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PubMed1976

A staff allocation model for mental health facilities.

This article describes a model for allocating staff within a large psychiatric hospital. The model provides an objective framework within which one can test alternative staff operating policies before making critical decisions concerning the employment of one category of personnel as opposed to another. It is based on objective data describing patient needs and staff functioning patterns, rather than subjective opinions concerning staff deployment. Besides being useful for the short-term deployment of staff and budgetary resources, it can also be used as a long-range planning tool for testing modifications in policy decisions and budget proposals. The algorithm employed, mixed-integer linear programming, is readily available; computer costs and running time are relatively minimal.

Hospitals, Psychiatric↗
PubMed1979

A user's experience with a standard non-linear regression program (BMDP3R).

A study was made to test and compare the behavior of a standard non-linear regression program (BMDP3R) in fitting data from six classical least-squares problems. The use of three program control parameters is discussed and four measures of regression failure are utilized to give a quantitative reference of success. Recommendations are given to aid the user of packaged programs in the parameter estimation of non-linear regression models.

Computers↗
PubMed1977

A new model for measuring breeding genetic distance.

A model is proposed for measuring the genetic 'distance' between two populations having gene frequencies p and p. The measure of distance is based on a hypothetical selection process as follows: From population P a subpopulation P can be selected having gene frequency p. Let Po be the largest subpopulation yielding gene frequency p, then the relative size of Po to p--denoted by thetao (p,p)--is a measure of the 'closeness' of populations having gene frequencies p and p, and 1-thetao (p,p) whould be a reasonable measure of genetic distance. We show that the calculation of thetao (p,p) is a special case of the linear programming problem and derive algebraic expressions for thetao (p,p) in the two-allele case. We discuse some of the implications of the use of this measure of distance and compare it to others which have been proposed. We use linear programming methods to calculate genetic distance for three alleles.

Alleles↗
PubMedDate not supplied

MLTIDOSE: a multiple-dose simulation program for linear systems characterized by exponential functions.

MLTIDOSE is a multiple-dose simulation program for use on IBM PC (and compatible) computers. It assumes dose-independent disposition and absorption (i.e., a linear system) and simulates blood concentration-time profiles (over a range of times or at specific times) upon administration of any combination of intravascular (i.v.) (bolus and/or intermittent constant rate infusions) and extravascular (e.v.) doses of fixed or variable size, administered at fixed or variable intervals. Input requirements include pharmacokinetic parameters obtained following single-dose administration (entered from the keyboard or from a data file). Options for printing data to files (e.g., ASCII and DIF) for further use are also provided.

Computer Simulation↗
PubMed1977

[Computer programming for radiocardiography and radiocyclography].

Digital radiocardiography with linear programming, on the ALGOL language, by means of an ODRA-1204 computer is described. Determination of cardiac dynamical parameters of patients in rest and under load was carried out. Radioisotopic methods were combined with conventional cardiologic examinations, particularly the microcatheterization.

Computers↗
PubMed1975

Impact of expanded-duty assistants on cost and productivity in dental care delivery.

Data from an experimental dental program are used to develop a linear programming model of dental care delivery that the authors use to examine the economic implications of introducing expanded-duty dental assistants (EDDA's) in three types of dental practices. The authors examine the changes in productivity and profitability that result from hiring one or more EDDAs and conclude that a dentist in solo practice can more than double his net revenue by hiring one EDDA but will not increase his productivity further by hiring additional EDDAs. Two- and three-dentist groups also can increase revenue by hiring EDDAs, but, beyond a certain point, an inverse relationship exists between the number of auxiliaries hired and net revenue generated.

Cost-Benefit Analysis↗
PubMed1977

Evaluation of a self-instructional unit for use in educational programs in histologic technique.

A linear programmed instructional booklet was developed and used to evaluate the acceptability of this learning strategy to histologic technique instructors and their students. Comparisons of students' cognitive knowledge of the relevant topics before and after using the booklet indicated that most were achieving the booklet's objectives. The post-test score was not significantly affected either by prior experience with programmed materials or by the way the booklet was used. The verbal attitude responses of the students were encouraging, and most indicated the booklet was an efficient way for them to learn, and it was helpful in clarifying concepts. The verbal attitudes of the instructors were also favorable. The indications were that booklet use shortened subsequent lecture time and that the booklet was most valuable as a supplement to conventional instructional methods.

Achievement↗
PubMed1990

From food basket to food security. The food factor in nutritional surveillance.

One important indicator of nutritional surveillance is the one devoted to monitor food security. The experience toward the development of one of such indicators is presented. This includes the development of a food basket, defined as the group of foods that meet the characteristics such as is now consumed by important population segments of the community; it contributes a substantial portion of the calories and proteins purchased, and is responsible for an important proportion of the food budget. The concept implies a dynamic food basket, the quantities of which are calculated in a way that simulates the behavior of the consumer and the best nutrition knowledge. For this purpose we use linear program techniques. A measure of the risk of being unable to buy the foods needed for a family is presented, and is used as a proxy for food security risk. In the appendix, the mathematical expressions of the model used for a linear program is also presented.

