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Synthesis and Characterization of Fluorinated Polyimide Derived from 3,3＇-Diisopropyl-4,4＇-diaminodiphenyl- 3＂,4＂-difluorophenylmethane

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Chinese Journal of Chemistry 2015年第10期33卷 1159-1166页

作者： Xiaohua Huang mei mei Chanjuan Liu Xianglin Pei chun Wei Key Laboratory of New Processing Technology for Nonferrous Metal & Materials Ministry of Education andSchool of Material Science and Engineering Guilin University of Technology Guilin Guangxi 541004 China Ministry of Education Key Laboratory for the Chemistry and Molecular Engineering of Medicinal Resources School of Chemistry and Pharmaceutical Science Guangxi Normal University Guilin Guangxi 541004 China

A novel aromatic diamine monomer, 3,3＇-diisopropyl-4,4＇-diaminodiphenyl-3＂,4＂-difluorophenylmethane （PAFM）, was successfully synthesized by coupling of 2-isopropylaniline and 3,4-difluorobenzaldehyde. The aro- matic diamine was adopted to synthesize a series of fluorinated polyimides by polycondensation with various dian- hydrides： pyromellitic dianhydride （PMDA）, 3,3＇,4,4＇-biphenyltetracarboxylic dianhydride （BPDA）, 4,4＇-oxydiph- thalic anhydride （ODPA） and 3,3＇,4,4＇-benzophenone tetracarboxylic dianhydride （BTDA） via the conventional one-step method. These polyimides presented excellent solubility in common organic solvents, such as N,N-dimeth- ylformamide （DMF）, N,N-dimethyl acetamide （DMAc）, dimethyl sulfoxide （DMSO）, N-methyl-2-pyrrolidone （NMP）, chloroform （CHC13）, tetrahydrofuran （THF） and so on. The glass transition temperatures （Tg） of fluorinated polyimides were in the range of 260--306 ℃ and the temperature at 10% weight loss in the range of 474--502 ℃ Their films showed the cut-off wavelengths of 330--361 nm and higher than 80% transparency in a wavelength range of 385--463 nm. Moreover, polymer films exhibited low dielectric properties in the range of 2.76--2.96 at 1 MHz, as well as prominent mechanical properties with tensile strengths of 66.7--97.4 MPa, a tensile modulus of 1.7--2.1 GPa and elongation at break of 7.2%- 12.9%. The polymer films also showed outstanding hydrophobicity with the contact angle in the range of 91.2°--97.9°.

关键词： fluorinated polyimides solubility transparency dielectric constant

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Consumer confidence and consumers’ preferences for infant formulas in China

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Journal of Integrative Agriculture 2019年第8期18卷 1793-1803页

作者： LI sai-wei ZHU Chen CHEN Qi-hui LIU Yu-mei College of Economics and Management China Agricultural University Beijing 100083 P.R.China Center for Food and Health Economic Research College of Economics and Management China Agricultural University Beijing100083 P.R.China

A series of safety incidents related to domestically-produced infant formulas(DIFs) almost destroyed Chinese consumer confidence in domestic dairy products. Understanding consumer confidence and its effect on consumption behavior is important to restore consumer confidence and enhance the competitiveness of domestic dairy industry. This article first measures Chinese consumer confidence in DIFs safety using a two-dimension scale(optimism and pessimism) and then investigates its effect on consumers’ preferences for DIFs through a choice experiment. Involving 450 consumers residing in Beijing, Tianjin and Shijiazhuang, the experiment elicited information on their preferences for DIFs with six attributes(organic raw milk, farm-to-table traceability, region of origin, quality certification, animal welfare, and price). Our analysis yields four findings. First, Chinese consumers still lack confidence in DIFs safety. Second, quality certification is the most preferred product characteristic, followed by organic raw milk and farm-to-table traceability. Third, serving as a signal of high quality, price exerts a positive impact on choices of DIFs for pessimistic consumers. Finally, consumer preferences for farm-to-table traceability and region of origin are significantly influenced by consumer confidence.

