Diatomic potential well depths from analyses of high-resolution electron energy spectra for autoionizing collision complexes

High-resolution energy spectra of electrons released in Penning ionization collisions of metastable rare gas atoms Rg*(ns) (Rg = He, Ne, Ar, Kr, Xe) with several open-shell and closed-shell atoms are analyzed to determine the well depth of the potential energy curve which describes the respective autoionizing collision complex. We thereby elucidate trends in the chemical interaction of Rg* with closed-shell target atoms A(ns ²) and establish a basis for detailed comparison with the respective interactions involving open-shell, ground state alkali atoms A(ns). From electron energy spectra due to␣associative ionization (RgH⁺ formation) in Rg* + H(1s) collisions, we determine binding energies for the RgH⁺(¹Σ) ground state potential (Rg = Ne, Ar, Kr, Xe) with uncertainties around 0.03 eV. Received: 30 June 1998 / Accepted: 5 August 1998 / Published online: 28 October 1998     

Surface composition of alloys

The practical importance of alloy surfaces in catalysis, corrosion andother aspects of materials performance is widely recognized. What is needed now is sufficient knowledge of the relationship between externally controllable factors — alloy composition, temperature, environment — and surface properties — composition, structure, chemical activity — to control materials performance in these applications. Our purpose here is to review progress in determining and predicting the relationship between one surface property, composition, and certain externally controllable variables: overall composition, temperature, environment and physical form.We find that theoretical treatments of metal alloy surface composition now include essentially all significant physical effects and can predict values for most parameters of interest. Though improvements are still possible, the accuracy of predictions is more often limited by uncertainties or absence of the basic data for the calculations (e.g., thermochemical values) than by the models themselves.Alloy surface composition can now be measured well. The first monolayercomposition of large alloy slabs can be determined quantitatively over a wide temperature range in ultra-high vacuum. Difficulties with specimens of practical interest still challenge experimentalists. Among these are supported catalysts, surfaces under chemisorbed layers and composition of layers below the first. Significant progress is being made and we expect the next few years will see success.     

Determination of steryl sulphates in invertebrate tissue by liquid chromatography–tandem mass spectrometry

A method for the identification and quantification of underivatised steryl sulphates in invertebrates by liquid chromatography (LC) coupled with tandem mass spectrometry (MS) involving a single cleanup step has been developed. Negative electrospray ionisation and positive and negative atmospheric-pressure chemical ionisation (APCI) spectra of steryl sulphate showed pseudomolecular ions ([M+H–H₂SO₄]⁺or [M–H]⁻). Collision-induced dissociation (CID) was efficient only in positive APCI. LC-MS in negative APCI was least susceptible to interference and possible differences in response factors. The detection limits (signal-to-noise ratio of 3) based on cholest-5-enyl-3-sulphate in positive and negative APCI modes are 3.66 and 0.73 pmol μL⁻¹, respectively. Calibration plots and response factors for cholest-5-enyl-3-sulphate relative to the internal standard, cholecalciferyl-3-sulphate, in both positive and negative polarities, were linear in the concentration range from 1.22 to 16.4 pmol μL⁻¹ with good coefficients of determination (R ²>0.98). It is suggested that the structure elucidation of steryl sulphates is best achieved in CID positive APCI mode, whereas their quantification should be carried out using negative APCI.     

Flow tagging velocimetry in a superorbital expansion tube

Abstract. A non-intrusive laser-based method for direct velocity measurements has been demonstrated in a superorbital flow facility. The method is based upon laser enhanced ionisation velocimetry in which a tagged region is created by two step excitation of sodium and subsequent collisional ionisation. The achieved depletion of neutral atoms is then interrogated by planar laser induced fluorescence. The velocities were measured in the freestream at a superorbital condition yielding km/s. These results compare favourably with the measured shock speeds in the facility. Received 15 March 1999 / Accepted 2 March 2000     

Review on recent and advanced applications of monoliths and related porous polymer gels in micro-fluidic devices

