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This study was performed to observe the effects of water on photosynthesis and water-related physiology in dominant shrubs in shell sand habitats. Four-year-old Periploca sepium seedlings were used as model species. A gradient of 12 water levels was established by artificially supplying the shell sand with water up to saturation and then allowing natural evapotranspiration to occur. The photosynthetic, chlorophyll fluorescence and stem sap flow parameters of P. sepium were measured under a range of water conditions. The different soil water conditions were classified according to the responses of these parameters. (1) With the increase in the relative water content (RWC) of the shell sand, the parameters of leaf photosynthesis, chlorophyll fluorescence and water-related physiology in P. sepium showed significant critical responses. The net photosynthetic rate (Pn), transpiration rate (Tr), instantaneous water use efficiency (WUE), potential water use efficiency (WUEi), maximum photochemical efficiency (Fv/Fm), actual photochemical efficiency (ΦPSII) and daily accumulation of stem sap flow all increased first and then decreased with increasing RWC, but the corresponding water conditions associated with their maximum values were not the same. An RWC of 69.40% was determined to be the optimal water condition for photosynthesis and water-related physiological activity in P. sepium. At an RWC of 36.61%, the mechanism of photosynthetic inhibition in P. sepium changed from stomatal limitation to nonstomatal limitation; this was also the minimum water requirement for maintaining normal photosynthetic processes. An RWC of 50.27% resulted in the highest WUE in P. sepium, indicating that moderate drought stress increased WUE. (2) Based on the quantitative relationship between the photosynthetic parameters of P. sepium and the shell sand water gradient, the soil water availability was classified into 6 water grades. The RWC range for maintaining strong photosynthesis and high WUE in P. sepium was 63.22–69.98%. (3) Gas exchange in P. sepium was inhibited under drought and waterlogging stresses. Under these conditions, the photosynthetic electron transport chain was blocked, and the dissipation of light energy as heat increased, which ultimately led to a decline in photosynthetic productivity; moreover, transpiration and dissipation were aggravated, and water transmission and utilization processes in P. sepium were hindered. A significant negative feedback regulation mechanism in the photosynthetic and water-related physiological processes of P. sepium was observed; this mechanism allowed P. sepium growing in shell sand to be highly adaptable to water stress.

A unique method is developed to synthesize Sn nanomaterials. Through an oxidation–reduction treatment, Sn particles are refined from the submicron (300 nm) to nanoscale (88 nm). With a series of ex...

In this study, physical vapor deposition was used to prepare TiN/Ti multilayer coatings as well as the corresponding monolithic coatings for comparison. Nanoindentation using a large load range (5–4800 mN) and finite element method (FEM) simulations were conducted to investigate the influence of various multilayer structures on the mechanical behavior of multilayer coatings. The nanoindentation results show that the TiN/Ti multilayer coating has the maximum hardness and Young's modulus while retaining good crack resistance and fracture toughness. The FEM results show that increasing the number of layers in the multilayer coatings reduced the hardness and Young's modulus as well as the maximum stress, while it increased the equivalent plastic strain. As the layer thickness ratio increased, both the hardness and Young's modulus gradually increased, and the stress in the coating reached its maximum at the highest thickness ratio. In addition, to consider the effect of the indentation depth on the coating, the influence of the number of layers and the layer thickness ratio on the multilayer coating is combined into the indentation response of the multilayer coating. Therefore, we establish an expression describing the relationship between the number of layers and the ratio of the layer thickness to the mechanical properties of TiN/Ti multilayer coatings.

The thermal expansion coefficient (CTE) is a vital design parameter for reducing the thermal-stress-induced structural failure of electronic chips/devices. At the micro- and nano-scale, the typical size range of the components in chips/devices, the CTEs are probably different from that of the bulk materials, but an easy and accurate measurement method is still lacking. In this paper, we present a simple but effective method for determining linear CTEs of micro-scale materials only using the prevalent nanoindentation system equipped with a heating stage for precise temperature control. By holding a constant force on the sample surface, while heating the sample at a constant rate, we measure two height–temperature curves at two positions, respectively, which are close to each other but at different heights. The linear CTE is obtained by analyzing the difference of height change during heating. This method can be applied to study the size effect or surface effect of CTE of embedded micro-scale structures, aiding the failure analysis and structural design in the semiconductor industry.

