bluuebunny/crossref_metadata_2025 huggingface dataset:
Self-Diffusion in Pure Polycrystalline Silver
Authors: Slifkin L. , Lazarus D. , Tomizuka T.
Published: April 2005

Self-diffusion in pure polycrystalline silver has been measured using Ag110 as a tracer. The results of the high temperature experiments, where volume diffusion is predominant, are in excellent agreement with those of other investigators. A least-squares calculation using all available data on volume diffusion of silver gives as a value for the diffusion coefficient D=0.724e−45, 500/RT. The occurence at low temperatures of grain boundary diffusion, in which the activity decreases exponentially with the first power of the penetration depth, as reported by Hoffman and Turnbull, is confirmed.
Reliability of Probe Measurements in Hot Cathode Gas Diodes
Authors: Wehner Gottfried , Medicus Gustav
Published: April 2005

Experimental investigations show that Langmuir probe measurements can give quite erroneous results, due to work function changes of the probe, insulating layers on the probe surface, or different work functions at different places of the probe. The deposition of evaporated cathode compounds, the adsorption of oxygen released from oxide cathodes, and the sputtering and evaporation from the probe may change the work function of a pure tungsten probe in time scales of seconds. In oxide cathode tubes especially, it is necessary to measure immediately after the probe has been thoroughly cleaned. An X - Y plotter, which recorded the whole probe characteristic in seconds, was found to be most suitable. No deviation from the Maxwellian velocity distribution of the plasma electrons could be found over a range of nearly four orders of magnitude in probe current, even in oxide cathode tubes under conditions where such deviations have been found by other authors.
Markings Found in the Oxide Replicas for Electron Microscopy
Authors: Yamaguchi Shigeto
Published: April 2005

There are two types of crystal edges in the electron micrographs of oxide replicas of metals. The first type is characterized by the edges being more transparent than the facets in reprinted crystals. In the second type of reprinted crystal there were found the opaque edges of crystal. These characteristics of crystal edges were explained by the orientation of crystallites composing the replica films. It is proposed in the present study that the width of transparent edge of reprinted crystal might serve as a rough measure of microscopic magnification.
Radiation from a Dielectric Wave Guide
Authors: Whitmer Robert M.
Published: April 2005

The radiation from an infinite dielectric slab fed by a line source has been calculated from a branch-cut integral. The modal efficiency of the device as a wave guide is defined as the ratio of the power propagated in a mode to the sum of the modal and radiated powers. For a range of the parameters such that only one mode can be propagated, the modal efficiency has been plotted numerically. Except for extreme values of the parameters, the efficiency runs around 80 percent to 90 percent.

The slab form is not one likely to be used in practice, but the efficiency of a cylinder would be expected to have about the same value.
On the Metallic Shadow-Casting Using a Nozzle System
Authors: Hibi Tadatosi
Published: April 2005

A new device for metallic shadow-casting by using the nozzle system is proposed, and an outline of the apparatus is given. The present device has a shutter, a nozzle, and a cover plate between specimen and filament in addition to the usual apparatus. The dimensions of the nozzle were chosen from the maximum of 3-mm diam, 1.5-mm diam, and 22 mm to the minimum 1.5-mm diam, 0.7-mm diam, and 38 mm as diameter at the entrance, diameter at the exit, and the length, respectively. It was found that this method was not only conspicuously effective in obtaining much more accurate shadows than that obtained by the usual method with the same shadowing material, but also brought into possible use metals, as shadowing materials, which could not be used for such a purpose by the usual method. Shadowing qualities of many kinds of evaporated metals are compared and a new rule for the order of aggregation of deposited metallic thin films is also proposed.
Reflection of Microwaves from Metal-Plate Media
Authors: Brady J. J. , Pearson M. D. , Peoples S. R.
Published: April 2005

The theory of Carlson and Heins and the extended theory of Lengyel has been verified experimentally for oblique angles of incidence. Both single surface and slab measurements were performed in the 3-cm band. Single surface measurements were made by using tapered wooden wedges as absorbing materials to eliminate back surface reflections. The effect of plate thickness was studied for five different thicknesses. The phase and amplitude of the reflection coefficient of a metal-plate slab were obtained for three angles of incidence, 10°, 25°, and 35°, and for values of 2a/λ ranging from 1.10 to 1.30.
Method for Determining Magnetic Moments and for Measuring Susceptibilities and Permeabilities
Authors: Barnett S. J.
Published: April 2005

Fundamentally, the method is closely related to one described by W. Weber in 1852 in his Elketrodynamische Maasbestimmungen and applied by him to the measurement of very small susceptibilities in cases in which it was desirable to exclude eddy currents from the specimens under examination. It is capable of being modified so as to measure magnetic moments and magnetic susceptibilities, large and small, under a great variety of conditions. The method has the advantage, for low permeabilities, over that of permeameters, that it measures precisely the (small) difference between the permeability of the specimen and that of air, and not the ratio of the two. It determines the magnetic moment of the specimen and the susceptibility k, from which the permeability μ may be derived from the relation μ=1+4πk.
A Statistical Approach to the Space-Charge Distribution in a Cut-Off Magnetron
Authors: Hok Gunnar
Published: April 2005

