A left-first search algorithm for planar graphs

We give anO(|V(G)|)-time algorithm to assign vertical and horizontal segments to the vertices of any bipartite plane graphG so that (i) no two segments have an interior point in common, and (ii) two segments touch each other if and only if the corresponding vertices are adjacent. As a corollary, we obtain a strengthening of the following theorem of Ringel and Petrovič. The edges of any maximal bipartite plane graphG with outer facebwb′w′ can be colored by two colors such that the color classes form spanning trees ofG−b andG−b′, respectively. Furthermore, such a coloring can be found in linear time. Our method is based on a new linear-time algorithm for constructing bipolar orientations of 2-connected plane graphs. The research of H. de Fraysseix and P. O. de Mendez was supported by ESPRIT Basic Research Action No. 7141 (ALCOM II). J. Pach's research was supported by NSF Grant CCR-91-22103, OTKA-4269, and ALCOM II.     

The effect of antibiotics on nitrification processes

Applied Biochemistry and Biotechnology - The effect of different antibiotics at several concentrations of ampicillin (0–250 mg/L),benzylpenicillin (0–250 mg/L), novobiocine (0–150...     

Potentiometric determination of hydrogen peroxide with permanganate in presence of fluoride, with iron as a catalyst: Application to the titanium-fluoride-peroxide mixed complex

A potentiometric permanganate titration has been developed for the determination of hydrogen peroxide in the presence of fluoride, as well as of the peroxide content in the titanium—fluoride—peroxide mixed complex. It is based on the stabilization of manganese(III) with an excess of fluoride in a moderately acidic medium (pH close to 3) and on the use of iron(III) as catalyst. Errors are less than 0.5%.     

Growth of magnetic materials and structures on Si(0 0 1) substrates using Co2Si as a template layer

We report in this paper the use of Co₂Si silicide as a template layer for the integration of magnetic materials and structures on silicon substrate. By undertaking Co deposition on silicon at a temperature of about 300 °C, we show that it is possible to obtain a smooth and epitaxial Co₂Si layer, which can act as a template layer preventing the reaction between Co and other transition metals with silicon. Two examples of over-growth of magnetic materials and structures on this template layer will be presented: growth of ferromagnetic Co layers and of magnetic tunnel junctions (Co(Fe)/AlO_x/NiFe).     

A Note on Circular Chromatic Number of Graphs with Large Girth and Similar Problems

In this short note, we extend the result of Galluccio, Goddyn, and Hell, which states that graphs of large girth excluding a minor are nearly bipartite. We also prove a similar result for the oriented chromatic number, from which follows in particular that graphs of large girth excluding a minor have oriented chromatic number at most 5, and for the pth chromatic number , from which follows in particular that graphs G of large girth excluding a minor have .     

Internal stress influence on the coercivity of FeCuNbSiB thin films

Thin films of Finemet-type alloy with thickness varying from 50 to 1000 nm have been deposited by RF sputtering and annealed at temperature ranging from 150 to 450 °C. Their magnetic and structural properties have been characterized using alternating gradient field magnetometry and X-ray diffraction. In addition, the stress in the films has been measured as a function of temperature from the curvature of the wafers using a laser scanning technique.The coercive field of the films first decreases with annealing temperature due to stress relaxation, and then increases again when crystallisation begins. The optimal annealing conditions comprises between the glass transition and the crystallisation temperature.Its is observed that the coercivity of the as-deposited material is continuously decreasing as the thickness increases, following an inverse square root dependence, in relation with the stress-induced magneto-elastic contribution to the total anisotropy. By opposition, it has been found that the coercive field of devitrified and totally relaxed films is inversely proportional to film thickness. In order to explain this evolution, a model is proposed, based on random anisotropy considerations applied to thin films in which the anisotropy was considered localised in the dimension of thickness.     

Fraternal augmentations, arrangeability and linear Ramsey numbers

We relate the notions of arrangeability and admissibility to bounded expansion classes and prove that these notions can be characterized by ₁(G). (The Burr–Erdős conjecture relates to ₀(G).) This implies the linearity of the Ramsey number and the bounded game chromatic number for some new classes of graphs.     

Structure of rutile TiO2 (110)-(1 x 2): formation of Ti2O3 quasi-1D metallic chains

Combining STM, LEED, and density functional theory, we determine the atomic surface structure of rutile TiO2 (110)-(1 x 2): nonstoichiometric Ti2O3 stripes along the [001] direction. LEED patterns are sharp and free of streaks, while STM images show monatomic steps, wide terraces, and no cross-links. At room temperature, atoms in the Ti2O3 group have large amplitudes of vibration. The long quasi-1D chains display metallic character, show no interaction between them, and cannot couple to bulk or surface states in the gap region, forming good atomic wires.