Agrobacterium tumefaciens infects various plants and causes crown gall diseases involving temporal expression of virulence factors. SghA is a newly identified virulence factor enzymatically releasing salicylic acid from its glucoside conjugate and controlling plant tumor development. Here, we report the structural basis of SghR, a LacI-type transcription factor highly conserved in Rhizobiaceae family, regulating the expression of SghA and involved in tumorigenesis. We identified and characterized the binding site of SghR on the promoter region of sghA and then determined the crystal structures of apo-SghR, SghR complexed with its operator DNA, and ligand sucrose, respectively. These results provide detailed insights into how SghR recognizes its cognate DNA and shed a mechanistic light on how sucrose attenuates the affinity of SghR with DNA to modulate the expression of SghA. Given the important role of SghR in mediating the signaling cross-talk during Agrobacterium infection, our results pave the way for structure-based inducer analog design, which has potential applications for agricultural industry.

Plant-derived allelochemicals have the potential to be used as eco-friendly measures for control of Microcystis aeruginosa blooms. However, the susceptibility of M. aeruginosa to plant allelochemicals under a range of environmental factors, such as alkalinity, is not clear. This study investigated the effects of different alkalinity treatments on 1,2,3-trihydroxybenzene (pyrogallol) toxicity to a toxic strain of the cyanobacterium, M. aeruginosa (FACHB 905). Pyrogallol toxicity to M. aeruginosa cultures, both pre-adapted to a range of alkalinity levels and un-adapted, increased when alkalinity was increased from 0.09 to 1.51 meq L−1. The mean inhibition ratios calculated according to OD650, cell concentration, Chl a, and carotenoid concentrations of M. aeruginosa cultures were highest in the highest alkalinity treatment (1.51 meq L−1), i.e., up to 74%, 80%, 73%, and 87% for alkalinity-adapted cells on day 3. The lowest cell concentrations and photosynthesis pigment concentrations were found in the highest alkalinity treatment (1.51 meq L−1) for un-adapted cells in 12-day bioassays. This trend was more obvious over time. Pyrogallol and TPC (total phenolic compounds) concentrations measured immediately after pyrogallol addition into the culture medium decreased more rapidly in higher alkalinity treatments. In contrast, faster oxygen consumption and higher production of quinone end products occurred within the first 30 min after pyrogallol addition at higher alkalinity levels. Quinones and oxygen radicals have been shown previously to be more toxic to cyanobacteria than pyrogallol itself. This provides a potential explanation for the enhanced pyrogallol toxicity to M. aeruginosa under higher alkalinity. Therefore, it is important to take alkalinity into account when considering pyrogallol as a potential biocide.

Investigate the growth adaptation law of the Tamarix chinensis root system in response to the groundwater level in a muddy coastal zone.The high groundwater level (0.7-0.9 m), medium groundwater level (1.1-1.3 m) and low groundwater level (1.5-1.7 m) T. chinensis forests on the beaches of the Yellow River Delta were used as the research objects. Full excavation methods were used to excavate root systems with different groundwater levels; then, the aboveground biomass, root biomass, root spatial distribution, root topological structure and fractal characteristics of T. chinensis response characteristics to groundwater level were measured and analysed.The results showed that with the decrease in the groundwater level, the soil water content and soil salt content showed upward trends. At high groundwater levels, T. chinensis reduced root biomass allocation to reduce the damage to roots caused by salinity. At low groundwater levels, T. chinensis strengthened the development of root systems, which greatly enhanced the ability of T. chinensis to balance its water intake. The root biomass at the high groundwater level was 43.06% lower than that at the low groundwater level. The relationship between root and shoot growth of T. chinensis at high groundwater levels and medium groundwater levels indicated allometric growth, and at low groundwater levels, roots and shoots grew uniformly. The root distribution of T. chinensis tended to be shallow at the different groundwater levels, showing the characteristics of a horizontal root type. At high groundwater levels, the root topological structure tended to be dichotomous, and the fractal dimension and fractal abundance values were both large, at 1.31 and 2.77, respectively. The branch complexity increased to achieve spatial expansion and increase plant stability. However, the topological structure of the medium and low groundwater level T. chinensis tended to be herringbone-like, the fractal dimension and fractal abundance values were small, the second branch was limited, and the structure was simple. The topological structure and fractal characteristics of the T. chinensis root system responded to different groundwater levels in a coordinated manner.Based on the differences in the growth and architecture of the T. chinensis root system, the T. chinensis root system has strong phenotypic plasticity to the heterogeneous water-salt habitat of the groundwater-soil system, and the T. chinensis root system shows strong root adaptability to water and salt stress.

