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  • 11
    Electronic Resource
    Electronic Resource
    Determination of composition and molecular weight of polyester urethanes by high resolution proton magnetic resonance spectrometry (1977)
    s.l. : American Chemical Society
    Analytical chemistry 49 (1977), S. 722-724 
    Details
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ac50014a014
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  • 12
    Electronic Resource
    Electronic Resource
    Applications of the evaluation map and transfer map theorems (1974)
    Springer
    Mathematische Annalen 211 (1974), S. 277-288 
    Details
    ISSN: 1432-1807
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01418225
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  • 13
    Electronic Resource
    Electronic Resource
    Comparative studies of SIMS and SNMS analyses during the build up of sputter equilibrium under oxygen and rare gas ion bombardment (1997)
    Springer
    Fresenius' journal of analytical chemistry 358 (1997), S. 47-50 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Sputtering of solid surfaces by using a focused ion beam is the basis for secondary ion mass spectrometry (SIMS) and sputtered neutral mass spectrometry (SNMS). The ion bombardment initiates not only redistribution of sample atoms but also massive changes in the surface and near surface composition of the bombarded area due to the sputter process and implantation of the primary ions. Changes in the matrix-composition affects the secondary ion yields and therefore a steady state (sputter equilibrium) has to be reached before SIMS data can give quantifiable results. SNMS is much less affected by those yield effects and therefore a combination of SIMS and SNMS can establish a basis for interpretation of SIMS data before the steady state is reached. In order to determine the effects of primary ion incorporation, we applied different primary ion species successively to generate different equilibria. An oxygen ion beam oxidizes the sample surface and by using a rare gas primary ion (PI) this oxide can be removed and analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050342
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  • 14
    Electronic Resource
    Electronic Resource
    Investigation of the analytical performance of gliding spark source mass spectrometry (GSSMS) for the trace analysis of nonconducting materials (1999)
    Springer
    Fresenius' journal of analytical chemistry 364 (1999), S. 763-767 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A radiofrequency (rf) spark discharge in vacuum developing across the surface of dielectrics – a so-called gliding spark – has been applied to the direct mass spectrometric trace analysis of nonconducting materials. The special configuration of the electrodes strengthened the electric field over the surface of a nonconducting sample and created optimum conditions for the sputtering and ionization of the sample material. Mass spectrometric investigations of the charge composition of atomic ion and molecular ion formation in radiofrequency gliding spark plasma showed a significant difference to that of the original rf spark discharge between two conducting electrodes. The analytical figures of merit (reproducibility, relative sensitivity factors and detection limits of chemical elements) of gliding spark source mass spectrometry have been studied by using the glass standard reference materials NIST SRM 610 and 611 for the determination of trace elements in glass matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051429
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  • 15
    Electronic Resource
    Electronic Resource
    The influence of an epitaxial CoSi2 layer on diffusion of B and Sb in underlying Si during oxidation (1999)
    Springer
    Fresenius' journal of analytical chemistry 365 (1999), S. 282-285 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effect of an epitaxial 20 nm thick CoSi2 layer on the diffusion of B and Sb in Si is investigated during oxidation and is compared to thermal diffusion in Si. B and Sb doping superlattices (DSLs) were grown by molecular beam epitaxy (MBE). They consisted of six spikes with peak concentrations of about 1018 cm–3 (B) and about 1019 cm–3 (Sb) and peak centres spaced 100 nm apart. The shallowest spike was capped with 100 nm of Si followed by 20 nm of CoSi2 grown by molecular beam allotaxy (MBA). Oxidation in dry O2 and annealing in pure N2 were performed at temperatures of 800 °C to 1200 °C. Concentration depth profiles were measured by secondary ion mass spectrometry (SIMS). The results showed that the diffusion of B and Sb in Si was markedly different for specimens with or without a CoSi2 layer. Oxidation enhanced diffusion (OED) of B and oxidation retarded diffusion (ORD) of Sb was observed for specimens without a CoSi2 layer. The effect of CoSi2 layer was a strong retardation of B diffusion and an enhancement of Sb diffusion. The B diffusivity was retarded by a factor of 2–10 as compared to the thermal diffusivity and by a factor of 20–100 as compared to the corresponding diffusivity for oxidation of Si without a CoSi2 layer. Sb diffusivity was enhanced by a factor of 2 with respect to thermal diffusivity and by about a factor of 5 as compared to the case without a CoSi2 layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160051489
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  • 16
    Electronic Resource
    Electronic Resource
    Multielemental analysis in small amounts of environmental reference materials with inductively coupled plasma mass spectrometry (2000)
    Springer
    Fresenius' journal of analytical chemistry 367 (2000), S. 407-413 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The lowest possible sample weight for performing multielemental trace element analysis on environmental and biological samples by ICP-MS has been investigated. The certified reference materials Bovine Liver NIST SRM 1577b, Human Hair NCS DC 73347 and Oriental Tobacco Leaves CTA-OTL-1 were applied at sample weights (1, 5, 20 and 50 mg aliquots, n = 10) which were significantly lower than those recommended with most recoveries in the range of 95–110%. Samples were digested in a mixture of nitric acid, hydrogen peroxide and hydrogen fluoride by closed-vessel microwave digestion. Multielemental analysis was performed with an optimized ICP-QMS method. Aqueous standard solutions were applied for external calibration with rhodium as the internal standard element. The detection limits varied between 0.02–¶0.38 μg/g for Li, Na, Cr, Mn, Ni, Cu, Zn, Sr, Cd, Ba and Pb, and up to 1.92 μg/g for Mg, Al, Ca, Fe and Ni. Digested human plasma samples were spiked with multielemental solution (0.5–10 μg/L) to test the analytical method and the recoveries were 95–105% for most analytes. Our results show that in the case of homogeneous SRMs it is possible to use them in very low amounts (1–5 mg) for method development and quality control.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000378
