Limitations and Future Directions

Like all LDW techniques, TPP suffers from low throughput. This drawback is quite unfavorable for industrial production, and it constitutes an obstacle (probably the major one) for a wider use of TPP in research laboratories too. As a consequence, many efforts have been committed to finding solutions that can decrease TPP processing time. In one approach, polymerization is performed with a multipoint scheme by employing a microlens array to focus the excitation beam in the resin [123-125]. In this way identical microstructures are fabricated at different positions simultaneously. When the number of points is on the order of several hundreds, an amplified femtosecond laser is necessary to produce sufficient laser intensities at each fabrication point. This increased complexity could be avoided in the future if photo-initiators with larger initiation efficiencies were to be used. 

The emergence of several technologies in the last two decades has stimulated the development of a set of unconventional microfabrication processes that go beyond the limits imposed by standard photolithography. TPP is one of these tools. Its distinctive capabilities to create complex 3D architectures vith high resolution, positions TPP as a key enabling microfabrication method for future advancements. 

1 Arnold, C.B. and Pique, A. (2007) Laser direct-write processing. MRS Bull., 

2 Borodovsky, Y. (2006) Marching to the Beat of Moore s law. Advances in Resist Technology and Processing XXIII (ed. Q. Lin), Proc. SPIE, vol. 6153, 

Serbin, J., and Gu, M. (2006) Two-photon polymerisation for three-dimensional micro-fabrication. 

---

H. Schreier, and S. M. Sawyer. Liposomal DNA vectors for cystic fibrosis gene therapy. Current applications, limitations, and future directions, Adv. Drug Del. Rev. 79 73-87 (1996). 

The importance of catalysis in biological as well as synthetic organic chemistry cannot be overstated. In Chapter 2, Donald Hilvert examines the scope and utility of asymmetric reactions under catalysis by antibodies. From a stereochemical point of view, this has significant impact not only in the production of important compounds in stereochemically defined form, but also in the ability of the antibody catalysts to alter the stereochemical course of organic reactions in fashions contrary to their natural tendencies. The most important chemical transformations carried out by catalytic antibodies are covered and provide the reader with an excellent snapshot of the state of the art of this emerging subfield in asymmetric catalysis. In addition, a critical appraisal of the limitations and future directions is included which should provide ample stimulation for thought. 

Bertrand, E, Grange, R, Pictet, R, Trans-acting Hammerhead Ribozymes in Vivo. Present limits and Future Directions, in Gene Regulation Biology of Antisense RNA and DNA, R.P. Erickson, Izant, J G, Editor. 1992, Raven New York. p. 71-81. 

In May 2007, the CSR organized a workshop on the topic Bioinspired Chemistry for Energy. This document summarizes the presentations and discussions that took place at the workshop and includes poster presenter abstracts. In accordance with the policies of the CSR, the workshop did not attempt to establish any conclusions or recommendations about needs and future directions, focusing instead on issues identified by the speakers. In addition, the organizing committee s role was limited to planning the workshop. The workshop summary has been prepared by the workshop rapporteurs Sandi Schwartz, Tina Masciangioli, and Boonchai Boonyaratanakomkit as a factual summary of what occurred at the workshop. 

In each section on the different ion channels, some unresolved issues and future directions will be addressed. In general, little is known about the precise molecular structures of the ion channels (e.g., K+ channels) in smooth muscle and our knowledge of endogenous agents as well as key signal transduction pathways that may modulate smooth muscle ion channels is far from complete. Further, as indicated previously, the modulation and expression of ion channels vary with the type of, and even within (e.g., large versus small arteries), smooth muscle. Studies on K+ channels in nonvascular types of smooth muscle will be discussed if similar material from arterial smooth muscle is limited. 

Once the organization of PKS-mediated biosynthesis was recognized, researchers sought ways to take advantage of the PKS modularity in order to engineer PKSs capable of making new PKs. To date, the most successful strategies have included (1) domain substitution and modification, (2) module substitution, and (3) precursor-directed biosynthesis. Examples of each of these approaches will be presented as well as a brief discussion of the current limitations and future outlook. 

Hence, catalysis may be considered as an enabling technology for this transition and, for this reason, it is necessary to better understand the limitations and possibilities in this field. We need to define future necessary directions of R D and the needs of fundamental and applied knowledge. In other words, there is the need to develop a roadmap for catalytic processes based on renewable feedstock. This book aims to provide an overview of the current state-of-the-art on which such a research agenda can be based. 

---