Management of periodic demands in distribution systems

The problem of the optimal scheduling of periodic demands for a given facility or commodity is presented and some properties of an integer programming model are discussed. Algorithms (both of implicit enumeration type and heuristic) are also given.     

On the behavior of α-brominated dimethyl o-benzenediacetate toward nitrogen nucleophiles . Part I. Reaction of dimethyl α,α'-dibromo o-benzenediacetate with hydrazines

Meso- ( 1a ) and racemic dimethyl α,α'-dibromo o-benzenediacetate ( 1b ) when condensed with hydrazine and methylhydrazine furnished respectively 1,3-dicarbomethoxyisoindole ( 5a ) and its N-methyl derivative ( 5b ). Reaction of phenylhydrazine with 1a led to the N-phenylisoindole ( 5c ) and to the N-anilino isoindoline ( 6 ) as the cis isomer; conversely, 1b was transformed into a mixture of the 2-phenyl-1,2,3,4-tetrahydrophthalazine ( 7 ), the trans isomer of ( 6 ), the N-anilinoisoindole ( 5d ) and dimethyl α-(N'-phenylhydrazino)-o-benzenediacetate ( 8 ). Compounds 1a and 1b were also condensed with acetylhydrazine to give a mixture of the N-acetylaminoisoindoline ( 12 ) and of the 2-acetyl-1,2,3,4-tetrahydrophthalazine ( 13 ).     

Can a synthetic thread act as an electrochemically switchable molecular device?

Here we report that at room temperature in acetonitrile after the reduction of the naphthalimide-site, a synthetic molecular thread undergoes a complete conformational change which makes possible an efficient conversion of chemical energy into mechanical work; such results point out the ability of the thread to act as a molecular device under electrochemical control.     

A macroporous polymer-supported cyclic anhydride for efficient sequestration of amines

The efficient removal of primary and secondary amines from organic solutions using a macroporous polymer-supported anhydride is described. The sequestering of primary amines by the anhydride via polymer-bound amide formation is completed within 2-4 h at room temperature. Secondary amines require typically 4 h for complete sequestration.     

Improved parameterization of the quantum harmonic oscillator model based on localized wannier functions to describe Van der Waals interactions in density functional theory

Recently, the quantum harmonic oscillator model has been combined with maximally localized Wannier functions to account for long‐range dispersion interactions in density functional theory calculations (Silvestrelli, J. Chem. Phys. 2013, 139, 054106). Here, we present a new, improved set of values for the three parameters involved in this scheme. To test the new parameter set we have computed the potential energy curves for various systems, including an isolated Ar2 dimer, two N2 dimers interacting within different configurations, and a water molecule physisorbed on pristine graphene. While the original set of parameters generally overestimates the interaction energies and underestimates the equilibrium distances, the new parameterization substantially improves the agreement with experimental and theoretical reference values. © 2016 Wiley Periodicals, Inc.     

High temperature superconductivity in sulfur and selenium hydrides at high pressure

Due to its low atomic mass, hydrogen is the most promising element to search forhigh-temperature phononic superconductors. However, metallic phases of hydrogen are onlyexpected at extreme pressures (400 GPa or higher). The measurement of the recordsuperconducting critical temperature of 203 K in a hydrogen-sulfur compound at 160 GPa ofpressure [A.P. Drozdov, M.I. Eremets, I.A. Troyan, arXiv:1412.0460[cond-mat.supr-con] (2014); A.P. Drozdov, M.I. Eremets, I.A. Troyan, V.Ksenofontov, S.I. Shylin, Nature 525, 73 (2015)], shows that metallization ofhydrogen can be reached at significantly lower pressure by inserting it in the matrix ofother elements. In this work we investigate the phase diagram and the superconductingproperties of the H-S systems by means of minima hopping method for structure predictionand density functional theory for superconductors. We also show that Se-H has a similarphase diagram as its sulfur counterpart as well as high superconducting criticaltemperature. We predict H₃Se to exceed 120 K superconductivity at 100 GPa. We showthat both H₃Se andH₃S, due to thecritical temperature and peculiar electronic structure, present rather unusualsuperconducting properties.     

An efficient LDA+U based tight binding approach

The functionals usually applied in DFT calculations have deficiencies in describing systems with strongly localized electrons such as transition metals or rare earth (RE) compounds. In this work, we present the self-consistent charge density based functional tight binding (SCC-DFTB) calculation scheme including LDA+U like potentials and apply it for the simulation of RE-doped GaN. DFTB parameters for the simulation of GaN and a selection of rare earth ions, where the f electrons were explicitly included in the valence, have been created. The results of the simulations were tested against experimental data (where present) and against various more sophisticated but computationally more costly DFT calculations. Our approach is found to correctly reproduce the geometry and the energetic of the studied systems.     

Density and Volume Properties of Ethane-1,2-diol + 1,2-Dimethoxyethane + Water Ternary Mixtures from −10° to 80°

Thermodynamic interactions in the ethane-1,2-diol (1) + 1,2-dimethoxyethane(2) + water (3) ternary system have been investigated in terms of the excessmolar volume, derived from density measurements at 19 different temperaturesfrom –10;dg to 80;dgC. Fourteen three-component mixtures have been considered,covering the entire composition range. The excess molar volumes are discussedin terms of conformational changes induced in each component by the presenceof another one. The results obtained support the hypothesis of the absence of anythree-component complex adducts under all experimental conditions investigated.