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Zirconium carbide (ZrC) nanoparticles with an average size of 5.6 nm were synthesized through laser fragmentation (LF) from as-received 20–60 nm ZrC particles, and LF-ZrC nanoparticle dispersion-strengthened tungsten (LF-WZC) samples were fabricated by spark plasma sintering method. The average grain size of LF-WZC is 1.91 μm and most ZrC particles in LF-WZC are smaller than 10 nm. LF-WZC exhibits finer grain size, higher yield strength and hardness but lower ductility as compared with W-ZrC samples using as-received ZrC (WZC). The results showed that finer ZrC nanoparticles dispersed in tungsten can enhance the strength by hindering the motion of dislocations, but they may also introduce stress concentration and thus reduce the ductility. The thermal shock resistance of the WZC and LF-WZC samples was investigated using an electron beam device. The LF-WZC sample also exhibits a higher cracking threshold (0.33–0.44 GW·m−2) than WZC (0.22–0.33 GW·m−2) at room temperature. The enhanced thermal shock resistance of LF-WZC could be attributed to its high yield strength.

Multiple resistance and pH adaptation (Mrp) complexes are sophisticated cation/proton exchangers found in a vast variety of alkaliphilic and/or halophilic microorganisms, and are critical for their survival in highly challenging environments. This family of antiporters is likely to represent the ancestor of cation pumps found in many redox-driven transporter complexes, including the complex I of the respiratory chain. Here, we present the three-dimensional structure of the Mrp complex from a Dietzia sp. strain solved at 3.0-A resolution using the single-particle cryoelectron microscopy method. Our structure-based mutagenesis and functional analyses suggest that the substrate translocation pathways for the driving substance protons and the substrate sodium ions are separated in two modules and that symmetry-restrained conformational change underlies the functional cycle of the transporter. Our findings shed light on mechanisms of redox-driven primary active transporters, and explain how driving substances of different electric charges may drive similar transport processes.

Human ATP‐binding cassette transporter 6 of subfamily B (ABCB6) is an ABC transporter involved in the translocation toxic metals and anti‐cancer drugs. Using cryo‐electron microscopy, we determined the molecular structure of full‐length ABCB6 in an apo state. The structure of ABCB6 unravels the architecture of a full‐length ABCB transporter that harbors two N‐terminal transmembrane domains which is indispensable for its ATPase activity in our in vitro assay. A slit‐like substrate binding pocket of ABCB6 may accommodate the planar shape of porphyrins, and the existence of a secondary cavity near the mitochondrial intermembrane space side would further facilitate substrate release. Furthermore, the ATPase activity of ABCB6 stimulated with a variety of porphyrin substrates showed different profiles in the presence of glutathione (GSH), suggesting the action of a distinct substrate translocation mechanism depending on the use of GSH as a cofactor.

Li7La3Zr2O12 (LLZO)-based ceramics are well-known as the most promising solid electrolytes for all-solid-state lithium metal batteries. However, its practical application has been significantly hin...

As promising candidates for plasma-facing materials, tungsten-based materials suffer the irradiation of high-energy neutrons in addition to the hydrogen isotopes and helium irradiation and the high-thermal flux. Radiation-produced defects, e.g. self-interstitial atoms (SIAs) and vacancies (Vs), can induce the hardening and embrittlement of tungsten, meanwhile enhancing the retention of hydrogen isotopes and helium in tungsten. Reducing the grain size of materials to introduce a high density of defect sinks, e.g., grain boundaries (GBs) prevalent in nano-/ultrafine-crystalline materials, was demonstrated to be an effective approach for mitigating irradiation damage in tungsten. In this paper, we reviewed the theoretical advances in exploring radiation-resistance of nano-structured tungsten at across scales. It was concentrated on the results of molecular dynamics, molecular statics, and the object kinetic Monte Carlo simulations on the fundamental interaction of the radiation-created Vs and SIAs with the GB. These mechanisms include GB-promoted V/SIA migration and SIA-V recombination, interstitial-emission induced annihilation, coupling of the V migration close to the GB with the SIA motion within the GB, and interstitial reflection by the locally dense GB structure. We proposed the remaining scientific issues on the defect-GB interactions at across scales and their relation to experimental observations. We prospected the possible trends for simulating the radiation damage accumulation and healing processes in nano-structured tungsten in terms of the development of the across-scale computational techniques and efficiency of the GB-enhanced tolerance of tungsten to irradiation under complex in-service conditions.

Li2ZrO3-coated and Al-doped micro-sized monocrystalline LiMn2O4 powder is synthesized through solid-state reaction, and the electrochemical performance is investigated as cathode materials for lithium-ion batteries. It is found that Li2ZrO3-coated LiAl0.06Mn1.94O4 delivers a discharge capacity of 110.90 mAhg−1 with 94% capacity retention after 200 cycles at room temperature and a discharge capacity of 104.4 mAhg−1 with a capacity retention of 87.8% after 100 cycles at 55 °C. Moreover, Li2ZrO3-coated LiAl0.06Mn1.94O4 could retain 87.5% of its initial capacity at 5C rate. This superior cycling and rate performance can be greatly contributed to the synergistic effect of Al-doping and Li2ZrO3-coating.

In this paper, high density nanocrystalline W with uniform dispersion of nanosized oxide particles was fabricated via a dissolution-precipitation process by well controlled high-energy ball milling of the raw powder materials of Y2O3, Ti and W and the subsequent spark plasma sintering (SPS). XRD and TEM analysis revealed that the Y2O3 and Ti were dissolved in W matrix during the high-energy ball milling and the Y2Ti2O7 particles were precipitated in the SPS process, resulting in the refinement in both W grains and oxide particles. The average grain size of W is 67 nm. The average size of particles in grain interior and at grain boundaries is 8.5 nm and 16.4 nm, respectively. The Vickers microhardness of such a nanostructured W alloy is as high as 1441 Hv, which is 2–3 times that of the ever reported W alloys. Such a dissolution-precipitation process offers a general pathway for manufacturing nanocrystalline refractory metals with dispersion of nanoscale oxides in a controllable manner.

