Showing papers by "National Physical Laboratory published in 1968"
TL;DR: The program, which employs the non-linear least-squares method, may be used to calculate equilibrium constants for hydrolysed metal ions, protonated ligands, and simple, Protonated, Hydrolysed, polynuclear, and mixed complexes.
297 citations
TL;DR: In this article, a method for the production of interference fringes equivalent to those produced by a series of linearly arranged pinholes without actually constructing such pinholes is described, which is similar to those occurring in multiple beam hologram interferometry and to the lobes produced by one dimensional antenna arrays.
Abstract: A method is described for the production of interference fringes equivalent to those produced by a series of linearly arranged pinholes without actually constructing such pinholes. Exposures of varying duration are recorded on a photographic plate which is successively displaced with respect to a laser speckle pattern. The Fourier transform of the pattern produced by these multiple exposures is then obtained optically by illuminating the plate with a converging spherical wave. The fringes observed are similar to those occurring in multiple beam hologram interferometry and to the lobes produced by one dimensional antenna arrays.
239 citations
TL;DR: In this paper, it was shown that the Taylor-vortex flow is stable against perturbations with the same axial wavelength and phase, but unstable with perturbation differing in phase by ½π.
Abstract: It is known experimentally that laminar circular Couette flow between two concentric circular cylinders, the outer of which is fixed, becomes unstable when the speed of the inner cylinder is high enough. The flow is then replaced by a new circumferential flow with superimposed toroidal (or Taylor) vortices spaced periodically along the axis. At a higher speed still the new flow develops another instability, and is replaced by a flow in which the axially periodic vortices are simultaneously periodic travelling waves in the azimuth.In the present paper an attack is made on the problem of instability of the Taylor-vortex flow against perturbations which are periodic both in the axial and azimuthal co-ordinates and, moreover, travel with some phase velocity in the latter. Subject to a number of assumptions and approximations, which are detailed in the paper, it is found that the Taylor-vortex flow is stable against perturbations with the same axial wavelength and phase, but unstable against perturbations differing in phase by ½π. After instability the new flow no longer has planes separating neighbouring vortices, but has wavy surfaces travelling in the azimuth. This feature is in accord with much (though not all) of the experimental evidence.The critical Taylor number (proportional to the square of the speed) at which the Taylor vortices become unstable is found theoretically to be about 8% above the value for which Taylor vortices first appear. This must be compared with a value in the range 5-20% for the experiments which our work models most closely. The azimuthal wave-number given a slight preference by theory is 1, in agreement with those experiments.
201 citations
TL;DR: In this paper, the signs and magnitudes of the spin-spin coupling constants of organo-phosphorus compounds have been examined by magnetic double resonance spectroscopy, and parallel behavior is noted between two types of coupling constants.
Abstract: Twenty-two organo-phosphorus compounds of a variety of structural types have been examined by $^1$H-{$^{13}$C} and $^1$H-{$^{31}$P} magnetic double resonance spectroscopy. The signs and magnitudes of the $^{31}$P-H and $^{31}$P-$^{13}$C spin-spin coupling constants are sensitive to the valency of the phosphorus atom, and the nature of the groups attached to it. Parallel behaviour is noted between two types of coupling constant. The $^{31}$P chemical shifts agree with results obtained by conventional $^{31}$P single resonance spectroscopy, and the $^{13}$C chemical shifts depend on the polarizability of the phosphorus atom and its associated groups.
153 citations
TL;DR: In this paper, the infra-red spectra of triphenylphosphine, triethylamine, and triphenlyphosphines are reported, together with the Raman spectrum of the first compound.
142 citations
TL;DR: In this article, a survey of the noise emitted by freely flowing traffic has been made on sites ranging from motorways to urban roads and the results provide an indication of present-day traffic noise conditions against which future comparisons may be made and also show how basic variables such as traffic density, speed and composition, and distance from the roadside affect the observed patterns of noise.
