Double addition of H2 to transition metal-borane complexes: a 'hydride shuttle' process between boron and transition metal centres

The addition of H(2) across a transition metal-borane bond is reported for the first time providing a mechanism for recharging borane functional groups to borohydride.     

Das Atomgewicht des Palladiums

Ohne Zusammenfassung     

The diffusion coefficient of a polymer in an array of obstacles is a non-monotonic function of the degree of disorder in the medium

Using Monte Carlo simulations, we have found that there is a surprising non-monotonic dependence of a polymer's diffusion coefficient upon the degree of disorder of the surrounding environment. Starting with a two-dimensional periodic lattice of obstacles, we randomly displace obstacles to create a quenched gel system with a tunable degree of disorder. Very small displacements increase the diffusion coefficient of polymers since they increase the width of the tube through which the polymer chains reptate. As we displace the obstacles further, however, entropic trapping is observed and the diffusion coefficient of the polymer decreases dramatically. This is a striking example of the delicate balance between entropic and frictional effects for a polymer diffusing in a dense system.     

Direct evidence of the dependence of surface state density on the size of SnO2 nanoparticles observed by scanning tunnelling spectroscopy

In this work, we report a scanning tunnelling spectroscopy (STS) study of 30 and 10 nm tin dioxide nanoparticles. The STS spectra give a surface band gap of 2.5 eV for both samples and show that the density of surface states in the band gap is around 6 times higher for the 30 nm particles than for the 10 nm particles. This provides direct experimental evidence for our theoretical model, which predicts a decrease in the surface state density as the particle size decreases, and partly accounts for the improved sensitivity of gas sensing devices fabricated with nanoparticles.     

Alteration of the profile of ink-jet-deposited UV-cured lenses using applied electric fields

Microlens arrays and microoptical components in general are integral components in a wide range of high-tech products. The ability to fabricate such elements cheaply and with a high degree of accuracy is vital for the development of the next generation of optics-based technologies. There are currently a wide range of microoptical element fabrication technologies. These techniques all have advantages and disadvantages and no one technique is yet sufficient to meet all possible application criteria. One method that has been examined recently is the ink-jet deposition method. This method applies well-established ink-jet printer technology and is thus one possible candidate for large-scale fabrication of inexpensive components. The lenses fabricated using this method are normally found to have spherical profiles. In this paper, we examine the possibility of modifying the profile of these spherical lenses using an applied electric field (E-field). We note that the resulting aspheric lenses have a wide number of applications. These include beam shaping and power transfer applications including fiber coupling. In this paper we describe initial experiments involving single lenses. The single lenses produced using applied E-Fields differ significantly from lenses produced with no applied E-field.     

LV-pIN-KDEL: a novel lentiviral vector demonstrates the morphology,dynamics and continuity of the endoplasmic reticulum in live neurones

Background  

The neuronal endoplasmic reticulum (ER) is an extensive, complex endomembrane system, containing Ca²⁺ pumps, and Ca²⁺ channels that permit it to act as a dynamic calcium store. Currently, there is controversy over the continuity of the ER in neurones, how this intersects with calcium signalling and the possibility of physical compartmentalisation. Unfortunately, available probes of ER structure such as vital dyes are limited by their membrane specificity. The introduction of ER-targeted GFP plasmids has been a considerable step forward, but these are difficult to express in neurones through conventional transfection approaches. To circumvent such problems we have engineered a novel ER-targeted GFP construct, termed pIN-KDEL, into a 3^rd generation replication-defective, self-inactivating lentiviral vector system capable of mediating gene transduction in diverse dividing and post-mitotic mammalian cells, including neurones.     

Thin film lithium aluminium negative plate material

LiAl thin film electrodes were formed by cathodic conversion of the surface of a 50 micron Al foil in a propylene carbonate based electrolyte. The films were cycled both in Li-doped poly(ethylene oxide) and propylene carbonate. On charging, an overpotential of 40 mV was required to sustain growth of the LiAl phase, but the diffusional overpotential was minimal. A simple diffusional model for the discharge predicted serious rate limitation due to slow diffusion in the α phase. However, measurements of the diffusion coefficient gave values many orders higher than previously reported and even greater values were required to explain the discharge rates. Cycling behaviour showed that the electrode degradation was less severe in the polymeric electrolyte than in propylene carbonate.     

Elementarerweichungen in Amorphen Polymeren

Thermally stimulated recovery behaviour of amorphous polymers is described in terms of a continuous distribution of sharply defined elementary softening processes in the polymer. It is proposed that each of these elementary processes is the result of a co-operative site-change mechanism. On exceeding the activation temperature for the process, the viscoelastic time constants fall abruptly by many orders of magnitude, as opposed to following an Arrhenius-type law. The implications of this type of behaviour are discussed.

Prof. Schwarzl zum 60. Geburtstag gewidmet.