Spectral indices to assess the carotenoid/chlorophyll ratio from adaxial and abaxial leaf reflectance

The ratio between the carotenoid and chlorophyll concentrations can indicate the physiology and phenology of plants. Most of the vegetation indices related to the ratio between the carotenoid and chlorophyll contents only consider the reflectance from the adaxial leaf surface. In this study, it was found that the leaf reflectance from the abaxial surface is lower than that of the adaxial surface in the visible wavelength region. On the contrary, the reflectance is higher on the adaxial surface in the near-infrared wavelength region. The difference ratio index resulted in the best correlation with the carotenoid/chlorophyll ratio and was the most robust among all the spectral indices studied when the spectral information on the adaxial and abaxial surfaces was pooled. The result indicated that this index can accurately estimate the carotenoid/chlorophyll ratio because of the insensitivity to the differences between adaxial and abaxial leaf surfaces.     

以间质隔离法研究CH3O分子在p-H2间质中的红外吸收光谱

本研究利用低温间质隔离技术搭配红外光谱仪研究CH3ONO在p-H2间质中的光解产生CH3O。实验观察到位于689.3/694.6cm-1、945.9/951.7cm-1、1041.8cm-1、1224.7cm-1、1235.5cm-1、1347.7cm-1、1365.4cm-1、1427.5cm-1、1519.5cm-1、1522.3cm-1等处的CH3O红外吸收谱线,并分析得出各振动模式分别为电子态E1/2a1对称性的ν6、电子态E1/2a2对称性的ν6、电子态E3/2对称性的ν2、电子态E3/2e对称性的ν6、电子态E1/2e对称性的ν6、电子态E1/2a1对称性的ν5、电子态E3/2对称性的ν2、电子态E1/2对称性的ν2、电子态E3/2e对称性的ν5及电子态E1/2e对称性的ν5。     

B、N掺杂对钠在石墨烯上吸附性能的影响

采用基于密度泛函理论的第一性原理方法,研究了本征石墨烯及缺陷石墨烯对Na原子的吸附行为。主要研究了三种石墨烯：本征石墨烯、B掺杂的石墨烯和N掺杂的石墨烯。结果表明,与本征石墨烯相比,B掺杂的石墨烯和N掺杂的石墨烯在吸附能、电荷密度、态密度和储钠量方面表现出很大的差异。B掺杂的石墨烯对Na原子的吸附能是-1.93 eV,约为本征石墨烯对Na原子吸附能的2.7倍;与本征石墨烯相比,N掺杂的石墨烯对Na原子的吸附能明显增大。态密度计算结果表明,Na原子与B掺杂的石墨烯中的B原子发生轨道杂化,而本征石墨烯和N掺杂的石墨烯中不存在轨道杂化现象。B掺杂的石墨烯对Na原子的吸附量是3个,与本征石墨烯相比显著提高。因此,B掺杂的石墨烯有望成为一种新型的储钠材料。     

基于准等重二甲基化标记的高通量蛋白质组选择性交叉标记装置

面对生物学及精准医学等领域多变量、大样本量的蛋白质组定量分析的需求,高通量的定量标记及分析已经成为近年来蛋白质组学方法发展的趋势。发展了一种基于准等重二甲基化标记策略的高通量肽段末端选择性交叉标记装置（pIDL-StageTip）,借助简单的装置及离心力,有效地增加了定量标记的通量,并保证了肽段末端两步标记反应时间的可控性及操作的简便性。通过优化酸性条件下NaBD₃CN与NaBH₃CN体系的标记条件,得到了标准蛋白质酶解产物100%的标记效率、95%以上的标记选择性;在人源蛋白质组复杂体系下,标记效率大于99%,标记选择性为100%。基于该装置的定量方法具有很高的定量准确度及精密度。该装置为实现高可操作性、高准确度、高通量的蛋白质组定量标记提供了一个可靠的解决方案。     

含等档的输电线面内自由振动理论

连续档导线运动方程包含平方和立方非线性项,倍频时会产生多模态耦合的复杂响应,因此研究连续档导线模态及共振的频率分布规律尤为重要．基于模态综合法获得了具有相等档距的连续档导线模态函数,基于动刚度理论得到了不同模态对应的频率理论公式,并应用有限元方法验证了模态及频率理论公式的准确性．研究了不同模态对应频率随几何参数的变化趋势,结果表明有相等档距的连续档导线的共振条件和单档导线有明显区别,连续档导线面内对称模态之间容易产生1:1共振,面内对称与反对称模态之间易产生1:2共振．本文研究内容可用来分析连续档导线内共振及其分岔行为．     

Photoconductive antenna as local oscillator in terahertz frequency measurement: heterodyne efficiency and bias effect

In a photoconductive antenna (PCA), femtosecond-laser-excited carriers will form a broadband terahertz photon-carrier (PC) comb, and the terahertz PC comb can be used as a multi-frequency local oscillator to carry out heterodyne detection of continuous terahertz sources with high frequency accuracy. In this paper, the heterodyne efficiency and the bias effects of a PCA terahertz PC comb are investigated. The results show that the pair beat signals (with the beat frequencies lower than the repetition frequency of femtosecond laser) of a continuous terahertz source and the two adjacent comb teeth do not decrease with the increase of beat frequency. Applying a bias voltage to the PCA can effectively enhance the terahertz emission efficiency. However, such a bias voltage has no positive effects on the heterodyne detection responsivity because the heterodyne detection is intrinsically based on the terahertz rectification effect that is proportional to the photo-excited electrons. In addition, by using a reference terahertz source with high frequency stability, it is possible to measure the fluctuation and the drift of the repetition frequency of femtosecond lasers with higher accuracy. The results are helpful for improving the performance of terahertz frequency measurement system based on PCA PC combs.     

