Behavior Of Relaxation Time Research Articles

Quasiuniversal behavior of shear relaxation times in simple fluids

Quasiuniversal behavior of shear relaxation times in simple fluids

In Vitro Digestion and Fermentation of Cowpea Pod Extracts and Proteins Loaded in Ca(II)-Alginate Hydrogels.

Antioxidants derived from food by-products are known for their bioactive properties and impact on human health. However, the gastrointestinal behavior is often poor due to their degradation during digestion. The development of Ca(II)-alginate beads supplemented with biopolymers and enriched with cowpea (Vigna unguiculata) extract could represent a novel environmentally friendly technological solution to produce functional ingredients in the food industry. The present study evaluates the impact of in vitro digestion/fermentation by analyzing global antioxidant response (GAR), production of short-chain fatty acids (SCFAs) as a modulation of gut microbiota, and behavior of proton transverse relaxation times by low-field nuclear magnetic resonance (as an indicator of gelation state and characterization of microstructure). Results revealed that guar gum and cowpea protein preserved a high GAR of total phenolic compounds and antioxidant capacity by ABTS and FRAP methods after digestion/fermentation, promoting an adequate protection of the bioactives for their absorption. Alginate-based beads have great potential as prebiotics, with the guar gum-containing system contributing the most to SCFAs production. Finally, the overall higher mobility of protons observed in the intestinal phase agrees with structural changes that promote the release of phenolic compounds during this stage. Beads are excellent carriers of bioactive compounds (cowpea phenolic compounds and peptides) with potential capacities.

PVA/CMC/PEG blended polymer loaded with ZnCo1.9Al0.1O4/carbon nanoparticles/PANi as a promising films for UV radiation shielding

Polyvinyl alcohol (PVA), carboxymethyl cellulose (CMC) and polyethylene glycol (PEG) have been employed as polymeric matrices for the synthesis of polymeric nanocomposite films that incorporate ZnCo1.9Al0.1O4, carbon nanoparticles (CNPs) and polyaniline (PANI) as fillers. X-ray diffraction technique was utilized to examine the structure of ZnCo1.9Al0.1O4 filler and the formed PVA/CMC/PEG/ZnCo1.9Al0.1O4/CNPs/x wt % PANi blends. The morphology of the doped blend was explored using the scanning electron microscopy technique. The increases in absorbance, especially in the UV spectrum, demonstrate the potential of these blends in UV-blocking and UV-filtering applications. The minimum direct and direct optical energy gaps are 5.62 and 4.77 eV obtained as the quantity of PANi became 0.3 wt %. The highest refractive index values (n = 1.66 at 600 nm) were acquired as the blend was doped with 0.4 wt % PANi. The impact of different fillers on the linear and nonlinear optical parameters was explored. The inclusion of ZnCo1.9Al0.1O4/CNPs/x wt % PANi resulted in an improvement in PVA/CMC/PEG blended polymer's optical conductivity. The FL intensities of the loaded blends are comparatively lower than those of the undoped blend. The values of the dielectric constants of doped blends with x = 0 or 0.4 are notably higher than those of other blends. Doped blend with x = 0.2 exhibited the highest energy density value (9 × 10−3 J/m3 at 1 kHz). The doped blend with x = 0.4 has the highest ac conductivity (1.53 × 10−8 Sm−1 at 1 kHz). The influence of doping on the relaxation time and capacitance behavior of the host blend was inspected. These outcomes suggest the opportunity of employing the created nanocomposites in capacitive energy storage and optoelectronic devices.

Dielectric properties, relaxation time and conduction behavior of MoO3 doped V2O5–ZnO–CuO glassy semiconducting system

Dielectric properties, relaxation time and conduction behavior of MoO3 doped V2O5–ZnO–CuO glassy semiconducting system

Polysaccharide Hydro-Gel from Arid Plant Seed

There is a limited information on the structure and gelation process in mucilagepolysaccharides because of the complex conformation and non-homogeneity of the constituent polysaccharides that typically show large molecular weights in excess of 1 MDa. Only a few works have been done in this area of characterizing mucilage structure and rheological behaviour for different gel solutions. Exploring this area would surely open the new horizons for drug delivery, soil conditioning and pharmaceutical industry. In this study, we aimed to extract polysaccharides found in P.ovata Seed (Isabgol) via mucilage extraction controlling molecular weight of polymers in hot water extraction stage and tried to formulate gel formation dissolving different conc. of extracted freeze-dried material along with the characterization of gel network through Rheological studies and Dynamic Light Scattering (DLS) studies in different solvents. The study confirmed the relationship between molecular associations, chain relaxation time and entanglement behaviour of P. ovata hot water extracted (HW) solutions using polydispersity index and shear rheology. Moreover, two power law regions obtained for different concentration solution are of great importance because of their wide applications in the industrial prospective.

