Grasp Embedded Scatter Search for the Multicommodity Capacitated Network Design Problem

A GRASP embedded Scatter Search is developed for the multicommodity capacitated network design problem. Difficulty for this problem arises from the fact that selection of the optimal network design is an NP-complete combinatorial problem. There exist no polynomial exact algorithms which can solve this problem in a reasonable period of time for realistically sized instances. In such cases, heuristic procedures are commonly used. Two strategies were designed for GRASP: a traditional approach and a memory based technique. As for Scatter Search, 5 different strategies were used to update the reference set. Computational results on a large set of randomly generated instances show the convenience of the proposed procedures.     

Diffraction of a Bose-Einstein condensate from a magnetic lattice on a microchip

We experimentally study the diffraction of a Bose-Einstein condensate from a magnetic lattice, realized by a set of 372 parallel gold conductors which are microfabricated on a silicon substrate. The conductors generate a periodic potential for the atoms with a lattice constant of 4 microm. After exposing the condensate to the lattice for several milliseconds we observe diffraction up to fifth order by standard time of flight imaging techniques. The experimental data can be quantitatively interpreted with a simple phase imprinting model. The demonstrated diffraction grating offers promising perspectives for the construction of an integrated atom interferometer.     

Unusual C-6 Lithiation of 2-Chloropyridine-Mediated by BuLi-Me(2)N(CH(2))(2)OLi. New Access to 6-Functional-2-chloropyridines and Chloro-bis-heterocycles

The reaction of 2-chloropyridine with alkylithium generally results in nucleophilic addition leading to the loss of chlorine atom while exclusive directed ortho metalation is obtained using LDA. Herein it is shown that the BuLi-Me(2)N(CH(2))(2)OLi (BuLi-LiDMAE) superbase promotes an unprecedented regioselective C-6 lithiation. The method was successfully applied to the preparation of potentially useful chlorinated pyridinic and bis-heterocyclic synthons.     

Work function changes during low pressure oxidation of aluminum at room temperature

The oxidation kinetics of clean bulk aluminum surfaces exposed to low oxygen pressures (10^?8 to 2 × 10^?6 torr) at room temperature were followed by measurement of work function changes. The interaction of oxygen with aluminum resulted in a decrease in the work function, indicating that the chemisorbed surface oxygen was unstable and incorporation into the subsurface region took place even at very small surface coverages. A “stable layer” of constant work function was finally formed on the aluminum surface. The limiting work functio nchange (work function change to form the “stable layer”) became less negative with increase in oxygen pressure. It was not possible to explain these results on the basis of previously published oxygen uptake models. A new model based on a pressure dependent limiting amount of outer surface and incorporated oxygen is proposed to explain the pressure dependence of the limiting work function change.     

Determinazione di alcuni composti ossiantrachinonici a mezzo di titolazione in solventi non acquosi

Riassunto E stato applicato il metodo di titolazione potenziometrica con metilato sodico a composti fenolici aventi formula simile come l'1–8 diossiantrachinone, l'1–8 diossi-3-metilantrachinone e l'1–8 diossi-3-metil antrone, di notevole importanza farmaceutica.Come solvente si è usata la piridina e come rivelatori del punto di equivalenza una coppia di elettrodi vetro-antimonio non essendo possibile usare indicatori data la forte colorazione delle soluzioni.

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Summary Potentiometric titration with sodium methylate was used ton determine derivatives whose constitution is similar to that of 1,8-dihydroxyanthraquinone, 1,8-dihydroxy-3-methylanthraquinone and l,8-dihydroxy-3-methylanthrone.The solvent is pyridine. The change point was determined by means of an electrode pair: glass electrode-antimony electrode, since the intense self-color of the solutions excludes the use of indicators.

