期刊文献+
共找到397篇文章
< 1 2 20 >
每页显示 20 50 100
Conformable and Caputo’s Derivatives in Generalized Viscoelastic Models
1
作者 Jorge Fujioka Rosalío Fernando Rodríguez Áurea Espinosa-Cerón 《Applied Mathematics》 2023年第9期580-601,共22页
We study two generalized versions of a system of equations which describe the time evolution of the hydrodynamic fluctuations of density and velocity in a linear viscoelastic fluid. In the first of these versions, the... We study two generalized versions of a system of equations which describe the time evolution of the hydrodynamic fluctuations of density and velocity in a linear viscoelastic fluid. In the first of these versions, the time derivatives are replaced by conformable derivatives, and in the second version left-handed Caputo’s derivatives are used. We show that the solutions obtained with these two types of derivatives exhibit significant similarities, which is an interesting (and somewhat surprising) result, taking into account that the conformable derivatives are local operators, while Caputo’s derivatives are nonlocal operators. We also show that the solutions of the generalized systems are similar to the solutions of the original system, if the order α of the new derivatives (conformable or Caputo) is less than one. On the other hand, when α is greater than one, the solutions of the generalized systems are qualitatively different from the solutions of the original system. 展开更多
关键词 Conformable derivatives Caputo’s derivatives Fractional derivatives Viscoelastic Fluids Hydrodynamic Fluctuations
下载PDF
采用两步炭化法和熔盐模板法制备N、S共掺杂煤基硬炭及共储钠性能
2
作者 牛慧祝 王海花 +6 位作者 孙立宇 杨晨榕 王雨 曹瑞 杨存国 王洁 舒珂维 《新型炭材料(中英文)》 SCIE EI CAS CSCD 北大核心 2024年第2期297-307,共11页
硬炭因资源丰富、结构稳定及安全性高等优势,已成为钠离子电池常用阳极材料。其中,煤基衍生硬炭受到了广泛的关注。本工作以长焰煤为碳源,硫脲为氮硫源,NaCl为模板,通过两步炭化工艺和杂原子掺杂相结合的方法合成了N和S共掺杂的煤基硬炭... 硬炭因资源丰富、结构稳定及安全性高等优势,已成为钠离子电池常用阳极材料。其中,煤基衍生硬炭受到了广泛的关注。本工作以长焰煤为碳源,硫脲为氮硫源,NaCl为模板,通过两步炭化工艺和杂原子掺杂相结合的方法合成了N和S共掺杂的煤基硬炭(NSPC1200)。两步炭化过程在调节碳微晶结构和扩大层间距方面发挥了重要的作用。N和S的共掺杂调节了炭材料的电子结构,赋予其更多的活性位点;此外,引入NaCl作为模板有助于孔结构的构建,有利于电极和电解质之间的接触,从而实现Na+和电子的有效传输。在协同作用下,样品NSPC1200表现出优异的储钠能力,在20 mA g^(−1)电流密度下呈现314.2 mAh g^(−1)的可逆容量。即使在100 mA g^(−1)下循环200次,仍保持224.4 mAh g^(−1)的比容量。这项工作成功实现了策略性调整煤基炭材料微观结构的目标,最终获得了具有优异的电化学性能的硬炭阳极。 展开更多
关键词 硬炭 钠离子电池 煤衍生炭 两步炭化 氮硫共掺杂
下载PDF
Optimality for Henig Proper Efficiency in Vector Optimization Involving Dini Set-Valued Directional Derivatives
3
作者 Guolin Yu Huaipeng Bai 《Applied Mathematics》 2011年第7期922-925,共4页
This note studies the optimality conditions of vector optimization problems involving generalized convexity in locally convex spaces. Based upon the concept of Dini set-valued directional derivatives, the necessary an... This note studies the optimality conditions of vector optimization problems involving generalized convexity in locally convex spaces. Based upon the concept of Dini set-valued directional derivatives, the necessary and sufficient optimality conditions are established for Henig proper and strong minimal solutions respectively in generalized preinvex vector optimization problems. 展开更多
关键词 VECTOR Optimization dini sET-VALUED Directional derivATIVE Generalized Preinvex Function Henig PROPER Efficiency
下载PDF
Noether's theorems of a fractional Birkhoffian system within Riemann-Liouville derivatives 被引量:17
4
作者 周燕 张毅 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第12期281-288,共8页
