Three-Dimensional Visualization of Oxygen-Vacancy Migration and Redistribution in Ca-Substituted BiFeO3.

Ionic movement has received renewed attention in recent years, particularly in the field of ferroelectric oxides, since it is intrinsically linked to chemical reaction kinetics and ferroelectric phase stability. The associated surface electrochemical processes coupled local ionic transport with an applied electric bias, exhibiting very high ionic mobility at room temperature based on a simple electrostatics scenario. However, few studies have focused on the applied-polarity dependence of ionic migration with directly visualized maps. Here, we use incorporated experiments of conductive scanning probe microscopy and time-of-flight secondary ion mass spectrometry to investigate oxygen ionic migration and cation redistribution in ionic oxides. The local concentrations of oxygen vacancies and other cation species are visualized by three-dimensional mappings, indicating that oxygen vacancies tend to be ejected toward the surface. An accumulation of oxygen vacancies and ionic redistribution strongly depend on tip polarity, thus corroborating their role in the electrochemical process. This work illustrates the interplay between ionic kinetics and electric switching.

Observation of Hidden Polar Phases and Flux Closure Domain Topology in Bi2WO6 Thin Films.

Topological textures of ferroelectric polarizations have promise as alternative devices for future information technology. A polarization rotation inevitably deviates from the stable orientation in axial ferroelectrics, but local energy losses compromise the global symmetry, resulting in a distorted shape of the topological vortex or inhibiting the vortex. Easy planar isotropy helps to promote rotating structures and, accordingly, to facilitate access to nontrivial textures. Here, we investigate the domain structure of an epitaxial thin film of bismuth tungsten oxide (Bi2WO6) grown on a (001) SrTiO3 substrate. By using angle-resolved piezoresponse force microscopy and scanning transmission electron microscopy, we find the existence of a hidden phase with ⟨100⟩-oriented ferroelectric polarizations in the middle of the four variant ⟨110⟩-oriented polarization domains, which assists in the formation of flux closure domains. The results suggest that this material is one step closer to becoming an isotropic two-dimensional polar material.

Reproductive condition of the black-lip pearl oyster Pinctada margaritifera during the lunar phase.

This study analyzed the relationship between the lunar phase and the reproductive cycle of Pinctada margaritifera inhabiting Weno Island, Chuuk Lagoon, Micronesia. We measured indicators of maturity (gonadosomatic index [GSI] and sexual maturation-related genes) and investigated changes in the gonadal maturity stages (GMS) of P. margaritifera over lunar cycle. GSI was higher around the full moon. GMS of P. margaritifera were classified as the early gametogenesis stage, ripe and spawning stage, and spent and degenerating stage. A large percentage of oysters was observed in the ripe and spawning stage at the first quarter moon in female and the full moon in male as well as in the spent and degenerating stages at the third quarter moon in both sexes. In addition, the expression of doublesex- and mab-3-related transcription factor 2 (DMRT2) in the male P. margaritifera black-lip pearl oyster was the highest during the full and third quarter moon phases, whereas no difference in expression was observed with the lunar phase in females. In contrast, the expression of vitellogenin (VTG) was the highest in female P. margaritifera during the first and third quarters. No difference in expression was observed according to the lunar phase in males. The results suggest that the lunar phase directly affects the expression of sexually mature gonads in P. margaritifera black-lip pearl oyster.

Configurable Crack Wall Conduction in a Complex Oxide.

Mobile defects in solid-state materials play a significant role in memristive switching and energy-efficient neuromorphic computation. Techniques for confining and manipulating point defects may have great promise for low-dimensional memories. Here, we report the spontaneous gathering of oxygen vacancies at strain-relaxed crack walls in SrTiO3 thin films grown on DyScO3 substrates as a result of flexoelectricity. We found that electronic conductance at the crack walls was enhanced compared to the crack-free region, by a factor of 104. A switchable asymmetric diode-like feature was also observed, and the mechanism is discussed, based on the electrical migration of oxygen vacancy donors in the background of Sr-deficient acceptors forming n+-n or n-n+ junctions. By tracing the temporal relaxations of surface potential and lattice expansion of a formed region, we determine the diffusivity of mobile defects in crack walls to be 1.4 × 10-16 cm2/s, which is consistent with oxygen vacancy kinetics.

