bluuebunny/crossref_metadata_2025 huggingface dataset:
Crystal Growth of GaAs from Ga by a Traveling Solvent Method
Authors: Mlavsky A. I. , Weinstein Martin
Published: April 2005

The temperature gradient zone-melting technique described by Pfann has been extended to the growth of semiconducting compounds from solution. In particular, single crystals of GaAs have been grown at temperatures much below the congruent melting point, using a thin zone of Ga as the solvent. The parameters influencing zone movement have been studied, including zone thickness, average temperature, temperature gradient, and seed orientation. For the case of the GaAs–Ga system, the rate of zone movement has been shown to be liquid diffusion limited. The passage of a pure Ga zone brings about considerable purification, as evidenced by the electrical properties of the grown crystals. Conversely, the passage of a suitably doped Ga zone can bring about the formation of abrupt p-n junctions. The electrical characteristics of such junctions are described.

Preliminary work has shown that the method is widely applicable to the growth of various classes of crystals and to the formation of various junction structures in semiconducting compounds.
Charged Particle Tracks in Glass
Authors: Fleischer R. L. , Price P. B.
Published: April 2005

Heavily ionizing particles passing through crystalline solids may produce trails of damage which can be seen either directly by electron microscopy or indirectly, by means of preferential chemical dissolution of the damaged material. Where both methods have been used, it has been shown that the method of chemical attack is the more sensitive. Here it is reported that this method of revealing irradiation effects is able also to display the paths of heavy particles in a great many noncrystalline materials, in this instance glass. It is shown that fission fragments from Cf252 leave damage trails in glass which may be etched to give conical pits. In some glasses the cone angles are small, so that the direction taken by the moving particles may be followed. Fission tracks can also be revealed in certain glasses by preferential precipitation of a metal such as silver along the damaged regions. This method has the advantage that a track does not have to intersect a free surface to be revealed.
Air-Cavity Explosive Charge for Accelerating Discrete Particles
Authors: Rolsten R. F. , Wellnitz J. N.
Published: April 2005

Discrete projectiles, covering the mass range 0.097 to 0.67 g, can be accelerated in air to speeds as high as 17 500 ft/sec (5200 m/sec), with one of two specially contoured air cavity shaped charges. When accelerated in vacuum, the mass can be lowered to 0.002 g and the velocity increased to 22 000 ft/sec (6600 m/sec) by confining the spherical projectile in a cylinder of Epocast that in turn is placed in a lead collet.
Small Signal Analysis of Molecular Beam Masers
Authors: Helmer J. C.
Published: April 2005

A perturbation calculation gives the resonance polarization of a molecule in an electric field as a function of time. An analysis is then made of maser operation with a divergent, univelocity beam. Equations are derived which give the relative beam intensity required to start oscillation and the molecular Q as a function of cavity length. An optimum cavity length is predicted. This theory is compared with a similar theory of K. Shimoda which assumes a Maxwell velocity distribution, and reasonable agreement is obtained. On the basis of this agreement it is possible to define an equivalent divergence of the velocity distributed beam.
Use of a Radiation-Calorimeter in Measurement of Stored Energy in Irradiated Graphite
Authors: Wechsler M. S. , Coltman R. R. , Kernohan R. H. , Wittels M. C.
Published: April 2005

The measurement of the stored energy of graphite taken from the lattice of the ORNL Graphite Reactor is described. The release of 26 cal/g of stored energy was observed upon heating to 218°C. The measurements were made using a new technique that depends upon the transfer of heat by radiation from the walls of the calorimeter to the sample.
Selective Delineation of Screw Dislocations by Cathodic Sputtering
Authors: Meckel B. B. , Swalin R. A.
Published: April 2005

A method of revealing screw component dislocations involving low-energy cathodic sputtering with argon ions is presented. It is observed that hillocks having the shape of truncated cones with a spiral pattern on their tops form at the sites of intersection of screw dislocations with the surface. The hillocks probably form by mobile surface atoms attaching themselves to the step provided at the intersection of a screw dislocation with the surface. It is shown that the density of screw dislocations on a given plane depends on the orientation of the plane with respect to the crystal growth axis.
Helical Flow of General Fluids
Authors: Coleman Bernard D. , Noll Walter
Published: April 2005

The problem of the helical flow of a general fluid is solved making no special constitutive assumptions other than incompressibility. It is shown that from a knowledge of the rheologists' viscosity function one can calculate the dependence of the velocity field in helical flow on the geometry and applied forces. The complete stress distribution (including normal stresses) may be calculated from a knowledge of three basic material functions which can, in principle, be determined from an experimental study of simple shearing flow. Expressions are derived for the discharge rate and for the angular velocities of the bounding cylinders as functions of the applied forces.
Solution Grown Crystals of an Acetal Resin
Authors: Geil P. H. , Symons N. K. J. , Scott R. G.
Published: April 2005

Single crystals of polyoxymethylene have been grown from dilute solution. They consist of hexagonal lamellae, often thickened by growth from screw dislocations. The chain molecules are normal to the lamellae which are 100 A thick. Thus, it is suggested that the molecules have a folded conformation. In many of the crystals double Bragg reflections were found in the electron diffraction patterns, resulting from rotation of the lamellae during growth. Dark field electron microscope photographs of these crystals exhibit moiré patterns.
Diffusion-Limited Growth of Precipitate Particles
Authors: Ham Frank S.
Published: April 2005

