SEARCH · PubMed Health
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.
Henneman's size principle of motor unit recruitment and rate coding reduces fatigue, minimizes error in transfer of information from the nervous system, and produces smooth force output. Plasticity present at various sites of the motor system may change endurance, force, speed, or precision with training, but not the recruitment order.
PURPOSE: Although many operative decisions are based on apparent changes in function detected by serial diuretic renography, the reliability of relative renal function data has been questioned. We investigated the effect of background subtraction on calculated renal function. MATERIALS AND METHODS: We reviewed 23 pediatric mercaptoacetyltriglycine renograms. Regions of interest for background subtraction were redrawn and relative renal function values were recalculated. RESULTS: In patients with left hydronephrosis left differential renal function was consistently underestimated by 7.3% compared to the superior and 4.7% compared to the average background subtraction technique. In patients with right hydronephrosis, when considering lower pole background activity only, right differential renal function was consistently overestimated by 15.8% compared to the superior and 2.4% compared to the average background subtraction technique. In patients younger than 1 year at the time of study these differences were exaggerated. CONCLUSIONS: Because of overlapping hepatic background activity, the position of regions of interest for background subtraction may greatly influence calculated renal function. We recommend that the preferred method of calculating background subtraction to minimize error be based on a region of interest surrounding the whole kidney. This method is especially pertinent in patients with right hydronephrosis and in those younger than 1 year. Reported relative renal function data should be interpreted with caution.
The reproducibility of the in vivo performance of a contact lens depends on how the specifications are determined and how the lens is made. Using reproducibility of edge clearance as a criterion, the peripheral curve design of a contact lens is analyzed. Optimum values of peripheral curve width exist which minimize errors of reproducibility.
Physicians should be knowledgeable of human factors (ergonomics) to address the workplace needs of their patients. Human factors is the discovery and application of principles concerning human capacities and capabilities to the design, evaluation, operation, and maintenance of the work system for the safe, effective, and satisfying use by people. Human factors encompasses a wide range of subjects that relate to the mutual interaction between the worker and the work system, which includes the following: the organization, the environment, and the workplace; the job and the tasks the worker performs; and the equipment and the tools used. The majority of work-related injuries and loss incidents have some contributory cause related to the interaction between the worker and the work system. The goal of human factors activities is to assess abnormal or excessive human stressors and minimize or eliminate the stress to improve performance and reliability and minimize error. Human factors is becoming an integral part of occupational medicine because it is increasingly important in the workplace. This overview of human factors emphasizes the current knowledge of prevention and intervention measures to enhance the functional quality of the workplace.
OBJECTIVES: The aim of this study was to evaluate the usability of the e-Ouch electronic chronic pain diary in adolescents with juvenile idiopathic arthritis. METHODS: A qualitative usability testing approach with semistructured, audiotaped interviews with two iterative cycles was used. A purposive sample of 10 adolescents per cycle was drawn from a rheumatology clinic in a university-affiliated pediatric tertiary care center. Participants were provided with a brief demonstration of the diary and then asked to use the diary "thinking aloud" to record the pain they experienced: (1) when they woke up that morning, (2) during that afternoon, and (3) from the previous evening. Adolescents were then asked a series of open-ended questions addressing ease of use of the diary. Qualitative thematic analysis was used to generate categories and emerging themes from interview data. RESULTS: All of the adolescents stated the e-Ouch diary was very easy to learn, use, and understand and was satisfying to complete. Participants took less than 9 minutes to complete all three of the diary entries with minimal errors. The usability evaluation revealed aspects of the interface that were suboptimal (eg, VAS slider) and impeded the performance of certain tasks. Adolescents generated ideas on how the diary interface could be improved. CONCLUSIONS: A multifaceted usability approach provided important insight regarding the use of technology by adolescents with arthritis and, more specifically, for understanding how adolescents can more effectively use an electronic chronic pain diary.
Current regulations require that departments of pathology have a structured and active program of quality assurance (QA) and quality improvement (QI), with the goals of enhancing patient safety, minimizing error, ensuring timely delivery of reports, and monitoring physician competence. Types of potential error may evolve over time and, as regulations become progressively more stringent, QA/QI programs need to be constantly updated. The Association of Directors of Anatomic and Surgical Pathology (ADASP) herein provides guidelines for QA and QI in surgical and autopsy pathology.
RATIONALE AND OBJECTIVES: Evaluation of the T2 relaxation time of articular cartilage holds great potential for quantitative assessment of internal changes of the cartilage matrix. The purpose of the present study was to assess the validity of multiecho-based cartilage T2 quantitation in a clinical MRI setting at 1.5 T. METHODS: Four multisection multiecho sequence variants dedicated for quantitative T2 mapping of human articular cartilage were implemented on a 1.5 T whole-body imager and tested for accuracy in CuSO4-agarose gel phantoms and human patellar cartilage. Sequence design was varied to minimize errors in T2 quantitation due to stimulated echoes. RESULTS: As compared with single spin-echo experiments, the apparent T2 values calculated from the multiecho sequence variants showed mean deviations ranging from +26% to -32% (phantoms) and from +42% to -18% (cartilage). The patellar cartilage T2 covered a range from about 25 milliseconds to 55 milliseconds, with longer T2 values observed in the more superficial layers. In cartilage, best results were obtained from the sequence design using improved section profiles and a spoiler gradient scheme for suppression of stimulated echoes. CONCLUSIONS: Our results revealed a clear dependence of apparent T2 relaxation times on the pulse sequence design, emphasizing that the "true" T2 is hard to find. In addition, the effect on the apparent T2 values resulting from the specific modification of any sequence variant varied according to the respective tissue's properties. Therefore, the acquisition technique in conjunction with the specific tissue on which T2 mapping is performed need to be reported in detail and should kept consistent to allow large-scale comparisons and monitoring of treatment strategies, e.g., in osteoarthritis.
