Determination of right ventricular dysfunction using the speckle tracking echocardiography method in patients with obstructive sleep apnea

Background: The speckle tracking echocardiography (STE) method shows the presence of right ventricular (RV) dysfunction before the advent of RV failure and pulmonary hypertension in patients with cardiopulmonary disease. We aimed to assess subclinical RV dysfunction in obstructive sleep apnea (OSA) using the STE method. Method: Twenty-one healthy individuals and 58 OSA patients were included. According to severity as determined by the apnea&#8211;hypopnea index (AHI), OSA patients were examined in three groups: mild, moderate and severe. RV free wall was used in STE examination. Results: Right ventricle strain (ST %) and systolic strain rate (STR-S 1/s) were decreasing along with the disease severity (ST &#8212; healthy: &#8211;34.05 &#177; &#8211;4.29; mild: &#8211;31.4 &#177; &#8211;5.37; moderate: &#8211;22.75 &#177; &#8211;4.89; severe: &#8211;20.89 &#177; &#8211;5.59; p < 0.003; STR-S &#8212; healthy: &#8211;2.93 &#177; &#8211;0.64; mild: &#8211;2.85 &#177; &#8211;0.73; moderate: &#8211;2.06 &#177; &#8211;0.43; severe: &#8211;1.43 &#177; &#8211;0.33; p < 0.03). Correlated with the disease severity, the RV early diastolic strain rate (STR-E) was decreasing and the late diastolic strain rate was increasing (STR-E &#8212; healthy: 2.38 &#177; 0.63; mild: 2.32 &#177; 0.84; moderate: 1.66 &#177; 0.55; severe: 1 &#177; 0.54; p < 0.003; STR-A &#8212; healthy: 2.25 &#177; 0.33; mild: 2.32 &#177; 0.54; moderate: 2.79 &#177; 0.66; severe: 3.29 &#177; 0.54; p < 0.03). The STR-E/A ratio was found to be in a decreasing trend along with the disease severity (healthy: 1.08 &#177; 0.34; mild: 1.06 &#177; 0.46; moderate: 0.62 &#177; 0.22; severe: 0.34 &#177; 0.23; p < 0.03). Conclusions: Subclinical RV dysfunction can be established in OSA patients even in the absence of pulmonary hypertension and pathologies which could have adverse effects on RV functions. In addition to the methods of conventional, Doppler and tissue Doppler echocardiography, using the STE method can determine RV dysfunction in the subclinical phase. (Cardiol J 2012; 19, 2: 130&#8211;139

A phenomenological approach to anomalous transport in complex or disordered media

We aim to derive a phenomenological approach to link the theories of anomalous transport governed by fractional calculus and stochastic theory with the conductivity behavior governed by the semi-empirical conductivity formalism involving Debye, Cole-Cole, Cole-Davidson, and Havriliak-Negami type conductivity equations. We want to determine the anomalous transport processes in the amorphous semiconductors and insulators by developing a theoretical approach over some mathematical instruments and methods. In this paper, we obtain an analytical expression for the average behavior of conductivity in complex or disordered media via using the fractional-stochastic differential equation, the Fourier-Laplace transform, some natural boundary-initial conditions, and familiar physical relations. We start with the stochastic equation of motion called the Langevin equation, develop its equivalent master equation called Klein-Kramers or Fokker-Planck equation, and consider the time-fractional generalization of the master equation. Once we derive the fractional master equation, then determine the expressions for the mean value of the variables or observables through some calculations and conditions. Finally, we use these expressions in the current density relation to obtain the average conductivity behavior.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Conduction and dielectric polarization in Se thin films

Se films were prepared by thermal evaporation technique in thickness range 150-8500 Angstrom. X-ray diffraction measurements showed that Se films are in the amorphous state. The ac conductivity and dielectric properties of the amorphous Se films have been investigated in the frequency range 100-100 KHz and 100-400 K temperature range. The ac conductivity sigma(ac)(omega) is found to be proportional to omega(s) where s < 1. The temperature dependence of both ac conductivity and the parameter s is reasonably well interpreted by the correlated barrier (CBH) model. The dc conductivity at the room temperature was also studied in the same thickness range. It was concluded that the same mechanism of carrier motion might be dominant in both ac polarization and dc conduction. This carrier transport mechanism might be electronic. (C) 2003 Elsevier Ltd. All rights reserved

Dielectric polarization in Sb2Te3 thin films

Dielectric properties of Sb2Te3 films prepared by thermal evaporation technique onto clean glass substrates using ohmic aluminum electrodes have been investigated in the frequency range of 0.01-100 kHz and within the temperature range of 293K-373 K. Both the dielectric constant epsilon(1) and dielectric loss factor were found to depend on frequency and temperature. The activation values were evaluated and good agreement between the activation energy values obtained from capacitance and dielectric loss factor measurements were obtained

Effect of thickness on the dielectric properties and glass transition of plasma poly(ethylene oxide) thin films

