TDI

TDI
  • 文章类型: Journal Article
    支气管上皮E-cadherin下调是重症哮喘的重要特征,包括对类固醇不敏感的哮喘.然而,E-cadherin破坏的机制尚不完全清楚。这项研究旨在研究葡萄糖转运蛋白1(GLUT1)在甲苯二异氰酸酯(TDI)诱导的类固醇不敏感哮喘中E-cadherin失调中的作用。通过TDI致敏和雾化吸入建立了类固醇不敏感哮喘的小鼠模型。选择性GLUT1拮抗剂WZB117和BAY876在气道攻击后给予BALB/c小鼠。体外,将在气道-液体界面(ALI)中培养的原代人支气管上皮细胞(HBEC)暴露于TDI。TDI暴露显著上调小鼠肺和HBECs中的GLUT1。用BAY876药物抑制GLUT1可降低气道高反应性,中性粒细胞和嗜酸性粒细胞积累,以及体内2型炎症。此外,TDI诱导的全长E-cadherin表达下调也部分恢复,伴随着可溶性E-cadherin(sE-cadherin)的分泌受到抑制。WZB117还表现出温和的治疗效果,虽然不重要。体外,用GLUT1抑制剂治疗减轻了TDI诱导的HBECs中E-cadherin的破坏。一起来看,我们的数据表明,在TDI诱导的类固醇不敏感型哮喘中,GLUT1可调节支气管上皮E-cadherin功能障碍的产生.
    UNASSIGNED: Down-regulation of bronchial epithelial E-cadherin is an important of feature of severe asthma, including steroid-insensitive asthma. Yet, the mechanisms involved in E-cadherin disruption are not fully understood. This study was aimed to investigate the role of glucose transporter 1 (GLUT1) in dysregulation of E-cadherin in toluene diisocyanate (TDI)-induced steroid-insensitive asthma.
    UNASSIGNED: A murine model of steroid-insensitive asthma was established by TDI sensitization and aerosol inhalation. Selective GLUT1 antagonists WZB117 and BAY876 were given to BALB/c mice after airway challenge. In vitro, primary human bronchial epithelial cells (HBECs) cultured in an airway-liquid interface (ALI) were exposed to TDI.
    UNASSIGNED: TDI exposure markedly up-regulated GLUT1 in murine lungs and HBECs. Pharmacological inhibition of GLUT1 with BAY876 decreased airway hyperresponsiveness, neutrophil and eosinophil accumulation, as well as type 2 inflammation in vivo. Besides, the TDI-induced down-regulated expression of full-length E-cadherin was also partly recovered, accompanied by inhibited secretion of soluble E-cadherin (sE-cadherin). WZB117 also exhibited mild therapeutic effects, though not significant. In vitro, treatment with GLUT1 inhibitor relieved the TDI-induced disruption of E-cadherin in HBECs.
    UNASSIGNED: Taken together, our data demonstrated that GLUT1 modulates bronchial epithelial E-cadherin dysfunction production in TDI-induced steroid-insensitive asthma.
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  • 文章类型: Journal Article
    背景:这项研究调查了从悉尼当地批发和零售市场以及纽卡斯尔当地超市收集的53种水果和蔬菜样品中的全氟和多氟烷基物质(PFAS)。由于市场上蔬菜中PFAS含量的信息有限,这项研究旨在填补这一空白,并评估食用这些蔬菜对人类的潜在风险。
    方法:QuEChERS萃取-固相萃取法,一个由\'quick组成的portmanteau词,easy,便宜,有效,崎岖,和安全,然后增强基质去除(EMR)-脂质清洁和LC-MS/MS分析用于检测蔬菜中的30个PFAS。
    结果:在53个样本中有7个检测到PFOA,浓度为0.038-1.996ng/g鲜重;仅在2个样品中检测到全氟辛烷磺酸,浓度范围为0.132至0.911ng/g鲜重。在本研究的任何样品中均未检测到PFHxS。在这项研究中,蔬菜中测得的PFOA和PFOS浓度构成每日摄入量为2.03ng/kg体重(BW)和1.98ng/kgBW,分别,根据澳大利亚统计局推荐的每日蔬菜摄入量和体重数据。最敏感的人群是4-8岁的女孩。根据澳大利亚食品标准(FSANZ),这些估计的暴露水平占PFOA(160ng/kgBW)可容忍每日摄入量(TDI)的1.3%和全氟辛烷磺酸(20ng/kgBW)的9.9%。从研究地点食用蔬菜对人类健康构成边际风险。本文受版权保护。保留所有权利。
    BACKGROUND: This study investigated per- and polyfluoroalkyl substances (PFASs) in 53 fruit and vegetable samples collected from a local wholesale and retail market in Sydney and a local supermarket in Newcastle. As there is limited information about PFAS levels in vegetables on the market, this study aimed to fill this gap and assess potential risks for humans through consumption of these vegetables.