108 citations
TL;DR: In this article, an improved version of Householder's algorithm for tridiagonalization of a real symmetric matrix was discussed. But the most efficient form of the procedure depends on the method used to solve the eigenproblem of the derived tridiagon matrix.
Abstract: In an early paper in this series [4] Householder’s algorithm for the tridiagonalization of a real symmetric matrix was discussed. In the light of experience gained since its publication and in view of its importance it seems worthwhile to issue improved versions of the procedure given there. More than one variant is given since the most efficient form of the procedure depends on the method used to solve the eigenproblem of the derived tridiagonal matrix.
100 citations
TL;DR: In this article, the formation and growth of three-dimensional wave packets in a laminar boundary layer is treated as a linear problem and the asymptotic form of the disturbed region developing from a point source is obtained in terms of parameters describing two-dimensional instabilities of the flow.
Abstract: The formation and growth of three-dimensional wave packets in a laminar boundary layer is treated as a linear problem. The asymptotic form of the disturbed region developing from a point source is obtained in terms of parameters describing two-dimensional instabilities of the flow. It is shown that a wave caustic forms and limits the lateral spread of growing disturbances whenever the Reynolds number is √2 times the critical value. The analysis is applied to the boundary layer on a flat plate and shapes of the wave-envelope are calculated for various Reynolds numbers. These show that all growing disturbances are contained within a wedge-shaped region of approximately 10° semi-angle.
98 citations
TL;DR: With several algorithms for finding the eigensystem of a matrix the volume of work is greatly reduced if the matrix A is first transformed to upper-Hessenberg form, i.e. to a matrix H such that h, ij 0 (i> i+1).
Abstract: With several algorithms for finding the eigensystem of a matrix the volume of work is greatly reduced if the matrix A is first transformed to upper-Hessenberg form, i.e. to a matrix H such that h, ij 0 (i> i+1). The reduction may be achieved in a stable manner by the use of either stabilized elementary matrices or elementary unitary matrices [2].
92 citations
89 citations
TL;DR: In this article, the authors reported additional infra-red and Raman data for methylphenyl sulphide and diphenyl disulphide, as well as new infra red data for Diphenyl sulphoxide and the complex [(C6H5)2SO]2CdI2.
TL;DR: Each of the eigenproblems Ax and A B x = λ x can be reduced to the standard symmetric eigenproblem by making use of the Cholesky factorization of B.
Abstract: In many fields of work the solution of the eigenproblems Ax = λBx and A B x = λ x (or related problems) is required, where A and B are symmetric and B is positive definite. Each of these problems can be reduced to the standard symmetric eigenproblem by making use of the Cholesky factorization [4] of B.
TL;DR: The standard thermal flux has been produced by sources consisting of beryllium targets bombarded by a deuteron beam from a Van de Graaff accelerator, and has been reproducible to ± 0·1 per cent over a period of 6 months as discussed by the authors.
TL;DR: The surface energy of pure δ phase iron was measured at 1410°C as a function of the oxygen content of the ambient atmosphere, by a zero-creep technique as discussed by the authors.
TL;DR: In this paper, a method of real-time analysis of the surface shape and to demonstrate its advantages is presented. But this method requires the use of a holographic model and is computationally expensive.
Abstract: Powell and Stetson1 have shown that holography can be used to study the vibration modes of a surface. The technique they employed was to record a hologram while the surface was actually vibrating. The reconstructed image from such a hologram varies in brightness with the total excursion of the surface movement, and gives a kind of “time-averaged” contour map of the vibration amplitude. We wish to report a method of real-time analysis of the surface shape and to demonstrate its advantages.
TL;DR: In this paper, the infrared spectra (380-40 cm−1) of triphenylphosphine (L) complexes L2MX2 and (LHgX2)2, M = Zn, Cd, or Hg; X = Cl, Br, or I, have been recorded.