Plasma poly(ethylene oxide) thin films at different thicknesses of 20, 100, 250, 500 nm were deposited by plasma-assisted physical vapor deposition on glass substrates between aluminum electrodes in capacitor form at 5 W plasma discharge power. The structural analyses were performed by Fourier transform in7frared spectroscopy. The dielectric properties such as dielectric constant kappa' and electric modulus M '' were defined by dielectric spectroscopy measurements. Dielectric spectroscopy measurements were performed in the angular frequency range of 10(-1)-10(6) rad/s and temperature range of 353-173 K range. The measurement results showed that alpha, beta, and gamma-relaxations, which are the expected relaxations in polymeric structures, are effective on total polarization in the investigated frequency and temperature range. Dielectric constant exhibits an increase till 500 nm, then reaches a saturation behavior. When resonance angular frequencies belonging to alpha-relaxation were fitted by Vogel-Fulcher-Tamman equation. It was observed that glass transition temperatures increase with decreasing thickness. These results support the influence of the dead layer to total polarization and the dynamics of the structure. Besides, it was shown that dielectric spectroscopy is a useful way to analyze the glass transition temperature in thin film form

Anisotropic and dielectric properties of TlSbSe2 chalcogenide compounds

A comprehensive analysis of the electrical conductivity of TlSbSe2 layered compounds prepared using the Bridgman-Stockbarger technique is presented. The temperature dependence of the electrical conductivity of TlSbSe2 and its anisotropy (as measured parallel and perpendicular to the layers) was studied for temperatures between 233 and 353 K. We show that the anisotropy of the electrical conductivity is temperature dependent. The ratio alpha of the conductivities parallel and perpendicular to the layers obeys an exponential law, with a barrier height of about 37 meV. The dielectric constant and dielectric loss of TlSbSe2 were determined using ohmic Au electrodes in the frequency range 10 Hz-100 kHz and within the temperature interval 233-373 K. The dielectric constant and the dielectric loss are found to decrease with increasing frequency and increase with increasing temperature. These behaviors are due to the polarization mechanisms in the samples. Lastly the activation energy values were derived from dielectric measurements

Thickness dependence of optical properties of amorphous indium oxide thin films deposited by reactive evaporation

The electrical conductivity and absorption coefficient of amorphous indium oxide thin films, thermally evaporated on glass substrates at room temperature, were evaluated. For direct transitions the variation of the optical band gap with thickness was determined and this variation was supposed to appear due to the variation of localized gap states, whereas the variation of conductivity with thickness was supposed to be due to the variation of carrier concentration. We attribute the variation of absorption coefficient with thickness to the variation of optical band gap energy rather than optical interference. (c) 2006 WILEYNCH Verlag GmbH & Co. KGaA, Weinheim

Structural and dielectrical characterization of low-k polyurethane composite films with silica aerogel

In this study, a hydrophobic silica aerogel was synthesized via one-step surface modification and polymer composite films based on a polyurethane (PU) matrix were prepared by doping with silica aerogel powder (at 2%, 3%, 5%, and 7% by weight = w/w%). The structural, thermal, morphological, and surface properties of the silica aerogel and PU composite films containing aerogel were investigated by Fourier transform infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry (DSC), scanning electron microscopy, and tensiometry. The dielectric properties of the silica aerogel and PU composite films containing the aerogel were determined over a temperature range of 293-423 K and a frequency range of 1-10(6) Hz. The contact angle of the silica aerogel was 10(6). Moreover, the PU composite film with 7% aerogel had the highest contact angle (theta = 105 degrees) among the composite samples, which was similar to contact angle of the silica aerogel. The dielectric constants and dielectric losses decreased with the frequency for all of the samples, whereas they increased with the temperature. The polarization regions and relaxation times were determined for all of the samples using the Cole Cole equation. The glass-transition temperatures (T-g) were determined for the silica aerogel and PU composite films containing aerogel by dielectric spectroscopy and compared with the DSC results. The dielectric constants were lower for the PU composite films than the PU film. The dielectric constant for the PU composite film doped with 2% silica aerogel was 2.9 at 10 MHz. Thus, the PU composite with a low dielectric constant and dielectric loss factor (tan delta) could be regarded as a potential dielectric constant candidate, with possible applications as a dielectric material in the microelectronics industry

Plasma discharge power dependent AC conductivity of plasma poly(ethylene oxide) thin films

Plasma polymerized poly(ethylene oxide) thin film samples with thickness of 500 nm were deposited using plasma assisted physical vapour deposition at radio-frequency plasma discharge powers of 0, 2, 5 and 30 W, respectively. For comparison, a conventional poly(ethylene oxide) precursor was also investigated. In order to investigate the effect of the plasma discharge power on the cross-linking density of the plasma poly(ethylene oxide) and poly(ethylene oxide) precursors, structural characterization using differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy was performed. Structural analysis showed that the density of cross-linking increased upon increasing the plasma discharge power. This increase was observed as an increase in the dynamic glass transition temperature during the DSC measurements. In addition to these characterizations, the dielectric response of the thin film plasma poly(ethylene oxide) samples and poly(ethylene oxide) precursors were measured. The dielectric spectroscopy results showed that changes in the cross-linking density changed the alternative current (AC) conductivity. The measured glass transition temperatures obtained using DSC are in accordance with the glass transition temperatures obtained from the temperature-dependent AC conductivity results. It was observed that the temperature-dependent AC conductivity exhibits Arrhenius behaviour. The activation energies obtained for the plasma polymer samples showed an increase from 0.38 eV to 0.5 eV upon increasing the plasma discharge power. The plasma discharge power dependent activation energy results also indicate the fragmentation of long polymer chains into more smaller oligomers and radicals occurred upon increasing the plasma power