Zeeman effect in the N.Q.R. of 81Br in single crystals of 2,4-dibromoanisole and 2,4,6-tribromoanisole

The influence of the intramolecular degrees of freedom on the vapour–liquid equilibrium properties of ammonia is studied for vapour pressure, saturated densities and enthalpy of vaporization. Molecular force fields with and without intramolecular degrees of freedom, keeping all other parameters unchanged, show significantly different phase envelopes. For ammonia, the angle potential is particularly important, because the hydrogen sites are more aligned in the liquid than in the vapour, leading to a significantly enhanced molecular dipole moment in the condensed phase. Based on a rigid force field for ammonia from prior work of our group [Eckl et al., Mol. Phys. 106, 1039 (2008)], a new accurate force field with intramolecular degrees of freedom is developed.     

Determination of K, Ca, Fe and Ni in Leptinotarsa decemlineata (Say) by EDXRF spectroscopy

The metal content of Colorado potato beetles elytra in Turkey was determined using the energy dispersive X-ray fluorescence method. A radioisotope excited X-ray fluorescence analysis using the method of standard addition is applied for the elemental analysis of Colorado potato beetles elytra. An annular ²⁴¹Am radioactive source and an annular ⁵⁵Fe radioactive source were used for excitation of characteristic K X-rays. An Si(Li) detector which has a full-width at half-maximum for photons was used for intensity measurements. The procedure of sample preparation and the results of analysis were presented.     

Using economic X control chart design methodology to estimate and optimize machine efficiency in the case of multimachine assignments

Estimation and optimization of machine efficiency in the case of multi machine assignments is a difficult issue for some industries such as textile industry, due to the machine interference. Although the problem is not new, the solutions proposed are not full satisfactory. For example, the analytical formulas are not suitable for high number of machines; queuing theory approaches are complex and impractical for mill managers. On the other hand, simulation methodology seems to be a perfect tool to estimate and analyze; however, the simulation package programs are expensive and are not suitable for systematic optimization. In this paper, Duncan's economic control chart design methodology is proposed as an alternative way for one of the oldest industrial problems. This study shows that this new approach is a more efficient solution to this stochastic problem. Copyright © 2009 John Wiley & Sons, Ltd.     

Simultaneous Determination of Fluoxetine,Estrone, Pesticides,and Endocrine Disruptors in Wastewater by Gas Chromatography–Mass Spectrometry (GC–MS) Following Switchable Solvent–Liquid Phase Microextraction (SS–LPME)

A simple and sensitive analytical method for the determination of fluoxetine, estrone and selected pesticides and endocrine disruptors has been proposed for wastewater analysis by gas chromatography–mass spectrometry (GC–MS). A switchable solvent was produced with N,N-dimethylbenzylamine by changing its hydrophobic properties by the addition of CO₂ for protonation. Sodium hydroxide was added to switch the solubility of the extraction solvent and to allow phase separation in the sample/standard medium. Analytical parameters affecting the extraction outputs such as volume of switchable solvent, concentration and volume of sodium hydroxide, mixing type and period were investigated to improve the extraction recovery of the selected analytes. Under the optimum conditions, limits of detection and limits of quantification for the analytes were calculated in the ranges of 0.16–8.6?ng mL^?1 and 0.54–29?ng mL^?1, respectively. The developed method was successfully applied to synthetic wastewater and two municipal wastewater samples. None of the selected analytes were detected in the samples. High recovery values demonstrated that the proposed method was reliable and applicable to complex matrices.     

The influence of nitridation time on the structural properties of GaN grown on Si (111) substrate

In the present paper, the effect of in-situ substrate nitridation time on crystalline quality of GaN films grown on Si (111) substrates by metal organic chemical vapor deposition (MOCVD) were investigated. A thin buffer layer of silicon nitride (SiN _x ) with various thicknesses was achieved through the nitridation of substrate at different nitiridation times ranging from 0 to 660 s. The structural characteristics, such as dislocation densities, correlation lengths of columnar crystallites, the tilt and twist of the mosaic structure, and the angles of rotational disorder, were all studied in detail by using a planar and cross-sectional view of high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (HRXRD) performed at different scattering geometries. It was found that the dislocation densities, lateral coherence lengths, vertical coherence lengths, and the tilt and twist of mosaic blocks in GaN films monotonically varies with the nitridation time. The experimental findings showed that the nitridation times had more influence on edge dislocation densities than the screw type.     

