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Results for “Programming, Linear”

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At least 523 records · Page 29Linked to original sources

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↗

PubMedDate not supplied

Combining pathway analysis with flux balance analysis for the comprehensive study of metabolic systems.

The elucidation of organism-scale metabolic networks necessitates the development of integrative methods to analyze and interpret the systemic properties of cellular metabolism. A shift in emphasis from single metabolic reactions to systemically defined pathways is one consequence of such an integrative analysis of metabolic systems. The constraints of systemic stoichiometry, and limited thermodynamics have led to the definition of the flux space within the context of convex analysis. The flux space of the metabolic system, containing all allowable flux distributions, is constrained to a convex polyhedral cone in a high-dimensional space. From metabolic pathway analysis, the edges of the high-dimensional flux cone are vectors that correspond to systemically defined "extreme pathways" spanning the capabilities of the system. The addition of maximum flux capacities of individual metabolic reactions serves to further constrain the flux space and has led to the development of flux balance analysis using linear optimization to calculate optimal flux distributions. Here we provide the precise theoretical connections between pathway analysis and flux balance analysis allowing for their combined application to study integrated metabolic function. Shifts in metabolic behavior are calculated using linear optimization and are then interpreted using the extreme pathways to demonstrate the concept of pathway utilization. Changes to the reaction network, such as the removal of a reaction, can lead to the generation of suboptimal phenotypes that can be directly attributed to the loss of pathway function and capabilities. Optimal growth phenotypes are calculated as a function of environmental variables, such as the availability of substrate and oxygen, leading to the definition of phenotypic phase planes. It is illustrated how optimality properties of the computed flux distributions can be interpreted in terms of the extreme pathways. Together these developments are applied to an example network and to core metabolism of Escherichia coli demonstrating the connections between the extreme pathways, optimal flux distributions, and phenotypic phase planes. The consequences of changing environmental and internal conditions of the network are examined for growth on glucose and succinate in the face of a variety of gene deletions. The convergence of the calculation of optimal phenotypes through linear programming and the definition of extreme pathways establishes a different perspective for the understanding of how a defined metabolic network is best used under different environmental and internal conditions or, in other words, a pathway basis for the interpretation of the metabolic reaction norm.

Glucose↗

PubMed1998

[The study of multi-phrase multi-criterion steretactic radiotherapy treatment planning].

Steretactic radiotherapy treatment planning is an important part of X-knife radiosurgery. In this paper the theory of multi-phrase-multi-criterion steretactic radiotherapy treatment planning is proposed, which is composed of three phrases. In the first stage, linear programming is used to reduce the resolution space. A kind of quadriatic programming is used in the second phrase in order to get high and well-distributed dose distribution. In the third phrase, an improved method of constrained simulated annealing is used to get the effect of conforming with the clinical practice. In correspondence with three-phrases optimization, three criterions are used respectively. The experiment results show that the theory proposed is correct.

Humans↗

PubMed1976

Adrenodoxin reductase-adrenodexin complex.

Adrenodoxin reductase and adrenodoxin have been shown (Chu, J.-W., and Kimura, T. (1973) J. Biol. Chem. 248, 5183-5187) to form a low dissociation constant, 1:1 complex when both proteins are in the oxidized form. We have found that when adrenodoxin: adrenodoxin reductase ratios are varied by increasing the adrenodoxin concentration, with adrenodoxin reductase held constant, an increasing rate of cytochrome c reduction, with NADPH as reductant, is seen up to a ratio of 1:1, indicating that cytochrome c reduction occurs via the protein-protein complex. Spectra observed during titration of this protein-protein complex with NADH were resolved into components by the linear programming method, using a computer program written in Fortran IV. Analysis of the data has shown that the flavoprotein is reduced prior to the iron sulfur protein, and that the midpoint oxidation-reduction potentials (pH 7.5) of the two proteins are -295 and -331 mV, respectively, when both are present in the complex. Complex formation does not alter the potential of adrenodoxin reductase, but changes that of adrenodoxin by -40 mV. Equilibrium constants derived from potential measurements show that the strength of the protein-protein interaction in the complex is unaltered by reduction of adrenodoxin reductase, but is decreased by about 1 kcal due to reduction of adrenodoxin. The low dissociation constants for both oxidized reduced forms of the adrenodoxin reductase-adrenodoxin complex indicate that the complex must remain associated throughout its catalytic cycle. Titration of the adrenodoxin reductase-adrenodoxin complex with the physiologic reductant, NADPH, was followed by EPR and visible spectra, and yielded an order of reduction of the components identical with that seen when NADH was used as reductant. Reduction of the protein-protein complex with NADPH yielded a ternary complex between NADP+, flavoprotein, and iron sulfur protein, with the two electrons located in a "charge transfer" complex between flavoprotein and pyridine nucleotide.

