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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Stochastic environmental research and risk assessment 3 (1989), S. 97-110 
    ISSN: 1436-3259
    Keywords: ARMA processes ; fractionally differencedARMA processes ; long memory ; spectral density ; maximum likelihood estimates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract A class of regression type estimators of the parameterd in a fractionally differencedARMA (p, q) process is introduced. This class is an extension of the estimator considered by Geweke and Porter-Hudak. In a simulation study, we compared three estimators from this class together with two approximate maximum likelihood estimators which are based on two separate approximations to the likelihood. One approximation ignores the determinant term in the likelihood and the other includes a compensating factor for the determinant. When the determinant term is included, the estimate tends to be much less biased and is in general superior to the other estimate. The approximate maximum likelihood estimator out performed, by a large margin, the regression type estimators for pureARIMA (0,d,0) processes. However, forARIMA (1,d,1) processes, a regression type estimator turned out to be the best for realizations of length 400 in 3 out of the 5 cases we tried.
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  • 2
    ISSN: 1435-604X
    Keywords: Mathematical model ; Laser surgery ; Optical fibres ; Tumours ; Thermal diffusion ; Multiple fibres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Physics , Technology
    Notes: Abstract A mathematical model is employed to discuss the region treated by local hyperthermia, when the source of heat is a laser whose energy is directed into the treatment region through four optical fibres ending at the corners of a square. If treatment is over a period that is substantially longer than the time for the temperature distribution to reach equilibrium, a steady state model using four point sources can be employed to obtain a general idea of the temperatures reached and the region treated for different power levels and sizes of square. For shorter times, and for more accurate estimation of the regions treated, numerical calculation on a computer is essential. The details of the calculation depend on individual cases, but we demonstrate here that such computations are possible, and present a series of typical results. A comparison is made with the results of a series of experiments on canine liver, showing that it is possible to obtain good qualitative and numerical agreement.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Catalysis letters 2 (1989), S. 1-7 
    ISSN: 1572-879X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract X-ray photoemission was used to investigate the initial stages of rhenium disulfide oxidation and the altered reactivity and core-level electronic structure of defect sites produced by argon ion sputtering of single crystal and polycrystalline ReS2-basal plane surfaces. Oxidation of polycrystalline-ReS2 with O2 at 100–300 ° C produced a mixture of surface oxides containing rhenium in the + 4 and + 7 oxidation states. Oxidation was facilitated by the presence of low coordination defect sites and was reversible upon resulfidization with H2S/H2 at 300 °C.
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 43 (1989), S. 370-377 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Theory of computing systems 22 (1989), S. 323-346 
    ISSN: 1433-0490
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract The predictive least squares criterion for order estimation is combined with an adaptive control strategy minimizing a quadratic cost and applied to multidimensional ARX systems. It is then shown that this combination enables us to estimate, recursively and in a strongly consistent way, both the order and the coefficients of the controlled system, while achieving asymptotically optimal cost.
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  • 6
    ISSN: 1432-2056
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Benthic microbial communities of the Arthur Harbor area were described by analysis of their cell membrane phospholipid ester-linked fatty acids (PELFA) and metabolic rates. Analysis revealed a biomass averaging 6 nM (phospholipid) or 3.5×108 cells per gram dry weight (gdw) of sediment for the four sites. Only slight biomass differences were detected between the four peninsula sites. All Arthur Harbor sites were determined to have a biomass similar to the lowest amount reported for a previously described McMurdo Sound site at New Harbor. Community structure based on signature phospholipids indicated only slight differences between the four peninsula sites with greater relative amounts of diatom marker lipids at a deeper site. Bacterial biomarker lipids were also determined in relatively equal proportions for the four Arthur Harbor sites with only one site indicating a somewhat decreased proportion. Metabolic rates of sodium [14C]-acetate and methyl [3H]-thymidine incorporation into lipid and bacterial DNA respectively also indicated only slight relative differences in microbial communities of Arthur Harbor study sites. Lipid metabolism (14C-acetate) ranged between 6 and 12 (x104) DPM/g/h for the four sites with 8 being the average. Bacterial (excluding sulfate-reducing bacteria (SRB)) cell divisions per g per h indicated increased rates at a deeper site with 14×105, compared to the average (5×105) for the three remaining sites. Average estimated total bacterial (excluding SRB's) community turnover was on the order of 0.6%/h for the four sites. Metabolic rate comparisons of Arthur Harbor with those of previously determined McMurdo Sound indicated a somewhat increased lipid metabolism and an order of magnitude greater bacterial cell division rate at Arthur Harbor.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of paleolimnology 2 (1989), S. 263-283 
    ISSN: 1573-0417
    Keywords: paleolimnology ; lake ; lake sediment ; Quaternary ; limnology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences
