右美托咪定复合全身麻醉在老年高血压肺癌患者胸腔镜根治术中的效果分析

目的探讨右美托咪定复合全身麻醉在老年高血压肺癌患者胸腔镜根治术中的应用效果。方法选取2016年7月—2019年2月在徐州市中心医院行胸腔镜根治术的老年高血压肺癌患者96例作为研究对象,采用随机数字表法分为实验组与对照组,每组48例。在麻醉诱导前30 min(T_(1)),实验组静脉注射右美托咪定,对照组给予等体积的生理盐水。比较T_(1)、麻醉诱导时(T_(2))、气管插管前(T_(3))、插管后即刻(T_(4))及手术30 min(T_(5))的心率(HR)、收缩压(SBP)及舒张压(DBP),并比较疼痛视觉模拟评分(VAS)、舒适度评分(BCS)和术后48 h内镇痛泵按压次数、使用其他镇痛药物率及药物不良反应。结果实验组与对照组T_(1)、T_(2)、T_(3)、T_(4)、T_(5)时的HR、SBP及DBP比较,在不同时间、不同组间及变化趋势上有差异(P <0.05)。对照组T_(1)、T_(2)及T_(4)的HR、SBP及DBP比较有差异(P <0.05)。实验组与对照组术前2 h及术后2 h、6 h、12 h、24 h、48 h的VAS评分和BCS评分比较,在不同时间、不同组间及变化趋势上有差异(P <0.05)。实验组术后48 h内镇痛泵按压次数少于对照组(P <0.05),且曲马多使用率低于对照组(P <0.05);两组药物不良反应发生率比较,差异无统计学意义(P>0.05)。结论对行胸腔镜根治术的老年高血压肺癌患者采用右美托咪定复合全身麻醉,可维持插管及术中的血流动力学稳定,减轻术后早期疼痛,减少疼痛药物的使用,提高患者舒适度,且具有一定的安全性。

Granulocyte-colony stimulating factor therapy improves survival in patients with hepatitis B virus-associated acuteon-chronic liver failure

AIM:To evaluate the safety and efficacy of granulocyte-colony stimulating factor(G-CSF) therapy in patients with hepatitis B virus(HBV)-associated acuteon-chronic liver failure(ACLF).METHODS:Fifty-five patients with HBV-associated ACLF were randomized into two groups:the treatment group and the control group.Twenty-seven patients in the treatment group received G-CSF(5 μg/kg per day,six doses) treatment plus standard therapy,and 28 patients in the control group received standard therapy only.The peripheral CD34 + cell count was measured consecutively by flow cytometry.Circulating white blood cell count,biochemical parameters,and other clinical data of these patients were recorded and analyzed.All patients were followed up for a period of 3 mo to evaluate the changes in liver function and survival rate.RESULTS:The peripheral neutrophil and CD34 + cell counts in the G-CSF group increased on day 3 from the onset of therapy,continued to rise on day 7,and remained elevated on day 15 compared to those of the control group.Child-Turcotte-Pugh score of patients in the treatment group was improved on day 30 from the onset of G-CSF therapy,compared to that in the controls(P = 0.041).Model for End-Stage of Liver Disease score of patients in the treatment group was improved on day 7(P = 0.004) and remained high on day 30 from the onset of G-CSF therapy(P < 0.001) compared to that in controls.After 3 mo of follow-up observation,the survival rate in the treatment group(48.1%) was significantly higher than that in the control group(21.4%)(P = 0.0181).CONCLUSION:G-CSF therapy promoted CD34 + cell mobilization in patients with HBV-associated ACLF,and improved the liver function and the survival rate of these patients.

