Showing papers by "National Physical Laboratory published in 2001"
Max Planck Society1, Scripps Institution of Oceanography2, National Center for Atmospheric Research3, Georgia Institute of Technology4, University of Maryland, College Park5, Utrecht University6, University of Innsbruck7, National Oceanic and Atmospheric Administration8, Physical Research Laboratory9, National Physical Laboratory10, Lawrence Berkeley National Laboratory11, University of California, Riverside12, Stockholm University13
TL;DR: It is shown that agricultural burning and especially biofuel use enhance carbon monoxide concentrations and Fossil fuel combustion and biomass burning cause a high aerosol loading, which gives rise to extensive air quality degradation.
Abstract: The Indian Ocean Experiment (INDOEX) was an international, multiplatform field campaign to measure long-range transport of air pollution from South and Southeast Asia toward the Indian Ocean during the dry monsoon season in January to March 1999. Surprisingly high pollution levels were observed over the entire northern Indian Ocean toward the Intertropical Convergence Zone at about 6°S. We show that agricultural burning and especially biofuel use enhance carbon monoxide concentrations. Fossil fuel combustion and biomass burning cause a high aerosol loading. The growing pollution in this region gives rise to extensive air quality degradation with local, regional, and global implications, including a reduction of the oxidizing power of the atmosphere.
725 citations
TL;DR: In this paper, the binding energy scales of x-ray photoelectron spectrometers were calibrated for general analytical purposes using unmonochromated Al or Mg x-rays or monochromate Al x-rams.
Abstract: This international standard specifies a method for calibrating the binding energy scales of x-ray photoelectron spectrometers, for general analytical purposes, using unmonochromated Al or Mg x-rays or monochromated Al x-rays. It is only applicable to instruments that have an ion gun for sputter cleaning. This international standard further specifies a method to establish a calibration schedule, to test for the binding energy scale linearity at one intermediate energy, to confirm the uncertainty of the scale calibration at one low and one high binding energy value, to correct for small drifts of that scale and to define the expanded uncertainty of the calibration of the binding energy scale for a confidence level of 95%. This uncertainty includes contributions for behaviour observed in inter-laboratory studies but does not cover all of the defects that could occur. This international standard is not applicable to instruments with binding energy scale errors that are significantly non-linear with energy, to instruments operated in the constant retardation ratio mode at retardation ratios of <10, to instruments with a spectrometer resolution worse than 1.5 eV or to instruments requiring tolerance limits of ±0.03 eV or less. This international standard does not provide a full calibration check, which would confirm the energy measured at each addressable point on the energy scale and would have to be performed in accordance with the manufacturer's recommended procedures. © Crown Copyright 2001. Published by John Wiley & Sons, Ltd.
255 citations
TL;DR: Sub-regional and sector level distribution of SO 2 and NO x emissions inventories for India have been estimated for all the 466 Indian districts using base data for years 1990 and 1995.
225 citations
TL;DR: Optical effectiveness of anisotropic etching of (1−0−0) silicon in inorganic alkaline solution has been studied from the view point of its application in commercial silicon solar cells as discussed by the authors.
193 citations
TL;DR: In this article, split-post dielectric resonators operating at frequencies 1.4-5 GHz were used to measure complex permittivity of single-crystal reference materials with well known dielectrics properties previously measured by other techniques.
Abstract: Split-post dielectric resonators operating at frequencies 1.4–5.5 GHz were used to measure complex permittivity of single crystal standard reference dielectric materials with well known dielectric properties previously measured by other techniques. Detailed error analysis of permittivity and dielectric loss tangent measurements has been performed. It was proved both theoretically and experimentally that using split post resonators it is possible to measure permittivity with uncertainty about 0.3% and dielectric loss tangent with resolution 2×10 −5 for well-machined laminar specimens.
188 citations
TL;DR: In this article, a polyaniline-acrylonitrile-butadiene-styrene composite film was used as a sensor material for aqueous ammonia.
Abstract: The present paper reports about polyaniline–(acrylonitrile–butadiene–styrene) composite film as a sensor material for aqueous ammonia. The resistance change of the composite film on exposure to different concentrations of aqueous ammonia shows its utility as a sensor material. The composite film on exposure to 10 −4 and 10 −5 N aqueous ammonia shows a well-defined response behaviour and this aspect has been utilized in designing the ammonia sensor.
