bluuebunny/crossref_metadata_2025 huggingface dataset:
The Effects of Acids and Alkalies on the Viscous and Structural Properties of Protoplasm
Authors: Seifriz William
Published: January 2005

Protoplasm becomes highly elastic, glutinous and fibrous, exhibits syneresis and changes from yellow to orange at the anode of an electric circuit. At the cathode, all properties are the opposite of those at the anode; the protoplasm becomes soft, lacks elastic, glutinous and fibrous qualities, shows no syneresis and becomes green in color. The change from the normal, which is intermediate, is due to the acid condition set up at the anode and the alkaline condition set up at the cathode. The anomalous (non-Newtonian) behavior of protoplasm, as well as its other characteristic jelly properties (imbibition, syneresis, coagulation, thixotropy, etc.) are attributed to the structural continuity which is responsible for the elastic qualities.
A New Feature in the Calibration of a Capillary-Tube Viscometer
Authors: Spooner Laurence W. , Serex Paul
Published: January 2005

Because of deviations from a truly cylindrical surface at the capillary wall or to an abnormal orifice at one end of the capillary, the value of the coefficient, m, of the kinetic energy correction may be abnormally high with one direction of flow while it remains quite normal with the other direction. This variation may even cause the value of the principal instrumental constant, C, to be slightly greater in one direction of flow than in the opposite. This effect has been shown to be definitely greater than experimental error and is thought to be due to a slight difference in the ``effective'' capillary radius in the two directions of flow. This study shows the necessity of determining both m and C for each direction of flow through the capillary. This suggests the use of two viscosity formulas: η=Clp0t−mlC′ρ/t for ``left-hand data,'' and η=Crp0t−mrC′ρ/t for ``right-hand data.'' Although a well-constructed viscometer may not require this unusual precaution, with it any commercially made capillary viscometer may be used with the highest possible accuracy.
V. The Correlation of Distillation Range with the Viscosity of Creosote
Authors: Frosch C. J.
Published: January 2005

The results of viscosity measurements of a series of creosotes distilled from a single tar are given. It was found that these creosotes are truly viscous solutions which permits the designation of the data as absolute viscosity. The viscosity-temperature data conform to two equations, one an empirical relationship previously found in an analogous series of crude oils, the other developed from theoretical considerations. It is remarkable that in spite of the complex nature of creosote, the viscosity data permit one to regard the material boiling below 355°C as solvent and the residue above that temperature as solute. This is not true for any other temperature limit customarily used in creosote analysis.
VI. The Correlation of the Distillation Range with the Surface Tension of Creosote
Authors: Frosch C. J.
Published: January 2005

The surface tension of each of a series of creosotes distilled from a common tar has been determined at various temperatures. The surface tensions of the several creosotes do not differ substantially at any given temperature. Differences in the rates of penetration of such creosotes into capillary materials are regarded as due to differences in the viscosities or the solid-liquid contact angles. The Langmuir theory of surface phenomena has been applied to explain the similarity of the surface tension values.
VII. The Correlation of Distillation Range with the Interfacial Tension of Creosote Against Water
Authors: Frosch C. J.
Published: January 2005

Measurements of interfacial tension against water of each of a series of creosotes distilled from a single tar are reported. It is found that the interfacial tension values of these creosotes varied as much as 30 percent although no definite trend was present which could be related to other physical properties. Two possible theories to explain the differences in the interfacial tensions are discussed.
Some Observations on the Movement and Demagnetization of Ferromagnetic Particles in Alternating Magnetic Fields
Authors: Davis C. W.
Published: January 2005

The movement of ferromagnetic particles in various types of alternating magnetic fields and the mechanisms involved are discussed. The conditions under which demagnetization takes place in magnetic fields produced by damped high frequency oscillatory discharges are described, and possible practical applications to the magnetic separation of ores and to routine laboratory magnetic testing of iron and steel are indicated.
The Determination of Arc Temperature from Sound Velocity Measurements. II
Authors: Poritsky Hillel , Suits Chauncey Guy
Published: January 2005

Experimentally determined values of the velocity c of sound in atmospheric pressure arcs in air are interpreted in terms of the temperature of the gas. The velocity may be expressed in general in the form: c=((RT/M)(1+R/Cv))12,which applies to pure gases or mixtures of gases that obey the perfect gas laws. In this relation T is the absolute temperature; M is the mean molecular weight defined as: M=ΣMipi/Σpi; Cv is the specific heat (per gram molecule) defined as: Cv=Σ(Cv)ipi/Σp i, where the summation is taken for all the gas components present. In the case of the arc in air, the components considered are the undissociated and dissociated oxygen and nitrogen. The values for the specific heat and degree of dissociation, taken from the equilibrium calculations of H. L. Johnston and associates are used, care being taken to apply the correct partial pressures. Possible sources of error due to thermal diffusion and other causes are considered.
Grating Theory and Study of the Magnetostatic Oscillator Frequency
Authors: Cleeton Claud E.
Published: January 2005