In this work, FeCr-based films with different Y2O3 contents were fabricated using radio frequency (RF) magnetron sputtering. The effects of Y2O3 content on their microstructure and mechanical properties were investigated through scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), inductive coupled plasma emission spectrometer (ICP) and a nanoindenter. It was found that the Y2O3-doped FeCr films exhibited a nanocomposite structure with nanosized Y2O3 particles uniformly distributed into a FeCr matrix. With the increase of Y2O3 content from 0 to 1.97 wt.%, the average grain size of the FeCr films decreased from 12.65 nm to 7.34 nm, demonstrating a grain refining effect of Y2O3. Furthermore, the hardness of the Y2O3-doped FeCr films showed an increasing trend with Y2O3 concentration, owing to the synergetic effect of dispersion strengthening and grain refinement strengthening. This work provides a beneficial guidance on the development and research of composite materials of nanocrystalline metal with a rare earth oxide dispersion phase.

A very broad distribution of microstructural length scales spanning few nm- to the μm-scale has proven effective to achieve exceptional materials properties. Here, we fabricate a Cu/Nb two-phase composite made of a hierarchically layered structure by modifying the conventional accumulative roll bonding (ARB) technique, where fresh Nb sheets are inserted and bonded during a repeated stacking and rolling process. This barcode-like multilayer with a designed hierarchical length scale distribution possesses densely distributed phase boundaries and rich interfacial structures. The composite demonstrates similar superconductivity characteristics as pure Nb, but is 3 × stronger, has theoretically better oxidation resistance, and retains considerable ductility. Under the helium irradiation environment, the unique interfacial structures featuring chemical intermixing zones (3-dimensional) are more immune to the formation of large helium clusters than atomically sharp interfaces (2-dimensional), screening them from radiation damage and improving their long-term mechanical integrity. This work signifies an effective strategy of constructing hierarchical laminates to achieve high-performance materials, which holds promise in fusion and fission energy applications., DOE Office of Nuclear Energy (Grant DE-NE0008827)

Summary During collective cell migration, front cells tend to extend a predominant leading protrusion, which is rarely present in cells at the side or rear positions. Using Drosophila border cells (BCs) as a model system of collective migration, we revealed the presence of a supracellular actomyosin network at the peripheral surface of BC clusters. We demonstrated that the Myosin II-mediated mechanical tension as exerted by this peripheral supracellular network not only mediated cell-cell communication between leading BC and non-leading BCs but also restrained formation of prominent protrusions at non-leading BCs. Further analysis revealed that a cytoplasmic dendritic actin network that depends on the function of Arp2/3 complex interacted with the actomyosin network. Together, our data suggest that the outward pushing or protrusive force as generated from Arp2/3-dependent actin polymerization and the inward restraining force as produced from the supracellular actomyosin network together determine the collective and polarized morphology of migratory BCs., Graphical Abstract, Highlights • A supracellular actomyosin network encompasses the surface of migratory BC cluster • The network mediates cell-cell communication and restrains protrusion formation • Dynamics of myosin patches correlate with protrusion behaviors • A cytoplasmic dendritic actin population interacts with the actomyosin network, Biological Sciences; Cell Biology; Organizational Aspects of Cell Biology; Functional Aspects of Cell Biology

In this work, to improve the cyclability and high-temperature performance of cubic spinel LiMn2O4 (LMO) as cathode materials, Nb5+-doped LiMn2O4 powders coated and uncoated with Al2O3 and/or B2O3 were synthesized via the modified solid-state reaction method. It was found that Nb5+-doped and B2O3 + Al2O3-coated LMO powders comprising 5 μm granular agglomerated fine primary particles smaller than 350 nm in diameter exhibited superior electrochemical properties with initial discharge capacity of 101.68 mA h g−1; we also observed capacity retention of 96.31% after 300 cycles at room temperature (RT) and that of 98% after 50 cycles at 55 °C and 1C rate.

Neutrons induce displacement damage to the tungsten-based plasma facing material by creating radiation-defects, e.g., vacancies (Vs) and self-interstitial atoms (SIAs). These defects will accumulate on the surface and further affect surface's role as defect sinks. In this work, by combining molecular statics (MS) and object kinetic Monte Carlo (OKMC) methods, we study the clustering of the V/SIA on the two typical low-index W surfaces (1 0 0) and (1 1 0) to uncover the effect of the agglomerated surface V/SIA on the segregation and annihilation of the V and SIA nearby. Results show that the Vn/SIAn could form on the two surfaces via the agglomeration of the V/SIA on the surfaces with the energy release and the reduced energy barrier for the V/SIA diffusion near the Vn/SIAn as respective energetic and kinetic driving force. Yet, the Vn/SIAn is more easily formed on surface (1 1 0) compared to surface (1 0 0) due to the much larger binding energy of a V with a Vn (or a SIA with a SIAn) and lower diffusion energy barrier of the V/SIA on surface (1 1 0) than that on surface (1 0 0). Long-term OKMC simulations of the V/SIA behavior near the surfaces at 1000 K show that surface (1 0 0) could develop to locally convex structures due to the SIA agglomeration, while surface (1 1 0) will evolve to locally concave-convex structures due to the V/SIA clustering. Meanwhile, the interaction mechanism of the V/SIA with the surface is changed from the fundamental segregation, annihilation and clustering of the V/SIA near a pure surface to the trapping for the V/SIA by the locally concave-convex structure and the junction.

