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F J Williams

Publications and source records attributed to F J Williams.

9 recordsLinked to original sources
PubMed2006

Adsorption geometry and core excitation spectra of three phenylpropene isomers on Cu(111).

Theoretical C 1s near edge x-ray absorption fine structure (NEXAFS) spectra for the C(9)H(10) isomers trans-methylstyrene, alpha-methylstyrene, and allylbenzene in gas phase and adsorbed at Cu(111) surfaces have been obtained from density functional theory calculations where adsorbate geometries were determined by corresponding total energy optimizations. The three species show characteristic differences in widths and peak shapes of the lowest C 1s-->pi(*) transitions which are explained by different coupling of the pi-electron system of the C(6) ring with that of the side chain in the molecules as well as by the existence of nonequivalent carbon centers. The adsorbed molecules bind only weakly with the substrate which makes the use of theoretical NEXAFS spectra of the oriented free molecules meaningful for an interpretation of experimental angle-resolved NEXAFS spectra of the adsorbate systems obtained in this work. However, a detailed quantitative account of relative peak intensities requires theoretical angle-resolved NEXAFS spectra of the complete adsorbate systems which have been evaluated within the surface cluster approach. The comparison with experiment yields almost perfect agreement and confirms the reliability of the calculated equilibrium geometries of the adsorbates. This can help to explain observed differences in the catalytic epoxidation of the three molecules on Cu(111) based on purely geometric considerations.

Journal Article↗
PubMed1992

Chloride is required for fluid transport by the rabbit corneal endothelium.

The role of chloride in fluid transport of the rabbit corneal endothelium was examined by measuring changes in corneal thickness following ion substitutions or addition of ion transport inhibitors in media superfusing the isolated tissue. Normal fluid transport is indicated by maintenance of constant thickness in a fresh cornea or thinning (deturgescence) of a preswollen deepithelialized cornea to its initial thickness at approximately 40 microns/h. These patterns are seen when tissues are superfused with HCO(3-)-Ringer containing 114 mM Cl-. When Cl- was substituted with gluconate, glucuronate, or SO4(2-) fresh and preswollen corneas immediately thinned at greater than 150 microns/h to a value less than 300 microns and then began to swell at 30 microns/h to above their original thickness. Substitution of Cl- with NO3- or Br- had a negligible immediate thinning effect, but fresh corneas subsequently swelled and preswollen corneas failed to deturgesce fully. The rapid thinning (called a "downtransient") observed with gluconate, glucuronate, and SO4(2-) also occurred in these media when ion and fluid transport were completely inhibited with ouabain or stilbenes or by absence of HCO3-, indicating that the thinning results from osmotic gradients induced by ionic reflection coefficients different from that of Cl-. When the downstransient was avoided in deepithelialized corneas by preswelling with the same Cl(-)-free media on both sides of the cornea, corneas maintained a constant but swollen thickness in gluconate and in NO3- or Br- deturgesced slowly and incompletely; ouabain or stilbenes caused further swelling in all media. We conclude that absence of Cl- partially impairs fluid transport, most probably via its role in a Cl(-)-HCO3- exchanger which has been proposed in a recent model of endothelial fluid transport.

Animals↗
PubMed1986

Computed tomography (CT) analysis of the effects of chemonucleolysis.

Computed tomography (CT) was performed on 30 patients with herniated lumbar discs before chemonucleolysis and at three and 12 months postinjection. At three months the compression produced by the herniated disc was reduced in 20 of the 30 patients; at 12 months there was complete relief of compression in all but four patients. Twenty-four patients developed diffuse bulging of the annulus. There was good correlation between the clinical results at three months and the reduction in compression as shown by the CT scan. At 12 months, no correlation was found between the remaining focal abnormalities and the clinical result. None of the patients developed epidural fibrosis. Chemonucleolysis has thus been shown to be an effective treatment of herniated lumbar discs, but it is definitely not indicated in cases where compression of the nerve root or dural sac is due to a bulging annulus.

Adult↗
PubMed1984

The effects of chemonucleolysis as demonstrated by computerised tomography.

Computerised tomography (CT) was performed in 30 patients with herniated lumbar discs; this was done both before chemonucleolysis and three months after. In 20 of the 28 patients who were CT positive, the compression produced by the herniated disc was eliminated or reduced. Twenty-three of the 28 patients developed diffuse bulging of the annulus. There was good correlation between the clinical results at three months and the alteration in compression as shown by the CT scan. No evidence of alteration in the bony relationship was seen in the scan and none of the patients developed epidural fibrosis. Chemonucleolysis has thus been shown to be an effective treatment of herniated lumbar discs, but it is definitely not indicated in cases where compression of the nerve root or dural sac is due to a bulging annulus.

Adult↗
PubMed1981

Wilson's disease. An analysis of the cranial computerized tomographic appearances found in 60 patients and the changes in response to treatment with chelating agents.

Sixty patients with Wilson's disease have been studied by means of computerized cranial tomography (CT). The findings are described and analysed with particular reference to their value, both diagnostic and prognostic, in the management of this disease. The commonest abnormalities were ventricular dilation, 73 per cent; cortical atrophy, 63 per cent; brain-stem atrophy, 55 per cent. Characteristic hypodense areas in the regions of the basal ganglia were present in 45 per cent and almost invariably these were accompanied by one or more of the other CT abnormalities. This combination of findings is considered specific for Wilson's disease in the appropriate clinical context. CT abnormalities were most common and most marked in patients with a neurological presentation, only 2 out of 40 having a normal scan. Similar changes were also demonstrated in three-quarters of the patients with an hepatic presentation and nearly half of those who were presymptomatic. Nineteen patients were scanned on more than one occasion to assess the influence of treatment with penicillamine or triethylene tetramine on the abnormalities recorded initially. Fourteen showed basal ganglia hypodensities on first scanning and in ten of these there was a moderate to marked improvement in this abnormality in response to therapy. Corresponding with this there was considerable clinical improvement. Despite the findings of quite severe CT abnormalities in patients with Wilson's disease. suggesting considerable loss of neurons, patients will still respond well to treatment. We conclude that although the CT. Examination of patients with Wilson's disease is of value both in diagnosis and management, it is of no great help in prognosis.

Adolescent↗