TL;DR: Measurements, performed at NBS, NPL, and PTB, on helium-neon lasers stabilized on the Lamb dip, have shown that the wavelengths of these lasers fell within approximately 1 part in 10(7).
Abstract: Measurements, performed at NBS, NPL, and PTB, on helium–neon lasers stabilized on the Lamb dip, have shown that the wavelengths of these lasers fell within approximately 1 part in 107. Beyond this limit, different lasers were found to emit different wavelengths. In addition, the wavelength of a given laser may vary during the life of its discharge tube. Pressure shifts appear to be a major cause of these variations.
TL;DR: Experiments using resting-cell suspensions of the hydrogenase-positive sulphate-reducing bacterium, Desulfovidrio vulgaris have shown that the organisms can depolarize the cathodic areas of a mild-steel surface, utilizing the polarizing hydrogen for the reduction of a suitable substrate and stimulating corrosion of the steel to a degree equivalent to the hydrogen used.
TL;DR: The scanning electron microscope provides a three-dimensional view of surface structure and it has been used for studying human blood cells for many years, but its view is still restricted to the superficial layers of the cell membrane.
Abstract: THE surface of the red blood cell has been studied extensively by means of the electron microscope. This requires replica techniques or the preparation of haemoglobin-free “ghosts”; the interpretation of the resulting pictures has been a matter of individual opinion and, frequently, of controversy, because they are restricted by limitations of dimensional perspective. The scanning electron microscope provides a three-dimensional view of surface structure and it has been used for studying human blood cells1,2. Although this instrument provides much greater depth of focus than the transmission electron microscope, its view is still restricted to the superficial layers of the cell membrane. To be able to see the cell membrane beneath its surface and the internal structure of the cell beneath would be of great value.
TL;DR: In this article, the surface defects are almost always present in glass, reducing its strength, and one way of overcoming this is to replace cations in the surface layer with larger cations from a molten salt.
Abstract: Surface defects are almost always present in glass, reducing its strength. One way of overcoming this is to replace cations in the surface layer with larger cations from a molten salt.
TL;DR: N.m.r., infrared, mass spectra and chemical methods have provided a unique structure for rubratoxin B that has been described in detail for the first time.
Abstract: N.m.r., infrared, mass spectra and chemical methods have provided a unique structure for rubratoxin B.
TL;DR: In this paper, the surface and grain boundary energies have been measured on silicon iron as a function of bulk silicon content, oxygen potential of the controlled atmosphere and temperature at 1410°c, the silicon concentration at the free surface of Fe 3% Si is approximately 13% A similar silicon enrichment occurs at grain boundaries.
Abstract: Absolute surface and grain boundary energies have been measured on silicon iron as a function of bulk silicon content, oxygen potential of the controlled atmosphere and temperature At 1410°c, the silicon concentration at the free surface of Fe–3% Si is approximately 13% A similar silicon enrichment occurs at grain boundaries By far the most important effect is that of oxygen adsorption, which reduces the surface energy severely, the saturation surface coverage at 1330°c being 0·47 of a monolayer An oxygen potential greater than that equivalent to pH2O/pH2=10−4 develops a (100) secondary recrystallization texture on thin foils, by virtue of the preferential adsorption of oxygen on (100) planes At pH2O/pH2 < 10−4, the foils show a (110) texture In addition, the temperature coefficient of surface energy which is -0·36 ergs cm−2°c−1 for a clean surface, becomes positive and equal to 0·55 ergs cm−2°c−1 in the presence of oxygen adsorption The relevance of the present observations to the seconda
TL;DR: In this paper, the vibrational spectra are presented and interpreted for six compounds containing the CH 3 Hg group; for diethylmercury and ethylmercuric bromide; for dibenzylmer cury, benzylmer curic chloride and bromides; and for allylmerculic iodide.
TL;DR: In this paper, a simple calculation can give some idea of the variations in solvation energy in a series of similar molecules, including aromatic heterocycles and singlet-triplet transitions in polycyclic aromatic hydrocarbons.
