簧上质量对油气弹簧阀系设计参数的影响

利用开阀压力和流量以及阀片变形之间的关系,分别建立了油气弹簧节流缝隙和单片节流阀片厚度与单轮簧上质量之间的关系式。在此基础上,对单轮簧上质量对阀系设计参数的影响因素进行了分析,求取了单轮簧上质量影响系数。通过实例,分别利用解析设计法与质量影响系数推算设计方法,对油气弹簧阀系参数进行了设计,对参数设计结果进行了比较和校核,并对设计的油气弹簧进行了特性试验。设计和试验结果表明,单轮簧上质量对油气弹簧阀系设计参数有影响,阀系参数的质量影响系数推算设计方法是可靠的。     

Simvastatin Attenuates the Oxidative Stress,Endothelial Thrombogenicity and the Inducibility of Atrial Fibrillation in a Rat Model of Ischemic Heart Failure

Increased atrial oxidative stress has an important role in inducing and maintaining atrial fibrillation (AF), and the activation of the small GTPase Rac1 contributes to the oxidative stress. We investigated the relationship of Rac1, atrial endothelial thromboprotective markers and AF inducibility and if simvastatin has a potential beneficial effect on a myocardial infarction (MI)-induced heart failure (HF) rat model. Rats were randomized into three groups (shams, MI group and simvastatin treatment group) and underwent echocardiography, AF induction studies and left atrial (LA) fibrosis analysis. Atrial Rac 1, sodium calcium exchanger (I_NCX), sarcoplasmic reticulum calcium ATPase (SERCA), endothelial nitric oxide synthase (eNOS) and induced nitric oxide synthase (iNOS) were measured. AF inducibility, AF duration and LA fibrosis were significantly higher in the MI group (p < 0.001 vs. sham), which were significantly reduced by simvastatin (p < 0.05 vs. MI). The reduced expressions of atrial eNOS, SERCA, thrombomodulin, tissue factor pathway inhibitor and tissue plasminogen activator in the MI group were significantly improved by simvastatin. Furthermore, the increased expression of atrial iNOS, I_NCX and Rac1 activity were significantly decreased by the simvastatin. Oxidative stress, endothelial dysfunction and thrombogenicity are associated with the promotion of AF in a rat model of ischemic HF. These were associated with increased Rac1 activity, and simvastatin treatment prevents these changes.     

Inhibition of hIAPP Amyloid Aggregation and Pancreatic β‐Cell Toxicity by OH‐Terminated PAMAM Dendrimer

Human islet amyloid polypeptide (hIAPP, or amylin) forms amyloid deposits in the islets of Langerhans, a phenomenon that is associated with type‐2 diabetes impacting millions of people worldwide. Accordingly, strategies against hIAPP aggregation are essential for the prevention and eventual treatment of the disease. Here, it is shown that generation‐3 OH‐terminated poly(amidoamine) dendrimer, a polymeric nanoparticle, can effectively halt the aggregation of hIAPP and shut down hIAPP toxicity in pancreatic MIN6 and NIT‐1 cells as well as in mouse islets. This finding is supported by high‐throughput dynamic light scattering experiment and thioflavin T assay, where the rapid evolution of hIAPP nucleation and elongation processes is halted by the addition of the dendrimer up to 8 h. Discrete molecular dynamics simulations further reveal that hIAPP residues bound strongly with the dendrimer near the c‐terminal portion of the peptide, where the amyloidogenic sequence (residues 22–29) locates. Furthermore, simulations of hIAPP dimerization reveal that binding with the dendrimer significantly reduces formation of interpeptide contacts and hydrogen bonds, thereby prohibiting peptide self‐association and amyloidosis. This study points to a promising nanomedicinal strategy for combating type‐2 diabetes and may have broader implications for targeting neurological disorders whose distinct hallmark is also amyloid fibrillation.     

