SYNTHESIS OF NOVEL BI-FUNCTIONAL COPOLYMER BEARING STERICALLY HINDERED PHENOL AND HINDERED AMINE GROUPS VIA RING-OPENING METATHESIS POLYMERIZATION

Norbornene derivatives exo,endo-2-[2-(3,5-di-tert-butyl-4-hydroxyphenoxy)-acetoxy]methyl-5-norbornene(M1) and 3,3,5,5-tetramethyl-4-piperidinyl 5-norbornene-exo,endo-2-carboxylate(M2)were synthesized and polymerized by RuCl_2(=CHPh)(PCy_3)_2 to prepare a novel kind of bi-functional polymer bearing sterically hindered phenol(SHP)and hindered amine(HLAS)groups via ring-opening metathesis polymerization(ROMP).The resulting copolymers were characterized by gel permeation chromatography(GPC),~1H-NMR and differen...

On the Factors Hindering Chinese College Students＇ English Reading and Possible Strategies

Chinese college students reading in a foreign language seem to read with less understanding and at a considerably slower speed. The factors that hinder Chinese college students' English reading were analyzed at the lexical level, the syntactic level,and the discourse level. And then, several reading strategies were recommended to overcome such reading difficulties.

COPOLYMERIZATION OF PROPYLENE WITH HINDERED PIPERIDINE MONOMER OVER A HIGH ACTIVITY SUPPORTED ZIEGLER-NATTA CATALYST

Copolymerization of propylene and hindered piperidine monomers was carried out over a high activity supported Ziegler-Natta catalyst, using Al(C2H5)(3) as cocatalyst. Factors which affect the copolymerization were studied, The copolymers exhibited high light stability without adding extra light stabilizers. A self-stabilized polypropylene was prepared.

Sphingosine-1-phosphate hinders the osteogenic differentiation of dental pulp stem cells in association with AKT signaling pathways

Sphingosine-1-phosphate(S1P)is an important lipid mediator that regulates a diverse range of intracellular cell signaling pathways that are relevant to tissue engineering and regenerative medicine.However,the precise function of S1P in dental pulp stem cells(DPSCs)and its osteogenic differentiation remains unclear.We here investigated the function of S1P/S1P receptor(S1PR)-mediated cellular signaling in the osteogenic differentiation of DPSCs and clarified the fundamental signaling pathway.Our results showed that S1P-treated DPSCs exhibited a low rate of differentiation toward the osteogenic phenotype in association with a marked reduction in osteogenesis-related gene expression and AKT activation.Of note,both S1PR1/S1PR3 and S1PR2 agonists significantly downregulated the expression of osteogenic genes and suppressed AKT activation,resulting in an attenuated osteogenic capacity of DPSCs.Most importantly,an AKT activator completely abrogated the S1P-mediated downregulation of osteoblastic markers and partially prevented S1P-mediated attenuation effects during osteogenesis.Intriguingly,the pro-inflammatory TNF-αcytokine promoted the infiltration of macrophages toward DPSCs and induced S1P production in both DPSCs and macrophages.Our findings indicate that the elevation of S1P under inflammatory conditions suppresses the osteogenic capacity of the DPSCs responsible for regenerative endodontics.

SYNTHESIS AND LIGHTFASTNESS PROPERTIES OF DYES CONTAINING HINDERED PIPERIDINE RESIDUES AS INTERNAL STABILIZING GROUPS

The representative azo and anthraquinone dyes containing an insulated hindered piperidinegroup were synthesized.The effect of these pendent groups on lightfastness properties of the dyeswas studied,both in ethyl acetate solution and on cellulose acetate and polyester films.The differ-ent trend of fading rates of azo dyes and anthraquinone dyes in solution and on substrates suggestsdifferent fading mechanisms operating in each case.

EFFECTS OF MOLECULE AGGREGATION STATE OF HINDERED PHENOL ON DYNAMIC MECHANICAL PROPERTIES OF CHLORINATED POLYETHYLENE

Hindered phenol compound 3,9-bis{1,1-dimethyl-2[β-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]ethyl}- 2,4,8,10-tetraoxaspiro[5,5]-undecane (AO-80) is a polymorphous material with different physical structures. The initial AO- 80 is highly crystalline, whereas AO-80 obtained by cooling from its molten state is an amorphous material. Annealing treatment below the melting point of AO-80 results in structural development. The mixture of chlorinated polyethylene (CPE) and vitrified AO-80 particles exhibits a dramatic change in the dynamic mechanical properties during heat treatment at 130'C. This change can be attributed to the decomposition of the vitrified AO-80 particles and the hybridization of two constituents. The vitrified AO-80 particles can crystallize again in a CPE matrix by annealing at 100'C, but this crystal is different from that of the initial AO-80 in its microstructure. In addition, the incorporation of CPE chains caused a dramatic increase in the modulus. As a result, the AO-80 crystal particles that contain some CPE chains act as multifunctional cross- links and the CPE/AO-80 hybrid was found to be a new type of elastomer.

