Adsorption model of atomic hydrogen on the surfaces of carbon nanotubes

A model for the adsorption of atomic hydrogen on the surfaces of single-walled zig-zag and armchair carbon nanotubes is constructed on the basis of the single-impurity periodic Anderson model. Features of the bands caused by the adsorption of hydrogen atoms in the structure of carbon nanotubes are studied. A reduction in the forbidden gap as a result of adsorption is revealed, and its dependence on the diameter of the semiconducting nanotubes is established. It is concluded that the model can be used to study the adsorption of other monovalent atoms on the surfaces of carbon particles.     

Meeting Report on the 3rd Chinese American Society for Mass Spectrometry Conference—Advancing Biological and Pharmaceutical Mass Spectrometry

Following the highly successful Chinese American Society for Mass Spectrometry (CASMS) conferences in the previous 2 years, the 3rd CASMS Conference was held virtually on August 28–31, 2023, using the Gather.Town platform to bring together scientists in the MS field. The conference offered a 4-day agenda with a scientific program consisting of two plenary lectures, and 14 parallel symposia in which a total of 70 speakers presented technological innovations and their applications in proteomics and biological MS and metabo-lipidomics and pharmaceutical MS. In addition, 16 invited speakers/panelists presented at two research-focused and three career development workshops. Moreover, 86 posters, 12 lightning talks, 3 sponsored workshops, and 11 exhibitions were presented, from which 9 poster awards and 2 lightning talk awards were selected. Furthermore, the conference featured four young investigator awardees to highlight early-career achievements in MS from our society. The conference provided a unique scientific platform for young scientists (i.e. graduate students, postdocs, and junior faculty/investigators) to present their research, meet with prominent scientists, learn about career development, and job opportunities ( http://casms.org ).     

对流层晴空湍流耗散率的风廓线雷达测量及特征

从Airda16000低平流层风廓线雷达的谱宽出发,扣除非湍流因素引起的谱宽加宽,得到湍流对谱宽的贡献,并计算出湍流耗散率。对对流层湍流耗散率的变化特征进行了分析,得出结论：对流层以下耗散率的量级在10-6~10-2 m2·s-3之间,并且随高度增加而减小。在3 km以下,晴空湍流耗散率具有明显的日变化特征,中午逐渐增大,在夜间和清晨偏小,并且随着高度增加,日变化规律随时间向后延迟;3 km以上则不具有明显的日变化规律。耗散率的季节变化很突出,不同季节耗散率随高度递减的程度有差异,2008年夏季耗散率随高度的递减率为5.67%;冬季耗散率随高度递减率为14.7%;秋季分别为12.5%;而09年春季递减率为11.5%。耗散率的变化可以反映出雷达的探测高度,夏季雷达探测高度可达12 km;冬季雷达探测高度很低,仅为7 km;春秋两季探测高度为8~10 km。     

Kaempferol 3-Rhamnoside on Glutamate Release from Rat Cerebrocortical Nerve Terminals Involves P/Q-Type Ca2+ Channel and Ca2+/Calmodulin-Dependent Protein Kinase II-Dependent Pathway Suppression

Excess synaptic glutamate release has pathological consequences, and the inhibition of glutamate release is crucial for neuroprotection. Kaempferol 3-rhamnoside (KR) is a flavonoid isolated from Schima superba with neuroprotective properties, and its effecton the release of glutamate from rat cerebrocortical nerve terminals was investigated. KR produced a concentration-dependent inhibition of 4-aminopyridine (4-AP)-evoked glutamate release with half-maximal inhibitory concentration value of 17 µM. The inhibition of glutamate release by KR was completely abolished by the omission of external Ca²⁺ or the depletion of glutamate in synaptic vesicles, and it was unaffected by blocking carrier-mediated release. In addition, KR reduced the 4-AP-evoked increase in Ca²⁺ concentration, while it did not affect 4-AP-evoked membrane potential depolarization. The application of selective antagonists of voltage-dependent Ca²⁺ channels revealed that the KR-mediated inhibition of glutamate release involved the suppression of P/Q-type Ca²⁺ channel activity. Furthermore, the inhibition of release was abolished by the calmodulin antagonist, W7, and Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) inhibitor, KN62, but not by the protein kinase A (PKA) inhibitor, H89, or the protein kinase C (PKC) inhibitor, GF109203X. We also found that KR reduced the 4-AP-induced increase in phosphorylation of CaMKII and its substrate synapsin I. Thus, the effect of KR on evoked glutamate release is likely linked to a decrease in P/Q-type Ca²⁺ channel activity, as well as to the consequent reduction in the CaMKII/synapsin I pathway.     