A special type of echelette grating for wavelength measurements of ultra-short electromagnetic waves is described. The one grating may be used over the entire wavelength range from 1 to 10 cm without loss of effectiveness due to an automatically changing groove form which keeps the direction of the center of the diffraction pattern fixed. The formula for the distribution of the energy diffracted from the grating is given and found to agree with the experimental values. The magnetostatic oscillator produces a band of frequencies unless it is adjusted for the conditions at which the tube gives the maximum output, in which case no conclusions as to the width of the band could be drawn as the resolution of the spectrometer was too low.
Floating Grid Direct-Current Amplifier
Authors: Macdonald P. A. , Campbell E. M.
Published: January 2005

It is shown that commercial screen grid radio tubes are suitable for high sensitivity direct-current amplifiers. The theoretical limit due to the Johnson effect has been observed and agrees with the calculated value. Tubes when operated at floating grid are capable of detecting 2×10−16 ampere, the theoretical limit of the tube. Absolute linearity of response exists at least up to currents of 2×10−12 ampere.
High Frequency Conductance of Pyrex Glass in the Presence of Vapors
Authors: Roberds W. M.
Published: January 2005

The electrical conductance of ``Pyrex'' brand glass 774 was measured at frequencies between 40 kc and 1000 kc in the presence of ethyl alcohol vapor and water vapor. Data were taken at 50°, 65°, 79° and 107°C. The relations between conductance, degree of saturation, and frequency were found to be of the same form at all temperatures. There is a distinct discontinuity in the curves of conductance vs. frequency at about 500 kc. Vapor pressures of alcohol up to 85 percent of saturation cause no change in the conductance of the test piece. However, above this degree of saturation the conductance increases rapidly with pressure, becoming very high if condensation occurs. Conductance decreased with increasing current unless the test element was aged in the vapor several hours. Surface conductivities for both alcohol and water vapor are computed. Those for water vapor agree, well within the limits of error, with the results found by Yager and Morgan. An unexplained resonance effect occurred when high currents were used to measure the conductance while the test element was in the presence of small amounts of either alcohol or water vapor. The effect shows the double resonance peak and many of the other characteristics of close coupling between oscillating circuits. However, the effect is in some way due to the energy absorbed in the test element in the presence of a minute amount of water or alcohol since either an increase or decrease of pressure will cause the disappearance of the phenomenon. It was impossible to produce the effect by the substitution of any combination of capacity and artificial leak.
A Theory of Two-Dimensional Longitudinal and Flexural Vibrations in Rectangular Isotropic Plates
Authors: Osterberg Harold , Cookson John W.
Published: January 2005

The differential equations of motion of a free, rectangular, isotropic plate are solved for the longitudinal and flexural cases upon the assumptions that the displacements are independent of one of the Cartesian coordinates and that the displacements parallel to this coordinate are negligible. The flexural and longitudinal cases are considered separately. The frequency expressions predict the effects due to mechanical coupling of two or more longitudinal modes or of two or more flexural modes. The effects of the lateral dimension of the plate upon the frequency of the longitudinal harmonics are also predicted. It is shown that in the longitudinal case only the odd harmonics of both of the modes in which the wave trains are propagated along X and Y, respectively, form a mechanically coupled system. Similarly, only the even harmonics of the flexural case form a mechanically coupled system. The law by which the displacements of two individual modes are combined to form two coupled modes is illustrated by means of photographs of interference patterns formed by a Y-cut plate of crystalline quartz which is vibrating flexurally. The mathematical methods which are developed in this paper can be employed in considering the coupling of the longitudinal modes with the flexural modes of vibration. The two-dimensional case here considered, i.e., that in which the displacements are limited to the XY plane, is of special importance since it can be shown that in quartz and tourmaline the differential equations of motion and the boundary conditions become identical in form to those of the rectangular isotropic plate when it is assumed that the displacements are restricted to the XY plane and are independent of z. The applications of this theory will be considered elsewhere.
Longitudinal, Shear and Transverse Modes of Vibration in Quartz and Tourmaline
Authors: Osterberg Harold , Cookson John W.
Published: January 2005

