Research on the mechanism of particle deposit effects and process optimization of nanosecond pulsed laser truing and dressing of materials

New plasma expansion models and change rate models of plasma excitation were established under cylindrical coordinates. Expansion models were used to numerically analyse the plasma expansion characteristics of the nanosecond pulsed laser truing and dressing of a bronze–diamond grinding wheel (LTDBDGW). The results showed that the plasma expansions in the X- and R-directions were approximately 8 × 10⁻⁴ m and 2.5 × 10⁻⁴ m, respectively. The plasma electron density calculated by the results was 1.0757 × 10¹⁶ cm⁻³. The calculation of the change rate models of the plasma excitation shows that the plasma excitation mechanism of LTDBDGW was controlled mainly by the thermal excitation effect. In response to high-temperature and high-speed collisions, black particles deposit onto the surface of the bronze–diamond grinding wheel, affecting the topography of the surface and reducing the height of the abrasive grains protruding from the binding agent. Plasma experiments were carried out via LTDBDGW. When the laser was vertically incident, and the laser power density was 3.359 × 10⁸ W cm⁻², the Boltzmann plot method and the Stark broadening method were used to get the plasma electron temperature and the plasma electron density, which were approximately 9700 K and 1.6128 × 10¹⁶ to 2.0636 × 10¹⁶ cm⁻², respectively. LTDBDGW experiments were conducted with and without assisted blowing. Surface quality improvement of the grinding wheel was confirmed with auxiliary blowing.

Plasma experiments for LTDBDGW were carried out with LTDBDGW. A high-speed camera captured the evolution of plasma expansion.     

Femtosecond-scale all-optical switching in oxyfluorogallate glass induced by nonlinear multiphoton absorption

Herein, all-optical switching based on a new type of oxyfluorogallate glass with high switching efficiency and ultrafast response time was reported in the near-infrared wavelength range, which is of great importance for applications in optical telecommunication. The structural and optical properties, as well as the nonlinear optical effects, of the oxyfluorogallate glass were investigated, demonstrating a good figure of merit applicable to nonlinear optical devices. Using pump–probe experiments, we found that the switching time in the oxyfluorogallate glass due to nonlinear multiphoton absorption was approximately 350 fs, which was limited by the pulse duration of the near-infrared probe pulse. Additionally, the largest on–off amplitude of this optical switching device could reach ∼12%, which is in sharp contrast to that of quartz glass. Thus, this study provides a suitable material for the manufacture of integrated photonic devices, which are crucial for promoting the application of glass on-chip photonics.

Ultrafast all-optical switching based on oxyfluorogallate glass induced by nonlinear multiphoton absorption is reported and the ultrafast response time ∼350 fs is achieved by the femtosecond laser pump and probe technology.     

Novel mesoporous Ag@SiO2 nanospheres as a heterogeneous catalyst with superior catalytic performance for hydrogenation of aromatic nitro compounds

Mesoporous core–shell structure Ag@SiO₂ nanospheres are constructed to prevent Ag nanoparticles from aggregation during the hydrogenation reaction. The prepared catalyst shows superior catalytic performance for hydrogenation of nitro compounds with 100% conversion and selectivity without any by-products, which also indicates good recycling performance for several times use.

Mesoporous core–shell structure Ag@SiO₂ nanospheres are constructed to prevent Ag nanoparticles from aggregation during the hydrogenation reaction.     

Stick,stretch, and scan imaging method for DNA and filaments

Biomolecules and organelles usually undergo changes to their structure or form as a result of mechanical stretching or stimulation. It is critical to be able to observe these changes and responses, which trigger mechano-chemical coupling or signal transduction. Advanced techniques have been developed to observe structure and form during manipulation; however, these require sophisticated methods. We have developed a simple approach to observe fine structure after stretching without fluorophore labeling. DNAs or molecules on the cell surface were bound to magnetic microbeads, followed by stretching with a magnetic field. After fixing, staining, and drying, the samples were examined by scanning electron microscopy with no need to build a functional surface with complex processes. Straight DNAs were observed rather than random-walk-like loose polymers. In our cellular experiment, the magnetic beads were bound to a Jurkat cell and formed a rosette which was later stuck to the substrate. A 41.3 μm filament on the base of a filopodium was pulled out via integrin from a cell. Therefore, our method can reveal long structures up to hundreds of micrometers at nanometer resolution after stretching or twisting. Our approach could have wide applications in structure–function studies of biomolecules, and in mechanobiology and cell biology when diffraction cannot used.

Magnetic force was applied to stretch single DNAs and cells which were stuck to magnetic beads and substrates via simple conjugation methods. Scanning electron microscopy images show that the filopodia of cells were pulled to extraordinary length.     

The binary aluminum scandium clusters AlxScy with x + y = 13: when is the icosahedron retained?

Geometrical and electronic structures of the 13-atom clusters Al_xSc_y with x + y = 13, as well as their thermodynamic stabilities were investigated using DFT calculations. Both anionic and neutral isomers of Al_xSc_y were found to retain an icosahedral shape of both Al₁₃ and Sc₁₃ systems in which an Al atom occupies the endohedral central position of the icosahedral cage, irrespective of the number of Al atoms present. Such a phenomenon occurs to maximize the number of stronger Al–Al and Sc–Al bonds instead of the weaker Sc–Sc bonds. NBO analyses were applied to examine their electron configurations and rationalize the large number of open shells and thereby high multiplicities of the mixed clusters having more than three Sc atoms. The SOMOs are the molecular orbitals belonged to the irreducible representations of the symmetry point group of the clusters studied, rather than to the cluster electron shells. Evaluation of the average binding energies showed that the thermodynamic stability of Al_xSc_y clusters is insignificantly altered as the number y goes from 0 to 7 and then steadily decreases when y attains the 7–13 range. Increase of the Sc atom number also reduces the electron affinities of the binary Al_xSc_y clusters, and thus they gradually lose the superhalogen characteristics with respect to the pure Al₁₃.