Effect of Mixture Composition on the Photophysics of Indoline Dyes in Imidazolium Ionic Liquid-Molecular Solvent Mixtures: A Femtosecond Transient Absorption Study.

We conducted a study on the photophysics of three indoline dyes, D102, D149, and D205, in binary mixtures of ionic liquids (IL) and polar aprotic molecular solvents (MS). Specifically, we examined the behavior of these dyes in IL-MS mixtures containing four different imidazolium-based ILs and three different polar aprotic MSs. Our investigation involved several techniques, including stationary absorption and emission measurements, as well as femtosecond transient absorption (TA) spectroscopy. Through our analysis, we discovered a peculiar behavior of several photophysical properties at low IL mole fractions (0 < XIL < 0.2). Indeed, in this range of mixture composition, the absorption maximum wavelength decreases noticeably, while the emission maximum wavelength and the Stokes shift, expressed in wavenumbers, reach a maximum. while a minimum occurs in the relative quantum yield and the excited state lifetime. These results indicate that the solvation of dye undergoes a large change in this range of mixture composition. We found that, at high ionic liquid content, the excited relaxation times are correlated with the high viscosity, while at low content, it is the polarity of the solvent that influences the behavior of the excited relaxation times. At a mixture composition of around 0.10, the behavior of the photophysical properties of the studied IL-MS mixtures indicates a crossover between situations where the solvation is dominated by that of ions and that dominated by the solvent.

The vanishing relaxation time behavior of multi-term nonlocal Jordan–Moore–Gibson–Thompson equations

The family of Jordan–Moore–Gibson–Thompson (JMGT) equations arises in nonlinear acoustics when a relaxed version of the heat flux law is employed within the system of governing equations of sound motion. Motivated by the propagation of sound waves in complex media with anomalous diffusion, we consider here a generalized class of such equations involving two (weakly) singular memory kernels in the principal and non-leading terms. To relate them to the second-order wave equations, we investigate their vanishing relaxation time behavior. The key component of this singular limit analysis are the uniform bounds for the solutions of these nonlinear equations of fractional type with respect to the relaxation time. Their availability turns out to depend not only on the regularity and coercivity properties of the two kernels, but also on their behavior relative to each other and the type of nonlinearity present in the equations.

Dynamics of heat passage in hybrid and tri-hybrid Oldroyd-B blood flows through a wedge-shaped artery: A medical application

This article investigates the heat transmission rate in hybrid and tri-hybrid particles that emerged in Oldroyed-B blood flow flowing through wedge shape arteries. The rate type Oldroyd-B flow model is considered to examine the behavior of relaxation and retardation times. The transmuted nondimensional conditions and boundary restrictions are solved using the bvp5c technique. It is observed that the heat transmission rate is high for the tri-hybrid (GO-Al2O3-TiO2) blood flow combination compared to the hybrid (Al2O3-TiO2) blood combination. This study can deliver a vibrant opinion concerning heat transmission behavior and the blood flow nature in a wedge shape artery.

Rheological properties and microstructure of thermodynamically stable microemulsions as factors influencing the release rate of liposoluble vitamins

Microemulsions (ME) are stable nano-sized emulsions that constitute one of the most effective ways to incorporate lipophilic active compounds into water-based food matrices. Great stability, colloidal domain droplets, and optical isotropy are some of the advantages of ME. The present work analyzed the influence of rheological behavior and microstructural characteristics of food microemulsions on the release rate of lipophilic vitamins E and D. A fluid ME was compared to a ME with a higher dispersed phase content and a bicontinuous structure (gel-ME). Additionally, carboxymethyl cellulose (CMC) was added to fluid ME (3.5 and 10 g/100 g), obtaining systems with different apparent viscosities and microstructure. The percentage of released vitamins was determined by HPLC, and mathematically modeled. All ME were characterized using TEM microscopy FTIR, rheological and viscoelastic analysis. Fluid and gel-ME reached higher percentages of vitamin release in a very fast manner, while systems containing CMC showed a matrix-driven nature of the release. Those systems with similar zero-shear viscosity and different microstructure exhibited significantly different viscoelastic behavior. Microemulsions with CMC exhibited a viscoelastic solid type behavior with G’ > G’’. Mechanical spectra were satisfactorily fitted with the Generalized Maxwell model and relaxation time spectra were determined. In the quiescent state, gel-ME exhibited a higher plateau modulus than those containing large amount of thickener in the continuous phase. The relaxation time behavior of the structure could explain the kinetic release of liposoluble vitamins from the inner lipid phase of the microemulsions.

