Showing papers by "Malcolm L. H. Green published in 2001"

Measurement of twitch transdiaphragmatic, esophageal, and endotracheal tube pressure with bilateral anterolateral magnetic phrenic nerve stimulation in patients in the intensive care unit.

Abstract: ObjectiveIn the critically ill, respiratory muscle strength usually has been assessed by measuring maximum inspiratory pressure. The maneuver is volitional, and results can be unreliable. The nonvolitional technique of bilateral anterolateral magnetic stimulation of the phrenic nerves, producing twi

Methane combustion over supported cobalt catalysts

Abstract: A series of cobalt-based catalysts with different supports have been prepared using impregnation method, and characterised by X-ray diffraction (XRD), laser Raman (LR), and infrared spectroscopy (IR). The catalytic activities for methane combustion were assessed in a micro-reactor. The ZrO2 and Al2O3 supports are themselves active in methane combustion, and ZrO2 supported cobalt catalyst was found to have the highest activity amongst the TiO2, Al2O3, MgO supported catalysts and bulk Co3O4. The Co content has a marked effect on the activity of the ZrO2 supported catalyst with 1.0 and 15 wt.% of Co having the lowest light-off temperature in methane combustion. In the MgO supported catalyst, Co oxide was highly dispersed over the MgO support surface or enters the lattice of MgO to form a solid solution, whose activity for methane combustion is reasonable. The zirconia supported cobalt catalysts are very active and stable when calcination or reaction temperature is no more than 900°C. Calcining the catalysts at temperatures above 900°C for more than 1 h decreases the catalyst activity. The deactivation of the catalyst probably results from the decrease of the surface area.

Effect of carburising agent on the structure of molybdenum carbides

Abstract: Molybdenum carbides have been prepared by the temperature programmed reaction method using mixtures of hydrogen and methane, hydrogen and ethane, and hydrogen and butane, and characterised with X-ray diffraction, transmission electron microscopy, 13C solid state NMR and EXAFS spectroscopy. The results show that the choice of hydrocarbon used to synthesise molybdenum carbide significantly affects the structure and texture of the resultant materials. Increasing the chain length of the carburising agent reduces the particle size and the temperature for complete phase transformation from molybdenum oxide to carbide is lowered. Carburising with a mixture of hydrogen and methane gives rise to hexagonal closed packed (hcp) carbide, while when using butane as the carbon source, molybdenum oxide is mainly reduced to face centred cubic (fcc) carbide. However, using ethane as the carbon source, the resultant carbide has a mixed phase composition with the hcp phase predominant. The molybdenum carbide prepared with ethane as the carbon source has the roughest surface and highest hydrogen adsorption capacity, while that prepared with butane has a very condensed surface. There is a substantial difference in the molybdenum co-ordination environments present among the carbides prepared with different carburising agents.

Synthesis and catalytic properties of oxalic amidinato complexes

Abstract: The oxalic amidine compounds C6H5NC(NHtBu)–C(NHtBu)=NC6H51 and C6H5NC{N(tBu)(SiMe3)}–C{N(tBu)(SiMe3)}=NC6H52 are described. The compound [(C6H5N)C(NHtBu)–C(NHtBu)(NHC6H5)][Br] 3* has been isolated from the reaction between 1 and [NiBr2(DME)]. Treatment of 1 with M(NMe2)4 (M = Zr or Ti), [Ta(NEt2)2Cl3(py)] or [Zr{N(SiMe3)2}3Cl] gives the bimetallic complexes [M(NMe2)3(C6H5N)C(NtBu)–]2 (M = Zr (4) or M = Ti (5)) and the mono-amidinato complexes [Ta(NEt2)Cl3{(C6H5N)C(NtBu)C(HNtBu)(NC6H5)}] 6* and [Zr{N(SiMe3)2}2Cl{(C6H5N)C(NtBu)C(HNtBu)(NC6H5)}] 7* respectively: * indicates the crystal structure has been determined. The activity toward ethylene polymerisation has been investigated for compounds 4, 5 and 7.

Potential utilisation of Indonesia's Natuna natural gas field via methane dry reforming to synthesis gas

Abstract: The utilisation of high CO2 content natural gas, such as that found at Natuna island in Indonesia, using methane dry reforming with carbon dioxide to synthesis gas is demonstrated. Highly active catalysts employed for coke-free, stable dry reforming include alumina-supported nickel, either as-prepared or doped with tungsten oxide or calcium oxide, and the supported group VIII metals. No deactivation was observed for the duration of any of the experiments (>70 h), and the methane conversion and product distributions were close to those predicted from thermodynamic equilibrium calculations. It is calculated that the application of dry reforming to the Natuna field alone, combined with known gas-to-liquids (GTL) technology, could provide liquid fuel to Indonesia for almost 18 years.