The general differential equations which describe the vibrations of plates of quartz or tourmaline are stated together with the corresponding boundary conditions for a free plate. Solutions are presented for the longitudinal modes in which pure compressional waves are propagated along X, Y or Z in quartz or tourmaline. Experiment shows that these modes are purest (i.e., their displacements most nearly limited to the direction of propagation) in rectangular plates whose greatest dimension is that along which the compressional wave trains are propagated. As this dimension is shortened, the longitudinal modes decrease in purity and finally fail to appear. The purest longitudinal mode in the usual X, Y or Z cuts of quartz is that in which compressional waves are propagated along X in Y or Z cuts. The vibrational patterns which correspond to the mode in which compressional waves are propagated along Y in X or Z cuts of quartz are so complicated that the correspondence is open to considerable doubt. These latter longitudinal modes were found in tourmaline, and appeared to be simpler than the corresponding modes in quartz. The elastic constants c11 and c33 were obtained with an experimental error of but 1/3 percent. These measurements differ by 3 to 7 percent from those made by Voigt. The simple shear, pure shear, transverse and the yz, zx and xy shear modes are defined and distinguished. The differential equations of motion are not satisfied by free periodic vibrations of the simple shear or the pure shear types. No experimental evidence was found for the existence of any type of free simple or pure shear modes in a large variety of X, Y and Z cuts of quartz. Whereas forced simple shear vibrations are theoretically possible in a Y cut, the free simple shear vibrations are not. Solutions are presented for the various types of transverse vibrations. Experimental evidence for these transverse vibrations was not obtained. More general theoretical considerations indicate that the free transverse modes do not exist. The yz, zx and xy shear modes were observed in suitably oriented Y cuts of α quartz. The observations upon the latter modes are compared with the observations of Mason and Lack, Willard and Fair. It is concluded that the mode which was employed by Lack, Willard and Fair was not a transverse mode, but rather, the xy shear mode. The predominant modes of vibration are of longitudinal, flexural or torsional nature. Crystals of β quartz are active oscillators even at 800°C and will be shown to be piezoelectric.
The Influence of an Electric Field on the Viscosity of Aeolotropic Liquids
Authors: Björnståhl Yngve
Published: January 2005

The viscosity of aeolotropic liquids between two plates has been found to increase when an electric field, steady or alternating, is applied perpendicularly to the plates; this effect is probably due to real or apparent orientation of the axis of the swarms parallel to the electric field. A change of electrical conductivity under shearing stress has also been found. Ordinary isotropic insulating liquids show some apparent decrease in viscosity with a steady field, but this is probably due to electrolysis.
A Note on Viscosity as a Function of Volume and Temperature of Oils
Authors: Dow R. B.
Published: January 2005

The viscosity-volume data of Kleinschmidt and Dow have been examined at various pressures and temperatures for lard, sperm and Pennsylvania medium oil. The viscosity-volume isotherms at 25°, 40° and 75°C are not identical for any of the oils studied, indicating that viscosity cannot be a function of the specific volume alone. The viscosity-volume curve for lard oil at 25° departs from the one at 75° by an amount sufficient to change the viscosity by a factor of 2.3 at a volume of 0.99, and by a factor of 3.2 at a volume of 0.93. Similar curves for Pennsylvania medium oil at the same temperatures are even more relatively displaced; the discrepancy in viscosity varies from a factor of 3.8 at a volume of 0.99 to 7.6 at 0.94. The three oils do not obey Batschinski's equation at atmospheric and higher pressures up to 4000 kg/cm2.
Velocity-Gradient Methods in Rheology
Authors: Richardson E. G.
Published: January 2005

Since in a colloidal or quasi-plastic material, the viscosity is a function of the rate of shear, it seems best to determine the velocity-gradient across a section perpendicular to the direction of flow under shearing forces, and to determine the coefficient of viscosity under a given velocity gradient. An account is given of the experimental methods at present available for this purpose, and a method indicated by which the viscosity may be calculated from such measurements. The viscometers described comprise instruments based on the optical, electromagnetic, hot-wire and colorband principles, respectively.
Heat Treatment of Magnetic Materials in a Magnetic Field II. Experiments with Two Alloys
Authors: Bozorth Richard M. , Dillinger Joy F.
Published: January 2005

The magnetization of two alloys, as affected by heat treatment in a magnetic field at various temperatures, is examined in some detail in order to elucidate the nature of the accompanying changes which result in some cases in a 30-fold increase in maximum permeability. The experiments show that these alloys (one containing approximately 35 percent iron and 65 percent nickel, the other 20 percent iron, 60 percent cobalt and 20 percent nickel) can be effectively heat treated in a magnetic field of 10 oersteds if the temperature is above 400°C and below the Curie point of the alloy. The time during which the magnetic properties change has been measured at different temperatures and is found to vary according to the equation τ=AeW/kT. The experiments are interpreted in terms of the domain theory of ferromagnetism. The changes which occur are due to the relief of magnetostrictive stresses which arise when the material becomes ferromagnetic upon cooling through the Curie point or when an external magnetic field is applied, and the relief comes about by plastic flow or diffusion in the separate domains. The values of A (about 10−12 second) and W (2.1 electron volts) are the same as those determined by Bragg and Williams for the above equation which also gives the time necessary for the establishment of a superstructure in alloys. The relation between the two processes, establishment of superstructure and the relief of magnetostrictive strains, is pointed out.
A General Solution for the Displacements of Piezoelectric Media Which Are Subjected to Constant Electric Fields
Authors: Hestenes Arnold D. , Osterberg Harold
Published: January 2005

A general solution is presented for the displacements induced in any piezoelectric medium by static electric fields which are constant throughout the medium. This solution is then specialized to the case of α-quartz. The solutions for α-quartz have been used by the second writer in an accurate remeasurement of its piezoelectric moduli. The piezoelectric behavior of α-quartz is found to be closely predicted by these solutions.
On Anchoring the Mercury Pool Cathode Spot
Authors: Tonks Lewi
Published: January 2005