Critical ionic transport across an oxygen-vacancy ordering transition.

Phase transition points can be used to critically reduce the ionic migration activation energy, which is important for realizing high-performance electrolytes at low temperatures. Here, we demonstrate a route toward low-temperature thermionic conduction in solids, by exploiting the critically lowered activation energy associated with oxygen transport in Ca-substituted bismuth ferrite (Bi1-xCaxFeO3-δ) films. Our demonstration relies on the finding that a compositional phase transition occurs by varying Ca doping ratio across xCa ≃ 0.45 between two structural phases with oxygen-vacancy channel ordering along <100> or <110> crystal axis, respectively. Regardless of the atomic-scale irregularity in defect distribution at the doping ratio, the activation energy is largely suppressed to 0.43 eV, compared with ~0.9 eV measured in otherwise rigid phases. From first-principles calculations, we propose that the effective short-range attraction between two positively charged oxygen vacancies sharing lattice deformation not only forms the defect orders but also suppresses the activation energy through concerted hopping.

The effects of low pH and high water temperature on oxidative stress and cell damage in juvenile olive flounder Paralichthys olivaceus: comparison of single and combined environmental conditions.

The use of fossil fuels by anthropogenic activities causes ocean acidification and warming, and these changes in the marine environment can negatively affect the metabolism, growth, and survival of fish. In the present study, we evaluated the ability of olive flounder Paralichthys olivaceus to cope with future marine environmental changes by investigating the oxidative stress (cortisol, HSP70), antioxidant enzyme (superoxide dismutase; SOD, catalase; CAT) activity, and apoptosis (caspase-3) after exposure to control conditions (20 °C and pH 8.1), warming (30 °C) and acidification (pH 7.5) conditions, and a combined environment (30 °C and pH 7.5) for 28 days. Under warming conditions, increased oxidative stress, activity of antioxidant enzymes, and apoptosis were observed. Acidifying conditions showed negative effects at the beginning of exposure, but these effects were offset over time. Even in a combined environment of acidification and warming, negative effects were seen only at the beginning of exposure and were not sustained. In conclusion, the effects of acidification on oxidative stress, antioxidant response, and apoptosis in P. olivaceus did not exceed the effects of warming. These results suggest that P. olivaceus can cope with the predicted future acidifying environment.

Effect of low pH and salinity conditions on the antioxidant response and hepatocyte damage in juvenile olive flounder Paralichthys olivaceus.

Climate change due to increasing CO2 emissions results in the increase in water temperatures, which is accompanied by the decrease in pH and salinity levels of the ocean. Ocean acidification reflects the gradual pH reduction due to changes in the carbon chemistry, which is caused by the increase in anthropogenic CO2 emissions. The subsequent changes in the water temperatures and carbon chemistry of the oceans affect the survival and distribution of aquatic animals. In this study, we analyzed the levels of cortisol, superoxide dismutase, catalase, and caspase-3 in the plasma of juvenile olive flounder Paralichthys olivaceus under combined hyposalinity and acidification. To evaluate the physiological response to these changes, the superoxide dismutase activity and apoptosis were analyzed in the liver cells. Hyposalinity caused oxidative stress and cell damage, while also activating the antioxidant system. Environmental acidification affected the stress response and antioxidant mechanism of P. olivaceus in the early stage of acclimation but did not appear to exceed hyposalinity stress. These findings suggest that a hyposaline environment may be a stronger environmental stressor than an acidifying environment for P. olivaceus, and will help understand the capacity of P. olivaceus to cope with expected future ocean acidification.

Orbital Order Melting at Reduced Dimensions.

The orbital degree of freedom, strongly coupled with the lattice and spin, is an important factor when designing correlated functions. Whether the long-range orbital order is stable at reduced dimensions and, if not, what the critical thickness is remains a tantalizing question. Here, we report the melting of orbital ordering, observed by controlling the dimensionality of the canonical eg1 orbital system LaMnO3. Epitaxial films are synthesized with vertically aligned orbital ordering planes on an orthorhombic substrate, so that reducing film thickness changes the two-dimensional planes into quasi-one-dimensional nanostrips. The orbital order appears to be suppressed below the critical thickness of about six unit cells by changing the characteristic phonon modes and making the Mn d orbital more isotropic. Density functional calculations reveal that the electronic energy instability induced by bandwidth narrowing via the dimensional crossover and the interfacial effect causes the absence of orbital order in the ultrathin thickness.