Colombia↗
PubMed1989

Estimation of blood flow distribution in skeletal muscle from inert gas washout.

A new method is evaluated for the estimation of blood flow-to-volume distribution in skeletal muscle from inert gas washout kinetics. Acetylene washout from the isolated, blood-perfused canine gracilis muscle was measured continuously with a blood gas catheter in combination with a mass spectrometer. The washout curves were transformed to flow-to-volume ratio distributions by means of a 50-compartment model. The algorithm fits the expression for the washout curve derived from the model by a least-squares method with enforced smoothing. The algorithm was evaluated using computer simulations in which artificial washout curves were generated by a multicompartment model with a known flow distribution. A wide range of given flow distributions could be recovered from the simulated data. The data were also analyzed using a linear programming technique. Analysis of the experimental data with the least-squares method showed that there is considerable heterogeneity in the distribution of perfusion in resting gracilis muscle. The distribution is characterized by at least two modes and a single compartment with a very low perfusion-to-volume ratio. Experimental noise made it impossible to obtain feasible flow distributions by means of linear programming.

Acetylene↗
PubMed1989

[Maximization of economic yield, minimum cost optimal diets and cultivation diversification for small scale farmers of the highland region of Guatemala].

The present study was conducted as part of an evaluation of the economic and nutritional effects of a crop diversification program for small-scale farmers in the Western highlands of Guatemala. Linear programming models are employed in order to obtain optimal combinations of traditional and non-traditional food crops under different ecological conditions that: a) provide minimum cost diets for auto-consumption, and b) maximize net income and market availability of dietary energy. Data used were generated by means of an agroeconomic survey conducted in 1983 among 726 farming households. Food prices were obtained from the Institute of Agrarian Marketing; data on production costs, from the National Bank of Agricultural Development in Guatemala. The gestation periods for each crop were obtained from three different sources, and then averaged. The results indicated that the optimal cropping pattern for the minimum-cost diets for auto consumption include traditional foods (corn, beans, broad bean, wheat, potato), non-traditional foods (carrots, broccoli, beets) and foods of animal origin (milk, eggs). A significant number of farmers included in the sample did not have sufficient land availability to produce all foods included in the minimum-cost diet. Cropping patterns which maximize net incomes include only non-traditional foods: onions, carrots, broccoli and beets for farmers in the low highland areas, and raddish, broccoli, cauliflower and carrots for farmers in the higher parts. Optimal cropping patterns which maximize market availability of dietary energy include traditional and non-traditional foods; for farmers in the lower areas: wheat, corn, beets, carrots and onions; for farmers in the higher areas: potato, wheat, raddish, carrots and cabbage.

Agriculture↗
PubMed1991

The use of integer programming in dairy sire selection.

A computerized sire selection integer program, IPSIRE, was developed to test the optimality of solutions obtained by using MAXBULL, a popular computerized sire selection aid. The IPSIRE program uses an optimization software package and a compatible spreadsheet; MAXBULL uses linear programming techniques. The computer programs were compared using large and small data sets. Multiple combinations were run, varying the levels requested for PD fat percentage, PD type, and price paid per unit of semen. All other constraints were held constant. The objective function for all combinations maximized PD milk. The IPSIRE program exceeded MAXBULL by an average of $2.5 for PD dollars and 7.3 kg (16.1 lb) for PD milk using the small bull data base. Sire averages for traits PD type, PD fat percentage, and price paid were not different between the two programs. Similar trends were seen using the large bull data base. The IPSIRE program exceeded MAXBULL by an average of $1.2 for PD dollars and 4.1 kg (9.0 lb) for PD milk, whereas sire averages for PD fat percentage, PD type, and price paid were not different between programs. The goal for PD type had the least influence of the three goals on sire averages for PD milk. The goal for price paid had the greatest impact on realized PD milk; higher goals for price paid produced solutions with higher values for realized PD milk. The IPSIRE program required longer computational times for finding solutions that maximized PD milk than MAXBULL.

Animals↗
PubMed1978

Distribution of spinal disc pressures in the seated posture subjected to impact.

A musculoskeletal model for the human spine developed by the authors is used for this study. The model takes into account the equilibrium of the vertebral bodies, the intervertebral discs and segments of the upper extremities under the influence of all major muscle and joint forces. Linear programming techniques are used to obtain the muscle load sharing and the disc pressures, based on a preselected linear criterion. The criterion is formulated as a combination of all muscles forces (F), joint forces and ligament action (R,M) with suitable weighting factors, and a minimization is sought of U = F + k1R + k2M. The model is used to study the effect of sudden forward or backward acceleration forces, such as during the impact situation, on the distribution of disc pressures in the spinal column in the unsupported seated posture.

