Showing papers by "Philips published in 1973"

Controlled nucleation for the regulation of the particle size in monodisperse gold suspensions

Abstract: MANY properties of colloids and suspensions depend on the particle size. Series of monodisperse suspensions of the same chemical composition but of rather different particle sizes may be used to study particle size dependent phenomena, such as Brownian motion, light scattering, sedimentation and electrophoresis of small particles. We have used such series to demonstrate the increased tendency of metal suspensions to coagulate in the presence of electrolytes as the radius of the particles increases1.

Electrical conduction in concentrated disordered transition metal alloys

Abstract: Results are presented of an investigation on the origin of the low temperature coefficient of resistance in NiCr thin films. It is shown that this low temperature coefficient is an intrinsic property of the alloy. Besides NiCr a large number of disordered alloys containing transition metals have similar conduction properties, both in bulk and as a thin film. For these materials a correlation has been found between the resistivity and its temperature coefficient. These anomalous conduction properties are probably caused by the very small electron mean free path in these materials.

The electronegativity parameter for transition metals: Heat of formation and charge transfer in alloys

Abstract: It is demonstrated that a cellular model gives an excellent account of the heat of formation of binary alloys of 27 transition metals. The energy effects are described by two terms, the first representing the difference in electronegativity between the two types of atoms in an alloy and the second term reflecting the discontinuity in the density of electrons at the boundary between dissimilar Wigner-Seitz atomic cells. The electronegativity is expressed in a scale which closely resembles that of the experimental work functions of pure metallic elements. The use of this scale also gives a clear insight into the heat effects which accompany the alloying of transition metals with non-transition metals. If the latter have p-electrons a negative term adds up to the heat of formation which apparently does not depend on the particular metals considered. As a result, simple rules for the alloying behaviour of transition metals are formulated which have an accuracy between 96 and 100%; the electronegativity concept is shown to apply also for hydrogen in metals. The relation between the charge transferred per atom, ΔZa, and the difference in electronegativity, Δφ∗, is discussed quantitatively. As an example, the result for solid solutions of two transition metals is ΔZa = 1.2 (1 − ca)Δφ∗, where ca is the concentration of metal A. Our analysis supports the idea that the work function of a metal is, in principle, proportional to the chemical potential for electrons in Wigner-Seitz atomic cells; the proportionality factor is found to be about 1·4.

A precision reference voltage source

Abstract: With increasing temperature the base-emitter voltage of a transistor with a constant current decreases, while the difference in base-emitter voltages of two identical (integrated) transistors having a constant current ratio increases. From the sum of the two voltages a nearly temperature- independent output voltage is obtained if this sum equals the gap voltage of silicon. A reference voltage source of 10 V based on the principle is described. The reference part of the circuit is an integrated circuit, and thin-film resistors with a small relative temperature coefficient are used. An operational amplifier and a few resistors and capacitors complete the circuit. The source has a parabolic temperature characteristic and the temperature peak can be controlled by resistor adjustment. A change of /spl plusmn/10 K in respect of the peak temperature causes an output voltage change of -250 /spl mu/V, while a change of /spl plusmn/30 K causes a change of -2.2 mV. A long-term stability of 10 ppm/month was measured. The circuit can compete with the best available Zener diode sources, and has the added advantage that practically no selection is necessary.

The laboratory evaluation of two promising new insecticides which interfere with cuticle deposition

Abstract: 1-(4-chlorophenyl)-3-(2,6-dichlorobenzoyl)-urea, PH 60-38 and 1-(4-chlorophenyl)-3-(2,6-difluorobenzoyl)-urea, PH 60-40, are representatives of a new class of insecticides with an unprecedented mode of action. Susceptibility of insect species of different orders is demonstrated and the compounds are expected to be quite safe towards mammals. The compounds are stomach poisons and they are not plant systemic. Their insecticidal activity demonstrates itself mainly as a failure to moult or pupate, resulting in death. Histological examination revealed the cause of this failure to be a defect in the process of cuticle deposition.

Computer-aided two-dimensional analysis of bipolar transistors

Abstract: A method for solving numerically the two-dimensional (2D) semiconductor steady-state transport equations is described. The principles of this method have been published earlier [1]. This paper discusses in detail the method and a number of considerable improvements. Poisson's equation and the two continuity equations are discretized on two networks of different rectangular meshes. The 2D continuity equations are approximated by a set of difference equations assuming that the hole and electron current density components along the meshlines are constant between two neighboring meshpoints in a way similar to that used by Gummel and Scharfetter [2] for the one-dimensional (1D) continuity equations. The resulting difference approximations have generally a much larger validity range than the conventional difference formulations where it is assumed that the change in electrostatic potential between two neighboring points is small compared with k T/q . Therefore, a much smaller number of meshpoints is necessary than for the conventional difference approximations. This reduces considerably the computation time and the required memory space. It will be shown that the matrix of the coefficients of this set of difference equations is always positive definite. This is an important property and guarantees convergence and stability of the numerical solution of the continuity equations. The way in which the difference approximations for the continuity equations are derived gives directly consistent expressions for the current densities that can be used for calculating the currents. In order to demonstrate the kind of solutions obtainable, steady-state results for a bipolar n-p-n silicon transistor are presented and discussed.

