CdSe量子点的制备及其光学性质调控

无机半导体纳米晶量子点以其独特的光学性质,在生物医学检测、显示器件、光催化等领域有广泛应用。以CdSe量子点的合成及光学性质调控为主题,设计一个科研型中级无机实验。以学生为主体,教师为主导,引导学生对科研中严苛的实验条件进行合理改良,拓宽学生眼界,训练学生科研创新及批判性思维,培养高水平化学科研后备力量。

A facile process to optimize performance of regenerated Nd-Fe-B sintered magnets:Chemo-selective dissolution washing

In this work,the recycled Nd-Fe-B powders and regenerated Nd-Fe-B sintered magnets with low impurity content were successfully prepared from Nd-Fe-B magnet sludge via reduction diffusion(RD)method followed by a chemo-selective dissolution washing proc ess.The chemo-selective dissolution effect of various solution(deionized water,dilute acetic acid solution,NH_(4)Cl-methanol solution) was evaluated by impurity content and magnetic properties of the recycled Nd-Fe-B powder.The NH_(4)Cl-methanol solution can selectively remove impurities with minimal damage to the magnetic phase.Besides,the optimal NH_(4)Cl concentration and liquid-to-solid ratio were investigated.As a consequence,the contents of Ca,O,and H after optimal washing process are reduced to 0.07 wt%,0.31 wt% and 0.22 wt%,respectively.Hence,M_(3) Tis increased to 146.72 emu/g,which is 33% higher than that of the initial sludge.Then,the regenerated Nd-Fe-B sintered magnets with properties of B_(r)=11.66 kG,H_(cj)=16.49 kOe,and(BH)_(m)=31.78 MGOe were successfully prepared by mixing with 40 wt% Nd4Fe14B alloy powders.Compared with the corresponding regenerated magnets washed with deionized water,the remanence and coercivity are increased by 18% and 59%,respectively.

Governor vessel-unblocking and mind-regulating acupuncture therapy for sensory and motor dysfunction after spinal cord injury

Objective： To observe the difference in clinical efficacy between governor vessel-unblocking and mind- regulating acupuncture therapy combined with conventional rehabilitation therapy and simply conventional rehabilitation therapy for sensory and motor dysfunction of patients with spinal cord injury. Methods： Forty patients with spinal cord injury （SCI） were randomly assigned into rehabilitation combined with acupuncture group （group A） and rehabilitation group （group B）, with 20 patients in each group. In group A, governor vessel-unblocking and mind-regulating acupuncture therapy combined with conventional rehabilitation therapy was adopted, and Baihui（百会 GV 20）, Fengffu （风府GV 16）, Dazhui （大椎GV 14）, Zhiyang （至阳GV 9）, Mingmen （命门 GV 4） and Yfioyangguan （腰阳关 GV 3） were adopted as the main acupoints. Conventional rehabilitation therapy was also applied, including the rehabilitation training of joint, motion, respiration, urinary bladder and intestinal tract. In group B, conventional rehabilitation therapy was adopted as same as the group A. Treatment in the two groups was conducted for once a day, 6 times a week, and 12 weeks in total. ASIA motor score （MS）, ASIA sensory score （SS） and activity of daily living （ADL） score of patients in the two groups were observed before and after the treatment. Results： Before treatment, the differences in MS, SS and ADL score of patients in the two groups were not statistically significant （all P 〉 0.05）, and the results were comparable. After treatment, MS, SS and ADL score of patients in the two groups were all higher than that before the treatment （all P 〈 0.05）, and MS, SS and ADL score of the patients in group A were all higher than that in group B （all P 〈 0.05）. Conclusion： The curative effect of governor vessel-unblocking and mind-regulating acupuncture therapy combined with conventional rehabilitation therapy was superior to that of simply conventional rehabilitation therapy in the treatment of sensory and motor dysfunction of the patients with SCI.

Calcium hydride reduced high-quality Nd-Fe-B powder from Nd-Fe-B sintered magnet sludge

The structural and magnetic properties were studied for recycling Nd-Fe-B powders from Nd-Fe-B sintered magnets sludge via reduction diffusion(RD)with calcium hydride(CaH_(2))particles.For comparison,traditional reducing agent calcium granules were applied to prepare recycled Nd-Fe-B powders.Finer particle size and better size distribution as well as lower impurity content are achieved by using CaH_(2)instead of Ca.In detail,the average particle size of the recycled Nd-Fe-B powder is reduced from 4.66 to 3.43μm,and the bimodal distribution disappears.Moreover,the residual calcium content and oxygen content are reduced to about 0.080 wt%and 0.32 wt%.As a consequence,the roomtemperature magnetization of the CaH_(2)-recycled Nd-Fe-B powder is increased to 146.30 emu/g,6.8%and 33%,respectively,higher than that of Ca-reduced powder and the initial sludge.Further analysis indicates that CaH_(2)is able to reduce the sludge at lower tempe rature to fabricate well-dispersed,unifo rm recycled powder with high magnetization arising from a combination factors of its low melting point,low thermodynamic behavior,and the release of hydrogen during the reaction.

大型体育赛事对股票流动性的影响——基于全运会的准自然实验

本文以我国全运会的举办作为外生冲击,采用多期双重差分法(difference in difference,DID),研究举办大型体育赛事对上市公司股票流动性的影响。研究发现:(1)与控制组公司相比,处理组公司股票流动性在全运会举办后显著提高;(2)机制检验结果显示,全运会对举办省份上市公司股票流动性的正向影响源于短期机构投资者持股比例的增加;(3)全运会举办对股票流动性的促进作用对非国有企业、绩效较好的企业、规模较小的企业、分析师跟踪人数较少的企业,以及广告与宣传费用支出增长较多的企业更为明显。本文丰富了体育赛事对资本市场影响的相关研究,具有一定的理论意义和现实意义,为权衡大型体育赛事的收益和成本提供了参考。