bluuebunny/crossref_metadata_2025 huggingface dataset:
Studies in Lubrication V. The Theory of the Thick Film Lubrication of Flooded Journal Bearings and Bearings with Circumferential Grooves
Authors: Muskat M. , Morgan F.
Published: January 2005

The successive approximation theory for the thick film lubrication of flooded journal bearings and bearings with circumferential grooves is developed through the fourth approximation, that is, including the fifth power of the journal eccentricity. The analysis applies to bearings of arbitrary length, the boundary conditions at the ends of the bearings being satisfied rigorously. It is found that the journal eccentricities and friction coefficients, for fixed Sommerfeld variable, are greater for bearings of finite length than for that of infinite length, the difference increasing with decreasing bearing length. On the other hand the load-carrying capacities, for fixed eccentricity, of the bearings of finite length are much less than that for the infinitely long bearing. The general theory for the bearing with a central circumferential groove is also developed and it is shown that the only hydrodynamic effect of such a groove is to cut the bearing into two separate end fed bearings, each of half the original bearing length. The load-carrying and friction properties of these end fed bearings are identical with those of flooded bearings of the same length. The main advantages of such grooving must lie in the maintenance of the lubricant viscosity by the cooling effect of the lubricant flow and in overcoming the negative pressures and possible film rupture that would develop in a flooded bearing without internal lubricant sources.
Phosphorescence of Zinc Silicate Phosphors
Authors: Fonda Gorton R.
Published: January 2005

At low contents of the manganese activator, the decay of phosphorescence takes place in two stages. The initial stage is exponential. It is complete in less than 0.1 second and is not affected by temperature. The second stage is at a much lower intensity level. It becomes noticeable after 0.03 second and persists for more than an hour. Its speed of decay increases with temperature. At − 196°C it is completely latent. A change in the intensity of the exciting light alters proportionally the luminescence caused by each stage of decay and has no effect upon the shape of the decay curves.

About fifty times as many electrons are involved in the second stage of decay as in the first. It is assumed that the second stage is caused by the retention of electrons in a metastable state, probably one associated with the presence of lattice imperfections. The exponential decay of the first stage would result from the recombination of manganese ions, relatively in excess, with those free electrons which had not been captured in the potential cups of the metastable state.

The decay of phosphors rich in manganese is always very abrupt and at a speed which rises rapidly with increase in temperature. The course of decay can be represented by the expression p−x=a+bt except at reduced temperatures where the two stages of decay characteristic of low manganese content are observable.
The Reignition of Short Arcs at High Pressures
Authors: Cobine J. D. , Power R. B. , Winsor L. P.
Published: January 2005

An investigation has been made of the reignition of short a.c. arcs in air at pressures from one to eight atmospheres, for currents less than 3.25 amperes (and with a resistance circuit). Pure graphite electrodes were used and were separated by a distance of 1 mm. The reignition voltage under these conditions increases with pressure and decreases as the current is increased. The characteristic of reignition potential vs. current has been found to exhibit a discontinuity at a critical current. For this current the reignition potential decreases by about 1000 volts to a new characteristic typical of the higher currents. This critical current increases with the gas pressure to a maximum of 2.25 amp. As the r.m.s. current is increased from low values to values near the critical, the number of cycles during which the reignition potential has the value given by the higher characteristic decreases. For currents equal to, or greater than the critical value, only the low reignition potentials are obtained. This transition is accompanied by an increase in the burning voltage of the arc.
The Dielectric Strength of Benzene and Heptane
Authors: Dornte Ralph W.
Published: January 2005

The dielectric strengths at 25°C of benzene and of heptane in a uniform electric field produced with a sphere gap and of heptane in a non-uniform field between concentric cylinders, were measured on the pure filtered liquids and with rigorous control of the electrode surface. With any one experimental procedure, the breakdown gradients were reproducible to within 5 percent provided all variables were carefully controlled. The most important of these variables, the character of the electrode surface, is influenced by such factors as the degree of polish or etching, adsorbed gas or ions, and the gases dissolved in the electrodes. Adsorbed oxygen or hydrogen, for example, induces incipient discharges in either liquid with molybdenum electrodes, but not in heptane with nickel electrodes; in the latter case, the gas adsorbed on the electrodes slightly increases the breakdown gradient. Below one atmosphere, the dielectric strengths of benzene and heptane are independent of the pressure. In a non-uniform field, the dielectric strength of heptane is the same for a.c. and d.c. of either polarity. Although reproducible dielectric strengths were obtained by any one experimental procedure, the results from different procedures varied from 100 to 1700 kv (Peak)/cm. It appears, therefore, that the dielectric strengths of pure liquids depend primarily on the nature of the electrode surface which varies with the experimental procedure.
The Effects of Irradiation, Humidity and Sphere Material on the Sparkover Voltage of the Two-Centimeter Sphere Gap
Authors: Lewis Arthur B.
Published: January 2005