关键词： consumer confidence food safety infant formula choice experiment willingness to pay China

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Calculation of half-life for ^(79)Se decay

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Nuclear Science and Techniques 2006年第1期17卷 21-23页

作者： ZHOU chun-mei WU Zhen-Dong China Nuclear Data Center Department of Nuclear Physics China Institute of Atomic Energy Beijing 102413 China

The half-life for 79Se decay is calculated by using the Logf1ut systematics method. Based on the data analysis and comparison with experimental data the 79Se half-life is recommended. The scheme for 79Se decay is also... 详细信息

关键词：半衰期计算 ^79Se衰变数据计算核衰变

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Multi-mode Einstein-Podolsky-Rosen Entangled State Representation and Its Applications

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Communications in Theoretical Physics 2008年第9期50卷 615-618页

作者： LI Heng-mei YUAN Hong-chun Institute for Theoretical Physics and Department of Modern Physics University of Science and Technology of China Hefei 230026 China Department of Physics Huaibei Coal Industry Teachers＇ College Huaibei 235000 China

Our primary purpose of this work is to explicitly construct the general multiparite Einstein-Podolsky- Rosen （EPR） entangled state in multi-mode Fock space for a system with different masses of particles, which makes up a new quantum mechanical representation owing to completeness relation and orthogonal property. Its entanglement can be seen more clearly by analyzing its standard Schmidt decomposition. In addition, some applications of the multipartite entanglement are proposed including deriving the generalized Wigner operator and squeezing operator.

关键词： Einstein-Podolsky-Rosen (EPR) entangled state representation

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Potential effects of the nursing work environment on the work-family conflict in operating room nurses

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World Journal of Clinical Cases 2021年第26期9卷 7738-7749页

作者： chun-mei Fu Jie Ou Xiao-mei Chen mei-Ye Wang Department of Ophthalmology Hainan West Central HospitalDanzhou 571700Hainan ProvinceChina Department of Critical Care Medicine Hainan General HospitalHaikou 570311Hainan ProvinceChina Operation Room The Second Affiliated Hospital of Hainan Medical CollegeHaikou 570311Hainan ProvinceChina Department of General Practice Hainan West Central HospitalDanzhou 571700Hainan ProvinceChina

BACKGROUND The nursing working environment is an important subsystem in the hospital environment.A good working environment could have a positive impact on ***,the work-family conflict and unsatisfactory working environment could significantly reduce their working enthusiasm,efficacy as well as the overall quality of the nursing,increase their fatigue,and thereby compromise their career *** To explore the possible status quo and to analyze the correlation between work environment perception and the work-family conflict among nurses in the operating *** A total of 312 operating room nurses from two first-class hospitals at Grade 2 and two first-class hospitals at Grade 3 in China from May to September 2017 were included in this research using the cluster sampling *** data,including the general information questionnaire,the practice environment scale of the nursing work index(PES-NWI),and the work-family conflict scale,were systematically *** correlation analysis was applied to analyze the correlation between the two scores,with influencing factors analyzed by hierarchical regression *** A total of 312 questionnaires were issued,and the response rate and effective questionnaire rate were both 96.15%(300/312).The total scores of the PES-NWI scale and the work-family conflict scale were 3.07±0.43(vs maximum up to 4 points)and 52.32±8.79(vs maximum up to 90 points),*** scores of the PES-NWI scale were negatively correlated with that of work-family conflict scale(all P<0.05).The perception of the nursing work environment and the number of night shifts per month were the major factors contributing to the workfamily conflict(all P<0.05).CONCLUSION The nursing work environment and the work-family conflict among nurses in the operating room were both found at a medium level with a negative correlation between the two.

