Improved quantitative capillary GC by the use of CO2 as secondary coolant in cold on-column injection

A comparison is made between air and carbon dioxide as secondary cooling gases in cold on-column injection into capillary columns. Because CO₂ is a more effective coolant than air, the injection zone can be kept at a colder temperature, thus preventing loss of sample vapor through the open injector even as the initial oven temperatures because greater than the boiling point of the solvent. Sample loss at these elevated temperatures is shown as a reduction in peak area as functions of column temperature during injection and different injection zone temperatures. The maximum allowable oven temperature during injection is significantly higher when CO₂ is used as secondary coolant rather than air.     

确定单光子计数系统中最佳甄别电压的实验研究

在光电倍增管相关理论的基础上从改变功率、积分时间、减光片、阴极电子加速电压等方面,通过实验利用Matlab软件对曲线进行拟合,通过该方法得到了光子计数率与功率、信噪比与功率、信噪比与积分时间之间的关系以及光电倍增管的相关特性.最后确定了单光子计数系统中最佳甄别电压的具体方法.     

A novel adenosine-based molecular beacon probe for room temperature nucleic acid rapid detection in cotton thread device

We used cotton thread as substrate to develop a novel room temperature DNA detection device for low-cost, sensitive and rapid detection of a human genetic disease, hereditary tyrosinemia type I related DNA sequences. A novel adenosine based molecular beacon (ABMB) probe modified on gold nanoparticle was used as reporter probe. In the presence of coralyne, a small molecule which can react with adenosines, the ABMB would form a hairpin structure just like traditional molecular beacon used extensively. In the presence of target DNA sequences, the hairpin structure of ABMB modified on gold nanoparticles will be opened and the biotin group modified at one end of the DNA probes will be released and react with the streptavidin immobilized on the test zone of the cotton thread. The response of the thread based DNA test device is linear over the range of 2.5–100 nM complementary DNA. The ability of our developed device for discriminating the single base mismatched DNA related to a human genetic disease, hereditary tyrosinemia type I, was improved comparing with previous report. It is worth mentioning that the whole assay procedure for DNA test is performed under room temperature which simplified the assay procedures greatly.     

Screening and characterizing the quality markers of Selaginella tamariscina (P. Beauv.) Spring using metabonomics and molecular networking

Quality control of traditional Chinese medicine (TCM) should be linked with the authentication and efficacy of TCM. Selaginella tamariscina is a frequently used traditional Chinese herbal medicine. However, its quality control is still difficult due to its multiple adulterants. We established quality markers (Q-markers) of S. tamariscina by using metabolomics, molecular networking and network pharmacology to improve the authenticity study and quality control of S. tamariscina. In this study, ultra high performance liquid chromatography-mass spectrum (UHPLC-MS) coupled with multivariate statistical analyses was applied to distinguish between S. tamariscina samples and their confusing adulterants. Principal component analysis, hierarchical clustering analysis (PCA), hierarchical clustering analysis (HCA) and partial least squares discriminant analysis (PLS-DA) were employed to screen the distinguishing markers from S. tamariscina samples and their adulterants. The top-2 distinguishing markers were isolated from S. tamariscina and identified by molecular networking together with nuclear magnetic resonance spectroscopy (NMR). Network pharmacology predicted the bioactivity and cytotoxicity of the top-2 distinguishing markers. The top-2 distinguishing markers were adopted as Q-markers of S. tamariscina for content determination. Based on the results of ultra performance liquid chromatography-quardrupole-time of flight mass spectrometry (UHPLC-QTOF-MS) metabolomics, we revealed that selaginellins could only be detected in S. tamariscina samples and contributed greatly to discriminating S. tamariscina samples from their confused species. The top-2 distinguishing markers were isolated and purified from S. tamariscina extract. Then, they were further identified as selaginellin and selaginellin A by molecular networking and NMR. Network pharmacology predicted the antitumor activity of selaginellin and selaginellin A, while the cytotoxicity assay verified their bioactivity. In conclusion, selaginellin and selaginellin A were selected as Q-markers for the determination and quality evaluation of S. tamariscina based on ultra performance liquid chromatography-triple quadrupole tandem mass spectrometry (UHPLC-QQQ-MS). The ranges of the concentrations of selaginellin and selaginellin A were 41.57–44.89 μg/g and 15.09–16.75 μg/g, respectively. This study provides a novel strategy combining Ultra performance liquid chromatography mass spectrometry based (UHPLC-MS-based) metabolomics with molecular networking for rapid species identification of S. tamariscina and discovery of the Q-markers of TCM.     