Significance Bacterial infection has been extensively investigated; however, little is known about how bacterial pathogens timely shut down infecting machinery after successful infections. Here, a previously unknown sucrose–SghR/SghA–SAG–SA signaling axis was identified which controls the timing to shut off bacterial virulence expression and fine-tune host immune response. Sucrose, salicylic acid (SA), and its storage form SAG are small chemicals produced in plants whereas SghR is a bacterial sensor of sucrose and SghA is a bacterial enzyme that releases SA from SAG. Given that SA is an imperative signaling molecule in defense against a variety of microbial pathogens, these results depict a previously unknown 2-way chemical signaling cross-talk during microbe–host coevolution and shed mechanistic insights into host–bacteria interaction., It is highly intriguing how bacterial pathogens can quickly shut down energy-costly infection machinery once successful infection is established. This study depicts that mutation of repressor SghR increases the expression of hydrolase SghA in Agrobacterium tumefaciens, which releases plant defense signal salicylic acid (SA) from its storage form SA β-glucoside (SAG). Addition of SA substantially reduces gene expression of bacterial virulence. Bacterial vir genes and sghA are differentially transcribed at early and later infection stages, respectively. Plant metabolite sucrose is a signal ligand that inactivates SghR and consequently induces sghA expression. Disruption of sghA leads to increased vir expression in planta and enhances tumor formation whereas mutation of sghR decreases vir expression and tumor formation. These results depict a remarkable mechanism by which A. tumefaciens taps on the reserved pool of plant signal SA to reprogram its virulence upon establishment of infection.

An CoCrFeMnNi high-entropy alloy (HEA) particles reinforced 2024Al alloy composite was prepared by spark plasma sintering (SPS). There is an interdiffusion (ID) layer between the HEA particle and the matrix. The composition and micromechanical properties of the diffusion layer were investigated by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), electron probe and nanoindentation. The unique element distribution in the diffusion layer and the obvious creep phenomenon are related to the sintering mode. The hardness of the composite is increased 63.7%, which was attributed to particle reinforcement and the relative low content of sintering defects in the matrix.

Hydrogen embrittlement of Inconel 718 alloy was investigated. Multi-scale observation technique were employed, comprising slow strain rate tensile tests, scanning electron microscopy and transmission electron microscopy analysis. The results demonstrate that hydrogen charging deteriorates mechanical properties of the alloy. Inconel 718 alloy shows partial Portevin-Le Chatelier (PLC) effect at room temperature when hydrogen charging current density is 220 mA cm−2 and 590 mA cm−2. Moreover, plastic deformation features with dislocation cells are detected in hydrogen-induced brittle zone. Thus, it is concluded that dragging effect of hydrogen atoms on dislocations contributes to PLC effect.

Hydrogen embrittlement behaviors of PH17-4 steel and PH13-8Mo steel used as steam turbine last stage blades were investigated by means of slow strain rate tensile tests and hydrogen permeation tests. The results indicate that PH13-8Mo steel exhibits higher strength level mainly due to higher precipitate strengthening and lath strengthening compared with PH17-4 steel in the absence of hydrogen. Moreover, pre-hydrogen charging does not affect tensile strength of PH17-4 steel, but decreases tensile strength of PH13-8Mo steel. The plasticity of PH17-4 steel and PH13-8Mo steel is degraded after hydrogen charging and the deterioration is accompanied with considerable change in fracture mode. The loss of plasticity of PH13-8Mo steel is higher than that of PH17-4 steel, indicating that PH13-8Mo steel exhibits lower resistance to hydrogen embrittlement, which is mainly related to higher hydrogen diffusion behaviors and higher strength level of PH13-8Mo steel. Additionally, PH17-4 steel exhibits lower apparent hydrogen diffusion coefficient and higher apparent hydrogen solubility in comparison with those of PH13-8Mo steel, which implies that incoherent Cu-rich precipitates in PH17-4 steel possess higher capability to trap hydrogen atoms than that of coherent NiAl precipitates in PH13-8Mo steel.