    METHODS: QuEChERS extraction - a solid-phase extraction method, a portmanteau word formed from \'quick, easy, cheap, effective, rugged and safe\' - followed by enhanced matrix removal-lipid cleaning and liquid chromatography-tandem mass spectrometry analysis were used to detect 30 PFASs in vegetables.
    RESULTS: PFOA was detected in 7 out of the 53 samples, with concentrations of 0.038-1.996 ng g-1 fresh weight; PFOS was detected in 2 samples only, with concentrations ranging from 0.132 to 0.911 ng g-1 fresh weight. PFHxS was not detected in any sample in this study. PFOA and PFOS concentrations measured in vegetables in this study constituted daily intake of 2.03 ng kg-1 body weight (BW) and 1.98 ng kg-1 BW, respectively, according to recommended daily vegetable intake and BW data from the Australian Bureau of Statistics. The most sensitive population group is girls of 4-8 years of age. These estimated exposure levels represent up to 1.3% of the tolerable daily intake for PFOA (160 ng kg-1 BW) and 9.9% for PFOS (20 ng kg-1 BW) according to Food Standards Australia New Zealand. Consumption of the vegetables from the study locations poses a marginal risk to human health. © 2024 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.
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  • 文章类型: Journal Article
    本文探讨微创手术在创伤中的作用,特别是腹腔镜和电视胸腔镜手术(VATS)。它讨论了腹腔镜手术优于传统剖腹手术的好处,包括其在检测腹膜侵犯和由穿透性创伤引起的腹膜内损伤方面的准确性。本文还探讨了腹腔镜检查作为腹部损伤非手术治疗的辅助手段以及腹部损伤不清的钝性创伤的辅助手段。此外,它强调了胸腔镜在诊断和治疗胸部损伤方面的好处,比如创伤性膈肌损伤,保留的血肿,和持续性气胸。
    This article delves into the role of minimally invasive surgeries in trauma, specifically laparoscopy and video-assisted thoracic surgery (VATS). It discusses the benefits of laparoscopy over traditional laparotomy, including its accuracy in detecting peritoneal violation and intraperitoneal injuries caused by penetrating trauma. The article also explores the use of laparoscopy as an adjunct to nonoperative management of abdominal injuries and in cases of blunt trauma with unclear abdominal injuries. Furthermore, it highlights the benefits of VATS in diagnosing and treating thoracic injuries, such as traumatic diaphragmatic injuries, retained hematomas, and persistent pneumothorax.
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  • 文章类型: Journal Article
    背景:由于不同的患病率,外伤性牙齿损伤(TDI)正在成为一种世界性的现象,他们的病因被认为是多因素和复杂的各种危险因素之间的相互作用。如果以所有可能的科学方式分析和解释风险因素,这些是可以预防的。这项研究的目的是评估世界卫生组织(WHO)指数适龄儿童和青少年(12岁和15岁)中的各种环境风险因素(TDI的发生地点)。
    方法:这是在阿里加尔市进行的流行病学横断面研究,北方邦,印度,2018年,样本量为1000。采用多阶段随机抽样技术。通过在城市不同地区的十个随机选择的采样点(学校)中进行牙科检查和自我准备的形式进行结构化访谈来收集研究数据。随后,将数据输入Excel表格,然后使用社会科学统计软件包(SPSS)软件进行卡方检验分析.
