Modulus Data Research Articles

Electrical and optical properties of a lead-free complex double perovskite BaNaFeMoO6: Photovoltaic and thermistor applications

In this communication, synthesis (solid-state reaction) and characterizations of a complex double perovskite BaNaFeMoO6 are reported. X-ray diffraction analysis (structure and lattice parameters) adopts a monoclinic structure while Raman spectroscopy provides information about the vibrational characteristics. Homogenous distribution of the grains is observed from the scanning electron microscope (SEM) whereas energy dispersive X-ray analysis (EDX) supports compositional consistency. Ultraviolet–visible (UV–vis) data provides a direct energy bandgap of 2.75 eV, which may be suitable for photovoltaic applications. The analysis of Maxwell-Wagner type of dielectric dispersion, resistance, relaxation, and transport mechanism are carried out using dielectric, impedance, modulus, and conductivity data recorded within an available range of frequency (1 kHz – 1 MHz) and temperature (25 °C – 500 °C). Both the theoretical fit of the Nyquist data using ZSIMPWIN software as well as temperature-dependent conductivity support a negative temperature coefficient of resistance (NTCR) nature. The scaling nature of modulus data supports the non-Debye type of relaxation. The obtained temperature-dependent thermistor constant (β), sensitivity factor (α), and activation energy make the prepared material suitable for thermistor-related device application. The study of polarization–electric field (P-E) loop suggests the possibility of ferroelectric nature in the reported material.

Covariant formulation of refracted gravity

We propose a covariant formulation of refracted gravity (RG), which is a classical theory of gravity based on the introduction of gravitational permittivity – a monotonic function of the local mass density – in the standard Poisson equation. Gravitational permittivity mimics dark matter phenomenology. The covariant formulation of RG (CRG) that we propose belongs to the class of scalar-tensor theories, where the scalar fieldφhas a self-interaction potential 𝒱(φ) = − Ξφ, with Ξ being a normalization constant. We show that the scalar field is twice the gravitational permittivity in the weak-field limit. Far from a spherical source of densityρs(r), the transition between the Newtonian and the RG regime appears below the acceleration scaleaΞ = (2Ξ − 8πGρ/φ)1/2, withρ = ρs + ρbgandρbgbeing an isotropic and homogeneous background. In the limit 2Ξ ≫ 8πGρ/φ, we obtainaΞ ∼ 10−10m s−2. This acceleration is comparable to the accelerationa0originally introduced in MOdified Newtonian Dynamics (MOND). From CRG, we also derived the modified Friedmann equations for an expanding, homogeneous, and isotropic universe. We find that the same scalar fieldφthat mimics dark matter also drives the accelerated expansion of the Universe. From the stress-energy tensor ofφ, we derived the equation of state of a redshift-dependent effective dark energywDE = pDE/ρDE. Current observational constraints onwDEand distance modulus data of type Ia supernovae suggest that Ξ has a comparable value to the cosmological constant Λ in the standard model. Since Ξ also plays the same role of Λ, CRG suggests a natural explanation of the known relationa0 ∼ Λ1/2. CRG thus appears to describe both the dynamics of cosmic structure and the expanding Universe with a single scalar field, and it falls within the family of models that unify the two dark sectors, highlighting a possible deep connection between phenomena currently attributed to dark matter and dark energy separately.

Strain-dependent shear properties of human adipose tissue in vivo

IntroductionHuman adipose tissue (fat) deforms substantially under normal physiological loading and during impact. Thus, accurate data on strain-dependent stiffness of fat is essential for the creation of accurate biomechanical models. Previous studies on ex vivo samples reported human fat to be nonlinear and viscoelastic. When static compression is combined with magnetic resonance (MR) elastography (an imaging technique used to measure viscoelasticity in vivo), the large deformation properties of tissues can be determined. Here, we use magnetic resonance elastography to quantify fat shear modulus in vivo under increasing compressive strain and compare it to the underlying passive gluteal muscle. MethodsThe right buttocks of ten female participants were incrementally compressed at four levels while MR elastography (50 Hz) and mDixon images were acquired. Maps of tissue shear modulus (G*) were reconstructed from the MR elastography phase images. Tissue strain was estimated from registration of deformed and undeformed mDixon images. Linear mixed models were fit to the natural logarithm of the compressive strain and shear modulus data for each tissue. ResultsShear modulus increased in an exponential relationship with compressive strain in fat: Gfat*=748.5*Cyy−1.18Pa, and to a lesser extent in muscle: Gmuscle*=956.4*Cyy−0.36Pa. The baseline (undeformed) stiffness of fat was significantly lower than that of muscle (mean G*fat = 752 Pa, mean G*muscle = 1000 Pa, paired samples t-test, t = −4.24, p = 0.001). However, fat exhibited a significantly higher degree of strain dependence (characterised by the exponent of the curve, t = −6.47, p = 0.0001). ConclusionStatic compression of human adipose tissue results in an increase in apparent viscoelastic shear modulus (stiffness), in an exponentially increasing relationship. The relationships defined here can be used in the development of physiologically realistic computational models for impact, injury and biomechanical modelling.

