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PubMed2002

Adaptive homodyne measurement of optical phase.

We present an experimental demonstration of the power of feedback in quantum metrology, confirming the predicted [H. M. Wiseman, Phys. Rev. Lett. 75, 4587 (1995)]] superior performance of an adaptive homodyne technique for single-shot measurement of optical phase. For measurements performed on weak coherent states with no prior knowledge of the signal phase, adaptive homodyne estimation approaches closer to the intrinsic quantum uncertainty than any previous technique. Our results underscore the importance of real-time feedback for reaching quantum limits in measurement and control.

Journal Article↗
PubMed2001

Cardiopulmonary exercise testing in children: an individualized protocol for workload increase.

OBJECTIVES: To investigate the feasibility of individualized workload increments, as used in adults, for exercise testing in children; and to investigate whether this individualized protocol makes it possible to satisfy the usual criteria for maximal exercise (clinical exhaustion, predicted maximum heart rate [HRmax], oxygen uptake [O(2)] plateau, maximal respiratory exchange ratio > 1.1). DESIGN: Prospective clinical study. SETTING: Pediatric exercise testing laboratory. SUBJECTS: Ninety-two children aged 5 to 17 years with various cardiac and respiratory diseases (33 with asthma, 11 with bronchopulmonary dysplasia, 6 with cystic fibrosis, 10 with congenital heart disease, and 32 miscellaneous). INTERVENTIONS: Individualized maximal incremental exercise testing. The increase in workload was adapted to the individual and was calculated from predicted maximal oxygen uptake (O(2)max) for each child. The test lasted 10 to 12 min. RESULTS: The exercise test was well tolerated by all children and was maximal in all but seven patients. A total of 65.7% of children reached the predicted O(2)max and 68.4% satisfied the criteria for a O(2) plateau at peak exercise. The predicted HRmax was achieved in all but two children. The mean maximal respiratory exchange ratio was 1.06. CONCLUSION: The individualized protocol for increasing workload, based on O(2) rather than power, was well tolerated by children. In our view, the best two criteria for assessing the maximality of the tests were clinical exhaustion and HRmax, especially if the O(2) plateau was not reached. These results suggest that individualized protocols could be used instead of standardized tests for exercise testing in children.

Adolescent↗
PubMed1998

How optimized is the translational machinery in Escherichia coli, Salmonella typhimurium and Saccharomyces cerevisiae?

The optimization of the translational machinery in cells requires the mutual adaptation of codon usage and tRNA concentration, and the adaptation of tRNA concentration to amino acid usage. Two predictions were derived based on a simple deterministic model of translation which assumes that elongation of the peptide chain is rate-limiting. The highest translational efficiency is achieved when the codon recognized by the most abundant tRNA reaches the maximum frequency. For each codon family, the tRNA concentration is optimally adapted to codon usage when the concentration of different tRNA species matches the square-root of the frequency of their corresponding synonymous codons. When tRNA concentration and codon usage are well adapted to each other, the optimal content of all tRNA species carrying the same amino acid should match the square-root of the frequency of the amino acid. These predictions are examined against empirical data from Escherichia coli, Salmonella typhimurium, and Saccharomyces cerevisiae.

Codon↗
PubMedDate not supplied

Adaptive rival penalized competitive learning and combined linear predictor model for financial forecast and investment.

We propose a prediction model called Rival Penalized Competitive Learning (RPCL) and Combined Linear Predictor method (CLP), which involves a set of local linear predictors such that a prediction is made by the combination of some activated predictors through a gating network (Xu et al., 1994). Furthermore, we present its improved variant named Adaptive RPCL-CLP that includes an adaptive learning mechanism as well as a data pre-and-post processing scheme. We compare them with some existing models by demonstrating their performance on two real-world financial time series--a China stock price and an exchange-rate series of US Dollar (USD) versus Deutschmark (DEM). Experiments have shown that Adaptive RPCL-CLP not only outperforms the other approaches with the smallest prediction error and training costs, but also brings in considerable high profits in the trading simulation of foreign exchange market.

Algorithms↗
PubMed2005

Outcome after traumatic brain injury: effects of aging on recovery.

