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PubMed2003

On-line reoptimization of filter designs for multivariate optical elements.

An automated method for producing multivariate optical element (MOE) interference filters that are robust to errors in the reactive magnetron sputtering process is described. Reactive magnetron sputtering produces films of excellent thickness and uniformity. However, small changes in the thickness of individual layers can have severe adverse effects on the predictive ability of the MOE. Adaptive reoptimization of the filter design during the deposition process can maintain the predictive ability of the final filter by changing the thickness of the undeposited layers to compensate for the errors in deposition. The merit function used, the standard error of calibration, is fundamentally different from the standard spectrum matching. This new merit function allows large changes in the transmission spectrum of the filter to maintain performance.

Journal Article↗
PubMed2000

Adaptive feeding across environmental gradients and its effect on population dynamics.

This paper analyzes a consumer's adaptive feeding response to environmental gradients. We consider a consumer-resource system where resources are distributed among many discrete resource patches. Each consumer exhibits a feeding morphology allowing it to remove resources from a patch down to some threshold density (or level) before having to seek resources elsewhere. Assuming consumers trade off resource extraction with patch access and predation, we show that for a given environment there often exists a single evolutionarily stable feeding threshold and it is an evolutionary attractor. We then investigate how the population dynamics of the resource and the consumer change as the environment changes. Two cases are considered: (i) all consumers exhibit a fixed feeding threshold that is adaptive for an intermediate environment; and (ii) the consumer population adapts and adopts the evolutionarily stable feeding threshold associated with the current environment. In less harsh environments (i.e., environments where consumers experience a lower risk of predation, or environments where resource patches are more abundant) the adaptive consumer population is predicted to evolve so that resources within a patch are depleted to lower densities. We show that the change in consumer density due to environmental change can be rather different depending on whether or not the population can adapt. In some situations we observe that when the consumer's environment becomes harsher, the consumer population may increase in density before a rapid crash to extinction. This result has implications for monitoring and managing a population.

Adaptation, Physiological↗
PubMed2000

Toward a developmental operational definition of autism.

Traditional approaches to diagnosing autism emphasize delays in communication and socialization. Traditional diagnostic schemes typically list symptoms (e.g., lack of eye contact), but provide little guidance on how to incorporate information about developmental level in making a diagnosis. Because standardized measures of adaptive behavior can provide information about children's communication, socialization, and other behavior relative to their age, they may be useful tools for diagnosing autism. This study investigated the ability of the Vineland Adaptive Behavior Scales to identify children with autism. Vineland scores and measures of intellectual functioning were obtained for children with autism, PDDNOS, and other developmental disorders (DD). Discriminant function analyses indicated that the autism and combined nonautism (PDDNOS and DD) groups could be differentiated on the basis of socialization, daily living skills, and serious maladaptive behaviors. Socialization alone accounted for 48% of the variance in diagnosis. Using regression analyses derived from a large normative sample, adaptive behavior scores were predicted from chronological age (CA) and mental age (MA). Socialization scores in the autism group were substantially below the level predicted from CA or MA. An index derived from the ratio of actual to predicted socialization scores correctly classified 86% of both autism and nonautism cases. Findings suggest that comparison of obtained Vineland socialization scores to those predicted by CA or MA may be useful in clarifying the diagnosis of autism.

Adaptation, Psychological↗
PubMed2002

Variable expression of Toll-like receptor in murine innate and adaptive immune cell lines.

Pattern recognition receptors (PRR) play an important roll in immediate responses to different conserved molecules produced by microbes. In this paper we describe the cloning of the mouse homolog of Toll-like receptor (TLR) 3, and present an analysis of the expression of this gene in innate and adaptive immune cell lines. We also performed a broad expression study on these cells of other TLR, including TLR family members whose expression pattern is not known, i.e. TLR7. The analysis was done in order to understand, and possibly predict, how innate and adaptive immune cells respond to microbial pattern antigens. This first large-scale analysis of immune cell TLR expression in the mouse reveals that cells of the innate immune system express a broader number of TLR than cells of the adaptive immune system, supporting preconceptions concerning the hierarchy of immune cells involved in direct pathogen recognition. Additionally, the expression of TLR transcripts by mast cells, neutrophils and microglial cells observed here suggests that pathogen-associated molecular pattern molecules could induce activation of these cells through TLR. Finally, the mouse homolog of human TLR3 identified here may, like its human counterpart, be an exceptional TLR molecule due to its lack of a conserved proline residue seen to be involved in existing TLR signaling capabilities found in other TLR family members.