X‐ray fluorescence analysis applying theoretical matrix corrections. Stainless steel

Abstract: The conversion of X-ray fluorescence intensities to concentrations by a mini-computer requires simple equations for routine use. The influence coefficients, accounting for inter-element effects in homogeneous samples, are calculated from fundamental parameters by means of a programme called ALPHAS operating on a large computer. These coefficients can subsequently be used in the simple routine equations for wide range calibration. The theoretical coefficients are a valuable support for wide range calibrations using multiple regression analysis. The number of required standards is significantly reduced. The exclusive use of theoretical influence coefficients is demonstrated for stainless steel.

A new insecticide inhibits chitin synthesis.

Abstract: Mos t of t he m e t h o d s t r ied so far are based on ion exchange, adsorp t ion , prec ip i ta t ion , and so lven t ex t rac t ion , b u t none seems l ikely to s a t i s fy t he above r equ i r emen t s . We h a d t he idea t h a t mic roo rgan i sms possess m a n y of the requi red proper t ies : se lec t iv i ty for b ind ing u r an i um, easy and inexpens ive p roduc t ion of t he b iomass , o p t i m u m degree of d ispers ion for fas t b ind ing kinet ics , and no was te problems. F r o m theore t ica l cons idera t ions and technological calcula t ions we devised a b a t c h process us ing cu l tu red algae exposed to f lowing sea water . For our e x p e r i m e n t s we used unicel lu lar green algae, m u t a t e d , selected, t e s t ed and cu l t iva t ed in l abora to ry exper imen t s . I n some cu l tures the m e d i u m was enr iched b y add i ng u r a n i u m sa l t in order to d e m o n s t r a t e t h a t even h i gh concen t ra t ions of u r a n i u m are no t po isonous to t he m u t a n t s . I n some experim e n t s a low e n r i c h m e n t was used for ana ly t ica l convenience . Some resu l t s are p re sen t ed in Tab le 1. A New Insecticide Inhibits Chitin Synthesis

Substituted benzoyl ureas

Abstract: New organic compounds derived from urea or thiourea, insecticidal preparations on the basis of the new substances and methods of producing the substances.

Torsional elasticity of human skin in vivo

Abstract: Measurements of physical properties of the intact human skin are described. An analysis of the measurements yields parameters that characterize elastic, visco-elastic and plastic properties. Between 6 and 61 years the elastic component of the extensibility of the skin under torsional conditions increases with age. The visco-elastic and plastic components are constant up to an age of fourty; at higher ages they show a small tendency to increase. Moduli of elasticity of the intact human skin derived from the torsion measurements yield values between about 2×104 N/m2 and 105 N/m2, the highest values corresponding to the youngest age. From these values the moduli of elasticity of the elastic fibres in the living skin are estimated between about 2×106 N/m2 and 107 N/m2.

Influence of Annealing on the Concentration Profiles of Boron Implantations in Silicon

Abstract: The influence of annealing on the concentration profiles of boron implanted into silicon with does of 1014 ions/cm2 up to 1016 ions/cm2 and an energy of 70 keV was studied. The concentration profiles were measured with Secondary Ion Mass Spectrometry (SIMS). The broadening of the concentration profiles during annealing can be described as a superposition of effects resulting from a relatively immobile and a mobile boron fraction. The properties of the immobile boron fraction were studied by measuring the influence of a boron implantation on the distribution of a homogeneous boron background dope. From these experiments it was concluded that the immobile boron fraction consists of boron precipitates. The properties of the mobile fraction were studied from concentration profiles that were obtained after annealing during different periods at the same temperature. It was found that during the initial stage of the annealing process a fast broadening of the profile occurs; this was assumed to be due to an interstitial type boron diffusion. After prolonged annealing the much slower substitutional type diffusion prevails, due to trapping of the interstitial boron atoms by vacancies. The reliability of the SIMS method, as applied to profile measurements, was checked for the high boron doses used in this investigation. Excessive boron precipitates, obtained after annealing of a high dose, such as 1016 ions/cm2 at about 1000°C, appear to give some increase of the ion yield.

