bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bidwell's Intercept Relation and the Thermal Conductivity of Liquid Metals
Authors: Powell R. W. 
Published: January 2005

A note pointing out that the claim made by Bidwell and Hogan [Journal of Applied Physics 18, 776 (1947)], that the relation k/ρC=K(1/T)+K1, where k is the thermal conductivity, ρ the density, C the specific heat, T the absolute temperature and K and K1 are constants, holds for aluminium, tin, lead and zinc with the intercept, K1, the same for the solid and liquid phase, is not so well supported by experimental evidence as the reader is led to believe.
The latest paper on aluminium makes no reference to Konno's appreciably different results for the thermal conductivity of liquid aluminium. Furthermore, adjustment appears necessary in the plotting of Bidwell and Hogan's two points for the liquid phase and this brings the intercept for the liquid phase about 30 percent above that for the solid phase.
Of the other three metals cited by Bidwell and Hogan as having been previously shown to conform to the intercept relationship, it is revealed that zinc does not on the experimental evidence of both Bidwell and Konno, lead does on the evidence of Bidwell but not on that of Konno, whilst tin does on the evidence of Konno only. Further experimental investigation is clearly necessary before any definite relationship such as that suggested can be accepted.
The Electron-Micrographic Structure of Shadow-Cast Films and Surfaces
Authors: Williams Robley C. , Backus Robert C. 
Published: January 2005

The lower limit of size of biological objects which can be photographed with the electron microscope, by the aid of shadow-casting, is shown to depend upon the smoothness of substrate upon which they can be mounted, and upon the continuity of structure of the thin films with which they are shadowed. Numerous attempts to improve the existing deficiencies are reported, both with respect to producing smoother substrate films, and to producing films for shadow-casting of high efficiency and continuity of structure.
No success has been encountered in producing a usable substrate film perceptibly smoother than the collodion and Formvar films commonly used. It is found that the best shadow-casting material for this type of film is uranium or uranium oxide.
Verification has been obtained of the severe granulation of gold films previously used in the pre-shadowed replica process, when subjected to the electron current of a biased-beam electron gun. Attempts to reduce the granulation to a satisfactory level have failed. Various methods of preparing pre-shadowed replicas are reported. The factors affecting the tenacity of evaporated films to glass surfaces are discussed. It is found that elements which oxidize readily are relatively adherent to glass, while the elements gold, palladium, platinum, and rhodium are not. Uranium sulfide can be used as a pre-shadowed replica material, but only with some uncertainty, owing to its chemical instability. It has been found that a palladium-platinum mixture is the most satisfactory material for use in the pre-shadowed replica technique, and that films of this mixture in a thickness of about 6A produce adequate shadows in which there is no sign of granulation. The surface of clean glass is again found to have the smoothest structure of any material known, with practically no sharp discontinuities in elevation as great as 10A.
An appendix is given, in which technical details of shadow-casting and replica production are described.
Erosion of Electrical Contacts on Make
Authors: Germer L. H. , Haworth F. E. 
Published: January 2005

When an electric current is set up by bringing two contacts together, they necessarily discharge a capacity. If the discharge takes place through an arc before the metallic circuit is established, erosion of the electrodes results. In a low voltage circuit the occurrence of an arc is dependent upon the condition of the electrode surfaces and upon the circuit inductance. For ``inactive'' surfaces, and a voltage of the order of 50, an arc does not occur if the inductance is greater than about 3 microhenries. Surfaces of various metals can be ``activated'' by vapors of certain unsaturated organic compounds, and in the active condition they give arcs even when the circuit inductance is greater than this limiting value by a factor of more than 103. The study of arcs between active metal surfaces is not yet complete, and most of this paper and all of the remainder of this abstract have to do with surfaces which are inactive.
When an arc occurs at the make of inactive metal surfaces, its energy, which in low voltage circuits of practical interest is drawn entirely from a charged condenser, is dissipated almost entirely upon the positive electrode, and melts out a crater intermediate in volume between the volume of metal which can be melted by the energy and that which can be vaporized. Some of the melted metal lands on the negative electrode and, with repeated operation, results in a mound of metal transferred from anode to cathode. This transfer is about 4×10−14 cc of metal per erg.
The arc voltage is of the order of 15. If the initial circuit potential is more than about 50 volts there may be more than one arc discharge, successive discharges being in opposite directions and resulting in the transfer of metal in opposite directions— always to the electrode which is negative.
The Scattering Cross Section of Spheres for Electromagnetic Waves
Authors: Brillouin L. 
Published: January 2005