This review critically summarises recent novel and advanced achievements in the application of monolithic materials and related porous polymer gels in micro-fluidic devices appearing within the literature over the period of the last 5 years (2005-2010). The range of monolithic materials has developed rapidly over the past decade, with a diverse and highly versatile class of materials now available, with each exhibiting distinct porosities, pore sizes, and a wide variety of surface functionalities. A major advantage of these materials is their ease of preparation in micro-fluidic channels by in situ polymerisation, leading to monolithic materials being increasingly utilised for a larger variety of purposes in micro-fluidic platforms. Applications of porous polymer monoliths, silica-based monoliths and related homogeneous porous polymer gels in the preparation of separation columns, ion-permeable membranes, preconcentrators, extractors, electrospray emitters, micro-valves, electrokinetic pumps, micro-reactors and micro-mixers in micro-fluidic devices are discussed herein. Procedures used in the preparation of monolithic materials in micro-channels, as well as some practical aspects of the micro-fluidic chip fabrication are addressed. Recent analytical/bioanalytical and catalytic applications of the final micro-fluidic devices incorporating monolithic materials are also reviewed.     

原子核质量精密测量的研究进展

原子核质量的精密测量是原子核物理学的重要课题之一,它对探索奇特原子核的结构和性质、重元素核合成之谜等均具有重大意义.文章简要介绍了原子核质量高精度测量的两个主要设备——储存环和潘宁阱,并回顾了近年来原子核质量精密测量在核结构、元素核合成、新同核异能素等领域中的研究亮点,探讨原子核质量测量的发展趋势.     

Application of dried blood spots combined with high-performance liquid chromatography coupled with electrospray ionisation tandem mass spectrometry for simultaneous quantification of vincristine and actinomycin-D

A sensitive, specific and efficient high-performance liquid chromatography-tandem mass spectrometry assay for the simultaneous determination of vincristine and actinomycin-D in human dried blood spots is presented. Dried blood spots were punched out of a collection paper with a 0.25-in.-diameter punch. The analytes were extracted from the punched-out disc using sonication during 15 min in a mixture of acetonitrile–methanol–water (1:1:1, v/v/v) containing the internal standard vinorelbine. Twenty-microlitre volumes were injected onto the HPLC system. Separation was achieved on a 50 × 2.1 mm ID Xbridge C₁₈ column using elution with 1 mM ammonium acetate–acetonitrile (70:30, v/v) adjusted to pH 10.5 with ammonia and run in a gradient with methanol at a flow rate of 0.4 mL/min. HPLC run time was 6 min. The assay quantifies vincristine from 1 to 100 ng/mL and actinomycine-D from 2 to 250 ng/mL using a blood sample obtained by a simple finger prick. Validation results demonstrate that vincristine and actinomycin-D can be accurately and precisely quantified in human dried blood spots with the presented method. The assay can now be used to support clinical pharmacologic studies with vincristine and actinomycin-D.     

A study of the analytical behaviour of selected synthetic and naturally occurring quinolines using electrospray ionisation ion trap mass spectrometry, liquid chromatography and gas chromatography and the construction of an appropriate database for quinoline characterisation

Mass spectral fragmentation of quinoline alkaloids of significance in plants has been investigated using electrospray ionisation ion trap mass spectrometry (ESI-MSⁿ) with a view to characterisation of molecules of unknown structure isolated from these natural sources. This investigation has led to the generation of an appropriate database incorporating data from ESI-MSⁿ and also from gas liquid chromatography (GLC) and liquid chromatography (HPLC) for these low molecular mass quinolines. This has been put to practical application in the identification of quinoline alkaloids in a plant extract. Thus, an acid extraction of the leaves of Choisya ternata containing such tertiary alkaloids was analysed by liquid chromatography-electrospray ionisation mass spectrometry (HPLC-ESI-MS) and the resulting behaviour of the quinolines was compared with that of the quinoline alkaloids in the database.