Search

The paper presents computation of second- and third-order elastic constants of Laves phase compounds ScOs2 and YOs2 at room temperature using Lennard-Jones potential model. The thermal relaxation time, ultrasonic velocity, ultrasonic attenuation and other related thermo-physical parameters (Debye average velocity, Debye temperature, thermal conductivity, specific heat and thermal energy density) are also calculated using second- and third-order elastic constants. The obtained elastic and ultrasonic properties of chosen compounds have been likened with the properties of other hexagonal structured materials for complete analysis and characterization. [ABSTRACT FROM AUTHOR]

The present article comprises computation of elastic, ultrasonic, and thermo-physical properties of RM (R = Tb, Dy, Ho, Er, Tm; M = Zn, Cu) compounds at 300 K. The second-order elastic constants (SOECs) and elastic moduli are evaluated initially, using potential model approach considering interaction up to second nearest neighbours. The ultrasonic velocities are obtained for wave propagation along <100>, <110>, and <111> crystallographic directions using evaluated SOECs. The Debye temperature, specific heat at constant volume, thermal energy density, thermal conductivity, and thermal relaxation time are also calculated. The obtained results are compared and analysed for justification and application of materials. [ABSTRACT FROM AUTHOR]

In present investigation, we studied the elastic, ultrasonic and thermal properties of SnAs, InTe and PbSb. The Coulomb and Born-Mayer potential model was utilized to compute the second and third order elastic constants up to second nearest neighbor. The direction dependent ultrasonic velocities for longitudinal and shear waves, Debye average velocity and mechanical constants such as bulk modulus, shear modulus, tetragonal modulus, Young's modulus, Poisson ratio, Pugh's indicator (shear modulus to bulk modulus ratio) and Zener anisotropy ratio were obtained with the use of the second order elastic constants and the density of the chosen materials. Since the Pugh's indicator is greater than 0.59 for all chosen materials, they have a brittle nature. Further the second and third order elastic constants with other associated acoustical parameters were used to compute the Debye temperature, thermal relaxation time, acoustic coupling constant and ultrasonic attenuation. The total ultrasonic attenuation is the smallest in the case of InTe along the <100> direction and highest for SnAs along the <111> direction. Thermo-elastic loss is insignificant in comparison to the loss due to the phonon-phonon interaction mechanism. Additionally, the thermal conductivity of these materials was found using Cahill's approach. The results of this investigation are discussed with the available findings and for other rock salt structured materials. [ABSTRACT FROM AUTHOR]

The ultrasonic attenuation in thulium monochalcogenides Tm X ( X=S, Se and Te) has been studied theoretically with a modified Mason’s approach in the temperature and range 100 K to 300 K along 〈100〉, 〈110〉 〈111〉 crystallographic directions. The thulium monochalcogenides have attracted a lot of interest due to their complex physical and chemical characteristics. TmS, TmSe and TmTe are trivalent metal, mixed valence state, and divalent semiconductor, respectively. Coulomb and Born-Mayer potential is applied to evaluate the second- and third-order elastic constants. These elastic constants are used to compute ultrasonic parameters such as ultrasonic velocities, thermal relaxation time, and acoustic coupling constants that, in turn, are used to evaluate ultrasonic attenuation. A comparison of calculated ultrasonic parameters with available theoretical/experimental physical parameters gives information about classification of these materials. [ABSTRACT FROM AUTHOR]

The ways in which animals sense the world changes throughout development. For example, young of many species have limited visual capabilities, but still make social decisions, likely based on information gathered through other sensory modalities. Poison frog tadpoles display complex social behaviors that have been suggested to rely on vision despite a century of research indicating tadpoles have poorly-developed visual systems relative to adults. Alternatively, other sensory modalities, such as the lateral line system, are functional at hatching in frogs and may guide social decisions while other sensory systems mature. Here, we examined development of the mechanosensory lateral line and visual systems in tadpoles of the mimic poison frog (Ranitomeya imitator) that use vibrational begging displays to stimulate egg feeding from their mothers. We found that tadpoles hatch with a fully developed lateral line system. While begging behavior increases with development, ablating the lateral line system inhibited begging in pre-metamorphic tadpoles, but not in metamorphic tadpoles. We also found that the increase in begging and decrease in reliance on the lateral line co-occurs with increased retinal neural activity and gene expression associated with eye development. Using the neural tracer neurobiotin, we found that axonal innervations from the eye to the brain proliferate during metamorphosis, with few retinotectal connections in recently-hatched tadpoles. We then tested visual function in a phototaxis assay and found tadpoles prefer darker environments. The strength of this preference increased with developmental stage, but eyes were not required for this behavior, possibly indicating a role for the pineal gland. Together, these data suggest that tadpoles rely on different sensory modalities for social interactions across development and that the development of sensory systems in socially complex poison frog tadpoles is similar to that of other frog species. [Display omitted] • Ranitomeya imitator tadpoles hatch with fully developed lateral line systems. • Use of mechanosensory stimuli for begging is dependent on developmental stage. • The visual system of R. imitator tadpoles continues to develop through metamorphosis. • When visual capabilities are poor, tadpoles rely more on mechanosensory inputs. [ABSTRACT FROM AUTHOR]

