bluuebunny/crossref_metadata_2025 huggingface dataset:
The Plasma Physics of Thermionic Converters
Authors: Bullis Robert H. , Hansen Lorin K. , Warner Charles , Houston John M. , Koskinen Michael F. , Rasor Ned S.
Published: January 2005

The plasma physics of thermionic converters is discussed in an attempt to develop a coherent physical picture of this aspect of the converter in all regions of operation. Emphasis is placed on the presentation of simple physical models consistent with experimental data: The usefulness of certain characteristic features of the I–V curve, in determining the physical processes governing converter operation, is pointed out. Nine regions of converter operation are identified by these features of the I–V curve and are discussed. The importance of two parameters of converter operation, the pressure—spacing product pd, and the relative amount of emitter-surface ion generation β, in controlling converter behavior is emphasized. The particular values of pd and β control which of the nine regions of converter operation appear on a particular I–V curve.
Seebeck Coefficient of Thin-Film Germanium
Authors: Hui W. L. C. , Corra J. P.
Published: January 2005

Thin films of germanium of p-type conductivity with Hall mobility values up to 350 cm2/V·sec, carrier concentrations of 1017 to 1019 cm−3, and resistivity values of 0.03 to 0.4Ω·cm were vacuum deposited. Values of Seebeck coefficient in the range from 150 to 400 μV(°C)−1 have been measured near room temperature in these films, and have been correlated with the carrier concentration and the resistivity of the films. This correlation is similar to that for single crystal and polycrystalline bulk germanium.
Electrical Properties of Nonstoichiometric Thorium Carbides
Authors: Auskern A. B. , Aronson S.
Published: January 2005

The resistivity, Hall coefficient, and thermoelectric power of ThCx, with x varying from 0.787 to 0.91, were measured from 4.2° to about 400°K. The results were analyzed in terms of a two-band conductivity model. The analysis showed that as carbon is removed from the structure, band overlap increases and the number of carriers is increased. The resistivity data were analyzed using Matthiessen's rule and the analysis indicated that the residual resistivity arises from carbon vacancies. The vacancy contribution to the resistivity increases with increasing vacancy concentration.
Photoconductivity Decay in Imperfect Crystals
Authors: Bube Richard H. , Grove Wayne M. , Murchison Rolf K.
Published: January 2005

The photoconductivity decay in imperfect crystals can be described in terms of an exponential trap distribution, Nt(E) = N0 exp(− E/kT*), where N0 and T* are two parameters characteristic of the distribution. Theoretical expressions for the decay as a function of excitation intensity and temperature can be derived in terms of N0 and T*, both of which can be determined from a Fermi-level analysis of the experimental decay curves. Such an analysis of experimental curves is carried out for a Cd(SSe) sintered photoconductor layer, and it is shown that an approximately exponential trap distribution with N0=2.0×1017 cm−3 eV−1 and T* = 852°K exists at least between 0.3 and 0.6 eV below the conduction band. The theoretical expressions, involving no additional undetermined parameters, are then used to calculate decay curves as a function of temperature between 298° and 348°K, and as a function of excitation intensity over two orders of magnitude, with satisfactory agreement with the experimental curves. It is concluded that the photoconductivity decay characteristics of imperfect crystals can be described over rather wide ranges of temperature and excitation intensity by specifying the electron lifetime, τ, and the two trap distribution parameters, N0 and T*.
Magnetic-Field Dependence of Josephson Current Influenced by Self-Field
Authors: Yamashita Tsutomu , Onodera Yutaka
Published: January 2005

The magnetic-field dependence of dc Josephson current IJ was measured using cross-type square junctions made of Sn thin films. The results and analysis indicate that owing to the self-field of IJ, the periodic pattern of IJ on magnetic field is modified and the value of the maximum IJ becomes smaller than theoretically expected value obtained Ambegaokar and Baratoff.
Intrinsic Optical Absorption of Gallium Phosphide between 2.33 and 3.12 eV
Authors: Dean P. J. , Kaminsky G. , Zetterstrom R. B.
Published: January 2005

Single ribbons of gallium phosphide have been synthesized which are very thin (down to ∼0.35 μ) and yet possess relatively large cross-sectional areas with uniform thickness so that high-resolution optical-absorption measurements can be extended well above the lowest energy direct interband electronic transition (Γ15→Γ1). The Γ15→Γ1 exciton energy gap is 2.873 eV below 25°K, and the internal binding energy of the direct exciton is about 5 meV. Direct transitions involving hole states in the split-off valence band can be clearly seen at low temperatures, and the spin-orbit splitting is 82±1 meV. Weak structure corresponding to indirect transitions at the Γ15→X3 energy gap is also observed at low temperatures, and the separation of the X3 and X1 conduction-band minima is 0.29±0.01 eV, in excellent agreement with the value obtained from interconduction-band absorption spectra. The temperature coefficient of the Γ15→Γ1 direct energy gap is − (5.2±0.1)×10−4 eV(°K)−1 near 300°K, more than twice the value for the Γ15→X1 indirect gap.
Microwave Heating by a Standing Wave in the Helium Afterglow
Authors: Cronson H. M.
Published: January 2005

