Absorbing Subalgebras, Cyclic Terms, and the Constraint Satisfaction Problem

The Algebraic Dichotomy Conjecture states that the Constraint Satisfaction Problem over a fixed template is solvable in polynomial time if the algebra of polymorphisms associated to the template lies in a Taylor variety, and is NP-complete otherwise. This paper provides two new characterizations of finitely generated Taylor varieties. The first characterization is using absorbing subalgebras and the second one cyclic terms. These new conditions allow us to reprove the conjecture of Bang-Jensen and Hell (proved by the authors) and the characterization of locally finite Taylor varieties using weak near-unanimity terms (proved by McKenzie and Mar\'oti) in an elementary and self-contained way

Microwave-assisted hydrothermal process for the preparation of SnO from an ammoniacal Sn6O4(OH)4 suspension

SnO powder with a specific surface area of 2 m2/g has been prepared by microwave-assisted hydrothermal processing of an ammoniacal Sn6O4(OH)4 suspension. We have examined the effect of pressure rise rate in a reaction mixture on the surface morphology and photocatalytic activity of SnO. Raising the pressure has been shown to reduce the SnO synthesis time, without influencing the surface morphology of SnO or its photocatalytic activity for methyl orange photodegradation

Photocatalytic activity of titania nanopowders prepared by a sol–gel process at various pHs

A strategy has been proposed to prepare photocatalytically active titania nanopowders through a sol-gel route using high-degree molecular separation upon the dilution of reagents, high water/alkoxide ratios, high reagent mixing rates, and pH effects. This strategy has been successfully used to isolate, from sols, anatase powders with high surface areas (100–310 m2/g) dependent on the pH value during the synthesis. The photocatalytic activity of titania nanopowders prepared by the sol-gel process at various pHs has been tested in photodestruction of organic dyes (Rodamine B, Methylene Blue, and Anthraquinone AcidBlue) in acid solutions. UV-radiation-induced dye destruction rates are found to depend on the surface properties (including surface area and ζ potential) and hydration specifics of the titania

The composition and structure of iron(III) complex compounds with salicylic acid in ethanol solution and in the solid thin film state

Owing to their properties iron(III) salicylate complexes are interest of for application in biomedicine and environmental monitoring. Recently this complex compounds also are investigated as a potential candidate for preparing Fe2O3 films by sol-gel method from ethanol film-forming solution. Relevance of the work was caused by necessity to determine the structure and composition of iron(III) salicylate complexes in ethanol solution and in the solid film state, which influence on film properties. Nowadays this information is absence in the literature. UV spectroscopy, NMR measurement, methods of isomolar series and thermal analysis were used to analyze the composition of complex in ethanol solution and in the solid state. It was found, that salicylic acid interacts with iron(III) chloride in ethanol solution promotes the formation of [FeC6H4OCOO]+ complex, where salicylate ligand behaves as bidentate ligand. After removal of the solvent from solution iron(III) chloride salicylate crystal hydrate complex of 1:1 stoichiometry was formed in solid state. Thermal decomposition of this compound led to formation α–Fe2O3

Superfluid Interfaces in Quantum Solids

One scenario for the non-classical moment of inertia of solid He-4 discovered by Kim and Chan [Nature 427, 225 (2004)] is the superfluidity of micro-crystallite interfaces. On the basis of the most simple model of a quantum crystal--the checkerboard lattice solid--we show that the superfluidity of interfaces between solid domains can exist in a wide range of parameters. At strong enough inter-particle interaction, a superfluid interface becomes an insulator via a quantum phase transition. Under the conditions of particle-hole symmetry, the transition is of the standard U(1) universality class in 3D, while in 2D the onset of superfluidity is accompanied by the interface roughening, driven by fractionally charged topological excitations.Comment: 4 revtex4 page

