Type Relaxation Research Articles

The Inhibitory Effect of Trimethylamine (TMA), an Intestinal Bacterial Metabolite, on Endothelial Vasorelaxation in Rat Mesenteric Artery

The effect of the gut microbiota metabolite trimethylamine-(TMA) in isolated vessels is unknown yet. Previously TMAO, the hepatic oxidation product of TMA, at 3 mM has been shown to inhibit endothelium-dependent vasorelaxations of isolated arteries only after 24-hour-interactions. In this study, the effects of TMA (at 1 mM) on endothelium-dependent relaxations with acute (1 or 4 hours) and longer (24 hours) incubation periods were evaluated in superior mesenteric arteries of rat. Acute exposure to TMA of 1 hour significantly inhibited acetylcholine-stimulated endothelium-derived hyperpolarizing (EDH) type relaxations, and this inhibition gradually intensified as the incubation period was prolonged to 4, and 24 hours. The area under the curves (AUCs) of the relaxation-response curves after 1 and 24 hours of TMA incubation were found significantly different compared to each other, whereas similar AUC values were obtained after 4, and 24 hours of incubations. Contractile responses to phenylephrine, and nitric oxide (NO)-mediated relaxations of acetylcholine were similar in arteries before and after pretreatment with TMA for 24 hours. These data indicate that TMA selectively inhibits EDH-type relaxations in rat isolated mesenteric arteries. Although the inhibitory effect of TMA intensifies over time, it appears to be more pronounced during acute incubation periods. The findings strengthen the evidence that TMA is a more toxic metabolite on vascular tone than TMAO.

AC conductivity and dielectric relaxation behavior of lamellar benzyltrimethylammonium/V2O5 nanocomposite

Lamellar benzyltrimethylammonium/V2O5 nanocomposite has been prepared hydrothermally. Electrical and dielectric properties as a function of temperature and frequency of the nanocomposite were reported. The decrease in Z′ with increasing temperatures indicates the existence of a negative temperature resistance coefficient (NTCR) characteristic of the semiconductor material. For T > 432 K, the values of the exponents decrease with increasing temperature indicating that the CBH model is the likely mechanism. When T < 432 K, the NSPT model is an adequate mechanism to characterize electrical conduction. Variation of log(σdc) versus 103/T reveals a rupture around 432 K and the average activation energy values are of the order of 0.240 and 0.085 eV. It has been found that the dielectric constant and the dielectric loss decrease when frequency increases which is explained by the hopping of electrons between V4+/V5+. Moreover, the presence of non-Debye type of relaxation was detected by the complex modulus analysis.

Sm and Mn doped enhancing the electrical properties of .68PMN–.32PT relaxor ferroelectric thin films

Abstract(1−x)Pb(Mg1/3Nb2/3)O3–xPbTiO3 (PMN–PT) has attracted attention due to its excellent electrical properties as a typical relaxor ferroelectric material. High‐quality Mn–Sm co‐doped 0.68PMN–0.32PT thin films were synthesized on the Pt/Ti/SiO2/Si substrates by sol–gel based on spin coating method. The results show that 1 mol% Mn–2 mol% Sm co‐doped PMN–PT thin films have high dielectric constant (εr ∼ 1895) and relatively low dielectric loss (tanδ ∼ .039) at 1 kHz. They also show superior ferroelectric polarization (Pmax ∼ 53.71 μC/cm2, Pr ∼ 30.85 μC/cm2) and high dielectric breakdown strength (∼1656.6 kV/cm), which are primarily due to the low leakage current density (∼10−7 A/cm2). This work suggests a practical approach to enhance the dielectricity, piezoelectricity, and ferroelectricity of PMN–PT thin films.

