Ultraviolet upconversion luminescence enhancement in Yb/Er-codoped Y2O3 nanocrystals induced by tridoping with Li ions

Ultraviolet (UV) upconversion (UC) luminescence in Yb³⁺/Er³⁺-codoped yttrium oxide (Y₂O₃) nanocrystals can be enhanced by orders of magnitude via tridoping further with Li⁺ ions under diode laser excitation of 970 nm. Sensitized three-photon UC radiations at 390 and 409 nm, corresponding to the ⁴G_11/2→⁴I_15/2 and ⁴H_9/2→⁴I_15/2 of Er³⁺ ions, respectively, present an enhancement time of about 33 times, which is larger than the 24 times enhancement for the UC green radiation. The UV UC radiation at 320 nm that corresponds to the ²P_3/2→⁴I_15/2 of Er³⁺ ions has also been greatly enhanced. Theoretical calculations interpret that all the observed enhancement times of UV UC radiations arise from the prolonged lifetimes of their intermediate states.     

Ultraviolet upconversion luminescence in Er-doped Y2O3 excited by 532 nm CW compact solid-state laser

Ultraviolet upconversion emissions at 262, 276, 308 and 320 nm were observed from Er³⁺-doped Y₂O₃ with a 532 nm continuous wave compact solid-state laser excitation. Power-dependence analysis demonstrates that two-photon upconversion process populates the ⁴D_5/2, ²H_9/2 and ²P_3/2 states. The energy transfer upconversion (ETU) plays an important role in populating ⁴D_5/2 and ²P_3/2 states. It appears that ²P_3/2 state population originates from ETU ²H_11/2+²H_11/2→⁴I_13/2+²P_3/2, moreover, a subsequent excited state absorption (ESA) from the ⁴I_9/2 level.     

以三种非极性氨基酸为例探讨氨基酸合成代谢的化学原理

由于氨基酸代谢的多样性和相对独立性,在基础教学中对相关内容的讨论和推广对培养21世纪新型跨学科人才是极其重要的。本文将以三种基本的非极性天然氨基酸——缬氨酸、异亮氨酸和亮氨酸为例,从氨基酸合成代谢的内容和方式等方面做教学模式的探索,并尝试归纳与总结自然界采取这样代谢路径的原因和逻辑。同时,其中相关的生物化学过程也体现出生命体系所采取的不同寻常的合成路径和反应机制。这对于本科生而言不仅是具有趣味性与启发性的良好的素材,也是了解目前研究热点和积累知识的有效渠道,期望对其后续深入的学习和研究有帮助。     

Fixation capability of recycling materials as potential additives for cesium immobilization in contaminated forest soil

The fixation capability of cesium on five recycling materials was compared through two sets of sorption experiments using the materials mixed with and without soil. The estimated Freundlich constant K and the distribution of sorbed cesium on the materials revealed a general order of the fixation capability as carbonized sludge > coconut shell biochar > incinerated sewage sludge ash > rice husk biochar > slag. Parametric strong positive correlations were found existent between the fixation capability of cesium and the property-related indexes of the materials such as cation exchange capacity, organic matter content and the potassium concentration.

     

双分子层膜人工离子通道的合成

离子通道(ion channels)是由细胞膜上的一类特殊亲水性蛋白质构成的微孔道,它的主要功能就是传输离子跨膜,相当于细胞的通气孔。其结构与功能的异常往往引起上千种疾病,统称为离子通道病,这种疾病目前不能靠常规的仪器来检查,在确诊上有一定的难度。因此通过化学手段合成人工离子通道来模拟生物体内细胞膜上的离子通道的结构与功能,对于深入研究这些疾病并发现特异性治疗药物均具有十分重要的理论和实际意义。本论文就近三十年来人们设计合成的不同种类人工离子通道进行了综述,介绍了其研究进展并总结了各种人工离子通道的分子结构设计以及在膜上传输离子行为,展望了其在模拟天然离子通道功能的同时在生物医药以及生命科学等领域的应用前景。     

