Solution chemistry of carbonate minerals and its effects on the flotation of hematite with sodium oleate

The effects of carbonate minerals (dolomite and siderite) on the flotation of hematite using sodium oleate as a collector were investigated through flotation tests, supplemented by dissolution measurements, solution chemistry calculations, zeta-potential measurements, Fourier transform infrared (FTIR) spectroscopic studies, and X-ray photoelectron spectroscopy (XPS) analyses. The results of flotation tests show that the presence of siderite or dolomite reduced the recovery of hematite and that the inhibiting effects of dolomite were stronger. Dissolution measurements, solution chemistry calculations, and flotation tests confirmed that both the cations (Ca2+ and Mg2+) and CO₃2- ions dissolved from dolomite depressed hematite flotation, whereas only the CO₃2- ions dissolved from siderite were responsible for hematite depression. The zeta-potential, FTIR spectroscopic, and XPS analyses indicated that Ca2+, Mg2+, and CO₃2- (HCO₃-) could adsorb onto the hematite surface, thereby hindering the adsorption of sodium oleate, which was the main reason for the inhibiting effects of carbonate minerals on hematite flotation.     

Microstructure and mechanical properties of Nb–Mo–ZrB2 composites prepared by hot-pressing sintering

Nb–Mo–ZrB₂ composites (V(Nb)/V(Mo)=1) with 15vol% or 30vol% of ZrB₂ were fabricated by hot-pressing sintering at 2000℃. The phases, microstructure, and mechanical properties were then investigated. The composites contain Nb-Mo solid solution (denoted as (Nb, Mo)ss hereafter), ZrB, MoB, and NbB phases. Compressive strength test results suggest that the strength of Nb–Mo–ZrB₂ composites increases with increasing ZrB₂ content; Nb–Mo–30vol%ZrB₂ had the highest compressive strength (1905.1 MPa). The improvement in the compressive strength of the Nb–Mo–ZrB₂ composites is mainly attributed to the secondary phase strengthening of the stiffer ZrB phase, solid-solution strengthening of the (Nb, Mo)ss matrix as well as fine-grain strengthening. The fracture toughness decreases with increasing ZrB₂ content. Finally, the fracture modes of the Nb–Mo–ZrB₂ composites are also discussed in detail.     

Insights on evolution of virulence and resistance from the whole-genome analysis of a predominant methicillin-resistantStaphylococcus aureus clone sequence type 239 in China

Earlier, we reported that ST239 was the 15-year predominant methicillin-resistant Staphylococcus aureus （MRSA） clone in China. In this study, MRSA strain CN79 belonging to ST239 and isolated from blood was used to determine the whole tive genomics analysis was genome sequence. Compara- done between MRSA CN79 and 25 sequenced S. aureus in the NCBI GenBank data- base. A total of 2,734 protein-encoding genes were iden- tified in the MRSA CN79 genome, which carries 11 antibiotic resistance genes and 65 virulence genes. Two prophages phiCN79A and phiNM3-1ike were found on the MRSA CN79 genome. MRSA CN79 carries 30 specific genes that are absent from the 25 sequenced S. aureus genomes. Most of them were prophage-related genes. Several antibiotic resistance genes, such as [3-1actamase and ABC-type multidrug transport system gene, were located on the genomic island vSal3. The antibiotic resis- tance genes, such as tet （M）, ermA1, and blaZ, were also located on different transposons. The virulence genes sea,map, hlb, and sak are located on phiNM3-1ike prophage and the exotoxin genes are carried on the genomic island vSaa. These results suggest that ST239 MRSA strains are widespread owing to horizontal acquisition of the mobile genetic elements harbored antibiotic resistance genes and virulence genes in response to environmental selective pressures, such as antibiotics and the human immune sys- tem during evolution.     

New Energy-Saving Cement-Iron-Rich FloorAlominate Cement

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Dispersion stability of thermal nanofluids

Thermal nanofluids, the engineered fluids with dispersed functional nanoparticles, have exhibited extraordinary thermophysical properties and added functionalities, and thus have enabled a broad range of important applications. The poor dispersion stability of thermal nanofluids, however, has been considered as a longexisting issue that limits their further development and practical application. This review overviews the recent efforts and progresses in improving the dispersion stability of thermal nanofluids such as mechanistic understanding of dispersion behavior of nanofluids, examples of both water-based and oil-based nanofluids, strategies to stabilize nanofluids, and characterization techniques for dispersion behavior of nanofluids. Finally, on-going research needs, and possible solutions to research challenges and future research directions in exploring stably dispersed thermal nanofluids are discussed.     