Hydrogen embrittlement of a nickel-based superalloy IN718 was investigated using slow strain rate tensile tests. Post-mortem observation of fractured samples was performed to explore hydrogen-assisted failure mechanisms of the alloy. The results reveal that hydrogen charging reduces yield strength, tensile strength, fracture strain and work hardening rate. With increasing current density, yield strength and tensile strength reduce linearly and fracture strain decreases exponentially. Furthermore, the crack initiation and propagation in hydrogen-charged region depends on the distribution of δ phase in the alloy. For needle-shaped δ phase within the grains, the nucleation of voids takes place at the intersections between dislocation slip bands and δ phase due to the hydrogen-enhanced localized plasticity (HELP)-assisted shear localization and possible hydrogen agglomeration. For δ phase along the grain boundaries, the impingement of slip bands and local hydrogen accumulation at γ-matrix/δ phase interfaces as well as hydrogen-enhanced decohesion (HEDE)-assisted decohesion lead to the void nucleation at the interfaces. Because of the decoration of δ phase at the grain boundaries, hydrogen-assisted cracking preferentially propagates along the grain boundaries. It is hence suggested that the synergistic interplay of HELP mechanism and HEDE mechanism can be used to explain the embrittlement of the alloy.

The present study was attempted to evaluate the hydrogen embrittlement (HE) of commercial 20SiMn2CrNiMo, PSB1080 and PH13-8Mo high strength steels using slow strain rate tensile tests with smooth cylindrical tensile specimens. The results reveal that three steels exhibit the superior strength and plasticity in the absence of hydrogen. However, the mechanical properties are deteriorated after hydrogen charging and the resistance to HE is 20SiMn2CrNiMo steel, PH13-8Mo steel and PSB1080 steel, which is ranked in a decreasing order. Fine lath boundaries in 20SiMn2CrNiMo steel disperse hydrogen atoms, reduce local hydrogen accumulation and then result in the lowest HE. Coherent NiAl precipitates in PH13-8Mo steel and O-Mg-Al-Si-Ca type inclusions in PSB1080 steel are responsible for the high HE susceptibility due to the concurrent effect of the stress concentration and hydrogen-enhanced decohesion mechanism. It is thus suggested that the inclusions in steels should be eliminated and the efforts concerning to obtain low HE susceptibility in steels strengthened by the coherent precipitates should be conducted to guarantee the safe service of engineering components fabricated from high strength steels.

The erosion of compressor blades by solid particles brings huge safety hazards to aero engines. The application of erosion-resistant hard coating has become a good solution to protect titanium alloy blades. In this work, TiN monolayer and TiN/Ti multilayer coatings were prepared on Ti-6Al-4V alloy using a magnetic filtered cathode vacuum arc system (FCVA) and a metal vapor vacuum arc (MEVVA) ion implantation device. The mechanical properties of the coatings were evaluated by nanoindentation and scratch tests. The damage evolution behavior and mechanism of TiN monolayer and TiN/Ti multilayer coatings are studied by single-particle impact test and finite element simulation. The results show that the fracture toughness of TiN monolayer coating is lower than that of TiN/Ti multilayer coating; TiN/Ti multilayer coatings exhibit good erosion resistance. The main reason lies in that the Ti layer dissipates part of impact energy by plastic deformation and reduces the tensile stress. The interfaces in the multilayer coating inhibited the propagation of cracks.

