bluuebunny/crossref_metadata_2025 huggingface dataset:
The Growth and Structure of Thin Metallic Films
Authors: Levinstein Henry
Published: January 2005

The structure of thin metallic films was studied by means of electron diffraction and electron microscopy. Microcrystal size can be correlated with the melting point of the metals, those with high melting points producing continuous films of small unoriented microcrystals while those with low melting points produce large microcrystals oriented preferentially with respect to the substrate. The effects of varying experimental conditions on the film structure of selected metals are reported. The electron beam of the electron microscope affects metals with low melting points most directly, producing melting, sublimation or crystallization. Variations in the velocity of the impinging atom, obtained by passing thermal atoms through a mechanical velocity selector, produce no effect for metals whose vapor is monatomic. Antimony whose vapor is found to consist of polyatomic molecules as well as atoms produces films whose grain size seems to vary with the size of the molecules forming the antimony film. The rate of evaporation merely determines whether zinc or cadmium films may or may not be formed while for antimony films it also determines the type of the films formed. Those formed by rapid evaporation consist of small crystallites while those formed by slow evaporation consist of large amorphous patches. This effect is explained on basis of the mobility of the atoms on the substrate, the mobility time being determined to be less than 2×10−5 second. The mobility time and therefore the structure depends upon the type of substrate. The degree of vacuum is critical when the residual vapor reacts with the film being formed, but if no reaction takes place between residual vapor and film, pronounced variation for films formed in a vacuum are produced only when the pressure is above 10−2 mm of mercury.
Point-to-Plane Impulse Corona
Authors: Moore Donald Baker , English William N.
Published: January 2005

The characteristics of impulse corona have been studied in a point-to-plane gap. Both positive and negative square voltage pulses of one- and two-microsecond duration were used with various voltages and pulse repetition rates. The impulse corona in air is found to be quite similar to the d.c. corona, except that the phenomena are exaggerated by the relative absence of space charge inhibition. At higher voltages, the negative impulse corona was found to have a ``spike'' or streamer type of discharge superimposed on the regular Trichel pulse corona. By using the nonelectron-attaching gases nitrogen and hydrogen, it is shown that these spikes are due to the negative ion space charge formed by the Trichel pulse in the gap. When the point is grounded, the intense field developed between this negative space charge and the positive space charge at the point is sufficient to cause a streamer to propagate.
On Surface-Fitting in Three Variables
Authors: Morduchow Morris
Published: January 2005

A simple systematic method, based on a theorem stated and proven here, is presented of obtaining a formula of the form z = f(x, y) from an experimental curve (Fig. 1) in which y is kept constant and a second experimental curve (Fig. 2) in which x is kept constant. Questions of the sufficiency of the original data are automatically answered by this method. Several examples are given to illustrate the procedure explicitly.
Influence of Atmospheric Pressure on the Phenomena Accompanying the Entry of Spheres into Water
Authors: Gilbarg David , Anderson Robert A.
Published: January 2005

High speed motion-picture studies were made of the dependence of air-water entry cavities on the relevant physical parameters—in particular, on the atmospheric pressure over the water surface. Experiments on the vertical entry of spheres ¼ in. to 1 in. in diameter, with entrance velocities between 15 ft./sec. and 100 ft./sec., and air pressures between 1/60 atmosphere and 3 atmospheres, show that surface sealing of the cavity is a major factor in controlling cavity formation, and is the factor most responsible for non-Froude scaling of cavity phenomena. Surface sealing is a function chiefly of the atmospheric density and projectile velocity, although surface tension is also important in its effect on splash formation. Froude's scaling is found to hold true in the region of low Froude's numbers and low atmospheric pressures. The measured average drag coefficient of the projectiles is independent of cavity size and shape. Jets are found to occur regularly and with great strength at both deep and surface closures of the cavity. The observed presence of jets in finite cavities is predicted by an extension of the Kirchhoff-Helmholtz theory of the infinite (two-dimensional) cavity to the case of finite cavities with finite cavitation numbers. Some of the results of this theory are mentioned.
The Rising Sun Magnetron
Authors: Millman S. , Nordsieck A. T.
Published: January 2005

A method for separating the π-mode from neighboring resonant modes in a multi-cavity magnetron without the use of ``straps'' is described. The new resonant circuit design known as the ``rising sun'' design utilizes two different resonator sizes arranged symmetrically around the cylindrical cathode-anode space, with resonators alternately larger and smaller. Some of the essential features of the mode spectrum and the electromagnetic field in the interaction space in this design are derived from a simple lumped-constant theory. The advantages of the rising sun over the strapped anode block become important in the short wave-length part of the microwave region, because of simpler construction and smaller radiofrequency losses. For very high power magnetrons the advantages of the rising sun structure apply to wave-length as long as 10 cm.
The Palletron, A New Electron Resonator and Its Proposed Application to the Generation of Potentials in the Million-Volt Range
Authors: Skellett A. M.
Published: January 2005

The kind of electrostatic field in which an electron or ion will follow simple harmonic motion is shown to have a parabolic potential distribution. A gap at the center of this field provides a means for exchange of energy between the electrons and the associated circuit. If energy is taken from the electrons the device provides an oscillator of high efficiency; if energy is given to them the device may be used to generate a high d.c. voltage. Both kinds of device have been operated successfully.

