Large Structural Domains Research Articles

Giant energy storage density, high efficiency and excellent stability achieved in lead-free KNN-based ceramic via a composition optimization strategy

The (1-x)K0.5Na0.5NbO3-xBi(Zn2/3Sb1/3)O3 ceramics, abbreviated as (1-x)KNN-xBZS with x values of 0.05, 0.10, 0.15, and 0.20, were prepared via solid-state reaction technique. Their structural and electrical characteristics, including dielectric and ferroelectric characteristics, were systematically examined. The achievement of an optimized phase transition-field and the broadening of the bandgap in the 0.85KNN-0.15BZS ceramics contribute to the delay of polarization and improvement in the breakdown field strength. Dielectric measurements indicate that the introduction of BZS disrupts the original large domain structure of KNN ceramics, giving rise to small domains and polar nano regions (PNRs). Specifically, the 0.85KNN-0.15BZS ceramic exhibits exceptional energy storage density (Wrec = 5.90 J/cm3) and an ultra-high energy efficiency (η = 79.9 %) at an applied electric field of 570 kV/cm. Furthermore, this ceramic displays excellent frequency stability in the range of 1–100 Hz and temperature stability between 30 and 150 °C. The remarkable energy storage properties of (1-x)KNN-xBZS ceramics position them as highly promising materials for future pulse power capacitors and various energy storage applications.

Experimental study on pre-hydrogenation of catalytic slurry oil and co-carbonization of middle distillate and high boiling point distillate

A catalytic slurry oil (SO) was treated by moderate pre-hydrotreating, and the structural compositions, the thermal stability, the distillate oil yield, and the coking behavior of SO before and after hydrotreating were analyzed. The carbonization performance as well as the co-carbonization performance of the middle distillate (350–500 °C) and the high boiling point distillate (500–550 °C) derived from the hydrogenated SO (HSO) were investigated. The results show that the content of naphthenes and hydrogenated aromatics of HSO increases, while the olefin content decreases, and the olefinic hydrogen content of HSO decreases from 2.71% to 0.97%. Thus, the thermal stability of HSO is fundamentally improved. Additionally, compared with SO, the yields of the middle distillate and the high boiling point distillate of HSO increased by 25.8% and 23.1%, respectively. More importantly, there is no significant coke formation during distillation of HSO. The carbonization experimental results show that the anisotropic textural structure of the coke obtained from the middle distillate derived from HSO is the large flow domain structure, and the coke has the lowest coefficient of thermal expansion (CTE) value of 2.25×10−6 °C−1. The carbonization performance of the high boiling point distillate derived from HSO is poor, while the co-carbonization with the middle distillate significantly improves the carbonization performance of the high boiling point distillate. The anisotropic textural structure of the coke derived from carbonization of combined fraction is the large flow domain structure and the CTE value is less than 2.30×10−6 °C−1, when the mass ratio of aromatic fraction to middle fraction is not higher than 2:1.

Unique recognition of the microalgal plastidial glycerol-3-phosphate acyltransferase for acyl-ACP

Plastidial glycerol-3-phosphate acyltransferases (GPATs) catalyze acyl-ACP and glycerol-3-phosphate to synthesize lysophosphatidic acid in vivo, which initiates the formation of various glycerolipids. Although the physiological substrates of plastidial GPATs are acyl-ACPs, acyl-CoAs have been commonly studied on the GPATs in vitro. However, little is known whether there are any distinct features of GPATs towards acyl-ACP and acyl-CoA. In this study, the results showed that the microalgal plastidial GPATs preferred acyl-ACP to acyl-CoA, while surprisingly, the plant-derived plastidial GPATs showed no obvious preferences towards these two acyl carriers. The key residues responsible for the distinct feature of microalgal plastidial GPATs were compared with plant-derived plastidial GPATs in their efficiency to catalyze acyl-ACP and acyl-CoA. Microalgal plastidial GPATs uniquely recognized acyl-ACP as compared to with other acyltransferases. The structure of the acyltransferases-ACP complex highlights only the involvement of the large structural domain in ACP in microalgal plastidial GPAT while in the other acyltransferases, both large and small structural domains were involved in the recognition process. The interaction sites on the plastidial GPAT from the green alga Myrmecia incisa (MiGPAT1) with ACP turned out to be K204, R212 and R266. A unique recognition between the microalgal plastidial GPAT and ACP was elucidated.

