Scheduling algorithms for a two-machine flexible manufacturing system

The flexible manufacturing system (FMS) considered in this paper is composed of two CNC machines working in series—a punching machine and a bending machine connected through rollers acting as a buffer system of finite capacity. The main difference between the present problem and the standard two-machine flow shop problem with finite intermediate capacity is precisely the buffer system, which in our problem consists of two stacks of parts supported by rollers: the first stack contains the output of the punching machine, while the second stack contains the input for the bending machine. When the second stack is empty, the first stack may be moved over. Furthermore, the capacity of each stack depends on the particular part type being processed. The FMS can manufacture a wide range of parts of different types. Processing times on the two machines are usually different so that an unbalance results in their total workload. Furthermore, whenever there is a change of the part type in production, the machines must be properly reset—that is, some tools need to be changed or repositioned. A second important difference between the present problem and the usual two-machine flow shop problem is the objective. Given a list ofp part types to be produced in known quantities, the problem considered here is how to sequence or alternate the production of the required part types so as to achieve various hierarchical targets: minimize the makespan (the total time needed to complete production) and, for instance, compress the idle periods of the machine with less workload into a few long enough intervals that could be utilized for maintenance or other reasons. Although Johnson's rule is optimal in some particular cases, the problem addressed in the paper isNP-hard in general: heuristic procedures are therefore provided.     

Phorbol ester-stimulated superoxide production by murine bone marrow-derived macrophages requires preexposure to cytokines

Murine resident peritoneal macrophages (RPM) generate superoxide (O2-) in response to stimulation with PMA or zymosan. Murine bone marrow-derived macrophages (BMM) generate O2- in response to zymosan but not PMA. However, the ability to generate O2- in response to PMA could be induced in BMM by pre-exposing the cells to certain cytokines, including granulocyte-macrophage CSF (GM-CSF), tumor necrosis factor-alpha (TNF-alpha), IFN-gamma, and, to a lesser extent, IL-1 alpha. Bacterial LPS also induced the ability to respond to PMA. These same agents were also shown to prime RPM for enhanced PMA-induced respiratory burst. In contrast to GM-CSF, CSF-1 did not enhance the ability of BMM or RPM to generate O2- in response to PMA. Pretreatment with GM-CSF or TNF-alpha did not significantly affect the zymosan-induced release of O2- by BMM. These results suggest that unprimed BMM have a deficiency in the PMA-dependent signaling pathway that is corrected by exposure to selected cytokines. The results also raise the possibility that the basal ability of tissue macrophages to generate a respiratory burst in response to PMA may be a reflection of in vivo exposure to cytokines.     

Association of LHIα(B870) Polypeptide with Phospholipids During Insertion in the Photosynthetic Membrane of an LHII− Mutant of Rhodobacter capsulatus

Membranes from in vivo labeled cells of Rhodobacter capsulatus U43[pTX35] grown photosynthetically carried 60% of the [³²P]-Pi in the “heavy” fraction (HM) after sucrose gradient sedimentation. Metal-chelating chromatography of either “heavy” or “light” (LM) membrane fractions rendered similar Bchl-protein complex profiles after octyl-glucoside treatment, including most of the radioactivity in the same corresponding elution fraction (F II). Similar labeling distribution of pigment-protein complexes was obtained for membranes of dark-grown cells induced by lowering oxygen tension. Fractions derived from HM showed highly labeled LHIα, whereas the same complex from LM was essentially [³²P]-Pi-free, as revealed by SDS-PAGE followed by autoradiography. Phospholipid analysis showed a similar pattern for membranes isolated from cells photosynthetically or semiaerobically grown, being the most abundant: phosphatidylglycerol, phosphatidylethanolamine, cardiolipin, and phosphatidylcholine. Part of the phospholipids from HM comigrated with LHIα during SDS-PAGE and dissociated from the complexes only after solvent extraction and hydrophobic chromatography. However, a small amount remained always attached to LHIα, indicating an unusual strong interaction. These results suggest the existence of two operationally defined membrane regions carrying LHIα complexes differing in phosphorylation status and protein-phospholipid interaction. Received: 10 August 1996 / Accepted: 10 September 1996     

The incidence of Weeksella- and Bergeyella-like bacteria in the food environment

Eighty-five catalase- and oxidase-positive Gram-negative rods and cocci susceptible to penicillin G were isolated from a variety of food sources. The phenotypic relationships of these isolates with reference cultures of Bergeyella -like, Chryseobacterium, Empedobacter, Myroides , Moraxella , Sphingobacterium and Weeksella -like strains were examined by numerical taxonomy. Seventy-three isolates were recovered in five groups; 80% of the isolates clustered in groups 1, 2 and 3 and produced indole, bearing a strong resemblance to Weeksella and Bergeyella . They could not, however, be regarded as belonging to the known species of W. virosa and B. zoohelcum . It is suggested that three species may be necessary to accommodate the environmental Weeksella - or Bergeyella -like bacteria. The isolates in groups 4 and 5 had white colonies and were unable to produce indole, in this way resembling the Moraxella genus.     

