As determined by high performance liquid chromatography, (-)-epicatechin concentrations among freshly harvested beans of verified genetic origin ranged from 21.89-43.27 mg/g of dry defatted samples. Fermented beans showed much lower concentrations (2-10 mg). During fermentation, a trend towards decrease in (-)-epicatechin content was observed. Commercial beans from areas with reputations for shipping well-fermented products contained lower levels of (-)-epicatechin than beans from regions where fermentation is less extensive.

The role of long-range strain interactions on domain wall dynamics is explored through macroscopic and local measurements of nonlinear behavior in mechanically clamped and released polycrystalline lead zirconate-titanate (PZT) films. Released films show a dramatic change in the global dielectric nonlinearity and its frequency dependence as a function of mechanical clamping. Furthermore, we observe a transition from strong clustering of the nonlinear response for the clamped case to almost uniform nonlinearity for the released film. This behavior is ascribed to increased mobility of domain walls. These results suggest the dominant role of collective strain interactions mediated by the local and global mechanical boundary conditions on the domain wall dynamics. The work presented in this Letter demonstrates that measurements on clamped films may considerably underestimate the piezoelectric coefficients and coupling constants of released structures used in microelectromechanical systems, energy harvesting systems, and microrobots. Strain in epitaxial oxide films has become a universally recognized method for tuning materials properties [1][2][3], enabling novel couplings between magnetic, lattice, and strain behaviors [4][5][6], stabilizing new phases [7] or domain morphologies [8]. Systematic studies of a material's response to strain enable exploration of the fundamental mechanisms responsible for, e.g., the ferroelectric instability [9][10][11][12].While strain effects on intrinsic properties [9,12] and domain morphologies [13,14] are readily amenable to theoretical and experimental studies, their role on local and emergent properties [15] in disordered materials, including polycrystalline ferroelectric films and relaxors, remains virtually unexplored [16,17], Indeed, many of these materials exhibit unique physical properties including giant electromechanical coupling coefficients, broad dispersions of dielectric permittivity, etc. [18][19][20][21]. These phenomena are often associated with the presence of nanoscale textures of domains or nanoscale phase separation [22][23][24]. In all these materials, the dominant order parameter is either strain (ferroelastics) or is strongly coupled to strain (relaxors, morphotropic systems), suggesting the significant role of frustrated or random strain interactions [25][26][27]. Correspondingly, tuning mechanical boundary conditions can significantly affect emergent behaviors in disordered ferroics and provide insight into corresponding coupling mechanisms.Here, we aim to explore domain wall dynamics as reflected in ferroelectric nonlinearities in model PbZr 0:52 Ti 0:48 O 3 thin films. In polycrystalline lead zirconate-titanate (PZT) ceramics, domain wall motion may contribute more than 50% of the dielectric and piezoelectric properties at room temperature [23,28]. However, in thin films these extrinsic contributions to the piezoelectric response can be severely limited by several factors, including substrate clamping [29]. Recent spatially resolved studies of piezoelectri...

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Bulk piezoelectric ceramics and single crystals are widely used in medical applications, including medical ultrasonic imaging, therapeutic ultrasound, and drug delivery. This paper reviews possibilities for thin film micromachined components as alternatives to the bulk devices. Particular emphasis is placed on the development of a CMOScompatible ultrasound system. For this purpose, a piezoelectric ultrasound system on a Si substrate was fabricated using a diaphragm geometry transducer with PZT films. A 1-D array of 8 elements was designed and fabricated using 4 photolithography steps. Cavities under the resonating elements were obtained by XeF 2 etching from the top-side of the wafer. Capacitance and admittance spectra showed a resonance at ∼ 42 MHz for the fabricated structures with a quality factor of 2.1, this resonance was higher than the one predicted by the natural frequency equation for circular plate. Catch-and pitch-mode tests were performed in water. Sensing and actuating functionalities were demonstrated for the fabricated devices, with collected signals of 40 mV peak-to-peak at a distance of 7.2 mm during the catch-mode test and amplitudes as high as 15 mV peak-to-peak at a distance of 7.4 mm during the pitch-mode test. A bandwidth of 83% was calculated during pitch-mode test.

In response to the practical need for restoring images which are degraded by systems which are bilinear, this paper focuses on the development and application of tools required for this purpose. When the blurring phenomenon can be modeled by a shift-variant bilinear system, the data restoration problem can be most conveniently formulated as a special system of linear equations with nonnegative coefficients, whose solution is required to satisfy constraints like nonnegativity in addition to it being factorable with the factors having a certain characterizing property. Recursive techniques for restoration are first developed when the blurring system is either causal or weakly causal. It is shown how these recursive techniques when applied several times and the solutions superposed can, sometimes, be used to restore images degraded by noncausal blurs. Algorithms based on noniterative and iterative schemes are, subsequently, developed to tackle directly the noncausal blurs. Performances of the various algorithms when applied to noisy images are briefly compared.