机械处理对花生壳纤维素纳米纤丝的性能影响

利用不同机械力对花生壳纯化纤维素进行逐级开纤处理,研究了不同尺度纤维素纳米纤丝(CNF)的微观形貌,采用抽滤法将CNF制备成膜,对比分析了不同样品的断面特征、力学性能、光学性能以及热性能。结果表明,研磨可从花生壳纯化纤维素中剥离出直径约200nm的CNF,纤丝制备成膜后结构较为疏松,层间距大,再经高压均质和超声连续处理可制备出高长径比花生壳CNF,纤丝直径分布在15nm左右,成膜后在膜断面形成了紧密连续结构。经研磨-均质-超声逐级细化后的CNF膜的透光率可达66.7%,相比研磨膜提高了近40%,同时表现出极佳的力学性能,拉伸强度和杨氏模量分别为181MPa和7.1GPa,较研磨膜分别提高了99%和22%,断裂伸长率亦提升至7.3%。此外,该薄膜的热膨胀系数低至12.2ppm/K,具有优异的热稳定性。     

Adenosine A2A Receptors Are Upregulated in Peripheral Blood Mononuclear Cells from Atrial Fibrillation Patients

Atrial fibrillation (AF) is the most common form of cardiac arrhythmia seen in clinical practice. While some clinical parameters may predict the transition from paroxysmal to persistent AF, the molecular mechanisms behind the AF perpetuation are poorly understood. Thus, oxidative stress, calcium overload and inflammation, among others, are believed to be involved in AF-induced atrial remodelling. Interestingly, adenosine and its receptors have also been related to AF development and perpetuation. Here, we investigated the expression of adenosine A2A receptor (A2AR) both in right atrium biopsies and peripheral blood mononuclear cells (PBMCs) from non-dilated sinus rhythm (ndSR), dilated sinus rhythm (dSR) and AF patients. In addition, plasma adenosine content and adenosine deaminase (ADA) activity in these subjects were also determined. Our results revealed increased A2AR expression in the right atrium from AF patients, as previously described. Interestingly, increased levels of adenosine content and reduced ADA activity in plasma from AF patients were detected. An increase was observed when A2AR expression was assessed in PBMCs from AF subjects. Importantly, a positive correlation (p = 0.001) between A2AR expression in the right atrium and PBMCs was observed. Overall, these results highlight the importance of the A2AR in AF and suggest that the evaluation of this receptor in PBMCs may be potentially be useful in monitoring disease severity and the efficacy of pharmacological treatments in AF patients.     

Mechanical,morphological and thermal properties of short carbon and aramid fibres-filled bromo-isobutylene-isoprene rubber vulcanised with 4, 4’ bis(maleimido)diphenylmethane

ABSTRACT

This paper describes the use of a combination of 4, 4’ bis(maleimido)diphenylmethane and ZnO as a high-temperature processable vulcanising agent for the short aramid and carbon fibre-filled bromo-isobutylene-isoprene rubber. The fibre breakage analysis, cure characteristics, mechanical, thermal and morphological properties of the composites were evaluated with different fibre loading. The fibre breakage analyses revealed that the aramid fibres have good length retention property compared to carbon fibres. The morphological analysis of the extracted aramid fibres showed severe surface roughness primarily due to fibrillation after shear mixing. The fibrillated aramid fibres lead to aggregation and poor dispersion of the fibres in the rubber matrix. However, fibrillation imparted surface roughness and increased surface area on the aramid fibres which improved the fibre–matrix interaction via mechanical anchoring. On the other hand, the carbon fibre-filled composite showed poor fibre–matrix interaction and inferior strength and modulus.     

