Determination of Rosmarinic Acid by High-Performance Liquid Chromatography and Its Application to Certain Salvia Species and Rosemary

This study describes a method development for the determination of rosmarinic acid (RA) by using a gradient high-performance liquid chromatography (HPLC) and its application to certain plant materials. The analysis was performed by utilizing a two solvents system [A: methanol/water/formic acid (10:88:2; v:v:v); B: methanol/water/formic acid (90:8:2; v:v:v)] on a reverse-phase column. The flow rate and injection volume were 1 ml min⁻¹ and 10 μl, respectively. Signals were detected at 280 nm. In addition, an internal standard (IS) technique was applied for the analysis of RA to increase precision, and propylparaben was employed for this purpose. The repeatability results as RSD% were 1.66, 1.17 and 1.26 for intra-day and 1.38 was for inter-day with the employment of (3.67 × 10⁻⁵ M) RA. A limit of linearity (LOL) was observed in a wide (1.13 × 10⁻⁵–5.65 × 10⁻⁴ M) concentration range. Linearity parameters were also examined in the range of 5.95 × 10⁻⁶–7.14 × 10⁻⁵ M RA, and very good correlation was observed. The limit of detection (LOD) and limit of quantification (LOQ) (for inter-day) were 1.60 × 10⁻⁶ M (signal/noise [S/N] = 3.3) and 4.80 × 10⁻⁶ M (S/N = 10), respectively. The method was applied to the extracts of certain Lamiaceae plants (Salvia candidissima Vahl. subsp. candidissima, S. sclarea L., S. verticillata L. subsp. verticillata and R. officinalis L.), and reasonable results were obtained.     

Effect of heat treatment conditions on microstructure and wear behaviour of Al4Cu2Ni2Mg alloy

Al4Cu2Ni2Mg alloy is an age-hardenable aluminum alloy. The effect of different solution and aging heat treatment conditions on the microstructure, hardness and wear resistance of the alloy was studied. The cast specimens were solution treated and then artificially aged. Optical microscopy and scanning electron microscopy were used to investigate the microstructures of the specimens. The hardness and wear tests were applied to understanding the effects of heat treatment. After aging for 8 h, the hardness of the alloy increases from HV₁₀ 96.5 to 151.1. Aging treatment for a longer duration causes a drop in the hardness because of over aging. Increasing the hardness of the alloy increases the wear resistance. As a result of all tests, solution heat treatment at 540 °C for 8 h and aging at 190 °C for 8 h were chosen for optimum heat treatment conditions for this alloy.     

Instrumented indentation and scratch testing evaluation of tribological properties of tin-based bearing materials

This paper describes a study of some fundamental tribological behavior of two different tin-based bearing materials using scratch and Martens hardness techniques. The scratch test results obtained from the two different tin-based bearing materials were correlated with a function of scratch hardness and coefficient of friction. It is easily observed that the friction coefficients of WM5 are lower than those of WM2 under all scratch test conditions. Beside this, it is clearly distinguished that both materials give higher friction coefficients at higher normal loads and scratch velocities. Also it is found that scratch hardness values of the WM5 materials are higher than WM2 generally. Moreover, optical microscopy was used to determine the scratch hardness of two different tin-based bearing materials by examining the scratch widths. Scanning electron microscopic observations of two different tin-based bearing materials were performed in order to identify the scratch-deformation mechanisms and trace morphology. Beside scratch tests, Martens hardness tests were carried out to evaluate the indentation of materials by considering both the force and displacement during plastic and elastic deformation. By monitoring the complete cycle of increasing and removal of the test force, hardness values were determined.     

Frequency and voltage dependence of dielectric properties,complex electric modulus,and electrical conductivity in Au/7% graphene doped‐PVA/n‐Si (MPS) structures

In order to increase the capacitance of Au/n‐Si (MS) structure, 7% graphene doped PVA was coated on n‐Si as an interfacial layer. The measured data of capacitance (C) and conductance (G/ω) of Au/7% graphene doped‐PVA/n‐Si (MPS) structure was utilized for the calculation of real and imaginary parts of complex permittivity (ε^* = ε′ − jε″), loss tangent (tanδ), complex electric modulus (M^* = M′ + jM″), and electrical conductivity (σ). The admittance measurements (C and G/ω) were carried out in the frequency range of 0.5 kHz to 1 MHz at room temperature. Frequency dependence of the dielectric constant (ε′), dielectric loss (ε″) and tanδ shows a dispersive behavior at low frequencies. This behavior was explained by Maxwell–Wagner relaxation. Due to the dipolar and the interfacial polarizations, as well as the surface states (N_ss) and the interfacial PVA layer, the parameters exhibited a strong dependence on frequency and applied bias voltage. The σ versus log(f) plot exhibited both low and high frequency dispersion phenomena such that at low frequencies σ value corresponding to the dc conductivity (σ_dc), but at high frequencies it corresponds to the ac conductivity (σ_ac). M′ and M″, both, have low values in the low frequency region. However, an increase is observed with the increasing frequency due to the short‐range mobility of charge carriers. As a result, the change in dielectric parameters and electric modulus with frequency is the result of relaxation phenomena and surface states. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43827.     

