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PubMed1990

Programming time in serial tapping responses as a function of pathway constraint.

This study varied the accuracy demand within a linear series of targets to investigate the effect of movement-pathway constraints on response-programming time. Sidaway, Christina, and Shea (1988) have suggested that constraints placed upon movement initiation by the demand for response precision may play an important role in determining the length of the programming process. By varying the subtended angles of a series of three targets, this experiment tested the specific prediction of Sidaway et al. that programming time may be a function of the target, within a line of targets, that subtends the smallest angle at the start position. It is this target that demands the greatest precision in the movement pathway. Subjects participated in a series of conditions in which the size and placement of the target that imposed the maximal constraint was varied. In each condition the subjects were required to strike a series of three targets with a stylus in a simple reaction-time paradigm. Analysis of the reaction-time results revealed a significant effect of size of constraint, but no effect of position of constraint. Analysis of the movement-time data dispelled movement-duration and movement-velocity interpretations of the results and intimated a possible online trajectory-correction process.

Adolescent↗
PubMed1995

Manual discrimination of compliance using active pinch grasp: the roles of force and work cues.

In these experiments, two plates were grasped between the thumb and the index finger and squeezed together along a linear track. The force resisting the squeeze, produced by an electromechanical system under computer control, was programmed to be either constant (in the case of the force discrimination experiments) or linearly increasing (in the case of the compliance discrimination experiments) over the squeezing displacement. After completing a set of basic psychophysical experiments on compliance resolution (Experiment 1), we performed further experiments to investigate whether work and/or terminal-force cues played a role in compliance discrimination. In Experiment 2, compliance and force discrimination experiments were conducted with a roving-displacement paradigm to dissociate work cues (and terminal-force cues for the compliance experiments) from compliance and force cues, respectively. The effect of trial-by-trial feedback on response strategy was also investigated. In Experiment 3, compliance discrimination experiments were conducted with work cues totally eliminated and terminal-force cues greatly reduced. Our results suggest that people tend to use mechanical work and force cues for compliance discrimination. When work and terminal-force cues were dissociated from compliance cues, compliance resolution was poor (22%) relative to force and length resolution. When work cues were totally eliminated, performance could be predicted from terminal-force cues. A parsimonious description of all data from the compliance experiments is that subjects discriminated compliance on the basis of terminal force.

Adult↗
PubMed1997

Measuring the implementation of injury prevention programs in state health agencies.

OBJECTIVE: Injury prevention programs have been implemented with varying degrees of success in the United States. The objective of this study was to identify the variables that influence the successful implementation of injury prevention programs. METHODS: The key indicators of implementation success and its correlates were identified through consultation with a panel of experts. This consultation informed the content of a mail questionnaire sent to all United States state health departments, followed by telephone interviews. Data were analyzed using factor analysis and regression to identify significant relationships between variables. RESULTS: Data were obtained from 64 programs, representing 44 states; these included 24 programs in injury control units, 12 in maternal and child health units, 10 in health promotion/education units; and eight in emergency medical services units. Analysis identified four factors that are associated with an index of successful injury prevention program implementation; (1) participation and advocacy by constituent groups; (2) organizational capacity; (3) administrative control; and (4) attributes of relevant policies. CONCLUSIONS: Findings indicated that constituent participation (the extent and efficacy of constituency support and advocacy) and organizational capacity (a function of program staff and their skill levels) had the greatest influence on successful program implementation. Support from advocacy groups and knowledgeable staff members, whose time is dedicated to the program, are critical for conducting the activities necessary for successful implementation of these programs.

Accident Prevention↗
PubMed2005

A new approach to improve TMJ morphological information from plain film radiographs.

The hard tissues of the temporomandibular joint (TMJ) can be assessed through radiographic imaging to provide information to assist in diagnosis and treatment. However, the quality of information gathered from such imaging is often less than desired due to the small size of the TMJ, the widely varying fossa and condylar morphology, and the surrounding dense osseous structures. These make a clear and undistorted radiographic image of the hard tissue of the joint technically difficult. It is postulated that, if the degree of inaccuracy of a given radiograph is known quantitatively and taken into account, the clinician will be able to make a better informed qualitative assessment of TMJ morphology. The aim of this study is: 1. to improve the qualitative information that can be acquired from routine clinical plain film radiographs of the TMJ; 2. to use quantitative data to test the novel Neural Network (NN) model; and 3. to statistically show the discrepancies between routine radiographic images and the actual joint. Linear measurements of excised TMJs and their radiographic images were used to train a multilayer perceptron (MP) type NN model to predict joint dimensions more accurately. Such a neural network, developed using a statistical software package such as SPSS (SPSS, Inc. Chicago, IL), functions as a computer software program and predicts joint dimensions with increased accuracy when radiographic measurements are entered into the program. The NN model described here predicts the actual linear distances of the TMJ more closely than radiographic measurements and is more reliable in assessing the TMJ morphology.