When the anode potential of a nonoscillating magnetron is lower than the cut-off potential, the discrete electron-to-electron interaction has an effect on the space-charge distribution which would be negligible if only resulting in fluctuations about a known steady state. However the states proposed by Brillouin, Slater, and others are not steady states in this sense. The electron interaction must, therefore, be expected to produce a steady drift away from such initial states. This paper discusses qualitatively the final steady state to be expected and its dependence on the ratio of anode voltage to cut-off voltage. Because of the involved nature of the electron distribution function no attempt is made to calculate the space-charge distribution explicitly.
The Determination of Complex Dielectric Constants of Absorptive Liquids by Microwave Interferometry
Authors: Branin Franklin H.
Published: April 2005

This paper describes both a traveling-wave method and a standing-wave method for determining complex dielectric constants of liquids from measurements made at 10-cm wavelength with a traveling probe immersed in a dielectric-filled slotted line. An interferometric null technique was developed for improving the accuracy of the measurements, especially in highly absorptive media. In the traveling-wave method, absolute measurements of both wavelength and absorption index can be made simultaneously; from these two quantities the complex dielectric constant is readily computed. In the standing-wave method, the absorption index is determined graphically from the power-standing-wave ratio while the wavelength is obtained by a modified null technique. For low loss media, a simplified standing-wave method is practical whereby the absorption index is obtained from measurements of the breadths of successive minima of the standing wave. Corrections for the finite resistance of the short circuit used in the standing-wave method and for conductor losses along the slotted line are fully treated.
Current Fluctuation Phenomena in Current-Carrying Sliding Contacts
Authors: Epprecht G. W.
Published: April 2005

Considerable noise voltages appear across sliding contacts mainly because of the fact that the current across the contact consists of a random series of short pulses, corresponding to the minute, fugacious conducting spots on the contact surface. The properties of this noise within a wide range of contact conditions (i.e., varying sliding speed and operating current) are analyzed theoretically and experimentally. Most of the observed noise characteristics can be explained by various thermic phenomena in the contact interface. Several basic ranges as to operating current and sliding speed may be distinguished, each dominated by a different mechanism.
Etching of Single Crystal Germanium Spheres
Authors: Ellis Ray C.
Published: April 2005

Spheres of single crystal germanium have been ground and etched. A series of polyhedra, consistent with the stability of the various crystal planes of germanium, was obtained.

Only (111) plane twins were found in germanium using this method.
Measurement of Temperatures in Flames of Complex Structure by Resonance Line Radiation. I. General Theory and Application to Sodium Line Reversal Methods
Authors: Strong H. M. , Bundy F. P.
Published: April 2005

Sodium line reversal temperature measurement by low resolving power spectroscopic instruments on complex flame structures gives temperatures intermediate between the highest and lowest temperature in the line of sight. This intermediate temperature is determined by the temperatures, optical depths and arrangement of the individual zones. By taking into account these factors, it is possible to derive temperatures for the inner zones of a complex flame. The theory, numerical data needed to apply the theory, and experimental examples are given.
Measurement of Temperatures in Flames of Complex Structure by Resonance Line Radiation. III. From Absolute Intensity Measurements at High Resolution
Authors: Bundy F. P. , Strong H. M.
Published: April 2005

A method for measuring flame temperatures is described which requires the determination of the intensity and emissivity of the flame at wavelengths within the intensity contour of a resonance spectral line such as a D line of sodium. An experiment is cited to illustrate the method in which a Fabry-Perot interferometer was used as the spectroscopic dispersion instrument. The emissivities were determined by comparing the brightnesses of the mirrored and unmirrored flame. The theory, procedure, and an example of using the method to find the temperature of a submerged zone of a flame are given.
Conversion of Heat to Electricity by Thermionic Emission
Authors: Wilson Volney C.
Published: April 2005

A heat engine and electric generator is described which is a vacuum or gas filled device containing a hot cathode and a cold anode. Heat at the cathode lifts electrons out of the cathode and to a high (negative) potential in the system. By collecting the electrons on a low work function surface, part of the potential energy may be retained to use in an external circuit. Thus part of the heat that lifts the electrons out of the cathode may be converted into electrical energy. Cs vapor filled tubes have been built and tested as thermionic converters. A hot surface ionized part of the Cs vapor to neutralize space charge between the cathode and anode. The Cs vapor was also used to adjust the work functions of the two surfaces. A thermionic converter has been built which converts 9.2% of the input heat into electricity. The output was 3.1 watts per cm2 of cathode surface—0.78 v at 4.0 amp per cm2 of cathode surface.
Sputtering as It Is Related to Hyperbolic Meteorites
Authors: Baker Robert M. L.
Published: April 2005

