bluuebunny/crossref_metadata_2025 huggingface dataset:
ASYMMETRY OF SOUND VELOCITY IN STRATIFIED FORMATIONS
Authors: McCollum Burton , Snell F. A.
Published: January 2005

In the course of explorations of subsurface geology by the seismograph the authors have frequently observed the pronounced effect of stratification on the velocity of seismic waves in shales, and this effect has often been utilized in practical seismography. Recently an opportunity was afforded for securing additional quantitative data on the velocity normal to and parallel to the bedding planes. The paper points out that the velocity parallel to the planes of stratification is, in some instances, as much as fifty percent higher than the velocity in a direction normal to the bedding planes. It is shown also that inclined stratified beds exhibit a higher apparent point-to-point velocity when sound travels in an up-dip direction than when traveling down-dip. The paper describes a procedure whereby this effect may be utilized for determining the direction and approximate magnitude of the dip in such stratified deposits. The method has proved to be of considerable practical importance where the stratified formations are obscured by overlying deposits.
AN X-RAY SPECTROMETER WITH STATIONARY ION CHAMBER
Authors: Hergenrother Rudolf C.
Published: January 2005

A Bragg type ionization x-ray spectrometer which was designed for making quantitative measurements of integrated x-ray intensities reflected from crystals is described. The essential feature of the design is that the ionization chamber is fixed in position, thus allowing a short fixed connection between ion chamber and electrometer (Hoffman). The ion chamber and x-ray tube used with the instrument are described.
THE CALCULATION OF DETECTION PERFORMANCE FOR LARGE SIGNALS
Authors: Woods J. P.
Published: January 2005

It is mathematically proven that a detector tube which has a broken straight line for its plate current-grid voltage static characteristic will detect the standard radio signal without distortion, regardless of signal strength. The plate detection performance of a tube having a given curve for its static characteristic can be calculated from the extended power series which represents the characteristic. The power series analysis of the curve is obtained from a Fourier series analysis by a method which saves labor and is more accurate than the method of simultaneous equations. Thus, by using twelve or fifteen terms of the power series instead of only the first two or three, and by setting up special formulae, detection performance can be calculated for any signal strength and any modulation. The method is applicable to the tube alone, to a circuit containing the tube and external resistances, and may be applied to any similar non-linear receiving system.
MULTIPLE PEAKS IN SUPERSONIC INTERFEROMETRY
Authors: Hershberger W. D.
Published: January 2005

An improved circuit for use in supersonic interferometry in gases is described in which regeneration is under control and by the use of which the amplitude of the exciting e.m.f. may be varied between wide limits. Multiple peaks in the plate current maxima are observed, and several causes for such peaks, particularly the use of crystals having ``parasitic'' frequencies, are pointed out.
INFLUENCE OF HYDROGEN ION CONCENTRATION ON THE CRYSTAL STRUCTURE OF ELECTRODEPOSITED COBALT
Authors: Kersten H.
Published: January 2005

Cobalt crystallizes in the cubic and hexagonal systems. This paper shows by means of x-ray diffraction analysis, that cobalt electrodeposited from high pH (alkaline) sulphate solutions has a hexagonal structure which changes into a mixture of hexagonal and cubic, as the pH is decreased.
The Size and Size Distribution of Fog Particles
Authors: Houghton H. G.
Published: January 2005

An apparatus for the microscopic measurement of fog particles is described. The particles were collected on a slightly greased glass slide and viewed with the aid of dark-field illumination. The particle sizes were measured either visually with an eyepiece micrometer or, more usually, by the subsequent measurement of photomicrographs. With the aid of this apparatus a series of fog particle size distribution curves were obtained. These curves are characterized by a single maximum which always occurs at a particle diameter which is an integral multiple of 3.1 microns. The curves approach the axis asymptotically for large particle diameters but have a definite minimum. An explanation for this minimum on the basis of certain properties of the nuclei of condensation is offered.
Preliminary Note on a New Magnetometer
Authors: Heiland C. A.
Published: January 2005

A vertical magnetometer is described which is believed to fill the need for an intermediate type between the dip needle and the Schmidt balance. It does not require a tripod and levels itself. The compass for orienting remains attached to the instrument; it may also readily be compensated for temperature. It utilizes a magnetic system suspended in jewels in or near its center of gravity; the magnetic vertical intensity is balanced by the torsion of a helical spring. The magnetic system is adjusted to the normal vertical intensity in the area under survey by a suitable setting of the spring and the anomaly is roughly proportional to the angle of deflection from the horizontal.
Resistance-Temperature Relation of Beryllium Oxide and Zinc Oxide
Authors: Osteen John A.
Published: January 2005