Palladium(II) complexes with the bidentate iminophosphine ligand [Ph2PCH2C(Ph)N(2,6-Me2C6H3)]

Abstract: A new iminophosphine ligand, [Ph2PCH2C(Ph)N(2,6-Me2C6H3)] (HL), and the complexes [PdX2(HL)], where X = Cl (1) and Br (2), [PdMeX(HL)], X = Cl (3) and Br (4), and [PdMe2(HL)] (5) have been prepared and characterised. Reaction of 2 with MeLi or KH leads to deprotonation of the neutral ligand to give [Pd2(μ-Br)2(L−)2], (6), where L− is [Ph2PCHC(Ph)N(2,6-Me2C6H3)]−. Similarly, reaction of 3 with KH and triphenylphosphine affords the neutral complex [PdMe(PPh3)(L−)] (7). Insertion of CO into the Pd–Me bond has been investigated, as well as the catalytic properties of [PdClMe(HL)] towards CO/ethylene copolymerisation. The crystal structures of HL, 1–3 and 5–7 have been determined.

Inspiratory Muscle Relaxation Rate Slows during Exhaustive Treadmill Walking in Patients with Chronic Heart Failure

Abstract: Exercise intolerance is a feature of chronic heart failure (CHF). We hypothesized that excessive loading of the respiratory muscle pump might contribute to exertional breathlessness. One marker of excessive muscle-loading is slowing of maximum relaxation rate (MRR) and, therefore, to test our hypothesis, we investigated the effect of exhaustive treadmill walking on inspiratory muscle MRR in patients with CHF. We studied eight stable patients with mildmoderate CHF walking on a treadmill until termination because of severe dyspnea. Inspiratory muscle MRR was determined from esophageal pressure (Pes) change during submaximal sniffs (Sn) before and immediately after exercise to a mean (SD) minute ventilation of 77 (18) L/min. For comparison, nine healthy subjects performed a similar protocol; exercise was terminated either by severe dyspnea or when minute ventilation reached 100 L/min. There were no significant differences in terms of heart rate, respiratory rate, tidal volume, or inspiratory duty cycle at cessation of exercise. The mean slowing of Sn Pes MRR in the first minute after termination of exercise in the CHF group was 22.4% and in the normal control group it was 2.8% (p , 0.01). Our data show that slowing of inspiratory muscle relaxation rate occurs in patients with CHF walking to severe breathlessness. We conclude that severe loading of the inspiratory muscles is a feature of exertional dyspnea in CHF. In chronic heart failure (CHF) a combination of disuse, underperfusion, and neurohormonal mechanisms lead to reduced peripheral muscle strength and endurance (1, 2). Although these changes may explain limb fatigue during exercise in CHF, it is less clear if exertional dyspnea can be attributed to similar mechanisms affecting the respiratory muscles. Although it is known that pulmonary compliance is reduced in CHF (3, 4), increasing the work of breathing, we have recently shown using detailed tests (5) that respiratory muscle strength is largely preserved in CHF. However, other observations suggest that an imbalance between the load applied to and the capacity of the inspiratory muscle pump could contribute to exercise-induced dyspnea in CHF. In particular it has been observed that exercise capacity can be extended if the work of breathing is reduced using a helium-oxygen mixture (6) or inspiratory pressure support (7). However, direct evidence supporting this hypothesis is currently lacking. When skeletal muscle operates under conditions of excessive load the maximum rate of relaxation slows; this property, which is an active process, can be determined for the inspiratory muscles from the esophageal pressure trace after a voluntary sniff (Sn Pes) (8, 9). We have previously shown that this method can detect changes in the maximum relaxation rate (MRR) of inspiratory (8) muscle in normal subjects after hyperventilation and in patients with chronic obstructive pulmonary disease (COPD) after exhaustive treadmill walking (10). In the present study we used measurement of MRR to test the hypothesis that exercise in CHF results in excessive loading of the inspiratory muscles; we therefore measured sniff esophageal pressure maximum relaxation rate (Sn Pes MRR) in patients with CHF walking to exhaustion on a treadmill. Our rationale was that slowing of Sn Pes MRR would support this hypothesis and suggest a possible contribution to the etiology of breathlessness in CHF. METHODS

Catalytic Combustion of Methane over Cobalt–Magnesium Oxide Solid Solution Catalysts

Abstract: A series of cobalt–magnesium oxide solid solution catalysts (CoMgO) have been prepared using urea combustion methods, and characterised by X-ray diffraction (XRD) and laser Raman (LR). The catalytic activities for methane combustion have been tested in a continuous-flow microreactor. The Co content has a significant effect on the activity of the cobalt–magnesium oxide solid solution catalysts. The catalysts containing 5 and 10% Co have the lowest light-off temperature in methane combustion. In the preparation of cobalt–magnesium oxide solid solution catalysts, higher urea to metal ratio favors the formation of the catalysts with smaller crystal particles and leads to a better catalytic performance for methane combustion. Addition of lanthanum nitrate to the solution of Co and Mg nitrate depressed the formation of the cobalt–magnesium oxide solid solution and decreased the activity of the catalysts for methane combustion. The cobalt–magnesium oxide solid solution catalysts are very stable when the calcination or reaction temperature is no more than 900°C. However, the catalytic activity decreases rapidly after high temperature (>1000°C) calcination, possibly due to sintering of the catalyst and thus decrease of the surface area.