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PubMed1994

Effects of fit and bonding characteristics of femoral stems on adaptive bone remodeling.

Bone atrophy caused by stress-shielding may cause serious complications for the long-term fixation of hip stems. In particular, uncemented total hip arthroplasty is threatened by this problem, because the stems are usually larger and, as a consequence, stiffer than those of cemented implants. In the present study, the effects of fit and bonding characteristics of femoral hip stems were investigated, using the (nonlinear) finite element method in combination with adaptive bone remodeling theory to predict the bone density distribution in a bone or bone/implant configuration. Unknown parameters used in the theory, such as a reference equilibrium loading stimulus and a threshold (dead) zone of this stimulus, were established (triggered) by using the method to predict the density distributions in the natural femur and around fully coated uncemented implants. The computer simulation method can provide long term predictions of remodeling patterns around various implant configurations. Several cases were analyzed, whereby the coating conditions (fully, partly, or noncoated) and the fit characteristics (press fitted or overreamed) were varied. The computer predictions showed that partly coating can only significantly reduce bone atrophy relative to fully coated stems, when the coating is applied at a small region at the utmost proximal part of the stem. For smooth press-fit stems the predicted amount of bone loss (35 percent in the proximal medial region) was less than for a one-third proximally coated or a fully coated stem (50 to 54 percent predicted bone loss in the proximal medial region).(ABSTRACT TRUNCATED AT 250 WORDS)

Adaptation, Physiological↗
PubMed2005

Different types and aspects of quality systems and their implications. A thematic comparison of seven quality systems at a university hospital.

Policy makers and managers face a difficult challenge in keeping up with the changing organisations and methods of health care. Organised systematic quality work, that is, quality systems, can make this task easier. The aim here was to study different quality systems, identify common characteristics, find types of quality systems and discuss the practical implications of the results. The study was designed as a qualitative study of seven clinics with quality systems at a large university hospital in Sweden. Purposefully selected, 19 managers or quality co-ordinators were interviewed. The interviews were audio taped, transcribed verbatim and analysed thematically. Six organisational aspects were present in the interviews: resources, administration, culture, co-operation, goal achievement and development of competence. The aspects were used to categorise the clinics' systems into three types: local, centralised and integrated systems. The responses indicated that local systems had a decentralised organisation, allowing for a high degree of adaptability. Centralised systems were reported to be more top-down orientated, allowing for a highly predictable output. Integrated systems were reported to have a management style that emphasized co-operation, allowing for both good adaptability and predictability. Policy makers and managers could use the described aspects and types of quality systems to help decide what type of quality system to implement in a specific setting, as a base line for evaluation, or as a framework for developing existing quality systems.

Hospitals, University↗
PubMed2000

Windows to the self in 8-year-olds: bridges to attachment representation and behavioral adjustment.

The present study investigated the links between aspects of the self (self-evaluations, self-worth), attachment representations and behavioral functioning in 8-year-old children. Self-evaluations were assessed with an interview in which children described themselves and discussed positive and negative aspects of the self; self-worth was assessed using a subscale from the Dimensions of Depression Inventory. Attachment representations were assessed using the Separation Anxiety Test. Mothers and teachers reported on children's behavior problems, school adaptation and peer competence. Following previous work with 5- (Verschueren & Marcoen, 1999; Verschueren, Marcoen, & Schoefs, 1996) and 6-year-olds (Cassidy, 1988), we predicted that aspects of the self would be positively associated with attachment security and behavioral adaptation. These predictions were confirmed. A rating of the child's ease of access to self-evaluations (EASE) during the interview was related to emotional security and coping responses during the Separation Anxiety Test. Children with greater ease of access to self-evaluations also had fewer internalizing and total behavior problems, according to both mothers and teachers, and their teachers reported more positive school adaptation, peer competence and egoresiliency.

Adaptation, Psychological↗
PubMed2006

[Markers predicting progression of disease in PAD: Which of them are both relevant to clinical practice and economically justifiable?].