The Noether symmetry and the conserved quantity of a fractional Birkhoffian system are studied within the Riemann–Liouville fractional derivatives. Firstly, the fractional Birkhoff's equations and the corresponding ... The Noether symmetry and the conserved quantity of a fractional Birkhoffian system are studied within the Riemann–Liouville fractional derivatives. Firstly, the fractional Birkhoff's equations and the corresponding transversality conditions are given. Secondly, from special to general forms, Noether's theorems of a standard Birhoffian system are given, which provide an approach and theoretical basis for the further research on the Noether symmetry of the fractional Birkhoffian system. Thirdly, the invariances of the fractional Pfaffian action under a special one-parameter group of infinitesimal transformations without transforming the time and a general one-parameter group of infinitesimal transformations with transforming the time are studied, respectively, and the corresponding Noether's theorems are established. Finally, an example is given to illustrate the application of the results. 展开更多
关键词 fractional Birkhoffian system Noether's theorem fractional conserved quantity Riemann–Liouville fractional derivative
下载PDF
Integral Inequalities of Hermite-Hadamard Type for Functions Whose 3rd Derivatives Are <i>s</i>-Convex 被引量:4
5
作者 Ling Chun Feng Qi 《Applied Mathematics》 2012年第11期1680-1685,共6页
In the paper, the authors find some new inequalities of Hermite-Hadamard type for functions whose third derivatives are s-convex and apply these inequalities to discover inequalities for special means.
关键词 INTEGRAL INEQUALITY Hermite-Hadamard’s INTEGRAL INEQUALITY s-Convex Function derivative Mean
下载PDF
Stem Cell Ophthalmology Treatment Study (SCOTS): bone marrow-derived stem cells in the treatment of Leber's hereditary optic neuropathy 被引量:10
6
作者 Jeffrey N. Weiss Steven Levy Susan C. Benes 《Neural Regeneration Research》 SCIE CAS CSCD 2016年第10期1685-1694,共10页
The Stem Cell Ophthalmology Treatment Study (SCOTS) is currently the largest-scale stem cell ophthal- mology trial registered at ClinicalTrials.gov (identifier: NCT01920867). SCOTS utilizes autologous bone marrow... The Stem Cell Ophthalmology Treatment Study (SCOTS) is currently the largest-scale stem cell ophthal- mology trial registered at ClinicalTrials.gov (identifier: NCT01920867). SCOTS utilizes autologous bone marrow-derived stem cells (BMSCs) to treat optic nerve and retinal diseases. Treatment approaches include a combination of retrobulbar, subtenon, intravitreal, intra-optic nerve, subretinal, and intravenous injection of autologous BMSCs according to the nature of the disease, the degree of visual loss, and any risk factors related to the treatments. Patients with Leber's hereditary optic neuropathy had visual acuity gains on the Early Treatment Diabetic Retinopathy Study (ETDRS) of up to 35 letters and Snellen acuity improvements from hand motion to 20/200 and from counting fingers to 20/100. Visual field improvements were noted. Macular and optic nerve head nerve fiber layer typically thickened. No serious complications were seen. The increases in visual acuity obtained in our study were encouraging and suggest that the use of autolo- gous BMSCs as provided in SCOTS for ophthalmologic mitochondrial diseases including Leber's hereditary optic neuropathy may be a viable treatment option. 展开更多
关键词 nerve regeneration Leber's hereditary optic neuropathy mitochondrial disease optic neuropathy bone marrow derived stem cells BLINDNEss visual loss neural regeneration
下载PDF
Intrauterine transplantation of autologous bone marrow derived mesenchymal stem cells followed by conception in a patient of severe intrauterine adhesions 被引量:10
7
作者 Yong Zhao Aiming Wang +4 位作者 Xiaorong Tang Min Li Ling Yan Wei Shang Meizhu Gao 《Open Journal of Obstetrics and Gynecology》 2013年第3期377-380,共4页
