Effect of external target prescence on visual adaptation with active and passive movement.
Explore the source record for details and available documents.
Eye Movements↗
SEARCH · PubMed Health
Results for “passive adaptation”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Passivity-based neural network adaptive output feedback control for nonlinear nonnegative dynamical systems.
The potential clinical applications of adaptive neural network control for pharmacology in general, and anesthesia and critical care unit medicine in particular, are clearly apparent. Specifically, monitoring and controlling the depth of anesthesia in surgery is of particular importance. Nonnegative and compartmental models provide a broad framework for biological and physiological systems, including clinical pharmacology, and are well suited for developing models for closed-loop control of drug administration. In this paper, we develop a neural adaptive output feedback control framework for adaptive set-point regulation of nonlinear uncertain nonnegative and compartmental systems. The proposed framework is Lyapunov-based and guarantees ultimate boundedness of the error signals corresponding to the physical system states and the neural network weighting gains. The approach is applicable to nonlinear nonnegative systems with unmodeled dynamics of unknown dimension and guarantees that the physical system states remain in the nonnegatiye orthant of the state-space for nonnegative initial conditions. Finally, a numerical example involving the infusion of the anesthetic drug midazolam for maintaining a desired constant level of depth of anesthesia for noncardiac surgery is provided to demonstrate the efficacy of the proposed approach.
Adaptation, Physiological↗
A PASSIVE CONDITION FOR RAPID ADAPTATION TO DISPLACED VISUAL DIRECTION.
Explore the source record for details and available documents.
Adaptation, Ocular↗
[Study of the immunodepressive effect of passive immunization on a model of adaptive immunity].
The effect of various doses of specific serum administered in passive immunization on the formation of primary and secondary adaptive immunity in mice of the CBA strain was studied. Primary and secondary response was more sensitive to passive immunization on a model of adaptive immunity than in vivo. Most sensitive to the immunodepressive action of specific antibodies IgM and IgG were plaque-forming cells, and most resistant -- rosette-forming cells and cells. This led to a supposition that antibodies administered in passive immunization depressed the development of the immunological response acting at the level of T- and B cells.
Animals↗
Calcium absorption in rats with distal intestinal resection: influence of type of dietary fat, cholecalciferol and nature of the adaptative response.
The effects of dietary fat and supplementation with cholecalciferol on calcium absorption at different luminal concentrations (2.07 mmol/l and 2.07 mmol/l with 0.5 mmol/l 2,4-dinitrophenol and 8.20 mmol/l) were studied in vivo in the perfused duodenum, residual jejunum and proximal colon of rats with resection of 50% of the distal small intestine, as well as the nature of the adaptative response (passive or active). Changing the source of dietary fat (diet B, containing 1/3 medium chain triglycerides, 1/3 olive oil, 1/3 sunflower oil) increased calcium absorption, preferentially via active transport, in both transected and resected rats. Supplementation of diet B with cholecalciferol further enhanced intestinal calcium absorption, especially in the colon. These results suggest the importance of diet in the adaptive processes and confirm that active mechanisms of transport adapt more readily to intestinal resection than do passive mechanisms.
Adaptation, Physiological↗
[Afferent proprioreceptive fibers in the rat and their distribution in the dorsal roots].