Cadaver↗
PubMed2003

Sustaining new parents in home visitation services: key participant and program factors.

OBJECTIVES: As prevention efforts have adopted more intensive service models, concerns over initial enrollment and retention rates have become more salient. This study examines the participant, provider and program factors that contribute to a longer length of stay and greater number of home visits for new parents enrolling in one national home visitation program. METHODS: Retrospective data were collected on a random sample of 816 participants served by one of 17 Healthy Families America (HFA) program sites around the country. Using case record reviews, research staff documented each participant's characteristics and service experiences. To capture relevant staff and program information, research staff collected basic descriptive information from published documents and interviews with program managers. All home visitors who had contact with sample families also completed a self-assessment instrument regarding personal and professional characteristics. Hierarchical linear modeling allowed us to examine the unique role of participant, provider and program characteristics while recognizing the lack of independence among these three sets of variables. RESULTS: The combined provider and program levels in the HLM model accounted for one-third of the variance in service duration and one-quarter of the variance in the number of home visits. Older participants, those unemployed, and those who enrolled in the program early in their pregnancy were more likely to remain in services longer and to complete a greater number of home visits. Compared to White participants, African Americans and Hispanics were significantly more likely to remain in services longer and, in the case of African Americans, to receive a greater number of home visits. Participants who were enrolled in school were more likely to remain in services longer. Age was the only consistent provider characteristic associated with positive results in both models, with younger home visitors performing better. Prior experience showed a significant relationship only in the service dosage model and African American workers demonstrated greater success than White home visitors did in retaining families in service. At the program level, programs with lower caseloads and greater success in matching their participants and providers on parenting status and race/ethnicity were significantly more likely to demonstrate stronger enrollment patterns.

Adult↗
PubMed2003

Catching up on health outcomes: the Texas Medication Algorithm Project.

OBJECTIVE: To develop a statistic measuring the impact of algorithm-driven disease management programs on outcomes for patients with chronic mental illness that allowed for treatment-as-usual controls to "catch up" to early gains of treated patients. DATA SOURCES/STUDY SETTING: Statistical power was estimated from simulated samples representing effect sizes that grew, remained constant, or declined following an initial improvement. Estimates were based on the Texas Medication Algorithm Project on adult patients (age > or = 18) with bipolar disorder (n = 267) who received care between 1998 and 2000 at 1 of 11 clinics across Texas. STUDY DESIGN: Study patients were assessed at baseline and three-month follow-up for a minimum of one year. Program tracks were assigned by clinic. DATA COLLECTION/EXTRACTION METHODS: Hierarchical linear modeling was modified to account for declining-effects. Outcomes were based on 30-item Inventory for Depression Symptomatology-Clinician Version. PRINCIPAL FINDINGS: Declining-effect analyses had significantly greater power detecting program differences than traditional growth models in constant and declining-effects cases. Bipolar patients with severe depressive symptoms in an algorithm-driven, disease management program reported fewer symptoms after three months, with treatment-as-usual controls "catching up" within one year. CONCLUSIONS: In addition to psychometric properties, data collection design, and power, investigators should consider how outcomes unfold over time when selecting an appropriate statistic to evaluate service interventions. Declining-effect analyses may be applicable to a wide range of treatment and intervention trials.

Adult↗
PubMed1986

Effect of controlled dietary consistency and cage environment on the rat mandibular growth.

