压力下应变异质结中施主杂质态的Stark效应

对应变GaN/Al_xGa_1-xN异质结系统,考虑理想界面突变势垒,引入简化相干势近似,采用变分法讨论了流体静压力下外界电场对束缚于界面附近的浅杂质态结合能的影响.对GaN为衬底的闪锌矿应变异质结,分别计算了(001)和(111)取向时杂质态的结合能随压力、杂质位置、电场强度以及组分的变化关系.结果表明,杂质态结合能随流体静压力呈近线性变化.电场对杂质态的Stark效应则随杂质位置不同而呈现谱线蓝、红移动.此外,还讨论了在不同压力情况下,Al组分对杂质结合能的影响.当杂质处于GaN材料中且距界面较远时,Al组分的增加使电子的二维特性增强,从而使结合能增大,且压力加剧增幅的增加;当杂质处于Al_xGa_1-xN材料中,Al组分的增加削弱了杂质与电子间的库仑相互作用,故而结合能降低. 关键词： xGa_1-xN异质结')" href="#">GaN/Al_xGa_1-xN异质结 杂质态 压力 Stark效应     

自旋为1的三粒子Heisenberg XXX链中杂质对热纠缠的影响

采用纠缠的度量方法Negativity研究了匀强磁场下自旋为1的含杂质三粒子Heisenberg XXX链的热纠缠特性.通过计算系统的杂质位与其余部分间的两体纠缠N_1-23及正常位与其余部分间的两体纠缠N_12-3,发现纠缠存在的临界温度T_c的改变来自杂质参数J₁的变化,随杂质参数J₁的增加而增加,外界磁场B< 关键词： 热纠缠 XXX链')" href="#">Heisenberg XXX链 杂质     

Unconventional ferromagnetism and transport properties of (In,Mn)Sb dilute magnetic semiconductor

Narrow-gap higher mobility semiconducting alloys In_1-xMn_xSb were synthesized in polycrystalline form and their magnetic and transport properties have been investigated. Ferromagnetic response in In_0.98Mn_0.02Sb was detected by the observation of clear hysteresis loops up to room temperature in direct magnetization measurements. An unconventional (reentrant) magnetization versus temperature behavior has been found. We explained the observed peculiarities within the frameworks of recent models which suggest that a strong temperature dependence of the carrier density is a crucial parameter determining carrier-mediated ferromagnetism of (III,Mn)V semiconductors. The correlation between magnetic states and transport properties of the sample has been discussed. The contact spectroscopy method is used to investigate a band structure of (InMn)Sb near the Fermi level. Measurements of the degree of charge current spin polarization have been carried out using the point contact Andreev reflection (AR) spectroscopy. The AR data are analyzed by introducing a quasiparticle spectrum broadening, which is likely to be related to magnetic scattering in the contact. The AR spectroscopy data argued that at low temperature the sample is decomposed on metallic ferromagnetic clusters with relatively high spin polarization of charge carriers (up to 65% at 4.2 K) within a cluster.     

The anomalous low temperature resistivity of thermally evaporated α-Mn thin film

Electrical resistivity measurements have been carried out on thermally evaporated α-Mn thin film between 300 and 1.4 K using the van der Pauw four probe technique. The film was grown on a glass substrate held at a temperature of 373 K, in an ambient pressure of 5×10⁻⁶ Torr. The results show a resistance minimum, a notable characteristic of α-Mn but at a (rather high) temperature of 194±1 K. Below the resistivity maximum which corresponds to 70 K, the resistivity drops by only 0.02 μΩm indicating a rather short range magnetic ordering. The low temperature results show a tendency towards saturation of the resistivity as the temperature approaches zero suggesting a Kondo scattering.     

药物中磺酸酯类基因毒性杂质研究进展

该文概述了近10年来有关药物中基因毒性杂质监管指南的完善历程与相关检测方法的研究进展。介绍了基因毒性杂质从早期的完全避免到目前的阶段化毒理学关注阈值（TTC）的风险控制理念以及各主流监管机构的具体要求。作为一类重要的基因毒性杂质,磺酸酯主要来源于磺酸及衍生物与低级醇（如甲醇、乙醇、异丙醇等）之间发生的副反应,具有化学结构类型多样化的特点。该文较为详尽地介绍了磺酸酯的形成机理和文献所采用的液相色谱法和气相色谱法,并对色谱方法的选择、预处理方式、衍生化方法及相应痕量水平的灵敏度和回收率等进行了评述。由此期望为合理控制药物中磺酸酯类基因毒性杂质,为保证药物的质量安全性提供有益的指导意见。     

托卡马克离子温度梯度湍流输运同位素定标修正中杂质的影响

托卡马克实验发现,在不同参数条件下,等离子体能量约束经验定标律会有或大或小的修正.为解释这种修正现象发生的原因,应用回旋动理学方法,对含重(钨)杂质等离子体离子温度梯度(ITG)(包括杂质模)湍流输运的同位素效应进行了数值研究.结果表明钨杂质效应极大地修改了同位素定标律和有效电荷效应.随着杂质离子电荷数Z和电荷集中度f_z的变化,同位素定标律在较大范围内变化. ITG模最大增长率定标大约为M_i~(-0.48→-0.12),杂质模的定标为M_i~(-0.46→-0.3),其中, M_i表示主离子质量数.在ITG模湍流中,有效电荷数越大,关于M_i的拟合指数偏离-0.5越远,表现为同位素质量依赖减弱.在两种模中,杂质电荷集中度越大,同位素质量依赖越弱.研究了杂质效应使定标关系发生偏离的原因,证实杂质种类、杂质电荷数和杂质浓度的不同,是引起同位素质量依赖发生改变的重要原因.结果证实并解释了不同参数条件下托卡马克同位素定标的差异性.研究成果可以为ITER实验安排及杂质相关输运实验中选择装置材料、工作气体和设置其他参数提供理论参考.     

