Slope Of Loop Research Articles

Stress-dependent Magnetization Processes in Co based Amorphous Microwires

Soft magnetic materials with high magnetic susceptibility are sensitive to changing magnetic fields and generate electrical voltage signals whose spectra contain higher harmonics. Magnetic susceptibility and saturation field are largely determined by magnetoelastic interactions in amorphous ferromagnets, respectively, the amplitudes of higher harmonics should depend on external mechanical stresses. In this work, we study the processes of magnetization reversal in amorphous microwires of two compositions: Co71Fe5B11Si10Cr3 and Co66.6Fe4.28B11.51Si14.48Ni1.44Mo1.69 under the action of external tensile stresses. For the first composition, mechanical stresses exceeding a certain limit (more than 350 MPa) lead to the transformation of the magnetic hysteresis from a bistable type to an inclined one. In this case, a sharp change of the harmonic spectrum is observed. In microwires of the second composition with an initially inclined loop, external stresses cause a monotonous increase in the slope of the hysteresis loop (a decrease in susceptibility). In this case, the amplitudes of higher harmonics change significantly at low stresses, less than 100 MPa. The results were obtained by remagnetization of microwire samples using a system of flat coils, which demonstrates the potential of using these materials as wireless sensors of mechanical stresses with remote reading.

Nonlinear response of magnetization obeying inertial dynamics to superimposed dc and ac fields and dynamic magnetic hysteresis

The nonlinear ac stationary responses of magnetization and the dynamic magnetic hysteresis of ferromagnetic particles with uniaxial anisotropy acted on by both external dc and ac magnetic fields are evaluated by employing the inertial Landau–Lifshitz–Gilbert equation. Analytical expressions are obtained for the components of the second- and third-order nonlinear susceptibility tensors using the perturbation method. The dynamic nonlinear susceptibility strongly depends on the dc field strength. The effect of inertia on the area and slope of the dynamic magnetic hysteresis loop is demonstrated. In addition to nutation resonance, the main nonlinear effects previously observed in the ferromagnetic resonance region (frequency doubling and appearance of weak subharmonic resonance peaks) are predicted in the nutation resonance frequency region.

Internal pressure dependence on viscoelasticity of arterial wall by ultrasonic measurement

Previously, we proposed an ultrasonic measurement method of arterial wall elasticity for the early detection of arteriosclerosis. Since vascular wall elasticity depends on blood pressure, in this study, the elasticity and viscosity were estimated using the hysteresis loop determined between the incremental strain in the wall and internal pressure by altering the internal pressure in the phantom and in vivo experiments. Consequently, both the estimated elasticity and viscosity increased with the internal pressure. Moreover, the slope of each hysteresis loop was larger than that of the approximated curve for the lowest blood pressures of the hysteresis loops with different internal pressures, as the blood pressure changed in the order of several hertz within a single heartbeat. Hence, we conclude that measuring both the blood pressure and the elastic and viscous moduli would be beneficial in comprehensively investigating more vessel wall properties that change with the progression of arteriosclerosis.

Understanding fluorescence time curves during ileal pouch-anal anastomosis with or without vascular ligation

BackgroundIntraoperative indocyanine green fluorescence angiography (ICG-FA) may be of added value during pouch surgery, in particular after vascular ligations as lengthening maneuver. The aim was to determine quantitative perfusion parameters within the efferent/afferent loop and explore the impact of vascular ligation. Perfusion parameters were also compared in patients with and without anastomotic leakage (AL).MethodsAll consenting patients that underwent FA-guided ileal pouch-anal anastomosis (IPAA) between July 2020 and December 2021 were included. After intravenous bolus injection of 0.1 mg/kg ICG, the near-infrared camera (Stryker Aim 1688) registered the fluorescence intensity over time. Quantitative analysis of ICG-FA from standardized regions of interests on the pouch was performed using software. Fluorescence parameters were extracted for inflow (T0, Tmax, Fmax, slope, Time-to-peak) and outflow (T90% and T80%). Change of management related to FA findings and AL rates were recorded.ResultsTwenty-one patients were included, three patients (14%) required vascular ligation to obtain additional length, by ligating terminal ileal branches in two and the ileocolic artery (ICA) in one patient. In nine patients the ICA was already ligated during subtotal colectomy. ICG-FA triggered a change of management in 19% of patients (n = 4/21), all of them had impaired vascular supply (ligated ileocolic/ terminal ileal branches). Overall, patients with intact vascular supply had similar perfusion patterns for the afferent and efferent loop. Pouches with ICA ligation had longer Tmax in both afferent as efferent loop than pouches with intact ICA (afferent 51 and efferent 53 versus 41 and 43 s respectively). Mean slope of the efferent loop diminished in ICA ligated patients 1.5(IQR 0.8–4.4) versus 2.2 (1.3–3.6) in ICA intact patients.ConclusionQuantitative analysis of ICG-FA perfusion during IPAA is feasible and reflects the ligation of the supplying vessels.

