bluuebunny/crossref_metadata_2025 huggingface dataset:
Redox regulation of neutrophil apoptosis and the systemic inflammatory response syndrome
Authors: MELLEY Daniel D. , EVANS Timothy W. , QUINLAN Gregory J.
Published: April 2005

SIRS (systemic inflammatory response syndrome) may result from a wide variety of non-infective insults. Surgery is a recognized cause of SIRS, the onset of which can have adverse prognostic significance. Neutrophil activation is a key histopathological feature of SIRS, and neutrophil clearance through programmed cell death or apoptosis is an essential step in its resolution. Increasingly, it is recognized that ROS (reactive oxygen species), such as those generated by activated neutrophils during cardiac surgery, may have a regulatory role, influencing neutrophil lifespan and thus inflammation. In this review, we discuss the continuing importance of SIRS as a herald of inflammation and the role of neutrophil longevity in the resolution of inflammation, and we consider recent evidence for the regulation of neutrophil apoptosis by ROS.
Repeatability of non-invasive measurement of intracerebral pulse wave velocity using transcranial Doppler
Authors: GLADDISH Sarah , MANAWADU Dulka , BANYA Winston , CAMERON James , BULPITT Christopher J. , RAJKUMAR Chakravarthi
Published: April 2005

In the present study, the repeatability of three techniques for measuring peripheral PWV (pulse wave velocity) has been studied. A transcranial Doppler provided a wave reading from the middle cerebral artery. Using the transit time between the R-wave of an ECG and the ‘foot’ of this wave we were able to calculate a PWV (PWV-brain). An ear clip transducer provided a pressure wave reading (PWV-ear). A third pressure reading came from a Finapres transducer on the left middle finger (PWV-finger). The PWV was calculated as distance between two points/transit time of the pulse wave. Eleven volunteers had three sets of readings averaged for each technique taken in two separate sessions. There was good agreement between observers for the mean PWV values, and good agreement for mean results in different sessions. The RC%s (repeatability coefficient percentages) for between-observer repeatability in each session were good and approximately equivalent for PWV-finger (5–7%) and PWV-brain (5–7%). The repeatability of the PWV-ear measurement was less satisfactory (8–18%). The RC% for the same observer between sessions was less good, being 11% for the PWV-finger, 16–17% for PWV-brain and 11–19% for PWV-ear. The RC%s for the inter-session inter-observer measurements were between 10.7–12.1% for the PWV-finger, 14.7–19.5% for PWV-brain and 8.3–15% for PWV-ear. The transit time RC%s were lower in most measurements. The between-observer repeatability of all measures was satisfactory. Owing to the less good repeatability on different occasions, the use of PWV-brain and PWV-ear will depend on the magnitude of differences to be expected.
Variation in non-invasive measurements of vascular function in healthy volunteers during daytime
Authors: ter AVEST Ewoud , HOLEWIJN Suzanne , STALENHOEF Anton F. H. , de GRAAF Jacqueline
Published: April 2005

Although it is often recommended to standardize the time of day when performing non-invasive measurements of vascular function, the exact influence of the time of day on the outcome of IMT (intima-media thickness), PWV (pulse wave velocity), AIX (augmentation index) and FMD (flow-mediated dilatation) measurements has not been reported before. Nineteen healthy volunteers visited our department on two different occasions: the first visit was at 09:00 hours after an overnight fast, and the second visit was at 14:00 hours after a standardized breakfast. Non-invasive measurements of atherosclerosis were performed twice at 09:00 hours and once on the second visit at 14:00 hours. Measurement of IMT, PWV, AIX and FMD was reproducible according to the method of Bland and Altman. The absolute difference between repeated measurements at 09:00 hours showed no significant difference compared with the absolute difference between 09:00 and 14:00 hours for IMT (0.029±0.014 compared with 0.021±0.014 mm; P=0.27), PWV (0.63±0.50 compared with 0.75±0.74 m/s; P=0.52), AIX (4.0±4.0 compared with 5.5±5.2%; P=0.35) and FMD (3.8±3.7 compared with 4.2±2.9%; P=0.70). In conclusion, our results show that, in healthy volunteers during the daytime, IMT, PWV, AIX and FMD outcomes are not confounded by variation in the exact time of the examination as long as other (exogenous) conditions, including food intake, smoking and intake of alcohol, are carefully controlled for.
5-HT in systemic hypertension: foe, friend or fantasy?
Authors: WATTS Stephanie W.
Published: April 2005

Since its discovery by Erspamer in the 1930s and identification by Page in the 1950s, 5-HT (5-hydroxytryptamine; serotonin) has been an elusive candidate as a substance that plays a role in the disease of high blood pressure, also known as hypertension. In both animal and human hypertension, arterial contraction to 5-HT is profoundly enhanced. Additionally, 5-HT is a vascular smooth muscle cell mitogen. Because both increased arterial contractility and smooth muscle growth contribute to the disease of hypertension, it is logical to believe that 5-HT is a potential cause of disease, and thus a foe. However, decades of research have produced conflicting results as to the potential role of 5-HT in hypertension. This review will discuss historical findings which both support and refute the involvement of 5-HT in hypertension, and pose some new questions that may reveal novel ways for 5-HT to modify vascular control of blood pressure.
The molecular make-up of a tumour: proteomics in cancer research
Authors: KOLCH Walter , MISCHAK Harald , PITT Andrew R.
Published: April 2005

