106 results on '"Han, Xun"'
Search Results
2. Bioinformatics-based prognostic analysis of non-small cell lung cancer
- Author
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Ming-Li Zhao, Yun-Xia Li, Shu Hao, Na Wu, Wen-Ding Zhou, Xiang-Han Xun, and Qing Bi
- Abstract
Background: With 75% of patients with non-small cell lung cancer (NSCLC) being found at an intermediate to advanced stage and a five-year survival rate of only 7%-17%, there is a need to find ways to improve the five-year survival rate of patients with NSCLC for prognosis. We used bioinformatics analysis of NSCLC samples from The Cancer Genome Atlas (TCGA) database to screen for differential genes and find multigene models for risk assessment of NSCLC patients, which is important for individualised clinical treatment and prognosis of NSCLC patients. Considering the limitations of the samples in this study, further validation in clinical and basic experiments is needed. Methods and results: The 519 samples associated with NSCLC were screened using bioinformatics in TCGA database, and the differential genes were selected by univariate analysis and Least Absolute Shrinkage and Selection Operator (LASSO) regression model. The most effective multi-gene model was selected by multi-gene analysis, and the validity of the multi-gene model was verified by survival analysis and Receiver Operating Characteristic (ROC) curves, and finally by the Kyoto Encyclopedia of Genes and Genomes (KEGG) database and The mRNA differential genes were enriched KEGG and Gene Ontology (GO) databases. The GO enrichment analysis showed that the differential genes were associated with extracellular structural tissues, external encapsulated structural tissues and extracellular matrix tissues. enrichment indicated that the differential genes were associated with histidine metabolism, calcium signalling pathways and cytokine-cytokine receptor interactions, among others. In conclusion, a polygenic model consisting of 22 genes can be used as a tool for the prognosis of NSCLC. Conclusion: Polygenic models provide an ideal and effective approach to the prognosis of NSCLC. In this study, we screened a set of multigene models as a risk assessment model for the prognosis of NSCLC.
- Published
- 2022
3. Diffusion-weighted imaging hyperintensities during the chronic stage of intracerebral hemorrhage with surgery: A new clinical situation or post-surgery artifact?
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Chen, Xiaoyan, Li, Ying, Guo, Shengli, Han, Xun, Liu, Ruozhuo, Tian, Chenglin, Cui, Rongtai, Dong, Zhao, and Yu, Shengyuan
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Neurology ,Neurology (clinical) - Abstract
Background and objectiveDiffusion-weighted imaging (DWI) hyperintensities were occasionally seen at previous hematoma in patients several months after intracerebral hemorrhage with surgery. Whether they are newly occurred clinical situations or post-surgery changes is unknown. This study aims to investigate the prevalence and possible mechanisms for this phenomenon.MethodsWe retrospectively reviewed the MRI database for intracerebral hemorrhage with surgery after 3 months of disease onset in our hospital. We also prospectively performed repeated multimodal MRI scans for two patients at the chronic stage after surgery for intracerebral hemorrhage.ResultsWe found that 14 out of 23 patients (60.9%) had DWI hyperintensities at the site of previous hematoma 3 months after intracerebral hemorrhage with surgery. All the DWI lesions were hyperintense on T1- and T2-weighted imaging, most of which appeared long and narrow in shape. The DWI lesions were usually located adjacent to the thin wall of the previous hematoma cavity close to the lateral ventricle. They were more associated with the basal ganglia hemorrhage than with the lobar hemorrhage (P = 0.02) and were more frequently seen for those with intraventricular hemorrhage than without (P = 0.02). Prospectively repeated MRI exams of two patients revealed unchanged DWI hyperintensity during the 18- and 2-month follow-up, respectively.ConclusionThe DWI lesions at previous hematoma were commonly seen in patients after surgery for intracerebral hemorrhage at the chronic stage which would persist for years. We hypothesized a possible mechanism by which extracellular methemoglobin “islands” are formed with delayed or no absorption by macrophages from adjacent thin residual brain tissue. Unnecessary further examinations and treatment would be avoided by realizing this imaging phenomenon.
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- 2022
4. Optimization of Ultrasound-Assisted Cellulase Extraction from
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Hui-Min, Liu, Sheng-Nan, Lei, Wei, Tang, Meng-Han, Xun, Zhi-Wei, Zhao, Ming-Yan, Cheng, Xiao-Dan, Zhang, and Wei, Wang
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Melanins ,Oxidative Stress ,Cellulase ,Nymphaea ,HaCaT Cells ,Humans ,Flowers ,Hydrogen Peroxide ,Reactive Oxygen Species ,Antioxidants - Abstract
In this study, ultrasonic-assisted cellulase extraction (UCE) was applied to extract flavonoids and polyphenols from the
- Published
- 2022
5. Vertical variation and economic strategy of leaf trait of major tree species in a typical mixed broadleaved-Korean pine forest
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Guang-Ze Jin, Yan-Han Xun, and Xue-Ying Di
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Canopy ,Chlorophyll content ,Leaf mass per area ,Variation (linguistics) ,Ecology ,Agronomy ,Pine forest ,Economic strategy ,Trait ,Plant Science ,Biology ,Tree species ,Ecology, Evolution, Behavior and Systematics - Published
- 2020
6. Additional file 1 of Gradually shifting clinical phenomics in migraine spectrum: a cross-sectional, multicenter study of 5438 patients
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Ran, Ye, Yin, Ziming, Lian, Yajun, Xu, Yanmei, Li, Yajie, Liu, Jiale, Gu, Qun, Yan, Fanhong, Ge, Zhaoli, Lian, Yu, Hu, Dongmei, Chen, Sufen, Wang, Yangyang, Wang, Xiaolin, Wang, Rongfei, Chen, Xiaoyan, Liu, Jing, Zhang, Mingjie, Han, Xun, Xie, Wei, Yu, Zhe, Cao, Ya, Li, Yingji, Li, Ke, Dong, Zhao, and Yu, Shengyuan
- Abstract
Additional file 1: Table 1. Prevalence of triggers of headache in MWoA and MWA. Table 2. Prevalence of mitigating factors of headache in MWoA and MWA. Table 3. Prevalence of premonitory symptoms of headache in MWoA and MWA. Table 4. Comparison between AWNM and AWM. Table 5. Comparison between MWoA and AWNM. Table 6. Multivariate analysis of clinical characteristics for distinction of MwoA and MwA. Table 7. Multivariate analysis of clinical characteristics for distinction of AWM and AWNM. Table 8. Fit statistics for the selected tree.
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- 2022
- Full Text
- View/download PDF
7. Possible Mechanisms of Oxidative Stress-Induced Skin Cellular Senescence, Inflammation, and Cancer and the Therapeutic Potential of Plant Polyphenols
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Hui-Min Liu, Ming-Yan Cheng, Meng-Han Xun, Zhi-Wei Zhao, Yun Zhang, Wei Tang, Jun Cheng, Jia Ni, and Wei Wang
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Inorganic Chemistry ,Organic Chemistry ,General Medicine ,Physical and Theoretical Chemistry ,Molecular Biology ,Spectroscopy ,Catalysis ,Computer Science Applications - Abstract
As the greatest defense organ of the body, the skin is exposed to endogenous and external stressors that produce reactive oxygen species (ROS). When the antioxidant system of the body fails to eliminate ROS, oxidative stress is initiated, which results in skin cellular senescence, inflammation, and cancer. Two main possible mechanisms underlie oxidative stress-induced skin cellular senescence, inflammation, and cancer. One mechanism is that ROS directly degrade biological macromolecules, including proteins, DNA, and lipids, that are essential for cell metabolism, survival, and genetics. Another one is that ROS mediate signaling pathways, such as MAPK, JAK/STAT, PI3K/AKT/mTOR, NF-κB, Nrf2, and SIRT1/FOXO, affecting cytokine release and enzyme expression. As natural antioxidants, plant polyphenols are safe and exhibit a therapeutic potential. We here discuss in detail the therapeutic potential of selected polyphenolic compounds and outline relevant molecular targets. Polyphenols selected here for study according to their structural classification include curcumin, catechins, resveratrol, quercetin, ellagic acid, and procyanidins. Finally, the latest delivery of plant polyphenols to the skin (taking curcumin as an example) and the current status of clinical research are summarized, providing a theoretical foundation for future clinical research and the generation of new pharmaceuticals and cosmetics.
