The deteriorated degradation resistance of Mg alloy microtubes for vascular stent under the coupling effect of radial compressive stress and dynamic medium

The degradation of Mg alloys relates to the service performance of Mg alloy biodegradable implants.In order to investigate the degradation behavior of Mg alloys as vascular stent materials in the near service environment,the hot-extruded fine-grained Mg-Zn-Y-Nd alloy microtubes,which are employed to manufacture vascular stents,were tested under radial compressive stress in the dynamic Hanks'Balanced Salt Solution(HBSS).The results revealed that the high flow rate accelerates the degradation of Mg alloy microtubes and its degradation is sensitive to radial compressive stress.These results contribute to understanding the service performance of Mg alloys as vascular stent materials.

Synthesis of hexagonal monocrystal AlN microtubes and nanowires at low temperature

This paper reports that pure hexagonal aluminium nitride microtubes and nanowires growing along the [0001] direction have been successfully synthesized by directly reacting AlCl3 with NaN3 at low temperature （450℃） under condition of non-solvent system. The grey-white powder of reacting product was characterized by high-resolution transmission electron microscope （HRTEM）, which shows that the powder is long straight-wire morphology with outer diameter from 40nm to 300 nm and length up to several micrometres. The results of both electron diffraction （ED） and x-ray diffraction （XRD） indicate that the AlN microtubes have a pure hexagonal monocrystal tubular structure with the combination of the curled AlN nanobelts. Room-temperature photoluminescence spectrum of the synthesized sample showed an emission peak, which is closely related to the small size of the microtubes.

Flow characteristics of liquid with pressure-dependent viscosities in microtubes

It is obvious that the pressure gradient along the axial direction in a pipe flow keeps constant according to the Hagen-Poiseuille equation. However, recent experiments indicated that the distribution of the pressure seemed no longer linear for liquid flows in microtubes driven by high pressure （1-30MPa）. Based on H-P equation with slip boundary condition and Bridgman＇s relation of viscosity vs. static pressure, the nonlinear distribution of pressure along the axial direction is analyzed in this paper. The revised standard Poiseuille number with the effect of pressure-dependent viscosity taken into account agrees well with the experimental results. Therefore, the dependence of the viscosity on the pressure is one of the dominating factors under high driven pressure, and is represented by an important property coefficient α of the liquid.

Science Letters: Equivalent thickness of materials of fused silica and stainless steel in the flow of microtubes

The deviation of flow characteristics from the predictions of the conventional theory for microtubes was attrib- uted to the change of fluid viscosity resulted from the interactions between the molecules on solid wall and in fluid. The degree of this departure is dependent on the microtubes materials. A concept of equivalent thickness with which conventional theory can be used to predict the flow in microtubes without modifying the fluid viscosity was put forward. The values of equivalent thickness for fused silica and stainless steel materials were determined as 1.8 μm and 1.5 μm, respectively, by repeated numeri- cal simulation.

In vitro corrosion properties of HTHEed Mg-Zn-Y-Nd alloy microtubes for stent applications:Influence of second phase particles and crystal orientation

Magnesium(Mg)alloys are promising materials for cardiovascular stent applications due to their good biocompatibility and biodegradability.However,in vitro and in vivo corrosion tests reveal that Mg alloy stents suffer from a rapid corrosion rate and severe localized corrosion,which is limiting their widespread application.To solve the problem of uneven degradation of stents,a HTHE(long-time and high-temperature heat treatment,large-reduction-ratio hot extrusion)process is used to manufacture Mg-Zn-Y-Nd alloy microtubes in this study.The heat treatment is to dissolve alloying elements and reduce the size of SPPs,and the hot extrusion is to acquire fine-grained and strongly textured microtubes.The microstructural characterization shows that coarse second phases in as-cast alloy are refined and uniformly distributed in matrix of microtubes.After hot extrusion,microtubes show strong texture with basal plain oriented parallel to the longitudinal section(LS).The corrosion testing indicates that severe localized corrosion occurs on the cross section(CS)while localized corrosion is alleviated on the LS.Based on the different corrosion properties of the LS and CS,HTHEed microtubes are promising for solving the problems of rapid corrosion rate and severe localized corrosion of Mg alloy stents.

