Resonance Tracking Research Articles

Nanoscale piezoelectric and ferroelectric behaviors of seashell by piezoresponse force microscopy

Seashells, the armor of one of the most ancient species, have demonstrated outstanding mechanical properties such as simultaneous strengthening and toughening. The seashells have also been proven to exhibit piezoelectric and ferroelectric properties, which may contribute to their mechanical behaviors and various functionalities. This work has elaborated in more details of the piezoelectric and ferroelectric behaviors of the nacre by using the DART (Dual-AC Resonance Tracking) and vector-PFM (Piezoresponse Force Microscope), as well as the SS-PFM (Switching Spectroscopy PFM) techniques. By using the vector-PFM technique, the local polarization directions of intracrystalline biopolymers are found to be very close to the direction perpendicular to the platelet surface, and it, therefore, shows strong piezoresponse along this direction. On the other hand, the interlamellar biopolymer shows strong piezoresponse in the direction parallel to the platelet surface. This intrinsic piezoelectric property of the biopolymer may be the basis for sensing and actuating during biomineralization process. Besides the piezoresponse, the locations of various biopolymers are also revealed in-situ by using the PFM technique. The ferroelectric behaviors of nacre have been observed by SS-PFM method. Based on the shapes of the ferroelectric hysteresis loops, it is found that the biopolymers in nacre exhibit the similar behaviors to that of the polyvinylidene fluoride (PVDF) based co- or ter-polymers for energy storage applications.

Influence of external shocks and internal noises on the resonant frequency tracking system in Coriolis vibratory gyroscope

Resonant frequency tracking system that ensures rapid capture and track of frequency when switching on the gyro at any temperature from the working temperature range in Coriolis vibratory gyro are proposed and analyzed in this work. The problems of external shocks and internal noises influence suppression on the performance of resonant frequency tracking system, built on the basis of phase lock loop by tuning PIDF controller coefficients, used in feedback control loop of the tracking system are investigated.

Pulsewidth Locked Loop (PWLL) for Automatic Resonant Frequency Tracking in LLC DC–DC Transformer (LLC -DCX)

In recently developed distributed power architecture, the LLC resonant converter has been widely used as a dc–dc transformer (DCX) to provide a semiregulated or unregulated bus voltage. In order to achieve the highest efficiency, this paper proposes a novel switching frequency control scheme for the LLC-DCX. First, the synchronous rectifier (SR) gate-driving signals are tuned by eliminating the body diode conduction. Then, the pulsewidth locked loop (PWLL) is presented, by minimizing the pulsewidth difference between the main switch and the well-tuned SR gate-driving signals, the LLC-DCX always runs at the $f_0$ point to achieve the highest efficiency. For rapid prototyping purposes, the PWLL used to track $f_{0}$ is realized in a Cyclone III field programmable gate array.

MRI—3D ultrasound—X-ray image fusion with electromagnetic tracking for transendocardial therapeutic injections: In-vitro validation and in-vivo feasibility

Myocardial infarction (MI) is one of the leading causes of death in the world. Small animal studies have shown that stem-cell therapy offers dramatic functional improvement post-MI. An endomyocardial catheter injection approach to therapeutic agent delivery has been proposed to improve efficacy through increased cell retention. Accurate targeting is critical for reaching areas of greatest therapeutic potential while avoiding a life-threatening myocardial perforation. Multimodal image fusion has been proposed as a way to improve these procedures by augmenting traditional intra-operative imaging modalities with high resolution pre-procedural images. Previous approaches have suffered from a lack of real-time tissue imaging and dependence on X-ray imaging to track devices, leading to increased ionizing radiation dose. In this paper, we present a new image fusion system for catheter-based targeted delivery of therapeutic agents. The system registers real-time 3D echocardiography, magnetic resonance, X-ray, and electromagnetic sensor tracking within a single flexible framework. All system calibrations and registrations were validated and found to have target registration errors less than 5 mm in the worst case. Injection accuracy was validated in a motion enabled cardiac injection phantom, where targeting accuracy ranged from 0.57 to 3.81 mm. Clinical feasibility was demonstrated with in-vivo swine experiments, where injections were successfully made into targeted regions of the heart.