Diffusion-limited precipitation rates are calculated, using theoretical methods derived previously, for systems of precipitate particles which may change shape as they grow. General formulas are presented, including suitable short- and long-time approximations. Explicit growth laws are derived for systems in which particles are disks and rods subjected to various constraints. The growth exponent n in the short-time approximation is found to be 2 for disks of constant thickness. Rods of constant radius that capture atoms only near their ends have n=1. Both disks and rods of constant ratio of their long and short dimensions have n=3/2. These values contrast with growth laws suggested by Wert and Zener for disks and rods, for which they found n=5/2 and 2, respectively. It is shown that growth conditions at the edge of a growing particle are not constant in diffusion-limited circumstances if the entire surface of the particle acts as a sink.
Theory and Application of a Minority Carrier Sweep-Out Effect
Authors: Larrabee R. D.
Published: April 2005

The minority carriers (and their compensating majority carriers) can be removed from a semiconductor by application of an electric field through ohmic contacts. A simplified analytical description of this phenomenon is derived and is illustrated by simple experiments. It is demonstrated that by utilizing this effect, along with Hall data, one can determine the density and drift mobility of both the majority and minority carriers. Consequently, it is possible to measure many parameters that depend on these quantities (e.g., intrinsic density, estimate of surface space charge and carrier mobility in inversion surfaces, etc.).
Alloyed, Thin-Base Diode Capacitors for Parametric Amplification
Authors: Mortenson K. E.
Published: April 2005

The design of double alloyed, thin-base diode capacitors for parametric amplification is described which indicates that capacitors with maximum Q's well in excess of 200 at 1 kmc and capacitive swings in excess of 15 are obtainable. The high Q's resulting from the type of fabrication and the small base thickness used; the large capacitive swing resulting from the abrupt p+n junction created.

Three figures of merit are defined and evaluated: (1) an over-all device figure, FD, proportional to the product of the maximum Q and capacitance ratio evaluated in terms of material parameters, degree of base doping, and geometry factors; (2) a Q factor, FQ, proportional to just the capacitor Q; and (3) a material factor, FM, by which different materials used for fabrication can be compared. Fixing the choice of material (with germanium shown to be superior to silicon for this purpose) and achieving the best geometry, FD and FQ are examined as a function of doping. It is shown that FQ is nearly constant over the entire practical range of doping while FD, because of the capacitive swing, increases substantially with lighter doping.

Results are presented for units with all soldered connections (no pressure contacts) fabricated from double alloyed pellets with a p+nn+ structure. To date, diode capacitors with maximum Q's in excess of 200 at 1 kmc and with capacitive swings in excess of 10 have been made. It is anticipated that this fabrication process will yield Q's in excess of 500 at 1 kmc with closer alloying control.
Reduction of Static Friction by Sonic Vibrations
Authors: Fridman Hans D. , Levesque Pascal
Published: April 2005

The effect of sonic vibrations on the coefficient of static friction was measured for highly polished, ground, and sand-pitted steel surfaces. The coefficient of static friction can virtually be reduced to zero as a result of increased vibrations at frequencies between 6 and 42 kc.
Characteristics of UC, ZrC, and (ZrC) (UC) as Thermionic Emitters
Authors: Pidd R. W. , Grover G. M. , Roehling D. J. , Salmi E. W. , Farr J. D. , Krikorian N. H. , Witteman W. G.
Published: April 2005

Uranium carbide is found to have the property of high thermionic emission in the observed temperature range from 1400 to 1800°K. The parameters of the Richardson equation which can be used to fit the data are A=7.3×105 amp/cm2 (°K)2 and φ=4.57 v. While these parameters accurately predict the observed saturated currents, it is doubtful that such anomalous values are of theoretical significance within the framework of the Richardson-Dushman derivation. A solid solution form of uranium carbide and zirconium carbide gives substantially the same thermionic emission as uranium carbide, and for other reasons appears to be the more useful emitter. The carbides require no surface preparation or activation schedule for use as emitters.
Dislocation Sources in Crystals
Authors: Gilman J. J.
Published: April 2005

Lithium fluoride crystals were subjected to short stress pulses (1–10 μsec in length) in order to study dislocation nucleation in them. It was found that several heterogeneities can lead to dislocation nucleation: (a) cleavage steps, (b) dislocation loops, (c) glide bands, (d) inclusions or ``dirt'' particles, (e) precipitates (as grown), and (f) radiation-induced precipitates.

Also, it was found that annealing treatments at moderate temperatures (200–600°C) followed by ``rapid'' cooling (>5°C/hr) made segments of previously pinned dislocations become mobile. These mobile segments multiplied as they moved through the crystals.

Several treatments were tried that were ineffective in producing dislocation nucleation. These included: temperature changes, surface wetting, simultaneous irradiation and stressing, reflections from free surfaces, and diagonal bending.