Hydrogen absorption and magnetic properties of LaCo5xNi5−5x compounds

Abstract: The lattice constants, the Curie temperature and the saturation magnetization of the pseudobinary system LaCo 5x Ni 5−5x have been determined as a function of composition. The variation of the lattice constants suggests an anisotropic magneto-volume effect accompanying the paramagnetic-ferromagnetic transition. The hydrogen absorption capacity decreases markedly with x in the series LaCo 5x Ni 5−5x . The nature of the hydride phases corresponding to the various plateau pressures of the absorption isotherms has been studied by X-ray diffraction. The hydrogen equilibrium pressure at the first hydride is strongly reduced when x increases. Dependent on x one can discern two regions where this equilibrium pressure varies as In p = Cx + q , the absolute value for C being largest for small x values.

The cobalt-rich regions of the samarium-cobalt and gadolinium-cobalt phase diagrams

Abstract: The boundaries of the homogeneity regions of the phases SmCo 5 , GdCo 5 and Gd 2 Co 17 have been determined by microscopic investigation. At elevated temperatures the homogeneity region of the phases SmCo 5 and GdCo 5 extends to the Co-rich as well as to the Co-deficient side whereas the phases Gd 2 Co 17 and Sm 2 Co 17 show almost no Co solubility. A tentative diagram is presented for the phase relationships involved in the transition between the two allotropic forms of Gd 2 Co 17 . The occurrence of various types of microstructures in as-cast and annealed RCo 5 samples is explained in terms of the peculiar shape of the solvus of the RCo 5 homogeneity regions at high temperatures.

Magnetic Anisotropy and Conduction-Electron Exchange Polarization in Ferromagnetic (Rare-Earth) Al 2 Compounds

Abstract: $^{27}\mathrm{Al}$ NMR in ferromagnetic $R{\mathrm{Al}}_{2}$ ($R=\mathrm{P}\mathrm{r},\phantom{\rule{0ex}{0ex}}\mathrm{N}\mathrm{d},\phantom{\rule{0ex}{0ex}}\mathrm{S}\mathrm{m},\phantom{\rule{0ex}{0ex}}\mathrm{G}\mathrm{d},\phantom{\rule{0ex}{0ex}}\mathrm{T}\mathrm{b},\phantom{\rule{0ex}{0ex}}\mathrm{D}\mathrm{y},\phantom{\rule{0ex}{0ex}}\mathrm{H}\mathrm{o}$) has been studied. The easy direction of magnetization has been observed experimentally for the first time and a theoretical calculation, in accord with the observation, has been developed. The $s\ensuremath{-}f$ exchange parameters have been examined and in addition to the isotropic exchange parameter ${\ensuremath{\Gamma}}_{\mathrm{sf}}$, the existence of a small but significant anisotropic $s\ensuremath{-}f$ exchange term is verified experimentally for the first time. The accurately determined (\ifmmode\pm\else\textpm\fi{}1%) isotropic exchange parameters are compared with presently available theoretical predictions.

The Nucleation with SnCl2 ‐ PdCl2 Solutions of Glass Before Electroless Plating

Abstract: It has been generally accepted that metallic palladium nuclei are formed by the nucleation procedure of nonconducting substrates with stannous chloride and palladium chloride solutions. However, results of experiments on glass using radioactive tracers and ellipsometry have shown that no metallic palladium is present after the nucleation procedure. The results indicate that presumably a tin‐palladium complex, containing one palladium atom per two tin atoms is formed and that this initiates the nickel‐phosphorus deposition from a suitable electroless plating solution.

Dielectric and optical properties of a quasi-ferroelectric PLZT ceramic

Abstract: Certain compositions within the quaternary lead-lanthanum-titanate-zirconate (PLZT) system exhibit neither a "true" ferroelectric nor a "true" paraelectric behavior and are therefore best characterized as quasi-ferroelectric. The dielectric, hysteresis, and optical properties of quasi-ferroelectric PLZT ceramics have been investigated for the representative 9/65/35 composition which was prepared as a transparent ceramic by means of a two-stage sintering-densification process. The results of these studies suggest that the quasi-ferroelectric behavior of PLZT compositions between their Curie temperature and a transition temperature T p is brought about by the existence of polar distorted microregions (polar short-range order). By applying an electric field a transition to a macroscopic ferroelectric (FE) state (polar long-range order) is enforced which is, however, not stable at zero field at T > T p . This concept, which explains the experimental observations, is compared with the possibility of a FE to anti-FE phase transition at T p . Attention is drawn to the quasi-static memory behavior of this type of material that can be realized by disconnecting the sample in its ON state from the voltage source and which might enlarge the scope of applications of quasi-ferroelectric PLZT ceramics.