Data have been obtained on the sparkover voltage of the two-centimeter sphere gap set at a gap of 4 mm (10.3-kv peak) showing that: (1) The effect of irradiation is to reduce the sparkover voltage by approximately 2.5 percent from its unirradiated value and to decrease the scattering of individual observations by a factor of about four. This irradiation effect is readily saturated by an open, coredcarbon, arc at 50 cm from the gap. (2) The effect of humidity, which is apparently independent of the sphere material for the five metals used here, is to increase the sparkover voltage by +0.13 percent per mm (of mercury) increase in vapor pressure of the water in the atmosphere. (3) There seems to be no choice between the metals used for spheres (aluminum, brass, chromium, nickel and steel) so far as repeatability of results is concerned, the probable error of a day's results averaging ±0.28 percent. This probable error can be largely if not wholly accounted for in terms of known sources of uncertainty. (4) The final sparkover voltages for the various metals, even when corrected to the same humidity, differ from each other by far more than can be accounted for by any definitely recognized source of uncertainty.
The Lack of ``Sucking'' Action by the Cathode Blast of Mercury Vapor in a Pool Rectifier
Authors: Tonks Lewi
Published: January 2005

In the all-glass mercury arc rectifier Hg vapor streams from the cathode pool past the side arms into the condensing dome. Experiments of von Engel and Steenbeck offer indirect evidence that this blast of vapor reduces the mercury vapor pressure in the side arms to as little as 116 of that in the dome. Direct measurements of vapor pressure have been made using ionization gauges on a side arm and on the condensing dome and using thermocouples on the rectifier wall at the condensation edge and on the dome. Both free and anchored cathode spots were used. No trace of ``sucking'' action was found. The theory of the Bernoulli Effect applied to this case gives a maximum possible reduction of pressure below that in the dome of 50 percent.
Temperature Dependence of Diamagnetism in Gamma-Brasses
Authors: Lane C. T.
Published: January 2005

A series of measurements on the temperature dependence (20–700°C) of the diamagnetic susceptibility of several gamma-phase brasses are reported. At room temperature the susceptibility is a linear function of composition, in agreement with previously reported work. At higher temperatures, however, this linearity no longer holds, the departure being greater at the higher temperatures. At the copper-rich end of the phase the susceptibility increases with temperature, while at the zinc-rich end the reverse is true, and the susceptibility is sensibly constant near the theoretical composition Cu5Zn8. The bearing of these results on the Bloch theory of metals is discussed.
The Cathode Region in the Glow Discharge
Authors: Brewer A. Keith , Westhaver J. W.
Published: January 2005

The present study of the cathode region in the glow discharge is divided into three sections: I. The range of the electrons in the negative glow. II. Positive ion formation in the Crookes dark space. III. Energy of the electron entering the negative glow. I. The length of the negative glow and the drop in potential across the Crookes dark space have been measured simultaneously for various gases over a wide current and pressure range. The observed lengths correspond exactly to the range of electrons as determined by Lehmann for voltages equivalent to the cathode potential drop. From this it is concluded that the energy of the electrons entering the negative glow must correspond to the entire difference in potential across the dark space. II. The length of the Crookes dark space has been measured under various conditions and the values obtained compared with the mean free path between ionizing collisions as given by Tate and Smith. The number of positive ions found in the dark space per electron of current has been computed by making use of Aston's equation for the potential distribution and Tate's values for the efficiency of ionization as a function of voltage. The number of positive ions so computed is, in general, materially less than one per electron; this contrasts sharply with from 50 to 100 estimated by some investigators. III. The energy distribution of the electron entering the negative glow has been measured by the deflection method, a nonhomogeneity of velocity in the electron beam being discernible by an elongation of the fluorescent spot on a Willemite screw. No change in the shape of the spot was detected for the electrons leaving the dark space although an elongation of it was observed for electrons in the negative glow. The experimental arrangement was such that fluctuations in voltage of more than 10 percent could have been observed. The general conclusion to be drawn from these studies is that the energy of the electrons entering the negative glow corresponds closely to the entire cathode potential drop, and that only a small fraction of the energy of the electrons leaving the cathode is expended in the Crookes dark space. A possible mechanism for the cathode region is briefly outlined.
A Characteristic of the Copper Arc During the Formative Period
Authors: Betz Paul L. , Karrer S.
Published: January 2005

This paper gives the results of an investigation of the voltage characteristic of the copper arc in air during the process of arc formation. A pair of copper electrodes, initially in contact and carrying current, were separated and the voltage arising across the arc gap was studied. Cathode-ray oscillograms indicate that at the instant of contact separation there develops across the gap a voltage of about 12.2 volts. This voltage was attained in less than 10−5 seconds. This rapidly developed voltage was found to be independent of arc current for current values up to 100 amperes, which suggests that the rapidly developed initial voltage corresponds to the cathode fall of the arc.
The Electrical Conductivity of Nickel-Sulphur Electrodeposits
Authors: Kersten H. , Young W. T.
Published: January 2005

