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PubMed1997

Heritability analysis of lipids and three gene loci in twins link the macrophage scavenger receptor to HDL cholesterol concentrations.

We studied 100 healthy monozygotic and 72 dizygotic twin pairs (mean age, 34 +/- 14 years) to test for genetic influences on blood lipids and to examine relevant gene loci. Total cholesterol (TC), LDL cholesterol (LDL-C), HDL cholesterol (HDL-C), and triglyceride (TG) levels were determined after a 12-hour fast. Zygosity was determined with the use of microsatellite markers. Heritability estimates were conducted by using the lisrel 8 program; a sib-pair analysis was conducted by using the sibpal program. Linear regression analyses were carried out between identical-by-descent status and squared within-pair differences of TC, LDL-C, HDL-C, and TG values. Heritability estimates of the lipid serum concentrations ranged from .58 to .66. A significant linkage relationship was found for HDL-C (P = .008) and TGs (P = .05) with D8S261 on chromosome 8p. However, no linkage was found between any of the lipid variables and the lipoprotein lipase gene locus (LPL GZ14/15 and D8S282). Because D8S261 is located approximately halfway between the LPL and macrophage scavenger receptor genes, we examined the nearby markers D8S549 and D8S1731. Linkage was found for HDL-C and D8S549 (P = .001) and for HDL-C and D8S1731 (P = .04). On the other hand, we found no linkage between the LDL receptor gene locus and LDL-C serum concentrations nor between the LPL gene locus and the various other lipid fractions. Our data suggest a significant influence of the macrophage scavenger receptor gene locus on HDL-C and weak influence on TG levels. We suggest that inherited variability in the macrophage scavenger receptor gene has an influence on serum lipid concentrations.

Adult↗

PubMed1991

Changes in rates of unscheduled hospital readmissions and changes in efficiency following the introduction of the Medicare prospective payment system. An analysis using risk-adjusted data.

The purpose of this study was to analyze changes in rates of unscheduled readmissions and changes in technical efficiency following the introduction of the Medicare Prospective Payment System (PPS). We developed the Risk-Adjusted Readmissions Index (RARI), which allowed us to make comparisons in rates of unanticipated readmissions across hospitals and over time. Data envelopment analysis (DEA), a linear programming technique, was used to measure changes in technical efficiency by comparing the inputs used and the outputs produced across a cohort of hospitals, while adjusting for changes over time in case mix and case complexity. Rates of unscheduled readmissions and efficiency scores were computed for a sample of 245 hospitals for each year. Although both readmission rates and efficiency scores increased for most hospitals, there was no evidence that those hospitals that experienced the greatest increases in efficiency had the largest increases in their rates of unscheduled readmissions.

Abstracting and Indexing↗

PubMed1990

Managing physician efficiency and effectiveness in providing hospital services.

Physicians control more than 80 percent of the decisions affecting health costs. Consequently, managing physician practice patterns is an important avenue to reducing health care costs. One approach to identifying inefficient practice patterns is demonstrated in this pilot study of physicians treating heart shock patients. Physicians are evaluated using data envelopment analysis (DEA), a relatively new linear-program-based efficiency evaluation tool. This approach (1) locates physicians using excess resources in treating patients, (2) estimates the amount of excess resources used, and (3) explicitly considers the quality of patient care in the overall assessment of the physician's practice patterns. Findings of physician inefficiency that are stable over time could be used to alter practice patterns and subsequently to assist in cost containment.

Data Collection↗

PubMed1993

Optimal design of a six-bar linkage with one degree of freedom for an anthropomorphic three-jointed finger mechanism.