The distribution in the dorsal roots of proprioceptive afferent fibres from tibialis anterior (TA) and extensor digitorum longus (EDL) muscles of the rat and the physiological characteristics of the related nervous endings have been investigated. Axons of proprioceptive endings from TA and EDL were found mainly in L4, only a few in L5. Afferent proprioceptive fibres from posterior superficial crural muscles (gastrocnemius, soleus, plantaris) pass mainly through root L5; axons of extrafusal motor units are distributed in a similar way. Sensory endings in TA and EDL were examined, after identification, by means of their static threshold to passive stretch. Almost all steady-state responses to passive stretch, within the physiological extension range, came from muscle spindles. 1-2 to 20 g loads were necessary to obtain steady-state discharges from these receptors. Spindle endings were classified as primary or secondary by measuring the conduction velocity of the afferent fibres, and according to the features of their passive behaviour. Threshold difference cannot be regarded as a fundamental characteristic, because of the considerable overlapping of the values obtained from the two types of endings. Conduction velocities of 50 to 80 m/sec for primary and of 20 to 40 m/sec for secondary afferent fibres were observed. Afferent fibres conducting at intermediate velocity often behave like primary ones. As a rule, tendon organs showed a higher static threshold to passive stretch; the loads employed only rarely elicited a steady-state response. As for these receptors, which usually showed marked adaptation characteristics, passive force is a less effective stimulus than active contraction. The conduction velocity range of afferent fibres from tendon organs is the same as that of primary afferents. The results are discussed.
Animals↗
Beneficial effects of exercising at moderate altitude on red cell oxygen transport and on exercise performance.
The effect of a ascent to moderate altitude (2,300 m) and altitude training on the O2-transport properties of Hb and their possible consequences on tissue oxygenation during exercise were studied on six control and six training subjects. A rapid increase in P-50 values (+2.4 mm Hg, 0.32 kPa) was measured within one day after ascent. At the end of the stay at altitude (13th day) P-50 values were higher in subjects performing training than in controls. At altitude a slow but constant increase in 2,3-DPG, pyruvate kinase activity and reticulocyte count was found, which was more pronounced in training subjects as compared to controls. Ascent to altitude resulted in a decreased maximal performance capacity (-9%), but both groups recovered during the stay. In training subjects maximal exercise performance was increased after descent. Exercise at altitude was performed at a lower heart rate (controls: -10/min; training: -18/min) and at a lower lactate concentration (-4 mmol/l). These data indicate a positive effect of adaptation to altitude on exercise performance. Training itself shifts the ODC to the right and adds this effect to the effects of passive altitude adaptation on the O2-binding properties of hemoglobin.
Acclimatization↗
Sociopsychological factors influencing response to levodopa therapy for Parkinson's disease.
This article examines the effect of a series of physical and sociopsychological variables on the response shown by Parkinson patients to levodopa therapy. Of the ten major variables examined, six measure relatively enduring personality adaptations: suggestibility, passivity, self-expectations, stigma, attitudes toward illness, and the perception of the expectations of others. Four are illness-related characteristics: diagnosis (primary or secondary parkinsonism); the existence of health problems in addition to Parkinson's disease; whether or not the patient was hospitalized at the beginning of treatment; and symptom improvement as rated by the patient's physician. Age, sex, severity and duration of disease, and use of anti-Parkinson drugs in addition to levodopa were controlled in all of the analyses. The effect of levodopa therapy was assessed in four major areas: activity, social participation, depression, and enjoyment of life. Findings can be summarized as follows: Five of the six personality variables do, in fact, modify the amount of social or psychological change shown by Parkinson patients treated with levodopa. The only one which fails to have such an effect is passivity; this may reflect a measurement problem. However, only two of the four illness-related characteristics which were examined made a difference in treatment outcome: diagnosis and symptomatic improvement, as rated by the patient's physician.
Adaptation, Psychological↗
Enhanced post crown retention in resin composite-reinforced, compromised, root-filled teeth: a case report.
The introduction of an intraradicular composite reinforcing technique, in conjunction with the reestablishment of matching post canal spaces, has allowed compromised, root-filled teeth to be restored with functional, esthetic post crowns. This clinical case report suggests that reconstituted post canals, in accurately adapting to passive, parallel-sided, matching, and well-fitting posts, can enhance the retention of post crowns. Other factors of clinical importance relating to the resin-reinforced technique are discussed, including fracture resistance, depth of polymerization, dentin adhesion, polymerization shrinkage, and coronal microleakage.
