Showing papers by "National Physical Laboratory published in 1981"
TL;DR: In this article, an analysis is presented of published sets of pure element sputtering yields with the objective of predicting data for elements for which measurements are not available, and it is shown that these data sets each correlate with Sigmund's target dependence predictions with a scatter of 20%.
151 citations
TL;DR: In this paper, the results of the determination of both the refractive index and the power absorption coefficient of seven common polymers (low and high density polyethylene, polyamide, polymethyl methacrylate, polytetrafluorethylene, polystyrene and poly 4 methyl pentene-1) at a temperature of 290K in the spectral region between 4 and 40cm −1 by the techniques of dispersive Fourier transform spectrometry are presented.
135 citations
TL;DR: Measurements of ion concentrations within selected subcellular compartments show that freeze-substitution with dry sectioning is a valuable preparative technique for analytical electron microscopy of highly vacuolate plant material.
Abstract: Grown under saline conditions, Suaeda maritima accumulates Na+ and Cl- into its leaves, where individual mesophyll cells behave differently in their compartmentation of these ions. Measurements of ion concentrations within selected subcellular compartments show that freeze-substitution with dry sectioning is a valuable preparative technique for analytical electron microscopy of highly vacuolate plant material. Using this approach, absolute estimates were made of Na+, K+ and Cl- concentrations in the cytoplasm, cell walls, chloroplasts and vacuoles of leaf mesophyll cells.
126 citations
TL;DR: In this paper, the authors evaluated the statistical contribution of sequential layer sputtering to depth resolution in concentration-depth profiles by combining with Auger electron spectroscopy and secondary ion mass spectrometry.
69 citations
TL;DR: In this article, the depth resolution in compositional profiles of layers on rough substrates, analysed by ion sputtering with Auger electron spectroscopy or other surface analytical techniques, is evaluated in detail to define the precise effect of the substrate.
68 citations
54 citations
TL;DR: The vapour pressure of benzene and hexafluorobenzene in the range 10 to 100 kPa were measured in the course of developing a comparative ebulliometric apparatus.
51 citations
TL;DR: In this article, the IR, 1H NMR and Mossbauer studies indicate an anisobidentate character for the dtc (dithiocarbamate) ligand in these complexes.
44 citations
TL;DR: In this article, the regimes of preference of each technique are delineated by considering individually each of the terms contributing to interface degradation for the various types of layered structures encountered in practice, e.g. evaporated films and oxide layers.
44 citations
TL;DR: In this paper, the vapour pressures of four esters of acetic acid and of three fatty acids were measured by comparative ebulliometry; the ranges covered were from about 3 to 200 kPa for methyl, ethyl and propyl acetates, and propionic acid.
44 citations
01 Jan 1981
TL;DR: In this paper, the authors reported that fracture initiation occurs at the intersection of the locus of the stress-state dependent fracture strain with the spatially varying strain across the notch throat.
Abstract: Notched specimens of Nimonic 80A with a Bridgman geometry have been creep tested at 750°C using nett section stresses of between 154 and 600 MFa. The material “notch-strengthened” on a nett section stress basis but reasonable agreement with plain bar lifetimes was found by comparing the results using the Bridgman effective stress as the representative rupture stress. The interesting observation was made that fracture initiated at the notch centre with the highest stresses but at the notch root with the lowest. This was not a consequence of any change in fracture micromechanism with stress level, since all fractures were intergranular and caused by creep cavitation. The explanation offered is that the spatial position of fracture initiation occurs at the intersection of the locus of the stress-state dependent fracture strain with the spatially varying strain across the notch throat. The stress-state dependent fracture strain locus can be explained, without invoking any stress-state dependence of cavity growth rate, by the observed stress-state variation of cavity nucleation rate.
TL;DR: In this paper, the problem of surface charging when analysing insulators by static SIMS is discussed, and it is shown that only by the correct design of an electron flood source can the surface be stabilized to a given constant reference potential.
Abstract: As part of an ongoing programme of reference work for surface analysis at the NPL, the problem of surface charging when analysing insulators by static SIMS is discussed. Meaningful analysis requires stabilization of the surface potential to a defined reference point, here taken as the potential that would exist if the insulator was a conductor. In SIMS spectra it is shown that both the absolute and relative intensities of peaks depend on the surface potential. It is also shown that, only by the correct design of an electron flood source, can the surface be stabilized to a given constant reference potential. The relevant design principles are illustrated by measurements on isolated targets which define the characteristics of the flood source. Stabilization is effected to within the ±0.5 eV required for static SIMS.
TL;DR: In this article, the authors used the Weibull distribution for the initial lengths of the cracks in the fibres to account for the time to failure of the bundle and the rate of failure of individual filaments during stress corrosion.
Abstract: Bundles of fibres loaded from their ends and immersed in a corrosive environment show times to failure that are extremely sensitive to the value of the applied load. This behaviour is accounted for by using the empirically established relation between rate of crack growth ( v ) and stress intensity-factor ( K I ) found for many brittle materials ( v ∝ K n 1 ) and by using a two-parameter Weibull distribution for the initial lengths of the cracks in the fibres. The theory accounts well for the time to failure of the bundle and for the rate of failure of individual filaments during stress corrosion. The dominant feature of the results is that time to failure depends on applied load to the power – n .
