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Search Results: 1 - 10 of 41398 matches for " Na Xiao "
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Experimental Investigation of CO2-Water-Rock Interactions during CO2 Flooding in Carbonate Reservoir  [PDF]
Na Xiao, Shi Li, Meiqin Lin
Open Journal of Yangtze Oil and Gas (OJOGas) , 2017, DOI: 10.4236/ojogas.2017.22008
Abstract: Injecting CO2 into underground reservoir to displace oil is a viable means of reducing greenhouse gas emission to the atmosphere and enhancing oil recovery. To evaluate the effect of CO2-water-rock interactions on the characteristics of carbonate reservoir at high pressure, the mineralogy of calcite, the ion concentration in the reacted solution, the surface texture of calcite, the permeability of calcite after reacted with injected CO2 and deionized water was investigated by X-ray diffraction (XRD), inductive coupled plasma-atomic emission spectrometry (ICP-AES), scanning electronic microscope (SEM), and sand-packed model at pressure of 5.0 MPa. The results show that the mineral dissolution of calcite would occur when interacting with injected CO2 and water. The mineral dissolution of calcite caused the change of surface texture of calcite and increase in Ca2+, HCO-3 ion concentration in the solution. With the increase of CO2 pressure, the surface dissolution of calcite appeared more obvious. With the increase of reaction temperature, the surface dissolution of calcite also appeared more obvious and?Ca2+, HCO-3 ion concentration in the solution increased first, then decreased. The mineral dissolution of calcite caused the improvement in water permeability of calcite/quartzsand-packed model.
A novel method to reconstruct phylogeny tree based on thechaos game representation  [PDF]
Na-Na Li, Feng Shi, Xiao-Hui Niu, Jing-Bo Xia
Journal of Biomedical Science and Engineering (JBiSE) , 2009, DOI: 10.4236/jbise.2009.28084
Abstract: We developed a new approach for the reconstruction of phylogeny trees based on the chaos game representation (CGR) of biological sequences. The chaos game representation (CGR) method generates a picture from a biological sequence, which displays both local and global patterns. The quantitative index of the biological sequence is extracted from the picture. The Kullback-Leibler discrimination information is used as a diversity indicator to measure the dissimilarity of each pair of biological sequences. The new method is inspected by two data sets: the Eutherian orders using concatenated H-stranded amino acid sequences and the genome sequence of the SARS and coronavirus. The phylogeny trees constructed by the new method are consistent with the commonly accepted ones. These results are very promising and suggest more efforts for further developments.
Three New Compounds Derived from Nitrofurantoin: X-Ray Structures and Hirshfeld Surface Analyses  [PDF]
Hao Wang, Hongping Xiao, Na Liu, Bo Zhang, Qian Shi
Open Journal of Inorganic Chemistry (OJIC) , 2015, DOI: 10.4236/ojic.2015.53008
Abstract: The polymorphism of nitrofurantoin (NF), 1), the cocrystals of NF:2,2’-bipyridyl = 2:1, 2) and NF: 1,10-phenanthroline = 1:1, 3) have been prepared and characterized. The crystal structure analyses show that there are various weak forces among the molecules, such as C/N-H···O, N-H···N hydrogen bond interactions and π···π/lone pair stacking interactions, which play a key role in the assembly of supramolecular networks. A thorough analysis of Hirshfeld surfaces and fingerprint plots facilitates a comparison of intermolecular interactions in 1 - 3, which are crucial in building supramolecular architectures.
Interior Matter Estimates of Rapidly Rotating Compact Stars
Na-na Pan,Xiao-ping Zheng
Physics , 2010,
Abstract: The authors try to probe the inner components of rapidly rotating compact stars such as the millisecond pulsar SAX J1808.4-3658 and the possible sub-millisecond pulsar XTE J1739-285 in their own way by comparing the genuine rotation frequencies under different theoretical models with the observational data, which may exert more stringent constraint on matter composition of compact stars. According to their treatment, the SAX J1808.4-3658 is a star with exotic matter and XTE J1739-285 a hybrid star.
Cooling of Hybrid Stars with Spin Down Compression
Kang Miao,Wang Xiao-Dong,Pan Na-Na
Physics , 2009, DOI: 10.1088/1674-4527/9/12/007
Abstract: We study the cooling of hybrid stars coupling with spin-down. Due to the spin-down of hybrid stars, the interior density continuously increases, different neutrino reactions may be triggered(from the modified Urca process to the quark and nucleon direct Urca process) at different stages of evolution. We calculate the rate of neutrino emissivity of different reactions and simulate the cooling curves of the rotational hybrid stars. The results show the cooling curves of hybrid stars clearly depend on magnetic field if the direct urca reactions occur during the spin-down. Comparing the results of the rotational star model with the transitional static model, we find the cooling behavior of rotational model is more complicated, the temperature of star is higher, especially when direct urca reactions appear in process of rotation. And then we find that the predicted temperatures of some rotating hybrid stars are compatible with the pulsar's data which are contradiction with the results of transitional method.
