Steviol glycosides are non-caloric sweeteners found in high concentrations in the leaves of the Paraguayan perennial herb
S. rebaudiana rebaudiana
. In the present study, an attempt has been made to ...analyze promoter regions of SG-related biosynthesis genes of
S. rebaudiana rebaudiana
and
Helianthus annuus
. The close relationship between
H. annuus
,
S. rebaudiana
, and the SGs biosynthesis genes in the
H. annuus
genome provides a remarkable opportunity for SGs production in the
H. annuus
leaves. Several cis-acting regulatory elements associated with plant development, plant hormonal regulation, and stress response were identified and found in varying frequencies within the two kbp of 5′ regulatory regions, including A-box, MYB, MSB, ABRE, LTR, ERE, STRE, ABA, ARE, DRE, MBSI, TC-RICH REPEATS, WUN-MOTIF, MYC, MYB. The number of cis-elements in both plants is equal. However,
S. rebaudiana
's
UGT
genes have significantly more elements than
H. annuus
. These results suggest that the lack of
H. annuus
SGs is related to the plant's cis-elements of
UGT
genes. This finding indicates the potential cis-acting regulatory factors involved in the expression and regulation of the SG gene in
H. annuus
and
S. rebaudiana
during cellular development or environmental stress situations. Further, tandem repeats and CPG islands were detected in the promoter regions. RT-PCR analysis of seven SG biosynthesis key genes, including
CDPS, KS, KO, KAH
, and three glucosyltransferases, namely
UGT85C2
,
UGT74G1
, and
UGT76G1
, revealed that only
KS
and
KO
genes are expressed in
H. annuus
leaves. Futuristically, this data will be a helpful resource for upgrading
H. annuus
leaves to
S. rebaudiana
sweeteners producers and understanding the regulation of SG-related genes.
Structural aspects of the psyllium gum prepared from the seed husk of the plant of
Plantago ovata Forsk was characterized by dynamic rheology and microscopy. Dynamic rheological properties of ...psyllium gel in the linear viscoelastic region, as a function of concentration (2, 2.5 and 3% w/w), temperature (5–95
°C) and pH (2.5–10) were investigated. Mechanical spectra of the psyllium gels were obtained by frequency sweep measurement classified into that of weak gels because
G′ was larger than
G″ throughout the tested frequency range and the separation of the two moduli (tan
δ) was greater than 0.1. The phase angle increased with temperature and a peak associated with gel melting appeared at about 40
°C. All gels at different pH presented a typical weak gel spectrum. Scanning electron microscopy showed porous structures with different pore-size distribution for psyllium gels under different conditions in terms of concentration, pH and temperature.
•Twinning activity was observed during the first cycle as well as subsequent fatigue life stages.•Mechanical testing information was supported by nondestructive evaluation.•Quantification of surface ...morphology was achieved for selected regions of interest.•A continuum dislocation dynamics allowing detwinning was implemented.
This article presents results relating macroscopic fatigue behavior to microplasticity, twinning activity, and early fatigue crack formation in wrought magnesium alloy specimens of the AZ series. Experimental data were obtained by testing standard-sized samples prepared to be also suitable for direct microstructural quantification using scanning electron microscopy and electron back scatter diffraction for texture, grain-scale observations and fractography, as well as surface morphology measurements using white-light interferometry. In addition, in situ nondestructive monitoring of the fatigue behavior was performed by using the Acoustic Emission method. To describe the plastic anisotropy, tension–compression asymmetry, pseudoelasticity and their evolution as a function of fatigue loading, strain-control experiments of varying amplitude were conducted in several steps. Experimental measurements at different stages of fatigue life revealed repeatable occurrences of twinning–detwinning, which is further shown to be coupled with reversible surface roughening. It was also found that although tension twinning contributes considerably to overall plasticity, it could also give rise to crack initiation towards the end of the fatigue life. The role of the reported microplasticity effects was additionally explored using a Continuum Dislocation Dynamics Viscoplastic Self-Consistent (CDD-VPSC) model for the first two cycles of the fatigue life. The intention of this section was to incorporate the effect of twinning–detwinning into the CDD-VPSC model and subsequently to capture the experimental effects associated with changes in the fatigue hysteresis observed between first and second cycle. These simulation results were consistent with the hypothesis that detwinning is responsible for the anomalous hardening behavior during the tensile part of the cyclic loading in the first few cycles of loading. This observation was confirmed for several imposed strain amplitudes and was achieved by properly defining an appropriate boundary condition that allows surface morphology changes. Furthermore, the experimental test plan allowed the quantification of the fatigue life in terms of hysteresis loop parameters including plastic/elastic energy, residual stiffness, as well as mean and extreme stresses. Finally, an energy-based relationship for the evaluation of fatigue behavior based on the Ellyin–Kujawski formulation was found to provide life predictions that agree with obtained experimental information.
A hybrid (photovoltaic, PV/wind/fuel cell, FC) system comprising different combinations of PV arrays, wind turbine, hydrogen tank, electrolyser, and FC has been investigated for stand-alone ...applications. Load demand was the electrical requirements of atypical residential apartment having a total area of 500 m
2
with a peak electrical load of 35 kW and a yearly load of 24.4 MWh in Kerman, Iran. The assessment criterion for the analysis was levellised cost of energy of each system configuration. National Renewable Energy Laboratory's Hybrid Optimization Model for Electric Renewable software was utilised as the assessment tool of the present study. The effect of electrical load profile on the optimisation results has also been investigated considering a demand load profile with a low peak of 12 kW. Also, a comparison was made between the hybrid (PV/wind/diesel/bat) systems and the hybrid (PV/wind/FC) system of the current study at different fuel price scenarios.
