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Efficient Transport (efficient + transport)
Selected AbstractsOrganic Electronics: High-mobility Ambipolar Transistors and High-gain Inverters from a Donor,Acceptor Copolymer Semiconductor (Adv. Mater.ADVANCED MATERIALS, Issue 4 20104/2010) The cover illustrates a polymer semiconductor highway for efficient transport of both electrons and holes. On p. 478, Samson A. Jenekhe, Mark D. Watson, and co-workers have demonstrated high-mobility single-component ambipolar field-effect transistors, by utilizing a new polymer semiconductor, and integrated them into complementary inverters. Polymer semiconductors with good ambipolar charge transport provide a simpler way to realize complementary circuits and other devices and functions in organic electronics. [source] Membrane engineering for process intensification: a perspectiveJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 3 2007Enrico Drioli Abstract Pushed by the increasing demand for materials, energy and products, chemical engineering today faces a crucial challenge: to support a sustainable industrial growth. One possible solution is process intensification (PI), the innovative design strategy aiming to improve manufacturing and processing by decreasing the equipment size/productivity ratio, energy consumption and waste production using innovative technical solutions. Membrane processes meet the requirements of PI because they have potential to replace conventional energy-intensive techniques, to accomplish the selective and efficient transport of specific components, and to improve the performance of reactive processes. Here, we identify the most interesting aspects of membrane engineering in some strategic industrial sectors. The opportunity to integrate conventional membrane units with innovative systems in order to exploit the potential advantages coming from their synergic applications is also emphasized. Copyright © 2007 Society of Chemical Industry [source] Current opportunities and challenges in skeletal muscle tissue engineeringJOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, Issue 6 2009Merel Koning Abstract The purpose of this article is to give a concise review of the current state of the art in tissue engineering (TE) of skeletal muscle and the opportunities and challenges for future clinical applicability. The endogenous progenitor cells of skeletal muscle, i.e. satellite cells, show a high proneness to muscular differentiation, in particular exhibiting the same characteristics and function as its donor muscle. This suggests that it is important to use an appropriate progenitor cell, especially in TE facial muscles, which have a exceptional anatomical and fibre composition compared to other skeletal muscle. Muscle TE requires an instructive scaffold for structural support and to regulate the proliferation and differentiation of muscle progenitor cells. Current literature suggests that optimal scaffolding could comprise of a fibrin gel and cultured monolayers of muscle satellite cells obtained through the cell sheet technique. Tissue-engineered muscle constructs require an adequate connection to the vascular system for efficient transport of oxygen, carbon dioxide, nutrients and waste products. Finally, functional and clinically applicable muscle constructs depend on adequate neuromuscular junctions with neural cells. To reach this, it seems important to apply optimal electrical, chemotropic and mechanical stimulation during engineering and discover other factors that influence its formation. Thus, in addition to approaches for myogenesis, we discuss the current status of strategies for angiogenesis and neurogenesis of TE muscle constructs and the significance for future clinical use. Copyright © 2009 John Wiley & Sons, Ltd. [source] Perfusion seeding of channeled elastomeric scaffolds with myocytes and endothelial cells for cardiac tissue engineeringBIOTECHNOLOGY PROGRESS, Issue 2 2010Robert Maidhof Abstract The requirements for engineering clinically sized cardiac constructs include medium perfusion (to maintain cell viability throughout the construct volume) and the protection of cardiac myocytes from hydrodynamic shear. To reconcile these conflicting requirements, we proposed the use of porous elastomeric scaffolds with an array of channels providing conduits for medium perfusion, and sized to provide efficient transport of oxygen to the cells, by a combination of convective flow and molecular diffusion over short distances between the channels. In this study, we investigate the conditions for perfusion seeding of channeled constructs with myocytes and endothelial cells without the gel carrier we previously used to lock the cells within the scaffold pores. We first established the flow parameters for perfusion seeding of porous elastomer scaffolds using the C2C12 myoblast line, and determined that a linear perfusion velocity of 1.0 mm/s resulted in seeding efficiency of 87% ± 26% within 2 hours. When applied to seeding of channeled scaffolds with neonatal rat cardiac myocytes, these conditions also resulted in high efficiency (77.2% ± 23.7%) of cell seeding. Uniform spatial cell distributions were obtained when scaffolds were stacked on top of one another in perfusion cartridges, effectively closing off the channels during perfusion seeding. Perfusion seeding of single scaffolds resulted in preferential cell attachment at the channel surfaces, and was employed for seeding scaffolds with rat aortic endothelial cells. We thus propose that these techniques can be utilized to engineer thick and compact cardiac constructs with parallel channels lined with endothelial cells. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010 [source] Active Transport of Amino Acids by a Guanidiniocarbonyl,Pyrrole ReceptorCHEMISTRY - A EUROPEAN JOURNAL, Issue 31 2010Christian Urban Dr. Abstract Herein we report the synthesis and characterization of a transporter 9 for N-acetylated amino acids. Transporter 9 is a conjugate of a guanidiniocarbonyl pyrrole cation, one of the most efficient carboxylate binding motifs reported so far, and a hydrophobic tris(dodecylbenzyl) group, which ensures solubility in organic solvents. In its protonated form, 9 binds N-acetylated amino acid carboxylates in wet organic solvents with association constants in the range of 104,M,1 as estimated by extraction experiments. Aromatic amino acids are preferred due to additional cation-,-interactions of the amino acid side chain with the guanidiniocarbonyl pyrrole moiety. U-tube experiments established efficient transport across a bulk liquid chloroform phase with fluxes approaching 10,6,mol,m,2,s,1. In experiments with single substrates, the release rate of the amino acid from the receptor,substrate complex at the interface with the receiving phase is rate determining. In contrast to this, in competition experiments with several substrates, the thermodynamic affinity to 9 becomes decisive. As 9 can only transport anions in its protonated form and has a pKa value of approximately 7, pH-driven active transport of amino acids is also possible. Transport occurs as a symport of the amino acid carboxylate and a proton. [source] | ||||||||||