SYNTHESES OF HINDERED ALKYL PHOSPHONATES AND PHOSPHONIC & PHOSPHINIC ACIDS

A series of di-n-hexyl alkyl phosphonates with bulky substituent on phosphorus was synthesized by PTC P-alkylation using crown ether.Upon saponification of the resulting di-n-hexyl alkylphosphonates in the presence of crown ether or quaternary ammonium halide, corresponding mono-hexyl esters of alkyl phosphonic acids were prepared.Ultrasonic wave, as we found, can catalyze the reaction between dialkyl phosphite & metallic sodium and hydrolysis of dihexyl alkyl phosphonates.A series of di-t-alkyl phosphinic acids were synthesized by the reaction of Grignard reagent with PCl_3 followed by oxidation with 30% H_2O_2.It was found that the reaction between dibutyl phosphite and Grignard reagent of t-alkyl chloride is a new synthetic method for the preparation of mono-esters of highly hindered alkyl phosphonic acids.

Investigation on UV-curing Reprocessable Thermosets Bearing Hindered Urea Bonds and Their Composites with Modified Zinc Oxide Nanoparticles

In this study,a series of hindered urea bond(HUB)containing polyurethane-urea methacrylate prepolymers and a none HUB containing polyurethane methacrylate prepolymer were prepared using isobornyl methacrylate as the reactive diluent via one-pot procedure.The prepolymers were characterized fully by various techniques.Then,their thermosets were fabricated via UV curing in presence of a photo initiator,and their mechanical property and thermal behavior were investigated and compared.Different from the none HUB containing thermoset,the HUB containing thermosets(defined as PUT)could be recycled and reprocessed by hot press under relatively mild conditions with high recovery ratio of mechanical property.Furthermore,zinc oxide(ZnO)nanoparticles were modified with 3-(trimethoxysilyl)propyl methacrylate and the modified ZnO(defined as ZnO-TPM)was dispersed and polymerized into PUT matrix to prepare their nanocomposites.The influence of ZnO-TPM on the mechanical performance of the composites was evaluated,which indicated that the Young’s modulus and tensile strength increased gradually to the maximum values at ZnO-TPM content of 1 wt%and then decreased.The composites also displayed good reprocessability with improved recovery ratio compared to the pure PUT sample.In addition,the composite materials exhibited strong UV absorption capacity,implying their potential application in the circumstance where UV-shielding was required.

Pressure-Tuned Intrinsic Anomalous Hall Conductivity in Kagome Magnets RV_(6)Sn_(6)(R=Gd,Tb)

Exploration of exotic phenomena in magnetic topological systems is at the frontier of condensed matter physics,holding a significant promise for applications in topological spintronics.However,complex magnetic structures carrying nontrivial topological properties hinder its progresses.Here,we investigate the pressure effect on the novel topological kagome magnets GdV_(6)Sn_(6) and TbV_(6)Sn_(6) to dig out the interplay between magnetic Gd/Tb layers and nonmagnetic V-based kagome sublattice.The pressure-tuned magnetic transition temperature Tm in both the compounds exhibit a turning point at the critical pressure P_(c),accompanied with a sign reversal in anomalous Hall effect(AHE).The separation of intrinsic and extrinsic contributions using the Tian-Ye-Jin scaling model suggests that the intrinsic mechanism originating from the electronic Berry curvature holds the priority in the competition with extrinsic mechanism in AHE.The above-mentioned findings can be attributed to the combined effect of pressure-tuned band topology and magnetic interaction in segregated layers.Our results provide a practical route to design and manipulate the intrinsic AHE in magnetic topological materials.

