Fluorescence assay of tyrosine in blood plasma

A more simple and sensitive assay for the quantitative determination of tyrosine in blood plasma is developed on the basis of a modification of the method of S. Udenfriend (1962). A volume of 0.2 ml of plasma is used in the analysis; after its deproteinization with trichloroacetic acid, it is reacted with sodium nitride, nitrous acid, and 1-nitroso-2-naphthol at 65°C, and the content of the reaction product is measured by the fluorescence at λ_ex/λ_em=460/570 nm. The consumption of plasma and reagents is reduced by a factor of 5–10 compared to the original method; in addition, the stage of extraction with an organic solvent is excluded. The linear dependence of the fluorescence signal on the tyrosine concentration within the range of 2–60 μg/ml, high specificity, accuracy, and reproducibility of the assay are shown. The importance of tyrosine determination in monitoring of glucocorticoid therapy and protein catabolism is discussed. Institute of Photobiology, National Academy of Sciences of Belarus, 27, Akademicheskaya St., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 366–371, May–June, 1998.     

4-Aminophthalimide Derivatives as Environment-Sensitive Probes

The potential of 4-aminophthalimide (AP) and its derivatives as fluorescence probes for organized media is highlighted. The fluorescence response of AP, as measured from the position of the fluorescence maximum, fluorescence intensity and lifetime, is highly sensitive to the polarity of the medium. The sensitivity of the fluorescence parameters is further enhanced due to the involvement of the emitting intramolecular charge transfer state in hydrogen bonding interaction with the solvent molecules containing hydroxyl groups. It is shown that the microheterogeneous environments of organized media such as cyclodextrins and micelles can be very conveniently monitored using this probe. The results of the investigations carried out employing AP and its derivatives as fluorescence probe molecules in these media clearly suggest that a combination of the hydrophobic interaction with the host media and hydrogen bonding interaction with the solvent molecules determine the location of the fluorophore, which in all cases is found to be the interfacial region separating the nonpolar core of the micelle or the cyclodextrin cavity and the polar aqueous environment. Guidelines for the design of probes of this class of systems for the nonpolar core region of the micelles are provided and possible ways to increase the sensitivity of the fluorescence response of the systems are suggested.     

用于激光吸收和散射光能量测量的4π盒式卡计

报道了国内第一台用于ＩＣＦ实验散射光和激光吸收能量精密测量的４π盒式卡计。性能测试表明，该盒式卡计的性能优于国外用热电堆作传感元件的盒式卡计的性能。     

全内反射瞬逝场照明高精度磁镊及其在DNA解旋酶研究中的应用

传统磁镊的测量精度受限于磁球的布朗涨落, 当磁力小于约10 pN时, 磁球的布朗涨落明显增大, 对应磁镊的空间分辨率显著下降. 为了提高传统磁镊在小力条件下的测量精度, 本文将全内反射荧光技术引入到磁镊技术中, 并建立相适应的“磁球-手柄-荧光微球-待测生物分子”单分子连接系统, 在小力条件下(小于10 pN)获得纳米量级的测量精度. 应用改进的磁镊对DNA发卡的折叠-去折叠态的转变过程进行了研究, 依据DNA发卡的折叠-去折叠态转变的性质对全内反射场的穿透深度进行了校正, 并结合实验结果对改进后的磁镊的测量精度进行分析. 观察了Bloom解旋酶的解旋动力学过程, 获得初步实验结果, 证实了改进的磁镊在单分子研究中的实用性. 关键词： 磁镊 全内反射荧光 DNA发卡 解旋酶     

原子荧光光谱法研究贝壳堤岛贝壳沙中As的空间分布特征

用原子荧光光谱法测定了贝壳沙中As元素含量,研究了As在黄河三角洲贝壳堤岛贝壳沙中的空间分布规律,分析了贝壳沙中As与其他营养元素的相关性,并对影响其含量与空间分布的因素进行探讨。结果表明：贝壳沙样品中As的含量范围为0.78～8.76 mg·kg-1,平均值为3.11 mg·kg-1,整体上处于清洁的水平。贝壳沙中As含量有随剖面深度增加而增大的趋势,贝壳沙粒径大小也影响贝壳沙中As的含量,贝壳沙粒径越小,As含量越高,且不同粒径贝壳沙中As含量差异显著(p≤0.05)。贝壳沙中As与全磷(total phosphor,TP)和全钾(total potassium,TK)以及Cu, Zn, Mn均具有极显著的正相关关系,与全氮(total nitrogen,TN)和Fe的相关性不显著。综合分析认为,贝壳沙中As主要来自于风化后的贝壳沙对环境中As元素的吸附与固定而非贝壳形成过程中对该元素的富集作用。     

原位微区X射线荧光分析在矿物学研究中的应用

从新疆采集了13件岩矿石样品,用于研究蚀变过程中矿物的元素含量变化特征。成都理工大学研制的IED-6000型原位微区X射线荧光分析仪被应用于获得蚀变过程中矿物的化学和物理数据。这种无损的微区X射线荧光分析仪主要是以低功耗X光管和电致冷Si-PIN半导体探测器为基础,采用毛细管X射线透镜实现微区测量的功能,并且能够集成到任何显微镜上进行测量,焦斑长轴直径约110 μm。通过微区X射线荧光测量,将黝铜矿更正为黄铁矿,提高了矿物鉴定的效率及准确性;在蚀变剖面研究中,矿化岩石样品的长石颗粒都富含Cu和Zn元素,可以作为找矿直接指示元素。Cr,Mn和Co等元素含量与矿化程度呈负相关。     