Electrical characterization of Sn modified barium bismuth zirconate

BaBi4Sn4O15, a Sn-modified ceramic sample of layered ferroelectric oxide family, is developed using a high-temperature mixed oxide route after firing for calcination at 810 °C for 6 h in steps of 50 °C starting from 600 °C. An introductory XRD study of the compound displays the development of the new orthorhombic structured single-phase compound at atmospheric conditions. The electrical behaviors of the compound are investigated in a wide temperature span (30–500 °C) and frequencies ranging from 0.1 kHz to 1 MHz using an impedance analyzer. Dielectric behavior informs that the compound has a phase transition from Ferro to Paraelectric at 370 °C, which is well above room temperature. The impact of temperature and frequency on complex immittance parameters (impedance and modulus) is analyzed using an LCR meter in a broad temperature & frequency span. The electrical properties confirm; (a) the existence of semiconductor-like NTCR (negative temperature coefficients of resistance) behavior, (b) the evidence of the electric relaxation process as a function of temperature, (c) the existence of electric relaxation ascribed to the simultaneous contribution of bulk & bulk interfaces to the electrical behavior, and (d) presence of the non-Debye type relaxation phenomena. The frequency-dependent conductivity follows Jonscher’s universal power law.

Green polymer electrolyte and activated charcoal-based supercapacitor for energy harvesting application: Electrochemical characteristics

Abstract The aim of this study is to address the growing concern about microplastics in the ocean and their potential harm to human health through ingestion. The MPs issue is largely a result of the increasing demand for electronic devices and their components. To tackle this challenge, the research aimed to develop a green polymer electrolyte that used glycerol as a plasticizing agent to improve ionic conductivity. The polymer host included chitosan and polyvinyl alcohol and was composed of sodium acetate. To evaluate the performance of the polymer electrolyte, various analytical techniques were used, including impedance and electrochemical studies. The ionic conductivity of 7.56 × 10−5 S·cm−1 was recorded. The dielectric property study confirmed the ionic conduction process in the system and revealed the existence of non-Debye type relaxation, as indicated by asymmetric peaks of tanδ spectra. The alternating conductivity exhibits three distinguished regions. The polymer electrolyte was discovered to be electrochemically stable up to 2.33 V and capable of storing energy as a non-Faradaic electrochemical double-layer capacitor (EDLC). The cyclic voltammetry pattern is a leaf like shape. The EDLC was able to be charged and discharged up to 1 V, and it showed cyclability and could be used in low-voltage applications.

Effect of Frequency and Temperature on Dielectric and Transport Properties of CaO stabilized ZrO2@mullite composites

AbstractThis study concerns the synthesis and structure related electrical property analysis of CaO doped ZrO2@mullite composites. Two synthesis techniques (solid state reaction route and thermal plasma sintering) are used which results the formation of a composite consisting of mixed phase of orthorhombic mullite, tetragonal and monoclinic zirconia. The lattice parameters, residual strains, average crystallite size and cell volume of these CaO‐doped ZrO2@mullite composites are obtained from XRD analysis. Stabilization of t‐ZrO2 phase at room temperature is confirmed. Porous microstructure observed in SEM images results in low dielectric constant value of these composites. At room temperature and selected frequency of 1MHz, the dielectric constant and loss factor of 4.7 and 3.826 × 10−2 is observed for conventional CaO stabilized ZrO2@mullite composite and that of 3.8 and 2.19 × 10−2 is reported for plasma sintered CaO stabilized ZrO2@mullite composite. The impedance spectroscopic analysis demonstrates the negative temperature coefficient of resistance (NTCR) behavior and non‐Debye type relaxation behavior of both the CaO stabilized ZrO2@mullite composites. A negligible effect of electrode polarization is realized in these composites. The electronic band gap of conventional and plasma sintered CaO stabilized ZrO2@mullite composites is found to be around 3eV.

Dynamics of one-dimensional maps and Gurtin–Maccamy's population model. Part I. Asymptotically constant solutions

UDC 517.9 Motivated by the recent work by Ma and Magal [Proc. Amer. Math. Soc. (2021); https://doi.org/10.1090/proc/15629] on the global stability property of the Gurtin–MacCamy's population model, we consider a family of scalar nonlinear convolution equations with unimodal nonlinearities. In particular, we relate the Ivanov and Sharkovsky analysis of singularly perturbed delay differential equations in [https://doi.org/10.1007/978-3-642-61243-5_5] with the asymptotic behavior of solutions of the Gurtin–MacCamy's system. According the classification proposed in [https://doi.org/10.1007/978-3-642-61243-5_5], we can distinguish three fundamental kinds of continuous solutions of our equations, namely, solutions of the asymptotically constant type, relaxation type and turbulent type. We present various conditions assuring that all solutions belong to the first of these three classes. In the setting of unimodal convolution equations, these conditions suggest a generalized version of the famous Wright's conjecture.