158 citations
TL;DR: In this article, an analysis of the correlation of theoretical predictions for photoelectron intensities is made with experimental data from an XPS digital database for 46 solid elements measured using a spectrometer with calibrated intensity and energy scales.
157 citations
TL;DR: In this article, the immobilization of lactate dehydrogenase (LDH) on electrochemically polymerized polypyrrole-polyvinylsulphonate (PPY-PVS) films has been accomplished via cross-linking technique using glutaraldehyde.
149 citations
TL;DR: In this article, a quantitative structure-property relationship (QSPR) was proposed to estimate the IMFP of polymers and other organic materials from their structural properties, which can be applied across a range of organic structures for kinetic energies of ∼200-2000 eV.
Abstract: Inelastic mean free path values are needed for quantitative XPS analysis of a range of important polymers and other organic materials. Measured reference data are limited, although some semi-empirical equations to estimate IMFP are available. Existing estimation methods often require values for such quantities as the bandgap (in electron-volts) or the density, for which accurate measurements may not be available.
Here we develop a scheme for estimation of the IMFP that can be applied across a range of organic structures for kinetic energies of ∼200–2000 eV. This involves a quantitative structure–property relationship (QSPR), which allows the IMFP to be estimated for any organic material from its structural formula alone, either via a straightforward calculation on paper or instantly using one of a number of commercial molecular-modelling software packages. The accuracy of this IMFP estimate is better than existing methods, such as the TPP-2M equation for organic materials. In the majority of analytical problems involving surface analysis in chemistry or biochemistry, the structural formula of the organic material is known or can be conjectured with reasonable confidence, so that the approach described here is more widely applicable in practise and likely to be more accurate than previous methods for estimating the IMFP in organic materials. © Crown Copyright 2001 Reproduced by permission of the Controller of HMSO.
146 citations
TL;DR: In this paper, the authors have estimated for 1990 and 1995 the inventory of greenhouse gases CO,C H and N O for India at a national and sub-regional district level.
138 citations
TL;DR: The hot plate technique for measuring the thermal conductivities of insulating materials has been in existence in various forms since 1898 as discussed by the authors, and it is now unarguably recognized as the most accurate technique for determining thermal conductivity of insulations, having an uncertainty of about 1.5% over a limited temperature range near ambient.
Abstract: The hot plate technique for measuring the thermal conductivities (the exact term for the quantity measured is thermal transmission, which, depending on the material being measured, can have components of convective, radiative and conductive heat transfer; it is commonly referred to as the effective or apparent thermal conductivity) of insulating materials has been in existence in various forms since 1898. A brief historical survey of the early development of the experimental technique is followed by a brief description of the basic principles of the method of measurement. The technique has since become very well established and is documented in the written standard ISO8302:1991. It is now unarguably recognized as the most accurate technique for determining the thermal conductivity of insulations, having an uncertainty of about 1.5% over a limited temperature range near ambient. Details of two guarded hot plate apparatuses designed and constructed at NPL over the last decade or so, one to measure insulations up to 250 mm thick at or around room temperature and the other to measure insulations and refractories at temperatures up to 850 °C, are given. Finally, there is a section on certified reference materials required for validating the performance of newly built guarded hot plate apparatus and for calibrating heat flow meter apparatus, a type of hot plate apparatus commonly used for quality control purposes in insulation manufacturing plant. A brief overview of these reference materials includes details of their availability, thermal conductivities and temperature ranges.
TL;DR: In this paper, the enzyme cholesterol oxidase (ChOx) was immobilized on these DBS-doped polypyrrole (PPY) films by a physical adsorption technique.