Forty Fischer strain inbred albino rats, evenly divided by sex, were obtained at 9 days of age. The animals were weaned at 21 days and randomly divided into the four experimental groups. Two variations on dietary consistency, hard and soft diet, as well as two variations on cage environment, normal and no biting surfaces, constituted the experimental groupings. The experimental period consisted of 16 weeks during which the animals were raised under the designated conditions. At the end of the experimental period the animals were killed with carbon dioxide, and the entire mandible, and both femurs, were dissected free. Weight and volumetric analysis were carried out in a standard fashion on the cleaned specimens. Area and linear measurements were performed and analyzed with a specially designed computer program. The results showed that there was sexual dimorphism in the Fischer rat both with respect to body weight and the weight, volume, area, and linear measurements of the mandible. The effects of dietary consistency had a greater influence on mandibular ramus size and form than did those caused by alteration in cage environment. The posterior region of the mandible, in association with the heavy muscles of mastication, was affected more by dietary consistency than was the anterior region. The entire region of the mandibular ramus acted as an area of adaptation and growth. The findings of this study indicate that dietary consistency has a small but significant effect on mandibular size in specific measurements. The cage environment used in this experiment did not limit function to the extent necessary to see measurable changes in mandibular measurements.

Animal Husbandry↗
PubMedDate not supplied

[Pulley system isokinetic training in knee rehabilitation--initial results].

AIM: The purpose of this study was to evaluate the results of a knee rehabilitation program after knee surgery, based on an isokinetic pulley System (Moflex, Recotec/Bernina, Switzerland). METHOD: In this prospective study, 73 patients participated in a standardized rehabilitation program (ACL reconstruction, ACL/all: n = ;51; patellar tendon, ACL/P: n = 30; semitendinosus tendon, ACL/S: n = 21; arthroscopic meniscus resection: n = 22). The major aspect of the program was an isokinetic pulley system with an implemented, linearly working knee device. RESULTS: Isokinetic training with the used device affords strict monitor feed-back to avoid critical torque values. Concentric training strength and workload which were attained without relevant pain were increased by about 130% within a mean of 16 rehabilitation days. At the end of the rehabilitation program, the maximum concentric strength of the affected knee measured by a rotating isokinetic system (Cybex, Kaphingst, Lahntal) increased by about 69% and amounted to about 90% of that of the unaffected knee. CONCLUSION: These first results demonstrate the value of the isokinetic pulley system in the rehabilitation after knee surgery as described above. The equipment may be used already in an early postoperative stage by the use of a passive or active-assistive mode. First results of strength increases using an isokinetic pulley system in knee rehabilitation are presented.

Adult↗
PubMed1997

Physiologic smoothing of blood time-activity curves for PET data analysis.

UNLABELLED: Blood or plasma time-activity curves (TACs) are used as the input function for mathematical models of tracer kinetics in several applications including PET. Uncertainty associated with both the blood data and the PET tissue data can result in uncertainty in the estimates of metabolic rates, blood flow, etc. METHODS: This article presents an approach to reduce the uncertainty in the blood TAC by fitting a model to the curve. The model includes a choice of bolus or infusion input and has three compartments (plasma, interstitial fluid and tissue fluid) with exchange between them. There is a parameter for loss from the plasma compartment. To test the utility of smoothing blood TACs with this approach, a program was set up, using the fluorodeoxyglucose (FDG) model, with simulated noisy blood and tissue TACs. The smoothed blood TAC was compared to a linearly interpolated TAC as the input function with a compartmental model parameter estimation program and with graphical analysis. RESULTS: With a well sampled blood TAC (19 points), the model approach is somewhat more accurate than linear interpolation if the s.d. of noise added to the data exceeded 10%. With sparsely sampled blood TACs (five points) or with a large gap in the blood TAC, the modeled approach was markedly better. For graphical analysis, the model smoothed TAC was also more accurate, although, in general, the results were not as sensitive to the input function. CONCLUSION: This approach, using a physiologically reasonable model to smooth the blood TAC, is a useful aid in PET data analysis, particularly when the data are quite noisy or when there are large gaps in the data.

Computer Simulation↗
PubMed1996

The implementation of Prime Vendor Europe and its successful impact on an overseas naval medical treatment facility.