    结果:总体而言,学校(63;46.7%)被发现是TDI最普遍的环境风险因素,其次是家庭(37;27.4%),路边(10;7.4%),和游乐场(9;6.7%)。十五名(11.1%)受影响人士未能回忆起TDI事件的地点,而0.7%(1)在其他地方有TDI发生。在12岁指数年龄的儿童中,家庭(15%;34.1%)是农村地区TDI最常见的地方,而学校(27;67.5%)是城市地区TDI最常见的地方。在15岁指数年龄的青少年中,学校(19;59.4%)被发现是农村地区最常见的地方,而学校(9;47.4%)是城市地区TDI最常见的地方。
    结论:环境因素,尤其是校舍,基础设施,和玩耍设施,需要升级和建造,强调为儿童提供更安全的环境。老师们,父母,应该对学童进行教育,并使他们了解学校和家庭中牙齿受伤的预防措施。在户外运动和娱乐活动中,儿童和青少年应强制使用适当的安全装备。
    BACKGROUND: Traumatic dental injuries (TDIs) are becoming a worldwide phenomenon owing to their variable prevalence, and their etiology is considered multifactorial and complex in interactions among various risk factors. These are preventable if risk factors are analyzed and interpreted in all possible scientific manners. The objective of this study was to assess the various environmental risk factors (places of occurrence of TDI) among World Health Organization (WHO) index-aged children and adolescents (12 and 15 years).
    METHODS: This was the epidemiological cross-sectional study conducted in Aligarh City, Uttar Pradesh, India, in the year 2018, with a sample size of 1000. Multistage random sampling technique was employed. Study data were collected by doing dental examination and structured interview with self-prepared pro forma in ten randomly selected sampling sites (schools) from different regions of the city. Subsequently, data were entered in an Excel sheet and then analyzed with the Chi-square test using the Statistical Package for the Social Sciences (SPSS) software.
    RESULTS: Overall, school (63; 46.7%) was found to be the most prevalent environmental risk factor for TDI followed by home (37; 27.4%), roadside (10; 7.4%), and playground (9; 6.7%). Fifteen (11.1%) affected individuals were not able to recall the place of the TDI incident, while 0.7% (1) had TDI occurrence in other places. Among 12-year index-aged children, home (15; 34.1%) was the most common place of TDI in rural regions, while school (27; 67.5%) was the most frequent place of TDI in urban regions. Among 15-year index-aged adolescents, school (19; 59.4%) was found to be the most common place in rural regions, whereas school (9; 47.4%) was the most frequent place of TDI in urban regions.
    CONCLUSIONS: Environmental factors, especially school premises, infrastructure, and playing facilities, need to be upgraded and built with an emphasis on a safer environment for children. Teachers, parents, and school children should be educated and made aware of the preventive measures for dental injuries in schools and homes. Appropriate safety gears should be mandatory to use among children and adolescents during outdoor sports and recreational activities.