This research concerns the design of a three-jointed, anthropomorphic, finger mechanism for use as a prosthesis or robotic end-effector. Based on a study of finger configurations for the human hand, a six-bar linkage with one degree of freedom is proposed. A model of the fingertip displacement of the mechanism is derived by a vector analysis approach. The effects of joint friction on the transmission efficiency are analysed. By measuring the joint positions of a human finger, a mathematical model of the pinching and holding configurations are developed. Optimal parameters for the finger mechanism are obtained by non-linear programming based on an objective functional involving motion posture and locus, transmission efficiency and weight subject to geometric and bionic constraints. Simulation results indicate that the mechanism is useful for a variety of prosthetic and robotic applications.

Biomechanical Phenomena↗

PubMed1998

[Nutritional analysis and complementation of a food basket derived from consumption].

INTRODUCTION: The DISEASE & PROCON Basket (DPB) is a list of basic foodstuffs, drawn up on the basis of a Standard of Living and Work Research project in S. Paulo city, Brazil. Seeing that it has been used as a standard for price variations, it is desirable that such an economic instrument as this, should also represent a truly healthy standard of nutrition. Thus, this study seeks to verify the adequacy of the food products in the DPB in relation to the nutritional needs of a typical reference family in S. Paulo city. It also proposes some techniques for dietary complementation. METHODOLOGY: A demographic census, undertaken in 1991 has been used to establish the reference family, as well as 2/3rds of RDA as corresponding to its nutritional needs, and the food composition tables of McCance & Widdowson to analyse the nutrient content of the DPB. Dietary complementation were undertaken by three different methods: Ad Hoc (direct suggestions), Linear Programming (computer software was utilized to minimize costs), and Hybrid (a combination of the first two). RESULTS: Food items in the DPB showed insufficient values for vitamins A, C, B2 and B6, and for minerals Ca, Mg, Fe, Zn, I and Se; besides, a relatively high fat content was found. The Hybrid Method of food complementation seems to present the best results, associating low cost and local dietary habits. DISCUSSION: A relation between the dietary deficiencies of the DPB and the nutritional transition in the developing countries may be infered. The epidemiological risks associated with these changes in eating patterns should not be incorporated into a reliable economic instrument.

Adolescent↗

PubMed1990

Feed intake, weaning weight and net returns comparisons for four breeding systems.

Feed intake, weaning weight and direct and maternal contributions to weaning weight were estimated for four breeding systems using data collected between 1979 and 1986 from 773 cow-calf pairs at the Elora Beef Research Centre. Breeding systems included purebred Hereford (HE), small rotational dual purpose (SR) (a four-way rotational crossing system utilizing Tarentaise, Angus, Gelbvieh and Pinzgauer breeds), large rotational beef (LR) (composed of Maine-Anjou, Simmental and Charolais) and Angus-sired large rotational beef (AL) utilizing Angus as the sire breed and LR as the maternal breed. Large rotational dams had the highest feed intakes for both dry (8.9 kg DM/d) and lactation (11.5 kg DM/d) periods. Conversely, HE calves consumed the greatest amounts of creep feed (309 kg DM), followed by AL, SR and LR. The large rotational system had the highest weaning weights (265 kg) and direct (12.3 kg greater than average of observations) and maternal (9.6 kg greater than average of observations) contributions to weaning weight, followed by AL, SR and HE for all three traits. An equation was derived for net returns that included parameters for feed intake and direct and maternal weaning weight. A linear programming model was designed to incorporate this equation as the objective function and determine the breeding system(s) that maximized net returns under various production conditions. In general, LR produced the greatest net returns, followed by SR and either AL or HE, depending on specific resource constraints (limited feed supply or herd size) included in the model.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Influence of variations in biological and economical parameters on beef production net returns.