OBJECTIVE: To identify differences in outcome after traumatic brain injury (TBI) compared with orthopedic injuries as a function of age. DESIGN: Longitudinal data analyses from an inception cohort. SETTING: Outpatient rehabilitation program. PARTICIPANTS: Eighty-two orthopedic injury patients and 195 TBI patients. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: Independent living, employment, and level of functioning 1 to 2 years after injury. RESULTS: Older patients and those with TBI were more likely to have increased dependence postinjury. Older TBI patients were more likely to have changes in employment status compared with orthopedic injury patients younger or TBI. The Mayo-Portland Adaptability Inventory and Disability Rating Scale were moderately predictive of level of functioning, return to employment, and independent living status 1 to 2 years postinjury. Injury severity was only mildly predictive of outcome. CONCLUSIONS: The effect of age on outcome affects recovery from neurologic injuries and, to a lesser extent, orthopedic injuries. Outcome after TBI is best predicted by patients' age and estimates of level of function at discharge. Findings suggest that older patients and those with TBI have a greater likelihood of becoming physically and financially dependent on others. Rehabilitation efforts should focus on maximizing levels of independence to limit financial and emotional costs to patients and their families.

Activities of Daily Living↗
PubMed2006

Long-term outcomes of adaptive functions for children with mucopolysaccharidosis I (Hurler syndrome) treated with hematopoietic stem cell transplantation.

Advances in medical treatment have prolonged the lives of children with Hurler syndrome or mucopolysaccharidosis I requiring increased attention to the assessment of their long-term outcomes and functional abilities. Adaptive functions are critical for understanding functional outcomes after treatment and developing focused interventions. We investigated the development of various adaptive functions in children who have had hematopoietic stem cell transplant (HSCT) for Hurler syndrome and risk factors that are associated with the development of these functions. We examined the development of 41 children who had 3 or more Vineland Adaptive Behavior Scales records assessed before and after transplant. Communication, daily living skills, socialization, and motor functions were measured. While standard scores decline over time, development of skills continue with a slower than average rate compared with peers. A cross-sectional nontransplanted comparison group showed more deficits after age 2 years than the transplanted group. In contrast to cognitive ability, age at transplant was not significantly associated with ultimate adaptive level. Baseline cognitive level before HSCT and growth of cognition after HSCT were associated with adaptive functions especially for communication and daily living skills. Socialization was predicted by cumulative medical risk factors, likely due to restricted social exposure in children with complicated transplant courses. Overall, measurement of adaptive behaviors demonstrated that HSCT allows long-term slow improvement of functional outcomes for children with Hurler syndrome. Children with Hurler syndrome with good cognitive levels before HSCT and continued growth of cognition after HSCT show good adaptive functions. Although cognitive and orthopedic problems as well as medical complications limit adaptive ability, identifying these problems early allow beneficial targeted interventions.

Activities of Daily Living↗
PubMed2005

Stereo-slant adaptation is high level and does not involve disparity coding.

We have investigated the potential stages of visual processing at which adaptation may occur to a slanted surface produced by horizontal magnification. Predictions of three hypotheses were tested utilizing a property of depth from binocular disparity, namely that slant scales with distance. If adaptation occurs at the disparity level, then the after-effect expressed in units of horizontal magnification will be independent of the test distance. If adaptation occurs at either a perceived slant or mapping level, then the after-effect, expressed in units of slant, will be independent of the test distance. If adaptation is contingent on distance, then the after-effect will not transfer over distance. Subjects adapted to a stereo-defined slanted surface at a distance of 57 cm. The after-effect was measured with a test stimulus at a distance of 28, 57, 85, or 114 cm by means of a nulling method. When the after-effect was expressed in units of slant, we found that it was larger at the adapting distance than other test distances, and that the after-effect was constant at test distances different from the adaptation distance. These results suggest that two types of adaptation occurred, namely adaptation on a mapping/perception level and adaptation contingent on distance.

Adaptation, Ocular↗
PubMed2005

Promoting adjustment after treatment for cancer.