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  • 文章类型: Journal Article
    肺癌患者肺切除术后心脏结构和功能的变化是具有挑战性的。因此,衡量这种变化的非侵入性和可靠的测量工具至关重要。本研究的目的是使用组织多普勒成像(TDI)比较肺切除术前后的心脏变化。共有43例原发性非小细胞肺癌(n=37)和肺转移癌(n=6)患者(19例男性和24例女性)纳入研究。nTDI用于确定升主动脉的厚度,上升阀门的开度大小,左心房和左心室的前后径,肺切除前后室间隔和右心室的厚度。左心室(LV)射血分数(EF),肺动脉瓣流速,三尖瓣环或二尖瓣叶尖早期(E)峰值/晚期(A)舒张期血流速度,三尖瓣返流,使用外侧二尖瓣环早期(e')舒张速度和二尖瓣E/e'比值来确定LV充盈压。结果显示,男性和女性患者在上行瓣膜的开口大小方面没有显着差异,左心室前后径和二尖瓣E/e比值。升主动脉的宽度有显著差异,左心房前后径,肺切除术前后的室间隔宽度和右心室(RV)直径。最后,EF和三尖瓣压力有显著变化。结果表明,TDI可用作评估肺切除术后左右心功能的非侵入性方法。LV和RV尺寸受到影响,但肺叶切除术后左心室充盈压得以保留。
    Changes in heart structure and function after lung resection in patients with lung cancer are challenging to manage. Therefore, a non-invasive and reliable measurement tool to gauge such changes is critical. The purpose of the present study was to compare cardiological changes before and after lung resection using tissue Doppler imaging (TDI). A total of 43 patients (19 men and 24 women) with primary non-small cell lung cancer (n=37) and metastatic cancer in the lungs (n=6) were enrolled in the study.nTDI was used to determine the thickness of the ascending aorta, the open size of the ascending valve, the anterior-oposterior diameters of the left atrium and left ventricle, and the thickness of the ventricular septum and right ventricle before and after lung resection. Left ventricular (LV) ejection fraction (EF), pulmonary valve flow rate, tricuspid annular or mitral leaflet tip early (E) peak/late (A) diastolic blood flow velocities, tricuspid regurgitation flow, the lateral mitral annulus early (e\') diastolic velocity and mitral E/e\' ratio were used to determine LV filling pressure. Results revealed no significant differences between male and female patients in terms of the open size of the ascending valve, the anterior-posterior diameter of the left ventricle and the mitral E/e\' ratio. Significant differences were found in the width of the ascending aorta, anterior-posterior diameter of the left atrium, width of the LV septum and right ventricular (RV) diameter before and after lung resection. Finally, there were significantchanges in EF and tricuspid pressure. The results indicated that TDI was useful as a non-invasive method for assessing left and right heart function following lung resection. The LV and RV dimensions were affected, but LV filling pressure was preserved after lobectomy.
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  • 文章类型: Journal Article
    在这项研究中,选择多元醇蓖麻油(CO)和甲苯-2,4-二异氰酸酯(TDI)改性PBAT,和蓖麻油基聚氨酯(COP)在PBAT基质中使用熔融共混和热压技术生产,以研究网络交联结构对生物基聚酯PBAT各种性能的影响,目的是引入CO和TDI来提高复合材料的力学性能。结果表明,当CO和TDI的总添加量为15%时,CO的羟基与TDI的异氰酸酯基团的比例为1:1时,力学性能最佳。复合材料的拉伸强度比纯PBAT高86.19%,断裂伸长率比PBAT高70.09%,玻璃化转变温度比纯PBAT高7.82℃。因此,CO和TDI对PBAT进行复合改性可以有效提高PBAT基复合材料的耐热性能和力学性能。
    In this study, polyol castor oil (CO) and toluene-2,4-diisocyanate (TDI) were selected to modify PBAT, and castor-oil-based polyurethane (COP) was produced in a PBAT matrix using melt-blending and hot-pressing technology to study the effect of network cross-linking structure on various properties of bio-based polyester PBAT, aiming to introduce CO and TDI to improve the mechanical properties of composite materials. The results showed that when the total addition of CO and TDI was 15%, and the ratio of the hydroxyl group of CO to the isocyanate group of TDI was 1:1, the mechanical properties were the best. The tensile strength of the composite was 86.19% higher than that of pure PBAT, the elongation at break was 70.09% higher than that of PBAT, and the glass transition temperature was 7.82 °C higher than that of pure PBAT. Therefore, the composite modification of PBAT by CO and TDI can effectively improve the heat resistance and mechanical properties of PBAT-based composites.