Bidwell showed that the resistance-temperature law for certain variable conductors (oxides, etc.) was of the form ρ = AeQ/RT+aT. Plotted in the form (1/ρ)(dρ/dT) = Q/RT2−a he obtained for Fe2O3 straight lines with a break near the recalescence point, the two lines having the same y intercept but different slopes. This law was also followed by metallic germanium. The present paper extends this work to zinc oxide and beryllium oxide. Beryllium oxide yields a straight line showing a transition at 750°C. Zinc oxide yields two straight lines with a transition in the interval 250°C—500°C. The two zinc oxide lines have different slopes but the same y intercepts. With successive heatings to 1050°C there occurs continued decreases in the slope of the line for the 500°C—1000°C range but no change in the y intercept. The line for the range 0°C—250°C changes on successive heatings to 1050°C and finally stabilizes to a value of slope and intercept which repeats on succeeding runs. On the suggesion that the indicated transformation was due to impurity, new material of special purity prepared by the New Jersey Zinc Company was studied. The behavior of this material was found to agree closely with that of the earlier specimen but gave a more clean cut transformation.
Capillary Flow Through an Ideal Uniform Soil
Authors: Smith W. O.
Published: January 2005

An ideal soil is an assemblage of spheres packed to a definite porosity, and for statistical purposes may be represented by grains placed in hexagonal array, with adjacent grain centers equidistant and at a distance (2r+d), where r is the grain radius and d a spacing constant adjusted to suit the observed porosity. Three sets of capillaries, found to extend continuously throughout the packing, furnish the channels through which fluid crosses the soil body. The velocity through the mean capillary is calculated by a method essentially due to Slichter; and from this quantity, the sectional area of the mean capillary, and the number of capillaries per cm2, the quantity of fluid per sec., f, crossing a soil of section area s and length L, is found to be f=0.00809 (1−P)2/3 {0.9850/(1−P)2/3−1}2 ΔpD2s/ηLP is the porosity, D the diameter of the grains, η the viscosity of the fluid, and Δp the pressure difference under which the flow occurs. Intrinsic permeabilities computed from this equation are compared with values for carefully sized glass spheres and quartz sands observed experimentally by Green and Ampt. A further comparison with corresponding values calculated from Slichter's equation is given.
The Penetration of Hydrogen Through Steel at Four Thousand Atmospheres
Authors: Poulter Thos C. , Uffelman Lester
Published: January 2005

A study is made of the penetration of hydrogen through a very fine grained steel as compared to the usual grade of steel used in the construction of pressure equipment. The penetration is studied in specially constructed cylinders and found to take place at much lower pressure than had previously been recorded. The penetrating effect of hydrogen is observed at as low as 4000 atmospheres, whereas 9000 atmospheres is the lowest pressure previously recorded for this effect.
A Magnetostriction Oscillator Producing Intense Audible Sound and Some Effects Obtained
Authors: Gaines Newton
Published: January 2005

Apparatus is developed capable of pushing the magnetostrictive oscillation of nickel to the limit set by its mechanical strength. The intense audible sound produced is introduced under water from beneath the surface, continuous operation of the vibrator being secured by spray cooling. The interiors of corks are charred to cinder by the sound. A fountain 6 cm high forms on the surface of water, and is proved to be due to pumping action of the reciprocating rod and not to radiation pressure. Erosion of metals and of glass by cavitation and resultant water hammer is obtained. Colloids of oil and of carbon in water are produced. Curious fatigue effects in glass are observed. Whitened appearance and erratic motions of air bubbles released in water in the presence of the sound are observed, and theory is developed to explain these and the ``atomization'' of liquids. Flattening of a drop of liquid against a vibrator is observed and attributed to sonic attraction and to the reaction of sonic radiation. Frogs, fish, larvae, and water fleas are killed by the sound. Bacteria are killed so quickly that partial sterilization of milk in continuous process is effected. Striations in a Kundt tube that are parallel to its axis are produced, and an explanatory theory developed.
Ionization Time of Thyratrons
Authors: Snoddy L. B.
Published: January 2005

The ionization time for four types of commercial Thyratron tubes has been determined for the following cases: (1) impulsive voltage applied to the anode with the grid biased positively or negatively, (2) impulsive voltage applied to the grid with the anode potential constant, and (3) impulsive voltage applied to grid and anode simultaneously. The principal factors in fixing the ionization time are (1) the tube design; (2) the mercury vapor pressure (the time lag in starting is increased and made more erratic by decreasing the vapor pressure); (3) the grid bias (increasing the bias negatively increases the time lag); (4) the steepness of the wave front applied to the system. The lags become less as the rate of building up of voltage increases. This is due partly to the higher voltages reached and partly to the greater induced grid voltages when the impulse is applied to the anode. This effect is computed for two kinds of applied voltage waves. The time between grid and anode breakdowns was measured for an FG-41 and an FG-17. The grid and anode currents during this interval were computed. For the particular FG-41 used, ianode=3igrid. A table of ionization times under these various conditions is given for four Thyratron tubes (FG-17, 33, 41, 57).
General Properties of Steady Temperatures in Solids Partially Exposed to Gas
Authors: Churchill R. V.
Published: January 2005