The icosahedral structure of the Al_xSc_y clusters with x + y = 13.     

微创冷冻消融迷宫Ⅳ手术治疗二尖瓣病变合并心房颤动的近中期结果

目的 分析胸腔镜辅助下微创切口二尖瓣手术同期行冷冻消融治疗心房颤动的近中期结果.方法 回顾性分析中南大学湘雅二医院心血管外科2013年8月至2017年10月完成的68例胸腔镜辅助下右胸微创切口二尖瓣手术同期行冷冻消融治疗心房颤动患者的临床资料,其中男28例、女40例,平均年龄(38.7±9.3)岁.于术后定期复查24h...     

腹腔镜辅助和传统开腹手术在进展期 胃癌根治术中的临床疗效比较

〔摘 要〕 目的：比较腹腔镜辅助、开腹术式用于进展期胃癌有关根治术中的效果。 方法：选取福州市中医院 2021 年 1 月至 2021 年 12 月收治的 60 例处在进展期胃癌患者,结合不同术式分成对照组（开腹根治术式）和观察组 （腹腔镜辅助根治术式）,分别为 30 例患者,比较两组患者不同术式下的手术及术后康复指标、并发症发生情况。 结果：观察组患者的切口长度适于对照组,且术中失血量均少于对照组,差异具有统计学意义（P ＜ 0.05）;观察组 患者排气恢复、下床活动、进食恢复及住院时间均短于对照组,差异具有统计学意义（P ＜ 0.05）;观察组患者并发 症总发生率低于对照组,差异具有统计学意义（P ＜ 0.05）。 结论：和开腹术式相比,进展期胃癌患者在腹腔镜辅助 下接受根治手术能减少手术创伤和并发症出现,加快术后康复。     

灯盏花制剂治疗急性脑梗死的网状Meta 分析

目的采用网状Meta分析的方法比较不同灯盏花制剂治疗急性脑梗死的疗效。方法计算机检索中国生物医学文献数据库(CBM)、中国知网(CNKI)、万方全文数据库(Wanfang),以及PubMed、Embase、the Cochrane Library,查找与灯盏花制剂相关的系统评价,检索时限为建库至2019年2月,对合格系统评价中包含的随机对照试验(RCT)进行筛选、数据提取及偏倚风险评价,并采用Stata 13.0软件进行网状Meta分析。结果共纳入74项RCT,包括8803名患者,涉及12种干预措施。网状Meta分析结果显示,在治疗急性脑梗死的总有效率方面,当疗程小于15 d时,不同的灯盏花制剂之间无统计学差异(P>0.05);当疗程大于20 d时,灯盏花素注射液治疗疗效优于灯盏细辛注射液[RR=1.16,95%CI(1.02,1.33),P<0.05],其余不同的灯盏花制剂之间互相比较无统计学差异(P>0.05),累积排序曲线下面积(SUCRA)由高到低排序为灯盏花素注射液、灯盏生脉胶囊、灯盏细辛注射液。在神经功能缺损评分方面,灯盏生脉胶囊组的治疗前后的美国国立卫生研究院卒中量表(NIHSS)变化值大于灯盏细辛注射液组[MD=1.95,95%CI(0.31,1.60),P<0.05],其余不同的灯盏花制剂之间互相比较无统计学差异(P>0.05)。SUCRA由高到低排序为灯盏生脉胶囊、灯盏花素注射液、灯盏细辛注射液。灯盏生脉胶囊的不良事件较其他灯盏花制剂少。结论灯盏花制剂均可在一定程度上提高急性脑梗死患者的有效率及改善神经功能缺损,而不同制剂的优势与疗程长短、结局指标差异有关。综合平衡疗效与安全性,灯盏生脉胶囊对于急性脑梗死的优势最为明显。     

人间充质干细胞移植改善四氯化碳诱导性肝硬化大鼠的肝纤维化

目的研究人间充质干细胞（MSCs）移植对四氯化碳诱导性肝硬化大鼠肝纤维化的影响.方法 实验动物随机分为对照组和肝硬化组,肝硬化组采用60%的四氯化碳植物油皮下注射7周制成肝硬化大鼠模型,再随机分成肝硬化7周组、MSC对照组和MSC移植组.在MSC移植组,人胚胎脐带血源的MSCs鉴定后,经肠系膜上静脉注射移植入大鼠体内,3周后处死所有大鼠,行肝组织冰冻切片,抗人表皮生长因子受体（EGF-R）的免疫组织化学显色和天狼猩红染色. 结果肝硬化7周组、MSC对照组和MSC移植组大鼠的血清碱性磷酸酶白蛋白（ALP）、（ALB）和胆固醇（CHO）含量出现了不同程度的异常.肝硬化7周组大鼠肝组织中有大量的胶原纤维增生并形成假小叶;MSC对白蛋白照组与肝硬化7周组相似;仅在MSC移植组的大鼠肝中观察到散在的棕黄色的抗人EGF-R阳性细胞,肝组织中胶原纤维的量明显小于MSC对照组.结论经肠系膜上静脉移植人MSC,可明显改善四氯化碳诱导性肝硬化大鼠的肝纤维化程度,为肝硬化的治疗提供实验依据.