关键词： Operating room nurses Perception of nursing work environment Workfamily conflict Correlation Influencing factors

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Differential Evolution Hemivariational Inequalities with Anti-periodic Conditions

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Acta Mathematica Sinica,English Series 2024年第4期40卷 1143-1160页

作者： Jing ZHAO chun mei GAN Zhen Hai LIU School of Mathematics and Quantitative Economics Guangxi University of Finance and EconomicsNanning 530003P.R.China Guangxi Colleges and Universities Key Laboratory of Optimization Control and Engineering Calculation Guangxi Minzu UniversityNanning 530006P.R.China

The goal of this paper is to deal with a new dynamic system called a differential evolution hemivariational inequality(DEHVI)which couples an abstract parabolic evolution hemivariational inequality and a nonlinear differential equation in a Banach ***,by apply ing surjectivity result for pseudomonotone multivalued mappins and the properties of Clarke's subgradient,we show the nonempty of the solution set for the parabolic hemivariational ***,some topological properties of the solution set are established such as boundedness,closedness and ***,we explore the upper semicontinuity of the solution ***,we prove the solution set of the system(DEHVI)is nonempty and the set of all trajectories of(DEHVI)is weakly compact in C(I,X).

关键词： Differential parabolic hemivariational inequality Clarke subdifferential hyperbolicparabolic system parabolic-parabolic system existence result

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Detection and comparison of matrix metalloproteinase in primary and recurrent pterygium fibroblasts

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International Journal of Ophthalmology(English edition) 2011年第4期4卷 353-356页

作者： mei-Xia An, Shao-chun Lin Department of Ophthalmolgy the Third Affiliated Hospital of Southern Medical University Guangzhou 510630 Guangdong Province China State Key Laboratory of Ophthalmolgy Zhongshan Phthalmic Center Sun Yat-sen University Guangzhou 510060 Guangdong Province China

AIM: To detect and compare the levels of matrix metalloproteinases (MMPs) secreted by primary and recurrent human pterygium fibroblasts (HPFs). METHODS: Primary and recurrent HPFs as well as human conjunctival fibroblasts (HCF) were cultured in RPMI 1640 medium at the same conditions. The protein levels of MMP-1, MMP-3 and MMP-9 were determined by enzyme-linked immune sorbent assay (ELISA), respectively. RESULTS: 1) The protein level of MMP-1 in serum-free supernatant from cultured primary and recurrent HPFs was higher than that in normal HCFs (P <0.05); similarly, the protein level of MMP-1 in serum-free supernatant from cultured primary HPFs was higher than that in recurrent HCFs (P <0.05). 2) The protein level of MMP-3 in serum-free supernatant from cultured primary HPFs was higher than that in normal HCFs (P<0.05); meanwhile, the protein level of MMP-3 in serum-free supernatant from cultured recurrent HPFs was lower when compared with that in primary HPFs and normal HCFs (P<0.05). 3) MMP-9 was not detected in primary and recurrent HPFs in the conditioned medium. CONCLUSION: The protein levels of MMP-1 and MMP-3 in supernatant secreted by primary HPFs are different from recurrent HPFs. Different pathological mechanisms may exist between primary and recurrent pterygia.

关键词： primary and recurrent pterygia matrix metalloproteinase

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Corneal endothelial cell density and morphology in low and moderate myopic Chinese eyes

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International Journal of Ophthalmology(English edition) 2013年第4期6卷 467-470页

作者： Samaneh Delshad Jane mei chun National Institute of Ophthalmic Sciences School of OptometryLot 2Lorong Utara BPetaling Jaya 46200Darul EhsanSelangorMalaysia