The transition from the period of diagnosis and medical treatment of cancer to survivorship (i.e., the reentry phase) is an understudied phase in the cancer trajectory. The objectives of this report were 1) to illustrate several adaptive tasks of the reentry phase, 2) to provide examples of research on factors that predict positive adjustment during this phase, and 3) to discuss interventions that address the adaptive tasks of early cancer survivorship. Although the pertinent empirical literature is scarce, accounts from cancer survivors, healthcare professionals, and qualitative researchers converge to suggest several themes in adaptive tasks during reentry. Drawing from the authors' work and that of others, the authors have described common expectancies held by many individuals approaching reentry (e.g., "I shouldn't need support"), typical concerns during this phase (e.g., concern over cancer recurrence), and personal and contextual factors that can facilitate and hinder adjustment. Promising psychosocial interventions have been developed for individuals in the reentry period. Continued research will be necessary to characterize this important phase of cancer survivorship.

Adaptation, Psychological↗
PubMedDate not supplied

Variable errors set a limit to adaptation.

This paper argues that variable error introduces a limit to the extent to which a person can be adapted to his or her environment in general, and for the extent to which the driver can be adapted to the traffic environment in particular. This is because variable error turns what is a deterministic and stable world into an uncertain one where it is only possible to be adapted in a statistical sense. A series of experiments are then discussed. These experiments show that drivers match their utilization of perceptual information to the validity of this information, i.e., they treat uncertainty introduced by variable error in the perceptual system in the same manner as they treat uncertainty in the physical system. This supports the main hypothesis of the paper. A driver may mitigate the effects of variable error by having a safety margin, but the relation between speeds and accident rates (predicted from the current hypothesis) shows that this adaptation is not effective enough. Safety authorities may mitigate the effects of variable error by decreasing the variability of the driving environment, e.g., by introducing speed limits.

Accidents, Traffic↗
PubMed1999

Predictive control of hollow-fiber bioreactors for the production of monoclonal antibodies.

The selection of medium feed rates for perfusion bioreactors represents a challenge for process optimization, particularly in bioreactors that are sampled infrequently. When the present and immediate future of a bioprocess can be adequately described, predictive control can minimize deviations from set points in a manner that can maximize process consistency. Predictive control of perfusion hollow-fiber bioreactors was investigated in a series of hybridoma cell cultures that compared operator control to computer estimation of feed rates. Adaptive software routines were developed to estimate the current and predict the future glucose uptake and lactate production of the bioprocess at each sampling interval. The current and future glucose uptake rates were used to select the perfusion feed rate in a designed response to deviations from the set point values. The routines presented a graphical user interface through which the operator was able to view the up-to-date culture performance and assess the model description of the immediate future culture performance. In addition, fewer samples were taken in the computer-estimated cultures, reducing labor and analytical expense. The use of these predictive controller routines and the graphical user interface decreased the glucose and lactate concentration variances up to sevenfold, and antibody yields increased by 10% to 43%.

Algorithms↗
PubMed2003

Prediction of SO2 levels using neural networks.

In this paper, we present an adaptation of the air pollution control help system in the neighborhood of a power plant in As Pontes (A Coruña, Spain), property of Endesa Generación S.A., to the European Council Directive 1999/30/CE. This system contains a statistic prediction made half an hour before the measurement, and it helps the staff in the power plant prevent air quality level episodes. The prediction is made using neural network models. This prediction is compared with one made by a semiparametric model.

Air Pollutants↗
PubMed2000

A physiological model of dark-adapted and light-adapted photoreceptors of the honeybee.

A physiological model of dark-adapted and light-adapted photoreceptors in the honeybee worker (Apis mellifera) has been developed. Almost all of the electrophysiological components of photoreceptors known up to date, e.g. the phototransduction cascade, the ion channels of the membrane, phototransduction gain and optical adaptation mechanisms, are adequately described by simple biophysical and biochemical models. The connections of these components were tried out in synthetic simulations for best fits of simulated to intracellularly recorded membrane potentials. Although the parameters of the best model were determined exclusively for the measured membrane potentials of dark-adapted photoreceptors, the model also accurately describes the light-adapted photoreceptor membrane potentials. Furthermore, the model correctly predicts the time-courses of measured photoreceptor responses with respect to squared-modulated flicker lights up to 200 Hz. This clearly demonstrates that the presented photoreceptor model is indeed a physiologically adequate description of the essential components of the phototransduction and the electrical membrane processes in the photoreceptors of the honeybee worker.