Certain metals projecting through a mercury surface are known to have the property of ``anchoring'' the cathode spot. A variety of metals have been examined for this ability and it has been found to exist for all of them tried, Fe, Pd, Zr, Pt, Cr, Cb, Ir, Mo, Ta, W. The property depends upon wetting of the metal by the mercury, and this in turn depends upon having a clean metallic surface. The spot lengthens into a fine bright cathode line (C.L.) at the meniscus edge. These metals differ in the ease of cleaning and of maintaining cleanliness. Electrolysis, hydrogen firing, vacuum firing and ion bombardment were used in different cases. The first five show attack by the cathode spot, the Mo shows slight disintegration. Besides the bright line spectrum, the C.L. has also a strong, continuous spectrum from red into ultraviolet which is quite different from hot body radiation. The C.L. consists of a multitude of small emitting areas which are in constant rapid and chaotic motion. The details as shown by moving film photographs differed with the anchor. Cb showed the most clear-cut phenomena. Its individual spots passed 0.22 amp. each and they moved with a predominant velocity of 46 cm/sec. They oscillated in intensity with a period of the order of 10−4 sec. Their current density was ∼9000 amp./cm2. The behavior of the C.L. under different kinds of varying current has been observed, and the change in C.L. length with current plotted. Increasing the arc current while maintaining the length of C.L. fixed resulted in a lowering of the C.L. even to below the pool level and to the formation of a trough in the liquid outside the C.L. This helps explain the mechanism of spot freeing at large current densities and gave the upper limit for a circular anchored spot at about 40 amp./cm.
Operating Characteristics of the FP54 Thermionic Direct-Current Amplifying Tube
Authors: Macdonald P. A. , Turnbull W. E.
Published: January 2005

The most suitable characteristics for steady deflection and electrometer use are discussed separately. For the former case it is shown that the mutual conductance may be increased three times the recognized value. When the tube is used as an electrometer a grid current as low as 10−17 ampere may be obtained with a voltage sensitivity of 10−4 volt/division. The capacity of the grid system being only 3×10−12 farad a highly satisfactory electrometer results.
Photographic Study of Lightning
Authors: Workman E. J. , Beams J. W. , Snoddy L. B.
Published: January 2005

Photographs of lightning taken with rotating film cameras near Albuquerque, New Mexico, in the summer of 1935 show three different types of electrical breakdown. In the first type the first flash starts at the cloud, proceeds about 1 km and stops abruptly in air. This was followed in 0.008 sec. by a second flash traversing the same path but extending it about 0.22 km. The third similar flash 0.01 sec. later extended the path 0.5 km. The fourth flash extended the path clear to earth 0.0098 sec. later. The second type showed the well-known ``leader'' type of breakdown of Schonland and others. The third type of breakdown consisted of only the main violent discharge between cloud and earth. The results are briefly discussed and a new possible mechanism for lightning breakdown pointed out.
Concentration Fields and Mechanical Forces in Metabolizing Systems
Authors: Young Gaylord
Published: January 2005

Some diffusion problems arising in biophysics are discussed for simple two-body cases. The steady state concentration field is determined, by a method of images, for cases of constant inflow over the surfaces of two external spheres, or two long parallel cylinders; both when the bodies are in an inactive environment, and when they are aligned with an external gradient. As an application, there is calculated the resultant force on each body arising from a normal surface pressure proportional to the concentration. The numerical value of these forces is of the same order of magnitude as that approximately estimated previously by N. Rashevsky.3
Atmospheric Potential Gradient Anomalies
Authors: Cooper Frank L.
Published: January 2005

A series of observations of the atmospheric potential gradient have been made over a period of six years and have been correlated with positions of the sun-spots and weather conditions. Maxima or minima of the potential gradient and storms appear to recur at intervals of approximately 27 days and at the same time that sun-spots appear near a plane through the axis of the sun and the earth. The supposition is made that the variations of the potential gradient and the storms are associated with radiation which travels approximately with the velocity of light from the sun. Since the light received from the sun-spot group cannot change rapidly as the group passes its position of nearest approach to the earth it seems more reasonable to suppose that a radiation not distributed according to Lambert's cosine law is involved.
The Motion of a Coil Spring Having Variable Tension and Variable Mass Per Unit Length
Authors: Wells D. A.
Published: January 2005

The problem here treated is that of finding the longitudinal motion of a long coil spring suspended vertically from a rigid support: the spring being sufficiently ``soft'' and long that it stretches appreciably under its own weight. Thus the tension and linear density each vary from top to bottom of the spring. A general solution involving displacements from the stretched static position is obtained and applied to three specific sets of boundary conditions; first, the lower end free, second the lower end rigidly fixed and lastly with a weight attached to the lower end. The natural periods corresponding to the first three fundamental modes of motion for each of the three conditions mentioned above have been determined experimentally for a long coil spring of piano wire and the results compared with the theoretically computed values. Before experimental results are given it is shown, by a second form of the equation of motion, that the natural frequencies of a spring are not affected by stretching.
A Preliminary Study of the After-Effect or Drift in Rubber Under Constant Load
Authors: Braun Milton L.
Published: January 2005