The reconstruction of constant jerk parameter with f(R, T) gravity in Bianchi-I spacetime

We have developed a Bianchi I cosmological model of the universe in $f(R,T)$ gravity theory which fit good with the present day scenario of accelerating universe. The model displays transition from deceleration in the past to the acceleration at the present. As in the $\Lambda$CDM model, we have defined the three energy parameters $\Omega_m$, $\Omega_{\mu}$ and $\Omega_{\sigma}$ such that $\Omega_m$ + $\Omega_{\mu}$ + $\Omega_{\sigma}$ = 1. The parameter $\Omega_m$ is the matter energy density (baryons + dark matter), $\Omega_{\mu}$ is the energy density associated with the Ricci scalar $R$ and the trace $T$ of the energy momentum tensor and $\Omega_{\sigma}$ is the energy density associated with the anisotropy of the universe. We shall call $\Omega_{\mu}$ dominant over the other two due to its higher value. We find that the $\Omega_{\mu}$ and the other two in the ratio 3:1. 46 Hubble OHD data set is used to estimate present values of Hubble $H_0$, deceleration $q_0$ and jerk $j$ parameters. 1$\sigma$, 2$\sigma$ and 3$\sigma$ contour region plots for the estimated values of parameters are presented. 580 SNIa supernova distance modulus data set and 66 pantheon SNIa data which include high red shift data in the range $0\leq z\leq 2.36$ have been used to draw error bar plots and likelihood probability curves for distance modulus and apparent magnitude of SNIa supernova's. We have calculated the pressures and densities associated with the two matter densities, viz., $p_{\mu}$, $\rho_{\mu}$, $p_m$ and $\rho_m$, respectively. The present age of the universe as per our model is also evaluated and it is found at par with the present observed values.

A novel approach to predict the rheological properties of rejuvenated binder subject to secondary aging

The recycling of asphalt concrete pavement not only requires to restore the original properties of reclaimed asphalt pavement (RAP) materials, but also consider the properties due to secondary aging simultaneously. Therefore, in order to design recycled asphalt mixtures for construction of sustainable pavement with good performances, it is very important to understand and predicted the viscoelastic behaviors of rejuvenated binders. However, limited studies on the effect of rejuvenator dosage and secondary aging in the rheological behavior of rejuvenated binder are reported. In this study, a novel approach was used to construct the dosage-aging master curves to describe and predict the viscoelastic behaviors of rejuvenated binders considering the effect of rejuvenator dosage, aging time and aging temperature. Experimental data of complex modulus and phase angle were used to validate the proposed approach. Rejuvenated binders with rejuvenators at four dosages were aged at various aging temperature and times. Complex shear modulus and phase angle isotherms of each rejuvenated binders for a range of frequencies were constructed simply starting from time-temperature superposed master curves. Two rotations and horizontal shifts procedure were applied to the master curves. Finally, the dosage-aging complex modulus and phase angle master curves were proposed. It was found the twice rotation of master curves of rejuvenated binder process was used to change the shapes of the master curves due to rejuvenator dosage and aging based on the dosage-aging rotation factor. The twice horizontally shifted process was used to shift the master curves after twice rotation to the master curves at the reference dosage, aging time and temperature based on the dosage-aging horizontal shift factor. The twice rotation and horizontal shift processes are suitable for rejuvenated binder for using other dosage under other aging conditions, the predicted dosage-aging master curves can be obtained and is good accordance with the measured master curve. Therefore, the complex shear modulus and phase angle values of rejuvenated binders over a range of dosages at any aging time and temperature can be predicted without actual testing.