Nano-sized ZrC dispersion strengthened tungsten alloy (W-0.5wt%ZrC) rods with enhanced mechanical properties and superior high-temperature stability were fabricated by high temperature rotary swaging. The effects of swaging and annealing on the microstructure and mechanical properties of W-0.5wt%ZrC alloys were investigated. The as-swaged W-0.5%ZrC rod showed noticeable ductility at 200 °C with a total elongation of 4.2% and a tensile strength of 724 MPa, and at 500 °C the strength remains as high as 547 MPa and the total elongation is 28%. The ductile-to-brittle transition temperature (DBTT) is about 200 °C. The recrystallization start temperature of swaged W-0.5wt%ZrC is about 1500 °C, which is about 300 °C higher than that of rolled pure W. The possible mechanisms for the enhanced mechanical properties and thermal stability were discussed.

Tungsten is considered as the most promising material for plasma facing components (PFCs) in the magnetic confinement fusion devices, due to its high melting temperature, high thermal conductivity, low swelling, low tritium retention and low sputtering yield. However, the brittleness, poor machinability and low strength at high-temperatures of tungsten limits its application. Focusing on this issue, various W alloys with enhanced mechanical properties have been developed over recent decades. Among them, the W-ZrC alloys exhibit high strength, high ductility, low ductile-to-brittle transition temperature, good high-temperature stability, excellent resistance to thermal shock and low H/He plasma etching, making it one of the most promising candidate plasma facing materials (PFMs) for the future fusion devices. Therefore, the R&D experience of W-ZrC materials for PFCs, including the design idea, optimization of composition, fabrication technology (from powder metallurgy processing to hot working, from small specimen to large-sized bulk material), microstructure and performance (mechanical properties, thermal conductivity, resistance to thermal shocks and to H/He irradiation, H isotope retention behaviors) were reviewed in this paper. Key words: Plasma-facing materials, Tungsten, ZrC, Microstructure, Mechanical property

Constant-capacitance deep-level transient Fourier spectroscopy is utilized to characterize the interface between a GaN epitaxial layer and a SiNx passivation layer grown by low-pressure chemical vapor deposition (LPCVD). A near-conduction band (NCB) state ELP (EC – ET = 60 meV) featuring a very small capture cross section of 1.5 × 10–20 cm–2 was detected at 70 K at the LPCVD-SiNx/GaN interface. A partially crystallized Si2N2O thin layer was detected at the interface by high-resolution transmission electron microscopy. Based on first-principles calculations of crystallized Si2N2O/GaN slabs, it was confirmed that the NCB state ELP mainly originates from the strong interactions between the dangling bonds of gallium and its vicinal atoms near the interface. The partially crystallized Si2N2O interfacial layer might also give rise to the very small capture cross section of the ELP owing to the smaller lattice mismatch between the Si2N2O and GaN epitaxial layer and a larger mean free path of the electron in the ...

Platelet-activating-factor receptor (PAFR) responds to platelet-activating factor (PAF), a phospholipid mediator of cell-to-cell communication that exhibits diverse physiological effects. PAFR is considered an important drug target for treating asthma, inflammation and cardiovascular diseases. Here we report crystal structures of human PAFR in complex with the antagonist SR 27417 and the inverse agonist ABT-491 at 2.8-Å and 2.9-Å resolution, respectively. The structures, supported by molecular docking of PAF, provide insights into the signal-recognition mechanisms of PAFR. The PAFR-SR 27417 structure reveals an unusual conformation showing that the intracellular tips of helices II and IV shift outward by 13 Å and 4 Å, respectively, and helix VIII adopts an inward conformation. The PAFR structures, combined with single-molecule FRET and cell-based functional assays, suggest that the conformational change in the helical bundle is ligand dependent and plays a critical role in PAFR activation, thus greatly extending knowledge about signaling by G-protein-coupled receptors.

The high-temperature stability and good mechanical strength of tungsten (W) alloys are highly desirable for a wide range of fusion applications, which can be achieved by dispersion strengthening. In this paper, TaC dispersion effects on the thermal stabilities, tensile properties and thermal shock resistances have been investigated. A hot-rolled W-1.0 wt% TaC plate has been fabricated which contains the high tensile strength and elongation. Nanosized particles in the W matrix improve the recrystallization temperature to about 1400 °C and the ultimate tensile strength to 571 MPa at 500 °C through hindering grain boundary migration, pinning dislocations and refining grains. The effects of edge-localized mode like transient heat events on the rolled and recrystallized W-1.0 wt% TaC alloys were investigated systematically. The cracking threshold (100 shots) at room temperature is in the range of 0.33–0.44 GW/m2 for the rolled W-1.0 wt% TaC. Recrystallization degrades mechanical strength and makes the material more prone to thermal shock damages. Coarse Ta2O5 and Ta-Cx-Oy particles are easy to fracture and introduce a preferential crack initiation in W matrix during cyclic heat loads.

The mechanical properties, microstructure and thermal stability of hot rolled pure W and W-0.5 wt%ZrC alloy manufactured using the same technology are systematically studied. The results of Vickers hardness and tensile tests show that the W-0.5 wt%ZrC alloy has a higher hardness, ultimate tensile strength, ductility and thermal stability compared to pure W. The recrystallization temperature of W-0.5 wt%ZrC alloy is about 1300 °C which is 100 °C higher than that of hot rolled pure W (1200 °C). The ductile to brittle transition temperature (DBTT) of W-0.5 wt%ZrC alloy is 50 °C lower than that of the rolled pure tungsten. The above results indicate that at the fully same fabrication technology, the trace ZrC does improve the mechanical properties and thermal stability of W. The possible micro-mechanisms were investigated and proposed.