    Notes: Abstract I describe Quaternary paleolimnology on the basis of a review of abstracts published for meetings of: (1) American Society of Limnology and Oceanography (ASLO), 10 meetings since 1980; (2) International Association of Theoretical and Applied Limnology (SIL), 4 since 1977, (3) International Symposia on Paleolimnology (ISP), 4 since 1967, and (4) International Union for Quaternary Research (INQUA), 5 since 1969. A total of 9538 abstracts were scanned to find 678 with paleolimnological content. A data base constructed from the 678 contains frequencies of coverage of techniques, parameters, themes, interpretive aspects, and character and geography of study sites. These data indicate that Quaternary paleolimnology has been a diverse science dealing with many of the same aspects of lakes as neolimnology but with a longer time perspective. Most frequently studied paleolimnological characteristics were trophic state, water chemistry (particularly salinity, pH, alkalinity (ANC), micronutrients and oxygen), water levels, lake morphology, and mixis and other hydrology. Lake biological parameters that received greatest attention were diatoms, pigments, Cladocera, Mallomonadaceae, non-siliceous algae, Ostracoda, and Mollusca. Most often considered to influence these characteristics and parameters were climate; catchment vegetation, soil, geology, land use and erosion; water chemistry; aerial and non aerial pollutants; sedimentation; and tectonism. Most frequent chronologic sequences were (1) late-glacial to present, and (2) modern (ca. 0.3 ka to present). Lakes in moist temperate and boreal regions were most heavily studied. Of the four series, INQUA covered the longest time scales (to late Tertiary), but emphasized the last 100 ka. INQUA stressed outside-lake geomorphology (as it relates to lake) and lake morphology, physical forcing functions (e.g., climate and tectonism), hydrologic factors including water levels, paleosalinities, and reconstruction of paleoclimates. In contrast, SIL and ASLO rarely covered pre-15 ka. Most SIL and ASLO abstracts dealt with only the most recent ∼ 0.3 ka. Of strong interest to SIL and ASLO were the effects of catchment vegetation and soils, land uses, and pollutants (e.g., acid deposition) on past lake chemistry, biology, and trophic conditions. To infer these conditions from sediment contents, frequent use was made of modern analogues and, starting in the 1970's of microfossil (mostly diatoms) transfer functions based on calibration data sets. In several respects, ISP subject coverage and approaches were intermediate between those of INQUA and SIL/ASLO. Major improvements in paleolimnology have occurred since the 1960's, particularly in the areas of chronology and use of multivariate statistical techniques for paleoenvironmental inference based on microfossils. I conclude this paper with several suggestions for further advancement of the science.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Immunogenetics 29 (1989), S. 355-357 
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-1211
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The purpose of this work was to study the genetic basis of histocompatibility antigens encoded by the mouse minor histocompatibility (H) locusH-3. Both class I major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTL) and class II MHC-restricted helper T cells (TH) specific for antigens encoded by genes within theH-3 locus were isolated and analyzed. Typing a number of mouse strains for expression of antigens recognized by these TH and CTL suggested that there was a different strain distribution pattern of expression of the antigens recognized by TH compared with those recognized by CTL. Separation of the genes whose products stimulate TH from those whose products stimulate CTL was suggested by: (1) analysis of the strain B10.FS(92NX)/Grf that has undergone recombination within theH-3 region; (2) genetic segregation studies of (B10.UW-H-3 b/Sn×C57BL/10Sn)F2 mice; and (3) F1 complementation studies in which CTL specific for products of the TH-defined gene(s) could not be detected, even in the absence of immune responses to products of the CTL-defined genes. Taken together, these data suggest that in addition to two genes (B2m andCd-1) within theH-3 region whose products typically stimulate class I MHC-restricted CTL, there is at least one additional gene whose product selectively stimulates class II MHC-restricted TH. This new gene is located telomeric from the CTL-defined genes and between the lociwe andun on chromosome 2. These data demonstrate a novel degree of complexity of theH-3 “locus” and suggest selective presentation of minor H gene products in the context of class I or class II MHC proteins.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Oecologia 80 (1989), S. 309-320 
    ISSN: 1432-1939
    Keywords: Chaparral ; Seedling survival ; Root depth ; Rhus ; Ceanothus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In a mature, even aged stand of mixed chaparral, Rhus laurina (facultative resprouter) had consistently higher water potentials and deeper roots than Ceanothus spinosus (facultative resprouter) and Ceanothus megacarpus (obligate seeder). For two years following a wildfire, the same stand of chaparral had resprouts with higher survivorships, predawn water potentials, stomatal conductances, photosynthetic rates and shoot elongation rates than seedlings. Supplemental irrigation of seedlings during summer months removed differences between resprouts and seedlings suggesting that the cause of such differences was limited water availability to the shoot tissues of seedlings. After two years of postfire regrowth, mean seedling survivorship for the obligate seeder (C. megacarpus) was 42%, whereas seedling survivorship for facultative resprouters was only 18% (C. spinosus) and 0.01% (R. laurina). Our results are consistent with the hypothesis that lack of resprouting ability among obligate seeders is offset by an enhanced ability to establish seedlings after wildfire, allowing obligate seeders to maintain themselves in mixed populations through many fire cycles.
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