Under certain conditions, an electrodeposit from an aqueous electrolyte containing essentially nickel ammonium sulphate and sodium thiosulphate has an amorphous crystal structure and contains approximately 13 percent S and 87 percent Ni. It is shown that if this deposit is warmed to about 170°C its electrical resistance suddenly decreases and its structure changes to crystalline, without appreciable change in weight.
Effect of Temperature on Stretched Rubber Bands
Authors: Braun Milton L.
Published: January 2005

Specimens of each of two vulcanized rubber compounds of known composition were subjected to various constant gravity loads in a controlled temperature chamber for several months. The lengths of the stretched bands were observed from time to time while the temperature was altered in gradual steps within a range of about thirty degrees centigrade centering around room temperature. A projection method for observing small changes in length was devised for the experiment. The contraction of stretched rubber with rise in temperature, first observed about the middle of the eighteenth century, was verified, as also was its positive elongation when unstretched or when but slightly stretched. The present experiment shows that the expansion or contraction for each specimen was constant when measured in cm per degree temperature change, but not when measured in percent of the prevailing length of the band. That is, the thermal elongation was most simply expressed when considered independent of the after effect or drift. For molded bands originally 1 mm in thickness, 4 mm in width, and 10 cm in mean circumference, and with loads ranging from 30 to 836 grams producing elongations up to about 700 percent, the rates of expansion were found to lie between plus 0.0037 and minus 0.0550 cm per degree. The relation between the rate of thermal elongation, dl/dθ, and the stretching load, w, was found to be linear within the limits of the experiment, and the constants c and d in the empirical equation, dl/dθ=cw+dhave been evaluated, the former being negative in sign. The critical tensions for which there appeared no thermal change in length were 63 and 97 grams, respectively, for the particular shapes and compositions used. These tensions are equivalent to critical stresses of 7.72 and 11.9×105 dynes/cm2 (based on the cross section of the unstretched band) or of 11.2 and 17.2 lb./in.2, respectively, for the two compounds. Extrapolation by placing w =0 does not seem justifiable because when the resulting rate is divided by one-half the circumference of the bands the magnitude of the coefficients of linear expansion turn out to be several times the generally accepted values based on volumetric determinations.
The Daylight Variation of Signal Strength
Authors: Colwell R. C. , Friend A. W.
Published: January 2005

A rapidly moving recording galvanometer (Micromax) is used to maintain balance in a Wheatstone bridge. Received radio signals unbalance this bridge, so that an automatic record of voltage signal strength is taken. On daylight signals from nearby stations, the signals fluctuate rapidly during each day and night signals show a relationship dependent upon the barometric pressure. The latter observations agree with those made by Martyn in Australia. As autumn approached in 1936 every station recorded showed an increase of signal strength during the daylight hours.
Modern Theory of Solids. II
Authors: Seitz Frederick , Johnson R. P.
Published: January 2005

In the preceding article we reviewed the classical theories of the solid state, and sketched an outline of the modern wave mechanical theory. We saw that the valence electrons of a solid occupy an energy spectrum composed of zones of energy levels, and that the observed differences among various solids can be correlated largely with differences in the distribution and population of these zones. In this issue we shall first discuss in turn each of the five main types of solids, to see what explanation the zone theory offers for their distinguishing peculiarities. Following this, we shall review very briefly the progress of the theory in interpreting certain structure-insensitive volume properties.
Plastic Behavior of Metals in the Strain-Hardening Range. Part II
Authors: Davis Evan A.
Published: January 2005

In order to observe the behavior of a material under various conditions of strain-hardening, copper bars were tested in tension, in compression and in torsion. The results of the different tests were plotted on the same set of coordinates as a means of correlation. The shearing stress in the octahedral planes was used as ordinates and the corresponding octahedral shearing strain was used as abscissae. Good agreement was found between the curves for tension, compression, and torsion for small strains, but for very large strains (as obtained near the ultimate strength of annealed copper) the curves tend to separate to a marked degree. Hardness readings were also taken to check the relation between hardness and strain.
The Effects of Pressure and Temperature on the Viscosity of Lubricating Oils
Authors: Dow R. B.
Published: January 2005

The viscosities of three lubricating oils have been investigated at 100°, 130°, 210.2°F at pressures ranging from atmospheric to 4000 atmospheres (57,000 lb./in.2). While the oils were from fields widely separated geographically, their initial viscosities were matched at 0.4 poise at 130°F. At a pressure of 26,000 lb./in.2 at 130°, however, the viscosities were strikingly different; the viscosity of the Pennsylvania oil increased 25-fold, and the Oklahoma oil 35-fold, but for the California sample the increase of viscosity was greater than 100-fold. The effect of pressure on the temperature coefficient of viscosity and the effect of temperature on the pressure coefficient of viscosity are discussed.
A Note on a Problem in Potential Theory
Authors: Muskat Morris
Published: January 2005