In order to clarify the effects of Zr and Ti addition on the refinement of the particle size of Y 2 O 3 in the oxide dispersion strengthened (ODS) steel, the reaction products between Zr and Ti with Y 2 O 3 after the high-energy ball-milling, annealing and subsequent consolidation processing (spark plasma sintering) were investigated in detail with both a larger amount of Zr, Ti and Y 2 O 3 additions (Fe-15 (Zr, Ti)-7.5Y 2 O 3 , wt%) and a smaller amount of Zr, Ti and Y 2 O 3 additions (Fe-2 (Zr, Ti)-1Y 2 O 3 , wt%). Experimental results indicate that the ball-milling does not lead to the reaction between Zr and Ti with Y 2 O 3 while the annealing and SPS cause the formation of Y-(Zr, Ti)-O complex phases. Y 0.28 Zr 0.72 O 1.862 structure is easily precipitated from the ball-milled powders at relatively lower annealing temperatures and it is further decomposed into YZrO 3 and ZrO phase at high annealing temperatures in Fe-15Zr-7.5Y 2 O 3 . While Y 2 O 3 (TiO 2 ) 2 and TiO 2 phase are precipitated at relatively lower annealing temperatures and are further combined into Y 2 Ti 2 O 7 phase at high annealing temperatures in Fe-15Ti-7.5Y 2 O 3 . Similar results are obtained as well in Fe-2 (Zr, Ti)-1Y 2 O 3 . Compared with the case of Zr addition, Ti addition can form the smaller size of Y-Ti-O particle than Y-Zr-O particle.

HfC dispersion strengthened tungsten alloys were prepared by the spark plasma sintering (SPS) and an ordinary sintering followed by swaging, respectively. The HfC content is optimized as 0.5 wt% through spark plasma sintering (SPS) processing. The thermal stability, thermal conductivity and mechanical properties of swaged W-0.5 wt%HfC (WHC05) alloys were systematically investigated. Grain of swaged WHC05 has an obvious round bar shaped morphology with an average diameter of 24.5 μm and an average length of 187 μm, respectively, which keeps stability with increasing annealing temperature up to 1400 °C. The ductile-brittle transition temperature of swaged WHC05 is about 250 °C, much lower than that of SPSed WHC05 samples (∼500 °C). The ultimate tensile strength of swaged WHC05 alloys annealed at 1200 °C has no significant drops in a wide tested temperature range from 300 °C to 800 °C. The thermal conductivity of swaged WHC05 annealed at 1200 °C is up to 174 W/m·K at room temperature and always larger than 137 W/m·K from RT to 500 °C, which is much higher than that of the unannealed one and just the same with ITER grade W.

Content of total fat and fatty acid composition of 37 walnut (Juglans regia L.) varieties was determined by soxhlet extraction and gas chromatography and the data were mined by variation analysis, correlation analysis, path analysis, principal component analysis and cluster analysis to provide a basis on cultivating, breeding and processing of different walnut varieties which were planed in Jinzhong Prefecture of Shanxi Province of China. It indicated that the content of fatty acid compositions was all positively correlated with total fat content. Oleic acid was an important part in the process of fatty acid metabolism in walnut, which was in good agreement with the theory in plant physiology. Quantitative relationship among fatty acid compositions was a reflection of dynamic balance in the anabolism process of them, as total fat content was regarded as a constant in the law of large numbers in statistics. In addition, the 37 walnut varieties in this study could be divided into “high oil content with linolenic acid” variety group and “low oil content with high oleic acid” variety group.

In this paper the tungsten-fibre-net-reinforced tungsten composites were produced by spark plasma sintering (SPS) using fine W powders and commercial tungsten fibres. The relative density of the samples is above 95%. It was found that the recrystallization area in the fibres became bigger with increasing sintering temperature and pressure. The tungsten grains of fibres kept stable when sintered at 1350°C/16 kN while grown up when sintered at 1800°C/16 kN. The composite sintered at 1350°C/16 kN have a Vickers-hardness of ~610 HV, about 2 times that of the 1800°C/16 kN sintered one. Tensile tests imply that the temperature at which the composites (1350°C/16 kN) begin to exhibit plastic deformation is about 200°C-250°C, which is 400°C lower than that of SPSed pure W. The tensile fracture surfaces show that the increasing fracture ductility comes from pull-out, interface debonding and fracture of fibres.

Multiple subtypes of dopamine receptors within the GPCR superfamily regulate neurological processes through various downstream signaling pathways. A crucial question about the dopamine receptor family is what structural features determine the subtype-selectivity of potential drugs. Here, we report the 3.5-angstrom crystal structure of mouse dopamine receptor D4 (DRD4) complexed with a subtype-selective antagonist, L745870. Our structure reveals a secondary binding pocket extended from the orthosteric ligand-binding pocket to a DRD4-specific crevice located between transmembrane helices 2 and 3. Additional mutagenesis studies suggest that the antagonist L745870 prevents DRD4 activation by blocking the relative movement between transmembrane helices 2 and 3. These results expand our knowledge of the molecular basis for the physiological functions of DRD4 and assist new drug design.

Gas generation degrades material properties in nuclear applications. The construction of self-assembled bubble channels was proposed to help release gas to the surface. In this study, thermal desorption spectroscopy, in-situ TEM heating and molecular dynamics simulations were carried out to assess the outgassing feasibility in helium-irradiated Cu/Nb multilayers with low structural damage. We found that the formation of outgassing networks has a hybrid diffusive-displacive nature, with diffusive bubble coalescence and crack-induced displacive fracture. The latter could destroy the integrity of the multilayer structure. This suggests that the outgassing strategy making use of self-assembled cavity networks should be carefully designed to avoid large-scale structural failure.

