Nanoscale chemical imaging by photoinduced force microscopy.

Correlating spatial chemical information with the morphology of closely packed nanostructures remains a challenge for the scientific community. For example, supramolecular self-assembly, which provides a powerful and low-cost way to create nanoscale patterns and engineered nanostructures, is not easily interrogated in real space via existing nondestructive techniques based on optics or electrons. A novel scanning probe technique called infrared photoinduced force microscopy (IR PiFM) directly measures the photoinduced polarizability of the sample in the near field by detecting the time-integrated force between the tip and the sample. By imaging at multiple IR wavelengths corresponding to absorption peaks of different chemical species, PiFM has demonstrated the ability to spatially map nm-scale patterns of the individual chemical components of two different types of self-assembled block copolymer films. With chemical-specific nanometer-scale imaging, PiFM provides a powerful new analytical method for deepening our understanding of nanomaterials

Placement and orientation of individual DNA shapes on lithographically patterned surfaces

Artificial DNA nanostructures show promise for the organization of functional materials to create nanoelectronic or nano-optical devices. DNA origami, in which a long single strand of DNA is folded into a shape using shorter 'staple strands', can display 6-nm-resolution patterns of binding sites, in principle allowing complex arrangements of carbon nanotubes, silicon nanowires, or quantum dots. However, DNA origami are synthesized in solution and uncontrolled deposition results in random arrangements; this makes it difficult to measure the properties of attached nanodevices or to integrate them with conventionally fabricated microcircuitry. Here we describe the use of electron-beam lithography and dry oxidative etching to create DNA origami-shaped binding sites on technologically useful materials, such as SiO_2 and diamond-like carbon. In buffer with ~ 100 mM MgCl_2, DNA origami bind with high selectivity and good orientation: 70–95% of sites have individual origami aligned with an angular dispersion (±1 s.d.) as low as ±10° (on diamond-like carbon) or ±20° (on SiO_2)

A Modified Protocol for Bisulfite Genomic Sequencing of Difficult Samples

The bisulfite genomic sequencing protocol is a widely used method for analyzing DNA methylation. It relies on the deamination of unmethylated cytosine residues to uracil; however, its high rates of DNA degradation and incomplete cytosine to uracil conversion often lead to failed experiments, uninformative results, and false positives. Here, we report the addition of a single-step multiple restriction enzyme digestion (MRED) designed to differentially digest polymerase chain reaction products amplified from unconverted DNA while leaving those of converted DNA intact. We show that for our model system, RARB2 P2 promoter, use of MRED increased informative sequencings ninefold, and MRED did not alter the clonal representation in one fully methylated cell line, H-596, treated or not with 5-azadeoxycytidine, a methylation inhibitor. We believe that this method may easily be adapted for analyzing other genes and provide guidelines for selecting the most appropriate MRED restriction enzymes

Teachers, principals, and severely disabled students in the regular classroom: A change perspective

The purpose of this study was fourfold. First, the study investigated regular teachers\u27 attitudes toward inclusion of severely disabled students in the classroom. Second, it assessed the change facilitator style of the principal. Third, it measured the level of special education training of the regular teachers. Finally, the study was conducted to test the hypothesis that teachers with higher levels of special education training in schools with principals demonstrating the initiator style of change facilitator would have the most positive attitudes toward the inclusion of students with severe disabilities. Questionnaires were mailed to 363 regular teachers in 13 schools in New York State that had included students with severe disabilities in the regular classroom. One questionnaire measured teachers\u27 attitudes toward six dimensions of inclusion: the educational soundness of the concept of inclusion, teacher\u27s responsibilities, effects of placement, student achievement organizational support, and personnel and resource support. Another questionnaire measured the change facilitator style of the principal as either responder, manager, or initiator. Demographic information concerning the teachers\u27 level of special education training was collected. Fifty-five percent of the teachers returned completed questionnaires. Regardless of whether teachers rated their principals as initiators, managers, or responders, teachers\u27 total attitudes toward the inclusion of students with severe disabilities in the regular classroom were neither strongly positive nor negative. However, a two-way analysis of variance indicated that teachers in schools with responder style principals had significantly less positive attitudes about personnel and resource support than teachers who rated their principals as either managers or initiators. Furthermore, the hypothesis that teachers\u27 attitudes would vary as a function of the teacher\u27s level of special education training was rejected. The hypothesis that there would be an interaction between teachers\u27 level of special education training, the change facilitator style of the principal, and teachers\u27 attitudes toward inclusion was also rejected. Further recommendations were made to practitioners and researchers concerned, in general, with the inclusion of severely disabled students in the regular classroom as part of the school reform agenda and, in particular, with issues affecting regular teachers who are key players in the implementation of inclusion

Syntheses and reactions of polymer-bound molybdenum complexes and hydrogenolyses of an alknyl cobalt carbonyl cluster

NOTE: Text or symbols not renderable in plain ASCII are indicated by [...]. Abstract is included in .pdf document. Co3(CO)9CCH2C(CH3)3 (1) was prepared and its hydrogen- mediated decomposition was studied. 1 reacted with hydrogen in aromatic solvents (60°C, 2-7 atm H2) to yield three products: 3,3-dimethylbutene (2), 2,2-dimethylbutane (3), and 4,4- dimethylpentanal (4). The final ratio of alkene to alkane to aldehyde was approximately 2.5 : 1.5 : 1.0. Kinetic data collected from both NMR- and vpc-monitored experiments indicated first order decomposition of starting material 1 and a hydrogen pressure dependence for the rate of appearance of total products. Nearly total inhibition of the hydrogenation was observed in the presence of carbon monoxide (CO:H2, 3.7:3.7 atm, 60°C). However, at elevated temperatures (85°), under the same CO/H2 atmosphere, aldehyde (4) production became the predominant reaction pathway at the expense of earlier-formed olefin 2. Incorporation of independently added olefins in the hydrogenation of 1 suggested the intermediacy of olefin in aldehyde and alkane production. A polystyrene-attached n[superscript 5}-cyclopentadienyl(tricarbony1)-hydridomolybdenum complex (P-6) was prepared and its reactions with several THF-soluble bases were investigated. Enolates of β-dicarbonyl compounds quantitatively deprotonated P-6, giving polymer-bound salts of the corresponding anion ([...]-Cp(CO)3Mo[...], P-7). Equilibration studies involving polymers P-6 and P-7 and their soluble monomeric analogues in THF demonstrated that little change in pKa was induced by binding the molybdenum hydride to the polymer. Even though the polymer-supported partners in these experiments were not soluble and therefore rendered the reactions heterogeneous, the systems adhered reasonably well to conventional equilibrium behavior, as exhibited by a simple equilibrium analysis which yielded effectively constant Keq values. A polymer-bound carboxylic acid (P-1) and its conjugate base (P-2) also displayed essentially conventional equilibrium dynamics

Three-Dimensional Nanostructure Construction via Nanografting: Positive and Negative Pattern Transfer

Three-dimensional nanostructures can be constructed using scanning probe lithography in combination with selective surface reactions. This letter introduces a successful approach using AFM-based nanografting to produce two-dimensional nanopatterns within self-assembled monolayer resists. These nanopatterns serve as an anchor to construct nanostructures in the third dimension via surface reactions. In this way, the nanometer-scale 20 pattern is transferred to chemically distinct 3D nanostructures. This approach offers the advantages of high spatial precision and selectivity in pattern transfer