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  • Articles  (24)
  • 1990-1994  (24)
Collection
Year
Journal
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 215 (1994), S. 53-58 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A class of non-vacuum expanding cosmological solutions of Wesson's 5D theory of gravity with variable rest mass is derived. The models are spatially homogeneous and isotropic and the source of gravitation is a pressureless fluid (dust) plus a cosmological constant term. The general and unified solution is found for the equations and some properties of different limiting cases are studied. Particularly, it is shown that for null cosmological constant the predicted age of the universe is smaller than the ones of the 4D FRW models.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Astrophysics and space science 219 (1994), S. 29-34 
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The age of the universe is computed for spatially homogeneous and isotropic cosmological models of the relativistic Wesson's 5D variable mass theory of gravity. It is shown that if the pressure in the mass dimension is negligible, ages old enough to agree with the observations can only be obtained if the cosmological constant is different from zero. In addition, unlike the standard FRW models in Einstein's 4D theory, the age value itself is not affected by the nature of the matter content (matter and radiation dominated models give the same age).
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    General relativity and gravitation 23 (1991), S. 455-463 
    ISSN: 1572-9532
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A Newtonian version of the spatially homogeneous and isotropic cosmological models with variable mass is presented. Under the assumption that the mass variation is a strict cosmological effect, its influence on the evolution of the scale function is established for the case of a dust-filled universe. Unlike the usual Newtonian models the present value of the deceleration parameter (q ≏ 1) obtained from the luminosity distance versus redshift relation can be fitted for a time-decreasing mass. It is also shown that the hyperbolic, parabolic or elliptic character of the fluid motion can be modified along the expansion. Likewise, a Friedmann-type equation with a variable “curvature term” indicates that in the frame-work of a full geometric variable mass theory, the same may occur with the open, flat or closed character of the universe spatial section.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    General relativity and gravitation 24 (1992), S. 171-177 
    ISSN: 1572-9532
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The existence of Newtonian analogs to spatially homogeneous and isotropic cosmological models of the relativistic 5D Wesson variable mass theory is investigated. By treating the continuous universe “matter creation process” by the methods of standard hydrodynamics, it is shown that classical analogs are obtained only if the cosmological constant is null and the spatial curvature is positive.
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    General relativity and gravitation 26 (1994), S. 909-916 
    ISSN: 1572-9532
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The phenomenological approach to investigating the decay of the vacuum energy density is generalized in the spirit of Dirac's large number hypothesis. Different arguments are outlined to justify an universal dependence of the type λ=ΒH 2 (Β is a pure number andH is the Hubble parameter). Such time-varying A does change the predictions of the earlier Dirac's cosmology. The deceleration parameter (q 0=(2−Β)/(1+Β)) and the age parameter (H 0t0=(1+Β)/3) are now compatible with the observations. The model also allows a “power-law” inflationary phase and a rate of matter creation smaller than the one present in the steady state universe.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of radioanalytical and nuclear chemistry 173 (1993), S. 179-184 
    ISSN: 1588-2780
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Methods to determine U, Th, and other constituent elements in mineral matrices through Instrumental Neutron Activation Analysis (INAA), have been widely utilized due to their capability to extract a large quantity of information from small samples. In the present work, an experimental methodology based on INAA associated to the cluster statistics technique was used to determine the uranium concentration and its correlation with other elements present in the mineral phosphorites from the northeast region of Brazil. Data for 22 elements including rare-earth elements are presented. A good correlation between uranium and rare-earth elements is observed. For the transition metals, correlation with uranium was not noted.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 21 (1990), S. 141-147 
    ISSN: 1573-0867
    Keywords: K response ; K x cultivar interaction ; K-uptake ; Oryza sativa L. ; grain yield ; dry matter ; soil K level
