Chinese deserts and sand fields in Last Glacial Maximum and Holocene Optimum

The Last Glacial Maximum (LGM, c. 26-16 ka) and the Holocene Optimum (HO, c. 9-5 ka) were characterized by cold-dry and warm-wet climates respectively in the recently geological Earth. How Chinese deserts and sand fields responded to these distinctive climatic changes is still not clear, however. To reconstruct environments of the deserts and sand fields during the LGM and HO is helpful to understand the forcing mechanisms of environment change in this arid region, and to test paleoclimatic modeling results. Through our long-term field and laboratory investigations, 400 optically stimulated luminescence (OSL) ages and more than 100 depositional records in the Chinese deserts and sand fields were obtained; on the basis of these data, we reconstruct spatial distributions of the deserts and sand fields during the LGM and HO. Our results show that the sand fields of Mu Us, Hunshandake, Horqin and Hulun Buir in northern and northeastern China had expanded 25%, 37%, 38% and 270%, respectively, during the LGM; the sand fields of Gonghe in the northeastern Qinghai-Tibetan Plateau had expanded 20%, and the deserts of Badain Jaran, Tengger in central northern China had expanded 39% and 29% separately during the LGM; the deserts of Taklimakan, Gurbantünggüt and Kumtag in northwestern China had expanded 10%-20% respectively, compared to their modern areas. On the other hand, all of the sand fields were nearly completely covered by vegetation during the HO; the deserts in northwestern and central northern China were reduced by around 5%-20% in area during this time. Lakes in this arid region were probably expanded during the HO but this conclusion needs more investigation. Compared with the geological distributions of deserts and sand fields, human activity has clearly changed (expanded) the area of active sand dunes at the present time. Our observations show that environmental conditions of Chinese deserts and sand fields are controlled by regional climate together with human activity.     

Cellular fluorescent high-throughput screening assays of the ATP-gated P2X7 receptor

The P2X 7 receptor (P2X7R) is an important member of the P2X family of ligand-gated ion channels that respond to ATP as the endogenous agonist. Studies suggest that P2X7R plays a potentially pivotal role in a variety of physiological functions, including peripheral and central neuronal transmission, smooth muscle contraction, and inflammation. Thus, P2X7R may be a potential target for drug development. Here, we used a FlexStation to examine the function of recombinant P2X7R stably expressed in human embryonic kidney 293 cells and to compare three high-throughput screening assays: a membrane potential assay, an ethidium bromide uptake assay, and a calcium influx assay. We found that all three assays were suitable for the analysis of P2X7R, but the calcium influx assay was the most robust and is the best choice as a first high-throughput screening assay when embarking on a P2X7R drug discovery project.     

Synthesis, structure of iron(Ⅲ)-containing imidazolium salts and their catalytic activity in the alkylation of aryl Grignard reagents

A series of iron(III)-containing imidazolium salts of the general formula [DRim][FeX 4 ] (R=2,6-diisopropylphenyl, IPr, X=Cl, 1; R=IPr, X=Br, 2; R=tertbutyl, t Bu, X=Cl, 3; R=isopropyl, i Pr, X=Cl, 4; R=benzyl, Bn, X=Cl, 5; R=Bn, X=Br, 6) have been prepared in high yields via reactions of anhydrous ferric halides with equivalent of the corresponding N,N-dihydro- carby-limidazolium halides, where 2-6 are novel ones. All of the complexes were characterized by elemental analysis, Raman spectroscopy, electrospray ionization mass spectroscopy, and X-ray crystallography for 1 and 2. All of them were non-hygroscopic and air-stable, with four of them existing as solids (1-4) and two as liquids (5 and 6) at room temperature. A preliminary catalytic study on the coupling of 4-tolylmagnesium bromide with cyclohexyl bromide revealed that 1 and 3 possessed the highest activity. In comparison, 2, 4 and 5 exhibited moderate activity and the least active complex was 6.     

Study on flow characteristics of solid/liquid system in lysozyme crystal growth

During the process of lysozyme protein crystallization with batch method,the macroscopic flow field of solid/liquid system was observed by particle image velocimetry(PIV). Furthermore,a normal growth rate of(110) face and local flow field around a single protein crystal were obtained by a long work dis-tance microscope. The experimental results showed that the average velocity,the maximal velocity of macroscopic solid/liquid system and the velocity of local flow field around single protein crystal were fluctuant. The effective boundary layer thickness δeff,the concentration at the interface Ci and the characteristic velocity V were calculated using a convection-diffusion model. The results showed that the growth of lysozyme crystal in this experiment was dominated by interfacial kinetics rather than bulk transport,and the function of buoyancy-driven flow in bulk transport was small,however,the effect of bulk transport in crystal growth had a tendency to increase with the increase of lysozyme concentra-tion. The calculated results also showed that the order of magnitude of shear force was about 10-21 N,which was much less than the bond force between the lysozyme molecules. Therefore the shear force induced by buoyancy-driven flows cannot remove the protein molecules from the interface of crystal.     

