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  • Articles  (107)
  • 1995-1999  (107)
  • Mathematics  (55)
  • Geography  (52)
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  • Articles  (107)
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  • 1
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    Patterns and processes in the development of coastal mire vegetation: Multi-site investigations from Walland Marsh, Southeast England (1999)
    Elsevier
    Details
    Publication Date: 1999-10-01
    Print ISSN: 0277-3791
    Electronic ISSN: 1873-457X
    Topics: Geography , Geosciences
    Published by Elsevier
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    PAPER CURRENT
  • 2
    Electronic Resource
    Electronic Resource
    Two-body Dirac equations for general covariant interactions and their coupled Schrödinger-like forms (1998)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 39 (1998), S. 124-160 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: We present new and useful "external potential" forms of the two-body Dirac equations of constraint dynamics for combined scalar, vector, pseudoscalar, pseudovector, and tensor interactions. These equations have potential applications in two-body problems for bound states in meson spectroscopy and phase shift analysis in nucleon–nucleon scattering. Toward this end, we derive their coupled Schrödinger-like forms using matrix techniques and obtain the corresponding radial equations to these forms from scalar and vector spherical harmonic decompositions. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.532311
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  • 3
    Electronic Resource
    Electronic Resource
    Acclimation of photosynthesis to elevated CO2 and temperature in five British native species of contrasting functional type (1997)
    Oxford, UK : Blackwell Science Ltd
    Global change biology 3 (1997), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Notes: Acclimation of photosynthesis to growth at elevated CO2 concentration varies markedly between species. Species functionally classified as stress-tolerators (S) and ruderals (R), are thought to be incapable, or the least capable, of responding positively in terms of growth to elevated [CO2]. Is this pattern of response also apparent in leaf photosynthesis of wild S- and R-strategists? Acclimatory loss of a photosynthetic and growth response to elevated [CO2] is assumed to reflect limitation on capacity to utilize additional photosynthate. The doubling of pre-industrial global [CO2] is expected to coincide with a 3 °C increase in mean temperature which could stimulate growth; will photosynthetic capacity at elevated [CO2] be greater when the concurrent temperature increase is simulated? Five species from natural grassland of NW Europe and of contrasting ecological strategy were grown in hemispherical greenhouses, environmentally controlled to track the external microclimate. Within a replicated design, plants were grown at (i) current ambient [CO2] and temperature, (ii) elevated [CO2] (ambient + 340 μmol mol–1) and ambient temperature, (iii) ambient [CO2] and elevated temperature (ambient + 3 °C), or (iv) elevated [CO2] and elevated temperature. After 75–104 days, the CO2 response of light-saturated rates of photosynthesis (Asat) was analysed in controlled-environment cuvettes in a field laboratory. There was no acclimatory loss of photosynthetic capacity with growth in elevated [CO2] or elevated temperature over this period in Poa alpina (S), Bellis perennis (R) or Plantago lanceolata (mixed C-S-R strategist), and a significant (P ??bl 0.05) increase in capacity in Helianthemum nummularium (S) and Poa annua (R). Photosynthetic rates of leaves grown and measured in elevated [CO2] were therefore significantly higher than rates for leaves grown and measured in ambient [CO2], for all species. With the exception of Poa alpina, stomatal conductance and stomatal limitation on Asat showed no acclimatory response to growth in elevated [CO2].Carboxylation efficiency, determined from the initial slope of the response of Asat to intercellular CO2 concentration was significantly increased by elevated [CO2] and elevated temperature in H.nummularium, implying a possible increase in in vivo RubisCO activity. Increased carboxylation efficiency of this species was also reflected by an increase in the CO2- and light-saturated rates of photosynthesis, indicating an increased capacity for regeneration of the primary CO2 acceptor in photosynthesis. The results show that R-strategists and slow-growing S-strategists, are inherently capable of large increases in leaf photosynthetic capacity with growth in elevated [CO2] in contrast to expectations from growth studies. With the exception of P.annua, where there was a significant negative interaction between CO2 and temperature, concurrent increase in growth temperature had little effect on this pattern of response.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2486.1997.00071.x
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  • 4
    Electronic Resource
    Electronic Resource
    Wheat growth under Global Environmental Change—an introduction (1995)
    Oxford, UK : Blackwell Publishing Ltd
    Global change biology 1 (1995), S. 0 
    Details
    ISSN: 1365-2486
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geography
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1365-2486.1995.tb00036.x
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  • 5
    Electronic Resource
    Electronic Resource
    222RN IN THE WATER DISTRIBUTION SYSTEM OF TUCSON, ARIZONA (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Journal of the American Water Resources Association 32 (1996), S. 0 
    Details
    ISSN: 1752-1688
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Architecture, Civil Engineering, Surveying , Geography
    Notes: : A study of 222Rn concentrations in the water distribution system of Tucson, Arizona, revealed levels of 60 to 1260 pCi/L in domestic waters. These measurements are comparable to levels of between 80 and 1400 pCi/l for 222Rn found in ground water samples in the North-Central Tucson basin (Kahn et al., 1994). Estimated loss of 222Rn due to radioactive decay during travel from the well head to the home ranges from 8 to 50 percent.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1752-1688.1996.tb04059.x
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  • 6
    Electronic Resource
    Electronic Resource
    A data assimilation technique applied to a predator-prey model (1995)
    Springer