The deformation behavior and damage mechanism of 17 vol% SiCp/Al composites under biaxial loading were studied by biaxial tension and nano-indentation tests. The results showed that in the process of biaxial tension, the composite in rolling normal direction has underwent less severe damage compared to that in the two tensile directions. However, interfacial debonding, particle shedding and microcrack propagation are accompanied in all three directions. The crack size becomes larger as the cracks gradually propagate on the surface of the material, leading to the failure of the composite. The micromechanical properties of the composite show a trend from a slow increase to a sharp increase. In addition, the distribution characteristics of stress, equivalent plastic strain and stress triaxiality of SiCp/Al composites under biaxial tensile stress are simulated by finite element method. The results showed that the stress and strain of composites increase rapidly along the diagonal direction. In the process of deformation, the stress triaxiality increases gradually, which makes the microcracks propagate easily, so the fracture surface of the composite presents a large number of dimples.

In this paper, high entropy alloy particles reinforced 5052 aluminum matrix composites were successfully prepared by vacuum hot pressing sintering technology. Interface layers with different thickness were formed in the composites by heat treatment. The effects of heat treatment temperature and time on the interface layer of composites were systematically studied by scanning electron microscopy (SEM), energy dispersion spectroscopy (EDS), X-ray diffraction (XRD), electron probe microanalysis (EPMA) and nano-indentation. The results show that the new core-shell structure particles are dominant in the composites with long holding time at 500 °C heat treatment. Hardness and Young’s modulus of the composites are obviously improved by the generation of the interface layer. With the increase of heat treatment time, the thickness of the interface layer increases, and the discontinuous interface layer will obviously increase the hardness and Young’s modulus of the composites, which is related to the stress concentration and the bonding degree between the interface and the matrix.

In this paper, the deformation, fracture and damage behavior of SiCp/Al composites are studied by experiments and finite element analysis. The crack cracking process of the material was observed by in-situ tensile test, it was found that the composite first produced microcracks near the particles, and the cracks mainly spread to depth and then to both sides. It is determined by a tensile test that the fracture mechanism of the material is the tearing of the aluminum matrix and the peeling between the particles and the matrix. The tensile damage mechanism of the composite material in three directions (rolling direction, rolling transverse direction and rolling normal direction) and different strains were determined. It is found that in the process of tensile deformation, micro-cracks are first formed at the defects (voids) and weak interfaces, and many fine cracks converge together to form large cracks leading to the fracture of the material, during which a few particles fall off, but there is no particle fracture. The global and local tensile tests of the composites were simulated by finite element method, the results of the stress-strain state under different strains and the effects of particles on the materials are analyzed in detail, and the validity of the test results is determined.

Understanding the melting behavior of metals at the microlevel and atomic level has been experimentally challenging due to the involvement of multiple phases at ultrafast time scale. By using the confocal scanning laser high-temperature microscope, differential scanning calorimetry, and environmental transmission electron microscope, we observed the transient process during melting of silver (Ag) nanoparticles below the equilibrium melting point. The melting point of Ag nanoparticles with the diameter of 60–120 nm is found to decrease by 100–400 °C, and the melting process is accompanied by a geometrical transformation at 840 °C, from an irregular polyhedron to a nearly spherical crystallinelike liquid with smooth facets. These results indicate that the melting of metal nanoparticles is not a direct sharp transformation from crystal to liquid but a gradual process via a certain intermediate state.Understanding the melting behavior of metals at the microlevel and atomic level has been experimentally challenging due to the involvement of multiple phases at ultrafast time scale. By using the confocal scanning laser high-temperature microscope, differential scanning calorimetry, and environmental transmission electron microscope, we observed the transient process during melting of silver (Ag) nanoparticles below the equilibrium melting point. The melting point of Ag nanoparticles with the diameter of 60–120 nm is found to decrease by 100–400 °C, and the melting process is accompanied by a geometrical transformation at 840 °C, from an irregular polyhedron to a nearly spherical crystallinelike liquid with smooth facets. These results indicate that the melting of metal nanoparticles is not a direct sharp transformation from crystal to liquid but a gradual process via a certain intermediate state.

