Some physico-chemical properties of pure and doped nickel oxide. Thermal analyses and X-ray diffraction studies

In this investigation pure and doped NiO with different concentrations of Al, Ga or In are thermally analysed. The results indicate the presence of two endothermic peaks at about 120 and 250°C which were attributed to the loss of adsorbed water and phase change, respectively. X-Ray data indicated that all samples belong to the cubic system. In the case of samples doped with high concentrations of Ga or In, a new line is observed which may be due to the formation of a spinel form. There is no systematic change between the calculated values of lattice parameters, α, of doped samples and the type or concentration of dopant. This change has been related to the difference in the values of the ionic radii of Ni²⁺ and those of dopant elements.     

One-level reformulation of the bilevel Knapsack problem using dynamic programming

In this paper, we consider the Bilevel Knapsack Problem (BKP), which is a hierarchical optimization problem in which the feasible set is determined by the set of optimal solutions for a parametric Knapsack Problem. We introduce a new reformulation of the BKP into a one-level integer programming problem using dynamic programming. We propose an algorithm that allows the BKP to be solved exactly in two steps. In the first step, a dynamic programming algorithm is used to compute the set of follower reactions to leader decisions. In the second step, an integer problem that is equivalent to the BKP is solved using a branch-and-bound algorithm. Numerical results are presented to show the performance of our method.     

Features of crystallization behavior of natural rubber/halloysite nanotubes composites using synchrotron wide-angle X-ray scattering

The correlation between the mechanical strength and the crystallization behavior of natural rubber (NR)/halloysite nanotubes (HNT) composites is discussed. The tensile strength of NR is improved with the addition of HNT. This improvement is attributed to the unique structure of HNT, which facilitates good dispersion and strong interfacial interaction. HNT also play an important role in assisting the strain-induced crystallization of NR. Crystallization under strain is observed using synchrotron wide-angle X-ray scattering. The stress–strain curves and the corresponding degree of crystallinity after straining provide further evidence. Based on these analyses, a mechanistic model for strain-induced crystallization and the evolution of the orientation of the network structure is proposed.     

Feasible Approach to Tricyclic and Tetracyclic cyclododecanone

2‐Bromocyclododecanone was utilized as precursor to synthesize polyfused heterocyclic cyclododecane ring systems. Transformation of 2‐bromocyclododecanone ( 5 ) with 1H‐benzimidazole‐2‐thiole ( 6 ), benzo[d]thiazole‐2‐thiol ( 9 ), 2‐naphthol ( 12 ), and thiophenol ( 15 ) afforded thiazolo[2,3‐b]benzimidazole ( 8 ), thiazolo[2,3‐b]benzothaizole derivative ( 11 ) naphtho[1,2‐d]furan derivative ( 14 ) and 2‐(phenylthio)cyclododecanone ( 16 ), respectively.     

A comparative study on the separation of radioyttrium from Sr- and Rb-targets via ion-exchange and solvent extraction techniques,with special reference to the production of no-carrier-added <Superscript>86</Superscript>Y, <Superscript>87</Superscript>Y and <Superscript>88</Superscript>Y using a cyclotron

The radiochemical separation of ⁸⁸Y from proton irradiated ^natSrCO₃ and alpha-particle irradiated ^natRbCl, of ⁸⁶Y from proton irradiated ⁸⁶SrCO₃, and of ⁸⁷Y from alpha-particle irradiated ^natRbCl were studied at no-carrier-added levels by two techniques, namely, ion-exchange chromatography using Dowex 50W-X8 and Dowex 21K resins, and solvent extraction using HDEHP. Out of all those methods, the ion-exchange chromatography using Dowex 50W-X8 (cation-exchanger) was found to be the best: the separation yield was high, the chemical impurity in the separated radioyttrium (inactive Sr or Rb) was low (0.5 μg) and the final product was obtained in the form of citrate. The optimized separation method using Dowex 50W-X8 was applied in practical production of ⁸⁶Y and ⁸⁸Y via proton irradiations of ⁸⁶SrCO₃ and ^natSrCO₃, respectively, at 16 MeV as well as of ⁸⁷Y and ⁸⁸Y via α-particle irradiation of ^natRbCl at 26 MeV. The tangible experimental yields of ⁸⁶Y and ⁸⁷Y amounted to 150 and 5.7 MBq/μA·h, respectively. The yields of ⁸⁸Y obtained were 0.06 MBq/μA·h and 1 MBq/μA·h for alpha-particle and proton irradiations, respectively. Each yield value corresponds to more than 70% of the respective theoretical value.     