Supramolecular electrostatic self-assembly of mesoporous thin-walled graphitic carbon nitride microtubes for highly efficient visible-light photocatalytic activities

For efficient solar energy conversion,the morphology engineering of hollow graphitic carbon nitride(gC3 N4)is one of the promising approachs benefiting from abundant exposed active sites and short photocarrier transport distances,but is difficult to control on account of easy structural collapse.Herein,a facile supramolecular electrostatic self-assembly strategy has been developed for the first time to fabricate mesoporous thin-walled g-C3N4 microtubes(mtw-CNT)with shell thickness of ca.13 nm.The morphological control of g-C3N4 enhances specific surface area by 12 times,induces stronger optical absorption,widens bandgap by 0.18 e V,improves photocurrent density by 2.5 times,and prolongs lifetimes of charge carriers from bulk to surface,compared with those of bulk g-C3N4.As a consequence,the transformed g-C3N4 exhibits the optimum photocatalytic H2-production rate of 3.99 mmol·h^-1·g^-1(λ>420 nm)with remarkable apparent quantum efficiency of 8.7%(λ=420±15 nm)and long-term stability.Moreover,mtw-CNT also achieves high photocatalytic CO2-to-CO selectivity of 96%(λ>420 nm),much better than those on the most previously reported porous g-C3N4 photocatalysts prepared by the conventional hard-templating and soft-templating methods.

Template-free synthesis of Co_(3)O_(4)microtubes for enhanced oxygen evolution reaction

To fully exploit the superiority of tubular structures,in this study,we systematically explore the optimal preparation conditions for Ni/Co_(3)O_(4),including cation species and content,additive species and content,and anion species.Our results reveal that the formation of an initial cobalt nickel acetate hydroxide prism is the key factor and directly affects the final microtubular structure.Moreover,P is subsequently doped into the Ni/Co_(3)O_(4)lattice to increase the M^(3+)/M^(2+)molar ratio(M=Co and Ni),promote reaction kinetics,and optimize electronic structure.Consequently,the oxygen evolution reaction performance of P-doped tubular Ni/Co_(3)O_(4)is significantly higher than that of undoped Ni/Co_(3)O_(4)and the state-of-the-art RuO_(2)electrocatalyst.

Iron-doped Ag/Ni_(2)(CO_(3))(OH)_(2)hierarchical microtubes for highly efficient water oxidation

Doping of foreign atoms and construction of unique structures are considered as effective approaches to design high-activity and strongdurability electrocatalysts.Herein,we report Fe-doped nickel hydroxide carbonate hierarchical microtubes with Ag nanoparticles(denoted Ag/NiFeHC HMTs)through hydrolysis precipitation process.Experimental tests and density functional theory calculations reveal that Fe doping can tune the electron configuration to enhance the conductivity,markedly improve the electrochemical surface area to expose more active sites,and act as reactive centers to lower the free energy of the rate determination step.In addition,the unique hierarchical structure can also offer active sites and excellent cycling stability.Benefitting from these advantages,the as-obtained Ag/NiFeHC HMTs show excellent oxygen evolution reaction activity,with an overpotential of 208 mV at 10 mA cm^(−2)in 1.0M KOH.Also,it could achieve long-term stability at a current density of 20 mA cm^(−2)for 24 h.

Water slip flow in superhydrophobic microtubes within laminar flow region

The fabrication of superhydrophobic surfaces and the studies on water flow characteristics therein are of great significance to many industrial areas as well as to science and technology development. Experiments were car- ried out to investigate slip characteristics of water flowing in circular superhydrophobic microtubes within lam- inar flow region. The superhydrophobic microtubes of stainless steel were fabricated with chemical etching- fluorination treatment. An experimental setup was designed to measure the pressure drop as function of water flow rate. For comparison, superhydrophilic tubes were also tested. Poiseuille number Po was found to be smaller for the superhydrophobic microtubes than that for superhydrophilic ones. The pressure drop reduc- tion ranges from 8% to 31%. It decreases with increasing Reynolds number when Re 〈 900, owing to the transition from Cassie state to Wenze] state. However, it is almost unchanged with further increasing Re after Re 〉 900. The slip length in superhydrophobic microtubes also exhibits a Reynolds number dependence similarly to the pressure drop reduction. The relation between slip length and Darcy friction factor is theoretically analyzed with consideration of surface roughness effect, which was testified with the experimental results.

