Study of Cu-Exchanged CHA Catalysts for the Selective Catalytic Reduction (SCR) Reaction

Eliminating the harmful NOx, which is the major pollutant in the exhaust gas of diesel engines, has long been the pursue of scientists. Cu-chabazite (Cu-CHA) zeolites system developed in 2008 is shown to be an efficient and thermal stable catalyst in the deNOx NH3-SCR reaction and has received intense study since then. Aiming to further improve its catalytic activity, a wide range of characterization techniques has been developed and applied to study the well-defined structures and catalysis. Study of SCR reaction over the Cu-CHA catalysts demands the understanding of active Cu sites, for which loading-dependent behaviour is first studied with UV-Vis spectroscopy and ex-situ EPR spectroscopy together with the reaction evaluation. To further investigate different Cu species, the combination of H2-TPR, NH3-TPD and EPR spectroscopy were applied to quantify the Cu speciation in the catalysts, from which the sequential domination of 2AlCu, 1AlCu and CuO species with increasing Cu loadings was observed. Subsequent study of dehydration and hydrothermal aging processes with EPR also reveals the transformation of Cu species from 1AlCu to 2AlCu through the formation of hydrated complexes and the decomposition of CuOx clusters. On the other hand, the interaction between Cu-CHA catalysts and SCR reactants was studied with in situ FTIR and operando NEXAFS, showing the adsorption of NO and NH3 molecules respectively. Aiming to uncover the key species in the SCR reaction and reveal the origin of different reactivity for 1AlCu and 2AlCu sites, the samples with different Cu distribution was studied with operando X-ray spectroscopy under SCR conditions. With the combination of HERFD-XANES, vtc-XES and time-resolved XAS at transient states, key intermediate CuNOx species is observed to be preferentially formed on the 1AlCu sites, while a framework coordinated CuI(NH3)xOfw species is identified to be the real species causing NH3 inhibition effect, hindering the re-oxidation of CuI especially at 2AlCu sites

Mapping of Cu and Pb Contaminations in Soil Using Combined Geochemistry, Topography, and Remote Sensing: A Case Study in the Le’an River Floodplain, China

Heavy metal pollution in soil is becoming a widely concerning environmental problem in China. The aim of this study is to integrate multiple sources of data, namely total Cu and Pb contents, digital elevation model (DEM) data, remote sensing image and interpreted land-use data, for mapping the spatial distribution of total Cu and Pb contamination in top soil along the Le’an River and its branches. Combined with geographical analyses and watershed delineation, the source and transportation route of pollutants are identified. Regions at high risk of Cu or Pb pollution are suggested. Results reveal that topography is the major factor that controls the spatial distribution of Cu and Pb. Watershed delineation shows evidence that the streamflow resulting from rainfall is the major carrier of metal pollutants

Neuroprotective Effects of Jitai Tablet, a Traditional Chinese Medicine, on the MPTP-Induced Acute Model of Parkinson’s Disease: Involvement of the Dopamine System

Jitai tablet (JTT) is a traditional Chinese medicine used to treat neuropsychiatric disorders. We previously demonstrated that JTT treatment led to increased level of dopamine transporter (DAT) in the striatum, thus indicating that JTT might have therapeutic potential for Parkinson’s disease (PD), which is characterized by dysregulated dopamine (DA) transmission and decreased striatal DAT expression. The aim of this study was to investigate the neuroprotective effect of JTT on MPTP-induced PD mice. Using locomotor activity test and rotarod test, we evaluated the effects of JTT (0.50, 0.15, or 0.05 g/kg) on MPTP-induced behavioral impairments. Tyrosine hydroxylase TH-positive neurons in the substantia nigra and DAT and dopamine D2 receptor (D2R) levels in the striatum were detected by immunohistochemical staining and/or autoradiography. Levels of DA and its metabolites were determined by HPLC. In MPTP-treated mice, behavioral impairments were alleviated by JTT treatment. Moreover, JTT protected against impairment of TH-positive neurons and attenuated the MPTP-induced decreases in DAT and D2R. Finally, high dose of JTT (0.50 g/kg) inhibited the MPTP-induced increase in DA metabolism rate. Taken together, results from our present study provide evidence that JTT offers neuroprotective effects against the neurotoxicity of MPTP and thus might be a potential treatment for PD

Discovery and biological characterization of geranylated RNA in bacteria

A general mass spectrometry-based screen for unusually hydrophobic cellular small-molecule RNA conjugates revealed geranylated RNA in E. coli, Enterobacter aerogenes, Pseudomonas aeruginosa, and Salmonella thyphimurium. The geranyl group is conjugated to the sulfur atom in two 5-methylaminomethyl-2-thiouridine nucleotides. These geranylated nucleotides occur in the first anticodon position of tRNA Glu UUC, tRNA Lys UUU, tRNA Gln UUG at a frequency of up to 6.7% (~400 geranylated nucleotides per cell). RNA geranylation levels can be increased or abolished by mutation or deletion of the selU (ybbB) gene in E. coli, and purified SelU protein in the presence of geranyl pyrophosphate and tRNA can produce geranylated tRNA. The presence or absence of the geranyl group in tRNA Glu UUC, tRNA Lys UUU, and tRNA Gln UUG affects codon bias and frameshifting during translation. These RNAs represent the first reported examples of oligoisoprenylated cellular nucleic acids.Chemistry and Chemical Biolog