Abstract: Dodecylbenzene sulfonate (DBS)-doped polypyrrole (PPY) conducting polymer films were electrochemically deposited onto the indium-tin-oxide (ITO)-coated glass plates in aqueous medium. The enzyme cholesterol oxidase (ChOx) was immobilized on these DBS–PPY films by a physical adsorption technique. These ChOx-immobilized DBS–PPY films were characterized by ultraviolet–visible and Fourier transform infrared spectroscopy. The enzyme activity studies indicate that ∼40% of ChOx leaches out from the ChOx/DBS–PPY film. The ChOx activity in the ChOx/DBS–PPY film was assayed as a function of cholesterol concentration. The results of amperometric measurements conducted on ChOx/DBS–PPY/ITO film show linearity over the range 2–8 mM of cholesterol solution. The ChOx/DBS–PPY/ITO electrodes exhibit a response time of 30 s and are stable for ∼3 months at 4 °C. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3486–3491, 2001
TL;DR: In this article, the characterization of the conducting polymer polyaniline and conducting fabrics was carried by spectroscopic techniques and thermogravimetric analysis, and the conducting fabric showed a shielding effectiveness of 35.61 dB.
TL;DR: In this paper, the authors carried out scratch tests on a range of ceramics and hard metals and found that fracture was a predominant form of damage to both hard and soft materials, but with the harder materials fracture occurred on a larger scale, often removing large fragments of material.
TL;DR: In this paper, the driving forces for the recent development of nanoscale features in conventional ceramic materials for both mechanical and functional reasons are discussed, and the causes of some of the resulting property enhancements are identified.
Abstract: The driving forces for the recent development of nanoscale features in conventional ceramic materials for both mechanical and functional reasons are discussed, and the causes of some of the resulting property enhancements are identified. Examples from the technical literature are examined, and the potential for future applications is assessed in terms of the tradeoff between enhanced properties and the added costs and difficulties of processing ultrafine powders.
TL;DR: An international intercomparison of the dosimetry of three beta particle emitting ophthalmic applicators was performed, which involved measurements with radiochromic film, thermoluminescence dosimeters (TLDs), alanine pellets, plastic scintillators, extrapolation ionization chambers, a small fixed-volume ionization chamber, a diode detector and a diamond detector.
Abstract: An international intercomparison of the dosimetry of three beta particle emitting ophthalmic applicators was performed, which involved measurements with radiochromic film, thermoluminescence dosimeters (TLDs), alanine pellets, plastic scintillators, extrapolation ionization chambers, a small fixed-volume ionization chambers, a diode detector and a diamond detector. The sources studied were planar applicators of 90Sr-90Y and 106Ru-106Rh, and a concave applicator of 106Ru-106Rh. Comparisons were made of absolute dosimetry determined at 1 mm from the source surface in water or water-equivalent plastic, and relative dosimetry along and perpendicular to the source axes. The results of the intercomparison indicate that the various methods yield consistent absolute dosimetry results at the level of 10%-14% (one standard deviation) depending on the source. For relative dosimetry along the source axis at depths of 5 mm or less, the agreement was 3%-9% (one standard deviation) depending on the source and the depth. Crucial to the proper interpretation of the measurement results is an accurate knowledge of the detector geometry, i.e., sensitive volume and amount of insensitive covering material. From the results of these measurements, functions which describe the relative dose rate along and perpendicular to the source axes are suggested.
TL;DR: In this paper, the authors developed simple equations, suitable for the analyst, based on the Monte Carlo calculations of Jablonski, for the corrections arising from elastic scattering, and derived more accurate equations for these parameters and the ratio of the attenuation length, L, to the inelastic mean free path (IMFP) based on a knowledge of ω.