Adrenal Cortex↗

PubMed1982

Randomness and order in the topology of settlement systems.

"The frequency distribution of settlement links forms the basis of a linear programming methodology which can be utilized to analyze the structure of settlement systems. The resulting index of system topology is compared to a more conventional measure, Geary's contiguity coefficient, which may be applied when the problem is conceptualized as one of spatial autocorrelation on a k-color map. The index of linkage similarity that is introduced appears to have a useful advantage over the Geary measure. The Geary and linkage similarity indices are used to examine the topology of four Canadian and two hypothetical settlement systems."

Americas↗

PubMed2002

Optimal operation of a potable water distribution network.

This paper presents an approach to an optimal operation of a potable water distribution network. The main control objective defined during the preliminary steps was to maximise the use of low-cost power, maintaining at the same time minimum emergency levels in all reservoirs. The combination of dynamic elements (e.g. reservoirs) and discrete elements (pumps, valves, routing) makes this a challenging predictive control and constrained optimisation problem, which is being solved by MINLP (Mixed Integer Non-linear Programming). Initial experimental results show the performance of this algorithm and its ability to control the water distribution process.

Engineering↗

PubMed2003

[Optimum meteorological factors and climate divisions of apple for good quality].

The investigation and laboratory analysis were carried out for apple quality of Fuji, Jonagold and Starkrimson grown in various ecological and climate regions of China. Multiple statistical analysis, linear program and computer technology were used to obtain the optimum values and scheme of major meteorological factors affecting the quality components of different apple varieties. The cluster analysis results showed that it was suitable for apple of Fuji, Jonagold and Starkrimson growing in the Loess Plateau and Longdong, Gansu Province. Bohaiwan bay regions were suitable for apple of Fuji and Jonagold and Southwestern mountainous region were suitable for apple Starkrimson. Advantage qualifications and limiting factors in each climate divisions were also pointed out.

Climate↗

PubMedDate not supplied

[The mathematical modeling of the optimal dose fields in radiation therapy of malignant tumors. Part 1 (Distance radiotherapy)].

The specificity of mathematical modeling of optimal dose fields in radiation therapy of malignant tumors is under consideration. The permissible dose field is set now for irradiated body as a system of linear limitations to the doses at control spots (CS) distributed in the lesion focus and in the healthy organs and tissues. It is for the first time that an issue related with choosing an adequate number and method of CS distribution, based on uniform continuity of the dose field, is addressed in the paper. An iterative procedure of building the local CS networks is suggested. The method of linear programming (LP) can be used to select an optimal irradiation plan. A method of serial input of limitations, which cuts both the LP task scope and its computer-aided solution, is described.

Algorithms↗

PubMed2004

[On the methods of ecological security design for nature reserves].