Reconstruction of an observationally constrained f(R,T) gravity model

In this paper, an attempt is made to construct a Friedmann–Lemaitre–Robertson–Walker model in [Formula: see text] gravity with a perfect fluid that yields acceleration at late times. We take [Formula: see text] as [Formula: see text]. As in the [Formula: see text]CDM model, we take the matter to consist of two components, viz., [Formula: see text] and [Formula: see text] such that [Formula: see text]. The parameter [Formula: see text] is the matter density (baryons [Formula: see text] dark matter), and [Formula: see text] is the density associated with the Ricci scalar [Formula: see text] and the trace [Formula: see text] of the energy–momentum tensor, which we shall call dominant matter. We find that at present [Formula: see text] is dominant over [Formula: see text], and that the two are in the ratio 3:1–3:2 according to the three data sets: (i) 77 Hubble OHD data set, (ii) 580 SNIa supernova distance modulus data set and (iii) 66 pantheon SNIa data which include high red shift data in the range [Formula: see text]. We have also calculated the pressures and densities associated with the two matter densities, viz., [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text], respectively. It is also found that at present, [Formula: see text] is greater than [Formula: see text]. The negative dominant matter pressure [Formula: see text] creates acceleration in the universe. Our deceleration and snap parameters show a change from negative to positive, whereas the jerk parameter is always positive. This means that the universe is at present accelerating and in the past it was decelerating. State finder diagnostics indicate that our model is at present a dark energy quintessence model. The various other physical and geometric properties of the model are also discussed.

Impact of ZnS/Mn on the Structure, Optical, and Electric Properties of PVC Polymer.

The most efficient way to create novel materials that may be used in a variety of optoelectronic applications is thought to be doped mixed polymers with appropriate fillers. Undoped and doped PVC polymers with ZnS/Mn formed at different temperatures were fabricated using the casting method. The Rietveld method was used to discover the structure and microstructure of Zn0.95Mn0.05S prepared at T = 300, 400, and 500 °C. The distribution and existence of the nanofiller over the PVC matrix were determined via XRD, FTIR, EDS, and SEM techniques. The effect of the preparation temperatures of the ZnS/Mn nanofiller on the absorption, transmittance, reflectance, refractive index, extinction coefficient, dielectric constant, AC conductivity, electrical modulus, and DC conductivity activation energy data of the PVC polymer was studied using the diffused reflectance technique. Doping PVC with ZnS/Mn (prepared at 300 °C) lowered the direct and indirect optical band gaps from 5.4 and 4.52 eV to minimum values of 4.55 and 3.63 eV. The fluorescence intensity of pure PVC is greatly enhanced upon loading with ZnS/Mn. The PVC exhibited two near UV peaks, one violet and one blue color, while, in addition, the doped polymers exhibited green and orange colors. The corresponding CIE diagram for all the samples was also determined.

Low-cost flame synthesized La2/3Cu3Ti4O12 electro-ceramic and extensive investigation on electrical, impedance, modulus, and optical properties

An environmentally-friendly synthesis route and low-cost starting materials are more appropriate for the production of ceramic materials at the industry level. With this concern we prepared the La2/3Cu3Ti4O12(LCTO), which is isostructural of CaCu3Ti4O12 (CCTO), using the low-cost TiO2 instead of a high-cost of titanium source (titanium isopropoxide or titanium chloride) using a low-cost wet-chemical route. Although, there are lots of synthetic methods reported for LCTO fabrication in terms of duration, cheap reagents, energy consumption, feasibility, etc. The present method is far better than the others. The prepared ceramic samples were sintered at 1050 °C/12 h and studied their structural, morphology and impedance, and modulus studies for further confirmation. The prepared LCTO ceramic shows the pure phase with the cubic type of morphology. The homogenous distribution of all the elements was observed through dispersive X-ray analysis. X-ray photoelectron spectroscopy studies revels that La is in +3 oxidation state, Cu is in a +2 oxidation state, and Ti is multiple (+3 and + 4) oxidation state. The LCTO ceramic displayed the very high dielectric constant (∼3852) and dielectric loss (0.322), at 1 kHz and at room temperature. Calculated the activation energy using the impedance and modulus data and it shows the superior to that of CCTO ceramic synthesized by the same method. The prepared samples exhibited Debye-type relaxation, which is evoked from the impedance and modulus studies. The calculated optical energy bandgap of LCTO (2.06 eV) is found to be lesser than that of the well-known structure of perovskites (BaTiO3 (3.28 eV), PbTiO3 (3.18 eV), LiNbO3 (3.78 eV) and BiFeO3 (2.67 eV) as well as structure of spinel CoCr2O4 (3.10 eV) and LuFe2O4 (2.18 eV)) materials.

