Investigation of the energy resolution with a RETGEM detector

A novel Micro-pattern gaseous detector (MPGD), thick GEM with electrodes made of a resistive material (RETGEM) is presented. In this paper we mainly investigate the energy resolution of a RETGEM in Ar+CO_2 with different gas mixtures. The results indicate that an energy resolution 30% in single and double mode can be obtained. The existence of an optimum energy resolution is discussed.     

Investigation of the energy resolution with a RETGEM detector

A novel Micro-pattern gaseous detector （MPGD）, thick GEM with electrodes made of a resistive material （RETGEM） is presented. In this paper we mainly investigate the energy resolution of a RETGEM in Ar＋CO2 with different gas mixtures. The results indicate that an energy resolution 30% in single and double mode can be obtained. The existence of an optimum energy resolution is discussed.     

Space-Selective Precipitation of Ba2TiSi2O8 Crystals in Sm3^＋-Doped BaO-TiO2-SiO2 Glass by Femtosecond Laser Irradiation

The ferroelectric crystal Ba2TiSi2O8 with high second-order optical nonlinearity is precipitated in Sm^3＋-doped BaO-TiO2-SiO2 glass by a focused 800hm, 250 kHz and 150fs femtosecond laser irradiation. No apparent blue and red emissions are observed at the beginning, while strong blue emission due to second harmonic generation and red emission due to the f-f transitions of Sm^3＋ are observed near the focal point of the laser beam after irradiation for 25s. Micro-Raman spectra confirm that Ba2 TiSi2O8 crystalline dots and lines are formed after laser irradiation. The mechanism of the phenomenon is discussed.     

Blue-to-Orange Tunable Luminescence from Europium Doped Yttrium--Silicon--Oxide--Nitride Phosphors

Europium-doped yttrium-silicon-oxide-nitride phosphors are synthesized by carbothermal reduction and nitridation method. The crystal structure of the phosphors changed gradually from oxide Y2Si2O7 to nitride YSi3N5 state with increasing dosage of Si3N4 and carbon powder. The Y2Si2O7：Eu phosphor shows a blue emission at 465 nm with 300 nm excitation and a characteristic red emission of Eu^3＋ at 612 nm with 230 nm excitation. The YSi3N5：EU phosphor shows a broad emission band centred at 595nm with some sharp peaks of Eu^3＋ with 325nm excitation. The absorption of the studied phosphors increases from 450 to 700hm with an increment in nitrogen content. Blue-to-orange tunable luminescence is observed with 390 nm excitation.     

退火对含氮氟非晶碳膜结构及光学带隙的影响

采用射频等离子体增强化学气相沉积法,在不同条件下制备了含氮氟非晶碳膜,着重考察了退火温度对膜结构和光学带隙的影响. 研究发现：在350℃时,膜仍很稳定,当退火温度达到400℃时,其内各化学键的相对含量发生很大的改变. 膜的光学带隙随着退火温度的升高而增大,红外和拉曼光谱分析显示其原因是：退火使得膜内F的相对浓度降低,sp²相对含量升高,导致σ-σ^*带边态密度降低. 关键词： 含氮氟非晶碳膜 退火 光学带隙     

Sonochemical synthesis of taper shaped HgSe nanorods in polyol solvent

A new shape nanosized HgSe was synthesized in the presence of ethylene glycol, which was found to act as both reducing agent and be favorable to the formation of tapered HgSe nanorods. It was also observed that the ultrasonic power played an important role for the shape of the final products. X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the HgSe nanorods. Other polyol solvents, such as diethylene glycol and polyethylene glycol 200, were also used to the preparation of HgSe nanoparticles. The possible mechanism of the formation of taper shaped HgSe nanorods was discussed.     

A novel covalent coupling method for coating of capillaries with liposomes in capillary electrophoresis

A novel covalent coupling method for coating of capillaries with liposomes has been developed, which includes three steps: (i) epoxy-diol coating, (ii) activation with 2,2,2-trifluoroethanesulfonyl chloride, and (iii) liposome coupling. The coating conditions, such as the reaction time and temperature of liposome coupling, the content of dimyristoylphosphatidylethanolamine in liposomes, were optimized. Vesicles were visualized on the inner silica wall as confirmed by atomic force microscopy. The effectiveness of the coating was demonstrated by investigating the effect of pH of BGE on EOF and separating neutral compounds. The intra- and inter-capillary variations in EOF are 4.02% RSD (n=30) and 6.72% RSD (n=4) respectively, and the coated capillaries can be used to perform analysis at least for one month without any performance deterioration when stored at 4 degrees C. A set of drugs with diverse structures was applied into the developed liposome-coated CE. The normalized capacity factor (K) was introduced to quantitatively evaluate drug-membrane interactions. The relationship between log K and the fraction dose absorbed in humans (Fa%) shows that the liposome-coated CE can be utilized for in vitro prediction of Fa% of drugs that follow the transcellular passive transport route.     

Graded Limits of Minimal Affinizations over the Quantum Loop Algebra of Type <Emphasis Type="Italic">G</Emphasis><Subscript>2</Subscript>

The aim of this paper is to study the graded limits of minimal affinizations over the quantum loop algebra of type G ₂. We show that the graded limits are isomorphic to multiple generalizations of Demazure modules, and obtain defining relations of them. As an application, we obtain a polyhedral multiplicity formula for the decomposition of minimal affinizations of type G ₂ as a \(U_{q}(\mathfrak {g})\)-module, by showing the corresponding formula for the graded limits. As another application, we prove a character formula of the least affinizations of generic parabolic Verma modules of type G ₂ conjectured by Mukhin and Young.     

Different two-dimensional metal-organic frameworks through ligand modification

Through ligand modification, we have replaced the central benzene ring of H₂TDBA ([1,1′:3′,1″-terphenyl]-4,4″-dicarboxylic acid) with the pyridine structurally related ligand H₂PDDA (4,4′-(pyridine-2,6-diyl)dibenzoic acid), which makes the central pyridine ring of H₂PDDA more coplanar with two benzene rings on both sides of the ligand. The modification results in a dramatically different linkage configuration, thereby allowing structural changes to the metal-organic frameworks (MOFs). Two 2-D MOFs, [Cu(TDBA)(DMA)₂]·H₂O (BUT-221, DMA = N,N-dimethylacetamide), and [Cu₃(PDDA)₃(DMA)₂(H₂O)]·5H₂O (BUT-223) have been synthesized through reactions of two ditopic carboxylate ligands with Cu(NO₃)₂·3H₂O under solvothermal conditions, and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, thermogravimetric analysis and infrared spectroscopy. Topological analysis shows that BUT-221 is a twofold parallel interpenetrating 4⁴ 2-D network with a skl topology, while BUT-223 is a 2-D network with a kgm topology.     

化学类专业实验教学改革的进展、趋势与重点

综述了过去近20年我国化学类专业实验教学改革的主要内容和取得的主要成绩,分析了当前实验教学中存在的主要问题和挑战,采用目标导向的方式,对实验教学目标、教学内容、教学模式、管理模式的改革趋势进行了分析,提出了改革的要求和思路.对今后的实验教学改革和建设具有一定的指导意义.