Let-7a gene knockdown protects against cerebral ischemia/reperfusion injury

The micro RNA（mi RNA） let-7 was one of the first mi RNAs to be discovered, and is highly conserved and widely expressed among species. let-7 expression increases in brain tissue after cerebral ischemia/reperfusion injury; however, no studies have reported let-7 effects on nerve injury after cerebral ischemia/reperfusion injury. To investigate the effects of let-7 gene knockdown on cerebral ischemia/reperfusion injury, we established a rat model of cerebral ischemia/reperfusion injury. Quantitative reverse transcription-polymerase chain reaction demonstrated that 12 hours after cerebral ischemia/reperfusion injury, let-7 expression was up-regulated, peaked at 24 hours, and was still higher than that in control rats after 72 hours. Let-7 gene knockdown in rats suppressed microglial activation and inflammatory factor release, reduced neuronal apoptosis and infarct volume in brain tissue after cerebral ischemia/reperfusion injury. Western blot assays and luciferase assays revealed that mitogen-activated protein kinase phosphatase-1（MKP1） is a direct target of let-7. Let-7 enhanced phosphorylated p38 mitogen-activated protein kinase（MAPK） and c-Jun N-terminal kinase（JNK） expression by down-regulating MKP1. These findings suggest that knockdown of let-7 inhibited the activation of p38 MAPK and JNK signaling pathways by up-regulating MKP1 expression, reduced apoptosis and the inflammatory reaction, and exerted a neuroprotective effect following cerebral ischemia/reperfusion injury.

Neuroprotective effects of SMAds in a rat model of cerebral ischemia/reperfusion

Previous studies have shown that up-regulation of transforming growth factor β1 results in neuroprotective effects. However, the role of the transforming growth factor β1 downstream molecule, SMAD2/3, following ischemia/reperfusion remains unclear. Here, we investigated the neuroprotective effects of SMAD2/3 by analyzing the relationships between SMAD2/3 expression and cell apoptosis and inflammation in the brain of a rat model of cerebral ischemia/reperfusion. Levels of SMAD2/3 mRNA were up-regulated in the ischemic penumbra 6 hours after cerebral ischemia/reperfusion, reached a peak after 72 hours and were then decreased at 7 days. Phos- phorylated SMAD2/3 protein levels at the aforementioned time points were consistent with the mRNA levels. Over-expression of SMAD3 in the brains of the ischemia/reperfusion model rats via delivery of an adeno-associated virus containing the SMAD3 gene could reduce tumor ne- crosis factor-a and interleukin-lβ mRNA levels, down-regulate expression of the pro-apoptotic gene, capase-3, and up-regulate expression of the anti-apoptotic protein, Bcl-2. The SMAD3 protein level was negatively correlated with cell apoptosis. These findings indicate that SMAD3 exhibits neuroprotective effects on the brain after ischemia/reperfusion through anti-inflamma- tory and anti-apoptotic pathways.

Accessory Breast Cancer Occurring Concurrently with Bilateral Primary Invasive Breast Carcinomas:A Report of Two Cases and Literature Review

The development of accessory breast tissue,which is found anywhere along the milk line,is attributed to the failure of milk line remnants to regress during embryogenesis.Primary tumors may arise from any ectopic breast tissue.Accessory breast cancer occurring concurrently with primary invasive breast cancer is extremely rare.Two such cases were reported in this article.One was a 43-year-old Chinese female who exhibited bilateral breast cancer(invasive ductal carcinoma,not otherwise specified,IDC-NOS) and an accessory breast carcinoma(IDC-NOS) incidentally identified in her left axilla.The ectopic breast tissue in her right axilla presented with adenosis.The patient was surgically treated,followed by postoperative docetaxel epirubicin(TE) chemotherapy.The second case was a 53-year-old Chinese female with bilateral breast cancer(apocrine carcinoma) accompanied by an accessory breast carcinoma(IDC-NOS) in her right axilla that was also incidentally identified.The patient was surgically treated after three doses of cyclophosphamide epirubicin docetaxel(CET) neoadjuvant chemotherapy,followed by adjuvant chemotherapy of the same regimen.