Experimental results on a small model of the voltage generator are given and a proposed design for the million-volt range is briefly described.
On the Velocity-Dependent Characteristics of High Frequency Tubes
Authors: Knipp Julian K.
Published: January 2005

The electronic transadmittances, transmodulation functions, and other characteristics of a planar, multigrid high frequency tube are expressed in terms of four fundamental admittance and modulation functions which are sufficient for the description of the low level r-f properties of the electron beam. A matrix representation is introduced based on the successive velocity moments of the beam which leads to the formulation of the characteristics as products involving excitation, grid transmission, modulation, and modulation admittance matrices. The electronic equations obtained are a formulation in which the Llewellyn approximation that the second and all higher velocity moments are zero is not made. Thus the theory allows for higher order velocity effects but is dependent on the knowledge of the fundamental admittance and modulation functions.
Stabilization of Breakdown Voltage and Measurement of Some Critical Currents in a Glow Tube
Authors: Pal A. B.
Published: January 2005

This paper describes a special technique by which it is possible to stabilize the breakdown voltage of a glow tube having zirconium electrodes in pure argon at a pressure of 8.5 mm Hg. A brief account is also given of some experimental methods by which it is possible to find the order of magnitude of two critical currents, whose concepts have been used in the theory of spark discharge at low pressures. One of these critical currents is the ``threshold current,'' which is defined as the maximum steadystate current in a glow tube just before a spark. The other critical current is the maximum electronic current (attained during the development of a spark) at cathode before space-charge distortion becomes appreciable. The methods described below were confined to two tubes having zirconium cathodes of area 0.3 sq. cm, the electrode spacing being 3.5 mm. One of these two tubes had a zirconium anode, and the other one had a thorium anode. The tubes contained pure argon at a pressure of 8.5 mm Hg. For both the tubes, the order of the ``threshold current'' was found to be 10−8 amp., and the order of the other critical current (electronic current at cathode) was estimated as 10−8 amp.
Dynamic Measurements of Polymer Physical Properties
Authors: Ballou J. W. , Smith J. C.
Published: January 2005

Dynamic methods for measuring the elastic and dissipative properties of high polymers in fiber and film form over four decades of frequency (3 to 30,000 cycles per second) are described. The experimental quantities resulting from the three different techniques necessary to cover this range are unified by deriving in each case the parameters of an equivalent Voigt Model (elastic and viscous element in parallel) which would behave in the same way as the polymer sample. Examples of the application of these techniques to the characterization of high polymers are given. The effect of frequency and chemical and physical structure on the derived parameters are discussed, along with the question of heat losses resulting from cyclical differential deformation. In addition, the application of two of the methods to the characterization of the stiffness-temperature behavior of high polymers is described.
Creep and Damping Properties of Polystyrene
Authors: Sauer J. A. , Marin J. , Hsiao C. C.
Published: January 2005

The anelastic behavior of polystyrene has been studied by means of creep tests under long-time load application and by means of damping capacity tests under rapidly varying repeated loading. Tensile creep data taken at various stress amplitudes reveal that the log of the creep rate (at 1000 hours) varies linearly with the log of the stress amplitude. A similar type of variation is obtained when damping capacity or energy absorbed per cycle is plotted against stress amplitude. From these two sets of data, the creep rate is found to be proportional to the square of the damping capacity. It would thus appear possible, for polystyrene at least, to predict 1000-hour creep rates from short-time measurements of absorbed energy under dynamic loading conditions.

The data obtained from the creep and damping tests, together with additional data from short-time tension and compression tests, seem to be consistent with an internal structure in which the linear polymer chains and groups of chains are in ordered or partially extended positions, but in which, in the absence of stress, no preference is shown for any particular direction. Under the action of stress—particularly if the stress is maintained for a long period of time—a tendency exists for the ordered regions to orient in the direction of the applied stress. The so-called ``crazing'' condition which has been observed to occur in the creep specimens is probably a manifestation of this orientation. X-ray evidence appears to support this point of view.
A Torsion Balance for Measuring Forces in Low Density Gas Flows
Authors: Estermann I. , Kane E. D.
Published: January 2005

A torsion balance, designed to measure the force on a flat plate (or other simple geometry) in a low density gas flow, is described. The balance has been used with two interchangeable torsion member sizes, with diameters of 0.00064″ and 0.00090″, which measured forces up to a maximum of 0.6 milligram and 2.4 milligrams, respectively. Calibrations (obtained in still air using weights) were reproducible within ±0.005 mg and ±0.04 mg for the two sizes. Data obtained for a flat plate in a gas stream under large molecular mean free path conditions are presented.
Transition Temperatures of Methyl Methacrylate Polymers at Ultrasonic Frequencies
Authors: Protzman Thomas F.
Published: January 2005