Enhancing of Electrical and Dielectric Properties of Barium Zirconate Titanate/Poly (Vinylidene Fluoride) Nano-Composites

The effects of poly (vinylidene fluoride, PVDF) on barium zirconate titanate nanoparticles has been studied. Different concentrations of (BZT-PVDF) nanocomposites using the formula [x (PVDF)/(1 − x) BZT] (where x = zero, 0.2, 0.4, 0.6, 0.8 and 1) were prepared using the hot pressing method. The BZT nanoparticle was prepared using the tartrate precursor route method. The Dc resistivity as a function of reciprocal temperature (1000/T) K−1 for the composite samples has been studied. The dielectric constant (ε) increases with the amount of BZT, which can be described as the increase of interfacial space charge polarization between (PVDF-BZT) nano-composites and the increase in the ionic mobility of the polymer. The ferroelectric hysteresis of prepared nano-composites has been investigated. The increase of BZT content raises the slope of the hysteresis loop and hence the dielectric polarization, which may be attributed to the dominance of smaller grain size and tetragonality. The increasing in dielectric properties for the prepared samples is very useful in industrial applications, such as sensors, actuators and transducers.

Pressure-Induced Mixed States Caused by Spin-Elastic Interactions during First-Order Spin Phase Transition in Spin Crossover Compounds.

Recently, the possibility of exploiting the phenomenon of spin transition (ST) has been intensively investigated; therefore, it is particularly important to study the behavior of ST under various stimuli. Here, the shape and content of the intermediate phase of ST in Hoffmann-like compounds [Fe(Fpz)2M(CN)4] (M = Pt, Pd) under external stimuli are studied. For this purpose, magnetic and Raman spectroscopy studies were carried out. In pressure-induced spin transition (PIST), a mixture of high-spin and low-spin states appears, while in temperature-induced spin transition (TIST), a homogeneous state occurs. The first-order ST induced by pressure has a hysteresis but is not abrupt. However, the temperature-induced spin transition at ambient pressure is hysteretic and abrupt. To investigate this difference, we discuss using a thermodynamic model that considers elastic interactions, showing that the slope of the hysteresis loop is related to the appearance of internal pressure, which is related to the difference in sample compressibility under high-spin and low-spin states.

A New High‐Speed Biaxial Testing System for Rodent Myocardium Viscoelastic Measurement under Dynamic Loadings