Ecological damage and loss of natural habitats have been resulting in the fragmentation of wild animal and plant population, and nature reserves have become the islands of habitats. The traditional approach that focuses on a single and isolated nature reserve is not enough to protect biodiversity. Ecological processes and components of biodiversity in broad temporal and spatial scope should be protected, and a whole conservation network should be established. Based on the requirements and the trends of biodiversity conservation at home and abroad, this paper presented the concept of ecological security design for nature reserves, which is a coordinated planning strategy that integrates ecological, social and economic aspects. Firstly, a network of nature reserves is designed at regional level; secondly, the area, shape, internal zoning of a nature reserve is designed at the node (nature reserve) of the network; and finally, the connectivity between the network and nodes (corridors) is designed. Network design of nature reserves should maintain the regional integrity and the ecological process integrity of ecosystems. Iterative method, integer linear programming, and Geographic Approach (GAP) should be employed to provide blueprints of conservation planning for one or multiple conservation objectives.

Biodiversity↗

PubMed2004

A simple method for inferring strengths of protein-protein interactions.

Various computational methods have been proposed for inference of protein-protein interactions since protein-protein interaction plays an essential role in many cellular processes. One of well-studied approaches is to infer protein-protein interactions based on domain-domain interactions. To extend this approach, we proposed a method called LPNM to infer ratios of interactions, which outperformed other existing methods in terms of error of predicted ratios. However, since the LPNM method is based on the linear programming approach, it may require a large amount of time to infer interactions for a large data set. In this paper, we propose a simple method to infer the ratios of protein-protein interactions based on the association method by Sprinzak et al. In an experiment with a data set of protein-protein interactions in yeast, it runs more than 150 times as fast as the LPNM method, and achieves almost the same accuracy. On implementing algorithms for the inference problem, it is essential to understand how difficult the problem is. Even though various methods for the problem have been already proposed, it has not been analyzed rigorously from a computational point of view. We hence define a problem to maximize correctly classified examples, and prove the problem is MAX SNP-hard, which also means the problem is NP-hard.

Algorithms↗

PubMed2002

Metabolic engineering--integrating methodologies of molecular breeding and bioprocess systems engineering.

Metabolic engineering is an integrating methodology of analysis and synthesis for the improvement of flux distribution of metabolic pathways in complicated bioprocesses, which are highly multi-hierarchical systems to extend from macroscopic to microscopic levels. Recent progress in metabolic engineering methodologies to improve metabolic pathways in microorganisms was reviewed with many studies in this paper. Metabolic flux distribution was analyzed under different environmental conditions, using a metabolic reaction model. The physiological states of microorganisms were understood by interpreting metabolic flux analysis (MFA). This analysis was also used for development of process operation and control strategy. Cell capability to form a targeted product was analyzed with a metabolic reaction model and linear programming (LP). The use of a 13C-enriched carbon source and nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry (GCMS) analyses of intracellular and extracellular metabolites enabled determination of a metabolic flux distribution more accurately than the flux distribution determined only by the metabolic reaction model, which involves not only metabolite balances but also energy and redox balances. The comparison of metabolic flux distributions between before and after genetic modification of cells yielded information on the mechanism of regulation of metabolic flux in microorganisms. Finally, integration of bioinformatics and metabolic engineering is discussed, and cyclic modification of the complex bionetwork and process development were emphasized.

Journal Article↗

PubMed2003

[Metabolic flux analysis of L-Tryptophan biosynthesis].

The metabolic flux balance model of L-Try synthesis by Corynebacterium glutamicum was constructed in this paper. Using this model, the metabolic flux distribution during the middle and late period were determined and the optimal flux distribution were calculated by linear program of MATLAB software. The analysis results indicate that 24.85% metabolic flux entered the HMP pathway and 75.15% entered the EMP cycle. But comparing to the optimal flux distributions, the production of L-Try should be improved from the genetic manipulation and fermentation control through reducing byproduct of amino acid and decreasing the metabolic flux of TCA and EMP.

Biosynthetic Pathways↗

PubMed1990

[The optimization of the dosimetric plan in the intracavity radiotherapy of patients with cancer of the corpus uteri].

The potentialities of mathematical optimization were investigated with respect to dosimetric design of radiation therapy of endometrial cancer patients using AGAT-V and AGAT-VU [correction of Agat-B and Agat-Y] apparatus. The effectiveness of linear programming for creating in a pathological focus and in normal tissues of a dose distribution, meeting clinical requirements to the maximum, was shown.

