Mechanics of nanoindentation on a monolayer of colloidal hollow nanoparticles

We explore the collective mechanical behavior of monolayer assemblies composed of close-packed arrays of hollow silica nanoparticles using a spherical nanoindentor. Seven types of well-defined hollow nanoparticles are studied with their radii ranging from 100 to 300 nm and shell thickness ranging from 14 to 44 nm. Micromechanical models reveal the underlying deformation mechanisms during indentation, where the consecutive contacting of the indentor with an increasing number of nanoparticles results in a nonlinear increase in the indentation force with penetration depth. Each contacted hollow nanoparticle successively locally bends, flattens, and then locally buckles. The effective indentation modulus of the monolayer film, which is obtained by a Hertzian fit to the experimental data, is found to be proportional to the elastic modulus of the nanoparticle shell material and scales exponentially with the ratio of particle shell thickness t to radius R to the power of 2.3. Furthermore, we find that for a constant film density with the same (t)/(R) of the constituent nanoparticles, smaller particles with a thinner shell can provide a higher effective indentation modulus, compared to their larger diameter and thicker shell counterparts. This study provides useful insights and guidance for constructing high-performance lightweight nanoparticle films and coatings with potential applications in tailoring stiffness and mechanical energy absorption.

Theoretical study on photonic devices based on a commensurate two-pattern photonic crystal

In two-dimensional optical chip applications, the optical wave is classified to two modes according to its polarization: TE and TM. It is desirable to integrate multiple optical wave control devices for different polarizations onto the same plane at the scale of the wavelength. Here we demonstrate a periodic two-pattern photonic crystal with a large, complete photonic bandgap (PBG). It comes from the superposition of two substructures: one contributes the TM PBG and the other contributes the TE PBG. By purposely introducing defects into the substructures, photonic devices for different polarizations can be integrated to bend, split, and resonate TM/TE waves simultaneously on the same plane.

Focused laser spike (FLaSk) annealing of photoactivated chemically amplified resists for rapid hierarchical patterning

Lithographic alternatives to conventional layer-by-layer processes for the design of 3D structures such as photonic or phononic crystals often present a dichotomy: patterning control versus patterning area. We demonstrate a combined technique of large area interference lithography and local area direct write focused laser spike (FLaSk) annealing that can enable the microscale patterning of hierarchical structures defined in their morphology by the interference and defined in placement and shape by the direct write. This is accomplished by doping a commercial chemically amplified photoresist (SU-8) with an absorbing dye to provide thermal activation at a wavelength shifted from that causing UV crosslinking. In this way, the necessary post-exposure bake to complete the crosslinking of the resist is locally performed by the FLaSk laser, rather than globally on a hot plate. By utilizing the same experimental setup as used by a 3D direct write system, it is possible to integrate another level of patterning by enabling fully dense, arbitrarily written features on multiple length scales. Both experimental and simulated results of this novel processing method are shown.

Pragmatic study of orlistat 60 mg on abdominal obesity

BACKGROUND/OBJECTIVES

It is well established that combining a reduced calorie, low-fat diet with the lipase inhibitor orlistat results in significantly greater weight loss than placebo plus diet. This weight loss is accompanied by changes in adipose tissue (AT) distribution. As 60 mg orlistat is now available as an over-the-counter medication, the primary objective of this study was to determine whether 60 mg orlistat is effective as a weight loss option in a free-living community population with minimal professional input.

METHODS

AT and ectopic lipid content were measured using magnetic resonance imaging and (1)H MR spectroscopy, respectively, in 27 subjects following 3 months treatment with orlistat 60 mg and a reduced calorie, low-fat diet.

RESULTS

Significant reductions in intra-abdominal AT (-10.6%, P=0.023), subcutaneous (-11.7% P<0.0001) and pericardial fat (-9.8%, P=0.034) volumes and intrahepatocellular lipids (-43.3%, P=0.0003) were observed. These changes in body fat content and distribution were accompanied by improvements in plasma lipids and decreases in blood pressure and heart rate.