Loss of micro RNA-124 expression in neurons in the peri-lesion area in mice with spinal cord injury

Micro RNA-124（mi R-124） is abundantly expressed in neurons in the mammalian central nervous system, and plays critical roles in the regulation of gene expression during embryonic neurogenesis and postnatal neural differentiation. However, the expression profile of mi R-124 after spinal cord injury and the underlying regulatory mechanisms are not well understood. In the present study, we examined the expression of mi R-124 in mouse brain and spinal cord after spinal cord injury using in situ hybridization. Furthermore, the expression of mi R-124 was examined with quantitative RT-PCR at 1, 3 and 7 days after spinal cord injury. The mi R-124 expression in neurons at the site of injury was evaluated by in situ hybridization combined with Neu N immunohistochemical staining. The mi R-124 was mainly expressed in neurons throughout the brain and spinal cord. The expression of mi R-124 in neurons significantly decreased within 7 days after spinal cord injury. Some of the neurons in the peri-lesion area were Neu N＋/mi R-124-. Moreover, the neurons distal to the peri-lesion site were Neu N＋/mi R-124＋. These findings indicate that mi R-124 expression in neurons is reduced after spinal cord injury, and may reflect the severity of spinal cord injury.

Cortactin Overexpression Correlates with Poor Prognosis in Hepatocellular Carcinoma

Objective： To investigate cortactin expression in hepatocellular carcinoma （HCC） and explore its significance in the prognosis of HCC patients. Methods： Immunohistochemistry was performed for paraffin samples of 119 pairs of HCC tissues （HCCs） and paratumorous liver tissues （PTLTs） to evaluate cortactin expression. The cortactin expression difference in HCCs and PTLTs were analyzed by the McNemar＇s test. The relationship of cortactin expressions in HCCs and clinicopathologic factors was analyzed with Mann-Whitney U test. The Kaplan-Meier method and log-rank test were employed to compare the overall survival between Cortactin negative expression group, weak expression group and strong expression group. Expression of cortactin was further determined in 19 pairs of fresh HCCs and PTLTs specimens with Western blotting. Results： Cortactin expression rate was significantly higher in HCCs （53/119, 44.5%） than that in PTLTs （2/119, 1.7%） （P〈0.001）. The upregulated cortactin expression in HCCs was significantly correlated to absence of capsule formation （P=0.012）, vascular invasion （P=0.037） and high Edmondson-Steiner grade （P=0.020）, and predicted shorter overall survival. Western blotting demonstrated that cortactin expression was upregulated in 9 out of 19 HCCs （47.4%） compared to corresponding PTLTs. Conclusion： Cortactin expression is upregulated in HCC and is related to shorter overall survival of patients, suggesting that cortactin might play roles in the metastasis of HCC and predict a poor prognosis of HCC patients.

Reducing host aldose reductase activity promotes neuronal differentiation of transplanted neural stem cells at spinal cord injury sites and facilitates locomotion recovery

Neural stem cell(NSC)transplantation is a promising strategy for replacing lost neurons following spinal cord injury.However,the survival and differentiation of transplanted NSCs is limited,possibly owing to the neurotoxic inflammatory microenvironment.Because of the important role of glucose metabolism in M1/M2 polarization of microglia/macrophages,we hypothesized that altering the phenotype of microglia/macrophages by regulating the activity of aldose reductase(AR),a key enzyme in the polyol pathway of glucose metabolism,would provide a more beneficial microenvironment for NSC survival and differentiation.Here,we reveal that inhibition of host AR promoted the polarization of microglia/macrophages toward the M2 phenotype in lesioned spinal cord injuries.M2 macrophages promoted the differentiation of NSCs into neurons in vitro.Transplantation of NSCs into injured spinal cords either deficient in AR or treated with the AR inhibitor sorbinil promoted the survival and neuronal differentiation of NSCs at the injured spinal cord site and contributed to locomotor functional recovery.Our findings suggest that inhibition of host AR activity is beneficial in enhancing the survival and neuronal differentiation of transplanted NSCs and shows potential as a treatment of spinal cord injury.