Exogenous cortisol and red light irradiation affect reproductive parameters in the goldfish Carassius auratus.

Reproductive hormones play essential roles in the control of reproduction and gonadal maturation in fish. The purpose of this study was to determine the effects of cortisol administration (10 µg/g or 50 µg/g) or red light irradiation at two intensities (0.5 W/m2 or 1.0 W/m2) on the reproductive hormones in goldfish (Carassius auratus). The effects of different treatments were analyzed by determining the mRNA expression levels of gonadotropin-inhibitory hormone receptor (GnIH-R), chicken gonadotropin-releasing hormone (cGnRH-II), salmon GnRH (sGnRH), FSHß, LHß, and plasma testosterone and the level of 17ß-estradiol for 48 h. Additionally, by double immunofluorescence staining, we detected the expression of both GnIH and GnRH in the diencephalons of goldfish brains. The mRNA expression of GnIH-R was significantly higher in the cortisol group and red light-irradiated group from 3 to 48 h than in the control group. Additionally, the mRNA levels of cGnRH-II, sGnRH, FSHß, LHß, testosterone, and 17ß-estradiol were significantly lower in the cortisol group than in the other groups from 3 to 48 h. These results indicated that both cortisol and red light-emitting diode (LED) light increased GnIH expression and inhibited GnRH expression. In particular, red light irradiation suppressed reproductive responses as much as the cortisol treatment at 48 h. Thus, it could be an alternative method for suppressing reproductive responses in future aquacultures.

Harnessing the topotactic transition in oxide heterostructures for fast and high-efficiency electrochromic applications.

Mobile oxygen vacancies offer a substantial potential to broaden the range of optical functionalities of complex transition metal oxides due to their high mobility and the interplay with correlated electrons. Here, we report a large electro-absorptive optical variation induced by a topotactic transition via oxygen vacancy fluidic motion in calcium ferrite with large-scale uniformity. The coloration efficiency reaches ~80 cm2 C-1, which means that a 300-nm-thick layer blocks 99% of transmitted visible light by the electrical switching. By tracking the color propagation, oxygen vacancy mobility can be estimated to be 10-8 cm2 s-1 V-1 near 300°C, which is a giant value attained due to the mosaic pseudomonoclinic film stabilized on LaAlO3 substrate. First-principles calculations reveal that the defect density modulation associated with hole charge injection causes a prominent change in electron correlation, resulting in the light absorption modulation. Our findings will pave the pathway for practical topotactic electrochromic applications.

Exposure of bay scallop Argopecten irradians to micro-polystyrene: Bioaccumulation and toxicity.

Marine microplastic pollution poses a threat to aquatic organisms, including bivalves. In this study, we investigated the accumulation of microplastics and their elicited antioxidant stress response in the bay scallop Argopecten irradians. Scallops were exposed to 1 µm diameter micro-polystyrene (MP) beads at 10, 100, and 1000 beads/mL concentrations for a 7 day period. Bead presence in the digestive diverticula and defense responses in the digestive diverticula and hemolymph were measured at 1, 3, 5, and 7 days. The activity and expression of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) and H2O2 in the digestive diverticula and/or hemolymph of scallops increased with microplastic concentration and exposure duration. These results suggest that microplastics can accumulate in the digestive diverticula of A. irradians, and that exposure to microplastics induces oxidative stress in bivalves. It is likely that exposure to high concentrations of micro- or nano-sized plastic particles could potentially have adverse effects in bivalves.

Physiological and oxidative stress response of goldfish Carassius auratus induced by a light dimming system.

