Luminescent properties and energy transfer of double-emitting NaSrPO4:Eu2+,Tb3+ phosphor for near-UV white LEDs

Novel blue/green NaSrPO₄ phosphors co-doped with Eu²⁺ and Tb³⁺ were synthesized by a conventional solid-state reaction. Their luminescent properties were characterized by using powder X-ray diffraction, photoluminescence excitation and emission spectra, lifetime, and temperature dependent emission spectra, respectively. The NaSrPO₄:Eu²⁺,Tb³⁺,Na⁺ phosphor showed an intense broad excitation band between 250 and 430 nm, which was in agreement with the near-UV chip (350–420 nm), and it exhibited two dominating emission bands at 445 and 545 nm, corresponding to the allowed 4f⁶5d¹→4f⁷(⁸S_7/2) transition of Eu²⁺ ion and the ⁵D₄→⁷F₅ transition of Tb³⁺ ion, respectively. The emission intensity and lifetime of Eu²⁺ ion decreased with the increasing concentration of Tb³⁺ ion, which strongly indicated that an effective energy transfer occurred from Eu²⁺ to Tb³⁺ in NaSrPO₄ host. The principle of the energy transfer should be the combined effect of the non-radiative resonant energy transfer and the phonon-assisted non-radiative process.     

分光光度法测量铝镓氮外延片中的铝含量

采用熔融的氢氧化钠刻蚀在蓝宝石衬底上生长的铝镓氮外延层,用深紫外光致发光光谱仪测量铝镓氮的荧光光谱来控制铝镓氮层的刻蚀深度,用盐酸将含铝氢氧化钠中和并调节至酸性(pH1~2)后转移至250 mL的容量瓶内定容,用铬天青S络合显色,用分光光度计在546 nm处测定吸光度来确定铝的浓度。该法测量结果的相对标准偏差为1.1%(n=5),加铝标准溶液做回收试验,回收率为96%~103%。该法可用于铝镓氮外延片中铝含量的准确测量。     

多孔介质中的非达西自然对流的分岔研究

利用分岔理论研究了多孔介质底部加热所引起的非达西自然对流。用有限差分方法计算了对流的分岔；确定了Beta数与临界瑞利数的关系。结果表明：随着Be从0增大到1，出现分岔的单胞对流的临界瑞利数Rac从39．35单调地增大到41．15。双胞对流亦有类似的趋势。这说明惯性－湍流效应有使对流稳定性增强的趋势。     

Asymmetric hydrogenation and allylic substitution reaction with novel chiral pinene-derived N,P-ligands

A series of new chiral tetrahydroquinoline ligands, derived from chiral α-pinene, were successfully synthesized. Iridium and palladium complexes of these ligands were proven to be efficient catalysts for enantioselective hydrogenation and allylic substitution reactions with moderate to excellent enantioselectivities (90–95% ee) and high yields.     

手性膦基二茂铁基噁唑啉铱配合物对乙酸肉桂酯衍生物的不对称氢化

以Fc-PHOX, [Ir(cod)Cl]2和NaBArF为原料高产率地合成了一系列手性Ir-Fc-PHOX配合物, 将其应用于乙酸肉桂酯衍生物的不对称氢化反应, 它们被证明是高效的催化剂, 可以得到完全的转化率和优良的对映选择性, 对映体过量高达99.5% ee.     

共焦扫描荧光显微镜的信噪比与信息量

在研制用于对厚的生物样品进行光学断层成像的共焦扫描荧光显微镜时，由于成像信号十分微弱及存在很强的多次散射作用，因此杂散光的抑制非常重要，而信噪比、信号背景比就成为决定能否获得高对比度、高分率图像的关键。运用光学信息量的概念，在已有的光学成像系统信息量计算、共焦扫描荧光显微镜信噪比及传递函数计算的基础上，详细分析了共焦扫描荧光显微镜信息量与信噪比等之间的定量关系。该关系表明，为了充分利用共焦扫描荧光显微镜的成像性能，必须选择适当的探测小孔。所得的结果对于共焦扫描荧光显微成像系统的研制有重要的实用价值。     