A theoretical discussion is presented of the phenomenon of cathode sputtering as it is related to high-speed meteorites, i.e., to meteorites whose speeds are high enough to have reached the Earth from interstellar space. The drag and heat transfer are found to be markedly affected by sputtering, even when the most conservative estimates of sputtering-yield and energy-transfer efficiency are employed. The paper shows that theoretically sputtering can account in part, at least, for the discrepancy between meteor photographs, which show no extra-solar meteorites, and certain visual-telescopic data which, on the contrary, show a significant number of meteorites to have an extra-solar origin.
Condensation in Nozzles
Authors: Wilde Kenneth A.
Published: April 2005

The extent of realization of vapor-liquid phase equilibrium in nozzles has been investigated as a function of initial particle size, kinetic parameters, and nozzle dimensions. It has been shown that condensation will occur on already present particles only for very small sizes and/or large nozzles 20–30 in. or more in diameter. The present rather rudimentary state of knowledge of spontaneous nucleation does not enable any reliable evaluation of condensation by this mechanism.
Dislocation Planes in Semiconductors
Authors: Mataré H. F.
Published: April 2005

Dislocations and mainly dislocation planes, as the most important nonchemical imperfections in semiconductor crystals, are discussed from the point of view of their influence on carrier transport. After a short review of the general properties of grain boundary planes of medium angle of misfit, the electrical effects are discussed, including the barrier behavior, the band structure, and lifetime anisotropy. Devices tructures based on these properties of dislocation planes are described among which the dislocation field effect transistor shows promising features as the first temperature independent transistor in the range 300°K to 2°K.
Dielectric Properties of Single-Crystal Nonstoichiometric Rutile (TiO2)
Authors: Hollander Lewis E. , Castro Patricia L.
Published: April 2005

The dielectric constant ε′ and dielectric loss ε″ have been determined from 30 to 300 000 cps in the a and c crystal directions for nonstoichiometric compositions of rutile with dc resistivities from 104 to 1013 Ω-cm. Measurements with asymmetrical electrodes and geometrical variations indicate that the properties are primarily a bulk effect. Quasi-ferroelectric effects were observed at field gradients greater than 500 V/cm and at frequencies above 0.5 cps. It is suggested that the dielectric properties of rutile can be explained by an artificial dielectric model consisting of conducting needles of heterogeneously distributed oxygen vacancies embedded in an insulating medium.
Tunneling of a Wave Packet
Authors: Hartman Thomas E.
Published: April 2005

Analytic expressions are given for the time spent by a particle tunneling through a potential barrier. The expressions are derived for an incident wave packet which is initially Gaussian, centered about a point an arbitrary distance away from a rectangular potential barrier and moving toward the barrier with constant average velocity. Upon collision with the barrier, the packet splits into a transmitted and a reflected packet. The resultant transmission time is positive, nonzero and in principle measurable. Although the transmission time becomes quite large as the incident kinetic energy becomes very small, in general, for nonzero incident momentum and finite potential barriers which are neither very thick nor very thin, the transmission times are less than the time that would be required for the incident particle to travel a distance equal to the barrier thickness. The transmission times for metal-insulator-metal thin film sandwiches, given approximately by δt3=ℏ/(Efφ)12, where Ef is the Fermi energy of the metal, and φ the vacuum work function, are of the order of 10−16 sec, compared to RC time constants of about 10−13 sec.
A Lower Bound and Other Properties of the Mean-Square Error of Linear Measurement Systems
Authors: Hammond Joseph L.
Published: April 2005

The central purpose of this paper is to establish a lower bound on the mean-square error of linear, noisy, dissipative measurement systems designed to measure a constant quantity. A lower bound on mean-square error is determined to be (2kTA)/t, where k is Boltzmann's constant, T is the absolute system temperature, t is the time consumed by the measurement, and A is a parameter of the measurement system closely related to its driving point immittance. This lower bound shows, among other things, that a nonzero measurement interval is required to obtain a useful estimate of the quantity being measured.

The lower bound is arrived at by considering a logical structure for linear noisy measurement systems and mathematical expressions derived for the mean-square error of such systems. The key step in establishing the lower bound is the consideration of the unavoidable random perturbation at the system input due to the generalized Nyquist noise discussed earlier by Callen and Welton. Use of the general lower bound is illustrated by establishing more specific lower bounds for two classes of systems, namely, current measuring galvanometers and thermal detectors. In these cases the lower bounds are consistent with minimum values for the mean-square error of such systems as previously reported in the literature by McCombie.
Piezoelectric Optical-Maser Modulator
Authors: Johnson L. F. , Kahng D.
Published: April 2005

An optical-maser modulator employing a transparent piezoelectric medium is described. The device is based on multiple interference in transmission or reflection, the intensity in the interference pattern being modulated by a change in thickness of the piezoelectric plate. Using barium titanate it is shown that 80% modulation and 20-Mc bandwidths are readily attainable. A sacrifice of modulation to 10% permits bandwidths ∼200 Mc. A slight modification allows the device to operate purely as a phase modulator.