Spatial variations of electron temperature in the late helium afterglow in the pressure range 0.55–68 Torr are measured experimentally. The variations are due to the presence of an applied standing wave at microwave frequencies. A normalized temperature profile is deduced from variations in the afterglow light quenching during a microwave pulse. Large temperature variations occur at higher pressures and smaller variations are seen at lower pressures. The observations are in good agreement with theory.
Effects of CO2, He, and N2 on the Lifetimes of the 00°1 and 10°0 CO2 Laser Levels and on Pulsed Gain at 10.6 μ
Authors: Cheo P. K.
Published: January 2005

Relaxation times of the 00°1 and 10°0 CO2 vibrational levels and the afterglow gain at 10.6 μ were studied by a pulsed-gain technique, for pure CO2, CO2:He, and CO2:N2 gas mixtures in 22-mm- and 34-mm-bore nonflowing laser amplifiers. Measurements of the exponential rise, τr, and decay, γd, times of the afterglow gain pulse were made using a cw 10.6-μ CO2 laser as the amplifier input radiation source. Evidence is presented to support the interpretation of τr and τd as measures of the effective lifetimes of the 10°0 and 00°1 CO2 laser levels, respectively. For the case of a pure CO2 gas in the pressure range from 1 to 8 Torr, the measured τr and τd values vary from 50 to 250 μsec and 0.3 to 2.5 msec, respectively. Both 1/τ00°1 and 1/τ10°0 increase almost linearly with increasing CO2 pressure for P>4 Torr. Collision cross sections for volume quenching in pure CO2 are computed to be σ00°1=2.86×10−19 cm2 and σ10°0=1.62×10−18 cm2, assuming Tgas=300°K. Addition of helium to CO2 causes essentially no change in τ00°1 but results in a substantial decrease in τ10°0. The measured collision cross section for quenching of the 10°0 level population by He is (σ10°0)He=1.04×10−18 cm2, about two-thirds of that obtained for CO2−CO2 collisions. Nitrogen, on the other hand, causes an increase in both τ00°1 and τ10°0 by much as a factor of two at P>5 Torr. The peak values of amplifier gain in the afterglow, Gp, in general, are higher and depend more critically on tube bore than those obtained for cw discharges. The relative values of optimum Gp for CO2, CO2:He, and CO2:N2 are consistent with those obtained from cw gain measurements.
Measurement of Atomic-Stopping Cross Sections at Low Energies
Authors: White W. , Mueller R. M.
Published: January 2005

A method for the measurement of the electronic-stopping cross section Sε for atomic particles in solids is presented and demonstrated by measurement of Sε for 1H and 4He in aluminim in the energy range 20 to 140 keV.
An Improved Furnace for the Growth and Treatment of Cadmium Sulfide Single-Crystal Platelets
Authors: Greene Lawrence C. , Geesner Charles R.
Published: January 2005

A furnance is described in which single-crystal platelets of cadmium sulfide can be grown under carefully controlled conditions of temperature and carrier-gas composition. Provision is also made for post-growth treatment without disturbing the crystals. A description is given of the fluorescence spectra of crystals grown in various carrier-gas compositions, and it is shown that there is a predictable relationship between growth conditions and fluorescence emission.
Modulation of the 3.39-μ Ne Line by Electro-Optic Gases
Authors: Landman A.
Published: January 2005

The Stark effect in several vibrational-rotational transitions in various gases which have the first vibrational excitation (the C–H stretching vibration) close to the 3.39-μ transition in neon have been studied in detail. Tuning of the source line from a He–Ne laser over a range of about 0.1 cm−1 was obtained by use of a solenoid. Observations were made of absolute and percentage modulation at various pressures of the gases and included the use of a buffer gas. Maximum modulation of 15% has been achieved. The possibilities for increasing this value and for attaining induced birefringence are also discussed.
Scanning Electron Microscope Investigation of Planar Diffused p-n Junction Profiles near the Edge of a Diffusion Mask
Authors: MacDonald N. C. , Everhart T. E.
Published: January 2005

A scanning electron microscope is used to determine the geometry of a planar p-n junction profile near the edge of a diffusion mask. The planar junctions are angle-lapped at large angles (∼45°) to expose the cross section of the p-n junction. Computer calculations of the theoretical p-n junction profiles are presented. The theoretical profiles, normalized with respect to the junction depth, are presented as a function of the lap angle, the angle the lapped surface makes with the electron probe, and the ratio of the bulk impurity concentration to the impurity concentration at the surface. The normalized theoretical profiles are found to compare quite well with the experimental profiles obtained with the Berkeley scanning electron microscope-I.
Transformation Theory of Guided Waves in Moving Media
Authors: Jiang Ching Lin
Published: January 2005

The problem of wave propagation in a waveguide filled with a moving medium is investigated theoretically. There is no limitation on the velocity of the medium. Without solving the Maxwell's equations in moving media as viewed by a stationary observer, the normal-mode wave solutions in the guide are constructed by a transformation of the field tensors. The orthogonality conditions and the mode completeness are shown to be still valid, and the power flow is also discussed.

