Showing papers by "Malcolm L. H. Green published in 2004"
TL;DR: In this article, an alternative method using urea as organic matrix to prepare CoS2/γ-Al2O3 HDS catalysts based on drying (urea-matrix drying, UMxD) or combustion (UREa-metrix combustion, UMXC) processes have been developed and compared with the traditional wet methods (sequential, WSI, and co-impregnation, WCI) and chelating method (ChM) in order to determine their influence on the HDS catalyst performance.
Abstract: An alternative method using urea as organic matrix to prepare CoMoS2/γ-Al2O3 HDS catalysts based on drying (urea-matrix drying, UMxD) or combustion (urea-matrix combustion, UMxC) processes have been developed and compared with the traditional wet methods (sequential, WSI, and co-impregnation, WCI) and chelating method (ChM) in order to determine their influence on the HDS catalytic process. The catalytic performance of the alumina-supported CoMo catalysts was evaluated in a continuous flow reactor using the hydrodesulfurization of thiophene as a model reaction. The oxidic precursors and the sulfurized catalysts were characterized using elemental analysis, X-ray diffraction (XRD), laser Raman spectroscopy (LRS), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), high resolution transmission electron microscopy (HRTEM), temperature-programmed reduction (TPR-H2) and BET surface area measurements. It has been found that the urea–organic matrix method facilitates well-dispersed Co- and Mo-oxo species (mono and polymolybdate) formation, whereas the conventional impregnation techniques lead to mixed-metal oxides formation. This was reflected in the sulfurized phase morphology and structural disorder degree of carbon material deposited on the catalyst surface upon the sulfurizing process using thiophene as sulfurizing agent. The preparation method notably affects the thiophene-HDS specific rates, showing the following activity order: UMxD>UMxC>WCI>WSI>ChM, while an opposite trend for relative rate of HYD to HDS reactions was observed. A carbon structural effect together with high stacking degree of the sulfurized phases seem to be mainly responsible for the high HDS activity of alumina-supported CoMo catalysts prepared by the urea–organic matrix method, which appears very promising for HDS catalysts development.
86 citations
TL;DR: Heating single-walled carbon nanotubes (SWNTs) with molten hydroxides MOH gave MOH@SWNT in good yield and high resolution transmission electron microscopy (HRTEM) indicated that CsOH in Cs OH@ SWNT often adopts twisted 1D crystal structures inside SWNTs.
46 citations
TL;DR: In this paper, single-wall carbon nanotubes filled with lead oxide, PbO, were investigated using transmission electron microscopy and Raman spectroscopy, and it was concluded that PbOs crystallizes in the orthorombic phase forming nanowires inside the nanotsubes.
Abstract: We investigated single-wall carbon nanotubes filled with lead oxide, PbO, by transmission electron microscopy and Raman spectroscopy. It is concluded that PbO crystallizes in the orthorombic phase forming nanowires inside the nanotubes. The positions of the PbO Raman lines are downshifted as compared to the bulk material as a result of the reduced dimensionality. As a consequence of the filling, nanotubes become sensitive to the laser irradiation. At higher laser power densities, they oxidize and the free PbO nanowires are left in the sample.
42 citations
TL;DR: Density functional calculations confirm the dihydrogen/hydride structure as the ground state for the molecule and give estimates for the energy of two hydrogen exchange processes in good agreement with experiment.