On a woman with severe intrauterine adhesions, hysteroscopy followed by cyclical hormone replacement therapy was tried for 5 months, for development of the endometrium. When this failed, autologous stem cells were tri... On a woman with severe intrauterine adhesions, hysteroscopy followed by cyclical hormone replacement therapy was tried for 5 months, for development of the endometrium. When this failed, autologous stem cells were tried as an alternative therapy. Adult autologous bone marrow mesenchymal stem cells isolated from patient’s own bone marrow and were cultured and placed in the endometrial cavity under ultrasound guidance after curettage. Patient was then given cyclical hormonal therapy. Endometrium was assessed intermittently using ultrasound. Three months later, endometrium partly recovered with improved ultrasonic echo. This resulted in spontaneous pregnancy followed by confirmation of gestational sac, yolk sac, and primitive heart tube pulse on ultrasound. Autologous bone marrow derived mesenchymal stem cells could regenerate injured endometrium not responding to conventional treatment and can be used as an alternative in females with severe Asherman’s syndrome. 展开更多
关键词 INTRAUTERINE ADHEsIONs Asherman’s syndrome Bone MARROW derivED MEsENCHYMAL stem Cells Pregnancy
下载PDF
Fractional Pfaff-Birkhoff Principle and Birkhoff′s Equations in Terms of Riesz Fractional Derivatives 被引量:3
8
作者 周燕 张毅 《Transactions of Nanjing University of Aeronautics and Astronautics》 EI 2014年第1期63-69,共7页
The dynamical and physical behavior of a complex system can be more accurately described by using the fractional model.With the successful use of fractional calculus in many areas of science and engineering,it is nece... The dynamical and physical behavior of a complex system can be more accurately described by using the fractional model.With the successful use of fractional calculus in many areas of science and engineering,it is necessary to extend the classical theories and methods of analytical mechanics to the fractional dynamic system.Birkhoffian mechanics is a natural generalization of Hamiltonian mechanics,and its core is the Pfaff-Birkhoff principle and Birkhoff′s equations.The study on the Birkhoffian mechanics is an important developmental direction of modern analytical mechanics.Here,the fractional Pfaff-Birkhoff variational problem is presented and studied.The definitions of fractional derivatives,the formulae for integration by parts and some other preliminaries are firstly given.Secondly,the fractional Pfaff-Birkhoff principle and the fractional Birkhoff′s equations in terms of RieszRiemann-Liouville fractional derivatives and Riesz-Caputo fractional derivatives are presented respectively.Finally,an example is given to illustrate the application of the results. 展开更多
关键词 fractional derivative fractional Pfaff-Birkhoff principle fractional Birkhoff′s equation transversality condition
下载PDF
Non-Noether symmetries of Hamiltonian systems with conformable fractional derivatives 被引量:3
9
作者 王琳莉 傅景礼 《Chinese Physics B》 SCIE EI CAS CSCD 2016年第1期647-652,共6页
In this paper, we present the fractional Hamilton's canonical equations and the fractional non-Noether symmetry of Hamilton systems by the conformable fractional derivative. First/y, the exchanging relationship betwe... In this paper, we present the fractional Hamilton's canonical equations and the fractional non-Noether symmetry of Hamilton systems by the conformable fractional derivative. First/y, the exchanging relationship between isochronous variation and fractional derivatives, and the fractional Hamilton principle of the system under this fractional derivative are proposed. Secondly, the fractional Hamilton's canonical equations of Hamilton systems based on the Hamilton principle are established. Thirdly, the fractional non-Noether symmetries, non-Noether theorem and non-Noether conserved quantities for the Hamilton systems with the conformable fractional derivatives are obtained. Finally, an example is given to illustrate the results. 展开更多