Adult↗
[Adaptive behavior of active and passive rats after intranasal administration of the corticotropin-releasing hormone].
Behavioural effect of intranasal application of corticotropin-releasing hormone (CRH) was investigated in rats with high (KHA) and low (KLA) rate of learning in "open field" and plus-maze (PM) active avoidance test. The neurohormone provoked the opposed changes in behaviour of rats of this strain in both tests. The level of locomotion and exploratory activity rose in KLA rats and decreased in KHA rats. After the CRH application, the KLA rats but not KHA rats spent more time in the opened alleys of the PM than the control animals. The same behavioural changes were observed in our previous research when CRH was injected in striatum. We suppose that CRH is an endogenous factor of precise correction of the adaptive behaviour.
Adaptation, Physiological↗
Adaptive behavior in active and passive rats after intranasal administration of corticotrophin-releasing hormone.
Rats with high (KHA) and low (KLA) rates of acquiring active avoidance reflexes were used to study the effects of intranasal administration of corticotrophin-releasing hormone on orientational-investigative behavior in an open field and anxiety in an elevated cross maze. Administration of the neurohormone induced opposite changes in the behavior of the rats of these lines in the two tests. In KLA rats, movement and investigative activity increased, while in KHA rats these behaviors decreased. In the elevated maze, KLA rats, unlike KHA rats, showed increases in the time spent in the open arms, which was evidence for a decrease in anxiety in these animals. Thus, intranasal hormone administration completely reproduced the effects seen after administration into the striatum. It is suggested that corticotrophin-releasing hormone is an endogenous factor for the detailed and appropriate correction of adaptive behavior.
Adaptation, Psychological↗
Comparison of the effects of general and regional anesthesia for cesarean section on neonatal neurologic and adaptive capacity scores.
Fifty-two neonates delivered by elective cesarean section were evaluated using the Neonatal Neurologic and Adaptive Capacity Scores. Twenty of the mothers received general anesthesia, 14 received epidural, and 18 received spinal anesthesia. All mothers receiving regional anesthesia were prehydrated with 1000 ml of lactated Ringer's solution and were given oxygen via a transparent face mask. All mothers undergoing general anesthesia received thiopental for induction followed by N2O-O2 (4 L:4 L) and 0.5% enflurane until delivery of the baby. All mothers were healthy, not in labor, and were scheduled for elective cesarean section. All neonates weighed 2500 g or more, had Apgar scores of 7 or more at 1 and 5 min, and had normal acid base and blood gas data. Neonates delivered with general anesthesia scored significantly lower on some of the test items for adaptive capacity, passive tone, active tone, primary reflexes, and total scores at both 15 min and 2 hr of age (P less than 0.05) than those delivered with either epidural or spinal anesthesia. Neonates delivered with epidural anesthesia scored lower than those delivered with spinal anesthesia on supporting reaction and motor activity at 2 hr of age (P less than 0.05). All neonates had high scores at 24 hr, at which time there were no significant differences between the three groups.
Adaptation, Psychological↗
Cardiovascular effects of amezinium in humans during passive upright tilt in comparison with norfenefrine and dihydroergotamine.
20 min after single i.v. administration of 10 mg 4-amino-6-methoxy-1-phenyl-pyridazinium methyl sulfate (ameziniummetilsulfate, LU 1631, Regulton), in the following briefly called amezinium, a new antihypotensive agent, was studied in comparison with 10 mg norfenefrine i.m. and 1 mg dihydroergotamine i.m. during orthostatic stress on a tilt table in a total group of 29 healthy volunteers with stable cardiovascular conditions. The study of each substance was preceded by a control tilting test. After amezinium a higher systolic blood pressure of 10 to 15 mmHg in comparison with the control test was maintained during 5 min upright tilt with both a smaller increase in the rise of heart rate and decrease in stroke volume. In comparison with control, pulse pressure was also clearly increased whereas cardiac output and total peripheral resistance were not significantly different. The increase in stroke volume in comparison with control was a result of the positive inotropic effect on the one hand, which could be seen in both a diminished prolongation of the preejection period and increase in the PEP/LVET ratio, and an increased venous return to the heart on the other hand. Systolic blood pressure and heart rate after norfenefrine were principally similar to those after amezinium, whereas the effect on stroke volume was of minor magnitude because of the absence of a positive inotropic action. Moreover, cardiac output decreased more with higher total peripheral resistance in comparison to control. Besides a slight reduction in heart rate, dihydroergotamine did not reveal any significant differences from control during orthostatic stress. At the dose studied, amezinium seemed to produce a better adaptation to passive upright tilt than the reference substances.