直链淀粉-三[(S)-1-苯乙基氨基甲酸酯]手性固定相拆分布地奈德对映体及其制剂含量的测定

22R-布地奈德的药物活性比22S-布地奈德的强2~3倍,开发布地奈德对映体拆分和定量分析方法,可为其药物研发及质量控制提供重要依据。目前,主要以反相C₁₈固定相对布地奈德对映体进行拆分,而采用手性固定相对其进行拆分少有报道。通过考察固定相、流动相和柱温对布地奈德对映体拆分的影响,建立了基于直链淀粉-三[(S)-1-苯乙基氨基甲酸酯]手性固定相快速拆分和检测布地奈德对映体的高效液相色谱方法,其色谱条件如下:色谱柱为Chiralpak AS-RH色谱柱(150 mm×4.6 mm, 5.0 μm),流动相为乙腈-水(45∶55, v/v),柱温40 ℃,流速1.0 mL/min,二极管阵列检测器(DAD),检测波长246 nm,进样量10 μL。在该色谱条件下,布地奈德的两个对映体得到较好拆分,22R-布地奈德和22S-布地奈德的保留时间分别6.40 min和7.77 min,分离度为4.64; 22R-布地奈德和22S-布地奈德分别在各自范围内线性关系良好,相关系数(R²)均为0.9999,检出限分别为0.05 μg/mL和0.07 μg/mL,定量限分别为0.16 μg/mL和0.20 μg/mL; 4个添加水平的样品加标回收率为102.63%~104.17%,相对标准偏差(RSD)为0.08%~0.57%(n=6)。将该方法应用于1批次4个吸入用布地奈德混悬液实际样品进行检测,22R-布地奈德和22S-布地奈德的含量分别为283.15~284.63 μg/mL和259.86~261.51 μg/mL。该方法操作简便,分析时间短,重复性好,准确度高,可用于布地奈德对映体的拆分及其制剂的质量控制。     

AN EFFICIENT DYNAMIC MODELING METHOD OF AN AXIALLY MOVING CANTILEVER BEAM AND FREQUENCY RESPONSE ANALYSIS

轴向移动梁动力学问题具有广泛的工程应用背景,如：机械手、机床主轴、武器身管等.计算轴向移动梁动力学响应是评估结构动力学性能以及最终指导结构设计的一个重要手段.采用Rayleigh-Ritz法、拉格朗日方程推导了轴向移动悬臂梁时变动力学方程.选取幂级数函数构造试函数对轴向移动系统动力问题进行求解.幂级数函数良好的积分与微分性能,使得推导容易以矩阵的形式快速进行,便于符号运算软件直接生成MATLAB程序.由于MATLAB基本数据单位为矩阵,符号软件生成的程序只需经过简单修改便可进行动力学计算.大大缩短了轴向移动梁从建模到动力学分析的时间,过程十分高效.通过四组算例,将本文方法计算得到的动力学响应与文献数据进行对比,对该方法准确性进行了验证,并给出了幂级数函数拟合阶数的选取原则.以此为基础,研究了轴向移动梁的频率响应特性.分为考虑重力与忽略重力两种情况,讨论了轴向振动幅度对其频率响应特性的影响.     

气相色谱法测定黑色PMMA燃烧产物中的一氧化碳和二氧化碳含量

利用气相色谱法检测黑色PMMA完全燃烧烟气中的常量二氧化碳和微量一氧化碳,建立了双气路双检测器的检测方法。恒定色谱柱温度,通过定量管进样,Poropak T色谱柱预分离后,采用阀切换及柱反吹技术使不同组分分别流入5A分子筛色谱柱和Poropak N色谱柱中。5A分子筛色谱柱用于分离一氧化碳,经Ni催化甲烷化转化后用FID检测器测定;Poropak N色谱柱分离二氧化碳后进入电导检测器测定。采用峰面积法建立标准曲线,一氧化碳和二氧化碳的线性相关系数分别为0.999 9和0.999 6。用该法测定标准气体,其测定值与标准值的相对误差小于2%,测定结果的相对标准偏差小于1%。该方法可用于烟气毒性的分析。     

Comparisons of Isolation Methods,Structural Features,and Bioactivities of the Polysaccharides from Three Common Panax Species: A Review of Recent Progress

Panax spp. (Araliaceae family) are widely used medicinal plants and they mainly include Panax ginseng C.A. Meyer, Panax quinquefolium L. (American ginseng), and Panax notoginseng (notoginseng). Polysaccharides are the main active ingredients in these plants and have demonstrated diverse pharmacological functions, but comparisons of isolation methods, structural features, and bioactivities of these polysaccharides have not yet been reported. This review summarizes recent advances associated with 112 polysaccharides from ginseng, 25 polysaccharides from American ginseng, and 36 polysaccharides from notoginseng and it compares the differences in extraction, purification, structural features, and bioactivities. Most studies focus on ginseng polysaccharides and comparisons are typically made with the polysaccharides from American ginseng and notoginseng. For the extraction, purification, and structural analysis, the processes are similar for the polysaccharides from the three Panax species. Previous studies determined that 55 polysaccharides from ginseng, 18 polysaccharides from American ginseng, and 9 polysaccharides from notoginseng exhibited anti-tumor activity, immunoregulatory effects, anti-oxidant activity, and other pharmacological functions, which are mediated by multiple signaling pathways, including mitogen-activated protein kinase, nuclear factor kappa B, or redox balance pathways. This review can provide new insights into the similarities and differences among the polysaccharides from the three Panax species, which can facilitate and guide further studies to explore the medicinal properties of the Araliaceae family used in traditional Chinese medicine.