- Published
- 2023
8. Eu3+-functionalized CQD hybrid material: synthesis, luminescence properties and sensing application for the detection of Cu2+
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Han-Xun Qiu, Fang-Fang Wang, Dan Liu, Ya-Qi Wang, and Ying Li
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Lanthanide ,Detection limit ,Materials science ,Photoluminescence ,Analytical chemistry ,Nanoprobe ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,Fluorescence ,0104 chemical sciences ,Ion ,Chemistry (miscellaneous) ,General Materials Science ,Emission spectrum ,0210 nano-technology ,Luminescence - Abstract
In this study, we developed a novel flexible method to construct a lanthanide dual-emitting ratiometric fluorescence nanoprobe with excellent luminescence properties and significant selectivity for the detection of copper ions, where the central Eu3+ ions are coordinated with 2,6-pyridinedicarboxylic acid (DPA) on the surface of CQDs. The structure and chemical sensing photoluminescence properties of the as-prepared fluorescent probe have been investigated in detail. Moreover, the results have shown that Eu-DPA–CQDs exhibit two fluorescence emissions at 450 nm and 613 nm, respectively, under an excitation wavelength of 285 nm. The responses of the two emissions towards Cu2+ ions are completely different and can provide references for each other. Therefore, it can be designed as a fluorescence sensor for the detection of Cu2+ ions. The emission spectrum at 613 nm is markedly quenched, while that at 450 nm slightly changed after the addition of Cu2+ ions. When the Cu2+ ion concentration was 0–150 μM, the FL ratio (IEu/ICQDs) showed a good linear relationship with the lowest detection limit (LOD) of 6 nM. Thus, the reported sensor has a high selectivity, satisfactory accuracy and precision, and it may provide the potential application in the biological and environmental fields.
- Published
- 2021
9. A Computing Task Offloading Scheme for Mobile Edge Computing
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Li Huahui, Wang Ben, Li Tingrui, and Han Xun
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Scheme (programming language) ,Task (computing) ,Mobile edge computing ,Edge device ,Computer science ,Distributed computing ,Minification ,Energy consumption ,Enhanced Data Rates for GSM Evolution ,computer ,Energy (signal processing) ,computer.programming_language - Abstract
The mobile edge computing (MEC) technology sinks the computing and storage resources to the network edge and reaches the goal of improving user service quality by formulating reasonable task offloading strategies. As the number of edge users increases, the energy consumption and energy cost of the MEC are also increasing. Therefore, we investigated the task offloading problem in MEC, and proposed a computational task offloading scheme based on immune clone. Taking the minimization of energy cost as the objective and in consideration of the relationship between number of users unloaded in the computing and energy price. It can be solved by the immune clone algorithm and determined the optimal offloading scheme. Simulation results demonstrate the superiority of the proposed scheme over other the traditional task computing scheme. That this scheme can effectively reduce the system energy cost and improve the solving efficiency as compared to the traditional task computing scheme, in terms of the solving efficiency.
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- 2021
10. Potential hazards to a tunnel caused by adjacent reservoir impoundment
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Yi wei Ye, Lian ze Zhang, Han xun Wang, Junliang Tao, Bin Zhang, and Lei Shi
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Engineering geology ,0211 other engineering and technologies ,Frost heaving ,Geology ,Excavation ,02 engineering and technology ,Inflow ,010502 geochemistry & geophysics ,Geotechnical Engineering and Engineering Geology ,01 natural sciences ,Permeability (earth sciences) ,Impervious surface ,Geotechnical engineering ,Surface runoff ,Groundwater ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences - Abstract
A reservoir impoundment located near a tunnel structure negatively affects groundwater seepage to varying degrees. This can result in water inflow, structural collapse, and other engineering hazards during tunnel excavation. In addition, in cold regions, reservoir impoundment and water seepage can exacerbate frost heave damage during tunnel operations. This paper describes a comprehensive case study on the quantitative evaluation of the seepage effects of the proposed Longsheng Reservoir on the adjacent proposed Kouzi village tunnel (located in Ulanchap, Inner Mongolia, North China). An engineering geology survey was conducted to identify the topography and geological features in the tunnel and reservoir area. A geohydrological survey was conducted to identify groundwater runoff patterns and to assess the possible seepage paths. Pumping and injection tests were conducted to characterize the in-situ permeability of the strata. Based on the detailed field information, the seepage field and stress field of the study area were investigated using COMSOL Multiphysics and ABAQUS software. From these numerical simulations, the evolution of the water inflow and the stress/strain field in the shallow buried section of the tunnel could be predicted quantitatively at different construction and operation stages. This study showed that the seepage influence of the Longsheng Reservoir on the Kouzi village tunnel during the excavation and operational stages will be relatively weak. However, structural collapse of the tunnel and water inflow are likely to occur beneath the two gullies. Mitigation measures such as impervious walls and inverted arch structural elements were proposed to address these potential hazards.
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- 2017
11. Microwave Involved Synthesis of Graphene/Polyaniline Nanocomposite with Superior Electrochemical Performance
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Jun He Yang, Han Xun Qiu, Jing Li, Fei Long Qiu, and Xue Bing Han
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Supercapacitor ,Materials science ,Nanocomposite ,Polyaniline nanofibers ,Graphene ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,01 natural sciences ,0104 chemical sciences ,Dielectric spectroscopy ,law.invention ,chemistry.chemical_compound ,chemistry ,law ,Polyaniline ,Cyclic voltammetry ,Fourier transform infrared spectroscopy ,Composite material ,0210 nano-technology - Abstract
A microwave irradiation involved process was applied to fabrication of graphene/polyaniline nanocomposite via in-situ polymerization of aniline monomers on graphene sheets. Structure and morphology of composites were characterized through scanning electron microscopy, Raman spectra, X-ray diffraction, Fourier transform infrared spectroscopy and X-ray photoelectron spectra. Electrochemical performances for energy storage applications were examined by cyclic voltammetry, electrochemical impedance spectroscopy and galvanostatic charge/discharge measurements. Owing to the homogeneous coating of polyanilline on the large surface of graphene, graphene/polyaniline composite-based electrode exhibits remarkably enhanced capacitive behavior with a specific capacitance of 429 F/g at 0.2 A g-1, a good cyclic stability and an excellent conducting behavior, which are much superior to those of individual components of composites. The improved electrochemical behavior of the composite resulting from the irradiation of microwave suggests the promising potentials for supercapacitors.