Quantitative assessment of biceps brachii muscle stiffness by using Young's modulus-Angle curve during passive stretching in stroke patients.

Purpose: This study aims to use shear wave elastography (SWE) to dynamically describe the characteristics of biceps brachii muscle stiffness during passive stretching in healthy participants, investigate changes in the Young's modulus-angle curve under various states of muscle tone in stroke patients, and develop a new method for measuring muscle tone quantitatively. Methods: In total, 30 healthy volunteers and 54 stroke patients were evaluated for elbow flexor muscle tone on both sides using passive motion examination and were divided into groups based on their muscle tone status. The real-time SWE video of the biceps brachii and the Young's modulus data were recorded during the passive straightening of the elbow. The Young's modulus-elbow angle curves were created and fitted using an exponential model. The parameters yielded from the model were subjected to further intergroup analysis. Results: The repeatability of the Young's modulus measurement was generally good. During passive elbow extension, the Young's modulus of the biceps brachii steadily increased as muscle tone increased, and it increased faster when the modified Ashworth scale (MAS) score got higher. The exponential model's fitness was generally good. The curvature coefficient was significantly different between the MAS 0 group and the hypertonia groups (MAS 1, 1+, and 2 groups). Conclusion: The passive elastic characteristics of the biceps brachii are consistent with the exponential model. The Young's modulus-elbow angle curve of the biceps brachii changes in distinct ways depending on the muscle tone status. SWE can be used to quantify muscular stiffness during passive stretching as a new way of muscle tone evaluation, allowing for quantitative muscle tone evaluation and mathematical assessment of muscle mechanical properties in stroke patients.

Small-Strain Characteristics of Reconstituted Soils: The Effect of Slurry Water Content and Fabric Anisotropy

Abstract Determination of small-strain properties of soils is essential for many geotechnical applications. Reconstituted specimens have conveniently been used to characterize small-strain properties of cohesive soils in the laboratory. In this study, the influence of slurry water content (ws) and fabric anisotropy on the small-strain properties of reconstituted kaolinite and illite specimens was investigated. Bender elements were employed, within triaxial testing equipment, to obtain vertically propagated, horizontally polarized, shear wave velocity measurements and corresponding shear moduli during the consolidation stage of undrained triaxial compression tests. The soils were initially prepared at water content values of one and one-half (1.5×) and three (3×) times the respective liquid limit for each soil type. The shear wave velocity and shear modulus data were normalized to the void index by following a procedure that was similar to procedures that have previously been used to normalize compression and undrained shear strength data. Unique “intrinsic” relationships for shear wave velocity or shear modulus, independent of soil fabric, were not observed during this study. Inherent fabric anisotropy was also assessed by comparing the aforementioned triaxial shear wave velocity data to measurements of horizontally propagated, vertically polarized, shear wave velocity that were obtained by utilizing bender elements within a consolidation device. The amount of fabric anisotropy was dissimilar and the characteristics of the cross-anisotropic fabric were not observed for the specimens. The amount of inherent fabric anisotropy (Vs,HV/Vs,VH) ranged from 0.63 to 0.97 for the kaolinite and illite specimens with ws values of 1.5× the liquid limit and ranged from 1.13 to 1.21 for kaolinite specimens with ws values of 3× the liquid limit. During the shearing stage, inconsistent and unreliable relationships were obtained for the shear wave velocity-vertical effective stress behavior and shear modulus-axial strain behavior. As discussed herein, the ws level should be considered when reconstituting soil specimens for small-strain stiffness determination.