Amino Acid Sequence↗
PubMed1992

Positive motion after-effect induced by bandpass-filtered random-dot kinematograms.

Using spatially filtered random-dot kinematograms (RDK) with a 1 octave bandwidth, the duration and direction of motion aftereffect (MAE) were measured while varying step displacement, and the results were compared to those for motion direction discrimination. We found that MAE and motion discrimination show quite different dependencies on displacement. At displacements around 0.5 cycles of the lowest frequency, while motion discrimination was still almost perfect, normal MAE vanished and MAE in the same direction as that of the adapting stimuli, which we name "positive MAE", was observed. Similar results were obtained for both 1- and 2-dimensional filtered patterns. A theoretical examination based on the Fourier components of the stimuli showed that the displacement dependency of MAE is predictable in terms of adaptation of first-order detectors, but that of motion discrimination is not. The present results indicate that direction perception and MAE for bandpass RDKs are mediated at least partially by separate mechanisms, and that direction perception at larger displacements is mediated by the second-order mechanism which detects movement of contrast modulation in the image.

Adaptation, Ocular↗
PubMed1992

Evaluation of transient responses of ammonia-selective potentiometric electrodes for quantitative applications.

An error-compensating, predictive kinetic method is adapted and evaluated for quantitative applications based on transient responses from an ammonia-selective electrode. Transient data collected during the early part of the electrode response are used with a curve-fitting method and appropriate mathematical models to predict the signal that would be measured if the response were monitored to equilibrium. Several different theoretical and empirical models were evaluated, and all but one of the models tested permitted reliable prediction of equilibrium potentials for most responses. Predicted values of equilibrium signal were close to measured values and exhibited the expected logarithmic dependence on ammonia concentration in the range from 0.1 to 100 mmol/L. Slopes of calibration plots E infinity vs log C, varied from about 50.5 to 65.0 mV per decade with an average value of 56.9 +/- 4.2 mV per decade. Quantitative data are used to rank the different models in terms of their utility for kinetic-based determinations of ammonia by using the ammonia-selective electrode.

Ammonia↗
PubMed1989

Diminished foveal sensitivity may predict the development of advanced age-related macular degeneration.

Visual function testing was performed on one eye with drusen from each of 18 elderly patients in 1984. Eleven patients had advanced age-related macular degeneration (AMD) in the fellow eye, and seven had only bilateral drusen. These patients were all followed prospectively (median, 45 months), at which time one eye had a new vessel membrane, three eyes had pigment epithelial detachments, and one eye had geographic atrophy. Only two of these five eyes had AMD-related visual loss in the fellow eye in 1984. The degree of loss of foveal dark-adapted sensitivity in 1984 predicted which patients developed advanced AMD with 100% sensitivity and 92% specificity. The presence of high-risk drusen characteristics in 1984 predicted the development of advanced AMD with 100% sensitivity but only 55% specificity. For this small group of patients, foveal dark-adapted sensitivity loss was an excellent predictor of the subsequent development of advanced AMD in eyes with drusen. A prospective study of a large group of patients with drusen is being undertaken to validate this finding.

Aged↗
PubMedDate not supplied

[The HLA system: a clinical help?].

