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PubMed1996

Relations between problem orientation and optimism, pessimism, and trait affectivity: a construct validation study.

This study investigated the construct validity of the Positive and Negative Problem Orientation scales of the Social Problem-Solving Inventory-Revised (SPSI-R) by examining the relations between these scales and measures of optimism, pessimism, and trait affectivity. Consistent with expectations based on social problem-solving theory, positive problem orientation was found to have a relatively large amount of variance in common with optimism and positive affectivity, and negative problem orientation was found to share a large amount of variance with pessimism and negative affectivity, but not enough to be considered redundant in either case. Positive problem orientation was found to add significant incremental validity to the prediction of adaptive problem-engagement coping even after partialing out the variance associated with optimism and positive affectivity. In addition, negative problem orientation was found to add unique variance to the prediction of psychological distress even after controlling for pessimism and negative affectivity.

Adaptation, Psychological↗
PubMed1977

Plasticity in the adult vestibulo-ocular reflex arc.

Human subjects with maintained reversal of their horizontal field of vision exhibit very substantial adaptive changes in their 'horizontal' vestibulo-ocular reflex (v.o.r.). Short durations (8 min) of vision reversal during natural head movement led to 20% v.o.r. attenuation while long periods (4 weeks) eventually led to approximate reversal of the reflex. The reversed condition is approached by a complex, but highly systematic, series of changes in gain and phase of the reflex response relative to normal. Recovery after return to normal vision exhibits a similar duration, but different pattern, to that of the original adaptation. A chronic cat preparation with long-term optical reversal of vision has now been developed and shows similar adaptive and recovery changes at low test stimulus amplitudes, but different patterns of adaptive response at high amplitudes. An adaptive neural model employing known vestibulo-ocular pathways is proposed to account for these experimentally observed plastic changes. The model is used to predict the adapted response to patterns of stimulation extending beyond the range of experimental investigation.

Adaptation, Physiological↗
PubMed1982

Stress, symptom proneness, and general adaptational distress during pregnancy.

Symptom proneness (SP), the 20 psychiatric items of the Cornell Medical Index, here called the Cornell Psychiatric Items (CPI), and a test developed partially from the Schedule of Recent Experiences called the Utah Stress Scales (STRESS) were used to predict general adaptational distress (GAD) symptoms during pregnancy on a sample of 1306 primigravidas. The causal model explored in seven path analyses developed for months 3-9 of pregnancy is that SP and STRESS affect CPI, and that SP, STRESS, and CPI directly affect GAD symptoms. Results suggest that CPI is most predictive of GAD symptoms until the ninth month when SP and STRESS become more predictive. It is suggested that GAD pregnancy symptoms are affected by situational stress, symptom proneness, and level of psychological upset and that this system of relations changes over the course of pregnancy. This information should have important implications for anticipating potential problems and improving the quality of nursing care of pregnant women.

Adaptation, Psychological↗
PubMed2002

Predicting the occurrence of genetic adaptation to dioxinlike compounds in populations of the estuarine fish Fundulus heteroclitus.

A population of the nonmigratory estuarine fish species Fundulus heteroclitus (mummichog) indigenous to a polychlorinated biphenyl (PCB)-contaminated Superfund site (New Bedford Harbor, MA, USA) demonstrated an inherited tolerance to local, dioxinlike contaminants (DLCs). These findings suggest that DLCs have acted as selective agents, allowing the survival of only the most tolerant individuals, forming DLC-adapted populations. We hypothesized that DLC-tolerant mummichog populations would reside where local conditions are toxic to sensitive individuals, and that toxic environmental conditions could be predicted based on responses of sensitive early life stages to laboratory exposures of DLCs. As a measure of DLC tolerance, progeny of field-collected fish were tested in the laboratory with a dioxinlike PCB congener, 3,3',4,4',5-pentachlorobiphenyl (PCB 126). Mummichog populations were collected from sites with sediment PCB concentrations predicted to range from nontoxic to toxic. Consistent with predictions, tolerant populations were indigenous to sites with elevated sediment PCB concentrations. Also, as predicted, DLC-tolerant populations were resident to sites far less contaminated than the Superfund site. These results suggest that exposures to persistent, bioaccumulative, and toxic contaminants may produce evolutionary effects on a geographic scale larger than previously envisioned. This study presents an approach and describes a model system that may improve understanding of the scale of occurrence for these potentially irreversible ecological effects.