Two methods are given for treating a new type of potential problem arising in a recent study of the author on the encroachment of water into an oil sand. The problem is that of finding the potential distributions in two regions of different ``constants'' (``conductivities''), separated by a moveable surface of unknown shape, this motion and shape to be determined by the conditions that each point of the interface should have a velocity proportional to the vector gradient of the potential at the point, and that the area swept out by the moving surface shall assume the ``constant'' appropriate to that of the encroaching side of the interface. The first method is a perturbation method, valid when the difference between the ``constants'' is small, and reduces the problem of determining the shape and motion of the interface and the potential distributions simultaneously, to a series of problems in which potential distributions are to be found on the sides of known interfaces, and the motion of the surface is to be found in a known (time varying) potential field. This same type of reduction is effected also in the second method, which is one of direct successive approximations, but which may be used for any values of the potential ``constants.'' The perturbation theory is carried through explicitly to the third order for the case of a one dimensional system, and agrees to that order with the exact results which were derived for this case in a previous paper. The method of successive approximations is carried out for this same case through the second approximation for a ratio of the ``conductivity'' of the interior side of the interface to that on the exterior side equal to 5, and through the third approximation for the ratio 1/5. In the former, the calculations give a rapid monotonic convergence to the correct solution, and in the latter the convergence is oscillatory, and only slightly less rapid. These behaviors are shown to be generally true for the linear problem, in the course of the construction of an analytic convergence proof for the one dimensional problem. The convergence proof of the method of successive approximations is also given for the case of radial symmetry.
The Use of the A.S.T.M. Penetration Equipment for Estimating the Viscosities of Materials of High Consistency
Authors: Rhodes E. O. , Volkmann E. W.
Published: January 2005

In a recent publication Thelen described experiments in which the standard penetrometer was used to determine the flow-shear diagrams for a number of asphalts. On the basis of these diagrams Thelen calculated viscosities which are of different magnitude from those expected from Saal's formula. In the present paper certain fallacies in Thelen's deductions are pointed out. A new method for analyzing Thelen's experimental results is shown which makes it possible to calculate absolute viscosities from penetration readings for a series of successive time intervals. The method is based upon the determination of viscosity by axial displacement of concentric vertical cylinders. Since the conditions under which viscosity can be determined by axial displacement are only approximated in the penetration test the new method cannot be expected to have a high degree of accuracy. Nevertheless from successive penetration readings on a coal tar pitch (penetration 100 g, 5 sec. at 25°C) an average viscosity of 383,000 poises was calculated which closely agrees with the value of 380,000 determined by a capillary rise viscometer. The viscosity as calculated from the initial penetration reading by the Saal formula was 355,000 poises.
Collected Results on Viscosity of Lubricants under Pressure. I. Fatty Oils
Authors: Hersey M. D. , Hopkins R. F.
Published: January 2005

In this paper the principal results of experiments on the viscosity of lubricating oils under high pressure, other than mineral oils, have been reduced to the same units and collected for comparison. The investigations reviewed are those of the American Society of Mechanical Engineers; J. H. Hyde at the National Physical Laboratory of Great Britain; S. Kiesskalt at the Technische Hochschule, Karlsruhe, Germany; and Y. Suge at the Institute of Physical and Chemical Research, Tokyo, Japan. Viscosity-pressure-temperature data are given for eleven different oils.
Concerning the Cutting of Glass
Authors: Jones Merton W. , Blair Julian M.
Published: January 2005

Glass plates were found to be more difficult to break when an interval elapsed between marking and breaking. This was associated with a decrease in the strain. Apparatus for applying uniform force in marking glass is described; also, a device for studying breaking loads. Marked samples of glass were found to break when subjected to diminished loads for appreciable intervals. A correlation was shown between the breaking load and the load on the marker.
An Electron Diffraction Study of the Effect of Heat upon the Structure of Gold Leaf
Authors: Clark G. L. , Wolthuis E.
Published: January 2005

The construction of an electron diffraction apparatus is described, adapted to both reflection and transmission studies of crystalline materials and built in the laboratory at a moderate cost. This apparatus involves several novel features of construction and utilizes an electrode magnet for obtaining a homogeneous beam of electrons. The application of the instrument to chemical problems is illustrated by the results of a study of the effect of heat and of various gaseous atmospheres upon the structure of gold leaf. Microscopic, x-ray and electron diffraction evidence indicate that at a temperature of about 400° the gold in a leaf flows into aggregates or larger crystal grains. This coagulation explains the contraction of the leaf as observed visually, the opacity of many patches in the heated leaf as observed microscopically, and the appearance of spots in the diffraction patterns. A ``many ring'' pattern observed when the leaf is heated in air or oxygen is attributed to the formation of an oxide which is rather unstable at about 400°. This observation clarifies some discrepant data in the literature.
Working Stresses for the Rational Design of Concrete Structures
Authors: Marin Joseph
Published: January 2005

