Showing papers by "Ghent University published in 1990"

Analysis of Scheduling Rules for an FMS

Abstract: SUMMARY We first discuss the characteristics of a general-purpose, user-oriented discrete event simulator for FMS. Then we briefly review the literature on scheduling rules for manufacturing systems. The performance of a number of dispatching rules is subsequently analysed using our modular simulator to mimic the operation of a real-life FMS. Results show that dispatching rules have a large impact on various system performance measures, such as average machine utilization. Considering the high investment costs of FMS it is certainly worthwhile to choose the best dispatching rule by use of simulation. This is especially true since modular and user-friendly simulators are now available so that the analysis can be performed quickly and at very moderate cost.

The nuclear shell model

Abstract: The basic assumption in the nuclear shell model is that, to first order, each nucleon (proton or neutron) is moving in an independent way in an average field. This is not so, a priori, since the nucleus constitutes an A-body problem interacting via the nucleon-nucleon force in the nuclear medium. It is clear from the very beginning that this nucleon-nucleon force will be different from the free nucleon-nucleon interaction (Bohr, Mottelson 1969). As was already expressed in the introduction to this book, the non-relativistic form of the nucleon-nucleon interaction behaves as shown in Fig.3.1. At large separations ∣r i–r j∣≅ 1.5 –2 fm, the force behaves according to a one-pion exchange potential (OPEP) which has an analytic dependence on r=∣r i–r j∣ of (Bohr, Mottelson 1969) $$V(r) = - \frac{{e^{ - \mu r} }}{{\mu r}}\left( {1 + \frac{3}{{\mu r}} + \frac{3}{{\left( {\mu r} \right)^2 }}} \right)$$ (3.1) .

Involvement of the hydrophobic patch of azurin in the electron‐transfer reactions with cytochrome c551 and nitrite reductase

Abstract: The electron-transfer reactions of site-specific mutants of the blue copper protein azurin from Pseudomonas aeruginosa with its presumed physiological redox partners cytochrome c551 and nitrite reductase were investigated by temperature-jump and stopped-flow experiments. In the hydrophobic patch of azurin Met44 was replaced by Lys, and in the His35 patch His35 was replaced by Phe, Leu and Gln. Both patches were previously thought to be involved in electron transfer. 1H-NMR spectroscopy revealed only minor changes in the three-dimensional structure of the mutants compared to wild-type azurin. Observed changes in midpoint potentials could be attributed to electrostatic effects. The slow relaxation phase observed in temperature-jump experiments carried out on equilibrium mixtures of wild-type azurin and cytochrome c551 was definitively shown to be due to a conformational relaxation involving His35. Analysis of the kinetic data demonstrated the involvement of the hydrophobic but not the His35 patch of azurin in the electron transfer reactions with both cytochrome c551 and nitrite reductase.

CLADISS-a longitudinal multimode model for the analysis of the static, dynamic, and stochastic behavior of diode lasers with distributed feedback

Abstract: A computer model called CLADISS is presented for the analysis of multisection diode lasers. The model allows for the analysis of a wide variety of multisection devices with discrete or distributed internal reflections. The simulator can carry out a threshold, DC, AC, and a noise analysis. The threshold analysis determines the threshold of the various longitudinal modes of the laser. The power versus current and the wavelength versus current characteristics are found with the self-consistent DC analysis. CLADISS includes all of the longitudinal variations by dividing each laser section in many short segments. Both the optical field and carrier density are discretized according to this segmentation. To demonstrate the capabilities of CLADISS some nonlinear effects in DFB lasers are treated. Instabilities induced in the side-mode suppression ratio by spatial hole burning are considered. The effects of spatial hole burning and side modes on the FM response on the linewidth are discussed. >

Gene escape model: transfer of heavy metal resistance genes from Escherichia coli to Alcaligenes eutrophus on agar plates and in soil samples.