In order to accurately control the microstructure and property of yttria-partially-stabilized-zirconia (YPSZ) coatings, this paper elaborated the particle in-flight behavior during supersonic atmospheric plasma spraying (SAPS) and its significance in determining the microstructure and thermal insulation properties of SAPS-YPSZ coatings. The results suggested that, for a Laval nozzle with an internal injection port, the influence of spray power on the particles velocity is more significant than the temperature. When the spray power and argon flow rate were kept unchanged, the increase of hydrogen percentage in the mixed plasma gas can increase the temperature while decrease the velocity. Compared with other spray parameters, the standoff distance had the most significant influence on both the temperature and velocity of in-flight particles. The particles temperature and velocity determined the melting state of particles and the content of unmelted nanoparticles of as-sprayed coatings, which decreased from 12% to 6% when the particles temperature and velocity increased by 10% and 14%, respectively. For a 300-μm-thick YPSZ coating, thermal insulation temperature increased from 69 °C to 90 °C (increased by 30%) when the unmelted nanoparticle content increased from 6% to 12%.

In this work, the METCO 307 (75 wt.% Ni + 25 wt.% graphite, M307) abradable seal coatings were deposited by conventional atmospheric plasma spraying system (APS) and high efficiency supersonic atmospheric plasma spraying system (SAPS), respectively. Comparative dry reciprocating sliding wear experiments on the as-sprayed coatings against a 440-C stainless steel ball were conducted on the CETR UMT-3 friction and wear tester. The results indicated that the average width and length of lubrication phase (graphite) were 3.54 ± 0.06 and 7.51 ± 0.13 μm in the SAPS-coating, which were lower than 4.15 ± 0.11 and 8.03 ± 0.09 μm in the APS-coating. The fine graphite phase improved the formation of homogeneous and continuous tribofilm during the reciprocating sliding friction process. The track depth of APS-coating increased from 0.093 to 0.161 mm, while that of SAPS-coating increased from 0.087 to 0.151 mm when the test temperature rose from 25 to 400 °C, indicating that the SAPS-coatings had a higher wear resistance.

In this work, yttria stabilised zirconia (YSZ) based thermal barrier coatings (TBCs) were deposited by a supersonic atmospheric plasma spray (SAPS). The influence of the unmelted nanoparticles on the thermomechanical properties of the nanostructured YSZ coatings was studied by heat insulation and thermal shock tests. The results indicated that nanostructured SAPS-coatings consisted of nano/micro-grains (60–150 nm) and unmelted nanoparticles (20–50 nm) and exhibited a bimodal microstructure. When the unmelted nanoparticle content increased from 4 to 11%, the Weibull modulus (M) decreased by 46% while the coating’s insulation temperature increased by 32%. The thermal cycling life of the nanostructured SAPS-coating was maximised when the unmelted nanoparticle content reached approximately 8%.

Nifedipine is a dihydropyridine calcium channel blocker used widely in the management of hypertension and other cardiovascular disorders. In this work, a simple, rapid and sensitive liquid chromatography/tandem mass spectrometry method was developed and validated to determine nifedipine in dog plasma using nimodipine as the internal standard. Chromatographic separation was carried out on a C8 column. The mobile phase consisted of a mixture of acetonitrile, water and formic acid (60:40:0.2, v/v/v) at a flow rate of 0.5 mL/min. Detection was performed on a triple quadrupole tandem mass spectrometer in selected reaction monitoring mode via an atmospheric pressure chemical ionization source. The method has a lower limit of quantification of 0.20 ng/mL with consumption of plasma as low as 0.05 mL. The linear calibration curves were obtained in the concentration range of 0.20–50.0 ng/mL (r = 0.9948). The recoveries of the liquid extraction method were 74.5–84.1%. Intra-day and inter-day precisions were 4.1–8.8 and 6.7–7.4%, respectively. The quantification was not interfered with by other plasma components and the method was applied to determine nifedipine in plasma after a single oral administration of two controlled-release nifedipine tablets to beagle dogs. Copyright © 2013 John Wiley & Sons, Ltd.

The crystallization of the novel virulence factors SghA and SghR is reported., Two proteins, SghA and SghR, which were recently identified and characterized as novel bacterial virulence factors regulating the infection of plant hosts by Agrobacterium, were cloned, overexpressed and purified with high yield. Both SghA and SghR form dimers in solution. The purified SghA and SghR were crystallized and the crystals diffracted to 1.9 and 2.1 Å resolution, respectively. Data were collected and processed, and the crystallographic parameters were within acceptable ranges. These results will help in the determination of their structures in order to uncover the molecular mechanism of how these two proteins together control the release of plant defence signals against agrobacteria during pathogen–host interaction.