This paper presents a new theory of failure for materials subjected to a combined state of stress. The theory is developed for brittle materials, such as concrete, in which the compressive and tensile strengths are of different magnitudes. It is a semi-empirical theory which has some experimental support. Based on it working stresses are defined for various loading conditions. The use of these proposed working stresses in some cases makes considerable difference in design as compared to the present specifications requirements. These working stress values are conveniently represented by a diagram to facilitate the computations in design. The application of this information can be made simply in most cases where there are stresses acting in two right-angled directions—such as slabs in buildings, roads and bridges, retaining walls, dams and other hydraulic structures of concrete and reinforced concrete.
On Convection Currents in High Pressure Mercury Arcs
Authors: Kenty Carl
Published: January 2005

Convection speeds in commercial high pressure Hg vapor lamps are measured by photographing on a moving film, the tracks of incandescent particles of CaO and MgO. A deep red filter and panchromatic film are used. The convection system is found to consist of a laminar flow of hot gas upward in the center and of cold gas downward near the walls. For the 400 watt lamp (p≅1 atmosphere, m = mass of Hg per cm of tube length = 11.5 mg cm−1) an upward speed of about 40 cm sec.−1 is found at the axis in the mid-section of the lamp. The speed is somewhat greater near the bottom, this effect increasing with m. Speeds are found to increase somewhat less rapidly than in proportion to m as predicted. An approximate theory of these currents is presented, based largely on the work of Elenbaas, which accounts sufficiently well for the order of magnitude of the observed speeds. For similar discharges, speeds do not depend on the tube diameter but simply on m; for such discharges the watts lost by convection are proportional to m2 and independent of diameter and length. Convection losses for the 400-w, 250-w and 85-watt lamps are calculated to be 12-w and roughly 0.9-w and 0.8-w, respectively. When a lamp is operated on half-wave a dark space develops at the bottom of the arc in the off half-cycle, due to uprush of cold gas from below. Convection speeds estimated from the length of this dark space and the period of zero current are about twice too high; probable reasons for this are given. When the lamp is operated in the horizontal position, the arc bows up against the wall of the tube and softens it. The magnetic force necessary to keep the arc in the axial position is measured and found to be proportional to m (F=0.126m dyne cm−1). This force will be independent of tube diameter for similar discharges. An approximate theory is developed which accounts sufficiently well for the order of magnitude of this force. Rotation is also used to center the arc in the horizontal position; for the 400-watt lamp a speed of at least 7 r.p.s. is necessary for this purpose. No appreciable changes in arc voltage or efficiency are found for horizontal operation with magnetic or rotational control as compared with vertical operation. Photographs of particle tracks show in a striking manner the migration of ions in the electric field; Ca and Mg vapors from the evaporating particles are strongly ionized and excited at the high temperatures and progress rapidly in the field.
Plastic Deformation of Lead, Copper and Aluminum Under Static Compression
Authors: Lyons W. James
Published: January 2005

Creep in metals under constant load indicates that plastic deformation depends on the duration as well as the magnitude of the compressive force. The dependence of deformation on duration is significant in the lead crushers used in measuring pressures. Static compression tests on lead, extending over 30-minute periods, and under various loads up to 109 kg have been conducted. The dependence of deformation on duration is found to be great under the higher loads, and much greater than the dependence in the case of copper and aluminum, on which comparative tests were made. The deformation-compression-time relation is found to be approximately linear under constant pressure. The present data are in agreement with the results of Bogomolov and Kunin on lead for pressures in a higher range. However, the law derived by them does not hold in the pressure-range of the present tests.
Drift of Magnetic Permeability at Low Inductions after Demagnetization
Authors: Patterson G. R.
Published: January 2005

Attempts at measurement of the magnetic properties of ferromagnetic materials at very low flux densities showed inconsistencies which were attributed either to errors in methods or to some behavior of the material. Check tests, using the same procedure in each case, eliminated the first supposition. The results of this investigation show that, with a steel of medium silicon content tested at 10 gausses over a period of 24 hours, there exists a 5 to 15 percent decrease in permeability. On the average, 50 to 60 percent of this drift occurred within one hour after demagnetization and none after 24 hours.
Stresses in a Heavy Disk Suspended from an Eccentric Peg
Authors: Mindlin Raymond D.
Published: January 2005

An exact solution of the two-dimensional elasticity equations for small strain is obtained which satisfies the boundary conditions for a heavy disk suspended in a vertical plane from an eccentric peg of small diameter.
Vitrification and Crystallization of Organic Cells at Low Temperatures
Authors: Goetz Alexander , Goetz S. Scott
Published: January 2005

I. Theoretical considerations.—The conditions which determine whether a homogeneous liquid will solidify into the crystalline or into the vitreous state are discussed and a brief account of the rôle of the speed of crystallization, V, and that of grain formation, N, is given. These concepts are applied to the causes of the death due to crystallization of nondehydrated organic cells, and the physical conditions of cooling are developed under which such organisms can be solidified with a minimum of crystallization, assuring to this extent the preservation of their potential life.