Abstract: Conjugal transfer from Escherichia coli to Alcaligenes eutrophus of the A. eutrophus genes coding for plasmid-borne resistance to cadmium, cobalt, and zinc (czc genes) was investigated on agar plates and in soil samples. This czc fragment is not expressed in the donor strain, E. coli, but it is expressed in the recipient strain, A. eutrophus. Hence, expression of heavy metal resistance by cells plated on a medium containing heavy metals represents escape of the czc genes. The two plasmids into which this DNA fragment has been cloned previously and which were used in these experiments are the nonconjugative, mobilizable plasmid pDN705 and the nonconjugative, nonmobilizable plasmid pMOL149. In plate matings at 28 to 30 degrees C, the direct mobilization of pDN705 occurred at a frequency of 2.4 x 10(-2) per recipient, and the mobilization of the same plasmid by means of the IncP1 conjugative plasmids RP4 or pULB113 (present either in a third cell [triparental cross] or in the recipient strain itself [retromobilization]) occurred at average frequencies of 8 x 10(-4) and 2 x 10(-5) per recipient, respectively. The czc genes cloned into the Tra- Mob- plasmid pMOL149 were transferred at a frequency of 10(-7) to 10(-8) and only by means of plasmid pULB113. The direct mobilization of pDN705 was further investigated in sandy, sandy-loam, and clay soils. In sterile soils, transfer frequencies at 20 degrees C were highest in the sandy-loam soil (10(-5) per recipient) and were enhanced in all soils by the addition of easily metabolizable nutrients.(ABSTRACT TRUNCATED AT 250 WORDS)

Phosphonate utilization by bacterial cultures and enrichments from environmental samples.

Abstract: A selection of axenic microbial strains and a variety of environmental samples were investigated with respect to the utilization of a series of natural and xenobiotic phosphonates as the sole phosphorus source for growth. Phosphonate degradation was observed only with bacteria and not with eucaryotic microorganisms. All representatives of the phosphonates examined supported bacterial growth, with the exception of methylphosphonate diethylester. Yet, distinctly different phosphonate utilization patterns were noted between phosphonate-positive strains. C-P bond cleavage by a photosynthetic bacterium is reported for the first time; growing photoheterotrophically, Rhodobacter capsulatus ATCC 23782 was able to utilize 2-aminoethylphosphonate and alkylphosphonates. Bacteria with the potential to utilize at least one of the phosphonate moieties from the xenobiotic phosphonates Dequest 2010, Dequest 2041, and Dequest 2060 were detected in all environments, with only two exceptions for Dequest 2010. Phosphonate P utilization to an extent of 94 and 97%, for Dequest 2010 and Dequest 2041, respectively, provided evidence that a complete breakdown of these compounds with respect to the C-P bond cleavage can be achieved by some bacteria. The results suggest that phosphonate-utilizing bacteria are ubiquitous, and that selected strains can degrade phosphonates that are more complex than those described previously.

Constitutional translocation t(1;17)(p36;q12-21) in a patient with neuroblastoma.

Abstract: A constitutional chromosome translocation t(1;17)(p36;q12-21) is reported in a boy with neuroblastoma. This is the first description of a cytogenetic abnormality possibly predisposing to the development of neuroblastoma.

The invasive phenotypes.