In addition, an optical-maser modulator employing a grating ruled on a piezoelectric medium is described. Spatial modulation is brought about by a change in grating constant via the piezoelectric effect. As a communication device in conjunction with an optical maser operating at 0.7μ, 10% modulation and a bandwidth ∼10 Mc can be obtained using barium titanate driven near the fundamental resonance frequency.
Departures from Vegard's Law
Authors: Gschneidner K. A. , Vineyard G. H.
Published: April 2005

A new method, based on second-order elasticity, has been developed to predict departures from Vegard's law in binary alloy systems in which the end members have similar outer-electronic structures. This method has been found to be successful in predicting the correct sign and order of magnitude of the deviation in 28 of 44 binary systems. It has also been compared with 7 techniques presented in the literature, and was found to be a significant improvement over the other techniques. The new approach described herein contributes to the understanding of departures from Vegard's law, and its general applicability to all systems has been noted.
Color Centers and the Flow Stress of LiF Single Crystals
Authors: Nadeau John S.
Published: April 2005

Lithium fluoride crystals were exposed to cobalt-60 gamma radiation at 300° and 78°K. Changes of the flow stress and of the optical absorption were measured in an effort to relate the hardening to identifiable color centers.

In crystals irradiated at 300°K there was found to be a good correlation between the flow stress and the concentration of F centers. The magnitude of the hardening, however, suggested that it was caused by interstitial defects. Comparison of the hardening produced by additive coloring with that produced by irradiation indicated that the hardening defects were interstitial fluorines. This direct relation between interstitials and F centers supports a Varley type of mechanism for F-center production in the bulk crystal. Some limited experiments with NaCl and KCl showed qualitatively the same behavior and suggest that the same F-center production mechanism may occur in them.

Irradiation of LiF at 78°K produced stable trapped-hole centers and pulse annealing experiments showed that the Vk center (self-trapped hole) contributed to the hardness at low temperatures. A sharp decrease of flow stress was observed at about 110°K where the paramagnetic resonance experiments of Kanzig and the optical measurements of Wiegand and Smoluchowski indicate disappearance of the Vk center.
Dislocation Damping in Magnesium Oxide Crystals at Low Frequencies
Authors: Dahlberg Philip , Carnahan R. D. , Brittain J. O.
Published: April 2005

Amplitude dependent internal friction measurements have been made on MgO crystals over the temperature range 0° to 300°C at frequencies of ∼5 cps. Analysis of the temperature dependency of the critical breakaway strain, delineating the transition from amplitude independent to amplitude dependent internal friction, permits an evaluation of the relative pinning strengths of the Fe2+ and Fe3+ ions, determined on specimens from bulk sources. The Fe3+ ion exhibits a binding energy of 0.035 eV, whereas the Fe2+ ion has either a lower binding energy and/or a lower mobility which precludes the development of an equilibrium atmosphere. Optical absorption measurements confirm the presence of the Fe3+ ion in one bulk crystal and its absence in the other.
Atomic Displacements in Metallic Solid Solutions
Authors: Webb W. W.
Published: April 2005

Local atomic displacements in copper-base solid solutions have been determined from measurements of the integrated intensities of Bragg diffraction of x rays by powder samples. The rms amplitudes of ``static'' displacements due to different effective atomic sizes of solute and solvent in solution were determined (but with low precision) to be given by (〈US2〉av)½=K[xB(1−xB)]½ (da/dxB)0, where xB is the atomic fraction solute, (da/dxB)0 is the limiting change of lattice parameter with solute concentration as xB→0, and K is a constant ∼0.3. The difficulty of distinguishing ``size'' effects of purely elastic origin from any atomic displacements due to valence electron screening is discussed. Debye temperatures of the alloys were determined and the value of the Debye temperature for copper was found to agree with the calorimetric value.
Etch Pit Studies of Dislocations in Copper Crystals Deformed by Bending: I. Annealed Crystals; II. Irradiated Crystals
Authors: Young F. W.
Published: April 2005

Annealed and irradiated copper crystals of low initial dislocation density were deformed by bending, and dislocation multiplication and motion were studied using an etch pit technique for observing the dislocations. For the annealed crystals there was dislocation motion and multiplication prior to macroscopic yielding, and the percentage of grown-in dislocations moved by the stress increased with the stress. The dislocations were hindered in the motion by subboundaries and by interaction with other dislocations. Relaxation effects were observed and were much greater for stresses less than the yield stress than for higher stresses. For the neutron-irradiated crystals there was no motion or multiplication of dislocations prior to yielding. The slip traces were long, with dislocations closely spaced in the trace. Although not conclusive, the evidence apparently was best interpreted in terms of source hardening. A cube-root dependance of the yield stress on neutron dose was observed. No hardening resulted from irradiation with 1018/cm2 cobalt γ rays.
Dependence of the Thermoelectric Figure of Merit on Orientation in Uniaxial Crystals
Authors: Madigan John R.
Published: April 2005