Walker-like domain wall breakdown in layered antiferromagnets driven by staggered spin\u2013orbit fields

Within linear continuum theory, no magnetic texture can propagate faster than the maximum group velocity of the spin waves. Here, by atomistic spin dynamics simulations and supported by analytical theory, we report that a strongly non-linear transient regime due to the appearance of additional magnetic textures results in the breaking of the Lorentz translational invariance. This dynamical regime is akin to domain wall Walker-breakdown in ferromagnets and involves the nucleation of an antiferromagnetic domain wall pair. While one of the nucleated domain walls is accelerated beyond the magnonic limit, the remaining pair remains static. Under large spin–orbit fields, a cascade of multiple generation and recombination of domain walls are obtained. This result may clarify recent experiments on current pulse induced shattering of large domain structures into small fragmented domains and the subsequent slow recreation of large-scale domains.

Alternative conformations and motions adopted by 30S ribosomal subunits visualized by cryo-electron microscopy.

It is only after recent advances in cryo-electron microscopy that it is now possible to describe at high-resolution structures of large macromolecules that do not crystalize. Purified 30S subunits interconvert between an “active” and “inactive” conformation. The active conformation was described by crystallography in the early 2000s, but the structure of the inactive form at high resolution remains unsolved. Here we used cryo-electron microscopy to obtain the structure of the inactive conformation of the 30S subunit to 3.6 Å resolution and study its motions. In the inactive conformation, an alternative base-pairing of three nucleotides causes the region of helix 44, forming the decoding center to adopt an unlatched conformation and the 3′ end of the 16S rRNA positions similarly to the mRNA during translation. Incubation of inactive 30S subunits at 42°C reverts these structural changes. The air–water interface to which ribosome subunits are exposed during sample preparation also peel off some ribosomal proteins. Extended exposures to low magnesium concentrations make the ribosomal particles more susceptible to the air–water interface causing the unfolding of large rRNA structural domains. Overall, this study provides new insights about the conformational space explored by the 30S ribosomal subunit when the ribosomal particles are free in solution.

Mesophase pitch production from FCC slurry oil: Optimizing compositions and properties of the carbonization feedstock by slurry-bed hydrotreating coupled with distillation

Slurry-bed hydrotreating coupled with distillation may optimize the compositions and properties of heavy oils, including improving their hydrogen-donating ability of heavy oils. The effects of slurry-bed hydrotreating coupled with distillation on the compositions and properties of FCC slurry oil were determined by various analytical methods. 1H NMR was used to characterize and determine the hydrogen-donating ability of FCC slurry oil, and the structure of mesophase pitches formed by carbonization of FCC slurry oil were characterized by polarizing microscope, softening point and X-ray diffraction method. The results showed that slurry-bed hydrotreating obviously prevents FCC slurry oil from coking behavior during the distillation process, and overall compositions and properties of FCC slurry oil after optimization meet the requirements for producing mesophase pitch. Most importantly, the hydrogen-donating ability of FCC slurry was drastically increased from 0.392 (mg-H/g-Oil) to 1.917 (mg-H/g-Oil). In turn, in contrast with the raw FCC slurry oil, the slurry oil after the slurry-bed hydrotreating coupled with distillation easily formed mesophase pitch with a large flow domain structure, low softening point, and ordered microcrystal structure through carbonization. Thus, the purpose of preparing high-quality mesophase pitch was achieved.

Effects of Inductive Condensation on Mesophase Development during Aromatic-Rich Oil Carbonization

A novel method was discussed for the preparation of petroleum-based mesophase pitch with a large domain structure and an ordered microcrystal structure. A condensation pitch with a certain amount o...