Abstract: In contrast to [Cp(2)MoH(3)](+), which is a thermally stable trihydride complex, the ansa-bridged analogue [(eta-C(5)H(4))(2)CMe(2)MoH(H(2))](+) (1) is a thermally labile dihydrogen/hydride complex. Partial deuteration of the hydride ligands allows observation of J(H)(-)(D) = 11.9 Hz in 1-d(1) and 9.9 Hz in 1-d(2) (245 K), indicative of a dihydrogen/hydride structure. There is a slight preference for deuterium to concentrate in the dihydrogen ligand. A rapid dynamic process interchanges the hydride and dihydrogen moieties in complex 1. Low temperature (1)H NMR spectra of 1 give a single hydride resonance, which broadens at very low temperature due to rapid dipole-dipole relaxation (T(1) = 23 ms (750 MHz, 175 K) for the hydride resonance in 1). Low temperature (1)H NMR spectra of 1-d(2) allow the observation of decoalescence at 180 K into two resonances. The bound dihydrogen ligand exhibits hindered rotation with DeltaG(150) = 7.4 kcal/mol, but H atom exchange is still rapid at all accessible temperatures (down to 130 K). Density functional calculations confirm the dihydrogen/hydride structure as the ground state for the molecule and give estimates for the energy of two hydrogen exchange processes in good agreement with experiment. The presence of the C ansa bridge is shown to decrease the ability of the metallocene fragment to donate to the hydrogens, thus stabilizing the (eta(2)-H(2)) unit and modulating the barrier to H(2) rotation.
33 citations
Journal Article•
TL;DR: In this paper, the role of inspiratory muscle dysfunction in chronic heart failure was investigated and it was shown that inspiration muscle endurance, expressed as a function of endurance time (Tlim) adjusted for inspiratory load and capacity, would be reduced in CHF.
Abstract: Background: Although breathlessness is common in chronic heart failure (CHF), the role of inspiratory muscle dysfunction remains unclear. We hypothesised that inspiratory muscle endurance, expressed as a function of endurance time (Tlim) adjusted for inspiratory muscle load and inspiratory muscle capacity, would be reduced in CHF.
Methods: Endurance was measured in 10 healthy controls and 10 patients …
33 citations
TL;DR: Although a marked reduction in endurance time was observed in CHF, much of this reduction was explained by the increased inspiratory muscle load to capacity ratio, suggesting that the major contributor to task failure was a maladaptive breathing pattern rather than impaired inspiratory Muscle endurance.
Abstract: Background: Although breathlessness is common in chronic heart failure (CHF), the role of inspiratory muscle dysfunction remains unclear. We hypothesised that inspiratory muscle endurance, expressed as a function of endurance time (Tlim) adjusted for inspiratory muscle load and inspiratory muscle capacity, would be reduced in CHF. Methods: Endurance was measured in 10 healthy controls and 10 patients with CHF using threshold loading at 40% maximal oesophageal pressure (Poes max ). Oesophageal pressure-time product (PTPoes per cycle) and Poes max were used as indices of inspiratory muscle load and capacity, respectively. Results: Although Poes max was slightly less in the CHF group (−117.7 (23.6) v −100.0 (18.3) cm H 2 O; 95% CI −37.5 to 2.2 cm H 2 O, p = 0.1), Tlim was greatly reduced (1800 v 306 (190) s; 95% CI 1368 to 1620 s, p max was increased (0.13 (0.05) v 0.21 (0.04); 95% CI −0.11 to −0.03, p = 0.001). Most of this increased inspiratory muscle load was due to a maladaptive breathing pattern, with a reduction in expiratory time (3.0 (5.8) v 1.1 (0.3) s; 95% CI 0.3 to 3.5 s, p = 0.03) accompanied by an increased inspiratory time relative to total respiratory cycle (Ti/Ttot) (0.43 (0.14) v 0.62 (0.07); 95% CI −0.3 to −0.1, p = 0.001). However, log Tlim, which incorporates the higher inspiratory muscle load to capacity ratio caused by this altered breathing pattern, was ⩾85% predicted in seven of 10 patients. Conclusions: Although a marked reduction in endurance time was observed in CHF, much of this reduction was explained by the increased inspiratory muscle load to capacity ratio, suggesting that the major contributor to task failure was a maladaptive breathing pattern rather than impaired inspiratory muscle endurance.
31 citations
TL;DR: Ni(2-x)MoxP (x = 0−1) ternary phosphide solids have been prepared for the first time and proven to be a series of solid solution as mentioned in this paper.
Abstract: Ni(2-x)MoxP (x = 0−1) ternary phosphide solids have been prepared for the first time and proven to be a series of solid solution.
28 citations
TL;DR: In this paper, the imaging and characterization of individual molecules and atomically thin, effectively one-dimensional crystals of rock salt and other halides encapsulated within single-walled carbon nanotubes are reviewed.