Study of Structural, Dielectric, and Electrical Properties of Gadolinium-Modified Bismuth Lanthanum Oxide

In this article, synthesis (solid-state reaction) and characterization (structure, microstructure, and electrical) of the gadolinium (Gd) modified bismuth lanthanum oxide (LaBi0.9Gd0.1O3, and LBGO) are reported. Rietveld refinement of the x-ray diffraction (XRD) data was done using MAUD software, which adopts an orthorhombic crystal symmetry. The average crystallite size in the prepared sample was calculated using Scherer’s relation. Scanning electron microscope (SEM) micrograph analysis reveals that grains are uniformly distributed over the sample’s surface through well-defined grain boundaries so that a dense sample is formed, which may be a possible reason for elevated dielectric properties. The study of energy dispersive analysis of the x-ray (EDX) spectrum confirms the presence of all constituent elements (Bi, La, Gd, and O) in the studied sample. The presence of Maxwell–Wagner type of dispersion is confirmed from the study of dielectric properties as a function of frequency. The analysis of the modulus study confirms the presence of a non-Debye type of relaxation. The negative temperature coefficient of resistance (NTCR) nature of the sample is confirmed by the impedance study. The study of ac conductivity suggests the presence of a thermally activated relaxation process in the studied sample. Again, analysis of the Nyquist plots confirms the semiconducting character and may be suitable for some energy storage devices applications.

Structural and electrical characteristics of manganese modified BaTiO3 ceramic

The material Ba(Ti0.5Mn0.5)O3 synthesized through the conventional solid-state reaction method has hexagonal structure free from any impurity phase. The complex dielectric dispersion, temperature and frequency-dependent dielectric, impedance, AC conductivity, and leakage behavior of the sample are studied. The impedance study of the material encloses non-Debye type relaxation, negative temperature coefficient of resistance nature and the grain and grain boundary effects. The ferroelectric to paraelectric phase transition occurs at T C ∼ 270 °C. The dielectric constant and loss-tangent values are found to be less as compared to that of the parent barium titanate sample. R g < R gb, that is, grain boundary has greater opposition than the grain region. The material follows correlated barrier hopping model. The carrier transport process through AC conductivity study obeys the Jonscher’s power law and the Arrhenius relation while varying with the frequency and temperature.

Effect of rare earth oxides on the energy storage performance of Sr0.7Bi0.2TiO3 ceramics

In this study, Sr0.7Bi0.2TiO3 (SBT) ceramics doped with Y2O3, Dy2O3 and Gd2O3 rare earth oxides were designed and prepared by the conventional solid-state reaction method. The results show that all ceramics exhibit typical relaxor ferroelectric behavior, and the breakdown strength (BDS) of SBT ceramics is improved. Among them, Sr0.7Bi0.15Y0.05TiO3 ceramics demonstrate excellent energy storage performance, with a high recoverable energy density (Wrec ) of 2.4 J/cm3 and an efficiency (η) of 88.1% under 290 kV/cm. Furthermore, Y2O3-doped SBT ceramics exhibit a rapid discharge speed of 0.05 µs and a high power density (PD ) of 144.1 MW/cm3 under 300 kV/cm in charge-discharge tests. These characteristics have significant potential in pulse power applications.