Adaptation, Physiological↗
PubMed1996

A model of the cerebellum in adaptive control of saccadic gain. II. Simulation results.

A large, realistic cerebellar neural network has been incorporated into a previously developed saccade model. Using this model, in the present paper, we simulate the complex spatiotemporal behavior of the neuronal subpopulations implicated in adaptive saccadic control. Our simulation results are in good agreement with neurophysiological and behavioral data. Furthermore, we suggest several new experiments to test the validity of our predictions on adaptive saccadic control.

Adaptation, Physiological↗
PubMed2001

Pre-clinical methods for detecting the hypersensitivity potential of pharmaceuticals: regulatory considerations.

Immune-based systemic hypersensitivities account for a significant number of adverse drug reactions. There appear to be no adequate nonclinical models to predict systemic hypersensitivity to small molecular weight drugs. Although there are very good methods for detecting drugs that can induce contact sensitization, these have not been successfully adapted for prediction of systemic hypersensitivity. Several factors have made the development of adequate models difficult. The term systemic hypersensitivity encompases many discrete immunopathologies. Each type of immunopathology presumably is the result of a specific cluster of immunologic and biochemical phenomena. Certainly other factors, such as genetic predisposition, metabolic idiosyncrasies, and concomitant diseases, further complicate the problem. Therefore, it may be difficult to find common mechanisms upon which to construct adequate models to predict specific types of systemic hypersensitivity reactions. There is some reason to hope, however, that adequate methods could be developed for at least identifying drugs that have the potential to produce signs indicative of a general hazard for immune-based reactions.

Animals↗
PubMed1989

The use of adaptive algorithms for obtaining optimal electrical shimming in magnetic resonance imaging (MRI).

A method of determining the dc coil current values to electrically shim the static magnetic fields used in magnetic resonance imaging (MRI) using modified steepest descent adaptive algorithm is described. Using a 32 cm diameter by a 40 cm long water phantom as the test volume, the algorithm achieved field homogeneities of 0.2 parts per million (ppm) peak-to-peak within a 20 cm diameter spherical imaging volume, and 1.3 ppm peak-to-peak within the entire phantom. The algorithm achieved an inhomogeneity variance of 0.18 ppm2. The shim system was successfully modeled as a sum of adaptive linear combiners. The model contains 13 parameters that can be varied, 12 shim coil currents, and the receiver mixer frequency. The model was then used to predict key adaptive algorithm parameters. Experimental verification of these parameters lends support to the accuracy of the model.

Algorithms↗
PubMed2006

Loudness adaptation in acoustic and electric hearing.

The present study is aimed to evaluate and compare loudness adaptation between normal hearing and cochlear-implant subjects. Loudness adaptation for 367-s pure tones was measured in five normal-hearing subjects at three frequencies (125, 1,000, and 8,000 Hz) and three levels (30, 60, and 90 dB SPL). In addition, loudness adaptation for 367-s pulse trains was measured in five Clarion cochlear-implant subjects at three stimulation rates (100, 991, and 4,296 Hz), three levels (10, 50, and 90% of the electric dynamic range), three stimulation positions (apical, middle and basal), and two stimulation modes (monopolar and bipolar). The method of successive magnitude estimation was used to quantify loudness adaptation. Similar to the previous results, we found that loudness adaptation in normal-hearing subjects increases with decreasing level and increasing frequency. However, we also found a small but significant loudness enhancement at 90 dB SPL in acoustic hearing. Despite large individual variability, we found that loudness adaptation in cochlear-implant subjects increases with decreasing levels, but is not significantly affected by the rate, place and mode of stimulation. A phenomenological model was proposed to predict loudness adaptation as a function of stimulus frequency and level in acoustic hearing. The present results were not fully compatible with either the restricted excitation hypothesis or the neural adaptation hypothesis. Loudness adaptation may have a central component that is dependent on the peripheral excitation pattern.

Acclimatization↗
PubMed1969

Changes in the maintained discharge with adaptation level in the cat retina.