The enormous progress in proteomics, enabled by recent advances in MS (mass spectrometry), has brought protein analysis back into the limelight of cancer research, reviving old areas as well as opening new fields of study. In this review, we discuss the basic features of proteomic technologies, including the basics of MS, and we consider the main current applications and challenges of proteomics in cancer research, including (i) protein expression profiling of tumours, tumour fluids and tumour cells; (ii) protein microarrays; (iii) mapping of cancer signalling pathways; (iv) pharmacoproteomics; (v) biomarkers for diagnosis, staging and monitoring of the disease and therapeutic response; and (vi) the immune response to cancer. All these applications continue to benefit from further technological advances, such as the development of quantitative proteomics methods, high-resolution, high-speed and high-sensitivity MS, functional protein assays, and advanced bioinformatics for data handling and interpretation. A major challenge will be the integration of proteomics with genomics and metabolomics data and their functional interpretation in conjunction with clinical results and epidemiology.
Visualizing Argumentation: Software Tools for Collaborative and Educational Sense-Making
Authors: Prudencio Ramon , Toledo S.
Published: April 2005

Paul A. Kirschner, Simon J. Buckingham Shum and Chad S. Carr (Eds) Published by Springer-Verlag, 2003, xxvi + 216 pages. ISBN 1–85233–664–1
The Use of Spraying Methods and of Volatile Suspending Media in the Preparation of Specimens for Electron Microscopy
Authors: Backus Robert C. , Williams Robley C.
Published: April 2005

Developments have been made in the use of spraying methods in the preparation of specimens for examination in the electron microscope. At the same time, two wholly volatile diluents, containing electrolytes and adjusted to normal pH, have been developed for use in forming the spray drops. The use of volatile electrolytes makes it unnecessary to wash the specimen after the droplet patterns have been formed on the specimen screens.

There are several qualitative and quantitative uses and advantages of the spray technique as described. The qualitative ones are these: (1) the brief drying time of the droplets helps to preserve the shapes of particles upon drying, and also allows studies to be made of rapidly reacting systems; (2) since the drop patterns are reproducibly representative samples of the suspension under investigation, qualitative assays of the particulate composition of the suspension can be made, and a comparison of the particulate composition of two closely similar suspensions can be made under ideal control conditions; (3) the droplet patterns are discretely bounded by blank areas of substrate film, and this fact makes practicable the detection of small and subtle differences between the fine structure of the specimen material and that of the substrate.

The quantitative uses of the spray technique are: (1) by use of reference particles of known numbers in a suspension it is readily possible to determine the volumes of droplets issuing from a spray-making device; (2) by use of reference particles it is also possible to make an assay of the number of other particles, such as a virus, per unit volume of mixed suspension; (3) if a suspension is highly purified, the particle weight of the material in suspension can be determined. Experiments involving the counting of about 10,000 particles show that the quantitative precision is as good as would be expected from the statistics of random sampling.

The construction and use of a spray gun are described, as well as the characteristics of two volatile diluents: ammonium acetate and ammonium carbonate.
Thermionic Work Function of the (100) Face of a Tungsten Single Crystal
Authors: Brown A. A. , Neelands L. J. , Farnsworth H. E.
Published: April 2005

A slab with one surface cut and etched parallel to (100) crystallographic planes formed the cathode in a low power electron microscope. The electron image of the cathode was formed on a fluorescent screen with a small hole at the center. An electron collector placed behind the hole permitted a measure of the electron current passing through the hole as a function of the temperature of the cathode as measured with an optical pyrometer.

The most probable value of the work function, φ, obtained after 2400 hours of outgassing in a sealed-off, gettered tube is 4.59±0.02 ev. This may be compared with 4.56 ev obtained previously by Nichols for the work function in the [100] direction of a tungsten single crystal wire.
Measurement of the Surface Temperature of Evaporating Water Drops
Authors: Johnson John C.
Published: April 2005

Measurements made of the surface temperature of evaporating water drops are in agreement with the requirements of the theory ennunciated by Fuchs which states that the temperature is determined by the difference between the ambient and saturated vapor density of the drop.
X-Ray Measurement of Order in Single Crystals of Cu3Au
Authors: Cowley J. M.
Published: April 2005

X-ray diffraction methods have been used to measure long- and short-range order parameters for single crystals of the alloy Cu3Au held at elevated temperatures. It is shown that short-range order parameters may be obtained by a three-dimensional Fourier analysis of the ``scattering power'' for the diffuse background scattering of x-rays, expressed as a function of reciprocal lattice coordinates. Appropriate experimental and computational procedures are outlined. Intensity measurements have been made with a special arrangement of a bent-crystal monochromator and a Geiger-counter spectrometer. Short-range parameters are given for the first ten shells of atoms surrounding a given atom for three temperatures above the critical temperature of Cu3Au. These results, and those for the long-range order parameter agree well with theoretical predictions.
A General Solution for the Bending of Beams on an Elastic Foundation of Arbitrary Continuity
Authors: Hetényi M.
Published: April 2005

In the analysis of beams which are supported elastically along their entire length, it is usually assumed that the elastic support is provided either by a series of independent springs, or by a completely continuous elastic medium.