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Zusammenfassung Die potentiometrische Titration mit Natriummethylat wurde zur Bestimmung von Derivaten herangezogen, deren Zusammensetzung dem 1,8-Dihydroxyanthrachinon, dem 1,8-Dihidroxy-3-methylanthrachinon und dem 1,8-Dihidroxy-3-methylanthron ähnlich ist.Als Lösungsmittel wird Pyridin verwendet. Der Umschlagspunkt wird mit Hilfe eines Elektrodenpaares Glaselektrode-Antimonelektrode festgestellt, da die starke Eigenfärbung der Lösungen den Gebrauch von Indikatoren ausschließt.

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Résumé Le titrage potentiométrique par le méthylate de sodium a été appliqué au dosage de dérivés dont la composition est semblable à celles de la 1, 8-dihydroxyanthraquinone, de la 1,8-dihydroxy-3-méthylanthraquinone et de la l,8-dihydroxy-3-méthylanthrone. On utilise la pyridine comme solvant.Le point final de titrage est déterminé à l'aide d'un système électrode de verre: électrode d'antimoine car la forte coloration des solutions interdit l'emploi d'indicateurs.

     

Local thermodynamic derivation of Young's equation

A derivation of Young's equation based on the energy balance near the contact line is presented. Our proposal is rigorous and avoids the errors identified in the usual local derivation. It is valid under very general conditions (for any geometry, in a gravitational field and for compressive fluids). Deviations of the contact angle from Young's equation are discussed in several cases: surfaces of high curvature and line tension. Finally, the relationship between surface tensions and surface energies comes as an additional, natural result. Our derivation also provides a new physical insight into the equilibrium of forces acting near the contact line. Its local character makes the recourse to integral analysis unnecessary, which results in a great simplification when compared to other general treatments.     

Observation of dynamical instability for a Bose-Einstein condensate in a moving 1D optical lattice

We have experimentally studied the unstable dynamics of a harmonically trapped Bose-Einstein condensate loaded into a 1D moving optical lattice. The lifetime of the condensate in such a potential exhibits a dramatic dependence on the quasimomentum state. This is unambiguously attributed to the onset of dynamical instability, after a comparison with the predictions of the Gross-Pitaevskii theory. Deeply in the unstable region we observe the rapid appearance of complex structures in the atomic density profile, as a consequence of the condensate phase uniformity breakdown.     

Time-delayed spread of viruses in growing plaques

The spread of viruses in growing plaques predicted by classical models is greater than that measured experimentally. There is a widespread belief that this discrepancy is due to biological factors. Here we show that the observed speeds can be satisfactorily predicted by a purely physical model that takes into account the delay time due to virus reproduction inside infected cells. No free or adjustable parameters are used.     

Diazaisoindigo bithiophene and terthiophene copolymers for application in field‐effect transistors and solar cells

Two donor–acceptor conjugated polymers with azaisoindigo as acceptor units and bithiophene and terthiophene as donor units have been synthesized by Stille polymerization. These two polymers have been successfully applied in field‐effect transistors and polymer solar cells. By changing the donor component of the conjugated polymer backbone from bithiophene to terthiophene, the density of thiophene in the backbone is increased, manifesting as a decrease in both ionization potential and in electron affinity. Therefore, the charge transport in field‐effect transistors switches from ambipolar to predominantly hole transport behavior. PAIIDTT exhibits hole mobility up to 0.40 cm²/Vs and electron mobility of 0.02 cm²/Vs, whereas PAIIDTTT exhibits hole mobility of 0.62 cm²/Vs. Polymer solar cells were fabricated based on these two polymers as donors with PC₆₁BM and PC₇₁BM as acceptor where PAIIDTT shows a modest efficiency of 2.57% with a very low energy loss of 0.55 eV, while PAIIDTTT shows a higher efficiency of 6.16% with a higher energy loss of 0.74 eV. Our results suggest that azaisoindgo is a useful building block for the development of efficient polymer solar cells with further improvement possibility by tuning the alternative units on the polymer backbone. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2691–2699