Investigation of frequency and temperature dependent impedance, modulus and conductivity properties of MgO@SiO2 core shell nanocomposites

In this paper, a detailed investigation of electrical and conductivity behavior of MgO@SiO2 core shell nanocomposites (MgO@SiO2 CSN) in the frequency range between 1 Hz and 1 MHz at selected temperatures was reported. The powder XRD analysis unveiled a face-centered cubic structure with Fm-3 m space group and the FTIR spectra identified Mg-O and Si-O-Si vibrational bands. The oxidation states of the elements were studied employing XPS technique. TEM analysis confirmed the core shell formation with average particle size of 113.3 ± 3.1 nm with the shell thickness measuring 7.4 ± 1.1 nm. The existence of the dielectric dispersion is ascribed to the Maxwell–Wagner interfacial polarization. The Nyquist plots indicate the presence of grain effects with negative temperature coefficient of resistance with non-Debye type of relaxation. The activation energy of 0.388 eV with a negative slope of 4.49, indicate that oxygen vacancies may have contributed to conduction mechanism.

Optical, vibrational and complex impedance studies of LiNaSrP2O7 ceramic

Due to high stability, safety and energy density properties, solid-state lithium-ion is expected to be used for the next-generation batteries. Recently, new solid electrolyte materials with high-ion conductivity have been widely explored. In this paper, a novel solid electrolyte LiNaSrP2O7 was successfully prepared by the conventional solid-state method and characterized by X-ray diffraction (XRD) analysis, electron microscopy and optical and impedance spectroscopy. XRD and Rietveld analysis show that the sample crystallizes in the orthorhombic structure with Pnma space group. The UV–Vis measurement, performed from 200 nm to 800 nm, show a direct optical band gap evaluated at 5.26 eV. Both impedance and modulus studies reveal the temperature-dependent non-Debye type relaxation conduction phenomenon. AC conductivity has been studied to understand the conduction mechanism. AC conductivity results show the role of quantum mechanical tunneling of charges in the conduction mechanism. Moreover, the electrical conductivity and modulus analysis findings revealed the activation energy obtained from suggests that the transport takes place through the ion hopping mechanism, dominated by the motion of the mixed Li+/Na+ ions in the structure of the investigated material.

Synthesis and investigation on the optical and complex impedance analysis in LiCrO2 prepared using solid-state reaction

Lithium-ion batteries (LIB) have been employed extensively as energy delivery and storage technologies in electronic devices, electric cars, and utility grids. In this paper, the LiCrO2 compound was successfully synthesized using the solid-state method. The X-ray powder diffraction (XRPD) data confirmed the formation of a single-phase with a rhombohedral structure (R3̅m space group). The surface morphology of the compound was studied by scanning electron microscopy (SEM), to find that the average size is around 3.5 µm. UV-Vis-NIR diffuse reflectance and impedance spectroscopy thoroughly investigated the optical and electrical properties. The optical band gap is approximately 2.2 ± 0.1 eV for direct transition, determined using the absorption spectrum. The latter proves a semiconductor characteristic of the studied sample. The Nyquist plots (-Z" vs. Z′) display the contribution of grains and grain boundaries in the electrical conductivity, confirming the existence of a non-Debye type relaxation. The studied compound displays enhanced capacitance behavior, semiconducting properties that follow the Arrhenius relation, and an increase in conductivity as a function of frequency for different voltage values in the range of 0.5–3 V. The best electrical response in terms of capacitance and conductivity was found for the voltage value of 3 V. This study will expand knowledge by shedding light on the electrical conductivity for this value. The hopping of charge carriers over the potential barrier and the tunneling of polarons created because of lattice deformation at high bias voltages combine to produce the electrical conduction in this ceramic.

Tunable electrical and impedance characteristics of Co–Zn doped M-type Sr Hexaferrites: Role of grain, grain boundaries, electrical transport mechanisms and software/circuit modeling