Five general properties of steady temperatures in solids of arbitrary shape are derived here. Although the derivations are mathematical they depend almost solely on the very fundamentals of the mathematical theory of heat conduction. The solid has any portion of its surface held at a fixed temperature distribution and the rest exposed to gas. The rate of transfer of heat between gas and surface is assumed to be any function of the position of the point and the temperature of the surface, for a given state of the gas. For a fixed temperature this function is called the emissivity. Briefly stated, the important properties are: I. In two geometrically similar solids exposed to the same surface temperature conditions at corresponding points, except that their emissivities are inversely proportional to their sizes, the temperatures at corresponding points are equal. I(a). If the entire surfaces of two geometrically similar solids are given fixed temperature distributions the temperatures at corresponding points are equal everywhere if they are equal on the surfaces. II. An increase in the size of a solid causes the same temperature change as an increase in its emissivity. IV. An increase in the size of a solid causes an increase in the temperature at each point if the solid is receiving heat from the gas, and a decrease if the solid is losing heat to the gas. V. From Newton's law of surface heat transfer there follows a linear relation between the steady temperature at any point and the uniform temperatures of the gas and the fixed-temperature surface. These properties are discussed at the end of the paper. Some of the results of IV seem contrary to expected results.
The Converse Piezoelectric Effect in Mixed Crystals Isomorphous with Rochelle Salt
Authors: Bloomenthal Sidney
Published: January 2005

The temperature dependence of the piezoelectric strain constant d14 was investigated in mixed crystals isomorphous with Rochelle salt. Crystals oriented for utilization of Voigt's theory of the converse piezoelectric effect in the hemihedral class of the orthorhombic system were grown at constant temperature from supersaturated solutions of Rochelle salt containing isomorphous impurities C4H4O6Na NH4·4H2O or C4H4O6Na Tl·4H2O and measurements of the strain resulting from an applied electric field were made in the range 10 to 35°C. Hysteresis and saturation occur in the range of large piezoelectric activity where d14 evaluated from the straight portion of the strain curve is approximately 5 × 10−4 in both the pure salt and mixed crystal, a value several times as large as that reported from measurements of the direct effect in Rochelle salt. The critical temperature for a mixed crystal lies below that of pure Rochelle salt (25+273°K) and the shift observed compares favorably in magnitude with the value calculated from the dipole theory of dielectrics. The region in which d14 decreases to about 10−5 covers 3°C. The value of d14 diminishes further as the temperature is raised. d14 is defined as twice the change in length per cm length of a narrow crystal cut at 45° with the Y and Z axes when unit electrostatic field is applied in the X direction.
The Plastic Properties of Several Types of Unvulcanized Rubber Stocks at High Rates of Shear
Authors: Dillon J. H. , Johnston N.
Published: January 2005

An extrusion plastometer operating at rates of shear comparable with those existing in rubber tubing machines (10 to 1000 sec.−1) is described. The relation between efflux rate and pressure at constant temperature for various types of rubber stocks was determined. For highly compounded rubber stocks, such as tread stocks, the efflux rate vs. pressure curves attain linearity at low rates of shear. Both the slope of the curves and the extrapolated pressure intercept vary rapidly with the temperature, indicating that both the mobility and the yield stress are functions of temperature for highly compounded stocks. For lightly compounded stocks and for crude rubber, the curves are of the power function type at the lower rates of shear, but appear to attain linearity at the very high rates. These linear portions of the curves, for a given stock at different temperatures, are approximately parallel. Elastic recovery was determined as a function of rate of efflux. The slope of the recovery vs. efflux rate curves decreases with increasing rates of efflux. The relation between efflux rate at constant temperature and pressure, and time of milling, is approximately linear. The extrusion plastometer is shown to be more sensitive to overmilling than is the Williams plastometer. The partial failure of the compression-type plastometer to correlate with the factory extrusion machine is explained on the basis of the much lower rates of shear employed in the compression-type instrument than those existing in the extrusion machine.
Progress Report on the Determination of Absolute Viscosity
Authors: Coe J. R.
Published: January 2005

An apparatus designed for the precise measurement of absolute viscosity is described. The liquid being studied is caused to flow from one reservoir through a capillary tube into a second reservoir, the pressure difference between the two being measured with a differential manometer. Various rates of flow are caused by injection of mercury into the upstream reservoir from a cylinder by means of a uniform piston driven at constant speed by a synchronous motor through a gear train. A number of interchangeable capillaries of different bore diameters and lengths can be employed. The displacement apparatus and the viscometer are thermostated in baths designed for precise temperature control. A machine designed and built to lap the bores of capillaries into right circular cylinders is described.
Fluctuation Noise Due to Collision Ionization in Electronic Amplifier Tubes
Authors: Ballantine Stuart
Published: January 2005

