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PubMed1991

A deterministic computer simulation model of life-cycle lamb and wool production.

A deterministic mathematical computer model was developed to simulate effects on life-cycle efficiency of lamb and wool production from genetic improvement of performance traits under alternative management systems. Genetic input parameters can be varied for age at puberty, length of anestrus, fertility, precocity of fertility, number born, milk yield, mortality, growth rate, body fat, and wool growth. Management options include mating systems, lambing intervals, feeding levels, creep feeding, weaning age, marketing age or weight, and culling policy. Simulated growth of animals is linear from birth to inflection point, then slows asymptotically to specified mature empty BW and fat content when nutrition is not limiting. The ME intake requirement to maintain normal condition is calculated daily or weekly for maintenance, protein and fat deposition, wool growth, gestation, and lactation. Simulated feed intake is the minimum of availability, DM physical limit, or ME physiological limit. Tissue catabolism occurs when intake is below the requirement for essential functions. Mortality increases when BW is depressed. Equations developed for calculations of biological functions were validated with published and unpublished experimental data. Lifetime totals are accumulated for TDN, DM, and protein intake and for market lamb equivalent output values of empty body or carcass lean and wool from both lambs and ewes. These measures of efficiency for combinations of genetic, management, and marketing variables can provide the relative economic weighting of traits needed to derive optimal criteria for genetic selection among and within breeds under defined industry production systems.

Animals↗
PubMed1990

A computer designed graph for administration of atracurium by i.v. infusion.

A bi-exponential mathematical computer model was used to develop a guidance graph for atracurium infusions. The model permitted variation in infusion rates, in pharmacokinetic parameters and in "effect" thresholds. Systematic experiments revealed a relationship between the rate of recovery from a fixed bolus loading dose and the most appropriate initial infusion rate. This relationship was expressed as a guidance graph or "ready reckoner". The quality of guidance was assessed in 50 anaesthetics, given consecutively. In 39 patients optimal myoneural block for surgery was maintained for the duration of the infusion without adjustments or supplementary bolus doses. The mean operating time was 92 min and the mean duration of infusion was 59 min.

Adult↗
PubMed1991

[Automated diagnosis of vibration disease].

Based on a multidimensional discriminant analysis of the clinical and physiological characteristics derived as a result of examination of 593 miners, classification functions were plotted, allowing the diagnosis of vibratory disease in the automatic mode by means of mathematic computations. Functional indicators of skin sensitivity, particularly vibratory, dynamometry, rheovasography and thermography of the hand and fingers, a "white spot" symptom, and characteristics derived on a mathematic analysis of heart rhythm were established to be informative for automated diagnosis. The diagnosis was found to be more accurate in case of using a two-stage variant of the discriminant analysis where the differentiation is first made between healthy workers and workers with a pathology, followed by the discrimination of the preclinical and clinical phase of the disease. The automated diagnostic system is demonstrated to compare very favourably with the conventional method of diagnosis.

Arctic Regions↗
PubMed1991

Modeling and simulation in biomedicine.

A group of researchers and educators in The Netherlands, Germany and Czechoslovakia have developed and adapted mathematical computer models of phenomena in the field of physiology and biomedicine for use in higher education. The models are graphical and highly interactive, and are all written in TurboPascal or the mathematical simulation language PSI. An educational shell has been developed to launch the models. The shell allows students to interact with the models and teachers to edit the models, to add new models and to monitor the achievements of the students. The models and the shell have been implemented on a MS-DOS personal computer. This paper describes the features of the modeling package and presents the modeling and simulation of the heart muscle as an example.

Computer Graphics↗
PubMedDate not supplied

[The mathematical modelling of the displacement of the hard palate tissues in conservative uranoplasty].

Presents a mathematical model of sparing uranoplasty techniques developed by the authors; using this model, a physician may assess before surgery the volume of tissues needed to close the palatal defect. Experience gained with 72 surgeries carried out in children with unilateral cleft palate confirms the desirability of preliminary computations. Mathematical models for the most prevalent sparing uranoplasty methods are offered.

Child↗
PubMed1989

Using mathematical programming to assess the relative performance of the health care industry.

Unlike conventional methods for evaluating program efficiency, a recently developed mathematical programming technique, Data Envelopment Analysis (DEA), is able to handle multiple inputs and outputs simultaneously without assigning arbitrary weights and does not require the use of homogeneous measurement units nor a prespecified functional relationship between inputs and outputs. Despite of its unfamiliarity to health care researchers and administrators, this technique is becoming increasingly popular as a means of evaluating relative performance in not-for-profit entities.

Decision Making, Organizational↗
PubMed1985

A mathematical model and computer program for adriamycin distribution and elimination.

A mathematical physiological flow model is described for the distribution and elimination of adriamycin in the rat. The model includes the volume or mass of, and blood flow to the following tissues: heart, plasma, muscle, skin, kidney, bone marrow, gut, liver and bile. A compartment is also included for tight or almost irreversible binding which occurs with this drug. The program was written in FORTRAN to compute the concentration of drug in each tissue as a function of time after bolus injection or short term infusion. The computed data is printed on a line printer and recorded on disk for use in a SAS program GPLOT to obtain precision plots.

