Evaluating Osteogenic Potential of Ligamentum Flavum Cells Cultivated in Photoresponsive Hydrogel that Incorporates Bone Morphogenetic Protein-2 for Spinal Fusion

Regenerative medicine is increasingly important in clinical practice. Ligamentum flava (LF) are typically removed during spine-related surgeries. LF may be a source of cells for spinal fusion that is conducted using tissue engineering techniques. In this investigation, LF cells of rabbits were isolated and then characterized by flow cytometry, morphological observation, and immunofluorescence staining. The LF cells were also cultivated in polyethylene (glycol) diacrylate (PEGDA) hydrogels that incorporated bone morphogenetic protein-2 (BMP-2) growth factor, to evaluate their proliferation and secretion of ECM and differentiation in vitro. The experimental results thus obtained that the proliferation, ECM secretion, and differentiation of the PEGDA-BMP-2 group exceeded those of the PEGDA group during the period of cultivation. The mineralization and histological staining results differed similarly. A nude mice model was utilized to prove that LF cells on hydrogels could undergo osteogenic differentiation in vivo. These experimental results also revealed that the PEGDA-BMP-2 group had better osteogenic effects than the PEGDA group following a 12 weeks after transplantation. According to all of these experimental results, LF cells are a source of cells for spinal fusion and PEGDA-BMP-2 hydrogel is a candidate biomaterial for spinal fusion by tissue engineering.     

Adaptive control of homogeneous charge compression ignition engines

This paper presents an adaptive controller, which maintains consistent ignition timing control of a gasoline homogeneous charge compression ignition engine with high dilution in the presence of uncertainty or unknown variation in plant parameters such as exhaust runner wall temperature and cylinder charge properties. The control of the combustion timing is based on manipulating the charge temperature through internal dilution, which is achieved by controlling the lift of a secondary opening of the exhaust valves, also known as the rebreathing lift. The adaptive controller is designed on the basis of a simplified bilinear parametric model, which contains only the cycle‐to‐cycle combustion timing dynamics. Implementation of the designed adaptive controller involves feedforward of the injected fuel and feedback of the combustion timings CA₅₀ and CA₉₀ when 50% and 90% of energy are released, respectively, which alleviates the impact of inevitable errors in estimation of in‐cylinder charge properties such as temperature, pressure, and compositions. It is shown through convergence analysis and closed‐loop simulation of a full‐order engine model that the adaptive controller is able to drive the combustion timing CA₅₀ to desired set points by stabilizing the bilinear dynamics when plant parameters are changing. Copyright © 2013 John Wiley & Sons, Ltd.     

Microalgal phycocyanin productivity: strategies for phyco‐valorization

Phyco‐valorization is the exploitation of microalgae and microalgal chemicals as valuable products. This paper discusses the optimization of microalgal bioreactor‐based systems for C‐phycocyanin pigment production. Various aspects contributing to system development and enhancement of phycocyanin productivity are described. A wide range of potential microalgal species have been identified for phycocyanin production; the selection of a species for mass culturing can be determined by desired bioreactor trophic mode and symbiotic relations. Research has demonstrated that species amenability to local lighting and climatic conditions, and to variations in bioreactor substrate concentrations and operational parameters, have significant impact on phycocyanin production. The simultaneous optimization of all factors contributing to system productivity may be accomplished efficiently through process modelling. A summary of established models for microalgal phycocyanin production is presented. A suggested strategy for increasing economic viability of phycocyanin production systems is their application in integrated resource recovery. Through the incorporation of phycocyanin productivity optimization principles within a phycoremediation process, the valorization of waste resources may be achieved. The simultaneous economic potential and environmentally‐forward concept of phyco‐valorization through phycocyanin production is a promising application of microalgal biotechnology awaiting further development for industrial implementation. © 2015 Society of Chemical Industry     

On the coupler-great-circle envelopes of spherical four-bar linkages

With use of the techniques developed for coupler-point curves, the tangential equation is derived for the envelope of a great circle attached to the coupler of a general spherical four-bar linkage in the motion of this mechanism. The class of this envelope is determined to be 8. The dual relationships between the coupler-point curve and the coupler-great-circle envelope are discussed. With this concept, the techniques for designing a spherical four-bar coupler-great-circle envelope generator are introduced.     

Flocculation of clay suspensions with water-insoluble starch grafting acrylamide/sodium allylsulfonated copolymer powder

Use of water-soluble and -insoluble starch grafting acrylamide/sodium allylsulfonated copolymers as flocculants to flocculate the clay suspension was investigated. The composition of acrylamide (AM), sodium allylsulfonated (SAS), and starch (St) repeating units in the water-soluble and -insoluble starch-grafted copolymer is about 0.718, 0.022, and 0.260 and 0.439, 0.014, and 0.547, respectively. For the water-soluble starch-grafted copolymer, the fast initial A_r decreasing rate and the lowest final A_r value occur at pH 2, 80 mg/L water-soluble starch-grafted copolymer and 100 mg/L clay suspension. As the suspension contains 1000 mg/L Na⁺ ion, the flocculating capability would be increased. For the water-insoluble starch-grafted copolymer, the initial A_r decreasing rate and the final A_r value are 1.6 times and 0.4 times, respectively, that of the water-soluble starch-grafted copolymer at the same test suspension. © 1995 John Wiley & Sons, Inc.     

An improved method for on-line calculation and compensation of the static deflection at a robot end-effector

Traditionally, robotic deflection analysis for a low-weight robot has been performed based on an assumption that each link is treated as a cantilever beam, which leads to no angular deflection at a joint. In practice, a robotic intermediate joint is linearly and angularly deflected when a load is applied at the end-effector. It is found in this study that the additional link deflection resulting from the angular deflection of a robotic revolute joint substantially contributes to the end-effector's total deflection. This article presents an improved method via a combination of classical beam theory, energy methods and the concepts of differential relationships to more accurately calculate the static deflection at the end-effector. A systematic approach to deflection calculation through three different Jacobians are presented. The study also shows that the end-effector's deflection heavily depends on robotic arm configurations. The deflection is then compensated based on the selected optimum configuration. The theoretical deflection analysis is verified by experimental results. A planar two-link robot and a six-degree-of-freedom Elbow Manipulator are used for numerical illustration and calculation procedure.     

Conceptual designs of AI-based systems for local prediction ofvoltage collapse

Vulnerability of modern power systems to locally initiated voltage collapse gives rise to a need for methods to measure local voltage security and to predict voltage instability. The paper presents a novel architecture based on a suite of AI technologies and three-dimensional PQV surfaces which provides prediction of local voltage collapse and indices of system voltage security. Robustness and adaptation are demonstrated on difficult and realistic power system simulation models     

Toward a practical performance index for predicting voltagecollapse in electric power systems

Voltage collapse is generally caused by either of two types of power system disturbances: load variations; and contingencies. A number of performance indices intended to measure the severity of the voltage collapse problem have been proposed in the literature. However, few of these performance indices can answer questions such as: “can the system withstand another 100 MVar increase on bus 11?” This paper presents a new performance index that provides a direct relationship between its value and the amount of load demand that the system can withstand before collapse. One of the features that distinguishes the proposed performance is its development in the load-demand space and its ability to answer questions such as: “can the system withstand a simultaneous increase of 70 MW on bus 2 and 50 MVAr on bus 6?” This feature makes the performance index readily interpretable to operators. Moreover, the computation involved in the proposed performance index is relatively inexpensive in comparison with those required in existing solutions. Simulation results on the IEEE 39-bus system and a 234-bus power system are presented with promising results