Ions formed by collision in electronic amplifier tubes move toward the cathode and control-grid and produce momentary increases in the space-charge limited current (current pulses). These current pulses are random in time and produce fluctuation noise analogous to the shot-effect. An approximate theory is presented, applicable to cathodes of large diameter (ca. 0.1 cm). Both the noise and the increase in the average value of the electron current due to the presence of ionization are calculated in terms of the ``size of the elementary event'' or the integral of the current pulse. It is not feasible to calculate the latter directly but it may be evaluated indirectly by measurements of the increase of average current. The noise calculated from the values so obtained and from the ionization probability data of Smith, Bleakney and Tate is in close agreement with that observed experimentally. The production of noise in tubes with oxide cathodes containing mercury vapor, argon and the gases naturally evolved from the electrodes and tube walls is investigated experimentally as affected by pressure and electron current density. In the case of a tetrode containing mercury vapor or evolved gases the variation with pressure is linear up to 10−3 mm; in the case of argon the noise varies as the 1.1 power of the pressure. In the mercury vapor tetrode a variation as the 3/2 power of the plate current was found, as compared to a 5/3 law, expected theoretically. These measurements were made at 620 kilocycles. The noise per frequency interval was measured as a function of frequency over the range 500–1500 k.c. At pressures of the order of 10−4 mm in mercury vapor a decrease at the higher frequencies was observed; with argon the noise was uniform. With mercury vapor at higher pressures (ca. 4×10−3) the noise spectrum became peaked, the frequencies of the peaks depending upon the electron current flowing (electrode potentials). The hypothesis that these peaks are due to oscillations of positive ions in the potential trough surrounding the cathode is in accord with the principal experimental facts. With further increase in pressure continuous oscillations are produced, sustained apparently by a regenerative action of the space charge upon the oscillating ions. The frequencies of these oscillations are affected only by the electrode potentials and not at all by the external electrical circuit.
An Extension of a Maxwell Mutual-Inductance Formula to Apply to Thick Solenoids
Authors: Dwight H. B. , Chen S. H.
Published: January 2005

The formula for the mutual inductance of two concentric solenoids which is used probably more than any other is the one originally given by Maxwell. Since the solenoids were taken to have negligible thickness in the above formula and since the effect of the thickness is often appreciable in practical cases, additional terms to give the effect of the thickness have been calculated and are presented in this article.
Mosaic Crystals of Zinc
Authors: Schilling Harold K.
Published: January 2005

Optically mosaic crystals of zinc have been grown by the Czochralski-Gomperz method. Three types have been distinguished. During growth mosaic crystals frequently change from one type to another. The conditions of growth under which they were obtained are described briefly. As yet their genesis and their evolutions during growth cannot be controlled or predetermined.
The Effect of Nascent Hydrogen on the Magnetic Properties of Iron
Authors: Reber R. K.
Published: January 2005

Hydrogen was electrolyzed into flat ring cathodes of magnetically soft iron in 0.5 N solutions of H2SO4 or of KOH. The design of the electrolytic cell permitted magnetic testing at intervals. Magnetic hardening began after many hours provided the electrolytic current density was kept above a lower limit depending on the electrolyte. This hardening proceeded, at adequate current density, to an end point beyond which longer charging at any current density rarely produced any further changes in magnetic properties. Removal of hydrogen by storage in air at room temperature for 5 months, or by annealing at 400°C in vacuum for 17 hours, did not diminish the magnetic hardness produced during electrolysis. It is suggested that the iron is locally cold-worked by non-uniform distribution in it of hydrogen in excess of the solubility limit at room temperature, and that uniformly distributed hydrogen up to this limit has very little effect on the ferromagnetic properties.
Viscometric Studies of Rubber Solutions
Authors: Reiner Markus
Published: January 2005

Support for the assumption that rubber particles in rubber-toluene solutions are solvated unordered aggregates is derived from a quantitative study of viscometric measurements, which shows that the forces acting between the primary particles (structural elements) must be very small.
The Electrical Conductivity of Glass Part II. Current Increase Phenomena with Highly Resistant Layers
Authors: Kiehl H. R.
Published: January 2005

With the production of certain types of highly resistant layers in some glasses, increases of current with time are observed, similar to those reported qualitatively by several earlier investigators. The nature of these current increases have been studied quantitatively and found to follow, for the cases here studied, the relationship, log (Im—It) =log a1—b1t, where Im is the maximum value of the current, It is the current at any time t after application of the field, and a1 and b1 are constants. The time T for the current to reach its maximum value seems related to the applied voltage by the equation T=K1/V—K2. The values of the constants K1 and K2 seem to decrease with increase in temperature. The time for the current to reach its maximum value decreases rapidly with increase in glass temperature. The possible importance of the phenomena observed in an explanation of the processes involved in the conductivity of glass is suggested, and the need for further investigation is emphasized. No theoretical explanation is given because of the apparent necessity for further investigations.
Dielectric Recovery of a.c. Arcs in Turbulent Gases
Authors: Browne T. E.
Published: January 2005