The velocity of sound in methyl methacrylate polymers (Plexiglas) has been measured at temperatures from 24° to 90°C, and frequencies from three to eleven megacycles. Optical diffraction methods were used to determine the sound velocity within a maximum error of 1 percent. This low experimental error made possible a detailed study of the sound velocity-temperature relationships. A previously unreported transition of a new type has been found. The sound velocity decreases linearly with increasing temperature, with an abrupt increase of slope occurring when a transition temperature is reached. The transition temperature is found to decrease linearly with frequency, falling from 64°C at three megacycles to 49°C at eleven megacycles. The observed transitions apparently are not manifestations of elastic relaxational effects and are tentatively attributed to the excitation of some mode of molecular motion, for example, molecular vibrations.
Semi-Conducting Properties in Oxide Cathodes
Authors: Hannay N. B. , MacNair D. , White Addison H.
Published: January 2005

It has been widely assumed, without adequate experimental verification, that barium-strontium oxide, as used in the oxide cathode, is an excess electronic semi-conductor. Accordingly, the electrical conductivity of (Ba, Sr)O has been studied as a function of temperature before and after activation with methane, extensive precautions being taken to exclude spurious effects. The increase in conductivity obtained characterizes (Ba, Sr)O as a ``reduction'' semi-conductor, and hence very probably as an electronic semi-conductor whose conduction electrons arise from a stoichiometric excess of (Ba, Sr) atoms in solid solution.

A basic prediction of the semi-conductor theory has been tested quantitatively with the finding that the electrical conductivity and the thermionic emission of a (Ba, Sr)O cathode are directly proportional through three orders of magnitude of activation; well-defined chemical and electrical activation and deactivation procedures were used in obtaining this result. It may be concluded that activation represents an increase in the chemical potential of the electrons in the oxide, little or no change in the state of the surface occurring. It has also been found that deviations from the proportionality of conductivity and emission may be expected under conditions leading to inhomogeneity in the oxide, in agreement with the semi-conductor theory also.
The Vaporization of the Cathode in the Electric Arc
Authors: Holm Ragnar
Published: January 2005

Calculations are carried out which show that, because of the smallness of the cathode spot, the cathode is not able to dissipate the heat generated with heavy currents by conduction. Therefore, a much higher vaporization of cathode material per coulomb occurs for heavy currents than for low currents.
Application of Thermodynamics to Chemical Problems Involving the Oxide Cathode
Authors: White Addison H.
Published: January 2005

Computations of the free energy of some chemical reactions involving dissociation or reduction of alkaline earth oxides have been made on the basis of rough estimates of the thermochemical quantities which have not been measured. The resulting values of free energy, equilibrium constant and equilibrium pressure of barium vapor derived for specified ideal conditions are tabulated. Several applications of these results are discussed.
A Generalization of Nyquist's Stability Criteria
Authors: Vazsonyi A.
Published: January 2005

A generalization of Nyquist diagrams is developed. These new diagrams yield a lower limit to the values of ``damping ratios'' and so permit the evaluation of the stability and the ``degree'' of stability of systems characterized by ordinary linear differential equations.
The Cyclotron. I
Authors: Livingston M. Stanley
Published: January 2005

The cyclotron is in process of a metamorphosis from an academic luxury for nuclear physicists to an indispensable tool for applied science and industry. Tracer experiments with induced radioactivities have become invaluable for basic studies in other sciences and as a guide to engineering development in many industries. The radioactivities and neutron radiations themselves are being put to use in industry and in medicine on an ever increasing scale. The time is near when the use of the cyclotron as a production unit may even outweigh its further scientific usefulness. Cyclotron physicists, well aware of this trend, are eager to push the development of the instrument to engineering perfection. To further this effort, this paper evaluates available information which may aid in improving the efficiency, reliability, and output and in determining most economical sizes and designs of cyclotrons for large scale applications.
Some Low Temperature Properties of Elastomers
Authors: Conant F. S. , Liska J. W.
Published: January 2005

A modification of the apparatus employed in measuring the Young's modulus of elastomers at low temperatures is described. The changes made in the apparatus permit the use of a simplified technique which can be adapted to routine testing procedure. The effects of various softeners on the low temperature bending moduli and the brittle point temperatures of stocks based on four butadiene-acrylonitrile (B/A) type copolymers are given. It is shown that the softeners tested have the same relative effects in all four types and that a wide variation in low temperature properties is imparted to the stocks by the different softeners. Bending modulus curves and brittle point temperatures are given for typical test stocks based on Thiokol FA, and ``mass'' and ``emulsion'' polymerized polybutadiene. It is shown that continued exposure to low temperature affects the Young's modulus of some but not all typical vulcanizates. Data are presented showing this effect on an uncured Hevea gum stock held at 0°C. Certain softeners have been found to induce time effects in one of the B/A type stocks, which exhibits no crystallization, and hence no progressive stiffening in the absence of the given softeners. A method for measuring and evaluating creep under dead load at low temperatures is presented. Accompanying data indicate that in the case of those stocks tested, the creep constant defined reaches a maximum at a definite temperature which is a characteristic of the given stock.
On the Silica Replica Method of Surface Examination with the Electron Microscope
Authors: Baker R. F. , Nicoll F. H.
Published: January 2005