Linear viscoelasticity and fatigue life: Relationships between properties of asphalt binders and corresponding mixtures

Asphalt mixture performance is affected by binder’s and aggregate’s properties. Mixtures and binders share some Linear ViscoElastic (LVE) properties when small number of loading cycles and strains are considered. It is still unclear how fatigue properties relate among different scales. Three binders associated to three mixtures were characterised by stiffness (ASTM D 7175 and AASTHO T342) and fatigue (AASHTO TP107) standard tests. For stiffness modelling, complex modulus was represented by the 2S2P1D model, while the SHStS (Shift-Homothety-Shift in time-Shift) transformation was used to relate the material scales. S-VECD (Simplified Viscoelastic Continuum Damage) model was used to describe fatigue. Six out of the nine 2S2P1D model constants fitted to the binder’s complex modulus data could be kept the same for their corresponding mixtures. SHStS proved suitable for material upscaling, showing that mixtures inherit most of their LVE behaviour from binders. Although it was difficult to relate S-VECD model constants among the different scales, classical fatigue parameters (γ6 and ε6, strain levels for fatigue failure after a million cycles) suggested good correlation between binders’ and mixtures’ fatigue properties.

Unveiling the high-temperature dielectric relaxation and conduction mechanisms in sol-gel derived LaFeO3 modified Sodium Bismuth Titanate ceramics

The lead-free NBT (Na0.5Bi0.5TiO3) ceramics doped with LaFeO3 having general chemical composition (1-x)Na0.5Bi0.5TiO3-(x)LaFeO3, where x = 0 and 0.05 (abbreviated as LFNBT0 and LFNBT5) were synthesized by sol-gel technique. These ceramics were characterized using X-Ray photoelectron spectroscopy to determine the elemental composition and chemical state of the samples whereas impedance spectroscopy was performed to investigate the electrical properties viz. dielectric constant, dielectric loss, impedance, modulus and conductivity over a wide temperature range (300–775 K) along with frequency (1 Hz - 1 MHz). XPS spectra at room temperature revealed the gradual reduction of valence states i.e., Fe3+ to Fe2+ and Ti4+ to Ti3+ resulting in the formation of oxygen vacancies in LFNBT system. A decrease in dielectric constant as well dielectric loss has been observed at room temperature i.e., from 898 to 541 and 0.75–0.25 respectively at 1 KHz frequency with the incorporation of LaFeO3 in the NBT. A phase transition from ferroelectric to para-electric phase is obtained at 583 K and 623 K for LFNBT0 and LFNBT5 respectively. The negative temperature coefficient of resistance (NTCR) behaviour is obtained from the analysis of impedance data. The Cole-Cole plots perceives the grain and grain boundary effect contribution of the materials with the non-Debye type of relaxation which is also confirmed by electric modulus data and aids in understanding of the transport phenomenon. The fitted conductivity data indicated that the conduction in the NBT system is governed by correlated barrier hopping (CBH). XPS analysis and activation energy values obtained from imaginary part of electrical impedance, modulus, and ac conductivity confirmed that the relaxation and conduction processes in LFNBT0 and LFNBT5 ceramics are attribute to the presence of oxygen vacancies.

Rheological Modeling of Bituminous Mixtures Including Polymer-Modified Binder and Fine Crumb Rubber Added through Dry Process

In recent years, both dry and wet processes to include waste rubber (WR) in bituminous mixtures have had little success in Italy due to technical and economic reasons. However, the necessity to recycle this waste material and the increasing interest in low-noise emitting pavement is encouraging researchers and stakeholders to explore new solutions. In this context, a hot-mix asphalt (HMA) manufactured with polymer-modified bitumen and fine WR added through a dry method has been recently developed. This paper deals with the rheological characterization and modeling of this innovative HMA, in comparison with two reference mixtures, with ordinary polymer-modified bitumen and with an asphalt rubber binder produced through a wet process. The complex modulus was measured through uniaxial cyclic compression tests at different temperatures and frequencies. The Huet-Sayegh rheological model was used to simulate the experimental data. The results showed that the time-temperature superposition principle is valid, despite the presence of polymers and WR. The Huet-Sayegh model allows a good fitting of the dynamic modulus and loss angle data to be achieved. The viscous response of the mixture including polymer-modified bitumen and rubber powder is higher than the other HMAs, which is mainly associated with the nature of the modifiers, the binder content in the mix and the less severe short-term aging.