关键词 conformable fractional derivative Hamilton's canonical equation non-Noether conserved quantity
下载PDF
Variational Calculus With Conformable Fractional Derivatives 被引量:4
10
作者 Matheus J.Lazo Delfim F.M.Torres 《IEEE/CAA Journal of Automatica Sinica》 SCIE EI CSCD 2017年第2期340-352,共13页
Invariant conditions for conformable fractional problems of the calculus of variations under the presence of external forces in the dynamics are studied. Depending on the type of transformations considered, different ... Invariant conditions for conformable fractional problems of the calculus of variations under the presence of external forces in the dynamics are studied. Depending on the type of transformations considered, different necessary conditions of invariance are obtained. As particular cases, we prove fractional versions of Noether's symmetry theorem. Invariant conditions for fractional optimal control problems, using the Hamiltonian formalism, are also investigated. As an example of potential application in Physics, we show that with conformable derivatives it is possible to formulate an Action Principle for particles under frictional forces that is far simpler than the one obtained with classical fractional derivatives. 展开更多
关键词 Conformable fractional derivative fractional calculus of variations fractional optimal control invariant variational conditions Noether’s theorem
下载PDF
四溴双酚A/S及其8种衍生物在清远土壤样品中的污染特征及生态风险评估 被引量:2
11
作者 杨慧 罗孝俊 +2 位作者 何家卓 曾艳红 麦碧娴 《地球化学》 CAS CSCD 北大核心 2023年第1期1-8,共8页
四溴双酚A(tetrabromobisphenol-A, TBBPA)、四溴双酚S(tetrabromobisphenol-S, TBBPS)和它们的衍生物作为阻燃剂被广泛应用于日常用品,以致在多种环境介质中都能检测出它们的存在。本研究分析了清远市龙塘镇的44个土壤样品中的TBBPA、T... 四溴双酚A(tetrabromobisphenol-A, TBBPA)、四溴双酚S(tetrabromobisphenol-S, TBBPS)和它们的衍生物作为阻燃剂被广泛应用于日常用品,以致在多种环境介质中都能检测出它们的存在。本研究分析了清远市龙塘镇的44个土壤样品中的TBBPA、TBBPS及其8种衍生物的含量,并评估了这10种目标物的环境风险。在所有检测的目标化合物中, TBBPA、四溴双酚A双缩水甘油醚(TBBPA-BGE)和四溴双酚A双(2,3-二溴丙基醚)(TBBPA-BDBPE)是样品中的主要污染物,对目标物总浓度的贡献率分别为30%、26%和40%。TBBPA、TBBPA-BGE和TBBPA-BDBPE的浓度平均值分别为1114、1890和853ng/g(干重),浓度范围分别为ND~13098、ND~15980和ND~6088 ng/g。TBBPA、TBBPA-BGE和TBBPA-BDBPE的风险商值大于1,表明这3类化合物对清远土壤存在一定生态环境风险,应当引起重视。本研究为进一步了解常用溴系阻燃剂TBBPA、TBBPS及其衍生物的环境归趋和风险暴露提供了数据支撑。 展开更多
关键词 四溴双酚A 四溴双酚s 衍生物 土壤 污染特征 生态风险
下载PDF
Adaptive Maxwell’s Equations Derived Optimization and Its Application in Antenna Array Synthesis 被引量:1
12
作者 Donglin Su Lilin Li +1 位作者 Shunchuan Yang Fei Wang 《China Communications》 SCIE CSCD 2021年第5期263-272,共10页
In this paper,a self-adaptive method for the Maxwell’s Equations Derived Optimization(MEDO)is proposed.It is implemented by applying the Sequential Model-Based Optimization(SMBO)algorithm to the iterations of the MED... In this paper,a self-adaptive method for the Maxwell’s Equations Derived Optimization(MEDO)is proposed.It is implemented by applying the Sequential Model-Based Optimization(SMBO)algorithm to the iterations of the MEDO,and achieves the automatic adjustment of the parameters.The proposed method is named as adaptive Maxwell’s equations derived optimization(AMEDO).In order to evaluate the performance of AMEDO,eight benchmarks are used and the results are compared with the original MEDO method.The results show that AMEDO can greatly reduce the workload of manual adjustment of parameters,and at the same time can keep the accuracy and stability.Moreover,the convergence of the optimization can be accelerated due to the dynamical adjustment of the parameters.In the end,the proposed AMEDO is applied to the side lobe level suppression and array failure correction of a linear antenna array,and shows great potential in antenna array synthesis. 展开更多