1. The mean rate, impulse interval distribution, and pulse number distribution of the maintained discharge of ganglion cells in the retina of the cat have been studied after prolonged adaptation at different luminance levels.2. From a state of complete dark adaptation up to a luminance of about 5 x 10(-3) cd/m(2) (viewed through a 7 mm(2) pupil) the mean rate of on-centre units increases. From darkness up to a somewhat higher luminance the mean rate of some off-centre units decreases, but others show little change.3. Above 10(-2) cd/m(2) the mean rate ceases to show a regular relation with adaptation level. On units often decrease and then increase again at a higher level. Rhythmical fluctuations are common near 10(-2) cd/m(2), especially if the retina is not in first class condition. Mean rates above 70/sec and below 1/sec are very rare at any adaptation level.4. Over the range where mean rate increases monotonically with adaptation level, it is shown that the surround of on-centre units does not inhibit and off responses cannot be elicited. When the monotonic increase is slowed or reversed it becomes possible to elicit responses from the surround. We suspect that the surround exerts a sustained, tonic, inhibiting effect at higher adaptation levels, thus holding down the maintained discharge.5. There are rare units, forming less than 1% of those isolated, that show a regularly increasing frequency with increase of adaptation level above 10(-2) cd/m(2). These units have concentric ;on' and ;off' zones in their receptive fields, but the responses to rapidly changing stimuli are sluggish and they have an unusually regular maintained discharge. They have been tentatively called ;luminance units'.6. The impulse-interval and pulse-number distributions of on-centre units change predictably with adaptation level; the variance of the pulse number distribution is usually several times the mean at very low adaptation levels, but only a fraction of the mean at high levels. Off-centre units do not show predictable changes. Luminance units fire more regularly, and have narrower pulse-number and impulse interval distributions than other concentric units.7. A simple model is proposed to account for the statistical characteristics of the maintained discharge of on-centre units.

Action Potentials↗
PubMed2006

Yolk androgens in the barn swallow (Hirundo rustica): a test of some adaptive hypotheses.

Maternal effects such as androgen in avian eggs can mediate evolutionary responses to selection, allowing manipulation of offspring phenotype and promoting trans-generational adaptive effects. We tested the predictions of two adaptive hypotheses that have been proposed to explain female variation in yolk androgen allocation in birds, using the barn swallow Hirundo rustica as a model. We found no support for the first hypothesis proposing that yolk androgen varies as a function of breeding density in order to prepare offspring for different breeding densities. However, we found experimental support for the hypothesis that female yolk androgen allocation depends on mate attractiveness and that it constitutes an example of differential allocation. Females increased the concentration of androgens in their eggs when mated to males with experimentally elongated tails. Female phenotypic quality as measured by arrival date and clutch size was positively related to egg androgen concentration, consistent with the hypothesis that this is a costly investment, constrained by female condition. We found correlative evidence of a direct relationship between egg androgen concentration and performance of offspring as measured by mass increase.

Adaptation, Physiological↗
PubMed2003

Concurrent and predictive validity of the cognitive adaptive test/clinical linguistic and auditory milestone scale (CAT/CLAMS) and the Mental Developmental Index of the Bayley Scales of Infant Development.

The Cognitive Adaptive Test/Clinical Linguistic and Auditory Milestone Scale (CAT/CLAMS) was designed for use by primary pediatric health care providers to identify children with developmental delays. This study assesses the concurrent and predictive validity of CAT/CLAMS developmental quotient (DQ) scores and the Mental Developmental Index (MDI) of the Bayley Scales of Infant Development in healthy children without risk factors for developmental delay. Overall CAT/CLAMS DQ scores correlated significantly with Bayley MDI scores at both 12 (r = 0.393; p = 0.008) and 30 months (r = 0.742; p = 0.0001) of age. Overall CAT/CLAMS DQ scores at 12 months of age also correlated modestly with Bayley MDI scores at 30 months of age (r = 0.181; p = 0.036). Despite its modest predictive validity at 12 months, its satisfactory concurrent validity plus its ease and speed of administration make the CAT/CLAMS a reasonable choice for assessment of early development by primary pediatric health care providers.

Child Development↗
PubMed1994

Mode of death and kinship in bereavement: focusing on "who" rather than "how".