Research on Control Strategy of Electronic Ballast for Electrodeless Lamp

This paper presented a novel resonant frequency tracking control method for electronic ballast of electrodeless lamp. The proposed method enables the operation frequency of the electronic ballast to continuously track the resonant frequency of the resonant tank by detecting the phase difference between input voltage of resonant tank and resonant capacitor voltage . Using the proposed control method, the ballast can be optimized to operate with its maximum power capability and guarantee good load matching, even when the resonant tank parameters vary. The detailed implementation of the controller was presented in this paper. Simulation and experimental results verify the performance of the proposed control method.

Resonant inverter with resonance frequency tracking for DBD plasma reactor supply

This document gives an overview of a power supply construction suitable for dielectric barrier discharge (DBD) reactor excitation. The influence of temperature and voltage change on DBD reactor parameters is discussed. A power electronic supply system topology allowing for continuous resonant frequency tracking is proposed together with simulation and test stand results of operation. An additional feature of proposed topology is the output peak to peak voltage control.

High sensitivity piezomagnetic force microscopy for quantitative probing of magnetic materials at the nanoscale

Accurate scanning probing of magnetic materials at the nanoscale is essential for developing and characterizing magnetic nanostructures, yet quantitative analysis is difficult using the state of the art magnetic force microscopy, and has limited spatial resolution and sensitivity. In this communication, we develop a novel piezomagnetic force microscopy (PmFM) technique, with the imaging principle based on the detection of magnetostrictive response excited by an external magnetic field. In combination with the dual AC resonance tracking (DART) technique, the contact stiffness and energy dissipation of the samples can be simultaneously mapped along with the PmFM phase and amplitude, enabling quantitative probing of magnetic materials and structures at the nanoscale with high sensitivity and spatial resolution. PmFM has been applied to probe magnetic soft discs and cobalt ferrite thin films, demonstrating it as a powerful tool for a wide range of magnetic materials.

Real‐time high‐resolution magnetic resonance tracking of macrophage subpopulations in a murine inflammation model: a pilot study with a commercially available cryogenic probe

Macrophages present different polarization states exhibiting distinct functions in response to environmental stimuli. However, the dynamic of their migration to sites of inflammation is not fully elucidated. Here we propose a real-time in vivo cell tracking approach, using high-resolution (HR)-MRI obtained with a commercially available cryogenic probe (Cryoprobe™), to monitor trafficking of differently polarized macrophages after systemic injection into mice. Murine bone marrow-derived mononuclear cells were differentiated ex vivo into nonpolarized M0, pro-inflammatory M1 and immunomodulator M2 macrophage subsets and labeled with citrate-coated anionic iron oxide nanoparticles (AMNP). These cells were subsequently intravenously injected to mice bearing calf muscle inflammation. Whole body migration dynamics of macrophage subsets was monitored by MRI at 4.7 T with a volume transmission/reception radiofrequency coil and macrophage infiltration to the inflamed paw was monitored with the cryogenic probe, allowing 3D spatial resolution of 50 µm with a scan time of only 10 min. Capture of AMNP was rapid and efficient regardless of macrophage polarization, with the highest uptake in M2 macrophages. Flow cytometry confirmed that macrophages preserved their polarization hallmarks after labeling. Migration kinetics of labeled cells differed from that of free AMNP. A preferential homing of M2-polarized macrophages to inflammation sites was observed. Our in vivo HR-MRI protocol highlights the extent of macrophage infiltration to the inflammation site. Coupled to whole body imaging, HR-MRI provides quantitative information on the time course of migration of ex vivo-polarized intravenously injected macrophages.

Optimal frequency tracking method for phase‐shift PWM inverter

AbstractThis paper proposes a new resonant frequency tracking control method for full‐bridge‐type high‐frequency inverters. Whereas the ordinary phase‐locked loop (PLL) based frequency control method uses a current sensor and a voltage sensor, the proposed technique can achieve the same purpose with a single current sensor. In high‐frequency power supply systems using a PLL, it is impossible to perform power control with an inverter. Therefore, an active converter must be used for power control, and the system grows larger. On the other hand, high‐frequency inverters using the proposed control system simultaneously enable power control and achieve the same resonant frequency tracking as a PLL, and thus high‐frequency power supply systems become extremely simple. This paper explains in detail the principle underlying the control method, and presents an example of a circuit to realize it. The theory is backed up by using a prototype high‐frequency power supply system which actually employs the proposed control system, thereby demonstrating its practical utility in industry. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

