Third-order nonlinear optical properties and structures of (E)-N-(4-nitrobenzylidene)-2,6-dimethylaniline and (E)-N-(4-nitrobenzylidene)-2,3-dimethylaniline

(E)-N-(4-Nitrobenzylidene)-2,6-dimethylaniline (1) and (E)-N-(4-nitrobenzylidene)-2,3-dimethylaniline (2) have been synthesized. The crystal structures of both compounds have been defined by X-ray diffraction analysis. The maximum one-photon absorption (OPA) wavelengths recorded by quantum mechanical computations using a configuration interaction (CI) method are estimated in the UV region to be shorter than 450 nm, showing good optical transparency to the visible light. To provide an insight into the microscopic third-order nonlinear optical (NLO) properties of the investigated molecules, both dispersion-free (static) and also frequency-dependent (dynamic) linear polarizabilities (α) and second hyperpolarizabilities (γ) at λ = 825–1125 nm and 1050–1600 nm wavelength areas have been computed using time-dependent Hartree–Fock (TDHF) method. According to the ab initio calculation results, the title molecules exhibit second hyperpolarizabilities with non-zero values, implying microscopic third-order NLO behavior.     

Preconcentration of Nickel and Cobalt Prior to Their Determination by Graphite Furnace Atomic Absorption Spectrometry Using the Water-Soluble Polymer Poly(Vinyl Pyrrolidinone)

The use of a water-soluble polymer, poly(vinyl pyrrolidinone) (PVP), for the preconcentration and separation of nickel and cobalt prior to their determination by graphite furnace atomic absorption spectrometry is described. For this purpose, the sample and the water-soluble polymer solutions were mixed, and the metal-bound polymer was precipitated by pouring the mixture into acetone. The precipitate was separated by decantation and dissolved with distilled-deionized water. The analyte elements were determined by graphite furnace atomic absorption spectrometry. The validity of the method was tested with spiked sea water and mineral water samples. The analytes added to the samples were quantitatively recovered within the range of 95% confidence limits. The proposed technique is fast, simple, precise and inexpensive. Its low blank values and high precision are other important advantages.     

The impact of [1,2,5]chalcogenazolo[3,4-f]-benzo[1,2,3]triazole structure on the optoelectronic properties of conjugated polymers

Two novel conjugated near-infrared (NIR) absorbing donor–acceptor type copolymers comprising benzodithiophene as the donor and [1,2,5]chalcogenazolo[3,4-f]-benzo[1,2,3]triazole derivatives as the acceptors, spaced with thiophene as the π-bridge, were designed and synthesized via Stille polycondensation reaction. The effect of acceptor strength on optoelectronic properties was targeted and investigated. Branched alkyl chains (the extended 2-octyl-1-dodecyl alkyl chain;  C₈C₁₂) were introduced to 5H-[1,2,3]triazolo[4′,5′:4,5]benzo[1,2-c][1,2,5]thiadiazole and 5H-[1,2,3]triazolo[4′,5′:4,5]benzo[1,2-c][1,2,5]selenadiazole for enhanced solubility of polymers which ease the processability hence device constructions. The strongly electron-withdrawing units lead to a substantial change in the absorption properties via promotion of the intramolecular charge transfer band alongside the π–π* transition. The resultant soluble polymers were characterized via cyclic voltammetry to determine highest occupied molecular orbital and lowest unoccupied molecular orbital energy levels as −5.00 and −3.92 eV for PSBT and −4.86 and −4.04 eV for PSeBT, respectively. Electronic band gaps of the copolymers were calculated as 1.08 eV for PSBT and 0.82 eV for PSeBT, respectively. NIR absorbing copolymers were used to construct electrochromic devices.     

A multi-period double coverage approach for locating the emergency medical service stations in Istanbul

We consider the multi-period location planning problem of emergency medical service (EMS) stations. Our objective is to maximize the total population serviced by two distinct stations within two different response time limits over a multi-period planning horizon. Our aim is to provide a backup station in case no ambulance is available in the closer station and to develop a strategic plan that spans multiple periods. In order to solve this problem, we propose a Tabu Search approach. We demonstrate the effectiveness of the proposed approach on randomly generated data. We also implement our approach to the case of Istanbul to determine the locations of EMS stations in the metropolitan area.     

Spectroscopic Studies and Crystal Structure of (<Emphasis Type="Italic">Z</Emphasis>)-6-[(2-hydroxyphenylamino)methylene]-2-methoxycyclohexa-2,4-dienone

Abstract  The Schiff base (Z)-6-[(2-hydroxyphenylamino)methylene]-2-methoxycyclohexa-2,4-dienone has been synthesized from the reaction of 2-aminophenol with 2-hydroxy-3-methoxybenzaldehyde. The title compound has been characterized by elemental analysis, FT-IR, ¹H-NMR, ¹³C-NMR and UV–Visible techniques. The structure of the title compound also was determined crystallographically. The crystal structure has been solved by direct methods and refined by full-matrix least squares. The title compound crystallize in the monoclinic space group P2₁/c with a = 10.438(1), b = 8.851(1), c = 12.746(1) ?, β = 95.72(1)°, V = 1171.7(2) ?³, D _x  = 1.379 g cm⁻³, respectively (R1 = 0.0522 and wR2 = 0.126 for 1442 reflections [I > 2σ(I)]). Index Abstract   N-salicylideneaniline derivatives have been shown to exist as tautomeric forms due to intramolecular proton shifts between the phenol-oxygen and the imine-nitrogen, via intramolecular hydrogen bonding O–H···N or O···H–N.      

Characterization of facility assignment costs for a location-inventory model under truckload distribution

We consider a two-stage distribution system, where the first stage consists of potential distribution centres (DCs) and the second stage consists of geographically dispersed existing retailers. Our goal is to determine the set of open DCs and assignment of open DCs to retailers simultaneously with inventory decisions of retailers. In addition to the DC-specific fixed facility location costs, we explicitly model the inventory replenishment and holding costs at the retailers and truckload transportation costs between the DCs and the retailers. The transportation costs are subject to truck/cargo capacity, leading to an integrated location-inventory problem with explicit cargo costs. We develop a mixed-integer nonlinear model and analyse its structural properties leading to exact expressions for the so-called implied facility assignment costs and imputed per-unit per-mile transportation costs. These expressions analytically demonstrate the interplay between strategic location and tactical inventory/transportation decisions in terms of resulting operational costs. Although both the theory and practice of integrated logistics have recognized the fact that strategic and tactical decisions are interrelated, to the best of our knowledge, our paper is the first to offer closed-form results demonstrating the relationship explicitly. We propose an efficient solution approach utilizing the implied facility assignment costs and we demonstrate that significant savings are realizable when the inventory decisions and cargo costs are modelled explicitly for facility location purposes.