II. Technical considerations.—Methods for obtaining cooling rates up to 104 deg. sec.−1 applicable to organic cells in a highly dispersed state are developed. As subject for the experiments, pure strains of yeast (Saccharomyces cerevisiae) were chosen on account of the high sensitivity to low temperatures. As death criterion, the permeability of the cells to a standard aqueous solution of methylene blue was chosen, the death rate was thus determined microphotographically or with a counting chamber. Different techniques of exposure favoring and preventing crystallization are developed.

III. Experimental results.—The rate of cooling of suspensions of living cells in aqueous media was varied from 1 to 104 deg. sec.−1 and thus conditions favoring either crystallization or vitrification of the cell plasma were produced. The death rate at an exposure of −185°C was thus varied from approximately 75 percent to approximately 3 percent. The duration of exposure at this temperature was varied from 5′ to 6000′; no appreciable influence of the time of exposure was found. The temperature to which the cells were cooled was varied from −50°C to −252°C and it was found that between −185°C and −252°C the temperature did not affect the death rate. Above app. −150°C an increase of the death rate was found, and a dependence upon the time of exposure, since the speed of crystallization begins to be appreciable. Repeated exposures of the same cells under conditions not especially favoring vitrification were studied and the integral death rate, δn (death rate after nth exposure) was investigated with respect to a constancy of the death rate (δ) at each freezing. It appears that the death rate for repeated freezings is not controlled by simple probability relations, but that other effects enter, such as weakening of cells by previous exposures and the selection of cold-resistant cells by survival.
The Evaluation of Yield Value With the Sphere Viscometer
Authors: Williams John C. , Fulmer Ellis I.
Published: January 2005

Various methods and formulas for determining yield value have been critically reviewed and a method is proposed for determining the yield value by means of the sphere viscometer.
A Geiger Counter for Beta-Rays
Authors: Brewer A. Keith , Bramley A.
Published: January 2005

A Geiger counter for beta-rays is described that is easy to construct and has the low back-ground count of two per minute. Two modifications are in use, one in which the rays are admitted through an aluminum foil supported by a copper grid; and the other in which the material to be tested is placed directly within the chamber. The characteristics of various gases are discussed; it is shown that while organic vapors tend to lower the background count they also lower the sensitivity. A simple method for measuring the counter efficiency for rays of different energies is outlined.
Experimental Analysis of Rein's Thermostromuhr for Small Flows
Authors: Herrick J. F. , Baldes Edward J. , Sedgwick F. P.
Published: January 2005

The experimental curve is determined which shows the relation between the flow of blood in cubic centimeters per minute and the deflection of the galvanometer in millimeters for a range of flows between zero and about 3 cc per minute. The curve is similar to that calculated by Burton for the Rein thermostromuhr and that experimentally obtained by Jongbloed and Noyons with their aerothermorheograph. The maximal deflection of the galvanometer occurs at a flow (Ringer's solution) of about 0.08 cc per minute and for smaller or greater flows the deflection decreases. Since the deflection of the galvanometer approaches zero for very small flows and becomes zero for cessation of flow, whereas it usually decreases for increase of flow, one must be careful to distinguish between a cessation of flow and an increase. Difficulty will not arise if sufficient time is allowed for the establishment of thermal equilibrium. Certain controversies have arisen because this particular limitation of Rein's thermostromuhr was disregarded. The method, as we use it, is wholly unsuited for indicating variations in blood flow which occur in less than sixty seconds. It may be very reliable for indicating changes in blood flow which occur over a longer period of time.
Photographic Study of Lightning
Authors: Holzer R. E. , Workman E. J. , Snoddy L. B.
Published: January 2005

A simple method of analyzing lightning photographs taken with moving film cameras is described. The results of analysis of two air discharges with some interesting features and one very unusual type of discharge are presented. Certain discharges at the close of storms and the correlation of electrical and photographic measurements are discussed.
Quantitative Measurements of Texture by the Magnetic Torque Method
Authors: Tarasov L. P.
Published: January 2005

Magnetic torque measurements offer a possibility of specifying texture in ferromagnetic materials in a quantitative fashion and several methods have been proposed for accomplishing this. The method of Akulov and Brüchatov, although formally correct, is shown to be so restricted by its assumptions as to be inapplicable even to the commonest texture. A method proposed by Bitter, involving root-mean-square deviations from some mean orientation, is found to fail in practice because of the uncertainty in the measurement of the magnetic energy. A modification of this method, in which x-ray data are used to establish a relationship between two of the root-mean-square deviations, gives results in fair agreement with the pole figure of a cold-rolled iron-silicon alloy.
Invariant Form of the Maxwell-Lorentz Field Equations for Accelerated Systems
Authors: Kron Gabriel
Published: January 2005