2-Hydroxyphenethylamine↗
Rib-vertebral angle asymmetry in idiopathic, neuromuscular and experimentally induced scoliosis.
The concave and convex rib-vertebral angle (RVA) at levels T2-T12 was measured on AP radiographs of 19 patients with right convex idiopathic thoracic scoliosis and 10 patients with major thoracic right convex neuromuscular scoliosis. The difference between the angles on the concave and the convex sides, the RVAD, was calculated. The RVAs were also measured on radiographs from three animal groups in which spinal curves had been induced experimentally in a variety of ways. Group 1 comprised 16 rabbits that had been subjected to selective electrostimulation of the latissimus dorsi, the erector spinae and the intercostal muscles. Group 2 comprised four dead rabbits whose spines had been subjected to manual bending. Group 3 comprised eight rabbits that had undergone mechanical elongation of one rib. In both the idiopathic and the neuromuscular group, the convex RVA was smaller than the concave RVA between levels T2 and T8, with a maximal difference between T4 to T5. From T9 to T12 the concave RVA was smaller than the convex. The RVA in relation to the scoliotic segment, i.e. the apex level of the curve and the two neighbouring vertebrae above and below this level, showed similar results. With increasing Cobb angle the RVADs increased linearly with the greatest difference at the second vertebra above the apex. In the three experimental groups the pattern of the RVADs between T6 to T12 was basically similar to the findings of the clinical study. From the results of these clinical and experimental studies, it is concluded that the typical pattern of the RVAs on the concave and convex sides seems to be independent of the underlying cause of the spinal curvature. It is likely that the RVADs result from a passive mechanical adaptation of the ribs to the lateral curvature of the spine.
Adolescent↗
The information needs and preferred roles in treatment decision-making of parents caring for infants with atopic dermatitis: a qualitative study.
BACKGROUND: Information needs and preferences in treatment decision-making of parents caring for infants with atopic dermatitis (AD) are unknown, despite emphasis on quality information-giving and involvement of health-care users in treatment decisions. OBJECTIVE: To explore information needs and decisional role-preferences of parents caring for infants with AD. METHODS: Qualitative study. Purposive sample: 31 parents caring for infants with AD. Tape-recorded focussed conversation-style interviews. Interview topic-guide literature-derived. Control Preferences Scale (5 sort-card vignettes 'very active' to 'very passive' role) adapted for use with parents; used to facilitate discussion. Thematic analysis of verbatim transcripts. RESULTS: Nine core information needs identified: AD-causation, role of diet, medication-use, medication-side-effects, exacerbating factors, new/alternative medication, nonpharmacological treatments, AD-prevention, AD and other atopic conditions. Parents desired verbal and written information. Many felt their baby's condition was not taken seriously, leading to delayed diagnosis and treatment. They had to be more active than they wished to obtain information/treatment. Parents preferred sharing decisions with their doctor. CONCLUSIONS: Parents caring for infants with AD have clearly defined, unmet information needs, forcing them into more active roles in the treatment decision-making process than they desire. The study-findings may inform the development of written information specifically for these parents and improve partnership during consultations.
