Complex topological configurations are fertile ground for exploring emergent phenomena and exotic phases in condensed-matter physics. For example, the recent discovery of polarization vortices and ...their associated complex-phase coexistence and response under applied electric fields in superlattices of (PbTiO
)
/(SrTiO
)
suggests the presence of a complex, multi-dimensional system capable of interesting physical responses, such as chirality, negative capacitance and large piezo-electric responses
. Here, by varying epitaxial constraints, we discover room-temperature polar-skyrmion bubbles in a lead titanate layer confined by strontium titanate layers, which are imaged by atomic-resolution scanning transmission electron microscopy. Phase-field modelling and second-principles calculations reveal that the polar-skyrmion bubbles have a skyrmion number of +1, and resonant soft-X-ray diffraction experiments show circular dichroism, confirming chirality. Such nanometre-scale polar-skyrmion bubbles are the electric analogues of magnetic skyrmions, and could contribute to the advancement of ferroelectrics towards functionalities incorporating emergent chirality and electrically controllable negative capacitance.
Topological solitons such as magnetic skyrmions have drawn attention as stable quasi-particle-like objects. The recent discovery of polar vortices and skyrmions in ferroelectric oxide superlattices ...has opened up new vistas to explore topology, emergent phenomena and approaches for manipulating such features with electric fields. Using macroscopic dielectric measurements, coupled with direct scanning convergent beam electron diffraction imaging on the atomic scale, theoretical phase-field simulations and second-principles calculations, we demonstrate that polar skyrmions in (PbTiO
)
/(SrTiO
)
superlattices are distinguished by a sheath of negative permittivity at the periphery of each skyrmion. This enhances the effective dielectric permittivity compared with the individual SrTiO
and PbTiO
layers. Moreover, the response of these topologically protected structures to electric field and temperature shows a reversible phase transition from the skyrmion state to a trivial uniform ferroelectric state, accompanied by large tunability of the dielectric permittivity. Pulsed switching measurements show a time-dependent evolution and recovery of the skyrmion state (and macroscopic dielectric response). The interrelationship between topological and dielectric properties presents an opportunity to simultaneously manipulate both by a single, and easily controlled, stimulus, the applied electric field.
Deterministic creation of multiple ferroelectric states with intermediate values of polarization remains challenging due to the inherent bi-stability of ferroelectric switching. Here we show the ...ability to select any desired intermediate polarization value via control of the switching pathway in (111)-oriented PbZr
Ti
O
films. Such switching phenomena are driven by kinetic control of the volume fraction of two geometrically different domain structures which are generated by two distinct switching pathways: one direct, bipolar-like switching and another multi-step switching process with the formation of a thermodynamically-stable intermediate twinning structure. Such control of switching pathways is enabled by the competition between elastic and electrostatic energies which favors different types of ferroelastic switching that can occur. Overall, our work demonstrates an alternative approach that transcends the inherent bi-stability of ferroelectrics to create non-volatile, deterministic, and repeatedly obtainable multi-state polarization without compromising other important properties, and holds promise for non-volatile multi-state functional applications.
AbstractHighway agencies around the world are looking into adopting cost-effective and accurate methods for assessing the condition of their infrastructure network. In such an effort, agencies ...explore alternative testing methods that can be used for assessing (1) as-built construction quality, and (2) in-service condition of bridges. Such information is crucial in bridge management systems (BMS) for managing the vast network of bridges and making wise and cost-effective decisions on maintenance and rehabilitation. Following the catastrophic collapse of the Morandi Bridge in Italy in 2018, bridge inspections were intensified for those in the lower condition category, like the one investigated herein. In this study, an old prestressed bridge deck in poor condition was surveyed with ground-penetrating radar (GPR). The bridge is located in the southeastern portion of Sicily, Italy. It was the objective of the study to assess the current conditions in terms of (1) asphalt overlay thickness, and (2) depth and potential deterioration of the reinforcement. The methodology and analysis used in this study confirmed the ability and reliability of GPR in assessing such conditions and thus could be used elsewhere to carry out such inspections.
Manufacturing processes are usually energy intensive, contributing to the global carbon dioxide emissions. Deep Drawing is one of the most common types of sheet metal forming processes with great ...potential for energy efficiency improvement. In this paper, the optimised combination of molybdenum disulphide (MoS2) and graphite is proposed as a solid lubricant to reduce the punching force and energy consumption of deep drawing process. Different mixtures of MoS2 and graphite are prepared and their tribological performance are measured using experimental tests on tribometer. In order to investigate the friction reduction rate in deep drawing process, finite element simulation of the drawing process is performed. Results show that friction reduction using proposed combination of lubricants has significant effect on punching force and would provide greater process efficiency.
