卤代芳香族羧酸与含氮配体合成镧系配合物的结构、热化学和荧光性质

采用室温溶液挥发法合成了五种结构新颖的镧系配合物,其结构通式为[Ln(2,4-DFBA)3(phen)]2(Ln=Sm 1,Eu2,Er 3,2,4-DFBA为2,4二氟苯甲酸的简写,phen为1,10-菲啰啉的简写),[Ln(2-Cl-6-FBA)2(terpy)(NO3)(H2O)]2(Ln=Tb4,Dy 5,2-Cl-6-FBA为2-氯-6-氟苯甲酸的简写,terpy为2,2’:6’2’’-三联吡啶的简写)。五个配合物可以分为两个系列,使用不同的镧系离子作为中心离子。通过X射线单晶分析,5种配合物均属于单斜晶系,空间群为P21/n。配合物1,2和配合物3虽然具有相同的分子通式,但配位方式明显不同,形成了前者为9配位的松饼型,后者是8配位的双帽三棱柱几何构型。二维面状超分子结构的形成方式也明显不同,区别在于配合物1和2通过微弱的π-π堆积作用形成。配合物4和5是同构的,结构中引入了硝酸根离子较为有趣,通过C―H···F氢键和π-π堆积作用形成二维面状超分子结构。在299.25–1073.15K温度下对配合物1–5通过热重-微分热重-差示扫描量热/红外光谱(TG-DTG-DSC/FTIR)联用技术进行热分解机理的研究。测定了配合物1,2,4,5的固体荧光,特征过渡峰位于^(4)G_(5/2)→^(6)H_(5/2),^(4)G_(5/2)→^(6)H_(7/2),^(4)G_(5/2)→^(6)H_(9/2)(1),^(5)D_(0)→^(7)F_(0),^(5)D_(0)→^(7)F_(1),^(5)D_(0)→^(7)F_(2),^(5)D_(0)→^(7)F_(3),^(5)D_(0)→^(7)F_(4)(2),^(5)D_(4)→^(7)F_(6),^(5)D_(4)→^(7)F_(5),^(5)D_(4)→^(7)F_(4),^(5)D_(4)→^(7)F_(3)(4),和^(4)F_(9/2)→^(6)H_(15/2),^(4)F_(9/2)→^(6)H_(13/2)(5),均表现出镧系离子的特征过渡峰。此外,还对配合物2和4进行了荧光寿命的研究,其荧光衰减时间分别为1.288和0.648 ms。

非肥胖性糖尿病小鼠干眼模型的初步建立

目的:初步建立非肥胖性糖尿病(NOD)小鼠蒸发过强型干眼模型,通过研究小鼠眼表组织病理变化,初步探讨其作为糖尿病性干眼模型的可行性。方法:选取40只雌性NOD小鼠,NOD小鼠自发糖尿病为实验组,同时选取未自发糖尿病的NOD小鼠作为正常对照组。实验组NOD小鼠置于40%以下湿度环境,每天皮下注射0.5mg/0.2mL氢溴酸菪胺,并置于可控干燥箱中,每天通风12h,制作蒸发过强型干眼模型。在造模后的第1、7、10、14d采用酚红棉线实验测量泪液分泌量,PAS染色检查结膜杯状细胞形态和数目;在造模后的第10d,进行角膜组织苏木精染色检测角膜上皮变化情况。结果:实验组NOD小鼠泪液分泌量随造模时间而逐渐降低,正常对照组未有明显变化。实验组的结膜杯状细胞体积变大,在造模后的第1d,杯状细胞密度较正常对照组减少(P=0.008),从造模后第7d开始,随时间延长,实验组杯状细胞数量逐渐减少,且较同一时间点正常对照组显著减少(均P<0.001)。此外,观察两组第10d的角膜上皮情况,实验组NOD小鼠角膜上皮层变薄,部分角膜上皮细胞变性、基底细胞水肿。结论:初步建立了NOD小鼠干眼模型,其眼表变化与临床上干眼症表现类似。