An essential step in the making of a silica replica by the Heidenreich technique consists in the evaporation of silica in a high vacuum. An alternate method for depositing silica has been investigated and is discussed in this paper. This method consists in the chemical deposition of silica from the compound SiCl4.
Electromagnetic Velometry. I. A Method for the Determination of Fluid Velocity Distribution in Space and Time
Authors: Kolin Alexander
Published: January 2005

A method is described which permits the determination of the local velocity of flow, as well as of turbulent fluctuations at a given point, or a prescribed series of points in a moving liquid. The method is based on the induction of a potential gradient in the flowing medium as it traverses a magnetic field perpendicularly to its direction. The absence of lag in the process of induction makes the method particularly suitable for the study of rapidly varying velocities and the sharp localization of measurements allows the determination of spatial velocity distributions. In an adaptation of the method for small scale laboratory experiments, the magnetic field is created by a large a.c. magnet in whose gap the conduit is placed, while two minute exploring electrodes pick up the induced e.m.f. at the desired locations. For large scale experiments and field work, a self-contained unit has been designed which comprises a minute electromagnet with attached pick-up electrodes. The applicability of this method is demonstrated by velocity distribution curves taken under different conditions and by records of liquid turbulence and transient velocity changes in different forms of flow. This paper is confined to the presentation of the principle involved, to the description of the apparatus, to the discussion of the experimental technique, and to demonstrations of the applicability of the method. A theoretical analysis of the characteristics and limitations of this method will be dealt with in a separate publication.
Twinning in Zinc Oxide
Authors: Fuller M. L.
Published: January 2005

A crystallographic analysis of a characteristic shape of particle found in zinc oxide produced by burning zinc vapor has been made with the aid of the electron microscope. This particle consists of four needle-shaped crystals united at a common juncture. The spatial angles among the four crystals were determined from stereoscopic micrographs with the use of the stereographic projection. The crystals were found to be united by twinning on planes of the form (112).
Theory of the Elasticity of Rubber
Authors: James Hubert M. , Guth Eugene
Published: January 2005

Natural rubber is the prototype of an important class of materials consisting of long flexible molecules which interact with each other in a particular way. Some of the properties of bulk rubber are strikingly similar to, and may be understood by a consideration of, those of single flexible molecules. For a complete understanding of the behavior of rubberlike materials it is necessary to understand the way in which they are built up from the component flexible molecules. In vulcanized materials, in which plasticity is suppressed, intermolecular bonds link the molecules into a coherent network, very irregular in detail but isotropic and homogeneous on the average. In lightly vulcanized materials these bonds are relatively few, and bring relatively small portions of adjacent molecules into fixed relations to each other. For the most part the interaction of neighboring molecules in the material is that characteristic of liquids. It is the presence of the intermolecular bonds, which link the molecules into a network and thus control its form, which differentiates rubberlike materials from liquids. It is the small number of these bonds, and their weak control of the form of material through the entropy rather than the internal energy, which differentiates rubberlike materials from ordinary solids. On the basis of this picture of the structure of rubber there is derived a form for the stress-strain curves at moderate extensions which is in good agreement with experiment.
Thermal Expansion and Second-Order Transition Effects in High Polymers: Part I. Experimental Results
Authors: Boyer R. F. , Spencer R. S.
Published: January 2005

Experimental values of second-order transition temperatures Tm and of cubical expansion coefficients below and above this temperature are presented for several new materials, notably saran. The thermal expansion behavior of two-component systems of incompatible materials (polystyrene plus polyolefins) has been studied. For relatively coarse dispersions (1000A), Tm is 82°C, independent of composition, while the difference Δβ in cubical expansion coefficient above and below Tm is directly proportional to the volume fraction of polystyrene in the mixture. Unplasticized saran behaves similarly in that Tm is constant while Δβ decreases linearly with increasing crystallinity. For molecular dispersions of incompatible materials both Tm and Δβ are functions of composition. It is shown that for most high polymers Tm increases with increasing intermolecular force constants, while the product of Tm and cubical coefficient of expansion above Tm is roughly constant (0.1 to 0.2).
Mechanical Models of Frequency Converters
Authors: Stockman Harry
Published: January 2005

The action of modern frequency converters can be lucidly and accurately described by easily-built mechanical models, which for a chosen type of operation record the output wave as function of input amplitudes and input frequencies.
Thermal and Electrical Conductivity of Graphite and Carbon at Low Temperatures
Authors: Buerschaper Robert A.
Published: January 2005

