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.

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.

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.

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.

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.

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.

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.

Ochrovirga pacifica gen. nov., sp. nov., a novel agar-lytic marine bacterium of the family Flavobacteriaceae isolated from a seaweed.

A strain designated as S85(T) was isolated from a seaweed collected from coastal area of Chuuk State in Micronesia. The strain was gram-negative, rod-shaped, and non-motile and formed yellow colonies on the SWY agar (0.2 % yeast extract and 1.5 % agar in seawater) and Marine agar 2216. The strain grew at pH 5-9 (optimum, pH 8), at 15-40 °C (optimum, 25-28 °C), and with 1-9 % (w/v) NaCl (optimum, 3 %). The phylogenetic analysis based on 16S rRNA gene sequence showed that strain S85(T) was related to Lutibacter litoralis CL-TF09(T) and Maritimimonas rapanae A31(T) with 91.4 % and with 90.5 % similarity, respectively. The dominant fatty acids were iso-C15:0, iso-C15:0 3-OH and iso-C17:0 3-OH, C16:0 3-OH and summed feature 3 (C16:1 ω7c and/or iso-C15:0 2-OH). The major isoprenoid quinone was MK-6. The DNA G+C content of the type strain was 34.6 mol %. The major polar lipids were phosphatidylethanolamine, an unknown glycolipid and two unknown polar lipids. Based on this polyphasic taxonomic data, strain S85(T) stands for a novel species of a new genus, and we propose the name Ochrovirga pacifica gen. nov., sp. nov. The type strain of O. pacifica is S85(T) (=KCCM 90106 =JCM 18327(T)).

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.

Algivirga pacifica gen. nov., sp. nov., a novel agar-degrading marine bacterium of the family Flammeovirgaceae isolated from Micronesia.

An aerobic, Gram-negative, coccoid to short rod-shaped and non-flagellated marine bacterial strain S354(T) was isolated from seawater of Micronesia. The strain was capable to degrade agar-forming slight depression into agar plate. Growth occurred at a temperature range of 12-44 °C, a pH range of 5-9, and a salinity range of 1-7 % (w/v) NaCl. Phylogenetic analyses based on 16S rRNA gene sequences suggested that S354(T) belongs to the family Flammeovirgaceae. The novel strain was most closely related to Limibacter armeniacum YM 11-185(T) with similarity of 92.5 %. The DNA G+C content was 43.8 mol%. The major fatty acids (>10 %) were iso-C15:0 and C16:1 ω5c. The predominant isoprenoid quinone was determined to be MK-7. Polar lipid profile of S354(T) consisted of phosphatidylethanolamine, unknown polar lipid, and unknown glycolipids. Based on the phenotypic, phylogenetic, biochemical, and physiological tests conducted in this study, S354(T) is proposed to represent a type strain of a novel genus and species. The 16S rRNA gene sequence of S354(T) is registered in GenBank under the accession number JQ639084. The type of strain Algivirga pacifica gen. nov., sp. nov. is S354(T) (=KCCM 90107(T)=JCM 18326(T)).

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.

Draft genome sequence of Marinobacterium stanieri S30, a strain isolated from a coastal lagoon in Chuuk state in Micronesia.

In this study, we isolated xylan-degrading bacteria from a coastal lagoon of Micronesia and identified the bacteria as Marinobacterium stanieri S30. GSFLX 454 pyrosequencing and sequence analysis of the M. stanieri S30 genome generated 4,007 predicted open reading frames (ORFs) that could be candidate genes for producing enzymes with different catalytic functions.

Identification of nickel response genes in abnormal early developments of sea urchin by differential display polymerase chain reaction.

Bioassays and biomarkers have been previously developed to assess the effects of heavy metal contaminants on the early life stages of the sea urchin. In this study, malformation in the early developmental processes was observed in sea urchin (Strongylocentrotus intermedius) larvae exposed to 10 ppm Ni for over 30 h. The most critical stage at which the triggering of nickel effects takes place is thought to be the blastula stage, which occurs after fertilization in larval development. To investigate the molecular-level responses of sea urchin exposed to heavy metal stress and to explore the differentially expressed genes that are induced or repressed by nickel, differential display polymerase chain reaction (DD-PCR) was used with sea urchin mRNAs. The malformation-related genes expressed in the early life stages of the sea urchin were cloned from larvae exposed to 10 ppm of nickel for 15 h, and accessed via DD-PCR. Sequence analysis results revealed that each of the genes evidenced high homology with EGF2, PCSK9, serine/threonine protein kinase, apolipophorin precursor protein, and MGC80921 protein/transcript variant 2. This result may prove useful in the development of novel biomarkers for the assessment of heavy metal stresses on sea urchin embryos.

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.

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.

Complete genome sequence of the agarase-producing marine bacterium strain s89, representing a novel species of the genus Alteromonas.

We report here the annotated genome sequence of the marine bacterium Alteromonas sp. S89 and the identification of six genes coding for agar-degrading enzymes. The sequenced Alteromonas sp. S89 genome is composed of a 3,864,871-bp circular chromosome that includes 3,236 complete open reading frames.

Whole-genome sequence of the xylanase-producing Mesoflavibacter zeaxanthinifaciens strain S86.

We isolated Mesoflavibacter zeaxanthinifaciens S86 as xylanase-producing bacteria from seawater sampled in Micronesia. Analysis of the M. zeaxanthinifaciens genome revealed that it contains a single circular chromosome of 3,704,661 bp with 3,249 putative open reading frames.

Complete genome sequence of strain s85, a novel member of the family Flavobacteriaceae.

An agar-degrading marine bacterium identified as a novel member of the family Flavobacteriaceae (strain S85) was isolated from seawater in Micronesia. The sequenced strain S85 genome is composed of 3,384,629 bp in a circular chromosome, which includes 2,883 complete open reading frames.

First characterisation of the populations and immune-related activities of hemocytes from two edible gastropod species, the disk abalone, Haliotis discus discus and the spiny top shell, Turbo cornutus.

The disk abalone Haliotis discus discus and the spiny top shell Turbo cornutus are edible gastropod species of high economic value, mainly in Asia. Mortality outbreaks and variations in worldwide stock abundance have been reported and suggested to be associated, at least in part, with pathogenic infections. Ecology, biology and immunology of both species are currently not well documented. The characterisation of the immune systems of these species is necessary to further assess the responses of H. discus discus and T. cornutus to environmental, chemical and disease stresses. In the present study, we investigated the morphology and immune-related activities of hemocytes in both species using light microscopy and flow cytometry. Two types of hemocytes were identified in the disk abalone hemolymph, blast-like cells and hyalinocytes; whereas four main hemocyte types were distinguished in the spiny top shell, blast-like cells, type I and II hyalinocytes, and granulocytes. Flow cytometric analysis also revealed differences between cell types in immune-related activities. Three subsets of hemocytes, defined by differing lysosomal characteristics, were observed in the hemolymph of the spiny top shell, and only one in the disk abalone. Phagocytic activity was higher in H. discus discus hemocytes than in T. cornutus hemocytes, and the kinetics of PMA-stimulated oxidative activity was different between hemocytes of the disk abalone and the spiny top shell. Finally our results suggest for the first time a predominant mitochondrial origin of oxidative activity in gastropod hemocytes.