The present paper proposes a method of solution for the intermediate cases, that is, for foundations of partial continuity, by assuming that such foundations may be represented by beams imbedded into an otherwise discontinuous supporting material. In a foundation of this type, there are three independent elastic constants, the resilience of the discontinuous spring layers above and below the beam that is within the foundation, and the flexural rigidity of the foundation beam itself. By changing the values of these three constants, elastic foundations of a wide variety may be produced or, conversely, the constants may be adjusted in such a manner as to represent approximately the characteristics of any given elastic supporting medium.

In the paper a general procedure is presented from which solutions can be derived for the bending of beams on such foundations under any loading or end conditions. The method is illustrated by examples showing the range of pressure distributions that may occur under beams supported on foundations of this type.
The Response Characteristics of Linear Systems
Authors: Cini Marcello
Published: April 2005

For a linear system, steady-state response to sinusoidal stress cannot have a unique dynamic modulus and phase shift, but these quantities must be related to rate of creep; particularly they cannot be independent of external frequency.

A proof is given that such linear system is always equivalent to a viscoelastic system. Finally the discrepancy between the relations deduced and experimental results of various authors is pointed out and discussed.
Formation of Crystal Nuclei in Liquid Metals
Authors: Turnbull D.
Published: April 2005

The known facts about nucleation phenomena in liquid metals are interpreted satisfactorily on the basis of the critical size and interfacial energy concepts. In large continuous masses nucleation is almost always catalyzed by extraneous interfaces. However, in very small droplets the probability that a catalytic inclusion is present is so much less that their minimum nucleation frequencies are reproducible and form a consistent set of values.

Interfacial energies, σ, between crystal nuclei and the corresponding liquids have been calculated from nucleation frequencies of small droplets on the basis of the theory of homogeneous nucleation. Energies of interfaces, σg, one atom thick and containing N atoms were calculated from the σ's. The ratio of σg to the gram atomic heat of fusion, ΔHf, was approximately 0.45 for most metals but ∼0.32 for H2O, Bi, Sb, and Ge.

The effect of relative complexity of crystal structure upon the supercooling behavior of pure metals apparently is a reflection of its effect upon ΔHf.
Shielding Properties of the Concrete Wall of the M.I.T. Cyclotron
Authors: Delano Victor , Goodman Clark
Published: April 2005

The shielding properties of the four-foot concrete wall of the M.I.T. cyclotron have been studied, using foils for neutrons and x-ray films for gammas. Fast neutrons were measured by counting the beta-active products of Al27(n, p)Mg27, Fe56(n, p)Mn56, and Al27(n, α)Na24 reactions, thermal activation being eliminated by Cd holders. Resonance (1.44 ev) and thermal neutron distributions, measured by Cd-In-Cd and In, with suitable corrections, were reduced to absolute intensities by comparison with a known flux. Measurements were made with cylindrical concrete blocks fitted into a 4½″ diameter hole which extended through the concrete wall. The results indicate an attenuation factor of 8.3 per foot for the fast neutron component and 10 per foot for thermal neutrons. An estimate of the fast neutron flux above 4.5 Mev showed a transmitted intensity slightly higher than the presently accepted tolerance value when bombarding Be. The absolute thermal neutron flux was below the tolerance level. The r.m.s. distance and the diffusion length for thermal and resonance neutrons in concrete were estimated by considering the distributed source to be equivalent to a point source at the inner face of the wall. The gamma-ray measurements were not convertible to roentgens. A mean energy of 2.7 Mev was obtained for the gamma-radiation within the wall. The attenuation factor for total gamma-radiation in the wall at large distances from the inner face was 5.9 per foot.
Storage of Small Signals on a Dielectric Surface
Authors: Harrington John V.
Published: April 2005

A mathematical analysis is presented which is believed to be applicable to a general class of storage tubes where signal storage is accomplished by depositing through secondary emission a charge pattern on a dielectric surface. The assumptions made to linearize and simplify the problem are outlined and plots are given of the predicted output signals for writing, reading, and cancellation operations when the input signal is a step function. Experimental evidence is presented to substantiate the analytical results.
Microwave Techniques for the Measurement of the Dielectric Constant of Fibers and Films of High Polymers
Authors: Shaw T. M. , Windle J. J.
Published: April 2005