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- 2017
12. Construction of three-dimensional all-carbon C60/graphene hybrids and their use as electrodes for high performance supercapacitors
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Lei Cheng, Xing-juan Li, Jing Li, Han-xun Qiu, Yu-hua Xue, Kuznetsova-Iren Evgenyeva, Vladimir Kolesov, Cheng-meng Chen, and Jun-he Yang
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General Materials Science ,General Chemistry - Published
- 2021
13. Dryocrassin ABBA Induces Apoptosis in Human Hepatocellular Carcinoma HepG2 Cells Through a Caspase-Dependent Mitochondrial Pathway
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Zhe Jin, Hemeng Wang, Jian-Ping Huang, Wen-Fei Wang, Ying Chang, and Han-Xun Ju
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Male ,0301 basic medicine ,Cancer Research ,Carcinoma, Hepatocellular ,Epidemiology ,Blotting, Western ,Apoptosis ,Real-Time Polymerase Chain Reaction ,Benzylidene Compounds ,Flow cytometry ,Mice ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,In vivo ,Annexin ,Tumor Cells, Cultured ,medicine ,Animals ,Humans ,RNA, Messenger ,Viability assay ,Propidium iodide ,Caspase ,Cell Proliferation ,Membrane Potential, Mitochondrial ,medicine.diagnostic_test ,biology ,Cyclohexanones ,Reverse Transcriptase Polymerase Chain Reaction ,Liver Neoplasms ,Public Health, Environmental and Occupational Health ,Xenograft Model Antitumor Assays ,Molecular biology ,Mitochondria ,Blot ,030104 developmental biology ,Oncology ,chemistry ,Caspases ,030220 oncology & carcinogenesis ,biology.protein ,Signal Transduction - Abstract
Background Biological and pharmacological activities of dryocrassin ABBA, a phloroglucinol derivative extracted from Dryopteris crassirhizoma, have attracted attention. In this study, the apoptotic effect of dryocrassin ABBA on human hepatocellular carcinoma HepG2 cells was investigated. Materials and methods We tested the effects of dryocrassin ABBA on HepG2 in vitro by MTT, flow cytometry, real-time PCR, and Western blotting. KM male mice were used to detect the effect of dryocrassin ABBA on H22 cells in vivo. Results Dryocrassin ABBA inhibited the growth of HepG2 cells in a concentration-dependent manner. After treatment with 25, 50, and 75 μg/mL dryocrassin ABBA, the cell viability was 68%, 60% and 49%, respectively. Dryocrassin ABBA was able to induce apoptosis, measured by propidium iodide (PI)/annexin V-FITC double staining. The results of real-time PCR and Western ting showed that dryocrassin ABBA up-regulated p53 and Bax expression and inhibited Bcl-2 expression which led to an activation of caspase-3 and caspase-7 in the cytosol, and then induction of cell apoptosis. In vivo experiments also showed that dryocrassin ABBA treatment significantly suppressed tumor growth, without major side effects. Conclusions Overall, these findings provide evidence that dryocrassin ABBA may induce apoptosis in human hepatocellular carcinoma cells through a caspase-mediated mitochondrial pathway.
- Published
- 2016
14. Part 2. Notch-sparing γ-secretase inhibitors: The study of novel γ-amino naphthyl alcohols
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Jing Zhang, Dennis J. Selkoe, Michael S. Wolfe, Wenjuan Ye, Han-Xun Wei, Dai Lu, Yongli Gu, Pamela Osenkowski, Corinne E. Augelli-Szafran, and Vivien Sun
- Subjects
0301 basic medicine ,Stereochemistry ,Clinical Biochemistry ,Pharmaceutical Science ,Naphthalenes ,Cleavage (embryo) ,Biochemistry ,Article ,Propanolamines ,Structure-Activity Relationship ,03 medical and health sciences ,Drug Discovery ,Amyloid precursor protein ,Animals ,Humans ,Protease Inhibitors ,γ secretase ,Receptor, Notch1 ,Molecular Biology ,Amyloid beta-Peptides ,030102 biochemistry & molecular biology ,biology ,Chemistry ,Organic Chemistry ,Amino Alcohols ,Peptide Fragments ,Rats ,030104 developmental biology ,Microsomes, Liver ,biology.protein ,Molecular Medicine ,Amyloid Precursor Protein Secretases - Abstract
One therapeutic approach for Alzheimer's disease is to inhibit the cleavage of the amyloid precursor protein (APP) by γ-secretase. At the beginning of a series of studies from our laboratories, a series of novel γ-amino alcohols (1) were found to possess γ-secretase inhibitory activity and Notch-sparing effects. A new one-pot synthesis of γ-amino alcohols and the structure-activity relationship (SAR) of these analogs will be discussed.
- Published
- 2016
15. Design and implementation of levee project information management system based on WebGIS
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Gang Mei, Xi-zhong Shen, Bin Zhang, Yi-wei Ye, and Han-xun Wang
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Information management ,010504 meteorology & atmospheric sciences ,Computer science ,geotechnical information management system ,browser/server mode ,010502 geochemistry & geophysics ,01 natural sciences ,Construction engineering ,WebGIS ,Engineering ,Decision management ,Project management ,lcsh:Science ,0105 earth and related environmental sciences ,Multidisciplinary ,Warning system ,business.industry ,ArcGIS Server ,Flood control ,Management information systems ,Office automation ,levee project ,lcsh:Q ,business ,Research Article - Abstract
The China Levee Project Information Management System (CLPIMS) is an information management platform that was established for levee project management within the seven major river basins in China. The system was developed on the basis of the VS.NET and ArcGIS Server and was combined with the database theory and key techniques of WebGIS, which has the features of real-time display, enquiry, statistics and management of spatial data under browser/server mode. Moreover, additional applications, such as real-time monitoring, safety assessment, early warning and danger forecasting and online analysis, can be further explored through reserved modules. The CLPIMS can serve not only as a scientific, systematic, visual tool for analysis and decision management in levee projects in China but also as a technical platform for flood control practice. Furthermore, the system is capable of unified management and sharing of the levee project information for the seven major river basins in China, and it is important for the improvement of office automation, E-government applications and the level of flood control operations.
- Published
- 2018
16. Emitter signal separation method based on multi-level digital channelization
- Author
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Han Xun, Wang Sujun, Yang Xinquan, Feng Ying, Ping Yifan, and Kuang Yin
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Computer science ,Electronic engineering ,Separation method ,Channelized ,Signal ,Common emitter - Published
- 2018
17. Separation and Purification of Total Phloroglucinols in Dryopteris crassirhizoma with DM-130 Macroporous Adsorption Resin
- Author
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Chang Ying, Ju Han-xun, Wang He-meng, Huang Jian-ping, Jin Zhe, and Ren Si-rui
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Chromatography ,Ethanol ,Dryopteris crassirhizoma ,biology ,Elution ,biology.organism_classification ,Volumetric flow rate ,Solvent ,chemistry.chemical_compound ,Sample volume ,Adsorption ,chemistry ,Desorption ,Botany - Abstract
To improve the purity of the total phloroglucinols from Dryopteris crassirhizoma extracts, the separation and purification conditions of the total phloroglucinols from Dryopteris crassirhizoma were studied with DM-130 macroporous adsorption resin in this study. Adsorption rate, elution rate and purity of the total phloroglucinols were used as indexes to investigate the adsorption and desorption capacity of the total phloroglucinols with DM-130 macroporous adsorption resin. Through the study, the optimum sample concentration of the total phloroglucinols and maximum sample volume were 1.5 mg • mL −1 and 7 BV (210 mL), respectively. The optimum desorption conditions were achieved by using 80% ethanol as desorption solvent at elution flow rate of 1.0 mL • min −1 . The result showed DM-130 macroporous adsorption resin performed effective adsorption and desorption. After purification, the purity of the total phloroglucinols increased by 11.5-fold.
- Published
- 2015
18. The Research of Remanufacturing Technology Applied to Lifting Machinery
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Chen Bo Yin, Han Xun Jin, Ming Guo, and Yue Gong
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Engineering ,Software ,Order (business) ,business.industry ,Key (cryptography) ,General Medicine ,business ,Remanufacturing ,Manufacturing engineering ,Variety (cybernetics) - Abstract
Lifting machinery usually fail or become scrapped after a certain period of use for a variety of reasons. Thus, they often need remanufacturing technology. The purpose of this paper is to research and analyze how to apply remanufacturing technology to lifting machinery. In this paper, the background of remanufacturing technology is firstly discussed. Then illuminate the specific processes of remanufacturing technology including the cleaning measures of those components after dismantled, the non-destructive examination (NDE), and assessment software using to test the perfectness of the produces remanufactured. Finally, the benefits of the widespread use of remanufactured lifting machinery which can make the best use of various resources to achieve energy saving, material saving and environment protection goals are discussed in order to draw key conclusions.