The high cardiovascular morbidity and mortality on peripheral arterial disease (PAD) are attributable to the pronounced tendency to generalization of the atherosclerotic process, the systemic progression of atherosclerosis. The crucial objective in management of a PAD consists in preventing systemic progression. The prognosis can be improved by early diagnosis and early prediction of individual risk with subsequent risk-adapted prevention and causal therapy. Early diagnosis and risk prediction are measures that are already part of the repertory of the general practitioner. Practicable and economically justifiable parameters that nevertheless have a high predictive value are therefore required to stratify individual risk. The vascular indicators ankle-arm index and the localization of the PAD as well as the classical cardiovascular risk factors including homocysteine are suitable. Weighting of these parameters in a multivariable risk score enable the population with the highest risk of early generalization of atherosclerosis to be identified in PAD.

Arterial Occlusive Diseases↗
PubMed2005

Physiological mechanisms of onset adaptation and contralateral suppression of DPOAEs in the rat.

An investigation was undertaken to measure medial olivocochlear (MOC) reflexes in anesthetized rats before and after sectioning of the middle-ear muscles. Distortion product otoacoustic emission (DPOAE) magnitude and phase temporal responses were measured ipsilaterally to study MOC-mediated "DPOAE onset adaptation" and in the presence of a contralateral noise to study MOC-mediated contralateral "suppression" (terms as used by previous researchers). Distortion product otoacoustic emission onset adaptation and contralateral suppression had predictable changes in direction of magnitude and phase that were dependent on the input-output function. After sectioning of the middle-ear muscles (MEMs), DPOAE onset adaptation and contralateral suppression were greatly reduced, and there were little, if any, changes in phase. These "residual" changes were interpreted as a result of the MOC reflex. The results suggest that what appears to be DPOAE onset adaptation and contralateral suppression can be mediated primarily by MEM reflexes. When studying MOC effects on otoacoustic emissions (OAEs) using acoustic stimulation, it is necessary to make recordings over a span of stimulus levels. In addition, looking at both magnitude and phase of the OAE may help separate what is due to the MOC reflex from MEM reflex.

Acoustic Stimulation↗
PubMed2006

Parenting stress and its relationship to the behavior of children with Joubert syndrome.

This study describes the relationship between parenting stress and behavior in children with Joubert syndrome, a rare genetic neurodevelopmental disorder. Parents (N = 43) reported severely impaired child adaptive behaviors. Most children did not show maladaptive behaviors, but a subset of approximately 20% displayed significant problems in areas such as inattention, overactivity, social withdrawal, and atypical behaviors. Mothers (59%) and fathers (40%) reported elevated levels of parenting stress. A hierarchical regression, including demographics, adaptive behavior, and maladaptive behavior, predicted 67% of the variance in mothers' stress and 40% of the variance in fathers' stress. Maladaptive behaviors uniquely contributed to maternal and paternal stress. The child's adaptive behavior level contributed significantly to parenting stress for mothers but not for fathers. Findings provide a better understanding of the impact of child behavior on parents caring for a child with Joubert syndrome.

Activities of Daily Living↗
PubMed2000

If bone is the answer, then what is the question?

In the 19th century, several scientists attempted to relate bone trabecular morphology to its mechanical, load-bearing function. It was suggested that bone architecture was an answer to requirements of optimal stress transfer, pairing maximal strength to minimal weight, according to particular mathematical design rules. Using contemporary methods of analysis, stress transfer in bones was studied and compared with anatomical specimens, from which it was hypothesised that trabecular architecture is associated with stress trajectories. Others focused on the biological processes by which trabecular architectures are formed and on the question of how bone could maintain the relationship between external load and architecture in a variable functional environment. Wilhelm Roux introduced the principle of functional adaptation as a self-organising process based in the tissues. Julius Wolff, anatomist and orthopaedic surgeon, entwined these 3 issues in his book The Law of Bone Remodeling (translation), which set the stage for biomechanical research goals in our day. 'Wolff's Law' is a question rather than a law, asking for the requirements of structural optimisation. In this article, based on finite element analysis (FEA) results of stress transfer in bones, it is argued that it was the wrong question, putting us on the wrong foot. The maximal strength/minimal weight principle does not provide a rationale for architectural formation or adaptation; the similarity between trabecular orientation and stress trajectories is circumstantial, not causal. Based on computer simulations of bone remodelling as a regulatory process, governed by mechanical usage and orchestrated by osteocyte mechanosensitivity, it is shown that Roux's paradigm, conversely, is a realistic proposition. Put in a quantitative regulatory context, it can predict both trabecular formation and adaptation. Hence, trabecular architecture is not an answer to Wolff's question, in the sense of this article's title. There are no mathematical optimisation rules for bone architecture; there is just a biological regulatory process, producing a structure adapted to mechanical demands by the nature of its characteristics, adequate for evolutionary endurance. It is predicted that computer simulation of this process can help us to unravel its secrets.