CONCLUSION

These findings suggest that over-the-counter 60 mg orlistat, in combination with the type of advice a subject could expect to be given when obtaining 60 mg orlistat in a community setting, does indeed result in potentially clinically beneficial changes in body composition and risk factors for metabolic diseases.

Visible mie scattering in nonabsorbing hollow sphere powders

Hollow silica nanoparticles (HSNP) with diameters comparable to visible wavelengths and with thin shells (<15 nm) feature an unexpected color effect. Single particle and powder spectroscopy, as well as calculations based on Mie theory were used to investigate this phenomenon. The use of HSNPs increases the transport mean free path of light significantly, which reduces multiple scattering, and thus the Mie resonances become visible to the bare eye.

Morphology of Rigid-Rod Polymer Fibers: an Overview

The current state of understanding of the morphology of the rigid-rod polymers PBZT and PBZO is reviewed. The morphology is sensitive to both the structure of the rigid polymer molecules and the nature of processing. Structural models of fiber morphology consistent with experiment are presented. An extensive bibliography is included.

Superamphiphilic Janus fabric

Janus fabrics with superamphiphilicity were fabricated via electrospinning of polyacrylonitrile (PAN). PAN nanofibrous mats were formed on an aluminum foil substrate and then thermally treated to cause hydrolysis. An identical PAN solution was subsequently electrospun onto the hydrolyzed PAN layer, followed by peeling off of the bicomposite film from the collector substrate to produce a free-standing Janus fabric. On one side, the electrospun PAN mat exhibited superhydrophobic properties, with a water contact angle of 151.2°, whereas the initially superhydrophobic PAN sheet on the opposite side of the fabric was converted to a superhydrophilic surface (water contact angle of 0°) through hydrolysis of the surface functional groups induced by the thermal treatment. The resulting Janus fabrics exhibited both superhydrophobicity, repelling water on the one side, and superhydrophilicity, absorbing water on the other side. The organic solvent resistance of the PAN nanofibrous sheets was remarkably improved by incorporation of a tetraethyl orthosilicate. This facile and simple technique introduces a new route for the design and development of functional smart, robust fabrics from an inexpensive, commercially available polymer.

Inorganic gyroid with exceptionally low refractive index from block copolymer templating

Nanoporous polymers with gyroid nanochannels can be fabricated from the self-assembly of degradable block copolymer, polystyrene-b-poly(l-lactide) (PS-PLLA), followed by the hydrolysis of PLLA blocks. A well-defined nanohybrid material with SiO2 gyroid nanostructure in a PS matrix can be obtained using the nanoporous PS as a template for sol-gel reaction. After subsequent UV degradation of the PS matrix, a highly porous inorganic gyroid network remains, yielding a single-component material with an exceptionally low refractive index (as low as 1.1).

Enhanced energy dissipation in periodic epoxy nanoframes

Periodic nanostructures fabricated by interference lithography can be precisely designed to have a specific cell geometry, topology, and porosity in contrast to typical stochastic cellular materials. We use nanoindentation to elucidate the mechanical characteristics of the nanoframe as a function of its relative density and model the deformation behavior via numerical simulations. The nanoframe exhibits a scaling exponent of relative modulus versus relative density of 1.26, which is less sensitive than for conventional foams. Moreover, the nanoframe shows large mechanical energy dissipation/volume (up to 4.5 MJ/m(3)), comparable to the highest values achieved in the conventional polymer foams but at a far smaller strain. Counterintuitively, a nanoframe of smaller relative density can dissipate more energy per volume because the geometry of the nanoframe evolves during deformation to engage more of the material in plastic deformation. The results demonstrate how geometrical control at the nano- and microstructural scale can tailor modulus and energy dissipation and suggest means for engineering of mechanically superior materials in the future.

Free-flow electrophoretic separation and electrical surface properties of subcellular particles from Guinea pig brain

Continuous free-flow electrophoretic separation has been used to obtain relatively pure preparations of synaptosomes and synaptic vesicles from crude fractions of guinea pig brain homogenates. Measurements of the contents of protein, neuraminic acid, and bound acetylcholine; the activities of succinic dehydrogenase, adenosine triphosphatase, choline acetylase, and 5'-nucleotidase; and the uptake of (14)C-labeled choline arid acetylcholine in the presence and absence of hemicholinium, all confirm the electron microscope evidence that the electrophoretic preparations are at least as pure as those obtained by ultracentrifugal methods. The electrophoretic mobility measurements have been used to calculate zeta potentials and surface charge densities for these particles.