血管紧张素转换酶基因rs4340和rs4343多态性与心房颤动的相关性

目的探讨血管紧张素转换酶(Angiotensin converting enzyme,ACE)基因rs4340和rs4343多态性与心房颤动(简称房颤)的相关性。方法选择重庆地区4家三甲医院就诊的102例房颤患者及同期住院的无房颤病史患者100例,抽取患者静脉血,分别提取基因组DNA,采用单核苷酸多态性-限制性片段长度多态性(Single nucleotide polymorphism,restriction fragmentlength polymorphism,SNP-RFLP)法及基因测序检测ACE基因rs4340和rs4343的基因型。结果房颤组ACE基因rs4340多态性的基因型及等位基因分布与对照组相比,差异无统计学意义(P>0.05),房颤组rs4343的基因型和等位基因分布与对照组间差异有统计学意义(P<0.001或P=0.001)。与对照组相比,房颤组GG+AG基因型频率明显高于AA基因型频率(P<0.001)。II/AA基因型在房颤组中出现的频率明显少于对照组(P=0.001),而II/AG基因型在房颤组中出现的频率明显高于对照组(P=0.002)。房颤组中rs4340和rs4343各基因型左房前后径与右房横径差异均无统计学意义(P>0.05);而将两位点联合分析发现,携带II/AA基因型房颤患者的左房前后径和右房横径均明显小于其他基因型(P<0.001),同时,携带II/AG基因型房颤患者的左房前后径和右房横径均明显大于其他基因型(P<0.001)。结论 ACE基因rs4343多态性与房颤显著相关,II/AA基因型是房颤发生发展的保护因子,而II/AG基因型是预测房颤发生发展的危险因子。     

PBO原纤化的研究

对聚对苯撑苯并二噁唑(PBO)纤维的原纤化过程进行了研究,对制备的PBO浆粕性能进行了表征。结果表明:PBO纤维的原纤化过程经过初步处理、皮层脱落、纤维分丝3个阶段,经PFI磨打浆40 000 r后,所得浆粕产生了较好的原纤化,其原纤结晶度由60.67%下降为43.62%,直径达到纳米级,比表面积从5.18 m~2/g增大到16.2 m~2/g,保水值从13.5%提高到217.3%。     

交联处理对Lyocell纤维抗原纤化性能的影响

对尚未干燥过的初生Lyocell纤维进行交联处理,并分析了各种交联条件下所制得的Lyocell纤维的原纤化性能。研究结果表明,交联剂的浓度及浸润时间、碱剂的浓度及处理时间都会对控制最终纤维的原纤化程度产生一定的影响。在研究范围内,当交联剂的体积质量浓度为40g/L、浸润时间为40min,且碱剂的体积质量浓度为30g/L、处理时间为30min时,最终所得Lyocell纤维的抗原纤化能力比未处理的普通Lyocell纤维提高了约7倍,由此表明交联处理是提高Lyocell纤维抗原纤化性能的一种有效途径。对纤维微观结构的分析结果进一步表明,经交联处理后,Lyocell纤维的基纤及基纤聚集束的尺寸减少且含量增加,这是导致纤维抗原纤化能力提高的关键结构原因。     

Lysophosphatidic Acid level and the incidence of silent brain infarction in patients with nonvalvular atrial fibrillation

Lysophosphatidic acid (LPA), which is proposed to play an important role in normal physiological situations such as wound healing, vascular tone, vascular integrity and reproduction, may be involved in the etiology of some diseases such as atherosclerosis, cancer, obesity or myocardial infarction. Abnormal findings, including silent brain infarction (SBI), are frequently observed by magnetic resonance imaging (MRI) in patients with nonvalvular atrial fibrillation (NVAF). However, whether there is a relationship between LPA level and the prevalence of SBI has not been extensively studied. In the present study, the association between them was investigated. 235 patients with NVAF, 116 cases of SBI without NVAF and 120 cases of healthy volunteers (control group), who did not receive any antithrombotic therapy, were enrolled in this study. Plasma LPA levels in the NVAF with SBI group were significantly higher than that in the control group (p < 0.01), NVAF without SBI group (p < 0.01) and SBI without NVAF group (p < 0.01). The LPA levels are lower in the control group than in the NVAF without SBI and SBI without NVAF groups (p < 0.01), however, the latter two groups did not significantly differ from each other for LPA levels (p > 0.05) There were significant differences in the positive rate of platelet activation between each of the groups (p < 0.01). The positive rate of platelet activation was significantly higher in the NVAF with SBI group. We suggest that LPA might be a novel marker for estimation of the status of platelet activation and the risk factor for SBI onset in NVAF patients. We expected that plasma LPA levels could predict the occurrence of SBI in NVAF patients.