Direct observation of macropore self-formation in hierarchically structured metal oxides

The current work presents an unprecedented direct observation of macropore formation in the spontaneous self-assembly process to obtain hierarchical meso/macroporous metal oxides made possible with the help of an unusual titanium alkoxide.     

Raman active soft modes and phase transitions in sodium tungsten bronzes

The temperature dependence of the Raman spectra of Na_xWO₃ for x > 0.5 is reported. A group theoretical analysis of the data confirms the space group assignments of Clarke⁸ and supports the existence of several phases derived from rigid tilts of the WO₆ octahedra. The phase diagram for high concentration Na_xWO₃ deduced from Raman measurements is in excellent agreement with that obtained from x-ray results particularly with regard to the previously undetected tetragonal to tetragonal transition.     

High precision delta(17)O isotope measurements of oxygen from silicates and other oxides: method and applications

The use of infrared laser-assisted fluorination to release oxygen from milligram quantities of silicates or other oxide mineral grains is a well-established technique. However, relatively few studies have reported the optimisation of this procedure for oxygen-17 isotope measurements. We describe here details of an analytical system using infrared (10 μm) laser-assisted fluorination, in conjunction with a dual inlet mass spectrometer of high resolving power ( approximately 250) to provide (17)O and (18)O oxygen isotope measurements from 0.5-2 mg of silicates or other oxide mineral grains. Respective precisions (1) of typically 0.08 and 0.04 per thousand are obtained for the complete analytical procedure. Departures from the mass-dependent oxygen isotope fractionation line are quantified by Delta(17)O; our precision (1) of such measurements on individual samples is shown to be +/-0.024 per thousand. In turn, this permits the offset between parallel, mass-dependent fractionation lines to be characterised to substantially greater precision than has been possible hitherto. Application of this system to investigate the (17)O versus (18)O relationship for numerous terrestrial whole-rock and mineral samples, of diverse geological origins and age, indicates that the complete data set may be described by a single, mass-dependent fractionation line of slope 0.5244+/- 0.00038 (standard error). Copyright 1999 John Wiley & Sons, Ltd.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

AC发泡剂中一种助发泡剂的鉴定

目前国内外通过在AC发泡剂中添加各种促进剂进而获得改性AC的方法已成为一种趋势。添加何种改性剂无疑是研究改性AC的关键。因此定性分析AC中的改性剂,对改性AC的研发将有极大的帮助。文章应用由作者在Vibrational Spectroscopy上首次提出的薄层色谱显微傅里叶红外联用的方法,鉴定出某改性AC中一种罕见添加剂的官能团,结合元素分析及化学物性分析等,推测出此添加剂的结构。通过对推测物质碎裂机理的解释和未知添加剂质谱图的分析,进一部验证了该添加剂为所推测的物质。这种鉴定方法同样适用于AC中其他无标准图谱的改性剂分析。     

FTIR microscopy of biological cells and tissue: data analysis using resonant Mie scattering (RMieS) EMSC algorithm

Transmission and transflection infrared microscopy of biological cells and tissue suffer from significant baseline distortions due to scattering effects, predominantly resonant Mie scattering (RMieS). This scattering can also distort peak shapes and apparent peak positions making interpretation difficult and often unreliable. A correction algorithm, the resonant Mie scattering extended multiplicative signal correction (RMieS-EMSC), has been developed that can be used to remove these distortions. The correction algorithm has two key user defined parameters that influence the accuracy of the correction. The first is the number of iterations used to obtain the best outcome. The second is the choice of the initial reference spectrum required for the fitting procedure. The choice of these parameters influences computational time. This is not a major concern when correcting individual spectra or small data sets of a few hundred spectra but becomes much more significant when correcting spectra from infrared images obtained using large focal plane array detectors which may contain tens of thousands of spectra. In this paper we show that, classification of images from tissue can be achieved easily with a few (<10) iterations but a reliable interpretation of the biochemical differences between classes could require more iterations. Regarding the choice of reference spectrum, it is apparent that the more similar it is to the pure absorption spectrum of the sample, the fewer iterations required to obtain an accurate corrected spectrum. Importantly however, we show that using three different non-ideal reference spectra, the same unique correction solution can be obtained.     

Comonomer Distribution in Polyethylenes Analysed by DSC After Thermal Fractionation

Ethylene copolymers exhibit a broad range of comonomer distributions. Thermal fractionation was performed on different grades of copolymers in a differential scanning calorimeter (DSC). Subsequent melting scans of fractionated polyethylenes provided a series of endothermic peaks each corresponding to a particular branch density. The DSC melting peak temperature and the area under each fraction were used to determine the branch density for each melting peak in the thermal fractionated polyethylenes. High-density polyethylene (HDPE) showed no branches whereas linear low-density polyethylenes (LLDPE) exhibited a broad range of comonomer distributions. The distributions depended on the catalyst and comonomer type and whether the polymerisation was performed in the liquid or gas phase. The DSC curves contrast the very broad range of branching in Ziegler—Natta polymers, particularly those formed in the liquid phase, with those formed by single-site catalysts. The metallocene or single-site catalysed polymers showed, as expected, a narrower distribution of branching, but broader than sometimes described. The ultra low-density polyethylenes (ULDPE) can be regarded as partially melted at room temperature thus fractionation of ULDPE should continue to sub-ambient temperatures. The thermal fractionation is shown to be useful for determining the crystallisation behaviour of polyethylene blends.This revised version was published online in November 2005 with corrections to the Cover Date.     

Reversed Annealing of Thermal Fractionated Polyethylenes by TMDSC

Polyethylene samples prepared by thermal fractionation (TF) were annealed in several consecutive cycles in a temperature modulated DSC (TMDSC) at a temperatures one °C below the peak temperatures, increased from cycle to cycle relative to these peaks. The transition enthalpy of each cooling cycle was greater or equal to that of the preceding heating cycle. The total heat-flows of each heating cycle corresponded to those of the samples in the reference state up until the vicinity of the annealing temperature. During the annealing, the heat capacities decreased to a lower value over a one minute period. The thermal memory effect caused by the thermal fractionation was eliminated by a small overheating of the material for a short time. The fast disappearance of the thermal memory by a relatively very small degree of heating above their melting temperature denies a long range physical separation of macromolecules by TF. This revised version was published online in July 2006 with corrections to the Cover Date.     

Microscopic study of polymorphism of a photographic coupler

Polymorphism and polymorphic transformation of a photographic coupler have been examined using hot stage optical microscopy (HSOM). Two different polymorphs, metastable needle-like crystals and stable cubic-like crystals, were identified on heating. A solid-state transformation was found to occur from the metastable form to the stable form. Both polymorphs can precipitate from coupler solutions. The needle-like crystals appear in all cases examined; the cubic-like crystals precipitate only with higher concentrations and lower cooling rates. The solution-mediated transformation occurs in an organic solvent through dissolution of the metastable polymorph and growth of the stable polymorph. The growth rate of the stable polymorph is dependent on temperature as well as concentration. The activation energy of the growth is estimated for coupler solutions with different concentrations.