Fine mapping of the SYM2 locus of pea linkage group 1

The symbiotic interaction between Rhizobium bacteria and leguminous plants results in the formation of root nodules which are specific, nitrogen-fixing organs that supply the plant with ammonia required for its growth. The formation of a nitrogen-fixing root nodule involves a complex series of steps requiring the expression of genes in both the rhizobial symbiont and the host plant. The necessary genes of rhizobia for nodulation, the nod genes, and for nitrogen fixation, the fix and nif genes, are well studied, nearly all of them having been cloned and characterized. In contrast the symbiosis genes of the legumes are not well understood. A number of plant genes which are specifically expressed in nodules or display enhanced expression in nodules, the so-called nodulin genes, have been identified in pea, soybean, alfalfa and other legumes by mRNA analysis and cDNA cloning. The time of expression of several nodulins has been analyzed in a number of cases and the nodulin genes which are expressed shortly after infection and in the first steps of nodule formation are referred to as early nodulins (ENODs).In addition, a large series of naturally occurring and induced plant mutants, the sym mutants, which have an altered symbiosis, have been described but the sym genes have not been characterized and the functions of the proteins encoded by these genes are not known. Since it seems a reasonable assumption that there will be a limited number of genes involved in nodule formation and metabolism it might well be that some of the sym mutants represent defects in nodulin-coding or controlling sequences. The study presented in this thesis is centred on one of the sym genes, sym2, as we suspected that the sym2 gene has a role in the first interaction between the Rhizobium bacteria and the legume host plant. A typical characteristic of the Rhizobium legume symbiosis is the host specific nature. Most Rhizobium species can nodulate only plants of a specific plant genus. In the recently past years it has been demonstrated that in the Rhizobium bacteria the nod genes are responsible for the strong specificity in the bacteria-plant interaction. The nod genes are involved in the synthesis of specific lipo-oligosaccharides called Nod factors, that can induce the early responses in host plants leading to root nodule formation. Nod factors with a very specific structure are required to induce these responses and they are active at very low concentrations. Therefore it is probable that, as a first step in inducing the reactions leading to nodule formation, the Nod factors are recognized by a special receptor in the host plant. There are now several reasons to presume that the plant sym2 gene might encode the receptor for the specific recognition of Nod factors. The aim of the study presented in this thesis is a further characterization of the interaction between sym2 containing pea lines and different strains of Rhizobium leguminosarium bv. viciae in an attempt to find further support for this hypothesis. At the same time, we have started the detailed genetic mapping of sym2 on the pea genome, in preparation for eventually cloning and molecular characterization of sym2 .In chapter 1 a general introduction summarizes the history of the discovery of the sym2 gene and presents the arguments for the hypothesis that sym2 might code for a receptor of rhizobial Nod factors. In chapter 2 a further genetic characterization of sym2 is given. Chapter 3 describes how a novel early nodulin gene of PsENOD7 was characterized and mapped near the sym2 locus. In chapter 4 a detailed map of the sym2 locus linkage group I is presented including some new molecular markers tightly linked to the sym2 locus. In chapter 5 it is demonstrated how the Rhizobium, nodO gene determines whether sym2 is a dominant or a recessive allele. The thesis ends with some concluding remarks on the nature of sym2 and the impact of the research described in the thesis for the cloning of sym2

Modeling Kelvin wave cascades in superfluid helium

We study two different types of simplified models for Kelvin wave turbulence on quantized vortex lines in superfluids near zero temperature. Our first model is obtained from a truncated expansion of the Local Induction Approximation (Truncated-LIA) and it is shown to possess the same scalings and the essential behaviour as the full Biot-Savart model, being much simpler than the later and, therefore, more amenable to theoretical and numerical investigations. The Truncated-LIA model supports six-wave interactions and dual cascades, which are clearly demonstrated via the direct numerical simulation of this model in the present paper. In particular, our simulations confirm presence of the weak turbulence regime and the theoretically predicted spectra for the direct energy cascade and the inverse wave action cascade. The second type of model we study, the Differential Approximation Model (DAM), takes a further drastic simplification by assuming locality of interactions in k-space via using a differential closure that preserves the main scalings of the Kelvin wave dynamics. DAMs are even more amenable to study and they form a useful tool by providing simple analytical solutions in the cases when extra physical effects are present, e.g. forcing by reconnections, friction dissipation and phonon radiation. We study these models numerically and test their theoretical predictions, in particular the formation of the stationary spectra, and closeness of numerics for the higher-order DAM to the analytical predictions for the lower-order DAM

Diagrammatic Monte Carlo for Correlated Fermions

We show that Monte Carlo sampling of the Feynman diagrammatic series (DiagMC) can be used for tackling hard fermionic quantum many-body problems in the thermodynamic limit by presenting accurate results for the repulsive Hubbard model in the correlated Fermi liquid regime. Sampling Feynman's diagrammatic series for the single-particle self-energy we can study moderate values of the on-site repulsion ($U/t \sim 4$) and temperatures down to $T/t=1/40$. We compare our results with high temperature series expansion and with single-site and cluster dynamical mean-field theory.Comment: 4 pages, 5 figures, stylistic change