关键词 electromagnetic compatibility Maxwell’s equations derived optimization adaptive Maxwell’s equations derived optimization sequential modelbased optimization antenna array synthesis
下载PDF
Fractional Optical Solitons and Fractional Noether’s Theorem with Ortigueira’s Centered Derivatives 被引量:1
13
作者 Jorge Fujioka Manuel Velasco Argel Ramírez 《Applied Mathematics》 2016年第12期1340-1352,共13页
This paper shows that the centered fractional derivatives introduced by Manuel Duarte Ortigueira in 2006 are useful in the description of optical solitons. It is shown that we can construct a fractional extension of t... This paper shows that the centered fractional derivatives introduced by Manuel Duarte Ortigueira in 2006 are useful in the description of optical solitons. It is shown that we can construct a fractional extension of the nonlinear Schr&ouml;dinger (NLS) equation which incorporates Ortigueira’s derivatives and has soliton solutions. It is also shown that this fractional NLS equation has a Lagrangian density and can be derived from a variational principle. Finally, a fractional extension of Noether’s theorem is formulated to determine the conserved quantities associated to the invariances of the action integral under infinitesimal transformations. 展开更多
关键词 Fractional derivatives Centered derivatives Noether’s Theorem Ortigueira Optical solitons
下载PDF
Some Inequalities of Hermite-Hadamard Type for Functions Whose 3rd Derivatives Are <i>P</i>-Convex 被引量:1
14
作者 Boyan Xi Shuhong Wang Feng Qi 《Applied Mathematics》 2012年第12期1898-1902,共5页
In the paper, the authors establish some new Hermite-Hadamard type inequalities for functions whose 3rd derivatives are P-convex.
关键词 INTEGRAL INEQUALITY Hermite-Hadamard’s INTEGRAL INEQUALITY P-Convex Function derivative
下载PDF
Anti-sense oligonucleotide labeled with technetium-99m using hydrazinonictinamide derivative and N-hydroxysuccinimidyl S-acetylmercaptoacetyltriglycline: A comparison of radiochemical behaviors and biological properties 被引量:4
15
作者 Yun-Chun Li Tian-Zhi Tan Jian-Guo Zheng Chun Zhang 《World Journal of Gastroenterology》 SCIE CAS CSCD 2008年第14期2235-2240,共6页
AIM:To explore and compare the radiochemical behavior and biological property of anti-sense oligonuc-leotide (ASON) labeled with technetium-99m using N-hydroxysuccinimidyl S-acetylmercaptoacetyltriglycl ine (NHS-MAG3)... AIM:To explore and compare the radiochemical behavior and biological property of anti-sense oligonuc-leotide (ASON) labeled with technetium-99m using N-hydroxysuccinimidyl S-acetylmercaptoacetyltriglycl ine (NHS-MAG3) and hydrazinonictinamide derivative (HYNIC). METHODS:After HYNIC and NHS-MAG3 were synthesized, ASON was labeled with technetium-99m using HYNIC and NHS-MAG3 as a bifunctional chelator. The in vivo and in vitro stability, binding rates of labeled compounds to serum albumen, biodistribution of 99mTc-MAG3-ASON and 99mTc-HYNIC-ASON in BALB/C mouse and its HT29 tumor cellular uptake were compared. RESULTS:The labeling efficiency and stability of 99mTc-MAG3-ASON were significantly higher than those of 99mTc-HYNIC-ASON (P = 0.02, and P = 0.03, respectively). 