Chiral Monolithic Silica-Based HPLC Columns for Enantiomeric Separation and Determination: Functionalization of Chiral Selector and Recognition of Selector-Selectand Interaction

This review draws attention to the use of chiral monolithic silica HPLC columns for the enantiomeric separation and determination of chiral compounds. Properties and advantages of monolithic silica HPLC columns are also highlighted in comparison to conventional particle-packed, fused-core, and sub-2-µm HPLC columns. Nano-LC capillary monolithic silica columns as well as polymeric-based and hybrid-based monolithic columns are also demonstrated to show good enantioresolution abilities. Methods for introducing the chiral selector into the monolithic silica column in the form of mobile phase additive, by encapsulation and surface coating, or by covalent functionalization are described. The application of molecular modeling methods to elucidate the selector–selectand interaction is discussed. An application for enantiomeric impurity determination is also considered.     

QuEChERS method combined with GC‒MS for pesticide residues determination in water

A miniaturized, QuEChERS based, liquid–liquid extraction method followed by gas chromatography–mass spectrometry was developed and validated for pesticide residues determination in water. Malathion, chlorpyrifos, profenofos, chlorfenapyr, pyriproxyfen, λ-cyhalothrin, coumaphos and α-cypermethrin were selected for this study. The accuracy, precision, specificity, linearity, limit of detection and limit of quantification were evaluated. The recovery ranged from 85.3 to 107% with RSD ranging from 1.8 to 15.4%. The linearity showed reliable range (0.995–0.999). The limit of detection ranged from 0.3 to 4 μg/L. Matrix effect was evaluated. The obtained results meet the European Commission standard legislations, implying that our method can be considered accurate and reproducible. The validated method was used to analyze river and well water samples. No residues of the investigated pesticides were detected in all collected water samples.     

NIR spectroscopic properties of aqueous acids solutions

Acid content is one of the important quality attributes in determining the maturity index of agricultural product, particularly fruits. Despite the fact that much research on the measurement of acidity in fruits through non-destructive spectroscopy analysis at NIR wavelengths between 700 to 1,000 nm has been conducted, the same response towards individual acids is not well known. This paper presents NIR spectroscopy analysis on aqueous citric, tartaric, malic and oxalic solutions through quantitative analysis by selecting a set of wavelengths that can best be used to measure the pH of the solutions. The aquaphotomics study of the acid solutions has generated R2 above 0.9 for the measurement of all acids. The most important wavelengths for pH are located at 918-925 nm and 990-996 nm, while at 975 nm for water.     

Nanosecond Pulses Generation with Samarium Oxide Film Saturable Absorber

Nanosecond pulse generation is demonstrated in a mode-locked erbium-doped fiber laser(EDFL) utilizing a samarium oxide(Sm_2O_3) film. The Sm_2O_3 film exhibits a modulation depth of 33%, which is suitable for modelocking operation. The passively pulsed EDFL operates stably at 1569.8 nm within a pumping power from 109 to 146 m W. The train of generated output pulses has a pulse width of 356 nm repeated at a fundamental frequency of 0.97 MHz. The average output power of 3.91 m W is obtained at a pump power of 146 m W, corresponding to 4.0 nJ pulse energy. The experimental result indicates that the proposed Sm_2O_3 saturable absorber is viable for the construction of a flexible and reliably stable mode-locked pulsed fiber laser operating in the 1.5 m region.     

Infrared absorption of chromium trioxide and its suboxides

The chromium oxides, obtained by the thermal decomposition of chromium trioxide, presented a bewildering array of possible mixed valency compounds. The IR absorption measurements in the range 400–5000 cm^?1 revealed the presence of the valencies +6, +5, +4, +3 in the samples between CrO₃ and Cr₂O₃.