AIM:To describe and compare the corneal endothelial cell density and morphology in young,low and moderate myopic Chinese adults in Malaysian Chinese population.·METHODS:Non-contact specular microscopy(Topcon SP3000P,Tokyo,Japan) was performed in low(n =78;21.22±1.51 years) and moderate(n =78;21.82±1.40 years)myopic *** mean of three consecutive measurements of endothelial cell density(MCD),coefficient of variation(CV) in the cell size,and hexagonal appearance of the cell were obtained.·RESULTS:In low myopic eyes the MCD was 3 063.0±176.2/mm2,the mean CV was 33.4 ±4.0% and the mean hexagonal appearance of the cell was 57.9 ±2.7%.In moderate myopic eyes the MCD was 2961.6 ±159.0/mm2,the mean CV was 33.9 ±3.6% and mean hexagonal appearance of the cell was 56.2 ±4.7%.There were statistically significant differences in MCD(P <0.000) and hexagonal appearance of the cell(P <0.005) between low and moderate myopic eyes.·CONCLUSION:The corneal endothelial cell layer in more myopic eyes tends to have less MCD and cell hexagonality compared to lower myopic ***,there is no significant difference in CV between low and moderate myopic eyes.

关键词： cornea myopic eyes specular microscopy endothelial cell density morphology

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Efficient coupling of evanescent waves in rectangular waveguides based on ultrathin planar capacitive metasurfaces

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Science China(Information Sciences) 2021年第8期64卷 182-194页

作者： Da YI Ming-chun TANG mei LI Xing-Chang WEI College of Microelectronics and Communication Engineering Chongqing University Zhejiang Provincial Key Laboratory of Advanced Microelectronic Intelligent Systems and Applications College of Information Science and Electronic Engineering Zhejiang University

This work proposes an approach to enable efficient coupling of evanescent waves below the cutoff frequency of a standard rectangular waveguide(RWG) system based on ultrathin planar capacitive metasurfaces(CMSs). It is demonstrated that the CMS at the RWG’s cross-section can couple the evanescent wave from one port to the other, and thus enable an efficient frequency-selective transmission below the cutoff frequency. Theoretical formulas, together with the equivalent circuit, are presented to quantitatively illustrate the operational mechanism of the proposed approach. The performance characteristics, including out-of-band suppression, Q-factor, transmission loss, and coupling bandwidth, are studied in a comprehensive manner. Three CMS samples with different surface impedance values are designed, fabricated, and *** measurement results show good agreement with the numerical values, validating their highly efficient evanescent wave coupling performance characteristic at selected frequencies below the cutoff frequency, with approximately 100% transmission efficiency. Benefiting from the admirable low-frequency coupling performance,this approach has potential applications in many miniaturized and high-performance transmission components, such as compact evanescent wave resonators, filters, and antennas.

关键词： cutoff frequency capacitive metasurface evanescent wave miniaturized components rectangular waveguide

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Spermatocytic tumor:A rare case report

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World Journal of Clinical Cases 2021年第35期9卷 11115-11121页

作者： mei-Ling Hao chun-Hui Li Department of Pathology Chengde Medical College Affiliated HospitalChengde 067000Hebei ProvinceChina

BACKGROUND Spermatocytic tumor is a rare,malignant neoplasm of the *** the prognosis for this tumor type is favorable,accurate diagnosis and differentiation from other malignant testicular neoplasms(classic seminoma and lymphoma)are *** add to the existing literature on the diagnosis of spermatocytic tumor,herein we report the detailed clinical and histopathologic findings for a case that we *** SUMMARY A 60-year-old Chinese man presented with a solid mass in the right *** mass was surgically removed and spermatocytic tumor was *** microscopy,the tumor cells displayed an unusual arrangement in lobules,presenting a pseudo-glandular *** summarize and compare the diagnostic features of this tumor and those of the differential diagnoses,we report our case findings and those mentioned in the literature for various testicular *** imaging methods can detect masses early in development,their diagnostic capabilities are ***,histopathology,and immunohistochemistry are necessary for confirmatory *** It is important to identify and review the key diagnostic features of spermatocytic tumor.

关键词： Spermatocytic tumor Germ cell tumor Immunohistochemistry Pseudoglandular Case report

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