Brief Report: Precise stellarator quasi-symmetry can be achieved with electromagnetic coils

Magnetic fields with quasi-symmetry are known to provide good confinement of charged particles and plasmas, but the extent to which quasi-symmetry can be achieved in practice has remained an open question. Recent work [M. Landreman and E. Paul, Phys. Rev. Lett. 128, 035001, 2022] reports the discovery of toroidal magnetic fields that are quasi-symmetric to orders-of-magnitude higher precision than previously known fields. We show that these fields can be accurately produced using electromagnetic coils of only moderate engineering complexity, that is, coils that have low curvature and that are sufficiently separated from each other. Our results demonstrate that these new quasi-symmetric fields are relevant for applications requiring the confinement of energetic charged particles for long time scales, such as nuclear fusion. The coils’ length plays an important role for how well the quasi-symmetric fields can be approximated. For the longest coil set considered and a mean field strength of 1 T, the departure from quasi-symmetry is of the order of Earth’s magnetic field. Additionally, we find that magnetic surfaces extend far outside the plasma boundary used by Landreman and Paul, providing confinement far from the core. Simulations confirm that the magnetic fields generated by the new coils confine particles with high kinetic energy substantially longer than previously known coil configurations. In particular, when scaled to a reactor, the best found configuration loses only 0.04% of energetic particles born at midradius when following guiding center trajectories for 200 ms.     

融合基因GM-CSF-BZLF1重组腺病毒表达载体的构建

目的构建粒细胞-巨噬细胞集落刺激因子(GM-CSF)和EB病毒即刻早期基因(BZLF1)融合基因的重组腺病毒表达载体。方法采用逆转录-聚合酶链反应分别获得GM-CSF和BZLF1编码序列的cDNA,应用剪接式重叠延伸(SOE)技术将两段基因通过多肽接头(Gly4Ser)3的DNA序列进行连接,构建融合基因GM-CSF-BZLF1。将融合基因GM-CSF-BZLF1定向亚克隆至pAdTrack-CMV质粒,在原核细胞E.coliBJ5183中完成穿梭质粒与骨架质粒pAdEasy-1的同源重组,构建融合基因GM-CSF-BZLF1真核表达载体pAd-GM-CSF-BZLF1。将真核表达载体pAd-GM-CSF-BZLF1转染293细胞,获得复制缺陷型重组腺病毒vAd-GM-CSF-BZLF1。RT-PCR鉴定感染重组腺病毒的293细胞中GM-CSF-BZLF1基因的表达。结果 GM-CSF-BZLF1基因插入重组腺病毒表达载体的预期位置,且插入序列完全正确;感染重组腺病毒vAd-GM-CSF-BZLF1的293细胞中检测到融合基因GM-CSF-BZLF1的转录表达。结论成功地构建了融合基因GM-CSF-BZLF1重组腺病毒表达载体,为进一步探讨GM-CSF-BZLF1的功能提供了理论基础和实验依据。     

Production of Dense Cu-10Sn Part by Laser Powder Bed Fusion with Low Surface Roughness and High Dimensional Accuracy

Tin-bronze alloys with a tin content of at least 10 wt% have excellent mechanical properties, wear resistance, and corrosion resistance. Among these alloys, Cu-10Sn was investigated in this study for production with the laser powder bed fusion process with a 500W Yb:YAG laser. In particular, a design of experiment (DoE) was developed in order to identify the optimal process parameters to obtain full density, low surface roughness, and high dimensional accuracy. Samples were characterized with Archimedes’ method and optical microscopy to determine their final density. It was shown that the first method is fast but not as reliable as the second one. A first mechanical characterization was performed through microhardness tests. Finally, a set of process parameters was identified to produce fully dense samples with low surface roughness and high accuracy. The results showed that the volumetric energy density could represent an approach that is too simplified, therefore limiting the direct correlation with the physical aspects of the process.     

Substituting Resistance Spot Welding with Flexible Laser Spot Welding to Join Ultra-Thin Foil of Inconel 718 to Thick 410 Steel

This paper investigated various aspects of replacing existing micro-resistance spot welding (micro-RSW) with micro-laser spot welding for joining Inconel 718 thin foils to thick 410 steel stack-up to allow faster, non-contact joining together with flexibility in spot positioning and removal of tip dressing required for RSW electrodes. The joint quality was evaluated based on the mechanical strength, microstructural characteristics and joint strength at elevated temperature as these joints are often used for high-temperature applications. Experimental investigations were performed using micro-RSW and micro-laser spot welding to obtain the 90° peel and lap shear specimens, each comprising four spots. The obtained strength from laser joints was significantly higher than that of micro-RSW joints due to larger weld nugget formation and interface width. The process map for obtaining good quality welds was also identified, and about a 17% reduction in joint strength was obtained when welded specimens were subjected to elevated temperature (i.e., 500 °C) in comparison with room temperature. This reduction was compensated for using the flexibility of laser welding to add two extra spots. The overall performance of the micro-laser spot welds was found to be better than the micro-RSW considering joint strength, flexibility in placing the spots and time to produce the welds.     

