Microstructure and texture evolution of fine-grained Mg-Zn-Y-Nd alloy micro-tubes for biodegradable vascular stents processed by hot extrusion and rapid cooling

Magnesium alloys have narrow available slip result from close-packed hexagonal structure that limit their processing properties.In the recent work,the Mg-2Zn-0.46Y-0.5Nd,as materials for degradable stents,was applied to produce as-extruded micro-tube with an outer diameter of 3.0mm and a wall thickness of 0.35mm by hot extrusion with an extrusion ratio of 105:1 at 653K and rapid cooling.The fine microstructure of the dynamic recrystallization of as-extruded micro-tube could be preserved by rapid cooling such as water-cooled,resulting in more excellent mechanical properties relative to air-cooled micro-tube.The addition of rare earth elements Y and Nd results in continuous dynamic recrystallization dominated the dynamic recrystallization mechanism.During the hot extrusion process,the activation of the non-basal slip system,especially the pyramidal(c+a)slip,could significantly weaken the texture strength,and the as-extruded micro-tube exhibits weak"RE"texture components(011^(-)1)||ED and(1^(-)21^(-)1)||ED.Hence,the magnesium alloy micro-tube prepared by the rapid cooling has fine microstructure and weak texture,which is favorable for further process and governance.

Micro-Tuber Production in Diploid and Tetraploid Potato after Gamma Irradiation of in Vitro Cuttings for Mutation Induction

Micro-tubers are important propagules in potato breeding and potato production, and they are also dormant and easily transported and therefore good targets for mutation induction in potato mutation breeding. A prerequisite for mutation breeding is to determine optimal mutation treatments. Therefore, radio-sensitivity tests of a tetraploid and a diploid potato to gamma irradiation were undertaken. Effects of different gamma sources on radio-activity were also studied. In vitro potato cuttings were gamma irradiated using a wide dose range (0, 3, 6, 9, 12, 15 and 20 Gy). The irradiated cuttings were then cultured to induce micro-tubers directly in vitro. Micro-tuber morphotypes were assessed after irradiation of cuttings using three gamma sources with emission activities of 1.8, 7.07 and 139 Gy/min. The diploid species (Solanum verrucosum) was more radio-sensitive than the tetraploid cultivar Desirée (Solanum tuberosum). Gamma dose rates had significant influences on subsequent micro-tuber production at various mutant generations. Effects included reductions in the number, size and weight of micro-tubers produced. Gamma dose was more lethal for the diploid potato genotype and micro-tubers produced were small compared to those produced by the tetraploid genotype after irradiation. Different treatments are recommended for diploid and tetraploid potato irradiation in producing large mutant micro-tuber populations. The mutant micro-tuber populations may then be screened for interesting mutations/trait for both genetics and plant breeding purposes.

Rational design, synthesis and prospect of biodegradable magnesium alloy vascular stents

Biodegradable magnesium(Mg) alloys are expected to be promising materials for cardiovascular stents(CVS), which can avoid the longterm clinical problems of current CVS, such as in-stent restenosis, late stent thrombosis, etc. Mg alloy stents exhibit superior biocompatibility and tunable biodegradability, compared with conventional permanent metallic stents. However, the poor formability and non-uniform corrosion of Mg alloy stents hinder their clinical application of CVS. This review focuses on the development of Mg alloys for CVS in recent years.According to the results of bibliometric analysis, we analyzed different biodegradable Mg alloy systems. Moreover, the structural design strategies for Mg alloy stents that can reduce the stress concentration, as well as the surface modification methods to control the corrosion behavior and biological performance of Mg alloy stents are also highlighted. At last, this review systematically discussed the potential directions and challenges of biodegradable magnesium stents(BMgS) in cardiovascular fields.

聚合物双腔微管直角挤出模具非对称流动平衡设计方法

针对聚合物双腔微管直角挤出模具非对称流道结构,基于聚合物流动平衡原理,建立了直角挤出模具非对称流道结构参数关系。在直角挤出模具的挤出成型方向上,采用反向流道的方法计算流道长度,并对反向流道的终点进行拟合,基于拟合偏差构建了目标函数,对模具非对称流道结构进行了优化设计。根据优化结果设计制造了双腔微管直角挤出模具,并且进行了挤出成型实验。实验结果表明挤出模具非对称流道设计是合理的,证明了聚合物双腔微管直角挤出模具非对称流动平衡设计方法的正确性和有效性。

