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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4438-4443 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have developed a novel grain-boundary diffusion model using the transmission-line matrix method. In conjunction with a two-dimensional Monte Carlo thin-film growth simulator, this model can be employed for the analysis of impurity diffusion in thin-film diffusion barriers with realistic microstructures. In the model, the impurity at the upper surface of the barrier layer may diffuse through rapid and irregularly shaped grain-boundary diffusion paths to reach the bottom surface. Calculations of the impurity concentration and out-diffusion flux as a function of elapsed diffusion time and position enable the evaluation of the effectiveness of the barrier layer at a microstructure level. Consequently, the diffusion process is depicted with less assumptions and more precisely than previously available approaches. This paper details the grain-boundary diffusion modeling method outlined above, with the emphasis on the treatment of various boundary conditions. A representative application to titanium nitride (TiN) thin-film diffusion barriers is also demonstrated, as befits the high level of interest in this particular material for very large scale integrated devices. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4948-4951 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The one-dimensional electromigration boundary value problem under pulsed dc conditions is numerically investigated by utilizing the transmission-line matrix modeling method. A perfectly blocking boundary, where void formation and failure occur, is assumed at one end of an interconnection line. At the other end, two physically plausible boundary conditions are considered. From the design-rule point of view, an approach is proposed to convert conveniently the pulsed stress into an equivalent dc stress that would produce electromigration damage at a similar rate. Based on the fundamental diffusion-drift model, we show that the vacancy buildup behavior under a pulsed dc stress γp can be described accurately by the dc stress γdc scaled according to the duty factor r of the current pulse, namely, γdc=rγp. This study also represents a theoretical confirmation for the (jr)−2 dependence of the pulsed electromigration failure (where j is the current density), which has been observed in a number of experimental studies. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 74 (1993), S. 7173-7180 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The use of the transmission-line-matrix (TLM) method for analyzing the grain boundary and interfacial diffusion problems in thin films is demonstrated. The method employed has a variable mesh and automatic time-stepping capability, and is highly versatile in treating complex structures and incorporating various boundary conditions. The present model takes account of separate diffusion coefficients in grain boundaries, grains, interfaces, and the substrate. The combined diffusion problems are solved as a function of position and time, and the concentration distributions are presented as clearly visible isometric projections and contour plots. The results are compared with those of semi-infinite samples (Whipple's analysis [Philos. Mag. 45, 1225 (1954)]) and idealized thin-film systems (Gilmer and Farrell's analysis [J. Appl. Phys. 47, 3792 (1976)]), with the emphasis being placed on the differences due to the treatment of concentration flux along the interface between the film and the substrate and into the substrate. The TLM method is shown to have considerable potential in practical applications for diffusion processes in thin films.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Science Ltd
    Freshwater biology 38 (1997), S. 0 
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. Polyunsaturated fatty acids (PUFA) are almost exclusively synthesized by plants. Animals can convert from one form of PUFA to another through elongation and desaturation, but very few can synthesize PUFA de novo. PUFA play an important role in regulating cell membrane properties, serve as precursors for important animal hormones and are essential for animals.2. In aquaculture studies, highly unsaturated fatty acids (HUFA), a subset of PUFA, have been found to be critical for maintaining high growth, survival and reproductive rates and high food conversion efficiencies for a wide variety of marine and freshwater organisms.3. The plankton literature suggests high food-quality algae species are rich in HUFA and low food-quality algae are poor in HUFA. Adding semi-pure emulsions of HUFA to algae monocultures can markedly increase the growth rates of zooplankton feeding on these mixtures.4. A study measuring zooplankton biomass accrual when feeding on natural phytoplankton found a strong correlation between phytoplankton HUFA (specifically eicosapentaenoic acid) content and herbivorous zooplankton production.5. The aquatic ecology literature suggests that planktonic foodwebs with high HUFA content phytoplankton have high zooplankton to phytoplankton biomass ratios, while systems with low HUFA phytoplankton have low zooplankton biomass. Also, the seasonal succession of plankton in many temperate lakes follows patterns tied to phytoplankton HUFA content, with intense zooplankton grazing and ‘clear-water-phases’ characteristic of periods when the phytoplankton is dominated by HUFA-rich species.6. Herbivorous zooplankton production is constrained by the zooplankton’s ability to ingest and digest phytoplankton. It is becoming increasingly clear, however, that much of the phytoplankton which is assimilated may be nutritionally inadequate. HUFA may be key nutritional constituents of zooplankton diets, and may determine energetic efficiency across the plant–animal interface, secondary production and the strength of trophic coupling in aquatic pelagic foodwebs.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-2427
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: 1. A series of experiments examined growth of Daphnia magna on three algal diets (Rhodomonas minuta, Scenedesmus acutus and Synechococcus sp.) at varying physiological states [nitrogen and phosphorus (P) limitations] to test whether variation in algal fatty acid and/or elemental composition can predict Daphnia growth.2. These algae differed widely in their essential fatty acid (EFA) composition while phosphorus (P) or nitrogen limitation had only a small influence on their ω3-polyunsaturated fatty acid (PUFA) content.3. Individually, algal ω3-PUFA content explained 69% of the variation in the normalised growth of D. magna, while algal phosphorus content explained 11% of the variation. Quantitative models for D. magna growth used both algal ω3-PUFA content and algal C : P ratio as food quality indices. Together, algal ω3-PUFA content and C : P ratio explained 70% of the variation in the normalised growth rate of D. magna.4. Our results indicate that EFA influenced algal food quality much more strongly than P. The EFA and mineral P impacts appear to be independent.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0021-8537
    Source: Cambridge Journals Digital Archives
    Topics: History
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Cambridge : Cambridge University Press
    The @journal of African history 27 (1986), S. 149-162 
    ISSN: 0021-8537
    Source: Cambridge Journals Digital Archives
    Topics: History
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Cambridge : Cambridge University Press
    The @journal of African history 25 (1984), S. 331-341 
    ISSN: 0021-8537
    Source: Cambridge Journals Digital Archives
    Topics: History
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Cambridge : Cambridge University Press
    The @journal of African history 24 (1983), S. 431-440 
    ISSN: 0021-8537
    Source: Cambridge Journals Digital Archives
    Topics: History
    Notes: Two fatwā-s or legal opinions of the jurist al-Qābisī at Qayrawān about the year A.D. 1000 show the way in which the Law of Islam was used to protect the Muslim against the hazards of trans-Saharan trade with the Bilād al-Sūdan. Trade was to be conducted as far as possible in accordance with the Law, and approval was given to the establishment of Muslim communities in the Bilād al-Sūdān under the authority of a nāzir or ‘watchman’, with the consent of the pagan king of the country. The formation of Muslim communities on this legal basis, and their incorporation into the pattern of West African society, were important for the subsequent character of Islam in West Africa. Meanwhile, among the ‘stateless’ Berber peoples of the Western Sahara, the doctrines of the Malikite school were subject to a different interpretation by Ibn Yasln, which came into open conflict with the views of al-Qābisī when the Almoravids sacked the Muslim city of Awdaghast for submitting to the pagan king of Ghana. This conflict of attitudes to paganism remained a feature of West African Islam down to the twentieth century.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Cambridge University Press
    International journal of Middle East studies 16 (1984), S. 149-150 
    ISSN: 0020-7438
    Source: Cambridge Journals Digital Archives
    Topics: Ethnic Sciences , History , Political Science
    Type of Medium: Electronic Resource
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