TL;DR: In this article, the spectral distribution of daylight at Delhi is described and the chromaticities calculated on the 1931 CIE system from 187 spectral curves, recorded over about a year, are presented and their distribution about the Planckian locus is discussed.
Abstract: The recording spectroradiometer for collecting data on the spectral distribution of daylight at Delhi is briefly described. The chromaticities calculated on the 1931 CIE system from 187 spectral curves, recorded over about a year, are presented and their distribution about the Planckian locus is discussed. The typical spectral distributions for the correlated color temperatures 4800, 5500, 6500, 7500, and 10 000°K, derived from the characteristic vectors are presented and discussed.
TL;DR: In this article, a simple model of the electrical double layer was used for computing the variation in optical behaviour of an electrode, with its surface charge, and the relevance to ellipsometric and electro-reflectance strudies was discussed.
TL;DR: In this article, the authors examined the operation of proportional counters, as used for 4πs detectors, and made measurements on both the electrical pulse and that induced in a photomultiplier which viewed the discharge directly.
TL;DR: In this article, the peak positions, halfwidths, and oscillator strengths of Cd (and Zn) bands in KBr and other uncolored alkali halides are given.
Abstract: The peak positions, half-widths, and oscillator strengths of Cd (and Zn) bands in KBr and other uncolored alkali halides are given. In uncolored KBr, Cd introduces three optical absorption bands at 202, 215, and 280 nm, respectively. Two new bands, ${D}_{1}$ and ${D}_{2}$, at 250 and 285 nm, respectively, are observed in the irradiated KBr: Cd crystals. The growth of absorption coefficients ${\ensuremath{\alpha}}_{F}$ and ${\ensuremath{\alpha}}_{M}$ at the peaks of $F$ and $M$ bands, respectively, was studied as a function of radiation dose. The value of $S$ in the relation ${\ensuremath{\alpha}}_{M}=S{{\ensuremath{\alpha}}_{F}}^{2}$ is suppressed by a factor \ensuremath{\sim}100 in crystals containing more than 20 ppm of Cd. In the crystals irradiated for short times, the $M$ band cannot be produced even by optically bleaching the $F$ band. The second-stage growth of the F band is also suppressed considerably by the Cd impurity, which supports the view that the second-stage $F$ centers are necessary for the formation of $M$ centers. The ${D}_{1}$ and ${D}_{2}$ bands observed in x-irradiated crystals are absent in the additively colored crystals. In the crystals colored additively at 460\ifmmode^\circ\else\textdegree\fi{}C, an ultraviolet band at 330 nm and a band at 750 nm are observed in addition to the F band. The $F$ band can be converted to the 750-nm band by optical or partial thermal bleaching of the crystal. In a crystal colored at 560\ifmmode^\circ\else\textdegree\fi{}C the 750-nm band is absent, and only the 330-nm band and a very stable $F$ band are present. On heating the crystals to 600\ifmmode^\circ\else\textdegree\fi{}C, the 330-nm band, $F$ band, and 750-nm band disappear, and a new band at 300 nm appears. The crystal containing the 300-nm band shows an EPR absorption line with Lorentzian shape and a $g$ value of 1.987, and enhanced conductivity above 500\ifmmode^\circ\else\textdegree\fi{}C. These results suggest that the centers responsible for this band are metallic colloidal particles of Cd. The equilibrium concentration of $F$ centers in crystals doped with 28 ppm of Cd and colored additively at 560\ifmmode^\circ\else\textdegree\fi{}C is 15% less than that in a pure crystal. At 560\ifmmode^\circ\else\textdegree\fi{}C the rate of diffusion of $F$ centers in the Cd-doped crystals is less by a factor \ensuremath{\sim}5 as compared to the rate in a pure crystal, and is less by a factor \ensuremath{\sim}50 as compared to rate the of diffusion of 330-nm band centers.