31 research outputs found
Single Endemic Genotype of Measles Virus Continuously Circulating in China for at Least 16 Years
The incidence of measles in China from 1991 to 2008 was reviewed, and the nucleotide sequences from 1507 measles viruses (MeV) isolated during 1993 to 2008 were phylogenetically analyzed. The results showed that measles epidemics peaked approximately every 3 to 5 years with the range of measles cases detected between 56,850 and 140,048 per year. The Chinese MeV strains represented three genotypes; 1501 H1, 1 H2 and 5 A. Genotype H1 was the predominant genotype throughout China continuously circulating for at least 16 years. Genotype H1 sequences could be divided into two distinct clusters, H1a and H1b. A 4.2% average nucleotide divergence was found between the H1a and H1b clusters, and the nucleotide sequence and predicted amino acid homologies of H1a viruses were 92.3%–100% and 84.7%–100%, H1b were 97.1%–100% and 95.3%–100%, respectively. Viruses from both clusters were distributed throughout China with no apparent geographic restriction and multiple co-circulating lineages were present in many provinces. Cluster H1a and H1b viruses were co-circulating during 1993 to 2005, while no H1b viruses were detected after 2005 and the transmission of that cluster has presumably been interrupted. Analysis of the nucleotide and predicted amino acid changes in the N proteins of H1a and H1b viruses showed no evidence of selective pressure. This study investigated the genotype and cluster distribution of MeV in China over a 16-year period to establish a genetic baseline before MeV elimination in Western Pacific Region (WPR). Continuous and extensive MeV surveillance and the ability to quickly identify imported cases of measles will become more critical as measles elimination goals are achieved in China in the near future. This is the first report that a single endemic genotype of measles virus has been found to be continuously circulating in one country for at least 16 years
Dynamics Modeling and Trajectory Tracking Control of a Quadrotor Unmanned Aerial Vehicle
Downregulation of miR-221 Inhibits Cell Migration and Invasion through Targeting Methyl-CpG Binding Domain Protein 2 in Human Oral Squamous Cell Carcinoma Cells
Oral squamous cell carcinoma (OSCC), the most frequent of all oral cancers, is a type of highly malignant tumors with a high capacity to invade locally and form distant metastases. An increasing number of studies have shown that microRNAs (miRNAs) play an important role in regulating cancer metastasis and invasion. In the present study, we detected the expression of miR-221 in two highly metastatic OSCC cell lines and two OSCC cell lines that are less metastatic using quantitative real-time PCR analysis (qRT-PCR). The qRT-PCR results indicate that miR-221 is upregulated in highly metastatic OSCC cell lines. Then, miR-221 expression was knocked down by transfection with miR-221 inhibitor, and UM1 cell migration and invasion were assessed using transwell migration and invasion assays. The results indicate that inhibition of miR-221 suppressed migration and invasion of UM1 cells. Furthermore, methyl-CpG binding domain protein 2 (MBD2) was identified as a direct target gene of miR-221. Additionally, MBD2 silencing could partly reverse the effect of miR-221 on cell migration and invasion. In conclusion, downregulation of miR-221 inhibits cell migration and invasion at least partially through targeting MBD2 in the human OSCC cell line UM1
A robust cooperative spectrum sensing scheme based on Dempster-Shafer theory and trustworthiness degree calculation in cognitive radio networks
Investigation on the dependence of flash point of diesel on the reduced pressure at high altitudes
Origin of the Enhanced Catalytic Activity of PtM/Pd (111) with Doped Atoms Changing from Chemically Inert Au to Active Os
Au
is a chemically inert metal, while Os is quite active to react
with oxygen. Although Au and Os are in the two extremes in chemical
properties, unexpectedly, both of them can enhance the oxygen reduction
reaction (ORR) activity of Pt-based alloys. In this work, a systematical
density functional theory calculation was used to elucidate the mechanisms
of enhanced activity in PtM/Pd with doped atoms changing from chemically
inert Au to active Os. The calculations show that different sites
on the PtAu/Pd and the PtOs/Pd surface adopt different ORR mechanisms
due to the heterogeneous electronic structures, such as uneven surface
charge and unequal d-band center. More importantly, all of the ORR
steps on the sites far away from the doped atoms in the PtAu/Pd and
PtOs/Pd display similar activation energy corresponding to better
catalytic activity than the other sites. The catalytic activity is
mainly affected by the ligand effect, and a proper distance between
the doped atoms and the Pt atoms should induce the catalysts to possess
the highest catalytic activity. These results also uncover why the
different content of doped atom can lead to the different activity
of catalysts
Malt1 Protease Is Critical in Maintaining Function of Regulatory T Cells and May Be a Therapeutic Target for Antitumor Immunity
Shape Fixing via Salt Recrystallization: A Morphology-Controlled Approach To Convert Nanostructured Polymer to Carbon Nanomaterial as a Highly Active Catalyst for Oxygen Reduction Reaction
Herein,
we report a “shape fixing via salt recrystallization”
method to efficiently synthesize nitrogen-doped carbon material with
a large number of active sites exposed to the three-phase zones, for
use as an ORR catalyst. Self-assembled polyaniline with a 3D network
structure was fixed and fully sealed inside NaCl via recrystallization
of NaCl solution. During pyrolysis, the NaCl crystal functions as
a fully sealed nanoreactor, which facilitates nitrogen incorporation
and graphitization. The gasification in such a closed nanoreactor
creates a large number of pores in the resultant samples. The 3D network
structure, which is conducive to mass transport and high utilization
of active sites, was found to have been accurately transferred to
the final N-doped carbon materials, after dissolution of the NaCl.
Use of the invented cathode catalyst in a proton exchange membrane
fuel cell produces a peak power of 600 mW cm<sup>–2</sup>,
making this among the best nonprecious metal catalysts for the ORR
reported so far. Furthermore, N-doped carbon materials with a nanotube
or nanoshell morphology can be realized by the invented method