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  • 17
    Electronic Resource
    Electronic Resource
    Precise and accurate isotope ratio measurements by ICP-MS (2000)
    Springer
    Fresenius' journal of analytical chemistry 368 (2000), S. 23-30 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The precise and accurate determination of isotope ratios by inductively coupled plasma mass spectrometry (ICP-MS) and laser ablation ICP-MS (LA-ICP-MS) is important for quite different application fields (e.g. for isotope ratio measurements of stable isotopes in nature, especially for the investigation of isotope variation in nature or age dating, for determining isotope ratios of radiogenic elements in the nuclear industry, quality assurance of fuel material, for reprocessing plants, nuclear material accounting and radioactive waste control, for tracer experiments using stable isotopes or long-lived radionuclides in biological or medical studies). Thermal ionization mass spectrometry (TIMS), which used to be the dominant analytical technique for precise isotope ratio measurements, is being increasingly replaced for isotope ratio measurements by ICP-MS due to its excellent sensitivity, precision and good accuracy. Instrumental progress in ICP-MS was achieved by the introduction of the collision cell interface in order to dissociate many disturbing argon-based molecular ions, thermalize the ions and neutralize the disturbing argon ions of plasma gas (Ar+). The application of the collision cell in ICP-QMS results in a higher ion transmission, improved sensitivity and better precision of isotope ratio measurements compared to quadrupole ICP-MS without the collision cell [e.g., for 235U/238U ∼ 1 (10 μg L–1 uranium) 0.07% relative standard deviation (RSD) vs. 0.2% RSD in short-term measurements (n = 5)]. A significant instrumental improvement for ICP-MS is the multicollector device (MC-ICP-MS) in order to obtain a better precision of isotope ratio measurements (with a precision of up to 0.002%, RSD). CE- and HPLC-ICP-MS are used for the separation of isobaric interferences of long-lived radionuclides and stable isotopes by determination of spallation nuclide abundances in an irradiated tantalum target.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160000481
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  • 18
    Electronic Resource
    Electronic Resource
    Analysis, classification, and coding of multielectrode spike trains with hidden Markov models (1994)
    Springer
    Biological cybernetics 71 (1994), S. 359-373 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. It is shown that hidden Markov models (HMMs) are a powerful tool in the analysis of multielectrode data. This is demonstrated for a 30-electrode measurement of neuronal spike activity in the monkey’s visual cortex during the application of different visual stimuli. HMMs with optimized parameters code the information contained in the spatiotemporal discharge patterns as a probabilistic function of a Markov process and thus provide abstract dynamical models of the pattern-generating process. We compare HMMs obtained from vector-quantized data with models in which parametrized output processes such as multivariate Poisson or binomial distributions are assumed. In the latter cases the visual stimuli are recognized at rates of more than 90% from the neuronal spike patterns. An analysis of the models obtained reveals important aspects of the coding of information in the brain. For example, we identify relevant time scales and characterize the degree and nature of the spatiotemporal variations on these scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004220050097
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  • 19
    Electronic Resource
    Electronic Resource
    Analysis, classification, and coding of multielectrode spike trains with hidden Markov models (1994)
    Springer
    Biological cybernetics 71 (1994), S. 359-373 
    Details
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract It is shown that hidden Markov models (HMMs) are a powerful tool in the analysis of multielectrode data. This is demonstrated for a 30-electrode measurement of neuronal spike activity in the monkey's visual cortex during the application of different visual stimuli. HMMs with optimized parameters code the information contained in the spatiotemporal discharge patterns as a probabilistic function of a Markov process and thus provide abstract dynamical models of the pattern-generating process. We compare HMMs obtained from vector-quantized data with models in which parametrized output processes such as multivariate Poisson or binomial distributions are assumed. In the latter cases the visual stimuli are recognized at rates of more than 90% from the neuronal spike patterns. An analysis of the models obtained reveals important aspects of the coding of information in the brain. For example, we identify relevant time scales and characterize the degree and nature of the spatiotemporal variations on these scales.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00239623
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  • 20
    Electronic Resource
    Electronic Resource
    Glycogen metabolism in resting and growing cells of Saccharomyces carlsbergensis (1979)
    Springer
    Archives of microbiology 123 (1979), S. 143-149 
    Details
    ISSN: 1432-072X
    Keywords: Saccharomyces carlsbergensis ; Yeast glycogen ; Glycogen metabolism ; Metabolic control ; Regulation ; Yeast-phosphorylase ; Yeast glycogen synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Saccharomyces carlsbergensis cells, growing under carbohydrate or nitrogen limitation, initially deplete their glycogen, which is resynthesized only during the late exponential phase. Cells, harvested in the carly exponential phase, are even unable to synthesize glycogen in glucose-containing phosphate buffer. This is in contrast to cells from the stationary phase which rapidly synthesize glycogen under the same conditions. Lack of O2 slows down glycogen synthesis. Contrary to cells suspended in complete medium, addition of ammonia alone to nitrogen free-media induced neither breakdown of glycogen, nor complete cessation of glycogen synthesis. Ammonia slowed down glycogen synthesis (both aerobic and anaerobic), only, in cells grown either under carbohydrate or under nitrogen limitation. Glycogen synthesis was observed 1 min after addition of glucose to a starved cell suspension in phosphate buffer. Removal of the sugar from the buffer resulted in an instantanous decrease of the glycogen level in the cells. The results indicate that glycogen-metabolism is regulated by a variety of endogenous and environmental factors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00446813
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