    Bulletin of mathematical biology 57 (1995), S. 593-617 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract A new approach for data assimilation, which is based on the adjoint method, but allows the computer code for the adjoint to be constructed directly from the model computer code, is described. This technique is straightforward and reduces the chance of introducing errors in the construction of the adjoint code. Implementation of the technique is illustrated by applying it to a simple predator-prey model in a model fitting mode. A series of identical twin numerical experiments are used to show that this data assimilation approach can successfully recover model parameters as well as initial conditions. However, the ease with which these values are recovered is dependent on the form of the model equations as well as on the type and amount of data that are available. Additional numerical experiments show that sufficient coefficient and parameter recoveries are possible even when the assimilated data contain significant random noise. Thus, for biological systems that can be described by ecosystem models, the adjoint method represents a powerful approach for estimating values for little-known biological parameters, such as initial conditions, growth rates, and mortality rates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02460785
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  • 7
    Electronic Resource
    Electronic Resource
    Additive Partitions and Continued Fractions (1999)
    Springer
    The Ramanujan journal 3 (1999), S. 55-72 
    Details
    ISSN: 1572-9303
    Keywords: combinatorial number theory ; additive number theory ; Beatty's theorem ; intermediate fractions ; avoidable sets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract A set S of positive integers is avoidable if there exists a partition of the positive integers into two disjoint sets such that no two distinct integers from the same set sum to an element of S. Much previous work has focused on proving the avoidability of very special sets of integers. We vastly broaden the class of avoidable sets by establishing a previously unnoticed connection with the elementary theory of continued fractions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009813309003
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  • 8
    Electronic Resource
    Electronic Resource
    A quasi-wavelet algorithm for second kind boundary integral equations (1999)
    Springer
    Advances in computational mathematics 11 (1999), S. 355-375 
    Details
    ISSN: 1572-9044
    Keywords: periodic quasi-wavelet ; integral equation ; multiscale ; 45G10 ; 65F10 ; 65J15 ; 65N30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In solving integral equations with a logarithmic kernel, we combine the Galerkin approximation with periodic quasi-wavelet (PQW) [4]. We develop an algorithm for solving the integral equations with only O(N log N) arithmetic operations, where N is the number of knots. We also prove that the Galerkin approximation has a polynomial rate of convergence.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018992413504
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  • 9
    Electronic Resource
    Electronic Resource
    Indexing domains of instability for Hamiltonian systems (1998)
    Springer
    Nonlinear differential equations and applications 5 (1998), S. 461-478 
    Details
    ISSN: 1420-9004
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract. Based upon the understanding of the global topologies of the singular subset, its complement, and the hyperbolic subset in the symplectic group, in this paper we study the domains of instability for hyperbolic Hamiltonian systems and define a characteristic index for such domains. This index is defined via the Maslov-type index theory for symplectic paths starting from the identity defined by C. Conley, E. Zehnder, and Y. Long, and the hyperbolic index of symplectic matrices. The old problem of the relation between the non-degenerate local minimality and the instability of hyperbolic extremal loops in the calculus of variation is also studied via this new index for the domains of instability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s000300050057
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  • 10
    Electronic Resource
    Electronic Resource
    Adaptive Disk Spindown via Optimal Rent-to-Buy in Probabilistic Environments (1999)
    Springer
    Algorithmica 23 (1999), S. 31-56 
    Details
    ISSN: 1432-0541
    Keywords: Key words. Mobile computing, On-line algorithms, Machine learning, Power conservation, Disk spindown, Rent-to-buy, Multiprocessor spin / block, IP-over-ATM, Virtual circuit holding time.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract. In the single rent-to-buy decision problem, without a priori knowledge of the amount of time a resource will be used we need to decide when to buy the resource, given that we can rent the resource for $1 per unit time or buy it once and for all for $c . In this paper we study algorithms that make a sequence of single rent-to-buy decisions, using the assumption that the resource use times are independently drawn from an unknown probability distribution. Our study of this rent-to-buy problem is motivated by important systems applications, specifically, problems arising from deciding when to spindown disks to conserve energy in mobile computers [4], [13], [15], thread blocking decisions during lock acquisition in multiprocessor applications [7], and virtual circuit holding times in IP-over-ATM networks [11], [19]. We develop a provably optimal and computationally efficient algorithm for the rent-to-buy problem. Our algorithm uses $ O(\sqrt{t}) $ time and space, and its expected cost for the t th resource use converges to optimal as $ O(\sqrt{ log t/t}) $ , for any bounded probability distribution on the resource use times. Alternatively, using O(1) time and space, the algorithm almost converges to optimal. We describe the experimental results for the application of our algorithm to one of the motivating systems problems: the question of when to spindown a disk to save power in a mobile computer. Simulations using disk access traces obtained from an HP workstation environment suggest that our algorithm yields significantly improved power/ response time performance over the nonadaptive 2-competitive algorithm which is optimal in the worst-case competitive analysis model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/PL00009249
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