Animals↗
PubMed1991

Contrast adaptation and contrast masking in human vision.

After a preliminary study of visual evoked potentials (VEPS) to a test grating seen in the presence of masks at different orientations, psychophysical data are presented showing the effects of adaptation and of masking on thresholds for detecting the same test grating. The test is a vertical grating of spatial frequency 2 cycles per degree; adapting and masking gratings differ from the test either in orientation or in spatial frequency. The effects of adaptation and masking are explained by a single mechanism model that assumes: (i) adaptation and masking both alter the contrast response (or transducer) function of the mechanism that detects the test; (ii) masks, but not adaptors, stimulate the mechanism that detects the test; and (iii) a test is detectable when it raises response level by a constant amount. The model incorporates two distinct tuning functions, a broad adaptive contrast function and a narrow effective contrast function. It accounts adequately for all the data, including the location and size of the facilitative dip found in some masking functions, the constant slopes of the threshold elevation segments of adaptation functions and the varying slopes of masking functions. It also predicts the sometimes surprising joint effects of adaptation followed by masking and of two masks operating simultaneously.

Adaptation, Ocular↗
PubMed2002

Problem behavior in boys with fragile X syndrome.

This study examines problem behavior over time in 59 boys with fragile X syndrome (FXS), aged 4-12 years, using the Child Behavior Checklist (CBCL). Approximately 49% of the boys scored within the borderline or clinical range on total problem behavior, while 56-57% scored in the borderline or clinical range on the attention and thought problems subscales, and 26% scored in this range on the social problems subscale. With a mean of 2.5 assessments per child, behavior problems were stable during the 3-year period of study. Total problem behavior was higher for children who displayed autistic behavior, were rated as low in adaptability, had mothers with higher maternal education levels, and were on medication. Mothers with more education also rated their children as having more attention, thought, and total problems. Children taking medication differed from boys who were not taking medication on social problems, but not on attention and thought problems. Low adaptability and more autistic characteristics predicted thought problems.

Adaptation, Psychological↗
PubMed1988

Chronic stress and sympathetic-adrenal medullary responsiveness.

Acute exposure of animals to stressful stimulation is attended by a significant activation of the sympathetic-adrenal medullary system. If animals are exposed to the same stressful stimulus each day for several weeks, a number of adaptive changes occur in the sympathetic-adrenal medullary system, including increased synthesis and storage of catecholamines, increased basal levels of circulating catecholamines, and decreased release of catecholamines into the circulation following exposure to the identical (homotypic) stressful stimulus. If chronically stressed animals are exposed to a novel (heterotypic) stressful stimulus, there is an exaggerated response of the sympathetic-adrenal medullary system compared to animals exposed to the same stressful stimulus for the first time. Other neuroendocrine systems share some characteristics with the sympathetic-adrenal medullary system in its pattern of adaptation to chronic stress. Several variables appear to influence this pattern of neuroendocrine adaptation to stressful stimulation, including predictability of the stressor, the intensity and duration of the stressor, the interval between each episode of stress, and the number of presentations of the stressor. The pattern of neuroendocrine adaptation to chronic intermittent stressful stimulation resembles in some respects the processes of habituation and sensitization.

Adrenal Medulla↗
PubMed2003

Experimental studies on multiple-model predictive control for automated regulation of hemodynamic variables.