It is pointed out that arc extinction in modern high voltage alternating-current circuit interrupters is actually achieved by subjecting the confined arc to a turbulence-producing gas blast, thus accelerating the arc's dielectric recovery near current zero. Experiments to investigate the effects of gas velocity, gas composition, arc current magnitude, and constriction of the arc space upon the rate of recovery of dielectric strength by the arc near current zero are described. Results of these experiments show that most of the dielectric recovery occurring in a turbulent arc space within a hundred or so micro-seconds of current zero takes place before the actual moment of zero current. With a 600-ampere confined arc in carbon dioxide, it was found that the dielectric strength at current zero could be increased from 100 to 215 volts per centimeter by increasing the gas velocity from 35 to 110 meters per second. Dielectric recovery continued after current zero at about 25 volts per centimeter per hundred micro-seconds, and was nearly independent of gas velocity. A reduction in distance between confining walls from 1.9 cm to 0.635 cm resulted in a one-third increase of dielectric strength at current zero and a 100 percent increase in rate of recovery subsequent to current zero. Decreasing the arc current from 600 to 200 amperes resulted in a 120 percent increase in dielectric strength at current zero and an eight-fold increase in subsequent rate of recovery. In various gases, the comparative results for a 600-ampere arc are given in the table. These results are analyzed from the standpoint of recent theory.
The Viscosity of Undercooled Liquid Glucose
Authors: Parks George S. , Barton Lois E. , Spaght Monroe E. , Richardson J. Wilfred
Published: January 2005

The viscosities of undercooled liquid glucose have been extensively studied by three very different methods. Between 145° and 80° about eighty determinations have been made by the falling sphere method; between 80° and 32° seventy-five determinations have been carried out by a concentric cylinder method; and between 34° and 22° thirty samples have been measured by a cylinder torsion method. A series of ``best values,'' ranging from 5.6 poises at 145° to 9.1(10)13 poises at 22°C, have been tabulated from these results. They represent ``true'' viscosities and not plasticities. That the viscosities of the glucose depend very much upon the history of the sample and its mode of preparation has been shown by several experiments. From a consideration of the variation of the viscosity with the reciprocal of the absolute temperature some ``disorientation'' energy values have been derived. These are much larger than the formal heat of fusion of glucose and indicate considerable association.
Some Rheologic Aspects of Petroleum Production
Authors: Loomis A. G. , Ambrose H. A. , Kennedy H. T.
Published: January 2005

A critical review and summary are given of some of the rheological aspects of the production and transportation of petroleum. It is shown how the proper flow characteristics of the colloidal dispersions known as drilling fluids may be controlled by chemico-physical methods, and the importance of these characteristics in the technique of drilling is analyzed. The laws of flow of gas-oil mixtures through porous media are approached by a study of the permeability factor of such media, and applied to the problems of ultimate production, production rate, effective drainage area, etc., of petroleum-producing horizons. The flow of gas-liquid mixtures through pipes is discussed from the standpoint of bringing oil to the surface from the reservoir. Pipeline flow of oil is discussed with particular reference to cold weather flow for oils that exhibit thixotropic properties because of a heavy content of wax. Unsolved problems in these various fields of the rheology of petroleum production are pointed out.
The Potential Distribution Between Parallel Plates and Concentric Cylinders Due to Any Arbitrary Distribution of Space Charge
Authors: Cady W. G.
Published: January 2005

Equations are derived for the electric potential and field intensity due to a distribution of space charge in a slab of dielectric between two infinite parallel conducting plates. The charge density may be any integrable function of the coordinate perpendicular to the plates. The corresponding solution for concentric cylinders is also given. A number of special cases are discussed, including that of a uniformly distributed charge, and one of sinusoidal distribution. The latter has an application in the theory of the piezoelectric resonator.
Potential Distributions About an Infinitely Extended Line Electrode on the Surface of a Horizontally Stratified Earth. II
Authors: Muskat Morris
Published: January 2005

The analytical theory is given for the potentials and gradients to be found on the surface of a horizontally stratified earth in which the current source is an infinitely extended cable or line electrode lying on the surface. Power series expansions in the distance from the electrode are derived for small distances and asymptotic expansions for large distances. Detailed treatments are given for the two layer earth, for all thicknesses of the surface layer, and for the three layer earth in which the thickness of the second layer either equals or is twice as great as that of the surface layer, as well as formal expansions for general many layered earths. Simple closed hyperbolic function expressions are derived for the surface gradients for three layer systems in which the lowest layer is either of infinite or zero conductivity. The solution for the direct interpretation problem in which the continuous vertical conductivity variation may be determined from a knowledge of the surface gradients is briefly outlined, following the method of Slichter and Langer for the case where the current source is a point electrode. The analytical results of the indirect interpretation problem for a stratified earth are illustrated by thirty numerical and graphical examples.
Shot Effects of Secondary Electron Currents
Authors: Hayner Lucy J.
Published: January 2005

The shot effect of secondary electron currents from plates of triode tubes was measured at 105 cycles. Calculations of the electronic charge from shot effects of temperature-limited primary currents, to check the method, agreed with Millikan's value within 1 percent. Measurements were made on five tubes having different secondary emissivities. The average number of secondaries per primary electron, ω, ranged from 1 to 4.5. The variation of ω with energy of the primaries is shown to agree qualitatively with existing theory. In every case the shot effects of both grid and plate currents were measured. Campbell's general expressions for the shot effect of secondary emission plate currents were extended to grid currents. From the observed differences between grid and plate shot effects it is concluded that secondary emission and primary impact are simultaneous within 10−6 second or less. The large shot effects found at high values of ω are correlated with the fluctuations of ω from one impact to another. A qualitative analysis of secondary emission processes shows that, from these data, information can be obtained as to the number of reflected primary electrons and the number of primaries which emit no secondaries. The results obtained are in reasonable agreement with data obtained by other methods.
The Effect of Changes in the Equilibrium Relative Vapor Pressure Upon the Capillary Structure of Wood
Authors: Stamm Alfred J.
Published: January 2005