Abstract: The expression of the invasive (I+ or I-) phenotypes determines cancer metastasis (M+ or M- phenotype). The invasive (I+ or I-) phenotypes can be divided according to time and site of expression into subphenotypes, which can be assessed separately. At various sites along the metastatic pathway the expression of the I phenotypes can be accompanined by the presence of uncontrolled growth (G+ phenotype) or its absence (G- phenotype). Various combinations of the I and G phenotypes determine the behaviour of metazoan or parasitic cells under normal, pathological non-neoplastic and neoplastic conditions. Although the G+I+M+ combination correlates with full malignancy, the sequence of events leading to the acquisition of these phenotypes during tumor development is not clear. Conditional invasion in experimental systems indicates that a tumor may be invasive and metastatic when part of its population temporarily expresses the I+ phenotype. These experiments further stress the importance of the tumor-host ecosystem for the regulation of the I phenotypes. As distinct from some parasites, the invasive morphotype of vertebrate cells cannot be simply identified. Nevertheless, within the tumor-host ecosystem morphological correlates of the activities of invasive cells may be recognized. They reflect one or more of the I+ functions, namely: motility; loss of homotypic cell-cell adhesion; establishment of alternative cell-substrate and heterotypic cell-cell adhesion; breakdown of extracellular matrices. These functions are not exclusive for I+ tumor cells, and neither are the molecular markers investigated so far. Oncogene activation leads mainly to G+ expression, and in this way serves as a signal amplifier for the I and M phenotypes. Attractive candidate molecular markers of I phenotypes are: regulators of hydrolase activities; cell-cell adhesion molecules; cell surface receptors. From data presently available, we hypothesize that invasion depends upon the balance between an I+ and an I- pathway, with both pathways being sensitive to stimulation and inhibition.

Reciprocity relations for the mutual inductances between orthogonal axis windings in saturated salient-pole machines

Abstract: It has been demonstrated in the literature that saturation in electrical machines leads to a flux linkage between orthogonal axis windings. Hence this magnetic coupling should be included in the mathematical model for the (small-signal) dynamic analysis of saturated machines. While in smooth air-gap machines the resulting incremental mutual inductances must be equal because of symmetry, in salient-pole-type machines the assumed saturation models do not settle the question whether the reciprocity property, which is well-known for linear inductors, is still valid for these saturated mutual inductances. It is shown that the reciprocity property can be extended to these cases, provided the losses are either negligible or modeled separately, as is usual in machine analysis. As a corollary, a condition is derived for the self-inductances of the orthogonal windings so that the total magnetizing current can be used to characterize the saturation level in both axes. >

A new DFB-laser diode with reduced spatial hole burning

Abstract: An index coupled antireflection-coated distributed-feedback (DFB)-laser diode which theoretically exhibits a longitudinally uniform power density is proposed. The structure contains an amplitude modulated grating and is far more efficient in reducing spatial hole burning than multiphase-shift lasers. The laser can be expected to be single mode up to high power levels. It can be of interest when long lasers with a reduced linewidth and a flat FM response are to be used or as a laser with small modulation distortion in analog communication. >

Improved performance of AR-coated DFB lasers for the introduction of gain coupling

Abstract: Antireflection (AR)-coated distributed-feedback (DFB) lasers with both gain- and index-coupled distributed feedback are studied numerically with respect to mode losses, mode suppression, and spatial hole burning. The mode losses and the spatial hole burning decrease with increasing gain coupling, while the mode suppression increases. It is shown that a large improvement in performance can already be obtained for small fractions of gain coupling. >

Enterococcus columbae, a species from pigeon intestines

Abstract: Gram-positive cocci which dominate in the intestinal flora of domestic pigeons were found to constitute a new species of the genus Enterococcus . The strains were most closely related to Enterococcus cecorum , originally described as Streptococcus cecorum , a carboxyphilic species from chicken intestines, and to Enterococcus avium . The pigeon strains resemble E. cecorum and also many E. avium strains in their lack of group D antigen and in being more sensitive to NaCl than other enterococci. The type strain is strain STR 345 ( = NCIMB 13013).

Genotype diversity and selection in asexual brine shrimp (artemia).

Abstract: An obligately asexual population of Artemia parthenogenetica at Salin de Giraud, France consists of numerous clones that are genetically and ecologically divergent. The clones are distributed in a nonrandom fashion among eight ponds of highly variable environments. A total of 63 allozymically unique genotypes were identified, with significant differences in numerous fitness traits found among a sample subset of clones. The frequencies of four alleles, as well as the percentage of loci polymorphic, were significantly correlated with salinity. Genotypes face rapid selection along salinity gradients in the field and this selection is reproducible in the lab. mtDNA analysis suggests that obligate asexuality in this population is of monophyletic origin.