2,4,6-三甲基苯甲酸与5,5'-二甲基-2,2'-联吡啶构筑的系列镧系超分子配合物的晶体结构、热分解机理和性能

利用2,4,6-三甲基苯甲酸和5,5ʹ-二甲基-2,2ʹ-联吡啶配体在溶剂热的条件下成功合成出系列三元稀土超分子配合物[Ln(2,4,6-TMBA)3(5,5ʹ-DM-2,2ʹ-bipy)]2(Ln=Pr 1,Nd 2,Sm 3,Eu 4,Gd 5,Dy 6),并对其进行了单晶X-射线衍射、元素分析、热重分析等一系列表征。研究结果表明配合物1-5同构,中心离子的配位数为9,配合物通过π–π堆积作用形成一维、二维的超分子结构。配合物6具有不同的结构,中心镝离子的配位数为8,分子间通过π–π堆积作用和C-H…O氢键形成一维、二维的超分子结构。利用TG/FTIR技术研究了配合物的热稳定性和热分解机理,荧光光谱表明配合物4可以发射出Eu^(3+)离子的特征荧光,同时对配合物6的磁性进行了初步探究。

石墨烯的分散性对石墨烯/尼龙6性能的影响

采用水辅熔融双螺杆挤出法制备了不同分散程度的石墨烯/PA6复合材料。通过光学显微镜和X射线衍射分析了石墨烯在复合材料中的分散性,通过热重分析仪、差示扫描量热仪和力学性能等测试表征了石墨烯的分散性对复合材料的热稳定性、结晶性能及力学性能的影响。结果表明,调控挤出工艺可显著改善石墨烯在PA6基体中的分散性。统计结果显示,复合材料中石墨烯的平均尺寸从5.82μm的团聚态,改变为平均粒径1.75μm的相对分散状态。并且,石墨烯在基体中良好的分散性使复合材料具有更高的热稳定性和力学性能,其中,复合材料的初始热降解温度提高了22℃,拉伸强度提高了19.2%。

热分析动力学研究方法的新进展

"非等温动力学"作为热分析动力学研究的核心,已经被广泛应用于化学、化工、冶金、地质、药物和环保等重要领域。热分析动力学研究的主要任务是确定机理函数、活化能和指前因子等动力学参数。在众多的热分析动力学研究方法中,"等转化率法"由于其可以在不涉及动力学模式函数的前提下,获得较为可靠的活化能值,因此被国际热分析与量热学协会(ICTAC)推荐使用。本文简要介绍了近十年来提出的热分析动力学研究方法,特别是等转化率方法的研究进展情况,评述了各种方法的特点与局限。同时,展望了热分析动力学研究方法未来的发展趋势。

Effect of c-fos antisense probe on prostaglandin E_2-induced upregulation of vascular endothelial growth factor mRNA in human liver cancer cells

AIM: To examine the effect of prostaglandin E2 (PGE2) on the expression of vascular endothelial growth factor (VEGF) mRNA in the human hepatocellular carcinoma (HCC) HepG2 cells and the possible involvement of c-fos protein in this process.METHODS: Human HCC HepG2 cells were divided into three groups treated respectively with PGE2, a combination of PGE2 and c-fos antisense oligodeoxynucleotide (ASO),and PGE2 plus c-fos sense oligodeoxynudeotide (SO). The expression of VEGF mRNA in HepG2 cells after different treatments was detected by reverse transcriptase-polymerase chain reaction (RT-PCR). The relative expression level of VEGF mRNA in HepG2 cells in each group was measured.RESULTS: Administration of PGE2 resulted in an increased expression of c-fosand VEGF mRNA in HepG2 cells. The relative expression level of c-fos mRNA reached the peak at 3 h (68.4±4.7%) after PGE2 treatment, which was significantly higher than that at 0 h (20.6±1.7%, P＜0.01).Whereas, the highest expression level of VEGF mRNA was observed at 6 h (100.5±6.1%) after PGE2 treatment, which was significantly higher than that at 0 h (33.2±2.4%,P＜0.01). C-fos ASO significantly reduced PGE2-induced VEGF mRNA expression in HepG2 cells.CONCLUSION: PGE2 increases the expression and secretion of VEGF in HCC cells by activating the transcription factor c-fos, promotes the angiogenesis of HCC and plays an important role in the pathogenesis of liver cancer.