Similar vulcanized rubber bands were subjected to four different tensions which produced immediate strains of approximately two to five times their original length. During the life of the bands this elongation was augmented an additional one to two hundred percent by the so-called after-strain or drift. Observations were taken at constant temperature. The average life of the bands was about 33 weeks. No correlation was found between the magnitude of the load and the time that the specimen could bear its load. Drift for all stresses continued to the breaking point. In all cases the initial time rate of drift was comparatively high. It declined with time to a positive minimum, passed through an inflection, and then steadily increased for the remaining life of the band. The inflection occurred after some weeks or months of drift. No correlation was found between the magnitude of the load and the time of inflection in the drift rate. During the interval between one and eighty minutes, the magnitude of the drift in at least one specimen was directly proportional to the log of the time. It then deviated from the log law and for three weeks closely followed a decreasing power law.
The Distribution of Relaxation Times in Typical Dielectrics
Authors: Yager William A.
Published: January 2005

K. W. Wagner's treatment of the distribution of relaxation times in dielectrics is reviewed; the effect of the density of distribution upon the frequency variation of the dielectric constant and dielectric loss factor is discussed; and a graphical method of evaluating the constants of Wagner's equation from experimental data is described. These constants have been evaluated for a number of typical dielectrics, and the frequency variations of the dielectric constant and dielectric loss factor as computed from Wagner's equations and from the simple equations for a single relaxation time are compared with the observed behavior. The quantitative correlation obtained between Wagner's equations and the experimental data investigated is viewed as a confirmation of Wagner's theory of a statistical distribution of relaxation times in dielectrics.
Electron Optics of an Image Tube
Authors: Morton G. A. , Ramberg E. G.
Published: January 2005

(1). Introduction: Description of fixed-focus and variable-focus electrostatic image tube; scope of paper. (2). Focusing properties: Measurement of the variation of image distances and magnification with object distance and ratio of applied voltages for both types of tubes; calculation of potential distributions and electron paths; comparison of experimental and theoretical results. (3) Aberrations: Classification of aberrations; measurement of tangential and sagittal image surfaces for fixed-focus tube; calculation of axial (chromatic and spherical) aberrations; calculation of field aberrations; comparison between measurements and calculation; reduction of field aberrations by curving the cathode.
The Thermal Response of the Skin to Radiation
Authors: Hardy James D. , Oppel Theodore W.
Published: January 2005

The thermal sensitivity of skin to radiation has been studied with a new technique and the temperature changes in the skin surface have been accurately measured. The change in skin response of both whites and negroes to visible, infrared radiation, and sunlight has been measured. Results show that the sensation evoked by the radiations depends upon the optical properties of the skin. White subjects were found to be more sensitive to heat than negroes. The effect of the exposed area upon the sensitivity was observed. The postulate that the magnitude of the sensation depends upon two factors, nerve impulse frequency and central association, was found to fit the present data. A formula for calculating the degree of association is proposed. The results show that the sensitivity to radiation increases as the exposed area is increased up to the point where the stimulus has dropped to 0.0004 gram cal./sec.·cm2. A radiation weaker than this will evoke no sensation regardless of the size of the area exposed. This was taken to be the threshold of the excitation of an end organ. The temperature change in the skin surface with this radiation rate was measured to be a rise in temperature at the rate of 0.0008°C per second; sensation is perceived after 3 seconds of exposure. The relationship of the temperature change of the skin was studied. It was found that neither the change (ΔT) nor rate of change (ΔT/Δt) of skin temperature is adequate to explain the sensory effect. An hypothesis is proposed which attributes the sensation to a differential change in the temperature of the blood vessel net work within 0.1 mm of the skin surface and another at 0.3 mm.
Further Studies on the Mathematical Physics of Metabolizing Systems with Reference to Living Cells. II
Authors: Rashevsky N.
Published: January 2005

A system of nonlinear differential equations, established in a previous paper, and describing the diffusion in a metabolizing system, which glycolizes and oxidizes sugar, is approximately integrated. With such values of the constants as are suggested by considerations of some biological systems, the average approximation obtained by this method is about three to five percent. The results are discussed and it is shown that they throw light on the variation of oxygen consumption of cells with varying oxygen concentration.
The Coefficient of Thermal Expansion of Magnesium Oxide
Authors: Durand Milo A.
Published: January 2005

The thermal expansion of single crystal magnesium oxide has been measured from 85°K to 480°K. The results are combined with those of Austin, so that data are available from 85°K to 1273°K. The observed thermal expansion of this substance is in excellent accord with the relation, due to Grüneisen, between thermal expansion and heat content.
A High Frequency Apparatus for Producing a Measured Heat Stimulus in Studies of Physiological Temperature Regulation
Authors: Hemingway Allan , Witts Glenn H.
Published: January 2005