The chemical constituents of fistular onion stalk obtained by supercritical CO(2) extraction were separated and purified by silica gel and sephadex LH-20 gel column chromatography and the preparative TLC method and four flavonoids were obtained. On the basis of the spectral data, they were structurally identified as (+)-catechin, (-)-epicatechin, astragalin, and 3-O-beta-D(2-O-beta-D-glucopyranosyl)-glucopyranosides of kaempferol.

Nifedipine is a dihydropyridine calcium channel blocker used widely in the management of hypertension and other cardiovascular disorders. In this work, a simple, rapid and sensitive liquid chromatography/tandem mass spectrometry method was developed and validated to determine nifedipine in dog plasma using nimodipine as the internal standard. Chromatographic separation was carried out on a C₈ column. The mobile phase consisted of a mixture of acetonitrile, water and formic acid (60:40:0.2, v/v/v) at a flow rate of 0.5 mL/min. Detection was performed on a triple quadrupole tandem mass spectrometer in selected reaction monitoring mode via an atmospheric pressure chemical ionization source. The method has a lower limit of quantification of 0.20 ng/mL with consumption of plasma as low as 0.05 mL. The linear calibration curves were obtained in the concentration range of 0.20-50.0 ng/mL (r = 0.9948). The recoveries of the liquid extraction method were 74.5-84.1%. Intra-day and inter-day precisions were 4.1-8.8 and 6.7-7.4%, respectively. The quantification was not interfered with by other plasma components and the method was applied to determine nifedipine in plasma after a single oral administration of two controlled-release nifedipine tablets to beagle dogs.

Intensive research interest has focused on small RNA-processing machinery and the RNA-induced silencing complex (RISC), key cellular machines in RNAi pathways. However, the structural mechanism regarding RISC assembly, the primary step linking small RNA processing and RNA-mediated gene silencing, is largely unknown. Human RNA helicase A (DHX9) was reported to function as an RISC-loading factor, and such function is mediated mainly by its dsRNA-binding domains (dsRBDs). Here, we report the crystal structures of human RNA helicase A (RHA) dsRBD1 and dsRBD2 domains in complex with dsRNAs, respectively. Structural analysis not only reveals higher siRNA duplex-binding affinity displayed by dsRBD1, but also identifies a crystallographic dsRBD1 pair of physiological significance in cooperatively recognizing dsRNAs. Structural observations are further validated by isothermal titration calorimetric (ITC) assay. Moreover, co-immunoprecipitation (co-IP) assay coupled with mutagenesis demonstrated that both dsRBDs are required for RISC association, and such association is mediated by dsRNA. Hence, our structural and functional efforts have revealed a potential working model for siRNA recognition by RHA tandem dsRBDs, and together they provide direct structural insights into RISC assembly facilitated by RHA.

The η-η transformation of interfacial Cu 6 Sn 5 in solder joints was studied. Two cooling rates were selected to obtain different grain sizes of intermetallic compounds (IMCs). In the case of air cooling, the compounds were tiny and no η-η transformation was detected in the as-soldered state. Under furnace cooling, however, thick and coarse interfacial IMCs were obtained and η was still stable. After aging 2d at 150 °C, η-η transformation was detected no matter what cooling rate. This indicates that effects of IMC thickness and grain size are negligible in some way. It is also shown that aging at 150 °C promoted the interfacial η-η transformation and the time needed was comparatively short to that of long-term aging study of solid/solid growth kinetics. These provide us a significant reference to understand the obtained reliability data and evaluate the possible threats of transformation to the interconnects. For Ni-bearing solder joints, interfacial (Cu,Ni) 6 Sn 5 was detected. Only η-phase was discovered after soldering and aging.

The formation of interfacial η’-Cu6Sn5 in Sn–0.7Cu/Cu solder joints at different aging temperatures was studied using x-ray diffraction (XRD). The time-temperature-formation curve was obtained and is discussed based on the phase transformation from existing η-Cu6Sn5 and interfacial reaction at temperatures below 186 °C. A minimum formation time was observed in the temperature range of 135–150 °C.