The thermoelectric figure of merit has been determined as a function of the angle between the principal symmetry axis and either the field vectors E and −∇T or the current densities j and q for uniaxial crystals assuming isotropy of the Seebeck coefficient. For any orientation of these vectors other than parallel or perpendicular to the principal symmetry axis, the figure of merit in the direction of the current densities is always less than that in the direction of the field vectors. The latter situation is realized experimentally in thin disk samples while the former is characteristic of long rods. When these expressions are averaged over the angle between the cleavage planes and the appropriate vectors, the figure of merit in the direction of the field vectors is 86% while that parallel to the current densities is 72% of the maximum value for Bi2Te3 crystals. These values should be characteristic of sintered powder samples.
Scattering of Plane Waves by a Cavity Ribbon in a Solid
Authors: Harumi K.
Published: April 2005

The scattering of plane compressional or shear waves by a cavity ribbon with width a in an elastic medium is computed by the use of the Mathieu functions when the displacement of the incident wave is in xy plane. The diffraction patterns for kca/2=1, 2, and 4, and for ks=2kc are obtained; the diffraction patterns by a cavity ribbon are similar to those of the sound wave by a perfectly absorbing ribbon only when the incident compressional waves propagate to the direction normal to the plane of the ribbon. The scattering cross sections Q/a are of the order of (ka)3 in the Rayleigh case. These facts support the conclusion of the previous paper (rigid ribbon).
Direct Observation of Antiphase Boundaries in the Fe3Al Superlattice
Authors: Marcinkowski M. J. , Brown N.
Published: April 2005

Antiphase boundaries have been observed in thin foils of a Fe3Al superlattice prepared from the bulk material, using transmission electron microscopy techniques. This particular alloy forms two distinct types of superlattice; the first is a high temperature modification based on an imperfect B2-type lattice, while the second is a lower temperature modification based on the more perfect DO3-type lattice. A distinct type of antiphase boundary has been found to be associated with each ordered configuration, and their geometry and energy have been analyzed in detail. The critical conditions necessary to reveal these antiphase boundaries by transmission electron microscopy have been treated. In particular, it is found that antiphase boundary contrast is obtained only when the foil is critically oriented for diffraction from a strong superlattice reflection. Furthermore, the detailed dynamical theory of electron diffraction has been applied successfully to the present observations. Finally, some contrast effects associated with intersecting antiphase boundaries have been observed and interpreted using the kinematical theory of electron diffraction.
Propagation Effects on Ferromagnetic Resonance in Dielectric Slabs
Authors: Pincus P.
Published: April 2005

The effects of displacement currents on ferromagnetic resonance are investigated for perfectly insulating slabs magnetized normal to their surfaces. The surface spins are assumed to be free. It is found that, at constant frequency, the usual ferromagnetic resonance shifts to higher fields. Also, for sufficiently thick samples, new resonances may be excited on the low-field side of the main resonances. For thinner samples, these additional resonances may not be resolved from the main resonance, but may contribute significantly to its intrinsic linewidth.
Electron Microscopy of Prismatic Dislocations in Silicon
Authors: Phillips V. A. , Dash W. C.
Published: April 2005

Transmission electron micrographs of (111) prismatic loops in gold-diffused silicon have been obtained. The loops were about 2 μ in diameter. From the contrast effects seen and for a number of other reasons it is concluded that the loops surround a stacking fault rather than coherent platelets of gold.
Theoretical Analysis of Light Scattering by Irregular Dislocation Networks
Authors: Theimer O. , Canfield J.
Published: April 2005

Light scattering by an irregular cubical network of dislocations, represented by identical rods, along the x, y, and z directions is computed by a method which is similar to the Patterson analysis of x-ray diffraction. It is assumed that the spacing d between neighboring dislocations has a Gaussian distribution of width δd̄ about the average spacing d̄, and it is shown that shallow maxima of the scattering intensity exist near the Laue spots of the regular lattice with spacing d̄. From these peaks the dislocation density d̄−2 may be calculated. The width of the peaks and the intensity ratio of scattering maxima and minima is found as a function of d̄, δ, and the wavelength λ, and it is concluded that the peaks could be experimentally resolved if (λ/δd̄) >π. This condition could be satisfied for fairly irregular networks, e.g., δ̄=1/π, by infrared radiation of wavelength λ≅d̄.
Resonances of a Microwave Cavity Partially Filled with a Plasma
Authors: Agdur B. , Enander B.
Published: April 2005

The resonant behavior of a cylindrical microwave cavity partially filled with a cold plasma of arbitrarily large density is studied theoretically and experimentally. Curves showing the resonant frequencies as functions of the plasma density are given for the lower order modes. The modes are generally not pure TE or TM modes but are of hybrid character. In addition to the modes that are related to those of the empty cavity, there is a class of modes of surface wave character that do not exist in the empty cavity. Experiments have been performed and are generally in agreement with the theory. However, for some modes great discrepancies are observed. These correspond to the unexplained additional resonances obtained in plasma resonance experiments.
Effect of Reflecting Boundaries on the Transport of Resonance Radiation
Authors: Weinstein M. A.
Published: April 2005