Light is an essential factor for organisms and affects the endocrine and stress regulation of fish in nature. However, sudden changes in light and dark conditions in artificial environments can negatively impact fish. In the present study, to evaluate the physiological and oxidative stress responses of goldfish (Carassius auratus) exposed to two different light conditions, sudden light changes and slowly dimming light changes for 24 h, we analyzed the mRNA expression and activity of stress indicators [corticotropin-releasing hormone (CRH) and pro-opiomelanocortin (POMC)], levels of plasma cortisol and glucose, mRNA expression of glucocorticoid receptor (GR), and activity of plasma oxidative stress indicators (superoxide dismutase and catalase). Consequently, the mRNA expressions and activities of CRH and POMC, plasma levels of cortisol and glucose, and mRNA expression of GR were found to be significantly increased during the light changes, particularly in the control group. Additionally, plasma levels of cortisol and glucose in the control group were significantly higher than those in the dimming group during the light changes. However, no significant differences in mRNA expression levels and activities of antioxidant enzymes both in the control and dimming groups were observed. These results indicate that dimming light induces less stress than sudden changes in light.

Protective effects of Fructus sophorae extract on collagen-induced arthritis in BALB/c mice.

Styphnolobium japonicum (L.) is utilized in Korean medicine for the treatment of various inflammatory diseases. The aim of the present study was to explore the effects of Fructus sophorae extract (FSE) isolated from the dried ripe fruit of S. japonicum (L.) on the development of type II collagen-induced arthritis (CIA) in BALB/c mice. The CIA mice were orally administered FSE or saline daily for 2 weeks. The incidence and severity of disease and the inflammatory response in the serum and the joint tissues were assessed. Macroscopic and histological investigation indicated that FSE protected against CIA development. FSE was associated with a significant reduction in the levels of total immunoglobulin G2a and proinflammatory cytokines and mediators in the serum. In addition, FSE suppressed the gene expression levels of proinflammatory cytokines and mediators, the mediator of osteoclastic bone remodeling, the receptor activator of nuclear factor κ-B ligand and matrix metalloproteinases in the joint tissues. The present results suggest that FSE may protect against inflammation and bone damage, and would be a valuable candidate for further investigation as a novel anti-arthritic agent.

Assessment of the fitness of the mussel Mytilus galloprovincialis two years after the Hebei Spirit oil spill.

In December 2007, >150km of the West coast of Korea were heavily polluted by crude oil leaked from the oil tanker Hebei Spirit, leading to mass mortality of bivalve mollusks on the intertidal areas. Two years after, mussels Mytilus galloprovincialis were collected from two impacted sites to investigate sub-lethal effects of the oil spill. Tissue content in polycyclic aromatic hydrocarbons (PAHs), hemocyte parameters, reproductive status and energetic reserves were analyzed. PAHs in tissues of mussels as well as hemocyte parameters were not different between impacted and control sites. Energetic reserves were altered in mussels from the impacted sites. Glycogen content remained low at polluted sites, whatever the season. Two years after the Hebei Spirit oil spill, mussels then presented altered energetic metabolism. Further investigations are thus warranted to monitor the sustainability of mussel populations on the oil spilled West coast of Korea.

Substantial changes in hemocyte parameters of Manila clam Ruditapes philippinarum two years after the Hebei Spirit oil spill off the west coast of Korea.

Two years after the Hebei Spirit oil spill occurred off the west coast of Korea, we determined sub-lethal effects of the spilled oil on hemocyte parameters of Ruditapes philippinarum in the damaged areas. Clams in the spilled sites displayed unusually high proportion of granulocytes, which may result in higher phagocytosis capacity and reactive oxygen species production. Hemocytes in clams from the polluted sites also displayed less DNA damage and mortality than in the control site, possibly due to a faster phagocytosis of the impaired cells. Glycogen, the major energetic reserve, was depleted in clams from the spilled sites, potentially due to energetic consumption for maintenance of a large pool of granulocytes, detoxification processes and oxidative stress. Modified hemocyte parameters in clams in the spilled area, may reflect sub-lethal physiological stresses caused by the residual oils in the sediment, in conjunction with environmental modifications such as food availability and pathogens pattern.

Variation of Spirulina maxima biomass production in different depths of urea-used culture medium.