The low recrystallization temperature (1200 °C) of pure W is a serious limitation for application as facing plasma materials in fusion reactor. In this paper, W-0.5wt.%ZrC-1wt.%Re (WZR) alloy with recrystallization temperature up to 1800 °C was prepared by mechanical milling and spark plasma sintering. The grain size of WZR alloy is about 2.6 μm, smaller than that of pure W (4.4 μm), which keeps unchanged until the annealing temperature increases to 1800 °C. Tensile tests indicate that the WZR alloys exhibit excellent comprehensive properties: the ductile to brittle transition temperature of WZR is in the range from 400 °C to 500 °C, about 200 °C lower than that of pure W prepared by the same process; the total elongation (TE) of WZR at 600 °C is above 30%, which is about 2 times that of pure W (at 700 °C). Meanwhile its tensile strength keeps ∼450 MPa before and after 1800 °C annealing as well as its TE increases after annealing. WZR alloy exhibits higher hardness (489HV) than that of pure W (453HV) at room temperature. Microstructure analysis indicates that the strengthening of nano-sized ZrC particles dispersion and Re solid solution improve tensile properties and thermal stability of WZR alloy.

The diffusion mechanisms of lithium ions in tetragonal phase as well as in Al and Nb stabilized cubic Li7La3Zr2O12 compounds were investigated by low-frequency internal friction technique. In the cubic Li7La3Zr2O12 phase, a remarkable relaxation-type internal friction peak PC with a peak height up to 0.12 was observed in the temperature range from 15°C to 60°C. In the tetragonal phase however, the height of the PT peak dropped to 0.01. The obvious difference of the relaxation strength between the cubic and tetragonal phases is due to the different distribution of lithium ions in lattice, ordered in the tetragonal phase and disordered in the cubic phase. Based on the crystalline structure of the cubic garnet-type Li7La3Zr2O12 compound, it is suggested that the high internal friction peak in the cubic phase may be attributed to two diffusion processes of lithium ions: 96h↔96h and 96h↔24d.

Yttria dispersion-strengthened tungsten with both enhanced strength and ductility was synthesized through sol–gel method followed by sintering and high-temperature swaging. The sol–gel synthesis process involving a molecular-level doping leads to a unique nanostructure that Y 2 O 3 nano-particles were homogeneously dispersed in tungsten grains interior. The nanosized Y 2 O 3 particles in sol–gel synthesized W-1%Y 2 O 3 are stable in size even under a high sintering temperature of 2300 °C. The swaged sol–gel W-1%Y 2 O 3 show ductility at a relative low temperature of 250 °C, which is about 100 °C and 250 °C lower than that of spark-plasma-sintered sol–gel W-1%Y 2 O 3 and ball-milling synthesized W-1%Y 2 O 3 , respectively. The sol–gel method provides a promising access to high-performance nanostructured tungsten materials with both high strength and ductility, and can be easily scaled for industrial production.

In previous experiments, compounds TiC, TaC, and ZrC are often added in W to improve the mechanical and thermal properties. However, it is still not clear how atomic Ti, Ta and Zr coexisted with C will affect H behaviors in W. In this work, systematical \emph{ab initio} calculations are carried out to study the interactions among alloying atoms (Ti, Ta and Zr), H, and C. The results illustrate that substitutional alloying atoms Ti, Ta, and Zr can trap H atom, and increase the retention of H in W. The effect of Ti on raising H retention is the strongest, followed by that of Zr and Ta. All Ti-C, Ta-C, and Zr-C can exist in W, and Zr-C is the most stable while the stability of Ta-C is relatively low. The stability of Ti-C is between Zr-C and Ta-C. The binding strength of Zr-C-H is the largest, followed by that of Ti-C-H and Ta-C-H in W, suggesting H retention in W-Zr-C may be the largest while H retention in W-Ta-C may be relatively low. The movement of H is much easier than that of C in W. The presence of alloying atoms Ti, Ta, and Zr in W affects the movement of H and C: the diffusion of H away from the alloying atoms is more difficult than that moving close to the alloying atoms, while the movement of C atoms approaching the alloying atoms is relatively difficult.

Neutron irradiation induces a large number of vacancies and self-interstitial atoms (SIAs) that interact with hydrogen atoms (H) and degrade the mechanical properties of tungsten (W) in a fusion environment. Vacancies increase free space and trap H atoms, however, the effects of SIAs on trapping H atoms are still unclear since SIAs decrease free space. We therefore perform systematical \emph{ab initio} calculations to study the interactions of SIAs and SIAs clusters with H atoms in W. Our results suggest that SIA $\langle111\rangle$ dumbbell makes interstitial H atoms easy to accumulate in W. With accumulation of H atoms near a SIA $\langle111\rangle$ dumbbell, the binding energy decreases firstly and then levels off at about 0.3 eV. For comparison, the interactions of SIAs and SIAs clusters with helium (He) atoms are considered. It is found that SIAs and SIAs clusters can also act as trapping centers for interstitial He atoms. The combinations of SIAs with H and He hinder the fast movement of SIAs in W to annihilate with vacancies, increasing the concentrations of SIAs and vacancies in grain. SIAs and vacancies provide more sites for trapping H and He atoms and thus increase irradiation damage in W. We therefore suggest reducing retention of H isotopes and He in W to suppress irradiation damage.