Two cases of the media are considered in detail: (a) the nondispersive dielectric and (b) the cold plasma. Several interesting features concerning the cutoff phenomena, phase velocity, and group velocity are discussed and compared for both cases.
Magnetostriction of Ytterbium and Cerium in YIG
Authors: Comstock R. L. , Raymond J. J.
Published: January 2005

Measurements using strain gauges of the magnetostriction constants of Yb3+ and Ce3+ ions in YIG are presented. The temperature dependence of the magnetostriction for Yb3+ in YIG is compared to theories by Callen and Callen based on crystal-field (single-ion) and anisotropic rare-earth-iron-exchange (two-ion) interactions. The measured temperature dependence of the magnetostriction for Yb3+ in YIG agrees closely with that predicted from the anisotropic exchange interaction. The measured temperature dependence of the magnetostriction of Ce3+ in YIG is difficult to interpret in terms of the two interactions because, in contrast to Yb3+, the sublattice magnetization cannot be evaluated analytically since the energy-level scheme of the rare-earth ground state is not completely determined and the higher levels of the ground state become populated at temperatures where the two interactions could be distinguished. The results are consistent with a ground-state exchange splitting of Ce3+ in YIG of ∼200 cm−1. Recent paramagnetic-resonance staticstrain measurements of Phillips and White are discussed.
Determination of Average Plasma Conductivity by rf Probes
Authors: Ciampi M. , Talini N.
Published: January 2005

Study of determination of the spatial average plasma conductivity by a radio-frequency probe is tackled for a cylindrical plasma assumed radially inhomogeneous.

The real and imaginary part of the probe impedance vs the probing frequency are found numerically for inhomogeneous plasmas with conductivity profiles of the type σ(ρ) = σmax(1−mρn).

With such an analysis only two independent average conductivities are found, both at low frequency.

The analytical form of the average conductivities is obtained, comparing, in a low-frequency approximation, the tested inhomogeneous medium with a fictitious homogeneous one for which the real or imaginary part of the probe impedance varies in the same way.

As a result of a measurement of the rf energy dissipation in the medium (effected by evaluating the probe Q-factor), the average conductivity is σ*=(4/R4) ∫ 0Rσ(r)r3dr;the average conductivity becomes σ**2=34[(4/R4) ∫ 0Rσ(r)r3dr]2+(3/2R6) ∫ 0Rr5dr[(4/r4) ∫ 0rσ(r)r3dr]2in case of a measurement of the inductance variation.

An application of the method is carried out in a flow facility plasma jet; with Q-factor measurements from 0.5 to 1.5 MHz, average conductivity values from 75 to 100 mho/m are obtained.

The probe is calibrated with electrolytic solutions (H2SO4) of standard conductivity.
X-Ray Diffraction by Multilayered Thin-Film Structures and Their Diffusion
Authors: Dinklage John B.
Published: January 2005

Five orders of soft x-ray diffraction by multilayered thin-film structures of Fe and Mg have been observed. The structures consisted of as many as 200 layers of Fe separated by Mg layers, providing layer spacings of 30–50 Å. The diffracting characteristics have been measured for the wavelength range 8.34 to 23.7 Å (AlKα to OKα). The integrated diffracted intensities from Fe–Mg layered structures and multilayered lead stearate soap-film structures are shown to be comparable. A diffracted x-ray peak intensity to background ratio of 80 and a resolution (λ/Δλ) of 25 have been observed for the diffraction of OKα radiation by the Fe–Mg structures. No diffusion in the Fe–Mg layers was detected at room temperature. The diffracted x-ray intensity from similar Au–Mg layered structures decreased to one-half in 15 days at room temperature because of interdiffusion. Diffusion in the Au–Mg layered system may be described by an effective interdiffusion constant that satisfies the equation Deff=4.3×10−9 exp[−18.3 kcal/(RT)] cm2 sec−1 for the temperature range 23–100°C. For Fe–Mg layered structures an effective interdiffusion constant Deff=7.9×10−20 cm2 sec−1 was measured at 260°C.
Ring Focusing of Negative Ions in a Cathode-Ray Beam
Authors: Bachman C. H.
Published: January 2005

An explanation is offered for the ring structure and some of the other configurational details associated with negative ion spots on fluorescent screens. Negative ion liberation by positive ion bombardment and the effect of the magnetic deflecting field on the positive ion paths are believed responsible for the apparent selective focusing of negative ions.
Velocity of Compressional Waves in Petroleum Fractions at Atmospheric and Elevated Pressures
Authors: Matteson Robert , Vogt C. J.
Published: January 2005

The problem of dynamics of liquid columns, particularly in Diesel engine injection systems, requires a knowledge of the velocity of propagation of compressional waves in the system. Approximate values are generally used in the solution of such problems. In an effort to correlate the physical properties of petroleum oils with the velocity of wave propagation and to relate the characteristics determined at atmospheric pressure with those at higher pressures, tests were conducted in the Physical Laboratories of the Standard Oil Company of California on thirty-seven hydrocarbon oils at atmospheric pressure. Five hydrocarbon oils were investigated in the Mechanical Engineering Laboratories at the University of California at four temperatures ranging from 57°F to 210°F, and pressures ranging from 500 lb. per square inch to 6000 lb. per square inch. In this paper the experimental methods are described and results presented.
A Mechanical Model for the Motion of Electrons in a Magnetic Field
Authors: Rose Albert
Published: January 2005