Measurements have been made of the equilibrium permeabilities of softwoods to air of different relative vapor pressures. Transverse sections less than the average fiber length in thickness, in which the open cavities account for practically all of the permeability, show practically no change in permeability with changes in the equilibrium relative vapor pressure. Sections thicker than the maximum fiber length, the permeabilities of which are dependent upon the size of the pit openings, show an increase in permeability with a decrease in equilibrium relative vapor pressure. When the square root of the permeability is plotted against the moisture content of the wood in equilibrium with the various relative vapor pressures of air, practically a linear relationship is obtained from 0 to 20 percent moisture content. At higher moisture contents the permeabilities are considerably less than the linear relationship calls for. This is due to films of water forming across the capillaries. Higher pressures than those used are required to overcome the effect of the surface tension of the water in these capillaries. A new means of determining the distribution of size of openings in a porous membrane based on these findings is given.
A Method for Measuring the Pressure in a Rubber Extruding Machine
Authors: Dillon J. H. , Torrance P. M.
Published: January 2005

A method for measuring the pressure exerted by rubber on the walls of the die of a tubing machine is described. An extrusion plastometer was used in these pressure measurements and the results obtained were employed in correlating the plastometer with a tube tubing machine. This was accomplished by determining the isothermal curve of efflux rate vs. pressure for the tubing machine and comparing with that for the extrusion plastometer. The measured values of the pressure at various speeds and temperatures of extrusion should be of value in the design of new types of extruding machines.
Rheological Properties of Asphalt II. Discussion of Penetration-Viscosity Relationships
Authors: Traxler R. N. , Pittman C. U. , Burns F. B.
Published: January 2005

Although a simple exponential type of equation such as that given by Saal and Koens may give an approximation suitable for many practical purposes, it does not relate the viscosity and penetration of asphalts with the accuracy warranted by the experimental data. An accurate correlation would require a much more complicated equation which would be of doubtful practical value. Asphalts obtained from different sources or those prepared or processed differently require distinctly characteristic constants in the equation proposed by Saal and Koens. This is true no matter whether the change in consistency is due to variations in the temperature of testing or in the method or extent of processing. An asphalt brought to a given penetration by regulating the temperature does not necessarily have a viscosity identical with that of the same type of asphalt having that penetration at a different temperature.
Ostwald Viscometers for Petroleum Oils
Authors: Willihnganz Eugene
Published: January 2005

A series of modified Ostwald viscometers is described. They are shown experimentally to have a time of flow that is proportional to the kinematic viscosity when they are used with petroleum oils of a viscosity between 2.17 and 1280 centistokes.
The Coercive Force of Magnetite Powders
Authors: Gottschalk V. H.
Published: January 2005

The coercive force of magnetite powder is increased by mere mechanical grinding. Measurements on sized powders of one natural and one artificial magnetite give a linear relation between coercive force and mean specific surface of the grains. It is suggested that this relation between coercive force and specific surface may prove to be important in deciding between theories of ferromagnetism.
Some Physico-Mathematical Aspects of Nerve Conduction. II
Authors: Rashevsky N.
Published: January 2005

In continuation of a previous paper, the equation of propagation of a nerve impulse is studied now under more general assumptions about the physical mechanism of excitation. Instead of H. A. Blair's excitation formula, used previously, a more general formula, proposed by the author elsewhere and having several advantages, is considered. It is found in this case, that the velocity of propagation is not strictly constant, but tends asymptotically to a constant value. This asymptotic value is reached practically within 10−3 sec. after the propagation of the impulse begins, and the initial velocity is only slightly different from the asymptotic value. The expression for this asymptotic value is in the first approximation identical with the expression deduced previously, and inasmuch as the latter was found to agree with experimental data, the same remains in the present case.
An Application of Infrared Spectroscopy to Rubber Chemistry
Authors: Williams Dudley
Published: January 2005

The applicability of infrared methods to some problems arising in the chemistry of rubber has been demonstrated. The spectra of isoprene, styrene, polymerized butadiene, and several types of rubber have been studied and certain variations in the 5.5μ—6.5μ regions are attributed to changes occurring during the processes of polymerization. The effects of vulcanization also appear in the spectra of the rubber samples. The methods of infrared analysis do not necessitate the use of solutions of rubber compounds in carbon tetrachloride or carbon disulphide as in the case of previous Raman work.
Note on Heat Effects in Capillary Flow
Authors: Hersey Mayo D.
Published: January 2005