Adaptation, Physiological↗
PubMed2005

FDG-PET after two cycles of chemotherapy predicts treatment failure and progression-free survival in Hodgkin lymphoma.

Risk-adapted lymphoma treatment requires early and accurate assessment of prognosis. This investigation prospectively assessed the value of positron emission tomography with 2-[18F]fluoro-2-deoxy-D-glucose (FDG-PET) after two cycles of chemotherapy for prediction of progression-free survival (PFS) and overall survival (OS) in Hodgkin lymphoma (HL). Seventy-seven consecutive, newly diagnosed patients underwent FDG-PET at staging, after two and four cycles of chemotherapy, and after completion of chemotherapy. Median follow-up was 23 months. After two cycles of chemotherapy, 61 patients had negative FDG-PET scans and 16 patients had positive scans. Eleven of 16 FDG-PET-positive patients progressed and 2 died. Three of 61 FDG-PET-negative patients progressed; all were alive at latest follow-up. Survival analyses showed strong associations between early FDG-PET after two cycles and PFS (P < .001) and OS (P < .01). For prediction of PFS, interim FDG-PET was as accurate after two cycles as later during treatment and superior to computerized tomography (CT) at all times. In regression analyses, early interim FDG-PET was stronger than established prognostic factors. Other significant prognostic factors were stage and extranodal disease. Early interim FDG-PET is a strong and independent predictor of PFS in HL. A positive early interim FDG-PET is highly predictive of progression in patients with advanced-stage or extranodal disease.

Adolescent↗
PubMed1999

Determinants of aggression, and adaptive and maladaptive behaviour in older people with Down's syndrome with and without dementia.

In a cross-sectional study of aggression, and adaptive and maladaptive behaviour in 128 subjects with Down's syndrome (DS), 29 of whom had dementia, the current authors found that the presence of dementia was not predictive of aggression or maladaptive behaviour. However, the level of adaptive behaviour was shown to be lower in subjects with dementia, and in those with lower levels of cognitive functioning, as measured on a rating instrument, the Test for Severe Impairment. Although the presence of aggressive behaviours is not higher in subjects with dementia and DS on cross-sectional review, it remains to be seen whether aggression will increase in individual cases with the onset or progression of dementia. The decline in adaptive behaviour shown in the present study confirms the findings of previous studies and indicates a direction for service development for persons with the dual diagnosis of dementia and DS.

Adult↗
PubMed1999

Electromyogram amplitude estimation with adaptive smoothing window length.

Typical electromyogram (EMG) amplitude estimators use a fixed window length for smoothing the amplitude estimate. When the EMG amplitude is dynamic, previous research suggests that varying the smoothing length as a function of time may improve amplitude estimation. This paper develops optimal time-varying selection of the smoothing window length using a stochastic model of the EMG signal. Optimal selection is a function of the EMG amplitude and its derivatives. Simulation studies, in which EMG amplitude was changed randomly, found that the "best" adaptive filter performed as well as the "best" fixed-length filter. Experimental studies found the advantages of the adaptive processor to be situation dependent. Subjects used real-time EMG amplitude estimates to track a randomly-moving target. Perhaps due to task difficulty, no differences in adaptive versus fixed-length processors were observed when the target speed was fast. When the target speed was slow, the experimental results were consistent with the simulation predictions. When the target moved between two constant levels, the adaptive processor responded rapidly to the target level transitions and had low variance while the target dwelled on a level.

Adolescent↗
PubMed1979

[The pharmacokinetics of nalidixic acid administered parenterally. Towards rational use in severe infections (author's transl)].

Nalidixic acid is effective toward Gram negative infections but its short half-life and potential neurological toxicity explain that its parenteral use is hazardous. Interindividual variations of its pharmacokinetic parameters explain also the absolute necessity of a careful drug monitoring adapted to each patient. The study of plasma kinetics of a single dose of nalidixic acid injected by intravenous route, shows these metabolic variations. With this results, the predicted plasma drug concentrations show that classical dosage regimens are adapted only to a little number of patients. Advantages and inadequacies of a single daily intravenous infusion of nalidixic acid are next analysed.

Bacterial Infections↗