ABSTRACT
The development of novel contactless aerodynamic laser heated levitation techniques is reported that enable thermophysical properties of refractory liquids to be measured in situ in the solid, liquid, and supercooled liquid state and demonstrated here for alumina. Starting with polished crystalline ruby spheres, we show how, by accurately measuring the changing radius, the known density in the solid state can be reproduced from room temperature to the melting point at 2323 K. Once molten, by coupling the floating liquid drop to acoustic oscillations via the levitating gas, the mechanical resonance and damping of the liquid can be measured precisely with high-speed high-resolution shadow cast imaging. The resonance frequency relates to the surface tension, the decay constant to the viscosity, and the ellipsoidal size and shape of the levitating drop to the density. This unique instrumentation enables these related thermophysical properties to be recorded in situ over the entire liquid and supercooled range of alumina, from the boiling point at 3240 K, until spontaneous crystallization occurs around 1860 K, almost 500 below the melting point. We believe that the utility that this unique instrumentation provides will be applicable to studying these important properties in many other high temperature liquids.
ABSTRACT
A review of diamond-metal contacts is presented with reference to reported values of interfacial potential (Schottky) barriers and their dependence on macroscopic and microscopic properties of the diamond surface, the interface and the metal. No simple model can account for the overall spread of p-diamond barriers, although there are, for certain metals, correlations with metal electronegativity, interface chemistry and diamond surface preparation. Detailed studies are presented for a selected contact (Al-p-diamond) using real-time monitoring during metal growth from sub-nanometre to bulk films and subsequent in situ heating to 1000 °C. This contact, prepared in a clean vacuum environment on characterized single-crystal substrates, provides a case study for a combined in situ electrical and spectroscopic investigation using IV measurements for macroscopic diodes and real-time photoelectron spectroscopy for nanoscale metal films. Band bending during growth leads to a rectifying contact with a measured IV barrier height of 1.05 V and an ideality factor of 1.4. A transition from layered to clustered growth of the metal film is revealed in the real-time measurements and this is confirmed by AFM. For the annealed contact, a direct correlation is revealed by real-time photoemission between the onset of interfacial carbide formation and the change from a rectifying to an ohmic contact at 482 °C.
ABSTRACT
We combine small-angle x-ray scattering (SAXS) and wide-angle x-ray scattering (WAXS) with aerodynamic levitation techniques to study in situ phase transitions in the liquid state under contactless conditions. At very high temperatures, yttria-alumina melts show a first-order transition, previously inferred from phase separation in quenched glasses. We show how the transition coincides with a narrow and reversible maximum in SAXS indicative of liquid unmixing on the nanoscale, combined with an abrupt realignment in WAXS features related to reversible shifts in polyhedral packing on the atomic scale. We also observed a rotary action in the suspended supercooled drop driven by repetitive transitions (a polyamorphic rotor) from which the reversible changes in molar volume (1.2 +/- 0.2 cubic centimeters) and entropy (19 +/- 4 joules mole(-1) kelvin(-1)) can be estimated.
ABSTRACT
The problem of how to retain experienced nurses within a given specialist field impacts on both nurses and managers. This article explores the development of a new clinical role which gives experienced E and F grade nurses the opportunity for personal and professional growth. Within the new role, 50% of the nurse's time is devoted to ward-based clinical work and the other 50% to developing an area of clinical practice or research, as is the case with some clinical nurse specialists. There is flexibility over the area of specialist interest to reflect the needs of the service and the expertise and interests of the individual, and there is also flexibility in relation to the clinical commitment which increases opportunities for job shares. This development has arisen from an organizational culture which recognizes the need for more flexible job classifications and work rules. This new model for practice also represents a new model for management. In fostering self-reliance within the workforce it enables all parties to work towards a shared vision which is mutually beneficial for nurses, managers, the organization and, most importantly, the patient.
Subject(s)
Career Mobility , Job Description , Models, Nursing , Nurse Clinicians/organization & administration , Humans , WorkloadABSTRACT
The activity of netilmicin, a semisynthetic aminoglycoside, was compared with that of gentamicin, tobramycin, and amikacin against 100 clinical isolates of Serratia marcescens. Minimum inhibitory concentrations (MIC) were determined by an agar dilution procedure. Defining amikacin resistance as an MIC of greater than 16 mg/l, and netilmicin, gentamicin and tobramycin resistance as an MIC greater than 4 mg/l, 1% were resistant to amikacin, 3% to netilmicin, 8% to tobramycin, and 43% to gentamicin. The majority of isolates that were resistant to both gentamicin and tobramycin were sensitive to netilmicin. These results indicate that the activity of netilmicin against Ser. marcescens is closely comparable to that of amikacin.
