Role of Rare-Earth Oxide Additives on Mechanical Properties and Oxidation Behavior of Si 3 N 4 /BN Fibrous Monolith Ceramics

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/65415/1/j.1551-2916.2006.00911.x.pd

Self consistent determination of plasmonic resonances in ternary nanocomposites

We have developed a self consistent technique to predict the behavior of plasmon resonances in multi-component systems as a function of wavelength. This approach, based on the tight lower bounds of the Bergman-Milton formulation, is able to predict experimental optical data, including the positions, shifts and shapes of plasmonic peaks in ternary nanocomposites without using any ftting parameters. Our approach is based on viewing the mixing of 3 components as the mixing of 2 binary mixtures, each in the same host. We obtained excellent predictions of the experimental optical behavior for mixtures of Ag:Cu:SiO2 and alloys of Au-Cu:SiO2 and Ag-Au:H2 O, suggesting that the essential physics of plasmonic behavior is captured by this approach.Comment: 7 pages and 4 figure

Robust nanopatterning by laser-induced dewetting of metal nanofilms

We have observed nanopattern formation with robust and controllable spatial ordering by laser-induced dewetting in nanoscopic metal films. Pattern evolution in Co film of thickness 1\leq h\leq8 nm on SiO_{2} was achieved under multiple pulse irradiation using a 9 ns pulse laser. Dewetting leads to the formation of cellular patterns which evolve into polygons that eventually break up into nanoparticles with monomodal size distribution and short range ordering in nearest-neighbour spacing R. Spatial ordering was attributed to a hydrodynamic thin film instability and resulted in a predictable variation of R and particle diameter D with h. The length scales R and D were found to be independent of the laser energy. These results suggest that spatially ordered metal nanoparticles can be robustly assembled by laser-induced dewetting

Investigation of pulsed laser induced dewetting in nanoscopic metal films

Hydrodynamic pattern formation (PF) and dewetting resulting from pulsed laser induced melting of nanoscopic metal films have been used to create spatially ordered metal nanoparticle arrays with monomodal size distribution on SiO_{\text{2}}/Si substrates. PF was investigated for film thickness h\leq7 nm < laser absorption depth \sim11 nm and different sets of laser parameters, including energy density E and the irradiation time, as measured by the number of pulses n. PF was only observed to occur for E\geq E_{m}, where E_{m} denotes the h-dependent threshold energy required to melt the film. Even at such small length scales, theoretical predictions for E_{m} obtained from a continuum-level lumped parameter heat transfer model for the film temperature, coupled with the 1-D transient heat equation for the substrate phase, were consistent with experimental observations provided that the thickness dependence of the reflectivity of the metal-substrate bilayer was incorporated into the analysis. The spacing between the nanoparticles and the particle diameter were found to increase as h^{2} and h^{5/3} respectively, which is consistent with the predictions of the thin film hydrodynamic (TFH) dewetting theory. These results suggest that fast thermal processing can lead to novel pattern formation, including quenching of a wide range of length scales and morphologies.Comment: 36 pages, 11 figures, 1 tabl

Effective permittivity of random plasmonic composites

An effective-medium theory (EMT) is developed to predict the effective permittivity \epsilon_eff of dense random dispersions of high optical-conductivity metals such as Ag, Au and Cu. Dependence of \epsilon_eff on the volume fraction \phi, a microstructure parameter \kappa related to the static structure factor and particle radius a is studied. In the electrostatic limit, the upper and lower bounds of \kappa correspond to Maxwell-Garnett and Bruggeman EMTs respectively. Finite size effects are significant when |\beta^2(ka/n)^3| becomes O(1) where \beta, k, and n denote the nanoparticle polarizability, wavenumber and matrix refractive index respectively. The coupling between the particle and effective medium results in a red-shift in the resonance peak, a non-linear dependence of \epsilon_eff on \phi, and Fano resonance in \epsilon_eff.Comment: Manuscript submitted to J. Opt. Soc. Am. B. 33 page

Understanding Video Game Developers as an Occupational Community

The video game industry has rapidly expanded over the last four decades; yet there is limited research about the workers who make video games. In examining these workers, this article responds to calls for renewed attention to the role of the occupation in understanding project-based workers in boundaryless careers. Specifically, this article uses secondary analysis of online sources to demonstrate that video game developers can be understood as a unique social group called an occupational community (OC). Once this classification has been made, the concept of OC can be used in future research to understand video game workers in terms of identity formation, competency development, career advancement and support, collective action, as well as adherence to and deviance from organizational and industry norms

Learned helplessness in chess players: The importance of task similarity and the role of skill

The effects of noncontingency between subjects' responses and outcomes were examined with respect to treatment/posttest similarity and skill in the task. The experimental design consisted of three groups. The first group had to solve chess problems with objective solutions and received veridical feedback; each member of the second group faced problems with no objective solutions, and received the same feedback as the member of the first group he was yoked with, but without any control on it; the control group received a waiting task. It was found that the group with unsolvable problems was more depressed than the two other groups at the end of the experiment. The mid-strength players were the most sensitive to the manipulation, and the weakest players showed little effect of learned helplessness. It was also found that the effects were proportional to the degree of similarity between the treatment and the posttest. The results limit the domain of applicability of the learned helplessness model

Naturally propped fractures caused by quartz cementation preserve oil reservoirs in basement rocks

MB is in receipt of a postgraduate studentship from PTDF (Nigeria). Skilled technical support was provided by M. Baron and J. Still. Two reviewers made valuable criticisms that improved the paper.Peer reviewedPostprin