IntroductionMyocardium stiffening is well known in heart failure (HF) development, and it contributes to cardiac dysfunction. Myocardium is viscoelastic, which means that both elastic and viscous resistance exist under dynamic loading. There are limited studies of myocardium viscoelasticity, particularly for the right ventricle (RV). Because viscoelasticity is a time‐ and strain‐dependent mechanical behavior, the measurement at physiological rates & non‐linear deformation is critical. This study aims to develop a high‐speed biaxial tester that induces physiological deformation to characterize RV viscoelasticity in rats.MethodsTo enable the viscoelasticity measurement at physiological conditions, we built a biaxial tester that induces non‐linear, cyclic stretch of myocardium at rodent heart rates. Biaxial sinusoidal stretches were induced by actuators (1400mm/s) (Zaber), forces were recorded by load cells (Honeywell) at 1 kHz, and strains were obtained by a high‐speed camera (Baumer) at up to 200 fps. The LabVIEW and MATLAB codes were developed for performing biaxial tests at various frequencies with synchronized force and image data acquisition. To validate the biaxial tester, isotropic polydimethylsiloxane (PDMS) was used due to its similar viscoelasticity to cardiovascular tissues. PDMS sheets were prepared (Sylgard 184) for equibiaxial tests. Then, consistency between different axes’ measurements, synchronization of the axes’ movement, and accurate viscoelastic measurement were evaluated. Next, we performed equibiaxial cyclic sinusoidal tests on healthy rat RVs. After euthanasia, RV free wall was dissected and mounted. The outflow track direction was defined as the longitudinal direction. The RV was placed in a relaxant solution prior to testing, then preloaded by ~0.1 N and preconditioned by 15 cycles. Stress‐strain loops were derived for viscoelastic analysis.ResultsFirst, we examined if the biaxial tester could achieve planar biaxial tests at desired frequencies. The equibiaxial data obtained from PDMS sheets showed that the tester induced cyclic sinusoidal stretch at various frequencies up to 8 Hz (Fig. 1a), and the viscoelastic behavior measured at two axes were very close (Fig. 1b), thus confirming the tester’s accurate biaxial measurement of the isotropic material. The PDMS clearly showed frequency‐dependent changes in the hysteresis loops (Fig. 1c), with trends of increasing elasticity (slope of loop) and viscosity (area of loop) at higher frequencies. We further derived the viscosity by measuring Tan(δ) (Fig. 1d). The frequency‐dependent elasticity and viscosity of the PDMS sheet were consistent with literature data. Next, we obtained preliminary viscoelasticity data of healthy rat RVs (at 0.1‐2 Hz). Our data showed strain‐rate dependent changes in the hysteresis loops (Fig. 2). The dissipated energy (loop area) as well as the stiffness (loop slope) of the RV tended to increase with increasing frequency. The RV tissue showed similar viscoelastic behavior in both directions at all frequencies.ConclusionOur data showed that this novel testing system enables biaxial viscoelastic measurement of myocardium under physiological conditions (0.1‐8Hz) across small and large animal species. The establishment of this system allows further exploration of RV tissues at higher frequencies (5‐8 Hz) and in diseased states, which will improve the understanding of cardiac biomechanics in HF progression.

Internal Jugular Vein Volume Pulsatility during Head‐Down Tilt and Lower Body Negative Pressure

The objective of this study was to investigate the impact of internal jugular vein (IJV) distension on blood volume pulsatility. We hypothesized that pulsatility would be enhanced during cephalad fluid shifts and attenuated during caudal fluid shifts. Thirteen young healthy participants (8/5 male/female) were assessed during supine rest (repeated); 3 and 6 degrees of head-down tilt (HDT); and -20, -30, -40 mmHg of lower body negative pressure (LBNP) after at least 5 minutes in each condition. The order of the HDT and LBNP protocols was randomized. Right-side IJV blood volume was estimated using widefield near-infrared spectroscopy and quantified as jugular venous optical attenuation (JVA). Central venous pressure (CVP) was measured using a transducer attached to a catheter inserted into an antecubital vein in the right arm and corrected to the level of the heart. Participants were rightward tilted throughout to facilitate venous pressure measurements. Continuous signals were acquired for 30s in each condition and time-synced at 60Hz. Volume and pressure pulsatility were calculated as the differences between peak and nadir points along the cardiac cycle in JVA and CVP, respectively. Pressure-volume loops were created after ensemble averaging waveforms normalized to the cardiac cycle. Area of the pressure-volume loops and slope of the pressure-volume relationship during atrial filling (i.e., venous drainage) were assessed. Group mean JVA and CVP were highest during 6° HDT and lowest during -40 mmHg LBNP (see figure). Compared to baseline, JVA pulsatility was attenuated during -30 mmHg LBNP (P=0.048) and -40 mmHg LBNP (P=0.004) and was unchanged during each level of HDT (P>0.9). In contrast, CVP pulsatility was attenuated compared to baseline during -20, -30, and -40 mmHg LBNP (P<0.001) and was unchanged during each level of HDT (P>0.68). Area (P=0.088) and slope (P=0.269) of the pressure-volume loop were unchanged across all conditions. In multiple regression analysis, loop area was associated directly with pressure amplitude (P<0.001) but not volume amplitude (P=0.130); model r2=0.69. These data suggest that, while volume pulsatility did decrease when venous distension was reduced by higher levels of LBNP, this was primarily a function of changes in pressure pulsatilty. IJV compliance appeared to be unchanged across a wide range of venous distension. This work has relevance to states where venous pressure and distension are altered, including heart failure and hemorrhagic shock.