Speciation analysis calls for rapid, simple systems for minimizing errors made in the most troublesome of all steps in the analytical process: sample preparation. In this context, continuous-flow systems are of great help. The evolution in the different methodologies enabled solutions to the main shortcomings occurring from the lack of selectivity of using RP-C18 as sorbent material. One solution was a shift to more sensitive and selective, but only partially automated, systems employing C60 fullerene and Grignard's reagent; another was a shift to completely automated systems employing sodium tetrapropylborate; and a final solution was to employ the simplest possible configuration by removing the reagent stream. The analytical methods developed allowed the identification and quantification of different organolead species at the pg/ml levels in rainwater samples, with precision (RSD) of about 5% and recoveries ranging from 92 to 100%.
Estimation on a noisy signal observed by a nonlinear sensor taking the form of a threshold quantizer is considered. The optimal Bayesian estimator with minimal error is derived in this nonlinear setting. The existence of conditions where the performance of this estimator can be improved by raising the level of noise is established, both theoretically and numerically. These results constitute a different instance of the nonlinear phenomenon of stochastic resonance for signal enhancement by noise.
Patients are often ill-equipped to know which speciality to choose for their health problem. Especially in the presence of non-specific symptoms, choosing the right specialist might not be so obvious. In such cases, misdirected self-referrals by patients to self-chosen specialists can sometimes lead to misdiagnosis resulting in unwarranted delays in getting the right treatment. The general physicians, on the other hand, are in a unique position to oversee the big picture of patients' health, and are therefore better equipped to identify and sort out their individual health problems. Hence instead of a specialist if the first place of contact for patients is a general physician, they are likely to be guided along the right path of treatment for their various health problems. Such a system will minimize errors on the part of the patients by making certain that they are referred to the appropriate specialists.
The irregular staircase appearance of the accommodation response to a ramp stimulus, slow movement of a target towards the subject's eye, suggests a switching between different states of control. Experiments and model simulations indicate that blur processing by retina and cortex underlies threshold triggering of the switch. The ON state consists of a fairly high gain, closed-loop control system that minimizes error. The OFF state provides for a quasi-open-loop state and a slow drift to a bias level, under the influence of a leaky integrator.
The electrolarynx (EL) voice prosthesis is widely used, but suffers from the inconvenience of requiring manual control. Therefore, a hands-free EL triggered by neck muscle electromyographic (EMG) activity was developed (EMG-EL). Signal processing circuitry in a belt-mounted control unit transforms EMG activity into control signals for initiation and termination of voicing. These control signals are then fed to an EL held against the neck by an inconspicuous brace. Performance of the EMG-EL was evaluated by comparison to normal voice, manual EL voice, and tracheo-esophageal (TE) voice in a series of reaction time experiments in seven normal subjects and one laryngectomy patient. The normal subjects produced voice initiation with the EMG-EL that was as fast as both normal voice and the manual EL. The laryngectomy subject produced voice initiation that was slower than with the manual EL, but faster than with TE voice. Voice termination with the EMG-EL was slower than normal voice for the normal subjects, but not significantly different than with the manual EL. The laryngectomy subject produced voice termination with the EMG-EL that was slower than with TE or manual EL. The EMG-EL threshold was set at 10% of the range of vocal-related EMG activity above baseline. Simulations of EMG-EL behavior showed that the 10% threshold was not significantly different from the optimum threshold produced through the process of error minimization. The EMG-EL voice reaction time appears to be adequate for use in a day-to-day conversation.
A neural-network-based framework has been developed to search for an optimal wavelet kernel that can be used for a specific image processing task. In this paper, a linear convolution neural network was employed to seek a wavelet that minimizes errors and maximizes compression efficiency for an image or a defined image pattern such as microcalcifications in mammograms and bone in computed tomography (CT) head images. We have used this method to evaluate the performance of tap-4 wavelets on mammograms, CTs, magnetic resonance images, and Lena images. We found that the Daubechies wavelet or those wavelets with similar filtering characteristics can produce the highest compression efficiency with the smallest mean-square-error for many image patterns including general image textures as well as microcalcifications in digital mammograms. However, the Haar wavelet produces the best results on sharp edges and low-noise smooth areas. We also found that a special wavelet whose low-pass filter coefficients are 0.32252136, 0.85258927, 1.38458542, and -0.14548269) produces the best preservation outcomes in all tested microcalcification features including the peak signal-to-noise ratio, the contrast and the figure of merit in the wavelet lossy compression scheme. Having analyzed the spectrum of the wavelet filters, we can find the compression outcomes and feature preservation characteristics as a function of wavelets. This newly developed optimization approach can be generalized to other image analysis applications where a wavelet decomposition is employed.
