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  • 1990-1994  (15)
  • 1
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 351-360 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: We describe an open one-dimensional reaction–diffusion system, the Couette reactor, which provides a permanent feed of fresh reactants and simultaneously preserves the diffusion process. Different compositions of variants of chlorite–iodide reactions are fed at both ends, but there is no net axial mass flux in the reactor. The effective diffusion coefficient is the same for all chemical species, and can easily be varied from 10−2 to 1 cm2/s, permitting large size reaction–diffusion structures. Spatial bistability was obtained with the minimal chlorite–iodide reaction in symmetric feed conditions. A larger variety of patterns was observed with the chlorite–iodide–malonic acid reaction and asymmetric feed conditions: a single steady chemical front, two steady fronts, three steady fronts, a single oscillating front, two oscillating fronts, three oscillating fronts, simple colliding fronts, and a bursting pattern. The patterns were studied as a function of several parameters to determine the sequences of bifurcations. Our observations demonstrate the existence of steady chemical patterns other than Turing patterns.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 6848-6855 
    ISSN: 1089-7690
    Quelle: AIP Digital Archive
    Thema: Physik , Chemie und Pharmazie
    Notizen: Lithium oxide clusters Li2n+pOn+ are generated by combining reactive nucleation in a gas aggregation source and photoionization. Unimolecular dissociation of mass selected cluster ions provides evidence that the excess of metal atoms evaporates first leading to the most stable species Li+(Li2O)n, which then evaporate Li2O molecules. The evaporation rate behavior as a function of cluster size demonstrates that Li+(Li2O)n can be prepared with different temperatures. It is discussed how metal evaporation from metal-rich oxide clusters leads to oxygen saturated clusters with a lower temperature. An estimate of the dissociation energies of Li+(Li2O)n are given for small sizes n≤10 from photoevaporation experiment.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 1212-1214 
    ISSN: 1077-3118
    Quelle: AIP Digital Archive
    Thema: Physik
    Notizen: The crucial problem in controlling and filtering the size of free neutral clusters generated by a cluster source is studied in the particular case of the Sattler source type. The present work shows that a velocity selector can be used to control the size of neutral clusters produced in the low-energy cluster beam deposition system. This velocity selector is also used to measure the kinetic energy of free Bi clusters. The experimental results obtained for Bi clusters are compared with previous theoretical predictions.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 4
    ISSN: 1432-1203
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Medizin
    Notizen: Abstract Polynesians have lower heterozygosities at minisatellite VNTR (Variable Number of Tandem Repeat) loci than have Melanesians; this has been taken as evidence of population-size bottlenecks during the colonisation of Polynesia. We have analysed the allelic distribution of several minisatellite loci in the population of Rapa, a Polynesian island that is known to have undergone a demographic reduction of approximately 95% since first contact with European explorers 200 years ago, leaving a surviving population of 120. We found that the minisatellite diversity of this population does not differ significantly from that of other Polynesian populations, and appears consistent with the neutral expectation of diversity assuming the infinite alleles model. This suggests that the demographic crisis that Rapa underwent did not perturb the allele distribution to the extent that the tests used here could detect. Thus we cannot say that a demographic change of this magnitude constitutes a genetic bottleneck detectable at these loci. The reduced diversity seen in Polynesia must therefore be explained either by more severe bottlenecks as might be expected during colonisation, or else by other causes.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Fresenius' Zeitschrift für analytische Chemie 346 (1993), S. 69-74 
    ISSN: 1618-2650
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The initial stages of oxidation of clean (110), (100), and (111) oriented β-NiAl single crystals, with and without Pt doping (50 nm), were followed at 973 K using LEED and AES. Upon oxidation, Al2O3 is selectively formed. On NiAl (110) a complex surface structure is observed which according to Jäger et al. [13] is a duplex oxide structure similar to α- or γ-Al2O3. On the (100) face, submicroscopic facetting occurs during oxidation. For the (111) oriented sample the hexagonal structure remains and only an increased background intensity for the LEED pattern is observed for the oxidized surface. After Pt doping, the phenomena observed for the Pt-free sample are not significantly changed. However the following differences exist: 1. the formation of the Al2O3 oxide is more difficult for the (110) and (111) samples but Pt doping facilitates facetting and oxide formation on the (100) oriented sample; 2. sputtering of the oxide layers on Pt-doped samples is retarded in all cases, a very stable and dense oxide seems to be formed which adheres well; 3. Pt seems to hinder the Al diffusion to the unoxidized surface of the samples.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 6
    ISSN: 1573-7284
    Schlagwort(e): HTLV-I ; Seroprevalence ; Pacific Islands
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract Different population groups of French Polynesia, Cook Islands and Fiji were screened for Human T-Lymphotropic Virus type I (HTLV-I) antibodies. Among 1487 individuals sampled in French Polynesia, twelve were considered Western Blot (WB) indeterminate and one was considered WB-positive for HTLV-I infection. This positive subject originated from France and was a blood donor. Out of 196 Polynesians of the Cook Islands, one was WB-indeterminate. Among populations sampled in Fiji, one of 222 Melanesians was found WB-indeterminate and one of 211 Indians was WB-indeterminate.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 7
    ISSN: 1573-7284
    Schlagwort(e): Dengue surveillance ; French Polynesia ; Mathematical analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Medizin
    Notizen: Abstract The excess number of weekly laboratory requests for confirmation of dengue diagnosis over the expected number of requests forecasted by the modified Serfling method is proposed for the surveillance of dengue in French Polynesia, in addition to conventional methods. Retrospective analysis of the seasonal curves of dengue activity related to the number of laboratory requests is described for the years 1982–1987 where dengue type 4 was the only active flavivirus at the time when the forecast was initiated. By using past epidemic data, the probability of,failing to recognize an increase in excess of requests as possibly epidemic was of 13.2% and 5.8%, respectively, when the criterion for epidemic increase was set respectively at 2 and 3 successive weeks during which the epidemic threshold is exceeded. A weekly surveillance was set up prospectively for 1988 using these criteria.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Plant cell, tissue and organ culture 28 (1992), S. 225-227 
    ISSN: 1573-5044
    Schlagwort(e): legume ; nodal explants
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Biotechnology techniques 7 (1993), S. 739-744 
    ISSN: 1573-6784
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Werkstoffwissenschaften, Fertigungsverfahren, Fertigung
    Notizen: Summary Protocols were developed for the immobilisation of Rhizopus arrhizus biomass using alginate, polyacrylamide, epoxy resin and polyvinylformal materials and the resulting biosorbents were tested for the removal of cadmium from solution. Polyvinyl formal immobilisation produced the optimal biosorbent with cell loadings of up to 80% and metal adsorption capacities of 84% of that of free biomass.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    The European physical journal 28 (1993), S. 67-72 
    ISSN: 1434-6079
    Schlagwort(e): 36.40.+d ; 71.28.+d
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Rare earth clusters of europium, thullium and ytterbium were generated by gas aggregation technique and probed by photoionization mass spectrometry. Their relative intensities in mass spectra have shown that their stabilities are governed by compact geometrical structures. The addition of oxygen gas in the nucleation region was used to produce the reactive nucleation. Several stages of oxidation were observed as a function of oxygen pressure up to saturation. For the maximal degree of oxidation the observed oxide ion compositions enable one to follow the valence of metal atom in its oxide as cluster size increases. This exhibits a divalent to trivalent valence change with cluster size. Moreover it emerges from the data that the divalent to trivalent transition for Tm, Yb, and Eu occurs at different size values.
    Materialart: Digitale Medien
    Standort Signatur Einschränkungen Verfügbarkeit
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