We hypothesized that there were diurnal differences in metabolism, with major transcriptional changes occurring early during the day and/or night between migratory and non-migratory states of avian migrants. Present study investigated this in captive Black-headed Buntings (Emberiza melanocephala) exhibiting long-day stimulated vernal migratory and post-breeding non-migratory states, by using RNA-Seq and qPCR assays of liver samples collected at 1 h into day (hour 1) and 1 h into night (hour 17) of the 16-h photoperiod (16L:8D). There were differentially expressed genes (DEGs) both within (day vs. night) and between (vernal migratory vs. non-migratory) states. Within the state, 358 and 52 DEGs were identified in migratory and non-migratory states, respectively. In the migratory state, genes associated with oxidative phosphorylation (sdh) had higher expression, and genes associated with fat metabolism (acaca and elovl6) and ABC transporters (abcg5, abcg8) had lower expression at night, compared to the daytime. In the non-migratory state, among genes associated with fat metabolism and gluconeogenesis, ppara and hmgcl had higher while aacs had lower expression at night. Between states, 35 and 180 DEGs were identified in day and night, respectively, with highly expressed genes associated with fat metabolism (acsbg2, cetp) found in migratory, and those associated with cell death (casp7), gluconeogenesis (stat3) and circadian rhythm pathway (cry1) in the non-migratory state. These results demonstrate differentially activated hepatic molecular pathways during photostimulated vernal migratory and post-breeding non-migratory states of buntings and provide molecular insights into differential metabolic support to physiologically contrasting seasonal life-history states in migratory songbirds. [ABSTRACT FROM AUTHOR]

Organic–inorganic hybrid materials with nanoscale morphologies gain significant attention as a potential candidate for energy storage applications. Herein, nickel hydroxide (Ni(OH)2) and benzo[2,1,3]selenadiazole (BSe)‐capped dipeptide amphiphiles are electrodeposited over flexible nickel foam (NF) substrates to fabricate organic–inorganic nanohybrids. The in situ electrochemical deposition of organic–inorganic nanohybrids is investigated by Fourier transform infrared spectroscopy, X‐ray photoelectron spectroscopy, energy dispersive‐electron microscopy, and elemental mapping. The nanostructured morphology of the nanohybrid material is investigated by field‐emission scanning electron microscopy and transmission electron microscopy. The electrochemical performance and supercapacitor properties are examined in 1 m KOH aqueous solution. Aromatic diphenylalanine (FF)‐based nanohybrid BSeFF/Ni(OH)2 deposited on the NF electrode exhibit a specific capacitance of 1250 F g−1, whereas dileucine (LL)‐based nanohybrids BSeLL/Ni(OH)2 show a specific capacitance of 689 F g−1 at a current density of 2 A g−1. [ABSTRACT FROM AUTHOR]

In this study, we investigated the behaviors of three representative actinide monocarbides (AnCs, where An = U, Pu, and Am) in terms of their superior mechanical and thermo-elastic properties. Coulomb and Born–Mayer potentials were used to calculate the temperature-dependent second order and third order elastic constants up to the second nearest neighbor. The Voigt–Reuss–Hill approximation was employed to compute the values of Young's modulus (Y), Zener anisotropy ratio (A), shear modulus (G), bulk modulus (B), Poisson's ratio (σ), and Pugh's indicator (B/G) using second order elastic constants. The Born stability criteria and Vicker's hardness parameter (H ν) were analyzed to determine the strength and nature of the materials. The Debye average velocities and Breazeale's nonlinearity parameters were calculated in the temperature range from 100 to 500 K. Thermal properties such as the lattice thermal conductivity, thermal relaxation time, crystal energy density, and acoustic coupling constant were computed at different temperatures and along various directions. The longitudinal and shear components of ultrasonic attenuation were evaluated along the three crystallographic directions comprising <100>, <110>, and <111>. The temperature- and direction-dependent ultrasonic properties were correlated with other thermo-physical properties to extract important information such as the material strength and thermal conductivity in order to assess the microstructural quality and nature of the materials, which are useful for industrial applications. • Superior elastic and mechanical properties of UC compared with PuC and AmC. • AnCs satisfy Born stability criteria. • AnCs exhibit brittle behavior and non-central nature of interaction potential. • Strong dependence of ultrasonic attenuation on crystallographic direction. [ABSTRACT FROM AUTHOR]