MAPPING STORAGE MODULUS AND LOSS MODULUS OF POLYOLEFIN/POLYSTYRENE BLENDS WITH ATOMIC FORCE MICROSCOPY

ABSTRACT The storage modulus and loss modulus of blends of polypropylene/polystyrene and polyethylene/polystyrene have been mapped quantitatively with contact resonance atomic force microscopy. Contact resonance spectra were collected in Dual AC Resonance Tracking (DART) mode, in which the phase and amplitude are monitored at two discrete frequencies, resulting in maps of contact resonance frequency and quality factor. These data are then used to compute quantitative storage and loss moduli parameters for the materials being imaged. Computed storage moduli compare favorably with the high-frequency, time–temperature, superposed, low-frequency dynamic mechanical analyzer (DMA) values, whereas the computed loss moduli exhibited greater uncertainty in comparison with the bulk DMA values.

Fast frequency sweeping in resonance-tracking SPM for high-resolution AFAM and PFM imaging

A new resonance-tracking (RT) method using fast frequency sweeping excitation was developed for quantitative scanning probe microscopy (SPM) imaging. This method allows quantitative imaging of elastic properties and ferroelectrical domains with nanoscale resolution at high data acquisition rates. It consists of a commercial AFM system combined with a high-frequency lock-in amplifier, a programmed function generator and a fast data acquisition card. The resonance-tracking method was applied to the atomic force acoustic microscopy (AFAM) and to the piezoresponse force microscopy (PFM) modes. Plots of amplitude versus time and phase versus time for resonant spectra working with different sweeping frequencies were obtained to evaluate the response speed of the lock-in amplifier. It was proved that this resonance-tracking method allows suitable spectral acquisition at a rate of about 5 ms/pixel, which is useful for SPM imaging in a practical scanning time. In order to demonstrate the system performance, images of RT-AFAM for TiN films and RT-PFM for GeTe are shown.

Effects of Iron Oxide Nanoparticle Labeling on Human Endothelial Cells

Iron oxide nanoparticles (INOPS) are a potential contrast agent for magnetic resonance (MR) tracking of transplanted endothelial cells. The objective of this study was to examine the effect of INOPS labeling on endothelial cells. The mixture of INOPS and poly-l-lysine (PLL) was used to label human endothelial cells. Labeling efficiency was examined by Prussian blue staining, transmission electron microscopy, and atomic absorption spectrometry. The effect of iron oxide concentration on cell viability and proliferation were determined. The correlation of reactive oxygen species (ROS) and apoptosis was also examined. In vitro MRI scanning was carried out using a 1.5T MR system. INOPS-PLL could be readily taken up by endothelial cells and subsequently induce MRI signal intensity changes. However, higher labeling concentration (>50 µg/ml) and longer incubation (48 h) can affect cell viability and proliferation. Mitochondrial damage, apoptosis, and autolysosmes were observed under high INOPS-PLL concentrations, which were correlated to ROS production. INOPS-PLL nanoparticles can be used to label transplanted endothelial cells. However, high concentration of INOPS can impair cell viability, possibly through ROS-mediated apoptosis and autophagy.

