Observation of room-temperature polar skyrmions.

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 (PbTiO3)n/(SrTiO3)n suggests the presence of a complex, multi-dimensional system capable of interesting physical responses, such as chirality, negative capacitance and large piezo-electric responses1-3. 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.

Local negative permittivity and topological phase transition in polar skyrmions.

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 (PbTiO3)n/(SrTiO3)n 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 SrTiO3 and PbTiO3 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.

Characterization of skin tissue soldering using diode laser and indocyanine green: in vitro studies.

Laser tissue soldering based on protein as biological glues and other compounds can provide greater bond strength and less collateral damage. Endogenous and exogenous materials such as indocyanine green (ICG) are often added to solders to enhance light absorption. The purpose of this in vitro study was to examine the impact of different parameters of laser soldering on the thermo-physical properties of the skin. A mixture of albumin solder and ICG was prepared, and then the coated samples were irradiated by an 810 nm diode laser under different conditions. The temperature rise, number of scans (N(s)), and scan velocity (V(s)) were investigated in this study. The results showed that, at each laser irradiance (I), the tensile strength (sigma) of incisions repaired in static mode was higher than in dynamic mode and that the sigma increased with both increasing N(s) and increasing I. It is therefore important to consider the trade off between scan velocity and surface temperature for achieving an optimum operating condition.

Kinetic control of tunable multi-state switching in ferroelectric thin films.

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 PbZr0.2Ti0.8O3 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.

Antinociceptive and anti-inflammatory effects of Sambucus ebulus rhizome extract in rats.

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 LD50 of the extract was 600 mg/kg.

Antinociceptive and anti-inflammatory effects of Elaeagnus angustifolia fruit extract.

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.

Post-streptococcal uveitis.

BACKGROUND: We report additional evidence supporting the association between the occurrence of bilateral nongranulomatous uveitis and previous infection by group A streptococci--i.e., post-streptococcal syndrome. METHODS: As shown through a series of case reports, physical examination and laboratory blood analysis--including antistreptolysin O (ASO) antibody titer--were ordered due to a recent history of sore throat and presence of nongranulomatous bilateral anterior uveitis. RESULTS: Serological laboratory testing revealed elevated ASO antibody titer. The etiology of the uveitis was attributed to streptococcal infection. Bilateral uveitis responded to topical corticosteroids. Systemic antibiotic treatment was used to treat possible post-streptococcal syndrome sequelae with resolution of symptoms. CONCLUSION: Uveitis should be considered a possible manifestation of post-streptococcal syndrome. ASO antibody quantification should be included in the serologic testing performed in evaluating the cause of seemingly idiopathic bilateral nongranulomatous anterior uveitis associated with signs and symptoms that suggest previous streptococcal infection.

Application of albumin protein and indocyanine green chromophore for tissue soldering by using an IR diode laser: ex vivo and in vivo studies.

OBJECTIVE: We sought to examine the impact of different parameters of laser soldering on the thermophysical properties of the skin and to optimize these parameters for sealing a full-thickness incision in the rat skin under closed feedback control under in vivo conditions. BACKGROUND DATA: Laser tissue soldering based on protein as biologic glues and other compounds can provide greater bond strength and less collateral damage. Endogenous and exogenous materials such as indocyanine green (ICG) are often added to solders to enhance light absorption. METHODS: In ex vivo study, the temperature increase, number of scan (Ns), and scan velocity (Vs) were investigated. In ex vivo studies, four skin incisions were made over rat dorsa and were closed by using two different methods: (a) wound closure by suture and (b) closure by using an automated temperature-controlled system. An automated soldering system was developed based on a diode laser, IR detector, photodiode, digital thermocouple, and camera. The true temperature of heated tissue was determined by using a calibration software method. RESULTS: The results showed that at each laser irradiance (I), the tensile strength (σ) of incisions repaired in the static mode is higher than in the dynamic mode. It must also be noted that the tensile strength of the repaired skin wound was increased by increasing the irradiance in both static and dynamic modes. However, in parallel, an increase in the corresponding temperature was observed. The tensile strength was measured for sutured and laser-soldered tissue after 2 to 10 postoperative days. Histopathologic studies showed a better healing and less inflammatory reactions than with those caused by standard sutures after day 7. CONCLUSIONS: It is demonstrated that automated laser soldering technique can be practical provided the optothermal properties of tissue is carefully optimized.