Dual Photo/Thermo-Responsive Polypeptoids

A series of polypeptoids with dual photo/thermo-responsiveness were prepared by incorporating both azobenzene(Azo)group and oligo(ethylene glycol)(OEG)segment into the side chains.Firstly,the N-substituted-N-carboxyanhydride(NNCA)monomers with different Azo and OEG groups were synthesized,and then a single NNCA ring-openning polymerization was performed to afford dual-responsive polypeptoids without any post-polymerization modification.The ultra-violet/visible(UV/Vis)photo-responsive behaviors of the polypeptoids were achieved by cis-trans photoisomerization of the Azo group and confirmed by both ^(1)H-NMR and UV/Vis spectroscopy.The thermo-responsive behaviors were realized by both OEG segment and Azo group and confirmed by UV/Vis spectroscopy and dynamic light scattering.This work demonstrated the synthetic pathway for dual responsive polypeptoids using NNCA monomers with two responsive groups and revealed the potential of polypeptoids as smart materials that could respond to different environmental stimuli.

Multi-Polymerization:From Simple to Complex

Multi-polymerization in which different polymerization mechanisms are performed together serves as an essential synthetic methodology for the construction of polymers with specific architectures,constitutions,and properties.Compared to single mechanism polymerization,the scope of multi-polymerization is significantly broadened by both the available synthetic methods and the synthesized polymeric materials.In this mini-review,multi-polymerizations are categorized into three major types based on the logical relationship between different mechanisms:sequential/tandem polymerization,orthogonal/concurrent polymerization,and hybrid polymerization.Each type of multi-polymerization is briefly introduced and summarized.This mini-review also discussed the importance of mutual influence in multi-polymerization and the potential research interests in this field.

2,5-二氯苯甲酸与5,5′-二甲基-2,2′-联吡啶稀土钬配合物的晶体结构、热分解反应动力学及热力学

本文通过常规溶剂挥发法,合成了钬的三元配合物:[Ho(2,5-DClBA)3(5,5′-DM-2,2′-bipy)]2(2,5-DClBA=2,5-二氯苯甲酸根;5,5′-DM-2,2′-bipy=5,5′-二甲基-2,2′-联吡啶)。通过EDTA络合滴定分析、元素分析、红外光谱以及X射线粉末衍射等手段对配合物进行了表征,利用X射线单晶衍射仪测定了钬配合物的单晶结构。晶体结构分析表明,该晶体是一个双核分子,属于三斜晶系, Pī空间群。每个双核分子包含两个Ho(Ⅲ)离子、6个2,5-二氯苯甲酸根配体和两个5,5′-二甲基-2,2′-联吡啶配体。相邻的双核单元通过C–H···Cl氢键以及Cl-π作用组装成一维和二维超分子结构。利用TG-DTG/FTIR技术研究了钬配合物的热分解机理。用非线性等转化率法得到钬配合物第二步分解反应的活化能E随转化率a的变化关系,结果表明该步是一个简单反应,因此,进一步采用改进的双等双步法来确定钬配合物第二步分解反应的机理函数。通过计算得到了钬配合物的动力学参数(活化能E和指前因子A)和热力学参数(ΔH≠、ΔG≠和ΔS≠)。利用差示扫描量热(DSC)技术对钬配合物的摩尔热容值进行了测定。将所得的平均摩尔热容值与折合温度利用最小二乘法进行拟合得到了多项式方程。将多项式方程结合热力学方程进行计算得到了配合物的舒平摩尔热容值以及焓变、熵变等热力学函数值。

