Search

Gas hydrates have been found in the western continental margin of South China Sea, which are revealed by widespread bottom simulating reflectors (BSRs) imaged from a three-dimensional (3D) seismic volume near the Guangle carbonate platform in the western South China Sea. Fluid-escape structures (faults and gas chimneys) are originated below BSR were distinguished. A comprehensive model in three-level structure was proposed to depict the gas hydrate accumulation in the study area. In Level 1, regional major faults and gas chimneys provide the first pathways of upward migration of gas near basement. In Level 2, pervasive polygonal faults in carbonate layer promote the migration of gas. In Level 3, gases sourced from near-basement accumulate within shallow sediment layers and form gas hydrate above the unit with faults once appropriate temperature and pressure occur. The gas hydrates in the study area are mainly in microbial origin, and their accumulation occurs only when fluid-escape structures align in all the three levels. The proposed model of the gas hydrate accumulation in western SCS margin provides new insights for further studies in this poorly studied area. [ABSTRACT FROM AUTHOR]

In this work, we obtain charged Taub-NUT-AdS black holes in f(R) gravity with the Maxwell term and deduce its thermodynamic first law. The holographic complexity of the black hole with inner and outer horizons is then studied using the “complexity equals action” (CA duality). We get a complexity growth rate considering all the contributions, including the bulk, boundary, and joint terms. At late times, the complexity growth rate can be expressed in a compact form which is significantly influenced by the Misner string and the correction from the f(R) gravity. Also, our result can reduce to that of the charged Taub-NUT-AdS black hole in Einstein-Maxwell gravity. [ABSTRACT FROM AUTHOR]

Yersinia pseudotuberculosis is an enteric bacterium causing yersiniosis in humans. The existing Yersinia pseudotuberculosis detection methods are time-consuming, requiring a sample pretreatment step, and are unable to discriminate live/dead cells. The current work reports a phage-based electrochemical biosensor for rapid and specific detection of Yersinia pseudotuberculosis. The conductive poly(indole-5-carboxylic acid), reduced graphene oxide, and gold nanoparticles are applied for surface modification of the electrode. They possess ultra-high redox stability and retain 97.7% of current response after performing 50 consecutive cycles of cyclic voltammetry.The specific bacteriophages vB_YepM_ZN18 we isolated from hospital sewage water were immobilized on modified electrodes by Au-NH2 bond between gold nanoparticles and phages. The biosensor fabricated with nanomaterials and phages were utilized to detect Yersinia pseudotuberculosis successfully with detection range of 5.30 × 102 to 1.05 × 107 CFU mL−1, detection limit of 3 CFU mL−1, and assay time of 35 min. Moreover, the biosensor can specifically detect live Yersinia pseudotuberculosis without responding to phage-non-host bacteria and dead Yersinia pseudotuberculosis cells. These results suggest that the proposed biosensor is a promising tool for the rapid and selective detection of Yersinia pseudotuberculosis in food, water, and clinical samples. [ABSTRACT FROM AUTHOR]

High-resolution multichannel seismic data enables the discovery of a previous, undocumented submarine canyon (Huaguang Canyon) in the Qiongdongnan Basin, northwest South China Sea. The Huaguang Canyon with a NW orientation is 140 km in length, and 2.5 km to 5 km in width in its upper reach and 4.6 km to 9.5 km in width in its lower reach. The head of the Huaguang Canyon is close to the Xisha carbonate platform and its tail is adjacent to the central canyon. This buried submarine canyon is formed by gravity flows from the Xisha carbonate platform when the sea level dropped in the early stage of the late Miocene (∼10.5 Ma). The internal architecture of the Huaguang Canyon is mainly characterized by high amplitude reflections, indicating that this ancient submarine canyon was filled with coarse-grained sediments. The sediment was principally scourced from the Xisha carbonate platform. In contrast to other buried large-scale submarine canyons (central canyon and Zhongjian Canyon) in the Qiongdongnan Basin, the Huaguang Canyon displays later formation time, smaller width and length, and single sediment supply. The coarse-grained deposits within Huaguang Canyon provide a good environment for reserving oil and gas, and the muddy fillings in Huaguang Canyon have been identified as regional caps. Therefore, Huaguang Canyon is potential area for future hydrocarbon exploration in the northwest South China Sea. Our results may contribute to a better understanding of the evolution of submarine canyons formed in carbonate environment. [ABSTRACT FROM AUTHOR]

Methanol steam reforming (MSR) is regarded as one of the effective technologies for in-situ hydrogen generation. A novel mesh-type γ-Al2O3/Al support was prepared by anodization technology. To decrease dimethyl ether (DME) yield in MSR system, magnesium was doped to the γ-Al2O3/Al to modify acidity. The results show that the acid density of the γ-Al2O3/Al support can be decreased from 1.423 μmol/m2 to 1.122 μmol/m2, resulting in the decrease in DME yield from 70.2 to 16.7%. Meanwhile, various CuMgx/γ-Al2O3/Al catalysts were prepared and the effects of MgO on the distribution and reducibility of CuO on the support were investigated. The results show that the dispersion of CuO was improved and reduction temperature was decreased with Mg doping. Finally, four pieces of mesh structured CuMg/γ-Al2O3/Al catalysts (4*8 cm2) were applied into the microreactor with the channel height of 2 mm. CuMg/γ-Al2O3/Al catalyst showed excellent catalytic performance with 100% methanol conversion, 98.2% hydrogen yield, without DME at 250 °C, 4000 mL/(g h) GHSV. Furthermore, the diffusion limitation was investigated by Damköhler number (Da), the results indicated the diffusion influence can be neglected in the microreactor over mesh-type catalysts. [ABSTRACT FROM AUTHOR]