Monitoring Structural Transitions in RNA Polymerase using Single Molecule FRET

Structural transitions in protein machines play a central role in their function. Such motions can be studied in great detail and in real-time using the method of single-molecule FRET (smFRET); however, the use of smFRET in visualizing protein motions has been limited by a lack of strategies for site-specific labeling of mobile protein modules. To address this challenge, we have developed methods for site-specific introduction of fluorescent probes into proteins such as the bacterial RNA polymerase (RNAP); the methods are highly selective and combine unnatural-amino-acid mutagenesis and bio-orthogonal labeling. We combine this breakthrough with smFRET on surface-immobilized molecules and look at conformational change of a large structural domain in the RNAP, “β clamp”. For the first time, we show directly that the clamp is highly dynamic, visiting three conformations. We also show that some antibiotics that target RNAP function by locking clamp into specific conformations; further, we discovered that a major stress-response factor (ppGpp) functions by modulating clamp dynamics. We then employed a similar strategy to a more difficult target, a less than 45 amino acid motif, “trigger loop” (TL), which is very close to the active center of RNAP. We succeeded in producing a fully functional TL-labeled RNAP and used smFRET to show directly that binding of correct NTP at the active site induces TL closure and that the TL ensures substrate specificity. Finally, we show using a real-time assay that TL opens and closes in each nucleotide addition cycle. Our strategies are general and provide insight into functioning of large multi-subunit protein machines.

Effects of different extracted components from petroleum pitch on mesophase development

Naphthenic-based petroleum pitch was divided into three components, including heptane-soluble (HS), heptane-insoluble/toluene-soluble (HITS) and toluene-insoluble (TI), by sequential extraction with heptane and toluene. Mesophase pitches were prepared by direct condensation of the extracted components and their mixtures. Effects of different components on formation and development of mesophase structures were investigated. Results showed that HITS was the optimal component for preparation of mesophase pitch with large domain structure, low softening point, high carbon residue and ordered microcrystal structure. Interactive effect indexes were cited to monitor the interaction of these components on mesophase development. The component HS with rich alkyl chains accelerated the carbonization via chain breaking at the initial stage of reaction, and HITS with abundant naphthenic structures alleviated the carbonization through hydrogen-transfer reaction during the aggregation process of aromatic molecules, and TI as initial nucleus could trigger the generation of mesophase spheres. However, the mixture of HS and TI possessed a weaker interactive effect on mesophase development compared to the other two mixtures. This was mainly due to the differences in molecular weight distribution and molecular structure between HS and TI. Furthermore, naphthenic structures had a better improving effect than alkyl chains on the generation of high-quality mesophase pitches.

Effects of In-Process Hydrogenation on Mesophase Development during the Thermal Condensation of Petroleum Aromatic-Rich Fraction

In this work, the mesophase pitch was generated from the thermal condensation of the petroleum aromatic-rich fraction. Tetrahydronaphthalene as a hydrogen donor was selected to treat the condensation intermediate using the in-process hydrogenation method. The objective of this work was to investigate the effects of in-process hydrogenation on the formation and development of mesophase structures. Results showed that the intermediate after in-process hydrogenation possessed a more-uniform molecular structure and narrower molecular-weight distribution, compared to the blank intermediate without in-process hydrogenation, which was attributed to the increasing content of naphthenic structures in the intermediate. From the characterization analysis of carbonized products, it can be found that the in-process hydrogenation of the condensation intermediate was conducive to the generation of mesophase pitch with a large domain structure, narrow molecular-weight distribution, low softening point, and carbon residue.

Understanding the large rotating magnetocaloric effect in TbMn1-xFexO3 single crystals upon q-Fermi Dirac nonextensive statistics

In magnetic materials, a large magnetocaloric effect is expected in those with large magnetocrystalline anisotropy in the vicinity of their magnetic phase transition temperature. Here we report a comparative study of rotating magnetocaloric effect in TbMn1-xFexO3 (x = 0, 0.75) single crystals by rotating them in a constant external field within ac plane from 2 to 50 K. We observed a large magnetic entropy change between a and c axes with strong magnetocrystalline anisotropy in TbMnO3 as well as TbMn0.25Fe0.75O3. For TbMn0.25Fe0.75O3, the large magnetocaloric effect appears close to a spin reorientation from Γ1(Ax,Gy,Cz) to Γ4(Gx,Ay,Fz) magnetic configuration at ∼16 K, which is distinguished from that of TbMnO3 near the antiferromagnetic ordering of Tb3+ ions at ∼9 K. The maximum of magnetic entropy change and refrigerant capacity of TbMnO3 (TbMn0.25Fe0.75O3) reach as high as 19.20 J/Kg K (14.84 J/Kg K), 411.97 J/Kg (260.80 J/Kg) under 7 T, respectively. Furthermore, using Lorentz transmission electron microscopy technique, we show the TbMn0.25Fe0.75O3 material displays a large single domain structure with dimension up to about 3 μm×3 μm, as an indicative of a large magnetocrystalline anisotropy in this system. Based on nonextensive thermodynamics, we further employ the q- Fermi Dirac statistics to demonstrate the good consistency between computed and experimental results of magnetization versus rotating angles. Our results clearly indicate the magnetocrystalline anisotropy energy plays a decisive role in the large differences of the magnetic properties and magnetocaloric properties in TbMn1-xFexO3 system.

