Time-dependent discrete road network design with both tactical and strategic decisions

This paper aims to model and investigate the discrete urban road network design problem, using a multi-objective time-dependent decision-making approach. Given a base network made up with two-way links, candidate link expansion projects, and candidate link construction projects, the problem determines the optimal combination of one-way and two-way links, the optimal selection of capacity expansion projects, and the optimal lane allocations on two-way links over a dual time scale. The problem considers both the total travel time and the total CO emissions as the two objective function measures. The problem is modelled using a time-dependent approach that considers a planning horizon of multiple years and both morning and evening peaks. Under this approach, the model allows determining the sequence of link construction, the expansion projects over a predetermined planning horizon, the configuration of street orientations, and the lane allocations for morning and evening peaks in each year of the planning horizon. This model is formulated as a mixed-integer programming problem with mathematical equilibrium constraints. In this regard, two multi-objective metaheuristics, including a modified non-dominated sorting genetic algorithm (NSGA-II) and a multi-objective B-cell algorithm, are proposed to solve the above-mentioned problem. Computational results for various test networks are also presented in this paper.     

A highly sensitive spectrophotometric determination of ultra trace amounts of azide ion in water and biological samples after preconcentration using dispersive liquid-liquid microextraction technique

A simple and highly sensitive method developed for preconcentration and spectrophotometric determination of ultra trace amounts of azide ion (N ₃ ^? ) in water and biological samples using dispersive liquid-liquid microextraction (DLLME) technique. The method is based on ion association formation of azide ion with malachite green and extraction of the ion pairing product using DLLME technique. Some important parameters, such as reaction conditions and the kind and volume of extraction solvent and disperser solvent were studied and optimized. The calibration curve was linear in the range of 0.5–50 μg/L of azide ion. Also, the enrichment factor and extraction recovery obtained were 24.7 and 98.7%, respectively. The method was applied to the determination of azide ion in water and biological samples.     

A novel method for risk assessment of electrostatic sensitivity of nitroaromatics through their activation energies of thermal decomposition

This study presents a novel relationship between electric spark sensitivity of nitroaromatic energetic compounds and their activation energies of thermal decomposition. The new correlation can help to elucidate the mechanism of initiation of energetic materials by electric spark. It can be used to predict the magnitude of electric spark sensitivity of new nitroaromatics, which is difficult to measure. The methodology assumes that electric spark sensitivity of a nitroaromatic energetic compound with general formula C_aH_bN_cO_d can be expressed as a function of its activation energy of thermal decomposition as well as optimized elemental composition and the contribution of specific molecular structural parameters. The new correlation has the root mean square and the average deviations of 1.43 and 1.17 J, respectively, for 22 nitroaromatic energetic compounds with different molecular structures. The proposed new method is also tested for eight nitroaromatic energetic compounds, which have complex molecular structures, e.g., 1,3,7,9-tetranitrophenoxazine, 2,4,6-tris(2,4,6-trinitrophenyl)-1,3,5-triazine, and 1-(2,4,6-trinitrophenyl)-5,7-dinitrobenzotriazole.     

Electrochemical synthesis and characterization of solid-phase microextraction fibers using conductive polymers: application in extraction of benzaldehyde from aqueous solution

In this work, polyaniline, polypyrrole, and polyaniline/polypyrrole composite fibers were synthesized in the absence and presence of oxidized multiwalled carbon nanotubes using electrochemical cyclic voltammetry with CF₃COOH as dopant. Thermal stability of these fibers was studied by differential scanning calorimetry. Then, headspace solid-phase microextraction process coupled with gas chromatography and flame ionization detector was used for comparing extraction capability of benzaldehyde from aqueous solution. Since polyaniline fiber showed better extraction efficiency than the other fibers, its preparation conditions including acid concentration, aniline concentration, scan rate, and amount of multiwalled carbon nanotubes were studied by means of the “one-factor-at-a-time method”. The analytical performance of polyaniline fibers were investigated to determine benzaldehyde from the aqueous solution. The morphology and texture of polyaniline fibers were examined by field emission scanning electron microscopy and Fourier transform infrared spectroscopy analyses. The attained results revealed that the perfect conditions for acid concentration, aniline concentration, scan rate, and multiwalled carbon nanotubes content were 0.5 M, 0.2 M, 25 mV s^?1, and 0.02 wt%, respectively. The limit of detection for the proposed polyaniline fiber was 15 ng ml^?1.     

Electrochemically Generated Nanoparticles of Halogen‐Bridged Mixed‐Valence Binuclear Metal Complex Chains

Spherical nanoparticles composed of MMX chains can be made by a polymerization strategy driven by electrochemical processes. In particular, the [Pt₂(MeCS₂)₄I₂] (MMI₂) dimetal subunit is employed as a monomer for the formation of [Pt₂(MeCS₂)₄I]_n spherical nanostructures on surfaces. We have paid particular attention to elucidating the general mechanism of the deposition process on the basis of in situ electrochemical measurements. The reduction of MMI₂ to give the electrodeposition of nanostructures agrees well with formation of the reduced [MMI₂]^? species followed by a disproportionation mechanism mediated by iodide anions. The chemical composition of the particles was determined by energy‐dispersive X‐ray spectroscopy (EDX) and X‐ray photoelectron spectroscopy (XPS) to reveal the MMI₂ polymer.     

