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Quantitative analysis of 3-isopropylamino-1,2-propanediol as a degradation product of metoprolol in pharmaceutical dosage forms by HILIC-CAD

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Journal of Pharmaceutical Analysis 2019年第6期9卷 431-436页

作者： qun xu Shane Tan Compendial Development Laboratory United States Pharmacopeial Convention (USP)

Aryloxypropanolamine is an essential structural scaffold for a variety of b-adrenergic receptor antagonists such as *** with such a structural motif tend to degrade into α,β ehydroxypropanolamine impurities via a radicaleinitiated oxidation *** impurities are typically polar and nonchromophoric,and are thus often overlooked using traditional reversed phase chromatography and UV *** this work,stress testing of metoprolol confirmed the generation of 3-isopropylamino-1,2-propanediol as a degradation product,which is a specified impurity of metoprolol in the European Pharmacopoeia(impurity N).To ensure the safety and quality of metoprolol drug products,hydrophilic interaction chromatography(HILIC)methods using Halo Penta HILIC column(150mm×4.6 mm,5 μm)coupled with charged aerosol detection(CAD)were developed and optimized for the separation and quantitation of metoprolol impurity N in metoprolol drug products including metoprolol tartrate injection,metoprolol tartrate tablets,and metoprolol succinate extended-release *** HILIC-CAD methods were validated per USP validation guidelines with respect to specificity,linearity,accuracy,and precision,and have been successfully applied to determine impurity N in metoprolol drug products.

关键词： Hydrophilic interaction chromatography(HILIC) Charged aerosol detection(CAD) Metoprolol tartrate injection Metoprolol tartrate tablets Metoprolol succinate extended-release tablets

A Double Varying-coefficient Modeling Approach for Analyzing Longitudinal Observations

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Acta Mathematicae Applicatae Sinica 2019年第3期35卷 671-688页

作者： qun-fang xu Rui LI School of Business Ningbo UniversityNingbo 315211China School of Statistics and Information Shanghai University of International Business and EconomicsShanghai 201620China Key Laboratory of Advanced Theory and Application in Statistics and Data Science East China Normal UniversityMinistry of EducationShanghai 200062China

The identification of within-subject dependence is important for constructing efficient estimation in longitudinal data *** this paper,we proposed a flexible way to study this dependence by using nonparametric regression ***,we considered the estimation of varying coefficient longitudinal data model with non-stationary varying coefficient autoregressive error process over observational time *** on spline approximation and local polynomial techniques,we proposed a two-stage nonparametric estimation for unknown functional coefficients and didn’t not drop any observations in a hybrid least square loss ***,we showed that the estimated coefficient functions are asymptotically normal and derived the asymptotic biases and variances *** Carlo studies and two real applications were conducted for illustrating the performance of our proposed methods.

关键词： autoregressive process double varying coefficient irregular time quantum locally linear

Efcient Estimation of Varying Coefcient Seemly Unrelated Regression Model

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Acta Mathematicae Applicatae Sinica 2014年第1期30卷 119-144页

作者： qun-fang xu Yang BAI School of Sciences Zhejiang Agriculture and Forestry University School of Statistics and Management Shanghai University of Finance and Economics Key Laboratory of Mathematical Economics (SUFE) Ministry of Education

In this paper, we propose a class of varying coefficient seemingly unrelated regression models, in which the errors are correlated across the equations. By applying the series approximation and taking the contemporaneous correlations into account, we propose an efficient generalized least squares series estimation for the unknown coefficient functions. The consistency and asymptotic normality of the resulting estimators are established. In comparison with the ordinary/east squares ones, the proposed estimators are more efficient with smaller asymptotical variances. Some simulgtlon＇studies and a real application are presented to demonstrate the finite sample performance of the proposed methods. In addition, based on a B-spline approximation, we deduce the asymptotic bias and variance of the proposed estimators.