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Even though K is an essential nutrient, the response of upland rice to K fertilization under field conditions has not been adequately documented. This research was conducted to examine the influence of K fertilization on yield of upland rice (Oryza sativa L.). In the first three years, K was broadcast at rates of 0, 42, 84, 126 and 168 kg K ha−1. In the last two years K was banded at rates of 0, 25, 50, 75 and 100 kg K ha−1. The experiment was conducted on an Oxisol (Typic Haplustox) during five consecutive years. Potassium significantly increased grain yields and dry matter production but response varied from cultivar to cultivar and year to year. Drought and panicle neck blast played an important role in limiting upland rice yield response to K fertilization. Potassium application rates associated with maximum grain yield varied from 83 to 127 kg K ha−1 when K was broadcast and from 47 to 67 kg K ha−1 when K was banded. Previous broadcast K, favorable weather and blast resistant cultivars probably contributed to higher yields with K banding in the fourth and fifth growing seasons.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Nutrient cycling in agroecosystems 21 (1990), S. 157-162 
    ISSN: 1573-0867
    Keywords: Lowland rice ; Oryza sativa L. ; K-concentration ; grain yield ; soil extractable K ; K response ; K x cultivar interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Not much is known about the response of lowland rice to K fertilization under Brazilian conditions. A field experiment was conducted during four consecutive years to determine the response of three lowland rice (Oryza sativa L.) cultivars to K fertilization on a Low Humic Gley soil. In the first two years, K was broadcast at rates of 0, 42, 84, 126, and 168 kg K ha−1. In the last two years K rates were reduced to 0, 25, 50, 75, and 100 kg K ha−1 and applied in a band. Potassium significantly (P 〈 0.01) increased grain yields but the response varied from cultivar to cultivar and year to year. Yield responses to K fertilization were superimposed on a general trend of increasing grain yields across the four growing seasons. Mean grain yields increased 14.3% with broadcast application of K in the first two years and 10.4% with banded application of K in the last two years when compared to the control treatments. Extractable soil K increased with K application rate and decreased with soil depth. Potassium was rapidly removed from the soil and yearly broadcast or banded application of K can be expected to result in a significant increase in grain yield of lowland rice in these soils.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemical Engineering & Technology - CET 17 (1994), S. 414-421 
    ISSN: 0930-7516
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Computer-aided design of a packed column to remove ethanol from aqueous solution with dibutyl butylphosphonate (DBBP) was accomplished with a programme based on the Pratt method and on the slip velocity equation. Reliable data for successful computation were obtained from literature correlations (drop size, hold-up and axial mixing coefficients for different types of packing) and from experimental work (equilibria and kinetics). Equilibrium studies on the H2O-ethanol-dibutyl butylphosphonate system were performed at different temperatures. A decrease in temperature increased the selectivity of the extractant while the distribution coefficient of ethanol, KD ≈ 1.0, remained constant. The behaviour of the system kinetics towards temperature is assessed in order to determine the initial mass transfer flux (892 × 10-3 kg m-2s-1, 30°C) and the activation energy, 22.9 kJ/kmol. The process is governed by the diffusion of the species involved. The influence of the type of packing of the column on its design is analyzed from the inventory volume of the solvent, the total volume of the column and the axial dispersion coefficients under normalised inlet and outlet conditions.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Two-charged-pion correlations were studied in $$\bar p$$ p(→2π*2π− nπ0,n≥0) annihilations at rest with the CPLEAR detector at the Low-Energy Antiproton Ring (LEAR). A strong enhancement was found in the production of pairs of like-sign pions with a small value of the relative fourmomentumQ, with respect to pairs of unlike-sign pions. The observed enhancement was interpreted as a consequence of the Bose-Einstein symmetrization of the two-pion wave function. The data are well represented by a correlation function parametrized as a double-Gaussian; an exponential parametrization is also statistically acceptable. The value of the correlation strength is found to be 〉1. The high-quality large data samples together with the ability for K± identification and final-state separation allowed the study of systematic effects impacting on theQ dependence of the correlation function and on the extracted space parameters of the pion sources.
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