XHSTT: an XML archive for high school timetabling problems in different countries

We present the progress on the benchmarking project for high school timetabling that was introduced at PATAT 2008. In particular, we announce the High School Timetabling Archive XHSTT-2011 with 21 instances from 8 countries and an evaluator capable of checking the syntax of instances and evaluating the solutions.     

Scheduling a triple round robin tournament with minitournaments for the Finnish national youth ice hockey league

This paper presents a method to schedule a triple round robin tournament, which involves minitournaments, each hosted by one team. A key issue is that at the end of the season the number of home games should be balanced over the teams, despite the fact that in minitournament matches only the host team plays at home. This format is played in the Finnish national ice hockey league for players under the age of 20 years, where the problem is further complicated by many other constraints, for example, preassigned matches resulting from away tours that should limit the distances travelled by the teams. To obtain a schedule for this league, we sequentially solve four distinct combinatorial problems. This method allows us to construct a schedule for the 2009–2010 season, which is superior to the official schedule: it has no hard constraint violations, and outperforms the official schedule on three of five soft constraints.     

Origin of the failure of classical nucleation theory: incorrect description of the smallest clusters

We carry out molecular Monte Carlo simulations of clusters in an imperfect vapor. We show that down to very small cluster sizes, classical nucleation theory built on the liquid drop model can be used very accurately to describe the work required to add a monomer to the cluster. However, the error made in modeling the smallest of clusters as liquid drops results in an erroneous absolute value for the cluster work of formation throughout the size range. We calculate factors needed to correct the cluster formation work given by the liquid drop model. The corrected work of formation results in nucleation rates in good agreement with recent nucleation experiments on argon and water.     

Hydrogen evolution catalyzed by electrodeposited nanoparticles at the liquid/liquid interface

Aqueous protons reduction by decamethylferrocene in 1,2-dichloroethane can be catalyzed efficiently by platinum and palladium nanoparticles electrogenerated in situ at the liquid-liquid interface.     

Conformational analysis XX—13C NMR studies of saturated heterocycles 5—substituent effects on the 13C chemical shifts of methyl substituted 1,3-dithiolanes

The ¹³C NMR chemical shifts for 1,3-dithiolane and 13 methyl substituted derivatives are reported. Substituent effects are derived and compared with those for cyclopentanes and 1,3-dioxolanes. The magnitude and variety of the substituent effects are best explained with the aid of a half-chair conformation where the S-1? C-2? S-3 plane passes between C-4 and C-5.     

Substituent effects on 13C chemical shifts of alkyl-substituted 4-oxo-1,3-dioxolanes and 5-oxo-1,3-oxathiolanes

The 13C NMR chemical shifts for 4-oxo-1,3-dioxolane (1) and its all methyl-substituted derivatives (2-10) as well as for 5-oxo-1,3-oxathiolane (11) and its nine alkyl-substituted derivatives (12-20) are reported. The magnitude and variety of the substituent effects are in accordance with the envelope conformations in which the oxygen or sulfur atom locates at the tip of the envelope as postulated on the basis of earlier data.     

Directional Young’s modulus of single-crystal and cold-rolled titanium from ab initio calculations: Preferred crystal orientation due to cold rolling

Titanium is a strong, corrosion resistant metal with low mass density, making it ideal for various purposes, including aviation and medical applications. In the present work, the elastic properties of titanium have been investigated using the first principles Exact Muffin-Tin Orbitals method. The focus of our study is the anisotropic elasticity of single-crystal and cold-rolled titanium. Both types of titanium are used in industrial applications because of their special mechanical properties compared to randomly ordered polycrystalline alloys. Single crystals have better creep resistance compared to polycrystalline metals, while cold-rolled ones, on the other hand, possess more strength. Here cold-rolled titanium is investigated for the first time using ab initio calculations. Single-crystal results are obtained directly from first principles total energy calculations, whereas the elasticity of the cold-rolled structure is estimated from the single-crystal data. The elasticity of cold-rolled titanium has previously been investigated only experimentally, and thus the present computational approach provides new insight and valuable complementary information, not only for cold-rolled titanium, but also for more complex structures. Our results are found to be in good agreement with experimental findings and therefore serve as a starting point for investigating the elasticity of titanium alloys, which, using our method, can be accomplished as easily as the pure titanium case.     