Although it is widely accepted that bereavement can result in health problems, little is still known about the factors that determine the impact of the loss on those left behind. The Leiden Bereavement Study attempted to address this problem, by examining the consequences of bereavement after suicide (N = 91), traffic accident (N = 93), and illness (N = 125) for first-degree family members. Seventy-three bereaved spouses, 68 parents, 86 siblings, and 82 adults who had lost a parent were interviewed in a longitudinal time-sample study. Multiple measures of physical, psychological, and social functioning, as well as details about the relationship and pre- and post-loss events, were obtained through in-depth structured interviews at 4 and 14 months after the loss. The results indicate that the influence of mode of death is small to absent for most aspects of psychosocial health. Post-traumatic stress symptoms were almost as common among the illness-bereaved group as they were among the unnatural death groups. The kinship relationship to the deceased played a prominent role in virtually all aspects of functioning, with parents (particularly mothers), widowers, and sisters of the deceased being more strongly affected than adult children, brothers, and widows. The characteristics of the relationship played a further important role in the level of problems after the loss. Early adaptation was highly predictive of longer-term adaptation. The implications of the findings for prevention and intervention are discussed.

Accidents, Traffic↗
PubMed2005

Improved prediction of octanol-water partition coefficients from liquid-solute water solubilities and molar volumes.

A volume-fraction-based solvent-water partition model for dilute solutes, in which the partition coefficient shows a dependence on solute molar volume (V), is adapted to predict the octanol-water partition coefficient (K(ow)) from the liquid or supercooled-liquid solute water solubility (Sw), or vice versa. The established correlation is tested for a wide range of industrial compounds and pesticides (e.g., halogenated aliphatic hydrocarbons, alkylbenzenes, halogenated benzenes, ethers, esters, PAHs, PCBs, organochlorines, organophosphates, carbamates, and amides-ureas-triazines), which comprise a total of 215 test compounds spanning about 10 orders of magnitude in Sw and 8.5 orders of magnitude in K(ow). Except for phenols and alcohols, which require special considerations of the K(ow) data, the correlation predicts the K(ow) within 0.1 log units for most compounds, much independent of the compound type or the magnitude in K(ow). With reliable Sw and V data for compounds of interest, the correlation provides an effective means for either predicting the unavailable log K(ow) values or verifying the reliability of the reported log K(ow) data.

Models, Theoretical↗
PubMed2006

Adaptation of wives to prostate cancer following diagnosis and 3 months after treatment: a test of family adaptation theory.

BACKGROUND: Prostate cancer challenges not only the men with the disease, but also their partners. Existing studies have focused on the relationship between type of treatment and sexual and urinary function in men, with recent qualitative work suggesting that men and their spouses have differing responses to the illness. Factors predicting women's adaptation to prostate cancer have not been examined. OBJECTIVES: Using a model derived from family stress and adaptation theory, this study examined (1) the contribution of urinary and sexual symptoms, sense of coherence, marital resources and situational appraisal to wives' global adaptation (PAIS) and emotional adaptation (POMS), and (2) the role of situational appraisal as a mediator between the set of independent variables and PAIS and POMS. DESIGN: In a prospective, correlational design, data were collected from 70 women following their partners' diagnosis and again 3 months later. METHODS AND RESULTS: Using a path analysis approach, between 30% and 62.7% of the variance in global adjustment and mood disturbance was explained across model tests. Sense of coherence was a strong and consistent predictor. Appraisal acted as a mediator only at time 2, mediating the effect of symptom distress on global adaptation. Change in sense of coherence and change in family resources predicted global adaptation and emotional adaptation at time 2, and predicted the change between time 1 and 2 in those variables. CONCLUSIONS: The findings suggest nursing interventions that mobilize and build wives' sense of the manageability, meaningfulness and comprehensibility of life events, and that foster cohesion and flexibility within the marital relationship. Interventions that mitigate the impact of urinary symptoms and the appraisal of threat in the illness event are also indicated. Additional model-testing studies based on family adaptation theory with patients and family members in other types of cancer would help build nursing knowledge for interventions in cancer.

Adaptation, Psychological↗
PubMed2006

Methyl tertiary hexyl ether and methyl tertiary octyl ether as gasoline oxygenates: assessing risks from atmospheric dispersion and deposition.

