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  • Springer  (82)
  • 1990-1994  (82)
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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Mathematical programming 55 (1992), S. 17-33 
    ISSN: 1436-4646
    Keywords: Parallel computing ; traveling salesman problem ; branch and bound
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract A parallel branch and bound algorithm that solves the asymmetric traveling salesman problem to optimality is described. The algorithm uses an assignment problem based lower bounding technique, subtour elimination branching rules, and a subtour patching algorithm as an upper bounding procedure. The algorithm is organized around a data flow framework for parallel branch and bound. The algorithm begins by converting the cost matrix to a sparser version in such a fashion as to retain the optimality of the final solution. Computational results are presented for three different classes of problem instances: (1) matrix elements drawn from a uniform distribution of integers for instances of size 250 to 10 000 cities, (2) instances of size 250 to 1000 cities that concentrate small elements in the upper left portion of the cost matrix, and (3) instances of size 300 to 3000 cities that are designed to confound neighborhood search heuristics.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The production of the neutral strange particlesK 0, Λ and $$\bar \Lambda $$ invp and $$\bar vp$$ charged current interactions is studied in an experiment with the Big European Bubble Chamber. Mean multiplicities are measured as a function of the event variablesE v,W 2 andQ 2 and of the hadron variablesx F,z andp T 2 .K *± (892) and∑ *± (1385) signals are observed, whereas there is no evidence for∑ *- (1385) production invp scattering. Forward, backward and total mean multiplicities are found to compare well with the predictions of an empirical model for deep-inelastic reactions in the case of the strange mesonsK 0 andK *± (892) but less so for the strange baryons Λ, $$\bar \Lambda $$ and∑ *± (1385). The strange baryon multiplicities are used to obtain the decuplet to octet baryon production ratio and to assess the probabilities of auu orud system to break up.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Evidence is presented for diffractive production of ρ-mesons and of ρπ-systems invp and $$\bar \nu p$$ chargedcurrent interactions. In the (anti-)neutrino energy range 10 GeV〈E v 〈60 GeV the cross sections for diffractive ρ and diffractive ρπ production are found to be (0.64±0.14 (stat.)±0.08 (syst.))% and (0.28±0.08 (stat.)±0.04 (syst.))% of the charged-current cross section. The diffractive ρπ signal is consistent with being entirely due to diffractivea 1 production. However, the data cannot distinguish between diffractivea 1 and diffractive nonresonant ρπ production. The experimental distributions ofW, Q 2,x Bj andy Bj for diffractive ρ and ρπ events are consistent with model predictions.
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  • 4
    ISSN: 1572-817X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Picosecond excite-probe studies are performed on a single quantum well waveguide modulator giving a direct measure of the escape of photogenerated carriers from a quantum well. Both the effects of exciton saturation and external field screening are observed in the transient transmission change. The results are consistent with the escape of carriers by thermionic emission.
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  • 5
    ISSN: 1572-8927
    Keywords: Zeta potential ; video enhanced microscopy ; didodecyldimethylammonium bromide and acetate ; ditetradecyldimethylammonium bromide and acetate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The zeta potential of 2 mM solutions of didodecyldimethylammonium and ditetradecyldimethylammonium surfactants containing a mixture of acetate and bromide are reported. The measuremtns were made using new electrophoretic cells which can be used with a video enhanced microscope. This permits the simultaneous visualization and zeta potential characterization of vesicles and microtobule surfactant solutions. With increasing acetate molar fraction, the zeta potential increases. These results are interpreted in terms of the charge density at the shear plane of the aggregate interface.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Archives of environmental contamination and toxicology 19 (1990), S. 40-48 
    ISSN: 1432-0703
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Notes: Abstract The acute toxicity (96-hr LC50) of un-ionized ammonia to mysids (Mysidopsis bahia) and larval inland silversides (Menidia beryllina) was influenced by pH and salinity in a species specific manner. With mysids, NH3 was most toxic at pH 7.0 and less toxic at pH 8.0 and 9.0. In contrast, NH3 toxicity to inland silversides was greatest at pH 7.0 and 9.0 and lowest at pH 8.0. A drop in salinity from 31 g/kg to 11 g/kg uniformly increased toxicity to mysids over this pH range. In contrast, in silversides at 11 g/kg, NH3 toxicity was less at pH 7.0, greater at pH 8, and slightly less at pH 9, relative to the toxicity at 31 g/kg. Temperature had no significant effect on the acute toxicity of un-ionized ammonia with acclimated mysids tested at 18, 25 and 32.5°C, but did have a small effect with acclimated larval sheepshead minnows (Cyprinodon variegatus) tested at 13, 25 and 32.5°C. The chronic toxicity value (the geometric mean of the highest no-effect concentration and lowest effect concentration) at pH 8.0, 25°C and 31 g/kg salinity is 0.061 mg NH3/L for inland silversides and 0.232 mg NH3/L for mysids; the acute: chronic ratio is 21.3 and 7.2, respectively.