Abstract: In this work we develop simple equations, suitable for the analyst, based on the Monte Carlo calculations of Jablonski, for the corrections arising from elastic scattering. These concern modification of the angular anisotropy in XPS and the absolute intensities in both Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) as a function of the atomic number Z. We also derive more accurate equations for these parameters and the ratio of the attenuation length, L, to the inelastic mean free path (IMFP) based on a knowledge of ω, where ω is the ratio of the IMFP to the sum of the transport mean free path (TrMFP) and the IMFP. The first equations give the corrections to the anisotropy, β eff (α)/β, and the total emission, Q(a), from Jablonski's work in terms of a total of four equations and a total of 19 coefficients to replace Jablonski's two equations with a total of 2376 coefficients. The present equations describe the dependencies of β eff (α)/β and Q(a) on the angle of electron emission a, the electron energy E and the atomic number of the matrix in the ranges 0° < a < 70°, 300 < E < 1500 eV and 6 < Z < 83. The standard deviation of the scatter with regard to Jablonski's calculations are 4.6% for β eff (α)/β and 1.35% for Q(a), giving an overall uncertainty for quantification, relative to the Monte Carlo calculations, of better than 2%. The equations allow values of β eff (α) to be calculated for revised values of β and for elements other than the 27 studied by Jablonski. They also allow Q(a) to be calculated for other elements and for energies appropriate to Auger electrons within the above ranges. More complex equations, derived from a slight modification to the transport equations, allow β eff (0)/β, Q(0) and the ratio L/IMFP to be derived from a knowledge of ω. These equations exhibit a standard deviation of scatter of 2.8%, 0.3% and 1.1%, respectively, compared with the Monte Carlo calculations of Jablonski and of Cumpson and Seah, leading to uncertainties in quantification of the order of 1%. These equations are more complex for the analyst to use than the simple equations as a function of Z, but have superior accuracies and accuracies that are probably limited by the precision of the Monte Carlo calculations.
TL;DR: In this paper, the authors reported the chemical synthesis and characterization of poly(aniline-co-fluoroanilines) [poly(An-FAn] using FTIR, UV-visible spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron micrography (SEM), and a four points-probe conductivity method.
Abstract: In the present article, we report the chemical synthesis and characterization of poly(aniline-co-fluoroaniline) [poly(An-FAn)]. The copolymerization of aniline and 2-fluoroaniline was carried out by chemical method in acidic medium. The characterization of poly(aniline-co-fluoroaniline) was done using FTIR, UV-visible spectroscopy, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), scanning electron micrography (SEM), and a four-points-probe conductivity method. X-ray diffraction (XRD) and SEM characterization reveal crystalline nature of doped copolymer compared to undoped copolymer. The observed decrease in the conductivity of the copolymer relative to polyaniline is attributed to the incorporation of the fluoro moieties into the polyaniline chain. The chemically synthesized copolymer shows good solubility in common organic solvents, and is, therefore, technological useful. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1460–1466, 2001
TL;DR: The value of the apparent Michaelis-Menten constant was experimentally determined to be 2.5 and 2.7 for physically adsorbed and electrochemically entrapped urease in PPY-PVS films, respectively.
Abstract: Immobilization of urease and glutamate dehydrogenase enzymes in electrochemically prepared polypyrrole-polyvinyl sulfonate films (PPY-PVS) was carried out using physical adsorption and electrochemical entrapment techniques. Detailed studies on optimum pH, Fourier transform infrared spectroscopy, cyclic voltammetry, and scanning electron microscopy of the enzymes in the immobilized state were conducted. The value of the apparent Michaelis-Menten constant was experimentally determined to be 2.5 and 2.7 for physically adsorbed and electrochemically entrapped urease in PPY-PVS films, respectively.
TL;DR: In this paper, the spectral characteristics of partially coherent light passing through a rectangular or a circular aperture were investigated in the near zone of the near Fresnel approximation, and it was shown that at a critical value of z (the distance between the aperture and the on-axis observation point), the gradual change in the spectral shift shows a rapid spectral switch.
Abstract: Within the Fresnel approximation, experimental investigations of the spectral characteristics are carried out in the near zone when partially coherent light passes through a rectangular or a circular aperture. It is seen that at a critical value of z (the distance between the aperture and the on-axis observation point), the gradual change in the spectral shift shows a rapid spectral switch. Experimental results are compared with the theoretically expected results.
TL;DR: The concept of edge chipping as a pragmatic way of ranking materials for toughness is now well established for brittle materials, but has some limitations for tougher materials such as hardmetals and tool steels as mentioned in this paper.
Abstract: The concept of edge chipping as a pragmatic way of ranking materials for toughness is now well established for brittle materials, but has some limitations for tougher materials such as hardmetals and tool steels. This paper reviews our current understanding of the process of quasi-static edge chipping or flaking. Issues of flake shape, statistics of flaking load and linearity of flaking load vs. distance from edge relationships are discussed. Based on experimental work, the `universal' relationship between edge toughness, defined as flaking load divided by distance of indentation from the edge, and fracture energy GIC, as evaluated by McCormick and Almond, is re-evaluated with improved statistics and found to be correct.