A mechanical model in the form of a gyroscope may be made to simulate the path of an electron in a uniform magnetic field acted upon by transverse electric fields. In using the model, one employs the following substitutions: The uniform magnetic field is replaced by the spin velocity of the gyroscope, the electric fields are replaced by magnetic fields which give the same field configuration, and the electron is replaced by one pole of a permanent magnet mounted on the axis of the gyroscope. The spin velocity may be arbitrarily chosen for convenient observation. Then, depending upon the value of the spin velocity, the dimensions of the gyroscope, the strength of the permanent magnet and the scale factor used in setting up the model, the strength of the magnetic field in the model is adjusted to correspond to the strength of the electric field in the actual case. The path described by the magnetic pole, under these conditions, corresponds to the actual path of the electron. Since the error involved in identifying the equations of motion of the gyroscope with those of the electron is of the order of θ2, where θ is the half-angle of the cone through which the spin axis is allowed to move, the range of observations must be restricted accordingly. Some familiar structures for which electron paths have been observed and photographed are deflection plates in a uniform magnetic field, a diode in an axial magnetic field, and a split-anode magnetron. By periodically reversing the current through the field magnets, it is possible to observe the effect of alternating electric fields. In one arrangement, in which the field was alternated in resonance with the revolution of the electron about the magnetic field lines, a path similar to that of charged particles in a cyclotron was obtained.
Electrolytic Polishing. II
Authors: Elmore W. C.
Published: January 2005

From the assumptions underlying the diffusion theory of electrolytic polishing two quantitative current-time relations are deduced and compared with the behavior of a copper-orthophosphoric acid cell. One equation relates the current through the cell to the time required for the growth of the concentration layer necessary for polishing. The other equation describes the fall in limiting current once the layer is formed. Both equations are in accord with the results of some simple experiments designed to test them. The present study removes some of the mystery in electrolytic polishing and permits a more intelligent use of it to be made.
A Graphical Method for Selecting Suitable Radiations for the Precision Determination of Noncubic Lattice Constants and for Indexing Back-Reflection Lines in Powder X-Ray Photograms
Authors: Carapella Louis A.
Published: January 2005

A simple method by which the proper radiation or combination of radiations may be selected for the precision determination of hexagonal, rhombohedral, and tetragonal lattice constants is described and illustrated in detail. The method involves the use of specially prepared charts. With a knowledge of the approximate lattice constants, positions of diffraction lines with θ>60°; i.e., back-reflection lines, can be predicted directly from the charts for any common radiation. From the number, distribution, and indices of back-reflection lines, a suitable target may be chosen for an accurate determination of lattice constants. Furthermore, the charts are useful for predicting positions of beta-lines, and for indexing without calculation back-reflection lines in powder x-ray photograms of hexagonal, rhombohedral, or tetragonal lattices.
An Investigation into the Gettering Powers of Various Metals for the Gases Hydrogen, Oxygen, Nitrogen, Carbon Dioxide and Air
Authors: Ehrke Louis F. , Slack Charles M.
Published: January 2005

Measurements of the ``gettering'' or clean-up ability of aluminum, magnesium, thorium, uranium, misch metal, zirconium and barium for the common gases were made. In most cases the measurements were quantitative and represent gettering powers unassisted by an electric discharge or other source of ions. The effect of temperature conditions on the gettering and keeping properties of several of the getters is given. The superior gettering powers of the diffuse layers produced by vaporizing the getters in the presence of a gas, as compared to those of the bright getter deposits produced in a high vacuum were confirmed. Barium and misch metal were found to be the most active of the materials tried, and the convenient forms which barium is now commercially obtainable would seem to make it first choice for most work, though it is not effective in the presence of Hg vapor. Magnesium and aluminum showed little activity without the presence of a discharge. Thorium and uranium showed considerable activity for H2 and O2, but the high temperatures needed for flashing, make them rather inconvenient to use.
Studies in Lubrication. VI. Electrolytic Models of Full Journal Bearings
Authors: Morgan F. , Muskat M. , Reed D. W.
Published: January 2005

An electrolytic model of a full journal bearing having a ratio of journal displacement to radial clearance of 0.1 has been constructed. The reliability of the model was established by comparing the results observed for the infinitely wide bearing with those predicted by the theory of Reynolds. The results obtained for models of journal bearings of finite width, bearings with circumferential grooves, and bearings with sources of lubricant are also in agreement with hydrodynamic theory.
The Relation of Fluidity to Volume in Organic Liquids
Authors: Bingham Eugene C. , Kinney Paul W.
Published: January 2005

The Batschinski expression relating the fluidity of a compound to the specific volume at various temperatures is inadequate in the cases of associated compounds and those of high molecular weight. A modification, herein given, consists of the introduction of a correction term. The new expression, which relates linearly the fluidity and the corrected molecular free volume, has universal applicability and it holds with a high degree of precision. The constants of the new relationship are related to the complexity of the compounds in homologous series. From the constants given, the fluidity of undetermined members of the homologous series studied can be calculated if the density is known at that temperature.
Conductivity Measurements on Potassium Halides
Authors: Brennecke Cornelius G.
Published: January 2005