Approximate mathematical solutions are given for the temperature distribution over the cross section of a capillary tube under two extreme conditions, (1) complete adiabatic flow, and (2) thermal equilibrium. By complete adiabatic flow is meant an ideal condition in which there is no heat conduction although sufficient time has elapsed since the beginning of flow to permit any particle of the fluid to travel the entire length of the tube. By thermal equilibrium is meant, in the present connection, a steady state in which the heat due to viscous resistance is conducted radially outward as fast as it is generated. In each case the mean temperature rise at efflux is calculated by integration. In the case of thermal equilibrium, formulas are also given for the decrease in apparent viscosity due to heat effects with increasing rate of flow.
Some Special Solutions for the Motion of the Powder Gas
Authors: Kent R. H.
Published: January 2005

An important error in Pidduck's special solution is pointed out. Special solutions for a perfect and an imperfect gas are obtained. Modifications to take account of projectile friction and the burning of the powder are given.
Cyclic-N3. II. Significant geometric phase effects in the vibrational spectra
Authors: Babikov Dmitri , Kendrick Brian K. , Zhang Peng , Morokuma Keiji
Published: January 2005

An accurate theoretical prediction of the vibrational spectra for a pure nitrogen ring (cyclic-N3) molecule is obtained up to the energy of the A22/B12 conical intersection. A coupled-channel approach using the hyperspherical coordinates and the recently published ab initio potential energy surface [D. Babikov, P. Zhang, and K. Morokuma, J. Chem. Phys. 121, 6743 (2004)] is employed. Two independent sets of calculations are reported: In the first set, the standard Born–Oppenheimer approximation is used and the geometric phase effects are totally neglected. In the second set, the generalized Born–Oppenhimer approximation is used and the geometric phase effects due to the D3h conical intersection are accurately treated. All vibrational states are analyzed and assigned in terms of the normal vibration mode quantum numbers. The magnitude of the geometric phase effect is determined for each state. One important finding is an unusually large magnitude of the geometric phase effects in the cyclic-N3: it is ∼100 cm−1 for the low-lying vibrational states and exceeds 600 cm−1 for several upper states. On average, this is almost two orders of magnitude larger than in the previously reported studies. This unique example suggests a favorable path to experimental validation.
Polarization effects and charge separation in AgCl-water clusters
Authors: Godinho S. S. M. C. , Cabral do Couto P. , Costa Cabral B. J.
Published: January 2005

Structural, energetic, vibrational, and electronic properties of salt ion pairs (AgCl and NaCl) in water (W) clusters were investigated by density functional theory. In agreement with recent theoretical studies of NaCl-water clusters, structures where the salt ion pair is separated by solvent molecules or solvent separated ion pair (SSIP) were found in AgCl–W6 and AgCl–W8 aggregates. Our results indicate that for small AgCl-water clusters, contact ion pair (CIP) structures are energetically more stable than SSIP, whereas an opposite tendency was observed for NaCl-water clusters. In comparison with CIP, SSIP are characterized by extensive electronic density reorganization, reflecting enhanced polarization effects. A major difference between AgCl-water and NaCl-water CIP aggregates concerns charge transfer. In AgCl-water CIP clusters, charge is transferred from the solvent (water) to the ion pair. However, in NaCl-water CIP clusters charge is transferred from the ion pair to the water molecules. The electronic density reorganization in the aggregates was also discussed through the analysis of electronic density difference isosurfaces. Time dependent density functional theory calculations show that upon complexation of AgCl and NaCl with water molecules, excitation energies are significantly blueshifted relative to the isolated ion pairs (∼2 eV for AgCl–W8 SSIP). In keeping with results for NaI-water clusters [Peslherbe et al., J. Phys. Chem. A 104, 4533 (2000)], electronic oscillator strengths of transitions to excited states are weaker for SSIP than for CIP structures. However, our results also suggest that the difference between excitation energies and oscillator strengths of CIP and SSIP structures may decrease with increasing cluster size.
Electronic structure of the calcium monohydroxide radical
Authors: Taylor Caroline M. , Chaudhuri Rajat K. , Freed Karl F.
Published: January 2005

Effective valence shell Hamiltonian Hv calculations are used to map out three-dimensional potential energy surfaces for the 12 lowest electronic states of the CaOH radical. Excitation energies and spectroscopic constants are compared with experiment and prior computations where available, but many previously unavailable data are provided, including excited state dipole moments and oscillator strengths. Particular attention is paid to clarify the nature of nonlinear and quasilinear excited states, Renner-Teller couplings, and state mixings. The F̃ 2Π and G̃ 2Π (6 2A′ and 8 2A′) states are both found to possess nonlinear local minima, due to an avoided crossing. Attention is also focused on the characteristics of basis sets necessary in high-accuracy calculations for the CaOH radical.
Growth and properties of AlGaInP resonant cavity light emitting diodes on Ge∕SiGe∕Si substrates
Authors: Kwon O. , Boeckl J. , Lee M. L. , Pitera A. J. , Fitzgerald E. A. , Ringel S. A.
Published: January 2005