A resonant cavity method is described for the determination of the dielectric constant of polymeric solids in the form of fibers, films, and thin cylinders. Methods for investigating electrical anisotropy are outlined. In the case of fibers, for the electric field parallel to the fiber axis, the dielectric constant is determined directly. For the electric field perpendicular to the fiber axis, the problem arises of calculating the dielectric constant of the fiber from that of an air-fiber mixture. For the latter purpose the Lichtenecker equation was found to be applicable. Illustrative measurements of the dielectric constant of wool, Nylon, and Cellophane are presented and discussed briefly.
The Propagation of Plastic Deformation in Solids
Authors: Von Karman Theodore , Duwez Pol
Published: April 2005

The stress wave caused by a longitudinal impact at the end of a cylindrical bar has been analyzed in the case where the impact velocity is large enough to produce plastic strain. The theory gives a method for computing the stress distribution along the bar at any instant during impact. It is shown that for a given material, there is a critical impact velocity such that when subjected to a tension impact with a velocity higher than the critical, the material should break near the impacted end with negligible plastic strain.

An experimental investigation was made concurrently with the theoretical study. Some of the most significant experimental results are presented in this paper.
On Crazing of Linear High Polymers
Authors: Hsiao C. C. , Sauer J. A.
Published: April 2005

The effect of various variables, such as type of stress, stress magnitude, duration of stressing, and environment on the initiation and development of crazing in linear polymers is discussed. The basic nature of crazing is investigated in some detail for polystyrene specimens by means of the light microscope, the electron microscope and the x-ray spectrometer. The results of these observations and their bearing on the fundamental group structure of polystyrene molecules is presented.

The relationship between crazing and orientation is discussed, as well as the effect of both of these factors on the mechanical properties. The experimental results are compared, wherever possible, with the previously reported data of other investigators. A short discussion is then given of a theory of crazing from the point of view of the molecular structure of the material.
Stress-Strain Properties of Natural Rubber under Biaxial Strain
Authors: Boonstra B. B. S. T.
Published: April 2005

Tube-shaped samples were stretched in a direction parallel to the tube axis and at the same time inflated to cause a tangential extension. In this way 600 percent axial and 300 percent tangential elongation could be attained simultaneously. The stresses were calculated from the pressure in the tube and the dynamometer readings.

The results are plotted as axial stress-strain curves at different tangential elongations ranging from 0–300 percent.

The curve for a higher tangential elongation lies at higher stresses than that for a lower tangential elongation; the differences are however larger than the theory predicts.

At 600 percent axial elongation stress relaxation was measured at different tangential elongations. It appears that the relaxation constant is independent of the tangential elongation.
Artificial Field Equations for a Region Where μ and ε Vary with Position
Authors: Smith P. D. P.
Published: April 2005

I. Theory. The field equations developed admit of solutions in regions where μ and ε vary with position. For regions of zero conductivity, they are symmetrical with respect to electric and magnetic quantities, and the TM case can be derived from the TE. Fields derivable from a single component 4-potential are examined, and their propagation equations are found. A table relates the tensor and pseudo-tensor components to the usual vector components.

II. Applications in cylindrical polar coordinates. For the TE case, three types of solution exist, called A, B, or C, where the E field is parallel to the elementary vectors dz, dr or rdθ, respectively (for the TM case, H replaces E). In each TM or TE case, two possible distributions of μ and ε occur, leading to separable propagation equations. TEM waves can be derived from both TM and TE cases, but the impedances are different.

TE, TM and TEM waves for certain specific distributions of μ and ε, and their applications to curved guides, horns, and co-axial lines are considered. Some expressions are obtained for the fields, propagation constants, cut-off frequencies, and impedance. These solutions are not necessarily of the most general type, for to meet the conditions that restrict their choice, μ and ε are taken to be independent of the coordinate to which the transverse component of E (in TE) or H (in TM) is parallel.
Electron Microscopy of Wet Biological Tissues by Replica Techniques
Authors: Fischbein Irwin W.
Published: April 2005

The study of wet biological tissues in situ using the electron microscope was made possible by modifying existing replica techniques and developing a new wet replication method. The shortcomings of existing replica techniques are discussed and the modifications necessitated are described.

Replicas of wet tissues were produced in extremely thin polystyrene films which could be observed directly in the electron microscope; however, superior results were obtained by preparing silica replicas from the replicated polystyrene films. A modified two-replica silica method proved satisfactory but the three-replica silica method developed was preferable. Electron micrographs of wet wood fiber surfaces used to illustrate these techniques reveal new data concerning submicroscopic cell wall structure.

The problem of interpreting replicas of partially degraded and disorganized materials is illustrated and discussed briefly.
Electrical Conductivity Method for Measuring Self-Diffusion of Metals
Authors: Dedrick J. H. , Kuczynski G. C.
Published: April 2005

A method has been proposed to measure self-diffusion in metals by measurement of the contact conductance of an interface between two metallic spheres or hemispheres. By combining Kuczynski's equation for self-diffusion with Bowden and Tabor's equation for the contact conductance between two metallic spheres a relationship has been obtained between contact conductance and the time of heating of the spheres. Thus by measurement of junction conductance as a function of time of heating, for different temperatures, diffusion coefficients and the heat of self-diffusion can be evaluated in the normal manner. A similar relationship has been obtained for two spheres or hemispheres initially pressed together to give a known contact conductance before heating.
Theory of Collinear Antennas
Authors: King Ronold
Published: April 2005

If N collinear antennas are individually center driven, the only transmission line in the neutral plane is the one for a central unit if N is odd. Since lines that are not in a neutral plane constitute antennas, such an array is not practically useful.