UNLABELLED: Chronic diseases are polymorph and influenced by many environmental and genetic factors. The HLA system is implicated in the modulation the onset and the evolution of chronic diseases. These observations are important to be considered for the prediction, prognosis and treatment adaptation. Evaluation tests are mainly statistical and are based on epidemiological studies. Thus, results must be considered with caution. Two aspects are to be considered: DIAGNOSIS: Associations between HLA alleles and chronic diseases are well known but concern very few diseases like narcolepsy or rheumatoid arthritis. Insulin dependent diabetes mellitus is particular because the prediction is limited to familial studies. PROGNOSIS: This point is less documented in clinical applications but is of interest particularly in inflammatory bowel diseases or systemic affections. This observation can be considered as a compartmental response which is a kind of adaptation to stress.

Alleles↗
PubMedDate not supplied

[The role of the environmental factors on the development of adaptive skills in intellectual disabilities subjects].

AIMS: The aims of the study was to evaluate if environmental factors can influence the effectiveness of therapeutic intervention of subjects with intellectual disabilities. METHODS: 46 adolescents and adults with mental retardation, in semi-residential rehabilitative treatment, have been assessed over a 2-years period. The evolution of adaptive functioning over time has been assessed through the AAMD-ABS. The development of the adaptive skills at follow-up has been correlated with socio-economic and cultural factors. RESULTS: Linear regression showed that age of both parents, mother's health status, lack of one parent, SES, and housing conditions, represent significant covariates to predicting evolution of the adaptive functioning; these factors independently influence effectiveness of the therapy from the kind of treatment. CONCLUSION: The results demonstrate that effectiveness of the therapy can be conditioned from ability to fulfil the needs of the families, through social and supporting programs.

Adaptation, Psychological↗
PubMed2005

A method for predicting a student's risk for academic probation in a professional program in allied health.

Identification of students at risk for academic difficulty in a physical therapy program would provide opportunities to implement preemptive measures designed to enhance successful academic performance. The purpose of this study was to determine if a method advocated for use in evidence-based practice could be adapted for use in predicting probationary status for students in a program in allied health, specifically physical therapy. Preadmission combined math and science grade point average; cumulative grade point average (TGPA); verbal Graduate Record Examination score (VGRE), quantitative Graduate Record Examination score (QGRE), and analytic Graduate Record Examination score; and probation status were obtained for 305 students (mean age, 25.5 years; SD, 4.14) accepted into one physical therapy program from 1995 to 2000. Predictors of probation were identified using stepwise logistic regression. Likelihood ratios were calculated for three score intervals derived from receiver operating characteristic analysis. TGPA, VGRE, and QGRE were significant predictors in the regression model (p < 0.05). VGRE was the only variable that consistently showed predictive capability (likelihood ratio, 2.9; 95% confidence interval, 1.2-6.9). Quantitative preadmission data can be used in combination to improve the predictive power of estimates of probation risk. We contend that the analytic methods illustrated in this report could be used in academic programs to assist faculty with management of students who are at risk for academic difficulties.

Adult↗
PubMed2000

Self-regulation phenomena in bacterial reaction centers. I. General theory.

A model for light-induced charge separation in a donor-acceptor system of the reaction center of photosynthetic bacteria is described. This description is predicated on a self-regulation of the flow of photo-activated electrons due to self-consistent, slow structural rearrangements of the macromolecule. Effects of the interaction between the separated charges and the slow structural modes of the biomolecule may accumulate during multiple, sequential charge transfer events. This accumulation produces non-linear dynamic effects on system function, providing a regulation of the charge separation efficiency. For a biomolecule with a finite number of different charge-transfer states, the quasi-stationary populations of these states with a localized electron on different cofactors may deviate from a Lagmuir law dependence with actinic light intensity. Such deviations are predicted by the model to be due to light-induced structural changes. The theory of self-regulation developed here assumes that light-induced changes in the effective adiabatic potential occur along a slow structural coordinate. In this model, a "light-adapted" conformational state appears when bifurcation produces a new minimum in the adiabatic potential. In this state, the lifetime of the charge-separated state may be quite different from that of the "dark-adapted" conformation. The results predicted by this theory agree with previously obtained experimental results on photosynthetic reaction centers.

