalp (57.8%) was the most common hidden site. All the three patients with DIP arthritis alone had nail lesions. ESR and C-reactive protein were elevated in 51.7% and 43.9% of patients respectively. Rheumatoid factor was positive in 3.4 % and antinuclear antibody (ANA) was present in 5.4% (3/56) of patients. HIV infection was detected in 2.3% (1/44) of patients. Radiographic features like sacroiliitis (11.2%), calcaneal spur (7.8%), erosions (5.2%) and syndesmophytes (5.2%) were observed. One patient had 'pencil-in-cup deformity'. CONCLUSION: Psoriatic arthritis is more common in males. Symmetric polyarthritis is the commonest subtype. Arthritis commonly follows the skin lesions. Psoriasis vulgaris is the most common skin lesion and scalp is the commonest hidden site. ESR and CRP can be normal in psoriatic arthritis.

Adolescent↗
PubMed1961

Genetic variability in populations of Aedes aegypti.

Although Aëdes aegypti shows extensive physiological, bionomic and morphological variation in different populations, the genetic basis for this variation has never been determined. Genetic plasticity influences disease transmission, resistance to control measures, and breeding behaviour. Solutions to problems of public health importance may depend upon an understanding of the present and potential degree of genetic resiliency in mosquito populations.The purpose of the work described in this paper was to demonstrate that a pattern of considerable genetic plasticity exists for A. aegypti and to indicate the range and some of the implications of this plasticity.Observations on over 30 strains of various geographical origins have revealed genetic variation with respect to sex ratio and at least 35 morphological characteristics. Balanced polymorphism is common in laboratory colonies and probably in field populations as well. Inbreeding experiments were conducted to determine the degree of heterozygosity in populations. On the average, every mosquito carried one hidden morphological mutation.

Aedes↗
PubMedDate not supplied

Cardiovascular mortality--the hidden peril of heat waves.

OBJECTIVE: Define the mortality associated with extremely hot weather during the 04 July through 14 July, 1993 heat wave that struck the northeastern United States. METHODS: DESIGN--A rapid field assessment was used to compare mortality occurring during the heat wave to mortality occurring during a period in which there was no heat wave using copies of death certificates. The findings of the rapid field assessment were validated, and it was determined whether increases in mortality occurred in other metropolitan east-coast counties also affected by the heat wave, by reviewing computerized mortality files. SETTING--Information was collected on all deaths occurring in Baltimore City, Maryland; Baltimore County, Maryland; Essex County, New Jersey; Newcastle County, Delaware; and Philadelphia County, Pennsylvania; during these specified study periods: 08-18 June (comparison period) and 06-16 July (heat wave study period), 1993. MAIN OUTCOME MEASURES--Ratios for total mortality, cause-specific mortality, and variables such as age, sex, race, residence, and day and place of death, that were available from death certificates were calculated. RESULTS: From the rapid field assessment, the following were observed: a 26% increase in total mortality and a 98% increase in cardiovascular mortality associated with the heat wave in Philadelphia. Data from the computerized mortality files showed an increase in total mortality in four of five counties examined and an increase in cardiovascular mortality in all five counties. The risk for death for those dying from cardiovascular disease increased significantly for people older than 64 years, for both sexes, and all races. CONCLUSION: As initially indicated by the Philadelphia Medical Examiner, there was excess mortality associated with a heat wave in Philadelphia. All other nearby counties examined also experienced excess mortality associated with the heat wave, although this excess was not recognized by the local health officials. The true impact of a heat wave that causes excess preventable mortality must be appropriately and rapidly ascertained. Using a national standard to certify a death as heat-related will provide the needed information rapidly so that public health resources can be more effectively allocated and mobilized to prevent further heat-related illnesses and death.

Adolescent↗