Mutational analysis of slyD, an Escherichia coli gene encoding a protein of the FKBP immunophilin family

slyD encodes a 196 amino acid polypeptide that is a member of the FKBP family of cis–trans peptidyl–prolyl isomerases (PPIases). slyD mutations affect plaque formation by the phage φX174 by blocking the action of the phage lysis protein E. Here we describe the selection of a set of spontaneous slyD mutations conferring resistance to the expression of gene E from a plasmid. These mutations occur disproportionately in residues of SlyD that, based on the structure of the prototype mammalian FKBP12, make ligand contacts with immunosuppressing drug molecules or are conserved in other FKBP proteins. A wide variation in the plating efficiency of φX174 on these E  ^R strains is observed, relative to the parental, indicating that these alleles differ widely in residual SlyD activity. Moreover, it is found that slyD mutations cause significant growth rate defects in Escherichia coli B and C backgrounds. Finally, overexpression of slyD causes filamentation of the host. Thus, among the FKBP genes found in organisms across the evolutionary spectrum, slyD is unique in having three distinct drug-independent phenotypes.     

Eosinophils preferentially use bromide to generate halogenating agents

Human eosinophils preferentially utilize bromide to generate a brominating agent, even at physiological halide concentrations, where chloride (140 mM) is over 1000-fold greater than bromide (20-100 microM). Under the same conditions, neutrophils use chloride to generate a chlorinating agent. The total amount of active halogen trapped by 1,3,5-trimethoxybenzene from eosinophils increases by over 2-fold as the added bromide concentration increases from 0 to 100 microM, with approximately 40 nmol of halogen trapped per million cells at the highest bromide level. At least 25-35% of the oxygen consumed by stimulated eosinophils is directed toward the generation of halogenating species. Since the relative halogenating behavior of eosinophil peroxidase and neutrophil myeloperoxidase in this bromide range is essentially identical to that of the cells, the specificity of eosinophils toward bromide is intrinsic to eosinophil peroxidase and not to any special cellular properties. These results suggest that human eosinophils use bromide in vivo and that a deficiency of bromide may influence their ability to produce halogenating agents.     

Generation of Lys-gamma 3-melanotropin from pro-opiomelanocortin 1-77 by a bovine intermediate lobe secretory vesicle membrane-associated aspartic protease and purified pro-opiomelanocortin converting enzyme

The ability of bovine intermediate lobe secretory vesicle membrane-associated enzyme(s) and purified, soluble paired basic residue-specific, pro-opiomelanocortin converting enzyme (Loh, Y.P., Parish, D. C., and Tuteja, R. (1985) J. Biol. Chem. 260, 7194-7205) to cleave bovine NH2-terminal pro-opiomelanocortin1-77 (N-POMC 1-77) was investigated. Purified pro-opiomelanocortin converting enzyme and an enzyme activity associated with the secretory vesicle membrane were shown to cleave bovine N-POMC1-77 to two major products: N-POMC1-49 and Lys-gamma 3-melanotropin (MSH), and one minor product, gamma 3-MSH. These products were identified by their retention times on high performance liquid chromatography, immunological characteristics, and for Lys-gamma 3-MSH, amino acid composition. The products generated indicate cleavage preferentially between Arg 49-Lys 50 of bN-POMC1-77 (where b indicates bovine), which is identical to the processing pattern found in the bovine intermediate lobe in situ. The membrane converting activity was shown to be stimulated by 5 mM Ca2+ and has a pH optimum of 4-5 and an inhibitor profile characteristic of an aspartic protease. This suggests that the membrane-associated enzyme involved is very similar or identical to the purified, soluble pro-opiomelanocortin converting enzyme, which has previously been reported to be an acidic, aspartic protease responsible for the initial steps of POMC processing. The results of this study lead to the proposal that the lack of processing of the Arg49-Lys50 site in POMC in the anterior lobe versus the intermediate lobe of the pituitary in vivo may be due to other regulatory mechanisms rather than invoking the existence in the intermediate lobe of another enzyme specific for this site, different from pro-opiomelanocortin converting enzyme.     

Medical Materials Based on Chitosan Succinamide–Glycerol Systems

The conditions to obtain materials with elastic-viscous properties based on chitosan succinamide have been studied. A decreased polymer content and a transition from visco-elastic liquids to elastic-viscous systems were shown upon the addition of glycerol to an aqueous solution of chitosan succinamide. The systemic response, biological compatibility, and dynamics of bioresorbability of the obtained materials were studied during implantation in laboratory animals.