Net returns were defined as a function of the monetary returns (revenue) generated by the outputs less the monetary costs generated by the variable inputs. Outputs included total weaning weights of steers and heifers, weight of cull cows and weight of open heifers. Inputs included both feed and nonfeed costs. The net returns equation was incorporated as the objective function in a linear programming model. By maximizing the objective function, the breeding system that generated the highest net returns could be identified considering certain resource constraints. Breeding systems included purebred Herefords; small rotational dual purpose (SR), utilizing the breeds Angus, Pinzgauer, Gelbvieh and Tarentaise; large rotational (LR), a three-way rotational cross with the breeds Charolais, Simmental and Maine-Anjou; and Angus-sired terminal (AL) utilizing Angus as the sire breed and LR heifers as the maternal breed. Large rotational generally produced the greatest net returns, followed by SR and either AL or HE, depending on specific resource constraints (limited feed supply or herd size), calving rates, management systems, environment, beef to feed price ratios and purchased or farm-produced (inexpensive) feed utilized. Only under the conditions of a herd size constraint and farm-produced feed did AL exceed SR in net returns. Hereford had larger net returns than LR only when the two breeding systems were evaluated in an environment assumed to be reproductively stressful to LR. Ranking of breeding systems were dependent on specific conditions and indicated that one must consider each resource constraint and environment in which cattle are expected to produce before making breeding system recommendations.

Animal Feed↗

PubMed1991

A Markovian decision model for beef cattle replacement that considers spring and fall calving.

In certain production environments, beef cows are mated during a breeding season that starts in early summer. Cows found not to be pregnant at the end of the breeding season could either be culled or retained and remated the following summer. Alternatively, nonpregnant cows could be mated in the winter. This option would result in having both a spring and a fall calving herd. The purpose of our study was to determine the optimal replacement policy (maximizing long-run average net returns) for a specific production environment by determining for each age of cow, reproductive status (nonpregnant or pregnant), and season of pregnancy checking (spring or fall) whether the cow should be retained to the next breeding season (summer or winter) or be replaced by a pregnant heifer. The problem was formulated as a Markovian decision process and the optimal policy was found by linear programming. The optimal policy was one in which nonpregnant cows were always culled and replaced by heifers in the summer breeding herd, resulting in spring calving only.

Animals↗

PubMed1975

Rumen modeling: rumen input-output balance models.

Two models of rumen fermentative relationships expressed as systems of simultaneous linear equations and based on requirements for maintenance of balances of elementary imput and output and metabolic pathways are presented in matrix format consistent with solution by linear programs. Matrix entries defining the two models were verified carefully based upon a survey of the literature, and conceptual bases of the models were validated by comparisons of model outputs with experimental data not used in model construction. The models then were used to evaluate interactions among feed composition, volatile fatty acid yields and patterns, microbial growth yields and efficiencies, and microbial metabolic pathways.

Amino Acids↗

PubMed1980

Computerized feeding management systems for economic decision-making.

Linear programming has been useful in the formulation of feeding guidelines for lactating cows. The most economical rations can be fed. Newer feeding management systems are being developed as new nutritional findings permit greater refinement. This report describes the use of computerized feeding management systems in helping dairy farmers make sound economic decisions. Such procedures are useful to the feed industry, dairy consultants, and in development of extension education programs.

Animals↗

PubMed1983

Selecting groups of sires by computer to maximize herd breeding goals.

A computerized linear program, MAXBULL, selects sires for dairymen to obtain maximum Predicted Difference milk while maintaining other goals. Goals are minimum average Predicted Differences fat percent and type, six individual type traits, and maximum average semen price. Individuals traits for bulls are coded +1, 0, -1 according to evaluations from breed associations. Dairymen restrict bulls offered to the program by specifying unacceptable repeatability, Predicted Differences, and price. They further control breed, stud organizations, minimum bull numbers, use of sires with low repeatability (less than 50%) and without type proofs, and maximum use of specific bulls and sons of sires. Goals for individual type are specified as the percentage of cows in the herd needing improvement in each trait. The solution contains at least that percentage of semen from sires coded +1 in each trait. The dairyman receives a count of bulls surviving each of his edits, a reiteration of his goals, a list of recommended units and all information for each sire, averages for all traits weighted by the units recommended, and the expected increase in Predicted Difference milk from relaxing each goal one unit. MAXBULL has led to individualized breeding programs characterized by reasonable goals, balance in emphasis among traits, and stability in goals over time.