Apparatus for reading a flat record carrier

Abstract: An apparatus for reading a flat record carrier on which information is recorded in at least one track which has an optical structure is described. By projecting onto the plane of the track part to be read three spots of radiation the dimensions of which correspond to the smallest detail in the optical structure and the positions of which, viewed in the direction of width of the track, are different, and by inserting a radiationsensitive detector in each of the radiation beams emanating from the spots of radiation it is possible to ascertain whether a read beam is correctly directed on to the track to be read.

Preparation and optical properties of single crystal thin films of bismuth substituted iron garnets for magneto-optic applications

Abstract: Single crystal thin films of Bi substituted iron garnets have been grown by the liquid phase epitaxy technique. The growth conditions and compositions are presented together with the segregation coefficients of Bi and Pb as a function of growth temperature. The Faraday rotation and optical absorption have been measured for wavelengths between 0.7 and 0.46 μm. The superior magneto-optic properties (Faraday rotations of up to ten times larger than that observed for Y3Fe5O12) make these epitaxial layers attractive for magneto-optic devices. The influence of Pb incorporation on the optical properties of the films is discussed. Compositions of Bi and Ga(Al) substituted Gd3Fe5O12, which exhibit a magnetic compensation temperature near room temperature and high Faraday rotation, have also been prepared. The magnetic switching behaviour as a function of temperature has been determined. It shows that these films are especially suited for thermomagnetic recording using an argon ion laser at a wavelength of 5145 A.

Electric and Dielectric Properties of Polycrystalline Yttrium Iron Garnet: Space-Charge-Limited Currents in an Inhomogeneous Solid

Abstract: The dc conductivity of $n$-type polycrystalline yttrium iron garnet has been measured at temperatures near room temperature as a function of the applied voltage. At voltages below a critical value an Ohmic behavior is observed, while above this value we find $i\ensuremath{\propto}{V}^{\ensuremath{\alpha}}$, with $\ensuremath{\alpha}=1.2\ensuremath{-}5.1$. ac conductivity and dielectric permittivity both show a large dispersion in the ${10}^{\ensuremath{-}3}$-${10}^{5}$-Hz frequency range, e.g., a static value of the relative permittivity ${\ensuremath{\epsilon}}_{s}\ensuremath{\approx}4000$ and a high-frequency value ${\ensuremath{\epsilon}}_{\ensuremath{\infty}}=18$. The results are interpreted in terms of a two-layer model with well-conducting grains (e.g., ${\ensuremath{\sigma}}_{300 \mathrm{K}}\ensuremath{\approx}7.2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}8}$ ${\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}1}$ ${\mathrm{cm}}^{\ensuremath{-}1}$) measuring 4 \ensuremath{\mu}m separated from each other by poorly conducting boundary layers (e.g., ${\ensuremath{\sigma}}_{300 \mathrm{K}}\ensuremath{\approx}1.8\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ ${\mathrm{\ensuremath{\Omega}}}^{\ensuremath{-}1}$ ${\mathrm{cm}}^{\ensuremath{-}1}$) of thickness 0.02 \ensuremath{\mu}m. At low voltages, conduction is determined by the boundary layer. At higher voltages, the current in the boundary layers is space-charge limited. A model is developed for space-charge-limited currents in an inhomogeneous solid of this kind. All experimental results can be explained qualitatively by this model. For one sample the measurements have been quantitatively analyzed. Good agreement with theory is found if we assume an exponential distribution of the density of states of the trapping centers in the boundary layers of the form ${\mathfrak{N}}_{t}(E)=\frac{{N}_{t}}{k{T}_{t}}{e}^{\frac{(E\ensuremath{-}{E}_{c})}{k{T}_{t}}}$, with ${N}_{t}=3.3\ifmmode\times\else\texttimes\fi{}{10}^{20}$ ${\mathrm{cm}}^{\ensuremath{-}3}$ and ${T}_{t}=1110$ K. At 300 K, in the region of Ohmic conduction in the grain boundary layer ($Vl10$ V), the Fermi level of this layer is situated 0.88 eV below the conduction band; upon charge injection its position rises, for an externally applied voltage of 500 V, to about 0.63 eV below the conduction band. Annealing experiments at different oxygen pressures show that the poorly conducting boundary layers are regions which are reoxidized during cooling from the sintering temperature of 1430 \ifmmode^\circ\else\textdegree\fi{}C to room temperature.

DEVICE FOR CONTROLLING THE AIR-FUEL RATIO λ IN A COMBUSTION ENGINE

Abstract: Device for controlling the air-fuel ratio λ of the mixture supplied to a combustion engine, comprising a pick-up sensitive to the carbon monoxide content of a gas mixture and arranged in an exhaust gas duct of the engine and producing a voltage increasing with said content, a member for controlling the air-fuel ratio λ and a feedback mechanism acting upon said member so that the ratio λ is increased when the voltage produced by the pick-up increases.