The stochastic bid generation problem in combinatorial transportation auctions

In this paper, we deal with the generation of bundles of loads to be submitted by carriers participating in combinatorial auctions in the context of long-haul full truckload transportation services. We develop a probabilistic optimization model that integrates the bid generation and pricing problems together with the routing of the carrier’s fleet. We propose two heuristic procedures that enable us to solve models with up to 400 auctioned loads.     

Optimizing the Electricity Consumption with a High Degree of Flexibility Using a Dynamic Tariff and Stackelberg Game

Journal of Optimization Theory and Applications - Recent advancements in the sensor industry, smart metering systems and communication technology have led to interesting electricity consumption...     

DFT study of structure–properties correlations in [MnTPP][TCNE] quasi-one-dimensional molecular magnets

We report the first band structure calculations of the quasi-one-dimensional [MnTPP][TCNE] compounds (TPP = meso-tetraphenylporphyrinato, TCNE = tetracyanoethylene), based on Density Functional Theory (DFT) methods, in order to interpret the magnetic ordering in these prototypic systems. We compare and contrast the results of broken-symmetry DFT calculations for extended systems, with periodic boundary conditions, and for finite systems, magnetic dimers modeling the actual molecular magnets. By varying systematically the main angles, we are able to determine the geometry dependence of the exchange interaction. Structure–properties correlations in these charge-transfer salts reveal the determinant role of the Mn-(N≡C)_TCNE bond angle on the strength of the ferrimagnetic coupling between the S ₁ = 2 spin located on the Mn^III-porphyrin donor and the S ₂ = 1/2 spin positioned on the cyanocarbon acceptor. When the Mn-(N≡C)_TCNE angle is decreased, the intrachain magnetic coupling strengthens, correlated with the increase in the d_z² - p* d_{{z^{2} }} - \pi * orbital overlap. The exchange coupling constants resulting from DFT calculations of extended systems, with periodic boundary conditions, were found to be consistent with those obtained for the dimers, but systematically smaller. The exchange constants vary strongly with the functional used, hybrid functionals such as B3LYP leading to results that better correlate with the experimental mean-field critical temperatures. The coupling constant varies significantly with the type of broken-symmetry approach, depending on the overlap between magnetic orbitals, but weakly on the basis set once polarization effects are included. The electronic structure calculations for the extended systems provide a density of states consistent with the energy spectrum of the corresponding dimer, allowing for an intuitive explanation of the intrachain ferrimagnetic ordering.     

A Comparative Loading and Release Study of Vancomycin from a Green Mesoporous Silica

Since its first use as a drug delivery system, mesoporous silica has proven to be a surprisingly efficient vehicle due to its porous structure. Unfortunately, most synthesis methods are based on using large amounts of surfactants, which are then removed by solvent extraction or heat treatment, leading to an undesired environmental impact because of the generated by-products. Hence, in the present study, we followed the synthesis of a silica material with a wormhole-like pore arrangement, using two FDA-approved substances as templates, namely Tween-20 and starch. As far as we know, it is the first study using the Tween-20/starch combo as a template for mesoporous silica synthesis. Furthermore, we investigated whether the obtained material using this novel synthesis had any potential in using it as a DDS. The material was further analyzed by XRD, TEM, FT-IR, N₂ adsorption/desorption, and DLS to investigate its physicochemical features. Vancomycin was selected as the active molecule based on the extensive research engaged towards improving its bioavailability for oral delivery. The drug was loaded onto the material by using three different approaches, assuming its full retention in the final system. Thermal analysis confirmed the successful loading of vancomycin by all means, and pore volume significantly decreased upon loading, especially in the case of the vacuum-assisted method. All methods showed a slower release rate compared to the same amount of the pure drug. Loadings by physical mixing and solvent evaporation released the whole amount of the drug in 140 min, and the material loaded by the vacuum-assisted method released only 68.2% over the same period of time, leading us to conclude that vancomycin was adsorbed deeper inside the pores. The kinetic release of the three systems followed the Higuchi model for the samples loaded by physical mixing and vacuum-assisted procedures, while the solvent evaporation loading method was in compliance with the first-order model.     

Die Bildung cyclischer Amidiniumiodide und -polyiodide aus 1,3,5-Trimethyl-hexahydro-1,3,5-triazin und Iod

Formation of cyclic Amidiniumiodides and -polyiodides from 1,3,5-Trimethyl-hexahydro-1,3,5-triazine and Iodine The reaction of 1,3,5-trimethyl-hexahydro-1,3,5-triazine (CH₃NCH₂)₃ with iodine in the molar ratio (CH₃NCH₂)₃:I₂ = 2:1 gives the new compound 1,3,5-trimethyl-tetrahydro-1,3,5-triazinium-iodide C₆H₁₄N₃I. This iodide adds one mole I₂ and forms 1,3,5-trimethyl-tetrahydro-1,3,5-triazinium-triiodide C₆H₁₄N₃I₃. The crystal structure analysis shows a cation, in which two methyl groups and five ring atoms are planar arranged. The third methyl group stands axial to the ring. 1,3,5-Trimethyl-tetrahydro-1,3,5-triazinium-pentaiodide is formed by adding a further mole I₂.     

The propagation of non-Lefschetz type, the Gottlieb group and related questions

This is a brief note which indicates how the property of being non-Lefschetz may be propagated by equivariant symplectic maps. We also discuss some questions related to the Gottlieb group and nilpotency of symplectic manifolds. To Vladimir Arnold, who taught me symplectic geometry without knowing it     

Mechanochemically initiated polymerizations. VIII. Influence of chemical nature of monomers

The article presents some results which prove that vinylic, acrylic, dienic, and cyclic monomers, as well as substances which cannot be polymerized by conventional methods (acetonitrile) are activated under the influence of mechanical energy, by vibratory milling, and participate in polymerization and copolymerization reactions.     

Copolymerizations mechanochemically initiated—I. Influence of some factors on the copolymerization of acrylonitrile with styrene

The possibility of initiating copolymerization mechanochemically is studied. Acrylonitrile and styrene were used as monomers; the mechanical energy was supplied by vibratory milling in metallic equipment. No additives were introduced to activate the reaction. The process was carried out at 18 ± 2° and study was made of the following parameters: duration, rate of wear of the grinding media, comonomer ratio. The reaction probably proceeds through radical-anions and catalysis by the apparatus walls. The copolymers thus synthesized are crystalline, thermostable compounds resistant to chemical agents.     

HYDROGEN GENERATION FROM ARTIFICIAL SEA HATER IN A SEMICONDUCTOR SEPTUM ELECTROCHEMICAL PHOTOVOLTAIC CELL

Visible light of the solar spectrum is directly converted to stored chemical energy of hydrogen from artificial sea water in a novel electrochemical photovoltaic cell. The principal element of the cell, modeled after the photosynthetic thylakoid membrane, is a semiconductor septum made of polycrystalline n-CdSe thin film deposited on nickel foil, which separates two aqueous solutions. Under short-circuit conditions, vigorous hydrogen evolution was seen at the Ni surface and continued as long as the cell was operated. The novel cell, the concept of which was derived from pigmented bilayer lipid membrane studies, is easy to construct, simple to operate, and appears to be a practical approach to the photochemical conversion and storage of solar energy.