For a single driven unit with symmetrical, parasitic, collinear elements, the driving transmission line is in the neutral plane and may be replaced by an equivalent generator and terminal-zone network. An array with two parasites is analyzed. Since the currents in the halves of the three units are not alike, three simultaneous integral equations occur. By making reasonable assumptions these are reduced to the single equation of the isolated antenna but with a different kernel. Approximate expressions are obtained for the currents and for the mutual and self-impedances of the elements.

The collinear antenna with outer elements driven from the central one by phase-reversing stubs is studied. For three elements components of the currents in the several possible modes are obtained with different degrees of approximation. The in-phase currents in the antennas are greatest, and are obtained with considerable accuracy. The currents in the outer units are not symmetrical, but with elements of length λ/2 the odd components of the currents are shown to be negligible.
Emissivity Changes of Thoria Cathodes
Authors: Weinreich O. A.
Published: April 2005

Spectral and total emissivity measurements of thoria-coated tungsten filaments show that irreversible and reversible changes of the emissivity occur. ελ (λ=0.65μ) varies from 0.2 to 0.7 and εt from 0.2 to 0.5.

Certain variations of the thermal radiation can be related to changes of thermionic emission.

Passage of current through the coating affects emissivity and thermionic emission. This is shown by measuring infra-red radiation and electron current simultaneously. The existing relationship between emissivity and thermionic activation is discussed.
Thermocouples of the Refractory Metals
Authors: Morgan F. Haydn , Danforth W. E.
Published: April 2005

The thermoelectric power of several refractory thermocouples was investigated, W-Ta for temperature measurements up to 3000°C, W-Mo up to 2600°C, Ta-Mo up to 2600°C and W-W/Mo (alloy 50 percent Mo/50 percent W) up to 2900°C.

Basic calibration was carried out using several melting points and the results were verified and interpolated by means of an optical pyrometer.

The couples W-Ta and W-Mo have been applied in this laboratory to the temperature measurement requirements in high temperature vacuum furnaces and determinations of spectral emissivity.
Determination of Crystallite Size with the X-Ray Spectrometer
Authors: Alexander Leroy , Klug Harold P.
Published: April 2005

The accuracy of the Scherrer crystallite size equation is limited in part by the uncertainty in β, the experimentally deduced pure diffraction broadening. Currently used procedures for estimating β from the observed breadth of a Debye-Scherrer line are not, in general, applicable to the x-ray spectrometer.

By making use of a scheme of convolution analysis for analyzing the effect of geometrical factors in broadening the pure diffraction contour, a correction curve is developed for determining β from the experimentally measured line breadths b and B (Jones' notation). The degree of reliability of this correction procedure is ascertained by applying Stokes' direct Fourier transform procedure for determining the form of the pure diffraction contour free of instrumental effects.

Suggestive procedures are given for crystallite size determination with the x-ray spectrometer in different size ranges, and several examples are described.
Radiofrequency Mass Spectrometer
Authors: Bennett Willard H.
Published: April 2005

A mass spectrometer tube using velocity selection is described. The tube has parallel plane grids made with knitted wire nets with a large percentage of open area. The grids are arranged in groups of three, and radiofrequency alternating potential is applied to the middle grid of each group. Stopping potentials are used to turn back all ions except those with the selected mass. The spectrometer has sufficient resolution for ordinary gas analysis requirements and is simpler, more compact, and more rugged than magnetic beam deflection devices.
The Reversal Theorem of Linearized Supersonic Airfoil Theory
Authors: Munk M. M.
Published: April 2005

It is demonstrated on simple dynamic principles that a supersonic airfoil under certain conditions exhibits the same drag and the same lift slope regardless of whether it flies forward or backward.
The Impact of a Body on a Water Surface at an Arbitrary Angle
Authors: Trilling Leon
Published: April 2005

This paper presents an approximate method of determining the pressure distribution during impact on the surface of a body which strikes a horizontal water surface at an arbitrary angle.