早期雾化对患者双腔支气管插管术后咽喉痛的影响

目的:探讨早期雾化吸入布地奈德混悬液对双腔支气管插管患者术后咽喉痛(POST)的效果。方法:胸科手术患者90例,随机分为3组:对照组(C组)、早期雾化组(G1组)和晚期雾化组(G2组),每组30例。拔管后3组患者送入PACU,G1组雾化吸入布地奈德混悬液1 mg。G2组2 h回病房后雾化吸入布地奈德混悬液1 mg。术后6 h间接喉镜检查患者声门,记录声带充血和声门水肿病例数。用VAS评估入PACU及6、24、48 h患者咽喉痛程度。结果 :术后6 h G1组声带充血和声门水肿病例数低于C组和G2组(P<0.05)。术后6、24 h患者咽喉部VAS评分G1组低于C组和G2组(P<0.05),术后48 h 3组患者咽喉部VAS评分无统计学差异(P>0.05)。结论:早期雾化吸入布地奈德混悬液明显减轻患者双腔支气管插管术后声带充血和声门水肿,从而降低POST程度,且效果优于晚期雾化。

复方利多卡因胶浆在双腔气管插管全身麻醉胸腔镜肺叶切除术中的应用

目的观察复方利多卡因胶浆在双腔支气管插管全身麻醉胸腔镜肺叶切除术中的效果。方法将80例全身麻醉行胸腔镜肺叶切除术的患者随机分为对照组和研究组,每组40例。对照组给予白凡士林均匀涂抹于双腔气管插管套囊及前端,研究组给予复方利多卡因胶浆涂擦于双腔气管插管套囊及前端。比较2组术中全麻用药量、拔管期咳嗽发生率以及不同时点血压、心率变化和术后不良反应发生率情况。结果 2组术中全麻药物用量、不同时点心率及T0、T1、T3时点血压、术后不良反应率比较差异均无统计学意义(P> 0.05)。研究组肺叶切除(T2)、拔除导管(T4)时点血压均低于对照组,差异有统计学意义(P <0.05)。研究组拔管期咳嗽发生率为20.00%,低于对照组的47.50%,差异有统计学意义(P <0.05)。结论复方利多卡因胶浆可减轻双腔气管插管全麻下行胸腔镜肺叶切除术患者围插管及拔管期应激反应。

Processing of a Novel Zn Alloy Micro-Tube for Biodegradable Vascular Stent Application

In recent years, zinc based alloys as a new biodegradable metal material aroused intensive interests. However, the processing of Zn alloys micro-tubes （named slender-diameter and thin-walled tubes） is very difficult due to their HCP crystal structure and unfavorable mechanical properties. This study aimed to develop a novel technique to produce micro-tube of Zn alloy with good performance for biodegrad- able vascular stent application. In the present work, a processing method that combined drilling, cold rolling and optimized drawing was proposed to produce the novel Zn-5Mg-1Fe （wt%） alloy micro- tubes. The micro-tube with outer diameter of 2.5 mm and thickness of 130 μm was fabricated by this method and its dimension errors are within 10 μm. The micro-tube exhibits a fine and homogeneous microstructure, and the ultimate tensile strength and ductility are more than 220 MPa and 20% respectively. In addition, the micro-tube and stents of Zn alloy exhibit superior in vitro corrosion and expansion performance. It could be concluded that the novel Zn alloy micro-tube fabricated by above method might be a promising candidate material for biodegradable stent.

Torsional wave in a circular micro-tube with clogging attached to the inner surface

In the present paper, we study the torsional wave propagation along a micro-tube with clog- ging attached to its inner surface. The clogging accumulated on the inner surface of the tube is modeled as an ＂elastic membrane＂ which is described by the so-called surface elasticity. A power-series solution is particularly developed for the lowest order of wave propagation. The dispersion diagram of the lowest-order wave is numerically presented with the surface （clogging） effect.

Numerical Simulations of a Micro-Channel Wall-Tube Condenser for Domestic Refrigerators

In recent years, microchannel heat exchangers have begun to be used in refrigeration and air conditioning systems. This paper introduces a microchannel condenser for domestic refrigerators with a theoretical model to evaluate its performance. The model was used to obtain the optimal design parameters for different numbers of tubes and tube lengths. The results show that the needed tube height of the down- ward section decreases with the number of tubes and the tube diameter. Compared with the original con- denser, the present optimal design parameters can reduce the total metal mass by 48.6% for the two wall two side design and by 26% for the two wall one side design. Thus, the present condenser is much better than the condensers usually used in actual domestic refrigerators.

Dielectric relaxation behavior of SDS/β-CD organized self-assembly in dilute aqueous solution

Dielectric relaxation behavior of SDS/β-CD self-organized with mass concentrations from 1% to 7% was investigated. The phase microstructure of SDS/β-CD aqueous solution was confirmed by analyzing the dielectric parameters. The dielectric relaxation behavior was attributed to the interracial polarization between vesicle and medium, and the relaxation distribution parameter can indicate the shape transition from vesicles to microtubules with increasing concentration. Dielectric relaxation provided a new method to study surfactant organized self-assembly.