Carefully cleaned glass spheres were pressed into contact with dislocation-free regions of a LiF crystal. In this way, shear stresses that were 100 times greater than the normal yield stress of the crystal (∼G/85) were reached without causing homogeneous dislocation nucleation.

It is concluded that small foreign heterogeneities cause most of the dislocation nucleation in real crystals. Homogeneous nucleation occurs only at high stresses (∼G/30). Relatively little dislocation multiplication results from classical Frank-Read sources (almost none in LiF). Most dislocation multiplication occurs as a prior dislocation moves through a crystal.
Transfer of Transient Electromagnetic Surface Waves into a Lossy Medium
Authors: Keilson J. , Row R. V.
Published: April 2005

The propagation of a transient surface wave in the form of an impulse into a lossy medium is examined via a simple two-dimensional plane wave model. The solution found exhibits characteristics of both wave propagation and diffusion. This impulse response is used as a basis for calculating the response to an arbitrary excitation at a point on the surface. For observation times longer than the time duration of the surface disturbance, the form of this solution is equivalent to a moment expansion. The limits imposed on the signalling band width by the losses in the medium are discussed.
Density Measurements of Some Thin Copper Films
Authors: Wainfan N. , Scott Nancy J. , Parratt L. G.
Published: April 2005

Density measurements have been made on vacuum-deposited copper films in the thickness ranges 50 to 150 A and 500 to 1000 A. To obtain the density, an analysis was made of the relation between the reflection coefficient and the glancing angle of incidence for 1.54 A x-rays. For films in the range 500 to 100 A, this analysis was augmented by a chemical determination of the average mass per unit area. Although there is evidence of nonuniform density with depth in the film, especially for the very thin films, the average density of a film thicker than about 300 A was found within the limits of the experimental accuracy to be equal to the bulk density. This conclusion is in disagreement with some previously published work; the discrepancy appears to lie in differences between the x-ray method of measuring film thickness and the conventional optical interference method.
Electron Emission from Plastically Strained Aluminum
Authors: Von Voss W. D. , Brotzen F. R.
Published: April 2005

Aluminum was strained in tension under a Geiger-Müller counter. Both the electron emission associated with plastic deformation and the subsequent delayed emission were observed. An attempt was made to correlate quantitatively the emission rates with the mechanical variables, i.e., strain and rate of deformation. The model used for this correlation links point imperfections formed during deformation with the emission from the oxide surface film.
Dielectric Breakdown of Porous Ceramics
Authors: Gerson Robert , Marshall Thomas C.
Published: April 2005

A statistical approach is used to determine the effect of porosity in ceramic materials on their dielectric breakdown strength. The calculated drop in dielectric strength is in good agreement with the experimental data for lead zirconate titanate ceramics. The theory shows that the measured dielectric strength in porous materials is a function of the porosity, the void size, and of the dimensions of the test sample.
Interaction of Oxygen with Incandescent Filaments
Authors: Young J. R.
Published: April 2005

With the aid of a mass spectrometer a study has been made of the gaseous contaminants present when oxygen is exposed to different incandescent filaments. In agreement with others CO and CO2 were the most abundant contaminants found. The amounts of CO and CO2 found, at a given filament temperature and oxygen pressure, were greater for Mo 0.031% C, W 0.012% C, and Re 0.010% C than for Ta 0.001% C. Also at the same oxygen pressure and filament temperature the quantity of CO found was much greater for a carbonized W filament than for any of the other filaments investigated. These results are consistent with the hypothesis that CO and CO2 are produced by the interaction of oxygen with the carbon present in the hot filaments. No evidence was found to indicate that the glass walls contribute to the formation of CO and CO2.
Some Effects of Low Fields on Luminescence of CdS
Authors: Bleil C. E. , Snyder D. D.
Published: April 2005

The effects produced on luminescence and conductivity in pure CdS crystals by application of electric fields up to ∼1000 v/cm are reported. A shift in the red and green cathodoluminescence peaks of ∼0.1 A/v/cm is observed. After application of the low fields, some crystals required over 90 minutes to recover their ``prefield'' luminescence. Fine structure in the luminescent peaks at room temperature is reported. A V-I plot shows a sublinear relation in this voltage range for several different levels of irradiation. An explanation of the observations is suggested based on self trapping of electrons.
Theory of Rolling Friction for Spheres
Authors: Flom D. G. , Bueche A. M.
Published: April 2005

A theory of rolling friction featuring the importance of elastic hysteresis losses is presented. A simple model of retarded elasticity is chosen to represent the physical properties of the material. A prediction resulting from the theory is that the coefficient of friction for a relatively hard sphere rolling on a softer base material should vary with speed so as to go through a maximum. This relationship resembles closely the variation of mechanical loss with frequency.

