平面Gunn器件中的雪崩弛豫振荡

为了寻找一个高效率的固体振荡器,我们研究了Gunn二极管中的雪崩弛豫振荡。本文描述有源区比较短的平面Gunn器件,在数倍于阚值的强场下工作时出现的雪崩弛豫振荡,这种振荡现象归结于畴雪崩后的电子空穴对的周期性出现和消失。它的振幅可以比Gunn振荡大得多,而频率比Gunn振荡小几倍,并且受外电路参数影响很大,在负载匹配好的情况下,粗略地测得总效率可达36％。     

Note on the harmonic oscillator calculation of two-nucleon transfer form factors

In a recent publication, Iano and Pinkston showed that the zero-range form factor for two-nucleon transfer reactions obtained through their shell model calculation was well approximated in the asymptotic region by the one calculated using the standard well-depth procedure. We wish to show that such an agreement is merely due to the restricted space which they have used. It is found that by including a larger working basis, the form factor may increase in the asymptotic region by as much as 50 % over the one obtained by the well-depth procedure; this in turn will bring the theoretical cross section to within $\text{2}\text{3}$ of the experimental one for the reaction ⁴⁰Ca(t, p)⁴²Ca.     

Isolation and structural elucidation of a novel rotenoid from the seeds of Clitoria fairchildiana

The seeds of Clitoria fairchildiana provided a new rotenoid, 6-hydroxy-2,3,9-trimethoxy-[1]benzopyrano[3,4-b][1]benzopyran-12(6H)-one. The structural elucidation was performed using detailed analyses of H- and 13C-NMR spectra including 2DNMR spectroscopic techniques (1H-13CHETCOR) and by comparison with spectrometric data from the literature. The anti-inflammatory activity was investigated using a capillary permeability assay.     

Elliptic operators with unbounded drift coefficients and Neumann boundary condition

We study the realization A_N of the operator in L2(Ω,μ) with Neumann boundary condition, where Ω is a possibly unbounded convex open set in , U is a convex unbounded function, DU(x) is the element with minimal norm in the subdifferential of U at x, and is a probability measure, infinitesimally invariant for . We show that A_N is a dissipative self-adjoint operator in L2(Ω,μ). Log-Sobolev and Poincaré inequalities allow then to study smoothing properties and asymptotic behavior of the semigroup generated by A_N.     

High performance liquid chromatography of aromatic carboxylic acids on p-tert-butyl-calix[8]arene-bonded silica gel stationary phase

A new p-tert-butyl-calix[8]arene-bonded silica gel stationary phase (CABS) was used for the separation of some aromatic carboxylic acids by HPLC. The chromatographic behaviour of the solutes on CABS was studied in comparison with conventional ODS. The results show that the calix[8]arene-bonded phase exhibits a stronger retention and better selectivity than ODS for the aromatic carboxylic acids. The different elution order of the analytes was also observed on both packings, which show the existence of distinct retention mechanisms. According to chromatographic data, it can be concluded that the high selectivity of CABS for aromatic carboxylic acids ascribes to various interactions between CABS and the analytes, such as hydrophobic interaction, hydrogen bonding interaction, π-π interaction and inclusion interaction.     

265Bh(Z=107)同位素的首次观测

在兰州的重离子加速器上用²⁶Mg离子束轰击²⁴³Am靶,产生了新同位素²⁶⁵Bh.通过观测新同位素²⁶⁵Bh和它的已知子核²⁶¹Db和²⁵⁷Lr之间的α衰变的关联,实现了对新核素的鉴别.实验中使用了一套新建立的具有数个探测器对的转轮收集探测系统.将该系统用于特殊的母–子核搜索模式,从而大大减少了本底.共测得了8个²⁶⁵Bh的α衰变关联事件;同时4个已知核²⁶⁴Bh的衰变关联事件也被鉴别出来.实验测得²⁶⁵Bh的α衰变能量为(9.24±0.05)MeV,半衰期为0.94+0.70–0.31s.     

The structure of a self-assembled calixarene aqua-channel system

The crystal structure of the complex 12.calix-[4]-arene dihydroxyphosphonic acid, 12.propane diammonium, 12.ethanol and 40.water molecules is based on dimeric units of the calix, assembled via trigonal units into a hexameric tube of 15 A radius and 16 A depth, further assemby via spanning propane diammonium cations and ethanol molecules forms a channel (40 A), selectively containing all the water molecules.     

偏最小二乘火焰原子吸收光谱法同时测定汞和钴

本文研究了偏最小二乘原子吸收光谱法同时测定Hg和Co的方法,校正中Co253.649nm对Hg 253.652nm的吸收红重叠干扰,用Hg空心阴极灯同时一合成样中的Hg和Co,方法快速、简单、准确,结果令人满意。     

矩阵损失下多维几何分布均值 的线性估计可容许性

本文在矩阵损失函数 (d - λ ) (d - λ )′下讨论多维几何分布均值参数 λ的线性估计在齐次线性 估计类中的可容许性 .