Vibrational spectroscopies using infrared radiation, Raman scattering, neutrons, low-energy electrons and inelastic electron tunnelling are powerful techniques that can analyse bonding arrangements, identify chemical compounds and probe many other important properties of materials. The spatial resolution of these spectroscopies is typically one micrometre or more, although it can reach a few tens of nanometres or even a few ångströms when enhanced by the presence of a sharp metallic tip. If vibrational spectroscopy could be combined with the spatial resolution and flexibility of the transmission electron microscope, it would open up the study of vibrational modes in many different types of nanostructures. Unfortunately, the energy resolution of electron energy loss spectroscopy performed in the electron microscope has until now been too poor to allow such a combination. Recent developments that have improved the attainable energy resolution of electron energy loss spectroscopy in a scanning transmission electron microscope to around ten millielectronvolts now allow vibrational spectroscopy to be carried out in the electron microscope. Here we describe the innovations responsible for the progress, and present examples of applications in inorganic and organic materials, including the detection of hydrogen. We also demonstrate that the vibrational signal has both high- and low-spatial-resolution components, that the first component can be used to map vibrational features at nanometre-level resolution, and that the second component can be used for analysis carried out with the beam positioned just outside the sample--that is, for 'aloof' spectroscopy that largely avoids radiation damage.

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The influence of the riser diameter on the axial and radial solids holdup profiles and flow development is studied by measuring local solids holdups with a fiber-optic probe in a 10-m twin-riser system with 0.076-and 0.203-m inner diameters, at solids circulation rates of up to 200 kg/(m 2 s) and superficial gas velocities of up to 8 m/s. It was found that the solids concentration increases with increasing riser diameter. Furthermore, the radial profiles of the solids concentration are steeper with larger-diameter risers. For both risers, the flow development in the riser center is nearly instantaneous, with the solids concentration remaining low under all operating conditions. In the wall region, the flow development slows down. Moreover, the flow development is slower in the larger-diameter riser. Increasing the solids flux also slows the flow development. However, increasing the superficial gas velocity makes the flow development faster while also lengthening the fully developed region.

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in Wiley InterScience (www.interscience.wiley.com).In this article a novel circulating-turbulent fluidized bed (C-TFB) featured by high solids holdup and high gross solids circulation has been introduced and tested. The purpose of the new design was to integrate conventional circulating and turbulent fluidized beds into a unique high-density fluidization system for more efficient gas-solid contact and significantly reduced solids backmixing. The hydrodynamic characteristics of the C-TFB were analyzed in terms of differential pressure, solids concentration, particle velocity, and local solids flux distributions. An axial homogeneous flow structure was easily obtained with cross-sectional average solids volume concentrations higher than 0.25 throughout the entire C-TFB. At all measuring positions there was no net downflow of solids and a good gas-solid mixing was observed.

for single-crystal X-ray structure analysis, and Solvias AG for the generous gift of chiral ligands. J.Z. thanks SIOC for a postdoctoral fellowship. G.C.T. thanks NSERC for a postgraduate scholarship.Supporting information for this article is available on the WWW under http://dx.

The activation and cleavage of benzyl fluorides by the electrophilic organofluorophosphonium catalyst, [(C6 F5 )3 PF][B(C6 F5 )4 ], is reported and used for the preparation of 1,1-diarylalkanes (37 examples) and substituted aryl homoallylic alkenes (14 examples). This procedure involves mild conditions, avoids harmful waste, and is compatible with a range of substituted arenes and allylic silanes.