- Published
- 2014
19. A Capillarity-dependent Model for Prediction of Chloride Penetration Process into Concrete in Artificial Splash Test
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Jianyi Zhang, Yunfei Guan, Cao Yongyong, and Han Xun
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Splash ,Chloride penetration ,Materials science ,Dependent model ,Scientific method ,Composite material - Abstract
In order to better simulate the penetration process of chloride ions in the splash zone of concrete, this paper modified existing chloride ion transport model on the basis of capillarity-dependent model under unsaturated and non-pressure conditions to make it applicable to the calcualtion of choride flow flux. The artificial splash tests is firstly designed and conducted under varied conditions of water to cement ratio, splash time duratinoa and splash period. Then the original chloride constitutive model is improved by enhancement of convection term calculation. At last, the authors simulate the chloride ions penetration process under different conditions by reasonble design of equivalent chloride and moisture boundary to verify the effectiveness of capillarity-dependent model.
- Published
- 2019
20. Numerical Simulation of Cold Extrusion Process of the ZA Alloy Car Sleeve Based on LS-DYNA
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Zhi Qiang Li, Bing Dong Liu, Zhang Yi Yu, and Han Xun Lv
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Materials science ,Computer simulation ,Metallurgy ,Alloy ,Forming processes ,General Medicine ,Plasticity ,engineering.material ,medicine.disease_cause ,Finite element method ,Mold ,medicine ,engineering ,Extrusion ,LS-DYNA ,Composite material - Abstract
In order to increase the useful life of sleeve, improve the organizational structure and reduce costs, ZA alloy materials can be used as a raw material using cold extrusion technology for production. The main content of this paper is simulating the change rules of the equivalent plastic strain, the equivalent stress and the flow in the forming process of ZA alloy in different extrusion speed and friction coefficient condition by finite element technology, making a contrastive study with the extrusion theory, and finding out the most appropriate extrusion processing parameters. The results not only provide sufficient theatrical support for the cold extrusion process of sleeve of ZA alloy, but also offer some new thoughts for the design of extrusion mold.
- Published
- 2013
21. The Macroeconomic Effect of Shadow Credit Market Financing
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Li Jianjun and Han Xun
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Finance ,0209 industrial biotechnology ,business.industry ,Immunology ,0211 other engineering and technologies ,Credit reference ,Financial system ,02 engineering and technology ,Installment credit ,020901 industrial engineering & automation ,Market depth ,Credit history ,iTraxx ,021105 building & construction ,Economics ,Credit crunch ,Credit enhancement ,business ,ComputingMilieux_MISCELLANEOUS ,Credit risk - Abstract
Shadow credit market is a credit creation market which is parallel to the bank credit market. It has the function of credit creation, liquidity conversion and maturity transformation. In this paper, based on the different participants of shadow credit market, we divides it to the dealer, formal financial institution and private lending credit markets and measures the scale of shadow credit market. Based on the monthly data from year 2006 to 2014, by constructing VAR model, the paper attempts to analyze the macroeconomic effect of the shadow credit market financing. The research results show, firstly, shadow credit market as a way of resource allocation, has certain positive effect in meeting the needs of social investment and financing and promoting economic growth. Secondly, shadow credit market has changed the traditional money supply model and transmission mechanism of monetary policy, expanding the money supply and weakening the effectiveness of monetary policy. Thirdly, the shadow credit market impact the price level through influencing credit market scale and money supply.
- Published
- 2016
22. Ovate family protein1 interaction with BLH3 regulates transition timing from vegetative to reproductive phase in Arabidopsis
- Author
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Hemeng Wang, Jin-Gui Chen, Yuanling Zhao, Xiaofei Zhang, Ying Chang, Shucai Wang, Han-Xun Ju, and Liguo Zhang
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0106 biological sciences ,0301 basic medicine ,Transcriptional Activation ,Mutant ,Biophysics ,Arabidopsis ,Repressor ,Biology ,01 natural sciences ,Biochemistry ,Protein–protein interaction ,03 medical and health sciences ,Bimolecular fluorescence complementation ,Transcription (biology) ,Gene Expression Regulation, Plant ,Molecular Biology ,Transcription factor ,Genetics ,Homeodomain Proteins ,Arabidopsis Proteins ,Reproduction ,Gene Expression Regulation, Developmental ,Cell Biology ,biology.organism_classification ,Repressor Proteins ,030104 developmental biology ,Homeobox ,010606 plant biology & botany ,Transcription Factors - Abstract
Three-Amino-acid-Loop-Extension(TALE) homeodomain transcription factor BLH3 regulates timing of transition from vegetative to reproductive phase. Previous preliminary results obtained using large-scale yeast two-hybrids indicate that BLH3 protein possibly interact with Ovate Family Proteins(OFPs) transcription co-regulators. Nevertheless, it is uncertain whether OFP1–BLH3 complex is involved in regulation of timing of transition from vegetative to reproductive phase in Arabidopsis. The interaction between BLH3 and OFP1 was re-tested and verified by a yeast two-hybrid system. We found that the BLH3–OFP1 interaction was mainly mediated through the BLH3 homeodomain. Meanwhile, this interaction was further confirmed by bimolecular fluorescence complementation (BiFC) in vivo. Further, by establishing protoplast transient expression, we discovered that BLH3 acts as a transcriptional activator, whereas OFP1 functioned as a repressor. The interactions between OFP1 and BLH3 can reduce BLH3 transcriptional activity. The ofp1 mutant lines and blh3 mutant lines, OFP1 overexpress lines and BLH3 overexpress lines can both influence timing of transition from vegetative to reproductive phase. Furthermore, 35s:OFP1/blh3 plants exhibited flowering and leaf quantity similar to that of the wild-type controls. 35s:BLH3/ofp1 plants flowered earlier and had less leaves than wild-type controls, indicating that OFP1 protein might depend partially on BLH3 in its function to regulate the timing of transition from vegetative to reproductive phase. These results support our assumption that, by interacting with OFP1, BLH3 forms a functional protein complex that controls timing of progression from vegetative to reproductive phase, and OFP1 might negatively regulate BLH3 or the BLH-KNOX complex, an important interaction for sustaining the normal transition from vegetative to reproductive phase.
- Published
- 2016
23. Part 3: Notch-sparing γ-secretase inhibitors: SAR studies of 2-substituted aminopyridopyrimidinones
- Author
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Yongli Gu, Han-Xun Wei, Jing Zhang, Michael S. Wolfe, Corinne E. Augelli-Szafran, Dennis J. Selkoe, and Dai Lu
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0301 basic medicine ,Pyridones ,Clinical Biochemistry ,Pharmaceutical Science ,Cleavage (embryo) ,Inhibitory postsynaptic potential ,Biochemistry ,Article ,03 medical and health sciences ,Structure-Activity Relationship ,Drug Discovery ,Structure–activity relationship ,Animals ,Humans ,Protease Inhibitors ,γ secretase ,Receptor, Notch1 ,Receptor ,Molecular Biology ,Amyloid beta-Peptides ,030102 biochemistry & molecular biology ,biology ,Chemistry ,Organic Chemistry ,Receptor-mediated endocytosis ,Peptide Fragments ,Rats ,030104 developmental biology ,Pyrimidines ,biology.protein ,Microsomes, Liver ,Molecular Medicine ,Amyloid Precursor Protein Secretases ,Amyloid precursor protein secretase - Abstract
In search for novel lead compounds as γ-secretase inhibitors, analogs of aminopyrido[2,3-d]pyrimidin-7-ones (I) were synthesized and evaluated for inhibitory effects on amyloid –β-peptide production and cleavage of the Notch1 receptor mediated by γ-secretase. Selected pyridopyrimidines, such as 1, 8, 9, 10, 11 and 16 are γ-secretase inhibitors that did not have an effect on Notch1 receptor processing.
