In this work, the effects of strontium addition on the structure and optical properties of nanostructured bismuth silicate (Bi4Si3O12) thin films prepared via sol-gel were studied. At first, different sols containing the optimum ratio of precursors were synthesized, and then, the prepared sols were coated on the substrate via dip coating. The dip coated samples were dried at 100oC and, in order...

The name ‘Haeckelite’ has been proposed to designate a three-fold coordinated network generated by a periodic arrangement of pentagons, hexagons and heptagons (Terrones H et al 2000 Phys. Rev. Lett 84 1716). Starting from a planar Haeckelite array, tubular structures are obtained by applying the same wrapping procedure as for the usual nanotubes, which are rolled up sheets of graphene. This pap...

The structure of real-world social networks in large part determines the evolution of social phenomena, including opinion formation, diffusion of information and influence, and the spread of disease. Globally, network structure is characterized by features such as degree distribution, degree assortativity, and clustering coefficient. However, information about global structure is usually not av...

In this article, ZnO and ZnO:Mn nanoparticles prepared by reverse micelle method. The various crystalline properties of these nanoparticles such as size, d-spacing, strain, stress, dislocation density and texture coefficient have been calculated with the help of XRD spectrum. The XRD results indicated that the synthesized ZnO and ZnO:Mn nanoparticles have a pure wurtzite (hexagonal phase) struc...

We prove restrictions on when a Costas array can contain a large corner region whose entries are all 0. In particular, we prove a 2010 conjecture due to Russo, Erickson and Beard. We constrain the vectors joining pairs of 1s in a Costas array by establishing a series of results on its number of “mirror pairs,” namely pairs of these vectors having the same length but opposite slopes.

We apply combinatorial arguments to establish structural constraints on Costas arrays. We prove restrictions on when a Costas array can contain a large corner region whose entries are all 0. In particular, we prove a 2010 conjecture due to Russo, Erickson and Beard. We then constrain the vectors joining pairs of 1s in a Costas array by establishing a series of results on its number of “mirror p...

We study structural properties of each of the mainsublanguages of XPath [8] commonly used in practice.First, we characterize the expressive power of these lan-guage fragments in terms of both logics and tree pat-terns. Second, we investigate closure properties, fo-cusing on the ability to perform basic Boolean oper-ations while remaining within the fragment. We give a<lb...

Miller has shown that disjunctions are not necessary in a large fragment of hereditary Harrop formulae, a class of formulae which properly includes Horn clauses. In this paper we extend this result to include existential quantiications, so that for each program D, there is a program D 0 which is operationally equivalent, but contains no disjunctions or existential quantiications. We may think o...

Dense graphs have been extensively studied in the context of Extremal Graph Theory. The outstanding Szemerédi Regularity Lemma [111] states that any dense network has properties which are close to the ones of a random graph. In particular, a large dense network cannot be too irregular. This structural result is one of the cornerstones of contemporary combinatorics (and one would like to say mat...

Denote by C the class of oracles relative to which P = NP (collapsing oracles), and by S the class of oracles relative to which P 6= NP (separating oracles). We present structural results on C and S. Using a diagonalization argument, we show that neither C nor S is closed under disjoint union, also known as join. We show that this implies that neither C nor S is closed under union, intersection...