含吡啶的大环席夫碱锰(Ⅱ)配合物:合成、表征及抗菌性质(英文)

在Mn髤模板作用下,2,6-diacetylpyridine(DAP)及合适链状胺化合物通过[1+1]环缩合反应,合成了3个大环席夫碱配合物,并进行了红外、元素分析、质谱及电导率等表征及研究。测得了配合物[MnL1(CH3CN)](ClO4)2的晶体结构,中心离子呈现出稍微扭曲的五角锥配位构型。研究了配合物对S.aureus(ATCC 6633),B.cereus(ATCC 7064),C.xerosis(ATCC 373)(gram-positive bacterial strains),E.coli(PTCC 10009),K.pneuomoniae(MTCC 109),and P.vulgaris(lio)(gram-negative bacterial strains)的抗菌活性。结果显示[MnL3](ClO4)2抗菌活性明显优于[MnL1(CH3CN)](ClO4)2and[MnL2](ClO4)2。在25℃条件下0.1 mol·L-1 KCl溶液中,通过电位计量法测定了化合物的质子化常数。     

Characterization and High Level Expression of Acidic Endoglucanase in Pichia pastoris

Bioconversion of cellulosic material into glucose needs cellulase enzymes. One of the most important organisms that produces cellulases is Trichoderma reesei, whose cellulose enzymes are probably the most widely used in the industry. However, these enzymes are not stable enough at high pH and temperatures. The optimized synthetic endoglucanase II gene with Pichia pastoris codon preferences was secretary expressed in P. pastoris. Recombinant enzyme characterization showed maximum activity at pH 4.8 and temperature 75 °C, and it demonstrated increasing thermal stability in high temperature. The enzyme maintained its activity in a wide pH range from 3.5 to 6.5. The optimization of fermentation medium was carried out in shaking flasks. Recombinant protein expression at optimum conditions (pH 7, temperature 25 °C, and 1 % methanol induction) for 72 h demonstrated 2,358.8 U/ml endoglucanase activity units. To our knowledge, this is the highest acidic thermophilic endoglucanase activity that is reported in crude intracellular medium in P. pastoris. We conclude that P. pastoris is an appropriate host for high-level expression of optimized endoglucanase gene with improved thermal stability.     

Electrospinning of nylon-6,6 solutions into nanofibers: Rheology and morphology relationships

The relationship between the rheological properties of nylon-6,6 solutions and the morphology of their electrospun nanofibers was established. The viscosity of nylon-6,6 in formic acid(90%) was measured in the concentration range of 5 wt%-25 wt% using a programmable viscometer. Electrospinning of nylon-6,6 solutions was carried out under controlled parameters. The chemical structure, morphology and thermal properties of the obtained nanofibers were investigated using Fourier transform infrared spectroscopy(FTIR), scanning electron microscopy(SEM) and differential scanning calorimetry(DSC), respectively. Entanglement concentration(ce) was found to be 15 wt% and a power law relationship between specific viscosity and solution concentration was observed with exponents of 2.0 and 3.3 for semi-dilute unentangled(c ce) and semi-dilute entangled(c ce) regimes, respectively. The diameter and uniformity of the nanofibers were found to be dependent on the viscosity. Moreover, the average diameter of electrospun nanofibers was found to be dependent on zero shear rate viscosity and normalized concentration(c/ce) in a power law relationship with exponents of 0.298 and 0.816, respectively. For nylon-6,6 solutions, the entanglement concentration(ce = 15 wt%) provides the threshold viscosity required for the formation of a stable polymeric jet during electrospinning and producing uniform beadless fibers. For concentrations less than ce, beaded fibers with some irregularities are formed. DSC analysis showed an increase in crystallinity of all electrospun samples compared to original polymer. Furthermore, Based on FTIR spectroscopy, α phase is dominant in electrospun nanofibers and minor amount of β and γ phases is also available.     

A unique path to reach thermostable polypyrrole/Pd microfibers via chemical oxidative polymerization

Polypyrrole/palladium (PPy/Pd) nanocomposites, labeled by PPy/Pd-2/1-0, PPy/Pd-2/1-25, and PPy/Pd-3/1-0, are synthesized via a direct redox reaction between pyrrole monomer and PdCl₂ in the presence of sodium dodecyl sulfate (SDS) stabilizer in chloroform (CHCl₃)/acetonitrile (CH₃CN) binary organic solvents with 2:1 and 3:1 volume ratios at two temperatures involving 0 and 25 °C. A Pd-unloaded polypyrrole (PPy-2/1-0) is also synthesized similarly using iron(III) chloride (FeCl₃) oxidant for comparison purposes. The volume ratio of the solvents used as well as the temperature at which the oxidative polymerization takes place affects significantly the thermostability of the resulting nanocomposites. According to the thermogravimetric analyses, the stability order towards heat is found to be PPy/Pd-2/1-25?>?PPy/Pd-2/1-0?>?PPy/Pd-3/1-0?>?PPy-2/1-0. The nanocomposite PPy/Pd-2/1-25 shows clearly more thermostability compared to PPy/Pd-2/1-0 analog at temperatures above 400 °C. Furthermore, whereas three discrete maxima can be obviously found in the differential thermal analysis (DTA) thermogram of PPy-2/1-0 pure sample, no distinctive exothermic peak is observed in the curves of the three Pd-loaded nanocomposites.