The results are not restricted to rolling but also apply to well-lubricated sliding where shearing forces have been minimized. Although the theory is developed for a material with idealized physical properties, it nevertheless affords a basis for comparing real materials and for predicting their frictional properties in cases where deformation losses are predominant.
Effect of Atmosphere Conditions on the Brittleness of NaCl
Authors: Machlin E. S. , Murray G. T.
Published: April 2005

Contrary to the results of previous investigators, it has been found that molecular O2 and N2 have no effect on the ductility of rock salt single crystals. Also, it has been found that air-aged crystals are brittle in summer and are ductile during a major fraction of the time in winter. Ductile rock salt crystals have been made brittle by subjecting them to ozone, NO, and atomic oxygen atmospheres. It is believed the ozone content of the atmosphere is responsible for the reported effects on brittleness. Other embrittling agents have been found.
Calculation of the Rate of Energy Deposition in Polyethylene by Reactor Radiation
Authors: Kline D. E. , Jacobs A.
Published: April 2005

An attempt is made in this discussion to determine the energy deposited in a small sample in terms of impinging reactor radiations, both neutron and gamma ray. The intensities of various radiations from a nuclear reactor are often presented in terms which are difficult to manipulate or interpret for energy deposition considerations. For example, the epithermal neutron flux is usually given as the integral neutron flux above the 0.4 ev cadmium resonance. However, for some energy deposition mechanisms, such as proton recoil, the neutron energy distribution is of utmost importance. These difficulties are partly resolved in this paper by using some empirical evidence of the characteristics of reactor radiations to convert the usual expression of intensities into energy deposited per gram-hour in polyethylene. This can be easily extended to other materials, particularly polymers. It is also emphasized in this paper, by specific calculations for two reactor types, that certain simplifying assumptions, which are often made with regard to the characteristics of reactor radiation, are invalid in energy deposition considerations.
Studies of Individual Dislocations in Crystals by X-Ray Diffraction Microradiography
Authors: Lang A. R.
Published: April 2005

The distribution of imperfections within the interior of crystals has been studied using ``projection topographs'' which are x-ray diffraction images showing a projection of a slice of crystal and the imperfections in it. Individual dislocations have been observed in single crystals of diamond, silicon, germanium, lithium fluoride, sodium chloride, silver chloride, magnesium oxide, calcite, quartz, and aluminum. From the variation of dislocation contrast with the orientation of the x-ray reflecting plane the direction of Burgers vector can be found. Dislocations can be seen with good contrast when the product of linear absorption coefficient μ and slice thickness t is of the order of unity or less. If μt≫1 the contrast is reversed through the Borrmann effect. Stereo pairs of projection topographs can be prepared from the pair of reflections hkl and h̄k̄l̄.
Temperature Dependence of Fractional Velocity Changes in a Germanium Single Crystal
Authors: Stein Frances , Einspruch Norman G. , Truell Rohn
Published: April 2005

An ultrasonic interferometer technique for measuring the temperature dependence of relative changes in elastic constants has been utilized to study the variation of c11 for germanium. Results are reported for measurements carried out as a function of frequency from 30 Mc/sec to 170 Mc/sec for compressional wave propagation along the [100] direction in two sets of compatible germanium samples over the temperature range from −60°C to 0°C. The mean value of (1/c11) (dc11/dT) is 78.87×10−6(°C)−1, and no systematic frequency dependence of (1/c11) (dc11/dT) was found.
Mechanism and Speed of Breakup of Drops
Authors: Gordon G. D.
Published: April 2005

A mathematical analysis has been made of the breakup of liquid drops in an air stream; only the mechanism in which the drops flatten, become bowl-shaped, inflate like a parachute, and finally burst is considered. The analysis provides an understanding of this process of breakup and the conditions for which the viscosity and surface tension become important factors. An estimate of the breakup time for a wide range of conditions is obtained as a function of the drop diameter, surface tension, viscosity, drop density, air density, and velocity difference. The results are compared with the available experimental data.
Elementary Dynamics of the Nonadiabatic Transverse Pinch
Authors: Fried Burton D.
Published: April 2005

The characteristics of the nonadiabatic transverse (Eθ,Bz) pinch are studied for configurations in which the discharge tube, current coils, and condenser form an integral structure, allowing very high voltage gradients (105 to 106 v/cm). The dynamics of the first pinch contraction are analyzed using the Garwin-Rosenbluth model of an infinitely conducting, collisionless plasma, and expressions are derived for the parameter values corresponding to maximum energy transfer to the gas for given energy per particle. Theoretical curves of pinch radius, current, and plasma kinetic energy as functions of time for typical cases are shown, and the relative merits of this transverse pinch and the more common longitudinal (Ez,Bθ) pinch are discussed.
Plastic Deformation of InSb by Uniaxial Compression
Authors: Duga J. J. , Willardson R. K. , Beer A. C.
Published: April 2005

Plastic deformation of InSb by uniaxial compression was found to produce decreases in both the electron mobility and magnetoresistance, but to have no effect on the Hall coefficient. Analyses of the temperature dependence of the conductivity mobility and the weak-field magnetoresistance, in terms of mixed scattering by acoustic lattice vibrations and ionized impurities, suggest that the principal effect of this mode of deformation is the creation of ionized vacancies and interstitials in approximately equal densities. The analysis permits an estimate of the density of point defects, which can then be related to the total energy expended during deformation. Reference is made to the effects of plastic bending of InSb where the carrier concentration is affected. This behavior is similar to results on silicon and germanium which have been analyzed in terms of the Shockley-Read trapping model.
Two-Terminal Asymmetrical and Symmetrical Silicon Negative Resistance Switches
Authors: Aldrich R. W. , Holonyak N.
Published: April 2005

