449 research outputs found
Parametrization of semi-dynamical quantum reflection algebra
We construct sets of structure matrices for the semi-dynamical reflection
algebra, solving the Yang-Baxter type consistency equations extended by the
action of an automorphism of the auxiliary space. These solutions are
parametrized by dynamical conjugation matrices, Drinfel'd twist representations
and quantum non-dynamical -matrices. They yield factorized forms for the
monodromy matrices.Comment: LaTeX, 24 pages. Misprints corrected, comments added in Conclusion on
construction of Hamiltonian
Structures in BC_N Ruijsenaars-Schneider models
We construct the classical r-matrix structure for the Lax formulation of BC_N
Ruijsenaars-Schneider systems proposed in hep-th 0006004. The r-matrix
structure takes a quadratic form similar to the A_N Ruijsenaars-Schneider
Poisson bracket behavior, although the dynamical dependence is more
complicated. Commuting Hamiltonians stemming from the BC_N
Ruijsenaars-Schneider Lax matrix are shown to be linear combinations of
particular Koornwinder-van Diejen ``external fields'' Ruijsenaars-Schneider
models, for specific values of the exponential one-body couplings. Uniqueness
of such commuting Hamiltonians is established once the first of them and the
general analytic structure are given.Comment: 18 pages, gzip latex fil
Spin chains from dynamical quadratic algebras
We present a construction of integrable quantum spin chains where local
spin-spin interactions are weighted by ``position''-dependent potential
containing abelian non-local spin dependance. This construction applies to the
previously defined three general quadratic reflection-type algebras:
respectively non-dynamical, semidynamical, fully dynamical.Comment: 12 pages, no figures; v2: corrected formulas of the last sectio
An assessment of nitrification inhibitors to reduce nitrous oxide emissions from UK agriculture
A trial was conducted consisting of 14 experiments across sites in England of contrasting soil type and annual rainfall to assess the effectiveness of nitrification inhibitors (predominantly dicyandiamide (DCD) but limited assessment also of 3, 4-dimethylpyrazole phosphate (DMPP) and a commercial product containing two pyrazole derivatives) in reducing direct nitrous oxide (N _2 O) emissions from fertilizer nitrogen (N), cattle urine and cattle slurry applications to land. Measurements were also made of the impact on ammonia (NH _3 ) volatilization, nitrate (NO _3 ^− ) leaching, crop yield and crop N offtake. DCD proved to be very effective in reducing direct N _2 O emissions following fertilizer and cattle urine applications, with mean reduction efficiencies of 39, 69 and 70% for ammonium nitrate, urea and cattle urine, respectively. When included with cattle slurry a mean, non-significant reduction of 56% was observed. There were no N _2 O emission reductions observed from the limited assessments of the other nitrification inhibitors. Generally, there were no impacts of the nitrification inhibitors on NH _3 volatilization, NO _3 ^− leaching, crop yield or crop N offtake. Use of DCD could give up to 20% reduction in N _2 O emissions from UK agriculture, but cost-effective delivery mechanisms are required to encourage adoption by the sector. Direct N _2 O emissions from the studied sources were substantially lower than IPCC default values and development of UK country-specific emission factors for use in inventory compilation is warranted
The Classical -Matrix for the Relativistic Ruijsenaars-Schneider System
We compute the classical -matrix for the relativistic generalization of
the Calogero-Moser model, or Ruijsenaars-Schneider model, at all values of the
speed-of-light parameter . We connect it with the non-relativistic
Calogero-Moser -matrix and the
sine-Gordon soliton limit.Comment: LaTeX file, no figures, 8 page
Liquid/Liquid Extraction Kinetics of Eu(III) and Am(III) by Extractants Designed for the Industrial Reprocessing of Nuclear Wastes
Results about the kinetics of extraction of Eu(III) and Am(III) by extractants designed for the industrial reprocessing of nuclear wastes are reported. They were obtained using the rotating membrane cell (RMC) technique. Extraction and stripping kinetic rate constants were determined for various compositions of the aqueous and organic phases. The transfer was studied at liquid/liquid interfaces between an aqueous nitric acid solution and an organic solvent containing the diglycolamide extractant molecule N,N,N′,N′-tetra-n-octyl-diglycolamide (TODGA) or a mixture of the bipyridine molecule CyMe4BTBP with TODGA (the latter being used as a phase-transfer catalyst), dissolved in an aliphatic diluent. In some experiments, an aqueous ligand (a sulfonated bis triazinyl pyridine, SO3-Ph-BTP, or a PyTri-diol) was added to the aqueous phase as a stripping agent. The diffusion coefficients of Eu(III) and Am(III), which are key in the analysis of the kinetic data, were measured using the RMC and the closed capillary technique. Whenever possible, mechanisms are proposed to interpret the experimental results
Integrable mappings and polynomial growth
We describe birational representations of discrete groups generated by
involutions, having their origin in the theory of exactly solvable
vertex-models in lattice statistical mechanics. These involutions correspond
respectively to two kinds of transformations on matrices: the
inversion of the matrix and an (involutive) permutation of the
entries of the matrix. We concentrate on the case where these permutations are
elementary transpositions of two entries. In this case the birational
transformations fall into six different classes. For each class we analyze the
factorization properties of the iteration of these transformations. These
factorization properties enable to define some canonical homogeneous
polynomials associated with these factorization properties. Some mappings yield
a polynomial growth of the complexity of the iterations. For three classes the
successive iterates, for , actually lie on elliptic curves. This analysis
also provides examples of integrable mappings in arbitrary dimension, even
infinite. Moreover, for two classes, the homogeneous polynomials are shown to
satisfy non trivial non-linear recurrences. The relations between
factorizations of the iterations, the existence of recurrences on one or
several variables, as well as the integrability of the mappings are analyzed.Comment: 45 page
Improving the reliability of material databases using multiscale approaches
This article addresses the propagation of constitutive uncertainties between
scales occurring in the multiscale modelling of fibre-reinforced composites.
The amplification of such uncertainties through upward or downward transitions
by a homogenisation model is emphasized and exemplified with the Mori-Tanaka
model. In particular, the sensitivity to data uncertainty in the inverse
determination of constituent parameters based on downward transitions is
stressed on an example. Then a database improvement method, which exploits
simultaneously the available information on constitutive uncertainties at all
scales instead of just propagating those associated with one scale, is
presented and shown to yield substantial reductions in uncertainty for both the
constitutive parameters and the response of structures. The latter finding is
demonstrated on two examples of structures, with significant gains in
confidence obtained on both
Fatty acid composition of sulfate-reducing bacteria isolated from deep-sea hydrothermal vent (13° N, East Pacific Rise)
Five strains of vibrio-shaped, mesophilic sulfate-reducing bacteria were isolated from the deep-sea hydrothermal vent site at 13° N on the East Pacific Rise. Phospholipid analyses demonstrated a high percentage of branched-chain fatty acids, including the known biomarker for Desulfovibrio, in all five strains. The cell-wall lipids showed a fatty acid composition markedly different from the phospholipids. While straight-chain fatty acids were predominant the biomarker fatty acid was absent. Based on the morphological characteristics and the fatty acid composition, we tentatively have assigned the isolates to the genus Desulfovibrio
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