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1.
Mixed-model assembly lines are becoming increasingly interesting as the use of just-in-time principles in manufacturing continues to expand. This paper presents, for the first time, complexity results for the underlying problem of product sequencing. It is shown that the problem is intractable for both the single station and the multiple station case. Nevertheless, efficient 1.5-approximation algorithms are developed for the early- and late-start models associated with the former case. Empirical results demonstrate that these algorithms perform extremely well in practice.  相似文献   
2.
Osteopotin is a secreted glycosylated phosphoprotein found in bone and other normal and malignant tissues. Osteopontin can be autophosphorylated on tyrosine residues and can also be phosphorylated on serine and threonine residues by several protein kinases. Autophosphorylation of osteopontin may generate sites for specific interactions with other proteins on the cell surface and/or within the extracelluar matrix. These interactions of osteopontin are thought to be essential for bone mineralization and function. The polyaspartic acid motif of osteopontin, in combination with neighboring sequences that include serine residues phosphorylated by protein kinases, could fold and assemble into a molecular structure that participates in the mineralization of the bone matrix.  相似文献   
3.
Coprolites are fossilized feces that can be used to provide information on the composition of the intestinal microbiota and, as we show, possibly on diet. We analyzed human coprolites from the Huecoid and Saladoid cultures from a settlement on Vieques Island, Puerto Rico. While more is known about the Saladoid culture, it is believed that both societies co-existed on this island approximately from 5 to 1170 AD. By extracting DNA from the coprolites, followed by metagenomic characterization, we show that both cultures can be distinguished from each other on the basis of their bacterial and fungal gut microbiomes. In addition, we show that parasite loads were heavy and also culturally distinct. Huecoid coprolites were characterized by maize and Basidiomycetes sequences, suggesting that these were important components of their diet. Saladoid coprolite samples harbored sequences associated with fish parasites, suggesting that raw fish was a substantial component of their diet. The present study shows that ancient DNA is not entirely degraded in humid, tropical environments, and that dietary and/or host genetic differences in ancient populations may be reflected in the composition of their gut microbiome. This further supports the hypothesis that the two ancient cultures studied were distinct, and that they retained distinct technological/cultural differences during an extended period of close proximity and peaceful co-existence. The two populations seemed to form the later-day Taínos, the Amerindians present at the point of Columbian contact. Importantly, our data suggest that paleomicrobiomics can be a powerful tool to assess cultural differences between ancient populations.  相似文献   
4.
Summary A water soluble agent made from waste crustacean shells that controls the growth of algal cells was identified. Growth of an Anabaena sp. was inhibited in the presence of varied concentrations of a chitosan-derivative, N-carboxymethylchitosan (NCMC). Application of a dilute water solutions of NCMC prevented algae from multiplication and enhanced aggregation of cells and assured clearing of algal suspension by filtration.  相似文献   
5.
Summary The most relevant properties of hypercycles were previously studied mainly from a theoretical point of view. We have developed a Monte Carlo method simulating hypercyclic organization to obtain information about the dynamics of this prebiotic organization. Nucleation, growth, and selective properties have been tested and the results obtained are in good agreement with those of the theoretical predictions. The influence of hypercyclic organization of the error threshold has also been studied. As a consequence of the emergence of a hypercycle, the value of this threshold decreases. The amount of this decrease depends on the population size. Moreover, for some interval of quality factor values, either the hypercycle organization or an error catastrophe can be produced, depending on the initial conditions. The influence of these phenomena on both the dynamic behavior and evolutionary advantages of the hypercycle, as well as their decisive roles on genome size, are discussed.Presented at the FEBS Symposium on Genome Organization and Evolution, held in Crete, Greece, September 1–5, 1986  相似文献   
6.
We have studied the effects of fetal neuronal grafts on the temporal pattern of drinking behavior of suprachiasmatic nuclei (SCN)-lesioned adult rats. Additionally, in an independent set of animals, the immunohistochemical staining for vasopressin, vasoactive intestinal polypeptide, and neuropeptide Y and the retinal connections to the hypothalamus were studied. The behavioral experiments indicate that anterior hypothalamic transplants induced reorganization of the temporal pattern of drinking behavior when placed in the third ventricle of adult hosts bearing complete SCN lesions, but not when placed in a cavity in the occipital cortex. Such rhythmicity persists only when the animals were recorded under constant darkness but not under constant light, indicating that the restored rhythmicity was generated endogenously but that the oscillator was extremely sensitive to light. Fetal occipital cortex induced reorganization of the temporal pattern of previously arrhythmic hosts, but it disappeared when the animals were recorded under constant light or constant darkness. It is clear that this rhythmicity was exogenous. In contrast to the cortical transplants, the hypothalamic transplants showed a morphological organization similar to that found in the normal hypothalamus regardless of their placement in the host brain. From these observations it is concluded that development of neocortex is more affected by environmental factors than that of the hypothalamus. Both hypothalamic and cortical transplants induced sprouting of retinal fibers into the anterior hypothalamus and the grafted tissue. It is possible that such fibers could be the neuroanatomical substrate by which rhythmicity is induced by cortical tissue.  相似文献   
7.