The electrical conductivities of flat crystal plates of KBr and KCl were measured over a temperature range of from 25°C to 600°C, at stresses of from 0.05 to 0.90 kv/cm. Ohm's law was found to hold, when cold conductivities were measured after preliminary heating. Current-time data indicated an exponential decay of current with time at the lower temperatures, and a current constant with time at the higher temperatures. An exponential relation between conductivity and temperature was found to hold for both KBr and KCl, but in the latter case an abrupt change in the slope of the curve was found to take place at a temperature between 200°C and 250°C.
Diffusion of Hydrogen from Water Through Steel
Authors: Norton Francis J.
Published: January 2005

Using a metal radio tube having a steel shell as an ionization gage, the diffusion of hydrogen through the steel into the interior was measured. This results from the fundamental corrosion reaction on the exterior, when it is dipped into water: Fe+H2O=FeO+H2.The protective paint on the tube prevents this, but a bare sandblasted iron surface admits hydrogen at 0.13 micron per hour with the shell in water at 25°C. Hydrogen does not diffuse into the tube when water vapor alone surrounds it. Rates of diffusion were measured through plain and composite metal shells, varying surface treatment and temperature.
The Solution of Torsion Problems by Numerical Integration of Poisson's Equation
Authors: Weller R. , Shortley G. H. , Fried B.
Published: January 2005

This paper considers numerical methods for the solution of Poisson's equation in an arbitrary two-dimensional region with given boundary values. The methods are similar to those discussed by Shortley and Weller for Laplace's equation. It is shown that the entire theory of networks may be applied to Poisson's equation without change. Formulas for the treatment of irregular points and for blocks of points are developed. In addition to the mathematical considerations, the application of the methods to the case of torsion in shafts of any cross section is described. Additional formulas are derived for the determination of the maximum shear at any point in a shaft as well as the torsional stiffness of such a shaft.
Equations of Finite Differences Applied to Torsional Oscillations of Crankshafts
Authors: Biot Maurice A.
Published: January 2005

From the viewpoint of torsional oscillations an internal combustion engine with a long crankshaft is generally considered to be equivalent to a uniform shaft carrying equidistant identical disks. It is here shown that advantage can be taken of the regularity of such a system to simplify the calculation of torsional oscillations. This is done by applying a mathematical method known as the calculus of finite differences. The procedure leads to a frequency equation (2.7) of remarkable symmetry in which appear as parameter the number n of cylinders in line and two simple functions K1 and K2 of the frequency which characterize the dynamical properties of the machines coupled at both ends of the crankshaft. These characteristic functions are of the nature of mechanical impedances, but due to their physical interpretation as a spring modulus (or spring constant) generalized to dynamic phenomena, the appellation dynamic modulus is being preferably used in the present paper. The concept of dynamic modulus is briefly introduced in the first section, while the second deals with the establishment of the frequency equation and an artifice for its rapid graphical solution avoiding the necessity of plotting an oscillatory function. Numerical applications to Diesel engines are treated in the last section. An example is also given of an extreme case where the fundamental frequency has a very low value and a special method is used for the calculation of this frequency.
Studies in Lubrication. VIII. Lubrication of Plane Sliders
Authors: Morgan F. , Muskat M. , Reed D. W.
Published: January 2005

The coefficient of friction has been experimentally determined in the thick film region of lubrication for both fixed angle and pivoted plane sliders as a function of the lubricant viscosity μ, the relative speed of sliding U, and the load W. Three steel, brass, or bronze sliders of one centimeter length and width constituted the stationary surfaces; the moving surface was of steel. Deviations between experiment and theory for the fixed angle wedges at low values of μN/W may be explained on the basis of variations and inaccuracies in the sliders themselves. However, in the case of the pivoted sliders the experimental results are in excellent agreement with theory, and, in fact, provide for the first time an absolute and quantitative direct empirical check of the hydrodynamic theory of lubrication.
Breakdown Potentials of Gases Under Alternating Voltages
Authors: Fox G. W. , McCoy D. O.
Published: January 2005

Starting potentials for hydrogen, nitrogen, helium, and argon of commercial purity at frequencies up to one million cycles per second were investigated using a discharge tube with spherical electrodes. Five gap distances were employed, ranging from 10 mm to 50 mm. The slope of the log pressure versus log distance curve was found to be independent of frequency and also of the gas for small gap distances.
A New Method for the Calculation of Cavity Resonators
Authors: Hahn W. C.
Published: January 2005

This article gives a series method for the calculation of the fields in certain circularly symmetric resonators. By the use of some new functions, partial tables of which are included, the necessary series are made to converge rapidly enough so that the method becomes useful for numerical calculations of resonance conditions and wall currents.
The Measurement of Artificial Radioactivity in Liquid Tracer Samples Using C11
Authors: Smith James H. C. , Cowie Dean B.
Published: January 2005

Using C11 as tracer for the study of carbon dioxide absorption in plants, unexpected analytical difficulties were encountered. However, a satisfactory technique was developed for the rapid measurement of radioactivity in liquid samples. A degree of precision was obtained so that after the elapse of 6 half-lives (2 hours) the sum of the activities taken from the reaction system was accurate to 1 or 2 percent. This required the determination of an accurate half-life value for C11 (20.35 min.). The experimental procedures are described.
Elastic Aftereffects and Dielectric Absorption in Glass
Authors: Taylor Nelson W.
Published: January 2005

Taylor and Doran have found that in stabilized glasses the total elastic adjustment under a given load may be represented as the sum of several terms of the type l=l0e−kt, and have drawn the conclusion that there are several sizes of complex silicate ions in glass which respond independently and with different rates to applied stress.

