On-chip temporal focusing of elastic waves in a phononic crystal waveguide.

The ability to manipulate acoustic and elastic waveforms in continuous media has attracted significant research interest and is crucial for practical applications ranging from biological imaging to material characterization. Although several spatial focusing techniques have been developed, these systems require sophisticated resonant structures with narrow bandwidth, which limit their practical applications. Here we demonstrate temporal pulse manipulation in a dispersive one-dimensional phononic crystal waveguide, which enables the temporal control of ultrasonic wave propagation. On-chip pulse focusing is realized at a desired time and position with chirped input pulses that agree perfectly with the theoretical prediction. Moreover, traveling four-wave mixing experiments are implemented, providing a platform on which to realize novel nonlinear phenomena in the system. Incorporating this dispersive pulse engineering scheme into nonlinear phononic crystal architecture opens up the possibility of investigating novel phenomena such as phononic solitons.

Broadband reconfigurable logic gates in phonon waveguides.

The high-quality-factor mechanical resonator in electromechanical systems has facilitated dynamic control of phonons via parametric nonlinear processes and paved the development of mechanical logic-elements. However, the narrow spectral bandwidth of the resonating element constrains the available nonlinear phenomena thus limiting the functionality of the device as well as the switching speeds. Here we have developed phonon waveguides, with a two-octave-wide phonon transmission band, in which mechanical four-wave-like mixing is demonstrated that enables the frequency of phonon waves to be converted over 1 MHz. We harness this platform to execute multiple binary mechanical logic gates in parallel, via frequency division multiplexing in this broadband, where each gate can be independently reconfigured. The fidelity of the binary gates is verified via temporal measurements yielding eye diagrams which confirm the availability of high speed logic operations. The phonon waveguide architecture thus offers the broadband functionality that is essential to realising mechanical signal processors.

Dispersive and dissipative coupling in a micromechanical resonator embedded with a nanomechanical resonator.

A micromechanical resonator embedded with a nanomechanical resonator is developed whose dynamics can be captured by the coupled-Van der Pol-Duffing equations. Activating the nanomechanical resonator can dispersively shift the micromechanical resonance by more than 100 times its bandwidth and concurrently increase its energy dissipation rate to the point where it can even be deactivated. The coupled-Van der Pol-Duffing equations also suggest the possibility of self-oscillations. In the limit of strong excitation for the nanomechanical resonator, the dissipation in the micromechanical resonator can not only be reduced, resulting in a quality factor of >3× 10(6), it can even be eliminated entirely resulting in the micromechanical resonator spontaneously vibrating.

Study on the usefulness of APR scores from the viewpoint of proinflammatory cytokines.

BACKGROUND: Delayed diagnosis and treatment of newborn infection adversely impact outcomes. Clinical laboratory parameters have aimed to obtain the most correct and prompt diagnosis and treatment of this disease. This study simultaneously observed changes over time in APR as well as proinflammatory cytokines and anti-proinflammatory cytokines and aims to clarify usefulness of APR scores. METHODS: We evaluated the usefulness of acute phase reactants (APR) in 46 newborns whose serum up to age 7 days had been stored, with comparison of three types (Group I: infection 15, Group F: fetal inflammatory response syndrome 17, and Group C: control 14) of APR-based scores, those of C-reactive protein (CRP), alpha1-acid glycoprotein (AGP), and haptoglobin (Hp), with proinflammatory cytokine levels. APR scores for CRP, AGP, and Hp and the levels of the proinflammatory cytokines IL-1ß, IL-6, IL-8, IL-10, and TNFα were determined. RESULTS: The cytokine levels started to increase from age 0 days and then decreased rapidly. The three APR scores, CRP, AG, and Hp, were elevated at age 0 days and then gradually decreased in infection (Group I) and fetal inflammatory response syndrome (Group F). The duration of antibiotic administration according to APR scores was significantly shorter in Group F than in Group I. CONCLUSION: This study demonstrated APR scores to be more useful for deciding whether antibiotics should be discontinued than proinflammatory cytokine levels.

Phonon waveguides for electromechanical circuits.

Nanoelectromechanical systems (NEMS), utilizing localized mechanical vibrations, have found application in sensors, signal processors and in the study of macroscopic quantum mechanics. The integration of multiple mechanical elements via electrical or optical means remains a challenge in the realization of NEMS circuits. Here, we develop a phonon waveguide using a one-dimensional array of suspended membranes that offers purely mechanical means to integrate isolated NEMS resonators. We demonstrate that the phonon waveguide can support and guide mechanical vibrations and that the periodic membrane arrangement also creates a phonon bandgap that enables control of the phonon propagation velocity. Furthermore, embedding a phonon cavity into the phonon waveguide allows mobile mechanical vibrations to be dynamically switched or transferred from the waveguide to the cavity, thereby illustrating the viability of waveguide-resonator coupling. These highly functional traits of the phonon waveguide architecture exhibit all the components necessary to permit the realization of all-phononic NEMS circuits.