Effect of a combined microwave-assisted drying and air drying on improving active nutraceutical compounds,flavor quality,and antioxidant properties of Camellia sinensis L.(cv.Longjing 43)flowers

Drying tea flowers into a high-quality product is important to its commodity value.In the present work,a combination of microwave-assisted drying and air drying(MAD-AD)was applied in the processing of fresh tea flowers and its effects on flavor quality,active nutraceutical compounds,and antioxidant capacities were studied.The results showed that compared to air drying and freeze drying tea flowers,the MAD-AD tea flowers had higher amounts of active compounds such as catechins,flavonol glycosides,and triterpenoid saponins,and possessed high antioxidant activities.Moreover,this drying method improved the tea flowers'color and preserved a more floral fragrance.This combined method could be of interest as an industrial method for drying tea flowers with the benefit of reduced processing time,more reserved active compounds and high quality of products.

Banking deregulation and corporate tax avoidance

We investigate whether tax avoidance substitutes for external financing. We exploit interstate banking deregulation as a quasi-external shock to examine whether firms engage in less tax avoidance after banking deregulation, because of cheaper and easier access to credit from banks. We find no empirical evidence to support this substitutive relation, even for firms with higher financial constraints or firms with higher external financing dependence.

Evaluation of channel-like porous-structured titanium in mechanical properties and osseointegration

The porous titanium with a channel-like pore structure fabricated by infiltration casting followed by selectively dissolving the precursor woven three dimensional(3D)structure technique was comprehensively investigated by means of mechanical tests,in vitro and in vivo evaluation.Such porous structure exhibited superiority in compressive,tensile strength and osseointegration.At 40%porosity,the average compressive and tensile strength reached about 145MPa and 85 MPa,which was superior to that of other porous titanium,e.g.,Selective Laser Melting or powder sintered ones,and was comparable to that of the human cortical bone.Without any bioactive surface treatment,this porous titanium exhibited good cell adhesion,rapid cell proliferation and excellent osseointegration.Based on the study,the 0.4mm pore size resulted in the most rapid cell proliferation and the maximal BV/TV ratio and trabecular bone number of the new bone that ingrew into the porous titanium.To balance the excellent osseointegration and adequate mechanical properties,the optimal structural parameters were 0.4mmpore size with 40%porosity.This porous titanium is very promising for orthopedic applications where compressive and tensile load-bearing is extremely important.

Crystal structures, antibacterial activity and thermal decomposition kinetics of lanthanide complexes with 4-chloro-2-methoxybenzoic acid and 1,10-phenanthroline

A series of lanthanide complexes [Ln(4-Cl-2-MOBA)3phen]2(Ln=Sm(1), Nd(2), Ho(3), Eu(4), Dy(5), and Tb(6); 4-Cl-2-MOBA=4-chloro-2-methoxybenzoate, phen=1,10-phenanthroline) were synthesized and characterized. The single-crystal X-ray diffraction demonstrates that 1–3 are isomorphous, which present dimeric structures with four 4-Cl-2-MOBA anions function as bridging ligands. Complexes 1 and 4–6 display their characteristic luminescence emission bands of central Ln3?ions. The heat capacities, the thermodynamic functions and the thermogravimetry–Fourier transform infrared spectra of gaseous products of complexes 1–6 were investigated.Their non-isothermal kinetics of the second decomposition stage was studied by the integral isoconversional non-linear method and Stark method. Furthermore, 1–6 exhibited excellent antibacterial activity against Candida albicans,Escherichia coli and Staphylococcus aureu.