We investigated spatio-temporal information processing in the primate motor system. Corticomotoneuronal (CM) cells provide monosynaptic excitatory connections from motor cortex to spinal motoneurons and contribute causally to the time-varying electromyogram (EMG) of their target muscle. A multilayer perceptron (MLP) was used to evaluate the transfer function between neural activity of single CM cells and their target muscle EMG, using data from in-vivo recordings in primate motor cortex. For an optimal MLP performance, i.e., minimal error between recorded target EMG and MLP-derived EMG, the CM cell input period had to span the latency observed between CM cell peak activity and EMG peak activity. We argue that the same spike train may code two types of information: 1) rate coding within the input window accounted for large-amplitude variations in the EMG signal and 2) temporal coding within a window of 40 ms just prior to the EMG output signal accounted for EMG variations of small amplitude. The transfer function of the MLP, thus, combines rate and temporal coding and suggests that CM cell output may also combine these two forms of coding. We predict that mutual constraints of rate and temporal coding would, however, would limit the CM output to code for particular temporal profiles of EMG, possibly adapted to bio-mechanical constraints.
In this paper we present and analyze a new structure for designing a radial basis function neural network (RBFNN). In the training phase, input layer of RBFNN is augmented with desired output vector. Generalization phase involves the following steps: (1) identify the cluster to which a previously unseen input vector belongs; (2) augment the input layer with an average of the targets of the input vectors in the identified cluster; and (3) use the augmented network to estimate the unknown target. It is shown that, under some reasonable assumptions, the generalization error function admits an upper bound in terms of the quantization errors minimized when determining the centers of the proposed method over the training set and the difference between training samples and generalization samples in a deterministic setting. When the difference between the training and generalization samples goes to zero, the upper bound can be made arbitrarily small by increasing the number of hidden neurons. Computer simulations verified the effectiveness of the proposed method.
Discriminative training refers to an approach to pattern recognition based on direct minimization of a cost function commensurate with the performance of the recognition system. This is in contrast to the procedure of probability distribution estimation as conventionally required in Bayes' formulation of the statistical pattern recognition problem. Currently, most discriminative training algorithms for nonlinear classifier designs are based on gradient-descent (GD) methods for cost minimization. These algorithms are easy to derive and effective in practice, but are slow in training speed and have difficulty selecting the learning rates. To address the problem, we present our study on a fast discriminative training algorithm. The algorithm initializes the parameters by the expectation-maximization (EM) algorithm, and then uses a set of closed-form formulas derived in this paper to further optimize a proposed objective of minimizing error rate. Experiments in speech applications show that the algorithm provides better recognition accuracy in a fewer iterations than the EM algorithm and a neural network trained by hundreds of GD iterations. Although some convergent properties need further research, the proposed objective and derived formulas can benefit further study of the problem.
AIM AND OBJECTIVES: The purpose of this paper is to describe a cross-cultural translation and validation methodology recommended by Vallerand. The translation technique has seven steps and ensures the instrument provides data that are valid and reliable. BACKGROUND: Translation of data collection instruments is a challenge increasingly being faced by overseas students studying in the West as they choose to research contextual issues of relevance to their home culture. METHODS: Six of Vallerand's seven steps are used and modified as the methodical translation of a survey from English to Mandarin. RESULTS: The results revealed there was no significant difference between the original English questionnaire and Mandarin questionnaire. The validation study indicated good internal consistency. The construct validity of the Mandarin version was determined except one item which failed the test. The validation demonstrates only minor effects of language translation. CONCLUSION: The Mandarin version thus is a valid tool for investigating from the perspective of school nurses, their role and potential contribution to health promotion in relation to the prevention of obesity among school children in Taiwan. RELEVANCE TO CLINICAL PRACTICE: The results of the study will enable school nurses and their managers to reflect critically on their contribution to the prevention of obesity among Taiwanese school children. The translation technique has enabled the researcher to minimize errors that may have occurred in translation. It adds to the quality of the instrument and offers opportunities in the future to undertake cross-cultural comparison in an issue of great concern globally.
Tuberculosis and other kinds of mycobacteriosis are serious illnesses for which early diagnosis is critical for disease control. Sputum sample analysis is a common manual technique employed for bacillus detection but current sample-analysis techniques are time-consuming, very tedious, subject to poor specificity and require highly trained personnel. Image-processing and pattern-recognition techniques are appropriate tools for improving the manual screening of samples. Here we present a new technique for sputum image analysis that combines invariant shape features and chromatic channel thresholding. Some feature descriptors were extracted from an edited bacillus data set to characterize their shape. They were statistically represented by using a Gaussian mixture model representation and a minimal error Bayesian classification procedure was employed for the last identification stage. This technique constitutes a step towards automating the process and providing a high specificity.