选择性融合术治疗老年人颈椎过伸性损伤

目的探讨选择性融合治疗合并多节段退变的颈椎过伸性损伤的手术疗效。方法对2002~2006年收治的16例颈椎过伸性损伤根据临床表现实施单节段椎间隙减压,植骨融合内固定术,术后予以脱水、抗感染等对症治疗。结果所有患者随访均获得了骨性融合,神经功能障碍按JOA评分由术前14~16(平均15.2±1.3)分改善至术后16~17(平均16.7±0.6)分。结论选择性融合治疗多节段退变的颈椎过伸性损伤是一种简单、安全的手术治疗方法,可以减少患者的创伤,最大程度地保留患者颈椎运动功能。     

神经节苷脂GM_1和GM_3对受体介导的转铁蛋白内吞过程的影响

我们从正常人脑及肝脏中分离得到纯化的神经节苷脂GM_1[Gal-GalNAc-(NeuNAc)Gal-Glc-Cer]和GM_3[NeuNAc-Gal-Glc-Cer],发现外源性GM_1或GM_3的加入能不同程度地抑制SMMC-7721人肝癌细胞的生长,但仅GM_3能抑制转铁蛋白(Tf)促进的细胞生长。进一步的研究发现,GM_3并不影响Tf与细胞膜表面受体的结合,而是抑制了受体介导的Tf内吞过程,内吞囊泡的形成及融合均受到影响。结果提示:GM_3在膜中的嵌入,可能使受体的构象发生变化或影响了膜的流动性,从而抑制Tf的内吞过程。     

p53蛋白的原核表达及其鸡卵黄抗体的制备

目的制备抗p53蛋白卵黄抗体。方法原核表达p53融合蛋白,纯化后免疫产蛋母鸡。结果融合蛋白能有效刺激母鸡产生抗体,末次免疫后其卵黄抗体滴度达到1∶106,并且能维持较长时间。结论本文介绍的方法是一种简便、经济、特异、高效、均一、来源充足的抗体产生方法。     

持续腰大池引流在颅内动脉瘤术后的临床应用价值

目的:探讨持续腰大池引流在颅内动脉瘤术后的临床应用价值.方法:颅内动脉瘤术后,治疗组72例行持续腰大池引流,对照组49例每天腰椎穿刺,通过比较两组并发症及预后评定疗效.结果:经过持续腰大池引流后,有症状性脑血管痉挛的发生率从34.69%降低为18.31%,脑积水的发生率从26.53%降低为11.27%,脑梗塞的发生率从20.4%降低为7.04%,出院时恢复良好者占76.06%,而对照组为57.14%,以上均有统计学意义(P＜0.05),治疗组并发症的发生率为5.63%,死亡率为零,对照组并发症的发生率为零,两组之间并发症的发生无统计学意义.结论:持续腰大池引流能够减少蛛网膜下腔中的痉挛因素,减轻脑血管痉挛的发生,减少并发症,改善预后.     

护士腰椎间盘突出症的现况调查

目的了解护士腰椎间盘突出症的发病情况。方法采用问卷式调查230名护士腰椎间盘突出症的情况。结果护士腰椎间盘突出症的现患率为17．83％;年龄越大护士腰椎间盘突出症的发病率越高;干部科室的护士腰椎间盘突出症的发病率高于普通科室。结论护士应重视腰椎间盘突出症的发病,卧床患者多的科室更应注意预防。     

循证护理对退行性腰椎滑脱患者生活质量和预后功能的影响

目的 探讨循证护理对退行性腰椎滑脱患者生活质量和预后功能的影响.方法 回顾性分析我院2013年3月至2016年2月收治的100例退行性腰椎滑脱患者的临床资料,依据护理措施不同分为对照组50例和循证护理组50例.比较两组患者护理干预前后的生活质量评分、脊髓功能(JOA)评分、预后功能和并发症发生情况.结果 两组患者护理前的生理功能、心理功能、社会功能、生活环境评分、主观症状、临床症状、日常活动、JOA总评分比较差异均无统计学意义(P>0.05);护理后两组患者的生理功能、心理功能、社会功能和生活环境评分、主观症状、临床症状、日常活动、JOA总评分均高于护理前,且循证护理组患者护理后的上述各项指标均高于对照组,差异均有统计学意义(P<0.05);循证护理组患者预后功能总有效率为100.0%,明显高于对照组的90.0%,并发症发生率为4.0%,明显低于对照组的26.0%,差异均有统计学意义(P<0.05).结论 循证护理应用于退行性腰椎滑脱患者可有效改善其生活质量和预后功能,值得临床推广应用.