The requirements of a high frequency diathermy machine for clinical therapy and for studies of physiological temperature regulation in regard to (1) frequency, (2) measurement of power output, (3) range of power output, (4) efficiency and construction are discussed. To conform with the above requirements a power oscillator of 1000 kilocycles has been built capable of delivering up to 200 watts of high frequency power. A description of the apparatus is given with circuit constants and meter values which have been found useful in physiological temperature studies on animals and human subjects. With this apparatus it is possible to measure the power consumption of a subject treated with diathermy from the voltmeter and ammeter readings.
Further Tests of the Elasticity of Protoplasm
Authors: Pfeiffer Hans H.
Published: January 2005

It is possible to produce changes in fluidity of protoplasts by means of the varying shearing stresses to which they are subjected. In consequence of the different fluidity of the objects, the speed of their deformation is dependent upon the pressure or shearing stress used. In further experiments the relative effects of changes of temperature and of different concentrations of anisotonic media were studied, and in supplementary experiments with inanimate model drops, it was verified that the phenomenon of increasing ``apparent fluidity'' depending on the shearing stress is probably due to the structure causing elasticity. Not only the plasmalemma, but also the interior of the protoplasts is more fluid as the shearing stress increases, for the Brownian movement of particles of the inner layer is more rapid. From these experimentally determined facts the conclusion is drawn that the tangential expansion for protoplasm, as of any non-Newtonian fluid, is a function of the tangential shear γ and its change in time: τ=f(γ·dγ/dt).
Mechanism of Division of Metabolizing Systems
Authors: Reiner John M.
Published: January 2005

In an extension of the work of N. Rashevsky, the problem is treated of the determination of the distribution of concentrations and consequent distribution of osmotic forces in a metabolizing liquid sphere subject to a general infinitesimal deformation. The principle of virtual displacements in the form of an inequality is applied as a criterion of the instability (tendency to divide) of the system. This gives an algebraic equation determining the critical radius at which the system becomes unstable, and the equation is analyzed in detail with reference to the influence of the physical parameters of the system. In particular, it is found that, for a certain range of size of the system, this critical value is practically independent of the surface tension. Finally, the diffusion equations are integrated for a system where the rate of reaction is not constant, but a linear function of the concentration, and a procedure similar to the above is outlined.
Molecular dynamics simulations of cluster nucleation during inert gas condensation
Authors: Krasnochtchekov Pavel , Averback R. S.
Published: January 2005

Molecular dynamics simulations of vapor-phase nucleation of germanium in an argon atmosphere were performed and a unexpected channel of nucleation was observed. This channel, vapor-induced cluster splitting, is important for more refractory materials since the critical nucleus size can fall below the size of a dimer. As opposed to conventional direct vapor nucleation of the dimer, which occurs by three-body collisions, cluster-splitting nucleation is a second-order reaction. The most important cluster-splitting reaction is the collision of a vapor atom and a trimer that leads to the formation of two dimers. The importance of the cluster-splitting nucleation channel relative to the direct vapor nucleation channel is observed to increase with decreasing vapor density and increasing ratio of vapor to carrier gas atoms.
Boundary effects on Raman free-electron laser with coaxial wiggler
Authors: Farokhi B. , Maraghechi B.
Published: January 2005

A three-dimensional theory of the stimulated Raman scattering mechanism for a coaxial free-electron laser (FEL) is developed. The relativistic mass correction is included in the analysis and the boundary effects through the radial dependencies of the wave field quantities are taken into account. The configuration consists of a coaxial cylindrical waveguide with annular electron beam. Parametric decay of the wiggler pump wave, in the beam frame, into a space-charge wave and an electric-magnetic waveguide mode is analyzed in three dimensions. A nonlinear wave equation for the three-wave interaction is used to obtain a formula for the spatial growth rate of the excited eigenmodes. Numerical analysis is conducted to study the growth rate and required relativistic factor. Growth rate is found to be substantially larger than in the case of one-dimensional coaxial wiggler. Significantly higher growth rate is also obtained compared to a similar FEL with a helical wiggler instead of the coaxial wiggler.
Two-fluid magnetic island dynamics in slab geometry. I. Isolated islands
Authors: Fitzpatrick Richard , Waelbroeck François L.
Published: January 2005

A set of reduced, two-dimensional, two-fluid, drift-MHD (magnetohydrodynamical) equations is derived. Using these equations, a complete and fully self-consistent solution is obtained for an isolated magnetic island propagating through a slab plasma with uniform but different ion and electron fluid velocities. The ion and electron fluid flow profiles around the island are uniquely determined, and are everywhere continuous. Moreover, the island phase velocity is uniquely specified by the condition that the island-induced modifications to the ion and electron velocity profiles remain localized in the vicinity of the island. Finally, the ion polarization current correction to the Rutherford island width evolution equation is evaluated and found to be stabilizing provided that the anomalous perpendicular ion viscosity significantly exceeds the anomalous perpendicular electron viscosity.
Two-fluid magnetic island dynamics in slab geometry. II. Islands interacting with resistive walls or resonant magnetic perturbations
Authors: Fitzpatrick Richard , Waelbroeck François L.
Published: January 2005