Prime Vendor Europe (PVE) is the commercial pharmaceutical ordering and delivery program that is revolutionizing overseas health care delivery at military health care treatment facilities located in the European theater. Mirroring civilian programs already available and replacing the Federal Supply System, PVE offers many benefits never before realized at overseas military health care treatment facilities, including: diminished order turnaround times with resultant decreased Operating Target requirements; rapid order confirmation after order placement; lower carrying costs and inventory needs; better dating of pharmaceuticals received; redistribution and increased efficiency of the current manhours needed to operate a pharmacy supply system; order tracking capabilities; and enhancement of the present cooperative and constructive dichotomous relationship between medical logistics and pharmacy regarding pharmaceutical purchasing practices. This paper will explore the fundamentals, past performance, continuous quality improvement of logistical functions, frame-work establishment for PVE, implementation of PVE, and subsequent observed command benefits of PVE realization.

Delivery of Health Care↗
PubMed1982

Simple linear filtering of time series data on a programmable calculator.

A program is presented for the Texas Instruments SR-52 programmable calculator which computes simple moving averages of time series data. Design and programming emphasis was placed on ease of use and time savings. The output from this program is useful in determining the shape of time-ordered sequences of data. The technique used for internally reordering the data after each individual calculation is explained is some detail as it may be useful in any program of an algorithm involving a moving window on a sequence of data.

Animals↗
PubMed1992

Chronolab: an interactive software package for chronobiologic time series analysis written for the Macintosh computer.

Methods based on periodic regression have been designed for the detection of periodic components in short, noisy, and nonequidistant time series (as they are usually present in medicine and biology). The procedure consists of fitting a set of (cosine) curves to the data, with the analyst choosing the domain of trial periods to be analyzed and the distance between consecutive trial periods. We here describe an interactive program for least-squares rhythmometry written in C language for the Macintosh computer. For any given number of time series to be analyzed at once, the program is able to perform two different kinds of analyses: (a) linear in time, for the sequential fit of trial periods; and (b) linear in frequency, for the sequential fit of harmonic components from an initial fundamental period. For each series and for each trial period fitted to the data, the program gives the following information: fitted period; percent rhythm; p value from testing the assumption of zero amplitude; rhythm-adjusted mean or mesor, amplitude, and acrophase, each with corresponding standard errors and 95% confidence intervals when the component is statistically significant; and (when required by the analyst) p values from tests of sinusoidality, normality of residuals, and homogeneity of variance. Additionally, the program provides a summary report for each time series analyzed, including descriptive statistics such as the number of data analyzed for that series, minimum, maximum, arithmetic mean, standard deviation, standard error, 90% range, and 50% range. The analyst is also able to transform the data before doing any rhythmometric analysis. Transformations already integrated in the program include square root, logarithm, inverse, data as percentage of mean, data as percentage of mesor, and elimination of values outside +/- 3 SD from the mean. When several periods are suspected to be statistically significant, a multiple-component analysis can be also used by the concomitant least-squares fit of several harmonics. The program allows the simultaneous analysis of several periods in several variables from several individuals, with limitations depending solely on internal memory availability and speed requirements from the user. When series from different subjects or different variables in the same subject are available for analysis, a parameter test also included in the program can be used for comparison of rhythm characteristics at any given period. All information required in a single analysis is given by the analyst in the form of self-explanatory commands grouped in different "menus."(ABSTRACT TRUNCATED AT 400 WORDS)

Biometry↗
PubMed1999

EasyBound--a user-friendly approach to nonlinear regression analysis of binding data.

The introduction of non-linear regression analysis of data from pharmacological experiments has provided an enormous advantage in making it possible to analyze raw data without any mathematical transformation. However, the disadvantage has been the lack of computer programs with simple user interfaces and the ability to easily handle large amounts of data. With the aim to develop a light-weight and still powerful program we have written an application called EasyBound which is designed to be used with Microsoft Excel and hence takes advantage of the abilities of the spreadsheet application to handle large amounts of data. Focus has been on creating an easy-to-understand user interface. There are commercial programs available, but they tend to be very complex and difficult to grasp for inexperienced users. EasyBound displays original data, calculated results and graphs on the same sheet/page. The program fully implements the most powerful algorithms for non-linear regression analysis, giving results that are more accurate than using built-in iterative analysis functions of the spreadsheet application without compromising ease of use.

Algorithms↗
PubMed1990

Using a pocket computer to calculate monitor units--outline of a program in BASIC.

A pocket computer was programmed in BASIC to calculate monitor units for a dual energy linear accelerator. Because of the relatively large RAM memory, it was possible to input the TMR (or the PDD) tables for both energies as DATA. The program was written with the intention of providing a back-up check of the hand calculations.

