The routine formation of nanometer-sized structures remains a challenge that limits advances in many fields of nanotechnology. Increasingly ªbottom±upº self-assembly approaches for the nanometer-scale patterning of surfaces are competing with traditional ªtop±downº lithographic processes such as scanned-probe lithography or high-resolution electron-beam (e-beam) lithography. Block copolymer thin films (< 100 nm) are among the more promising materials being examined as they offer ease of processing combined with phase separation induced structure formation on the nanometer scale.Recent work in block copolymer thin film pattern formation has included the use of poly(styrene-block-isoprene) to form periodic structures combined with ozonolysis to remove the isoprene phase, thereby creating arrays of holes in the polymer thin film.[1] In another case, poly(styrene-blockmethyl methacrylate) has been processed in electric fields to align a cylinder phase perpendicular to the film surface, and subsequently exposed to UV light to both mildly crosslink the styrene phase and degrade the methyl methacrylate domains.[2] Similar strategies have been employed to process other block copolymer systems that contain a variety of chemical structures and architectures.[3] Examples of desirable target applications of such porous thin films include photonic bandgap materials, structures to serve as molecular sieves, or templates for magnetic structures.[4]A typical means for improving the processing of bulk polymers is through the use of small-molecule additives.[5] While such additives in bulk polymer structures are ubiquitous, their application in block copolymer thin film processing has not been substantially explored to date. Given the enormous numbers of property variations possible this is surprising. Here we will show several strategies for the use of additivedriven chemistries that take place in only one type of the nanosized domains of block copolymer thin films. We then use such an approach to examine the convergence of ªtop± downº with ªbottom±upº fabrication through light-driven processes.In Figure 1, the structures of the three polymer systems and their respective phase selective additives are introduced. They are: (system 1) poly(a-methyl styrene-b-4-hydroxystyrene) (P(aMS-b-HOST)) and tetramethoxymethyl glycuril (TMMU) with photoacid generator; (system 2) poly(a-methyl styrene-b-isoprene) (P(aMS-b-I)) and 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TPO); and (system 3) poly(isoprene-b-ethylene oxide), (P(I-b-EO)) and 3-glycidoxypropyltrimethoxysilane/aluminum sec-butoxide (GLYMO)/ Al(O s Bu) 3 . While the first two systems are all-organic, in the case of P(I-b-EO) inorganic additives were used. All polymers were produced using living anionic polymerization, because of its excellent control of architecture and molecular weight (Fig. 1). Films of various controlled thicknesses down to monolayer (see below) were obtained by spin-coating from dilute solution onto silicon wafers.Selection of the appropriate chemistry makes...

To determine the effect of different promoters on the expression of an altered dihydrofolate reductase (DHFR) gene conferring methotrexate (MTX) resistance in different cell types, double-copy retroviral vectors were constructed carrying a murine mutant DHFR under the control of five different promoters, i.e., human adenosine deaminase (ADA), simian virus 40 (SV40), thymidine kinase (TK), human beta-actin, and cytomegalovirus (CMV). Their expression was compared in NIH-3T3 cells, three human leukemia cell lines, and mouse bone marrow. The variant DHFR is readily expressed from these various promoters in retroviral vectors at a selectable level. In 3T3 cells, the DHFR constructs containing the SV40 promoter conferred the highest levels of resistance to MTX. In K562 and Raji cells, the construct with the TK promoter produced the highest level of resistance. However granulocyte-macrophage colony-forming unit (CFU-GM) colonies from mouse marrow were more resistant to MTX when infected with vectors containing the SV40 promoter and ADA promoter as compared to the other promoter constructs. These studies show that mouse fibroblast cell lines such as NIH-3T3 do not predict the effectiveness of retroviral-mediated gene transfer for marrow progenitor cells, and that the activity of retroviral vector-encoded promoters vary in an unpredictable manner from cell type to cell type. Possible implications for basic gene transfer studies and clinical applications are discussed.

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7028 Background: In this study we assess the utility of direct tumor tissue MALDI-MS in a large prospective collection of surgically resected lung cancers to distinguish cancer from non-cancer, histology, occult lymph node involvement, and survival. Methods: 175 non-small cell lung cancer specimens and 62 histologically normal lung tissues obtained at the time of surgery were used in this analysis. Twelve micron thick frozen sections were placed on conductive glass slides. Sections were stained with Cresyl Violet and matrix applied to areas identified by a pathologist under microscopic guidance as containing greater than 80% tumor before three separate areas involved with tumor was analyzed by MALDI MS. Relative intensities of selected peaks were used for class comparison. A class prediction model was built based on the weighted flexible compound covariate method of analysis (WFCCM). Results: We created a prediction model from a training cohort consisting 81 tumors and 19 histologically normal tissue samples. A total of 221 peaks were used for statistical analysis. In tumor/normal discrimination, 46 peaks were used for the prediction model (p<0.0001), while, 22 were used (p<0.005) to predict histology, 11 (p<0.05) to predict nodal involvement, and 14 (p<0.005) in survival prediction. Using these prediction models, classification accuracy was 90% in normal/tumor discrimination, 81.8% in histology and 61.7% in nodal involvement prediction. In the survival prediction model, patients with longer than median survival could be distinguished from those with shorter than median survival (p<0.0001, Log-rank test). We then validated the same features in a blind test set from the remaining 93 tumors and 43 normals. For tumor/normal discrimination, prediction accuracy in test cohort was 94.3%. Histology prediction accuracy was 93.9% in predicting squamous cell carcinoma. Nodal involvement prediction accuracy was 49.3%. Longer or shorter median survival was also predicted in this set with statistical significance p<0.08. (Log rank test). Conclusion: We report the analysis of a large set of tumor and normal samples by MALDI MS and confirm similar accuracy in tumor/normal, histology and survival discrimination to previous our report. This project was supported by the Lung SPORE P50 CA90949 (DPC) and NCI 5R33CA86243 (RMC). No significant financial relationships to disclose.