99mTc-MAG3-ASON had a significantly lower rate of binding to serum albumen than 99mTc-HYNIC-ASON (P < 0.05). In contrast to 99mTc-HYNIC-ASON, the biodistribution of 99mTc-MAG3-ASON was significantly lower in blood, heart, liver and stomach (P < 0.05), slightly lower in intestines and spleen (P > 0.05) and significantly higher in lung and kidney (P < 0.05). The HT29 tumor cellular uptake rate of 99mTc-MAG3-ASON was significantly higher than that of 99mTc-HYNIC-ASON (P < 0.05). CONCLUSION:99mTc-MAG3-ASON shows superior radiochemical behaviors and biological properties than 99mTc-HYNIC-ASON. 99mTc-MAG3-ASON is a potential radiopharmaceutical agent for in vivo application. 展开更多
关键词 寡核苷酸 放射性同位素 锝-99 治疗方法
下载PDF
QSAR Studies on 6-(1-Naphthylmethyl) Substituted S-DABO Derivatives as Novel Non-nucleoside HIV-1 Reverse Transcriptase Inhibitors 被引量:2
16
作者 殷丽琴 余仕问 +2 位作者 姚凌峰 何严萍 谢小光 《Chinese Journal of Structural Chemistry》 SCIE CAS CSCD 北大核心 2008年第10期1214-1222,共9页
The AM1 and B3LYP methods were employed to calculate the structural properties of 20 6-(1-naphthylmethyl) substituted S-DABO derivatives with β-carbonyl group on the C(2) side chain as novel potent non-nucleoside... The AM1 and B3LYP methods were employed to calculate the structural properties of 20 6-(1-naphthylmethyl) substituted S-DABO derivatives with β-carbonyl group on the C(2) side chain as novel potent non-nucleoside HIV-1 reverse transcriptase inhibitors. The correlation analysis (CA) and stepwise multiple regression analysis (SMR) were performed. The QSAR models indicate that the physicochemical parameters of Qc9, MRR1, ELUMO, ∏R2 and μ have significant influence on the activities of these derivatives. The substitution of hydrophobic R2 and bulky aromatic R1 to form a conjugated system with the frame of those S-DABO series compounds should be considered to design new potent compounds for anti-HIV-1. 展开更多
关键词 s-DABO derivatives correlation analysis stepwise regression analysis QsAR LUMO
下载PDF
Deficiency of platelet-derived growth factor receptor-α-positive cells in Hirschsprung's disease colon 被引量:2
17
作者 Anne-Marie O'Donnell David Coyle Prem Puri 《World Journal of Gastroenterology》 SCIE CAS 2016年第12期3335-3340,共6页
AIM: To investigate whether the expression of plateletderived growth factor receptor-α-positive(PDGFRα^+)-cells is altered in Hirschsprung's disease(HD).METHODS: HD tissue specimens(n = 10) were collected at the... AIM: To investigate whether the expression of plateletderived growth factor receptor-α-positive(PDGFRα^+)-cells is altered in Hirschsprung's disease(HD).METHODS: HD tissue specimens(n = 10) were collected at the time of pull-through surgery, while colonic control samples were obtained at the time of colostomy closure in patients with imperforate anus(n = 10). Immunolabelling of PDGFRα^+-cells was visualized using confocal microscopy to assess the distribution of these cells, while Western blot analysis was undertaken to quantify PDGFRα protein expression.RESULTS: Confocal microscopy revealed PDGFRα+-cells within the mucosa, myenteric plexus and smooth muscle in normal controls, with a marked reduction in PDGFRα^+-cells in the HD specimens. Western blotting revealed high levels of PDGFRα protein expression in normal controls, while there was a striking decrease in PDGFRα protein expression in the HD colon.CONCLUSION: These findings suggest that the altered distribution of PDGFRα^+-cells in both the aganglionic and ganglionic HD bowel may contribute to the motility dysfunction in HD. 展开更多
关键词 PLATELET-derivED growth factor receptor ALPHA Hirschsprung’s disease GAsTROINTEsTINAL MOTILITY Agang
下载PDF
CALCULUS ON CANTOR TRIADIC SET (I)-DERIVATIVE
18
