Cytotoxic activity of greener synthesis of cerium oxide nanoparticles using carrageenan towards a WEHI 164 cancer cell line

Carrageenan hydrogel as a “greener” and a vegetable-based stabilizing agent has the potential for many biosyntheses of different nanoparticles by sol-gel method. Herein, we describe for the first time an economic and eco-friendly preparation of cerium oxide nanoparticles (CeO₂-NPs) using carrageenan. When carrageenan hydrogel comes in contact with a cerium nitrate solution, cerium ions anchor themselves to the –SO₃^- groups into the carrageenan and after the gelation process, have fewer opportunities escaping from the polymeric network. The CeO₂-NPs were well-prepared and successfully characterized by PXRD, FTIR, FESEM, UV–Vis, and TGA-DTA. The calcined CeO₂-NPs showed strong UV absorption (λ_max = 328?nm) with the calculated band gap of 2.69?eV. The results obtained from FESEM images indicate that CeO₂-NPs obtained at 600?°C ranges from 18 to 60?nm and have a mean diameter of ~34?nm. The in vitro cytotoxicity study on WEHI 164 cell line has mentioned low toxic and non-toxic CeO₂-NPs in a range of concentrations (0.97–250?μg/ml), thus, we reckon that the greener synthesized CeO₂-NPs will have persistent utilization in various fields of medical applications.     

The influence of heat treatment on the microstructure,flux pinning and magnetic properties of bulk BSCCO samples prepared by sol-gel route

We study the combined influence of calcination and sintering temperature on the microstructure, superconducting and pinning properties of Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+θ (Bi-2223) prepared by the sol-gel route. Using several characterization techniques, including X-rays diffractometry and electrical transport measurements, we find that the powders calcined at 820 °C often result in a crystal higher critical current density (J_c) compared those calcined at 830 °C. The powder calcined at 820 °C and sintered at 850 °C (Bi-2223 ₈₂₀⁸⁵⁰) showed the best grain morphology and the largest magnetic hysteresis loop and a J_c equal to 12.94 $\times$ 10⁵ A/cm², comparable to the best results found in the literature for Bi-2223. The enhancement in J_c for Bi-2223 ₈₂₀⁸⁵⁰ seems to be due to improved grain structure rather than creation of effective pinning centers, because the scaling behavior of flux pinning force densities indicates that the main pinning mechanism for all samples is normal point pinning.     

A fast and accurate moving object tracker in active camera model

Detecting and tracking moving objects within a scene is an essential step for high-level machine vision applications such as video content analysis. In this paper, we propose a fast and accurate method for tracking an object of interest in a dynamic environment (active camera model). First, we manually select the region of the object of interest and extract three statistical features, namely the mean, the variance and the range of intensity values of the feature points lying inside the selected region. Then, using the motion information of the background’s feature points and k-means clustering algorithm, we calculate camera motion transformation matrix. Based on this matrix, the previous frame is transformed to the current frame’s coordinate system to compensate the impact of camera motion. Afterwards, we detect the regions of moving objects within the scene using our introduced frame difference algorithm. Subsequently, utilizing DBSCAN clustering algorithm, we cluster the feature points of the extracted regions in order to find the distinct moving objects. Finally, we use the same statistical features (the mean, the variance and the range of intensity values) as a template to identify and track the moving object of interest among the detected moving objects. Our approach is simple and straightforward yet robust, accurate and time efficient. Experimental results on various videos show an acceptable performance of our tracker method compared to complex competitors.     

A high-resolution time-resolved study of incoherent interface motion during the massive transformation in TiAl alloy

Frame-by-frame analyses of in-situ high-resolution transmission electron microscope (HRTEM) heating experiments performed on a high-index incoherent massive transformation interface in TiAl alloy at 575 °C show that the interface displays dynamic fluctuations in its trace that can be described in terms of a wavelike function with an amplitude of 0.21 nm and a fundamental wavelength of 1.15 nm. The interface moves forward with a constant average velocity of 0.023 nm/s, due to spreading of critical-size advancing fluctuations along the interface at different locations, which causes it to remain relatively planar as it advances. This interface behavior is remarkably similar to that observed during previous in-situ optical microscopy studies on massive transformation interfaces in Cu-Ga alloy and is distinctly different from the behavior of highly faceted interphase boundaries. This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under the auspices of the TMS Alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee.     

Material flow determination for radial flexible profile ring rolling

Regarding the increasing demand on annular components with complex geometries, a flexible process has been developed at the IBF to profile sleeve shaped rings. Unlike processes using grooved tools, here diverse contours can be realized on the inner surface using one “universal” tool. By extending the tool kinematics and developing an adequate forming strategy the general feasibility of the process has been shown on a bench scaled model ring rolling rig using a wax based model material. Parameters such as ring/tool geometry and roller feed strategy were detected as having an effect on material flow resistance in the rolling and transverse directions. Expressing them by geometric ratios, the material flow distribution could be determined in numerous experiments and quantified by a newly-defined extension coefficient with a certainty of 95%. This achievement enables us to predict the material flow in axial and tangential directions to manufacture complex geometries reproducibly.     