The problem discussed in this paper is that of the scattering of electromagnetic waves by a spherical obstacle. The classical theory is well known. Stratton's ``Electromagnetic Theory,'' for instance, contains a very good summary of that discussion. The computation of the scattering cross section, according to this theory, leads to some difficulties. In the case of large spheres, where geometrical optics should apply, the rigorous theory yields a scattering cross section equal to twice the actual cross section of the sphere!
The discussion presented in this paper explains this strange result and shows the role played by the shadow and by the diffraction fringes surrounding the shadow. A reasonable system of approximations yields the well known ``Babinet's principle.'' The physical interpretation is of such general character that it must certainly apply to a variety of similar problems in acoustics or wave mechanics. The spherical shape of the obstacle is essential in the present discussion, but similar results would certainly be found for other shapes of the obstacle. The case of a circular cylinder, investigated by E. B. Moullin and L. G. Reynolds, also leads to a total cross section twice as large as the actual cross section, for large cylinders. The explanation is the same as for the spheres. Experiments very carefully designed by Dr. Sinclair and Professor V. K. LaMer gave a very precise check of the theoretical predictions.
Electron Optical Mapping of Electromagnetic Fields
Authors: Marton L. , Lachenbruch S. H. 
Published: January 2005

Two techniques have been devised for the exploration of electrostatic and magnetic fields where conventional methods fail. Both use electron lens systems to magnify the deflecting effect of the fields on electron beams. One technique is the electron optical analog of the ``Schlieren'' method; the other involves deformed shadows of a thin obstruction.
For several reasons the ``Schlieren'' patterns obtained experimentally thus far have been interpreted only qualitatively. The patterns obtained by the shadow method, however, have been used for quantitative evaluation of field strengths. Experimental patterns of both types, produced by the fields of magnetized recording wires, are shown.
The shadow method is theoretically applicable to the quantitative evaluation of a wide variety of electric and magnetic fields. It utilizes formulas based on relations between field distribution and electron deflection, and between the latter and the geometrical parameters of a focusing system. Such formulas are derived and applied to several simple types of field.
An application of the theory to the magnetized wires used in the experiments yields relations from which each field distribution is evaluated by fitting a line to experimentally determined points. The theory also predicts the geometrical properties of the experimental patterns.
The agreement between theory and experiment is sufficiently good to justify the underlying theoretical assumptions and approximations.
Collimation Error in Small Angle X-Ray Scattering
Authors: Yudowitch K. L. 
Published: January 2005

It has been shown that excessive error may be introduced in small angle x-ray scattering by the use of an incident beam of finite cross section. To account for this error the usual procedure has required multiple integrations for rays reaching a single point P on the film from all points within each slit. However, the common effect from both finite slit height and width is a range of scattering angle for rays reaching P. The integrations over each slit dimension are reduced to a single integration over scattering angle, which entails finding the limits of scattering angle.
The assumption of a constant distribution of intensity throughout the range allows the range of scattering angle δε to be taken as a measure of the collimation error. Minimization of δε permits determination of optimum values of slit height-width ratio. For two slit collimation, it further leads to determination of optimum slit spacing and optimum relative slit sizes.
Density and Packing in an Aggregate of Mixed Spheres
Authors: Hudson Douglas Rennie 
Published: January 2005