By making use of an emitter region shorted by a metallic contact to an adjacent base region, a new form of p-n-p-n switch is obtained. Several new structures are described, including a symmetrical (or ac) switch. Typical experimental results on switches which breakdown in the range from 25 to 40 v are presented.
Grain-Boundary Diffusion of Zinc in Copper Measured by the Electron-Probe Microanalyzer
Authors: Achter M. R. , Birks L. S. , Brooks E. J.
Published: April 2005

Grain-boundary and lattice diffusion of zinc vapor into copper at 550°C were measured with the electron-probe microanalyzer and the results were used to calculate the diffusion coefficients. The lattice diffusion coefficient DL increases from 5×10−13 to 3×10−11 over the concentration range from 2 to 27.5 atomic percent zinc. Over the same concentration range, the grain boundary diffusion coefficient DB changes from 1×10−7 to 7×10−6. The ratio of grain boundary diffiusion coefficient to lattice diffusion DB/DL remains at approximately 106.
Characteristics of a Plasma Thermocouple
Authors: Pidd R. W. , Grover G. M. , Salmi E. W. , Roehling D. J. , Erickson G. F.
Published: April 2005

The operation of a cesium plasma thermocouple is described for a range of hot-junction temperatures from 1600°K to 2600°K and for a range of cesium pressures from 10−5 mm Hg to 2 mm Hg. Electromotive force and short-circuit current data are presented for cells containing three different emitter substances: Ta, ZrC, and (ZrC) (UC). In the range of pressure and temperature variation studied, the observed electromotive forces are between 1 and 4.5 volts. Short-circuit current depends markedly on the current emission properties of the hot electrode. The largest short-circuit current density observed for the (ZrC) (UC) emitter, is 62 amperes per square centimeter.
Noise Propagation on Uniformly Accelerated Multivelocity Electron Beams
Authors: Mueller W. M. , Currie M. R.
Published: April 2005

The characteristics of noise propagation through a multi-velocity region with linearly increasing dc potential have been calculated using the density-function formulation of Siegman, Watkins, and Hsieh. [J. Appl. Phys. 28, 1138 (1957)]. This type of noise transducer approximates that found experimentally in electron guns which have produced noise figures of 3 db and less at S band. It is shown that arbitrarily low values of beam noisiness can be obtained by reducing the slope of the potential profile and that adjustment of this parameter provides the practical possibility of attaining very low noise figures in slow space-charge wave amplifiers as frequency is increased. The calculated results are compared with experimental data at S band and X band.
Electrical Measurements on Photographic Emulsion Grains. I. Dark Conductivity
Authors: Hamilton J. F. , Brady L. E.
Published: April 2005

By exposing with light flashes delayed by short time intervals after the application of electric field pulses, it is possible to measure ionic conduction on large silver bromide grains from a photographic emulsion. Values of conductivity were obtained by an analysis of the transient decay of internal field pulses resulting from the application of known pulses of the external field. The internal field was measured by means of its effect in causing displacement of latent-image centers formed by the exposure flashes. The room-temperature ionic conductance of these grains was found to be the equivalent of about 9×10−6Ω−1 cm−1 with an activation energy of about 0.42 ev. This conductance is several powers of ten higher than that reported for large silver bromide crystals of high purity and is thought to be primarily the result of surface effects. The implications of this result in terms of modern theories of photographic latent-image formation are discussed.
Optimal Accuracy Rocket Trajectories
Authors: Baker George A. , Ford Kenneth W. , Porter Charles E.
Published: April 2005

The rocket optimization formulation of B.D. Fried is modified slightly to facilitate the study of maximum accuracy trajectories. Various illustrative special solutions are obtained, particularly perturbation results valid for small thrust. For surface-to-surface rockets in a Kepler field, optimal thrust programs are obtained numerically, their accuracy is studied quantitatively, and comparison of range and of accuracy is made with rockets using a constant-angle thrust program. Optimization leads to only a slight increase in range but to a substantial gain in accuracy. The possible application of rocket optimization methods to the focusing of charged particles is also suggested.
Isolation of Rotational Reversal in Ferromagnetic Films
Authors: Hanzel Alfred L. , Conger Robert L.
Published: April 2005

Quantitative data are presented which show the relative contributions of wall motion and domain rotation to the magnetization reversal process in thin ferromagnetic films for driving fields ranging from the coercivity to many times the anisotropy field. Also, an equation for the total magnetization reversal time is developed. This expression consists of two distinct components: one represents wall motion reversal time and the other reversal time due to domain rotation. The equation is similar to one published previously but contains a more realistic and more suitable wall nucleation distribution function.
Theoretical Approach to the Asymmetrical Magnetization Curve
Authors: Aharoni A. , Frei E. H. , Shtrikman S.
Published: April 2005

The method previously used to calculate the magnetization curve of an infinite cylinder is applied to the new Meiklejohn and Bean material which is made of Co particles in a CoO shell. It is assumed that the interface of the ferromagnetic and antiferromagnetic materials is held parallel to the cylindrical axis and does not change its direction for any value of the applied field. The crystal anisotropy is neglected.

