Ptesculentoside, a novel norsesquiterpene glucoside from the Australian bracken fern Pteridium esculentum

A novel norsesquiterpene glucoside ptesculentoside has been isolated from the Australian bracken Pteridium esculentum, together with the known bracken carcinogen ptaquiloside and lesser amounts of caudatoside. The structure of ptesculentoside is determined by analysis of 1D and 2D NMR spectra, and via its conversion into previously known pterosin G.     

Swelling properties and intrinsic reactivities of coal chars produced at elevated pressures and high heating rates

A high-temperature, high-pressure flat-flame burner reactor was developed to prepare char at different pressures. This system achieves particle heating rates of 10⁵ K/s, which better mimics industrial conditions than conventional drop tube or radiative flow reactors. Previous data at atmospheric pressure demonstrated a significant decrease in particle swelling during devolatilization as heating rates increased from 10⁴ K/s (the typical drop tube heating rate) to 10⁵ K/s. Pyrolysis experiments were performed at pressures from 1 to 15 atm at 1300 °C for two bituminous coals and a lignite. Average swelling was determined from a combination of the mass release and the average density. The results indicate significantly lower swelling ratios at elevated pressures than reported in the literature. Scanning electron micrographs show that the bubbles in the bituminous coal particles popped before significant swelling at these elevated heating rates. Lignite particles exhibited shrinkage rather than swelling, but still showed a small effect of pressure. TGA oxidation reactivities were determined for the Pitt #8 and Knife River lignite char samples at their respective char preparation pressures. The oxidation reactivities of both the bituminous and lignite chars decreased with increasing pressure.     

The [1,2]-thio-Wittig rearrangement: evidence for a radical mechanism and its suppression

The lithium enolate formed from methyl S-trityl mercaptoacetate can be C-alkylated in high yield at or below −40 °C, but at higher temperatures the [1,2]-thio-Wittig rearrangement of the enolate is the predominant process; ESR evidence indicates that this rearrangement occurs by a radical mechanism.     

Frame quasi-uniformities

This paper presents an entourage-like theory of quasi-uniformities for frames. The theory comprises the theory of uniformities for frames as well as the classical theory of quasi-uniformities for spaces.     

Multivariate analysis of extremely large ToFSIMS imaging datasets by a rapid PCA method

Principal component analysis (PCA) and other multivariate analysis methods have been used increasingly to analyse and understand depth profiles in X‐ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and secondary ion mass spectrometry (SIMS). These methods have proved equally useful in fundamental studies as in applied work where speed of interpretation is very valuable. Until now these methods have been difficult to apply to very large datasets such as spectra associated with 2D images or 3D depth‐profiles. Existing algorithms for computing PCA matrices have been either too slow or demanded more memory than is available on desktop PCs. This often forces analysts to ‘bin’ spectra on much more coarse a grid than they would like, perhaps even to unity mass bins even though much higher resolution is available, or select only part of an image for PCA analysis, even though PCA of the full data would be preferred. We apply the new ‘random vectors’ method of singular value decomposition proposed by Halko and co‐authors to time‐of‐flight (ToF)SIMS data for the first time. This increases the speed of calculation by a factor of several hundred, making PCA of these datasets practical on desktop PCs for the first time. For large images or 3D depth profiles we have implemented a version of this algorithm which minimises memory needs, so that even datasets too large to store in memory can be processed into PCA results on an ordinary PC with a few gigabytes of memory in a few hours. We present results from ToFSIMS imaging of a citrate crystal and a basalt rock sample, the largest of which is 134GB in file size corresponding to 67 111 mass values at each of 512 × 512 pixels. This was processed into 100 PCA components in six hours on a conventional Windows desktop PC. © 2015 The Authors. Surface and Interface Analysis published by John Wiley & Sons Ltd.     

Fritz Scholz and Robert Smail Jack (Eds): Wilhelm Ostwald. The Autobiography

Journal of Solid State Electrochemistry -     

Milli-free flow electrophoresis: I. Fast prototyping of mFFE devices

We coin a term of milli-free flow electrophoresis (mFFE) to describe mid-scale FFE with flow rates intermediate to macro-FFE and micro-FFE (μFFE). Introduced decades ago, mFFE did not find practical applications. We revive mFFE, as we view it as a viable purification complement to continuous synthesis in capillary reactors with product flow rates of ～5 to 2000 μL/min, too small for macro-FFE but too large for μFFE. The development of the tandem of continuous synthesis/purification will require the production and evaluation of a large number of prototypes of mFFE devices. As the first step, we developed a fast (<24 h) and economical (～$10) method for prototyping mFFE devices using a robotic milling machine. mFFE prototypes are constructed from two machined matching poly(methyl methacrylate) (PMMA) substrates, which are bonded in 10 min using dichloromethane to provide a strong and irreversible seal. Using the developed prototyping technology, we designed and evaluated 25 prototypes of mFFE devices. By optimizing the feed rates and rotational speeds of the drills, the depth of the electrode channels, the dimensions of the entrance and exit reservoirs, the sample flow rate, and the diameter and position of the sample input, we were able to achieve indefinitely long operation of the device with cycles of alternating 15-min electrophoresis and 0.5-min regeneration (bubble removal). The test analytes, rhodamine B and fluorescein, were baseline resolved by mFFE for flow rates ranging from 10 to 600 μL/min. These results prove that our prototyping approach is suitable for the challenging task of multi-parameter optimization of mFFE devices.     

Beyond the Butler-Volmer equation. Curved Tafel slopes from steady-state current-voltage curves

We report the discovery and analysis of curved Tafel slopes from the electrochemical reduction of hexamminecobalt(III) under steady-state conditions. In order to confirm the existence of the curvature, random assemblies of carbon microelectrodes (RAM? electrodes) were employed to obtain experimental data over more than three orders of magnitude, without significant double layer charging currents and without ohmic distortion. Since the rate-determining step in the reduction reaction is electron transfer, and no ligand substitution reactions occur on the timescale of experiments, the curvature of the Tafel plot is attributed to the dependence of the symmetry factor on electrode potential.