Analytical Performance and Greenness Evaluation of Five Multi-Level Design Models Utilized for Impurity Profiling of Favipiravir,a Promising COVID-19 Antiviral Drug

In 2018, the discovery of carcinogenic nitrosamine process related impurities (PRIs) in a group of widely used drugs led to the recall and complete withdrawal of several medications that were consumed for a long time, unaware of the presence of these genotoxic PRIs. Since then, PRIs that arise during the manufacturing process of the active pharmaceutical ingredients (APIs), together with their degradation impurities, have gained the attention of analytical chemistry researchers. In 2020, favipiravir (FVR) was found to have an effective antiviral activity against the SARS-COVID-19 virus. Therefore, it was included in the COVID-19 treatment protocols and was consequently globally manufactured at large-scales during the pandemic. There is information indigence about FVR impurity profiling, and until now, no method has been reported for the simultaneous determination of FVR together with its PRIs. In this study, five advanced multi-level design models were developed and validated for the simultaneous determination of FVR and two PRIs, namely; (6-chloro-3-hydroxypyrazine-2-carboxamide) and (3,6-dichloro-pyrazine-2-carbonitrile). The five developed models were classical least square (CLS), principal component regression (PCR), partial least squares (PLS), genetic algorithm-partial least squares (GA-PLS), and artificial neural networks (ANN). Five concentration levels of each compound, chosen according to the linearity range of the target analytes, were used to construct a five-level, three-factor chemometric design, giving rise to twenty-five mixtures. The models resolved the strong spectral overlap in the UV-spectra of the FVR and its PRIs. The PCR and PLS models exhibited the best performances, while PLS proved the highest sensitivity relative to the other models.     

压力对金属铌中氦原子凝聚的影响

 采用零温条件下的赝势-平面波方法和有限温度下的Car-Parrinello分子动力学方法,模拟了不同压力环境下氦原子在金属铌中的行为特征,研究了宿主缺陷和氦泡的形成机制。结果表明,闭电子壳层的氦原子在金属铌中具有刚球模型特征,其占据区域为金属自由电子的禁区,从而破坏铌原子之间的金属性键合。在常温条件下,局域高浓度的氦原子优先凝聚于近邻宿主空位缺陷处,从而形成氦泡;完整晶格中高浓度的氦将促使铌原子易位,形成间隙-空位模式的宿主缺陷,氦原子聚集于空位区域。完整宿主在压力（40 GPa）的作用下,晶格参数减小,铌原子之间的相互作用增强,尽管氦原子的存在削弱了铌原子之间的相互作用,位于格点上的铌原子仍难以借助热振动偏离格点形成空位,因而未能形成间隙-空位对和氦泡。     

毛细管色谱法测定苯类产品馏程

彩和毛细管色谱法,以OV101石英毛细管色谱柱为分离柱,用氢火焰离子化检测器（FID）和面积归一法计算出各影响苯类产品馏程的杂质百分含量,通过建立馏程与杂质百分含量关系式,建立了用毛细管色谱法测定杂质百分含量代替测定苯类产品馏程的国家标准方法GB／T3146－82（色谱法）中的峰高,方法测得的馏程数据与GB／T3146－82（色谱法）的测定值相一致,且操作简便,分析时间短。     

Ecofriendly chromatographic estimation of spasmolytic pharmaceutical mixture along with official toxic impurity, 3,5-dichloroaniline: Complete green profile appraisal

Nowadays, Green Analytical Chemistry is widely applied to provide various analytical methods with eco-friendly procedures employing the least toxic, harmful reagents on humans and the environment without affecting the efficacy of the determination. Accordingly, two eco-friendly, accurate, and reliable high-performance thin-layer chromatography-densitometry and high-performance liquid chromatographic methods were established for the determination and separation of two antispasmodic drugs, namely phloroglucinol and trimethylphloroglucinol in their pure, combined dosage form along with phloroglucinol toxic impurity, 3,5-dichloroaniline. For high-performance thin-layer chromatography-densitometry, efficient separation was developed via utilizing the stationary phase of high-performance thin-layer chromatography silica gel 60 F₂₅₄ plates and developing a system comprising of ethyl acetate-butanol-ammonia in the ratio of 8.0:2.0:0.2, by volume and scanning of the developed bands at 210.0 nm. The subsequent method is isocratic high-performance liquid chromatography with diode array detection in which separation was successively attained using XTerra RP-C₁₈ (250 × 4.6 mm, 5 μm) column as stationary phase and methanol-10.0 mM phosphate buffer, pH 3.7 ± 0.1 as mobile phase in the ratio of 75.0:25.0, v/v at flow rate 1.0 ml/min and scanning at 220.0 nm. The developed liquid chromatography methods were validated according to the International Council for Harmonization guidelines, and all results acknowledged their efficacy. Additionally, the proposed methods worked well for assessing the cited drugs in binary combined commercially available pharmaceutical formulation. The greenness profile of the present methods was assessed and estimated using various assessment tools, namely; Green Analytical Procedure Index, analytical eco-scale method, National Environmental Method Index in addition to Analytical GREEnness tool to evaluate the greenness of the provided methods with a statistical comparison between them to assess the more green ones.