- Published
- 2016
24. Numeral Simulation Study on Pipeline Corrosion Defects under Different Sizes and Pressures Based on FEM
- Author
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Rui Hua Dong, Han Xun Lv, and Han Wu Liu
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Engineering ,business.industry ,Pipeline (computing) ,General Medicine ,Mechanics ,Structural engineering ,Finite element method ,Corrosion ,Stress (mechanics) ,Pipeline transport ,Electric current ,business ,Excitation ,Voltage - Abstract
Finite element analysis software ANSYS is used to establish a three-dimensional finite element model of the pipeline corrosion defects by applying the boundary conditions of square wave excitation to simulate the distributions of current and induced magnetic field in the pipeline under various defect volumes. The results of the study show: When there is no corrosion defect in the pipeline, the electric current in the pipeline is basically even distribution. The magnetic field is distributed for the symmetrical vortex shape from head to foot, and it has not obviously gather phenomenon. When there are some corrosion defects in the pipeline, the electric current forms partial symmetrical vortex shape in both sides of the corrosion defect, and it is obviously assembled in the defect place. The simulation results of the different size defects show that the maximum magnetic field strength and the maximum current value increase with the defect depth increasing, while the output voltage decreases with the defect depth increasing. For the analysis of the stress distributions of the pipeline corrosion defect with certain size under different pressures, it was found that the maximum stress is 596 MPa when the bearing limit work pressure of the pipeline is 7 MPa, which is smaller than the yield strength with ensuring the safely running of the pipelines with defects.
- Published
- 2012
25. Computer Simulation of Forming Technology of Thin Aluminum Engine Cylinder Liners Based on LS-DYNA
- Author
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Hong De Ren, Han Wu Liu, and Han Xun Lv
- Subjects
Materials science ,business.product_category ,Mechanical engineering ,Forming processes ,General Medicine ,Cylinder (engine) ,law.invention ,Stress (mechanics) ,law ,Die (manufacturing) ,Extrusion ,LS-DYNA ,Deformation (engineering) ,business ,Spinning - Abstract
The high-silicon aluminum alloy by spray deposition forming is well suited for the engine cylinder liner because of the need of high strength and abrasion resistance, but its forming process is much complex, and many process parameters are involved. In order to lower the investments of time, labor power and money due to the traditional processing methods that need to adjust the craft parameters frequently, the thermal extrusion process and the spinning process that are the most important forming processes in aluminum alloy cylinder liner forming are simulated by the finite element simulation technology. It is found that during the extrusion process, the equivalent stresses near the die are larger, and uneven, the stress gradient is very large, but the maximum stress does not exceed the allowable stress of the material through the numerical simulation; In the spinning process, the stress and deformation are larger at the beginning of the process, but they will have a slight decreasing with the spinning process going on. Throughout the spinning process, the equivalent stress and strain distribution of the spinning component maintained a relatively balanced state basically, which is consistent with the later experimental results. It proves the reliability of the the simulation.
- Published
- 2012
26. Study on the Preparation and Properties of Nano-SiC/MC Nylon 6 Composites
- Author
-
Jun Jie Wang, Han Xun Liang, Zhi Yuan Li, and Bo Fen Huang
- Subjects
chemistry.chemical_compound ,Vicat softening point ,Nylon 6 ,Materials science ,Flexural strength ,chemistry ,Composite number ,Ultimate tensile strength ,Nano ,General Engineering ,Izod impact strength test ,Composite material ,Fourier transform infrared spectroscopy - Abstract
Nano-SiC/MC nylon6 (MCPA6) composites were prepared by in situ anionic polymerization,followed by properties’ characterization of composites and morphology. FTIR shows that there is no change in the functional groups of MCPA6 by adding nano- SiC and only physical interaction happening in the composites. SEM reveales that bonding state of the two-phase interface of the composites has been affected by the ratio of nano-SiC. Nano-SiC (2.5 wt-%) is fine dispersed in MCPA6 matrix, which enhances interface compatibility and bind strength between nano-SiC and MCPA6, the best comprehensive properties of the composite are obtained. Comparing with untreated MCPA6, the notched Izod impact strength, tensile strength and flexural strength are respectively increased by 208.8%, 81.1% and 27.9%, while the Vicat softening temperature is increased by 20.2%.
- Published
- 2012
27. Synthesis and Characterization of Phenol-Formaldehyde Resin Coated Graphitized Needle Coke
- Author
-
Han Xun Qiu, Jia Ni Xuan, Guang Zhi Yang, Dong Feng Li, and Jun He Yang
- Subjects
chemistry.chemical_classification ,Materials science ,Chemical engineering ,Coating ,chemistry ,Carbonization ,Phenol formaldehyde resin ,technology, industry, and agriculture ,General Engineering ,Petroleum coke ,engineering ,engineering.material ,Composite material - Abstract
Phenol-formaldehyde (PF) resin coated graphitized needle coke was synthesized by mixing graphitized needle coke with PF alcohol solution, stirring for a long time and then drying. Different processes of direct drying and drying followed filtration were performed to see the effect of coating. The coated materials were also carbonized, graphitized and then characterized. Experiment showed that filtration before dryness process can lead to uniform coating. The concentration of PF resin had an important effect on the coating amount of PF resin. When the PF resin concentration was 30% (wt%), the content of PF resin coated could possibly attain 15% (wt%) for the most. After carbonization, only small amount of carbon residue from PF resin was left which did not affect the crystal structure of graphitized needle coke.
- Published
- 2011
28. Synthesis and Characterization of Polyacrylonitrile Microspheres by Soapless Emulsion Polymerization
- Author
-
Han Xun Qiu, Xian Ying Wang, Chun Feng Zhu, Jun He Yang, Lei Zhang, and Guang Zhi Yang
- Subjects
chemistry.chemical_compound ,Materials science ,Monomer ,Chemical engineering ,chemistry ,Polymer chemistry ,General Engineering ,Polyacrylonitrile ,Emulsion polymerization ,Acrylonitrile ,Microsphere ,Characterization (materials science) - Abstract
Polyacrylonitrile(PAN) microspheres were synthesized by soapless emulsion polymerization of acrylonitrile(AN) in water. The effects of monomer and initiator concentration on the conversion of AN and the diameter of microspheres were investigated. The results showed that when the concentration of monomer increases, the conversion of AN decreases while the diameter of PAN microspheres increases. When the concentration of initiator increases, the conversion of AN and the diameter of PAN microspheres both increase. For this method of PAN microspheres synthesis, the highest conversion of AN is about 60% and the diameter can be controlled in need ranging from approximately 140 to 500nm.
- Published
- 2011
29. Effect of ferrum-based flux on the melting characteristics of coal ash from coal blends using the Liu-qiao No.2 Coal Mine in Wan-bei
- Author
-
Benxian Shen, Ji-gang Zhao, Han-xun Li, Ji-bing Li, and Ji-ming Wang
- Subjects
Hercynite ,Chemistry ,business.industry ,Metallurgy ,technology, industry, and agriculture ,Coal mining ,Mullite ,respiratory system ,engineering.material ,complex mixtures ,respiratory tract diseases ,Fly ash ,otorhinolaryngologic diseases ,engineering ,Melting point ,Fayalite ,Coal ,business ,Eutectic system - Abstract
The effect of ferrum-based flux on the melting characteristics of coal ash in coal blends from the Liu-qiao No.2 Coal Mine in Wan-bei (AQ) was investigated. The change of the compositions of mineral under various temperatures before and after adding ferrum-based flux into AQ was studied by XRD and FT-IR. Results show that the presence of mullite formed over 1000°C increases the melting point of coal-ash, leading to high melting temperature of AQ coal-ash. The coal ash fusion temperature will be decreased by adding ferrum-based flux. The eutectic mixtures such as fayalite and hercynite are easily formed between ferrum compounds under high temperature, which remarkably decreases the coal ash fusion temperature.