It is shown that in close packing of spheres, two types of interstice exist, bounded by six and by four convex spherical surfaces. These are termed ``square'' and ``triangular.'' They are connected by a continuous labyrinth through which a ball not exceeding (2/√3−1)r in radius can be threaded. In both cubic and hexagonal arrangements, their shape and size are identical, but their distribution differs. Radii R for n smaller balls, which can take up patterns with cubic symmetry within each square interstice, are calculated for values of n up to 27 and plotted. The expression (R/r)=(2−1)/n12is used as a test for efficiency of packing.
When R/r is plotted against the density increment attributable to this interstitial packing, a set of spires is obtained. At n=8 and n=9 (R/r being, respectively, 0.2289 and 0.2166) twin peaks of 13 percent and 12 percent appear, which are accentuated by first entry of a sphere into the triangular interstice at R/r = 0.22475; this contributes another 3 percent. The peak of 16 percent at n=21, R/r = 0.1782, is also reinforced by first entry of 4 spheres in a body-centered tetrahedron at 0.1716, which gives an additional 6 percent density increment. Applications to bulk storage, ceramics, and interstitial compounds and solid solutions are considered. None of the special packs gives a density increment (∂Δsquare +∂Δtriangular)/Δ even approaching the 26 percent for fine spherical filler close packed in the interstices.
Particle Size Determination by Soft X-Ray Scattering
Authors: Yudowitch K. L. 
Published: January 2005

Small angle x-ray scattering measurements are made on samples of colloidal gold of radius from 50 to 400 angstroms. Copper (1.54 angstrom wave-length) and aluminum (8.32 angstrom wave-length) radiation are used.
The usual method of analysis is shown to be valid only for particles of radius less than 120 wave-lengths. Extension of the method to larger particles is achieved, giving improved electron microscope correlation.
The use of longer wave-lengths and optimum shaped slits are shown to reduce geometry errors sufficiently to give clear evidence of predicted intensity maxima. The first three secondary shape function maxima are observed.
An additional interference maximum attributable to particle-to-particle interference is observed. The position and magnitude of this maximum are correctly predicted by an expression based on earlier fluid scattering theory.
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.
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.
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.
Electroviscous Fluids. II. Electrical Properties
Authors: Klass Donald L. , Martinek Thomas W. 
Published: January 2005

The induced interfacial polarization mechanism invoked to explain electroviscosity requires a direct relationship between the rheological and electrical properties of an electroviscous system. Static and dynamic measurements of the electric and dielectric properties of electroviscous silica dispersions were made to study these relationships. An electrokinetic potential and conductivity and a small dc power output that depend upon shear rate were observed. Electroviscous fluids under shear exhibit the characteristics of small electric cells. Shear-induced desorption of weakly held charge carriers out of the double layer is suggested to explain these effects.
On application of an external electric field, electroviscosity appears at the onset of current flow. Dielectric measurements under zero-shear conditions show that the medium in contact with the disperse phase is essentially a low-dielectric-constant vehicle while the particles are composites having higher dielectric constants, thereby facilitating interfacial polarization. Anomalous dispersion occurs under zero-shear conditions at low frequencies as expected on the basis of the proposed interfacial polarization mechanism. Simultaneous dielectric-constant, loss, and electroviscosity measurements under shear conditions correlate with the effects of changing shear rate, field strength, temperature, and frequency. Increasing temperatures promote polarization while shear stresses transverse to the direction of the applied field perturb the field-induced polarization. When an electroviscous dispersion is subjected to both mechanical shearing and an external electric field, a dynamic equilibrium is established between the rheological and electrical properties of the system.
Diffusion-Induced Defects in Silicon. II
Authors: Levine E. , Washburn J. , Thomas G. 
Published: January 2005