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  • 文章类型: Journal Article
    背景:患有创伤性牙齿损伤(TDI)的儿童可能同时遭受创伤性脑损伤(TBI)。这项研究的目的是调查患有TDI的儿童并发TBI的风险。
    方法:确定了2010年至2019年在主要儿童医院急诊科寻求TDI治疗的儿童(≤18岁)。合并TBI的儿童被指定为病例患者(TDI和TBI)。两名对照患者(仅TDI)与每个病例患者随机进行年龄和性别匹配。使用6个逻辑回归模型测试了TDI变量与伴随的TBI之间的关联。
    结果:在2,126名患有TDI的儿童中,119例合并TBI(病例患者)。对照组由238名仅患有TDI的儿童组成,他们与病例患者年龄和性别相匹配。儿童的平均(SD)年龄为8.9(4.8)岁。27%的病例患者为女性,对照组为32%。受伤的牙齿总数与伴随的TBI之间存在统计学上显著的直接关联(P=0.01;比值比,2.42;95%CI,1.22至4.79)。每颗牙齿受伤,合并TBI的几率增加了45%(P<.001;赔率比,1.45;95%CI,1.18至1.79)。移位的牙齿数量,撕脱或侵入的存在,牙齿骨折的数量,存在复杂的牙齿骨折,肺泡骨折的存在与合并TBI的几率无显著相关性.
    结论:在这种情况下,受伤的牙齿总数与合并TBI的较高几率呈正相关。
    结论:在急诊科设置中,患有各种类型TDI的儿童持续伴随TBI。每颗牙齿受伤,合并TBI的几率增加了45%.临床医生必须系统地评估患有任何TDI的儿童,以排除合并TBI的可能性。
    Children with traumatic dental injuries (TDIs) may simultaneously sustain a traumatic brain injury (TBI). The aim of this study was to investigate the risk of concomitant TBI in children with TDIs.
    Children (≤ 18 years) who sought treatment at the emergency department of a major children\'s hospital for TDIs from 2010 through 2019 were identified. Children with a concomitant TBI were assigned as case patients (TDI and TBI). Two control patients (TDI only) were randomly age- and sex-matched with each case patient. Associations between variables of TDI and concomitant TBI were tested using 6 logistic regression models.
    Of 2,126 children with TDIs, 119 had concomitant TBIs (case patients). The control group consisted of 238 children with TDIs only who were age- and sex-matched with case patients. Mean (SD) age of children was 8.9 (4.8) years. Twenty-seven percent of case patients were female vs 32% of control patients. There was a statistically significant direct association between total number of injured teeth and concomitant TBIs (P = .01; odds ratio, 2.42; 95% CI, 1.22 to 4.79). For every tooth injured, the odds of concomitant TBI increased by 45% (P < .001; odds ratio, 1.45; 95% CI, 1.18 to 1.79). Number of displaced teeth, presence of avulsion or intrusion, number of fractured teeth, presence of complicated tooth fracture, and presence of alveolar fracture were not significantly associated with the odds of concomitant TBI.
    The total number of injured teeth was positively associated with higher odds of concomitant TBI in this setting.
    In an emergency department setting, children with various types of TDIs sustained concomitant TBIs. For every tooth injured, the odds of concomitant TBI increased by 45%. Clinicians must systematically evaluate children with any TDI to rule out the possibility of concomitant TBI.