Hopkinson proposed that there are several independent ``elements'' responding to the application of an electric field to a glass condenser, and von Schweidler showed that the anomalous charging current accompanying dielectric polarization is the sum of several terms of the type i=Ae−t/T. This expression is identical in form with that for elastic polarization if the rate constant k is replaced by a characteristic relaxation time constant 1/T. The dielectric phenomena thus appear to support the concept of independently acting ions in glass. This idea is in harmony with the x-ray evidence of a random ionic network, and with other physico-chemical evidence.

An interpretation of memory phenomena such as reversal effects in glass and rubber has been offered. Such reversals appear to be due to the superposition of two or more independent operations with different rate constants and directions.
Determination of Object Thickness in Electron Microscopy
Authors: Marton L. , Schiff L. I.
Published: January 2005

It is proposed that the thicknesses of electron microscope objects be determined by measuring the diminution in intensity of the electron beam caused by the object. Since this method would only be applied to specimens so thin that multiple scattering can be neglected, one need know only the total cross section for single scattering of electrons outside the aperture angle of the electron microscope objective. These cross sections are calculated for fast electrons (energies greater than 10,000 ev) by means of the Born approximation for several cases of practical interest, and the results are applied to some experimental observations.
The Evaporation of Molten Metals from Hot Filaments
Authors: Caldwell Wallace C.
Published: January 2005

The selection of filament material from which another metal can be evaporated successfully depends largely upon the three properties of wetting (W), reaction or alloying (R), and evaporation (E). Nine filament materials and twenty-seven evaporated metals have been investigated and the results summarized in a table using the above symbols with subscripts 1, 2 and 3 to indicate the degree of favorable properties. A second table lists satisfactory filament materials for the evaporation of twenty-six metals.
An Operational Treatment of Electromagnetic Waves Along Wires
Authors: Pipes Louis A.
Published: January 2005

Starting with the fundamental field equations of Maxwell, the equations governing the propagation of electromagnetic waves along two parallel wires are derived. The treatment is greatly facilitated by the use of the Laplacian transformation or modern rigorous operational calculus. First the case of waves traveling along perfectly conducting wires is considered and the dissipative case is treated as a perturbation of the ideal perfectly conducting one. An expression for the deformation of the front of an initially rectangular wave due to the ``skin-effect'' is derived and the manner in which the wave progresses along the wire is studied.
Electrical Characteristics of Stroboscopic Flash Lamps
Authors: Murphy P. M. , Edgerton H. E.
Published: January 2005

This paper describes the electrical characteristics of gas-filled discharge tubes when flashed by a condenser discharge. The object of the experiments was to determine the effects of tube dimensions, pressure, voltage, and capacity upon the performance. The results are of an experimental nature and cover a limited range of values of tubes and circuit constants. An empirical constant called tube resistance is defined and evaluated. This constant is useful in predicting the performance of tubes in electrical circuits.
The Production of Proton Beams
Authors: Lamar E. S. , Buechner W. W. , Van De Graaff R. J.
Published: January 2005

An account is given of further work on capillary ion sources of the diffusion type. Both metal and glass capillaries have been investigated. The performance of the metal sources is affected by surface conditions which are difficult to control. The average proton yield from these sources is about ten percent. It was found that the yield could be increased to about fifty percent by coating the surface with phosphorus pentoxide. Sources constructed of Pyrex have a proton yield of about sixty percent and also greater stability in operation, as well as certain other advantages. Various characteristics of the output of both types of source are described as functions of the source geometry, arc current, and other variables.
An Experimental Investigation of Ion Beam Focusing
Authors: Buechner W. W. , Lamar E. S. , Van De Graaff R. J.
Published: January 2005

An experimental investigation has been made of the initial focusing of ions from capillary sources of the diffusion type described in the previous paper. The lens system used consisted of a 90-degree cone at the ion source followed by three coaxial cylinders which were arranged at various potentials up to 25 kilovolts. Since the beams are rendered slightly luminous by traces of gas in the high vacuum region, they have been studied by a photographic method. The beams have also been studied by an electrical scanning method. Both types of investigation were made as functions of the electrode potentials and arc variables and are in good agreement. Based on these observations a focusing and canal arrangement suitable for differential pumping has been tested. This arrangement has been embodied in a design for a projected ion gun assembly.
Use of the Radioactive Properties of Thorium for a Quantitative Study of Phagocytosis
Authors: Maxfield F. A. , Mortensen O. A.
Published: January 2005