Fewer studies have assessed the outdoor cultivation of Spirulina maxima compared with S. platensis, although the protein content of S. maxima is higher than S. platensis. Spirulina growth medium requires an increased amount of NaHCO3, Na2CO3, and NaNO3, which increases the production cost. Therefore, the current study used a low-cost but high-efficiency biomass production medium (Medium M-19) after testing 33 different media. The medium depth of 25 cm (group A) was sub-divided into A1 (50% cover with a black curtain (PolyMax, 12 oz ultra-blackout), A2 (25% cover), and A3 (no cover). Similarly the medium depths of 30 and 35 cm were categorized as groups B (B1, B2, and B3) and C (C1, C2, and C3), respectively, and the effects of depth and surface light availability on growth and biomass production were assessed. The highest biomass production was 2.05 g L-1 in group A2, which was significantly higher (p < 0.05) than that in all other groups and sub-groups. Spirulina maxima died in B1 and C1 on the fifth day of culture. The biochemical composition of the biomass obtained from A2 cultures, including protein, carbohydrate, lipid, moisture, and ash, was 56.59%, 14.42%, 0.94%, 5.03%, and 23.02%, respectively. Therefore, S. maxima could be grown outdoors with the highest efficiency in urea-enriched medium at a 25-cm medium depth with 25% surface cover or uncovered.

Variation of Spirulina maxima biomass production in different depths of urea-used culture medium

Fewer studies have assessed the outdoor cultivation of Spirulina maxima compared with S. platensis, although the protein content of S. maxima is higher than S. platensis. Spirulina growth medium requires an increased amount of NaHCO3, Na2CO3, and NaNO3, which increases the production cost. Therefore, the current study used a low-cost but high-efficiency biomass production medium (Medium M-19) after testing 33 different media. The medium depth of 25 cm (group A) was sub-divided into A1 (50% cover with a black curtain (PolyMax, 12 oz ultra-blackout), A2 (25% cover), and A3 (no cover). Similarly the medium depths of 30 and 35 cm were categorized as groups B (B1, B2, and B3) and C (C1, C2, and C3), respectively, and the effects of depth and surface light availability on growth and biomass production were assessed. The highest biomass production was 2.05 g L-1 in group A2, which was significantly higher (p < 0.05) than that in all other groups and sub-groups. Spirulina maxima died in B1 and C1 on the fifth day of culture. The biochemical composition of the biomass obtained from A2 cultures, including protein, carbohydrate, lipid, moisture, and ash, was 56.59%, 14.42%, 0.94%, 5.03%, and 23.02%, respectively. Therefore, S. maxima could be grown outdoors with the highest efficiency in urea-enriched medium at a 25-cm medium depth with 25% surface cover or uncovered.

Stable isotope analysis of a newly established macrofaunal food web 1.5 years after the Hebei Spirit oil spill.

We examined trophic relationships in a newly established community 1.5 years after the Hebei Spirit oil spill on the west coast of Korea. Carbon and nitrogen stable isotope ratios in consumers and their potential food sources were compared between the oil-spill site and reference site, located 13.5 km from the oil-spill spot. The isotopic mixing model and a novel circular statistics rejected the influx of petrogenic carbon into the community and identified spatial consistencies such as the high contributions of microphytobenthos, food-chain length, and the isotopic niche of each feeding guild between sites. We suggested that high level of trophic plasticity and the prevalence of omnivory of consumers may promote the robustness of food web against the oil contamination. Furthermore, we highlighted the need of holistic approaches including different functional groups to quantify changes in the food web structure and assess the influence of different perturbations including oil spill.

Kisspeptin regulates the somatic growth-related factors of the cinnamon clownfish Amphiprion melanopus.

This study aimed to test the effects of kisspeptin (Kiss) on somatic growth in the cinnamon clownfish Amphiprion melanopus. We investigated the effects of Kiss treatment on the growth by measuring the mRNA expressions of the growth hormone (GH), insulin-like growth hormone factor (IGF-I), somatolactin (SL), and melatonin receptor (MT). The expression levels of GH and SL of the pituitary gland and IGF-I of the liver increased after Kiss treatment (in vivo and in vitro). In addition, the MT mRNA expression increased in the pituitary gland and brain after Kiss treatment (in vivo and in vitro). These results support the hypothesis that Kiss directly regulates the somatic growth-related factors, such as GH, SL, and MT, and IGF-I in the cinnamon clownfish. Further, injection of Kiss resulted in significantly higher levels of plasma melatonin than that in the control. We, therefore, conclude that Kiss plays a role in modulating growth and artificially induced rapid growth in cinnamon clownfish.