Large ferroelectric domain structures of epitaxial Bi2FeMnO6 thin films on Nb-doped SrTiO3 substrates

Epitaxial Bi2FeMnO6 (BFMO) thin films were deposited on Nb-dopedSrTiO3(Nb:STO) substrates via pulsed laser deposition. The 100-nm-thick BFMO thin films had a relatively high tetragonality with a high c/a ratio of 1.04, confirmed by X-ray diffraction. The BFMO thin film had low leakage currents and good ferroelectric properties along with an enhanced remanent polarization of about 25.0 μC/cm2. The BFMO thin films had large ferroelectric domain structures compared to conventional ferroelectric thin films, such as PbTiO3 thin films, which is due to their high domain wall energy.

Relationship between Structural Modification of Aromatic-Rich Fraction from Heavy Oil and the Development of Mesophase Microstructure in Thermal Polymerization Process

In this study, the aromatic-rich fraction from heavy oil was modified by polyacrylic acid and oleic acid to obtain the modified raw materials which were used for producing mesophase pitch via polymerization reaction. First, the properties of modified feedstocks were analyzed by Fourier transform infrared spectrometry (FTIR), simulated distillation, and elemental analysis. The optical texture and molecular and microcrystal structure of the mesophase were characterized by the techniques of polarized optical microscopy, FTIR, 1H nuclear magnetic resonance, X-ray diffraction, and Raman spectroscopy. The influence of alkyl structures contained in modified feedstocks on the preparation of the mesophase was studied. The results suggested that the amounts of alkyl chains in modified raw materials increased first and then decreased with raising the amount of the additives. The short and long alkyl chains in mesophase pitches from modified feedstocks were resulted by treatment of polyacrylic acid and oleic acid, respectively. In addition, the mesophase pitches with finer microcrystal structures, less crystalline imperfection, and high degree of graphitization were generated from modified raw materials. Moreover, an appropriate amount of short alkyl chains or a small number of long alkyl chains was favorable for the formation of a mesophase with a large domain structure, low softening point, high carbon residue, and fine microcrystal structure.

Evaluation of free modeling targets in CASP11 and ROLL.

We present an assessment of 'template-free modeling' (FM) in CASP11and ROLL. Community-wide server performance suggested the use of automated scores similar to previous CASPs would provide a good system of evaluating performance, even in the absence of comprehensive manual assessment. The CASP11 FM category included several outstanding examples, including successful prediction by the Baker group of a 256-residue target (T0806-D1) that lacked sequence similarity to any existing template. The top server model prediction by Zhang's Quark, which was apparently selected and refined by several manual groups, encompassed the entire fold of target T0837-D1. Methods from the same two groups tended to dominate overall CASP11 FM and ROLL rankings. Comparison of top FM predictions with those from the previous CASP experiment revealed progress in the category, particularly reflected in high prediction accuracy for larger protein domains. FM prediction models for two cases were sufficient to provide functional insights that were otherwise not obtainable by traditional sequence analysis methods. Importantly, CASP11 abstracts revealed that alignment-based contact prediction methods brought about much of the CASP11 progress, producing both of the functionally relevant models as well as several of the other outstanding structure predictions. These methodological advances enabled de novo modeling of much larger domain structures than was previously possible and allowed prediction of functional sites. Proteins 2016; 84(Suppl 1):51-66. © 2015 Wiley Periodicals, Inc.

Macroscopic inhomogeneous deformation behavior arising in single crystal Ni–Mn–Ga foils under tensile loading

This study investigated macroscopic inhomogeneous deformation occurring in single-crystal Ni–Mn–Ga foils under uniaxial tensile loading. Two types of single-crystal Ni–Mn–Ga foil samples were examined as-received and after thermo-mechanical training. Local strain and the strain field were measured under tensile loading using laser speckle and digital image correlation. The as-received sample showed a strongly inhomogeneous strain field with intermittence under progressive deformation, but the trained sample result showed strain field homogeneity throughout the specimen surface. The as-received sample is a mainly polycrystalline-like state composed of the domain structure. The sample contains many domain boundaries and large domain structures in the body. Its structure would cause large local strain band nucleation with intermittence. However, the trained one is an ideal single-crystalline state with a transformation preferential orientation of variants after almost all domain boundary and large domain structures vanish during thermo-mechanical training. As a result, macroscopic homogeneous deformation occurs on the trained sample surface during deformation.

