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- Aardal, Karen, et al.
(författare)
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Decomposition principles applied to the dynamic production and work-force scheduling problem
- 1987
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Ingår i: Engineering Costs and Production Economics. - 0167-188X .- 1878-4011. ; 12:1-4, s. 39-49
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Tidskriftsartikel (refereegranskat)abstract
- One of the most important problems in the production and inventory planning field, is the scheduling of production and work force in a dynamic environment. Although this problem can be formulated as a linear program, it is often quite difficult to solve directly, due to its large scale. Instead, it might be fruitful to use a decomposition approach. Decomposition, in general, means decomposing a difficult problem into several easier, or a sequence of easier problems which are later coordinated to reconstruct the original problem.In this report we discuss several possibilities of applying the most common decomposition principles, namely Benders (primal) and Datnzig-Wolfe (dual), as well as a relatively new decomposition method, called cross decomposition, to the dynamic, multiproduct production and employment planning problem. A number of special cases are also presented.
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- Aardal, Karen, et al.
(författare)
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On the resemblance between the Kornai-Liptak and cross decomposition techniques for block-angular linear programs
- 1990
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Ingår i: European Journal of Operational Research. - : Elsevier BV. - 0377-2217 .- 1872-6860. ; 46:3, s. 393-398
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Tidskriftsartikel (refereegranskat)abstract
- In this paper the resemblance is demonstrated between the master- and subproblems generated by the Kornai-Liptak algorithm and the subproblems obtained by using the cross decomposition method on linear optimization problems with block-angular structure. The significance of the similarity between these two algorithms becomes apparent considering the main disadvantage attributed to cross decomposition. In cross decomposition a master problem has to be solved from time to time since the subproblems alone do not always give a converging sequence of primal and dual solutions. But if the cross decomposition algorithm is modified in such a way that the successive primal and dual subproblem solutions are taken into consideration with equal weights, this results in the Kornai-Liptak algorithm for which convergence is guaranteed
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- Aareleid, Tiiu, et al.
(författare)
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Lung cancer in Estonia in 1968-87 : time trends and public health implications.
- 1994
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Ingår i: European Journal of Cancer Prevention. - 0959-8278 .- 1473-5709. ; 3:5, s. 419-425
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Tidskriftsartikel (refereegranskat)abstract
- Changes in lung cancer incidence and mortality in Estonia were studied for 20 years (1968-87). A steady upward trend was observed for men and women. The 1983-87/1968-72 age-standardized incidence rate ratio was 1.22 (95% confidence interval (CI) 1.15-1.29) in men and 1.34 (95% CI 1.16-1.54) in women. The corresponding mortality rate ratio was 1.26 (95% CI 1.18-1.34) in men and 1.35 (95% CI 1.16-1.57) in women. The age-specific incidence and mortality rates increased clearly towards the younger birth cohorts. For men and women, the increase was most evident for the age group 45-64 years. In women there was a more rapid increase in incidence and mortality than in men. It may be a result of a substantial increase of tobacco smoking, particularly among women, after the World War II. The high and still rising occurrence of lung cancer is closely related to the high prevalence of smoking; in addition, high tar yields in domestic cigarettes could have been responsible for an elevated lung cancer risk during the past decades. There is not tobacco control programme in Estonia, and existing legislation and regulations do not defend the non-smoking population.
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- Abdul-Rahman, A, et al.
(författare)
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Local cerebral blood flow in the rat during severe hypoglycemia, and in the recovery period following glucose injection
- 1980
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Ingår i: Acta Physiologica Scandinavica. - 0001-6772. ; 109:3, s. 307-314
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Tidskriftsartikel (refereegranskat)abstract
- In order to assess the influence of severe hypoglycemia on local cerebral blood flow (1-CBF) artificially ventilated rats, maintained on 70% N2O, were injected with insulin to provide either an EEG pattern of slow-wave polyspikes, or cessation of spontaneous EEG activity for 5, 15 or 30 min ("coma"). In other animals, glucose was injected at the end of a 30 min period of "coma" and 1-CBF was measured after recovery periods of 5, 30, 90, or 180 min. Local CBF was measured autoradiographically with 14C-iodoantipyrine as the diffusible tracer. In the slow-wave polyspike period 1-CBF was increased in most of the structures studied, and reached values that were 1.4 to 3.2 times greater than control. In many structures, cessation of EEG activity was accompanied by a further increase in 1-CBF, with some structures (thalamus, hypothalamus, pontine gray, and cerebellar cortex) showing flow rates of 400--500% of control. The increase in 1-CBF was unrelated to arterial hypertension, hypercapnia, or hypoxia. 5 min after glucose injection the hyperemia persisted in only some of the structures studied; in others, the 1-CBF were close to, or below, control values. During the subsequent recovery period 1-CBF was markedly reduced with some structures (cerebral cortical areas, hippocampus, and caudate-putamen) showing flow rates of only 20--35% of control. In others, notably pontine gray and cerebellar cortex, secondary hypoperfusion was never observed. The hypoperfusion was unrelated to arterial hypertension, hypocapnia, or increase in intracranial pressure. It is concluded that, like hypoxia and ischemia, substrate deficiency due to hypoglycemia is accompanied by vasodilatation in the brain. Furthermore, like long-lasting ischemia, severe hypoglycemia is followed by a delayed hypoperfusion syndrome that, by restricting oxygen supply, may well contribute to the final cell damage incurred.
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- Abdulkarim, Farhad, et al.
(författare)
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Missense substitutions lethal to essential functions of EF-Tu
- 1991
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Ingår i: Biochimie. - : Elsevier BV. - 0300-9084 .- 1638-6183. ; 73:12, s. 1457-1464
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Tidskriftsartikel (refereegranskat)abstract
- We have used a simple selection and screening method to isolate function defective mutants of EF-Tu. From 28 mutants tested, 12 different missense substitutions, individually lethal to some essential function of EF-Tu, were identified by sequencing. In addition we found a new non-lethal missense mutation. The frequency of isolation of unique mutations suggests that this method can be used to easily isolate many more. The lethal mutations occur in all three structural domains of EF-Tu, but most are in domain II. We aim to use these mutants to define functional domains on EF-Tu.
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- Abdulkarim, Farhad, et al.
(författare)
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Mutations to kirromycin resistance occur in the interface of domains I and III of EF-Tu.GTP
- 1994
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Ingår i: FEBS Letters. - : Wiley. - 0014-5793 .- 1873-3468. ; 352, s. 118-122
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Tidskriftsartikel (refereegranskat)abstract
- The antibiotic kirromycin inhibits protein synthesis by binding to EF-Tu and preventing its release from the ribosome after GTP hydrolysis.We have isolated and sequenced a collection of kirromycin resistant tuf mutations and identified thirteen single amino acid substitutions at sevendifferent sites in EF-Tu. These have been mapped onto the 3D structures of EF-Tu’GTP and EF-Tu.GDP. In the active GTP form of EF-Tu themutations cluster on each side of the interface between domains I and III. We propose that this domain interface is the binding site for kirromycin.
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