Animals↗
PubMedDate not supplied

Anatomical macroelements in the study of craniofacial rat growth.

In order to avoid the arbitrary division of biological structures, rational polynomial interpolants are utilized to study growth. The major advantage of this method is the elimination of artificial internal element boundaries through anatomical structures. Since the boundary element methodology is employed in the finite element setting, other benefits, without additional computer coding, include the ability to use elements with any number of sides and reference frame invariance. Longitudinal landmark coordinates from midsagittal X-ray tracings of 22 albino female rat skulls of various ages were averaged. The skull was partitioned into three macroelements: a neural skull and two functionally distinct portions of the facial skull--olfactory and respiratory. The digital computer programming was carried out in the computer mathematics environment of Mathematica. Maximum elongation ratios were calculated for approximately 400 interior points. The elongation ratios in the neural skull compared well with previously documented growth behavior of internal brain structures. The calculated ratios from the facial skull were used to analyze the behavior of macroelement interpolation close to common anatomical boundaries.

Animals↗
PubMed1990

Long-term arterial pressure control: an analysis from animal experiments and computer and graphic models.

Long-term arterial pressure control is very different from acute control, because many of the acute control systems are overridden by a single long-term mechanism that has little to do with short-term control. This is the renal fluid volume mechanism for pressure control. It is based on a simple functional property of the kidney: as the arterial pressure rises, the kidney output of water and electrolytes increases dramatically. When the output rises above the net intake of water and electrolytes, negative body fluid balance occurs, causing both the body fluid volume and the pressure to decrease. This decrease continues until the kidney fluid output exactly balances the net fluid intake. Conversely, if the pressure falls below the exact level for balance, intake becomes greater than output; then fluid builds up in the body and the pressure rises until intake and output again exactly balance each other. This fluid mechanism for pressure control has been known from the beginning of blood pressure research. However, its overpowering importance was not appreciated until a mathematical computer analysis in 1966 demonstrated the renal-fluid feedback mechanism to have infinite feedback gain for long-term pressure control. This is the principal topic of the present review.

Animals↗
PubMed1990

The modified minimal model: application to measurement of insulin sensitivity in children.

The modified minimal model (MMM), a recently introduced method that assesses insulin sensitivity (SI) by a computed mathematical analysis of the relation between the change in insulin and glucose clearance after a bolus of iv glucose, followed 20 min later by a bolus of tolbutamide, has been standardized in adults, but this method has not been validated in children. We performed an abbreviated 90-min MMM test in 50 children who were siblings of patients with insulin-dependent diabetes mellitus and 7 healthy adult volunteers and compared the results to the standard 180-min MMM test in 11 of these subjects. The cohort consisted of 29 prepubertal children [16 males and 13 females; 8.7 +/- 2.0 (mean +/- SEM) yr old]; 16 pubertal children defined as less than 17 yr of age and Tanner stage 2-5 (8 males and 8 females; 13.4 +/- 1.8 yr old), and 12 postpubertal subjects (7 males and 5 females; 18.2 +/- 0.9 yr old), with no significant difference in the weight for length index (WLI) among the 3 groups and with sera of all subjects negative for islet cell antibodies and insulin autoantibodies. The test procedure consisted of 3 baseline blood samples over 30 min, followed at zero time by 0.3 g/kg 25% dextrose infused iv over 1 min and an iv injection of tolbutamide (5 mg/kg) 20 min later; sequential blood samples for glucose and insulin measurements were withdrawn from zero time until completion 90 or 180 min later. In the 11 subjects who underwent both the standard and the abbreviated tests, there was no significant difference between the SI estimated by the 2 methods provided that glucose and insulin values were interpolated at 180 min during the computer calculations of the abbreviated test. Using the 90-min abbreviated test, the SI of the pubertal subjects (2.92 +/- 0.45) was markedly less than that of the prepubertal subjects (6.57 +/- 0.45; P = 0.0001). While the postpubertal group value of 4.63 +/- 0.86 was significantly higher than that of the pubertal group (P = 0.0001), the pre- and postpubertal groups remained significantly different (P = 0.0001). The 10 obese subjects with WLI greater than 120% had a lower SI (3.5 +/- 0.53) than the 47 nonobese subjects with WLI less than 120% (SI = 5.48 +/- 0.42; P less than 0.04), and there was a negative correlation between SI and WLI. None of the study subjects experienced symptomatic hypoglycemia during the test.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1977

The validity of two clinical tests of visual-motor perception.

The study investigated the relative efficiency of the Bender and MPD as assessors of achievement-related errors in visual-motor perception. Clinical experience with these two tests suggests that beyond first grade the MPD is more sensitive than the Bender for purposes of measuring deficits in visual-motor perception that interfere with effective classroom learning. The sample was composed of 153 third-grade children from two upper-middle-class elementary schools in a surburban school system in central Ohio. For three of the four achievement criteria, the results were clearly congruent with the hypothesis stated above. That is, SpCD errors from the MPD not only showed significantly higher negative rs with the criteria (reading vocabulary, reading comprehension, and mathematics computation) than Koppitz errors from the Bender, but also accounted for a much higher proportion of the variance in these criteria. Thus, the findings suggest that psychologists engaged in the assessment of older children seriously should consider adding the MPD to their assessment battery.