Robust block copolymer mask for nanopatterning polymer films

The formation of well-oriented cylinders with perpendicular morphology for polystyrene-b-polydimethylsiloxane (PS-PDMS) thin films was achieved by spin coating. The self-assembled PS-PDMS nanostructured thin films were used as templates for nanopatterning; the PDMS blocks can be oxidized as silicon oxy carbide microdomains, whereas the PS blocks were degenerated by a simple oxygen plasma treatment for one-step oxidization. As a result, freestanding silicon oxy carbide thin films with hexagonally packed nanochannels were directly fabricated and used as masks for pattern transfer to underlying polymeric materials by oxygen reaction ion etching (RIE) to generate topographic nanopatterns. By taking advantage of robust property and high etching selectivity of the SiOC thin films under oxygen RIE, this nanoporous thin film can be used as an etch-resistant and reusable mask for pattern transfer to various polymeric materials. This approach demonstrates a simple, convenient, and cost-effective nanofabrication technique to create the topographic nanopatterns of polymeric materials.

Abstract 3301: Tumor biomarkers in mammary adenocarcinoma cell clones of different metastatic potential

Changes in the pattern of protein expression by tumor cells reflect the stage of tumor progression, the potential for invasion and metastasis, and drug resistance. Objectives: To use proteomic analysis to detect differences in protein expression that serve as biomarkers of tumor cell properties and to translate the results into diagnostic and prognostic tools based on immuno-cytological staining and immunoassay. Methods: Two-dimensional isoelectric focusing and gel electrophoresis (2-DG) followed by mass spectrometry were used to detect, measure, and identify changes in protein expression. MTC is a non-metastatic cell clone derived from a primary rat mammary adenocarcinoma. MTLn2 and MTLn3 are low and high metastatic potential cell clones derived from lung metastases of the primary tumor. 2-DG was performed simultaneously on samples of 3 extracts from cultured cells of each of the 3 clones. The 9 gels were stained with SYPRO Ruby. Matching of protein spots, densitometric analysis, and statistical analysis were performed using PDQuest 7.1 software. Excised proteins were identified by comparing the mass and sequence of tryptic peptides with those of all known rat proteins using liquid chromatography electrospray-ionization quadrupole ion trap mass spectrometry, SEQUEST software, and the NCBI protein database. Results: A total of 1500 proteins were detected. The patterns of protein expression of MTLn2 and MTLn3 cells were similar. Only 5 spots had a greater than 3-fold difference in staining intensity that was statistically significant (p&lt;0.05), whereas 48 spots differed between MTC and MTLn3 cells. Twenty spots were selected for further study, 10 that had a positive correlation of staining intensity with metastatic potential and 10 that had a negative correlation. Of the 17 unique proteins that were identified, five were of special interest because they are often cited as potential tumor biomarkers. These included the positive biomarkers nucleophosmin (NPM) and protein 14-3-3 sigma and the negative biomarkers raf kinase inhibitor protein (RKIP), peroxiredoxin-2, and galectin-1. Immuno-cytological staining and ELISA confirmed increased NPM and protein 14-3-3 sigma expression and decreased galectin-1 expression. The results suggest a role for stromal elements in biomarker expression. Conclusions: Increased metastatic potential is associated with positive and negative changes in protein expression. Proteins that are positively correlated with metastatic potential may be more useful as clinical biomarkers, whereas those with negative correlations may provide information about underlying mechanisms of metastatic spread and possible stromal influences. Changes in protein expression with differences in tumor properties will provide a consensus panel of biomarkers for diagnostic and prognostic tests. Supported in part by the Sam Mount, Jr. Endowment for Oral Cancer Research.

Note: This abstract was not presented at the AACR 101st Annual Meeting 2010 because the presenter was unable to attend.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 3301.