A model-based control methodology was developed for automated regulation of mean arterial pressure and cardiac output in critical care subjects using inotropic and vasoactive drugs. The control algorithm used a multiple-model adaptive approach in a model predictive control framework to account for variability and explicitly handle drug rate constraints. The controller was experimentally evaluated on canines that were pharmacologically altered to exhibit symptoms of hypertension and depressed cardiac output. The controller performed better as compared to experiments on manual regulation of the hemodynamic variables. After the model bank was determined, mean arterial pressure was held within +/- 5 mm Hg 88.9% of the time with a standard deviation of 3.9 mm Hg. The cardiac output was held within +/- 1 l/min 96.1% of the time with a standard deviation of 0.5 l/min. The manual runs maintain mean arterial pressure only 82.3% of the time with a standard deviation of 5 mm Hg, and cardiac output 92.2% of the time with a standard deviation of 0.6 l/min.

Algorithms↗
PubMed1989

Coping styles in youths with insulin-dependent diabetes mellitus.

The relationships between two coping styles (i.e., use of personal and interpersonal resources; ventilation and avoidance) and two health outcomes (i.e., adherence and metabolic control) were evaluated in 135 youths with insulin-dependent diabetes mellitus (IDDM). Individual characteristics (i.e., age, duration of illness) and contextual variables (i.e., stress, family relations) were used to predict coping styles. Poor adherence to treatment, older adolescent age, and long duration of IDDM were correlated with ventilation and avoidance coping. Youths with short duration of IDDM were more likely to cope through the use of personal and interpersonal resources, although this strategy was not associated with health outcomes. A multiple regression analysis indicated that high ventilation and avoidance coping was predicted by high stress, low family cohesion, and older adolescent age. In addition, the interaction between family adaptability and duration of IDDM significantly predicted ventilation and avoidance coping.

Adaptation, Psychological↗
PubMed2000

Three novel lossless image compression schemes for medical image archiving and telemedicine.

In this article, three novel lossless image compression schemes, hybrid predictive/vector quantization lossless image coding (HPVQ), shape-adaptive differential pulse code modulation (DPCM) (SADPCM), and shape-VQ-based hybrid ADPCM/DCT (ADPCMDCT) are introduced. All are based on the lossy coder, VQ. However, VQ is used in these new schemes as a tool to improve the decorrelation efficiency of those traditional lossless predictive coders such as DPCM, adaptive DPCM (ADPCM), and multiplicative autoregressive coding (MAR). A new kind of VQ, shape-VQ, is also introduced in this article. It provides predictive coders useful information regarding the shape characters of image block. These enhance the performance of predictive coders in the context of lossless coding. Simulation results of the proposed coders applied in lossless medical image compression are presented. Some leading lossless techniques such as DPCM, hierarchical interfold (HINT), CALIC, and the standard lossless JPEG are included in the tests. Promising results show that all these three methods are good candidates for lossless medical image compression.

Computer Storage Devices↗
PubMed1999

The evolutionary genetics of adaptation: a simulation study.

It is now clear that the genetic basis of adaptation does not resemble that assumed by the infinitesimal model. Instead, adaptation often involves a modest number of factors of large effect and a greater number of factors of smaller effect. After reviewing relevant experimental studies, I consider recent theoretical attempts to predict the genetic architecture of adaptation from first principles. In particular, I review the history of work on Fisher's geometric model of adaptation, including recent studies which suggest that adaptation should be characterized by exponential distributions of gene effects. I also present the results of new simulation studies that test the robustness of this finding. I explore the effects of changes in the distribution of mutational effects (absolute versus relative) as well as in the nature of the character studied (total phenotypic effect versus single characters). The results show that adaptation towards a fixed optimum is generally characterized by an exponential effects trend.

Adaptation, Physiological↗
PubMed1991

Peer reputation in middle childhood as a predictor of adaptation in adolescence: a seven-year follow-up.