Thermal and electrical conductivities of graphite and carbon were measured at various temperatures in the range between −191°C and 100°C. Thermal conductivity of graphite was found to increase at an increasing rate as the temperature was lowered and two values were always found for Acheson graphite, a longitudinal and transverse conductivity, the latter being about ½ the former. This effect has not been reported for artificial graphite although Wooster reported an anisotropy in natural graphite with respect to thermal conductivity, the values along the axis being about four times that at right angles. X-ray patterns give no evidence of crystalline alignment in Acheson graphite and the explanation of this anisotropy has not been found. The electrical conductivity of graphite increases with rise of temperature as contrasted with the decrease of the thermal conductivity with temperature rise. Thus the Wiedmann-Franz law does not hold, nor is the Lorentz number a constant. Carbon shows no anisotropy. The thermal and electrical conductivities both increase with temperature rise, the thermal conductivity linear, in the temperature range −191° to 100°C.
Extension of the Conventional Twist Multiple Formula to New Materials
Authors: Gerhard S. L.
Published: January 2005

Mathematical relations between a few geometric yarn properties are used to develop the concept of relative density. With the aid of this idea it is possible to deal with yarns made of different materials but having the same relative density as though they were made of the same material, so far as their geometric properties are concerned. A simple formula is derived to convert twist multiples from one yarn count system to another. The figure obtained for the twist to be put into the new yarn is only an ``educated guess,'' but it is hoped that it will shorten the amount of experimentation necessary for determining the optimum twist in new yarns.
Mutual and Self-Impedance for Coupled Antennas
Authors: King Ronold , Harrison Charles W.
Published: January 2005

A general theory for the current in coupled antennas is formulated in terms of the vector potential and applied to determine the self-impedance Zs1 and the mutual impedance Z12 of a center-driven antenna in the presence of a second parallel, identical antenna which may be center-driven or center-loaded in an arbitrary way. Each antenna has a half-length h, a radius a, and the distance between them is b. Curves are shown for Zs1 and Z12 for h=λ/4; Ω=2 ln (2h/a) = ∞, 30, 20, 10; 0.05≦b/λ≦0.4; and for h=λ/2; Ω=2 ln (2h/a) = 30, 20, 10; 0.05≦b/λ≦0.5. It is shown that except for the special case of an indefinitely thin antenna (Ω= ∞) the self-impedance Zs1 of an antenna in the presence of a second antenna differs from the self-impedance Z0 when the antenna is isolated and varies with b/λ. The input impedance Zlin is determined and plotted for the same values of h and Ω, and the same ranges of b/λ for the following special cases: 1. The antennas are both center-driven in phase by identical generators. 2. The antennas are both center-driven in opposite phase by identical generators; or a driven antenna is parallel to a perfectly conducting plane. 3. Antenna 1 is center-driven; antenna 2 is parasitic and unloaded. 4. Antenna 1 is center-driven, antenna 2 is parasitic and center-tuned to self-resonance (h=λ/2 only).
An Approximate Representation of the Electromagnetic Field in the Vicinity of a Symmetrical Radiator
Authors: Harrison Charles W.
Published: January 2005

The actual quadrature components of current along a symmetrical center-driven antenna of non-vanishing radius are represented by simple distribution functions. The magnetic and electric vectors in the near zone are then determined by carrying out the calculus of the field theory involved. The resulting expressions, while more intricate than existing formulas based on the assumption that the current in any antenna is sinusoidally distributed, represent approximately the field conditions about antennas used in practice.
Poisson's Ratio at High Temperatures
Authors: Everett F. L. , Miklowitz Julius
Published: January 2005

A method is presented whereby both the modulus of elasticity in tension and compression E and the modulus of elasticity in shear G may be obtained simultaneously from a simple test on a cantilever specimen subjected to combined bending and twist. By means of the relation ν = (E/2G) − 1, values of Poisson's ratio at various temperatures from ambient to 1000°F were obtained for five common steels.
A Simple Vector Method for the Determination of Orientations of Cubic Single Crystals from Back Reflection X-Ray Photographs
Authors: Decker Beulah Field
Published: January 2005

This paper describes a new and simpler method for the determination of orientations of cubic single crystals from back reflection x-ray photographs by use of vectors in the reciprocal lattice. An example is given to illustrate the usefulness of the method.
On the Representation of Rigid Rotations
Authors: Benedikt Elliot T.
Published: January 2005

The group of formulae of Euler and Rodriguez describing the (finite) rotation of a rigid body is written under absolute (coordinate—free) tensor form. Formulae for the products and powers of certain tensors appearing in the transformation formulae are established. By their application, it is shown that the tensor which, operating on a radius vector defining the position of a point of a rigid body with respect to a point 0 defining the position of the same point after the body has been subjected to a rotation of amplitude θ around an axis containing 0, and parallel to the unit vector h, can be written under the form eθh×. This representation is compared to the one obtained using quaternions.
Some Physical Properties of Elastomers at Low Temperature
Authors: Greene H. E. , Loughborough D. L.
Published: January 2005