Novel self-anchored CFRP cable system: Concept and anchorage behavior

CFRP cables are promising to be utilized in bridge engineering, but their effective anchorage remains a challenge for engineers. To solve this problem, novel self-anchored CFRP cables with different anchorage configurations were designed and tested, with main variables including the radius, thickness, and slope of the CFRP loop at the anchorages. The results indicate that the mechanical behavior of the self-anchored cables is mainly determined by the thickness and radius of the CFRP loop and by increasing these characteristics, the cable’s material strength can be fully exploited. With optimized anchorage configurations, the anchor efficiency of the proposed self-anchor CFRP cable system can reach 95% or larger. Additionally, finite element analysis was conducted, with good agreement between the numerical and experimental results. Finally, the influence of the radius and thickness of the CFRP loop on the anchoring capacity and the nominal anchor efficiency was further discussed based on an orthotropic thick-walled cylinder model.

Determining mechanical properties of a pressure fire hose the type of «T»

Experimental research into determining the mechanical properties (elastic and dissipative) of the pressure fire hose of type «T» with an inner diameter of 66 mm under conditions of static load were presented. The experiment was conducted on the experimental setup, which makes it possible to measure force and deformation. In the course of research, a series of field experiments in stretching with the sample under conditions of static loading-unloading cycles was carried out. The tests consisted of 5 cycles (modes) of loading-unloading, which were performed with a two-minute interval. Taking into consideration the experimental data, the elasticity module at stretching the material of the hose in the longitudinal (along the base) direction was determined. It was established that numerical results of mechanical properties depend on the hose loading «history», that is, in the first two load modes, elasticity modules increased and were stabilized only in the subsequent modes. The above, along with a significant reduction in residual deformations, increases the elastic properties of the fire hose material.The results of the conducted studies showed that in the first two cycles, the material demonstrates short-term creep, which gets stabilized in modes 4–5. To generalize the experimental research, the results were approximated by corresponding trend lines. The curves of the sample deformation, which under conditions of cyclic loading-unloading formed the hysteresis loops, were determined. The hysteresis loops obtained during the study showed that in the first two modes, the loop are subjected to quantitative and qualitative changes, specifically, the slope of the hysteresis loop and its area decreases.It was determined that a change of the properties of the material of the fire hose at consecutive loading-unloading deformation cycles are reversed, the gaps between the deformation cycles result in partial restoration of the mechanical characteristics, approximating them to the initial values. Relaxation time is from several hours to several days and even weeks, which depends heavily on the magnitude of the previous relative deformation

Characteristics of Magnetization Reversal of Magnetostatically Coupled Microwire-Based System

The magnetization reversal process of a system consisted of one Co67Fe3.9Ni1.5B12.5Si14.5Mo0.6 and one Fe74B13Si11C2 microwires was studied. The change of the magnetic characteristics of a system (slope and shape of the hysteresis loop, coercive force) under effect of the neighbor and the length of the system (in the range of 3–20 mm) was considered and analyzed in terms of effective demagnetizing field influence.