Animals↗

PubMed1999

Optimized dairy grazing systems in the northeast United States and New Zealand. I. Model description and evaluation.

Parallels exist in the recent developments of dairy systems in the Northeast United States and New Zealand because of greater use of pasture grazing and feed supplements, respectively. Lessons can be learned from each system. However, major differences exist between the regions in the patterns of pasture production, the costs of supplementary feed, and milk prices. These differences affect the optimum use of feed. In this paper, a linear programming model developed to determine optimum feeding strategies for dairy systems in each country is presented. The model optimizes grazing management (rotation lengths) and the conservation of pasture subject to constraints on their use. Other feed resources include N fertilizer, grain, corn silage, and alfalfa silage. All feeds are represented in energy terms. The substitution of pasture intake by grain and forage supplements is included, and cow performance can be optimized by choosing from 73 seasonal calving herds that vary in calving date, lactation length, and daily milk production. The model predicts that marginal responses to grain feeding are between 1.35 and 1.8 kg of milk/kg of grain dry matter supplement, well within the range of responses reported in the literature. Evaluation of the model against data from nine grazing system treatments in New Zealand and two in Pennsylvania showed that model predictions averaged +3% (New Zealand) and +0.04% (Northeast) of measured milk production. The model could be used with confidence to study systems in both the Northeast United States and New Zealand.

Agriculture↗

PubMed1999

Optimized dairy grazing systems in the northeast United States and New Zealand. II. System analysis.

Factors that optimize milk production from Northeast United States and New Zealand grazing systems are compared using a linear programming model. The objective function maximized gross margin per hectare of land farmed. The experimental design compared the optimum characteristics of each system over a range of milk prices. The Northeast has a shorter grazing season and lower cropping costs than New Zealand. The optimum pasture area was 49% of the farm for Northeast systems. Gross margins declined rapidly above 55% or below 36% pasture area. The optimum stocking rate was 1.13 cows/ha, or 2.3 cows/ha of pasture. Optimum per cow production was higher for Northeast [7105 kg of fat-corrected milk (FCM)] than New Zealand (5710 kg of FCM) systems. This was related to lower grain relative to milk prices in the Northeast. New Zealand, all-pasture systems gave the lowest cost per unit of milk but also gave the lowest gross margin across all milk price scenarios. The best use of purchased feed in New Zealand systems was to support increased stocking rate rather than per cow production. Optimum grazing management practices were similar for supplemented New Zealand and Northeast systems. All-pasture New Zealand systems are characterized by short lactations and long autumn rotations to transfer pasture in situ for winter feeding. Higher costs per unit of milk produced will be an inevitable consequence of maximizing gross margin at high milk prices in New Zealand systems.

Agriculture↗

PubMed1990

Formulation, nutritive value and sensory evaluation of a new weaning food based on sweet corn (Nutrimaiz) dehydrated pulp.

The objective of the present work was to develop a formulation for complementary infant and child feeding employing linear programing as a mathematical model for optimization. High lysine/high tryptophan sweet corn pulp in the dehydrated form was used as the main ingredient. The restrictions imposed on the model were nutrient requirements, adequate protein/energy ratio and minimum cost. The formula derived by the computer (FC) matched the amino acid requirements, the protein/energy ratio (NDPCal%) and was rated high in laboratory tests in terms of sensory qualities. The cost determined for this formula was competitive in relation to commercial products used for the same purpose. Formula A, which contained 5% more sweet corn pulp and 10% less whole powdered milk, did not differ in nutritional, sensorial and functional properties from the formula FC and was chosen for the field acceptability trial because of its lower cost. Formula A had protein efficiency ratio and Biological Value similar to casein for the rat but protein digestibility and net protein utilization were statistically lower (p less than 0.05) for formula A than for casein. Acceptability tested on children who were 8-18 months of age ranged from 80-90%, average value 87%.

