15,001 research outputs found
Small angle neutron scattering contrast variation reveals heterogeneities of interactions in protein gels
The structure of model gluten protein gels prepared in ethanol/water is
investigated by small angle X-ray (SAXS) and neutrons (SANS) scattering. We
show that gluten gels display radically different SAXS and SANS profiles when
the solvent is (at least partially) deuterated. The detailed analysis of the
SANS signal as a function of the solvent deuteration demonstrates
heterogeneities of sample deuteration at different length scales. The
progressive exchange between the protons (H) of the proteins and the deuteriums
(D) of the solvent is inhomogeneous and 60 nm large zones that are enriched in
H are evidenced. In addition, at low protein concentration, in the sol state,
solvent deuteration induces a liquid/liquid phase separation. Complementary
biochemical and structure analyses show that the denser protein phase is more
protonated and specifically enriched in glutenin, the polymeric fraction of
gluten proteins. These findings suggest that the presence of H-rich zones in
gluten gels would arise from the preferential interaction of glutenin polymers
through a tight network of non-exchangeable intermolecular hydrogen bonds.Comment: Soft Matter, Royal Society of Chemistry, 201
Exact solution of the lattice vertex model analog of the coupled Bariev XY chains
We present the algebraic Bethe Ansatz solution for the vertex model recently
proposed by Zhou as the classical analog of the Bariev interacting XY chains.
The relevant commutation rules between the creation fields contain the Hecke
symmetry pointed out recently by Hikami and Murakami. The eigenvalues of the
corresponding transfer matrix are explicitly given.Comment: Plain latex, 8 pag
On the solution of a supersymmetric model of correlated electrons
We consider the exact solution of a model of correlated electrons based on
the superalgebra . The corresponding Bethe ansatz equations have an
interesting form. We derive an expression for the ground state energy at half
filling. We also present the eigenvalue of the transfer matrix commuting with
the Hamiltonian.Comment: Palin latex , 8 page
Analytic Bethe Ansatz for 1-D Hubbard model and twisted coupled XY model
We found the eigenvalues of the transfer matrices for the 1-D Hubbard model
and for the coupled XY model with twisted boundary condition by using the
analytic Bethe Ansatz method. Under a particular condition the two models have
the same Bethe Ansatz equations. We have also proved that the periodic 1-D
Hubbard model is exactly equal to the coupled XY model with nontrivial twisted
boundary condition at the level of hamiltonians and transfer matrices.Comment: 22 pages, latex, no figure
Fire regime in a Mexican forest under indigenous resource management.
The Rara´ muri (Tarahumara) people live in the mountains and canyons of the Sierra Madre Occidental of Chihuahua, Mexico. They base their subsistence on multiple-use strategies of their natural resources, including agriculture, pastoralism, and harvesting of native plants and wildlife. Pino Gordo is a Rara´ muri settlement in a remote location where the forest has not been commercially logged. We reconstructed the forest fire regime from firescarred trees, measured the structure of the never-logged forest, and interviewed community members about fire use. Fire occurrence was consistent throughout the 19th and 20th centuries up to our fire scar collection in 2004. This is the least interrupted surface-fire regime reported to date in North America. Studies from other relict sites such as nature reserves in Mexico or the USA have all shown some recent alterations associated with industrialized society. At Pino Gordo, fires recurred frequently at the three study sites, with a composite mean fire interval of 1.9 years (all fires) to 7.6 years (fires scarring 25% or more of samples). Per-sample fire intervals averaged 10–14 years at the three sites. Approximately two-thirds of fires burned in the season of cambial dormancy, probably during the pre-monsoonal drought. Forests were dominated by pines and contained many large living trees and snags, in contrast to two nearby similar forests that have been logged. Community residents reported using fire for many purposes, consistent with previous literature on fire use by indigenous people. Pino Gordo is a valuable example of a continuing frequent-fire regime in a never-harvested forest. The Rara´muri people have actively conserved this forest through their traditional livelihood and management techniques, as opposed to logging the forest, and have also facilitated the fire regime by burning. The data contribute to a better understanding of the interactions of humans who live in pine forests and the fire regimes of these ecosystems, a topic that has been controversial and difficult to assess from historical or paleoecological evidence
A variational approach for the Quantum Inverse Scattering Method
We introduce a variational approach for the Quantum Inverse Scattering Method
to exactly solve a class of Hamiltonians via Bethe ansatz methods. We undertake
this in a manner which does not rely on any prior knowledge of integrability
through the existence of a set of conserved operators. The procedure is
conducted in the framework of Hamiltonians describing the crossover between the
low-temperature phenomena of superconductivity, in the
Bardeen-Cooper-Schrieffer (BCS) theory, and Bose-Einstein condensation (BEC).
The Hamiltonians considered describe systems with interacting Cooper pairs and
a bosonic degree of freedom. We obtain general exact solvability requirements
which include seven subcases which have previously appeared in the literature.Comment: 18 pages, no eps figure
Algebraic Bethe ansatz approach for the one-dimensional Hubbard model
We formulate in terms of the quantum inverse scattering method the algebraic
Bethe ansatz solution of the one-dimensional Hubbard model. The method
developed is based on a new set of commutation relations which encodes a hidden
symmetry of 6-vertex type.Comment: appendix additioned with Boltzmann weigths and R-matrix. Version to
be published in J.Phys.A:math.Gen. (1997
Investigations on the Genus Rhizoecus (Hemiptera: Rhizoecidae) with Description of Two New Species from South America
Neotropical species of the scale insect genus Rhizoecus Kunckel d'Herculais (Hemiptera: Coccomorpha: Rhizoecidae) found in soil sample material of the Hungarian Natural History Museum were studied. Two new Rhizoecus species, Rhizoecus kontschani Kaydan and Konczne Benedicty sp. n., and Rhizoecus granaradewillinkae Kaydan and Szita sp. n., are described and illustrated based on the adult females. Also, the adult females of Rhizoecus keysensis Hambleton and Rhizoecus pseudocacticans Hambleton are illustrated. An identification key and new additional locality records for the currently known Rhizoecus species are provided
Eight state supersymmetric model of strongly correlated fermions
An integrable eight state supersymmtric model is proposed, which is a
fermion model with correlated single-particle and pair hoppings as well as
uncorrelated triple-particle hopping. It has an supersymmetry and
contains one symmetry-preserving free parameter. The model is solved and the
Bethe ansatz equations are obtained.Comment: Some cosmetic changes; to appear in Phys. Rev.
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