Hundreds of variants clustered in genomic loci and biological pathways affect human height

Most common human traits and diseases have a polygenic pattern of inheritance: DNA sequence variants at many genetic loci influence the phenotype. Genome-wide association (GWA) studies have identified more than 600 variants associated with human traits, but these typically explain small fractions of phenotypic variation, raising questions about the use of further studies. Here, using 183,727 individuals, we show that hundreds of genetic variants, in at least 180 loci, influence adult height, a highly heritable and classic polygenic trait. The large number of loci reveals patterns with important implications for genetic studies of common human diseases and traits. First, the 180 loci are not random, but instead are enriched for genes that are connected in biological pathways (P = 0.016) and that underlie skeletal growth defects (P?相似文献   

Activation pretreatment of limonitic laterite ores by alkali-roasting using NaOH

Activation pretreatment of Cr-containing limonitic laterite ores by NaOH roasting to remove Cr, Al, and Si, as well as its effect on Ni and Co extraction in the subsequent pressure acid leaching process was investigated. Characterization results of X-ray diffraction (XRD) and scanning electron microscopy/X-ray energy dispersive spectroscopy (SEM/XEDS) show that goethite is the major Ni-bearing mineral, and chromite is the minor one. Experimental results show that the leaching rates of Cr, Al, and Si are 95.6wt%, 83.8wt%, and 40.1wt%, respectively, under the optimal alkali-roasting conditions. Compared with the direct pressure acid leaching of laterite ores, the leaching rates of Ni and Co increase from 80.1wt% to 96.9wt% and 70.2wt% to 95.1wt% after pretreatment, respectively. Meanwhile, the grade of acid leaching iron residues increases from 54.4wt% to 62.5wt%, and these residues with low Cr content are more suitable raw materials for iron making.     

Hedgehog is an early and late mediator of pancreatic cancer tumorigenesis

Hedgehog signalling--an essential pathway during embryonic pancreatic development, the misregulation of which has been implicated in several forms of cancer--may also be an important mediator in human pancreatic carcinoma. Here we report that sonic hedgehog, a secreted hedgehog ligand, is abnormally expressed in pancreatic adenocarcinoma and its precursor lesions: pancreatic intraepithelial neoplasia (PanIN). Pancreata of Pdx-Shh mice (in which Shh is misexpressed in the pancreatic endoderm) develop abnormal tubular structures, a phenocopy of human PanIN-1 and -2. Moreover, these PanIN-like lesions also contain mutations in K-ras and overexpress HER-2/neu, which are genetic mutations found early in the progression of human pancreatic cancer. Furthermore, hedgehog signalling remains active in cell lines established from primary and metastatic pancreatic adenocarcinomas. Notably, inhibition of hedgehog signalling by cyclopamine induced apoptosis and blocked proliferation in a subset of the pancreatic cancer cell lines both in vitro and in vivo. These data suggest that this pathway may have an early and critical role in the genesis of this cancer, and that maintenance of hedgehog signalling is important for aberrant proliferation and tumorigenesis.     

Keyword Extraction Based on tf/idf for Chinese News Document

Keyword extraction is an important research topic of information retrieval. This paper gave the specification of keywords in Chinese news documents based on analyzing linguistic characteristics of news documents and then proposed a new keyword extraction method based on tf/idf with multi-strategies. The approach selected candidate keywords of uni-, hi- and tri-grams, and then defines the features according to their morphological characters and context information. Moreover, the paper proposed several strategies to amend the incomplete words gotten from the word segmentation and found unknown potential keywords in news documents. Experimental results show that our proposed method can significantly outperform the baseline method. We also applied it to retrospective event detection. Experimental results show that the accuracy and efficiency of news retrospective event detection can be significantly improved.     

Progress of phase-field investigations of γrafting in nickel-base single-crystal superalloys

With the development of nucleation theory,the calculation of phase diagrams(CALPHAD)method and microscopic elasto-plasticity mechanics,it is possible to apply the phase-field method to simulate the γrafting behavior of nickel-base single-crystal superalloys under the conditions of heat treatment,fatigue and creep testing.Based on the experimental progress in γrafting behavior and in combination with the microstructural simulation of the precipitation and rafting of c0phase,this paper reviews the phase-field investigation of γrafting in nickel–base single-crystal superalloys.     

Derivation of P–T paths for Middle–Late Triassic very low-grade metapelite from Hongcan Well 1 in the Zoigê Depression and their tectonic implications

Using XRD measurements of illite crystallinity,b0values of K-rich white micas and chemical compositions of chlorites combined with homogenization temperatures of fluid inclusions in calcite,the metamorphic P–T conditions of very low-grade metapelites from different depths in the 7 km Hongcan Well 1 in the Zoige?Depression,Sichuan,China,have been obtained in this paper.Knowledge of the tectonic evolution of the studied basin allows us to derive geothermal curves for Middle and Late Triassic time(the geothermal peak)and the present day(from thermal logging of the borehole).The retrograde P–T tracks from clockwise P–T–t loops have been revealed by the plotting of individual samples on each geotherm,which can be interpreted by the lithospheric thickening due to sedimentation and folding followed by continuous uplift and erosion.A stratigraphic log indicates that the Well penetrates the steep limb of a fold which perturbed the peak geotherm and caused some P–T paths to cross.