Achievement↗
PubMed1989

Converting relative risks to absolute risks: a graphical approach.

This paper presents a graphical method for converting relative risks to absolute risks. These absolute risk estimates are a function of the patient's current age, the patient's risk of developing cancer relative to some baseline population, the age specific cancer hazard in the baseline population, and the patient's competing mortal risk from all other causes. Graphs for breast cancer morbidity in women, cardiovascular mortality in men, and lung cancer morbidity in men illustrate the method. These graphs provide the probability of developing cancer in the next twenty years given the patient's current age and relative risk. They are derived under the proportional hazards model. A graph for lung cancer in men that uses a plausible exponential hazards model is also provided. The paper illustrates the importance of competing mortal hazard from other causes on absolute cancer risk. The strengths and weaknesses of this method are discussed. The graphs presented in this paper may be used as an aid in clinical decision making and in patient counselling.

Adult↗
PubMed1990

Eccentric and concentric torque-velocity relationships during arm flexion and extension. Influence of strength level.

Forty men were tested with a computerized dynamometer for concentric and eccentric torques during arm flexion and extension at 0.52, 1.57, and 2.09 rad.s-1. Based on the summed concentric and eccentric torque scores, subjects were placed into a high strength (HS) or low strength (LS) group. The eccentric and concentric segments of the torque-velocity curves (TVCs) were generated using peak torque and constant-angle torque (CAT) at 1.57 and 2.36 rad. Angle of peak torque was also recorded. Compared to LS, HS had significantly greater estimated lean body mass (+10.2 kg) and approximately 25% greater average torque output. Reliability of the peak torque scores on 2 days in 20 subjects was r greater than or equal to 0.85. The difference between observed torques and the mathematically computed criterion torque scores averaged 1% for three validation loads that ranged from 11.4 to 90.4 kg. Statistical analysis revealed that torque output in LS plateaued at low concentric velocities and was also flattened with increasing eccentric velocities. Conversely, torque output for HS increased with decreasing concentric velocities and increased with increasing eccentric velocities. The method of plotting the TVCs for peak or CAT did not influence the pattern of TVC. Eccentric flexion peak torque occurred at a significantly shorter muscle length (1.88 rad) than concentric torque (2.12 rad). This difference was also present for extension; it was 1.88 rad for eccentric and 2.03 rad for concentric torque.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1979

A key to the understanding of extraoral forces.

By following certain basic principles, the effects, advantages, and disadvantages of the wide assortment of extraoral assemblies marketed are easily understood. The key to this understanding is the appreciation of the relationship of the line of action of the force application to the center of resistance of the tooth. These principles are discussed in three planes of space: sagittal, coronal, and transverse. Because of the many variables and complexity of mathematically computing the force effects of unilateral or asymmetric extraoral assemblies on molar teeth, a mechanical testing apparatus was designed to accommodate the various face-bows. Not all the designs proved effective, and many of the clinical side effects of the respective face-bow designs became manifest on mechanical testing.

Cephalometry↗
PubMed1987

A simplex procedure for fitting nonlinear pharmacokinetic models.

A convenient and readily modifiable nonlinear regression procedure, based on two Pascal programs, is described. This procedure, suitable for running on both microcomputers and mainframes, is presented as utilized in ongoing clinical pharmacokinetic work. One program uses the simplex algorithm to fit data conforming to any of six models of drug disposition. In addition to the regression terms, it generates logarithmic plots of the function and calculates derived kinetic variables of drug distribution, elimination and clearance. This program is driven by another which batches together required data and parameter information to build a control file for solving multiple curve-fitting problems.

Algorithms↗
PubMed1988

Selecting a processor for computations in molecular biophysics.

A number of relatively low-cost processors are now available which employ architectural features previously found only on very expensive supercomputers. The speed of these computers makes it possible to reduce the time to solution of certain problems and to resolve large problems that previously were too time consuming to perform locally. A brief overview of this type of processor is given and the implications for computations in molecular biophysics are discussed in reference to the results of a benchmark that uses the refinement of a protein structure from X-ray crystallographic data.

Computers↗
PubMed1990

A CPU benchmark for protein crystallographic refinement.

The CPU time required to complete a cycle of restrained least-squares refinement of a protein structure from X-ray crystallographic data using the FORTRAN codes PROTIN and PROLSQ are reported for 48 different processors, ranging from single-user workstations to supercomputers. Sequential, vector, VLIW, multiprocessor, and RISC hardware architectures are compared using both a small and a large protein structure. Representative compile times for each hardware type are also given, and the improvement in run-time when coding for a specific hardware architecture considered. The benchmarks involve scalar integer and vector floating point arithmetic and are representative of the calculations performed in many scientific disciplines.

Computers↗