Conic hyperspectral dispersion mapping applied to semiconductor plasmonics

The surface plasmon resonance tracking over metal surfaces is a well-established, commercially available, biochemical quantification tool primarily applied in research. The utilization of such a tool is, however, constrained to highly specialized industries, capable of justifying the human and instrumental resource investments required by the characterization method. We have proposed to expand the field of application of this biosensing approach by redesigning this method through the integration and miniaturization within a semiconductor platform. Uncollimated and broadband emission from a light-emitting semiconductor is employed to couple a continuum of surface plasmon modes over a metal–dielectric architecture interfaced with a GaAs–AlGaAs substrate. A tensor version of rigorous coupled wave theory is employed to optimize the various fabrication specifications and to predict the light scatterings over a wide range of variables. We then present a hyperspectral characterization microscope capable of directly mapping the dispersion relation of scattered light, including diffracted surface plasmons, as an intensity distribution versus photon energy and surface wavevectors. Measurements carried out in a buffered solution demonstrate the accurate description of the uncollimated and broadband surface plasmon states. Finally, we introduce a simplified method of dispersion mapping, in which quasi-conic cross-sections of the light's scattering can be acquired directly, thus monitoring surficial responses in as fast as 1.2 s. This is over 300 times faster than required by implementing full dispersion mapping. While compromising on the volume of collected information, this method, combined with the solid-state integration of the platform, shows great promise for the fast detection of biochemical agents. Researchers have miniaturized surface plasmon resonance experiments by using microchips embedded with gallium arsenide ‘quantum wells’. One of the best ways to track biochemical agents is through surface plasmon resonance spectroscopy, a technique that uses vibrations from a thin metal layer to detect specific molecular adsorption events. However, observing surface plasmons for biosensing traditionally requires the use of large, precisely tuned light sources. The scheme developed by Dubowski and co-workers employs hyperspectral imaging—a means of measuring data from hundreds of different spectral bands—to record how the broadband light of quantum well nanostructures scatters after striking a metal film. Advanced algorithms then pick out surface plasmons from the light-scattering data and enable near real-time analysis. Solid-state integration and pre-analysed output make this device ideal for future commercial ventures that could go beyond the application of surface plasmon resonance for biosensing.

Characterization of local piezoelectric behavior of ferroelectric GeTe and Ge2Sb2Te5 thin films

We studied the ferroelectric properties of GeTe and Ge2Sb2Te5 thin films through the analysis of capacitance-temperature, contact resonance piezoresponse force, resonance tracking piezoresponse force, and switching piezoresponse force microscopy measurements. These alloys are non-typical ferroelectric materials with low electrical resistivity, which makes their ferroelectric properties difficult to investigate by other conventional techniques. On the basis of measurement values of the Curie temperature, ferroelectric domain structure, piezoelectric coefficient d33, and coercive voltage were obtained. For the first time, hysteresis loops, and switching effects of domains under electrical field were observed in chalcogenide materials.

Biologistics—Diffusion coefficients for complete proteome of Escherichia coli

Motivation: Biologistics provides data for quantitative analysis of transport (diffusion) processes and their spatio-temporal correlations in cells. Mobility of proteins is one of the few parameters necessary to describe reaction rates for gene regulation. Although understanding of diffusion-limited biochemical reactions in vivo requires mobility data for the largest possible number of proteins in their native forms, currently, there is no database that would contain the complete information about the diffusion coefficients (DCs) of proteins in a given cell type.Results: We demonstrate a method for the determination of in vivo DCs for any molecule—regardless of its molecular weight, size and structure—in any type of cell. We exemplify the method with the database of in vivo DC for all proteins (4302 records) from the proteome of K12 strain of Escherichia coli, together with examples of DC of amino acids, sugars, RNA and DNA. The database follows from the scale-dependent viscosity reference curve (sdVRC). Construction of sdVRC for prokaryotic or eukaryotic cell requires ~20 in vivo measurements using techniques such as fluorescence correlation spectroscopy (FCS), fluorescence recovery after photobleaching (FRAP), nuclear magnetic resonance (NMR) or particle tracking. The shape of the sdVRC would be different for each organism, but the mathematical form of the curve remains the same. The presented method has a high predictive power, as the measurements of DCs of several inert, properly chosen probes in a single cell type allows to determine the DCs of thousands of proteins. Additionally, obtained mobility data allow quantitative study of biochemical interactions in vivo.Contact: rholyst@ichf.edu.plSupplementary information: Supplementary data are available at Bioinformatics Online.

Resonance Tracking of Nonlinear MEMS Resonators

In this paper, the frequency control loop performance of nonlinear microelectromechanical resonators is investigated. A phase-locked loop (PLL) controller is used to track the resonance frequency of a nonlinear resonator and to compensate for the changes in the natural frequency. Based on the harmonic balance approach, governing equations of the dynamics of a nonlinear resonator are obtained, and using the mathematical model of the PLL, a new stability criterion for the closed-loop system is proposed. The relationship between the amplitude of the external driving force command and the stability of the control loop is elaborated for both hardening and softening nonlinearities. A nonlinear gain control strategy is proposed for the frequency-tracking loop, and its effectiveness is shown through simulation studies.