Little has been published concerning the effect of low temperature on the elasticity of rubbers. Since in many applications this is the only property which justifies their use, some attention must be paid to this problem. Rubbers can be characterized by the temperature at which they become brittle and by the width of the transition region. The sharpness of the transition between the elastic and the glassy states is greatest when the testing time is long compared to the molecular relaxation times. Other physical factors such as sample shape, stress at which the modulus is calculated, and the previous history of the sample affect the absolute nature of the elastic properties measured. A test is described which gives the values of the elastic constants at slow rates of extension, at moderate extensions, on previously flexed samples. For these conditions the superiority of gum stocks at low temperature decrease in the order polybutadiene, natural rubber, Butyl, Neoprene FR. The comparative values of the stocks can be changed by compounding variations. Addition of plasticizer shifts the relative modulus vs. temperature curve down the temperature scale without producing a significant change in shape. Addition of reinforcing materials decreases the sharpness of the transition without changing the position of the curve.
The Absorption Displacement in X-Ray Diffraction by Cylindrical Samples
Authors: Warren B. E.
Published: January 2005

In the precision determination of lattice constants from back reflection Debye-Scherrer patterns, one of the systematic errors arises from the effect of absorption in the sample. The magnitude and form of the error is calculated for a cylindrical sample, for both parallel and diverging primary beams, and for a representative variety of values of the absorption coefficient. Calling 2φ the back scattering angle (φ=90−θ), it is found that the error in φ caused by absorption can be set proportional to φ. The form of the absorption correction allows it to be lumped in with the other systematic errors for a linear extrapolation according to either Δd/d =Kφ tan φ or Δd/d=K sin2 φ. There is some preference for the former.
Gas Flow in the Mass Spectrometer
Authors: Honig Richard E.
Published: January 2005

If a mass spectrometer is to be used successfully for gas analyses, the gas flow through the system must meet a number of requirements. The three modes of gas flow—molecular, intermediate, and viscous—are reviewed, and their working ranges are discussed in terms of the pressure of the system. The upper limit for molecular flow, through capillaries or through small openings, is found to lie at a pressure where the mean free path of the molecules is between 15 and 40 times the diameter of such a gas leak. Expressions are developed to show that, for molecular flow, the ion beam intensity is independent of molecular weight but is a linear function of the sample pressure, and that the principle of linear superposition applies to mixture peaks. Since the composition of a gas mixture in a reservoir is found to change with time (a numerical example is worked out), the necessity for analyses of short duration becomes evident. The practical aspects of designing the gas system for molecular flow and for efficient ion production are discussed in detail. The various flow requirements are best met by a gas leak consisting of a small hole in a diaphragm, or several holes in parallel. A relatively high gas pressure within the electron beam boundaries and resulting large ion currents are produced by introducing the gas as a molecular beam into a gas-tight ionizing region.
The Use of Direct Current in Induction Electron Accelerators
Authors: Westendorp W. F.
Published: January 2005

The application of a direct-current bias in the magnetic circuit of induction accelerators is described. In its simplest form this bias reduces power consumption to approximately 30 percent; in especially designed machines a reduction of the weight to 50 percent or less is an additional advantage. A machine with a closed central core is discussed and the use of orbit contraction by saturation over a range of x-ray energies is described.
A Double-Solenoid Coil System for Magnetic Measurements
Authors: Frowe E. W. , Aronson C. J.
Published: January 2005

A double-solenoid coil system is described which can be used as a neutralizing coil having large internal and small external magnetic fields. Its application in the measurement of magnetic moments of small magnets is also discussed.
The Class of Electron Lenses Which Satisfy Newton's Image Relation
Authors: Hutter R. G. E.
Published: January 2005

Newton's image relations are satisfied for all electron lenses if object and image are located outside the region of the electromagnetic fields. It will be shown that a special class of electron lenses exists for which these relations hold for any object and image position. The results will be compared with those obtained by W. Glaser.
Determination of Coexisting Phases in Heterogeneous Systems of Many Components
Authors: Beck Paul A.
Published: January 2005

A general investigation was made of the coexistence relationships of n+1 phases in the isothermic-isobaric sections of n-component systems. It was found that for a given set of n+1 phases there are at most only two coexistence patterns possible. As a result in n-component systems, as well as in ternary systems, theoretically only a single well-chosen sample has to be examined for the phases it contains in order to completely clarify the phase coexistence relationships of n+1 phases whose composition is already known. The results obtained were further used to develop a general classification of the types of non-variant equilibria occurring in many component systems.
High Dispersion Electron Diffraction by Primary Magnification
Authors: Simard G. L. , Burton Charles J. , Barnes R. Bowling
Published: January 2005