M-type hexaferrites SrCoxZnxFe12-2xO19 (x = 0.0, 0.2, 0.4, 0.6, 0.8, and 1.0) have been synthesized using the sol-gel method. The structural, dielectric, and electrical properties of Zn2+ and Co2+ substituted strontium ferrite have been carried out. The dielectric and electric properties of prepared hexaferrites have been examined over the frequency range of 100 Hz to 2 MHz. The formation of the hexagonal phase has been confirmed by the X-ray diffraction (XRD) analysis. The substitution of Co2+ and Zn2+ causes a reduction in crystallite size from 39.50 to 26.42 nm being the smallest in the case of x = 1.0. Scanning electron microscopy (SEM) indicates the formation of honeycomb-like grain structures in composition x = 1.0. The dielectric spectrum shows that the dielectric constant and loss tangent vary non-monotonically with the doping of Co–Zn content. A non-Debye type relaxation is shown by the electric modulus of the prepared compositions. There is a reduction in relaxation time with the increase in doping of Co–Zn. The impedance spectra indicate the effects of both grain and grain boundaries on the electrical properties. The impedance analysis has been presented with the modeling of electrical processes in the samples using an equivalent circuit model comprising of parallel RC circuit for grains and grain boundaries. The obtained simulated results are in agreement with the measured results.

Structural, dielectric, impedance, and electric modulus characteristics of Y2CaCuO5 high-k dielectric ceramics

With the increasing trends of integrated circuit densification, device miniaturization, and exponential growth of microelectronic components there is a huge responsibility on the part of material researchers to derive, design, and develop new materials. Materials that can overcome the existing limitations in the present compounds available in the market or can expedite the process of material fabrication are of great interest. This feat can be achieved by the fabrication of new materials, and analysis of various characterizations viz. (structural, dielectric, transport behavior, and impedance spectroscopy). With this perspective, in this communication, a high permittivity dielectric material belonging to the Y-Ba-Cu-O ternary systems where barium is replaced by calcium (Y2CaCuO5) is synthesized using solid-state reaction route. X-ray diffraction, scanning electron micrograph, and energy-dispersive X-ray spectroscopic study confirm the phase and microstructure of the sample. The observed higher value of the dielectric constant is understood from Koop’s phenomenological theory and internal barrier layer capacitance model. The dispersive behavior of conductivity is interpreted by Jonscher’s power law. Overlapping large polaron tunneling model for conduction is observed. Impedance spectroscopy analysis reveals non-Debye type of relaxation with variable time constants. According to Nyquist plots; up to 250 °C only grain effect (bulk) is dominantly present; however, at higher temperatures, the contribution from both grain and grain boundary is seen.

Effect of Substitution of Mn on Electrical Properties of Bismuth Ferrite

Bi(Fe0.5Mn0.5)O3 is an Mn substituted Bismuth ferrite ferroelectric synthesized following mixed oxide process method of solid-state reaction technique after calcined at 800 °C for 8 h. XRD study approves the development of an orthorhombic single-phase new crystal structure. Electrical characterization of the compound is done by an impedance analyzer. The dielectric and impedance study of the material is investigated in a wide span of frequency (102–106 Hz) and temperature (30–500 °C). The parent compound bismuth ferrite has a higher transition temperature (∼830 °C) which markedly decreases to 470 °C on substitution of Mn is substituted at the B site. Impedance study of the compound exhibits non-Debye type relaxation process. With the rising temperature, the relaxation frequency shifts toward the high frequency side. From the plots of complex impedance, negative temperature coefficient of resistance (NTCR) behavior like semiconductor is noticed. The conductivity is mainly contributed by the grain in the material.

Complex dielectric and impedance analysis in Dy1-XPrXMnO3 compounds: Partial substitution effects

Synthesis and characterization of single phasic Dy1-xPrxMnO3 (DPMO) ceramic samples through solid-state reaction (SSR) method are reported in present study. XRD analysis confirmed the structural formation of DPMO and revealed lattice changes induced by Pr substitution that affect JT-distortion and tilting of MnO6 octahedra. Fine-grained microstructures with a micrometre-sized grain size were observed using FESEM images, which increased with increasing Pr concentration. The variation of activation energy in DPMO was found to be induced by modification in Mn–O bond distances. The dielectric behaviour of DPMO was significantly enhanced, which was explained using the UDR model fitting. Impedance analysis confirmed the existence of non-Debye type relaxation and negligible electronic polarization mechanisms in all DPMO samples. With the increase in temperature, a reduction in the magnitude of Z' was observed, indicating a decrease in the resistance of contributing electroactive components such as grains, grain boundaries, and electrode interfaces. Electric modulus studies revealed the existence of grain and grain boundary relaxation processes throughout the studied frequency and temperature range in DPMO compounds. Overall, the study provides deep insights into the effect of Pr substitution on the structural, electrical, and dielectric properties of DPMO and highlights the potential of DPMO for future electronic and energy device applications.