It is shown that the easiest nucleation mode for small radii is buckling and for large radii is curling. The transition from buckling to curling is at about RIsA−½=2, where R is the radius of the cylinder, Is is the saturation magnetization and A is the exchange constant.

Numerical solution of the nonlinear equations involved, yields two branches in the magnetization curve, which are both stable with respect to curling perturbations. The general stability is not tested.

A similar calculation is carried out for an infinite slab with the spins on the surface held at a fixed direction and with the crystal anisotropy neglected.
Note on the Saturation of the Main Resonance in Ferromagnetics
Authors: Suhl H.
Published: April 2005

The course of χ″ at resonance versus applied power is traced for various ratios of intrinsic to scattering line widths. It is assumed that the line width contribution from thermal spin-wave agitation is negligible.
Eddy-Current Method for Measuring the Resistivity of Metals
Authors: Bean C. P. , DeBlois R. W. , Nesbitt L. B.
Published: April 2005

A method for measuring the resistivity of metallic specimens is described. The measurement is made by noting the rate of decay of flux from a bar situated in an external magnetic field that has been rapidly reduce to zero. The method is suitable for specimens greater than 5×10−3 cm in diameter. For a specimen 1 cm in diameter, resistivities from 10−11 to 10−3 ohm-cm may be measured with an error of less than three percent. The method requires no contact to the specimen, and local values of resistivity may be measured. Several applications are described.
Temperature Diffuse Scattering of X-Rays in Cubic Powders. II. Corrections to Integrated Intensity Measurements
Authors: Chipman D. R. , Paskin Arthur
Published: April 2005

In order to obtain accurate values for the integrated Bragg intensities, it is necessary to correct for the fact that temperature diffuse scattering (TDS) peaks in the same regions of reciprocal space in which Bragg peaks occur. On the basis of recent calculation of TDS in cubic powders it is possible to calculate the contribution of TDS to apparent measured Bragg intensities. Measurements were made on a counter spectrometer using crystal-monochromated CuKα radiation. The contribution of TDS to the measured Bragg intensities is demonstrated on several peaks of lead. A simple relationship is derived for the correction and compared with a graphical solution obtained by plotting TDS under the Bragg peak. The agreement between the two methods of correcting for TDS is good. The magnitude of the correction varies with the material, the wavelength of the x-rays and the region of reciprocal space studied. For a typical material such as copper using copper radiation, the correction is about 3% of the integrated intensity. For lead, again using copper radiation, it is about 15%.
High-Temperature Mechanical Properties of Graphite. I. Creep in Compression
Authors: Wagner Paul , Driesner Allen R.
Published: April 2005

Measurements have been made on the steady-state rates of compressive creep of graphite in the temperature range 2270 to 2780°K. Creep to failure was observed to occur in one of two ways; three out of seventeen samples exhibited a third stage of creep before failure occurred, the remaining fourteen samples failed in a manner analogous to that observed for graphite in tension, that is fracture without the appearance of a third stage. All the latter type creep data are correlated by a classical rate equation of the form: rate=K(σ/σB)n exp(−E/RT).
T-F Theory of Electron Emission in High-Current Arcs
Authors: Lee T. H.
Published: April 2005

Electron emission as a function of electric field, temperature, and work function has been calculated numerically on a digital computer over wide ranges of these variables. The results are then combined with the space-charge equation to show that electron emission from the cathode of a high-current arc on low boiling point materials like copper and silver can be explained by the T-F mechanism. It is also shown that the positive ion current density required by the electron emission condition is of the right magnitude to satisfy the energy balance condition at the cathode.
Accurate Determination of the Capacitance of Rectangular Parallel-Plate Capacitors
Authors: Reitan Daniel Kinseth
Published: April 2005

The basic theory of calculation of the capacitance of a parallel-plate capacitor by the method of subareas is advanced. This method enables accurate approximation of the long-standing problem of the accurate evaluation of the capacitance of a rectangular parallel-plate capacitor. A universal curve enabling rapid determination of the capacitance of the commonly used square-plate capacitor of side a is given.
Vaporization-Crystallization Method for Growing CdS Single Crystals
Authors: Boyd D. R. , Sihvonen Y. T.
Published: April 2005

A self-refining method for growing three different forms of CdS single crystals is described together with fabrication details of the 1300-watt three-temperature zone furnace employed. The growth chamber measuring 1¾ in. in diam×21 in. long is charged with CdS powder and either H2S or argon at a pressure of 1 atmosphere or less, and subjected from 4 to 7 days to different temperatures (1250±2°C maximum) and gradients depending on the type of crystal desired. Single crystals vary from thin plates, rods, and whiskers weighing fractions of a gram to 10-g polygonal chunks. The method is believed to be suitable for growing single crystals of many other elemental and compound semiconductors.
Dislocation Etch Pits in Bismuth
Authors: Lovell L. C. , Wernick J. H.
Published: April 2005

Etch pits which are probably the sites of dislocations have been produced on the (111) cleavage plane of bismuth. Evidence that the pits are dislocation sites was obtained from deformation and annealing studies and from density counts on intersecting boundaries.
Correlation of Secondary X-Ray Intensities
Authors: Banerjee Bani R.
Published: April 2005