It is shown that the invariant field equations of Maxwell for stationary bodies are also valid for accelerated bodies, if all ordinary differentiations are replaced by absolute differentiation. The affine connection Γγαβ appearing in the absolute derivatives refers to a general non-Riemannian metric space, with a holonomic or nonholonomic reference frame. The field equations are in a more general form than those used in the five-dimensional unified field theory and reduce to the latter as a special case. However, the presence of an electrostatic field is not assumed in this paper. The motion of an accelerated body possessing mass, electric current and magnetic flux is given by an extended form of the dynamical equations of Lagrange containing the same general affine connection as the field equations. The material terms of the dynamical equations are expressed by a mechanical impulse-energy tensor and the resultant motion of the material body under the influence of an electromagnetic field and a mechanical force is expressed by a combined impulse-energy equation. The equations are calculated for a representative rotating electrical machine used in industry.
Time Constants of Incandescent Lamps
Authors: Forsythe W. E. , Easley M. A. , Hinman D. D.
Published: January 2005

Candescence and nigrescence curves are shown for a number of tungsten lamps, vacuum and gas-filled, ranging in size from the automobile lamps up to the 30-volt, 30-ampere lamp and the 1000-watt photoflood lamp. Data are given for similar filaments mounted in vacuum lamps and in lamps filled with argon, nitrogen, hydrogen, and helium. The filament of a vacuum lamp reaches 90 percent brightness on heating in time t=0.060I0.54; 10 percent brightness on cooling in time t=0.022I0.70; for gas-filled lamps, t=0.15I0.70 and t=0.070I0.70, respectively. (I is the normal operating current of the lamp.) The percent of total variation, P, in brightness during a cycle for a vacuum lamp on 60-cycle a.c. is P=34D−1.06, on 25-cycle a.c., P=28D−1.37; for a gas-filled lamp, P=75D−0.89 and P=63D−0.91, respectively. (D is the filament diameter in mils.)
The Reflection of Plane Wave Pulses from Plane Parallel Plates
Authors: Muskat Morris
Published: January 2005

A wave theory analysis is given for the reflection of wave pulses from plates, which heretofore has been treated by the methods of geometrical optics. The general theorem is proved that if the reflection coefficient for a harmonic wave system is exactly periodic in the frequency of the waves, the reflections from the plate due to an incident pulse will consist of a series of wave trains of exactly the same form as the incident pulse. This theorem may be applied to electromagnetic waves polarized in and normal to the plane of incidence, longitudinal waves in fluid media, and transverse waves polarized normal to the plane of incidence in general elastic media, when absorptive and dispersive effects can be neglected.
The Effect of Pressure Upon the Elastic Parameters of Isotropic Solids, According to Murnaghan's Theory of Finite Strain
Authors: Birch Francis
Published: January 2005

Murnaghan's theory of finite deformations is applied to a discussion of the effect of hydrostatic pressure upon the elastic coefficients of an isotropic body, for small strains superposed on the hydrostatic strain. Stress-strain equations for the small strains, and the equations of small motion, are shown to have the same form as those of the classical theory, with elastic parameters which depend upon the pressure. Using a form of elastic potential identical with that of the classical theory, explicit results are found for the pressure coefficients of compressibility, Young's modulus, rigidity and so on; these are compared with such experimental results as are available, with good agreement. A single-constant formula is derived which gives the volume change of such compressible materials as sodium and cesium up to the highest experimental pressure, 45,000 kg/cm2, within the experimental error.
Contribution to the Problem of Arcback in High Voltage Discharge Devices
Authors: Klemperer H.
Published: January 2005

It has been found in rectifier and ignitron practice that arcback can occur after deionization of the discharge path at such vapor pressures where no self-sustaining glow can develop. Experiments to study this kind of an arc breakdown were made in Hg vapor vessels between cold electrodes at voltages between 10 and 60 kv. It appeared that the start of arc breakdown was not dependent on the Paschen law. At the voltages used and distances between the electrodes of less than 50 cm arc breakdown always started at PD values which were much lower than those required to sustain a glow discharge. This is contrary to earlier experience at lower voltages. With rising voltage arc breakdown frequency increased in an exponential manner. Changes in vapor pressure and electrode spacing had no definite effect on arc breakdown frequency as long as glow discharge conditions were not approached. Changes in partial air pressure did not affect arc breakdown frequency if air pressure was below 10 percent of mercury vapor pressure. Heat treatment of the cathode (graphite ``anode'') has a large effect in reducing arc breakdown. Even well heat-treated ``anodes'' show seasoning effect, i.e. steady decrease of arc breakdown frequency after initial maximum. Phenomena on cathode surface are believed to be responsible for formation of arc breakdown.
A Note on Certain Guided Waves in Slightly Noncircular Tubes
Authors: Schelkunoff S. A.
Published: January 2005