Tm3+,Yb3+共掺钨酸钙多晶材料的上转换发光及荧光温度特性

采用高温固相法制备了Tm³⁺,Yb³共掺CaWO₄多晶材料. 980 nm二极管激光器激发下,在可见区获得了¹G₄→³H₆,¹G₄→³H₄,³H₂,³H₃→³H₆ 跃迁产生的上转换荧光. 讨论了Yb³⁺ 离子浓度的变化对Tm³⁺ 的上转换发光强度的影响,同时根据荧光强度比的方法研究了689 和705 nm 红色上转换荧光在313–773 K 范围内的温度特性. 结果表明：基于Tm³⁺,Yb³⁺ 共掺CaWO₄ 多晶材料的红色上转换荧光可以实现温度监测,其测温的最大灵敏度值为5.7×10^-4 K^-1,相应的测量温度为458 K. 关键词： 上转换发光 3+')" href="#">Tm³⁺ 钨酸钙 荧光温度传感     

New Interfaces and Approaches to Machine Learning When Classifying Gestures within Music

Interactive music uses wearable sensors (i.e., gestural interfaces—GIs) and biometric datasets to reinvent traditional human–computer interaction and enhance music composition. In recent years, machine learning (ML) has been important for the artform. This is because ML helps process complex biometric datasets from GIs when predicting musical actions (termed performance gestures). ML allows musicians to create novel interactions with digital media. Wekinator is a popular ML software amongst artists, allowing users to train models through demonstration. It is built on the Waikato Environment for Knowledge Analysis (WEKA) framework, which is used to build supervised predictive models. Previous research has used biometric data from GIs to train specific ML models. However, previous research does not inform optimum ML model choice, within music, or compare model performance. Wekinator offers several ML models. Thus, we used Wekinator and the Myo armband GI and study three performance gestures for piano practice to solve this problem. Using these, we trained all models in Wekinator and investigated their accuracy, how gesture representation affects model accuracy and if optimisation can arise. Results show that neural networks are the strongest continuous classifiers, mapping behaviour differs amongst continuous models, optimisation can occur and gesture representation disparately affects model mapping behaviour; impacting music practice.     

一种快速测量共聚焦X射线分析装置探测微元尺寸方法

共聚焦X射线荧光技术是一种无损的三维光谱分析技术,在材料,生物,矿物样品分析,考古,证物溯源等领域具有广泛应用。共聚焦X射线荧光谱仪的核心部件为两个多毛细管X光透镜。一个为多毛细管X光会聚透镜（PFXRL）,其存在一后焦点,作用是把X光管所发出的发散X射线会聚成几十微米大小的高增益焦斑。另一透镜为多毛细管X光平行束透镜（PPXRL）,其存在一几十微米大小前焦点,置于X射线能量探测器前端,其作用是接收特定区域的X射线荧光信号。在共聚焦Ｘ射线荧光谱仪中,PFXRL的后焦点与PPXRL的前焦点重合,所形成的区域称作探测微元。只有置于探测微元区域的样品能够被谱仪检测到,使样品与探测微元相对移动,逐点扫描,便能够对样品进行三维无损的X射线分析。探测微元的尺寸决定共聚焦X射线荧光谱仪的空间分辨率,因此精确测量谱仪的探测微元的尺寸是非常重要的。如图1所示,谱仪探测微元可以近似为椭球体,其尺寸可以用水平方向分辨率X, Y,和深度分辨率Z表示。目前,常采用金属细丝或金属薄膜通过刀口扫描的方法测量谱仪探测微元尺寸。为了精确的从三个维度测量探测微元尺寸,金属细丝直径要小于探测微元尺寸。金属细丝和探测微元都是数十微米级别的尺寸大小,很难把金属靠近探测微元。为了得到探测微元在不同X射线能量下尺寸变化曲线,要采用多种金属细丝测量。采用单个金属细丝依次测量比较耗费时间。采用金属薄膜可以很方便地测量探测微元的深度分辨率Z,但是当测量水平分辨率X, Y时,难以准确测量。为了解决以上谱仪探测微元测量中存在的问题,本文提出采用多种金属丝平行粘贴在硬纸片上作为样品用于快速测量探测微元尺寸。附有金属细丝的硬纸片靠近谱仪探测微元,可以将探测微元置于硬纸片所在平面。由于硬纸片与金属细丝在同一水平面,在谱仪摄像头的协助下,可以把金属细丝迅速的靠近探测微元。靠近探测微元后,在全自动三维样品台的协助下,金属细丝沿两个方向对探测微元分别进行一次二维扫描。通过对二维扫描数据的处理便可以获得探测微元尺寸随入射X射线能量变化曲线。采用此方法对实验室所搭建的共聚焦X射线荧光谱仪的探测微元进行了测量。     

Robust reward–risk ratio optimization with application in allocation of generation asset

In this article, we study reward–risk ratio models under partially known message of random variables, which is called robust (worst-case) performance ratio problem. Based on the positive homogenous and concave/convex measures of reward and risk, respectively, the new robust ratio model is reduced equivalently to convex optimization problems with a min–max optimization framework. Under some specially partial distribution situation, the convex optimization problem is converted into simple framework involving the expectation reward measure and conditional value-at-risk measure. Compared with the existing reward–risk portfolio research, the proposed ratio model has two characteristics. First, the addressed problem combines with two different aspects. One is to consider an incomplete information case in real-life uncertainty. The other is to focus on the performance ratio optimization problem, which can realize the best balance between the reward and risk. Second, the complicated optimization model is transferred into a simple convex optimization problem by the optimal dual theorem. This indeed improves the usability of models. The generation asset allocation in power systems is presented to validate the new models.