Humans↗
PubMed2000

Dynamic optimization of a linear-quadratic model with incomplete repair and volume-dependent sensitivity and repopulation.

PURPOSE: The linear-quadratic model typically assumes that tumor sensitivity and repopulation are constant over the time course of radiotherapy. However, evidence suggests that the growth fraction increases and the cell-loss factor decreases as the tumor shrinks. We investigate whether this evolution in tumor geometry, as well as the irregular time intervals between fractions in conventional hyperfractionation schemes, can be exploited by fractionation schedules that employ time-varying fraction sizes. METHODS: We construct a mathematical model of a spherical tumor with a hypoxic core and a viable rim, which is most appropriate for a prevascular tumor, and is only a caricature of a vascularized tumor. This model is embedded into the traditional linear-quadratic model by assuming instantaneous reoxygenation. Dynamic programming is used to numerically compute the fractionation regimen that maximizes the tumor-control probability (TCP) subject to constraints on the biologically effective dose of the early and late tissues. RESULTS: In several numerical examples that employ five or 10 fractions per week on a 1-cm or 5-cm diameter tumor, optimally varying the fraction sizes increases the TCP significantly. The optimal regimen incorporates large Friday (afternoon, if 10 fractions per week) fractions that are escalated throughout the course of treatment, and larger afternoon fractions than morning fractions. CONCLUSION: Numerical results suggest that a significant increase in tumor cure can be achieved by allowing the fraction sizes to vary throughout the course of treatment. Several strategies deserve further investigation: using larger fractions before overnight and weekend breaks, and escalating the dose (particularly on Friday afternoons) throughout the course of treatment.

Algorithms↗
PubMed2004

A comparison of weight average and direct boundary fitting of sedimentation velocity data for indefinite polymerizing systems.

Analysis of sedimentation velocity data for indefinite self-associating systems is often achieved by fitting of weight average sedimentation coefficients (s(20,w)) However, this method discriminates poorly between alternative models of association and is biased by the presence of inactive monomers and irreversible aggregates. Therefore, a more robust method for extracting the binding constants for indefinite self-associating systems has been developed. This approach utilizes a set of fitting routines (SedAnal) that perform global non-linear least squares fits of up to 10 sedimentation velocity experiments, corresponding to different loading concentrations, by a combination of finite element simulations and a fitting algorithm that uses a simplex convergence routine to search parameter space. Indefinite self-association is analyzed with the software program isodesfitter, which incorporates user provided functions for sedimentation coefficients as a function of the degree of polymerization for spherical, linear and helical polymer models. The computer program hydro was used to generate the sedimentation coefficient values for the linear and helical polymer assembly mechanisms. Since this curve fitting method directly fits the shape of the sedimenting boundary, it is in principle very sensitive to alternative models and the presence of species not participating in the reaction. This approach is compared with traditional fitting of weight average data and applied to the initial stages of Mg(2+)-induced tubulin self-associating into small curved polymers, and vinblastine-induced tubulin spiral formation. The appropriate use and limitations of the methods are discussed.

Animals↗
PubMedDate not supplied

Reliability block diagrams to model disease management.

BACKGROUND AND OBJECTIVES: Studies of diagnostic or therapeutic procedures in the management of any given disease tend to focus on one particular aspect of the disease and ignore the interaction between the multitude of factors that determine its final outcome. The present article introduces a mathematical model that accounts for the joint contribution of various medical and non-medical components to the overall disease outcome. METHODS: A reliability block diagram is used to model patient compliance, endoscopic screening, and surgical therapy for dysplasia in Barrett's esophagus. RESULTS: The overall probability of a patient with a Barrett's esophagus to comply with a screening program, be correctly diagnosed with dysplasia, and undergo successful therapy is 37%. The reduction in the overall success rate, despite the fact that the majority of components are assumed to function with reliability rates of 80% or more, is a reflection of the multitude of serial subsystems involved in disease management. Each serial component influences the overall success rate in a linear fashion. Building multiple parallel pathways into the screening program raises its overall success rate to 91%. Parallel arrangements render systems less sensitive to diagnostic or therapeutic failures. CONCLUSIONS: A reliability block diagram provides the means to model the contributions of many heterogeneous factors to disease outcome. Since no medical system functions perfectly, redundancy provided by parallel subsystems assures a greater overall reliability.

Barrett Esophagus↗