Methyl tertiary hexyl ether (MtHxE) and methyl tertiary octyl ether (MtOcE) are currently being developed as replacement oxygenates for methyl tertiary butyl ether (MtBE) in gasoline. As was the case with MtBE, the introduction of these ethers into fuel supplies guarantees their introduction into the environment as well. In this study, a screening-level risk assessment was performed by comparing predicted environmental concentrations (PEC) of these ethers to concentrations that might cause adverse effects to humans or ecosystems. A simple box model that has successfully estimated urban air concentrations of MtBE was adapted to predict atmospheric concentrations of MtHxE and MtOcE. Expected atmospheric concentrations of these ethers were also estimated using the European Union System for the Evaluation of Substances (EUSES) multimedia fate model, which simultaneously calculates PECs in the various environmental compartments of air, water, soil, and sediment. Because little or no data are available on the physicochemical, environmental, and toxicological properties of MtHxE and MtOcE, estimation methods were used in conjunction with EUSES to predict both the PECs and the concentrations at which these ethers might pose a threat. The results suggest that these ethers would contaminate the air of a moderately sized U.S. city (Boston, MA) at levels similar to those found previously for MtBE. The risk assessment module in EUSES predicted risk characterization ratios of 10(-3) and 10(-2) for MtHxE and MtOcE, respectively, in Boston, and 10(-2) and 10(-1) in very large urban centers, suggesting that these ethers pose only a minimal threat to ecosystems at the anticipated environmental concentrations. The assessment also indicates that these compounds are possible human carcinogens and that they may be present in urban air at concentrations that pose an unacceptable cancer risk. Therefore, testing of the toxicological properties of these compounds is recommended before they replace MtBE in gasoline.

Animals↗
PubMed2001

The rhythm of microbial adaptation.

The evolutionary biologist "studies the steps by which the miraculous adaptations so characteristic of every aspect of the organic world have evolved". But the general nature of such adaptive steps is still unclear. Evolution is often thought to be random and dependent on unpredictable events. In this light, one might expect the steps taken by adaptation to be completely random, both biologically and temporally. Here I present a mathematical derivation to show that, on the contrary, adaptive steps can have fairly strong rhythm. I find that the strength of the adaptive rhythm, that is its relative temporal regularity, is equal to a constant that is the same for all microbial populations. As a consequence, numbers of accumulated adaptations are predicted to have a universal variance/mean ratio. The theory derived here is potentially applicable to the study of molecular evolution.

Adaptation, Physiological↗
PubMed2003

Orientation-specific adaptation in human visual cortex.

Nearly all methods for analyzing and interpreting functional magnetic resonance imaging (fMRI) data assume that the fMRI signal behaves in an approximately linear manner. However, it has been shown that the mean fMRI response to a pair of briefly presented visual stimuli is significantly smaller than would be expected from the response to a single stimulus. This smaller response could be the result of either a nonlinearity in the fMRI signal or neuronal adaptation. We tested the neuronal adaptation hypothesis by measuring the fMRI response to sequential pairs of sinusoidal gratings that had either the same or orthogonal orientation. The adaptation hypothesis predicts that brain areas with orientation-selective neurons should show a more linear response when the stimulus pair is orthogonal than when the pair is identical. Our results show no orientation-specific adaptation effects in primary visual cortex (V1) but increasing effects along the hierarchy of visual areas (V2, V3, and V4V). A psychophysical contrast detection experiment, using similar oriented gratings as adapters, shows evidence of orientation-specific adaptation in the visual system. These results have implications for the interpretation of rapid event-related fMRI experiments, as well as for recently developed methods that use adaptation as a tool to measure the response properties of underlying neuronal subpopulations.

Adaptation, Physiological↗
PubMed1997

Functional neuromuscular stimulation controlled by surface electromyographic signals produced by volitional activation of the same muscle: adaptive removal of the muscle response from the recorded EMG-signal.

In order to use the volitional electromyography (EMG) as a control signal for the stimulation of the same muscle, it is necessary to eliminate the stimulation artifacts and the muscle responses caused by the stimulation. The stimulation artifacts, caused by the electric field in skin and tissue generated by the stimulation current, are relatively easy to eliminate by shutting down the EMG-amplifier at the onset of the stimulation pulses. The muscle response is a nonstationary signal, therefore, an adaptive linear prediction filter is proposed. The filter is implemented and for three filter lengths tested on both simulated and real data. The filter performance is compared with a conventional fixed comb filter. The simulations indicate that the adaptive filter is relatively insensitive to variations in amplitude of the muscle responses, and for all filter lengths produces a good filtering. For variations in shape of the muscle responses and for real data, an increased filter performance can be achieved by increasing the filter length. Using a filter length of up to seven stimulation periods, it is possible to reduce real muscle responses to a level comparable with the background noise. Using the shut-down circuit and the adaptive filter both the stimulation artifacts and the muscle responses can be effectively eliminated from the EMG signal from a stimulated muscle. It is therefore possible to extract the volitional EMG from a partly paralyzed muscle and use it for controlling the stimulation of the same muscle.

Artifacts↗