Orthographic Processing of Developmental Dyslexic Children in China: Evidence from an Event-Related Potential Study

Objective:This study aimed to explore the orthographic processing of simplified Chinese characters in developmental dyslexic children in Kashgar,Xinjiang,China,and provide a theoretical basis for intervention strategies for developmental dyslexia in Chinese.Methods:Using event-related potential(ERP)measures,18 developmental dyslexic children and 23 typically developing children performed a character decision task with three types of stimuli:real characters(RCs),pseudocharacters(PCs),and noncharacters(NCs).Results:Behavioral results showed that the control children displayed a faster and higher accurate performance than the dyslexic children across PCs and NCs.ERP data revealed that the RCs and PCs elicited a stronger P200 than the NCs.Compared with the RCs and NCs,children in the control group showed more N400 negatives for PCs.It is worth mentioning that dyslexic children did not show any difference on N400,which reflected the insufficient orthographic processing of dyslexic children in China.Conclusion:These results show that Chinese dyslexic children had orthographic processing defects.

Comparative Study on“Long-Dan”,“Qin-Jiao”and Their Adulterants by HPLC Analysis

“Long-Dan”and“Qin-Jiao”are two important TCM herbs since ancient times in China.In the Chinese Pharmacopoeia,the dried roots and rhizomes of four species from the genus Gentiana,e.g.Gentiana manshurica,G.scabra,G.triflora and G.rigescens,are recorded under the name of Gentianae Radix et Rhizoma(“Long-Dan”in Chinese),while the other four species from the same genus including G.macrophylla,G.crassicaulis,G.straminea and G.duhurica are recorded and used as the raw materials of Gentianae Macrophyllae Radix(“Qin-Jiao”in Chinese).On the basis of the establishment of a validated HPLC–UV method for quantifying simultaneously,five iridoid glycosides,e.g.loganic acid(1),swertiamarinin(2),gentiopicroside(3),sweroside(4)and 20-(o,m-dihydroxybenzyl)sweroside(5)have been used successfully as chemical markers for the comparison of the species used as“Long-Dan”,“Qin-Jiao”and their adulterants in the present study.The results suggested that four iridoid glycosides 1–4 commonly existed in both“Long-Dan”and“Qin-Jiao”,while 20-(o,m-dihydroxybenzyl)sweroside(5)also existed as one of the major components in“Dian-Long-Dan”species.Moreover,the contents of compounds 1–5 were various in different“LongDan”and“Qin-Jiao”species.Herein,we profiled and compared three“Long-Dan”species,four“Qin-Jiao”species and five adulterants by applying multivariate statistical techniques to their HPLC data sets to establish the differences and/or similarities.

Application of adipose-derived stem cells in treatment of neurodegenerative diseases:A review

Neurodegenerative diseases are a class of progressive degenerative diseases that mainly include neuronal function decline and loss,such as Alzheimer's disease(AD);Cerebral troke;Parkinson's disease(PD);etc.These diseases are difficult to cure and seriously affect people's quality of life.Adipose derived stem cells(ADSCs)are derived from mesenchymal stem cells isolated and purified from adipose tissue.They have the characteristics of multidirectional differentiation and are widely used in the treatment of neurodegenerative diseases.Therefore,the use of ADSCs to treat this type of disease has potential application value.This article discusses the role of ADSCs in neurodegenerative diseases and their regeneration characteristics,and discusses the current clinical applications and future challenges of ADSCs,in order to provide references for the clinical application of ADSCs.

Advance of glial cells in Alzheimer's disease

Alzheimer's disease(AD)has an unknown pathogenesis,which is one of the key factors leading to the death of the elderly.Recent studies have shown that glial cells,including microgli、astrocytes、oligo-dendrocytes and oligodendrocyte progenitor cells(NG2 glial cells),are closely related to the pathogenesis of AD.It is believed that activated microglial cells are very easy to induce neuritis and then lead to neurodegeneration.In this paper,the characteristics of the above four glial cells,their functions and their correlation with AD were reviewed,in order to provide a reference for the further study of the pathogenesis of AD.