Comparative transcriptomic analyses of two sugarcane Saccharum L. cultivars differing in drought tolerance

Sugarcane (Saccharum spp.) is an important cash crop, and drought is an important factors limiting its yield. To study the drought resistance mechanism of sugarcane, the transcriptomes of two sugarcane varieties with different levels of drought resistance were compared under different water shortage levels. The results showed that the transcriptomes of the two varieties were significantly different. The differentially expressed genes were enriched in starch and sucrose metabolism, linoleic acid metabolism, glycolysis/gluconeogenesis, and glyoxylate and dicarboxylate metabolic pathways. Unique trend genes of the variety with strong drought resistance (F172) were significantly enriched in photosynthesis, mitogen-activated protein kinases signaling pathway, biosynthesis of various plant secondary metabolites, and cyanoamino acid metabolism pathways. Weighted correlation network analysis indicated that the blue4 and plum1 modules correlated with drought conditions, whereas the tan and salmon4 modules correlated with variety. The unique trend genes expressed in F172 and mapped to the blue4 module were enriched in photosynthesis, purine metabolism, starch and sucrose metabolism, beta-alanine metabolism, photosynthesis-antenna proteins, and plant hormone signal transduction pathways. The expression of genes involved in the photosynthesis-antenna protein and photosynthesis pathways decreased in response to water deficit, indicating that reducing photosynthesis might be a means for sugarcane to respond to drought stress. The results of this study provide insights into drought resistance mechanisms in plants, and the related genes and metabolic pathways identified may be helpful for sugarcane breeding in the future

Large-area, freestanding single-crystal gold of single nanometer thickness

Two-dimensional single-crystal metals are highly sought after for next-generation technologies. Here, we report large-area (>10^4 {\mu}m2), single-crystal two-dimensional gold with thicknesses down to a single-nanometer level, employing an atomic-level-precision chemical etching approach. The ultrathin thickness and single-crystal quality endow two-dimensional gold with unique properties including significantly quantum-confinement-augmented optical nonlinearity, low sheet resistance, high transparency and excellent mechanical flexibility. By patterning the two-dimensional gold into nanoribbon arrays, extremely-confined near-infrared plasmonic resonances are further demonstrated with quality factors up to 5. The freestanding nature of two-dimensional gold allows its straightforward manipulation and transfer-printing for integration with other structures. The developed two-dimensional gold provides an emerging platform for fundamental studies in various disciplines and opens up new opportunities for applications in high-performance ultrathin optoelectronic, photonic and quantum devices

Measurements of the observed cross sections for exclusive light hadron production in e^+e^- annihilation at \sqrt{s}= 3.773 and 3.650 GeV

By analyzing the data sets of 17.3 pb$^{-1}$ taken at $\sqrt{s}=3.773$ GeV and 6.5 pb$^{-1}$ taken at $\sqrt{s}=3.650$ GeV with the BESII detector at the BEPC collider, we have measured the observed cross sections for 12 exclusive light hadron final states produced in $e^+e^-$ annihilation at the two energy points. We have also set the upper limits on the observed cross sections and the branching fractions for $\psi(3770)$ decay to these final states at 90% C.L.Comment: 8 pages, 5 figur

Measurements of psi(2S) decays to octet baryon-antibaryon pairs

With a sample of 14 million psi(2S) events collected by the BESII detector at the Beijing Electron Positron Collider (BEPC), the decay channels psi(2S)->p p-bar, Lambda Lambda-bar, Sigma0 Sigma0-bar, Xi Xi-bar are measured, and their branching ratios are determined to be (3.36+-0.09+-0.24)*10E-4, (3.39+-0.20+-0.32)*10E-4, (2.35+-0.36+-0.32)*10E-4, (3.03+-0.40+-0.32)*10E-4, respectively. In the decay psi(2S)->p p-bar, the angular distribution parameter alpha is determined to be 0.82+-0.17+-0.04.Comment: 8 pages, 8 figure

Search for the Rare Decays J/Psi --> Ds- e+ nu_e, J/Psi --> D- e+ nu_e, and J/Psi --> D0bar e+ e-

We report on a search for the decays J/Psi --> Ds- e+ nu_e + c.c., J/Psi --> D- e+ nu_e + c.c., and J/Psi --> D0bar e+ e- + c.c. in a sample of 5.8 * 10^7 J/Psi events collected with the BESII detector at the BEPC. No excess of signal above background is observed, and 90% confidence level upper limits on the branching fractions are set: B(J/Psi --> Ds- e+ nu_e + c.c.)<4.8*10^-5, B(J/Psi --> D- e+ nu_e + c.c.) D0bar e+ e- + c.c.)<1.1*10^-5Comment: 10 pages, 4 figure