The effect of the splash is neglected and the pressure on the free boundary is assumed proportional to the potential, as if the process were an impulse. The shape of the submerged portion of the striking body is approximated by a semi-ellipse (two dimensions), by a hemisphere, half an ellipsoid of revolution and half a general ellipsoid. Under those conditions, explicit results for the pressure distribution are found. As a special example, the impact pressures on a sphere striking at 45° angle are computed in detail.
Evaporation and Outgassing in an Inert Atmosphere
Authors: Longini R. L.
Published: April 2005

Experiments on the evaporation outgassing of antimony in vacuum and in an inert atmosphere show that an inert atmosphere is advantageous for outgassing antimony if loss of antimony by evaporation is intollerable. A simple theory based on well-established kenetic theory considerations is given which may explain and did predict the results.
Transmission of Elastic Waves through a Stratified Solid Medium
Authors: Thomson William T.
Published: April 2005

The transmission of a plane elastic wave at oblique incidence through a stratified solid medium consisting of any number of parallel plates of different material and thickness is studied theoretically. The matrix method is used to systematize the analysis and to present the equations in a form suitable for computation.
Microwave Angle Separation on a Two and One-Half Mile Overwater Path
Authors: Straiton A. W. , LaGrone A. H.
Published: April 2005

This paper describes the results of radio angle-separation measurements on a 2.50-mile path over Lake Buchanan near Austin, Texas. The measurements were made to test the angle-separation equipment developed at The University of Texas, and to compare these results with measurements obtained by rocking a 20-foot parabolic antenna.
Measurements of Mechanical Properties of Polyisobutylene at Audiofrequencies by a Twin Transducer
Authors: Marvin Robert S. , Fitzgerald Edwin R. , Ferry John D.
Published: April 2005

Apparatus has been developed for measuring the dynamic viscosity and rigidity of soft rubber-like solids in small oscillating deformations. A plate rigidly attached between two identical coils in two permanent magnets shears a pair of disk-shaped samples when a driving current is passed through one coil. The open circuit voltage from the other coil is compared in amplitude and phase with the driving current by a method in which all measurements are in the form of settings of a potential divider. The apparatus has two advantages over the more familiar resonance devices: (a) the amplitudes of motion, which need not be measured directly, are extremely small, thus minimizing any non-linear effects, or temperature change due to heat dissipation; (b) a continuous range of frequencies, spaced as closely as desired, is available without adjusting masses. The dynamic rigidity and viscosity of two samples of polyisobutylene, of molecular weights 1.2 and 0.47 million, have been measured at 15, 25, and 35°C at frequencies from 20 to 600 cycles/ sec., with a reproducibility of five percent or better. The rigidity increases and the viscosity decreases with increasing frequency. Both decrease with increasing temperature, and are almost independent of molecular weight. The temperature dependence is quantitatively explained by the assumption that stresses relax by flow processes whose apparent activation energies are all identical with that characterizing the steady flow viscosity.
The Dielectric Strength of Gaseous Fluorocarbons
Authors: Wilson W. A. , Simons J. H. , Brice T. J.
Published: April 2005

The sixty-cycle dielectric strengths of some gaseous fluorocarbons have been measured between three differently shaped electrode pairs at pressures up to three atmospheres. The breakdown potentials for propforane, butforane, and pentforane were found, in most instances, to be equal to or greater than those for sulfur hexafluoride under comparable conditions, and to be far greater than those for nitrogen. Fluorocarbons thus have possible uses as gaseous insulators in high voltage apparatus.
Electric Breakdown in CO2 from Low Pressures to the Liquid State
Authors: Young D. R.
Published: April 2005

The electric breakdown in CO2 has been investigated from low pressures through the critical point into the liquid state. Paschen's similarity law is verified for low pressures. At high pressures small departures are observed for long gap-lengths and large departures for small gap-lengths. Simultaneously the scatter of the breakdown voltage becomes independent of illumination and the breakdown strength dependent on the cathode material; this appears due to the onset of field emission. Measurements of prebreakdown currents have yielded values for Townsend's first coefficient as well as for the field emission constants. For small gap-lengths the prebreakdown currents are higher than the normal field emission equation predicts, indicating some new process effective at short gap-lengths. The transition from the gaseous to the liquid state does not produce a discontinuous change of the breakdown voltage.
A Method for the Numerical Calculation of Hydrodynamic Shocks
Authors: VonNeumann J. , Richtmyer R. D.
Published: April 2005

The equations of hydrodynamics are modified by the inclusion of additional terms which greatly simplify the procedures needed for stepwise numerical solution of the equations in problems involving shocks. The quantitative influence of these terms can be made as small as one wishes by choice of a sufficiently fine mesh for the numerical integrations. A set of difference equations suitable for the numerical work is given, and the condition that must be satisfied to insure their stabilty is derived.
Separation of Gases by Fractional Permeation through Membranes
Authors: Weller Sol , Steiner Waldo A.
Published: April 2005

The permeability of a number of thin organic films toward oxygen and nitrogen has been measured. For an ethyl cellulose film the studies were extended to include CO2, A, He, and H2. The enrichment of a binary gas mixture in a single stage of permeation has been calculated for the extreme cases of perfect mixing and no mixing. Application of these results indicates that the use of a fractional permeation process may be of practical importance in effecting the separation of oxygen from air, helium from natural gas, and hydrogen from coke-oven gas, as examples.
Analysis of a Sampling Servo Mechanism
Authors: Miller Kenneth S. , Schwarz Ralph J.
Published: April 2005

