64 research outputs found
Periodic orbit analysis of an elastodynamic resonator using shape deformation
We report the first definitive experimental observation of periodic orbits
(POs) in the spectral properties of an elastodynamic system. The Fourier
transform of the density of flexural modes show peaks that correspond to stable
and unstable POs of a clover shaped quartz plate. We change the shape of the
plate and find that the peaks corresponding to the POs that hit only the
unperturbed sides are unchanged proving the correspondence. However, an exact
match to the length of the main POs could be made only after a small rescaling
of the experimental results. Statistical analysis of the level dynamics also
shows the effect of the stable POs.Comment: submitted to Europhysics Letter
Gaussian random waves in elastic media
Similar to the Berry conjecture of quantum chaos we consider elastic analogue
which incorporates longitudinal and transverse elastic displacements with
corresponding wave vectors. Based on that we derive the correlation functions
for amplitudes and intensities of elastic displacements. Comparison to numerics
in a quarter Bunimovich stadium demonstrates excellent agreement.Comment: 4 pages, 4 figure
Directing Cluster Formation of Au Nanoparticles from Colloidal Solution
Discrete clusters of closely spaced Au nanoparticles can be utilized in devices from photovoltaics to molecular sensors because of the formation of strong local electromagnetic field enhancements when illuminated near their plasmon resonance. In this study, scalable, chemical self-organization methods are shown to produce Au nanoparticle clusters with uniform nanometer interparticle spacing. The performance of two different methods, namely electrophoresis and diffusion, for driving the attachment of Au nanoparticles using a chemical cross-linker on chemically patterned domains of polystyrene-block-poly(methyl methacrylate) (PS-b-PMMA) thin films are evaluated. Significantly, electrophoresis is found to produce similar surface coverage as diffusion in 1/6th of the processing time with an ~2-fold increase in the number of Au nanoparticles forming clusters. Furthermore, average interparticle spacing within Au nanoparticle clusters was found to decrease from 2-7 nm for diffusion deposition to approximately 1-2 nm for electrophoresis deposition, and the latter method exhibited better uniformity with most clusters appearing to have about 1 nm spacing between nanoparticles. The advantage of such fabrication capability is supported by calculations of local electric field enhancements using electromagnetic full-wave simulations from which we can estimate surface-enhanced Raman scattering (SERS) enhancements. In particular, full-wave results show that the maximum SERS enhancement, as estimated here as the fourth power of the local electric field, increases by a factor of 100 when the gap goes from 2 to 1 nm, reaching values as large as 10(10), strengthening the usage of electrophoresis versus diffusion for the development of molecular sensors
Experimentelle Validierung eines Kinetikmodells fĂŒr die Methanolsynthese anhand einer MiniplantâAnlage
Experimentelle Validierung eines Kinetikmodells fĂŒr die Methanolsynthese anhand einer MiniplantâAnlage
Determination of mineral content and organic matrix in bone samples using dual photon absorptiometry
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