Classification of Unifloral Honeys from SARDINIA (Italy) by ATR-FTIR Spectroscopy and Random Forest

Nowadays, the mislabeling of honey floral origin is a very common fraudulent practice. The scientific community is intensifying its efforts to provide the bodies responsible for controlling the authenticity of honey with fast and reliable analytical protocols. In this study, the classification of various monofloral honeys from Sardinia, Italy, was attempted by means of ATR-FTIR spectroscopy and random forest. Four different floral origins were considered: strawberry-tree (Arbutus Unedo L.), asphodel (Asphodelus microcarpus), thistle (Galactites tormentosa), and eucalyptus (Eucalyptus calmadulensis). Training a random forest on the infrared spectra allowed achieving an average accuracy of 87% in a cross-validation setting. The identification of the significant wavenumbers revealed the important role played by the region 1540–1175 cm⁻¹ and, to a lesser extent, the region 1700–1600 cm⁻¹. The contribution of the phenolic fraction was identified as the main responsible for this observation.     

Remote interactions on two distributed quantum systems： nonlocal unambiguous quantum-state discrimination

Remote quantum-state discrimination is a critical step for the implementation of quantum communication network and distributed quantum computation. We present a protocol for remotely implementing the unambiguous discrimination between nonorthogonal states using quantum entanglements, local operations, and classical communications. This protocol consists of a remote generalized measurement described by a positive operator valued measurement （POVM）. We explicitly construct the required remote POVM. The remote POVM can be realized by performing a nonlocal controlled-rotation operation on two spatially separated qubits, one is an ancillary qubit and the other is the qubit which is encoded by two nonorthogonal states to be distinguished, and a conventional local Von Neumann orthogonal measurement on the ancilla. The particular pair of states that can be remotely and unambiguously distinguished is specified by the state of the ancilla. The probability of successful discrimination is not optimal for all admissible pairs. However, for some subset it can be very close to an optimal value in an ordinary local POVM.     

一种用于旋转不变分类识别的线性判别函数

提出利用线性判别函数，ｄ（ｘ）＝Ｗ＇ｘ，对轰炸机和战斗机两类目标进行旋转不变识别。每一目标有７２个旋转模式，其中９个为训练样本，６３个为测试样本，在每个目标的训练样本中随机取一个相减作为线性判别函数的系数（Ｗｉｊ）的初始值，然后利用误判的训练样本优化判别函数的权值以提高函数的正确识别率。为便于光电实现，线性判别函数的权值系数只有２、１、０、－１、－２五个值。计算机模拟表明利用此判别函数进行分类的正     

On the classification of observations structured into groups

The paper is concerned with the problem of classifying a specific group into two populations (insect eggs of the same clutch belonging therefore to the same species). Two approaches, one parametric and the other non-parametric, are described. The classical likelihood ratio procedure is derived. An interpretation and a decomposition of the test criteria is given. A misclassification estimate using the Chernoff–Kullback–Kailath region is provided.     

α-氨基丁酸对映异构体在DMF+水混合溶剂中的焓对作用

利用等温滴定微量热法(ITC)分别测定了298.15K时L-α-氨基丁酸和D-α-氨基丁酸两种对映异构体在不同组成的二甲基甲酰胺(DMF)+水混合溶剂中的稀释焓.根据统计热力学的McMillan-Mayer理论计算各溶剂组成下的同系焓对作用系数(hxx).从溶质-溶质和溶质-溶剂相互作用的观点出发探讨了三元水溶液中疏水-疏水、疏水-亲水和亲水-亲水作用的竞争平衡.实验发现,在所研究的混合溶剂组成范围内(wDMF=0-0.3),α-氨基丁酸两种对映体的hxx都是较大的正值,且都随wDMF的增大而逐渐减小,而有趣的是L型对映体的hxx值普遍比D型的大(hLLhDD),说明ITC可以区分对映异构体的同手性焓对作用.结果表明:在α-氨基丁酸+水+DMF三元溶液体系中,疏水-疏水和疏水-亲水作用在分子对作用过程中占优势;在α-氨基丁酸的同种对映体发生分子对作用时,L-L分子对比D-D分子对在构型上更有利于α-碳上疏水侧链(CH3CH2-)的靠拢,疏水基团的水合壳层发生交盖,局部破坏而释放出部分结构化的水,过程自发、吸热且伴随显著熵增(ΔG0,ΔH0,ΔS=(ΔH-ΔG)/T0),因而在稀释时释放出更多热量,hxx具有较大的正值.     

分子模型及其在手性识别机理研究上的应用

介绍了近十几年来在色谱手性识别机理研究中的分子模型。在这些模型中,采用量子力学、分子力学和分子动力学等方法计算了手性选择试剂与对映体之间的相互作用,并借助X射线晶体学、核磁共振技术和计算机模拟等技术建立了各种分子模型,研究在手性化合物分离过程中的手性识别机理。