The dynamics of a propagating magnetic island interacting with a resistive wall or an externally generated, resonant magnetic perturbation is investigated using two-fluid, drift-(magnetohydrodynamical) (MHD) theory in slab geometry. In both cases, the island equation of motion is found to take exactly the same form as that predicted by single-fluid MHD theory. Three ion polarization terms are found in the Rutherford island width evolution equation. The first is the drift-MHD polarization term for an isolated island, and is unaffected by the interaction with a wall or magnetic perturbation. Next, there is the polarization term due to interaction with a wall or magnetic perturbation which is predicted by single-fluid MHD theory. This term is always destabilizing. Finally, there is a hybrid of the other two polarization terms. The sign of this term depends on many factors. However, under normal circumstances, it is stabilizing if the noninteracting island propagates in the ion diamagnetic direction (with respect to the wall or magnetic perturbation) and destabilizing if it propagates in the electron diamagnetic direction.
Collision statistics, thermodynamics, and transport coefficients of hard hyperspheres in three, four, and five dimensions
Authors: Lue L.
Published: January 2005

The collision statistics of hard hyperspheres are investigated. An exact, analytical formula is developed for the distribution of speeds of a sphere on collision, which is shown to be related to the average time between collisions for a sphere with a particular velocity. In addition, the relationship between the collision rate and the compressibility factor is generalized to arbitrary dimensions. Molecular dynamics simulations are performed for d=3, 4, and 5 dimensional hard-hypersphere fluids. From these simulations, the equation of state of these systems, the self-diffusion coefficient, the shear viscosity, and the thermal conductivity are determined as a function of density. Various aspects of the collision statistics and their dependence on the density and dimensionality of the system are also studied.
Temperature-dependent spectral generalized magneto-optical ellipsometry for ferromagnetic compounds
Authors: Rauer R. , Neuber G. , Kunze J. , Bäckström J. , Rübhausen M.
Published: January 2005

Spectral generalized magneto-optical ellipsometry is presented as an optical tool for the simultaneous measurement of the complex index of refraction ñ=n+ik, the complex magneto-optical coupling parameter Q=Qr+iQi (i.e., the Voigt-parameter), and the orientation of the saturation magnetization Ms of isotropic ferromagnetic bulk materials. For wavelengths between 220nm and 790nm and at temperatures between 4.2K and 800K measurements on iron and permalloy demonstrate the comfortable application of this technique in order to resolve the spectral response of spin-polarized carriers and bands, which can provide valuable insight about the formation of the ferromagnetic state.
Oxygen island formation on Pt(111) studied by dynamic Monte Carlo simulation
Authors: Nagasaka Masanari , Kondoh Hiroshi , Nakai Ikuyo , Ohta Toshiaki
Published: January 2005

The formation of oxygen islands on the Pt(111) surface has been studied as a function of temperature by low energy electron diffraction (LEED) experiments and dynamic Monte Carlo (DMC) simulations. By raising the temperature, the (2×2) LEED spot intensity increases gradually and decays after a peak at around 255 K (Tp) with full width of half maximum of 160 K. This behavior is interpreted by DMC simulations with the kinematical LEED analysis. In the DMC simulation, an oxygen atom hops to the neighboring site via the activation barrier of the saddle point. The potential energies at initial, saddle, and final points are changed at each hopping event depending on the surrounding oxygen atoms. By comparing the observed Tp with the simulated one, the interaction energy E of oxygen atoms on Pt(111) was determined to be 25±3 meV at 2a0. The DMC simulations visualize how the oxygen islands are formed and collapse on Pt(111) with increase of the temperature and well reproduce the surface configurations observed by scanning tunneling microscopy.
Coarse-grained computations for a micellar system
Authors: Kopelevich Dmitry I. , Panagiotopoulos Athanassios Z. , Kevrekidis Ioannis G.
Published: January 2005

We establish, through coarse-grained computation, a connection between traditional, continuum numerical algorithms (initial value problems as well as fixed point algorithms), and atomistic simulations of the Larson model of micelle formation. The procedure hinges on the (expected) evolution of a few slow, coarse-grained mesoscopic observables of the Monte Carlo simulation, and on (computational) time scale separation between these and the remaining “slaved,” fast variables. Short bursts of appropriately initialized atomistic simulation are used to estimate the (coarse grained, deterministic) local dynamics of the evolution of the observables. These estimates are then in turn used to accelerate the evolution to computational stationarity through traditional continuum algorithms (forward Euler integration, Newton-Raphson fixed point computation). This “equation-free” framework, bypassing the derivation of explicit, closed equations for the observables (e.g., equations of state), may provide a computational bridge between direct atomistic/stochastic simulation and the analysis of its macroscopic, system-level consequences.
Static and dynamic structures of spherical nonionic surfactant micelles during the disorder-order transition
Authors: Imai M. , Yoshida I. , Iwaki T. , Nakaya K.
Published: January 2005