Adsorbate/adsorbent interactions in microporous zeolites: mechanistic insights from NMR relaxation and DFT calculations

Nuclear magnetic resonance (NMR) relaxation is an effective and non-invasive technique for probing guest-host interactions in porous materials. In particular, the ratio of longitudinal-to-transverse nuclear spin relaxation time constants T1/T2 has been demonstrated as a robust indicator of adsorbate/adsorbent interactions in mesoporous media. However, the use of NMR relaxation times in microporous materials to probe interactions and dynamics remains relatively unexplored. Herein, we investigate and describe the effect of the aluminium content in microporous HZSM-5 zeolites on the NMR relaxation times of a range of common liquid probe molecules. In particular, we discuss the NMR relaxation time behavior of liquids with hydrophilic (water, methanol) and hydrophobic (toluene, methyl cyclohexane) properties adsorbed over HZSM-5 samples with varying silica-to-alumina ratios (SAR = SiO2/Al2O3). Our results demonstrate that highly polar molecules show high sensitivity to aluminium content (i.e., surface acidity), with T1/T2 ratios increasing significantly for higher acidity zeolites. Conversely, for molecules with low polarity, the T1/T2 ratio as a function of SAR remains approximately constant, and in the zeolites with low SAR is much lower compared to that of water and methanol. Density functional theory (DFT) calculations are employed to contrast the surface interaction mechanisms of water and toluene within model zeolite structures of varying SAR, and provide molecular level insights into the observed trends in NMR relaxation behavior.

Prediction of Unwanted Crystallization of Freeze-Dried Protein Formulations Using α-Relaxation Measurements.

There is a lack of methods to predict the isothermal crystallization behavior of amorphous freeze-dried formulations stored below the glass transition temperature. This study applies isothermal microcalorimetry to predict long-term crystallization during product storage time. The relaxation curve of a fresh sample recorded within 12 h after lyophilization is correlated with the long-term crystallization time at the same temperature. Storage conditions of 25 °C and 40 °C are examined and five model formulations containing either sucrose or trehalose with different concentrations of an IgG1 antibody are investigated. The amorphous formulations were created by different freeze-drying processes only differing in their freezing step (random nucleation; additional annealing step of 1.5 h and 3 h, controlled nucleation; quench cooling). Samples that crystallized during the study time of 12 months showed a promising correlation between their relaxation time and crystallization behavior upon storage. Furthermore, the study shows that polysorbate 20 strongly accelerates crystallization of sucrose and that the freezing step itself has a strong impact on the relaxation phenomena that is not levelled out by primary and secondary drying.

Quasielastic Light Scattering in the Broadband Brillouin Spectra of Relaxor Ferroelectric PbMg1/3Nb2/3O3

In this paper, the behavior of quasielastic light scattering (QELS) in a PbMg1/3Nb2/3O3 (PMN) crystal under broadband Brillouin light scattering in a temperature range from 750 K to 80 K was studied. It was shown that QELS consists of two components: narrow (0.9 GHz to 11 GHz) and wide (80 GHz to 600 GHz). The dependencies of the intensity, I, of these components on the frequency, ν, are well described by the power law I ~ eνα, with different α, and are determined by the distribution of the relaxation times. The analysis of the Brillouin spectra showed that the behavior of the relaxation time of both the components of QELS with temperature change is well described by the Arrhenius law. Additionally, in the vicinity of the intermediate temperature T* ≈ 380 K, a critical relaxation time behavior for the narrow component of QELS was detected. In the vicinity of the same temperature, a maximum in the integral intensity of both the components of QELS was observed, which is adjacent to another maximum in the region of the Vogel-Fulcher temperature TVF ≈ 250 K corresponding to the transformation of the crystal to a nonergodic state.