Darkness↗
PubMed2003

Description and interpretation of adaptive evolution of Escherichia coli K-12 MG1655 by using a genome-scale in silico metabolic model.

Genome-scale in silico metabolic networks of Escherichia coli have been reconstructed. By using a constraint-based in silico model of a reconstructed network, the range of phenotypes exhibited by E. coli under different growth conditions can be computed, and optimal growth phenotypes can be predicted. We hypothesized that the end point of adaptive evolution of E. coli could be accurately described a priori by our in silico model since adaptive evolution should lead to an optimal phenotype. Adaptive evolution of E. coli during prolonged exponential growth was performed with M9 minimal medium supplemented with 2 g of alpha-ketoglutarate per liter, 2 g of lactate per liter, or 2 g of pyruvate per liter at both 30 and 37 degrees C, which produced seven distinct strains. The growth rates, substrate uptake rates, oxygen uptake rates, by-product secretion patterns, and growth rates on alternative substrates were measured for each strain as a function of evolutionary time. Three major conclusions were drawn from the experimental results. First, adaptive evolution leads to a phenotype characterized by maximized growth rates that may not correspond to the highest biomass yield. Second, metabolic phenotypes resulting from adaptive evolution can be described and predicted computationally. Third, adaptive evolution on a single substrate leads to changes in growth characteristics on other substrates that could signify parallel or opposing growth objectives. Together, the results show that genome-scale in silico metabolic models can describe the end point of adaptive evolution a priori and can be used to gain insight into the adaptive evolutionary process for E. coli.

Adaptation, Physiological↗
PubMed2003

Family and community factors that predict internalizing and externalizing symptoms in low-income, African-American children: a preliminary report.

To learn more about the roots of internalizing and externalizing problems in low-income, African-American children, aged 8-12 years, particularly for family and community factors, we aimed to determine which variables (mother's psychological functioning, mother's intimate partner violence status [IPV], family cohesion and adaptability, neighborhood disorder) uniquely predicted a child's internalizing distress and externalizing distress, and the amount of variance explained by the model. Results from the regression model predicting internalizing distress indicates that the five predictor variables accounted for 38% of the variance. Two of the five predictors were significantly related to child's internalizing distress scores: mother's intimate partner violence status and maternal psychological distress. Results from the regression model predicting externalizing distress indicates that the five predictor variables accounted for 8% of the variance. The two predictors significantly related to child's externalizing distress scores were levels of family cohesion and maternal psychological distress. Directions for future research and clinical implications are provided.

Adolescent↗
PubMed1993

Light adaptation of human rod receptors: the leading edge of the human a-wave and models of rod receptor activity.

The human rod receptors can be studied by measuring the leading edge of the rod a-wave of the ERG. Computational models, previously shown to fit the recordings from single rods, are fitted to dark-adapted a-wave responses. A model proposed by Lamb and Pugh [(1992) Journal of Physiology, 499, 719-758] fits slightly better than the traditional models based upon n-stage exponential filters. To test alternative models of rod light adaptation, a-waves were recorded to flashes presented upon steady adapting lights. Steady adapting lights decrease the rods' sensitivity. Human rods must adapt as response compression alone predicts far greater decreases in sensitivity. The evidence suggests that the mechanism(s) of adaptation include a change in the time-course of the rod's response. Human rods appear to adapt in much the same manner as do the rods of other vertebrates.

Adaptation, Ocular↗
PubMed2003

Adaptive evolution of genes and gene families.

The huge influx of genomic sequence and new statistical methods is making the discovery of genes subjected to adaptive evolution increasingly common. The use of comparative genomics to identify adaptive evolution is resulting in predictions of functionally important genes and gene regions. However, the selective pressure driving the adaptive evolution of most genes remains mysterious.

Adaptation, Physiological↗
PubMed1990

Speech perception in low-pass filtered noise for normal and hearing-impaired listeners.