Nonlinear disturbance observer design for robotic manipulators

Robotic manipulators are highly nonlinear and coupled systems that are subject to different types of disturbances such as joint frictions, unknown payloads, varying contact points, and unmodeled dynamics. These disturbances, when unaccounted for, adversely affect the performance of the manipulator. Employing a disturbance observer is a common method to reject such disturbances. In addition to disturbance rejection, disturbance observers can be used in force control applications. Recently, research has been done regarding the design of nonlinear disturbance observers (NLDOs) for robotic manipulators. In spite of good results in terms of disturbance tracking, the previously designed nonlinear disturbance observers can merely be used for planar serial manipulators with revolute joints [Chen, W. H., Ballance, D. J., Gawthorp, P. J., O'Reilly, J. (2000). A nonlinear disturbance observer for robotic manipulators. IEEE Transactions on Industrial Electronics, 47 (August (4)), 932–938; Nikoobin, A., Haghighi, R. (2009). Lyapunov-based nonlinear disturbance observer for serial n-link manipulators. Journal of Intelligent & Robotic Systems, 55 (July (2–3)), 135–153]. In this paper, a general systematic approach is proposed to solve the disturbance observer design problem for robotic manipulators without restrictions on the number of degrees-of-freedom (DOFs), the types of joints, or the manipulator configuration. Moreover, this design method does not need the exact dynamic model of the serial robotic manipulator. This method also unifies the previously proposed linear and nonlinear disturbance observers in a general framework. Simulations are presented for a 4-DOF SCARA manipulator to show the effectiveness of the proposed disturbance observer design method. Experimental results using a PHANToM Omni haptic device further illustrate the effectiveness of the design method.     

A high-resolution time-resolved study of incoherent interface motion during the massive transformation in TiAl alloy

Frame-by-frame analyses of in-situ high-resolution transmission electron microscope (HRTEM) heating experiments performed on a high-index incoherent massive transformation interface in TiAl alloy at 575°C show that the interface displays dynamic fluctuations in its trace that can be described in terms of a wavelike function with an amplitude of 0.21 nm and a fundamental wavelength of 1.15 nm. The interface moves forward with a constant average velocity of 0.023 nm/s, due to spreading of criticalsize advancing fluctuations along the interface at different locations, which causes it to remain relatively planar as it advances. This interface behavior is remarkably similar to that observed during previous in-situ optical microscopy studies on massive transformation interfaces in Cu−Ga alloy and is distinctly different from the behavior of highly faceted interphase boundaries. This article is based on a presentation made in the “Hume-Rothery Symposium on Structure and Diffusional Growth Mechanisms of Irrational Interphase Boundaries,” which occurred during the TMS Winter meeting, March 15–17, 2004, in Charlotte, NC, under the auspices of the TMS Alloy Phases Committee and the co-sponsorship of the TMS-ASM Phase Transformations Committee.     

Investigation of the Soret effect in copper nanoparticle colloids by self-phase modulation and Z-scan

A theoretical investigation is reported on the photo-thermal response of copper nanoparticle colloids in the presence of thermal and mass diffusion processes. The absorbed laser beam energy is converted into heat and generates a temperature gradient, which causes nanoparticle concentration variation in the fluid. Transverse spatial redistribution of the nanoparticles induces changes in absorption and refraction of the medium. Experimentally, the photo-thermal response was determined by measuring absorption and refraction changes of the nanoparticle colloids using the far-field diffraction patterns and Z-scan technique. This allowed evaluation of the Soret coefficient of the nanoparticle colloids and excellent agreement is found in measuring this coefficient using both the far-field diffraction pattern and Z-scan technique.     

The effects of low-frequency workpiece vibration on low-power CO2 laser cutting of PMMA: an experimental investigation

The effect of workpiece vibration on low-power CO₂ laser cutting of polymethyl methacrylate (PMMA) has been investigated. 6-mm-thick PMMA sheets have been cut using a 70-W continuous wave CO₂ laser moving at speeds in the range of 0.1–2.0?m/min. The workpiece was vibrated in a direction parallel to the laser cut at frequencies of 0, 12, 18 and 24?Hz. The use of workpiece vibration was shown to enhance the cutting process. At 12?Hz, the cutting speed was increased to 0.4?m/min compared to 0.2?m/min for the 0-Hz sample. However, the extent of the HAZ increased when workpiece vibration was used.