Development and Experimental Validation of Novel Thevenin-Based Hysteretic Models for Li-Po Battery Packs Employed in Fixed-Wing UAVs

Lithium batteries employed in lightweight fixed-wing UAVs are required to operate with large temperature variations and, especially for the emerging applications in hybrid propulsion systems, with relevant transient loads. The detailed dynamic modelling of battery packs is thus of paramount importance to verify the feasibility of innovative hybrid systems, as well as to support the design of battery management systems for safety/reliability enhancement. This paper deals with the development of a generalised approach for the dynamic modelling of battery packs via Thevenin circuits with modular hysteretic elements (open circuit voltage, internal resistance, RC grids). The model takes into account the parameters’ dependency on the state of charge, temperature, and both the amplitude and sign of the current load. As a relevant case study, the modelling approach is here applied to the Li-Po battery pack (1850 mAh, 6 cells, 22.2 V) employed in the lightweight fixed-wing UAV Rapier X-25 developed by Sky Eye Systems (Cascina, Italy). The procedure for parameter identification with experimental measurements, obtained at different temperatures and current loads, is firstly presented, and then the battery model is verified by simulating an entire Hybrid Pulse Power Characterisation test campaign. Finally, the model is used to evaluate the battery performance within the altitude (i.e., temperature) envelope of the reference UAV. The experiments demonstrate the relevant hysteretic behaviour of the characteristic relaxation times, and this phenomenon is here modelled by inserting Bouc–Wen hysteresis models on RC grid capacitances. The maximum relative error in the terminal output voltage of the battery is smaller than 1% for any value of state of charge greater than 10%.

Anderson and many-body localization in the presence of spatially correlated classical noise

We study the effect of spatially correlated classical noise on both Anderson and many-body localization of a disordered fermionic chain. By analyzing the evolution of the particle density imbalance following a quench from an initial charge density wave state, we find prominent signatures of localization also in the presence of the time-dependent noise, even though the system eventually relaxes to the infinite temperature state. In particular, for sufficiently strong static disorder we observe the onset of metastability, which becomes more prominent the stronger the spatial correlations of the noise. In this regime we find that the imbalance decays as a stretched-exponential - a behavior characteristic of glassy systems. We identify a simple scaling behavior of the relevant relaxation times in terms of the static disorder and of the noise correlation length. We discuss how our results could be exploited to extract information about the localization length in experimental setups.

Cattaneo-Christov Double Diffusion (CCDD) on Sutterby Nanofluid with Irreversibility Analysis and Motile Microbes Due to a RIGA Plate.

In this article, a Riga plate is exhibited with an electric magnetization actuator consisting of permanent magnets and electrodes assembled alternatively. This Riga plate creates an electric and magnetic field, where a transverse Lorentz force is generated that contributes to the flow along the plate. A new study field has been created by Sutterby nanofluid flows down the Riga plate, which is crucial to the creation of several industrial advancements, including thermal nuclear reactors, flow metres, and nuclear reactor design. This article addresses the second law analysis of MHD Sutter by nanofluid over a stretching sheet with the Riga plate. The Cattaneo–Christov Double Diffusion heat and mass flux have been created to examine the behaviour of relaxation time. The bioconvection of motile microorganisms and chemical reactions are taken into consideration. Similarity transformations are used to make the governing equations non-dimensional ordinary differential equations (ODE’s) that are subsequently solved through an efficient and powerful analytic technique, the homotopy analysis method (HAM). The effect of pertained variables on velocity, temperature, concentration, and motile microorganism distributions are elaborated through the plot in detail. Further, the velocity distribution enhances and reduces for greater value Deborah number and Reynold number for the two cases of pseudoplastic and dilatant flow. Microorganism distribution decreases with the augmented magnitude of Peclet number , Bioconvection Lewis number , and microorganism concentration difference number . The entropy production distribution is increased for the greater estimations of the Reynolds number and Brinkman parameter . Two sets of graphical outputs are presented for the Sutterby fluid parameter. Finally, for the justification of these outcomes, tables of comparison are made with various variables.

Entropy Analysis of Sutterby Nanofluid Flow over a Riga Sheet with Gyrotactic Microorganisms and Cattaneo–Christov Double Diffusion

In this article, a Riga plate is exhibited with an electric magnetization actuator consisting of permanent magnets and electrodes assembled alternatively. This exhibition produces electromagnetic hydrodynamic phenomena over a fluid flow. A new study model is formed with the Sutterby nanofluid flow through the Riga plate, which is crucial to the structure of several industrial and entering advancements, including thermal nuclear reactors, flow metres and nuclear reactor design. This article addresses the entropy analysis of Sutterby nanofluid flow over the Riga plate. The Cattaneo–Christov heat and mass flux were used to examine the behaviour of heat and mass relaxation time. The bioconvective motile microorganisms and nanoparticles are taken into consideration. The system of equations for the current flow problems is converted from a highly non-linear partial system to an ordinary system through an appropriate transformation. The effect of the obtained variables on velocity, temperature, concentration and motile microorganism distributions are elaborated through the plots in detail. Further, the velocity distribution is enhanced for a greater Deborah number value and it is reduced for a higher Reynolds number for the two cases of pseudoplastic and dilatant flows. Microorganism distribution decreases with the increased magnitude of Peclet number, Bioconvection Lewis number and microorganism concentration difference number. Two types of graphical outputs are presented for the Sutterby fluid parameter (β = −2.5, β = 2.5). Finally, the validation of the present model is achieved with the previously available literature.