高效液相色谱法测定水产品中残留的吡喹酮

建立了一种灵敏度高、操作简单的定量分析水产品中残留的微量吡喹酮的高效液相色谱方法。样品经乙酸乙酯提取、极性硅胶柱净化后进行高效液相色谱分析,以乙腈-水(体积比为50∶50)为流动相,流速为0.9 mL/min,ZORBAX C18色谱柱分离,紫外检测波长为214 nm。在此条件下吡喹酮在0.02～20 mg/L范围内呈线性关系,相关系数为0.99998;吡喹酮的加标回收率在85%以上,检出限为10 μg/kg。     

pVT系统的独立可测偏导数的确定

与可测量α(等压膨胀系数 )、β(等温压缩系数 )、Ｃｐ(恒压热容 )直接相关的 3个偏导数 Ｖ Ｔ ｐ, Ｖ ｐ Ｔ和 Ｓ Ｔ ｐ为独立可测偏导数。“独立”的意思是指这 3个偏导数完全确定了单纯ｐＶＴ系统的平衡性质。在教学中如能从理论上加以论证对学生是有益的 ,下面我们应用热力学特性函数的概念说明这 3个偏导数的独立性。1　热力学特性函数　　有了状态方程、内能和熵这 3个最基本的热力学函数以后 ,均匀系的平衡性质就完全确定了 ,这是因为一切其他热力学函数都可由这 3个基本函数导出[1] 。而且这 3个基本函数相应于 3个基本规律 ,一是…     

高效液相色谱法测定染发剂中的22种染料成分

建立了染发剂中22种染料成分的高效液相色谱测定方法。使用Discovery RP-Amide C16柱(250 mm×4.6 mm,5 μm),以乙腈-0.025 mol/L磷酸盐缓冲液(pH 6.0,含0.1%的庚烷磺酸钠离子对试剂)为流动相,流速为1.0 mL/min;使用二极管阵列检测器(DAD),检测波长为260 nm和280 nm,柱温为25 ℃。该方法除了对低浓度的甲苯-2,5-二胺硫酸盐、2-甲基雷锁辛和N,N-二乙基甲苯-2,5-二胺HCl外,对其他各组分的含量测定值的相对标准偏差(RSD)均小于10%,加标回收率为77.6%～122.8%。该方法简便、准确、快速,适于氧化型染发剂中染料成分的检测。     

Channel noise-induced temporal coherence transitions and synchronization transitions in adaptive neuronal networks with time delay

Using spike-timing-dependent plasticity (STDP), we study the effect of channel noise on temporal coherence and synchronization of adaptive scale-free Hodgkin-Huxley neuronal networks with time delay. It is found that the spiking regularity and spatial synchronization of the neurons intermittently increase and decrease as channel noise intensity is varied, exhibiting transitions of temporal coherence and synchronization. Moreover, this phenomenon depends on time delay, STDP, and network average degree. As time delay increases, the phenomenon is weakened, however, there are optimal STDP and network average degree by which the phenomenon becomes strongest. These results show that channel noise can intermittently enhance the temporal coherence and synchronization of the delayed adaptive neuronal networks. These findings provide a new insight into channel noise for the information processing and transmission in neural systems.     

基于乙酸为溶剂和催化剂的芳乙酮Mannich反应

采用乙酸作溶剂和催化剂, 将芳乙酮与甲醛和二级胺进行Mannich反应及热解反应, 并未得到预期的Mannich碱或α,β-不饱和酮(2), 而是以较高产率(65%~73%)生成了乙酸(2-芳甲酰基)烯丙酯(3a~3o). 通过核磁共振波谱、 高分辨质谱和红外光谱表征了化合物3a~3o的结构, 研究了此“异常”反应的发生条件, 并提出了可能的反应机理. 结果表明, 芳乙酮的特殊结构及反应中过量的乙酸是产生化合物3a~3o的决定因素.