Amino Acids↗

PubMed1989

Indirect calorimetry evaluation of dietary protein and animal fat effects on energy utilization of laying hens.

A multichamber indirect calorimeter was constructed and used to measure energy utilization of laying hens. Four basic diets were formulated by a least cost linear program for use in this study. The first diet was formulated to meet the 1984 National Research Council (NRC) recommendations and contained by analysis 14.5% protein, .58% TSAA, and .68% lysine (designated NRC). The second diet (NRCAA) was formulated to the same amino acid specifications without a protein restriction and contained 12.9% protein, .57% TSAA, and .69% lysine. Another pair of diets was formulated with higher protein (HP) and amino acid restrictions. The HP diet contained 16% protein, .67% TSAA, and .85% lysine; whereas the HPAA diet had 14% protein, .68% TSAA, and .86% lysine. Four additional diets were formulated with the inclusion of 3% animal fat, using the same protein and amino acid restrictions as were used to formulate the first four diets. Animal fat supplementation significantly (P less than .05) improved energy balance (retention) of birds fed all formulations compared with the diets without added fat. Formulation of a diet based on amino acid restrictions significantly increased net energetic efficiency of birds fed amino acid levels higher than those recommended by the NRC (79.2 for HPAA vs. 62.1% for HP), but did not significantly affect net efficiency of birds fed the lower amino acid levels (NRC and NRCAA).

Animal Feed↗

PubMed1984

Two techniques for alternatives analysis.

The two techniques described span the range of problem-solving and decision-making techniques. Brainstorming is a very personal and innovative tool when a fresh viewpoint and creativity are called for. It can strengthen individual and organizational relationships by making staff a part of the solution to problems. In contrast, linear programming is a planning tool that enables a manager to organize facts about problems and alternatives, aiding the manager in planning the action required to translate the conclusions into operational reality. It is an efficient procedure that is particularly effective when results must be precise and will find growing application in health care as we enter the era of contracting for patient populations, prospective payment systems and limited resources.

Decision Making↗

PubMed2000

Health care financing reform and the productivity change in Finnish hospitals.

The purpose of this study was to analyze productivity and efficiency changes in the production of hospital care in Finland during the period 1988-1994. A special interest was directed to years 1993-1994 because of health care financing reform that took place in 1993. The analysis is based on the Malmquist index approach using linear programming. Positive productivity changes were found particularly towards the end of the observation period, although a few years did not show significant improvements in productivity and efficiency. There was a significantly higher rate of productivity change in 1992-1993 and 1993-1994, suggesting that the state subsidy reform in 1993 may have strengthened hospitals' efforts to improve performance.

Diagnosis-Related Groups↗

PubMed2000

A practical algorithm for optimal inference of haplotypes from diploid populations.

The next phase of human genomics will involve large-scale screens of populations for significant DNA polymorphisms, notably single nucleotide polymorphisms (SNP's). Dense human SNP maps are currently under construction. However, the utility of those maps and screens will be limited by the fact that humans are diploid, and that it is presently difficult to get separate data on the two "copies". Hence genotype (blended) SNP data will be collected, and the desired haplotype (partitioned) data must then be (partially) inferred. A particular non-deterministic inference algorithm was proposed and studied before SNP data was available, and extensively applied more recently to study the first available SNP data. In this paper, we consider the question of whether we can obtain an efficient, deterministic variant of that method to optimize the obtained inferences. Although we have shown elsewhere that the optimization problem is NP-hard, we present here a practical approach based on (integer) linear programming. The method either returns the optimal answer, and a declaration that it is the optimal, or declares that it has failed to find the optimal. The approach works quickly and correctly, finding the optimal on all simulated data tested, data that is expected to be more demanding than realistic biological data.

Algorithms↗