Teschovirus A is currently the sole species in the genus Teschovirus, whose members are divided into 13 subtypes: porcine teschovirus (PTV) 1–13. However, recent discoveries of novel PTV genotypes have suggested that a new species, "Teschovirus B", should be established. Here, we have identified six of the 19 known genotypes and two novel genotypes (PTV 17–18), revealing the high genetic diversity of the PTV subpopulation in indigenous pigs of western Jiangxi, China. Moreover, we determined the nearly complete genome sequences of PTV 17-SG9 and PTV 18-SG10. Together with PTV 1–13, these novel genotypes were confirmed to be members of the species Teschovirus A based on phylogenetic and genetic divergence analysis. Consequently, the species Teschovirus A now includes at least 15 PTV genotypes. [ABSTRACT FROM AUTHOR]

Porcine circovirus 2 (PCV2) has been widely prevailing in China since the first report in 2001, causing huge economic losses to the pig industry. In the present study, 674 samples were collected from 2006 to 2016 in Hunan province, and 62% were positive for PCV2. An increase was observed from 2006 to 2011 (72.1%-89.1%), and a decrease was observed from 2012 to 2016 (78.9%-36.8%). The prevalence of genotype PCV2a, PCV2b, and PCV2d was 0, 44.7% and 67%, respectively. During 2006-2007, PCV2b was the main genotype circulating in Hunan, while, in 2008, PCV2d became the predominant one. Coinfection with PCV2b and PCV2d was observed frequently, and the positive rates of coinfection ranged from 6.3% to 18.9% during 2006-2016. The complete genome was sequenced for 54 positive samples, and four were identified as PCV2b-1, 22 as PCV2b-2, four as PCV2d-1 and 24 as PCV2d-2, based on phylogenetic analysis of the complete genome and ORF2 region. Recombination analysis using the complete genome sequences of these isolates revealed a high recombination rate of 27.7% (17/54), and showed that recombination occurred mainly in the ORF1 region. This shows that the prevalence of PCV2 has clearly decreased in recent years and that PCV2d has become a predominant genotype since 2008. In addition, frequent recombination events were observed in the PCV2 isolates from Hunan, China. [ABSTRACT FROM AUTHOR]

The authors describe a voltammetric immunosensor with antibody immobilized on a glassy carbon electrode (GCE) modified with N-doped graphene (N-GS), electrodeposited gold nanoparticles (AuNPs) and chitosan (Chit). The preparation is simple and the thickness of the electrodeposited films can be well controlled. Due to the specific advantages of N-GS, AuNPs and Chit, the electrode has a large specific surface, improved conductivity, high stability. A new label-free immunosensor for the model antigen (alpha fetoprotein, AFP) detection was then designed by employing N-GS-AuNP-Chit as the antibody immobilization and signal amplification platform. Differential pulse voltammetry and electrochemical impedance spectroscopy were used for the characterization of the stepwise assembly process. Under the optimized conditions, at a typical working potential of +0.20 V (vs. SCE), and by using hexacyanoferrate as an electrochemical probe, the immunosensor has a detection limit as low as 1.6 pg mL and a linear analytical range that extends from 5 pg mL to 50 ng mL. AFP was quantified in spiked human serum samples with acceptable precision. [ABSTRACT FROM AUTHOR]

Outbreaks of diarrhea in piglets cause serious economic consequences in China. Diarrhetic fecal samples from 20 Hunan farm piglets were tested and found to be positive for porcine epidemic diarrhea virus (PEDV) by RT-PCR, although incubation with porcine kidney (PK-15) cells failed to produce infectious PEDV. Four porcine sapelovirus (PSV) strains (designated as PSV-HuNs) were isolated from four of the samples. Genomic sequence analysis revealed open reading frames encoding polyproteins of 2,331 (HuN1, 2 and 3) and 2,332 (HuN4) amino acids. Homology comparisons of the VP1 gene of the four Hunan strains with previously reported PSV strains revealed nucleotide sequence identities ranging from 74.2 to 98.6%, and deduced amino acid sequence identities from 79.5 to 98%. Phylogenetic analyses based on full-length and partial VP1 gene sequences showed that 3 of the PSV-HuN strains (HuN2, 3 and 4) clustered within a clade distinct from HuN1 as well as from all PSVs previously isolated in China, thereby showing that genetic diversity exists within Chinese PSVs. In addition, recombination analysis among PSVs indicates that a recombinant (HuN2 strain) exist in China. [ABSTRACT FROM AUTHOR]