A method for attaining high dispersion in electron diffraction is presented. High dispersion may be obtained by primary magnification of a diffraction pattern formed in the normal manner at the object plane of a magnetic or electrostatic lens. Dispersion may be varied continuously by changing the lens current or voltage. The design of diffraction cameras of this type is discussed and their value in diffraction problems pointed out. The validity of the method is established by diffraction patterns obtained using a modified electron microscope adapter.
Coil Systems for Producing Transverse and Longitudinal Magnetic Gradients
Authors: Shortley George H. , May Albert
Published: January 2005

A coil system is described which produces very constant magnetic gradients throughout a considerable part of the volume occupied by the coil assembly. One modification produces constant transverse and longitudinal gradients of the field transverse to a long cylindrical region; another modification produces constant transverse and longitudinal gradients of the magnetic field throughout a spherical volume. Gradient data are given for both modifications.
Crystal Interference Phenomena in Electron Microscope Images
Authors: Heidenreich R. D. , Sturkey L.
Published: January 2005

The observation of electron reflections in electron microscope images is reviewed and further data are presented. The observations of the reflected beams with the objective limiting diaphragm removed and the determination of the planes responsible for the reflections by this means are described. The results of the dynamical theory of electron diffraction are briefly discussed and the values of the ``characteristic'' crystal thickness D0 are computed. These values of D0 are compared with the experimental values and are in reasonably good agreement for the MgO (200) reflections at 60, 96, and 103 kv, MgO (220) reflections and CdO (200) reflections at 60 kv. The dynamical theory accounts satisfactorily for the intensity variations except as modified by inelastic scattering and the results may be considered as experimental verification of the theory.
The General Theory of Stresses and Displacements in Layered Soil Systems. II
Authors: Burmister D. M.
Published: January 2005

The equations of stresses and displacements in a two-layer system are derived in this paper for Case 2 with a frictionless interface between the two layers.
The Validity of the Pole Figure
Authors: Decker Beulah Field
Published: January 2005

A [110] pole figure for cold-rolled and annealed silicon steel, constructed from data obtained with an integrating x-ray camera, is compared with a stereographic projection of [110] poles for one hundred individual grains in the same samples. From this comparison, it is concluded that pole figures are accurate enough to determine preferred orientations when the exact percentage of crystals in each orientation is not required.
The Determination of Molecular-Weight Distribution in High Polymers by Means of Solubility Limits
Authors: Morey D. R. , Tamblyn J. W.
Published: January 2005

By means of polymer fractions of known molecular weight, dissolved in solutions of known compositions, it is possible to determine the solubility law which relates the point of solution saturation to the molecular weight and concentration of the dissolved polymer. Having established such a calibration, it is possible to determine the molecular-weight distribution in a heterogeneous sample of the polymer by suitable operation on a curve relating the mass of polymer precipitated to the amount of precipitant added to the solution. Optical means, making use of scattering from the precipitate, are used to obtain this latter curve. The method is applied to cellulose acetate butyrate and is shown to give results in agreement with gravimetrically obtained distribution curves.
Microwave Impedance Measurements with Application to Antennas. II
Authors: King Ronold , King D. D.
Published: January 2005

Following a critical discussion of the problems of theory and experiment and their coordination, experimentally determined curves for the impedance of a symmetrical, cylindrical antenna terminating a two-wire line are given and interpreted. The conclusion is reached that the impedance of an antenna, especially near anti-resonance, depends in a large measure on the proximity and the nature of the input terminals.
The Secondary Electron Emission of Pyrex Glass
Authors: Mueller C. W.
Published: January 2005

The total secondary emission of Pyrex glass is measured by a method utilizing the conductivity of the heated glass to carry the current. Necessary precautions for this type of measurement are pointed out. The secondary emission is measured over the bombarding voltage range of 50 to 10,000 volts. No temperature variation of secondary emission is observed.
The Structure of Certain Muscle Fibrils as Revealed by the Use of Electron Stains
Authors: Hall C. E. , Jakus M. A. , Schmitt F. O.
Published: January 2005

Fibrils from certain molluscan muscles, in particular the adductor muscles of the clam Venus mercenaria, were examined with the electron microscope and found to possess periodic variations in structure. In order to make these structural variations visible, it was necessary to treat the fibrils with reagents of high electron scattering power (electron stains). Phosphotungstic acid was found to be particularly suitable. This stain combines with specific regions in the fibrils, forming a remarkably regular geometrical pattern of which the most prominent feature is a regular cross striation, representing a fiber-axis spacing of about 145A. Within each stained band, the stain is more highly concentrated in spots spaced about 193A from center to center across the band. A line drawn through any such spot parallel to the fiber axis passes through other similar spots, spaced five cross bands apart, making the length of the fiber-axis period precisely five times the fiber-axis spacing. X-ray diffraction data obtained by Bear from the intact muscles are compared with the electron microscope observations. The small angle diffractions are in close agreement with those which would be expected from the observed structure except for the magnitude of the lateral spacing. Electron microscope values for this spacing are significantly smaller than the 325A indicated by the x-ray data, probably as a result of lateral shrinkage in the vacuum-dried electron microscope specimens. No significant difference in axis spacing has been observed in fibrils isolated from muscles fixed with alcohol in contracted and extended states.
Flow Orientation in Isotropic Fluids
Authors: Bondi A.
Published: January 2005