The primary structure of the HLA-A2 subtype A*0204 (isoelectric focusing variant A2.A) has been determined. cDNA encoding this subtype was amplified by the polymerase chain reaction. Four independent full-lenght cDNA clones encoding A*0204 were analyzed to obtain a consensus sequence for this subtype. A*0204 differs from A*0201 by a single nucleotide change of G to T through the coding regions, resulting in an Arg to Met change at position 97. This substitution accounts for the isoelectric focusing pattern of the subtype. The same change occurs in other HLA-A specificities in association with other changes in its vicinity. The absence of additional substitutions in A*0204 suggests that it could have arisen from A*0201 by point mutation, and that recurrent mutations may take place during HLA diversification. The spatial location of this change implies that A*0204 must be a functional variant. Comparison of its sequence with other HLA-A2 subtypes reveals that much of the HLA-A2 subtype polymorphism is generated by variations in four neighboring positions, including position 97, which are located in two adjacent -strands on the floor of the peptide binding site of the molecule.The nucleotide sequence data reported in this paper have been submitted to the EMBL nucleotide sequence database and have been assigned the accession number X57954. Address correspondence and offprint requests to: J. A. López de Castro.  相似文献   
8.
9.
As part of a study on the role of vasoactive amines in experimental autoimmune encephalomyelitis (EAE), we have found that treatment beginning 7 days post-inoculation (dpi) with the specific alpha 1-adrenoceptor antagonist prazosin can significantly suppress clinical signs of disease in the Lewis rat. In this paper we have addressed the effect of treatment with prazosin commencing at varying times in the disease process. The results show that treatment during the early inductive stage (1 to 6 dpi) has no effect on the clinical course of the disease, whereas treatment commencing at the time of onset of early clinical signs (10 to 16 dpi) still significantly suppresses EAE. Leakage of serum proteins into the central nervous system (CNS) and histologic expression of EAE are also suppressed. Prazosin had no effect on lymphocyte responses to mitogen or antigen as determined by lymphocyte transformation tests when lymphocytes were exposed to prazosin in vitro, and the responses of lymphocytes from prazosin-treated animals were similar to those from saline-treated animals. These results support the hypothesis that prazosin suppresses EAE through a direct vascular effect although they do not preclude an immunologic component to its mechanism of action.  相似文献   
10.
Using an in vitro system, we studied the effect of postischemic reoxygenation on cerebral lipid peroxidation in relation to the dietary intake of vitamin E (VE) in rats. Homogenates prepared from VE-deficient, -normal, and -supplemented brains, which were previously rendered ischemic for 30 min by decapitation, were incubated under air or nitrogen gas for 60 min. The extent of peroxidation in brain tissue was estimated by a thiobarbituric acid (TBA) test and by diene conjugation in total lipid extracts. The brain levels of alpha-tocopherol and of total and free fatty acids (FAs) were also determined. Aerobic incubation increased TBA reactants in all dietary groups; the effect was largest in the VE-deficient group, intermediate in the VE-normal group, and smallest in the VE-supplemented group. In contrast, nitrogen incubation did not alter the basal levels of TBA reactants except for a small rise associated with VE deficiency. Conjugated dienes changed in parallel with TBA reactants. alpha-Tocopherol decreased after aerobic incubation and also, to a lesser degree, after nitrogen incubation in each dietary group. Only in the reoxygenated samples of the VE-deficient group was there a significant fall in total polyunsaturated FAs. The levels of free FAs continuously increased throughout ischemia and subsequent incubation. However, the level of free polyunsaturated FAs was similar after aerobic and nitrogen incubation in each dietary group, and was not affected by VE. Thus, cerebral reoxygenation after ischemia propagates peroxidative reactions within esterified polyunsaturated FAs. The modification by VE of reoxygenation-induced lipid peroxidation suggests free radical mediation.  相似文献   
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