Microbubble shape oscillations excited through ultrasonic parametric driving\ud

An air bubble driven by ultrasound can become shape-unstable through a parametric instability. We report time-resolved optical observations of shape oscillations (mode n=2 to 6) of micron-sized single air bubbles. The observed mode number n was found to be linearly related to the ambient radius of the bubble. Above the critical driving pressure threshold for shape oscillations, which is minimal at the resonance of the volumetric radial mode, the observed mode number n is independent of the forcing pressure amplitude. The microbubble shape oscillations were also analyzed numerically by introducing a small nonspherical linear perturbation to a Rayleigh-Plesset-type equation, capturing the experimental observations in detail.\ud \u

High frequency nonlinear scattering from a micrometer to submicrometer sized lipid encapsulated contrast agent

An experimental lipid encapsulated contrast agent comprised substantially of micrometer to submicrometer diameter bubbles was evaluated for its capacity to produce nonlinear scattering in response to high transmit frequencies. Agent characterization experiments were conducted at transmit frequencies of 20 and 30 MHz with bandwidths of 5, 15 and 25% using a broadband focused PVDF transducer. The presence of subharmonic energy was observed for all bandwidths at a wide range of pressures (0.49 to 5.7 MPa and 0.45 to 4.5 MPa for the 20 and 30 MHz cases, respectively). Distinct ultraharmonics were observed only in the 5% bandwidth cases. Second harmonic energy was also present, but this was at least partly due to nonlinear propagation, as indicated by linear scatterer signals. Evidence of destruction was found only at higher peak negative pressures (e.g., >2 MPa for 30 MHz 5% bandwidth pulse). The results suggest that small lipid bubble formulations may be useful for the purposes of high frequency nonlinear contrast imaging. (E-mail: [email protected]

Analytical parametrization and shape classification of anomalous HH production in the EFT approach

20 pages, 10 figures, LHC Higgs Cross Section Working Group report http://cds.cern.ch/record/2199287In this document we study the effect of anomalous Higgs boson couplings on non-resonant pair production of Higgs bosons ($HH$) at the LHC. We explore the space of the five parameters $\kappa_{\lambda}$, $\kappa_{t}$, $c_2$, $c_g$, and $c_{2g}$ in terms of the corresponding kinematics of the final state, and describe a partition of the space into a limited number of regions featuring similar phenomenology in the kinematics of $HH$ final state. We call clusters the sets of points belonging to the same region; to each cluster corresponds a representative point which we call a benchmark. We discuss a possible technique to estimate the sensitivity of an experimental search to the kinematical differences between the phenomenology of the benchmark points and the rest of the parameter space contained in the corresponding cluster. We also provide an analytical parametrization of the cross-section modifications that the variation of anomalous couplings produces with respect to standard model $HH$ production along with a recipe to translate the results into other parameter-space bases. Finally, we provide a preliminary analysis of variations in the topology of the final state within each region based on recent LHC results

THREE MAIN SPATIAL TECHNIQUES of SPATIAL MIXING SYSTEM

This written review is to have a deep review for three techniques to realize spatial effects, which are Head Related Transfer Functions, Image Source Method, and Schroeder Reverberation, utilized in Spatial Mixing System, 2nd lab report.Architecture & Allied Art

Microbubble Surface Modes

We have investigated surface vibrations generated by ultrasound excitation of individual unencapsulated micron-sized bubbles. In addition, we present surface modes (n=2 and 3) observed for phospholipid-coated ultrasound contrast agents excited through excitation of radial modes at frequencies between 1 and 4 MHz. Even higher modes of vibration (up to mode 5) are observed for coated microbubbles at insonation frequencies of 10 and 19 MHz. The potential relevance of surface modes for medical ultrasound is discussed, including the possible implications for current theoretical models of ultrasound contrast agents