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Clay often has severe detrimental impacts on cement-based materials. Therefore, it is necessary to investigate the mechanism causing the deterioration to improve the service life of cement-based materials. Based on accurate dimensional analysis, a mechanism that influences clay is proposed: the intercalation of the side chains of superplasticizer molecules in the interlayer space of the clay. To lessen this harmful effect, a new clay-resistant admixture (CRA) possessing cationic groups of small molecular size was synthesized through a novel dimensional design. The length and width of the side chains of this superplasticizer molecule were 9.50–17.50 and 0.25–0.40 nm, respectively, with a radius of ~3.74 nm in solvent, which is larger than the interlayer spacing of montmorillonite (i.e. 1.09–2.14 nm). The longitudinal and latitudinal lengths of the CRA molecule were 0.468 and 9.456 nm, respectively, ensuring intercalation in the interlayer of montmorillonite. The increase in interlayer spacing of the clay was 0.364 nm following addition of polycarboxylate superplasticizer (PCE) plus CRA and 0.632 nm following addition of PCE, which suggests that the CRA plays the role of a ‘sacrificial agent’ that is preferentially intercalated into the interlayer space of clay to further prevent the side chains of the superplasticizer molecules from entering the interlayer. The aim of this study was to propose a suitable means of synthesizing a new CRA to address the impact of clay through dimensional design and mechanism analysis, which contributes to the theoretical study and technological improvement of cement-based materials.
Mach reflection in steady supersonic flow with two incident shock waves that reflect at the same point on the reflecting surface has been studied recently. Under some conditions we have pre-Mach reflection, where the first incident shock wave produces Mach reflection, the reflected shock wave of which intersects the second incident shock wave, leading to a type I shock interference structure. In this study, we find that a critical condition exists to have a double solution of this shock interference, i.e. we may either have type I interference or type II interference. However, numerical simulation shows that, for inverted Mach reflection, the double solution domain is below the theoretical one and for usual Mach reflection, the double solution domain is above the theoretical one. This discrepancy is found to be due to secondary Mach waves on the initial segment of the slipline of the Mach reflection, thus demonstrating for the first time a case where the transition criterion is modified by secondary Mach waves developed over the primary flow structure.
This study aimed to examine the efficacy of combining paroxetine and mirtazapine v. switching to mirtazapine, for patients with major depressive disorder (MDD) who have had an insufficient response to SSRI monotherapy (paroxetine) after the first 2 weeks of treatment.
This double-blind, randomized, placebo-controlled, three-arm study recruited participants from five hospitals in China. Eligible participants were aged 18–60 years with MDD of at least moderate severity. Participants received paroxetine during a 2-week open-label phase and patients who had not achieved early improvement were randomized to paroxetine, mirtazapine or paroxetine combined with mirtazapine for 6 weeks. The primary outcome was improvement on the Hamilton Rating Scale for Depression 17-item (HAMD-17) scores 6 weeks after randomization.
A total of 204 patients who showed early non-response to paroxetine monotherapy were randomly assigned to receive either mirtazapine and placebo (n = 68), paroxetine and placebo (n = 68) or mirtazapine and paroxetine (n = 68), with 164 patients completing the outcome assessment. At week 8, the least squares (LS) mean change of HAMD-17 scores did not significantly differ among the three groups, (12.98 points) in the mirtazapine group, (12.50 points) in the paroxetine group and (13.27 points) in the mirtazapine plus paroxetine combination group. Participants in the paroxetine monotherapy group were least likely to experience adverse effects.
After 8 weeks follow-up, paroxetine monotherapy, mirtazapine monotherapy and paroxetine/mirtazapine combination therapy were equally effective in non-improvers at 2 weeks. The results of this trial do not support a recommendation to routinely offer additional treatment or a switch in treatment strategies for MDD patients who do not show early improvement after 2 weeks of antidepressant treatment.
Thermal conductivity of uranium dioxide (UO2) is an important nuclear fuel performance property. Radiation- and fission-induced defects and microstructures, such as xenon (Xe) gas bubbles, can degrade the thermal conductivity of UO2 significantly. Here, molecular dynamics simulations are conducted to study the effect of Xe bubble size and pressure on the thermal conductivity of UO2. At a given porosity, thermal conductivity increases with Xe cluster size, then reaches a nearly saturated value at a cluster radius of 0.6 nm, demonstrating that dispersed Xe atoms result in a lower thermal conductivity than clustering them into bubbles. In comparison with empty voids of the same size, Xe-filled bubbles lead to a lower thermal conductivity when the number ratio of Xe atoms to uranium vacancies (Xe:VU ratio) in bubbles is high. Detailed atomic-level analysis shows that the pressure-induced distortion of atoms at bubble surface causes additional phonon scattering and thus further reduces the thermal conductivity.