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  • 7
    ISSN: 1420-9071
    Keywords: Insecta ; Scolytidae ; phenylalanine ; aromatics ; axenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary The pine engraver,Ips pini (Say), was found to produce toluene and 2-phenylethanol when boring into fresh pine logs. The hypotheses that phenylalanine is a precursor of these compounds and that beetles without their symbiotic microorganisms can perform these conversions were confirmed by treating wild and axencially-reared males and females topically with L-phenyl-d5-alanine. Extracts of these beetles invariably contained deuterio-toluene, and extracts of males contained deuterio-2-phenylethanol as well.
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  • 8
    ISSN: 1432-1203
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Ribosomal gene activity and levels of DNA methylation were investigated by cytochemical and immunological methods in the nucleolar organizer regions (NORs) of individually recognised acrocentric chromosomes. Mendelian inheritance of ribosomal gene activity in a three generation family was demonstrated, together with consistent behaviour of individual gene clusters in different carriers, even when environmental conditions were changed. For most chromosomes, an inverse relationship between gene activity and the level of DNA methylation was observed. Exceptions were the two chromosomes 15 and chromosomes 13cp and 22p, all being strongly chromomycin-A3-positive in their short arms. These chromosomes bound to anti-5-MeC antibodies with differential frequencies in the different carriers. The possibility of involvement of repetitive GC-rich DNA in this behaviour is discussed.
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  • 9
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A plasmid clone containing highly repeated DNA sequence fromAcropora formosa was used to probe slot blots of genomic DNA and Southern blots of Taq I digests from other Acroporidae. Homologous repeated DNA sequences were detected in 12 otherAcropora species, but not in three other species of Acroporidae (Astreopora sp.,Montipora digitata andM. aequituberculata). Slot-blot experiments indicated that the repeated sequences inAcropora latistella, A. tenuis, A. longicyathus andA. nobilis were distantly homologous with the clonedA. formosa repeat, whereas those inA. pulchra, A. millepora, A. valida, A. hyacinthus andA. microphthalma were highly homologous with this probe and those inA. digitifera were intermediate. Relatedness of the highhomology group toA. formosa was assessed by comparison of Taq I-digestion patterns. The predominant repeats inA. pulchra andA. hyacinthus had two Taq I sites per repeat unit (as didA. formosa), whereas repeats inA. digitifera, A. valida andA. microphthalma had one Taq I site per repeat; the pattern given byA. millepora implied that its highly homologous repeat units contained either one or two Taq I sites. Within the high-homology group, decreasing number of Taq I sites implies increasing taxonomic distance fromA. formosa. The relatedness series implied by these data differs from that based on morphological criteria.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Marine biology 104 (1990), S. 489-492 
    ISSN: 1432-1793
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A method is described for isolating high molecular weight DNA from somatic tissue of soft corals. The method avoids problems associated with the presence of nucleases, pigments and other secondary metabolites in soft corals. Tissue is frozen in liquid nitrogen, pulverized with a pestle and mortar, and the powder extracted with buffered sodium dodecyl sulphate at 4°C in the presence of phenol/chloroform. This technique has been applied toAlcyonium, Sinularia, Sarcophyton andLobophytum species. Repeated sequences have been cloned fromAlcyonium sp., and used to probe slot-blots of genomic DNA and Southern blots of restriction digests. Homologous repeated sequences were detected in threeAlcyonium sp., but not in threeSinularia sp., despite these genera being closely related.
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