Graft copolymerization of acrylic acid on cellulose: Reaction kinetics of copolymerization

Acrylic acid (AA) was grafted to cellulose by using ceric ammonium nitrate (CAN) initiator in aqueous nitric acid solution at 30, 50, 70, and 90°C during reaction periods of 30 to 180 minutes. About 45% of the AA was polymerized at 90°C after 180 minutes. The grafted polymer and homopolymer were isolated by acetone from the reaction mixture, dried, and subjected to Soxhlet extraction with dioxane to separate the homopolymer, poly(acrylic acid), from the graft copolymer. The water absorption capacities and grafting values of grafted cellulose were also determined. The maximum grafting yield was obtained at 30°C. It was also observed that polyacrylic acid-grafted cellulose produced at 30°C had the highest water retention capacity. The time dependence of AA conversion allowed calculation of first-order reaction rate constants. These rate constants were then used to determine apparent activation energies. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 66: 929–934, 1997     

A pattern-based genetic algorithm for multi-robot coverage path planning minimizing completion time

Sensor-based multi-robot coverage path planning problem is one of the challenging problems in managing flexible, computer-integrated, intelligent manufacturing systems. A novel pattern-based genetic algorithm is proposed for this problem. The area subject to coverage is modeled with disks representing the range of sensing devices. Then the problem is defined as finding a sequence of the disks for each robot to minimize the coverage completion time determined by the maximum time traveled by a robot in a mobile robot group. So the environment needs to be partitioned among robots considering their travel times. Robot turns cause the robot to slow down, turn and accelerate inevitably. Therefore, the actual travel time of a mobile robot is calculated based on the traveled distance and the number of turns. The algorithm is designed to handle routing and partitioning concurrently. Experiments are conducted using P3-DX mobile robots in the laboratory and simulation environment to validate the results.     

A software for performance evaluation and comparison of people detection and tracking methods in video processing

Digital video content analysis is an important item for multimedia content-based indexing (MCBI), content-based video retrieval (CBVR) and visual surveillance systems. There are some frequently-used generic object detection and/or tracking (D&T) algorithms in the literature, such as Background Subtraction (BS), Continuously Adaptive Mean Shift (CMS), Optical Flow (OF) and etc. An important problem for performance evaluation is the absence of stable and flexible software for comparison of different algorithms. This software is able to compare them with the same metrics in real-time and at the same platform. In this paper, we have designed and implemented the software for the performance comparison and the evaluation of well-known video object D&T algorithms (for people D&T) at the same platform. The software works as an automatic and/or semi-automatic test environment in real-time, which uses the image and video processing essentials, e.g. morphological operations and filters, and ground-truth (GT) XML data files, charting/plotting capabilities and etc.     

Statistical fibre failure and single crack behaviour in uniaxially reinforced ceramic composites

A lower bound to the work of pull-out is estimated for a ceramic composite under uniaxial loading assuming that matrix crumbling does not occur. Fibre failure is assumed to be governed by Weibull distribution. In order to compute a lower bound to the energy dissipation it is assumed that the failure occurs by a single matrix crack. The fibre/matrix interface is assumed to be constrained by friction only. The work of pull-out estimated from the present model is compared to the energy dissipation before fibre failure which was computed by Aveston, Cooper and Kelly (ACK) in 1971. Comparisons are made with the surface energy of monolithic materials.     

An Optimized Image Segmentation Approach Based on Boltzmann Machine

Image segmentation with complex background is a tedious task. In our study, a convex spline is constructed based on Good Features to Track (GF2T) method’s region-based salient feature (i.e., corner) set. For an optimized edge-based segmentation, an ellipse shape prior based on this convex spline is useful in edge regularization procedure with region-based features. This kind of optimization is achieved by Boltzmann machine (BM) to automatically form an elliptical foreground mask of the GrabCut method. We demonstrated our approach’s usability through traveling salesman problem (TSP), thus, we consider that the TSP’s valid tour’s path solved by BM can be taken as an optimized convex spline for edge-based segmentation. In our experiments, proposed BM-based approach has the performance improvement of segmentation to stand-alone GF2T as 29.79% improvement based on bounding boxes evaluation and as 38.67% improvement based on the overlapping pixel regions for a quantitative evaluation via objective metrics.     

Effects of L‐carnitine supplementation to diets with different fat sources and energy levels on fatty acid composition of egg yolk of laying hens

BACKGROUND: The present study was carried out to determine the effects of feeding diets with two different levels of metabolisable energy (ME) (11.51 or 10.88 MJ ME kg^?1 diet) and three different sources of fat (palm oil, sunflower oil or fish oil) with or without supplemental L ‐carnitine (0 or 500 mg kg^?1 diet) on the fatty acid (FA) composition of egg yolk and the passage of n3 polyunsaturated FAs to egg yolk in laying hens. RESULTS: The ∑n3, particularly C22:6n‐3, FA contents of egg yolk were significantly reduced by adding of L ‐carnitine (C2) to different fat sources (P < 0.01). The ratio of n6/n3 was reduced from 53.77 to 17.72 in eggs yolks when ME was lowered in the diet with C2‐sunflower oil (SFO) whereas it was enhanced from 2.19 to 9.31 in C2‐E2 (low energy) diet with fish oil (FO) (P < 0.001). The diet with E2 or C2 containing FO resulted in a decrease of the C22:5n‐3, C22:6n‐3 and ∑n3 FA contents of egg yolk (P < 0.001). On the other hand, supplementation of C2 to diets with SFO or palm oil (PO) caused to a decrease in the C22:6n‐3 and ∑n3 FA contents of egg yolk (P < 0.01). A significant increase of the ratio of n6/n3 in egg yolk can be seen by feeding with E2 diet by adding of C2 to all fat sources like in E1 (normal energy) diet (P < 0.001). CONCLUSION: Dietary treatments resulted in major changes in FA composition of egg yolk. The supplemental C2 in diet decreased the C22:5n‐3, C22:6n‐3 and ∑n3FA contents in egg yolk. The use of FO in diets with E2 significantly reduced the passage rate of C22:6n‐3 FA to egg yolk. Copyright © 2008 Society of Chemical Industry