Abstract
Mesenchymal stem cells (MSCs) can be isolated from several tissues in the body, have the ability to self-renewal, show immune suppressive properties and are multipotent, being able to generate various cell types. At present, due to their intrinsic characteristics, MSCs are considered very promising in the area of tissue engineering and regenerative medicine. In this context, genetic modification can be a powerful tool to control the behavior and fate of these cells and be used in the design of new cellular therapies. Viral systems are very effective in the introduction of exogenous genes inside MSCs. However, the risks associated with their use are leading to an increasing search for non-viral approaches to attain the same purpose, even if MSCs have been shown to be more difficult to transfect in this way. In the past few years, progress was made in the development of chemical and physical methods for non-viral gene delivery. Herein, an overview of the application of those methods specifically to MSCs is given and their use in tissue engineering and regenerative medicine therapeutic strategies highlighted using the example of bone tissue. Key issues and future directions in non-viral gene delivery to MSCs are also critically addressed.

Abstract
This paper is concerned with the harmonic behavior of variable-speed wind turbines during a control fault. Different topologies for the power-electronic converters are considered, namely two-level and multilevel converters. A three-mass drive train model is considered, and a fractional-order control strategy is proposed for the wind turbines. The performance of disturbance attenuation and system robustness is ascertained. Finally, conclusions are duly drawn. © 2011 IEEE.

Abstract

Abstract

Abstract
This paper is on variable-speed wind turbines with permanent magnet generator. A three-mass drive train model and two different topologies for the power-electronic converters are considered. The two different topologies considered are respectively a matrix and a multilevel converter. A control strategy, based on fractional-order controllers, is proposed for the wind turbines. Previous papers were mainly focused on the transient stability of variable-speed wind turbines at external grid faults. Instead, this paper considers the possibility of an internal abnormal operating condition, namely a converter control malfunction. The influence of the converter control malfunction on the harmonic current emissions is studied. Comprehensive results are presented, and conclusions are duly drawn. © 2011 IEEE.

Abstract
Functional programs often combine separate parts using intermediate data structures for communicating results. Programs so defined are modular, easier to understand and maintain, but suffer from inefficiencies due to the generation of those gluing data structures. To eliminate such redundant data structures, some program transformation techniques have been proposed. One such technique is shortcut fusion, and has been studied in the context of both pure and monadic functional programs. In this paper, we study several shortcut fusion extensions, so that, alternatively, circular or higher-order programs are derived. These extensions are also provided for effect-free programs and monadic ones. Our work results in a set of generic calculation rules, that are widely applicable, and whose correctness is formally established. © 2011 Springer Science+Business Media, LLC.