Showing papers by "George Davey Smith published in 1986"

Pulsed laser atom probe analysis of semiconductor materials

Abstract: SUMMARY As the size of semiconductor devices is reduced the active volumes of material in each device is also decreased. Under these circumstances it becomes more important to understand the microchemistry of semiconducting materials, as small fluctuations in composition can dramatically affect both the operation of the devices, and of the contacts to semiconductors. Atom probe microanalysis has been shown to be able to analyse the microchemistry of metallic materials with plane-by-plane resolution, and by using a pulsed laser to replace the more conventional voltage pulses the analysis of semiconducting and insulating materials becomes possible. The pulsed laser atom probe has been shown to give very accurate chemical analysis of the stoichiometry of extremely small volumes of III-V compound semiconductors, and the composition of the interfacial layer between silicon dioxide and silicon has been identified as SiO of thickness about 0.3 nm. It has been shown to be possible to prepare specimens for analysis from thin films of semiconductors, thus allowing the microanalysis of a wide range of materials that are deposited in thin film form.

Changes in plasma catecholamine concentrations following infiltration with large volumes of local anaesthetic solution containing adrenaline

Abstract: Plasma catecholamine concentrations have been measured in nine patients undergoing rhinoplasty following infiltration to the facial area of 21 ml of 0.5% lignocaine with adrenaline 1: 200 000 and in seven patients undergoing brachial plexus blockade with 40 ml of 0.5% lignocaine, 0.25% bupivacaine and adrenaline 1: 200 000. In the rhinoplasty group there was a 566% increase in plasma adrenaline concentration 2 min after cessation of infiltration, whilst in the brachial plexus group a 112% increase in the plasma concentration of adrenaline occurred at 10 min after completion of the block. There was no change in plasma noradrenaline concentration in either group. It is concluded that the so-called safe dose of adrenaline (1.0 fig kg−1 during halothane anaesthesia) is meaningless unless the site of administration is specified.

Effect of halothane on cardiovascular and plasma catecholamine responses to tracheal intubation

Abstract: The catecholamine and cardiovascular responses to intubation were investigated during halothane anaesthesia. Thirty patients were allocated randomly to two groups. Following induction of anaesthesia and muscle relaxation, group 1 was ventilated with 70% nitrous oxide in oxygen before intubation; group 2 received 1 % halothane in addition. After intubation, both groups received 0.5% halothane. Arterial pressure and heart rate, and plasma noradrenaline and adrenaline concentrations were measured throughout the induction sequence. In group 1 intubation was associated with increases {from pre-induction values) in systolic arterial pressure of 13% and diastolic arterial pressure of 35%, although the plasma concentrations of noradrenaline did not alter significantly. In group 2, although there was a pressor response to intubation, no overall change in systolic arterial pressure and only a 13% increase in diastolic arterial pressue occurred when compared with pre-induction values. This response was associated with a 78% increase in the noradrenaline concentration; the adrenaline concentration did not alter significantly.

Absorption of controlled release morphine sulphate in the immediate postoperative period

Abstract: The absorption of morphine sulphate, given orally as a controlled release preparation, was studied in 10 patients who had undergone peripheral vascular surgery with a standard opioid-based general anaesthetic technique. Serum morphine concentrations were measured (high pressure liquid chromatography) every 2 h for the first 16 h after surgery and the results were strongly suggestive of a decrease in the rate of absorption of morphine in this situation.

Improvements in atom probes

Abstract: An atom probe with an ion detector (7) capable of giving direct electrical indication of the position of incidence of ions field-evaporated from a specimen (1). Position information is obtained serially for successive ions and correlatd with time of flight signals related to the same ions. In this way data is made available for subsequent computer-assisted three-dimensional reconstruction of the atomic-scale chemistry of the specimen.

Statistical analysis of atom probe data

Abstract: This paper gives some suggestions and caveats on how to estimate the confidence limits on data obtained from atom-probe experiments. There are four sections covering autocorrelation, the use of contingency tables, estimation of ordering parameters and testing for clustering. This paper certainly does not exhaust the possibilities for statisitical tests which may be applied to atom probe data, but demonstrates some useful techniques, which as far as the authors are aware have not been used before.

