92 research outputs found
Triple molybdates one-, one - and three(two)valence metals
The authors thank Ph. D. M. K. Alibaeva, Ph. D. I. A. Gudkova and Ph. D. I. V. Korolkova for participation in the research.The review summarizes experimental data on the phase formation, structure and properties of new complex oxide compounds group - triple molybdates containing tetrahedral molybdate ion, two different singly charged cation, together with tri- or divalent cation. The several structural families of these compounds were distinguished and it shown that many of them are of interest as luminescent, laser, ion-conducting or nonlinear optical materials.The work is executed at partial support of the Russian Foundation for basic research (projects No. 08-03-00384, 13-03-01020 and 14-03-00298)
Confirmation of a one-dimensional spin-1/2 Heisenberg system with ferromagnetic first-nearest-neighbor and antiferromagnetic second-nearest-neighbor interactions in RbCuMoO
We have investigated magnetic properties of RbCuMoO
powder. Temperature dependence of magnetic susceptibility and magnetic-field
dependence of magnetization have shown that this cuprate is a model compound of
a one-dimensional spin-1/2 Heisenberg system with ferromagnetic
first-nearest-neighbor (1NN) and antiferromagnetic second-nearest-neighbor
(2NN) competing interactions (competing system). Values of the 1NN and 2NN
interactions are estimated as K and K (). This value of suggests that the ground state is a
spin-singlet incommensurate state. In spite of relatively large and
, no magnetic phase transition appears down to 2 K, while an
antiferromagnetic transition occurs in other model compounds of the competing
system with ferromagnetic 1NN interaction. For that reason,
RbCuMoO is an ideal model compound to study properties of
the incommensurate ground state that are unconfirmed experimentally.Comment: 6 pages, 4 figure
Gallot-Tanno Theorem for closed incomplete pseudo-Riemannian manifolds and applications
We extend the Gallot-Tanno Theorem to closed pseudo-Riemannian manifolds. It
is done by showing that if the cone over a manifold admits a parallel symmetric
tensor then it is Riemannian. Applications of this result to the
existence of metrics with distinct Levi-Civita connections but having the same
unparametrized geodesics and to the projective Obata conjecture are given. We
also apply our result to show that the holonomy group of a closed
-manifold does not preserve any nondegenerate splitting of
.Comment: minor correction
1D Frustrated Ferromagnetic Model with Added Dzyaloshinskii-Moriya Interaction
The one-dimensional (1D) isotropic frustrated ferromagnetic spin-1/2 model is
considered. Classical and quantum effects of adding a Dzyaloshinskii-Moriya
(DM) interaction on the ground state of the system is studied using the
analytical cluster method and numerical Lanczos technique. Cluster method
results, show that the classical ground state magnetic phase diagram consists
of only one single phase: "chiral". The quantum corrections are determined by
means of the Lanczos method and a rich quantum phase diagram including the
gapless Luttinger liquid, the gapped chiral and dimer orders is obtained.
Moreover, next nearest neighbors will be entangled by increasing DM interaction
and for open chains, end-spins are entangled which shows the long distance
entanglement (LDE) feature that can be controlled by DM interaction.Comment: 8 pages, 9 figure
A scalable algorithm to explore the Gibbs energy landscape of genome-scale metabolic networks
The integration of various types of genomic data into predictive models of
biological networks is one of the main challenges currently faced by
computational biology. Constraint-based models in particular play a key role in
the attempt to obtain a quantitative understanding of cellular metabolism at
genome scale. In essence, their goal is to frame the metabolic capabilities of
an organism based on minimal assumptions that describe the steady states of the
underlying reaction network via suitable stoichiometric constraints,
specifically mass balance and energy balance (i.e. thermodynamic feasibility).
The implementation of these requirements to generate viable configurations of
reaction fluxes and/or to test given flux profiles for thermodynamic
feasibility can however prove to be computationally intensive. We propose here
a fast and scalable stoichiometry-based method to explore the Gibbs energy
landscape of a biochemical network at steady state. The method is applied to
the problem of reconstructing the Gibbs energy landscape underlying metabolic
activity in the human red blood cell, and to that of identifying and removing
thermodynamically infeasible reaction cycles in the Escherichia coli metabolic
network (iAF1260). In the former case, we produce consistent predictions for
chemical potentials (or log-concentrations) of intracellular metabolites; in
the latter, we identify a restricted set of loops (23 in total) in the
periplasmic and cytoplasmic core as the origin of thermodynamic infeasibility
in a large sample () of flux configurations generated randomly and
compatibly with the prior information available on reaction reversibility.Comment: 11 pages, 6 figures, 1 table; for associated supporting material see
http://www.ploscompbiol.org/article/info:doi/10.1371/journal.pcbi.100256
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