Rate effect on sharing of passive lumbar motion segment under load-controlled sagittal flexion: viscoelastic finite element analysis

Industrial epidemiological studies have shown that jobs requiring a higher speed of trunk motion contribute to a higher risk of industrial low back disorders. Consideration of the loading dynamic characteristics, such as lifting at different speeds, requires modeling of the viscoelastic behavior of passive tissues. Detailed systematic analysis of the effects of loading rate has been lacking in the literature. A validated viscoelastic finite element model of a L2–L3 motion segment was used to identify the load sharing among the passive elements at different loading rates. Force controlled complex flexion movement was simulated by applying load at the top of the upper vertebra without constraining any coupled sagittal rotation, whereas the lower vertebra was fixed at the bottom. The load reached its maximum values of 2000 N compression, 400 N anterior shear, and 20 Nm flexion in three different durations of 0.3, 3 and 30 s to represent fast, medium and slow movement. The global force–displacement response of the motion segment, forces in facet joints and ligaments, stresses and strains in anulus fibrosus, and intradiscal pressure were compared across different rates. The higher rate of loading while reaching a prescribed complex forward flexion loading increased the intradiscal pressure and the stress in the anulus fibers at the posterolateral innermost layers, but reduced the global displacements, ligament forces and facet joint forces. The distribution of stress and strain was markedly affected by the loading rate. Consideration of the time-dependent material properties of passive elements is essential to improve our understanding of the responses of the motion segment to dynamic loading conditions. Speed of the manual materials handling (MMH) tasks should be included as a risk factor in the biomechanical and epidemiological studies and guidelines for safe lifting.     

Comparison of flow structures in the downstream region of a cylinder and sphere

An experimental investigation of flow structures downstream of a circular cylinder and sphere immersed in a free-stream flow is performed for Re = 5000 and 10,000 using qualitative and quantitative flow visualization techniques. The obtained results are presented in terms of time-averaged velocity vectors, patterns of streamlines, vorticity, Reynolds stress correlations and turbulent kinetic energy distributions. Flow data reveal that the size of wake flow region, the location of singular and double points, the peak values of turbulence quantities, such as Reynolds stress correlations, vorticity fluctuations and turbulent kinetic energy vary as a function of models’ geometry and Reynolds Numbers. The concentration of small scale vortices is more dominant in the wake of the sphere than that of the cylinder. The maximum value of turbulent kinetic energy (TKE) occurs close to the saddle point for the cylinder case while two maximum values of TKE occur along shear layers for the sphere one because of the 3-D flow behavior.     

Weakly distributive modules. Applications to supplement submodules

In this paper, we define and study weakly distributive modules as a proper generalization of distributive modules.We prove that, weakly distributive supplemented modules are amply supplemented. In a weakly distributive supplemented module every submodule has a unique coclosure. This generalizes a result of Ganesan and Vanaja. We prove that π-projective duo modules, in particular commutative rings, are weakly distributive. Using this result we obtain that in a commutative ring supplements are unique. This generalizes a result of Camillo and Lima. We also prove that any weakly distributive ⊕-supplemented module is quasi-discrete.     

An assessment of the poincare scheme for non-linear oscillators and an improvement of its range of validity

The range of validity of the Poincare method is studied by comparison with the exact solution for the anharmonic and Morse oscillators. The exact solutions for these cases are expressible respectively in terms of elliptic and inverse trigonometric functions. The oscillation frequency is taken as the basis for the comparison. It is seen that the Poincare perturbation gives fairly accurate results up to amplitudes that are 20–30 per cent of the maximum value allowed for periodic solutions depending on the form of the potential energy. A new method is presented as a slight variation over the standard Poincare method. This method differs from the former only by a rearrangement of the differential equation through a collocation approximation for the potential. In spite of its simplicity, the method proves to be a better approximation than the standard Poincare method and gives remarkably accurate results for amplitudes up to 60–70 per cent of the maximum value allowed for periodic solutions.     

Determining the interaction and characterization of asphaltene in alkylbenzene solvents using nuclear-electron double resonance

This study uses ¹H dynamic nuclear polarization (DNP) methods to determine asphaltene aggregates and the interaction between asphaltene extracted from MC800 asphalt and alkylbenzene solvents, as well as elemental analysis for the characterization of asphaltene. The asphaltene sample was characterized using the elemental analysis of carbon (C), hydrogen (H), nitrogen (N), and sulfur (S). The results show that asphaltenes have the highest carbon content. The sulfur and hydrogen contents are nearly the same and nitrogen content is the smallest. The DNP data provided good results for characterizing asphaltene behavior in alkylbenzene solvents.