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Abstract: An amplified graphene oxide (GO) based fluorescence aptasensor based on target-triggered aptamer hairpin switch and strand-displacement polymerization recycling is developed for bioassays. The dye-labeled single-strand DNA (aptamer hairpin) was adsorbed on the surface of GO, which result in the fluorescence quenching of dye, and exhibiting minimal background fluorescence. Upon the target, primer and polymerase, the stem of the aptamer hairpin was opened, and binds with the primer to triggers the circular target strand-displacement polymerization reaction, which produces huge amounts of duplex helixes DNA and lead to strong fluorescence emission due to shielding of nucelobases within its double-helix structure. During the polymerization reaction, the primer was extended, and target was displaced. And the displaced target recognizes and hybridizes with another hairpin probe, triggering the next round of polymerization reaction, and the circle process induces fluorescence signal amplification for the detection of analyte. To test the feasibility of the aptasensor systems, interferon-gamma (IFN-γ) was employed as a model analyte. A detection limit as low as 1.5fM is obtained based on the GO aptasensor with a linear range of three orders of magnitude. The present method was successfully applied for the detection of IFN-γ in human plasma. [Copyright &y& Elsevier]

Abstract: Analytical solutions of contaminant transport in multi-dimensional media are significant for theoretical and practical purposes. However, due to the problems for which the solutions are sought which are complex in most of the cases, most available analytical solutions in multi-dimensional media are not given in their closed forms. Integrals are often included in the solution expressions, which may limit the practitioners to use the solutions. In addition, available multi-dimensional solutions for the third-type sources in bounded media are fairly limited. In this paper, a stepwise superposition approach for obtaining approximate multi-dimensional transport solutions is developed. The approach is based on the condition that the one-dimensional solution along the flow direction is known. The solutions are expressed in their closed forms without integrals. The transport media to the solutions are flexible and can be finite, semi-infinite, or infinite in the transverse directions. The solutions subject to the first- and third-type boundary conditions at the inlet with a distributed source over the domain are obtained. The integrals in some known solutions can also be evaluated by the approach if they can be derived to include known longitudinal integrals with respect to time. The accuracy and efficiency of the solutions proposed in this paper are verified through test problems and calculation examples. [Copyright &y& Elsevier]

Abstract: The microgravity environment of spaceflight expeditions has been associated with altered microbial responses. This study explores the characterization of Serratia marcescensis grown in a spaceflight environment at the phenotypic, transcriptomic and proteomic levels. From November 1, 2011 to November 17, 2011, a strain of S. marcescensis was sent into space for 398h on the Shenzhou VIII spacecraft, and ground simulation was performed as a control (LCT-SM213). After the flight, two mutant strains (LCT-SM166 and LCT-SM262) were selected for further analysis. Although no changes in the morphology, post-culture growth kinetics, hemolysis or antibiotic sensitivity were observed, the two mutant strains exhibited significant changes in their metabolic profiles after exposure to spaceflight. Enrichment analysis of the transcriptome showed that the differentially expressed genes of the two spaceflight strains and the ground control strain mainly included those involved in metabolism and degradation. The proteome revealed that changes at the protein level were also associated with metabolic functions, such as glycolysis/gluconeogenesis, pyruvate metabolism, arginine and proline metabolism and the degradation of valine, leucine and isoleucine. In summary S. marcescens showed alterations primarily in genes and proteins that were associated with metabolism under spaceflight conditions, which gave us valuable clues for future research. [Copyright &y& Elsevier]