The solid blocks and walls of the oxide dispersion strengthened (ODS) ferritic steel with nominal composition of Fe–18Cr–2W–0.5Ti–0.3Y2O3 were fabricated by electron beam selective melting (EBSM) method. Processes of melting, grain morphology, tensile properties and fracture behavior of this kind of steel were characterized. It was shown that formation mechanism of columnar grains and equiaxed grains is different during the two scan strategy melting processes. The added nano-scale oxide particles evenly distributed in the molten metal, and the size of these particles did not coarsen during the rapid melting and cooling steps. The ultimate tensile strength of the annealed blocks and walls is superior to the plates with same composition consolidated by powder metallurgy. Especially, wall builds tested parallel to the columnar growth orientation exhibit the outstanding mechanical properties at high temperature owing to the grain anisotropy and uniform distribution of fine Y-rich particles. In addition, the morphology of the individual fracture surfaces demonstrates the grain structure of the cross-section and fracture mode. A certain number of nanoscopic dispersoids are retained in dimples of all the EBSM builds, leading to enhanced strengthening. Keywords: Electron beam melting deposition, Oxide dispersion strengthened ferritic steel, Grain morphology, Microstructure, Mechanical properties

The grain morphology, nano-oxide particles and mechanical properties of oxide dispersion strengthened (ODS)-316L austenitic steel synthesized by electron beam selective melting (EBSM) technique with different post-working processes, were explored in this study. The ODS-316L austenitic steel with superfine nano-sized oxide particles of 30–40 nm exhibits good tensile strength (412 MPa) and large total elongation (about 51%) due to the pinning effect of uniform distributed oxide particles on dislocations. After hot rolling, the specimen exhibits a higher tensile strength of 482 MPa, but the elongation decreases to 31.8% owing to the introduction of high-density dislocations. The subsequent heat treatment eliminates the grain defects induced by hot rolling and increases the randomly orientated grains, which further improves the strength and ductility of EBSM ODS-316L steel.

W-(0.2, 0.5, 1.0)wt% ZrC alloys with a relative density above 97.5% were fabricated through the spark plasma sintering (SPS) method. The grain size of W-1.0wt% ZrC is about 2.7 μm, smaller than that of pure W and W-(0.2, 0.5)wt% ZrC. The results indicated that the W-ZrC alloys exhibit higher hardness at room temperature, higher tensile strength at high temperature, and a lower ductile to brittle transition temperature (DBTT) than pure W. The tensile strength and total elongation of W-0.5wt% ZrC alloy at 700 °C is 535 MPa and 24.8%, which are respectively 59% and 114% higher than those of pure W (337 MPa, 11.6%). The DBTT of W-(0.2, 0.5, 1.0)wt% ZrC materials is in the range of 500°C–600°C, which is about 100 °C lower than that of pure W. Based on microstructure analysis, the improved mechanical properties of the W-ZrC alloys were suggested to originate from the enhanced grain boundary cohesion by ZrC capturing the impurity oxygen in tungsten and nano-size ZrC dispersion strengthening.

Garnet-like Li6.8La3Zr1.8Bi0.2O12 (LLZBO) + x mol.% Al2O3 (x = 0, 1.25, 2.50) lithium ionic electrolytes were prepared by conventional solid state reaction method under two different sintering temperatures of 1000°C and 1100°C. XPS, induced coupled plasma optical emission spectrometer (ICP-OES), XRD and AC impedance spectroscopy were applied to investigate the bismuth valance, lithium concentration, phase structure and lithium ionic conductivity, respectively. Electrical measurement demonstrated that ionic conductivity of Al-added LLZBO compounds could be obviously improved when the sample sintering temperature increased from 1000°C to 1100°C. The highest ionic conductivity 6.3×10-5 S/cm was obtained in the LLZBO-1.25%Al sample sintered at 1100°C, in consistent with the lowest activation energy 0.45 eV for the lithium ion migration. The mechanism related with good ionic conductivity in the Al-added LLZBO sample was attributed to the lattice distortion induced by the partial Al substitution at Zr sites, which is helpful to improve the migration ability of Li ions in lattice.

Internal friction technique was used to investigate the microstructural stability of equal-channel angular pressed (ECAP) 9Cr1Mo steel (T91), Fe-18wt.%Cr alloy, and pure W. Several non-relaxation internal friction peaks are observed in three ECAP-strained specimens, which are related to the microstructural transition from a severely deformed state to a static recovery state of dislocations, and to recrystallized state. Along with the disappearance of the P1 peak, another relaxation internal friction peak P2 is observed during the second heating run only in Fe-18wt.%Cr alloy, and it does not disappear even during subsequent third heating run. This peak is not observed in T91 steel and W. The P2 peak is likely associated with a process of grain boundary (GB) sliding. Unlike T91, no abundant carbide precipitates distribute on GBs to pin GB and repulse GB sliding, thus, the P2 peak only occurs in Fe-18wt.%Cr alloy. It is concluded that high-temperature internal friction measurements are required to detect the grain boundary peak in pure W.

Inappropriately high stocking density can lead to chronic stress that causes many problems in fish culture. We examined the influence of stocking density on growth performance and a number of key serum parameters of Atlantic salmon (Salmo salar) to investigate stress-induced changes. Salmon were reared at low-density (~7.57-15.71kg/m(3), initial to final density), medium-density (~15.12-31.11kg/m(3)), and high-density (~30.18-61.34kg/m(3)) stocking levels for 10weeks. The results showed that stocking density had significant influence on the growth rate, specific growth rate, and feed conversion ratio (p < 0.05) but not on condition factor and mortality. All examined seven serum parameters showed significant change in the first few weeks. Five parameters increased in all three stocking densities, while the serum superoxide dismutase (SOD) and alkaline phosphatase (ALP) activities decreased. At the end of the experiment, the immunoglobulin M level and SOD activity were lowest in the high-density group (p < 0.05), while the cortisol level, ALP activity, and maleic dialdehyde content were significantly higher than in the other two groups (p < 0.05). The acid phosphatase (ACP) and lysozyme activities were not affected by stocking density. These results indicate that high stocking density could affect the growth of Atlantic salmon and the selected serum parameters, except for lysozyme and ACP, could be used as good indicators for chronic stress caused by stocking densities that are too high.