CRISPR/Cas9介导的高效四倍体马铃薯试管薯基因编辑体系的建立

【目的】基因编辑技术的发展使得马铃薯实现精准分子育种成为了可能,试管薯作为遗传转化的理想材料,但其诱导和转化具有基因型依赖性,建立高效且普遍适用的试管薯基因编辑技术体系可为其精准分子育种提供技术支撑。【方法】以四倍体栽培马铃薯品种青薯9号和并薯6号为材料,对试管薯诱导及其遗传转化体系进行摸索;同时,转化CRISPR/Cas9基因编辑载体进行基因组编辑。另外,利用筛选的条件对其他3个马铃薯品种进行测试。【结果】全黑暗条件下,采用2叶/段的扩繁方式,在含有10%蔗糖和5 mg/L激动素的培养基上,5个马铃薯品种均可成功诱导出试管薯,但诱导效果存在差异。青薯9号的最佳分化激素配方为0.5 mg/L 6-苄氨基腺嘌呤、0.2 mg/L吲哚-3-乙酸、0.2 mg/L赤霉素、2 mg/L玉米素,再生效率、转化频率和基因编辑效率分别为41.5%、51.9%和82.1%。利用上述筛选的激素配方,在其他4个四倍体马铃薯品种中均可高效地实现试管薯的遗传转化再生,其中并薯6号、Desiree和晋薯16号的编辑效率分别为63.2%、33.3%和10%。【结论】建立了5个不同基因型四倍体马铃薯高效的试管薯遗传转化再生体系,其中的4份材料成功地实现了基因组编辑。

纳米纤维素嵌合型晶胶微球的多微管成形与模拟

利用多微管反应器,采用结晶致孔与低温聚合方法可实现纳米纤维素嵌合型晶胶微球的规模化制备。该过程中内嵌纳米纤维素的甲基丙烯酸羟乙酯单体溶液经多微管反应器的成形是首要条件,研究其成形过程的动力学特性具有重要意义。利用高速成像和计算流体力学(CFD)模拟方法对不同入口流速(6、8、10 mm·s^(-1))下内嵌不同比例(单体质量的1%、3%、5%)纳米纤维素的甲基丙烯酸羟乙酯液滴形成过程进行可视化研究,考察了纳米纤维素含量对液滴成形、液滴直径分布、颈缩线长度、液滴下落速度等因素的影响规律。结果表明,内嵌纳米纤维素的甲基丙烯酸羟乙酯液滴经多微管反应器的成形及滴落,会经历拉伸与压缩过程,最后稳定为球状,测得液滴直径和颈缩线长度与纤维素浓度呈正相关,纤维素含量的增加使得单体溶液黏度和表面张力系数增加,从而增大液滴尺寸和颈缩线长度,模拟得到的结果与实验基本一致,液滴直径差异为2.1%~6.3%,颈缩线长度差异为7.2%~11.9%;在对液滴成形的放大模拟中,10 mm·s^(-1)的入口流速下液滴平均直径为3.98 mm,平均颈缩线长为4.14 mm。最终,利用多微管反应器成功制备了纳米纤维素嵌合型晶胶微球,微球有效孔隙率可达80%以上,绝干孔隙率接近90%,是生物分离领域与微生物贴壁生长的理想载体。

合成生物学表型测试生物反应器及其装备化研究进展

合成生物学经过多年的发展,形成了典型的细胞工厂创制“设计-构建-测试-学习”(design-build-testlearn,DBTL)循环,成为支撑面向加速生物制造发展的智慧生物育种的重要方法。其中,测试环节是对前期所设计与构建的生物体系进行表型测试,以提供大量数据用于后续的学习和迭代升级。测试阶段的通量主要依赖于细胞自身或其培养测试所使用的生物反应器及其装备,是整个DBTL流程的限速步骤。本文系统综述了合成生物学表型测试所开发的面向不同通量的生物反应器及装备,从单细胞检测和筛选及不同尺度生物反应器包括皮纳升级生物反应器、微升级生物反应器、毫升级生物反应器和升级生物反应器等,系统地介绍了各自的特点和应用场景。同时,指出了现有生物反应器及其装备的应用潜力、面临的挑战与发展趋势,为合成生物学表型测试技术研究提供重要参考。