Senktide blocks aberrant RTN3 interactome to retard memory decline and tau pathology in social isolated Alzheimer’s disease mice

Sporadic or late-onset Alzheimer’s disease(LOAD)accounts for more than 95%of Alzheimer’s disease(AD)cases without any family history.Although genome-wide association studies have identified associated risk genes and loci for LOAD,numerous studies suggest that many adverse environmental factors,such as social isolation,are associated with an increased risk of dementia.However,the underlying mechanisms of social isolation in AD progression remain elusive.In the current study,we found that 7 days of social isolation could trigger pattern separation impairments and presynaptic abnormalities of the mossy fibre-CA3 circuit in AD mice.We also revealed that social isolation disrupted histone acetylation and resulted in the downregulation of 2 dentate gyrus(DG)-enriched miRNAs,which simultaneously target reticulon 3(RTN3),an endoplasmic reticulum protein that aggregates in presynaptic regions to disturb the formation of functional mossy fibre boutons(MFBs)by recruiting multiple mitochondrial and vesicle-related proteins.Interestingly,the aggregation of RTN3 also recruits the PP2A B subunits to suppress PP2A activity and induce tau hyperphosphorylation,which,in turn,further elevates RTN3 and forms a vicious cycle.Finally,using an artificial intelligence-assisted molecular docking approach,we determined that senktide,a selective agonist of neurokinin3 receptors(NK3R),could reduce the binding of RTN3 with its partners.Moreover,application of senktide in vivo effectively restored DG circuit disorders in socially isolated AD mice.Taken together,our findings not only demonstrate the epigenetic regulatory mechanism underlying mossy fibre synaptic disorders orchestrated by social isolation and tau pathology but also reveal a novel potential therapeutic strategy for AD.

Alkenyl-type ligands functionalized tin-lanthanide oxo nanoclusters as molecular lithography resists

Both the cluster chemistry of tin and lanthanides have attracted extensive research interest,showing wide applications in catalysis,magnetism,luminescence,and lithography.However,their fusion into heterometallic Sn-Ln oxo clusters is still to be explored.In this study,through the stabilization of alkenyl-type cis-5-norbornene-endo-2,3-dicarboxylic acid(H_(2)NE)ligands,a series of atomically precise Sn-Ln oxo nanoclusters have been successfully constructed from the assembly of heterometallic tetranuclear Sn_(x)Ln((4-x))building blocks.Thereinto,Sn_(12)Eu_(8) and Sn_(13)Er_(6) with the highest nuclearities are built from multiple assembly of 8{Sn_(2)Eu_(2)}units and 6{Sn_(3)Er}and{Sn_(2)Er_(2)}units,respectively.ESI-MS analysis indicates that Sn_(13)Er_(6) has high solution stability,allowing their packing into thin films for lithography applications.As a result of electron beam lithography(EBL)studies,the condensation of Sn_(13)Er_(6) can be triggered by low energy radiation of 10μC/cm^(2),and 50 nm lines have been fabricated at expose energy of 50μC/cm^(2),confirming the satisfying sensitivity and resolution of Sn_(13)Er_(6).Hence,the success of this study develops the chemistry of heterometallic tin-lanthanide clusters that can be applied as novel negative photoresist materials.

Liver Dysfunction and Its Association with the Risk of Death in COVID-19 Patients:A Prospective Cohort Study