A theory of flow orientation was developed which is based on a relation giving the change in entropy accompanying molecular orientation under the influence of a stress field, and on the applicability of the Eyring theory of viscous flow. The proposed theory predicts the ratio of the viscosity at attainment of complete orientation to the viscosity of ``normal'' i.e., random flow to be equal to the ratio of the average length v⅓ to the actual length of the (fully stretched) molecule. The thermodynamics of a flow-oriented system are outlined, predicting the temperature changes, accompanying adiabatic orientation and disorientation. It is also suggested that the relaxation times in viscous media are large enough to prevent observation of flow orientation in capillary viscosimeters in many cases.
Elementary Treatment of Longitudinal Debunching in a Velocity Modulation System
Authors: Feenberg Eugene
Published: January 2005

Certain configurations of anode, grid sections, and uniformly emitting cathode produce rectilinear motion of the electrons, both with and without velocity modulation. These systems are (a) plane parallel electrodes and grid sections of unlimited extent, (b) coaxial circular electrodes and grid sections of infinite length along the axis, and (c) concentric spherical electrodes and grid sections. The uni-dimensional character of the motion permits a complete evaluation of the effect of space charge on the bunching process in the range of drift space where overtaking (crossing of orbits) does not occur.
Luminescence of (Zn, Be) 2SiO4:Mn and Other Manganese-Activated Phosphors
Authors: Schulman James H.
Published: January 2005

Spectral energy distribution and luminous efficiency measurements of Zn2SiO4:Mn and of various samples of (Zn, Be)2SiO4:Mn are reported. Quantum efficiencies of these phosphors under 2537A excitation are calculated from this data. The introduction of beryllium into alphawillemite causes a decrease of the ``green'' luminescence band of this phosphor and the growth of a new emission band with a peak in the neighborhood of 6100A, the high quantum efficiency being preserved. The general role of manganese as an activator is considered, and the resulting picture used to explain the effect of beryllium and other substituents for Zn+2 or Si+4 on the spectral properties and on the luminescence decay of manganese-activated materials.
Recent Ozone Investigations
Authors: Ewell Arthur W.
Published: January 2005

This paper is supplementary to one which appeared in the December, 1942 issue of this journal. In many applications of bactericidal lamps in air conditioning—such as food preservation, processing, etc.—low concentrations of ozone are desirable to protect surfaces and air pockets not reached by the radiation. A few tenths of one part of ozone per million parts of air is generally sufficient and is obtainable by selecting a lamp with a wall which transmits in addition to the very bactericidal 2537A radiation a few percent of 1850A. The latter is absorbed by the oxygen in the air forming ozone. The reciprocity law (amount of bactericidal action proportional to concentration×duration of ozone) is applicable for moderate concentration ranges. The bactericidal effect of ozone is nearly independent of humidity for surface infection of foods, etc., while high humidity is required for destruction of air borne bacteria. No oxides of nitrogen are produced by high transmission glass or quartz lamps. The ozone output of a lamp is reduced by decomposition by intense 2537 radiation either from the same lamp or from another lamp nearby. Moderate increases in the temperature of a high transmission lamp does not affect the ozone output but increases the dissociation constant until, at 150°F, practically all the ozone is immediately decomposed. The ozone concentration produced by a lamp is substantially reduced by rise in relative humidity, which moderately absorbs 1850 radiation and decomposes much of the ozone produced. Approximate reflection coefficients for 1850 radiation at various surfaces have been obtained by an indirect method.
Properties of Welded Contact Germanium Rectifiers
Authors: North H. Q.
Published: January 2005

In the contact rectifier described, the cat whisker has been solidly welded to a germanium surface. The welding process has brought about several extraordinary properties not found in the usual point rectifier: (1) Mechanical stability is achieved without the use of a compound to fill the cartridge. Protection against moisture is gained through the use of a glass-metal seal. (2) The forward dynamic resistance of the microwave unit at 0.5 volt is exceptionally low (2 to 4 ohms), and the back resistance at 0.5 volt is high (0.01 to 1.0 megohm). These values of resistance are accompanied by a low contact capacity at zero bias (below 0.2 μμf). (3) The forward d.c. characteristic follows the law, IF=I0 exp (αVF) over more than three decades of current. (4) The low forward resistance is responsible in part for conversion gain when the crystals are mismatched to microwave radiation at the r-f terminals. (5) Specially welded crystals used as microwave harmonic generators have yielded more than twenty times the harmonic (4-mm wave-length) power output of standard silicon crystals.