Biomechanical Phenomena↗
PubMed1991

Programmed instruction booklet for cardiac rehabilitation teaching.

Programmed instruction is an underused approach for educating hospitalized patients. This educational technique is based on the work of Skinner, who developed the linear programmed instruction technique. To test the effectiveness of this technique as a patient education tool, a programmed instruction booklet was developed for patients who were hospitalized after myocardial infarction. The booklet included basic information on cardiac anatomy and pathology, risk factors, diet, exercise, and medications. A quasi-experimental study design was implemented in which 59 hospitalized patients who had had a myocardial infarction underwent pretesting and posttesting. Patients were alternately assigned to a control group or an experimental group. The control group (n = 30) participated in the hospital's existing cardiac rehabilitation program, and the experimental group (n = 29) used the programmed instruction booklet. A one-way analysis of variance revealed a statistically significant improvement (p less than 0.05) in the posttest scores of the experimental group. The results of this study support the use of the programmed instruction method as one means of teaching cardiac rehabilitation information to hospitalized patients after myocardial infarction.

Adult↗
PubMed1991

Planning replacement of natural gas distribution systems under constraints on acceptable risk from explosions.

Natural gas distribution systems in the United States were developed primarily in the first half of this century, utilizing materials such as cast iron and then steel. Over time, cast iron and steel pipe sections became weak from corrosion and are subject to failure which in turn can lead to explosions and possible injury and loss of life. Gas utilities maintain system integrity through repair-replacement programs where pipe sections are prioritized for replacement in any given year through cost-benefit analysis; however, the total annual amount to be budgeted for replacement is left to engineering judgment. This approach has left some utilities vulnerable to criticism that their current replacement rate on cast iron pipe is not great enough and that public safety is being compromised. This paper addresses the problem situation by formulating a linear programming replacement decision model which augments cost-benefit analysis with explicit constraints on acceptable risk to human life from fire/explosion. The model is illustrated for a hypothetical utility.

Cost-Benefit Analysis↗
PubMed1990

Information content of the multibreath nitrogen washout: effects of experimental error.

Methods that recover a continuous distribution of specific ventilation (ventilation-to-volume ratio, VA/V) from the multibreath N2 washout curve theoretically can resolve up to four modes of ventilation and reveal the major characteristics of the underlying distribution if experimental error is absent. This paper quantitatively assesses the effects of experimental error on resolution. The washout curves from five typical distributions were studied using linear programming and Monte Carlo methods. A measurement error of 0.1% was assumed in the mixed-expired N2 signal. Only 7 of the first 17 breaths contribute independent information about the underlying distribution, and only rough resolution of the underlying distribution is possible in the presence of error. Only two modes of ventilation plus an estimate of dead space can be confidently resolved. It is not possible to separate VA/V greater than 10 from dead space. A 10-fold reduction in experimental error will not greatly improve resolution. Experimental error, by reducing the linear independence of the defining kernels, significantly limits the information content and resolution of the multibreath N2 washout.

Humans↗
PubMed1977

High-performance liquid chromatographic analysis of methadone hydrochloride oral solution.

A direct and rapid high-performance liquid chromatographic assay for methadone hydrochloride in a flavored oral solution dosage form is described. A syrup sample, one part diluted with three parts of water, is introduced onto a column packed with octadecylsilane bonded on 10 micrometer porous silica gel (reversed phase). A formic acid-ammonium formate-buffered mobile phase is linear programmed with acetonitrile. The absorbance is monitored continuously at 280 or 254 nm, using a flow-through, UV, double-beam photometer. An aqueous methadone hydrochloride solution is used for external standardization. The relative standard deviation was not more than 1.0%. Drug recovery from a syrup base was better than 99.8%.

Administration, Oral↗
PubMed1992

Fast structure alignment for protein databank searching.

A fast method is described for searching and analyzing the protein structure databank. It uses secondary structure followed by residue matching to compare protein structures and is developed from a previous structural alignment method based on dynamic programming. Linear representations of secondary structures are derived and their features compared to identify equivalent elements in two proteins. The secondary structure alignment then constrains the residue alignment, which compares only residues within aligned secondary structures and with similar buried areas and torsional angles. The initial secondary structure alignment improves accuracy and provides a means of filtering out unrelated proteins before the slower residue alignment stage. It is possible to search or sort the protein structure databank very quickly using just secondary structure comparisons. A search through 720 structures with a probe protein of 10 secondary structures required 1.7 CPU hours on a Sun 4/280. Alternatively, combined secondary structure and residue alignments, with a cutoff on the secondary structure score to remove pairs of unrelated proteins from further analysis, took 10.1 CPU hours. The method was applied in searches on different classes of proteins and to cluster a subset of the databank into structurally related groups. Relationships were consistent with known families of protein structure.

Amino Acid Sequence↗