Monte-Carlo calculations of cloud returns for ground-based and space-based LIDARS

A Monte-Carlo model is described which has been developed for calculation of multiply scattered LIDAR returns. Results are shown for the common problem selected by the MUSCLE (MUltiple SCattering LIDAR Experiments) group for intercomparison, which represents a typical ground-based cloud-sensing scenario. This is contrasted with returns from the same cloud sensed by a space-based LIDAR, where multiple-scattering effects are much greater. The magnitude of multiple-scattering effects is seen to be largely determined by the optical depth across the receiver field of view at the cloud.     

Selectivity differences between sol-gel coated and immobilized liquid film open-tubular columns for gas chromatography

The solvation parameter model is used to determine the system constants for two sol-gel coated open-tubular columns at five equally spaced temperatures in the range 60-140 degrees C. Differences in the system constants as a function of temperature are used to determine the affect of sol-gel structure on the selectivity of SolGel-l and SolGel-Wax columns compared with conventionally coated and immobilized poly(dimethylsiloxane) and poly(ethylene glycol) stationary phases. The sol-gel columns should be suitable for similar separations to those presently performed on conventional immobilized liquid film columns of the same type but selectivity differences for polar compounds, which depend on temperature, should be anticipated.     

Atomic force microscopy studies of the KF (100) surface: formation of water-rich surface phases in moist N,N-dimethylformamide

A water rich surface phase is observed in the system KF-DMF-H2O by atomic force microscopy; the effects on surface morphology and likely implications for halogen exchange reactions using KF are discussed.     

Differential hydrogen exchange during the biosynthesis of fatty acids in Anacystisnidulans: the incorporation of [2,2,2-2H3, 2-13Co;1] acetate

¹³C NMR studies (with $\text{simultaneous}$¹H, ²H-decoupling) of ¹³C, ²H-labelled methyl palmitate showed a gradation of ²H-retention along the acyl chain. The results are rationalized within the known steps of fatty acid biosynthesis.     

Electronic structure of the valence bands of SnF2 studied by ultraviolet photoelectron spectroscopy

The main features of the photoelectron spectrum of the valence bands of solid-phase SnF₂ are susccessfully interpreted in terms of linear combination of atomic orbitals-molecular orbital theory.     

Mapping of the cerebral response to acetazolamide using graded asymmetric spin echo EPI

Cerebral vascular reactivity in different regions of the rat brain was quantitatively characterized by spatial and temporal measurements of blood oxygenation level-dependent (BOLD)-fMRI signals following intravenous administration of the carbonic anhydrase inhibitor acetazolamide: this causes cerebral vasodilatation through a cerebral extracellular acidosis that spares neuronal metabolism and vascular smooth muscle function, thus separating vascular and cerebral metabolic events. An asymmetric spin echo-echo planar imaging (ASE-EPI) pulse sequence sensitised images selectively to oxygenation changes in the microvasculature; use of a surface coil receiver enhanced image signal-to-noise ratios (SNRs). Image SNRs and hardware integrity were verified by incorporating quality assurance procedures; cardiorespiratory stability in the physiological preparations were monitored and maintained through the duration of the experiments. These conditions made it possible to apply BOLD contrast fMRI to map regional changes in cerebral perfusion in response to acetazolamide administration. Thus, fMRI findings demonstrated cerebral responses to acetazolamide that directly paralleled the known physiological actions of acetazolamide and whose time courses were similar through all regions of interest, consistent with acetazolamide's initial distribution in brain plasma, where it affects cerebral haemodynamics by acting at cerebral capillary endothelial cells. However, marked variations in the magnitude of the responses suggested relative perfusion deficits in the hippocampus and white matter regions correlating well with their relatively low vascularity and the known vulnerability of the hippocampus to ischaemic damage.     

Stereoselective synthesis of tetrahydropyran-3-ones by rearrangement of oxonium ylides generated from metal carbenoids

The synthesis of tetrahydropyran-3-ones by copper-catalysed reactions of diazo ketone tethered allylic ethers has been explored. Product distribution can be explained by the intermediacy of a free ylide or direct rearrangement of a metal-bound ylide equivalent.     

A rapid and economical method for profiling feature heights during microfabrication

Quality control is an important and integral part to any microfabrication process. While the widths of features often can be easily assessed by light microscopy, the heights of the fabricated structures are more difficult to determine. Here, we present a rapid, accurate, and low-cost method to measure the heights of microfabricated structures during and after the fabrication process. This technique is based on white-light interferometry, which offers accuracy on the submicrometre scale.