关键词： series approximation varying coefficient seemingly unrelated regression contemporaneous correlation asymptotic normality

Neuroimaging studies on cognitive impairment due to cerebral small vessel disease

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Stroke & Vascular Neurology 2019年第2期4卷 99-101页

作者： Jing Du qun xu Neurology Shanghai Jiao Tong University School of Medicine Affiliated Renji HospitalShanghaiChina Health Manage Center Shanghai Jiao Tong University School of Medicine Affiliated Renji HospitalShanghaiChina

Vascular cognitive impairment (VCI) is a major contributor to age-related dementing illnesses which imposes a tremendous burden on families and society. It is a heterogeneous group of brain disorders. However, cerebral small vessel disease (CSVD) accounts for about 50%-70% of VCI, which represented a more homogeneous subtype of VCI. Advanced multimodal neuroimaging techniques like brain network connectome analyses are currently applied to explore the underlying mechanism of VCI. Some progress in the field of structural and functional brain network researches on a poststroke longitudinal CSVD cohort (Renji CSVD Cohort Study) was reported. Global and regional brain network characters were compared between patients with CSVD and healthy control. It suggested that distributed brain structural network disruption may play a pivot role in the cognitive decline. The results showed that brain structural network characters have distinctive differentiating capacity on the cognition of patients with CSVD.

关键词： cerebral impairment network

Numerical modeling on the interaction of internal solitary wave with slope-shelf and modal analysis

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Acta Oceanologica Sinica 2007年第6期26卷 139-149页

作者： LI qun xu Zhaoting CHEN xu YU Jia Physical Oceanography Laboratory and Institute of Physical Oceanography Ocean University of China Qingdao 266100 China

On the basis of a nonhydrostatic numerical model, the interaction of internal solitary wave with slope - shelf was studied. The breaking and polarity transformation were analyzed. A ＂kink＂ structure, due to shoaling topography and higher nonlinear effect, was found to be generated by the leading wave before breaking. Coherent vortex shedding behind the leading wave was presented. The evolution characteristics of the modal structure were analyzed based on the empirical orthogonal function method. The modal structure was complicated due to the effect of the variable topography, especially when breaking occurred. In the performed experiments, the contributions to the total variance from higher mode jumped from no more than 20% to over 40%.

关键词： internal solitary wave modal structure empirical orthogonal function

Supercritical CO_(2)-driven,periodic patterning on one-dimensionals carbon nanomaterials

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Science China Chemistry 2010年第7期53卷 1525-1533页

作者： ZHENG XiaoLi xu qun LI ZongPeng College of Material Science and Engineering Zhengzhou UniversityZhengzhou 450052China

One-dimensional carbon nano-materials,in particular carbon nanotubes (CNTs) and carbon nanofibers (CNFs),are of scientific and technological interest due to their satisfactory properties and ability to serve as templates for directed *** this work,linear high density polyethylene (PE) was periodically decorated on CNTs and CNFs using a supercritical carbon dioxide (scCO_(2))antisolvent-induced polymer epitaxy (SAIPE) method,leading to nano-hybrid shish-kebab (NHSK) *** formation mechanism of different morphologies of PE lamellae on CNTs and CNFs has been *** nanoparticles were synthesized and immobilized on the PE/CNF NHSK structure with the assistance of scCO_(2).The obtained hierarchical nano-hybrid architecture may find applications in microfabrication and other related fields.

关键词： carbon nanotube carbon nanofiber polyethylene supercritical carbon dioxide shish-kebab palladium nanoparticle

Recent Progress on Two-Dimensional Nanoflake Ensembles for Energy Storage Applications

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Nano-Micro Letters 2018年第4期10卷 122-151页

作者： Huicong Xia qun xu Jianan Zhang College of Materials Science and Engineering Zhengzhou University

The rational design and synthesis of two-dimensional(2D) nanoflake ensemble-based materials have garnered great attention owing to the properties of the components of these materials, such as high mechanical flexibility, high specific surface area, numerous active sites,chemical stability, and superior electrical and thermal conductivity. These properties render the 2D ensembles great choices as alternative electrode materials for electrochemical energy storage systems. More recently,recognition of the numerous advantages of these 2D ensemble structures has led to the realization that the performance of certain devices could be significantly enhanced by utilizing three-dimensional(3D) architectures that can furnish an increased number of active sites. The present review summarizes the recent progress in 2D ensemble-based materials for energy storage applications,including supercapacitors, lithium-ion batteries, and sodium-ion batteries. Further, perspectives relating to the challenges and opportunities in this promising research area are discussed.