Electrical conductivity and relaxation in lithium-doped barium vanadate glasses investigated by impedance spectroscopy

We present herein a detailed study of the electric and dielectric properties of glasses with the composition 60V2O5–(40–x)BaO–xLi2O, where x = 10, 15, 20, or 25 mol%. The conduction and relaxation mechanisms have been studied by impedance spectroscopy over the frequency range from 40 Hz to 10 MHz and at various temperatures. With constant transition metal oxide content, the conductivity variation in the glasses is assumed to be mainly due to an ionic contribution. The dependence of electrical conductivity on frequency has been analysed using Jonscher's power law. Properties of the glasses, such as electric modulus loss and relaxation mechanism, have been analysed in terms of electric modulus using the Kohlrausch–William–Watts (KWW) equation, which describes the relaxation behaviour of the mobile ions as non-Debye in nature. Scaling of ac conductivity and electric modulus data has shown that conductivity relaxation is independent of temperature. The non-monotonic variation in the stretching parameter β has been found to show a positive correlation with various activation energies, namely electrical activation energy, relaxation activation energy, and the activation energy from the Anderson–Stuart model. The anomalous behaviour of activation energy with respect to conductivity has been substantiated through structural insight. The conductivity was found to be highest in glasses with 25 mol% Li2O, while coupling between the mobile ions was best for glasses with 20 mol% Li2O.

Filament extrusion-based additive manufacturing of 316L stainless steel: Effects of sintering conditions on the microstructure and mechanical properties

Filament extrusion-based additive manufacturing of metals offers an alternative to the widespread beam-based counterparts. The microstructure obtained from extrusion-based techniques differs greatly from the ones obtained by beam-based additive manufacturing, as a sintering process is used, in contrast to the rapid solidification of a melt pool. In this study, the microstructure of 316L stainless steel fabricated by filament extrusion is investigated as a function of debinding and sintering conditions. High-speed nanoindentation correlated with energy-dispersive X-ray mapping is employed for microstructural characterization. High sintering temperatures of 1350 °C, an atmosphere of pure H2, and a cooling rate of 60 K/m are found to result in the optimal microstructure. High densities are obtained due to accelerated densification, enabled by the introduction of diffusion paths due to δ-ferrite formation. At the same time, hard phases like oxides or σ-precipitates with detrimental effects on the mechanical properties can be avoided. It is shown that the porosity can be quantified by analysis of hardness and modulus data from nanoindentation mapping. The values obtained are in good agreement with optical and Archimedes immersion method measurements. Tensile tests of 3D-printed and sintered specimens show excellent ductility and strength in comparison to literature. We demonstrate that 3D printing of 316L filaments and sintering with the optimized conditions results in material properties comparable to bulk values.

Charge density wave transitions, soft phonon, and possible electronic nematicity in BaNi2(As1−xPx)2

A detailed investigation of ${\mathrm{BaNi}}_{\text{2}}{({\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x})}_{\text{2}}$ single crystals using high-resolution thermal-expansion, heat-capacity, Young's-modulus, and resistivity measurements is presented. The phase diagram of ${\mathrm{BaNi}}_{\text{2}}{({\mathrm{As}}_{1\ensuremath{-}x}{\mathrm{P}}_{x})}_{\text{2}}$ is shown to be much richer than suggested by the original data of Kudo et al. [Phys. Rev. Lett. 109, 097002 (2012)]. The transition to the commensurate charge density wave (C-CDW) is always preceded by a fourfold symmetry-breaking transition associated with the long-range ordering of a strongly fluctuating unidirectional incommensurate charge density wave (I-CDW). Significant precursors above the I-CDW and C-CDW transitions are seen in the thermal expansion and resistivity and are particularly evident in the temperature dependence of the $c/a$ ratio of the lattice parameters. Heat-capacity measurements of the crystals with a higher P content and a higher critical temperature of 3.2 K uncover a Debye-like behavior of a soft-phonon mode with a very low ${\mathrm{\ensuremath{\Theta}}}_{\text{Debye}}$ of roughly 50 K. Associated with this soft phonon are unusually large thermal-expansion anomalies, resulting in logarithmically diverging uniaxial phonon Gr\"uneisen parameters. Young's-modulus data of these higher-${T}_{c}$ crystals exhibit a significant softening in both ${B}_{1g}$ and ${B}_{2g}$ channels, which is argued to be incompatible with nematic criticality and is rather associated with a broad phase transition to an hitherto unknown structure. Possible origins of the increase in the superconducting critical temperature with P substitution are discussed.