In several lately published studies, the association between single-nucleotide polymorphism (SNP, rs12252) of IFITM3 and the risk of influenza is inconsistent. To further understand the association between the SNP of IFITM3 and the risk of influenza, we searched related studies in five databases including PubMed published earlier than 9 November 2017. Ten sets of data from nine studies were included and data were analysed by Revman 5.0 and Stata 12.0 in our updated meta-analysis, which represented 1365 patients and 5425 no-influenza controls from four different ethnicities. Here strong association between rs12252 and influenza was found in all four genetic models. The significant differences in the allelic model (C vs. T: odds ratio (OR) = 1.35, 95% confidence interval (CI) (1.03–1.79), P = 0.03) and homozygote model (CC vs. TT: OR = 10.63, 95% CI (3.39–33.33), P < 0.00001) in the Caucasian subgroup were discovered, which is very novel and striking. Also novel discoveries were found in the allelic model (C vs. T: OR = 1.37, 95% CI (1.08–1.73), P = 0.009), dominant model (CC + CT vs. TT: OR = 1.48, 95% CI (1.08–2.02), P = 0.01) and homozygote model (CC vs. TT: OR = 2.84, 95% CI (1.36–5.92), P = 0.005) when we compared patients with mild influenza with healthy individuals. Our meta-analysis suggests that single-nucleotide T to C polymorphism of IFITM3 associated with increasingly risk of severe and mild influenza in both Asian and Caucasian populations.
Mach reflection in steady supersonic flow with two incident shock waves is studied. The second incident shock wave is produced by an additional deflection of the wedge lower surface, at some point ensuring that the two incident shock waves would intersect at the reflecting surface in case of normal reflection. Both theory and computational fluid dynamics (CFD) are used to study the flow structure and the influence of the second incident shock wave. The overall flow configuration, in case of Mach reflection, is shown to be composed of a triple shock structure, a shock/shock interaction structure and a shock/slipline reflection structure. Similar phenomenon, triggered by a high downstream pressure, has been observed before numerically, but not studied theoretically. The second incident shock wave reflects over the slipline to deflect the slipline more towards the reflecting surface, increasing thus the Mach stem height, advancing the transition of regular reflection to Mach reflection of the first incident shock wave, and causing an inverted Mach reflection below the usual von Neumann condition. A Mach stem height model built for a weak second incident shock wave is used to study the influence of the second incident shock wave on the Mach stem height. Both theory and CFD predict a maximum of the Mach stem height at some additional wedge deflection angle.
As the largest industrial and population centre in China, the Pearl River Delta is facing a growing threat of heavy metal pollution from local mining and power industries. This study investigates the distribution and potential health risks of copper (Cu), cadmium (Cd), lead (Pb) and zinc (Zn) in paddy soils and rice at four typical sites. The Nemerow synthetic pollution index (PN) of soils from Fogang, Dabao Mountain, Shaoguan and Lechang were 8.40, 9.10, 4.64 and 10.28, respectively, indicating serious pollution at all four sampling sites. The average concentrations of Cu, Cd, Pb and Zn in rice grains were 2.23, 10.98, 29.84 and 1.62 times their corresponding maximum allowable levels, indicating potential health risks to humans. Cd has greater bioavailability because of its high mobility from soil to roots, and its subsequent transfer to grains. Pb mainly accumulates in roots because of its lower translocation rate from roots to grains. The greatest health risk index for Cd and Pb for adults and children was at the Shaoguan site, probably due to pollution from atmospheric deposition. Cd and Pb had greater health risk indices than Cu and Zn at almost all sites, indicating a major health risk to local people.
A new sharp interface method with the combination of Ghost Fluid Method (GFM) and Cut Cell scheme is developed to study compressible multi-phase flows with clear interfaces. Straight-line cutting is applied on the cells passed by the interface. A new real-ghost mixing method is presented and applied around the cut cells to deal with very small cut cells. A cut face reconstruction method similar to volume of fluid is applied to deal with topological change problems. A high order Level Set (LS) method is applied to evolve the free interface, with the Level Set velocities from exact Riemann solver on the cut faces. Various 1D and 2D numerical examples are tested to show the robustness and ability of the present method in wide flow variable domains. This method benefits from cut cell on the sharp interface description, shows good conservation performance, and does not have the topological change difficulty of the full cut cell method presented in Chang, Deng & Theofanous, J. Comput. Phys., 242 (2013), pp. 946–990.