► Electric field distribution in microwave heating of materials is simulated. ► Finite-difference time-domain (FDTD) is used as simulation tool. ► The simulations are validated by comparing the ...experimental and simulated ΔT/Δt. ► Simulation results found to be in good agreement with experimental measurements.
Microwave assisted preparation has been shown to improve the performance of hematite photoelectrodes for solar driven water splitting. To understand the microwave heating process further, the distribution of the electromagnetic (EM) fields within the material is analysed using finite-difference time-domain (FDTD) EM software. The rate of the increase in temperature is calculated from the simulated EM field distributions. In order to validate the simulation results, the calculated temperatures were compared with the experimental temperatures obtained using a thermal imaging camera.
In this study, probable antinociceptive and anti-inflammatory effects of
Elaeagnus angustifolia fruit components, were evaluated. For evaluation of antinociceptive effects, the chronic (formalin ...test) and acute (tail-flick) pain models of rats were used. For the anti-inflammatory effects, the paw inflammation model was used through subcutaneous injection of 5% formalin to the paw of male rats. Water extracts of the fruit and its components in the single dose were assessed through comparison with the antinociceptive and anti-inflammatory effects of sodium salicylate (SS) as a positive control. Administration of 300 mg/kg of SS (i.p.) had no effect on tail flick latency, while 1000 mg/kg of total (i.p. and p.o.) and endocarp (i.p.) extract, increased this latency (
P<0.01,
P<0.001, respectively), which was not reversed by naloxone (2 mg/kg). In the formalin test, SS (300 mg/kg, i.p.) and the extract (1000 mg/kg, p.o.) alleviated the animals nociception in the second phase, while in the first phase they were not effective. The total and endocarp extracts (1000 mg/kg, i.p.) showed a significant effect on both phases (
P<0.01,
P<0.001, respectively) which was also not reversed by naloxone (2 mg/kg, i.p.). In the acute anti-inflammatory test, the total extract and the aqueous extract of individual fruit components showed a significant effect (
P<0.001). This anti-inflammatory effect was not significant compared with the anti-inflammatory effect of SS. Because of the extract effect on the tail-flick latency and both phases of the formalin test, the site of its analgesic action is probably central, and the mechanism of antinociceptive action of the extract are not related to the opioid system. Our phytochemical studies indicated that aqueous extract of
E. angustifolia fruit contains flavonoids, terpenoids and cardiac glycosides.
In this study, a new, simple, and reproducible high-performance liquid chromatographic method was developed for the determination of pioglitazone in human plasma. After liquid—liquid extraction with ...diethylether, samples were quantitated on a Nova- Pak C8 column using a mixture of acetonitrile—140mM K2HPO4 (40:60, v/v, pH = 4.45) as mobile phase with UV detection at 269 nm. The flow rate was set at 1.4 mL/min. Ethylparaben was used as internal standard and the total run time of analysis was approximately 7 min. The method was linear over the range of 25–1500 ng/mL of pioglitazone in plasma (r2 > 0.999). The withinand between-day precision values were in the range of 2.4–6.8%. The limit of quantitation of the method was 25 ng/mL. The method was successfully used to study the pharmacokinetics of pioglitazone in healthy volunteers.
In this study we used the chronic (formalin test) and acute (tail flick) pain models of rats for evaluation of probable analgesic and anti-inflammatory effect of
Sambucus ebulus (Se) rhizome extract. ...Sodium salicylate (SS) was used as a positive control. A total of 300 mg/kg of SS (i.p.) had no effect on tail flick latency, while 100 and 200 mg/kg i.p. of extract increased this latency (
P<0.01 and
P<0.001, respectively). In formalin test, SS (300 mg/kg i.p.) and extract (100 mg/kg i.p.) alleviated the animals’ nociception in the second phases, while in the first phase, only the extract caused an anti nociceptive effect (
P<0.05). A total of 200 mg/kg of the extract showed a significant effect on both phases (
P<0.001), which was not reversed by naloxone (2 mg/kg i.p.). On the other hand in the acute anti-inflammatory test, the plant extract (200 mg/kg i.p.) showed a significant effect, (e.g. SS
P<0.01) and was not reversed by naloxone (2 mg/kg i.p.).Therefore, it seems that the mechanism of the antinociceptive and anti-inflammatory actions of extract are not related to the opioid system, of course the comparison of chronic administration of SS and Se showed a rapid onset of action for Se rather than SS, and because of its effect on tail flick latency and both phases of formalin test, the site of its analgesic action is probably central. Our phytochemical studies indicate that methanol extract of plant rhizome contains flavonoids, steroids, glycosides and tannins. The LD
50 of the extract was 600 mg/kg.
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