Use has been made of the radioactive properties of colloidal thorium dioxide, intravenously injected into rabbits, to study the functional capacity of the reticulo-endothelial cells for phagocytosis. A mathematical analysis of the problem is presented which indicates that when the system is not overloaded, the foreign material should be removed from the blood according to the relation n=n0e−at+b2αn0e−bt. Here a≫b and n is the number of particles remaining in the blood at any time t. Experiments on 13 rabbits substantiate this prediction. With a standard injection of 1 cc of colloidal thorium dioxide per kilogram of body weight, n decreases according to three distinct exponential relations. The system is apparently overloaded initially, but after n decreases to about one-sixth its initial value (at t=0), the fraction of the amount of material present that is removed in unit time increases and the rest of the curve follows the predicted relation. The fact that the system is initially overloaded was checked by the use of smaller amounts of thorium. In all cases more than 99 percent of the thorium was removed from the blood stream within 6 or 8 hours after the injection. The technique reported here should serve as a basis for testing many theories of phagocytosis now largely based on deduction.
X-Rays in Medicine
Authors: Cassen Benedict
Published: January 2005

Radiography, fluoroscopy, and therapy are medical terms that the x-ray specialist knows. Here the equipment and the techniques of present-day practice are described. The importance of physical instruments in advancing the art are made evident.
Electron Diffraction Observations of Surface Reaction of Hydrogen Selenide on Zinc Oxide
Authors: Fuller M. L. , Siller C. W.
Published: January 2005

The reaction of hydrogen selenide and pigment zinc oxide at room temperature has been investigated, using electron and x-ray diffraction as a means of examining the reaction product. It was found that hydrogen selenide reacts with zinc oxide to form zinc selenide as a coating around the zinc oxide particles. After approximately one-tenth of the zinc oxide is converted to zinc selenide by this surface reaction, the resulting coating of zinc selenide prevents the continuance of the reaction. Since the effective depth of penetration of electrons under the conditions of electron diffraction is much less than the average diameter of the pigment particles used in this investigation, the electron diffraction photograms necessarily arise largely from the particle surfaces. For this reason electron diffraction was successfully used to demonstrate that the reaction proceeded in the manner described. The paper illustrates the applicability of electron diffraction to the general problem of the examination of the surfaces of pigment particles.
Some Relations of Flow and Physical Properties with Formulation in Cellulose Acetate Plastics
Authors: Gloor W. E.
Published: January 2005

Data are presented showing flow and physical properties of cellulose acetate plastics made using five plasticizers (previously described by Kirkpatrick before the Society of Rheology) with cellulose acetates of 2.3 and 2.6 acetyl groups per C6 unit. Single plasticizers exert specific effects on flow and physical properties of the plastics. Mixtures of such plasticizers give plastics with properties which may be predicted by a simple proportion based on the amount of each plasticizer used. Results of Rockwell hardness, elastic modulus, impact strength, and water absorption tests of molded plastics are discussed. No general relation is found between flow properties of the plastics at molding heats and physical properties at room temperatures. An attempt is made to relate these results to the criteria for high elasticity set up by Houwink.
Frictional Phenomena. I
Authors: Gemant Andrew
Published: January 2005

This series of articles will be concerned with the present knowledge of viscous and related frictional processes, to be considered from a logical, unified standpoint. It will consist of three main parts covering, respectively, gases, liquids and solids. Theories, experimental data, and technical applications in the fields of mechanics, electricity, and chemical technology will be discussed.
Influence of Certain Variables on the Stresses in Gear Teeth
Authors: Dolan Thomas J.
Published: January 2005

A photoelastic study was made to obtain a more accurate picture of the localized stresses in gear tooth fillets than can be obtained from the commonly used Lewis equation. A set of approximate stress concentration factors are presented for fillets in gear teeth based upon a set of variables such as the radius r of the fillets, thickness t of tooth, height h of load position on the tooth, etc. The problem was attacked by making a series of tests of ``conventionalized gear teeth'' in the form of short cantilever beams in which one factor at a time could be varied. The values of stress concentration factor were computed as the ratio of the maximum stress in the fillet to the calculated stress at the ``assumed weakest section,'' as defined by Lewis' equation. In general, it was noted that as the height of load position (h/t) was increased, the maximum stress increased, but the stress concentration factor decreased. An approximate equation for the tensile stress concentration factors, k, for the conventionalized models with sides of the tooth parallel is: k=1.25(t′/r)0.2(t/h)0.3. A definite decrease in the tensile stress concentration factor was observed as the tooth model was gradually tapered inward to approach Lewis' ideal shape of the parabola of uniform strength, whereas no change in the compressive stress concentration factor occurred as the angle was varied over a 25° range. Tests now in progress on generated gear teeth having a 14½-degree pressure angle and a diametral pitch of 2 indicate that the stress concentration factor for the tensile fillet is given fairly accurately by the formula: K=0.22(t/r)0.2(t/h)0.4.
A Simple and Rigorous Method for the Determination of the Heat Requirements of Simple Intermittently Heated Exterior Walls
Authors: Smith Elmer G.
Published: January 2005

