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771.
772.
Yu-Chung Tsao Tsung-Hui Chen Sheng-Min Huang 《Flexible Services and Manufacturing Journal》2011,23(1):48-63
Making production decisions that will reduce total cost is a goal that most manufacturers pursue actively. However, the traditional production model development assumed that all products are perfect quality, which is far from reality. Since trade credit is a popular payment method in today??s business environment, this paper analyzes the production problem under trade credit and imperfect product reworking conditions. This work extends the traditional production model by considering reworking imperfect items and trade credit to cope with realistic situations. The objective of this study is to determine the optimal production lot size while minimizing the total cost. This paper develops an easy-to-use algorithm to solve the problem described, provides numerical examples to illustrate the proposed solution procedure, and discusses the impact of various system parameters. 相似文献
773.
Decreased levels of guanyl nucleotide-binding regulatory protein alpha-subunits in Y1 adrenocortical tumor cell mutants resistant to forskolin. 总被引:1,自引:0,他引:1
Forskolin-resistant mutants arise from Y1 mouse adrenocortical tumor cells with a frequency indicative of a mutational event at a single genetic locus and exhibit adenylyl cyclases that are resistant to activation by forskolin, corticotropin, and guanyl-5'-yl-imidodiphosphate. This study examined the levels of guanyl nucleotide-binding regulatory protein subunits (G) in plasma membranes from the forskolin-resistant mutants by Western blot immunoanalysis. In plasma membranes prepared from parental Y1 cells and from four forskolin-resistant mutants, 10r-2, 10r-3, 10r-6, and 10r-9, the levels of the alpha-subunits of Gs and Gi-2 were reduced by 70-80% relative to the levels in parental Y1 cells. The levels of the beta 36-subunit were much less affected, and the levels of the alpha i-3 and beta 35-subunits varied independently of the forskolin-resistant phenotype. As determined by slot blot hybridization analyses, the levels of Gs alpha and Gi alpha RNA in the forskolin-resistant mutants were equivalent to those in the Y1 parent. Therefore, the decreased levels of Gs alpha and Gi alpha-2 subunits observed in the forskolin-resistant mutants did not result from decreased expression of the genes encoding these proteins. Our observations suggest that the forskolin-resistant phenotype of Y1 mutants resulted from single mutations that affected the processing of specific G alpha subunits or their incorporation into the plasma membrane. 相似文献
774.
Pyruvate kinase (ATP:pyruvate phosphotransferase, EC 2.7.1.40), extracted from the mycelium of Neurospora crassa has been purified 560-fold by precipitation with ammonium sulphate, chromatography with DEAE-Sephadex, and gel filtration with Sephadex G-200. Potassium and magnesium are required for enzyme activity. Fructose, 1,6-diphosphate is the only physiological activator found for the enzyme. In decreasing order of potency, citrate, oxalacetate, calcium, and ATP are inhibitors. Phosphoenolpyruvate is cooperatively bound by the enzyme and the cooperatively is reduced by ATP and completely eliminated by fructose-1,6-diphosphate. Lowering of pH from 7-5 to 5-5 changes the Hill coefficient from 2-7 to 1-0. Substitution of ADP by other nucleotides reduces enzyme activity. Manganese can substitute for the cofactor magnesium, but the reaction velocity is then reduced. MgADP- is cooperatively bound by the enzyme and inhibition of the enzyme occurs only when either magnesium or ADP is in excess of the other beyond the optimum concentration. These kinetics properties of pyruvate kinase are compatible with the role of a regulator of glycolysis in Neurospora crassa. 相似文献