基于正交试验的医用微管挤出工艺参数优化

为得到多腔医用微管挤出成型的最佳工艺参数组合,提高微管制品质量,进行了医用微管挤出模具设计,并且,采用Polyflow有限元软件进行数值模拟。通过正交试验,分析注气压力p、入口流量Q及牵引速度v对医用微管内外轮廓椭圆度、直径及月牙腔壁厚的相对误差的影响,采用极差分析得到最佳工艺参数组合注气压力p为25 Pa、入口流量Q为540 mm3/s、牵引速度v为36 mm/s。最后,采用最佳工艺参数组合进行医用微管挤出成型实验。结果表明,数值模拟与挤出成型实验结果均满足医用微管制品尺寸精度公差要求,并且,两者各项误差的差值均小于5%。与无工艺参数挤出成型相比,引入注气压力和牵引速度作为工艺参数后,挤出成型的微管截面形状及尺寸精度均得到了优化,挤出制品质量得到了提高。

Impact of Plant Density on the Formation of Potato Mimitubers Derived from Microtubers and Tip-Cuttings in Plastic Houses

The potato minitubers have been widely used for the elite seed propagation to improve the seed potato system in China. However, little information is available for an efficient production of the minitubers with high plant density in the protected growing conditions like plastic houses. In present research, the minitubers of a wide-grown potato variety, Favorita, were produced with the microtubers from tissue culture and the tip-cuttings of the microtuber plants. Three plant densities, 200, 400 and 600 microtubers or plants m-2 were set up with the randomized block design of 3 replications and the experiment was repeated in 4 seasons in 2009-2010. The canopy development, light interception, dry weight production and partitioning, tuberization and tuber weight were investigated to elucidate the mechanism by which the plant density affects the formation and growth of the minitubers. The results showed that the number of the tubers formed per unite area was in line with the increase in plant density. The difference in leaf area index （LAI） between the plant densities, especially in early stage of the plant growth, resulted in more radiation interception and dry weight producing in higher plant density than in lower one. However, our analysis demonstrated that the conversion coefficient of the cumulative intercepted radiation to plant weight and the dry weight partition rate to the tubers were constant between plant densities, suggesting that less amount of the photoassimilates partitioned to individual tubers is causal for more small tubers in high plant density. A negative exponential curve model, determined by total number of tubers produced per unit area and the mean tuber weight, fitted well to the tuber size distribution pattern. The optimum plant density could be estimated from this model for a maximum production of the minitubers with desired size.

The Effect of Plant Growth Regulator and Active Charcoal on the Development of Microtubers of Potatoes

With the detoxicated seedling of a potato cultivation breed named “Mire” as the material, the effect of auxins CCC, 6-BA, and active carbon to microtubers of potato (Solanum tubersum L.) was investigated under the in-vitro circumstances. The result indicated the exogenous auxins improved the production and quality of microtubers of potatoes. The effect of induction can be described as CCC > CCC + 6-BA > 6-BA > CK, the number of microtubers in per flask is 8.17 > 7.67 > 7.29 > 5.46, and the number of large potatoes in per flask is 6.33 > 5.17 > 3.17 > 1. In addition, by adding 0.5‰ of active charcoal, the growth period was shortened from 25.0 days to 9.33 days on average, and the amount of larger potatoes increased 8.54%. These results benefited the growth of microtubers of potato.

Environmental, morphological and physiological factors analyzes for optimization of potato (<i>Solanum tuberosum</i>L.) microtuber <i>in vitro</i>germination

The microtuber is considered one of the most effective means of spreading basic materials, as well as transporting and preserving potato germplasm varieties. To define the optimal conditions for the potato microtuber in vitro germination of Aida, Atlas and Odessa varieties, the effects of temperature, physiological age and grade (size) were evaluated. The study conducted at three different temperature levels has demonstrated that the most favorable temperature for microtuber germination at a higher and faster germination rate was 25℃, regardless of the variety. In addition, microtubers of large caliber, greater than 4 mm, germinate more quickly, with a higher germination rate, than smaller size ones (less than 4 mm) for all genotypes. For Atlas, Aida and Odessa varieties, a germination rate equal to 86.66%, 70% and 70% respectively, was obtained for microtubers with a caliber superior to 4 mm. Physiological age influences microtuber germination. The mean length of sprouts, reached after a 7 week incubation period, was more marked at “multiple sprout” and “branched sprout” stages than at a “monosprout” stage. The average length was 2.35 cm, 2.48 cm and 1.5 cm, respectively. Thus, it is necessary to plant microtubers at a “multiple sprout” stage to optimize their yield in plants and minitubers.