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  • 文章类型: Journal Article
    在本研究中,我们开发了一种新的瑞典磷硅藻指数(PDISE),以改善现有指数的适应性差,以满足水管理者检测和减轻富营养化的需求。我们利用了近年来收集的大量数据(820个瑞典流站点)。在我们的工作中,我们发现了硅藻组合对磷的一个意想不到的双峰反应。分类单元聚集到具有低或高位点特异性平均TP最佳值(计算值由硅藻分类单元特异性最佳值组成)的组合中。对于具有中间位点特异性平均TP最优值的位点,我们找不到特征性的硅藻组合。据我们所知,这种双峰社区反应尚未在早些时候显示。PDISE比目前使用的TDI与TP浓度变化的相关性更强。因此,PDISE应取代瑞典标准方法中的TDI。对于索引中包含的大多数分类单元,建模的TP最优值(表示为类别)与TDI不同,这表明这些morphotaxa的实现生态位在瑞典和英国之间是不同的,TDI最初是在英国开发的。r2为0.68,PDISE与TP的相关性是全球其他硅藻营养素指数报告的最高相关性之一;因此,我们认为,在地理和气候相似的其他生物区域进行测试可能是值得的。
    In the present study, we developed a new Swedish phosphorus diatom index (PDISE) to improve the poor fit of existing indices to match the needs of water managers to detect and mitigate eutrophication. We took advantage of a large amount of data (820 Swedish stream sites) collected in recent years. During our work, we found an unexpected bimodal response of the diatom assemblages to phosphorus. The taxa clustered either into an assemblage with a low or with a high site-specific averaged TP optimum (a calculated value comprised of the diatom taxa-specific optima). We could not find a characteristic diatom assemblage for sites with intermediate site-specific averaged TP optima. To our knowledge, this bimodal community response has not been shown earlier. The PDISE correlated more strongly than the currently used TDI to changes in TP concentrations. Thus, the PDISE should replace the TDI in the Swedish standard method. The modeled TP optima (expressed as categories) were different compared to the TDI for most of the taxa included in the index, indicating that the realized niche for these morphotaxa was different between Sweden and the UK where the TDI was developed originally. With a r2 of 0.68, the correlation of the PDISE to TP is among the highest reported for other diatom nutrient indices globally; thus, we believe that it might be worth to test it for other bioregions with similar geography and climate.
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  • 文章类型: Journal Article
    2015年,EFSA建立了每天4μg/kg体重(bw)的BPA的临时每日耐受摄入量(t-TDI)。2016年,欧盟委员会授权EFSA重新评估食品中BPA的存在对公众健康的风险,并建立可容忍的每日摄入量(TDI)。为了重新评估,使用了经过公众咨询的预先建立的方案.CEP小组的结论是,双酚A通过直接机制呈现遗传毒性危害的可能性很小。考虑到动物数据的证据和人类观察研究的支持,免疫系统被确定为对BPA暴露最敏感。对小鼠Th17细胞的影响被确定为关键效应;这些细胞在细胞免疫机制中至关重要,并参与炎症的发展。包括自身免疫和肺部炎症。每天8.2纳克/千克体重的参考点(RP),表示为人体等效剂量,被确定为关键效果。不确定性分析评估了57-73%的概率,即其他健康影响的最低估计基准剂量(BMD)低于基于Th17细胞的RP。鉴于此,CEP小组判断,建立TDI需要额外的不确定因子(UF)2.对RP应用50的整体UF,确定TDI为每天0.2ngBPA/kgbw。该TDI与2015年EFSA意见的饮食暴露估计值的比较表明,所有年龄组的平均和第95百分位饮食暴露均超过TDI两到三个数量级。即使考虑到暴露评估中的不确定性,超限如此之大,CEP小组得出的结论是,饮食中的BPA暴露存在健康问题。
    In 2015, EFSA established a temporary tolerable daily intake (t-TDI) for BPA of 4 μg/kg body weight (bw) per day. In 2016, the European Commission mandated EFSA to re-evaluate the risks to public health from the presence of BPA in foodstuffs and to establish a tolerable daily intake (TDI). For this re-evaluation, a pre-established protocol was used that had undergone public consultation. The CEP Panel concluded that it is Unlikely to Very Unlikely that BPA presents a genotoxic hazard through a direct mechanism. Taking into consideration the evidence from animal data and support from human observational studies, the immune system was identified as most sensitive to BPA exposure. An effect on Th17 cells in mice was identified as the critical effect; these cells are pivotal in cellular immune mechanisms and involved in the development of inflammatory conditions, including autoimmunity and lung inflammation. A reference point (RP) of 8.2 ng/kg bw per day, expressed as human equivalent dose, was identified for the critical effect. Uncertainty analysis assessed a probability of 57-73% that the lowest estimated Benchmark Dose (BMD) for other health effects was below the RP based on Th17 cells. In view of this, the CEP Panel judged that an additional uncertainty factor (UF) of 2 was needed for establishing the TDI. Applying an overall UF of 50 to the RP, a TDI of 0.2 ng BPA/kg bw per day was established. Comparison of this TDI with the dietary exposure estimates from the 2015 EFSA opinion showed that both the mean and the 95th percentile dietary exposures in all age groups exceeded the TDI by two to three orders of magnitude. Even considering the uncertainty in the exposure assessment, the exceedance being so large, the CEP Panel concluded that there is a health concern from dietary BPA exposure.