Abstract: The imaging and characterization of individual molecules and atomically thin, effectively one-dimensional crystals of rock salt and other halides encapsulated within single-walled carbon nanotubes are reviewed in this article. These species were imaged by conventional and super-resolved high-resolution transmission electron microscopy and by scanning tunneling microscopy, revealing the detailed atomic structure of these nanoscopic species.
25 citations
TL;DR: In this paper, a sample of DWNTs synthesized by a modified arc-evaporation method was analyzed using high-resolution transmission electron microscopy (HRTEM), and the detailed microstructure of one representative DWNT was obtained by applying a digital image restoration approach to a focal series of HRTEM images.
18 citations
TL;DR: The most common structure type observed within SWNTs was the rocksalt archetype, although CsI was observed to form both body-centred cubic (bcc) and rocksalt structure types.
Abstract: Single-walled carbon nanotubes (SWNTs) have been used as growth templates for spatially confined crystal growth. The comparative crystallization and high-resolution transmission electron microscopy imaging properties of simple binary halides formed by the alkali iodides MI (M = Li, K, Na, Rb and Cs) within SWNTs are described. The most common structure type observed within SWNTs was the rocksalt archetype, although CsI was observed to form both body-centred cubic (bcc) and rocksalt structure types. ThCl4 was found to form a chain structure of Th[Cl]8 polyhedra. HgI2 crystallized within nanotubes with ultra-narrow (i.e. 0.8 nm) capillaries was observed to form helical 2 x 1 layer crystals.
15 citations
TL;DR: In this article, it was shown that the charge transfer to the acyl group on Lewis acid coordination is more significant in the σ than the π system, thus π populations cannot be inferred from the distance changes.
TL;DR: In this article, the 1-tert-butylimidazolium-cyclopentadienylide (1-TBED) has been synthesised and the intermediate 3,3'-trans-3,5-cycledcyclopentenyl)di(1-TERt-base-dimentional bromide isolated and structurally characterised.
TL;DR: In this paper, a series of M-W-Mn/SiO2 catalysts (M- Li, Na, K, Ba, Ca, Fe, Co, Ni, and A1) have been prepared and their catalytic performances for OCM were evaluated.
Abstract: A series of M-W-Mn/SiO2 catalysts (M- Li, Na, K, Ba, Ca, Fe, Co, Ni, and A1) have been prepared and their catalytic performances for OCM were evaluated. The roles of the WO 4 tetrahedra and the WO 6 octahedra on the catalyst surface have been investigated using X-ray photoelectron spectroscopy (XPS) and laser Raman spectroscopy (LRS).
TL;DR: In this article, a ferrocenyl phosphane ligand incorporating Si-P linkages was described and its molecular structures were determined by single crystal X-ray diffraction.
01 Jan 2004
TL;DR: In this paper, the filling of single walled carbon nanotubes (SWNTs) is described, and the structures of the nanocrystals encapsulated inside SWNTs show other significant differences compared to the corresponding bulk materials.
Abstract: Carbon nanotubes have hollow interiors with internal diameters ranging from 0.5 – 20 nm although more typically 1 – 4 nm. It is now well established that these internal cavities can be filled with crystalline and molecular materials. Filling of single walled carbon nanotubes (SWNTs) are normally filled by direct mixing of the molten filling material and the nanotubes at elevated temperature. Characterisation of filled carbon nanotubes relies mainly on high-resolution transmission electron microscopy (HRTEM) and extended resolution HRTEM techniques. The crystals formed within the narrower SWNTs are often only a few atoms in cross section with a large proportion of atoms lying on the surface of the encapsulated crystals. An extreme example is in the case of a 2 × 2 crystal of potassium iodide which is effectively an ‘all surface’ crystal. The structures of the nanocrystals encapsulated inside SWNTs show other significant differences compared to the corresponding bulk materials. For example, inter-atomic differences can be substantially greater (i.e. by as much as ~20%) for SWNT encapsulated materials. Several examples of filled SWNTs are described including those filled with simple metal halide salts, covalent metal halides and molecular species as in o-carborane.