Trichinella spiralis is a parasitic helminth that can infect almost all mammals, including humans. Trichinella spiralis infection elicits a typical type 2 immune responses, while suppresses type 1 immune responses, which is in favour of their parasitism. DNA vaccines have been shown to be capable of eliciting balanced CD4+ and CD8+ T cell responses as well as humoral immune responses in small-animal models, which will be advantage to induce protective immune response against helminth infection. In this study, serine protease (Ts-NBLsp) was encoded by a cDNA fragment of new-born T. spiralis larvae, and was inserted after CMV promoter to construct a DNA vaccine [pcDNA3·1(+)-Ts-NBLsp]. Ts-NBLsp expression was demonstrated by immunofluorescence. Sera samples were obtained from vaccinated mice, and they showed strong anti-Ts-NBLsp-specific IgG response. Mice immunized with the pcDNA3·1(+)-Ts-NBLsp DNA vaccine showed a 77·93% reduction in muscle larvae (ML) following challenge with T. spiralis ML. Our results demonstrate that the vaccination with pcDNA3·1(+)-Ts-NBLsp plasmid promoted the balance of type 1 and 2 immune responses and produced a significant protection against T. spiralis infection in mice.
Perovskite solar cells (PSCs) based on organometal halide light absorbers have hit the limelight in recent years owing to their low temperature solution processability, material abundance and rapidly rising efficiency. To rival the leading photovoltaic technologies, efficiency and long-term stability of PSCs represent two prime facets of the challenges currently facing the research community. Herein we summarize the strategies for improving efficiency and stability of PSCs by drawing on our recent work. Emphasis is given to the importance of perovskite film growth, electron/hole transport materials and interface materials in cell performance. We also discuss possible degradation mechanisms of PSCs.
For any given matrix A ∈ℂnxn, a preconditioner tU(A) called the
superoptimal preconditioner was proposed in 1992 by Tyrtyshnikov. It has been
shown that tU(A) is an efficient preconditioner for
solving various structured systems, for instance, Toeplitz-like systems. In this
paper, we construct the superoptimal preconditioners for different functions of
matrices. Let f be a function of matrices from ℂnxn to ℂnxn. For any A ∈ ℂ nxn, one may construct two superoptimal preconditioners for f(A):
tU(f(A)) and f(tU(A)).
We establish basic properties of tU(f(A)) and
f(tU(A)) for different functions of
matrices. Some numerical tests demonstrate that the proposed preconditioners are
very efficient for solving the system f(A)x = b.
Escherichia albertii is a newly emerging enteric pathogen that has been associated with gastroenteritis in humans. Recently, E. albertii has also been detected in healthy and sick birds, animals, chicken meat and water. In the present study, the prevalence and characteristics of the eae-positive, lactose non-fermenting E. albertii strains in retail raw meat in China were evaluated. Thirty isolates of such strains of E. albertii were identified from 446 (6·73%) samples, including duck intestines (21·43%, 6/28), duck meat (9·52%, 2/21), chicken intestines (8·99%, 17/189), chicken meat (5·66%, 3/53), mutton meat (4·55%, 1/22) and pork meat (2·44%, 1/41). None was isolated from 92 samples of raw beef meat. Strains were identified as E. albertii by phenotypic properties, diagnostic PCR, sequence analysis of the 16S rRNA gene, and housekeeping genes. Five intimin subtypes were harboured by these strains. All strains possessed the II/III/V subtype group of the cdtB gene, with two strains carrying another copy of the I/IV subtype group. Pulsed-field gel electrophoresis showed high genetic diversity of E. albertii in raw meats. Our findings indicate that E. albertii can contaminate various raw meats, posing a potential threat to public health.
Rhizoma et Radix Notopterygii is often used as a traditional medicine in China. In our recent work, we found that the ethanol crude extract of Rhizoma et Radix Notopterygii could reduce phytotoxicity of acetochlor on rice. The crude extract of Rhizoma et Radix Notopterygii was isolated and purified by activity-guided fractionation. Two coumarins, isopimpinellin and 5-methoxypsoralen (5-MOP) were identified, and their bioactivity was tested in a growth chamber. The results showed that the two coumarins increased herbicide tolerance of rice shoots, and 5-MOP demonstrated better protection than isopimpinellin. The treatment of 5-MOP at 50 g ai ha−1 recovered the shoot height of rice from 42.6% (treated with acetochlor only) to 81.6% of the control treated without acetochlor, whereas the phytocidal activity of acetochlor on barnyardgrass was not impaired by 5-MOP. Further study suggested that 5-MOP increases herbicide tolerance of rice by enhancing the glutathione S-transferase level of activity in rice. Our findings suggest that isopimpinellin and 5-MOP have the potential to be applied as safeners for rice.