An analysis of a sampling servo mechanism with an error-clamping device and linear forward and return paths is given. The method leads to a determination of the continuous output of the system in terms of quadratures and gives explicitly the value of the output at the discrete sampling instants. Frequently this is all that is needed in order to study the output variation with time. The question of stability is discussed and a criterion for testing the stability of the system is given in terms of the system parameters.
Effect of Change of Scale on Sintering Phenomena
Authors: Herring Conyers
Published: April 2005

It is shown that when certain plausible assumptions are fulfilled simple scaling laws govern the times required to produce, by sintering at a given temperature, geometrically similar changes in two or more systems of solid particles which are identical geometrically except for a difference of scale. It is suggested that experimental studies of the effect of such a change of scale may prove valuable in identifying the predominant mechanism responsible for sintering under any particular set of conditions, and may also help to decide certain fundamental questions in fields such as creep and crystal growth.
The Electronic Isograph for Roots of Polynomials
Authors: Marshall Byron O.
Published: April 2005

An electronic apparatus which assists in the finding of the roots of polynomials is described. The device accepts the coefficients of polynomials of degree 10 or less and yields the absolute magnitude of the roots to a precision of 0.01 relative to the largest coefficient in the polynomial and an angular accuracy of 0.3 degree on the angle of the root.

The method used is the electronic analog of the expression ω= ∑ anzn= ∑ anrn cosnθ+j ∑ anrn sinnθ.Sinnθ and cosnθ are generated by a motor-driven commutator. The radius r is controlled manually. Hence a plot of ω is placed on the oscilloscope for a fixed r as a function of θ. To find the root r is manipulated until ω crosses the origin in the ω-plane. The value of θ is found by inserting a pip on the intensity of the oscilloscope under a variable phase control. When this pip is moved to the origin of the ω-plane the phase meter indicates the angle of the root in the z plane.
Air Temperature Modification by Vertical Transport
Authors: Fleagle Robert G.
Published: April 2005

It is suggested that when the air temperature increases upward an efficient and economical method for modifying low temperatures near the ground is to force air downward through vertical stacks from the relatively warm air aloft. Theory is developed which shows that the necessary power per unit mass is mainly a function of the air velocity in the stack. The energy required by this method is compared with the energy required to heat the air originally near the ground, and it is shown that under a strong temperature inversion the power method requires considerably less energy than the heating method.
A Bending Method for Measurement of the Tensile Strength and Young's Modulus of Glass Fibers
Authors: Sinclair David
Published: April 2005

The tensile strength and Young's modulus of Johns-Manville experimental drawn glass fibers were measured by a bending method which consists of twisting a loop in a fiber and pulling the ends until the loop breaks. The tensile strength observed by this method was two to three times higher than observed by the conventional straight fiber method, while Young's modulus was practically unchanged. These results may be accounted for by the presence of flaws, since the probability is small that the weakest flaw will occur in the loop, while the straight fiber will always break at the weakest flaw. The apparatus used, a modified Chainomatic balance, is described and the equation of the looped fiber is derived. The method is used to measure the maximum tensile stress and strain attained at the point of minimum radius of curvature of the loop as well as the breaking tensile stress and strain at the actual break point of the fiber. The stress at the break point was found to be as small as one-half the maximum attained in the loop, showing that the strength of the fiber was not uniform.
Semiconductive Colloidal Suspensions with Non-Linear Properties
Authors: Hollmann Hans E.
Published: April 2005

Semiconductive particles in a colloidal suspension, when subjected to an electric polarizing field, form semiconductive chains. Once the suspension is polarized, its conductivity increases with increasing fields because the forces of electrostatic attraction press the individual particles together, thus strengthening the transition contacts along the chains. Both effects result in an over-all electric non-linearity that is the subject of extensive investigation.

The non-linear characteristics of such colloidal resistors are oscillographed and described in relation to the polarizing field strength by means of simple formulas based on field coefficients of the first and second order.

In addition to a true rectification, resulting from the curved characteristics, a ``pseudo-rectification'' occurs which corresponds to an average pre-polarization by stronger alternating fields. The alternating forces of electrostatic attraction assure a high frequency response, so that non-linear Lissajous-figures and harmonics, up to radiofrequencies, are produced.
Aluminum Oxide Replicas for Electron Microscopy Produced by a Two-Step Process
Authors: Hass G. , McFarland M. E.
Published: April 2005

A two-step method is described for preparing aluminum oxide replicas of aluminum and non-aluminum specimens. In this method a thick layer of aluminum is evaporated onto the surface to be studied and pulled off the surface with Scotch Tape or cement covered glass. Aluminum oxide is formed on the side of the aluminum film which has been in contact with the specimen by anodizing in 3 percent ammonium tartrate at about 40 volts. The aluminum oxide film, which represents a positive replica of the specimen surface, is released from its substrate in dilute hydrochloric acid, washed with distilled water, and mounted for the electron microscope investigation. The applicability of the described method is demonstrated with electron micrographs of various specimens. The aluminum oxide films produced in ammonium tartrate are free of pores and grain structure. Films only 100 to 150A in thickness can be prepared and are suitable as temperature resistant supporting membranes for electron microscope and electron diffraction investigations.
Diffusional Viscosity of a Polycrystalline Solid
Authors: Herring Conyers
Published: April 2005