The Holstein-Biberman theory of the transport of resonance radiation in gases is generalized to include the case in which the boundary is partially reflecting. The problem is formulated in a manner which follows conventional transport theory somewhat more closely than the earlier treatments of Holstein and Biberman. Using the incoherent scattering approximation, we first write down the two coupled Boltzmann equations describing the mutual transport of excited atoms and resonance photons. The photon equation is then solved, with (diffuse) reflecting boundary conditions, by a slight extension of the interreflection method, and inserting the result into the excited atom equation leads at once to the appropriate generalization of the Holstein-Biberman transport equation. The kernel of this integrodifferential equation, G(r,r′), represents the mean probability that a resonance quantum emitted at r′ is absorbed at r, taking into account the contribution of paths which strike the boundary an arbitrary number of times; G(r,r′) is expressed quite generally in terms of the resolvent kernel of the interreflection equation. The theory is used to calculate the effect of a slightly reflecting boundary on the imprisonment time in a gas discharge.
Some Considerations of Dynamic Behavior in the Plasma Thermocouple
Authors: Bussard R. W.
Published: April 2005

An analysis is presented of the role which stable electron oscillations of large amplitude may play in determining observed ``steady-state'' characteristics of a plasma-filled thermionic diode. The mechanism considered is that of coupling between electrostatic plasma oscillations, driven by the energy of the entrant electron ``beam'' from the emitter surface, and the potential distribution in the emitter sheath region. In operation such that net current flow is controlled by the sheath potential distribution, it is found that the time-averaged net current may increase markedly in transition from nonoscillatory to oscillatory operation, with a concurrent change in cell and load potential drops such that the diode acts as a negative resistance source of potential over a limited range. Conditions which restrict attainment of the oscillatory mode are discussed, and it is found that large amplitude electron waves may be generated and maintained over a fairly wide, and experimentally accessible range of plasma electron density. Comparison is made with some experimental results, and an experiment is suggested for direct test of the driven-wave hypothesis discussed herein.
Effect of Solutes on Polygonization in Bent Zinc Crystals
Authors: Sinha P. P. , Beck Paul A.
Published: April 2005

The development of a reagent for dislocation etching of high-purity zinc alloys with copper or aluminum, not requiring decoration of the dislocations, allowed the study of dislocation arrangements in bent alloy crystals. Most of the dislocations were found in the unannealed condition to be arranged in disconnected wall segments perpendicular to the basal plane, showing that the solutes had little, if any, effect on mechanical polygonization during bending. Their effect on the rate of subsequent thermal polygonization and of subgrain growth was also found to be surprisingly slight.
Folded Molecules in Lamellas Crystallized from Molten Polymers
Authors: Geil P. H.
Published: April 2005

Single crystals of polypropylene consisting of lamellas have been grown from the melt. Electron diffraction patterns indicate that the molecules are folded within the lamellas and have crystallized in a hexagonal unit cell.
Some Theoretical Considerations on the Geometry of Low-Angle Dislocation Boundaries
Authors: Kuhlmann-Wilsdorf Doris
Published: April 2005

Frank's vector formula defining low-angle boundaries is rewritten into six independent scalar equations which can be represented in the form of three simple two-dimensional vector diagrams. These diagrams facilitate the discussion and construction of low-angle boundaries, and in particular allow to construct four-grid boundaries due to glide dislocations on arbitrary planes.
Asymmetries in the Surface Properties of the (111) and (1̄1̄1̄) Faces of Zinc Telluride
Authors: Dillon J. A.
Published: April 2005

Photoelectric emission studies have been made for the (111) and (1̄1̄1̄) surfaces of ZnTe which were cleaned in high vacuum by the ion bombardment and annealing process. Differences in the adsorption and etching properties reflected the asymmetry in atomic species on the two faces. The (111) or Zn face was insensitive to oxygen adsorption at room temperature while the (1̄1̄1̄) face adsorbed oxygen with a sticking coefficient of about 10−3. The photoelectric properties of both surfaces were varied by the adsorption of water vapor.
Role of Defects in Evaporated Silver Films on the Nucleation of Sulfide ``Patches''
Authors: Phillips V. A.
Published: April 2005

The role of defects in the formation of silver sulfide tarnish patches on silver was studied by transmission electron microscopy. The patches were formed on thin (001) single-crystal films of pure silver at room temperature by exposure to the atmosphere. The observations showed that (1) stacking faults (2) partial dislocations and (3) hole edges were the main sites for nucleation. The patches were roughly square in shape and were of two sorts, one with sides parallel to 〈110〉 Ag directions nucleating at type (1) and (2) sites, the second with sides parallel to 〈100〉 Ag directions nucleating at type (3) sites. Both sorts of patches were probably single crystal oriented overgrowths. Their orientations could not be identified. The patch density was typically about 3×109 cm−2. Positive identification of the patches as monoclinic beta Ag2S was only possible in a duplicate experiment in which randomly nucleated patches of irregular shape were obtained. These patches were highly oriented, predominantly with (001) β-Ag2S parallel to (001) Ag.
Parallel Dislocations in Cobalt Whiskers
Authors: Dragsdorf R. Dean , Johnson R. T.
Published: April 2005