组织绩效管理系统对技术创新的影响机制研究综述——基于技术创新类型的视角

技术创新对于组织的生存、实现竞争优势以及取得卓越的绩效都非常重要。在现实中,组织中的绩效管理系统被广泛应用于技术创新管理实践中,然而其实际应用效果差异很大。究其原因,学术文献中有关绩效管理系统与技术创新之间关系的研究尚未得到一致的结论。本文根据权变的观点,从技术创新的不同类型,以及技术创新类型与绩效管理系统设计相匹配的角度,系统回顾和分析有关管理控制系统和技术创新的文献研究,对过往研究矛盾的结果从新的角度给予解释,在此基础上揭示此领域未来的研究方向,并从匹配恰当性的角度为组织创新管理的实践提供借鉴。

用于水性车漆的受阻胺光稳定剂的合成及性能

设计、合成了一种受阻胺光稳定剂(HALS)TM-3。首先,三聚氯氰和N-丁基-2,2,6,6-四甲基-4-哌啶胺通过亲核取代反应合成了N-丁基-4,6-二氯-N-(2,2,6,6-四甲基-4-哌啶基)-1,3,5-三嗪-2-胺(中间体Ⅰ);中间体Ⅰ再与N,N-双(2,2,6,6-四甲基-4-哌啶基)-1,6-己二胺反应生成了N2,N2'-(己烷-1,6-二基)双[N4-丁基-6-氯-N2,N4-双(2,2,6,6-四甲基哌啶-4-基)-1,3,5-三嗪-2,4-二胺](中间体Ⅱ);最后,中间体Ⅱ水解生成目标化合物6,6'-{己烷-1,6-二基双[(2,2,6,6-四甲基哌啶-4-基)氮二基]}双{4-[丁基(2,2,6,6-四甲基哌啶-4-基)氨基]-1,3,5-三嗪-2-醇}(TM-3)。采用1HNMR、13CNMR、HRMS表征了TM-3的结构,通过UV-Vis、TGA考察了其性能,比较了TM-3和双(2,2,6,6-四甲基-4-哌啶基)癸二酸酯(HALS770)在汽车清漆涂料中的光稳定性。结果表明,TM-3在210 nm处具有强烈的UV-Vis吸收;热稳定性能良好,在400℃以前能保持热稳定,可以耐受较高的温度;TM-3在含水的有机溶剂中比HALS770具有更好的溶解性。加入TM-3的样品(样品4)在模拟紫外光照射800 h后色差为6.01,光泽损失率为4.6%;而加入HALS770的样品(样品5)色差达到6.72,光泽损失率为6.7%,说明TM-3的光稳定优于HALS770。

受阻胺光稳定剂与紫外吸收剂协同改进GPPS树脂抗紫外光老化性能研究

采用黄度指数仪、激光扫描共聚焦显微镜(CLSM)和透光率雾度测定仪等研究了2种紫外光吸收剂(UV-A、UV-B)与受阻胺光稳定剂(HALS)协同使用对通用级聚苯乙烯(GPPS)树脂抗紫外光老化性能的影响。结果表明:加入HALS,UV-A,UV-B均可有效抑制GPPS树脂因紫外光老化作用而发生降解。在紫外光环境下,紫外光吸收剂(UV-A,UV-B)对样品抗紫外老化性能的提升效果均优于HALS,其中,UV-A最优。HALS与2种紫外光吸收剂(UV-A,UV-B)复配时均表现出良好的抗紫外光老化协同作用。

头颈部恶性肿瘤放疗患者接受管饲的促进及障碍因素研究

目的了解头颈部恶性肿瘤放疗患者接受管饲的促进和障碍因素,为医护人员制订提高患者管饲接受度的干预措施提供参考。方法通过目的抽样纳入患者、家属及医务人员进行半结构化访谈,采用定向内容分析法结合健康信念模式进行资料提取与分析。结果共20名受访者,提取出3个促进因素(感知到未来症状严重、获知管饲的益处、获得提示因素)和4个障碍因素(感知到的威胁较小、感知到障碍、缺乏自我效能、缺乏相关知识)。结论未来医护人员应指导患者和家属树立正确的健康信念、加强相关知识培训,增强其自我效能,提高患者管饲意愿。

老年共病患者心理危机自我表露阻碍和促进因素的质性研究

目的 深入探究老年共病患者心理危机表露的阻碍和促进因素,为促进老年患者面临心理危机时的自我表露提供依据。方法 采用现象学研究方法,访谈14例老年共病患者。结果 阻碍因素包括个人因素(内向/隐忍型性格、担心给家人带来困扰、对生命状态的负性心理)和动机因素(消极反馈、认知缺乏、时间弱化),促进因素包括感知表露后益处、良好的支持系统、个人表达意愿强。结论 老年共病患者心理危机表露存在阻碍和促进因素,应通过让患者感知表露后益处、给予良好的支持系统、丰富多种表露途径、加强患者对心理危机的认知等措施来促进老年共病患者主动表露其心理危机。