气象参数估算气溶胶光学厚度方法的实验验证

利用水平能见度和水汽压资料估算气溶胶光学厚度,并和太阳辐射计实测数据对比,用均方根偏差和相对偏差评估估算方法的精度。对气溶胶光学厚度日平均值的分析结果表明:实测值与估算值变化趋势大致相同;估算方法存在系统偏差。提出修正因子对估算方法进行修正,修正后的估算方法精度明显提高。     

6H-SiC缺陷的慢正电子研究

The defect formation and annealing behavior in as-grown and electron-irradiated 6H-SiC wafers were investi-gated by variable-energy slow positron beam. For the n-type as-grown samples, it was found that annealing decreased the defect concentration due to recombination with interstitial, and when it was annealed at 1400 ±C for 30 min in vacuum, a 20 nm thick Si layer was found on the top of SiC substrate, which is a direct proof of the Si atom diffusing to the surface when annealed at the high temperature stages. During the high temperature annealing stage, we found an obvious surface effect occurred that induced the higher S parameter close to the surface. This may be caused by the diffusion of the Si atoms to the surface during annealing. After 10 MeV electron irradiation of the n-type 6H-SiC, the positron effective diffusion length decreased from 86.2 nm to 39.1 nm. This shows that there are some defects created in n-type 6H-SiC. But in the p-type 6H-SiC irradiated by 10 MeV electrons, the change is very small. This may be because of the opposite charge of the vacancy defects. The same annealing behavior as that of as-grown 6H-SiC samples was also observed for the 1.8 MeV electron-irradiated 6H-SiC samples except that after being annealed at 300 ±C, its defect concentration increased. This may be explained as the generation of carbon vacancies, due to either the recombination between divacancies and silicon interstitial, or the charge of the charge states.     

The Atomic Structure and Mechanical Properties of ZIF-4 under High Pressure: Ab Initio Calculations

The effects of pressure on the structural and electronic properties and the ionic configuration of ZIF-4 were investigated through the first-principles method based on the density functional theory. The elastic properties, including the isotropic bulk modulus K, shear modulus G, Young’s modulus E, and Poisson’s ratio ν of the orthorhombic-type structure ZIF-4 were determined using the Voigt–Reuss–Hill averaging scheme. The results show that the ZIF-4 phase is ductile according to the analysis of K/G and Cauchy pressure. The Debye temperatures obtained from the elastic stiffness constants increase with increasing pressure. Finally, the pressure-dependent behaviors of the density of states and ionic configuration are successfully calculated and discussed.     

稳定核84Sr的高自旋态研究

利用75MeV的¹⁸O束流,通过⁷⁰Zn(¹⁸O,4n)反应布居了⁸⁴Sr核的高自旋态,测量了激发函数,γ–γ符合及DCO比值和γ射线强度,观察到了12条新能级,近30条新γ跃迁,建立了新的能级纲图,与D.C.M.(deformod configuration-mixing shell model)理论计算结果符合得很好,发现其负宇称带有强烈的振动性.     

CD唱片作反射光栅演示教具

通过用ＣＤ唱片作反射光栅的演示实验教具，简略介绍了ＣＤ唱片的特点。