A study of 30 cobalt whiskers obtained by hydrogen reduction of the halide is herein reported. The whiskers were grown in the face-centered cubic phase but were cooled through the phase transformation to the hexagonal phase before being examined. The majority of the whiskers had a [10·0] axis; however, whiskers with [00·1], [11·1], and [1̄1·1] axes were also observed. These hexagonal axes are related to simple growth directions in the face-centered cubic system. An axial strain caused perhaps by a screw dislocation restricts the atom movement in this phase transformation to the close-packed planes perpendicular to the whisker axis. Single and multicrystal whiskers were obtained. Aligned edge dislocations parallel to the whisker axis gave rise to multicrystal filaments. Heating the multicrystals resulted in the disappearance of the symmetric small angle grain boundaries through the movement of the edge dislocations toward the central core of the whisker.
Gaseous Optical Maser with External Concave Mirrors
Authors: Rigrod W. W. , Kogelnik H. , Brangaccio D. J. , Herriott D. R.
Published: April 2005

A helium-neon optical maser has been operated successfully with concave mirrors external to the gas-discharge tube. The latter is sealed at both ends with optically flat windows at the Brewster angle to the beam axis. This arrangement simplifies the tube construction and enhances its versatility. The alignment of concave mirrors is considerably less critical than that of plane mirrors. Measured beat frequencies between several pairs of concave resonator modes agree closely with computed values.
Frequency Dependence of Acoustic Fluctuations in a Randomly Inhomogeneous Medium
Authors: LaCasce E. O. , Stone R. G. , Mintzer D.
Published: April 2005

When a series of uniform acoustic pulses is transmitted through a medium whose refractive index varies in a random manner, the received pulses vary randomly about an average amplitude. A theory developed by Mintzer [J. Acoust. Soc. Am. 25, 922 (1953)] predicts that the coefficient of variation V, defined as the fractional standard deviation of a series of pulses, is directly proportional to k (2π/acoustic wavelength), provided that the range from the source to receiver is greater than ka2, where a is the correlation distance of the refractive index variations. In a scaled model experiment the refractive index variations are caused by heating the medium (water) from below, thus causing turbulent convection. Observations show the linear dependence of V upon frequency for r>ka2 as predicted by the theory. At the higher frequencies, observations indicate possible oscillations in V as it tends toward a frequency independent value.
Velocities and Densities of Dislocations in Germanium and Other Semiconductor Crystals
Authors: Chaudhuri A. R. , Patel J. R. , Rubin L. G.
Published: April 2005

The average velocities of dislocations have been measured in four semiconductor crystals-silicon, germanium, gallium antimonide, and indium antimonide. The range of measured velocities was between 10−6 and 2×10−1 cm/sec. The dislocation velocities in these crystals are relatively insensitive to stress when compared to LiF or Si-Fe. The effect of temperature, in the range 0.5 to 0.8TM, on the velocities at various constant stresses was measured and the activation energies for the dislocation velocities were obtained in each of the crystals. No marked dependence of activation energy as a function of the applied stress was obtained.

The effect of strain on the dislocation densities was measured as a function of orientation, temperature, and strain rate. It was found that even in initially dislocation-free crystals, dislocations were generated at quite low stresses. From direct measurements of etch pits and dislocation velocities it was possible to estimate the fraction of mobile dislocations. Under certain conditions the percentage of mobile dislocations was as low as 3 to 8%.
Measurement of Nitrogen Diffusion in Chromium by Anelastic Methods
Authors: De Morton M. E.
Published: April 2005

The internal friction peak for nitrogen in dilute solutions in very pure chromium occurs at 160°C for ∼1 cps but is unstable due to partial precipitation of nitrogen. Interpretation of internal friction data at low frequencies and elastic aftereffect measurements in terms of the theory of Snoek gives the lattice diffusion rate of nitrogen in chromium as D=3×10−4 exp (−24 300/RT).
Quenching Rate and Quenched-In Lattice Vacancies in Gold
Authors: Mori T. , Meshii M. , Kauffman J. W.
Published: April 2005

The quenched-in resistivity in gold was measured for cooling rates from 104 to 105 °C/sec. The quenched-in resistivity increases considerably with increasing cooling rate and depends strongly on the quenching temperature over much of the range investigated; for example, for a cooling rate of 20 000°C/sec about 12% of the residual resistivity recovers during the quenching process for a quench from 700°C and about 20% recovers for a quench from 800°C. For the lower quenching temperatures the quenched-in resistivity appears to approach saturation at the fastest quenching rates obtained. A linear relation between the logarithm of quenched-in resistivity and the reciprocal of quenching rate was observed. This allowed linear extrapolation to infinite quenching rate. The quenched-in resistivity ρ∞ obtained by extrapolating to infinite rate, is expressed by ρ∞=ρ0 exp(−Hf/kT), where ρ0=5.0×10−4 Ω-cm and the formation enthalpy, Hf=0.97 eV. Assuming ρ∞ corresponds to single vacancies rather than clusters, measurements of the length change of the quenched specimens and using Tewordt's result that a vacancy has 0.47 atomic volume, the following constants were obtained: The resistivity of 1 at. % of vacancies, 1.7×10−6 Ω-cm; the entropy of formation of a vacancy, 0.95×10−4 eV/°K; and the fractional concentration at the melting point, 6.4×10−4.
Calculations of Cathode-Fall Characteristics
Authors: Ward A. L.
Published: April 2005