- Published
- 2009
30. Anti-selective and regioselective aldol addition of ketones with aldehydes using MgI2 as promoter
- Author
-
Han-Xun Wei, Paul W. Paré, Richard L. Jasoni, Huawa Shao, and Jiali Hu
- Subjects
chemistry.chemical_classification ,Base (chemistry) ,High selectivity ,Organic Chemistry ,Regioselectivity ,General Medicine ,Combinatorial chemistry ,Biochemistry ,Magnesium iodide ,Coupling reaction ,chemistry.chemical_compound ,Aldol reaction ,chemistry ,Yield (chemistry) ,Drug Discovery ,Organic chemistry ,Amine gas treating ,Piperidine - Abstract
The first example of a direct aldehyde–ketone coupling using the secondary amine piperidine as base in the presence of MgI2 to generate high selectivity of anti-aldol products from unmodified ethyl ketones in high yield is reported. The coupling reactions were carried out in a one-pot reaction by mixing four reaction components at room temperature. In the case of unsymmetrical ketones, addition was made to the less hindered α-side.
- Published
- 2004
31. Z/E Stereoselective synthesis of β-bromo Baylis–Hillman ketones using MgBr2 as promoter via a one-pot three-component reaction
- Author
-
Richard L. Jasoni, Paul W. Paré, Jiali Hu, Han-Xun Wei, and Guigen Li
- Subjects
Turn (biochemistry) ,Bromine ,chemistry ,Component (thermodynamics) ,Organic Chemistry ,Drug Discovery ,Organic chemistry ,chemistry.chemical_element ,Stereoselectivity ,Biochemistry ,Adduct - Abstract
The first time steroselective synthesis of ( Z )-β-bromo Baylis–Hillman ketones has been achieved using a one-pot three-component reaction. The new system uses MgBr 2 as both the Lewis acidic promoter and the bromine source for the Michael-type addition with α,β-acetylenic ketones to form an active β-bromo allenolate intermediate, which in turn attacks various aldehydes to afford β-bromo Baylis–Hillman adducts in good yields and Z -selectivity.
- Published
- 2004
32. Experimental Support for Planar Pseudopericyclic Transition States in Thermal Cheletropic Decarbonylations
- Author
-
Chun Zhou, Sihyun Ham, David M. Birney, Han-Xun Wei, and Jonathan M. White
- Subjects
Bond length ,Crystallography ,Planar ,Computational chemistry ,Chemistry ,Organic Chemistry ,Thermal ,Decarbonylation ,Crystal structure ,Physical and Theoretical Chemistry ,Biochemistry ,Transition state ,Reaction coordinate - Abstract
Low-temperature crystal structures of three pyrrolediones (3-5) and a furandione (9) were obtained and compared to structurally related compounds that cannot undergo decarbonylation. Systematic trends in bond lengths and angles are consistent with distortions along the reaction coordinate, in accord with the structure correlation principle of Dunitz. Since the pyrroledione and furandione rings in 3-5 and 9 are planar, these ground-state geometries prefigure the calculated planar, pseudopericyclic transition states.
- Published
- 2004
33. Synthesis of Substitutedα-(Hydroxymethyl)-β-iodoacrylatesvia MgI2-Promoted Stereoselective Aldol Coupling
- Author
-
Han-Xun Wei, Guigen Li, Richard L. Jasoni, Paul W. Paré, and Jiali Hu
- Subjects
chemistry.chemical_classification ,Reaction mechanism ,Stereochemistry ,Organic Chemistry ,Biochemistry ,Aldehyde ,humanities ,Catalysis ,Coupling reaction ,Adduct ,Inorganic Chemistry ,chemistry.chemical_compound ,Aldol reaction ,chemistry ,Drug Discovery ,Stereoselectivity ,Hydroxymethyl ,Lewis acids and bases ,Physical and Theoretical Chemistry - Abstract
The efficient and highly stereoselective syntheses of a variety of (Z)-configured, substituted α-(hydroxymethyl)-β-iodo-acrylates from prop-2-ynoate and various aldehydes was achieved. The synthetic protocol involves a simple one-pot coupling reaction under mild conditions, promoted by MgI2, which serves both as a Lewis acid and iodine source for a BaylisHillman-type reaction. All adducts were generated in good-to-excellent yields, the (Z)-isomers being formed in high selectivity (>98%). The conversion of methyl prop-2-ynoate into an active ‘β-iodo allenolate’ intermediate, which then nucleophilically attacks an aldehyde, is proposed as a plausible reaction mechanism.
- Published
- 2004
34. Asymmetric synthesis of chiral β-iodo Baylis–Hillman esters using MgI2 as promoter via a one-pot three-component reaction
- Author
-
Paul W. Paré, Guigen Li, Xin Xu, Dianjun Chen, and Han-Xun Wei
- Subjects
Chiral auxiliary ,Chemistry ,Silica gel ,Component (thermodynamics) ,Organic Chemistry ,Enantioselective synthesis ,Diastereomer ,General Medicine ,Catalysis ,Inorganic Chemistry ,chemistry.chemical_compound ,Product (mathematics) ,Organic chemistry ,Physical and Theoretical Chemistry ,Conjugate - Abstract
An asymmetric synthesis of β-iodo-α-(hydroxyalkyl)acrylates has been developed involving conjugate addition of I− to menthyl propiolates to give β-iodo allenolate intermediates which undergo 1,2-addition to form β-iodo Baylis–Hillman products. Modest diastereoselectivities (37–58% de) and excellent yields (80–87%) were obtained when (1R,2S,5R)-(−)-menthol was used as a chiral auxiliary. The two diastereoisomers of the product were separated by silica gel chromatography to give diastereomerically pure products.
- Published
- 2003
35. Synthesis of β-iodo-α-(hydroxyalkyl)acrylates: a convenient and stereoselective reaction
- Author
-
Han-Xun Wei, Paul W. Paré, Joe J. Gao, and Guigen Li
- Subjects
animal structures ,Chemistry ,Organic Chemistry ,virus diseases ,Aluminium iodide ,chemistry.chemical_element ,Iodine ,Biochemistry ,Medicinal chemistry ,humanities ,Coupling reaction ,Adduct ,Turn (biochemistry) ,chemistry.chemical_compound ,Drug Discovery ,heterocyclic compounds ,Stereoselectivity ,Lewis acids and bases - Abstract
An efficient one-pot, three-component coupling reaction for the synthesis of β-iodo-α-(hydroxyalkyl) acrylates has been developed. As the iodine source as well as the Lewis acid mediator, diethyl aluminium iodide undergoes a Michael-type addition with methyl propynoate to form an active β-iodo allenolate intermediate, which in turn attacks various aldehydes or ketones to afford β-iodo Baylis–Hillman adducts in excellent yields with high Z-selectivity.
- Published
- 2002
36. Electrophilic Diamination of Alkenes by Using FeCl3−PPh3 Complex as the Catalyst
- Author
-
Han-Xun Wei, Guigen Li, and Sun Hee Kim
- Subjects
chemistry.chemical_classification ,Magnetic Resonance Spectroscopy ,Ketone ,Molecular Structure ,Chemistry ,Organic Chemistry ,Imidazoles ,Regioselectivity ,Esters ,Stereoisomerism ,Alkenes ,Ketones ,Ferric Compounds ,Catalysis ,chemistry.chemical_compound ,Cyclization ,Imidazolidine ,Electrophile ,Combinatorial Chemistry Techniques ,Organic chemistry ,Stereoselectivity ,Amines ,Enone ,Amination - Abstract
The FeCl(3)-PPh(3) complex was found to effectively catalyze the electrophilic diamination reaction of electron-deficient alkenes. Improvements on yields and stereoselectivity have been achieved for both alpha,beta-unsaturated carboxylic esters and ketones. Under the new catalytic system, alpha,beta-unsaturated carboxylic esters were found to be superior to their ketone counterparts, which is opposite to the previous (C(3)F(7)CO(2))(2)Rh](2)-catalyzed diamination. The reaction employs readily available N,N-dichloro-p-toluenesulfonamide (TsNCl(2)) and acetonitrile as the nitrogen sources and is very easy to perform at room temperature without the special protection of inert gases. The resulting diamino products belong to imidazolidine analogue and can further strengthen the importance of the new reaction. Modest to good yields (52-84%) and high regio- and stereoselectivity have been achieved for 10 examples.