Background and Aims:Coronavirus disease 2019(COVID-19)is a new respiratory infectious disease caused by severe acute respiratory syndrome coronavirus-2(commonly known as SARS-CoV-2)with multiple organ injuries.The aim of this study was to analyze COVID-19-associated liver dysfunction(LD),its association with the risk of death and prognosis after discharge.Methods:Three-hundred and fifty-five COVID-19 patients were recruited.Clinical data were collected from electronic medical records.LD was evaluated and its prognosis was tracked.The association between LD and the risk of death was analyzed.Results:Of the 355 COVID-19 patients,211 had mild disease,88 had severe disease,and 51 had critically ill disease.On admission,223(62.8%)patients presented with hypoproteinemia,151(42.5%)with cholestasis,and 101(28.5%)with hepatocellular injury.As expected,LD was more common in critically ill patients.By multivariate logistic regression,male sex,older age and lymphopenia were three important independent risk factors predicting LD among COVID-19 patients.Risk of death analysis showed that the fatality rate was higher in patients with hypoproteinemia than in those without hypoproteinemia(relative risk=9.471,p<0.01).Moreover,the fatality rate was higher in patients with cholestasis than those without cholestasis(relative risk=2.182,p<0.05).Follow-up observation found that more than one hepatic functional index of two-third patients remained abnormal at 14 days after discharge.Conclusions:LD at early disease stage elevates the risk of death of COVID-19 patients.COVID-19-associated LD does not recover completely by 14 days after discharge.

Synthesis and AO Resistant Properties of Novel Polyimide Fibers Containing Phenylphosphine Oxide Groups in Main Chain

A series of co-polyimide(PI)fibers containing phenylphosphine oxide(PPO)group were synthesized by incorporating the bis(4-aminophenoxy)phenyl phosphine oxide(DAPOPPO)monomer into the PI molecular chain followed by dry-jet wet spinning.The effects of DAPOPPO molar content on the atomic oxygen(AO)resistance of the fibers were investigated systematically.When the AO fluence increased from 0to 3.2×1020the mass loss of the fibers showed the dependence on DAPOPPO molar content in co-PI fibers.The PI fiber containing 40%DAPOPPO showed lower mass loss compared to those containing 0%and 20%DAPOPPO.At higher AO fluence,the higher DAPOPPO content gave rise to dense carpet-like surface of fibers.XPS results indicated that the passivated phosphate layer was deposited on the fiber surface when exposed to AO,which effectively prevented fiber from AO erosion.With the DAPOPPO content increasing from 0%to 40%,the retentions of tensile strength and initial modulus for the fibers exhibited obvious growth from 44%to 68%,and 59%to 70%,after AO exposure with the fluence of 3.2×1020The excellent AO resistance benefits the fibers for application in low Earth orbit as flexible construction components.

Family history of esophageal cancer modifies the association of serum lipids and malignant esophageal lesions:a nested case-control study from the"Endoscopic Screening for Esophageal Cancer in China"trial

Background:The association of lipids and cancer has varied greatly among different cancer types,lipid components and study populations.This study is aimed to investigate the association of serum lipids and the risk of malignant lesions in esophageal squamous epithelium.Methods:In the"Endoscopic Screening for Esophageal Cancer in China"(ESECC)trial,serum samples were collected and tested for total cholesterol(TC),triglycerides,low-density lipoprotein cholesterol(LDL-C),and high-density lipoprotein cholesterol at the time of subject enrollment.Cases were defined as malignant esophageal lesions identified by baseline endoscopic examination or by follow-up to May 31,2018.Controls were randomly selected using incidence density sampling in the same cohort.Conditional logistic models were applied to identify the association of serum lipids and the risk of malignant esophageal lesions.Effect modification was evaluated by testing interaction terms of the factor under assessment and these serum lipid indicators.Results:No consistent association between serum lipid levels and esophageal malignant lesions were found in a pooled analysis of 211 cases and 2101 controls.For individuals with a family history of esophageal cancer(EC),high TC,and LDL-C were associated with a significantly increased risk of having malignant lesions(odds ratio[OR]Highvs.Low TC=2.22,95%confidence interval[CI]:1.14-4.35;ORHighvs.Low LDL-C=1.93,95%CI:1.01-3.65).However,a negative association was observed in participants without an EC family history(ORHighvs.Low TC=0.69,95%CI:0.48-0.98,Pinteraction=0.002;ORHighvs.Low LDL-C=0.50,95%CI:0.34-0.76,Pinteraction<0.001).Conclusions:In this study,we found that the association of serum lipids and malignant esophageal lesions might be modified by EC family history.The stratified analysis would be crucial for population-based studies investigating the association of serum lipids and cancer.The mechanism by which a family history of EC modifies this association warrants further investigation.