Resonance Tracking of Continua Using Self-Sensing Actuators

This paper proposes and develops an innovative method to solve the resonance tracking problem for actuator and sensor applications to obtain maximum power transmission or signal selectivity using a modified phase-locked loop (PLL). The tracking of a higher eigenfrequency is very useful in some cases, but it is more challenging than the excitation of the only eigenfrequency of a 1-DoF system. The resonances are identified through employing their characteristic phase difference. The conventional PLL was modified to track a certain phase difference without deviation. The closed loop is a nonlinear control system due to the conversion between harmonic signals and phase signals. However, a model simplification to linear elements allows the goal oriented determination of the controller parameters. The advantages of self-sensing in combination with resonance tracking are attractive for practical applications such as ultrasonic motors and compact force sensors. The conducted experiments approved the effectiveness of the resonant excitation of higher oscillation modes of continua using self-sensing actuators.

고체형 정밀 공진 자이로스코프를 위한 이차 PLL 루프필터 기반 위상제어루프 설계

This paper suggests a design method of an improved phase control loop for tracking resonant frequency of solid type precision resonant gyroscope. In general, a low cost MEMS gyroscope adapts the automatic gain control loops by taking a velocity feedback configuration. This control technique for controlling the resonance amplitude shows a stable performance. But in terms of resonant frequency tracking, this technique shows an unreliable performance due to phase errors because the AGC method cannot provide an active phase control capability. For the resonance control loop design of a solid type precision resonant gyroscope, this paper presents a phase domain control loop based on linear PLL (Phase Locked Loop). In particular, phase control loop is exploited using a higher order PLL loop filter by extending the first order active PI (Proportion-Integral) filter. For the verification of the proposed loop design, a hemispherical resonant gyroscope is considered. Numerical simulation result demonstrates that the control loop shows a robust performance against initial resonant frequency gap between resonator and voltage control oscillator. Also it is verified that the designed loop achieves a stable oscillation even under the initial frequency gap condition of about 25 Hz, which amounts to about 1% of the natural frequency of a conventional resonant gyroscope.

Nitroxide Radicals@US‐Tubes: New Spin Labels for Biomedical Applications

AbstractThe encapsulation of nitroxide radicals within ultrashort (ca. 50 nm) single‐walled carbon nanotubes (US‐tubes) is achieved. Tempo‐ and Iodo‐Tempo@US‐tubes are characterized by thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Electron paramagnetic resonance (EPR) spectra display characteristic signals due to the detection of the spin probes within the US‐tubes. Longitudinal proton relaxivities (r1) of both nitroxide@US‐tubes samples are 7 to 13 times greater than the free nitroxide radicals in solution, giving relaxivities comparable to the clinical contrast agent (CA) Magnevist. In addition, transverse proton relaxivities (r2) show unprecedented proton relaxation enhancement in comparison to any other reported nitroxide radical‐based system or the clinically approved T2 CA, Resovist, under the same conditions. T2‐weighted magnetic resonance imaging (MRI) phantom images show that the encapsulation of nitroxide radicals within the US‐tubes produces good contrast enhancement due to their high r2 relaxivities. The nitroxide radicals@US‐tube agents are a new promising class of spin probes for MRI and electronic paramagnetic resonance imaging (EPRI) labeling, tracking, and diagnosis.

Impact of the crystallographic structure of epitaxially grown strained sodium–bismuth–titanate thin films on local piezo- and ferroelectric properties

Thin films of different phases of lead-free sodium–bismuth–titanate were epitaxially grown on SrTiO3 and NdGaO3 substrates by metal–organic chemical vapor deposition. Aurivillius phases with m=3, m=3.5 and m=4 and the Na0.5Bi0.5TiO3 perovskite phase were obtained by varying the substrate temperature and the Na/Bi ratio in the gas phase. Investigations of the impact of crystallographic structure and incorporated film lattice strain on local piezo- and ferroelectric properties were carried out by piezoresponse force microscopy experiments using dual AC resonance tracking combined with a tip-sample contact modeling procedure to determine an effective value for the piezoelectric coefficient for each sample. Comparative piezoresponse force microscopy measurements revealed a significant increase of the average effective piezoelectric coefficient dzz when the film structure changed from an Aurivillius phase to the perovskite phase. Films of perovskite phase have also shown the possibility of local tip-induced polarization switching.