TL;DR: In this article, the authors studied the spatial variability in the amount of biomass burnt and the contribution of different components viz., bole, branch, and mixed leaf litter in the burning process affecting the combustion factors.
TL;DR: In this article, the results of tests that were performed using a modified ASTM dry sand rubber wheel test system were presented, and it was found that although there was only a small increase in wear as the relative speed increased, a sudden increase of wear of two orders of magnitude was observed as the load was increased for both the Tungsten carbide-cobalt (WC-Co) hardmetals and tool steels.
TL;DR: In this article, Annealing effects in a reducing environment (flowing nitrogen) in the temperature range of $200--600\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ are reported on the high Tl content.
Abstract: Annealing effects in a reducing environment (flowing nitrogen) in the temperature range of $200--600\ifmmode^\circ\else\textdegree\fi{}\mathrm{C}$ are reported on the high Tl content $({\mathrm{Cu}}_{1\ensuremath{-}x}{\mathrm{Tl}}_{x}){\mathrm{Ba}}_{2}{\mathrm{Ca}}_{2}{\mathrm{Cu}}_{3}{\mathrm{O}}_{y}$ system, synthesized under high pressure (4.5 GPa). A considerable enhancement in ${T}_{c}$ from 97 K (as-synthesized) to $g130 \mathrm{K}$ (annealed at $550\ifmmode^\circ\else\textdegree\fi{}\mathrm{C})$ and an anomalous behavior in the resistivity with annealing is found. The results have been analyzed in the context of the loss of oxygen and Tl valence change.
TL;DR: In this paper, the authors developed reference methods for the measurement of ultrasonic power with a validated measurement uncertainty of < 7% at power levels of 1 to 20 W over the frequency range 1 to 3 MHz of collimated beams.
Abstract: A project has been completed to develop reference methods for the measurement of ultrasonic power with a validated measurement uncertainty of < 7% at power levels of 1 to 20 W over the frequency range 1 to 3 MHz of collimated beams. The project is the result of collaborative research between the Physikalisch-Technische Bundesanstalt, Germany (PTB, DE), the National Physical Laboratory, UK (NPL, UK) and the Netherlands Organisation for Applied Scientific Research, Prevention and Health (TNO-PG, NL). The work has been undertaken under the 4th Framework Programme of the European Community (EC). Primary standard designs of radiation force balances based on both absorbing and reflecting targets have been constructed. To avoid heating effects, the measurements should be done relatively quickly (10 to 20 s). The methods have been validated using ultrasound (US) transducers that demonstrated an adequate short and long-term stability; a method to detect cavitation based on monitoring the acoustic signals produced by bubble oscillation and collapse has been confirmed. It has been shown that only the detection of the subharmonic can be used in practice as cavitation detector. Different procedures for obtaining degassed water have been investigated. A method showing significant promise to be used in a clinical or manufacturer's environment involves the addition of sodium sulphite (Na2SO3). During the validation process, commercially available radiation force balances and ultrasonic physiotherapy devices have also been evaluated. Limitations of current measurement methods and practices, including power measurements made on transducers exhibiting a diverging beam, have been identified. It has been shown that a reflecting target is not appropriate to measure powers of transducers with a ka-value < 30. Based on beam shape and target distance, it has been shown also that proper power measurements using a 45 degrees convex-conical reflecting target can never be performed for transducers with a ka-value < 17.4.
TL;DR: In this paper, a "round robin" project has been carried out to detennine the accuracy and reliability of various models used to estimate the viscosities of industrial slags.
Abstract: A "round robin" project has been carried out to detennine the accuracy and reliability of various models used to estimate the viscosities of industrial slags. The 21 participants were divided into measurement suppliers and modelling participants. Reference materials were issued to the measurement suppliers to check the validity of the viscosity data supplied. A data base of viscosity-temperature-composition data was established for eight different categories of slags. Chemical compositions were issued to the different modelling participants and the predicted viscosities were compared with calculated values. For mould fluxes the global % errors associated with the various models were: modified lida (25), Riboud (30), Gupta (35), NPL (37). For non-fluoride slag systems, the Ling Zhang, KTH and modified Iida models all perfonned well.