Intensities of primary characteristic x-rays generated by electron bombardment of a target are logarithmically related to the difference between the electron-accelerating voltage and the critical excitation potential for the observed radiation. An analogous relationship has now been developed for secondary x-rays, generated by x-ray bombardment of a secondary target. The correlation was further extended to elements having atomic numbers from 28 to 56, and including several that are industrially important. This unexpected extension of the correlation to many elements should be particularly useful in fluorescent x-ray analysis.
Internal Friction of Copper and Copper Alloys
Authors: Beshers Daniel N.
Published: April 2005

A systematic experimental study has been made of the effect of adding small amounts of gold to copper on the dislocation damping in copper measured at 37 kc in longitudinal resonance. The results have been classified in terms of the dependence of the damping on strain amplitude and time with temperature and composition as parameters. The data on amplitude dependence confirm the theoretical results of Granato and Lücke over the range 10−4 to 10−3 atom % gold, where the decrement, Δ, is given as a function of the strain amplitude of oscillation, ε, by Δ=Δ0+(B′/ε½) exp (−A′/ε). The dependence of A′ and B′ on concentration and other parameters is discussed. Above 150°C, at strains large enough for the damping to vary with strain amplitude, the damping may depend on time, t, at constant amplitude in a reversible manner. This dependence may be represented by α exp(−βt⅔)+ct+d with the exponential dominating in the pure specimens and the linear term at 10−3 atom % gold. A detailed consideration of this behavior points strongly towards a vacancy-dislocation interaction as the source. About 280°C, and independently of gold concentration, the damping starts to rise steeply with at least one thermally activated process involved. It appears that vacancies are involved here too. In supplementary measurements, the increase of resistivity of copper due to gold impurities was determined as 0.472 μohm cm per atom % gold.
Diffusion of Impurities into Evaporating Silicon
Authors: Batdorf R. L. , Smits F. M.
Published: April 2005

Steady-state impurity distributions are produced when impurities are diffused into a piece of silicon, the surface of which is evaporating. The moving boundary condition results under steady state in an exponential impurity distribution. The silicon evaporation rate has been determined for temperatures between 1200 and 1325°C from weight loss measurements. No difference in the evaporation rate from various crystallographic planes could be observed from the diffusion technique but flat-bottomed etch pits which formed on surfaces closely orientated to the (111) plane indicated that this plane is probably the most stable. Single diffusions as well as simultaneous double diffusions of phosphorus and gallium into silicon have been studied.
Electron Beam Density Probe for Measurements in Rarefied Gas Flows
Authors: Hurlbut F. C.
Published: April 2005

It is the purpose of this report to describe an instrument for the determination of densities in rarefied gas streams which utilizes the attenuation of an electron beam. The electron beam in passage through a rarefied gas becomes scattered in a number of elastic and inelastic processes, and decays to a fraction of its initial intensity in the distance of a few electron mean free paths. Where the optical aperture of the detector is suitably small, the familiar linear absorption law applies. The mass absorption coefficient in this case is higher and more favorable for work at the lowest test section densities than in other absorption techniques investigated to the present. The instrument was used in an investigation of air flows about a sphere and a wedge, and in the undisturbed stream. The flow was maintained constant for all portions of the test at Mach 1.95, Re/in. ∼200, test section static pressure ∼80 μ Hg. Plots of the original and the reduced data show adequate internal consistency and a qualitative conformity with expected configurations.
Pulse Width Dependence of the Switching Velocity in BaTiO3 Crystal
Authors: Husimi K. , Kataoka K.
Published: April 2005

The maximum switching velocity (ΔP/Δt)max·1/Ps in BaTiO3 single crystals, obtained by the ultrasonic method, is discussed not only as the function of the applied pulse field, but also of the pulse width. Maximum switching current response (dP/dt) measured by the single pulse method and expressed as the exponential function of the field by Merz, is also considered as the limiting case of our expression as the applied pulse width becomes infinitely wide.
Electrodynamic Containment of Charged Particles
Authors: Wuerker R. F. , Shelton H. , Langmuir R. V.
Published: April 2005

Electrically charged iron and aluminum particles having diameters of a few microns have been contained in a confined region of space by means of alternating and static electric fields. The theory is essentially that of alternating gradient focusing; here the motion is governed by Mathieu's equation. Under certain circumstances when many particles are confined the three dimensional focusing force and the Coulomb repulsion results in a ``crystaline'' array which can be ``melted'' and reformed.
Magnetic Moments of Alloys and Compounds of Iron and Cobalt with Rare Earth Metal Additions
Authors: Nesbitt E. A. , Wernick J. H. , Corenzwit E.
Published: April 2005

In order to determine whether ferromagnetic or antiferromagnetic exchange coupling would result from alloying the rare earth metals with cobalt or iron, a number of melts were made containing these elements. The data on saturation magnetization with composition and on saturation magnetization with temperature obtained on the cobalt-gadolinium system indicates strongly that antiferromagnetic exchange coupling exists in this system.
Magnetocrystalline Anisotropy Constant of 3.1% Si–Fe at Room Temperature and Below
Authors: Graham C. D.
Published: April 2005