作者 XI LIFENG 《Applied Mathematics(A Journal of Chinese Universities)》 SCIE CSCD 1997年第4期483-492,共10页
For real valued functions defined on Cantor triadic set, a derivative with corresponding formula of Newton Leibniz’s type is given. In particular, for the self similar functions and alternately jumping f... For real valued functions defined on Cantor triadic set, a derivative with corresponding formula of Newton Leibniz’s type is given. In particular, for the self similar functions and alternately jumping functions defined in this paper, their derivative and exceptional sets are studied accurately by using ergodic theory on Σ 2 and Duffin Schaeffer’s theorem concerning metric diophantine approximation. In addition, Haar basis of L 2(Σ 2) is constructed and Haar expansion of standard self similar function is given. 展开更多
关键词 FRACTAL derivative on Cantor set exceptional set ergodic theory DUFFIN schaeffer’ s theorem
下载PDF
New optically active poly(amide-imide)s derived from N,N'-(4,4-diphthaloyl)-bis-L-leucine and hydantoin derivatives:Synthesis and properties
19
作者 Khalil Faghihi 《Chinese Chemical Letters》 SCIE CAS CSCD 2009年第10期1153-1156,共4页
Six new optically active poly(amide-imide)s (5a-f) were synthesized through the direct polycondensation reaction of N,N′-(4,4′- diphthaloyl)-bis-L-leucine (3) with six hydantoin derivatives (4a-f). Tripben... Six new optically active poly(amide-imide)s (5a-f) were synthesized through the direct polycondensation reaction of N,N′-(4,4′- diphthaloyl)-bis-L-leucine (3) with six hydantoin derivatives (4a-f). Tripbenyl phosphite (TPP)/pyridine in the presence of calcium chloride (CaCl2) and N-methyl-2-pyrrolidone (NMP) were successfully applied for direct polycondensation. The polycondensation reactions produce a series of new poly(amide-imide)s (5a-f) in high yields, and inherent viscosity between 0.42 and 0,55 dL/g. The resulting poly(amide-imide)s (5a-f) were characterized by elemental analysis, viscosity measurements, thermal gravimetric analysis (TGA and DTG), solubility test and FT-IR spectroscopy. 展开更多
关键词 High performance polymers Poly(amide-imide)s Direct polycondensation Hydantoin derivatives
下载PDF
POLYMERIZATION OF N,N'-(PYROMELLITOYL)-BIS-L-LEUCINE DIACID CHLORIDE WITH HYDANTOIN DERIVATIVES BY MICROWAVE IRRADIATION
20
作者 Khalil Faghihi 《Chinese Journal of Polymer Science》 SCIE CAS CSCD 2004年第4期343-348,共6页
Facile and rapid polycondensation reactions of N,N'-(pyromellitoyl)-bis-L-leucine diacid chloride 1 with eight different derivatives of hydantoin compounds 2a-h were developed by using a domestic microwave oven in... Facile and rapid polycondensation reactions of N,N'-(pyromellitoyl)-bis-L-leucine diacid chloride 1 with eight different derivatives of hydantoin compounds 2a-h were developed by using a domestic microwave oven in the presence of a small amount of polar organic medium such as o-cresol. The polycondensation reactions proceeded rapidly, compared with the conventional solution polycondensation, and was completed within 7-10 min, producing a series of novel optically active poly(amide-imide)s 3a-h with high yield and inherent viscosity of 0.35-0.65 dL/g. All of the above polymers were fully characterized by FT-IR, elemental analyses, inherent viscosity (η inh ), solubility test and specific rotation. Some structural characterization and physical properties of these optically active poly(amide-imide)s are reported. 展开更多
关键词 Microwave-assisted rapid polycondensation Optically active polymers Poly(amide-imide)s Hydantoin derivatives N N'-(Pyromellitoyl)-bis-L-leucine diacid chloride
下载PDF
上一页 1 2 20 下一页 到第
使用帮助 返回顶部