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  • 文章类型: Journal Article
    聚乙二醇(PEG)和甲苯二异氰酸酯(TDI)通常用作固体推进剂中的粘合剂和固化剂的主要成分,它们的老化是推进剂储存和使用中的一个重要问题。研究硝酸酯增塑聚醚推进剂(NEPE)基质在贮存过程中的老化行为及老化机理,在(U)B3LYP/6-311G(d,P)理论水平,并通过CVT理论计算了298-1000K温度范围内的速率系数。结果表明,粘结剂有五种老化反应,其中包括分解,硝化,H抽象,氧化,和交联反应。其中,氧化和H提取反应的能垒相对较低(79.3-91.2kJ·mol-1),并且是粘合剂老化的主要反应类型。固化剂的主要老化反应是分解。与粘结剂的老化反应相比,固化剂的能障较高(196.6-282.7kJ·mol-1),反应较难发生。通过比较不同反应的能垒和速率常数,发现NEPE推进剂基质的老化可分为两个阶段。在第一阶段,推进剂基质主要经历H提取和氧化反应,随着反应的进行,产品交联形成-O-O-,-C-C-,和-C-O-C-键。此时,推进剂基质的长链分子交联,并且分子量增加。该阶段对应于推进剂老化过程中机械性能的上升阶段。在第二阶段,推进剂基质主要经历分解和硝化,导致降解,分子量的降低,以及基体中孔和微裂纹的出现。该阶段对应于推进剂老化过程中机械性能的下降。上述模拟结果与老化实验现象吻合较好,揭示了NEPE推进剂老化过程中宏观性能变化的微观机理,为NEPE推进剂老化性能和抗老化技术的相关研究提供理论依据。
    Polyethylene glycols (PEG) and toluene diisocyanate (TDI) are often used as the main components of binders and curing agents in solid propellants, and their aging is an important issue in the storage and use of propellants. To study the aging behavior and aging mechanism of nitrate ester plasticized polyether propellant (NEPE) matrix during storage, the transition states of aging reactions of binder and curing agent were optimized at the (U)B3LYP/6-311G(d,p) level of theory, and the rate coefficients over the temperature range of 298-1000 K were calculated by CVT theory. The results showed that there were five kinds of aging reactions for binder, which included decomposition, nitration, H abstraction, oxidation, and crosslinking reactions. Among them, theenergy barriers of oxidation and H abstraction reactions were relatively low (79.3-91.2 kJ·mol-1) and the main reaction types of binder aging. The main aging reaction of curing agent was decomposition. Compared with the aging reactions of binder, the energy barriers of curing agent are higher (196.6-282.7 kJ·mol-1) and the reaction is more difficult to occur. By comparing the energy barriers and rate constants of different reactions, it is found that the aging of NEPE propellant matrix can be divided into two stages. In the first stage, the propellant matrix mainly undergoes H abstraction and oxidation reaction, and as the reaction proceeds, the products crosslink to form -O-O-, -C-C-, and -C-O-C- bonds. At this time, the long chain molecules of the propellant matrix crosslink, and the molecular weight increases. This stage corresponds to the rising stage of mechanical properties in the aging process of the propellant. In the second stage, the propellant matrix mainly undergoes decomposition and nitration, resulting in degradation, the reduction of molecular weights, and the appearance of holes and microcracks in the matrix. This stage corresponds to the decline of mechanical properties in the aging process of the propellant. The above simulation results are in good agreement with the aging experimental phenomena, revealing the microscopic mechanism of the changes in the macroscopic properties of NEPE propellant during the aging process, and providing a theoretical basis for the related research on the aging properties and anti-aging technology of NEPE propellant.
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