The Meso–Cenozoic stratigraphic succession of the Col de Braus area (Maritime Alps, SE France)

ABSTRACTThe 1:10,000 geological map here presented extends over about 32 km2 around the Col de Braus pass in the Maritime Alps (SE France). This area has attracted the attention of geologists since the late eighteenth century due to superb exposures of the Jurassic–Cretaceous Provençal succession, and has become a classic geological locality continuously studied until the present day. In this area, Early Cretaceous synsedimentary tectonics is evidenced by important lateral thickness and facies variations. This sector is presently placed at the western termination of a large structural domain extending from the westernmost Ligurian Alps into the French–Italian Maritime Alps, thus representing a key-area for understanding the structural setting of this part of the Western Alps.

Temperature-driven growth of antiferromagnetic domains in thin-film FeRh

The evolution of the antiferromagnetic phase across the temperature-driven ferromagnetic (FM) to antiferromagnetic (AF) phase transition in epitaxial FeRh thin films was studied by x-ray magnetic linear and circular dichroism (XMLD and XMCD) and photoemission electron microscopy. By comparing XMLD and XMCD images recorded at the same temperature, the AF phase was identified, its structure directly imaged, and its evolution studied across the transition. A quantitative analysis of the correlation length of the images shows differences between the characteristic length scale of the two phases with the AF phase having a finer feature size. The asymmetry of the transition from FM to AF upon cooling and AF–FM upon heating is evidenced: upon cooling the formation of AF phase is dominated by nucleation at defects, with little subsequent growth, resulting in a small and non-random final AF domain structure, while upon heating, heterogeneous nucleation at different sites followed by significant domain size growth of the FM phase is observed, resulting in a non-reproducible final FM large domain structure.

Room temperature ferroelectricity of YCrO3 thin films on Rh single crystals

We investigated the multiferroic properties of YCrO3 thin films grown by pulsed laser deposition on single crystal Rh substrates. The YCrO3 thin films exhibited room temperature ferroelectricity with a remanent polarization of about 9μC/cm2 as well as weak ferromagnetism below 150K. The piezoelectric force microscopy study revealed that the YCrO3 thin films have a larger domain structure than those of the PbTiO3 thin films although the YCrO3 thin films have a slightly lower domain wall energy. The large domain structures of the YCrO3 thin films are due to the significantly lower ferroelectric polarizations compared to PbTiO3 thin films.

Magnetic domain structure of La0.7Sr0.3MnO3 thin-films probed at variable temperature with scanning electron microscopy with polarization analysis

The domain configuration of 50 nm thick La0.7Sr0.3MnO3 films has been directly investigated using scanning electron microscopy with polarization analysis (SEMPA), with magnetic contrast obtained without the requirement for prior surface preparation. The large scale domain structure reflects a primarily four-fold anisotropy, with a small uniaxial component, consistent with magneto-optic Kerr effect measurements. We also determine the domain transition profile and find it to be in agreement with previous estimates of the domain wall width in this material. The temperature dependence of the image contrast is investigated and compared to superconducting-quantum interference device magnetometry data. A faster decrease in the SEMPA contrast is revealed, which can be explained by the technique's extreme surface sensitivity, allowing us to selectively probe the surface spin polarization which due to the double exchange mechanism exhibits a distinctly different temperature dependence than the bulk magnetization.

The roles of conditional disorder in redox proteins

Cells are constantly exposed to various oxidants, either generated endogenously due to metabolic activity or exogenously. One way that cells respond to oxidants is through the action of redox-regulated proteins. These proteins also play important roles in oxidant signaling and protein biogenesis events. The key sensors built into redox-regulated proteins are cysteines, which undergo reversible thiol oxidation in response to changes in the oxidation status of the cellular environment. In this review, we discuss three examples of redox-regulated proteins found in bacteria, mitochondria, and chloroplasts. These proteins use oxidation of their redox-sensitive cysteines to reversibly convert large structural domains into more disordered regions or vice versa. These massive structural rearrangements are directly implicated in the functions of these proteins.