- Published
- 2002
37. Z/ESTEREOSELECTIVE SYNTHESIS OF β-BROMO BAYLIS-HILLMAN KETONES VIA A ONE-POT THREE-COMPONENT X–C/C–C FORMATION REACTION
- Author
-
Han-Xun Wei, Guigen Li, Jeremy Johnson, and Joe J. Gao
- Subjects
Reaction formation ,Stereochemistry ,Chemistry ,Organic Chemistry ,Stereoselectivity ,Selectivity - Abstract
Highly stereoselective synthesis of (E)-β-bromo Baylis-Hillman ketones has been achieved using a three-component X–C/C–C formation reaction. The synthesis involves the Michael-type addition of TiBr4 to α,β-acetylenic ketones without using any bases and carbonyl coupling with aldehydes. Modest yields (50–65%) and complete E/Z geometric selectivity have been realized for 10 examples.
- Published
- 2002
38. Multiple target tracking based separation of Micro-Doppler signals from coning target
- Author
-
Shao Changyu, Han Xun, Du Lan, and Liu Hongwei
- Subjects
Computer science ,business.industry ,Estimation theory ,Pulse-Doppler radar ,Feature extraction ,Pattern recognition ,Tracking (particle physics) ,Moving target indication ,Space-time adaptive processing ,Stationary target indication ,Computer vision ,Artificial intelligence ,business ,Low probability of intercept radar - Abstract
Micro-Doppler (m-D) signature based target classification methods have received the intensive attention from the radar automatic target recognition (RATR) community. Since the m-D signals of a coning target with micro-motion are always multicomponent, it is important to separate these m-D frequency components for feature extraction and parameter estimation. This paper develops a separation algorithm based on multiple target tracking (MTT) technology, where the m-D frequency curves are assumed to be the tracks of maneuvering targets. The proposed method shows the good performance on the electromagnetic computation data in the experiments.
- Published
- 2014
39. Substoichiometric TiCl4-mediated vicinal difunctionalization of α,β-acetylenic ketones for the synthesis of β-halo Baylis–Hillman olefins
- Author
-
Ju J. Gao, Guigen Li, and Han-Xun Wei
- Subjects
Tandem ,Organic Chemistry ,chemistry.chemical_element ,Biochemistry ,Medicinal chemistry ,Adduct ,chemistry.chemical_compound ,chemistry ,Drug Discovery ,Halogen ,Titanium tetrachloride ,Stereoselectivity ,Vicinal difunctionalization ,Titanium - Abstract
A substoichiometric amount of titanium tetrachloride was found to be effective to promote and participate in the tandem α-hydroxyalkylation/β-chlorination of α,β-acetylenic ketones in the presence of (n-Bu)4NI. This method provides the concise synthesis of (E)-β-halo Baylis–Hillman adducts. No β-iodo products were detected when using this combination of halogen sources. The reaction process involves 1,4-addition of chloro anion released from TiCl4 onto α,β-acetylenic ketones to give TiCl3–allenolate intermediates followed by the titanium Lewis acid-promoted carbonyl addition. Modest to good yields (53–77%) and excellent E/Z stereoselectivity (>95%) have been obtained for 10 examples.
- Published
- 2001
40. A Novel Electrophilic Diamination Reaction of Alkenes
- Author
-
Han-Xun Wei, Sun Hee Kim, Guigen Li, and Michael D. Carducci
- Subjects
Dimer ,chemistry.chemical_element ,Homogeneous catalysis ,General Chemistry ,General Medicine ,Catalysis ,Rhodium ,chemistry.chemical_compound ,chemistry ,Diamine ,Electrophile ,Organic chemistry ,Stereoselectivity ,Amination - Abstract
A three-component electrophilic reaction transforms olefins into imidazoline and diamine derivatives. Rhodium(II) heptafluorobutyrate dimer (2 mol %) was utilized as the catalyst and N,N-dichloro-p-toluenesulfonamide (TsNCl2 ) and acetonitrile as the nitrogen sources. Modest to good yields (45-82 %) and high regio- and stereoselectivity were achieved.
- Published
- 2001
41. Unexpected copper-catalyzed aminohalogenation reaction of olefins using N-halo-N-metallo-sulfonamide as the nitrogen and halogen sources
- Author
-
Guigen Li, Han-Xun Wei, and Sun Hee Kim
- Subjects
chemistry.chemical_classification ,Olefin fiber ,Organic Chemistry ,chemistry.chemical_element ,Biochemistry ,Copper ,Combinatorial chemistry ,Styrene ,Sulfonamide ,Catalysis ,chemistry.chemical_compound ,chemistry ,Drug Discovery ,Halogen ,Chlorine ,Vicinal - Abstract
N-Chloro-N-sodium-sulfonamide was found to react with olefins in the presence of copper catalyst to give vicinal haloamine derivatives instead of aziridines. The resulting regio and stereochemistry indicates that this unexpected reaction could proceed through the formation of unprecedented N-chloro-N-copper-2-nitrobenzenesulfonyl aziridinium intermediates, which can increase the successful chance to render the asymmetric version of the aminohalogenation reaction. In addition, this finding provides a more convenient protocol by the use of solely pure NsNClNa for the aminohalogenation reaction as compared to the mixed nitrogen and chlorine sources consisting of NsNCl2 and NsNHNa as previously reported by us. Two new simple olefin substrates, trans-stilbene and styrene, were also found to be effective for this new reaction system.
- Published
- 2001
42. The first transition metal–ligand complex-catalyzed regioselective and stereoselective aminohalogenation of cinnamic esters
- Author
-
Han-Xun Wei, Guigen Li, and Sun Hee Kim
- Subjects
Transition metal ,Ligand ,Chemistry ,Organic Chemistry ,Drug Discovery ,Chlorine ,Regioselectivity ,chemistry.chemical_element ,Stereoselectivity ,Biochemistry ,Medicinal chemistry ,Catalysis - Abstract
Transition metal–ligand complex-catalyzed regio- and stereoselective aminohalogenation of cinnamic esters has been developed using p-TsNCl2 as the nitrogen and chlorine sources. Dichloro-(1,10-phenanthroline)-palladium (II) as the catalyst can be handled very conveniently due to its property of less hygroscopic as compared with other aminohalogenation catalysts. The reaction is suggested to proceed through the mechanism involving N-tosyl N-chloro aziridinium intermediate. Eight examples are presented with modest to good yields (56–82%) and excellent stereoselectivity (>10:1).
- Published
- 2001
43. The Asymmetric Catalytic Aldol Reaction of Allenolates with Aldehydes Using N-Fluoroacyl Oxazaborolidine as the Catalyst
- Author
-
Han-Xun Wei, David W. Purkiss, Guigen Li, Sun Hee Kim, and Brian S. Phelps
- Subjects
N-fluoroacyl oxazaborolidine ,Silylation ,Aldol reaction ,Chemistry ,Organic Chemistry ,Enantioselective synthesis ,Molecule ,Organic chemistry ,Stereoisomerism ,Physical and Theoretical Chemistry ,Biochemistry ,Catalysis ,Adduct - Abstract
The asymmetric catalytic aldol reaction of silyl allenolates with aldehydes has been achieved by using N-C(3)F(7)CO oxazaborolidine as the catalyst. The fluoroacyl group of the catalyst was found to be crucial for control of enantioselectivity. The reaction provides the first enantioselective approach to beta-halo Baylis-Hillman-type adducts.