Sugar Will Eventually be Exported Transporters (SWEETs) are recently identified sugar transporters that can discriminate and transport di- or monosaccharides across a membrane following the concentration gradient. SWEETs play key roles in plant biological processes, such as pollen nutrition, nectar secretion, seed filling, and phloem loading. SWEET13 from Arabidopsis thaliana (AtSWEET13) is an important sucrose transporter in pollen development. Here, we report the 2.8-A resolution crystal structure of AtSWEET13 in the inward-facing conformation with a substrate analog, 2′-deoxycytidine 5′-monophosphate, bound in the central cavity. In addition, based on the results of an in-cell transport activity assay and single-molecule Forster resonance energy transfer analysis, we suggest a mechanism for substrate selectivity based on the size of the substrate-binding pocket. Furthermore, AtSWEET13 appears to form a higher order structure presumably related to its function.

In this study, LiAl-layered double hydroxides Lithium aluminum hydrotalcite (LiAl-LDH) with different specific surface area were prepared by the separate nucleation and aging steps (SNAS) method and then were employed to prepare calcium sulfoaluminate cement-based grouting material (CBGM) paste. The influence of LiAl-LDH slurries on fresh and hardened properties of the CBGM paste was investigated in terms of fluidity, stability, setting time, and compressive strength. Additionally, the hydration process and hydration products of the CBGM paste were characterized by hydration heat, X-ray diffraction, differential thermal analysis–thermogravimetry, and Fourier transform infrared analyses. The acquired results illustrated that LiAl-LDH with larger specific surface area led to a faster hydration rate at early age, a lower fluidity, a shorter setting time, and a higher stability. Furthermore, due to the crystal nucleation effect, the addition of LiAl-LDH slurries did not cause a new phase to form but changed the morphology and increased the amount of hydration products, yielding higher compressive strength.

Based on the differential signal in the Goos-Hanchen shift, a method for stabilizing the laser wavelength with high sensitivity is proposed. In the symmetrical metal-cladding waveguide, the Goos-Hanchen is largely enhanced and highly responds to the variation in the wavelength of incident light. Since the measurement of the Goos-Hanchen shift is immune to the intensity fluctuation in laser source, the wavelength shift down to 0.1 pm can be detected in our method. The proposed device could have potential applications in the optical commutation system.

The prokaryotic 5′-methylthioadenosine/S-adenosylhomocysteine nucleosidase (MTAN) catalyzes the irreversible cleavage of the glycosidic bond in 5′-methylthioadenosine (MTA) and S-adenosylhomocysteine (SAH), a process that plays a key role in several metabolic pathways. Its absence in all mammalian species has implicated this enzyme as a promising target for antimicrobial drug design. Here, we report the crystal structure of Bm MTAN in complex with its product adenine at a resolution of 2.6 A determined by single-wavelength anomalous dispersion method. 11 key residues were mutated for kinetic characterization. Mutations of Tyr134 and Met144 resulted in the largest overall increase in Km , whereas mutagenesis of residues Glu18, Glu145 and Asp168 completely abolished activity. Glu145 and Asp168 were identified as active site residues essential for catalysis. The catalytic mechanism and implications of this structure for broad-based antibiotic design are discussed.

Copper is an essential micronutrient for plant growth and development, and copper transporter plays a pivotal role for keeping copper homeostasis. However, little is known about copper transporters in wheat. Here, we report a novel copper transporter gene family, TaCT1, in common wheat. Three TaCT1 homoeologous genes were isolated and assigned to group 5 chromosomes. Each of the TaCT1 genes (TaCT1-5A, -5B or -5D) possesses 12 transmembrane domains. TaCT1 genes exhibited higher transcript levels in leaf than in root, culm and spikelet. Excess copper down-regulated the transcript levels of TaCT1 and copper deficiency-induced TaCT1 expression. Subcellular experiments localized the TaCT1 to the Golgi apparatus. Yeast expression experiments and virus-induced gene silencing analysis indicated that the TaCT1 functioned in copper transport. Site-directed mutagenesis demonstrated that three amino acid residues, Met(35), Met(38) and Cys(365), are required for TaCT1 function. Phylogenetic and functional analyses suggested that homologous genes shared high similarity with TaCT1 may exist exclusively in monocot plants. Our work reveals a novel wheat gene family encoding major facilitator superfamily (MFS)-type copper transporters, and provides evidence for their functional involvement in promoting copper uptake and keeping copper homeostasis in common wheat.

Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were conducted on PAN-based intermediate modulus carbon fibers to investigate the structure and surface hydrophilicity of the carbon fibers before and after gamma irradiation. Two methods were used to determine Young’s modulus of the carbon fibers. The results show that gamma ray irradiation improved the degree of graphitization and introduced compressive stress into carbon fiber surface. Gamma ray also improved the carbon fiber surface hydrophilicity through increasing the value of O/C and enhancing the quantity of oxygen functional groups on carbon fibers. No distinct morphology change was observed after gamma ray irradiation. The Young’s modulus of the fibers increased with increasing irradiation dose.

Effects of Si3+ and H+ irradiation on tungsten were investigated by internal friction (IF) technique. Scanning electron microscope (SEM) analysis revealed that sequential dual Si+H irradiation resulted in more serious damage than single Si irradiation. After irradiation, the IF background was significantly enhanced. Besides, two obvious IF peaks were initially found in temperature range of 70~330 K in the sequential Si+H irradiated tungsten sample. The mechanism of increased IF background for the irradiated samples was suggested to originate from the high density dislocations induced by ion irradiation. On the other hand, the relaxation peak PL and non-relaxation peak PH in the Si+H irradiated sample were ascribed to the interaction process of hydrogen atoms with mobile dislocations and transient processes of hydrogen redistribution, respectively. The obtained experimental results verified the high sensitivity of IF method on the irradiation damage behaviors in nuclear materials.