This investigation examines the predictive significance of peer reputation in elementary school for the quality of adaptation in adolescence. A normative sample (N = 207) of third to sixth graders was administered the Revised Class Play (RCP). Each received 3 scores (Sociability-Leadership, Aggression-Disruption, and Sensitivity-Isolation). 7 years later, 88% of these children and their parents participated in a questionnaire follow-up study utilizing a broad range of adolescent outcome measures (e.g., social and athletic competence, academic performance, behavioral symptoms, well-being). The 3 RCP scores were significantly related to both adolescent competence and psychopathology, supporting the predictive validity of the RCP as well as the continuity of general adaptation. Each dimension of peer reputation had a different pattern of prediction depending on the outcome criteria under consideration, suggesting the importance of a multidimensional approach to peer reputation. Positive peer reputation proved to be an important predictor of later adjustment. Sex differences were examined; results suggested somewhat different patterns of prediction for boys and girls, especially for the sensitive-isolated dimension.

Adaptation, Psychological↗
PubMed1986

The predictive validity of psychosocial factors for patients' acceptance of rhinoplasty.

Adaptation to rhinoplasty one year postoperatively was studied in 56 patients and the results compared with their preoperative psychosocial profiles. Of the patients, 21 (37%) reported unfavorable experiences with the operation, such as dissatisfaction with the results and/or increased nervous symptoms. Patients dissatisfied with the operational result were more often men who had experienced a nose trauma as an adult. A high consumption of alcohol, poorly established social relations, and an outgoing sthenic attitude were other characteristics. Patients reacting with increased mental symptoms after the operation had expected the operation to result in a substantial change in their general life situation. Their sensitivity regarding the shape of their noses was, in some cases, of a delusional severity. The remaining 35 patients (63%) adapted fairly well to the operation. By a system of different weights given to interview items, it was possible to demonstrate a significant predictive validity of the preoperative psychosocial evaluation with regard to postoperative adaptation. Application of this evaluation technique therefore should increase the possibility of reliably predicting the outcome. Operations on patients not suited to rhinoplasty might be avoided with the application of such a technique.

Adaptation, Psychological↗
PubMed1998

Family environment, glycemic control, and the psychosocial adaptation of adults with diabetes.

OBJECTIVE: To evaluate whether the family system variables of adults with diabetes relate to the adequacy of metabolic control or the psychosocial adaptation to the illness. RESEARCH DESIGN AND METHODS: A total of 150 insulin-requiring adults were assessed on a single occasion. They completed two family system measures (the Family Environment Scale [FES] and the Diabetes Family Behavior Checklist [DFBC]), two quality-of-life measures (the Diabetes Quality of Life Scale and the Medical Outcomes Study Health Survey-36), and one measure of cognitive appraisal (the Appraisal of Diabetes Scale). Glycemic control was assessed using HbA1c results. Demographic data (age, sex, diabetes type, duration of diabetes, and number of diabetes-related medical complications) were gathered from the patients' charts. RESULTS: Concerning glycemic control, none of the family system measures were significant predictors of HbA1c. Older age and longer duration of diabetes predicted higher HbA1c values. For psychosocial adaptation, when family members behaved in ways that supported the diabetes care regimen (measured by the DFBC), the individual with diabetes was more satisfied with his or her adaptation to the illness and reported less interference in role function due to emotional problems. Family cohesion (measured by the FES) also related to better physical function. Women reported higher levels of diabetes satisfaction. The Appraisal of Diabetes Scale predicted glycemic control and psychosocial adaptation. CONCLUSIONS: For insulin-treated adults with diabetes, family system variables do not relate to glycemic control, but they do relate to psychosocial adaptation. Future work should explore the impact of family-centered interventions on adaptation, sex differences in adaptation, and the use of the Appraisal of Diabetes Scale as a first-line clinical screening tool.

Adaptation, Psychological↗
PubMed1996

Causes of age-related decline in adaptive behavior of adults with Down syndrome: differential diagnoses of dementia.

Although a decline in adaptive behavior with age in adults with Down syndrome has been established, the underlying causes of the decline remain unresolved. Differential causes of the decline in 201 adults with Down syndrome were investigated. Aging, dementia, and severity of mental retardation were found to be significant factors. Absence of a medical illness was a factor that predicted a higher level of adaptive behavior. No significant difference in age-related maladaptive behaviors was found. However, a clinical diagnosis of dementia was a predictive factor for increased maladaptive behavior. Clinical implications of these findings were discussed.

Adolescent↗