On a class of branching problems in broadcasting and distribution

We introduce the following network optimization problem: given a directed graph with a cost function on the arcs, demands at the nodes, and a single source s, find the minimum cost connected subgraph from s such that its total demand is no less than lower bound D. We describe applications of this problem to disaster relief and media broadcasting, and show that it generalizes several well-known models including the knapsack problem, the partially ordered knapsack problem, the minimum branching problem, and certain scheduling problems. We prove that our problem is strongly NP-complete and give an integer programming formulation. We also provide five heuristic approaches, illustrate them with a numerical example, and provide a computational study on both small and large sized, randomly generated problems. The heuristics run efficiently on the tested problems and provide solutions that, on average, are fairly close to optimal.     

Bioinformatics and its role in the study of the evolution and probiotic potential of lactic acid bacteria

Food Science and Biotechnology - Due to their numerous well-established applications in the food industry, there have been many studies regarding the adaptation and evolution of lactic acid...     

Excess molar enthalpies for the binary and ternary mixtures of ether compounds (di-isopropyl ether, di-butyl ether, propyl vinyl ether) with ethanol and isooctane at 298.15 K

Excess molar enthalpy (H ^E ) data at 298.15 K are reported for the binary systems di-isopropyl ether (1)+ethanol (2), di-isopropyl ether (1)+isooctane (2), ethanol (1)+isooctane (2), di-butyl ether (1)+ethanol (2), di-butyl ether (1)+isooctane (2), propyl vinyl ether (1)+ethanol (2) and propyl vinyl ether (1)+isooctane (2). These data were obtained by using an isothermal flow calorimeter. The experimental binary H ^E data were well correlated with the Redlich-Kister model, and infinitely dilute partial excess molar enthalpies for each binary were calculated with the fitted Redlich-Kister parameters. Additionally, the isoclines of H ^E for ternary systems di-isopropyl ether (1)+ethanol (2)+isooctane (3), di-butyl ether (1)+ethanol (2)+isooctane (3) and propyl vinyl ether (1)+ethanol (2)+isooctane (3) at 298.15 K were calculated by using the Radojkovič equation. H ^E for all the measured systems in this work shows that mixing is endothermic.     

Determination and prediction of Kow and dimensionless Henry's constant (H) for 6 ether compounds at several temperatures

The octanol–water partition coefficient (K_ow) and air–water partition coefficient (K_aw) as well as the dimensionless Henry's constant (H) are used to calculate the transport and fate of chemicals in the environment or eco-system. In this work, the K_ow and the H were measured for 6 ether compounds; di-n-butyl ether (DBE), di-isopropyl ether (DIPE), tert-butyl ethyl ether (ETBE), tert-butyl methyl ether (MTBE), propyl vinyl ether (PVE) and tert-amyl methyl ether (TAME) at 4 different temperatures. The K_ow was directly measured by using a conventional slow stirring (SS) method, while the H was measured using headspace gas chromatography (HSGC). Additionally, the measured K_ow and H values were compared with the predicted values by the fragment constant method or HENRYWIN program approaches.     

Liquid–liquid equilibria for ternary systems of dimethyl carbonate + C1–C4 alcohols + water at 298.15 K and atmospheric pressure

The ternary liquid–liquid equilibria (LLE) of the following systems were analytically determined at 298.15 K and atmospheric pressure using stirred and thermo-regulated cells: {dimethyl carbonate (DMC) + methanol + water}, {DMC + ethanol + water}, {DMC + 1-propanol + water}, {DMC + 2-propanol + water}, {DMC + 1-butanol + water} and {DMC + 2-butanol + water}. The experimental ternary LLE data were correlated with the non-random two liquid (NRTL) and UNIversal QUAsiChemical (UNIQUAC) activity coefficient models. In addition, the Bachman–Brown correlation was used to ascertain the reliability of the experimental data for each system.