Ageing and tempering of ferrous martensites

Abstract: Etude du vieillissement a basse temperature d'une martensite Fe-15% poids Ni-1% poids C par microscopie ionique a emission de champ et par sonde atomique. On montre que l'amplitude et la longueur d'onde des fluctuations de composition du carbone observees pendant le vieillissement a temperature ambiante augmentent avec le temps, indiquant que l'alliage se decompose par un processus spinodal

The atom probe analysis of a cast duplex stainless steel

Abstract: Analyse par sonde atomique de l'acier double phase CF8 vieilli 105000 h a 280 C, 3000 h ou 70000 h a 300 C ou 3000 h a 400 h. Mise en evidence d'une reaction spinodale dans la ferrite et de la presence de petits amas atomiques de Si et Mo dans le materiel vieilli 70000 h a 300 C

The quantitative analysis of copper in iron based alloys

Abstract: Dosage de faibles quantites de cuivre au moyen de la sonde atomique Oxford VG FIM 100. Etablissement des conditions operatoires optimales pour des resultats precis d'analyse, a partir de materiaux de reference sous forme d'alliages binaires Fe−Cu

Evaluation of the Combined Effects of Atropine and Neostigmine on the Lower Oesophageal Sphincter

Abstract: The effects, on the lower oesophageal sphincter, of the simultaneous administration of atropine and neostigmine were studied in 10 healthy patients undergoing gynaecological surgery. Atropine 1.2 mg and neostigmine 2.5 mg were given to antagonize neuromuscular blockade at the termination of surgery. For the succeeding 15–20 min, frequent measurements of lower oesophageal sphincter pressure (LOSP) were made whilst anaesthesia was maintained. It was demonstrated that this drug combination resulted in a significant decrease in LOSP initially, but that this potentially deleterious effect was transient in nature.

Alloy carbide precipitation in a high cobalt-nickel secondary hardening steel

Abstract: The process of alloy carbide precipitation in a high cobalt-nickel secondary hardening steel, AF1410 (Fe - 14 wt%Co - 10%Ni - 2%Cr - 1%Mo - 0.16%C) has been studied by FIM and atom probe techniques. The evolution of the alloy carbides has been followed in detail for the standard heat treatment temperature of 510°C. The first evidence of brightly-imaging solute clusters is observed after an ageing time of 1 minute, and the first traces of a rod-like morphology emerge after 30 minutes. Very slow growth of the rod-like carbides takes place between 30 minutes and 5 hours ageing, accompanied by a slow decrease in hardness. This is followed by rapid coarsening and spheroidisation, during which a marked loss of hardness occurs. The size and composition variation of the carbides has been followed throughout the ageing treatment. A model for the growth and coarsening of the particles is presented.

Pulsed laser atom probe analysis of iii-v compound semiconductors

Abstract: The pulsed laser atom probe has been shown to give stoichiometrically correct analyses of GaAs and InAs. Temperature rises under pulsed laser irradiation are investigated and the generation of As cluster ions is found to be primarily due to field evaporation at elevated temperatures. Preliminary results on the analysis of ternary materials is presented, showing local composition variations in a GaAlAs layer.

An FIM-atom probe and TEM study of Alnico permanent magnetic material

Abstract: Etude d'echantillons a l'Alnico 8 apres vieillissement thermomagnetique et traitement thermique ulterieur a l'aide d'un microscope ionique a emission de champ et d'un microscope electronique a haute tension

A comparative study of diazepam with sustained-release diazepam as oral premedication in minor gynaecological surgery

Abstract: SummarySixty patients undergoing elective minor gynaecological surgery received oral pre-operative medication with 10 mg diazepam in either conventional tablet form on the morning of operation or as the sustained-release tablet the night before. Subjective and objective assessments of the effectiveness of premedication were made. Patients receiving sustained-release diazepam on the night before surgery experienced fewer periods of wakefulness than those who received placebo. Patients who were given diazepam on the morning of surgery felt more drowsy pre-operatively than those who received sustained-release diazepam the night before.

Anxiety levels in junior anaesthetists during early training.

Abstract: Summary Trait anxiety levels (predisposition to anxiety) and personality profiles were recorded in four novice anaesthetists prior to the start of their training in anaesthesia. State anxiety (the extent of anxiety at the moment of testing) was also assessed before and afer the transition from accompanied to solo anaesthetic practice. There was no demonstrable difference in anxiety scores as a result of ‘going solo’ in any subject.