Calculations of the variation of cathode-fall voltage, the cathode-fall distance, and the Aston dark space with current density have been made for the rare gases and a few molecular gases on an electronic computer. The calculations were based upon Townsend's ionization equations, but included the field distortion due to space charge. New analyses of the field variation of Townsend's first ionization coefficient and ion mobilities are presented. The length of the dark space has been obtained from the calculated distribution of light output across the gap and agrees with the cathode-fall distance calculated from the field distribution. Comparisons of the calculated cathode-fall characteristics with published experimental results indicate the probable validity of the model used for the calculations.
Interactions between the Corona Discharge and a Zinc Oxide Electrode
Authors: Elder Tait
Published: April 2005

In a negative point-to-plane corona discharge in air, mutual interactions are observed between the electrode and the discharge when the anode is a film composed of zinc oxide incorporated in a resin binder. The current carried by the corona discharge increases by more than fivefold as the zinc oxide becomes negatively charged. When the electrostatic charge on the zinc oxide surface is dissipated by light the current falls to the value which is observed when a metal conductor replaces the zinc oxide resin film electrode in an identical geometry.

Another feature of the discharge interaction is that the zinc oxide resin films are able to accept and retain over 109 electronic charges per square centimeter of excess negative electrostatic charge despite the fact that the bulk conductivity of the films measured electrodynamically either before or after corona charging is often greater than 10−11 Ω−1 cm−1. Selected single crystals of zinc oxide have also been observed to accept and retain electrostatic charge for several seconds after exposure to the negative corona discharge, while concurrent measurements show that the conductivity of the crystals remains unchanged at 10−2 Ω−1 cm−1 throughout the experimental treatment. In both cases the charge can be dissipated by less than 1014 photons/cm2 of actinic light. It was thus possible to make Xerographic prints on single zinc oxide crystals. No effects comparable to these are observed with a positive corona discharge.

The paper is primarily experimental in scope. Support is introduced for the hypothesis that the effect of negative ions of the corona discharge on the zinc oxide resin film surface is the creation of small isolated charged regions, presumably the result of the ``blocking contact'' made with the zinc oxide surface by individual negative ions from the discharge. These regions behave as islands of high resistivity which can accept and retain electrostatic charge even when immersed in a relatively conducting sea of unaltered film material. The anomalous, or unexpectedly high, corona current is then attributed to an increase in conductivity of the corona gap resulting from additional ionization of the air near the charged zinc oxide resin film surface. This ionization is caused by localized high potential gradients in the vicinity of excess negative charges isolated on these islands, and the dissipation of these charges by light thus produces the observed photosensitive decrease in corona current. A comparison is made between the resistive island model and the model which constrains the pigment resin film to behave as a homogeneous insulator after electrostatic charging.
Lorentz Effect in Electron Diffraction Patterns of a Decomposing Gold-Nickel Alloy
Authors: De Keijzer A. A. , Burgers W. G.
Published: April 2005

Electron diffraction transmission patterns of a decomposing ferromagnetic supersaturated gold-nickel alloy show a Lorentz shift of the diffraction lines, which passes through a maximum for a certain decomposition state. It is probable that the maximum in the shift is determined by a maximum in the coercive force of the decomposing alloy.
Preparation of Single-Crystal Cobalt Ferrites from the Melt
Authors: Horn F. H.
Published: April 2005

Cobalt ferrites, Co3−xFexO4, particularly for x about or less than 2 are difficultly prepared as single crystal from the melt because they dissociate except at high partial pressures of oxygen. A two-step procedure is described for obtaining single-crystal cobalt ferrites from the melt at gas pressures of an atmosphere. The steps involve growth of a two-phase ``single crystal''—possible because of the congruency of the oxygen lattice of the coexisting oxides. The two-phase crystal is converted to the single-phase crystal by appropriate oxidation under conditions in which diffusion is rapid.
Measurements of the Output from a Ruby Laser with a Central Hole in One of the End Mirrors
Authors: Aagard R. L.
Published: April 2005

The average transmission of one of the Fabry-Perot mirrors in a ruby laser has been varied by changing the diameter of a hole in the center of one of the aluminum end coatings. Measurements of the output of the laser as a function of average transmission with fixed input energy show that the output is maximum for a particular value of transmission. The optimum transmission depends upon the input energy. A relationship between the optimum transmission and threshold for stimulated emission is shown.
Sources of Error in the Microwave Diagnostics of Plasmas
Authors: Warder R. , Brodwin M. , Cambel Ali Bulent
Published: April 2005

Errors in the microwave diagnostics of plasmas were investigated with the use of dielectric and conducting models. The results indicate that plasma property measurements utilizing reflection and transmission techniques are in considerable error for small samples and also that a planar analysis may not be used to infer the properties of a cylindrical plasma.