TL;DR: In this paper, a direct relationship between the primary Young's modulus of the precursor and the Young's Modulus of carbon fiber developed therefrom has been established for the first time.
TL;DR: In this article, a unified and simple treatment of the subject, correct to all orders of approximation, in which radiation pressure appears as a true field parameter was developed, and it is shown that the definition of radiation pressure proposed here can be reconciled with most of the current definitions and that much of the apparent contradiction is illusory.
TL;DR: In this paper, a transpiration apparatus and a gas chromatograph are combined for measurement of vapour concentration, in which the functions of transpiration and chromatography are combined, and two modes of operation are described, one discriminates against impurities.
TL;DR: The optical properties of thin dielectric films prepared by vacuum deposition and r.f. sputtering have been measured using guided waves, ellipsometry and reflectometry to assess the relative merits and disadvantages of the three techniques.
Abstract: The optical properties of thin dielectric films prepared by vacuum deposition and r.f. sputtering have been measured using guided waves, ellipsometry and reflectometry to assess the relative merits and disadvantages of the three techniques. Particular attention has been given to the effect on these measurements of typical film imperfections, for example refractive index inhomogeneity and anisotropy. The guided wave technique is shown to possess the highest precision of measurement, to be relatively insensitive to film inhomogeneity and to provide the most suitable method for studying film birefringence. Ellipsometry has a high sensitivity of measurement that can be usefully applied to thinner films than those required by the other techniques. The method is well suited for studying inhomogeneity, but because of its sensitivity to this film defect, ellipsometric measurements must always be interpreted with care. Reflectometry, although only of limited accuracy in measuring film properties, is widely applica...
TL;DR: In this paper, a radionuclide generator is described for the rapid recovery of82Rb, the 1.25 min half-life decay product of82Sr. An outline is given of the quality control procedure adopted to ensure that the 82Rb is suitable for clinical use.
Abstract: 82Sr has now been produced by the spallation of Molybdenum by protons of up to 800 MeV. The radiochemical recovery of strontium is described together with a description of the analytical techniques used to estimate recovered yields of the various radionuclides generated. A radionuclide generator is described for the rapid recovery of82Rb, the 1.25 min half-life decay product of82Sr. An outline is given of the quality control procedure adopted to ensure that the82Rb is suitable for clinical use.
TL;DR: In this article, the heat capacity and enthalpy between 230 and 800 K have been determined by differential scanning calorimetry for several alloy compositions in the Cu+Sb, Ag + Sb, Au+ Sb and Au + Bi systems.
TL;DR: In this paper, a cavity growth model is developed which is consistent both with present work and previously unexplained results on the pressure dependence of secondary creep rates, and its main microstructural effect, apart from the important influence on sub-structure strengthening, was to increase markedly the grain boundary cavity density over that found in the parent material.
01 Jan 1981-International Journal of Human-computer Studies \/ International Journal of Man-machine Studies
TL;DR: This paper investigates the effect of different presentation speeds on performance in a learning task and found that performance deteriorated at speeds similar to, or faster than reading speed.
Abstract: When a computer generates text for a Visual Display Unit, it is usually presented at the fastest speed available. The experiments described in this paper investigate the effect of different presentation speeds on performance in a learning task. It was found that performance deteriorated at speeds similar to, or faster than reading speed. If understanding and retention of textual material is important, the optimum presentation speed is in the range 10-15 characters per second.
TL;DR: In this article, a non-resonance technique with bidirectional strain gauges was used to measure various storage moduli and damping factors of glassy polymers in the frequency range 10 −2 to 10 −7 Hz.
TL;DR: In this paper, the components of the complex tensile modulus E∗, Poisson's ratio v∗, shear modulus G∗ and bulk modulus K∗ have been determined at 21°C in the frequency range 10−2 to 107 Hz for PMMA and rigid PVC.
TL;DR: In this paper, repeated measurements of the sensitivity of both triode and Bayard-Alpert types of ionization gauge have been made as a function of the number of operating hours of the gauges.
TL;DR: In this paper, the influence of grain size ranging from 0.3 to 3 mm on the performance of p on n polycrystalline silicon solar cells having columnar grains has been investigated.
TL;DR: In this paper, the vapour pressure of bis(2-hydroxyethyl) ether (diethylene glycol) was measured by comparative ebulliometry, and the results were fitted by third-order Chebyshev equations.
TL;DR: In this paper, the enthalpy of transformation and fusion has been derived for 16 alloys from the Cu + Ga, Ag + Ga and Ag + In systems, and the endotherms monitored in this study provide valuable information concerning the various phase transformations occurring in these systems.
TL;DR: The ordering of a large number of pleochroic azo and anthraquinone dyes, has been investigated in two technologically important mesogenic mixtures E 1 and PCH-1132 at various temperatures as mentioned in this paper.
Abstract: The ordering of a large number of pleochroic azo and anthraquinone dyes, has been investigated in two technologically important mesogenic mixtures E 1 and PCH-1132 at various temperatures. The effect of molecular geometry (i.e. length and breadth) of the dyes and the nature of the host on the order parameter of these dyes are examined.