Magnetic Loss Versus Frequency in Non-Oriented Steel Sheets and Its Prediction: Minor Loops, PWM, and the Limits of the Analytical Approach

The pulsewidth modulation (PWM) technique is commonly used to supply modern high-speed electrical machines. The fundamental frequency is typically in the kilohertz range, with switching frequencies of several tens of kilohertz, as determined by the new SiC- or GaAs-based power transistors modules. Switching introduces minor loops in the major hysteresis cycle, with durations of the order of $100~\mu \text{s}$ or lower, with the resulting magnetization dynamics influenced by strong skin effect. However, since these minor loops have relatively small amplitude, their constitutive equation may be described by an equivalent permeability (real or complex), depending on the mean slope of the minor loop and its static energy loss. By retrieving this permeability, the classical loss is straightforwardly calculated by analytical solution of Maxwell's equations. In this paper, we measure and calculate, according to the quasi-linear approximation for the minor loops, the magnetic energy losses of 0.194 mm thick non-oriented Fe–Si 3.2% sheets subjected to PWM induction waveform. Minor loop peak amplitudes ranging between 50 mT and 0.2 T and frequencies up to 10 kHz are investigated. The results are consistent with the proposed model, to within 5%.

Fatigue and reliability analysis of nano-modified scarf adhesive joints in carbon fiber composites

Abstract Enhancing the fatigue performance of scarf adhesive joints (SAJs) in carbon fiber-reinforced epoxy (CFRE) composite structures via incorporation of nanofillers into the epoxy adhesive has not yet been fully investigated and is the subject of this study. The optimum weight percentages of multi-walled carbon nanotubes (MWCNTs), SiC and Al2O3 nanofillers were ultrasonically dispersed in Epocast 50-A1/946 epoxy. The nanophased matrices were used to fabricate the SAJs with 5° scarf angle. Fatigue tests were conducted at constant-load amplitude, frequency of 10 Hz and stress ratio of 0.1. Result from fatigue tests showed that the gain/loss in the fatigue lives of the modified SAJs with MWCNTs, SiC and Al2O3 are respectively 19%, 52% and −22% at fatigue limit of 36 MPa. The load-displacement hysteresis loops of the nano-modified SAJs showed higher fatigue stiffness compared to neat epoxy-SAJ. The stiffness of the SAJs was increased with increasing number of cycles up to about N/Nf = 0.01. As the number of cycles increases the damage level is increased and thus the slope of the hysteresis loop (stiffness) is decreased and the hysteresis loop area becomes wider. The highest penalty paid to gain safe lives was observed for Al2O3-SAJs, which has highest scatter in the fatigue lives.

Role of Intergrain and Intragrain Coupling on Switching Field of Granular Exchange Coupled Composite Media Using Microwave Assisted Magnetic Recording

Microwave assisted magnetic recording is one interesting magnetic recording technology to improve writability for high areal density of hard disk drive. In this work, the role of intergrain and intragrain coupling and microwave field is investigated by micromagnetic simulation based on the Landau - Lifshitz - Gilbert equation. The results show that the switching field, Hsw, of media with microwave field, Hac, of 10 GHz is lower than that for media without Hac. The exchange coupling between nearest neighbor grains hardly affects the Hsw of media and slightly affects the slope of hysteresis loop. In addition, the slope of hysteresis loops and Hsw decrease with increasing exchange coupling in each grain. The results from this work can lead to obtain the improvement writability and increasing areal density of hard disk drive.

Assessment of respiratory system compliance with electrical impedance tomography using a positive end-expiratory pressure wave maneuver during pressure support ventilation: a pilot clinical study.