Baker's yeast as a potential substitute for live algae in aquaculture diets artemia as a case study

Abstract: In this study baker's yeast was evaluated as a substitute for live Dunuliella tertiolecta algae in the culture of the brine shrimp Artemia. Consumption of fresh baker's yeast resulted in poor growth and survival of brine shrimp. However, the nutritional value of the yeast sigaificantly improved after complete removal of the yeast cell wall by enzymatic treatment. Baker's yeast was also made digestible for Artemia by simple chemical treatment which did not reduce rigidity of the yeast cell. The external mannoprotein layer of the yeast cell wall is probably the major barrier to digestion by Artemia. Chemically treated baker's yeast offers promising possibilities as a substitute for algal feeds in aquaculture.

A double-blind single dose comparison of intramuscular ketorolac tromethamine and pethidine in the treatment of renal colic.

Abstract: The efficacy of a single dose of intramuscular ketorolac 10 mg or 90 mg was compared with pethidine 100 mg in a randomized double-blind study in 121 patients reporting at least moderate pain due to renal colic. Pain was assessed before drug administration, and then at 1 hour and 12 hours after the dose. Sedation was also assessed at these times, and additionally at the 12 hour assessment the time of the next analgesic dose was recorded. At 1 hour after dosing, pain scores had decreased in all groups; the largest decrease was seen in the ketorolac 90 mg group. The difference in the decrease was significant between the two ketorolac groups, but the differences between ketorolac and pethidine were not significant. Fewer patients in the ketorolac 90 mg group (17%) required a further dose of analgesic within 10 hours than in either the ketorolac 10 mg group (39%) or the pethidine 100 mg group (47%). The difference between ketorolac 90 mg and pethidine 100 mg was statistically significant. At both assessment times the proportion of patients with no sedation was higher in the two ketorolac groups than in the pethidine group. The overall incidence of adverse events was low with all drugs, notably so for the occurrence of vomiting after ketorolac. The results of the study show that intramuscular ketorolac is efficacious in the treatment of renal colic.

A comparative study of medetomidine/ketamine and xylazine/ketamine anaesthesia in dogs.

Abstract: The anaesthetic and physiological effects of a combination of 40 micrograms medetomidine with 2.5 ketamine, 5.0 or 7.5 mg/kg administered intramuscularly were compared with the effects of a combination of 1 mg/kg xylazine and 15 mg/kg ketamine. All the combinations rapidly induced an anaesthetic state that permitted endotracheal intubation, with the absence of the pedal reflex and with good muscle relaxation, and induced bradycardia that was less pronounced as the dose of ketamine was increased. All the combinations produced a decrease in respiratory rate. Increasing the dose of ketamine combined with medetomidine resulted in a very significant prolongation of the duration of anaesthesia, the duration of muscle relaxation and the arousal time. The duration of the anaesthetic effects of 40 micrograms/kg medetomidine with 5 mg/kg ketamine was comparable to that provided by the recommended xylazine/ketamine combination but the period of muscle relaxation was significantly longer. The recovery from medetomidine/ketamine took longer than recovery from xylazine/ketamine but there were fewer side effects.

Asymmetric alkylation of α-aryl substituted carbonyl compounds by means of chiral phase transfer catalysts. Applications for the synthesis of (+)-podocarp-8(14)-en-13-one and of (−)-Wy-16,225, a potent analgesic agent

Abstract: Asymmetric induction in the alkylation (alkyl halides and enones) of α-aryl substituted ketones, esters and lactones by means of CPTC has been evaluated. The catalysts used are the bromides of N-(p-trifluoromethyl) benzyl derivatives of cinchonine, cinchonidine, dihydrocinchonine and dihydrocinchonidine. The potential of the method is illustrated by the asymmetric synthesis of (+)-podocarp-8(14)-ene-13-one ( 13 ) and of (−)-Wy-16,225 ( 10 ), a bridged aminotetralin with potent analgesic properties.