Abstract: The environment in space could affect microorganisms by changing a variety of features, including proliferation rate, cell physiology, cell metabolism, biofilm production, virulence, and drug resistance. However, the relevant mechanisms remain unclear. To explore the effect of a space environment on Bacillus cereus, a strain of B. cereus was sent to space for 398h by ShenZhou VIII from November 1, 2011 to November 17, 2011. A ground simulation with similar temperature conditions was simultaneously performed as a control. After the flight, the flight and control strains were further analyzed using phenotypic, genomic, transcriptomic and proteomic techniques to explore the divergence of B. cereus in a space environment. The flight strains exhibited a significantly slower growth rate, a significantly higher amikacin resistance level, and changes in metabolism relative to the ground control strain. After the space flight, three polymorphic loci were found in the flight strains LCT-BC25 and LCT-BC235. A combined transcriptome and proteome analysis was performed, and this analysis revealed that the flight strains had changes in genes/proteins relevant to metabolism. In addition, certain genes/proteins that are relevant to structural function, gene expression modification and translation, and virulence were also altered. Our study represents the first documented analysis of the phenotypic, genomic, transcriptomic, and proteomic changes that occur in B. cereus during space flight, and our results could be beneficial to the field of space microbiology. [Copyright &y& Elsevier]

N doped and N, S co-doped TiO 2 hollow spheres photocatalysts have been successfully synthesized by a simple hydrothermal method with water as the only solvent. The XRD results show that the all samples are crystalline without further sintering treatment. The measured photocatalytic activity under simulated solar light, monitored by the decomposition of Rhodamine-B, demonstrated that N or N, S loading could significantly enhance the photocatalytic activity of TiO 2 . UV–vis diffuse reflectance spectra indicate that N-doping or N, S-codoping into a TiO 2 crystal lattice can result in the shift of the valence band of TiO 2 to a positive direction. It may lead to its higher oxidative ability than pure TiO 2 , which is important for organic pollutant degradation under visible-light irradiation. This work provides some insights into the rational design and development of high-performance photocatalysts using sunlight as an energy source. [ABSTRACT FROM AUTHOR]

For the island-reef engineering construction background in the South China Sea, the research studied the preparation technology, mechanical properties and chloride ion diffusion behavior of coral aggregate seawater concrete and discussed the steel bars corrosion behavior of coral aggregate seawater concrete (CASC) and reliability analysis of service life, which provide a low cost, high durability CASC and its application technology for island-reef engineering. The results showed that: according to the theory of grout concrete and the design principle of high-performance concrete, the cube compressive strength (f cu) of CASC can reach C80. Uniaxial compression whole stress-strain curve of CASC with different strength grades and constitutive relation were obtained. The "three high" Cl− diffusion characteristics, high initial chloride ion content (C 0), high surface chloride ion content (C s) and high apparent chloride ion diffusion coefficient (D a) in CASC, were established, which easily result in steel bars corrosion. It suggests to choose organic newly coated steel bars, which the thickness of the concrete protective cover is greater than 5.5 cm, concrete strength grade is greater than C50 and use "slow-release effect of micropump" of coral aggregate to pre-absorb and incorporate the amino alcohols inhibitor, which can significantly reduce steel bars corrosion of CASC structures. Finally, the study determined the durability design methods of CASC structures that meet the 20–100 years of service life requirement. [ABSTRACT FROM AUTHOR]

Abstract: A novel label-free DNAzyme molecular beacon (MBzyme) strategy was for the first time developed for colorimetric amplification detection of target nucleic acids. The MBzyme, which is designed to contain peroxidase-mimicking DNAzyme that is locked by a common hairpin, was engineered to form a catalytically active MBzyme through hybridizing with the target p53 DNA. The MBzyme is a multifunctional label-free probe that can act as the target recognition element, catalytic DNAzyme and the primer of polymerization. The target p53 DNA hybridization can induce the isothermal circular strand-displacement polymerization even without any chemical modification and other DNA sequences. This unique amplifying strategy leads to the generation of multiple numbers of active MBzyme molecules even if one hybridization event occurs, achieving a dynamic range of seven orders of magnitude and giving a detection limit down to 25fM which is 3–5 orders of magnitude lower than those of related literature reports. These achievements might be helpful in the design of highly efficient enhancers for G-quadruplex–hemin DNAzymes to be applied on the fundamental research, biotechnology, and biomedical diagnosis. [Copyright &y& Elsevier]