Copolymerization of glycolic,d,l-lactic and d,l-2-hydroxybutyric acid mixtures present in kraft black liquors

A series of copolymers of glycolic acid (GA), d,l-lactic acid (dl-LA) and d,l-2-hydroxybutyric acid (dl-2HBA) were prepared via melt condensation polymerization. The utilized monomers represent mixtures that are present and potentially obtainable from kraft black liquor by fractionation. Polymerizations were performed in 165 °C at nitrogen atmosphere and reduced pressure using stannous octoate as catalyst. Copolymerizations were conducted with varying dl-2HBA content in order to observe how the presence of the dl-2HBA monomer affects the properties of the polymers. Prepared copolymers were characterized with ¹H NMR and ¹³C NMR, size exclusion chromatography, differential scanning calorimetry and thermogravimetric analysis. The obtained copolymers had molecular weights between M_w = 3500–10,000 g/mol. dl-2HBA had a lowering effect on the glass transition temperatures and molecular weights of the copolymers. However, significant lowering of molecular weight was observed only when the amount of dl-2HBA in the feed exceeded 60%. The results indicate that dl-2HBA can be copolymerized with GA and dl-LA and therefore the corresponding kraft black liquor fractions can be utilized for polymerizations.     

Analysis of nucleation ability of cluster configurations with Monte Carlo simulations of argon

We determine the nucleation ability of argon clusters from Monte Carlo simulations. The nucleation rate appears to be defined by a sole characteristic of the clusters, namely, the stability. The stability is calculated as the ratio of grand canonical growth and decay rates and can be assigned to individual cluster configurations. We study the connection between the stability of the cluster configurations and their volume and total potential energy. Neither the potential energy nor the volume of a cluster configuration has a clear relation to its stability, and thus to the nucleation ability. On the other hand, we show that it is possible to use a specific volume for each cluster size to calculate the work of the cluster formation. These clusters with a unique volume have the same average stability as the full set of clusters. Our simulation method allows us to study the effect of possible deviations from equilibrium in the cluster configuration distributions. We argue that the nucleation process itself can produce a source for such a deviation. We show that even a small deviation from equilibrium in the cluster configuration distribution can lead to a dramatic deceleration of the nucleation rate. Although our simulations may overestimate the magnitude of the effect, they give qualitative estimates for its importance.     

Partial Molar Volume,Ionization, Viscosity and Structure of Glycine Betaine in Aqueous Solutions

Densities, partial molar volumes, and viscosities of aqueous solutions of betaine have been measured at 5, 10, 15, 20, 25, 30, 37, and 45 °C over the concentration range 0.05 to 5.0 mol⋅L⁻¹. The partial molar volumes show that betaine exists partly as a monohydrate and partly in its anhydrous form. The proportion of the anhydrous form increases with increasing temperature. Also, an associated form of betaine appears in concentrated betaine solutions, possibly with water as a bridging group. The significance of the viscosity B-coefficient is discussed. The signs of B _st, the increment of the viscosity B-coefficients arising from structural changes of water, are negative and the signs of dB/dT, the temperature derivative of B, are positive. These results show that betaine is a water structure breaker especially at lower temperatures, and this effect decreases to insignificance at higher temperatures. The ionization equilibria of betaine were investigated in aqueous 0.5 mol⋅L⁻¹ and 1.0 mol⋅L⁻¹ NaNO₃ at 5, 15, 25, and 37 °C by a potentiometric method. Using the least-square computer program SUPERQUAD, the complex forms are deduced to be betanium BH, bis(betanium) BHB, and bis(betaine) B₂ or bis(betaine)hydrate BH₂OB.