Minimizing the excitation of parasitic modes of vibration in slender power ultrasonic devices

The design of slender power ultrasonic devices can often be challenging due to the excitation of parasitic modes of vibration during operation. The excitation of these modes is known to manifest from behaviors such as modal coupling which if not controlled or designed out of the system can, under operational conditions, lead to poor device performance and device failure. However, a report published by the authors has indicted that the excitation of these modes of vibration could be minimized through device design, specifically careful location of the piezoceramic stack. This paper illustrates that it is possible, through piezoceramic stack position, to minimize modal coupling between a parasitic mode and the tuned longitudinal mode of vibration for slender ultrasonic devices

The influence of piezoceramic stack location on nonlinear behavior of langevin transducers

Power ultrasonic applications such as cutting, welding, and sonochemistry often use Langevin transducers to generate power ultrasound. Traditionally, it has been proposed that the piezoceramic stack of a Langevin transducer should be located in the nodal plane of the longitudinal mode of vibration, ensuring that the piezoceramic elements are positioned under a uniform stress during transducer operation, maximizing element efficiency and minimizing piezoceramic aging. However, this general design rule is often partially broken during the design phase if features such as a support flange or multiple piezoceramic stacks are incorporated into the transducer architecture. Meanwhile, it has also been well documented in the literature that power ultrasonic devices driven at high excitation levels exhibit nonlinear behaviors similar to those observed in Duffing-type systems, such as resonant frequency shifts, the jump phenomenon, and hysteretic regions. This study investigates three Langevin transducers with different piezoceramic stack locations by characterizing their linear and nonlinear vibrational responses to understand how the stack location influences nonlinear behavior

Is slower early growth beneficial for long-term cardiovascular health?

Background - Accelerated neonatal growth increases the later propensity to cardiovascular disease (CVD) in animals, whereas slower growth is thought to have a beneficial effect. To test this hypothesis in humans, we measured flow-mediated endothelium-dependent dilation (FMD) in a population subject to slower early growth and in healthy controls.Methods and Results - High-resolution vascular ultrasound was used to measure the change in brachial artery diameter in response to reactive hyperemia in adolescents age 13 to 16 years who were either part of a cohort born preterm and followed up prospectively (n = 216) or controls born at term ( n = 61). Greater weight gain or linear growth in the first 2 weeks postnatally was associated with lower FMD at adolescence ( regression coefficient, - 0.026-mm change in mean arterial diameter per 100-g increase in weight; 95% CI, - 0.040 to - 0.012 mm; P = 0.0003) independent of birthweight and potential confounding factors. Mean FMD in the half of the preterm population with the lowest rates of early growth was higher than in both the half with the greatest growth ( P = 0.001) and subjects born at term ( P = 0.03).Conclusions - FMD was 4% lower in adolescents with the highest compared with the lowest rate of weight gain in the first 2 weeks after birth, a substantial negative effect similar to that for insulin-dependent diabetes mellitus or smoking in adults. Our findings are consistent with the adverse effects of accelerated neonatal growth on long-term cardiovascular health and suggest that postnatal growth patterns could explain the previously reported association between birthweight and later CVD

Adiabatic Electron-Phonon Interaction and High-Temperature Thermodynamics of A15 Compounds

Inelastic neutron scattering was used to measure the phonon densities of states of the A15 compounds V_3Si, V_3Ge, and V_3Co at temperatures from 10 to 1273 K. It was found that phonons in V_3Si and V_3Ge, which are superconducting at low temperatures, exhibit an anomalous stiffening with increasing temperature, whereas phonons in V_3Co have a normal softening behavior. First-principles calculations show that this anomalous increase in phonon frequencies at high temperatures originates with an adiabatic electron-phonon coupling mechanism. The anomaly is caused by the thermally induced broadening of sharp peaks in the electronic density of states of V_3Si and V_3Ge, which tends to decrease the electronic density at the Fermi level. These results show that the adiabatic electron-phonon coupling can influence the phonon thermodynamics at temperatures exceeding 1000 K

Scalable simultaneous multi-qubit readout with 99.99% single-shot fidelity

We describe single-shot readout of a trapped-ion multi-qubit register using space and time-resolved camera detection. For a single qubit we measure 0.9(3)x10^{-4} readout error in 400us exposure time, limited by the qubit's decay lifetime. For a four-qubit register (a "qunybble") we measure an additional error of only 0.1(1)x10^{-4} per qubit, despite the presence of 4% optical cross-talk between neighbouring qubits. A study of the cross-talk indicates that the method would scale with negligible loss of fidelity to ~10000 qubits at a density <~1 qubit/um^2, with a readout time ~1us/qubit.Comment: 4 pages, 3 figures; simulations added to fig.3, with some further text and figure revisions. Main results unchanged

Influence of leptin on arterial distensibility - A novel link between obesity and cardiovascular disease?

Background-The mechanisms by which obesity increases the risk of atherosclerotic cardiovascular disease (CVD) are poorly understood. In experimental models, leptin, a hormone produced by adipose tissue, has been shown adversely to affect vascular health. Therefore, we tested the hypothesis that high leptin concentrations are associated with lower arterial distensibility, an index of circulatory function relevant to the atherosclerotic process.Methods and Results-Noninvasive, high-resolution, vascular ultrasound was used to measure brachial artery distensibility in 294 healthy adolescents (aged 13 to 16 years) who had a broad range of body mass indexes. Fat mass was measured by bioelectric impedance analysis; fasting serum leptin concentration by radioimmunoassay; and lipid profile, fasting insulin, glucose, and C-reactive protein concentrations by standard laboratory techniques. Higher leptin concentrations were associated with impaired arterial distensibility (regression coefficient, -1.3% change in arterial distension per 10% increase in leptin; 95% CI, -1.9% to -0.8%; P<0.001). This association was independent of fat mass, blood pressure, and C-reactive protein, fasting insulin, or LDL cholesterol concentrations.Conclusions-Elevation in leptin was associated with impaired vascular function, independent of the metabolic and inflammatory disturbances associated with obesity. Our observations are consistent with data from experimental models and suggest that high leptin concentration is an important mechanism for the adverse influence of body fatness on CVD

Emergence of long-range order in BaTiO3 from local symmetry-breaking distortions

By using a symmetry motivated basis to evaluate local distortions against pair distribution function data (PDF), we show without prior bias, that the off-centre Ti displacements in the archetypal ferroelectric BaTiO3 are zone centred and rhombohedral-like in nature across its known ferroelectric and paraelectric phases. With our newly-gained insight we construct a simple Monte Carlo (MC) model which captures our main experimental findings and demonstrate how the rich crystallographic phase diagram of BaTiO3 emerges from correlations of local symmetry-breaking distortions alone. Our results strongly support the order-disorder picture for these phase transitions, but can also be reconciled with the soft-mode theory of BaTiO3 that is supported by some spectroscopic techniques.Comment: 5 pages, 3 figure