Association of birdshot retinochoroidopathy and HLA-A29 antigen.

Abstract: In 1980 Ryan and Maumenee described a new clinical entity characterized by hypopigmented spots in a typical patterned distribution in association with vitritis and retinal vasculopathy leading to cystoid macular oedema and papilloedema. In a recent study of a large group of European patients (n=102) with birdshot retinochoroidopathy, the importance of the different clinical manifestations and their diagnostic value were assessed. Data on HLA-A29 typing were obtained in 49 patients with birdshot retinochoroidopathy. We could confirm the high association between HLA-A29 and this disease, as found by Nussenblatt in 1982. In 47 of these patients (95.5%) the HLA-A29 antigen was present. This association is presently the highest HLA class I disease association reported with a relative risk of 224.35.

Marking the rhizopseudomonas strain 7NSK2 with a Mu d(lac) element for ecological studies.

Abstract: The mini Mu element Mu dII1681, which contains the lac operon genes and a kanamycin resistance gene, was inserted in the chromosome of plant growth-beneficial Pseudomonas aeruginosa 7NSK2 to construct a marked strain (MPB1). In MPB1, beta-galactosidase is permanently expressed under the culture conditions used. The MPB1 strain could be recovered with an efficiency of about 100% from a sandy loam soil on 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside medium containing sebacic acid and kanamycin. The limit of detection is about 10 CFU/g of soil. A detailed comparison was made between the wild-type strain 7NSK2 and the Mu dII1681-containing MPB1 strain. The results showed that no genes essential for growth, siderophore production, survival in sterile and nonsterile conditions, plant growth stimulation, or root colonization had been damaged in the MPB1 strain, which means that MPB1 can reliably be used for ecological studies in soil. MPB1 survived well at 4 or 28 degrees C but died off relatively rapidly in air-dried soil or at subzero temperatures. In these conditions, however, the MPB1 strain did not completely disappear from the soil but survived at a very low level of about 100 CFU/g of soil for more than 3 months. This observation stresses the need for very sensitive counting methods for ecological studies and for the evaluation of released microorganisms. Maize was inoculated with MPB1 via seed inoculation or soil inoculation. Upon seed inoculation, only the upper root parts were effectively colonized, while soil inoculation resulted in a complete colonization of the root system.

Typhloplanid flatworms (Mesostoma and related genera): mechanisms of predation and evidence that they structure aquatic invertebrate communities.

Abstract: Mesostoma species and other typhloplanid flatworms are predators found in a wide variety of habitats. Laboratory observations of some Mesostoma spp found in shallow aquatic habitats (referred to as ‘littoral species’) have revealed a wide variety of prey killing mechanisms: 1) mucus trapping, 2) sit-and-wait predation, 3) releasing a toxin into the water, and 4) active searching. We review the existing literature on these mechanisms. We also describe for the first time the predatory behavior of a pelagic Mesostoma sp. found in Brazilian lakes.

Salmonella-TEK, a rapid screening method for Salmonella species in food.

Abstract: A micro-enzyme-linked immunosorbent assay (micro-ELISA) using the Salmonella-TEK screen kit was tested for the detection of Salmonella spp. in pure cultures as well as in 30 artificially contaminated food samples and in 45 naturally contaminated food samples. Different raw, fleshy foods and processed foods were used as test products. The artificially contaminated minced meat samples were preenriched in buffered peptone water, and after incubation, different selective enrichment broths were tested. The micro-ELISA optical density values after enrichment and isolation of the different broths were very analogous. The quickest method to detect Salmonella spp. in different foods is to enrich them with Salmosyst broth, which reduces the total analysis time to 31 h. The Salmonella-TEK kit for Salmonella spp. provides a promising test for the detection of Salmonella antigens in food even when they are present at a low concentration (1 to 5 CFU/25 g). The cross-reaction of the anti-Salmonella antibodies, especially to other gram-negative bacteria, is nil.