IntroductionAssessment of respiratory system compliance (Crs) can be used for individual optimization of positive end-expiratory pressure (PEEP). However, in patients with spontaneous breathing activity, the conventional methods for Crs measurement are inaccurate because of the variable muscular pressure of the patient. We hypothesized that a PEEP wave maneuver, analyzed with electrical impedance tomography (EIT), might be suitable for global and regional assessment of Crs during assisted spontaneous breathing.MethodsAfter approval of the local ethics committee, we performed a pilot clinical study in 18 mechanically ventilated patients (61 ± 16 years (mean ± standard deviation)) who were suitable for weaning with pressure support ventilation (PSV). For the PEEP wave, PEEP was elevated by 1 cmH2O after every fifth breath during PSV. This was repeated five times, until a total PEEP increase of 5 cmH2O was reached. Subsequently, PEEP was reduced in steps of 1 cmH2O in the same manner until the original PEEP level was reached. Crs was calculated using EIT from the global, ventral and dorsal lung regions of interest. For reference measurements, all patients were also examined during controlled mechanical ventilation (CMV) with a low-flow pressure-volume maneuver. Global and regional Crs(low-flow) was calculated as the slope of the pressure-volume loop between the pressure that corresponded to the selected PEEP and PEEP +5 cmH2O. For additional reference, Crs during CMV (Crs(CMV)) was calculated as expired tidal volume divided by the difference between airway plateau pressure and PEEP.ResultsRespiratory system compliance calculated from the PEEP wave (Crs(PEEP wave)) correlated closely with both reference measurements (r = 0.79 for Crs(low-flow) and r = 0.71 for Crs(CMV)). No significant difference was observed between the mean Crs(PEEP wave) and the mean Crs(low-flow). However, a significant bias of +17.1 ml/cmH2O was observed between Crs(PEEP wave) and Crs(CMV).ConclusionAnalyzing a PEEP wave maneuver with EIT allows calculation of global and regional Crs during assisted spontaneous breathing. In mechanically ventilated patients with spontaneous breathing activity, this method might be used for assessment of the global and regional mechanical properties of the respiratory system.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-014-0679-6) contains supplementary material, which is available to authorized users.

Fabrication and Characterization of (100),(001)-Oriented Reduction-Resistant Lead-Free Piezoelectric (Ba,Ca)TiO3 Ceramics Using Platelike Seed Crystals

The preparation of reduction-resistant (Ba,Ca)TiO3 ceramics as lead-free piezoelectric materials was studied. To improve their electrical properties, (100),(001)-oriented (Ba0.85Ca0.15)TiO3 ceramics were fabricated by the reactive templated grain growth method using a mixture of platelike CaTiO3 and BaTiO3 particles. The platelike CaTiO3 and BaTiO3 particles were prepared through a topochemical microcrystal conversion process using CaBi4Ti4O15 and BaBi4Ti4O15 plate-like precursor crystals. The 100 orientation degree of the grain-oriented (Ba0.85Ca0.15)TiO3 ceramics was 92%, as estimated by Lotgering's equation. In addition, 1 mol % Ba excess and 1 mol % Mn-doped (Ba0.85Ca0.15)TiO3 sintered bodies, which were sintered at 1350 °C in an Ar flow containing H2 (0.3%), had sufficient resistivity to allow the characterization of electrical properties. The ferroelectric and field-induced strain properties of the (Ba0.85Ca0.15)TiO3 ceramics, sintered in the reducing atmosphere, were markedly improved as a result of fabricating grain-oriented samples. The field-induced strain coefficient (estimated from the slope of the unipolar strain loop) of the nonreducible (100),(001)-oriented (Ba0.85Ca0.15)TiO3 ceramics reached 570 pm/V, which was higher than that of polycrystals (260 pm/V) with no preferential orientation.

The Role of Magnetoelastic Field Related to Underlayers on Magnetic Properties of FeCo Thin Films

In this work, the influence of the magnetoelastic field on the magnetic properties of FeCo thin film is analyzed by the micromagnetic model. Formula of magnetoelastic energy related to the stress between the FeCo and the underlayer are derived to analysis the role of stress on soft magnetic properties. The cubic anisotropy determines the symmetry of the loops. For the magnetoelastic field, the main term Hma has significant influence on the easy-axis coercivity and the cross term Hmb affects the slope of the hard-axis loop. Good in-plane anisotropy of FeCo thin film, which can be obtained by using certain underlayers (such as Cu, NiFe, CoFe), is corresponding to low value of Hma and Hmb. The magnetization 4πMs at amorphous grain boundary has great effect on the properties of FeCo film.