Brachytherapy↗

PubMed1988

Quantitative management techniques in dietetics: improving practice through technology transfer.

A content analysis of articles appearing chronologically in the Journal of The American Dietetic Association since its inception in 1925 reveals the breadth and depth of management practice in the dietetic profession. This historical review highlights the introduction, demonstration, and adoption of management tools and techniques in the profession, with particular emphasis on quantitative management science techniques. Seven classifications of management science techniques were used for the content analysis. Although applications of forecasting, simulation, linear programming, and queuing models have been reported in the Journal, a gap is evident between the demonstration of management science techniques and operational use of these techniques in dietetic practice. Dietetic researchers, practitioners, and educators have vital roles in facilitating the transfer of quantitative management science technology into operational dietetic practice. Assessment of the state-of-the-art of dietetic management practice relative to proven quantitative management science techniques reveals the need for improved technology transfer to enhance professional ability in both tactical and strategic decision making.

Dietetics↗

PubMed1986

Are larger dental practices more efficient? An analysis of dental services production.

Whether cost-efficiency in dental services production increases with firm size is investigated through application of an activity analysis production function methodology to data from a national survey of dental practices. Under this approach, service delivery in a dental practice is modeled as a linear programming problem that acknowledges distinct input-output relationships for each service. These service-specific relationships are then combined to yield projections of overall dental practice productivity, subject to technical and organizational constraints. The activity analysis reported here represents arguably the most detailed evaluation yet of the relationship between dental practice size and cost-efficiency, controlling for such confounding factors as fee and service-mix differences across firms. We conclude that cost-efficiency does increase with practice size, over the range from solo to four-dentist practices. Largely because of data limitations, we were unable to test satisfactorily for scale economies in practices with five or more dentists. Within their limits, our findings are generally consistent with results from the neoclassical production function literature. From the standpoint of consumer welfare, the critical question raised (but not resolved) here is whether these apparent production efficiencies of group practice are ultimately translated by the market into lower fees, shorter queues, or other nonprice benefits.

Cost-Benefit Analysis↗

PubMed1986

A model to assess the quality-cost tradeoff in nursing homes.

We develop a model for assessing quality-cost tradeoffs as they arise in nurse staffing and task assignment decisions commonly faced by nursing home administrators and industry regulators. As prospective reimbursement schemes and resource utilization groups (RUGs) are implemented, we expect that tradeoffs such as these will become even more critical than they are now. The model permits the inclusion of quality-related considerations, such as restricting tasks to personnel at specified skill levels, requiring minimum staff levels at each skill level, and selective raising of wage rates. The model is also sensitive to changes in patient needs, labor availability, and technological innovations, permitting its use for general staffing purposes. Because it utilizes linear programming techniques, standard computer software can be used to find solutions very quickly, even on a small personal computer. We describe the application of this model to a nursing home in upstate New York, but the procedure is widely applicable to other health care facilities.

Aged↗

PubMed1985

[Results of radiotherapy of lung cancer in women].

Radiation therapy was provided to 38 (11.5%) of 331 lung cancer female patients at the N. N. Petrov Research Institute of Oncology, USSR Ministry of Health. The combination of radiation- and chemotherapy was used in 9 patients. The Rokus, Rad gamma-therapeutic units or a linear accelerator were used for radiation therapy. Daily single focal doses were 1.2-2.0 Gy, the summary dose was 40-60 Gy. Two-five irradiation fields with the choice of optimum conditions on a computer using the linear programming method were used. The lymph outflow tracts were irradiated from isolated fields and in central lung cancer the tumor and mediastinal region (the root, bifurcation and paratracheal lymph nodes on the affected side) were incorporated in the irradiated zone. Five women received split course irradiation. An analysis of the long-term results of conservative therapy of lung cancer in women has shown that radiation therapy or its combination with chemotherapy is the most effective. These results were slightly better than those in men.

Adenocarcinoma↗