A Novel mRNA Signature Related to Immunity to Predict Survival and Immunotherapy Response in Hepatocellular Carcinoma

Background and Aims:Hepatocellular carcinoma(HCC)is the most common primary liver cancer and the incidence and mortality rates are increasing.Given the limited treatments of HCC and promising application of immunotherapy for cancer,we aimed to identify an immune-related prognostic signature that can predict overall survival(OS)rates and immunotherapy response in HCC.Methods:The initial signature development was conducted using a training dataset from the Cancer Genome Atlas followed by independent internal and external validations from that resource and the Gene Expression Omnibus.A signature based nomogram was generated using multivariate Cox regression analysis.The associations of signature score with tumor immune phenotype and response to immunotherapy were analyzed using single-sample gene set enrichment analysis and tumor immune dysfunction and exclusion algorithm.A cohort from Zhongshan Hospital was employed to verify the pre dictive robustness of the signature regarding prognostic risk and immunotherapy response.Results:The prognostic signature,IGS_(HCC),consisting of 22 immune-related genes,had independent prognostic ability,with training and validation cohorts.Also,IGS_(HCC)stratified HCC patients with different outcomes in subgroups.The prognostic accuracy of IGS_(HCC)was better than three reported prognostic signatures.The IGS_(HCC)-based nomogram had high accuracy and significant clinical benefits in predicting 3-and 5-year OS.IGS_(HCC)reflected distinct immunosuppressive phenotypes in low-and high-score groups.Patients with low IGS_(HCC)scores were more likely than those with high scores to benefit from immunotherapy.Conclusions:IGS_(HCC)predicted HCC prognosis and response to immunotherapy,and contributed to individualized clinical management.

The predictive value of chromosome 8p deletion for metastasis of hepatocellular carcinoma:a summary of works in 10 years

Hepatocellular carcinoma(HCC)represents an extremely poor prognostic cancer,which is mainly due to the high frequency of metastasis/recurrence after surgical operation.Exploring the molecular mechanisms involved in HCC metastasis could be helpful in the pre-diction and early diagnosis of HCC recurrence and could also provide new therapeutic targets for HCC metastasis.In the recent decade,we analyzed the genomic aberrations of the clinical specimens,as well as the metastatic models and cell lines of human HCC to identify the genetic mar-kers related to HCC metastasis and to verify their clinical values in the prediction and control of metastasis of HCC.Using the comparative genomic hybridization(CGH)technique,we compared the differences of chromosomal aberrations between primary HCC tumors and their matched metastatic lesions,and found that chromosome 8p deletions might contribute to HCC metastasis.This novel finding was further confirmed by comparison between nude mice models of HCC with different meta-static potentials.By the more sensitive genome-wide microsatellite analysis,8p deletion was defined to 8p23.3 and 8p11.2,which are two likely regions harboring meta-stasis-related genes of HCC.Using‘8p-specific’microar-rays,two novel metastatic suppressors(HTPAP and MRSA)were identified,and were proven to suppress in vitro invasion and in vivo metastasis of HCC.Clinical studies indicate that 8p deletion detected in HCC or cir-culating plasma DNA of patients is a useful predictor for metastatic recurrence and prognosis,even for patients with early stage HCC.These novel findings are regarded as important advances in the study of the molecular mechanisms of HCC metastasis,which provide not only a holistic view on the molecular cytogenetic bases of HCC metastasis,but also candidate regions for further study to identify metastatic suppressor genes.

Advancing from unimechanism polymerization to multimechanism polymerization: binary polymerization

Polymerizations with multiple mechanisms performed simultaneously are promising but very challenging. As the key limitation,the complicated mutual influence between different mechanisms can be hardly defined and measured. Herein we establish a universal framework for the assessment of mutual influence between different mechanisms using binary polymerization for demonstration. The kinetics and thermodynamics of polymerization with two mechanisms are compared with the corresponding homopolymerization and the difference is expressed by a hybrid function. The hybrid function is composed of a hybrid parameter that describes the extent of mutual influence and a function that describes necessary conditions for mutual influence to occur. The extent of mutual influence can be calculated using kinetic and thermodynamic data without details of reaction mechanisms, for the first time providing a straightforward method to assess the mutual influence between different polymerization mechanisms.We envision that the method has potential in more complex systems with multiple mechanisms/monomers with mutual influence.