Terahertz transmission characteristics across the phase transition in VO2 films deposited on Si, sapphire, and SiO2 substrates

Vanadium dioxide (VO2) films were deposited on high-purity Si, sapphire, and SiO2 substrates by an organic sol-gel method. The effect of the substrate on the structure, morphology, and phase transition properties of the VO2 films was demonstrated. We proposed that the film-substrate interaction induced the differences in the fraction of the +4 valence state vanadium oxide phase, surface morphology, and grain size for the VO2 films. The VO2 film on the Si substrate exhibited a switching property of about 2 orders of change in electrical resistivity. By contrast, the VO2 films on the sapphire and SiO2 substrates exhibited a switching property of about 3 orders of change in resistivity. The THz transmission across the phase transition in the VO2 films was quite different in the transmission modulation ratio, the width, and the slope of the hysteresis loop. In particular, the VO2 films on the sapphire and SiO2 substrates have the same reduction in THz transmission by about 46% comparing with about 35% in the VO2 film on the Si substrate. Furthermore, the VO2 film on the SiO2 substrate exhibits the widest hysteresis loop with the steepest slope.

Aortic stiffness in vivo in hypertensive rat via echo-tracking: analysis of the pulsatile distension waveform

Large-artery stiffening is a major risk factor in aging and hypertension. Elevated blood pressure (BP) and vascular wall properties participate in arterial stiffening; we aimed to evaluate their respective role by combining echo-tracking and the spontaneously hypertensive rats (SHR) treated with low doses of a nitric oxide synthase inhibitor, shown to have arterial stiffening. Normotensive [Wistar-Kyoto (WKY)], SHR, and SHR treated for 2 wk with N(G)-nitro-L-arginine methyl ester (SHRLN) were anesthetized; BP and distension (pulsatile displacement) of the aortic walls with the ArtLab echo-tracking device were measured. Stiffness index increased in SHRLN vs. SHR; compliance, distensibility, and the slopes and area of the distension-pressure loop curve decreased. The pulsatile distension and pressure waveforms were strongly altered in SHRLN. Maximal values were decreased and increased, respectively, and the waveform kinetics also differed. Thus the area under the curve adjusted to heart rate (AUC/ms) was calculated. Acute BP reductions were induced by diltiazem in SHR and SHRLN, to levels similar to those of WKY. In SHR, compliance, distensibility, stiffness index, and the ascending slope of the distension-pressure loop reached the values of WKY, whereas they were only partially improved in SHRLN. Aortic distension (maximal value and AUC/ms) and the area of the distension-pressure loop were improved in SHR, but not in SHRLN. These data confirm the aortic stiffening induced by nitric oxide reduction in SHR. They show that the ArtLab system analyzes aortic stiffness in rats, and that the aortic pulsatile distension waveform is a parameter strongly dependent on the vascular wall properties.

Growth and properties of highly oriented lead-free Mn-doped NaNbO3–BaTiO3 piezoelectric thin films prepared by chemical solution deposition

Highly oriented lead-free piezoelectric NaNbO3–BaTiO3 (NN–BT) thin films have been fabricated by a chemical solution deposition method. Alkoxy-derived 1.0 and 3.0mol% Mn-doped 0.95NaNbO3–0.05BaTiO3 thin films directly crystallized into a perovskite phase with a (100) preferred orientation on Pt(100)/MgO(100) substrates at 650°C. The three-dimensional relationship between NN–BT(100) and Pt(100)/MgO(100) is confirmed by the fourfold symmetry of the pole figure. The fourfold symmetry indicates that synthesized films are oriented in both the c and a, b directions on the Pt(100) surface. The (100)-oriented Mn-doped 0.95NaNbO3–0.05BaTiO3 thin films showed typical ferroelectric polarization (P)–electric field (E) hysteresis and field-induced displacement curves at room temperature. The remanent polarization and coercive field values of the oriented 1.0 and 3.0mol% Mn-doped 0.95NaNbO3–0.05BaTiO3 films were 10.4, 11.6μC/cm2 and 62, 54kV/cm, respectively. Furthermore, from the slope of the field-induced butterfly loop characterized using a scanning probe microscopy, the effective piezoelectric coefficient (AFM-d33) of the films was found to be approximately 35–50pm/V.