According to a suggestion of Nabarro, any crystal can change its shape by self-diffusion in such way as to yield to an applied shearing stress, and this can cause the macroscopic behavior of a polycrystalline solid to be like that of a viscous fluid. It is possible that this phenomenon is the predominant cause of creep at very high temperatures and very low stresses, though not under more usual conditions. The theory underlying it is developed quantitatively, and calculations of rate of creep, or equivalently of effective viscosity, are given for aggregates of quasi-spherical grains and for wires composed of cylindrical grains. Allowance is made for the effect of tangential stress relaxation at the grain boundaries. It is suggested that mosaic boundaries and boundaries between grains of nearly the same orientation may be unable to serve as sources or sinks of the diffusion currents, in which case the creep rate will depend only on the configuration of grain boundaries having a sizable orientation difference. Numerical comparison of the theory with experiments on the high temperature creep of wires favors this view, but is not entirely satisfactory. Suggestions for further experiments are made.
Upper and Lower Bounds of Eigenvalues for Composite-Type Regions
Authors: Chu E. L.
Published: April 2005

A survey is made to compare the essential features of different variational methods. Schwinger's method is found to have special merits for boundary value and eigenvalue problems concerning composite-type regions. It can give both an upper bound and a lower bound for the eigenvalue of any mode, one bound being as good as the other. It closely resembles the Courant-Trefftz method and is simpler. In both methods the trial functions are so chosen as to satisfy the differential equation while the boundary or continuity conditions are perturbed. The applicability and power of Schwinger's method, being hitherto demonstrated only for particular examples, are exhibited for a whole class of problems by a general formulation of the method in precise terms. The formulation for the upper-bound case presents no difficulty, and a simple proof is given in this paper. A similar proof for the lower-bound case is possible but has a more restricted field of application. The general formulation places the two different cases on equal footing. A way of avoiding the difficulty of having no exact knowledge of the lower eigenfunctions in higher mode cases is discussed in detail.
Random Noise in Dielectric Materials
Authors: Boyer R. F.
Published: April 2005

When thin films of polar plastic materials are subjected to d.c. potentials of 10 to 300 volts per mil they exhibit current fluctuations (with frequencies in the range of 60 to 1000 c.p.s.) which last for minutes and which even persist for a few seconds on removing the voltage. These fluctuations are about 1000 fold above the noise level of the circuit and are about 1 percent of the steady d.c. current. They eventually die out but can usually be restored by reversing the polarity. This noise is greater the more polar the nature of the polymer and the higher its moisture content. The effect seems to arise from water or impurity ions which can jump whenever a hole opens between polymer chains and is thus an activated rate process sufficiently slowed down by the highly viscous nature of the polymeric medium to be readily observable. On an oscillograph screen it is possible to see both the forward and the backward diffusion. This noise is most pronounced in Cellophane, Nylon, and copolymers of vinylidene chloride with acrylonitrile, but also appears with polystyrene stored at 86 percent relative humidity. Films of methylcellulose do not show the effect. Numerically the effect seems to arise from the random motion of groups of several hundred ions as a unit. As an extension of these ideas it is suggested and demonstrated that the moisture vapor diffusion constants for a series of polymers increase with the frequency of the loss factor maximum while the moisture vapor permeability increases with the direct current conductivity.
Transitions in High Polymeric Materials
Authors: Buchdahl Rolf , Nielsen Lawrence E.
Published: April 2005

The evidence for and against the interpretation of the ``second-order'' transition in polymers in terms of a thermodynamic transition of the second order is reviewed and some new experimental data concerning transition in mixtures of polymers are presented. It is shown that the relaxation theory is insufficient to explain the transition, as observed by mechanical, electrical and thermal measurements. The usual objections which are raised against the assumption of a thermodynamic transition are shown to be invalid. Various molecular processes responsible for a thermodynamic transition are discussed and it is shown that the general mechanism of ``hindered'' rotation (changes in rotational configuration) is the most likely.
Studies in Plasticization of Polyvinyl Chloride. I. Physical Changes and Their Measurement
Authors: Dannis M. L.
Published: April 2005

The softening of a hard resin, polyvinyl chloride, by a liquid, dioctyl phthalate, is a set of processes occurring in sequence. Imbibition of the liquid is accompanied by volume reduction in the system. Dilatometer methods evaluate the amount and rate of volume decrease. The rate is temperature dependent, activation energy about 80 kcal. Solution of liquid into the resin follows with no further volume, but large dielectric change. Dielectric changes are measured on material in a cylindrical condenser, using a Schering bridge, and are rate dependent, activation energy about 110 kcal. Data are best described, assuming that segments of the polymer molecule ``react'' independently of one another.