The defect substructure produced by a double diffusion of boron and phosphorus into a silicon wafer has been studied by transmission electron microscopy. Specimens were examined at all stages in the diffusion and at all important levels in the final n-p-n transistor wafer for both {111}- and {110}-oriented wafers. Similar specimens in the {112} orientation were examined at the emitter surface only.
Diffusion-induced dislocations and precipitates were observed at the emitter surface in all orientations. No defects were found at other levels in the doubly diffused wafers except for {110} foils in which long dislocations capable of glide on the inclined {111} planes were observed at the emitter base junction.
The precipitates were in the form of thin platelets which produced displacement fringes parallel to their intersection with the surface (g·R contrast) and parallel moiré fringe contrast. In addition they were strongly attacked by both HF and HNO3 solutions. Diffraction patterns from the precipitates were indexed as from a base-centered orthorhombic structure with a=6.3, b=3.8, and c=6.75 Å. The orientation relationship with the silicon matrix was [111] Si ‖ [011]p. The thin platelets appeared to be a partially coherent precipitate with an associated misfit vector of ∼⅓[111] such that the platelets compressively stressed the matrix. This compressive stress acts to partially relieve the diffusion-induced tensile stress normal to the habit plane, and so the operating planes are those which are most perpendicular to the diffusion front so as to have the greatest possible resolved compressive stress in the diffusion front.
Thermogravimetric and Seebeck-Effect Measurements on Li-Doped CoO at High Temperatures
Authors: Fisher B. , Wagner J. B. 
Published: January 2005

Gravimetric and Seebeck-effect measurements have been made on CoO single crystals doped with Li in the temperature range of 900°–1200°C and partial pressures of oxygen up to 1 atm.
For low-doped crystals and high oxygen pressures, the gravimetric and Seebeck-effect results confirm a simple model by which the positive-charge carriers are given at equilibrium by the singly ionized vacancies and the Li ions. By this model the concentration of holes is increased, and the concentration of vacancies is decreased by the addition of Li.
The results at low pressures of oxygen for the low-doped samples as well as the results in all the range of oxygen pressures for the heavier-doped samples show that the model has to be enlarged, taking into account the contribution of Co interstitials to the defect structure of CoO(Li) and that of electrons to the conductivity in CoO(Li).
Molecular Mechanics of Point Defects in Polyethylene
Authors: McMahon P. E. , McCullough R. L. , Schlegel A. A. 
Published: January 2005

Certain properties of crystalline polymers can be associated with the presence of local defects, e.g., deviations of short segments of the chain from the predominant conformation allied with the crystal structure. General methods are developed by which such chain defects may be simulated by computer techniques. The application of these methods to the polyethylene system gives detailed information concerning: stable defect structures, low-energy conversion paths between stable structures (molecular motions), interactions in defect assemblies, and intermolecular interactions between chains and crystalline environments.
Such an investigation of all fold structures containing seven (or less) dihedral angles indicates the existence of a small number of stable but immobile structures. The intramolecular energy of these structures is somewhat high and they do not pack efficiently. Expansion of fold structures to include eight and nine dihedral angles and slight relaxation of orientation constraints provides lower-energy structures which are mobile, more efficient packing, and a low-energy path for conversion between diagonal and b-axis folds.
In addition, stable structures and motions of other local defects (i.e., kinks and jogs) are identified, rigid segment rotation is found to be questionable, and certain mechanical properties are interpreted in terms of the over-all results.
Estimation of Nucleation Parameters from Continuous Cooling Droplet Experiments
Authors: Price Fraser P. , Gornick Fred 
Published: January 2005

A theoretical and computational investigation has been made of the effect of temperature and of various energetic parameters upon the course of homogeneous nucleation in suspensions of droplets undergoing cooling at a constant rate. The applicable theory involves integrals, unsolvable in closed form, that were evaluated numerically. For a given size distribution of droplets, the plots of number-fraction crystallized vs time have virtually identical shapes regardless of the cooling rate. The curves can be superposed by translation along the time axis. This superposability obtains regardless of the breadth of the size distribution. Thus, the superposability assumption tacitly invoked by early investigators in this field is justified. Furthermore, it was found that the integrations performed numerically gave, in the range of experimental interest, results within 3% of the analytical solution obtained by Burns and Turnbull by series expansion of the integrand.
The pre-exponential term in the expression for the nucleation rate is calculable for specific values of droplet size and cooling rate and is extremely sensitive to the magnitude of the energetically determined constant term appearing in the exponent. For the specific case of suspensions of polyethylene droplets a change of 10% in the constant term, necessitates a change of three orders of magnitude in the exponential.
Finally, values of the interfacial energy product, σ2σe, of 1.59×104 and 1.50×104 erg3·cm−6 were calculated for polyethylene from the droplet cooling data of two independent groups of investigators.