Precipitation of spherical boehmite from concentrated sodium aluminate solution by adding gibbsite as seed

The precipitation of spherical boehmite was studied by surface energy calculations, measurements of precipitation ratios, Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The surface energy calculation results show that the (001) and (112) planes of gibbsite surfaces are remarkably stable because of their low surface energies. In addition, the (010) plane of boehmite grows preferentially during precipitation because of its low surface energy. Thus, we propose a method to precipitate spherical boehmite from a supersaturated sodium aluminate solution by adding gibbsite as seed in a heterogeneous system. In this method, gibbsite acts as the preliminary seed and saturation modifier. The results show that the fine boehmite first nucleates on the (001) and (112) planes of gibbsite and then grows vertically on the (001) and (112) basal planes of gibbsite via self-assembly, thereby forming spherical boehmite. Simultaneously, gibbsite is dissolved into the aluminate solution to maintain the saturation for the precipitation of boehmite. The precipitation ratio fluctuates (forming an M-shaped curve) because of gibbsite dissolution and boehmite precipitation. The mechanism of boehmite precipitation was further discussed on the basis of the differences in surface energy and solubility between gibbsite and boehmite. This study provides an environmentally friendly and economical method to prepare specific boehmite in a heterogeneous system.     

Meta-analysis identifies common variants associated with body mass index in east Asians

Multiple genetic loci associated with obesity or body mass index (BMI) have been identified through genome-wide association studies conducted predominantly in populations of European ancestry. We performed a meta-analysis of associations between BMI and approximately 2.4 million SNPs in 27,715 east Asians, which was followed by in silico and de novo replication studies in 37,691 and 17,642 additional east Asians, respectively. We identified ten BMI-associated loci at genome-wide significance (P < 5.0 × 10(-8)), including seven previously identified loci (FTO, SEC16B, MC4R, GIPR-QPCTL, ADCY3-DNAJC27, BDNF and MAP2K5) and three novel loci in or near the CDKAL1, PCSK1 and GP2 genes. Three additional loci nearly reached the genome-wide significance threshold, including two previously identified loci in the GNPDA2 and TFAP2B genes and a newly identified signal near PAX6, all of which were associated with BMI with P < 5.0 × 10(-7). Findings from this study may shed light on new pathways involved in obesity and demonstrate the value of conducting genetic studies in non-European populations.     

多输入模糊协调控制算法及应用研究

针对某新2#焦炉集气管压力波动幅值大、压力振荡剧烈且具有突变的特性,提出了三输入模糊协调控制算法.首先,根据工况的不同,选择相应的三输入模糊控制算法,该算法在两输入模糊控制算法的基础上,引入偏差瞬时变化率作为输入,较好地预测了集气管压力的即时变化趋势,并能对其跟踪控制.然后,采用蝶阀控制算法适应蝶阀的流量特性,提高控制品质.最后,通过仿真实验以及实际运行结果证明了该方法的有效性和优越性.     

Preparation,characterization and photocatalytic properties of nanometer zinc ferrite

A combustion synthesis method was adapted for the efficient preparation of pure zinc ferrite particles (ZnFe₂O₄). It is based on the exothermic reaction of the corresponding metal nitrates with a reducing agent, to produce extremely fine-grained ashes that readily convert into pure ZnFe₂O₄ with treating thermally. The composition and microstructure of the so-obtained samples were studied by XRD (X-ray powder diffraction), TEM (Transmission Electron Microscopy) and AFM (Atomic Force Microscopy). These results showed that the range of particle size of ZnFe₂O₄ is about 15-25 nm. Photocatalytic activities of nanometer ZnFe₂O₄ were also evaluated by degradation of the curcumin solution.     

Dynamic recrystallization of electroformed copper liners of shaped charges in high-strain-rate plastic deformation

The microstructures in the electroformed copper liners of shaped charges after high-strain-rate plastic deformation were investigated by transmission electron microscopy (TEM). Meanwhile, the orientation distribution of the grains in the recovered slug was examined by the electron backscattering Kikuchi pattern (EBSP) technique. EBSP analysis illustrated that unlike the as-formed electroformed copper linersof shaped charges the grain orientations in the recovered slug are distributed along randomly all the directions after undergoing heavily strain deformation at high-strain rate. Optical microscopy shows a typical recrystallization structure, and TEM examination reveals dislocation cells existed in the thin foil specimen. These results indicate that dynamic recovery and recrystallization occur during this plastic deformation process, and the associated deformation temperature is considered to be higher than 0.6 times the melting point of copper.