Adult↗
Adaptive eigenvalue decomposition algorithm for passive acoustic source localization
To find the position of an acoustic source in a room, the relative delay between two (or more) microphone signals for the direct sound must be determined. The generalized cross-correlation method is the most popular technique to do so and is well explained in a landmark paper by Knapp and Carter. In this paper, a new approach is proposed that is based on eigenvalue decomposition. Indeed, the eigenvector corresponding to the minimum eigenvalue of the covariance matrix of the microphone signals contains the impulse responses between the source and the microphone signals (and therefore all the information we need for time delay estimation). In experiments, the proposed algorithm performs well and is very accurate.
Journal Article↗
Kinematic adaptations during running: effects of footwear, surface, and duration.
UNLABELLED: Repetitive impacts encountered during locomotion may be modified by footwear and/or surface. Changes in kinematics may occur either as a direct response to altered mechanical conditions or over time as active adaptations. PURPOSE: : To investigate how midsole hardness, surface stiffness, and running duration influence running kinematics. METHODS: In the first of two experiments, 12 males ran at metabolic steady state under six conditions; combinations of midsole hardness (40 Shore A, 70 Shore A), and surface stiffness (100 kN x m, 200 kN x m, and 350 kN x m). In the second experiment, 10 males ran for 30 min on a 12% downhill grade. In both experiments, subjects ran at 3.4 m x s on a treadmill while 2-D hip, knee, and ankle kinematics were determined using high-speed videography (200 Hz). Oxygen cost and heart rate data were also collected. Kinematic adaptations to midsole, surface, and running time were studied. RESULTS: Stance time, stride cycle time, and maximal knee flexion were invariant across conditions in each experiment. Increased midsole hardness resulted in greater peak ankle dorsiflexion velocity (P = 0.0005). Increased surface stiffness resulted in decreased hip and knee flexion at contact, reduced maximal hip flexion, and increased peak angular velocities of the hip, knee, and ankle. Over time, hip flexion at contact decreased, plantarflexion at toe-off increased, and peak dorsiflexion and plantarflexion velocity increased. CONCLUSION: Lower-extremity kinematics adapted to increased midsole hardness, surface stiffness, and running duration. Changes in limb posture at impact were interpreted as active adaptations that compensate for passive mechanical effects. The adaptations appeared to have the goal of minimizing metabolic cost at the expense of increased exposure to impact shock.
Adaptation, Physiological↗
[Fitness training during nasal ventilation in diseases limited by dyspnea].
METHODS: Five patients with chronic ventilatory failure demonstrated by arterial hyperkapnia and overloaded respiratory muscles under spontaneous ventilation (P01/P01 max) were adapted to passive noninvasive ventilation (ISB). Three of them suffered from severe COPD (FEV1 < 50%), two patients from severe restriction (VC < 30%). These patients had to undergo a bicycle ergometer exercise with and without nasal ventilation until they reached physical exhaustion with standardised incremental increase in external workload. RESULTS: In both settings all patients were able to manage exercise up to their physical exhaustion. The anaerobic limit was exceeded each time. The total ventilation volume had to be increased two- to threefold during exercise with nasal ventilation to maintain the passive ventilation. The reduced load on the respiratory muscles was generally proven by lower pCO2 and higher pH levels. Without ventilation discontinuation of the exercise was caused by dyspnoea, whereas this was due to weakness in the legs under ventilation. In all five cases the achieved level of external workload was higher when supporting the respiratory muscles (43 watts vs. 36 watts) at lower lactate levels. CONCLUSION: On a bicycle ergometer the respiratory muscles can be sufficiently relieved using noninvasive nasal ventilation. A higher level of workload, longer duration and a higher quality of exercise can be achieved thereby. The fact that patients without relief of load of the respiratory muscles complained of dyspnoea, whereas the fact that patients with ventilation complained of weakness in their legs indicates the high efficiency of this method, although the tested patients are severely handicapped individuals who usually do not undergo comparable physical exercise in their daily activities.
Aged↗