Acceleration of Microtuber Induction in Potato by Cytokinine and Photoperiod Adjustment

Protocol was developed for acceleration of microtuber induction in potato. It was observed that cytokinine (Kin), and both dark and light period had great influence on in vitro tuberization. Regarding concentration of Kin, 8 mg/l was found excellent for microtuber induction and formation under both dark and light conditions. Under continuous dark condition, higher percentage of explants (shoot) induced microtuber was observed than the short and long period of light conditions. For increasing the number and weight of microtuber product/explant, use of long photoperiod (16 h) is recommended.

Effects of Sucrose on Total RNA Concentration during Formation of Microtubers of Pinellia ternata in vitro

[ Objective] This study aimed to investigate the variation rule of total RNA concentration during formation of microtubers of PineUia ternata induced by sucrose. [ Method ] Plantlets of P. ternata were used as experimental materials. Total RNA concentration was determined with spectrophotometer, and the variation of total RNA was analyzed before and after formation of P. ternata microtubers treated with different concentrations of sucrose using DDRT-PCR technology. [ Result] Total RNA concentration of P. ternata treated with different concentrations of sucrose varied greatly, which showed an upward trend in the first 15 d, de- clined from 15~ d to 25th d, and slightly raised from 25＇h d to 30＇8 d. Microtubers formed under various sucrose treatments showed an increase in RNA concentration after induction, and it was assumed that the treatment of high concentrations of sucrose might have activated the expression of development-related＇ genes in P. ter- nata microtubers. [ Conclusion] This study provides the basis for revealing the related gene expression information and molecular mechanism during formation of P. ternata microtubers induced by sucrose.

Residual Effects of Sucrose and Hormonal Treatments of the Tuberization Medium on <i>in Vitro</i>Germination of Potato (<i>Solanum tuberosum</i>L.) Microtubers

The residual effects of sucrose concentrations (80 or 100 g·L-1) and hormonal treatments (BAP + Kinetin or Coumarin) of tuberization medium on in vitro microtubers germination of three potato varieties (Solanum tuberosum L.) so called Aida, Atlas and Odessa, are described. After 3 weeks of incubation at 28℃ ± 1℃, 70% of Aida microtubers variety, previously formed in the MT2 medium [MS/2 + 80 g·L-1 Sucrose], germinated. The best germination rate for varieties Atlas (100%) and Odessa (66.66%) was obtained on microtubers previously formed in the medium MT2 [MS/2 + 100 g·L-1 Sucrose]. The addition of hormones in the tuberization medium allowed optimizing the microtubers germination of the Aida variety unlike the other varieties. Indeed, for the Aida variety, the combination M5 [Kin 2.5 mg·L-1 + Coum 0.025 mg·L-1 + Sucrose 80 g·L-1] increased the germination rate from 70% up to 93.33%. The best germination rate (90%), noticed with microtubers of Atlas variety, initially formed in M2 medium [Kin 1 mg·L-1 + BAP 1 mg·L-1 + Sucrose 100 g·L-1], was lower than that one (100%) obtained on medium without hormones. For Odessa variety, the maximum germination rate (53.33%) of microtubers, from the medium M4 [Kin 2.5 mg·L-1 + BAP 1 mg·L-1 + Sucrose 100 g·L-1], was also lower than that one (66.66%) observed in the medium without hormones. Aida and Atlas varieties thus offer a better germination rate than Odessa after their cold storage.

光质对马铃薯试管薯诱导结薯和膨大的研究进展

光质对植物的形态建成、光合作用、物质代谢、基因表达以及内源激素水平的产生均有调控作用,马铃薯试管薯形成、块茎膨大期物质积累连同光合作用产物的输送都依赖于光质的调节作用。基于组织培养技术生产的马铃薯试管薯是构建种薯工厂化生产的主要途径,探索光质影响试管薯生育进程的机制,将有助于从物理光谱角度提升试管薯产量与质量。综述讨论了单色光和组合光对试管薯形成的影响,同时探讨光受体对试管薯形成的分子作用机制,为马铃薯试管薯诱导专用光源的开发提供理论依据。