There are 1,132,835,421,602,062,347 nonisomorphic one‐factorizations of K14

We establish by means of a computer search that a complete graph on 14 vertices has 98,758,655,816,833,727,741,338,583,040 distinct and 1,132,835,421,602,062,347 nonisomorphic one‐factorizations. The enumeration is constructive for the 10,305,262,573 isomorphism classes that admit a nontrivial automorphism. © 2008 Wiley Periodicals, Inc. J Combin Designs 17: 147–159, 2009     

Emergent reaction-diffusion phenomena in capillary tubes

Pattern formation in the Belousov-Zhabotinsky reaction experiments carried out by filling capillary glass tubes with catalyst-immobilized gel for the reaction is reported. Under unperturbed and oscillatory conditions, helicoidal waves appear spontaneously. Quantitative structural data of those helices are obtained by devising an optical tomography technique for extracting rotationally symmetric structures from time-lapse data. Space-time representation of the catalyst oxidation reveals wave transmission phenomenon that is studied further by numerical simulations of a reduced spatial model.     

Tick size and stock returns

Tick size is an important aspect of the micro-structural level organization of financial markets. It is the smallest institutionally allowed price increment, has a direct bearing on the bid-ask spread, influences the strategy of trading order placement in electronic markets, affects the price formation mechanism, and appears to be related to the long-term memory of volatility clustering. In this paper we investigate the impact of tick size on stock returns. We start with a simple simulation to demonstrate how continuous returns become distorted after confining the price to a discrete grid governed by the tick size. We then move on to a novel experimental set-up that combines decimalization pilot programs and cross-listed stocks in New York and Toronto. This allows us to observe a set of stocks traded simultaneously under two different ticks while holding all security-specific characteristics fixed. We then study the normality of the return distributions and carry out fits to the chosen distribution models. Our empirical findings are somewhat mixed and in some cases appear to challenge the simulation results.     

Kinetics of island growth in models of physisorbed and chemisorbed systems

A brief review is given of recent computer simulation studies of the kinetics of island formation in submonolayers of physisorbed and chemisorbcd systems. Examples include models of O/W(112). O/W(110) and orientational ordering in N₂ on graphite.     

Polarizability of shallow donors in EuSe

Permittivity measurements at a microwave frequency 24 GHz have been made on n-type EuSe at low temperatures 4.2–77 K after various annealing times. Consideration of different models for annealing dependent permittivity leads to the polarizability of Se vacancy defects as the most likely explanation. Donor polarizability $\text{α}{}_{\mathrm{d}}\text{= 3.2 × 10}{}^6\text{A}\text{?}{}^3$is found and further an estimation for electron effective mass $\text{m}{}^1\text{= 0.28m}{}_0$.     

Emergence of communities in weighted networks

Topology and weights are closely related in weighted complex networks and this is reflected in their modular structure. We present a simple network model where the weights are generated dynamically and they shape the developing topology. By tuning a model parameter governing the importance of weights, the resulting networks undergo a gradual structural transition from a module-free topology to one with communities. The model also reproduces many features of large social networks, including the "weak links" property.     

Castor oil-based biopolyurethane reinforced with wood microfibers derived from mechanical pulp

Wood fibers with high lignin content show promise to function in numerous applications with advantageous properties if the fiber features are appropriately exploited. The present study introduces a new approach to disintegrate and disperse wood fibers from groundwood pulp (GWP) directly to polyol without additional solvent exchanges or chemical modifications. In comparison bleached chemical pulp with low lignin content was ground in the polyol, but only low consistency (1 wt%) operation was possible, whereas up to 5 wt% consistency with GWP was carried out with ease. The micron sized fibers in polyol were reacted with polymeric diphenylmethane diisocyanate to produce fiber reinforced biopolyurethane (bioPU) composites. The mechanical properties of the composites improved compared to reference bioPU showing 14.6% increase in Young’s modulus, 54.5% in tensile strength and 26.1% in strain at break. The tan δ peaks shifted to higher temperature from 5.5 to 10.4 °C when fibers up to 5.1 wt% were incorporated to bioPU. Overall, the bulk microfibers from GWP with low degree of processing were cost-effective reinforcements for bioPUs, which improved the qualities of the fabricated composites and showed good compatibility with polyurethane.     

Sobolev embeddings in metric measure spaces with variable dimension

In this article we study metric measure spaces with variable dimension. We consider Lebesgue spaces on these sets, and embeddings of the Riesz potential in these spaces. We also investigate Hajłasz-type Sobolev spaces, and prove Sobolev and Trudinger inequalities with optimal exponents. All of these questions lead naturally to function spaces with variable exponents. Supported the Research Council of Norway, Project 160192/V30.     

Diffusion blocking at low particle concentration

The rate equations describing classical particle hopping in periodic lattices are integrated to obtain exact, self-consistent expressions for the occupancy correlation functions at low atomic concentration. The long-wavelength, small-frequency behaviour is analyzed analytically. Exact results for labelled particle diffusion are obtained which properly include the correlation and atomic blocking effects.