The effect of different number of diffusion gradients on SNR of diffusion tensor-derived measurement maps  [PDF]
Na Zhang, Zhen-Sheng Deng, Fang Wang, Xiao-Yi Wang
Journal of Biomedical Science and Engineering (JBiSE) , 2009, DOI: 10.4236/jbise.2009.22018
Abstract: Diffusion tensor imaging (DTI) is mainly applied to white matter fiber tracking in human brain, but there is still a debate on how many diffusion gradient directions should be used to get the best results. In this paper, the performance of 7 protocols corresponding to 6, 9, 12, 15, 20, 25, and 30 noncollinear number of diffusion gradi-ent directions (NDGD) were discussed by com-paring signal-noise ratio (SNR) of tensor- de-rived measurement maps and fractional ani-sotropy (FA) values. All DTI data (eight healthy volunteers) were downloaded from the website of Johns Hopkins Medical Institute Laboratory of Brain Anatomi-cal MRI with permission. FA, apparent diffusion constant mean (ADC-mean), the largest eigen-value (LEV), and eigenvector orientation (EVO) maps associated with LEV of all subjects were calculated derived from tensor in the 7 proto-cols via DTI Studio. A method to estimate the variance was presented to calculate SNR of these tensor-derived maps. Mean ± standard deviation of the SNR and FA values within re-gion of interest (ROI) selected in the white mat-ter were compared among the 7 protocols. The SNR were improved significantly with NDGD increasing from 6 to 20 (P<0.05). From 20 to 30, SNR were improved significantly for LEV and EVO maps (P<0.05), but no significant dif-ferences for FA and ADC-mean maps (P>0.05). There were no significant variances in FA val-ues within ROI between any two protocols (P> 0.05). The SNR could be improved with NDGD in-creasing, but an optimum protocol is needed because of clinical limitations.
$L^p$ $(p\geq 1)$ solutions of multidimensional BSDEs with monotone generators in general time intervals
Lishun Xiao,Shengjun Fan,Na Xu
Mathematics , 2013, DOI: 10.1142/S0219493715500021
Abstract: In this paper, we are interested in solving general time interval multidimensional backward stochastic differential equations in $L^p$ $(p\geq 1)$. We first study the existence and uniqueness for $L^p$ $(p>1)$ solutions by the method of convolution and weak convergence when the generator is monotonic in $y$ and Lipschitz continuous in $z$ both non-uniformly with respect to $t$. Then we obtain the existence and uniqueness for $L^1$ solutions with an additional assumption that the generator has a sublinear growth in $z$ non-uniformly with respect to $t$.
Asymmetric Combined Cycle-Encoding Light 3D Measurement Technique
S. Li-Na,Y. Xiao-Yang,F. Xiao
Information Technology Journal , 2010,
Abstract: In order to eliminate the periodic dislocation and improve the measurement speed, a method named asymmetric combined cycle-encoding is presented. This method replaces the sinusoidal phase-shifting with trapezoidal for optimizing measurement speed. The traditional periodic dislocation is solved by building the non-symmetrical correspondence between two kinds of codes. The inherent error of cyclic code is eliminated by modify the period of cyclic code and trapezoidal phase shifting intensity code. The measurement speed is improved significantly. Experimental results show that the presented method in this study greatly reduces the measurement error. The measurement error is less than 1.7 mm in the range of 1000 mm.
The antioxidant activity and hypolipidemic activity of the total flavonoids from the fruit of Rosa laevigata Michx  [PDF]
Yue-Tao Liu, Bi-Nan Lu, Li-Na Xu, Lian-Hong Yin, Xiao-Na Wang, Jin-Yong Peng, Ke-Xin Liu
Natural Science (NS) , 2010, DOI: 10.4236/ns.2010.23027
Abstract: In the present work, the antioxidant activity in vitro and hypolipidemic activity of the total fla-vonoids (TFs) from the Rosa laevigata Michx fruit was evaluated, and the antioxidant effect in vivo was also discussed. The TFs exhibited a high scavenging effect on 2, 2-diphenyl-1- picrylhydrazyl (?DPPH) with IC50 values 0.01 mg/mL, and a stong reduce power in the test. Hyperli-pemic mice were intragastric administrated with TFs (25, 50 mg/kg/day) for 4 weeks, and fenofi-brate was used as the positive reference sub-stance. After the experiment, the levels of TC (total cholesterol), TG (triglyceride), LDL- C (low density lipoprotein-cholesterol) of the mice ad-ministrated with high-dose of TFs were mark-edly declined by 45.02%, 33.86% and 73.68%, re-spectively, while HDL-C (high density lipopro-tein-cholesterol) was significantly increased com-pared with model group. To investigate the hepatoprotective effect, histopathological assay, ALT (alanine aminotransferase), AST (aspartate aminotransefrase) and ALP (alkaline phosphatase) were also studied, and the results showed that TFs exhibited a favorable effect on liver protec-tion, of which the levels of ALT, AST and ALP were elevated by 55.85%, 29.15% and 25.68%, respectively. Furthermore, the TFs could sig-nificantly decrease the MDA (malondialdehyde) level and improve the levels of CAT (Catalas), SOD (superoxide dismutase), GSH (reduced glutathione), and GPX (glutathione peroxidase) compared with hyperlipemia mice. Our results suggested that TFs has a high antioxidant ac-tivity and hypolipidemic activity, which can be used as a potential medicine for cardiovascular diseases.
4-{[4-(3,5-Dimethoxybenzamido)phenyl]sulfanyl}-N-methylpyridine-2-carboxamide
Ting-Ting Huang,Na-Na Meng,Xiao-Yu Qing,Luo-Ting Yu
Acta Crystallographica Section E , 2011, DOI: 10.1107/s1600536811006490
Abstract: There are two independent molecules in the asymmetric unit of the title compound, C22H21N3O4S. The central benzene ring makes dihedral angles of 74.28 (6) and 68.84 (6)° with the pyridine and 3,5-dimethoxyphenyl rings, respectively, in one molecule [86.66 (6) and 81.14 (6)° respectively, in the other]. Each of the molecules forms a centrosymmetric dimer with another molecule via pairs of intermolecular N—H...O hydrogen bonds. These hydrogen bonds connect the N—H groups and the O atoms of the carbonyl groups next to the 3,5-dimethoxyphenyl rings. Additional intermolecular N—H...O interactions link the dimers in the crystal structure.
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