- Published
- 2001
44. Discovery of Notch-Sparing γ-Secretase Inhibitors
- Author
-
Dai Lu, Yongli Gu, Jing Zhang, Han-Xun Wei, Wenjuan Ye, Michael S. Wolfe, Pamela Osenkowski, Corinne E. Augelli-Szafran, and Ting Yang
- Subjects
Proteases ,biology ,medicine.diagnostic_test ,Drug discovery ,Proteolysis ,Notch signaling pathway ,P3 peptide ,Pharmacology ,Cell biology ,Neurology ,Alpha secretase ,biology.protein ,medicine ,Amyloid precursor protein ,Neurology (clinical) ,Amyloid precursor protein secretase - Abstract
Overwhelming evidence supports a central role for the amyloid β-peptide (Aβ) in the pathogenesis of Alzheimers disease (AD), and the proteases that produce Aβ from its precursor protein APP are top targets for therapeutic intervention. Considerable effort has focused on targeting γ-secretase, which generates the C-terminus of Aβ; however, γ- secretase inhibitors cause serious toxicities due to interference with the Notch signaling pathway. We have been working toward compounds that directly alter γ-secretase activity to reduce Aβ production without affecting the proteolysis of Notch. Using purified enzyme and substrate, we have shown that γ-secretase can be selectively inhibited in this way by naphthyl-substituted γ-aminoketones and γ-aminoalcohols. These early hits, however, suffered from chemical instability and/or poor potency. Iterative design, synthesis and evaluation have led to the discovery of Notch-sparing γ-secretase inhibitors with substantially increased potencies in biochemical and cellular assays. These compounds are of low molecular weight and are under evaluation for drug-like properties. The discovery and development of these compounds will be discussed.
- Published
- 2010
45. α,β-Differentiated tandem diamination of cinnamic esters using N,N-dichloro-2-nitrobenzenesulfonamide and acetonitrile as the nitrogen sources
- Author
-
Han-Xun Wei, Guigen Li, and Sun Hee Kim
- Subjects
chemistry.chemical_classification ,Tandem ,Organic Chemistry ,chemistry.chemical_element ,Biochemistry ,Nitrogen ,Medicinal chemistry ,chemistry.chemical_compound ,chemistry ,Diamine ,Drug Discovery ,Stereoselectivity ,Acetonitrile ,Nitrogen source ,Alkyl - Abstract
Tandem diamination of cinnamic esters provides a new approach to anti alkyl Nα-(2-Ns), Nβ-Ac diaminophenylpropionates. The new reaction proceeds to completion within 3 hours at room temperature using N,N-dichloro-2-nitrobenzenesulfonamide (2-NsNCl2) as the nitrogen source in acetonitrile, which is also involved in the reaction process. Seven diamine derivatives have been obtained with good yields and stereoselectivity.
- Published
- 2000
46. Copper-Catalyzed Aminohalogenation Using the 2-NsNCl2/2-NsNHNa Combination as the Nitrogen and Halogen Sources for the Synthesis of anti-Alkyl 3-Chloro-2-(o-nitrobenzenesulfonamido)-3-arylpropionates
- Author
-
Sun Hee Kim, Guigen Li, and Han-Xun Wei
- Subjects
chemistry.chemical_classification ,Sulfonamides ,Nitrogen ,Organic Chemistry ,chemistry.chemical_element ,Stereoisomerism ,Biochemistry ,Copper ,Catalysis ,chemistry ,Cinnamates ,Halogen ,Chlorine ,Organic chemistry ,Stereoselectivity ,Amines ,Propionates ,Physical and Theoretical Chemistry ,Trifluoromethanesulfonate ,Alkyl ,Amination - Abstract
New regio- and stereoselective aminohalogenation of cinnamic esters has been developed using the combination of 2-NsNCl(2)/2-NsNHNa as the nitrogen and chlorine sources and copper(I) triflate as the catalyst. The new procedure provides an efficient synthesis of anti-alkyl 3-chloro-2-(o-nitrobenzenesulfonamido)-3-phenylpropionate derivatives. Nine examples are presented with good yields (62-82%) and stereoselectivity ((5:1)-(30:1)).
- Published
- 2000
47. Highly Stereoselective α-Hydroxyalkylation/Chlorination of α,β-Acetylenic Ketones—An Efficient Approach to β-Halogeno Baylis–Hillman Adducts
- Author
-
Thomas D. Caputo, David W. Purkiss, Sun Hee Kim, Guigen Li, and Han-Xun Wei
- Subjects
Chemistry ,Organic Chemistry ,Biochemistry ,Adduct ,chemistry.chemical_compound ,Column chromatography ,Drug Discovery ,Electrophile ,Titanium tetrachloride ,Organic chemistry ,Stereoselectivity ,Lewis acids and bases ,Selectivity ,Conjugate - Abstract
A highly stereoselective method for the synthesis of (E)-β-halogeno Baylis–Hillman adducts has been developed. The new method involves a tandem α-hydroxyalkylation/β-chlorination of α,β-acetylenic ketones by using TiCl4 as the chlorine source for α,β-conjugate addition, and concurrently as the Lewis acid promoter for the carbonyl addition. The new system tolerates a broad scope of reactants in which aliphatic and aromatic α-acetylenic ketones can be subjected to the conjugate addition. Both aliphatic and aromatic aldehydes can also be employed as electrophilic acceptors. Good yields (61–88%) and high E/Z stereoselectivity have been obtained for the nine examples which were examined, only in one case was E/Z selectivity of 17/1 observed and the two individual isomers are separable via flash column chromatography.
- Published
- 2000
48. TiCl4-Mediated Baylis–Hillman and aldol reactions without the direct use of a Lewis base
- Author
-
Han-Xun Wei, Joe J. Gao, Guigen Li, and Thomas D. Caputo
- Subjects
Coupling (electronics) ,Aldol reaction ,Chemistry ,Organic Chemistry ,Drug Discovery ,Polymer chemistry ,Baylis–Hillman reaction ,Lewis acids and bases ,Benzoxalinone ,Biochemistry ,Acceptor ,Conjugate - Abstract
TiCl4-Mediated Baylis–Hillman and aldol reactions were developed without the direct use of a Lewis base. These processes involve the conjugate addition of TiCl4 to α,β-unsaturated substrates followed by carbonyl coupling. Baylis–Hillman olefins were obtained when α,β-unsaturated ketones were employed as the substrates, whereas β-halogenated aldol products were generated with an α,β-unsaturated N-acyl benzoxalinone as the Michael-type acceptor.
- Published
- 2000
49. Highly Efficient Deprotection of N-p-Toluenesulfinyl Group of β-Branched Baylis–Hillman Adducts by Using Amberlite IR-120 (Plus) Ion-Exchange Resin
- Author
-
Sun Hee Kim, Han-Xun Wei, and Guigen Li
- Subjects
chemistry.chemical_compound ,Chemistry ,Group (periodic table) ,Organic Chemistry ,Drug Discovery ,Organic chemistry ,Amberlite ,Methanol ,Ion-exchange resin ,Biochemistry ,Solution phase ,Racemization ,Adduct - Abstract
An efficient deprotection of N - p -toluenesulfinyl group of β-branched Baylis–Hillman adducts has been developed by using Amberlite IR-120 (plus) ion-exchange resin in methanol solution at room temperature. Good to quantitative yields have been obtained for six examples. No racemization was detected under the mild conditions. This new method provides a simultaneous deprotection/purification, which has the great advantage over the solution phase deprotection technique of simplicity of work-up.
- Published
- 2000
50. A Mild Procedure for the Stereospecific Transformation of trans Cinnamic Acid Derivatives to cis β-Bromostyrenes
- Author
-
Guigen Li, Han-Xun Wei, Steven Willis, and Sun Hee Kim
- Subjects
chemistry.chemical_compound ,Transformation (genetics) ,Stereospecificity ,Chemistry ,Stereochemistry ,Organic Chemistry ,Selectivity ,Triethylamine ,Cinnamic acid ,Direct transformation - Abstract
A new mild procedure has been developed for the synthesis of cis β-bromostyrene analogs with complete Z/E selectivity and good to excellent yields (58.4 - 90.9%). The process involves carboxyl-halo-elimination of cinnamic acid dibromides by using triethylamine in N,N-dimethylformamide at room temperature. A one-pot procedure has also been described for the direct transformation of cinnamic acids to β-bromostyrenes.
- Published
- 1999
Catalog
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