High energy neutrinos from gamma-ray bursts with precursor supernovae

The high energy neutrino signature from proton-proton and photo-meson interactions in a supernova remnant shell ejected prior to a gamma-ray burst provides a test for the precursor supernova, or supranova, model of gamma-ray bursts. Protons in the supernova remnant shell and photons entrapped from a supernova explosion or a pulsar wind from a fast-rotating neutron star remnant provide ample targets for protons escaping the internal shocks of the gamma-ray burst to interact and produce high energy neutrinos. We calculate the expected neutrino fluxes, which can be detected by current and future experiments.     

Aging in subdiffusion generated by a deterministic dynamical system

We investigate aging behavior in a simple dynamical system: a nonlinear map which generates subdiffusion deterministically. Asymptotic behaviors of the diffusion process are described using aging continuous time random walks. We show how these processes are described by an aging diffusion equation which is of fractional order. Our work demonstrates that aging behavior can be found in deterministic low dimensional dynamical systems.     

Effect of chemical modifications on the electronic structure of poly(3‐hexylthiophene)

The widespread use of poly(3‐hexylthiophene) (P3HT) in the active layers of organic solar cells indicates that it possesses chemical stability and solubility suitable for such an application. However, it would be desirable to have a material that can maintain these properties but with a smaller bandgap, which would lead to more efficient energy harvesting of the solar spectrum. Fifteen P3HT derivatives were studied using the Density Functional Theory. The conclusion is that it is possible to obtain compounds with significantly smaller bandgaps and with solubility and stability similar to that of P3HT, mostly through the binding of oxygen atoms or conjugated organic groups to the thiophenic ring. © 2013 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys., 2013     

The vapour pressures over saturated aqueous solutions of dl-2-aminobutyric acid, 4-aminobutyric acid,sodium-d-gluconate,sodium hippurate,and potassium magnesium-l-aspartate

Vapour pressures of water over saturated solutions of dl-2-aminobutyric acid, 4-aminobutyric acid, sodium-d-gluconate, sodium hippurate, and potassium magnesium-l-aspartate were determined over the (278 to 322) K temperature range. The determined vapour pressures were used to obtain the water activities, the molar enthalpies of vaporization, and the osmotic coefficients of sodium-d-gluconate.     

Sharp concentration of the chromatic number on random graphsG n,p

The distribution of the chromatic number on random graphsG _{n, p} is quite sharply concentrated. For fixedp it concentrates almost surely in √n ω(n) consecutive integers where ω(n) approaches infinity arbitrarily slowly. If the average degreepn is less thann ^1/6, it concentrates almost surely in five consecutive integers. Large deviation estimates for martingales are used in the proof.     

Labeling algorithm for the shortest path problem with turn prohibitions with application to large-scale road networks

In real road networks, the presence of no-left, no-right or no U-turn signs, restricts the movement of vehicles at intersections. These turn prohibitions must be considered when calculating the shortest path between a starting and an ending point in a road network. We propose an extension of Dijkstra’s algorithm to solve the shortest path problem with turn prohibitions. The method uses arc labeling and a network structure with low memory requirements. We compare the proposed method with the dual graph approach in a set of randomly generated networks and Bogotá’s large-scale road network. Our computational experiments show that the performance of the proposed method is better than that of the dual graph approach, both in terms of computing time and memory requirements. We co-developed a Web-based decision support system for computing shortest paths with turn prohibitions that uses the proposed method as the core engine.     

Copolymerization of styrene and methacrylic acid in concentrated emulsions

Copolymerization of styrene and methacrylic acid was carried out by the concentrated emulsion polymerization method, using sodium dodecylsulfate and AIBN as emulsifier and initiator, respectively. Compared to conventional emulsion polymerization, a much smaller amount of water (5–25 vol %) is employed as the continuous phase and thus the loss of methacrylic acid, which is very soluble in water, is minimized. The concentrated emulsion, which has the appearance of a gel, was prepared at room temperature, and was polymerized at 40°C. The size of copolymer latexes is affected by the internal phase ratio, and was in the range of 0.2–0.3 μm in diameter. Potentiometric titration was used to determine the surface density of the carboxylic groups of the copolymer latexes and its dependence on the feed molar ratio of methyacrylic acid to styrene. NMR and IR spectroscopies have been employed to determined the composition of the copolymer latexes.     

Bijective proofs of two broken circuit theorems

We prove, by means of explicit bijections, theorems of Whitney and Stanley that express the coefficients of the chromatic polynomial of a graph G and the number of acyclic orientations of G in terms of numbers of sets of edges that contain no broken circuits of G.     

Characterization of Ascentis RP-Amide column: Lipophilicity measurement and linear solvation energy relationships

This study investigates lipophilicity determination by chromatographic measurements using the polar embedded Ascentis RP-Amide stationary phase. As a new generation of amide-functionalized silica stationary phase, the Ascentis RP-Amide column is evaluated as a possible substitution to the n  -octanol/water partitioning system for lipophilicity measurements. For this evaluation, extrapolated retention factors, log k^′_w$\text{log}{k^{\prime }}_w$, of a set of diverse compounds were determined using different methanol contents in the mobile phase. The use of n-octanol enriched mobile phase enhances the relationship between the slope (S  ) of the extrapolation lines and the extrapolated log k^′_w$\text{log}{k^{\prime }}_w$ (the intercept of the extrapolation), as well as the correlation between log P   values and the extrapolated log k^′_w$\text{log}{k^{\prime }}_w$ (1:1 correlation, r² = 0.966). In addition, the use of isocratic retention factors, at 40% methanol in the mobile phase, provides a rapid tool for lipophilicity determination. The intermolecular interactions that contribute to the retention process in the Ascentis RP-Amide phase are characterized using the solvation parameter model of Abraham. The LSER system constants for the column are very similar to the LSER constants of the n-octanol/water extraction system. Tanaka radar plots are used for quick visual comparison of the system constants of the Ascentis RP-Amide column and the n-octanol/water extraction system. The results all indicate that the Ascentis RP-Amide stationary phase can provide reliable lipophilic data.