关键词： 2D nanoflakes Ensembles 3D architectures Supercapacitors Lithium-ion batteries Sodium-ion batteries

SYNTHESIS OF CROSS-CONJUGATED(p-PHENYLENE)S-POLY(p-PHENYLENEVINYLENE)S HYBRIDS WITH LOW CONTENT OF STRUCTURAL DEFECTS

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Chinese Journal of Polymer Science 2007年第2期25卷 171-179页

作者： Shi-jun Zheng qun xu Shao-kui Cao College of the Material Science and Engineertng Zhengzhou University Zhengzhou 450052 China

The novel shish-kebab-type liquid crystalline cross-conjugated （p-phenylene）s-poly（p-phenylenevinylene）s hybrid was synthesized through Gilch polymerization. Their structures and properties were characterized by NMR, GPC, DSC, X-ray diffraction and polarizing optical microscope （POM）. ^1H-NMR investigation of the polymers indicates that the shish-kebab-structure has a strong ability to suppress the structural defects in the polymers. The polymers are enantiotropic liquid crystals. The melting point （Tm） of the polymers decreases when the length of the alkoxy tails of the mesogenic units increases. The mesophase was identified by X-ray diffraction method. They showed not only a smectic LC phase, but also a strong green fluorescence in chloroform. The maximum absorption band of the ＂kebabs＂ of the two, 5-bis（4＇- alkoxyphenyl）benzene at 280 nm did not appear in absorption spectra of the polymers. The same phenomena were also observed in the fluorescence spectra. These results imply that the polymers have formed a cross-conjugated uniform structure and achieved an extended n-conjugation polymer.

关键词： Gilch polymerization Conjugated polymer Liquid crystal Shish-kebab Fluorescence.

CO_(2)-Induced Modulation of Si-O Bonds for Low Temperature Plastic Deformation of Amorphous Silica Nanoparticles with Enhanced Photoluminescence

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Energy & Environmental Materials 2024年第4期7卷 404-412页

作者： Kang Huang Wenzhuo Wu Song xu Pengfei Yan Zhongming Wei qun xu Henan Institute of Advanced Technology Zhengzhou UniversityZhengzhou 450001China College of Materials Science and Engineering Zhengzhou UniversityZhengzhou 450001China State Key Laboratory of Superlattices and Microstructures Institute of Semiconductors Chinese Academy of SciencesBeijing 100083China

Modulation of Si-O bonds under mild conditions has been a challenging issue in the field of material science,which is critical to manufacture highperformance silica-based optical and photonic ***,we introduce a nondestructive technique to achieve Si-O bond rearrangement,leading to plastic deformation and photoluminescence enhancement of amorphous silica nanoparticles using supercritical carbon dioxides in EtOH/H_(2)O solution under mild ***,plastic deformation is achieved by treating hollow mesoporous silica nanospheres using supercritical CO_(2)at 40°C under 20 *** and theoretical studies revealed the critical role of supercritical CO_(2)in the plastic deformation process,which can be intercalated into the hollow mesoporous silica nanospheres with anisotropic stresses and induces the rearrangement of Si-O bonds and transformation of ring *** work suggests a novel approach to engineer high-performance nano-silica glass components for numerous optical and photonic devices under mild condition.

关键词： amorphous silica anisotropic stress photoluminescence plastic deformation supercritical CO_(2)