Comparison of Different Methods for Determining the Imidization Degree of Polyimide Fibers

In this study, polyimide fibers at different stages of imidization were characterized by TGA, DSC, and FTIR. The imidization degree （ID） calculated by TGA was based on the weight loss of each sample, which was caused by the imidization of residual amic acid groups. The results of TGA showed good regularity with the thermal treatment temperature of the PI fibers. For DSC, the ID was calculated based on the area of endothermal peak of each sample. Compared with TGA, DSC showed a relatively higher value because the endothermal peak was reduced by the exothermic re-formation of polyamic acid which may be partially degraded during thermal treatment. The IDs obtained by the FTIR spectra generally showed poorer regularities than those obtained by both TGA and DSC, especially for the results calculated using the 730 cm^-1 band. Based on the 1350 cm^-1 band, the obtained IDs showed better agreement with the TGA or DSC results. The results obtained by these three methods were compared and analyzed. The ID obtained by TGA showed much more reliability among these three methods.

Synthesis and Properties of Novel Polyimide Fibers Containing Phosphorus Groups in the Side Chain (DATPPO)

A series of polyamic acid copolymers(co-PAAs) containing phosphorous groups in the side chains were synthesized from [2,5-bis(4-aminophenoxy) phenyl] diphenylphosphine oxide(DATPPO) and 4,4′-oxydianiline(ODA) with 3,3′,4,4′-biphenyltetracarboxylic dianhydride(s-BPDA) through the polycondensation in N,N′-dimethyacetamide(DMAc). The co-PAA solutions were spun into fibers by a dry-jet wet spinning process followed by thermal imidization to obtain co-polyimide(co-PI) fibers. FTIR spectra and elemental analysis confirmed the chemical structure of PI fibers. SEM results indicated that the resulting PI fibers had a smooth and dense surface, a uniform and circle-shape diameter. The thermogravimetric measurements showed that with the increase of DATPPO content, the resulting PI fibers possessed high decomposition temperature and residual char yield, indicating that the PI fibers had good thermal stability. The corresponding limiting oxygen index(LOI) values from the experiment results showed that the co-PI fibers possessed good flame-retardant property. Furthermore, the mechanical properties of the co-PI fibers were investigated systematically. When the DATPPO content increased, the tensile strength and initial modulus of the co-PI fibers decreased. However, the mechanical properties were improved by increasing the draw ratio of the fibers. When the draw ratio was up to 2.5, the tensile strength and initial modulus of the co-PI fibers reached up to 0.64 and 10.02 GPa, respectively. The WAXD results showed that the order degree of amorphous matter increased with increased stretching. In addition, the SAXS results displayed that valuably drawing the fibers could eliminate the voids inside and lead to better mechanical property. WAXD revealed that the orientation of the amorphous polymer influenced the mechanical properties of the fibers.

Mechanical Properties of Polyimide/Multi-walled Carbon Nanotube Composite Fibers

A series of polyimide（PI）/multi-walled carbon nanotube（MWCNT） composite fibers were prepared by copolymerizing a mixture of monomers and carboxylic-functionalized MWCNTs, followed by dry-jet wet spinning, thermal imidization, and hot-drawing process. The content of the carboxylic groups of MWCNTs significantly increased when treated with mixed acid, whereas their length decreased with treatment time. Both the carboxylic content and length of MWCNTs influenced the mechanical properties of the composite fibers. Fiber added with 0.1 wt% MWCNTs treated for 4 h exhibited the best mechanical properties, i.e., 1.4 GPa tensile strength and 14.30% elongation at break, which were 51% and 32% higher than those of pure PI fibers, respectively. These results indicated that a suitable MWCNT content strengthened and toughened the resultant PI composite fibers, simultaneously. Moreover, raising draw ratio resulted in the increase of tensile strength and tensile modulus of the composite fibers.