A novel procedure for the nonlinear vibration analysis of curved beam is presented. The Non-Uniform Rational B-Spline (NURBS) is combined with the Euler−Bernoulli beam theory to define the curvature ...of the structure. The governing equation of motion and the general frequency formula, using the NURBS variables, is applicable for any type of curvatures, is developed. The Galerkin procedure is implemented to obtain the nonlinear ordinary differential equation of curved system and the multiple time scales method is utilized to find the corresponding frequency responses. As a case study, the nonlinear vibration of carbon nanotubes with different shapes of curvature is investigated. The effect of oscillation amplitude and the waviness on the natural frequency of the curved nanotube is evaluated and the primary resonance case of system with respect to the variations of different parameters is discussed. For the sake of comparison of the results obtained with those from the molecular dynamic simulation, the natural frequencies evaluated from the proposed approach are compared with those reported in literature for few types of carbon nanotube simulation.
Free and forced vibrations of triangular plate are investigated. Diverse types of stiffeners were attached onto the plate to suppress the undesirable large-amplitude oscillations. The governing ...equation of motion for a triangular plate, based on the von Kármán theory, is developed and the nonlinear ordinary differential equation of the system using Galerkin approach is obtained. Closed-form expressions for the free undamped and large-amplitude vibration of an orthotropic triangular elastic plate are presented using the two well-known analytical methods, namely, the energy balance method and the variational approach. The frequency responses in the closed-form are presented and their sensitivities with respect to the initial amplitudes are studied. An error analysis is performed and the vibration behavior, as well as the accuracy of the solution methods, is evaluated. Different types of the stiffened triangular plates are considered in order to cover a wide range of practical applications. Numerical simulations are carried out and the validity of the solution procedure is explored. It is demonstrated that the two methods of energy balance and variational approach have been quite straightforward and reliable techniques to solve those nonlinear differential equations. Subsequently, due to the importance of multiple resonant responses in engineering design, multi-frequency excitations are considered. It is assumed that three periodic forces are applied to the plate in three specific positions. The multiple time scaling method is utilized to obtain approximate solutions for the frequency resonance cases. Influences of different parameters, namely, the position of applied forces, geometry and the number of stiffeners on the frequency response of the triangular plates are examined.
A metamaterial unit cell based on double split ring resonator has been designed. The SRRs consist of a pair of concentric square copper rings. The metamaterial unit cell designed in millimeter ...scales. Effect of some geometric parameters of the split ring resonator such as the size of the gap, the width of the split ring resonator copper wires, the length of the inner ring and the length of the outer ring on the magnetic permeability has been investigated. The magnetic resonance frequency, the magnetic plasma frequency, the resonance bandwidth and the effective magnetic permeability at 9.5 GHz related to each metamaterial unit cell with specified geometric parameters has been calculated. Using these metamaterial unit cells, an invisible cloak operating in microwave regime is designed. The situation of the gaps in the double split ring resonator with two and four gaps is also changed and the effective permeability for each of them is obtained.
Both equal channel angular pressing and friction stir processing have the ability to refine the grain size of twin roll cast AZ31 magnesium and potentially improve its superplastic properties. This ...work used isochronal and isothermal heat treatments to investigate the microstructural stability of twin roll cast, equal channel angular pressed and friction stir processed AZ31 magnesium. For both heat treatment conditions, it was found that the twin roll casted and equal channel angular pressed materials were more stable than the friction stir processed material. Calculations of the grain growth kinetics showed that severe plastic deformation processing decreased the activation energy for grain boundary motion with the equal channel angular pressed material having the greatest Q value of the severely plastically deformed materials and that increasing the tool travel speed of the friction stir processed material improved microstructural stability. The Hollomon–Jaffe parameter was found to be an accurate means of identifying the annealing conditions that will result in substantial grain growth and loss of potential superplastic properties in the severely plastically deformed materials. In addition, Humphreys' model of cellular microstructural stability accurately predicted the relative microstructural stability of the severely plastically deformed materials and with some modification, closely predicted the maximum grain size ratio achieved by the severely plastically deformed materials.
•ECAP and FSP both decreased the thermal microstructural stability of TRC AZ31 Mg.•An annealing parameter was used to find the thermal limits of superplastic forming.•The recrystallization mechanism was affected by the FSP conditions.•Humphreys' model accurately described the annealing behavior of the SPD materials.
In this paper, Hamiltonian Approach (HA) is applied to obtain the analytical approximate solution of the nonlinear oscillators with Rational and Irrational Elastic Terms. Periodic solutions are ...analytically verified and consequently the relationship between the natural frequency and the initial amplitude is obtained in an analytical form. A comparison of the period of oscillation and obtained solutions with the exact results illustrates that the Hamiltonian approach is very effective and quite accurate for nonlinear equations.
The method of Hamiltonian approach and the energy balance method are applied to obtain the periodic solutions of nonlinear oscillations of a punctual charge in the electric field of charged ring. The ...obtained approximate frequencies are accurate for the entire range of oscillation amplitudes. A good agreement of the approximate frequencies and periodic solutions with the exact ones are demonstrated and discussed. It is also proved that the results of the energy balance method are better than the Hamiltonian approach for solving this equation.
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