Amongst electric waves that can be propagated inside metal tubes of circular cross section there are some with attenuation constants diminishing indefinitely with increasing frequency. The purpose of this note is to discuss what happens to these waves as the tubes are slightly deformed from perfect circularity. The conclusion is that in a deformed tube the attenuation constants of the above-mentioned waves diminish with increasing frequency until a certain frequency is reached, depending upon the degree of departure from perfect circularity, and then they begin to increase indefinitely with further increase in frequency.
The Reflection Coefficient of Mercury
Authors: Mason R. C.
Published: January 2005

Two new methods for measuring the reflection coefficient of mercury atoms from a mercury surface are described. In the first, a micromanometer gives both the change in pressure on the surface, and the subsequent rate of evaporation, when a mercury pool is exposed to an opposing liquid air cooled condensing target. From these, reflection coefficients from 0.93 to over 0.99 are obtained. In the second, from measurement of the vapor density between evaporating and condensing surfaces by an ionization gauge, the reflection coefficient can be calculated. With careful purification of the mercury, quite small reflection coefficients result, a mean of 0.2, and a minimum of 0.07 being found. Exposure of the mercury surface to the atmosphere for half an hour brings the reflection up to 0.8, while after 10 days' exposure the reflection coefficient becomes 0.92.
X-Ray Investigation of the Form of Acetylsalicylic Acid in Certain Sugars
Authors: Sidhu S. S.
Published: January 2005

X-ray studies of samples made of sucrose, glucose, and acetylsalicylic acid were made to determine if the latter is in solid solution with the sugars. The main constituent of the samples was sucrose and the amounts of acetylsalicylic acid varied from one and a half to twenty per cent. The samples were prepared by melting and heating the sugar combinations to 160°C, removing essentially all the water and allowing to cool. The acetylsalicylic acid was then incorporated in one set of samples at 140°C and in another at a temperature between 110–115°C, that is, both above and below the melting point (133–5°C) of the compound. The former samples were far more hygroscopic than the latter, but in neither case did the acetylsalicylic acid seem to form a solid solution with the rest of the constituents.
CAPILLARY RISE IN SANDS OF UNIFORM SPHERICAL GRAINS
Authors: Smith W. O. , Foote Paul D. , Busang P. F.
Published: January 2005

Uniform spheres packed in regular array form a non-cylindrical cyclic capillary, characterized by a maximum and minimum capillary rise with intermediate positions of possible equilibrium. In practice spheres may be packed to a variety of porosities P thus requiring a mixture of regular and irregular pilings arranged in a very distorted pattern. However the meniscus is also distorted to conform in a general way with the distortions of the lattice. Accordingly positions of maximum and minimum rise may be expected. The meniscus for maximum rise tends to pass through the plane of centers of neighboring spheres. Slight deviations from this condition due to the rise at sphere contacts are shown to be of minor importance. Any piling may be treated statistically as a hexagonal array with a spacing 2r+d where d is computed to give the observed porosity. In such a system three types of cell occur with a definite frequency, and these cell types are assumed present in the meniscus with the same frequency distribution. Hence it is possible to evaluate pr/a = ρghr/σ where p = perimeter, r = grain radius, a = area of pore opening, g = acceleration of gravity, σ = surface tension, ρ = density and h = capillary rise. The final formula so derived reduces to pra=ρghrσ=2[0.9590/(1−P)2/3]−1.This agreed with experiments made with several sizes of grains, porosities, and liquids. The minimum rises were also determined but a satisfactory interpretation in terms of a model has not been effected.
AN EXPERIMENTAL METHOD OF DETERMINING CERTAIN CHARACTERISTICS OF THE FLOW AT THE SURFACE OF AN AIRFOIL
Authors: Scott Merit
Published: January 2005

The heat dissipation per unit area from the surface of model airfoils is experimentally measured by means of narrow resistance strips mounted parallel to the span and flush with the surface. Results, covering variation with distance from the leading edge, with velocity as well as with change of angle of attack, show that the heat dissipation is in no simple way related to the velocity at the strip, as measured by the static pressure, but is evidently characteristic of the airflow at the surface. Further significance of the heat dissipation is sought. The relation of heat dissipation to viscous resistance (Reynold's law) is discussed with relation to (1) two-dimensional flow between parallel plates, (2) a plate plate parallel to the flow and (3) the general case. It is concluded that the law is applicable to (1) and (2) but not to the general case. An integral relation is developed from which it is shown that the heat dissipation, as above measured, is proportional to the velocity gradient at the surface and hence to the viscous resistance. Curves present measurements made upon two airfoils and these are briefly discussed.
THE DEPOSITION OF DUST ON WALLS
Authors: Hooper W. J.
Published: January 2005

An apparent uncertainty exists in literature dealing with the cause for the peculiar deposition of dust on plaster and lath walls wherein the course of the laths and rafters behind the plaster is outlined in dust, popularly called ``lath marks.'' Conclusive experimental proof of a thermal cause is given which is in agreement with the general theory of the behavior of small particles suspended in an atmosphere in which a temperature gradient exists. Experimental evidence is produced to show that this phenomenon may be reduced to a negligible degree by thermal insulation.