Graphene multilayer as nanosized optical strain gauge for polymer surface relief gratings.

In this paper, we show how graphene can be utilized as a nanoscopic probe in order to characterize local opto-mechanical forces generated within photosensitive azobenzene containing polymer films. Upon irradiation with light interference patterns, photosensitive films deform according to the spatial intensity variation, leading to the formation of periodic topographies such as surface relief gratings (SRG). The mechanical driving forces inscribing a pattern into the films are supposedly fairly large, because the deformation takes place without photofluidization; the polymer is in a glassy state throughout. However, until now there has been no attempt to characterize these forces by any means. The challenge here is that the forces vary locally on a nanometer scale. Here, we propose to use Raman analysis of the stretching of the graphene layer adsorbed on top of polymer film under deformation in order to probe the strength of the material transport spatially resolved. With the well-known mechanical properties of graphene, we can obtain lower bounds on the forces acting within the film. Upon the basis of our experimental results, we can deduce that the internal pressure in the film due to grating formation can exceed 1 GPa. The graphene-based nanoscopic gauge opens new possibilities to characterize opto-mechanical forces generated within photosensitive polymer films.

Local chemical composition of nanophase-separated polymer brushes.

Using scattering scanning nearfield infrared microscopy (s-SNIM), we have imaged the nanoscale phase separation of mixed polystyrene-poly(methyl methacrylate) (PS-PMMA) brushes and investigated changes in the top layer as a function of solvent exposure. We deduce that the top-layer of the mixed brushes is composed primarily of PMMA after exposure to acetone, while after exposure to toluene this changes to PS. Access to simultaneously measured topographic and chemical information allows direct correlation of the chemical morphology of the sample with topographic information. Our results demonstrate the potential of s-SNIM for chemical mapping based on distinct infrared absorption properties of polymers with a high spatial resolution of 80 nm × 80 nm.

Structural characterization of a spin-assisted colloid-polyelectrolyte assembly: stratified multilayer thin films.

The assembly of polyelectrolytes and gold nanoparticles yields stratified multilayers with very low roughness and high structural perfection. The films are prepared by spin-assisted layer-by-layer self-assembly (LbL) and are characterized by X-ray reflectivity (XRR), UV-vis spectroscopy, atomic force microscopy (AFM), and transmission electron microscopy (TEM). Typical structures have four repeat units, each of which consists of eight double layers (DL) of poly(sodium 4-styrenesulfonate)/poly(allylamine hydrochloride), one monolayer of gold nanoparticles (10 nm diameter), and another layer of poly(allylamine hydrochloride). XRR scans show small-angle Bragg peaks up to seventh order, evidencing the highly stratified structure. Pronounced Kiessig fringes indicate a low global roughness, which is confirmed by local AFM measurements. TEM images corroborate the layered structure in the growth direction and nicely show the distinct separation of the individual particle layers. An AFM study reveals the lateral gold particle distribution within one individual particle layer. Interestingly, the spin-assisted deposition of polyelectrolytes reduces the roughness induced by the particle layers, leading to self-healing of roughness defects and a rather perfect stratification.

Combinations of cytochrome P-450 genotypes and risk of early-onset lung cancer in Caucasians and African Americans: a population-based study.

Polymorphisms in CYP1A1 and CYP1B1 genes in humans are associated with reduction of enzymatic activity towards several substrates, including those found in tobacco smoke. To investigate the potential role these polymorphisms have as modulators of early-onset lung cancer risk, a population-based case-control study involving early-onset lung cancer cases was performed. Biological samples were available for 383 individuals diagnosed prior to 50 years of age identified from the metropolitan Detroit Surveillance, Epidemiology and End Results (SEER) program and 449 age, race and sex-matched controls ascertained through random digit dialing. Genotype frequencies varied significantly by race for CYP1A1 Ile(462)Val and CYP1B1 Leu(432)Val genotypes, so all analyses were stratified by race. No association was seen between lung cancer risk and polymorphisms in CYP1A1 Msp1 or CYP1B1 Leu(432)Val for Caucasians or African Americans, after adjusting for age at diagnosis, sex, pack years of smoking and family history of lung cancer. In Caucasians, those with the IIe/Val genotype at CYP1A1 Ile(462)Val locus were at decreased risk of having lung cancer compared to those with the lle/lle genotype, after adjusting for age at diagnosis, sex, pack years of smoking and family history of cancer (OR=0.41 95% Cl 0.19-0.90). These results were not replicated among the African American population, nor were they modified by amount of smoking.

CYP1A1 and CYP1B1 polymorphisms and risk of lung cancer among never smokers: a population-based study.

The cytochrome P450 (CYP) superfamily of enzymes catalyse one of the first steps in the metabolism of carcinogens such as polycyclic aromatic hydrocarbons, nitroaromatics and arylamines. Polymorphisms within the CYP1A1 gene have been shown to be associated with lung cancer risk, predominantly among Asian populations. Despite functional evidence of a possible role of CYP1B1 in lung cancer susceptibility, only a few studies have evaluated polymorphisms in this gene in relation to lung cancer susceptibility. This population-based study evaluates polymorphisms in both of these CYP genes within never smokers, most of whom had environmental tobacco smoke (ETS) exposure. Cases (n = 160) were identified through the metropolitan Detroit Surveillance, Epidemiology and End Results program, and age, sex and race-matched population-based controls (n = 181) were identified using random digit dialing. Neither CYP1A1 MspI nor CYP1A1 Ile(462)Val was associated with lung cancer susceptibility among Caucasians or African-Americans. Among Caucasians, however, CYP1B1 Leu(432)Val was significantly associated with lung cancer susceptibility odds ratio (OR) for at least one valine allele = 2.87 [95% confidence interval (CI) 1.63-5.07]. Combinations of this Phase I enzyme polymorphism along with selected Phase II enzyme polymorphisms (GSTM1 null, GSTP1 Ile(105)Val and NQO1 C(609)T) were evaluated. The combination of CYP1B1 Leu(432)Val and NQO1 C(609)T appeared to be associated with the highest risk of lung cancer (OR = 4.14, 95% CI 1.60-10.74), although no combinations differed significantly from the risk associated with CYP1B1 Leu(432)Val alone. When individuals were stratified by household ETS exposure (yes/no), CYP1B1 Leu(432)Val alone and in combination with Phase II enzyme polymorphisms was more strongly associated with increased lung cancer susceptibility among those with at least some household ETS exposure. Additional studies will be required to further validate these findings among never smokers and to evaluate the effects of this polymorphism among smoking populations as well.

Effects of synthetic voice output on attitudes toward the augmented communicator.

This study investigated the effects of four different voice synthesizers on attitudes of nondisabled individuals toward an augmented communicator. Subjects (N = 284) viewed one of four videotapes depicting an adult VOCA (voice output communication aid) user having a conversation with a normal-speaking individual. The voice synthesizers used in the respective videotapes were ArticR65B male voice, Smoothtalker 3.0 male voice, RealVoice female, and DECtalk "Beautiful Betty." The Attitudes Toward Nonspeaking Persons Scale (ATNP) was used as the primary dependent variable. Results showed that attitudes toward the augmented communicator are more favorable in terms of evaluation and potential interaction when the synthetic voice is "easier to listen to." Gender-appropriate voice did not produce more favorable attitudes than gender-inappropriate voice. Implications of these findings for technological development of augmentative devices are discussed.