Buildings such as churches and auditoriums that are not continuously heated need larger heating plants than continuously heated buildings because of the large transient heat currents that must be supplied to the cold walls while the temperature of the building is being raised. The present unsatisfactory practice is to estimate the magnitude of these currents by various unreliable empirical methods. The purpose of this paper is twofold. First, for simple exterior walls, an equation is derived by means of which tables can be computed that will make rapid and reliable determinations possible. Second, the equation is put into such a form that the actual calculation of the tables can be carried out by N. Y. A. boys whose services can be obtained without cost. The unidirectional heat flow equation is solved for the boundary conditions that the outdoor temperature remains constant, the temperature of the wall is constant previous to time t=0, and after that time a constant heat current is applied to the wall. The solution is obtained in a form simple enough for the boys to handle by putting part of it in dimensionless form which makes it possible to plot a family of curves, which in turn make it possible to obtain numerical solutions without resorting to the very tedious ``cut and try'' process.
The Heat Requirements of Simple Intermittently Heated Interior Walls and Furniture
Authors: Smith Elmer G.
Published: January 2005

This paper does for simple interior walls and furniture what the previous paper did for simple exterior walls. Unidirectional heat flow is assumed and the boundary conditions are simpler than for the simple exterior wall so that the solution is easily expressed in the form of a formula. The treatment of the interior surface resistance as a constant quantity is justified.
The Structure and Dynamics of Liquids
Authors: Roseveare W. E. , Powell R. E. , Eyring Henry
Published: January 2005

By coordinating our information on viscosity, diffusion, melting, and other rate and thermodynamic properties, we arrive at a detailed picture of liquid structure. Thus we find that a liquid is best thought of as a solid to which a large number of empty equilibrium positions are added. In fact the expansion on melting, as well as the expansion with a rise in temperature, arises almost entirely from this introduction of new equilibrium positions, and only to a minor extent from lattice expansion. We shall obtain information as to the number, size and energy of formation of these empty lattice points.
Correlation Between Elastic Moduli and Viscosity of Liquids and Plastics
Authors: Gemant Andrew
Published: January 2005

The purpose of the paper is to indicate a method by means of which elastic constants (bulk and Young's moduli) and viscosity can be computed, one from the other, under conditions in which the direct determination of one of the data required is difficult or not feasible, and the other of the two quantities in question is known.
On the Resistance to the Uniform Motion of a Solid Through a Viscous Liquid. II.
Authors: Block Raymond B.
Published: January 2005

This paper constitutes the author's answer to some adverse criticisms by John T. Burwell, Jr., of an earlier paper having the same title and reporting evidence for the assumption of liquid slip at the surface of a solid in motion through a viscous liquid. The importance of the results contained in the earlier paper to viscosimetry by the rolling-ball method is emphasized. This relation exists because the author's apparatus was essentially a rolling-ball viscosimeter. References are given to independent studies by other investigators which also support the hypothesis of liquid slip. The possibility of the phenomenon's being apparent, only, is brought out by presenting two other interpretations of the author's observations. A new and more accurate method for converting time of roll into viscosity of the liquid than the current graphical one is presented for the rolling-ball viscosimeter, together with an apparent reason for believing that the calibration curve of this viscosimeter may not always be independent of pressure. The author's reasons for considering this new source of error in the use of the rolling-ball apparatus for high pressure viscosimetry to be actually non-existent are given. And finally the author describes an original method for checking the validity of the hypothesis of liquid slip in the case of the rolling-ball viscosimeter that is entirely different from the method he used in his earlier paper.
A Rapid Infra-Red Analytical Method for Hydrocarbon Mixtures and A Routine Spectrophotometer for Plant Control
Authors: Brattain R. Robert , Beeck O.
Published: January 2005

A rapid method has been developed for the infra-red spectroscopic analysis of simple mixtures of hydrocarbons. Through the construction of special equipment this method has been reduced to a routine procedure which can be carried out by comparatively inexperienced operators. The instruments built have proven sufficiently sturdy to be used for control work in plant operation. By basing the analytical method on an empirical calibration, the calculations involved have been reduced to a minimum. The instruments are relatively simple and permit the use of comparatively large spectral slit widths. This has eliminated the necessity for amplification of the thermopile output energy and for the determination of any continuous absorption curve. However, small spectral slit widths can be attained with the more versatile spectrophotometer if this should be required.
Note on Temperature Correction Methods in Calorimetry
Authors: Jessup R. S.
Published: January 2005

The problem of correcting calorimetric data for thermal leakage has been discussed by King and Grover in a recent paper in this Journal. From their analysis of the problem these authors have concluded that large errors are involved in the usual methods of correcting the data of bomb-calorimetric measurements, and of experiments by the method of mixtures. In the present note it is shown, in agreement with W. P. White's treatment of calorimetric lag, that in the case of bomb-calorimetric measurements the errors in question are practically completely eliminated by calibrating the calorimeter experimentally. Since experimental calibration of the calorimeter is the usual practice in modern bomb-calorimetric measurements, the results of such measurements are not affected by the errors discussed by King and Grover. In the case of measurements by the method of mixtures these errors can be avoided by so conducting the experiment that the final temperature of the calorimeter will be very near the convergence temperature.