The first crystal anisotropy constant of a 3.1% Si–Fe alloy has been determined from torque measurements on a {100} single-crystal disk, in fields up to 20 000 oersteds and at temperatures of 77, 195, and 300°K. The values of K1 at these three temperatures are 425±10×103, 405±10×103, and 365±10×103 ergs/cm3.
Nitrogen in Silicon
Authors: Kaiser W. , Thurmond C. D.
Published: April 2005

Liquid silicon has been exposed to gaseous ambients containing varying concentrations of N2 or NH3. Under certain conditions, Si3N4 needles may be grown on the surface and into the body of the melt. The molten zone of silicon was supported between two rods of solid silicon. We have found that the concentration of nitrogen in molten silicon which is saturated with respect to silicon nitride at a temperature near the melting point of silicon is around 1019 atoms per cm3. During the freezing of the melt, Si3N4 precipitates from the supersaturated liquid phase.

The concentration of electrically active impurity states in silicon grown from melts containing around 1019 atoms per cm3 of nitrogen is less than 1012 atoms per cm3.
Structure of Quenched and Irradiated Metals
Authors: Smallman R. E. , Westmacott K. H.
Published: April 2005

The effect of introducing point defects into pure metals by (a) quenching and (b) irradiation has been studied using the small-angle x-ray scatter technique. Scattering was obtained from both quenched copper and aluminum after appropriate ageing treatments, from α-irradiated copper after annealing, and from neutron-irradiated copper. The source of scattering has been considered in each case.

Direct observation of the scattering defects has been obtained for the quenched, neutron-, and α-irradiated metals using thin film electron transmission microscopy. The quenched copper and aluminum contain dislocation loops of the order of a few hundred angstroms diameter formed by the condensation of vacancies, while the α-irradiated metal contains small cavities. Some additional electron microscopic studies of quenched silver and gold are also mentioned and the results discussed in relation to the mechanical and physical properties of quenched metals. No direct evidence has yet been found in neutron-irradiated copper (because of the difficulties in electropolishing), but the small-angle scattering when considered with mechanical property measurements strongly suggests the existence of small ``regions'' ∼100 A diameter. Direct observation of ``damage'' in neutron-irradiated aluminium is observed, however, and shows the existence of dislocation loops, ``jogged'' dislocations, and ``spiral'' dislocations in agreement with theoretical predictions.
Small Angle Scattering of X-Rays by Plastically Deformed Single Crystals
Authors: Robinson W. H. , Smoluchowski R.
Published: April 2005

The small angle scattering of x-rays from single crystals of magnesium plastically deformed in simple shear has been measured in the angular range of 4′ to 5°. The crystals were subjected to both unidirectional and cyclic shear stresses applied along the [112̄0] direction. Thin slices of the deformed single crystals were prepared using strain-free cutting and polishing techniques. The thin slices had orientations such that the slip direction was either parallel or perpendicular to the incident x-ray beam in order to observe any anisotropy in the scattering that might be due to dislocations. It was found that those samples which contained deformation twins within the irradiated volume produced rather large scattered intensity. This scattered intensity is interpreted as being due to double Bragg scattering. The scattered intensity from other specimens was attributed to surface scattering. No evidence for small angle scattering by dislocations was found.
Small-Angle Scattering of X-Rays from Neutron Irradiated Copper
Authors: Atkinson H. H. , Smallman R. E. , Westmacott K. H.
Published: April 2005

The scattering of x-rays at small angles from polycrystalline copper is found to increase when the recrystallized metal is bombarded with fast neutrons. The observed effects above 2° are due to double Bragg reflections; below about 1½° they can be explained in terms both of double reflections and ``true'' small-angle scattering. The results indicate that either small coherent regions (of diameter about 100 A) or severe strains are present in the irradiated metal. The results are consistent with other measurements (particularly of mechanical properties) on irradiated metals.
On the Mechanism of the Small Angle X-Ray Scattering from Cold Worked Metals
Authors: Neynaber R. H. , Brammer W. G. , Beeman W. W.
Published: April 2005

The characteristic small angle x-ray scattering from cold worked polycrystalline foils of Cu, Al, and Ni is found to appear immediately when the foil is stretched in the x-ray beam at liquid air temperature. The scattering at a fixed angle is a reversible function of foil temperature as long as recrystallization temperatures are not exceeded. The temperature dependence is about twice that expected from the Debye temperature factor of an average Bragg reflection. It is postulated that the small angle scattering is the result of two successive Bragg reflections from two slightly misoriented subgrains of the same grain. The small angle scattering is found to be polarized. This can be understood only on the double Bragg scattering model. The double Bragg model was suggested by our observation of occasional isolated small angle peaks from annealed foils. These have unusual characteristics which quickly eliminate any possible single scattering source. They are double scattering from two large annealed grains which sometimes accidentally satisfy all the orientation requirements.
Ferrimagnetic Resonance Modes in Spheres
Authors: Fletcher P. C. , Bell R. O.
Published: April 2005

The magnetostatic solutions of ferrimagnetic resonance in ferrite spheres are briefly derived. General and specific solutions are given for values of n up to five for the magnetostatic potentials, rf distributions of magnetization, and fields for resonance. Some experimental results are given and compared with the theory.