TL;DR: In this article, an extension has been made of previous analyses of peak area intensities for elemental spectra in digital Auger and x-ray photoelectron databases, instead of being analysed after removal of the extrinsic characteristic loss background calculated by deconvolving the relevant angle-averaged reflected electron energy-loss spectroscopy (REELS) spectrum.
Abstract: An extension has been made of previous analyses of peak area intensities for elemental spectra in digital Auger and x-ray photoelectron databases. The intensities, instead of being analysed after removal of a background derived from the Tougaard Universal cross-section, are now analysed after removal of the extrinsic characteristic loss background calculated by deconvolving the relevant angle-averaged reflected electron energy-loss spectroscopy (REELS) spectrum. The angle-averaged REELS data for each element are calculated from a digital REELS database using a recently defined scaling of the measured characteristic losses from the elastic peak. The new background removal procedure leads to an improvement in the correlation between experiment and theory for intensities in both AES and XPS. Analysis of these correlations shows that a systematic divergence remains for each element, which is the same for XPS as for AES. This divergence is attributed to an inadequacy either of the angle-averaged REELS method or of the material-to-material dependence of the TPP-2M equation used in the calculation of the inelastic mean free paths. Correction for this is possible in a new matrix-less quantification formulation using average matrix sensitivity factors. This leads to correlations between experiment and theory with scatter factors of ×/÷1.08 and ×/÷1.11 for AES and XPS, respectively, for a wide range of elements and peaks. These scatter factors are much better than for previous correlations and underpin the choice of formulae to calculate the relevant theoretical intensity predictions. These calculations lead directly to values of average matrix sensitivity factors, appropriate for use with spectrometers giving true spectra or with those spectrometers that may be calibrated to provide such spectra. © Crown Copyright 2001. Published by John Wiley & Sons, Ltd.
TL;DR: The CODATA Task Group on Fundamental Physical Constants (CODATA) as discussed by the authors has published a review of the measurements relevant to the determination of the values of fundamental physical constants.
Abstract: The measurements of quantities providing information on the values of the fundamental physical constants bring together a wide variety of measurements in very different parts of physics in a unique way. Taken both separately and together these measurements provide stringent tests of theory. They also throw light on the question: `How well do we understand physics via measurements at the highest level of accuracy?' They also have important practical applications. In this way they can point the way to the inadequacies and strengths of our knowledge and be used to benefit mankind. The first thorough review of the measurements relevant to the determination of the values of fundamental physical constants was that of Birge in 1929, and the latest CODATA review by Mohr and Taylor was published in 2000. Over the intervening period most of the old textbook methods have either disappeared or been considerably refined. Many of them have been replaced by determinations based on developments in such diverse areas as, for example, quantum electrodynamics, solid-state physics, low-temperature physics and laser spectroscopy. These have improved our knowledge of the values of the fundamental constants by many orders of magnitude. In accordance with their role as the natural units of physics, many of the methods have already found important applications for both defining and maintaining the SI units. These provide the basic units for the measurements used in science, technology and everyday life. The measurements involved in the latest evaluation by the CODATA Task Group on Fundamental Physical Constants are discussed together with the likely developments in the next few years. The pace of the subject reflects the overall pace of physics and technology and this can be used as a guide to future developments.
TL;DR: In this article, the spin Hamiltonian parameters, dipolar hyperfine coupling parameter, P, and Fermi contact interaction interaction interaction parameter, K, have been calculated for the vanadium ion.
TL;DR: Gill as mentioned in this paper reports from a recent symposium, where first steps toward tomorrow9s even more accurate optical clocks were reported, which play a key role in the Global Positioning System, serve as international timekeeping standards and enable fundamental laws of physics to be tested.
Abstract: Accurate clocks play a fundamental role in science and technology. They play a key role in the Global Positioning System, serve as international timekeeping standards, and enable fundamental laws of physics to be tested. Atomic clocks are today9s most accurate clocks. In his Perspective,
Gill
reports from a recent symposium, where first steps toward tomorrow9s even more accurate optical clocks were reported.