Two experiments were conducted concerning speech perception in noise. In Experiment 1, a comparison was made between adaptive and fixed-level procedures to estimate the S/N ratio at which 50% correct performance occurred for nonsense syllables for normal-hearing listeners. The two methods yield similar S/N ratio estimates, but the consonant confusions found with the fixed-level method could not be predicted accurately from the adaptive procedure. In Experiment 2, the adaptive procedure was used to estimate the S/N ratio for a 50% performance level in low-pass filtered noise with a range of cutoff frequencies. Data were obtained from 5 normal-hearing listeners at two speech levels (50 and 75 dB SPL) and 4 hearing-impaired listeners at one speech level (75 dB SPL). The hearing-impaired listeners required a better S/N ratio than the normal listeners at either presentation level for all except the widest bandwidth, where their S/N ratios began to converge with the normal values. In addition, the S/N ratios for the hearing-impaired listeners plateaued at relatively narrow bandwidths (0.75 to 2.5 kHz) compared to the normal-hearing group (3.0 to 5.0 kHz). That is, the addition of high-frequency components to the noise did not alter performance. These findings suggest that the hearing-impaired listeners may have relied upon either low-frequency cues or prosodic cues in the perception of these test items.

Adaptation, Physiological↗
PubMed1986

Sex ratio variation in mammals.

Parents will increase their fitness by varying the sex ratio of their progeny in response to differences in the costs and benefits of producing sons and daughters. Sex differences in energy requirements or viability during early growth, differences in the relative fitness of male and female offspring, and competition or cooperation between siblings or between siblings and parents might all be expected to affect the sex ratio. Although few trends have yet been shown to be consistent, growing numbers of studies have demonstrated significant variation in birth sex ratios in non-human mammals. These are commonly cited as evidence of adaptive manipulation of the sex ratio. However, several different mechanisms may affect the birth sex ratio, and not all of them are likely to be adaptive. Valid evidence that sex ratio trends are adaptive must be based either on the overall distribution of those trends or on cases in which the sex ratio can be shown to vary with the relative fitness of producing sons and daughters. The distribution of observed sex ratio trends does not conform closely to the predictions of any single adaptive theory. Some recent studies, however, indicate that, within species, the sex ratio varies with the costs or benefits of producing male or female offspring.

Adaptation, Physiological↗
PubMed2003

Models for predicting dry matter intake of Holsteins during the prefresh transition period.

The objectives of this study were to develop and validate a model for predicting dry matter intake (DMI) of Holsteins during the prefresh transition period. The original database (ODB) for model development was established by compiling parity, body condition score (BCS), and DMI data during the final 3 wk of gestation from 366 Holsteins fed 24 different diets that were used in eight experiments conducted at three universities. For model validation, a validation database (VDB) was established by compiling data from 333 prefresh transition Holsteins fed 25 different diets that were used in eight experiments conducted at five universities. Dry matter intake during the prefresh transition period was fitted to an exponential function: DMI(t) = a + pe(kt), where DMI(t) = DMI as a percentage of body weight (BW) at time t, a = asymptotic intercept at time--infinity, p = change in intake (kg) from the asymptotic intercept until parturition, k = rate constant influencing the shape of the curve, and t = day relative to parturition expressed as days pregnant--280. The model developed from the ODB predicted DMI of heifers in the VDB with satisfactory accuracy and precision. However, this was not true for cows, probably due to differences in BCS of cows and diets fed to cows from the two data sets. When a subset of cows was selected from each data set that had similar BCS (> 4.0) and were fed similar diets, accuracy and precision of the model predicting DMI was improved. Finally, both databases were combined to develop final models for predicting DMI of heifers and cows. Proposed models for predicting mean daily DMI of heifers and cows during the prefresh transition period were DMI(t) = 1.713-0.688e(0.344t) (R2 = 0.96) and DMI(t) = 1.979-0.756e(0.154t) (R2 = 0.97), respectively. Adjustment factors for animal and dietary factors were generated to demonstrate the plausibility of adaptive fitting of the prediction. The regression coefficients of prediction models (a, p, and k) were affected by BCS and dietary organic macronutrient concentrations.

Animal Nutritional Physiological Phenomena↗