Shape reconstruction methods with incomplete data

We investigated the effect of changing arterial input impedance over three selected frequency ranges on stroke volume (SV) in nine isolated canine left ventricles. The input impedance was simulated with a three-element Windkessel model (i.e., resistance, characteristic impedance, and compliance) and was imposed on the ventricles with a servo-controlled loading system. Under a constant end-diastolic volume [33.1 +/- 1.5 (SE) ml], we changed the modulus of the afterloaded impedance over a low frequency range (below 0.13 Hz) by changing the resistance, over a transitional frequency range (in which the impedance modulus decreases from total resistance to characteristic impedance) by changing the compliance, and over a high frequency range (above 2.0 Hz) by changing the characteristic impedance. Each of the impedance components was changed from control to 50 and 200% of control. SV sensitively decreased from 16.1 +/- 0.7 to 7.4 +/- 0.5 ml in response to the increase in the low-frequency impedance modulus. SV was relatively insensitive, however, to the same percent increase in the impedance modulus over the transitional frequency range (from 11.2 +/- 0.6 to 12.3 +/- 0.7 ml) and over the high frequency range (from 11.9 +/- 0.6 to 11.6 +/- 0.7 ml). The average relative sensitivities of SV to the increase and decrease in impedance moduli in these frequency ranges were 1.2:0.12:0.04. We conclude that the modulus of impedance in the low frequency range is, by far, a more important determinant of SV than those in the transitional and high frequency ranges.

Understanding electrical properties of polymer nanocomposites is of great significance in order to diagnose and analyze physical and chemical behaviors of the composites as well as their own dielectric properties and can provide valuable data for improving the characteristics of the nanocomposites. In this work, the solution compounding method was used to prepare the polyethylene (PE)/aluminum (Al) nanocomposites. The dielectric permittivity and loss tangent of the PE/Al nanocomposites with different nanofiller loadings were investigated in the broad frequency range from 0.1 Hz to 10 MHz and the direct current (dc) conductivity and the dielectric breakdown strength of the PE/Al nanocomposites were also studied. The research results have shown that the dielectric permittivity shows different behaviors in the low and high frequency range. The permittivity values of the nanocomposites with the nanofiller loading levels of 0−48 wt % are found to show no percolative characteristics in the low frequency range below a few kilohertz whereas they tend to increase with the nanofiller loading increasing up to 24 wt % and show the percolative threshold. dc conductivity and dielectric breakdown strength of the nanocomposite are also observed to have percolation threshold characteristics, but the percolation phenomenon is observed to be rather early in the dielectric breakdown strength measurement than that found in the dielectric permittivity and dc conductivity tests because of the difference of the applied voltage level.

Heart rate variability (HRV) and baroreceptor sensitivity (BRS) quantify autonomic variability in heart pacing and the autonomic response to blood pressure changes respectively. By necessity, the signals used to calculate HRV and BRS (systolic blood pressure (SBP) and RR interval) have one data point every cardiac cycle. Due to inherent variability in heart rate, these are non-uniformly sampled data. A number of calculation methods exist that adjust for non-uniform sampled signals. This study compared frequency domain methods of HRV and BRS calculation to ascertain whether more complex methods resulted in different results to simpler methods. Wistar rats (n=10), and rats with induced diabetes (n=8) were anesthetized and SBP and RR interval measured for a period of approximately 5 minutes. This data were analyzed using the sequence technique (for BRS), fast Fourier transform (FFT), non-uniform discrete Fourier transform (NDFT) and an extended Lomb-Scargle Periodogram (LSP). There were small but significant differences in NDFT from LSP technique for both BRS in the low frequency range (p=0.005) and HRV in the high frequency range (p=0.001). The NDFT technique was also significantly different to FFT technique for BRS in the low frequency range (p=0.023). All other methods were not statistically different. However, all techniques showed the same results comparing diabetic to control rats. This study shows more complex methods that correct for the non-uniformity of the sampling have significant differences but those differences are small to the point of not altering findings associated with HRV or BRS.

This study aimed to investigate heart rate variability (HRV) characteristics of cold pattern with repeated measurement data. Participants were taken from a Daejeon University cohort study from 2015 to 2018. Forty-seven of the participants studied displayed cold pattern while 23 showed signs of non-cold pattern. HRV was measured in supine position for 5 minutes at each year, and an 8-item cold pattern questionnaire was used for the diagnosis of cold pattern. SDNN (standard deviation of the NN intervals) and RMSSD (the square root of the mean squared differences of successive NN intervals) were used as time domain analysis, and TP (total power), VLF (power in very low frequency range), LF (power in low frequency range), HF (power in high frequency range), LF norm (LF power in normalized units), HF norm (HF power in normalized units) and LF/HF were used as frequency domain analysis. In the Mann-Whitney U test, LF norm, HF norm, and LF/HF showed differences between the cold pattern group and non-cold pattern group at every measurement, and in the independent t-test, the differences were also observed at three points except for the baseline (2015). In the repeated measures ANOVA, the interaction effects were not observed in all HRV parameters, but the time period effects were observed in SDNN, RMSSD, TP, VLF, LF and HF. There were significant differences between those two groups in LF norm, HF norm and LF/HF. This study suggests that LF norm, HF norm and LF/HF might be a useful indicator of cold pattern properties.