Kashin-Beck disease (KBD) is a chronic endemic osteoarthropathy, which mainly occurs in West and Northeast China. Epidemiological studies suggest that Se deficiency is an important environmental factor for the incidence of KBD. Glutathione peroxidase 4 (GPx4) belongs to the glutathione peroxidase family, which is crucial for optimal antioxidant defences. Our purpose is to investigate the putative association between GPx4 polymorphisms and the risk of KBD. Restriction fragment length polymorphism-PCR was used to detect two SNP (rs713041, rs4807542) in 219 cases and 194 controls in Han Chinese subjects, and quantitative analysis for the GPx4 mRNA level was performed by the real-time PCR method. The results revealed that linkage disequilibrium existed in the two SNP. A significant difference was observed in the haplotype A-T (P = 0·0066) of GPx4, which was obviously lower in the KBD cases (0·006 v. 0·032 %). Correlation analysis based on a single locus showed no association between each SNP and KBD risk. Furthermore, the GPx4 mRNA level was dramatically lower in the blood of KBD patients. Overall, our finding indicated GPx4 polymorphisms and decreased mRNA level may be related to the development of KBD in the Chinese population, suggesting GPx4 as a possible candidate susceptibility gene for KBD.
An efficient AHL (N-acyl-homoserine lactone) bioassay strain, JZA1, of Agrobacterium tumefaciens was used to detect the AHL production from Acidovorax avenae subsp. citrulli [the pathogen causing bacterial fruit blotch (BFB) of melons], and the results showed that A. avenae subsp. citrulli produced a 3-O-C8-homoserine (HSL) type signal molecule. Gene aiiA, which could degrade AHL molecules, was transformed into A. avenae subsp. citrulli strain NJF10, creating strain NJF10-aiiA. The AHL production from NJF10-aiiA was significantly reduced compared with wild-type NJF10. Inoculation tests showed that NJF10-aiiA had an obvious reduction of virulence on watermelon fruits. Our finds showed that AHL production by A. avenae subsp. citrulli was related to its pathogenicity. This work might provide a novel way to control BFB by QS (quorum sensing) interference.
Nano-crystalline films of pure cubic ZrO2 have been produced by ion beam assisted deposition (IBAD) processes which combine physical vapor deposition with the concurrent ion beam bombardment in a high vacuum environment and exhibit superior properties and strong adhesion to the substrate. Oxygen and argon gases are used as source materials to generate energetic ions to produce these coatings with differential nanoscale (7 to 70 nm grain size) characteristics that affect the wettability, roughness, mechanical and optical properties of the coating. The nanostructurally stabilized chemically pure cubic phase has been shown to possess hardness as high as 16 GPa and a bulk modulus of 235 GPa. We examine the mechanical properties and the phase stability in zirconia nanoparticles using first principle electronic structure method. The elastic constants of the bulk systems were calculated for monoclinic, tetragonal and cubic phases. We find that calculated bulk modulus of cubic phase (237GPa) agrees well with the measured values, while that of monoclinic (189GPa) or tetragonal (155GPa) are considerably lower. We observe considerable relaxation of lattice in the monoclinic phase near the surface. This effect combined with surface tension and possibly vacancies in nanostructures are sources of stability of cubic zirconia at nanoscale.
Nanowires and nanotubes have attracted significant interest during recent years due to their novel electrical, magnetic, and photonic properties. Quantum confinement, proximity interaction, and surface plasmon enhancement effects are among a few unique phenomena associated with these materials. A convenient procedure to prepare these materials is through anodized aluminum oxide (AAO) template synthesis. Nanoporous AAO membranes with pore diameters ranging from 10 to 200 nm can be prepared with anodization in oxalic, sulfuric and phosphoric acids under various reaction conditions. With repeated anodization-etching cycles, highly ordered straight channels can be prepared through self-organization. With electro- and electroless deposition, a variety of nanowires and nanotubes such as Ni, Co, Au, Pb, Bi, etc. have been prepared. The synthesis, characterization, and physical properties of these materials are presented.
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