落体偏东在惯性系中的分析

在惯性系中,讨论了落体偏东问题,从落体对地轴的转动角来分析偏东数值,最终得到落体偏东的数值计算式,并说明在实际教学中,采用惯性参考系来解释此现象的直观性.     

Synthesis of New (±) Pterocarpans by Heck Oxyarylation

Among a wide variety of synthetic routes to pterocarpan prototypes, a mild approach uses a reaction known as Heck oxyarylation. This method involves a reaction between 2H-chromenes and 2-chloromercuriophenols in the presence of Li₂PdCl₄. __________ Published in Khimiya Prirodnykh Soedinenii, No. 4, pp. 311–312, July–August, 2005.     

具有HfN/HfO2栅结构的p型MOSFET中的负偏置-温度不稳定性研究

研究了HfN/HfO2高K栅结构p型金属-氧化物-半导体(MOS)晶体管(MOSFET)中,负偏置-温度应力引起的阈值电压不稳定性(NBTI)特征.HfN/HfO2高K栅结构的等效氧化层厚度(EOT)为1.3nm,内含原生缺陷密度较低.研究表明,由于所制备的HfN/HfO2高K栅结构具有低的原生缺陷密度,因此在p-MOSFET器件中观察到的NBTI属HfN/HfO2高K栅结构的本征特征,而非工艺缺陷引起的;进一步研究表明,该HfN/HfO2高K栅结构中观察到的NBTI与传统的SiO2基栅介质p-MOSFET器件中观察到的NBTI具有类似的特征,可以被所谓的反应-扩散(R-D)模型表征: HfN/HfO2栅结构p-MOSFET器件的NBTI效应的起源可以归为衬底注入空穴诱导的界面反应机理,即在负偏置和温度应力作用下,从Si衬底注入的空穴诱导了Si衬底界面Si-H键断裂这一化学反应的发生,并由此产生了Si+陷阱在Si衬底界面的积累和H原子在介质层内部的扩散,这种Si+陷阱的界面积累和H原子的扩散导致了器件NBTI效应的发生.     

The effects of the ageing on the characteristic parameters of polyaniline/p-type Si/Al structure

A detailed study of the effects of the ageing on the characteristic parameters of polyaniline/p-type Si/Al structure has been presented. The polyaniline film has been formed on a p-type Si substrate by means of an anodization process. The polyaniline/p-Si/Al structure has demonstrated clearly rectifying behavior by the current–voltage (I–V) curves studied at room temperature. The current–voltage curves of the structure have been measured immediately, 15, 30, 60, 90 and 120 days after fabrication of the polyaniline/p-Si/Al structure. It has been seen that the characteristic parameters, such as barrier height (BH), ideality factor and series resistance of polyaniline/p-type Si/Al structure have slowly changed with increasing ageing time. The diode shows non-ideal I–V behavior with an ideality factor greater than unity that can be ascribed to the interfacial layer, the interface states and the series resistance.     

Intégrales-fibres pour une formule de Chowla - Selberg

The Chowla-Selberg formula links the class number of negative fundamental quadratic discriminant to values of the Dedekind eta function evaluated over representatives of the class group. It enables the explicit calculation of a large class of elliptic integrals, especially the complete elliptic integrals of the first kind. In this work, we use the integral-fibre theory to offer a new proof of a significant case of this fundamental formula. The method we present here seems susceptible of getting a direct analytic access to a generalization of the explicit instances of the Chowla-Selberg formula in higher dimensions.     

Chemical constituents from the leaves of Pinus dalatensis Ferré

A phytochemical study of n-hexane and ethyl acetate extracts of Pinus dalatensis Ferré leaves led to the isolation of 11 compounds, including one caryolane sesquiterpenoid (1), five labdane diterpenoids (2, 3, 4, 5, 6), one serratane triterpenoid (7), one diacylated flavonoid glucoside (8), one stilbenoid (9) and two sterols (10, 11). The structural characterisation of the isolated compounds was elucidated by spectroscopic data and comparison with the literature report on the chemical constituents from Pinus dalatensis Ferré. Futhermore, three compounds 1, 4 and 6 were obtained for the first time from the genus Pinus. Besides, compounds (2, 3, 5, 8, 9) were also subjected to cytotoxicity effect on SK-LU-1, MCF-7 and Hep-G2 cell lines, but only compound 9 expressed activities with IC₅₀ values of 141.22, 127.81 and 166.84 μM, respectively.     

The effect of magnetic nanoparticles upon the smectic-A to smectic-C* phase transition

We report on wide-angle X-ray scattering measurements along the smectic-A to chiral ferroelectric smectic-C* phase transition of the liquid crystal SCE9 and its mixture with maghemite magnetic nanoparticles of typical dimension 20 nm. The temperature profiles of the tilt angle are fitted by an extended mean-field model. Neither pre-transitional order effects nor variations in the SmA layer thickness are observed, indicating a rather negligible influence of these nanoparticles upon the molecular orientation at the smectic-A to smectic-C* phase transition of SCE9. These results are very different from what was observed for smaller CdSe nanoparticles (3.5 nm) where both a dilation of the smectic layers in the SmA phase and a crossover behaviour for the smectic-A to smectic-C* transition away from tricriticality have been observed for analogous concentrations.     

Fast determination of anthocyanins and free pelargonidin in fruits,fruit juices,and fruit wines by high‐performance liquid chromatography using a core–shell column

Anthocyanins are water‐soluble pigments that are liable for colors ranging from red to blue of most fruits, vegetables, and flowers. A novel and fast method was developed for the determination of five anthocyanins and free pelargonidin by high‐performance liquid chromatography coupled to photodiode array detection. A 10% formic acid and acetonitrile mixture was employed as mobile phase in the gradient elution mode. Mobile phase composition, column temperature, flow rate, injection volume, and column conditioning time were optimized by employing a stepwise strategy. Using a C₁₈ core–shell column (100 × 4.6 mm, 2.7 μm), the separation of six analytes was accomplished in less than 9.5 min with a run‐to‐run analysis time of 19 min. The developed method was validated with respect to linearity (r > 0.9999), limit of detection, limit of quantification, intra‐/interday precision (<2%), accuracy (98.6–104.4%), and specificity. Afterwards, the method was applied to the determination of anthocyanins present in 15 different samples including fruits, fruit juices, and fruit wines.     

Temperature‐Induced Irreversible Phase Transition From Perovskite to Diamond But Pressure‐Driven Back‐Transition in an Ammonium Copper Formate

The compound [CH₃CH₂NH₃][Cu(HCOO)₃] undergoes a phase transition at 357 K, from a perovskite to a diamond structure, by heating. The backward transition can be driven by pressure at room temperature but not cooling under ambient or lower pressure. The rearrangement of one long copper–formate bond, the switch of bridging‐chelating mode of the formate, the alternation of N?H???O H‐bonds, and the flipping of ethylammonium are involved in the transition. The strong N?H???O H‐bonding probably locks the metastable diamond phase. The two phases display magnetic and electric orderings of different characters.