基于自然与人文耦合视域的高寒生态功能区宜居性评价及阻滞因子诊断--以青海省为例

宜居性是自然生态环境和人文社会环境的有机统一体,厘清高寒生态功能区宜居性及其阻滞因子,是精准提升生态安全屏障内宜居水平并促进其人与自然和谐共生的重要前提。基于城乡宜居性评价基本范式、顾及高寒生态功能区人居系统的独特性,从自然与人文耦合视域构建由自然环境、居住环境、设施环境、社会环境4个维度、8个一级指标及24个二级指标组成的高寒生态功能区宜居性指标体系,以青海省45个县域单元为例定量评价其宜居性及阻滞因子,并探讨宜居性与生态重要性、社会经济发展状态的交互关系。结果显示:(1)青海省总体宜居水平偏低,并呈现由河湟谷地生态区、柴达木盆地生态区、环青海湖生态区、三江源生态区依次递减的地域分异;(2)宜居水平和生态重要性的空间耦合不协调,三江源生态区等生态重要区的宜居水平低,宜居水平与人口规模、经济发展均成正比;(3)青海省宜居性主要受到居住环境和社会环境的阻滞,生态地理分区层面,在自然因子的主要制约下,三江源生态区、环青海湖生态区、柴达木盆地生态区分别受设施、居住、社会环境的强约束;(4)针对不同生态地理分区宜居性特征提出未来人口引导及宜居性优化模式,即按宜居性及社会经济生态引力明确人口集聚型、疏散型和稳定型3种空间集疏类型,通过人口城镇化、就业移民、教育移民等跨区域移民及就近生态移民增强宜居性与人口分布的空间适配性,以三江源生态区等弱势区域以及饮水设施、道路设施、物流配送、网络通讯等基础设施阻滞因子为重点,提升高寒生态功能区人居系统的设施配置与供给能力。

学习压力源对全日制体育硕士研究生学习倦怠的影响机制

目的基于压力源二维结构理论,探讨挑战性压力源与阻碍性压力源这两种压力源和全日制体育硕士研究生学习倦怠的关系及其作用机制。方法采用挑战性和阻碍性压力源量表、学习倦怠量表、应对方式量表和心理弹性量表,对广东省地区415名全日制体育硕士研究生进行调查。结论1)挑战性学习压力源对学习倦怠无显著影响,而阻碍性学习压力源对学习倦怠具有显著正向影响。2)挑战性学习压力源通过积极应对方式的完全中介作用对学习倦怠有负向影响,阻碍性学习压力源通过消极应对方式的部分中介作用对学习倦怠有正向影响。3)心理弹性负向调节阻碍性学习压力源与学习倦怠的关系,相对于高心理弹性的学生,低心理弹性的学生其阻碍性学习压力源对学习倦怠的正向影响更强。本研究扩宽了压力源二维结构理论的应用范围,为高校对体育硕士研究生学习倦怠的干预提供参考借鉴。

Transformation of Commodity Poly(hydroxyether of bisphenol A)into Vitrimers via Post Crosslinking with Hindered Urea Bonds

In this contribution,we reported the preparation of vitrimers by using commodity thermoplastics via post crosslinking with hindered urea bonds(HUBs).First,three hindered urea diisocyanates(HUDIs)were synthesized via the reactions of N,N'-di-tert-butylethylenediamine,N,N'-diethylethylenediamine,and piperazine with isophorone diisocyanate(IPDI).Thereafter,these HUDIs were used as the crosslinking agents to crosslink poly(hydroxyether of bisphenol A)(PH),a commodity thermoplastics.Fourier transform infrared(FTIR)spectroscopy and dynamic mechanical thermal analyses(DMTA)indicated that the PH thermosets were successfully obtained.It was found that the thermosets displayed the behavior of vitrimers.The PH thermosets can be reprocessed at elevated temperature without using catalyst and the mechanical strengths of vitrimers were recovered as high as 95%.The reprocessing properties are attributable to dynamic exchange reaction of hindered urea bonds,contingent on types of hindered urea bonds.