HR MAS NMR, dielectric impedance and XRD characterization of polyethylene oxide films for structural phase transitions

The amorphous/crystalline phase transition behavior of PEO films prepared by spin casting method was studied. According to X-ray diffraction (DELTA) analysis, PEO film has a semicrystalline nature at room temperature. The amorphous to crystalline nature of PEO increases with temperature until reaching an amorphous state at 333 K. 1H NMR spectra of PEO in the temperatures between 298 K and 323 K exhibit two main peaks at around 1.132 ppm and 3.174 ppm with very different widths, where the narrow component can be assigned to the mobile polymer chains in the amorphous phase, whereas the broad component is assigned to the more rigid molecules in the crystalline phase. The calculated activation energies from the Arrhenius fit of the Γ1 data of the crystalline and amorphous phases are comparable and found to be 0.252 eV and 0.221 eV, respectively. Form fitting dielectric loss (ε″) and the electrical modulus (M″) data with the Havriliak-Negami model with addition of the electrical conductivity term in the case of ε″, it was deduced that the inverse relaxation time (τ−1), dielectric strength (Δε) and electrical conductivity (σ) follow an Arrhenius-like behavior plot versus reciprocal temperature.

Dependency of the cosmographic tension of standard model to statistical errors of observational data ‎

In this work, we study the standard model of cosmology in the context of cosmographic approach. We want to determine whether the cosmographic tension of the standard model that is reported in recent studies, depends on the statistical errors of the observational data or not. To do this, we produce three catalogues of mock data for the distance modulus of type Ia supernovae using a canonical value for matter density in the framework of standard model. In the first catalogue, the errors of mock data have been chosen equal to the errors of real data in Pantheon catalogue. In the second and third catalogues, the errors of mock data have been chosen equal to half and twice the real errors in Pantheon sample, respectively. In the next step, using the generated mock data, we minimize the least square function in the context of Markov Chain Monte Carlo method and put constraints on the cosmographic parameters in both model independent cosmographic approach and standard model. Our results show that decreasing the error of mock data can remove the cosmographic tension of the standard model. Also, the larger errors increase the deviation of standard model from cosmographic method. Hence, the cosmographic tension of the standard model which is recently reported by the Hubble diagrams of quasars and Gamma-Ray-Burst can be essentially due to large error bars of these observational data and so not a physical tension.

A modeling approach to predict the mechanical response of materials to irradiation damage from external sources: Nanoindentation of Pb-implanted ZrSiO4

Materials exposed to external irradiation undergo damage and detoriation of mechanical properties that decays with the distance from the surface. Finite element simulations are used to predict the hardness and Young´s modulus as function of depth. The model incorporates the homogenized mechanical properties and the volumetric swelling, determined from micromechanical simulations, as function of the locally induced damage. Predicted Young's modulus data showed a good agreement with nanoindentation results and confirmed the established mapping of damage into depth dependent amorphous phase fraction in form of sigmoidal functions. The comparison of predicted hardness profiles with experimental data suggests a relaxation mechanism that removes the residual stress in the damaged surface layer during the ion implantation process. Furthermore, the results support the hypothesis that mechanical properties determined from intrinsic damage can be used to model also external radiation damage. The presented model is applicable to other types of materials and irradiation sources.

Mechanical and thermal properties versus effective cubic lattice constant in Cu2-II-IV-VI4 quaternary compounds

The present work aims to study the dependence of the bulk modulus B and the Debye temperature θD with the effective cubic lattice constant aeff of some Cu2-II-IV-VI4 compounds. We are also studied the correlation between the bulk modulus B, the Debye temperature θD, the microhardness H and the melting point Tm.The fits of the data of the bulk modulus B and the Debye temperature θD versus the effective cubic lattice constant aeff show that B of Cu2-II-IV-VI4 semiconducting materials decreases almost linearly with increase of the effective cubic lattice constant aeff, while that of Debye Temperature θD decreases exponentially with a rising of the effective cubic lattice constant aeff. The coefficients of the correlation were found at around -0.78 for the bulk modulus B, and at around -0.94 for the Debye temperature, respectively.For the bulk modulus B, the best fit was obtained using the following expression: B = - 596.52 aeff + 393.4, where B is expressed in GPa, and aeff in nm, while that of θD is: θD = 165.46 + 3.8 exp (-57.2 aeff), respectively. The average error on the estimation of B was found at around 10%, while that on the estimation of θD is only around 4.5%, respectively. Our expressions perhaps used with high accurate to predict the bulk modulus B and the Debye temperature θD of other quaternary Cu2-II-IV-VI4 semiconducting materials.