Determining the internal orientation, degree of ordering, and volume of elongated nanocavities by NMR: Application to studies of plant stem

This study investigates the fibril nanostructure of fresh celery samples by modeling the anisotropic behavior of the transverse relaxation time (T2) in nuclear magnetic resonance (NMR). Experimental results are interpreted within the framework of a previously developed theory, which was successfully used to model the nanostructures of several biological tissues as a set of water filled nanocavities, hence explaining the anisotropy the T2 relaxation time in vivo. An important feature of this theory is to determine the degree of orientational ordering of the nanocavities, their characteristic volume, and their average direction with respect to the macroscopic sample. Results exhibit good agreement between theory and experimental data, which are, moreover, supported by optical microscopic resolution. The quantitative NMR approach presented herein can be potentially used to determine the internal ordering of biological tissues noninvasively.

Calculation of the spin-lattice relaxation time and the activation energy near the IV–III phase transition in pyridinium fluorosulfonate (C5NH6)FSO3

The spin-lattice relaxation time T1 H for protons nuclei is calculated in term of the pseudospin–phonon (PS) coupled and the energy fluctuation (EF) models close to the IV–III solid–solid phase transition of in (C5NH6)FSO3. This calculation was performed by associating the observed second moment of the 1H as the order parameter below T C and the disorder parameter above T C. Values of the activation energy for the cation reorientation in this crystal are also deduced by using both models. In addition, the observed dielectric permittivity of this crystal is analyzed within the framework of the Landau theory and values of the spontaneous polarization (P S) are determined as a function of temperature. The normalized values of P S are used in the PS and EF models to extract the activation energy for the reorientation of the dipole moment of this compound arising from cation–anion interaction. Our results show that the PS and EF models can describe the observed behavior of the spin-lattice relaxation time adequately for the IV–III solid–solid transition in (C5NH6)FSO3.

Highly stable soliton and bound soliton generation from a fiber laser mode-locked by VSe2 nanosheets.

We demonstrate the highly stable soliton generation from a fiber laser mode-locked by the VSe2 nanosheets experimentally. The VSe2 nanosheets prepared via the liquid phase exfoliation method exhibit ultrafast relaxation time and excellent nonlinear optical behavior with saturation intensity and modulation depth of 14.28 MW/cm2 and 19.11%, respectively. A highly stable mode-locked Er3+-doped fiber laser with pulse duration of 714 fs and signal-to-noise ratio of 78.44 dB has been delivered successfully based on the VSe2 nanosheets saturable absorber. In addition, the transition from the conventional soliton to bound-state soliton has been observed experimentally. Our results reveal that VSe2 nanosheets possess excellent nonlinear optical performance and can act as a robust optical platform for versatile optical applications.

The Debye length and anionic transport properties of composite membranes based on supported ionic liquid-like phases (SILLPS).

An analysis of the ionic transport properties of BMIM [NTf2] in supported ionic-liquid-like phase (SILLP)-based membranes has been carried out based on experimental impedance spectroscopy measurements. The direct current (dc)-conductivity was analyzed to determine the temperature and frequency dependence. The fit of the loss tangent curve data with the Cole-Cole approximation of the electrode polarization model provides the conductivity, diffusivity, and density of charge carriers. Among these quantities, a significant increase in conductivity is observed when an ionic liquid is added to the polymeric matrix containing imidazolium fragments. The use of a recent generalization of Eyring's absolute rate theory allowed the elucidation of how the local entropy restrictions, due to the porosity of the polymeric matrix, control the conductive process. The fit of the conductivity data as a function of temperature manifests the behavior of the excess entropy with respect to the temperature. The activation entropy and enthalpy were also determined. Our results correlate the Debye length (LD) with the experimental values of conductivity, electrode polarization relaxation time, and sample relaxation time involved. Our work provides novel insights into the description of ionic transport in membranes as the diffusivity, mobility, and free charge density depend on the LD. Moreover, we discuss the behavior of the polarization relaxation time, the sample relaxation time, and the static permittivity as a function of the temperature.