Based on the modal dispersion equation and attenuated total reflection spectrum, a multi-step algorithm for calculating the refractive index of analyte in symmetrical metal-cladding waveguide (SMCW) is proposed, and thus the large error generated by the utilization of m -line method to the SMCW-based large-range refractometer is avoided. Our algorithm is simple, quick and accurate. The calculation processes are as follow: the thickness of the guiding layer is obtained from the resonant angles when air is acted as guiding layer, then the refractive index of analyte is calculated from the obtained optimal thickness and the resonant angles when analyte is employed as guiding layer. The calculation mechanism of these two processes is that the approximate range can be given by dichotomy and the sum of reflectivity at all resonant angles should be minimal. Taking pure water as an example, the calculated refractive index agrees well with the actual one.

The aging behaviors of irradiated tungsten by high energy Si3+ and H+ ions are mainly investigated using internal friction (IF) method combined with SEM technology. The SEM analysis indicates that more severe irradiation damage appears in the surface of simultaneous dual Si3+ + H+ irradiated specimen than that in the sequential dual Si3+ + H+ irradiated specimen or the single Si3+ irradiated specimens because of the synergistic effect of Si and H irradiation. The IF background of the irradiated sample is about one order of magnitude higher than that of the unirradiated sample owing to the existence of high density fresh dislocations induced by Si/H irradiation. In the sequential dual Si3+ and H+ irradiated specimen, the hydrogen Snoek-Ke-Koster (SKK) peak associated with the movement of dislocations dragging hydrogen atoms is observed and its height decreases with aging time at room temperature. As for the simultaneous dual Si3+ + H+ irradiated specimen, however, there is no such hydrogen SKK peak. The reason can be explained as hydrogen diffusion and pinning effect of dislocations.

This work presents an experimental study to enhance the thermal contact conductance of high performance thermal interface materials (TIMs) using gallium alloy. In this experiment, the gallium alloy-based TIMs are synthesized by a micro-oxidation reaction method, which consists of gallium oxides (Ga2O3) dispersed uniformly in gallium alloys. An experimental apparatus is designed to measure the thermal resistance across the gallium alloy-based TIMs under steady-state conditions. The existence of Ga2O3 can effectively improve the wettability of gallium alloys with other materials. For example, they have a better wettability with copper and anodic coloring 6063 aluminum-alloy without any extrusion between the interface layers. Gallium binary alloy-based TIMs (GBTIM) or ternary alloy based-TIMs (GTTIM) are found to increase the operational temperature range comparing with that of the conventional thermal greases. The measured highest thermal conductivity is as high as 19.2 Wm−1K−1 for GBTIM at room temperature. The wide operational temperature, better wettability, and higher thermal conductivity make gallium alloy-based TIMs promising for a wider application as TIMs in electronic packaging areas. The measured resistance is found to be as low as 2.2 mm2 KW−1 for GBTIM with a pressure of 0.05 MPa, which is much lower than that of the best commercialized thermal greases. In view of controlling pollution and raw materials wasting, the gallium alloy-based TIMs can be cleaned by 30% NaOH solution, and the pure gallium alloys are recycled, which can satisfy industrial production requirements effectively.

Glycoside hydrolase family 43 (GH43) consists of a variety of enzymes distributed widely in prokaryotes and eukaryotes. The mechanism by which GH43 enzymes hydrolyze oligosaccharides requires three essential acidic amino acid residues. However, one of them is thought to be missing in galactan β-1,3-galactosidases from the GH43 family. Ct1,3Gal43A, from Clostridium thermocellum, is comprised of a GH43 domain, a CBM13 domain, and a dockerin domain and exhibits an unusual ability to hydrolyze β-1,3-galactan in the presence of a β-1,6 linked branch. Here, we present its crystal structure at 2.7 Å resolution and complex structures of the enzyme with several substrates and analogs. Two modes of substrate binding were observed at the β site of the CtCBM13 domain, and one galactobiose molecule was found in an "L" shaped pocket of the CtGH43 domain, which appears large enough to accommodate two more galactose units. In addition, we found that mutating Glu112 to Gln or Ala eliminated the galactan hydrolysis activity of Ct1,3Gal43A while did not disrupt its ligand binding ability. Combining this results and the crystal structure we identified Glu112 in Ct1,3Gal43A as the 'missing' essential acidic residue in galactan β-1,3-galactosidases. Structural information presented here also suggests a mechanism by which Ct1,3Gal43A bypasses β-1,6 linked branches in the substrate and another mechanism by which the substrate is delivered 'in trans' from the CBM13 domain to the catalytic GH43 domain.

A typical approach involving Pechini method and spark plasma sintering (SPS) method was presented for the preparation of high density Li5+x Sr x La3−x Bi2O12 (x = 0, 1) ceramics. Phase formation, microstructure, grain size and electrical properties of the specimens were examined using XRD, SEM and alternating current impedance spectroscopy (ACIS). Dense Li5La3Bi2O12 and Li6SrLa2Bi2O12 ceramics with pure garnet-like phase, relative density of 97% and average grain size of about 5 μm were fabricated using this approach. The total conductivities at 298 K of Li5La3Bi2O12 and Li6SrLa2Bi2O12 ceramics prepared by the SPS method are 5.1×10−5 and 6.8×10−5 S/cm, respectively, 2 times higher than that of samples prepared by the conventional sintering method.