利用糖芯片研究半乳寡糖与蓖麻凝集素和鸡冠刺桐凝集素间的相互作用

建立了用糖芯片技术研究寡糖与凝集素相互作用的方法.以新乳糖-N-四糖(LNnT)、乳糖-N-四糖(LNT)、λ-卡拉胶四糖(L4)和琼胶五糖(A5)为原料,经还原胺化法分别将其与1,2-十六烷基磷脂酰乙醇胺偶联得到拟糖脂,再将其与卵磷脂和胆固醇按4∶2∶5比例混合制备成脂质体后,用全自动芯片点样仪将其点印在硝酸纤维素膜包被的玻片上制成糖芯片,并进行寡糖与凝集素的结合实验.结果表明,蓖麻凝集素(Rieinus communis agglutinin 120,RCA120)特异性识别非还原端糖残基为Galβ(1 →4)的寡糖,而鸡冠刺桐凝集素(Erythrina cristagalli lectin,ECL)特异性识别非还原端糖残基为Galβ(1→4)GlcNAc的LNnT.采用接触式芯片点样仪制备糖芯片,并用荧光扫描仪对糖与凝集素结合信号进行检测,增加了灵敏度和准确性.本方法不仅适合于糖与蛋白相互作用的研究,也有助于加快糖类药物的发现.     

Determination of peimine and peiminine in Bulbus Fritillariae Thunbergii by capillary electrophoresis by indirect UV detection using N-(1-naphthyl)ethylenediamine dihydrochloride as probe

A simple and inexpensive CE method was developed for the determination of peimine and peiminine. Because of the lack of an UV chromophore of peimine and peiminine, the detection method chosen was indirect UV detection, with N‐(1‐naphthyl)ethylenediamine dihydrochloride (NED) as the UV absorbing probe. It was thought that NED, a chromophoric ion, may form hydrogen bonding pairs with the analytes to cause significant changes in separation selectivity. Additionally, the hydrophobic interactions between analytes and the probe also play a crucial role in achieving a resolution between the two analytes. The analyses were carried out with a background electrolyte composed of 66% MeOH–ACN (1:1, v/v), 34% aqueous buffer containing 15 mM NaH₂PO₄, 2.5 mM NED, 4 mM H₃PO₄. MeOH–ACN mixtures used as organic modifiers can not only reduce the adsorption of NED to the capillary wall, but also decrease the baseline noise and drift. The method provided a linear response ranging from 5 to 200 μg/mL. The limits of detection (LODs) for peimine and peiminine were 3.9 and 4.1 μg/mL, respectively. The repeatabilities (n = 3) reached relative standard deviation values (RSDs) of 3.4 and 4.1% for the peak areas, 4.0 and 4.4% for the peak heights, and 0.29 and 0.30% for the migration time of peimine and peiminine, respectively. Regression equations revealed linear relationships (r = 0.9995–0.9996) between the peak area of each analyte and the concentration. The method developed was successfully applied to quantify peimine and peiminine in chloroform extracts of the ground Bulbus Fritillariae Thunbergii.     

Monomeric adenine decay dynamics influenced by the DNA environment

We report on‐the‐fly surface‐hopping dynamics simulations of single adenine embedded in solvated DNA oligomers, (dA)₁₀ and (dA)₁₀·(dT)₁₀. Both model systems are found to decay from the S₁ to the S₀ state via distinct monomeric channels, on account of the strong hydrogen‐bonding interactions between the Watson–Crick pair in the double‐stranded oligomer. Surprisingly, the decay times (several picoseconds) for the current models are 10 times longer than those of adenine in the gas or aqueous phase, while matching one of the time constants observed experimentally. We discuss possible reasons for these longer decay times, including steric hindrance in the DNA strands, electronic effects of the environment, and the presence of other local excited‐state minima. We present optimized geometries and relative energies for representative S₀ and S₁ minima as well as conical intersections related to the hopping events. We have also computed steady‐state and time‐dependent fluorescence spectra that may help understand the experimental observations. © 2012 Wiley Periodicals, Inc.     

Color Point Tuning in Lu3−x−yMnxAl5−xSixO12:yCe3+ for White LEDs

A series of the solid‐solution phosphors Lu_3?x?yMn_xAl_5?xSi_xO₁₂:yCe³⁺ is synthesized by solid‐state reaction. The obtained phosphors possess the garnet structure and exhibit similar excitation properties as the phosphor Lu₃Al₅O₁₂:Ce³⁺, but with an effectively improved red component in the emission spectrum. This can be attributed to the energy transfer from Ce³⁺ to Mn²⁺. Our investigation reveals that electric dipole–quadrupole interactions dominate the energy‐transfer mechanism and that the critical distance determined by the spectral overlap method is about 9.21 Å. The color‐tunable emissions of the Lu_3?x?yMn_xAl_5?xSi_xO₁₂:yCe³⁺ phosphor as a function of Mn₃Al₂Si₃O₁₂ content are realized by continuously shifting the chromaticity coordinates from (0.354, 0.570) to (0.462, 0.494). They indicate that the obtained material may have potential application as a blue radiation‐converting phosphor for white LEDs with high‐quality white light.