Visible AlGaInP resonant cavity light emitting diodes (RCLEDs) were grown by molecular beam epitaxy and fabricated on low-dislocation density, SiGe∕Si metamorphic substrates. A comparison with identical devices grown on GaAs and Ge substrates shows that not only did the RCLED device structure successfully transfer to the SiGe∕Si substrate, but also a higher optical output power was obtained. This result is attributed to enhanced lateral current spreading by the low residual dislocation density (∼1×106cm−2) network within the virtual Ge substrate and the superior thermal conductivity of the underlying Si wafer. In addition, the growth of an AlGaAs current spreading layer and a modified top metal contact were incorporated in the RCLED on SiGe to optimize device performance. The measured electroluminescent output power was 166μW at a 665nm peak wavelength under 500mA current injection. Extremely narrow electroluminescence linewidths were achieved with a full width half maximum value of 3.63nm under 50mA current injection. These results demonstrate great promise for the monolithic integration of visible band optical sources with Si-based electronic circuitry.
Investigation of phase-separated electronic states in 1.5 μm GaInNAs∕GaAs heterostructures by optical spectroscopy
Authors: Sun H. D. , Clark A. H. , Calvez S. , Dawson M. D. , Gilet P. , Grenouillet L. , Million A.
Published: January 2005

We report on the comparative electronic state characteristics of particular GaInNAs∕GaAs quantum well structures that emit near 1.3 and 1.5 μm wavelength at room temperature. While the electronic structure of the 1.3 μm sample is consistent with a standard quantum well, the 1.5 μm sample demonstrate quite different characteristics. By using photoluminescence (PL) excitation spectroscopy at various detection wavelengths, we demonstrate that the macroscopic electronic states in the 1.5 μm structures originate from phase-separated quantum dots instead of quantum wells. PL measurements with spectrally selective excitation provide further evidence for the existence of composition-separated phases. The evidence is consistent with phase segregation during the growth leading to two phases, one with high In and N content which accounts for the efficient low energy 1.5 μm emission, and the other one having lower In and N content which contributes metastable states and only emits under excitation in a particular wavelength range.
Near-edge x-ray absorption fine-structure study of ion-beam-induced phase transformation in Gd2(Ti1−yZry)2O7
Authors: Nachimuthu P. , Thevuthasan S. , Shutthanandan V. , Adams E. M. , Weber W. J. , Begg B. D. , Shuh D. K. , Lindle D. W. , Gullikson E. M. , Perera R. C. C.
Published: January 2005

The structural and electronic properties of Gd2(Ti1−yZry)2O7 (y=0–1) pyrochlores following a 2.0-MeV Au2+ ion-beam irradiation (∼5.0×1014Au2+∕cm2) have been investigated by Ti2p and O1s near-edge x-ray absorption fine structure (NEXAFS). The irradiation of Gd2(Ti1−yZry)2O7 leads to the phase transformation from the ordered pyrochlore structure (Fd3m) to the defect fluorite structure (Fm3m) regardless of Zr concentration. Irradiated Gd2(Ti1−yZry)2O7 with y⩽0.5 are amorphous, although significant short-range order is present. Contrasting to this behavior, compositions with y⩾0.75 retain crystallinity in the defect fluorite structure following irradiation. The local structures of Zr4+ in the irradiated Gd2(Ti1−yZry)2O7 with y⩾0.75 determined by NEXAFS are the same as in the cubic fluorite-structured yttria-stabilized zirconia (Y–ZrO2), thereby providing conclusive evidence for the phase transformation. The TiO6 octahedra present in Gd2(Ti1−yZry)2O7 are completely modified by ion-beam irradiation to TiOx polyhedra, and the Ti coordination is increased to eight with longer Ti–O bond distances. The similarity between cation sites and the degree of disorder in Gd2Zr2O7 facilitate the rearrangement and relaxation of Gd, Zr, and O ions∕defects. This inhibits amorphization during the ion-beam-induced phase transition to the radiation-resistant defect fluorite structure, which is in contrast to the ordered Gd2Ti2O7.
A high-pressure scanning tunneling microscope for studying heterogeneous catalysis
Authors: Rößler M. , Geng P. , Wintterlin J.
Published: January 2005

We describe an experimental setup for studying gas adsorption and chemical surface reactions by scanning tunneling microscopy (STM) at gas pressures ranging from ultrahigh vacuum (UHV) to 1bar. The apparatus is designed for experiments to bridge the so-called pressure gap in catalysis research by obtaining atomic scale information about catalytic reaction mechanisms under steady-state conditions. It combines a UHV chamber for sample preparation and post-reaction surface analysis with a small high-pressure cell (volume 1.5l) which contains the STM. Several concepts to improve the variable-pressure performance of existing high-pressure STM designs are described. These include access to the entire pressure range between UHV and 1bar without triggering gas discharges, the potential for high-speed scanning and for variable temperature measurements. The design also features a fast transfer mechanism from the reactor to UHV, thus allowing for fast analysis of surface species after high-pressure experiments. First results with atomic resolution were obtained on a Ru(0001) surface at high oxygen pressures. The images show an O(1×1) adsorbate layer not observed in UHV experiments at room temperature.