Unusual energy–structure–property relation in a metallic glass coupled with temperature-dependent relaxation memories

Elucidating the individual effects of high- and low-temperature relaxations on the internal structure and material properties is a fascinating theme in the field of metallic glasses because it can lay the foundation for an advanced glass-property tuning scheme through the control of different types of relaxations. In this study, several glass models were constructed using melt-quenching (MQ) processes, in which high- and low-temperature relaxations were controlled by their cooling rates. We found unusual energy–structure–property relationships; even when the glass alloys had equivalent potential energies (or free volumes), they exhibited different local-order development, elastic stiffness, and plastic deformation properties, which depended on the thermal histories in the glass-forming MQ process. The local-order development was primarily affected by the high-temperature relaxation occurring at approximately the glass transition temperature. Meanwhile, the plastic deformation behavior of the metallic glasses was significantly affected by both low- and high-temperature relaxations. We also found an interesting relaxation memory effect in the glass alloys constructed by the present MQ processes; the glass alloys exhibited an atomic-scale dynamic that was affected by the temperature-dependent relaxation memories (i.e., high and-low-temperature relaxation memories) of previous MQ processes. These results provide new insights into the relaxation physics of glass-forming liquids and imply the possibility of an advanced tuning scheme for metallic glasses.

In vitro study design derived from an in vivo lifting task

AbstractBiomechanical properties of the spinal tissue constituents, especially in the intervertebral disc (IVD), contribute to disability and high costs. The IVD is considered to be one of the main etiologies of chronic low back pain. Changes in the biomechanical properties of the spine, especially in the IVD, are related to multiple factors such as type and duration of loading, recovery periods, osmosis, relaxation, and diffusion processes. To quantify spinal burden in vivo, various dose models have been developed in the context of ergonomics research. In our work both in vivo and in vitro studies were conducted to investigate the effects of loading and rest periods alteration on mechanical properties of the spine. A multibody simulation (MBS) was used to translate the collected motion data from the in vivo study into forces and moments as boundary conditions for the in vitro study. An in vitro spine test rig is used to apply axial compression forces and pure moment loading in flexion/extension direction to spinal segments according to the conditions that have been determined in the MBS. In this article, an approach is presented to coordinate the boundary conditions in vivo and in vitro in order to carry out a holistic investigation. In addition, it is shown why cyclic preconditioning seems to be a more suitable preparation of the samples compared to a constant one in this experimental context.

Electrical conduction mechanism in multiferroic Gd doped GaFeO3

A detail analysis on the structural, morphological, dielectric, conductivity, ferroelectric, magnetic and electrical behaviour of Gd doped GaFeO3 prepared by mixed oxide method is presented. XRD analysis, by using Rietveld refinement method, validates that all the samples have single phase orthorhombic structure. Decrement in the grain size with rise in Gd content is found from FESEM analysis. The dispersive characteristic of dielectric constant is described by the Maxwell-Wagner model and Koop's theory. The value of εr is found to increase with Gd content. The modified Debye formula is used to fit εr with frequency data, which indicates the existence of more than one relaxation processes. The frequency dependant ac conductivity curve is found to obey Jonscher's power law and the conduction mechanism for all the samples is explained by of small polaron hopping (SPH) transport model. The modulus and impedance spectra confirms the presence of non- Debye type of relaxation. The presence of semicircular curves of complex impedance plot suggests the effect of grain boundary contribution to the conduction process for all the samples at low temperatures. The value of remanent polarization is found to fall with Gd content. From M-H loop, magnetisation at M (30kOe) is found to rise while non-saturation is found to decrease with Gd content and analysed on the basis of Law of Approach.