Charge carrier relaxation in solid VO•• conductors

Dielectric relaxation processes in stoichiometric Ge:Sb:Te amorphous films

Electromagnetic properties of soil (electrical conductivity, dielectric permittivity, and magnetic susceptibility) depend on its physical and chemical properties that are of interest to applications such as precision agriculture or environmental monitoring. State-of-the-art electromagnetic induction (EMI) sensors operate in the lower frequency range well below 100 kHz in which they are most sensitive to the magnetic susceptibility of the soil, and to a lesser degree to its electrical conductivity. In addition to such EMI sensors, the ground-penetrating radar (GPR) is often employed for the dielectric permittivity mapping at the frequencies above several tens of megahertz. The EMI soil sensing in the higher frequency range from 1 MHz to 20 MHz can bridge the gap between the EMI sensors in the low frequency range and the GPR. In this frequency range, both electrical conductivity and dielectric permittivity of the soil affect the measurement. In this paper, we present a simple EMI sensor operating in the range between 1 MHz and 10 MHz with an estimated resolution of 15 mS/m. We evaluate the sensor sensitivity to the electrical conductivity and discuss the influences of the dielectric permittivity and liftoff. We compare the conductivity measurements with the presented analytical sensor model.

Attenuation properties of the lithosphere around the Koyna-Warna seismic zone is studied by estimating the coda-Q c from 30 local earthquakes of magnitude varying from 1.5 to 3.8. An average lapse time of 65 sec used in the single scattering model sampled a circular area with an average radius of 114 km. The estimated Q c values show a frequency-dependent relation, Q c = 169 f0.77, and range from 169 at I Hz to 1565 at 18 Hz. A comparison of worldwide Q studies reveals that for a large frequency range the Q for active regions is low as compared to that for stable regions. However, South Carolina and Norway are exceptions in that their Q is low in the low frequency range while New England and North Iberia are exceptions as they have a Q value similar to that for active regions like Spain, Turkey, Italy and Garhwal Himalaya (STIH), in the higher frequency range. In contrast to this, the Q for the Koyna-Warna area, which belongs to a stable region, is low in the entire frequency range as compared to the stable regions and similar to the active STIH regions.

The steady‐state vibration of a subway‐soil‐building system is determined using an appropriate finite element model. The vibration level in the podium block of the building is obtained for two different track support systems: direct fixation and a floating slab. A pair of unit harmonic loads is used to simulate the wheel loading from a single train. Because the subway consists of twin double boxes, different loading combinations are used to determine the maximum velocity response in the podium for the frequency range of interest. It is found that the vibration levels for the floating slab track system exceed those of the direct fixation track system in the low frequency range. However, in the high frequency range, the floating slab track system behaves as an effective vibration isolator.

Impedance and simulation studies of the cell electrode/hydrous antimonic acid/electrode

The effect of frequency at room temperature of the ac impedance, permittivity and electric modulus of pure Polypyrrole and KBr Polypyrrole powders with different ratios was investigated in the frequency range 0.1 Hz. to 106 Hz. The frequency dependence of the ac impedance is similar to that observed in RC network in parallel. The real component of ac impedance is frequency independent in low frequency range and becomes proportional to the inverse of frequency at high frequency range. The equivalent bulk resistance decreases with increasing the KBr content while the equivalent capacitance remains nearly unchanged. The relaxation transition in KBr dispersed Polypyrrole is assigned to a summation of relaxations occurring within the bulk.

We have demonstrated Ru(4+) induced colossal magnetoimpedance (MI) at room temperature in a ∼1 Tesla magnetic field with a pulsed laser deposited La0.7Ca0.3Mn0.7Ru0.3O3 thin film. This composition showed a large negative ∼12% MI in the low frequency range (<5 MHz), a colossal positive MI > 120% in the intermediate frequency range (5 MHz to ∼13 MHz) and a negative MI in the high frequency range (∼13 MHz to 40 MHz) at room temperature. XAS data confirmed the predominant Ru valence state was 4+ in La0.7Ca0.3Mn0.7Ru0.3O3. Ru(4+) induced (i) charge carrier localization and (ii) reduced hole carrier density enhances the MI in this composition, which otherwise was not significant in mixed valences Mn(3+)/Mn(4+) containing La0.7Ca0.3MnO3 and Ru(4+)/Ru(5+) and Mn(3+)/Mn(4+) mixed valences containing Ru = 0.1 and Ru = 0.2 compositions in La0.7Ca0.3Mn1-xRuxO3 (0 ≤x≤ 0.3) thin films.

Nano-clusters blind films of phenyl C61-butyric acid methyl ester (PCBM) and poly(3-hexylthiophene) (P3HT) were deposited on fluorine doped tin-oxide (FTO) substrate by spin coating and applied as counter electrodes instead of platinum for a new FTO/TiO2 + K30 dye-sensitized solar cell. The photovoltaic parameters of the fabricated solar cell; open circuit voltage, short circuit current, output power and fill factor, were studied under various light intensities in the range 20:110 mW cm−2. An impedance spectroscopy study was also performed in a wide frequency range (5 kHz–1 MHz) to study the electron transport properties of the solar cells. The capacitance–voltage of the prepared DSSC is characterized by two parts: positive values of capacitance at low frequency range, f ≤ 100 kHz and negative capacitance i.e., an inductive behavior, in higher frequency range f ≥ 300 kHz Conducting polymer electrode based on PCBM:P3HT/FTO can be used as a counter electrode in a DSSC.

We experimentally demonstrate a broadband terahertz (THz) intensity modulator operating at low current and frequency range. The modulator consists of VO2 and meander–wire hybrid metamaterials. The measured 3-dB bandwidth for normal incidence is 0.5 THz, while the maximum modulation depth of 99% is achieved at 0.28 A. The physical mechanism of the device’s electrical tunability is attributed to an ohmic-heating-induced transition. An equivalent circuit model is proposed for the upper cut-off frequency. This scheme paves the way for a full electric control of the intensity of a THz wave at a broad band, low current, and low frequency range.

Experimental investigations on the wall pressure measurement on the blade of axial flow fans