We have investigated the static and dynamic structures of nonionic surfactant micelles, a C12E8/water binary system, during the disorder-order transition using small angle x-ray scattering, static light scattering, and dynamic light scattering techniques. In the disordered phase, the micelles have spherical shape and intermicellar interactions are governed by the hard core and weak long ranged attractive potentials. With increase of the micellar concentration, the disordered micelles transform to the three characteristic ordered micellar phases, a hexagonally close packed lattice, a body centered cubic lattice, and an A15 lattice having area-minimizing structure. The stability of these phases is well explained by balance of a close packing rule and a minimal-area rule proposed by Ziherl and Kamien [Phys. Rev. Lett. 85, 3528 (2000)]. The role of hydrodynamic interactions in surfactant micellar solutions was compared with that in hard sphere colloidal particle suspensions.
Comment on “A centroid molecular dynamics study of liquid para hydrogen and ortho deuterium” [J. Chem. Phys. 121, 6412 (2004)]
Authors: Miller Thomas F. , Manolopoulos David E. , Madden Paul A. , Konieczny Martin , Oberhofer Harald
Published: January 2005

We show that the two phase points considered in the recent simulations of liquid para hydrogen by Hone and Voth lie in the liquid-vapor coexistence region of a purely classical molecular dynamics simulation. By contrast, their phase point for ortho deuterium was in the one-phase liquid region for both classical and quantum simulations. These observations are used to account for their report that quantum mechanical effects enhance the diffusion in liquid para hydrogen and decrease it in ortho deuterium.
Mean-field cage theory for the freezing of hard-sphere fluids
Authors: Wang Xian-Zhi
Published: January 2005

Using some observations and some mean-field approximations, we develop a mean-field cage theory for the freezing of hard-sphere fluids with vf⩾ad and obtain the freezing densities as functions of the closest-packing densities and the spatial densities, which are in good agreement with the experimental and simulation results.
Feedback loops for chaos in activator-inhibitor systems
Authors: Sensse Anke , Eiswirth Markus
Published: January 2005

Previous investigations have revealed that special constellations of feedback loops in a network can give rise to saddle-node and Hopf bifurcations and can induce particular bifurcation diagrams including the occurrence of various codimension-two points. To elucidate the role of feedback loops in the generation of more complex dynamics, a minimal prototype for these networks will be taken as purely periodic starting model which will be extended by an additional species in different feedback loops. The dynamics of the resulting systems will be analyzed numerically for the occurrence of chaotic attractors. Especially, the consequences of codimension-two bifurcations and the role of homoclinic orbits in view of the emergence of Shil’nikov chaos will be discussed.
Averaging peak-to-peak voltage detector for absolute mass determination of single particles with quadrupole ion traps
Authors: Peng Wen-Ping , Lee Yuan T. , Ting Joseph W. , Chang Huan-Cheng
Published: January 2005

A sine wave that controls a quadrupole ion trap is generated from a low voltage source, boosted to high voltage through a transformer. Since not even the best transformers can keep a flat amplitude response with respect to frequency, knowing the accurate peak-to-peak value of the sine wave is paramount when the frequency is varied. We have developed an averaging peak-to-peak voltage detector for such measurements and demonstrated that the device is an essential tool to make possible high-precision mass determination of single charged microparticles with masses greater than 1×1011u. Tests of the detector with sine waves from a FLUKE 5720A standard source in the neighborhood of 1400Vpp and frequencies ranging from 100to700Hz showed a measurement accuracy better than 10ppm. The detector settled within 5s after each reset to 5 digits of DVM rock-steady reading, and the calibration against the same source after 3weeks of continuous use of the circuit produced a mere overall 1ppm difference.
Correction and alignment strategies for the beam separator of the photoemission electron microscope 3 (PEEM3)
Authors: Schmid Peter , Feng Jun , Padmore Howard , Robin David , Rose Harald , Schlueter Ross , Wan Weishi , Forest Étienne , Wu Ying
Published: January 2005

A high-resolution aberration-corrected photoemission electron microscope (PEEM3) will be installed on an undulator beamline at the Advanced Light Source at the Lawrence Berkeley National Laboratory. The aim of this instrument is to provide a substantial flux and resolution improvement by employing an electron mirror for correcting both the third-order spherical aberration and the primary chromatic aberration. In order to utilize this concept of correction, a beam separator is a prerequisite. Crucial to achieving a resolution of 5nm for the high-resolution mode, and a 16-fold increase in throughput at the same resolution as its predecessor, PEEM2, specified as 20nm at 2% transmission, for the high flux mode is the double-symmetric design of the beam separator, which eliminates all the second-order geometric aberrations. Nonetheless, substantial tuning capabilities must be incorporated into the PEEM3 design to compensate for both systematic and random errors. In this article, we investigate how to correct for nonsystematic imperfections and for systematic uncertainties in the accuracy of the magnetic fields and focus on how degradation of the resolution and the field of view can be minimized. Finally, we outline a tentative correction strategy for PEEM3.